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Volume 10, February-1

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Appl. Sci., Volume 10, Issue 4 (February-2 2020) – 256 articles

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Open AccessArticle
Wasserstein Generative Adversarial Networks Based Data Augmentation for Radar Data Analysis
Appl. Sci. 2020, 10(4), 1449; https://doi.org/10.3390/app10041449 (registering DOI) - 20 Feb 2020
Abstract
Ground-based weather radar can observe a wide range with a high spatial and temporal resolution. They are beneficial to meteorological research and services by providing valuable information. Recent weather radar data related research has focused on applying machine learning and deep learning to [...] Read more.
Ground-based weather radar can observe a wide range with a high spatial and temporal resolution. They are beneficial to meteorological research and services by providing valuable information. Recent weather radar data related research has focused on applying machine learning and deep learning to solve complicated problems. It is a well-known fact that an adequate amount of data is a positively necessary condition in machine learning and deep learning. Generative adversarial networks (GANs) have received extensive attention for their remarkable data generation capacity, with a fascinating competitive structure having been proposed since. Consequently, a massive number of variants have been proposed; which model is adequate to solve the given problem is an inevitable concern. In this paper, we propose exploring the problem of radar image synthesis and evaluating different GANs with authentic radar observation results. The experimental results showed that the improved Wasserstein GAN is more capable of generating similar radar images while achieving higher structural similarity results. Full article
(This article belongs to the Section Computing and Artificial Intelligence)
Open AccessArticle
Correlation between LAA Morphological Features and Computational Fluid Dynamics Analysis for Non-Valvular Atrial Fibrillation Patients
Appl. Sci. 2020, 10(4), 1448; https://doi.org/10.3390/app10041448 (registering DOI) - 20 Feb 2020
Abstract
The left atrial appendage (LAA) is a complex cardiovascular structure which can yield to thrombi formation in patients with non-valvular atrial fibrillation (AF). The study of LAA fluid dynamics together with morphological features should be investigated in order to evaluate the possible connection [...] Read more.
The left atrial appendage (LAA) is a complex cardiovascular structure which can yield to thrombi formation in patients with non-valvular atrial fibrillation (AF). The study of LAA fluid dynamics together with morphological features should be investigated in order to evaluate the possible connection of geometrical and hemodynamics indices with the stroke risk. To reach this goal, we conducted a morphological analysis of four different LAA shapes considering their variation during the cardiac cycle and computational fluid dynamics (CFD) simulations in AF conditions were carried out. The analysis of main geometrical LAA parameters showed a huger ostium and a reduced motility for the cauliflower and cactus shapes, as well as a lower velocity values from the CFD analysis. Such findings are in line with literature and highlight the importance of coupling dynamics imaging data with CFD calculations for providing information not available at clinical level. Full article
(This article belongs to the Special Issue Computer-aided Biomedical Imaging 2020: Advances and Prospects)
Open AccessArticle
Kinematic Modelling and Experimental Validation of a Foldable Pneumatic Soft Manipulator
Appl. Sci. 2020, 10(4), 1447; https://doi.org/10.3390/app10041447 (registering DOI) - 20 Feb 2020
Abstract
A foldable pneumatic soft manipulator, which has the foldability to switch between a contraction state and an expanded state, is proposed in this investigation. The soft manipulator is a structure composed of pneumatic actuators and inflatable straight arms. The directional movement is driven [...] Read more.
A foldable pneumatic soft manipulator, which has the foldability to switch between a contraction state and an expanded state, is proposed in this investigation. The soft manipulator is a structure composed of pneumatic actuators and inflatable straight arms. The directional movement is driven by the pneumatic actuators and the foldability is realized by the inflatable straight arms. Based on this design, the kinematic model of one foldable pneumatic module is developed and presented. The shape deformation and workspace of the pneumatic module is numerically calculated and analyzed. To validate the correctness of the kinematic model, the prototype of one foldable pneumatic module, as well as the relevant pneumatic control system, is designed and developed. The repeatability of the pneumatic module and the model prediction accuracy are tested and validated by the experiment. Full article
(This article belongs to the Special Issue Modeling, Design, and Optimization of Flexible Mechanical Systems)
Open AccessArticle
Evaluation of Effective Cognition for the QGIS Processing Modeler
Appl. Sci. 2020, 10(4), 1446; https://doi.org/10.3390/app10041446 (registering DOI) - 20 Feb 2020
Abstract
This article presents an evaluation of the QGIS Processing Modeler from the point of view of effective cognition. The QGIS Processing Modeler uses visual programming language for workflow design. The functionalities of the visual component and the visual vocabulary (set of symbols and [...] Read more.
This article presents an evaluation of the QGIS Processing Modeler from the point of view of effective cognition. The QGIS Processing Modeler uses visual programming language for workflow design. The functionalities of the visual component and the visual vocabulary (set of symbols and line connectors) are both important. The form of symbols affects how workflow diagrams may be understood. The article discusses the results of assessing the Processing Modeler’s visual vocabulary in QGIS according to the Physics of Notations theory. The article evaluates visual vocabularies from the older QGIS 2.x and newer 3.x versions. The paper identifies serious design flaws in the Processing Modeler. Applying the Physics of Notations theory resulted in certain practical recommendations, such as changing the fill colour of symbols, increasing the size and variety of inner icons, removing functional icons, and using a straight connector line instead of a curved line. Another recommendation was to provide a supplemental preview window for the entire model in order to improve user navigation in huge models. Objective eye-tracking measurements validated some results of the evaluation using the Physics of Notations. The respondents read workflows to solve different tasks and their gazes were tracked. Evaluation of the eye-tracking metrics revealed the respondents’ reading patterns of the diagram. Evaluation using both Physics of Notation theory and eye-tracking measurements inspired recommendations for improving visual notation. A set of recommendations for users is also given, which can be applied easily in practice using a contemporary visual notation. Full article
(This article belongs to the Special Issue Recent Advances in Geographic Information System for Earth Sciences)
Open AccessArticle
Sudden Variation Effect of Aerodynamic Loads and Safety Analysis of Running Trains When Entering Tunnel Under Crosswind
Appl. Sci. 2020, 10(4), 1445; https://doi.org/10.3390/app10041445 (registering DOI) - 20 Feb 2020
Abstract
Sudden variation of aerodynamic loads is a potential source of safety accidents of high-speed trains (HSTs). As a follow-up investigation on the aerodynamic response of a HST that enters a tunnel under crosswind environment, this paper focuses on the transient response of a [...] Read more.
