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31 pages, 12314 KiB  
Article
Utilizing Attention-Enhanced Deep Neural Networks for Large-Scale Preliminary Diabetes Screening in Population Health Data
by Hongwei Hu, Wenbo Dong, Jianming Yu, Shiyan Guan and Xiaofei Zhu
Electronics 2024, 13(21), 4177; https://doi.org/10.3390/electronics13214177 - 24 Oct 2024
Viewed by 802
Abstract
Early screening for diabetes can promptly identify potential early stage patients, possibly delaying complications and reducing mortality rates. This paper presents a novel technique for early diabetes screening and prediction, called the Attention-Enhanced Deep Neural Network (AEDNN). The proposed AEDNN model incorporates an [...] Read more.
Early screening for diabetes can promptly identify potential early stage patients, possibly delaying complications and reducing mortality rates. This paper presents a novel technique for early diabetes screening and prediction, called the Attention-Enhanced Deep Neural Network (AEDNN). The proposed AEDNN model incorporates an Attention-based Feature Weighting Layer combined with deep neural network layers to achieve precise diabetes prediction. In this study, we utilized the Diabetes-NHANES dataset and the Pima Indians Diabetes dataset. To handle significant missing values and outliers, group median imputation was applied. Oversampling techniques were used to balance the diabetes and non-diabetes groups. The data were processed through an Attention-based Feature Weighting Layer for feature extraction, producing a feature matrix. This matrix was subjected to Hadamard product operations with the raw data to obtain weighted data, which were subsequently input into deep neural network layers for training. The parameters were fine-tuned and the L2 regularization and dropout layers were added to enhance the generalization performance of the model. The model’s reliability was thoroughly assessed through various metrics, including the accuracy, precision, recall, F1 score, mean squared error (MSE), and R2 score, as well as the ROC and AUC curves. The proposed model achieved a prediction accuracy of 98.4% in the Pima Indians Diabetes dataset. When the test dataset was expanded to the large-scale Diabetes-NHANES dataset, which contains 52,390 samples, the test precision of the model improved further to 99.82%, with an AUC of 0.9995. A comparative analysis was conducted using multiple models, including logistic regression with L1 regularization, support vector machine (SVM), random forest, K-nearest neighbors (KNNs), AdaBoost, XGBoost, and the latest semi-supervised XGBoost. The feature extraction method using attention mechanisms was compared with the classical feature selection methods, Lasso and Ridge. The experiments were performed on the same dataset, and the conclusion was that the Attention-based Ensemble Deep Neural Network (AEDNN) outperformed all the aforementioned methods. These results indicate that the model not only performs well on smaller datasets but also fully leverages its advantages on larger datasets, demonstrating strong generalization ability and robustness. The proposed model can effectively assist clinicians in the early screening of diabetes patients. This is particularly beneficial for the preliminary screening of high-risk individuals in large-scale, extensive healthcare datasets, followed by detailed examination and diagnosis. Compared to the existing methods, our AEDNN model showed an overall performance improvement of 1.75%. Full article
(This article belongs to the Special Issue Advancements in Robotics: Perception, Manipulation, and Interaction)
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<p>Multi-head attention feature weighting module.</p>
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<p>The workflow and structure of the diabetes prediction system.</p>
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<p>The Pima Indians Diabetes dataset employs boxplot annotation for the identification of outliers.</p>
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<p>The Diabetes-NHANES dataset employs boxplot annotation for the identification of outliers.</p>
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<p>Scatter plots can visually display missing values and outliers.</p>
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<p>The histograms of the raw data, respectively, show the data distribution of the 8 features.</p>
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<p>The histograms of the imputed data, obtained after group median imputation, can be compared with the histograms of the raw data.</p>
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<p>Performance differences in the same algorithm on the same dataset under different data imputation methods.</p>
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<p>Attention-Enhanced Deep Neural Network.</p>
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<p>Attention-based Feature Weighting Layer.</p>
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<p>The 5-fold cross-validation process.</p>
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<p>The ROC curve of the baseline model (without attention).</p>
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<p>The ROC curve of the same model using raw data.</p>
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<p>Five cross-validation scores and mean CV scores.</p>
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<p>Performance comparison of the AEDNN model on the PIDD and the Diabetes-NHANES dataset.</p>
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<p>The ROC curve and AUC reached 0.99.</p>
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26 pages, 6394 KiB  
Article
Semi-Supervised Soft Computing for Ammonia Nitrogen Using a Self-Constructing Fuzzy Neural Network with an Active Learning Mechanism
by Hongbiao Zhou, Yang Huang, Dan Yang, Lianghai Chen and Le Wang
Water 2024, 16(20), 3001; https://doi.org/10.3390/w16203001 - 21 Oct 2024
Viewed by 672
Abstract
Ammonia nitrogen (NH3-N) is a key water quality variable that is difficult to measure in the water treatment process. Data-driven soft computing is one of the effective approaches to address this issue. Since the detection cost of NH3-N is [...] Read more.
Ammonia nitrogen (NH3-N) is a key water quality variable that is difficult to measure in the water treatment process. Data-driven soft computing is one of the effective approaches to address this issue. Since the detection cost of NH3-N is very expensive, a large number of NH3-N values are missing in the collected water quality dataset, that is, a large number of unlabeled data are obtained. To enhance the prediction accuracy of NH3-N, a semi-supervised soft computing method using a self-constructing fuzzy neural network with an active learning mechanism (SS-SCFNN-ALM) is proposed in this study. In the SS-SCFNN-ALM, firstly, to reduce the computational complexity of active learning, the kernel k-means clustering algorithm is utilized to cluster the labeled and unlabeled data, respectively. Then, the clusters with larger information values are selected from the unlabeled data using a distance metric criterion. Furthermore, to improve the quality of the selected samples, a Gaussian regression model is adopted to eliminate the redundant samples with large similarity from the selected clusters. Finally, the selected unlabeled samples are manually labeled, that is, the NH3-N values are added into the dataset. To realize the semi-supervised soft computing of the NH3-N concentration, the labeled dataset and the manually labeled samples are combined and sent to the developed SCFNN. The experimental results demonstrate that the test root mean square error (RMSE) and test accuracy of the proposed SS-SCFNN-ALM are 0.0638 and 86.31%, respectively, which are better than the SCFNN (without the active learning mechanism), MM, DFNN, SOFNN-HPS, and other comparison algorithms. Full article
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<p>Classification of semi-supervised learning.</p>
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<p>Active learning process.</p>
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<p>Topological structure of the FNN.</p>
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<p>The selection process for high-quality unlabeled samples.</p>
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<p>Diagram of fuzzy rule pruning.</p>
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<p>Flowchart of the SCFNN-DCP.</p>
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<p>Flowchart of the SS-SCFNN-ALM.</p>
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<p>Soft computing system for ammonia nitrogen.</p>
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<p>Nonlinear dynamics of input variables.</p>
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<p>Denoising effect of wavelet packet: (<b>a</b>) original NH<sub>3</sub>-N; and (<b>b</b>) NH<sub>3</sub>-N after denoising.</p>
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<p>Feature selection results: (<b>a</b>) the value of one-dimensional MI; and (<b>b</b>) the value of high-dimensional MI.</p>
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<p>DFNN with and without feature selection: (<b>a</b>) change in fuzzy rule number; and (<b>b</b>) prediction error.</p>
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<p>SCFNN-DCP with and without feature selection: (<b>a</b>) change in fuzzy rule number; and (<b>b</b>) prediction error.</p>
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<p>Prediction effect: (<b>a</b>) prediction results; and (<b>b</b>) prediction error.</p>
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<p>Changes in fuzzy rule number and training RMSE: (<b>a</b>) fuzzy rule number; and (<b>b</b>) training RMSE.</p>
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<p>Prediction results: (<b>a</b>) prediction output; (<b>b</b>) prediction error; (<b>c</b>) prediction output; and (<b>d</b>) prediction error.</p>
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<p>Prediction results of GPR model for unlabeled samples: (<b>a</b>) prediction output; and (<b>b</b>) cut-off.</p>
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<p>Prediction results of SS-SCFNN-ALM: (<b>a</b>) number of rules; (<b>b</b>) training RMSE; (<b>c</b>) prediction output; and (<b>d</b>) prediction error.</p>
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<p>Performance of SCFNN-DCP under different combinations: (<b>a</b>) test RMSE; and (<b>b</b>) fuzzy rule number.</p>
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<p>Performance of the SS-SCFNN-ALM under different combinations: (<b>a</b>) test RMSE; and (<b>b</b>) fuzzy rule number.</p>
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21 pages, 4851 KiB  
Article
A Semi-Supervised Method for Grain Boundary Segmentation: Teacher–Student Knowledge Distillation and Pseudo-Label Repair
by Yuanyou Huang, Xiaoxun Zhang, Fang Ma, Jiaming Li and Shuxian Wang
Electronics 2024, 13(17), 3529; https://doi.org/10.3390/electronics13173529 - 5 Sep 2024
Viewed by 864
Abstract
Grain boundary segmentation is crucial for the quantitative analysis of grain structures and material optimization. However, challenges persist due to noise interference, high labeling costs, and low detection Accuracy. Therefore, we propose a semi-supervised method called Semi-SRUnet, which is based on teacher–student [...] Read more.
