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961.
962.
963.
Coalbed methane can be detected employing the amplitudevariation-with-offset technique. However, there are two issues in applying this technique to a coalbed: strong azimuthal anisotropy resulting from high-density fractures, and the seismic response being composed of many or several individual reflections within the coalbed. To overcome these difficulties, we present an exact solution for reflections in extensive dilatancy anisotropy media. First, we build a three-layer model and simulate the wave propagation in this model. Then we derive an exact P- and converted S-wave reflection coefficient equation based on boundary conditions. Finally, substituting given model parameters into the exact equation, we obtain the variation in the reflection coefficient with incidence angle. The results show that the fracture factors, wavelet frequency and thickness of the coalbed have different effects on the reflection coefficient. Furthermore, we create a synthetic seismogram by forward calculation, and the result fits well with results of the exact equation. 相似文献
964.
Spatiotemporal variation and driving forces of reference evapotranspiration in Jing River Basin,northwest China 总被引:1,自引:0,他引:1 下载免费PDF全文
Lihong Xu Zhongjie Shi Shulan Zhang Xinzheng Chu Pengtao Yu Wei Xiong Haijun Zuo Yunni Wang 《水文研究》2015,29(23):4846-4862
Evapotranspiration is an important component of the hydrological cycle, which integrates atmospheric demands and surface conditions. Research on spatial and temporal variations of reference evapotranspiration (ETo) enables understanding of climate change and its effects on hydrological processes and water resources. In this study, ETo was estimated by the FAO‐56 Penman–Monteith method in the Jing River Basin in China, based on daily data from 37 meteorological stations from 1960 to 2005. ETo trends were detected by the Mann–Kendall test in annual, seasonal, and monthly timescales. Sensitivity coefficients were used to examine the contribution of important meteorological variables to ETo. The influence of agricultural activities, especially irrigation on ETo was also analyzed. We found that ETo showed a decreasing trend in most of the basin in all seasons, except for autumn, which showed an increasing trend. Mean maximum temperature was generally the most sensitive parameter for ETo, followed by relative humidity, solar radiation, mean minimum temperature, and wind speed. Wind speed was the most dominant factor for the declining trend in ETo. The more significant decrease in ETo for agricultural and irrigation stations was mainly because of the more significant decrease in wind speed and sunshine hours, a mitigation in climate warming, and more significant increase in relative humidity compared with natural stations and non‐irrigation stations. Changes in ETo and the sensitivity coefficient of meteorological variables in relation to ETo were also affected by topography. Better understanding of ETo response to climate change will enable efficient use of agricultural production and water resources, which could improve the ecological environment in Jing River Basin. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
965.
The exploration of the spatial association between Medicare physician spending and population densities and sizes could possibly facilitate the investigation of the causal mechanisms beneath the variation in medical care. We acquired the U.S. Medicare physician expenditures and regional demographic and geographic data in 2006 from the Dartmouth Atlas of Health Care. Six geographic units—states, counties, Hospital Referral Regions, Hospital Service Areas, Metropolitan Statistical Areas, and state non-Metropolitan Statistical Areas—were used as units of study. Pearson correlation analysis, multivariable regression, and partial correlation analysis were employed. Among six geographic units, Pearson correlation coefficients between Medicare physician expenditures and logarithmic population densities ranged from 0.42 to 0.63 (p < 0.05 for all), and between the expenditures and logarithmic population sizes from 0.31 to 0.65 (p < 0.05 for all). When population health, differential demand, market structure, and data reporting bias were controlled, population densities and sizes were positively associated with Medicare physician expenditures in most models. Population densities and sizes could explain considerable amounts of regional variation in Medicare physician spending. We concluded that Medicare physician spending was contingent on population densities and sizes. Because population densities and sizes are produced by more fundamental qualities such as natural environments and resources and thus are not easily manipulated, they are suggestive in health policy studies. Further research might investigate population distribution associated properties such as geographic distribution of health care resources, spatial dynamics of medical technology distribution, and cultural and psychological factors. 相似文献
966.
Grilli Stéphan T. Shelby Mike Kimmoun Olivier Dupont Guillaume Nicolsky Dmitry Ma Gangfeng Kirby James T. Shi Fengyan 《Natural Hazards》2017,86(1):353-391
Natural Hazards - We perform numerical simulations to assess how coastal tsunami hazard from submarine mass failures (SMFs) is affected by slide kinematics and rheology. Two types of two-layer SMF... 相似文献
967.
磨刀门已由"径流型"向"径流-波浪型"河口转变,波浪已是该河口主要动力之一,但波浪对河口洪季水流及泄洪的影响缺少研究。在2-D潮流数学模型中添加随潮位实时变化的波浪辐射应力,建立波浪潮流耦合数学模型;波浪求解采用缓坡方程,背景水深由潮流模型实时提供,可通过比较考虑和未考虑波浪影响的河口流场来分析波浪对泄洪的影响。在年均常浪作用下,磨刀门河口洪季涨落潮阶段均有明显的波生环流结构。由于波浪作用方向向陆,波生流减弱了浅滩区的向海余流,增大了浅滩向陆余流;受浅滩向海余流减弱影响,河口动力自调整后形成归槽水流,促使深槽内向海余流增大。波浪有顶托河口泄洪之势,可改变滩槽泄洪分配比例;年均常浪的波高较小,其对潮流及泄洪的影响区域限制在浅水区,故对泄洪的负面影响有限。 相似文献
968.
对于总体最小二乘而言,经常需要处理不同精度或者不同类型的观测数据,根据先验方差来定权往往不准确,同时观测数据中可能含有粗差。针对这两个问题,提出稳健总体最小二乘Helmert方差分量估计,将稳健估计和Helmert方差分量估计同时应用于总体最小二乘中。最后通过两个实验的计算结果表明,该方法是可行的、有效的。 相似文献
969.
利用重力多尺度分解资料反演青藏高原东北缘地壳厚度 总被引:1,自引:1,他引:0
通过重力异常分解模型,选用小波基函数“bior3.7”,分解得出青藏高原东北缘布格重力异常资料的小波4阶近似成分,利用其主要由莫霍面产生的布格重力异常,以6条人工地震剖面信息做初始控制条件,反演得出青藏高原东北缘的地壳厚度。 相似文献
970.
Feng He Haishen Wen Dahui Yu Jifang Li Bao Shi Caifang Chen Jiaren Zhang Guoxiong Jin Xiaoyan Chen Dan Shi Yanping Yang 《中国海洋大学学报(英文版)》2010,9(4):395-398
Follicle stimulating hormone β (FSHβ) of Japanese flounder (Paralichthys olivaceus) plays a key role in the regulation of gonadal development.This study aimed to investigate molecular genetic characteristics of the FSHβ gene and elucidate the effects of single nucleotide polymorphisms (SNPs) of FSHβ on reproductive traits in Japanese flounder.We used polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) and sequencing of the FSHβ gene in 60 individuals.We identified only an SNP (T/C) in the coding region of exon3 of FSHβ.The SNP (T/C) did not lead to amino acid changes at the position 340 bp of FSHβ gene.Statistical analysis showed that the SNP was significantly associated with testosterone (T) level and gonadosomatic index (GSI) (P0.05).Individuals with genotype TC of the SNP had significantly higher serum T levels and GSI (P0.05) than that of genotype CC.Therefore, FSHβ gene could be a useful molecular marker in selection for prominent reproductive trait in Japanese Flounder. 相似文献