Applied Sciences

15 pages, 2051 KiB

Open AccessArticle

Moisture Buffering of Multilayer Internal Wall Assemblies at the Micro Scale: Experimental Study and Numerical Modelling

by Dobrosława Kaczorek

Appl. Sci. 2019, 9(16), 3438; https://doi.org/10.3390/app9163438 - 20 Aug 2019

Cited by 16 | Viewed by 3516

Abstract

In this paper, a series of experiments assessing the moisture buffer value (MBV) of four internal wall assembly samples made from hygroscopic materials was performed. A modified Nordtest protocol was used. Moisture buffer values of all the investigated wall assemblies, with varying moisture [...] Read more.

In this paper, a series of experiments assessing the moisture buffer value (MBV) of four internal wall assembly samples made from hygroscopic materials was performed. A modified Nordtest protocol was used. Moisture buffer values of all the investigated wall assemblies, with varying moisture loads in the range of 50% to 80%, showed a moderate moisture buffer value (MBV: 0.5–1.0 (g·m⁻²·%RH⁻¹)). The results showed that in a wall assembly where the MBV of the whole assembly is lower than the MBV of the outer layers, the moisture-buffering capacity of the inner layer is untapped. Outer layers affect inner layers by changing their moisture-buffering capacity, which in turn changes the overall performance of the whole assembly. In addition, it was observed that if the penetration depth value of the outer layer is greater than its thickness, vapour reaches into the deeper layer and wall assemblies made of layers with materials characterized by a lower value of penetration depth reach steady state more slowly. The WUFI Pro tool was used to compare the simulated and experimental results. Despite the discrepancies between these results, it offers a simplified method, helping designers make decisions about which materials to choose to improve the moisture-buffering effect. Full article

(This article belongs to the Special Issue Energy Efficiency in Buildings and Innovative Materials for Building Construction)

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23 pages, 6118 KiB

Open AccessArticle

Generating a Cylindrical Panorama from a Forward-Looking Borehole Video for Borehole Condition Analysis

by Zhaopeng Deng, Maoyong Cao, Yushui Geng and Laxmisha Rai

Appl. Sci. 2019, 9(16), 3437; https://doi.org/10.3390/app9163437 - 20 Aug 2019

Cited by 8 | Viewed by 3508

Abstract

Geological exploration plays a fundamental and crucial role in geological engineering. The most frequently used method is to obtain borehole videos using an axial view borehole camera system (AVBCS) in a pre-drilled borehole. This approach to surveying the internal structure of a borehole [...] Read more.

Geological exploration plays a fundamental and crucial role in geological engineering. The most frequently used method is to obtain borehole videos using an axial view borehole camera system (AVBCS) in a pre-drilled borehole. This approach to surveying the internal structure of a borehole is based on the video playback and video screenshot analysis. One of the drawbacks of AVBCS is that it provides only a qualitative description of borehole information with a forward-looking borehole video, but quantitative analysis of the borehole data, such as the width and dip angle of fracture, are unavailable. In this paper, we proposed a new approach to create a whole borehole-wall cylindrical panorama from the borehole video acquired by AVBCS, which provides a possibility for further analysis of borehole information. Firstly, based on the Otsu and region labeling algorithms, a borehole center location algorithm is proposed to extract the borehole center of each video image automatically. Afterwards, based on coordinate mapping (CM), a virtual coordinate graph (VCG) is designed in the unwrapping process of the front view borehole-wall image sequence, generating the corresponding unfolded image sequence and reducing the computational cost. Subsequently, based on the sum of absolute difference (SAD), a projection transformation SAD (PTSAD), which considers the gray level similarity of candidate images, is proposed to achieve the matching of the unfolded image sequence. Finally, an image filtering module is introduced to filter the invalid frames and the remaining frames are stitched into a complete cylindrical panorama. Experiments on two real-world borehole videos demonstrate that the proposed method can generate panoramic borehole-wall unfolded images from videos with satisfying visual effect for follow up geological condition analysis. From the resulting image, borehole information, including the rock mechanical properties, distribution and width of fracture, fault distribution and seam thickness, can be further obtained and analyzed. Full article

(This article belongs to the Special Issue Advanced Intelligent Imaging Technology)

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13 pages, 1390 KiB

Open AccessArticle

Cellulose Nanofibril (CNF) Films and Xylan from Hot Water Extracted Birch Kraft Pulps

by Marc Borrega and Hannes Orelma

Appl. Sci. 2019, 9(16), 3436; https://doi.org/10.3390/app9163436 - 20 Aug 2019

Cited by 22 | Viewed by 4481

Abstract

The effects of xylan extraction from birch kraft pulp on the manufacture and properties of cellulose nanofibril (CNF) films were here investigated. Hot water extractions of bleached and unbleached kraft pulps were performed in a flow-through system to remove and recover the xylan. [...] Read more.

The effects of xylan extraction from birch kraft pulp on the manufacture and properties of cellulose nanofibril (CNF) films were here investigated. Hot water extractions of bleached and unbleached kraft pulps were performed in a flow-through system to remove and recover the xylan. After the extraction, the pulps were oxidized with 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and fibrillated in a high-pressure microfluidizer. Compared to CNF from bleached kraft pulp, the CNF dispersions obtained from water-extracted pulps were less viscous and generally contained a higher amount of microfiber fragments, although smaller in size. In all cases, however, smooth and highly transparent films were produced from the CNF dispersions after the addition of sorbitol as plasticizer. The CNF films made from water-extracted pulps showed a lower tensile strength and ductility, probably due to their lower xylan content, but the stiffness was only reduced by the presence of lignin. Interestingly, the CNF films from water-extracted bleached pulps were less hydrophilic, and their water vapour permeability was reduced up to 25%. Therefore, hot water extraction of bleached birch kraft pulp could be used to produce CNF films with improved barrier properties for food packaging, while obtaining a high-purity xylan stream for other high-value applications. Full article

(This article belongs to the Special Issue Cellulosic Nanofibers and Their Applications)

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13 pages, 3699 KiB

Open AccessArticle

Real-Time Monitoring of Indoor Air Quality with Internet of Things-Based E-Nose

by Mehmet Taştan and Hayrettin Gökozan

Appl. Sci. 2019, 9(16), 3435; https://doi.org/10.3390/app9163435 - 20 Aug 2019

Cited by 103 | Viewed by 18543

Abstract

Today, air pollution is the biggest environmental health problem in the world. Air pollution leads to adverse effects on human health, climate and ecosystems. Air is contaminated by toxic gases released by industry, vehicle emissions and the increased concentration of harmful gases and [...] Read more.

