206 resultados para D-InSAR

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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针对目前现代黄河三角洲地区普遍存在的地面沉降问题,本文以整个现代黄河三角洲平原地区为研究对象,通过收集的重复性水准测量数据、遥感影像、渤海海底及三角洲平原沉积物物理力学数据、长期验潮站数据以及前人文献数据等资料,综合运用雷达差分干涉测量技术(D-InSAR)、工程地质学、GIS和随机动态分析方法,探讨了现代黄河三角洲地区近期地面沉降的现状,并对其自然因素影响下的形成与发展过程进行了综合分析,最后探讨了地面沉降对三角洲发育演化的环境地质效应。 研究结果表明:现代黄河三角洲在以宁海为顶点的河口扇形区域,近期均经历了不同程度的地表下沉过程,但是随区域地理位置和时间的不同,地表变化空间差异性比较明显;三角洲顶点附近区域的下沉速率自上世纪末开始逐渐减小,后期甚至出现轻微的抬升;滨海沿岸附近地区的地表形变特征相对比较复杂,各期叶瓣相互叠置及其各类沉积物的不均匀分配,使由沉积物自然固结压实引起的地表形变具有显著的空间差异;目前,除清水沟流路叶瓣表现为快速沉降以外,其它滨海沿岸区基本上都表现为微弱的下沉。自然状态下三角洲平原的地面沉降分布主要受中―高压缩性软土层和黏性土层固结沉降的控制,分别占沉积物总固结沉降量的40~95%和3~12%(或30~50%)。三角洲平原区沉积层的自重固结沉降已进入后期缓慢沉降阶段,软弱土层的性质及厚度是控制本区不均匀沉降的主导因素。黄河新近沉积物的自重应力对海底浅层沉积物和前三角洲沉积层的固结压缩影响较大,特别是海底淤泥和淤泥质土层在受压初期会发生快速固结压缩,足以引起明显的地表下沉。近几十年来,因区域构造运动和均衡运动引起的地表绝对下沉速率约为3.42 mm/a。该区地面沉降的时空差异性及其在相对海平面上升中的叠加作用,不仅关系到三角洲的垂向发育过程,且对黄河尾闾的摆动、下游河道的淤积、海岸侵蚀和潮滩冲刷等方面都有着重要的影响。

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采用面一面接触的三维离散元刚性块体模型,从实测节理面中取出其中的三组,按照其倾向、倾角和节理间距将三峡永久船闸未开挖的区域划分为10~5个离散单元,通过施加力边界条件,给出了与实测初始地应力场接近的数值模拟结果;然后,分4步模拟了永久船闸的开挖过程。计算结果表明:开挖过程会引起节理面出现张开趋势,个别岩体还会沿着节理面滑移。岩体位移的不对称现象较为自然地说明了由节理引起的岩体各向异性特征。

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Based on the first-order upwind and second-order central type of finite volume( UFV and CFV) scheme, upwind and central type of perturbation finite volume ( UPFV and CPFV) schemes of the Navier-Stokes equations were developed. In PFV method, the mass fluxes of across the cell faces of the control volume (CV) were expanded into power series of the grid spacing and the coefficients of the power series were determined by means of the conservation equation itself. The UPFV and CPFV scheme respectively uses the same nodes and expressions as those of the normal first-order upwind and second-order central scheme, which is apt to programming. The results of numerical experiments about the flow in a lid-driven cavity and the problem of transport of a scalar quantity in a known velocity field show that compared to the first-order UFV and second-order CFV schemes, upwind PFV scheme is higher accuracy and resolution, especially better robustness. The numerical computation to flow in a lid-driven cavity shows that the under-relaxation factor can be arbitrarily selected ranging from 0.3 to 0. 8 and convergence perform excellent with Reynolds number variation from 102 to 104.

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A two-dimensional (2-D) vortex-induced vibration (VIV) prediction model for high aspect ratio (LID) riser subjected to uniform and sheared flow is studied in this paper. The nonlinear structure equations are considered. The near wake dynamics describing the fluctuating nature of vortex shedding is modeled using classical van der Pol equation. A new approach was applied to calibrate the empirical parameters in the wake oscillator model. Compared the predicted results with the experimental data and computational fluid dynamic (CFD) results. Good agreements are observed. It can be concluded that the present model can be used as simple computational tool in predicting some aspects of VIV of long flexible structures. (C) 2008 Elsevier Ltd. All rights reserved.

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Elastodynamic stress intensity factor histories of an unbounded solid containing a semi-infinite plane crack that propagates at a constant velocity under 3-D time-independent combined mode loading are considered. The fundamental solution, which is the response of point loading, is obtained. Then, stress intensity factor histories of a general loading system are written out in terms of superposition integrals. The methods used here are the Laplace transform methods in conjunction with the Wiener-Hopf technique.

