Technologies

13 pages, 948 KiB

Open AccessEditor’s ChoiceArticle

Effective Complex Properties for Three-Phase Elastic Fiber-Reinforced Composites with Different Unit Cells

by Federico J. Sabina, Yoanh Espinosa-Almeyda, Raúl Guinovart-Díaz, Reinaldo Rodríguez-Ramos and Héctor Camacho-Montes

Technologies 2021, 9(1), 12; https://doi.org/10.3390/technologies9010012 - 01 Feb 2021

Cited by 2 | Viewed by 2363

Abstract

The development of micromechanical models to predict the effective properties of multiphase composites is important for the design and optimization of new materials, as well as to improve our understanding about the structure–properties relationship. In this work, the two-scale asymptotic homogenization method (AHM) [...] Read more.

The development of micromechanical models to predict the effective properties of multiphase composites is important for the design and optimization of new materials, as well as to improve our understanding about the structure–properties relationship. In this work, the two-scale asymptotic homogenization method (AHM) is implemented to calculate the out-of-plane effective complex-value properties of periodic three-phase elastic fiber-reinforced composites (FRCs) with parallelogram unit cells. Matrix and inclusions materials have complex-valued properties. Closed analytical expressions for the local problems and the out-of-plane shear effective coefficients are given. The solution of the homogenized local problems is found using potential theory. Numerical results are reported and comparisons with data reported in the literature are shown. Good agreements are obtained. In addition, the effects of fiber volume fractions and spatial fiber distribution on the complex effective elastic properties are analyzed. An analysis of the shear effective properties enhancement is also studied for three-phase FRCs. Full article

(This article belongs to the Special Issue Advances in Multiscale and Multifield Solid Material Interfaces)

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18 pages, 6776 KiB

Open AccessEditor’s ChoiceArticle

Intelligent System for Vehicles Number Plate Detection and Recognition Using Convolutional Neural Networks

by Nur-A- Alam, Mominul Ahsan, Md. Abdul Based and Julfikar Haider

Technologies 2021, 9(1), 9; https://doi.org/10.3390/technologies9010009 - 20 Jan 2021

Cited by 37 | Viewed by 11033

Abstract

Vehicles on the road are rising in extensive numbers, particularly in proportion to the industrial revolution and growing economy. The significant use of vehicles has increased the probability of traffic rules violation, causing unexpected accidents, and triggering traffic crimes. In order to overcome [...] Read more.

Vehicles on the road are rising in extensive numbers, particularly in proportion to the industrial revolution and growing economy. The significant use of vehicles has increased the probability of traffic rules violation, causing unexpected accidents, and triggering traffic crimes. In order to overcome these problems, an intelligent traffic monitoring system is required. The intelligent system can play a vital role in traffic control through the number plate detection of the vehicles. In this research work, a system is developed for detecting and recognizing of vehicle number plates using a convolutional neural network (CNN), a deep learning technique. This system comprises of two parts: number plate detection and number plate recognition. In the detection part, a vehicle’s image is captured through a digital camera. Then the system segments the number plate region from the image frame. After extracting the number plate region, a super resolution method is applied to convert the low-resolution image into a high-resolution image. The super resolution technique is used with the convolutional layer of CNN to reconstruct the pixel quality of the input image. Each character of the number plate is segmented using a bounding box method. In the recognition part, features are extracted and classified using the CNN technique. The novelty of this research is the development of an intelligent system employing CNN to recognize number plates, which have less resolution, and are written in the Bengali language. Full article

(This article belongs to the Special Issue Networking, Computing and Immersive Technologies for Smart Environments)

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26 pages, 12035 KiB

Open AccessEditor’s ChoiceReview

A Survey of Robots in Healthcare

by Maria Kyrarini, Fotios Lygerakis, Akilesh Rajavenkatanarayanan, Christos Sevastopoulos, Harish Ram Nambiappan, Kodur Krishna Chaitanya, Ashwin Ramesh Babu, Joanne Mathew and Fillia Makedon

Technologies 2021, 9(1), 8; https://doi.org/10.3390/technologies9010008 - 18 Jan 2021

Cited by 152 | Viewed by 29421

Abstract

In recent years, with the current advancements in Robotics and Artificial Intelligence (AI), robots have the potential to support the field of healthcare. Robotic systems are often introduced in the care of the elderly, children, and persons with disabilities, in hospitals, in rehabilitation [...] Read more.

In recent years, with the current advancements in Robotics and Artificial Intelligence (AI), robots have the potential to support the field of healthcare. Robotic systems are often introduced in the care of the elderly, children, and persons with disabilities, in hospitals, in rehabilitation and walking assistance, and other healthcare situations. In this survey paper, the recent advances in robotic technology applied in the healthcare domain are discussed. The paper provides detailed information about state-of-the-art research in care, hospital, assistive, rehabilitation, and walking assisting robots. The paper also discusses the open challenges healthcare robots face to be integrated into our society. Full article

(This article belongs to the Collection Selected Papers from the PETRA Conference Series)

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11 pages, 1697 KiB

Open AccessEditor’s ChoiceArticle

Radiation Efficiency Enhancement of Graphene Plasmonic Devices Using Matching Circuits

by Stamatios Amanatiadis, Theodoros Zygiridis and Nikolaos Kantartzis

Technologies 2021, 9(1), 4; https://doi.org/10.3390/technologies9010004 - 02 Jan 2021

Cited by 1 | Viewed by 2240

Abstract

In the present work, the radiation properties of a graphene plasmonic patch antenna are investigated and enhanced in terms of efficiency, utilizing circuit-matching techniques. Initially, the reflection coefficient of graphene surface waves due to discontinuities is studied, while the power flow towards free-space [...] Read more.

In the present work, the radiation properties of a graphene plasmonic patch antenna are investigated and enhanced in terms of efficiency, utilizing circuit-matching techniques. Initially, the reflection coefficient of graphene surface waves due to discontinuities is studied, while the power flow towards free-space is numerically extracted. This analysis indicates that the radiated power is increased for higher values of the chemical potential, although the surface wave is weakly confined and prone to degradation due to interference. For this reason, a graphene sheet that supports strongly confined surface waves is terminated via a matching layer, in order to enhance the radiating power. In particular, the matching layer consists of an appropriately selected larger chemical potential value, in order to minimize the reflection coefficient and boost the radiation performance. The numerical investigation of this setup validates the upgraded performance, since the radiating power is significantly increased. Then, a realistic setup that includes a graphene patch antenna is examined numerically, proving the augmentation of the radiation efficiency when the matching layer is utilized. Finally, the latter is designed with a graded increment in the chemical potential, and the computational analysis highlights the significant enhancement of the graphene plasmonic antenna gain towards the desired direction. Consequently, a more reliable framework for wireless communications between plasmonic devices at THz frequencies is established, which corresponds to the practical significance of the proposed methodology for improved radiation efficiency. All numerical results are extracted by means of an efficient modification of the Finite-Difference Time-Domain (FDTD) scheme, which models graphene accurately. Full article

(This article belongs to the Special Issue Reviews and Advances in Internet of Things Technologies)

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19 pages, 852 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Bug Prediction in JavaScript Programs with Hybrid Call-Graph Based Invocation Metrics

by Gábor Antal, Zoltán Tóth, Péter Hegedűs and Rudolf Ferenc

Technologies 2021, 9(1), 3; https://doi.org/10.3390/technologies9010003 - 30 Dec 2020

Cited by 6 | Viewed by 3063

Abstract

Bug prediction aims at finding source code elements in a software system that are likely to contain defects. Being aware of the most error-prone parts of the program, one can efficiently allocate the limited amount of testing and code review resources. Therefore, bug [...] Read more.

Bug prediction aims at finding source code elements in a software system that are likely to contain defects. Being aware of the most error-prone parts of the program, one can efficiently allocate the limited amount of testing and code review resources. Therefore, bug prediction can support software maintenance and evolution to a great extent. In this paper, we propose a function level JavaScript bug prediction model based on static source code metrics with the addition of a hybrid (static and dynamic) code analysis based metric of the number of incoming and outgoing function calls (HNII and HNOI). Our motivation for this is that JavaScript is a highly dynamic scripting language for which static code analysis might be very imprecise; therefore, using a purely static source code features for bug prediction might not be enough. Based on a study where we extracted 824 buggy and 1943 non-buggy functions from the publicly available BugsJS dataset for the ESLint JavaScript project, we can confirm the positive impact of hybrid code metrics on the prediction performance of the ML models. Depending on the ML algorithm, applied hyper-parameters, and target measures we consider, hybrid invocation metrics bring a 2–10% increase in model performances (i.e., precision, recall, F-measure). Interestingly, replacing static NOI and NII metrics with their hybrid counterparts HNOI and HNII in itself improves model performances; however, using them all together yields the best results. Full article

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22 pages, 5657 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Survey on Contrastive Self-Supervised Learning

by Ashish Jaiswal, Ashwin Ramesh Babu, Mohammad Zaki Zadeh, Debapriya Banerjee and Fillia Makedon

Technologies 2021, 9(1), 2; https://doi.org/10.3390/technologies9010002 - 28 Dec 2020

Cited by 598 | Viewed by 44264

Abstract

Self-supervised learning has gained popularity because of its ability to avoid the cost of annotating large-scale datasets. It is capable of adopting self-defined pseudolabels as supervision and use the learned representations for several downstream tasks. Specifically, contrastive learning has recently become a dominant [...] Read more.

Self-supervised learning has gained popularity because of its ability to avoid the cost of annotating large-scale datasets. It is capable of adopting self-defined pseudolabels as supervision and use the learned representations for several downstream tasks. Specifically, contrastive learning has recently become a dominant component in self-supervised learning for computer vision, natural language processing (NLP), and other domains. It aims at embedding augmented versions of the same sample close to each other while trying to push away embeddings from different samples. This paper provides an extensive review of self-supervised methods that follow the contrastive approach. The work explains commonly used pretext tasks in a contrastive learning setup, followed by different architectures that have been proposed so far. Next, we present a performance comparison of different methods for multiple downstream tasks such as image classification, object detection, and action recognition. Finally, we conclude with the limitations of the current methods and the need for further techniques and future directions to make meaningful progress. Full article

(This article belongs to the Collection Selected Papers from the PETRA Conference Series)

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25 pages, 984 KiB

Open AccessEditor’s ChoiceArticle

Tykhonov Well-Posedness and Convergence Results for Contact Problems with Unilateral Constraints

by Mircea Sofonea and Meir Shillor

Technologies 2021, 9(1), 1; https://doi.org/10.3390/technologies9010001 - 24 Dec 2020

Cited by 4 | Viewed by 1783

Abstract

This work presents a unified approach to the analysis of contact problems with various interface laws that model the processes involved in contact between a deformable body and a rigid or reactive foundation. These laws are then used in the formulation of a [...] Read more.

