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Volume 14
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Appl. Sci., Volume 14, Issue 9 (May-1 2024) – 416 articles

Cover Story (view full-size image): Forestry remains one of the most demanding and dangerous professions worldwide, with an increasing number of fatalities highlighting the pressing need for enhanced workplace safety measures. By analyzing large datasets with techniques like decision trees, random forests, and neural networks, Artificial Intelligence research uncovers intricate decision-making processes from basic associations to complex causal inferences. It emphasizes the importance of causal analysis in deriving actionable insights for accident prevention. Advances in the field of explainable AI, specifically in its application to occupational safety, by introducing novel perspectives to decision support systems in the forestry sector, ultimately aim to safeguard worker health and well-being in line with global sustainability goals. View this paper
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17 pages, 3227 KiB  
Article
Combined Cubature Kalman and Smooth Variable Structure Filtering Based on Multi-Kernel Maximum Correntropy Criterion for the Fully Submerged Hydrofoil Craft
by Hongmin Niu and Sheng Liu
Appl. Sci. 2024, 14(9), 3952; https://doi.org/10.3390/app14093952 - 6 May 2024
Cited by 1 | Viewed by 1261
Abstract
This paper introduces a novel filter algorithm termed as an MKMC-CSVSF which combined square-root cubature Kalman (SR-CKF) and smooth variable structure filtering (SVSF) under multi-kernel maximum correntropy criterion (MKMC) for accurately estimating the state of the fully submerged hydrofoil craft (FSHC) under the [...] Read more.
This paper introduces a novel filter algorithm termed as an MKMC-CSVSF which combined square-root cubature Kalman (SR-CKF) and smooth variable structure filtering (SVSF) under multi-kernel maximum correntropy criterion (MKMC) for accurately estimating the state of the fully submerged hydrofoil craft (FSHC) under the influence of uncertainties and multivariate heavy-tailed non-Gaussian noises. By leveraging the precision of the SR-CKF and the robustness of the SVSF against system uncertainties, the MKMC-CSVSF integrates these two methods by introducing a time-varying smooth boundary layer along with multiple fading factors. Furthermore, the MKMC is introduced for the adjustment of kernel bandwidths across different channels to align with the specific noise characteristics of each channel. A fuzzy rule is devised to identify the appropriate kernel bandwidths to ensure filter accuracy without undue complexity. The precision and robustness of state estimation in the face of heavy-tailed non-Gaussian noises are improved by modifying the SR-CKF and the SVSF using a fixed-point approach based on the MKMC. The experimental results validate the efficacy of this algorithm. Full article
(This article belongs to the Section Marine Science and Engineering)
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Figure 1
<p>The state trajectory of the CSVSF.</p> Full article ">Figure 2
<p>The estimation of heave motion of the FSHC.</p> Full article ">Figure 3
<p>The estimation error of heave motion of the FSHC.</p> Full article ">Figure 4
<p>The estimation of heave velocity of the FSHC.</p> Full article ">Figure 5
<p>The estimation error of heave velocity of the FSHC.</p> Full article ">Figure 6
<p>The estimation of pitch angle of the FSHC.</p> Full article ">Figure 7
<p>The estimation error of pitch angle of the FSHC.</p> Full article ">Figure 8
<p>The estimation of pitch angle velocity of the FSHC.</p> Full article ">Figure 9
<p>The estimation error of pitch angle velocity of the FSHC.</p> Full article ">Figure 10
<p>The RMSE of heave motion of the FSHC.</p> Full article ">Figure 11
<p>The RMSE of heave velocity of the FSHC.</p> Full article ">Figure 12
<p>The RMSE of pitch angle of the FSHC.</p> Full article ">Figure 13
<p>The RMSE of pitch angle velocity of the FSHC.</p> Full article ">
18 pages, 5254 KiB  
Article
Methodology for Evaluating the Generalization of ResNet
by Anan Du, Qing Zhou and Yuqi Dai
Appl. Sci. 2024, 14(9), 3951; https://doi.org/10.3390/app14093951 - 6 May 2024
Cited by 3 | Viewed by 1802
Abstract
Convolutional neural networks (CNNs) have achieved promising results in many tasks, and evaluating the model’s generalization ability based on the trained model and training data is paramount for practical applications. Although many measures for evaluating the generalization of CNN models have been proposed, [...] Read more.
Convolutional neural networks (CNNs) have achieved promising results in many tasks, and evaluating the model’s generalization ability based on the trained model and training data is paramount for practical applications. Although many measures for evaluating the generalization of CNN models have been proposed, the existing works are limited to small-scale or simplified model sets, which would result in poor accuracy and applicability of the derived methods. This study addresses these limitations by leveraging ResNet models as a case study to evaluate the model’s generalization ability. We utilized Intersection over Union (IoU) as a method to quantify the ratio of task-relevant features to assess model generalization. Class activation maps (CAMs) were used as a representation of the distribution of features learned by the model. To systematically investigate the generalization ability, we constructed a diverse model set based on the ResNet architecture. A total of 2000 CNN models were trained on the ImageNet subset by systematically changing commonly used hyperparameters. The results of our experiments revealed a strong correlation between the IoU-based evaluation method and the model’s generalization performance (Pearson correlation coefficient more than 0.8). We also performed extensive experiments to demonstrate the feasibility and robustness of the evaluation methods. Full article
(This article belongs to the Special Issue Application of Artificial Intelligence in Visual Processing)
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Figure 1
<p>Examples of class activation maps.</p> Full article ">Figure 2
<p>Examples of distribution of features learned by models and category object locations (i.e., the green bounding box) with different generalization abilities.</p> Full article ">Figure 3
<p>Detailed flowchart for calculating the ratio of task-relevant features.</p> Full article ">Figure 4
<p>Generalization gap distribution in the model set.</p> Full article ">Figure 5
<p>Quantity distribution of models in different generalization gap ranges.</p> Full article ">Figure 6
<p>Examples of generated saliency maps and original manually labeled bounding boxes (i.e., the green box), where the first row is the original image and the second row is the corresponding saliency map and bounding box. Columns (<b>a</b>–<b>e</b>) are five examples, in descending order of quality from the saliency map.</p> Full article ">Figure A1
<p>The curves illustrate the variation in loss and accuracy during the training of a model trained for 150 epochs. (<b>a</b>–<b>d</b>) Training process of four models under different hyperparameters.</p> Full article ">
21 pages, 7251 KiB  
Article
Exploiting Image Processing and Artificial Intelligence Techniques for the Determination of Antimicrobial Susceptibility
by Emrah Gullu, Sebnem Bora and Burak Beynek
Appl. Sci. 2024, 14(9), 3950; https://doi.org/10.3390/app14093950 - 6 May 2024
Cited by 1 | Viewed by 2846
Abstract
Antimicrobial susceptibility tests, achieved through the use of antibiotic-impregnated disks in a suitable laboratory environment, are conducted to determine which antibiotics are effective against the bacteria present in the body of an infected patient. The Kirby–Bauer method, a type of disk diffusion antimicrobial [...] Read more.
Antimicrobial susceptibility tests, achieved through the use of antibiotic-impregnated disks in a suitable laboratory environment, are conducted to determine which antibiotics are effective against the bacteria present in the body of an infected patient. The Kirby–Bauer method, a type of disk diffusion antimicrobial susceptibility test, is currently widely applied in microbiology laboratories due to its proven effectiveness. In our study, we developed an algorithm that utilizes image processing techniques to detect the inhibition zones of bacteria. A certain color depth acts as the threshold for the inhibition zone, with its radius determined according to the size of the reference object. This approach facilitates the measurement of inhibition zones and employs machine learning and deep learning to categorize antibiograms, followed by determination of whether a bacterium on the disk is sensitive or resistant to the antibiotics applied. The focus of this research is creating an automated interpretation system for antimicrobial susceptibility testing using the disk diffusion technique, thus simplifying the measurement and interpretation of inhibition zone sizes. Full article
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Figure 1
<p>Original image in RGB format.</p> Full article ">Figure 2
<p>Circles in the image of the antibiotic disk.</p> Full article ">Figure 3
<p>Images of the cropped antibiotic disks.</p> Full article ">Figure 4
<p>(<b>a</b>) Gray image, (<b>b</b>) image with median blur (17) applied.</p> Full article ">Figure 5
<p>The circled zone inhibition measurements: (<b>a</b>) test_1.jpg; (<b>b</b>) test_2.jpg; (<b>c</b>) test_3.jpg; (<b>d</b>) test_4.jpg; (<b>e</b>) test_5.jpg; (<b>f</b>) test_6.jpg.</p> Full article ">Figure 5 Cont.
<p>The circled zone inhibition measurements: (<b>a</b>) test_1.jpg; (<b>b</b>) test_2.jpg; (<b>c</b>) test_3.jpg; (<b>d</b>) test_4.jpg; (<b>e</b>) test_5.jpg; (<b>f</b>) test_6.jpg.</p> Full article ">Figure 6
<p>For the test_6.jpg image: (<b>a</b>) 1st zone pixel value distribution, (<b>b</b>) 2nd zone pixel value distribution, (<b>c</b>) 3rd zone pixel value distribution, (<b>d</b>) 4th zone pixel value distribution, (<b>e</b>) 5th zone pixel value distribution.</p> Full article ">Figure 6 Cont.
<p>For the test_6.jpg image: (<b>a</b>) 1st zone pixel value distribution, (<b>b</b>) 2nd zone pixel value distribution, (<b>c</b>) 3rd zone pixel value distribution, (<b>d</b>) 4th zone pixel value distribution, (<b>e</b>) 5th zone pixel value distribution.</p> Full article ">Figure 7
<p>Example of measuring the diameter of a zone of inhibition in mm. Source: <a href="https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_Laboratory_Manual_%28Hartline%29/01%3A_Labs/1.40%3A_Bacterial_Susceptibility_to_Antibiotics_%28Kirby-Bauer_Test%29" target="_blank">https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_Laboratory_Manual_%28Hartline%29/01%3A_Labs/1.40%3A_Bacterial_Susceptibility_to_Antibiotics_%28Kirby-Bauer_Test%29</a><span class="html-italic">,</span> accessed on 15 April 2023.</p> Full article ">Figure 8
<p>Pixel changes in the inhibition zone.</p> Full article ">Figure 9
<p>Part of the sample image dataset.</p> Full article ">Figure 10
<p>CNN architecture.</p> Full article ">Figure 11
<p>Visualization of the sequential model.</p> Full article ">Figure 12
<p>Summary of the sequential model.</p> Full article ">Figure 13
<p>(<b>a</b>) Training score: Epochs, (<b>b</b>) Training/Validation Loss: Epochs, (<b>c</b>) Learning Rate: Epochs.</p> Full article ">Figure 14
<p>Error matrix of the best fold.</p> Full article ">
29 pages, 8036 KiB  
Article
Random Responses of Shield Tunnel to New Tunnel Undercrossing Considering Spatial Variability of Soil Elastic Modulus
by Xiaolu Gan, Nianwu Liu, Adam Bezuijen and Xiaonan Gong
Appl. Sci. 2024, 14(9), 3949; https://doi.org/10.3390/app14093949 - 6 May 2024
Cited by 1 | Viewed by 1258
Abstract
This paper investigates the effect of spatial variability of soil elastic modulus on the longitudinal responses of the existing shield tunnel to the new tunnel undercrossing using a random two-stage analysis method (RTSAM). The Timoshenko–Winkler-based deterministic method considering longitudinal variation in the subgrade [...] Read more.
This paper investigates the effect of spatial variability of soil elastic modulus on the longitudinal responses of the existing shield tunnel to the new tunnel undercrossing using a random two-stage analysis method (RTSAM). The Timoshenko–Winkler-based deterministic method considering longitudinal variation in the subgrade reaction coefficient and the random field of the soil elastic modulus discretized by the Karhunen–Loeve expansion method are combined to establish the RTSAM. Then, the proposed RTSAM is applied to carry out a random analysis based on an actual engineering case. Results show that the increases in the scale of fluctuation and the coefficient of variation of the soil elastic modulus lead to higher variabilities of tunnel responses. A decreasing pillar depth and mean value of the soil elastic modulus and an increasing skew angle strengthen the effect of the spatial variability of the soil elastic modulus on tunnel responses. The variabilities of tunnel responses under the random field of the soil elastic modulus are overestimated by the Euler–Bernoulli beam model. The results of this study provide references for the uncertainty analysis of the new tunneling-induced responses of the existing tunnel under the random field of soil properties. Full article
(This article belongs to the Section Civil Engineering)
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Figure 1
<p>Deterministic two-stage analysis method considering longitudinal variation in subgrade reaction coefficient: (<b>a</b>) cross-section view; (<b>b</b>) plan view.</p> Full article ">Figure 2
<p>Force analysis for an element of the existing tunnel.</p> Full article ">Figure 3
<p>Hypothetical scenario of an existing tunnel under-crossed by a new tunnel.</p> Full article ">Figure 4
<p>Comparison between tunnel responses obtained from proposed method and analytical solution: (<b>a</b>) Settlement, (<b>b</b>) Bending moment; (<b>c</b>) Shear force.</p> Full article ">Figure 5
<p>Calculation procedure of proposed RTSAM.</p> Full article ">Figure 6
<p>Relative position for the existing tunnel and the new tunnel in random analysis.</p> Full article ">Figure 7
<p>Longitudinal tunnel responses obtained from 500 realizations of the random field: (<b>a</b>) Settlement, (<b>b</b>) Bending moment; (<b>c</b>) Shear force.</p> Full article ">Figure 8
<p>The convergence of statistical results of normalized maximum tunnel responses: (<b>a</b>) Mean value, (<b>b</b>) Coefficient of variation.</p> Full article ">Figure 9
<p>Mean values of normalized maximum tunnel responses under different <span class="html-italic">θ<sub>E</sub></span> values: (<b>a</b>) Normalized maximum tunnel settlement, (<b>b</b>) Normalized maximum bending moment; (<b>c</b>) Normalized maximum shear force.</p> Full article ">Figure 10
<p>COVs of normalized maximum tunnel responses under different <span class="html-italic">θ<sub>E</sub></span> values.</p> Full article ">Figure 11
<p>CDFs of normalized maximum tunnel responses under different <span class="html-italic">θ<sub>E</sub></span> values: (<b>a</b>) Normalized maximum tunnel settlement, (<b>b</b>) Normalized maximum bending moment; (<b>c</b>) Normalized maximum shear force.</p> Full article ">Figure 12
<p>Effect of COV<span class="html-italic"><sub>E</sub></span> on mean values of normalized maximum tunnel responses under different <span class="html-italic">θ<sub>E</sub></span> values: (<b>a</b>) Normalized maximum tunnel settlement, (<b>b</b>) Normalized maximum bending moment; (<b>c</b>) Normalized maximum shear force.</p> Full article ">Figure 13
<p>Effect of COV<span class="html-italic"><sub>E</sub></span> on COVs of normalized maximum tunnel responses under different <span class="html-italic">θ<sub>E</sub></span> values: (<b>a</b>) Normalized maximum tunnel settlement, (<b>b</b>) Normalized maximum bending moment; (<b>c</b>) Normalized maximum shear force.</p> Full article ">Figure 14
<p>Effect of <span class="html-italic">μ<sub>E</sub></span> on mean values of normalized maximum tunnel responses under different <span class="html-italic">θ<sub>E</sub></span>: (<b>a</b>) Normalized maximum tunnel settlement, (<b>b</b>) Normalized maximum bending moment; (<b>c</b>) Normalized maximum shear force.</p> Full article ">Figure 15
<p>Effect of <span class="html-italic">μ<sub>E</sub></span> on COVs of normalized maximum tunnel responses under different <span class="html-italic">θ<sub>E</sub></span> values: (<b>a</b>) Normalized maximum tunnel settlement, (<b>b</b>) Normalized maximum bending moment; (<b>c</b>) Normalized maximum shear force.</p> Full article ">Figure 16
<p>Effect of <span class="html-italic">P</span> on mean values of normalized maximum tunnel responses under different <span class="html-italic">θ<sub>E</sub></span> values: (<b>a</b>) Normalized maximum tunnel settlement, (<b>b</b>) Normalized maximum bending moment; (<b>c</b>) Normalized maximum shear force.</p> Full article ">Figure 17
<p>Effect of <span class="html-italic">P</span> on COVs of normalized maximum tunnel responses under different <span class="html-italic">θ<sub>E</sub></span> values: (<b>a</b>) Normalized maximum tunnel settlement, (<b>b</b>) Normalized maximum bending moment; (<b>c</b>) Normalized maximum shear force.</p> Full article ">Figure 18
<p>Effect of <span class="html-italic">a</span> on mean values of normalized maximum tunnel responses under different <span class="html-italic">θ<sub>E</sub></span> values: (<b>a</b>) Normalized maximum tunnel settlement, (<b>b</b>) Normalized maximum bending moment; (<b>c</b>) Normalized maximum shear force.</p> Full article ">Figure 19
<p>Effect of <span class="html-italic">a</span> on COVs of normalized maximum tunnel responses under different <span class="html-italic">θ<sub>E</sub></span> values: (<b>a</b>) Normalized maximum tunnel settlement, (<b>b</b>) Normalized maximum bending moment; (<b>c</b>) Normalized maximum shear force.</p> Full article ">Figure 20
<p>Effect of <span class="html-italic">ξ</span> on mean values of normalized maximum tunnel responses: (<b>a</b>) Normalized maximum tunnel settlement, (<b>b</b>) Normalized maximum bending moment; (<b>c</b>) Normalized maximum shear force.</p> Full article ">Figure 21
<p>Effect of <span class="html-italic">ξ</span> on COVs of normalized maximum tunnel responses: (<b>a</b>) Normalized maximum tunnel settlement, (<b>b</b>) Normalized maximum bending moment; (<b>c</b>) Normalized maximum shear force.</p> Full article ">
15 pages, 7952 KiB  
Article
A Model of an Extending Front Loader
by Marek Gralak and Konrad Jan Waluś
Appl. Sci. 2024, 14(9), 3948; https://doi.org/10.3390/app14093948 - 6 May 2024
Viewed by 2112
Abstract
Front loaders used in agriculture are characterized by a compact structure, which limits the scope of their application. The loading possibilities are expanded by designing front loaders equipped with telescopic arms. This design increases the loader’s working area, making it easier to load [...] Read more.
