薄膜生长工艺对TiO_2基紫外探测器光电性能的影响

分别采用磁控溅射和溶胶-凝胶工艺制备了相同厚度的TiO2薄膜,并用以制备了金属-半导体-金属(MSM)结构TiO2基紫外探测器。通过紫外光电性能测试、扫描电子显微镜(SEM)观察及X射线衍射(XRD)分析,研究了TiO2薄膜生长工艺对探测器光电性能的影响规律。结果表明:磁控溅射工艺下,探测器的光电流虽然较低,但响应时间和暗电流远小于溶胶-凝胶工艺制备的探测器,其具备了高辐射灵敏度和快速响应特性。磁控溅射工艺制备的TiO2薄膜结构较为致密,晶界和缺陷较少,方阻较高,这是其取得优良的光电特性的原因。     

Sequential ensemble optimization based on general surrogate model prediction variance and its application on engine acceleration schedule design

The Efficient Global Optimization (EGO) algorithm has been widely used in the numerical design optimization of engineering systems. However, the need for an uncertainty estimator limits the selection of a surrogate model. In this paper, a Sequential Ensemble Optimization (SEO) algorithm based on the ensemble model is proposed. In the proposed algorithm, there is no limitation on the selection of an individual surrogate model. Specifically, the SEO is built based on the EGO by extending the EGO algorithm so that it can be used in combination with the ensemble model. Also, a new uncertainty estimator for any surrogate model named the General Uncertainty Estimator (GUE) is proposed. The performance of the proposed SEO algorithm is verified by the simulations using ten well-known mathematical functions with varying dimensions. The results show that the proposed SEO algorithm performs better than the traditional EGO algorithm in terms of both the final optimization results and the convergence rate. Further, the proposed algorithm is applied to the global optimization control for turbo-fan engine acceleration schedule design.     

间断探测器在间断Galerkin方法中的应用

在二维非结构网格上,对高阶间断Galerkin方法求解定常二维欧拉方程进行数值研究。为了很好地抑制解在流场间断附近处产生的伪振荡,采用了间断探测器和限制器相结合的方法,并分别对Krivodonova间断探测器和基于激波物理特征的激波探测器进行了比较和研究。数值结果表明：如果流场中只存在激波时,两者探测效果相似,且后者更适合应用于求解激波问题。如果流场更加复杂,即存在多种间断时,前者依然可以比较准确地用来探测间断单元,能够很好抑制流场间断附近处产生的伪振荡,而后者失效。     

Photon counting detector for space debris laser tracking and lunar laser ranging

We are reporting on a design, construction and performance of solid state photon counting detector package which has been designed for laser tracking of space debris. The detector has been optimized for top photon detection efficiency and detection delay stability. The active area of the commercially available avalanche photodiode manufactured on Si (SAP500 supplied by Laser Components, Inc.) is circular with a diameter of 500 μm. The newly designed control circuit enables to operate the detection sensor at a broad range of biases 5–50 V above its breakdown voltage of 125 V. This permits to select a right trade-off between photon detection efficiency, timing resolution and dark count rate. The photon detection efficiency exceeds 70% at the wavelength of 532 nm. This is the highest photon detection efficiency ever reported for such a device. The timing properties of the detector have been investigated in detail. The timing resolution is better than 80 ps r.m.s, the detection delay is stable within units of picoseconds over several hours of operation. The detection delay stability in a sense of time deviation of 800 fs has been achieved. The temperature change of the detection delay is 0.5 ps/K. The detector has been tested as an echo signal detector in laser tracking of space debris at the satellite laser station in Graz, Austria. Its application in lunar laser ranging is under consideration by several laser stations.     