This work presents a unified approach to the analysis of contact problems with various interface laws that model the processes involved in contact between a deformable body and a rigid or reactive foundation. These laws are then used in the formulation of a general static frictional contact problem with unilateral constraints for elastic materials, which is governed by three parameters. A weak formulation of the problem is derived, which is in the form of an elliptic variational inequality, and the Tykhonov well-posedness of the problem is established, under appropriate assumptions on the data and parameters, with respect to a special Tykhonov triple. The proof is based on arguments on coercivity, compactness, and lower-semicontinuity. This abstract result leads to different convergence results, which establish the continuous dependence of the weak solution on the data and the parameters. Moreover, these results elucidate the links among the weak solutions of the different models. Finally, the corresponding mechanical interpretations of the conditions and the results are provided. The novelty in this work is the application of the Tykhonov well-posedness concept, which allows a unified and elegant framework for this class of static contact problems. Full article

(This article belongs to the Special Issue Advances in Multiscale and Multifield Solid Material Interfaces)

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15 pages, 553 KiB

Open AccessEditor’s ChoiceArticle

Modeling Cylindrical Inhomogeneity of Finite Length with Steigmann–Ogden Interface

by Lidiia Nazarenko, Henryk Stolarski and Holm Altenbach

Technologies 2020, 8(4), 78; https://doi.org/10.3390/technologies8040078 - 18 Dec 2020

Cited by 6 | Viewed by 1866

Abstract

A mathematical model employing the concept of energy-equivalent inhomogeneity is applied to analyze short cylindrical fiber composites with interfaces described by the Steigmann–Ogden material surface model. Real inhomogeneity consists of a cylindrical fiber of finite length, and its surface possessing different properties is [...] Read more.

A mathematical model employing the concept of energy-equivalent inhomogeneity is applied to analyze short cylindrical fiber composites with interfaces described by the Steigmann–Ogden material surface model. Real inhomogeneity consists of a cylindrical fiber of finite length, and its surface possessing different properties is replaced by a homogeneous, energy-equivalent cylinder. The properties of the energy-equivalent fiber, incorporating properties of the original fiber and its interface, are determined on the basis of Hill’s energy equivalence principle. Closed-form expressions for components of the stiffness tensor of equivalent fiber have been developed and, in the limit, shown to compare well with the results available in the literature for infinite fibers with the Steigmann–Ogden interface model. Dependence of those components on the radius, length of the cylindrical fiber, and surface parameters is included in these expressions. The effective stiffness tensor of the short-fiber composites with so-defined equivalent cylindrical fibers can be determined by any homogenization method developed without accounting for interface. Full article

(This article belongs to the Special Issue Advances in Multiscale and Multifield Solid Material Interfaces)

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20 pages, 439 KiB

Open AccessEditor’s ChoiceArticle

A Review of Extended Reality (XR) Technologies for Manufacturing Training

by Sanika Doolani, Callen Wessels, Varun Kanal, Christos Sevastopoulos, Ashish Jaiswal, Harish Nambiappan and Fillia Makedon

Technologies 2020, 8(4), 77; https://doi.org/10.3390/technologies8040077 - 10 Dec 2020

Cited by 121 | Viewed by 17176

Abstract

Recently, the use of extended reality (XR) systems has been on the rise, to tackle various domains such as training, education, safety, etc. With the recent advances in augmented reality (AR), virtual reality (VR) and mixed reality (MR) technologies and ease of availability [...] Read more.

Recently, the use of extended reality (XR) systems has been on the rise, to tackle various domains such as training, education, safety, etc. With the recent advances in augmented reality (AR), virtual reality (VR) and mixed reality (MR) technologies and ease of availability of high-end, commercially available hardware, the manufacturing industry has seen a rise in the use of advanced XR technologies to train its workforce. While several research publications exist on applications of XR in manufacturing training, a comprehensive review of recent works and applications is lacking to present a clear progress in using such advance technologies. To this end, we present a review of the current state-of-the-art of use of XR technologies in training personnel in the field of manufacturing. First, we put forth the need of XR in manufacturing. We then present several key application domains where XR is being currently applied, notably in maintenance training and in performing assembly task. We also reviewed the applications of XR in other vocational domains and how they can be leveraged in the manufacturing industry. We finally present some current barriers to XR adoption in manufacturing training and highlight the current limitations that should be considered when looking to develop and apply practical applications of XR. Full article

(This article belongs to the Collection Selected Papers from the PETRA Conference Series)

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22 pages, 573 KiB

Open AccessEditor’s ChoiceArticle

A Machine Learning Based Classification Method for Customer Experience Survey Analysis

by Ioannis Markoulidakis, Ioannis Rallis, Ioannis Georgoulas, George Kopsiaftis, Anastasios Doulamis and Nikolaos Doulamis

Technologies 2020, 8(4), 76; https://doi.org/10.3390/technologies8040076 - 07 Dec 2020

Cited by 8 | Viewed by 6984

Abstract

Customer Experience (CX) is monitored through market research surveys, based on metrics like the Net Promoter Score (NPS) and the customer satisfaction for certain experience attributes (e.g., call center, website, billing, service quality, tariff plan). The objective of companies is to maximize NPS [...] Read more.

Customer Experience (CX) is monitored through market research surveys, based on metrics like the Net Promoter Score (NPS) and the customer satisfaction for certain experience attributes (e.g., call center, website, billing, service quality, tariff plan). The objective of companies is to maximize NPS through the improvement of the most important CX attributes. However, statistical analysis suggests that there is a lack of clear and accurate association between NPS and the CX attributes’ scores. In this paper, we address the aforementioned deficiency using a novel classification approach, which was developed based on logistic regression and tested with several state-of-the-art machine learning (ML) algorithms. The proposed method was applied on an extended data set from the telecommunication sector and the results were quite promising, showing a significant improvement in most statistical metrics. Full article

(This article belongs to the Collection Selected Papers from the PETRA Conference Series)

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13 pages, 299 KiB

Open AccessEditor’s ChoiceArticle

Analysis of the Behavioral Change and Utility Features of Electronic Activity Monitors

by Zakkoyya H. Lewis, Maddison Cannon, Grace Rubio, Maria C. Swartz and Elizabeth J. Lyons

Technologies 2020, 8(4), 75; https://doi.org/10.3390/technologies8040075 - 05 Dec 2020

Cited by 3 | Viewed by 2934

Abstract

The aim of this study was to perform a content analysis of electronic activity monitors that also evaluates utility features, code behavior change techniques included in the monitoring systems, and align the results with intervention functions of the Behaviour Change Wheel program planning [...] Read more.

The aim of this study was to perform a content analysis of electronic activity monitors that also evaluates utility features, code behavior change techniques included in the monitoring systems, and align the results with intervention functions of the Behaviour Change Wheel program planning model to facilitate informed device selection. Devices were coded for the implemented behavior change techniques and device features. Three trained coders each wore a monitor for at least 1 week from December 2019–April 2020. Apple Watch Nike, Fitbit Versa 2, Fitbit Charge 3, Fitbit Ionic—Adidas Edition, Garmin Vivomove HR, Garmin Vivosmart 4, Amazfit Bip, Galaxy Watch Active, and Withings Steel HR were reviewed. The monitors all paired with a phone/tablet, tracked exercise sessions, and were wrist-worn. On average, the monitors implemented 27 behavior change techniques each. Fitbit devices implemented the most behavior change techniques, including techniques related to the intervention functions: education, enablement, environmental restructuring, coercion, incentivization, modeling, and persuasion. Garmin devices implemented the second highest number of behavior change techniques, including techniques related to enablement, environmental restructuring, and training. Researchers can use these results to guide selection of electronic activity monitors based on their research needs. Full article

(This article belongs to the Special Issue Wearable Technologies II)

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12 pages, 7303 KiB

Open AccessEditor’s ChoiceArticle

Comparative Analysis of Real-Time Fall Detection Using Fuzzy Logic Web Services and Machine Learning

by Bhavesh Pandya, Amir Pourabdollah and Ahmad Lotfi

Technologies 2020, 8(4), 74; https://doi.org/10.3390/technologies8040074 - 03 Dec 2020

Cited by 11 | Viewed by 3027

Abstract

Falls are the main cause of susceptibility to severe injuries in many humans, especially for older adults aged 65 and over. Typically, falls are being unnoticed and interpreted as a mere inevitable accident. Various wearable fall warning devices have been created recently for [...] Read more.

Falls are the main cause of susceptibility to severe injuries in many humans, especially for older adults aged 65 and over. Typically, falls are being unnoticed and interpreted as a mere inevitable accident. Various wearable fall warning devices have been created recently for older people. However, most of these devices are dependent on local data processing. Various algorithms are used in wearable sensors to track a real-time fall effectively, which focuses on fall detection via fuzzy-as-a-service based on IEEE 1855–2016, Java Fuzzy Markup Language (FML) and service-oriented architecture. Moreover, several approaches are used to detect a fall using machine learning techniques via human movement positional data to avert any accidents. For fuzzy logic web services, analysis is performed using wearable accelerometer and gyroscope sensors, whereas in machine learning techniques, k-NN, decision tree, random forest and extreme gradient boost are used to differentiate between a fall and non-fall. This study aims to carry out a comparative analysis of real-time fall detection using fuzzy logic web services and machine learning techniques and aims to determine which one is better for real-time fall detection. Research findings exhibit that the proposed fuzzy-as-a-service could easily differentiate between fall and non-fall occurrences in a real-time environment with an accuracy, sensitivity and specificity of 90%, 88.89% and 91.67%, respectively, while the random forest algorithm of machine learning achieved 99.19%, 98.53% and 99.63%, respectively. Full article

(This article belongs to the Collection Selected Papers from the PETRA Conference Series)

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24 pages, 11090 KiB

Open AccessEditor’s ChoiceArticle

Influence of Postprocessing on Wear Resistance of Aerospace Steel Parts Produced by Laser Powder Bed Fusion

by Alexander S. Metel, Sergey N. Grigoriev, Tatiana V. Tarasova, Anastasia A. Filatova, Sergey K. Sundukov, Marina A. Volosova, Anna A. Okunkova, Yury A. Melnik and Pavel A. Podrabinnik

Technologies 2020, 8(4), 73; https://doi.org/10.3390/technologies8040073 - 02 Dec 2020

Cited by 11 | Viewed by 2825

Abstract

The paper is devoted to the research of the effect of ultrasonic postprocessing—specifically, the effects of ultrasonic cavitation-abrasive finishing, ultrasonic plastic deformation, and vibration tumbling on surface quality, wear resistance, and the ability of real aircraft parts with complex geometries and with sizes [...] Read more.

