Spatial Extent Models for Natural Language Phrases Involving Directional Containment          下载免费PDF全文

Gaurav Singh  Rolf A. de By 《Transactions in GIS》2015,19(2):202-224

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Water resources in mountain regions: a methodological approach to assess the water balance in a highland‐lowland‐system     

Rolf Weingartner  Daniel Viviroli  Bruno Schädler 《水文研究》2007,21(5):578-585

Mountains and highlands are typically areas that provide considerable quantities of water, the latter being an important resource for the lowlands. These run‐off quantities remain discernible in the superior‐scale river systems and significantly contribute to the global water resources. Therefore, mountain regions ought to be given specific consideration with regard to management endeavours. Although well known in principle, details of water resources originating from mountains remain under discussion. A new approach has been introduced, which depicts the water balance of Switzerland in a spatially distributed manner, based on catchments of about 150 km². The main feature of this approach is the areal precipitation, which is calculated using run‐off, evaporation and storage change of glaciers, instead of being derived from gauged precipitation values. This methodology was selected because measurement and regionalization of precipitation remain subject to large uncertainties in mountainous areas. Subsequently, the view is widened to the European Alps, which, as compared with the surrounding lowlands, contribute considerably higher annual discharge, especially in the summer months. Finally, the focus is put on the hydrological significance of mountains in general. In dry regions, mountains, in particular, are indispensable contributors to the water resources downstream. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

A seismic field test with a Low-level Acoustic Combustion Source and Pseudo-Noise codes     

Bjørn Askeland  Bent Ole Ruud  Halvor Hobæk  Rolf Mjelde 《Journal of Applied Geophysics》2009,67(1):66-73

The Low-level Acoustic Combustion Source (LACS) which can fire its pulses at a high rate, has been tested successfully as a seismic marine source on shallow ice-age sediments in Byfjorden at Bergen, Norway. Pseudo-Noise pulsed signals with spiky autocorrelation functions were used to detect the sediments. Each transmitted sequence lasted 10 s and contained 43 pulses. While correlation gave a blurry result, deconvolution between the near-field recordings and the streamer recordings gave a clear seismic section. Compared to the section acquired with single air-gun shots along the same profile, the LACS gave a more clear presentation of the sediments and basement.  相似文献   

Magmatic evolution of the Andean Eastern Cordillera of Colombia during the Cretaceous: Influence of previous tectonic processes     

Mónica Vásquez  Uwe Altenberger  Rolf L. Romer  Masafumi Sudo  Juan Manuel Moreno-Murillo 《Journal of South American Earth Sciences》2010,29(2):171-186

The Eastern Cordillera of the Colombian Andes represents an inverted Cretaceous basin where Cretaceous magmatism is characterized by rare mafic dykes and sills. We use ⁴⁰Ar/³⁹Ar, Sr–Nd–Pb isotopes, as well as major and trace elements analyses of Cretaceous intrusions from both flanks of the Eastern Cordillera in combination with structural data to document the complex evolution of the basin. Magmatism, which is diachronous and geochemically diverse, seems to be related to mantle melting beneath the most subsiding segments of each sub-basin during enhanced extensional tectonics. The mafic intrusions display two different compositional series: an alkaline one with OIB-like pattern and a tholeiitic one with MORB-like features. This indicates at least two diverse mantle sources. Trace-element patterns suggest that the intrusions were emplaced in an extensional setting. ⁴⁰Ar/³⁹Ar dating on primary plagioclase and hornblende provides plateau ages between ～136 and ～74 Ma.The geochemical and temporal diversities show that the emplacement of the magmas was tectonically controlled, each sub-basin reflecting an individual subsidence event.  相似文献   

Interannual variability of NDVI and bird species diversity in Kenya     

Boniface O Oindo  Rolf A de By  Andrew K Skidmore 《International Journal of Applied Earth Observation and Geoinformation》2000,2(3-4)

Species richness, or simply the number of species in a given area, is commonly used as an important indicator of biological diversity. Spatial variability in species richness has been postulated to depend upon environmental factors such as climate and climatic variability, which in turn may affect net primary productivity. The Advanced Very High Resolution Radiometer (AVHRR) derived Normalized Difference Vegetation Index (NDVI) has been shown to be correlated with climatic variables including rainfall, actual evapotranspiration and net primary productivity. To determine factors favoring high species richness, we examined the relationship between interannual NDVI variables and species richness of birds at a quarter degree scale (55 × 55 km). Results revealed a strong positive correlation between species richness and maximum average NDVI. Conversely, species richness showed negative correlation with standard deviation of maximum NDVI and the coefficient of variation. Though these relationships are indirect, they apparently operate through the green vegetation cover. Understanding such relationships can help in mapping and monitoring biological diversity, as well as in estimating changes in species richness in response to global climatic change.  相似文献   