Front loaders used in agriculture are characterized by a compact structure, which limits the scope of their application. The loading possibilities are expanded by designing front loaders equipped with telescopic arms. This design increases the loader’s working area, making it easier to load trucks. It is necessary to work on the arm extension drive and perform strength analyses on the new structures. This article presents a FEM numerical analysis of the structure of an extending front loader and an assessment of the state of stress and the value of displacements under the influence of load. This study discusses the advantages and disadvantages of front loaders compared to telehandlers and the legal requirements and standards for the design of front loaders in Europe. This work presents the concept of loader arm movement and assesses the effectiveness of using hydraulic motors coupled with a screw gear. The obtained results prove that the newly designed extending front loader system is safe and stable. Full article
(This article belongs to the Section Mechanical Engineering)
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Figure 1
<p>Construction of the front loader [own work]: 1—attachment bracket to the tractor; 2—parallel guide long; 3—frame; 4—actuator responsible for lifting the whole structure; 5—actuator responsible for moving the frame; 6—triangle connecting the frame, actuator, and parallel guide long; 7—parallel guide short; 8—hanger; and 9—frame for attaching the attachment.</p> Full article ">Figure 2
<p>View of a 3D model of an extending front loader [own work].</p> Full article ">Figure 3
<p>Force distribution in bottom position without and with extension [own work].</p> Full article ">Figure 4
<p>Von Misses stress distribution of the loader arm without extension (number of mesh elements 49,740, number of nodes 101,251) [own work].</p> Full article ">Figure 5
<p>Detailed view of the most stressed areas of the loader arm without extension [own work].</p> Full article ">Figure 6
<p>Deflection of loader arm structure without extension [own work].</p> Full article ">Figure 7
<p>Von Misses stress distribution of extending loader arm (number of mesh elements 52,397, number of nodes 107,068) [own work].</p> Full article ">Figure 8
<p>Detailed view of the most stressed areas of extending loader arm [own work].</p> Full article ">Figure 9
<p>Deflection of the extending loader arm structure [own work].</p> Full article ">Figure 10
<p>EURO frame deflection analysis [own work].</p> Full article ">Figure 11
<p>Deflection analysis of the frame link, long straight rod, and work tool control actuator (number of elements 26,214, number of nodes 47,632) [own work].</p> Full article ">Figure 12
<p>Deflection analysis of a parallel guide short (number of elements 110,630, number of nodes 182,340) [own work].</p> Full article ">Figure 13
<p>Hanger deflection analysis (number of elements 52,828, number of nodes 87,368) [own work].</p> Full article ">Figure 14
<p>Conceptual model of extension control using a hydraulic motor and helical gearbox [own work].</p> Full article ">Figure 15
<p>View of the mounted loader arm extension drive system [own work].</p> Full article ">
18 pages, 14222 KiB  
Article
Design and Experimentation of Tensegrity Jumping Robots
by Guoxin Tang, Qi Yang and Binbin Lian
Appl. Sci. 2024, 14(9), 3947; https://doi.org/10.3390/app14093947 - 6 May 2024
Cited by 1 | Viewed by 1494
Abstract
Jumping robots possess the capability to surmount formidable obstacles and are well-suited for navigating through complex terrain environments. However, most of the existing jumping robots face challenges in achieving stable jumping and they also have low energy utilization efficiency, which limits their practical [...] Read more.
Jumping robots possess the capability to surmount formidable obstacles and are well-suited for navigating through complex terrain environments. However, most of the existing jumping robots face challenges in achieving stable jumping and they also have low energy utilization efficiency, which limits their practical applications. In this work, a two-module jumping robot based on tensegrity structure is put forward. Firstly, the structural design and jumping mechanism of the robot are elaborated in the article. Then, dynamic models, including the two modules’ simultaneous jumping and step-up jumping process of the robot, are established utilizing the Lagrange dynamic modeling method. On this basis, the effects of parameters, including the stiffness of elastic cables and the initial tilt angle of the robot, on the jumping performance of the robot can be obtained. Finally, simulations are carried out and a prototype is developed to verify the rationality of the tensegrity-based jumping robot proposed in this work. The experiment results show that our jumping robot can achieve a stable jumping process and the step-up jumping of each module of the prototype can have higher energy efficiency than that of simultaneous jumping of each module, which enables the robot a better jumping performance. This research serves as a valuable reference for the design and analysis of jumping robots. Full article
(This article belongs to the Section Robotics and Automation)
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<p>Tensegrity jumping robot design process. (<b>a</b>) 2-Strut 4-Cable. (<b>b</b>) Basic unit of tensegrity. (<b>c</b>) Tensegrity jumping robot basic unit. (<b>d</b>) Robot’s deformation forms.</p> Full article ">Figure 2
<p>Three-dimensional models. (<b>a</b>) Initial state. (<b>b</b>) Compressed state. (<b>c</b>) Step-up state. (<b>d</b>) Trigger device.</p> Full article ">Figure 3
<p>Diagram of the simultaneous jump.</p> Full article ">Figure 4
<p>Diagram of the step-up jump.</p> Full article ">Figure 5
<p>Dual module simultaneous jump. (<b>a</b>) Vertical jump height. (<b>b</b>) Horizontal jump distance. (<b>c</b>) Schematic diagram of jumps at 8° and 16 N/mm.</p> Full article ">Figure 6
<p>Dual module step-up jump. (<b>a</b>) Jump height and jump distance at four moments. (<b>b</b>) Choice of jumping moments; (<b>c</b>) Schematic diagram of jumps at 8° and 16 N/mm.</p> Full article ">Figure 7
<p>Simultaneous jump simulation. (<b>a</b>) Vertical jump height. (<b>b</b>) Horizontal jump distance.</p> Full article ">Figure 8
<p>Release order and time. (<b>a</b>) Method 1; (<b>b</b>) Method 2; (<b>c</b>) Release order; (<b>d</b>) Release time.</p> Full article ">Figure 9
<p>Step-up jumping simulation. (<b>a</b>) Vertical jump height. (<b>b</b>) Horizontal jump distance.</p> Full article ">Figure 10
<p>Prototype of the robot with two modules.</p> Full article ">Figure 11
<p>Environment of the experiment.</p> Full article ">Figure 12
<p>Experiments with simultaneous jumping.</p> Full article ">Figure 13
<p>Experiments with step-up jumping.</p> Full article ">Figure 14
<p>Data from experiments. (<b>a</b>) Simultaneous jumping. (<b>b</b>) Step-up jumping.</p> Full article ">
20 pages, 4271 KiB  
Article
The Efficiency of YOLOv5 Models in the Detection of Similar Construction Details
by Tautvydas Kvietkauskas, Ernest Pavlov, Pavel Stefanovič and Birutė Pliuskuvienė
Appl. Sci. 2024, 14(9), 3946; https://doi.org/10.3390/app14093946 - 6 May 2024
Cited by 4 | Viewed by 3172
Abstract
Computer vision solutions have become widely used in various industries and as part of daily solutions. One task of computer vision is object detection. With the development of object detection algorithms and the growing number of various kinds of image data, different problems [...] Read more.
Computer vision solutions have become widely used in various industries and as part of daily solutions. One task of computer vision is object detection. With the development of object detection algorithms and the growing number of various kinds of image data, different problems arise in relation to the building of models suitable for various solutions. This paper investigates the influence of parameters used in the training process involved in detecting similar kinds of objects, i.e., the hyperparameters of the algorithm and the training parameters. This experimental investigation focuses on the widely used YOLOv5 algorithm and analyses the performance of different models of YOLOv5 (n, s, m, l, x). In the research, the newly collected construction details (22 categories) dataset is used. Experiments are performed using pre-trained models of the YOLOv5. A total of 185 YOLOv5 models are trained and evaluated. All models are tested on 3300 images photographed on three different backgrounds: mixed, neutral, and white. Additionally, the best-obtained models are evaluated using 150 new images, each of which has several dozen construction details and is photographed against different backgrounds. The deep analysis of different YOLOv5 models and the hyperparameters shows the influence of various parameters when analysing the object detection of similar objects. The best model was obtained when the YOLOv5l was used and the parameters are as follows: coloured images, image size—320; batch size—32; epoch number—300; layers freeze option—10; data augmentation—on; learning rate—0.001; momentum—0.95; and weight decay—0.0007. These results may be useful for various tasks in which small and similar objects are analysed. Full article
(This article belongs to the Special Issue Computer Vision in Automatic Detection and Identification)
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<p>The workflow of the experimental investigation.</p> Full article ">Figure 2
<p>A sample of the dataset used to train the YOLOv5 models.</p> Full article ">Figure 3
<p>A sample of the dataset used to evaluate the YOLOv5 models.</p> Full article ">Figure 4
<p>A sample of the dataset used to evaluate the best YOLOv5 model, with several dozen details in one image.</p> Full article ">Figure 5
<p>The highest correct detection ratio of each YOLOv5 model.</p> Full article ">Figure 6
<p>The evaluation of the YOLOv5l model.</p> Full article ">Figure 7
<p>The confusion matrices of the best obtained model.</p> Full article ">Figure 8
<p>A sample of construction detail detection in real-world simulation.</p> Full article ">
20 pages, 29850 KiB  
Article
Comprehensive Performance Evaluation between Visual SLAM and LiDAR SLAM for Mobile Robots: Theories and Experiments
by Yu-Lin Zhao, Yi-Tian Hong and Han-Pang Huang
Appl. Sci. 2024, 14(9), 3945; https://doi.org/10.3390/app14093945 - 6 May 2024
Cited by 5 | Viewed by 4454
Abstract
SLAM (Simultaneous Localization and Mapping), primarily relying on camera or LiDAR (Light Detection and Ranging) sensors, plays a crucial role in robotics for localization and environmental reconstruction. This paper assesses the performance of two leading methods, namely ORB-SLAM3 and SC-LeGO-LOAM, focusing on localization [...] Read more.
SLAM (Simultaneous Localization and Mapping), primarily relying on camera or LiDAR (Light Detection and Ranging) sensors, plays a crucial role in robotics for localization and environmental reconstruction. This paper assesses the performance of two leading methods, namely ORB-SLAM3 and SC-LeGO-LOAM, focusing on localization and mapping in both indoor and outdoor environments. The evaluation employs artificial and cost-effective datasets incorporating data from a 3D LiDAR and an RGB-D (color and depth) camera. A practical approach is introduced for calculating ground-truth trajectories and during benchmarking, reconstruction maps based on ground truth are established. To assess the performance, ATE and RPE are utilized to evaluate the accuracy of localization; standard deviation is employed to compare the stability during the localization process for different methods. While both algorithms exhibit satisfactory positioning accuracy, their performance is suboptimal in scenarios with inadequate textures. Furthermore, 3D reconstruction maps established by the two approaches are also provided for direct observation of their differences and the limitations encountered during map construction. Moreover, the research includes a comprehensive comparison of computational performance metrics, encompassing Central Processing Unit (CPU) utilization, memory usage, and an in-depth analysis. This evaluation revealed that Visual SLAM requires more CPU resources than LiDAR SLAM, primarily due to additional data storage requirements, emphasizing the impact of environmental factors on resource requirements. In conclusion, LiDAR SLAM is more suitable for the outdoors due to its comprehensive nature, while Visual SLAM excels indoors, compensating for sparse aspects in LiDAR SLAM. To facilitate further research, a technical guide was also provided for the researchers in related fields. Full article
(This article belongs to the Section Robotics and Automation)
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<p>Overview of a typical RGB-D reconstruction process.</p> Full article ">Figure 2
<p>Hardware and coordinate system.</p> Full article ">Figure 3
<p>Two types of RGB-D reconstruction processing methods are referred to in this paper. (<b>a</b>) Based on ORB-SLAM3, RGB-D reconstruction with a loop closure. (<b>b</b>) Based on ground truth, RGB-D reconstruction.</p> Full article ">Figure 4
<p>The ground truth of the robot poses obtained from one of the indoor datasets (I3).</p> Full article ">Figure 5
<p>I3 RPE with regard to the translation part (m) for delta = 1 (frames) using consecutive pairs (with SE(3) Umeyama alignment, while processing panning rotation and scale): (<b>a</b>) ORB-SLAM3 with loop closure; (<b>b</b>) SC-LeGO-LOAM with loop closure; (<b>c</b>) ORB-SLAM3 without loop closure; and (<b>d</b>) SC-LeGO-LOAM without loop closure.</p> Full article ">Figure 6
<p>A top-view perspective of the LiDAR SLAM mapping result. The colored point clouds depict the robot’s poses. The white boxes represent specific scenarios: (1.) Multiple corners. (2.) Extended corridor.</p> Full article ">Figure 7
<p>Local reconstructed indoor maps within a depth range of 7 m. (<b>a</b>) The first perspective (1) based on ground truth; (<b>b</b>) The first perspective (1) based on ORB-SLAM3; (<b>c</b>) The second perspective (2) based on ground truth; (<b>d</b>) The second perspective (2) based on ORB-SLAM3.</p> Full article ">Figure 7 Cont.
<p>Local reconstructed indoor maps within a depth range of 7 m. (<b>a</b>) The first perspective (1) based on ground truth; (<b>b</b>) The first perspective (1) based on ORB-SLAM3; (<b>c</b>) The second perspective (2) based on ground truth; (<b>d</b>) The second perspective (2) based on ORB-SLAM3.</p> Full article ">Figure 8
<p>Blind spots in local mapping around corners.</p> Full article ">Figure 9
<p>The ground truth of the robot poses was obtained from one of the outdoor datasets (O4).</p> Full article ">Figure 10
<p>O4 RPE with regard to the translation part (m) for delta = 1 (frames) using consecutive pairs (with SE(3) Umeyama alignment, while processing panning rotation and scale): (<b>a</b>) ORB-SLAM3 with loop closure; (<b>b</b>) SC-LeGO-LOAM with loop closure; (<b>c</b>) ORB-SLAM3 without loop closure; and (<b>d</b>) SC-LeGO-LOAM without loop closure.</p> Full article ">Figure 10 Cont.
