Applied Sciences

13 pages, 4688 KiB

Open AccessArticle

Effective Prediction of Bearing Fault Degradation under Different Crack Sizes Using a Deep Neural Network

by Hung Ngoc Nguyen¹, Cheol-Hong Kim² and Jong-Myon Kim^1,*

¹ School of IT Convergence, University of Ulsan, Ulsan 44610, Korea

² School of Electronics and Computer Engineering, Chonnam National University, Gwangju 61186, Korea

Appl. Sci. 2018, 8(11), 2332; https://doi.org/10.3390/app8112332 - 21 Nov 2018

Cited by 14 | Viewed by 4668

Abstract

Exact evaluation of the degradation levels in bearing defects is one of the most essential works in bearing condition monitoring. This paper proposed an efficient evaluation method using a deep neural network (DNN) for correct prediction of degradation levels of bearings under different [...] Read more.

Exact evaluation of the degradation levels in bearing defects is one of the most essential works in bearing condition monitoring. This paper proposed an efficient evaluation method using a deep neural network (DNN) for correct prediction of degradation levels of bearings under different crack size conditions. An envelope technique was first used to capture the characteristic fault frequencies from acoustic emission (AE) signals of bearing defects. Accordingly, a health-related indicator (HI) calculation was performed on the collected envelope power spectrum (EPS) signals using a Gaussian window method to estimate the fault severities of bearings that served as an appropriate dataset for DNN training. The proposed DNN was then trained for effective prediction of bearing degradation using the Adam optimization-based backpropagation algorithm, in which the synaptic weights were optimally initialized by the Xavier initialization method. The effectiveness of the proposed degradation prediction approach was evaluated through different crack size experiments (3, 6, and 12 mm) of bearing faults. Full article

(This article belongs to the Special Issue Fault Detection and Diagnosis in Mechatronics Systems)

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21 pages, 4252 KiB

Open AccessArticle

Combustion State Recognition of Flame Images Using Radial Chebyshev Moment Invariants Coupled with an IFA-WSVM Model

by Meng Yang

, Yongming Bian^*, Jixiang Yang and Guangjun Liu

School of Mechanical Engineering, Tongji University, Shanghai 201804, China

Appl. Sci. 2018, 8(11), 2331; https://doi.org/10.3390/app8112331 - 21 Nov 2018

Cited by 8 | Viewed by 3184

Abstract

Accurate combustion state recognition of flame images not only plays an important role in social security, but also contributes to increasing thermal efficiency and product quality. To improve the accuracy of feature extraction and achieve the combustion state recognition, a novel method based [...] Read more.

Accurate combustion state recognition of flame images not only plays an important role in social security, but also contributes to increasing thermal efficiency and product quality. To improve the accuracy of feature extraction and achieve the combustion state recognition, a novel method based on radial Chebyshev moment invariants (RCMIs) and an improved firefly algorithm-wavelet support vector machine (IFA-WSVM) model is proposed. Firstly, the potential flame pixels and the potential flame contour are obtained in the pre-processing phase. Then, the rotation, translation and scaling (RTS) invariants of radial Chebyshev moments are derived. Combing the region and contour moments, the RCMIs of pre-processed and edge images are calculated to construct multi-feature vectors. To enhance the recognition performance, an IFA-WSVM model is built, where the IFA is applied to search the best parameters of WSVM. Then, the IFA-WSVM model is used to recognize the combustion state. Finally, the result for case studies show that the proposed method is superior to methods based on HMIs and ZMIs, achieving the highest rate of 99.07% in real time. The IFA algorithm also outperforms other benchmark algorithms. Even for the images transformed by RTS and small size of training sets, the proposed method continues to exhibit the best performance. Full article

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15 pages, 6336 KiB

Open AccessArticle

Li-Ion Battery-Flywheel Hybrid Storage System: Countering Battery Aging During a Grid Frequency Regulation Service

by Sebastian Dambone Sessa^*

, Andrea Tortella

, Mauro Andriollo

and Roberto Benato

Department of Industrial Engineering, University of Padova, 35131 Padova, Italy

Appl. Sci. 2018, 8(11), 2330; https://doi.org/10.3390/app8112330 - 21 Nov 2018

Cited by 26 | Viewed by 5361

Abstract

In this paper, a hybrid storage system solution consisting of flywheels and batteries with a Lithium-manganese oxide cathode and a graphite anode is proposed, for supporting the electrical network primary frequency regulation. The aim of the paper is to investigate the benefits of [...] Read more.

In this paper, a hybrid storage system solution consisting of flywheels and batteries with a Lithium-manganese oxide cathode and a graphite anode is proposed, for supporting the electrical network primary frequency regulation. The aim of the paper is to investigate the benefits of flywheels in mitigation of the accelerating aging that li-ion batteries suffer during the grid frequency regulation operation. For this purpose, experimental aging tests have been performed on a lithium-manganese oxide battery module and an electrical battery model which takes into account the battery aging has been developed in a Simulink environment. Then, a flywheel electrical model has been implemented, taking into account the thermal and the electromechanical phenomena governing the electrical power exchange. This more complete model of a hybrid storage system enables us to simulate the same aging cycles of the battery-based storage system and to compare the performances of the latter with the hybrid storage system. The simulation results suggest that suitable control of the power shared between the batteries and the flywheels could effectively help in countering Li-ion battery accelerated aging due to the grid frequency regulation service. Full article

(This article belongs to the Special Issue Flywheel Energy Storage)

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10 pages, 1769 KiB

Open AccessArticle

A Simplified Analysis to Predict the Fire Hazard of Primary Lithium Battery

by Mingyi Chen^1,2,*

, Jiahao Liu^3,*, Ouyang Dongxu⁴, Shuchao Cao⁵, Zhi Wang⁴ and Jian Wang⁴

¹ School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013, Jiangsu, China

² Firefighting and Rescue Technology Key Laboratory of the Ministry of Public Security, China People’s Police University, Langfang 065000, Hebei, China

³ College of Ocean Science and Engineering, Shanghai Maritime University, Shanghai 201306, China

⁴ State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230026, Anhui, China

⁵ School of Automotive and Traffic Engineering, Jiangsu University, Zhenjiang 212013, Jiangsu, China

Appl. Sci. 2018, 8(11), 2329; https://doi.org/10.3390/app8112329 - 21 Nov 2018

Cited by 10 | Viewed by 5301

Abstract

To better understand the fire risk of primary lithium batteries, the combustion properties of different numbers of primary lithium batteries were investigated experimentally in this work. Based on the t² fire principle and total heat release results from the experiments, a simplified [...] Read more.

To better understand the fire risk of primary lithium batteries, the combustion properties of different numbers of primary lithium batteries were investigated experimentally in this work. Based on the t² fire principle and total heat release results from the experiments, a simplified analysis was developed to predict the fire hazard, and especially the heat release rate, of primary lithium batteries. By comparing the experiment and simulation results, the simulation line agrees well with the heat release rate curve based on the oxygen consumption measurements of a single primary lithium battery. When multiple batteries are burned, each battery ignites at different times throughout the process. The ignition time difference parameter is introduced into the simulation to achieve similar results as during multiple batteries combustion. These simulation curves conform well to the experimental curves, demonstrating that this heat release rate simulation analysis is suitable for application in batteries fires. Full article

(This article belongs to the Section Energy Science and Technology)

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20 pages, 2541 KiB

Open AccessArticle

Evaluating the Energy-Saving Potential of Solar Dedicated Ventilation Systems Based on ADRC

by Lian Zhang^1,*

, Zijian Chen¹ and Lijuan Wang²

¹ Tianjin Sino-German University of Applied Sciences, Tianjin 300350, China

² School of Energy and Safety Engineering, Tianjin Chengjian University, Tianjin 300384, China

Appl. Sci. 2018, 8(11), 2328; https://doi.org/10.3390/app8112328 - 21 Nov 2018

Cited by 3 | Viewed by 2981

Abstract

A solar dedicated ventilation system based on active disturbance rejection controller (ADRC) has been designed in this study and tested by experimental research to acquire better control accuracy and energy-saving potential compared with former systems. This system involves photovoltaic, solar thermal, and dedicated [...] Read more.

