Next Issue
Volume 10, November-2
Previous Issue
Volume 10, October-2

Appl. Sci., Volume 10, Issue 21 (November-1 2020) – 562 articles

Cover Story (view full-size image): Additive manufacturing enables the transformation of manufacturing processes, encouraging the redesign of products. Besides its technological potentials, the definition of product/process parameters, the selection of redesign variants, the file exchange and data management still represent common issues, which require methods and tools to support designers. This paper presents a redesign approach integrating design for additive manufacturing and topology optimisation, which leads to the objective selection of the best redesigned configuration in accordance with the key performance indicators. The case study shows the redesign of a medical assistive device, previously developed in fused filament fabrication and now optimised for being 3D printed with selective laser melting. View this paper
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Order results
Result details
Select all
Export citation of selected articles as:
Open AccessArticle
A Study on Data Pre-Processing and Accident Prediction Modelling for Occupational Accident Analysis in the Construction Industry
Appl. Sci. 2020, 10(21), 7949; https://doi.org/10.3390/app10217949 - 09 Nov 2020
Viewed by 360
Abstract
In the construction industry, it is difficult to predict occupational accidents because various accident characteristics arise simultaneously and organically in different types of work. Furthermore, even when analyzing occupational accident data, it is difficult to deduce meaningful results because the data recorded by [...] Read more.
In the construction industry, it is difficult to predict occupational accidents because various accident characteristics arise simultaneously and organically in different types of work. Furthermore, even when analyzing occupational accident data, it is difficult to deduce meaningful results because the data recorded by the incident investigator are qualitative and include a wide variety of data types and categories. Recently, numerous studies have used machine learning to analyze the correlations in such complex construction accident data; however, heretofore the focus has been on predicting severity with various variables, and several limitations remain when deriving the correlations between features from various variables. Thus, this paper proposes a data processing procedure that can efficiently manipulate accident data using optimal machine learning techniques and derive and systematize meaningful variables to rationally approach such complex problems. In particular, among the various variables, the most influential variables are derived through methods such as clustering, chi-square, Cramer’s V, and predictor importance; then, the analysis is simplified by optimally grouping the variables. For accident data with optimal variables and elements, a predictive model is constructed between variables, using a support vector machine and decision-tree-based ensemble; then, the correlation between the dependent and independent variables is analyzed through an alluvial flow diagram for several cases. Therefore, a new processing procedure has been introduced in data preprocessing and accident prediction modelling to overcome difficulties from complex and diverse construction occupational accident data, and effective accident prevention is possible by deriving correlations of construction accidents using this process. Full article
(This article belongs to the Special Issue Artificial Intelligence Technologies for Structural Health Monitoring)
Show Figures

Figure 1

Open AccessArticle
Influence of Powder and Liquid Multi-Wall Carbon Nanotubes on Hydration and Dispersion of the Cementitious Composites
Appl. Sci. 2020, 10(21), 7948; https://doi.org/10.3390/app10217948 - 09 Nov 2020
Viewed by 329
Abstract
Two types of multi-walled carbon nanotubes (MWCNTs), powder and liquid, were added to cementitious composites to build self-sensing concrete. To properly evaluate and quantify the effect of MWCNTs on electrical resistance, various tests, including isothermal conduction calorimetry, were carried out. One of primary [...] Read more.
Two types of multi-walled carbon nanotubes (MWCNTs), powder and liquid, were added to cementitious composites to build self-sensing concrete. To properly evaluate and quantify the effect of MWCNTs on electrical resistance, various tests, including isothermal conduction calorimetry, were carried out. One of primary issues of self-monitoring concrete is dispersion, so ultrasonication was used to properly mix the CNTs in the dispersion solution, and silica fume was employed to make the specimens. Scanning electron microscopy (SEM), Raman spectroscopy, and porosity analyses were performed to investigate the physical properties of the composites and to confirm uniform dispersion. The distance of the electrical resistance was also measured, and the dosages and types of MWCNTs were analyzed. Full article
(This article belongs to the Special Issue Multifunctional Cement Composites for Structural Health Monitoring)
Show Figures

Figure 1

Open AccessReview
Process Optimisation of Anaerobic Digestion Treating High-Strength Wastewater in the Australian Red Meat Processing Industry
Appl. Sci. 2020, 10(21), 7947; https://doi.org/10.3390/app10217947 - 09 Nov 2020
Viewed by 269
Abstract
This work represents and reviews a compilation of investigations into improving anaerobic digestion performance of high-strength wastewater in the Australian Red Meat Processing industry. The industry produces significant quantities of organic-rich wastewater which requires treatment prior to release to the environment. Anaerobic lagoons [...] Read more.
This work represents and reviews a compilation of investigations into improving anaerobic digestion performance of high-strength wastewater in the Australian Red Meat Processing industry. The industry produces significant quantities of organic-rich wastewater which requires treatment prior to release to the environment. Anaerobic lagoons are a cost-effective method of waste treatment where land availability is not an issue; however, the high fat load in the wastewater can negatively impact the anaerobic lagoon system and result in compromised anaerobic digestion performance. This paper will discuss the importance of upstream primary pre-treatment and review a series of investigations focused on optimising digester performance and improving fat biodegradability. These studies include: 1. the effect of temperature and mixing; 2. the influence of feedstock trace element composition and supplementation, and; 3. the potential benefit from pre-treatments such as chemical, thermobaric, thermochemical and bio-surfactant. This paper discusses the implications of these findings for covered anaerobic lagoon operation and provides recommendations to promote optimum digester performance and future opportunities in adopting alternate anaerobic digestion technology options. Finally, the paper provides recent trends toward the use of other waste streams for co-digestion and discusses this in terms of digester optimization and technology options. Full article
(This article belongs to the Special Issue Industrial Application of Anaerobic Digestion)
Show Figures

