用于照射量仪校准工作的监测电离室

本文描述用于照射量仪校准工作的薄窗监测电离室的结构、性能及使用方法．就重复性而言，电离室的读数在０．２％以内相符；用于校准现场仪器时，在中等过滤的情况下误差小于１％，重过滤下不大于２％．     

数字仪表的设计实验

本介绍一个综合性、设计性研究实验－数字仪表的设计。实验具有探索性和延展性，有助于培养学生的研究能力和创新能力。     

利用FY-3(D)卫星电离层光度计数据反演电离层O/N2

磁暴等空间天气事件会引起热层中性成分O和N₂浓度的显著变化,故常将氧原子和氮分子的柱密度之比O/N₂作为电离层热层受扰动的标志。研究表明,O和N₂柱密度之比O/N₂与远紫外气辉OⅠ 135.6 nm和N₂ Lyman-Birge-Hopfield(LBH)的柱辐射强度之比135.6/LBH具有很好的相关性,因此远紫外光学遥感探测对于监测磁暴等空间天气事件显得尤为重要。自20世纪70年代以来,国外就开展了远紫外气辉电离层探测的研究工作,并相继发射了多颗相关卫星,尤其是美国、日本以及瑞典等国家。而我国在轨运行的星载光学遥感探测仪器中,只有一些工作在微波波段、可见光波段的载荷,还没有在远紫外波段工作的遥感探测仪器,直到2017年11月风云三号D气象卫星的成功发射,卫星上搭载的电离层光度计是我国首台星载远紫外气辉遥感探测载荷,它为我们提供了一系列具有自主知识产权的远紫外探测数据,为开展电离层O/N₂特性的研究奠定了基础。首先阐述了利用柱辐射强度之比135.6/LBH来反演热层中性成分柱密度之比O/N₂的理论依据。其次,基于MSISE-00大气模型,利用AURIC来仿真计算135.6/LBH与O/N₂之间的比例系数,然后利用电离层光度计实时观测的远紫外气辉数据来反演电离层O/N₂,进一步验证磁暴期间电离层中性成分受扰动的情况。在数据处理过程中,采用了切比雪夫滤波器滤波方式针对数据中的带外杂散光进行了处理,进一步抑制了杂散光信号对远紫外光谱信号的影响。最后,将电离层光度计O/N₂的反演结果与国外光学遥感载荷全球紫外成像仪GUVI（Global Ultraviolet Imager）的结果进行对比,结果显示二者对磁暴的响应一致,O/N₂的产品误差RMS约为0.319 6,文中对造成两者差异的可能原因做出了初步分析,为后续工作的开展奠定了基础。此次研究,首次利用我国自主研发的远紫外气辉遥感探测载荷进行数据反演和分析,这对我国电离层远紫外遥感探测技术的发展具有重要意义。     

Vortex shedding from a circular cylinder with a slit and concave rear surface

Vortex shedding from short circular cylinders with a slit was studied using a flow visualization and amplitude spectrum analysis of a thermoanemometry probe signal. It was found that a circular cylinder with a slit and concave rear surface produces stronger vortices than other bluff cylinders but that these vortices are very vulnerable to the end wall conditions. It was established that two small splitter plates (tails) fixed directly behind the cylinder at the end walls effectively isolate the vortices shed from the cylinder from the end wall boundary layer effects. For this arrangement a perfect regularity of vortex shedding and almost constant Strouhal number were achieved in the Reynolds number test range of about 250 to 43,000.On a leave from Technical University, 60965 Poznan, Piotrowo 3, Poland.     

