Stability of GaAs photocathodes under different intensities of illumination

The photocurrent curves of reflection-mode GaAs photocathodes as a function of time, when were illuminated by white light with an intensity of 0, 33 and 100 Ix, respectively, were measured using a multi-information measurement system. The calculated lifetimes of cathodes are 320, 160 and 75 min, respectively, showing that the stability of cathodes degraded with the increase of light intensity. The lifetime of cathode, illuminated by white light with an intensity of 100 Ix, while no photocurrent was being drawn during the illumination, was 100 min. Through comparison, we found that the influence of illumination on cathodes stability is greater than that of photocurrent. The quantum-yield curves of cathodes as a functions of time, when illuminated by white light with an intensity of 33 Ix, were measured also. The measured results show that the shape of the yield curves changes with increasing illumination time due to the faster quantum-yield degradation rate of low energy photons. Based on the revised quantum-efficiency equations for the reflection-mode cathodes, the variation of yield curves are analyzed to be due to the intervalley diffusion of photoelectrons and the evolution of the surface potential barrier profile of the photocathodes during degradation process.

需求变更影响分析模型及相关技术研究

需求是后续开发活动的基准，早期的一些研究者认为应该在需求完全确定之后再进行后续开发，Royce所提出的瀑布模型就是这种思想的一个体现。但是，实践经验告诉我们，不管前期的需求分析做的多么完美，需求还是会发生变更。一方面是因为需求本身很复杂，对它的分析、理解和描述是一个循序渐进的过程，不可能一蹴而就；另一方面由于用户期望和偏好的改变、市场环境的转变、使用环境的日益复杂、技术的革新等都会使得原有的软件系统无法满足各涉众的利益。因此，需求变更是软件开发中固有的规律，是不可避免和普遍存在的。 需求变更通常会导致需求间及需求与后续工作产品间的不一致。因此，频繁的需求变更会造成产品质量下降、进度延期、成本超支等问题。变更影响分析(Change Impact Analysis)通过分析变更对象及其相关工作产品间的关系来评估变更造成的影响，从而控制变更。现有方法多数是从软件维护的角度，对代码的变更影响进行分析，过于细节和技术化，不能对需求变更影响分析提供有力支持。即使针对需求变更的影响分析方法也只是基于形式化需求规约，通过分析需求间的关系来识别影响范围，并未考虑需求变更对后续工作产品造成的影响，同时形式化需求规约的应用困难也限制了该方法的实用性。此外，随着需求和工作产品的规模与复杂性日益增加，使得手工建立和维护需求间及需求与工作产品间关系面临着不小的难度。 基于以上分析，本文提出了针对自然语言需求规约的需求变更影响分析模型RCIAM (Requirement Change Impact Analysis Model)，围绕着如何自动识别和筛选需求间的关系——横向需求跟踪关系(Horizontal Requirement Traceability)、如何自动识别和筛选需求与工作产品间的关系——纵向需求跟踪关系(Vertical Requirement Traceability)、如何较全面的进行需求变更影响计算和决策三个问题展开了研究。 本文的主要贡献有： (1) 提出了需求变更影响分析模型RCIAM 本文对RCIAM进行了形式化定义。该模型不但提供了需求变更影响分析算法和对决策的支持，还提供了自动识别横向和纵向需求跟踪关系的方法。RCIAM主要包含数据处理和数据分析两个层次。数据处理层采用了文本处理(Text Processing)技术实现了横向和纵向需求跟踪关系的自动识别，为数据分析层提供需求跟踪关系数据；数据分析层基于需求跟踪关系数据，在产生需求变更申请(Change Request)时，进行量化影响计算，并提供决策支持。 (2) 提出了横向需求跟踪关系的识别与筛选方法 在对自然语言需求规约文档进行深入分析后，我们发现了两种与需求变更影响密切相关的关系类型，并从文本相似性的角度将它们定义为相似跟踪关系和引用跟踪关系。在将需求项拆分为需求片段的基础上，利用信息检索技术(Information Retrieval，IR)计算需求片段间的文本相似度，并设计了相应的算法对相似跟踪关系和引用跟踪关系进行自动识别。最后，提出了“变更影响跟踪”的规则来辅助对候选跟踪关系的人工筛选。 (3) 提出了纵向需求跟踪关系的识别与筛选方法 已有的研究多采用IR技术来自动建立需求与工作产品之间的跟踪关系，但是却存在着精度不理想的问题。我们从查全率(Recall)和查准率(Precision)的角度，分析了应用IR技术自动建立需求与代码跟踪关系的方法中产生的错误关系，发现了造成精度问题的根源所在。依据这一发现，基于现有方法，本文方法加入了相关反馈(Relvant Feedback)辅助识别和代码注释信息辅助识别等改进措施，并提供了人工筛选策略。 (4) 提出了需求变更影响分析计算与决策方法 本文通过矩阵运算说明了需求变更影响通过需求跟踪关系传播到其它需求和工作产品的过程，并设计了相应的需求变更影响分析算法。该算法考虑变更发生在不同阶段时对不同类型工作产品的影响，采用变更类型和关系强度两个因子加权计算影响值，并提出了根据影响值来进行变更决策的方法。 (5) 应用研究 结合中科方德公司Qone平台的开发，对以上工作进行了应用研究和性能分析。在Qone平台的需求管理工具版本1.0的开发中，首先采用本文方法对横向和纵向需求跟踪关系进行了自动识别，然后对开发期间发生的十次需求变更申请进行了影响分析和决策。在项目完成后，设计了实验对横向和纵向需求跟踪关系的识别进行了性能分析。结果表明，本文方法能够有效辅助进行需求变更影响分析。

