Applied Sciences

17 pages, 4095 KiB

Open AccessArticle

Development of a New KPI for the Economic Quantification of Six Big Losses and Its Implementation in a Cyber Physical System

by Paula Morella, María Pilar Lambán, Jesús Royo, Juan Carlos Sánchez and Jaime Latapia

Appl. Sci. 2020, 10(24), 9154; https://doi.org/10.3390/app10249154 - 21 Dec 2020

Cited by 7 | Viewed by 4345

Abstract

The purpose of this work is to develop a new Key Performance Indicator (KPI) that can quantify the cost of Six Big Losses developed by Nakajima and implements it in a Cyber Physical System (CPS), achieving a real-time monitorization of the KPI. This [...] Read more.

The purpose of this work is to develop a new Key Performance Indicator (KPI) that can quantify the cost of Six Big Losses developed by Nakajima and implements it in a Cyber Physical System (CPS), achieving a real-time monitorization of the KPI. This paper follows the methodology explained below. A cost model has been used to accurately develop this indicator together with the Six Big Losses description. At the same time, the machine tool has been integrated into a CPS, enhancing the real-time data acquisition, using the Industry 4.0 technologies. Once the KPI has been defined, we have developed the software that can turn these real-time data into relevant information (using Python) through the calculation of our indicator. Finally, we have carried out a case of study showing our new KPI results and comparing them to other indicators related with the Six Big Losses but in different dimensions. As a result, our research quantifies economically the Six Big Losses, enhances the detection of the bigger ones to improve them, and enlightens the importance of paying attention to different dimensions, mainly, the productive, sustainable, and economic at the same time. Full article

(This article belongs to the Special Issue Industry 4.0 Based Smart Manufacturing Systems)

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Graphical abstract

20 pages, 6804 KiB

Open AccessArticle

Scattering or Pushing for Object Singulation in Cluttered Environment: Case Study with Soma Cube

by Muhammad Umair Ahmad Khan, Abid Imran, Sanghwa Kim, Hyunho Hwang, Ji Yeong Lee, Sungon Lee and Byung-Ju Yi

Appl. Sci. 2020, 10(24), 9153; https://doi.org/10.3390/app10249153 - 21 Dec 2020

Cited by 1 | Viewed by 3574

Abstract

This paper proposes a hybrid singulation approach combining dynamic scattering and pushing techniques. Using the impulse-based dynamic model, a guideline is provided to decide whether scattering or pushing is conducted for object singulation. The Soma cube consisting of seven blocks is used as [...] Read more.

This paper proposes a hybrid singulation approach combining dynamic scattering and pushing techniques. Using the impulse-based dynamic model, a guideline is provided to decide whether scattering or pushing is conducted for object singulation. The Soma cube consisting of seven blocks is used as the test example. The target is to singulate all the blocks. The dynamic scattering technique was initially applied to separate blocks in the formation. However, scattering alone does not provide target singulation in all the cases. So we combine the quasi-static pushing technique to complete the singulation of all the blocks. In pushing, image segmentation based on principal component analysis (PCA) algorithm was employed to singulate multiple blocks in clutter and prehensile manipulation was used to remove isolated blocks. Several 2-D formations of the Soma cube are used as the test cases. To validate the effectiveness of our approach, we have conducted comparative analysis which clearly shows that the hybrid singulation achieves singulation in much less time as compared to the pure pushing approach. Full article

(This article belongs to the Special Issue Object Recognition, Robotic Grasping and Manipulation)

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42 pages, 1248 KiB

Open AccessFeature PaperReview

Electrical Resistivity and Electrical Impedance Measurement in Mortar and Concrete Elements: A Systematic Review

by Gloria Cosoli, Alessandra Mobili, Francesca Tittarelli, Gian Marco Revel and Paolo Chiariotti

Appl. Sci. 2020, 10(24), 9152; https://doi.org/10.3390/app10249152 - 21 Dec 2020

Cited by 67 | Viewed by 11150

Abstract

This paper aims at analyzing the state-of-the-art techniques to measure electrical impedance (and, consequently, electrical resistivity) of mortar/concrete elements. Despite the validity of the concept being widely proven in the literature, a clear standard for this measurement is still missing. Different methods are [...] Read more.

This paper aims at analyzing the state-of-the-art techniques to measure electrical impedance (and, consequently, electrical resistivity) of mortar/concrete elements. Despite the validity of the concept being widely proven in the literature, a clear standard for this measurement is still missing. Different methods are described and discussed, highlighting pros and cons with respect to their performance, reliability, and degree of maturity. Both monitoring and inspection approaches are possible by using electrical resistivity measurements; since electrical resistivity is an important indicator of the health status of mortar/concrete, as it changes whenever phenomena modifying the conductivity of mortar/concrete (e.g., degradation or attacks by external agents) occur, this review aims to serve as a guide for those interested in this type of measurements. Full article

(This article belongs to the Special Issue Non-destructive Testing in Civil Engineering)

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17 pages, 3110 KiB

Open AccessArticle

Machine Learning-Based Prediction of Air Quality

by Yun-Chia Liang, Yona Maimury, Angela Hsiang-Ling Chen and Josue Rodolfo Cuevas Juarez

Appl. Sci. 2020, 10(24), 9151; https://doi.org/10.3390/app10249151 - 21 Dec 2020

Cited by 101 | Viewed by 12813

Abstract

Air, an essential natural resource, has been compromised in terms of quality by economic activities. Considerable research has been devoted to predicting instances of poor air quality, but most studies are limited by insufficient longitudinal data, making it difficult to account for seasonal [...] Read more.

Air, an essential natural resource, has been compromised in terms of quality by economic activities. Considerable research has been devoted to predicting instances of poor air quality, but most studies are limited by insufficient longitudinal data, making it difficult to account for seasonal and other factors. Several prediction models have been developed using an 11-year dataset collected by Taiwan’s Environmental Protection Administration (EPA). Machine learning methods, including adaptive boosting (AdaBoost), artificial neural network (ANN), random forest, stacking ensemble, and support vector machine (SVM), produce promising results for air quality index (AQI) level predictions. A series of experiments, using datasets for three different regions to obtain the best prediction performance from the stacking ensemble, AdaBoost, and random forest, found the stacking ensemble delivers consistently superior performance for R² and RMSE, while AdaBoost provides best results for MAE. Full article

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26 pages, 14098 KiB

Open AccessArticle

Analytical Evaluation of MCE Collapse Performance of Seismically Base Isolated Buildings Located at Low-to-Moderate Seismicity Regions

by Hyung-Joon Kim and Dong-Hyeon Shin

Appl. Sci. 2020, 10(24), 9150; https://doi.org/10.3390/app10249150 - 21 Dec 2020

Viewed by 1992

Abstract

The promising seismic response emerged by the concept of base isolation leads to increasing practical applications into buildings located at low-to-moderate seismicity regions. However, it is questionable that their collapse capacities can be ensured with reasonable reliability, although they would be designed according [...] Read more.