Today, air pollution is the biggest environmental health problem in the world. Air pollution leads to adverse effects on human health, climate and ecosystems. Air is contaminated by toxic gases released by industry, vehicle emissions and the increased concentration of harmful gases and particulate matter in the atmosphere. Air pollution can cause many serious health problems such as respiratory, cardiovascular and skin diseases in humans. Nowadays, where air pollution has become the largest environmental health risk, the interest in monitoring air quality is increasing. Recently, mobile technologies, especially the Internet of Things, data and machine learning technologies have a positive impact on the way we manage our health. With the production of IoT-based portable air quality measuring devices and their widespread use, people can monitor the air quality in their living areas instantly. In this study, e-nose, a real-time mobile air quality monitoring system with various air parameters such as CO₂, CO, PM₁₀, NO₂ temperature and humidity, is proposed. The proposed e-nose is produced with an open source, low cost, easy installation and do-it-yourself approach. The air quality data measured by the GP2Y1010AU, MH-Z14, MICS-4514 and DHT22 sensor array can be monitored via the 32-bit ESP32 Wi-Fi controller and the mobile interface developed by the Blynk IoT platform, and the received data are recorded in a cloud server. Following evaluation of results obtained from the indoor measurements, it was shown that a decrease of indoor air quality was influenced by the number of people in the house and natural emissions due to activities such as sleeping, cleaning and cooking. However, it is observed that even daily manual natural ventilation has a significant improving effect on air quality. Full article

(This article belongs to the Special Issue Indoor Air Quality)

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16 pages, 2229 KiB

Open AccessArticle

Durability Evaluation Study for Crumb Rubber–Asphalt Pavement

by Xuancang Wang, Zhenyang Fan, Li Li, Hongyao Wang and Minghui Huang

Appl. Sci. 2019, 9(16), 3434; https://doi.org/10.3390/app9163434 - 20 Aug 2019

Cited by 21 | Viewed by 4462

Abstract

In this study, the failure mechanism of crumb rubber–asphalt pavement was analyzed under the combined effects of low temperature, water, and traffic load. The investigation was carried out based on the mechanical and deformational properties of crumb rubber–asphalt mixture and the typical environmental [...] Read more.

In this study, the failure mechanism of crumb rubber–asphalt pavement was analyzed under the combined effects of low temperature, water, and traffic load. The investigation was carried out based on the mechanical and deformational properties of crumb rubber–asphalt mixture and the typical environmental and load conditions such pavement is typically exposed to. A method was proposed for objective evaluation of the interfacial adhesion between rubber crumbs and asphalt through consideration of the effects of the characteristics of the materials and the working environment. The main evaluation method used herein included the indirect tensile strength test under freeze–thaw–boiling cycle, and the Cántabro abrasion test under water-immersion was adopted as an auxiliary method. The evaluation system has the advantages of simple implementation, realistic simulation of the actual working state of the mixture, and reliable results. Moreover, it is a durability evaluation method that can be specifically applied to asphalt mixtures with some special aggregates or stone mastic asphalt (SMA) mixtures. Full article

(This article belongs to the Special Issue Asphalt Materials)

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17 pages, 2683 KiB

Open AccessArticle

Tonic Cold Pain Detection Using Choi–Williams Time-Frequency Distribution Analysis of EEG Signals: A Feasibility Study

by Rami Alazrai, Saifaldeen AL-Rawi, Hisham Alwanni and Mohammad I. Daoud

Appl. Sci. 2019, 9(16), 3433; https://doi.org/10.3390/app9163433 - 20 Aug 2019

Cited by 17 | Viewed by 3695

Abstract

Detecting pain based on analyzing electroencephalography (EEG) signals can enhance the ability of caregivers to characterize and manage clinical pain. However, the subjective nature of pain and the nonstationarity of EEG signals increase the difficulty of pain detection using EEG signals analysis. In [...] Read more.

Detecting pain based on analyzing electroencephalography (EEG) signals can enhance the ability of caregivers to characterize and manage clinical pain. However, the subjective nature of pain and the nonstationarity of EEG signals increase the difficulty of pain detection using EEG signals analysis. In this work, we present an EEG-based pain detection approach that analyzes the EEG signals using a quadratic time-frequency distribution, namely the Choi–Williams distribution (CWD). The use of the CWD enables construction of a time-frequency representation (TFR) of the EEG signals to characterize the time-varying spectral components of the EEG signals. The TFR of the EEG signals is analyzed to extract 12 time-frequency features for pain detection. These features are used to train a support vector machine classifier to distinguish between EEG signals that are associated with the no-pain and pain classes. To evaluate the performance of our proposed approach, we have recorded EEG signals for 24 healthy subjects under tonic cold pain stimulus. Moreover, we have developed two performance evaluation procedures—channel- and feature-based evaluation procedures—to study the effect of the utilized EEG channels and time-frequency features on the accuracy of pain detection. The experimental results show that our proposed approach achieved an average classification accuracy of 89.24% in distinguishing between the no-pain and pain classes. In addition, the classification performance achieved using our proposed approach outperforms the classification results reported in several existing EEG-based pain detection approaches. Full article

(This article belongs to the Special Issue Signals in Health Care)

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15 pages, 2669 KiB

Open AccessArticle

Calibration of Design Buckling Curves for Lateral-Torsional Buckling of Cantilever Beams Made of Glass—Experimental and Numerical Investigations

by Ralph Timmers and Tobias Neulichedl

Appl. Sci. 2019, 9(16), 3432; https://doi.org/10.3390/app9163432 - 20 Aug 2019

Cited by 2 | Viewed by 4365

Abstract

Using glass as a primary load-carrying element is becoming more and more popular in architecture. Probably the most used application is the single-span girder, but another important system is the cantilever beam, which is widely used, e.g., as a canopy in front of [...] Read more.

Using glass as a primary load-carrying element is becoming more and more popular in architecture. Probably the most used application is the single-span girder, but another important system is the cantilever beam, which is widely used, e.g., as a canopy in front of an entrance. Research on the lateral-torsional buckling behavior of glass beams has been typically performed on single-span girders. As a consequence, the design buckling curves provided in literature are usually too conservative for the widely used case of a cantilever beam, which is also related to the loading situation. Therefore, experimental and numerical investigations have been performed for this special case. Based on the obtained results, design buckling curves have been developed and resulted in being more economical than the curves already given in the literature. Among others, information on the shape and size of the real imperfections, a testing device for cantilever beams, and experimentally and numerically obtained load-deflection curves are additional outcomes of the investigations presented here. Full article

(This article belongs to the Section Civil Engineering)

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11 pages, 3327 KiB

Open AccessArticle

Technical Performance of an Inflatable Solar Dryer for Drying Amaranth Leaves in Kenya

by Sebastian Romuli, Steffen Schock, Marcus Nagle, Christine G. Kiria Chege and Joachim Müller

Appl. Sci. 2019, 9(16), 3431; https://doi.org/10.3390/app9163431 - 20 Aug 2019

Cited by 11 | Viewed by 4511

Abstract

The technical performance of an inflatable solar dryer (ISD) to dry amaranth leaves (Amaranthus spp.) was investigated. To handle the drying of lightweight materials, modification was made by adding an air deflector and trays inside the ISD. Computational performance of the ISD [...] Read more.

