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Chinese Journal of Aeronautics 2022年第5期35卷 333-346页

作者： Bofan DONG zhenzhou LU School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China

In the field of the system reliability analysis with multiple failure modes,the advances mainly involve only random *** upper bound of the system failure probability with multiple failure modes is usually employed to quantify the safety level under Random and Interval Hybrid Uncertainty(RI-HU).At present,there is a lack of an efficient and accurate method for estimating the upper bound of the system failure *** paper proposed an efficient Kriging model based on numerical simulation algorithm to solve the system reliability analysis under *** method proposes a system learning function to train the system Kriging models of the system limit state *** convergent Kriging models are used to replace the limit state functions of the system multi-mode for identifying the state of the random *** proposed system learning function can adaptively select the failure mode contributing most to the system failure probability from the system and update its Kriging ***,the efficiency of the Kriging training process can be improved by avoiding updating the Kriging models contributing less to estimating the system failure *** presented examples illustrate the superiority of the proposed method.

关键词： Failure probability Kriging model Random and interval hybrid uncertainty System learning function System reliability

Revised regional importance measures in the presence of epistemic and aleatory uncertainties

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Science China(Physics,Mechanics & Astronomy) 2015年第1期58卷 84-94页

作者： CHENG Lei LU zhenzhou WU DanQing School of Aeronautics Northwestern Polytechnical University

Two revised regional importance measures(RIMs),that is,revised contribution to variance of sample mean(RCVSM)and revised contribution to variance of sample variance(RCVSV),are defined herein by using the revised means of sample mean and sample variance,which vary with the reduced range of the epistemic *** RCVSM and RCVSV can be computed by the same set of samples,thus no extra computational cost is introduced with respect to the computations of CVSM and *** the plots of RCVSM and RCVSV,accurate quantitative information on variance reductions of sample mean and sample variance can be read because of reduced upper bound of the range of the epistemic *** general form of quadratic polynomial output,the analytical solutions of the original and the revised RIMs are *** example is employed and results demonstrate that the analytical results are consistent and *** engineering example is applied to testify the validity and rationality of the revised RIMs,which can give instructions to the engineers about how to reduce variance of sample mean and sample variance by reducing the range of epistemic parameters.

关键词： revised rims sample mean sample variance variance reduction analytical solution

Growth of Casting Microcrack and Micropore in Single-crystal Superalloys Analysed by Three-Dimensional Unit Cell

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Journal of Materials Science & Technology 2006年第2期22卷 183-189页

作者： Jiansong WAN zhenzhou LU Zhufeng YUE Department of Engineering Mechanics Northwestern Polytechnical University Xi＇an 710072 China

Finite element （FE） analysis was employed to investigate the casting microcrack and micropore growth in nickel-base single-crystal superalloys DD3. Based on the finite deformation rate-dependent crystallographic constitutive equation, the simulations of casting microcrack and micropore growth in three-dimensional unit cell model were carried out in a range of parameters including stress triaxiality, Lode parameter and type of activated slip systems. The FE results show that the stress triaxiality has profound effects on growth behavior, and the Lode parameter is also important for the casting microcrack and micropore growth. The type of operative slip systems has remarkable effect on casting microcrack and micropore growth, so the life of single- crystal component is associated with the type of activated slip systems, which is related to Schmid factor and the number of activated slip systems. The growth comparison between microcrack and micropore reveals that when the material is subjected to large deformation, the growth rate of microcrack is faster than that of micropore, i.e. microcrack is more dangerous than micropore; the microcrack is easier to result in brittle fracture than micropore. The stress triaxiality and Lode parameter have strong influence on the growth of microcrack and micropore.

关键词： Casting micropore Casting crack Single-crystal superalloys Crystallographic constitutive equation

A novel method for importance measure analysis in the presence of epistemic and aleatory uncertainties

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Chinese Journal of Aeronautics 2014年第3期27卷 568-576页

作者： Ren Bo Lu zhenzhou Zhou Changcong School of Aeronautics Northwestern Polytechnical University