The promising seismic response emerged by the concept of base isolation leads to increasing practical applications into buildings located at low-to-moderate seismicity regions. However, it is questionable that their collapse capacities can be ensured with reasonable reliability, although they would be designed according to a current seismic design code. This paper aims to investigate the collapse capacities of isolated buildings governed by the prescribed design criteria on the displacement and strength capacities of the employed isolation systems. In order to evaluate their collapse capacity under maximum considered earthquakes (MCEs), simplified numerical models are constructed for a larger number of nonlinear incremental dynamic analyses. The influential factors on the collapse probabilities of the prototype buildings are found out to specifically suggest the potential modifications of the design requirements. Although the MCE collapse probabilities of all isolated buildings are smaller than those expected for typical non-isolated buildings, these values are significantly different according to the degree of seismicity. The MCE collapse probabilities are dependent upon the governing collapse mechanism and the total system uncertainty. For the prototype buildings located at low-to-moderate seismicity regions, this study proposed the acceptable uncertainty to achieve a similar collapse performance to the corresponding buildings built at high seismicity regions. Full article

(This article belongs to the Section Civil Engineering)

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14 pages, 775 KiB

Open AccessArticle

Building Reliable Massive Capacity SSDs through a Flash Aware RAID-Like Protection

by Jaeho Kim and Jung Kyu Park

Appl. Sci. 2020, 10(24), 9149; https://doi.org/10.3390/app10249149 - 21 Dec 2020

Cited by 2 | Viewed by 2908

Abstract

The demand for mass storage devices has become an inevitable consequence of the explosive increase in data volume. The three-dimensional (3D) vertical NAND (V-NAND) and quad-level cell (QLC) technologies rapidly accelerate the capacity increase of flash memory based storage system, such as SSDs [...] Read more.

The demand for mass storage devices has become an inevitable consequence of the explosive increase in data volume. The three-dimensional (3D) vertical NAND (V-NAND) and quad-level cell (QLC) technologies rapidly accelerate the capacity increase of flash memory based storage system, such as SSDs (Solid State Drives). Massive capacity SSDs adopt dozens or hundreds of flash memory chips in order to implement large capacity storage. However, employing such a large number of flash chips increases the error rate in SSDs. A RAID-like technique inside an SSD has been used in a variety of commercial products, along with various studies, in order to protect user data. With the advent of new types of massive storage devices, studies on the design of RAID-like protection techniques for such huge capacity SSDs are important and essential. In this paper, we propose a massive SSD-Aware Parity Logging (mSAPL) scheme that protects against n-failures at the same time in a stripe, where n is protection strength that is specified by the user. The proposed technique allows for us to choose the strength of protection for user data. We implemented mSAPL on a trace-based simulator and evaluated it with real-world I/O workload traces. In addition, we quantitatively analyze the error rates of a flash based SSD for different RAID-like configurations with analytic models. We show that mSAPL outperforms the state-of-the-art RAID-like technique in the performance and reliability. Full article

(This article belongs to the Section Computing and Artificial Intelligence)

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13 pages, 1100 KiB

Open AccessArticle

Insights from Learning Analytics for Hands-On Cloud Computing Labs in AWS

by Germán Moltó, Diana M. Naranjo and J. Damian Segrelles

Appl. Sci. 2020, 10(24), 9148; https://doi.org/10.3390/app10249148 - 21 Dec 2020

Cited by 1 | Viewed by 3394

Abstract

Cloud computing instruction requires hands-on experience with a myriad of distributed computing services from a public cloud provider. Tracking the progress of the students, especially for online courses, requires one to automatically gather evidence and produce learning analytics in order to further determine [...] Read more.

Cloud computing instruction requires hands-on experience with a myriad of distributed computing services from a public cloud provider. Tracking the progress of the students, especially for online courses, requires one to automatically gather evidence and produce learning analytics in order to further determine the behavior and performance of students. With this aim, this paper describes the experience from an online course in cloud computing with Amazon Web Services on the creation of an open-source data processing tool to systematically obtain learning analytics related to the hands-on activities carried out throughout the course. These data, combined with the data obtained from the learning management system, have allowed the better characterization of the behavior of students in the course. Insights from a population of more than 420 online students through three academic years have been assessed, the dataset has been released for increased reproducibility. The results corroborate that course length has an impact on online students dropout. In addition, a gender analysis pointed out that there are no statistically significant differences in the final marks between genders, but women show an increased degree of commitment with the activities planned in the course. Full article

(This article belongs to the Special Issue Innovations in the Field of Cloud Computing and Education)

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11 pages, 1585 KiB

Open AccessArticle

Defatted Hydroethanolic Extract of Ammodaucus leucotrichus Cosson and Durieu Seeds: Antidiabetic and Anti-Inflammatory Activities

by Imane Es-Safi, Hamza Mechchate, Amal Amaghnouje, Anna Calarco, Smahane Boukhira, Omar M. Noman, Ramzi A. Mothana, Fahd A. Nasr, Hicham Bekkari and Dalila Bousta

Appl. Sci. 2020, 10(24), 9147; https://doi.org/10.3390/app10249147 - 21 Dec 2020

Cited by 18 | Viewed by 2548

Abstract

The seeds of Ammodaucus leucotrichus Cosson and Durieu have been used in the North African Sahara as a traditional medicine to treat diabetes. The present study investigates the antidiabetic, antihyperglycemic, and anti-inflammatory properties of the defatted hydroethanolic extract of Ammodaucus leucotrichus (DHEAM). The [...] Read more.

