新疆地区2000 ～ 2012 年加卸载响应比时空演化特征分析     

唐兰兰  刘月  刘建明  温少妍  李金  尼鲁帕尔·买买吐孙 《中国地震》2014,30(3):442-453

对新疆地区进行了加卸载响应比的时空扫描计算,考察了研究区2000 ～ 2012年期间加卸载响应比异常区域的时空演化特征,利用孕震积分定量统计了新疆地区5级以上地震与LURR的时空关系;并用2011 ～2012年的扫描结果与次年实际发生的5级以上地震进行对比,发现绝大部分的中强地震都发生在前1年的预测区域内.基于加卸载响应比的时空扫描结果,分别对2011 ～2012年发生的4个6级地震进行了孕震积分时程曲线分析,结果显示,实际地震发生之前几个月孕震积分均会达到峰值,并在高值波动过程中或高值回落后发震.  相似文献   

Comment on “Dynamical Implications of Block Averaging” by G. Treviño and E.L Andreas     

Richard M. Eckman 《Boundary-Layer Meteorology》2008,127(2):345-351

A 2006 article in Boundary-Layer Meteorology by G. Treviño and E.L Andreas presents a derivation that questions the use of time averaging for computing turbulence statistics. Their derivation shows that time averaging over a finite interval always leads to a zero integral time scale. As a result, Treviño and Andreas argue that any turbulence quantities derived from time averaging are tainted and incompatible with the Navier–Stokes equations. While Treviño and Andreas are correct that time averaging does produce integral scales that are quite different from what researchers commonly expect, this comment demonstrates that the theoretical implications are not as dire as they claim.  相似文献   

Hurricane Wind Power Spectra, Cospectra, and Integral Length Scales   总被引：1，自引：0，他引：1  

Bo Yu  Arindam Gan Chowdhury  Forrest James Masters 《Boundary-Layer Meteorology》2008,129(3):411-430

Atmospheric turbulence is an important factor in the modelling of wind forces on structures and the losses they produce in extreme wind events. However, while turbulence in non-hurricane winds has been thoroughly researched, turbulence in tropical cyclones and hurricanes that affect the Gulf and Atlantic coasts has only recently been the object of systematic study. In this paper, Florida Coastal Monitoring Program surface wind measurements over the sea surface and open flat terrain are used to estimate tropical cyclone and hurricane wind spectra and cospectra as well as integral length scales. From the analyses of wind speeds obtained from five towers in four hurricanes it can be concluded with high confidence that the turbulent energy at lower frequencies is considerably higher in hurricane than in non-hurricane winds. Estimates of turbulence spectra, cospectra, and integral turbulence scales presented can be used for the development in experimental facilities of hurricane wind flows and the forces they induce on structures.  相似文献   

Effect of Vertical Wind Shear on Concentration Fluctuation Statistics in a Point Source Plume     

Trevor Hilderman  David J. Wilson 《Boundary-Layer Meteorology》2008,129(1):65-97

Measurements of concentration fluctuation intensity, intermittency factor, and integral time scale were made in a water channel for a plume dispersing in a well-developed, rough surface, neutrally stable, boundary layer, and in grid-generated turbulence with no mean velocity shear. The water-channel simulations apply to full-scale atmospheric plumes with very short averaging times, on the order of 1–4 min, because plume meandering was suppressed by the water-channel side walls. High spatial and temporal resolution vertical and crosswind profiles of fluctuations in the plume were obtained using a linescan camera laser-induced dye tracer fluorescence technique. A semi-empirical algebraic mean velocity shear history model was developed to predict these concentration statistics. This shear history concentration fluctuation model requires only a minimal set of parameters to be known: atmospheric stability, surface roughness, vertical velocity profile, and vertical and crosswind plume spreads. The universal shear history parameter used was the mean velocity shear normalized by surface friction velocity, plume travel time, and local mean wind speed. The reference height at which this non-dimensional shear history was calculated was important, because both the source and the receptor positions influence the history of particles passing through the receptor position.  相似文献   

A simple soil model for low frequency cyclic loading     

《Computers and Geotechnics》2017

A three-dimensional elastoplastic soil constitutive model capable of capturing the response of granular soils under low-frequency cyclic loading is introduced and verified. The model is piecewise linear with a hyperbolic stress-strain relationship. The size of the hysteresis loop is controlled using different scaling factors with a shift in the backbone curve at load reversal. The model introduces a new algorithm to better capture the soil’s response upon reloading for plane strain. Model verification with experimental results at different scales shows that the model has good capabilities in capturing the response of granular soils under low frequency cyclic loading.  相似文献   

Semi-analytical solutions of groundwater flow in multi-zone (patchy) wedge-shaped aquifers     