Undrained behaviour of silt under static and cyclic loading     

Yang Shaoli  Rolf Sandven  Lars Grande 《中国海洋大学学报(英文版)》2002,1(2):176-182

In this study, the undrained behaviour of silt under low stress level is studied. An effective preparation method for built—in silt samples in the triaxial test was firstly developed. By triaxial testing of samples at low confining pressures it was found that silt easily loses stability and liquefies. Loose silt may show temporary liquefaction under static loading, and develop full liquefaction under cyclic loading. The most important factors influencing the silt behaviour are porosity, confining pressure, consolidation state, cyclic loading level and number of cycles. The maximum obtainable shear stress is primarily a function of the confining pressure and the internal frictional angle. The actual structure of the silt material is the key factor in controlling its behaviour.  相似文献   

The Sabaloka ring complex revisited: palaeomagnetism and rockmagnetism     

H. C. Soffel  S. Saradeth  J. C. Briden  V. Bachtadse  C. Rolf 《Geophysical Journal International》1990,102(2):411-420

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Models of force-free magnetic fields in resistive media     

Rolf Boström 《Astrophysics and Space Science》1973,22(2):353-380

A review is given of some of the basic properties of force-free fields under circumstances when the conductivity of the medium is finite. Then the electric current density is related not only to the magnetic field, but also by Ohm's law to the electric field and plasma velocity, which must be considered in the solutions. It is pointed out that the natural constraint that the electric field and plasma velocity should be finite everywhere is not fulfilled in some previously used models. Models with a constant ratio of the electric current density and magnetic field intensity have been used extensively in the past. They are of some importance since solutions with the plasma at rest are possible only if is constant. However, it is shown that solutions of constant cannot be matched to an external current-free region of finite conductivity since can have no discontinuity in a medium where the conductivity varies continuously. Hence, for most applications models with a varying and a moving plasma must be used. Some new, simple and consistent models, especially of cylindrical symmetry, are derived by prescribing the form of the magnetic field lines, or one electic field component, or one time-dependent electric current component.  相似文献   

Optical microscope-cathodoluminescence (OM–CL) imaging as a powerful tool to reveal internal textures of minerals     

Jens Götze  Hans-Peter Schertl  Rolf D. Neuser  Ulf Kempe  John M. Hanchar 《Mineralogy and Petrology》2013,107(3):373-392

Optical microscope-cathodoluminescence (OM-CL) microscopy is a modern luminescence technique with widespread applications in geosciences. Many rock-forming and accessory minerals show specific CL properties that can be successfully used in geoscience and materials science research. One of the most spectacular applications is the visualization of growth textures, alteration, and other internal textures in minerals that are not discernible with other analytical techniques. These results provide information about the real structure of minerals and materials and can be used for the reconstruction of geological processes of mineral formation and subsequent alteration. The information obtained from CL imaging in combination with spectral measurements of the CL emission allows for a more thorough understanding of structural states of solids and/or trace-element incorporation. Additional information can be obtained when luminescence studies are combined with other analytical techniques with high sensitivity and high spatial resolution.  相似文献   

Contribution of Starlette,Stella, and AJISAI to the SLR-derived global reference frame   总被引：3，自引：3，他引：0  

Krzysztof Sośnica  Adrian Jäggi  Daniela Thaller  Gerhard Beutler  Rolf Dach 《Journal of Geodesy》2014,88(8):789-804

The contribution of Starlette, Stella, and AJISAI is currently neglected when defining the International Terrestrial Reference Frame, despite a long time series of precise SLR observations and a huge amount of available data. The inferior accuracy of the orbits of low orbiting geodetic satellites is the main reason for this neglect. The Analysis Centers of the International Laser Ranging Service (ILRS ACs) do, however, consider including low orbiting geodetic satellites for deriving the standard ILRS products based on LAGEOS and Etalon satellites, instead of the sparsely observed, and thus, virtually negligible Etalons. We process ten years of SLR observations to Starlette, Stella, AJISAI, and LAGEOS and we assess the impact of these Low Earth Orbiting (LEO) SLR satellites on the SLR-derived parameters. We study different orbit parameterizations, in particular different arc lengths and the impact of pseudo-stochastic pulses and dynamical orbit parameters on the quality of the solutions. We found that the repeatability of the East and North components of station coordinates, the quality of polar coordinates, and the scale estimates of the reference are improved when combining LAGEOS with low orbiting SLR satellites. In the multi-SLR solutions, the scale and the \(Z\) component of geocenter coordinates are less affected by deficiencies in solar radiation pressure modeling than in the LAGEOS-1/2 solutions, due to substantially reduced correlations between the \(Z\) geocenter coordinate and empirical orbit parameters. Eventually, we found that the standard values of Center-of-mass corrections (CoM) for geodetic LEO satellites are not valid for the currently operating SLR systems. The variations of station-dependent differential range biases reach 52 and 25 mm for AJISAI and Starlette/Stella, respectively, which is why estimating station-dependent range biases or using station-dependent CoM, instead of one value for all SLR stations, is strongly recommended. This clearly indicates that the ILRS effort to produce CoM corrections for each satellite, which are site-specific and depend on the system characteristics at the time of tracking, is very important and needs to be implemented in the SLR data analysis.  相似文献