多功能水声收发机的设计与实现

基于长基线水下航行器定位导航系统的工作原理,设计并实现了一套可独立完成水声询问信号发射、水声遥控指令编码及发射控制、应答信号接收及处理、时延估计及数据传输控制等多功能的水声收发机,论述了水声收发机中信号检测、时延估计等信号处理关键技术,介绍了软、硬件设计思想和实施方案,并给出了该套系统经过模拟器、湖试和海试的试验结果。试验结果表明,该系统性能可靠、功能完善,具有一定的工程应用价值。     

加强车辆装备野战抢救抢修技能训练必须注重解决好四个问题

提高思想认识。抓好训练的全员性。现代高技术条件下局部战争,具有全时空、全天候、突发性强、机动快、高损耗等显著特点。在有限的时空内,如果仅仅依靠车辆修理分队独立完成大量战损装备的抢救抢修任务,难度十分大,有时甚至不可能。各级务必站在为战斗力负责、为确保打赢负责的高度,充分认清车辆装备战场抢救抢修的重要性,把车辆装备战场抢救抢修训练纳入部队军事训练的整体规划,制定阶段目标和长远计划,采取得力措施,确保全员性车辆装备战场抢救抢修训练“四落实”。     

城市轨道交通接触网的防冰害措施

以大连快轨3号线为例,阐述环境状况对轨道交通运营的影响,分析覆冰现象产生的原因,提出解决接触网冰害问题的方法,包括除冰和防冰的各项措施.     

Influences on the spatial directivity of acoustic vector sensor by finite cylinder baffle and future prospects about eliminating the effects

The directivity of acoustic vector sensor can be distorted by the sound diffraction wave of baffle. According to Helmholtz integral equation, the directivity of acoustic vector sensor under the condition of finite cylinder baffle is calculated by using boundary element method (BEM). Considering the problem of nearly singular integrals of BEM, the exponent parts of fundamental solutions are expanded in trigonometric functions. The singular and the nonsingular parts are separated: the nonsingular parts are calculated by Gaussian integral method; the singular parts are regularized by subsection integral method. Then the surface integrals are reduced into line integrals along the elements?? contour which can be calculated by Gaussian integral method. The sound diffraction field of a plane wave under the condition of finite cylinder baffle at different frequencies and incident angles is calculated, and the characteristics of directivity of pressure and vibration velocity at different frequencies are analyzed. The experimental data are treated and the errors between the experimental and theoretical results are analyzed. Finally, according to the research results about the influences on the directivity of acoustic vector sensor by baffle at present, some future prospects about eliminating the effects of sound diffraction field by baffle are presented.