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Appl. Sci., Volume 8, Issue 1 (January 2018)

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Cover Story (view full-size image) In recent years, organic optic electronic devices have been attracting extensive research interest. [...] Read more.
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Editorial

Jump to: Research, Review, Other

Open AccessEditorial Editorial for Special Issue: “Application of Artificial Neural Networks in Geoinformatics”
Appl. Sci. 2018, 8(1), 55; doi:10.3390/app8010055
Received: 27 December 2017 / Revised: 27 December 2017 / Accepted: 28 December 2017 / Published: 2 January 2018
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Abstract
Recently, a need has arisen for prediction techniques that can address a variety of problems by combining methods from the rapidly developing field of machine learning with geoinformation technologies such as GIS, remote sensing, and GPS.[…] Full article
Open AccessEditorial Acknowledgement to Reviewers of Applied Sciences and Announcement of the 2017 Outstanding Reviewer Awards Winners
Appl. Sci. 2018, 8(1), 133; doi:10.3390/app8010133
Received: 10 January 2018 / Revised: 10 January 2018 / Accepted: 10 January 2018 / Published: 18 January 2018
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Abstract
Peer review is an essential part in the publication process, ensuring that Applied Sciences maintains high quality standards for its published papers [...]
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Research

Jump to: Editorial, Review, Other

Open AccessArticle A High-Power Continuous-Wave Mid-Infrared Optical Parametric Oscillator Module
Appl. Sci. 2018, 8(1), 1; doi:10.3390/app8010001
Received: 31 October 2017 / Revised: 11 December 2017 / Accepted: 12 December 2017 / Published: 21 December 2017
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Abstract
We demonstrate here a compact optical parametric oscillator module for mid-infrared generation via nonlinear frequency conversion. This module weighs only 2.5 kg and fits within a small volume of 220 × 60 × 55 mm3. The module can be easily aligned
[...] Read more.
We demonstrate here a compact optical parametric oscillator module for mid-infrared generation via nonlinear frequency conversion. This module weighs only 2.5 kg and fits within a small volume of 220 × 60 × 55 mm3. The module can be easily aligned to various pump laser sources, and here we use a 50 W ytterbium (Yb)-doped fiber laser as an example. With a two-channel MgO-doped periodically poled lithium niobate crystal (MgO:PPLN), our module covers a tuning range of 2416.17–2932.25 nm and 3142.18–3452.15 nm. The highest output power exceeds 10.4 W at 2.7 μm, corresponding to a conversion efficiency of 24%. The measured power stability is 2.13% Root Meat Square (RMS) for a 10 h duration under outdoor conditions. Full article
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Open AccessArticle A Network-Based Method for the EMU Train High-Level Maintenance Planning Problem
Appl. Sci. 2018, 8(1), 2; doi:10.3390/app8010002
Received: 9 November 2017 / Revised: 12 December 2017 / Accepted: 19 December 2017 / Published: 21 December 2017
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Abstract
Electric Multiple Unit (EMU) high-level maintenance planning is a typical discrete system. EMU high-level maintenance (HM) planning determines when to undergo HM or execute transportation task for train-sets, based on practical requirements such as passenger transport demand, workshop maintenance capacity, and maintenance regulations.
[...] Read more.
Electric Multiple Unit (EMU) high-level maintenance planning is a typical discrete system. EMU high-level maintenance (HM) planning determines when to undergo HM or execute transportation task for train-sets, based on practical requirements such as passenger transport demand, workshop maintenance capacity, and maintenance regulations. This research constructs a time-state network that can display the transformation processes between different states. On this basis, a path based model and its improvement are developed to minimize the HM costs with consideration of all necessary regulations and practical constraints. To handle the solution space, a path set generation method is presented. A real-world instance from Shanghai Railway, which is the largest affiliate in China Railway Corporation, was conducted to demonstrate the efficiency and effectiveness of the proposed approach, which indicates that the model can be solved to optimum within short computational times by the state-of-the-art solver Gurobi. Moreover, a sensitivity analysis was also performed to evaluate the effects of the variation in average daily operating mileage, HM capacity at the depot and the assumed minimum value of cumulative mileage. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Modeling of Malachite Green Removal from Aqueous Solutions by Nanoscale Zerovalent Zinc Using Artificial Neural Network
Appl. Sci. 2018, 8(1), 3; doi:10.3390/app8010003
Received: 11 November 2017 / Revised: 9 December 2017 / Accepted: 18 December 2017 / Published: 21 December 2017
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Abstract
The commercially available nanoscale zerovalent zinc (nZVZ) was used as an adsorbent for the removal of malachite green (MG) from aqueous solutions. This material was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The advanced experimental design tools were adopted to study the
[...] Read more.
The commercially available nanoscale zerovalent zinc (nZVZ) was used as an adsorbent for the removal of malachite green (MG) from aqueous solutions. This material was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The advanced experimental design tools were adopted to study the effect of process parameters (viz. initial pH, temperature, contact time and initial concentration) and to reduce number of trials and cost. Response surface methodology and rapidly developing artificial intelligence technologies, i.e., artificial neural network coupled with particle swarm optimization (ANN-PSO) and artificial neural network coupled with genetic algorithm (ANN-GA) were employed for predicting the optimum process variables and obtaining the maximum removal efficiency of MG. The results showed that the removal efficiency predicted by ANN-GA (94.12%) was compatible with the experimental value (90.72%). Furthermore, the Langmuir isotherm was found to be the best model to describe the adsorption of MG onto nZVZ, while the maximum adsorption capacity was calculated to be 1000.00 mg/g. The kinetics for adsorption of MG onto nZVZ was found to follow the pseudo-second-order kinetic model. Thermodynamic parameters (ΔG0, ΔH0 and ΔS0) were calculated from the Van’t Hoff plot of lnKc vs. 1/T in order to discuss the removal mechanism of MG. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle Characterizing the Dissolution Rate of CO2-Brine in Porous Media under Gaseous and Supercritical Conditions
Appl. Sci. 2018, 8(1), 4; doi:10.3390/app8010004
Received: 28 November 2017 / Revised: 15 December 2017 / Accepted: 18 December 2017 / Published: 21 December 2017
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Abstract
The CO2-brine dissolution homogenizes the distribution of residual CO2 and reduces the leakage risk in the saline aquifer. As a key parameter to immobilize the free CO2, the dissolution rate of CO2-brine could be accelerated through
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The CO2-brine dissolution homogenizes the distribution of residual CO2 and reduces the leakage risk in the saline aquifer. As a key parameter to immobilize the free CO2, the dissolution rate of CO2-brine could be accelerated through mechanisms like diffusion and dispersion, which are affected by the subsurface condition, pore structure, and background hydrological flow. This study contributed the calculated dissolution rates of both gaseous and supercritical CO2 during brine imbibition at a pore-scale. The flow development and distribution in porous media during dynamic dissolution were imaged in two-dimensional visualization using X-ray microtomography. The fingerings branching and expansion resulted in greater dissolution rates of supercritical CO2 with high contact between phases, while the brine bypassed the clusters of gaseous CO2 with a slower dissolution and longer duration due to the isolated bubbles. The dissolution rate of supercritical CO2 was about two or three orders of magnitude greater than that of gaseous CO2, while the value distributions both spanned about four orders of magnitude. The dissolution rates of gaseous CO2 increased with porosity, but the relationship was the opposite for supercritical CO2. CO2 saturation and the Reynolds number were analyzed to characterize the different impacts on gaseous and supercritical CO2 at different dissolution periods. Full article
(This article belongs to the Special Issue The Applications of Supercritical Carbon Dioxide)
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Open AccessArticle Temporal Response of Ultrafast Grating Monochromators
Appl. Sci. 2018, 8(1), 5; doi:10.3390/app8010005
Received: 5 December 2017 / Revised: 15 December 2017 / Accepted: 20 December 2017 / Published: 21 December 2017
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Abstract
The temporal response of double-grating monochromators is analyzed considering two effects on the ultrafast pulse given by the configuration. The first effect is the compensation of the pulse-front tilt, i.e., all the rays emitted by the source in different directions at the same
[...] Read more.
The temporal response of double-grating monochromators is analyzed considering two effects on the ultrafast pulse given by the configuration. The first effect is the compensation of the pulse-front tilt, i.e., all the rays emitted by the source in different directions at the same wavelength have to travel the same optical path. The second effect is the group delay introduced by the two gratings, i.e., different wavelengths within the bandwidth transmitted by the slit travel different paths. The methodology to calculate the group delay introduced by the double-grating configuration is presented. Some practical design examples are provided to show the design rules and the achieved performances. Full article
(This article belongs to the Special Issue Advanced EUV and X-Ray Optics)
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Open AccessFeature PaperArticle A Synthetic Nervous System Controls a Simulated Cockroach
Appl. Sci. 2018, 8(1), 6; doi:10.3390/app8010006
Received: 14 November 2017 / Revised: 19 December 2017 / Accepted: 19 December 2017 / Published: 22 December 2017
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Abstract
The purpose of this work is to better understand how animals control locomotion. This knowledge can then be applied to neuromechanical design to produce more capable and adaptable robot locomotion. To test hypotheses about animal motor control, we model animals and their nervous
[...] Read more.
The purpose of this work is to better understand how animals control locomotion. This knowledge can then be applied to neuromechanical design to produce more capable and adaptable robot locomotion. To test hypotheses about animal motor control, we model animals and their nervous systems with dynamical simulations, which we call synthetic nervous systems (SNS). However, one major challenge is picking parameter values that produce the intended dynamics. This paper presents a design process that solves this problem without the need for global optimization. We test this method by selecting parameter values for SimRoach2, a dynamical model of a cockroach. Each leg joint is actuated by an antagonistic pair of Hill muscles. A distributed SNS was designed based on pathways known to exist in insects, as well as hypothetical pathways that produced insect-like motion. Each joint’s controller was designed to function as a proportional-integral (PI) feedback loop and tuned with numerical optimization. Once tuned, SimRoach2 walks through a simulated environment, with several cockroach-like features. A model with such reliable low-level performance is necessary to investigate more sophisticated locomotion patterns in the future. Full article
(This article belongs to the Special Issue Bio-Inspired Robotics)
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Open AccessArticle A Method to Decompose the Streamed Acoustic Emission Signals for Detecting Embedded Fatigue Crack Signals
Appl. Sci. 2018, 8(1), 7; doi:10.3390/app8010007
Received: 12 November 2017 / Revised: 13 December 2017 / Accepted: 19 December 2017 / Published: 22 December 2017
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Abstract
The data collection of Acoustic Emission (AE) method is typically based on threshold-dependent approach, where the AE system acquires data when the output of AE sensor is above the pre-defined threshold. However, this approach fails to detect flaws in noisy environment, as the
[...] Read more.
The data collection of Acoustic Emission (AE) method is typically based on threshold-dependent approach, where the AE system acquires data when the output of AE sensor is above the pre-defined threshold. However, this approach fails to detect flaws in noisy environment, as the signal level of noise may overcome the signal level of AE from flaws, and saturate the AE system. Time-dependent approach is based on streaming waveforms and extracting features at every pre-defined time interval. It is hypothesized that the relevant AE signals representing active flaws are embedded into the streamed signals. In this study, a decomposition method of the streamed AE signals to separate noise signal and crack signal is demonstrated. The AE signals representing fatigue crack growth in steel are obtained from the laboratory scale testing. The streamed AE signals in a noisy operational condition are obtained from the gearbox testing at the Naval Air Systems Command (NAVAIR) facility. The signal addition and decomposition is achieved to determine the minimum detectable signal to noise ratio that is embedded into the streamed AE signals. The developed decomposition approach is demonstrated on detecting burst signals embedded into the streamed signals recorded in the spline testing of the helicopter gearbox test rig located at the NAVAIR facility. Full article
(This article belongs to the Section Acoustics)
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Open AccessArticle Rule Based Coordinated Control of Domestic Combined Micro-CHP and Energy Storage System for Optimal Daily Cost
Appl. Sci. 2018, 8(1), 8; doi:10.3390/app8010008
Received: 17 November 2017 / Revised: 16 December 2017 / Accepted: 19 December 2017 / Published: 22 December 2017
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Abstract
This paper presents a novel control algorithm for optimising operational costs of a combined domestic micro-CHP (combined heat and power), battery and heat storage system. Using a minute by minute basic time-step, this work proposes a simple and computationally efficient rule based whole-system
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This paper presents a novel control algorithm for optimising operational costs of a combined domestic micro-CHP (combined heat and power), battery and heat storage system. Using a minute by minute basic time-step, this work proposes a simple and computationally efficient rule based whole-system management, developed from empirical study of realistic simulated domestic electricity and heat loads. The CHP availability is considered in two binary states which, together with leveraging storage effectively, maximises CHP efficiency, and gives the algorithm increased real world feasibility. In addition, a novel application of a dual battery system is proposed to support the micro-CHP with each battery supplying just one of the distinctive morning and evening electrical load peaks, and thus inherently improving overall battery system lifetime. A case study is presented where the algorithm is shown to yield approximately 23% energy cost savings above the base case, almost 3% higher savings than that of the closest previous work, and 96.8% of the theoretical minimum cost. In general, the algorithm is shown to always yield better than 88% of the theoretical minimum cost, a ratio that will be considerably higher when real-world CHP limitations are factored into the theoretical minimum calculation. Full article
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Open AccessFeature PaperArticle Online Identification of Photovoltaic Source Parameters by Using a Genetic Algorithm
Appl. Sci. 2018, 8(1), 9; doi:10.3390/app8010009
Received: 26 November 2017 / Revised: 12 December 2017 / Accepted: 15 December 2017 / Published: 22 December 2017
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Abstract
In this paper, an efficient method for the online identification of the photovoltaic single-diode model parameters is proposed. The combination of a genetic algorithm with explicit equations allows obtaining precise results without the direct measurement of short circuit current and open circuit voltage
[...] Read more.
