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Low-dimensional data-based surrogate model of a continuum-mechanical musculoskeletal system based on non-intrusive model order reduction

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ARCHIVE OF APPLIED MECHANICS 2023年第9期93卷 3637-3663页

作者： Kneifl, Jonas Rosin, David Avci, Okan Roehrle, Oliver Fehr, Joerg Univ Stuttgart Inst Engn & Computat Mech Pfaffenwaldring 9 D-70569 Stuttgart Baden Wurttembe Germany Univ Stuttgart Inst Modelling & Simulat Biomech Syst Pfaffenwaldring 5A D-70569 Stuttgart Baden Wurttembe Germany Fraunhofer IPA Biomechatron Syst Nobelstr 12 D-70569 Stuttgart Baden Wurttembe Germany

Over the last decades, computer modeling has evolved from a supporting tool for engineering prototype design to an ubiquitous instrument in non-traditional fields such as medical rehabilitation. This area comes with unique challenges, e.g. the complex modeling of soft tissue or the analysis of musculoskeletal systems. Conventional modeling approaches like the finite element (FE) method are computationally costly when dealing with such models, limiting their usability for real-time simulation or deployment on low-end hardware, if the model at hand cannot be simplified without losing its expressiveness. Non-traditional approaches such as surrogate modeling using data-driven model order reduction are used to make complex high-fidelity models more widely available regardless. They often involve a dimensionality reduction step, in which the high-dimensional system state is transformed onto a low-dimensional subspace or manifold, and a regression approach to capture the reduced system behavior. While most publications focus on one dimensionality reduction, such as principal component analysis (PCA) (linear) or autoencoder (nonlinear), we consider and compare PCA, kernel PCA, autoencoders, as well as variational autoencoders for the approximation of a continuum-mechanical system. In detail, we demonstrate the benefits of the surrogate modeling approach on a complex musculoskeletal system of a human upper-arm with severe nonlinearities and physiological geometry. We consider both, the model's deformation and the internal stress as the two main quantities of interest in a FE context. By doing so we are able to create computationally low-cost surrogate models which capture the system behavior with high approximation quality and fast evaluations.

关键词： Model reduction Machine learning Human body models Kernel PCA variational autoencoder

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Attention-driven multi-model architecture for unbalanced network traffic intrusion detection via extreme gradient boosting

INTELLIGENT SYSTEMS WITH APPLICATIONS

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INTELLIGENT SYSTEMS WITH APPLICATIONS 2025年 26卷

作者： Abdulganiyu, Oluwadamilare Harazeem Tchakoucht, Taha Ait Alaoui, Ahmed El Hilali Saheed, Yakub Kayode Euro Mediterranean Univ Fes EuroMed Res Ctr Sch Digital Engn & Artificial Intelligence Fes 30030 Morocco Univ Maiduguri Maiduguri Nigeria Amer Univ Nigeria Sch IT & Comp Yola Nigeria

Network Intrusion Detection Systems (NIDS) face significant challenges in identifying rare attack instances due to the inherent class imbalance and diversity in network traffic. This imbalance, often characterized by a dominance of benign network traffic data, reduces the effectiveness of traditional detection methods. To address this, we proposed CWFLAM-VAE, an attention-driven multi-model architecture that combines Class-Wise Focal Loss, variational autoencoder, and Extreme Gradient Boosting. CWFLAM-VAE generates synthetic rare-class attack data while preserving the original feature distribution, mitigating imbalance and improving classification performance. The effectiveness of our proposed system was evaluated by employing two datasets, one of which is the NSL-KDD, which exhibits a skewed distribution of network traffic favoring the majority class, and CSE-CIC-IDS2018 dataset, where approximately 83 % of the data consists of benign network traffic. We compared our method with existing sampling techniques (SMOTE, ROS, ADASYN, RUS) and existing classifiers (Logistic Regression, KNN, SVM, Decision Tree, LSTM, CNN). The experimental findings distinctly reveal the efficacy of the CWFLAM-VAE in resolving class imbalance concerns, with Extreme Gradient Boosting surpassing alternative machine learning techniques particularly in the detection of rare instances of attack traffic with an fscore of 97.6 % and 98.1 %, as well as a false positive rate of 0.17 and 0.27 for both data respectively.

