Rocking vibrations of a rigid embedded foundation in a poroelastic half‐space     

X. Q. Hu  Y. Q. Cai  G. Y. Ding  J. Wang 《国际地质力学数值与分析法杂志》2010,34(13):1409-1430

This paper presents an analysis of the rocking vibrations of a rigid cylindrical foundation embedded in poroelastic soil. The foundation is subjected to time‐harmonic rocking excitation and is perfectly bonded to the surrounding soil. The soil underlying the foundation base is represented by a homogeneous poroelastic half‐space, whereas the soil along the side of the foundation is modeled as an independent poroelastic stratum composed of a series of infinitesimally thin layers. The behavior of the soil is governed by Biot's poroelastodynamic theory. The contact surface between the foundation base and the poroelastic soil is assumed to be smooth and either fully permeable or impermeable. The dynamic interaction problem is solved by employing a simplified analytical method. Some numerical results for the nondimensional rocking dynamic impedance and nondimensional angular displacement amplitude of the foundation are presented to show the effect of nondimensional frequency of excitation, poroelastic material parameters, hydraulic boundary condition, depth ratio and mass ratio of the foundation. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

利用HLA的分布式虚拟森林环境构建     

唐丽玉  陈崇成  林定 《武汉大学学报(信息科学版)》2010,(3)

以分布式虚拟森林灭火环境为例,基于HLA/RTI协议,设计和初步实现了地形、树木、林火、灭火工具联邦成员组成的分布式森林灭火仿真系统虚拟场景的三维动态生成与显示。系统将仿真的底层通讯和上层的模型控制框架、三维图形绘制分离开来,形成各个独立的模块,具有扩展性和重用性。  相似文献   

AN IMPROVED LAND-SURFACE PROCESS MODEL AND ITS SIMULATION EXPERIMENT——PART I:LAND-SURFACE PROCESS MODEL AND ITS“OFF-LINE”TESTS AND PERFORMANCE ANALYSES     

张晶  丁一汇 《Acta Meteorologica Sinica》1999,(3)

Based on the existing land-surface schemes and models,an improved Land-surface ProcessModel(LPM-ZD)has been developed.It has the following major characteristics:(1)Thecombination of physical equations and empirical analytical formulae are used to construct thegoverning equations of soil temperature and moisture.Higher resolution of model level andphysical equations are adopted for the upper soil layers,and for the lower soil layers,lowerresolution of model level is adopted and empirical analytical formulae are used.(2)In land surfacehydrological process,the sub-grid distribution of rainfall and its effects are taken into account.(3)A simple snow cover submodel has been used,which includes effects of snow cover on soilthermodynamics and hydrology,as well as albedo.By use of this model and three groups of point observation data,a series of“off-line”testshave been carried out.The simulation results indicate that land-surface process model has goodperformance and can well simulate diurnal and seasonal variation of land surface processes for manykinds of land surface covers(forest,grass,crops and desert)in different climate zone.The resultssimulated by the model are consistent with the observations.Later,by use of one group ofobservation data and the model,a series of sensitivity experiments have been done.It is shownthat the model is much sensitive to some parameters,such as initial soil moisture,vegetationphysical parameters as well as the proportion of the grid covered with rain.Therefore it is muchimportant for land-surface process model to define these parameters as accurately as possible.  相似文献   

Low-velocity structure beneath Africa from forward modeling   总被引：1，自引：0，他引：1  

Sidao Ni  Xiaoming Ding  Donald V Helmberger  Michael Gurnis 《Earth and Planetary Science Letters》1999,170(4):21-507

