Reply to the comment of F. H. Brown & P. N. Gathogo on ''Recent tectonics in the Turkana Rift (North Kenya): an integrated approach from drainage network, satellite imagery and reflection seismic analyses''     

William Vétel  Bernard Le Gall 《Basin Research》2005,17(2):329-335

  相似文献   

Transformations of magnetic mineralogy in rocks revealed by difference of hysteresis loops measured after stepwise heating: theory and case studies     

Bernard Henry  Diana Jordanova  Neli Jordanova  Maxime Le Goff 《Geophysical Journal International》2005,162(1):64-78

  相似文献   

GIS在交通管理部门的应用实例     

邹凤  许乐 《测绘与空间地理信息》2000,23(1):31-33

交通地理信息系统（Ｇｅｏｇｒａｐｈｉｃ　Ｉｎｆｏｒｍａｔｉｏｎ　Ｓｙｓｔｅｍ　ｆｏｒ Ｔｒａｎｓｐｏｒｔａｔｉｏｎ）简称 ＧＩＳ— Ｔ,它是 ＧＩＳ技术在交通领域的延伸,是ＧＩＳ与多种交通信息分析和处理技术的集成。动态分段是模拟和分析线性特征的有效方法,是交通管理信息系统中不可缺少的工具模块,本文以安徽省公路管理地理信息系统为例,研究动态分段功能的实际应用,实践取得满意效果。  相似文献   

The FFT Moving Average (FFT-MA) Generator: An Efficient Numerical Method for Generating and Conditioning Gaussian Simulations   总被引：10，自引：0，他引：10  

Mickaële Le Ravalec  Benoît Noetinger  Lin Y. Hu 《Mathematical Geology》2000,32(6):701-723

A fast Fourier transform (FFT) moving average (FFT-MA) method for generating Gaussian stochastic processes is derived. Using discrete Fourier transforms makes the calculations easy and fast so that large random fields can be produced. On the other hand, the basic moving average frame allows us to uncouple the random numbers from the structural parameters (mean, variance, correlation length, ... ), but also to draw the randomness components in spatial domain. Such features impart great flexibility to the FFT-MA generator. For instance, changing only the random numbers gives distinct realizations all having the same covariance function. Similarly, several realizations can be built from the same random number set, but from different structural parameters. Integrating the FFT-MA generator into an optimization procedure provides a tool theoretically capable to determine the random numbers identifying the Gaussian field as well as the structural parameters from dynamic data. Moreover, all or only some of the random numbers can be perturbed so that realizations produced using the FFT-MA generator can be locally updated through an optimization process.  相似文献   

From GCM scales to hydrological scales: rainfall variability in West Africa     

T. Lebel  F. Delclaux  L. Le Barbé  J. Polcher 《Stochastic Environmental Research and Risk Assessment (SERRA)》2000,14(4):275-295

  相似文献   

Water and the density of silicate glasses     

Pascal Richet  Alan Whittington  François Holtz  Harald Behrens  Susanne Ohlhorst  Max Wilke 《Contributions to Mineralogy and Petrology》2000,138(4):337-347

A review of published and newly measured densities for 40 hydrous silicate glasses indicates that the room-temperature partial molar volume of water is 12.0 ± 0.5 cm³/mol. This value holds for simple or mineral compositions as well as for complex natural glasses, from rhyolite to tephrite compositions, prepared up to 10–20 kbar pressures and containing up to 7 wt% H₂O. This volume does not vary either with the molar volume of the water-free silicate phase, with its degree of polymerization or with water speciation. Over a wide range of compositions, this constant value implies that the volume change for the reaction between hydroxyl ions and molecular water is zero and that, at least in glasses, speciation does not depend on pressure. Consistent with data from Ochs and Lange (1997, 1999), systematics in volume expansion for SiO₂–M₂O systems (M=H, Li, Na, K) suggests that the partial molar thermal expansion coefficient of H₂O is about 4 × 10⁻⁵ K⁻¹ in silicate glasses. Received: 30 June 1999 / Accepted: 5 November 1999  相似文献   

Post-glacial colluvium in western Norway: depositional processes, facies and palaeoclimatic record   总被引：1，自引：0，他引：1  

