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921.
China will establish a 2-meter space-based astronomical telescope. Its main science goals are performing a sky survey for research about dark matter and dark energy, and high resolution observations. Some experts suggest that this space telescope should be installed inside the Chinese space station. In accord with this suggestion we put forward our first configuration, i.e., to adopt a coud′e system for this telescope.This coud′e system comes from the Chinese 2.16 m telescope's coud′e system, which includes a relay mirror so that excellent image quality can be obtained. In our second configuration, we suggest that the whole space telescope fly freely as an independent satellite outside the space station. When it needs servicing, for example, changing instruments, refilling refrigerant or propellant, etc., this space telescope can fly near or even dock with the core space station. Although some space stations have had accompanying satellites, the one we propose is a space telescope that will be much larger than other accompanying satellites in terms of weight and volume. On the basis of the second configuration, we also put forward the following idea: the space station can be composed of several large independent modules if necessary. 相似文献
922.
本文在探讨斜坡破坏危险性分区中,试用模糊模型判识方法,依斜坡演变趋势与影响因素间的关联性,进行模糊聚类和相容度的分析,从而对斜坡破坏危险性做以分级分区研究并对斜坡的环境质量做以评价。 相似文献
923.
<正>七十年代以来,国内用线性渗流确定性模型对地下水系统进行数值模似(反求参数,预报人工流场),已取得丰富的成果和经验,但也存在一些问题。其中重要的问题之一是模型预报时边界条件的非确定性。对于该问题虽然有不同的解决办法,也有一些较大的分歧,至今还缺乏一套科学依据较严密的处理原则和求值方法。 相似文献
924.
The regularity of CH4 emission from marshland in the Sanjiang Plain was studied by sampling in the open field and analyzing under laboratory condition,
the annual emission amount is also estimated. By Grey Relatively Analysis we know that the soil temperature in the 10-cm depth
of grass-root layer is close related with CH4 emission. CH4 emission has different kinds of diurnal emission modes:before-dawn maximum mode, night maximum mode and irregular fluctuation
mode. The seasonal variation trend of CH4 emission rates is going up steadily from May to August and dropping down from September, the maximum lies behind the maximum
of temperature. CH4 emission rates of different marshland types are different, the CH4 emission rate of Glyceriaspiculosa — Carex marshland is always higher than that of Carex lasiocarpa marshland. The paper also studies the difference of CH4 emission rates in different managing modes and analyzes the emission rates between China and U. S. A. The result shows: the
average value of CH4 emission rate is 17.26mg/(m2·h), the annual amount of CH4 emission is about 0.75Tg.
Supported by National Natural Sciences Foundation of China, and thank the Ecological Test Station of Mires and Wetlands in
the Sanjiang Plain, the Chinese Academy of Sciences. 相似文献
925.
The environmental problems in the seriously polluted cities in China have been paid attention to by policy-makers and foreign
and domestic scholars. However, it is very difficult to improve the environmental quality fundamentally due to its complexity,
for example the formation of the seriously deteriorated environment. It is considered that the terminal harnessing is an important
way, but the spread of high-level terminal treatment is restricted by the limit of funds and technological level. Therefore,
the way for a sustainable development of the seriously polluted cities should be multiple-sided, which is to correlate the
operation of environmental protection with the operation of city construction. To achieve an identity of these opposites,
measures should be taken during economic development and environmental protection in every developing stage. In this paper,
the authors take Benxi City as a case study. 相似文献
926.
The method of empirical orthogonal modes has been widely used since the 1970's in physical oceanography to study and rebuild
vertical structures of ocean dynamic factors. Because of the dominance of the low modes, the dynamic profile data can be largely
reduced.
Up to now, all expressions of empirical orthogonal modes are numerical. In this study, an analytic expression for empirical
orthogonal ocean modes is constructed for convenient use whereby any numerical expressions can be repeated.
The features of the normal modes decomposed from the buoyance frequency profiles obtained in October of 1986, 1987 and 1988
by the R/VScience 1 in the western Pacific are quantitatively examined in this study.
Contribution No. 1724 from the Institute of Oceanology, Academia Sinica 相似文献
927.
Hybrid tilapia were reared at densities of 1, 5 or 10 fish per tank for four weeks. Mortality was 0 at 1 and 10 fish per tank,
but was 25% at 5 fish per tank. Specific growth rate was highest at 1 fish per tank, and lowest at 5 fish per tank. The lower
growth rate at the intermediate stocking density was associated with reduced feed efficiency, but there was no reduction in
feed intake or digestibility. The results suggested increased metabolic cost caused by aggressive behaviour at intermediate
stocking density, which can be suppressed by a further increase in density.
This project was financially supported by the State Key Laboratory of Freshwater Ecology and Biotechnology of China and by
Shanghai Fisheries University (Project SFU. 200003). 相似文献
928.
Discriminant functions link vegetation zones and surface pollen along the woodland–steppe ecotone in northern China. These links were utilised to reconstruct palaeovegetation using fossil pollen data from four lake sediment sites within the ecotone. Holocene movements of the vegetation zones were derived from the above results and were interpreted as the results of climatic, topographic and edaphic factors. This study shows that climatic change was the driving factor for ecotonal movement, but that the positions of vegetational zones were nevertheless controlled by topographical and edaphic conditions, and consequently boundaries between different vegetational zones responded individualistically. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
929.
Ren-Xin Xu Xiao-Hong Cui Guo-Jun Qiao Department of Astronomy School of Physics Peking University Beijing 《中国天文和天体物理学报》2006,6(2):217-226
The global structure of current flows in pulsar magnetosphere is investigated, with rough calculations of the circuit elements. It is emphasized that the potential of the critical field lines (the field lines that intersect the null surface at the light cylinder radius) should be the same as that of interstellar medium, and that pulsars whose rotation axes and magnetic dipole axes are parallel should be positively charged, in order to close the pulsar's current flows. The statistical relation between the radio luminosity and pulsar's electric charge (or the spindown power) may hint that the millisecond pulsars could be low-mass bare strange stars. 相似文献
930.
Surveys in Geophysics - Fluid discrimination is challenging for reservoir prediction, especially for tight sandstones with special petrophysical properties. In this paper, we first review the... 相似文献