Technologies

15 pages, 869 KiB

Open AccessEditor’s ChoiceArticle

SET Pulse Characterization and SER Estimation in Combinational Logic with Placement and Multiple Transient Faults Considerations

by Georgios Ioannis Paliaroutis, Pelopidas Tsoumanis, Nestor Evmorfopoulos, George Dimitriou and Georgios I. Stamoulis

Technologies 2020, 8(1), 5; https://doi.org/10.3390/technologies8010005 - 10 Jan 2020

Cited by 4 | Viewed by 3944

Abstract

Integrated circuit susceptibility to radiation-induced faults remains a major reliability concern. The continuous downscaling of device feature size and the reduction in supply voltage in CMOS technology tend to worsen the problem. Thus, the evaluation of Soft Error Rate (SER) in the presence [...] Read more.

Integrated circuit susceptibility to radiation-induced faults remains a major reliability concern. The continuous downscaling of device feature size and the reduction in supply voltage in CMOS technology tend to worsen the problem. Thus, the evaluation of Soft Error Rate (SER) in the presence of multiple transient faults is necessary, since it remains an open research field. In this work, a Monte-Carlo simulation-based methodology is presented taking into consideration the masking mechanisms and placement information. The proposed SER estimation tool exploits the results of a Single Event Transient (SET) pulse characterization process with HSPICE to obtain an accurate assessment of circuit vulnerability to radiation. A new metric, called Glitch Latching Probability, which represents the impact of the masking effects on a SET, is introduced to identify gate sensitivity and, finally, experimental results on a set of ISCAS’ 89 benchmarks are presented. Full article

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

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22 pages, 9745 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Integrating Animated Computational Fluid Dynamics into Mixed Reality for Building-Renovation Design

by Yuehan Zhu, Tomohiro Fukuda and Nobuyoshi Yabuki

Technologies 2020, 8(1), 4; https://doi.org/10.3390/technologies8010004 - 29 Dec 2019

Cited by 17 | Viewed by 8115

Abstract

In advanced society, the existing building stock has a high demand for stock renovation, which gives existing buildings new lives, rather than building new ones. During the renovation process, it is necessary to simultaneously achieve architectural, facilities, structural, and environmental design in order [...] Read more.

In advanced society, the existing building stock has a high demand for stock renovation, which gives existing buildings new lives, rather than building new ones. During the renovation process, it is necessary to simultaneously achieve architectural, facilities, structural, and environmental design in order to accomplish a healthy, comfortable, and energy-saving indoor environment, prevent delays in problem-solving, and achieve a timely feedback process. This study tackled the development of an integrated system for stock renovation by considering computational fluid dynamics (CFD) and mixed reality (MR) in order to allow the simultaneous design of a building plan and thermal environment. The CFD analysis enables simulation of the indoor thermal environment, including the entire thermal change process. The MR system, which can be operated by voice command and operated on head-mounted display (HMD), enables intuitive visualization of the thermal change process and, in a very efficient manner, shows how different renovation projects perform for various stakeholders. A prototype system is developed with Unity3D engine and HoloLens HMD. In the integrated system, a new CFD visualization method generating 3D CFD animation sequence for the MR system is proposed that allows stakeholders to consider the entirety of changes in the thermal environment. Full article

(This article belongs to the Special Issue Computer-Aided Architectural Design)

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12 pages, 1270 KiB

Open AccessEditor’s ChoiceArticle

Time Jitter, Turbulence and Chromatic Dispersion in Underwater Optical Wireless Links

by George D. Roumelas, Hector E. Nistazakis, Argyris N. Stassinakis, George K. Varotsos, Andreas D. Tsigopoulos and George S. Tombras

Technologies 2020, 8(1), 3; https://doi.org/10.3390/technologies8010003 - 22 Dec 2019

Cited by 9 | Viewed by 4648

Abstract

The performance of an underwater optical wireless communication link is investigated by taking into account—for the first time and to the best of our knowledge—the simultaneous influence of the chromatic dispersion, the time jitter and the turbulence effects, by assuming chirped longitudinal Gaussian [...] Read more.

The performance of an underwater optical wireless communication link is investigated by taking into account—for the first time and to the best of our knowledge—the simultaneous influence of the chromatic dispersion, the time jitter and the turbulence effects, by assuming chirped longitudinal Gaussian pulse propagation as information carriers. The estimation procedure is presented and a novel probability density function is extracted in order to describe the irradiance fluctuations at the receiver side. Furthermore, the availability of the link is investigated by means of its probability of fade and various numerical results are presented using typical parameters for the underwater optical wireless communication systems. Full article

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

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9 pages, 1734 KiB

Open AccessEditor’s ChoiceCommunication

Needleless Electrospinning of a Chitosan Lactate Aqueous Solution: Influence of Solution Composition and Spinning Parameters

by Daria N. Poshina, Igor A. Khadyko, Arina A. Sukhova, Ilya V. Serov, Natalia M. Zabivalova and Yury A. Skorik

Technologies 2020, 8(1), 2; https://doi.org/10.3390/technologies8010002 - 19 Dec 2019

Cited by 5 | Viewed by 5003

Abstract

The biological activity of chitosan determines its broad application as a biopolymer for non-woven wound dressings fabricated by electrospinning. The electrospinning process is affected by a large number of different factors that complicate its optimization. In the present work, the electrospinning of chitosan [...] Read more.

The biological activity of chitosan determines its broad application as a biopolymer for non-woven wound dressings fabricated by electrospinning. The electrospinning process is affected by a large number of different factors that complicate its optimization. In the present work, the electrospinning of chitosan lactate was carried out using a needleless technique from water solutions of different compositions. Surface response methodology was used to evaluate the effects of the concentration of chitosan, polyethylene oxide, and ethanol on solution properties, such as viscosity, surface tension, and conductivity, as well as the process characteristics and fiber quality. The viscosity of the spinning solution is determined by the polymer concentration as well as by the interpolymer interactions. The addition of ethanol to the spinning solutions effectively decreases the solution surface tension and conductivity, while increasing the volatility of the solvent, to provide more intense fiber spinning. Atomic force microscopy revealed that the chitosan lactate fibers were obtained without defects and with a narrow thickness distribution. The spinning parameters, voltage, distance between electrodes, and rotation speed of the spinning electrode had insignificant influences on the fiber diameter during needleless electrospinning. Full article

(This article belongs to the Special Issue Electrospinning Technologies for Biomedical and Biotechnological Applications)

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16 pages, 6579 KiB

Open AccessEditor’s ChoiceArticle

Incremental and Multi-Task Learning Strategies for Coarse-To-Fine Semantic Segmentation

by Mazen Mel, Umberto Michieli and Pietro Zanuttigh

Technologies 2020, 8(1), 1; https://doi.org/10.3390/technologies8010001 - 18 Dec 2019

Cited by 9 | Viewed by 6667

Abstract

The semantic understanding of a scene is a key problem in the computer vision field. In this work, we address the multi-level semantic segmentation task where a deep neural network is first trained to recognize an initial, coarse, set of a few classes. [...] Read more.

The semantic understanding of a scene is a key problem in the computer vision field. In this work, we address the multi-level semantic segmentation task where a deep neural network is first trained to recognize an initial, coarse, set of a few classes. Then, in an incremental-like approach, it is adapted to segment and label new objects’ categories hierarchically derived from subdividing the classes of the initial set. We propose a set of strategies where the output of coarse classifiers is fed to the architectures performing the finer classification. Furthermore, we investigate the possibility to predict the different levels of semantic understanding together, which also helps achieve higher accuracy. Experimental results on the New York University Depth v2 (NYUDv2) dataset show promising insights on the multi-level scene understanding. Full article

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

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16 pages, 6348 KiB

Open AccessEditor’s ChoiceArticle

An Inverse Pheromone Approach in a Chaotic Mobile Robot’s Path Planning Based on a Modified Logistic Map

by Eleftherios K. Petavratzis, Christos K. Volos, Lazaros Moysis, Ioannis N. Stouboulos, Hector E. Nistazakis, George S. Tombras and Kimon P. Valavanis

Technologies 2019, 7(4), 84; https://doi.org/10.3390/technologies7040084 - 06 Dec 2019

Cited by 16 | Viewed by 4208

Abstract

One major topic in the research of path planning of autonomous mobile robots is the fast and efficient coverage of a given terrain. For this purpose, an efficient method for covering a given workspace is proposed, based on chaotic path planning. The method [...] Read more.