面向电信企业的商业智能分析系统

首先分析国内电信企业对于商业智能的需求及一些现有电信企业商业智能系统的不足,如投资大、建设周期长等,然后提出解决措施,通过采用数据集市和配置文件的方式控制建设成本、降低实施难度,并描述面向电信企业的商业智能应用分析系统TEIAS(Telecom Enterprise Information Analysis System)的系统结构和实现,最后提出改进方向。

Ruby:一个基于移动设备的个人信息管理系统

为满足移动环境对非结构化个人信息管理的自然性和高效性的需求,提出一个基于移动设备的个人信息管理系统Ruby.首先分析了移动环境对个人信息管理的需求,描述了系统框架,接着介绍了系统界面和交互过程,并阐述了支持该系统的2个主要技术:非结构化笔记编辑技术和基于笔迹标签的检索技术.对2个技术和整个系统的评估结果表明,该系统能够满足移动环境对自然交互、非结构化信息采集加工及个人信息自然检索的需求.

船载综合信息显示系统半实物仿真设计与实现

针对船载综合信息显示系统在实体船舶内开发不方便的问题,提出了一种半实物仿真系统的设计与实现方法。结合"科学三号"海洋科学考察船的综合信息显示系统的设计和开发过程,从体系结构、信息流程和实现方法3个方面对半实物仿真系统的设计和实现过程进行了探索。实践结果表明,这种半实物仿真系统一方面可以为实际系统的体系结构、信息流程设计提供支持,另一方面可以为实际系统应用软件的开发提供较为真实的环境,有效的缩短开发时间和降低开发风险。

无线电子吊秤信息传输系统

设计出一种以电阻应变式荷重传感器作为一次测量元件的无线电子吊秤信息传输系统．该系统利用两片８０Ｃ５１微处理器，通过其串行口加一套高频载波调制解调器，以点对点通讯的方式，实现了测量数据的无线电传输。

新型托辊柔性装配线制造信息系统

本文介绍了目前第一条完全由国内生产的全自动托辊装配线及其制造信息系统。该套装系统除具有较高的自动化程度外,还充分利用先进的伺服控制技术,采用先进的SIMOTION运动控制系统,实现了托辊产品装配的柔性化。同时在软件及信息管理方面充分考虑到先进制造管理的理念,为企业的MES系统及管理信息系统的实施和升级提供了充分的接口,从而打造出一条具有较高科技含量和先进性的自动装配线。

