Isolation of plane shear wave using water saturated trench barrier     

《Soil Dynamics and Earthquake Engineering》2014

The article presents a theoretical investigation of the propagation of normally and obliquely incident plane shear waves past a rectangular trench filled up with water saturated soil sandwiched between anisotropic elastic media. The motivation for this work is due to the effectiveness of the isolation of waves by the in-filled rectangular trench. Unlike the most of the previous researchers, this model considers the soil–structure interaction effects and directly determines the influence of barrier in the form of in-filled trench on the mode of wave propagation. It is of interest to determine the reflection and transmission coefficients, and the energy partition distribution of shear waves in the in-filled rectangular trench showing the influence of barrier on the propagation of waves. An extensive parametric study through numerical computation is carried out to investigate the influence of the material properties of the in-filled trench and the amplitude ratios on shear waves. The in-filled trench barrier directly declines the intensity of waves significantly in such a way that the waves do not create any hazards to the nearby structures, if exists at all.  相似文献   

青藏高原能量与水循环国际合作研究的进展与展望   总被引：2，自引：0，他引：2  

马耀明  姚檀栋  胡泽勇  王介民 《地球科学进展》2009,24(11)

青藏高原能量与水循环过程对我国、东亚乃至全球的天气和气候系统都有着非常重要的作用.1996年以来,在国家自然科学基金委员会、中国科学院、中国气象局等相关部门和日本政府的大力支持下,我们针对青藏高原能量和水循环过程的重要性,成功地开展了青藏高原尺度和藏北地区中尺度的"全球能量水循环之亚洲季风青藏高原试验研究"(GAME/Tibet)项目和"全球协调加强观测计划之亚澳季风青藏高原试验研究"(CAMP/Tibet)项目近10余年的连续观测,取得了以往高原试验从未有过的大量极其珍贵的综合观测资料.而且在利用试验资料分析、卫星遥感及数值模拟等手段研究青藏高原能量与水循环方面取得大量的阶段性成果.介绍了青藏高原能量与水循环的研究进展及国际合作在项目执行过程中所起到的作用,同时介绍国际合作在吸纳境外研究资源及培养青年科技人才中所起的作用.最后提出了国际合作中存在的问题,并给出了相关的建议.  相似文献   

北大西洋风暴轴高低空分布及其能量诊断     

余霄  黄菲  王鑫  管承扬  张荣望 《气候与环境研究》2017,22(6):658-670

利用1979~2013年NCEP再分析数据,通过经验正交分解对比了前冬时期北大西洋风暴轴的高低空分布,并用涡动动能(Eddy Kinetic Energy,EKE)方程对风暴轴高低空分布型差异进行了诊断。研究结果表明:上层和下层第一空间分布型差异巨大,对流层下层风暴轴中心偏北,靠近极地,而上层风暴轴中心偏西南,靠近北美沿岸。EKE方程诊断结果表明:正压转换项在高低空符号相反,导致了EKE在上、下层分布出现显著差异,即上层正压转换项为负,在扰动发展中起能量耗散作用,而下层正压转换项为正,且极大值区域对应下层EKE极大值区域,为风暴轴下层向极区域增强的主要原因。而斜压转换和非地转位势通量散度在上层均为正,且远大于下层,为风暴轴上层涡动能量维持的原因,也从涡动能量收支上解释了风暴轴的主体出现在上层。  相似文献   

有限差分格式与物理量守恒性          下载免费PDF全文

季仲贞  王斌  杨诗芳 《地球物理学报》2004,47(6):991-996

为了成功地开展大气数值模拟,如何构造相应的离散格式是一项十分重要的工作.本文以大气球面浅水方程为例,从不同形式的微分方程组出发,分别构造了能量守恒格式、准辛格式和多守恒格式,并作相应的数值检验和比较,从中可以清楚地看到三类格式的优劣.这三类格式构造方法不同,所保持的物理守恒性不完全相同,数值计算时所需机时也不同,这些比较结果为实际工作的不同使用需求提供了选择依据.  相似文献   

An Effective Control System of Thrust and Moment Modulation for a Dynamically Positioned Vessel     

Cho-Chung Liang  Tso-Liang Teng  Wen-Hui Cheng 《Marine Geodesy》2013,36(4):211-227

Dynamic positioning (DP) is an operation method whereby the position of a surface vessel is maintained in close proximity to a required position in the horizontal plane through the controlled application of forces and moments generated by purposely installed thrusters. When estimating thrust, this kind of conventional control system often uses many acceleration sensors, velocity sensors, environment sensors, and filters. Usually, these sensors have measured electrical errors. To reduce the number of sensors used and to decrease the measurement errors, this article presents an effective control system for estimating thrust and moment commands, which is based on energy and impulsemomentum principles. Donha and Brinati's example is followed to verify the feasibility of the present control system, which performs semisubmersible platform positioning using an LQG controller, and the results are feasible and economical. A simulated coring vessel marine positioning in southern Taiwan is presented, which can estimate the counterthrust and moment commands, and the complex environmental forces and moments are described. The results can provide a valuable control system for dynamically positioned vessels.  相似文献   

