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991.
由于地震资料是带限的,而井资料约束反演过程中的地震反演频带的展宽也是有一定限度的,使得反演地震波阻抗也是带限的。如何进一步拓宽反演地震波阻抗的频带宽度,提高地震资料的分辨率是文中研究的内容。利用井约束下的地震反演波阻抗资料、地震资料及井资料,借鉴地质模拟技术,研究如何利用地层的空间相对稳定性特征,通过相关函数的分析,估计反演更高分辨率的地震波阻抗资料。考虑到地质体空间的相关性及分辨率,相关半径取相关函数从最大点到第1个极值点的范围。在目标函数的计算过程中,既考虑当前计算点的权系数信息,又考虑井外推时的权系数信息,这样使计算结果更加稳定可靠。通过综合模拟计算,能够识别较小砂体 相似文献
992.
苏北潮滩湿地不同生态带碳、氮、磷分布特征* 总被引:1,自引:0,他引:1
通过对比苏北潮滩湿地不同生态带的表层以及柱状沉积物中总有机碳、总氮、总磷和有机磷含量,并结合不同植被不同植株部位中碳、氮、磷的含量变化,分析了潮滩沉积物中碳、氮、磷的垂向和水平分布特征与规律,探讨了不同生态带以及潮滩植被对碳、氮、磷等生源要素的富集作用。对比分析结果表明:苏北潮滩湿地各生态带对不同的测量指标有着不同的富集作用,互花米草滩的总有机碳、总氮和有机磷含量要远大于其他几个生态带,光滩沉积物中总磷的含量最高; 粒度效应是控制互花米草前缘地带以及互花米草滩沉积物中有机碳和氮分布的一个重要因素,盐蒿和芦苇滩中有机碳和氮的分布更多的是受粒度之外的其他因素影响; 不同生态带表层沉积物中的C/N比值分布,大致可反映其有机物来源的差异,而不同生态带中柱状沉积物中的C/N比值相对接近,很难根据C/N比值大小来对不同生态带中的有机物来源进行判断,这可能是埋藏在柱状沉积物中的有机物更多的受到了早期成岩作用造成的。植被对潮滩湿地中碳、氮、磷的分布有着重要影响,3种物质在互花米草、盐蒿和芦苇中的含量差别不是很大,因此潮滩植被对沉积物中上述3种物质的贡献差别主要是由不同植被的生物量和其所处环境的沉积动力差异造成的。 相似文献
993.
Wind tunnel experiments were carried out to measure the spatial distribution in equilibrium transport of four types of mixed sand. The flux profiles of each grain size group were calculated. It is found that the vertical distribution of mean grain size has a close relation with the grain size distribution in the sand bed. In a log-linear plot, the flux profiles of main grain size groups are all straight lines and their slopes are nearly equal. It is also found that the ratio of transport rate of each size group to the whole transport rate is directly proportional to the mass ratio of each size group in the sand bed and the proportion value is only dependent on the grain size. This harmonious law is applicable to all four types of mixed sand used in the experiment. 相似文献
994.
Application and verification of fuzzy algebraic operators to landslide susceptibility mapping 总被引:4,自引:2,他引:4
Saro Lee 《Environmental Geology》2007,52(4):615-623
The aim of this study was to apply and to verify the use of fuzzy logic to landslide susceptibility mapping in the Gangneung
area, Korea, using a geographic information system (GIS). For this aim, in the study, a data-derived model (frequency ratio)
and a knowledge-derived model (fuzzy operator) were combined. Landslide locations were identified by changing the detection
technique of KOMPSAT-1 images and checked by field studies. For landslide susceptibility mapping, maps of the topography,
lineaments, soil, forest, and land cover were extracted from the spatial data sets, and the eight factors influencing landslide
occurrence were obtained from the database. Using the factors and the identified landslide, the fuzzy membership values were
calculated. Then fuzzy algebraic operators were applied to the fuzzy membership values for landslide susceptibility mapping.
Finally, the produced map was verified by comparing with existing landslide locations for calculating prediction accuracy.
Among the fuzzy operators, in the case in which the gamma operator (λ = 0.975) showed the best accuracy (84.68%) while the
case in which the fuzzy or operator was applied showed the worst accuracy (66.50%). 相似文献
995.
Lauren Patterson Marie Urban Aaron Myers Budhendra Bhaduri Eddie Bright Phillip Coleman 《GeoJournal》2007,69(1-2):93-102
Geospatial technologies and digital data have developed and disseminated rapidly in conjunction with increasing computing
efficiency and Internet availability. The ability to store and transmit large datasets has encouraged the development of national
infrastructure datasets in geospatial formats. National datasets are used by numerous agencies for analysis and modeling purposes
because these datasets are standardized and considered to be of acceptable accuracy for national scale applications. At Oak
Ridge National Laboratory a population model has been developed that incorporates national schools data as one of the model
inputs. This paper evaluates spatial and attribute inaccuracies present within two national school datasets, Tele Atlas North
America and National Center of Education Statistics (NCES).
