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Appl. Sci., Volume 12, Issue 24 (December-2 2022) – 542 articles

Cover Story (view full-size image): Human–robot collaboration (HRC) is becoming increasingly important in industrial assembly and requires a reasonable allocation of tasks to humans or robots. The article presents a new approach for dynamic task allocation, its integration into an intuitive block-based process planning framework, and its evaluation in comparison to both manual assembly and static task allocation. A systematic methodology for the comprehensive evaluation of task allocation approaches is proposed, followed by a user study. For the dynamic task allocation, the results show a higher HRC fluency with good adaptation to process delays, and a reduction in cycle time for assembly processes with sufficiently high degrees of parallelism. Based on the study results, assembly scenarios in which manual assembly or collaborative assembly with static or dynamic task allocation is most appropriate are discussed. View this paper
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Article
Mechanical Characteristics of Pre-Peak Unloading Damage and Mechanisms of Reloading Failure in Red Sandstone
Appl. Sci. 2022, 12(24), 13046; https://doi.org/10.3390/app122413046 - 19 Dec 2022
Viewed by 603
Abstract
The mining of deep coal resources occurs in a high-stress geological environment as well as an engineering environment of rock excavation and unloading. Research on the re-bearing capacity characteristics and damage mechanism of rock masses damaged by peak front unloading is critical in [...] Read more.
The mining of deep coal resources occurs in a high-stress geological environment as well as an engineering environment of rock excavation and unloading. Research on the re-bearing capacity characteristics and damage mechanism of rock masses damaged by peak front unloading is critical in revealing the destabilization and rupture law of deep rock bodies. The triaxial pre-peak unloading point was controlled to prepare damaged sandstone specimens, and the RMT-150C rock mechanics test loading system and the AEwin USB-type acoustic emission monitor were used to perform uniaxial reloading tests on the pre-peak unloading-damaged sandstone and to monitor the acoustic emission signals during the rupture process. Among them, the peak front unloading point was set to 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, and 90% of the peak strength at 10 MPa of the surrounding pressure for a total of 11 working conditions. The test results show that: (1) The degree of unloading before the peak controls the uniaxial reload deformation characteristics of sandstone. The higher the unloading point, the faster the deformation of the rock sample, even directly into the crack instability extension stage, and the sandstone deformation characteristics transform from plastic—elastic to elastic—viscous. (2) The cumulative energy characteristics of the 40% to 60% sandstone at the unloading point are comparable to those of the complete sandstone and are separated into smooth, steady growth, and secondary smooth phases. The acoustic emission energy characteristics of the 65% and 70% sandstone at the unloading point are mostly focused on during the crack expansion stage. The sandstone’s acoustic emission energy characteristics exhibit a “double peak” occurrence at 75% of the unloading point. The cumulative energy characteristics of the 80% to 90% sandstone at the unloading point reveal a “stepped” rise. (3) Sandstone’s pre-peak unloading rupture morphology influences the reload damage characteristics: 40% to 70% of the specimens at the unloading point exhibit “Y”-type double-slope shear damage features. The predominant cause of specimen damage in 75% of the specimens at the unloading point is secondary primary cracks based on the pre-peak tensile rupture pattern. The damage path of 80% to 90% of the specimens at the point of unloading occurs in shear damage along the pre-peak unloading rupture pattern. (4) A closed crack mechanics analysis model under uniaxial reload was established, and the basic solution of pseudo-force for fine microcracks subjected to far-field stress, the stress intensity factor at the crack tip, and the crack fracture angle were theoretically derived. Furthermore, the relationship between the fracture angle θ of rock compression-shear cracks, the crack angle β, and the friction coefficient f at the crack surface was clarified. Full article
(This article belongs to the Special Issue Mechanics, Damage Properties and Impacts of Coal Mining)
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Article
Operational Stability Analysis of Blue Thermally Activated Delayed Fluorescence Organic Light-Emitting Diodes Using the Capacitance-Voltage Method
Appl. Sci. 2022, 12(24), 13045; https://doi.org/10.3390/app122413045 - 19 Dec 2022
Viewed by 478
Abstract
We analyzed the degradation features by measuring the capacitance–voltage characteristics after electrically aging blue thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs). The measurement was investigated in terms of the hole transfer layer (HTL) and electron transfer layer (ETL) structures. For the [...] Read more.
We analyzed the degradation features by measuring the capacitance–voltage characteristics after electrically aging blue thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs). The measurement was investigated in terms of the hole transfer layer (HTL) and electron transfer layer (ETL) structures. For the HTL, three different materials—N,N′–bis(naphthalen–1–yl)–N,N′–bis(phenyl)–benzidine (NPB), 4,4′,4″-tris(carbazol–9–yl)triphenylamine (TCTA), and 1,3–bis(carbazol–9–yl)benzene (mCP)—were used at the HTL/emission layer (EML) interface; the TCTA/EML interface had the highest stability among the interfaces. For the ETL, bis [2–(diphenylphosphino)phenyl] ether oxide (DPEPO) without further dopants was used as an exciton blocking layer (ExBL) to effectively confine the excitons at the EML. However, DPEPO has low stability and carrier mobility. Therefore, 0, 10, and 40 nm-thick ExBL devices were investigated; it was found that the 0 nm-thick ExBL device was the most stable. However, the 10 nm-thick ExBL is essential to confine the excitons at the EML, which ensures a high EL performance. Full article
(This article belongs to the Section Optics and Lasers)
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Article
Hybrid Algorithm of Improved Beetle Antenna Search and Artificial Fish Swarm
Appl. Sci. 2022, 12(24), 13044; https://doi.org/10.3390/app122413044 - 19 Dec 2022
Viewed by 382
Abstract
The beetle antenna search algorithm (BAS) converges rapidly and runs in a short time, but it is prone to yielding values corresponding to local extrema when dealing with high-dimensional problems, and its optimization result is unstable. The artificial fish swarm algorithm (AFS) can [...] Read more.
