检索结果-南通市图书馆

Chinese Physics B 2017年第1期26卷 290-297页

作者： Xiao-yan Sun Yu-ru Zhang Xue-Chun li You-Nian Wang Key Laboratory of Materials Modification by Laser Ion and Electron Beams （Ministry of Education） School of Physics and Optoelectronic Technology Dalian University of Technology Dalian 116024 China

Planar radio frequency inductively coupled plasmas（ICP） are employed for low-voltage ion implantation processes,with capacitive pulse biasing of the substrate for modulation of the ion energy. In this work, a two-dimensional（2D） selfconsistent fluid model has been employed to investigate the influence of the pulsed bias power on the nitrogen plasmas for various bias voltages and pulse frequencies. The results indicate that the plasma density as well as the inductive power density increase significantly when the bias voltage varies from 0 V to-4000 V, due to the heating of the capacitive field caused by the bias power. The N＋fraction increases rapidly to a maximum at the beginning of the power-on time, and then it decreases and reaches the steady state at the end of the glow period. Moreover, it increases with the bias voltage during the power-on time, whereas the N2-＋ fraction exhibits a reverse behavior. When the pulse frequency increases to 25 kHz and40 kHz, the plasma steady state cannot be obtained, and a rapid decrease of the ion density at the substrate surface at the beginning of the glow period is observed.

关键词： fluid simulation low-voltage plasma immersion ion implantation N2 inductive discharge

Land development suitability analysis for transport planning evaluation and optimization in mountainous ecological region

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2022年第3期19卷 862-873页

作者： ZHU Gao-ru WANG Man li Qi-li liU Jie ZHAO yan-ni GAO Jia-wei XU Hong-lei Laboratory of Transport Pollution Control and Monitoring Technology Transport Planning and Research InstituteMinistry of TransportBeijing 100028China College of Urban and Environmental Sciences Peking UniversityBeijing 100871China Key Laboratory for Environmental and Urban Sciences School of Urban Planning&DesignShenzhen Graduate SchoolPeking UniversityShenzhen 518055China

Transportation planning is a critical component for creating an orderly,intensive,and sustainable pattern of land *** comprehensively considering the potential and suitability of transport construction,a comprehensive method combining resources and environmental carrying capacity(RECC)and land development suitability(LDS)was developed by using techniques of GIS,analytic hierarchy process(AHP)and threedimensional magic *** Aba prefecture in Sichuan Province of Southwest China as a case study,LDS for transportation was analyzed from three aspects,including overall planning layout,different transport modes,and transportation *** results showed that the transport planning scales of most counties in Aba were suitable,and the order of LDS of different transport modes was railway>highway=superhighway>tourism track,which already included 42 new transportation *** found that two counties(Maoxian County and Jiuzhaigou County)should improve the ecological protection level of transportation,in which the railway network construction should be encouraged,and some transportation projects with low LDS should be postponed or constructed *** suggest the combination of RECC and LDS for transportation could enhance the territorial space optimization and sustainable transport construction.

关键词： Land development suitability Resources and environment carrying capacity Transport planning Evaluation Optimization Spatial analysis Mountainous ecological region

Synthesis and Insecticidal Activity of Novel Camptothecin Derivatives Containing Analogs of Chrysanthemic Acid Moieties

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2014年第6期13卷 1320-1330页

作者： DENG li ZHANG Lan CAO li-dong XIE ru-liang ZHANG yan-ning HE Wei-zhi JIANG Hong-yun Hong-yun State Key Laboratory for Biology of Plant Diseases and Insect Pests Institute of Plant Protection Chinese Academy of Agricultural Sciences State Key Laboratory for Biology of Plant Diseases and Insect Pests Institute of Plant Protection Chinese Academy of Agricultural Sciences

Creating high-efifcient and environment-friendly pesticides is very important to produce the pollution free agriculture food and maintain the balance of the survival environmental of the human being. According to reports, camptothecin （CPT） and its derivatives are now being explored as a class of botanical insecticide in agriculture due to its novel mode of action. In order to improve the insecticidal activity of CPT, ten novel camptothecin （1） and 10-hydroxycamptothecin （2） derivatives （1a, 1b, 1c, 1d, 1e;2a, 2b, 2c, 2d, 2e） were designed and synthesized via esteriifcation with analogs of chrysanthemic acid, which have outstanding insecticidal activity. The results showed that compound 2a exhibited potent antifeeding effect and the best contact toxicity among the target compounds against the third-instar larvae of beet armyworm, Spodoptera exigua H＆#252;bner. Compound 2a was also found to be the most effective cytotoxic compound to the tested insect cell lines, IOZCAS-Spex-II, which were established from the fat bodies of S. exigua. It was proposed that the 10-hydroxyl group in the camptothecin derivatives is a key factor for the antifeeding activity of a compound. The nature of the substituents was considered the major factor in determining the insecticidal activity of these compounds.

