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Prediction of the microstructure of cold-compacted Astaloy 85Mo with deep generative models

COMPUTATIONAL MATERIALS SCIENCE 2024年 242卷

作者： Schenk, Oliver Becker, Marco Deng, Yuanbin Niemietz, Philipp Bergs, Thomas Broeckmann, Christoph Chair & Inst Mat Applicat Mech Engn Augustinerbach 4 D-52062 Aachen Germany Rhein Westfal TH Aachen Mfg Technol Inst MTI Campus Blvd 30 D-52074 Aachen Germany Fraunhofer Inst Prod Technol IPT Steinbachstr 17 D-52074 Aachen Germany

In powder metallurgy, iron -based powders are compacted to so-called green bodies, which undergo a subsequent sintering process. The microstructure of the green bodies affects the sintering process and the resulting properties of the produced component. Assessing the microstructure experimentally is time consuming and costly, while simulation approaches rely on simplifications that significantly affect relevant microstructural information. This work investigates the suitability of deep generative models to synthetically generate realistic micrographs of green bodies as an alternative to experiments and simulations. For that purpose experiments comparing Generative Adversarial Neural Networks and variational autoencoders were conducted. The two deep learning frameworks were used to train models which produce synthetic micrographs in dependence of two parameters, namely powder particle size and green body porosity. The data utilized to train and evaluate the models was acquired from compacted water -atomized Astaloy 85Mo via scanning electron microscopy. Besides visual inspection, the trained models were evaluated via quantitative metrics. Distributions of relevant microstructural parameters such as pore perimeter or minimum and maximum pore feret diameter of the synthetically generated micrographs were compared to those of experimentally acquired micrographs. The results indicate that Generative Adversarial Networks represent a promising approach to train models, which produce synthetic micrographs that capture relevant properties of green body micrographs in dependence of given parameters such as powder particle size. In contrast, the variational autoencoders trained for this study did not capture microstructural properties well.

关键词： Generative models Generative Adversarial Network variational autoencoder Micrograph Powder metallurgy Microstructure

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A deep learning factor analysis model based on importance-weighted variational inference and normalizing flow priors: Evaluation within a set of multidimensional performance assessments in youth elite soccer players

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STATISTICAL ANALYSIS AND DATA MINING-AN ASA DATA SCIENCE JOURNAL 2023年第5期16卷 474-487页

作者： Kilian, Pascal Leyhr, Daniel Urban, Christopher J. Hoener, Oliver Kelava, Augustin Univ Tubingen Methods Ctr Tubingen Germany Univ Tubingen Inst Sports Sci Methods Ctr Tubingen Germany Univ North Carolina Chapel Hill Dept Psychol & Neurosci Chapel Hill NC USA Univ Tubingen Inst Sports Sci Tubingen Germany

Exploratory factor analysis is a widely used framework in the social and behavioral sciences. Since measurement errors are always present in human behavior data, latent factors, generating the observed data, are important to identify. While most factor analysis methods rely on linear relationships in the data-generating process, deep learning models can provide more flexible modeling approaches. However, two problems need to be addressed. First, for interpretation, scaling assumptions are required, which can be (at least) cumbersome for deep generative models. Second, deep generative models are typically not identifiable, which is required in order to identify the underlying latent constructs. We developed a model that uses a variational autoencoder as an estimator for a complex factor analysis model based on importance-weighted variational inference. In order to receive interpretable results and an identified model, we use a linear factor model with identification constraints in the measurement model. To maintain the flexibility of the model, we use normalizing flow latent priors. Within the evaluation of performance measures in a talent development program in soccer, we found more clarity in the separation of the identified underlying latent dimensions with our models compared to traditional PCA analyses.