One major topic in the research of path planning of autonomous mobile robots is the fast and efficient coverage of a given terrain. For this purpose, an efficient method for covering a given workspace is proposed, based on chaotic path planning. The method is based on a chaotic pseudo random bit generator that is generated using a modified logistic map, which is used to generate a chaotic motion pattern. This is then combined with an inverse pheromone approach in order to reduce the number of revisits in each cell. The simulated robot under study has the capability to move in four or eight directions. From extensive simulations performed in Matlab, it is derived that motion in eight directions gives superior results. Especially, with the inclusion of pheromone, the coverage percentage can significantly be increased, leading to better performance. Full article

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

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13 pages, 2729 KiB

Open AccessEditor’s ChoiceArticle

Compensation for Geometrical Deviations in Additive Manufacturing

by Christoph Hartmann, Philipp Lechner, Benjamin Himmel, Yannick Krieger, Tim C. Lueth and Wolfram Volk

Technologies 2019, 7(4), 83; https://doi.org/10.3390/technologies7040083 - 02 Dec 2019

Cited by 15 | Viewed by 6162

Abstract

The design of additive manufacturing processes, especially for batch production in industrial practice, is of high importance for the propagation of new additive manufacturing technology. Manual redesign procedures of the additive manufactured parts based on discrete measurement data or numerical meshes are error [...] Read more.

The design of additive manufacturing processes, especially for batch production in industrial practice, is of high importance for the propagation of new additive manufacturing technology. Manual redesign procedures of the additive manufactured parts based on discrete measurement data or numerical meshes are error prone and hardly automatable. To achieve the required final accuracy of the parts, often, various iterations are necessary. To address these issues, a data-driven geometrical compensation approach is proposed that adapts concepts from forming technology. The measurement information of a first calibration cycle of manufactured parts is the basis of the approach. Through non-rigid transformations of the part geometry, a new shape for the subsequent additive manufacturing process was derived in a systematic way. Based on a purely geometrical approach, the systematic portion of part deviations can be compensated. The proposed concept is presented first and was applied to a sample fin-shaped part. The deviation data of three manufacturing cycles was utilised for validation and verification. Full article

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

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14 pages, 32289 KiB

Open AccessEditor’s ChoiceArticle

3D Model Generation on Architectural Plan and Section Training through Machine Learning

by Hang Zhang

Technologies 2019, 7(4), 82; https://doi.org/10.3390/technologies7040082 - 15 Nov 2019

Cited by 19 | Viewed by 10945

Abstract

Machine learning, especially the GAN (Generative Adversarial Network) model, has been developed tremendously in recent years. Since the NVIDIA Machine Learning group presented the StyleGAN in December 2018, it has become a new way for designers to make machines learn different or similar [...] Read more.

Machine learning, especially the GAN (Generative Adversarial Network) model, has been developed tremendously in recent years. Since the NVIDIA Machine Learning group presented the StyleGAN in December 2018, it has become a new way for designers to make machines learn different or similar types of architectural photos, drawings, and renderings, then generate (a) similar fake images, (b) style-mixing images, and (c) truncation trick images. The author both collected and created input image data, and specially made architectural plan and section drawing inputs with a clear design purpose, then applied StyleGAN to train specific networks on these datasets. With the training process, we could look into the deep relationship between these input architectural plans or sections, then generate serialized transformation images (truncation trick images) to form the 3D (three-dimensional) model with a decent resolution (up to 1024 × 1024 × 1024 pixels). Though the results of the 3D model generation are difficult to use directly in 3D spatial modeling, these unexpected 3D forms still could inspire new design methods and greater possibilities of architectural plan and section design. Full article

(This article belongs to the Special Issue Computer-Aided Architectural Design)

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12 pages, 4248 KiB

Open AccessEditor’s ChoiceCommunication

AFM Characterization of Stir-Induced Micro-Flow Features within the AA6082-T6 BFSW Welds

by Abbas Tamadon, Dirk J. Pons and Don Clucas

Technologies 2019, 7(4), 80; https://doi.org/10.3390/technologies7040080 - 07 Nov 2019

Cited by 12 | Viewed by 4769

Abstract

Bobbin Friction Stir Welding (BFSW) is a thermomechanical process containing severe plastic deformation by mechanical stirring and Dynamic Recrystallization (DRX) during recooling. Here we report the three-dimensional characteristics of the micro-flow patterns within the aluminium weld structure. The Surface topography observations by Atomic [...] Read more.

Bobbin Friction Stir Welding (BFSW) is a thermomechanical process containing severe plastic deformation by mechanical stirring and Dynamic Recrystallization (DRX) during recooling. Here we report the three-dimensional characteristics of the micro-flow patterns within the aluminium weld structure. The Surface topography observations by Atomic Force Microscopy (AFM) show the stirred-induced microstructural evolution where the rearrangement of dislocations at the sub-grain scale, and the subsequent High- and Low-Angle Grain Boundaries (HAGBs, LAGBs) exhibit specific alterations in grain size and morphology of the weld texture. The dislocations interaction in different regions of the weld structure also was observed in correlation to the thermomechanical behaviour of the BFSW process. These micro-flow observations within the weld breadth give a new insight into the thermomechanical characteristics of the FSW process during the stirring action where the plastic flow has a key role in the formation of the weld region distinct from the base metal. Full article

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

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14 pages, 9581 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Advanced Coatings by Thermal Spray Processes

by Shrikant Joshi and Per Nylen

Technologies 2019, 7(4), 79; https://doi.org/10.3390/technologies7040079 - 01 Nov 2019

Cited by 30 | Viewed by 6904

Abstract

Coatings are pivotal in combating problems of premature component degradation in aggressive industrial environments and constitute a strategic area for continued development. Thermal spray (TS) coatings offer distinct advantages by combining versatility, cost-effectiveness, and the ability to coat complex geometries without constraints of [...] Read more.

Coatings are pivotal in combating problems of premature component degradation in aggressive industrial environments and constitute a strategic area for continued development. Thermal spray (TS) coatings offer distinct advantages by combining versatility, cost-effectiveness, and the ability to coat complex geometries without constraints of other in-chamber processes. Consequently, TS techniques like high-velocity oxy-fuel (HVOF) and atmospheric plasma spray (APS) are industrially well-accepted. However, they have reached limits of their capabilities while expectations from coatings progressively increase in pursuit of enhanced efficiency and productivity. Two emerging TS variants, namely high-velocity air-fuel (HVAF) and liquid feedstock thermal spraying, offer attractive pathways to realize high-performance surfaces superior to those hitherto achievable. Supersonic HVAF spraying provides highly adherent coatings with negligible porosity and its low processing temperature also ensures insignificant thermal ‘damage’ (oxidation, decarburization, etc.) to the starting material. On the other hand, liquid feedstock derived TS coatings, deposited using suspensions of fine particles (100 nm–5 µm) or solution precursors, permits the production of coatings with novel microstructures and diverse application-specific architectures. The possibility of hybrid processing, combining liquid and powder feedstock, provides further opportunities to fine tune the properties of functional surfaces. These new approaches are discussed along with some illustrative examples. Full article

(This article belongs to the Special Issue Processing and Fabrication of Advanced Materials)

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13 pages, 4021 KiB

Open AccessEditor’s ChoiceArticle

An Improved Calculation Model for the Prediction of the Wear of Coated Electrical Contacts

by Haomiao Yuan and Jian Song

Technologies 2019, 7(4), 77; https://doi.org/10.3390/technologies7040077 - 31 Oct 2019

Cited by 3 | Viewed by 4548

Abstract

To connect terminals in a cyber–physical system, large quantities of electrical contacts are used. In order to guarantee a high reliability of the system, the lifetime of the electrical contacts should be very long. Thus, it is of great importance to understand the [...] Read more.