关键词： camptothecin analogs of chrysanthemic acid synthesis antifeeding activity contact toxicity cytotoxicity

Resonant Peak Splitting for Ballistic Conductance in Two-Dimensional Electron Gas Under Electromagnetic Modulation

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2000年第8期17卷 598-600页

作者： WANG ru-Zhi yan Xiao-Hong Department of Physics Xiangtan UniversityXiangtan 411105

By developing a transfer-matrix method,the resonant peaks splitting of ballistic conductance are investigated into the two-dimensional electron gas system with both electric and magnetic modulations of nanoscale *** is found that there exists the n-fold resonant peak splitting for ballistic conductance through n perpendicular magnetic barriers to n electric *** a combination of m magnetic barriers and n electric barriers by increasing the amplitude of electric field,the folds of the splitting would shift from m- to n-1.

关键词： splitting resonant conductance

AABN: Anonymity Assessment Model Based on Bayesian Network With Application to Blockchain

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

China Communications 2019年第6期16卷 55-68页

作者： Tianbo Lu ru yan Min Lei Zhimin lin School of Software Engineering Beijing University of Posts and Telecommunications100876 BeijingChina Key Laboratory of Trustworthy Distributed Computing and Service(Beijing University of Posts and Telecommunications) Ministry of Education100876 BeijingChina Information Security Center School of Cyberspace SecurityBeijing University of Posts and TelecommunicationsBeijing 100876China

Blockchain is a technology that uses community validation to keep synchronized the content of ledgers replicated across multiple users,which is the underlying technology of digital currency like *** anonymity of blockchain has caused widespread *** this paper,we put forward AABN,an Anonymity Assessment model based on Bayesian ***,we investigate and analyze the anonymity assessment techniques,and focus on typical anonymity assessment *** the related concepts involved in the assessment model are introduced and the model construction process is described in ***,the anonymity in the MIX anonymous network is quantitatively evaluated using the methods of accurate reasoning and approximate reasoning respectively,and the anonymity assessment experiments under different output strategies of the MIX anonymous network are analyzed.

关键词： blockchain anonymity assessment bayesian network MIX

Grid trust based on pre-measure and two-level reputation

在线全文

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2007年第4期14卷 70-76页

作者： ZHANG lin WANG ru-chuan WANG Hai-yan School of Computer Nanjing Univesity of Posts and TelecommunicationsNanjing 210003 China

Security has been the focus of grid systems recently. As a kind of tool, grid security infrastructure （GSI） provides the authentication and authorization services and so on. These mechanisms mostly belong to the objective factors, which have not met the needs of security. As the subjective factor, trust model plays an important role in security field. A new two-level reputation trust architecture for grid is given to reduce the costs of system management largely, in which trust relationships amongst virtual organizations （VOs） are built on domain trust managers （DTMs） rather than resource nodes （RNs）. Taking inter-domain trust propagation for example, trust model is improved by integrating global reputation and the subjective trust concept of each recommender into synthesizing final trust value. Moreover, before the grid starts to interact with the trustworthy entities, the pre-measure scheme is presented to filter distrustful entities further, which is based on accuracy and honesty. Experimental results indicate that the model can prevent from the malicious attacks better.

关键词： grid computing trust model reputation pre-measure

Rigidity of closed submanifolds in a locally symmetric Riemannian manifold

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics(A Journal of Chinese Universities) 2016年第2期31卷 237-252页

作者： GU Juan-ru LENG yan XU Hong-wei Department of Applied Mathematics Zhejiang University of Technology Hangzhou 310023 China Center of Mathematical Sciences Zhejiang University Hangzhou 310027 China

Let Mn（n ≥ 4） be an oriented closed submanifold with parallel mean curvature in an （n ＋ p）-dimensional locally symmetric Riemannian manifold Nn＋p. We prove that if the sectional curvature of N is positively pinched in [5, 1], and the Ricci curvature of M satisfies a pinching condition, then M is either a totally umbilical submanifold, or δ= 1, and N is of constant curvature. This result generalizes the geometric rigidity theorem due to Xu and Gu [15].

关键词： Submanifold Ejiri rigidity theorem Ricci curvature Mean curvature.