关键词： complex factor analysis deep latent variable models latent variable identification soccer talent research variational autoencoder

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Layer-constrained variational autoencoding kernel density estimation model for anomaly detection

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KNOWLEDGE-BASED SYSTEMS 2020年 196卷

作者： Lv, Peng Yu, Yanwei Fan, Yangyang Tang, Xianfeng Tong, Xiangrong Ocean Univ China Dept Comp Sci & Technol Qingdao 266100 Shandong Peoples R China Yantai Univ Sch Comp & Control Engn Yantai 264005 Shandong Peoples R China Shanghai Jiao Tong Univ Shanghai Key Lab Adv High Temp Mat & Precis Formi Shanghai 200240 Peoples R China Penn State Univ Coll Informat Sci & Technol University Pk PA 16802 USA

Unsupervised techniques typically rely on the probability density distribution of the data to detect anomalies, where objects with low probability density are considered to be abnormal. However, modeling the density distribution of high dimensional data is known to be hard, making the problem of detecting anomalies from high-dimensional data challenging. The state-of-the-art methods solve this problem by first applying dimension reduction techniques to the data and then detecting anomalies in the low dimensional space. Unfortunately, the low dimensional space does not necessarily preserve the density distribution of the original high dimensional data. This jeopardizes the effectiveness of anomaly detection. In this work, we propose a novel high dimensional anomaly detection method called LAKE. The key idea of LAKE is to unify the representation learning capacity of layer-constrained variational autoencoder with the density estimation power of kernel density estimation (KDE). Then a probability density distribution of the high dimensional data can be learned, which is able to effectively separate the anomalies out. LAKE successfully consolidates the merits of the two worlds, namely layer-constrained variational autoencoder and KDE by using a probability density-aware strategy in the training process of the autoencoder. Extensive experiments on six public benchmark datasets demonstrate that our method significantly outperforms the state-of-the-art methods in detecting anomalies and achieves up to 37% improvement in F-1 score. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Anomaly detection variational autoencoder Kernel density estimation Layer constraint Deep learning

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A Lightweight Unsupervised Intrusion Detection Model Based on variational Auto-Encoder

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SENSORS 2023年第20期23卷 8407页

作者： Ren, Yi Feng, Kanghui Hu, Fei Chen, Liangyin Chen, Yanru Sichuan Univ Sch Comp Sci Chengdu 610065 Peoples R China Sichuan Univ Inst Ind Internet Res Chengdu 610065 Peoples R China

With the gradual integration of internet technology and the industrial control field, industrial control systems (ICSs) have begun to access public networks on a large scale. Attackers use these public network interfaces to launch frequent invasions of industrial control systems, thus resulting in equipment failure and downtime, production data leakage, and other serious harm. To ensure security, ICSs urgently need a mature intrusion detection mechanism. Most of the existing research on intrusion detection in ICSs focuses on improving the accuracy of intrusion detection, thereby ignoring the problem of limited equipment resources in industrial control environments, which makes it difficult to apply excellent intrusion detection algorithms in practice. In this study, we first use the spectral residual (SR) algorithm to process the data;we then propose the improved lightweight variational autoencoder (LVA) with autoregression to reconstruct the data, and we finally perform anomaly determination based on the permutation entropy (PE) algorithm. We construct a lightweight unsupervised intrusion detection model named LVA-SP. The model as a whole adopts a lightweight design with a simpler network structure and fewer parameters, which achieves a balance between the detection accuracy and the system resource overhead. Experimental results on the ICSs dataset show that our proposed LVA-SP model achieved an F1-score of 84.81% and has advantages in terms of time and memory overhead.

关键词： industrial control systems intrusion detection variational autoencoder

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Towards physical interaction-based sequential mobility assistance using latent generative model of movement state

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ADVANCED ROBOTICS 2021年第1期35卷 64-79页

作者： Itadera, Shunki Kobayashi, Taisuke Nakanishi, Jun Aoyama, Tadayoshi Hasegawa, Yasuhisa Nagoya Univ Dept Micronano Mech Sci & Engn Nagoya Aichi Japan Nara Inst Sci & Technol Div Informat Sci Nara Japan Meijo Univ Dept Mech Engn Nagoya Aichi Japan

In this paper, we address sequential mobility assistance for daily elderly care through physical human-robot interaction. The goal of this work is to develop a robotic assistive system to provide physical support in daily life such as movement transition, e.g. sit-to-stand and walking. Using a mobile human support robotic platform, we propose an unsupervised learning-based approach to providing desirable physical support through an adaptive impedance parameter selection strategy according to the recognized user's movement state in an online manner. Using a latent generative model with a long short-term memory-based variational autoencoder, we first estimate the probability of the user's current movement state based on the sensory information in a low dimensional latent space. Then, the desired impedance parameters are selected adaptively according to the estimated movement state. One of the benefits of such an unsupervised learning approach is that no labeling is necessary in the training phase. Furthermore, our proposed framework is capable of detecting possible novel states such as falling over based on the obtained latent space. In order to demonstrate the proof of concept of our proposed approach, we present the experimental results of performance evaluations of online movement state recognition as well as novel movement detection.

