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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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17 pages, 4661 KiB  
Article
Forecast of Airblast Vibrations Induced by Blasting Using Support Vector Regression Optimized by the Grasshopper Optimization (SVR-GO) Technique
Appl. Sci. 2022, 12(19), 9805; https://doi.org/10.3390/app12199805 - 29 Sep 2022
Cited by 11 | Viewed by 1247
Abstract
Air overpressure (AOp) is an undesirable environmental effect of blasting. To date, a variety of empirical equations have been developed to forecast this phenomenon and prevent its negative impacts with accuracy. However, the accuracy of these methods is not sufficient. In addition, they [...] Read more.
Air overpressure (AOp) is an undesirable environmental effect of blasting. To date, a variety of empirical equations have been developed to forecast this phenomenon and prevent its negative impacts with accuracy. However, the accuracy of these methods is not sufficient. In addition, they are resource-consuming. This study employed support vector regression (SVR) optimized with the grasshopper optimizer (GO) algorithm to forecast AOp resulting from blasting. Additionally, a novel input selection technique, the Boruta algorithm (BFS), was applied. A new algorithm, the SVR-GA-BFS7, was developed by combining the models mentioned above. The findings showed that the SVR-GO-BFS7 model was the best technique (R2 = 0.983, RMSE = 1.332). The superiority of this model means that using the seven most important inputs was enough to forecast the AOp in the present investigation. Furthermore, the performance of SVR-GO-BFS7 was compared with various machine learning techniques, and the model outperformed the base models. The GO was compared with some other optimization techniques, and the superiority of this algorithm over the others was confirmed. Therefore, the suggested method presents a framework for accurate AOp prediction that supports the resource-saving forecasting methods. Full article
(This article belongs to the Special Issue Blast and Impact Engineering on Structures and Materials)
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21 pages, 7008 KiB  
Article
An Explainable Classification Method of SPECT Myocardial Perfusion Images in Nuclear Cardiology Using Deep Learning and Grad-CAM
Appl. Sci. 2022, 12(15), 7592; https://doi.org/10.3390/app12157592 - 28 Jul 2022
Cited by 9 | Viewed by 2440
Abstract
Background: This study targets the development of an explainable deep learning methodology for the automatic classification of coronary artery disease, utilizing SPECT MPI images. Deep learning is currently judged as non-transparent due to the model’s complex non-linear structure, and thus, it is considered [...] Read more.
Background: This study targets the development of an explainable deep learning methodology for the automatic classification of coronary artery disease, utilizing SPECT MPI images. Deep learning is currently judged as non-transparent due to the model’s complex non-linear structure, and thus, it is considered a «black box», making it hard to gain a comprehensive understanding of its internal processes and explain its behavior. Existing explainable artificial intelligence tools can provide insights into the internal functionality of deep learning and especially of convolutional neural networks, allowing transparency and interpretation. Methods: This study seeks to address the identification of patients’ CAD status (infarction, ischemia or normal) by developing an explainable deep learning pipeline in the form of a handcrafted convolutional neural network. The proposed RGB-CNN model utilizes various pre- and post-processing tools and deploys a state-of-the-art explainability tool to produce more interpretable predictions in decision making. The dataset includes cases from 625 patients as stress and rest representations, comprising 127 infarction, 241 ischemic, and 257 normal cases previously classified by a doctor. The imaging dataset was split into 20% for testing and 80% for training, of which 15% was further used for validation purposes. Data augmentation was employed to increase generalization. The efficacy of the well-known Grad-CAM-based color visualization approach was also evaluated in this research to provide predictions with interpretability in the detection of infarction and ischemia in SPECT MPI images, counterbalancing any lack of rationale in the results extracted by the CNNs. Results: The proposed model achieved 93.3% accuracy and 94.58% AUC, demonstrating efficient performance and stability. Grad-CAM has shown to be a valuable tool for explaining CNN-based judgments in SPECT MPI images, allowing nuclear physicians to make fast and confident judgments by using the visual explanations offered. Conclusions: Prediction results indicate a robust and efficient model based on the deep learning methodology which is proposed for CAD diagnosis in nuclear medicine. Full article
(This article belongs to the Special Issue Information Processing in Medical Imaging)
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13 pages, 3732 KiB  
Review
Principle and Implementation of Stokes Vector Polarization Imaging Technology
Appl. Sci. 2022, 12(13), 6613; https://doi.org/10.3390/app12136613 - 29 Jun 2022
Cited by 10 | Viewed by 2089
Abstract
Compared with traditional imaging methods, polarization imaging has its unique advantages in many directions and has great development prospects. It is one of the hot spots of research and development at home and abroad. Based on the polarization imaging principle of Stokes vector, [...] Read more.
Compared with traditional imaging methods, polarization imaging has its unique advantages in many directions and has great development prospects. It is one of the hot spots of research and development at home and abroad. Based on the polarization imaging principle of Stokes vector, the realization methods of non-simultaneous polarization imaging and simultaneous polarization imaging are introduced, respectively according to the different polarization modulation methods of Stokes vector acquisition. Non-simultaneous polarization imaging is mainly introduced in two ways: rotary polarization imaging, electrically controlled polarization imaging, and the simultaneous polarization imaging is mainly introduced in three ways: divided amplitude polarization imaging, divided aperture polarization imaging, and divided focal plane polarization imaging. In this paper, the principle and realization of polarization imaging based on Stokes vector are introduced to boost the application of polarization imaging and promote the research and development of polarization imaging technology. Full article
(This article belongs to the Special Issue Novel Biophotonics Technologies and Applications)
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11 pages, 2019 KiB  
Article
O-Band Multimode Interference Coupler Power Combiner Using Slot-Waveguide Structures
Appl. Sci. 2022, 12(13), 6444; https://doi.org/10.3390/app12136444 - 24 Jun 2022
Cited by 8 | Viewed by 1845
Abstract
Photonic transmitters that operate with a high data transfer rate (over 150 Gb/s) at the O-band range (1260–1360 nm) require at least 100 milliwatts of power to overcome the power losses that are caused by using high-speed modulators. A laser with higher power [...] Read more.
Photonic transmitters that operate with a high data transfer rate (over 150 Gb/s) at the O-band range (1260–1360 nm) require at least 100 milliwatts of power to overcome the power losses that are caused by using high-speed modulators. A laser with higher power can probably handle this requirement; however, for the transmitter system, this solution can be problematic due to the nonlinear effects that can happen, which may lead to high noise in the transmitter system. Thus, to solve this issue, we propose a new design of a 2 × 1 multimode interference (MMI) power combiner using silicon nitride (SiN) slot waveguide structures. The MMI power combiner and the SiN slot waveguide structures were optimized using the full-vectorial beam propagation method (FV-BPM) and the finite difference time domain (FDTD) method. After combining two sources, high efficiency was obtained of 94.8–97.6% from the total power after a short coupling length of 109.81 µm over the O-band range with a low back reflection of 44.94 dB. Thus, the proposed device can be very useful for combining two O-band sources to gain a higher power level, which can be utilized to improve performances in transmitter systems. Full article
(This article belongs to the Special Issue Recent Advances in Silicon Photonics Design)
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14 pages, 2227 KiB  
Review
A Review of Optical Neural Networks
Appl. Sci. 2022, 12(11), 5338; https://doi.org/10.3390/app12115338 - 25 May 2022
Cited by 7 | Viewed by 5208
Abstract
With the continuous miniaturization of conventional integrated circuits, obstacles such as excessive cost, increased resistance to electronic motion, and increased energy consumption are gradually slowing down the development of electrical computing and constraining the application of deep learning. Optical neuromorphic computing presents various [...] Read more.
With the continuous miniaturization of conventional integrated circuits, obstacles such as excessive cost, increased resistance to electronic motion, and increased energy consumption are gradually slowing down the development of electrical computing and constraining the application of deep learning. Optical neuromorphic computing presents various opportunities and challenges compared with the realm of electronics. Algorithms running on optical hardware have the potential to meet the growing computational demands of deep learning and artificial intelligence. Here, we review the development of optical neural networks and compare various research proposals. We focus on fiber-based neural networks. Finally, we describe some new research directions and challenges. Full article
(This article belongs to the Collection New Trends in Optical Networks)
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14 pages, 2370 KiB  
Article
Estimation of Cosmic-Ray-Induced Atmospheric Ionization and Radiation at Commercial Aviation Flight Altitudes
Appl. Sci. 2022, 12(11), 5297; https://doi.org/10.3390/app12115297 - 24 May 2022
Cited by 6 | Viewed by 1747
Abstract
The main source of the ionization of the Earth’s atmosphere is the cosmic radiation that depends on solar activity as well as geomagnetic activity. Galactic cosmic rays constitute a permanent radiation background and contribute significantly to the radiation exposure inside the atmosphere. In [...] Read more.
The main source of the ionization of the Earth’s atmosphere is the cosmic radiation that depends on solar activity as well as geomagnetic activity. Galactic cosmic rays constitute a permanent radiation background and contribute significantly to the radiation exposure inside the atmosphere. In this work, the cosmic-ray-induced ionization of the Earth’s atmosphere, due to both solar and galactic cosmic radiation during the recent solar cycles 23 (1996–2008) and 24 (2008–2019), was studied globally. Estimations of the ionization were based on the CRAC:CRII model by the University of Oulu. The use of this model allowed for extensive calculations from the Earth’s surface (atmospheric depth 1033 g/cm2) to the upper limit of the atmosphere (atmospheric depth 0 g/cm2). Monte Carlo simulations were performed for the estimation quantities of radiobiological interest with the validated software DYASTIMA/DYASTIMA-R. This study was focused on specific altitudes of interest, such as the common flight levels used by commercial aviation. Full article
(This article belongs to the Special Issue Advances in Environmental Applied Physics)
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13 pages, 10605 KiB  
Article
Applications of Decision Tree and Random Forest as Tree-Based Machine Learning Techniques for Analyzing the Ultimate Strain of Spliced and Non-Spliced Reinforcement Bars
Appl. Sci. 2022, 12(10), 4851; https://doi.org/10.3390/app12104851 - 11 May 2022
Cited by 31 | Viewed by 2078
Abstract
The performance of both non-spliced and spliced steel bars significantly affects the overall performance of structural reinforced concrete elements. In this context, the mechanical properties of reinforcement bars (i.e., their ultimate strength and strain) should be determined in order to evaluate their reliability [...] Read more.
