一种有效光强校准装置中闪光灯稳定性的修正方法

脉冲光源在航空、军事、警示等领域均有重要应用,有效光强是表征脉冲光源光度特性的基本评价参数,有效光强测试仪是测量脉冲光源有效光强的仪器。使用闪光灯对有效光强测试仪进行校准时,由于闪光灯自身的稳定性,会带来较大的误差。在我们建立的有效光强标准装置中,引入监视探测器来监测闪光灯有效光强的变化,可以大幅改善闪光灯自身稳定性对校准结果的影响。     

光纤出射光强分布研究

对多模光纤出射光束的光强分布用横向位移法进行了理论分析和实验研究,并用数值计算的方法分析实验测量数据.结果表明,高斯光束可以很好地描述光纤出射光强的分布,光纤出射光束光强分布参数主要与光纤芯径和出纤光功率等有关,为强度调制型光纤传感器的优化研制提供了必要的实验依据.     

闪光光源有效光强标准测量装置研究与建立

建立了可溯源到国家照度工作标准的有效光强标准装置,该装置由闪光光源、中性滤光片、光度探测器、波形采集和处理单元组成,可定标相关测量仪器。分析了氙灯闪光灯和测试LED闪光灯,LED闪光灯具有上升沿陡峭、稳定性好等优点,可进一步优化作为有效光强标准灯。对影响实验的因素进行了分析,结果表明整套装置测量有效光强的不确定度水平达到2.4%(k=2)。     

激光光强分布测量中面阵CCD信号畸变的校正

当面阵ＣＣＤ用于激光能量空间分布测量时，由于ＣＣＤ探测器光电响应非线性、光电响应非均匀性等因素影响，必然使信号产生畸变。本文通过理论分析与实验对畸变进行了校正，收到了良好的效果。     

发光二极管光强的测量

本文研究了发光二极管光强的测量，分析了测试距离和二种不同定标方式对精度的影响，建立了光强测试仪，精度为７．３％     

闪光对焊技术研究现状及发展趋势

详细介绍了闪光对焊工艺和设备的研究及其应用现状,探讨了闪光对焊的机理,并分析了闪光焊接过程产生的主要缺陷,讨论了其预防措施.最后着重介绍了闪光对焊技术的发展趋势.     

轿车水性金属闪光涂料的研究开发

轿车涂装趋势表明,金属闪光涂料涂装将逐渐成为汽车面漆的主流。出于环境保护目的,低污染化的水性金属闪光涂料则将逐渐直到全部取代溶剂型金属闪光涂料,成为主流产品。 我院从1996年起率先在国内进行轿车水性金属闪光涂料的研究开发,到目前为止已取得了实质性进展。1 取得的成果 (1)技术的突破 通过合成核-亮型分散聚合物,获得了所用颜料在基料中的良好取向,开发内交联微凝胶技术,解决了两涂一烘工艺抗清漆     

矩阵剂量仪半导体探测器性能测试技术研究

针对加速器不适宜在实验室使用且发出的射线会伤害人体等问题,为方便考察仪器性能,采用标准光源模拟加速器照射的方法,对矩阵剂量仪半导体探测器进行性能测试。经过刻度之后,矩阵剂量仪能够完成在加速器照射下的实际测量。实验结果表明:采用标准光源模拟加速器照射矩阵剂量仪,对半导体探测器进行性能测试的技术是可行的。     

机外照明灯具夜视(NIVS)辐射强度测试技术研究

参照国内外对夜视(NIVS)兼容机外照明灯具的辐射强度设计要求标准,比较了有关夜视(NIVS)兼容机外照明灯具辐射强度的测量原理及方法.提出了使用带余弦修正器快速光谱辐射计测试系统,基于标准灯方法对快速光谱辐射计进行NVIS A类和B类的辐射强度定标校准,从而实现夜视(NIVS)兼容机外照明灯具辐射强度的准确测试.结果表明:带余弦修正器快速光谱辐射计测试系统在机外照明灯具的辐射强度测试方面具有较为广阔的应用前景.     