To connect terminals in a cyber–physical system, large quantities of electrical contacts are used. In order to guarantee a high reliability of the system, the lifetime of the electrical contacts should be very long. Thus, it is of great importance to understand the failure mechanism and then to predict the lifetime of the electrical contacts. For the applications under high thermal and/or mechanical loads, noble plating is a good choice, considering its inertness to oxidation. For noble plating, one of the most critical failure mechanisms is the fretting wear. Wear debris generated in the contact area, acting as the third bodies, will greatly influence the further wear behavior and electrical performance. In this study, the state of the art regarding third bodies is firstly reviewed, and then the influence of the third bodies on the wear and electrical performance is investigated, from the aspects of lifetime and the element distributions in contact area. Finally, an example of prediction of the wear of noble plating is shown with the consideration of the third bodies. Based on this study, by involving the third bodies, the wear of noble plating can be predicted with a higher accuracy. Full article

(This article belongs to the Special Issue Microswitching Technologies)

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22 pages, 5032 KiB

Open AccessEditor’s ChoiceArticle

From Undesired Flaws to Esthetic Assets: A Digital Framework Enabling Artistic Explorations of Erroneous Geometric Features of Robotically Formed Molds

by Malgorzata A. Zboinska

Technologies 2019, 7(4), 78; https://doi.org/10.3390/technologies7040078 - 31 Oct 2019

Cited by 2 | Viewed by 4647

Abstract

Until recently, digital fabrication research in architecture has aimed to eliminate manufacturing errors. However, a novel notion has just been established—intentional computational infidelity. Inspired by this notion, we set out to develop means than can transform the errors in fabrication from an undesired [...] Read more.

Until recently, digital fabrication research in architecture has aimed to eliminate manufacturing errors. However, a novel notion has just been established—intentional computational infidelity. Inspired by this notion, we set out to develop means than can transform the errors in fabrication from an undesired complication to a creative opportunity. We carried out design experiment-based investigations, which culminated in the construction of a framework enabling fundamental artistic explorations of erroneous geometric features of robotically formed molds. The framework consists of digital processes, assisting in the explorations of mold errors, and physical processes, enabling the inclusion of physical feedback in digital explorations. Other complementary elements embrace an implementation workflow, an enabling digital toolset and a visual script demonstrating how imprecise artistic explorations can be included within the computational environment. Our framework application suggests that the exploration of geometrical errors aids the emergence of unprecedented design features that would not have arisen if error elimination were the ultimate design goal. Our conclusion is that welcoming error into the design process can reinstate the role of art, craft, and material agency therein. This can guide the practice and research of architectural computing onto a new territory of esthetic and material innovation. Full article

(This article belongs to the Special Issue Computer-Aided Architectural Design)

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16 pages, 5228 KiB

Open AccessEditor’s ChoiceArticle

Analysis of a Chaotic System with Line Equilibrium and Its Application to Secure Communications Using a Descriptor Observer

by Lazaros Moysis, Christos Volos, Viet-Thanh Pham, Sotirios Goudos, Ioannis Stouboulos, Mahendra Kumar Gupta and Vikas Kumar Mishra

Technologies 2019, 7(4), 76; https://doi.org/10.3390/technologies7040076 - 24 Oct 2019

Cited by 11 | Viewed by 4605

Abstract

In this work a novel chaotic system with a line equilibrium is presented. First, a dynamical analysis on the system is performed, by computing its bifurcation diagram, continuation diagram, phase portraits and Lyapunov exponents. Then, the system is applied to the problem of [...] Read more.

In this work a novel chaotic system with a line equilibrium is presented. First, a dynamical analysis on the system is performed, by computing its bifurcation diagram, continuation diagram, phase portraits and Lyapunov exponents. Then, the system is applied to the problem of secure communication. We assume that the transmitted signal is an additional state. For this reason, the nonlinear system is rewritten in a rectangular descriptor form and then an observer is constructed for achieving synchronization and input reconstruction. If we assume some rank conditions (on the nonlinearities and the solvability of a linear matrix inequality (LMI)) on the system matrices then the observer synchronization can be feasible. We evaluate and demonstrate our approach with specific numerical results. Full article

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

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25 pages, 2518 KiB

Open AccessEditor’s ChoiceReview

Towards Safer Primers: A Review

by Stefan Lundgaard, Soon Hock Ng, Damien Cahill, Johan Dahlberg, Dong Ruan, Nerida Cole, Paul R. Stoddart and Saulius Juodkazis

Technologies 2019, 7(4), 75; https://doi.org/10.3390/technologies7040075 - 18 Oct 2019

Cited by 10 | Viewed by 13680

Abstract

Primers are used to reliably initiate a secondary explosive in a wide range of industrial and defence applications. However, established primer technologies pose both direct and indirect risks to health and safety. This review analyses a new generation of primer materials and ignition [...] Read more.

Primers are used to reliably initiate a secondary explosive in a wide range of industrial and defence applications. However, established primer technologies pose both direct and indirect risks to health and safety. This review analyses a new generation of primer materials and ignition control mechanisms that have been developed to address these risks in firearms. Electrically or optically initiated metal, oxide and semiconductor-based devices show promise as alternatives for heavy metal percussive primers. The prospects for wider use of low-cost, safe, reliable and non-toxic primers are discussed in view of these developments. Full article

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21 pages, 6669 KiB

Open AccessEditor’s ChoiceArticle

Open Source Waste Plastic Granulator

by Arvind Ravindran, Sean Scsavnicki, Walker Nelson, Peter Gorecki, Jacob Franz, Shane Oberloier, Theresa K. Meyer, Andrew R. Barnard and Joshua M. Pearce

Technologies 2019, 7(4), 74; https://doi.org/10.3390/technologies7040074 - 14 Oct 2019

Cited by 12 | Viewed by 18874

Abstract

In order to accelerate deployment of distributed recycling by providing low-cost feed stocks of granulated post-consumer waste plastic, this study analyzes an open source waste plastic granulator system. It is designed, built, and tested for its ability to convert post-consumer waste, 3D printed [...] Read more.

In order to accelerate deployment of distributed recycling by providing low-cost feed stocks of granulated post-consumer waste plastic, this study analyzes an open source waste plastic granulator system. It is designed, built, and tested for its ability to convert post-consumer waste, 3D printed products and waste into polymer feedstock for recyclebots of fused particle/granule printers. The technical specifications of the device are quantified in terms of power consumption (380 to 404 W for PET and PLA, respectively) and particle size distribution. The open source device can be fabricated for less than $2000 USD in materials. The experimentally measured power use is only a minor contribution to the overall embodied energy of distributed recycling of waste plastic. The resultant plastic particle size distributions were found to be appropriate for use in both recyclebots and direct material extrusion 3D printers. Simple retrofits are shown to reduce sound levels during operation by 4dB-5dB for the vacuum. These results indicate that the open source waste plastic granulator is an appropriate technology for community, library, maker space, fab lab, or small business–based distributed recycling. Full article

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

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11 pages, 278 KiB

Open AccessEditor’s ChoiceArticle

Psychosocial Impact of Powered Wheelchair, Users’ Satisfaction and Their Relation to Social Participation

by Inês Domingues, João Pinheiro, João Silveira, Patrícia Francisco, Jeffrey Jutai and Anabela Correia Martins

Technologies 2019, 7(4), 73; https://doi.org/10.3390/technologies7040073 - 10 Oct 2019

Cited by 6 | Viewed by 8775

Abstract

Several studies showed positive effects of assistive technologies on psychosocial impact and participation of adults with mobility impairments. The purpose of this study was to assess the psychosocial and participation impact of powered wheelchairs. Participants were thirty persons with disabilities who use powered [...] Read more.

