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Microdamage study of granite under thermomechanical coupling based on the particle flow code

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Frontiers of Structural and Civil Engineering 2023年第9期17卷 1413-1427页

作者： Chong SHI Yiping zhang yulong zhang Xiao CHEN Junxiong YANG Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering Hohai UniversityNanjing 210098China College of Civil and Transportation Engineering Hohai UniversityNanjing 210098China Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines College of Resources and Civil EngineeringNortheastern UniversityShenyang 110819China Department of Civil and Mineral Engineering University of TorontoToronto M5S1A1Canada

The thermomechanical coupling of rocks refers to the interaction between the mechanical and thermodynamic behaviors of rocks induced by temperature *** study of this coupling interaction is essential for understanding the mechanical and thermodynamic properties of the surrounding rocks in underground *** this study,an improved temperature-dependent linear parallel bond model is introduced under the framework of a particle flow simulation.A series of numerical thermomechanical coupling tests are then conducted to calibrate the micro-parameters of the proposed model by considering the mechanical behavior of the rock under different thermomechanical *** agreement between the numerical results and experimental data are obtained,particularly in terms of the compression,tension,and elastic responses of *** this improved model,the thermodynamic response and underlying cracking behavior of a deep-buried tunnel under different thermal loading conditions are investigated and discussed in detail.

关键词： thermomechanical coupling effect granite improved linear parallel bond model thermal property particle flow code

Accurate and efficient exploit capture and classification

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Science China(Information Sciences) 2017年第5期60卷 193-209页

作者： Yu DING Tao WEI Hui XUE yulong zhang Chao zhang Xinhui HAN Institute of Computer Science and Technology Peking University Eletrical Engineering and Computer Sciences UC Berkeley

Software exploits, especially zero-day exploits, are major security threats. Every day, security experts discover and collect numerous exploits from honeypots, malware forensics, and underground ***, no easy methods exist to classify these exploits into meaningful categories and to accelerate diagnosis as well as detailed analysis. To address this need, we present Seismo Meter, which recognizes both control-flowhijacking, and data-only attacks by combining approximate control-flow integrity, fast dynamic taint analysis and API sandboxing schemes. Once it detects an exploit incident, Seismo Meter generates a succinct data representation, called an exploit skeleton, to characterize the captured exploit. Seismo Meter then classifies the captured exploits into different exploit families by performing distance computing on the extracted *** evaluate the efficiency of Seismo Meter, we conduct a field test using exploit samples from public exploit databases, such as Metasploit, as well as wild-captured exploits. Our experiments demonstrate that Seismo Meter is a practical system that successfully detects and correctly classifies all these exploit attacks.

关键词： software security exploit classification exploit attack capture control flow integrity JIT security

Construction of Short-Block Nonbinary LDPC Codes Based on Cyclic Codes

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China Communications 2017年第8期14卷 1-9页

作者： Hengzhou Xu Baoming Bai Min Zhu Bo zhang yulong zhang School of Network Engineering Zhoukou Normal UniversityZhoukou 466001China State Key Laboratory of Integrated Service Networks Xidian UniversityXi'an 710071China Zhoukou Hydrology and Water Resoures Survey Bureau of Henan Province Zhoukou 466001China

In this paper, we focus on shortblock nonbinary LDPC(NB-LDPC) codes based on cyclic codes. Based on Tanner graphs' isomorphism, we present an efficient search algorithm for finding non-isomorphic binary cyclic LDPC codes. Notice that the parity-check matrix H of the resulting code is square and not of full rank, and its row weight and column weight are the same. By replacing the ones in the same column of H with a nonzero element of fi nite fi elds GF(q), a class of NB-LDPC codes over GF(q) is obtained. Numerical results show that the constructed codes perform well over the AWGN channel and have fast decoding convergence. Therefore, the proposed NB-LDPC codes provide a promising coding scheme for low-latency and high-reliability communications.