The paper is devoted to the research of the effect of ultrasonic postprocessing—specifically, the effects of ultrasonic cavitation-abrasive finishing, ultrasonic plastic deformation, and vibration tumbling on surface quality, wear resistance, and the ability of real aircraft parts with complex geometries and with sizes less than and more than 100 mm to work in exploitation conditions. The parts were produced by laser powder bed fusion from two types of anticorrosion steels of austenitic and martensitic grades—20Kh13 (DIN 1.4021, X20Cr13, AISI 420) and 12Kh18N9T (DIN 1.4541, X10CrNiTi18-10, AISI 321). The finishing technologies based on mechanical action—plastic deformation, abrasive wear, and complex mechanolysis showed an effect on reducing the submicron surface roughness, removing the trapped powder granules from the manufactured functional surfaces and their wear resistance. The tests were completed by proving resistance of the produced parts to exploitation conditions—vibration fatigue and corrosion in salt fog. The roughness arithmetic mean deviation R_a was improved by 50–52% after cavitation-abrasive finishing, by 28–30% after ultrasonic plastic deformation, and by 65–70% after vibratory tumbling. The effect on wear resistance is correlated with the improved roughness. The effect of used techniques on resistance to abrasive wear was explained and grounded. Full article

(This article belongs to the Special Issue 3D Printing Technologies II)

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17 pages, 1138 KiB

Open AccessEditor’s ChoiceArticle

Deep Learning Based Fall Detection Algorithms for Embedded Systems, Smartwatches, and IoT Devices Using Accelerometers

by Dimitri Kraft, Karthik Srinivasan and Gerald Bieber

Technologies 2020, 8(4), 72; https://doi.org/10.3390/technologies8040072 - 02 Dec 2020

Cited by 22 | Viewed by 5200

Abstract

A fall of an elderly person often leads to serious injuries or even death. Many falls occur in the home environment and remain unrecognized. Therefore, a reliable fall detection is absolutely necessary for a fast help. Wrist-worn accelerometer based fall detection systems are [...] Read more.

A fall of an elderly person often leads to serious injuries or even death. Many falls occur in the home environment and remain unrecognized. Therefore, a reliable fall detection is absolutely necessary for a fast help. Wrist-worn accelerometer based fall detection systems are developed, but the accuracy and precision are not standardized, comparable, or sometimes even known. In this work, we present an overview about existing public databases with sensor based fall datasets and harmonize existing wrist-worn datasets for a broader and robust evaluation. Furthermore, we are analyzing the current possible recognition rate of fall detection using deep learning algorithms for mobile and embedded systems. The presented results and databases can be used for further research and optimizations in order to increase the recognition rate to enhance the independent life of the elderly. Furthermore, we give an outlook for a convenient application and wrist device. Full article

(This article belongs to the Collection Selected Papers from the PETRA Conference Series)

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17 pages, 615 KiB

Open AccessEditor’s ChoiceReview

Review on the Evaluation of the Impacts of Wastewater Disposal in Hydraulic Fracturing Industry in the United States

by Munshi Md. Shafwat Yazdan, Md Tanvir Ahad, Ishrat Jahan and Mozammel Mazumder

Technologies 2020, 8(4), 67; https://doi.org/10.3390/technologies8040067 - 12 Nov 2020

Cited by 30 | Viewed by 4426

Abstract

This paper scrutinized hydraulic fracturing applications mainly in the United States with regard to both groundwater and surface water contamination with the purpose of bringing forth objective analysis of research findings. Results from previous studies are often unconvincing due to the incomplete database [...] Read more.

This paper scrutinized hydraulic fracturing applications mainly in the United States with regard to both groundwater and surface water contamination with the purpose of bringing forth objective analysis of research findings. Results from previous studies are often unconvincing due to the incomplete database of chemical additives; after and before well-founded water samples to define the change in parameters; and specific sources of water pollution in a particular region. Nonetheless, there is a superior chance of both surface and groundwater contamination induced by improper and less monitored wastewater disposal and management practices. This report has documented systematic evidence for total dissolved solids, salinity, and methane contamination regarding drinking water correlated with hydraulic fracturing. Methane concentrations were found on an average rate of 19.2 mg/L, which is 17 times higher than the acceptance rate and the maximum value was recorded as 64.2 mg/L near the active hydraulic fracturing drilling and extraction zones than that of the nonactive sites (1.1 mg/L). The concentration of total dissolved solids (350 g/L) was characterized as a voluminous amount of saline wastewater, which was quite unexpectedly high. The paper concludes with plausible solutions that should be implemented to avoid further contamination. Full article

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12 pages, 3879 KiB

Open AccessEditor’s ChoiceArticle

In-Ear Electrode EEG for Practical SSVEP BCI

by Surej Mouli, Ramaswamy Palaniappan, Emmanuel Molefi and Ian McLoughlin

Technologies 2020, 8(4), 63; https://doi.org/10.3390/technologies8040063 - 05 Nov 2020

Cited by 8 | Viewed by 4014

Abstract

Steady State Visual Evoked Potential (SSVEP) methods for brain–computer interfaces (BCI) are popular due to higher information transfer rate and easier setup with minimal training, compared to alternative methods. With precisely generated visual stimulus frequency, it is possible to translate brain signals into [...] Read more.

Steady State Visual Evoked Potential (SSVEP) methods for brain–computer interfaces (BCI) are popular due to higher information transfer rate and easier setup with minimal training, compared to alternative methods. With precisely generated visual stimulus frequency, it is possible to translate brain signals into external actions or signals. Traditionally, SSVEP data is collected from the occipital region using electrodes with or without gel, normally mounted on a head cap. In this experimental study, we develop an in-ear electrode to collect SSVEP data for four different flicker frequencies and compare against occipital scalp electrode data. Data from five participants demonstrates the feasibility of in-ear electrode based SSVEP, significantly enhancing the practicability of wearable BCI applications. Full article

(This article belongs to the Section Assistive Technologies)

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24 pages, 83021 KiB

Open AccessEditor’s ChoiceArticle

Prototype of a Low-Cost Compact Horticultural Chamber for Indoor Cultivation of Tropical Highland Wetland Flora

by Mateusz Wrazidlo and Anna Bzymek

Technologies 2020, 8(4), 62; https://doi.org/10.3390/technologies8040062 - 03 Nov 2020

Viewed by 4480

Abstract

An environmental chamber is a specialistic device used for testing effects of given controlled conditions on a variety of objects. In case of plant growth chambers, the conditions are controlled usually for plant cultivation and propagation or botanical examination undertaken on living plant [...] Read more.

An environmental chamber is a specialistic device used for testing effects of given controlled conditions on a variety of objects. In case of plant growth chambers, the conditions are controlled usually for plant cultivation and propagation or botanical examination undertaken on living plant material. The aim of the project was to design and build a prototype of a desktop device with a control system capable of being used as a chamber supporting plant cultivation and propagation processes by the means of partial automation of environment control. The conditions controlled in the chamber are based on the environmental requirements of plant genera, such as Heliamphora, Drosera, Orectanthe, Cyrilla, Stegolepis, Maguireothamnus, or Utricularia. These plants occur naturally in the Guiana Highlands region of Venezuela, Brazil, and Guyana, especially around the upper parts of table-shaped mountain massifs called tepuis. The chamber was designed to simulate some of the peculiar natural factors and phenomena occurring in the high-tepui and surrounding mid-elevation wetland habitats, being the most significant for amateur-level plant cultivation, keeping the design as simple and low cost as possible. It was proven on the basis of the results of several tests made during the evaluation phase that the designed prototype of the chamber operates in a satisfying way, providing basic functionality matching the base assumptions. Full article

(This article belongs to the Section Environmental Technology)

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28 pages, 3044 KiB

Open AccessEditor’s ChoiceArticle

Analog Realization of Fractional-Order Skin-Electrode Model for Tetrapolar Bio-Impedance Measurements

by Vassilis Alimisis, Christos Dimas, Georgios Pappas and Paul P. Sotiriadis

Technologies 2020, 8(4), 61; https://doi.org/10.3390/technologies8040061 - 02 Nov 2020

Cited by 18 | Viewed by 6127

Abstract

This work compares two design methodologies, emulating both AgCl electrode and skin tissue Cole models for testing and verification of electrical bio-impedance circuits and systems. The models are based on fractional-order elements, are implemented with active components, and capture bio-impedance behaviors up to [...] Read more.

This work compares two design methodologies, emulating both AgCl electrode and skin tissue Cole models for testing and verification of electrical bio-impedance circuits and systems. The models are based on fractional-order elements, are implemented with active components, and capture bio-impedance behaviors up to 10 kHz. Contrary to passive-elements realizations, both architectures using analog filters coupled with adjustable transconductors offer tunability of the fractional capacitors’ parameters. The main objective is to build a tunable active integrated circuitry block that is able to approximate the models’ behavior and can be utilized as a Subject Under Test (SUT) and electrode equivalent in bio-impedance measurement applications. A tetrapolar impedance setup, typical in bio-impedance measurements, is used to demonstrate the performance and accuracy of the presented architectures via Spectre Monte-Carlo simulation. Circuit and post-layout simulations are carried out in 90-nm CMOS process, using the Cadence IC suite. Full article

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11 pages, 285 KiB

Open AccessEditor’s ChoiceArticle

Asymptotic Justification of Models of Plates Containing Inside Hard Thin Inclusions

by Evgeny Rudoy

Technologies 2020, 8(4), 59; https://doi.org/10.3390/technologies8040059 - 28 Oct 2020

Cited by 12 | Viewed by 1887

Abstract

An equilibrium problem of the Kirchhoff–Love plate containing a nonhomogeneous inclusion is considered. It is assumed that elastic properties of the inclusion depend on a small parameter characterizing the width of the inclusion

ε

as

ε^{N}

with

N < 1

. The [...] Read more.

An equilibrium problem of the Kirchhoff–Love plate containing a nonhomogeneous inclusion is considered. It is assumed that elastic properties of the inclusion depend on a small parameter characterizing the width of the inclusion

ε

as

ε^{N}

with

N < 1

. The passage to the limit as the parameter

ε

tends to zero is justified, and an asymptotic model of a plate containing a thin inhomogeneous hard inclusion is constructed. It is shown that there exists two types of thin inclusions: rigid inclusion (

N < - 1

) and elastic inclusion (

N = - 1

). The inhomogeneity disappears in the case of

N \in (- 1, 1)

. Full article

(This article belongs to the Special Issue Advances in Multiscale and Multifield Solid Material Interfaces)

24 pages, 4718 KiB

Open AccessEditor’s ChoiceArticle

Nonlinear Dynamic Behavior of Porous and Imperfect Bernoulli-Euler Functionally Graded Nanobeams Resting on Winkler Elastic Foundation

by Rosa Penna and Luciano Feo

Technologies 2020, 8(4), 56; https://doi.org/10.3390/technologies8040056 - 20 Oct 2020

Cited by 9 | Viewed by 2305

Abstract

Nonlinear free vibrations of functionally graded porous Bernoulli–Euler nano-beams resting on an elastic foundation through a stress-driven nonlocal elasticity model are studied taking into account von Kármán type nonlinearity and initial geometric imperfection. By using the Galerkin method, the governing equations are reduced [...] Read more.