<p>O4 RPE with regard to the translation part (m) for delta = 1 (frames) using consecutive pairs (with SE(3) Umeyama alignment, while processing panning rotation and scale): (<b>a</b>) ORB-SLAM3 with loop closure; (<b>b</b>) SC-LeGO-LOAM with loop closure; (<b>c</b>) ORB-SLAM3 without loop closure; and (<b>d</b>) SC-LeGO-LOAM without loop closure.</p> Full article ">Figure 11
<p>LiDAR SLAM outdoor mapping and the real scene. (<b>a</b>) Top view of the reconstructed map; (<b>b</b>) Side view of the reconstructed map; (<b>c</b>) The real scene.</p> Full article ">Figure 11 Cont.
<p>LiDAR SLAM outdoor mapping and the real scene. (<b>a</b>) Top view of the reconstructed map; (<b>b</b>) Side view of the reconstructed map; (<b>c</b>) The real scene.</p> Full article ">Figure 12
<p>Local reconstructed outdoor maps within a depth range of 7 m. (<b>a</b>) The first perspective (1) based on ground truth; (<b>b</b>) The first perspective (1) based on ORB-SLAM3; (<b>c</b>) The second perspective (2) based on ground truth; (<b>d</b>) The second perspective (2) based on ORB-SLAM3.</p> Full article ">Figure 12 Cont.
<p>Local reconstructed outdoor maps within a depth range of 7 m. (<b>a</b>) The first perspective (1) based on ground truth; (<b>b</b>) The first perspective (1) based on ORB-SLAM3; (<b>c</b>) The second perspective (2) based on ground truth; (<b>d</b>) The second perspective (2) based on ORB-SLAM3.</p> Full article ">Figure 13
<p>(<b>a</b>) Visual SLAM based on ground truth and (<b>b</b>) LiDAR SLAM based on 3D LiDAR. The colored point clouds depict the robot’s poses. The white boxes represent specific scenarios: (1.) Reconstruction with loop. (2.) Reconstruction without loop.</p> Full article ">
14 pages, 4019 KiB  
Article
Performance of API Design for Interoperability of Medical Information Systems
by Leticia Dávila Nicanor, Abraham Banda Madrid, Jesús E. Martínez Hernández and Irene Aguilar Juárez
Appl. Sci. 2024, 14(9), 3944; https://doi.org/10.3390/app14093944 - 6 May 2024
Viewed by 2231
Abstract
After the experience of the COVID-19 pandemic, it has become evident that efficient and secure interoperability of medical information is crucial for effective diagnoses and medical treatments. However, a significant challenge arises concerning the heterogeneity of the systems storing patient information in medical [...] Read more.
After the experience of the COVID-19 pandemic, it has become evident that efficient and secure interoperability of medical information is crucial for effective diagnoses and medical treatments. However, a significant challenge arises concerning the heterogeneity of the systems storing patient information in medical centers or hospitals. Memory management becomes a pivotal element for the effective operation of the proposed API, as it must seamlessly execute across various devices, ranging from healthcare units, such as mobile phones, to servers in cloud computing. This proposal addresses these issues through techniques designed to enhance the performance of the software architecture in creating a medical interoperability API. This API has the capacity to be cloned and distributed to facilitate the exchange of data related to a patient’s medical history. To tackle heterogeneity, efficient memory management was implemented by utilizing an object-oriented approach and leveraging design patterns like abstract factory and wrapper. Regarding the evaluation of the proposal, this study showed an estimated performance of 94.5 percent, which was indirectly demonstrated through the assessment of operation sequences. This result suggests a satisfactory level based on complexity and coupling. Full article
(This article belongs to the Special Issue Smart Systems in Medical Informatics)
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<p>Interoperability API’s use case.</p> Full article ">Figure 2
<p>Interoperability APIs architectural design.</p> Full article ">Figure 3
<p>HCE state diagram design.</p> Full article ">Figure 4
<p>Interoperability APIs operation.</p> Full article ">Figure 5
<p>Interoperability API’s ACG.</p> Full article ">Figure 6
<p>Dispersion performance of API architectural design.</p> Full article ">
15 pages, 7428 KiB  
Article
Removal of Bisphenol A from Water by Single-Walled Carbon Nanotubes Loaded with Iron Oxide Nanoparticles
by Luying Chen, Jintao Jiang and Leimei Sheng
Appl. Sci. 2024, 14(9), 3943; https://doi.org/10.3390/app14093943 - 6 May 2024
Viewed by 1701
Abstract
Single-walled carbon nanotubes (SWCNTs) loaded with magnetic iron oxide nanoparticles were prepared by the arc discharge method and air heat treatment. The nanocomposite was characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, vibrating sample magnetometry, etc. The results showed that the heat-treated [...] Read more.
Single-walled carbon nanotubes (SWCNTs) loaded with magnetic iron oxide nanoparticles were prepared by the arc discharge method and air heat treatment. The nanocomposite was characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, vibrating sample magnetometry, etc. The results showed that the heat-treated nanocomposites (SWCNTs/FexOy) had iron oxide phases and superparamagnetic properties with a saturation magnetization of 33.32 emu/g. Compared with the non-heat-treated materials, SWCNTs/FexOy had a larger specific surface area and pore volume. Using SWCNTs/FexOy to remove the organic contaminant (bisphenol A, BPA), it was found that under the conditions of pH = 3 and adsorbent dosage of 0.2 g/L, the maximum adsorption capacity of the composite was 117 mg/g, and the adsorption could reach more than 90% in only 5 min when the BPA content was below 0.05 mmol/L. The fitting results of the Langmuir and D-R models are more consistent with the experimental data, indicating a relatively uniform distribution of the adsorption sites and that the adsorption process is more consistent with physical adsorption. The kinetic calculations showed that the SWCNTs/FexOy exhibits chemical effects on both the surface and the gap, and the adsorption process is controlled by the π-π bonds and the hydrophobicity of the SWCNTs/FexOy. Full article
(This article belongs to the Topic Nanomaterials for Energy and Environmental Applications)
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<p>Scanning electron micrographs of (<b>a</b>) low-magnification as-grown SWCNTs and (<b>b</b>) high-magnification as-grown SWCNTs; (<b>c</b>) EDS image.</p> Full article ">Figure 2
<p>(<b>a</b>) XRD images and (<b>b</b>) Raman spectra of as-grown SWCNTs and SWCNTs/Fe<sub>x</sub>O<sub>y</sub>.</p> Full article ">Figure 3
<p>XPS spectra of SWCNTs/Fe<sub>x</sub>O<sub>y</sub> and as-grown SWCNTs.</p> Full article ">Figure 4
<p>(<b>a</b>) N<sub>2</sub> adsorption–desorption curves and (<b>b</b>) pore size distribution of as-grown SWCNTs and SWCNTs/Fe<sub>x</sub>O<sub>y</sub>.</p> Full article ">Figure 5
<p>(<b>a</b>) Hysteresis loop of SWCNTs/Fe<sub>x</sub>O<sub>y</sub> and (<b>b</b>) a photo of a small experiment.</p> Full article ">Figure 6
<p>As-grown SWCNTs and SWCNTs/Fe<sub>x</sub>O<sub>y</sub> adsorption curves (T = 25 °C, pH = 6, adsorbent dosage = 0.2 g/L, C<sub>BPA</sub> = 0.025 mmol/L).</p> Full article ">Figure 7
<p>Effect of different initial concentrations (T = 25 °C, pH = 6, adsorbent dosage = 0.2 g/L).</p> Full article ">Figure 8
<p>Effect of adsorbent dosage (T = 25 °C, pH = 6, C<sub>BPA</sub> = 0.075 mmol/L).</p> Full article ">Figure 9
<p>(<b>a</b>) Effect of pH value and (<b>b</b>) the point of zero charge of SWCNTs/Fe<sub>x</sub>O<sub>y</sub>.</p> Full article ">Figure 10
<p>Langmuir, Freundlich, and D-R adsorption isotherms (T = 25 °C, pH = 6, adsorbent dosage = 0.2 g/L).</p> Full article ">Figure 11
<p>Kinetic fitting curves: (<b>a</b>) pseudo first-order kinetics; (<b>b</b>) pseudo second-order kinetic (T = 25 °C, pH = 6, adsorbent dosage = 0.2 g/L).</p> Full article ">Figure 12
<p>Weber–Morris curves (T = 25 °C, pH = 6, adsorbent dosage = 0.2 g/L).</p> Full article ">Figure 13
<p>The main mechanism of adsorption of SWCNTs/Fe<sub>x</sub>O<sub>y</sub> on BPA.</p> Full article ">
16 pages, 1060 KiB  
Article
Constituents from Ageratina pichinchensis and Their Inhibitory Effect on Nitric Oxide Production
by Mariana Sánchez-Ramos, Araceli Guerrero-Alonso, Antonio Romero-Estrada, Judith González-Christen, Laura Alvarez, Juan José Acevedo-Fernández, Angélica Román-Guerrero, Francisco Cruz-Sosa and Silvia Marquina-Bahena
Appl. Sci. 2024, 14(9), 3942; https://doi.org/10.3390/app14093942 - 6 May 2024
Viewed by 1411
Abstract
In this study, we report on the isolation, purification, and anti-inflammatory evaluation of compounds from the plant species Ageratina pichinchensis. Using open-column chromatography, 11 known compounds were purified, which chemical structures were elucidated by nuclear magnetic resonance techniques (1D and 2D). All [...] Read more.
In this study, we report on the isolation, purification, and anti-inflammatory evaluation of compounds from the plant species Ageratina pichinchensis. Using open-column chromatography, 11 known compounds were purified, which chemical structures were elucidated by nuclear magnetic resonance techniques (1D and 2D). All compounds were evaluated in an in vitro model of RAW 264.7 mouse macrophage cells, measuring the nitric oxide inhibition to determine the anti-inflammatory effect. The compound betuletol 3-O-β-glucoside (11) inhibited nitric oxide with a half-maximal inhibitory concentration (IC50) of 75.08 ± 3.07% at 75 µM; additionally, it inhibited the secretion of interleukin 6 (IL-6) and activation of the nuclear factor (NF-kβ). These results suggest that the anti-inflammatory effect attributed to A. pichinchensis species is promoted by compound 11, which could be considered a potential anti-inflammatory agent by suppressing the expression of NF-kβ target genes, such as those involved in the proinflammatory pathway and inducible nitric oxide synthase (iNOS). Full article
(This article belongs to the Section Chemical and Molecular Sciences)
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<p>Anti-inflammatory effect of in vivo extracts of leaves and stems of <span class="html-italic">A. pichinchensis</span>. F-HA: ethanol:H<sub>2</sub>O (95:05 <span class="html-italic">v</span>/<span class="html-italic">v</span>): hydroalcoholic ethanolic extract of flowers; L-EA: ethyl acetate extract of leaves; L-MeOH: methyl extract of leaves; S-EA: ethyl acetate extract of stems; S-MeOH: methyl extract of stems. Data are expressed as mean ± SD values of experiments in three independent assays. Significance was determined using ANOVA followed by Dunnett’s multiple comparisons test. *** <span class="html-italic">p</span> &lt; 0.001, ns: not significant vs. indomethacin-treated extracts, and #### <span class="html-italic">p</span> &lt; 0.001 vs. vehicle acetone.</p> Full article ">Figure 2
<p>Compounds isolated from aerial parts of <span class="html-italic">A. pichinchensis</span>.</p> Full article ">Figure 3
<p>Effect of compound <b>11</b> on (<b>a</b>) NO, (<b>b</b>) IL-6, and (<b>c</b>) NF-kβ of RAW 264.7 macrophages activated with LPS. Data were expressed as the mean ± SD values of experiments in three independent assays. ** <span class="html-italic">p</span> &lt; 0.01, *** <span class="html-italic">p</span> &lt; 0.001 vs. LPS-treated cells, and #### <span class="html-italic">p</span> &lt; 0.001 vs. vehicle control.</p> Full article ">
17 pages, 561 KiB  
Article
An Adaptive Contextual Relation Model for Improving Response Generation
by Meiqi Wang, Shiyu Tian, Caixia Yuan and Xiaojie Wang
Appl. Sci. 2024, 14(9), 3941; https://doi.org/10.3390/app14093941 - 6 May 2024
Viewed by 1304
Abstract
Context modeling has always been the groundwork for the dialogue response generation task, yet it presents challenges due to the loose context relations among open-domain dialogue sentences. Introducing simulated dialogue futures has been proposed as a solution to mitigate the problem of low [...] Read more.
Context modeling has always been the groundwork for the dialogue response generation task, yet it presents challenges due to the loose context relations among open-domain dialogue sentences. Introducing simulated dialogue futures has been proposed as a solution to mitigate the problem of low history–response relevance. However, these approaches simply assume that the history and future of a dialogue have the same effect on response generation. In reality, the coherence between dialogue sentences varies, and thus, history and the future are not uniformly helpful in response prediction. Consequently, determining and leveraging the relevance between history–response and response–future to aid in response prediction emerges as a pivotal concern. This paper addresses this concern by initially establishing three context relations of response and its context (history and future), reflecting the relevance between the response and preceding and following sentences. Subsequently, we annotate response contextual relation labels on a large-scale dataset, DailyDialog (DD). Leveraging these relation labels, we propose a response generation model that adaptively integrates contributions from preceding and succeeding sentences guided by explicit relation labels. This approach mitigates the impact in cases of lower relevance and amplifies contributions in cases of higher relevance, thus improving the capability of context modeling. Experimental results on public dataset DD demonstrate that our response generation model significantly enhances coherence by 3.02% in long sequences (4-gram) and augments bi-gram diversity by 17.67%, surpassing the performance of previous models. Full article
(This article belongs to the Special Issue New Technologies and Applications of Natural Language Processing (NLP), 2nd Edition)
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<p>The overall framework of the dialogue generation model.</p> Full article ">Figure 2
<p>Two cases of the generated responses from different models.</p> Full article ">
17 pages, 5413 KiB  
Article
Winter Wheat Mapping in Shandong Province of China with Multi-Temporal Sentinel-2 Images
by Yongyu Feng, Bingyao Chen, Wei Liu, Xiurong Xue, Tongqing Liu, Linye Zhu and Huaqiao Xing
Appl. Sci. 2024, 14(9), 3940; https://doi.org/10.3390/app14093940 - 5 May 2024
Cited by 2 | Viewed by 1916
Abstract
Wheat plays an important role in China’s and the world’s food supply, and it is closely related to economy, culture and life. The spatial distribution of wheat is of great significance to the rational planning of wheat cultivation areas and the improvement of [...] Read more.
