基于大功率LED扩展光源的均匀光斑光辐射模拟器设计

基于边缘光线原理和光学扩展量守恒思想,结合复合抛物面聚光器和轴对称自由曲面透镜,设计并研制了大功率发光二极管扩展光源的反射/折射准直器.运用Tracepro软件对系统进行光束追迹模拟仿真和实验,研制出均匀光斑的光辐射模拟器.模拟器输出发散角为±12°光束,测量距离出射面50cm处光屏的光斑,在尺寸为14cm×14cm的光照范围内,测得光斑水平方向中心线上的光度均匀度优于4.1%,竖直方向中心线上的光度均匀度优于3.8%.     

声源分布和超声频率对清洗声场均匀性的优化*

驻波和换能器指向性等影响声场均匀性，造成清洗死角，影响清洗效果。采用COMSOL仿真软件建立了单个换能器位于底部的三维模型，通过染色法实验结果验证模型的有效性。研究了换能器同时位于底部和侧面、多排换能器位于底部时的声场，用声压幅值相对标准差来量化均匀性，发现该两种换能器分布方式能够有效优化声场均匀性。通过调节频率研究频率对声场的影响，进一步优化声场均匀性。对声源分布的确定、频率的选择以满足声场均匀化需求有指导意义。     

An algorithmic approach to finding factorial designs with generalized minimum aberration

Factorial designs are arguably the most widely used designs in scientific investigations. Generalized minimum aberration (GMA) and uniformity are two important criteria for evaluating both regular and non-regular designs. The generation of GMA designs is a non-trivial problem due to the sequential optimization nature of the criterion. Based on an analytical expression between the generalized wordlength pattern and a uniformity measure, this paper converts the generation of GMA designs to a constrained optimization problem, and provides effective algorithms for solving this particular problem. Moreover, many new designs with GMA or near-GMA are reported, which are also (nearly) optimal under the uniformity measure.     

The asymptotic estimate for the sum of two correlated classes of discounted aggregate claims with heavy tails

Consider a risk model with two correlated classes of insurance business and a constant force of interest. We assume that the correlation comes from a common shock and that the claim-size distribution is heavy-tailed. Under this setting, we investigate the tail behavior of the sum of the two correlated classes of discounted aggregate claims. We obtain the uniform asymptotic formulas for some subclass of subexponential distributions.     

Weakly Pseudocompact Frames

We define the notion of weak pseudocompactness for frames and present several characterizations. Among them are characterizations in terms of strong inclusions, uniformities and cozero bases. Noteworthy is the fact that these internal characterizations are not translated from characterizations of weakly pseudocompact spaces.      

Worst-case distribution analysis of stochastic programs

We show that for even quasi-concave objective functions the worst-case distribution, with respect to a family of unimodal distributions, of a stochastic programming problem is a uniform distribution. This extends the so-called ``Uniformity Principle' of Barmish and Lagoa (1997) where the objective function is the indicator function of a convex symmetric set.     

记录光强变化对光折变晶体多重存储衍射效率均匀性的影响

光折变晶体多重存储中,为获得均匀的衍射效率,要根据记录晶体的时间常数计算相继写入全息图的曝光时间,而晶体的时间常数是记录光强的幂函数.本文分析了光强变化对衍射效率的影响.结果表明,对曝光时间加以适当修正,可补偿光强变化对衍射效率均匀性的影响.     

Sampling and metrology

The result of a measurement refers in principle only to the amount of substance actually contributing to the analytical signal. However, an appropriate definition of the measurand must include a specification of the system for which the result of the measurement should apply. All systems being inherently heterogeneous, representativity assumes importance for the metrological quality of a measurement, and the process needed to ascertain representativity is sampling. The contribution from this characteristic must be included when expressing the uncertainty of the reported value of the measurand. Representative sampling of systems that are infinite or non-uniform was developed by Pierre Gy in his Theory of Sampling. Finite systems can achieve uniformity by mechanical treatment and mixing; the heterogeneity of these systems can be characterized by a sampling constant, expressed in units of weight, for each particular species being determined. Examples of the contribution of sampling to the uncertainty of analytical results are discussed for some biological materials. Presented at the 2nd International Conference on Metrology – Trends and Applications in Calibration and Testing Laboratories, November 4–6, 2003, Eilat, Israel.     

多边形棒状透镜出端辐射均匀性的研究

研究了用多角形棒状透镜产生高均匀性正方形和圆形照明的最佳结构参量.结果表明,对于正方形棒状透镜,输出端的照明均匀性随透镜的长度振荡变化,在某些特定长度达到极小值.对于圆形照明面积,比较了从三角到八角的六种多边形.利用三角形积分透镜可以获得最佳的照明均匀性,但光能利用率相对较低,六角形积分透镜可同时获得较高的照明均匀性和光能利用率.     

1×7 锥形混合棒塑料光纤耦合器

利用光线追迹法进行数值仿真得到了锥形混合棒塑料光纤耦合器的分光比与其长度的关系.数值仿真表明:这种耦合器的分光比随锥形光波导长度增加,在0.143(即均分处)上下呈振荡型变化.选择一均分且分光比变化平缓的区域作为制作光波导的长度,通过拉伸粗的光波导棒成锥形且达到所需的长度,并采用精密的机械连接,制作出了1×7塑料光纤耦合器.测试数据表明:这种塑料光纤耦合器具有很高的均匀性.