检索结果-南通市图书馆

Dynamic Modeling and Analysis of Electrodynamic Multi-tether System

在线全文

学校读者我要写书评

暂无评论

Space(Science & Technology) 2023年第1期3卷 375-388页

作者： Xialin Li Keying Yang Lincheng Li Fuzhen yao Beijing Institute of Technology Beijing 100081People’s Republic of China Beihang University Beijing 100191People’s Republic of China York University Toronto M3J 1P3Canada

Electrodynamic tether(EDT)is a key prospective technique for space-debris removal without the use of ***,there are 2 main shortcomings of the classical EDT *** is that the conductive tether with a single wire should exceed several kilometers to produce the expected force,which increases the risk of collision and *** other is the heavy current or high voltage caused by the overlong tether,which may even melt ***,a novel electrodynamic multi-tether(EMT)system has been proposed here to overcome the above disadvantages of the classical EDT *** EMT system has multi tethers connecting the 2 end bodies,which has more complex dynamic behaviors than the EDT *** order to promote the application of the EMT system,this paper will pay attention to the dynamic modeling and analysis of the EMT system,to reveal the primary dynamic ***,the dynamic equation of the novel EMT system was ***,the linear assumption and vibration theory were utilized to illustrate its primary dynamic ***,the expressions of the vibration period and critical current of tether were given and numerical simulations were conducted to verify these *** results showed that the tether libration equation can be simplified when the size of main satellite is much smaller than that of ***,the tether will go tumbling immediately when the practical current exceeds the critical current.

关键词： dynamic connecting overcome

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

ZnO压敏电阻组合波回路输出的仿真

高电压技术 2009年第10期35卷 2390-2394页

作者：陈景亮姚学玲孙伟西安交通大学电气工程学院西安710049 西安建筑科技大学西安710055

为了仿真分析压敏电阻对组合波短路电流波形参数的影响规律,采用了三折线法了建立了压敏电阻的仿真物理模型,在组合波未加任何负载时,短路电流的波前时间、半峰值时间、反极性震荡以及虚拟电阻分别为7.67μs、21.59μs、12.48%和2.07Ω... 详细信息

为了仿真分析压敏电阻对组合波短路电流波形参数的影响规律,采用了三折线法了建立了压敏电阻的仿真物理模型,在组合波未加任何负载时,短路电流的波前时间、半峰值时间、反极性震荡以及虚拟电阻分别为7.67μs、21.59μs、12.48%和2.07Ω。加入压敏电阻负载的仿真研究得出:对于压敏电压U1mA为18V的压敏电阻负载,当储能电容上电压从200V变化到15kV时,组合波短路电流波的波前时间由7.35μs变化到7.67μs,变化率为4.35%,半峰值时间由21.16μs变化到21.66μs,变化率为2.36%;虚拟阻抗由2.48Ω变化到1.999Ω,变化率为19.40%。而对于压敏电压U1mA为330V的压敏电阻负载,当储能电容上的充电电压从1000V变化到15kV时,组合波8/20μs短路电流波的波前时间由5.79μs变化到7.5625μs,变化率为30.6%,组合波8/20μs短路电流波的半峰值时间由18.1μs变化到21.43μs,变化率为18.4%,虚拟阻抗由6.434Ω变化到2.16Ω,变化率达66.4%。研究结果对压敏电阻的特性研究和组合波电路的设计提供了理论依据。

关键词：压敏电阻非线性特性仿真模型动态电阻组合波波形参数

Dynamically Authorized Role-Based Access Control for Grid Applications

在线全文

学校读者我要写书评

暂无评论

Geo-Spatial Information Science 2006年第3期9卷 223-228,233页

作者： yao Hanbing HU Heping LU Zhengding LI Ruixuan College of Computer Science and Technology Huazhong University of Science and Technology Guanshan Wuhan 430074 China

Grid computing is concerned with the sharing and coordinated use of diverse resources in distributed “virtual organizations”. The heterogeneous, dynamic and multi-domain nature of these environments makes challenging security issues that demand new technical approaches. Despite the recent advances in access control approaches applicable to Grid computing, there remain issues that impede the development of effective access control models for Grid applications. Among them there are the lack of context-based models for access control, and reliance on identity or capability-based access control schemes. An access control scheme that resolve these issues is presented, and a dynamically authorized role-based access control (D-RBAC) model extending the RBAC with context constraints is proposed. The D-RABC mechanisms dynamically grant permissions to users based on a set of contextual information collected from the system and user’s environments, while retaining the advantages of RBAC model. The implementation architecture of D-RBAC for the Grid application is also described.