ENSO事件对西北太平洋热带气旋影响的分级研究   总被引：2，自引：0，他引：2  

曹智露  胡邦辉  杨修群  王学忠  何雪松  谭言科 《海洋学报》2013,35(2):21-34

采用1951-2006年联合台风警报中心(JTWC)最佳路径数据集和气候预测中心(CPC) ENSO资料,分析了西北太平洋不同等级热带气旋累积能量(accumulated cyclone energy,ACE)与ENSO指数之间的关系.结果表明;ACE与ENSO指数间存在正相关关系;分级热带气旋中,ENSO事件主要通过超强台风(Super TY)的活动与ACE指数联系起来的,超强台风频数在El Ni(n)o期间多于La Ni(n)a 期间,同时持续时间也更长;ENSO指数和热带气旋活跃季超强台风ACE指数的滞后相关(ENSO指数滞后5个月内)与它们的同时相关大小相当.此外,还研究了分级热带气旋持续时间、强度和频数分别对ACE指数的贡献,结果显示超强台风频数的贡献最大.接下来,利用1951-2006年不同ENSO位相情况下NCEP再分析资料,分析了ENSO影响超强台风发生发展的物理机制.主要结论为:西北太平洋存在一些SuperTY频数与源地分布在ENSO年与平常年相比有明显差异的关键区;ENSO事件改变关键区低层相对涡度以及海表温度是其影响SuperTY源地及频数变化的重要途径.  相似文献   

Evapotranspiration Estimation Based on MODIS Products and Surface Energy Balance Algorithms for Land （SEBAL） Model in Sanjiang Plain, Northeast China   总被引：1，自引：1，他引：0  

DU Jia  SONG Kaishan  WANG Zongming  ZHANG Bai  LIU Dianwei 《中国地理科学(英文版)》2013,23(1):73-91

In this study,the Surface Energy Balance Algorithms for Land(SEBAL) model and Moderate Resolution Imaging Spectroradiometer(MODIS) products from Terra satellite were combined with meteorological data to estimate evapotranspiration(ET) over the Sanjiang Plain,Northeast China.Land cover/land use was classified by using a recursive partitioning and regression tree with MODIS Normalized Difference Vegetation Index(NDVI) time series data,which were reconstructed based on the Savitzky-Golay filtering approach.The MODIS product Quality Assessment Science Data Sets(QA-SDS) was analyzed and all scenes with valid data covering more than 75% of the Sanjiang Plain were selected for the SEBAL modeling.This provided 12 overpasses during 184-day growing season from May 1st to October 31st,2006.Daily ET estimated by the SEBAL model was misestimaed at the range of-11.29% to 27.57% compared with that measured by Eddy Covariance system(10.52% on average).The validation results show that seasonal ET from the SEBAL model is comparable to that from ground observation within 8.86% of deviation.Our results reveal that the time series daily ET of different land cover/use increases from vegetation on-going until June or July and then decreases as vegetation senesced.Seasonal ET is lower in dry farmland(average(Ave):491 mm) and paddy field(Ave:522 mm) and increases in wetlands to more than 586 mm.As expected,higher seasonal ET values are observed for the Xingkai Lake in the southeastern part of the Sanjiang Plain(Ave:823 mm),broadleaf forest(Ave:666 mm) and mixed wood(Ave:622 mm) in the southern/western Sanjiang Plain.The ET estimation with SEBAL using MODIS products can provide decision support for operational water management issues.  相似文献   

节能减排空间信息系统的设计架构     

李涛  范新成 《地理信息世界》2013,(4):91-95

节能减排是遵循人类社会发展的规律,顺应当今世界发展潮流的重大策略。节能减排工作必须依靠先进能源科学管理工具和决策分析工具,掌握各企业在节能减排工作中的基础数据和过程数据,实现对其节能减排工作的过程评价和动态监管。借助GIS强大的数据处理、可视化和空间分析能力,我们构建了节能减排空间信息系统。在对系统关键技术分析的基础上,构建了系统的技术框架,基于WebGIS的节能减排空间信息系统可以应用于很多行业,该系统有助于推进企业加快结构调整,转变发展方式,努力建设和推进资源节约型、环境友好型的企业发展进程。  相似文献   

Modeling the effects of historical vegetation change on near-surface atmosphere in the northern Chihuahuan Desert     

Adriana Beltrn-Przekurat  Roger A. Pielke Sr.  Debra P.C. Peters  Keirith A. Snyder  Albert Rango 《Journal of Arid Environments》2008,72(10):1897-1910

Our goal was to evaluate effects of broad-scale changes in vegetation from grasslands to shrublands over the past 150 years on near-surface atmosphere over the Jornada Experimental Range in the northern Chihuahuan Desert, using a regional climate model. Simulations were conducted using 1858 and 1998 vegetation maps, and data collected in the field. Overall, the vegetation shift led to small changes in sensible heat (SH) and an increase in latent heat (LH). The impacts of shrub encroachment depended on shrubland type: conversion from grass to mesquite cools the near-surface atmosphere and from grass to creosotebush warms it. Higher albedo of mesquite relative to grasses reduced available energy, which was dissipated mainly as LH due to the deeper root system in mesquite. In creosotebush-dominated areas, a decrease in albedo, an increase in roughness length and displacement height contributed to the SH increase and warmer temperatures. Sensitivity simulations showed that an increase in soil moisture content enhanced shrub LH and a reduction in mesquite cover enhanced the temperature differences. The observed shift in vegetation led to complex interactions between land and surface fluxes, demonstrating that vegetation itself is a weather and climate variable as it significantly influences temperature and humidity.  相似文献   

Effect of non-linear soil deformation on the interaction among energy piles     

《Computers and Geotechnics》2017

This study investigates the effect of non-linear soil deformation on the displacement interaction among energy piles. The work is based on interaction factor analyses of full-scale pile group tests, whose results are compared with experimental evidence. The results presented highlight the tendency of interaction factor analyses that ignore non-linear soil deformation to overestimate the interaction and the displacement of energy pile groups. This outcome, in accordance with previous studies for conventional pile groups subjected to mechanical loads, may be considered in the analysis and design of energy pile groups subjected to thermal (and mechanical) loads through the interaction factor method.  相似文献