Nonlinear free vibrations of functionally graded porous Bernoulli–Euler nano-beams resting on an elastic foundation through a stress-driven nonlocal elasticity model are studied taking into account von Kármán type nonlinearity and initial geometric imperfection. By using the Galerkin method, the governing equations are reduced to a nonlinear ordinary differential equation. The closed form analytical solution of the nonlinear natural flexural frequency is then established using the Hamiltonian approach to nonlinear oscillators. Several comparisons with existing models in the literature are performed to validate the accuracy and reliability of the proposed approach. Finally, a numerical investigation is developed in order to analyze the effects of the gradient index coefficient, porosity volume fraction, initial geometric imperfection, and the Winkler elastic foundation coefficient, on the nonlinear flexural vibrations of metal–ceramic FG porous Bernoulli–Euler nano-beams. Full article

(This article belongs to the Section Innovations in Materials Processing)

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13 pages, 5627 KiB

Open AccessEditor’s ChoiceArticle

Microwave Plasma System for Continuous Treatment of Railway Track

by Julian Swan and Marilena Radoiu

Technologies 2020, 8(4), 54; https://doi.org/10.3390/technologies8040054 - 14 Oct 2020

Viewed by 4261

Abstract

Braking conditions are a fundamental issue for the railway and have been a limiting factor in network capacity and timetabling. Leaf fall, especially during the autumn season, creates low-adhesion problems on railways, causing braking problems for trains. To address the requirements of the [...] Read more.

Braking conditions are a fundamental issue for the railway and have been a limiting factor in network capacity and timetabling. Leaf fall, especially during the autumn season, creates low-adhesion problems on railways, causing braking problems for trains. To address the requirements of the novel plasma industrial applications towards environmental applications, this work developed and tested a 2.45 GHz microwave atmospheric pressure plasma system for in situ removal of the third body layer deposited onto the railway so as to improve braking. The plasma reactor consisted of a 15 kW, 2.45 GHz magnetron-based microwave generator and a plasma reactor (dielectric tube placed in a TE01 monomode microwave cavity); the atmospheric plasma ignited and sustained at different power levels (2–15 kW) in different gases (nitrogen, argon) as well as mixtures of these gases with reactive molecules (water, oxygen) was jetted directly onto the railhead as to change the conditions for the wheel–rail interface. This technology is hoped to be a game-changer in enabling predictable and optimized braking on the railway network. Challenges encountered during the demonstration phase are discussed. Subsequent work should validate the results on a working railway line during the autumn season. Full article

(This article belongs to the Section Innovations in Materials Processing)

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15 pages, 3510 KiB

Open AccessEditor’s ChoiceArticle

The Road to Improved Fiber-Reinforced 3D Printing Technology

by S M Fijul Kabir, Kavita Mathur and Abdel-Fattah M. Seyam

Technologies 2020, 8(4), 51; https://doi.org/10.3390/technologies8040051 - 28 Sep 2020

Cited by 36 | Viewed by 7824

Abstract

Three-dimensional printing (3DP) is at the forefront of the disruptive innovations adding a new dimension in the material fabrication process with numerous design flexibilities. Especially, the ability to reinforce the plastic matrix with nanofiber, microfiber, chopped fiber and continuous fiber has put the [...] Read more.

Three-dimensional printing (3DP) is at the forefront of the disruptive innovations adding a new dimension in the material fabrication process with numerous design flexibilities. Especially, the ability to reinforce the plastic matrix with nanofiber, microfiber, chopped fiber and continuous fiber has put the technology beyond imagination in terms of multidimensional applications. In this technical paper, fiber and polymer filaments used by the commercial 3D printers to develop fiber-reinforced composites are characterized to discover the unknown manufacturing specifications such as fiber–polymer distribution and fiber volume fraction that have direct practical implications in determining and tuning composites’ properties and their applications. Additionally, the capabilities and limitations of 3D printing software to process materials and control print parameters in relation to print quality, structural integrity and properties of printed composites are discussed. The work in this paper aims to present constructive evaluation and criticism of the current technology along with its pros and cons in order to guide prospective users and 3D printing equipment manufacturers on improvements, as well as identify the potential avenues of development of the next generation 3D printed fiber-reinforced composites. Full article

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30 pages, 9548 KiB

Open AccessEditor’s ChoiceArticle

Wire Tool Electrode Behavior and Wear under Discharge Pulses

by Sergey N. Grigoriev, Marina A. Volosova, Anna A. Okunkova, Sergey V. Fedorov, Khaled Hamdy, Pavel A. Podrabinnik, Petr M. Pivkin, Mikhail P. Kozochkin and Artur N. Porvatov

Technologies 2020, 8(3), 49; https://doi.org/10.3390/technologies8030049 - 20 Sep 2020

Cited by 19 | Viewed by 3366

Abstract

This work is devoted to researching the tool electrode behavior and wear under discharge pulses at electrical discharge machining. The experiments were conducted on the workpieces of 12Kh18N10T (AISI 321) chrome-nickel anti-corrosion steel and D16 (AA 2024) duralumin by a 0.25-mm-diameter CuZn35 brass [...] Read more.

This work is devoted to researching the tool electrode behavior and wear under discharge pulses at electrical discharge machining. The experiments were conducted on the workpieces of 12Kh18N10T (AISI 321) chrome-nickel anti-corrosion steel and D16 (AA 2024) duralumin by a 0.25-mm-diameter CuZn35 brass tool in a deionized water medium. The developed diagnostic and monitoring mean based on acoustic emission registered the oscillations accompanying machining at 4–8 kHz. The obtained workpiece and non-profiled tool surfaces were investigated by optical and scanning electron microscopy. Calculated volumetric and mass removal rates showed the difference in the character of wear at roughing and finishing. It was shown that interaction between material components in anti-corrosion steel machining had an explosive character between Zn of brass and Ni of steel at a micron level and formed multiple craters of 30–100 µm. The secondary structure and topology of worn tool surfaces were caused by material sublimation, chemical interaction between material components at high heat (10,000 °C), explosive deposition of the secondary structure. Acoustic diagnostics adequately registered the character of interaction. The observed phenomena at the submicron level and microstructure of the obtained surfaces provide grounding on the nature of material interactions and electrical erosion wear fundamentals. Full article

(This article belongs to the Special Issue Reviews and Advances in Materials Processing)

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25 pages, 3356 KiB

Open AccessEditor’s ChoiceReview

Hydrogel-Based Technologies for the Diagnosis of Skin Pathology

by Christian Wiraja, Xiaoyu Ning, Mingyue Cui and Chenjie Xu

Technologies 2020, 8(3), 47; https://doi.org/10.3390/technologies8030047 - 02 Sep 2020

Cited by 8 | Viewed by 5702

Abstract

Hydrogels, swellable hydrophilic polymer networks fabricated through chemical cross-linking or physical entanglement are increasingly utilized in various biomedical applications over the past few decades. Hydrogel-based microparticles, dressings and microneedle patches have been explored to achieve safe, sustained and on-demand therapeutic purposes toward numerous [...] Read more.

Hydrogels, swellable hydrophilic polymer networks fabricated through chemical cross-linking or physical entanglement are increasingly utilized in various biomedical applications over the past few decades. Hydrogel-based microparticles, dressings and microneedle patches have been explored to achieve safe, sustained and on-demand therapeutic purposes toward numerous skin pathologies, through incorporation of stimuli-responsive moieties and therapeutic agents. More recently, these platforms are expanded to fulfill the diagnostic and monitoring role. Herein, the development of hydrogel technology to achieve diagnosis and monitoring of pathological skin conditions are highlighted, with proteins, nucleic acids, metabolites, and reactive species employed as target biomarkers, among others. The scope of this review includes the characteristics of hydrogel materials, its fabrication procedures, examples of diagnostic studies, as well as discussion pertaining clinical translation of hydrogel systems. Full article

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20 pages, 1645 KiB

Open AccessEditor’s ChoiceArticle

Hardware Implementation of a Softmax-Like Function for Deep Learning

by Ioannis Kouretas and Vassilis Paliouras

Technologies 2020, 8(3), 46; https://doi.org/10.3390/technologies8030046 - 28 Aug 2020

Cited by 20 | Viewed by 8950

Abstract

In this paper a simplified hardware implementation of a CNN softmax-like layer is proposed. Initially the softmax activation function is analyzed in terms of required numerical accuracy and certain optimizations are proposed. A proposed adaptable hardware architecture is evaluated in terms of the [...] Read more.

In this paper a simplified hardware implementation of a CNN softmax-like layer is proposed. Initially the softmax activation function is analyzed in terms of required numerical accuracy and certain optimizations are proposed. A proposed adaptable hardware architecture is evaluated in terms of the introduced error due to the proposed softmax-like function. The proposed architecture can be adopted to the accuracy required by the application by retaining or eliminating certain terms of the approximation thus allowing to explore accuracy for complexity trade-offs. Furthermore, the proposed circuits are synthesized in a 90 nm 1.0 V CMOS standard-cell library using Synopsys Design Compiler. Comparisons reveal that significant reduction is achieved in area × delay and power × delay products for certain cases, respectively, over prior art. Area and power savings are achieved with respect to performance and accuracy. Full article

(This article belongs to the Special Issue MOCAST 2019: Modern Circuits and Systems Technologies on Electronics)

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19 pages, 649 KiB

Open AccessEditor’s ChoiceArticle

Perceived Usefulness, Satisfaction, Ease of Use and Potential of a Virtual Companion to Support the Care Provision for Older Adults

by Ana Luísa Jegundo, Carina Dantas, João Quintas, João Dutra, Ana Leonor Almeida, Hilma Caravau, Ana Filipa Rosa, Ana Isabel Martins and Nelson Pacheco Rocha

Technologies 2020, 8(3), 42; https://doi.org/10.3390/technologies8030042 - 25 Jul 2020

Cited by 16 | Viewed by 6163

Abstract

This article reports a study aiming to determine the perceptions of older adults needing formal care about the usefulness, satisfaction, and ease of use of CaMeLi, a virtual companion based on an embodied conversational agent, and the perceptions of formal caregivers about the [...] Read more.

This article reports a study aiming to determine the perceptions of older adults needing formal care about the usefulness, satisfaction, and ease of use of CaMeLi, a virtual companion based on an embodied conversational agent, and the perceptions of formal caregivers about the potential of virtual companions to support care provision. An observational study involving older adults needing formal care was conducted to assess CaMeLi using a multi-method approach (i.e., an auto-reported questionnaire—the Usefulness, Satisfaction, and Ease of use questionnaire; a scale for the usability assessment based on the opinion of observers—the International Classification of Functioning Disability and Health-based Usability Scale; and critical incident registration). Moreover, a focus group was conducted to collect data regarding the perceived utility of virtual companions to support care provision. The observational study was conducted with 46 participants with an average age of 63.6 years, and the results were associated with a high level of usefulness, satisfaction, and ease of use of CaMeLi. Furthermore, the focus group composed of four care providers considered virtual companions a promising solution to support care provision and to prevent loneliness and social isolation. The results of both the observational study and the focus group revealed good perceptions regarding the role of virtual companions to support the care provision for older adults. Full article

(This article belongs to the Section Information and Communication Technologies)

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16 pages, 1215 KiB

Open AccessEditor’s ChoiceArticle

A Space-Time Correlation Model for MRC Receivers in Rayleigh Fading Channels

by Ramiro Sámano-Robles

Technologies 2020, 8(3), 41; https://doi.org/10.3390/technologies8030041 - 22 Jul 2020

Cited by 1 | Viewed by 3452

Abstract

This paper presents a statistical model for maximum ratio combining (MRC) receivers in Rayleigh fading channels enabled with a temporal combining process. This means that the receiver effectively combines spatial and temporal branch components. Therefore, the signals that will be processed by the [...] Read more.