Wheat plays an important role in China’s and the world’s food supply, and it is closely related to economy, culture and life. The spatial distribution of wheat is of great significance to the rational planning of wheat cultivation areas and the improvement of wheat yield and quality. The current rapid development of remote sensing technology has greatly improved the efficiency of traditional agricultural surveys. The extraction of crop planting structure based on remote sensing images and technology is a popular topic in many researches. In response to the shortcomings of traditional methods, this research proposed a method based on the fusion of the pixel-based and object-oriented methods to map the spatial distribution of winter wheat. This method was experimented and achieved good results within Shandong Province. The resulting spatial distribution map of winter wheat has an overall accuracy of 92.2% with a kappa coefficient of 0.84. The comparison with the actual situation shows that the accuracy of the actual recognition of winter wheat is higher and better than the traditional pixel-based classification method. On this basis, the spatial pattern of winter wheat in Shandong was analyzed, and it was found that the topographic undulations had a great influence on the spatial distribution of wheat. This study vividly demonstrates the advantages and possibilities of combining pixel-based and object-oriented approaches through experiments, and also provides a reference for the next related research. Moreover, the winter wheat map of Shandong produced in this research is important for yield assessment, crop planting structure adjustment and the rational use of land resources. Full article
(This article belongs to the Special Issue Geographic Information System (GIS) for Various Applications)
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<p>The geographical location, city boundaries, topography in Shandong Province.</p> Full article ">Figure 2
<p>The spatial distribution of the samples and the ultra-high-resolution images with real conditions in different growth periods of winter wheat.</p> Full article ">Figure 3
<p>The workflow for winter wheat mapping in this research.</p> Full article ">Figure 4
<p>Feature importance of random forest. (<b>a</b>) refers to the importance of each type of features; (<b>b</b>) is the importance of various features of each month.</p> Full article ">Figure 5
<p>Winter wheat map with 10 m resolution and close-up views of Shandong Province.</p> Full article ">Figure 6
<p>Finer comparison of winter wheat extraction in different maps, from (<b>a</b>–<b>d</b>): the Sentinel-2 images, ChinaWheat30 in 2020, ChinaWheat10 in 2020, winter wheat map of this research.</p> Full article ">Figure 7
<p>Ultra-high-resolution image from MAPWORLD of Shandong in April 2020 (<b>a1</b>,<b>a2</b>,<b>a3</b>,<b>a4</b>), image object layer generated based on Sentinel-2 by SNIC (<b>b1</b>,<b>b2</b>,<b>b3</b>,<b>b4</b>), the pixel-based classification (<b>c1</b>,<b>c2</b>,<b>c3</b>,<b>c4</b>) and final result produced by the integration method (<b>d1</b>,<b>d2</b>,<b>d3</b>,<b>d4</b>).</p> Full article ">Figure 8
<p>Spatial distribution of croplands in relation to its topography.</p> Full article ">Figure 9
<p>Distribution of winter wheat in three-dimensional space, (<b>a</b>) refers to the distribution over elevation and (<b>b</b>) refers to the distribution over different slopes.</p> Full article ">Figure 10
<p>Spatial distribution of winter wheat in relation to multi-level rivers.</p> Full article ">
28 pages, 17751 KiB  
Article
An Effective Arbitrary Lagrangian-Eulerian-Lattice Boltzmann Flux Solver Integrated with the Mode Superposition Method for Flutter Prediction
by Tianchi Gong, Feng Wang and Yan Wang
Appl. Sci. 2024, 14(9), 3939; https://doi.org/10.3390/app14093939 - 5 May 2024
Cited by 2 | Viewed by 1650
Abstract
An arbitrary Lagrangian-Eulerian lattice Boltzmann flux solver (ALE-LBFS) coupled with the mode superposition method is proposed in this work and applied to study two- and three-dimensional flutter phenomenon on dynamic unstructured meshes. The ALE-LBFS is applied to predict the flow field by using [...] Read more.
An arbitrary Lagrangian-Eulerian lattice Boltzmann flux solver (ALE-LBFS) coupled with the mode superposition method is proposed in this work and applied to study two- and three-dimensional flutter phenomenon on dynamic unstructured meshes. The ALE-LBFS is applied to predict the flow field by using the vertex-centered finite volume method with an implicit dual time-stepping method. The convective fluxes are evaluated by using lattice Boltzmann solutions of the non-free D1Q4 lattice model and the viscous fluxes are obtained directly. Additional fluxes due to mesh motion are calculated directly by using local conservative variables and mesh velocity. The mode superposition method is used to solve for the dynamic response of solid structures. The exchange of aerodynamic forces and structural motions is achieved through interpolation with the radial basis function. The flow solver and the structural solver are tightly coupled so that the restriction on the physical time step can be removed. In addition, geometric conservation law (GCL) is also applied to guarantee conservation laws. The proposed method is tested through a series of simulations about moving boundaries and fluid–structure interaction problems in 2D and 3D. The present results show good consistency against the experiments and numerical simulations obtained from the literature. It is also shown that the proposed method not only can effectively predict the flutter boundaries in both 2D and 3D cases but can also accurately capture the transonic dip phenomenon. The tight coupling of the ALE-LBFS and the mode superposition method presents an effective and powerful tool for flutter prediction and can be applied to many essential aeronautical problems. Full article
(This article belongs to the Section Aerospace Science and Engineering)
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<p>Schematic of an interface boundary where fluid (<math display="inline"><semantics> <mrow> <msub> <mo>Ω</mo> <mi>f</mi> </msub> </mrow> </semantics></math>) and solid domain (<math display="inline"><semantics> <mrow> <msub> <mo>Ω</mo> <mi>s</mi> </msub> </mrow> </semantics></math>) meet and their outward normal vectors <math display="inline"><semantics> <mrow> <msub> <mi>n</mi> <mi>f</mi> </msub> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi>n</mi> <mi>s</mi> </msub> </mrow> </semantics></math> point in opposite directions.</p> Full article ">Figure 2
<p>Control volume of a median-dual cell-vertex scheme for (<b>left</b>) 2D and (<b>right</b>) 3D.</p> Full article ">Figure 3
<p>Distribution of discrete lattice velocities in 1D model.</p> Full article ">Figure 4
<p>Streaming process in the D1Q4 model.</p> Full article ">Figure 5
<p>Computational flowchart for the tight-coupling method.</p> Full article ">Figure 6
<p>Displacement and force transfer between fluid and structure solver.</p> Full article ">Figure 7
<p>Flowchart of the solution process for the FSI problem.</p> Full article ">Figure 8
<p>Comparison of <math display="inline"><semantics> <mrow> <msub> <mi>C</mi> <mi>L</mi> </msub> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi>C</mi> <mi mathvariant="normal">m</mi> </msub> </mrow> </semantics></math> for NACA 0012 airfoil with the numerical and experimental results. (<b>a</b>) Coefficient of lift. (<b>b</b>) Coefficient of moment.</p> Full article ">Figure 9
<p>Comparison of pressure coefficients distributed on NACA 0012 airfoil for four different snapshots in one pitch cycle. (<b>a</b>) <math display="inline"><semantics> <mrow> <mi>α</mi> <mo>=</mo> <msup> <mrow> <mn>4.59</mn> </mrow> <mo>∘</mo> </msup> <mo>,</mo> <mi>ϕ</mi> <mo>=</mo> <msup> <mrow> <mn>45</mn> </mrow> <mo>∘</mo> </msup> </mrow> </semantics></math>. (<b>b</b>) <math display="inline"><semantics> <mrow> <mi>α</mi> <mo>=</mo> <msup> <mrow> <mn>5.30</mn> </mrow> <mo>∘</mo> </msup> <mo>,</mo> <mi>ϕ</mi> <mo>=</mo> <msup> <mrow> <mn>90</mn> </mrow> <mo>∘</mo> </msup> </mrow> </semantics></math>. (<b>c</b>) <math display="inline"><semantics> <mrow> <mi>α</mi> <mo>=</mo> <msup> <mrow> <mn>4.59</mn> </mrow> <mo>∘</mo> </msup> <mo>,</mo> <mi>ϕ</mi> <mo>=</mo> <msup> <mrow> <mn>135</mn> </mrow> <mo>∘</mo> </msup> </mrow> </semantics></math>. (<b>d</b>) <math display="inline"><semantics> <mrow> <mi>α</mi> <mo>=</mo> <msup> <mrow> <mn>2.89</mn> </mrow> <mo>∘</mo> </msup> <mo>,</mo> <mi>ϕ</mi> <mo>=</mo> <msup> <mrow> <mn>180</mn> </mrow> <mo>∘</mo> </msup> </mrow> </semantics></math>.</p> Full article ">Figure 9 Cont.
<p>Comparison of pressure coefficients distributed on NACA 0012 airfoil for four different snapshots in one pitch cycle. (<b>a</b>) <math display="inline"><semantics> <mrow> <mi>α</mi> <mo>=</mo> <msup> <mrow> <mn>4.59</mn> </mrow> <mo>∘</mo> </msup> <mo>,</mo> <mi>ϕ</mi> <mo>=</mo> <msup> <mrow> <mn>45</mn> </mrow> <mo>∘</mo> </msup> </mrow> </semantics></math>. (<b>b</b>) <math display="inline"><semantics> <mrow> <mi>α</mi> <mo>=</mo> <msup> <mrow> <mn>5.30</mn> </mrow> <mo>∘</mo> </msup> <mo>,</mo> <mi>ϕ</mi> <mo>=</mo> <msup> <mrow> <mn>90</mn> </mrow> <mo>∘</mo> </msup> </mrow> </semantics></math>. (<b>c</b>) <math display="inline"><semantics> <mrow> <mi>α</mi> <mo>=</mo> <msup> <mrow> <mn>4.59</mn> </mrow> <mo>∘</mo> </msup> <mo>,</mo> <mi>ϕ</mi> <mo>=</mo> <msup> <mrow> <mn>135</mn> </mrow> <mo>∘</mo> </msup> </mrow> </semantics></math>. (<b>d</b>) <math display="inline"><semantics> <mrow> <mi>α</mi> <mo>=</mo> <msup> <mrow> <mn>2.89</mn> </mrow> <mo>∘</mo> </msup> <mo>,</mo> <mi>ϕ</mi> <mo>=</mo> <msup> <mrow> <mn>180</mn> </mrow> <mo>∘</mo> </msup> </mrow> </semantics></math>.</p> Full article ">Figure 10
<p>Schematic diagram of the uCRM-13.5 wing.</p> Full article ">Figure 11
<p>Distribution on the wing surface in a steady state. (<b>a</b>) Pressure coefficient contour. (<b>b</b>) Pressure coefficient distribution along <math display="inline"><semantics> <mrow> <mrow> <mi>y</mi> <mo>/</mo> <mi>b</mi> </mrow> <mo>=</mo> <mn>0.35</mn> </mrow> </semantics></math>. (<b>c</b>) Pressure coefficient distribution along <math display="inline"><semantics> <mrow> <mrow> <mi>y</mi> <mo>/</mo> <mi>b</mi> </mrow> <mo>=</mo> <mn>0.89</mn> </mrow> </semantics></math>.</p> Full article ">Figure 12
<p>Time-dependent <math display="inline"><semantics> <mrow> <msub> <mi>C</mi> <mi>p</mi> </msub> </mrow> </semantics></math> for the wing at <math display="inline"><semantics> <mrow> <mrow> <mi>y</mi> <mo>/</mo> <mi>b</mi> </mrow> <mo>=</mo> <mn>0.35</mn> </mrow> </semantics></math>. (<b>a</b>) Mode 1, frequency 0.505 Hz. (<b>b</b>) Mode 2, frequency 1.670 Hz. (<b>c</b>) Mode 3, frequency 2.733 Hz. (<b>d</b>) Mode 4, frequency 3.843 Hz.</p> Full article ">Figure 12 Cont.
<p>Time-dependent <math display="inline"><semantics> <mrow> <msub> <mi>C</mi> <mi>p</mi> </msub> </mrow> </semantics></math> for the wing at <math display="inline"><semantics> <mrow> <mrow> <mi>y</mi> <mo>/</mo> <mi>b</mi> </mrow> <mo>=</mo> <mn>0.35</mn> </mrow> </semantics></math>. (<b>a</b>) Mode 1, frequency 0.505 Hz. (<b>b</b>) Mode 2, frequency 1.670 Hz. (<b>c</b>) Mode 3, frequency 2.733 Hz. (<b>d</b>) Mode 4, frequency 3.843 Hz.</p> Full article ">Figure 13
<p>Time-dependent <math display="inline"><semantics> <mrow> <msub> <mi>C</mi> <mi>p</mi> </msub> </mrow> </semantics></math> for the wing at <math display="inline"><semantics> <mrow> <mrow> <mi>y</mi> <mo>/</mo> <mi>b</mi> </mrow> <mo>=</mo> <mn>0.89</mn> </mrow> </semantics></math>. (<b>a</b>) Mode 1, frequency 0.505 Hz. (<b>b</b>) Mode 2, frequency 1.670 Hz. (<b>c</b>) Mode 3, frequency 2.733 Hz. (<b>d</b>) Mode 4, frequency 3.843 Hz.</p> Full article ">Figure 14
<p>Pressure distribution on 3D pitching wing. (<b>a</b>) Mean pressure distribution. (<b>b</b>) Mean pressure coefficient at 60% wing span.</p> Full article ">Figure 15
<p>The variation in terms of the amplitude and phase when the forced oscillation frequency f = 10 Hz. (<b>a</b>) Amplitude. (<b>b</b>) Phase.</p> Full article ">Figure 16
<p>Schematic of (<b>a</b>) the typical section wing model and (<b>b</b>) AGARD 445.6 wing.</p> Full article ">Figure 16 Cont.
<p>Schematic of (<b>a</b>) the typical section wing model and (<b>b</b>) AGARD 445.6 wing.</p> Full article ">Figure 17
<p>Flutter speed index <math display="inline"><semantics> <mrow> <msubsup> <mi>V</mi> <mi>f</mi> <mo>∗</mo> </msubsup> </mrow> </semantics></math> as a function of a free-stream Mach number for NACA 64A010.</p> Full article ">Figure 18
<p>History of plunge and pitch for (<b>a</b>) damped response; (<b>b</b>) divergent response; (<b>c</b>) limit cycle oscillation (LCO).</p> Full article ">Figure 19
<p>Pressure coefficient contours at four snapshots in a circle of LCO when Ma = 0.85. The red solid line represents the initial contour of the airfoil.</p> Full article ">Figure 19 Cont.
<p>Pressure coefficient contours at four snapshots in a circle of LCO when Ma = 0.85. The red solid line represents the initial contour of the airfoil.</p> Full article ">Figure 20
<p>Geometry of AGARD 445.6 and its NACA 65A004 airfoil.</p> Full article ">Figure 21
<p>Mesh for (<b>a</b>) shell model and (<b>b</b>) plate model with constant thickness.</p> Full article ">Figure 22
<p>The contour of mode shape and deformation diagram for the first four mode frequencies. (<b>a</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mn>1</mn> </msub> <mo>=</mo> <mn>9.6224</mn> </mrow> </semantics></math>. (<b>b</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mn>2</mn> </msub> <mo>=</mo> <mn>40.925</mn> </mrow> </semantics></math>. (<b>c</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mn>3</mn> </msub> <mo>=</mo> <mn>49.863</mn> </mrow> </semantics></math>. (<b>d</b>) <math display="inline"><semantics> <mrow> <msub> <mi>f</mi> <mn>4</mn> </msub> <mo>=</mo> <mn>98.796</mn> </mrow> </semantics></math>.</p> Full article ">Figure 23
<p>Generalized displacement for the first three modes for Ma = 0.96 and <math display="inline"><semantics> <mrow> <msubsup> <mi>V</mi> <mi>f</mi> <mo>∗</mo> </msubsup> <mo>=</mo> <mn>0.292</mn> </mrow> </semantics></math>.</p> Full article ">Figure 24
<p>Displacement in x-, y-, z-directions at the probe of (<b>a</b>) the leading edge and (<b>b</b>) the trailing edge for Ma = 0.96 and <math display="inline"><semantics> <mrow> <msubsup> <mi>V</mi> <mi>f</mi> <mo>∗</mo> </msubsup> <mo>=</mo> <mn>0.292</mn> </mrow> </semantics></math>.</p> Full article ">Figure 25
<p>Flutter speed index <math display="inline"><semantics> <mrow> <msubsup> <mi>V</mi> <mi>f</mi> <mo>∗</mo> </msubsup> </mrow> </semantics></math> as a function of a free-stream Mach number for AGARD 445.6 wing.</p> Full article ">Figure 26
<p>Displacement in x-, y-, z-directions at the probe of (<b>a</b>) the leading edge and (<b>b</b>) the trailing edge for Ma = 0.499 and <math display="inline"><semantics> <mrow> <msubsup> <mi>V</mi> <mi>f</mi> <mo>∗</mo> </msubsup> <mo>=</mo> <mn>0.44</mn> </mrow> </semantics></math>.</p> Full article ">
22 pages, 11688 KiB  
Article
The Research on Deep Learning-Driven Dimensionality Reduction and Strain Prediction Techniques Based on Flight Parameter Data
by Wenbo Huang, Rui Wang, Mengchuang Zhang and Zhiping Yin
Appl. Sci. 2024, 14(9), 3938; https://doi.org/10.3390/app14093938 - 5 May 2024
Viewed by 1496
Abstract
Loads and strains in critical areas play a crucial role in aircraft structural health monitoring, the tracking of individual aircraft lifespans, and the compilation of load spectra. Direct measurement of actual flight loads presents challenges. This process typically involves using load-strain stiffness matrices, [...] Read more.