The beetle antenna search algorithm (BAS) converges rapidly and runs in a short time, but it is prone to yielding values corresponding to local extrema when dealing with high-dimensional problems, and its optimization result is unstable. The artificial fish swarm algorithm (AFS) can achieve good convergence in the early stage, but it suffers from slow convergence speed and low optimization accuracy in the later stage. Therefore, this paper combines the two algorithms according to their respective characteristics and proposes a mutation and a multi-step detection strategy to improve the BAS algorithm and raise its optimization accuracy. To verify the performance of the hybrid composed of the AFS and BAS algorithms based on the Mutation and Multi-step detection Strategy (MMSBAS), AFS-MMSBAS is compared with AFS, the Multi-direction Detection Beetle Antenna Search (MDBAS) Algorithm, and the hybrid algorithm composed of the two (AFS-MDBAS). The experimental results show that, with respect to high-dimensional problems: (1) the AFS-MMSBAS algorithm is not only more stable than the MDBAS algorithm, but it is also faster in terms of convergence and operation than the AFS algorithm, and (2) it has a higher optimization capacity than the two algorithms and their hybrid algorithm. Full article
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Article
Agreement and Differences between Fat Estimation Formulas Using Kinanthropometry in a Physically Active Population
Appl. Sci. 2022, 12(24), 13043; https://doi.org/10.3390/app122413043 - 19 Dec 2022
Viewed by 491
Abstract
The importance of fat mass estimation in multiple areas related to health and sports has led to the emergence of a large number of methods and formulas for its estimation. The aim of the present study was to compare the agreement and differences [...] Read more.
The importance of fat mass estimation in multiple areas related to health and sports has led to the emergence of a large number of methods and formulas for its estimation. The aim of the present study was to compare the agreement and differences between different formulas for estimating fat mass by anthropometry. Eighty-seven subjects underwent an anthropometric assessment following the protocol from the International Society for the Advancement of Kinanthropometry (ISAK). The fat percentage was calculated with 14 different formulas for men and with 12 different formulas for women. In the case of men, they were proposed by Durnin-Womersley, Yuhasz, Faulkner, Carter, Peterson, Katch-McArdle, Sloan, Wilmore, Evans, Lean, Reilly, Civar, Hastuti, and Kerr. In the case of women, the equations used were those proposed by Durnin-Womersley, Yuhasz, Faulkner, Carter, Peterson, Katch-McArdle, Sloan, Wilmore, Evans, Lean, Thorland, and Kerr. Significant differences were found between the formulas in both men (8.90 ± 2.17% to 17.91 ± 2.84%; p < 0.001–0.016) and women (15.33 ± 2.94% to 28.79 ± 3.30%; p < 0.001–0.004). It was observed that in the case of men, the Carter and Yuhasz formulas and the Civar and Faulkner formulas showed moderate agreement with each other (CCC = 0.910–0.915). In the case of women, it was observed that the Carter and Yuhasz formulas showed moderate agreement with each other (CCC = 0.974). In conclusion, the formulas used for the estimation of lipid mass in anthropometry reported significantly different results between them and were therefore not comparable. Full article
Article
Diversity and Safety Aspects of Coagulase-Negative Staphylococci in Ventricina del Vastese Italian Dry Fermented Sausage
Appl. Sci. 2022, 12(24), 13042; https://doi.org/10.3390/app122413042 - 19 Dec 2022
Viewed by 518
Abstract
Ventricina del Vastese is a traditional dry fermented sausage from Central Italy not yet characterized for the occurrence, identity and safety of coagulase-negative staphylococci (CNS), a bacterial group technologically important for this kind of product. Therefore, in this study, 98 CNS isolates from [...] Read more.
Ventricina del Vastese is a traditional dry fermented sausage from Central Italy not yet characterized for the occurrence, identity and safety of coagulase-negative staphylococci (CNS), a bacterial group technologically important for this kind of product. Therefore, in this study, 98 CNS isolates from four manufacturers were differentiated using repetitive element palindromic PCR (Rep-PCR) and identified using 16S rRNA gene sequencing. These were examined for genes encoding biogenic amine (BA) production, resistance to aminoglycosides, β-lactams, tetracyclines and staphylococcal enterotoxins (SEs). Staphylococcus succinus (55%) predominated, followed by S. xylosus (30%), S. epidermidis (7.4%), S. equorum (3.1%), S. saprophyticus (3.1%) and S. warneri (1%). One S. succinus subsp. casei isolate was slightly β-hemolytic. SEs and the histidine decarboxylase gene hdcA were not detected, whereas the tyrosine decarboxylase gene tdcA was detected in four S. xylosus isolates. The blaZ beta-lactamase gene in an S. equorum isolate, tetracycline resistance genes tetK in six S. succinus isolates and tetA in one S. succinus isolate also bearing tetK were found. The product examined is characterized by a peculiar CNS species ratio and a low occurrence and diversity of AR transferable genes than found in other studies, as a probable consequence of production only with meat from animals raised in small farms with extensive rearing systems in which antibiotic usage is infrequent. Full article
(This article belongs to the Special Issue State-of-Art of Microbial Concerns in Food Safety)
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Article
Mobility Prediction of Mobile Wireless Nodes
Appl. Sci. 2022, 12(24), 13041; https://doi.org/10.3390/app122413041 - 19 Dec 2022
Viewed by 746
Abstract
Artificial intelligence (AI) is a fundamental part of improving information technology systems. Essential AI techniques have revolutionized communication technology, such as mobility models and machine learning classification. Mobility models use a virtual testing methodology to evaluate new or updated products at a reasonable [...] Read more.
Artificial intelligence (AI) is a fundamental part of improving information technology systems. Essential AI techniques have revolutionized communication technology, such as mobility models and machine learning classification. Mobility models use a virtual testing methodology to evaluate new or updated products at a reasonable cost. Classifiers can be used with these models to achieve acceptable predictive accuracy. In this study, we analyzed the behavior of machine learning classification algorithms—more specifically decision tree (DT), logistic regression (LR), k-nearest neighbors (K-NN), latent Dirichlet allocation (LDA), Gaussian naive Bayes (GNB), and support vector machine (SVM)—when using different mobility models, such as random walk, random direction, Gauss–Markov, and recurrent self-similar Gauss–Markov (RSSGM). Subsequently, classifiers were applied in order to detect the most efficient mobility model over wireless nodes. Random mobility models (i.e., random direction and random walk) provided fluctuating accuracy values when machine learning classifiers were applied—resulting values ranged from 39% to 81%. The Gauss–Markov and RSSGM models achieved good prediction accuracy in scenarios using a different number of access points in a defined area. Gauss–Markov reached 89% with the LDA classifier, whereas RSSGM showed the greatest accuracy with all classifiers and through various samples (i.e., 2000, 5000, and 10,000 steps during the whole experiment). Finally, the decision tree classifier obtained better overall results, achieving 98% predictive accuracy for 5000 steps. Full article
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Article
Intelligent Control of Mushroom Growing Conditions Using an Electronic System for Monitoring and Maintaining Environmental Parameters
Appl. Sci. 2022, 12(24), 13040; https://doi.org/10.3390/app122413040 - 19 Dec 2022
Viewed by 708
Abstract
In order to make plant cultivation as economical and efficient as possible, and to reduce the amount of human errors and labour costs, autonomous systems for growing plants and, in this case, also mushrooms, are increasingly being implemented. In this work, a prototype [...] Read more.
