大载流高速滑动电接触表面瞬态温度分析

高速滑动过程中接触表面瞬态高温会改变接触表面环境,烧蚀接触表面,加重摩擦磨损.本文针对大载流下高速滑动电接触表面瞬态温度场进行测量与分析研究,结合传热学和有限元基本理论,对接触表面瞬态温度场进行热分析,建立温度场计算模型,研究了不同热源对接触表面温度场的影响.利用高速滑动电接触试验机,采用非接触式辐射测温方法,对大载流高速滑动电接触瞬态温度进行测量,并将实际测量数据与有限元模拟结果相结合,验证了仿真模型的正确性,进一步分析了滑动速度及电流载荷的变化对接触表面温度场的影响.本文对大载流高速滑动电接触表面温度场的研究结果,为如何降低接触表面温度、选择合适接触材料以及减小损耗等提供了技术依据.     

抑制宽带双激励换能器发射响应起伏的电学方法

针对双激励宽带换能器发射响应起伏较大的问题,本文提出了在前后压电陶瓷堆分别串联电阻来降低换能器工作频带内的发射电压响应起伏,拓展换能器工作频带的方法.推导了双激励换能器的等效电路,计算了在前后压电陶瓷堆分别串联不同电阻时换能器发射电压响应起伏随频率的变化关系,并通过有限元数值仿真证明,在前后压电陶瓷堆上串联合适的电阻,可以有效降低换能器发射电压响应在工作频带内的起伏.最后制作了工作频带在14~34 kHz的双激励超声换能器,测试了该换能器在串联不同电阻时的发射电压响应随频率的变化关系.实验测试结果表明在前后压电陶瓷堆串联电阻,可以有效地降低换能器的发射响应起伏,换能器在14~34 kHz的工作频带内发射电压响应的起伏由原来的12 dB降低到7.3 dB,换能器工作频带内的发射响应起伏得到明显的改善.研究结果对双激励宽带换能器的设计具有一定的意义.     

压电陶瓷变压器的研究进展

压电陶瓷变压器是一种新型固态电子器件，具有高转换效率、高能量密度、结构简单、体积小、无电磁噪声的特点，在电子产品微型化的过程中起到了十分重要的作用。本文回顾了压电陶瓷变压器的发展历史，阐述了压电陶瓷变压器的基本工作原理，介绍了压电陶瓷变压器所用的新型压电材料、振动模式和几何结构、外围电路三大方面的最新研究进展。通过对比国内外在压电变压器领域的研究和应用现状，指出了我国发展压电变压器的优势和前景，并提出了压电变压器产业的发展方向。     

基于有限元方法的圆简直线感应电机变化气隙场瞬态特性分析

本文将电机的三维场问题转化为二维场问题，运用有限元法对圆筒直线感应电动机的二维电磁场进行了数值计算。在此理论分析的基础上，采用电磁场分析的专用软件AnsoflMaxwell2D对样机的瞬态特性进行仿真分析，得到电机运行过程中某一时刻的磁感应强度分布、磁力线、电流密度及气隙磁密等曲线；并在加额定电压条件下，研究了不同气隙下电机磁场及力特性的变化，将分析结果用来指导直线感应电机的理论研究以及本体和其控制系统的设计。     

超声疲劳振动体的有限元计算及动态模态分析

从超声疲劳载荷的主要特征出发，通过三维有限元计算及动态模态分析，研究了超声疲劳载荷下包括整体裂纹扩展试件及聚能器在内的振动体的应力、应变场和位移分布；分别讨论了超声疲劳载荷（Ｒ＝－１）和超声疲劳载荷叠加平均应力（Ｒ〉－１）两种情况下振动体固有振动模态的变化规律，为便于理解，简要综述了超声疲劳试验机的工作原理以及应用超声疲劳试验技术研究工程结构材料疲劳裂纹扩展性能的方法。     

大兴矿采区巷道热害分析及其模拟

基于煤矿深井高温的原因，结合实际的勘查和测定来分析大兴矿采区巷道热害的主要热量来源，并给出各个热源放热量的具体计算方法。运用CFD软件对采区巷道的温度场进行模拟。     

