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非线性波消波及波场分布研究 总被引:1,自引:1,他引:0
本文基于雷诺平均N-S方程,并结合RNG k-e方程建立了粘性数值波浪水槽,对不同波陡、不同相对水深、不同相对波高的非线性规则波的阻尼消波问题和波场分布进行研究。文中提出了两种描述消波区内部阻尼变化的阻尼函数,分别适用于小波陡情形和高波陡情形。研究结果表明,小波陡组消波区可设为一个波长,阻尼系数取10~4~10~5即可满足消波要求,计算结果与实验结果及造波理论吻合良好;高波陡组消波区可设为两个波长,阻尼系数取10~4~10~5亦可满足消波要求,计算结果与实验结果吻合良好。此外,当波陡较小时,波场内反射情况的小幅改变即可对整个波场造成影响,特别是当水深较浅时这种影响极为明显,需谨慎考虑。当波陡较大时,水波能量较高,整个波场沿水波传播方向可观测到明显的衰减现象,在具体试验中需进行考虑。 相似文献
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In this paper, we give a brief introduction to the proposal and development history of the earthquake magnitude concept. Moment magnitude MW is the best physical quantity for measuring earthquakes. Compared with other magnitude scales used traditionally, moment magnitude is not saturated for all earthquakes, regardless of big and small earthquakes, deep and shallow earthquakes, far field and near field seismic data, geodetic and geological data, moment magnitude can be measured, and can be connected with well-known magnitude scales such as surface wave magnitude MS. Moment magnitude is a uniform magnitude scale, which is suitable for statistics with wide magnitude range. Moment magnitude is the preferred magnitude selected by the International Seismological community, and it is preferred by the departments responsible for publishing seismic information to the public.Moment magnitude is a uniform magnitude scale, which is suitable for statistics with wide magnitude range. Moment magnitude is a preferred magnitude for international seismology, it is preferred by the agency responsible for providing information about earthquakes to the public. We provide all formulas used in the calculation of moment magnitude, and the calculation steps in detail. We also analyzed some problems and rules to solve these problems by using different formulas and numerical value calculation steps. 相似文献
95.
Youssef Wehbe Marouane Temimi Dawit T. Ghebreyesus Adam Milewski Hamid Norouzi Elsy Ibrahim 《水文科学杂志》2018,63(3):408-425
The regional-scale consistency between four precipitation products from the GPCC, TRMM, WM, and CMORPH datasets over the Arabian Peninsula was assessed. Their macroscale relationships were inter-compared with soil moisture and total water storage (TWS) estimates from AMSR-E and GRACE. The consistency analysis was studied with multivariate statistical hypothesis testing and Pearson correlation metrics for the period from January 2000 to December 2010. The products and GRACE estimates were assessed over a representative sub-domain (United Arab Emirates) with available in situ well observations. Next, geographically temporally weighted regression (GTWR) was employed to examine the interdependencies among the peninsula’s hydrological components. The results showed GPCC-TRMM recording the highest correlation (0.85) with insignificant mean differences over more than 90% of the peninsula. The highest GTWR predictive performance of TWS (R2 = 0.84) was achieved with TRMM forcing, which indicates its potential to monitor changes in TWS over the arid peninsular region. 相似文献
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Assessment of alternative adsorption models and global sensitivity analysis to characterize hexavalent chromium loss from soil to surface runoff 下载免费PDF全文
We investigate our ability to assess transfer of hexavalent chromium, Cr(VI), from the soil to surface runoff by considering the effect of coupling diverse adsorption models with a two‐layer solute transfer model. Our analyses are grounded on a set of two experiments associated with soils characterized by diverse particle size distributions. Our study is motivated by the observation that Cr(VI) is receiving much attention for the assessment of environmental risks due to its high solubility, mobility, and toxicological significance. Adsorption of Cr(VI) is considered to be at equilibrium in the mixing layer under our experimental conditions. Four adsorption models, that is, the Langmuir, Freundlich, Temkin, and linear models, constitute our set of alternative (competing) mathematical formulations. Experimental results reveal that the soil samples characterized by the finest grain sizes are associated with the highest release of Cr(VI) to runoff. We compare the relative abilities of the four models to interpret experimental results through maximum likelihood model calibration and four model identification criteria (i.e., the Akaike information criteria [AIC and AICC] and the Bayesian and Kashyap information criteria). Our study results enable us to rank the tested models on the basis of a set of posterior weights assigned to each of them. A classical variance‐based global sensitivity analysis is then performed to assess the relative importance of the uncertain parameters associated with each of the models considered, within subregions of the parameter space. In this context, the modelling strategy resulting from coupling the Langmuir isotherm with a two‐layer solute transfer model is then evaluated as the most skilful for the overall interpretation of both sets of experiments. Our results document that (a) the depth of the mixing layer is the most influential factor for all models tested, with the exception of the Freundlich isotherm, and (b) the total sensitivity of the adsorption parameters varies in time, with a trend to increase as time progresses for all of the models. These results suggest that adsorption has a significant effect on the uncertainty associated with the release of Cr(VI) from the soil to the surface runoff component. 相似文献
98.
断层和断裂带的有效识别是地震资料解释中的重要环节,断层在地震信号响应中以断面波的形式体现,因此断面波成像的质量关系到断层的精细识别与刻画.本文利用精度较高的交错网格有限差分正演模拟方法对断面波成像的影响因素进行了正演研究,主要正演分析的参数包括采集因素中的电缆长度和采集方向,地质因素中的断层倾角、断距、反射系数,以及处理因素中的偏移方法等几个方面.通过正演论证得出:采用合理的采集参数能够提高断面波的照明度;有效结合地质因素能够提高断面波的解释精度;利用合理的偏移方法能够使断层归位更加准确,断面波有效成像.基于以上结论,对于断面波的精确识别与刻画,应综合采集因素,处理因素及地质因素,只有这样才能提高断层的解释精度,有效减小解释误差. 相似文献
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华南陆缘是我国重要的矿产、地热资源区.晚中生代以来,在太平洋板块西向俯冲,地幔热对流活动共同作用下,该区出现多期岩浆-热事件和大规模爆发式成矿作用.在前人研究基础上,本文利用地表热流观测资料、地震剪切波资料、重力位球谐系数,计算了壳-幔温度结构,分析了动力学背景.计算结果表明:华南陆缘东南沿海地带,地壳10 km以浅温度达200℃以上,居里点温度475℃,莫霍面平均温度550℃.地壳浅层较热,花岗岩中放射性元素衰变放热是地壳浅层地下水热活动的重要热源,但地壳总体温度不高,为"冷壳热幔"型热结构.地幔中,90 km深度,温度950~1250℃;120 km深度,温度1050~1400℃;150 km深度,温度1200~1450℃;220 km深度,温度1500~1700℃."热"岩石圈底界深度在110~150 km之间,西深东浅.岩石圈内,地幔应力场为挤压-伸展相间格局;岩石圈之下,地幔应力场为一个以南昌为中心、长轴NE-SW向的椭圆.分析认为,晚中生代以来,太平洋板块的西向俯冲,导致华南陆缘在区域性SE向地幔对流背景上叠加局域性不稳定热扰动,在175~85Ma期间,上地幔物质向上流动,形成不同的岩浆活动高峰期.同时,岩石圈地幔受俯冲洋壳流体的影响,含水量高,黏度小,在地幔流切向应力场作用下,岩石圈底界由西向东"波浪"状减薄.现今岩石圈之下仍具备地幔小尺度热对流温度条件,但除地表浅层外,地壳整体温度不高,岩石圈构造稳定. 相似文献
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