In order to make plant cultivation as economical and efficient as possible, and to reduce the amount of human errors and labour costs, autonomous systems for growing plants and, in this case, also mushrooms, are increasingly being implemented. In this work, a prototype of an electronic/automatic system was designed and manufactured for the monitoring and control of the parameters of mushroom growing conditions. Appropriate sensors were used to monitor the application parameters such as CO2 level, temperature and humidity, and the data were sent to the main logic controller using an RS 485 interface-based local data transmission network. Both the main controller and the individual parts of the system were made on the basis of PIC18F25K83 microcontrollers, using the C programming language to create the program code. In order to achieve optimal system operation, a software algorithm was created to ensure fast system operation. During the production, the PCBs of the system were optimized to achieve the smallest possible dimensions and optimal construction and the arrangement of the active electronic elements. For the convenience of the user, a system application was created so that it is possible to monitor information from the environmental sensors and the process of parameter control. This work aimed to show that such autonomous systems based on environmental sensor monitoring are universal and can be applied to a large number of plant species. In addition, the capabilities of the plant cultivation system can be expanded if needed by additionally connecting relevant environmental sensors and environmental parameter regulation units. Full article
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Article
Novel Liposomal Formulation with Azelaic Acid: Preparation, Characterization, and Evaluation of Biological Properties
Appl. Sci. 2022, 12(24), 13039; https://doi.org/10.3390/app122413039 - 19 Dec 2022
Viewed by 354
Abstract
Azelaic acid (AA), as a natural product, was proven to be effective in targeting multiple causes of acne and related dermatological conditions, as it is well tolerated using different classical formulations (gel, cream, etc.). However, its limited aqueous solubility and inadequate penetration across [...] Read more.
Azelaic acid (AA), as a natural product, was proven to be effective in targeting multiple causes of acne and related dermatological conditions, as it is well tolerated using different classical formulations (gel, cream, etc.). However, its limited aqueous solubility and inadequate penetration across the stratum corneum might be related to different possible side effects such as itching and burning. The aim of our work was to elaborate a novel liposomal formulation based on azelaic acid, with enhanced biocompatibility, bio-availability, antimicrobial, antigenotoxic, and anti-inflammatory properties. The liposomal formulations were prepared by the lipid film hydration method with different concentrations of azelaic acid (15%, 20%, 25%) and characterized in terms of morphological features, physico-chemical properties, antimicrobial, cytotoxic, and in vitro wound healing effect. Successful encapsulation with 80.42% efficiency, with a size of up to 500 nm and good stability, was achieved, as demonstrated by FTIR spectroscopy (Fourier Transform Infrared Spectroscopy), DLS (dynamic light scattering), and zeta-potential measurements. In terms of antibacterial activity, all the liposomal formulations exhibited a better effect compared to free AA solution against Staphylococcus aureus and Enterococcus faecalis. Cytotoxicity assays and an in vitro “scratch” test performed with normal human dermal fibroblasts revealed an accelerating healing effect, while a comet assay evidenced the protective effect of AA liposomal formulations against hydrogen-peroxide-induced DNA damage in fibroblasts. The optimum formulation in terms of both the antimicrobial and wound healing effect was AALipo20% (liposomes with 20% azelaic acid included). Full article
(This article belongs to the Special Issue Advances in Natural Bioactive Compounds and Biological Effects II)
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Article
Analysis of a Cardiac-Necrosis-Biomarker Release in Patients with Acute Myocardial Infarction via Nonlinear Mixed-Effects Models
Appl. Sci. 2022, 12(24), 13038; https://doi.org/10.3390/app122413038 - 19 Dec 2022
Viewed by 401
Abstract
The release of the cardiac troponin T (cTnT) in patients with acute myocardial infarction (AMI) has been analyzed through a methodology based on nonlinear mixed-effects (NME) models. The aim of this work concerns the investigation of any possible relationship between clinical covariates and [...] Read more.
The release of the cardiac troponin T (cTnT) in patients with acute myocardial infarction (AMI) has been analyzed through a methodology based on nonlinear mixed-effects (NME) models. The aim of this work concerns the investigation of any possible relationship between clinical covariates and the dynamics of the release of cTnT to derive more detailed and useful clinical information for the correct treatment of these patients. An ad-hoc mechanistic model describing the biomarker release process after AMI has been devised, assessed, and exploited to evaluate the impact of the available clinical covariates on the cTnT release dynamic. The following approach was tested on a preliminary dataset composed of a small number of potential clinical covariates: employing an unsupervised approach, and despite the limited sample size, dyslipidemia, a known risk factor for cardiovascular disease, was found to be a statistically significant covariate. By increasing the number of covariates considered in the model, and patient cohort, we envisage that this approach may provide an effective means to automatically classify AMI patients and to investigate the role of interactions between clinical covariates and cTnT release. Full article
(This article belongs to the Section Biomedical Engineering)
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Article
Anaerobic Digestion of Synthetic Municipal Wastewater (MWW) in a Periodic Anaerobic Baffled Reactor (PABR): Assessment of COD Removal and Biogas Production
Appl. Sci. 2022, 12(24), 13037; https://doi.org/10.3390/app122413037 - 19 Dec 2022
Viewed by 389
Abstract
The benchmark approach for municipal wastewater treatment is based on biological oxidation. Due to high energy consumption, alternative treatment schemes are proposed, among which anaerobic digestion is the most promising. In this work, the direct anaerobic digestion of municipal wastewater in a high-rate [...] Read more.
