Hydrodynamical models of elliptical galaxies     

E. Moreno  P. Pi§mi§ 《Celestial Mechanics and Dynamical Astronomy》1988,45(1-3):81-82

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Correction to: Observational Investigation of the Statistical Properties of Surface-Layer Turbulence in a Suburban Area of São Paulo,Brazil: Objective Analysis of Scaling-Parameter Accuracy and Uncertainties     

da Silveira  Lucas Cardoso  de Oliveira  Amauri Pereira  Sánchez  Maciel Piñero  Codato  Georgia  Ferreira  Maurício Jonas  Filho  Edson Pereira Marques  Božnar  Marija Zlata  Mlakar  Primož 《Boundary-Layer Meteorology》2022,185(2):197-197

Boundary-Layer Meteorology -  相似文献   

Multi‐scale assessment of overflow‐driven lateral connectivity in floodplain and backwater channels using LiDAR imagery          下载免费PDF全文

Katarina Džubáková  Hervé Piégay  Jérémie Riquier  Milan Trizna 《水文研究》2015,29(10):2315-2330

Overflow‐driven lateral connectivity significantly influences the spatial distribution and diversity of floodplain habitats and biota. Proper understanding of lateral connectivity in floodplain and backwater channels is therefore critical for assessment of river quality and for targeting management or restoration actions. In this study, we present a methodological framework for spatial and temporal assessments of overflow‐driven lateral connectivity at two spatial scales: bypass reach and backwater channel. Firstly, we compute the relative elevations, as well as overflow discharge, duration, and frequency using a simple, raster‐based method that uses a LiDAR digital elevation model (DEM), rating curves, and streamflow time series. Subsequently, we analyse the accuracy of this approach with respect to the accuracy of a DEM and evaluate its further applications. Altogether, four 10‐km‐long bypass reaches and 11 backwater channels are analysed, located along the Rhône River corridor in France. The results proved the precision of the method to be affected by the LiDAR DEM accuracy, which was on average more precise in a typically homogeneous floodplain setting rather than for backwater channel plugs with pronounced topographic complexity and usually riparian forest canopy. Amongst the four studied reaches, Brégnier Cordon proved to have the greatest flooding dynamics, followed by Belley and Chautagne. The hydrological connectivity pattern of Pierre Bénite differed significantly. Three longitudinal patterns of hydrological connectivity of backwater channels displayed stepwise advancement of the water. The presented results can be used to assess ecological potential of floodplain habitats and their historic and prospective evolution through time. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

First-order phase transitions in rotating hybrid stars and pulsar glitches     

Fei Xiao  Chun-Mei Pi  Shu-Hua Yang  Ai-Zhi Zhou  Xiao-Ping Zheng 《中国天文和天体物理学报》2011,(6)

The first order deconfinement phase transitions in rotating hybrid stars are studied and it is found that if the surface tension is sufficiently large, the transition from metastable hadron matter to stable mixed hadron-quark matter during the spindown history of a hybrid star can cause a glitch.  相似文献   

胜利油田滩浅海地区地震勘探技术   总被引：9，自引：2，他引：7  

崔汝国  王彦春  曹国滨  皮金云 《物探与化探》2006,30(5):441-445

滩浅海地区由于特殊的地表条件和复杂多变的表层结构,既不同于陆上勘探也不同于海上勘探,尤其在两栖地带存在海陆2种施工方式。笔者对滩浅海地区地震勘探的激发震源、检波器和观测系统等野外采集各环节进行了系统研究,提出解决滩浅海地区野外难以采集到高品质地震资料问题的方法,开展了地震记录上的干扰波压制、差异校正等方面的深入研究,形成一整套适用于滩浅海地区油气资源探查的高精度实用性的特色技术,取得了较好的地质效果。  相似文献   

库布齐沙漠治理对京津冀地区空气质量影响:2017年5月3-6日沙尘天气模拟     

魏巍  张稳定  陈焕盛  任远哲  皮冬勤  吴剑斌  陈婷婷  肖林鸿  罗保刚  晏平仲 《中国沙漠》2020,40(1):77-87

作为影响京津冀地区的沙尘途经地和发源地，对库布齐沙漠的治理工作一直在持续，成为使用科学技术手段将沙漠变废为宝、变害为利的成功案例，同时也是全球治沙范例。为研究库布齐沙漠治理工作对京津冀地区空气质量的改善效果，利用手工采样数据和城市空气质量监测数据，结合气团轨迹，筛选库布齐沙漠起沙并对京津冀地区产生影响的沙尘天气。选取2017年5月3-6日作为典型个例代表，使用嵌套网格空气质量预报模式系统（NAQPMS），设计不同的起沙权重系数敏感试验，模拟研究该地区起沙和治理对京津冀地区的空气质量影响。结果表明：（1）气象模式较好地把握天气系统的演变以及地面风场的特征，保证NAQPMS模式可合理模拟沙尘的起沙区域、影响范围以及时空演变特征；（2）受沙尘影响城市的PM₁₀浓度模拟量值及变化与观测较为一致，表明模式合理再现了沙尘的输送过程；（3）库布齐沙漠起沙对京津冀地区的PM₁₀浓度贡献为35~150 μg·m^-3，贡献比例为10%~40%；（4）库布齐沙漠治理可使京津冀地区PM₁₀浓度降低35~75 μg·m^-3，下降比例为5%~20%，受影响城市PM₁₀浓度下降比例为7%~37%，沙漠治理工作可有效降低受影响地区的PM₁₀浓度。  相似文献   

