Study on startup characteristics of heat pipe cooled and AMTEC conversion space reactor system

Future exploration of deep space requires space power with high power density, light weight, low cost and high reliability. Space reactor is an excellent candidate with its unique characteristics of high specific power, low cost, strong environment adaptability and so on. Among all types of space reactors, heat pipe cooled space reactor, which adopts the passive heat pipe as core cooling component, is considered as one of the most promising choice and is widely studied all over the world. Startup characteristics of this type space reactor are an active topic.Previous studies mainly focused on the startup from high temperature rather than environmental temperature. In order to simulate the transient startup process from frozen state, a transient analysis code (TAPIRS) for heat pipe cooled space reactor power system (HPS) has been developed and applied to investigate the system transient performance during a startup from zero cold power to full power. The code integrates separately validated point reactor kinetics model, lumped parameter core heat transfer model, combined heat pipe (HP) model (self-diffusion model, flat-front startup model and network model), energy conversion model of alkali metal thermal-to-electric conversion units (AMTEC), and HP radiator model. By comparing the simulation results of the models and steady state with those in the references, the rationality of the models and the solution method is validated. It is found that by adjusting the control drum's rotational speed, the reactor can startup from subcritical state to full power state while the heat pipe and AMTEC from solid state to normal operational state. HPS can startup entirely depending on the nuclear power, and the maximum temperature of the heat pipe does not exceed 1250 K in the whole startup process. The maximum errors of the parameters between the simulation results of this paper and those in the literature at the full power condition are less than 5%. Under the accident of control drum failure with largest reactivity insertion, the fuel temperature can be controlled within the safety limits. These show that the reactor system has characteristics of no single-point failures, the self-stabilization capability under accident conditions.     

现代办公空间设计的新趋向

本文结合当前的社会现状,对现代办公空间的新模式作以总结和概括,并对现代办公空间环境设计的新趋向作以展望。     

Active vibration suppression of a flexible structure using sliding mode control

In this paper, sliding mode control (SMC) is designed and applied to an elastic structure to suppress some of its vibration modes. The system is an elastic beam clamped on one end and the designed controller uses only the deflection measurement of the free end. The infinite dimensional mathematical model of the beam is reduced to an ordinary differential equation set to represent the behavior of required modes. Since the states of the finite dimensional model are not physically measurable quantities, an observer is designed to estimate these states by measuring the tip deflection of the beam. The performance of the observer is important because the observed states are used in the SMC design. In this study, by using the output information, an observer is designed and tested to estimate the states of the finite dimensional model of the beam. Then the designed SMC is applied to the experimental beam system which gives satisfactory suppressed vibrations.     

并联机床空间曲线等弦长插补算法研究

通过对空间隐式方程曲线、参数方程曲线的插补算法的研究,把等弦长插补算法用于并联机床,用微小直线段拟合曲线。首先根据弦长求出各离散点,并求出其对应杆长,根据相邻两点之间的杆长增量按比例进给。插补无累积误差,从而提高了插补算法的准确性和高效性。     

对临近空间平台的信息对抗问题研究

介绍临近空间与临近空间平台的概念与特点,然后探讨临近空间平台在军事上的应用.分别对临近空间平台在侦察探测、通信和导航定位3种应用中的弱点进行分析,提出可行的信息对抗的手段与方法.     

椭圆轨道星际链路模型研究

根据椭圆轨道的卫星通信链路中空间参数的变化规律,定义地心惯性坐标系下不同轨道两颗卫星的星际链路向量,建立椭圆轨道卫星星际链路数学模型,定义t时刻两卫星间星际链路可通的条件建立链路可见性数学判据。对于卫星通信系统的星座设计、组网、星载天线跟踪系统设计和多层卫星网络最优化路由搜索算法有参考价值。     

实腹式巨型框架与空腹式巨型框架抗震受力性能对比研究

运用有限元分析软件SAP2000对实腹式巨型框架与空腹式巨型框架的抗震受力性能进行地震反应的弹性时程分析,比较实腹式巨型框架与空腹式巨型框架抗震受力性能的差别;为简便起见,本文只比较实腹式巨型框架梁与空腹式巨型框架梁的不同抗震特性.分析表明,空腹式巨型结构在受力性能上要优于实腹式巨型结构.     

用户体验理论在武汉里分民居环境改善中的应用

住区环境是人类生存最重要的一个空间,里分民居更是武汉历史发展过程中留下的宝贵历史遗产。通过引用用户体验的相关理论,对武汉里分民居的住区环境进行走访调查研究,并从使用者的心理需求出发,提出切实可行的解决方案,认为要实现里分民居住区环境与使用者需求的真正连接,做到里分民居环境的改善,需做到：整改当前混乱境况,保证居民的生理与安全需求;加强人与环境互动,拓展民居住区的交往与休闲空间;充分利用建筑的独特风格,提升民居的艺术与历史价值。     

中小山水城市绿地系统塑造城市特色的途径和方法

绿地是形成城市特色的重要组成部分,城市绿地系统与城市自然人文环境相结合是城市特色构建的一个重要方面。中小山水城市绿地系统规划在塑造城市特色方面具有独特的代表性。文章总结了中小山水城市的特色,提出绿地系统塑造城市特色的手法,并且以泾县为例来分析绿地系统塑造中小山水城市特色的手法。首先分析整理城市特色资源,对主要的关键词进行抽取比较,得到主要的城市特色;然后从整体出发为绿地系统定位,通过城市绿地系统结构布局强化城市山水环境;通过绿道体系的构建打造城市特色的展示体系;最后从树种规划的角度出发塑造城市的宣纸之都的城市特色.     

Das elektrische Verhalten hochohmiger Stäube

Highly resistive dusts show markedly non‐ohmic properties. The property known as specific resistivity is strongly dependent on the dust layer thickness and on the polarity of the high voltage. The current transport occurs by excess charges of both polarities, which leads to high space charge densities and induces strong electrostatic fields. The theory of electrets provides a consistent explanation of the phenomena observed so far. To investigate the electrical properties, highly resistive dusts were exposed to an electrical field with interfering corona discharges within a tip‐plate arrangement.