Grain boundary segmentation is crucial for the quantitative analysis of grain structures and material optimization. However, challenges persist due to noise interference, high labeling costs, and low detection Accuracy. Therefore, we propose a semi-supervised method called Semi-SRUnet, which is based on teacher–student knowledge distillation and pseudo-label repair to achieve grain boundary detection for a small number of labels. Specifically, the method introduces SCConv (Spatial and Channel Reconstruction Convolution) and boundary regression to improve the U-Net (a convolutional neural network architecture) as a teacher network. These innovations aim to reduce spatial and channel redundancy, expand the receptive field, and effectively capture contextual information from images, thereby improving feature extraction robustness and boundary precision in noisy environments. Additionally, we designed a pseudo-label repair algorithm to enhance the Accuracy of pseudo-labels generated by the teacher network and used knowledge distillation to train a lightweight student network. The experimental results demonstrate that Semi-SRUnet achieves 88.86% mean Intersection over Union (mIoU), 96.64% mean Recall (mRecall), 91.5% mean Precision (mPrecision), and 98.77% Accuracy, surpassing state-of-the-art models and offering a novel approach for reliable grain boundary segmentation and analysis. Full article
(This article belongs to the Special Issue Applications of Artificial Intelligence in Computer Vision)
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<p>Grain boundary labeling (<b>a</b>) cropped portion of the OM image, (<b>b</b>) Labelme tool to label grain boundaries, (<b>c</b>) ground truth labeler.</p>
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<p>Overview of the Semi-SRUnet model.</p>
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<p>Teacher –student network: (<b>a</b>) SCConv structure, (<b>b</b>) SRUnet network structure.</p>
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<p>Effect of Algorithm 1: (<b>a</b>) skeleton extraction (white lines). (<b>b</b>) two-breakpoint connection (red lines), (<b>c</b>) breakpoint and fork point connection (red lines), (<b>d</b>) breakpoint extension (red lines), (<b>e</b>) grain boundary expansion and black–white inversion.</p>
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<p>Comparison of grain segmentation with supervised algorithms. From left to right are the OM images; manually labeled images, including the results of U-Net, UNet++, ResUNet++, DSCNet models; and the results of our Semi-SRUnet model. The orange rectangle in each image indicates the local zoomed-in region and the three local zoomed-in regions are placed to its right. The red circles, blue circles, and green circles in the magnified regions indicate noise points, boundary blur, and scratches, respectively.</p>
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<p>Comparison with semi-supervised algorithm for grain segmentation. From left to right are the OM images; manually labeled images, including the results of MT, UC-MT, SCC, and CLCC models; and the results of our Semi-SRUnet model. The red circles and blue rectangles in each image indicate the regions of noise points and scratches, respectively.</p>
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<p>Comparison with an unsupervised algorithm for grain segmentation. From left to right, the results are shown for metallographs, manually labeled images, and models such as Canny, R2V with regularization, Watershed Algorithm, and Semi-SRUnet. Red rectangles indicate defects.</p>
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<p>Comparison of the model’s predictions under different noise conditions is presented. The right side shows the zoomed-in region of the red rectangle in the original image. Below the cropped original image is the ground truth label, while to the right of the cropped original are the images with various added noise. Below each noisy image is the model’s prediction result.</p>
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17 pages, 1421 KiB  
Technical Note
Angle Estimation Using Learning-Based Doppler Deconvolution in Beamspace with Forward-Looking Radar
by Wenjie Li, Xinhao Xu, Yihao Xu, Yuchen Luan, Haibo Tang, Longyong Chen, Fubo Zhang, Jie Liu and Junming Yu
Remote Sens. 2024, 16(15), 2840; https://doi.org/10.3390/rs16152840 - 2 Aug 2024
Viewed by 875
Abstract
The measurement of the target azimuth angle using forward-looking radar (FLR) is widely applied in unmanned systems, such as obstacle avoidance and tracking applications. This paper proposes a semi-supervised support vector regression (SVR) method to solve the problem of small sample learning of [...] Read more.
