移动Agent系统安全技术研究

移动Agent作为新一代网络分布处理技术，能在网路上任意移动，自动执行使用者所设计和赋予的工作任务。移动Agent的安全问题是该项技术能否成功应用的关键。对移动Agent可能存在的安全问题以及遭受的攻击类型作了较详细的论述。从检测和保护两方面来阐述目前解决移动Agent安全问题的方法以及存在的问题。最后，引入具有监控和授权功能的安全管理器，提出了一种新的移动Agent系统安全模型，并分析了该模型的整个工作流程。     

基于攻击图模型的网络安全风险评估研究

提出一种基于攻击图的多智能代理(Agent)的网络安全风险评估模型.首先,提出了基于多Agent的风险评估架构并给出了主Agent和子Agent的主要模块的功能设计,以网络中主机上的组件为基本节点,采用多Agent协同工作的方式构建攻击图.其次,定义五种风险指数并给出网络安全风险指数的计算方法.最后,基于Java的Agent开发框架(Java Agent Development Framework,JADE)实现了该评估模型,通过对仿真网络的风险评估验证了此模型的可行性和有效性.     

应用环境密钥的移动Agent系统安全模型

移动Agent必须在不同环境安全条件的主机上运行。文中提出了一种基于信任的安全机制,用于改进移动Agent安全。安全机制基于Agent与环境之间的动态交互,在交互中收集信息并产生环境密钥,由该密钥可知主机的信任度与允许移动Agent适应它的执行环境。     

可信移动Agent的研究及在分布式网络管理中的应用

为解决分布式网络管理的安全问题,利用移动Agent框架作为底层平台,应用VMC概念将移动Agent和SNMPAgent相融合,构建一种基于可信移动Agent的安全体系结构。实验结果表明,采用此体系结构的网络管理系统能够确保移动Agent的可信性。因此,该体系结构在受到Agent到Agent平台或Agent到Agent攻击情况下的安全性得到评估,证明在网络管理任务中其性能是可信的。     

基于电子货币技术的移动代理系统安全保护机制的研究

移动代理系统提供了一个新的计算方式，程序以软件代理的形式出现，它能在一台主机上停止它的执行，通过移动到另一台主机上恢复执行。随着移动软件混合性的增加，也伴随着对安全的威胁。尤其是对拒绝服务攻击这类消耗系统资源的攻击，目前还没有什么好的方法。提出了将电子货币引入系统来抵御这类攻击，并给出了一个应用模型。     

移动Agent的资源申请与分配策略模型

随着移动Agent技术的发展，用户可以根据需要中断某个正在运行的程序，然后将相关的数据或控制信息打成包，通过网络传送互另一台计算机，并从断点处开始执行，当执行完毕后，将最终结果返回到源结点。显然，现实的原因导致目标主机的主人不可能允许移动程序无限制在使用自己的主机资源，文章将根据现有的情况讨论如何构造满足移动程序与主机要求的资源申请与分配模型，通过设计调度树的方法，在主机的资源使用限制与用户程序的服务质量间取得平衡，在文章的最后，讨论了与移动Agent相关的其它问题，并就下一步的研究提出了方向。     

移动Agent技术在电子商务安全中的应用研究

文章通过分析电子商务模式和移动Agent技术的特点,研究了不可靠环境下基于移动Agent协作式电子商务的安全性问题,论述了安全电子商务模式的技术特点和安全风险,并分析了主要的解决方案。应用结果表明,从不可靠主机环境和移动Agent本身两方面出发,综合使用多种安全技术措施可以较好地实现基于移动Agent的安全电子商务。     

基于移动Agent的分布式层次化入侵检测系统

在目前的入侵检测系统中，由于检测组件的位置固定和通信的问题，使得入侵检测系统本身易受到攻击。为此提出将内部节点封装为移动Agent。此外，为了保障系统的安全，特别讨论了移动Agent位置随机化、Agent之间安全通信、选举服务器等多种机制以提高抵抗攻击的能力。     

改进的基于层次化身份加密的移动Agent安全方案

移动Agent的安全性是限制其广泛应用的一个重要因素。论文提出了一种改进的基于层次化身份加密的移动Agent安全方案,更简单、高效地实现了分布式环境下移动Agent与主机的相互认证,同时实现了对移动Agent的路径追踪,为移动Agent系统提供了可靠的安全性和稳健性保证,具有较高的实用价值。     

移动数据库中移动Agent技术的应用与研究

目前，移动数据库技术的研究与应用是数据库领域和移动计算领域的一个研究热点。首先介绍了移动数据库和移动Agent的特点，分析了基于移动Agent的移动数据库体系结构，最后提出一种基于移动Agent的移动查询处理模型并叙述了其实现过程。     

A compact model of MOSFET mismatch for circuit design

This paper presents a compact model for MOS transistor mismatch. The mismatch model uses the carrier number fluctuation theory to account for the effects of local doping fluctuations along with an accurate and compact dc MOSFET model. The resulting matching model is valid for any operation condition, from weak to strong inversion, from the linear to the saturation region, and allows the assessment of mismatch from process and geometric parameters. Experimental results from a set of transistors integrated on a 0.35 /spl mu/m technology confirm the accuracy of our mismatch model under various bias conditions.     

Study of Area Scaling Effect on Integrated Circuit Reliability Based on Yield Models

Two models for the effect of area scaling on reliability are derived from two distinct yield models with different assumptions on defect distributions. One is derived from the Poisson yield model assuming a uniform random distribution of defects as in an early model. The other is based on the negative binomial yield model to account for deviation from a uniform random distribution of defects caused by clustering. Experimental data from backend test structures show that the model based on defect clustering explains observed data well while the model assuming a uniform random distribution shows a significant departure from it.     