Loads and strains in critical areas play a crucial role in aircraft structural health monitoring, the tracking of individual aircraft lifespans, and the compilation of load spectra. Direct measurement of actual flight loads presents challenges. This process typically involves using load-strain stiffness matrices, derived from ground calibration tests, to map measured flight parameters to loads at critical locations. Presently, deep learning neural network methods are rapidly developing, offering new perspectives for this task. This paper explores the potential of deep learning models in predicting flight parameter loads and strains, integrating the methods of flight parameter preprocessing techniques, flight maneuver recognition (FMR), virtual ground calibration tests for wings, dimensionality reduction of flight data through Autoencoder (AE) network models, and the application of Long Short-Term Memory (LSTM) network models to predict strains. These efforts contribute to the prediction of strains in critical areas based on flight parameters, thereby enabling real-time assessment of aircraft damage. Full article
(This article belongs to the Section Aerospace Science and Engineering)
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<p>Flowchart for F-35 Aircraft load Monitoring (The green box represents the recorded data).</p> Full article ">Figure 2
<p>The flowchart of strain prediction.</p> Full article ">Figure 3
<p>Flowchart for a general maneuver recognition method.</p> Full article ">Figure 4
<p>The flow chart of proposed sequence important point-based method.</p> Full article ">Figure 5
<p>Schematic wing diagram of the FEM and bridge arrangements: (<b>a</b>) schematic diagram of the wing FEM; (<b>b</b>) arrangement of bending moment bridge; (<b>c</b>) arrangement of the shear bridge; and (<b>d</b>) arrangement of the torque bridge.</p> Full article ">Figure 6
<p>Diagram of bridge group method.</p> Full article ">Figure 7
<p>Virtual ground calibration test. (<b>a</b>) Boundary conditions; (<b>b</b>) positions of the loading points.</p> Full article ">Figure 8
<p>The structure of AE model.</p> Full article ">Figure 9
<p>The results of dimensionality reduction achieved by AE model: (<b>a</b>) results of dimensional clusters; (<b>b</b>) the mean squared error (MSE) of reconstruction; (<b>c</b>) the change history of MSE along with time sequence.</p> Full article ">Figure 10
<p>The mean squared error (MSE) of reconstruction by (<b>a</b>) LLE model and (<b>b</b>) PCA model.</p> Full article ">Figure 11
<p>MSE plot obtained by (<b>a</b>) RNN deep learning model and (<b>b</b>) LSTM deep learning model.</p> Full article ">Figure 12
<p>Comparison results between real flight data and the predicted one by (<b>a</b>) LSTM model and (<b>b</b>) RNN model predicted data and real data.</p> Full article ">Figure 12 Cont.
<p>Comparison results between real flight data and the predicted one by (<b>a</b>) LSTM model and (<b>b</b>) RNN model predicted data and real data.</p> Full article ">Figure 13
<p>Comparison results by LSTM: (<b>a</b>) with FMR at maneuver state 1; (<b>b</b>) without FMR at maneuver state 1; (<b>c</b>) with FMR at maneuver state 3; (<b>d</b>) without FMR at maneuver state 3.</p> Full article ">Figure 13 Cont.
<p>Comparison results by LSTM: (<b>a</b>) with FMR at maneuver state 1; (<b>b</b>) without FMR at maneuver state 1; (<b>c</b>) with FMR at maneuver state 3; (<b>d</b>) without FMR at maneuver state 3.</p> Full article ">Figure A1
<p>The characteristic analysis of strain gauge bridge.</p> Full article ">
15 pages, 4037 KiB  
Article
Geological Conditions Evaluation of Coalbed Methane of Dacun Block in the Guxu Mining Area, Southern Sichuan Coalfield
by Xushuang Zhu, Zheng Zhang, Yonggui Wu, Zhengjiang Long and Xiaodong Lai
Appl. Sci. 2024, 14(9), 3937; https://doi.org/10.3390/app14093937 - 5 May 2024
Viewed by 1283
Abstract
The geological conditions evaluation of coalbed methane (CBM) is of great significance to CBM exploration and development. The CBM resources in the Southern Sichuan Coalfield (SSC) of China are very abundant; however, the CBM investigation works in this area are only just beginning, [...] Read more.
The geological conditions evaluation of coalbed methane (CBM) is of great significance to CBM exploration and development. The CBM resources in the Southern Sichuan Coalfield (SSC) of China are very abundant; however, the CBM investigation works in this area are only just beginning, and the basic geological research of CBM is seriously inadequate, restricting CBM exploration and development. Therefore, in this study, a representative CBM block (Dacun) in the SSC was selected, and the CBM geological conditions were evaluated based on field injection/fall-off well testing, gas content and composition measurements, and a series of laboratory experiments. The results show that the CH4 concentrations of coal seams in the Dacun Block, overall, take on an increasing trend as the depth increases, and the CH4 weathering zone depth is 310 m. Due to the coupled control of temperature and formation pressure, the gas content shows a “increase→decrease” trend as the depth increases, and the critical depth is around 700 m. The CBM is enriched in the hinge zone of the Dacun syncline. The moisture content shows a negative correlation with CBM gas content. The porosities of coal seams vary from 4.20% to 5.41% and increase with the Ro,max. The permeabilities of coal seams show a strong heterogeneity with values ranging from 0.001mD to 2.85 mD and present a decreasing trend with the increase in depth. Moreover, a negative relationship exists between coal permeability and minimum horizontal stress magnitude. The reservoir pressure coefficients are between 0.51 and 1.26 and show a fluctuation change trend (increase→decrease→increase) as the depth increases, reflecting that three sets of independent superposed gas-bearing systems possibly exist vertically in the Longtan Formation of the study area. The Langmuir volumes (VL) of coals range from 22.67 to 36.84 m3/t, indicating the coals have strong adsorptivity. The VL presents a parabolic change of first increasing and then decreasing with the increase in depth, and the turning depth is around 700 m, consistent with the critical depth of gas content. The gas saturations of coal seams are, overall, low, with values varying from 29.10% to 116.48% (avg. 68.45%). Both gas content and reservoir pressure show a positive correlation with gas saturation. The CBM development in the Dacun Block needs a large depressurization of reservoir pressure due to the low ratio (avg. 0.37) of critical desorption pressure to reservoir pressure. Full article
(This article belongs to the Section Energy Science and Technology)
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<p>(<b>a</b>) Location of Sichuan Province in China. (<b>b</b>) Location of Guxu coalfield in Sichuan Province. (<b>c</b>) The major structures in the Guxu coalfield and the location of the Dacun Block in the Guxu coalfield.</p> Full article ">Figure 2
<p>Comprehensive stratigraphic column of Permian coal measures in the Dacun Block.</p> Full article ">Figure 3
<p>The scatter plots between the (<b>a</b>) CH<sub>4</sub>, (<b>b</b>) N<sub>2</sub>, (<b>c</b>) CO<sub>2</sub>, (<b>d</b>) H<sub>2</sub>, and (<b>e</b>) C<sub>2+</sub> concentrations and the depth of the coal seam in the Dacun Block.</p> Full article ">Figure 4
<p>The relationship between the (<b>a</b>) burial depth, (<b>b</b>) moisture contents, and gas content of coal seams in the Dacun Block.</p> Full article ">Figure 5
<p>The gas content isoline of coal seams C<sub>17</sub> (<b>a</b>) and C<sub>25</sub> (<b>b</b>) in the Dacun Block.</p> Full article ">Figure 6
<p>Distribution ranges of porosities of different coal seams in the Longtan Formation of the Dacun Block.</p> Full article ">Figure 7
<p>Relationship between coal porosity and R<span class="html-italic"><sub>o,max</sub></span> in the Dacun Block.</p> Full article ">Figure 8
<p>Distribution ranges of well testing permeabilities of different coal seams of the Dacun Block.</p> Full article ">Figure 9
<p>The relationship between the (<b>a</b>) burial depth, (<b>b</b>) minimum horizontal stress, and permeabilities of coal seams in the Dacun Block.</p> Full article ">Figure 10
<p>The relationship between the (<b>a</b>) reservoir pressure, (<b>b</b>) reservoir pressure coefficient, and depth of coal seams in the Dacun Block.</p> Full article ">Figure 11
<p>The relationship between the (<b>a</b>) R<span class="html-italic"><sub>o,max</sub></span>, (<b>b</b>) depth, and Langmuir volumes (V<sub>L</sub>) of coals in the Dacun Block.</p> Full article ">Figure 12
<p>The relationship between the (<b>a</b>) gas contents, (<b>b</b>) reservoir pressure, and gas saturations of coals in the Dacun Block.</p> Full article ">Figure 13
<p>The relationship between the gas content and the critical desorption pressure (<span class="html-italic">p<sub>cd</sub></span>) of the coal reservoir in the Dacun Block.</p> Full article ">
17 pages, 4768 KiB  
Article
Modal Derivatives for Efficient Vibration Prediction of Geometrically Nonlinear Structures with Friction Contact
by Fahimeh Mashayekhi and Stefano Zucca
Appl. Sci. 2024, 14(9), 3936; https://doi.org/10.3390/app14093936 - 5 May 2024
Cited by 3 | Viewed by 1275
Abstract
This paper evaluates the performance of the Rubin reduction methods, enhanced with static modal derivatives, for vibration analysis of geometrically nonlinear structures with friction contact. Static modal derivatives are computed numerically based on Rubin reduction, which includes free interface normal modes and residual [...] Read more.
This paper evaluates the performance of the Rubin reduction methods, enhanced with static modal derivatives, for vibration analysis of geometrically nonlinear structures with friction contact. Static modal derivatives are computed numerically based on Rubin reduction, which includes free interface normal modes and residual flexibility attachment modes, by introducing a finite displacement around these modes. Then, the most relevant static modal derivatives are selected using an improved strategy that incorporates weighting factors derived from both a nonlinear static analysis and a geometrically linear transient run. This enhanced Rubin method is also compared with the previously used enhanced Craig–Bampton method, which is based on fixed normal modes, constraint modes, and their static derivatives. The effectiveness of these methods is demonstrated through vibration analysis of a geometrically nonlinear beam in different contact configurations. Both methods proved their robustness, achieving accurate results with a relatively small number of modes in the reduced space, thus ensuring low online computation times. Furthermore, the analyses show the significant impact of using a geometrically nonlinear model on the accurate prediction of a contact state. Full article
(This article belongs to the Special Issue Advances in Nonlinear Vibration: Modeling, Data-Based Methods and Applications)
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<p>Selection of modes to obtain projection basis.</p> Full article ">Figure 2
<p>Newmark time integration algorithm.</p> Full article ">Figure 3
<p>Model of a planar cantilever beam with friction contact at its end.</p> Full article ">Figure 4
<p>Frequency response function of the beam tip with four values of contact normal preload.</p> Full article ">Figure 5
<p>(<b>a</b>) Beam deformations, (<b>b</b>) contact normal displacement, and (<b>c</b>) the beam tip displacement in slip–liftoff configuration.</p> Full article ">Figure 6
<p>(<b>a</b>) Contact node states, (<b>b</b>) contact tangential, and (<b>c</b>) contact normal forces in slip-liftoff configuration (<math display="inline"><semantics> <msub> <mi>N</mi> <mn>0</mn> </msub> </semantics></math> = 40 N, Freq = 3.2 Hz).</p> Full article ">Figure 7
<p>(<b>a</b>) Contact node states, (<b>b</b>) contact tangential, and (<b>c</b>) contact normal forces with a geometrically linear model (<math display="inline"><semantics> <msub> <mi>N</mi> <mn>0</mn> </msub> </semantics></math> = 40 N, <math display="inline"><semantics> <mrow> <mi>F</mi> <mi>r</mi> <mi>e</mi> <mi>q</mi> </mrow> </semantics></math> = 3.2 Hz).</p> Full article ">Figure 8
<p>Response error and the size of reduction basis vs. the number of normal modes in slip–liftoff configuration (two load cases).</p> Full article ">Figure 9
<p>Accuracy of reduced models in response prediction to the size of reduced space in slip–liftoff configuration.</p> Full article ">Figure 10
<p>The transverse displacement (<b>left</b>) and the axial displacement (<b>right</b>) of the selected SMDs of free interface vibration modes and residual flexibility attachment modes.</p> Full article ">Figure 11
<p>The transverse displacement (<b>left</b>) and the axial displacement (<b>right</b>) of the selected SMDs of fixed interface vibration modes and constraint modes.</p> Full article ">Figure 12
<p>(<b>a</b>) Beam deformations, (<b>b</b>) contact normal displacement, and (<b>c</b>) the beam tip displacement in stick–slip configuration.</p> Full article ">Figure 13
<p>(<b>a</b>) Contact node states, (<b>b</b>) contact tangential, and (<b>c</b>) contact normal forces in stick-slip configuration.</p> Full article ">Figure 14
<p>Accuracy of reduced models in response prediction to the number of normal modes (<math display="inline"><semantics> <msub> <mi>N</mi> <mn>0</mn> </msub> </semantics></math> = 250 N and Excitation Frequency = 8.1 Hz).</p> Full article ">
14 pages, 2025 KiB  
Article
Facile Fabrication of Superhydrophobic and Superoleophilic Polyurethane Foil with Micropillar and Microporous Structures for Efficient Oil/Water Separation
by Weibin Wu, Mingjin Xu, Qinqin Wang, Xue Yang and Changgeng Shuai
Appl. Sci. 2024, 14(9), 3935; https://doi.org/10.3390/app14093935 - 5 May 2024
Cited by 1 | Viewed by 1054
Abstract
Oil spill cleanup in water remains a critical challenge due to the harmful secondary pollution from conventional methods such as burning or chemical degradation. Herein, we present a facile method to fabricate a superhydrophobic and superoleophilic polyurethane (PU) foil for efficient and environmentally [...] Read more.
