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Energy-Efficient Trajectory Planning for UAV-Aided Secure Communication

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China Communications 2018年第5期15卷 51-60页

作者： Qian Wang Zhi Chen hang li National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of China

Wireless communication with unmanned aerial vehicles(UAVs) has aroused great research interest recently. This paper is concerned with the UAV's trajectory planning problem for secrecy energy efficiency maximization(SEEM) in the UAV communication system. Specifically, we jointly consider the secrecy throughput and UAV's energy consumption in a three-node(fixed-wing UAV-aided source, destination, and eavesdropper) wiretap channel. By ignoring the energy consumption on radiation and signal processing, the system's secrecy energy efficiency is defined as the total secrecy rate normalized by the UAV's propulsion energy consumption within a given time horizon. Nonetheless, the SEEM problem is nonconvex and thus is intractable to solve. As a compromise, we propose an iterative algorithm based on sequential convex programming(SCP) and Dinkelbach's method to seek a suboptimal solution for SEEM. The algorithm only needs to solve convex problems, and thus is computationally efficient to implement. Additionally, we prove that the proposed algorithm has Karush-KuhnTucker(KKT) point convergence guarantee. Lastly, simulation results demonstrate the efficacy of our proposed algorithm in improving the secrecy energy efficiency for the UAV communication system.

关键词： physical layer security UAV-aided communications secrecy energy efficiency trajectory planning

Current progress and future prospects in phylofloristics

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Plant Diversity 2018年第4期40卷 141-146页

作者： Rong li lishen Qian hang Sun Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China University of Chinese Academy of Sciences Beijing 100049 China

The species composition of regional plant assemblages can in large part be explained by a long history of biogeographical and evolutionary events. Traditional attempts of floristic studies typically focus on the analyses of taxonomic composition, often ignoring the rich context that evolutionary history can provide. In 2014, Swenson and Umafia introduced the term ＇phylofloristics＇ to define a phylogenetically enabled analysis of the species composition of regional floras. Integrating phylogenetic information into tradi- tional floristic analysis can provide a promising way to explore the ecological, biogeographic, and evolutionary processes that drive plant assemblies at multiple spatial scales. In this review, we sum- marize the current progress on the phylogenetic structure, spatial phylogenetic pattern, origin and diversification, phylogenetic regionalization of fioristic assemblages, and application of phylogenetic information in biodiversity conservation. These summaries highlight the importance of incorporating phylogenetic information to improve our understanding of floristic assembly from an evolutionary perspective. The review ends with a brief outlook on future challenges for phylofloristic studies, including generating a highly resolved species-level phylogenetic tree, compiling detailed and refined information regarding the geographic distribution of all plant life, extracting trait information from publications and herbarium specimens, and developing technological and methodological approaches for big data analysis.

关键词： Big data Biogeography Ecology Evolution Flora Mega-phylogeny

Solidification of Mg-Zn-Zr Alloys:Grain Growth Restriction,Dendrite Coherency and Grain Size

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Acta Metallurgica Sinica(English Letters) 2020年第11期33卷 1477-1486页

作者： Pei li Danhui hou En-hou Han Rongshi Chen Zhiwei Shan State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong UniversityXi'an 710049China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China

The solidification characterization of Mg-xZn-0.5Zr(x=0,1,3,4,5 wt%)alloys has been extensively investigated through thermal analysis,microstructure characterization and thermodynamic *** impact of Zn content on the grain growth restriction,dendrite coherency and thus the final grain size has been investigated and *** Zn content,the grain size of Mg-xZn-0.5Zr alloy was firstly refined and then coarsened with the finest grain size of^50μm for the Mg-3 Zn-0.5 Zr(ZK31)*** effects of the grain size on the mechanical properties were observed in the investigated *** combination of growth restriction factor theory and dendrite coherency point provides a reasonable explanation of the grain size *** helps to further understand the mechanisms of grain refinement and grain coarsening related to solute content,providing reference for alloy design and grain size prediction.

