国际石油市场与东盟国家能源安全

1.原油价格不稳定的背景 自1998年以来,国际石油市场上的原油价格呈现出一种滑道式的波动。以西得克萨斯中质原油(WTI)这种有代表性的标志原油为例。其接近一个月交货的期货价格从1998年初的17.4美元/桶降至1998年12月的10.7美元/桶,下降39％。然后,价格在1999年3月突然上升,到2000年9月达     

北欧海主要海盆海面热通量的多年变化

北欧海有暖流和寒流注入,又发生大量回流,水团特性异常复杂。由于北欧海的环流受地形控制,其水团的分布与4个海盆的分布有密切的关系。本文研究各个海盆热通量变化的差异,以研究获取对北欧海海气相互作用区域差异的认识。北欧海的热量夏季以太阳短波辐射为主,冬季以来自海洋的长波辐射、感热和潜热通量为主。海盆间的差异主要体现在格陵兰海,其变化幅度短波辐射高出50%,长波辐射高出大约40%,潜热高出大约60%,感热高出近4倍。可能的原因是,格陵兰海强烈的感热和潜热释放导致海温降低,气温也受北极冷空气的影响,形成与暖流区迥异的自然环境。过去30年发生了2次显著的热量减少事件。其中,1987年的事件很可能与冰岛的火山喷发有关,火山喷发对短波辐射的影响长达一年之久,导致感热和潜热也同步减少。1998年格陵兰海的潜热和感热明显减少,与北极海冰输出导致的海温偏低有显著关系。文章分析了4个主要海盆热通量的变化与北极涛动(AO)指数的关系。结果表明,发生在冰岛海的向下短波辐射和发生在格陵兰海的感热和潜热与AO相关度较高,体现了与AO的密切关系。这些热通量与AO指数的滑动相关系数表明,1992年以前冰岛海的短波辐射与AO的相关性非常高,而格陵兰海的感热和潜热在1993年后与AO高度相关,是值得深入研究的现象。本文的结果支持以下观点:北欧海对北极涛动的贡献主要是格陵兰海的感热和潜热释放通过冰岛低压区的上升气流影响冰岛低压的云量,从而影响到达的太阳辐射而导致大气环流的变化。     

水力开挖技术使开挖施救更高效更安全

本文简要介绍了一种应用于施救抢险的水力开挖技术,采用该技术可以更高效、更安全。     

Atmospheric Corrections Using MODTRAN for TOA and Surface BRDF Characteristics from High Resolution Spectroradiometric/Angular Measurements from a Helicopter Platform

High-resolution spectral radiance measurements were taken by a spectral radiometer on board a heli copter over the US Oklahoma Southern Great Plain near the Atmospheric Radiation Measurements (ARM) site during August 1998. The radiometer has a spectral range from 350 nm to 2500 nm at 1 nm resolution. The measurements covered several grass and cropland scene types at multiple solar zenith angles. Detailed atmospheric corrections using the Moderate Resolution Transmittance (MODTRAN) radiation model and in-situ sounding and aerosol measurements have been applied to the helicopter measurements in order to re trieve the surface and top of atmosphere (TOA) Bidirectional Reflectance Distribution Function (BRDF) characteristics. The atmospheric corrections are most significant in the visible wavelengths and in the strong water vapor absorption wavelengths in the near infrared region. Adjusting the BRDF to TOA requires a larger correction in the visible channels since Rayleigh scattering contributes significantly to the TOA reflectance. The opposite corrections to the visible and near infrarred wavelengths can alter the radiance dif ference and ratio that many remote sensing techniques are based on, such as the normalized difference vege tation index (NDVI). The data show that surface BRDFs and spectral albedos are highly sensitive to the veg etation type and solar zenith angle while BRDF at TOA depends more on atmospheric conditions and the vi ewing geometry. Comparison with the Clouds and the Earth＇s Radiant Energy System (CERES) derived clear sky Angular Distribution Model (ADM) for crop and grass scene type shows a standard deviation of 0.08 in broadband anisotropic function at 25° solar zenith angle and 0.15 at 50° solar zenith angle, respectively.     

