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Small-scale switch in cover-perimeter relationships of patches indicates shift of dominant species during grassland degradation

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Journal of Plant Ecology 2020年第6期13卷 704-712页

作者： Ming-Hua Song Johannes HCCornelissen Yi-Kang Li Xing-Liang xu Hua-Kun Zhou Xiao-Yong Cui yan-Fen Wang rong-yan xu Qi Feng Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China Key Laboratory of Restoration Ecology of Cold Area in Qinghai Province Northwest Institute of Plateau BiologyChinese Academy of SciencesXining 810008China Systems Ecology Department of Ecological ScienceFaculty of Earth and Life SciencesVU UniversityDe Boelelaan 10851081 HV AmsterdamThe Netherlands College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China Plant Science Research Center Shanghai Key Laboratory of Plant Functional Genomics and ResearchPlant Science Research CenterShanghai Chenshan Botanic GardenShanghai 201602China Key Laboratory of Ecohydrology of Inland River Basin Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China

Aims Grasslands are globally threatened by climate changes and unsustainable land-use,which often cause transitions among alternative stable states,and even catastrophic transition to *** vegetation patch configurations have been shown to signify such transitions at large spatial ***,we demonstrate how small-scale patch configurations can also indicate state *** The whole spatial series of degradation successions were chosen in alpine grasslands characterized as seven typical *** numbers,and perimeter and cover of each patch were recorded using adjacent quadrats along transects in each type of the *** abundance within each patch was *** Findings Across seven grazing-induced degradation stages in the world’s largest expanse of grassland,from dense ungrazed turf to bare black-soil crust,patch numbers and perimeters first increased as patch cover *** and perimeters then decreased rapidly beyond an intersection point at 68%of initial continuous vegetation *** this point,the vegetation fluctuated back and forth between the sedge-dominated grassland breaking-up phase and the forb-dominated phase,suggesting impending shift of grassland *** study thus demonstrates how ground-based small-scale vegetation surveys can provide a quantitative,easy-to-use signals for vegetation degradation,with promise for detecting the catastrophic transition to desertification.

关键词： grassland degradation state transition Tibetan Plateau trade-off vegetation patchiness

The Caching and Pricing Strategy for Information-Centric Networking with Advertisers’Participation

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China Communications 2024年第3期21卷 283-295页

作者： Zheng Quan yan Wenliang Wu rong Tan Xiaobin yang Jian Yuan Liu xu Zhenghuan Laboratory for Future Networks Department of AutomationUniversity of Science and Technology of ChinaHefei 230026China Institute of Artificial Intelligence Hefei Comprehensive National Science CenterHefei 230088China Institute of Advanced Technology University of Science and Technology of ChinaHefei 230088China Suzhou Nuclear Power Research Institute Suzhou 215004China National Engineering Laboratory for Public Safety Risk Perception and Control by Big Data(NEL-PSRPC) China Academy of Electronics and Information Technology of CETCBeijing 100041China

As users’access to the network has evolved into the acquisition of mass contents instead of IP addresses,the IP network architecture based on end-to-end communication cannot meet users’***,the Information-Centric Networking(ICN)came into *** a technical point of view,ICN is a promising future network *** and customizing a reasonable pricing mechanism plays a positive role in promoting the deployment of *** current research on ICN pricing mechanism is focused on paid ***,we study an ICN pricing model for free content,which uses game theory based on Nash equilibrium to *** this work,advertisers are considered,and an advertiser model is established to describe the economic interaction between advertisers and ICN *** solution can formulate the best pricing strategy for all ICN entities and maximize the benefits of each *** extensive analysis and numerical results show that the proposed pricing framework is significantly better than existing solutions when it comes to free content.