In this paper, an efficient method for the online identification of the photovoltaic single-diode model parameters is proposed. The combination of a genetic algorithm with explicit equations allows obtaining precise results without the direct measurement of short circuit current and open circuit voltage that is typically used in offline identification methods. Since the proposed method requires only voltage and current values close to the maximum power point, it can be easily integrated into any photovoltaic system, and it operates online without compromising the power production. The proposed approach has been implemented and tested on an embedded system, and it exhibits a good performance for monitoring/diagnosis applications. Full article
(This article belongs to the Special Issue Computational Intelligence in Photovoltaic Systems)
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Open AccessArticle Attenuation of Temperature Fluctuations on an External Surface of the Wall by a Phase Change Material-Activated Layer
Appl. Sci. 2018, 8(1), 11; doi:10.3390/app8010011
Received: 29 October 2017 / Revised: 18 December 2017 / Accepted: 20 December 2017 / Published: 22 December 2017
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Abstract
Periodical changes of temperature on an external surface of building envelope, e.g., thermal stress or excessive heat gains, is often an undesirable phenomenon. The idea proposed and described in the following paper is to stabilize the external surface temperature in a period of
[...] Read more.
Periodical changes of temperature on an external surface of building envelope, e.g., thermal stress or excessive heat gains, is often an undesirable phenomenon. The idea proposed and described in the following paper is to stabilize the external surface temperature in a period of significant heat gains by the originally developed, novel composite modified by phase change material (PCM) and applied as an external, thin finishing plaster layer. The PCM composite is made from porous, granulated perlite soaked with paraffin wax (Tm = 25 °C) and macro-encapsulated by synthetic resin. The effect of temperature attenuation was estimated for two designated periods of time—the heat gains season (HGS) and the heat losses season (HLS). The attenuation coefficient (AC) was proposed as evaluation parameter of isothermal storage of heat gains determining the reduction of temperature fluctuations. The maximum registered temperature of an external surface for a standard insulation layer was around 20 K higher than for the case modified by PCM. The calculated values of AC were relatively constant during HGS and around two times lower for PCM case. The obtained results confirmed that the proposed modification of an external partition by equipped with additional PCM layer can be effectively used to minimize temperature variations and heat flux in the heat gains season. Full article
(This article belongs to the Special Issue Phase Change Material (PCM) 2017)
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Open AccessArticle Na-Doping Effects on Thermoelectric Properties of Cu2−xSe Nanoplates
Appl. Sci. 2018, 8(1), 12; doi:10.3390/app8010012
Received: 23 November 2017 / Revised: 15 December 2017 / Accepted: 20 December 2017 / Published: 22 December 2017
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Abstract
For this work, a β-phase Cu2−xSe nanowire and nanoplate, and a Na-doped Cu2−xSe nanoplate were successfully synthesized using solution syntheses. The morphologies of the Cu2−xSe nanowire and nanoplate could be easily controlled by changing the synthetic condition.
[...] Read more.
For this work, a β-phase Cu2−xSe nanowire and nanoplate, and a Na-doped Cu2−xSe nanoplate were successfully synthesized using solution syntheses. The morphologies of the Cu2−xSe nanowire and nanoplate could be easily controlled by changing the synthetic condition. The Na-doped Cu2−xSe nanoplate was prepared by a simple treatment of the Cu2−xSe nanoplate with a sodium hydroxide-ethylene glycol solution. The nanopowders were then consolidated to bulk materials using spark plasma sintering (SPS). The phase structure and the microstructure of all of the samples were checked using X-ray diffraction (XRD), high-resolution transmission electron microscope (HR-TEM), and scanning electron microscope (SEM) analyses. The thermoelectric transport properties, such as the electrical conductivity, Seebeck coefficient, carrier concentration, carrier mobility, and thermal conductivity, were measured at temperature ranges from 323 to 673 K. The results show that Na played two important roles: one is reducing the carrier concentration, thereby improving the Seebeck coefficient, the other is reducing the thermal conductivity. Overall, the maximum thermoelectric figure of merit (ZT) of 0.24 was achieved at 673 K in the Na-doped Cu2−xSe nanoplate. Full article
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Open AccessArticle Study on Driving Decision-Making Mechanism of Autonomous Vehicle Based on an Optimized Support Vector Machine Regression
Appl. Sci. 2018, 8(1), 13; doi:10.3390/app8010013
Received: 16 November 2017 / Revised: 19 December 2017 / Accepted: 20 December 2017 / Published: 22 December 2017
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Abstract
Driving Decision-making Mechanism (DDM) is identified as the key technology to ensure the driving safety of autonomous vehicle, which is mainly influenced by vehicle states and road conditions. However, previous studies have seldom considered road conditions and their coupled effects on driving decisions.
[...] Read more.
Driving Decision-making Mechanism (DDM) is identified as the key technology to ensure the driving safety of autonomous vehicle, which is mainly influenced by vehicle states and road conditions. However, previous studies have seldom considered road conditions and their coupled effects on driving decisions. Therefore, road conditions are introduced into DDM in this paper, and are based on a Support Vector Machine Regression (SVR) model, which is optimized by a weighted hybrid kernel function and a Particle Swarm Optimization (PSO) algorithm, this study designs a DDM for autonomous vehicle. Then, the SVR model with RBF (Radial Basis Function) kernel function and BP (Back Propagation) neural network model are tested to validate the accuracy of the optimized SVR model. The results show that the optimized SVR model has the best performance than other two models. Finally, the effects of road conditions on driving decisions are analyzed quantitatively by comparing the reasoning results of DDM with different reference index combinations, and by the sensitivity analysis of DDM with added road conditions. The results demonstrate the significant improvement in the performance of DDM with added road conditions. It also shows that road conditions have the greatest influence on driving decisions at low traffic density, among those, the most influential is road visibility, then followed by adhesion coefficient, road curvature and road slope, while at high traffic density, they have almost no influence on driving decisions. Full article
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Open AccessArticle Grasping Claws of Bionic Climbing Robot for Rough Wall Surface: Modeling and Analysis
Appl. Sci. 2018, 8(1), 14; doi:10.3390/app8010014
Received: 16 November 2017 / Revised: 12 December 2017 / Accepted: 21 December 2017 / Published: 22 December 2017
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Abstract
Aiming at the inspection of rough stone and concrete wall surfaces, a grasping module of cross-arranged claw is designed. It can attach onto rough wall surfaces by hooking or grasping walls. First, based on the interaction mechanism of hooks and rough wall surfaces,
[...] Read more.
Aiming at the inspection of rough stone and concrete wall surfaces, a grasping module of cross-arranged claw is designed. It can attach onto rough wall surfaces by hooking or grasping walls. First, based on the interaction mechanism of hooks and rough wall surfaces, the hook structures in claw tips are developed. Then, the size of the hook tip is calculated and the failure mode is analyzed. The effectiveness and reliability of the mechanism are verified through simulation and finite element analysis. Afterwards, the prototype of the grasping module of claw is established to carry out grasping experiment on vibrating walls. Finally, the experimental results demonstrate that the proposed cross-arranged claw is able to stably grasp static wall surfaces and perform well in grasping vibrating walls, with certain anti-rollover capability. This research lays a foundation for future researches on wall climbing robots with vibrating rough wall surfaces. Full article
(This article belongs to the Special Issue Bio-Inspired Robotics)
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Open AccessArticle Measurement of Static Stiffness after Motion on a Three-Axis CNC Milling Table
Appl. Sci. 2018, 8(1), 15; doi:10.3390/app8010015
Received: 15 November 2017 / Revised: 5 December 2017 / Accepted: 11 December 2017 / Published: 23 December 2017
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Abstract
This paper deals with a modified methodology for measuring the static stiffness of the machine tool. Inspiration to modify the commonly used expanded method of static stiffness measurement resulted from considerably different experimentally measured static stiffness values in the simulated process of load
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This paper deals with a modified methodology for measuring the static stiffness of the machine tool. Inspiration to modify the commonly used expanded method of static stiffness measurement resulted from considerably different experimentally measured static stiffness values in the simulated process of load application under laboratory conditions compared to the standard method. An important takeaway from the measurements is that the measured static stiffness of the table depends greatly on the previous work performed thereon and on the method of the load application onto the table. This modified view of the static stiffness of the machine can have an impact on the increased emphasis on eliminating the phenomena related thereto. It is applicable in engineering practice, in particular in the field of machine tool design, where it will ensure higher machining precision under comparable conditions. In the experiments performed, deformations and displacements were measured with a laser interferometer. Full article
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Open AccessCommunication Optimal Steady-State Range Prediction Filter for Tracking with LFM Waveforms
Appl. Sci. 2018, 8(1), 17; doi:10.3390/app8010017
Received: 31 October 2017 / Revised: 13 December 2017 / Accepted: 20 December 2017 / Published: 23 December 2017
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Abstract
This communication proposes a gain design method of an α-β filter with linear frequency-modulated (LFM) waveforms to achieve optimal range prediction (tracking) of maneuvering targets in steady-state. First, a steady-state root-mean-square (RMS) prediction error, called an RMS-index, is analytically derived for
[...] Read more.
This communication proposes a gain design method of an α - β filter with linear frequency-modulated (LFM) waveforms to achieve optimal range prediction (tracking) of maneuvering targets in steady-state. First, a steady-state root-mean-square (RMS) prediction error, called an RMS-index, is analytically derived for a constant-acceleration target. Next, a design method of the optimal gains that minimizes the derived RMS-index is proposed. Numerical analyses demonstrate the effectiveness of the proposed method, as well as producing a performance improvement over the conventional Kalman filter-based design method. Moreover, the theoretical relationship between range tracking performance and a coefficient for range-Doppler coupling of LFM waveforms is clarified. Numerical simulations using the proposed method demonstrate LFM radar tracking of maneuvering targets and prove the method’s effectiveness. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle A Game Player Expertise Level Classification System Using Electroencephalography (EEG)
Appl. Sci. 2018, 8(1), 18; doi:10.3390/app8010018
Received: 30 October 2017 / Revised: 11 December 2017 / Accepted: 19 December 2017 / Published: 23 December 2017
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Abstract
The success and wider adaptability of smart phones has given a new dimension to the gaming industry. Due to the wide spectrum of video games, the success of a particular game depends on how efficiently it is able to capture the end users’
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The success and wider adaptability of smart phones has given a new dimension to the gaming industry. Due to the wide spectrum of video games, the success of a particular game depends on how efficiently it is able to capture the end users’ attention. This leads to the need to analyse the cognitive aspects of the end user, that is the game player, during game play. A direct window to see how an end user responds to a stimuli is to look at their brain activity. In this study, electroencephalography (EEG) is used to record human brain activity during game play. A commercially available EEG headset is used for this purpose giving fourteen channels of recorded EEG brain activity. The aim is to classify a player as expert or novice using the brain activity as the player indulges in the game play. Three different machine learning classifiers have been used to train and test the system. Among the classifiers, naive Bayes has outperformed others with an accuracy of 88 % , when data from all fourteen EEG channels are used. Furthermore, the activity observed on electrodes is statistically analysed and mapped for brain visualizations. The analysis has shown that out of the available fourteen channels, only four channels in the frontal and occipital brain regions show significant activity. Features of these four channels are then used, and the performance parameters of the four-channel classification are compared to the results of the fourteen-channel classification. It has been observed that support vector machine and the naive Bayes give good classification accuracy and processing time, well suited for real-time applications. Full article
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Open AccessArticle Theoretical Assessment of DC/DC Power Converters’ Basic Topologies. A Common Static Model
Appl. Sci. 2018, 8(1), 19; doi:10.3390/app8010019
Received: 19 November 2017 / Revised: 11 December 2017 / Accepted: 18 December 2017 / Published: 23 December 2017
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Abstract
By the application of well-known circuit analysis techniques, this paper develops an intuitive approach to model the steady state regime of the three DC/DC power converters’ basic topologies (buck, boost and buck-boost). The developed approach can be considered new, realistic, accurate, general and
[...] Read more.