关键词： Physical human– robot interaction mobility assistance movement detection latent generative model variational autoencoder

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Research on Insider Threat Detection Method Based on variational Autoencoding

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电脑学刊 2021年第4期32卷 201-210页

作者： Zhenjiang Zhang Lulu Zhao Yang Zhang Hongde Zhou Wei Li

In recent years, internal attacks have posed a serious threat to the security of individuals, companies and even the country. Machine learning is currently a common method of insider threat detection. However, this technology requires a series of complex feature engineering, which has certain limitations in practical applications. This paper comprehensively considers the user's business operation behavior data and internal psychological data, and establishes an internal threat detection model to analyze their potential associations. The main tasks are as follows: In order to improve the fine-grained features of heterogeneous behavior log data and accurately reflect user behavior attributes, a session-based full feature extraction method is proposed. In this method, combined with a variational autoencoder, a long and shortterm memory variational autoencoder (LVE) model is proposed. Taking into account the time characteristics of user behavior, a long and short-term memory network is used in the codec part, that is, input data, generate hidden variables, and then restore output data through hidden variables. The results show that this method improves the recall rate compared with other algorithms. Finally, the main work and improvement prospects are summarized.

关键词： detection efficiency insider threat user behavior analysis variational autoencoder

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Convolutional Neural Network Graph-based Embedding for Neural Architecture Search

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Procedia Computer Science 2023年 229卷 47-54页

作者： Evgeny Bessonnitsyn Vsevolod Shaldin Valeria Efimova Viacheslav Shalamov ITMO University Kronverksky Pr. 49 bldg. A St. Petersburg 197101 Russia

Recently, network architecture search is gaining popularity. The neural network representation as a directed acyclic graph is considered for subsequent architecture optimization. Currently, most of the existing encoders rely only on the model layer properties and do not take into account the attributes of layers. This work proposes an algorithm for mapping a CNN network to a vector space considering the layer attributes, such as different dimensions of a particular layer. The proposed algorithm was compared with D-VAE and DVAE-EMB and showed less information loss caused by the mapping of a network to a vector space. As the results show, the performance of the model was shown after direct conversion to embedding and reverse conversion to architecture. The method allows more accurate neural network architecture mapping into a vector form, which will improve the search for the best architecture. The method implementation is publicly available at https://***/Turukmokto/GraphEmbedding-dev .

关键词： neural network architecture search vector representation variational autoencoder graphs with attributes

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An Auto-Encoder with Genetic Algorithm for High Dimensional Data: Towards Accurate and Interpretable Outlier Detection

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ALGORITHMS 2022年第11期15卷

作者： Li, Jiamu Zhang, Ji Bah, Mohamed Jaward Wang, Jian Zhu, Youwen Yang, Gaoming Li, Lingling Zhang, Kexin Nanjing Univ Aeronaut & Astronaut Sch Comp Sci & Technol Nanjing 210016 Peoples R China Univ Southern Queensland Sch Math Phys & Comp Toowoomba Qld 4350 Australia Zhejiang Lab Big Data Intelligence Res Ctr Hangzhou 311121 Peoples R China Anhui Univ Sci & Technol Sch Comp Sci & Engn Huainan 243002 Peoples R China Zhengzhou Univ Aeronaut Sch Intelligent Engn Zhengzhou 450046 Peoples R China