Sudden variation of aerodynamic loads is a potential source of safety accidents of high-speed trains (HSTs). As a follow-up investigation on the aerodynamic response of a HST that enters a tunnel under crosswind environment, this paper focuses on the transient response of a HST’s safety indices based on the train–track coupling interaction model. Firstly, a wind–train–track coupling dynamic model is proposed by introducing transient aerodynamic loads into the vehicle–track system. Secondly, the temporal evolution of safety coefficients indicates that the train’s safety risk increases during tunnel entry with crosswind. Results show that the derailment coefficients and wheel load reduction rate during tunnel entry are not only larger than those in open air, but also those inside the tunnel are due to the sudden disappearance of wind excitation at the tunnel entrance. In addition, the characteristic wind curve, which is the wind velocity against the train speed, is presented for application based on the current specification of the safety criteria threshold. The investigation will be useful in assessing the safety risk of a running train subjected to other aerodynamic attacks, such as the coupling effect of an infrastructure scenario and crosswind in a windy area. Full article
(This article belongs to the Special Issue Interactions between Railway Subsystems)
Open AccessArticle
Studies on the Antibacterial Influence of Two Ionic Liquids and their Corrosion Inhibition Performance
Appl. Sci. 2020, 10(4), 1444; https://doi.org/10.3390/app10041444 (registering DOI) - 20 Feb 2020
Abstract
In this paper the anti-bacterialand the anti-corrosion effect of two different ionic liquids, namely 1-(2-hydroxyethyl)-3-methylimidazolinium chloride ([OH-EMIm]Cl) and 1-ethyl-3-methyleimidazolinium chloride ([EMIm]Cl) was demonstrated. The results revealed that the corrosion inhibition influence of the ionic liquid [OH-EMIm]Cl is higher than that of the ionic [...] Read more.
In this paper the anti-bacterialand the anti-corrosion effect of two different ionic liquids, namely 1-(2-hydroxyethyl)-3-methylimidazolinium chloride ([OH-EMIm]Cl) and 1-ethyl-3-methyleimidazolinium chloride ([EMIm]Cl) was demonstrated. The results revealed that the corrosion inhibition influence of the ionic liquid [OH-EMIm]Cl is higher than that of the ionic liquid [EMIm]Cl. Furthermore, the ionic liquid [OH-EMIm]Cl showed better biocidal influence compared with the ionic liquid [EMIm]Cl. This indicates the synergistic effect due to the incorporation of the hydroxyl group into the side chain of the imidazolium cation leading to enhanced antibacterial and anticorrosion effect. Full article
(This article belongs to the Section Chemistry)
Open AccessArticle
Parametric and Nonparametric PI Controller Tuning Method for Integrating Processes Based on Magnitude Optimum
Appl. Sci. 2020, 10(4), 1443; https://doi.org/10.3390/app10041443 (registering DOI) - 20 Feb 2020
Abstract
Integrating systems are frequently encountered in the oil industry (oil–water–gas separators, distillation columns), power plants, paper-production plants, polymerisation processes, and in storage tanks. Due to the non-self-regulating character of the processes, any disturbance can cause a drift of the process output signal. Therefore, [...] Read more.
Integrating systems are frequently encountered in the oil industry (oil–water–gas separators, distillation columns), power plants, paper-production plants, polymerisation processes, and in storage tanks. Due to the non-self-regulating character of the processes, any disturbance can cause a drift of the process output signal. Therefore, efficient closed-loop control of such processes is required. There are many PI and PID controller tuning methods for integrating processes. However, it is hard to find one requiring only a simple tuning procedure on the process, while the tuning method is based either on time-domain measurements or on a process transfer function of arbitrary order, which are the advantages of the magnitude optimum multiple integration (MOMI) tuning method. In this paper, we propose the extension of the MOMI tuning method to integrating processes. Besides the mentioned advantages, the extension provides efficient closed-loop control, while PI controller parameters calculation is still based on simple algebraic expressions, making it suitable for less-demanding hardware, like simpler programmable logic controllers (PLC). Additionally, the proposed method incorporates reference weighting factor b that allows users to emphasize either the disturbance-rejection or reference-following response. The proposed extension of the MOMI method (time-domain approach) was also tested on a charge-amplifier drift-compensation system, a laboratory hydraulic plant, on an industrial autoclave, and on a solid-oxide fuel-cell temperature control. All closed-loop responses were relatively stable and fast, all in accordance with the magnitude optimum criteria. Full article
(This article belongs to the Section Electrical, Electronics and Communications Engineering)
Open AccessArticle
Research on Ride Comfort and Driving Safety under Hybrid Damping Extension Control for Suspension Systems
Appl. Sci. 2020, 10(4), 1442; https://doi.org/10.3390/app10041442 (registering DOI) - 20 Feb 2020
Abstract
This paper is concerned with the conflicting performances of ride comfort and driving safety for semi-active suspension systems. To alleviate this conflict, a novel hybrid damping extension control (HDEC) method is proposed. This method adopts various control methods and the weights of each [...] Read more.
