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在地震波正反演研究中，考虑起伏地表和地震各向异性具有非常重要的理论意义和实际应用价值.本文在前人研究的基础上，将最短路径追踪算法引入到起伏地表各向异性介质模型的地震波走时计算中.模型剖分时，整体模型划分成正方形单元，起伏边界附近以不规则网格逼近，进而采用非规则节点布置实现非规则网格处的最短路径计算.追踪计算中采用Sena群速度近似公式，得到各向异性地震波的走时，实现了复杂地表情况下各向异性介质模型中地震波的射线追踪.理论模型计算结果显示，本文方法能够可靠地应用于复杂各向异性介质模型，具有较高的计算精度. 相似文献
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本文主要介绍了针对无锡轧钢厂设备基座的精密工程测量,并结合测量中的实际情况,重点提出如何避免和降低误差对大型机械设备测量的影响. 相似文献
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Turbulent heat transfer in a swinging tube with a serrated twist tape insert was experimentally examined to reveal the effects of swinging oscillations on heat transfer for such a swirl tube under sea-going conditions. This swirl tube swings about two orthogonal axes under single and compound rolling and pitching oscillations. A selection of Nusselt number (Nu) measurements illustrates the influences of swinging oscillations with and without buoyancy interaction on heat transfer performances. Single rolling or pitching oscillation with the swinging frequencies ranging from 0.333 to 1 Hz reduces heat transfer levels from the static references. Synergistic effects of compound rolling and pitching oscillations with either harmonic or non-harmonic rhythms improve heat transfer performances. Buoyancy effects in the swinging swirl tube elevate local Nu, but are weakened as the relative strength of swinging force increases. A set of heat transfer correlations is derived that permits the individual and interactive effects of single and compound swinging force effects with buoyancy interactions on the developed flow heat transfer value () to be quantified. 相似文献
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东营市季、年降水量与北半球500hPa高度场的相关关系及其预报 总被引：1，自引：0，他引：1
用滚动式相关分析方法分析了营市季、年降水量与500hPa高度场的相关关系。用相关显著的典型因子场做季、年降水量预报，效果良好。 相似文献
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A field study of surface-air exchange of carbon, water, and energy was conducted at a mid-latitude, mixed forest on non-flat terrain to investigate how to best interpret biological signals from the eddy flux data that may be subject to advective influences. It is shown that during periods of Southwest winds (sector with mild topography), the eddy fluxes are well-behaved in terms of energy balance closure, the existence of a constant flux layer, consistency with chamber observations and the expected abiotic controls on the fluxes. Advective influences are evident during periods with wind from a steep (15%) slope to the Northeast of the tower. These influences appear more severe on CO2 flux, particularly in stable air, than on the energy fluxes. Large positive flux of CO2 (> 23 mol m-2 s-1) occurs frequently at night. The annual sum of the carbon flux is positive, but the issue about whether the forest is a source of atmospheric carbon remains inconclusive.Attempts are made to assess vertical advectionusing the data collected on a single tower. Over the Southwestsector, vertical advection makes a statistically significant but small contribution to the 30-min energy imbalance and CO2 flux variations. Contributions by horizontal advection may be larger but cannot be verified directly by the current experimental method. 相似文献
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在湿陷性黄土地区,黄土作为高速公路地基的主要原料其强度和变形特性不能满足要求,主要有振动碾压、冲击碾压和强夯3种有效且实用的处治方法。本文根据原位试验和室内试验的数据,进行有限元模拟,在不同高度路堤和不同加载方式情况下,地基沉降变形随着处治能级的增加而减小,路堤本身的沉降保持不变。对于地基处理的深度和沉降变形减小的效果,强夯最好,冲碾次之,振碾最弱。处治前后地表中心沉降变形值与加载路堤高度之间的关系均可用二阶多项式回归拟合。2～4m高的路堤采用振碾的方式处理地基,5～10m高的路堤采用冲碾方法,大于10m的路堤多用强夯或者直接修桥来代替,对于黄土地区高速公路建设与维护具有重要意义。 相似文献
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The grains of lunar regolith are characterized with rough surfaces, angular shapes and mutual adhesions due to short-range interactions. These features control the macroscopic mechanical behavior of lunar regolith but have not been completely captured by contact models in previous Discrete Element Method (DEM) analyses. In this paper, a simplified two-dimensional microscopic contact model is proposed for high efficiency DEM analyses of lunar regolith. The model consists of three components in the normal, tangential and rolling directions respectively, plus two new parameters. A shape parameter is used to control the rolling resistance ability at the contact area between two particles to capture the features of grain shape and interlocking. The second parameter, micro-separation, which denotes the nominal minimum distance between the molecules of the two contacting particles, is introduced to account for van der Waals force as the major component of the short-range interactions that contribute to the adhesion of regolith grains in lunar environment conditions. The novel model has been implemented in a two-dimensional DEM code for numerical simulations of biaxial compression tests on lunar regolith. The effects of interparticle friction, grain shape, lunar environment conditions and void ratio on the strength of lunar regolith were numerically investigated. The results show that soils in the simulated lunar environment exhibit greater strength and more apparent strain-softening and shear dilatancy than on the Earth. The proposed model can capture the main features of the mechanical behavior of lunar regolith (apparent cohesion and high peak friction angle) and a wide range of strength indices can be obtained by the contact model. 相似文献