This paper presents a statistical model for maximum ratio combining (MRC) receivers in Rayleigh fading channels enabled with a temporal combining process. This means that the receiver effectively combines spatial and temporal branch components. Therefore, the signals that will be processed by the MRC receiver are collected not only across different antennas (space), but also at different instants of time. This suggests the use of a retransmission, repetition or space-time coding algorithm that forces the receiver to store signals in memory at different instants of time. Eventually, these stored signals are combined after a predefined or dynamically optimized number of time-slots or retransmissions. The model includes temporal correlation features in addition to the space correlation between the signals of the different components or branches of the MRC receiver. The derivation uses a frequency domain approach (using the characteristic function of the random variables) to obtain closed-form expressions of the statistics of the post-processing signal-to-noise ratio (SNR) under the assumption of equivalent correlation in time and equivalent correlation in space. The described methodology paves the way for the reformulation of other statistical functions as a frequency-domain polynomial root analysis problem. This is opposed to the infinite series approach that is used in the conventional methodology using directly the probability density function (PDF). The results suggest that temporal diversity is a good complement to receivers with limited spatial diversity capabilities. It is also shown that this additional operation could be maximized when the temporal diversity is adaptive (i.e., activated by thresholds of SNR), thus leading to a better resource utilization. Full article

(This article belongs to the Special Issue Reviews and Advances in Internet of Things Technologies)

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51 pages, 7503 KiB

Open AccessEditor’s ChoiceArticle

The Requirements for New Tools for Use by Pilots and the Aviation Industry to Manage Risks Pertaining to Work-Related Stress (WRS) and Wellbeing, and the Ensuing Impact on Performance and Safety

by Joan Cahill, Paul Cullen, Sohaib Anwer, Keith Gaynor and Simon Wilson

Technologies 2020, 8(3), 40; https://doi.org/10.3390/technologies8030040 - 06 Jul 2020

Cited by 12 | Viewed by 14887

Abstract

Work is part of our wellbeing and a key driver of a person’s health. Pilots need to be fit for duty and aware of risks that compromise their health/wellbeing. Recent studies suggest that work-related stress (WRS) impacts on pilot health and wellbeing, performance, [...] Read more.

Work is part of our wellbeing and a key driver of a person’s health. Pilots need to be fit for duty and aware of risks that compromise their health/wellbeing. Recent studies suggest that work-related stress (WRS) impacts on pilot health and wellbeing, performance, and flight safety. This paper reports on the advancement of new tools for pilots and airlines to support the management of WRS and wellbeing. This follows from five phases of stakeholder evaluation research and analysis. Existing pre-flight checklists should be extended to enable the crew to evaluate their health and wellbeing. New checklists might be developed for use by pilots while off duty supporting an assessment of (1) their biopsychosocial health status and (2) how they are coping. This involves the advancement of phone apps with different wellness functions. Pending pilot consent, data captured in these tools might be shared in a de-identified format with the pilot’s airline. Existing airline safety management systems (SMS) and flight rostering/planning systems might be augmented to make use of this data from an operational and risk/safety management perspective. Fatigue risk management systems (and by implication airline rostering/flight planning systems) need to be extended to consider the relationship between fatigue risk and the other dimensions of a pilot’s wellbeing. Further, pending permission, pilot data might be shared with airline employee assistance program (EAP) personnel and aeromedical examiners. In addition, new training formats should be devised to support pilot coping skills. The proposed tools can support the management of WRS and wellbeing. In turn, this will support performance and safety. The pilot specific tools will enable the practice of healthy behaviors, which in turn strengthens a pilot’s resistance to stress. Healthy work relates to the creation of positive wellbeing within workplaces and workforces and has significant societal implications. Pilots face many occupational hazards that are part of their jobs. Pilots, the aviation industry, and society should recognize and support the many activities that contribute to positive wellbeing for pilots. Social justice is a basic premise for quality of employment and quality of life. Full article

(This article belongs to the Section Information and Communication Technologies)

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18 pages, 5428 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Wear Resistance and Titanium Adhesion of Cathodic Arc Deposited Multi-Component Coatings for Carbide End Mills at the Trochoidal Milling of Titanium Alloy

by Marina A. Volosova, Sergey V. Fyodorov, Stepan Opleshin and Mikhail Mosyanov

Technologies 2020, 8(3), 38; https://doi.org/10.3390/technologies8030038 - 30 Jun 2020

Cited by 7 | Viewed by 4109

Abstract

The work was devoted to the study of the effectiveness of the application of multi-component coatings, TiN–Al/TiN, TiN–AlTiN/SiN, and CrTiN–AlTiN–AlTiCrN/SiN, obtained by cathodic arc deposition to increase the wear resistance of 6WH10F carbide end mills in trochoidal milling of titanium alloy. The surface [...] Read more.

The work was devoted to the study of the effectiveness of the application of multi-component coatings, TiN–Al/TiN, TiN–AlTiN/SiN, and CrTiN–AlTiN–AlTiCrN/SiN, obtained by cathodic arc deposition to increase the wear resistance of 6WH10F carbide end mills in trochoidal milling of titanium alloy. The surface morphology of the tool with coatings was studied using scanning electron microscopy, and surface roughness texture was estimated. Microhardness and elastic modulus of the coated carbide tool surface layer were determined by nanoindentation. The process of sticking titanium to the working surface of the tool and quantitative evaluation of end mill wear with multi-component coatings at the trochoidal strategy of milling titanium alloy was studied. The CrTiN–AlTiN–AlTiCrN/SiN coating showed the maximum value of the plasticity index at the level of 0.12. The maximum effect of reducing the wear rate was achieved when using a tool with a CrTiN –AlTiN–AlTiCrN/SiN coating when the operating time to failure of end mills was increased by 4.6 times compared to samples without coating, by 1.4 times compared with TiN–Al/TiN coating and 1.15 times compared with TiN–AlTiN/SiN coating. Full article

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14 pages, 1592 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of Epidemic-Based Information Dissemination in a Wireless Network Testbed

by Andreana Stylidou, Alexandros Zervopoulos, Aikaterini Georgia Alvanou, George Koufoudakis, Georgios Tsoumanis and Konstantinos Oikonomou

Technologies 2020, 8(3), 36; https://doi.org/10.3390/technologies8030036 - 28 Jun 2020

Cited by 2 | Viewed by 3270

Abstract

Information dissemination is an integral part of modern networking environments, such as Wireless Sensor Networks (WSNs). Probabilistic flooding, a common epidemic-based approach, is used as an efficient alternative to traditional blind flooding as it minimizes redundant transmissions and energy consumption. It shares some [...] Read more.

Information dissemination is an integral part of modern networking environments, such as Wireless Sensor Networks (WSNs). Probabilistic flooding, a common epidemic-based approach, is used as an efficient alternative to traditional blind flooding as it minimizes redundant transmissions and energy consumption. It shares some similarities with the Susceptible-Infected-Recovered (SIR) epidemic model, in the sense that the dissemination process and the epidemic thresholds, which achieve maximum coverage with the minimum required transmissions, have been found to be common in certain cases. In this paper, some of these similarities between probabilistic flooding and the SIR epidemic model are identified, particularly with respect to the epidemic thresholds. Both of these epidemic algorithms are experimentally evaluated on a university campus testbed, where a low-cost WSN, consisting of 25 nodes, is deployed. Both algorithm implementations are shown to be efficient at covering a large portion of the network’s nodes, with probabilistic flooding behaving largely in accordance with the considered epidemic thresholds. On the other hand, the implementation of the SIR epidemic model behaves quite unexpectedly, as the epidemic thresholds underestimate sufficient network coverage, a fact that can be attributed to implementation limitations. Full article

(This article belongs to the Special Issue Reviews and Advances in Internet of Things Technologies)

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35 pages, 27448 KiB

Open AccessEditor’s ChoiceReview

Unsupervised Domain Adaptation in Semantic Segmentation: A Review

by Marco Toldo, Andrea Maracani, Umberto Michieli and Pietro Zanuttigh

Technologies 2020, 8(2), 35; https://doi.org/10.3390/technologies8020035 - 21 Jun 2020

Cited by 93 | Viewed by 13996

Abstract

The aim of this paper is to give an overview of the recent advancements in the Unsupervised Domain Adaptation (UDA) of deep networks for semantic segmentation. This task is attracting a wide interest since semantic segmentation models require a huge amount of labeled [...] Read more.

The aim of this paper is to give an overview of the recent advancements in the Unsupervised Domain Adaptation (UDA) of deep networks for semantic segmentation. This task is attracting a wide interest since semantic segmentation models require a huge amount of labeled data and the lack of data fitting specific requirements is the main limitation in the deployment of these techniques. This field has been recently explored and has rapidly grown with a large number of ad-hoc approaches. This motivates us to build a comprehensive overview of the proposed methodologies and to provide a clear categorization. In this paper, we start by introducing the problem, its formulation and the various scenarios that can be considered. Then, we introduce the different levels at which adaptation strategies may be applied: namely, at the input (image) level, at the internal features representation and at the output level. Furthermore, we present a detailed overview of the literature in the field, dividing previous methods based on the following (non mutually exclusive) categories: adversarial learning, generative-based, analysis of the classifier discrepancies, self-teaching, entropy minimization, curriculum learning and multi-task learning. Novel research directions are also briefly introduced to give a hint of interesting open problems in the field. Finally, a comparison of the performance of the various methods in the widely used autonomous driving scenario is presented. Full article

(This article belongs to the Section Information and Communication Technologies)

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15 pages, 4125 KiB

Open AccessEditor’s ChoiceArticle

Investigation of Methods to Extract Fetal Electrocardiogram from the Mother’s Abdominal Signal in Practical Scenarios

by Sadaf Sarafan, Tai Le, Amir Mohammad Naderi, Quoc-Dinh Nguyen, Brandon Tiang-Yu Kuo, Tadesse Ghirmai, Huy-Dung Han, Michael P. H. Lau and Hung Cao

Technologies 2020, 8(2), 33; https://doi.org/10.3390/technologies8020033 - 05 Jun 2020

Cited by 21 | Viewed by 5658

Abstract

Monitoring of fetal electrocardiogram (fECG) would provide useful information about fetal wellbeing as well as any abnormal development during pregnancy. Recent advances in flexible electronics and wearable technologies have enabled compact devices to acquire personal physiological signals in the home setting, including those [...] Read more.