关键词： Grid security RBAC context-based access control

Static and dynamic characterization of droplets on hydrophobic surfaces

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2012年第10期57卷 1095-1101页

作者： yao ZhaoHui HAO PengFei ZHANG XiWen HE Feng School of Aerospace Tsinghua University Beijing 100084 China

We report on our study of the static and dynamic wetting property of hydrophobic surfaces with micro-and dual micro/nano-scale *** based on the lattice Boltzmann method showed that the apparent contact angle of water droplets on hy-drophobic surfaces with micro-scale structures increases as solid area decreases,whereas dual micro/nano-scale structures not only increase surface hydrophobicity but also greatly stabilize the Cassie state of *** falling on a superhydrophobic surface distort and,depending of free energy,sometimes bounced on the surface before finally adhering to the *** phenomena are in agreement with experimental *** results also show that micro/nano-scale surface structures can increase droplet rebound height,which depends on static apparent contact angle.

关键词：疏水表面格子Boltzmann方法动态特性静态液滴纳米尺度表面结构表面润湿性

Approximation Algorithms for Vertex Happiness

在线全文

学校读者我要写书评

暂无评论

Journal of the Operations Research Society of China 2019年第3期7卷 429-448页

作者： yao Xu Yong Chen Peng Zhang Randy Goebel Department of Computing Science University of AlbertaEdmontonAB T6G 2E8Canada Department of Mathematics Hangzhou Dianzi UniversityHangzhou 310018China School of Computer Science and Technology Shandong UniversityJinan 250101China

We investigate the maximum happy vertices(MHV)problem and its complement,the minimum unhappy vertices(MUHV)*** order to design better approximation algorithms,we introduce the supermodular and submodular multi-labeling(SUP-ML and SUB-ML)problems and show that MHV and MUHV are special cases of SUP-ML and SUB-ML,respectively,by rewriting the objective functions as set *** convex relaxation on the I ovasz extension,originally presented for the submodular multi-partitioning problem,can be extended for the SUB-ML problem,thereby proving that SUB-ML(SUP-ML,respectively)can be approximated within a factorof2-2/k(2/k,respectively),where k is the number of *** general results imply that MHV and MUHV can also be approximated within factors of 2/k and 2-2/k,respectively,using the same approximation *** the MUHV problem,we also show that it is approximation-equivalent to the hypergraph multiway cut problem;thus,MUHV is Unique Games-hard to achieve a(2-2/k-e)-approximation,for anyε>*** the MHV problem,the 2/k-approximation improves the previous best approximation ratio max{1/k,1/(△+1/g(△)},where△is the maximum vertex degree of the input graph and g(△)=(√△+√△+1)2△>4△*** also show that an existing LP relaxation for MHV is the same as the concave relaxation on the Lovasz extension for SUP-ML;we then prove an upper bound of 2/k on the integrality gap of this LP relaxation,which suggests that the 2/k-approximation is the best possible based on this LP ***,we prove that it is Unique Games-hard to approximate the MHV problem within a factor of S2(log2 k/k).

关键词： Vertex happiness Multi-labeling Submodular/supermodular set function Approximation algorithm Polynomial-time reduction Integrality gap

Symplectic schemes and symmetric schemes for nonlinear Schr¨odinger equation in the case of dark solitons motion

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

International Journal of Modeling, Simulation, and Scientific Computing 2021年第6期12卷 150-167页

作者： Yiming yao Miao Xu Beibei Zhu Quandong Feng College of Science Beijing Forestry University Beijing 100083P.R.China School of Mathematics and Physics University of Science and Technology Beijing Beijing 100083 P.R.China

In this paper,symplectic schemes and symmetric schemes are presented to simulate Nonlinear Schrodinger Equation(NLSE)in case of dark soliton ***,by Ablowitz–Ladik model(A–L model),the NLSE is discretized into a non-canonical Hamiltonian ***,different kinds of coordinate transformations can be used to standardize the non-canonical Hamiltonian ***,the symplectic schemes and symmetric schemes can be employed to simulate the solitons motion and test the preservation of the invariants of the A–L model and the conserved quantities approximations of the original *** numerical experiments show that symplectic schemes and symmetric schemes have similar simulation effect,and own significant superiority over non-symplectic and non-symmetric schemes in long-term tracking the motion of solitons,preserving the invariants and the approximations of conserved ***,it is obvious that coordinate transformations with more symmetry have a better simulation effect.