《Advances in water resources》2015

Alluvial fans are potential sites of potable groundwater in many parts of the world. Characteristics of alluvial fans sediments are changed radially from high energy coarse-grained deposition near the apex to low energy fine-grained deposition downstream so that patchy wedge-shaped aquifers with radial heterogeneity are formed. The hydraulic parameters of the aquifers (e.g. hydraulic conductivity and specific storage) change in the same fashion. Analytical or semi-analytical solutions of the flow in wedge-shaped aquifers are available for homogeneous cases. In this paper we derive semi-analytical solutions of groundwater flow to a well in multi-zone wedge-shaped aquifers. Solutions are provided for three wedge boundary configurations namely: constant head–constant head wedge, constant head–barrier wedge and barrier–barrier wedge. Derivation involves the use of integral transforms methods. The effect of heterogeneity ratios of zones on the response of the aquifer is examined. The results are presented in form of drawdown and drawdown derivative type curves. Heterogeneity has a significant effect on over all response of the pumped aquifer. Solutions help understanding the behavior of heterogeneous multi-zone aquifers for sustainable development of the groundwater resources in alluvial fans.  相似文献   

Boundary element analysis of axially loaded piles embedded in a multi-layered soil   总被引：1，自引：0，他引：1  

Z.Y. Ai  J. Han 《Computers and Geotechnics》2009

In a field, piles are likely installed in a multi-layered soil. Analysis of axially loaded piles in a multi-layered soil is complicated and deserves more attention. A boundary element method is used in this study to analyze an axially loaded single pile in a multi-layered soil using the solution for vertical and horizontal axisymmetric ring loads in a multi-layered elastic medium. Good and reasonable agreement is obtained between the proposed and published solutions for a single pile in a homogenous soil, a finite soil, and a Gibson soil. The proposed solution is also used to evaluate an axially loaded single pile in a multi-layered (8 layers) soil.  相似文献   

Integral equation method for analysis of piled rafts with dissimilar piles under vertical loading     

Fayun Liang  Longzhu Chen  Jie Han 《Computers and Geotechnics》2009

In a piled raft, the length and arrangement of piles has a significant effect on the stresses and deflections of the raft. The use of piles with different dimensions and properties below a raft is an innovative concept and can optimize the design of a piled raft. In this study, an integral equation method with a fictitious pile model was adopted to analyze the piled raft foundation with dissimilar piles. The Fredholm integral equations of the second kind were obtained for this problem. The loads shared by piles and subsoil, the load transfer, and the settlement of the piled raft were obtained using numerical calculation. The results from the present method were compared with those in the literature. An optimization technique was introduced to design piled rafts with dissimilar piles. The stiffening effect of piles on the surrounding soil is also discussed as compared the conventional interaction factor approach.  相似文献   

约束Delaunay三角网点删除的一体化凸耳消元法(IEE)   总被引：4，自引：1，他引：3  

王彦兵  吴立新  贾晓林  史文中 《地理与地理信息科学》2004,20(6):31-34

对Delaunay三角网(CD—TIN)点删除算法——凸耳消元法(EE)进行剖析,提出约束Delaunay三角网的点删除算法——体化凸耳消元法(IEE)。该算法将CD-TIN的点删除转化为点的影响域重构,并保证重构后的CD—TIN满足CD—TIN的可视性与空圆法则,确保了CD—TIN的拓扑完备性,实现了CD—TIN中约束点与非约束点删除的一体化操作和局部更新,并得到实验验证。  相似文献   

基于ZY3 DEM和SRTM DEM的北京平原区地貌特征探析     

王艳萍  Pinliang Dong  廖顺宝 《第四纪研究》2019,39(5):1211-1221

研究区主要包括北京东部的通州、平谷、顺义、燕郊、大厂和三河,位于华北沉降带北部、阴山东西向构造带南缘。该区地势总体上西北略高,东南略低,为大型缓倾斜平原,地形不仅受本区内北东向断裂的影响,还受北西向断裂的影响。资源三号卫星立体影像(ZY3)DEM和NASA航天飞机雷达地形任务(SRTM)DEM在北京地区地貌特征研究中显示出了许多优于其他DEM的优势。文章利用包括水系偏转、河长坡降指标(SL)、面积-高程积分值(HI)、等值线分级色彩显示和地形粗糙度等几种地形参数,分析了地形特征与断层构造活动性的关系。水系的右旋偏转证实了该区北东向断裂的右旋走滑活动,如夏垫断裂和其他相邻断裂。SL指数表明,河床纵剖面在横跨断层处均是陡坡;HI的高值主要集中在南口-孙河断裂与该区其他北东向断裂的交汇处,夏垫断裂的中段,以及香河县西北部,反映了该区强烈的构造活动,同时也反映出可能存在隐伏断层。另外,研究表明,面积、高程积分值的高值区与低值区相邻衔接处,往往是地震危险性较大的地方。此外,平原区相同值域的面积-高程积分所反映的构造活动强度应该与山区不同,因此地貌演化阶段划分标准也应与山区有所不同。等值线分级色彩显示对地形变化非常敏感,当与已识别的断层重叠时,大部分地形突变的地方都与断层活动有关。地形粗糙度分析显示不同断裂带的地形粗糙度与断裂活动强度呈正相关关系。  相似文献