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Towards fully automatic modelling of the fracture process in quasi-brittle and ductile materials:a unified crack growth criterion

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第7期9卷 867-877页

作者： Zhen-jun YANG guo-hua LIU College of Civil Engineering and Architecture Zhejiang University Hangzhou 310027 China

Fully automatic finite element(FE) modelling of the fracture process in quasi-brittle materials such as concrete and rocks and ductile materials such as metals and alloys,is of great significance in assessing structural integrity and presents tre-mendous challenges to the engineering community. One challenge lies in the adoption of an objective and effective crack propagation criterion. This paper proposes a crack propagation criterion based on the principle of energy conservation and the cohesive zone model(CZM) . The virtual crack extension technique is used to calculate the differential terms in the criterion. A fully-automatic discrete crack modelling methodology,integrating the developed criterion,the CZM to model the crack,a simple remeshing procedure to accommodate crack propagation,the J2 flow theory implemented within the incremental plasticity framework to model the ductile materials,and a local arc-length solver to the nonlinear equation system,is developed and im-plemented in an in-house program. Three examples,i.e.,a plain concrete beam with a single shear crack,a reinforced concrete(RC) beam with multiple cracks and a compact-tension steel specimen,are simulated. Good agreement between numerical predictions and experimental data is found,which demonstrates the applicability of the criterion to both quasi-brittle and ductile materials.

关键词： Finite element method (FEM) Crack propagation criterion Cohesive zone model (CZM) Virtual crack extension(VCE) Arc-length method

Designing Bézier surfaces minimizing the L^2-norm of the Gaussian curvature

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第1期8卷 142-148页

作者： MO guo-liang WU Ming-hua Department of Information and Computational Science Zhejiang University City College Hangzhou 310015 China

In freeform surface modelling, developable surfaces have much application value. But, in 3D space, there is not always a regular developable surface which interpolates the given boundary of an arbitrary piecewise smooth closed curve. In this paper, tensor product Bézier surfaces interpolating the closed curves are determined and the resulting surface is a minimum of the functional defined by the L2-integral norm of the Gaussian curvature. The Gaussian curvature of the surfaces is minimized by the method of solving nonlinear optimization problems. An improved approach trust-region form method is proposed. A simple application example is also given.

关键词： ensor product polynomial surfaces Gaussian curvature L^2-integral norm Texture mapping Nonlinear optimization

A new method in highway route design:joining circular arcs by a single C-Bézier curve with shape parameter

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第4期10卷 562-569页

作者： hua-hui CAI guo-jin WANG Institute of Computer Graphics and Image Processing State Key Lab of CAD & CG Zhejiang University Hangzhou 310027 China

We constructed a single C-Bezier curve with a shape parameter for G^2 joining two circular arcs. It was shown that an S-shaped transition curve, which is able to manage a broader scope about two circle radii than the Bezier curves, has no curvature extrema, while a C-shaped transition curve has a single curvature extremum. Regarding the two kinds of curves, specific algorithms were presented in detail, strict mathematical proofs were given, and the effectiveness of the method was shown by examples This method has the following three advantages：（1） the pattern is unified; （2） the parameter able to adjust the shape of the transition curve is available; （3） the transition curve is only a single segment, and the algorithm can be formulated as a low order equation to be solved for its positive root. These advantages make the method simple and easy to implement.

关键词： Transition curve C-Bezier curve Monotone curvature Shape parameter

Combination of Organic and Inorganic Electrolytes for Composite Membranes Toward Applicable Solid Lithium Batteries

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Chemical Research in Chinese Universities 2021年第2期37卷 246-253页

作者： mu Shuang BI Zhijie GAO Shenghan guo Xiangxins College of Physics Qingdao UniversityQingdao266071P.R.China

To meet the demand for long-range electric vehicles with high-energy-density batteries,the solid-state batteries(SSBs)have attracted ever-increasing attention due to their enormous potential in affording the energy density greater than 400 W·h/*** the key materials,the solid electrolytes can be classified as inorganic electrolyte and organic *** former usually has high ionic conductivity,good stability and mechanical properties,whereas being heavy and *** latter is usually flexible,light and easy to mass produce,nevertheless has poor ionic conductivity and ***,the combination of the organic and the inorganic electrolytes for the composite membranes has become the inevitable trend to achieve the high energy density and safety of lithium *** the perspective of practical application,this paper discusses how to construct the ideal organic-inorganic composite solid electrolyte with low areal specific resistance,thin texture,wide electrochemical window and high safety for applicable ***,the critical challenges and future development directions are prospected for the composite solid electrolytes.

关键词： Composite electrolyte Solid-state lithium battery Energy density Security

Sweet potato and potato residual flours as potential nutritional and healthy food material

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Journal of Integrative Agriculture 2017年第11期16卷 2632-2645页

作者： JU Dong mu Tai-hua SUN Hong-nan Key Laboratory of Agro-Products Processing Ministry of Agriculture/Institute of Food Science and Technology Chinese Academyof Agricultural Sciences Beijing 100193 P.R.China

In this study, the proximate composition, mineral content and amino acid composition of starch processing residues from 10 cultivars of sweet potato and 10 cultivars of potato were determined, and the nutritional and health-related values of these residues were investigated. The residual flours contained 20.63-31.48 g and 17.14-28.57 g rich dietary fiber per 100 g dry weight for sweet potato and potato, respectively, as well as mineral elements, including potassium, ferrum, zinc and copper. The highest limiting amino acid score （AAS） of the almost balanced amino acid composition were observed to be 71.07 and 57.96 for sweet potato and potato residues, respectively. A grey relational analysis showed that the nutritional values of Jishu 4 at 0.7519 and LT-5 at 0.7281 were the highest among the sweet potato and potato residues, respectively. The evaluation of the sweet potato/potato residues, the by-products of the starch industry, based on recommended daily intake （RDI） standards, indicated that the residues have potential nutritional and health-related food values.

