空气流速和自热效应对湿度传感器测量准确度的影响

通过对多种典型型号湿度传感器在不同空气流速条件下对同一相对湿度测量结果的变化的实验研究,得出了0～1.5 m/s流速范围内湿度传感器的示值随流速的变化趋势,即示值随流速增大而增大,总变化量最大达2%RH以上,且变化主要发生0.5 m/s以下的低流速情况下,同时传感器表面温度随流速增大而降低,两者变化趋势相互吻合。进一步分析表明,上述现象是湿度传感器的自热效应和空气与传感器之间的对流换热效应共同作用的结果,它给湿度传感器的测量结果带来新增不确定度。     

环刷刷丝接触压力检测系统设计

环刷是导电滑环的重要组成部件,其接触压力是滑环使刷丝变形后产生的刷丝对滑环的作用力。环刷刷丝接触压力值微小,影响因素较多,但环刷刷丝接触压力的大小将直接关系着导电滑环的技术性能和使用寿命。本文针对环刷的特点详细研究了环刷刷丝接触压力的测量方法和技术,并设计了一套环刷刷丝接触压力检测系统,实现了对环刷刷丝接触压力的自动精密测量。     

离轴三反(TMA)相机在轨成像的偏流角计算与控制

推导了离轴三反(TMA)相机在轨成像的偏流角计算公式,并根据推导过程给出了偏流角的闭环和开环两种控制方式。分析了转序定义对控制的影响,获得了最佳转序。     

Cycle slip detection using multi-frequency GPS carrier phase observations: A simulation study

The detection and repair of the cycle slip or gross error is a key step for high precision global positioning system (GPS) carrier phase navigation and positioning due to interruption or unlocking of GPS signal. A number of methods have been developed to detect and repair cycle slips in the last two decades through cycle slip linear combinations of available GPS observations, but such approaches are subject to the changing GPS sampling and complex algorithms. Furthermore, the small cycle slip and gross error cannot be completely repaired or detected if the sampling is quite longer under some special observation conditions, such as Real Time Kinematic (RTK) positioning. With the development of the GPS modernization or Galileo system with three frequencies signals, it may be able to better detect and repair the cycle slip and gross error in the future. In this paper, the cycle slip and gross error of GPS carrier phase data are detected and repaired by using a new combination of the simulated multi-frequency GPS carrier phase data in different conditions. Results show that various real-time cycle slips are completely repaired with a gross error of up to 0.2 cycles.     

AZ91镁合金负压消失模铸造充型速度的研究

真空度、浇注温度及模样厚度对AZ91镁合金消失模铸造充型速度影响的全因子实验的结果表明 ,它们都对充型速度起积极的作用 ,真空度是决定充型速度的一个关键工艺参数。在不抽真空时 ,充型速度非常小且随充型过程的进行逐渐降低 ,浇注温度对充型速度的影响也很小 ;抽真空时 ,充型速度在充型过程中不断变化且呈现不出任何规律 ,其起伏的幅度随真空度、浇注温度和模样厚度的增大而增大 ;在真空度较低时 ,随着真空度和 或浇注温度的提高 ,平均充型速度迅速增大 ,真空度与浇注温度对充型速度的交互作用增强 ;在较高的真空度下 ,平均充型速度仍随浇注温度的提高而增大 ,但平均充型速度的增大速率却随真空度的进一步提高而降低 ,真空度与浇注温度对充型速度的交互作用很弱。模样厚度对平均充型速度影响在抽真空时有所提高。     

Progress in the Study of Galaxies: Structures,Collective Phenomena and Methods

The review contains the important achievements in dynamics of the galactic disks. Among them there are I. New structures discovered recently: • giant vortices (including giant anticyclone in the Solar vicinity); • slow bar; • inner oscillating structure within spiral arms similar that of enveloped soliton; • chaotic streamlines in the velocity field of the gaseous disk of a real galaxy. II. New collective phenomina discovered recently: • new overreflection instability initiating ‘mini-spiral’ in the innermost central parsec of Galaxy; • large-scale convection caused by nonlinear interaction of density wave with disk gas; • non-kolmogorovian spectrum of weak turbulence corresponding to the observed one in the • Solar vicinity. III. New methods worked out recently: • reconstruction of full three-dimensional vector field of gas velocity from the observed line-of- • sight velocity field; • observational test for verification of the wave-nature of the spiral arms; • observational test to distinguish two types of vertical motions: warp and z-motions in the • density wave; • derivation of correct system of two-dimensional dynamical equations from the initial three- • dimensional one. This revised version was published online in June 2006 with corrections to the Cover Date.     

航空发动机离合器试验台扭矩测控系统的实现

提出了一种由异步电动机实现扭矩加载和控制的新方法，不需扭矩传感器和专门的加载装置实现了扭矩的测量和控制。采用Fuzzy-PID控制算法代替常规PID算法，能较好地模拟离合器的磨合、接合和超越等性能试验。     

剪切波速评价饱和砂土抗液化性能研究

从三方面总结了用剪切波速评价饱和砂土抗液化性能的研究进展：基于现场震害调查的研究成果具有重要参考价值，但不便于开展系统研究；室内土样剪切波速的测试手段出现了弯曲单元和扭剪法两种新技术，与弯曲单元相比较，扭剪法更加可靠；剪切波速与抗液化强度相关性已通过大量的研究得到证实。指出要实现用剪切波速评价原位土层的抗液化性能需要解决：抗液化强度对于剪切波速的敏感性，如何进行地震等效，如何将原位与室内剪切波速建立联系以及如何选取区分不同土类的指标等4个问题。     

自由剪切层速度比对大尺度相干结构的影响

 自由剪切层的速度比对层中大尺度相干结构空间发展有重要影响。本文采用数值模拟方法对其进行了探讨,所得结果与稳定性理论结果及实验数据符合较好。     

流速测量方法综述及仪器的最新进展

对流速测量领域的技术和方法作了综述。特别对近现代的激光和图像测速技术进行了介绍，结合美国TSI公司目前流动测量仪器的特点对最新技术的具体实现也作了阐述，对各种测量手段进行了对比并介绍了应用范围。