Oil spill cleanup in water remains a critical challenge due to the harmful secondary pollution from conventional methods such as burning or chemical degradation. Herein, we present a facile method to fabricate a superhydrophobic and superoleophilic polyurethane (PU) foil for efficient and environmentally friendly oil/water separation. More specifically, micropillar arrays were embedded onto the foil surface through a nanoimprinting process. Microporous structures were generated at the foil cross-section by a supercritical carbon dioxide (CO2) saturation method. The dimensions of pillar and pore structures were optimized with the aim of boosting selective wetting (i.e., water repellency and oil attraction) properties. As a result, the developed PU foil shows an oil absorption efficiency nearly 4 times higher than a pristine reference. Moreover, the structured PU foil stably retains the absorbed oil for over a week, demonstrating an absorption capacity of nearly 400%, which is also much superior than the unstructured sample. Our concept of combining both topographical micropillars and cross-sectional micropores onto PU foil provides a novel approach for achieving efficient and environmental friendly oil/water separation. Full article
(This article belongs to the Special Issue Ultra-Precision Machining Technology and Equipments)
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<p>Schematic procedure of the developed approach for fabricating micropillar and microporous structures on PU foil. (<b>a</b>) Flat PU chip between two silicon templates. (<b>b</b>) The whole setup was put into a supercritical CO<sub>2</sub> environment for saturation. (<b>c</b>) Pressure quenching and depressurization caused CO<sub>2</sub> to nucleate into numerous tiny pores within the polymer. (<b>d</b>) Pore size grew (foaming) with CO<sub>2</sub> diffusion. (<b>e</b>) The resulting PU foil showed a micropillar array on the surface and micropores at the cross-section. (<b>f</b>) SEM image indicating the free layer (about 25 µm thickness) without pores below the pillars. (<b>g</b>) Post hole array in hexagonal lattice on the topography of the silicon template. (<b>h</b>) Specifications of micropillar array. (<b>i</b>) A photo of the fabricated PU foil. For clarity, the schematic foil in (<b>a</b>–<b>e</b>) is not to scale and the thickness decrease after nanoimprinting as well as the volume increase due to foaming is not shown.</p> Full article ">Figure 2
<p>SEM images of the topographical micropillar arrays as well as the cross-sectional microporous structures on the PU foil. Pillar spacings of (<b>a</b>) 5 μm, (<b>b</b>) 10 μm, and (<b>c</b>) 15 μm were fabricated. The respective height of pillars was tailored, resulting in aspect ratios of 2.5, 0.75, and 1. The imprinting condition for the three surfaces was the same (80 °C and 5 MPa for 1 min). With the cross-sectional samples, the average pore sizes (taken in the center of foil cross-section) amounted to (<b>d</b>) 50 µm, (<b>e</b>) 75 µm, and (<b>f</b>) 125 µm, obtained at the foaming pressures of 20 MPa, 18 MPa, and 16 MPa, respectively. The saturation temperature was the same for three samples (60 °C). The overall thicknesses of three foamed PU foils were also similar (approximately 1 mm).</p> Full article ">Figure 3
<p>Pore size distribution at the cross-section for three different PU foils. A similar Gaussian distribution pattern was observed for all samples, whereas the average pore size differed. The average value <span class="html-italic">μ</span> and its corresponding standard deviation <span class="html-italic">σ</span> of each dataset are shown in the legend. The dashed curve is the corresponding fitting trend to each dataset. The foaming pressures for samples showing pore sizes from small to large were 20 MPa, 18 MPa, and 16 MPa, respectively. The foaming temperature was 60 °C.</p> Full article ">Figure 4
<p>Picture of water (left column) and oil (right column) droplets on the PU foil. (<b>a</b>) Water and (<b>b</b>) oil contact angles on a flat PU surface. (<b>c</b>) Water and (<b>d</b>) oil contact angles on a micropillar surface. The pillar spacing is 5 μm. The respective height of the pillars is 5 μm, resulting in an aspect ratio of 1. (<b>e</b>) Water and (<b>f</b>) oil contact angles on microporous cross-section of a PU foil. The average pore size of the specific sample used in the experiment is around 126 μm. The droplet volume is 1 μL.</p> Full article ">Figure 5
<p>Influence of (<b>a</b>) micropillar spacing and (<b>b</b>) height/diameter ratio on the selective wetting property of PU foil. In (<b>a</b>) the pillar height is kept constant at 5 μm (i.e., <span class="html-italic">AR</span> = 1). In (<b>b</b>) the pillar spacing remains 5 μm on different samples. For each sample, three measurements were conducted at arbitrary positions. The average values and corresponding statistical error are shown as columns and error bars in the figure.</p> Full article ">Figure 6
<p>Water contact angle on the porous cross-section of PU foil with different pore sizes. The result of a bulk sample was plotted as a comparison. Each bar in the figure represents an average value from three arbitrary measurements. The error bar is the corresponding statistical error.</p> Full article ">Figure 7
<p>Time-lapse of the developed PU foil absorbing oil (in red) in water (in blue). The oil spill was completely removed within 10 s. A micropillar array of <span class="html-italic">s</span> = 5 μm and <span class="html-italic">AR</span> = 1 was fabricated on the foil surface. The average pore size at the foil cross-section of the specific sample used in this experiment was around 124.6 μm.</p> Full article ">Figure 8
<p>Oil absorption capacity plotted as a function of (<b>a</b>) pore size and (<b>b</b>) porosity at the cross-section of the structured PU foil. On all examined samples, a micropillar array of <span class="html-italic">s</span> = 5 μm and <span class="html-italic">AR</span> = 1 was fabricated on the surface. Each data point in the figure represents the measured absorption capacity of a newly fabricated, single-use foil. The foaming pressure for these foils ranged from 16 MPa to 20 MPa.</p> Full article ">Figure 9
<p>Comparison of oil absorbing performance between the structured and unstructured PU foils. (<b>a</b>) Absorption capacity and time. (<b>b</b>) Absorption capacity as a function of oil retention time within both foils. The time axis is plotted as a logarithmic scale in (<b>b</b>) for easy illustration. The structured foil possessed a micropillar array of <span class="html-italic">s</span> = 5 μm and <span class="html-italic">AR</span> = 1 on the surface. The mean pore size at the cross-section was characterized as around 130 μm. Both foils were stored under ambient conditions (25 °C, in air) during the long-term retention experiment. Each experiment was conducted with a new, single-use foil.</p> Full article ">
22 pages, 6228 KiB  
Article
Detecting Malicious Devices in IPSEC Traffic with IPv4 Steganography
by Gabriel Jekateryńczuk, Damian Jankowski, René Veyland and Zbigniew Piotrowski
Appl. Sci. 2024, 14(9), 3934; https://doi.org/10.3390/app14093934 - 5 May 2024
Viewed by 1434
Abstract
This study investigates the application of steganography for enhancing network security by detecting and promptly eliminating malicious packets to prevent flooding and consequent denial of service attacks while also identifying malicious equipment. The paper discusses foundational concepts such as the prisoner’s dilemma, covert [...] Read more.
This study investigates the application of steganography for enhancing network security by detecting and promptly eliminating malicious packets to prevent flooding and consequent denial of service attacks while also identifying malicious equipment. The paper discusses foundational concepts such as the prisoner’s dilemma, covert channels, qualitative metrics, and existing steganography techniques in computer communications. An architecture was developed to assess the effectiveness of this solution, and experiments were conducted, with their results presented. This contribution leverages established steganographic principles and seamlessly integrates with widely adopted IPsec protocols, offering a solution to improve covert communication within computer networks. Full article
(This article belongs to the Special Issue Emerging Technologies in Network Security and Cryptography)
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<p>Relationship between cryptography, steganography, and watermarking [<a href="#B4-applsci-14-03934" class="html-bibr">4</a>].</p> Full article ">Figure 2
<p>Prisoner’s dilemma.</p> Full article ">Figure 3
<p>Covert channels in ICT networks.</p> Full article ">Figure 4
<p>Relationships between qualitative measures.</p> Full article ">Figure 5
<p>Structure of packets for AH and ESP transport and tunnel modes.</p> Full article ">Figure 6
<p>ESP tunnel mode packet structure.</p> Full article ">Figure 7
<p>Normal traffic packets sequence.</p> Full article ">Figure 8
<p>Modified malicious traffic packet sequence.</p> Full article ">Figure 9
<p>The standard architecture of site-to-site IPsec connection over several networks.</p> Full article ">Figure 10
<p>Use case with two probes for controlling an IPsec flow with a hacker.</p> Full article ">Figure 11
<p>Use case with probes per inter-router link.</p> Full article ">Figure 12
<p>Message encoding/decoding per proximity to the router.</p> Full article ">Figure 13
<p>Use case with a mix of sender, listener, and relay probes.</p> Full article ">Figure 14
<p>Dashboards in Grafana.</p> Full article ">Figure 15
<p>Creating threshold alert in Grafana.</p> Full article ">Figure 16
<p>Notification for fired alert.</p> Full article ">Figure 17
<p>For example, MAC address interception output.</p> Full article ">Figure 18
<p>Network overhead test dashboard.</p> Full article ">
23 pages, 5523 KiB  
Article
Experimental Studies and Performance Characteristics Analysis of a Variable-Volume Heat Pump in a Ventilation System
by Anton Frik, Juozas Bielskus, Rasa Džiugaitė-Tumėnienė and Violeta Motuzienė
Appl. Sci. 2024, 14(9), 3933; https://doi.org/10.3390/app14093933 - 5 May 2024
Cited by 1 | Viewed by 1801
Abstract
Air-to-air heat pumps are used in today’s ventilation systems increasingly often as they provide heating and cooling for buildings. The energy transformation modes of these units are subject to constant change due to the varying outdoor air state, including temperature and humidity. When [...] Read more.
Air-to-air heat pumps are used in today’s ventilation systems increasingly often as they provide heating and cooling for buildings. The energy transformation modes of these units are subject to constant change due to the varying outdoor air state, including temperature and humidity. When choosing how to operate and control energy transformers, it is important to be able to adapt effectively to the changing outside air conditions. Nowadays, modern commercial heat pumps offer two levels of control flexibility: a compressor with a variable speed and an electronic expansion valve. This combination of control elements has boosted the seasonal energy efficiency of heat pumps. For a long time, cycle control possibilities have been dominated by electronic controls. The authors of this paper aim to present an additional element to the traditional heat pump controls, which provides a third level of control over the cycle. To achieve the objective, experimental investigations of a heat pump integrated into a ventilation unit have been carried out under real-life conditions. The experiments involved varying the operating modes of the unit by adjusting the compressor speed, the position of the expansion valve, and the volume of the system loop. The study examined the performance characteristics of the heat pump and found that the performance of a variable-volume heat pump is comparable to that of a conventionally operated typical constant-volume heat pump system. In addition, the study found that by adding a third level of volume control to the active heating circuit, in combination with conventional controls, the heat pump’s heat output range could be extended by 69.62%. The study determined the variation of the heat pump cycle in the p-h diagram with the variation of the loop volume. The benefits and drawbacks of a heat pump with a variable-volume loop are discussed in this study. Full article
(This article belongs to the Special Issue Energy Implications of Thermal Comfort in Buildings considering Climate Change)
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<p>The schematic diagram of a ventilation unit with an integrated heat pump.</p> Full article ">Figure 2
<p>The dependence of condensation, evaporation temperatures and the COP on the heating power of HP [<a href="#B49-applsci-14-03933" class="html-bibr">49</a>].</p> Full article ">Figure 3
<p>The schematic diagram of the experimental test bench with its main components.</p> Full article ">Figure 4
<p>A multi-stage volumetric enlarger for increasing the volume of a heat pump.</p> Full article ">Figure 5
<p>Digital photos of the experimental bench: (<b>a</b>) the experimental bench without thermal isolation and volume expansion; (<b>b</b>) the experimental bench with thermal isolation and a volume expansion unit.</p> Full article ">Figure 6
<p>The relationship between the compressor pressure ratio P<sub>1</sub>/P<sub>5</sub> and the flow rate (experimental data).</p> Full article ">Figure 7
<p>The relationship between the compressor pressure ratio and the flow rate (manufacturers’ data).</p> Full article ">Figure 8
<p>The relationship between the refrigerant flow rate and the evaporation temperature (experimental data).</p> Full article ">Figure 9
<p>The relationship between the refrigerant flow rate and the evaporation temperature (manufacturers’ data).</p> Full article ">Figure 10
<p>Heating power vs. flow rate (experimental data).</p> Full article ">Figure 11
<p>Heating power vs. flow rate (manufacturers’ data).</p> Full article ">Figure 12
<p>The heating power of the HP during the experiment.</p> Full article ">Figure 13
<p>The COP during the experiment.</p> Full article ">Figure 14
<p>The dependence of the heat pump parameters on the outside air temperature: (<b>a</b>) heating power vs. outdoor air temperature; (<b>b</b>) COP vs. the outdoor air temperature.</p> Full article ">Figure 15
<p>The operation cycles of the HP in a <span class="html-italic">p-h</span> diagram (compressor speeds: 1800 and 2220 rpm; expansion valve capacity: 70%; volume: V0).</p> Full article ">Figure 16
<p>The operation cycles of the HP in a <span class="html-italic">p-h</span> diagram (compressor speed: 2100 rpm; expansion valve capacity: 30, 50, 70%; volume: V0).</p> Full article ">Figure 17
<p>The operation cycles of the HP in a <span class="html-italic">p-h</span> diagram (compressor speed: 1800 rpm; expansion valve capacity: 30%; volumes: V0, V1, V2, V3).</p> Full article ">
12 pages, 664 KiB  
Article
The Aerodynamics of New Design Soccer Balls Using a Three-Dimensional Printer
by Sungchan Hong, John Eric Goff and Takeshi Asai
Appl. Sci. 2024, 14(9), 3932; https://doi.org/10.3390/app14093932 - 5 May 2024
Viewed by 1226
Abstract
Eight balls were manufactured with a 3D printer to resemble various types of 32-panel soccer balls. One ball was completely smooth, whereas the other seven possessed various dimple patterns on their surface panels. Seam width and seam depth were also varied. Wind-tunnel experiments [...] Read more.
Eight balls were manufactured with a 3D printer to resemble various types of 32-panel soccer balls. One ball was completely smooth, whereas the other seven possessed various dimple patterns on their surface panels. Seam width and seam depth were also varied. Wind-tunnel experiments were performed to extract aerodynamic coefficients, and also to determine the critical Reynolds number for each manufactured ball. A new surface roughness parameter is introduced, and a fitting formula is presented, which allows for the prediction of the critical Reynolds number if the new parameter is known. Full article
(This article belongs to the Special Issue Advances in Unsteady Aerodynamics and Aeroelasticity)
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<p>Eight balls manufactured by 3D printer.</p> Full article ">Figure 2
<p>Schematic illustration (not to scale) of the distance between neighboring dimples, <span class="html-italic">b</span>, dimple width, <span class="html-italic">c</span>, and dimple depth, <span class="html-italic">k</span>, for the three types of dimples on six of the manufactured balls.</p> Full article ">Figure 3
<p>Schematic illustration (not to scale) of the radius of curvature, <math display="inline"><semantics> <msub> <mi>r</mi> <mi>s</mi> </msub> </semantics></math>, seam width, <math display="inline"><semantics> <msub> <mi>c</mi> <mi>s</mi> </msub> </semantics></math>, and seam depth, <math display="inline"><semantics> <msub> <mi>k</mi> <mi>s</mi> </msub> </semantics></math>, for seven of the manufactured balls.</p> Full article ">Figure 4
<p>Wind tunnel experimental setup.</p> Full article ">Figure 5
<p>Drag coefficients of manufactured balls versus Reynolds number. Also shown for comparison are drag data for an actual soccer ball, the Telstar 18 [<a href="#B6-applsci-14-03932" class="html-bibr">6</a>].</p> Full article ">Figure 6
<p>Comparison between data and fitting equation, given by Equation (<a href="#FD6-applsci-14-03932" class="html-disp-formula">6</a>). Letters next to points correspond to the ball labels given in <a href="#applsci-14-03932-f001" class="html-fig">Figure 1</a>.</p> Full article ">
19 pages, 15358 KiB  
Article
Graphic Reconstruction of a Roman Mosaic with Scenes of the Abduction of Europa
by Gregor Oštir, Dejana Javoršek, Primož Stergar, Tanja Nuša Kočevar, Aleksandra Nestorović and Helena Gabrijelčič Tomc
Appl. Sci. 2024, 14(9), 3931; https://doi.org/10.3390/app14093931 - 5 May 2024
Cited by 1 | Viewed by 1631
Abstract
This paper presents the reconstruction framework of the Roman mosaic with the central scene from the abduction of Europa. The mosaic depicting Europa, discovered in Ptuj (Slovenia) and dated from the second half of the third to the beginning of the fourth century [...] Read more.