Seismic waveforms observed in South Africa containing the first arrival crossover of S to SKS (70° to 110°) are analyzed. The data consist of analog records from the World Wide Seismographic Station Network (WWSSN) of deep events beneath South America. The S-waves arrive 2 to 3 s early relative to PREM at ranges from 70° to 95° and then become increasingly delayed, becoming 5 to 6 s late at 110°. The SKS phase is late by 3 to 5 s over the entire range. This pushes crossover between S and SKS, normally observed at about 81°, out about 2° to 3°, which is the most anomalous shift ever reported. To model such features, we modified Grand's tomography model [Grand et al., GSA Today 7 (1997) 1–7], and generated 2D synthetics to match the data. The overall shape and position of the lower mantle low-velocity anomaly proposed by Grand predicts good results if lower mantle anomalies are enhanced to a level of about 4%. This results in a complex tabular structure extending upward from the core–mantle boundary about 1500 km into the mantle. These features appear to be consistent with a large young plume which is erupting off the CMB.  相似文献   

Snowdrift effect on snow deposition: Insights from a comparison of a snow pit profile and meteorological observations in east Antarctica     

MingHu Ding  Tong Zhang  CunDe Xiao  ChuanJin Li  Bo Jin  LinGen Bian  ShuJie Wang  DongQi Zhang  DaHe Qin 《中国科学:地球科学(英文版)》2017,60(4):672-685

A high-frequency and precise ultrasonic sounder was used to monitor precipitated/deposited and drift snow events over a 3-year period(17 January 2005 to 4 January 2008) at the Eagle automatic weather station site,inland Antarctica.Ion species and oxygen isotope ratios were also generated from a snow pit below the sensor.These accumulation and snowdrift events were used to examine the synchronism with seasonal variations of δ~(18)O and ion species,providing an opportunity to assess the snowdrift effect in typical Antarctic inland conditions.There were up to 1-year differences for this 3-year-long snow pit between the traditional dating method and ultrasonic records.This difference implies that in areas with low accumulation or high wind,the snowdrift effect can induce abnormal disturbances on snow deposition.The snowdrift effect should be seriously taken into account for high-resolution dating of ice cores and estimation of surface mass balance,especially when the morphology of most Antarctic inland areas is similar to that of the Eagle site.  相似文献   

Processes of initial collision and suturing between India and Asia   总被引：6，自引：0，他引：6  

Lin Ding  Satybaev Maksatbek  FuLong Cai  HouQi Wang  PeiPing Song  WeiQiang Ji  Qiang Xu  LiYun Zhang  Qasim Muhammad  Baral Upendra 《中国科学:地球科学(英文版)》2017,60(4):635-651

The initial collision between Indian and Asian continents marked the starting point for transformation of land-sea thermal contrast, uplift of the Tibet-Himalaya orogen, and climate change in Asia. In this paper, we review the published literatures from the past 30 years in order to draw consensus on the processes of initial collision and suturing that took place between the Indian and Asian plates. Following a comparison of the different methods that have been used to constrain the initial timing of collision, we propose that the tectono-sedimentary response in the peripheral foreland basin provides the most sensitive index of this event, and that paleomagnetism presents independent evidence as an alternative, reliable, and quantitative research method. In contrast to previous studies that have suggested collision between India and Asia started in Pakistan between ca. 55 Ma and 50 Ma and progressively closed eastwards, more recent researches have indicated that this major event first occurred in the center of the Yarlung Tsangpo suture zone (YTSZ) between ca. 65 Ma and 63 Ma and then spreading both eastwards and westwards. While continental collision is a complicated process, including the processes of deformation, sedimentation, metamorphism, and magmatism, different researchers have tended to define the nature of this event based on their own understanding, an intuitive bias that has meant that its initial timing has remained controversial for decades. Here, we recommend the use of reconstructions of each geological event within the orogenic evolution sequence as this will allow interpretation of collision timing on the basis of multidisciplinary methods.  相似文献   

地磁绝对子夜均值年变化量空间分布特征     

孙贵成  胡秀娟  丁成  李文军  孙澎涛  张玉林  相传芳 《地震地磁观测与研究》2017,38(5):62-65

选用中国21个地磁基准台站2011年的绝对子夜均值数据,分析D、H、Z分量年变化量空间分布特征。结果显示,各分量年变化量等值线分布比较均匀,其中:D分量年变化量等值线大致沿南北向分布,零经线附近台站年变化量较小;H分量年变化量等值线大致呈U型分布,且中心点位于甘肃省;Z分量年变化量等值线沿纬线方向,随纬度减小而增大。  相似文献   