The benchmark approach for municipal wastewater treatment is based on biological oxidation. Due to high energy consumption, alternative treatment schemes are proposed, among which anaerobic digestion is the most promising. In this work, the direct anaerobic digestion of municipal wastewater in a high-rate system is examined. The reactor utilized for the study is the periodic anaerobic baffled reactor (PABR). Two distinct experimental cycles were conducted, during which the operational parameters of the PABR were consecutively modified: in the first cycle, six phases were conducted where the hydraulic retention time (HRT) varied from 10 to 1 days, the period T between 2.5 days and 0.25, while the OLR remained constant at values near 1.0 gsCOD/L/d. During the second cycle, four distinct phases were conducted with no switching imposed. The HRT varied from 4 to 1 d. The last experimental phase of both cycles was the most significant, due to feedstock resemblance to raw wastewater. The biogas and the biomethane production rates reached 66.8 L/d and 41.1 L/d, respectively, while the COD reduction rate reached 73.7%. Conclusively, the PABR is a high-rate AD system, capable of treating MWW under extreme operational conditions. Full article
(This article belongs to the Special Issue Anaerobic Digestion for Waste/Wastewater Treatment)
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Article
Role-Based Access Control Model for Inter-System Cross-Domain in Multi-Domain Environment
Appl. Sci. 2022, 12(24), 13036; https://doi.org/10.3390/app122413036 - 19 Dec 2022
Viewed by 381
Abstract
Information service platforms or management information systems of various institutions or sectors of enterprises are gradually interconnected to form a multi-domain environment. A multi-domain environment is convenient for managers to supervise and manage systems, and for users to access data across domains and [...] Read more.
Information service platforms or management information systems of various institutions or sectors of enterprises are gradually interconnected to form a multi-domain environment. A multi-domain environment is convenient for managers to supervise and manage systems, and for users to access data across domains and systems. However, given the complex multi-domain environment and many users, the traditional or enhanced role-based access control (RBAC) model still faces some challenges. It is necessary to address issues such as role naming conflicts, platform–domain management conflicts, inter-domain management conflicts, and cross-domain sharing difficulties. For the above problems, a role-based access control model for inter-system cross-domain in multi-domain environment (RBAC-IC) is proposed. This paper formally defines the model, divides roles into abstract roles and specific roles, and designs the operating process of the access control model. The model has four characteristics: support role name repetition, platform–domain isolation management, inter-domain isolation management, and fine-grained cross-domain sharing. By establishing security violation formulas for security analysis, it is finally shown that RBAC-IC can operate safely. Full article
(This article belongs to the Special Issue Information Security and Privacy)
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Article
Experimental Study on the Seismic Performance of New Energy Dissipation Connectors in an Autoclaved Aerated Concrete Panel with Assembled Steel Frame
Appl. Sci. 2022, 12(24), 13035; https://doi.org/10.3390/app122413035 - 19 Dec 2022
Viewed by 366
Abstract
This study proposes a new energy dissipation connector (NEDC) to connect an external autoclaved aerated concrete (AAC) wall panel with an assembled steel frame. To investigate the seismic performance and working mechanism of the NEDC under seismic action, horizontal low-cyclic loading tests were [...] Read more.
This study proposes a new energy dissipation connector (NEDC) to connect an external autoclaved aerated concrete (AAC) wall panel with an assembled steel frame. To investigate the seismic performance and working mechanism of the NEDC under seismic action, horizontal low-cyclic loading tests were conducted on two sets of steel frames with different connectors using an MTS actuator. Similarly, the seismic performance and working mechanism of the AAC wall panels were elucidated using horizontal low-cyclic loading tests. Test results revealed that the NEDC increased ductility by 10.69–21.12% and energy consumption by 101.14% when compared to those obtained using hook bolt connectors. Overall, the NEDC provides good seismic performance, large deformability, and high energy consumption capacity, thereby rendering it ideal for assembled steel buildings. Furthermore, the NEDC can reduce wall panel damage during earthquake action and enhance the seismic performance of composite frames. Full article
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Article
An Analysis of Commercial Noni Juice: LC-MS/MS Phenolic Profiles and Cytotoxic Activity
Appl. Sci. 2022, 12(24), 13034; https://doi.org/10.3390/app122413034 - 19 Dec 2022
Viewed by 722
Abstract
Fermented juice from the noni tree (Morinda citrifolia) is a traditional medicinal product used by South Pacific Islanders to treat a wide range of ailments, including cancer, inflammation and obesity, as well as improving overall wellbeing. Many of its bioactive properties [...] Read more.
Fermented juice from the noni tree (Morinda citrifolia) is a traditional medicinal product used by South Pacific Islanders to treat a wide range of ailments, including cancer, inflammation and obesity, as well as improving overall wellbeing. Many of its bioactive properties have been suggested to arise from the high antioxidant capacity and phenolic content found in the juice. However, there have been limited investigations into the phenolic profiles of noni juice produced locally in the Pacific. This study aimed to investigate the chemical composition and bioactive properties of noni juice. The first phase of this study used liquid chromatography with tandem mass spectrometry (LC-MS/MS) to characterise the phenolic composition of five brands of commercial noni juice produced in the South Pacific region. A total of 21 phenolic compounds were putatively identified, with the most abundant generally being rutin, 4-hydroxybenzoic acid and gentisic acid. Vastly differing phenolic profiles were found between the noni juice brands. Significant differences were also found in their antioxidant capacities and total phenolic contents. Of the three major phenolic compounds identified, gentisic acid showed the highest antioxidant activity (640% higher than Trolox). Additionally, the noni juice showed no significant anti-acetylcholinesterase activity and no to moderate cytotoxicity against two cancer cell lines (HeLa and HT29). These results indicate that the phytochemical profiles—and hence, the expected bioactive properties—are likely to vary significantly between different noni juice brands. Furthermore, the anti-cancer activity of non-concentrated noni juice appears to be relatively low. Full article
(This article belongs to the Special Issue New Insights into Natural Antioxidants in Foods)
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Article
Experimental Study on Cooling Performance of a Hybrid Microchannel and Jet Impingement Heat Sink
Appl. Sci. 2022, 12(24), 13033; https://doi.org/10.3390/app122413033 - 19 Dec 2022
Viewed by 416
Abstract
Thermal management at a high heat flux is crucial for high-power electronic devices, and jet impingement cooling is a promising solution. In this paper, a hybrid heat sink combining a microchannel and jet impingement was designed, fabricated and tested in a closed-loop system [...] Read more.