This paper is concerned with the conflicting performances of ride comfort and driving safety for semi-active suspension systems. To alleviate this conflict, a novel hybrid damping extension control (HDEC) method is proposed. This method adopts various control methods and the weights of each method are determined by extension theory. Firstly, body acceleration and tire dynamic transformation are selected to evaluate ride comfort and driving safety performance for the semi-active suspension system and their frequency responses of passive suspension, sky-hook control, ground hook control, and S-GH (sky-ground hook) control are analyzed based on a two degree-of-freedom (2-DOF) model. Secondly, extension theory is introduced and the extension control system, which contains three modes and corresponding control algorithms, is established. In addition, the low-frequency excitation and high-frequency excitation simulations are designed to determine the parameters of the extension control system. Finally, ve-DYNA vehicle suspension model simulation is applied to prove the feasibility and effectiveness of the extension control. The simulation results show that, based on the suspension state, extension control can improve the performance of ride comfort and driving safety. Full article
(This article belongs to the collection Recent Applications of Active and Passive Noise Control)
Open AccessArticle
Investigation on Recycled Sawdust in Controlling Sulphate Attack in Cemented Clay
Appl. Sci. 2020, 10(4), 1441; https://doi.org/10.3390/app10041441 (registering DOI) - 20 Feb 2020
Abstract
Application of sawdust in civil engineering projects, specifically those with geotechnical applications, has been the interest of many studies. This study focuses on exposure of soil samples treated with sawdust to MgSO4. This study was conducted in three stages. The first stage was [...] Read more.
Application of sawdust in civil engineering projects, specifically those with geotechnical applications, has been the interest of many studies. This study focuses on exposure of soil samples treated with sawdust to MgSO4. This study was conducted in three stages. The first stage was compaction. In this stage, the compaction characteristics of each mixture were derived. The second stage was to run unconfined compressive strength (UCS) testing and report the UCS peaks relevant to each mixture. The third stage was microstructural examination (i.e., SEM) conducted on the chosen samples before and after sulphate exposure to highlight the reactions during exposure. The results of first stage (i.e., compaction tests) suggested that increasing sawdust content, the OMC (Optimum moisture content) decreased and MDD (Maximum dry density) decreased. In the second stage, the UCS (Unconfined compressive strength) testing was conducted on 640 samples [including reliability tests] and the outcome suggested that sawdust increased the resistance of samples against sulphate attack. In stage three, the micro analysis backed the main body results, suggesting that sawdust had a positive effect on helping to form a better connection between the particles and therefore more resistance noted. Full article
Open AccessArticle
An Evaluation of the Zeeman Shift of the 87Sr Optical Lattice Clock at the National Time Service Center
Appl. Sci. 2020, 10(4), 1440; https://doi.org/10.3390/app10041440 (registering DOI) - 20 Feb 2020
Abstract
The Zeeman shift plays an important role in the evaluation of optical lattice clocks since a strong bias magnetic field is applied for departing Zeeman sublevels and defining a quantization axis. We demonstrated the frequency correction and uncertainty evaluation due to Zeeman shift [...] Read more.
The Zeeman shift plays an important role in the evaluation of optical lattice clocks since a strong bias magnetic field is applied for departing Zeeman sublevels and defining a quantization axis. We demonstrated the frequency correction and uncertainty evaluation due to Zeeman shift in the 87Sr optical lattice clock at the National Time Service Center. The first-order Zeeman shift was almost completely removed by stabilizing the clock laser to the average frequency of the two Zeeman components of mF = ±9/2. The residual first-order Zeeman shift arose from the magnetic field drift between measurements of the two stretched-state center frequencies; the upper bound was inferred as 4(5) × 10−18. The quadratic Zeeman shift coefficient was experimentally determined as –23.0(4) MHz/T2 and the final Zeeman shift was evaluated as 9.20(7) × 10−17. The evaluation of the Zeeman shift is a foundation for overall evaluation of the uncertainty of an optical lattice clock. This measurement can provide more references for the determination of the quadratic coefficient of 87Sr. Full article
(This article belongs to the Special Issue Optical Trapping)
Open AccessArticle
Accumulation of Selenium in Candida utilis Growing in Media of Increasing Concentration of this Element
Appl. Sci. 2020, 10(4), 1439; https://doi.org/10.3390/app10041439 (registering DOI) - 20 Feb 2020
Abstract
Selenium is considered an essential component of all living organisms. Studies on the enrichment of yeast cells with selenium, using the ability of cell biomass to bind this element, are being reported more and more. Yeast cultures were cultivated in YPD medium enriched [...] Read more.
Selenium is considered an essential component of all living organisms. Studies on the enrichment of yeast cells with selenium, using the ability of cell biomass to bind this element, are being reported more and more. Yeast cultures were cultivated in YPD medium enriched with Na2SeO3 salts for 72 h at 28 °C on a shaker utilizing reciprocating motion. Selenium in cell biomass was determined with the use of ICP–MS. It was observed that the addition of selenium to the experimental medium (in the range of 4–100 mg/L) increased the content of this element in the yeast cell biomass. During the extension of cultivation time, the number of yeast cells and biomass yield exhibited a decreasing trend. Based on the obtained results, it was concluded that yeast cells exhibited the ability to accumulate selenium in both logarithmic and stationary growth phases. The dose of 20 and 30 mg/L of selenium in the culture medium meets the expectations in terms of both the content of selenium bound to yeast cells (1944 ± 110.8 μg/g dry weight) under 48-h cultivation. The obtained results confirmed that the Candida utilis ATCC 9950 strain exhibits the ability to bind selenium, which means that the biomass of these yeasts may be used as a natural source of selenium in the diet of humans and animals. Full article
(This article belongs to the Special Issue Selenium: Properties and Sources in the Food Industry)
Open AccessArticle
Preparation of a Biofunctionalized Surface on Titanium for Biomedical Applications: Surface Properties, Wettability Variations, and Biocompatibility Characteristics
Appl. Sci. 2020, 10(4), 1438; https://doi.org/10.3390/app10041438 (registering DOI) - 20 Feb 2020
Abstract
This study developed a promising approach (low-temperature plasma polymerization with allylamine) to modify the titanium (Ti) surface, which helps the damaged tissue to heal faster. The Ti surface was first cleaned by argon (Ar) plasma, and then the functional amino-groups were coated on [...] Read more.