Figure 1

Open AccessArticle
Improvement and In-Situ Application of an Evaluation Method of Ballasted-Track Condition Using Digital 2-D Image Analysis
Appl. Sci. 2020, 10(21), 7946; https://doi.org/10.3390/app10217946 - 09 Nov 2020
Viewed by 270
Abstract
The advancement in digital image analysis methods has led to the development of various techniques, i.e., quantification of ballast gravel abrasion. In this study, the recognition rate of gravel aggregates has been significantly increased by improving the image analysis methods. The correlation between [...] Read more.
The advancement in digital image analysis methods has led to the development of various techniques, i.e., quantification of ballast gravel abrasion. In this study, the recognition rate of gravel aggregates has been significantly increased by improving the image analysis methods. The correlation between the track quality index (TQI), which is the standard deviation of vertical track irregularity and represents the condition of a high-speed railway, and the number of maintenance works was analyzed by performing an image analysis on the samples collected from various locations of a high-speed railway. The results revealed that roundness has the highest correlation with the TQI, whereas sphericity has the highest correlation with the number of maintenance works. The ballast replacement would be performed to improve maintenance efficiency if the abrasion of the ballast aggregates becomes approximately 10%. Full article
(This article belongs to the Special Issue Monitoring and Maintenance Systems for Railway Infrastructure)
Show Figures

Figure 1

Open AccessArticle
Exchange Rate Analysis for Ultra High Bypass Ratio Geared Turbofan Engines
Appl. Sci. 2020, 10(21), 7945; https://doi.org/10.3390/app10217945 - 09 Nov 2020
Viewed by 371
Abstract
This paper investigates the impact of thermal management methods on the design point and synthesis exchange rates of an ultra-high bypass ratio geared turbofan engine. In a typical thermal management system, where heat is managed by means of heat exchangers that transfer engine [...] Read more.
This paper investigates the impact of thermal management methods on the design point and synthesis exchange rates of an ultra-high bypass ratio geared turbofan engine. In a typical thermal management system, where heat is managed by means of heat exchangers that transfer engine waste heat into oil, air, or fuel. However, the utilization of air–oil and fuel–oil heat exchangers has an adverse impact on engine performance. This paper investigates the impact on and engine’s specific fuel consumption and summarizes it into common exchange rates for different thermal management configurations. The results show that any pressure loss in the bypass duct results in a severe specific fuel consumption penalty (an increase of 1% pressure loss in the bypass duct causes a 2% specific fuel consumption increase at cruise conditions). In addition, quite severe is the impact of extracting air from the gas path, particularly when the bleed location is in the bypass duct or the high-pressure compressor. It is also found that the utilization of a fuel–oil heat exchanger improves the specific fuel consumption at a higher rate than an air–oil heat exchanger. For the performance characteristics of the examined engine, the specific fuel consumption benefit with the former is 1.33%, while for the latter it is 0.38%. Full article
(This article belongs to the Special Issue Environmentally Friendly Gas Turbines)
Show Figures

Figure 1

Open AccessArticle
Modular System-Level Modeling Method for the Susceptibility Prediction of Balise Information Transmission System
Appl. Sci. 2020, 10(21), 7944; https://doi.org/10.3390/app10217944 - 09 Nov 2020
Viewed by 218
Abstract
For high-speed train, balise transmission module (BTM) system is easily interfered with by other equipment of the train. This could cause the train to malfunction. Studying the electromagnetic susceptibility (EMS) of the BTM is very important for the performance and efficiency of the [...] Read more.
For high-speed train, balise transmission module (BTM) system is easily interfered with by other equipment of the train. This could cause the train to malfunction. Studying the electromagnetic susceptibility (EMS) of the BTM is very important for the performance and efficiency of the train. In this paper, a modular, system-level modeling method is proposed to predict the EMS of BTM systems. Based on object-oriented technology and a modular method, the BTM system is disassembled into several modules according to the electromagnetic characteristics of the whole system rather than the physical structure. All the modules are mutually independent, and the total EMS could be evaluated by the output of them. The modules of three key elements of electromagnetic compatibility (EMC), i.e., sources, coupling paths, and sensitive equipment, are established by the theoretical method, full-wave simulation method, and black-box test method, respectively, and put into different layers. According to the functions of the BTM system, the EMS of BTM is given by analyzing the interrelation of input and output of modules. Results of the proposed model were verified by measurement. Full article
(This article belongs to the Special Issue Recent Advances in Sustainable Process Design and Optimization)
Show Figures

Figure 1

Open AccessArticle
Investigation of 2D-WH/TS OCDMA Code Stability in Systems with SOA-Based Device
Appl. Sci. 2020, 10(21), 7943; https://doi.org/10.3390/app10217943 - 09 Nov 2020
Viewed by 276
Abstract
This paper investigates for the first time how the implementation of semiconductor optical amplifier (SOA)-based devices in photonic networks can negatively impact the integrity of two-dimensional wavelength-hopping time-spreading (2D-WH/TS) optical code-division multiple access (OCDMA) codes based on multi-wavelength picosecond code carriers. It is [...] Read more.
This paper investigates for the first time how the implementation of semiconductor optical amplifier (SOA)-based devices in photonic networks can negatively impact the integrity of two-dimensional wavelength-hopping time-spreading (2D-WH/TS) optical code-division multiple access (OCDMA) codes based on multi-wavelength picosecond code carriers. It is demonstrated and confirmed by simulations that the influence of an SOA under driving currents of 50 mA to 250 mA causes a 0.08 to 0.8 nm multi-wavelength picosecond code carriers’ wavelength redshift. The results obtained are then used to calculate the degradation of OCDMA system performance in terms of the probability of error Pe and the decrease in the number of simultaneous users. It is shown that, when the SOA-induced 0.8 nm code carriers redshift becomes equal to the code carries wavelength channel spacing, the (8,53)-OCDMA system performs only as a (7,53)-OCDMA system, and the number of simultaneous users drops from 14 to 10 or 84 to 74 with the forward error correction (FEC) Pe of 10−9, respectively. The impact of the 0.8 nm redshift is then shown on a (4,53)-OCDMA system, where it causes a drop in the number of simultaneous users from 4 to 3 or 37 to 24 with the FEC Pe of 10−9, respectively. Full article
(This article belongs to the Special Issue Applications of Semiconductor Optical Amplifiers II)
Show Figures

