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Appl. Sci., Volume 10, Issue 3 (February-1 2020) – 463 articles

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Cover Story (view full-size image) Our research asserts that roof-top opaque photovoltaic panels installed in greenhouses, shading [...] Read more.
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Open AccessArticle
Tunable Mid-Infrared Graphene Plasmonic Cross-Shaped Resonator for Demultiplexing Application
Appl. Sci. 2020, 10(3), 1193; https://doi.org/10.3390/app10031193 - 10 Feb 2020
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Abstract
In this study, a tunable graphene plasmonic filter and a two-channel demultiplexer are proposed, simulated, and analyzed in the mid-infrared (MIR) region. We discuss the optical transmission spectra of the proposed cross-shaped resonator and the two-channel demultiplexer. The transmission spectra of the proposed [...] Read more.
In this study, a tunable graphene plasmonic filter and a two-channel demultiplexer are proposed, simulated, and analyzed in the mid-infrared (MIR) region. We discuss the optical transmission spectra of the proposed cross-shaped resonator and the two-channel demultiplexer. The transmission spectra of the proposed MIR resonator are tunable by change of its dimensional parameters and the Fermi energy of the graphene. Our proposed structures have a single mode in the wavelength range of 5–12 µm. The minimum full width at half maximum (FWHM) and the maximum transmission ratio of the proposed resonator respectively reached 220 nm and 55%. Simulations are performed by use of three-dimensional finite-difference time-domain (3D-FDTD) method. Coupled mode theory (CMT) is used to investigate the structure theoretically. The numerical and the theoretical results are in good agreement. The performance of the proposed two-channel demultiplexer is investigated based on its crosstalk. The minimum value of crosstalk reaches −48.30 dB. Our proposed structures are capable of providing sub-wavelength confinement of light waves, useful in applications in MIR region. Full article
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Open AccessArticle
Investigation of Vocal Fatigue Using a Dose-Based Vocal Loading Task
Appl. Sci. 2020, 10(3), 1192; https://doi.org/10.3390/app10031192 - 10 Feb 2020
Viewed by 347
Abstract
Vocal loading tasks are often used to investigate the relationship between voice use and vocal fatigue in laboratory settings. The present study investigated the concept of a novel quantitative dose-based vocal loading task for vocal fatigue evaluation. Ten female subjects participated in the [...] Read more.
Vocal loading tasks are often used to investigate the relationship between voice use and vocal fatigue in laboratory settings. The present study investigated the concept of a novel quantitative dose-based vocal loading task for vocal fatigue evaluation. Ten female subjects participated in the study. Voice use was monitored and quantified using an online vocal distance dose calculator during six consecutive 30-min long sessions. Voice quality was evaluated subjectively using the CAPE-V and SAVRa before, between, and after each vocal loading task session. Fatigue-indicative symptoms, such as cough, swallowing, and voice clearance, were recorded. Statistical analysis of the results showed that the overall severity, the roughness, and the strain ratings obtained from CAPE-V obeyed similar trends as the three ratings from the SAVRa. These metrics increased over the first two thirds of the sessions to reach a maximum, and then decreased slightly near the session end. Quantitative metrics obtained from surface neck accelerometer signals were found to obey similar trends. The results consistently showed that an initial adjustment of voice quality was followed by vocal saturation, supporting the effectiveness of the proposed loading task. Full article
(This article belongs to the Special Issue Medical Informatics and Data Analysis)
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Open AccessArticle
Contextual Coefficients Excitation Feature: Focal Visual Representation for Relationship Detection
Appl. Sci. 2020, 10(3), 1191; https://doi.org/10.3390/app10031191 - 10 Feb 2020
Viewed by 267
Abstract
Visual relationship detection (VRD), a challenging task in the image understanding, suffers from vague connection between relationship patterns and visual appearance. This issue is caused by the high diversity of relationship-independent visual appearance, where inexplicit and redundant cues may not contribute to the [...] Read more.
Visual relationship detection (VRD), a challenging task in the image understanding, suffers from vague connection between relationship patterns and visual appearance. This issue is caused by the high diversity of relationship-independent visual appearance, where inexplicit and redundant cues may not contribute to the relationship detection, even confuse the detector. Previous relationship detection models have shown remarkable progress in leveraging external textual information or scene-level interaction to complement relationship detection cues. In this work, we propose Contextual Coefficients Excitation Feature (CCEF), a focal visual representation, which is adaptively recalibrated from original visual feature responses by explicitly modeling the interdependencies between features and their contextual coefficients. Specifically, contextual coefficients are obtained by calculation of both the spatial coefficients and generated-label ones. In addition, a conditional Wasserstein Generative Adversarial Network (WGAN) regularized with a relationship classification loss is designed to alleviate inadequate training of generated-label coefficients due to long tail distribution of relationship. Experimental results demonstrate the effective improvements of our method on relationship detection. In particular, our method improves the recall from 8.5% to 23.2% of predicting unseen relationship from zero-shot set. Full article
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Open AccessArticle
Image Dehazing Based on (CMTnet) Cascaded Multi-scale Convolutional Neural Networks and Efficient Light Estimation Algorithm
Appl. Sci. 2020, 10(3), 1190; https://doi.org/10.3390/app10031190 - 10 Feb 2020
Viewed by 228
Abstract
Image dehazing plays a pivotal role in numerous computer vision applications such as object recognition, surveillance systems, and security systems, where it can be considered as an introductory stage. Recently, many proposed learning-based works address this significant task; however, most of them neglect [...] Read more.