The measurement of the target azimuth angle using forward-looking radar (FLR) is widely applied in unmanned systems, such as obstacle avoidance and tracking applications. This paper proposes a semi-supervised support vector regression (SVR) method to solve the problem of small sample learning of the target angle with FLR. This method utilizes function approximation to solve the problem of estimating the target angle. First, SVR is used to construct the function mapping relationship between the echo and the target angle in beamspace. Next, by adding manifold constraints to the loss function, supervised learning is extended to semi-supervised learning, aiming to improve the small sample adaptation ability. This framework supports updating the angle estimating function with continuously increasing unlabeled samples during the FLR scanning process. The numerical simulation results show that the new technology has better performance than model-based methods and fully supervised methods, especially under limited conditions such as signal-to-noise ratio and number of training samples. Full article
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<p>Geometry of forward-looking radar (FLR) for high-speed platform.</p>
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<p>Illustration of antenna pattern deconvolution in beamspace with FLR.</p>
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<p>Schematic diagram of semi-supervised learning framework for FLR angle estimation (SSL-FAE).</p>
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<p>The FLR angle estimation result with (<b>a</b>) MVDR, (<b>b</b>) Bayesian, (<b>c</b>) SVR, (<b>d</b>) Doppler-MVDR, (<b>e</b>) Doppler-Bayesian and (<b>f</b>) SSL-FAE (Case 1).</p>
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<p>The FLR angle estimation result (Case 2).</p>
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<p>The FLR angle estimation result (Case 3).</p>
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<p>The FLR angle estimation result (Case 4).</p>
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<p>The FLR angle estimation result (Case 5).</p>
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<p>The comparison of kernel functions of (<b>a</b>) Case 2, (<b>b</b>) Case 3 and (<b>c</b>) Case 4 with Case 1, and the comparison of combination coefficients of (<b>d</b>) Case 2, (<b>e</b>) Case 3 and (<b>f</b>) Case 4 with Case 1 when the target is at <math display="inline"><semantics> <msup> <mn>10</mn> <mo>∘</mo> </msup> </semantics></math>.</p>
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<p>The comparison of kernel functions of (<b>a</b>) Case 2, (<b>b</b>) Case 3 and (<b>c</b>) Case 4 with Case 1, and the comparison of combination coefficients of (<b>d</b>) Case 2, (<b>e</b>) Case 3 and (<b>f</b>) Case 4 with Case 1 when the target is at <math display="inline"><semantics> <mrow> <mo>−</mo> <msup> <mn>5.3</mn> <mo>∘</mo> </msup> </mrow> </semantics></math>.</p>
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<p>Statistical performance of different algorithms.</p>
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<p>Performance of different algorithms under clutter conditions.</p>
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24 pages, 37834 KiB  
Article
Data Matters: Rethinking the Data Distribution in Semi-Supervised Oriented SAR Ship Detection
by Yimin Yang, Ping Lang, Junjun Yin, Yaomin He and Jian Yang
Remote Sens. 2024, 16(14), 2551; https://doi.org/10.3390/rs16142551 - 11 Jul 2024
Cited by 2 | Viewed by 1066
Abstract
Data, in deep learning (DL), are crucial to detect ships in synthetic aperture radar (SAR) images. However, SAR image annotation limitations hinder DL-based SAR ship detection. A novel data-selection method and teacher–student model are proposed in this paper to effectively leverage sparse labeled [...] Read more.
Data, in deep learning (DL), are crucial to detect ships in synthetic aperture radar (SAR) images. However, SAR image annotation limitations hinder DL-based SAR ship detection. A novel data-selection method and teacher–student model are proposed in this paper to effectively leverage sparse labeled data and improve SAR ship detection performance, based on the semi-supervised oriented object-detection (SOOD) framework. More specifically, we firstly propose a SAR data-scoring method based on fuzzy comprehensive evaluation (FCE), and discuss the relationship between the score distribution of labeled data and detection performance. A refined data selector (RDS) is then designed to adaptively obtain reasonable data for model training without any labeling information. Lastly, a Gaussian Wasserstein distance (GWD) and an orientation-angle deviation weighting (ODW) loss are introduced to mitigate the impact of strong scattering points on bounding box regression and dynamically adjusting the consistency of pseudo-label prediction pairs during the model training process, respectively. The experiments results on four open datasets have demonstrated that our proposed method can achieve better SAR ship detection performances on low-proportion labeled datasets, compared to some existing methods. Therefore, our proposed method can effectively and efficiently reduce the burden of SAR ship data labeling and improve detection capacities as much as possible. Full article
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<p>(<b>a</b>) Annotation results of oriented bounding box (OBB) and horizontal bounding box (HBB). (<b>b</b>) Some difficulties in labeling ship targets in SAR images: high sidelobe levels, strong sea clutter, and interference.</p>
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<p>The pipeline of our proposed framework for semi-supervised oriented SAR ship detection. Each input batch contains both labeled and unlabeled data, with labeled data selected offline via the refined data selector (RDS). In the unsupervised training part, the teacher model uses weakly augmented data, while the student model uses strongly augmented data, where only the student model is trained and the teacher model is updated through the exponential moving average (EMA). The unsupervised loss is calculated by combining the prediction maps of the teacher model and the student model, where the bounding box loss is the Gaussian Wasserstein distance (GWD) loss, which is then weighted by the orientation-angle deviation. The supervised training loss is calculated based on the difference between the ground truth and the student model’s predictions on the labeled data. The overall loss is obtained by weighting and summing the supervised training loss and the unsupervised training loss.</p>
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<p>Overall structure of this paper.</p>
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<p>Schematic diagram of the RDS: firstly, calculate the evaluation indicators of SAR images; then, FCE is used to score the data; finally, select the appropriate data from all the data according to the score. The green histogram represents the score distribution of all data, while the blue histogram represents the score distribution of the selected data.</p>
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<p>Two different scenes are compared: The images in the left column are demo images; the middle column contains the histograms of their gray-scale value distribution with the green line as smoothed values; the right column shows the results after morphological processing.</p>
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<p>Membership function.</p>
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<p>Model of the oriented bounding box as a 2D Gaussian distribution. The right image shows the two-dimensional Gaussian distribution after modeling. The closer to red, the nearer to the center of the ship target.</p>
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<p>Schematic diagram of the Long Edge definition method used in RSDD-SAR.</p>
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<p>There are eight representative sample images, partially enlarged details, morphological results, and their gray-scale histograms.</p>
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<p>The seven blue histograms are the indicator histograms used for FCE, and the green histogram is the final comprehensive score histogram.</p>
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<p>The influence of labeled data distribution on training performance. In Figure (<b>a</b>), the solid data points are obtained by random sampling, while the hollow data points are obtained by RDS sampling.</p>
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<p>The visual comparison results of the algorithms mentioned in <a href="#remotesensing-16-02551-t004" class="html-table">Table 4</a>, where the red circle indicates missing detection, the yellow circle indicates false alarm, and the blue circle indicates poor regression results of the bounding box. The fewer and smaller the circles, the better the algorithm’s performance. The images of the wharf and harbor are locally enlarged to achieve better visualization. * indicates that the RDS is adopted.</p>
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<p>The visualization results of the ablation experiments are presented. The first row shows the ground truth. In the scenes of the first two columns, the SCR is high, and the edges of the ships are clear. In the scenes of the last five columns, the SCR is low, or the edges of the ships are affected by high sidelobes.</p>
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19 pages, 4104 KiB  
Article
Research on CC-SSBLS Model-Based Air Quality Index Prediction
by Lin Wang, Yibing Wang, Jian Chen, Shuangqing Zhang and Lanhong Zhang
Atmosphere 2024, 15(5), 613; https://doi.org/10.3390/atmos15050613 - 19 May 2024
Viewed by 1195
Abstract
Establishing reliable and effective prediction models is a major research priority for air quality parameter monitoring and prediction and is utilized extensively in numerous fields. The sample dataset of air quality metrics often established has missing data and outliers because of certain uncontrollable [...] Read more.
