对象关系转换接口在飞行仿真建模环境的应用研究

飞行仿真建模环境是构造飞机飞行仿真模型并进行飞行仿真实验的软件平台.作为一项复杂的大系统,FSME采用了当今流行的面向对象建模工具--统一建模语言UML对系统进行建模,因此在FSME系统的前台飞行仿真模型是以对象的形式存在.由于当今数据库市场上面向对象数据库产品还很少,因此存储飞行仿真模型的模型库采用了当今主流的关系型数据库库管理系统.因此仿真前台对象和后台存储的关系表格之间存在着"阻抗不匹配"的问题.该文主要阐述对象关系转换接口的设计、实现及在飞行仿真建模环境中的应用.     

基于WEB分布式仿真的CORBA/JAVA实现方法

基于Web的分布式仿真是目前仿真技术发展的最新分支,对研究仿真软件的集成与重用具有重要意义。文章分析介绍了面向对象的仿真技术、CORBA机制、JAVA技术,提出了基于三者结合的方法开发基于CORBA软总线的开放式体系结构和支撑框架,以此实现基于Web的分布式仿真应用系统,最后阐述了CORBA/JAVA开发基于Web的仿真系统的优势与不足。     

面向对象的分布式CORBA技术及其实现

当今,面向对象的技术是软件界努力追求的目标,分布式组件对象标准极大地推动了以异构环境下协同工作为目标的虚拟环境研究。该文主要讨论了CORBA技术及其在Delphi中的实现方法。     

基于CORBA的智能组件Agent

软件组件技术是面向对象技术的最新发展,它具有开放性、集成性、灵活性、模块性、可管理性、安全性和透明性等特点.将软件组件技术应用于包括分布式在内的网络系统,这是网络计算技术的最新进展,即分布式对象技术.在基于这种技术所建立的应用系统,其基本工作(计算)单元就是分布式对象,也就是组件.这种应用系统由于具有分布式计算的特征,它与传统的集中计算系统相比具备更好的灵活性、可靠性、性能价格比、可扩展性.分布式对象目前存在两种主流技术:OMG(对象管理集团)的CORBA(公共对象请求代理体系结构)和Microsoft的COM/DCOM(分布式对象模型).基于这两种技术编写的组件都与具体的实现语言无关,组件间能进行有效的互操作,但CORBA提供跨平台支持,COM/DCOM则局限于微软操作系统.     

CORBA体系中ORB互操作性实现机理的研究

对象请求代理ORB是支持CORBA构件相互作用的“软总线”，它保证了在分布式异构环境中，透明地向对象发送和接收请求，帮助实现应用组件之间的互操作。而ORB互操作性问题是CORBA技术的核心，就此，总结并分析了ORB互操作性实现的机理以及具体实现的技术和方法。     

POA的CORBA应用研究与Java实现

CORBA是当前主流的分布式组件技术。ORB是CORBA规范的核心，而OS作为ORB的重要组成部分，在接收客户请求及定位对象乃至请求处理等许多方面都起着关键性的作用。POA是一种“便携式”的OA，它提供了在不同的ORB产品间的良好移植性。就POA的实现机理进行研究，并给出其Java实现。     

基于CORBA的特定领域网上应用系统开发支撑平台机制研究

分步式组件对象技术CORBA与Web相结合会给Internet上的应用系统带来了巨大的优势。文章介绍了一个可移植性、可扩充性都优于传统客户机/服务器模式的网上应用系统开发支撑平台。该平台实现了CORBA、Java、Internet三者的整合,以此作为该平台的底层通信与分布式组件调用的基础,采用三层体系结构,开发出的组件对象符合CORBA标准,便于应用系统的无缝可扩充     

COM和CORBA桥接的实现

介绍了COM和CORBA这两种分布式应用平台的不同特点,从理论上阐述了这两种用平台互操作的可行性。当建立一个分布式对象解决方案时,COM和CORBA都有其各自的优点,COM是组件体系的主流,CORBA是远程体系结构主流。只有清楚认识到每种技术的优点才能在任何情况下做出合适的选择。为了使COM和CORBA的优势都得到发挥,可以让COM和CORBA对象实现互操作,即实现COM和CORBA的桥接。最后给出一个在Delphi下实现的一个COM和CORBA桥接的简单例子,说明如何在Delphi中实现COM和CORBA的桥接。     

基于CORBA异步消息的连接管理服务

事务管理是当今数据库领域的重要研究内容。基于CORBA异步消息的连接管理服务,作为对象事务管理器(OTM)的一部分,把分布式对象技术、事务处理技术(TP-Monitor)及异步消息技术相结合,实现了对松耦合的分布式计算环境中事务的良好管理。本文主要介绍基于CORBA异步消息的连接管理服务的系统功能及实现技术。     

分布式多媒体仿真建模与表现环境

本文探讨了分布式处理技术和多媒体技术在计算机仿真技术中的作用，提出了分布式多媒体仿真的概念，讨论了分布式多媒体仿真系统的功能和结构，同时讨论了分布式多媒体仿真系统中的建模环境和表现环境，给出了一个导弹武器系统攻防对抗的分布式多媒体仿真系统原型。     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).