A solar dedicated ventilation system based on active disturbance rejection controller (ADRC) has been designed in this study and tested by experimental research to acquire better control accuracy and energy-saving potential compared with former systems. This system involves photovoltaic, solar thermal, and dedicated ventilation systems and ADRC. The solar energy replaces traditional energy to realize energy-saving potential, and ADRC takes the place of a conventional controller to gain control accuracy. The experimental results show that the temperature standard deviation is from 0.09 to 0.15 °C and difference between maximum and minimum is 0.33 to 0.49 °C (<0.5 °C) at different outdoor conditions to meet accurate control requirements. The results also show the energy-saving potential of the solar dedicated ventilation system as being equal to the power consumption of traditional systems, not including extreme situations. The solar dedicated ventilation system was used for actual operation of the cooling system of a laboratory precisely and efficiently. Consequently, the solar dedicated ventilation system based on ADRC is most suitable for hot and humid places to achieve the energy-saving objective. Full article

(This article belongs to the Section Environmental Sciences)

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31 pages, 10526 KiB

Open AccessArticle

Investigation on Ship Hydroelastic Vibrational Responses in Waves

by Haicheng Yu¹, Yi Xia², Jialong Jiao³

and Huilong Ren^1,*

¹ College of Shipbuilding Engineering, Harbin Engineering University, Harbin 150001, China

² Department of Civil, Environmental & Ocean Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, USA

³ School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510641, China

Appl. Sci. 2018, 8(11), 2327; https://doi.org/10.3390/app8112327 - 21 Nov 2018

Cited by 6 | Viewed by 4368

Abstract

The hydroelastic vibrational responses of a large ship sailing in regular and irregular head waves are investigated numerically and experimentally. A 3D time-domain nonlinear hydroelastic mathematical model is established in which the hydrostatic restoring forces and incident wave forces are calculated on the [...] Read more.

The hydroelastic vibrational responses of a large ship sailing in regular and irregular head waves are investigated numerically and experimentally. A 3D time-domain nonlinear hydroelastic mathematical model is established in which the hydrostatic restoring forces and incident wave forces are calculated on the instantaneous wetted hull surface to consider nonlinear effects of the rigid motion and elastic deformation of the hull in harsh waves. Radiation and diffraction wave forces are computed on the mean wetted surface based on the 3D frequency-domain potential flow theory. The slamming loads are calculated by momentum theory and integrated into the hydrodynamic forces. The 1D Timoshenko beam theory is adopted to model the vibrational structural response and is fully coupled with the presented hydrodynamic theory in time-domain to generate the hydroelastic equation of motion. Moreover, self-propelled segmented model tests were conducted in a laboratory wave tank to experimentally investigate the hydroelastic responses of a target ship in regular and irregular head seas. The numerical and experimental results are systemically compared and analyzed, and the established hydroelastic analysis model turns out to be reliable and effective in the prediction of ship hydroelastic responses in waves. Full article

(This article belongs to the Section Acoustics and Vibrations)

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13 pages, 601 KiB

Open AccessArticle

Target Speaker Localization Based on the Complex Watson Mixture Model and Time-Frequency Selection Neural Network

by Ziteng Wang^1,2,*, Junfeng Li^1,2 and Yonghong Yan^1,2,3

¹ Key Laboratory of Speech Acoustics and Content Understanding, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China

² University of Chinese Academy of Sciences, Beijing 100190, China

³ Xinjiang Laboratory of Minority Speech and Language Information Processing, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumchi 830001, China

Appl. Sci. 2018, 8(11), 2326; https://doi.org/10.3390/app8112326 - 21 Nov 2018

Cited by 11 | Viewed by 5395

Abstract

Common sound source localization algorithms focus on localizing all the active sources in the environment. While the source identities are generally unknown, retrieving the location of a speaker of interest requires extra effort. This paper addresses the problem of localizing a speaker of [...] Read more.

Common sound source localization algorithms focus on localizing all the active sources in the environment. While the source identities are generally unknown, retrieving the location of a speaker of interest requires extra effort. This paper addresses the problem of localizing a speaker of interest from a novel perspective by first performing time-frequency selection before localization. The speaker of interest, namely the target speaker, is assumed to be sparsely active in the signal spectra. The target speaker-dominant time-frequency regions are separated by a speaker-aware Long Short-Term Memory (LSTM) neural network, and they are sufficient to determine the Direction of Arrival (DoA) of the target speaker. Speaker-awareness is achieved by utilizing a short target utterance to adapt the hidden layer outputs of the neural network. The instantaneous DoA estimator is based on the probabilistic complex Watson Mixture Model (cWMM), and a weighted maximum likelihood estimation of the model parameters is accordingly derived. Simulative experiments show that the proposed algorithm works well in various noisy conditions and remains robust when the signal-to-noise ratio is low and when a competing speaker exists. Full article

(This article belongs to the Section Acoustics and Vibrations)

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7 pages, 3503 KiB

Open AccessArticle

A Real-Time Measurement Method of Air Refractive Index Based on Special Material Etalon

by Guo-Ying Ren^1,2,*, Xing-Hua Qu¹ and Shuang Ding¹

¹ State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin 300072, China

² National Institute of Metrology, Beijing 100029, China

Appl. Sci. 2018, 8(11), 2325; https://doi.org/10.3390/app8112325 - 21 Nov 2018

Cited by 3 | Viewed by 3767

Abstract

In the precise displacement measurement based on laser interferometry, the measurement technology for the refractive index of air is widely used to improve the measurement accuracy. However, the existing measurement method of the refractive index of air based on direct measurement is not [...] Read more.

In the precise displacement measurement based on laser interferometry, the measurement technology for the refractive index of air is widely used to improve the measurement accuracy. However, the existing measurement method of the refractive index of air based on direct measurement is not easy to realize in practical work because of its complex measurement principle and the huge volume of the measurement device; while the measurement accuracy and speed based on the indirect method cannot adapt to the real-time, fast and accurate measurement requirements of industrially changing environments, resulting in distortion of the results. In this study, a measurement method of the refractive index of air based on a special material etalon is proposed. The method enables rapid and direct measurement of the air refractive index when the environment changes and it is given the realization process. Finally, the experimental results show that the deviation between this method and the modified Edlen formula is about 2.5 × 10⁻⁷, and that this method can quickly reflect the changes of the environment, which prove the correctness of this method and its ability manage rapid environmental responses. This method is worth popularizing in industrial measurement. Full article

(This article belongs to the Special Issue Precision Dimensional Measurements)

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16 pages, 858 KiB

Open AccessArticle

Assessing and Prioritising Delay Factors of Prefabricated Concrete Building Projects in China

by Yingbo Ji¹, Lin Qi¹, Yan Liu¹, Xinnan Liu¹, Hong Xian Li^2,*

and Yan Li²

¹ Department of Civil Engineering, North China University of Technology, Beijing 100043, China

² School of Architecture and Built Environment, Deakin University, Geelong 3220, Australia

Appl. Sci. 2018, 8(11), 2324; https://doi.org/10.3390/app8112324 - 21 Nov 2018

Cited by 53 | Viewed by 7244

Abstract

Prefabricated construction has been widely accepted as an alternative to conventional cast-in-situ construction, given its improved performance. However, prefabricated concrete building projects frequently encounter significant delays. It is, therefore, crucial to identify key factors affecting schedule and explore strategies to minimise the schedule [...] Read more.