关键词： Intrusion detection system Artificial intelligence Imbalanced network traffic Attention mechanism variational autoencoder Class wise focal loss Extreme gradient boosting

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Machine and Representation Learning-Based GNSS Spoofing Detectors Utilizing Feature Set From Generic GNSS Receivers

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IEEE TRANSACTIONS ON CONSUMER ELECTRONICS 2024年第1期70卷 574-583页

作者： Iqbal, Asif Aman, Muhammad Naveed Sikdar, Biplab Natl Univ Singapore Dept Elect & Comp Engn 4 Engn Dr 3 Singapore 117583 Singapore Univ Nebraska Sch Comp Lincoln NE 68588 USA

The Global Navigation Satellite System (GNSS) plays critical role in providing precise timing and positioning information for various applications. However, its civilian signals are vulnerable to spoofing attacks, necessitating robust detection methods. While supervised learning has shown promise in spoof detection, it requires distinct features in the training data for effective learning. In this study, we propose a novel training feature set that combines power and Signal Quality Monitoring (SQM) metrics from a single-antenna GNSS receiver. We introduce a Two-Stage Artificial Neural Network (TS-ANN) that leverages this feature set alongside multi-correlator finger values for effective spoof detection. Furthermore, supervised learning models often struggle with previously unseen attacks due to limited overlap with the training data. To address this, we present a zero-day attack detector based on unsupervised representation learning using a variational autoencoder (VAE) which is trained exclusively on authentic datasets, enhancing its ability to detect novel attack patterns. Experimental results on publicly available TEXBAT datasets demonstrate that our TS-ANN achieves a detection probability (PD) exceeding 99% for similar test datasets. In more sophisticated attack scenarios, such as DS-7, performance may decrease to 50.68%. Nevertheless, our zero-day detector maintains a PD exceeding 92.5%, highlighting its resilience to previously unseen attacks.

关键词： Global navigation satellite system Feature extraction Measurement Detectors Correlators Supervised learning Monitoring GNSS attack variation GNSS spoofing detection neural networks signal quality monitoring (SQM) TEXBAT variational autoencoder zero-day detection

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SiRCle (Signature Regulatory Clustering) model integration reveals mechanisms of phenotype regulation in renal cancer

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GENOME MEDICINE 2024年第1期16卷 1-26页

作者： Mora, Ariane Schmidt, Christina Balderson, Brad Frezza, Christian Boden, Mikael Univ Queensland Sch Chem & Mol Biosci Mol Biosci Bldg 76 St Lucia Qld 4072 Australia Univ Cambridge Hutchison MRC Res Ctr Med Res Council Canc Unit Box 197Cambridge Biomed Campus Cambridge CB2 0X2 England Univ Cologne Fac Med & Univ Hosp Cologne Inst Metabol Ageing Cluster Excellence Cellular Stress Responses Aging Joseph Stelzmann Str 26 D-50931 Cologne Germany Univ Cologne Inst Genet Fac Math & Nat Sci Cluster Excellence Cellular Stress Responses Aging Cologne Germany

BackgroundClear cell renal cell carcinoma (ccRCC) tumours develop and progress via complex remodelling of the kidney epigenome, transcriptome, proteome and metabolome. Given the subsequent tumour and inter-patient heterogeneity, drug-based treatments report limited success, calling for multi-omics studies to extract regulatory relationships, and ultimately, to develop targeted therapies. Yet, methods for multi-omics integration to reveal mechanisms of phenotype regulation are ***, we present SiRCle (Signature Regulatory Clustering), a method to integrate DNA methylation, RNA-seq and proteomics data at the gene level by following central dogma of biology, i.e. genetic information proceeds from DNA, to RNA, to protein. To identify regulatory clusters across the different omics layers, we group genes based on the layer where the gene's dysregulation first occurred. We combine the SiRCle clusters with a variational autoencoder (VAE) to reveal key features from omics' data for each SiRCle cluster and compare patient subpopulations in a ccRCC and a PanCan *** SiRCle to a ccRCC cohort, we showed that glycolysis is upregulated by DNA hypomethylation, whilst mitochondrial enzymes and respiratory chain complexes are translationally suppressed. Additionally, we identify metabolic enzymes associated with survival along with the possible molecular driver behind the gene's perturbations. By using the VAE to integrate omics' data followed by statistical comparisons between tumour stages on the integrated space, we found a stage-dependent downregulation of proximal renal tubule genes, hinting at a loss of cellular identity in cancer cells. We also identified the regulatory layers responsible for their suppression. Lastly, we applied SiRCle to a PanCan cohort and found common signatures across ccRCC and PanCan in addition to the regulatory layer that defines tissue *** results highlight SiRCle's ability to reveal mechanisms of p