关键词： nonbinary LDPC codes tanner graph isomorphism iterative decoding

Master crack types and typical acoustic emission characteristics during rock failure

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International Journal of Coal Science & Technology 2023年第1期10卷 73-86页

作者： Tongbin Zhao Pengfei zhang Yaxun Xiao Weiyao Guo yulong zhang Xiufeng zhang State Key Laboratory of Mining Disaster Preventionand Control Co-founded By Shandong Provinceand the Ministry of Science and Technology ShandongUniversity of Science and TechnologyQingdao 266590China College of Energy and Mining Engineering ShandongUniversity of Science and TechnologyQingdao 266590China State Key Laboratory of Geomechanics and GeotechnicalEngineering Institute of Rock and Soil MechanicsChineseAcademy of SciencesWuhan 430071China Research Center for Rock Burst Control Shandong EnergyGroup Co.Ltd.Jinan 250014China

Acoustic emission(AE)signals contain substantial information about the internal fracture characteristics of rocks and are useful for revealing the laws governing the release of energy stored *** here is the evolution of rock failure with diferent master crack types as investigated using Brazilian splitting tests(BSTs),direct shear tests(DSTs),and uniaxial compression tests(UCTs).The AE parameters and typical modes of each fracture type were obtained,and the energy release characteristics of each fracture mechanism were *** the observed changes in the AE parameters,the rock fracture process exhibits characteristics of staged *** scale and energy level of crack activity in the BSTs were signifcantly lower than those in the DSTs and *** proportion of tensile cracks in the BSTs was 65%–75%,while the proportions of shear cracks in the DSTs and UCTs were 75%–85%and 70%–75%,*** the rock loading process under diferent conditions,failure was accompanied by an increased number of shear *** amplitude,duration,and rise time of the AE signal from rock failure were larger when the failure was dominated by shear cracks rather than tensile ones,and most of the medium-and high-energy signals had medium to low *** calculating the proposed energy amplitude ratio,the energy release of shear cracks was found to exceed that of tensile cracks at the same fracture scale.

关键词： Rock failure Fracture mechanism Acoustic emission Master crack type Energy release

Spray-coated electret materials with enhanced stability in a harsh environment for an MEMS energy harvesting device

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Microsystems & Nanoengineering 2021年第1期7卷 151-159页

作者： Anxin Luo Yixin Xu yulong zhang Mi zhang Xiaoqing zhang Yan Lu Fei Wang School of Microelectronics Southern University of Science and Technology518055 ShenzhenChina State Key Laboratory of AMS-VLSI Institute of MicroelectronicsUniversity of Macao(UM)999078 MacaoChina Department of Electrical and Computer Engineering FSTUM999078 MacaoChina Engineering Research Center of Integrated Circuits for Next-Generation Communications Ministry of EducationSouthern University of Science and Technology518055 ShenzhenChina Department of Mechanical Engineering Boston UniversityBostonMAUSA College of New Materials and New Energies Shenzhen Technology University518118 ShenzhenChina Shanghai Key Laboratory of Special Artificial School of Physics Science and Engineering Tongji University200092 ShanghaiChina

The charge stability of electret materials can directly affect the performance of electret-based devices such as electrostatic energy *** this paper,a spray-coating method is developed to deposit an electret layer with enhanced charge *** long-term stability of a spray-coated electret is investigated for 500 days and shows more stable performance than a spin-coated layer.A second-order linear model that includes both the surface charge and space charge is proposed to analyze the charge decay process of electrets in harsh environments at a high temperature(120°C)and high humidity(99%RH);this model provides better accuracy than the traditional deep-trap *** further verify the stability of the spray-coated electret,an electrostatic energy harvester is designed and fabricated with MEMS(micro-electromechanical systems)*** electret material can work as both the bonding interface and electret layer during fabrication.A maximum output power of 11.72μW is harvested from a vibrating source at an acceleration of 28.5 m/*** the energy harvester with the spray-coated electret is exposed to a harsh environment(100°C and 98%RH),an adequate amount of power can still be harvested even after 34 h and 48 h,respectively.

