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991.
研究区域水资源不平衡背后的“俱乐部趋同”现象,对于水资源调节以及水资源均衡配置具有重要的理论和实践意义。基于2004-2015年我国31个省(市、区)的人均水资源数据,利用扩展的马尔科夫链模型检测了不同时长下我国省际水资源量分布的俱乐部趋同现象,并分析了其时间特征。结果表明:即使在5 a的时间积累下,我国人均水资源量仍存在着明显的俱乐部趋同现象,高水平和低水平地区水资源量分布高度固化,且俱乐部趋同程度在2008年开始向恶化的趋势发展,可见当前我国区域水资源调节力度有待进一步加强。最后论文根据各地区人均水资源在考察期各年所属俱乐部类型、类型转移频率等因素对各地区进行了分类,以对区域水资源调节提供支持和参考。 相似文献
992.
Determining absolute surface ages for bodies in the Solar System is, at present, only possible for Earth and Moon with radiometric dating for both bodies and biologic proxies such as fossils for Earth. Relative ages through cratering statistics are recognized as one of the most reliable proxies for relative ages, calibrated by lunar geologic mapping and Apollo program sample returns. In this work, we have utilized the Mars Reconnaissance Orbiter’s ConTeXt Camera’s images which provide the highest resolution wide-scale coverage of Mars to systematically crater-age-date the calderas of 20 of Mars’ largest volcanoes in order to constrain the length of time over which these volcanoes - and major volcanic activity on the planet, by extension - were active. This constitutes the largest uniform and comprehensive research on these features to date, eliminating unknown uncertainties by multiple researchers analyzing different volcanoes with varied data and methods. We confirm previous results that Mars has had active volcanism throughout most of its history although it varied spatially and temporally, with the latest large-scale caldera activity ending approximately 150 ma in the Tharsis region. We find a transition from explosive to effusive eruption style occurring in the Hesperian, at approximately 3.5 Ga ago, though different regions of the planet transitioned at different times. Since we were statistically complete in our crater counts to sizes as small as ∼60 m in most cases, we also used our results to study the importance of secondary cratering and its effects on crater size-frequency distributions within the small regions of volcanic calderas. We found that there is no “golden rule” for the diameters secondaries become important in crater counts of martian surfaces, with one volcano showing a classic field of secondaries ∼2 crater diameters from the center of its primary but not affecting the size-frequency distribution, and another clearly showing an influence but from no obvious primary. 相似文献
993.
This paper deals about pure hydrodynamic and radiation hydrodynamic codes developed at LUTH, dedicated to astrophysical simulations.
The studied phenomena in this area are often encountered at high Mach number and in a radiation regime where no a priori assumption can be made on the radiation transfer. The radiative hydrodynamic code HADES has to can perform simulations as
well as any optical depths, from smallest to highest. Validation of numerical schemes or physical assumptions will be made
by laboratory astrophysical experiments. Therefore a very wide domain of initial conditions has to be accepted for computing.
A succinct presentation of three codes is done, accompanied with some astrophysical applications. 相似文献
994.
Giorgio Perrotta M. Stipa D. Silvi S. Coltellacci G. Curti G. Colonna T. Formica V. Casali T. Fossati F. Di Matteo M. Zelli M. Rinaldi L. Ansalone A. Di Salvo 《Experimental Astronomy》2011,32(1):63-82
The Mission MAGIA (Missione Altimetrica Geofisica GeochImica lunAre) was proposed in the framework of the ??Bando per Piccole Missioni?? of ASI (Italian Space Agency) in 2007. The mission was selected for a phase A study by ASI on February 7th 2008. The tight budget allocation, combined with quite ambitious scientific objectives, set challenging requirements for the satellite design. The paper gives a fast overview of the payloads complement and of the mission-constrained design drivers, including cost minimization, risk reduction, and AIT flexibility. The spacecraft architecture is then outlined, along with an overview of the key subsystems and trade-offs. Some details are given of a Moon gravitometric experiment based on a mother?Cdaughter satellite configuration with the daughter being a subsatellite released from the MAGIA satellite and intended to circle the Moon at a very low altitude. Budgets are appended at the end of the paper showing the key study results. 相似文献
995.