Image dehazing plays a pivotal role in numerous computer vision applications such as object recognition, surveillance systems, and security systems, where it can be considered as an introductory stage. Recently, many proposed learning-based works address this significant task; however, most of them neglect the atmospheric light estimation and fail to produce accurate transmission maps. To address such a problem, in this paper, we propose a two-stage dehazing system. The first stage presents an accurate atmospheric light algorithm labeled “A-Est” that employs hazy image blurriness and quadtree decomposition. Te second stage represents a cascaded multi-scale CNN model called CMT n e t that consists of two subnetworks, one for calculating rough transmission maps (CMCNN t r ) and the other for its refinement (CMCNN t ). Each subnetwork is composed of three-layer D-units (D indicates dense). Experimental analysis and comparisons with state-of-the-art dehazing methods revealed that the proposed system can estimate AL and t efficiently and accurately by achieving high-quality dehazing results and outperforms state-of-the-art comparative methods according to SSIM and MSE values, where our proposed achieves the best scores of both (91% average SSIM and 0.068 average MSE). Full article
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Open AccessArticle
Laser Irradiation Effects at Different Wavelengths on Phenology and Yield Components of Pretreated Maize Seed
Appl. Sci. 2020, 10(3), 1189; https://doi.org/10.3390/app10031189 - 10 Feb 2020
Viewed by 275
Abstract
This study aims to compare the effects of different laser wavelengths, exposure times, and low-power-intensity laser irradiation on maize seeds. Seeds were exposed to He–Ne (632.8 nm) red laser, Nd:YAG second-harmonic-generation (532 nm) green laser, and diode (410 nm) blue laser. Four different [...] Read more.
This study aims to compare the effects of different laser wavelengths, exposure times, and low-power-intensity laser irradiation on maize seeds. Seeds were exposed to He–Ne (632.8 nm) red laser, Nd:YAG second-harmonic-generation (532 nm) green laser, and diode (410 nm) blue laser. Four different exposure times (45, 65, 85, and 105 s) with different intensity (2 and 4 mW/cm2), for each laser were tested. Phenology and yield components (plant height, leaf area, number of rows per ear, seed yield, harvest index, yield efficiency, and grain weight) were determined. The experiment was conducted in a randomized complete block design with three replications. Plant height was found comparatively high in blue laser light—211 cm at 85 s. Blue and green laser lights showed significant increases in the number of rows per ear to 39.1 at 85 s and 45 at 65 s, respectively, compared to the control of 36 rows/ear. The order of seed yield was blue (7003.4 kg/ha) > green (6667.8 kg/ha) > red (6568.01 t/ha) based on different exposure times of 85 s, 85 s, and 105 s, respectively, compared to the control of 6.9 kg/ha. The findings indicate the possibility of using blue laser light to manipulate the growth and yield of maize. Full article
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Open AccessArticle
Experimental Study on Dynamic Compression Mechanical Properties of Aluminum Honeycomb Structures
Appl. Sci. 2020, 10(3), 1188; https://doi.org/10.3390/app10031188 - 10 Feb 2020
Viewed by 228
Abstract
In this paper, dynamic compression tests are developed to investigate the dynamic compression mechanical properties of the aluminum honeycomb structures at different strain rates, especially at the high strain rates. The difficulties at the high strain rates exist due to the large deformation, [...] Read more.
In this paper, dynamic compression tests are developed to investigate the dynamic compression mechanical properties of the aluminum honeycomb structures at different strain rates, especially at the high strain rates. The difficulties at the high strain rates exist due to the large deformation, the low wave resistance and the size effect of the honeycomb structures. The Split Hopkinson Pressure Bar (SPHB) test method is carried out and special measures such as the adoption of waveform shaper, the size optimization of the impact bar and the specimen, and employment of the semiconductor strain gauge, etc. are taken to overcome the difficulties. It is discovered that the dynamic compression mechanical properties possess a stress hardening effect at a high strain rate from 1.3 × 103 s−1 to 2.0 × 103 s−1, but then a stress softening effect at a high strain rate of 4.6 × 103 s−1. It is also discovered that the yield strength and the average plateau stress at the strain rate of 2.0 × 103 s−1 is higher than that at the strain rate of 1.3 × 103 s−1. However, the yield strength and the average plateau stress at the strain rate of 4.6 × 103 s−1 is lower than that at the strain rate of 2.0 × 103 s−1 and 1.3 × 103 s−1, but higher than that at a quasi-static state. This indicates that the aluminum honeycomb structure is sensitive to the strain rate. Additionally, the damage mode of the aluminum honeycomb structure is plastic buckling, collapse and folding of the cell wall, which is carried out using dynamic compression tests. The folding length of the cell wall at a higher strain rate is found to be longer than that at a lower strain rate. The test results can also be used as the stress–strain curves of the honeycomb constitutive model at the high strain rates to carry out the numerical simulation of high-speed impact. Full article
(This article belongs to the Section Mechanical Engineering)
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Open AccessArticle
Effect of Rejuvenation Heat Treatment on the Creep Property and Microstructural Evolution of a Ni-Base Superalloy
Appl. Sci. 2020, 10(3), 1187; https://doi.org/10.3390/app10031187 - 10 Feb 2020
Viewed by 205
Abstract
Interrupted creep tests were performed on a polycrystalline Ni-base superalloy, and rejuvenation heat treatment (RHT) was carried out to restore the creep resistance. During creep deformation, the microstructural evolution can be characterized as coarsening and rafting of γ′ precipitates, formation of dislocation networks [...] Read more.
Interrupted creep tests were performed on a polycrystalline Ni-base superalloy, and rejuvenation heat treatment (RHT) was carried out to restore the creep resistance. During creep deformation, the microstructural evolution can be characterized as coarsening and rafting of γ′ precipitates, formation of dislocation networks in matrix channels, γ′ shearing by dislocations and carbides transformation from MC to M6C type. In the sample with low precrept strain, the dislocation networks can be effectively removed after RHT and the size and morphology of γ′ particles were similar to that just after heat treatment. However, the microstructure in the sample with higher creep strain after RHT cannot be fully restored to the original state in terms of dislocations and distribution of γ′ particles. The subsequent creep results exhibit that creep property is also relevant to the precrept strain, which exhibits a good agreement with microstructure observations. In addition, RHT cannot reverse the carbide transformation from MC to M6C type but enhances this process, which can be evident by the change of the area fraction of these two types of carbides. The effect of carbides transformation on the creep resistance of K465 alloy is not pronounced. Full article
(This article belongs to the Special Issue Microstructural and Mechanical Properties of Metallic Materials)
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Open AccessArticle
CFD-Rotordynamics Sequential Coupling Simulation Approach for the Flow-Induced Vibration of Rotor System in Centrifugal Pump
Appl. Sci. 2020, 10(3), 1186; https://doi.org/10.3390/app10031186 - 10 Feb 2020
Viewed by 280
Abstract
Vibration of the rotor system is closely related with the operation stability of centrifugal pump, and it is inevitably induced by the unsteady inner flow. An unsteady computational fluid dynamics model coupling with a rotordynamics model was presented, and the corresponding numerical calculation [...] Read more.