关键词： stability. stability electrostatic

Influence of phosphate on deposition and detachment of TiO2 nanoparticles in soil

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Frontiers of Environmental Science & Engineering 2019年第5期13卷 163-173页

作者： Zhan Wang Chongyang Shen Yichun Du yulong zhang Baoguo Li Department of Soil and Water Sciences China Agricultural UniversityBeijing 100193China College of Land and Environment Shenyang Agricultural UniversityShenyang 110866China Key Laboratory of Degraded and Unused Land Consolidation Engineering Ministry of Land and ResourcesShaanxi Provincial Land Engineering Construction Group Co.Ltd.Xi’an 710075China

The widespread use of TiO2 nanoparticles (NPs) makes inevitable their release into the soil. Phosphate is also widespread within soil, and is likely copresent with TiO2 NPs. However, the influence of phosphate on deposition/release— and thereby on transport— of TiO2 NPs in soil is yet to be elucidated. In this study we conducted saturated column experiments to systematically examine the transport of TiO2 NPs in soil amended with phosphate at different ionic strengths (ISs) (1, 10, 100 mmol/L NaCl) and pHs (4 and 9). Results show that the deposition of TiO2 NPs decreased with decreasing IS, increasing pH, and when soil absorbed phosphate. These observations are qualitatively in agreement with Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy calculations, because the repulsive energy barrier is larger and secondary minimum depth is smaller at a lower IS, higher pH, and in the presence of phosphate. Accordingly, both primary- and secondary-minimum deposition were inhibited. Interestingly, although the deposition was less at higher pH and in the presence of phosphate, the subsequent spontaneous detachment and detachment by reduction of solution IS in these cases were greater. In addition, the presence of phosphate in the solution can cause a small quantity of attached TiO2 NPs to detach, even without perturbations of physical and chemical conditions. Our study was the first to investigate the influence of phosphate on detachment of TiO2 NPs and the results have important implication for accurate prediction of fate and transport of TiO2 NPs in subsurface environments.

关键词： Phosphate TiO2 nanoparticles Transport Soil Deposition Detachment

Ag-Pd alloy decorated ZnIn_(2)S_(4) microspheres with optimal Schottky barrier height for boosting visible-light-driven hydrogen evolution

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Journal of Materials Science & Technology 2022年第19期114卷 81-89页

作者： Chao Liu yulong zhang Jiaxin Wu Hailu Dai Chengjian Ma Qinfang zhang Zhigang Zou School of Materials Science and Engineering Yancheng Institute of TechnologyYancheng 224051China Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province Yancheng Institute of TechnologyYancheng 224051China Analytical and Testing Center Yancheng Institute of TechnologyYancheng 224051China Eco-Materials and Renewable Energy Research Centre(ERERC) Nanjing UniversityNanjing 210093China

Rapid charge carrier recombination rate and insufficient light harvesting capacity are two dominat-ing drawbacks encountered in zinc indium sulfide(ZnIn_(2)S_(4))for photocatalytic ***,a chemical reduction method was performed to combine bimetallic Ag-Pd alloy nanoparticles(NPs)with spherical-like ZnIn_(2)S_(4)(ZIS).By optimizing Ag:Pd molar ratio and overall loading amount,the optimal Ag_(0.25)Pd_(0.75)-ZIS sample exhibited a maximum H_(2)evolution rate(125.4μmol/h)under visible light,which was higher than that of ZIS,Ag-ZIS and *** loading of Ag NPs contribution to PHE reaction by its plasmonic effect was negligible compared to that of Pd loading(Schottky effect).The apparent quan-tum yield(AQY)values over Ag_(0.25)Pd_(0.75)-ZIS sample could reach up to 18.3%at 400 nm and 15.8%at 420 *** enhanced activity for photocatalytic hydrogen evolution(PHE)over Ag_(0.25)Pd_(0.75)-ZIS sample was mainly due to the bimetallic synergistic effect that presented as ***,the plasmon hy-bridization by loading Ag-Pd bimetallic alloy can significantly increase light harvesting capacity of ***,the optimal Schottky barrier height formed between Ag-Pd alloy and ZIS interface was benefi-cial for prolonging electron-hole pair lifetimes,promoting charge carrier separation and thus facilitating PHE *** functional theory(DFT)analysis indicated that the adsorption energy of H∗over Pd_(0.75)Ag_(0.25)alloy was very close to zero and thus theoretically possessed the highest activity for H_(2)evo-lution,which is in line with experimental *** theoretical calculation with experimental results,a reasonable photocatalytic mechanism was proposed and verified.