关键词： Integration Multi-omics Regulation Machine learning variational autoencoder Clear cell renal cell carcinoma PanCan Metabolism

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SyntheVAEiser: augmenting traditional machine learning methods with VAE-based gene expression sample generation for improved cancer subtype predictions

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GENOME BIOLOGY 2024年第1期25卷 1-18页

作者： Karlberg, Brian Kirchgaessner, Raphael Lee, Jordan Peterkort, Matthew Beckman, Liam Goecks, Jeremy Ellrott, Kyle Oregon Hlth & Sci Univ Biomed Engn 3181 SW Sam Jackson Pk Rd Portland OR 97239 USA H Lee Moffitt Canc Ctr & Res Inst Dept Machine Learning Tampa FL USA

The accuracy of machine learning methods is often limited by the amount of training data that is available. We proposed to improve machine learning training regimes by augmenting datasets with synthetically generated samples. We present a method for synthesizing gene expression samples and test the system's capabilities for improving the accuracy of categorical prediction of cancer subtypes. We developed SyntheVAEiser, a variational autoencoder based tool that was trained and tested on over 8000 cancer samples. We have shown that this technique can be used to augment machine learning tasks and increase performance of recognition of underrepresented cohorts.

关键词： Sample synthesis Synthetic data Data augmentation Generative modeling Feature engineering Cancer subtyping Molecular subtyping variational autoencoder Transcriptomics Gene expression

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Hybrid 3D Medical Image Segmentation Using CNN and Frequency Transformer Fusion

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ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 2024年 1-14页

作者： Labbihi, Ismayl Meslouhi, Othmane El Elassad, Zouhair Elamrani Abou Benaddy, Mohamed Kardouchi, Mustapha Akhloufi, Moulay Ibn Zohr Univ Fac Sci LabSI Lab Agadir 80000 Morocco Cadi Ayyad Univ Natl Sch Appl Sci SARS Grp Safi 46000 Morocco Univ Moncton Dept Comp Sci PRIME Lab 18 Antonine Maillet Ave Moncton NB E1A 3E9 Canada

Medical image segmentation poses a significant challenge, particularly with 3D images. This study presents a novel hybrid network for 3D medical image segmentation, which sequentially integrates convolutional neural networks (CNNs) and transformer models. Structured with an encoder-decoder architecture, the network comprises a frequency transformer branch and a variational autoencoder branch. Initially, the CNN encoder extracts the features of volumetric spatial from the input 3D image. These features are subsequently converted into vectors and incorporated into a frequency transformer. This transformer employs fast Fourier transforms instead of self-attention to mitigate computational complexity. Significantly, this research marks the inaugural utilization of the Fourier transform on transformers for image segmentation employing 3D datasets. The network's efficacy was evaluated on kidney, tumor, and brain 3D datasets. It achieved remarkable results, such as a 97.54% dice score and a 95%-Hausdorff distance (95%-HD) of 3.26 mm for kidney segmentation, and an 86.92% dice score with a 95%-HD of 2.57 mm for brain tumor segmentation. These results underscore the network's potential for accurate and reliable segmentation in diverse medical imaging applications.

关键词： 3D medical image segmentation Convolutional neural networks Frequency transformer variational autoencoder Fourier transforms

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The Use of Conditional variational autoencoders for Simulation of EAS Images from IACTs

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MOSCOW UNIVERSITY PHYSICS BULLETIN 2023年第SUPPL 1期78卷 S37-S44页

作者： Kryukov, A. P. Polyakov, S. P. Vlaskina, A. A. Gres, E. O. Demichev, A. P. Dubenskaya, Yu. Yu. Zhurov, D. P. Lomonosov Moscow State Univ Skobeltsyn Inst Nucl Phys Moscow 119991 Russia Lomonosov Moscow State Univ Fac Phys Moscow 119991 Russia Irkutsk State Univ Appl Phys Inst Irkutsk 664003 Russia

Imaging atmospheric Cherenkov telescopes are used to record images of extensive area showers caused by high-energy particles colliding with the upper atmosphere. The images are analyzed to determine events' physical parameters, such as the type and the energy of the primary particles. The distributions of some of the physical parameters can be used as well, for example, to determine the properties of a gamma ray source. The key problem of any experiment is the calibration of experimental data. For this purpose, Monte Carlo simulated data with known values of the physical parameters are used. The main disadvantage of this method is its extremely high requirements for computing resources and the large amount of time spent on modelling. In this paper, we use an alternative approach: Cherenkov telescope images are simulated with conditional variational autoencoders. We compare the characteristics of both the individual images and their Hillas parameter distributions with those of the images generated by the Monte Carlo method.