A pulse of the Earth:A 27.5-Myr underlying cycle in coordinated geological events over the last 260 Myr

We performed spectral analyses on the ages of 89 well-dated major geological events of the last 260 Myr from the recent geologic literature.These events include times of marine and non-marine extinctions,major ocean-anoxic events,continental flood-basalt eruptions,sea-level fluctuations,global pulses of intraplate magmatism,and times of changes in seafloor-spreading rates and plate reorganizations.The aggregate of all 89 events shows ten clusters in the last 260 Myr,spaced at an average interval of～26.9 Myr,and Fourier analysis of the data yields a spectral peak at 27.5 Myr at the≥96％confidence level.A shorter period of～8.9 Myr may also be significant in modulating the timing of geologic events.Our results suggest that global geologic events are generally correlated,and seem to come in pulses with an underlying～27.5-Myr cycle.These cyclic pulses of tectonics and climate change may be the result of geophysical processes related to the dynamics of plate tectonics and mantle plumes,or might alterna-tively be paced by astronomical cycles associated with the Earth's motions in the Solar System and the Galaxy.     

波的传播

由于IRIS的计划、全球台网的建设,同时辅以PASSCAL设备的便携式台站的使用,使台站的建设也取得了很大进展,这些都为地震波传播的研究开辟了一个广阔的领域,大到以整个地球为研究对象的最大标准模型,小到重视上地壳或余震系列细节的区域性实验。在过去20年中,地震仪器快速发展使     

PSV波传播的有限差分模拟位移—位方法

本文提出了在非均匀各向同性介质中Ｐ－ＳＶ波传播模拟的一种新的有限差分公式。该方法中，波动方程分离成两组方程，其中一组是关于位移场的，另一组是关于位场的。这两组方程仅包含一阶空间导数。利用位函数，Ｐ－ＳＶ波场可以分离Ｐ和Ｓ波位场，这位不同方法模拟Ｐ和Ｓ波传播提供了，通过假定常密度和剪切模量，Ｐ波和Ｓ波位均可用标量波动方程形式表示，因此能够对标量波使用Ｌｉｎｄｍａｎ“自由空间”边界条件。通过在吸收边界     

Subsidence Analysis and Burial History of the Late Carboniferous to Early Jurassic Soutpansberg Basin, Limpopo Province, South Africa

The subsidence history of the Soutpansberg Basin was reconstructed by a tectonic subsidence analysis coupled with backstripping calculations based on data of newly interpreted sequence boundaries. Furthermore,burial and time plots were constructed in order to understand the burial and thermal history of the basin. Input data were based on facies,lithostratigraphic models and tectonic interpretations. The studied succession is up to 1000 m and is underlain by the Achaean Limpopo Mobile Belt. The subsidence within the basin supports the primary graben system which must have been centred within the present basins,and later became a region of faulting. The subsidence and burial history curves suggests two phases of rapid subsidence during the Early-Late Permian(300–230 Ma) and Middle Triassic(215–230 Ma). The areas of greater extension subsided more rapidly during these intervals. Two slow subsidence phases are observed during the Late Triassic(215–198 Ma) and Early Jurassic(198–100 Ma). These intervals represent the post-rift thermal subsidence and are interpreted as slow flexural subsidence. Based on these observations on the subsidence curves,it is possible to infer that the first stage of positive inflexion(300 Ma) is therefore recognised as the first stage of the Soutpansberg Basin formation.     

勘查地球化学:过去 现在和未来

历史的剖析在寻找金属的早期,找矿者很快便擅长通过基岩和地表环境特征来查明矿床.河流沉积物中的岩石和矿物碎屑使早期找矿者可以从那一连串的分散物追溯到基岩源头.最早期找矿者和现代勘查地球化学工作者之间的主要差异在于,找矿者运用了矿物调查,而地球化学工作者则使用化学分析. 在30年代,苏联和斯堪的纳维亚的工作者首先使用现代地球化学方法.发射光谱这种当时微