The performance of both non-spliced and spliced steel bars significantly affects the overall performance of structural reinforced concrete elements. In this context, the mechanical properties of reinforcement bars (i.e., their ultimate strength and strain) should be determined in order to evaluate their reliability prior to the construction procedure. In this study, the application of Tree-Based machine learning techniques is implemented to analyze the ultimate strain of non-spliced and spliced steel reinforcements. In this regard, a database containing the results of 225 experimental tests was collected based on the research investigations available in peer-reviewed international publications. The database included the mechanical properties of both non-spliced and mechanically spliced bars. For better accuracy, the databases of other splicing methods such as lap and welded-spliced methods were excluded from this research. The database was categorized as two sub-databases: training (85%) and testing (15%) of the developed models. Various effective parameters such as splice technique, steel grade of the bar, diameter of the steel bar, coupler geometry—including length and outer diameter along with the testing temperatures—were defined as the input variables for analyzing the ultimate strain using tree-based approaches including Decision Trees and Random Forest. The predicted outcomes were compared to the actual values and the precision of the prediction models was assessed via performance metrics, along with a Taylor diagram. Based on the reported results, the reliability of the proposed ML-based methods was acceptable (with an R2 ≥ 85%) and they were time-saving and cost-effective compared to more complicated, time-consuming, and expensive experimental examinations. More importantly, the models proposed in this study can be further considered as a part of a comprehensive prediction model for estimating the stress-strain behavior of steel bars. Full article
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13 pages, 6182 KiB  
Article
Wear Resistance Comparison Research of High-Alloy Protective Coatings for Power Industry Prepared by Means of CMT Cladding
Appl. Sci. 2022, 12(9), 4568; https://doi.org/10.3390/app12094568 - 30 Apr 2022
Cited by 14 | Viewed by 1357
Abstract
In this study, four protective coating materials: Inconel 718, Inconel 625, Alloy 33 and Stellite 6 were deposited on 16Mo3 steel tubes by means of CMT (Cold Metal Transfer), as an advanced version of MAG (Metal Active Gas) welding method. In the next [...] Read more.
In this study, four protective coating materials: Inconel 718, Inconel 625, Alloy 33 and Stellite 6 were deposited on 16Mo3 steel tubes by means of CMT (Cold Metal Transfer), as an advanced version of MAG (Metal Active Gas) welding method. In the next step, the surface of the deposited coating was remelted by means of TIG (Tungsten Inert Gas) welding method. SEM microstructure of coatings–substrate has been reported, and an EDX-researched chemical composition of the coatings was compared to the nominal chemical composition. The hardness distribution in the cross-section was performed, which revealed that among investigated coatings, Stellite 6 layer is the hardest, at about 500 HV0.2. Other materials such as Inconel 625, Inconel 718 and Alloy 33 represented a cladded zone hardness about 250 HV0.2. Stellite 6 layer had the lowest wear resistance in the dry sand/rubber wheel test, and Stellite 6 layer had the highest wear resistance in the erosive blasting test. This proved the existence of different wear mechanisms in the two test methods used. In the dry sand/rubber wheel test, the Alloy 33 and Inconel 718 only represented higher wear resistance than substrate 16Mo3 steel. In abrasive blasting tests all coatings had higher wear resistance than 16Mo3 steel; however, Stellite 6 coatings represented an approximately 5 times higher durability than other investigated (Inconel 625, Inconel 718, and Alloy 33) coatings. Full article
(This article belongs to the Special Issue Advances in Surface Modification of the Materials)
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15 pages, 2755 KiB  
Review
Characteristics and Applications of Biochar in Soil–Plant Systems: A Short Review of Benefits and Potential Drawbacks
Appl. Sci. 2022, 12(8), 4051; https://doi.org/10.3390/app12084051 - 16 Apr 2022
Cited by 19 | Viewed by 5730
Abstract
The available literary data suggest the general applicability and benefits of different biochar products in various soil–plant–environment systems. Due to its high porosity, biochar might generally improve the physicochemical and biological properties of supplemented soils. Among the direct and indirect effects are (i) [...] Read more.
The available literary data suggest the general applicability and benefits of different biochar products in various soil–plant–environment systems. Due to its high porosity, biochar might generally improve the physicochemical and biological properties of supplemented soils. Among the direct and indirect effects are (i) improved water-retention capacity, (ii) enhanced soil organic matter content, (iii) pH increase, (iv) better N and P availability, and (v) greater potential uptake of meso- and micronutrients. These are connected to the advantage of an enhanced soil oxygen content. The large porous surface area of biochar might indirectly protect the survival of microorganisms, while the adsorbed organic materials may improve the growth of both bacteria and fungi. On the other hand, N2-fixing Rhizobium bacteria and P-mobilizing mycorrhiza fungi might respond negatively to biochar’s application. In arid circumstances with limited water and nutrient availability, a synergistic positive effect was found in biochar–microbial combined applications. Biochar seems to be a valuable soil supplement if its application is connected with optimized soil–plant–environment conditions. This work aims to give a general review of the potential benefits and drawbacks of biochar application to soil, highlighting its impacts on the soil–plant–microbe system. Full article
(This article belongs to the Special Issue Biochar: Preparation and Surface Adsorption Applications)
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16 pages, 2298 KiB  
Review
Orthopedics-Related Applications of Ultrafast Laser and Its Recent Advances
Appl. Sci. 2022, 12(8), 3957; https://doi.org/10.3390/app12083957 - 14 Apr 2022
Cited by 10 | Viewed by 2452
Abstract
The potential of ultrafast lasers (pico- to femtosecond) in orthopedics-related procedures has been studied extensively for clinical adoption. As compared to conventional laser systems with continuous wave or longer wave pulse, ultrafast lasers provide advantages such as higher precision and minimal collateral thermal [...] Read more.
The potential of ultrafast lasers (pico- to femtosecond) in orthopedics-related procedures has been studied extensively for clinical adoption. As compared to conventional laser systems with continuous wave or longer wave pulse, ultrafast lasers provide advantages such as higher precision and minimal collateral thermal damages. Translation to surgical applications in the clinic has been restrained by limitations of material removal rate and pulse average power, whereas the use in surface texturing of implants has become more refined to greatly improve bioactivation and osteointegration within bone matrices. With recent advances, we review the advantages and limitations of ultrafast lasers, specifically in orthopedic bone ablation as well as bone implant laser texturing, and consider the difficulties encountered within orthopedic surgical applications where ultrafast lasers could provide a benefit. We conclude by proposing our perspectives on applications where ultrafast lasers could be of advantage, specifically due to the non-thermal nature of ablation and control of cutting. Full article
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11 pages, 2735 KiB  
Review
An Overview of Terahertz Imaging with Resonant Tunneling Diodes
Appl. Sci. 2022, 12(8), 3822; https://doi.org/10.3390/app12083822 - 10 Apr 2022
Cited by 9 | Viewed by 2765
Abstract
Terahertz (THz) imaging is a rapidly growing application motivated by industrial demands including harmless (non-ionizing) security imaging, multilayer paint quality control within the automotive industry, insulating foam non-invasive testing in aerospace, and biomedical diagnostics. One of the key components in the imaging system [...] Read more.
Terahertz (THz) imaging is a rapidly growing application motivated by industrial demands including harmless (non-ionizing) security imaging, multilayer paint quality control within the automotive industry, insulating foam non-invasive testing in aerospace, and biomedical diagnostics. One of the key components in the imaging system is the source and detector. This paper gives a brief overview of room temperature THz transceiver technology for imaging applications based on the emerging resonant tunneling diode (RTD) devices. The reported results demonstrate that RTD technology is a very promising candidate to realize compact, low-cost THz imaging systems. Full article
(This article belongs to the Special Issue Terahertz Applications for Nondestructive Testing)
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18 pages, 3347 KiB  
Article
THz Time-Domain Ellipsometer for Material Characterization and Paint Quality Control with More Than 5 THz Bandwidth
Appl. Sci. 2022, 12(8), 3744; https://doi.org/10.3390/app12083744 - 08 Apr 2022
Cited by 7 | Viewed by 1712
Abstract
Quality control of car body paint in the automotive industry is a promising industrial application of terahertz technology. Terahertz time-domain spectroscopy in reflection geometry enables accurate, fast, and nondestructive measurement of individual layer thicknesses of multi-layer coatings. For high precision thickness measurements, the [...] Read more.
Quality control of car body paint in the automotive industry is a promising industrial application of terahertz technology. Terahertz time-domain spectroscopy in reflection geometry enables accurate, fast, and nondestructive measurement of individual layer thicknesses of multi-layer coatings. For high precision thickness measurements, the frequency dependent complex refractive index of all layers must be calibrated very accurately. THz time-domain ellipsometry is self-referencing and provides reliable, frequency resolved material properties with high signal-to-noise ratio. The method is characterized by a high sensitivity to optical material properties and layer thicknesses. We present characterization results in the frequency range 0.1–6 THz for typical automotive paints and different substrates such as polypropylene (PP), which features a high material anisotropy. We demonstrate that the broadband material properties derived from ellipsometry allow for inline thickness measurements of multi-layer car body paints with high accuracy. Full article
(This article belongs to the Special Issue Terahertz Applications for Nondestructive Testing)
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14 pages, 1153 KiB  
Article
Polymer Pellet Fabrication for Accurate THz-TDS Measurements
Appl. Sci. 2022, 12(7), 3475; https://doi.org/10.3390/app12073475 - 29 Mar 2022
Cited by 7 | Viewed by 1978
Abstract
We investigate fabrication of compacts using polytetrafluoroethylene (PTFE) and polyethylene (PE), and the effect of compaction conditions on their terahertz transmission properties. The conditions used to fabricate compressed powder samples for terahertz time-domain spectroscopy (THz-TDS) can impact the accuracy of the measurements and [...] Read more.