Vibration of the rotor system is closely related with the operation stability of centrifugal pump, and it is inevitably induced by the unsteady inner flow. An unsteady computational fluid dynamics model coupling with a rotordynamics model was presented, and the corresponding numerical calculation program, including a self-designed rotordynamics code, was developed on the commercial package ANSYS Workbench. The validity of the numerical calculation model was verified by a hydraulic performance and vibration test based on an industrial centrifugal pump. The hydraulic radial forces on impeller, pressure pulsation, deformation, and vibration of the main shaft under nine different flow rates were systematically investigated and explained preliminarily from the view of inner unstable flow. Results show that the blade passing frequency is the dominant frequency in the fluctuation of the above dynamical behaviors, which is closely related to the rotor–stator interaction between the impeller and volute casing. This study built the connection between internal fluid flow in the centrifugal pump and the vibration of its external rotor structure, and may provide theoretical references for the design of vibration-reducing and safety monitoring strategies design of centrifugal pumps. Full article
(This article belongs to the Special Issue Computational Fluid Mechanics and Heat Transfer)
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Open AccessArticle
Prediction of the Load-Bearing Behavior of SPSW with Rectangular Opening by RBF Network
Appl. Sci. 2020, 10(3), 1185; https://doi.org/10.3390/app10031185 - 10 Feb 2020
Viewed by 243
Abstract
As a lateral load-bearing system, the steel plate shear wall (SPSW) is utilized in different structural systems that are susceptible to seismic risk and because of functional reasons SPSWs may need openings. In this research, the effects of rectangular openings on the lateral [...] Read more.
As a lateral load-bearing system, the steel plate shear wall (SPSW) is utilized in different structural systems that are susceptible to seismic risk and because of functional reasons SPSWs may need openings. In this research, the effects of rectangular openings on the lateral load-bearing behavior of the steel shear walls by the finite element method (FEM) is investigated. The results of the FEM are used for the prediction of SPSW behavior using the artificial neural network (ANN). The radial basis function (RBF) network is used to model the effects of the rectangular opening in the SPSW with different plate thicknesses. The results showed that the opening leads to reduced load-bearing capacity, stiffness and absorbed energy, which can be precisely predicted by employing RBF network model. Besides, the suitable relative area of the opening is determined. Full article
(This article belongs to the Special Issue Soft Computing Techniques in Structural Engineering and Materials)
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Open AccessArticle
Enhanced Phase Retrieval Method Based on Random Phase Modulation
Appl. Sci. 2020, 10(3), 1184; https://doi.org/10.3390/app10031184 - 10 Feb 2020
Viewed by 202
Abstract
The phase retrieval method based on random phase modulation can wipe out any ambiguity and stagnation problem in reconstruction. However, the two existing reconstruction algorithms for the random phase modulation method are suffering from problems. The serial algorithm from the spread-spectrum phase retrieval [...] Read more.
The phase retrieval method based on random phase modulation can wipe out any ambiguity and stagnation problem in reconstruction. However, the two existing reconstruction algorithms for the random phase modulation method are suffering from problems. The serial algorithm from the spread-spectrum phase retrieval method can realize rapid convergence but has poor noise immunity. Although there is a parallel framework that can suppress noise, the convergence speed is slow. Here, we propose a random phase modulation phase retrieval method based on a serial–parallel cascaded reconstruction framework to simultaneously achieve quality imaging and rapid convergence. The proposed serial–parallel cascaded method uses the phased result from the serial algorithm to serve as the initialization of the subsequent parallel process. Simulations and experiments demonstrate that the superiorities of both serial and parallel algorithms are fetched by the proposed serial–parallel cascaded method. In the end, we analyze the effect of iteration numbers from the serial process on the reconstruction performance to find the optimal allocation scope of iteration numbers. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessArticle
Semantic 3D Reconstruction for Robotic Manipulators with an Eye-In-Hand Vision System
Appl. Sci. 2020, 10(3), 1183; https://doi.org/10.3390/app10031183 - 10 Feb 2020
Viewed by 220
Abstract
Three-dimensional reconstruction and semantic understandings have attracted extensive attention in recent years. However, current reconstruction techniques mainly target large-scale scenes, such as an indoor environment or automatic self-driving cars. There are few studies on small-scale and high-precision scene reconstruction for manipulator operation, which [...] Read more.
Three-dimensional reconstruction and semantic understandings have attracted extensive attention in recent years. However, current reconstruction techniques mainly target large-scale scenes, such as an indoor environment or automatic self-driving cars. There are few studies on small-scale and high-precision scene reconstruction for manipulator operation, which plays an essential role in the decision-making and intelligent control system. In this paper, a group of images captured from an eye-in-hand vision system carried on a robotic manipulator are segmented by deep learning and geometric features and create a semantic 3D reconstruction using a map stitching method. The results demonstrate that the quality of segmented images and the precision of semantic 3D reconstruction are effectively improved by our method. Full article
(This article belongs to the Special Issue Augmented Reality, Virtual Reality & Semantic 3D Reconstruction)
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Open AccessFeature PaperArticle
TLS for Dynamic Measurement of the Elastic Line of Bridges
Appl. Sci. 2020, 10(3), 1182; https://doi.org/10.3390/app10031182 - 10 Feb 2020
Viewed by 271
Abstract
The evaluation of the structural health of a bridge and the monitoring of its bearing capacity are performed by measuring different parameters. The most important ones are the displacements due to fixed or mobile loads, whose monitoring can be performed using several methods, [...] Read more.
