海洋测绘与海战地理环境信息保障   总被引：3，自引：0，他引：3  

梁开龙 《测绘工程》2001,10(1):11-13

简要介绍了海洋测绘研究的内容及其特点，重点分析了几项主要的海洋测绘技术与海军作战地理环境建设的关系，说明了海洋测绘工作在未来高科技海战中的重要地位。  相似文献   

Lessons Learned from the Tragedy during the 100 km Ultramarathon Race in Baiyin,Gansu Province on 22 May 2021     

Qinghong ZHANG  Chan-Pang NG  Kan DAI  Jun XU  Jian TANG  Juanzhen SUN  Mu MU 《大气科学进展》2021,38(11):1803-1810

Twenty-one runners died of hypothermia during the 100 km Ultramarathon Mountain race in Baiyin, Gansu Province on 22 May 2021. The hypothermia was caused by a combination of low temperatures, precipitation, and high winds associated with a typical large-scale cold front passing by the race site that morning. Based on historical hourly records of13 meteorological surface stations over the past six years, temperature(3.0°C) and apparent temperature(-5.1°C) at 1200 LST as well as gust wind speed(11.2 m s-1) at 1100 LST on the day of the tragedy were found to be within the top or bottom 5 th percentile for the month of May. The precipitation was only moderate at this time, but when temperature lower than 3.0°C,gust wind speed greater than 11.2 m s-1, and precipitation greater than 0.1 mm for any adjacent three hours were combined together, 1200 LST 22 May fell within the top 0.1% of cases. The European Centre for Medium-range Weather Forecasting model produced reasonably good forecasts of the low temperature and high wind one day and seven days before the event,respectfully. Based on this study, lessons that can be learned from this tragedy are summarized from an academic perspective: Hazard and impact forecasts of high-impact weather events should be developed to increase the value of weather forecasts. Probability forecasts should be issued by government weather agencies and communicated well to the public. And more importantly, knowledge of how to evaluate the impact of weather should be delivered to the public in the future.We would like to extend our deepest condolences to the families and loved ones of the people who lost their lives in this tragedy, including 21 runners and one officer. May our efforts honor those who lost their lives by highlighting the value of weather forecasting and calling for greater action in the future.  相似文献   

Dynamic response of a group of flexible foundations to incident seismic waves   总被引：1，自引：0，他引：1  

L.G. Tham  J. Qian  Y.K. Cheung 《Soil Dynamics and Earthquake Engineering》1998,17(2):127-137

The dynamic response of a finite number of flexible surface foundations subjected to harmonic incident Rayleigh or SH waves is presented. The foundations are assumed to be resting on an elastic half-space. The results show that the foundation stiffness has a marked effect on the vertical response, while there is only a minor effect on the horizontal displacements. In general, the dynamic response decreases with increasing foundation stiffness. In cases of Rayleigh wave incidence, the existence of an adjacent foundation generates a certain amount of horizontal response in the direction perpendicular to the incident wave and subsequently causes the system to undergo a torsional motion; while in cases of horizontally incident SH waves, a vertical response has been observed and its magnitude is comparable to the response in the direction of the incident wave.  相似文献   

胶东晚中生代金矿成矿的硫同位素组成及热动力源   总被引：5，自引：1，他引：5  

邢树文  孙景贵  李东旭  刘洪文  陈军强 《吉林大学学报(地球科学版)》2003,33(2):141-146

胶东地区晚中生代金矿床均有一个与岛弧玄武质、安山质岩浆相一致的δ^34(6．5‰-7.0‰)硫源，而全铜矿床的δ^34为4．5‰-5．0‰，与岛弧玄武质岩浆的δ^34接近。可初步认为该区全(铜)成矿流体的热源来自地慢或俯冲地慢楔产生的玄武岩浆。成矿流体的产生与岛弧玄武质岩浆底侵／内侵作用密切相关，形成于被加热的地壳。  相似文献   

Stresses and excess pore pressure induced in saturated poroelastic halfspace by moving line load   总被引：2，自引：0，他引：2  

B. Jin  Z. Q. Yue  L. G. Tham 《Soil Dynamics and Earthquake Engineering》2004,24(1):25-33

This paper examines stresses and excess pore fluid pressure that are induced in a saturated poroelastic soil of halfspace extent by a concentrated line load. The line load is moving at a constant velocity along the surface of the poroelastic halfspace. The governing equations for the proposed analysis are based on the Biot's theory of dynamics in saturated poroelastic soils. The governing partial differential equations are solved using Fourier transforms. The solutions for the stresses and excess pore pressure are expressed in the forms of inverse Fourier transforms. The numerical results are obtained by performing the numerical inversion of the transform integrals. A parametric study is presented to illustrate the influences of the velocity of moving load and the poroelastic material parameters on the stresses and excess pore pressure. At a high velocity, the maximum values of the stresses in a poroelastic halfspace are smaller than those in an elastic solid, whilst at a low velocity the stresses in a poroelastic halfspace are larger than those in an elastic halfspace. The potential of diffusivity has an important influence on the stresses and excess pore pressure.  相似文献   