For structural systems with both epistemic and aleatory uncertainties, research on quantifying the contribution of the epistemic and aleatory uncertainties to the failure probability of the systems is conducted. Based on the method of separating epistemic and aleatory uncertainties in a variable, the core idea of the research is firstly to establish a novel deterministic transition model for auxiliary variables, distribution parameters, random variables, failure probability, then to propose the improved importance sampling （IS） to solve the transition model. Furthermore, the distribution parameters and auxiliary variables are sampled simultaneously and independently;therefore, the inefficient sampling procedure with an＇＇inner-loop＇＇ for epistemic uncertainty and an＇＇outer-loop＇＇ for aleatory uncertainty in traditional methods is avoided. Since the proposed method combines the fast convergence of the proper estimates and searches failure samples in the interesting regions with high efficiency, the proposed method is more efficient than traditional methods for the variance-based failure probability sensitivity measures in the presence of epistemic and aleatory uncertainties. Two numerical examples and one engineering example are introduced for demonstrating the efficiency and precision of the proposed method for structural systems with both epistemic and aleatory uncertainties.

关键词： Aleatory uncertainty Epistemic uncertaintyImportance sampling Sensitivity analysis Uncertainty system

Threshold-type memristor-based crossbar array design and its application in handwritten digit recognition

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Journal of Systems Engineering and Electronics 2023年第2期34卷 324-334页

作者： LI Qingjian LIANG Yan LU zhenzhou WANG Guangyi School of Electronic and Information Hangzhou Dianzi UniversityHangzhou 310018China

Neuromorphic computing simulates the operation of biological brain function for information processing and can potentially solve the bottleneck of the Von Neumann *** by the real characteristics of physical memristive devices,we propose a threshold-type nonlinear voltage-controlled memristor mathematical model which is used to design a novel memristor-based crossbar *** presented crossbar array can simulate the synaptic weight in real number field rather than only positive number *** analysis and simulation results of a 2×2 image inversion operation validate the feasibility of the proposed crossbar array and the necessary training and inference ***,the presented crossbar array is used to construct the neural network and then applied in the handwritten digit *** Mixed National Institute of Standards and Technology(MNIST)database is adopted to train this neural network and it achieves a satisfactory accuracy.

关键词： memristor threshold characteristic modelling electrical synapse crossbar array

Potential friendship discovery in social networks based on hybrid ensemble multiple collaborative filtering models in a 5G network environment

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Digital Communications and Networks 2022年第6期8卷 868-876页

作者： Hexuan Hu zhenzhou Lin Qiang Hu Ye Zhang Key Laboratory of Water Big Data Technology of Ministry of Water Resources Hohai UniversityNanjingChina College of Computer and Information Hohai UniversityNanjingChina Office of Teaching Affairs Nanjing University of Finance and EconomicsNanjingChina Electric Engineering College Tibet Agriculture&Animal Husbandry UniversityTibetChina

At present, 5G network technology is being applied to various social network modes, and it can provide technical and traffic support for social networks. Potential friendship discovery technology in 5G-enabled social networks is beneficial for users to make potential friends and expand their range of activities and social hierarchy, which is highly sought after in today's social networks and has great economic and application value. However, the sparsity of the dominant user association dataset in 5G-enabled social networks and the limitations of traditional collaborative filtering algorithms are two major challenges for the friend recommendation problem. Therefore, in order to overcome these problems regarding previous models, we propose a Hybrid Ensemble Multiple Collaborative Filtering Model (HEMCF) for discovering potential buddy relationships. The HEMCF model draws on a special autoencoder method that can effectively exploit the association matrix between friends and additional information to extract a hidden representation of users containing global structural information. Then, it uses the random walk-based graph embedding algorithm DeepWalk to extract another hidden representation of users in the buddy network containing local structural information. Finally, in the output module, the HEMCF model stacks and multiplies the two types of hidden representations of users to ensure that the information mentioned above is concentrated in the final output to generate the final prediction value. The magnitude of the prediction value represents the probability of the users being friends, with larger values representing a high probability of the two users being friends, and vice versa. Experimental results show that the proposed method boosts the accuracy of the relationship prediction over baselines on 3 real-world public datasets dramatically.