The seeds of Ammodaucus leucotrichus Cosson and Durieu have been used in the North African Sahara as a traditional medicine to treat diabetes. The present study investigates the antidiabetic, antihyperglycemic, and anti-inflammatory properties of the defatted hydroethanolic extract of Ammodaucus leucotrichus (DHEAM). The antidiabetic and the antihyperglycemic studies were assessed on alloxan-induced diabetic with orally administered doses of DHEAM (100 and 200 mg/kg). At the same time, its anti-inflammatory propriety was evaluated by measuring edema development in the Wistar rats paw induced with carrageenan. Treatment of diabetic mice with DHEAM for four weeks managed their high fasting blood glucose levels, improved their overall health, and also revealed an excellent antihyperglycemic activity. Following the anti-inflammatory results, DHEAM exhibited a perfect activity. HPLC results revealed the presence of seven molecules (chlorogenic acid, 3-p-coumaroylquinic acid, gallic acid, ferulic acid, myricetin, quercetin, luteolin). This work indicates that the DHEAM has an important antidiabetic, antihyperglycemic, and anti-inflammatory effect that can be well established as a phytomedicine to treat diabetes. Full article

(This article belongs to the Special Issue Application of Plant Natural Compounds)

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12 pages, 3207 KiB

Open AccessArticle

Systematic Quantification of Cell Confluence in Human Normal Oral Fibroblasts

by Ching-Hsiang Chiu, Jyh-Der Leu, Tzu-Ting Lin, Pin-Hua Su, Wan-Chun Li, Yi-Jang Lee and Da-Chuan Cheng

Appl. Sci. 2020, 10(24), 9146; https://doi.org/10.3390/app10249146 - 21 Dec 2020

Cited by 5 | Viewed by 10170

Abstract

Background: The accurate determination of cell confluence is a critical step for generating reasonable results of designed experiments in cell biological studies. However, the cell confluence of the same culture may be diversely predicted by individual researchers. Herein, we designed a systematic quantification [...] Read more.

Background: The accurate determination of cell confluence is a critical step for generating reasonable results of designed experiments in cell biological studies. However, the cell confluence of the same culture may be diversely predicted by individual researchers. Herein, we designed a systematic quantification scheme implemented on the Matlab platform, the so-called “Confluence-Viewer” program, to assist cell biologists to better determine the cell confluence. Methods: Human normal oral fibroblasts (hOFs) seeded in 10 cm culture dishes were visualized under an inverted microscope for the acquisition of cell images. The images were subjected to the cell segmentation algorithm with top-hat transformation and the Otsu thresholding technique. A regression model was built using a quadratic model and shape-preserving piecewise cubic model. Results: The cell segmentation algorithm generated a regression curve that was highly correlated with the cell confluence determined by experienced researchers. However, the correlation was low when compared to the cell confluence determined by novice students. Interestingly, the cell confluence determined by experienced researchers became more diverse when they checked the same images without a time limitation (up to 1 min). Conclusion: This tool could prevent unnecessary human-made mistakes and meaningless repeats for novice researchers working on cell-based studies in health care or cancer research. Full article

(This article belongs to the Special Issue Image Processing Techniques for Biomedical Applications)

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17 pages, 358 KiB

Open AccessArticle

Metaheuristics and Support Vector Data Description for Fault Detection in Industrial Processes

by Jesús Alejandro Navarro-Acosta, Irma D. García-Calvillo, Vanesa Avalos-Gaytán and Edgar O. Reséndiz-Flores

Appl. Sci. 2020, 10(24), 9145; https://doi.org/10.3390/app10249145 - 21 Dec 2020

Cited by 3 | Viewed by 2149

Abstract

In this study, a system for faults detection using a combination of Support Vector Data Description (SVDD) with metaheuristic algorithms is presented. The presented approach is applied to a real industrial process where the set of measured faults is scarce. The original contribution [...] Read more.

In this study, a system for faults detection using a combination of Support Vector Data Description (SVDD) with metaheuristic algorithms is presented. The presented approach is applied to a real industrial process where the set of measured faults is scarce. The original contribution in this work is the industrial context of application and the comparison of swarm intelligence algorithms to optimize the SVDD hyper-parameters. Four recent metaheuristics are compared hereby to solve the corresponding optimization problem in an efficient manner. These optimization techniques are then implemented for fault detection in a multivariate industrial process with non-balanced data. The obtained numerical results seem to be promising when the considered optimization techniques are combined with SVDD. In particular, the Spotted Hyena algorithm outperforms other metaheuristics reaching values of F1 score near 100% in fault detection. Full article

(This article belongs to the Section Computing and Artificial Intelligence)

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27 pages, 2238 KiB

Open AccessReview

The Beneficial Health Effects of Vegetables and Wild Edible Greens: The Case of the Mediterranean Diet and Its Sustainability

by Elena Chatzopoulou, Márcio Carocho, Francesco Di Gioia and Spyridon A. Petropoulos

Appl. Sci. 2020, 10(24), 9144; https://doi.org/10.3390/app10249144 - 21 Dec 2020

Cited by 36 | Viewed by 7841

Abstract

The Mediterranean diet (MD) concept as currently known describes the dietary patterns that were followed in specific regions of the area in the 1950s and 1960s. The broad recognition of its positive effects on the longevity of Mediterranean populations also led to the [...] Read more.

The Mediterranean diet (MD) concept as currently known describes the dietary patterns that were followed in specific regions of the area in the 1950s and 1960s. The broad recognition of its positive effects on the longevity of Mediterranean populations also led to the adoption of this diet in other regions of the world, and scientific interest focused on revealing its health effects. MD is not only linked with eating specific nutritional food products but also with social, religious, environmental, and cultural aspects, thus representing a healthy lifestyle in general. However, modern lifestyles adhere to less healthy diets, alienating people from their heritage. Therefore, considering the increasing evidence of the beneficial health effects of adherence to the MD and the ongoing transitions in consumers’ behavior, the present review focuses on updating the scientific knowledge regarding this diet and its relevance to agrobiodiversity. In addition, it also considers a sustainable approach for new marketing opportunities and consumer trends of the MD. Full article

(This article belongs to the Special Issue Potential Health Benefits of Fruits and Vegetables)

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32 pages, 4391 KiB

Open AccessReview

Four-Dimensional (Bio-)printing: A Review on Stimuli-Responsive Mechanisms and Their Biomedical Suitability

by Pedro Morouço, Bahareh Azimi, Mario Milazzo, Fatemeh Mokhtari, Cristiana Fernandes, Diana Reis and Serena Danti

Appl. Sci. 2020, 10(24), 9143; https://doi.org/10.3390/app10249143 - 21 Dec 2020

Cited by 32 | Viewed by 4887

Abstract

The applications of tissue engineered constructs have witnessed great advances in the last few years, as advanced fabrication techniques have enabled promising approaches to develop structures and devices for biomedical uses. (Bio-)printing, including both plain material and cell/material printing, offers remarkable advantages and [...] Read more.

