贝叶斯网络诱导的内积空间

概率模型和核函数相结合的方法是学习系统的热点研究领域,贝叶斯网络是重要的一类概率图形模型。文中主要讨论了变量取值在布尔域上的两类分类任务,重点讨论了几个常见贝叶斯网络诱导的内积空间的最低维数,为解决一些常见的分类问题提供了理论依据。文中通过分析概念类的VC维来确定其欧几里德维数的下界,VC维还可用于估计贝叶斯网络概念类的复杂性和判断概念类的分类性能。     

System-level modeling of IEEE 802.16E mobile wimax networks: Key issues [recent advances and evolution of WLAN and WMAN standards

WiMAX1 has attracted a lot of attention recently in the telecommunication community including researchers, product developers, and service providers. Numerous papers have been published on various design issues of WiMAX networks. Since the issues being discussed are usually ahead of product availability, most of these studies require simulation. It is important to have some common features among these models so that their results can be compared. Therefore, the Application Working Group of the WiMAX Forum has developed a standard simulation methodology that describes the key features to be simulated, the method of simulating these features, and various parameter values to be used. This system-level methodology has been used in several public and commercial WiMAX simulation models. This article presents a summary of the simulation methodology, and discusses the key issues and common mistakes in simulating various features of network configuration, and the physical, MAC, and application layers.     

Common randomness in information theory and cryptography. II. CRcapacity

For pt.I see ibid., vol.39, p.1121, 1993. The common randomness (CR) capacity of a two-terminal model is defined as the maximum rate of common randomness that the terminals can generate using resources specified by the given model. We determine CR capacity for several models, including those whose statistics depend on unknown parameters. The CR capacity is shown to be achievable robustly, by common randomness of nearly uniform distribution no matter what the unknown parameters are. Our CR capacity results are relevant for the problem of identification capacity, and also yield a new result on the regular (transmission) capacity of arbitrarily varying channels with feedback     

Synchronous Parallel Optical I/O on CMOS: A Case Study of the Uniformity Issue

Short-range parallel optical interconnect between integrated circuits can alleviate bandwidth, power, and packaging density issues that are associated with low-latency high-bandwidth input-output over electrical interconnect. In this paper, we evaluate the option of using true source-synchronous signaling over optical interconnect with a large number of channels, reducing the substantial per-channel clock synchronization circuitry to one instance. We also look into dc-unbalanced signaling to remove the need for data coding. Uniformity across channels is key to the feasibility of such an approach. An actual 64-channel parallel optical interconnect setup at 1.25 Gb/s/channel is examined, and models for the performance and uniformity of the different constituent parts of the interconnect are drawn up. Major attention is given to the statistical modeling of the coupling efficiency between a vertical cavity surface emitting laser array and a multifiber connector. Although derived in the context of a uniformity study, the stochastic models and the modeling approach are valuable in their own right. In our case study, the usage of a common logic threshold across all channels, which is required for dc-unbalanced signaling, appears infeasible after all models are combined. Efficient true source-synchronous signaling turns out to be within reach in carefully designed systems.     

Efficient parasitic substrate modeling for monolithic mixed-A/D circuit design and verification

Parasitic analog-digital noise coupling has been identified as a key issue facing designers of mixed-signal integrated circuits. In particular, signal crosstalk through the common chip substrate has become increasingly problematic. This paper demonstrates a methodology for developing simulation, synthesis, and verification models to analyze the global electrical behavior of the non-ideal semiconductor substrate. First, a triangular discretization method is employed to generate RC equivalent-circuit substrate models which are far less complex than those formulated by conventional techniques. The networks are then accurately approximated for subsequent analysis by an efficient reduction algorithm which uses a well-conditioned Lanczos moment-matching process. Through congruence transformations, the network admittance matrices are transformed to reduced equivalents which are easily post-processed to derive passive, SPICE-compatible netlist representations of the reduced models. The pure-RC properties of the extracted substrate networks are fully exploited to formulate an efficient overall algorithm. For validation, the strategy has been successfully applied to several mixed-signal circuit examples.     

面向方面编程及其应用现状的研究

面向方面编程(AOP)弥补了面向对象的编程(OOP)在跨越模块行为上的不足.它引进了Aspect将影响多个类的行为封装到一个可重用模块中,从而消除了OOP引起的代码混乱和分散问题,增强了系统的可维护性和代码的重用性.文章首先对AOP的基本思想、关键技术和编程过程进行了叙述,然后重点研究和分析了AOP在异常处理、分布式系统、日志管理和设计模式方面的应用,最后描述了它的研究应用热点.     

