Comment on Special Issue on Geostatistics with Guest Editor A. G. Journel     

Kyrre Bratvedt  Erik Bølviken  Tore Gimse  Helge Holden  Lars Holden  Ragnar Knarud 《Mathematical Geology》1998,30(2):245-246

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Permeability and stress in crystalline rocks   总被引：2，自引：0，他引：2  

David Banks  Noelle E. Odling  Helge Skarphagen  Erik Rohr-Torp 《地学学报》1996,8(3):223-235

Groundwater from crystalline rocks is a significant resource in many areas of the world. It is also an important medium for contaminant transport from, for example, deep nuclear waste repositories. Stress distributions in fractured rocks are important in controlling groundwater flow in several ways: (i) palaeostress fields are responsible for the evolution of fracture systems which transmit groundwater; (ii) current in situ stress fields will influence the shape and aperture of fractures; (iii) humans can influence the natural stress field in a rock mass to enhance fracture flows. The significance of stresses for groundwater flow can be investigated by field techniques (hydraulic fracturing), laboratory techniques (stress cells) or by numerical modelling.  相似文献   

Zum Werdegang der Erze     

Helge G. Backlund 《International Journal of Earth Sciences》1941,32(1-2):60-66

Ohne Zusammenfassung  相似文献   

A Laboratory-Testing-Based Study on the Strength,Deformability, and Dilatancy of Carbonate Rocks at Low Confinement     

G. Walton  J. Arzúa  L. R. Alejano  M. S. Diederichs 《Rock Mechanics and Rock Engineering》2015,48(3):941-958

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Sensitivity analysis of 18 different potential evapotranspiration models to observed climatic change at German climate stations   总被引：3，自引：0，他引：3  

Helge Bormann 《Climatic change》2011,104(3-4):729-753

Potential evapotranspiration models very often are important part of hydrological catchment models to calculate potential evapotranspiration (PET) which then is used to estimate actual evapotranspiration considering the soil moisture status. As many different approaches exist, the question arises in which way the choice of the PET model affects the impact of climate change on the calculated water balance? Therefore, 18 different PET models were compared with respect to their sensitivity to observed climate change. Long-term climate data of six German climate stations were used to identify changes in the climate data itself and changes in the calculated PET. The results show that all investigated PET models are sensitive to significant trends in climate data. However, it is also shown that all models show different sensitivities, and that the sensitivities cannot be grouped in terms of different types of PET models such as the aerodynamic concept, radiation or temperature based approaches and combination equations. Predominantly, the variability within a group of models of the same type is comparable to the variability between different model types. Therefore it can be concluded that PET models should be validated in a regional context before they are applied to a certain region within a climate change study despite the poor availability of long-term PET measurements.  相似文献   

The Cretaceous/Tertiary boundary: sedimentology and micropalaeontology at El Mulato section, NE Mexico     

L. Alegret  I. Arenillas  J. A. Arz  C. Liesa  A. Meléndez  E. Molina  A. R. Soria  E. Thomas 《地学学报》2002,14(5):330-336

ABSTRACT In the El Mulato section (NE Mexico), the Upper Cretaceous marly Méndez and the Lower Palaeogene marly Velasco Formations are separated by a clastic unit. Benthic foraminifera from both marly formations indicate lower bathyal depths. The clastic unit, in contrast, contains platform sands, muddy pebbles and neritic (shallow) faunas mixed with microspherules, indicating that it was allochthonously deposited into the deep basin. The diversity and the variability in origin of the components in the clastic unit, and its sedimentological features, support a model of deposition by turbidity currents related to mass-wasting processes triggered by the Cretaceous/Tertiary (K/T) boundary impact. Planktic foraminifera were affected by a catastrophic extinction at the K/T boundary, whereas benthic foraminifera show reorganization of the community structure rather than significant extinction. The benthic faunal turnover may have resulted from the drop in primary productivity after the asteroid impact at the end of the Cretaceous.  相似文献   

The effect of diapycnal mixing on the ventilation and CFC-11 uptake in the Southern Ocean     