Prefabricated construction has been widely accepted as an alternative to conventional cast-in-situ construction, given its improved performance. However, prefabricated concrete building projects frequently encounter significant delays. It is, therefore, crucial to identify key factors affecting schedule and explore strategies to minimise the schedule delays for prefabricated concrete building projects. This paper adopts the decision-making trial and evaluation laboratory (DEMATEL) model and analytic network process (ANP) method to quantify the cause-and-effect relationships and prioritise the key delay factors in terms of their importance in the Chinese construction industry. The DEMATEL model evaluates the extent to which each factor impacts other factors. The quantified extents are then converted into a prioritisation matrix through ANP. The delay factors of prefabricated construction projects are selected and categorised based on a literature review and an expert interview. Questionnaires are then implemented to collect the data. The results reveal that the issue of inefficient structural connections for prefabricated components is found to be the most significant factor and most easily affected by other delay factors. This research also suggests prioritising major delay factors, such as ‘lack of communication among participants’ and ‘low productivity’, in the Chinese construction industry during scheduling control. Overall, this research contributes an assessment framework for decision making in the scheduling management of prefabricated construction. Full article

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15 pages, 4223 KiB

Open AccessReview

Pursuing High Quality Phase-Only Liquid Crystal on Silicon (LCoS) Devices

by Huang-Ming Philip Chen^1,*, Jhou-Pu Yang¹

, Hao-Ting Yen¹, Zheng-Ning Hsu¹, Yuge Huang² and Shin-Tson Wu²

¹ Department of Photonics, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan

² College of Optics and Photonics, University of Central Florida, Orlando, FL 32816, USA

Appl. Sci. 2018, 8(11), 2323; https://doi.org/10.3390/app8112323 - 21 Nov 2018

Cited by 79 | Viewed by 10800

Abstract

Fine pixel size and high-resolution liquid crystal on silicon (LCoS) backplanes have been developed by various companies and research groups since 1973. The development of LCoS is not only beneficial for full high definition displays but also to spatial light modulation. The high-quality [...] Read more.

Fine pixel size and high-resolution liquid crystal on silicon (LCoS) backplanes have been developed by various companies and research groups since 1973. The development of LCoS is not only beneficial for full high definition displays but also to spatial light modulation. The high-quality and well-calibrated panels can project computer generated hologram (CGH) designs faithfully for phase-only holography, which can be widely utilized in 2D/3D holographic video projectors and components for optical telecommunications. As a result, we start by summarizing the current status of high-resolution panels, followed by addressing issues related to the driving frequency (i.e., liquid crystal response time and hardware interface). LCoS panel qualities were evaluated based on the following four characteristics: phase linearity control, phase precision, phase stability, and phase accuracy. Full article

(This article belongs to the Special Issue Liquid Crystal on Silicon Devices: Modeling and Advanced Spatial Light Modulation Applications)

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20 pages, 7468 KiB

Open AccessArticle

A Joint Dual-Frequency GNSS/SINS Deep-Coupled Navigation System for Polar Navigation

by Lin Zhao, Mouyan Wu^*

, Jicheng Ding^* and Yingyao Kang

College of Automation, Harbin Engineering University, Harbin 150001, China

Appl. Sci. 2018, 8(11), 2322; https://doi.org/10.3390/app8112322 - 21 Nov 2018

Cited by 10 | Viewed by 3659

Abstract

The strategic position of the polar area and its rich natural resources are becoming increasingly important, while the northeast and northwest passages through the Arctic are receiving much attention as glaciers continue to melt. The global navigation satellite system (GNSS) can provide real-time [...] Read more.

The strategic position of the polar area and its rich natural resources are becoming increasingly important, while the northeast and northwest passages through the Arctic are receiving much attention as glaciers continue to melt. The global navigation satellite system (GNSS) can provide real-time observation data for the polar areas, but may suffer low elevation problems of satellites, signals with poor carrier-power-to-noise-density ratio (C/N₀), ionospheric scintillations, and dynamic requirements. In order to improve the navigation performance in polar areas, a deep-coupled navigation system with dual-frequency GNSS and a grid strapdown inertial navigation system (SINS) is proposed in the paper. The coverage and visibility of the GNSS constellation in polar areas are briefly reviewed firstly. Then, the joint dual-frequency vector tracking architecture of GNSS is designed with the aid of grid SINS information, which can optimize the tracking band, sharing tracking information to aid weak signal channels with strong signal channels and meet the dynamic requirement to improve the accuracy and robustness of the system. Besides this, the ionosphere-free combination of global positioning system (GPS) L1 C/A and L2 signals is used in the proposed system to further reduce ionospheric influence. Finally, the performance of the system is tested using a hardware simulator and semiphysical experiments. Experimental results indicate that the proposed system can obtain a better navigation accuracy and robust performance in polar areas. Full article

(This article belongs to the Special Issue Signal Processing for Satellite Positioning Systems)

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23 pages, 88186 KiB

Open AccessArticle

Identifying Real Estate Opportunities Using Machine Learning

by Alejandro Baldominos^1,2,*

, Iván Blanco³, Antonio José Moreno², Rubén Iturrarte², Óscar Bernárdez² and Carlos Afonso²

¹ Computer Science Department, Universidad Carlos III de Madrid, 28911 Leganés, Spain

² Artificial Intelligence Group, Rentier Token, 28050 Madrid, Spain

³ Finance Department, Colegio Universitario de Estudios Financieros, 28040 Madrid, Spain

Appl. Sci. 2018, 8(11), 2321; https://doi.org/10.3390/app8112321 - 21 Nov 2018

Cited by 100 | Viewed by 16116

Abstract

The real estate market is exposed to many fluctuations in prices because of existing correlations with many variables, some of which cannot be controlled or might even be unknown. Housing prices can increase rapidly (or in some cases, also drop very fast), yet [...] Read more.