Several studies showed positive effects of assistive technologies on psychosocial impact and participation of adults with mobility impairments. The purpose of this study was to assess the psychosocial and participation impact of powered wheelchairs. Participants were thirty persons with disabilities who use powered wheelchairs with diverse medical conditions. The Quebec User Evaluation of Satisfaction with Assistive Technology, the Psychosocial Impact of Assistive Devices Scale and the Activities and Participation Profile Related to Mobility were used, in addition to demographic, clinical and wheelchair related questions. The participants were satisfied with both the assistive technology and related services, with the lowest satisfaction scores belonging to those who had been using their wheelchairs for a longer period of time. We noticed significant restrictions in participation mostly among persons with longer wheelchair utilization. The most satisfied were the ones with better performance in terms of social participation. Psychosocial scores showed a positive impact with higher adaptability among persons who transitioned from a manual compared to those who already had a powered wheelchair. There was a positive psychosocial impact and therefore an increase in quality of life of its users. Full article

(This article belongs to the Section Assistive Technologies)

17 pages, 3350 KiB

Open AccessEditor’s ChoiceArticle

A Cold-Pressing Method Combining Axial and Shear Flow of Powder Compaction to Produce High-Density Iron Parts

by Sergey N. Grigoriev, Alexandr M. Dmitriev, Natalya V. Korobova and Sergey V. Fedorov

Technologies 2019, 7(4), 70; https://doi.org/10.3390/technologies7040070 - 24 Sep 2019

Cited by 5 | Viewed by 6168

Abstract

Highly performance methods for cold pressing (cold die forging) of preforms from iron powder with subsequent heat treatment and producing ready parts made of powder are described in the paper. These methods allow fabricating parts with smooth surfaces and improved mechanical characteristics—porosity, tensile [...] Read more.

Highly performance methods for cold pressing (cold die forging) of preforms from iron powder with subsequent heat treatment and producing ready parts made of powder are described in the paper. These methods allow fabricating parts with smooth surfaces and improved mechanical characteristics—porosity, tensile strength. Application of the traditional design set-up with a single-axial loading is restricted to high stresses in the dies to deform the preforms that lead to cracks formation. New powder compaction schemes by applying active friction forces (shear-enhanced compaction) make it possible to unload dies and produce high-quality parts by cold pressing. The scheme allows moving the die in the direction of the material flow with a velocity that exceeds the material flow velocity. Full article

(This article belongs to the Special Issue Processing and Fabrication of Advanced Materials)

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12 pages, 4490 KiB

Open AccessEditor’s ChoiceArticle

Transient Contact Opening Forces in a MEMS Switch Using Au/MWCNT Composite

by Thomas G. Bull and John W. McBride

Technologies 2019, 7(4), 69; https://doi.org/10.3390/technologies7040069 - 23 Sep 2019

Cited by 1 | Viewed by 4522

Abstract

Most failures in micro electromechanical system (MEMS) switches can be attributed to the degradation of contact surfaces and sticking contacts. A wear-tolerant composite contact material, composed of a Au film supported by multi walled carbon nanotubes (Au/MWCNT), has been engineered to provide wear [...] Read more.

Most failures in micro electromechanical system (MEMS) switches can be attributed to the degradation of contact surfaces and sticking contacts. A wear-tolerant composite contact material, composed of a Au film supported by multi walled carbon nanotubes (Au/MWCNT), has been engineered to provide wear resistance and enhanced switching lifetime with conductive properties close to pure Au. Switching lifetimes of billions of cycles have been demonstrated, representing greatly increased performance over thin film Au. Below the arcing threshold (~12 V) the wear mechanism has been shown to be a combination of the fine transfer of contact material by the molten metal bridge (MMB) phenomenon and a delamination of the Au. In this study, the composite contact is hot switched at low current DC conditions (4 V DC and 20 mA) while the contact force is measured at the micro Newton scale in nanosecond resolution. The characteristic voltage waveform associated with the MMB is observed with forces detected as the contact softens, melts, and separates. The presence of a delamination event (DE) is also observed, where the contact opens abruptly with no MMB phenomenon apparent. The DE contact openings are associated with a transient peak force of 21.6 ± 2.3 µN while the MMBs are linked to a lower peak force of 18.1 ± 2.5 µN. Full article

(This article belongs to the Special Issue Microswitching Technologies)

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19 pages, 7135 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of Wirelessly Transmitted Video Quality Using a Modular Fuzzy Logic System

by Abdussalam Salama and Reza Saatchi

Technologies 2019, 7(3), 67; https://doi.org/10.3390/technologies7030067 - 14 Sep 2019

Cited by 6 | Viewed by 5116

Abstract

Video transmission over wireless computer networks is increasingly popular as new applications emerge and wireless networks become more widespread and reliable. An ability to quantify the quality of a video transmitted using a wireless computer network is important for determining network performance and [...] Read more.

Video transmission over wireless computer networks is increasingly popular as new applications emerge and wireless networks become more widespread and reliable. An ability to quantify the quality of a video transmitted using a wireless computer network is important for determining network performance and its improvement. The process requires analysing the images making up the video from the point of view of noise and associated distortion as well as traffic parameters represented by packet delay, jitter and loss. In this study a modular fuzzy logic based system was developed to quantify the quality of video transmission over a wireless computer network. Peak signal to noise ratio, structural similarity index and image difference were used to represent the user’s quality of experience (QoE) while packet delay, jitter and percentage packet loss ratio were used to represent traffic related quality of service (QoS). An overall measure of the video quality was obtained by combining QoE and QoS values. Systematic sampling was used to reduce the number of images processed and a novel scheme was devised whereby the images were partitioned to more sensitively localize distortions. To further validate the developed system, a subjective test involving 25 participants graded the quality of the received video. The image partitioning significantly improved the video quality evaluation. The subjective test results correlated with the developed fuzzy logic approach. The video quality assessment developed in this study was compared against a method that uses spatial efficient entropic differencing and consistent results were observed. The study indicated that the developed fuzzy logic approaches could accurately determine the quality of a wirelessly transmitted video. Full article

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14 pages, 1414 KiB

Open AccessEditor’s ChoiceArticle

A Bayesian Study of the Dynamic Effect of Comorbidities on Hospital Outcomes of Care for Congestive Heart Failure Patients

by Dimitrios Zikos, Stelios Zimeras and Neli Ragina

Technologies 2019, 7(3), 66; https://doi.org/10.3390/technologies7030066 - 13 Sep 2019

Cited by 3 | Viewed by 4632

Abstract

Comorbidities can have a cumulative effect on hospital outcomes of care, such as the length of stay (LOS), and hospital mortality. This study examines patients hospitalized with congestive heart failure (CHF), a life-threatening condition, which, when it coexists with a burdened disease profile, [...] Read more.

Comorbidities can have a cumulative effect on hospital outcomes of care, such as the length of stay (LOS), and hospital mortality. This study examines patients hospitalized with congestive heart failure (CHF), a life-threatening condition, which, when it coexists with a burdened disease profile, the risk for negative hospital outcomes increases. Since coexisting conditions co-interact, with a variable effect on outcomes, clinicians should be able to recognize these joint effects. In order to study CHF comorbidities, we used medical claims data from the Centers for Medicare and Medicaid Services (CMS). After extracting the most frequent cluster of CHF comorbidities, we: (i) Calculated, step-by-step, the conditional probabilities for each disease combination inside this cluster; (ii) estimated the cumulative effect of each comorbidity combination on the LOS and hospital mortality; and (iii) constructed (a) Bayesian, scenario-based graphs, and (b) Bayes-networks to visualize results. Results show that, for CHF patients, different comorbidity constructs have a variable effect on the LOS and hospital mortality. Therefore, dynamic comorbidity risk assessment methods should be implemented for informed clinical decision making in an ongoing effort for quality of care improvements. Full article

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19 pages, 6798 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Data-Driven Recognition and Extraction of PDF Document Elements

by Matthias Hansen, André Pomp, Kemal Erki and Tobias Meisen

Technologies 2019, 7(3), 65; https://doi.org/10.3390/technologies7030065 - 11 Sep 2019

Cited by 7 | Viewed by 11304

Abstract

In the age of digitalization, the collection and analysis of large amounts of data is becoming increasingly important for enterprises to improve their businesses and processes, such as the introduction of new services or the realization of resource-efficient production. Enterprises concentrate strongly on [...] Read more.