Yongqi GAO  Helge DRANGE 《大气科学进展》2004,21(5):755-766

1. Introduction Ocean General Circulation Models (OGCMs) arekey tools in the assessment of the future ocean up-take of atmospheric greenhouse gases and heat. Fur-thermore, whereas nature experiences one realisationof the climate state, climate models can be used as alaboratory to produce a multitude of climate realisa-tions, and by that contribute to the understanding ofthe variability and stability properties of the system.It is, in this respect, crucial to evaluate the climatemodels ag…  相似文献   

The formation and structure of cleantech clusters: Insights from San Diego,Dublin, and Graz     

Helge Lea Tvedt 《Norsk geografisk tidsskrift. Norwegian journal of geography》2019,73(1):53-64

ABSTRACT

In recent years cleantech (clean technology) clusters have emerged in many industrialized regions. Cleantech clusters are heralded as a key solution in the transformation toward a greener economy, with the potential to foster regional economic growth while simultaneously mitigating environmental challenges. Despite witnessing a growing tendency for cleantech activities to be organized in clusters, the research literature remains rather vague on what cleantech clusters are and how they emerge. The author therefore explores these questions with the use of empirical data from three internationally recognized cleantech clusters: (1) Cleantech San Diego, in Southern California, USA, (2) Green Tech Valley, located in the province of Styria, Austria, and (3) Sustainable Nation Ireland, located in the Dublin region, Ireland. The data and information used in the article were derived from empirical accounts sourced from existing literature, secondary data sources, on-site observations, and face-to-face interviews carried out between October 2015 and June 2016. The findings show that the cleantech clusters can be perceived as knowledge, innovation, and collaboration clusters that span industrial and institutional boundaries. The formation of the cleantech clusters is largely the outcome of strategic leadership on the one hand, and place-specific conditions and local capabilities on the other hand.  相似文献   

Effects of the bottom boundary condition in numerical investigations of dense water cascading on a slope     

Jarle Berntsen  Guttorm Alendal  Helge Avlesen  Øyvind Thiem 《Ocean Dynamics》2018,68(4-5):553-573

The flow of dense water along continental slopes is considered. There is a large literature on the topic based on observations and laboratory experiments. In addition, there are many analytical and numerical studies of dense water flows. In particular, there is a sequence of numerical investigations using the dynamics of overflow mixing and entrainment (DOME) setup. In these papers, the sensitivity of the solutions to numerical parameters such as grid size and numerical viscosity coefficients and to the choices of methods and models is investigated. In earlier DOME studies, three different bottom boundary conditions and a range of vertical grid sizes are applied. In other parts of the literature on numerical studies of oceanic gravity currents, there are statements that appear to contradict choices made on bottom boundary conditions in some of the DOME papers. In the present study, we therefore address the effects of the bottom boundary condition and vertical resolution in numerical investigations of dense water cascading on a slope. The main finding of the present paper is that it is feasible to capture the bottom Ekman layer dynamics adequately and cost efficiently by using a terrain-following model system using a quadratic drag law with a drag coefficient computed to give near-bottom velocity profiles in agreement with the logarithmic law of the wall. Many studies of dense water flows are performed with a quadratic bottom drag law and a constant drag coefficient. It is shown that when using this bottom boundary condition, Ekman drainage will not be adequately represented. In other studies of gravity flow, a no-slip bottom boundary condition is applied. With no-slip and a very fine resolution near the seabed, the solutions are essentially equal to the solutions obtained with a quadratic drag law and a drag coefficient computed to produce velocity profiles matching the logarithmic law of the wall. However, with coarser resolution near the seabed, there may be a substantial artificial blocking effect when using no-slip.  相似文献   

The role of eddies on pathways,transports, and entrainment in dense water flows along a slope     

Berntsen  Jarle  Alendal  Guttorm  Avlesen  Helge 《Ocean Dynamics》2019,69(7):841-860

Ocean Dynamics - The flow of dense water along slopes has been investigated in several numerical investigations based on the Dynamics of Overflow Mixing and Entrainment (DOME) setup. In the present...  相似文献