关键词： machine learning variational autoencoder image generation gamma astronomy extensive air shower IACT

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Latent Out: an unsupervised deep anomaly detection approach exploiting latent space distribution

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MACHINE LEARNING 2023年第11期112卷 4323-4349页

作者： Angiulli, Fabrizio Fassetti, Fabio Ferragina, Luca Univ Calabria DIMES I-87036 Arcavacata Di Rende Italy

Anomaly detection methods exploiting autoencoders (AE) have shown good performances. Unfortunately, deep non-linear architectures are able to perform high dimensionality reduction while keeping reconstruction error low, thus worsening outlier detecting performances of AEs. To alleviate the above problem, recently some authors have proposed to exploit variational autoencoders (VAE) and bidirectional Generative Adversarial Networks (GAN), which arise as a variant of standard AEs designed for generative purposes, both enforcing the organization of the latent space guaranteeing continuity. However, these architectures share with standard AEs the problem that they generalize so well that they can also well reconstruct anomalies. In this work we argue that the approach of selecting the worst reconstructed examples as anomalies is too simplistic if a continuous latent space autoencoder-based architecture is employed. We show that outliers tend to lie in the sparsest regions of the combined latent/error space and propose the VAEOut and LatentOut unsupervised anomaly detection algorithms, identifying outliers by performing density estimation in this augmented feature space. The proposed approach shows sensible improvements in terms of detection performances over the standard approach based on the reconstruction error.

关键词： Anomaly detection variational autoencoder Nearest neighbor density estimation

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A Generative Verification Framework on Statistical Stability for Data-Driven Controllers

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IEEE ACCESS 2023年 11卷 5267-5280页

作者： Lee, Suwon Kookmin Univ Dept Future Mobil Seoul 02707 South Korea

This study proposes a novel framework for evaluating the stability of data-driven controllers and the concept of statistical stability. The proposed framework can be used when it is challenging to show stability through conventional control theory. The novelty of this paper lies in that it provides a method for scientifically analyzing the stability of data-driven controllers, thereby improving the quality of data-driven controllers. The proposed framework consists of three parts: the generative model, controller optimizer, and verification model. A variational autoencoder is used to classify and randomly generate data, and the generated data are used to train the controller. A support vector machine is used to classify areas where the controller is statistically stable. The statistical stability of an optimal controller designed using a deep neural network structure is analyzed using the proposed framework.

关键词： Neural networks Deep learning Control systems Numerical stability Stability criteria Adaptive control Lyapunov methods Data-driven analysis deep neural network nonlinear controller nonlinear system verification optimal control performance analysis statistical stability variational autoencoder

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Experimental Validation of Machine Learning-Based Joint Failure Management and Quality of Transmission Estimation

IEEE PHOTONICS JOURNAL

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IEEE PHOTONICS JOURNAL 2023年第6期15卷 1页

作者： Kruse, Lars E. Kuehl, Sebastian Dochhan, Annika Pachnicke, Stephan Univ Kiel Chair Commun D-24143 Kiel Germany

The exponentially growing demand for high-speed data necessitates more complex and versatile networks. Optimization and reliability assurance of such high-complexity networks is getting increasingly important. In this article, we experimentally validate our a machine learning-based framework that combines quality of transmission (QoT) estimation with soft-failure detection, identification, and localization based on the same latent space of a variational autoencoder running on optical spectra obtained by optical spectrum analyzers at high priority nodes in the network. We further investigate the advantages of a variational autoencoder-based soft-failure detection mechanism over a QoT metric-based approach. We use data acquired from optical transmission experiments involving different modulation formats and channel configurations. The results demonstrate that the proposed framework achieves reliable QoT estimation in real world scenarios. Additionally, it effectively detects soft-failures, identifies specific failure types and accurately localizes the occurrence of failures.

关键词： Nonlinear optics Logic gates Optical fiber networks Estimation Optical noise Signal to noise ratio Adaptive optics Quality of transmission estimation optical performance monitoring soft-failures variational autoencoder recurrent neural networks

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