Converting Mathematical Models of Physiological Systems to Relational Database Schemes for Analysis and Comparison

It is proposed that computable mathematical models of physiological systems can be explained and studied by a query language based upon converting the source code into a relation database scheme. In such a scheme, each assignment statement is assumed to be equivalent to a functional dependency. The dependencies formed constitute a lossless decomposition of the model scheme when the derived dependencies are augmented by a key consisting of input attributes. The method is demonstrated on two common computational forms: simultaneous equations and the Euler solution to ordinary differential equations. A simple example is used to show that computing closure on attributes can establish the difference between two models.     

A dynamic key management solution to access hierarchy

Hierarchical access control (HAC) has been a fundamental problem in computer and network systems. Since Akl and Taylor proposed the first HAC scheme based on number theory in 1983, cryptographic key management techniques for HAC have appeared as a new and promising class of solutions to the HAC problem. Many cryptographic HAC schemes have been proposed in the past two decades. One common feature associated with these schemes is that they basically limited dynamic operations at the node level. In this paper, by introducing the innovative concept of ‘access polynomial’ and representing a key value as the sum of two polynomials in a finite field, we propose a new key management scheme for dynamic access hierarchy. The newly proposed scheme supports full dynamics at both the node level and user level in a uniform yet efficient manner. Furthermore, the new scheme allows access hierarchy to be a random structure and can be flexibly adapted to many other access models such as ‘transfer down’ and ‘depth‐limited transfer’. Copyright © 2007 John Wiley & Sons, Ltd.     

Turbo-Like Codes for Transmission of Correlated Sources over Noisy Channels

In this article we focus on distributed coding of correlated sources that are transmitted through either separated noisy channels (one per source) or over a multiple access channel (MAC). For simplicity, we consider only two sources, but the proposed approach can be easily extended to the case of more sources. The two sources are encoded independently of each other (i.e., for a given source neither the realization from the other source nor the correlation model are available at the encoder site) and transmitted through the channel. Then, the correlation between the sources is exploited at a common receiver, aiming at the reconstruction of the two sources. Although this problem has many practical applications e.g., in the case of sensor networks (where correlated data has to be communicated between the different nodes) and video/image applications, we will focus in the key ideas without discussing specific applications. For simplicity, we will assume simple correlation models and binary sources.     

Secrecy Capacities for Multiterminal Channel Models

Shannon-theoretic secret key generation by several parties is considered for models in which a secure noisy channel with one input terminal and multiple output terminals and a public noiseless channel of unlimited capacity are available for accomplishing this goal. The secret key is generated for a set A of terminals of the noisy channel, with the remaining terminals (if any) cooperating in this task through their public communication. Single-letter characterizations of secrecy capacities are obtained for models in which secrecy is required from an eavesdropper that observes only the public communication and perhaps also a set of terminals disjoint from A. These capacities are shown to be achievable with noninteractive public communication, the channel input terminal sending no public message and each output terminal sending at most one public message, not using randomization. Moreover, when the input terminal belongs to the set A, it can generate the secret key at the outset and transmit it over the noisy channel, suitably encoded, whereupon the output terminals in A securely recover this key using public communication as above. For models in which the eavesdropper also possesses side information that is not available to any of the terminals cooperating in secrecy generation, an upper bound for the secrecy capacity and a sufficient condition for its tightness are given.     

High Performance Group Merging/Splitting Scheme for Group Key Management

The group merging/splitting event is different to the joining/leaving events in which only a member joins or leaves group, but in the group merging/splitting event two small groups merge together into a group or a group is divided into two independent parts. Rekeying is an importance issue for key management whose target is to guarantee forward security and backward security in case of membership changes, however rekeying efficiency is related to group scale in most existing group key management schemes, so as to those schemes are not suitable to the applications whose rekeying time delay is limited strictly. In particular, multiple members are involved in the group merging/splitting event, thus the rekeying performance becomes a worried problem. In this paper, a high performance group merging/splitting group key management scheme is proposed based on an one-encryption-key multi-decryption-key key protocol, in the proposed scheme each member has an unique decryption key that is corresponding to a common encryption key so as to only the common encryption key is updated when the group merging/splitting event happens, however the secret decryption key still keeps unchanged. In efficiency aspect, since no more than a message on merging/splitting event is sent, at time the network load is reduced since only a group member’s key material is enough for other group members to agree a fresh common encryption key. In security aspect, our proposed scheme achieves the key management security requirements including passive security, forward security, backward security and key independence. Therefore, our proposed scheme is suitable to the dynamitic networks that the rekeying time delay is limited strictly such as tolerate delay networks.     