By the application of well-known circuit analysis techniques, this paper develops an intuitive approach to model the steady state regime of the three DC/DC power converters’ basic topologies (buck, boost and buck-boost). The developed approach can be considered new, realistic, accurate, general and practical. The approach is new because it is not present in the literature; realistic because it considers the main non-idealities of the different passive and active components that make up the converters; accurate because its theoretical results fit properly to those obtained in actual converters; general because it is valid for the three basic topologies; and practical because its applicability is easy and immediate from the data sheets of the converters’ components (no measurements are needed). The developed model transforms a complex system with strong non-idealities in the form of distributed parameters, in a simple and intuitive scheme of concentrated parameters (just three), which accurately reflects the actual behavior of the three basic converters’ topologies. The characteristic parameters of the model and its main relationships are determined analytically. The quality of the developed approach has been tested in the paper and can be considered excellent. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Stability Augmentation of a Grid-Connected Wind Farm by Fuzzy-Logic-Controlled DFIG-Based Wind Turbines
Appl. Sci. 2018, 8(1), 20; doi:10.3390/app8010020
Received: 30 November 2017 / Revised: 17 December 2017 / Accepted: 19 December 2017 / Published: 24 December 2017
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Abstract
Wind farm (WF) grid codes require wind generators to have low voltage ride through (LVRT) capability, which means that normal power production should be resumed quickly once the nominal grid voltage has been recovered. However, WFs with fixed-speed wind turbines with squirrel cage
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Wind farm (WF) grid codes require wind generators to have low voltage ride through (LVRT) capability, which means that normal power production should be resumed quickly once the nominal grid voltage has been recovered. However, WFs with fixed-speed wind turbines with squirrel cage induction generators (FSWT-SCIGs) have failed to fulfill the LVRT requirement, which has a significant impact on power system stability. On the other hand, variable-speed wind turbines with doubly fed induction generators (VSWT-DFIGs) have sufficient LVRT augmentation capability and can control the active and reactive power delivered to the grid. However, the DFIG is more expensive than the SCIG due to its AC/DC/AC converter. Therefore, the combined use of SCIGs and DFIGs in a WF could be an effective solution. The design of the rotor-side converter (RSC) controller is crucial because the RSC controller contributes to the system stability. The cascaded control strategy based on four conventional PI controllers is widely used to control the RSC of the DFIG, which can inject only a small amount of reactive power during fault conditions. Therefore, the conventional strategy can stabilize the lower rating of the SCIG. In the present paper, a new control strategy based on fuzzy logic is proposed in the RSC controller of the DFIG in order to enhance the LVRT capability of the SCIG in a WF. The proposed fuzzy logic controller (FLC) is used to control the reactive power delivered to the grid during fault conditions. Moreover, reactive power injection can be increased in the proposed control strategy. Extensive simulations executed in the PSCAD/EMTDC environment for both the proposed and conventional PI controllers of the RSC of the DFIG reveal that the proposed control strategy can stabilize the higher rating of the SCIG. Full article
(This article belongs to the Special Issue Large Grid-Connected Wind Turbines)
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Open AccessArticle TFR: A Novel Approach for Clock Synchronization Fault Recovery in Precision Time Protocol (PTP) Networks
Appl. Sci. 2018, 8(1), 21; doi:10.3390/app8010021
Received: 17 November 2017 / Revised: 18 December 2017 / Accepted: 21 December 2017 / Published: 24 December 2017
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Abstract
Accurate and precise clock synchronization is one of the fundamental requirements for various applications, such as telecommunication systems, measurement and control systems, and smart grid systems. Precision time protocol (PTP) was designed and specified in IEEE 1588 to meet that requirement. PTP provides
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Accurate and precise clock synchronization is one of the fundamental requirements for various applications, such as telecommunication systems, measurement and control systems, and smart grid systems. Precision time protocol (PTP) was designed and specified in IEEE 1588 to meet that requirement. PTP provides a mechanism for synchronizing the clocks in a PTP system to a high degree of accuracy and precision based on exchange synchronization messages through a master–slave hierarchy. The best master clock (BMC) algorithm is currently used to establish the master–slave hierarchy for PTP. However, the BMC algorithm does not provide a fast recovery mechanism in case of master failures. The accuracy and precision of the PTP clocks could be deteriorated by the occurrence of failure in the network (link or node failure). These fault occurrences will affect network performance and reliability, and cause clock time drifting of the PTP nodes. In this paper, we present a novel approach, called timing fault recovery (TFR), to significantly reduce clock time drifting in PTP systems. TFR detects the fault occurrence in the network and recovers it by using a handshake mechanism with a short duration. Therefore, the TFR approach provides clock stability and constancy and increases the reliability and the availability of PTP systems. The performance of TFR has been analyzed and compared to that of the standard PTP. Various simulations were conducted to validate the performance analysis. The results show that, for our sample network, the TFR approach reduces clock drifting by 90% in comparison to the standard PTP, thus providing better clock firmness and synchronization accuracy for PTP clocks. Full article
(This article belongs to the Special Issue Smart Grid and Information Technology)
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Open AccessCommunication Facile Synthesis of Two-Dimensional Porous MgCo2O4 Nanosheets as Anode for Lithium-Ion Batteries
Appl. Sci. 2018, 8(1), 22; doi:10.3390/app8010022
Received: 31 October 2017 / Revised: 11 December 2017 / Accepted: 20 December 2017 / Published: 24 December 2017
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Abstract
Lithium-ion batteries (LIBs) have drawn considerable attention due to their high energy density and good cycling stability. As a transition-metal oxide, MgCo2O4 (MCO) is a promising candidate for energy storage applications because of its low-cost and environmental characteristics. Here, MCO
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Lithium-ion batteries (LIBs) have drawn considerable attention due to their high energy density and good cycling stability. As a transition-metal oxide, MgCo2O4 (MCO) is a promising candidate for energy storage applications because of its low-cost and environmental characteristics. Here, MCO porous nanosheets have been successfully synthesized by a microwave-assisted liquid phase method followed by an annealing procedure. As a result, MCO annealed at 600 °C exhibited optimal rate and cycling performances for Lithium storage application. Specifically, when tested as anode materials for Lithium ion batteries, MCO porous nanosheets delivered a high specific capacity of 1173.8 mAh g−1 at 200 mA g−1, and the specific capacity reached 1130.1 mAh g−1 after 100 cycles at 200 mA g−1, achieving 96.3% for the retention rate. The excellent electrochemical performances are mainly attributed to the monolayer porous nanosheet, which provides short transport paths for Li ions and electrons. Results demonstrated that the MCO porous nanosheets are promising electrode materials for Lithium ion batteries applications. Full article
(This article belongs to the Special Issue Electrode Materials for Lithium-ion Batteries/Super-capacitors)
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Open AccessArticle Estimate of Passive Time Reversal Communication Performance in Shallow Water
Appl. Sci. 2018, 8(1), 23; doi:10.3390/app8010023
Received: 21 November 2017 / Revised: 20 December 2017 / Accepted: 21 December 2017 / Published: 25 December 2017
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Abstract
Time reversal processes have been used to improve communication performance in the severe underwater communication environment characterized by significant multipath channels by reducing inter-symbol interference and increasing signal-to-noise ratio. In general, the performance of the time reversal is strongly related to the behavior
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Time reversal processes have been used to improve communication performance in the severe underwater communication environment characterized by significant multipath channels by reducing inter-symbol interference and increasing signal-to-noise ratio. In general, the performance of the time reversal is strongly related to the behavior of the q -function, which is estimated by a sum of the autocorrelation of the channel impulse response for each channel in the receiver array. The q -function depends on the complexity of the communication channel, the number of channel elements and their spacing. A q -function with a high side-lobe level and a main-lobe width wider than the symbol duration creates a residual ISI (inter-symbol interference), which makes communication difficult even after time reversal is applied. In this paper, we propose a new parameter, E q , to describe the performance of time reversal communication. E q is an estimate of how much of the q -function lies within one symbol duration. The values of E q were estimated using communication data acquired at two different sites: one in which the sound speed ratio of sediment to water was less than unity and one where the ratio was higher than unity. Finally, the parameter E q was compared to the bit error rate and the output signal-to-noise ratio obtained after the time reversal operation. The results show that these parameters are strongly correlated to the parameter E q . Full article
(This article belongs to the Special Issue Underwater Acoustics, Communications and Information Processing)
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Open AccessArticle Message Collision Avoidance Protocols for Detecting Stray Nodes in a Scuba Diving Group Using Ultrasonic Multi-Hop Message Communication
Appl. Sci. 2018, 8(1), 24; doi:10.3390/app8010024
Received: 30 October 2017 / Revised: 21 December 2017 / Accepted: 22 December 2017 / Published: 25 December 2017
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Abstract
Recent years have seen a growing interest in underwater communication and some progress has been made in this area. However, underwater communication is still immature compared with terrestrial communication. A prime reason for this is that the underwater environment is intrinsically not suitable
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Recent years have seen a growing interest in underwater communication and some progress has been made in this area. However, underwater communication is still immature compared with terrestrial communication. A prime reason for this is that the underwater environment is intrinsically not suitable for propagation of electric waves. Instead, ultrasonic waves are mainly used for underwater communication. Since ultrasonic waves cannot provide sufficient communication speed or capacity, they cannot use existing network technologies, which assume use of radio waves. In particular, communication in shallow water is still an uncharted territory. Few communication technologies are employed in environments where people enjoy scuba diving. This paper addresses problems faced by recreational scuba divers. It proposes constructing an ad hoc mesh-shaped network between divers within a group and use ultrasonic waves as transmission media in order to enable the detection of a stray diver. It also proposes a communication protocol in which messages are relayed in multiple hops, and a message collision avoidance method, which is intended to reduce the rate of packet loss caused by message propagation delay. We have implemented the proposed methods in a network simulator, and compared them with an existing communication method that has no message collision avoidance function, in terms of the packet loss rate, the stray driver detection rate, and the rate of the ability to communicate in multiple hops. Full article
(This article belongs to the Special Issue Underwater Acoustics, Communications and Information Processing)
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Open AccessArticle Broken Rotor Bar Fault Detection and Classification Using Wavelet Packet Signature Analysis Based on Fourier Transform and Multi-Layer Perceptron Neural Network
Appl. Sci. 2018, 8(1), 25; doi:10.3390/app8010025
Received: 30 August 2017 / Revised: 17 November 2017 / Accepted: 5 December 2017 / Published: 25 December 2017
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Abstract
As a result of increasing machines capabilities in modern manufacturing, machines run continuously for hours. Therefore, early fault detection is required to reduce the maintenance expenses and obviate high cost and unscheduled downtimes. Fault diagnosis systems that provide features extraction and patterns classification
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As a result of increasing machines capabilities in modern manufacturing, machines run continuously for hours. Therefore, early fault detection is required to reduce the maintenance expenses and obviate high cost and unscheduled downtimes. Fault diagnosis systems that provide features extraction and patterns classification of the fault are able to detect and classify the failures in machines. The majority of the related works that reported a procedure for detection of rotor bar breakage so far have applied motor current signal analysis using discrete wavelet transform. In this paper, the most appropriate features are extracted from the coefficients of a wavelet packet transform after fast Fourier transform of current signal. The aim of this study is to develop an effective and sensitive method for fault detection under low load conditions. Through combining the strength of both time-scale and frequency domain analysis techniques, a unified wavelet packet signature analysis pinpoints the fault signature in the special fault-oriented frequency bands. The wavelet analysis combined with a feed-forward neural network classifier provides an intelligent methodology for the automatic diagnosis of the fault severity during runtime of the motor. The faults severity is considered as one, two, and three broken rotor bars. The results have confirmed that the proposed method is effective for diagnosing rotor bar breakage fault in an induction motor and classification of fault severity. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Enhancement of Chlorophyll a Production from Marine Spirulina maxima by an Optimized Ultrasonic Extraction Process
Appl. Sci. 2018, 8(1), 26; doi:10.3390/app8010026
Received: 2 November 2017 / Revised: 13 December 2017 / Accepted: 20 December 2017 / Published: 25 December 2017
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Abstract
Under the optimal ultrasonification extraction conditions of 20.52 kHz for the frequency, 32.59 °C for the temperature, and 4.91 h for the process time, 17.98 mg/g of chlorophyll a was obtained. It was much higher than 13.81 mg/g from conventional 70% ethanol extraction
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Under the optimal ultrasonification extraction conditions of 20.52 kHz for the frequency, 32.59 °C for the temperature, and 4.91 h for the process time, 17.98 mg/g of chlorophyll a was obtained. It was much higher than 13.81 mg/g from conventional 70% ethanol extraction and even higher than other data from Spirulina. This yield was close to the predicted value of 18.21 mg/g from the second-order polynomial model with a regression coefficient of 0.969. This model showed the greatest significance with the ultrasonic frequency and process time and the least significance with the temperature. The extracts also showed high α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging activities as 69.38%, compared to 58.25% for the extracts from the 70% ethanol extraction. It was first shown that the optimal extraction was effective at enhancing the neuroprotective activities possibly due to the synergistic effects of higher amounts of chlorophyll a and other bioactive substances in the extract, revealing a 90% protection of the growth of mouse neuronal cells and a great reduction in Reactive Oxygen Species (ROS) production. Full article
(This article belongs to the Special Issue Ultrasound in Extraction Processing)
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Open AccessArticle Noninvasive Grading of Glioma Tumor Using Magnetic Resonance Imaging with Convolutional Neural Networks
Appl. Sci. 2018, 8(1), 27; doi:10.3390/app8010027
Received: 4 October 2017 / Revised: 15 November 2017 / Accepted: 18 December 2017 / Published: 25 December 2017
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Abstract
In recent years, Convolutional Neural Networks (ConvNets) have rapidly emerged as a widespread machine learning technique in a number of applications especially in the area of medical image classification and segmentation. In this paper, we propose a novel approach that uses ConvNet for
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In recent years, Convolutional Neural Networks (ConvNets) have rapidly emerged as a widespread machine learning technique in a number of applications especially in the area of medical image classification and segmentation. In this paper, we propose a novel approach that uses ConvNet for classifying brain medical images into healthy and unhealthy brain images. The unhealthy images of brain tumors are categorized also into low grades and high grades. In particular, we use the modified version of the Alex Krizhevsky network (AlexNet) deep learning architecture on magnetic resonance images as a potential tumor classification technique. The classification is performed on the whole image where the labels in the training set are at the image level rather than the pixel level. The results showed a reasonable performance in characterizing the brain medical images with an accuracy of 91.16%. Full article
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Open AccessArticle Comparative Study on KNN and SVM Based Weather Classification Models for Day Ahead Short Term Solar PV Power Forecasting