This study developed a promising approach (low-temperature plasma polymerization with allylamine) to modify the titanium (Ti) surface, which helps the damaged tissue to heal faster. The Ti surface was first cleaned by argon (Ar) plasma, and then the functional amino-groups were coated on the Ti surface via plasma polymerization. The topography characteristics, wettability, and optimal plasma modification parameters were investigated through atomic force spectroscopy, secondary ion mass spectroscopy, and response surface methodology (RSM). Analytical results showed that the formation of a porous surface was found on the Ar plasma-modified Ti surfaces after Ar plasma modification with different parameters. The Ar plasma modification is an effective approach to remove surface contaminants and generate a porous topography on the Ti surface. As the Ti with Ar plasma modification was at 100 W and 190 m Torr for 12 min, the surface exhibited the maximum hydrophilic performance. In the allylamine plasma modifications, the contact angle values of the allylamine plasma-modified Ti surfaces varied between 70.15° and 88.26° in the designed parameters. The maximum concentration of amino-groups (31.58 nmole/cm2) can be obtained from the plasma-polymerized sample at 80 W and 150 mTorr for 22 min. Moreover, the cell response also demonstrated that the allylamine plasma-modified Ti sample with an optimal modification parameter (80 W, 22 min, and 150 mTorr) possessed great potential to increase cell adhesion ability. Thus, the optimal parameters of the low-temperature plasma polymerization with allylamine can be harvested using the RSM design. These data could provide new scientific information in the surface modification of Ti implant. Full article
(This article belongs to the Special Issue Application of the Biocomposite Materials on Bone Reconstruction)
Open AccessArticle
Characteristics of the Wind Environment above Bridge Deck near the Pylon Zone and Wind Barrier Arrangement Criteria
Appl. Sci. 2020, 10(4), 1437; https://doi.org/10.3390/app10041437 (registering DOI) - 20 Feb 2020
Abstract
Due to the complex arrangement of structural components in the vicinity of bridge pylon zones, the wind environment above bridge decks is very complicated. A sudden change in wind speed exerts an adverse effect on vehicle control stability. In order to investigate the [...] Read more.
Due to the complex arrangement of structural components in the vicinity of bridge pylon zones, the wind environment above bridge decks is very complicated. A sudden change in wind speed exerts an adverse effect on vehicle control stability. In order to investigate the characteristics of the flow field in the vicinity of the bridge pylon, the wind environment near an inverted Y-shaped pylon is studied by experimental and numerical methods. From the flow visualization and the wind speed measurement in the wind tunnel and the numerical simulation created using Fluent software, specific patterns of the direction and magnitude of wind speed at a range of vehicle height above the bridge deck near the pylon zone were observed along the longitudinal direction. This distribution pattern of the wind environment can effectively guide the wind barrier arrangement near the bridge pylon zone. Combined with the two safety evaluation indicators proposed in this paper, the optimal arrangement scheme of wind barriers in the bridge pylon zone of Sutong Bridge is determined. This paper deepens the understanding of the wind environment near the pylon zone and proposes an evaluation method for the wind environment near the pylon zone, which can serve as the basis for wind barrier arrangement in similar research projects. Full article
(This article belongs to the Special Issue Bridge Dynamics)
Open AccessArticle
Computational Investigation of Liquid Holdup and Wetting Efficiency Inside Trickle Bed Reactors with Different Catalyst Particle Shapes
Appl. Sci. 2020, 10(4), 1436; https://doi.org/10.3390/app10041436 (registering DOI) - 20 Feb 2020
Abstract
Liquid holdup and wetting efficiency are essential parameters for design of trickle bed reactors. Both parameters play an important role in reactor performance including pressure drop, conversion, and heat transfer. Empirical formulas are usually employed to calculate liquid holdup and wetting efficiency. However, [...] Read more.
Liquid holdup and wetting efficiency are essential parameters for design of trickle bed reactors. Both parameters play an important role in reactor performance including pressure drop, conversion, and heat transfer. Empirical formulas are usually employed to calculate liquid holdup and wetting efficiency. However, factors such as particle shape and the wetting ability of liquid on the particle surface are not described clearly in traditional formulas. In this paper, actual random packing was built by DEM and CFD simulations were performed to investigate the factors affecting liquid holdup and wetting efficiency in trickle bed reactors, including particle shape, surface tension, contact angle, liquid viscosity, liquid density, liquid, and gas superficial velocity. Detailed fluid flow and liquid-solid interaction were described by VOF model. Four different particle shapes were investigated. It showed the particle shape has great effect and the 4-hole cylinder packing gained both highest liquid holdup and wetting efficiency. The overall simulations gave a detailed description of phase interactions and fluid flow in the voids between catalyst particles and these results could give further guidance for the design and operation of trickle bed reactors. Full article
Open AccessArticle
A Hybrid Tolerance Design Method for the Active Phased-Array Antenna
Appl. Sci. 2020, 10(4), 1435; https://doi.org/10.3390/app10041435 (registering DOI) - 20 Feb 2020
Abstract
With the increase of the working frequency of the array antenna, tolerance design has become increasingly important. The state-of-art tolerance design methods mainly deal with the position tolerance of the discrete elements. However, the geometric errors of the whole array have resulted from [...] Read more.