Schools are an important component of the population model, because they are spatially dense clusters of vulnerable populations.
It is therefore essential to validate the quality of school input data. Schools were also chosen since a validated schools
dataset was produced in geospatial format for Philadelphia County; thereby enabling a comparison between a local dataset and
the national datasets.
Analyses found the national datasets are not standardized and incomplete, containing 76 to 90 percent of existing schools.
The temporal accuracy of updating annual enrollment values resulted in 89 percent inaccuracy for 2003. Spatial rectification
was required for 87 percent of NCES points, of which 58 percent of the errors were attributed to the geocoding process. Lastly,
it was found that by combining the two national datasets, the resultant dataset provided a more useful and accurate solution. 相似文献
996.
Åsa Fransson 《Hydrogeology Journal》2007,15(2):307-313
Two methods, both using data from fixed-interval-length hydraulic tests and geological mapping on different scales, have been
utilised to estimate transmissivity distributions of individual fractures. Individual fracture properties are of importance
in estimating transport of water and solutes; they influence the spreading of grout when sealing tunnels. One of the methods
is non-parametric, while the other is based on combinatorics and the multiplication principle. The study verified the usefulness
of both methods for estimating the probability of conductive and non-conductive fractures, and the transmissivity distributions.
Data for estimating transmissivity distributions originate from flow logging of a borehole in Sweden. Fracture frequency data
are from core logging and images using a borehole image processing system (BIPS). Estimated transmissivity distributions,
based on flow log data from 3-m sections (test scale length, L: 3 m, and step length, dL: 3 m), were compared with transmissivities
obtained directly from detailed, overlapping flow logging which identify individual conductive fractures (test scale, L: 0.5 m,
step length, dL: 0.1 m). The latter data are considered to be an acceptable approximation of the individual fracture transmissivities;
the agreement, compared with the calculated transmissivity distributions based on 3-m section data, is good for both methods.
Resumen Se han utilizado dos métodos, ambos procesando datos de pruebas hidráulicas de longitud e intervalo fijo y mapas geológicos en distintas escalas, para estimar las distribuciones de transmisividad de fracturas individuales. Las propiedades de fracturas individuales son de importancia para estimar el transporte de agua y solutos; las propiedades influyen en la propagación de lechada al sellar túneles. Uno de los métodos es no paramétrico mientras que el otro se basa en el principio de multiplicación y combinatorio. El estudio verifica la utilidad de ambos métodos para estimar la probabilidad de fracturas conductivas y no conductivas y las distribuciones de transmisividad. Los datos para estimar las distribuciones de transmisividad se originan del registro de flujo de un pozo en Suecia. Los datos de frecuencia de fracturas provienen de registros de núcleo e imágenes usando un Sistema de Procesamiento de Imágenes de Pozo (BIPS). Se compararon las distribuciones estimadas de transmisividad basadas en datos del registro de flujo en secciones de 3 m (longitud de escala de la prueba L: 3 m, y escalón de longitud dL: 3 m), con transmisividades obtenidas directamente de registros detallados de flujo superpuesto el cual identifica fracturas conductivas individuales (escala de la prueba, L: 0.5 m, escalón de longitud, dL: 0.1 m). Los últimos datos se consideran una aproximación aceptable de las transmisividades de fracturas individuales; la consistencia, comparada con las distribuciones de transmisividad calculada basadas en datos de sección de 3 m, es buena para ambos métodos.
Résumé Deux méthodes ont été testées afin d’estimer la distribution des transmissivités de fractures unitaires; toutes deux utilisent des données issues de tests hydrauliques effectués à intervalles réguliers et de cartographies géologiques à plusieurs échelles. La connaissance des propriétés des fractures unitaires est importante pour estimer le transport d’eau et de solutés; elles influencent en outre l’étalement du coulis lors du scellement des tunnels. La première méthode est non-paramétrique, et la seconde repose sur l’analyse combinatoire et le principe de multiplication. Cette étude a vérifié l’utilité des deux méthodes pour estimer la probabilité d’occurrence de fractures conductrices et non-conductrices, et la distribution des transmissivités. Les distributions des transmissivités ont été estimées à partir de diagraphies effectuées sur un forage situé en Suède. Les densités de fracturation proviennent de carottages et d’imagerie BIPS (Borehole Image Processing System). Les distributions estimées des transmissivités, basées sur des diagraphies de flux effectuées sur des sections de 3 m (échelle du test L:3 m; pas dL:3 m), ont été comparées aux transmissivités obtenues sur des diagraphies de flux détaillées et se chevauchant, identifiant les fractures conductrices unitaires (échelle du test L: 0.5 m ; pas dL: 0.1 m). Il est admis que ces dernières données représentent une approximation satisfaisante des transmissivités des fractures unitaires; les deux méthodes sont en accord avec les distributions des transmissivités calculées à partir des données acquises sur des sections de 3 m.相似文献
997.