Appl. Sci. 2018, 8(1), 28; doi:10.3390/app8010028
Received: 30 November 2017 / Revised: 21 December 2017 / Accepted: 21 December 2017 / Published: 25 December 2017
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Abstract
Accurate solar photovoltaic (PV) power forecasting is an essential tool for mitigating the negative effects caused by the uncertainty of PV output power in systems with high penetration levels of solar PV generation. Weather classification based modeling is an effective way to increase
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Accurate solar photovoltaic (PV) power forecasting is an essential tool for mitigating the negative effects caused by the uncertainty of PV output power in systems with high penetration levels of solar PV generation. Weather classification based modeling is an effective way to increase the accuracy of day-ahead short-term (DAST) solar PV power forecasting because PV output power is strongly dependent on the specific weather conditions in a given time period. However, the accuracy of daily weather classification relies on both the applied classifiers and the training data. This paper aims to reveal how these two factors impact the classification performance and to delineate the relation between classification accuracy and sample dataset scale. Two commonly used classification methods, K-nearest neighbors (KNN) and support vector machines (SVM) are applied to classify the daily local weather types for DAST solar PV power forecasting using the operation data from a grid-connected PV plant in Hohhot, Inner Mongolia, China. We assessed the performance of SVM and KNN approaches, and then investigated the influences of sample scale, the number of categories, and the data distribution in different categories on the daily weather classification results. The simulation results illustrate that SVM performs well with small sample scale, while KNN is more sensitive to the length of the training dataset and can achieve higher accuracy than SVM with sufficient samples. Full article
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Open AccessArticle Robust Control Examples Applied to a Wind Turbine Simulated Model
Appl. Sci. 2018, 8(1), 29; doi:10.3390/app8010029
Received: 25 November 2017 / Revised: 16 December 2017 / Accepted: 19 December 2017 / Published: 26 December 2017
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Abstract
Wind turbine plants are complex dynamic and uncertain processes driven by stochastic inputs and disturbances, as well as different loads represented by gyroscopic, centrifugal and gravitational forces. Moreover, as their aerodynamic models are nonlinear, both modeling and control become challenging problems. On the
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Wind turbine plants are complex dynamic and uncertain processes driven by stochastic inputs and disturbances, as well as different loads represented by gyroscopic, centrifugal and gravitational forces. Moreover, as their aerodynamic models are nonlinear, both modeling and control become challenging problems. On the one hand, high-fidelity simulators should contain different parameters and variables in order to accurately describe the main dynamic system behavior. Therefore, the development of modeling and control for wind turbine systems should consider these complexity aspects. On the other hand, these control solutions have to include the main wind turbine dynamic characteristics without becoming too complicated. The main point of this paper is thus to provide two practical examples of the development of robust control strategies when applied to a simulated wind turbine plant. Extended simulations with the wind turbine benchmark model and the Monte Carlo tool represent the instruments for assessing the robustness and reliability aspects of the developed control methodologies when the model-reality mismatch and measurement errors are also considered. Advantages and drawbacks of these regulation methods are also highlighted with respect to different control strategies via proper performance metrics. Full article
(This article belongs to the Special Issue Renewable Energy 2018)
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Open AccessArticle Efficient Disruption of Escherichia coli for Plasmid DNA Recovery in a Bead Mill
Appl. Sci. 2018, 8(1), 30; doi:10.3390/app8010030
Received: 5 November 2017 / Revised: 20 December 2017 / Accepted: 22 December 2017 / Published: 26 December 2017
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Abstract
The release kinetics of pDNA in a bead mill was studied. Samples taken during the process were analyzed to determine total pDNA (pDNA(t)) and supercoiled pDNA (pDNA(sc)) concentration. In order to identify important variables of the process and to develop an empirical model
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The release kinetics of pDNA in a bead mill was studied. Samples taken during the process were analyzed to determine total pDNA (pDNA(t)) and supercoiled pDNA (pDNA(sc)) concentration. In order to identify important variables of the process and to develop an empirical model for optimal pDNA(t) and pDNA(sc) release, a two level 23 factorial design was used with variables: mill frequency, cell concentration, and bead size. The results were analyzed by response surface methodology. The optimized conditions for pDNA(t) yield 13.26 mg/g dcw (93.41% recovery), with a mill frequency of 30 Hz, a bead size of 0.10–0.25 mm, and a cell concentration of 20 g wcw/L. However, the optimized conditions for pDNA(sc) yield 7.65 mg/g dcw (92.05% recovery), with a mill frequency of 15 Hz, a bead size of 0.10–0.25 mm, and a cell concentration of 10 g wcw/L. Cell disruption in a bead mill was proved efficient for the release of pDNA(t) and pDNA(sc) compared to the alkaline treatment. The results obtained suggest a compromise between pDNA(sc) purity and recuperation in the process development. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle Germinal Center Optimization Applied to Neural Inverse Optimal Control for an All-Terrain Tracked Robot
Appl. Sci. 2018, 8(1), 31; doi:10.3390/app8010031
Received: 16 November 2017 / Revised: 15 December 2017 / Accepted: 21 December 2017 / Published: 27 December 2017
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Abstract
Nowadays, there are several meta-heuristics algorithms which offer solutions for multi-variate optimization problems. These algorithms use a population of candidate solutions which explore the search space, where the leadership plays a big role in the exploration-exploitation equilibrium. In this work, we propose to
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Nowadays, there are several meta-heuristics algorithms which offer solutions for multi-variate optimization problems. These algorithms use a population of candidate solutions which explore the search space, where the leadership plays a big role in the exploration-exploitation equilibrium. In this work, we propose to use a Germinal Center Optimization algorithm (GCO) which implements temporal leadership through modeling a non-uniform competitive-based distribution for particle selection. GCO is used to find an optimal set of parameters for a neural inverse optimal control applied to all-terrain tracked robot. In the Neural Inverse Optimal Control (NIOC) scheme, a neural identifier, based on Recurrent High Orden Neural Network (RHONN) trained with an extended kalman filter algorithm, is used to obtain a model of the system, then, a control law is design using such model with the inverse optimal control approach. The RHONN identifier is developed without knowledge of the plant model or its parameters, on the other hand, the inverse optimal control is designed for tracking velocity references. Applicability of the proposed scheme is illustrated using simulations results as well as real-time experimental results with an all-terrain tracked robot. Full article
(This article belongs to the Special Issue Bio-Inspired Robotics)
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Open AccessArticle A Fusion Link Prediction Method Based on Limit Theorem
Appl. Sci. 2018, 8(1), 32; doi:10.3390/app8010032
Received: 3 December 2017 / Revised: 17 December 2017 / Accepted: 22 December 2017 / Published: 28 December 2017
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Abstract
The theoretical limit of link prediction is a fundamental problem in this field. Taking the network structure as object to research this problem is the mainstream method. This paper proposes a new viewpoint that link prediction methods can be divided into single or
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The theoretical limit of link prediction is a fundamental problem in this field. Taking the network structure as object to research this problem is the mainstream method. This paper proposes a new viewpoint that link prediction methods can be divided into single or combination methods, based on the way they derive the similarity matrix, and investigates whether there a theoretical limit exists for combination methods. We propose and prove necessary and sufficient conditions for the combination method to reach the theoretical limit. The limit theorem reveals the essence of combination method that is to estimate probability density functions of existing links and nonexistent links. Based on limit theorem, a new combination method, theoretical limit fusion (TLF) method, is proposed. Simulations and experiments on real networks demonstrated that TLF method can achieve higher prediction accuracy. Full article
(This article belongs to the Special Issue Selected Papers from IEEE ICICE 2017)
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Open AccessFeature PaperArticle Metallic, 3D-Printed, K-Band-Stepped, Double-Ridged Square Horn Antennas
Appl. Sci. 2018, 8(1), 33; doi:10.3390/app8010033
Received: 18 October 2017 / Revised: 30 November 2017 / Accepted: 20 December 2017 / Published: 27 December 2017
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Abstract
This paper presents K-band-stepped, double-ridged square horn antennas fabricated by metallic 3D printing technology in copper (85% copper and 15% stannum) and aluminum alloy (89.5% aluminum, 10% silicon, and 0.5% magnesium). Compared with the popular dielectric 3D-printed horn antenna, the metallic counterpart features
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This paper presents K-band-stepped, double-ridged square horn antennas fabricated by metallic 3D printing technology in copper (85% copper and 15% stannum) and aluminum alloy (89.5% aluminum, 10% silicon, and 0.5% magnesium). Compared with the popular dielectric 3D-printed horn antenna, the metallic counterpart features better mechanical robustness in terms of material. Moreover, the metallic horns are printed in one piece in one run, different from the dielectric horns that are printed in split pieces and electroplated, they simplify the process and thus result in reduced cost. The agreement between the simulation and measurement results verified the antenna’s performance. Both the 3D-printed copper and aluminum alloy antenna have an impedance bandwidth across the K-band, with a maximum gain of 13.23 dBi @ 25 GHz and 13.5 dBi @ 24 GHz, respectively. The metallic, 3D-printed horn antennas are preferable alternatives to replace traditionally-fabricated antennas. Full article
(This article belongs to the Special Issue 3D Printed Antennas)
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Open AccessArticle Forced Response Prediction of Turbine Blades with Flexible Dampers: The Impact of Engineering Modelling Choices
Appl. Sci. 2018, 8(1), 34; doi:10.3390/app8010034
Received: 2 December 2017 / Revised: 19 December 2017 / Accepted: 23 December 2017 / Published: 27 December 2017
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Abstract
This paper focuses on flexible friction dampers (or “strips”) mounted on the underside of adjacent turbine blade platforms for sealing and damping purposes. A key parameter to ensure a robust and trustworthy design is the correct prediction of the maximum frequency shift induced
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This paper focuses on flexible friction dampers (or “strips”) mounted on the underside of adjacent turbine blade platforms for sealing and damping purposes. A key parameter to ensure a robust and trustworthy design is the correct prediction of the maximum frequency shift induced by the strip damper coupling adjacent blades. While this topic has been extensively addressed on rigid friction dampers, both experimentally and numerically, no such investigation is available as far as flexible dampers are concerned. This paper builds on the authors’ prior experience with rigid dampers to investigate the peculiarities and challenges of a robust dynamic model of blade-strips systems. The starting point is a numerical tool implementing state-of-the-art techniques for the efficient solution of the nonlinear equations, e.g., multi-harmonic balance method with coupled static solution and state-of-the-art contact elements. The full step-by-step modelling process is here retraced and upgraded to take into account the damper flexibility: for each step, key modelling choices (e.g., mesh size, master nodes selection, contact parameters) which may affect the predicted response are addressed. The outcome is a series of guidelines which will help the designer assign numerical predictions the proper level of trust and outline a much-needed experimental campaign. Full article
(This article belongs to the Section Mechanical Engineering)
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Open AccessArticle A Real-Time Sound Field Rendering Processor
Appl. Sci. 2018, 8(1), 35; doi:10.3390/app8010035
Received: 3 November 2017 / Revised: 5 December 2017 / Accepted: 18 December 2017 / Published: 28 December 2017
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Abstract
Real-time sound field renderings are computationally intensive and memory-intensive. Traditional rendering systems based on computer simulations suffer from memory bandwidth and arithmetic units. The computation is time-consuming, and the sample rate of the output sound is low because of the long computation time
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Real-time sound field renderings are computationally intensive and memory-intensive. Traditional rendering systems based on computer simulations suffer from memory bandwidth and arithmetic units. The computation is time-consuming, and the sample rate of the output sound is low because of the long computation time at each time step. In this work, a processor with a hybrid architecture is proposed to speed up computation and improve the sample rate of the output sound, and an interface is developed for system scalability through simply cascading many chips to enlarge the simulated area. To render a three-minute Beethoven wave sound in a small shoe-box room with dimensions of 1.28 m × 1.28 m × 0.64 m, the field programming gate array (FPGA)-based prototype machine with the proposed architecture carries out the sound rendering at run-time while the software simulation with the OpenMP parallelization takes about 12.70 min on a personal computer (PC) with 32 GB random access memory (RAM) and an Intel i7-6800K six-core processor running at 3.4 GHz. The throughput in the software simulation is about 194 M grids/s while it is 51.2 G grids/s in the prototype machine even if the clock frequency of the prototype machine is much lower than that of the PC. The rendering processor with a processing element (PE) and interfaces consumes about 238,515 gates after fabricated by the 0.18 µm processing technology from the ROHM semiconductor Co., Ltd. (Kyoto Japan), and the power consumption is about 143.8 mW. Full article
(This article belongs to the Special Issue Sound and Music Computing)
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Open AccessArticle PHD and CPHD Algorithms Based on a Novel Detection Probability Applied in an Active Sonar Tracking System
Appl. Sci. 2018, 8(1), 36; doi:10.3390/app8010036
Received: 27 November 2017 / Revised: 23 December 2017 / Accepted: 25 December 2017 / Published: 27 December 2017
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Abstract
Underwater multi-targets tracking has always been a difficult problem in active sonar tracking systems. In order to estimate the parameters of time-varying multi-targets moving in underwater environments, based on the Bayesian filtering framework, the Random Finite Set (RFS) is introduced to multi-targets tracking,
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Underwater multi-targets tracking has always been a difficult problem in active sonar tracking systems. In order to estimate the parameters of time-varying multi-targets moving in underwater environments, based on the Bayesian filtering framework, the Random Finite Set (RFS) is introduced to multi-targets tracking, which not only avoids the problem of data association in multi-targets tracking, but also realizes the estimation of the target number and their states simultaneously. Usually, the conventional Probability Hypothesis Density (PHD) and Cardinalized Probability Hypothesis Density (CPHD) algorithms assume that the detection probability is known as a priori, which is not suitable in many applications. Some methods have been proposed to estimate the detection probability, but most assume that it is constant both in time and surveillance region. In this paper, we model the detection probability through the active sonar equation. When fixed the false detection probability, we can get the analytic expression for the detection probability, which is related to target position. In addition, this novel detection probability is used in PHD and CPHD algorithms and applied to underwater active sonar tracking systems. Also, we use the adaptive ellipse gate strategy to reduce the computational load in PHD and CPHD algorithms. Under the linear Gaussian assumption, the proposed detection probability is illustrated in both Gaussian Mixture Probability Hypothesis Density (GM-PHD) and Gaussian Mixture Cardinalized Probability Hypothesis Density (GM-CPHD), respectively. Simulation results show that the proposed Pd-GM-PHD and Pd-GM-CPHD algorithms are more realistic and accuratein underwater active sonar tracking systems. Full article
(This article belongs to the Special Issue Underwater Acoustics, Communications and Information Processing)
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Open AccessArticle Parameter Determination of a Minimal Model for Brake Squeal
Appl. Sci. 2018, 8(1), 37; doi:10.3390/app8010037
Received: 10 November 2017 / Revised: 20 December 2017 / Accepted: 21 December 2017 / Published: 1 January 2018
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Abstract
In the research into the mechanism of brake squeal, minimal models with two degrees of freedom (DoFs) are widely used. Compared with the finite element method, the minimal model is more concise and efficient, making it easier to analyze the effect of parameters.