The applications of tissue engineered constructs have witnessed great advances in the last few years, as advanced fabrication techniques have enabled promising approaches to develop structures and devices for biomedical uses. (Bio-)printing, including both plain material and cell/material printing, offers remarkable advantages and versatility to produce multilateral and cell-laden tissue constructs; however, it has often revealed to be insufficient to fulfill clinical needs. Indeed, three-dimensional (3D) (bio-)printing does not provide one critical element, fundamental to mimic native live tissues, i.e., the ability to change shape/properties with time to respond to microenvironmental stimuli in a personalized manner. This capability is in charge of the so-called “smart materials”; thus, 3D (bio-)printing these biomaterials is a possible way to reach four-dimensional (4D) (bio-)printing. We present a comprehensive review on stimuli-responsive materials to produce scaffolds and constructs via additive manufacturing techniques, aiming to obtain constructs that closely mimic the dynamics of native tissues. Our work deploys the advantages and drawbacks of the mechanisms used to produce stimuli-responsive constructs, using a classification based on the target stimulus: humidity, temperature, electricity, magnetism, light, pH, among others. A deep understanding of biomaterial properties, the scaffolding technologies, and the implant site microenvironment would help the design of innovative devices suitable and valuable for many biomedical applications. Full article

(This article belongs to the Special Issue Smart Biomaterials for Tissue Regeneration)

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12 pages, 702 KiB

Open AccessArticle

A Large-Deformation Gradient Damage Model for Single Crystals Based on Microdamage Theory

by Ozgur Aslan and Emin Bayraktar

Appl. Sci. 2020, 10(24), 9142; https://doi.org/10.3390/app10249142 - 21 Dec 2020

Cited by 3 | Viewed by 2174

Abstract

This work aims at the unification of the thermodynamically consistent representation of the micromorphic theory and the microdamage approach for the purpose of modeling crack growth and damage regularization in crystalline solids. In contrast to the thermodynamical representation of the microdamage theory, micromorphic [...] Read more.

This work aims at the unification of the thermodynamically consistent representation of the micromorphic theory and the microdamage approach for the purpose of modeling crack growth and damage regularization in crystalline solids. In contrast to the thermodynamical representation of the microdamage theory, micromorphic contribution to flow resistance is defined in a dual fashion as energetic and dissipative in character, in order to bring certain clarity and consistency to the modeling aspects. The approach is further extended for large deformations and numerically implemented in a commercial finite element software. Specific numerical model problems are presented in order to demonstrate the ability of the approach to regularize anisotropic damage fields for large deformations and eliminate mesh dependency. Full article

(This article belongs to the Special Issue Latest Trends in Physics and Engineering Mathematics: Theory and Application)

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28 pages, 902 KiB

Open AccessReview

A Review of Pretreatment Methods to Enhance Solids Reduction during Anaerobic Digestion of Municipal Wastewater Sludges and the Resulting Digester Performance: Implications to Future Urban Biorefineries

by Bimi Shrestha, Rafael Hernandez, Dhan Lord B. Fortela, Wayne Sharp, Andrei Chistoserdov, Daniel Gang, Emmanuel Revellame, William Holmes and Mark E. Zappi

Appl. Sci. 2020, 10(24), 9141; https://doi.org/10.3390/app10249141 - 21 Dec 2020

Cited by 45 | Viewed by 5477

Abstract

The rapid increase in the population is expected to result in the approaching of design capacity for many US wastewater treatment plants (WWTPs) over the next decade. WWTPs treat both municipal and industrial wastewater influents, resulting in the production of biosolids after digestion. [...] Read more.

The rapid increase in the population is expected to result in the approaching of design capacity for many US wastewater treatment plants (WWTPs) over the next decade. WWTPs treat both municipal and industrial wastewater influents, resulting in the production of biosolids after digestion. Biogas, a potential recovered alternative energy source, is also produced as an output from successful anaerobic digestion. More than 7M of dry tons/year of biosolids produced in the US are most often disposed in either landfills or land-applied (~80%). These options are becoming more challenging to implement due to increases in transportation costs and tipping fees, decreases in the availability of landfill/landfarm space, and most importantly, increased regulations. This situation is strongly encouraging WWTPs to find alternatives for the disposal of biosolids. Developing alternative management/disposal options for biosolids are evolving. One of the most attractive alternative option from a sustainability perspective are biorefineries (converts waste to commercial products), which are a fast-growing option given the push toward circular urban source economies (little to no waste generation). Anaerobic digestion has been widely applied in WWTPs to reduce the volume of activated sludge due to its low energy requirements, effective handling of fluctuations due to organic loading rate, relative flexibility with temperature and pH changes, and since biogas is produced that can be transformed into energy. Various pretreatment methods for waste sludges prior to digestion that have been studied to reduce solids production and increase the energetic content of the biogas are presented and discussed. Solids handling and management, which comprises ~60% of the operational cost of a WWTP, is estimated to save more than $100 M annually by achieving at least 20% reduction in the annual production of biosolids within the US. This review incorporates an assessment of various pretreatment methods to optimize the anaerobic digestion of waste sludges with a focus on maximizing both biosolids reduction and biogas quality. Full article

(This article belongs to the Special Issue Water-Energy-Environment Nexus (WEEN-2021))

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16 pages, 2159 KiB

Open AccessArticle

Comparison between Occlusal Errors of Single Posterior Crowns Adjusted Using Patient Specific Motion or Conventional Methods

by Ye-Chan Lee, Chunui Lee, June-Sung Shim, Ji-Man Park, Yooseok Shin, Jong-Eun Kim and Keun-Woo Lee

Appl. Sci. 2020, 10(24), 9140; https://doi.org/10.3390/app10249140 - 21 Dec 2020

Cited by 6 | Viewed by 4911

Abstract

Recently, digital technology has been used in dentistry to enhance accuracy and to reduce operative time. Due to advances in digital technology, the integration of individual mandibular motion into the mapping of the occlusal surface is being attempted. The Patient Specific Motion (PSM) [...] Read more.