Two measurement techniques for determining effective stress intensity factors

Two methods were studied for determining crack closure and locking effects under combinations of mixed mode I and II loading, namely the strain gauge and the surface replica methods. They demonstrated that strain gauges are able to detect the mode I crack closure but not mode II crack locking. As an alternative, the surface replica method is suggested as a practical technique for measuring mode II crack locking effects. The effective mode II stress intensity factor range can be estimated by comparison of the actual measured sliding range between a pair of crack faces and the theoretical sliding range.     

Introducing the compliance ratio concept for determining effective stress intensity

Local crack tip strain measurements show that the conventional determination of ΔK effective may be misleading, especially when opening loads are relatively high as is often the case in the near-threshold regime. The conventional method assumes that K-opening can be directly related to a deviation in the linearity of a load vs crack mouth displacement curve (‘compliance offset method'). Although this deviation in linearity can be attributed to closure, local strain measurements show that significant crack tip strain can occur below the K-opening load. The redistribution of stresses associated with a partially open crack and the effect of this redistribution on the stress field in front of the crack cannot be determined simply on the basis of a change in the slope of the load–displacement curve. However, a recent addition to ASTM E-647 (Recommended Practice for Determination of Fatigue Crack Opening Load from Compliance) implies that it can. An alternative ‘compliance ratio' technique based on local crack tip strain is presented. A modification of this technique allowing the use of remote compliance measurements to account for crack tip strain below the opening load is suggested.     

An effective method of stress intensity factor calculation for cracks emanating from a triangular or square hole under biaxial loads

This paper is concerned with stress intensity factors for cracks emanating from a triangular or square hole under biaxial loads by means of a new boundary element method. The boundary element method consists of the constant displacement discontinuity element presented by Crouch and Starfied and the crack‐tip displacement discontinuity elements proposed by the author. In the boundary element implementation, the left or the right crack‐tip displacement discontinuity element is placed locally at the corresponding left or right crack tip on top of the constant displacement discontinuity elements that cover the entire crack surface and the other boundaries. The method is called a Hybrid Displacement Discontinuity Method (HDDM). Numerical examples are included to show that the method is very efficient and accurate for calculating stress intensity factors for plane elastic crack problems. In addition, the present numerical results can reveal the effect of the biaxial loads on stress intensity factors.     

Modelling of catastrophic flashing releases

Several low boiling point materials are stored in closed vessels at ambient temperature, using their own vapour pressure to maintain a liquid state. These materials are often toxic, flammable, or both, and thus any uncontrolled release can have potentially disastrous consequences. There are many ways in which an accidental release can occur, the most severe being due to catastrophic vessel failure. Although not the most common, this mode of failure has the potential to result in an instantaneous loss of the entire vessel inventory in the form of a rapidly expanding, two-phase, vaporising cloud. This paper provides a comprehensive review of the physical processes of existing models and of available experimental and incident data to model such scenarios. Subsequently, this has enabled the development of an improved methodology for the characterisation of the source conditions following catastrophic vessel failures.     

房间内早期反射声方向分布的声强法测量

早期反射声的方向分布,对空间感音质参量的评价具有重要意义。室内音质不仅与反射声到达的时间、能量有关,而且与反射声到达的方向特性具有密切的关系,反映反射声方向特性的客观音质参量在音质评价中得到了越来越多的应用。根据声强测量的互谱法原理,论文提出采用不在同一平面上的任意四只传声器进行瞬时声强的测量,经合成得到各频带早期反射声方向分布特性的方法。该测量方法弱化了常规传声器阵列测试方法中对传输器位置的严格要求,同时也可有效降低由于传输器之间的相位不匹配带来的测量误差,因而更适合于现场测量。运用该测量方法,在消声中对单入射声条件下的入射方向进行了实验测量验证,表明其具有较高的准确性,同时对一实际房间中早期反射声的方向分布进行了测量,给出了直角坐标系中三个相互垂直平面上的反射声能量与入射方向的分布图。测量结果表明该测试方法可应用于实际房间中早期反射声方向分布的测量。