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In the research into the mechanism of brake squeal, minimal models with two degrees of freedom (DoFs) are widely used. Compared with the finite element method, the minimal model is more concise and efficient, making it easier to analyze the effect of parameters. However, how to accurately determine its kinetic parameters is rarely reported in the literature. In this paper, firstly, the finite element model of a disc brake is established and the complex eigenvalue analysis (CEA) is carried out to obtain unstable modes of the brake. Then, an unstable mode with seven nodal diameters predicted by CEA is taken as an example to establish the 2-DoF model. In order that the natural frequency, Hopf bifurcation point and real parts of eigenvalues of the minimal model coincide with that of the unstable mode with seven nodal diameters, the response surface method (RSM) is applied to determine the kinetic parameters of the minimal model. Finally, the parameter-optimized minimal model is achieved. Furthermore, the negative slope of friction-velocity characteristic is introduced into the model, and transient analysis (TA) is used to study the effect of braking velocity on stability of the brake system. The results show that the brake system becomes unstable when braking velocity is lower than a critical value. The lower the velocity is, the worse the stability appears, and the higher the brake squeal propensity is. Full article
(This article belongs to the Section Acoustics)
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Open AccessArticle A Novel Approach for the Estimation of Doubly Spread Acoustic Channels Based on Wavelet Transform
Appl. Sci. 2018, 8(1), 38; doi:10.3390/app8010038
Received: 29 October 2017 / Revised: 20 December 2017 / Accepted: 20 December 2017 / Published: 1 January 2018
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Abstract
In this paper, the estimation of doubly spread underwater acoustic (UWA) channels is investigated. The UWA channels are characterized by severe delay spread and significant Doppler effects, and can be well modeled as a multi-scale multi-lag (MSML) channel. Furthermore, exploiting the sparsity of
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In this paper, the estimation of doubly spread underwater acoustic (UWA) channels is investigated. The UWA channels are characterized by severe delay spread and significant Doppler effects, and can be well modeled as a multi-scale multi-lag (MSML) channel. Furthermore, exploiting the sparsity of UWA channels, MSML channel estimation can be transformed into the estimation of parameter sets (amplitude, Doppler scale factor, time delay). Based on this, the orthogonal matching pursuit (OMP) algorithm has been widely used. However, the estimation accuracy of OMP depends on the size of the dictionary, which is related with both delay spread and Doppler spread. Thus it requires high computational complexity. This paper proposes a new method, called wavelet transform (WT) based algorithm, for the UWA channel estimation. Different from OMP algorithm which needs to search in both time domain and Doppler domain, WT-based algorithm only needs to search in time domain by using the Doppler invariant characteristic of hyperbolic frequency modulation (HFM) signal. The performance of the proposed algorithm is evaluated by computer simulations based on BELLHOP. The simulation results show that WT-based algorithm performs slightly better than OMP algorithm in low signal to noise ratio (SNR) while can greatly reduce computational complexity. Full article
(This article belongs to the Special Issue Underwater Acoustics, Communications and Information Processing)
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Open AccessFeature PaperArticle Slot Waveguide Enhanced Bloch Surface Waves
Appl. Sci. 2018, 8(1), 39; doi:10.3390/app8010039
Received: 1 December 2017 / Revised: 22 December 2017 / Accepted: 26 December 2017 / Published: 30 December 2017
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Abstract
The paper presents a novel concept for the on-chip integration of a multilayer platform sustaining Bloch surface waves further enhanced by the so-called slot waveguide effect. Through simulations, we demonstrate that a carefully designed polymer waveguide arrangement coated with a subwavelength dielectric multilayer
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The paper presents a novel concept for the on-chip integration of a multilayer platform sustaining Bloch surface waves further enhanced by the so-called slot waveguide effect. Through simulations, we demonstrate that a carefully designed polymer waveguide arrangement coated with a subwavelength dielectric multilayer can be efficiently used to first excite a Bloch surface wave at the surface of the multilayer and second to enhance this wave and allow longer propagation of the surface mode by constructive superimposition of two evanescent tails inside a narrow gap. Full article
(This article belongs to the Special Issue Surface Waves on Planar Photonic Crystals)
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Open AccessArticle An Efficient Numerical Approach for Field Infrared Smoke Transmittance Based on Grayscale Images
Appl. Sci. 2018, 8(1), 40; doi:10.3390/app8010040
Received: 9 December 2017 / Revised: 26 December 2017 / Accepted: 26 December 2017 / Published: 29 December 2017
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Abstract
Infrared smoke screen has been playing an important role in electro-optical countermeasures on the battlefield. Smoke transmittance is one of the most important parameters which can evaluate the obscuration performance of smoke. In this paper, an efficient numerical approach for field infrared smoke
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Infrared smoke screen has been playing an important role in electro-optical countermeasures on the battlefield. Smoke transmittance is one of the most important parameters which can evaluate the obscuration performance of smoke. In this paper, an efficient numerical approach for field infrared smoke transmittance based on grayscale images is presented. Firstly, a field trial experimental setup is introduced. Then a grayscale smoke transmittance mathematical model is deduced and built. In addition, an image processing algorithm is used to extract the gray values of certain pixel points from grayscale images, and the positions of the selected points are discussed. Lastly, a field trial sample calculation is included to illustrate the procedure of the proposed method. The results prove to be of enough precision for engineering applications, and the method has greatly simplified the field trial process, thus improving efficiency. Full article
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Open AccessArticle Research on the Transportation of Low-Strength Composites Sheets
Appl. Sci. 2018, 8(1), 41; doi:10.3390/app8010041
Received: 26 November 2017 / Revised: 21 December 2017 / Accepted: 22 December 2017 / Published: 31 December 2017
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Abstract
The novel non-combustible sandwich panel is extremely fragile in manufacturing and cannot be tensioned between rolls. Previous studies on the roll-to-roll system, which mainly focused on the high-tension situations and little described the low-strength materials, are insufficient. To explore the transportation of low-strength
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The novel non-combustible sandwich panel is extremely fragile in manufacturing and cannot be tensioned between rolls. Previous studies on the roll-to-roll system, which mainly focused on the high-tension situations and little described the low-strength materials, are insufficient. To explore the transportation of low-strength materials, we study the tension distribution of continuous moving flexible one-dimensional materials on a steady-state track. First, we propose a numerical method to calculate the steady-state track of low-strength sheet between rolls considering the gravity, as well as size and position of rolls. Then we obtain the optimum sag at different size and position of rolls. We find out that there is a lower limit of the sheet’s strength-density ratio (the Minimum Specific Strength) for a specific set of size and position of rolls. Finally, we establish a method to calculate the lower limit approximately for engineering use. Our method can be generalized in manufacturing other low-strength flexible thin-sheet materials as well. Full article
(This article belongs to the Section Mechanical Engineering)
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Open AccessArticle Finite Difference/Collocation Method for a Generalized Time-Fractional KdV Equation
Appl. Sci. 2018, 8(1), 42; doi:10.3390/app8010042
Received: 1 November 2017 / Revised: 27 December 2017 / Accepted: 28 December 2017 / Published: 1 January 2018
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Abstract
In this paper, we studied the numerical solution of a time-fractional Korteweg–de Vries (KdV) equation with new generalized fractional derivative proposed recently. The fractional derivative employed in this paper was defined in Caputo sense and contained a scale function and a weight function.
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In this paper, we studied the numerical solution of a time-fractional Korteweg–de Vries (KdV) equation with new generalized fractional derivative proposed recently. The fractional derivative employed in this paper was defined in Caputo sense and contained a scale function and a weight function. A finite difference/collocation scheme based on Jacobi–Gauss–Lobatto (JGL) nodes was applied to solve this equation and the corresponding stability was analyzed theoretically, while the convergence was verified numerically. Furthermore, we investigated the behavior of solution of the generalized KdV equation depending on its parameter δ , scale function z ( t ) in fractional derivative. We found that the full discrete scheme was effective to obtain a numerical solution of the new KdV equation with different conditions. The wave number δ in front of the third order space derivative term played a significant role in splitting a soliton wave into multiple small pieces. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Virtual Reality-Wireless Local Area Network: Wireless Connection-Oriented Virtual Reality Architecture for Next-Generation Virtual Reality Devices
Appl. Sci. 2018, 8(1), 43; doi:10.3390/app8010043
Received: 15 November 2017 / Revised: 23 December 2017 / Accepted: 27 December 2017 / Published: 3 January 2018
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Abstract
In order to enhance the user experience of virtual reality (VR) devices, multi-user VR environments and wireless connections should be considered for next-generation VR devices. Wireless local area network (WLAN)-based wireless communication devices are popular consumer devices with high throughput and low cost
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In order to enhance the user experience of virtual reality (VR) devices, multi-user VR environments and wireless connections should be considered for next-generation VR devices. Wireless local area network (WLAN)-based wireless communication devices are popular consumer devices with high throughput and low cost using unlicensed bands. However, the use of WLANs may cause delays in packet transmission, owing to their distributed nature while accessing the channel. In this paper, we carefully examine the feasibility of wireless VR over WLANs, and we propose an efficient wireless multiuser VR communication architecture, as well as a communication scheme for VR. Because the proposed architecture in this paper utilizes multiple WLAN standards, based on the characteristics of each set of VR traffic, the proposed scheme enables the efficient delivery of massive uplink data generated by multiple VR devices, and provides an adequate video frame rate and control frame rate for high-quality VR services. We perform extensive simulations to corroborate the outstanding performance of the proposed scheme. Full article
(This article belongs to the Special Issue Wearable Wireless Devices)
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Open AccessArticle Upper-Body Control and Mechanism of Humanoids to Compensate for Angular Momentum in the Yaw Direction Based on Human Running
Appl. Sci. 2018, 8(1), 44; doi:10.3390/app8010044
Received: 23 October 2017 / Revised: 25 December 2017 / Accepted: 27 December 2017 / Published: 3 January 2018
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Abstract
Many extant studies proposed various stabilizing control methods for humanoids during the stance phase while hopping and running. Although these methods contribute to stability during hopping and running, humanoid robots do not swing their legs rapidly during the flight phase to prevent rotation
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Many extant studies proposed various stabilizing control methods for humanoids during the stance phase while hopping and running. Although these methods contribute to stability during hopping and running, humanoid robots do not swing their legs rapidly during the flight phase to prevent rotation in the yaw direction. Humans utilize their torsos and arms when running to compensate for the angular momentum in the yaw direction generated by leg movement during the flight phase. In this study, we developed an angular momentum control method based on human motion for a humanoid upper body. The method involves calculation of the angular momentum generated by the movement of the humanoid legs and calculation of the torso and arm motions required to compensate for the angular momentum of the legs in the yaw direction. We also developed a humanoid upper-body mechanism having human link length and mass properties, using carbon-fiber-reinforced plastic and a symmetric structure for generating large angular momentum. The humanoid robot developed in this study could generate almost the same angular momentum as that of a human. Furthermore, when suspended in midair, the humanoid robot achieved angular momentum compensation in the yaw direction. Full article
(This article belongs to the Special Issue Bio-Inspired Robotics)
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Open AccessArticle Application of the Wave Propagation Approach to Sandwich Structures: Vibro-Acoustic Properties of Aluminum Honeycomb Materials
Appl. Sci. 2018, 8(1), 45; doi:10.3390/app8010045
Received: 3 December 2017 / Revised: 16 December 2017 / Accepted: 16 December 2017 / Published: 1 January 2018
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Abstract
Sandwich structures are manufactured using multiple combinations of materials for core and laminates. The real performances are influenced by variability in the composing layers and even by the uncertainties introduced while bonding them together. Therefore, experimental tests are usually the preferred way to
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Sandwich structures are manufactured using multiple combinations of materials for core and laminates. The real performances are influenced by variability in the composing layers and even by the uncertainties introduced while bonding them together. Therefore, experimental tests are usually the preferred way to assess the most important parameters required to develop and to characterize the product, the main downsides lying in their cost and time consumption. This work explores a practical application of the wave propagation approach by means of a case study, in which some significant properties of an aluminum honeycomb panel are obtained starting from simple vibro-acoustic tests carried out on beam specimens. After determining the frequency-dependent bending stiffness function, the sound transmission loss is predicted and compared with the experimental results obtained in sound transmission suites. The same vibro-acoustic tests are used to estimate the core shear modulus. Finally, a parametric study is proposed to show how this technique can be effectively used in the early design stage, when producing physical samples is often impossible due to time and money constraints. The method proved to be a reliable and powerful tool in all the tested applications, providing good results with limited computational effort. Full article
(This article belongs to the Section Acoustics)
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Open AccessFeature PaperArticle Impact of a Porous Si-Ca-P Monophasic Ceramic on Variation of Osteogenesis-Related Gene Expression of Adult Human Mesenchymal Stem Cells
Appl. Sci. 2018, 8(1), 46; doi:10.3390/app8010046
Received: 4 December 2017 / Revised: 20 December 2017 / Accepted: 21 December 2017 / Published: 1 January 2018
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Abstract
This work evaluates in vitro the influence of a new biocompatible porous Si-Ca-P monophasic (7CaO·P2O5·2SiO2) ceramic on the cellular metabolic activity, morphology and osteogenic differentiation of adult human mesenchymal stem cells (ahMSCs) cultured in basal
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This work evaluates in vitro the influence of a new biocompatible porous Si-Ca-P monophasic (7CaO·P2O5·2SiO2) ceramic on the cellular metabolic activity, morphology and osteogenic differentiation of adult human mesenchymal stem cells (ahMSCs) cultured in basal growth medium and under osteogenic inductive medium. Alamar Blue Assay and FESEM were carried out in order to monitor the cell proliferation and the shape of the cells growing on the Si-Ca-P monophasic ceramic during the study period. The osteogenic differentiation of ahMSCs was investigated by means of immunofluorescent staining (osteocalcin, osteopontin, heparan sulphate and collagen type I expression), quantitative reverse transcription polymerase chain reaction (qRT-PCR) (integrin-binding sialoprotein, osteocalcin, alkaline phosphatase, osteopontin, osteonectin, runt-related transcription factor 2 and collagen type I) and expression of surface markers (CD73, CD90 and CD105). We could check osteogenic differentiation in ahMSCs growing under the influence of Si-Ca-P monophasic ceramics itself, but especially when growth medium was replaced by osteogenic medium in the culture conditions. These results allowed us to conclude that the new Si-Ca-P monophasic scaffold greatly enhanced ahMSCs proliferation and osteogenic differentiation; therefore, it may be considered to be employed as a new bone graft substitute or scaffold for bone tissue engineering. Full article