Thermal management at a high heat flux is crucial for high-power electronic devices, and jet impingement cooling is a promising solution. In this paper, a hybrid heat sink combining a microchannel and jet impingement was designed, fabricated and tested in a closed-loop system with R134a as the working fluid. The thermal contact resistance was measured by using the steady-state method, and the thermal resistance of the heat sink was obtained at different heat fluxes and flow rates. The maximum heat dissipation of 400 W/cm2 is achieved on a heater area of 210 mm2, and the thermal resistance of the heat sink is 0.11 K/W with a pressure drop of 13.5 kPa under a flow rate of 1.90 L/min. Low thermal resistance can be achieved for the hybrid heat sink stemming from the highly-dense micro-jet array with separate inflow and outflow microchannels. Full article
(This article belongs to the Topic Applied Heat Transfer)
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Editorial
Artificial Intelligence Trends and Applications in Service Systems
Appl. Sci. 2022, 12(24), 13032; https://doi.org/10.3390/app122413032 - 19 Dec 2022
Viewed by 530
Abstract
Artificial intelligence (AI) has been increasingly adopted in service production systems [...] Full article
(This article belongs to the Special Issue Smart Services: Artificial Intelligence in Service Systems)
Article
Wind Speed Forecasting with a Clustering-Based Deep Learning Model
Appl. Sci. 2022, 12(24), 13031; https://doi.org/10.3390/app122413031 - 19 Dec 2022
Viewed by 419
Abstract
The predictability of wind energy is crucial due to the uncertain and intermittent features of wind energy. This study proposes wind speed forecasting models, which employ time series clustering approaches and deep learning methods. The deep learning (LSTM) model utilizes the preprocessed data [...] Read more.
The predictability of wind energy is crucial due to the uncertain and intermittent features of wind energy. This study proposes wind speed forecasting models, which employ time series clustering approaches and deep learning methods. The deep learning (LSTM) model utilizes the preprocessed data as input and returns data features. The Dirichlet mixture model and dynamic time-warping method cluster the time-series data features and then deep learning in forecasting. Particularly, the Dirichlet mixture model and dynamic warping method cluster the time-series data features. Next, the deep learning models use the entire (global) and clustered (local) data to capture the long-term and short-term patterns, respectively. Furthermore, an ensemble model is obtained by integrating the global model and local model results to exploit the advantages of both models. Our models are tested on four different wind data obtained from locations in Turkey with different wind regimes and geographical aspects. The numerical results indicate that the proposed ensemble models achieve the best accuracy compared to the deep learning method (LSTM). The results imply that the feature clustering approach accommodates a promising framework in forecasting. Full article
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Article
Influence of Biosynthesized Nanoparticles Addition and Fibre Content on the Mechanical and Moisture Absorption Behaviour of Natural Fibre Composite
Appl. Sci. 2022, 12(24), 13030; https://doi.org/10.3390/app122413030 - 19 Dec 2022
Viewed by 581
Abstract
This study looks at how incorporating nanofiller into sisal/flax-fibre-reinforced epoxy-based hybrid composites affects their mechanical and water absorption properties. The green Al2O3 NPs are generated from neem leaves in a proportion of leaf extract to an acceptable aluminium nitrate combination. [...] Read more.
This study looks at how incorporating nanofiller into sisal/flax-fibre-reinforced epoxy-based hybrid composites affects their mechanical and water absorption properties. The green Al2O3 NPs are generated from neem leaves in a proportion of leaf extract to an acceptable aluminium nitrate combination. Both natural fibres were treated with different proportions of NaOH to eliminate moisture absorption. The following parameters were chosen as essential to achieving the objectives mentioned above: (i) 0, 5, 10, and 15% natural fibre concentrations; (ii) 0, 2, 4, and 6% aluminium powder concentrations; and (iii) 0, 1, 3, and 5% NaOH concentrations. Compression moulding was used to create the hybrid nanocomposites and ASTM standards were used for mechanical testing such as tension, bending, and impact. The findings reveal that combining sisal/flax fibre composites with nanofiller improved the mechanical features of the nanocomposite. The sisal and flax fibre hybridised successfully, with 10% fibres and 4% aluminium filler. The water absorption of the hybrids rose as the fibre weight % increased, and during the next 60 h, all of the specimens achieved equilibrium. The failed samples were examined using scanning electron Microscopic (SEM) images better to understand the composite’s failure in the mechanical experimentations. Al2O3 NPs were confirmed through XRD, UV spectroscope and HPLC analysis. According to the HPLC results, the leaf’s overall concentrations of flavonoids (gallocatechin, carnosic acid, and camellia) are determined to be 0.250 mg/g, 0.264 mg/g, and 0.552 mg/g, respectively. The catechin concentration is higher than the phenolic and caffeic acid levels, which could have resulted in a faster rate of reduction among many of the varying configurations, 4 wt.% nano Al2O3 particle, 10 wt.% flax and sisal fibres, as well as 4 h of NaOH with a 5 wt.% concentration, producing the maximum mechanical properties (59.94 MPa tension, 149.52 Mpa bending, and 37.9 KJ/m2 impact resistance). According to the results, it can be concluded that botanical nutrients may be used effectively in the manufacturing of nanomaterials, which might be used in various therapeutic and nanoscale applications. Full article
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Technical Note
Numerical Simulations of Sudden Oil Spills in Typical Cross-Border Rivers in the Yangtze River Delta Region
Appl. Sci. 2022, 12(24), 13029; https://doi.org/10.3390/app122413029 - 19 Dec 2022
Cited by 1 | Viewed by 407
Abstract
The Taipu River is an important cross-border river in the Yangtze River Delta region and a direct channel connecting Taihu Lake and Huangpu River. Along the main stream of the Taipu River are many sources of water, such as the Wujiang, Dingzha, and [...] Read more.
The Taipu River is an important cross-border river in the Yangtze River Delta region and a direct channel connecting Taihu Lake and Huangpu River. Along the main stream of the Taipu River are many sources of water, such as the Wujiang, Dingzha, and Liantang Rivers. Many boats traverse these rivers transporting a wide variety of goods, including large quantities of oil, chemicals, and other dangerous goods. In the event of accidents on these vessels, spilled cargo will directly threaten the drinking water safety of people in the region. Aiming at simulating and assessing the environmental risks of sudden oil spills in rivers in the Yangtze River Delta region, this paper established a two-dimensional oil spill model of the typical transboundary Taipu River based on the MIKE21 water environment numerical simulation software developed by the Danish Institute of Water Conservancy. The established model will improve emergency response and treatment plans as well as our understanding of river oil spill progressions. Full article
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Editorial
Special Issue on the Advance of the Mechanical Properties of Dental Materials
Appl. Sci. 2022, 12(24), 13028; https://doi.org/10.3390/app122413028 - 19 Dec 2022
Viewed by 407
Abstract
In the oral environment, restorative and prosthetic materials and appliances are exposed to chemical, thermal and mechanical challenges. The mechanical properties of a material define how it responds to the application of physical force. This Special Issue focuses on all the recent technology [...] Read more.