996.
Francesco Di Benedetto Francesco D’Acapito Fabio Capacci Gabriele Fornaciai Massimo Innocenti Giordano Montegrossi Werner Oberhauser Luca A. Pardi Maurizio Romanelli 《Physics and Chemistry of Minerals》2014,41(3):215-225
We investigated the speciation of Fe in bulk and in suspended respirable quartz dusts coming from ceramic and iron-casting industrial processes via X-ray absorption spectroscopy, with the aim of contributing to a better understanding of the variability of crystalline silica toxicity. Four different bulk industrial quartz powders, nominally pure quartz samples with Fe contents below 200 ppm, and three respirable dusts filters were selected. Fe speciation was determined in all samples through a coupled study of the X-ray absorption near-edge structure and extended X-ray absorption fine structure regions, operating at the Fe–K edge. Fe speciation revealed common features at the beginning of the different production processes, whereas significant differences were observed on both respirable dusts and bulk dusts exiting from the production process. Namely, a common pollution of the raw quartz dusts by elemental Fe was evidenced and attributed to residuals of the industrial production of quartz materials. Moreover, the respirable samples indicated that reactivity occurs after the suspension of the powders in air. The gravitational selection during the particle suspension consistently allowed us to clearly discriminate between suspended and bulk dusts. On the basis of the obtained results, we provide an apparent spectroscopic discrimination between the raw materials used in the considered industrial processes, and those that are effectively inhaled by workers. In particular, an amorphous FeIII oxide, with an unsaturated coordination sphere, can be related to silica reactivity (and health consequences). 相似文献
997.
998.
准确反演区域尺度的蒸散发对于水资源循环、气候变化、科学灌溉及干旱与洪涝监测等方面的研究具有重要的科学意义,本文以漳河灌区为典型案例,构建了遥感蒸散发的SEBS模型,验证了其精度,分析了其时空规律。结果表明:①2009—2018年钟祥、荆门、团林站点的(蒸散发) ET观测值与模拟值的平均相关系数分别为0.86、0.84和0.83,RMSE平均值分别为0.61、0.67和0.62 mm/d。年际间的ET观测值与模拟值变化幅度均小于10%,相关系数范围为0.7~0.9,RMSE范围为0.4~0.8 mm/d,标准差比率范围为0.8~1.5。②研究区2009—2018年ET的平均值为427.34 mm,整体呈上升趋势。③年尺度、季尺度和月尺度ET与气温和降水在时间序列上均有较好的一致性。多时间尺度ET均呈东北和西南部高、西部低的空间分布特征。研究结果能够较好地呈现ET的高时空异质特征和年际间空间差异,本文将为漳河灌区水资源开发管理和科学灌溉提供科学依据。 相似文献
999.
为准确刻画资料缺乏、地表水–地下水转换频繁的泽令沟盆地地表水?地下水不同时空尺度上的转换关系,利用河道径流数据、遥感蒸散发数据、地下水位观测数据等对SWAT-MODFLOW耦合模型进行率定和验证,在此基础上对泽令沟盆地水循环过程进行模拟分析。结果显示:① SWAT-MODFLOW耦合模型模拟效果较好,率定期和验证期月径流量的R2≥0.73,NSE≥0.67,PBIAS在?20%~20%。其各子流域实际蒸散发的R2均大于0.91,NSE均大于0.85,PBIAS在?10%~10%。此外,模拟地下水位与实测值误差在0.6 m以内,R2为0.94。② 地表水补给地下水的河道占整个河道长度90.31%,年平均补给量占年总交换水量的50.20%;季节尺度上,补给的最大值出现在7月,为331043.31 m3/d,最小值出现在12月份,为41208.33 m3/d。地下水对地表水的补给量较为稳定,季节性变幅在?2.5%~2.5%,年际变幅处于?6.5%~0.6%之间。 相似文献
1000.