数字图书馆中图像信息库的检索技术

简要介绍了基于内容的检索技术在数字图书馆中图像信息库检索方面的应用 ,着重对基于对象特征的检索技术做了一定的探讨。并给出了检索效果评价准则

港西油田现代油藏管理研究与实践

Through years of practice, reservoir management has already become the basic mode of foreign oil companies to realize the high-efficient development of the oil field. From the view of reservoir development and technological economy, reservoir management regards the study of the reservoir engineering, designs of reservoir projects and the dynamic analysis of the reservoir's performance as a system. In the fields of reservoir description, the establishment of the geological models and development models, the dynamic simulations of reservoir exploitation and the design of the oil engineering, reservoir management emphasizes the cooperation of the geology and the engineering, the combination of the engineering technology and the economic evaluation. In order to provide the means and basis for the reservoir geology study, reservoir evaluation, reserves calculation, numerical simulation, development plan and risk analysis, it adopts the reservoir management activities(team work) to make and implement the optimized oil field development management strategies so that secientific and democratic decision making can be achieved. Under the planned economic system for a long time, the purpose of Chinese reservoir development has been to fulfill the" mandatory" production task. With the deepening of the reform, the management organization of Chinese petroleum enterprises has been gradually going through the transition and reforms to the operational entity and the establishment of the mode of oil companies under the socialist market economy system. This research aims at introducing the advanced reservoir management technique from foreign countries to further improve the reservoir development results and wholly raise the economic benefits of Chinese mature land facieses sandstone reservoirs in the later stage of the water flooding. We are going to set up a set of modern reservoir management modes according to the reservoir features, current situation and existing problems of GangXi oil field of DaGang oil company. Through the study and implementation of the reservoir description and numerical simulation technology effectively, we plan to work out integrated adjustment projects, to study the related technology of oil recovery; to set up the effective confirmable data procedure and data management system of the reservoir management, to establish the coordinated model and workbench related to geology, engineering and economy in order to realize the real time supervision and evaluation on the process of reservoir development. We hope to stipulate modernization management tools for GangXi oil fields to rationally utilize various kinds of existing technological methods and to realize the economic exploitation and achieve the maximum benefits from the reservoir. The project of the modem reservoir management will be carried out on the GangXi oil field of DaGang oil company for this oil field is typical and has integrated foundamental materials and perfect networks. Besides, it is located in the good geographical position enjoying very convenient traffic. Implementing modern reservoir management will raise the recovery ratio, reduce the production cost and improve the working efficiency. Moreover, the popularization of modern reservoir management will improve the comprehensive benefits of DaGang oil company and even the whole Petro China. Through the reserch of this project, the following technical indicators can be reached: Establishing the concept of modern reservoir management. Establishing a set of integrated data information management system adapt to the features of GangXi reservoir. 3. Forming technical research modes of modern reservoir management suitable for mature reservoirs in the later developing stage. 4. Advancing projects of GangXi reservoir which are maxium optimized in engineering technique and economic benefits of oil exploitation. Besides, this set of technology, research principle and method can guide the mature reservoir of DaGang oil field and even the whole PetroChina to develop the further research of reservoir adjustment and improve the reservoir recovery factor and developing level constantly.

Tutorial TaxTools.

A ferramenta TaxTools foi desenvolvida pelo Laboratório de Inteligência Computacional (Labic) do Instituto de Ciência Matemática e de Computação (ICMC) da Universidade de São Paulo (USP), campus de São Carlos, SP, com o objetivo de auxiliar no processo de mineração de textos. Atualmente, ela tem sido mantida e evoluída pelo Laboratório de Inteligência Computacional (LabIC) da Embrapa Informática Agropecuária. Esse tutorial abrange apenas as opções disponíveis na TaxTools, que completam o processo de obtenção de uma taxonomia de tópicos (MOURA et al., 2008); como clusterização, cálculos de medidas intercluster e de joinability, métodos de podas, métodos de visualização de resultados e algumas opções auxiliares.