各向异性激光晶体的热—光性能

研究了热导率各向异性的激光晶体棒的温度分布和热流方向,得到椭圆的等温线和非径向流动的热量.指出在某个方向上激光棒的横向热导率是各向同性的.用简单的模型分析了YAlO_3激光晶体棒的热双折射现象.对于c轴棒得到正交偏光的干涉条纹是两组双曲线.对于b轴棒是椭圆.理论能满意地解释所观察到的现象.     

椭圆口径天线的一种新的设计方法

利用口径坐标变换，比较了圆口径和椭圆口径天线方向函数的差异，得出了将圆口径分布方向图特性映射到椭圆口径的条件，并将圆口径天线最佳综合方法圆Taylor综合应用于椭圆口径天线的设计。将这一条件应用于椭圆离散阵设计，给出了设计实例，比较了连续圆口径分布与椭圆离散阵的特性，扩展了椭圆阵列的常规设计方法。     

瞬态非傅里叶导热效应判据的探讨

讨论了通用傅里叶导热定律的数学模型,推导了半无限大物体在第一类边界条件下的基于非傅里叶导热定律的双曲线型偏微分方程的解析解。通过分析非傅里叶导热定律在瞬态条件下温度分布的变化过程,提出了非傅里叶导热效应的瞬态判据以及非傅里叶导热的作用范围,对研究工程中瞬态导热问题(如激光处理,电子束处理等)有重要意义。     

瞬态非傅里叶导热效应判据的探讨

讨论了通用傅里叶导热定律的数学模型,推导了半无限大物体在第一类边界条件下的基于非傅里叶导热定律的双曲线型偏微分方程的解析解.通过分析非傅里叶导热定律在瞬态条件下温度分布的变化过程,提出了非傅里叶导热效应的瞬态判据以及非傅里叶导热的作用范围,对研究工程中瞬态导热问题(如激光处理,电子束处理等)有重要意义.     

渐变太赫兹椭圆-双曲线形连接器的理论分析

为了实现太赫兹高斯光束与双曲线形金属波导的高效耦合,设计了一个渐变的椭圆-双曲线形金属波导连接器。此波导连接器的输入端是矩形的,输出端是椭圆-双曲线形的。在渐变的过程中,矩形金属波导的TE01模逐渐转变成双曲线形金属波导的椭圆偏振模。根据WKB近似,这个缓慢渐变的波导消除了反射和散射,TE01模和椭圆偏振模的耦合效率可以高达94%。最终,经过这个渐变连接器,高斯光束和双曲线形金属波导的耦合效率可以提高到69.1%。     

二极管泵浦板条激光介质的二维温度和应力分布

用有限差分法对各种边界条件下二极管侧泵浦板条介质通光截面上的温度和应力二维分布作了数值计算。并对此作了分析,由此提出了适用于不同泵浦水平二极管泵浦板条激光器的冷却方案。     

二极管泵浦板条激光介质的二维温度和应力分布

用有限差分法对各种边界条件下二极管侧泵浦板条介质通光截面上的温度和应力二维分布作了数值计算。并对此作了分析，由此提出了适用于不同泵浦水平二极管泵浦板条激光器的冷却方案。     

反求控制点生成椭圆的方法

针对绘制生成椭圆或圆的目的,采用建立以椭圆或圆中心为直角坐标系原点的坐标系统的方法,将椭圆或圆分成四个曲线段,每段曲线段用有理二次Bezier曲线表示;通过由椭圆参数方程得到每段有理二次Bezier曲线上的三个点Q0、Q1、Q2,再用这三个点反求出有理二次Bezier曲线上三个控制点p0、p1、p2,进而得出绘制生成椭圆或圆的若干个点。经算法测试,与已有的生成椭圆或圆的方法相比,该方法生成的椭圆或圆更光滑,算法更简单。     

