Application of model of mixture of probabilistic distributions for definition of the signals of radiophysical probing

The article describes a model representation of radar probing data in form of a mixture of background and target samples, which is the sum of two random variables with very different parameters. For model development we research the behavior of the central moments of the distribution mix without assuming the distribution law form. An example it is described the detection of the signal at the output of compression system of chirp ionosonde.     

Interpretation of responses of visual cells of limulus

Assuming that visual responses are due to the action of particles on the membrane of the visual cells, the stochastic variability of the response should be a function of the number of particles producing it. Quantitative predictions can be made with the aid of a model proposed in previous articles. It is found that responses produced in visual cells of Limulus by absorption of a single photon have the stochastic properties which would be expected if the response to one photon were brought about by 25 particles. It is concluded from this that the processes leading to visual responses produce multiplication of particles. The effects of temperature and of metabolic poisons suggest that these processes are of chemical nature.     

非同相口径场瞬态辐射的计算

利用电磁脉冲的口径瞬态辐射场计算公式,针对圆形口径的线性相移、平方律相移等非同相口径场情况,计算了辐射高斯脉冲时的能量方向图、半能量波瓣宽度、面积利用系数等参数.计算表明,对于圆形口径非同相口径场,最大辐射场的方向为口径面法线方向,同时能量方向图关于口径面法线方向对称;随着口径的增大,波瓣变窄,无副瓣;随着平方律相移的滞后参数的增加,波瓣变宽,主瓣不分裂.     

自聚焦透镜的长度对斐索干涉仪面形测量的影响

讨论了自聚焦透镜的长度对自聚焦透镜斐索干涉仪面形测量的影响 ,给出了面形干涉图中相邻干涉条纹半径的平方差随自聚焦透镜长度和面形曲率半径变化的三维曲线、待测面 R→∞时的二维曲线以及自聚焦透镜的长度对面形测量范围的影响 ,并用平面作待测面给出实验值 ,验证了实验与理论的一致性     

近红外光谱技术在水果品质无损检测中应用的研究与现状

简单概述了我国水果产业的发展现状,着重阐述了国内外利用近红外光谱技术进行水果品质无损检测的最新研究进展,分析了当今研究中存在的问题,并对利用近红外光谱技术进行水果检测的前景进行了展望,提出了一些建议。     

影响镀镍层内应力的因素及排除方法

对影响镍镀层内应力的因素做了介绍和分析,提出了对收缩应力的一种解释,提供了排除这些因素影响的方法,指出重视镀液的管理是减少各种影响内应力因素的主要办法。     

杂质吸收对光子晶体滤波器设计的影响

为了研究杂质的吸收对光子晶体滤波器设计的影响,引入复折射率并利用特征矩阵法,计算了滤波透射峰的峰值和半峰全宽。滤波透射峰的峰值随杂质的消光系数增加而迅速减小,滤波通道透射峰的半峰全宽随消光系数增加而增大,滤波透射峰的峰值和半峰全宽都随吸收杂质的光学厚度的增加而减小。结果表明,设计光子晶体滤波器时,必须考虑杂质吸收这一重要因素,应选择消光系数小于0.002的掺杂材料,并且杂质的光学厚度应设计在2(λ0/4)左右。     

“计算机组成原理”设计性实践教学模式研究

本文阐述了"计算机组成原理"设计性实验教学的重要性,对设计性实验教学的目的和基本特征进行了归纳,对"计算机组成原理"设计性实验教学的现状进行了调查,对存在的问题进行了较深入的分析;在此基础上.对组成原理设计性实验的教学模式进行了研究,对设计性实验的体系进行了初步设计,并对"计算机组成原理"设计性实验的实施方法进行了探讨.     

Tail of the distribution of sums of log-normal variates

It is shown that the asymptotic behavior of the tail of the sum distribution of a finite number of individually log-normal distributed variates displays the log-normal character of those variates with maximum logarithmic variance. A quantitative definition of the sum-distribution "tail" is established in terms of upper bounds on the relative error or deviation from the asymptotic log-normal property.     

Differential method of analysis of luminescence spectra of semiconductors

A method for analyzing the luminescence spectra of semiconductors is suggested. The method is based on differentiation of the spectra. The potentialities of the method are demonstrated for luminescence in the region of the fundamental absorption edge of Si and SiGe alloy single crystals. The method is superior in accuracy to previously known luminescence methods of determining the band gap of indirect-gap semiconductors and practically insensitive to different conditions of outputting radiation from the sample.     

Computer simulation of the processes of formation of microclusters on the basis of scaling invariance of random walk

On the basis of scaling invariance of the process of random walk, a discrete three-dimensional algorithm is developed and implemented for computer simulation of the multistage processes of formation of porous clusters in a crystal matrix. A software package is worked out that provides the simulation of dynamic processes of clustering deep in the crystals with allowance for surface processes, applied external fields, and chemical reactions accompanying the processes of clustering. The morphological pattern of pores formed by the simulation is correlated with the behavior of the current-voltage characteristic of anodizing.     

