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Effects of intermediate stress on deep rock strainbursts under true triaxial stresses

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第3期15卷 659-682页

作者： lihua hu Liyuan Yu Minghe Ju Xiaozhao Li Chun’an Tang State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou221116China Sate Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian116024China Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education School of Civil and Architecture EngineeringGuangxi UniversityNanning530004China

The effect of intermediate stress(in situ tunnel axial)on a strainburst is studied with a threedimensional(3D)bonded block distinct element method(DEM).A series of simulations of strainbursts under true triaxial in situ stress conditions(*** tangential stress,moderate intermediate stress and low radial stress)of near-boundary rock masses are *** with the experimental results,the DEM model is able to capture the stress-strain response,failure pattern and energy balance of *** fracturing processes of strainbursts are also numerically *** results show that,as the intermediate stress increases:(1)The peak strain of strainbursts increases,the yield stress increases,the rock strength increases linearly,and the ratio of yield stress to rock strength decreases,indicating that the precursory information on strainbursts is enhanced;(2)Tensile and shear cracks increase significantly,and slabbing and bending of rock plates are more pronounced;and(3)The stored elastic strain energy and dissipated energy increase linearly,whereas the kinetic energy of the ejected rock fragments increases approximately exponentially,implying an increase in strainburst *** comparing the experimental and numerical results,the effect of intermediate stress on the rock strength of strainbursts is discussed in order to address three key ***,the Mogi criterion is applied to construct new strength criteria for strainbursts by converting the one-face free true triaxial stress state of a strainburst to its equivalent true triaxial stress *** summary,the effect of intermediate stress on strainbursts is a double-edged sword that can enhance the rock strength and the precursory information of a strainburst,but also increase its intensity.

关键词： Strainbursts Intermediate stress Distinct element method(DEM) Structural failure True triaxial Strength criterion

Tree-ring response of Larix chinensis on regional climate and sea-surface temperature variations in alpine timberline in the Qinling Mountains

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Journal of Forestry Research 2020年第1期31卷 209-218页

作者： Boqian Yan Jian Yu Qijing Liu lihua Wang Lile hu Department of Plant Sciences Beijing University of AgricultureBeijing 110016People’s Republic of China Forestry College Beijing Forestry UniversityTsinghua East Road No.35Haidian DistrictBeijing 100083People’s Republic of China Department of Urban Construction Beijing City UniversityBeijing 100085People’s Republic of China China Environmental Resources Technology Co. Ltd.Beijing 100012People’s Republic of China

Tree-ring width chronologies of Larix chinensis were developed from the northern and southern slopes of the Qinling Mountains in Shaanxi Province,and climatic factors affecting the tree-ring widths of *** were *** analysis showed that similar correlations between tree-ring width chronologies and climatic factors demonstrated that radial growth responded to climate change on both *** radial growth of *** was mainly limited by temperature,especially the growing *** contrast,both chronologies were negatively correlated with precipitation in May of the previous year and April of the current *** climate-correlation analyses with gridded land-surface climate data revealed that our tree-ring width chronologies contained a strong regional temperature signal over much of northcentral and eastern *** correlation with seasurface temperature fields highlights the influence of the Pacific Ocean,Indian Ocean,and North Atlantic *** coherence analysis indicated the existence of some decadal and interannual cycles in the two tree-ring width *** may suggest the influences of El Nin˜o-Southern Oscillation and solar activity on tree growth in the Qinling *** findings will help us understand the growth response of *** to climate change in the Qinling region,and they provide critical information for future climate reconstructions based on this species in semi-humid regions.

关键词： Climate response Dendroclimatic Tree-ring width L.chinensis Qinling Mountains

Distributed Resilient Fusion Filtering for Nonlinear Systems with Random Sensor Delays:Optimized Algorithm Design and Boundedness Analysis

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Journal of Systems Science & Complexity 2023年第4期36卷 1423-1442页

作者： hu Jun hu Zhibin dong Hongli LIU Hongjian School of Automation Harbin University of Science and TechnologyHarbin 150080China Department of Mathematics Harbin University of Science and TechnologyHarbin 150080China Heilongjiang Provincial Key Laboratory of Optimization Control and Intelligent Analysis for Complex Systems Harbin University of Science and TechnologyHarbin 150080China Heilongjiang Provincial Key Laboratory of Networking and Intelligent Control Northeast Petroleum UniversityDaqing 163318China School of Mathematics-Physics and Finance Anhui Polytechnic UniversityWuhu 241000China

This paper is concerned with the distributed resilient fusion filtering(DRFF)problem for a class of time-varying multi-sensor nonlinear stochastic systems(MNSSs)with random sensor delays(RSDs).The phenomenon of the RSDs is modeled by a set of random variables with certain statistical *** addition,the nonlinear function is handled via Taylor expansion in order to deal with the nonlinear fusion filtering *** aim of the addressed issue is to propose a DRFF scheme for MNSSs such that,for both RSDs and estimator gain perturbations,certain upper bounds of estimation error covariance(EEC)are given and locally minimized at every sample *** the light of the obtained local filters,a new DRFF algorithm is developed via the matrix-weighted fusion ***,a sufficient condition is presented,which can guarantee that the local upper bound of the EEC is ***,a numerical example is provided,which can show the usefulness of the developed DRFF approach.