In the oral environment, restorative and prosthetic materials and appliances are exposed to chemical, thermal and mechanical challenges. The mechanical properties of a material define how it responds to the application of physical force. This Special Issue focuses on all the recent technology that can enhance the mechanical properties of materials used in all of the different branches of dentistry. This Special Issue is closed, but the topic is certainly of interest, and therefore new research will be needed to explore further evolution in dental materials. Full article
(This article belongs to the Special Issue Advance of the Mechanical Properties of Dental Materials)
Article
Research on Non-Circular Raceway of Single-Row Four-Point Contact Ball Bearing Based on Life Optimization
Appl. Sci. 2022, 12(24), 13027; https://doi.org/10.3390/app122413027 - 19 Dec 2022
Viewed by 384
Abstract
The traditional slewing bearing with circular raceway has the problem of stress concentration under the large overturning moment. In this paper, a new non-circular raceway of a slewing ball bearing was presented to conquer this problem. To obtain the new non-circular raceway, first, [...] Read more.
The traditional slewing bearing with circular raceway has the problem of stress concentration under the large overturning moment. In this paper, a new non-circular raceway of a slewing ball bearing was presented to conquer this problem. To obtain the new non-circular raceway, first, the static equilibrium equations of the slewing ball bearing was established by the vector method, which is a constraint condition for life optimization; secondly, the life optimization function was established to calculate the contact load distribution in the bearing when the bearing life is at its maximum; finally, through the contact deformation with the contact load, the non-circular inner raceway corresponding to the maximum bearing life was obtained, and the non-circular shape corresponding to the raceway under axial load and overturning moment was studied. The results show that the non-circular raceway devised by this method can evenly reduce the contact force of the raceway and effectively improve the bearing capacity. Moreover, the position where the non-circular raceway deformation occurs is the position where the contact force is different before and after optimization. Therefore, the overturning moment has an effect on the shape of the raceway, whereas the axial load only affects the amplitude of the deformation, and has no obvious effect on the shape of the raceway. Full article
(This article belongs to the Special Issue Structural Optimization Methods and Applications)
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Article
Ultrasonic Attenuation of Ceramic and Inorganic Materials Using the Through-Transmission Method
Appl. Sci. 2022, 12(24), 13026; https://doi.org/10.3390/app122413026 - 19 Dec 2022
Viewed by 453
Abstract
Ultrasonic attenuation coefficients of ceramic and inorganic materials were determined for the longitudinal and transverse wave modes. Sample materials included hard and soft ceramics, common ceramics, ceramic-matrix composites, mortars, silicate glasses, rocks, minerals and crystals. For ceramic attenuation measurements, a standardized method has [...] Read more.
Ultrasonic attenuation coefficients of ceramic and inorganic materials were determined for the longitudinal and transverse wave modes. Sample materials included hard and soft ceramics, common ceramics, ceramic-matrix composites, mortars, silicate glasses, rocks, minerals and crystals. For ceramic attenuation measurements, a standardized method has existed, but this method based on a buffer-rod arrangement was found to be inconsistent, producing vastly different results. Resonant ultrasound spectroscopy was also found to be unworkable from its sample preparation requirements. Experimental reevaluation of the buffer-rod method showed its impracticality due to unpredictable reflectivity parameters, yielding mostly negative attenuation coefficients. In this work, attenuation tests relied on a through-transmission method, which incorporated a correction procedure for diffraction losses. Attenuation exhibited four types of frequency (f) dependence, i.e., linear, linear plus f4 (called Mason-McSkimin relation), f2 and f3. The first two types were the most often observed. Elastic constants of tested materials were also tabulated, including additional samples too small for attenuation tests. Observed levels of attenuation coefficients will be useful for designing test methods for ultrasonic nondestructive evaluation and trends on ultrasonic attenuation are discussed in terms of available theories. However, many aspects of experimental findings remain unexplained and require future theoretical developments and detailed microstructural characterization. This study discovered a wide range of attenuation behaviors, indicating that the attenuation parameter can aid in characterizing the condition of intergranular boundaries in combination with imaging studies. Full article
(This article belongs to the Topic Recent Advances in Structural Health Monitoring)
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Article
Analysis of Leg Muscle Activities and Foot Angles while Pressing the Accelerator Pedal by Different Foot Postures
Appl. Sci. 2022, 12(24), 13025; https://doi.org/10.3390/app122413025 - 19 Dec 2022
Viewed by 472
Abstract
The accelerator pedal in a vehicle can be pressed by either of two (natural and rotated) foot postures, according to driver preference. Since the rotated foot posture requires only foot motion to switch between the brake and accelerator pedals, most drivers prefer it [...] Read more.
The accelerator pedal in a vehicle can be pressed by either of two (natural and rotated) foot postures, according to driver preference. Since the rotated foot posture requires only foot motion to switch between the brake and accelerator pedals, most drivers prefer it over the natural foot posture, which requires both leg and foot motions to switch between the pedals. However, the rotated foot posture may require more leg-muscle efforts and an awkward foot posture while operating the accelerator pedal, due to an inappropriate contact between the sole of the foot and the top surface of the accelerator pedal. This study examined the effects of foot postures on leg-muscle activities and foot angles while pressing the accelerator pedal for 10 male drivers. The experimental data revealed that %MVC (maximum voluntary contraction) of leg muscles for the rotated posture (6.39%) was significantly higher than that of the natural posture (3.86%). Both foot postures showed shared patterns in foot angles while pressing the accelerator pedal; however, a slight awkward foot inversion was observed in the rotated posture while pressing the accelerator pedal. The findings of this study suggest that a new design of accelerator pedal is needed for a better user experience while pressing the accelerator pedal with the rotated foot posture. Full article
(This article belongs to the Special Issue Novel Approaches and Applications in Ergonomic Design II)
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Article
Effect of Local Cyclic Loading on Direct Shear Strength Characteristics of Shear-Zone Soil
Appl. Sci. 2022, 12(24), 13024; https://doi.org/10.3390/app122413024 - 19 Dec 2022
Viewed by 488
Abstract
The reservoir landslide in the Three Gorges Reservoir Area (TGRA) often suffers from local cyclic loading scenarios produced by surge waves, groundwater level fluctuation, traffic loading, and seismic activity. However, the effects of local cyclic loading on the shear resistance of the shear-zone [...] Read more.