Recently, digital technology has been used in dentistry to enhance accuracy and to reduce operative time. Due to advances in digital technology, the integration of individual mandibular motion into the mapping of the occlusal surface is being attempted. The Patient Specific Motion (PSM) is one such method. However, it is not clear whether the occlusal design that is adjusted using PSM could clinically show reduced occlusal error compared to conventional methods based on static occlusion. In this clinical comparative study including fifteen patients with a single posterior zirconia crown treatment, the occlusal surface after a clinical adjustment was compared to no adjustment (NA; design based on static occlusion), PSM (adjusted using PSM), and adjustment using a semi-adjustable articulator (SA) for the assessment of occlusal error. The root mean square (RMS; μm), average deviation value (±AVG; μm), and proportion inside the tolerance (in Tol; %) were calculated using the entire, subdivided occlusal surface and the out of tolerance area. Using a one-way ANOVA, the RMS and +AVG from the out of tolerance area showed a statistical difference between PSM (202.3 ± 39.8 for RMS, 173.1 ± 31.3 for +AVG) and NA (257.0 ± 73.9 for RMS, 210.9 ± 48.6 for +AVG). For the entire and subdivided occlusal surfaces, there were no significant differences. In the color-coded map analysis, PSM demonstrated a reduced occlusal error compared to NA. In conclusion, adjustment occlusal design using PSM is a simple and effective method for reducing occlusal errors that are difficult to identify in a current computer-aided design (CAD) workflow with static occlusion. Full article

(This article belongs to the Special Issue Advances in Dental Materials: A Look inside Digital Workflows)

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17 pages, 493 KiB

Open AccessArticle

Autonomous Underwater Vehicle Localization Using Sound Measurements of Passing Ships

by Jonghoek Kim

Appl. Sci. 2020, 10(24), 9139; https://doi.org/10.3390/app10249139 - 21 Dec 2020

Cited by 3 | Viewed by 2259

Abstract

This paper introduces the localization method of an Autonomous Underwater Vehicle (AUV) in environments (such as harbors or ports) where there can be passing ships near the AUV. It is assumed that the AUV can access the trajectory and approximate source level of [...] Read more.

This paper introduces the localization method of an Autonomous Underwater Vehicle (AUV) in environments (such as harbors or ports) where there can be passing ships near the AUV. It is assumed that the AUV can access the trajectory and approximate source level of a passing ship, while identifying the ship by processing the ship’s sound. This paper considers an AUV which can localize itself by integrating propeller and Inertial Measurement Units (IMU). Suppose that the AUV has been moving in underwater environments for a long time, under the IMU-only localization. To fix long-term drift in the IMU-only localization, we propose that the AUV localization uses sound measurements of passing ships whose trajectories are known a priori. As far as we know, this AUV localization method is novel in using sound measurements of passing ships of which the trajectories are known a priori. The performance of the proposed localization method is verified utilizing MATLAB simulations. The simulation results show significant estimation improvements, compared to IMU-only localization. Moreover, using measurements from multiple ships gives better estimation results, compared to the case where the measurement of a single ship is used. Full article

(This article belongs to the Special Issue Advances in Robot Path Planning)

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11 pages, 23533 KiB

Open AccessArticle

The Problem of Accounting for Heat Exchange between the Flow and the Flow Part Surfaces When Modeling a Viscous Flow in Low-Flow Stages of a Centrifugal Compressor

by Sergey Kartashov, Yuri Kozhukhov, Vycheslav Ivanov, Aleksei Danilishin, Aleksey Yablokov, Aleksey Aksenov, Ivan Yanin and Minh Hai Nguyen

Appl. Sci. 2020, 10(24), 9138; https://doi.org/10.3390/app10249138 - 21 Dec 2020

Viewed by 1907

Abstract

In this paper, we review the problem of accounting for heat exchange between the flow and the flow part surfaces when creating a calculation model for modeling the workflow process of low-flow stages of a centrifugal compressor using computational fluid dynamics (CFD). The [...] Read more.

In this paper, we review the problem of accounting for heat exchange between the flow and the flow part surfaces when creating a calculation model for modeling the workflow process of low-flow stages of a centrifugal compressor using computational fluid dynamics (CFD). The objective selected for this study was a low-flow intermediate type stage with the conditional flow coefficient Փ = 0.008 and the relative width at the impeller exit b₂/D₂ = 0.0133. We show that, in the case of modeling with widespread adiabatic wall simplification, the calculated temperature in the gaps between the impeller and the stator elements is significantly overestimated. Modeling of the working process in the flow part was carried out with a coupled heat exchanger, as well as with simplified accounting for heat transfer by setting the temperatures of the walls. The gas-dynamic characteristics of the stage were compared with the experimental data, the heat transfer influence on the disks friction coefficient was estimated, and the temperature distributions in the gaps between disks and in the flow part of the stage were analyzed. It is shown that the main principle when modeling the flow in low-flow stage is to ensure correct temperature distribution in the gaps. Full article

(This article belongs to the Section Mechanical Engineering)

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21 pages, 2992 KiB

Open AccessArticle

Sampling-Based Motion Planning for Free-Floating Space Robot without Inverse Kinematics

by Hongwen Zhang and Zhanxia Zhu

Appl. Sci. 2020, 10(24), 9137; https://doi.org/10.3390/app10249137 - 21 Dec 2020

Cited by 11 | Viewed by 2596

Abstract

Motion planning is one of the most important technologies for free-floating space robots (FFSRs) to increase operation safety and autonomy in orbit. As a nonholonomic system, a first-order differential relationship exists between the joint angle and the base attitude of the space robot, [...] Read more.

Motion planning is one of the most important technologies for free-floating space robots (FFSRs) to increase operation safety and autonomy in orbit. As a nonholonomic system, a first-order differential relationship exists between the joint angle and the base attitude of the space robot, which makes it pretty challenging to implement the relevant motion planning. Meanwhile, the existing planning framework must solve inverse kinematics for goal configuration and has the limitation that the goal configuration and the initial configuration may not be in the same connected domain. Thus, faced with these questions, this paper investigates a novel motion planning algorithm based on rapidly-exploring random trees (RRTs) for an FFSR from an initial configuration to a goal end-effector (EE) pose. In a motion planning algorithm designed to deal with differential constraints and restrict base attitude disturbance, two control-based local planners are proposed, respectively, for random configuration guiding growth and goal EE pose-guiding growth of the tree. The former can ensure the effective exploration of the configuration space, and the latter can reduce the possibility of occurrence of singularity while ensuring the fast convergence of the algorithm and no violation of the attitude constraints. Compared with the existing works, it does not require the inverse kinematics to be solved while the planning task is completed and the attitude constraint is preserved. The simulation results verify the effectiveness of the algorithm. Full article

(This article belongs to the Special Issue Advances in Robot Path Planning)

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18 pages, 3767 KiB

Open AccessArticle

Analysis of a Three-Level Bidirectional ZVS Resonant Converter

by Bor-Ren Lin and Wei-Po Liu

Appl. Sci. 2020, 10(24), 9136; https://doi.org/10.3390/app10249136 - 21 Dec 2020

Cited by 2 | Viewed by 2506

Abstract

A bidirectional three-level soft switching circuit topology is proposed and implemented for medium voltage applications such as 750 V dc light rail transit, high power converters, or dc microgrid systems. The studied converter is constructed with a three-level diode-clamp circuit topology with the [...] Read more.

