PuO2含量对MOX燃料组件物理特性的影响

当超临界水冷堆组件采用铀与钚的氧化物混合而成的MOX燃料时,与普通UO_2燃料相比其中子学特性存在差异。为了研究PuO_2含量对组件物理特性的影响,采用蒙特卡罗方法计算得到了不同PuO_2含量时MOX燃料物理特性参数,包括俘获裂变比、总微观裂变截面、燃料每次裂变平均释放的能量、每次裂变释放的中子数及有效裂变中子数。进一步得到了装载不同含量PuO_2时MOX燃料组件特性参数,包括能谱、Keff、相对功率、相对功率峰值和缓发中子份额。研究结果对MOX燃料组件的设计有一定参考价值。     

用MCM验证测长仪示值误差的测量不确定度GUM法评定

本文用蒙特卡洛法对测长仪示值误差的测量不确定度的GUM法评定进行了验证,结果一致,验证通过。     

Non-fragile dynamic output feedback H∞ control for discrete-time systems with FWL consideration

The non-fragile dynamic output feedback H _∞ controller design problem is investigated. The controller to be designed is assumed to be with additive gain variations. A two-step procedure is proposed to develop sufficient conditions for the non-fragile H _∞ controller design by employing the structured vertex separator. A comparison between the proposed and the existing controller design methods is provided, and a numerical example is carried out to support the theoretical findings.     

基于词性的文本挖掘算法在IDS日志中的应用

提出一种以词性为参考值的文本挖掘算法,能有效挖掘与种子词有关的关联规则。基于Bootstrapping算法思想,既减少了预处理阶段对于词根还原的依赖,能处理日志中出现的中文词汇。增加了对于日志文本上下的理解,提高了关联规则的有效性,并应用与IDS日志挖掘之中,有效改善挖掘效率,为规则库提供关联规则。     

A multi-strategy knowledge interoperability framework for heterogeneous learning objects

This paper presents a knowledge exchange framework that can leverage the interoperability among semantically heterogeneous learning objects. With the release of various e-Learning standards, learning contents and digital courses are easy to achieve cross-platform sharing, exchanging, and even reorganizing. However, knowledge sharing in semantic level is still a challenge due to that the learning materials can be presented in any form, such as audios, videos, web pages, and even flash files. The proposed knowledge exchange framework allows users to share their learning materials (also called “learning objects”) in semantic level automatically. This framework contains two methodologies: the first is a semantic mapping between knowledge bases (i.e. ontologies) which have essentially similar concepts, and the second is an ontology-based classification algorithm for sharable learning objects. The proposed algorithm adopts the IMS DRI standard and classifies the sharable learning objects from heterogeneous repositories into a local knowledge base by their inner meaning instead of keyword matching. Significance of this research lies in the semantic inferring rules for ontology mapping and learning objects classification as well as the full automatic processing and self-optimizing capability. Focused on digital learning materials and contrasted to other traditional technologies, the proposed approach has experimentally demonstrated significantly improvement in performance.     

A TCAM-based solution for integrated traffic anomaly detection and policy filtering

The survivability of the future Internet is largely dependent on whether it will be able to successfully address both security and performance issues facing the Internet. On one hand, the Internet becomes more and more vulnerable due to fast spreading malicious attacks. On the other hand, it is under great stress to meet ever growing/changing application demands while having to sustain multi-gigabit forwarding performance. In this paper, we propose a Ternary Content Addressable Memory (TCAM) coprocessor based solution for high speed, integrated TCP flow anomaly detection and policy filtering. The attacking packets with spoofed source IP addresses are detected through two-dimensional (2D) matching. The key features of the solution are: (1) setting flag bits in TCAM action code to support various packet treatments; (2) managing TCP flow state in pair to do 2D matching. We evaluate the solution’s ability to detect TCP-based flooding attacks based on real-world-trace simulations. The results show that the proposed solution can match up OC-192 line rate. The possible modifications of the solution for the detection of low rate TCP-targeted attacks are also discussed.     

Utility function of TCP

Understanding the TCP congestion control mechanism from a global optimization point of view is not only important in its own right, but also crucial to the design of other transport layer traffic control protocols with provable properties. In this paper, we derive a global utility function and the corresponding optimal control law, known as TCP control law, which maximizes the global utility. The TCP control law captures the essential behaviors of TCP, including slow start, congestion avoidance, and the binary nature of congestion feedback in TCP. We find that the utility function of TCP is linear in the slow start phase and is proportional to the additive increase rate and approaches the well-known logarithm function as the data rate becomes large in the congestion avoidance phase. We also find that understanding the slow start phase with a fixed threshold is critical to the design of new transport layer control protocols to enable quality of service features. Finally, as an application, we design a Minimum Rate Guaranteed (MRG) traffic control law that shares the same utility function as the TCP control law. Our simulation study of the MRG control law indicates that it is indeed TCP friendly and can provide minimum rate guarantee as long as the percentage of network resource consumed by the MRG flows is moderately small.     

基于CORBA框架的RPC包装集成技术

文章从分析系统集成策略对信息系统研究和发展的重要作用入手,阐述了建立通用一致应用系统集成框架的重要性,并给出基于ＣＯＲＢＡ规范的集成框架总体结构及实现策略;在此基础上实现了ＲＰＣ部件的包装集成,并对遇到的关键技术问题进行论述。     

一种基于模块化结构的大学英语四级MCAI系统实现方法研究

Authorware是一种优秀的多种媒体开发工具,能实现非常复杂的多媒体接入及程序流程控制,但在开发功能结构类似,信息资源丰富的模块时,还存在程序设计复复,代码重复量大,模块功能更改困难等问题,本文针对以上问题,在设计大学英国四级多媒体教学系统时,提出了一套基于模块化结构的大学英语四级MCAI教学软件的设计思想,并以听力部分为例,详细介绍了该部分各功能模块的实现。