光滑粒子流体动力学（SPH）中摩擦接触的模拟

光滑粒子流体动力学（SPH）无网格法是岩土体崩塌与流动大变形计算的有力工具，但是，如何在SPH框架内模拟摩擦接触现象尚无系统方法，迫切需要开展研究．提出一种在SPH框架内模拟土与刚性或柔性结构摩擦接触的算法，该算法根据所存在的接触边界，将计算域分解为若干个子域，以接触力为桥梁在各子域间建立联系，最终实现接触问题的整体求解．在各子域内对土体的运动控制方程进行SPH离散时，修正了SPH固有的边界缺陷，使得位于接触边界附近的SPH粒子具有准确的加速度，保证了接触探测的精度．然后，假设允许土体SPH粒子局部侵入结构体，根据允许的残余侵入量，运用动量原理，计算沿接触面法向和切向的接触力，并应用滑移条件对切向力进行修正使其不超过极限摩擦力．与现有的在SPH中处理接触通常采用“粒子．粒子”接触或忽略摩擦滑移的方法相比，方法具有更高的计算效率和精度，适用于岩土材料与刚性或可变形结构之间相互作用的模拟．通过多个算例对此方法的精度和稳定性进行了验证，计算表明，基于接触算法的SPH计算成果与理论解或有限元解吻合很好，算法是有效的，可用于拓展SPH的计算能力与应用范围．     

螺母型超声电机驱动的集成透镜调焦系统

介绍一款螺母型超声电机驱动的集成光学调焦模组系统. 该系统用光学镜头(M6或M7)作为转子, 粘有压电元件的多面体铜管作为定子, 成像传感器安放在定子轴的底部. 驱动芯片(IC)控制电机运行. AF模组尺寸是8.5 mm×8.5 mm×5.9 mm. 转子的外螺纹与定子的内螺纹相互啮合. 当驱动IC激励定子上的压电片时, 在定子中激励出沿圆周传播的面内弯曲行波. 图像质量由多次成像的清晰度反馈到驱动IC, 再由驱动IC对镜头位置进行控制, 从而实现AF功能. 工作时功耗小于0.25 W, 静止时功耗为0. 调焦精度<10 mm, 运动速度>3 r/s, 响应时间<10 ms. 该系统模组还具有耐冲击和抗跌落, 机构简单没有附加传动机构等特点. 在试验样机中已经获得3~5 MP的图像分辨率.     

燃料电池气、水、热平衡分析及综合管理系统设计

建立了质子交换膜燃料电池系统的气、水和热平衡计算模型，总结了电堆气、水和热管理相关物理量的计算方法；以60kW电堆为例计算分析，认为气、水、热管理三者有着密切的联系，应建立综合管理的概念；设计了气、水、热综合管理系统，该系统充分回收利用了电堆的尾气、电化学反应生成的水和电堆产生的热量。     

一种实际不可逆循环系统的等价热力变换分析法

提出一种等价热力变换分析法，它根据有效能消耗总伴随着热量输运过程的物理事实，定义了各子过程和循环的等效热力温度，把实际不可逆循环的热力／热泵循环系统等价变换为简单的正／逆卡诺循环系统进行分析，导出的等效高温热源温度计算式奠定了等价热力变换分析法的基础；提出采用玮．h图和TR—q图作为热力／热泵系统性能分析和有效能消耗分析的工具图，可直观表示热力系统中多种物质的热量、功量交换和焓的变化，易于计算出系统性能系数和各项有效能消耗；以热泵热水器和R22工质为例，系统介绍了等价热力变换分析法，示范性给出了等价热力变换分析法中关键参数的拟合式，展示了该分析法在变工况性能模拟和推算应用中的优势和良好前景．     

The effects on thermoregulation of intracerebroventricular injections of L-aspartic acid in the sheep

Summary L-Aspartic acid was injected into a lateral cerebral ventricle of the sheep at ambient temperatures between 0° and 40°C. Doses of 100 or 500 nmoles·kg^–1 caused a rise in heat production and/or a decrease in heat loss; rectal temperature rose. Atropine sulphate attenuated or prevented these effects.     

Newton's Contribution to the Science of Heat

The contents of Scala Graduum Caloris are described, supplemented by unpublished material. Both temperature measurements by his linseed oil thermometer and those based upon his law of cooling are shown to be reasonably accurate to 300°C, but above that value they are much too low. The apparent agreement and the deviation are explained by the differences between the assumptions that Newton made in deriving his law of cooling and the conditions in which he used it. Newton's attempts to link terrestrial and celestial science in applications in the Principia are shown to fail from his confounding the concepts of temperature, heat and radiant intensity and his ignorance of most factors affecting the temperature rise of irradiated materials. Other comments on varied aspects of heat, mainly published in the Queries, are set out and analysed. His originality is assessed.     