A bidirectional three-level soft switching circuit topology is proposed and implemented for medium voltage applications such as 750 V dc light rail transit, high power converters, or dc microgrid systems. The studied converter is constructed with a three-level diode-clamp circuit topology with the advantage of low voltage rating on the high-voltage side and a full-bridge circuit topology with the advantage of a low current rating on the low-voltage side. Under the forward power flow operation, the three-level converter is operated to regulate load voltage. Under the reverse power flow operation, the full-bridge circuit is operated to control high-side voltage. The proposed LLC resonant circuit is adopted to achieve bidirectional power operation and zero-voltage switching (ZVS). The achievability of the studied bidirectional ZVS converter is established from the experiments. Full article

(This article belongs to the Special Issue Resonant Converter in Power Electronics Technology)

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24 pages, 4730 KiB

Open AccessArticle

Feed Rate Variation Strategy for Semi-Conical Shell Workpiece in Ball Head End Milling Process

by Peng Qin, Min Wang and Lele Sun

Appl. Sci. 2020, 10(24), 9135; https://doi.org/10.3390/app10249135 - 21 Dec 2020

Cited by 4 | Viewed by 2532

Abstract

The semi-conical shell workpiece is a special kind of thin-wall part that is commonly used in aerospace and mold industries. Due to the special stiffness distribution and weak rigidity for the area with a large radius, the machining quality of the semi-conical shell [...] Read more.

The semi-conical shell workpiece is a special kind of thin-wall part that is commonly used in aerospace and mold industries. Due to the special stiffness distribution and weak rigidity for the area with a large radius, the machining quality of the semi-conical shell is sensitive to both cutting force and vibration. Conventionally, constant conservative machining parameters are chosen to ensure the workpiece deformation and surface quality, which will reduce the machining efficiency. Based on the cutting force and vibration response simulation of the whole milling process. A feed rate variation strategy is proposed for the ball head end milling process of the semi-conical shell workpiece. The cutting force, dynamic performance and stability prediction are obtained considering the shape and boundary conditions of the workpiece and the contour tool path of the milling process. Variable feed rate is used in the milling simulation to find the harmony between machining quality and efficiency. User-defined vibration amplitude and another user-defined cutting force threshold are used to find the optimal feed rate for each simulation segment. Both continuous and discrete feed rate variation strategies are proposed, and the improved discrete feed rate variation is applied in the milling experiment. About 25% of the consumed time is saved with almost the same machining quality by the experimental results. Full article

(This article belongs to the Special Issue Advanced Manufacturing of Metals)

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14 pages, 2569 KiB

Open AccessArticle

Correlating Natural, Dry, and Saturated Ultrasonic Pulse Velocities with the Mechanical Properties of Rock for Various Sample Diameters

by Hasan Arman and Safwan Paramban

Appl. Sci. 2020, 10(24), 9134; https://doi.org/10.3390/app10249134 - 21 Dec 2020

Cited by 4 | Viewed by 2561

Abstract

P-wave velocity is employed in various fields of engineering to estimate the mechanical properties of rock, as its measurement is reliable, convenient, rapid, nondestructive, and economical. The present study aimed to (i) correlate natural, dry, and saturated P-wave velocities with the mechanical properties [...] Read more.

P-wave velocity is employed in various fields of engineering to estimate the mechanical properties of rock, as its measurement is reliable, convenient, rapid, nondestructive, and economical. The present study aimed to (i) correlate natural, dry, and saturated P-wave velocities with the mechanical properties of limestone and (ii) investigate how the ultrasonic P-wave velocities and mechanical properties of limestone are affected by the sample diameter. This study reveals that P-wave velocities under different environmental conditions can be correlated with the mechanical properties of limestone. Further, the R-value variations with different P-wave velocities for a given sample diameter are (i) negligible in terms of the uniaxial compressive strength (UCS) excluding 63.2 mm, (ii) limited for the diametrical point load index (PLI^D) except for 53.9 mm, (iii) perceived in case of the axial point load index (PLI^A) for 47.7 mm, (iv) observed for the indirect tensile strength (ITS), but generally insignificant, and (v) detected in terms of Schmidt hammer value (SHV) except for 47.7 mm. Full article

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25 pages, 4322 KiB

Open AccessArticle

Geometric Morphometric Data Augmentation Using Generative Computational Learning Algorithms

by Lloyd A. Courtenay and Diego González-Aguilera

Appl. Sci. 2020, 10(24), 9133; https://doi.org/10.3390/app10249133 - 21 Dec 2020

Cited by 8 | Viewed by 3703

Abstract

The fossil record is notorious for being incomplete and distorted, frequently conditioning the type of knowledge that can be extracted from it. In many cases, this often leads to issues when performing complex statistical analyses, such as classification tasks, predictive modelling, and variance [...] Read more.

The fossil record is notorious for being incomplete and distorted, frequently conditioning the type of knowledge that can be extracted from it. In many cases, this often leads to issues when performing complex statistical analyses, such as classification tasks, predictive modelling, and variance analyses, such as those used in Geometric Morphometrics. Here different Generative Adversarial Network architectures are experimented with, testing the effects of sample size and domain dimensionality on model performance. For model evaluation, robust statistical methods were used. Each of the algorithms were observed to produce realistic data. Generative Adversarial Networks using different loss functions produced multidimensional synthetic data significantly equivalent to the original training data. Conditional Generative Adversarial Networks were not as successful. The methods proposed are likely to reduce the impact of sample size and bias on a number of statistical learning applications. While Generative Adversarial Networks are not the solution to all sample-size related issues, combined with other pre-processing steps these limitations may be overcome. This presents a valuable means of augmenting geometric morphometric datasets for greater predictive visualization. Full article

(This article belongs to the Section Computing and Artificial Intelligence)

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17 pages, 1512 KiB

Open AccessArticle

Non-Intrusive Load Disaggregation Based on a Multi-Scale Attention Residual Network

by Liguo Weng, Xiaodong Zhang, Junhao Qian, Min Xia, Yiqing Xu and Ke Wang

Appl. Sci. 2020, 10(24), 9132; https://doi.org/10.3390/app10249132 - 21 Dec 2020

Cited by 3 | Viewed by 2455

Abstract

Non-intrusive load disaggregation (NILD) is of great significance to the development of smart grids. Current energy disaggregation methods extract features from sequences, and this process easily leads to a loss of load features and difficulties in detecting, resulting in a low recognition rate [...] Read more.

