塔里木河流域人工与天然绿洲转化过程与适宜比例研究

In the Tarim River Basin, rapid development of social economy had lead to huge expansion of artificial oases and continuous shrinking of natural oases. It is of great scientific and practical significance to ensure the ecological safety and social prosperity and stability of oasis by realizing the coordinated and sustainable development of natural and artificial oases. According to the different Topographic and Geomorphic conditions and the main factors restricting oasis development, and combined with field investigation, this study divided the nine source stream and the main stream of the Tarim River Basin into three distribution patterns. Three typical river basins were chosen to analyze the artificial oasis expansion and natural oasis shrinking process in the last 20 years. Based on the principle of water balance, the quantitative relationship between artificial and natural oasis transformation and the disappearance and decline area of natural vegetation after 1 × 108 m3 water was consumed by artificial oasis. The suitable area proportion of the artificial and natural oasis of different oasis distribution patterns was put forward. This study provides theoretical support and scientific basis for the comprehensive management of the Tarim River Basin. The main conclusions are stated as follows:(1) Nine sources streams and main stream were divided into inland river desert area pattern, alluvial-proluvial fan pattern and main stream pattern. The Hotan River Basin, Keriya River Basin and Qarqan River Basin belong to inland river desert area pattern; the Weigan-Kuche River Basin, Dina River Basin, Kaidu-Kongque River Basin and Aksu River Basin belong to alluvial-proluvial fan pattern; the middle reach of the Tarim River, Yarkant River Basin and Kashgar River Basin belong to main stream pattern.(2)The total oasis areas of the representative river basins had no clear change, but the area proportion of artificial and natural oasis increased. The area proportions of artificial and natural oasis in the Weigan-Kuche River Basin were 3:7, 5:5 and 6:4 in 1990, 2000 and 2010 respectively. The area proportion of artificial and natural oasis in the Keriya River Basin was 3:7 in both 1990 and 2000, and in 2010 the proportion increased to 4:6. The area proportions of artificial and natural oasis in the Yarkant River Basin were 4:6, 5:5 and 6:4 in 1990, 2000 and 2010 respectively.(3) Cultivated land expansion not only lead to the gradual exsciccation of natural vegetation, but also lead to a larger area of natural vegetation decline. The area proportions of cultivated land expansion and declining and dying Populus euphratica are 1:3.6 and 1:32.7, respectively. (4) The appropriate artificial and natural oases area proportioning of inland river desert area pattern should be between 3:7 to 4:6. The appropriate artificial and natural oases area proportioning of alluvial-proluvial fan pattern should be between 4:6 to 5:5. The appropriate artificial and natural oases area proportioning of main stream pattern should be strictly controlled not more than 4:6

Web-based Collaborative CAPP System

本文以沈阳鼓风机厂工艺设计为背景，对基于Web的协同式LAPP原型系统的体系结构、关键技术和系统实现进行阐述。系统采用三层B/S体系结构，将显示信息与系统应用逻辑相分离。客户层采用JSP开发，包含系统登录、工艺规则输入、工艺文件输出和工艺文件修改等功能模块；中间层包含BOM处理、工艺文件生成、推理机等功能模块，封装在JavaBeans中；数据库层由典型工艺数据库、专用工艺数据库和BOM数据库组成；工艺决策规则采用产生式表达方式。本系统在基于Web的计算机辅助工艺设计方面进行了一次新的尝试，由于系统采用了BIS方式的三层体系结构，将工艺规划逻辑与用户设计页面相分离，提高了系统的效率。系统采用大型关系数据库存储典型工艺和专用工艺，工艺检索方便，同时有利于网络化制造环境下各子系统间的信息、共享和信息、集成。系统提供了通用的知识表达方式，规则中条件部分和结论部分采用基于函数的前缀表示，而且函数可以多层嵌套，增强了系统的算术、逻辑表达能力。由于将算逻表示和数据库操作表示统一成一种模式，简化了知识表达，用户易一于掌握。知识表达方式可以将复杂的问题分解成易于处理的简单问题，增强了系统的处理能力。本系统的推理机采用了递归算法，该算法的优点是算法结构清晰，能对较复杂的规则完成一次性推理计算。工艺文件为动态生成，工艺人员可以在异地协同设计。生成的工艺文件可以在线修改，提高了系统的实用性和灵活性