Figure 1

Open AccessArticle
On the Use of Importance Measures in the Reliability of Inventory Systems, Considering the Cost
Appl. Sci. 2020, 10(21), 7942; https://doi.org/10.3390/app10217942 - 09 Nov 2020
Viewed by 278
Abstract
In order to maximize inventory benefits or minimize costs, reliability and cost of inventory control models need to be identified and analyzed. These importance measures are one important approach to recognize and evaluate system weaknesses. However, importance measures have fewer applications in inventory [...] Read more.
In order to maximize inventory benefits or minimize costs, reliability and cost of inventory control models need to be identified and analyzed. These importance measures are one important approach to recognize and evaluate system weaknesses. However, importance measures have fewer applications in inventory systems’ reliability. Considering the cost, this paper mainly discusses the reliability change of performance parameters with the importance measures in inventory systems. The calculation methods of differential importance and Birnbaum importance are studied in the inventory control model with shortages. By comparing the importance values of various parameters in the model, the optimization analysis of the inventory model can be used to identify the key parameters, so as to effectively reduce the total inventory cost. The importance order and the identification of key parameters are helpful to increase the operational efficiency of the inventory control and provide effective methods for improving the inventory management. Lastly, a case study with a shortage and limited inventory capacity is used to demonstrate the proposed model. Full article
(This article belongs to the Special Issue Systems Engineering: Availability and Reliability)
Show Figures

Figure 1

Open AccessArticle
Compressive Ghost Imaging of the Moving Object Using the Low-Order Moments
Appl. Sci. 2020, 10(21), 7941; https://doi.org/10.3390/app10217941 - 09 Nov 2020
Viewed by 226
Abstract
Ghost imaging reconstructs the image based on the second-order correlation of the repeatedly measured light fields. When the observed object is moving, the consecutive sampling procedure leads to a motion blur in the reconstructed images. To overcome this defect, we propose a novel [...] Read more.
Ghost imaging reconstructs the image based on the second-order correlation of the repeatedly measured light fields. When the observed object is moving, the consecutive sampling procedure leads to a motion blur in the reconstructed images. To overcome this defect, we propose a novel method of ghost imaging to obtain the motion information of moving object with a small number of measurements, in which the object could be regarded as relatively static. Our method exploits the idea of compressive sensing for a superior image reconstruction, combining with the low-order moments of the images to directly extract the motion information, which has the advantage of saving time and computation. With the gradual motion estimation and compensation during the imaging process, the experimental results show the proposed method could effectively overcome the motion blur, also possessing the advantage of reducing the necessary measurement number for each motion estimation and improving the reconstructed image quality. Full article
(This article belongs to the Section Optics and Lasers)
Show Figures

Figure 1

Open AccessArticle
Block Data Record-Based Dynamic Encryption Key Generation Method for Security between Devices in Low Power Wireless Communication Environment of IoT
Appl. Sci. 2020, 10(21), 7940; https://doi.org/10.3390/app10217940 - 09 Nov 2020
Viewed by 293
Abstract
The Internet of Things uses low-power wireless communication for wireless connectivity and efficient energy. Low-power wireless communication is applied to IoT for wireless connection and efficient energy consumption in various areas such as wearable devices, smart homes, and power plants in order to [...] Read more.
The Internet of Things uses low-power wireless communication for wireless connectivity and efficient energy. Low-power wireless communication is applied to IoT for wireless connection and efficient energy consumption in various areas such as wearable devices, smart homes, and power plants in order to send and receive data and control the environment. Security is becoming more important because the Internet of Things controls real physical systems. For the security of the Internet of Things, the encryption key is important to identify and authenticate devices that are trusted. The static encryption key method used for devices is likely to be calculated in reverse through the value of the key and is vulnerable to exploitation attacks. This requires the application of dynamic encryption keys that generate keys periodically. However, in the case of low-power wireless communication, the asynchronous communication method and the packet loss make it difficult to apply existing dynamic encryption key technologies. In this paper, we proposed dynamic encryption key method that applies the mechanism of the block chain to solve these problems. Based on the history of sensor data between devices, encryption keys are dynamically generated. The proposed method is to generate the same encryption key between devices with only one step of asynchronous communication considering packet loss. The proposed method is also validated in terms of availability and security in the Internet of Things low-power wireless communication. Full article
(This article belongs to the Special Issue Advances in Blockchain Technology and Applications II)
Show Figures

Figure 1

Open AccessArticle
Korean Historical Documents Analysis with Improved Dynamic Word Embedding
Appl. Sci. 2020, 10(21), 7939; https://doi.org/10.3390/app10217939 - 09 Nov 2020
Viewed by 241
Abstract
Historical documents refer to records or books that provide textual information about the thoughts and consciousness of past civilisations, and therefore, they have historical significance. These documents are used as key sources for historical studies as they provide information over several historical periods. [...] Read more.
Historical documents refer to records or books that provide textual information about the thoughts and consciousness of past civilisations, and therefore, they have historical significance. These documents are used as key sources for historical studies as they provide information over several historical periods. Many studies have analysed various historical documents using deep learning; however, studies that employ changes in information over time are lacking. In this study, we propose a deep-learning approach using improved dynamic word embedding to determine the characteristics of 27 kings mentioned in the Annals of the Joseon Dynasty, which contains a record of 500 years. The characteristics of words for each king were quantitated based on dynamic word embedding; further, this information was applied to named entity recognition and neural machine translation.In experiments, we confirmed that the method we proposed showed better performance than other methods. In the named entity recognition task, the F1-score was 0.68; in the neural machine translation task, the BLEU4 score was 0.34. We demonstrated that this approach can be used to extract information about diplomatic relationships with neighbouring countries and the economic conditions of the Joseon Dynasty. Full article
(This article belongs to the Special Issue Advances in Deep Learning Ⅱ)
Show Figures