The evaluation of the structural health of a bridge and the monitoring of its bearing capacity are performed by measuring different parameters. The most important ones are the displacements due to fixed or mobile loads, whose monitoring can be performed using several methods, both conventional and innovative. Terrestrial Laser Scanner (TLS) is effectively used to obtain the displacements of the decks for static loads, while for dynamic measurements, several punctual sensors are in general used. The proposed system uses a TLS, set as a line scanner and positioned under the bridge deck. The TLS acquires a vertical section of the intrados, or a line along a section to be monitored. The instantaneous deviations between the lines detected in dynamic conditions and the reference one acquired with the unloaded bridge, allow to extract the displacements and, consequently, the elastic curve. The synchronization of TLS acquisitions and load location, obtained from a Global Navigation Satellite System GNSS receiver or from a video, is an important feature of the method. Three tests were carried out on as many bridges. The first was performed during the maneuvers of a heavy truck traveling on a bridge characterized by a simply supported metal structure deck. The second concerned a prestressed concrete bridge with cantilever beams. The third concerned the pylon of a cantilever spar cable-stayed bridge during a load test. The results show high precision and confirm the usefulness of this method both for performing dynamic tests and for monitoring bridges. Full article
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Open AccessArticle
GREG: A Global Level Relation Extraction with Knowledge Graph Embedding
Appl. Sci. 2020, 10(3), 1181; https://doi.org/10.3390/app10031181 - 10 Feb 2020
Viewed by 281
Abstract
In an age overflowing with information, the task of converting unstructured data into structured data are a vital task of great need. Currently, most relation extraction modules are more focused on the extraction of local mention-level relations—usually from short volumes of text. However, [...] Read more.
In an age overflowing with information, the task of converting unstructured data into structured data are a vital task of great need. Currently, most relation extraction modules are more focused on the extraction of local mention-level relations—usually from short volumes of text. However, in most cases, the most vital and important relations are those that are described in length and detail. In this research, we propose GREG: A Global level Relation Extractor model using knowledge graph embeddings for document-level inputs. The model uses vector representations of mention-level ‘local’ relation’s to construct knowledge graphs that can represent the input document. The knowledge graph is then used to predict global level relations from documents or large bodies of text. The proposed model is largely divided into two modules which are synchronized during their training. Thus, each of the model’s modules is designed to deal with local relations and global relations separately. This allows the model to avoid the problem of struggling against loss of information due to too much information crunched into smaller sized representations when attempting global level relation extraction. Through evaluation, we have shown that the proposed model yields high performances in both predicting global level relations and local level relations consistently. Full article
(This article belongs to the Section Computing and Artificial Intelligence)
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Open AccessFeature PaperArticle
FT-IR Characterization of Antimicrobial Hybrid Materials through Sol-Gel Synthesis
Appl. Sci. 2020, 10(3), 1180; https://doi.org/10.3390/app10031180 - 10 Feb 2020
Viewed by 271
Abstract
Silica/polycaprolactone and titania/polycaprolactone hybrid organic/inorganic amorphous composites were prepared via a sol-gel method starting from a multi-element solution containing tetramethyl orthosilicate (TMOS) or titanium butoxide (TBT), polycaprolactone (PCL), water and methylethylketone (MEK). The molecular structure of the crosslinked network was based on the [...] Read more.
Silica/polycaprolactone and titania/polycaprolactone hybrid organic/inorganic amorphous composites were prepared via a sol-gel method starting from a multi-element solution containing tetramethyl orthosilicate (TMOS) or titanium butoxide (TBT), polycaprolactone (PCL), water and methylethylketone (MEK). The molecular structure of the crosslinked network was based on the presence of the hydrogen bonds between organic/inorganic elements as confirmed by Fourier Transform Infra-Red (FT-IR) analysis. In particular, the structure of crosslinked network was realized by hydrogen bonds between the X-OH (X = Si or Ti) group (H donator) in the sol-gel intermediate species and ester groups (H-acceptors) in the repeating units of the polymer. The morphology of the hybrid materials; pore size distribution, elemental homogeneity and surface features, was studied by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and by atomic force microscopy (AFM). The bioactivity of the synthesized hybrid materials was confirmed by observing the formation of a layer of hydroxyapatite (HAP) on the surface of the samples soaked in a simulated body fluid. The antimicrobial behavior of synthetized hybrids was also assessed against Escherichia coli bacteria. In conclusion, the prepared hybrid materials are proposed for use as future bone implants. Full article
(This article belongs to the Special Issue Synthesis, Characterization and Application of Hybrid Composites)
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Open AccessArticle
A Robust Levitation Control of Maglev Vehicles Subject to Time Delay and Disturbances: Design and Hardware Experimentation
Appl. Sci. 2020, 10(3), 1179; https://doi.org/10.3390/app10031179 - 10 Feb 2020
Viewed by 254
Abstract
Maglev vehicles have become a new type of transportation system with higher speed, lower noise, and commercial appeal. Magnetic-suspension systems, which have high nonlinearity and open-loop instability, are the core components of maglev vehicles. The high-performance control of maglev vehicles has been the [...] Read more.