An analytical two-dimensional model for silicon MESFETs

A model that predicts small-geometry effects in Si MESFETs has been developed. It is based on a two-dimensional (2-D) analytical solution of Poisson's equation in the subthreshold regime that applies to the junction-isolated structure typical of silicon devices. The model is in excellent agreement with numerical simulations from the PISCES 2-D device analysis program. The analytical model provides the physical basis for a subthreshold current model for small-geometry MESFETs. A scaling scheme for MESFETs, derived from the analytical model, that predicts a minimum-acceptable gate length of 0.15 μm for these devices is proposed     

Transformation of continuous-time model of a linear multivariable system from its discrete-time model

The problem of identification of the state-space model of a multivariable continuous system from the samples of its input-output data is considered. Hence, a method is suggested for determining the continuous-time model of a system from its discrete-time model obtained from the samples of its input-output data.     

A stochastic model for the indicated pressure process and thedynamics of the internal combustion engine

Some of the research problems pertaining to cyclic combustion variability are reformulated from a perspective markedly different from the fluid dynamic and thermodynamic models which traditionally characterize this research: a system viewpoint is embraced to construct a stochastic model for the cylinder pressure process and the dynamics of the internal combustion engine. A deterministic model for the dynamics of the engine is briefly described, and a stochastic model is proposed for the cylinder pressure process. The deterministic model and the stochastic representation are tied together in a Kalman filter model. Experimental results that validate the models are discussed     

Identification of Thermal Model for Human Tissue

A simple model structure of spatial and temporal temperature distribution in human tissue, exposed to electromagnetic heating and surface cooling, is developed. This model, denoted the control model, is useful for thermal dosimetry in hyperthermia cancer therapy. The theoretical control model parameter values for various types of homogeneous tissue are determined from a priori knowledge about tissue composition and parameters. The control model parameters for real tissue are estimated from patient treatment data through the use of a system identification technique. The results indicate that the control model structure is adequate. With the available a priori knowledge the theoretically determined control model parameter values do not accurately reproduce the experimentally estimated values. Accordingly, an identification based on experimental data is recommended, if an accurate model is required.     

A monitor-decoupled pharmacodynamic model of propofol in children using state entropy as clinical endpoint

This paper presents a new monitor-decoupled model of propofol pharmacodynamics (PD) using the state entropy (SE) as the clinical endpoint of interest. In our model, the dynamics of the entropy monitor are separated from the PD response of the patient by explicitly accounting for the model of the entropy monitor in the PD identification process. The monitor model was then excluded from the identified PD model for the patient. The PD model, thus, obtained is distinct from its traditional counterpart in that it reflects the PD response of a patient with the dynamic effects of the monitor included as a specific entity. System identification trials using SE data of 31 pediatric subjects show that the PD models derived from the proposed approach are an improvement on the traditional approach. For the Paedfusor pharmacokinetic (PK) model, population-averaged effect site equilibration rate constant k(e0) was 5.4 and 3.0 for the proposed and traditional PD models ( p < 0.001), respectively. For the Kataria PK model, population-averaged k(e0) was 2.3 and 1.4 (p < 0.01). This significant difference suggests that the effects of the monitor must be considered when searching for the intrinsic PD of a patient that is free from the bias induced by the monitor characteristics.     

从2D条形图重建3D曲面模型

本文给出了一种从多角度2D条形图重建三维曲面模型的方法。该方法从不同侧面曲面物体的2D条形图出发，经过条形线段匹配，三维空间坐标计算，获得三维条形图，再经过一维插值，重建出三维曲面模型。该方法已在PⅢ800的PC机上进行了验证，成功的重建了一人头石膏像的3D表面模型。     

A substrate-dependent CAD model for ceramic multilayer capacitors

In this paper, a substrate-dependent lumped-element model for ceramic multilayer capacitors is presented. The height and dielectric constant of a substrate have a significant impact on the frequency response of a chip capacitor, and these effects cannot be treated independently from the capacitor model. Rather, the equivalent-circuit parameters in the model must be made to vary in accordance with changes in the substrate. The model presented in this paper is suitable for microstrip-mounted components, and has been applied up to 10 GHz for values from 0.5 pF to 0.47 μF, and for FR-4 substrates ranging in height from 5 to 62 mil. The modeling and extraction procedure is demonstrated for 0805- and 1206-style capacitors     

Physics-based compact model for ultra-scaled FinFETs

A physical and explicit compact model for lightly doped FinFETs is presented. This design-oriented model is valid for a large range of silicon Fin widths and lengths, using only a very few number of model parameters. The quantum mechanical effects (QMEs), which are very significant for thin Fins below 15 nm, are included in the model as a correction to the surface potential. A physics-based approach is also followed to model short-channel effects (roll-off), drain-induced barrier lowering (DIBL), subthreshold slope degradation, drain saturation voltage, velocity saturation, channel length modulation and carrier mobility degradation. The quasi-static model is then developed and accurately accounts for small-geometry effects as well. This compact model is accurate in all regions of operation, from weak to strong inversion and from linear to saturation regions. It has been implemented in the high-level language Verilog-A and exhibits an excellent numerical efficiency. Finally, comparisons of the model with 3D numerical simulations show a very good agreement making this model well-suited for advanced circuit simulations.