关键词： Distributed resilient fusion filtering matrix-weighted fusion nonlinear time-varying systems random sensor delays

Number of edges in inhomogeneous random graphs

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Science China Mathematics 2021年第6期64卷 1321-1330页

作者： Zhishui hu Liang dong Department of Statistics and Finance School of ManagementUniversity of Science and Technology of ChinaHefei 230026China

We study the number of edges in the inhomogeneous random graph when vertex weights have an infinite mean and show that the number of edges is O(n log n).Central limit theorems for the number of edges are also establis... 详细信息

关键词： inhomogeneous random graphs number of edges power law complex network infinite mean

Marginal Attacks of Generating Adversarial Examples for Spam Filtering

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Chinese Journal of Electronics 2021年第4期30卷 595-602页

作者： GU Zhaoquan XIE Yushun hu Weixiong YIN lihua HAN Yi TIAN Zhihong Cyberspace Institute of Advanced Technology Guangzhou University

Digit information has been used in many areas and has been widely spread in the Internet era because of its convenience. However, many ill-disposed attackers, such as spammers take advantage of such convenience to send unsolicited information, such as advertisements, frauds, and pornographic messages to mislead users and this might cause severe *** many spam filters have been proposed in detecting spams, they are vulnerable and could be misled by some carefully crafted adversarial *** this paper, we propose the marginal attack methods of generating such adversarial examples to fool a naive Bayesian spam ***, we propose three methods to select sensitive words from a sentence and add them at the end of the sentence. Through extensive experiments, we show that the generated adversarial examples could largely reduce the filter's detecting accuracy, e.g. by adding only one word, the accuracy could be reduced from 93.6% to 55.8%. Furthermore, we evaluate the transferability of the generated adversarial examples against other traditional filters such as logic regression, decision tree and linear support vector machine based filters. The evaluation results show that these filters' accuracy is also reduced dramatically; especially,the decision tree based filter's accuracy drops from 100%to 1.51% by inserting only one word.

关键词： Spam filtering Marginal attack Adversarial example Machine learning

Power Synchronization Compensation Strategy Based on Second-order Compensation Links for Voltage-controlled Inverters in Microgrids

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Journal of Modern Power Systems and Clean Energy 2023年第6期11卷 1935-1947页

作者： Jiawei dong Chunyang Gong Jun Bao lihua Zhu hui Chen Zhixin Wang School of Electronic Information and Electrical Engineering Shanghai Jiao Tong UniversityShanghaiChina Shanghai University of Electrical Power ShanghaiChina Shanghai Xilong Solar Energy Technology Co. Ltd.ShanghaiChina Shanghai Chint Power Systems Co. Ltd.ShanghaiChina College of Automation Engineering Shanghai University of Electric PowerShanghaiChina

A second-order compensation link is adopted to control voltage-controlled inverters(VCIs) in microgrid systems to enhance the performance of the power synchronization process of the inverter. The second-order compensation link is classified as both a real pole compensator(RPC) and a complex pole compensator(CPC) according to the pole position. Given a model for the VCI power output, the design process for the second-order compensation link, which is equipped with an RPC and a CPC, is detailed. Moreover, the frequency-domain compensation effects of the RPC and CPC are analyzed using the root locus and Bode diagrams of the system before and after compensation. Finally, the compensation effects of the two types of second-order compensators are compared with the commonly used high-pass filter using MATLAB/Simulink, which verifies the RPC and CPC strategies. Simulation results show that the two types of compensators designed in this study can effectively increase the system cutting frequency and improve the phase margin in the frequency domain while accelerating the power synchronization process, simultaneously making it smoother and reducing overshoot in the time domain. The RPC has better gain robustness, whereas the CPC has better time constant robustness. By implementing an RPC or a CPC, the dynamic time of the power synchronization compensation strategy is reduced within 0.5 s, and the overshoot is reduced within 10% in the experiments with two inverters.