The reservoir landslide in the Three Gorges Reservoir Area (TGRA) often suffers from local cyclic loading scenarios produced by surge waves, groundwater level fluctuation, traffic loading, and seismic activity. However, the effects of local cyclic loading on the shear resistance of the shear-zone of the reservoir landslide are poorly understood. This study experimentally investigates the effects of local cyclic loading on the shear strength and the deformation of shear-zone material using cyclic direct shear tests. A series of cyclic direct shear tests are performed with different normal stresses, cyclic periods, and numbers of cycles. The experimental results indicate that: (1) Compared with monotonic loading, local cyclic loading can significantly decrease the shear stress of shear-zone soil. (2) Shear-zone soil exhibits greater volumetric contraction under local cyclic loading conditions than that under monotonic loading. (3) Under different vertical stresses, the differentiation of shear deformation after 40 cycles of loading was slight and virtually insignificant. The research results reveal the weakening law of the mechanical strength of shear-zone soil under local cyclic loading, which provides a foundation for investigating the mechanism of the reservoir landslide under the fluctuation of water levels. Full article
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Article
Effect of High-Mass Fraction of Aluminum on Catalytic Hybrid Rocket Motor
Appl. Sci. 2022, 12(24), 13023; https://doi.org/10.3390/app122413023 - 19 Dec 2022
Viewed by 510
Abstract
Catalytic hybrid rocket motors using hydrogen peroxide (HP) are easy and efficient to achieve multiple starts and stops, and hydroxyl-terminated polybutadiene (HTPB) grains are commonly used due to their excellent mechanical properties. The low regression rate of HTPB grains limits the application of [...] Read more.
Catalytic hybrid rocket motors using hydrogen peroxide (HP) are easy and efficient to achieve multiple starts and stops, and hydroxyl-terminated polybutadiene (HTPB) grains are commonly used due to their excellent mechanical properties. The low regression rate of HTPB grains limits the application of hybrid rocket motors. Furthermore, the addition of solid aluminum particles can effectively improve the regression rate and performance of hybrid rocket motors. However, the experimental results of a high mass fraction of aluminum and hydrogen peroxide available at present are not sufficient. In this research, the impact of a high mass fraction of aluminum on the motor performance and ablation rate of nozzles is studied experimentally. A solution of 95% hydrogen peroxide and HTPB with an aluminum additive are adopted as propellants. The variation in the axial regression rate of the grains is obtained by computed tomography (CT) scans and pre-test parameter measurements. The instantaneous regression rate method is adopted to obtain the real-time regression rate of the motor. The surface appearance and composition of the front and the end of the grains after the tests are analyzed by electron microscopy. Carbon ceramic and tungsten-bronze nozzles are used to explore the effect of a high mass fraction of aluminum on nozzle ablation. The experimental results show that the addition of aluminum raises the specific impulse and decreases the optimal oxygen-to-fuel ratio of the propellant combination. The high mass fraction of the aluminum particles has a severe ablative effect on carbon ceramic nozzles, while the effect on tungsten-bronze nozzles is minimal for a hot test lasting four to five seconds. Our results can provide experimental guidance for the application of a high mass fraction of aluminum and hydrogen peroxide hybrid rocket motor. Full article
(This article belongs to the Section Aerospace Science and Engineering)
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Article
Additive Manufacturing of Glass-Ceramic Parts from Recycled Glass Using a Novel Selective Powder Deposition Process
Appl. Sci. 2022, 12(24), 13022; https://doi.org/10.3390/app122413022 - 19 Dec 2022
Viewed by 698
Abstract
Additive manufacturing technologies have been in continuous growth due to their advantages over traditional manufacturing. The iro3d is a powder deposition machine designed to build metal parts. This research work proposed the adaptation of the iro3d selective powder deposition process to allow the [...] Read more.
Additive manufacturing technologies have been in continuous growth due to their advantages over traditional manufacturing. The iro3d is a powder deposition machine designed to build metal parts. This research work proposed the adaptation of the iro3d selective powder deposition process to allow the production of glass-ceramic parts using recycled glass powders. Various specimens were produced using different deposition strategies such as build orientation and sintering holding times. Specimens were evaluated in terms of geometric distortions (shrinking and warping) and in terms of mechanical performance (flexural behavior and hardness). Two geometrically complex test parts were also produced to infer the minimum feature size capabilities of the process. The results denoted parts that displayed significant geometrical deviations, which could be correlated with some of the tested parameters. Through the addition of sand to the tested specimens, we demonstrated that distortions could be mitigated with proper control of the powder’s coalescence. In the end, the specimens’ fracture surfaces were examined, and the presence of porosities was correlated with their mechanical properties. The results demonstrated that the iro3d SPD process could be used to produce additively manufactured glass parts. Full article
(This article belongs to the Special Issue Advanced Materials in 3D Printing)
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Article
TOF Analysis of Ions Accelerated at High Repetition Rate from Laser-Induced Plasma
Appl. Sci. 2022, 12(24), 13021; https://doi.org/10.3390/app122413021 - 19 Dec 2022
Viewed by 554
Abstract
The generation, detection, and quantification of high-energy proton spectra that are produced from laser-target interaction methodologies is a field of increasingly growing popularity over the last 20 years. Generation methods such as target normal sheath acceleration or similar allow for collimated laminar ion [...] Read more.
The generation, detection, and quantification of high-energy proton spectra that are produced from laser-target interaction methodologies is a field of increasingly growing popularity over the last 20 years. Generation methods such as target normal sheath acceleration or similar allow for collimated laminar ion beams to be produced in a compact environment through the use of short-burst terawatt lasers and are a growing field of investment. This project details the development and refinement of a python-based code to analyze time-of-flight ion spectroscopy data, with the intent to pinpoint the maximum proton energy within the incident beam to as reliable and accurate a value as possible within a feasible processing time. TOF data for 2.2 × 1016 W/cm2 intensity laser shots incident on a 2 mm Cu target that were gathered from the PERLA 1 kHz laser at the HiLASE center were used as training and testing data with the implementation of basic machine learning techniques to train these methods to the data being used. These datasets were used to ensure more widely applicable functionality, and accurate calculation to within 1% accuracy of an assumed correct value was seen to be consistently achievable for these datasets. This wider functionality indicates a high level of accuracy for previously unseen TOF datasets, regardless of signal/noise levels or dataset size, allowing for free use of the code in the wider field. Full article
(This article belongs to the Special Issue Plasma Technology and Its Application)
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Article
An Effective Blockchain-Based Defense Model for Organizations against Vishing Attacks
Appl. Sci. 2022, 12(24), 13020; https://doi.org/10.3390/app122413020 - 19 Dec 2022
Viewed by 700
Abstract
Social engineering (SE) attacks (also called social hacking) refer to various methods used by cybercriminals to exploit the weak nature of human beings rather than the logical and physical security measures used by organizations. This research paper studies the various methods of SE [...] Read more.