关键词： advertisers cache free content Information-Centric Networking pricing strategy

Design of Robust Var Reserve Contract for Enhancing Reactive Power Ancillary Service Market Efficiency

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 767-771页

作者： Yunyang Zou yan xu School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore 639798Singapore

In a deregulated Var market, market power issue is more serious than in an energy market since reactive power cannot be transmitted over long distances. This letter designs a multi-timescale Var market framework, where market power that may arise in the hourly-ahead Var support service market due to system configuration deficiency and market structure flaws can be eliminated by day-ahead contract-based Var reserve service market. Settlement of day-ahead Var reserve contract is formulated as a two-stage robust optimization (TSRO) model considering worst case of uncertainty realization and potential market power that may arise in hourly-ahead market. TSRO with integer recourses is then solved by a new column and constraint generation algorithm. Results show a robust Var reserve contract can fully eliminate market power, and prevent suppliers from manipulating market prices.

关键词： Market efficiency market power reactive power ancillary service two-stage robust optimization Var reserve

Disinfection Byproducts and Their Precursors in Drinking Water Sources:Origins,Influencing Factors,and Environmental Insights

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Engineering 2024年第5期36卷 36-50页

作者： rong Xiao yang Deng Zuxin xu Wenhai Chu State Key Laboratory of Pollution Control and Resource Reuse College of Environmental Science and EngineeringTongji UniversityShanghai 200092China Ministry of Education Key Laboratory of the yangtze River Water Environment Tongji UniversityShanghai 200092China Department of Earth and Environmental Studies Montclair State UniversityMontclairNJ 07043USA

Tracing the contamination origins in water sources and identifying the impacts of natural and human processes are essential for ecological safety and public ***,current analysis approaches are not ideal,as they tend to be laborious,time-consuming,or technically *** byproducts(DBPs)are a family of well-known secondary pollutants formed by the reactions of chemical disinfectants with DBP precursors during water disinfection *** DBP precursors have various origins(e.g.,natural,domestic,industrial,and agricultural sources),and since the formation of DBPs from different precursors in the presence of specific disinfectants is distinctive,we argue that DBPs and DBP precursors can serve as alternative indicators to assess the contamination in water sources and identify pollution *** providing a retrospective of the origins of DBPs and DBP precursors,as well as the specific formation patterns of DBPs from different precursors,this article presents an overview of the impacts of various natural and anthropogenic factors on DBPs and DBP precursors in drinking water *** practice,the DBPs(i.e.,their concentration and speciation)originally present in source water and the DBP precursors determined using DBP formation potential tests—in which water samples are dosed with a stoichiometric excess of specific disinfectants in order to maximize DBP formation under certain reaction conditions—can be considered as alternative *** jointly used with other water quality parameters(e.g.,dissolved organic carbon,dissolved organic nitrogen,fluorescence,and molecular weight distribution)and specific contaminants of emerging concern(e.g.,certain pharmaceuticals and personal care products),DBPs and DBP precursors in drinking water sources can provide a more comprehensive picture of water pollution for better managing water resources and ensuring human health.

关键词： Disinfection byproducts Disinfection byproduct precursors Drinking water sources Contamination indicator Natural factors Human factors

Malware Evasion Attacks Against IoT and Other Devices: An Empirical Study

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Tsinghua Science and Technology 2024年第1期29卷 127-142页

作者： yan xu Deqiang Li Qianmu Li Shouhuai xu School of Computer Science and Engineering Nanjing University of Science and TechnologyNanjing 210094China School of Computer Science Nanjing University of Posts and TelecommunicationsNanjing 210023China Department of Computer Science University of Colorado Colorado SpringsColorado SpringsCO 80918USA

The Internet of Things(loT)has grown rapidly due to artificial intelligence driven edge *** enabling many new functions,edge computing devices expand the vulnerability surface and have become the target of malware ***,attackers have used advanced techniques to evade defenses by transforming their malware into functionality-preserving *** systematically analyze such evasion attacks and conduct a large-scale empirical study in this paper to evaluate their impact on *** specifically,we focus on two forms of evasion attacks:obfuscation and adversarial *** the best of our knowledge,this paper is the first to investigate and contrast the two families of evasion attacks *** apply 10 obfuscation attacks and 9 adversarial attacks to 2870 malware *** obtained findings are as follows.(1)Commercial Off-The-Shelf(COTS)malware detectors are vulnerable to evasion attacks.(2)Adversarial attacks affect COTS malware detectors slightly more effectively than obfuscated malware examples.(3)Code similarity detection approaches can be affected by obfuscated examples and are barely affected by adversarial attacks.(4)These attacks can preserve the functionality of original malware examples.