关键词： Photocatalytic hydrogen evolution ZnIn_(2)S_(4) Bimetallic alloy Schottky barrier Theoretical calculation

Spatial–temporal variability of terrestrial vegetation productivity in the Yangtze River Basin during 2000–2009

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Journal of Plant Ecology 2014年第1期7卷 10-23页

作者： yulong zhang Conghe Song Kerong zhang Xiaoli Cheng Quanfa zhang Key Laboratory of Aquatic Botany and Watershed Ecology Wuhan Botanical GardenChinese Academy of Sciences1 Moshan RoadWuhan 430074China Department of Geography University of North Carolina209 South RoadChapel HillNC 27599USA Department of Life Science University of the Chinese Academy of Sciences19 Yuquan RoadBeijing 100049China School of Forestry and Landscape Architecture Anhui Agricultural University130 West Changjiang RoadHefeiAnhui 230026China

Aims Terrestrial net primary production(NPP),the balance of gross primary production(GPP)and autotrophic respiration(AR),is a critical measure of carbon sequestration capacity for the Earth’s land *** aim of this study was to understand the spatio-temporal variability of NPP associated with GPP and AR in the Yangtze River Basin(YRB),China,from 2000 to 2009 during which the basin warmed *** We first derived AR and carbon-use efficiency(CUE)from the improved Moderate Resolution Imaging Spectroradiometer GPP/NPP products(MOD17)and then conducted spatial analysis to quantify how NPP relates to GPP,AR and their relationship with key observed climate variables(temperature,precipitation and sunshine percentage)in the YRB during 2000–*** Findings The spatial pattern of NPP in the YRB was predominantly determined by GPP and further modified by *** GPP and relatively low AR made the southern Jinshajiang sub-basin the most productive area in NPP in the YRB.A large portion of the YRB experienced a warmer and drier climate trend in the growing season during 2000–*** the upper reaches of the basin,possessing a relatively low temperature base,increases in temperature led to greater increases in GPP than those in AR,resulting in greater increased ***,in the middle and lower reaches of the basin where the base temperature is relatively high,increases in temperature led to greater increases in AR than those in GPP,leading to decreases in ***,86.7%of the vegetated area showed a consistent GPP and NPP trend through time with 71.3%of the vegetated area having a positive trend both in GPP and NPP,and the remaining 13.3%of vegetated areas showed an opposite trend in GPP and NPP,with positive GPP and negative NPP trajectories dominating(10.1%of vegetated area)the *** climate warming generally had positive effects on vegetation growth in most areas of the basin,areas with increased NPP(74.5%)were less extensive than t

关键词： Yangtze River Basin climate warming GPP AR NPP CUE spatial-temporal variability

Performance Evaluation and Optimization of a Novel System Combining a Photovoltaic/Thermal Subsystem&an Organic Rankine Cycle Driven by Solar Parabolic Trough Collector

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Journal of Thermal Science 2021年第5期30卷 1513-1525页

作者： LIU Zhijian WEI Tianhe WU Di zhang yulong LI Guiqiang YANG Xinyan Department of Power Engineering North China Electric Power UniversityBaoding 071003China Research Centre for Sustainable Energy Technologies University of HullHull HU67RXUK Institute of Building Environment and Energy China Academy of Building ResearchBeijing 100013China

A novel coupling system that combines a photovoltaic/thermal(PV/T)subsystem and an Organic Rankine Cycle(ORC)driven by solar parabolic trough collector(PTC)is presented in this *** mathematical model is initially *** the basis,the influence of area ratio of two collectors(PV/T and PTC)on the performance of system is *** results show that the optimal area ratio of PV/T to PTC is 8:2,which can achieve the maximum energy ***,the performance of the coupling system and two independent systems(PV/T and ORC system)are compared and *** results show that the coupling system is more reliable and its total output energy(heat and electricity)is the highest,compared with the other two independent *** solar energy utilization efficiency of the coupling system is 40%higher than that of the other two independent systems in the steady-state ***,the annual output energy per unit area collector of the coupling system is 13%higher than that of the other two independent systems in the dynamic ***,in the dynamic simulation of a typical day,the PV panels’temperature of the coupling system is 5℃–7℃ lower than that of the independent PV/T *** means that the power generation efficiency of PV panels can be increased by 1.5%–3.5%.This study aims to explore the operation characteristics of the novel solar energy utilization coupling system and promote the development of renewable energy utilization models,which provides a reference for the design and optimization of related energy systems.

关键词： solar energy utilization efficiency photovoltaic/thermal Organic Rankine Cycle novel coupling system area ratio