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161.
Malcolm Gray 《Astrophysics and Space Science》2005,295(1-2):309-318
I review a number of diagnostic techniques, based upon the excitation and variability of astrophysical masers, which can be applied to dense gas. In each case, I consider the observations necessary and the amount of interpretation, or modelling, required to complete the analysis of a source, presenting examples of each diagnostic method. 相似文献
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163.
Inundation patterns in two of the largest savanna floodplains of South America were studied by analysis of the 37‐GHz polarization difference observed by the Scanning Multichannel Microwave Radiometer (Nimbus‐7 satellite). Flooded area was estimated at monthly intervals for January 1979 through to August 1987 using mixing models that account for the major landscape units with distinctive microwave emission characteristics. Results are presented separately for five subregions in each of the two floodplain regions to show the spatial as well as temporal variability in inundation patterns. The total area inundated during the 9 years varied between 2069 and 78 460 km2 in the Llanos de Moxos (also spelled as Mojos; median area, 23 383 km2) and 1278 and 105 454 km2 in the Llanos del Orinoco (median, 25 374 km2), not including the open‐water area of permanent lakes and river channels. The correlation between flooded area and river stage was used to extend the inundation records over a 30‐year period in the Moxos (1967–97) and a 58‐year period (1927–85) in the Orinoco. Interannual variability in inundation is greater in the Moxos than the Orinoco. Comparison of these data, however, with a previously published analysis of the Pantanal wetland shows that inundation patterns in these two floodplain regions are not as variable across years as they are in the Pantanal. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
164.
AGN天体的主要特征之一,就是它们的光谱中有宽而强的发射线,因此,这些宽发射线的产生区域BLR为人们提供了一个了解AGN天体物理本质的独特而重要的场。在文中围绕讨论了BLR基本物理特征,评述近年来有关的理论和观测研究进展及其现状在文(Ⅱ)中主要涉及BLR的几何结构和尺度及其运动学研究的进展和现状。 相似文献
165.
Yang Ji-song Liu Jing-shuang Yu Jun-bao Wang Jin-da Qin Sheng-jin Li Xin-hua 《中国地理科学(英文版)》2005,15(3):262-268
Soil respiration is a main dynamic process of carbon cycle in wetland. It is important to contribute to global climate changes.
Water table and nutritious availability are significant impact factors to influence responses of CO2 emission from wetland soil to climate changes. Twenty-four wetland soil monoliths at 4 water-table positions and in 3 nitrogen
status have been incubated to measure rates of CO2 emission from wetland soils in this study. Three static water-table controls and a fluctuant water-table control, with 3
nitrogen additions in every water-table control, were carried out. In no nitrogen addition treatment, high CO2 emissions were found at a static low water table (I) and a fluctuant water table (IV), averaging 306.7mg/(m2·h) and 307.89mg/(m2·h), respectively, which were 51%–57% higher than that at static high water table (II and III). After nitrogen addition, however,
highest CO2 emission was found at II and lowest emission at III. The results suggested that nutritious availability of wetland soil might
be important to influence the effect of water table on the CO2 emission from the wetland soil. Nitrogen addition led to enhancing CO2 emissions from wetland soil, while the highest emission was found in 1N treatments other than in 2N treatments. In 3 nutritious
treatments, low CO2 emissions at high water tables and high CO2 emissions at low water tables were also observed when water table fluctuated. Our results suggested that both water table
changes and nutritious imports would effect the CO2 emission from wetland.
Foundation item: Under the auspices of the National Natural Science Foundation of China (No. 90211003) and the Knowledge Innovation
Program of Chinese Academy of Sciences (No. KACX3-SW-332)
Biography: YANG Ji-song (1978-), male, a native of Chengwu of Shandong Province, Ph.D. candidate, specialized in environmental
ecology and wetland biogeochemistry. E-mail: yangjisong@neigae.ac.cn 相似文献
166.
对XPer新发射相连续四年的光学光谱和近红外光度监测结果,XPer近两年的变化不同寻常,主要表现以下两点:(1)尽管它的光学光度V星等只恢复至失去气壳前的亮度,但Ha发射线等值宽度和近红外,J,H和K光度地超过了历史记录的最大值,分别达到了16.34A和5.3^m,5.3^m和5.1^m,表明XPer新发射相气南的密度和尺度较都大,(2)我们首次观测到XPer近红外光度和Hα发射线等值宽度变化趋势 相似文献
167.
168.
Low-frequency radio observations offer unique diagnostics of the solar corona and solar wind. After a prolongued hiatus, there is renewed interest in this important frequency regime. Two new ground-based instruments will provide critical new low-frequency observations: the low-frequency array (LOFAR) and the frequency agile solar radiotelescope (FASR). This brief topical review summarizes low-frequency radio phenomena that will be accessible to detailed study by LOFAR and FASR in the coming decade. Energy release, drivers of space weather, and studies of the solar wind are emphasized. Both instruments are expected to play important roles in both basic research problems and national and international space weather capabilities. While FASR is a solar-dedicated instrument, LOFAR is not. Solar observing requirements for LOFAR are briefly discussed. 相似文献
169.
170.
Xue-Bing Wu Wei Zhang Xu Zhou Department of Astronomy School of Physics Peking University Beijing National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2004,4(1):17-27
With a recently constructed composite quasar spectrum and the X2 minimization technique, we describe a general method for estimating the photometric redshifts of a large sample of quasars by deriving theoretical color-redshift relations and comparing the theoretical colors with the observed ones. We estimated the photometric redshifts from the 5-band SDSS photometric data of 18678 quasars in the first major data release of SDSS and compared them with their spectroscopic redshifts. The difference is less than 0.1 for 47% of the quasars and less than 0.2 for 68%. Based on the calculation of the theoretical color-color diagrams of stars, galaxies and quasars both on the SDSS system and on the BATC system, we expect that we would be able to select candidates of high redshift quasars more efficaciously with the latter than with the former, provided the BATC survey can detect objects with magnitudes fainter than 21. 相似文献