Monitoring of fetal electrocardiogram (fECG) would provide useful information about fetal wellbeing as well as any abnormal development during pregnancy. Recent advances in flexible electronics and wearable technologies have enabled compact devices to acquire personal physiological signals in the home setting, including those of expectant mothers. However, the high noise level in the daily life renders long-entrenched challenges to extract fECG from the combined fetal/maternal ECG signal recorded in the abdominal area of the mother. Thus, an efficient fECG extraction scheme is a dire need. In this work, we intensively explored various extraction algorithms, including template subtraction (TS), independent component analysis (ICA), and extended Kalman filter (EKF) using the data from the PhysioNet 2013 Challenge. Furthermore, the modified data with Gaussian and motion noise added, mimicking a practical scenario, were utilized to examine the performance of algorithms. Finally, we combined different algorithms together, yielding promising results, with the best performance in the F1 score of 92.61% achieved by an algorithm combining ICA and TS. With the data modified by adding different types of noise, the combination of ICA–TS–ICA showed the highest F1 score of 85.4%. It should be noted that these combined approaches required higher computational complexity, including execution time and allocated memory compared with other methods. Owing to comprehensive examination through various evaluation metrics in different extraction algorithms, this study provides insights into the implementation and operation of state-of-the-art fetal and maternal monitoring systems in the era of mobile health. Full article

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26 pages, 3694 KiB

Open AccessEditor’s ChoiceReview

Electrical Discharge Machining Non-Conductive Ceramics: Combination of Materials

by Marina A. Volosova, Anna A. Okunkova, Sergey V. Fedorov, Khaled Hamdy and Mariya A. Mikhailova

Technologies 2020, 8(2), 32; https://doi.org/10.3390/technologies8020032 - 28 May 2020

Cited by 25 | Viewed by 6202

Abstract

One of the promising processing methods for non-conductive structural and functional ceramics based on ZrO₂, Al₂O₃, and Si₃N₄ systems is electrical discharge machining with the assistance of an auxiliary electrode that can be presented [...] Read more.

One of the promising processing methods for non-conductive structural and functional ceramics based on ZrO₂, Al₂O₃, and Si₃N₄ systems is electrical discharge machining with the assistance of an auxiliary electrode that can be presented in the form of conductive films with a thickness up to 4–10 µm or nanoparticles - granules, tubes, platelets, multidimensional particles added in the working zone as a free poured powder the proper concentration of which can be provided by ultrasound emission or by dielectric flows or as conductive additives in the structure of nanocomposites. However, the described experimental approaches did not reach the production market and industry. It is related mostly to the chaotic development of the knowledge and non-systematized data in the field when researchers often cannot ground their choice of the material for auxiliary electrodes, assisting powders, or nano additives or they cannot explain the nature of processes that were observed in the working tank during experiments when their results are not correlated to the measured specific electrical conductivity of the electrodes, particles, ceramic workpieces or nanocomposites but depends on something else. The proposed review includes data on the main electrophysical and chemical properties of the components in the presence of heat when the temperature in the interelectrode gap reaches 10,000 °C, and the systematization of data on ceramic pressing methods, including spark plasma sintering, the chemical reactions that occur in the interelectrode gap during sublimation of primary (brass and copper) and auxiliary electrodes made of transition metals Ti, Cr, Co, and carbon, auxiliary electrodes made of metals with low melting point Zn, Ag, Au, Al, assisting powder of oxide ceramics TiO₂, CeO₂, SnO₂, ITO, conductive additives Cu, W, TiC, WC, and components of Al₂O₃ and Zr₂O workpieces in interaction with the dielectric fluid - water and oil/kerosene medium. Full article

(This article belongs to the Special Issue Reviews and Advances in Materials Processing)

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23 pages, 1936 KiB

Open AccessEditor’s ChoiceReview

The Influence of Smart Manufacturing towards Energy Conservation: A Review

by Shane Terry, Hao Lu, Ismail Fidan, Yunbo Zhang, Khalid Tantawi, Terry Guo and Bahram Asiabanpour

Technologies 2020, 8(2), 31; https://doi.org/10.3390/technologies8020031 - 25 May 2020

Cited by 34 | Viewed by 8004

Abstract

Today, the current trends of manufacturing are towards the adaptation and implementation of smart manufacturing, which is a new initiative to turn the traditional factories into profitable innovation facilities. However, the concept and technologies are still in a state of infancy, since many [...] Read more.

Today, the current trends of manufacturing are towards the adaptation and implementation of smart manufacturing, which is a new initiative to turn the traditional factories into profitable innovation facilities. However, the concept and technologies are still in a state of infancy, since many manufacturers around the world are not fully knowledgeable about the benefits of smart manufacturing compared to their current practices. This article reviews several aspects of smart manufacturing and introduces its advantages in terms of energy-saving and production efficiency. This article also points out that some areas need further research so that smart manufacturing can be shaped better. Full article

(This article belongs to the Section Innovations in Materials Processing)

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18 pages, 2379 KiB

Open AccessEditor’s ChoiceArticle

Thermal and Visual Imaging to Assist with Juvenile Idiopathic Arthritis Examination of the Knees

by Harriet Nwaizu, Reza Saatchi, Daniel Philip Hawley and Oliver Ward

Technologies 2020, 8(2), 30; https://doi.org/10.3390/technologies8020030 - 24 May 2020

Cited by 6 | Viewed by 4065

Abstract

Juvenile idiopathic arthritis (JIA) causes inflammation of the joints, and it is frequently associated with their pain and stiffness. Its timely diagnosis is important to avoid its progressive damage to the bones and cartilage. Increases in the joint’s temperature and redness could be [...] Read more.

Juvenile idiopathic arthritis (JIA) causes inflammation of the joints, and it is frequently associated with their pain and stiffness. Its timely diagnosis is important to avoid its progressive damage to the bones and cartilage. Increases in the joint’s temperature and redness could be indicators of active JIA, hence their accurate quantification could assist with diagnosis. Thermal and visual images of the knees in 20 JIA participants (age: mean = 11.2 years, standard deviation = 2.3 years) were studied. The median temperature of knees with active inflammation was 3.198% higher than that of inactive knees. This difference, examined by a Wilcoxon signed-rank test, was statistically significant (p = 0.0078). In six out of the eight participants who had one active inflamed knee, thermal imaging identified the corresponding knee as warmer. In 16 out of 20 participants, the knee identified as warmer by thermal imaging was also identified as having a greater colour change by visual imaging as compared to their respective reference regions. The devised methods could accurately quantify the colour and temperature of the knees. It was concluded that thermal and visual imaging methods can be valuable in examining JIA. Further studies involving a larger number of participants and more detailed explorations would be needed prior to clinical application. Full article

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10 pages, 2229 KiB

Open AccessEditor’s ChoiceArticle

Engineering Micropatterned Surfaces for Controlling the Evaporation Process of Sessile Droplets

by Navid Kashaninejad, Nam-Trung Nguyen and Weng Kong Chan

Technologies 2020, 8(2), 29; https://doi.org/10.3390/technologies8020029 - 19 May 2020

Cited by 4 | Viewed by 3515

Abstract

Controlling the evaporation process of a droplet is of the utmost importance for a number of technologies. Also, along with the advances of microfabrication, micropatterned surfaces have emerged as an important technology platform to tune the wettability and other surface properties of various [...] Read more.

Controlling the evaporation process of a droplet is of the utmost importance for a number of technologies. Also, along with the advances of microfabrication, micropatterned surfaces have emerged as an important technology platform to tune the wettability and other surface properties of various fundamental and applied applications. Among the geometrical parameters of these micropatterns, it is of great interest to investigate whether the arrangement of the patterns would affect the evaporation process of a sessile liquid droplet. To address this question, we fabricated four microhole arrays with different arrangements, quantified by the parameter of “eccentricity”. The results suggested that, compared to smooth substrates, the evaporation mode was not only affected by engineering the microhole arrays, but also by the eccentricity of these micropatterns. The values of contact angle hysteresis (CAH) were used to quantify and test this hypothesis. The CAH could partially explain the different evaporation modes observed on the microhole arrays with zero and non-zero values of eccentricity. That is, on microhole arrays with zero eccentricity, CAH of water droplets was comparatively low (less than 20

°

). Consistently, during the evaporation, around 60% of the life span of the droplet was in the mixed evaporation mode. Increasing the eccentricity of the microhole arrays increases the values of CAH to above 20

°

. Unlike the increasing trend of CAH, the evaporation modes of sessile droplets on the microhole array with non-zero values of eccentricity were almost similar. Over 75% of the life span of droplets on these surfaces was in constant contact line (CCL) mode. Our findings play a significant role in any technology platform containing micropatterned surfaces, where controlling the evaporation mode is desirable. Full article

(This article belongs to the Section Innovations in Materials Processing)

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17 pages, 13338 KiB

Open AccessEditor’s ChoiceArticle

A Zynq-Based Robotic System for Treatment of Contagious Diseases in Hospital Isolated Environment

by Christos Paparizos, Nikolaos Tsafas and Michael Birbas

Technologies 2020, 8(2), 28; https://doi.org/10.3390/technologies8020028 - 15 May 2020

Cited by 3 | Viewed by 3952

Abstract

The rapid evolution of smart assisted living operations in combination with the blooming of commercial robots calls for the use of robotic based systems. Specifically, certain circumstances such as the handling of critical, contagious virus outbreaks like the recent novel Coronavirus epidemic can [...] Read more.

The rapid evolution of smart assisted living operations in combination with the blooming of commercial robots calls for the use of robotic based systems. Specifically, certain circumstances such as the handling of critical, contagious virus outbreaks like the recent novel Coronavirus epidemic can be benefited by an assisting mobile robot system controlled remotely, complementing measures like the isolation of patients from medical stuff. Within this context, the robotic-based solution to be employed needs to be easy to deploy, able to manufacture with low cost, and able to operate with ease by non-trained personnel. Also, to address the needs of existing hospitals, traditional or smart ones, as well as the temporary risk management facilities in, for example, quarantined cities, ease of integration in terms of size and infrastructure requirements is a must. In this work, the design and implementation of a robotic chassis bearing an arm manipulator is presented, addressing all these needs efficiently. Special attention has been given to the ease of teleoperation with minimal need for equipment and expertise, utilizing a Leap Motion virtual reality sensor which outweighs Microsoft’s Kinect capabilities. Furthermore, a reconfigurable hardware and software integrated system has been used to control the communication, algorithm processing and motion control utilizing a Xilinx Zynq system on chip (SoC). Full article

(This article belongs to the Special Issue MOCAST 2019: Modern Circuits and Systems Technologies on Electronics)

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16 pages, 234 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Psychosocial Implications of Large-Scale Implementations of Solar Power in Malaysia

by Ai Ni Teoh, Yun Ii Go and Tze Chuen Yap

Technologies 2020, 8(2), 26; https://doi.org/10.3390/technologies8020026 - 14 May 2020

Cited by 2 | Viewed by 3476

Abstract

The present study aimed to investigate the psychosocial impacts of large-scale solar (LSS) power projects. There were 225 participants (n = 109 women, n = 3 did not indicate gender) participated in our study by completing a series of questionnaires. We found that [...] Read more.