With the increase of the working frequency of the array antenna, tolerance design has become increasingly important. The state-of-art tolerance design methods mainly deal with the position tolerance of the discrete elements. However, the geometric errors of the whole array have resulted from two aspects: (1) the position errors of the discrete elements and (2) the form errors of the continuous reflection plate. To optimize the position tolerance and flatness simultaneously, a hybrid tolerance design method is proposed. First, the relation between the performance of the array antenna and hybrid tolerances was determined based on the second order Taylor expansion. Then the expectation and variance of the performance were derived. Finally, the hybrid tolerances were optimized and the performance of the antenna was improved. Simulation results proved the effectiveness and efficiency of the proposed hybrid tolerance design method. Full article
Open AccessArticle
Smart Transformers as Active Interfaces Enabling the Provision of Power-Frequency Regulation Services from Distributed Resources in Hybrid AC/DC Grids
Appl. Sci. 2020, 10(4), 1434; https://doi.org/10.3390/app10041434 (registering DOI) - 20 Feb 2020
Abstract
Smart Transformers (STs) are being envisioned as a key element for the controllability of distribution networks in a future context of Renewable Energy Source (RES), Energy Storage System (ESS) and Electric Vehicle (EV) massification. Additionally, STs enable the deployment of hybrid AC/DC networks, [...] Read more.
Smart Transformers (STs) are being envisioned as a key element for the controllability of distribution networks in a future context of Renewable Energy Source (RES), Energy Storage System (ESS) and Electric Vehicle (EV) massification. Additionally, STs enable the deployment of hybrid AC/DC networks, which offer important advantages in this context. In addition to offering further degrees of controllability, hybrid AC/DC networks are more suited to integrate DC resources such as DC loads, PV generation, ESS and EV chargers. The purpose of the work developed in this paper is to address the feasibility of exploiting STs to actively coordinate a fleet of resources existing in a hybrid AC/DC network supplied by the ST aiming to provide active power-frequency regulation services to the upstream AC grid. The feasibility of the ST to coordinate the resources available in the hybrid distribution AC/DC network in order to provide active power-frequency regulation services is demonstrated in this paper through computational simulation. It is demonstrated that the aforementioned goal can be achieved using droop-based controllers that can modulate controlled variables in the ST. Full article
Open AccessFeature PaperArticle
Unrepeatered 240-km 64-QAM Transmission Using Distributed Raman Amplification over SMF Fiber
Appl. Sci. 2020, 10(4), 1433; https://doi.org/10.3390/app10041433 (registering DOI) - 20 Feb 2020
Abstract
We present a theoretical and experimental investigation of unrepeatered transmission over standard single-mode fiber (SMF-28) using several schemes of distributed Raman amplification, including first, second, and dual order. In order to further extend the transmission distance, we utilize advanced bidirectional higher-order ultra-long Raman [...] Read more.
We present a theoretical and experimental investigation of unrepeatered transmission over standard single-mode fiber (SMF-28) using several schemes of distributed Raman amplification, including first, second, and dual order. In order to further extend the transmission distance, we utilize advanced bidirectional higher-order ultra-long Raman fiber laser-based amplification, where we use fiber Bragg gratings (FBGs) to reflect Stokes-shifted light from the secondary pumps. Our work demonstrates the possibility of transmission up to 240-km span length with a total span loss of 52.7 dB. Here, we use a 28-Gbaud signal using a 64-quadrature amplitude modulation (QAM) modulation format. Our results highlight the contribution of nonlinear compensation using digital back propagation in a digital signal processor (DSP) code at the receiver. Full article
Open AccessArticle
Reliability Analysis and Imprecise Component Importance Measure of Redundant Systems of OWTs Based on Component Swapping
Appl. Sci. 2020, 10(4), 1432; https://doi.org/10.3390/app10041432 (registering DOI) - 20 Feb 2020
Abstract
Due to the high cost of failures of wind turbines, redundancy designs are commonly applied in wind turbines for improving the reliability and availability of systems. For this reason, replacing failed components with other working components of the same type in redundant systems [...] Read more.
Due to the high cost of failures of wind turbines, redundancy designs are commonly applied in wind turbines for improving the reliability and availability of systems. For this reason, replacing failed components with other working components of the same type in redundant systems is becoming an attractive option of maintenance strategies towards more resilient systems. To quantitatively evaluate system’s reliability, this paper focuses on the reliability analysis of redundant systems of offshore wind turbines based on swapping existing components. The survival signature-based component swapping method is introduced to describe the new structure-function of the system upon swapping. Furthermore, the reliability model of redundant systems is established using the fault tree and survival signature. Following this, the influences of component swapping on component reliability importance measure (marginal reliability importance and joint reliability importance) without and with considerations of the imprecision of failure rates are explored. Finally, a 5MW offshore wind turbine is presented to show the applicability of the proposed approach for redundant systems, and the results show that the proposed approach can obtain realistic reliability assessment of redundant systems and considering component swapping can significantly improve system reliability. Full article
Open AccessArticle
Compliance Control of Slave Manipulator Using EMG Signal for Telemanipulation
Appl. Sci. 2020, 10(4), 1431; https://doi.org/10.3390/app10041431 (registering DOI) - 20 Feb 2020
Abstract
Telemanipulation systems have been widely utilized in industrial, surgical, educational, and even military fields. One of the important issues is that when a robot interacts with environment or objects, it can damage the robot itself or the objects due to hard contact. To [...] Read more.
