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131.
黔东南暴雨气候特征及其地形影响 总被引:2,自引:2,他引:2
利用1960~2000年贵州省黔东南地区降水观测资料,统计分析黔东南地区暴雨时空分布特征,进一步揭示其活动规律及主要影响因素。结果表明:黔东南地区暴雨有显著年代际变化特征,存在准15年的周期变化,并与贵州降水和长江中下游降水呈同位相;存在两个暴雨多发中心,夜间暴雨较多。黔东南暴雨地域分布极为复杂,局地性暴雨较多,这与黔东南特殊地形有着密切关系,地形因素是影响黔东南地区暴雨的重要原因,对形成上述特征的气候学成因做了初步讨论。 相似文献
132.
133.
Upscaling is a major issue regarding mechanical and transport properties of rocks. This paper examines three issues relative
to upscaling. The first one is a brief overview of Effective Medium Theory (EMT), which is a key tool to predict average rock
properties at a macroscopic scale in the case of a statistically homogeneous medium. EMT is of particular interest in the
calculation of elastic properties. As discussed in this paper, EMT can thus provide a possible way to perform upscaling, although
it is by no means the only one, and in particular it is irrelevant if the medium does not adhere to statistical homogeneity.
This last circumstance is examined in part two of the paper. We focus on the example of constructing a hydrocarbon reservoir
model. Such a construction is a required step in the process of making reasonable predictions for oil production. Taking into
account rock permeability, lithological units and various structural discontinuities at different scales is part of this construction.
The result is that stochastic reservoir models are built that rely on various numerical upscaling methods. These methods are
reviewed. They provide techniques which make it possible to deal with upscaling on a general basis. Finally, a last case in
which upscaling is trivial is considered in the third part of the paper. This is the fractal case. Fractal models have become
popular precisely because they are free of the assumption of statistical homogeneity and yet do not involve numerical methods.
It is suggested that using a physical criterion as a means to discriminate whether fractality is a dream or reality would
be more satisfactory than relying on a limited data set alone. 相似文献
134.
Zircon LA-ICP-MS U-Pb dating and Sr-Nd isotope study of the Guposhan granite complex, Guangxi, China
GU Shengyan HUA Renmin QI Huawen 《中国地球化学学报》2007,26(3):290-300
Zircon U-Pb dating by the LA-ICP-MS method was applied to determining the ages of different units of the Guposhan granite complex, among which the East Guposhan unit is 160.8±1.6 Ma, the West Guposhan unit is 165.0±1.9 Ma, and the Lisong unit is 163.0±1.3 Ma in age. Much similarity in ages of the three units has thus proved that the whole Guposhan granite complex was formed in the same period of time. They were the products of large-scale granitic magmatism through crust-remelting in the first stage of the Middle Yanshanian in South China. However, the three units have differences both in petrology and in geochemistry. Besides the differences in major, trace and rare-earth elements, they are distinct in their Rb-Sr and Sm-Nd isotopic compositions. The East Guposhan unit and Lisong unit and its enclaves have a similar (87Sr/86Sr)i value of 0.7064 with an average of εNd(t)=-3.03, indicating that more mantle material was evolved in the magma derivation; whereas the West Guposhan unit has a higher (87Sr/86Sr)i value of 0.7173 but a lower εNd(t) value of -5.00, and is characterized by strong negative Eu anomalies and higher Rb/Sr ratios, suggesting that its source materials were composed of relatively old crust components and new mantle-derived components. In addition, an inherited zircon grain in the East Guposhan unit (GP-1) yielded a 206Pb/238U age of 806.4 Ma, which is similar to the ages of the Jiulin cordierite granite in northern Jiangxi and of the Yinqiao migmatic granite in Guangxi in the HZH granite zone. All this may provide new evidence for Late Proterozoic magmatism in the HZH granite zone. 相似文献
135.
“2007.4.1”四川盆地强寒潮天气过程分析 总被引:1,自引:0,他引:1
利用T2131°×1°和欧洲中心实时资料,对2007年4月1~3日四川盆地区域性寒潮天气过程的环流背景及影响系统进行了分析,结果表明:500hPa乌拉尔山到贝加尔湖以东为宽广深厚的低压带,地面上巴湖附近为冷高压,此冷高压在500hPa脊前西北气流的引导下东移南压,是造成此次寒潮大风天气的主要原因;而且低空急流也对降温有一定的作用。 相似文献
136.