关键词： sweet potato residue potato residue component analysis comprehensive nutritional value grey relationalanalysis

Private Keyword-Search for Database Systems Against Insider Attacks

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Journal of Computer Science & Technology 2017年第3期32卷 599-617页

作者： Peng Jiang Yi mu Fuchun guo Qiao-Yan Wen State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications Beijing 100876 China Centre for Computer and Information Security Research School of Computing and Information Technology University of Wollongong Wollongong NSW 2522 Australia

The notion of searchable encrypted keywords introduced an elegant approach to retrieve encrypted data without the need of decryption. Since the introduction of this notion, there are two main searchable encrypted keywords techniques, symmetric searchable encryption （SSE） and public key encryption with keyword search （PEKS）. Due to the complicated key management problem in SSE, a number of concrete PEKS constructions have been proposed to overcome it. However, the security of these PEKS schemes was only weakly defined in presence of outsider attacks;therefore they suffer from keyword guessing attacks from the database server as an insider. How to resist insider attacks remains a challenging problem. We propose the first searchable encrypted keywords against insider attacks （SEK-IA） framework to address this problem. The security model of SEK-IA under public key environment is rebuilt. We give a concrete SEK-IA construction featured with a constant-size trapdoor and the proposed scheme is formally proved to be secure against insider attacks. The performance evaluations show that the communication cost between the receiver and the server in our SEK-IA scheme remains constant, independent of the sender identity set size, and the receiver needs the minimized computational cost to generate a trapdoor to search the data from multiple senders.

关键词： public key encryption with keyword search keyword privacy insider attack searchable encrypted keyword

An Exact Generalized Test for Homogeneity of Inverse Gaussian Scale Parameters

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Acta Mathematicae Applicatae Sinica 2019年第4期35卷 761-769页

作者： Xu-hua LIU Xing-zhong XU Wei-yan mu Department of Mathematics China Agricultural University Beijing 100083 China College of Mathematics Beijing Institute of Technology Beijing 100081 China School of Science Beijing University of Civil Engineering and Architecture Beijing 100044 China

In this paper, we propose a new generalized p-value for testing homogeneity of scale parameters λi from k independent inverse Gaussian populations. The proposed generalized p-value is proved to have exact frequentist property, and it is also invariant under the group of scale transformation. Simulation results indicate that the proposed test is better than existing approximate χ^2 test.

关键词： Inverse Gaussian distribution Generalized p-value Exact frequentist property

Using FEM to predict tree motion in a wind field

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第7期9卷 907-915页

作者： Xiao-yi HU Wei-ming TAO Yi-mu guo Department of Mechanical Engineering Zhejiang University Hangzhou 310027 China School of Engineering Zhejiang Forestry University Hangzhou 311300 China

In this paper we propose a finite element(FE) simulation method to predict tree motion in a wind field. Two FE tree models were investigated:One model was generated based on a realistic nature-looking geometric tree model,and the other was a symmetric model to investigate the influence of asymmetric material properties on tree motion. The vortex-induced vibration(VIV) theory is introduced to estimate the fluctuating wind force being exerted on tree stems and the fluid-structure interaction(FSI) analysis is also included in the simulation. The results indicate that asymmetric material properties result in the crosswind displacement of the investigated node and the main swaying direction deviation. The simulation reveals that under wind loading,a tree with leaves has much larger swaying amplitude along the wind direction and longer swaying period than a tree without leaves. However,the crosswind swaying amplitude is mainly due to branch interaction. The numerical simulation proved that the inter-action of tree branches can prevent dangerous swaying motion developing.

关键词： Finite element method (FEM) Fluid-structure interaction (FSI) Vortex-induced vibration (VIV) Asymmetric Wind field

Residual-Based False Data Injection Attacks Against multi-Sensor Estimation Systems

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IEEE/CAA Journal of Automatica Sinica 2023年第5期10卷 1181-1191页

作者： Haibin guo Jian Sun Zhong-hua Pang the National Key Laboratory of Autonomous Intelligent Unmanned Systems School of AutomationBeijing Institute of TechnologyBeijing 100081China the Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120China the Key Laboratory of Fieldbus Technology and Automation of Beijing North China University of TechnologyBeijing 100144China

This paper investigates the security issue of multisensor remote estimation *** optimal stealthy false data injection(FDI)attack scheme based on historical and current residuals,which only tampers with the measurement residuals of partial sensors due to limited attack resources,is proposed to maximally degrade system estimation *** attack stealthiness condition is given,and then the estimation error covariance in compromised state is derived to quantify the system performance under *** optimal attack strategy is obtained by solving several convex optimization problems which maximize the trace of the compromised estimation error covariance subject to the stealthiness ***,due to the constraint of attack resources,the selection principle of the attacked sensor is provided to determine which sensor is attacked so as to hold the most impact on system ***,simulation results are presented to verify the theoretical analysis.

关键词： Cyber-physical systems(CPSs) false data injection(FDI)attacks remote state estimation stealthy attacks