V. Sasi Kumar S. Sampath P. V. S. S. K. Vinayak R. Harikumar 《Journal of Earth System Science》2007,116(5):451-463
Rainfall intensities measured at a few stations in Kerala during 2001–2005 using a disdrometer were found to be in reasonable
agreement with the total rainfall measured using a manual rain gauge. The temporal distributions of rainfall intensity at
different places and during different months show that rainfall is of low intensity (< 10 mm/hr), 65% to 90% of the time.
This could be an indication of the relative prevalence of stratiform and cumuliform clouds. Rainfall was of intensity < 5
mm/hr for more than 95% of the time in Kochi in July 2002, which was a month seriously deficient in rainfall, indicating that
the deficiency was probably due to the relative absence of cumuliform clouds. Cumulative distribution graphs are also plotted
and fitted with the Weibull distribution. The fit parameters do not appear to have any consistent pattern. The higher intensities
also contributed significantly to total rainfall most of the time, except in Munnar (a hill station). In this analysis also,
the rainfall in Kochi in July 2002 was found to have less presence of high intensities. This supports the hypothesis that
the rainfall deficiency was probably caused by the absence of conditions that favoured the formation of cumuliform clouds. 相似文献
998.
Application of bivariate extreme value distribution to flood frequency analysis: a case study of Northwestern Mexico 总被引:1,自引:0,他引:1
Carlos Escalante-Sandoval 《Natural Hazards》2007,42(1):37-46
In Mexico, poverty has forced people to live almost on the water of rivers. This situation along with the occurrence of floods
is a serious problem for the local governments. In order to protect their lives and goods, it is very important to account
with a mathematical tool that may reduce the uncertainties in computing the design events for different return periods.
In this paper, the Logistic model for bivariate extreme value distribution with Weibull-2 and Mixed Weibull marginals is proposed
for the case of flood frequency analysis. A procedure to estimate their parameters based on the maximum likelihood method
is developed. A region in Northwestern Mexico with 16 gauging stations has been selected to apply the model and regional at-site
quantiles were estimated. A significant improvement occurs, measured through the use of a goodness-of-fit test, when parameters
are estimated using the bivariate distribution instead of its univariate counterpart. Results suggest that it is very important
to consider the Mixed Weibull distribution and its bivariate option when analyzing floods generated by a␣mixture of two populations. 相似文献
999.
In order to investigate the distribution characteristics of stable carbon isotope ratios (δ
13C) in the desert plant Reaumuria soongorica, the δ
13C values of leaves were measured in 407 individuals of 21 populations. Soil physicochemical properties including soil water
content, soil total dissolved solids, soil total nitrogen, soil total phosphorus and soil organic content were also analyzed
in order to survey the major factors influencing δ
13C values on spatial variation. Leaves and soil samples were simultaneously collected from the ten major distribution areas
in Northwest China at altitudes from 394 m to 1 987 m above sea level, at latitudes from 36°10′N to 44°33′N, and at longitudes
from 81°43′E to 106°37′E. These ten areas include Shihezi, Baicheng, Yiwu areas in Xinjiang Uygur Autonomous Region; Anxi,
Zhangye, Baiyin, Lanzhou areas in Gansu Province; Shapotou, Yinchuan areas in Ningxia Hui Autonomous Region; and Alashan County
in Inner Mongolia Autonomous Region. The results show that the δ
13C value of R. soongorica ranges from −22.77‰ to −29.85‰ with an average of −26.52‰. Foliar d13C values in R. soongorica are not significantly correlated with altitude, latitude or longitude, and a spatial distribution trend of d13C values of
R. soongorica is not obvious on a large scale. However, when d13C values of two R. soongorica populations under the same climate conditions are compared, δ
13C values increase obviously from east to west and from north to south. As none of the soil total dissolved solids, soil total
nitrogen, soil total phosphorus, and soil organic content shows a uniform trend from east to west and from north to south,
we suppose that the small-scaled spatial distribution pattern of δ
13C values of R. soongorica is mainly controlled by the soil water content.
Translated from Quaternary Sciences, 2006, 26(6): 947–954 [译自: 第四纪研究] 相似文献
1000.
河西走廊风能时空特征 总被引:3,自引:0,他引:3
利用河西走廊地区1970-2004年风速气候资料和2004年9月-2005年8月周年风塔精细资料,采用气候订正和即时风速订正,得到接近自然的风速,依此研究了该区域近地面70 m层内风能分布。结果表明:河西走廊区域风速变幅较小、气候变化趋势较稳定;有效风速(≥3 m/s)时数在6 000 h/a,10 m高度风能大多在150 w/m2以上,风能随高度线形增长(在70 m高度层内),平均每升高10 m风能增加28 w/m2;10~70 m层内总风能年储量相当丰富,普遍在1.5×1016kWh/m2(千瓦时/平方米)以上,潜在年产值达千万亿元。河西走廊风能存在明显周日和月季变化,风能和有效风速时数存在空间差异,其时空差异与河西走廊独特的戈壁下垫面关系密切。 相似文献