微型飞行器的研究进展

本文阐述了微型飞行器的概念、研究背景、发展现状、主要技术和研究途径;介绍了微型飞行器的主要研究机构和典型产品;展望微型飞行器的应用前景和发展趋势

A linear constant current LED driver circuit

随着人们对照明设备节能环保和耐用低价的要求逐步提高,lEd光源的研究与应用也日趋广泛。然而lEd光源并没有得到普遍应用,主要难题是成本高和驱动电路的不稳定。针对此问题,在研究lEd特性的基础上提出了高稳定性和低成本的lEd线性恒流驱动电路,且具有结构简单、效率高、体积小等特点。通过模拟电网的波动,测试了此电路在实际电网中的恒流特性,还测试了此电路的效率和lEd的结温,经实际电路测试,此驱动电路能很好地实现恒流控制,电路效率较高,且lEd的结温较低,使lEd的控制特性得到改善。With increasing demands in energy-saving,durable and low-cost lighting equipments,the research and application on LED light soure is becoming widely spread.However,due to high costs and instability of its driver,LED source light has not been universally applied.Based on studying in LED characteristics,this article designed a linear constant current LED driver circuit of high stability and low-cost and so on.It has the characteristics of simple structure,high efficiency,little size.It is tested that this driver circuit can realize well control of constant current.The efficiency of this circuit is more higher,and the temperature of LED junction is more lower.In short,the LED control characteristic gets improvement

基于Maxwell2D/3D的多线圈磁模型建模与仿真

多线圈变压器可以实现多对多电池间电荷均衡,实现快速、安全、低损耗的电池充放电均衡,是一种智能控制的串联电池组双向均衡方式。根据动力锂电池均衡控制策略的需求,分析了多线圈变压器的等效电路以及磁交叉耦合问题,并通过有限元电磁场分析软件AnSOfTMAXWEll进行了验证,为均衡充电控制系统的设计提供了准确的理论和设计依据

Measurement of temperature, velocity and water vapor concentration in a scramjet combustor based on nearinfrared diode laser absorption

A multi-channel Tunable Diode Laser Absorption Spectroscopy (TDLAS) system was designed and constructed for flow parameters diagnostics in a scramjet combustor. Two fiber coupled distributed feedback (DFB) lasers with narrow line width were used to probe two H2O absorption features (7185.597cm-1,7444.35cm-1+7444.37cm-1(c ombined)) by using direct absorption Time-Division-Multiplexing (TDM) strategy at a 4-kHz repetition rate. Laser light was split into five beams and transmitted across the test region. Two motorized precision translation stages were used to move the collimators during the test, so that the three beams located near the cavity and at the exit of the combustor can scan the cross sections respectively. Flow parameters could be obtained simultaneous which included average temperature, water vapor concentration and velocity at the entrance of the combustor, the distribution of temperature, water vapor concentration at a cross section near the cavity, the distribution of temperature, water vapor concentration and velocity at the exit cross section of the combustor. The parameters of the flow entering and exiting the combustor could be used to evaluate the performance of the direct-connected scramjet facility and the combustion efficiency of the combustor. The parameters at the cross section in the combustor could also be used to analysis combustion characteristics in the combustor

基于DEFORM有限元仿真的弧齿锥齿轮热处理过程残余应力与变形分析

基于传热学基本原理和热弹塑性理论,采用有限元方法,建立了弧齿锥齿轮热处理分析模型,利用DEFORM软件模拟了渗碳淬火工艺对轮齿残余应力分布和变形量的影响,得到了渗碳淬火过程中微观组织、齿面残余应力和轮齿变形随时间的变化规律,并研究了不同淬火温度对轮齿残余应力、变形及抗疲劳性能的影响规律。仿真结果表明,热处理后轮齿齿面形成压应力,芯部形成拉应力,随着淬火温度的升高,残余压应力增大,这有利于改善弧齿锥齿轮的疲劳特性和使用性能,同时轮齿齿面变形量的分析能够为后续的弧齿锥齿轮磨削加工工艺参数的确定提供一定的理论指导

基于残余应力的轮齿齿根强化对弯曲疲劳强度影响研究综述

随着工程技术的不断发展，弯曲疲劳强度成为齿轮进一步发展的重要限制因素，且弯曲疲劳失效相较于齿面失效更具危险性。结合齿轮弯曲疲劳折断机理及裂纹扩展过程，系统阐述了齿根裂纹萌生重要影响因素（包括齿根过渡圆角、磨削台阶及残余应力场等）对齿根弯曲疲劳性能的影响；基于残余应力和表面及亚表面组织可控的齿面强化机理，进一步分析了改善齿轮弯曲疲劳性能的表面强化工艺（包括喷丸强化、齿根磨削工艺等）及其研究进展；着重探讨了齿根磨削对齿轮弯曲疲劳性能的影响。为工程实际中优化齿轮设计及制造、改善齿轮弯曲疲劳性能提供理论依据和技术参考

基于椭圆法的摆线轮齿廓修形

为得到更加理想的摆线轮齿廓线型,提出一种新的摆线轮齿廓修形方法。在保证短幅系数,偏心距不变的情况下,利用椭圆对摆线轮的标准理论轮廓线滚动切割修形,得到修形后的齿面轮廓线,并推导出其方程表达式。与常用的齿廓修形方法相比,修形后的齿廓曲线在主要工作段更加逼近完全共轭齿廓,并且通过控制椭圆的形状参数,可对摆线轮与针齿轮的啮合间隙进行调整,简单灵活。分析该修形齿廓的法向齿廓间隙、初始啮合间隙、接触应力以及回差影响,验证了该修形方法的合理性

利用接收函数与面波频散联合反演峨眉山大火成岩省地壳横波速度结构

峨眉山大火成岩省是指我国西南滇-川-黔地区(即扬子克拉通西缘)出露的大面积大陆溢流玄武岩,其形成被认为与二叠纪末期的古地幔柱事件相关。前人基于沉积地层学、岩石地球化学等系列证据,提出了内带下方的"地幔柱头熔融"成因模型。开展峨眉山大火成岩省地壳精细结构重建,有