The real estate market is exposed to many fluctuations in prices because of existing correlations with many variables, some of which cannot be controlled or might even be unknown. Housing prices can increase rapidly (or in some cases, also drop very fast), yet the numerous listings available online where houses are sold or rented are not likely to be updated that often. In some cases, individuals interested in selling a house (or apartment) might include it in some online listing, and forget about updating the price. In other cases, some individuals might be interested in deliberately setting a price below the market price in order to sell the home faster, for various reasons. In this paper, we aim at developing a machine learning application that identifies opportunities in the real estate market in real time, i.e., houses that are listed with a price substantially below the market price. This program can be useful for investors interested in the housing market. We have focused in a use case considering real estate assets located in the Salamanca district in Madrid (Spain) and listed in the most relevant Spanish online site for home sales and rentals. The application is formally implemented as a regression problem that tries to estimate the market price of a house given features retrieved from public online listings. For building this application, we have performed a feature engineering stage in order to discover relevant features that allows for attaining a high predictive performance. Several machine learning algorithms have been tested, including regression trees, k-nearest neighbors, support vector machines and neural networks, identifying advantages and handicaps of each of them. Full article

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18 pages, 3981 KiB

Open AccessArticle

Interpolation of Turbulent Boundary Layer Profiles Measured in Flight Using Response Surface Methodology

by Hidemi Takahashi^1,*

, Mitsuru Kurita², Hidetoshi Iijima² and Monami Sasamori²

¹ Research and Development Directorate, Japan Aerospace Exploration Agency, Kakuda, Miyagi 981-1525, Japan

² Aeronautical Technology Directorate, Japan Aerospace Exploration Agency, Chofu, Tokyo 182-8522, Japan

Appl. Sci. 2018, 8(11), 2320; https://doi.org/10.3390/app8112320 - 21 Nov 2018

Cited by 5 | Viewed by 3524

Abstract

Turbulent boundary layer profiles on the aircraft surface were characterized by pitot-rake measurements conducted in flight experiments at high subsonic Mach number ranges. Due to slight variations in atmospheric air conditions or aircraft attitudes, such as angles of attack and absolute flight speeds [...] Read more.

Turbulent boundary layer profiles on the aircraft surface were characterized by pitot-rake measurements conducted in flight experiments at high subsonic Mach number ranges. Due to slight variations in atmospheric air conditions or aircraft attitudes, such as angles of attack and absolute flight speeds at different flights even under the same premised flight conditions, the boundary layer profiles measured at different flights can exhibit different shape and velocity values. This concern leads to difficulty in evaluating the efficiency of using some kind of drag-controlling device such as riblets in the flight test, since the evaluation would be conducted by comparing the profiles measured with and without using riblets at different flights. An approach was implemented to interpolate the boundary layer profile for a flight condition of interest based on the response surface method, in order to eliminate the influence of the flight conditional difference. Results showed that the interpolation with the 3rd-degree response surface model with a combination of two independent variables of flight Mach number and total pressure successfully eliminated the influence of the flight conditional difference, and interpolated the boundary layer profiles measured at different flights within an inaccuracy of 4.1% for the flight Mach number range of 0.5 to 0.78. Full article

(This article belongs to the Section Mechanical Engineering)

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16 pages, 2244 KiB

Open AccessArticle

Evaluation of Effective Elastic Properties of Nitride NWs/Polymer Composite Materials Using Laser-Generated Surface Acoustic Waves

by Evgeny Glushkov¹

, Natalia Glushkova¹

, Bernard Bonello²

, Lu Lu³

, Eric Charron², Noëlle Gogneau³, François Julien³, Maria Tchernycheva³ and Olga Boyko^2,*

¹ Institute for Mathematics, Mechanics and Informatics, Kuban State University, 350080 Krasnodar, Russia

² CNRS, Institut des NanoSciences de Paris (INSP), Sorbonne Universités, CEDEX 05, 75252 Paris, France

³ Centre de Nanosciences et de Nanotechnologies, UMR 9001 CNRS, Univ. Paris Sud, Univ. Paris-Saclay, 8 Avenue de la Vauve, 91120 Palaiseau, France

Appl. Sci. 2018, 8(11), 2319; https://doi.org/10.3390/app8112319 - 21 Nov 2018

Cited by 10 | Viewed by 3723

Abstract

In this paper we demonstrate a high potential of transient grating method to study the behavior of surface acoustic waves in nanowires-based composite structures. The investigation of dispersion curves is done by adjusting the calculated dispersion curves to the experimental results. The wave [...] Read more.

In this paper we demonstrate a high potential of transient grating method to study the behavior of surface acoustic waves in nanowires-based composite structures. The investigation of dispersion curves is done by adjusting the calculated dispersion curves to the experimental results. The wave propagation is simulated using the explicit integral and asymptotic representations for laser-generated surface acoustic waves in layered anisotropic waveguides. The analysis of the behavior permits to determine all elastic constants and effective elastic moduli of constituent materials, which is important both for technological applications of these materials and for basic scientific studies of their physical properties. Full article

(This article belongs to the Special Issue Laser Ultrasonics)

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13 pages, 5901 KiB

Open AccessArticle

LIDAR Point Cloud Registration for Sensing and Reconstruction of Unstructured Terrain

by Qingyuan Zhu^1,*

, Jinjin Wu¹, Huosheng Hu²

, Chunsheng Xiao¹

and Wei Chen¹

¹ Department of Mechanical and Electrical Engineering, Xiamen University, Xiamen 361005, China

² School of Computer Science & Electronic Engineering, University of Essex, Colchester CO4 3SQ, UK

Appl. Sci. 2018, 8(11), 2318; https://doi.org/10.3390/app8112318 - 21 Nov 2018

Cited by 14 | Viewed by 5759

Abstract

When 3D laser scanning (LIDAR) is used for navigation of autonomous vehicles operated on unstructured terrain, it is necessary to register the acquired point cloud and accurately perform point cloud reconstruction of the terrain in time. This paper proposes a novel registration method [...] Read more.

When 3D laser scanning (LIDAR) is used for navigation of autonomous vehicles operated on unstructured terrain, it is necessary to register the acquired point cloud and accurately perform point cloud reconstruction of the terrain in time. This paper proposes a novel registration method to deal with uneven-density and high-noise of unstructured terrain point clouds. It has two steps of operation, namely initial registration and accurate registration. Multisensor data is firstly used for initial registration. An improved Iterative Closest Point (ICP) algorithm is then deployed for accurate registration. This algorithm extracts key points and builds feature descriptors based on the neighborhood normal vector, point cloud density and curvature. An adaptive threshold is introduced to accelerate iterative convergence. Experimental results are given to show that our two-step registration method can effectively solve the uneven-density and high-noise problem in registration of unstructured terrain point clouds, thereby improving the accuracy of terrain point cloud reconstruction. Full article

(This article belongs to the Special Issue LiDAR and Time-of-flight Imaging)

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21 pages, 4404 KiB

Open AccessArticle

Impulse Noise Denoising Using Total Variation with Overlapping Group Sparsity and Lp-Pseudo-Norm Shrinkage

by Lingzhi Wang, Yingpin Chen^*, Fan Lin, Yuqun Chen, Fei Yu and Zongfu Cai

School of Physics and Information Engineering, Minnan Normal University, Zhangzhou 363000, China

Appl. Sci. 2018, 8(11), 2317; https://doi.org/10.3390/app8112317 - 20 Nov 2018

Cited by 15 | Viewed by 4516

Abstract

Models based on total variation (TV) regularization are proven to be effective in removing random noise. However, the serious staircase effect also exists in the denoised images. In this study, two-dimensional total variation with overlapping group sparsity (OGS-TV) is applied to images with [...] Read more.