In the age of digitalization, the collection and analysis of large amounts of data is becoming increasingly important for enterprises to improve their businesses and processes, such as the introduction of new services or the realization of resource-efficient production. Enterprises concentrate strongly on the integration, analysis and processing of their data. Unfortunately, the majority of data analysis focuses on structured and semi-structured data, although unstructured data such as text documents or images account for the largest share of all available enterprise data. One reason for this is that most of this data is not machine-readable and requires dedicated analysis methods, such as natural language processing for analyzing textual documents or object recognition for recognizing objects in images. Especially in the latter case, the analysis methods depend strongly on the application. However, there are also data formats, such as PDF documents, which are not machine-readable and consist of many different document elements such as tables, figures or text sections. Although the analysis of PDF documents is a major challenge, they are used in all enterprises and contain various information that may contribute to analysis use cases. In order to enable their efficient retrievability and analysis, it is necessary to identify the different types of document elements so that we are able to process them with tailor-made approaches. In this paper, we propose a system that forms the basis for structuring unstructured PDF documents, so that the identified document elements can subsequently be retrieved and analyzed with tailor-made approaches. Due to the high diversity of possible document elements and analysis methods, this paper focuses on the automatic identification and extraction of data visualizations, algorithms, other diagram-like objects and tables from a mixed document body. For that, we present two different approaches. The first approach uses methods from the area of deep learning and rule-based image processing whereas the second approach is purely based on deep learning. To train our neural networks, we manually annotated a large corpus of PDF documents with our own annotation tool, of which both are being published together with this paper. The results of our extraction pipeline show that we are able to automatically extract graphical items with a precision of 0.73 and a recall of 0.8. For tables, we reach a precision of 0.78 and a recall of 0.94. Full article

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

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14 pages, 3773 KiB

Open AccessEditor’s ChoiceArticle

Surface Hardening of Massive Steel Products in the Low-pressure Glow Discharge Plasma

by Sergey Grigoriev, Alexander Metel, Marina Volosova, Yury Melnik, Htet A. Ney and Enver Mustafaev

Technologies 2019, 7(3), 62; https://doi.org/10.3390/technologies7030062 - 28 Aug 2019

Cited by 4 | Viewed by 5088

Abstract

A process vacuum chamber is filled with a homogeneous plasma of glow discharge with electrostatic electron confinement, which is used for surface hardening of massive products. At the current of 2–20 A and the gas pressure ranging from 0.1 to 1 Pa the [...] Read more.

A process vacuum chamber is filled with a homogeneous plasma of glow discharge with electrostatic electron confinement, which is used for surface hardening of massive products. At the current of 2–20 A and the gas pressure ranging from 0.1 to 1 Pa the discharge voltage amounts to 350–500 V. When a bias voltage of 2 kV is applied to an immersed in the plasma hollow cylinder with a mass of 15 kg, electrical power spent on heating it by accelerated ions exceeds by an order of magnitude the power spent on the discharge maintenance. The massive cylinder is heated up to 700 °C for 15 min. When argon mixture with nitrogen (30%) is used, the nitriding for 3h results in an increase in the surface hardness from 400 up to 1000 HV50 and the nitrided layer thickness grows to ~100 μm. The nitriding rate is enhanced by a high degree of nitrogen dissociation due to decomposition by fast electrons and surface structural defects due to bombardment by high-energy ions. Full article

(This article belongs to the Special Issue Processing and Fabrication of Advanced Materials)

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16 pages, 1084 KiB

Open AccessEditor’s ChoiceReview

Smart Cities and Healthcare: A Systematic Review

by Nelson Pacheco Rocha, Ana Dias, Gonçalo Santinha, Mário Rodrigues, Alexandra Queirós and Carlos Rodrigues

Technologies 2019, 7(3), 58; https://doi.org/10.3390/technologies7030058 - 16 Aug 2019

Cited by 31 | Viewed by 10903

Abstract

Objectives: The study reported in this article aimed to identify: (i) the most relevant applications supported by smart city infrastructure with an impact on the provision of healthcare; (ii) the types of technologies being used; (iii) the maturity levels of the applications being [...] Read more.

Objectives: The study reported in this article aimed to identify: (i) the most relevant applications supported by smart city infrastructure with an impact on the provision of healthcare; (ii) the types of technologies being used; (iii) the maturity levels of the applications being reported; and (iv) major barriers for their dissemination. Methods: A systematic review was performed based on a literature search. Results: A total of 44 articles were retrieved. These studies reported on smart city applications to support population surveillance, active ageing, healthy lifestyles, disabled people, response to emergencies, care services organization, and socialization. Conclusions: Most of the included articles were either of a descriptive and conceptual nature or in an early stage of development, which means that a major barrier for their dissemination is their lack of concreteness. Full article

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11 pages, 3275 KiB

Open AccessEditor’s ChoiceArticle

Effects of the Infill Density on the Mechanical Properties of Nylon Specimens Made by Filament Fused Fabrication

by Svetlana Terekhina, Innokentiy Skornyakov, Tatiana Tarasova and Sergei Egorov

Technologies 2019, 7(3), 57; https://doi.org/10.3390/technologies7030057 - 16 Aug 2019

Cited by 44 | Viewed by 6841

Abstract

Additive manufacturing of polymer products over the past decade has become widespread in various areas of industry. Using the fused filament fabrication (FFF) method, one of the most technologically simple methods of additive manufacturing, it is possible to produce parts from a large [...] Read more.

Additive manufacturing of polymer products over the past decade has become widespread in various areas of industry. Using the fused filament fabrication (FFF) method, one of the most technologically simple methods of additive manufacturing, it is possible to produce parts from a large number of different materials, including wear-resistant nylon. The novelty of the work is properties investigation of ±45° filling configuration with different filling degree for nylon, as well as calculating the effect of infill on the strength characteristics, excluding the shell. This article reflects the process of manufacturing samples from nylon using FFF technology with various internal topologies, as well as tensile tests. The analysis of the obtained results is performed and the relationship between the structure of the sample and the limit of its strength is established. To calculate real filling degree and the effect of internal filling on the strength characteristics of the specimen, it is proposed to use a method based on the geometric and mass parameters. The FFF method is promising for developing methods for producing a composite material. The results of this article can be useful in choosing the necessary manufacturing parameters. Full article

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

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18 pages, 12923 KiB

Open AccessEditor’s ChoiceArticle

Choreographic Pattern Analysis from Heterogeneous Motion Capture Systems Using Dynamic Time Warping

by Ioannis Rallis, Eftychios Protopapadakis, Athanasios Voulodimos, Nikolaos Doulamis, Anastasios Doulamis and Georgios Bardis

Technologies 2019, 7(3), 56; https://doi.org/10.3390/technologies7030056 - 16 Aug 2019

Cited by 7 | Viewed by 5222

Abstract

The convention for the safeguarding of Intangible Cultural Heritage (ICH) by UNESCO highlights the equal importance of intangible elements of cultural heritage to tangible ones. One of the most important domains of ICH is folkloric dances. A dance choreography is a time-varying 3D [...] Read more.