The technical performance of an inflatable solar dryer (ISD) to dry amaranth leaves (Amaranthus spp.) was investigated. To handle the drying of lightweight materials, modification was made by adding an air deflector and trays inside the ISD. Computational performance of the ISD solar energy system was evaluated using MATLAB Simulink. The estimated air mass flow in the inlet of the ISD was 0.75 kg/s. Using computational fluid dynamics (CFD), the uniformity of air distribution in the ISD was evaluated. The solar radiation reported during good drying performance ranged between 510 and 950 W/m². In a controlled charging system, a 100 W_p PV module typically generated voltage between 10.22 and 18.75 V. Drying conditions at temperatures of 40 °C or above were typically achieved in the ISD from 12:00 to 16:00. Temperature inside the ISD could reach up to 69.4 °C during the day and 13.4 °C during the night. The highest relative humidity of 97.4% was recorded during the night. Opening the ISD while mixing the product could lead to considerable heat loss. Fluctuation of solar radiation and shaded areas in the ISD appeared to be the major factors affecting the drying performance. Full article

(This article belongs to the Special Issue Renewable Energy in Agriculture)

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15 pages, 2096 KiB

Open AccessArticle

Electrochemical Conversion of the Lignin Model Veratryl Alcohol to Veratryl Aldehyde Using Manganese(III)-Schiff Base Homogeneous Catalysts

by Lara Rouco, M. Isabel Fernández-García, Ana M. González-Noya, Gustavo González-Riopedre, Alexei M. Tyryshkin and Marcelino Maneiro

Appl. Sci. 2019, 9(16), 3430; https://doi.org/10.3390/app9163430 - 20 Aug 2019

Cited by 9 | Viewed by 3037

Abstract

Lignin and other colored structures need to be bleached after the Kraft process in the pulp industry. Development of environmentally-safe bleaching catalysts or electrocatalysts constitutes an attractive strategy for selective removal of lignin. Seven manganese(III)-complexes with Schiff base ligands 1–7 were synthetized and [...] Read more.

Lignin and other colored structures need to be bleached after the Kraft process in the pulp industry. Development of environmentally-safe bleaching catalysts or electrocatalysts constitutes an attractive strategy for selective removal of lignin. Seven manganese(III)-complexes with Schiff base ligands 1–7 were synthetized and characterized by different analytical and spectroscopic techniques. The tetragonally elongated octahedral geometry for the manganese coordination sphere and the global µ-aquo dimeric structure were revealed by X-ray diffraction (XRD) studies for 1, Mn₂L¹₂(H₂O)₂(N(CN)₂)₂ (N(CN)₂ = dicyanamide). Complexes 1–4 behave as more efficient peroxidase mimics as compared to 5–7. Electrochemical oxidation of the lignin model veratrylalcohol (VA) to veratrylaldehyde (VAH) is efficiently catalyzed by a type of dimanganese(III) complexes in a chlorine-free medium. The electrocatalytic reaction proceeds through the oxidation of chloride into hypochlorite at alkaline pH along with the formation of hydrogen from water as a subproduct. Full article

(This article belongs to the Section Chemical and Molecular Sciences)

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20 pages, 10721 KiB

Open AccessArticle

The Influence of the Damage of Mortise-Tenon Joint on the Cyclic Performance of the Traditional Chinese Timber Frame

by Ben Sha, Hao Wang and Aiqun Li

Appl. Sci. 2019, 9(16), 3429; https://doi.org/10.3390/app9163429 - 20 Aug 2019

Cited by 23 | Viewed by 4490

Abstract

In this article, the finite element method is used to build the analytical model of a traditional Chinese timber frame with straight mortise-tenon joints. The analytical model is then subjected to the lateral cyclic loading and verified based on the results of an [...] Read more.

In this article, the finite element method is used to build the analytical model of a traditional Chinese timber frame with straight mortise-tenon joints. The analytical model is then subjected to the lateral cyclic loading and verified based on the results of an experiment. Three types of damage in the straight mortise-tenon joint, including the gap between the mortise and tenon, damage in the top and the end of tenon, are proposed and idealized so that the analytical model can be modified accordingly. The hysteresis curve, stiffness and energy dissipation capacity derived from these damaged models with different damage extents are analyzed. The results indicate that the proposed damages of the joints have adverse influences on the lateral behavior of the timber frame. Both stiffness and energy dissipation capacity of the timber frame are weakened by these damages. Full article

(This article belongs to the Section Civil Engineering)

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14 pages, 2345 KiB

Open AccessArticle

Quantitative CT Analysis for Predicting the Behavior of Part-Solid Nodules with Solid Components Less than 6 mm: Size, Density and Shape Descriptors

by Andrea Borghesi, Alessandra Scrimieri, Silvia Michelini, Giulio Calandra, Salvatore Golemi, Andrea Tironi and Roberto Maroldi

Appl. Sci. 2019, 9(16), 3428; https://doi.org/10.3390/app9163428 - 20 Aug 2019

Cited by 7 | Viewed by 3722

Abstract

Persistent part-solid nodules (PSNs) with a solid component <6 mm usually represent minimally invasive adenocarcinomas and are significantly less aggressive than PSNs with a solid component ≥6 mm. However, not all PSNs with a small solid component behave in the same way: some [...] Read more.

Persistent part-solid nodules (PSNs) with a solid component <6 mm usually represent minimally invasive adenocarcinomas and are significantly less aggressive than PSNs with a solid component ≥6 mm. However, not all PSNs with a small solid component behave in the same way: some nodules exhibit an indolent course, whereas others exhibit more aggressive behavior. Thus, predicting the future behavior of this subtype of PSN remains a complex and fascinating diagnostic challenge. The main purpose of this study was to apply open-source software to investigate which quantitative computed tomography (CT) features may be useful for predicting the behavior of a select group of PSNs. We retrospectively selected 50 patients with a single PSN with a solid component <6 mm and diameter <15 mm. Computerized analysis was performed using ImageJ software for each PSN and various quantitative features were calculated from the baseline CT images. The area, perimeter, mean Feret diameter, linear mass density, circularity and solidity were significantly related to nodule growth (p ≤ 0.031). Therefore, quantitative CT analysis was helpful for predicting the future behavior of a select group of PSNs with a solid component <6 mm and diameter <15 mm. Full article

(This article belongs to the Special Issue Computer-aided Biomedical Imaging 2020: Advances and Prospects)

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18 pages, 1656 KiB

Open AccessArticle

Seismic Control of SDOF Systems with Nonlinear Eddy Current Dampers

by Longteng Liang, Zhouquan Feng and Zhengqing Chen

Appl. Sci. 2019, 9(16), 3427; https://doi.org/10.3390/app9163427 - 20 Aug 2019

Cited by 20 | Viewed by 3977

Abstract

The nonlinear model and energy dissipation of a rotary axial eddy current damper (ECD) and the dynamic responses to harmonic and seismic base excitations of a linear elastic SDOF system with the nonlinear ECD (SDOF-ECD) are investigated. Firstly, the nonlinear force-velocity relationship of [...] Read more.