基于人工神经网络的红外探测效果评估

红外探测设备是红外系统中的重要组成部分,对其性能评估具有实际意义。分析研究了影响红外探测效果的主要因素,选取环境温度、相对湿度、能见度、辐通量、目标高度和探测距离为评价指标。针对神经网络良好的非线性映射功能及高精度的特点,构建了BP网络评估模型,实验表明,该方法简单有效,评估精度较高,具有很强的实际应用价值。     

恒压式气体微流量计的测控系统研制

恒压式气体微流量计的测控系统是在工控机控制下 ,采用电容薄膜规、光电编码器、铂电阻温度计等高精度传感器测量出变容室内气体的压力、体积变化率、温度等参量 ;采用两种恒压控制模式 ,在流量测量的动态过程中将变容室内气体的压力波动控制在± 0 0 1%之内 ;工作软件具有虚拟仪器界面 ,操作方便 ,实现了对流量计的计算机自动化控制和管理。恒压式气体微流量计能够提供 (3 96× 10 -4～ 3 6 4× 10 -8)Pa·m3 /s范围内的气体微流量。在 10 -8Pa·m3 /s范围内的相对合成标准不确定度为 1% ,在 (1× 10 -7～ 1× 10 -4)Pa·m3 /s范围内的相对合成标准不确定度为 0 7%。     

多介质气体微小流量标准装置设计探讨

介绍了气体流量计量发展的特点及需求,提出建立一套多介质气体微小流量标准装置。结合实际装置指标需求,比较分析了常用气体流量标准原理特点,确定采用了PVTt法原理,根据设计指标需求及原理提出了多介质气体微小流量装置整体初步设计方案,并进行了测量不确定度分析。     

基于定点旋转的遥操作前端视觉自标定

为解决遥操作过程中当前端视觉内参数改变时的标定问题,特别是在一些危险的或是人无法到达的环境下,在前端放置标定物用传统的方法进行标定是不可能的,因此采用了一种基于定点旋转的自标定技术来进行标定.对基于定点旋转的自标定方法进行了理论推导,得到了标定步骤.在试验过程中,摄像机固定在一种旋转装置上进行拍摄,采用SIFT(Scale Invariant Feature Transformation)算法对拍摄的图像进行特征点检测和匹配,采用牛顿算法进行计算.为和传统的标定方法进行比较,对自制的平面模板进行拍摄,利用Harris算子对平面模板图像进行角点检测,用传统的标定方法重新对摄像机进行标定.结果表明两种方法得到的答案相近,用传统标定方法标定结果是接近摄像机真实参数值的,说明这种新的标定方法是一种有效的标定方法.      

热工艺对Ti3Al基合金力学性能和焊接性影响

研究了不同热工艺(锻造、热轧和固溶处理)条件下Ti-24Al-15Nb-1Mo合金显微结构和力学性能特点,比较了它们钨极氩弧焊的焊接性。结果表明,热加工工艺对母材显微结构和力学性能影响显著,固溶温度影响相对较小;锻制的母材具有较低的冷裂纹敏感性和较高的接头力学性能;降低接头拘束度、控制接头焊后冷却速度和焊后及时热处理是防止裂纹的有效工艺措施。     

Assessment of converting approach to efficient design of micro-turboprop engines

The design, manufacture and experiment of a shaft power unit for converting a micro-turbojet engine to a micro-turboprop in the class of less than 20 kW with the aim of obtaining maximum shaft power were described in this study. For this purpose, a Wren100 micro-turbojet engine was used as the gas generator, and the specifications of its outflow were measured. The optimal configuration of the inter-stage diffuser, which was an annular S-type diffuser, was selected based on its small total pressure drop and outlet flow uniformity. The power turbine was a single stage axial turbine that was designed based on the fixed nozzle angle assumption without any taper or twist in its stator. The turbine rotor was a bladed disk (Blisk) in which its unique blade profiles were designed based on the Wilson method. Subsequently, the shaft power unit was completed by designing and manufacturing an exhaust complex and gearbox. Finally, the micro-turboprop engine was tested with an overloading propeller. The results show a significant increase in the extracted power, an acceptable efficiency of the power turbine, and a significant reduction in the Specific Fuel Consumption (SFC) compared to other engines that use similar gas generators.