Maglev vehicles have become a new type of transportation system with higher speed, lower noise, and commercial appeal. Magnetic-suspension systems, which have high nonlinearity and open-loop instability, are the core components of maglev vehicles. The high-performance control of maglev vehicles has been the focus of numerous studies. Encountering challenges in the levitation control of maglev vehicles in the form of uncertain time delays and disturbances is unavoidable. To cope with these problems, this study presents the design of an adaptive robust controller based on the Riccati method and sliding-mode technology, simultaneously taking into account the influence of time delays and disturbances. The asymptotic stability of the closed-loop system with the proposed control law is proved by the Lyapunov method. Control performances of the proposed controller are shown in the simulation results. Together with the consistently stabilizing outputs, the presented control approach can handle time delays and disturbances well. Finally, experiments were also implemented to examine its practical control performance of the robust levitation-control law. Full article
(This article belongs to the Special Issue Selected Papers from IMETI 2018)
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Open AccessArticle
Facile Solution Synthesis, Processing and Characterization of n- and p-Type Binary and Ternary Bi–Sb Tellurides
Appl. Sci. 2020, 10(3), 1178; https://doi.org/10.3390/app10031178 - 10 Feb 2020
Viewed by 393
Abstract
The solution synthesis route as a scalable bottom-up synthetic method possesses significant advantages for synthesizing nanostructured bulk thermoelectric (TE) materials with improved performance. Tuning the composition of the materials directly in the solution, without needing any further processing, is important for adjusting the [...] Read more.
The solution synthesis route as a scalable bottom-up synthetic method possesses significant advantages for synthesizing nanostructured bulk thermoelectric (TE) materials with improved performance. Tuning the composition of the materials directly in the solution, without needing any further processing, is important for adjusting the dominant carrier type. Here, we report a very rapid (2 min) and high yield (>8 g/batch) synthetic method using microwave-assisted heating, for the controlled growth of Bi2–xSbxTe3 (x: 0–2) nanoplatelets. Resultant materials exhibit a high crystallinity and phase purity, as characterized by XRD, and platelet morphology, as revealed by SEM. Surface chemistry of as-made materials showed a mixture of metallic and oxide phases, as evidenced by XPS. Zeta-potential analysis exhibited a systematic change of isoelectric point as a function of the material composition. As-made materials were directly sintered into pellets by using spark plasma sintering process. TE performance of Bi2−xSbxTe3 pellets were studied, where the highest ZT values of 1.04 (at 440 K) for Bi2Te3 and 1.37 (at 523 K) for Sb2Te3 were obtained, as n- and p-type TE materials. The presented microwave-assisted synthesis method is energy effective, a truly scalable and reproducible method, paving the way for large scale production and implementation of towards large-area TE applications. Full article
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Open AccessArticle
Optimal Design of the Vertical Earthing with Electrodes Arranged in Line
Appl. Sci. 2020, 10(3), 1177; https://doi.org/10.3390/app10031177 - 10 Feb 2020
Viewed by 206
Abstract
The design methods of earthing from standards recommend the choice of electrode lengths and propose that the distances between electrodes to be 1–3 times larger than their length. The number of electrodes is determined from the condition of achieving the design earth resistance, [...] Read more.
The design methods of earthing from standards recommend the choice of electrode lengths and propose that the distances between electrodes to be 1–3 times larger than their length. The number of electrodes is determined from the condition of achieving the design earth resistance, while the design ends with the choice of one of the variants. This paper presents the methodology for calculating the earthing system with cylindrical, vertical electrodes arranged in a line. The main variables are the length and the number of earth electrodes, as well as the distance between adjacent ones. Firstly, a set of technologically advantageous values for the earth electrode length is established (e.g., 10 values). For each value of the electrode length and different numbers of electrodes (e.g., 11 values), the distance between adjacent electrodes is determined (e.g., for 110 cases), which leads to the design value resistance. Finally, optimal solutions are identified based on the five optimal applied criteria. The proposed optimal criteria for earthing design are the footprint area, the total earthing volume, the total dispersion surface, the total metal mass, and the investment costs. Comparing the optimal solutions with other technically possible solutions clearly highlights substantial savings concerning space, material, and cost. Full article
(This article belongs to the Section Energy)
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Open AccessArticle
Blob Detection and Deep Learning for Leukemic Blood Image Analysis
Appl. Sci. 2020, 10(3), 1176; https://doi.org/10.3390/app10031176 - 10 Feb 2020
Viewed by 281
Abstract
In microscopy, laboratory tests make use of cell counters or flow cytometers to perform tests on blood cells, like the complete blood count, rapidly. However, a manual blood smear examination is still needed to verify the counter results and to monitor patients under [...] Read more.
In microscopy, laboratory tests make use of cell counters or flow cytometers to perform tests on blood cells, like the complete blood count, rapidly. However, a manual blood smear examination is still needed to verify the counter results and to monitor patients under therapy. Moreover, the manual inspection permits the description of the cells’ appearance, as well as any abnormalities. Unfortunately, manual analysis is long and tedious, and its result can be subjective and error-prone. Nevertheless, using image processing techniques, it is possible to automate the entire workflow, both reducing the operators’ workload and improving the diagnosis results. In this paper, we propose a novel method for recognizing white blood cells from microscopic blood images and classify them as healthy or affected by leukemia. The presented system is tested on public datasets for leukemia detection, the SMC-IDB, the IUMS-IDB, and the ALL-IDB. The results are promising, achieving 100% accuracy for the first two datasets and 99.7% for the ALL-IDB in white cells detection and 94.1% in leukemia classification, outperforming the state-of-the-art. Full article
(This article belongs to the Special Issue Image Processing Techniques for Biomedical Applications)
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Open AccessFeature PaperArticle
New Ecological Solutions Involved in the Cleaning of a 19th Century Icon
Appl. Sci. 2020, 10(3), 1175; https://doi.org/10.3390/app10031175 - 10 Feb 2020
Viewed by 232
Abstract
Cleaning of old icons requires special attention to selecting the processes and systems compatible with the chemical nature and adhesions of the deposits, to not affect the polychrome layer or their conservation status. The study was carried out on a 19th century icon [...] Read more.