The nonlinear model and energy dissipation of a rotary axial eddy current damper (ECD) and the dynamic responses to harmonic and seismic base excitations of a linear elastic SDOF system with the nonlinear ECD (SDOF-ECD) are investigated. Firstly, the nonlinear force-velocity relationship of the ECD is studied using finite element simulation, experimental testing and mathematical model fitting. Secondly, the energy dissipated by the nonlinear ECD under a cycle of harmonic motion is derived analytically and its optimal critical velocity is determined such that the energy dissipation is maximized. Finally, the responses of the SDOF-ECDs subjected to harmonic and seismic base excitations are calculated using numerical algorithm, where the displacement and acceleration control performance and the energy dissipation capacity of the ECD are compared with those of the conventional fluid viscous dampers (FVDs). The results indicate that the seismic control performance of ECDs outperforms that of FVDs in most cases and it is anticipated that the ECDs can be used as good alternative devices to conventional FVDs for seismic control applications. Full article

(This article belongs to the Special Issue Energy Dissipation and Vibration Control: Materials, Modeling, Algorithm and Devices)

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12 pages, 2364 KiB

Open AccessArticle

The Synergic Effect of Terpenoid and Steroidal Saponins Can Improve Bone Healing, by Promoting the Osteogenic Commitment of Adipose Mesenchymal Stem Cells: An In Vitro Study

by Gloria Bellin, Chiara Gardin, Letizia Ferroni, Paolo Ghensi, Barbara Zavan and Marco Tatullo

Appl. Sci. 2019, 9(16), 3426; https://doi.org/10.3390/app9163426 - 20 Aug 2019

Cited by 1 | Viewed by 4243

Abstract

Bone regeneration involves several biological processes that consistently impact the quality of tissue healing. An important step consists of the local recruitment and differentiation of mesenchymal stem cells that migrate in the site to regenerate from bone marrow. Mesenchymal stem cells (MSCs) may [...] Read more.

Bone regeneration involves several biological processes that consistently impact the quality of tissue healing. An important step consists of the local recruitment and differentiation of mesenchymal stem cells that migrate in the site to regenerate from bone marrow. Mesenchymal stem cells (MSCs) may be pushed towards osteogenic commitment by specific substances, often naturally present in plants. Yunnan Baiyao (YB) is a Chinese herbal medicine, mainly working through the synergic effect of terpenoid and steroidal saponins. YB is well known for its numerous biomedical effects, including the ability to favor improved bone tissue healing. In our in vitro study, we used adipose mesenchymal stem cells (ADSCs) as a study-model: We selected samples to harvest and isolate ADSCs and investigate their viability; moreover, we performed bone-related gene expression to evaluate the differentiation of MSCs. To confirm this behavior, we analyzed alkaline phosphate activity and calcium deposition, with ADSCs cultured in basal and osteogenic media, with YB at different concentrations in the medium, and at different time-points: 7, 14 and 21 days. Our results indicate that the synergic effect of terpenoid and steroidal saponins slightly favor the late ADSCs differentiation towards the osteoblasts phenotype. In osteogenic committed cells, the treatment with the lower dose of YB promoted the up-regulation of the alkaline phosphatase gene (ALPL) at day seven and 14 (p < 0.01); at day 21, the alkaline phosphatase (ALP) activity showed a slight increase, although in basal condition it maintains low rates. We assume that such molecular synergy can promote the osteogenic commitment of adipose mesenchymal stem cells, thus improving the timing and the quality of bone healing. Full article

(This article belongs to the Special Issue Patient-Tailored Biomimetic Scaffold Constructs for Bone Regeneration)

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13 pages, 7554 KiB

Open AccessFeature PaperArticle

Oblique Wide-Angle Multi-Sector Metamaterial Absorber for Space Applications

by Olivier Rance, Anne Claire Lepage, Xavier Begaud, Kevin Elis and Nicolas Capet

Appl. Sci. 2019, 9(16), 3425; https://doi.org/10.3390/app9163425 - 20 Aug 2019

Cited by 5 | Viewed by 3752

Abstract

This article presents the design, realization and measurement of lightweight absorbing material for space applications. The electromagnetic absorber, operating on the [2 GHz, 2.3 GHz] frequency band, is designed for oblique incidence ranging from 35° to 65°. Wide-angle designs are demonstrated to be [...] Read more.

This article presents the design, realization and measurement of lightweight absorbing material for space applications. The electromagnetic absorber, operating on the [2 GHz, 2.3 GHz] frequency band, is designed for oblique incidence ranging from 35° to 65°. Wide-angle designs are demonstrated to be particularly challenging at oblique incidence and an approach consisting in dividing the surface in two different sectors with respect to the incoming angle is proposed. A specific measurement setup is presented in order to characterize this new kind of evolutive absorber. The measurement results show that the sectorial absorber achieves a reflection coefficient inferior to −11.5 dB, corresponding to an absorptivity above 0.965 on the frequency band [2 GHz, 2.3 GHz] for both TE and TM polarizations for angles of incidence varying from 35° to 65°. Full article

(This article belongs to the Special Issue Advanced Active and Passive Metasurfaces)

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20 pages, 8923 KiB

Open AccessArticle

Assessment of Performance of Fiber Reinforced Geopolymer Composites by Experiment and Simulation Analysis

by Khoa V. A. Pham, Tan Khoa Nguyen, Tuan Anh Le, Sang Whan Han, Gayoon Lee and Kihak Lee

Appl. Sci. 2019, 9(16), 3424; https://doi.org/10.3390/app9163424 - 20 Aug 2019

Cited by 32 | Viewed by 4325

Abstract

In this work, the experimental and simulation analysis of the performance of geopolymer composites reinforced with steel fiber and polypropylene fiber is investigated. By embedding hooked end steel fiber and polypropylene fiber with various volume fractions of 0%, 0.5%, 1%, 1.5% to the [...] Read more.