We investigate fabrication of compacts using polytetrafluoroethylene (PTFE) and polyethylene (PE), and the effect of compaction conditions on their terahertz transmission properties. The conditions used to fabricate compressed powder samples for terahertz time-domain spectroscopy (THz-TDS) can impact the accuracy of the measurements and hence the interpretation of results. This study investigated the effect of compaction conditions on the accuracy of the THz-TDS analysis. Two polymers that are commonly used as matrix materials in terahertz spectroscopy studies were explored using a compaction simulator and a hydraulic press for sample preparation. THz-TDS was used to determine the refractive index and loss coefficient to compare the powder compacts (pellets) to the values of solid material. Sample porosity, axial relaxation and tensile strength were measured to assess the material’s suitability for terahertz spectroscopy. It was found that PTFE is the preferable material for creating THz-TDS samples due to its low porosity and high tensile strength. PE was found to show significant porosity at all compaction pressures, making it an unsuitable material for the accurate determination of optical parameters from THz-TDS spectroscopy measurements. The larger particle sizes of PE resulted in compacts that exhibited significantly lower tensile strength than those made from PTFE making handling and storage difficult. Full article
(This article belongs to the Special Issue Terahertz Applications for Nondestructive Testing)
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26 pages, 4898 KiB  
Article
The Behavior of Hybrid Fiber-Reinforced Concrete Elements: A New Stress-Strain Model Using an Evolutionary Approach
Appl. Sci. 2022, 12(4), 2245; https://doi.org/10.3390/app12042245 - 21 Feb 2022
Cited by 21 | Viewed by 3324
Abstract
Several stress-strain models were used to predict the strengths of steel fiber reinforced concrete, which are distinctive of the material. However, insufficient research has been done on the influence of hybrid fiber combinations (comprising two or more distinct fibers) on the characteristics of [...] Read more.
Several stress-strain models were used to predict the strengths of steel fiber reinforced concrete, which are distinctive of the material. However, insufficient research has been done on the influence of hybrid fiber combinations (comprising two or more distinct fibers) on the characteristics of concrete. For this reason, the researchers conducted an experimental program to determine the stress-strain relationship of 30 concrete samples reinforced with two distinct fibers (a hybrid of polyvinyl alcohol and steel fibers), with compressive strengths ranging from 40 to 120 MPa. A total of 80% of the experimental results were used to develop a new empirical stress-strain model, which was accomplished through the application of the particle swarm optimization (PSO) technique. It was discovered in this investigation that the new stress-strain model predictions are consistent with the remaining 20% of the experimental stress-strain curves obtained. Case studies of hybrid–fiber–reinforced concrete constructions were investigated in order to better understand the behavior of such elements. The data revealed that the proposed model has the highest absolute relative error (ARE) frequencies (ARE 10%) and the lowest absolute relative error (ARE > 15%) frequencies (ARE > 15%). Full article
(This article belongs to the Special Issue Structural Application of Advanced Concrete Materials)
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9 pages, 965 KiB  
Article
High-Efficiency Quantum Dot Lasers as Comb Sources for DWDM Applications
Appl. Sci. 2022, 12(4), 1836; https://doi.org/10.3390/app12041836 - 10 Feb 2022
Cited by 9 | Viewed by 1970
Abstract
The trend of data center transceivers is to increase bandwidth while simultaneously decreasing their size, power consumption, and cost. While data center links have previously relied on vertical-cavity surface-emitting lasers (VCSELs) or in-plane lasers using coarse wavelength division multiplexing (WDM) to encode data, [...] Read more.
The trend of data center transceivers is to increase bandwidth while simultaneously decreasing their size, power consumption, and cost. While data center links have previously relied on vertical-cavity surface-emitting lasers (VCSELs) or in-plane lasers using coarse wavelength division multiplexing (WDM) to encode data, recently, dense WDM (DWDM) has moved to the forefront for next-generation links. Several approaches exist as light sources for DWDM links; DFB arrays, nonlinear microcombs, and semiconductor mode-locked lasers (MLLs). This paper focuses on quantum dot MLLs (QDMLLs), which currently offer the best efficiency, simplicity, and size. The efficiency of optical combs generated by QDMLLs is analyzed in depth in this study. Full article
(This article belongs to the Special Issue Quantum Dot Lasers and Laser Dynamics)
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14 pages, 5182 KiB  
Article
Effects of Adding Alkali Metals and Organic Cations to Cu-Based Perovskite Solar Cells
Appl. Sci. 2022, 12(3), 1710; https://doi.org/10.3390/app12031710 - 07 Feb 2022
Cited by 23 | Viewed by 2322
Abstract
First-principles electronic band calculations were used to investigate the effects of alkali metals and organic cations added to Cu-based perovskite solar cells. The copper d-orbital band was slightly above the valence-band maximum and functioned as an acceptor level for carrier generation. Excitation from [...] Read more.
First-principles electronic band calculations were used to investigate the effects of alkali metals and organic cations added to Cu-based perovskite solar cells. The copper d-orbital band was slightly above the valence-band maximum and functioned as an acceptor level for carrier generation. Excitation from iodine p-orbitals and copper d-orbitals to alkali metal s-orbitals could suppress carrier recombination and promote carrier transport. Experimental solar conversion efficiencies increased after adding both Cu and Na, in agreement with the calculations. Total-energy calculations indicated that the perovskite crystal stability increased with the addition of ethyl ammonium, although the total energy decreased with the addition of Cu and Na. Full article
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23 pages, 4808 KiB  
Article
Dynamic Characteristics of Unsteady Aerodynamic Pressure on an Enclosed Housing for Sound Emission Alleviation Caused by a Passing High-Speed Train
Appl. Sci. 2022, 12(3), 1545; https://doi.org/10.3390/app12031545 - 31 Jan 2022
Cited by 5 | Viewed by 1663
Abstract
Train speed is increasing due to the development of high-speed railway technology. However, high-speed trains generate more noise and discomfort for residents, enclosed housing for sound emission alleviation is needed to further reduce noise. Because these enclosed housings for sound emission alleviation restrain [...] Read more.
Train speed is increasing due to the development of high-speed railway technology. However, high-speed trains generate more noise and discomfort for residents, enclosed housing for sound emission alleviation is needed to further reduce noise. Because these enclosed housings for sound emission alleviation restrain the air flow, strong and complicated aerodynamic pressures are generated inside the housing for sound emission alleviation when a train passes through at a high speed. This train-induced aerodynamic pressure, particularly its dynamic characteristics, is a key parameter in structural design. In the present study, the train-induced unsteady aerodynamic pressure in an enclosed housing for sound emission alleviation is simulated using the dynamic mesh method, and the dynamic characteristics of the aerodynamic pressure are investigated. The simulation results show that when the train is running in the enclosed housing for sound emission alleviation, the unsteady aerodynamic pressure is complicated and aperiodic, and after the train leaves the housing for sound emission alleviation, the aerodynamic pressure reverts to periodic decay curves. Two new terms, the duration of the extreme aerodynamic pressure and the pressure change rate, are proposed to evaluate the dynamic characteristics when the train passes through the barrier. The dominant frequency and decay rate are adopted to express the dynamic characteristics after the train exits. When the train runs in the enclosed housing for sound emission alleviation, the longest durations of the positive and negative extreme aerodynamic pressures are in the middle section, and the maximum change rate of aerodynamic pressure occurs at the entrance area. After the train exits the housing for sound emission alleviation, the pressure amplitude at the central region is always higher than those close to the entrance/exit. The dominant frequency of the aerodynamic pressure is identified and explained using wave propagation theory, the decay rate of the aerodynamic pressure at all sections is close. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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7 pages, 2403 KiB  
Article
In-Target Proton–Boron Nuclear Fusion Using a PW-Class Laser
Appl. Sci. 2022, 12(3), 1444; https://doi.org/10.3390/app12031444 - 28 Jan 2022
Cited by 24 | Viewed by 21786
Abstract
Nuclear reactions between protons and boron-11 nuclei (p–B fusion) that were used to yield energetic α-particles were initiated in a plasma that was generated by the interaction between a PW-class laser operating at relativistic intensities (~3 × 1019 W/cm2) and [...] Read more.
Nuclear reactions between protons and boron-11 nuclei (p–B fusion) that were used to yield energetic α-particles were initiated in a plasma that was generated by the interaction between a PW-class laser operating at relativistic intensities (~3 × 1019 W/cm2) and a 0.2-mm thick boron nitride (BN) target. A high p–B fusion reaction rate and hence, a large α-particle flux was generated and measured, thanks to a proton stream accelerated at the target’s front surface. This was the first proof of principle experiment to demonstrate the efficient generation of α-particles (~1010/sr) through p–B fusion reactions using a PW-class laser in the “in-target” geometry. Full article
(This article belongs to the Special Issue Laser-Driven Accelerators, Radiations, and Their Applications)
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22 pages, 930 KiB  
Perspective
Making Sense of Light: The Use of Optical Spectroscopy Techniques in Plant Sciences and Agriculture
Appl. Sci. 2022, 12(3), 997; https://doi.org/10.3390/app12030997 - 19 Jan 2022
Cited by 10 | Viewed by 2913
Abstract
As a result of the development of non-invasive optical spectroscopy, the number of prospective technologies of plant monitoring is growing. Being implemented in devices with different functions and hardware, these technologies are increasingly using the most advanced data processing algorithms, including machine learning [...] Read more.
As a result of the development of non-invasive optical spectroscopy, the number of prospective technologies of plant monitoring is growing. Being implemented in devices with different functions and hardware, these technologies are increasingly using the most advanced data processing algorithms, including machine learning and more available computing power each time. Optical spectroscopy is widely used to evaluate plant tissues, diagnose crops, and study the response of plants to biotic and abiotic stress. Spectral methods can also assist in remote and non-invasive assessment of the physiology of photosynthetic biofilms and the impact of plant species on biodiversity and ecosystem stability. The emergence of high-throughput technologies for plant phenotyping and the accompanying need for methods for rapid and non-contact assessment of plant productivity has generated renewed interest in the application of optical spectroscopy in fundamental plant sciences and agriculture. In this perspective paper, starting with a brief overview of the scientific and technological backgrounds of optical spectroscopy and current mainstream techniques and applications, we foresee the future development of this family of optical spectroscopic methodologies. Full article
(This article belongs to the Special Issue Applications of Optical Spectroscopy in Plant Sciences)
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17 pages, 5434 KiB  
Review
Recent Progress of the PAL-XFEL
Appl. Sci. 2022, 12(3), 1010; https://doi.org/10.3390/app12031010 - 19 Jan 2022
Cited by 9 | Viewed by 2347
Abstract
The X-ray free-electron laser of the Pohang Accelerator Laboratory (PAL-XFEL) was opened to users in 2017. Since then, significant progress has been made in PAL-XFEL operation and beamline experiments. This includes increasing the FEL pulse energy, increasing the FEL photon energy, generating self-seeding [...] Read more.