Telemanipulation systems have been widely utilized in industrial, surgical, educational, and even military fields. One of the important issues is that when a robot interacts with environment or objects, it can damage the robot itself or the objects due to hard contact. To address this problem, we propose a novel compliance control of a slave robot using the electromyography (EMG) signal, which is measured by the sensors attached onto the master operator’s arm. The EMG signal is used since it is easy to process and it provides humans with an intuitive capability to perform the operational work. Furthermore, it has been proved that the EMG signal is useful in the control of the stiffness of the slave robot. This research identifies the muscle that is the best suitable to a precision-grip operation, and a series of experiments were performed. A compliance control algorithm with a variable stiffness of a slave robot is proposed, where the stiffness is changed based on the EMG signal, and it is confirmed by a series of experiments using a two-channel force/position teleoperation architecture. Full article
(This article belongs to the Section Mechanical Engineering)
Open AccessArticle
Phase Space Reconstruction from a Biological Time Series: A Photoplethysmographic Signal Case Study
Appl. Sci. 2020, 10(4), 1430; https://doi.org/10.3390/app10041430 (registering DOI) - 20 Feb 2020
Abstract
In the analysis of biological time series, the state space is comprised of a framework for the study of systems with presumably deterministic and stationary properties. However, a physiological experiment typically captures an observable that characterizes the temporal response of the physiological system [...] Read more.
In the analysis of biological time series, the state space is comprised of a framework for the study of systems with presumably deterministic and stationary properties. However, a physiological experiment typically captures an observable that characterizes the temporal response of the physiological system under study; the dynamic variables that make up the state of the system at any time are not available. Only from the acquired observations should state vectors be reconstructed to emulate the different states of the underlying system. This is what is known as the reconstruction of the state space, called the phase space in real-world signals, in many cases satisfactorily resolved using the method of delays. Each state vector consists of m components, extracted from successive observations delayed a time τ . The morphology of the geometric structure described by the state vectors, as well as their properties depends on the chosen parameters τ and m. The real dynamics of the system under study is subject to the correct determination of the parameters τ and m. Only in this way can be deduced features have true physical meaning, revealing aspects that reliably identify the dynamic complexity of the physiological system. The biological signal presented in this work, as a case study, is the photoplethysmographic (PPG) signal. We find that m is five for all the subjects analyzed and that τ depends on the time interval in which it is evaluated. The Hénon map and the Lorenz flow are used to facilitate a more intuitive understanding of the applied techniques. Full article
(This article belongs to the Special Issue Signal Processing and Machine Learning for Biomedical Data)
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Open AccessArticle
Interval Identification of Thermal Parameters Using Trigonometric Series Surrogate Model and Unbiased Estimation Method
Appl. Sci. 2020, 10(4), 1429; https://doi.org/10.3390/app10041429 (registering DOI) - 20 Feb 2020
Abstract
Metal-foam materials have been applied in many engineering fields in virtue of its high specific strength and desirable of thermodynamic properties. However, due to the inherent uncertainty of its attribute parameters, reliable analysis results are often ambiguous to obtain accurately. To overcome this [...] Read more.
Metal-foam materials have been applied in many engineering fields in virtue of its high specific strength and desirable of thermodynamic properties. However, due to the inherent uncertainty of its attribute parameters, reliable analysis results are often ambiguous to obtain accurately. To overcome this drawback, this paper proposes a novel interval parameter identification method. Firstly, a novel modelling methodology is proposed to simulate the geometry of engineering metal foams. Subsequently, the concept of intervals is introduced to represent the uncertainty relationship between variables and responses in heat transfer systems. To improve computational efficiency, a novel augmented trigonometric series surrogate model is constructed. Moreover, unbiased estimation methods based on different probability distributions are presented to describe system measurement intervals. Then, a multi-level optimization-based identification strategy is proposed to seek the parameter interval efficiently. Eventually, an engineering heat transfer system is given to verify the feasibility of the proposed parameter identification method. This method can rapidly identify the unknown parameters of the system. The identification results demonstrate that this interval parameter identification method can quantify the uncertainty of a metal-foam structure in engineering heat transfer systems efficiently, especially for the actual case without sufficient measurements. Full article
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Open AccessFeature PaperArticle
Microwave Healing Performance of Asphalt Mixture Containing Electric Arc Furnace (EAF) Slag and Graphene Nanoplatelets (GNPs)
Appl. Sci. 2020, 10(4), 1428; https://doi.org/10.3390/app10041428 (registering DOI) - 20 Feb 2020
Abstract
Pavement preventive maintenance is an important tool for extending the service life of the road pavements. Microwave heating seems to be a promising technology for this application, as bituminous materials have the potential to self-repair above a certain temperature. As ordinary asphalt mixture [...] Read more.
Pavement preventive maintenance is an important tool for extending the service life of the road pavements. Microwave heating seems to be a promising technology for this application, as bituminous materials have the potential to self-repair above a certain temperature. As ordinary asphalt mixture has low microwave absorbing properties, some additives should be used to improve the heating efficiency. In this paper, the effect of adding Electric Arc Furnace (EAF) slag and Graphene Nanoplatelets (GNPs) on the microwave heating and healing efficiency of asphalt mixtures was evaluated. Microwave heating efficiency was assessed by heating the specimens using several heating times. In addition, the electrical resistivity of the mixtures was measured to understand its possible relationship with the microwave heating process. Furthermore, the healing rates of the asphalt mixtures were assessed by repeated Indirect Tensile Strength (ITS) tests. The results obtained indicate that the additions of graphene and EAF slag can allow important savings, up to 50%, on the energy required to perform a good healing process. Full article
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Open AccessArticle
Exocentric Distance Judgment and Accuracy of Head-Mounted and Stereoscopic Widescreen Displays in Frontal Planes
Appl. Sci. 2020, 10(4), 1427; https://doi.org/10.3390/app10041427 (registering DOI) - 20 Feb 2020
Abstract
An experiment was done to explore the effects of two virtual display systems on the accuracy of exocentric distance judgment and position. Sixteen participants viewed animated virtual targets using either a head-mounted display (HMD) or a stereoscopic widescreen display (SWD). The virtual targets [...] Read more.