Figure 1

Open AccessFeature PaperArticle
Dispatchable Substation for Operation and Control of Renewable Energy Resources
Appl. Sci. 2020, 10(21), 7938; https://doi.org/10.3390/app10217938 - 09 Nov 2020
Viewed by 264
Abstract
Renewable generation in power systems has proved to be challenging for system operators owing to the increasing levels of penetration. The operation of power systems currently requires additional flexibility and reserves due to the intermittency and unpredictability of renewable generators. However, it is [...] Read more.
Renewable generation in power systems has proved to be challenging for system operators owing to the increasing levels of penetration. The operation of power systems currently requires additional flexibility and reserves due to the intermittency and unpredictability of renewable generators. However, it is difficult to precisely predict and control the stochastic nature of renewable sources; nevertheless, its capacity continues to increase. To monitor and control renewable generators efficiently, the entire system needs to be established in a hierarchical order. This study proposed the concept of a substation that is uniquely designed for renewable interconnection. The purpose of this substation is simple: to make the renewable generators dispatchable to operators such that each group of renewable generators is sufficiently stable to be considered as conventional generators. For this purpose, methods for sizing and controlling energy storage system are proposed based on forecasts and error distributions. Full article
Show Figures

Figure 1

Open AccessFeature PaperReview
Freshness Monitoring of Packaged Vegetables
Appl. Sci. 2020, 10(21), 7937; https://doi.org/10.3390/app10217937 - 09 Nov 2020
Viewed by 329
Abstract
Smart packaging is an emerging technology that has a great potential in solving conventional food packaging problems and in meeting the evolving packaged vegetables market needs. The advantages of using such a system lies in extending the shelf life of products, ensuring the [...] Read more.
Smart packaging is an emerging technology that has a great potential in solving conventional food packaging problems and in meeting the evolving packaged vegetables market needs. The advantages of using such a system lies in extending the shelf life of products, ensuring the safety and the compliance of these packages while reducing the food waste; hence, lessening the negative environmental impacts. Many new concepts were developed to serve this purpose, especially in the meat and fish industry with less focus on fruits and vegetables. However, making use of these evolving technologies in packaging of vegetables will yield in many positive outcomes. In this review, we discuss the new technologies and approaches used, or have the potential to be used, in smart packaging of vegetables. We describe the technical aspects and the commercial applications of the techniques used to monitor the quality and the freshness of vegetables. Factors affecting the freshness and the spoilage of vegetables are summarized. Then, some of the technologies used in smart packaging such as sensors, indicators, and data carriers that are integrated with sensors, to monitor and provide a dynamic output about the quality and safety of the packaged produce are discussed. Comparison between various intelligent systems is provided followed by a brief review of active packaging systems. Finally, challenges, legal aspects, and limitations facing this smart packaging industry are discussed together with outlook and future improvements. Full article
(This article belongs to the Section Food Science and Technology)
Show Figures

Figure 1

Open AccessArticle
Accumulation of Methylmercury in the High-Altitude Lake Uru Uru (3686 m a.s.l, Bolivia) Controlled by Sediment Efflux and Photodegradation
Appl. Sci. 2020, 10(21), 7936; https://doi.org/10.3390/app10217936 - 09 Nov 2020
Viewed by 299
Abstract
In shallow aquatic environments, sediment is a significant source of monomethylmercury (MMHg) for surface water (SW). High-altitude aquatic ecosystems are characterized by extreme hydro-climatic constraints (e.g., low oxygen and high UV radiation). We studied, during two seasons, the diel cycles of MMHg in [...] Read more.
In shallow aquatic environments, sediment is a significant source of monomethylmercury (MMHg) for surface water (SW). High-altitude aquatic ecosystems are characterized by extreme hydro-climatic constraints (e.g., low oxygen and high UV radiation). We studied, during two seasons, the diel cycles of MMHg in SW and sediment porewaters (PW) of Lake Uru Uru (3686 m a.s.l, Bolivia) contaminated by urban and mining activities. Our results show that diel changes in SW MMHg concentrations (up to 1.8 ng L−1) overwhelm seasonal ones, with higher MMHg accumulation during the night-time and the dry season. The calculation of MMHg diffusive fluxes demonstrates that the sediment compartment was the primary source of MMHg to the SW. Most MMHg efflux occurred during the dry season (35.7 ± 17.4 ng m−2 day−1), when the lake was relatively shallow, more eutrophicated, and with the redoxcline located above the sediment–water interface (SWI). Changes in MMHg accumulation in the PWs were attributed to diel redox oscillations around the SWI driving both the bacterial sulfate reduction and bio-methylation. Finally, we highlight that although MMHg loading from the PW to the SW is large, MMHg photodegradation and demethylation by microorganisms control the net MMHg accumulation in the water column. Full article
Show Figures

Graphical abstract

Open AccessArticle
Lateral Capacitance–Voltage Method of NanoMOSFET for Detecting the Hot Carrier Injection
Appl. Sci. 2020, 10(21), 7935; https://doi.org/10.3390/app10217935 - 09 Nov 2020
Viewed by 197
Abstract
In this paper, the dependence of the capacitance of lateral drain–substrate and source–substrate junctions on the linear size of the oxide trapped charge in MOSFET is simulated. It is shown that, at some range of linear sizes of the trapped charge, the capacitance [...] Read more.
In this paper, the dependence of the capacitance of lateral drain–substrate and source–substrate junctions on the linear size of the oxide trapped charge in MOSFET is simulated. It is shown that, at some range of linear sizes of the trapped charge, the capacitance of lateral junctions linearly depends on the linear size of the trapped charge. The dependence of the difference between drain–substrate and source–substrate capacitances on the linear size of trapped charges is also simulated. The revealed dependence can be used in measurements to estimate the linear size of oxide trapped charges induced by hot carrier injection, which can occur during MOSFET operation at defined conditions. Full article
(This article belongs to the Special Issue Device Modeling for TCAD and Circuit Simulation)
Show Figures