关键词： Symplectic schemes symmetric schemes nonlinear Schr¨odinger equation dark solitons motion Ablowitz–Ladik model

A New Furostanol Saponin from Dioscorea futshauensis

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

Chinese Chemical Letters 2002年第3期13卷 241-244页

作者： Hong Wei LIU Ge Xia QU Xin Sheng yao Department of Natural Products Chemistry Shenyang Pharmaceutical UniversityShenyang 110015

A new furostanol saponin presenting moderate bioactivity of inducing morphological deformation of Pyricularia oryzae mycelia was isolated from Dioscorea futshauensis *** by bioactivity-guided fractionation. The structure was established as 26-O-b-D-glucopyranosyl-3b, 26-diol-23(S)-methoxyl-(25R)-furost-5,20 (22)-diene-3-O-[a-L-rhamnopyranosyl (12)-b-D- glucopyranosyl (13)]-b-D-glucopyranoside on the basis of chemical evidencesand spectral analysis, especially by 2D-NMR techniques.

关键词： Furostanol glycoside Dioscorea futshauensis Pyricularia oryzae.

电沉积Ni_(80)Fe_(20)/Cu纳米多层膜及其巨磁电阻效应

在线全文

学校读者我要写书评

暂无评论

化工学报 2008年第2期59卷 503-507页

作者：张卫国姜莹姚素薇天津大学化工学院杉山表面技术研究室天津300072

采用单槽控电位双脉冲技术在n-Si(111)晶面上制备了[Ni80Fe20/Cu]n多层膜,用SEM观测了多层膜的断面形貌,利用X射线衍射(XRD)表征了多层膜的超晶格结构。采用四探针法研究了多层膜的巨磁电阻(GMR)性能,结果表明,多层膜的GMR值随着Cu层厚... 详细信息

采用单槽控电位双脉冲技术在n-Si(111)晶面上制备了[Ni80Fe20/Cu]n多层膜,用SEM观测了多层膜的断面形貌,利用X射线衍射(XRD)表征了多层膜的超晶格结构。采用四探针法研究了多层膜的巨磁电阻(GMR)性能,结果表明,多层膜的GMR值随着Cu层厚度的变化发生周期性振荡,随着NiFe层厚度的增加先增大后减小;当样品结构为[NiFe(1.6nm)/Cu(2.6nm)]80时,GMR值可达6.4%;多层膜的最低饱和磁场仅为750Oe。磁滞回线测试结果表明,反铁磁耦合多层膜具有较小的矩形比,更适宜作为磁头材料。

关键词：电沉积多层膜巨磁电阻超晶格 NiFe/Cu

Electrochemically modified piezoelectric crystal biosensor for detection of Staphylococcus aureus

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 1996年第3期14卷 222-227页

作者： Si, SH Chen, JH He, FJ Nie, LH yao, SZ HUNAN UNIV NEW MAT RES INSTCHANGSHA 410082HUNANPEOPLES R CHINA

Electropolymerized o-phenylenediamine firm is used as a functional coating for the immobilization of anti-S. aureus antibody on the surface of a gold-plated piezoelectric crystal, and this piezoelectric immunosensor is applied to detect S. aureus. The frequency shift (Delta F = F-20s - F-380s, Hz) between the frequency at the 20th second (after the addition of sample, F-20s) and that at 380 seconds later (F-380s) was introduced to construct a calibration graph, and shortening of assay time was achieved. The S. aureus concentrations in the range of 10(5)-10(9) cells/mL can be detected by this system.

关键词： piezoelectric biosensor detection of S-aureus electrochemical modification