Thermoregulatory effects on the sheep of intracerebroventricular injections of L-glutamic acid

L-glutamic acid injected in doses of 200--1000 n moles . kg-1 into the cerebral ventricles of sheep had dose-dependent thermoregulatory effects: an increase in heat production and/or a decrease in respiratory frequency, and a rise in rectal temperature. A dose of 800 nmoles . kg-1 had effects comparable with those of a similar injection of 3 nmoles . kg-1 carbamylcholine.     

利用 CFD技术对管壳式换热器壳程结构的模拟分析

以某公司所制造的水源热泵为基础,针对制冷量 Q0=180kW 的蒸发器的内部结构,利用 CFD技术对其壳程侧做了流场与热场的模拟分析,得到了具有一定价值的分析结果:1)原设计中不仅单弓形折流板的数量较多而且折流板较厚,占用了一定有效换热面积,势必影响了壳程水侧的换热效果和造成了较大压降;2)由于进水管侧的水温与制冷剂的蒸发温度之间存在较大的温差,会在管板上产生较大的热应力,有造成管板与换热管的接触破坏的可能;3)通过对原设计的速度矢量分析,可以较为清楚地看到,原设计存在较多的流动死区,这些流动死区,会影响水侧换热.根据这些分析结果,提出了相应地解决方案,并建立了改进后的蒸发器模型     

The effect of global warming on mortality

There is a significant relationship between ambient temperature and mortality. In healthy individuals with no underlying co-morbid conditions, there is an efficient heat regulation system which enables the body to effectively handle thermal stress. However, in vulnerable groups, especially in elderly over the age of 65 years, infants and individuals with co-morbid cardiovascular and/or respiratory conditions, there is a deficiency in thermoregulation. When temperatures exceed a certain limit, being cold winter spells or heat waves, there is an increase in the number of deaths. In particular, it has been shown that at temperatures above 27 °C, the daily mortality rate increases more rapidly per degree rise compared to when it drops below 27 °C.This is especially of relevance with the current emergency of global warming. Besides the direct effect of temperature rises on human health, global warming will have a negative impact on primary producers and livestock, leading to malnutrition, which will in turn lead to a myriad of health related issues. This is further exacerbated by environmental pollution.Public health measures that countries should follow should include not only health-related information strategies aiming to reduce the exposure to heat for vulnerable individuals and the community, but improved urban planning and reduction in energy consumption, among many others. This will reduce the carbon footprint and help avert global warming, thus reducing mortality.     

Variation de la chaleur spécifique du caoutchouc en fonction de l'élongation

Summary The variation of the specific heat with extension was determined for several samples of rubber. Non-vulcanized rubber shows no change of the specific heat when extended between 0 and 300%. For vulcanized rubber, there is a very slight increase of the specific heat, proportional to the extension. For some samples a knee in the curve appears at about 200% (at room temperature), the linear increase of specific heat being about ten times higher for higher extensions. It is supposed that this sudden increase is related to the «heat of crystallization».     

Thermoregulatory effects on the sheep of intracerebroventricular injections of L-glutamic acid

Summary L-glutamic acid injected in doses of 200–1000 nmoles·kg^–1 into the cerebral ventricles of sheep had dose-dependent thermoregulatory effects: an increase in heat production and/or a decrease in respiratory frequency, and a rise in rectal temperature. A dose of 800 nmoles·kg^–1 had effects comparable with those of a similar injection of 3 nmoles·kg^–1 carbamylcholine.We wish to thank Miss Jill Thexton for invaluable assistance.     

Characteristics of dry friction backward whirl-A self-excited oscillation in rotor-to-stator contact systems

In this paper, the response characteristics of dry friction backward whirl of a general rotor/stator model, which accounts for both the dynamics of the rotor and the stator as well as the friction and the deformation at the contact surfaces, are investigated. The existence boundaries and the whirl frequencies of the dry friction backward whirl are determined analytically. It is found that there are two or three existence boundaries of the dry friction backward whirl that usually form two existence regions, ...     

Dynamic substructure model for multiple impact responses of micro/nano piezoelectric precision drive system

A dynamic substructure technique which considers the electromechanical coupling effect of the PZT and the inertial effect of flexible components is presented to study the multiple impact dynamic behavior of micro/nano piezoelectric impact drive systems.It can investigate the step-like motion of object body and the multiple impacts behaviors reasonably by the comparison of the experimental data and the numerical solution of the spring-mass model.It is expected to have higher accuracy in the numerical simulat...