An experiment was done to explore the effects of two virtual display systems on the accuracy of exocentric distance judgment and position. Sixteen participants viewed animated virtual targets using either a head-mounted display (HMD) or a stereoscopic widescreen display (SWD). The virtual targets have been shown, one at a time, at three depth levels and with two corresponding exocentric distances and three target sizes at each target distance and, afterward, via pointing by holding a stick to estimate the exocentric distance and position of each target. The position data were collected using an OptiTrack motion capture system. The results showed that the accuracy of exocentric distance judgment was higher with the head-mounted displays than with the stereoscopic widescreen displays. In addition, higher position accuracy in the X-direction was obtained from the stereoscopic widescreen displays, whereas no significant difference was observed in position accuracy in the Y-direction. However, it is possible that the HMD could give better accuracy in both exocentric distance and position judgments in the frontal plane, if the HMD had been perfectly mounted and flawlessly fit the participant’s eyes. The result also revealed that exocentric distance judgment was significantly higher at the farthest target distances than at the nearest distance. Similarly, the position accuracy significantly increased as exocentric distance decreased. Moreover, engineers may allude to the findings as the evidence from the study suggests that the intermediate target distances might be fitting or ideal distances to design and structure 3D applications. Full article
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Open AccessArticle
Hierarchical Multi-Stage Cyber Attack Scenario Modeling Based on G&E Model for Cyber Risk Simulation Analysis
Appl. Sci. 2020, 10(4), 1426; https://doi.org/10.3390/app10041426 (registering DOI) - 20 Feb 2020
Abstract
With the advancement in cyber-defense capabilities, cyber attacks have continued to evolve like living creatures to breach security. Assuming the possibility of various enemy attacks, it is necessary to select an appropriate course of action by proactively analyzing and predicting the consequences of [...] Read more.
With the advancement in cyber-defense capabilities, cyber attacks have continued to evolve like living creatures to breach security. Assuming the possibility of various enemy attacks, it is necessary to select an appropriate course of action by proactively analyzing and predicting the consequences of a particular security event. Cyber attacks, especially in large-scale military network environments, have a fatal effect on security; therefore, various experiments and analyses must be conducted to establish the necessary preparations. Herein, we propose a hierarchical multi-stage cyber attack scenario modeling based on the goal and effect (G&E) model and analysis system, which enables expression of various goals of attack and damage effects without being limited to specific type. The proposed method is applicable to large-scale networks and can be utilized in various scenario-based cyber combat experiments. Full article
(This article belongs to the Section Electrical, Electronics and Communications Engineering)
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Open AccessArticle
Experimental Study on the Flexural Behavior of Steel-Textile-Reinforced Concrete: Various Textile Reinforcement Details
Appl. Sci. 2020, 10(4), 1425; https://doi.org/10.3390/app10041425 (registering DOI) - 20 Feb 2020
Abstract
In this study, one reinforced concrete specimen and six textile reinforced concrete (TRC) specimens were produced to analyze the flexural behavior of steel-textile-reinforced concrete. The TRC specimen was manufactured using a total of four variables: textile reinforcement amount, textile reinforcement hook, textile mesh [...] Read more.
In this study, one reinforced concrete specimen and six textile reinforced concrete (TRC) specimens were produced to analyze the flexural behavior of steel-textile-reinforced concrete. The TRC specimen was manufactured using a total of four variables: textile reinforcement amount, textile reinforcement hook, textile mesh type, textile lay out form. Flexural performance increases with textile reinforcement amount, textile reinforcement hook type and textile reinforcement mesh type. The flexural performance was improved when physical hooks were used. Furthermore, textile reinforcement was verified as being effective at controlling the deflection. Full article
(This article belongs to the Section Civil Engineering)
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Open AccessArticle
Data Driven Water Surface Elevation Forecasting Model with Hybrid Activation Function—A Case Study for Hangang River, South Korea
Appl. Sci. 2020, 10(4), 1424; https://doi.org/10.3390/app10041424 (registering DOI) - 20 Feb 2020
Abstract
To date, physical, numerical or data-driven models have been used to forecast water surface elevation in rivers for specific times or locations in the literature. Recently, the trend of forecasting water surface elevation changed from physical and numerical models to data-driven models with [...] Read more.
To date, physical, numerical or data-driven models have been used to forecast water surface elevation in rivers for specific times or locations in the literature. Recently, the trend of forecasting water surface elevation changed from physical and numerical models to data-driven models with the help of the development of big data processing technology and fast simulating time of data-driven models. In this study, a data-driven model with Long Short-Term Memory (LSTM) was developed using TensorFlow, one of the famous deep learning frameworks and forecasting of water surface elevation affected tidal river was performed in Hangang River, Korea. From many types of field measurements, the hourly hydrological data, precipitation, outlet discharge of dam upstream and tidal levels were selected as the input dataset through a t-test and a p-value. In particular, the hybrid activation function was proposed to alleviate the vanishing gradient and dying neuron problems generally issued in the application of the activation function. The model showed that the root mean square error (RMSE) and peak error (PE) decreased by 0.22–0.25 m and 0.11–0.21 m, respectively, and the Nash-Sutcliffe efficiency (NSE) increased up to 79.3%–97.0% compared with the single activation functions. For w 1 = 0.6 and w 2 = 0.4 in the hybrid activation function, the improvement of accuracy and the enhancement of the application range of the leading time interval were obtained through a sensitivity analysis. Moreover, the hybrid activation function showed a good performance. The forecasting results provided by this model can be used as reference data for the establishment of the emergency action plan (EAP). Full article
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Open AccessArticle
An Experimental Study on Milling Titanium Alloy with a Revolving Cycloid Milling Cutter
Appl. Sci. 2020, 10(4), 1423; https://doi.org/10.3390/app10041423 (registering DOI) - 20 Feb 2020
Abstract
In this paper, a revolving cycloid milling cutter was designed with a larger effective cutting helix angle and rake angle than a ball end milling cutter of the same diameter. This new type of milling cutter can solve the problems of low machining [...] Read more.