Establishing reliable and effective prediction models is a major research priority for air quality parameter monitoring and prediction and is utilized extensively in numerous fields. The sample dataset of air quality metrics often established has missing data and outliers because of certain uncontrollable causes. A broad learning system based on a semi-supervised mechanism is built to address some of the dataset’s data-missing issues, hence reducing the air quality model prediction error. Several air parameter sample datasets in the experiment were discovered to have outlier issues, and the anomalous data directly impact the prediction model’s stability and accuracy. Furthermore, the correlation entropy criteria perform better when handling the sample data’s outliers. Therefore, the prediction model in this paper consists of a semi-supervised broad learning system based on the correlation entropy criterion (CC-SSBLS). This technique effectively solves the issue of unstable and inaccurate prediction results due to anomalies in the data by substituting the correlation entropy criterion for the mean square error criterion in the BLS algorithm. Experiments on the CC-SSBLS algorithm and comparative studies with models like Random Forest (RF), Support Vector Regression (V-SVR), BLS, SSBLS, and Categorical and Regression Tree-based Broad Learning System (CART-BLS) were conducted using sample datasets of air parameters in various regions. In this paper, the root mean square error (RMSE) and mean absolute percentage error (MAPE) are used to judge the advantages and disadvantages of the proposed model. Through the experimental analysis, RMSE and MAPE reached 8.68 μg·m−3 and 0.24% in the Nanjing dataset. It is possible to conclude that the CC-SSBLS algorithm has superior stability and prediction accuracy based on the experimental results. Full article
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<p>BLS network operation principle diagram.</p>
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<p>SSBLS network operation principle diagram.</p>
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<p>CC-SSBLS network operation principle diagram.</p>
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<p>Plot of metric results on the four datasets of the BLS algorithm: (<b>a</b>) RMSE, (<b>b</b>) MAPE, (<b>c</b>) MAE, and (<b>d</b>) R<sup>2</sup>.</p>
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<p>Plot of metric results on the four datasets of the BLS algorithm: (<b>a</b>) RMSE, (<b>b</b>) MAPE, (<b>c</b>) MAE, and (<b>d</b>) R<sup>2</sup>.</p>
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<p>Prediction results of the BLS algorithm on the Xuzhou dataset are plotted.</p>
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<p>Plot of metric results on the four datasets of the SSBLS algorithm: (<b>a</b>) RMSE, (<b>b</b>) MAPE, (<b>c</b>) MAE, and (<b>d</b>) R<sup>2</sup>.</p>
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<p>Prediction results of the SSBLS algorithm for the Xuzhou dataset are plotted.</p>
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<p>Plot of metrics results on the four datasets of the CC-SSBLS algorithm: (<b>a</b>) RMSE, (<b>b</b>) MAPE, (<b>c</b>) MAE, and (<b>d</b>) R<sup>2</sup>.</p>
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<p>Prediction results of the CC-SSBLS algorithm on the Xuzhou dataset are plotted.</p>
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<p>Optimal evaluation metric values for the three algorithms on the four datasets. (<b>a</b>) Graph representing the RMSE optima of the three algorithms on the four datasets. (<b>b</b>) Graph representing the MAPE optima of the three algorithms on the four datasets. (<b>c</b>) Graph representing the MAE optima of the three algorithms on the four datasets. (<b>d</b>) Graph representing the R<sup>2</sup> optima of the three algorithms on the four datasets.</p>
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<p>Prediction results of the RF algorithm on the Xuzhou dataset are plotted.</p>
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<p>Prediction results of the V-SVR algorithm on the Nanjing dataset are plotted.</p>
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<p>Prediction results of the ANN algorithm on the Beijing dataset are plotted.</p>
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<p>Prediction results of the RNN algorithm on the Changchun dataset are plotted.</p>
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22 pages, 1823 KiB  
Article
Semi-Supervised Machine Learning Method for Predicting Observed Individual Risk Preference Using Gallup Data
by Faroque Ahmed, Mrittika Shamsuddin, Tanzila Sultana and Rittika Shamsuddin
Math. Comput. Appl. 2024, 29(2), 21; https://doi.org/10.3390/mca29020021 - 15 Mar 2024
Cited by 1 | Viewed by 2235
Abstract
Risk and uncertainty play a vital role in almost every significant economic decision, and an individual’s propensity to make riskier decisions also depends on various circumstances. This article aims to investigate the effects of social and economic covariates on an individual’s willingness to [...] Read more.
Risk and uncertainty play a vital role in almost every significant economic decision, and an individual’s propensity to make riskier decisions also depends on various circumstances. This article aims to investigate the effects of social and economic covariates on an individual’s willingness to take general risks and extends the scope of existing works by using quantitative measures of risk-taking from the GPS and Gallup datasets (in addition to the qualitative measures used in the literature). Based on the available observed risk-taking data for one year, this article proposes a semi-supervised machine learning-based approach that can efficiently predict the observed risk index for those countries/individuals for years when the observed risk-taking index was not collected. We find that linear models are insufficient to capture certain patterns among risk-taking factors, and non-linear models, such as random forest regression, can obtain better root mean squared values than those reported in past literature. In addition to finding factors that agree with past studies, we also find that subjective well-being influences risk-taking behavior. Full article
(This article belongs to the Section Social Sciences)
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<p>An overview of the research methodology used to predict ORP values for the Gallup data.</p>
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<p>An overview of the data usage and the contributions of this research work.</p>
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<p>Overview of the evaluation schemes used to evaluate the benchmark and semi-supervised models.</p>
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<p>A schematic overview of the self-training semi-supervised learning mechanism using base learners. These base learners can be linear (e.g., find linear patterns only) or non-linear models (e.g., finds linear and non-linear patterns).</p>
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<p>Feature sets for <math display="inline"><semantics> <msub> <mi>D</mi> <mrow> <mi>E</mi> <mi>x</mi> <mi>p</mi> <mi>e</mi> <mi>r</mi> <mi>t</mi> </mrow> </msub> </semantics></math>, <math display="inline"><semantics> <msub> <mi>D</mi> <mrow> <mi>P</mi> <mi>o</mi> <mi>s</mi> <mi>s</mi> <mi>i</mi> <mi>b</mi> <mi>l</mi> <mi>e</mi> </mrow> </msub> </semantics></math>, <math display="inline"><semantics> <msub> <mi>D</mi> <mrow> <mi>C</mi> <mi>o</mi> <mi>m</mi> <mi>p</mi> <mi>E</mi> <mi>x</mi> </mrow> </msub> </semantics></math>.</p>
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<p>Benchmark LR Model Evaluation. Independent variables are chosen by the human expert.</p>
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<p>Scatter plot comparison for LR Self-training, first iteration, Step 1 (<b>left</b>) and Step 2 (<b>right</b>). This particular figure uses the <math display="inline"><semantics> <msub> <mi>D</mi> <mrow> <mi>E</mi> <mi>x</mi> <mi>p</mi> <mi>e</mi> <mi>r</mi> <mi>t</mi> </mrow> </msub> </semantics></math> dataset.</p>
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<p>The RMSE values of the four ML regression models over the ten iterations of the self-training stage plus the initially supervised base learner.</p>
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<p>The performance of the LR and RFR model on the three datasets, <math display="inline"><semantics> <msub> <mi>D</mi> <mrow> <mi>E</mi> <mi>x</mi> <mi>p</mi> <mi>e</mi> <mi>r</mi> <mi>t</mi> </mrow> </msub> </semantics></math>, <math display="inline"><semantics> <msub> <mi>D</mi> <mrow> <mi>P</mi> <mi>o</mi> <mi>s</mi> <mi>s</mi> <mi>i</mi> <mi>b</mi> <mi>l</mi> <mi>e</mi> </mrow> </msub> </semantics></math>, <math display="inline"><semantics> <msub> <mi>D</mi> <mrow> <mi>C</mi> <mi>o</mi> <mi>m</mi> <mi>p</mi> <mi>E</mi> <mi>x</mi> </mrow> </msub> </semantics></math>. The best regression prediction is by RFR on <math display="inline"><semantics> <msub> <mi>D</mi> <mrow> <mi>C</mi> <mi>o</mi> <mi>m</mi> <mi>p</mi> <mi>E</mi> <mi>x</mi> </mrow> </msub> </semantics></math>.</p>
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<p>Benchmark LR Model coefficients for the merged data from the year 2012.</p>
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<p>Detailed coefficients of base learner based on computational expert features.</p>
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23 pages, 19390 KiB  
Article
Semi-Symmetrical, Fully Convolutional Masked Autoencoder for TBM Muck Image Segmentation
by Ke Lei, Zhongsheng Tan, Xiuying Wang and Zhenliang Zhou
Symmetry 2024, 16(2), 222; https://doi.org/10.3390/sym16020222 - 12 Feb 2024
Cited by 3 | Viewed by 1401
Abstract
Deep neural networks are effectively utilized for the instance segmentation of muck images from tunnel boring machines (TBMs), providing real-time insights into the surrounding rock condition. However, the high cost of obtaining quality labeled data limits the widespread application of this method. Addressing [...] Read more.