In this work, the experimental and simulation analysis of the performance of geopolymer composites reinforced with steel fiber and polypropylene fiber is investigated. By embedding hooked end steel fiber and polypropylene fiber with various volume fractions of 0%, 0.5%, 1%, 1.5% to the geopolymer concrete mixture, the mechanical behavior was enhanced significantly through experimental results. The compressive strength was improved 26% with 0.5% of polypropylene fiber and 46% with 1% of hooked end steel fiber while the increment of splitting tensile strength was 12% and 28%, respectively. The flexural strength of specimens using two fiber types was also improved when compared with the non-fiber geopolymer concrete. The highest increment obtained with 1.5% of fiber volume content was from 26% to 42%. The compressive performance and flexural performance of fiber-reinforced geopolymer concrete were also better than specimens without fiber, with a higher load carrying capacity, higher stress, higher toughness and smaller strain. Using hooked end steel fiber resulted in better mechanical strength than using polypropylene fiber, and the presence of fibers is an important factor related to the strength improvements. A finite element analysis was modeled by the ANSYS program, and this showed that the load–deflection response and crack patterns also agreed quite well with experimental results. Full article

(This article belongs to the Special Issue Structural Performances of Concrete Composite Members: Experimental, Theoretical, Numerical Approaches)

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9 pages, 743 KiB

Open AccessArticle

Relationship between Kinematic Variables of Jump Throwing and Ball Velocity in Elite Handball Players

by Abdel-Rahman Akl, Ibrahim Hassan, Amr Hassan and Phillip Bishop

Appl. Sci. 2019, 9(16), 3423; https://doi.org/10.3390/app9163423 - 20 Aug 2019

Cited by 5 | Viewed by 6355

Abstract

The purpose of this pilot study was to evaluate the relationship between the kinematic variables of the right hand and left leg with ball velocity during jump-throwing phases in handball for better-informed training. We investigated ball velocity and the key kinematic variables of [...] Read more.

The purpose of this pilot study was to evaluate the relationship between the kinematic variables of the right hand and left leg with ball velocity during jump-throwing phases in handball for better-informed training. We investigated ball velocity and the key kinematic variables of jump throwing during different throwing phases in three strides. Ten right-handed male handball professional players who had competed in the Egyptian Handball Super League participated in this study. Jump throwing performance was divided into three phases (cocking, acceleration and follow-through), which included eight events during the throwing. Five trials were captured for each player, and a 3D analysis was performed on the best trial. Results indicated that the velocity of the throwing hand was the most important variable during jump throwing, which was correlated with ball velocity during the three phases of performance in four events: Initial contact (IC) (r = 0.66*), initial flight (IF) (r = 63*), maximum height of the throwing hand (Max-HH) (r = 0.78*) and ground contact (GC) (r = 0.83*). In addition, the initial flight was the most important event in which players need to be using the best angles during performance, particularly the shoulder angle. Full article

(This article belongs to the Special Issue Biomechanical Spectrum of Human Sport Performance)

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19 pages, 1515 KiB

Open AccessFeature PaperArticle

Circular Economy and E-Waste: An Opportunity from RFID TAGs

by Alessia Condemi, Federica Cucchiella and Domenico Schettini

Appl. Sci. 2019, 9(16), 3422; https://doi.org/10.3390/app9163422 - 19 Aug 2019

Cited by 28 | Viewed by 11028

Abstract

In this work, a deep economic and technical analysis for the enhancement of e-waste hierarchy applied to the Radio Frequency Identification (RFID) tags is presented. Nowadays, the RFID technology represents a valuable solution for many applications to improve the quality and efficiency of [...] Read more.

In this work, a deep economic and technical analysis for the enhancement of e-waste hierarchy applied to the Radio Frequency Identification (RFID) tags is presented. Nowadays, the RFID technology represents a valuable solution for many applications to improve the quality and efficiency of the supply chain, as well as for enhanced people or object identification and smart devices. This leads to massive usage of such devices that could represent a threat to the environment, since they are often considered as generic waste and no specific e-waste policy has been identified for RFID. For these reasons, the paper presents a study based on the desk research technique to propose several possibilities currently available for producers of different RFID devices in order to mitigate this problem at every e-waste hierarchy stage, i.e., ecological design and prevention, reuse, recycle, and disposal. Moreover, a cost/benefit analysis has been reported in order to highlight the economic advantages related to the RFID tags reuse, as well as environmental impact reduction. Results proved that passive RFID tags represent the major candidate for the e-waste hierarchy enhancement at every level, demonstrating that it is more convenient for the producer to consider an ecologically aware design and promote a take-back system for tags in order to take advantages from the solution proposed for the RFID e-waste hierarchy. Full article

(This article belongs to the Special Issue Electronic Waste: Management and Recovery Technologies)

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12 pages, 3263 KiB

Open AccessArticle

A Multi-Scale Modeling of CH₄ and H₂O Adsorption on Coal Molecules and the Water Blocking Effect in Coalbed Methane Extraction

by Yanhui Yang, Ling Lin, Mengxi Li, Xueying Zhang, Chunli Yang, Yuting Wang, Bin Fan, Congmei Chen and Wenjia Luo

Appl. Sci. 2019, 9(16), 3421; https://doi.org/10.3390/app9163421 - 19 Aug 2019

Cited by 8 | Viewed by 2900

Abstract

Coalbed methane (CBM) is of great economic value. However, at the same time, CBM is facing a multitude of technological challenges. The water blocking effect (WBE) is one of the physical effects that controls the production of CBM. To alleviation WBE, it is [...] Read more.

Coalbed methane (CBM) is of great economic value. However, at the same time, CBM is facing a multitude of technological challenges. The water blocking effect (WBE) is one of the physical effects that controls the production of CBM. To alleviation WBE, it is necessary to study its mechanisms at the molecular level. In this study, we used a combined first-principles calculation and molecular simulation approach to investigate the adsorption and diffusion of both methane and water in coal. The results suggest that water does not compete with methane in the adsorption on coal surfaces, yet the presence of water significantly slows down the diffusion of methane within the micropores of coal. This work not only explains the fundamental mechanisms of the WBE but also provides a simulation framework for building strategies to alleviate WBE. Full article

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15 pages, 2284 KiB

Open AccessArticle

Optimal Charging of Plug-In Electric Vehicle: Considering Travel Behavior Uncertainties and Battery Degradation

by Hanif Tayarani, Hamidreza Jahangir, Razieh Nadafianshahamabadi, Masoud Aliakbar Golkar, Ali Ahmadian and Ali Elkamel

Appl. Sci. 2019, 9(16), 3420; https://doi.org/10.3390/app9163420 - 19 Aug 2019

Cited by 18 | Viewed by 3819

Abstract

The negative environmental impacts of using fossil fuel-powered vehicles underlined the need for inventing an alternative eco-friendly transportation fleet. Plug-in electrical vehicles (PEVs) are introduced to cut the continuing increase in energy use and carbon emission of the urban mobility. However, the increased [...] Read more.

