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.

Sleeping sites of Rhinopithecus bieti at Mt. Fuhe, Yunnan

Data on sleeping site selection were collected for a group of black-and-white snub-nosed monkeys (Rhinopithecus bieti; around 80) at Mt. Fuhe, Yunnan, China (99degrees20'E, 26degrees25'N, about 3,000 m asl) from November 2000 to January 2002. At the site mainly three vegetation types were present in an elevation-ascending order: deciduous broad leaf forest, mixed coniferous and broad leaf forest, and dark coniferous forest. In addition, bamboo forest presented in areas burned in 1958. Sleeping sites (n = 10) were located in the coniferous forest, where trees were the tallest, bottommost branches were the highest, the diameter of crowns was the second largest, and the gradient of the ground was the steepest. Monkeys usually kept quiet during entering and staying at a sleeping site. The site choice and the quietness may be tactics to avoid potential predators. In the coniferous forest, however, monkeys did not sleep in the valley bottom where trees were the largest, but frequently slept in the middle of the slope towards the east/southeast, in the shadow of ridges in three other directions, to avoid strong wind and to access sunshine; in winter-spring, they ranged in a more southern and lower area than in summer-autumn. These may be behavioral strategies to minimize energy stress in the cold habitat. Monkeys often slept in the same sleeping site on consecutive nights, which reflected a reduced pressure of predation probably due to either the effectiveness of anti-predation through sleeping site selection, or the population decline of predators with increasing human activities in the habitat. The group's behavioral responses to interactive and sometimes conflicting traits of the habitat are site-specific and conform to expectations for a temperate zone primate.

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。

Deceptive female oviposition behaviour elicits male ejaculation in the European bitterling

In European bitterling Rhodeus amarus, fish that lay their eggs in the gill chambers of living freshwater mussels, females perform conspicuous behaviours associated with spawning that increases the probability of males performing ejaculatory behaviour and participating in a spawning. A significant positive association was detected between behaviour in which a female performs a spawning action but without releasing eggs, here termed 'deceptive female oviposition', and ejaculatory behaviour by courting males.

黄土高原植被恢复与建设策略

以中国水土流失与生态安全综合科学考察——西北黄土区考察组获得的资料为依据,对黄土高原地区植被恢复的基础和潜力进行了系统分析,提出了植被恢复的目标和策略。黄土高原天然群落恢复的基本措施是封育,有条件的区域应实施人工促进,使植被自然恢复力与人为促进力相结合;人工植被建设应充分利用乡土树草种,合理利用外来种,采用防护性整地和管理措施,造林种草后引导乡土物种进入群落,进行天然化培育;以流域为治理单元,优化景观斑块空间布局和面积构成,逐步改造具有退化特征的人工群落,使建群种能够自我更新,群落可永续利用;政府部门在政策上要保护现有成果,扩大自然修复比例;保护大户承包治理的积极性,鼓励多元化投资,进行植被建设;扩大黄土区植被建设和科研投资力度,培育黄土区植被恢复方面的科技创新能力。

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.

中国西部退耕还林基本策略研究

21世纪,生态危机成为人类面临的最大威胁,森林作为陆地生态系统的主体,自然成为世人瞩目的集点.由于中国西部水土流失、土地沙化、水资源紧张、生物多样性锐减等问题越来越突出,给人民的生活与国民经济发展造成巨大损失.退耕还林成为中华民族生存与发展的根本大计,这不仅关系到当代人的生存与发展,而且关系到子孙后代的生存与发展.文章在上述背景下,提出了符合中国实际的对策,供决策部门参考.

纸房沟流域生态经济系统演变分析

通过对纸房沟流域土地利用结构和收入结构的简要分析 ,提出了生态系统与经济系统演变的一般规律 ,受生态系统与经济系统演变规律的启示 ,提出了纸房沟流域生态经济系统进一步建设的策略。

基于网络环境的地理信息系统-WebGIS

Web GIS作为一门新兴的技术学科 ,依托互联网的环境和 Internet实用技术 ,成为地理信息系统理论研究和技术创新的增长点。随着网络技术和应用市场的不断发展和扩大 ,将促进 GIS新兴信息产业的形成。本文结合工作实践 ,论述了 Web GIS的技术背景与发展 ,以及系统功能等基础理论 ,重点讨论了 Web GIS的体系结构、实现策略和技术方法

一个用于自治智能移动式机器人导航和监控的实验系统

文中重点讨论了系统实现过程中,任务分解与行走命令下达,时序分配与同步,路标定位与行走误差修正.动态障碍感知,测定与响应和特别情况紧急处理等难题的解决策略及遇到的问题.