关键词： Android malware obfuscation adversarial examples

In-situ coupling construction of interface bridge to enhance electrochemical stability of all solid-state lithium metal batteries

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Journal of Energy Chemistry 2024年第2期89卷 18-26,I0003页

作者： Qianwei Zhang rong yang Chao Li Lei Mao Bohai Wang Meng Luo Yinglin yan Yiming Zou Lisheng Zhong Yunhua xu International Research Center for Composite and Intelligent Manufacturing Technology Institute of Chemical Power SourcesXi’an University of TechnologyXi’an 710048ShaanxiChina School of Materials Science and Engineering Xi’an University of TechnologyXi’an 710048ShaanxiChina School of Electrical Engineering Xi’an University of TechnologyXi’an 710048ShaanxiChina Yulin University Yulin 719000ShaanxiChina

Polymer-based composite electrolytes composed of three-dimensional Li_(6.4)La_(3)Zr_(2)Al_(0.2)O_(12)(3D-LLZAO)have attracted increasing attention due to their continuous ion conduction and satisfactory mechanical ***,the organic/inorganic interface is incompatible,resulting in slow lithium-ion transport at the ***,the compatibility of organic/inorganic interface is an urgent problem to be *** by the concept of“gecko eaves”,polymer-based composite solid electrolytes with dense interface structures were *** bridging of organic/inorganic interfaces was established by introducing silane coupling agent(3-chloropropyl)trimethoxysilane(CTMS)into the PEO-3D-LLZAO(PL)*** in-situ coupling reaction improves the interface affinity,strengthens the organic/inorganic interaction,reduces the interface resistance,and thus achieves an efficient interface ion transport *** prepared PEO-3D-LLZAO-CTMS(PLC)electrolyte exhibits enhanced ionic conductivity of 6.04×10^(-4)S cm^(-1)and high ion migration number(0.61)at 60℃and broadens the electrochemical window(5.1 V).At the same time,the PLC electrolyte has good thermal stability and high mechanical ***,the Li Fe PO_(4)|PLC|Li battery has excellent rate performance and cycling stability with a capacity decay rate of 2.2%after 100 cycles at 60℃and 0.1 *** advantages of PLC membranes indicate that this design approach is indeed practical,and the in-situ coupling method provides a new approach to address interface compatibility issues.

关键词： Organic/inorganic interphase Coupling effect Composite electrolyte Interface compatibility

SEMI-IMPLICIT SPECTRAL DEFERRED CORRECTION METHODS BASED ON SECOND-ORDER TIME INTEGRATION SCHEMES FOR NONLINEAR PDES

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Journal of Computational Mathematics 2024年第1期42卷 111-133页

作者： Ruihan Guo yan xu School of Mathematics and Statistics Zhengzhou UniversityZhengzhou 450001China School of Mathematical Sciences University of Science and Technology of ChinaHefei 230026China

In[20],a semi-implicit spectral deferred correction(SDC)method was proposed,which is efficient for highly nonlinear partial differential equations(PDEs).The semi-implicit SDC method in[20]is based on first-order time integration methods,which are corrected iteratively,with the order of accuracy increased by one for each additional *** this paper,we will develop a class of semi-implicit SDC methods,which are based on second-order time integration methods and the order of accuracy are increased by two for each additional *** spatial discretization,we employ the local discontinuous Galerkin(LDG)method to arrive at fully-discrete schemes,which are high-order accurate in both space and *** experiments are presented to demonstrate the accuracy,efficiency and robustness of the proposed semi-implicit SDC methods for solving complex nonlinear PDEs.