Cleaning of old icons requires special attention to selecting the processes and systems compatible with the chemical nature and adhesions of the deposits, to not affect the polychrome layer or their conservation status. The study was carried out on a 19th century icon made in fat tempera, on a thin layer of preparation that presents fouling. The cleaning was done using extracts obtained from sage, St. John’s Wort, and, respectively, licorice root teas obtained through different extraction processes: microwave, ultrasound, boiling, and room temperature, respectively. The washing capacity of the new system used was analyzed by analytical methods of assessing the cleaning degree: UV-Vis reflection, reflective colorimetry type CIE L*a*b*, co-assisted with optical microscopy and scanning electrone microscopy (SEM-EDX). Full article
(This article belongs to the Special Issue Obtaining, Characterization and Applications of Advanced Materials)
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Open AccessArticle
Hybrid Flow Shop Scheduling Problems Using Improved Fireworks Algorithm for Permutation
Appl. Sci. 2020, 10(3), 1174; https://doi.org/10.3390/app10031174 - 10 Feb 2020
Viewed by 283
Abstract
Prior studies are lacking which address permutation flow shop scheduling problems and hybrid flow shop scheduling problems together to help firms find the optimized scheduling strategy. The permutation flow shop scheduling problem and hybrid flow shop scheduling problems are important production scheduling types, [...] Read more.
Prior studies are lacking which address permutation flow shop scheduling problems and hybrid flow shop scheduling problems together to help firms find the optimized scheduling strategy. The permutation flow shop scheduling problem and hybrid flow shop scheduling problems are important production scheduling types, which widely exist in industrial production fields. This study aimed to acquire the best scheduling strategy for making production plans. An improved fireworks algorithm is proposed to minimize the makespan in the proposed strategies. The proposed improved fireworks algorithm is compared with the fireworks algorithm, and the improvement strategies include the following: (1) A nonlinear radius is introduced and the minimum explosion amplitude is checked to avoid the waste of optimal fireworks; (2) The original Gaussian mutation operator is replaced by a hybrid operator that combines Cauchy and Gaussian mutation to improve the search ability; and (3) An elite group selection strategy is adopted to reduce the computing costs. Two instances from the permutation flow shop scheduling problem and hybrid flow shop scheduling problems were used to evaluate the improved fireworks algorithm’s performance, and the computational results demonstrate the improved fireworks algorithm’s superiority. Full article
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Open AccessArticle
Rapid and Nondestructive Discrimination of Geographical Origins of Longjing Tea using Hyperspectral Imaging at Two Spectral Ranges Coupled with Machine Learning Methods
Appl. Sci. 2020, 10(3), 1173; https://doi.org/10.3390/app10031173 - 10 Feb 2020
Viewed by 250
Abstract
Longjing tea is one of China’s protected geographical indication products with high commercial and nutritional value. The geographical origin of Longjing tea is an important factor influencing its commercial and nutritional value. Hyperspectral imaging systems covering the two spectral ranges of 380–1030 nm [...] Read more.
Longjing tea is one of China’s protected geographical indication products with high commercial and nutritional value. The geographical origin of Longjing tea is an important factor influencing its commercial and nutritional value. Hyperspectral imaging systems covering the two spectral ranges of 380–1030 nm and 874–1734 nm were used to identify a single tea leaf of Longjing tea from six geographical origins. Principal component analysis (PCA) was conducted on hyperspectral images to form PCA score images. Differences among samples from different geographical origins were visually observed from the PCA score images. Support vector machine (SVM) and partial least squares discriminant analysis (PLS-DA) models were built using the full spectra at the two spectral ranges. Decent classification performances were obtained at the two spectral ranges, with the overall classification accuracy of the calibration and prediction sets over 84%. Furthermore, prediction maps for geographical origins identification of Longjing tea were obtained by applying the SVM models on the hyperspectral images. The overall results illustrate that hyperspectral imaging at both spectral ranges can be applied to identify the geographical origin of single tea leaves of Longjing tea. This study provides a new, rapid, and non-destructive alternative for Longjing tea geographical origins identification. Full article
(This article belongs to the Special Issue Hyperspectral Imaging, Methods and Applications)
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Open AccessArticle
Using Fast Frequency Hopping Technique to Improve Reliability of Underwater Communication System
Appl. Sci. 2020, 10(3), 1172; https://doi.org/10.3390/app10031172 - 10 Feb 2020
Cited by 1 | Viewed by 286
Abstract
Acoustic underwater communication systems designed to work reliably in shallow coastal waters must overcome major limitations such as multipath propagation and the Doppler effect. These restrictions are the reason for the complexity of receivers being built, whose task is to decode a symbol [...] Read more.
Acoustic underwater communication systems designed to work reliably in shallow coastal waters must overcome major limitations such as multipath propagation and the Doppler effect. These restrictions are the reason for the complexity of receivers being built, whose task is to decode a symbol on the basis of the received signal. Additional complications are caused by the low propagation speed of the acoustic wave in the water and the relatively narrow bandwidth. Despite the continuous development of communication systems using coherent modulations, they are still not as reliable as is desirable for reliable data transmission applications. This article presents an acoustic underwater communication system that uses one of the varieties of the spread spectrum technique i.e., the fast frequency hopping technique (FFH). This technique takes advantage of binary frequency-shift keying (BFSK) with an incoherent detection method to ensure the implementation of a system whose main priority is reliable data transmission and secondary priority is the transmission rate. The compromised choice of parameters consisted of the selection between the narrow band of the hydroacoustic transducer and the maximum number of carrier frequency hops, which results from the need to take into account the effects of the Doppler effect. In turn, the number of hops and the symbol duration were selected adequately for the occurrence of multipath propagations of an acoustic wave. In addition, this article describes experimental communication tests carried out using a laboratory model of the FFH-BFSK data transmission system in the shallow water environment of Lake Wdzydze/Poland. The test results obtained for three channels of different lengths are discussed. Full article
(This article belongs to the Special Issue Underwater Acoustic Communications and Networks)
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Open AccessReview
Application of Image Fusion in Diagnosis and Treatment of Liver Cancer
Appl. Sci. 2020, 10(3), 1171; https://doi.org/10.3390/app10031171 - 09 Feb 2020
Viewed by 359
Abstract
With the accelerated development of medical imaging equipment and techniques, image fusion technology has been effectively applied for diagnosis, biopsy and radiofrequency ablation, especially for liver tumor. Tumor treatment relying on a single medical imaging modality might face challenges, due to the deep [...] Read more.