Debris-flow susceptibility of upland catchments     

Mélanie Bertrand  Frédéric Liébault  Hervé Piégay 《Natural Hazards》2013,67(2):497-511

Over the last three decades, many regional studies in mountain ranges under temperate climate revealed that it is possible to discriminate debris-flow and fluvial fans from morphometric indicators measured at the scale of the catchment and the fan itself. The most commonly used indicators are the Melton index (R), a normalized index of the gravitational energy of the catchment, and the fan slope (S). A wide range of thresholds have been proposed for discriminating purpose, but these are generally based on a small population of catchments and may be highly influenced by ambiguous fans included in the data set. A database of 620 upland catchments from several mountain ranges under temperate climate was compiled from the literature to propose robust discriminant morphometric thresholds for debris-flow versus fluvial responses. Linear discriminant analysis (LDA) and logistic regression (LR) were performed using the whole data set, and a leave-one-out cross-validation was used to evaluate performances of the models. Sensitivity and specificity scores obtained for LDA and LR were 0.96 and 0.73, and 0.95 and 0.75, respectively. It is also shown that the channel slope above which debris-flow is observed decreases with the gravitational energy of the catchment. Limitations of the morphometric discrimination are discussed.  相似文献   

Ceilometer observations of the boundary layer over Warsaw,Poland     

Iwona S. Stachlewska  Michał Piądłowski  Szymon Migacz  Artur Szkop  Anna J. Zielińska  Paweł L. Swaczyna 《Acta Geophysica》2012,60(5):1386-1412

Jenoptik’s CHM 15k ceilometer was used to monitor the vertical structure of the atmospheric boundary layer (ABL) over Warsaw, from 2008 until 2011, on Mondays and Thursdays, in 24h periods. Hereby, we present an assessment of the signal-to-noise ratio along with a sensitivity study of signal smoothing methods developed in-house. With the proposed averaging, ceilometer attenuated-backscatter signals reached the high troposphere, which makes this sensor competitive to a single-wavelength elastic lidar. The smoothed signals were employed as an input for algorithms developed to automatically detect the ABL height, clouds, fog, and precipitation in the lower troposphere. The classification of weather conditions was validated by the METAR reports from the Warsaw Airport. The obtained ABL heights were compared to those assessed from radio-soundings from a nearby meteorological station WMO12374 in Legionowo. An inter-comparison of the ABL heights, derived by using the Jenoptik’s automated routine against the in-house developed algorithms, is in favor of the latter. The presented four annual cycles of the ABL height, obtained with various derivative-based methods, are the first such long-term results reported using the CHM 15k sensor in Eastern Europe.  相似文献   

Floods at the northern foothills of the Tatra Mountains — A Polish-Swiss research project   总被引：1，自引：1，他引：0  

Zbigniew W. Kundzewicz  Markus Stoffel  Ryszard J. Kaczka  Bartłomiej Wyżga  Tadeusz Niedźwiedź  Iwona Pińskwar  Virginia Ruiz-Villanueva  Ewa Łupikasza  Barbara Czajka  Juan Antonio Ballesteros-Canovas  Łukasz Małarzewski  Adam Choryński  Karolina Janecka  Paweł Mikuś 《Acta Geophysica》2014,62(3):620-641

The present paper introduces the topical area of the Polish-Swiss research project FLORIST (Flood risk on the northern foothills of the Tatra Mountains), informs on its objectives, and reports on initial results. The Tatra Mountains are the area of the highest precipitation in Poland and largely contribute to flood generation. The project is focused around four competence clusters: observation-based climatology, model-based climate change projections and impact assessment, dendrogeomorphology, and impact of large wood debris on fluvial processes. The knowledge generated in the FLORIST project is likely to have impact on understanding and interpretation of flood risk on the northern foothills of the Tatra Mountains, in the past, present, and future. It can help solving important practical problems related to flood risk reduction strategies and flood preparedness.  相似文献   

西班牙交通基础设施与城市体系建设     

Lois-GonzálezRubénC  Piñeira-MantiñánMJ  翟炜  顾朝林 《地理研究》2016,35(7):1353-1369

从社会和地方融合、均衡性与土地异质性、交通网等级体系和支路网与交通可持续性四个角度探讨西班牙交通基础设施网建设对土地开发和土地规划相关国家法规的影响。从城市地理学视角分析中央政府基于改善城市和区域连接度和可达性进行的高速公路网、高铁网、机场和港口等交通基础设施规划,通过1950年代以来土地开发和房价涨跌、新兴产业培育和交通状况改善刺激不同级别城市蔓延和分化的人口增长,重塑西班牙国家城市体系格局。随后,概括了蔓延的城市增长模式和房地产与交通投资泡沫破裂后带给区域增长中心的影响,对通过交通基础设施规划进行投机性投资政策进行了批评。最后建议中央政府应该避免投机投资行为,基于现有的城市体系层级改善核心城市和大城市周边的机动性,优化基础设施建设,建立新的城市与区域增长模式。  相似文献