Figure 1

Open AccessArticle
Femtosecond Optical Laser System with Spatiotemporal Stabilization for Pump-Probe Experiments at SACLA
Appl. Sci. 2020, 10(21), 7934; https://doi.org/10.3390/app10217934 - 09 Nov 2020
Viewed by 289
Abstract
We constructed a synchronized femtosecond optical laser system with spatiotemporal stabilization for pump-probe experiments at SPring-8 Angstrom Compact Free Electron Laser (SACLA). Stabilization of output power and pointing has been achieved with a small fluctuation level of a few percent by controlling conditions [...] Read more.
We constructed a synchronized femtosecond optical laser system with spatiotemporal stabilization for pump-probe experiments at SPring-8 Angstrom Compact Free Electron Laser (SACLA). Stabilization of output power and pointing has been achieved with a small fluctuation level of a few percent by controlling conditions of temperature and air-flow in the optical paths. A feedback system using a balanced optical-microwave phase detector (BOMPD) has been successfully realized to reduce jitter down to 50 fs. We demonstrated the temporal stability with a time-resolved X-ray diffraction measurement and observed the coherent phonon oscillation of the photo-excited Bi without the post-processing using the timing monitor. Full article
(This article belongs to the Special Issue Ultrafast X-ray Spectroscopies)
Show Figures

Figure 1

Open AccessArticle
Micro Artificial Immune System for Traffic Light Control
Appl. Sci. 2020, 10(21), 7933; https://doi.org/10.3390/app10217933 - 09 Nov 2020
Viewed by 224
Abstract
A new bio-inspired meta-heuristic, called the micro artificial immune system (MAIS), has been developed in order to reduce the rates of pollution for a specific region of Mexico City through the optimization of vehicular flow. Simulation of urban mobility (SUMO) was used to [...] Read more.
A new bio-inspired meta-heuristic, called the micro artificial immune system (MAIS), has been developed in order to reduce the rates of pollution for a specific region of Mexico City through the optimization of vehicular flow. Simulation of urban mobility (SUMO) was used to simulate the effects of the programming of the traffic lights obtained by the MAIS. Currently, pollution and travel times from one place to another are increasing due to the number of inhabitants that live in big cities, which has generated a decrease in people’s quality of life. Hence, we propose the optimization of the programming of the sequences of traffic lights through this bio-inspired meta-heuristic. The obtained results show that the MAIS outperforms most of the algorithms tested in this research. Full article
(This article belongs to the Section Computing and Artificial Intelligence)
Show Figures

Figure 1

Open AccessArticle
Double Trapezoidal Wave Transmitting System with Controllable Turn-Off Edge
Appl. Sci. 2020, 10(21), 7932; https://doi.org/10.3390/app10217932 - 09 Nov 2020
Viewed by 207
Abstract
For time domain transient electromagnetic measurement, the negative sign often appears in the polarization region, which contains the induced polarization information. It is considered that the polarization effect is caused by the capacitance charge of the earth. Extending the turn-off time of the [...] Read more.
For time domain transient electromagnetic measurement, the negative sign often appears in the polarization region, which contains the induced polarization information. It is considered that the polarization effect is caused by the capacitance charge of the earth. Extending the turn-off time of the emission current means increasing the charging time, and reducing the charging voltage, which makes the polarization effect easier to observe. Therefore, a double trapezoidal wave transmitting system with a controllable turn-off edge is designed in this paper. In the process of current transmitting, the turn-off time can be controlled by changing the clamping voltage depending on the passive clamping technology. By cutting into the absorption resistance, the current oscillation can be eliminated under the condition of ensuring linearity. To verify the effectiveness of the system, we designed a polarized wire loop based on the filament model simulating the polarized earth. Comparing the response of the wire loop, the emission current with short and long turn-off times contributes to inducing the induction and polarization fields respectively. The double trapezoidal wave transmitting system with a controllable turn-off edge is suitable for measuring the induced polarization effect. Full article
(This article belongs to the Section Earth Sciences and Geography)
Show Figures

Figure 1

Open AccessArticle
Focus-Adjustable Head Mounted Display with Off-Axis System
Appl. Sci. 2020, 10(21), 7931; https://doi.org/10.3390/app10217931 - 09 Nov 2020
Viewed by 245
Abstract
An off-axis system refers to an optical system in which the optical axis and the normal vector at the vertex of each surface do not match. An off-axis optical system can be applied in order to construct a thin and light optical system. [...] Read more.
An off-axis system refers to an optical system in which the optical axis and the normal vector at the vertex of each surface do not match. An off-axis optical system can be applied in order to construct a thin and light optical system. In particular, the optical system used for a see-through head-mounted display (HMD) must be designed asymmetrically, with respect to the optical axis. Because the vision of a human is different for each individual, HMD requires focus adjustment. The effective focal length (EFL) of the optical system must be calculated to obtain the focus adjustment. However, the off-axis optical system cannot be calculated by conventional methods. In this study, the EFL was calculated by rotating the coordinates of the rays near the optical axis by the angle of reflection or refraction at the intersection of each surface, with the rays coinciding with the optical axis. The magnitude of movement of the micro-display for focus adjustment was obtained from the calculated EFL, for a see-through type HMD. Full article
(This article belongs to the Special Issue Geometrical Optics: Theoretical Achievements and Applications)
Show Figures

Figure 1

Open AccessArticle
VaNetChain: A Framework for Trustworthy Exchanges of Information in VANETs Based on Blockchain and a Virtualization Layer
Appl. Sci. 2020, 10(21), 7930; https://doi.org/10.3390/app10217930 - 09 Nov 2020
Viewed by 274
Abstract
Vehicular ad hoc networks (VANETs) face challenges related to the reliability of the data exchanged and the unstability of the communication links. These shortcomings have hampered the development of the long-awaited applications that would turn roads into a smart environment. We present a [...] Read more.
Vehicular ad hoc networks (VANETs) face challenges related to the reliability of the data exchanged and the unstability of the communication links. These shortcomings have hampered the development of the long-awaited applications that would turn roads into a smart environment. We present a framework to deploy such services, in which a virtualization layer ensures means to efficiently deliver messages between vehicles and roadside units (RSUs) and, on top of that, blockchain technology is used to enable features of data integrity, traceability, and reliability that cannot be furnished by existing consensus and reputation mechanisms. A simulation experiment is included to determine the optimal number of RSUs to be installed as supporting infrastructure in a city. Full article
(This article belongs to the Special Issue Implementation of Vehicular Cloud Networks Using Wireless Sensor)
Show Figures

