Is the dark halo of our Galaxy spherical?     

Amina Helmi 《Monthly notices of the Royal Astronomical Society》2004,351(2):643-648

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洛阳市供水前景预测及对策探讨     

王绍先  程孝生 《河南国土资源》1994,(3)

洛阳市地下水资源量丰质优，远期供水前景较为乐观。然而，由地下水开采引起的环境水文地质问题仍属客观存在。本文在供水前景预测的基础上，提出了五项对策，对城市远期供水规划具借鉴意义。  相似文献   

The formation of close binary systems by dynamical interactions and orbital decay     

Matthew R. Bate  Ian A. Bonnell  Volker Bromm 《Monthly notices of the Royal Astronomical Society》2002,336(3):705-713

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Continuous fluorescence assessment of organic matter variability on the Bournbrook River,Birmingham, UK     

Elfrida M. Carstea  Andy Baker  Gabriela Pavelescu  Ian Boomer 《水文研究》2009,23(13):1937-1946

Continuous monitoring of dissolved organic matter (DOM) character and concentration at hourly resolution is rare, despite the importance of analysing organic matter variability at high‐temporal resolution to evaluate river carbon budgeting, river water health by detecting episodic pollution and to determine short‐term variations in chemical and ecological function. The authors report a 2‐week experiment performed on DOM sampled from Bournbrook, Birmingham, UK, an urban river for which spectrophotometric (fluorescence, absorbance), physiochemical (dissolved organic carbon [DOC], electrical conductivity, pH) and isotopic (D/H) parameters have been measured at hourly frequency. Our results show that the river had sub‐daily variations in both organic matter concentration and characteristics. In particular, after relatively high‐magnitude precipitation events, organic carbon concentration increased, with an associated increase in intensity of both humic‐like and tryptophan‐like fluorescence. D/H isotopic ratio demonstrates different hydrological responses to different rainfall events, and organic matter character reflects this difference. Events with precipitation < 2 mm typically yielded isotopically heavy water with relatively hydrophilic DOM and relatively low specific absorbance. Events with precipitation > 2 mm had isotopically lighter water with higher specific absorbance and a decrease in the proportion of microbially derived to humic‐like fluorescence. In our heavily urbanized catchment, we interpret these signals as one where riverine DOM is dominated by storm sewer‐derived ‘old’ organic matter at low‐rainfall amounts and a mixed signal at high‐precipitation amounts where ‘event’ surface runoff‐derived organic matter dominate during storm sewer and combined sewer overflow routed DOM. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Effects of topography on the spatial distribution of evapotranspiration over a complex terrain using two‐source energy balance model with ASTER data     

H. K. Kafle  Y. Yamaguchi 《水文研究》2009,23(16):2295-2306

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奇异星壳层塌缩的数值研究     

贾建军  黄永锋 《天文学报》2004,45(1):33-41

当奇异星表面的电场不足以支撑整个壳层的时候,壳层就有可能全部落入奇异核中.对这一过程的研究,可以为观测上证认奇异星提供一些可能的理论线索.数值计算表明,底部密度为-8.3×1010gcm-3,亦即质量为-3 4×10-6M(?)的壳层在约5.4×10-3s时间内塌缩到奇异核中,可导致一次持续约0.15s的爆发事件.在过程中平均每个重子释放约6.3 MeV的能量,总辐射能则可高达-1046-1047ergs.这可以用来解释宇宙中一些爆发现象.  相似文献   

水污染物浓度的神经网络预测模式及效果检验     

于扬  薛丽梅  聂伊辰 《成都信息工程学院学报》2004,19(1):100-103

污染物浓度预测是环境保护的重要内容,将神经网络用于水中有机污染物浓度的预测并对效果进行检验.结果表明,预测值与观测值符合较好.  相似文献   

Bipolar outflow on the asymptotic giant branch – the case of IRC+10011     

Dejan Vinkovi&#;  Thomas Blöcker  Karl-Heinz Hofmann  Moshe Elitzur  Gerd Weigelt 《Monthly notices of the Royal Astronomical Society》2004,352(3):852-862

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HAXTEL: A Laue lens telescope development project for a deep exploration of the hard X-ray sky (> 60 keV)     

F. Frontera  A. Pisa  G. Loffredo  D. Pellicciotta  V. Carassiti  F. Evangelisti  K. Andersen  P. Courtois  L. Amati  E. Caroli  T. Franceschini  G. Landini  S. Silvestri  J. Stephen 《Experimental Astronomy》2005,20(1-3):241-251

A review of the HAXTEL project devoted to the development of a Laue lens telescope for hard X-/gamma-ray observation of the continuum spectra of celestial sources is presented. Main design properties, open issues, the status of the project and an example of multi-lens configuration with sensitivity expectations are discussed.  相似文献   

Geochronology and geochemistry of lithium-rich tuffs in the Sichuan basin,western Yangtze: Implication for the magmatic origin and final closure of eastern Paleo-Tethys     

《地学前缘(英文版)》2023,14(1):101480

The felsic volcanogenic tuffs named “green-bean rocks” (GBRs), characterized by a green or yellowish green color, are widely distributed in the western Yangtze platform and have a high lithium content (286–957 ppm). This paper studies the ages, origin and tectonic setting of the GBRs in the Sichuan basin on the western margin of the Yangtze platform through the whole-rock geochemistry and zircon trace elements by using U–Pb dating and Hf–O isotopes. The GBR samples from the Quxian and Beibei sections yielded zircon U–Pb ages of 245.5 ± 1.8 Ma and 244.8 ± 2.2 Ma. These samples can be used as the isochronous stratigraphic marker of the Early–Middle Triassic boundary (EMTB) for regional correlation. The whole-rock and zircon geochemistry, and zircon Hf–O isotopes exhibited S-type geochemical affinities with high positive δ¹⁸O values (9.28‰–11.98‰), low negative ε_Hf(t) values (?13.87 to ? 6.79), and T_DM² ages of 2150–1703 Ma, indicating that the lithium-rich GBRs were generated by the remelting of the pre-existing ancient Paleoproterozoic layer without mantle source contamination in the arc-related/orogenic tectonic setting. The results of this study demonstrate that the lithium-rich GBRs in the western Yangtze platform were derived from arc volcanic eruptions along the Sanjiang orogen, triggered by the closure of the eastern Paleo-Tethys Ocean and the syn-collision between the continental Indochina and Yangtze blocks at ca. 247 Ma. This was marked by a major shift from I-type magmas with intermediate ε_Hf(t) values to S-type magmas with low negative ε_Hf(t) values. Collectively, our results provide new insights into the origin of the GBRs and decodes the closure of the eastern Paleo-Tethys.  相似文献