The convention for the safeguarding of Intangible Cultural Heritage (ICH) by UNESCO highlights the equal importance of intangible elements of cultural heritage to tangible ones. One of the most important domains of ICH is folkloric dances. A dance choreography is a time-varying 3D process (4D modelling), which includes dynamic co-interactions among different actors, emotional and style attributes, and supplementary elements, such as music tempo and costumes. Presently, research focuses on the use of depth acquisition sensors, to handle kinesiology issues. The extraction of skeleton data, in real time, contains a significant amount of information (data and metadata), allowing for various choreography-based analytics. In this paper, a trajectory interpretation method for Greek folkloric dances is presented. We focus on matching trajectories’ patterns, existing in a choreographic database, to new ones originating from different sensor types such as VICON and Kinect II. Then, a Dynamic Time Warping (DTW) algorithm is proposed to find out similarities/dissimilarities among the choreographic trajectories. The goal is to evaluate the performance of the low-cost Kinect II sensor for dance choreography compared to the accurate but of high-cost VICON-based choreographies. Experimental results on real-life dances are carried out to show the effectiveness of the proposed DTW methodology and the ability of Kinect II to localize dances in 3D space. Full article

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19 pages, 6469 KiB

Open AccessEditor’s ChoiceArticle

A Cellular Automata Model of the Relationship between Adverse Events and Regional Infrastructure Development in an Active War Theater

by Halil Bozkurt, Waldemar Karwowski, Erman Çakıt and Tareq Ahram

Technologies 2019, 7(3), 54; https://doi.org/10.3390/technologies7030054 - 07 Aug 2019

Cited by 1 | Viewed by 4767

Abstract

This study presents a cellular automata (CA) model to assist decision-makers in understanding the effects of infrastructure development projects on adverse events in an active war theater. The adverse events are caused by terrorist activities that primarily target the civilian population in countries [...] Read more.

This study presents a cellular automata (CA) model to assist decision-makers in understanding the effects of infrastructure development projects on adverse events in an active war theater. The adverse events are caused by terrorist activities that primarily target the civilian population in countries such as Afghanistan. In the CA-based model, cells in the same neighborhood synchronously interact with one another to determine their next states, and small changes in iteration yield to complex formations of adverse event risks. The results demonstrate that the proposed model can help in the evaluation of infrastructure development projects in relation to changes in the reported adverse events, as well as in the identification of the geographical locations, times, and impacts of such developments. The results also show that infrastructure development projects have different impacts on the reported adverse events. The CA modeling approach can be used to support decision-makers in allocating infrastructure development funds to stabilize active war regions with higher adverse event risks. Such models can also improve the understanding of the complex interactions between infrastructure development projects and adverse events. Full article

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9 pages, 2557 KiB

Open AccessEditor’s ChoiceArticle

The Effect of the Terminal Functional Groups on Fluoropolymer on Electrowetting Device Performance

by Eri Oishi, Noritoshi Araki, Teruya Goto, Hiroshi Awano and Tatsuhiro Takahashi

Technologies 2019, 7(3), 52; https://doi.org/10.3390/technologies7030052 - 27 Jul 2019

Cited by 2 | Viewed by 5555

Abstract

Electrowetting on dielectric (EWOD) devices were fabricated using two hydrophobic organic fluoropolymers, comprising CYTOP (a product name) having different chemical structures only at the terminal functional groups. These devices were subsequently characterized by applying a range of direct current (DC) voltages. The data [...] Read more.

Electrowetting on dielectric (EWOD) devices were fabricated using two hydrophobic organic fluoropolymers, comprising CYTOP (a product name) having different chemical structures only at the terminal functional groups. These devices were subsequently characterized by applying a range of direct current (DC) voltages. The data demonstrated that the EWOD performance was dramatically improved upon incorporating a CYTOP polymer having highly polar terminal functional groups, as compared to a polymer having terminal groups with lower polarity. The new finding about the positive effect of highly polar terminal functional groups on the enhancement of EWOD was exhibited through various careful experiments, changing only the quantitative amount of polar terminal functional groups while keeping other factors constant (thickness, substrate, etc.). Full article

(This article belongs to the Special Issue Smart Systems (SmaSys2018))

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12 pages, 4683 KiB

Open AccessEditor’s ChoiceArticle

A Self-Deformation Robot Design Incorporating Bending-Type Pneumatic Artificial Muscles

by Hiroki Tomori, Kenta Hiyoshi, Shonosuke Kimura, Naoya Ishiguri and Taisei Iwata

Technologies 2019, 7(3), 51; https://doi.org/10.3390/technologies7030051 - 23 Jul 2019

Cited by 4 | Viewed by 5828

Abstract

With robots becoming closer to humans in recent years, human-friendly robots made of soft materials provide a new line of research interests. We designed and developed a soft robot that can move via self-deformation toward the practical application of monitoring children and the [...] Read more.

With robots becoming closer to humans in recent years, human-friendly robots made of soft materials provide a new line of research interests. We designed and developed a soft robot that can move via self-deformation toward the practical application of monitoring children and the elderly on a daily basis. The robot’s structure was built out of flexible frames, which are bending-type pneumatic artificial muscles (BPAMs). We first provide a description and discussion on the nature of BPAM, followed by static characteristics experiment. Although the BPAM theoretical model shares a similar tendency with the experimental results, the actual BPAMs moved along the depth direction. We then proposed and demonstrated an effective locomotion method for the robot and calculated its locomotion speed by measuring its drive time and movement distance. Our results confirmed the reasonability of the robot’s speed for monitoring children and the elderly. Nevertheless, during the demonstration, some BPAMs were bent sharply by other activated BPAMs as the robot was driving, leaving a little damage on these BPAMs. This will be addressed in our future work. Full article

(This article belongs to the Special Issue Smart Systems (SmaSys2018))

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23 pages, 1429 KiB

Open AccessEditor’s ChoiceArticle

ThingsLocate: A ThingSpeak-Based Indoor Positioning Platform for Academic Research on Location-Aware Internet of Things

by Luca De Nardis, Giuseppe Caso and Maria Gabriella Di Benedetto

Technologies 2019, 7(3), 50; https://doi.org/10.3390/technologies7030050 - 16 Jul 2019

Cited by 14 | Viewed by 8339

Abstract

Seamless location awareness is considered a cornerstone in the successful deployment of the Internet of Things (IoT). Support for IoT devices in indoor positioning platforms and, vice versa, availability of indoor positioning functions in IoT platforms, are however still in their early stages, [...] Read more.

Seamless location awareness is considered a cornerstone in the successful deployment of the Internet of Things (IoT). Support for IoT devices in indoor positioning platforms and, vice versa, availability of indoor positioning functions in IoT platforms, are however still in their early stages, posing a significant challenge in the study and research of the interaction of indoor positioning and IoT. This paper proposes a new indoor positioning platform, called ThingsLocate, that fills this gap by building upon the popular and flexible ThingSpeak cloud service for IoT, leveraging its data input and data processing capabilities and, most importantly, its native support for cloud execution of Matlab code. ThingsLocate provides a flexible, user-friendly WiFi fingerprinting indoor positioning service for IoT devices, based on Received Signal Strength Indicator (RSSI) information. The key components of ThingsLocate are introduced and described: RSSI channels used by IoT devices to provide WiFi RSSI data, an Analysis app estimating the position of the device, and a Location channel to publish such estimate. A proof-of-concept implementation of ThingsLocate is then introduced, and used to show the possibilities offered by the platform in the context of graduate studies and academic research on indoor positioning for IoT. Results of an experiment enabled by ThingsLocate with limited setup and no coding effort are presented, focusing on the impact of using different devices and different positioning algorithms on positioning accuracy. Full article

(This article belongs to the Special Issue Technology Advances on IoT Learning and Teaching)

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16 pages, 302 KiB

Open AccessEditor’s ChoiceArticle

Recommendations with a Nudge

by Randi Karlsen and Anders Andersen

Technologies 2019, 7(2), 45; https://doi.org/10.3390/technologies7020045 - 13 Jun 2019

Cited by 33 | Viewed by 13255

Abstract

In areas such as health, environment, and energy consumption, there is a need to do better. A common goal in society is to get people to behave in ways that are sustainable for the environment or support a healthier lifestyle. Nudging is a [...] Read more.