Figure 1

Open AccessArticle
An Analysis of the Performance of Trolleybus Brushes Developed from Recycled Materials
Appl. Sci. 2020, 10(21), 7929; https://doi.org/10.3390/app10217929 - 09 Nov 2020
Viewed by 270
Abstract
The paper presents an analysis of the performance of traction brushes produced from waste materials. Brushes are used to ensure good electrical contact between the rail and the pantograph. Slides are produced by the process of hot pressing, with the parameters of heating [...] Read more.
The paper presents an analysis of the performance of traction brushes produced from waste materials. Brushes are used to ensure good electrical contact between the rail and the pantograph. Slides are produced by the process of hot pressing, with the parameters of heating up to max 175 °C, at the minimal pressure value of 200 MPa. Some of the developed brushes with a high (55–60%) content of recycled materials are more durable and break-resistant than their commercial counterparts. Full article
Show Figures

Figure 1

Open AccessArticle
Novel Application of Uncertainty Analysis Methods for Quantitative Precipitation Estimation Based on Weather Radars in the Korean Peninsula
Appl. Sci. 2020, 10(21), 7928; https://doi.org/10.3390/app10217928 - 09 Nov 2020
Viewed by 236
Abstract
Several sources of bias are involved at each stage of a quantitative precipitation estimation process because weather radars measure precipitation amounts indirectly. Conventional methods compare the relative uncertainties between different stages of the process but seldom present the total uncertainty. Therefore, the objectives [...] Read more.
Several sources of bias are involved at each stage of a quantitative precipitation estimation process because weather radars measure precipitation amounts indirectly. Conventional methods compare the relative uncertainties between different stages of the process but seldom present the total uncertainty. Therefore, the objectives of this study were as follows: (1) to quantify the uncertainty at each stage of the process and in total; (2) to elucidate the ratio of the uncertainty at each stage in terms of the total uncertainty; and (3) to explain the uncertainty propagation process at each stage. This study proposed novel application of three methods (maximum entropy method, uncertainty Delta method, and modified-fractional uncertainty method) to determine the total uncertainty, level of uncertainty increase, and percentage of uncertainty at each stage. Based on data from 18 precipitation events that occurred over the Korean Peninsula, the applicability of the three methods was tested using a radar precipitation estimation process that comprised two quality control algorithms, two precipitation estimation methods, and two post-processing precipitation bias correction methods. Results indicated that the final uncertainty of each method was reduced in comparison with the initial uncertainty, and that the uncertainty was different at each stage depending on the method applied. Full article
(This article belongs to the Section Civil Engineering)
Show Figures

Figure 1

Open AccessArticle
Fabrication of g-C3N4 Quantum Dots/MnCO3 Nanocomposite on Carbon Cloth for Flexible Supercapacitor Electrode
Appl. Sci. 2020, 10(21), 7927; https://doi.org/10.3390/app10217927 - 09 Nov 2020
Viewed by 259
Abstract
In this study, the nanocomposite of g-C3N4 quantum dots/MnCO3 on carbon cloth (q-MC//CC) is prepared via a simple hydrothermal method. The obtained q-MC//CC composite is employed for a flexible supercapacitor electrode. The g-C3N4 quantum dots could [...] Read more.
In this study, the nanocomposite of g-C3N4 quantum dots/MnCO3 on carbon cloth (q-MC//CC) is prepared via a simple hydrothermal method. The obtained q-MC//CC composite is employed for a flexible supercapacitor electrode. The g-C3N4 quantum dots could effectively improve the interface electrical conductivity and ion transportation of the MnCO3 electrode, which results in superior electrochemical performance. The q-MC//CC electrode delivers a high specific capacity of 1001 F·g−1 at a current density of 1 A·g−1 and a good cycling performance of 96% capacity retention after 5000 cycles. Moreover, an asymmetric flexible supercapacitor (ASC) is assembled with q-MC//CC and carbon cloth as a positive and negative electrode, respectively, which exhibits a high energy density of 27.1 Wh·kg−1 at a power density of 500 W·kg−1. In addition, the fabricated ASC device demonstrates the ability to power the light-emitting diode effectively under mechanical bending. Full article
(This article belongs to the Section Energy)
Show Figures

Figure 1

Open AccessArticle
Efficient Algorithm for Providing Live Vulnerability Assessment in Corporate Network Environment
Appl. Sci. 2020, 10(21), 7926; https://doi.org/10.3390/app10217926 - 09 Nov 2020
Viewed by 362
Abstract
The time gap between public announcement of a vulnerability—its detection and reporting to stakeholders—is an important factor for cybersecurity of corporate networks. A large delay preceding an elimination of a critical vulnerability presents a significant risk to the network security and increases the [...] Read more.
The time gap between public announcement of a vulnerability—its detection and reporting to stakeholders—is an important factor for cybersecurity of corporate networks. A large delay preceding an elimination of a critical vulnerability presents a significant risk to the network security and increases the probability of a sustained damage. Thus, accelerating the process of vulnerability identification and prioritization helps to red the probability of a successful cyberattack. This work introduces a flexible system that collects information about all known vulnerabilities present in the system, gathers data from organizational inventory database, and finally integrates and processes all collected information. Thanks to application of parallel processing and non relational databases, the results of this process are available subject to a negligible delay. The subsequent vulnerability prioritization is performed automatically on the basis of the calculated CVSS 2.0 and 3.1 scores for all scanned assets. The environmental CVSS vector component is evaluated accurately thanks to the fact that the environmental data is imported directly from the organizational inventory database. Full article
(This article belongs to the Special Issue Novel Algorithms and Protocols for Networks)
Show Figures