(This article belongs to the Special Issue Bioceramics and Their Applications)
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Open AccessArticle Swarming Behavior Emerging from the Uptake–Kinetics Feedback Control in a Plant-Root-Inspired Robot
Appl. Sci. 2018, 8(1), 47; doi:10.3390/app8010047
Received: 15 November 2017 / Revised: 12 December 2017 / Accepted: 26 December 2017 / Published: 1 January 2018
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Abstract
This paper presents a plant root behavior-based approach to defining the control architecture of a plant-root-inspired robot, which is composed of three root-agents for nutrient uptake and one shoot-agent for nutrient redistribution. By taking inspiration and extracting key principles from the uptake of
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This paper presents a plant root behavior-based approach to defining the control architecture of a plant-root-inspired robot, which is composed of three root-agents for nutrient uptake and one shoot-agent for nutrient redistribution. By taking inspiration and extracting key principles from the uptake of nutrient, movements and communication strategies adopted by plant roots, we developed an uptake–kinetics feedback control for the robotic roots. Exploiting the proposed control, each root is able to regulate the growth direction, towards the nutrients that are most needed, and to adjust nutrient uptake, by decreasing the absorption rate of the most plentiful one. Results from computer simulations and implementation of the proposed control on the robotic platform, Plantoid, demonstrate an emergent swarming behavior aimed at optimizing the internal equilibrium among nutrients through the self-organization of the roots. Plant wellness is improved by dynamically adjusting nutrients priorities only according to local information without the need of a centralized unit delegated for wellness monitoring and task allocation among the agents. Thus, the root-agents can ideally and autonomously grow at the best speed, exploiting nutrient distribution and improving performance, in terms of exploration capabilities and exploitation of resources, with respect to the tropism-inspired control previously proposed by the same authors. Full article
(This article belongs to the Special Issue Bio-Inspired Robotics)
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Open AccessArticle Methodology of Classifying the Causes of Occupational Accidents Involving Construction Scaffolding Using Pareto-Lorenz Analysis
Appl. Sci. 2018, 8(1), 48; doi:10.3390/app8010048
Received: 26 October 2017 / Revised: 19 December 2017 / Accepted: 25 December 2017 / Published: 1 January 2018
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Abstract
This article presents the developed methodology of classifying and evaluating the causes of accidents involving construction scaffolding. This methodology allows the causes of accidents to be identified, classified into generic groups, and also allows the importance of individual causes in their generic groups
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This article presents the developed methodology of classifying and evaluating the causes of accidents involving construction scaffolding. This methodology allows the causes of accidents to be identified, classified into generic groups, and also allows the importance of individual causes in their generic groups to be assessed. For the classification of causes, the Technical–Organizational–Human (TOH) method was used. Its assumption is the division of causes into technical (T), organizational (O), and human (H) ones. Pareto-Lorenz analysis and ABC classification were used to identify the most important causes. The developed methodology was used to analyze and assess the causes of accidents that involve construction scaffolding using the data of accidents that occurred in Poland as an example. The use of the proposed methodology in different countries will enable the results of the conducted studies and analysis to be compared, and conclusions that would be of a great importance in accident prevention to be drawn. Full article
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Open AccessArticle Linear Approximation Signal Detection Scheme in MIMO-OFDM Systems
Appl. Sci. 2018, 8(1), 49; doi:10.3390/app8010049
Received: 29 September 2017 / Revised: 25 November 2017 / Accepted: 13 December 2017 / Published: 1 January 2018
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Abstract
In this paper, a linearly approximate signal detection scheme is proposed in multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) systems. The huge MIMO-OFDM system, which uses many transmit antennas and high order modulation, requires a detection scheme at the receiver with very
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In this paper, a linearly approximate signal detection scheme is proposed in multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) systems. The huge MIMO-OFDM system, which uses many transmit antennas and high order modulation, requires a detection scheme at the receiver with very low complexity for practical implementation. In the proposed detection scheme, one N × N MIMO-OFDM system is divided into N / 2 2 × 2 MIMO-OFDM systems for linear increase of complexity. After the partial zero-forcing (ZF), decision feedback equalizer (DFE) and QR decomposition-M algorithm (QRD-M) are applied to each 2 × 2 MIMO-OFDM system. Despite nonlinear detection schemes, the overall complexity of the proposed algorithm increases almost linearly because the DFE and the QRD-M are applied to 2 × 2 MIMO-OFDM systems. Also, the value of M in the QRD-M is fixed according to position of the center point in constellation for efficient signal detection. In simulation results, the proposed detection scheme has higher error performance and lower complexity than the conventional ZF. Also, the proposed detection scheme has very lower complexity than the conventional DFE, with slight loss of error performance. Full article
(This article belongs to the Special Issue Advanced Internet of Things for Smart Infrastructure System)
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Open AccessArticle IR Reflectography and Active Thermography on Artworks: The Added Value of the 1.5–3 µm Band
Appl. Sci. 2018, 8(1), 50; doi:10.3390/app8010050
Received: 11 December 2017 / Revised: 28 December 2017 / Accepted: 29 December 2017 / Published: 1 January 2018
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Abstract
Infrared Radiation (IR) artwork inspection is typically performed through active thermography and reflectography with different setups and cameras. While Infrared Radiation Reflectography (IRR) is an established technique in the museum field, exploiting mainly the IR-A (0.7–1.4 µm) band to probe for hidden layers
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Infrared Radiation (IR) artwork inspection is typically performed through active thermography and reflectography with different setups and cameras. While Infrared Radiation Reflectography (IRR) is an established technique in the museum field, exploiting mainly the IR-A (0.7–1.4 µm) band to probe for hidden layers and modifications within the paint stratigraphy system, active thermography operating in the IR-C range (3–5 μ m) is less frequently employed with the aim to visualize structural defects and features deeper inside the build-up. In this work, we assess to which extent the less investigated IR-B band (1.5–3 μ m) can combine the information obtained from both setups. The application of IR-B systems is relatively rare as there are only a limited amount of commercial systems available due to the technical complexity of the lens coating. This is mainly added as a so-called broadband option on regular Mid-wave infrared radiation (MWIR) (IR-C’/3–5 μ m) cameras to increase sensitivity for high temperature applications in industry. In particular, four objects were studied in both reflectographic and thermographic mode in the IR-B spectral range and their results benchmarked with IR-A and IR-C images. For multispectral application, a single benchmark is made with macroscopic reflection mode Fourier transform infrared (MA-rFTIR) results. IR-B proved valuable for visualisation of underdrawings, pencil marks, canvas fibres and wooden grain structures and potential pathways for additional applications such as pigment identification in multispectral mode or characterization of the support (panels, canvas) are indicated. Full article
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Open AccessArticle Omnidirectional Jump of a Legged Robot Based on the Behavior Mechanism of a Jumping Spider
Appl. Sci. 2018, 8(1), 51; doi:10.3390/app8010051
Received: 14 November 2017 / Revised: 27 December 2017 / Accepted: 29 December 2017 / Published: 1 January 2018
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Abstract
To find a common approach for the development of an efficient system that is able to achieve an omnidirectional jump, a jumping kinematic of a legged robot is proposed based on the behavior mechanism of a jumping spider. To satisfy the diversity of
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To find a common approach for the development of an efficient system that is able to achieve an omnidirectional jump, a jumping kinematic of a legged robot is proposed based on the behavior mechanism of a jumping spider. To satisfy the diversity of motion forms in robot jumping, a kind of 4 degrees of freedom (4DoFs) mechanical leg is designed. Taking the change of joint angle as inspiration by observing the behavior of the jumping spider during the acceleration phase, a redundant constraint to solve the kinematic is obtained. A series of experiments on three types of jumping—vertical jumping, sideways jumping and forward jumping—is carried out, while the initial attitude and path planning of the robot is studied. The proposed jumping kinematic is verified on the legged robot experimental platform, and the added redundant constraint could be verified as being reasonable. The results indicate that the jumping robot could maintain stability and complete the planned task of jumping, and the proposed spider-inspired jumping strategy could easily achieve an omnidirectional jump, thus enabling the robot to avoid obstacles. Full article
(This article belongs to the Special Issue Bio-Inspired Robotics)
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Open AccessArticle Thermal Stability and Tuning of Thermoelectric Properties of Ag1−xSb1+xTe2+x (0 ≤ x ≤ 0.4) Alloys
Appl. Sci. 2018, 8(1), 52; doi:10.3390/app8010052
Received: 14 November 2017 / Revised: 16 December 2017 / Accepted: 25 December 2017 / Published: 4 January 2018
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Abstract
Introduction of nonstoichiometry to AgSbTe2-based materials is considered to be an effective way to tune thermoelectric properties similarly to extrinsic doping. To prove this postulate, a systematic physicochemical study of the Ag1−xSb1+xTe2+x alloys
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Introduction of nonstoichiometry to AgSbTe2-based materials is considered to be an effective way to tune thermoelectric properties similarly to extrinsic doping. To prove this postulate, a systematic physicochemical study of the Ag1−xSb1+xTe2+x alloys (0 ≤ x ≤ 0.4) was performed. In order to investigate the influence of the cooling rate after synthesis on phase composition and thermoelectric performance, slowly cooled and quenched Ag1−xSb1+xTe2+x alloys (x = 0; 0.1; 0.17; 0.19; 0.3; 0.4) were prepared. Single-phase material composed of the β phase (NaCl structure type) was obtained for the quenched x = 0.19 sample only. The other alloys must be regarded as multi-phase materials. The cooling rate affects the formation of the phases in the Ag-Sb-Te system and influences mainly electronic properties, carrier mobility and carrier concentration. The extremely low lattice thermal conductivity is an effect of the mosaic nanostructure. The maximal value of the figure of merit ZTmax = 1.2 is observed at 610 K for the slowly cooled multi-phase sample Ag0.9Sb1.1Te2.1. Thermoelectric properties are repeatedly reproducible up to 490 K. Full article
(This article belongs to the Special Issue Recent Progress in the Development of Thermoelectric Materials)
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Open AccessArticle Correlation between the Golden Ratio and Nanowire Transistor Performance
Appl. Sci. 2018, 8(1), 54; doi:10.3390/app8010054
Received: 25 November 2017 / Revised: 13 December 2017 / Accepted: 22 December 2017 / Published: 2 January 2018
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Abstract
An observation was made in this research regarding the fact that the signatures of isotropic charge distributions in silicon nanowire transistors (NWT) displayed identical characteristics to the golden ratio (Phi). In turn, a simulation was conducted regarding ultra-scaled n-type Si (NWT) with respect
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An observation was made in this research regarding the fact that the signatures of isotropic charge distributions in silicon nanowire transistors (NWT) displayed identical characteristics to the golden ratio (Phi). In turn, a simulation was conducted regarding ultra-scaled n-type Si (NWT) with respect to the 5-nm complementary metal-oxide-semiconductor (CMOS) application. The results reveal that the amount of mobile charge in the channel and intrinsic speed of the device are determined by the device geometry and could also be correlated to the golden ratio (Phi). This paper highlights the issue that the optimization of NWT geometry could reduce the impact of the main sources of statistical variability on the Figure of Merit (FoM) of devices. In the context of industrial early successes in fabricating vertically stacked NWT, ensemble Monte Carlo (MC) simulations with quantum correction are used to accurately predict the drive current. This occurs alongside a consideration of the degree to which the carrier transport in the vertically stacked lateral NWTs are complex. Full article
(This article belongs to the Special Issue Silicon Nanowires and Their Applications)
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Open AccessFeature PaperArticle A Bio-Inspired Control Strategy for Locomotion of a Quadruped Robot
Appl. Sci. 2018, 8(1), 56; doi:10.3390/app8010056
Received: 4 October 2017 / Revised: 30 November 2017 / Accepted: 20 December 2017 / Published: 2 January 2018
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Abstract
In order to effectively plan the robot gaits and foot workspace trajectory (WT) synchronously, a novel biologically inspired control strategy for the locomotion of a quadruped robot based on central pattern generator—neural network—workspace trajectory (CPG-NN-WT) is presented in this paper. Firstly, a foot
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In order to effectively plan the robot gaits and foot workspace trajectory (WT) synchronously, a novel biologically inspired control strategy for the locomotion of a quadruped robot based on central pattern generator—neural network—workspace trajectory (CPG-NN-WT) is presented in this paper. Firstly, a foot WT is planned via the Denavit-Hartenberg (D-H) notation and the inverse kinematics, which has the advantages of low mechanical shock, smooth movement, and sleek trajectory. Then, an improved central pattern generator (CPG) based on Hopf oscillators is proposed in this paper for smooth gait planning. Finally, a neural network is designed and trained to convert the CPG output to the preplanned WT, which can make full use of the advantages of the CPG-based method in gait planning and the WT-based method in foot trajectory planning simultaneously. Furthermore, virtual prototype simulations and experiments with a real quadruped robot are presented to validate the effectiveness of the proposed control strategy. The results show that the gait of the quadruped robot can be controlled easily and effectively by the CPG with its internal parameters; meanwhile, the foot trajectory meets the preplanned WT well. Full article
(This article belongs to the Special Issue Bio-Inspired Robotics)
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Open AccessArticle Low-Voltage Ride-Through Control Strategy for a Grid-Connected Energy Storage System
Appl. Sci. 2018, 8(1), 57; doi:10.3390/app8010057
Received: 13 November 2017 / Revised: 27 December 2017 / Accepted: 28 December 2017 / Published: 2 January 2018
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Abstract
This paper presents a low-voltage ride-through (LVRT) control strategy for grid-connected energy storage systems (ESSs). In the past, researchers have investigated the LVRT control strategies to apply them to wind power generation (WPG) and solar energy generation (SEG) systems. Regardless of the energy
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This paper presents a low-voltage ride-through (LVRT) control strategy for grid-connected energy storage systems (ESSs). In the past, researchers have investigated the LVRT control strategies to apply them to wind power generation (WPG) and solar energy generation (SEG) systems. Regardless of the energy source, the main purpose of the LVRT control strategies is to inject reactive power into the grid depending on the grid-code regulations using the grid-side inverter; the proposed LVRT control strategy for grid-connected ESSs also has the same purpose. However, unlike the WPG and SEG systems having unidirectional power flow, grid-connected ESSs have a bidirectional power flow. Therefore, the charging condition of the grid-connected ESSs should be considered for the LVRT control strategy. The proposed LVRT control strategy for grid-connected ESSs determines the injection quantity of the active and reactive currents, and the strategy depends on the voltage drop ratio of the three-phase grid. Additionally, in this paper, we analyzed the variations of the point of common coupling (PCC) voltage depending on the phase of the reactive current during the charging and discharging conditions. The validity of the proposed LVRT control strategy is verified and the variations of the PCC voltage of the grid-connected ESS are analyzed by simulation and experimental results. Full article