In this paper, a revolving cycloid milling cutter was designed with a larger effective cutting helix angle and rake angle than a ball end milling cutter of the same diameter. This new type of milling cutter can solve the problems of low machining efficiency, severe tool wear, and low surface quality in titanium alloy processing. A comparison of the cutting performance of titanium alloys processed by the revolving cycloid milling cutter and the ball end milling cutter was carried out to obtain the variation laws of the cutting force and the processing surface quality under different tool wear conditions. The result shows that the wear zone of the revolving cycloid milling cutter is shallow and wide compared to that of the ball end milling cutter. As the wear speeds up, the spoon-shaped wear gathering zone found in the ball-end milling cutter does not happen with the revolving cycloid milling cutter. The revolving cycloid milling cutter can significantly lower the axial force, the tangential force, and the ratio of the axial force to the tangential force with a stable cutting process. Full article
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Open AccessArticle
Roughening in Nonlinear Surface Growth Model
Appl. Sci. 2020, 10(4), 1422; https://doi.org/10.3390/app10041422 (registering DOI) - 20 Feb 2020
Abstract
The aim of this paper is to examine the coarsening process in the evolution of the surface morphology during molecular beam epitaxy (MBE). A numerical approach for modeling the evolution of surface roughening in film growth by MBE is proposed. The model is [...] Read more.
The aim of this paper is to examine the coarsening process in the evolution of the surface morphology during molecular beam epitaxy (MBE). A numerical approach for modeling the evolution of surface roughening in film growth by MBE is proposed. The model is based on the nonlinear differential equations by Kuramoto–Sivashinsky (KS) namely, KS and CKS (conserved KS). In particular, we propose a “combined version” of KS and CKS equations, which is solved as a function of a parameter r for the 1 + 1 dimensional case. The computation provides film height as a function of space and time. From this quantity the change of the width of the film over time has numerically been studied as a function of r. The main result of the research is that the surface width is exponentially increasing with increasing time and the change in surface width for smaller r values is significantly greater over longer time interval. Full article
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Open AccessArticle
Dual Thermal-/Electrical-Responsive Luminescent ‘Smart’ Window
Appl. Sci. 2020, 10(4), 1421; https://doi.org/10.3390/app10041421 (registering DOI) - 20 Feb 2020
Abstract
As buildings are a large energy user, it is important to not only reduce their consumption, but also have them generate their own electricity. Here, we describe a smart window that could reduce electricity consumption, normally used for air conditioning and lighting, by [...] Read more.
As buildings are a large energy user, it is important to not only reduce their consumption, but also have them generate their own electricity. Here, we describe a smart window that could reduce electricity consumption, normally used for air conditioning and lighting, by absorbing excess solar radiation with dichroic fluorescent dye molecules aligned in a switchable liquid crystal host and guiding the re-emitted light energy to the edges of the device, where it can be used to generate electricity via attached photovoltaic cells. The liquid crystals are responsive both to temperature changes and applied electrical fields. At higher temperatures, transmission decreases due to increased disorder in the liquid crystals, while the application of an electrical field increases transmission by effectively realigning the dyes for minimal absorption. Using alternative configurations, a window with a transparent rest state was also produced, in which transmission can be decreased by applying an electrical field; the thermal response remains identical. Full article
(This article belongs to the Special Issue Luminescent Solar Concentrator Photovoltaics)
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Open AccessFeature PaperArticle
Non-Similar Solution of G-jitter Induced Unsteady Magnetohydrodynamic Radiative Slip Flow of Nanofluid
Appl. Sci. 2020, 10(4), 1420; https://doi.org/10.3390/app10041420 (registering DOI) - 20 Feb 2020
Abstract
We present a mathematical model and numerical simulation of the unsteady 2-D g-jitter-free and forced the convective flow of water-based nanofluid from a flat plate, considering both the velocity slip and thermal slip conditions imposed on the wall of the plate. The Darcian [...] Read more.
We present a mathematical model and numerical simulation of the unsteady 2-D g-jitter-free and forced the convective flow of water-based nanofluid from a flat plate, considering both the velocity slip and thermal slip conditions imposed on the wall of the plate. The Darcian model is used, and both cases of a calm and moving free stream are considered. In place of the extensively used linearly varying radiative heat flux, the nonlinearly varying heat flux calculation is applied to produce practically useful results. Further, we incorporate the “zero mass flux boundary condition” which is believed to be more realistic than the earlier extensively used “actively” controlled model. The parameter influences the non-dimensional velocity, temperature, nanoparticle volume fraction, skin friction and heat transfer rates are visualized graphically and discussed in detail. Special cases of the results are benchmarked with those existing in the literature, and a good arrangement is obtained. It is found that the rate of heat transfer is lower for the calm free stream rather than the moving free stream. Full article
(This article belongs to the Section Mechanical Engineering)
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