Models based on total variation (TV) regularization are proven to be effective in removing random noise. However, the serious staircase effect also exists in the denoised images. In this study, two-dimensional total variation with overlapping group sparsity (OGS-TV) is applied to images with impulse noise, to suppress the staircase effect of the TV model and enhance the dissimilarity between smooth and edge regions. In the traditional TV model, the L1-norm is always used to describe the statistics characteristic of impulse noise. In this paper, the Lp-pseudo-norm regularization term is employed here to replace the L1-norm. The new model introduces another degree of freedom, which better describes the sparsity of the image and improves the denoising result. Under the accelerated alternating direction method of multipliers (ADMM) framework, Fourier transform technology is introduced to transform the matrix operation from the spatial domain to the frequency domain, which improves the efficiency of the algorithm. Our model concerns the sparsity of the difference domain in the image: the neighborhood difference of each point is fully utilized to augment the difference between the smooth and edge regions. Experimental results show that the peak signal-to-noise ratio, the structural similarity, the visual effect, and the computational efficiency of this new model are improved compared with state-of-the-art denoising methods. Full article

(This article belongs to the Special Issue Advanced Intelligent Imaging Technology)

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20 pages, 7524 KiB

Open AccessArticle

Progressive Collapse Analysis of SRC Frame-RC Core Tube Hybrid Structure

by Xingxing Chen^1,*, Wei Xie¹, Yunfeng Xiao², Yiguang Chen³ and Xianjie Li¹

¹ School of Urban Construction, Yangtze University, Jingzhou 434023, China

² School of Civil Engineering and Mechanics, Huazhong University of Science and Technology, Wuhan 430074, China

³ Wuhan Construction Engineering Group CO., LTD, Wuhan 430056, China

Appl. Sci. 2018, 8(11), 2316; https://doi.org/10.3390/app8112316 - 20 Nov 2018

Cited by 12 | Viewed by 4595

Abstract

Steel reinforced concrete (SRC) frame-reinforced concrete (RC) core tube hybrid structures are widely used in high-rise buildings. Focusing on the progressive collapse behavior of this structural system, this paper presents an experiment and analysis on a 1/5 scaled, 10-story SRC frame-RC core tube [...] Read more.

Steel reinforced concrete (SRC) frame-reinforced concrete (RC) core tube hybrid structures are widely used in high-rise buildings. Focusing on the progressive collapse behavior of this structural system, this paper presents an experiment and analysis on a 1/5 scaled, 10-story SRC frame-RC core tube structural model. The finite element (FE) model developed for the purpose of progressive collapse analysis was validated by comparing the test results and simulation results. The alternate load path method (APM) was applied in conducting nonlinear static and dynamic analyses, in which key components including columns and shear walls were removed. The stress state of the beams adjacent to the removed component, the structural behavior including inter-story drift ratio and shear distribution between frame and tube were investigated. The demand capacity ratio (DCR) was applied to evaluate the progressive collapse resistance under loss of key components scenarios. The results indicate that the frame and the tube cooperate in a certain way to resist progressive collapse. The core tube plays a role as the first line of defense against progressive collapse, and the frame plays a role as the second line of defense against progressive collapse. It is also found that the shear distribution is related to the location of the component removed, especially the corner column and shear walls. Full article

(This article belongs to the Special Issue Computational Methods for Fracture)

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11 pages, 2666 KiB

Open AccessArticle

Designing a Diving Protocol for Thermocline Identification Using Dive Computers in Marine Citizen Science

by Salih Murat Egi^1,2

, Pierre-Yves Cousteau³, Massimo Pieri¹, Carlo Cerrano^4,*

, Tamer Özyigit^2,*

and Alessandro Marroni¹

¹ Research Department, DAN Europe Foundation, 64026 Roseto degli Abruzzi, Italy

² Department of Computer Engineering, MTF, Galatasaray University, Istanbul 34349, Turkey

³ Cousteau Divers, 75017 Paris, France

⁴ Department of Life and Environmental Sciences—DiSVA, Università Politecnica delle Marche, 60131 Ancona, Italy

Appl. Sci. 2018, 8(11), 2315; https://doi.org/10.3390/app8112315 - 20 Nov 2018

Cited by 6 | Viewed by 4563

Abstract

Dive computers have an important potential for citizen science projects where recreational SCUBA divers can upload the depth temperature profile and the geolocation of the dive to a central database which may provide useful information about the subsurface temperature of the oceans. However, [...] Read more.

Dive computers have an important potential for citizen science projects where recreational SCUBA divers can upload the depth temperature profile and the geolocation of the dive to a central database which may provide useful information about the subsurface temperature of the oceans. However, their accuracy may not be adequate and needs to be evaluated. The aim of this study is to assess the accuracy and precision of dive computers and provide guidelines in order to enable their contribution to citizen science projects. Twenty-two dive computers were evaluated during real ocean dives for consistency and scatter in the first phase. In the second phase, the dive computers were immersed in sufficient depth to initiate the dive record inside a precisely controlled sea aquarium while using a calibrated device as a reference. Results indicate that the dive computers do not have the accuracy required for monitoring temperature changes in the oceans, however, they can be used to detect thermoclines if the users follow a specific protocol with specific dive computers. This study enabled the authors to define this protocol based on the results of immersion in two different sea aquarium tanks set to two different temperatures in order to simulate the conditions of a thermocline. Full article

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18 pages, 5357 KiB

Open AccessFeature PaperArticle

A Fully Coupled Computational Fluid Dynamics Method for Analysis of Semi-Submersible Floating Offshore Wind Turbines Under Wind-Wave Excitation Conditions Based on OC5 Data

by Yin Zhang

and Bumsuk Kim^*

Faculty of Wind Energy Engineering Graduate School, Jeju National University, Jeju City 63243, Korea

Appl. Sci. 2018, 8(11), 2314; https://doi.org/10.3390/app8112314 - 20 Nov 2018

Cited by 58 | Viewed by 10183

Abstract

Accurate prediction of the time-dependent system dynamic responses of floating offshore wind turbines (FOWTs) under aero-hydro-coupled conditions is a challenge. This paper presents a numerical modeling tool using commercial computational fluid dynamics software, STAR-CCM+(V12.02.010), to perform a fully coupled dynamic analysis of the [...] Read more.

Accurate prediction of the time-dependent system dynamic responses of floating offshore wind turbines (FOWTs) under aero-hydro-coupled conditions is a challenge. This paper presents a numerical modeling tool using commercial computational fluid dynamics software, STAR-CCM+(V12.02.010), to perform a fully coupled dynamic analysis of the DeepCwind semi-submersible floating platform with the National Renewable Engineering Lab (NREL) 5-MW baseline wind turbine model under combined wind–wave excitation environment conditions. Free-decay tests for rigid-body degrees of freedom (DOF) in still water and hydrodynamic tests for a regular wave are performed to validate the numerical model by inputting gross system parameters supported in the Offshore Code Comparison, Collaboration, Continued, with Correlations (OC5) project. A full-configuration FOWT simulation, with the simultaneous motion of the rotating blade due to 6-DOF platform dynamics, was performed. A relatively heavy load on the hub and blade was observed for the FOWT compared with the onshore wind turbine, leading to a 7.8% increase in the thrust curve; a 10% decrease in the power curve was also observed for the floating-type turbines, which could be attributed to the smaller project area and relative wind speed required for the rotor to receive wind power when the platform pitches. Finally, the tower-blade interference effects, blade-tip vortices, turbulent wakes, and shedding vortices in the fluid domain with relatively complex unsteady flow conditions were observed and investigated in detail. Full article

(This article belongs to the Special Issue Wind Turbine Aerodynamics)

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20 pages, 1279 KiB

Open AccessArticle

Frequency-Domain Filtered-x LMS Algorithms for Active Noise Control: A Review and New Insights

by Feiran Yang¹

, Yin Cao¹, Ming Wu¹, Felix Albu²

and Jun Yang^1,3,*

¹ State Key Laboratory of Acoustics and Key Laboratory of Noise and Vibration Research, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China

² Department of Electronics, Valahia University of Targoviste, Targoviste 130082, Romania

³ School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China

Appl. Sci. 2018, 8(11), 2313; https://doi.org/10.3390/app8112313 - 20 Nov 2018

Cited by 76 | Viewed by 9737

Abstract

This paper presents a comprehensive overview of the frequency-domain filtered-x least mean-square (FxLMS) algorithms for active noise control (ANC). The direct use of frequency-domain adaptive filters for ANC results in two kinds of delays, i.e., delay in the signal path and delay in [...] Read more.