Figure 1

Open AccessArticle
Thermodynamic, Economic and Sustainability Analysis of Solar Organic Rankine Cycle System with Zeotropic Working Fluid Mixtures for Micro-Cogeneration in Buildings
Appl. Sci. 2020, 10(21), 7925; https://doi.org/10.3390/app10217925 - 09 Nov 2020
Viewed by 282
Abstract
Globally there are several viable sources of renewable, low-temperature heat (below 130 °C), particularly solar energy, geothermal energy, and energy generated from industrial wastes. Increased exploitation of these low-temperature options has the definite potential of reducing fossil fuel consumption with its attendant very [...] Read more.
Globally there are several viable sources of renewable, low-temperature heat (below 130 °C), particularly solar energy, geothermal energy, and energy generated from industrial wastes. Increased exploitation of these low-temperature options has the definite potential of reducing fossil fuel consumption with its attendant very harmful greenhouse gas emissions. Researchers have universally identified the organic Rankine cycle (ORC) as a practicable and suitable system to generate electrical power from renewable sources based on its beneficial usage of volatile organic fluids as working fluids (WFs). In recent times, researchers have also shown a preference towards deployment of zeotropic mixtures as ORC WFs because of their capacity to improve thermodynamic performance of ORC systems, a feat enabled through the greater matching of the temperature profiles of the WF and the heat source/sink. This paper demonstrates the thermodynamic, economic and sustainability feasibility, and the notable advantages of using zeotropic mixtures as WFs through a simulation study of an ORC system. The study examines first the thermodynamic performance of ORC systems using zeotropic mixtures to generate electricity powered by a low-temperature solar heat source for building applications. A thermodynamic model is developed with a solar-driven ORC system both with and excluding a regenerator. Twelve zeotropic mixtures with varying compositions are evaluated and compared to identify the best combinations of mixtures that can yield high performance and high efficiency in their system cycles. The study also examines the effects of the volume flow ratio, and evaporation and condensation temperature glides on the ORC’s thermodynamic performance. Following a detailed analysis of each mixture, R245fa/propane and butane/propane are selected for parametric study to investigate the influence of operating parameters on the system’s efficiency and sustainability index. For zeotropic mixtures, results disclosed that there is an optimal composition range within which binary mixtures are inclined to perform more efficiently than the component pure fluids. In addition, a substantial enhancement in cycle efficiency can be obtained by a regenerative ORC, with cycle efficiency ranging between 3.1–9.8% and 8.6–17.4% for ORC both without and with regeneration, respectively. Results also revealed that exploiting zeotropic mixtures could enlarge the limitation experienced in selecting WFs for low-temperature solar ORCs. Moreover, a detailed economic with a sensitivity analysis of the solar ORC system was performed to evaluate the cost of the electricity and other economic criteria. The outcome of this investigation should be useful in the thermo-economic feasibility assessments of solar-driven ORC systems using working fluid mixtures to find the optimum operating range for maximum performance and minimum cost. Full article
Show Figures

Figure 1

Open AccessArticle
Development of 340-GHz Transceiver Front End Based on GaAs Monolithic Integration Technology for THz Active Imaging Array
Appl. Sci. 2020, 10(21), 7924; https://doi.org/10.3390/app10217924 - 09 Nov 2020
Viewed by 285
Abstract
Frequency multipliers and mixers based on Schottky barrier diodes (SBDs) are widely used in terahertz (THz) imaging applications. However, they still face obstacles, such as poor performance consistency caused by discrete flip-chip diodes, as well as low efficiency and large receiving noise temperature. [...] Read more.
Frequency multipliers and mixers based on Schottky barrier diodes (SBDs) are widely used in terahertz (THz) imaging applications. However, they still face obstacles, such as poor performance consistency caused by discrete flip-chip diodes, as well as low efficiency and large receiving noise temperature. It is very hard to meet the requirement of multiple channels in THz imaging array. In order to solve this problem, 12-μm-thick gallium arsenide (GaAs) monolithic integrated technology was adopted. In the process, the diode chip shared the same GaAs substrate with the transmission line, and the diode’s pads were seamlessly connected to the transmission line without using silver glue. A three-dimensional (3D) electromagnetic (EM) model of the diode chip was established in Ansys High Frequency Structure Simulator (HFSS) to accurately characterize the parasitic parameters. Based on the model, by quantitatively analyzing the influence of the surface channel width and the diode anode junction area on the best efficiency, the final parameters and dimensions of the diode were further optimized and determined. Finally, three 0.34 THz triplers and subharmonic mixers (SHMs) were manufactured, assembled, and measured for demonstration, all of which comprised a waveguide housing, a GaAs circuit integrated with diodes, and other external connectors. Experimental results show that all the triplers and SHMs had great performance consistency. Typically, when the input power was 100 mW, the output power of the THz tripler was greater than 1 mW in the frequency range of 324 GHz to 352 GHz, and a peak efficiency of 6.8% was achieved at 338 GHz. The THz SHM exhibited quite a low double sideband (DSB) noise temperature of 900~1500 K and a DSB conversion loss of 6.9~9 dB over the frequency range of 325~352 GHz. It is indicated that the GaAs monolithic integrated process, diodes modeling, and circuits simulation method in this paper provide an effective way to design THz frequency multiplier and mixer circuits. Full article
(This article belongs to the Special Issue Terahertz Sensing and Imaging)
Show Figures

Figure 1

Open AccessArticle
Stability Control for Vehicle Dynamic Management with Multi-Objective Fuzzy Continuous Damping Control
Appl. Sci. 2020, 10(21), 7923; https://doi.org/10.3390/app10217923 - 08 Nov 2020
Viewed by 449
Abstract
Vehicle dynamic management (VDM) is a vehicle chassis integrated control system based on electronic stability program (ESP) and continuous damping control (CDC) that has been developed in recent years. In this work, the ideal yaw angle rate and sideslip angle of the mass [...] Read more.
Vehicle dynamic management (VDM) is a vehicle chassis integrated control system based on electronic stability program (ESP) and continuous damping control (CDC) that has been developed in recent years. In this work, the ideal yaw angle rate and sideslip angle of the mass center are calculated deriving an ideal monorail model with two degrees of freedom. Then, a direct yaw moment proportional-integral-differential control strategy for ESP is proposed as the foundation of VDM. In addition, a multi-objective fuzzy continuous damping control (MFCDC) is proposed to achieve comfort, handling stability, and rollover prevention. The effect of the MFCDC strategy is analyzed and verified through a sine wave steer input test, double line change test, and fishhook test. The results indicate that MFCDC-ESP has a significant advantage in preventing rollover. MFCDC-ESP can maintain the optimized distribution of damping force through its own compensation under possible instability and predict the critical stable state to some extent. MFCDC-ESP exhibits strong real-time sensitivity to the control state of the damping force of each wheel. Hence, it can ensure the comfort of passengers under good driving conditions and exert strong adaptability and control effects under extreme working conditions. Full article
Show Figures

