Variational Message Passing and Local Constraint Manipulation in Factor Graphs

Accurate evaluation of Bayesian model evidence for a given data set is a fundamental problem in model development. Since evidence evaluations are usually intractable, in practice variational free energy (VFE) minimization provides an attractive alternative, as the VFE is an upper bound on negative model log-evidence (NLE). In order to improve tractability of the VFE, it is common to manipulate the constraints in the search space for the posterior distribution of the latent variables. Unfortunately, constraint manipulation may also lead to a less accurate estimate of the NLE. Thus, constraint manipulation implies an engineering trade-off between tractability and accuracy of model evidence estimation. In this paper, we develop a unifying account of constraint manipulation for variational inference in models that can be represented by a (Forney-style) factor graph, for which we identify the Bethe Free Energy as an approximation to the VFE. We derive well-known message passing algorithms from first principles, as the result of minimizing the constrained Bethe Free Energy (BFE). The proposed method supports evaluation of the BFE in factor graphs for model scoring and development of new message passing-based inference algorithms that potentially improve evidence estimation accuracy.     

Extended Variational Message Passing for Automated Approximate Bayesian Inference

Variational Message Passing (VMP) provides an automatable and efficient algorithmic framework for approximating Bayesian inference in factorized probabilistic models that consist of conjugate exponential family distributions. The automation of Bayesian inference tasks is very important since many data processing problems can be formulated as inference tasks on a generative probabilistic model. However, accurate generative models may also contain deterministic and possibly nonlinear variable mappings and non-conjugate factor pairs that complicate the automatic execution of the VMP algorithm. In this paper, we show that executing VMP in complex models relies on the ability to compute the expectations of the statistics of hidden variables. We extend the applicability of VMP by approximating the required expectation quantities in appropriate cases by importance sampling and Laplace approximation. As a result, the proposed Extended VMP (EVMP) approach supports automated efficient inference for a very wide range of probabilistic model specifications. We implemented EVMP in the Julia language in the probabilistic programming package ForneyLab.jl and show by a number of examples that EVMP renders an almost universal inference engine for factorized probabilistic models.     

短消息系统未来网络建设趋势

论述了短消息在国内外的发展现状及短消息的服务功能,分析了中国移动的“移动梦网”计划,并阐述了短消息系统网络的发展趋势和前景。     

学生成绩管理系统的设计与实现

以管理信息系统技术和Java语言程序设计理论为基础，结合Windows Access数据库服务器的相关技术，用JBuilder X作为前台应用程序开发工具，阐述构建一个普遍适用于学校、班级的学生成绩管理系统的全过程，建立一套在现有Windows操作系统下的单机版学生成绩管理系统。该系统适合一般学校和班级使用。管理系统具有简单实用、操作方便，可靠性强等特点。可供一般学生登陆查询，管理员则拥有查询、添加、修改、删除学生成绩的功能。该成绩信息管理不仅可以实现传统管理应用中的属性数据的管理，而且可以针对不同的用户需求建立对空间数据的管理机制，因而可以得到广泛的应用。     

A Multi-Directional Search technique for image annotation propagation

Image annotation has attracted lots of attention due to its importance in image understanding and search areas. In this paper, we propose a novel Multi-Directional Search framework for semi-automatic annotation propagation. In this system, the user interacts with the system to provide example images and the corresponding annotations during the annotation propagation process. In each iteration, the example images are clustered and the corresponding annotations are propagated separately to each cluster: images in the local neighborhood are annotated. Furthermore, some of those images are returned to the user for further annotation. As the user marks more images, the annotation process goes into multiple directions in the feature space. The query movements can be treated as multiple path navigation. Each path could be further split based on the user’s input. In this manner, the system provides accurate annotation assistance to the user - images with the same semantic meaning but different visual characteristics can be handled effectively. From comprehensive experiments on Corel and U. of Washington image databases, the proposed technique shows accuracy and efficiency on annotating image databases.     

基于Delta3D的气象仿真框架设计与实现

为解决传统气象仿真方法复用性差,耦合性高等问题,提出了基于组件、以事件为中心的独立气象仿真框架,并在Windows平台下形成一个动态链接库,该动态链接库可以方便的动态载入到各种仿真系统中。运用VC++2005和虚拟现实开发引擎Delta3D,通过键盘响应特定气象事件,实现了常见气象现象的仿真。实验结果表明,利用该方法不仅降低了系统的耦合性,还提高了仿真系统的开发和运行效率。     

基于GSM网络的无线抄表系统的设计

随着全球移动通信系统移动通信网络的迅速普及,基于短消息业务的各种应用也蓬勃发展起来。具体研究了基于GSM网络短消息业务的无线抄表系统组成结构、工作过程以及控制中心的VB程序的设计,同时简要介绍了移动通信模块、短消息各字段的含义以及短消息业务存在的问题和发展前景。     

基于C8051F040的CAN总线智能节点的设计

CAN总线现在已被公认为是最有前途的现场总线之一。Cygnal公司的片上系统(SoC)级单片机C8051F040功能强大,代表了目前8位单片机控制系统的发展方向。详细介绍了基于C8051F040的CAN总线智能节点的硬件和软件设计,给出了详细的硬件原理图和软件流程,并提供了部分源代码。所给的硬件和软件设计方案已经全部通过了验证。     

电信级骨干网传输技术

城域以太网论坛（MEF）提出了电信级以太网（CE）的概念,以改进以太网技术并使之成为下一代网络（NGN）传输汇聚层的解决方案。运营商骨干网传输（PBT）技术是对早期以太网技术进行增强以及改进的产物,是一种有前途的新版CE实现技术和标准。通过研究与PBT有关的技术、PBT网络结构、PBT作为传输汇聚层解决方案的优势及其未来的发展趋势,可以看出虽然PBT还存在一些有待解决的问题,但在NGN中PBT将是传输汇聚层的优选技术。     

3Com中小局域网络解决方案

本文着重介绍了基于3Com先进软件的500信息点以内的中小局域网络建设,并介绍了该公司推出的局域网络产品和解决方案。