This paper presents a comprehensive overview of the frequency-domain filtered-x least mean-square (FxLMS) algorithms for active noise control (ANC). The direct use of frequency-domain adaptive filters for ANC results in two kinds of delays, i.e., delay in the signal path and delay in the weight adaptation. The effects of the two kinds of delays on the convergence behavior and stability of the adaptive algorithms are analyzed in this paper. The first delay can violate the so-called causality constraint, which is a major concern for broadband ANC, and the second delay can reduce the upper bound of the step size. The modified filter-x scheme has been employed to remove the delay in the weight adaptation, and several delayless filtering approaches have been presented to remove the delay in the signal path. However, state-of-the-art frequency-domain FxLMS algorithms only remove one kind of delay, and some of these algorithms have a very high peak complexity and hence are impractical for real-time systems. This paper thus proposes a new delayless frequency-domain ANC algorithm that completely removes the two kinds of delays and has a low complexity. The performance advantages and limitations of each algorithm are discussed based on an extensive evaluation, and the complexities are evaluated in terms of both the peak and average complexities. Full article

(This article belongs to the Special Issue Active and Passive Noise Control)

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16 pages, 1333 KiB

Open AccessArticle

Surveying the Environmental and Technical Dimensions of Sustainability in Software Development Companies

by José Alberto García-Berna

, Juan Manuel Carrillo de Gea^*

, Begoña Moros

, José Luis Fernández-Alemán

, Joaquín Nicolás

and Ambrosio Toval

Department of Informatics and Systems, University of Murcia, 30100 Murcia, Spain

Appl. Sci. 2018, 8(11), 2312; https://doi.org/10.3390/app8112312 - 20 Nov 2018

Cited by 7 | Viewed by 3486

Abstract

The growing concern over the state of degradation of the environment has led to a consideration of aspects relating to sustainability in software. Bearing this in mind, we have carried out a survey of practitioners, aiming to gather information about their awareness of [...] Read more.

The growing concern over the state of degradation of the environment has led to a consideration of aspects relating to sustainability in software. Bearing this in mind, we have carried out a survey of practitioners, aiming to gather information about their awareness of sustainable software, not only during the development process, but also throughout the period in which the software is used. Using the data gathered, we studied professionals’ perspectives on sustainability in software development, and were able to get a picture of the current situation of the application of sustainability practices in this sector. We focused on the environmental and technical dimensions of sustainability aimed at extending the longevity of information systems and making them more energy efficient. From the results, we observed that there is a widespread desire to pursue sustainable behavior at work, even though there are not always clear guidelines on how to proceed in this endeavor. Full article

(This article belongs to the Section Environmental Sciences)

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23 pages, 1701 KiB

Open AccessArticle

Ethylene- and Propylene-Glycol Based Nanofluids: A Litterature Review on Their Thermophysical Properties and Thermal Performances

by Ghofrane Sekrani and Sébastien Poncet^*

Université de Sherbrooke, Faculté de Génie, Département de Génie Mécanique 2500 Boulevard de l’Université, Sherbrooke, QC J1K 2R1, Canada

Appl. Sci. 2018, 8(11), 2311; https://doi.org/10.3390/app8112311 - 20 Nov 2018

Cited by 51 | Viewed by 8347

Abstract

Nanofluids are considered a promising way to improve the heat transfer capability of base fluids. Water is the most commonly-used heat transfer fluid. However, in refrigeration systems, it may be necessary to mix water with either ethylene- or propylene-glycol to lower its freezing [...] Read more.

Nanofluids are considered a promising way to improve the heat transfer capability of base fluids. Water is the most commonly-used heat transfer fluid. However, in refrigeration systems, it may be necessary to mix water with either ethylene- or propylene-glycol to lower its freezing point and prevent from ice formation. In the same way, for car radiators or industrial heat exchangers, the boiling point of water can be pushed up by mixing it with glycol-based fluids. The increasing awareness of energy saving and industrial energy efficiency improvement results in the growing interest in ethylene- or propylene-glycol-based nanofluids for applications in various thermal systems. The present paper proposes an extensive review of the most recent and relevant experimental and numerical works on the thermophysical properties and performances of ethylene- or propylene-glycol-based nanofluids. Research perspectives are also provided with the long-term objective that these nanofluids be more widely considered in real industrial applications. Full article

(This article belongs to the Special Issue Nanofluids and Their Applications)

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19 pages, 5373 KiB

Open AccessFeature PaperReview

Microparticle Manipulation and Imaging through a Self-Calibrated Liquid Crystal on Silicon Display

by Haolin Zhang^1,*, Angel Lizana¹

, Albert Van Eeckhout¹, Alex Turpin^2,3, Claudio Ramirez^1,4, Claudio Iemmi⁵ and Juan Campos¹

¹ Departamento de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain

² Leibniz Institute of Photonic Technology, Albert-Einstein-Straße 9, 07745 Jena, Germany

³ School of Physics and Astronomy, Kelvin Building, University of Glasgow, Glasgow G12 8QQ, UK

⁴ Instituto de Ciencias Aplicadas y Tecnología (ICAT), Universidad Nacional Autónoma de México, 04510 Mexico City, Mexico

⁵ Departamento de Física, Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, 1428 Buenos Aires, Argentina

Appl. Sci. 2018, 8(11), 2310; https://doi.org/10.3390/app8112310 - 20 Nov 2018

Cited by 7 | Viewed by 5157

Abstract

We present in this paper a revision of three different methods we conceived in the framework of liquid crystal on silicon (LCoS) display optimization and application. We preliminarily demonstrate an LCoS self-calibration technique, from which we can perform a complete LCoS characterization. In [...] Read more.

We present in this paper a revision of three different methods we conceived in the framework of liquid crystal on silicon (LCoS) display optimization and application. We preliminarily demonstrate an LCoS self-calibration technique, from which we can perform a complete LCoS characterization. In particular, two important characteristics of LCoS displays are retrieved by using self-addressed digital holograms. On the one hand, we determine its phase-voltage curve by using the interference pattern generated by a digital two-sectorial split-lens configuration. On the other hand, the LCoS surface profile is also determined by using a self-addressed dynamic micro-lens array pattern. Second, the implementation of microparticle manipulation through optical traps created by an LCoS display is demonstrated. Finally, an LCoS display based inline (IL) holographic imaging system is described. By using the LCoS display to implement a double-sideband filter configuration, this inline architecture demonstrates the advantage of obtaining dynamic holographic imaging of microparticles independently of their spatial positions by avoiding the non-desired conjugate images. Full article

(This article belongs to the Special Issue Liquid Crystal on Silicon Devices: Modeling and Advanced Spatial Light Modulation Applications)

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20 pages, 23284 KiB

Open AccessArticle

Agustín de Betancourt’s Double-Acting Steam Engine: Analysis through Computer-Aided Engineering

by José Ignacio Rojas-Sola^1,*

and Eduardo De la Morena-De la Fuente²

¹ Department of Engineering Graphics, Design and Projects, University of Jaén, 23071 Jaén, Spain

² ‘Engineering Graphics and Industrial Archaeology’ Research Group, University of Jaén, 23071 Jaén, Spain

Appl. Sci. 2018, 8(11), 2309; https://doi.org/10.3390/app8112309 - 20 Nov 2018

Cited by 15 | Viewed by 6589

Abstract

This article analyses the double-acting steam engine designed by Agustín de Betancourt in 1789 and based on the steam engine of James Watt. Its novelty and scientific interest lies in the fact that from the point of view of industrial archaeology and the [...] Read more.