Social engineering (SE) attacks (also called social hacking) refer to various methods used by cybercriminals to exploit the weak nature of human beings rather than the logical and physical security measures used by organizations. This research paper studies the various methods of SE used by criminals to exploit the psychological vulnerabilities of human beings. On this basis, the paper proposes a new defense categorization of SE attacks based on two security principles: dual control (i.e., more than one entity to complete the task) and split knowledge (i.e., dual controlling of the knowledge to complete the task). We describe how those measures could stop SE attacks and avoid human weaknesses. Then, we propose an original new SE defense model that implements the security principles using blockchain technology to both dual control the transactions and record them safely for organizations. The proposed model’s first aim is to avoid the dependence on the cognitive or psychological status of the victim and enable more verification steps to be taken in a fast and flexible manner. The paper demonstrates the quick and easy adoption of the existing private blockchain platform to implement the proposed SE defense model. Full article
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Article
Improved SOSK-Means Automatic Clustering Algorithm with a Three-Part Mutualism Phase and Random Weighted Reflection Coefficient for High-Dimensional Datasets
Appl. Sci. 2022, 12(24), 13019; https://doi.org/10.3390/app122413019 - 19 Dec 2022
Viewed by 554
Abstract
Automatic clustering problems require clustering algorithms to automatically estimate the number of clusters in a dataset. However, the classical K-means requires the specification of the required number of clusters a priori. To address this problem, metaheuristic algorithms are hybridized with K-means to extend [...] Read more.
Automatic clustering problems require clustering algorithms to automatically estimate the number of clusters in a dataset. However, the classical K-means requires the specification of the required number of clusters a priori. To address this problem, metaheuristic algorithms are hybridized with K-means to extend the capacity of K-means in handling automatic clustering problems. In this study, we proposed an improved version of an existing hybridization of the classical symbiotic organisms search algorithm with the classical K-means algorithm to provide robust and optimum data clustering performance in automatic clustering problems. Moreover, the classical K-means algorithm is sensitive to noisy data and outliers; therefore, we proposed the exclusion of outliers from the centroid update’s procedure, using a global threshold of point-to-centroid distance distribution for automatic outlier detection, and subsequent exclusion, in the calculation of new centroids in the K-means phase. Furthermore, a self-adaptive benefit factor with a three-part mutualism phase is incorporated into the symbiotic organism search phase to enhance the performance of the hybrid algorithm. A population size of 40+2g was used for the symbiotic organism search (SOS) algorithm for a well distributed initial solution sample, based on the central limit theorem that the selection of the right sample size produces a sample mean that approximates the true centroid on Gaussian distribution. The effectiveness and robustness of the improved hybrid algorithm were evaluated on 42 datasets. The results were compared with the existing hybrid algorithm, the standard SOS and K-means algorithms, and other hybrid and non-hybrid metaheuristic algorithms. Finally, statistical and convergence analysis tests were conducted to measure the effectiveness of the improved algorithm. The results of the extensive computational experiments showed that the proposed improved hybrid algorithm outperformed the existing SOSK-means algorithm and demonstrated superior performance compared to some of the competing hybrid and non-hybrid metaheuristic algorithms. Full article
(This article belongs to the Special Issue Evolutionary Algorithms and Large-Scale Real-World Applications)
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Article
An Integrated Approach for Structural Health Monitoring and Damage Detection of Bridges: An Experimental Assessment
Appl. Sci. 2022, 12(24), 13018; https://doi.org/10.3390/app122413018 - 19 Dec 2022
Viewed by 647
Abstract
The issue of monitoring the structural condition of bridges is becoming a top priority worldwide. As is well known, any infrastructure undergoes a progressive deterioration of its structural conditions due to aging by normal service loads and environmental conditions. At the same time, [...] Read more.
The issue of monitoring the structural condition of bridges is becoming a top priority worldwide. As is well known, any infrastructure undergoes a progressive deterioration of its structural conditions due to aging by normal service loads and environmental conditions. At the same time, it may suffer serious damages or collapse due to natural phenomena such as earthquakes or strong winds. For this reason, it is essential to rely on efficient and widespread monitoring techniques applied throughout the entire road network. This paper aims to introduce an integrated procedure for structural and material monitoring. With regard to structural monitoring, an innovative approach for monitoring based on Vehicle by Bridge Interaction (VBI) will be proposed. Furthermore, with regard to material monitoring, to evaluate concrete degradation, a non-invasive method based on the continuous monitoring of the pH, as well as chloride and sulfate ions concentration in the concrete, is presented. Full article
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Article
Model Test Analysis of Subsurface Cavity and Ground Collapse Due to Broken Pipe Leakage
Appl. Sci. 2022, 12(24), 13017; https://doi.org/10.3390/app122413017 - 19 Dec 2022
Viewed by 483
Abstract
Urban ground collapse is a common geological disaster characterized by its invisible nature, particularly in China, and results in significant socioeconomic losses and even loss of life. Underground pipeline breakage is the most common factor leading to urban ground collapses. Hence, it is [...] Read more.
Urban ground collapse is a common geological disaster characterized by its invisible nature, particularly in China, and results in significant socioeconomic losses and even loss of life. Underground pipeline breakage is the most common factor leading to urban ground collapses. Hence, it is essential to study how different types of pipeline breakages initiate the collapse mechanism. In this study, an indoor model test was conducted to directly observe the process of collapse due to broken pipe leakage. A broken pipe was put into a model box and tested by an experimental device. The results showed that among the different pipeline breakage types, vertical damage had the greatest influence on the degree of cavity development and ground collapse. Similarities were observed in the patterns of cavity evolution development and the extent of ground collapse as well, further revealing the significance of the cavity evolution process in predicting ground collapses. Full article
(This article belongs to the Special Issue Advances in Underground Pipeline Technology)
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