Figure 1

Open AccessArticle
The Use of Artificial Intelligence Methods to Assess the Effectiveness of Lean Maintenance Concept Implementation in Manufacturing Enterprises
Appl. Sci. 2020, 10(21), 7922; https://doi.org/10.3390/app10217922 - 08 Nov 2020
Viewed by 450
Abstract
The increase in the performance and effectiveness of maintenance processes is a continuous aim of production enterprises. The elimination of unexpected failures, which generate excessive costs and production losses, is emphasized. The elements that influence the efficiency of maintenance are not only the [...] Read more.
The increase in the performance and effectiveness of maintenance processes is a continuous aim of production enterprises. The elimination of unexpected failures, which generate excessive costs and production losses, is emphasized. The elements that influence the efficiency of maintenance are not only the choice of an appropriate conservation strategy but also the use of appropriate methods and tools to support the decision-making process in this area. The research problem, which was considered in the paper, is an insufficient means of assessing the degree of the implementation of lean maintenance. This problem results in not only the possibility of achieving high efficiency of the exploited machines, but, foremost, it influences a decision process and the formulation of maintenance policy of an enterprise. The purpose of this paper is to present the possibility of using intelligent systems to support decision-making processes in the implementation of the lean maintenance concept, which allows the increase in the operational efficiency of the company’s technical infrastructure. In particular, artificial intelligence methods were used to search for relationships between specific activities carried out under the implementation of lean maintenance and the results obtained. Decision trees and rough set theory were used for the analysis. The decision trees were made for the average value of the overall equipment effectiveness (OEE) indicator. The rough set theory was used to assess the degree of utilization of the lean maintenance strategy. Decision rules were generated based on the proposed algorithms, using RSES software, and their correctness was assessed. Full article
(This article belongs to the Special Issue Design and Management of Manufacturing Systems)
Show Figures

Figure 1

Open AccessArticle
Calibrated Integral Equation Model for Bare Soil Moisture Retrieval of Synthetic Aperture Radar: A Case Study in Linze County
Appl. Sci. 2020, 10(21), 7921; https://doi.org/10.3390/app10217921 - 08 Nov 2020
Viewed by 401
Abstract
Soil moisture plays a significant role in surface energy balance and material exchange. Synthetic aperture radar (SAR) provides a promising data source to monitor soil moisture. However, soil surface roughness is a key difficulty in bare soil moisture retrieval. To reduce the measurement [...] Read more.
Soil moisture plays a significant role in surface energy balance and material exchange. Synthetic aperture radar (SAR) provides a promising data source to monitor soil moisture. However, soil surface roughness is a key difficulty in bare soil moisture retrieval. To reduce the measurement error of the correlation length and improve the inversion accuracy, we used the surface roughness (Hrms, root mean surface height) and empirical correlation length lopt as proposed by Baghdadi to introduce analytical equations of the backscattering coefficient using the calibrated integral equation model (CIEM). This empirical model was developed based on analytical equations to invert soil moisture for Hrms between 0.5 and 4 cm. Experimental results demonstrated that when the incidence angle varied from 33.5° to 26.3°, R2 of the retrieved and measured soil moisture decreased from 0.67 to 0.57, and RMSE increased from 2.53% to 5.4%. Similarly, when the incidence angle varied from 33.5° to 26.3°, R2 of the retrieved and measured Hrms decreased from 0.64 to 0.51, and RMSE increased from 0.33 to 0.4 cm. Therefore, it is feasible to use the empirical model to invert soil moisture and surface roughness for bare soils. In the inversion of the soil moisture and Hrms, using Hrms and the empirical correlation length lopt as the roughness parameters in the simulations is sufficient. The empirical model has favorable validity when the incidence angle is set to 33.5° and 26.3° at the C-band. Full article
(This article belongs to the Special Issue Advanced Materials and Technologies for Aerospace Applications)
Show Figures

Figure 1

Open AccessArticle
“Blurry Touch Finger”: Touch-Based Interaction for Mobile Virtual Reality with Clip-on Lenses
Appl. Sci. 2020, 10(21), 7920; https://doi.org/10.3390/app10217920 - 08 Nov 2020
Viewed by 407
Abstract
In this paper, we propose and explore a touch screen based interaction technique, called the “Blurry Touch Finger” for EasyVR, a mobile VR platform with non-isolating flip-on glasses that allows the fingers accessible to the screen. We demonstrate that, with the proposed technique, [...] Read more.
In this paper, we propose and explore a touch screen based interaction technique, called the “Blurry Touch Finger” for EasyVR, a mobile VR platform with non-isolating flip-on glasses that allows the fingers accessible to the screen. We demonstrate that, with the proposed technique, the user is able to accurately select virtual objects, seen under the lenses, directly with the fingers even though they are blurred and physically block the target object. This is possible owing to the binocular rivalry that renders the fingertips semi-transparent. We carried out a first stage basic evaluation assessing the object selection performance and general usability of Blurry Touch Finger. The study has revealed that, for objects with the screen space sizes greater than about 0.5 cm, the selection performance and usability of the Blurry Touch Finger, as applied in the EasyVR configuration, was comparable to or higher than those with both the conventional head-directed and hand/controller based ray-casting selection methods. However, for smaller sized objects, much below the size of the fingertip, the touch based selection was both less performing and usable due to the usual fat finger problem and difficulty in stereoscopic focus. Full article
(This article belongs to the Special Issue Virtual and Augmented Reality Systems)
Show Figures

Figure 1

Previous Issue
Back to TopTop