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In the present paper, a multifluid model of two-phase flows with pulverized-coal combustion, based on a continuum-trajectory model with reacting particle phase, is developed and employed to simulate the 3-D turbulent two-phase hows and combustion in a new type of pulverized-coal combustor with one primary-air jet placed along the wall of the combustor. The results show that: (1) this continuum-trajectory model with reacting particle phase can be used in practical engineering to qualitatively predict the flame stability, concentrations of gas species, possibilities of slag formation and soot deposition, etc.; (2) large recirculation zones can be created in the combustor, which is favorable to the ignition and flame stabilization.

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The dynamic stress intensity factor histories for a half plane crack in an otherwise unbounded elastic body are analyzed. The crack is subjected to a traction distribution consisting of two pairs of suddenly-applied shear point loads, at a distance L away from the crack tip. The exact expression for the combined mode stress intensity factors as the function of time and position along the crack edge is obtained. The method of solution is based on the direct application of integral transforms together with the Wiener-Hopf technique and the Cagniard-de Hoop method, which were previously believed to be inappropriate. Some features of solutions are discussed and the results are displayed in several figures.

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This study was designed to comprehensively analyze the differential expression of proteins from human umbilical vein endothelial cells (HUVECs) exposed to tumor conditioned medium (TCM) and to identify the key regulator in the cell cycle progression. The HUVECs were exposed to TCM from breast carcinoma cell line MDA-MB-231, then their cell cycle distribution was measured by flow cytometer (FCM). The role of protein in cell cycle progression was detected via two-dimensional polyacrylamide gel electrophoresis (2-DE) and western blotting. Following the stimulation of TCM, HUVECs showed a more cells in the S phase than did the negative control group (ECGF-free medium with 20% FBS), but the HUVECs' level was similar to the positive control group (medium with 25 mug/ml ECGF and 20% FBS). Increased expression of cyclin D-1/E and some changes in other related proteins occurred after incubation with TCM. From our results, we can conclude that breast carcinoma cell line MDA-MB-231 may secrete soluble pro-angiogenic factors that induce the HUVEC angiogenic switch, during which the expression of cell cycle regulator cyclin D-1/E increases and related proteins play an important role in this process.

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Gas film lubrication of a three-dimensional flat read-write head slider is calculated using the information preservation (IP) method and the direct simulation Monte Carlo (DSMC) method, respectively. The pressure distributions on the head slider surface at different velocities and flying heights obtained by the two methods are in excellent agreement. IP method is also employed to deal with head slider with three-dimensional complex configuration. The pressure distribution on the head slider surface and the net lifting force obtained by the IP method also agree well with those of DSMC method. Much less (of the order about 10(2) less) computational time (the sum of the time used to reach a steady stage and the time used in sampling process) is needed by the IP method than the DSMC method and such an advantage is more remarkable as the gas velocity decreases.

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An optical communication scheme of 2-D pattern transfer based on imaging optics for submarine laser uplink communication (SLUC) is suggested. Unlike the methods aiming at avoiding neighboring crosstalk used in traditional multi-channel optical beam transferring, we make full use of the overlapping of each spreading beam other than controlling divergence effect of each beam to avoid interference noise. The apparent parameters have been introduced to simplify theoretical analysis of optical pattern transfer problem involving underwater condition, with the help of which the complex beam propagation inside two kinds of mediums can be easily reduced to brief beam transfer only inside air medium. In this paper, optical transmission path and receiver terminal optics geometry have been described in detail. The link range equation and system uplink performance analysis have also been given. At last, results of a proof-of-concept experiment indicate good feasibility of the proposed SLUC model. © 2007 Elsevier GmbH. All rights reserved.

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利用5m长的D型双包层掺Yb^3+光纤,采用声光调制锁模信号系统,实验上成功研制出输出320MHz的高重复频率脉冲列的光纤放大器,得到了20dB的增益输出,输出激光波长1064nm,输出平均功率1.02W,该光纤放大器可作为空间激光通信系统发射源。整个实验系统装置由作为信号源的特高重频脉冲列激光器、作为放大环节的光纤放大器和绿光倍频三个部分组成,另外对光纤放大器自激振荡谱线的各影响因素做了一些相关的实验研究,并对结果进行了分析讨论,提出了改进措施。

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Tellurite glass is proposed as a host for broadband erbium-doped fiber amplifiers because of their excellent optical and chemical properties. A single-mode Er3+-doped tellurite glass fiber with D-shape cladding was fabricated in this work. The characterization of amplified spontaneous emission (ASE) from this newly fabricated Er3+-doped tellurite fibers are exhibited. When pumped at 980 nm, a very broad erbium ASE nearly 150 nm around 1.53 mum is observed. The changes in ASE with regard to fiber lengths and pumping power were measured and discussed. The output of 2 mW from Er3+-doped tellurite fiber ASE source was obtained under the pump power of 660 mW. The broad 1.53 mum emission of Er3+ in tellurite glass fiber can be used as host material for potential broadband optical amplifier and tunable fiber lasers. (C) 2004 Elsevier B.V. All rights reserved.