This article analyses the double-acting steam engine designed by Agustín de Betancourt in 1789 and based on the steam engine of James Watt. Its novelty and scientific interest lies in the fact that from the point of view of industrial archaeology and the study of technical historical heritage there is no worldwide study on this invention, which marked a historic milestone in the design of the steam engines of the Industrial Revolution (1760–1840). This underscores the utility and originality of this research. To this end, a study of computer-aided engineering (CAE) was carried out using the parametric software Autodesk Inventor Professional, consisting of a static analysis using the finite-element method of the 3D CAD model of the invention under real operating conditions. The results have shown that the double-acting steam engine was correctly designed considering that the values of the maximum von Mises stress (188.4 MPa) obtained were taken away from the elastic limit of the material it was made of (cast iron), as well as to the maximum deformations (0.14% with respect to its length) obtained in the same element that presents the maximum stress (opening axle of the high pressure steam valve). Similarly, the maximum displacements (18.74 mm) are located in the mobile counterweights that transmit certain inertia to facilitate the opening and closing of the valves. Finally, if we look at the results of the safety coefficient, whose lowest value was 4.02, we could say that the invention was oversized, following constructive criteria of the time, as there were no resistance tests on materials that would help in the optimization of the design of the invention. Full article

(This article belongs to the Special Issue Applied Sciences to the Study of Technical Historical Heritage and/or Industrial Heritage)

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15 pages, 5494 KiB

Open AccessArticle

Induction Heating-Assisted Compaction in Porous Asphalt Pavements: A Computational Study

by Changhong Zhou^1,2

, Xueyan Liu^2,*, Panos Apostolidis²

, A. (Tom) Scarpas²

and Liang He³

¹ School of Transportation and Logistics, Dalian University of Technology, Dalian 116024, China

² Civil Engineering and Geosciences, Delft University of Technology, 2628 CD Delft, The Netherlands

³ School of Civil Engineering, Chongqing Jiaotong University, Chongqing 400074, China

Appl. Sci. 2018, 8(11), 2308; https://doi.org/10.3390/app8112308 - 20 Nov 2018

Cited by 17 | Viewed by 4357

Abstract

Low temperature asphalt (LTA) technologies, such as warm-mixed asphalt mixes, are utilized in the paving industry to lower energy demands and greenhouse gas emissions during asphalt mixing and pavement construction. However, the asphalt mixes developed that incorporate LTA additives are more sensitive than [...] Read more.

Low temperature asphalt (LTA) technologies, such as warm-mixed asphalt mixes, are utilized in the paving industry to lower energy demands and greenhouse gas emissions during asphalt mixing and pavement construction. However, the asphalt mixes developed that incorporate LTA additives are more sensitive than hot-mixed asphalts to temperature reduction during compaction, which leads to inadequate compaction and subsequent poor pavement performance. The induction heating-assisted compaction of pavement structures appears to be an effective way to ameliorate such issues and to improve mix compactability at lower temperatures. Considering that induction-assisted compaction is a complex process, a computational methodology is proposed in this paper. A porous asphalt concrete mix was considered as case material. For the pavement compaction analyses after induction, the temperature field generated by electromagnetic induction was predicted and the material parameters of asphalt mortar were adjusted. The effect of induction heating on asphalt compaction effectiveness, the tendency of mix density changing, the increase in compactor passes, and the influence of temperature on compaction at different locations in the pavement were studied as well. Full article

(This article belongs to the Special Issue Achievements and Prospects of Functional Pavement: Materials and Structures)

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20 pages, 9966 KiB

Open AccessArticle

Asymptotic Analysis for the Effects of Anode Inlet Humidity on the Fastest Power Attenuation Single Cell in a Vehicle Fuel Cell Stack

by Yongfeng Liu^1,2,*, Jianhua Gao^1,*, Na Wang¹ and Shengzhuo Yao¹

¹ Beijing Key Laboratory of Performance Guarantee on Urban Rail Transit Vehicles, School of Machine-Electricity and Vehicle Engineering, Beijing University of Civil Engineering and Architecture, Beijing 100044, China

² State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing 100084, China

Appl. Sci. 2018, 8(11), 2307; https://doi.org/10.3390/app8112307 - 20 Nov 2018

Cited by 8 | Viewed by 3513

Abstract

A three-dimensional and isothermal anode relative humidity (ARH) model is presented and used to study the anode inlet humidity effects on the fastest power attenuation single cell in a vehicle fuel cell stack. The ARH model is based on the phenomenon that the [...] Read more.

A three-dimensional and isothermal anode relative humidity (ARH) model is presented and used to study the anode inlet humidity effects on the fastest power attenuation single cell in a vehicle fuel cell stack. The ARH model is based on the phenomenon that the anode is more sensitive than the cathode to water flooding. The pressure drop is considered in the ARH model, and saturation pressure is established by a pressure drop. Based on the pressure drop and relative humidity, simulations and tests are completed. First, the geometric model and computational grids are established, based on real structure of the proton exchange membrane fuel cell (PEMFC). Second, single cell distribution in the stack, test schematic and experimental conditions are demonstrated. Finally, polarization curves with 10 cells are displayed and discussed under these conditions that working temperature 70 °C, and diverse relative humidity (40%, 55%, 70%, 85%, and 100%). The test results of 34 cm² fuel cell stack are compared against simulation results. The results show that C10 (the single cell with the farthest distance from the gas inlet) power attenuation is the fastest and that its performance is the poorest under the experimental conditions. The polarization curves predicted by the ARH model indicate fairly good coherence with the experimental results, compared against the Fluent original model. The ARH model calculation deviation is 28% less than the Fluent model at 360 mA·cm⁻² for a relative humidity of 85%. The current density distribution is almost uniform, and membrane water content is negatively affected by high humidity. Full article

(This article belongs to the Section Energy Science and Technology)

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20 pages, 7243 KiB

Open AccessArticle

Response Characteristics of the DeepCwind Floating Wind Turbine Moored by a Single-Point Mooring System

by Yingyi Liu^1,*

, Shigeo Yoshida¹

, Hiroshi Yamamoto², Akinori Toyofuku², Guanghua He³

and Shunhan Yang⁴

¹ Research Institute for Applied Mechanics, Kyushu University, Kasuga 8168580, Japan

² Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga 8168580, Japan

³ School of Naval Architecture and Ocean Engineering, Harbin Institute of Technology, Weihai 264209, China

⁴ Department of Mechanics and Maritime Sciences, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden

Appl. Sci. 2018, 8(11), 2306; https://doi.org/10.3390/app8112306 - 20 Nov 2018

Cited by 28 | Viewed by 7375

Abstract

In recent years, the SPM (Single-Point Mooring) concept has been widely employed in several branches of the naval architecture and marine engineering field, such as FPSOs (Floating Production, Storage and Offloading units), offshore oil rigs, etc., but not yet popular in the offshore [...] Read more.