Cd_xHg_(1-x)Te铸造的热模拟试验

在制备Cd_xHg_(1-x)Te晶体的铸造—再结晶—退火工艺中,最重要的一步是快速淬火,以便形成细小晶粒的多晶锭,然后进行高温退火促进晶粒生长。在铸造阶段控制热散失是决定最终晶体结构的关键。为了模拟铸造时的热流,作了电模拟,并用计算机分析。模型给出热流、温度分布(等温线)和冷却速率。模拟了石英安瓿对辐射的部分透明性。在强制冷却安瓿底部时,给出了晶体/熔体的热导率、气体的热导率和铸造速率的变化对冷却速率和等温线形状的影响。把从模型中获得的等温线与在铸造锭上看到的枝蔓晶结构作了比较,发现理论和实验很一致。     

基于ABCD定律的LD-SMF高斯光束模式匹配方法的研究

在高斯场分布挖的前提下,根据矩阵光学理论和高斯光束转换的ＡＢＣＤ定律,从模式匹配的角度描述了半导体激光器（ＬＤ）与单模光纤（ＳＭＦ）之间的光耦合理论,提出了实现ＬＤ椭圆高斯光束与ＳＭＦ圆高斯光束间模式匹配的设计方法。这不仅对提高ＬＤ－ＳＭＦ的耦合效率有理论指导意义,而且也为其它场合下解决高斯光束的准直扩速及实现椭圆－圆高斯光转换等问题提供了有效依据。     

Two-dimensional model of heat flow in broad-area laser diode: Discussion of the upper boundary condition

This paper presents a discussion of the upper boundary condition, which should be assumed in calculations of temperature distribution in a laser diode. Using the isothermal condition instead of convection or thermal insulation is proposed. Theoretical results are compared with temperature map obtained by thermoreflectance method. The model is based on the solution of two-dimensional, stationary heat conduction equation obtained by separation-of-variables approach. Full analytical expressions are provided. All considerations deal with p-side down mounted devices.     

高功率掺镱双包层光纤激光器热效应理论研究

针对高功率双包层光纤激光器热效应严重制约着光纤激光器的输出功率和光束质量这一现象,利用热传导方程和边界条件推导出了双包层光纤激光器温度分布的解析解,进而分析了热效应引起的应力分布,温度和应力引起的折射率变化以及热效应引起的光程差。结果表明,在纤芯轴线处切向、法向、轴向应力分别达到负的最小值,而在光纤表面处径向应力为0,法向、轴向达到正的最大值;应力引起的折射率变化与温度引起的折射率变化相比较小;温度变化是热效应引起光程差主要原因,热膨胀和热应力引起的光程差较小。     

Analyses of thermal stresses and control schemes for fasttemperature ramps of batch furnaces [IC manufacture]

This work studies fast temperature ramps of batch furnaces under different control schemes based on thermal and stress analyses. A thermal model is first developed to predict temperature distributions on silicon wafers during ramping processes. Thermoelastic model of stresses is then used to predict the onset of slip-line generation under dynamic conditions. Three control schemes, one based on a maximum allowable within-wafer temperature difference, one with a constant cooling rate, and the third based on the condition for onset of slip generation, are then analyzed. The results show that in order to achieve the highest ramp rates while maintaining defect-free wafer processing, the ultimate criterion for temperature control of the furnaces should be the condition for the onset of defect generation instead of the conventional scheme based on constant ramp rates     

On circularity

Circularity is an assumption that was originally introduced for the definition of the probability distribution function of complex normal vectors. However, this concept can be extended in various ways for nonnormal vectors. The first purpose of the paper is to introduce and compare some possible definitions of circularity. From these definitions, it is also possible to introduce the concept of circular signals and to study whether or not the spectral representation of stationary signals introduces circular components. Therefore, the relationships between circularity and stationarity are analyzed in detail. Finally, the theory of linear mean square estimation for complex signals exhibits some connections with circularity, and it is shown that without this assumption, the estimation theory must be reformulated     

过渡圆角对工字型钢结构温度场影响的仿真

借助Ansys有限元分析软件,对工字型钢结构加热过程进行了有限元模拟,研究了加热过程中的热边界条件,分析了温度场的分布及其变化.对比有无过渡圆角的工字型钢结构,在升温过程的温度分布情况,结果表明它们的温度分布场是不同的.分析结果对于掌握工字型钢结构的加热过程温度变化、分析残余应力具有实际指导意义.     