关键词： 5G network Social network Collaborative filtering Recommendation system Friendship discovering

Contribution to sample failure probability plot and its solution by Kriging method

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Science China(Technological Sciences) 2013年第4期56卷 866-877页

作者： LI DaWei Lü zhenzhou ZHOU ChangCong School of Aeronautics Northwestern Ploytechnical University

To analyze the effect of the region of the model inputs on the model output,a novel concept about contribution to the sample failure probability plot(CSFP) is proposed based on the contribution to the sample mean plot(CSM) and the contribution to the sample variance plot(CSV).The CSFP can be used to analyze the effect of the region of the model inputs on the failure *** the definition of CSFP,its property and the differences between CSFP and CSV/CSM are *** proposed CSFP can not only provide the information about which input affects the failure probability mostly,but also identify the contribution of the regions of the input to the failure probability *** employing the Kriging model method on optimized sample points,a solution for CSFP is *** computational cost for solving CSFP is greatly decreased because of the efficiency of Kriging surrogate *** examples are used to illustrate the validity of the proposed CSFP and the applicability and feasibility of the Kriging surrogate method based solution for CSFP.

关键词： sample failure probability plot sensitivity analysis optimization sample points Kriging model region of the inputs

Importance measure system of fuzzy and random input variables and its solution by point estimates

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Science China(Technological Sciences) 2011年第8期54卷 2167-2179页

作者： LI LuYi LU zhenzhou LI Wei School of Aeronautics Northwestern Polytechnical University Xi'an 710072 China

For structure system with fuzzy input variables as well as random ones, a new importance measure system is presented for evaluating the effects of the two kinds of input variables on the output response. Based on the fact that the fuzziness of the output response is determined by that of the input variable, the presented measure system defines the importance measures which evaluate the effect of the fuzzy input variable. And for the random input variable, the importance measure system analyzes its effect from two aspects, i.e. its effect on the central distribution position and that on the fuzzy degree of the membership function of the output response. Taking the effects of the two kinds of input variables on the first moment and second one of the output response into account, the definitions of the importance measures of the input variables are given and their engineering significations are demonstrated. Combining with the advantages of the point estimates of Zhao and Ono, a solution of the proposed importance measures is provided. Several examples show that the proposed measure system is comprehensive and reasonable, and the proposed solution can improve computational efficiency considerably with acceptable precision.

关键词： random input variable fuzzy input variable importance measure conditional probability moment unconditional probability moment point estimates

Reliability Sensitivity Algorithm Based on Stratified Importance Sampling Method for Multiple Failure Modes Systems

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Chinese Journal of Aeronautics 2010年第6期23卷 660-669页

作者： Zhang Feng Lu zhenzhou Cui Lijie Song Shufang School of Mechanics and Civil and Architecture Northwestern Polytechnical University Xi 'an 710072 China School of Aeronautics Northwestern Polyteehnical University. Xi 'an 710072 China

Combining the advantages of the stratified sampling and the importance sampling, a stratified importance sampling method （SISM） is presented to analyze the reliability sensitivity for structure with multiple failure modes. In the presented method, the variable space is divided into several disjoint subspace by n-dimensional coordinate planes at the mean point of the random vec- tor, and the importance sampling functions in the subspaces are constructed by keeping the sampling center at the mean point and augmenting the standard deviation by a factor of 2. The sample size generated from the importance sampling function in each subspace is determined by the contribution of the subspace to the reliability sensitivity, which can be estimated by iterative simulation in the sampling process. The formulae of the reliability sensitivity estimation, the variance and the coefficient of variation are derived for the presented SISM. Comparing with the Monte Carlo method, the stratified sampling method and the importance sampling method, the presented SISM has wider applicability and higher calculation efficiency, which is demonstrated by numerical examples. Finally, the reliability sensitivity analysis of flap structure is illustrated that the SISM can be applied to engineering structure.

关键词： multiple failure modes reliability sensitivity Monte Carlo simulation stratified sampling method importance sam-piing method stratified importance sampling method (SISM)

A novel global optimization method of truss topology

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Science China(Technological Sciences) 2011年第10期54卷 2723-2729页

作者： WANG Qi LU zhenzhou TANG ZhangChun School of Aeronautics Northwestern Polytechnical University Xi'an 710072 China

This paper proposes a global topology optimization algorithm based on subset simulation for the singular optimum problem subject to stress constraints of trusses. The constraints are handled by a fitness function which reflects their degree of violation. The rational and global topology results are guaranteed by the judgment of the samples’ rationality and the Metropolis-Hasting algorithm. Three examples show that the established method can quickly reduce the searching region to the feasible region and converge to the global optimum precisely enough for the singular optimum problem.

关键词： topology optimization truss subset simulation singular optimum global optimization