本文首先分析了我国土地开发整理的地位和现状,回顾了“十五”期间我国在土地开发整理方面做出的巨大的成绩,展望了“十一五”期间我国在土地整理工作上的投入力度和方向。在此基础上,对我国土地整理工作所采用的技术手段进行了分析,提出了实施土地开发整理工作的信息化是解决目前存在问题的有效措施,为了保证国家每年投资数十亿资金的土地开发整理项目从审查到实施各个环节的科学性和规范性,迫切要求充分利用计算机技术、网络通信技术和3S技术等先进手段加强项目的全程管理。接着,对“国家投资土地开发整理项目管理信息系统”从功能角度进行了详细的阐述,将系统划分为若干个子系统进行开发,并对一些子系统的功能进行了阐述。最后介绍了系统的应用情况。 相似文献
137.
为了探索BP网络的参数调整特性,进行了参数α、β的选取对BP算法的收敛速度和模型的稳定性的影响研究。通过BP网络用于气象预测建模的参数调整个例分析表明:参数α、β的取值对BP模型的稳定性无显著影响,但参数值的调整尤其是β值的调整对建模的收敛速度有明显的影响。 相似文献
138.
转变地勘单位的经济增长方式,提高各生产要素的使用效率,进而提高经济效益,推动地勘单位的经济持续、健康、全面的发展是当前急需解决的首要问题。本文在分析了地勘单位经济增长方式现状的基础上,指出了优化认识、优化资金配置、优化资本运行机制、优化内部管理、优化经营规模、优化人才成长环境等六个方面是转变地勘单位经济增长方式可选择的主要思路和途径。 相似文献
139.
The purpose of this study is to develop a technique to discriminate artificial explosions from local small earthquakes ( M ≤ 4.0) in the time–frequency domain. In order to obtain spectral features of artificial explosions and earthquakes, 3-D spectrograms (frequency, time and amplitude) have been used. They represent a useful tool for studying the frequency content of entire seismic waveforms observed at local and regional distances (Kim, Simpson & Richards 1994). P and S(L g ) waves from quarry blasts show that the frequency content associated with the dominant amplitude appears above 10 Hz and Rg phases are observed at close distances. P and S(L g ) waves from the Tongosan earthquake have strong amplitudes below 10 Hz. For the Munkyong earthquake, however, a broader frequency content up to 20 Hz is found.
For discrimination between small earthquakes and explosions, Pg/L g spectral ratios are used below 10 Hz, and through spectrogram analysis we can see different frequency contents of explosions and earthquakes. Unfortunately, because explosion data recorded at KSRS array are digitized at 20 sps, we cannot avoid analysing below 10 Hz because of the Nyquist frequency. In order to select time windows, the group velocity was computed using multiple-filter analysis (MFA), and free-surface effects have been removed from all three-component data in order to improve data quality. Using FFT, a log-average spectral amplitude is calculated over seven frequency bands: 0.5 to 3, 2 to 4, 3 to 5, 4 to 6, 5 to 7, 6 to 8 and 8 to 10 Hz. The best separation between explosions and earthquakes is observed from 6 to 8 Hz. In this frequency band we can separate explosions with log ( Pg/L g ) above −0.5, except EXP1 recorded at SIHY1-1, and earthquakes below −0.5, except the Munkyong earthquake record at station KMH. 相似文献
For discrimination between small earthquakes and explosions, Pg/L g spectral ratios are used below 10 Hz, and through spectrogram analysis we can see different frequency contents of explosions and earthquakes. Unfortunately, because explosion data recorded at KSRS array are digitized at 20 sps, we cannot avoid analysing below 10 Hz because of the Nyquist frequency. In order to select time windows, the group velocity was computed using multiple-filter analysis (MFA), and free-surface effects have been removed from all three-component data in order to improve data quality. Using FFT, a log-average spectral amplitude is calculated over seven frequency bands: 0.5 to 3, 2 to 4, 3 to 5, 4 to 6, 5 to 7, 6 to 8 and 8 to 10 Hz. The best separation between explosions and earthquakes is observed from 6 to 8 Hz. In this frequency band we can separate explosions with log ( Pg/L g ) above −0.5, except EXP1 recorded at SIHY1-1, and earthquakes below −0.5, except the Munkyong earthquake record at station KMH. 相似文献
140.