Non-intrusive load disaggregation (NILD) is of great significance to the development of smart grids. Current energy disaggregation methods extract features from sequences, and this process easily leads to a loss of load features and difficulties in detecting, resulting in a low recognition rate of low-use electrical appliances. To solve this problem, a non-intrusive sequential energy disaggregation method based on a multi-scale attention residual network is proposed. Multi-scale convolutions are used to learn features, and the attention mechanism is used to enhance the learning ability of load features. The residual learning further improves the performance of the algorithm, avoids network degradation, and improves the precision of load decomposition. The experimental results on two benchmark datasets show that the proposed algorithm has more advantages than the existing algorithms in terms of load disaggregation accuracy and judgments of the on/off state, and the attention mechanism can further improve the disaggregation accuracy of low-frequency electrical appliances. Full article

(This article belongs to the Special Issue Efficiency and Optimization of Buildings Energy Consumption: Volume II)

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10 pages, 221 KiB

Open AccessArticle

Relative Weights of Physical Strength Factors in Sports Events: Focused on Similarity Sports Events Group According to the Sports Physiological View

by Kyoung-Hyun Lee, Jin-Seok Lee, Byung-Chan Lee and Eun-Hyung Cho

Appl. Sci. 2020, 10(24), 9131; https://doi.org/10.3390/app10249131 - 21 Dec 2020

Cited by 5 | Viewed by 2295

Abstract

The purpose of this study was to investigate the relative weights of physical strength factors in sports events. We selected 16,645 people as a sample group who participated in physical fitness measurements through eight sports science centers across the country from 2016 until [...] Read more.

The purpose of this study was to investigate the relative weights of physical strength factors in sports events. We selected 16,645 people as a sample group who participated in physical fitness measurements through eight sports science centers across the country from 2016 until August of 2018, and divided into four sports types depending on the sports physiological view: type A: short-term muscular power and short-term muscular endurance, type B: mid-term muscular power, type C: long-term cardiorespiratory endurance, type D: coordination capability (CC), agility, flexibility, and balance. Categorized the performance level into excellent athletes and non-excellent athletes, and standardized (T-score) the measured value after considering sex, age and sports type group. Used logistic regression analysis for the method of analysis, and calculated the relative weights of physical strength factor with different sports by using Wald value which was calculated from logistic regression analysis. As a result, the relative weights of physical factor in type A were power 30%, muscular power (MP) 18%, CC 16%, agility 11%, flexibility 10%, cardiorespiratory endurance (CE) 1%, and balance 0%. The relative weights of physical factor in type B were muscular endurance (ME) 43%, MP 25%, power 20%, balance 9%, CE 2%, flexibility 1%, agility 0%, and CC 0%. The relative weights of physical factor in type C were ME 41%, CE 37%, power 10%, agility 8%, flexibility 2%, CC 2%, ME 0%, and balance 0%. Need more specific classification standard for type D sports. Hope the results of this study were used to measure physical fitness level and used as baseline data for recruiting future talents. Full article

(This article belongs to the Special Issue Biotechnology and Sports Engineering)

11 pages, 1688 KiB

Open AccessArticle

Evaluation of the Temperature and Time in Centrifugation-Assisted Freeze Concentration

by Tamara Santana, Jorge Moreno, Guillermo Petzold, Roberto Santana and Guido Sáez-Trautmann

Appl. Sci. 2020, 10(24), 9130; https://doi.org/10.3390/app10249130 - 21 Dec 2020

Cited by 6 | Viewed by 3421

Abstract

Centrifugation is a technique applied to assist in the freeze concentration of fruit juices and solutions. The aim of this work was to study the influence of the time–temperature parameters on the centrifugation process as a technique applied to assist in the first [...] Read more.

Centrifugation is a technique applied to assist in the freeze concentration of fruit juices and solutions. The aim of this work was to study the influence of the time–temperature parameters on the centrifugation process as a technique applied to assist in the first cycle of the freeze concentration of blueberry juice. A completely randomized 4 × 3 factorial design was performed using temperature and time as the factors, and the response variables included the percentage of concentrate, efficiency and solutes recovered. The results were evaluated using multiple linear regression, random forest regression, and Gaussian processes. The solid content in the concentrate doubled compared to the initial sample (18 °Brix) and approached 60% in the first cycle of blueberry juice freeze concentration. The combination of factors affected the percentage of the concentrate and solutes recovered, and the optimum of concentration was obtained at 15 °C with a centrifugation time of 20 min. Gaussian processes are suggested as suitable machine learning techniques for modelling the quantitative effect of the relevant factors in the centrifugation process. Full article

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13 pages, 7803 KiB

Open AccessArticle

Estimation of Finite Finger Joint Centers of Rotation Using 3D Hand Skeleton Motions Reconstructed from CT Scans

by Xiaopeng Yang, Zhichan Lim, Hayoung Jung, Younggi Hong, Mengfei Zhang, Dougho Park and Heecheon You

Appl. Sci. 2020, 10(24), 9129; https://doi.org/10.3390/app10249129 - 21 Dec 2020

Cited by 8 | Viewed by 3076

Abstract

The present study proposed a method to estimate the finite finger joint centers of rotation (CoRs) with high accuracy using 3D hand skeleton motions reconstructed from CT scans. Ten hand postures starting from a fully extended posture and ending at a fist posture [...] Read more.