In recent years, the SPM (Single-Point Mooring) concept has been widely employed in several branches of the naval architecture and marine engineering field, such as FPSOs (Floating Production, Storage and Offloading units), offshore oil rigs, etc., but not yet popular in the offshore wind energy. To investigate the response characteristics of an SPM-moored FWT (Floating Wind Turbine), in the present work, we perform a numerical study on the DeepCwind semisubmersible wind turbine, using the state-of-the-art open-source tool FAST. The free-decay test results show that the SPM layout affects the natural periods of the wind turbine in rotational modes, as well as the mooring stiffness of the diagonal rotational and crossing rotational-translational terms, especially in relation to the yaw mode. Comparisons of the RAOs (Response Amplitude Operators) elucidate that the presence of wind influences significantly the sway, roll and yaw motions of the SPM layout. Finally, the weathervane test shows that an asymmetry exists in the free-yaw motion response when the semisubmersible wind turbine is moored by an SPM system. Full article

(This article belongs to the Special Issue Offshore Wind Energy)

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15 pages, 3033 KiB

Open AccessArticle

Design and Implementation of a Security Improvement Framework of Zigbee Network for Intelligent Monitoring in IoT Platform

by S M Sohel Rana¹, Miah Abdul Halim²

and M. Humayun Kabir^1,*

¹ Department of Electrical and Electronic Engineering, Islamic University, Kushtia 7003, Bangladesh

² Department of Mechanical Engineering, University of Utah, Salt Lake City, UT 84112, USA

Appl. Sci. 2018, 8(11), 2305; https://doi.org/10.3390/app8112305 - 20 Nov 2018

Cited by 22 | Viewed by 5849

Abstract

Internet of Things (IoT) opens new horizons by enabling automated procedures without human interaction using IP connectivity. IoT deals with devices, called things, represented as any items from our daily life that are enhanced with computing or communication facilities. Among various mobile communications, [...] Read more.

Internet of Things (IoT) opens new horizons by enabling automated procedures without human interaction using IP connectivity. IoT deals with devices, called things, represented as any items from our daily life that are enhanced with computing or communication facilities. Among various mobile communications, Zigbee communication is broadly used in controlling or monitoring applications due to its low data rate and low power consumption. Securing IoT systems has been the main concern for the research community. In this paper, different security threats of Zigbee networks in the IoT platform have been addressed to predict the potential security threats of Zigbee protocol and a Security Improvement Framework (SIF) has been designed for intelligent monitoring in an office/corporate environment. Our proposed SIF can predict and protect against various potential malicious attacks in the Zigbee network and respond accordingly through a notification to the system administrator. This framework (SIF) is designed to make automated decisions immediately based on real-time data which are defined by the system administrator. Finally, the designed SIF has been implemented in an office security system as a case study for real-time monitoring. This office security system is evaluated based on the capacity of detecting potential security attacks. The evaluation results show that the proposed SIF is capable of detecting and protecting against several potential security attacks efficiently, enabling a more secure way of intelligent monitoring in the IoT platform. Full article

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14 pages, 7505 KiB

Open AccessEditor’s ChoiceArticle

Feasibility Study of Steel Bar Corrosion Monitoring Using a Piezoceramic Transducer Enabled Time Reversal Method

by Linsheng Huo¹

, Chuanbo Li¹, Tianyong Jiang^2,*

and Hong-Nan Li^1,*

¹ Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China

² School of Civil Engineering, Changsha University of Science and Technology, Changsha 410114, China

Appl. Sci. 2018, 8(11), 2304; https://doi.org/10.3390/app8112304 - 19 Nov 2018

Cited by 71 | Viewed by 4786

Abstract

Steel bars, which are commonly used as reinforcements in concrete structures, are slender rods and are good conduits for stress wave propagation. In this paper, a lead zirconate titanate (PZT)-based steel bar corrosion monitoring approach was proposed. Two PZT transducers are surface-bonded on [...] Read more.

Steel bars, which are commonly used as reinforcements in concrete structures, are slender rods and are good conduits for stress wave propagation. In this paper, a lead zirconate titanate (PZT)-based steel bar corrosion monitoring approach was proposed. Two PZT transducers are surface-bonded on the two ends of a steel rod, respectively. One works as actuator to generate stress waves, and the other functions as a sensor to detect the propagated stress waves. Time reverse technology was applied in this research to monitor the corrosion of the steel bars with a high signal to noise ratio (SNR). Accelerated corrosion experiments of steel bars were conducted. The anti-corrosion performance of the protected piezoceramic transducers was tested first, and then they were used to monitor the corrosion of the steel bar using the time reversal method. The degree of corrosion in the steel bar was determined by the ratio of mass loss during the experiment. The experimental results show that the peak values of the signal that were obtained by time reversal operation are linearly related to the degree of corrosion of the steel bar, which demonstrates the feasibility of the proposed approach for monitoring the corrosion of steel bars using the time reversal method enabled by piezoceramic transducers. Full article

(This article belongs to the Special Issue Structural Damage Detection and Health Monitoring)

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16 pages, 2134 KiB

Open AccessReview

A Review of the Developed New Model Biodiesels and Their Effects on Engine Combustion and Emissions

by Shenghua Liu^1,*

, Wei Chen¹, Zengqiang Zhu¹, Sa Jiang¹, Tongtong Ren¹ and Hejun Guo²

¹ School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China

² Xi’an Research Institute of High Technology, 603 PO Box, Xi’an 710025, China

Appl. Sci. 2018, 8(11), 2303; https://doi.org/10.3390/app8112303 - 19 Nov 2018

Cited by 11 | Viewed by 3660

Abstract

Biodiesel is regarded to be a renewable, CO₂ neutral and thus sustainable biological alternative diesel fuel. With attention to the reduction of petroleum import, PM 2.5 aerosol particles and the greenhouse effect gas CO₂, biodiesel has drawn great research interests [...] Read more.

Biodiesel is regarded to be a renewable, CO₂ neutral and thus sustainable biological alternative diesel fuel. With attention to the reduction of petroleum import, PM 2.5 aerosol particles and the greenhouse effect gas CO₂, biodiesel has drawn great research interests and efforts in the past decade in China. Generally, biodiesel refers to fatty acid methyl ether (FAME) which has a proved effect in reducing diesel emission, particularly PM. However, FAME has a limited cetane number and oxygen content, to study the effects of elevated cetane number and oxygen content on fuel properties, engine combustion and emissions, ethylene glycol monomethyl ether is used to produce a series of new models of biodiesels by transesterification method. The feedstocks are rapeseed oil, soybean oil, peanut oil, palm oil and cottonseed oil. Ether group alcohols used in this study include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether. The molecular structure was proved by FT-IR and NMR analyses. Fuel properties were measured based on the corresponding standards. The developed new model biodiesels have cetane number (CN) over 70 and oxygen content over 17% by mass, which are higher than FAME (50 CN and 11% oxygen). They have the same level of lower heating value as FAME, but have a higher density, which helps to compensate the decrease of engine power. Meanwhile, the engine tests were carried out to investigate the effects of ether ester group on engine combustion and emissions. The test results show that FAME reduced smoke 30% to 50%, while the new model biodiesel fuels reduced engine smoke as high as 80% and have the potential to decrease engine HC, CO and NO_x emissions 50% or more. Full article

(This article belongs to the Special Issue Combustion Study of Biodiesel and Biofuel)

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