With the accelerated development of medical imaging equipment and techniques, image fusion technology has been effectively applied for diagnosis, biopsy and radiofrequency ablation, especially for liver tumor. Tumor treatment relying on a single medical imaging modality might face challenges, due to the deep positioning of the lesions, operation history and the specific background conditions of the liver disease. Image fusion technology has been employed to address these challenges. Using the image fusion technology, one could obtain real-time anatomical imaging superimposed by functional images showing the same plane to facilitate the diagnosis and treatments of liver tumors. This paper presents a review of the key principles of image fusion technology, its application in tumor treatments, particularly in liver tumors, and concludes with a discussion of the limitations and prospects of the image fusion technology. Full article
(This article belongs to the Special Issue Computer-aided Biomedical Imaging 2020: Advances and Prospects)
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Open AccessArticle
Investigation of the Acoustical Environment in A Shopping Mall and Its Correlation to the Acoustic Comfort of the Workers
Appl. Sci. 2020, 10(3), 1170; https://doi.org/10.3390/app10031170 - 09 Feb 2020
Viewed by 269
Abstract
Noise in shopping centers and restaurants can reduce intelligibility and affect the comfort of the employees working for long periods in such environments. In this study, the interior acoustics of a shopping mall are studied by measuring the reverberation time (RT), with no [...] Read more.
Noise in shopping centers and restaurants can reduce intelligibility and affect the comfort of the employees working for long periods in such environments. In this study, the interior acoustics of a shopping mall are studied by measuring the reverberation time (RT), with no occupation, and the equivalent sound pressure levels (LAeq), with occupations at different times of the day, over a period of one week. The measurements were done at different locations, chosen based on their usage (shopping areas, entrances, food courts, and playing area). The values are correlated to the subjective acoustic comfort and the experience of loudness of the staff working at these locations, as measured through a questionnaire. The average RT values that were measured ranged between 0.9 s in the food court and 1.4 s for the main entrance. The LAeq was measured with a minimum of 58 dB in the shopping area in the early morning and a maximum of 83 dB in the playing area in the evening. The results showed an increase in the LAeq for the afternoon and evening in comparison with the early morning and midday time (p < 0.05); similarly, the sound levels for the weekends were higher than the weekdays (p < 0.05). The questionnaire results showed that headaches and difficulties in communicating with others (speech intelligibility) are the most important problems induced by the noise in shopping malls, occurring for 47.1% and 38.2% of respondents, respectively. Full article
(This article belongs to the Special Issue Advances in Room Acoustics of Non-performing Public Spaces)
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Open AccessArticle
Analytical Model of Wellbore Stability of Fractured Coal Seam Considering the Effect of Cleat Filler and Analysis of Influencing Factors
Appl. Sci. 2020, 10(3), 1169; https://doi.org/10.3390/app10031169 - 09 Feb 2020
Viewed by 259
Abstract
Currently, coal borehole collapses frequently occur during drilling. Considering that the coal near to the wellbore is cut into blocks, and the cleat filler of the coal influences the stress distribution near the wellbore, a new theoretical solution of a near-wellbore Stress Field [...] Read more.
Currently, coal borehole collapses frequently occur during drilling. Considering that the coal near to the wellbore is cut into blocks, and the cleat filler of the coal influences the stress distribution near the wellbore, a new theoretical solution of a near-wellbore Stress Field in coal bed wells is established. In addition, according to the limit equilibrium theory and the E.MG-C criterion, the limit sliding formula of the quadrilateral and triangular block is deduced, and the slipping direction of the blocks is further judged. Finally, the wellbore stability model of the coal seam is established. The accuracy of the theoretical model is verified through a numerical method by using the PFC software. Based upon this wellbore stability theoretical model of coal, many cleat affecting factors such as cleat spacing, cleat length, cleat angle and the cleat geometric position, are studied, and the results show that a quadrilateral block slides off more easily than a triangular block under the same boundary condition; the bigger the cleat spacing and cleat length are, the lower is the risk that blocks slide off, and increasing the cleat angle could cause blocks to slide off easily. Under the same boundary condition, whether blocks slide off or not is closely related to the well round angle. Full article
(This article belongs to the Special Issue Fracture and Fatigue Assessments of Structural Components)
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Open AccessArticle
Design of a Multi-Band Microstrip Textile Patch Antenna for LTE and 5G Services with the CRO-SL Ensemble
Appl. Sci. 2020, 10(3), 1168; https://doi.org/10.3390/app10031168 - 09 Feb 2020
Viewed by 311
Abstract
A textile multi-band antenna for LTE and 5G communication services, composed by a rectangular microstrip patch, two concentric annular slots and a U-Shaped slot, is considered in this paper. In the ground plane, three sleeved meanders have been introduced to modify the surface [...] Read more.
A textile multi-band antenna for LTE and 5G communication services, composed by a rectangular microstrip patch, two concentric annular slots and a U-Shaped slot, is considered in this paper. In the ground plane, three sleeved meanders have been introduced to modify the surface current distribution, leading to a bandwidth improvement. The U-Shaped slot, the dual circular slots, and the meanders shape have been optimized by means of the Coral Reefs Optimization with Substrate Layer algorithm (CRO-SL). This population-based meta-heuristic approach is a kind of ensemble algorithm for optimization (multi-method), in which different search operators are considered within the algorithm. We show that the CRO-SL is able to obtain a robust multi-band textile antenna, including LTE and 5G frequency bands. For the optimization process, the CRO-SL is guided by means of a fitness function obtained after the antenna simulation by a specific simulation software for electromagnetic analysis in the high frequency range. Full article
(This article belongs to the Special Issue Passive Planar Microwave Devices)
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Open AccessArticle
Environmental Attention-Guided Branchy Neural Network for Speech Enhancement
Appl. Sci. 2020, 10(3), 1167; https://doi.org/10.3390/app10031167 - 09 Feb 2020
Viewed by 255
Abstract
The performance of speech enhancement algorithms can be further improved by considering the application scenarios of speech products. In this paper, we propose an attention-based branchy neural network framework by incorporating the prior environmental information for noise reduction. In the whole denoising framework, [...] Read more.