The X-ray free-electron laser of the Pohang Accelerator Laboratory (PAL-XFEL) was opened to users in 2017. Since then, significant progress has been made in PAL-XFEL operation and beamline experiments. This includes increasing the FEL pulse energy, increasing the FEL photon energy, generating self-seeding FEL, and trials of two-color operation. In the beamline, new instruments or endstations have been added or are being prepared. Overall, beamline operation has been stabilized since its initiation, which has enabled excellent scientific results through efficient user experiments. In this paper, we describe details of the recent progress of the PAL-XFEL. Full article
(This article belongs to the Special Issue Latest Trends in Free Electron Lasers)
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20 pages, 653 KiB  
Article
Efficient Decomposition of Unitary Matrices in Quantum Circuit Compilers
Appl. Sci. 2022, 12(2), 759; https://doi.org/10.3390/app12020759 - 12 Jan 2022
Cited by 12 | Viewed by 3068
Abstract
Unitary decomposition is a widely used method to map quantum algorithms to an arbitrary set of quantum gates. Efficient implementation of this decomposition allows for the translation of bigger unitary gates into elementary quantum operations, which is key to executing these algorithms on [...] Read more.
Unitary decomposition is a widely used method to map quantum algorithms to an arbitrary set of quantum gates. Efficient implementation of this decomposition allows for the translation of bigger unitary gates into elementary quantum operations, which is key to executing these algorithms on existing quantum computers. The decomposition can be used as an aggressive optimization method for the whole circuit, as well as to test part of an algorithm on a quantum accelerator. For the selection and implementation of the decomposition algorithm, perfect qubits are assumed. We base our decomposition technique on Quantum Shannon Decomposition, which generates O(344n) controlled-not gates for an n-qubit input gate. In addition, we implement optimizations to take advantage of the potential underlying structure in the input or intermediate matrices, as well as to minimize the execution time of the decomposition. Comparing our implementation to Qubiter and the UniversalQCompiler (UQC), we show that our implementation generates circuits that are much shorter than those of Qubiter and not much longer than the UQC. At the same time, it is also up to 10 times as fast as Qubiter and about 500 times as fast as the UQC. Full article
(This article belongs to the Special Issue Quantum Software Engineering and Programming)
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17 pages, 9051 KiB  
Article
Ultrasonic Inspection for Welds with Irregular Curvature Geometry Using Flexible Phased Array Probes and Semi-Auto Scanners: A Feasibility Study
Appl. Sci. 2022, 12(2), 748; https://doi.org/10.3390/app12020748 - 12 Jan 2022
Cited by 8 | Viewed by 3188
Abstract
Pipes of various shapes constitute pipelines utilized in industrial sites. These pipes are coupled through welding, wherein complex curvatures such as a flange, an elbow, a reducer, and a branch pipe are often found. Using phased array ultrasonic testing (PAUT) to inspect weld [...] Read more.
Pipes of various shapes constitute pipelines utilized in industrial sites. These pipes are coupled through welding, wherein complex curvatures such as a flange, an elbow, a reducer, and a branch pipe are often found. Using phased array ultrasonic testing (PAUT) to inspect weld zones with complex curvatures is faced with different challenges due to parts that are difficult to contact with probes, small-diameter pipes, spatial limitations due to adjacent pipes, nozzles, and sloped shapes. In this study, we developed a flexible PAUT probe (FPAPr) and a semi-automatic scanner that was improved to enable stable FPAPr scanning for securing its inspection data consistency and reproducibility. A mock-up test specimen was created for a flange, an elbow, a reducer, and a branch pipe. Artificial flaws were inserted into the specimen through notch and hole processing, and simulations and verification experiments were performed to verify the performance and field applicability of the FPAPr and semi-automatic scanner. Full article
(This article belongs to the Special Issue Applications on Ultrasonic Wave ‖)
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16 pages, 9335 KiB  
Article
Cold Atmospheric Pressure Plasma Jet Operated in Ar and He: From Basic Plasma Properties to Vacuum Ultraviolet, Electric Field and Safety Thresholds Measurements in Plasma Medicine
Appl. Sci. 2022, 12(2), 644; https://doi.org/10.3390/app12020644 - 10 Jan 2022
Cited by 15 | Viewed by 3081
Abstract
Application desired functionality as well as operation expenses of cold atmospheric pressure plasma (CAP) devices scale with properties like gas selection. The present contribution provides a comparative investigation for a CAP system operated in argon or helium at different operation voltages and distance [...] Read more.
Application desired functionality as well as operation expenses of cold atmospheric pressure plasma (CAP) devices scale with properties like gas selection. The present contribution provides a comparative investigation for a CAP system operated in argon or helium at different operation voltages and distance to the surface. Comparison of power dissipation, electrical field strength and optical emission spectroscopy from vacuum ultraviolet over visible up to near infrared ((V)UV-VIS-NIR) spectral range is carried out. This study is extended to safety relevant investigation of patient leakage current, induced surface temperature and species density for ozone (O3) and nitrogen oxides (NOx). It is found that in identical operation conditions (applied voltage, distance to surface and gas flow rate) the dissipated plasma power is about equal (up to 10 W), but the electrical field strength differs, having peak values of 320 kV/m for Ar and up to 300 kV/m for He. However, only for Ar CAP could we measure O3 up to 2 ppm and NOx up to 7 ppm. The surface temperature and leakage values of both systems showed different slopes, with the biggest surprise being a constant leakage current over distance for argon. These findings may open a new direction in the plasma source development for Plasma Medicine. Full article
(This article belongs to the Special Issue Frontiers in Atmospheric Pressure Plasma Technology)
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17 pages, 5622 KiB  
Article
Effect of Rice Straw on Tensile Properties of Tailings Cemented Paste Backfill
Appl. Sci. 2022, 12(1), 526; https://doi.org/10.3390/app12010526 - 05 Jan 2022
Cited by 6 | Viewed by 2289
Abstract
It is important and difficult to improve the tensile strength of backfill material to ensure the stability of goafs. In this study, rice straw (RS) in fiber form is used to improve the tensile properties of cemented paste backfill (CPB). An orthogonal experiment [...] Read more.
It is important and difficult to improve the tensile strength of backfill material to ensure the stability of goafs. In this study, rice straw (RS) in fiber form is used to improve the tensile properties of cemented paste backfill (CPB). An orthogonal experiment was designed, Brazilian indirect tensile strength tests were conducted to test the tensile performance of RS fiber-reinforced cemented paste backfill (RSCPB) under different fiber content (1, 2, 3 kg/m3) and fiber length (0.8~1, 1~3, 3~5 cm), and the microstructure of RSCPB was analyzed with scanning electron microscopy (SEM). The results showed that, compared with the conventional cemented paste backfill (CCPB), the increase in tensile strength of RSCPB ranged from 115.38% to 300.00% at 3 days curing age, 40.91% to 346.15% at 7 days, and −38.10% to 28.00% at 28 days, and the strain was slightly reduced during the curing period. The tensile strength, strain, and percentage increase of the RSCPB compared to the CCBP did not show a monotonic pattern of variation with the RS fiber content and length during the curing period. The RSCPB samples fractured under peak stress, showing obvious brittle failure. In addition, sulfate generated from S2− in the tailings inhibits the hydration reaction, and generates swelling products that form weak structural surfaces, which, in turn, lead to a 28-day tensile strength and strain of RSCPB lower than those at 7 days. Full article
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27 pages, 9350 KiB  
Article
The DEMO Water-Cooled Lead–Lithium Breeding Blanket: Design Status at the End of the Pre-Conceptual Design Phase
Appl. Sci. 2021, 11(24), 11592; https://doi.org/10.3390/app112411592 - 07 Dec 2021
Cited by 46 | Viewed by 3138
Abstract
The Water-Cooled Lead–Lithium Breeding Blanket (WCLL BB) is one of the two blanket concept candidates to become the driver blanket of the EU-DEMO reactor. The design was enacted with a holistic approach. The influence that neutronics, thermal-hydraulics (TH), thermo-mechanics (TM) and magneto-hydro-dynamics (MHD) [...] Read more.
The Water-Cooled Lead–Lithium Breeding Blanket (WCLL BB) is one of the two blanket concept candidates to become the driver blanket of the EU-DEMO reactor. The design was enacted with a holistic approach. The influence that neutronics, thermal-hydraulics (TH), thermo-mechanics (TM) and magneto-hydro-dynamics (MHD) may have on the design were considered at the same time. This new approach allowed for the design team to create a WCLL BB layout that is able to comply with different foreseen requirements in terms of integration, tritium self-sufficiency, and TH and TM needs. In this paper, the rationale behind the design choices and the main characteristics of the WCLL BB needed for the EU-DEMO are reported and discussed. Finally, the main achievements reached during the pre-conceptual design phase and some remaining open issues to be further investigated in the upcoming conceptual design phase are reported as well. Full article
(This article belongs to the Special Issue Breeding Blanket: Design, Technology and Performance)
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34 pages, 5176 KiB  
Review
Fe3O4 Nanoparticles: Structures, Synthesis, Magnetic Properties, Surface Functionalization, and Emerging Applications
Appl. Sci. 2021, 11(23), 11301; https://doi.org/10.3390/app112311301 - 29 Nov 2021
Cited by 108 | Viewed by 18070
Abstract
Magnetite (Fe3O4) nanoparticles (NPs) are attractive nanomaterials in the field of material science, chemistry, and physics because of their valuable properties, such as soft ferromagnetism, half-metallicity, and biocompatibility. Various structures of Fe3O4 NPs with different sizes, [...] Read more.