When dealing with high-dimensional data, such as in biometric, e-commerce, or industrial applications, it is extremely hard to capture the abnormalities in full space due to the curse of dimensionality. Furthermore, it is becoming increasingly complicated but essential to provide interpretations for outlier detection results in high-dimensional space as a consequence of the large number of features. To alleviate these issues, we propose a new model based on a variational autoencoder and Genetic Algorithm (VAEGA) for detecting outliers in subspaces of high-dimensional data. The proposed model employs a neural network to create a probabilistic dimensionality reduction variational autoencoder (VAE) that applies its low-dimensional hidden space to characterize the high-dimensional inputs. Then, the hidden vector is sampled randomly from the hidden space to reconstruct the data so that it closely matches the input data. The reconstruction error is then computed to determine an outlier score, and samples exceeding the threshold are tentatively identified as outliers. In the second step, a genetic algorithm (GA) is used as a basis for examining and analyzing the abnormal subspace of the outlier set obtained by the VAE layer. After encoding the outlier dataset's subspaces, the degree of anomaly for the detected subspaces is calculated using the redefined fitness function. Finally, the abnormal subspace is calculated for the detected point by selecting the subspace with the highest degree of anomaly. The clustering of abnormal subspaces helps filter outliers that are mislabeled (false positives), and the VAE layer adjusts the network weights based on the false positives. When compared to other methods using five public datasets, the VAEGA outlier detection model results are highly interpretable and outperform or have competitive performance compared to current contemporary methods.

关键词： outlier detection variational autoencoder genetic algorithm abnormal subspace

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Collaborative Filtering Based on a variational Gaussian Mixture Model

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FUTURE INTERNET 2021年第2期13卷 1-11页

作者： Yang, FengLei Liu, Fei Liu, ShanShan Shanghai Univ Sch Comp Engn & Sci Shanghai 200444 Peoples R China

Collaborative filtering (CF) is a widely used method in recommendation systems. Linear models are still the mainstream of collaborative filtering research methods, but non-linear probabilistic models are beyond the limit of linear model capacity. For example, variational autoencoders (VAEs) have been extensively used in CF, and have achieved excellent results. Aiming at the problem of the prior distribution for the latent codes of VAEs in traditional CF is too simple, which makes the implicit variable representations of users and items too poor. This paper proposes a variational autoencoder that uses a Gaussian mixture model for latent factors distribution for CF, GVAE-CF. On this basis, an optimization function suitable for GVAE-CF is proposed. In our experimental evaluation, we show that the recommendation performance of GVAE-CF outperforms the previously proposed VAE-based models on several popular benchmark datasets in terms of recall and normalized discounted cumulative gain (NDCG), thus proving the effectiveness of the algorithm.

关键词： recommendation system variational autoencoder collaborative filtering Gaussian mixture model

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CBN-VAE: A Data Compression Model with Efficient Convolutional Structure for Wireless Sensor Networks

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SENSORS 2019年第16期19卷 3445页

作者： Liu, Jianlin Chen, Fenxiong Yan, Jun Wang, Dianhong China Univ Geosci Sch Mech Engn & Elect Informat Wuhan 430074 Hubei Peoples R China

Data compression is a useful method to reduce the communication energy consumption in wireless sensor networks (WSNs). Most existing neural network compression methods focus on improving the compression and reconstruction accuracy (i.e., increasing parameters and layers), ignoring the computation consumption of the network and its application ability in WSNs. In contrast, we pay attention to the computation consumption and application of neural networks, and propose an extremely simple and efficient neural network data compression model. The model combines the feature extraction advantages of Convolutional Neural Network (CNN) with the data generation ability of variational autoencoder (VAE) and Restricted Boltzmann Machine (RBM), we call it CBN-VAE. In particular, we propose a new efficient convolutional structure: Downsampling-Convolutional RBM (D-CRBM), and use it to replace the standard convolution to reduce parameters and computational consumption. Specifically, we use the VAE model composed of multiple D-CRBM layers to learn the hidden mathematical features of the sensing data, and use this feature to compress and reconstruct the sensing data. We test the performance of the model by using various real-world WSN datasets. Under the same network size, compared with the CNN, the parameters of CBN-VAE model are reduced by 73.88% and the floating-point operations (FLOPs) are reduced by 96.43% with negligible accuracy loss. Compared with the traditional neural networks, the proposed model is more suitable for application on nodes in WSNs. For the Intel Lab temperature data, the average Signal-to-Noise Ratio (SNR) value of the model can reach 32.51 dB, the average reconstruction error value is 0.0678 degrees C. The node communication energy consumption can be reduced by 95.83%. Compared with the traditional compression methods, the proposed model has better compression and reconstruction accuracy. At the same time, the experimental results show that the model has goo

关键词： wireless sensor networks data compression variational autoencoder downsampling-convolutional restricted boltzmann machine

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