The negative environmental impacts of using fossil fuel-powered vehicles underlined the need for inventing an alternative eco-friendly transportation fleet. Plug-in electrical vehicles (PEVs) are introduced to cut the continuing increase in energy use and carbon emission of the urban mobility. However, the increased demand for mobility, and therefore energy, can create constraints on the power network which can reduce the benefits of electrification as a certain and reliable source. Thus, the rise in the use of electric vehicles needs electric grids to be able to feed the increased energy demand while the current infrastructure supports it. In this paper, we introduce a methodological framework for scheduling smart PEVs charging by considering the uncertainties and battery degradation. This framework includes an economic model for charging and discharging of PEVs which has been implemented in a 21-node sample distribution network with a wind turbine as a distributed generation (DG) unit. Our proposed approach indicates that the optimal charging of the PEVs has a high impact on the distribution network operation, particularly under the high market penetration of PEVs. Thus, the smart grid to vehicle (G2V) charging mode is a potential solution to maximize the PEV’s owner profit, while considering the battery degradation cost of the PEVs. The simulation result indicates that smart charging effectuation is economical. Full article

(This article belongs to the Special Issue Hybrid Vehicle Technologies for a Sustainable Future Mobility)

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17 pages, 6624 KiB

Open AccessArticle

Novel Hand Gesture Alert System

by Sebastien Mambou, Ondrej Krejcar, Petra Maresova, Ali Selamat and Kamil Kuca

Appl. Sci. 2019, 9(16), 3419; https://doi.org/10.3390/app9163419 - 19 Aug 2019

Cited by 8 | Viewed by 4252

Abstract

Sexual assault can cause great societal damage, with negative socio-economic, mental, sexual, physical and reproductive consequences. According to the Eurostat, the number of crimes increased in the European Union between 2008 and 2016. However, despite the increase in security tools such as cameras, [...] Read more.

Sexual assault can cause great societal damage, with negative socio-economic, mental, sexual, physical and reproductive consequences. According to the Eurostat, the number of crimes increased in the European Union between 2008 and 2016. However, despite the increase in security tools such as cameras, it is usually difficult to know if an individual is subject to an assault based on his or her posture. Hand gestures are seen by many as the natural means of nonverbal communication when interacting with a computer, and a considerable amount of research has been performed. In addition, the identifiable hand placement characteristics provided by modern inexpensive commercial depth cameras can be used in a variety of gesture recognition-based systems, particularly for human-machine interactions. This paper introduces a novel gesture alert system that uses a combination of Convolution Neural Networks (CNNs). The overall system can be subdivided into three main parts: firstly, the human detection in the image using a pretrained “You Only Look Once (YOLO)” method, which extracts the related bounding boxes containing his/her hands; secondly, the gesture detection/classification stage, which processes the bounding box images; and thirdly, we introduced a module called “counterGesture”, which triggers the alert. Full article

(This article belongs to the Special Issue Advanced Intelligent Imaging Technology)

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15 pages, 5209 KiB

Open AccessArticle

Battery Surface and Edge Defect Inspection Based on Sub-Regional Gaussian and Moving Average Filter

by Haibing Hu, Bo Zhang, Dongjian Xu and Guo Xia

Appl. Sci. 2019, 9(16), 3418; https://doi.org/10.3390/app9163418 - 19 Aug 2019

Cited by 4 | Viewed by 3836

Abstract

Detecting the defects of a battery on the surface and edge has always been difficult, especially for concave and convex ones, thereby seriously affecting its quality. Thus, sub-regional Gaussian and moving average filtering are innovatively proposed in this study considering the effect of [...] Read more.

Detecting the defects of a battery on the surface and edge has always been difficult, especially for concave and convex ones, thereby seriously affecting its quality. Thus, sub-regional Gaussian and moving average filtering are innovatively proposed in this study considering the effect of the nonuniform background illumination of the battery edge and the difference between the edge background and the internal surface defects of the battery. The battery surface image is divided into two areas, namely, edge area

W_{1}

and inner area

W_{2}

. Gaussian and moving average filtering are carried out row-by-row and column-by-column in the inner area

W_{2}

and the edge area

W_{1}

, respectively. The algorithm is tested on 600 battery samples that mainly possess concave and convex defects. The proposed method has higher detection accuracy and lower omission detection rate than the traditional unpartitioned processing method, especially in detecting the accuracy of edge defects. The accuracy rates were approximately 20% higher than that obtained by the traditional processing algorithm. The proposed method has remarkable real-time performance that can process four 8192 × 10,240 pixel battery images per second, thereby meeting the industrial production line speed requirements while satisfying accuracy. The proposed method has been applied in actual production for defect inspection. Full article

(This article belongs to the Section Applied Industrial Technologies)

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15 pages, 2932 KiB

Open AccessArticle

Calibration Method for Angular Positioning Deviation of a High-Precision Rotary Table Based on the Laser Tracer Multi-Station Measurement System

by Hongfang Chen, Bo Jiang, Hu Lin, Shuang Zhang, Zhaoyao Shi, Huixu Song and Yanqiang Sun

Appl. Sci. 2019, 9(16), 3417; https://doi.org/10.3390/app9163417 - 19 Aug 2019

Cited by 14 | Viewed by 3530

Abstract

This paper proposes a calibration method for angular positioning deviation of a high-precision rotary table based on the laser tracer multi-station measurement system. The algorithm error of the calibration method for angular positioning deviation of a high-precision rotary table based on the laser [...] Read more.

This paper proposes a calibration method for angular positioning deviation of a high-precision rotary table based on the laser tracer multi-station measurement system. The algorithm error of the calibration method for angular positioning deviation of a high-precision rotary table based on the laser tracer multi-station measurement system was mainly discussed. During the experiments, the laser tracer was fixed on the work surface of the rotary table, and the rotary was fixed on the work surface of the coordinate measurement machine (CMM). The rotary table was rotated with the same angular interval. In this case, an optimization method for calculating the coordinates of a laser tracer station by using Levenberg–Marquardt algorithm and singular value decomposition transform was proposed. Then, the angular positioning deviation of the rotary table was calibrated by an established geometric relationship model between the coordinates of laser tracer stations and the rotation angle of the rotary table. The angular positioning deviation of the high-precision rotary table was as low as ±0.9″, and the error of the calibration method was ±0.4″. The experimental results proved the feasibility of the proposed calibration method. The calibration method proposed in this paper is suitable for the case that the rotary table is not linked with the CMM, especially for large high-precision rotary tables. Full article

(This article belongs to the Section Electrical, Electronics and Communications Engineering)

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11 pages, 3517 KiB

Open AccessArticle

Aerodynamic and Structural Characteristics of a Centrifugal Compressor Impeller

by T R Jebieshia, Senthil Kumar Raman and Heuy Dong Kim

Appl. Sci. 2019, 9(16), 3416; https://doi.org/10.3390/app9163416 - 19 Aug 2019

Cited by 10 | Viewed by 4222

Abstract

The present study focuses on the aerodynamic performance and structural analysis of the centrifugal compressor impeller. The performance characteristics of the impeller are analyzed with and without splitter blades by varying the total number of main and splitter blades. The operating conditions of [...] Read more.