Deep neural networks are effectively utilized for the instance segmentation of muck images from tunnel boring machines (TBMs), providing real-time insights into the surrounding rock condition. However, the high cost of obtaining quality labeled data limits the widespread application of this method. Addressing this challenge, this study presents a semi-symmetrical, fully convolutional masked autoencoder designed for self-supervised pre-training on extensive unlabeled muck image datasets. The model features a four-tier sparse encoder for down-sampling and a two-tier sparse decoder for up-sampling, connected via a conventional convolutional neck, forming a semi-symmetrical structure. This design enhances the model’s ability to capture essential low-level features, including geometric shapes and object boundaries. Additionally, to circumvent the trivial solutions in pixel regression that the original masked autoencoder faced, Histogram of Oriented Gradients (HOG) descriptors and Laplacian features have been integrated as novel self-supervision targets. Testing shows that the proposed model can effectively discern essential features of muck images in self-supervised training. When applied to subsequent end-to-end training tasks, it enhances the model’s performance, increasing the prediction accuracy of Intersection over Union (IoU) for muck boundaries and regions by 5.9% and 2.4%, respectively, outperforming the enhancements made by the original masked autoencoder. Full article
(This article belongs to the Special Issue Symmetry Applied in Computer Vision, Automation, and Robotics)
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<p>Characteristics of TBM muck image. (<b>a</b>) A sample muck image collected during TBM advancing. (<b>b</b>) The muck chips may present unfavorable characteristics such as the following: ① Invisible boundary; ② Overlapping; ③ Confusing texture. (<b>c</b>) The local image indicated by the blue and violet boxes, with the dashed boxes showing the results after rotation. (<b>d</b>) Muck chip annotations in blue box.</p>
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<p>Overview of masked autoencoders using the figure borrowed from the original work [<a href="#B33-symmetry-16-00222" class="html-bibr">33</a>].</p>
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<p>Schematic diagram of sparse convolution operator. (<b>a</b>) Dense convolution; (<b>b</b>) Sparse convolution.</p>
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<p>Schematic diagram of trivial solution derived from MSE loss. (<b>a</b>) A grayscale image with resolution of 5 × 5; (<b>b</b>) Another visually similar image; (<b>c</b>) A trivial solution.</p>
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<p>Schematic diagram of calculation steps for HOG descriptor. (<b>a</b>) Cell-wise HOG descriptor with 8 bins; (<b>b</b>) Block-wise normalization by sliding window; (<b>c</b>) Filling and concatenation.</p>
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<p>Schematic diagram of calculation steps for Laplacian feature.</p>
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<p>Macrostructure of MuckSeg-SS-FCMAE.</p>
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<p>Structure of stem block in MuckSeg-SS-FCMAE.</p>
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<p>Schematic diagram of information leakage phenomenon.</p>
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<p>Structure of MuckSeg for formal segmentation task.</p>
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<p>Data preparation procedure: (<b>a</b>) Image acquisition system; (<b>b</b>) ROI and crop boxes; (<b>c</b>) Training samples.</p>
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<p>Sample muck images.</p>
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<p>Learning rate graph under a cyclic schedule.</p>
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<p>Loss curve during training process.</p>
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<p>Comparison of image reconstruction capabilities under various schemes.</p>
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<p>Overview of feature maps generated by an un-masked input under various schemes.</p>
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<p>Most valuable feature map in each encoder tier under various schemes.</p>
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<p>Error map generated by various schemes.</p>
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<p>Model performance and computational cost curves across non-independent hyperparameters.</p>
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<p>Model performance and computational cost curves across independent hyperparameters.</p>
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21 pages, 1062 KiB  
Article
Validation of Instruments for the Improvement of Interprofessional Education through Educational Management: An Internet of Things (IoT)-Based Machine Learning Approach
by Mustafa Mohamed, Fahriye Altinay, Zehra Altinay, Gokmen Dagli, Mehmet Altinay and Mutlu Soykurt
Sustainability 2023, 15(24), 16577; https://doi.org/10.3390/su152416577 - 6 Dec 2023
Cited by 1 | Viewed by 1536
Abstract
Educational management is the combination of human and material resources that supervises, plans, and responsibly executes an educational system with outcomes and consequences. However, when seeking improvements in interprofessional education and collaborative practice through the management of health professions, educational modules face significant [...] Read more.
Educational management is the combination of human and material resources that supervises, plans, and responsibly executes an educational system with outcomes and consequences. However, when seeking improvements in interprofessional education and collaborative practice through the management of health professions, educational modules face significant obstacles and challenges. The primary goal of this study was to analyse data collected from discussion sessions and feedback from respondents concerning interprofessional education (IPE) management modules. Thus, this study used an explanatory and descriptive design to obtain responses from the selected group via a self-administered questionnaire and semi-structured interviews, and the results were limited to averages, i.e., frequency distributions and summary statistics. The results of this study reflect the positive responses from both subgroups and strongly support the further implementation of IPE in various aspects and continuing to improve and develop it. Four different artificial intelligence (AI) techniques were used to model interprofessional education improvement through educational management, using 20 questions from the questionnaire as the variables (19 input variables and 1 output variable). The modelling performance of the nonlinear and linear models could reliably predict the output in both the calibration and validation phases when considering the four performance metrics. These models were shown to be reliable tools for evaluating and modelling interprofessional education through educational management. Gaussian process regression (GPR) outperformed all the models in both the training and validation stages. Full article
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<p>Medical and health professional learners’ distribution.</p>
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<p>Results of open-discussion interviews.</p>
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<p>Time-series performance of AI models.</p>
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<p>Scatter plot performance of AI models.</p>
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<p>Error demonstrated by AI models.</p>
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2 pages, 179 KiB  
Abstract
Partial Least Square–Cox Regression to Investigate Association between Patterns of Dietary Exposure to Persistent Organic Pollutants and Breast Cancer Risk in the E3N Cohort
by Pauline Frenoy, Francesca Mancini and Vittorio Perduca
Proceedings 2023, 91(1), 39; https://doi.org/10.3390/proceedings2023091039 - 15 Nov 2023
Viewed by 718
Abstract
Exposure to persistent organic pollutants (POPs) is suspected to play a role in the occurrence of estrogen receptor-positive breast cancer (ER-positive BC). Our objective was to investigate the association between patterns of dietary exposure to POPs and ER-positive BC risk in the E3N [...] Read more.