Large Eddy Simulation for Plunge Breaker and Sediment Suspension   总被引：1，自引：1，他引：1  

BAI  Yuchuan 《中国海洋工程》2002,16(2):151-164

Breaking waves are a powerful agent for generating turbulence that plays an important role in many fluid dynamical processes, particularly in the mixing of materials. Breaking waves can dislodge sediment and throw it into suspension, which will then be carried by wave-induced steady current and tidal flow. In order to investigate sediment suspension by breaking waves, a numerical model based on large-eddy-simulation (LES) is developed. This numerical model can be used to simulate wave breaking and sediment suspension. The model consists of a free-surface model using the surface marker method combined with a two-dimensional model that solves the flow equations. The turbulence and the turbulent diffusion are described by a large-eddy-simulation (LES) method where the large turbulence features are simulated by solving the flow equations, and a subgrid model represents the small-scale turbulence that is not resolved by the flow model. A dynamic eddy viscosity subgrid scale stress model has been used for the  相似文献   

Mud-Wave Interaction： A Viscoelastic Model     

张雪岩  吴朝安 《中国海洋工程》2006,20(1):15-26

1 .IntroductionThe interaction between waves propagating onthe surface of a body of water andthe bed materialis a long standing coastal problem.The problemis practicallyimportant because the waves can be at-tenuated at a muchfaster rate whenthe bed materi…  相似文献   

离心试验中的地下水模拟控制研究   总被引：1，自引：0，他引：1  

张敏  吴宏伟 《岩土力学》2010,31(2):355-360

为了通过离心模型试验研究地下水位变化对边坡稳定性的影响,设计和使用了一套地下水模拟控制系统。这套系统包括了供水系统以及水位控制系统。通过设置孔压传感器,反馈水位信息以及旋转中电磁阀的开合,可以控制地下水位的上升与下降。由于离心机旋转的特性,孔压的测定以及传感器位置确定存在一定误差,研究了这些误差对试验结果的影响。通过一个地下水上升的砂土边坡离心模型试验,成功应用了该套地下水模拟控制系统。  相似文献   

澳门土壤剪切波速的相关性分析     

陆万海  李熙烨  吴玉棠 《华南地震》2014,(3):6-11

土壤的剪切波速(VS),是抗震设计的一个重要参数,但有关澳门土层的相关资料则十分稀少。研究的主要目的是根据近期野外测试的结果,探讨澳门土层的VS与标准贯入试验的打击锤数(N)的关系,并以简单之幂函数建立VS与N值的关系式。作为澳门轻轨交通系统之勘察计划,研究进行了五组下孔法(DH),地震波圆锥触探试验(S-CPT)以及标准贯入试验(SPT)的测试。根据试验结果所得的关系式估算剪切波速高于较澳门轻轨设计大纲的建议值,而使用另一有关澳门土层的数据库来验证新的关系式,亦可获得合理的决定系数。  相似文献   

地下水位循环变化时隧道开挖对群桩的长期影响研究     

马少坤  邵羽  吕虎  WONG K S  吴宏伟  陈欣  江杰 《岩土力学》2016,37(6):1563-1568

为解决地下水位随季节升降变化时隧道开挖对邻近桩基的长期影响难题,通过三维离心模型试验,研究了地下水位循环变化时隧道对群桩的长期影响。主要分析水位循环变化时地表长期沉降、桩顶长期附加沉降、桩身长期附加弯矩和附加轴力的变化规律。试验结果表明：在隧道附近,地下水位循环变化尤其是降水对地表长期沉降影响更为明显。地表长期附加沉降随着地下水位循环次数增加而增大,且呈衰减式变形,即使经过3次水位升降循环也不能稳定;桩基长期附加沉降显著,其附加沉降量占总沉降量的50%以上;前、后桩的长期附加轴力基本为正值,桩总轴力增加,对既有受压桩极为不利,附加轴力拐点位置及最大值有所区别;经过3次地下水位循环变化后,前、后桩桩身弯矩反弯点个数减少,但桩身最大附加弯矩均明显变大,当达到极限弯矩,桩身出现塑性铰,这对穿越厚软弱层地基中的既有受压柔性桩极为危险。  相似文献