Intergalactic stars in z∼ 0.25 galaxy clusters: systematic properties from stacking of Sloan Digital Sky Survey imaging data     

Stefano Zibetti  Simon D. M. White  Donald P. Schneider  Jon Brinkmann 《Monthly notices of the Royal Astronomical Society》2005,358(3):949-967

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Snow water content estimation from measured snow temperature     

李志军  赵海清  冯恩民  程斌  卢鹏 《极地研究(英文版)》2007,18(1):1-7

The vertical temperature profiles of snow and sea ice have been measured in the Arctic during the 2nd Chinese National Arctic Research Expedition in 2003(CHINARE2003).The high-resolution temperature profile in snow is solved by one-dimensional heat transfer equation.The effective heat diffusivity,internal heat sources are identified.The internal heat source refers to the penetrated solar radiation which usually warms the lower part of the snow layer in summer.By temperature gradient analysis,the zero level can be clarified quantitatively as the boundary of the dry and wet snow.According to the in situ time series of vertical temperature profile,the time series of water content in snow is obtained based on an evaluation method of snow water content associated with the snow and ice physical parameters.The relationship of snow water content and snow temperature and temporal-spatial distribution of snow water content are presented  相似文献   

用全数字摄影测量系统高效获取4D数字产品的方法   总被引：2，自引：0，他引：2  

马东岭  丁宁  蔡菲 《地理空间信息》2009,7(4):69-71

以北京某地区为例，详细介绍利用JX-4C全数字摄影测量工作站制作4D（DRG、DLG、DEM、DOM）数字产品的作业方法，最后得出该地区的4D产品成果图。证明利用该方法制作4D产品的速度快、精度高，可广泛应用于测绘生产过程。  相似文献   

关于《地理信息-数据产品规范》标准的思考     

苏山舞  赵园春 《地理信息世界》2006,4(6):28-31

随着地理信息产品日益广泛的应用,生产者如何定义产品,用户又如何陈述对数据的需求亟需一个准确的技术描述,即数据产品规范。本文通过对国内外标准的介绍,阐述了采用ISO/TC21119131《Geographic information-Data product specifications》(《地理信息-数据产品规范》)标准的意义和必要性,并依据该标准简要介绍了数据产品规范的定义,并以北京市导航电子地图为例,描述了该数据产品的规范。  相似文献   

QINGHAI-XIZANG SURFACE LONG-WAVE RADIATION PARAMETERIZATION WITH ITS CLIMATIC CALCULATION          下载免费PDF全文

《Acta Meteorologica Sinica》1998,(2)

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Magnetic Properties of Metric Noise Storms Associated with Coronal Mass Ejections     

Ya-Yuan Wen  Jing-Xiu Wang  Yu-Zong Zhang National Astronomical Observatories  Chinese Academy of Sciences  Beijing   《中国天文和天体物理学报》2007,7(2):265-280

Using Nancay Radioheliograph (NRH) imaging observations, combined with SOHO/Michelson Doppler Imager (MDI) magnetogram observations and coronal magnetic field extrapolation, we studied the magnetic nature of metric noise storms that are associated with coronal mass ejections (CMEs). Four events are selected: the events of 2000 July 14, 2001 April 26, 2002 August 16 and 2001 March 28. The identified noise storm sources cover or partially cover the active regions (ARs), but the centers of storm sources are offset from the ARs. Using extrapolated magnetic field lines, we find that the noise storm sources trace the boundary between the open and closed field lines. We demonstrate that the disappearance of noise storm source is followed by the appearance of the burst source. The burst sources spread on the solar disk and their distributions correspond to the extent of the CME in LASCO C2 field of view. All the SOHO/Extreme Ultraviolet Imaging Telescope (EIT) dimmings associ- ated with noise storm sources are located at the periphery of noise storms where the magnetic lines of force were previously closed and low-lying. When the closed field becomes partially or fully open, the basic configurations of noise storm sources are changed, then the noise storm sources are no longer observed. These observations provide the information that the variations of noise storms manifest the restructuring or reconfiguring of the coronal magnetic field.  相似文献   

The role of afterglow break-times as gamma-ray burst jet angle indicators     

L. Nava  G. Ghisellini  G. Ghirlanda  J. I. Cabrera  C. Firmani  V. Avila-Reese 《Monthly notices of the Royal Astronomical Society》2007,377(4):1464-1472

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Measurements of transpiration in four tropical rainforest types of north Queensland,Australia     

David McJannet  Peter Fitch  Mark Disher  Jim Wallace 《水文研究》2007,21(26):3549-3564

Transpiration of four different rainforest types in north Queensland, Australia, was determined using the heat pulse technique for periods ranging between 391 and 657 days. Despite the complexity of the natural rainforest systems being studied, the relationship between sample tree size and daily water use was found to be strong, thus providing a robust means by which to scale transpiration from individual trees to the entire forest stand. Transpiration was shown to be dependent on solar radiation and atmospheric demand for moisture with little evidence of limitation by soil moisture supply. Total stand transpiration was controlled by forest characteristics such as stem density, size distribution and sapwood area. Annual transpiration for each of the four sites ranged between 353 mm for cloud forest and 591 mm for montane rainforest. In comparison with the international literature, transpiration from Australian rainforests is low; the reasons for this could be related to a combination of differences in forest structure, climatic conditions, canopy wetness duration and tree physiology. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Quantum tunneling makes a Reissner–Nordstrom black hole turn into a Kerr–Newman black hole under angular momentum conservation     

Wenbiao Liu 《Astrophysics and Space Science》2007,310(1-2):81-84

Hawking radiation can be viewed as a process of particle quantum tunneling near a black hole horizon. When a particle with angular momentum tunnels across the event horizon of a Reissner–Nordstrom black hole, the black hole will change into a Kerr–Newman one. In previous papers, axisymmetric black hole has been studied only when a keeps constant. Changing from Reissner–Nordstrom to Kerr–Newman should be a simple case when a varies. After this, more general radiation including changed a in Kerr or Kerr–Newman spacetimes can be studied in the future. The emission rate of the massless particles with angular momentum is calculated, and the result is consistent with an underlying unitary theory.   相似文献   

Interaction between nulls and emission in the pulsar B0834+06     

Joanna M. Rankin  Geoffrey A. E. Wright 《Monthly notices of the Royal Astronomical Society》2007,379(2):507-517

We present a detailed study of the single pulses of the bright radio pulsar B0834+06, and offer evidence that the dominant periodic modulation in this pulsar's emission governs the occurrence of nulls. The nulls of B0834+06 constitute approximately 9 per cent of the total pulses and we demonstrate that they do not occur at random in the pulse sequence. On the contrary, they are found to occur preferentially close to the minimum of the pulsar's emission cycle, whose period jitters around a central value of P ₃≈ 2.17 rotation periods. It is likely that the intrinsic duration of the nulls averages about 0.2 times the pulsar rotation period. Surprisingly, the clearly distinct population of nulls and partial nulls of B0834+06 exhibit a two-peak profile slightly broader than that of the normal emission. This is in contrast to the profile of extremely weak normal pulses, which is narrower than the overall profile. A flow/counterflow model for the pulsar's two components can reproduce the essential observed features of the emission in its dominant mode, with nulls occurring at the point where the minima of the two systems are aligned. This suggests that the observed nulling rate is determined by the chance positioning of our sightline with respect to the system. If the flow is interpreted as part of a circulating carousel, a fit yields a best estimate of 14 'sparks'.  相似文献