This paper presents the reconstruction framework of the Roman mosaic with the central scene from the abduction of Europa. The mosaic depicting Europa, discovered in Ptuj (Slovenia) and dated from the second half of the third to the beginning of the fourth century AD, once decorated the representative room of a Roman villa. The experimental section addresses the materials and methods used in the 2D reconstruction of the mosaic, including the creation of line drawings of the mosaic based on the preserved part of the mosaic, photogrammetric acquisition, and the creation and processing of 1:1 raster reconstructions of the entire mosaic. This is followed by color management and interpretation approaches which allow the mosaic elements to be implemented in a 3D animation. The presented approaches could be implemented in the reconstruction process of other mosaics and archaeological objects with adaptations to the specifics of related objects. Full article
(This article belongs to the Special Issue Advanced Technologies in Digitizing Cultural Heritage Volume II)
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<p>Mosaic with the scene of the abduction of Europa exhibited in the Universalmuseum Joanneum in Graz (photo: Barbara Porod).</p> Full article ">Figure 2
<p>Close-up of the mosaic with the scene of the abduction of Europa (photo: Aleksandra Nestorović).</p> Full article ">Figure 3
<p>Reconstruction workflow.</p> Full article ">Figure 4
<p>Reference mosaic line drawing reconstruction (<b>upper left</b>) by Nejka Uršič and reconstructed vector plot (<b>upper right</b>) after Djurić, outlines of the preserved mosaic on the foil in actual dimensions (<b>bottom left</b>) and the process of vector drawing based on the notes on the foil 1:1 by Nejka Uršič (<b>bottom right</b>).</p> Full article ">Figure 5
<p>Vector drawing of the entire mosaic with a superimposed photo of the original (<b>left</b>) and details (<b>right</b>).</p> Full article ">Figure 6
<p>Reference points around the mosaic.</p> Full article ">Figure 7
<p>Generated dense point cloud from photos in Agisoft Metashape (<b>left</b>) and created digital elevation map (DEM) in Agisoft Metashape (<b>right</b>) which displays the different rectangular surfaces of the mosaic, probably after the restoration intervention of the relocation of the mosaic.</p> Full article ">Figure 8
<p>Representative colors of the mosaic.</p> Full article ">Figure 9
<p>Comparison of photos of the mosaic without (<b>left</b>) and with the attached color profile (<b>right</b>) (photo: Primož Stergar).</p> Full article ">Figure 10
<p>Example of mapping and attempt to match the original.</p> Full article ">Figure 11
<p>Key steps of raster reconstruction, (<b>a</b>) upper original half of the mosaic, (<b>b</b>) reconstruction of the right side, (<b>c</b>) added triangle (one of the four), (<b>d</b>) added frame border with a multi-colored doublestrand guilloche, the black band and a white frame band, (<b>e</b>) reconstructed right part of the mosaic, (<b>f</b>) mapping of the preserved part of the mosaic on the left side, (<b>g</b>–<b>i</b>) reworking of the left part with the addition of the missing triangle and the missing part of the multi-colored doublestrand guilloche of the central field with a figurative scene, (<b>j</b>) improvement of the final product, (<b>k</b>,<b>l</b>) cleaning up the damage on the white frame band.</p> Full article ">Figure 12
<p>The final digital graphic reconstruction of the entire mosaic.</p> Full article ">Figure 13
<p>A darker band of tesserae probably caused by the continuous shadow casting on the mosaic by the ceiling of the museum (<b>left,</b> marked with blue box) and visual artifacts on the surface of the lower left part of the mosaic (<b>right,</b> marked with blue box).</p> Full article ">Figure 14
<p>Video frames of the interpretative animation with the reconstruction procedure: (<b>a</b>) line drawing of the preserved part of the mosaic with the central scene of the abduction of Europa; (<b>b</b>) a photo of the mosaic with a simple line drawing; (<b>c</b>) a photo of the mosaic with a partially completed line drawing; (<b>d</b>) a photo of the mosaic with completed simple line drawing; (<b>e</b>) a photo of the mosaic with a schematic reconstruction of the details; (<b>f</b>) schematic reconstruction of the mosaic with the central scene of the abduction of Europa, the whole with all details (author of illustrations and color graphic reproduction: Gregor Oštir, author of the video: Anže Mrak).</p> Full article ">Figure 15
<p>Video frames with the interpretative 3D animation—(<b>top</b>), and 3D procedural approach with particles—(<b>bottom</b>) (author of illustrations and color graphic reproduction: Gregor Oštir, video author: Anže Mrak).</p> Full article ">
10 pages, 1367 KiB  
Article
Thymic Hyperplasia and COVID-19 Pulmonary Sequelae: A Bicentric CT-Based Follow-Up Study
by Michaela Cellina, Maurizio Cè, Andrea Cozzi, Simone Schiaffino, Deborah Fazzini, Enzo Grossi, Giancarlo Oliva, Sergio Papa and Marco Alì
Appl. Sci. 2024, 14(9), 3930; https://doi.org/10.3390/app14093930 - 5 May 2024
Viewed by 1573
Abstract
This study aimed to investigate the role of the thymus in influencing long-term outcomes of COVID-19 by comparing the thymic appearance in patients with and without COVID-19 pulmonary sequelae at chest computed tomography (CT). A total of 102 adult patients previously hospitalized for [...] Read more.
This study aimed to investigate the role of the thymus in influencing long-term outcomes of COVID-19 by comparing the thymic appearance in patients with and without COVID-19 pulmonary sequelae at chest computed tomography (CT). A total of 102 adult patients previously hospitalized for COVID-19 underwent a follow-up chest CT three months after discharge. Pulmonary sequelae and thymic appearance were independently assessed by two experienced radiologists. The thymus was detectable in 55/102 patients (54%), with only 7/55 (13%) having any kind of pulmonary sequelae, compared to 33 out of 47 (70%, p < 0.001) in patients without thymic visibility, as confirmed in age-stratified analysis and at logistic regression analysis, where thymic involution had a 9.3 odds ratio (95% CI 3.0–28.2, p < 0.001) for the development of pulmonary sequelae. These results support the hypothesis that thymic reactivation plays a protective role against adverse long-term outcomes of COVID-19. Full article
(This article belongs to the Special Issue Medical Imaging for Radiotherapy)
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<p>(<b>a</b>) Mediastinal window showing a grade 2 T score, with approximately 50% of the thymus with fatty involution and 50% characterized by soft-tissue-attenuated tissue. No pulmonary alterations are visible on the lung parenchyma CT reconstruction (<b>b</b>).</p> Full article ">Figure 2
<p>Complete fatty involution of the thymus, visible in the mediastinal window (<b>a</b>). With the lung parenchyma reconstruction algorithm (<b>b</b>), a grade 5 pulmonary sequelae score is visible as bilateral ground-glass opacities involving more than 50% of pulmonary parenchyma with the coexistence of crazy paving aspects.</p> Full article ">Figure 3
<p>Partial fatty involution of the thymus, visible in the mediastinal window (<b>a</b>), associated with mild parenchymal abnormalities graded as pulmonary sequelae score 2, in parenchymal reconstructions (panels <b>b</b>,<b>c</b>).</p> Full article ">Figure 4
<p>Study flowchart. Red lines represent dichotomization thresholds.</p> Full article ">Figure 5
<p>Follow-up unenhanced chest CT images of a 64-year-old (panels <b>a</b>,<b>b</b>) and a 65-year-old (panels <b>c</b>,<b>d</b>) male patient. The first patient had a complete fat involution of the thymus on the mediastinal window (<b>a</b>); coronal multiplanar reconstruction with lung parenchymal window shows bilateral persistence of ground-glass opacities involving &lt;50% of pulmonary parenchyma (<b>b</b>). The second patient showed a well-identifiable thymus with partial fat involution (<b>c</b>), without any sign of parenchymal sequelae (<b>d</b>).</p> Full article ">
16 pages, 5346 KiB  
Article
Solvothermal Treatment of Micron-Sized Commercial SrAl2O4:Eu2+, Dy3+ Phosphors and One-Step Preparation of Nanophosphors for Fingerprint Imaging
by Rungang Liu, Xueting Liu, Weikai Lin and Yingliang Liu
Appl. Sci. 2024, 14(9), 3929; https://doi.org/10.3390/app14093929 - 4 May 2024
Cited by 1 | Viewed by 1539
Abstract
Preparing submicron and nanoscale phosphors with good optical properties for practical applications is a challenging task for current inorganic long afterglow luminescent materials. This study utilized commercialized SrAl2O4:Eu2+, Dy3+ phosphors (SAOED) as raw materials and employed [...] Read more.
Preparing submicron and nanoscale phosphors with good optical properties for practical applications is a challenging task for current inorganic long afterglow luminescent materials. This study utilized commercialized SrAl2O4:Eu2+, Dy3+ phosphors (SAOED) as raw materials and employed solvents with lower polarity or non-polar solvents for dynamic solvothermal treatment. The commercialized phosphor’s overall average particle size was reduced from 42.3 μm to 23.6 μm while maintaining the fluorescence intensity at 91.39% of the original sample. Additionally, the study demonstrated the applicability of the dynamic solvothermal method to most other commercialized inorganic phosphors. The experiment produced a high-brightness nano-sized phosphor with a yield of 5.64%. The average diameter of the phosphor was 85 nm, with an average thickness of 16 nm. The quantum efficiency of the phosphor was 74.46% of the original sample. The fingerprint imaging results suggest that the nano-sized phosphors have potential for practical applications. Full article
(This article belongs to the Section Applied Thermal Engineering)
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<p>(<b>a</b>) X-ray diffraction (XRD) patterns of original phosphors and S-phosphor. (<b>b</b>) X-ray photoelectron spectroscopy (XPS) pattern of S-phosphor. (<b>c</b>) Energy dispersive analysis (EDS) pattern of S-phosphor. (<b>d</b>) Selective area electron diffraction (SAED) pattern of S-phosphor. (<b>e</b>) Scanning electron microscopy (SEM) image of original phosphors. (<b>f</b>) SEM image of S-phosphor.</p> Full article ">Figure 2
<p>Size distribution of: (<b>a</b>) Original phosphor and (<b>b</b>) S-phosphor.</p> Full article ">Figure 3
<p>(<b>a</b>) Excitation spectra, (<b>b</b>) emission spectra, and (<b>c</b>) afterglow decay curves of original phosphors and S-phosphor.</p> Full article ">Figure 4
<p>Scanning electron microscopy (SEM) images of cracks appearing during the reaction process. (<b>a</b>) Untreated commercial phosphor; (<b>b</b>) 1 h; (<b>c</b>) 4 h; (<b>d</b>) 8 h; (<b>e</b>) 12 h; (<b>f</b>) 24 h; (<b>g</b>–<b>i</b>) block tearing surface.</p> Full article ">Figure 5
<p>Crushing mechanism of block phosphor.</p> Full article ">Figure 6
<p>Before and after reaction. (<b>a</b>) Emission spectra of SrAl<sub>2</sub>O<sub>4</sub>:Eu<sup>2+</sup>, Dy<sup>3+</sup> phosphors (SAOED) with different particle sizes. (<b>b</b>–<b>d</b>) Size distribution of SAOED with different particle sizes. Emission spectra of (<b>e</b>) Sr<sub>4</sub>Al<sub>14</sub>O<sub>25</sub> and (<b>f</b>) Sr<sub>2</sub>MgSi<sub>2</sub>O<sub>7</sub>. Size distribution of (<b>g</b>) Sr<sub>4</sub>Al<sub>14</sub>O<sub>25</sub> and (<b>h</b>) Sr<sub>2</sub>MgSi<sub>2</sub>O<sub>7</sub>.</p> Full article ">Figure 7
<p>Scanning electron microscopy (SEM) images of surface morphology change of bulk phosphor after solvent thermal reaction with different reaction times. (<b>a</b>) Untreated commercial phosphor; (<b>b</b>) 4 h; (<b>c</b>) 12 h; (<b>d</b>) 18 h; (<b>e</b>) 24 h; (<b>f</b>) 48 h.</p> Full article ">Figure 8
<p>Scanning electron microscopy (SEM) image of phosphor after ultrasonic dispersion. (<b>a</b>,<b>b</b>) Overall morphology of block phosphor. (<b>c</b>,<b>d</b>) Surface morphology of block phosphor. (<b>e</b>) Needle phosphor extracted by ultrasound. (<b>f</b>) Block phosphor after extraction of needle phosphor.</p> Full article ">Figure 9
<p>(<b>a</b>) X-ray diffraction (XRD) spectra of the nanophosphor; (<b>b</b>) energy dispersive analysis (EDS) spectra of the nanophosphor; (<b>c</b>) X-ray photoelectron spectroscopy (XPS) spectra of the nanophosphor; (<b>d</b>) lattice fringes of the nanophosphor (insets are diffractograms); (<b>e</b>–<b>g</b>) HRTEM images of the nanophosphor; (<b>h</b>,<b>i</b>) atomic force microscopy (AFM) images of the nanophosphor.</p> Full article ">Figure 10
<p>(<b>a</b>) Variable temperature emission spectrum. (<b>b</b>) Temperature-dependent emission intensity in the range of 325–460 K. (<b>c</b>) Quantum efficiency plot. (<b>d</b>) Emission spectrum. (<b>e</b>) Room temperature afterglow decay curve. (<b>f</b>) Variable temperature phosphorescence emission spectroscopy. (<b>g</b>) Afterglow intensity at different temperatures.</p> Full article ">Figure 11
<p>Fingerprint imaging applications.</p> Full article ">
20 pages, 1827 KiB  
Article
Efficient Crowd Anomaly Detection Using Sparse Feature Tracking and Neural Network
by Sarah Altowairqi, Suhuai Luo, Peter Greer and Shan Chen
Appl. Sci. 2024, 14(9), 3928; https://doi.org/10.3390/app14093928 - 4 May 2024
Cited by 3 | Viewed by 2042
Abstract
Crowd anomaly detection is crucial in enhancing surveillance and crowd management. This paper proposes an efficient approach that combines spatial and temporal visual descriptors, sparse feature tracking, and neural networks for efficient crowd anomaly detection. The proposed approach utilises diverse local feature extraction [...] Read more.
Crowd anomaly detection is crucial in enhancing surveillance and crowd management. This paper proposes an efficient approach that combines spatial and temporal visual descriptors, sparse feature tracking, and neural networks for efficient crowd anomaly detection. The proposed approach utilises diverse local feature extraction methods, including SIFT, FAST, and AKAZE, with a sparse feature tracking technique to ensure accurate and consistent tracking. Delaunay triangulation is employed to represent the spatial distribution of features in an efficient way. Visual descriptors are categorised into individual behaviour descriptors and interactive descriptors to capture the temporal and spatial characteristics of crowd dynamics and behaviour, respectively. Neural networks are then utilised to classify these descriptors and pinpoint anomalies, making use of their strong learning capabilities. A significant component of our study is the assessment of how dimensionality reduction methods, particularly autoencoders and PCA, affect the feature set’s performance. This assessment aims to balance computational efficiency and detection accuracy. Tests conducted on benchmark crowd datasets highlight the effectiveness of our method in identifying anomalies. Our approach offers a nuanced understanding of crowd movement and patterns by emphasising both individual and collective characteristics. The visual and local descriptors facilitate high-level analysis by closely relating to semantic information and crowd behaviour. The analysis observed shows that this approach offers an efficient framework for crowd anomaly detection, contributing to improved crowd management and public safety. The proposed model achieves accuracy of 99.5 %, 96.1%, 99.0% and 88.5% in the UMN scenes 1, 2, and 3 and violence in crowds datasets, respectively. Full article
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<p>A schematic representation of the proposed approach.</p> Full article ">Figure 2
<p>Spatial proximity using Delaunay triangulation to better represent the neighbourhood. (<b>a</b>,<b>b</b>) represent Delaunay triangles on crowd scenes with no abnormal activities. (<b>c</b>) represents Delaunay triangles on crowd scene with abnormal activity. Green lines: Delaunay triangle edges, structuring crowd area. Red dots: indicate anomaly hotspots in crowd dynamics.</p> Full article ">Figure 3
<p>Summary of the performance of CAD on the UMN dataset (<b>a</b>–<b>c</b>) and on violence in crowds (<b>d</b>) using the SIFT, FAST, and AKAZE descriptors.</p> Full article ">
13 pages, 2025 KiB  
Article
Evaluation of Antimutagenic and Antioxidant Properties in Fomes fomentarius L.: Potential Development as Functional Food
by Chang-Gyun Park and Heung-Bin Lim
Appl. Sci. 2024, 14(9), 3927; https://doi.org/10.3390/app14093927 - 4 May 2024
Cited by 2 | Viewed by 1813
Abstract
Numerous studies derived from medicinal herbs have been conducted to explore bioactive compounds as potential alternatives to synthetic drugs, aiming to mitigate harmful side effects and alleviate economic burdens. In this study, we assessed the safety and potential biological activities of extracts from [...] Read more.
