让舰艇练就护体内功:抗冲击能力——中国舰船史600年和60年的思考

@@ 2009年4月23日,在中国人民海军创立60周年之际,中央军委主席胡锦涛在青岛奥帆中心附近海域检阅了多国海军舰队.阅兵开始,中国海军的导弹驱逐舰、护卫舰、核潜艇跃现海面,举世瞩目,见证了中国"建设一支强大的人民海军"的步伐.

大鲵的水下发声与相关行为(英文)

无尾类两栖动物的复杂的声行为对其繁殖与物种的识别具有重要的作用,而有尾类除了少数种类可以发出 微弱的“吱吱”声或吠声外,在过去一直被认为是基本不发声的。但是,最近的基于解剖学的证据的研究显示隐腮 鲵科(Cryptobranchidae)可能是一个例外。为了检验这一假说,作者对实验室严格控制的条件下的4只中国大鲵(An- drias davidianus)进行了观察。观察结果不仅表明动物在水下发声,同时也观察到了与之相关联的行为。作者对进 一步在野生条件下开展研究提出了建议。

Determination of the interdiffusion coefficients of liquid Zn and Sn using Ta/Zn-Sn/Si trilayers

In this paper we present a new method for measuring diffusion coefficients in liquid metals under convection-less conditions with solid/liquid-liquid/solid trilayer. The advantage of this kind of trilayer is that effects from gravity-induced convection and Marangoni-convection can be omitted, so that the diffusion coefficient is determined more accurately. The Ta/Zn-Sn/Si trilayer were prepared with a multi-target ion-beam sputtering deposition technique and annealed in an electric furnace under an argon atmosphere. The interdiffusion of liquid zinc and tin at 500 degrees degree C was investigated. The diffusion concentration profiles were determined by energy dispersive spectroscopy. The interdiffusion coefficients range from 1.0x10(-6)cm(2)/s to 2.8x10(-6)cm(2)/s, which is less than previous values measured by capillary reservoir technique under 1g-environment where various convection exist. The precise interdiffusion coefficients of liquid zinc and tin result from the removing of disturbances of various kinds of convection.

Electronic and vibrational Raman scattering in resonance with yellow luminescence transitions in GaN on sapphire substrate

We analyze low-temperature Raman and photoluminescence spectra of MBE-grown GaN layers on sapphire. Strong and sharp Raman peaks are observed in the low frequency region. These peaks, which are enhanced by excitation in resonance with yellow luminescence transitions, are attributed to electronic transitions related to shallow donor levels in hexagonal GaN. It is proposed that a low frequency Raman peak at 11.7 meV is caused by a pseudo-local vibration mode related to defects involved in yellow luminescence transitions. The dependence of the photoluminescence spectra on temperature gives additional information about the residual impurities in these GaN layers.

Short and long waves over a muddy seabed

The available experimental results have shown that in time-periodic motion the rheology of fluid mud displays complex viscoelastic behaviour. Based on the measured rheology of fluid mud from two field sites, we study the interaction of water waves and fluid mud by a two-layered model in which the water above is assumed to be inviscid and the mud below is viscoelastic. As the fluid-mud layer in shallow seas is usually much thinner than the water layer above, the sharp contrast of scales enables an approximate analytical theory for the interaction between fluid mud and small-amplitude waves with a narrow frequency band. It is shown that at the leading order and within a short distance of a few wavelengths, wave pressure from above forces mud motion below. Over a Much longer distance, waves are modified by the accumulative dissipation in mud. At the next order, infragravity waves owing to convective inertia (or radiation stresses) are affected indirectly by mud motion through the slow modulation of the short waves. Quantitative predictions are made for mud samples of several concentrations and from two different field sites.

新型轮—腿—履带复合移动机构及稳定性分析

为提高反恐防暴机器人对非结构环境的适应能力,设计出了一种具有良好的机动性能和转向性能的新型轮—腿—履带复合移动机构.通过机器人机构分析与本体的稳定性分析,论证了其结构设计的可行性及好的稳定性.

反恐防暴机器人机构与控制的研究

西方国家早在20世纪60年代就开始采用防暴机器人处理爆炸物。自从9.11事件后，国际社会恐怖活动更是愈演愈烈，许多国家相继对此给予了高度重视。反恐防暴机器人可应用于核工业、军事、燃化、铁路、公安、武警等部门，代替人在危险、恶劣、有害环境中执行探查、排除或销毁爆炸物、消防、抢救人质以及与恐怖分子对抗等任务。本项目依托课题由最初的“危险作业机器人”到现在的“反恐防暴机器人的产业化研究”，由国家“863”计划资金滚动支持。就现有的反恐防暴机器人，存在速度较慢或机动灵活性不强或可靠性不高等不足，现研究出一种新型反恐防暴机器人，目的是在保证适应一定的非结构环境的前提下（适用所有的非结构环境的移动机构设计是不可取的，也是不现实的），提高机器人本体转向性能和移动速度，降低功耗，机构简单化，同时在硬件与软件设计时采取一些相应的措施，提高其在实际应用环境中的可靠性和抗干扰能力。首先，通过对以往反恐防暴机器人在非结构环境中采用的复合移动机构对比分析研究，提出了一种新型的轮-履带-腿复合移动机构，应用在”灵豹”机器人上。它的特色是移动机构继承了“灵蜥”系列反恐防暴机器人轮与履带移动方式自动切换功能，并且针对“灵蜥”系列机器人轮式移动时，四轮滑动转向灵活性不高、功耗大的问题，提出了三轮式移动机构，在狭小移动空间有着广泛的应用。并对该机器人本体做了运动学分析和稳定性分析，论证了该机构的可行性。其次，根据课题项目研究的需要，在控制方面，主要完成了“灵狐”小型反恐防暴机器人的系统构建与功能实现。通过从事“灵蜥”系列机器人项目开发，积累了一些移动机构设计与分析以及控制系统一些问题解决的实际经验，在“灵狐”控制系统设计过程中，由于采用单片机作为微控制单元，因此着重考虑了提高系统可靠性与抗干扰能力。在“灵狐”机器人样机试验中取得了好的效果，均达到预期目标。