The present study aimed to investigate the psychosocial impacts of large-scale solar (LSS) power projects. There were 225 participants (n = 109 women, n = 3 did not indicate gender) participated in our study by completing a series of questionnaires. We found that participants who lived farther from the LSS power project location and those who viewed the project as being impactful were optimistic about the benefits LSS power projects could bring. Our participants also demonstrated support for renewable energy development in Malaysia. These findings may provide important implications for the implementation and execution of LSS power projects and policies. Full article

(This article belongs to the Section Environmental Technology)

15 pages, 1077 KiB

Open AccessEditor’s ChoiceArticle

Gate Sizing Methodology with a Novel Accurate Metric to Improve Circuit Timing Performance under Process Variations

by Zahira Perez-Rivera, Esteban Tlelo-Cuautle and Victor Champac

Technologies 2020, 8(2), 25; https://doi.org/10.3390/technologies8020025 - 13 May 2020

Cited by 4 | Viewed by 3304

Abstract

The impact of process variations on circuit performance has become more critical with the technological scaling, and the increasing level of integration of integrated circuits. The degradation of the performance of the circuit means economic losses. In this paper, we propose an efficient [...] Read more.

The impact of process variations on circuit performance has become more critical with the technological scaling, and the increasing level of integration of integrated circuits. The degradation of the performance of the circuit means economic losses. In this paper, we propose an efficient statistical gate-sizing methodology for improving circuit speed in the presence of independent intra-die process variations. A path selection method, a heuristic, two coarse selection metrics, and one fine selection metric are part of the new proposed methodology. The fine metric includes essential concepts like the derivative of the standard deviation of delay, a path segment analysis, the criticality, the slack-time, and area. The proposed new methodology is applied to ISCAS Benchmark circuits. The average percentage of optimization in the delay is 12%, the average percentage of optimization in the delay standard deviation is 27.8%, the average percentage in the area increase is less than 5%, and computing time is up to ten times less than using analytical methods like Lagrange Multipliers. Full article

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14 pages, 2932 KiB

Open AccessEditor’s ChoiceArticle

An Interactive Real-Time Cutting Technique for 3D Models in Mixed Reality

by Paolo Caligiana, Alfredo Liverani, Alessandro Ceruti, Gian Maria Santi, Giampiero Donnici and Francesco Osti

Technologies 2020, 8(2), 23; https://doi.org/10.3390/technologies8020023 - 12 May 2020

Cited by 13 | Viewed by 5678

Abstract

This work describes a Mixed Reality application useful to modify and cut virtual objects. A digital simulation of surgical operations is presented. Following this approach, surgeons can test all the designed solutions of the preoperative stage in a Mixed Reality environment. High precision [...] Read more.

This work describes a Mixed Reality application useful to modify and cut virtual objects. A digital simulation of surgical operations is presented. Following this approach, surgeons can test all the designed solutions of the preoperative stage in a Mixed Reality environment. High precision in surgery applications can be achieved thanks to the new methodology. The presented solution is hands free and does not need the use of a mouse or computer’s keyboard: it is based on HoloLens, Leap Motion device and Unity. A new cutting algorithm has been developed in order to handle multiple objects and speed up the cut with complex meshes and preserve geometry quality. A case study presents the cut of several bones in order to simulate surgeon’s operations. A reduction in cut time compared to the original method is noticed, together with a high flexibility of the tool and a good fidelity of the geometry. Moreover, all the object fragments generated from the algorithm are available for manipulation and new cuts. Full article

(This article belongs to the Special Issue Computer Vision and Image Processing Technologies)

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23 pages, 7486 KiB

Open AccessEditor’s ChoiceArticle

Recognition of Holoscopic 3D Video Hand Gesture Using Convolutional Neural Networks

by Norah Alnaim, Maysam Abbod and Rafiq Swash

Technologies 2020, 8(2), 19; https://doi.org/10.3390/technologies8020019 - 15 Apr 2020

Cited by 4 | Viewed by 8699

Abstract

The convolutional neural network (CNN) algorithm is one of the efficient techniques to recognize hand gestures. In human–computer interaction, a human gesture is a non-verbal communication mode, as users communicate with a computer via input devices. In this article, 3D micro hand gesture [...] Read more.

The convolutional neural network (CNN) algorithm is one of the efficient techniques to recognize hand gestures. In human–computer interaction, a human gesture is a non-verbal communication mode, as users communicate with a computer via input devices. In this article, 3D micro hand gesture recognition disparity experiments are proposed using CNN. This study includes twelve 3D micro hand motions recorded for three different subjects. The system is validated by an experiment that is implemented on twenty different subjects of different ages. The results are analysed and evaluated based on execution time, training, testing, sensitivity, specificity, positive and negative predictive value, and likelihood. The CNN training results show an accuracy as high as 100%, which present superior performance in all factors. On the other hand, the validation results average about 99% accuracy. The CNN algorithm has proven to be the most accurate classification tool for micro gesture recognition. Full article

(This article belongs to the Special Issue Computer Vision and Image Processing Technologies)

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13 pages, 2774 KiB

Open AccessEditor’s ChoiceArticle

Energy Conservation with Open Source Ad Blockers

by Joshua M. Pearce

Technologies 2020, 8(2), 18; https://doi.org/10.3390/technologies8020018 - 30 Mar 2020

Cited by 2 | Viewed by 50249

Abstract

Internet-related electricity consumption is rising rapidly as global Internet users spend more than 6.5 h per day online. Open source ad blockers have the potential to reduce the time and thus electricity spent using computers by eliminating ads during Internet browsing and video [...] Read more.

Internet-related electricity consumption is rising rapidly as global Internet users spend more than 6.5 h per day online. Open source ad blockers have the potential to reduce the time and thus electricity spent using computers by eliminating ads during Internet browsing and video streaming. In this study, three open source ad blockers are tested against a no-ad blocker control. Page load time is recorded for browsing a representative selection of the globally most-accessed websites, and the time spent watching ads on videos is quantified for both trending and non-trending content. The results show that page load time dropped 11% with AdBlock+, 22.2% with Privacy Badger, and 28.5% with uBlock Origin. Thus, uBlock Origin has the potential to save the average global Internet user more than 100 h annually. The energy conserved if everyone in the United States used the open source ad blocker would save over 36 Americans lives per year if it were to offset coal-fired electricity generated-based pollution. In the United States, if all Internet users enabled Privacy Badger on their computers, Americans would save more than $91 million annually. Globally, uBlock Origin could save consumers more than $1.8 billion/year. Open source ad blockers are a potentially effective technology for energy conservation. Full article

(This article belongs to the Section Information and Communication Technologies)

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21 pages, 14268 KiB

Open AccessEditor’s ChoiceArticle

ExerTrack—Towards Smart Surfaces to Track Exercises

by Biying Fu, Lennart Jarms, Florian Kirchbuchner and Arjan Kuijper

Technologies 2020, 8(1), 17; https://doi.org/10.3390/technologies8010017 - 17 Mar 2020

Cited by 7 | Viewed by 4819

Abstract

The concept of the quantified self has gained popularity in recent years with the hype of miniaturized gadgets to monitor vital fitness levels. Smartwatches or smartphone apps and other fitness trackers are overwhelming the market. Most aerobic exercises such as walking, running, or [...] Read more.

The concept of the quantified self has gained popularity in recent years with the hype of miniaturized gadgets to monitor vital fitness levels. Smartwatches or smartphone apps and other fitness trackers are overwhelming the market. Most aerobic exercises such as walking, running, or cycling can be accurately recognized using wearable devices. However whole-body exercises such as push-ups, bridges, and sit-ups are performed on the ground and thus cannot be precisely recognized by wearing only one accelerometer. Thus, a floor-based approach is preferred for recognizing whole-body activities. Computer vision techniques on image data also report high recognition accuracy; however, the presence of a camera tends to raise privacy issues in public areas. Therefore, we focus on combining the advantages of ubiquitous proximity-sensing with non-optical sensors to preserve privacy in public areas and maintain low computation cost with a sparse sensor implementation. Our solution is the ExerTrack, an off-the-shelf sports mat equipped with eight sparsely distributed capacitive proximity sensors to recognize eight whole-body fitness exercises with a user-independent recognition accuracy of 93.5% and a user-dependent recognition accuracy of 95.1% based on a test study with 9 participants each performing 2 full sessions. We adopt a template-based approach to count repetitions and reach a user-independent counting accuracy of 93.6%. The final model can run on a Raspberry Pi 3 in real time. This work includes data-processing of our proposed system and model selection to improve the recognition accuracy and data augmentation technique to regularize the network. Full article

(This article belongs to the Collection Selected Papers from the PETRA Conference Series)

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13 pages, 2599 KiB

Open AccessEditor’s ChoiceArticle

A New Simplified Model and Parameter Estimations for a HfO₂-Based Memristor †

by Valeri Mladenov

Technologies 2020, 8(1), 16; https://doi.org/10.3390/technologies8010016 - 07 Mar 2020

Cited by 2 | Viewed by 3814

Abstract

The purpose of this paper was to propose a complete analysis and parameter estimations of a new simplified and highly nonlinear hafnium dioxide memristor model that is appropriate for high-frequency signals. For the simulations; a nonlinear window function previously offered by the author [...] Read more.

The purpose of this paper was to propose a complete analysis and parameter estimations of a new simplified and highly nonlinear hafnium dioxide memristor model that is appropriate for high-frequency signals. For the simulations; a nonlinear window function previously offered by the author together with a highly nonlinear memristor model was used. This model was tuned according to an experimentally recorded current–voltage relationship of a HfO₂ memristor. This study offered an estimation of the optimal model parameters using a least squares algorithm in SIMULINK and a methodology for adjusting the model by varying its parameters overbroad ranges. The optimal values of the memristor model parameters were obtained after minimizing the error between the experimental and simulated current–voltage characteristics. A comparison of the obtained errors between the simulated and experimental current–voltage relationships was made. The error derived by the optimization algorithm was a little bit lower than that obtained by the used methodology. To avoid convergence problems; the step function in the considered model was replaced by a differentiable tangent hyperbolic function. A PSpice library model of the HfO₂ memristor based on its mathematical model was created. The considered model was successfully applied and tested in a multilayer memristor neural network with bridge memristor–resistor synapses Full article

(This article belongs to the Special Issue MOCAST 2019: Modern Circuits and Systems Technologies on Electronics)

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14 pages, 829 KiB

Open AccessEditor’s ChoiceArticle

High Throughput Implementation of the Keccak Hash Function Using the Nios-II Processor

by Argyrios Sideris, Theodora Sanida and Minas Dasygenis

Technologies 2020, 8(1), 15; https://doi.org/10.3390/technologies8010015 - 10 Feb 2020

Cited by 15 | Viewed by 5678

Abstract

Presently, cryptographic hash functions play a critical role in many applications, such as digital signature systems, security communications, protocols, and network security infrastructures. The new standard cryptographic hash function is Secure Hash Algorithm 3 (SHA-3), which is not vulnerable to attacks. The Keccak [...] Read more.