In areas such as health, environment, and energy consumption, there is a need to do better. A common goal in society is to get people to behave in ways that are sustainable for the environment or support a healthier lifestyle. Nudging is a term known from economics and political theory, for influencing decisions and behavior using suggestions, positive reinforcement, and other non-coercive means. With the extensive use of digital devices, nudging within a digital environment (known as digital nudging) has great potential. We introduce smart nudging, where the guidance of user behavior is presented through digital nudges tailored to be relevant to the current situation of each individual user. The ethics of smart nudging and the transparency of nudging is also discussed. We see a smart nudge as a recommendation to the user, followed by information that both motivates and helps the user choose the suggested behavior. This paper describes such nudgy recommendations, the design of a smart nudge, and an architecture for a smart nudging system. We compare smart nudging to traditional models for recommender systems, and we describe and discuss tools (or approaches) for nudge design. We discuss the challenges of designing personalized smart nudges that evolve and adapt according to the user’s reactions to the previous nudging and possible behavioral change of the user. Full article

(This article belongs to the Special Issue Next Generation of Recommender Systems)

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18 pages, 547 KiB

Open AccessEditor’s ChoiceReview

A Perspective on Terahertz Next-Generation Wireless Communications

by John F. O’Hara, Sabit Ekin, Wooyeol Choi and Ickhyun Song

Technologies 2019, 7(2), 43; https://doi.org/10.3390/technologies7020043 - 12 Jun 2019

Cited by 93 | Viewed by 14320

Abstract

In the past year, fifth-generation (5G) wireless technology has seen dramatic growth, spurred on by the continuing demand for faster data communications with lower latency. At the same time, many researchers argue that 5G will be inadequate in a short time, given the [...] Read more.

In the past year, fifth-generation (5G) wireless technology has seen dramatic growth, spurred on by the continuing demand for faster data communications with lower latency. At the same time, many researchers argue that 5G will be inadequate in a short time, given the explosive growth of machine connectivity, such as the Internet-of-Things (IoT). This has prompted many to question what comes after 5G. The obvious answer is sixth-generation (6G), however, the substance of 6G is still very much undefined, leaving much to the imagination in terms of real-world implementation. What is clear, however, is that the next generation will likely involve the use of terahertz frequency (0.1–10 THz) electromagnetic waves. Here, we review recent research in terahertz wireless communications and technology, focusing on three broad topic classes: the terahertz channel, terahertz devices, and space-based terahertz system considerations. In all of these, we describe the nature of the research, the specific challenges involved, and current research findings. We conclude by providing a brief perspective on the path forward. Full article

(This article belongs to the Special Issue Terahertz Technologies)

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81 pages, 49064 KiB

Open AccessEditor’s ChoiceReview

Flexible Sensors—From Materials to Applications

by Júlio C. Costa, Filippo Spina, Pasindu Lugoda, Leonardo Garcia-Garcia, Daniel Roggen and Niko Münzenrieder

Technologies 2019, 7(2), 35; https://doi.org/10.3390/technologies7020035 - 09 Apr 2019

Cited by 141 | Viewed by 33021

Abstract

Flexible sensors have the potential to be seamlessly applied to soft and irregularly shaped surfaces such as the human skin or textile fabrics. This benefits conformability dependant applications including smart tattoos, artificial skins and soft robotics. Consequently, materials and structures for innovative flexible [...] Read more.

Flexible sensors have the potential to be seamlessly applied to soft and irregularly shaped surfaces such as the human skin or textile fabrics. This benefits conformability dependant applications including smart tattoos, artificial skins and soft robotics. Consequently, materials and structures for innovative flexible sensors, as well as their integration into systems, continue to be in the spotlight of research. This review outlines the current state of flexible sensor technologies and the impact of material developments on this field. Special attention is given to strain, temperature, chemical, light and electropotential sensors, as well as their respective applications. Full article

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

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22 pages, 1246 KiB

Open AccessEditor’s ChoiceReview

Integration of Biometrics and Steganography: A Comprehensive Review

by Ian McAteer, Ahmed Ibrahim, Guanglou Zheng, Wencheng Yang and Craig Valli

Technologies 2019, 7(2), 34; https://doi.org/10.3390/technologies7020034 - 08 Apr 2019

Cited by 19 | Viewed by 9565

Abstract

The use of an individual’s biometric characteristics to advance authentication and verification technology beyond the current dependence on passwords has been the subject of extensive research for some time. Since such physical characteristics cannot be hidden from the public eye, the security of [...] Read more.

The use of an individual’s biometric characteristics to advance authentication and verification technology beyond the current dependence on passwords has been the subject of extensive research for some time. Since such physical characteristics cannot be hidden from the public eye, the security of digitised biometric data becomes paramount to avoid the risk of substitution or replay attacks. Biometric systems have readily embraced cryptography to encrypt the data extracted from the scanning of anatomical features. Significant amounts of research have also gone into the integration of biometrics with steganography to add a layer to the defence-in-depth security model, and this has the potential to augment both access control parameters and the secure transmission of sensitive biometric data. However, despite these efforts, the amalgamation of biometric and steganographic methods has failed to transition from the research lab into real-world applications. In light of this review of both academic and industry literature, we suggest that future research should focus on identifying an acceptable level steganographic embedding for biometric applications, securing exchange of steganography keys, identifying and address legal implications, and developing industry standards. Full article

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

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28 pages, 7498 KiB

Open AccessEditor’s ChoiceReview

Nematic Liquid Crystal Composite Materials for DC and RF Switching

by Mohiuddin Munna, Farhana Anwar and Ronald A. Coutu, Jr.

Technologies 2019, 7(2), 32; https://doi.org/10.3390/technologies7020032 - 02 Apr 2019

Cited by 17 | Viewed by 11308

Abstract

Liquid Crystals (LCs) are widely used in display devices, electro-optic modulators, and optical switches. A field-induced electrical conductivity modulation in pure liquid crystals is very low which makes it less preferable for direct current (DC) and radio-frequency (RF) switching applications. According to the [...] Read more.

Liquid Crystals (LCs) are widely used in display devices, electro-optic modulators, and optical switches. A field-induced electrical conductivity modulation in pure liquid crystals is very low which makes it less preferable for direct current (DC) and radio-frequency (RF) switching applications. According to the literature, a conductivity enhancement is possible by nanoparticle doping. Considering this aspect, we reviewed published works focused on an electric field-induced conductivity modulation in carbon nanotube-doped liquid crystal composites (LC-CNT composites). A two to four order of magnitude switching in electrical conductivity is observed by several groups. Both in-plane and out-of-plane device configurations are used. In plane configurations are preferable for micro-device fabrication. In this review article, we discussed published works reporting the elastic and molecular interaction of a carbon nanotube (CNT) with LC molecules, temperature and CNT concentration effects on electrical conductivity, local heating, and phase transition behavior during switching. Reversibility and switching speed are the two most important performance parameters of a switching device. It was found that dual frequency nematic liquid crystals (DFNLC) show a faster switching with a good reversibility, but the switching ratio is only two order of magnitudes. A better way to ensure reversibility with a large switching magnitude is to use two pairs of in-plane electrodes in a cross configuration. For completeness and comparison purposes, we briefly reviewed other nanoparticle- (i.e., Au and Ag) doped LC composite’s conductivity behavior as well. Finally, based on the reported works reviewed in this article on field induced conductivity modulation, we proposed a novel idea of RF switching by LC composite materials. To support the idea, we simulated an LC composite-based RF device considering a simple analytical model. Our RF analysis suggests that a device made with an LC-CNT composite could show an acceptable performance. Several technological challenges needed to be addressed for a physical realization and are also discussed briefly. Full article

(This article belongs to the Special Issue Microswitching Technologies)

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14 pages, 1204 KiB

Open AccessEditor’s ChoiceArticle

Emotion Recognition from Speech Using the Bag-of-Visual Words on Audio Segment Spectrograms

by Evaggelos Spyrou, Rozalia Nikopoulou, Ioannis Vernikos and Phivos Mylonas

Technologies 2019, 7(1), 20; https://doi.org/10.3390/technologies7010020 - 04 Feb 2019

Cited by 22 | Viewed by 8622

Abstract

It is noteworthy nowadays that monitoring and understanding a human’s emotional state plays a key role in the current and forthcoming computational technologies. On the other hand, this monitoring and analysis should be as unobtrusive as possible, since in our era the digital [...] Read more.

