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981.
本文扼要介绍了中国科学院东川泥石流观测研究站对外开放三年来,在泥石流观测试验研究和防灾减灾工作中的新进展,同时也简述了站设基金课题、国家基金课题和中外合作交流项目的进展情况,并对今后的观测研究工作提出了展望和建议。 相似文献
982.
Vanessa Doublier 《Astrophysics and Space Science》2002,281(1-2):211-212
Planetary Nebulae have proven to be an essential key to understand the long term chemical enrichment of the interstellar medium
due to low mass stars. They allow to study the original abundances of the star, and the effect of the star on the interstellar
medium. Blue compact dwarf galaxies are known to host violent star formation in very heavy element depleted environments.
They also show traces of past star formation (Doublier et al., 1999; 2001), including AGB starsand red giants which are responsible
for long term enrichment. However, models fails to reproduce the low metallicities observed if those stars are taken into
account. We observed PNe in BCDGs, and made a comparative study of the abundances in the HII regions and of the PNe.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
983.
984.
985.
The physical basis of the linkage between magnitude and timing of channel flow hydrographs and drainage network morphometry is reviewed. Small Hortonian and structurally Hortonian networks are analysed using numerical runoff simulation. For Hortonian networks the variability of the geometry of individual channels and subcatchments within each Strahler order has generally little effect upon the overall character of the hydrograph in channels of higher order. If the network is also structurally Hortonian, the analysis of the simultaneous formation, travel, and concentration of the hydrographs in all channels of the network can be simplified to a sequence of one representative hydrograph per channel order. This approach is used in this study. Three major runoff processes control the flow hydrograph characteristics: the overland flow process which determines the water supply to the drainage network; the channel flow process which translates the hydrograph in space and time; and the drainage network process which concentrates and magnifies the flow at the junctions of the drainage network. Functional relations for the hydrograph peak, timing, and flow velocity are presented. For a given uniform rainfall and infiltration rate, the peak of the channel flow hydrograph is shown to increase geometrically with channel order, and its magnitude is directly related to the bifurcation ratio. The travel time of the peak also increases geometrically with channel order, and it is directly related to the channel length ratio over velocity ratio. The flow velocity of the peak changes in a downstream direction as a function of the bifurcation and slope ratio. It was also found that for negligible channel storage the channel flow and drainage network processes do not contribute significantly to the observed nonlinear response of a watershed to precipitation. 相似文献
986.
Shock metamorphism of the lunar samples is discussed. All types of lunar glasses formed by various-size collision-type impact are found as impact glass, ropy glass and agglutinates. The agglutinates bonded by crystal and glassy materials contain hydrogen and helium from the solar wind components. Lunar shocked minerals of plagioclase and silica show anomalous compositions and densities. There are typical two formation processes on planetary materials formed by shock events; that is (1) shocked quartz formed by silica-rich target rocks (esp. on evolved planets of the Earth and Mars), and (2) shocked silica with minor Al contents formed from plagioclase-rich primordial crusts of the Moon. The both shocked silica grows to coarse-grain normal crystals after high-temperature metamorphism which cannot distinguish the original main formation event of impact process. 相似文献
987.
周训 《地球科学与环境学报》1992,(3)
本文以四川盆地中部的L_1井为例,讨论深层卤水自喷钻井卤水产出特征、水文地球化学特征和开采动态特征,并对钻井的测试资料进行分析,预测该钻井的卤水可采资源量。 相似文献
988.
989.
L. Tanvuia W.W. Zeilinger P. Focardi B. Kelm R. Rampazzo 《Astrophysics and Space Science》2003,284(2):459-462
This is a study concerning the investigation of galaxy formation and evolution in small-scale structures and the influence
of the environment on the properties of galaxies. The environment plays a key role in the evolution of galaxies since it governs
the type of encounters. We present results from low-resolution spectroscopy and R-band surface photometry of multiplets of
galaxies found in low-density environments and compare them to cluster environments. Properties such as induced galaxy activity,
star formation enhancements, AGN activity and the connection between merging and galaxy morphology are investigated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
990.