The performance of speech enhancement algorithms can be further improved by considering the application scenarios of speech products. In this paper, we propose an attention-based branchy neural network framework by incorporating the prior environmental information for noise reduction. In the whole denoising framework, first, an environment classification network is trained to distinguish the noise type of each noisy speech frame. Guided by this classification network, the denoising network gradually learns respective noise reduction abilities in different branches. Unlike most deep neural network (DNN)-based methods, which learn speech reconstruction capabilities with a common neural structure from all training noises, the proposed branchy model obtains greater performance benefits from the specially trained branches of prior known noise interference types. Experimental results show that the proposed branchy DNN model not only preserved better enhanced speech quality and intelligibility in seen noisy environments, but also obtained good generalization in unseen noisy environments. Full article
(This article belongs to the Section Computing and Artificial Intelligence)
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Open AccessArticle
A Novel Digital Modulation Recognition Algorithm Based on Deep Convolutional Neural Network
Appl. Sci. 2020, 10(3), 1166; https://doi.org/10.3390/app10031166 - 09 Feb 2020
Viewed by 256
Abstract
The modulation recognition of digital signals under non-cooperative conditions is one of the important research contents here. With the rapid development of artificial intelligence technology, deep learning theory is also increasingly being applied to the field of modulation recognition. In this paper, a [...] Read more.
The modulation recognition of digital signals under non-cooperative conditions is one of the important research contents here. With the rapid development of artificial intelligence technology, deep learning theory is also increasingly being applied to the field of modulation recognition. In this paper, a novel digital signal modulation recognition algorithm is proposed, which has combined the InceptionResNetV2 network with transfer adaptation, called InceptionResnetV2-TA. Firstly, the received signal is preprocessed and generated the constellation diagram. Then, the constellation diagram is used as the input of the InceptionResNetV2 network to identify different kinds of signals. Transfer adaptation is used for feature extraction and SVM classifier is used to identify the modulation mode of digital signal. The constellation diagram of three typical signals, including Binary Phase Shift Keying(BPSK), Quadrature Phase Shift Keying(QPSK) and 8 Phase Shift Keying(8PSK), was made for the experiments. When the signal-to-noise ratio(SNR) is 4dB, the recognition rates of BPSK, QPSK and 8PSK are respectively 1.0, 0.9966 and 0.9633 obtained by InceptionResnetV2-TA, and at the same time, the recognition rate can be 3% higher than other algorithms. Compared with the traditional modulation recognition algorithms, the experimental results show that the proposed algorithm in this paper has a higher accuracy rate for digital signal modulation recognition at low SNR. Full article
(This article belongs to the Special Issue Wireless Sensor Networks in Smart Environments)
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Open AccessArticle
Real-Time Haze Removal Using Normalised Pixel-Wise Dark-Channel Prior and Robust Atmospheric-Light Estimation
Appl. Sci. 2020, 10(3), 1165; https://doi.org/10.3390/app10031165 - 09 Feb 2020
Viewed by 280
Abstract
This study proposes real-time haze removal from a single image using normalised pixel-wise dark-channel prior (DCP). DCP assumes that at least one RGB colour channel within most local patches in a haze-free image has a low-intensity value. Since the spatial resolution of the [...] Read more.
This study proposes real-time haze removal from a single image using normalised pixel-wise dark-channel prior (DCP). DCP assumes that at least one RGB colour channel within most local patches in a haze-free image has a low-intensity value. Since the spatial resolution of the transmission map depends on the patch size and it loses the detailed structure with large patch sizes, original work refines the transmission map using an image-matting technique. However, it requires high computational cost and is not adequate for real-time application. To solve these problems, we use normalised pixel-wise haze estimation without losing the detailed structure of the transmission map. This study also proposes robust atmospheric-light estimation using a coarse-to-fine search strategy and down-sampled haze estimation for acceleration. Experiments with actual and simulated haze images showed that the proposed method achieves real-time results of visually and quantitatively acceptable quality compared with other conventional methods of haze removal. Full article
(This article belongs to the Special Issue Advances in Image Processing, Analysis and Recognition Technology)
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Open AccessReview
Selected Aspects Regarding the Restoration/Conservation of Traditional Wood and Masonry Building Materials: A Short Overview of the Last Decade Findings
Appl. Sci. 2020, 10(3), 1164; https://doi.org/10.3390/app10031164 - 09 Feb 2020
Viewed by 389
Abstract
Vernacular buildings are usually constructed using materials at hand, including wood, natural stone and bricks (either clay or mud bricks). All those materials are exposed to a series of environmental factors, affecting their structure and integrity. The literature review was conducted using different [...] Read more.
Vernacular buildings are usually constructed using materials at hand, including wood, natural stone and bricks (either clay or mud bricks). All those materials are exposed to a series of environmental factors, affecting their structure and integrity. The literature review was conducted using different databases (Scopus, Web of Science, ScienceDirect, SpringerLink) using as keywords the historical material, “heritage” and the terms regarding the desired effect, within the envisaged time period (2010–2019). The assessment of the results was performed by manual inspection (reading the entire article) and the selection of the works to be inserted in the current review was made by evaluating the contribution to the field. This review summarizes different aspects related to the restoration and conservation of wooden and masonry elements of traditional buildings, including materials used for biocidal interventions, protection against abiotic factors, cleaning and consolidation agents. Finally, a critical discussion regarding the current limitations and future perspectives concludes the review work, envisaging the role of researchers specialized in materials science in the context of cultural heritage conservation. Full article
(This article belongs to the Special Issue Obtaining, Characterization and Applications of Advanced Materials)
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