关键词： Magnesium alloy Grain size Solute content Growth restriction Dendrite coherency Solidifi cation

Effects of Chlorination on Soil Chemical Properties and Nitrogen Uptake for Tomato Drip Irrigated with Secondary Sewage Effluent

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Journal of Integrative Agriculture 2014年第9期13卷 2049-2060页

作者： li Yan-feng li Jiu-sheng Zhang hang State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower Research National Center of Efficient Irrigation Engineering and Technology Research-Beijing

Chlorination is usually an economical method for treating clogging in drip emitters during sewage application. Appropriate assessment of the responses of soil and crop is essential for determining an optimal chlorination scheme. During 2008 to 2009, field experiments were conducted in a solar-heated greenhouse for tomato drip irrigated with secondary sewage effluent, to investigate the influences of chlorine injection intervals and levels on soil chemical properties and nitrogen uptake. Injection intervals ranging from two to eight weeks and injection concentrations ranging from 2 to 50 mg L-1 were used. A salinity factor and a nutrient factor were extracted from the pool of the nine soil chemical constituents using factor analysis method. The results demonstrated that chlorination practices increased the residual Cl in the soil, resulting in an increased salinity factor, especially for the frequent chlorination at a high injection concentration. Chlorination weakened the accumulation of nutrients factor in the upper soil layer. Nitrogen uptake of the tomato plants also was inhibited by the increased salinity in the upper soil layer caused by high chlorination levels. In order to reduce the unfavorable effect on soil chemical properties and nitrogen uptake, chlorination scheme with concentrations of lower than 20 mg L-1 was recommended.

关键词： chlorination drip irrigation soil chemical properties nitrogen uptake sewage effluent

Characteristics and sources of polycyclic aromatic hydrocarbons in impervious surface run-off in an urban area in Shanghai, China

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第10期14卷 751-759页

作者： Juan hou Lu BIAN Tian li State Key Laboratory of Pollution Control and Resource Reuse Tongji University

Rainwater and run-off from three kinds of impervious surface in the Shanghai urban area,China were *** aromatic hydrocarbons(PAHs) were measured in the samples,and their sources were *** mean sum of the 16 PAH concentrations measured in rainwater and run-offs from ceramic tiles,asphalt roofs,and asphalt roads were 873,1404,1743,and 4023 ng/L,*** PAH concentrations found in this study were moderate compared to PAH concentrations found in run-offs in other *** main PAH components in the rainwater,roof run-off,and asphalt road run-off samples were 3-ring PAHs,3–4-ring PAHs,and 4–6-ring PAHs,*** apportionment results indicated that combustion(47.4%–55.5%) and vehicular emissions(30.5%–33.0%) were the major contributors to PAHs in roof *** emissions were the most significant contributors to asphalt road run-off(47.2%),followed by combustion(23.5%),and petroleum(16.3%).Vehicular emissions and coal and natural gas combustion are therefore the most significant sources of PAHs in run-off from impervious surfaces in the Shanghai urban area.

关键词： Polycyclic aromatic hydrocarbons(PAHs) Impervious surface Run-off pollution Source apportionment

Novel load balancing DHT scheme for the heterogeneous system

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Journal of Systems Engineering and Electronics 2008年第4期19卷 835-842页

作者： li Yujun Lu Xianliang hou Mengshu School of Computer Science and Engineering Univ. of Electronics Science and Technology of China Chengdu 610054 P. R. China

The capacities of the nodes in the peer-to-peer system are strongly heterogeneous, hence one can benefit from distributing the load, based on the capacity of the nodes. At first a model is discussed to evaluate the load balancing of the heterogeneous system, and then a novel load balancing scheme is proposed based on the concept of logical servers and the randomized binary tree, and theoretical guarantees are given. Finally, the feasibility of the scheme using extensive simulations is proven.