关键词： Frequency-domain analysis power synchronization second-order compensation link stability voltage-controlled inverter(VCI) microgrid

Regeneration of deactivated CeCoxO2 catalyst by simple thermal treatment

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Journal of Rare Earths 2020年第8期38卷 899-905,I0003页

作者： Yandi Cai lihua Wang Shuohan Yu Jingfang Sun Baochun Liu Lin dong College of Chemistry and Molecular Engineering Nanjing Tech UniversityNanjing 211800China Jiangsu Key Laboratory of Vehicle Emissions Control School of the EnvironmentCenter of Modern AnalysisNanjing UniversityNanjing 210093China Key Laboratory of Mesoscopic Chemistry of MOE School of Chemistry and Chemical EngineeringNanjing UniversityNanjing 210093China

Active species loss owing to reactant stream washing is a general problem which industrial catalysts suffer *** case of catalysts synthesized by co-precipitation method,which have active species unused in bulk phase,can be regenerated by a simple thermal treatment that leads to active species in bulk phase migration to surface of the deactivated *** this work,the influence of regeneration temperature was investigated by employing ammonium hydroxide washing to simulate reactant stream washing of CeCoxO2 catalysts for NO+CO *** is found that the deactivated catalyst can be regenerated by simple thermal treatment and increasing calcination temperature could accelerate the Co species migration from the bulk phase to surface of catalysts.

关键词： NO+CO CeO2 Catalyst regeneration Thermal migration Rare earths

Wear Properties of Plasma Transferred Arc Fe-based Coatings Reinforced by Spherical WC Particles

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Journal of Wuhan University of Technology(Materials Science) 2019年第2期34卷 433-439页

作者：范丽董耀华 CHEN Haiyan dong lihua YIN Yansheng College of Mechanical and Electronic Engineering Shanghai Jian Qiao University School of Mechanical Engineering Shanghai Jiaotong University College of Ocean Science and Engineering Shanghai Maritime University

Fe-based coatings reinforced by spherical WC particles were produced on the 304 stainless steel by plasma transferred arc(PTA) to enhance the surface wear properties. Three different Fe/WC composite powder mixtures containing 0 wt%, 30 wt%, and 60 wt% of WC were investigated. The microstructure and phase composition of the Fe/WC composite PTA coatings were evaluated systemically by using scanning electron microscope(SEM) and X-ray diffraction(XRD). The wear properties of the three fabricated PTA coatings were investigated on a BRUKER UMT TriboLab. The morphologies of the worn tracks and wear debris were characterized by using SEM and 3 D non-contract profiler. The experimental results reveal that the microhardness on the cross-section and the wear resistance of the fabricated coatings increase dramatically with the increasing adding WC contents. The coating containing 60 wt% of WC possesses excellent wear resistance validated by the lower coefficients of friction(COF), narrower and shallower wear tracks and smaller wear rate. In the pure Fe-based coating, the main wear mechanism is the combination of adhesion and oxidative wear. Adhesive and two-body abrasive wear are predominated in the coating containing 30 wt% of WC, whereas threebody abrasion wear mechanism is predominated in the coating containing 60 wt% of WC.

关键词： plasma transferred arc(PTA) metal matrix composite coatings(MMCs) spherical tungsten carbide Fe-based alloys wear resistance

Toxicity of copper,lead,and cadmium on the motility of two marine microalgae Isochrysis galbana and Tetraselmis chui

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Journal of Environmental Sciences 2011年第2期23卷 330-335页

作者： Guangxu Liu Xueliang Chai Yanqing Shao lihua hu Qilang Xie Hongxi Wu College of Animal Sciences Zhejiang University Hangzhou 310029 China Zhejiang Mariculture Research Institute Wenzhou 325005 China Zhejiang Key Laboratory of Exploitation and Preservation of Costal Bio-resources Wenzhou 325005 China

Computer assisted movement tracking was used to characterize the motility of two marine microalgae, lsochrysis galbana and Tetraselmis chui, and to investigate the toxicity of Cu, Pb, and Cd on motile percentage, curvilinear velocity, average path velocity, straight line velocity, linearity, straightness, and wobble. Except for motile percentage, all other motility parameters differed significantly between L galbana and T. chui. Based on relative motile percentage data, the median effective concentration （ECs0） of Cu on the motility of L galbana and T. chui was 31.4 and 1.3 gmol/L, respectively, while for Pb it was 37.8 and 10.9 ~tmol/L and for Cd it was 12 1.6 and 37.8 ~tmol/L, respectively. Compared to L galbana, T. chui was more sensitive to all tested metals. The toxic effect of the heavy metals on motility exhibited the following decreasing order for both species： Cu 〉 Pb 〉 Cd. Our results indicate that L galbana and T. chui motility is sensitive to heavy metals and can be used as an indicator for toxicology bioassays.

关键词： copper lead cadmium motility lsochrysis galbana Tetraselmis chui