The present study focuses on the aerodynamic performance and structural analysis of the centrifugal compressor impeller. The performance characteristics of the impeller are analyzed with and without splitter blades by varying the total number of main and splitter blades. The operating conditions of the compressor under centrifugal force and pressure load from the aerodynamic analysis are applied to the impeller blade and hub to perform the one-way Fluid–Structure Interaction (FSI). For the stress assessment, maximum equivalent von Mises stresses in the impeller blades are compared with the maximum allowable stress of the impeller material. The effects of varying the pressure field on the deformation and stress of the impeller are also calculated. The aerodynamic and structural performance of the centrifugal compressor at 73,000 rpm are investigated in terms of the efficiency, pressure ratio, equivalent von Mises stress, and total deformation of the impeller. Full article

(This article belongs to the Section Mechanical Engineering)

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13 pages, 6427 KiB

Open AccessArticle

A New Method of Angle Measurement Error Analysis of Rotary Encoders

by Hua-Kun Jia, Lian-Dong Yu, Hui-Ning Zhao and Yi-Zhou Jiang

Appl. Sci. 2019, 9(16), 3415; https://doi.org/10.3390/app9163415 - 19 Aug 2019

Cited by 28 | Viewed by 5533

Abstract

In this article, a method of error source analysis and detection to improve the angle measurement accuracy of rotary encoders in precision measuring instruments is proposed. The angle measurement error caused by the installation eccentricity of the grating disk and the radial error [...] Read more.

In this article, a method of error source analysis and detection to improve the angle measurement accuracy of rotary encoders in precision measuring instruments is proposed. The angle measurement error caused by the installation eccentricity of the grating disk and the radial error motion of the rotating shaft is analyzed, and the error model is built. The method of measuring the radial error motion is introduced, and the visual system and image processing technology is proposed to detect the eccentricity. The verification experiment by the use of an autocollimator and a polygon is carried out. The residual error after comparison within ±6″ accounts for 9% of the angle measurement error. The proposed error model is verified, and the angle measurement error can be predicted if the installation eccentricity and radial error motion are known. Full article

(This article belongs to the Section Mechanical Engineering)

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14 pages, 856 KiB

Open AccessArticle

An LSTM-Based Deep Learning Approach for Classifying Malicious Traffic at the Packet Level

by Ren-Hung Hwang, Min-Chun Peng, Van-Linh Nguyen and Yu-Lun Chang

Appl. Sci. 2019, 9(16), 3414; https://doi.org/10.3390/app9163414 - 19 Aug 2019

Cited by 118 | Viewed by 8311

Abstract

Recently, deep learning has been successfully applied to network security assessments and intrusion detection systems (IDSs) with various breakthroughs such as using Convolutional Neural Networks (CNN) and Long Short-Term Memory (LSTM) to classify malicious traffic. However, these state-of-the-art systems also face tremendous challenges [...] Read more.

Recently, deep learning has been successfully applied to network security assessments and intrusion detection systems (IDSs) with various breakthroughs such as using Convolutional Neural Networks (CNN) and Long Short-Term Memory (LSTM) to classify malicious traffic. However, these state-of-the-art systems also face tremendous challenges to satisfy real-time analysis requirements due to the major delay of the flow-based data preprocessing, i.e., requiring time for accumulating the packets into particular flows and then extracting features. If detecting malicious traffic can be done at the packet level, detecting time will be significantly reduced, which makes the online real-time malicious traffic detection based on deep learning technologies become very promising. With the goal of accelerating the whole detection process by considering a packet level classification, which has not been studied in the literature, in this research, we propose a novel approach in building the malicious classification system with the primary support of word embedding and the LSTM model. Specifically, we propose a novel word embedding mechanism to extract packet semantic meanings and adopt LSTM to learn the temporal relation among fields in the packet header and for further classifying whether an incoming packet is normal or a part of malicious traffic. The evaluation results on ISCX2012, USTC-TFC2016, IoT dataset from Robert Gordon University and IoT dataset collected on our Mirai Botnet show that our approach is competitive to the prior literature which detects malicious traffic at the flow level. While the network traffic is booming year by year, our first attempt can inspire the research community to exploit the advantages of deep learning to build effective IDSs without suffering significant detection delay. Full article

(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2019)

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13 pages, 5271 KiB

Open AccessArticle

Precise Flowrate Control of Fluid Gear Pumps in Automated Painting Systems Using a Repetitive Controller

by Kiyang Park, Minsu Chang and Doyoung Jeon

Appl. Sci. 2019, 9(16), 3413; https://doi.org/10.3390/app9163413 - 19 Aug 2019

Cited by 3 | Viewed by 3477

Abstract

The fluid gear pump-based system has repetitive disturbances, such as flow ripples, due to the mechanical characteristics of the gear system. The periodic disturbances have negative effects on the precise flowrate control, which is essential for consistent coating quality in the painting process. [...] Read more.

The fluid gear pump-based system has repetitive disturbances, such as flow ripples, due to the mechanical characteristics of the gear system. The periodic disturbances have negative effects on the precise flowrate control, which is essential for consistent coating quality in the painting process. This study proposes a precise flowrate control method of the fluid gear pump-based painting system to compensate for the periodic disturbances. The compensation value of the controller output can be obtained by a repetitive controller. A compensation lookup table corresponding to the reference speed and the rotation angle can be generated through the repetitive controller. In order to secure robustness against various situations, a closed-loop system consists of the conventional proportional-derivative (PD) controller and a compensation lookup table in the form of the feedforward controller. The lookup table-based feedforward controller was compared with the open-loop controller and PD controller. Experimental results show that the proposed method is more effective than existing controllers in terms of periodic disturbance compensation. By using the results of this study, it is possible to improve the performance of the fluid gear pump-based painting system and precisely control the paint spray amount. Full article

(This article belongs to the Section Applied Industrial Technologies)

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17 pages, 1998 KiB

Open AccessArticle

Minimum Frequency and Voltage Stability Constrained Unit Commitment for AC/DC Transmission Systems

by Ningyu Zhang, Qian Zhou and Haoming Hu

Appl. Sci. 2019, 9(16), 3412; https://doi.org/10.3390/app9163412 - 19 Aug 2019

Cited by 12 | Viewed by 3145

Abstract

An increased use of the high-voltage direct current (HVDC) technologies can have important effects on frequency performance and voltage stability of the receiving-end grid during normal operation as well as during blocking failure. The main reasons are the inherent characteristics of the HVDC [...] Read more.

