土壤槽三分量天平

本文通过实例表明,常规风洞测力天平移植于对沙漠的研究是成功的。设计排除了土壤的自重影响,天平有较高的灵敏度,整机可根据不同土壤槽而升沉,是研究沙粒迁移的较好工具。     

多点压力扫描阀测量系统在激波／湍流边界层干扰实验中的应用

多点压力测量是航空气动力研究及高性能流体机械研究中的重要测试手段。利用计算机和多点压力扫描阀系统，可以高效地完成这项任务，并可能在实验中实现数据采集及整个实验过程的自动化。我们利用ＨＰ１０００／Ａ７００计算机－ＨＰ２２５０－测控装置－压力传感器－高速扫描阀组成的测量控制系统，在超音速风洞内对激波／湍流边界层干扰产生的流场进行了快速多点压力数据采集，并取得了可靠的结果。本文对测试和校正过程中的程序设计、测试方法和应用经验进行了介绍。     

Designing to MIL-STD-2165: Testability

The V-22 avionic hardware is the first to be designed under MIL-STD-2165 testability program requirements. This paper presents an overview of the avionics design-for-testability approach and lessons learned to date relative to the application of MIL-STD-2165. The paper will discuss incorporation of testability requirements up front in the avionics design which will drive the supportability philosophy at both the Organizational and Depot levels of maintenance. The paper will compare previous avionics hardware testability requirements versus those applied to the V-22 avionics and highlight areas of improvement. A discussion of testability design impacts on reduced level of testing (i.e. WRA/SRA/System) will be included. In addition, the paper discusses an innovative approach to meeting the user requirements for a man-portable forward deployed maintenance capability that forms the basis for a two level support scenario (Organizational and Depot). The innovation comes from the fact that the on-board Central Integrated Checkout system will provide data as well as fault isolation and will use this data as a mechanism to reduce the size and complexity of the stimulus and measurement hardware at either the Organizational or Depot level depending on the deployment requirements.     

Attitude control of a bias momentum satellite using moment ofinertia

Analysis on the attitude controller based upon moment of inertia distribution for a bias momentum satellite is discussed. Spacecraft moment of inertia distribution is represented in the form of product of inertia terms in the system inertia matrix. The product of inertia between orthogonal body axes of the satellite is used to build a controller which controls the nutational motion caused by the angular momentum of the wheel. The attitude controller in the pitch axis controlling the pitch motion as well as nutational dynamics in the roll/yaw planes is analyzed in detail. Analytic expressions using linearized equations are derived providing further insight into the dynamic coupling effect among orthogonal body axes     

概念辨析过程中的数学变式教学--以矩阵的相似与合同为例

矩阵的相似与矩阵的合同这两个概念很容易混淆,所以需要对它们进行辨析.它们的相同点、不同点及二者的相互转化,都体现着数学变式教学的观点.以这一观点作为出发点和归宿,既验证了数学变式教学本身的解释力,又为辨析矩阵的相似与矩阵的合同这两个概念找到新的研究视角.     

晶须和短纤维混杂增强铝基复合材料研究

简要介绍了ＳｉＣ晶须和Ａｌ２Ｏ３短纤维混杂增强铝基复合材料的制造工艺，并对材料的力学性能进行了测试，对金相组织和扫描断口进行了观察。结果表明，用该工艺制造出增强剂分布均匀的复合材料，材料的性能尤其是抗拉强度有了较大幅度的提高，复合材料中晶短纤维的增强机理明显不同，该材料有望在大功率发动机上得到应用。     

Needs in space education for the 21st century

There is increasingly broad concern in the USA today about the quality, vibrancy and appeal of science and technical education in general and space education in particular. There needs to be a robust link between the educational community (i.e. the primary and secondary schools as well as colleges and universities) and a well-defined space research and exploration agenda that is strongly supported by the space industry, NASA and other relevant US governmental agencies. Without such a renewal of mission and new goals it will be difficult to re-invigorate and expand quality space education programs. A workshop was therefore convened in 2003 to analyze the problem, discuss new initiatives, organize a survey inviting suggestions from a range of relevant players and draw conclusions on what the USA needs to do to improve space education in the 21st century. Although the focus of this workshop was on space education in the USA the international dimensions of this problem were also addressed and the firm conclusion was reached that similar issues and concerns apply in Europe, Canada, Japan and other spacefaring nations. This article is an edited version of a White Paper subsequently produced to highlight the problem, summarize the proceedings of the workshop and present the results of the survey. Greater clarity in the definition of national space goals, the upgrading of teachers’ skills and an increase in technical scholarships are among the steps recommended.     

Path visualization: a method for objective measurement of spatial visualization

ABSTRACT

The ability to mentally represent spatial information is a fundamental cognitive process. To many people, this process feels a bit like visual perception, hence the term ‘spatial visualization’. In this paper, we describe a method for measuring the accuracy of spatial visualization, specifically visualization of a complex path in imaginary space. A critical feature of this method (called Path Visualization) is that it relies on the detection of intersections in a visualized path. Intersection detection is an inherently spatial task that requires a spatial representation. In this paper, we show how the Path Visualization method works, and how it can be customized to address several key research issues in human spatial cognition.     

Evaluating the Wind-Induced Mechanical Noise on the InSight Seismometers

The SEIS (Seismic Experiment for Interior Structures) instrument onboard the InSight mission to Mars is the critical instrument for determining the interior structure of Mars, the current level of tectonic activity and the meteorite flux. Meeting the performance requirements of the SEIS instrument is vital to successfully achieve these mission objectives. Here we analyse in-situ wind measurements from previous Mars space missions to understand the wind environment that we are likely to encounter on Mars, and then we use an elastic ground deformation model to evaluate the mechanical noise contributions on the SEIS instrument due to the interaction between the Martian winds and the InSight lander. Lander mechanical noise maps that will be used to select the best deployment site for SEIS once the InSight lander arrives on Mars are also presented. We find the lander mechanical noise may be a detectable signal on the InSight seismometers. However, for the baseline SEIS deployment position, the noise is expected to be below the total noise requirement \(>97~\%\) of the time and is, therefore, not expected to endanger the InSight mission objectives.     

半固态2618铝合金二次加热及成形试验

采用电阻炉加热的方法对喷射沉积法制备的2618铝合金进行了二次加热实验，观察了显微组织的变化；并通过电阻炉加热、半固态挤压铸造的方法成功地试制了摩托车零件。