Hydrogen-based mineral phase transformation mechanism investigation of pyrolusite ore

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2024年第11期31卷 2445-2457页

作者： ruofeng Wang Shuai Yuan yanjun li Peng Gao ru li School of Resources and Civil Engineering Northeastern UniversityShenyang 110819China National-local Joint Engineering Research Center of High-efficient exploitation technology for Refractory Iron Ore Resources Shenyang 110819China

Pyrolusite comprises the foremost manganese oxides and is a major source of manganese *** innovative hydrogenbased mineral phase transformation technology to pyrolusite was proposed,where a 96.44%distribution rate of divalent manganese(Mn^(2+))was observed at an optimal roasting temperature of 650℃,a roasting time of 25 min,and an H2 concentration of 20vol%;under these *** manganese predominantly existed in the form of *** study investigated the generation mechanism of manganosite based on the reduction kinetics,phase transformation,and structural evolution of pyrolusite and revealed that high temperature improved the distribution rate,and the optimal kinetic model for the reaction was the random nucleation and growth model(reaction order,n=3/2)with an activation energy(E_(a))of 24.119 kJ·mol^(−1).Throughout the mineral phase transformation,manganese oxide from the outer layer of particles moves inward to the *** addition,pyrolusite follows the reduction sequence of MnO_(2)→Mn_(2)O_(3)→Mn_(3)O_(4)→MnO,and the reduction of manganese oxides in each valence state simultaneously *** findings provide significant insight into the efficient and clean utilization of pyrolusite.

关键词： reduction pyrolusite phase transformation microstructural evolution

Stereoselective Ring-opening Polymerization of rac-Lactide by Bulky Chiral and Achiral N-heterocyclic Carbenes

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2018年第2期36卷 231-236页

作者： Hui li Bai-ru Ai Miao Hong Key Laboratory of Marine Materials and Related Technologies Key Laboratory of Marine Materials and Protective Technologies of Zhejiang Province Ningbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China University of Chinese Academy of Sciences Beijing 100049China State Key Laboratory of Organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032China

Despite the extraordinary success has been achieved in metal catalyst-promoted stereoselective ring-opening polymerization（ROP） of rac-lactide（rac-LA）, well-controlled stereoselective rac-LA ROP by organic catalyst still remains a scientific challenge. Here we report our investigations into organocatalytic stereoselective ROP of rac-LA by utilizing novel bulky chiral and achiral N-heterocyclic carbenes（NHC）, 1,3-bis-（1′-naphthylethyl）imidazolin-2-ylidene. The effect of polymerization conditions（e.g. solvent, temperature, alcohol initiator） on ROP behavior by these bulky NHCs has been fully studied, leading to the formation of isotactic-rich stereoblock polylactide（Pi = 0.81） under optimized conditions with high activity（Conv. = 98% in 30 min） and narrow molecular weight dispersity（D = 1.05）.

关键词： Polylactide Ring-opening polymerization Stereoselectivity Organic catalyst N-heterocyclic carbene

Evaluation of CMIP6 HighResMIP models in simulating precipitation over Central Asia

在线全文

学校读者我要写书评

暂无评论

Advances in Climate Change Research 2022年第1期13卷 1-13页

作者： liang-liang li Jian li ru-Cong YU College of Atmospheric Sciences Lanzhou UniversityLcmzhou 730000China State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081China Research Center for Disastrous Weather Over Hengduan Mountains&Low-Latitude Plateau China Meteorological AdministrationKunming 650034China

The High Resolutio n Model Intercomparison Project(HighResMIP)experiment within the Coupled Model In tercomparison Project Phase 6(CMIP6),for the first time,has provided an opportunity to evaluate the performance of climate models over complex *** on the HighResMIP's historical simulations of atmospheric general circulation models,the performances of global high-resolution models,with a horizontal resolution finer than 50 km,in representing precipitation over Central Asia were evaluated using rain gauge observation *** the models successfully reproduce the large precipitation regions that are located over the mountainous areas and Northern Central ***,nearly all the models overestimate precipitation frequency over Central Asia and large overestimations of precipitation amount and frequency are located over the mountainous *** the HighResMIP multi-model ensemble mean performs better than all individual models at simulating the spatial pattern of precipitation frequency,it is inferior to HadGEM3-GC31-HM and ECMWF-IFS-HR at simulating that of precipitation *** simulation performance exhibits remarkable regional *** the Qilian Mountains,the relationship between precipitation and elevation is totally captured by climate *** contrast,over the Tianshan Mountains,the models fail to simulate the decrease in precipitation frequency after elevation higher than the maximum precipitation *** models successfully reproduce the annual cycle shape of precipitation amount over the Southern Central Asia,Qilian Mountains and Tianshan Mountains,but fail to reproduce it over the Northern Central *** than half of the high-resolution GCMs have a reduced bias relative to the corresponding low-resolution *** performances of most high-resolution GCMs in simulating precipitation pattern are well over the Tianshan Mountains.

关键词： CMIP6 HighResMIP Model evaluation Precipitation Elevation Central Asia