Web-based Collaborative CAPP System

本文以沈阳鼓风机厂工艺设计为背景，对基于Web的协同式LAPP原型系统的体系结构、关键技术和系统实现进行阐述。系统采用三层B/S体系结构，将显示信息与系统应用逻辑相分离。客户层采用JSP开发，包含系统登录、工艺规则输入、工艺文件输出和工艺文件修改等功能模块；中间层包含BOM处理、工艺文件生成、推理机等功能模块，封装在JavaBeans中；数据库层由典型工艺数据库、专用工艺数据库和BOM数据库组成；工艺决策规则采用产生式表达方式。本系统在基于Web的计算机辅助工艺设计方面进行了一次新的尝试，由于系统采用了BIS方式的三层体系结构，将工艺规划逻辑与用户设计页面相分离，提高了系统的效率。系统采用大型关系数据库存储典型工艺和专用工艺，工艺检索方便，同时有利于网络化制造环境下各子系统间的信息、共享和信息、集成。系统提供了通用的知识表达方式，规则中条件部分和结论部分采用基于函数的前缀表示，而且函数可以多层嵌套，增强了系统的算术、逻辑表达能力。由于将算逻表示和数据库操作表示统一成一种模式，简化了知识表达，用户易一于掌握。知识表达方式可以将复杂的问题分解成易于处理的简单问题，增强了系统的处理能力。本系统的推理机采用了递归算法，该算法的优点是算法结构清晰，能对较复杂的规则完成一次性推理计算。工艺文件为动态生成，工艺人员可以在异地协同设计。生成的工艺文件可以在线修改，提高了系统的实用性和灵活性

Marginal Diminishing on Poverty-Reduction Effects of Government Spending in Rural China

中国农村的改革开放取得了巨大的成功,同时也使农村的贫困问题凸现出来;财政投资是解决农村贫困问题的有效途径,然而财政投资的效率边界也使新世纪的扶贫工作面临新的课题。本文分析了农村财政投资对减贫的作用机理,并在此基础上给出了当前农村减贫中财政投资在不同地区、项目上的合理区间和运作方式。Accompanying the success of the reform in rural area, the poverty problem is increasingly turning up. Government spending is efficient for poverty reduction in rural area. However, its efficiency limitations make it a new challenge for China to continuously reduce poverty. This article analyses the mechanism of government spending in rural area on poverty reduction effect and proposes ways that the G.A.S should be used and distributed

An Agent Oriented Programming Shell System

文章提出了一个面向Agent的程序设计框架系统,包括:Agent的表达和相关函数,Agent外部格式到计算机内部的转换;Agent的解释机制;Agent之间的通讯和一个该框架系统的实际应用

一个多机环境中的Ada 编译系统

PC单机上的Ada编译系统未能充分发挥并发多任务的优势% 我们对该 编译及其运行系统做了改造, 在四台PC机所构成的多机环境中实现了任务的分布 和并行执行.本文即讨论这方面的技术问题

The Combination of Improved Sliding-mode Observer and I-f Startup Strategy For PMSM Sensorless Vector Control

为了提高永磁同步电机的无传感器矢量控制性能,在中高速段对传统的滑膜观测器进行了改进,使用sigmoid函数代替sign函数,削弱了抖振。针对传统启动方式抗负载扰动能力差的问题,深入研究了电流闭环的I-f启动策略,预定位后,在电机绕组中输入幅值恒定、频率逐渐增大的旋转电流矢量,实现电机的电流闭环启动。为了设置合适的指令角加速度,引入平均转矩的概念,得到其取值的约束范围。仿真结果表明,I-f启动和基于改进后的滑膜观测器无传感器控制方法能够可靠运行,具有良好的动态性能和抗负载扰动能力

Ada程序的一种并行分解策略

提出一种对, Ada程序进行大粒度并行分解的策略, 其实现可在单机原有,ADa编译系统的基础上经过改造、扩充而成。根据这一策略实现的软件系统己安装在两种多机环境中

Study of aerodynamic characteristics of coupled-forced pitching and rolling of a delta wing

基于刚性动网格的技术,选用B-L湍流模型,利用有限控制体积法对N-S方程进行数值离散,对76°大后掠三角翼的受迫俯仰滚转耦合运动进行了数值模拟,在此基础上,对俯仰滚转耦合运动的气动力特性和流场结构进行了分析.计算结果表明:俯仰滚转耦合运动时,三角翼上表面的涡分布的非对称性将产生横侧方向的偏航力矩和滚转力矩,滚转力矩和偏航力矩随着滚转振幅角和滚转缩减频率的增大而增大,但对法向力影响不大

Effects of non-state discharge on ephemeral gully erosion sediment and hydraulic parameters

浅沟侵蚀是黄土高原独特的侵蚀类型,在坡面侵蚀中占有重要的地位。关于浅沟侵蚀的研究,以往多采用恒定流量进行冲刷试验,而在实际中流量是变化的,有关非恒定流的浅沟侵蚀实验尚未见报道。采用野外放水冲刷试验,定量分析10～15、15～20、20～25 L/min 3个非恒定流的放水流量级和10、15、20 L/min 3个恒定流量的放水流量级对14°坡耕地坡面浅沟侵蚀产沙及其水动力参数的影响。结果表明:恒定流量级的流速、雷诺数、弗劳德数、剪切力、水流功率和径流含沙量分别较变流量后的非恒定流小6.64%～13.44%、2.73%～8.26%、6.15%～49.59%、0.27%～10.27%、4.27%～15.77%和2.02%～19.36%;恒定流的阻力系数则较与其相对应的非恒定流增大23.45%～43.41%