Magnetite (Fe3O4) nanoparticles (NPs) are attractive nanomaterials in the field of material science, chemistry, and physics because of their valuable properties, such as soft ferromagnetism, half-metallicity, and biocompatibility. Various structures of Fe3O4 NPs with different sizes, geometries, and nanoarchitectures have been synthesized, and the related properties have been studied with targets in multiple fields of applications, including biomedical devices, electronic devices, environmental solutions, and energy applications. Tailoring the sizes, geometries, magnetic properties, and functionalities is an important task that determines the performance of Fe3O4 NPs in many applications. Therefore, this review focuses on the crucial aspects of Fe3O4 NPs, including structures, synthesis, magnetic properties, and strategies for functionalization, which jointly determine the application performance of various Fe3O4 NP-based systems. We first summarize the recent advances in the synthesis of magnetite NPs with different sizes, morphologies, and magnetic properties. We also highlight the importance of synthetic factors in controlling the structures and properties of NPs, such as the uniformity of sizes, morphology, surfaces, and magnetic properties. Moreover, emerging applications using Fe3O4 NPs and their functionalized nanostructures are also highlighted with a focus on applications in biomedical technologies, biosensing, environmental remedies for water treatment, and energy storage and conversion devices. Full article
(This article belongs to the Special Issue Advances in Magnetic Nanomaterials and Nanostructures)
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20 pages, 2095 KiB  
Article
Chronic Effects of Diazinon® Exposures Using Integrated Biomarker Responses in Freshwater Walking Catfish, Clarias batrachus
Appl. Sci. 2021, 11(22), 10902; https://doi.org/10.3390/app112210902 - 18 Nov 2021
Cited by 35 | Viewed by 2987
Abstract
Diazinon exposures have been linked to the onset of toxic pathways and adverse outcomes in aquatic species, but the ecological implications on model species are not widely emphasized. The objective of this study was to determine how the organophosphate pesticide diazinon affected hematological [...] Read more.
Diazinon exposures have been linked to the onset of toxic pathways and adverse outcomes in aquatic species, but the ecological implications on model species are not widely emphasized. The objective of this study was to determine how the organophosphate pesticide diazinon affected hematological (hemoglobin, total red blood count, total white blood count, and mean corpuscular hemoglobin), growth (condition factor, hepatosomatic index, specific growth rate), biochemical (total serum glucose, total serum protein), and endocrine (growth hormone, tri-iodothyronine, and thyroxine) parameters in Clarias batrachus after chronic exposure. Diazinon was administered at predefined exposure doses (0.64 and 1.28 mg/L) and monitored at 15, 30, and 45 days into the investigation. Observation for most biomarkers revealed patterns of decreasing values with increasing toxicant concentration and exposure duration. Correlation analysis highlighted a significant inverse relationship between variables (mean corpuscular hemoglobin, condition factor, specific growth rate, tri-iodothyronine, thyroxine, and total serum protein) and elevated chronic diazinon exposure concentrations. The integrated indices (IBR and BRI) indexes were used to provide visual and understandable depictions of toxicity effects and emphasized the relativity of biomarkers in terms of sensitivity and magnitude or severity of responses under graded toxicant exposures. The significant damage reflected by evaluated parameters in diazinon exposure groups compared to control portends risks to the health of local fish populations, including Clarias batrachus in aquatic systems adjacent to agrarian landscapes. Full article
(This article belongs to the Special Issue Fate, Treatment and Impact of Natural and Synthetic Compounds)
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14 pages, 9008 KiB  
Article
Environmentally Relevant Concentrations of Triclosan Induce Cyto-Genotoxicity and Biochemical Alterations in the Hatchlings of Labeo rohita
Appl. Sci. 2021, 11(21), 10478; https://doi.org/10.3390/app112110478 - 08 Nov 2021
Cited by 24 | Viewed by 2738
Abstract
Xenobiotic Triclosan (TCS) is of great concern because of its existence in a variety of personal, household and healthcare products and continuous discharge in water worldwide. Excessive use of TCS-containing sanitizers and antiseptic products during the COVID-19 pandemic further increased its content in [...] Read more.
Xenobiotic Triclosan (TCS) is of great concern because of its existence in a variety of personal, household and healthcare products and continuous discharge in water worldwide. Excessive use of TCS-containing sanitizers and antiseptic products during the COVID-19 pandemic further increased its content in aquatic ecosystems. The present study deals with the cyto-genotoxic effects and biochemical alterations in the hatchlings of Labeo rohita on exposure to environmentally relevant concentrations of TCS. Three-days-old hatchlings were exposed to tap water, acetone (solvent control) and 4 environmentally relevant concentrations (6.3, 12.6, 25.2 and 60 µg/L) of TCS for 14 days and kept for a recovery period of 10 days. The significant concentration-dependent decline in cell viability but increase in micronucleated cells, nucleo-cellular abnormalities (NCAs) and DNA damage parameters like tail length, tail moment, olive tail moment and percent of tail DNA after exposure persisted till the end of recovery period. Glucose, triglycerides, cholesterol, total protein, albumin, total bilirubin, uric acid and urea (except for an increase at 60 µg/L) showed significant (p ≤ 0.05) concentration-dependent decrease after 14 days of exposure. The same trend (except for triglycerides, albumin and total bilirubin) continued till 10 days post exposure. In comparison to control, transaminases (alanine and aspartate aminotransferases) increased (p ≤ 0.05) after exposure as well as the recovery period, while a decline in alkaline phosphatase after exposure was followed by a significant increase during the recovery period. The results show that the environmentally relevant concentrations of TCS cause deleterious effects on the hatchlings of L. rohita. Full article
(This article belongs to the Special Issue Fate, Treatment and Impact of Natural and Synthetic Compounds)
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34 pages, 6360 KiB  
Review
Non-Destructive Testing Applications for Steel Bridges
Appl. Sci. 2021, 11(20), 9757; https://doi.org/10.3390/app11209757 - 19 Oct 2021
Cited by 40 | Viewed by 7184
Abstract
The growing population and increasing demand for surface transportation have highlighted the importance of maintaining safe and reliable civil infrastructures for daily use. Among all civil infrastructures, bridges are one of the most important elements in the transportation system. As such, to prevent [...] Read more.
The growing population and increasing demand for surface transportation have highlighted the importance of maintaining safe and reliable civil infrastructures for daily use. Among all civil infrastructures, bridges are one of the most important elements in the transportation system. As such, to prevent any failures caused by aging and environmental impacts, bridges require periodic inspections. This becomes even more critical due to climate change and its effect on bridges, especially in the coastal regions. Most of the inspections conducted incorporate the visual type of evaluation due to its simplicity. However, with the current developments in new technologies, there is a need for more advanced techniques of structural health monitoring (SHM) methods to be incorporated in the maintenance programs for more accurate and efficient surveys. In this paper, non-destructive testing (NDT) methods applicable to steel bridges are reviewed, with a focus on methods applicable to local damage detection. Moreover, the methodology, advantages and disadvantages, and up-to-date research on NDT methods are presented. Furthermore, the application of novel NDT techniques using innovative sensors, drones, and robots for the rapid and efficient assessment of damages on small and large scales is emphasized. This study is deemed necessary as it compiles in one place the available information regarding NDT methods for in-service steel bridges. Access to such information is critical for researchers who intend to work on new or improved NDT techniques. Full article
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14 pages, 6757 KiB  
Article
Effect of Printing Layer Thickness on the Trueness and Margin Quality of 3D-Printed Interim Dental Crowns
Appl. Sci. 2021, 11(19), 9246; https://doi.org/10.3390/app11199246 - 05 Oct 2021
Cited by 22 | Viewed by 3237
Abstract
The information in the literature on the effect of printing layer thickness on interim 3D-printed crowns is limited. In the present study, the effect of layer thickness on the trueness and margin quality of 3D-printed composite resin crowns was investigated and compared with [...] Read more.
The information in the literature on the effect of printing layer thickness on interim 3D-printed crowns is limited. In the present study, the effect of layer thickness on the trueness and margin quality of 3D-printed composite resin crowns was investigated and compared with milled crowns. The crowns were printed in 3 different layer thicknesses (20, 50, and 100 μm) by using a hybrid resin based on acrylic esters with inorganic microfillers or milled from polymethylmethacrylate (PMMA) discs and digitized with an intraoral scanner (test scans). The compare tool of the 3D analysis software was used to superimpose the test scans and the computer-aided design file by using the manual alignment tool and to virtually separate the surfaces. Deviations at different surfaces on crowns were calculated by using root mean square (RMS). Margin quality of crowns was examined under a stereomicroscope and graded. The data were evaluated with one-way ANOVA and Tukey HSD tests. The layer thickness affected the trueness and margin quality of 3D-printed interim crowns. Milled crowns had higher trueness on intaglio and intaglio occlusal surfaces than 100 μm-layer thickness crowns. Milled crowns had the highest margin quality, while 20 μm and 100 μm layer thickness printed crowns had the lowest. The quality varied depending on the location of the margin. Full article
(This article belongs to the Special Issue 3D Printed Materials Dentistry)
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24 pages, 2422 KiB  
Review
BIM Visual Programming Tools Applications in Infrastructure Projects: A State-of-the-Art Review
Appl. Sci. 2021, 11(18), 8343; https://doi.org/10.3390/app11188343 - 08 Sep 2021
Cited by 19 | Viewed by 4635
Abstract
The Building Information Modeling (BIM) methodology improves architectural and infrastructure projects by digitizing their processes throughout their life cycle stages, such as design, construction, management, monitoring, and operation. In recent years, the automation of these processes has been favored by the use of [...] Read more.
