Estimation of codaQ using the maximum likelihood method     

Motoaki Takahara  Kiyoshi Yomogida 《Pure and Applied Geophysics》1992,139(2):255-268

A seismic coda wave from local earthquakes is an indication of heterogeneity in the crust and upper mantle, and codaQ (Q _c ) is the parameter defining the temporal decay of the coda wave. ButQ _c estimates obtained with the conventional least-square method are not based on any solid statistical background, assuming the Gaussian distributiona priori. In this study, we propose a statistically reliable estimation method of estimatingQ _c using the maximum likelihood method, and show its validity and usefulness with the data from the 1986 Joint Seismological Research in the western Nagano Prefecture. We found first that theQ _c estimation with the maximum likelihood method is statistically valid and its reliability can be checked with the x1251514817280/xxlarge967.gif" alt="chi" align="MIDDLE" BORDER="0">-square test. Next,Q _c around Ohtaki village, within the studied area, is estimated using the maximum likelihood method. The averageQ _c value at low frequencies (up to 2 Hz) is one of the lowest in the world, which is in harmony with the geological setting of the site condition directly above an active fault.  相似文献   

岩溶泉流量衰减曲线分析   总被引：5，自引：0，他引：5       下载免费PDF全文

常勇  吴吉春  刘玲  罗跃 《水文》2016,36(1):15-21

由于岩溶含水介质的强烈非均质性和各向异性,如何有效认识岩溶含水层内部的水文地质特征为研究难点之一,岩溶泉衰减曲线分析为认识岩溶含水层的一种有效手段。总结了目前广泛用于泉流量衰减曲线分析的几种常见方法,主要包括指数型衰减、非指数型衰减分析方法以及综合型的衰减曲线分析方法,讨论了管道可能对泉流量衰减曲线的影响,最后提出了今后对岩溶泉流量衰减曲线分析拟解决的一些关键问题。  相似文献   

New estimation of usually neglected forces acting on Galilean system     

V. Lainey  A. Vienne  L. Duriez 《Celestial Mechanics and Dynamical Astronomy》2001,81(1-2):115-122

We studied small perturbations acting on Galilean satellites. Most of them are still not computed in the analytical theories and could probably improve the ephemeris of these satellites which are outside the precision of the observations. We used a numerical method to test the effect of such perturbations. Here are reporting the main results we obtained.  相似文献   

Gas and Particle Products Distribution from the Reaction of β-Caryophyllene with Ozone     

M. Jaoui  S. Leungsakul  R. M. Kamens 《Journal of Atmospheric Chemistry》2003,45(3):261-287

Gas and particulate reaction products from the ozonolysis of x7v278255207/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0"> -caryophyllene (I) in the presence of atmospheric air were investigated using a combination of gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC). A Scanning Mobility Particle Sizer system (3936, TSI) and a Condensation Particle Counter (3025A, TSI) were used to study secondary organic aerosol formation. The nighttime oxidation was carried out in a large outdoor smog chamber (190 m³). A wide range of ring retaining and ring opening products in the gas and particle phase are reported over the course of the reaction. On average, measured gas and particle phase products accounted for x7v278255207/xxlarge8764.gif" alt="sim" align="MIDDLE" BORDER="0">64% of the reacted x7v278255207/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0"> -caryophyllene (I) carbon. Measurements show that a number of reaction products with low vapor pressure (e.g., x7v278255207/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-caryophyllone aldehyde (IV), x7v278255207/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-norcaryophyllone aldehyde (V), x7v278255207/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-caryophyllonic acid (VIII), x7v278255207/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-14-hydroxycaryophyllonic acid (XIV)) were found in the sample taken during the first 20 min of the reaction and may play an important role in the early formation of secondary organic aerosol. A detailed mechanism is proposed to account for most products observed in this investigation.  相似文献   

New latest Cretaceous microvertebrate fossil assemblages from the Haţeg Basin (Romania)     

Grigorescu  Dan  Venczel  Márton  Csiki  Zoltán  Limberea  Romeo 《Geologie en Mijnbouw》1999,78(3-4):301-314

Late Cretaceous terrestrial ecosystems in southern Europe are relatively poorly known, although much progress has been made during the past decade, principally with regard to the microvertebrate components of these ecosystems. The Maastrichtian terrestrial deposits of the Hax226x8738153t62/xxlarge355.gif" alt="tcedil" align="MIDDLE" BORDER="0">eg Basin, at the easternmost end of the South European archipelago and well known for reptilian fossils (e.g., turtles, crocodilians, pterosaurs and dinosaurs), have been thoroughly screened during the past five years. Important microvertebrate assemblages, both quantitatively and qualitatively speaking, were found at Pui (Sînpetru Formation), Tux226x8738153t62/xxlarge351.gif" alt="scedil" align="MIDDLE" BORDER="0">tea and, particularly, Vx226x8738153t62/xxlarge259.gif" alt="abreve" align="BASELINE" BORDER="0">lioara (Densux226x8738153t62/xxlarge351.gif" alt="scedil" align="MIDDLE" BORDER="0">-Ciula Formation). Several new taxa are noted here for the first time for the Hax226x8738153t62/xxlarge355.gif" alt="tcedil" align="MIDDLE" BORDER="0">eg Basin, including gars, discoglossids, albanerpetontids, scincomorphan and anguimorphan lizards; dromaeosaurids and multituberculates are confirmed. Most of the microvertebrate remains are poorly preserved and precise systematic assignment has proved difficult. The Hax226x8738153t62/xxlarge355.gif" alt="tcedil" align="MIDDLE" BORDER="0">eg fauna appears to be primitive and endemic, with a Neopangean core composition, and suggests a composite palaeobiogeographic origin for the Late Cretaceous European ecosystems, confirming conclusions reached in studies of the larger vertebrates.  相似文献   