Aerosol properties over an urban site in central East China derived from ground sun-photometer measurements     

Qi Liu  WeiDong Ding  Lei Xie  JinQiang Zhang  Jun Zhu  XiangAo Xia  DongYang Liu  RenMin Yuan  YunFei Fu 《中国科学:地球科学(英文版)》2017,60(2):297-314

Sun-photometer measurements at Hefei, an urban site located in central East China, were examined to investigate the variations of aerosol loading and optical properties. It is found that aerosol optical thickness (AOT) keeps higher in winter/spring and gets relatively lower in summer/autumn. The large AOT in winter is caused by anthropogenic sulfate/nitrate aerosols, while in spring dust particles elevate the background aerosol loading and the excessive fine-mode particles eventually lead to severe pollution. There is a dramatic decline of AOT during summer, with monthly averaged AOT reaching the maximum in June and soon the minimum in August. Meanwhile, aerosol size decreases consistently and single scattering albedo (SSA) reaches its minimum in July. During summertime large-sized particles play a key role to change the air from clean to mild-pollution situation, while the presence of massive small-sized particles makes the air being even more polluted. These complicated summer patterns are possibly related to the three key processes that are active in the high temperature/humidity environment concentrating on sulfate/nitrate aerosols, i.e., gas-to-particle transformation, hygroscopic growth, and wet scavenging. Regardless of season, the increase of SSA with increasing AOT occurs across the visible and near-infrared bands, suggesting the dominant negative/cooling effect with the elevated aerosol loading. The SSA spectra under varying AOT monotonically decrease with wavelength. The relatively large slope arises in summer, reinforcing the dominance of sulfate/nitrate aerosols that induce severe pollution in summer season around this city.  相似文献   

COVID-19疫情期间全球空气质量变化:臭氧响应的区域间差异          下载免费PDF全文

Rong Tang  Xin Huang  Derong Zhou  Haikun Wang  Jiawei Xu  Aijun Ding 《大气和海洋科学快报》2021,14(4):45-51

疫情期间全球各地一次排放大幅削减,而臭氧等二次污染的响应则存在着区域间差异.结合地面和卫星观测发现,同在氮氧化物大幅下降的情况下,臭氧在东亚和欧洲呈现出可达14ppb的上升信号,而北美则下降为主(约2-4ppb).我们结合气象分析和臭氧敏感性进一步讨论了臭氧响应差异性的原因,一方面受臭氧与前体物间关系的影响;另一方面来自于气象,尤其是温度.研究明晰了人为排放,化学和气象三者的内在关联,强调了在臭氧控制过程中考虑前体物削减和气象条件协同的重要性.  相似文献   

黄海、东海夏季温、盐度逆转结构分布及其成因的初步分析     

丁宗信 《海洋科学集刊》1994,(35):11-21

在我国,关于黄海、东海温、盐度逆转结构的分析研究,主要是在80年代以后开始的。翁学传等(1984)、曹欣中等(1982)和丁宗信(1983)对东海某一特定海域的温、盐度逆转结构进行过分析,但是对整个黄海、东海海区来说,有关这方面的研究尚未见报道。 本文根据1983-1986年中国科学院海洋研究所在黄海、东海每年夏季调查的CTD观测资料,同时参考1963年以来国家海洋局调查的标准断面资料,对黄海、东海夏季(6-8月)温、盐度逆转結构的分布及其成因进行初步的分析研究。 根据资料和兰淑芳等(1985)的分析,北黄海很少出现温、盐度逆转结构的类型,虽偶有出现,但分布也不规律,因此本文把研究海区重点放在南黄海和东海(图1)。  相似文献