The Building Information Modeling (BIM) methodology improves architectural and infrastructure projects by digitizing their processes throughout their life cycle stages, such as design, construction, management, monitoring, and operation. In recent years, the automation of these processes has been favored by the use of visual programming (VP) tools that have replaced conventional programming languages for visual schemes. The use of these tools in architectural projects is becoming increasing popular. However, this is not the case in infrastructure projects, for which the use of VP algorithms remains scarce. The aim of this work is to encourage both scholars and engineers to implement VP tools in infrastructure projects. For this purpose, this work reviews, for the first time in the literature, the state-of-the-art and future research trends of VP tools in infrastructure projects. Full article
(This article belongs to the Section Civil Engineering)
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12 pages, 1293 KiB  
Article
Ozonized Water Administration in Peri-Implant Mucositis Sites: A Randomized Clinical Trial
Appl. Sci. 2021, 11(17), 7812; https://doi.org/10.3390/app11177812 - 25 Aug 2021
Cited by 43 | Viewed by 2750
Abstract
Peri-implant mucositis represents an inflammatory lesion of the mucosa surrounding an endosseous implant, without the loss of the supporting peri-implant bone. Considering its reversible nature, every effort should be made to contrast it, thus avoiding the eventual progression towards peri-implantitis. The aim of [...] Read more.
Peri-implant mucositis represents an inflammatory lesion of the mucosa surrounding an endosseous implant, without the loss of the supporting peri-implant bone. Considering its reversible nature, every effort should be made to contrast it, thus avoiding the eventual progression towards peri-implantitis. The aim of the present randomized clinical trial is to evaluate the efficacy of the ozonized water against peri-implant mucositis. A total of 26 patients diagnosed for this latter clinical condition were randomly divided according to the professional oral hygiene protocol performed on the pathological sites at baseline, at T1 (1 month), and T2 (2 months). Group 1 underwent an ozonized water administration (experimental treatment), whereas Group 2 underwent a pure water one (control treatment). Both administrations were performed with the same professional irrigator (Aquolab® professional water jet, Aquolab s.r.l. EB2C S.r.l., Milano, Italy) with no differences in color or taste between the two substances delivered. At each appointment, the following indexes were assessed: the Probing Pocket Depth (PPD), Plaque Index (PI), Bleeding on Probing (BoP), and Bleeding Score (BS). As regards intragroup differences, in Group 1 ozonized water significantly and progressively reduced all the clinical indexes tested, except for PI in the period T1–T2, whereas no significant differences occurred within the control group. Despite this, no significant intergroup differences were generally detected between the two treatments. Accordingly, the role of ozone for the management of peri-implant mucositis deserves to be further investigated. Full article
(This article belongs to the Special Issue Material Science, Implants, and Peri-Implant Tissues)
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28 pages, 2394 KiB  
Review
A Literature Review of Energy Efficiency and Sustainability in Manufacturing Systems
Appl. Sci. 2021, 11(16), 7366; https://doi.org/10.3390/app11167366 - 10 Aug 2021
Cited by 38 | Viewed by 9177
Abstract
Climate change mitigation, the goal of reducing CO2 emissions, more stringent regulations and the increment in energy costs have pushed researchers to study energy efficiency and renewable energy sources. Manufacturing systems are large energy consumers and are thus responsible for huge greenhouse [...] Read more.
Climate change mitigation, the goal of reducing CO2 emissions, more stringent regulations and the increment in energy costs have pushed researchers to study energy efficiency and renewable energy sources. Manufacturing systems are large energy consumers and are thus responsible for huge greenhouse gas emissions; for these reasons, many studies have focused on this topic recently. This review aims to summarize the most important papers on energy efficiency and renewable energy sources in manufacturing systems published in the last fifteen years. The works are grouped together, considering the system typology, i.e., manufacturing system subclasses (single machine, flow shop, job shop, etc.) or the assembly line, the developed energy-saving policies and the implementation of the renewable energy sources in the studied contexts. A description of the main approaches used in the analyzed papers was discussed. The conclusion reports the main findings of the review and suggests future directions for the researchers in the integration of renewable energy in the manufacturing systems consumption models. Full article
(This article belongs to the Special Issue Planning and Scheduling of Manufacturing Systems)
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23 pages, 4354 KiB  
Article
An Integrated SWOT-PESTLE-AHP Model Assessing Sustainability in Adaptive Reuse Projects
Appl. Sci. 2021, 11(15), 7134; https://doi.org/10.3390/app11157134 - 02 Aug 2021
Cited by 33 | Viewed by 12325
Abstract
In the recent past, sustainable development has been considered a major issue for urban and regional studies. Adaptive reuse appears to be a practical solution for sustainable urban development. Beyond and in addition to a conceptual base consistent with circular economy and sustainability [...] Read more.
In the recent past, sustainable development has been considered a major issue for urban and regional studies. Adaptive reuse appears to be a practical solution for sustainable urban development. Beyond and in addition to a conceptual base consistent with circular economy and sustainability principles, how do we know if adaptive reuse is actually sustainable, provided that it constitutes a multidisciplinary and multilevel process? The present study aims at evaluating, in as much as feasible quantitative terms, adaptive reuse practices sustainability. This was attained using a set of indicators, developed combining PESTLE (the Political, Economic, Technical, Social, Legal, and Environmental aspects) and SWOT (the Strengths, Weaknesses, Opportunities, and Threats) approaches, of which the results were subjected to evaluation by experts (pairwise comparisons), following the Analytic Hierarchy Process (AHP). The indicators representing strengths and opportunities of the process were calculated to be of higher value (overall level of final cumulative indicators values; 70.4%) compared with indicators representing weaknesses and threats. Enhancing strengths and opportunities and counteracting weaknesses and threats contribute making the potential of adaptive reuse practices in urban sustainability more evident. Among analysis dimensions, political and economic aspects rank first, followed by environmental, socio-cultural, technological-technical, and legal aspect. The empirical results of this paper serve as a useful reference point for decision-making and policy formulation addressing adaptive reuse practices in sustainable development strategies. Full article
(This article belongs to the Special Issue Novel Concept and Technologies of Sustainable Building Design)
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22 pages, 12333 KiB  
Article
Experimental Validation of Non-Marker Simple Image Displacement Measurements for Railway Bridges
Appl. Sci. 2021, 11(15), 7032; https://doi.org/10.3390/app11157032 - 30 Jul 2021
Cited by 11 | Viewed by 1703
Abstract
Simple bridge displacement measurement using a video camera is effective in realizing the efficient management of numerous railway structures via condition-based maintenance. Although non-marker image measurement is significantly influenced by the measuring environment, its practical applicability considering the displacement measurement accuracy of non-marker [...] Read more.
Simple bridge displacement measurement using a video camera is effective in realizing the efficient management of numerous railway structures via condition-based maintenance. Although non-marker image measurement is significantly influenced by the measuring environment, its practical applicability considering the displacement measurement accuracy of non-marker images and the influence of various environments is not completely understood. In this study, the accuracy of non-marker image displacement measurement and the influence of illuminance are confirmed using a model bridge, and the accuracy and applicable range are discussed. Moreover, field tests on two bridges—a steel and a concrete bridge—on low-speed and high-speed railways confirm the accuracy and practical application of non-marker image measurement in a real environment. The displacement was observed to be measured with an accuracy of ~1/30 pixel (error of ~0.4 mm at 20 m position) in the daytime with sufficient brightness. Moreover, the settings for subset positions and post-processing methods to ensure accuracy in non-marker image measurement on concrete bridges with low surface contrast are discussed. Full article
(This article belongs to the Special Issue Advanced Railway Infrastructures Engineering)
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29 pages, 4104 KiB  
Review
BIM-Based Digital Twin and XR Devices to Improve Maintenance Procedures in Smart Buildings: A Literature Review
Appl. Sci. 2021, 11(15), 6810; https://doi.org/10.3390/app11156810 - 24 Jul 2021
Cited by 54 | Viewed by 8281
Abstract
In recent years, the use of digital twins (DT) to improve maintenance procedures has increased in various industrial sectors (e.g., manufacturing, energy industry, aerospace) but is more limited in the construction industry. However, the operation and maintenance (O&M) phase of a building’s life [...] Read more.
In recent years, the use of digital twins (DT) to improve maintenance procedures has increased in various industrial sectors (e.g., manufacturing, energy industry, aerospace) but is more limited in the construction industry. However, the operation and maintenance (O&M) phase of a building’s life cycle is the most expensive. Smart buildings already use BIM (Building Information Modeling) for facility management, but they lack the predictive capabilities of DT. On the other hand, the use of extended reality (XR) technologies to improve maintenance operations has been a major topic of academic research in recent years, both through data display and remote collaboration. In this context, this paper focuses on reviewing projects using a combination of these technologies to improve maintenance operations in smart buildings. This review uses a combination of at least three of the terms “Digital Twin”, “Maintenance”, “BIM” and “Extended Reality”. Results show how a BIM can be used to create a DT and how this DT use combined with XR technologies can improve maintenance operations in a smart building. This paper also highlights the challenges for the correct implementation of a BIM-based DT combined with XR devices. An example of use is also proposed using a diagram of the possible interactions between the user, the DT and the application framework during maintenance operations. Full article
(This article belongs to the Special Issue Buildings Operation and Maintenance)
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16 pages, 8055 KiB  
Article
Application of an Additive Manufactured Hybrid Metal/Composite Shock Absorber Panel to a Military Seat Ejection System
Appl. Sci. 2021, 11(14), 6473; https://doi.org/10.3390/app11146473 - 13 Jul 2021
Cited by 14 | Viewed by 2361
Abstract
In this work, a preliminary numerical assessment on the application of an additive manufactured hybrid metal/composite shock absorber panels to a military seat ejection system, has been carried out. The innovative character of the shock absorber concept investigated is that the absorbing system [...] Read more.
In this work, a preliminary numerical assessment on the application of an additive manufactured hybrid metal/composite shock absorber panels to a military seat ejection system, has been carried out. The innovative character of the shock absorber concept investigated is that the absorbing system has a thickness of only 6 mm and is composed of a pyramid-shaped lattice core that, due to its small size, can only be achieved by additive manufacturing. The mechanical behaviour of these shock absorber panels has been examined by measuring their ability to absorb and dissipate the energy generated during the ejection phase into plastic deformations, thus reducing the loads acting on pilots. In this paper the effectiveness of a system composed of five hybrid shock absorbers, with very thin thickness in order to be easily integrated between the seat and the aircraft floor, has been numerically studied by assessing their ability to absorb the energy generated during the primary ejection phase. To accomplish this, a numerical simulation of the explosion has been performed and the energy absorbed by the shock-absorbing mechanism has been assessed. The performed analysis demonstrated that the panels can absorb more than 60% of the energy generated during the explosion event while increasing the total mass of the pilot-seat system by just 0.8%. Full article
(This article belongs to the Special Issue Additive Manufacturing for Composite Materials)
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29 pages, 4695 KiB  
Review
A Survey on Change Detection and Time Series Analysis with Applications
Appl. Sci. 2021, 11(13), 6141; https://doi.org/10.3390/app11136141 - 01 Jul 2021
Cited by 55 | Viewed by 6728
Abstract
With the advent of the digital computer, time series analysis has gained wide attention and is being applied to many fields of science. This paper reviews many traditional and recent techniques for time series analysis and change detection, including spectral and wavelet analyses [...] Read more.