Re-examined principles of thrust generation by a track on soft ground

Dr. Bekker’s first book Theory of land locomotion offers in fact two different concepts of thrust generation on soft ground with respect to the slip: (a) as the push of grousers causing horizontal soil “distortion” and (b) as the shear force in the failure plane linked with the shear deformation. Bekker preferred the second concept and backed it up by the unique shear-ring measuring technique. To clear up the matter, the author decided to re-examine the thrust generation by a track plate experimentally in field conditions. The tests have shown that the initial stage of thrust generation in compressible ground is always horizontal soil compression by grousers, which divides the soil under a track into separate blocks initially at rest. This compression increases at least to the transition point, when a block is sheared off simultaneously at the bottom and in both lateral planes and starts sliding along the channel formed by the preceding grouser. The analysis of these measurements enabled to define the compressive displacement of the face of the soil block (travel of the grouser) appurtenant to the mentioned transition point, useful to define the thrust–slip curve. The case may also be described by the conventional shear stress–shear displacement relationship, imagined to take place in the bottom failure plane, however, namely the “shear displacement” is rather an unusual quantity.     

核探测器中混合气配制新方法

以质量流敏感器件和系统控制器为主要部件,建立起一套新的混合气配制系统,其配比误差小于满量程的1%,动态响应时间小于3s,有很好的长期稳定性,能满足核探测器对混合气体的多种需要.     

超高压下冲击波速度直接测量技术

针对超高压下透明材料的高压离化机理,分析了透明材料中冲击波直接诊断技术的基本方法. 利用Drude-自由电子气模型,分析了不同冲击压力下冲击波阵面反射率的变化. 从理论上比较了不同探针光波长反射率的区别,发现探针光波长为660 nm时比探针光波长为532 nm时获得的冲击波阵面反射率要高. 对探测器"致盲"问题也进行了研究. 通过分析反射信号的时间顺序和强度大小,发现"致盲"效应是由X光对透明窗口离化引起的. 同时,发现方波驱动脉冲平台的前沿到达时刻和X光离化效应出现的时刻相同,冲击波信号到达时刻晚于X光离化时刻. 通过实验结果,得到蓝宝石中冲击波速度为35 km/s时,其波阵面的反射率约为40%. 通过理论分析和实验数据比对的方法,验证了蓝宝石中的减速曲线. 给出了加蓝宝石窗口后的测速公式. 经过和实验对比,确认了测速公式的正确性. 关键词： 冲击波 光学诊断 成像 干涉仪     

脉冲加热-热导法测定高锌铝合金中氢含量

对含锌铝合金中氢分析的取样量、取样方法和加热释氢功率等方面进行了探索性试验,建立了脉冲加热-热导法测定铝合金中氢含量的测定方法.经过条件试验和对比试验,确定了最佳取样量为2.0～4.0 g,表面氢加热功率为850～900W,体积氢加热功率为1250～1350 W.试样9次重复测定结果的相对标准偏差小于6%.用该法对标准...     

Development of filter radiometer based high accurate calibration facility for solar UV meters

A reference filter radiometer based measurement system was established in the laboratory to calibrate solar UV radiometers. Filter radiometer was constructed from three-element silicon photodiode based reflection type trap detector, band-pass filters and precision aperture in a temperature-controlled enclosure. Spectral responsivity of trap detector was determined as traceable to the cryogenic radiometer and electrically calibrated pyroelectric detector. Relative uncertainties in the filter radiometer's responsivities at six wavelengths between 291 nm and 434 nm were calculated. In order to engage this radiometer in various types of implementations, filter(s) having previously known spectral transmittance was used in the radiometer housing. Calibration of solar UV meters can be achived accurately by using the developed system.     

基于PIV测量的超声波流量计内流场特性研究

采用PIV(Particle Image Velocimetry)测量手段,考察了小口径超声波流量计的流动特性。首先针对前端安装直管段时,不同流量条件下的流场特性建立基本认识,实验结果表明,在低流量条件下,流量计内流场存在明显的不稳定演变和非定常流动特征。进一步以上游前端安装球阀为典型案例,考察了安装条件对超声波流量计响应特性和测量偏差的影响。结合直管段的实验观测结果,发现此种结构超声波流量计的适应性与其流场非定常性的关系具有很好的一致性,即流场结构稳定则适应性强。此外,综合多参数的实验结果表明,雷诺数是判断小口径超声波流量计测量准确性的重要无量纲参数。