压电双晶片动态机电耦合特性分析

基于压电双晶片本构方程，采用机电耦合系数的一种新的“更为合理的定义方法，分析了动态情况下悬臂梁式双晶片执行器或换能器的机电耦合特性，仿真了分析了机电耦合特性与器件材料，几何尺寸以及信号频率之间的关系，结果表明，机电耦合系数随双晶片几何尺寸及信号频率起伏变化，起伏幅度随信号频率的增大而减小，随双晶片长度厚度比的增大而减小。     

星载差分吸收光谱仪转动部件测试系统设计

基于星载差分吸收光谱仪转动部件控制需求,设计了星载光谱仪转动部件的测试系统。采用微动开关复位加定步的电机运动方式实现电机的精确定位。采用脉冲调制（PWM）的方式实现驱动电流的精细调节。并搭建平台对系统进行重复性测试,实验结果表明,测试系统具有较高的可靠性和稳定性,能够满足光谱仪的精确定位要求,使电机在工作寿命内按计划完成定标工作。     

北斗三号卫星伪距测量误差特征分析

随着卫星导航系统广播星历和钟差参数的精度提升,下行导航信号伪距测量误差对于用户定位授时精度的提升益发显著。由于独特的卫星星座和系统体制,北斗二号卫星伪距测量与仰角呈现线性相关的变化特征,且幅度显著于 GPS 卫星,是北斗二号服务性能提升的关键瓶颈。 随着北斗三号系统的建设,空间星座逐步以 MEO 卫星为主。本文利用 iGMAS 公开数据全面评估北斗卫星下行伪距测量的多路径误差特征,结果表明,北斗三号卫星伪距多路径误差随仰角变化的趋势已得到明显改善,峰峰值为±1m,分布较为随机,与 GPS 卫星特征类似。     

基于数字电视整体平移的遥控器的选择之我见

从红外遥控器的分类出发,介绍了“固定编码＋学习型”遥控器的结构、部件的选择,以及功能按键的选择、排列,然后从其技术规格及技术测试方面介绍了其选择的一些重点项目,最后,就弥补学习型遥控器的网络遥控器的应用作了简单分析。     

基于“实践问题”的“电子电路基础”翻转课堂建设

以提高学生能力为主线的翻转课堂,对促进我国的课程教学改革向纵深的方向发展有非常积极的作用,但同时翻转课堂也对教师和学生提出了更高的要求。本文以电子电路基础课程为例,展示了理论和实践结合类课程的翻转课堂的设计思路和教学案例,为翻转课堂的内容建设提供了一种思路。实施效果表明,基于实践内容研讨的翻转课堂激发了学生的学习兴趣,提高了翻转课堂中学生的参与积极性,提升了学生发现、分析和解决问题的能力,起到了良好的教学效果。     

Two sources of excitation of photoluminescence of porous silicon

The change occurring in the photoluminescence spectra and the photoluminescence excitation spectra during aging of porous-silicon samples in air and in vacuum has been investigated. It was found that the character of the photoluminescence changes occurring during aging depends on the wavelength of the exciting light: In the case of excitation in the visible-range band of the luminescence excitation spectrum (λ_exc>490 nm) the photoluminescence decreases and in the case of excitation in the ultraviolet band it predominantly increases. It is shown that the two bands of the luminescence excitation spectrum (visible and ultraviolet) correspond to two different objects on the surface of the porous layer. Fiz. Tekh. Poluprovodn. 31, 908–911 (August 1997)     

Solvability of problems of excitation of plane-layered metamaterial media

It is shown that the problem of excitation of a magnetodielectric layer with parameters ? and μ equal to minus unity by a point source is not always solvable. Conditions under which the problem has a solution are established. It is found that, in the vicinity of the singular point ? = μ = ?1, determination of the field is an illposed problem: Small variations in these parameters result in large changes of the field.     

一种提高白光LED相关色温分布均匀性的方法

提出一种新的白光LED荧光粉涂敷方式,将荧光粉与硅胶混合体涂敷在白光LED封装用透镜内侧,将透镜倒置后使荧光粉与硅胶混合体由透镜内侧中心点向四周流散,固化得到厚度相对比较均匀的荧光粉层,然后再用硅胶灌封。根据这种新的荧光粉涂敷方式制成白光LED样品,对样品性能进行测试,并与传统的荧光粉涂敷方式的白光LED比较,结果表明,采用新的荧光粉涂层技术制成的白光LED,在相关色温均匀性和稳定性等方面都有明显的提高。