Methodology to resolve the transport equation with the discrete ordinates code TORT into the IPEN/MB-01 reactor

Resolution of the steady-state Neutron Transport Equation in a nuclear pool reactor is usually achieved by means of two different numerical methods: Monte Carlo (stochastic) and Discrete Ordinates (deterministic). The Discrete Ordinates method solves the Neutron Transport Equation for a set of selected directions, obtaining a set of directional equations and solutions for each equation which are the angular flux. In order to deal with the energy dependence, an energy multi-group approximation is commonly performed, obtaining a set of equations depending on the number of energy groups. In addition, spatial discretization is also required and the problem is solved by sweeping the geometry mesh. However, special cross-sections are required due to the energy and directional discretization, thus a methodology based on NJOY99 code capabilities has been used. Finally, in order to demonstrate the capability of this method, the 3D discrete ordinates code TORT has been applied to resolve the IPEN/MB-01 reactor.     

浅谈新形势下如何提高航道的竞争力

自2009-01-01起实行税费改革后,我国又推出了事业单位机构改革。面对改革后的严峻形势,作为航道管理部门,航道部门又该如何提升自身的竞争力？     

搬运机器人在钻杆生产线物料输送系统中的应用

针对钻杆生产线中物料输送的特点和难点,设计了基于搬运机器人的智能输送系统,介绍了系统的组成、工作流程、以及Profibus总线配置。调试表明,该系统能够满足搬运物料的设计目的,对提高生产效率具有较高的应用价值。     

基于SDN的本地综合承载传送网技术研究

该文通过对SDN本地综合承载传送网技术应用现状的分析,明确社会使用的需求,进而提出构建SDN的本地综合承载传送网技术网络架构和模型的方法,对SDN的本地综合承载传送网技术进行全面的分析。     

Modelling water flow,nitrogen transport and root uptake including physical non-equilibrium and optimization of the root water potential

A model is presented for the simulation of water flow, heat flow, and nitrate and ammonium transport. Two approaches are used for modelling plant water uptake as well as for plant nitrogen uptake. Nitrogen transformations are accounted for in a very simple way. This paper focuses mainly on water flow modelling, solute transport, and water uptake. Richards' equation is used to model water flow in layered soil profiles with a great variety of boundary conditions. Solute transport is simulated with either a simple convection dispersion equation or with a two-region physical non-equilibrium model to distinguish between mobile and immobile water and solute exchange between these two regions. A macroscopic sink term is added to Richards' equation to account for plant water uptake. This term can be calculated along two different approaches, one of which is based on the concept of root water potential. The root water potential is then continuously optimized to minimize the difference between the climatic demand and the uptake rate.Simulation results are compared with field data from the Netherlands to illustrate the degree to which the model is able to predict water flow, solute transport and plant water uptake. The root water potential optimization model seems to provide the best prediction of water distribution. In particular the shape of the profile, revealing uptake patterns, is quite well reproduced with this model. Comparison of simulated and observed water content profiles seems also to reveal the presence of preferential pathways. The comparisons show also how predicted solute distributions can be improved by using a two-region approach rather than a simple convection-dispersion model.     

网格环境下基于传输代价的副本优化策略*

在深入分析影响副本策略性能的各种因素的基础上,将多种因素和传输代价联系起来进行建模,提出一种副本优化策略。优化策略基于传输代价,综合考虑文件访问次数、大小、存在时间等多种因素,并充分利用文件访问次数的集合特征,提供了一个动态、全局的副本管理方法。在网格仿真器OptorSim中对基于传输代价的优化策略进行了实现和评估分析。实验分析证明,优化后的副本策略较现有策略有明显优势。     

多式联运中运输方式与运输路径集成优化模型研究*

运输方式和运输路径选择问题是影响多式联运时间和费用的关键问题,直接影响承运人和客户的利益。依据运输方式选择和运输路径优化的关系特点,采用主从混合智能启发式方法,构建了运输方式选择和运输路径优化集成模型,给出了粒子群—蚁群双层优化算法求解方案,解决了运输网络多节点、多方式、多路径的集成优化问题。实验结果表明,该方案优于蚁群算法和遗传算法。     

基于JMF的音视频会议系统的研究与实现

介绍了Java媒体框架应用编程接口（JMF）的结构特点及其实时传输协议（RTP）支持,实现了端对端的实时音视频网络会议系统.文中阐述了小型多人视频会议系统的工作原理以及RTP传输、数据源复用等关键技术问题,最后重点描述了基于JMF的音视频会议系统的设计方案,并详细介绍了系统软件的具体实现.     

Time-resolved studies of electronic transport in Si and Ge polymer dielectrics

Time of flight drift mobility studies of alkyl- and aryl-substituted Si and Ge polymers are described. Three key results are emphasized: (1) elucidation of the mechanism of electronic transport in the glassy state; (2) identification of the attribute of a given chemical impurity which governs its activity as a trap for transiting charge carriers—this is intimately related to the mechanism of chemical modification of drift mobility by doping; and (3) delineation of the impact on transport behavior of thermal transitions including that underlying thermochromism in certain aliphatic polysilylenes.This review was presented at the Second International Topical Workshop, Advances in Silicon-Based Polymer Science.