Numerous studies derived from medicinal herbs have been conducted to explore bioactive compounds as potential alternatives to synthetic drugs, aiming to mitigate harmful side effects and alleviate economic burdens. In this study, we assessed the safety and potential biological activities of extracts from Fomes fomentarius L. (FFL). The FFL extracts were obtained through various ethanol concentrations, as follows: 0%, 30%, 50%, 70%, and 100%, respectively. All extracts did not induce mutagenicity even up to 5 mg/plate concentration. In the assessment of antioxidant activity, only the hot water extract exhibited weaker antioxidant activity than the other ethanol extracts. Notably, all extracts exhibited significant antimutagenetic effects only with a metabolically active enzyme system (S9 mix). The condition of 70% ethanol extract displayed the most robust antimutagenic activity; thus, the extract was sequentially fractionated with solvents of varying polarities to isolate inhibitory components. After the fractionization, the diethyl ether and butanol fractions effectively suppressed the growth of mutated colonies, suggesting that those such as essential oils, vitamins, alkaloids, and flavonoids can be considered major active compounds. Overall, our study demonstrated that FFL extracts induce potent antioxidant and antimutagenic effects. Further investigations are warranted to verify specific active compounds which induce an antimutagenic effect. Our findings provide valuable insights into FFL as a promising source for potential functional food development. Full article
(This article belongs to the Special Issue Advances in Biological Activities of Natural Products)
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<p>Procedure and yields for solvent fractionations.</p> Full article ">Figure 2
<p>Mutagenicity activity of two strains by FFL extracts in the presence and absence of S9 mix; (<b>a</b>,<b>b</b>) TA98 strain; (<b>c</b>,<b>d</b>) TA100 strain. The number of spontaneous revertant colonies is shown as means ± SD.</p> Full article ">Figure 3
<p>The antioxidant activities of the <span class="html-italic">Fomes fomentarius</span> L. (FFL) extracts. The activities were assessed through (<b>a</b>) DPPH free radical scavenging, (<b>b</b>) ABTS total antioxidant capacity, and (<b>c</b>) DTT activity. Different letters (a–c, A–C, and <span class="html-italic">a</span>–<span class="html-italic">c</span>) in the same concentrations are significantly different at <span class="html-italic">p</span> &lt; 0.05 by Duncan’s test. The data are shown as means ± SD. AC: ascorbic acid.</p> Full article ">Figure 4
<p>Antimutagenicity effects of two strains by FFL extracts in the presence and absence of S9 mix; (<b>a</b>,<b>b</b>) TA98 strain; (<b>c</b>,<b>d</b>) TA100 strain. The inhibitory effect was tested using the mutagens (4-nitroquinoline-1-oxide (4NQO), sodium azide (SA), and 2-aminoanthracene (2-AA)). For the indirect mutation (+S9 mix), 2-AA was applied at 0.5 μg/plate. For the direct mutation (−S9 mix), 4NQO (TA98) and SA (TA100) were applied at 1.0 and 0.5 μg/plate, respectively. The inhibition rate is shown as means ± SD.</p> Full article ">Figure 5
<p>Antimutagenicity effects of two strains by the fractionized FFL extracts in the presence of the S9 mix; (<b>a</b>) TA98 strain; (<b>b</b>) TA100 strain. The inhibitory effect was tested using 2-aminoanthracene (2-AA; 0.5 μg/plate). The inhibition rate is shown as means ± SD.</p> Full article ">
15 pages, 4761 KiB  
Article
Transverse Spin Hall Effect and Twisted Polarization Ribbons at the Sharp Focus
by Victor V. Kotlyar, Alexey A. Kovalev, Alexey M. Telegin, Elena S. Kozlova, Sergey S. Stafeev, Alexander Kireev, Kai Guo and Zhongyi Guo
Appl. Sci. 2024, 14(9), 3926; https://doi.org/10.3390/app14093926 - 4 May 2024
Viewed by 1042
Abstract
In this work, using a Richards-Wolf formalism, we derive explicit analytical relationships to describe vectors of the major and minor axes of polarization ellipses centered in the focal plane when focusing a cylindrical vector beam of integer order n. In these beams, the [...] Read more.
In this work, using a Richards-Wolf formalism, we derive explicit analytical relationships to describe vectors of the major and minor axes of polarization ellipses centered in the focal plane when focusing a cylindrical vector beam of integer order n. In these beams, the major axis of a polarization ellipse is found to lie in the focal plane, with the minor axis being perpendicular to the focal plane. This means that the polarization ellipse is perpendicular to the focal plane, with its polarization vector rotating either clockwise or anticlockwise and forming “photonic wheels”. Considering that the wave vector is also perpendicular to the focal plane, we conclude that the polarization ellipse and the wave vector are in the same plane, so that at some point these can coincide, which is uncharacteristic of transverse electromagnetic oscillations. In a cylindrical vector beam, the spin angular momentum vector lies in the focal plane, so when making a circle centered on the optical axis, at some sections, the handedness of the spin vector and circular motion are the same, being opposite elsewhere. This effect may be called an azimuthal transverse spin Hall effect, unlike the familiar longitudinal spin Hall effect found at the sharp focus. The longitudinal spin Hall effect occurs when opposite-sign longitudinal projections of the spin angular momentum vector are spatially separated in the focal plane. In this work, we show that for the latter, there are always an even number of spatially separated regions and that, when making an axis-centered circle, the major-axis vector of polarization ellipse forms a two-sided twisted surface with an even number of twists. Full article
(This article belongs to the Section Optics and Lasers)
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<p>Intensity distribution (a slightly elliptical white-yellow-red ring) and projections of polarization ellipses onto the focal plane for the original field (1), describing a horizontally linearly polarized optical vortex (<span class="html-italic">n</span> = 3). In-ellipse arrows mark the direction of the major axis of the polarization ellipse. Blue ellipses correspond to the left-handed circular polarization and negative longitudinal SAM projection (<span class="html-italic">S<sub>z</sub></span> &lt; 0), with red ellipses corresponding to right-handed circular polarization and positive longitudinal spin (<span class="html-italic">S<sub>z</sub></span> &gt; 0).</p> Full article ">Figure 2
<p>Intensity pattern (squeezed white-yellow-red ring) across the tight focus from the original cylindrical second-order vector beam in (17) at <span class="html-italic">n</span> = 2 and polarization ellipse projections onto the focal plane. In-ellipse arrows show the direction of the polarization ellipse major axis. Note that with the polarization ellipses being perpendicular to the focal plane, their projections on the plane coincide with the arrows. Blue arrows mark left-handed circular polarization, and red ones mark right-handed circular polarization. The axes are plotted in microns.</p> Full article ">Figure 3
<p>An intensity pattern (marked white-yellow-red) at the focus of an azimuthally polarized field in (21) at topological charge <span class="html-italic">n</span> = 1 and a pattern of polarization ellipse distribution in the focal plane. The green arrows inside the ellipses mark the major axis vector. Red ellipses mark right-handed elliptic polarization (<span class="html-italic">S<sub>z</sub></span> &gt; 0), and blue ellipses mark left-handed elliptic polarization (<span class="html-italic">S<sub>z</sub></span> &lt; 0). The axes are plotted in microns.</p> Full article ">
21 pages, 1841 KiB  
Article
Hemp Flour as a Functional Ingredient for the Partial Replacement of Nitrites in a Minced Meat Model: Effect on Nutrient Composition, Antioxidant Profile and Sensory Characteristics
by Georgios Papatzimos, Paraskevi Mitlianga, Zoitsa Basdagianni and Eleni Kasapidou
Appl. Sci. 2024, 14(9), 3925; https://doi.org/10.3390/app14093925 - 4 May 2024
Cited by 3 | Viewed by 1264
Abstract
Consumers are becoming increasingly concerned about synthetic preservatives like nitrites in meat, prompting the meat industry to explore alternatives in order to lower nitrite levels. This study investigated the effects of incorporating hemp flour on the chemical and shelf-life characteristics of minced meat [...] Read more.
Consumers are becoming increasingly concerned about synthetic preservatives like nitrites in meat, prompting the meat industry to explore alternatives in order to lower nitrite levels. This study investigated the effects of incorporating hemp flour on the chemical and shelf-life characteristics of minced meat products with reduced nitrite content. Three types of products were prepared: HF0 (control) (0% hemp flour, 30 mg/kg NaNO2), HF4 (4% hemp flour, 15 mg/kg NaNO2), and HF6 (6% hemp flour, 15 mg/kg NaNO2). Analyses were conducted on proximate composition, fatty acid composition, antioxidant properties, lipid oxidation, colour, texture, and sensory characteristics. The addition of hemp flour at 6% reduced moisture content and influenced ash and sodium chloride levels in minced meat products. Despite the favorable fatty acid profile of hemp flour, its inclusion did not significantly alter the composition of the products. However, it did lead to significantly lower levels of lipid oxidation and modified the antioxidant capacity. Colour attributes were affected, with a higher hemp flour content resulting in colour deterioration. Cooking loss increased with a higher hemp flour content, and the minced meat products were significantly harder. Visual and olfactory sensory evaluation indicated that there were no significant differences in most traits, suggesting consumer acceptance of hemp-flour-enriched minced meat products. Overall, this study highlights the potential of hemp as a functional ingredient in minced meat products, also exhibiting the ability to reduce lipid oxidation. Full article
(This article belongs to the Special Issue Advances in Meat Quality and Processing)
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<p>Minced meat products on display day 1.</p> Full article ">Figure 2
<p>Total colour difference (Δ<span class="html-italic">E</span><sub>Lab</sub>) between control (HF0) and samples containing hemp flour (HF4 and HF6).</p> Full article ">Figure 3
<p>Taste panel scores for raw (<b>a</b>) and cooked (<b>b</b>) minced meat products.</p> Full article ">
14 pages, 2948 KiB  
Case Report
The Occurrence of a Rare Mandibular Retromolar Triangle Schwannoma and Its Differentiation from Other Rare and Atypical Oral Cavity Tumours
by Kamil Nelke, Maciej Janeczek, Edyta Pasicka, Krzysztof Żak, Szczepan Barnaś, Jan Nienartowicz, Grzegorz Gogolewski, Irma Maag and Maciej Dobrzyński
Appl. Sci. 2024, 14(9), 3924; https://doi.org/10.3390/app14093924 - 4 May 2024
Cited by 1 | Viewed by 1921
Abstract
Cone-beam computed tomography (CBCT) remains the diagnostic modality of choice. The involvement of the cortical bone and adjacent teeth can be easily established via CBCT. Magnetic resonance can be helpful in the estimation of any other soft-tissue tumour spread within this anatomical area. [...] Read more.
Cone-beam computed tomography (CBCT) remains the diagnostic modality of choice. The involvement of the cortical bone and adjacent teeth can be easily established via CBCT. Magnetic resonance can be helpful in the estimation of any other soft-tissue tumour spread within this anatomical area. The soft, hard-tissue, or mixed aetiology of tumours requires a differential diagnosis and accurate evaluation. If such pathologies arise, an adequate biopsy or incisional biopsy is essential to evaluate the type of tumour histopathologically. The occurrence of some neural tumours in the oral cavity is rare. Schwannomas (SCs), like some neuromas and other types of neural tumours, are rare and atypical. During clinical examination, a smooth, sponge-like, elastic mass could indicate other small salivary gland tumours rather than an oral neural tumour. Such pathologies of neural origins are quite rare and are uncommon findings in the oral cavity; therefore, their appearance may be conflated with other more typical benign or malignant tumours in the oral cavity. Establishing the status of bone via CBCT, the tooth involvement and the composition of the cortical bone may be helpful for establishing the best treatment of choice. The presented case report describes a rare schwannoma localised at the mandibular retromolar trigone. Full article
(This article belongs to the Special Issue Orthodontics and Maxillofacial Surgery)
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<p>Preoperative panx (panoramic radiograph) showing four fully visible retained wisdom teeth (18, 28, 38, 48) and no osteolytic changes in the right retromolar mandibular trigone. The impacted left mandibular wisdom teeth had a visible follicular-like cyst appearance surrounding the crown; the fully retained right wisdom teeth are fully embedded in the bone in an ankylotic-like manner, without any cysts, in direct proximity to the inferior alveolar nerve.</p> Full article ">Figure 2
<p>Intraoral photograph of the right mandibular retromolar trigone soft-tissue tumour.</p> Full article ">Figure 3
<p>Cone-beam computed tomography in the sagittal plane before biopsy. The superior part of the cortical bone remained clear and intact without any lesion or perforation.</p> Full article ">Figure 4
<p>Cone-beam computed tomography one month after biopsy. Half of the fully retained third molar is visible.</p> Full article ">Figure 5
<p>Intraoral photographs one month after the surgery.</p> Full article ">Figure 6
<p>A routine panoramic (panx) radiograph one year after revision surgery and extended radical removal of the schwannoma. Kinking of the inferior alveolar nerve canal is visible along with the remnants of the impacted third molar crown.</p> Full article ">Figure 7
<p>Intraoral photograph after three years. No tumour reoccurrences were present. Some tissue was scarce and contracted in the mandibular retromolar trigone area.</p> Full article ">Figure 8
<p>Cone-beam computed tomography with visible remnants of a fully retained crown of the lower wisdom teeth. No osteolytic, cystic, or inflammatory changes are visible in the bone or adjacent structures. The inferior alveolar nerve is visible in close proximity to the dental crown remnants.</p> Full article ">Figure 9
<p>Cone-beam computed tomography after three years in the sagittal plane showing good healing of the bone superiorly placed from the remnants of the molar crown. Adjacent second molars and adjacent bone without any radiological changes in their structure.</p> Full article ">
19 pages, 2803 KiB  
Article
Exploring Flexural Strength Variation in Polymeric Materials for Provisional Fixed Prosthetic Structures: Comparative Analysis with and without Reinforcement through Laboratory Experimentation and Statistical Evaluation
by Mariana Dimova-Gabrovska, Todor Uzunov, Angela Gusiyska, Dobromira Shopova, Iva Taneva, Ivan Gerdzhikov and Stefan Rangelov
Appl. Sci. 2024, 14(9), 3923; https://doi.org/10.3390/app14093923 - 4 May 2024
Cited by 1 | Viewed by 1185
Abstract
Provisional fixed partial dentures represent a critical phase in dental treatment, necessitating heightened mechanical durability, particularly in comprehensive and extended treatment plans. Strengthening these structures with various reinforcing materials offers a method to enhance their resilience. Utilizing a three-point testing methodology on standardized [...] Read more.
Provisional fixed partial dentures represent a critical phase in dental treatment, necessitating heightened mechanical durability, particularly in comprehensive and extended treatment plans. Strengthening these structures with various reinforcing materials offers a method to enhance their resilience. Utilizing a three-point testing methodology on standardized trial specimens allows for a comparative assessment of various materials and reinforcement techniques for pre-prosthetic applications. This study aims to validate and assess the significance of integrating different reinforcing materials into standardized test bodies. The study focuses on test specimens comprising three types of unreinforced laboratory and clinical polymers for provisional constructions (n = 6)—heat-cured PMMA (Superpont C+B, Spofa Dental, Czech Republic), CAD-CAM prefabricated PMMA (DD temp MED, Dental Direkt, Germany), CAD-CAM printing resin (Temporary CB Resin, FormLabs, USA), self-polymerizing PEMA (DENTALON plus, Kulzer, Germany), light-polymerizing composite (Revotek LC, GC, Japan), and dual-polymerizing composite (TempSpan, Pentron, USA). Additionally, laboratory polymers are evaluated in groups with five types of reinforcing filaments (n = 15)—Glass Fiber (Fiber Splint One-Layer, Polydentia, Switzerland), Polyethylene thread (Ribbond Regular 4.0 mm, Ribbond Inc., USA), triple-stranded chrome-cobalt wire for splinting 015″ (Leone S.p.a., Italy), Aesthetic ligature wire 012″ (Leone S.p.a., Italy), and Glass Fiber coated with light-cured composite 8.5 × 0.2 mm (Interlig, Angelus, Brazil). Analysis of the data using Generalized Linear Models (GLMs) reveals that the experimental bodies, produced via the subtractive digital method using PMMA (DD temp MED, Dental Direkt GmbH, Germany) as the polymer and glass filaments as the reinforcement, exhibit superior mechanical properties, particularly when pre-wetted with Interlig liquid composite (Angelus, Brazil). Full article
(This article belongs to the Section Applied Dentistry and Oral Sciences)
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<p>Preview of the appliance, utility model #4383 U1.</p> Full article ">Figure 2
<p>(<b>a</b>) A test specimen with a channel for manufacturing using CAM technologies; (<b>b</b>) cross section if the same object.</p> Full article ">Figure 3
<p>Effect of reinforcement types on flexural strength (FS/MPa).</p> Full article ">Figure 4
<p>Effect of reinforcement types on maximum strength before fracture (Fmax/N).</p> Full article ">Figure 5
<p>Effect of reinforcement types on modulus of elasticity (E/MPa).</p> Full article ">Figure 6
<p>Effect of polymer types on flexural strength (FS/MPa).</p> Full article ">Figure 7
<p>Effect of polymer types on maximum strength before fracture (Fmax/N).</p> Full article ">Figure 8
<p>Effect of polymer types on modulus of elasticity (E/MPa).</p> Full article ">
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