Tracking of time-varying mobile radio channels .1. The Wiener LMSalgorithm

Adaptation algorithms with constant gains are designed for tracking smoothly time-varying parameters of linear regression models, in particular channel models occurring in mobile radio communications. In a companion paper, an application to channel tracking in the IS-136 TDMA system is discussed. The proposed algorithms are based on two key concepts. First, the design is transformed into a Wiener filtering problem. Second, the parameters are modeled as correlated ARIMA processes with known dynamics. This leads to a new framework for systematic and optimal design of simple adaptation laws based on prior information. The algorithms can be realized as Wiener filters, called learning filters, or as "LMS/Newton" updates complemented by filters that provide predictions or smoothing estimates. The simplest algorithm, named the Wiener LMS, is presented. All parameters are here assumed governed by the same dynamics and the covariance matrix of the regressors is assumed known. The computational complexity is of the same order of magnitude as that of LMS for regressors which are either white or have autoregressive statistics. The tracking performance is, however, substantially improved     

Relations among Security Models for Authenticated Key Exchange

Usually, key‐establishment protocols are suggested in a security model. However, there exist several different security models in the literature defined by their respective security notions. In this paper, we study the relations between the security models of key establishment. For the chosen security models, we first show that some proven key‐establishment protocols are not secure in the more restricted security models. We then suggest two compilers by which we can convert a key‐establishment protocol that is secure in a specific security model into a key‐establishment protocol that is still secure in a more restricted security model.     

基于刚性约束的双移动机器人协同定位

准确、快速的状态估计是保证多机器人顺利完成协作搬运任务的关键.然而,大部分现有多机器人协同定位方法都存在一定的局限性,往往无法同时兼顾定位精度与计算复杂度.因此,本文从协作搬运任务的特点出发,将距离与方位的刚性约束条件引入协同定位中,同时根据机器人之间的紧密耦合关系建立起通用有效的运动模型和量测模型.最终在此刚性约束系统建模的基础上,提出一种基于高斯-厄米特求积分卡尔曼滤波（Quadrature Kalman Filter,QKF）的双移动机器人协同定位方法.仿真实验结果表明：与基于无约束模型的QKF协同定位方法相比,本文所提方法不但具有更高的定位精度,而且计算复杂度大大降低,有助于实现多机器人实时协同定位.     

机载防撞系统垂直防撞的物理模型

如何准确预测和估算本机与入侵飞机相遇时在最接近点的垂直间隔距离,是机载防撞系统(TCAS)在垂直方向上选择防撞措施的关键问题.采用空间相遇几何学的方法,建立了本机与入侵飞机相遇时垂直防撞的两种物理模型,基于该模型推导出了预测两机之间垂直间隔距离的计算公式,并且进行了计算机仿真.仿真结果表明,该模型能够准确预测本机与入侵飞机相遇时在最接近点的垂直间隔距离.最后,给出了本机在垂直方向上选择防撞措施的决策咨询条件和逻辑处理流程.     

Hole-traps in silicon dioxides. Part II. Generation mechanism

After studying the properties of hole traps in Part I, attention is turned to the physical processes responsible for generating hole traps in Part II of this work. The applicability of four models to hole-trap creation will be examined. These are the trapped hole-electron recombination model, the electrical field energy model, the hole injection model, and the hydrogen model. To testify these models, stresses have to be carried out not only under substrate hole injection (SHI), but also under Fowler-Nordheim injection (FNI). By combining FNI with SHI, we will be able to control hole fluency independent of the electron-induced hydrogen release. This allows us to determine how important hydrogen is for hole-trap generation. Although it was reported that hydrogen could play a major role in positive charge generation for devices with an Al gate or without a gate, we will show that hydrogen does not dominate hole-trap generation, when poly-si gated devices are stressed under our test conditions. Unambiguous results will also be given to show that key predictions of the recombination model and the electrical field energy model are not observed here. In this paper, the most important process for hole-trap generation is found to be the direct interaction of injected holes with the oxide.     

V2X PKI信任模型研究分析

信任模型是建立公钥基础设施信任体系的基础,决定着在构建整个PKI信任体系及进行跨域认证的技术框架。在车联网V2X PKI体系中,建立不同CA之间的信任模型,解决CA之间的互信互认是车联网V2X PKI大规模商用必须解决的问题。文章通过深入分析常见的几种CA信任模型的基础上,结合欧美V2X PKI信任模型的比较,并结合我国PKI标准及行业发展现状,对我国V2X PKI的网络信任模型进行了分析并提出建议。     

Biometric-based personal identity-authentication system and security analysis

1 Introduction Personal authentication system is a system that verifies a person’s identity, which he (she) claims to be, usually through login name or smart card, etc. Traditional authentication is based on the possession of a secret key, that is, once the user possesses the key, his (her) authenticity is established. Personal authentication based on PKI is one of the most prevalent authentication methods, which uses a private key to prove the user’s identity. Usually cryptographic keys a…