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961.
关于数字城市地理空间框架建设的研究 总被引:1,自引:0,他引:1
随着我国城市化进程的发展,城市规模不断扩大,传统的城市管理方法远远不能满足现代城市管理的要求。随着"数字中国"战略的提出,"数字城市"应运而生。当前以"数字城市"为标志的城市信息化建设正在全国范围内迅速开展,网络基础设施和空间信息基础设施是数字城市建设中两个最为重要的基础设施,而地理空间框架是空间信息基础设施的重要组成部分,是经济社会信息化发展的基础支撑平台。 相似文献
962.
964.
Three-dimensional variational data assimilation of WindSat ocean surface winds for the genesis and forecasting of tropical storm Henri 总被引:2,自引:1,他引:1
With available high-resolution ocean surface wind vectors retrieved from the U.S. Naval Research Laboratorys WindSat on Coriolis, the impact of these data on genesis and forecasting of tropical storm Henri is examined using the non-hydrostatic, fifth-generation mesoscale model (MM5) of Pennsylvania State University-National Center for Atmospheric Research plus its newly released three-dimensional variational data assimilation (3DVAR) system. It is shown that the assimilation of the WindSat-retrieved ocean surface wind vectors in the 3DVAR system improves the model initialization fields by introducing a stronger vortex in the lower troposphere. As a result, the model reproduces the storm formation and track reasonably close to the observations. Compared to the experiment without the WindSat surface winds, the WindSat assimilation reduced an error between the model simulated track and observations of more than 80 km and also improved the storm intensity by nearly 2 hPa. It suggests that these data could provide early detection and prediction of tropical storms or hurricanes. 相似文献
965.
超强台风"桑美"在浙江省温州市苍南县登陆,登陆时中心附近最大风力达17级,中心气压920hPa,是近50年来登陆我国大陆最强的台风。为了认识超强台风"桑美"强度突然增强的机制机理,气象工作者做了许多有意义的工作,如"桑美"的观测分析、数值模拟、强度突增原因探究等。文章对以往研究成果进行了简述,指出了目前在此方面研究存在的问题,如数值模拟台风强度突增的量值偏小,强度突增的机理没有新的明显突破,以及气候变暖对台风强度突增如何影响涉及较少等。 相似文献
966.
967.
分析了软枝杨桃在闽南地区栽培中低温霜冻、大风、干旱、暴雨等灾害性天气的影响,并提出相应的防御措施. 相似文献
968.
969.
Xin Wang Xuelei Chen Zheng Zheng † Fengquan Wu Pengjie Zhang Yongheng Zhao 《Monthly notices of the Royal Astronomical Society》2009,394(4):1775-1790
The Large Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) is a dedicated spectroscopic survey telescope being built in China, with an effective aperture of 4 m and equipped with 4000 fibres. Using the LAMOST telescope, one could make redshift survey of the large-scale structure (LSS). The baryon acoustic oscillation features in the LSS power spectrum provide standard rulers for measuring dark energy and other cosmological parameters. In this paper, we investigate the measurement precision achievable for a few possible surveys: (1) a magnitude-limited survey of all galaxies, (2) a survey of colour-selected luminous red galaxies (LRG) and (3) a magnitude-limited, high-density survey of z < 2 quasars. For each survey, we use the halo model to estimate the bias of the sample, and calculate the effective volume. We then use the Fisher matrix method to forecast the error on the dark energy equation of state and other cosmological parameters for different survey parameters. In a few cases, we also use the Markov Chain Monte Carlo method to make the same forecast as a comparison. The fibre time required for each of these surveys is also estimated. These results would be useful in designing the surveys for LAMOST. 相似文献
970.
Christian Wolf Alfonso Aragón-Salamanca Michael Balogh Marco Barden Eric F. Bell Meghan E. Gray Chien Y. Peng David Bacon Fabio D. Barazza Asmus Böhm John A. R. Caldwell Anna Gallazzi Boris Häußler Catherine Heymans Knud Jahnke Shardha Jogee Eelco van Kampen Kyle Lane Daniel H. McIntosh Klaus Meisenheimer Casey Papovich Sebastian F. Sánchez y Taylor Lutz Wisotzki Xianzhong Zheng 《Monthly notices of the Royal Astronomical Society》2009,393(4):1302-1323
We investigate the properties of optically passive spirals and dusty red galaxies in the A901/2 cluster complex at redshift ∼0.17 using rest-frame near-ultraviolet–optical spectral energy distributions, 24-μm infrared data and Hubble Space Telescope morphologies from the STAGES data set. The cluster sample is based on COMBO-17 redshifts with an rms precision of σ cz ≈ 2000 km s−1 . We find that 'dusty red galaxies' and 'optically passive spirals' in A901/2 are largely the same phenomenon, and that they form stars at a substantial rate, which is only four times lower than that in blue spirals at fixed mass. This star formation is more obscured than in blue galaxies and its optical signatures are weak. They appear predominantly in the stellar mass range of log M * /M⊙ =[10, 11] where they constitute over half of the star-forming galaxies in the cluster; they are thus a vital ingredient for understanding the overall picture of star formation quenching in clusters. We find that the mean specific star formation rate (SFR) of star-forming galaxies in the cluster is clearly lower than in the field, in contrast to the specific SFR properties of blue galaxies alone, which appear similar in cluster and field. Such a rich red spiral population is best explained if quenching is a slow process and morphological transformation is delayed even more. At log M * /M⊙ < 10 , such galaxies are rare, suggesting that their quenching is fast and accompanied by morphological change. We note that edge-on spirals play a minor role; despite being dust reddened they form only a small fraction of spirals independent of environment. 相似文献