With the advent of the digital computer, time series analysis has gained wide attention and is being applied to many fields of science. This paper reviews many traditional and recent techniques for time series analysis and change detection, including spectral and wavelet analyses with their advantages and weaknesses. First, Fourier and least-squares-based spectral analysis methods and spectral leakage attenuation methods are reviewed. Second, several time-frequency decomposition methods are described in detail. Third, several change or breakpoints detection methods are briefly reviewed. Finally, some of the applications of the methods in various fields, such as geodesy, geophysics, remote sensing, astronomy, hydrology, finance, and medicine, are listed in a table. The main focus of this paper is reviewing the most recent methods for analyzing non-stationary time series that may not be sampled at equally spaced time intervals without the need for any interpolation prior to the analysis. Understanding the methods presented herein is worthwhile to further develop and apply them for unraveling our universe. Full article
(This article belongs to the Section Computing and Artificial Intelligence)
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24 pages, 3409 KiB  
Review
A Review on the Lifecycle Strategies Enhancing Remanufacturing
Appl. Sci. 2021, 11(13), 5937; https://doi.org/10.3390/app11135937 - 25 Jun 2021
Cited by 18 | Viewed by 4047
Abstract
Remanufacturing is a domain that has increasingly been exploited during recent years due to its numerous advantages and the increasing need for society to promote a circular economy leading to sustainability. Remanufacturing is one of the main end-of-life (EoL) options that can lead [...] Read more.
Remanufacturing is a domain that has increasingly been exploited during recent years due to its numerous advantages and the increasing need for society to promote a circular economy leading to sustainability. Remanufacturing is one of the main end-of-life (EoL) options that can lead to a circular economy. There is therefore a strong need to prioritize this option over other available options at the end-of-life stage of a product because it is the only recovery option that maintains the same quality as that of a new product. This review focuses on the different lifecycle strategies that can help improve remanufacturing; in other words, the various strategies prior to, during or after the end-of-life of a product that can increase the chances of that product being remanufactured rather than being recycled or disposed of after its end-of-use. The emergence of the fourth industrial revolution, also known as industry 4.0 (I4.0), will help enhance data acquisition and sharing between different stages in the supply chain, as well boost smart remanufacturing techniques. This review examines how strategies like design for remanufacturing (DfRem), remaining useful life (RUL), product service system (PSS), closed-loop supply chain (CLSC), smart remanufacturing, EoL product collection and reverse logistics (RL) can enhance remanufacturing. We should bear in mind that not all products can be remanufactured, so other options are also considered. This review mainly focuses on products that can be remanufactured. For this review, we used 181 research papers from three databases; Science Direct, Web of Science and Scopus. Full article
(This article belongs to the Special Issue Sustainable Manufacturing Systems Using Big Data)
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13 pages, 4283 KiB  
Article
N-Heterocyclic Carbene-Gold(I) Complexes Targeting Actin Polymerization
Appl. Sci. 2021, 11(12), 5626; https://doi.org/10.3390/app11125626 - 18 Jun 2021
Cited by 16 | Viewed by 2030
Abstract
Transition metal complexes are attracting attention because of their various chemical and biological properties. In particular, the NHC-gold complexes represent a productive field of research in medicinal chemistry, mostly as anticancer tools, displaying a broad range of targets. In addition to the already [...] Read more.
Transition metal complexes are attracting attention because of their various chemical and biological properties. In particular, the NHC-gold complexes represent a productive field of research in medicinal chemistry, mostly as anticancer tools, displaying a broad range of targets. In addition to the already known biological targets, recently, an important activity in the organization of the cell cytoskeleton was discovered. In this paper, we demonstrated that two NHC-gold complexes (namely AuL4 and AuL7) possessing good anticancer activity and multi-target properties, as stated in our previous studies, play a major role in regulating the actin polymerization, by the means of in silico and in vitro assays. Using immunofluorescence and direct enzymatic assays, we proved that both the complexes inhibited the actin polymerization reaction without promoting the depolymerization of actin filaments. Our outcomes may contribute toward deepening the knowledge of NHC-gold complexes, with the objective of producing more effective and safer drugs for treating cancer diseases. Full article
(This article belongs to the Special Issue Anticancer Drugs Activity and Underlying Mechanisms)
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22 pages, 9807 KiB  
Article
Virtual Geosite Communication through a WebGIS Platform: A Case Study from Santorini Island (Greece)
Appl. Sci. 2021, 11(12), 5466; https://doi.org/10.3390/app11125466 - 12 Jun 2021
Cited by 22 | Viewed by 4052
Abstract
We document and show a state-of-the-art methodology that could allow geoheritage sites (geosites) to become accessible to scientific and non-scientific audiences through immersive and non-immersive virtual reality applications. This is achieved through a dedicated WebGIS platform, particularly handy in communicating geoscience during the [...] Read more.
We document and show a state-of-the-art methodology that could allow geoheritage sites (geosites) to become accessible to scientific and non-scientific audiences through immersive and non-immersive virtual reality applications. This is achieved through a dedicated WebGIS platform, particularly handy in communicating geoscience during the COVID-19 era. For this application, we selected nine volcanic outcrops in Santorini, Greece. The latter are mainly associated with several geological processes (e.g., dyking, explosive, and effusive eruptions). In particular, they have been associated with the famous Late Bronze Age (LBA) eruption, which made them ideal for geoheritage popularization objectives since they combine scientific and educational purposes with geotourism applications. Initially, we transformed these stunning volcanological outcrops into geospatial models—the so called virtual outcrops (VOs) here defined as virtual geosites (VGs)—through UAV-based photogrammetry and 3D modeling. In the next step, we uploaded them on an online platform that is fully accessible for Earth science teaching and communication. The nine VGs are currently accessible on a PC, a smartphone, or a tablet. Each one includes a detailed description and plenty of annotations available for the viewers during 3D exploration. We hope this work will be regarded as a forward model application for Earth sciences’ popularization and make geoheritage open to the scientific community and the lay public. Full article
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12 pages, 1903 KiB  
Review
Nanoparticles—Plant Interaction: What We Know, Where We Are?
Appl. Sci. 2021, 11(12), 5473; https://doi.org/10.3390/app11125473 - 12 Jun 2021
Cited by 21 | Viewed by 2397
Abstract
In recent years; the interaction of nanoparticles (NPs) with plants has been intensively studied. Therefore, more and more aspects related to both the positive and negative impact of NP on plants are well described. This article focuses on two aspects of NP interaction [...] Read more.
In recent years; the interaction of nanoparticles (NPs) with plants has been intensively studied. Therefore, more and more aspects related to both the positive and negative impact of NP on plants are well described. This article focuses on two aspects of NP interaction with plants. The first is a summary of the current knowledge on NP migration through the roots into the plant body, in particular, the role of the cell wall. The second aspect summarizes the current knowledge of the participation of the symplast, including the plasmodesmata (PD), in the movement of NP within the plant body. We highlight the gaps in our knowledge of the plant–NP interactions; paying attention to the need for future studies to explain the mechanisms that regulate the composition of the cell wall and the functioning of the PD under the influence of NP. Full article
(This article belongs to the Special Issue Interaction between Nanoparticles and Plants)
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15 pages, 4359 KiB  
Article
Land Suitability Mapping Using Geochemical and Spatial Analysis Methods
Appl. Sci. 2021, 11(12), 5404; https://doi.org/10.3390/app11125404 - 10 Jun 2021
Cited by 18 | Viewed by 2392
Abstract
Assessing the suitability of urban and agricultural land is essential for planning sustainable urban and agricultural systems. The main objective of this study is to evaluate the suitability of land in Ioannina plain (western Greece) concerning the soil contents of two potentially toxic [...] Read more.
Assessing the suitability of urban and agricultural land is essential for planning sustainable urban and agricultural systems. The main objective of this study is to evaluate the suitability of land in Ioannina plain (western Greece) concerning the soil contents of two potentially toxic elements, cadmium (Cd) and cobalt (Co). Geochemical and spatial analysis methods were applied to assess the distribution of Cd and Co in the soil of the Ioannina plain and identify their origin. The primary anthropogenic sources of Cd and Co in the topsoil of the study area can be attributed to traffic emissions, aircraft operations, vehicle crushing and dismantling activities. Element content is compared to international guidelines and screening values. Cadmium and Co concentration in the soil of the study area is well above the European topsoil mean. Thus, the urban and agricultural lands cover the vast majority (92%) of the total area. Cadmium concentration in soil of the study area with a mean (mg kg−1) 1.7 and 2.0 was observed in agricultural and urban land use, respectively. Cobalt content in soil of the area studied with a mean (mg kg−1) 30.8 and 37.1 was recorded in agricultural and urban land use, respectively. Land evaluation suitability by adopting criteria provided from the international literature is discussed. Full article
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23 pages, 317 KiB  
Review
Current Challenges and Future Opportunities for XAI in Machine Learning-Based Clinical Decision Support Systems: A Systematic Review
Appl. Sci. 2021, 11(11), 5088; https://doi.org/10.3390/app11115088 - 31 May 2021
Cited by 135 | Viewed by 15787
Abstract
Machine Learning and Artificial Intelligence (AI) more broadly have great immediate and future potential for transforming almost all aspects of medicine. However, in many applications, even outside medicine, a lack of transparency in AI applications has become increasingly problematic. This is particularly pronounced [...] Read more.