The present study proposed a method to estimate the finite finger joint centers of rotation (CoRs) with high accuracy using 3D hand skeleton motions reconstructed from CT scans. Ten hand postures starting from a fully extended posture and ending at a fist posture with about 10° difference in flexion between the adjacent postures were captured by a CT scanner for 15 male participants, and their 3D hand skeletons were reconstructed using the CT scans. Each bone segment from the full extension posture was registered to the corresponding bone segments of the remaining hand postures. The proximal bone segments of a joint from two postures were aligned to estimate the finite CoR of the joint between the two postures. Centerlines of the distal bone segments of the joint were then identified using the principal component analysis method, and the finite CoR of the joint was determined as the intersection point of the identified centerlines. The proposed method reduced the variation of estimated finite joint CoRs by 16.0% to 67.0% among the finger joints compared to the existing methods. The variation of estimated finite joint CoRs decreased as the rotation angle of the joint increased. The proposed method can be used for the simulation of finger movement with high accuracy. Full article

(This article belongs to the Special Issue Novel Approaches and Applications in Ergonomic Design)

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16 pages, 1472 KiB

Open AccessArticle

Implementation and Evaluation of a Serious Game for Working Memory Enhancement

by Agisilaos Chaldogeridis and Thrasyvoulos Tsiatsos

Appl. Sci. 2020, 10(24), 9128; https://doi.org/10.3390/app10249128 - 21 Dec 2020

Cited by 6 | Viewed by 3166

Abstract

The amount of information which can be stored in the human brain is limited and dependent on memory capacity. Over the last few years there has been a trend in training cognitive skills, not only to prevent cognitive decline, which is inevitable as [...] Read more.

The amount of information which can be stored in the human brain is limited and dependent on memory capacity. Over the last few years there has been a trend in training cognitive skills, not only to prevent cognitive decline, which is inevitable as a person grows older, but also to increase or at least preserve mental abilities that will allow a person to function at a higher cognitive level. Memory is one of those key aspects among cognitive skills that has a significant role in a person’s mental performance. Specifically, focus is given to Working Memory (WM), as evidence has shown that it can be increased by applying targeted interventions. An intervention program like this is the main object of this current paper. Using a Serious Game (SG), we designed and created a video game which targets WM training. Its effectiveness was tested and evaluated through an evaluation process where forty people participated in a seven-week training program. Post-results showed that participants had an increase in their WM performance, especially those who had lower scores at the pre-test, while those with high pre-test scores just preserved their initial status. Additionally, all participants agreed that the game is fun and enjoyable to play and that it helps them to increase WM performance. Full article

(This article belongs to the Special Issue Applications of Cognitive Infocommunications (CogInfoCom))

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20 pages, 9546 KiB

Open AccessArticle

Analysis of a Novel Automatic Control Approach for the Free Forging Hammer

by Xiaopeng Yan and Baijin Chen

Appl. Sci. 2020, 10(24), 9127; https://doi.org/10.3390/app10249127 - 21 Dec 2020

Cited by 4 | Viewed by 3474

Abstract

This paper proposes an electro-hydraulic servo control method and realizes the automatic control and remote control of free forging hammers for the first time. A configuration and control strategy for the program-control free forging hammer are constructed. Based on the configuration, a single-acting [...] Read more.

This paper proposes an electro-hydraulic servo control method and realizes the automatic control and remote control of free forging hammers for the first time. A configuration and control strategy for the program-control free forging hammer are constructed. Based on the configuration, a single-acting differential servo cylinder system is proposed to drive the follow-up spool valve and then control the motion state of the hammerhead. Furthermore, a non-contact measurement method is adopted to detect the real-time position of the hammerhead, and the installation position of the measuring sensor is isolated from the hammer body and foundation, thereby reducing the influence of vibration and impact on the accuracy of the feedback signal and ensuring the successive forming process of the forging hammer. In addition, a blow energy model of the forging hammer processing system is established, and a fuzzy-PID control scheme for the forging hammer is then adopted. Based on the control strategy, the striking accuracy of the proposed automatic forging hammer is significantly improved compared with the traditional forging hammer. Finally, the method is applied to an 8 MN forging hammer, and the results show its better processing performance than traditional hammers in terms of all indices. Full article

(This article belongs to the Special Issue Industry 4.0 Based Smart Manufacturing Systems)

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17 pages, 573 KiB

Open AccessArticle

On Ad Hoc Communication in Industrial Environments

by Christian Sauer, Marco Schmidt and Eike Lyczkowski

Appl. Sci. 2020, 10(24), 9126; https://doi.org/10.3390/app10249126 - 21 Dec 2020

Cited by 6 | Viewed by 2433

Abstract

Wireless communication is becoming vital in the industrial environment. New communication technologies, including ad hoc communication, are researched for this application. A thorough understanding regarding the connection characteristics of industrial networks could benefit this trend. In this work it was possible to record [...] Read more.

Wireless communication is becoming vital in the industrial environment. New communication technologies, including ad hoc communication, are researched for this application. A thorough understanding regarding the connection characteristics of industrial networks could benefit this trend. In this work it was possible to record the time-variant network topology of such a network utilizing a novel method. Using this method and the generated recordings, novel insights into the behavior of industrial ad hoc networks are presented. The recorded time-variant topology, the tools and method of acquisition, and tools for processing and examination are published. This enables researchers and engineers to check their communication technologies in terms of applicability to the industrial use case and record more network topologies in a wide variety of wireless networking scenarios. Full article

(This article belongs to the Special Issue Industry 4.0 Based Smart Manufacturing Systems)

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14 pages, 7428 KiB

Open AccessArticle

Highly Transparent Broadband and Polarization-Insensitive Absorber Based on Metasurface

by Houdi Xiao, Ruiru Qin, Mingyun Lv and Chuanzhi Wang

Appl. Sci. 2020, 10(24), 9125; https://doi.org/10.3390/app10249125 - 21 Dec 2020

Cited by 13 | Viewed by 2627

Abstract

A highly transparent polarization-insensitive metamaterial absorber with wideband microwave absorption is presented. The broadband absorption (6.0~16.7 GHz, absorptance > 85%) is achieved using three patterned resistive metasurfaces. The visible light transmittance of the absorber is as high as 85.7%. The thickness of the [...] Read more.

A highly transparent polarization-insensitive metamaterial absorber with wideband microwave absorption is presented. The broadband absorption (6.0~16.7 GHz, absorptance > 85%) is achieved using three patterned resistive metasurfaces. The visible light transmittance of the absorber is as high as 85.7%. The thickness of the absorber is 4.42 mm, which is only 0.088 times of the upper-cutoff wavelength. A prototype sample is fabricated and measured to demonstrate its excellent performance. The experimental results agree well with the simulation results. In view of its wide band absorption, high transmittance, low profile, polarization insensitivity and wide incidence angle stability, the presented absorber has a wide range of potential applications. Full article

(This article belongs to the Special Issue Functional Metamaterials)

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