关键词： Spectral deferred correction method Nonlinear PDEs Local discontinuous Galerkin method Second-order scheme

Identification of high oxygen-consuming substances in stormwater drainage systems illicitly connected with sewage system

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Journal of Environmental Sciences 2024年第4期138卷 132-140页

作者： Chen xu Zuxin xu Wenhai Chu Shanshan Wu rong Xiao Lei Su State Key Laboratory of Pollution Control and Resource Reuse College of Environmental Science and EngineeringTongji UniversityShanghai 200092China Ministry of Education Key Laboratory of yangtze River Water Environment Tongji UniversityShanghai 200092China Guangzhou Resource Environmental Protection Technology Co. Ltd.Guangzhou 510030China

The dissolved oxygen content in water is an important indicator for assessing the quality of the water environment,and maintaining a certain amount of dissolved oxygen is essential for the healthy development of the ecological *** a water body is anoxic,the activity of anaerobic microorganisms increases and organic matter is decomposed to produce a large number of blackening and odorizing substances,resulting in black and odorous water bodies,which is a very common and typical phenomenon in ***,there is still a relatively universal occurrence of illicitly connected stormwater and sewage pipes in the urban drainage pipe network in China,which makes oxygen-consuming substances be directly discharged into rivers through stormwater pipes and consume the dissolved oxygen in the water bodies,resulting in an oxygen deficiency of the *** induces seasonal or year-round black and stink phenomena in urban ***,identifying high oxygen-consuming substances,which lays the foundation for the subsequent removal of oxygen-consuming substances,is *** a series of comparisons of water quality indicators and analysis of organic characteristics,it was found that the oxygen consumption capacity of domestic sewage was higher than that of industrial wastewater in the selected area of this study,and the oxygen-consuming substances of domestic sewage were small molecular amino *** comparing 20 conventional free amino acids,it was found that seven of them consumed oxygen easily,and compared with chemical oxygen consumption,biological oxygen consumption was in a leading position.

关键词： Urban drainage system Oxygen-consuming substances Domestic sewage Amino acid

High-speed penetration of ogive-nose projectiles into thick concrete targets:Tests and a projectile nose evolution model

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Defence Technology（防务技术） 2024年第2期32卷 553-571页

作者： xu Li yan Liu Junbo yan Zhenqing Shi Hongfu Wang Yingliang xu Fenglei Huang State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing401120China China Research and Development Academy of Machinery Equipment Beijing100089China

The majority of the projectiles used in the hypersonic penetration study are solid flat-nosed cylindrical projectiles with a diameter of less than 20 *** study aims to fill the gap in the experimental and analytical study of the evolution of the nose shape of larger hollow projectiles under hypersonic *** the hypersonic penetration test,eight ogive-nose AerMet100 steel projectiles with a diameter of 40 mm were launched to hit concrete targets with impact velocities that ranged from 1351 to 1877 m/*** erosion of the projectiles was observed during high-speed penetration of heterogeneous targets,and apparent localized mushrooming occurred in the front nose of recovered *** examining the damage to projectiles,a linear relationship was found between the relative length reduction rate and the initial kinetic energy of projectiles in different penetration ***,microscopic analysis revealed the forming mechanism of the localized mushrooming phenomenon for eroding penetration,i.e.,material spall erosion abrasion mechanism,material flow and redistribution abrasion mechanism and localized radial upsetting deformation ***,a model of highspeed penetration that included erosion was established on the basis of a model of the evolution of the projectile nose that considers radial upsetting;the model was validated by test data from the literature and the present *** upon the impact velocity,v0,the projectile nose may behave as undistorted,radially distorted or *** to the effects of abrasion of the projectile and enhancement of radial upsetting on the duration and amplitude of the secondary rising segment in the pulse shape of projectile deceleration,the predicted DOP had an upper limit.

关键词： High-speed penetration Concrete target Erosion Projectile nose evolution model