It is noteworthy nowadays that monitoring and understanding a human’s emotional state plays a key role in the current and forthcoming computational technologies. On the other hand, this monitoring and analysis should be as unobtrusive as possible, since in our era the digital world has been smoothly adopted in everyday life activities. In this framework and within the domain of assessing humans’ affective state during their educational training, the most popular way to go is to use sensory equipment that would allow their observing without involving any kind of direct contact. Thus, in this work, we focus on human emotion recognition from audio stimuli (i.e., human speech) using a novel approach based on a computer vision inspired methodology, namely the bag-of-visual words method, applied on several audio segment spectrograms. The latter are considered to be the visual representation of the considered audio segment and may be analyzed by exploiting well-known traditional computer vision techniques, such as construction of a visual vocabulary, extraction of speeded-up robust features (SURF) features, quantization into a set of visual words, and image histogram construction. As a last step, support vector machines (SVM) classifiers are trained based on the aforementioned information. Finally, to further generalize the herein proposed approach, we utilize publicly available datasets from several human languages to perform cross-language experiments, both in terms of actor-created and real-life ones. Full article

(This article belongs to the Special Issue The PErvasive Technologies Related to Assistive Environments (PETRA))

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24 pages, 3277 KiB

Open AccessEditor’s ChoiceReview

On Distributed Denial of Service Current Defense Schemes

by Seth Djane Kotey, Eric Tutu Tchao and James Dzisi Gadze

Technologies 2019, 7(1), 19; https://doi.org/10.3390/technologies7010019 - 30 Jan 2019

Cited by 24 | Viewed by 8381

Abstract

Distributed denial of service (DDoS) attacks are a major threat to any network-based service provider. The ability of an attacker to harness the power of a lot of compromised devices to launch an attack makes it even more complex to handle. This complexity [...] Read more.

Distributed denial of service (DDoS) attacks are a major threat to any network-based service provider. The ability of an attacker to harness the power of a lot of compromised devices to launch an attack makes it even more complex to handle. This complexity can increase even more when several attackers coordinate to launch an attack on one victim. Moreover, attackers these days do not need to be highly skilled to perpetrate an attack. Tools for orchestrating an attack can easily be found online and require little to no knowledge about attack scripts to initiate an attack. Studies have been done severally to develop defense mechanisms to detect and defend against DDoS attacks. As defense schemes are designed and developed, attackers are also on the move to evade these defense mechanisms and so there is a need for a continual study in developing defense mechanisms. This paper discusses the current DDoS defense mechanisms, their strengths and weaknesses. Full article

(This article belongs to the Special Issue Technologies for Industry 4.0)

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29 pages, 10715 KiB

Open AccessEditor’s ChoiceArticle

A Comprehensive Review of RFID and Bluetooth Security: Practical Analysis

by Santiago Figueroa Lorenzo, Javier Añorga Benito, Pablo García Cardarelli, Jon Alberdi Garaia and Saioa Arrizabalaga Juaristi

Technologies 2019, 7(1), 15; https://doi.org/10.3390/technologies7010015 - 24 Jan 2019

Cited by 19 | Viewed by 12586

Abstract

The Internet of Things (IoT) provides the ability to digitize physical objects into virtual data, thanks to the integration of hardware (e.g., sensors, actuators) and network communications for collecting and exchanging data. In this digitization process, however, security challenges need to be taken [...] Read more.

The Internet of Things (IoT) provides the ability to digitize physical objects into virtual data, thanks to the integration of hardware (e.g., sensors, actuators) and network communications for collecting and exchanging data. In this digitization process, however, security challenges need to be taken into account in order to prevent information availability, integrity, and confidentiality from being compromised. In this paper, security challenges of two broadly used technologies, RFID (Radio Frequency Identification) and Bluetooth, are analyzed. First, a review of the main vulnerabilities, security risk, and threats affecting both technologies are carried out. Then, open hardware and open source tools like: Proxmark3 and Ubertooth as well as BtleJuice and Bleah are used as part of the practical analysis. Lastly, risk mitigation and counter measures are proposed. Full article

(This article belongs to the Special Issue Technology Advances on IoT Learning and Teaching)

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13 pages, 1067 KiB

Open AccessEditor’s ChoiceArticle

Adapting Engineering Education to Industry 4.0 Vision

by Selim Coşkun, Yaşanur Kayıkcı and Eray Gençay

Technologies 2019, 7(1), 10; https://doi.org/10.3390/technologies7010010 - 10 Jan 2019

Cited by 111 | Viewed by 14648

Abstract

Industry 4.0 is originally a future vision described in the high-tech strategy of the German government that is conceived upon information and communication technologies like Cyber-Physical Systems, Internet of Things, Physical Internet, and Internet of Services to achieve a high degree of flexibility [...] Read more.

Industry 4.0 is originally a future vision described in the high-tech strategy of the German government that is conceived upon information and communication technologies like Cyber-Physical Systems, Internet of Things, Physical Internet, and Internet of Services to achieve a high degree of flexibility in production (individualized mass production), higher productivity rates through real-time monitoring and diagnosis, and a lower wastage rate of material in production. An important part of the tasks in the preparation for Industry 4.0 is the adaption of the higher education to the requirements of this vision, in particular the engineering education. In this work, we introduce a road map consisting of three pillars describing the changes/enhancements to be conducted in the areas of curriculum development, lab concept, and student club activities. We also report our current application of this road map at the Turkish German University, Istanbul. Full article

(This article belongs to the Special Issue Technologies for Industry 4.0)

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16 pages, 276 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Towards Analyzing the Complexity Landscape of Solidity Based Ethereum Smart Contracts

by Péter Hegedűs

Technologies 2019, 7(1), 6; https://doi.org/10.3390/technologies7010006 - 03 Jan 2019

Cited by 41 | Viewed by 9549

Abstract

Blockchain-based decentralized cryptocurrency platforms are currently one of the hottest topics in technology. Although most of the interest is generated by cryptocurrency related activities, it is becoming apparent that a much wider spectrum of applications can leverage the blockchain technology. The primary concepts [...] Read more.

Blockchain-based decentralized cryptocurrency platforms are currently one of the hottest topics in technology. Although most of the interest is generated by cryptocurrency related activities, it is becoming apparent that a much wider spectrum of applications can leverage the blockchain technology. The primary concepts enabling such general use of the blockchain are the so-called smart contracts, which are special programs that run on the blockchain. One of the most popular blockchain platforms that supports smart contracts is Ethereum. As smart contracts typically handle money, ensuring their low number of faults and vulnerabilities are essential. To aid smart contract developers and help to mature the technology, we need analysis tools and studies for smart contracts. As an initiative for this, we propose the adoption of some well-known OO metrics for Solidity smart contracts. Furthermore, we analyze more than 40 thousand Solidity source files with our prototype tool. The results suggest that smart contract programs are short, neither overly complex nor coupled too much, do not rely heavily on inheritance, and either quite well-commented or not commented at all. Moreover, smart contracts could benefit from an external library and dependency management mechanism, as more than 85% of the defined libraries in Solidity files code the same functionalities. Full article

(This article belongs to the Special Issue Blockchain Technology and Applications)

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