Exposure to persistent organic pollutants (POPs) is suspected to play a role in the occurrence of estrogen receptor-positive breast cancer (ER-positive BC). Our objective was to investigate the association between patterns of dietary exposure to POPs and ER-positive BC risk in the E3N cohort. The study included 67,879 women. The intake of 81 POPs, including dioxins, polychlorinated biphenyls (PCBs), per- and polyfluoroalkyl substances (PFASs), brominated flame retardants (BFRs) and polycyclic aromatic hydrocarbons (PAHs), was estimated using food consumption data, collected through a validated semi-quantitative food frequency questionnaire, and food contamination data, as measured in the second French Total Diet Study. ER-positive BC cases were identified through self-administered questionnaires, from next-of-kin spontaneous reports, or through information from the national cause-of-death registry. Partial least square–Cox regression (PLS–Cox), a supervised dimension reduction method, was used to identify POPs patterns associated with ER-positive BC occurrence. Cox proportional hazard models were then used to estimate hazard ratios (HRs) and their 95% confidence intervals (CIs) for the associations between the PLS–Cox patterns retained and the risk of ER-positive BC, adjusted on potential confounders identified using a directed acyclic graph. The women were followed for a maximum of 21.4 years, and 5,686 developed incident ER-positive BC. Based on POP intake estimates, five patterns were retained. The first pattern was characterized by positive weights for almost all POPs, especially PAHs and some dioxins. The other principal components were characterized by both positive and negative weights. A significant non-linear and non-monotonic association was highlighted between exposure to the first pattern and ER-positive BC risk, and significant positive linear associations were highlighted between exposure to the second, fourth and fifth patterns and ER-positive BC risk. The use of the PLS–Cox method allowed the identification of relevant patterns in POPs explaining, as far as possible, the covariance between the exposures and the outcomes. Identifying such patterns can help to better clarify the pollutants involved in BC occurrence and to estimate their cumulative effect. Full article
(This article belongs to the Proceedings of The 14th European Nutrition Conference FENS 2023)
31 pages, 4390 KiB  
Article
A Quality Prediction Method Based on Tri-Training Weighted Ensemble Just-in-Time Learning–Relevance Vector Machine Model
by Xuhang Chen, Jinlong Zhao, Min Xu, Mingyi Yang and Xinguang Wu
Processes 2023, 11(11), 3129; https://doi.org/10.3390/pr11113129 - 1 Nov 2023
Viewed by 1157
Abstract
The core quality data, such as interior ballistic performance, are seriously unbalanced in the plasticizing and molding process, which makes it difficult for traditional supervised learning methods to accurately predict this kind of index. A Tri-training weighted ensemble JITL-RVM model based on an [...] Read more.
The core quality data, such as interior ballistic performance, are seriously unbalanced in the plasticizing and molding process, which makes it difficult for traditional supervised learning methods to accurately predict this kind of index. A Tri-training weighted ensemble JITL-RVM model based on an integrated confidence evaluation strategy is proposed to solve the above problem. The method is based on Tri-training semi-supervised regression architecture and uses both labeled and unlabeled data for modeling. First of all, the traditional single similarity measure method is difficult to use to evaluate the real similarity between data samples reliably and stably. This method realizes diversity enhancement and data expansion of the data set for modelling through ensemble just-in-time modelling based on three homologous and heterogeneous mixed similarity measures. Secondly, a new integrated confidence evaluation strategy is used to select the unlabeled samples, and the pseudo-labeled data, which can improve the prediction performance of the model, can be selected. To improve the prediction effect of the model, the pseudo-label value of the data is revised continuously. The integrated confidence evaluation strategy can overcome many shortcomings of the traditional confidence evaluation method based on Co-training regression (Coreg). Finally, the final quality prediction value is obtained through weighted integration fusion, which reflects the difference between different models and further improves the prediction accuracy. The experimental results of interior ballistic performance prediction of single-base gun propellant show the effectiveness and superiority of the proposed method, and it can improve the RMSE, R2, and PHR to 0.8074, 0.9644, and 93.3%, respectively. Full article
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<p>Comparison of system architecture between just-in-time learning and traditional global modeling.</p>
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<p>Schematic diagram of unlabeled data processing method based on Tri-training-JITL-RVM.</p>
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<p>Updating process of historical database and data set partition diagram after unlabeled data processing.</p>
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<p>Online quality prediction flow chart based on Tri-training diversity-enhanced EJITL modeling.</p>
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<p>Offline parameter optimization method based on K-fold cross validation.</p>
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<p>Flow diagram of the penicillin fermentation process.</p>
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<p>Prediction performance comparison of test batch 1 using RVM and IC-Tri-WEJITL-RVM methods for penicillin concentration.</p>
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<p>Process flow and instrument diagram of plasticizing and molding process of single-based gun propellant.</p>
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<p>Comparison charts of prediction result for each batch using JITL1-RVM and Tri-JITL1-RVM method.</p>
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<p>Comparison charts of prediction results for each batch using JITL2-RVM and Tri-JITL2-RVM methods.</p>
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<p>Comparison charts of prediction results for each batch using JITL3-RVM and Tri-JITL3-RVM methods.</p>
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<p>Comparison charts of prediction results for each batch using JITL3-RVM and EJITL-RVM methods.</p>
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<p>Comparison charts of prediction results for each batch using Tri-JITL3-RVM and Tri-EJITL-RVM methods.</p>
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<p>Comparison charts of prediction results for each batch using Tri-EJITL-RVM and Tri-WEJITL-RVM methods.</p>
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<p>Comparison charts of prediction results for each batch using Tri-WEJITL-RVM and IC-Tri-WEJITL-RVM methods.</p>
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21 pages, 2760 KiB  
Article
Robust Semi-Supervised Point Cloud Registration via Latent GMM-Based Correspondence
by Zhengyan Zhang, Erli Lyu, Zhe Min, Ang Zhang, Yue Yu and Max Q.-H. Meng
Remote Sens. 2023, 15(18), 4493; https://doi.org/10.3390/rs15184493 - 12 Sep 2023
Cited by 5 | Viewed by 1867
Abstract
Due to the fact that point clouds are always corrupted by significant noise and large transformations, aligning two point clouds by deep neural networks is still challenging. This paper presents a semi-supervised point cloud registration (PCR) method for accurately estimating point correspondences and [...] Read more.