(This article belongs to the Special Issue Renewable Energy 2018)
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Open AccessArticle Study on the Structure of an Efficient Receiver for Covert Underwater Communication Using Direct Sequence Spread Spectrum
Appl. Sci. 2018, 8(1), 58; doi:10.3390/app8010058
Received: 16 November 2017 / Revised: 20 December 2017 / Accepted: 22 December 2017 / Published: 3 January 2018
Cited by 1 | PDF Full-text (1548 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes an underwater communication receive model based on the spread spectrum technique in order to provide the characteristic of a low probability of interception. To do this, turbo equalization techniques employing Bahl-Cocke-Jelinek-Raviv (BCJR) decoding to improve performance through repetition are applied
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This paper proposes an underwater communication receive model based on the spread spectrum technique in order to provide the characteristic of a low probability of interception. To do this, turbo equalization techniques employing Bahl-Cocke-Jelinek-Raviv (BCJR) decoding to improve performance through repetition are applied to offer excellent performance even at a low signal to noise ratio (SNR) of transmitted signals due to the spread spectrum technique. A turbo equalization model based on RAKE which increase signal power by summing the received signal through the multipath is proposed to compensate distorted data due to multipath channel and the performance improvements were proven by applying the threshold and weighted coefficient in the RAKE receiver model. The model was applied to covert underwater communication in a multi-sensor environment, and the efficiency of the proposed method was proven through underwater experiments. Full article
(This article belongs to the Special Issue Underwater Acoustics, Communications and Information Processing)
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Open AccessArticle Automatic Speech-to-Background Ratio Selection to Maintain Speech Intelligibility in Broadcasts Using an Objective Intelligibility Metric
Appl. Sci. 2018, 8(1), 59; doi:10.3390/app8010059
Received: 13 November 2017 / Revised: 21 December 2017 / Accepted: 27 December 2017 / Published: 3 January 2018
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Abstract
While mixing, sound producers and audio professionals empirically set the speech-to- background ratio (SBR) based on rules of thumb and their own perception of sounds. There is no guarantee that the speech content will be intelligible for the general population consuming content over
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While mixing, sound producers and audio professionals empirically set the speech-to- background ratio (SBR) based on rules of thumb and their own perception of sounds. There is no guarantee that the speech content will be intelligible for the general population consuming content over a wide variety of devices, however. In this study, an approach to automatically determine the appropriate SBR for a scene using an objective intelligibility metric is introduced. The model-estimated SBR needed for a preset minimum intelligibility level was compared to the listener-preferred SBR for a range of background sounds. It was found that an extra gain added to the model estimation is needed even for listeners with normal hearing. This gain is needed so an audio scene can be auditioned with comfort and without compromising the sound effects contributed by the background. When the background introduces little informational masking, the extra gain holds almost constant across the various background sounds. However, a larger gain is required for a background that induces informational masking, such as competing speech. The results from a final subjective rating study show that the model-estimated SBR with the additional gain, yields the same listening experience as the SBR preferred by listeners. Full article
(This article belongs to the Section Acoustics)
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Open AccessArticle Broadband Electromagnetic Dipole Resonance by the Coupling Effect of Multiple Dielectric Nanocylinders
Appl. Sci. 2018, 8(1), 60; doi:10.3390/app8010060
Received: 30 November 2017 / Revised: 26 December 2017 / Accepted: 27 December 2017 / Published: 3 January 2018
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Abstract
Broadband resonant scattering in a visible region that can be obtained by coupled multiple silicon nanocylinders. For a single high refractive index silicon nanocylinder, the electric dipole and magnetic dipole resonances can be observed. By constructing a silicon nanocylinder dimer, the interaction between
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Broadband resonant scattering in a visible region that can be obtained by coupled multiple silicon nanocylinders. For a single high refractive index silicon nanocylinder, the electric dipole and magnetic dipole resonances can be observed. By constructing a silicon nanocylinder dimer, the interaction between the particles plays an important role in broadband scattering. Interestingly, due to magnetic-magnetic dipole interaction, a splitting phenomenon of magnetic resonance mode is revealed. A new magnetic resonant mode emerges at a longer wavelength in dimer and trimer by changing the diameter of one nanocylinder in dimer or trimer, and the gap size between nanocylinders. The scattering bandwidth can further increase with the effect of substrate, which is attributed to the extension of resonant mode into substrate. The broadband optical response can be revealed by the calculated scattering resonant spectra and the spatial electromagnetic field distributions. Furthermore, the transmission of periodic nanocylinder structure, including single nanocylinder and dimer, is demonstrated. By decreasing the gap between nanocylinders in dimer for periodic array structure, a new electric resonant mode occurs. These results can provide a guideline to realize broadband resonant optical elements. Full article
(This article belongs to the Special Issue Sub-wavelength Optics)
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Open AccessArticle Passive Sonar Target Detection Using Statistical Classifier and Adaptive Threshold
Appl. Sci. 2018, 8(1), 61; doi:10.3390/app8010061
Received: 16 September 2017 / Revised: 24 December 2017 / Accepted: 27 December 2017 / Published: 3 January 2018
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Abstract
This paper presents the results of an experimental investigation about target detecting with passive sonar in Persian Gulf. Detecting propagated sounds in the water is one of the basic challenges of the researchers in sonar field. This challenge will be complex in shallow
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This paper presents the results of an experimental investigation about target detecting with passive sonar in Persian Gulf. Detecting propagated sounds in the water is one of the basic challenges of the researchers in sonar field. This challenge will be complex in shallow water (like Persian Gulf) and noise less vessels. Generally, in passive sonar, the targets are detected by sonar equation (with constant threshold) that increases the detection error in shallow water. The purpose of this study is proposed a new method for detecting targets in passive sonars using adaptive threshold. In this method, target signal (sound) is processed in time and frequency domain. For classifying, Bayesian classification is used and posterior distribution is estimated by Maximum Likelihood Estimation algorithm. Finally, target was detected by combining the detection points in both domains using Least Mean Square (LMS) adaptive filter. Results of this paper has showed that the proposed method has improved true detection rate by about 24% when compared other the best detection method. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessFeature PaperArticle Bloch Surface Wave Photonic Device Fabricated by Femtosecond Laser Polymerisation Technique
Appl. Sci. 2018, 8(1), 63; doi:10.3390/app8010063
Received: 30 November 2017 / Revised: 29 December 2017 / Accepted: 30 December 2017 / Published: 4 January 2018
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Abstract
We applied femtosecond laser polymerisation technique to fabricate a novel Bloch surface wave integrated photonic device with a compact coupling scheme. The device consisted of a waveguide, coupling and decoupling gratings and focusing and defocusing triangles. We manufactured an array of devices with
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We applied femtosecond laser polymerisation technique to fabricate a novel Bloch surface wave integrated photonic device with a compact coupling scheme. The device consisted of a waveguide, coupling and decoupling gratings and focusing and defocusing triangles. We manufactured an array of devices with varying geometrical parameters of waveguide. Excitation and propagation of Bloch surface wave waveguide modes were studied by direct and back focal plane imaging. The obtained results prove that the maskless and flexible femtosecond laser polymerisation technique may be applied for fabrication of Bloch-surface-wave based integrated photonics. Full article
(This article belongs to the Special Issue Surface Waves on Planar Photonic Crystals)
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Open AccessArticle Plasmonics in the Ultraviolet with Aluminum, Gallium, Magnesium and Rhodium
Appl. Sci. 2018, 8(1), 64; doi:10.3390/app8010064
Received: 5 December 2017 / Revised: 26 December 2017 / Accepted: 28 December 2017 / Published: 4 January 2018
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Abstract
Ultraviolet plasmonics (UV) has become an active topic of research due to the new challenges arising in fields such as biosensing, chemistry or spectroscopy. Recent studies have pointed out aluminum, gallium, magnesium and rhodium as promising candidates for plasmonics in the UV range.
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Ultraviolet plasmonics (UV) has become an active topic of research due to the new challenges arising in fields such as biosensing, chemistry or spectroscopy. Recent studies have pointed out aluminum, gallium, magnesium and rhodium as promising candidates for plasmonics in the UV range. Aluminum and magnesium present a high oxidation tendency that has a critical effect in their plasmonic performance. Nevertheless, gallium and rhodium have drawn a lot of attention because of their low tendency of oxidation and, at the same time, good plasmonic response in the UV and excellent photocatalytic properties. Here, we present a short overview of the current state of UV plasmonics with the latest findings in the plasmonic response and applications of aluminum, gallium, magnesium and rhodium nanoparticles. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessArticle Standing Wave Field Distribution in Graded-Index Antireflection Coatings
Appl. Sci. 2018, 8(1), 65; doi:10.3390/app8010065
Received: 8 December 2017 / Revised: 27 December 2017 / Accepted: 28 December 2017 / Published: 4 January 2018
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Abstract
Standing wave field distributions in three classic types of graded-index antireflection coatings are studied. These graded-index antireflection coatings are designed at wavelengths from 200 nm to 1200 nm, which is the working wavelength range of high energy laser system for inertial-fusion research. The
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Standing wave field distributions in three classic types of graded-index antireflection coatings are studied. These graded-index antireflection coatings are designed at wavelengths from 200 nm to 1200 nm, which is the working wavelength range of high energy laser system for inertial-fusion research. The standing wave field distributions in these coatings are obtained by the numerical calculation of electromagnetic wave equation. We find that standing wave field distributions in these three graded-index anti-reflection coatings are quite different. For the coating with linear index distribution, intensity of standing wave field decreases periodically from surface to substrate with narrow oscillation range and the period is proportional to the incident wavelength. For the coating with exponential index distribution, intensity of standing wave field decreases periodically from surface to substrate with large oscillation range and the period is also proportional to the incident wavelength. Finally, for the coating with polynomial index, intensity of standing wave field is quickly falling down from surface to substrate without an obvious oscillation. We find that the intensity of standing wave field in the interface between coating and substrate for linear index, exponential index and polynomial index are about 0.7, 0.9 and 0.7, respectively. Our results indicate that the distributions of standing wave field in linear index coating and polynomial index coating are better than that in exponential index coating for the application in high energy laser system. Moreover, we find that the transmittance of linear index coating and polynomial index coating are also better than exponential index coating at the designed wavelength range. Present simulation results are useful for the design and application of graded-index antireflection coating in high energy laser system. Full article
(This article belongs to the Special Issue Radiation Effects of Materials with Laser, Ion Beam and Rays)
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Open AccessArticle Challenges of the Usual Graphical Methods Used to Characterize Phase Change Materials by Differential Scanning Calorimetry
Appl. Sci. 2018, 8(1), 66; doi:10.3390/app8010066
Received: 21 November 2017 / Revised: 19 December 2017 / Accepted: 20 December 2017 / Published: 9 January 2018
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Abstract
Modeling the thermal behavior of a plant or devices using Phase Change Materials (PCM) requires to know their thermophysical properties. The Differential Scanning Calorimetry (DSC) is a technic largely used to investigate them. However, under the pretext to experiment with small samples, some
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Modeling the thermal behavior of a plant or devices using Phase Change Materials (PCM) requires to know their thermophysical properties. The Differential Scanning Calorimetry (DSC) is a technic largely used to investigate them. However, under the pretext to experiment with small samples, some authors consider the DSC curves as directly representing the properties of the materials without realizing that this interpretation is very often incompatible with the thermodynamics laws: as an example, although a pure substance melts at a fixed temperature T F , it is proposed a melting through a temperature range higher than T F and depending on the experiments (heating rates, sample masses...), for solutions the suggested characteristic temperatures are incompatible with the phase diagram, and also a hysteresis phenomenon is invented... In this paper, we demonstrate by a model coupling thermodynamics and conduction heat transfers, that the DSC curves are exactly compatible with the thermodynamics of phase changes (melting at fixed temperature for pure substances, in conformity with phase diagrams for solutions...). The cases of pure substances, saline solutions, substances with impurities or solid solutions are detailed. We indicate which information can, however, be given by the curves. We also propose a more sophisticated method by inverse calculations to determine the specific enthalpy whose all the thermodynamical properties can be deduced. Finally, we give some indications to understand and use the results indicating supercooling. Full article
(This article belongs to the Special Issue Phase Change Material (PCM) 2017)
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Open AccessFeature PaperArticle Multi-Agent System for Demand Prediction and Trip Visualization in Bike Sharing Systems
Appl. Sci. 2018, 8(1), 67; doi:10.3390/app8010067
Received: 15 December 2017 / Revised: 1 January 2018 / Accepted: 2 January 2018 / Published: 5 January 2018
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Abstract
This paper proposes a multi agent system that provides visualization and prediction tools for bike sharing systems (BSS). The presented multi-agent system includes an agent that performs data collection and cleaning processes, it is also capable of creating demand forecasting models for each
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This paper proposes a multi agent system that provides visualization and prediction tools for bike sharing systems (BSS). The presented multi-agent system includes an agent that performs data collection and cleaning processes, it is also capable of creating demand forecasting models for each bicycle station. Moreover, the architecture offers API (Application Programming Interface) services and provides a web application for visualization and forecasting. This work aims to make the system generic enough for it to be able to integrate data from different types of bike sharing systems. Thus, in future studies it will be possible to employ the proposed system in different types of bike sharing systems. This article contains a literature review, a section on the process of developing the system and the built-in prediction models. Moreover, a case study which validates the proposed system by implementing it in a public bicycle sharing system in Salamanca, called SalenBici. It also includes an outline of the results and conclusions, a discussion on the challenges encountered in this domain, as well as possibilities for future work. Full article