Health-monitoring method of note PC for cooling performance degradation and load assessment

Health monitoring technologies, which can evaluate the performance degradation, load history and degree of fatigue, have the potential to improve the effective maintenance, the reliability design method and the availability in the improper use conditions of electronic equipment. In this paper, we propose a method to assess the cooling performance degradation and load history of printed circuit boards in electronic equipment by use of a hierarchical Bayes model based on Computer Aided Engineering (CAE) results of thermal-stress simulation and experiment data from observed measurements. We applied this method to note PC that can monitor the device load factor and revolution number of cooling fan. It is shown that this method can estimate the temperature and deformation distribution of the printed circuit board from monitoring variables through latent variables such as thermal dissipation of the device and thermal boundary condition by use of the hierarchical Bayes model. And it is confirmed that the statistical load assessment concerning thermal cyclic load and the maximum load distribution can be conducted using the estimated temperature and deformation data. Furthermore, we verified that the cooling performance degradation can be assessed, if the temperature difference per unit thermal value between two suitable points on the printed circuit board can be obtained. It is concluded that the proposed method can be effective to assess the thermal load history and cooling performance degradation.     

功率变换器肋片散热器的理论分析与优化设计

针对现有散热器模型的不足,建立了恒热流的边界条件下的散热器的数学模型,得到了散热器的温度分布公式。提出了散热器的优化方法,并利用Flux软件对现有功率变换器的散热器在自然空气冷却条件下进行优化。得到了两种优化方案,都在功率器件允许的温度范围内减小散热器的体积和质量,从而充分发挥了散热器的作用。     

Heating Pattern in a Multi-Layered Material Exposed to Microwaves (Short Papers)

The electromagnetic-induced heating pattern in a multiIayered slab material exposed to uniform plane microwaves is studied. A general expression taking into account the multiple reflections at the interfaces is derived for the power dissipated per unit volume in the medium. A numerical method is developed for solving the heat transport equation describing the temperature distribution in this material. A steady, as well as a transient solution is obtained for either a Dirichlet- or a Neumann-type of boundary condition. The effect on the temperature distribution of a cooling fluid circulating inside the slab is considered. The method is applied to the special case of a three-layered material having characteristics similar to those of a biological structure. The possibility of achieving a preferential heating of one of the layers by, means of standing waves created with the aid of a flat reflector is demonstrated.     

Spatial distribution of the gain and temperature across the flow in a slit-nozzle supersonic chemical oxygen-iodine laser with transonic and supersonic schemes of iodine injection

Spatial distributions of the gain and temperature across the flow were studied for transonic and supersonic schemes of the iodine injection in a slit-nozzle supersonic chemical oxygen-iodine laser as a function of the iodine and secondary nitrogen flow rate, jet penetration parameter, and gas pumping rate. The mixing efficiency for supersonic injection of iodine (/spl sim/0.85) is much larger than for transonic injection (/spl sim/0.5), the maximum values of the gain being /spl sim/0.65%/cm for both injection schemes. Measurements of the gain distribution as a function of the iodine molar flow rate nI/sub 2/ were carried out. For transonic injection, the optimal value of nI/sub 2/ at the now centerline is smaller than that at off axis locations. The temperature is distributed homogeneously across the flow, increasing only in the narrow boundary layers near the walls. Opening a leak downstream of the cavity in order to decrease the Mach number results in a much larger mixing efficiency (/spl sim/0.8) than for a closed leak.     

行波管强迫风冷散热设计

本文利用流体仿真软件Fluent对一高功率螺旋线脉冲行波管进行散热器模拟计算,通过分析比较两种散热方案,表明在相同散热条件下,强迫风冷的散热能力明显优于传导冷却的方案;因此在条件许可时尽可能使用强迫风冷设计,利于提高行波管工作可靠性。