Due to the fact that point clouds are always corrupted by significant noise and large transformations, aligning two point clouds by deep neural networks is still challenging. This paper presents a semi-supervised point cloud registration (PCR) method for accurately estimating point correspondences and handling large transformations using limited prior datasets. Firstly, a modified autoencoder is introduced as the feature extraction module to extract the distinctive and robust features for the downstream registration task. Unlike optimization-based pairwise PCR strategies, the proposed method treats two point clouds as two implementations of a Gaussian mixture model (GMM), which we call latent GMM. Based on the above assumption, two point clouds can be regarded as two probability distributions. Hence, the PCR of two point clouds can be approached by minimizing the KL divergence between these two probability distributions. Then, the correspondence between the point clouds and the latent GMM components is estimated using the augmented regression network. Finally, the parameters of GMM can be updated by the correspondence and the transformation matrix can be computed by employing the weighted singular value decomposition (SVD) method. Extensive experiments conducted on both synthetic and real-world data validate the superior performance of the proposed method compared to state-of-the-art registration methods. These experiments also highlight the method’s superiority in terms of accuracy, robustness, and generalization. Full article
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<p>The overview of the proposed PCR method. The equations denoted by the green dashed line are used to estimate the latent source GMM component, while the equations denoted by the orange dashed line in the lower right corner are used in the weighted SVD module.</p>
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<p>The architecture of the proposed autoencoder module.</p>
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<p>Comparison results on the noisy dataset. Even when noise is relative large (<math display="inline"><semantics> <mrow> <msup> <mi>σ</mi> <mn>2</mn> </msup> <mo>=</mo> </mrow> </semantics></math> 0.04), the proposed method achieves accurate and robust performances.</p>
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<p>Qualitative registration results on the noisy ModelNet40 dataset (<math display="inline"><semantics> <mrow> <msup> <mi>σ</mi> <mn>2</mn> </msup> <mo>=</mo> <mn>0.04</mn> </mrow> </semantics></math>). The figures in three rows show the registration results of three classes of objects, including person, stool, and toilet. The source and target point cloud are shown in green and blue, respectively.</p>
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<p>Comparison results on different density levels. The results confirm that our algorithm consistently exhibits accuracy and robustness in sparse PCR experiments.</p>
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<p>Qualitative registration results on noisy ModelNet40 dataset (<math display="inline"><semantics> <mrow> <msup> <mi>σ</mi> <mn>2</mn> </msup> <mo>=</mo> <mn>0.04</mn> </mrow> </semantics></math>). Figures in two rows show the registration results of two classes of objects, including wardrobe and table. The results show that our algorithm has better robustness to the used sparse data.</p>
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<p>Qualitative registration results on partial data. The figures show the registration results of CPD, DeepGMR, and ours.</p>
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<p>Qualitative registration results on the real-world dataset. Figures in two rows show the registration results of two classes of scenes, including the kitchen and office.</p>
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<p>Comparison results of different density levels on the 7Scene dataset. The point numbers of the source and target point clouds range from 1 k to 10 k. In all registration experiments, our method maintains accuracy and robustness.</p>
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<p>Qualitative registration results on partial data in the 7Scene dataset. The figures show the registration results of CPD, DeepGMR, and ours.</p>
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27 pages, 5918 KiB  
Article
Exploring Random Forest Machine Learning and Remote Sensing Data for Streamflow Prediction: An Alternative Approach to a Process-Based Hydrologic Modeling in a Snowmelt-Driven Watershed
by Khandaker Iftekharul Islam, Emile Elias, Kenneth C. Carroll and Christopher Brown
Remote Sens. 2023, 15(16), 3999; https://doi.org/10.3390/rs15163999 - 11 Aug 2023
Cited by 16 | Viewed by 4733
Abstract
Physically based hydrologic models require significant effort and extensive information for development, calibration, and validation. The study explored the use of the random forest regression (RFR), a supervised machine learning (ML) model, as an alternative to the physically based Soil and Water Assessment [...] Read more.
Physically based hydrologic models require significant effort and extensive information for development, calibration, and validation. The study explored the use of the random forest regression (RFR), a supervised machine learning (ML) model, as an alternative to the physically based Soil and Water Assessment Tool (SWAT) for predicting streamflow in the Rio Grande Headwaters near Del Norte, a snowmelt-dominated mountainous watershed of the Upper Rio Grande Basin. Remotely sensed data were used for the random forest machine learning analysis (RFML) and RStudio for data processing and synthesizing. The RFML model outperformed the SWAT model in accuracy and demonstrated its capability in predicting streamflow in this region. We implemented a customized approach to the RFR model to assess the model’s performance for three training periods, across 1991–2010, 1996–2010, and 2001–2010; the results indicated that the model’s accuracy improved with longer training periods, implying that the model trained on a more extended period is better able to capture the parameters’ variability and reproduce streamflow data more accurately. The variable importance (i.e., IncNodePurity) measure of the RFML model revealed that the snow depth and the minimum temperature were consistently the top two predictors across all training periods. The paper also evaluated how well the SWAT model performs in reproducing streamflow data of the watershed with a conventional approach. The SWAT model needed more time and data to set up and calibrate, delivering acceptable performance in annual mean streamflow simulation, with satisfactory index of agreement (d), coefficient of determination (R2), and percent bias (PBIAS) values, but monthly simulation warrants further exploration and model adjustments. The study recommends exploring snowmelt runoff hydrologic processes, dust-driven sublimation effects, and more detailed topographic input parameters to update the SWAT snowmelt routine for better monthly flow estimation. The results provide a critical analysis for enhancing streamflow prediction, which is valuable for further research and water resource management, including snowmelt-driven semi-arid regions. Full article
(This article belongs to the Topic Hydrology and Water Resources Management)
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<p>The study watershed (Rio Grande Headwaters) at the Upper Rio Grande.</p>
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<p>Flow chart for RF model connecting predictors and target variable.</p>
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<p>Comparison of monthly simulated and observed streamflow during calibration and validation.</p>
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<p>Comparison of yearly simulated and observed streamflow during calibration and validation period.</p>
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<p>Random forest variable importance (i.e., IncNodePurity) for training period 1991–2010, 1996–2010, and 2001–2010 consecutively from left to right.</p>
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<p>Snow depth versus simulated and predicted streamflow in the watershed.</p>
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<p>Generated SWAT subbasins and stream network.</p>
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<p>SWAT subbasins and streamflow distribution.</p>
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<p><span class="html-italic">p</span>-value and t-stat for the watershed parameters.</p>
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<p>Correlation matrices of the input variables.</p>
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<p>Scatter Plots for the predictions through RFML and SWAT.</p>
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<p>FLOW_OUTm^3 vs. PRECIP mm vs. SNOWMELT mm.</p>
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<p>FLOW_OUTm^3 vs. SNOWMELTmm inputs from largest to smallest.</p>
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<p>FLOW_OUTm^3 vs. PRECIPmm from largest to smallest.</p>
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15 pages, 1306 KiB  
Article
Molecular Descriptors Property Prediction Using Transformer-Based Approach
by Tuan Tran and Chinwe Ekenna
Int. J. Mol. Sci. 2023, 24(15), 11948; https://doi.org/10.3390/ijms241511948 - 26 Jul 2023
Cited by 5 | Viewed by 3024
Abstract
In this study, we introduce semi-supervised machine learning models designed to predict molecular properties. Our model employs a two-stage approach, involving pre-training and fine-tuning. Particularly, our model leverages a substantial amount of labeled and unlabeled data consisting of SMILES strings, a text representation [...] Read more.