(This article belongs to the Special Issue Multi-Agent Systems)
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Open AccessArticle A Study of Order Modification for Reactive Power Support by Wind Farm during Communication Failure
Appl. Sci. 2018, 8(1), 68; doi:10.3390/app8010068
Received: 10 October 2017 / Revised: 25 December 2017 / Accepted: 3 January 2018 / Published: 5 January 2018
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Abstract
Various control methods and applications have been introduced to power systems in order to alleviate the uncertainties of relying on renewable sources. This paper, focusing on a reactive power allocation process, discusses the development of a self-modification algorithm and its introduction to an
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Various control methods and applications have been introduced to power systems in order to alleviate the uncertainties of relying on renewable sources. This paper, focusing on a reactive power allocation process, discusses the development of a self-modification algorithm and its introduction to an online reference management system. The algorithm is designed to predict unexpected situations occurring in real-time operations, when, due to technical issues, the control system becomes unavailable. A test system has been formed to check the feasibility of the composed method. As the main purpose of the feasibility study is checking availability with a complex solution, case studies are designed to adapt a reactive power allocation method based on loss minimization. When unexpected systemic errors were induced, the proposed modification plan changed order automatically with maintaining previous objective function. The improved effects, caused by realistic responses, are classified according to EMTDC (Electro-Magnetic Transient Design and Control) analysis. Full article
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Open AccessFeature PaperArticle Estimation of Mental Distress from Photoplethysmography
Appl. Sci. 2018, 8(1), 69; doi:10.3390/app8010069
Received: 11 November 2017 / Revised: 20 December 2017 / Accepted: 3 January 2018 / Published: 5 January 2018
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Abstract
This paper introduces the design of a new wearable photoplethysmography (PPG) sensor and its assessment for mental distress estimation. In our design, a PPG sensor obtains blood volume information by means of an optical plethysmogram technique. A number of temporal, morphological and frequency
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This paper introduces the design of a new wearable photoplethysmography (PPG) sensor and its assessment for mental distress estimation. In our design, a PPG sensor obtains blood volume information by means of an optical plethysmogram technique. A number of temporal, morphological and frequency markers are computed using time intervals between adjacent normal cardiac cycles to characterize pulse rate variability (PRV). In order to test the efficiency of the developed wearable for classifying distress versus calmness, the well-known International Affective Picture System has been used to induce different levels of arousal in forty-five healthy participants. The obtained results have shown that temporal features present a single discriminant power between emotional states of calm and stress, ranging from 67 to 72%. Moreover, a discriminant tree-based model is used to assess the possible underlying relationship among parameters. In this case, the combination of temporal parameters reaches 82.35% accuracy. Considering the low difficulty of metrics and methods used in this work, the algorithms are prepared to be embedded into a micro-controller device to work in real-time and in a long-term fashion. Full article
(This article belongs to the Special Issue Socio-Cognitive and Affective Computing)
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Open AccessArticle Placing Visual Sensors Using Heuristic Algorithms for Bridge Surveillance
Appl. Sci. 2018, 8(1), 70; doi:10.3390/app8010070
Received: 1 November 2017 / Revised: 20 December 2017 / Accepted: 3 January 2018 / Published: 6 January 2018
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Abstract
This study addresses the camera placement problem for bridge surveillance and proposes solutions that minimize the cost while satisfying the minimum coverage level. We discuss the field of view of cameras in the three-dimensional space. We also consider occlusions, the characteristics of surveillance
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This study addresses the camera placement problem for bridge surveillance and proposes solutions that minimize the cost while satisfying the minimum coverage level. We discuss the field of view of cameras in the three-dimensional space. We also consider occlusions, the characteristics of surveillance targets, and different pan-tilt-zoom cameras in the visibility test. To solve the camera placement problem while minimizing the total cost, we propose a genetic algorithm (GA) and a uniqueness score with a local search algorithm (ULA). Problem sets for a large-scale dimension scenario are generated based on the data of actual bridges in the Republic of Korea. For three simulation sets and a case study of Samoonjin Bridge, the proposed ULA yields better results than GA. Full article
(This article belongs to the Special Issue Advanced Internet of Things for Smart Infrastructure System)
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Open AccessArticle Phase Coherence Index, HHT and Wavelet Analysis to Extract Features from Active and Passive Distribution Networks
Appl. Sci. 2018, 8(1), 71; doi:10.3390/app8010071
Received: 27 November 2017 / Revised: 30 December 2017 / Accepted: 4 January 2018 / Published: 7 January 2018
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Abstract
The modern Power Distribution Systems (PDS) operate more and more often with distributed generators and the optimal operation of the utility distribution systems has to take into account the possibility of bi-directional energy flows, although this event may only occur for some of
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The modern Power Distribution Systems (PDS) operate more and more often with distributed generators and the optimal operation of the utility distribution systems has to take into account the possibility of bi-directional energy flows, although this event may only occur for some of the PDS. For this reason, the analysis methods that are usually employed to investigate the electrical behavior of the PDS can be more or less effective, depending on the typology of electrical loads connected to the line and on the presence or absence of Renewable Energy Sources (RES). This paper proposes either a methodology to select the best performing mathematical tool to investigate the electrical behavior of the PDS—depending on their linearity and stationarity—either an index to discriminate the PDS on the basis of a different amount of PV penetration. The proposed approach is applied to three real cases of PDS with different characteristics: residential and commercial, in the presence or absence of PV plants. In addition, two indices that are able to characterize the PDS in terms of periodicity and disturbance of the electrical signal are considered, specifically the phase coherence between two arbitrary signals and the phase coherence between an arbitrary signal and a reference one. The combined use of these indices can give valuable information about the degree of non-linearity and can be a measure of the PV penetration in a distribution circuit. Full article
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Open AccessArticle A Low-Power WLAN Communication Scheme for IoT WLAN Devices Using Wake-Up Receivers
Appl. Sci. 2018, 8(1), 72; doi:10.3390/app8010072
Received: 15 November 2017 / Revised: 21 December 2017 / Accepted: 5 January 2018 / Published: 7 January 2018
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Abstract
In this paper, we propose a delay- and power-efficient, multi-user, low-power wireless local area network (WLAN) communication scheme for Internet of Things (IoT) WLAN devices. Extremely low-power operation is one of the key requirements of emerging IoT devices. However, the current duty-cycle-based power
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In this paper, we propose a delay- and power-efficient, multi-user, low-power wireless local area network (WLAN) communication scheme for Internet of Things (IoT) WLAN devices. Extremely low-power operation is one of the key requirements of emerging IoT devices. However, the current duty-cycle-based power saving approach may incur large access delay times owing to the trade-offs between the power consumption and the access delay. In order to reduce this delay and enhance the power-saving performance, wake-up receiver-based schemes have been proposed. However, because wake-up receiver-based schemes do not consider multiuser operation in dense communication environments, large delays are inevitable in the case of multiuser operation. In order to provide extremely low-power operation and under 1-mW standby power with reduced delay, we employed the optimized multiuser transmission scheduling of IEEE 802.11ax in the proposed scheme and proper enhanced distributed channel access (EDCA) parameter settings. This is with the aim to reduce the delay caused by long wake-up times, and to avoid collisions caused by simultaneous transmission in uplink multiuser scenario. By using the proposed scheme, simultaneous IoT communication with multiple mobile IoT devices is possible while providing low-power operation. Simulation results verified the outstanding delay performance of the proposed scheme. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Controllable Micro-Particle Rotation and Transportation Using Sound Field Synthesis Technique
Appl. Sci. 2018, 8(1), 73; doi:10.3390/app8010073
Received: 4 December 2017 / Revised: 26 December 2017 / Accepted: 3 January 2018 / Published: 8 January 2018
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Abstract
Rotation and transportation of micro-particles using ultrasonically-driven devices shows promising applications in the fields of biological engineering, composite material manufacture, and micro-assembly. Current interest in mechanical effects of ultrasonic waves has been stimulated by the achievements in manipulations with phased array. Here, we
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Rotation and transportation of micro-particles using ultrasonically-driven devices shows promising applications in the fields of biological engineering, composite material manufacture, and micro-assembly. Current interest in mechanical effects of ultrasonic waves has been stimulated by the achievements in manipulations with phased array. Here, we propose a field synthesizing method using the fewest transducers to control the orientation of a single non-spherical micro-particle as well as its spatial location. A localized acoustic force potential well is established and rotated by using sound field synthesis technique. The resultant acoustic radiation torque on the trapped target determines its equilibrium angular position. A prototype device consisting of nine transducers with 2 MHz center frequency is designed and fabricated. Controllable rotation of a silica rod with 90 μm length and 15 μm diameter is then successfully achieved. There is a good agreement between the measured particle orientation and the theoretical prediction. Within the same device, spatial translation of the silica rod can also be realized conveniently. When compared with the existing acoustic rotation methods, the employed transducers of our method are strongly decreased, meanwhile, device functionality is improved. Full article
(This article belongs to the Section Acoustics)
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Open AccessArticle A General Euler Angle Error Model of Strapdown Inertial Navigation Systems
Appl. Sci. 2018, 8(1), 74; doi:10.3390/app8010074
Received: 24 October 2017 / Revised: 29 December 2017 / Accepted: 3 January 2018 / Published: 12 January 2018
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Abstract
Attitude error models play an important role in analyzing the characteristics of navigation error propagation for the design and operation of strapdown inertial navigation systems (SINS). However, the majority of existing attitude error models focus on misalignment, rather than Euler angle errors. Misalignment
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Attitude error models play an important role in analyzing the characteristics of navigation error propagation for the design and operation of strapdown inertial navigation systems (SINS). However, the majority of existing attitude error models focus on misalignment, rather than Euler angle errors. Misalignment cannot directly describe attitude error propagation, which is an indirect measurement. To solve the problem, a general Euler angle error model of SINS is proposed. Based on Euler angle error propagation analysis, relative Euler angle errors, and convected Euler angle errors are introduced to compose the general Euler angle error model. Simulation experiments are carried out to verify the proposed model. Full article
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Open AccessArticle Real-Time Strength Monitoring for Concrete Structures Using EMI Technique Incorporating with Fuzzy Logic
Appl. Sci. 2018, 8(1), 75; doi:10.3390/app8010075
Received: 29 November 2017 / Revised: 2 January 2018 / Accepted: 3 January 2018 / Published: 8 January 2018
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Abstract
This study estimates the strength of a special mixture of high-strength concrete (HSC) with admixtures for use in a nuclear power plant (NPP). Nuclear power plant structures need a HSC with some additional qualities to operate the safe options. For this purpose, the
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This study estimates the strength of a special mixture of high-strength concrete (HSC) with admixtures for use in a nuclear power plant (NPP). Nuclear power plant structures need a HSC with some additional qualities to operate the safe options. For this purpose, the experimented concrete was specially designed to fulfill the required qualities of NPP. For gaining these desirable qualities, it needs to monitor the concrete strength development process. Here, the PZT materials were used as sensors to acquire data by measuring the electromechanical impedance (EMI), and then cross correlation (CC) was calculated to look at changes according to strength development. Data were measured for 28 days, and over this period concrete can gain up to 96% of its design strength. This technique is based on a single sensor. After casting concrete, the PZT material starts vibrating as an actuator to produce vibrations. At the same time, it also works as a sensor to measure the dynamic response of the structure to the vibrations. With strength development, the resonant frequencies of the EMI start changing. To estimate the strength development, a fuzzy logic tool was used to analyze the parameters, allowing for us to estimate and predict the concrete strength. For cross-checking, the estimated strength was compared with the actual strength of concrete; this was determined by examining cuboid cores taken from specimens during experiments at the 1st, 3rd, 7th, 14th, and 28th days. According to the results, this approach of strength estimation and monitoring the strength development is useful for forecasting the stability of structures. Full article
(This article belongs to the Section Materials)
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Open AccessArticle Prescribed Performance Constraint Regulation of Electrohydraulic Control Based on Backstepping with Dynamic Surface
Appl. Sci. 2018, 8(1), 76; doi:10.3390/app8010076
Received: 16 November 2017 / Revised: 25 December 2017 / Accepted: 25 December 2017 / Published: 8 January 2018
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Abstract
In electro-hydraulic system (EHS), uncertain nonlinearities such as some hydraulic parametric uncertainties and external load disturbance often degrade the output dynamic performance. To address this problem, a prescribed performance constraint (PPC) control method is adopted in EHS to restrict the tracking position error
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In electro-hydraulic system (EHS), uncertain nonlinearities such as some hydraulic parametric uncertainties and external load disturbance often degrade the output dynamic performance. To address this problem, a prescribed performance constraint (PPC) control method is adopted in EHS to restrict the tracking position error of the cylinder position to a prescribed accuracy and guarantee the dynamic and steady position response in a required boundedness under these uncertain nonlinearities. Furthermore, a dynamic surface is designed to avoid the explosion of complexity due to the repeatedly calculated differentiations of the virtual control variables derived in backstepping. The effectiveness of the proposed controller has been verified by a comparative results. Full article
(This article belongs to the Special Issue Power Transmission and Control in Power and Vehicle Machineries)
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Open AccessArticle New Insights in the Ion Beam Sputtering Deposition of ZnO-Fluoropolymer Nanocomposites
Appl. Sci. 2018, 8(1), 77; doi:10.3390/app8010077
Received: 4 December 2017 / Revised: 21 December 2017 / Accepted: 31 December 2017 / Published: 9 January 2018
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