Machine Learning and Artificial Intelligence (AI) more broadly have great immediate and future potential for transforming almost all aspects of medicine. However, in many applications, even outside medicine, a lack of transparency in AI applications has become increasingly problematic. This is particularly pronounced where users need to interpret the output of AI systems. Explainable AI (XAI) provides a rationale that allows users to understand why a system has produced a given output. The output can then be interpreted within a given context. One area that is in great need of XAI is that of Clinical Decision Support Systems (CDSSs). These systems support medical practitioners in their clinic decision-making and in the absence of explainability may lead to issues of under or over-reliance. Providing explanations for how recommendations are arrived at will allow practitioners to make more nuanced, and in some cases, life-saving decisions. The need for XAI in CDSS, and the medical field in general, is amplified by the need for ethical and fair decision-making and the fact that AI trained with historical data can be a reinforcement agent of historical actions and biases that should be uncovered. We performed a systematic literature review of work to-date in the application of XAI in CDSS. Tabular data processing XAI-enabled systems are the most common, while XAI-enabled CDSS for text analysis are the least common in literature. There is more interest in developers for the provision of local explanations, while there was almost a balance between post-hoc and ante-hoc explanations, as well as between model-specific and model-agnostic techniques. Studies reported benefits of the use of XAI such as the fact that it could enhance decision confidence for clinicians, or generate the hypothesis about causality, which ultimately leads to increased trustworthiness and acceptability of the system and potential for its incorporation in the clinical workflow. However, we found an overall distinct lack of application of XAI in the context of CDSS and, in particular, a lack of user studies exploring the needs of clinicians. We propose some guidelines for the implementation of XAI in CDSS and explore some opportunities, challenges, and future research needs. Full article
34 pages, 1454 KiB  
Review
Applications of Nanosized-Lipid-Based Drug Delivery Systems in Wound Care
Appl. Sci. 2021, 11(11), 4915; https://doi.org/10.3390/app11114915 - 27 May 2021
Cited by 41 | Viewed by 5241
Abstract
Impaired wound healing is an encumbering public health issue that increases the demand for developing new therapies in order to minimize health costs and enhance treatment efficacy. Available conventional therapies are still unable to maximize their potential in penetrating the skin at the [...] Read more.
Impaired wound healing is an encumbering public health issue that increases the demand for developing new therapies in order to minimize health costs and enhance treatment efficacy. Available conventional therapies are still unable to maximize their potential in penetrating the skin at the target site and accelerating the healing process. Nanotechnology exhibits an excellent opportunity to enrich currently available medical treatments, enhance standard care and manage wounds. It is a promising approach, able to address issues such as the permeability and bioavailability of drugs with reduced stability or low water solubility. This paper focuses on nanosized-lipid-based drug delivery systems, describing their numerous applications in managing skin wounds. We also highlight the relationship between the physicochemical characteristics of nanosized, lipid-based drug delivery systems and their impact on the wound-healing process. Different types of nanosized-lipid-based drug delivery systems, such as vesicular systems and lipid nanoparticles, demonstrated better applicability and enhanced skin penetration in wound healing therapy compared with conventional treatments. Moreover, an improved chemically and physically stable drug delivery system, with increased drug loading capacity and enhanced bioavailability, has been shown in drugs encapsulated in lipid nanoparticles. Their applications in wound care show potential for overcoming impediments, such as the inadequate bioavailability of active agents with low solubility. Future research in nanosized-lipid-based drug delivery systems will allow the achievement of increased bioavailability and better control of drug release, providing the clinician with more effective therapies for wound care. Full article
(This article belongs to the Special Issue Biomaterials, Polymers and Tissue Engineering)
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25 pages, 551 KiB  
Review
Multi-Agent Reinforcement Learning: A Review of Challenges and Applications
Appl. Sci. 2021, 11(11), 4948; https://doi.org/10.3390/app11114948 - 27 May 2021
Cited by 95 | Viewed by 14476
Abstract
In this review, we present an analysis of the most used multi-agent reinforcement learning algorithms. Starting with the single-agent reinforcement learning algorithms, we focus on the most critical issues that must be taken into account in their extension to multi-agent scenarios. The analyzed [...] Read more.
In this review, we present an analysis of the most used multi-agent reinforcement learning algorithms. Starting with the single-agent reinforcement learning algorithms, we focus on the most critical issues that must be taken into account in their extension to multi-agent scenarios. The analyzed algorithms were grouped according to their features. We present a detailed taxonomy of the main multi-agent approaches proposed in the literature, focusing on their related mathematical models. For each algorithm, we describe the possible application fields, while pointing out its pros and cons. The described multi-agent algorithms are compared in terms of the most important characteristics for multi-agent reinforcement learning applications—namely, nonstationarity, scalability, and observability. We also describe the most common benchmark environments used to evaluate the performances of the considered methods. Full article
(This article belongs to the Section Computing and Artificial Intelligence)
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25 pages, 12733 KiB  
Article
Experimental Investigation and Artificial Neural Network Based Prediction of Bond Strength in Self-Compacting Geopolymer Concrete Reinforced with Basalt FRP Bars
Appl. Sci. 2021, 11(11), 4889; https://doi.org/10.3390/app11114889 - 26 May 2021
Cited by 16 | Viewed by 2256
Abstract
The current research on concrete and cementitious materials focuses on finding sustainable solutions to address critical issues, such as increased carbon emissions, or corrosion attack associated with reinforced concrete structures. Geopolymer concrete is considered to be an eco-friendly alternative due to its superior [...] Read more.
The current research on concrete and cementitious materials focuses on finding sustainable solutions to address critical issues, such as increased carbon emissions, or corrosion attack associated with reinforced concrete structures. Geopolymer concrete is considered to be an eco-friendly alternative due to its superior properties in terms of reduced carbon emissions and durability. Similarly, the use of fibre-reinforced polymer (FRP) bars to address corrosion attack in steel-reinforced structures is also gaining momentum. This paper investigates the bond performance of a newly developed self-compacting geopolymer concrete (SCGC) reinforced with basalt FRP (BFRP) bars. This study examines the bond behaviour of BFRP-reinforced SCGC specimens with variables such as bar diameter (6 mm and 10 mm) and embedment lengths. The embedment lengths adopted are 5, 10, and 15 times the bar diameter (db), and are denoted as 5 db, 10 db, and 15 db throughout the study. A total of 21 specimens, inclusive of the variable parameters, are subjected to direct pull-out tests in order to assess the bond between the rebar and the concrete. The result is then compared with the SCGC reinforced with traditional steel bars, in accordance with the ACI 440.3R-04 and CAN/CSA-S806-02 guidelines. A prediction model for bond strength has been proposed using artificial neural network (ANN) tools, which contributes to the new knowledge on the use of Basalt FRP bars as internal reinforcement in an ambient-cured self-compacting geopolymer concrete. Full article
(This article belongs to the Special Issue Artificial Neural Networks Applied in Civil Engineering)
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19 pages, 2446 KiB  
Review
Applications of Cold Atmospheric Pressure Plasma Technology in Medicine, Agriculture and Food Industry
Appl. Sci. 2021, 11(11), 4809; https://doi.org/10.3390/app11114809 - 24 May 2021
Cited by 88 | Viewed by 15034
Abstract
In recent years, cold atmospheric pressure plasma (CAPP) technology has received substantial attention due to its valuable properties including operational simplicity, low running cost, and environmental friendliness. Several different gases (air, nitrogen, helium, argon) and techniques (corona discharge, dielectric barrier discharge, plasma jet) [...] Read more.
In recent years, cold atmospheric pressure plasma (CAPP) technology has received substantial attention due to its valuable properties including operational simplicity, low running cost, and environmental friendliness. Several different gases (air, nitrogen, helium, argon) and techniques (corona discharge, dielectric barrier discharge, plasma jet) can be used to generate plasma at atmospheric pressure and low temperature. Plasma treatment is routinely used in materials science to modify the surface properties (e.g., wettability, chemical composition, adhesion) of a wide range of materials (e.g., polymers, textiles, metals, glasses). Moreover, CAPP seems to be a powerful tool for the inactivation of various pathogens (e.g., bacteria, fungi, viruses) in the food industry (e.g., food and packing material decontamination, shelf life extension), agriculture (e.g., disinfection of seeds, fertilizer, water, soil) and medicine (e.g., sterilization of medical equipment, implants). Plasma medicine also holds great promise for direct therapeutic treatments in dentistry (tooth bleaching), dermatology (atopic eczema, wound healing) and oncology (melanoma, glioblastoma). Overall, CAPP technology is an innovative, powerful and effective tool offering a broad application potential. However, its limitations and negative impacts need to be determined in order to receive regulatory approval and consumer acceptance. Full article
(This article belongs to the Special Issue Recent Advances in Atmospheric-Pressure Plasma Technology)
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15 pages, 4386 KiB  
Article
Geometry and Distortion Prediction of Multiple Layers for Wire Arc Additive Manufacturing with Artificial Neural Networks
Appl. Sci. 2021, 11(10), 4694; https://doi.org/10.3390/app11104694 - 20 May 2021
Cited by 21 | Viewed by 3085
Abstract
Wire arc additive manufacturing (WAAM) is a direct energy deposition (DED) process with high deposition rates, but deformation and distortion can occur due to the high energy input and resulting strains. Despite great efforts, the prediction of distortion and resulting geometry in additive [...] Read more.
Wire arc additive manufacturing (WAAM) is a direct energy deposition (DED) process with high deposition rates, but deformation and distortion can occur due to the high energy input and resulting strains. Despite great efforts, the prediction of distortion and resulting geometry in additive manufacturing processes using WAAM remains challenging. In this work, an artificial neural network (ANN) is established to predict welding distortion and geometric accuracy for multilayer WAAM structures. For demonstration purposes, the ANN creation process is presented on a smaller scale for multilayer beads on plate welds on a thin substrate sheet. Multiple concepts for the creation of ANNs and the handling of outliers are developed, implemented, and compared. Good results have been achieved by applying an enhanced ANN using deformation and geometry from the previously deposited layer. With further adaptions to this method, a prediction of additive welded structures, geometries, and shapes in defined segments is conceivable, which would enable a multitude of applications for ANNs in the WAAM-Process, especially for applications closer to industrial use cases. It wo