In this study, we introduce semi-supervised machine learning models designed to predict molecular properties. Our model employs a two-stage approach, involving pre-training and fine-tuning. Particularly, our model leverages a substantial amount of labeled and unlabeled data consisting of SMILES strings, a text representation system for molecules. During the pre-training stage, our model capitalizes on the Masked Language Model, which is widely used in natural language processing, for learning molecular chemical space representations. During the fine-tuning stage, our model is trained on a smaller labeled dataset to tackle specific downstream tasks, such as classification or regression. Preliminary results indicate that our model demonstrates comparable performance to state-of-the-art models on the chosen downstream tasks from MoleculeNet. Additionally, to reduce the computational overhead, we propose a new approach taking advantage of 3D compound structures for calculating the attention score used in the end-to-end transformer model to predict anti-malaria drug candidates. The results show that using the proposed attention score, our end-to-end model is able to have comparable performance with pre-trained models. Full article
(This article belongs to the Special Issue Recent Advances in Computational Structural Bioinformatics)
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<p>Overview of our model with two stages: pre-training on large-scale unlabeled datasets and fine-tuning on smaller labeled datasets for downstream tasks.</p>
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<p>Transfer learning for fine-tuning performance versus pre-training loss from MLM to ClinTox classification. The dotted lines represent linear models fit to the data points.</p>
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<p>Transfer learning for fine-tuning performance versus pre-training loss from MLM to Bace regression. The dotted lines represent linear models fit to the data points.</p>
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<p>Overview of the pre-training stage with MLM.</p>
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<p>Overview of the fine-tuning stage with MLM for classification and regression tasks.</p>
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<p>Example of a contact map. Although two Nitrogen atoms are at least six positions apart in SMILES string, they are within 8 Å of each other.</p>
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<p>Overview of our model for anti-malaria drugs classification.</p>
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19 pages, 1630 KiB  
Article
SNM Radiation Signature Classification Using Different Semi-Supervised Machine Learning Models
by Jordan R. Stomps, Paul P. H. Wilson, Kenneth J. Dayman, Michael J. Willis, James M. Ghawaly and Daniel E. Archer
J. Nucl. Eng. 2023, 4(3), 448-466; https://doi.org/10.3390/jne4030032 - 4 Jul 2023
Cited by 2 | Viewed by 2427
Abstract
The timely detection of special nuclear material (SNM) transfers between nuclear facilities is an important monitoring objective in nuclear nonproliferation. Persistent monitoring enabled by successful detection and characterization of radiological material movements could greatly enhance the nuclear nonproliferation mission in a range of [...] Read more.
The timely detection of special nuclear material (SNM) transfers between nuclear facilities is an important monitoring objective in nuclear nonproliferation. Persistent monitoring enabled by successful detection and characterization of radiological material movements could greatly enhance the nuclear nonproliferation mission in a range of applications. Supervised machine learning can be used to signal detections when material is present if a model is trained on sufficient volumes of labeled measurements. However, the nuclear monitoring data needed to train robust machine learning models can be costly to label since radiation spectra may require strict scrutiny for characterization. Therefore, this work investigates the application of semi-supervised learning to utilize both labeled and unlabeled data. As a demonstration experiment, radiation measurements from sodium iodide (NaI) detectors are provided by the Multi-Informatics for Nuclear Operating Scenarios (MINOS) venture at Oak Ridge National Laboratory (ORNL) as sample data. Anomalous measurements are identified using a method of statistical hypothesis testing. After background estimation, an energy-dependent spectroscopic analysis is used to characterize an anomaly based on its radiation signatures. In the absence of ground-truth information, a labeling heuristic provides data necessary for training and testing machine learning models. Supervised logistic regression serves as a baseline to compare three semi-supervised machine learning models: co-training, label propagation, and a convolutional neural network (CNN). In each case, the semi-supervised models outperform logistic regression, suggesting that unlabeled data can be valuable when training and demonstrating value in semi-supervised nonproliferation implementations. Full article
(This article belongs to the Special Issue Nuclear Security and Nonproliferation Research and Development)
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<p>The two underlying SSML assumptions include the cluster assumption (left) and the manifold assumption (right). In each plot, pluses and triangles are labeled instances, and dots are unlabeled instances. Colors (blue and orange) represent different classes. Note how the inclusion of unlabeled data in a ML model would improve its learned decision boundary. (Image source: [<a href="#B16-jne-04-00032" class="html-bibr">16</a>]).</p>
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<p>Here is an example of a radiation spectrum taken from MINOS. Note several spectral features, including photopeaks associated with background radiation (labeled).</p>
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<p>A radiation spectrum taken when material was present (orange). Note the high count-rate and low energy distribution associated with a transfer. In an attempt to accentuate this feature, an approximated background distribution (gray) is subtracted from the event spectrum to obtain a difference (blue) only associated with the anomalous features.</p>
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<p>One-minute gamma radiation spectrum measurements collected over one month, collected into one plot. Here, each vertical slice (energy bin) is a normalized frequency histogram. Color indicates the frequency at which the count-rate associated with each energy was measured at that specific magnitude.</p>
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<p>RadClass expects a standardized data format that can be abstracted to an <span class="html-italic">n</span> by <span class="html-italic">m</span> matrix with <span class="html-italic">n</span> temporal instances and <span class="html-italic">m</span> bins of data. For MINOS radiation measurements, this would be 1-second temporal instances and 1000 energy bins. For example, one month would be approximately a 43,200 × 1000 matrix. Given an integration time, RadClass will collapse and integrate a set of rows for every column. If the integration time is 60 seconds, every 60 rows will be integrated column-wise. An optional stride parameter could be defined to overlap or skip rows for integration.</p>
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<p>ROC for one node and one month of data using energy-independent, 1-minute count rates. Individual red points on the curve indicate different significance levels, which vary how strictly to enforce the measurement equivalence. As the significance level becomes larger, more and more null hypotheses are rejected, capturing more true and false positives. The gray dotted line indicates a 50–50 ratio, equivalent to an algorithm that makes a random guess for classification.</p>
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<p>The breakdown for sample splits between labeled training, labeled testing, and unlabeled data from the labeling heuristic. Note that using 5 months and 6 nodes worth of data results in 1991 anomalous measurements, where 814 are discarded since their label could not be resolved by the heuristic, and the rest are divided proportionally into train, test, and unlabeled subsets.</p>
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<p>The test accuracy for each co-training model as trained using Algorithm 1. Test accuracy is defined as the percentage of correctly classified samples in a test set not used in training the models (refer to Equation (<a href="#FD12-jne-04-00032" class="html-disp-formula">12</a>)). Ideally, both models would converge to a higher accuracy, indicating that information passed between models was helpful for learning and pattern recognition. A marginal increase is observed here.</p>
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<p>The base (prior to hyperparameter optimization) architecture for the CNN used by <span class="html-small-caps">Shadow</span> EAAT. This consists of two convolution layers with max pooling and dropout, resulting in a representation that is passed to linear, connected layers ending in a binary classification prediction. This was offered as an example architecture for analyzing MNIST data by <span class="html-small-caps">Shadow</span> [<a href="#B21-jne-04-00032" class="html-bibr">21</a>], adjusted for accepting 1D spectra rather than 2D images.</p>
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<p>The results of training for the best <span class="html-small-caps">Shadow</span> model found via hyperparameter optimization. (<b>a</b>) The results of the loss function optimized during training: cross-entropy loss with EAAT optimized using SGD. (<b>b</b>) Accuracy on test data for every epoch. Accuracy notionally increases as the model is optimized, with early stopping resulting in a test accuracy greater than 70%.</p>
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<p>Confusion matrices on test datasets for each machine learning model. Note that the scores above for each confusion matrix are its respective balanced accuracy. SNM, class label 0, represents a positive, and other, class label 1, represents a negative.</p>
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