耀斑加速电子能谱的不变点及其意义     

甘为群  林春梅 《紫金山天文台台刊》1999,18(2):125-127

在厚靶非热韧致辐射模型下,考察产生耀斑硬Ｘ 射线暴的非热电子幂律能谱随时间的变化。结果发现,对有些耀斑,不同时刻的非热电子能谱总是具有一个粗略的共同交点。该交点可能反映了有些电子加速机制的固有性质———饱和及低端阈能。  相似文献   

Variation of the oxygen content and point defects in olivines, (Fe x Mg 1−x )2SiO4, 0.2 ≤ x ≤ 1.0     

T.-L. Tsai  R. Dieckmann 《Physics and Chemistry of Minerals》2002,29(10):680-694

 The variation of the oxygen content in olivines, (Fe _x Mg_{1− x} )₂SiO₄, with 0.2 ≤ x ≤ 1.0, was investigated by thermogravimetric measurements. Mass changes occurring upon oxygen activity changes were measured as a function of oxygen activity and cationic composition at 1130 and 1200 °C. During the measurements the samples were in direct contact with gases containing CO, CO₂ and N₂ and, at a few spots at the bottom of the sample stack, also with SiO₂. By fitting experimental data of mass changes to equations derived using point defect thermodynamics, it was shown for olivines with 0.2 ≤ x ≤ 1.0 at 1130 °C and 0.2 ≤ x ≤ 0.7 at 1200 °C within the oxygen activity ranges investigated that the observed variations in the oxygen contents are compatible with cation vacancies and Fe³⁺ ions on M sites and Fe³⁺ ions on silicon sites as majority defects if it is assumed that only three types of point defects occur as majority defects. Different cases were considered, closed systems, taking into account that ξ=[Si]/([Si]+[Fe]+[Mg]) is not necessarily equal to 1/3, and olivines in equilibrium with SiO₂ or pyroxenes. The oxygen content variations observed in this study are significantly smaller than those reported previously in the literature. It is proposed that these differences are related to the dissolution of Fe into noble metal containers used as sample holders in earlier studies and/or to the presence of secondary phases. Received: 1 November 1995 / Accepted: 15 September 2002 Acknowledgements This work was supported by the Cornell Center for Materials Research (CCMR), a Materials Research Science and Engineering Center of the National Science Foundation (DMR-0079992). The authors thank Mr. Daniel M. DiPasquo and Mr. Jason A. Schick for helping in experimental work.  相似文献   

三维叠前偏移新技术   总被引：3，自引：2，他引：3       下载免费PDF全文

陈必远  马在田 《地球物理学报》1994,37(3):400-407

首次采用空间（ｘ，ｙ）坐标旋转的方法推导出了适应于任何炮检方向并与炮检方向相关的三维波动方程，理论上定量地说明了炮检方向及炮检距与偏移响应的关系，进而证明３Ｄ－ＤＭＯ（叠前部分偏移）只需在炮检方向上进行二维ＤＭＯ即可得以实现。理论模型试算结果表明，该方法正确描述了波的实际传播过程，实现了三维叠前全偏移及３Ｄ－ＤＭＯ处理。  相似文献   

计算横向非均匀介质体波理论地震图的Maslov渐近法          下载免费PDF全文

朱良保 《地球物理学报》1989,(2)

本文运用Maslov渐近理论编写的二维横向非均匀介质中的理论地震图程序,与其它类型算法作了精确对比,结果表明,在层状介质模型中,本程序的结果无论振幅还是波形对比都与反射率法基本相同。对于二维横向非均匀模型,在射线理论的非奇点处,本算法与射线方法基本一致,在射线理论的奇异点处,Maslov方法消除了射线理论所固有奇点,提高了计算精度。  相似文献   

Test Of Turbulence Models For Wind Flow Over Terrain With Separation And Recirculation     

H. G. Kim  V. C. Patel 《Boundary-Layer Meteorology》2000,94(1):5-21

Several two-equation turbulence models using isotropic eddy viscosity and wall functions are assessed by solution of the neutral atmospheric boundary layer over a flat surface and wind flow over two- and three-dimensional models and real terrain. Calculations are presented for wind flow over the Sirhowy Valley in Wales, an embankment along the Rhine in Germany and the Askervein Hill in Scotland. Comparisons of predictions with previous work, and laboratory and field data, show that the RNG-based k–x4114p68/xxlarge8712.gif" alt="isin" align="MIDDLE" BORDER="0"> model gives the best agreement with respect to the flow profiles and length of the separated flow region. The results of this model are analyzed with a non-linear stress-strain relation to gauge the potential effect of turbulence anisotropy.  相似文献