Analysis of FBRM measurements by means of a 3D optical model

Continuous process monitoring is desirable for many particulate processes such as the crystallization of active pharmaceutical ingredients. Only an in-line measurement technique can achieve such a continuous monitoring.A popular in-line measurement technique, which can be applied without dilution, is the focussed beam reflectance measurement (FBRM). However, FBRM is at this point mainly used for qualitative measurements. The measured chord length distribution is different from a particle size distribution. For a quantitative measurement a sound understanding of the measurement principle is necessary. In this paper, an optical model of the FBRM probe and a three-dimensional simulation of the measurement are presented.A three-dimensional particle field is generated with a Monte-Carlo approach. The back scattered light intensity is calculated as a function of the position of the laser beam with respect to this particle field. A vector of scattering intensities is obtained for a given laser path. This vector is processed with the simulated electronics of the Lasentec FBRM system. The output of this processing step is a chord length distribution which can be compared to the output of the Lasentec FBRM system.Simulation studies with mono-disperse polystyrene particles of different sizes and concentrations are conducted and compared to measurements of a Lasentec D600L FBRM probe. With the presented model yet unexplained massive over-estimation of small particles and concentration-dependent changes in the chord length distribution can be described.     

基于两种P2P协议的数据自销毁技术

随着云计算等互联网应用的兴起,个人数据更多地存储于网络上,其数据安全面临着极大挑战,传统的数据加密方式有时候存在加密密钥不能及时销毁的问题,存在着安全隐患。针对当前个人网络数据安全问题,采用Chord和Kademlia两种P2P协议设计了个人应用数据的自销毁协议,利用P2P协议固有的扰动特性进行个人网络数据的自动销毁数据,使用OMNEST仿真软件进行了两种协议对数据自销毁的性能分析,其仿真结果表明使用Kademlia协议的数据自销毁性能更优。     

一种基于Echord协议的网格资源发现方法

针对网格集中式的资源发现方法存在单点失效、负载均衡差等问题,提出利用P2P技术进行网格资源发现方法.该方法通过改进Chord协议的后继节点函数和finger表,提出Echord(Enhanced Chord)协议,结合Echord协议特点,将网格中的虚拟组织构建成环状拓扑结构.网格资源被描述成基于XML的RDF形式,并按照一定的资源部署算法被均衡地发布在网格节点上.给出了如何应用Echord协议进行网格资源发现的算法.理论分析和仿真实验结果表明,相比于基于Chord的网格资源发现方法,该方法能改善系统的平均查找长度、消息传播性能、资源随机查找成功率.     

基于分布式缓存管理架构的P2P VoD系统

针对P2PVoD系统中怎样有效地管理和使用节点所缓存的媒体内容的问题,本文提出了一种基于分布式的缓存管理架构。在这一架构中每个节点存储系相应的媒体分块,所存储的媒体分块可以组合成一个完整的媒体文件的所有节点分布在一个环内。因此在一个环内可以快速定位到这个媒体文件的不同分块,提高了资源搜素的效率。仿真证明这种架构可以有效地管理和使用节点所缓存的媒体内容支持用户的VCR操作。     

Effect of retrofit strategies on mitigating progressive collapse of steel frame structures

In this study, the effect of three retrofit strategies on enhancing the response of existing steel moment resisting frames designed for gravity loads is investigated using Alternate Path Methods (APM) recommended in the General Services Administration (GSA) and the Department of Defense (DoD) guidelines for resisting progressive collapse. The response is evaluated using 3-D nonlinear dynamic analysis. The studied models represent 6-bay by 3-bay 18-storey steel frames that are damaged by being subjected to six scenarios of sudden removal of one column in the ground floor. Four buildings with bay spans of 5.0 m, 6.0 m, 7.5 m, and 9.0 m were studied. The response of the damaged frames is evaluated when retrofitted using three approaches, namely, increasing the strength of the beams, increasing the stiffness of the beams, and increasing both strength and stiffness of the beams.The objective of this paper is to assess effectiveness of the studied retrofit strategies by evaluating the enhancement in three performance indicators which are chord rotation, tie forces, and displacement ductility demand for the beams of the studied building after being retrofitted.     

一种基于P2P-SIP的无中Presence业务方法

本文在介绍Presence业务模型的基础上，分析了当前Presence业务提供方法在健壮性和扩展性方面存在的问题，并结合P2P-SIP的网络结构体系，提出了一种无中心的Presence业务提供方法。该方法基于DHT的storage模型，实现了Presence信息的分布式发布与查询，有效地解决了传统Presence业务提供中的单点失效和热点效应问题。本文详细描述了这种业务提供方法的系统结构、业务流程和信令流程等，也给出了该方法的相关特点分析和总结。     

一种用于模块间解耦的对象访问模式

为了有效解决模块之间因共享数据而产生的交互耦合，提出了一种新的设计模式——注册仓模式。该模式封装了共享数据，避免了数据在各个使用者之间传递，分离了数据的提供者和使用者，实现了模块间一种简化的数据访问协议，降低了模块间的耦合度。理论和实践证明注册仓模式能良好地适用基于组件或模块的软件体系架构下面向对象的程序设计。     

Rational quadratic circles are parametrized by chord length

We show that the chord length parameter assignment is exact for circle segments in standard rational quadratic form.     

Determination of microstructural parameters of random spatial surface fractals by measuring chord length distributions

An experimental procedure for determining the micro-structural parameters of random spatial surface fractals is proposed. The procedure is based on chord length distribution measurements of planar sections of the investigated material at different linear resolutions, and comparison of the experimental results with the corresponding parameters of a well-defined structure model. The variability of the model allows microstructures with arbitrary volume fraction and fractal dimension to be considered. Furthermore, both discrete and continuous scaling behaviour have been studied.     

基于分布式协议对等网的安全研究

本文在基于分布式对等网的系统结构上,提出网络参与者通过路由对系统攻击的手段,并提出 对应的解决方案。