An increased use of the high-voltage direct current (HVDC) technologies can have important effects on frequency performance and voltage stability of the receiving-end grid during normal operation as well as during blocking failure. The main reasons are the inherent characteristics of the HVDC such as its much larger capacity than thermal plants and lack of voltage supporting ability to the alternating current (AC) grid. These has led to new challenges for AC/direct current (DC) power grid operators in terms of ensuring power system security. To address these challenges, a unit commitment (UC) of the receiving-end in the AC/DC hybrid grid is presented in this paper. In the proposed model, primary frequency modulation constraints are added to provide sufficient capacity for HVDC blocking. Besides, grid security constraint after secondary frequency regulation is also considered because HVDC blocking failure would cause large range power transfer and transmission lines overload. Meanwhile, voltage stability constraints are employed to guarantee enough voltage supporting capacity from thermal plants at the HVDC feed-in area. Based on the characteristics of the model, Benders decomposition and mixed integer programming algorithm are used to get the optimal transmission power of the HVDC and schedule of thermal units. The study is done by considering the IEEE-39 and Jiangsu power grid in eastern China, containing two HVDC transmission projections respectively. The results are also validated by simulation of different HVDC blocking failure scenarios. Full article

(This article belongs to the Special Issue Control and Operation of AC and DC Systems)

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16 pages, 4248 KiB

Open AccessFeature PaperArticle

Optimal Non-Integer Sliding Mode Control for Frequency Regulation in Stand-Alone Modern Power Grids

by Zahra Esfahani, Majid Roohi, Meysam Gheisarnejad, Tomislav Dragičević and Mohammad-Hassan Khooban

Appl. Sci. 2019, 9(16), 3411; https://doi.org/10.3390/app9163411 - 19 Aug 2019

Cited by 42 | Viewed by 3554

Abstract

In this paper, the concept of fractional calculus (FC) is introduced into the sliding mode control (SMC), named fractional order SMC (FOSMC), for the load frequency control (LFC) of an islanded microgrid (MG). The studied MG is constructed from different autonomous generation components [...] Read more.

In this paper, the concept of fractional calculus (FC) is introduced into the sliding mode control (SMC), named fractional order SMC (FOSMC), for the load frequency control (LFC) of an islanded microgrid (MG). The studied MG is constructed from different autonomous generation components such as diesel engines, renewable sources, and storage devices, which are optimally planned to benefit customers. The coefficients embedded in the FOSMC structure play a vital role in the quality of controller commands, so there is a need for a powerful heuristic methodology in the LFC study to adjust the design coefficients in such a way that better transient output may be achieved for resistance to renewable sources fluctuations. Accordingly, the Sine Cosine algorithm (SCA) is effectively combined with the harmony search (HS) for the optimal setting of the controller coefficients. The Lyapunov function based on the FOSMC is formulated to guarantee the stability of the LFC mechanism for the test MG. Finally, the hardware-in-the-loop (HIL) experiments are carried out to ensure that the suggested controller can suppress the frequency fluctuations effectively, and that it provides more robust MG responses in comparison with the prior art techniques. Full article

(This article belongs to the Special Issue Microgrids)

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12 pages, 10124 KiB

Open AccessArticle

Cm-Level Photonic-Crystal-Like Subwavelength Waveguide Platform with High Integration Density

by Xiangxin Huang, Gengxin Chen, Wen Zhou and Xuguang Huang

Appl. Sci. 2019, 9(16), 3410; https://doi.org/10.3390/app9163410 - 19 Aug 2019

Cited by 4 | Viewed by 3344

Abstract

In this paper, the cm-level photonic-crystal-like subwavelength waveguide platform is developed and analyzed by using the finite-difference time-domain method. The configuration can be considered as a hybrid waveguide combining with the advantages of a metal-dielectric-metal waveguide and a photonic crystal waveguide. The symmetric [...] Read more.

In this paper, the cm-level photonic-crystal-like subwavelength waveguide platform is developed and analyzed by using the finite-difference time-domain method. The configuration can be considered as a hybrid waveguide combining with the advantages of a metal-dielectric-metal waveguide and a photonic crystal waveguide. The symmetric and high reflection effect of metallic sidewall and the effect of the photonic crystal structure on the light-guiding mechanism and integration characteristics of the waveguide are systematically investigated. The results reveal that the cm-level photonic-crystal-like waveguide platform provides subwavelength confinement and very low propagation loss with the isolation more than 30 dB, which are promising for high-density photonic integration. The tradeoff between integration density and propagation loss is optimized. In addition, a T-shaped power splitter based on the waveguide platform is proposed. The excess loss of the T-shaped power splitter is less than

0.4

dB. A set of passive components can be exploited on the proposed cm-level photonic-crystal-like subwavelength waveguide platform in future work to constitute the large-scale integrated photonic systems. Full article

(This article belongs to the Special Issue Light Matter Interaction at Nanoscale: What Matters Most)

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16 pages, 15569 KiB

Open AccessArticle

Deformation Analysis of Large-Scale Rock Slopes Considering the Effect of Microseismic Events

by Linlu Dong, Ying Yang, Bo Qian, Yaosheng Tan, Hailong Sun and Nuwen Xu

Appl. Sci. 2019, 9(16), 3409; https://doi.org/10.3390/app9163409 - 19 Aug 2019

Cited by 6 | Viewed by 3099

Abstract

To research the macroscopic deformation of rock microseismic damage, a high-precision microseismic monitoring system was established on the left bank slope of the Baihetan hydropower station in Southwestern China. Based on the microseismic monitoring and field deformation data, the seismic source radius was [...] Read more.

To research the macroscopic deformation of rock microseismic damage, a high-precision microseismic monitoring system was established on the left bank slope of the Baihetan hydropower station in Southwestern China. Based on the microseismic monitoring and field deformation data, the seismic source radius was applied to characterize the rock fracture scale. Numerical simulations introduced the rock micro-fracture information into the three-dimensional numerical model of the left bank slope and established the damage constitutive model. The unloading deformation process of the left bank abutment rock mass is described by numerical calculations. The feedback analysis method considering the effect of microseismic damage is preliminary exploratory research, which provides a new idea for the stability analysis of similar high rock slopes. Full article

(This article belongs to the Section Civil Engineering)

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