关键词： distributed hash table heterogeneity randomized binary tree load balancing

High-Precision Time Delay Estimation Based on Closed-Form Offset Compensation

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Computer Modeling in Engineering & Sciences 2023年第3期134卷 2123-2136页

作者： Yingying li hang Jiang lianjie Yu Jianfeng li The Key Laboratory of Dynamic Cognitive Systemof Electromagnetic Spectrum Space Ministry of Industry and Information TechnologyNanjing University of Aeronautics and AstronauticsNanjing211106China State Key Laboratory of Marine Resource Utilization in South China Sea Hainan UniversityHaikou570100China

To improve the estimation accuracy,a novel time delay estimation(TDE)method based on the closed-form offset compensation is ***,we use the generalized cross-correlation with phase transform(GCC-PHAT)method to obtain the initial ***,a signal model using normalized cross spectrum is established,and the noise subspace is extracted by eigenvalue decomposition(EVD)of covariance *** the orthogonal relation between the steering vector and the noise subspace,the first-order Taylor expansion is carried out on the steering vector reconstructed by the initial ***,the offsets are compensated via simple least squares(LS).Compared to other state-of-the-art methods,the proposed method significantly reduces the computational complexity and achieves better estimation *** on both simulation and real-world data verify the efficiency of the proposed approach.

关键词： Time delay estimation(TDE) time difference of arrival(TDOA) taylor expansion super-resolution

Controllable CPL response driven by achiral UV-photosensitive dichroic dye through cholesteric liquid crystals

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Science China Chemistry 2024年第4期67卷 1250-1255页

作者： Yihan Chen Yang li hang li Lulu li Yiwu Quan Yixiang Cheng State Key Laboratory of Analytical Chemistry for life Science School of Chemistry and Chemical EngineeringNanjing UniversityNanjing 210023China Key Laboratory of High-Performance Polymer Material and Technology of Ministry of Education School of Chemistry and Chemical EngineeringNanjing UniversityNanjing 210023China School of Environmental and Chemical Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China

Versatile stimuli-responsive circularly polarized luminescent(CPL)materials have potential applications in information storage,security encryption,and intelligent *** this study,the Z/E isomerization of ultraviolet(UV)-photosensitive achiralα-cyanostilbene derivative was used as an achiral dichroic dye(Switch)to drive the controllable CPL-active response in cholesteric liquid crystals(CLCs).Under irradiation by 365 nm UV light,the resulting CLCs-Z-Switch underwent a Z-to-E configuration isomerization as CLCs-E-Switch,accompanied by a decrease in its dichroic order parameter(SFvalue)from 0.15to *** the quantum yield(QY)of CLCs-E-Switch increased from 8.1%(CLCs-Z-Switch)to 16.8%,the corresponding glumvalues of CPL emission decreased from+0.55/-0.57 to+0.37/-0.39 due to a decrease in the order of helical arrangement of E-Switch in E7 *** study enables photosensitive CLCs-Switch to be applied for optical information storage devices.

关键词： circularly polarized luminescent photosensitive dichroic dye cholesteric liquid crystals chiral induction

Quasi in-situ EBSD analysis of twinning-detwinning and slip behaviors in textured AZ31 magnesium alloy subjected to compressive-tensile loading

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Journal of Magnesium and Alloys 2022年第4期10卷 956-964页

作者： Yuzhi Zhu Dewen hou Qizhen li School of Mechanical and Materials Engineering Washington State UniversityPullmanWA 99164United States Micron School of Materials Science and Engineering Boise State UniversityBoise 83725-1030 IDUnited States

Twinning and detwinning behavior,together with slip behavior,are studied in a textured AZ31 magnesium alloy under compressive and tensile strains along the rolling direction(RD)after each interrupted mechanical test via quasi in-situ electron backscattered diffraction *** results show that twinning firstly takes place under the compressive strain along the *** the increasing compressive strain,{1012}tensile twins firstly nucleate,then propagate,and finally *** under a reversed tensile strain along the RD,detwinning *** nucleation happens during ***,tensile twins can detwin at lower tensile strain,followed by thinning,shortening,and *** are also activated to accommodate the plastic *** the matrix,prismatic slip can only dominate at relatively high ***,basal slip *** in the twins,prismatic slip can activate at lower strains,which is ascribed to the texture reorientation.

关键词： Magnesium alloy Twinning Detwinning Prismatic slip quasi in-situ EBSD