基于PC与PLC的开放式数控实验系统

介绍了由PC机与西门子PLC组成的开放式数控实验系统,讨论了实验系统的组成、通信数据格式及数控功能的实现方法,为开放式数控实验教学及相关实验教学提供了一个良好的实验开发平台．     

数据包络分析(DEA)模型及其在绩效评价中的应用综述

近年出现很多新的生产绩效评价方法,大多考虑到评估系统的整体性,从而克服了单纯依靠财务指标评价的很多弱点.然而,随之而来的是评价过程和指标系统的复杂化,以及实施成本大大增加.数据包络分析(Data Envelopment Analysis,DEA)是一种基于线性规划理论的模型,它将多输入指标和多输出指标综合成为单个评价指标.同时,该模型形成一个优化的效率前沿面,为评价者提供了提高绩效的目标,旨在综述数据包络分析模型的发展及其在绩效评价中的应用案例,以此作为论证,将DEA有效地引入制造企业生产管理过程中的可行性的理论准备,用以指导数据包络分析方法在制造生产领域的实际实施.     

基于面向油田开发决策支持系统的数据仓库

以油田开发决策支持系统软件为依托,对元数据管理、联机分析、数据挖掘、决策支持等数据库解决方案中的关键技术进行了综合分析论证,并结合石油专业领域特色,提出了建立基于数据仓库的石油企业勘探开发决策支持系统的新思路,并创新地建立数据仓库与知识库相结合的石油企业决策支持系统的结构模型.     

短时交通流预测方法综述

以交通流预测研究的步骤为主线,对短时交通流预测的方法进行研究.对现存预测方法进行了分类分析:基于统计理论的方法、基于神经网络的方法、基于非线性理论的方法以及基于新兴技术的预测方法.将人工神经网络模型与其他领域的研究相结合的综合预测模型要比单一神经网络预测模型、常规预测模型的预测效果好;基于非线性理论的预测方法有较好的发展前景.     

数据包截获仿真实验平台研究与实现

网络实验的计算机仿真是利用计算机对所研究的系统结构、系统功能和系统行为进行动态实时模仿,即通过计算机程序的运行来模拟网络内部数据传送过程,一些网络层原理的实验一般只能通过设计仿真系统进行试验验证。本文分析了网络数据包截获的实现原理和方法,在此基础上设计了一个网络数据包截获仿真实验平台,该平台可供计算机网络学习者进行仿真实验,同时也可给基于数据流异常挖掘的入侵检测系统设计提供参考。     

Evaluation of a 3dVAR system for the South China Sea

The authors evaluate a three-dimensional variational （3dVAR） system for the South China Sea （SCS） in this study. The assimilation method applied in the system takes into consideration error correlation along each ground track and uses recursive filter for optimiza- tion. Data from three R/V cruises during the spring and summer of 1998 and the summer of 2000 are used to evaluate the system. The root-mean-square error and bias are reduced significantly and when the altimeter data are assimilated, the distribution of the error is much closer to the Gaussian distribution. Precipitation and river discharge in the southwestern SCS are reproduced, and the variability of sea surface height is efficiently transferred to the subsurface. The 3dVAR system performs well for each of the three cruises, suggesting that it is steady for routine usage.     

基于神经网络技术的序列加密方法

在密码学中,序列密码是非常重要的一种加密方法。神经网络模拟人脑的思维方式,具有输入与输出是一个高度非线性映射关系以及高智能、可训练、超大容量等特点。基于神经网络的序列加密可以达到非常完美的加密效果。文中在传统加密算法的基础上分析了基于神经网络加密的优越性,得到了基于神经网络的序列加密方法。     

基于场景感知的动态信息分发系统

为了提高移动用户对移动业务的体验度和满意度,设计了基于场景感知的动态信息分发系统,对移动网络层和移动终端进行了相应的设计,并对移动业务产业链和移动序列接入模式进行了分析,根据移动用户使用业务的时间、位置和喜好,挖掘出相应的频繁序列移动接入模式.研究结果表明,该系统可以根据频繁序列移动接入模式进行分发相应的信息给移动用户,进一步提高了用户对移动业务的满意度.     

Direct assimilation of satellite radiance data in GRAPES variational assimilation system

Variational method is capable of dealing with observations that have a complicated nonlinear relation with model variables representative of the atmospheric state, and so make it possible to directly assimilate such measured variables as satellite radiance, which have a nonlinear relation with the model variables. Assimilation of any type of observations requires a corresponding observation operator, which establishes a specific mapping from the space of the model state to the space of observation. This paper presents in detail how the direct assimilation of real satellite radiance data is implemented in the GRAPES-3DVar analysis system. It focuses on all the components of the observation operator for direct assimilation of real satellite radiance data, including a spatial interpolation operator that transforms variables from model grid points to observation locations, a physical transformation from model variables to observed elements with different choices of model variables, and a data quality control. Assimilation experiments, using satellite radiances such as NOAA17 AMSU-A and AMSU-B （Advanced Microwave Sounding Unit）, are carried out with two different schemes. The results from these experiments can be physically understood and clearly reflect a rational effect of direct assimilation of satellite radiance data in GRAPES-3DVar analysis system.     

Development of a middle and low latitude theoretical ionospheric model and an observation system data assimilation experiment

On the basis of previous work, we develop a middle and low latitude theoretical ionospheric model in this paper, named Theoretical Ionospheric Model of the Earth in the Institute of Geology and Geophysics, Chinese Academy of Sciences （TIME-IGGCAS）. TIME-IGGCAS solves the equations of mass continuity, motion and energy of electron and ions self-consistently and uses an eccentric dipole field approximation to the Earth＇s magnetic field. We combine the Eulerian and Lagrangian approaches in the model and take account of the plasma ExB drift velocity. Calculation results reveal that the model is steady and credible and can reproduce most large-scale features of ionosphere. By using TIME-IGGCAS, we carried out an observation system data assimilation experiment. Assimilation results show that the ExB drift velocity can be accurately estimated by ingesting the observed foF2 and hmF2 into the model applying nonlinear least-square fit method. We suggest that this work is of great significance in the development of ionospheric data assimilation model to give better nowcast and forecast of ionosphere.