Presently, cryptographic hash functions play a critical role in many applications, such as digital signature systems, security communications, protocols, and network security infrastructures. The new standard cryptographic hash function is Secure Hash Algorithm 3 (SHA-3), which is not vulnerable to attacks. The Keccak algorithm is the winner of the NIST competition for the adoption of the new standard SHA-3 hash algorithm. In this work, we present hardware throughput optimization techniques for the SHA-3 algorithm using the Very High Speed Integrated Circuit Hardware Description Language (VHDL) programming language for all output lengths in the Keccak hash function (224, 256, 384 and 512). Our experiments were performed with the Nios II processor on the FPGA Arria 10 GX (10AX115N2P45E1SG). We applied two architectures, one without custom instruction and one with floating point hardware 2. Finally, we compare the results with other existing similar designs and found that the proposed design with floating point 2 optimizes throughput (Gbps) compared to existing FPGA implementations. Full article

(This article belongs to the Special Issue MOCAST 2019: Modern Circuits and Systems Technologies on Electronics)

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11 pages, 3355 KiB

Open AccessEditor’s ChoiceArticle

Demonstration of Reconfigurable BPFs with Wide Tuning Bandwidth Range Using 3λ/4 Open- and λ/2 Short- Ended Stubs

by Salman Arain, Abdul Quddious, Symeon Nikolaou and Photos Vryonides

Technologies 2020, 8(1), 14; https://doi.org/10.3390/technologies8010014 - 03 Feb 2020

Cited by 1 | Viewed by 3488

Abstract

In this paper, two implementations of reconfigurable bandwidth bandpass filters (BPFs) are demonstrated both operating at a fixed center frequency of 2.4 GHz. The proposed reconfigurable bandwidth filters are based on a square ring resonator loaded with λ_g/4 open-ended stubs that [...] Read more.

In this paper, two implementations of reconfigurable bandwidth bandpass filters (BPFs) are demonstrated both operating at a fixed center frequency of 2.4 GHz. The proposed reconfigurable bandwidth filters are based on a square ring resonator loaded with λ_g/4 open-ended stubs that are permanently connected to the ring and converted to either 3λ_g/4 open-ended stubs or λ_g/2 short-ended stubs by means of positive-intrinsic-negative(PIN) diodes to implement two reconfigurable bandwidth states for each case. Due to the symmetrical nature of the design, even- and odd-mode analysis is used to derive the closed-form to describe the reconfigurable filters’ behavior. The switching between narrowband and wideband is achieved using PIN diodes. In the first implementation (λ_g/4 open-ended stubs to 3λ_g/4 open-ended stubs), a reconfigurable bandwidth bandpass filter is proposed where additional out-of-band transmission zeros are generated by integrating a λ_g/2 open-ended stub at the input port. In the second implementation (λ_g/4 open-ended stubs to λ_g/2 short-ended stubs), further improvement in the upper stopband is achieved by utilizing a pair of parallel coupled lines (PCLs) as feeding lines and a pair of λ_g/4 high impedance short-ended stubs implemented at the input and output ports. To verify the validity of the simulated results, the prototypes of the proposed reconfigurable filters were fabricated. For the first case, measured insertion loss is less than 1.8 dB with a switchable 3-dB fractional bandwidth (FBW) range from 28% to 54%. The measured results for the second case exhibit a low insertion loss of less than 1 dB and a 3-dB fractional bandwidth that can be switched from 34% to 75%, while the center frequency is kept constant at 2.4 GHz in both cases. Full article

(This article belongs to the Special Issue MOCAST 2019: Modern Circuits and Systems Technologies on Communications)

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18 pages, 1605 KiB

Open AccessEditor’s ChoiceArticle

A Parametric EIT System Spice Simulation with Phantom Equivalent Circuits

by Christos Dimas, Nikolaos Uzunoglu and Paul Peter Sotiriadis

Technologies 2020, 8(1), 13; https://doi.org/10.3390/technologies8010013 - 01 Feb 2020

Cited by 15 | Viewed by 6401

Abstract

In this paper a number of LT Spice simulations have been carried out on an Electrical Impedance Tomography (EIT) system, which includes the whole analog and digital circuitry as well as the subject to be examined (phantom model). The aim of this study [...] Read more.

In this paper a number of LT Spice simulations have been carried out on an Electrical Impedance Tomography (EIT) system, which includes the whole analog and digital circuitry as well as the subject to be examined (phantom model). The aim of this study is to show how the analog and digital parts, the electrodes and the subject’s physical properties may impact the measurements and the quality of the reconstructed image. This could provide a useful tool for designing an EIT system. Special attention has been given to the current source’s output impedance and swing, to the noise produced by the circuits and to the Analog to Digital Converters (ADCs) resolution and sampling rate. Furthermore, some 3D phantom subjects have been modeled and simulated as equivalent circuits, merged with the EIT simulated hardware, in order to observe how changes on their properties interact with the whole circuitry and affect the final result. Observations show that mirrored current sources with

z_{o u t}

> 350 k

Ω

and sufficiently high ADC acquisition sampling rate (

f_{s a m p l e} \geq 16 f_{i n}

) can result to accurate impedance measurements and therefore quality image reconstruction within a frequency span of at least 10 to 100 kHz. Moreover, possible hardware failures (electrode disconnections and imbalanced contact impedances) can be detected with a simple examination of the first extracted image and measurement set, so that by direct modification of the reconstruction process, a corrected result can be obtained. Full article

(This article belongs to the Special Issue MOCAST 2019: Modern Circuits and Systems Technologies on Electronics)

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11 pages, 1399 KiB

Open AccessEditor’s ChoiceArticle

Accelerometer and Magnetometer Joint Calibration and Axes Alignment

by Konstantinos Papafotis and Paul P. Sotiriadis

Technologies 2020, 8(1), 11; https://doi.org/10.3390/technologies8010011 - 23 Jan 2020

Cited by 10 | Viewed by 4779

Abstract

In this work, we propose an algorithm for joint calibration and axes alignment of a 3-axis accelerometer and a 3-axis magnetometer. The proposed algorithm applies when the two sensors are fixed on the same rigid platform. It achieves accurate calibration without requiring any [...] Read more.

In this work, we propose an algorithm for joint calibration and axes alignment of a 3-axis accelerometer and a 3-axis magnetometer. The proposed algorithm applies when the two sensors are fixed on the same rigid platform. It achieves accurate calibration without requiring any external piece of equipment like a turntable for the accelerometer or Gauss magnetic chamber and Maxwell coils setup for the magnetometer. The efficiency and accuracy of the proposed algorithm are evaluated using experimental data. Full article

(This article belongs to the Special Issue MOCAST 2019: Modern Circuits and Systems Technologies on Electronics)

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18 pages, 5650 KiB

Open AccessEditor’s ChoiceArticle

Engineering Tests to Evaluate the Feasibility of an Emerging Solar Pavement Technology for Public Roads and Highways

by Ronald A. Coutu, Jr., David Newman, Mohiuddin Munna, Joseph H. Tschida and Scott Brusaw

Technologies 2020, 8(1), 9; https://doi.org/10.3390/technologies8010009 - 21 Jan 2020

Cited by 18 | Viewed by 13304

Abstract

Concrete and asphalt are the primary materials used to construct roadways for motor vehicles, paths for pedestrians and bicyclists, and runways for aircraft. Solar Roadways^®, Inc. (SR) proposed a novel solar pavement technology (i.e., solar road panels (SRP)) as an alternative [...] Read more.

Concrete and asphalt are the primary materials used to construct roadways for motor vehicles, paths for pedestrians and bicyclists, and runways for aircraft. Solar Roadways^®, Inc. (SR) proposed a novel solar pavement technology (i.e., solar road panels (SRP)) as an alternative material and energy source. SR performed load, traction, and impact testing to use SRPs in non-critical applications like parking lots. To use SRP in public roads, engineering tests including freeze/thaw, moisture absorption, heavy vehicle, and shear testing were accomplished on “SR3” prototypes. Testing was performed at Marquette University in the Engineering Materials and Structural Testing Laboratory and the SR Pilot Project area. Moisture absorption and freeze/thaw tests showed “SR3” resistant to extreme weather and moisture environments. Heavy vehicle testing revealed no physical damage to the “SR3” after approximately 989,457 equivalent single axle loads were continuously rolled over a prototype pavement. Shear testing was conducted to investigate “SR3” laminate structure properties. In all cases, electrical failure was defined when “SR3” photovoltaic voltage dropped to zero volts. The maximum shear stress and applied torque for “SR3”’ (S/N’s Paver 1, 002B, 007C, and 004B) were 1756 kPa, 1835 kPa, 1643 kPa, 2023 kPa; and 121.2 kN·m, 131.3 kN·m, 117.6 kN·m, 144.8 kN·m, respectively. In addition, the “SR3” “heartbeat” light emitting diode (LED) remained operational (i.e., indicates computer bus traffic) in all phases of shear testing. Overall, the results show “SR3” prototypes to be robust, resilient, and functional when subjected to “real-world” test conditions. Full article

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15 pages, 936 KiB

Open AccessEditor’s ChoiceArticle

A TensorFlow Extension Framework for Optimized Generation of Hardware CNN Inference Engines

by Vasileios Leon, Spyridon Mouselinos, Konstantina Koliogeorgi, Sotirios Xydis, Dimitrios Soudris and Kiamal Pekmestzi

Technologies 2020, 8(1), 6; https://doi.org/10.3390/technologies8010006 - 13 Jan 2020

Cited by 6 | Viewed by 7175

Abstract

The workloads of Convolutional Neural Networks (CNNs) exhibit a streaming nature that makes them attractive for reconfigurable architectures such as the Field-Programmable Gate Arrays (FPGAs), while their increased need for low-power and speed has established Application-Specific Integrated Circuit (ASIC)-based accelerators as alternative efficient [...] Read more.

The workloads of Convolutional Neural Networks (CNNs) exhibit a streaming nature that makes them attractive for reconfigurable architectures such as the Field-Programmable Gate Arrays (FPGAs), while their increased need for low-power and speed has established Application-Specific Integrated Circuit (ASIC)-based accelerators as alternative efficient solutions. During the last five years, the development of Hardware Description Language (HDL)-based CNN accelerators, either for FPGA or ASIC, has seen huge academic interest due to their high-performance and room for optimizations. Towards this direction, we propose a library-based framework, which extends TensorFlow, the well-established machine learning framework, and automatically generates high-throughput CNN inference engines for FPGAs and ASICs. The framework allows software developers to exploit the benefits of FPGA/ASIC acceleration without requiring any expertise on HDL development and low-level design. Moreover, it provides a set of optimization knobs concerning the model architecture and the inference engine generation, allowing the developer to tune the accelerator according to the requirements of the respective use case. Our framework is evaluated by optimizing the LeNet CNN model on the MNIST dataset, and implementing FPGA- and ASIC-based accelerators using the generated inference engine. The optimal FPGA-based accelerator on Zynq-7000 delivers 93% less memory footprint and 54% less Look-Up Table (LUT) utilization, and up to 10× speedup on the inference execution vs. different Graphics Processing Unit (GPU) and Central Processing Unit (CPU) implementations of the same model, in exchange for a negligible accuracy loss, i.e., 0.89%. For the same accuracy drop, the 45 nm standard-cell-based ASIC accelerator provides an implementation which operates at 520 MHz and occupies an area of 0.059 mm

^{2}

, while the power consumption is ∼7.5 mW. Full article

(This article belongs to the Special Issue MOCAST 2019: Modern Circuits and Systems Technologies on Electronics)

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