Pascal Bertran  & Vincent Jomelli 《Sedimentology》2000,47(5):1053-1058

  相似文献   

核磁共振找水方法的现状和发展趋势   总被引：15，自引：0，他引：15  

潘玉玲  万乐  袁照令  李振宇 《地质科技情报》2000,19(1):105-108

简要介绍了利用核磁共振（ｎｕｃｌｅａｒ ｍａｇｎｅｔｉｃ ｒｅｓｏｎａｎｃｅ,缩写为ＮＭＲ）技术找水方法的发展状况、原理和方法特点,重点介绍了中国地质大学（武汉）ＮＭＲ科研组,利用ＮＭＲ找水方法在中国一些地区找水取得的成效,最后指出了ＮＭＲ找水方法的发展趋势。  相似文献   

辽宁省循环经济指标体系的建立与评价   总被引：5，自引：0，他引：5       下载免费PDF全文

安乐  李宇斌 《气象与环境学报》2007,23(3):23-27

根据循环经济的基本原理,阐述了建立辽宁省循环经济指标体系的原则,提出了构建包括经济系统、资源系统和环境系统在内的循环经济指标体系,并运用AHP(层次分析法)方法,对2004年辽宁省14个市的循环经济发展现状进行了评价。结果表明:循环经济发展水平居前7位的城市分别为沈阳、大连、盘锦、鞍山、抚顺、葫芦岛和营口。研究成果可为辽宁省循环经济发展提供技术依据。  相似文献   

Isotopic compositions of different presolar silicon carbide size fractions from the Murchison meteorite     

Sachiko AMARI  Ernst ZINNER  Roy S. LEWIS 《Meteoritics & planetary science》2000,35(5):997-1014

Abstract— We report measurements of isotopic ratios of C, N, Mg, Si, Ca, Ti, Cr, and Fe in bulk samples (aggregates of many grains) of up to seven different fractions of silicon carbide (SiC), ranging from 0.38 to 3.0μm in diameter, from the Murchison CM2 carbonaceous chondrite. Ratios of ¹²C/¹³C range from 37 to 42 and ¹⁴N/¹⁵N ratios from 370 to 520, within the range of single‐grain measurements on coarser samples and in agreement with an asymptotic giant branch (AGB) star origin of most of the grains. Variations among size fractions do not show any simple trend and can be explained by varying contamination with isotopically normal material. Silicon isotopic ratios vary only little and, with one exception, lie to the right of the singlegrain mainstream correlation line. This might indicate a higher percentage of the minor populations Y and Z among finer grain‐size fractions. All bulk samples have large ²⁶Mg excesses attributed to the presence of short‐lived ²⁶Al at the time of grain formation. Inferred ²⁶Al/²⁷Al ratios are much larger than those measured in single larger mainstream grains. This is probably because of the presence of SiC grains of type X; we obtain an estimate of 0.4 for their ²⁶Al/²⁷Al ratio. Our Ca‐isotopic measurements, the first made on presolar SiC grains, show excesses in ⁴²Ca and ⁴³Ca, which is in general agreement with theoretical expectations for AGB stars. Calcium‐44 excesses are much larger than expected and are probably because of X grains, which have high⁴⁴Ca excesses because of the decay of short‐lived ⁴⁴Ti produced in supernova explosions. We arrive at an estimate of 0.014 for the initial ⁴⁴Ti/⁴⁸Ti ratio of the X grains, within the range obtained from previous single X grain measurements. The Ti‐isotopic ratios of the bulk samples show a V‐shaped pattern with excesses of all isotopes relative to ⁴⁸Ti. Isotopes ⁴⁶Ti, ⁴⁷Ti, and ⁵⁰Ti show excesses relative to the correlation between Ti and Si ratios for single grains and are in general agreement with theoretical models of s‐process nucleosynthesis in AGB stars. In contrast, ⁴⁹Ti does not show any excess relative to the singlegrain data; it also fails to agree with theory, which predicts much larger excesses than observed. Measured ⁵³Cr/⁵²Cr and ⁵⁷Fe/⁵⁶Fe ratios are normal within errors. The first result is expected even for Cr in AGB star envelopes, but the second result suggests that most of the Fe analyzed originates from contamination. We have found no simple trends in isotopic composition with respect to grain size that can be interpreted in terms of nucleosynthetic origin, unlike the results for Kr, Xe, Ba, and Sr.  相似文献