The Radial Basis Functions Method for Improved Numerical Approximations of Geological Processes in Heterogeneous Systems     

Piret  Cécile  Dissanayake  Nadun  Gierke  John S.  Fornberg  Bengt 《Mathematical Geosciences》2020,52(4):477-497

Mathematical Geosciences - A robust, high order modeling approach is introduced, based on the finite difference-based radial basis functions method, for solving the groundwater flow equation in the...  相似文献   

On the importance of auroral processes in the Universe     

Bengt Hultqvist   《Journal of Atmospheric and Solar》2008,70(18):2235-2245

Acceleration of charged particles in magnetic field-aligned electric potential differences at Earth and at the outer planets in the solar system is summarized and its general importance in the Universe is briefly discussed.The role of field-aligned currents, driven by parallel electric fields, in causing filamentary structure in stellar atmospheres is briefly reviewed.The differences between auroral optical emissions at various planets are summarized.The important role of field-aligned potential differences in the generation of AKR and corresponding emissions from other objects is discussed.Finally, aurora-associated processes for ejection of planetary plasma into space are briefly reviewed.  相似文献   

Validation of very high cloud droplet number concentrations in air masses transported thousands of kilometres over the ocean     

Bengt G. Martinsson  Göran Frank  Sven&#;Inge Cederfelt  Olle H. Berg  Besim Mentes  Giorgos Papaspiropoulos  Erik Swietlicki  Jingchuan Zhou  Michael Flynn  Keith N. Bower  Tom W. Choularton  Jyrki Mäkelä  Aki Virkkula  Rita Van Dingenen 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):801-814

The microstructure of orographic clouds related to the aerosol present was studied during the second Aerosol Characterisation Experiment (ACE‐2). Very high cloud droplet number concentrations (almost 3000 cm⁻³) were observed. These high concentrations occurred when clouds formed on a hill slope at Tenerife in polluted air masses originating in Europe that had transported the order of 1000 km over the Atlantic Ocean. The validity of the measured droplet number concentrations was investigated by comparing with measurements of the aerosol upstream of the cloud and cloud interstitial aerosol. Guided by distributions of the ratios between the measurements, three criteria of typically 30% in maximum deviation were applied to the measurements to test their validity. Agreement was found for 88% of the cases. The validated data set spans droplet number concentrations of 150–3000 cm⁻³. The updraught velocity during the cloud formation was estimated to 2.2 m s⁻¹ by model calculations, which is typical of cumuliform clouds. The results of the present study are discussed in relation to cloud droplet number concentrations previously reported in the literature. The importance of promoting the mechanistic understanding of the aerosol/cloud interaction and the use of validation procedures of cloud microphysical parameters is stressed in relation to the assessment of the indirect climatic effect of aerosols.  相似文献   

Modelling cloud processing of aerosol during the ACE‐2 HILLCLOUD experiment     

Michael L. Flynn  Keith N. Bower  Thomas W. Choularton  Wolfram Wobrock  Jyrki M. Mäkelä  Bengt Martinsson  Göran Frank  Hans&#;Christen Hansson  Hans Karlsson  Paolo Laj 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):779-800

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The changing social relations of a community-based mangrove forest project in Zanzibar     

Fred Saunders  Salim M. Mohammed  Narriman Jiddawi  Karolina Nordin  Bengt Lundèn  Sara Sjöling 《Ocean & Coastal Management》2010,53(4):150-160

Coastal areas in East Africa are experiencing rapid economic, resource management, demographic and technological shifts. In response diverse Community-based Natural Resource Management (CBNRM) applications have been embraced to provide mutual conservation and use benefits. These initiatives have met with mixed success in practice. Reflecting on the limitations of past research using common pool resources theory theory to study CBNRM we use insights from actor oriented theory combined with satellite image analysis to describe and discuss the forces dynamically influencing institutional and mangrove forest cover change at Kisakasaka, Zanzibar focussing on the formal CBNRM project period between 1996 and 2001, but also considering the period before and after this. We examine the shifting social relations that affected the performance and viability of the formal CBNRM arrangements. An integrated approach was taken to the presentation and discussion of results where it was possible to enrich and expand explanations of socio-environmental change, which was driven by a lack of government support, the undermining effects of party political divisions, and the lack of institutional adaptive capacity. We conclude that this was a useful approach to explain CBNRM intervention events at Kisakasaka.  相似文献   

Synthetic stellar and SSP libraries as templates for Gaia simulations     

Rosanna Sordo  Antonella Vallenari  Rosaria Tantalo  France Allard  Ronny Blomme  Jean-Claud Bouret  Ines Brott  Yves Fremat  Christophe Martayan  Yassine Damerdji  Bengt Edvardsson  Eric Josselin  Bertrand Plez  Oleg Kochukhov  Mary Kontizas  Ulisse Munari  Tenay Saguner  Jean Zorec  Andreas Schweitzer  Paraskevi Tsalmantza 《Astrophysics and Space Science》2010,328(1-2):331-335

ESA’s Gaia mission will collect low resolution spectroscopy in the optical range for ～10⁹ objects. Complete and up-to-date libraries of synthetic stellar spectra are needed to built algorithms aimed to automatically derive the classification and the parametrization of this huge amount of data. In addition, libraries of stellar spectra are one of the main ingredients of stellar population synthesis models, aiming to derive the properties of unresolved stellar populations from their integrated light. We present (a) the newly computed libraries of synthetic spectra built by the Gaia community, covering the whole optical range (300–1100 nm) at medium-high resolution of (0.3 nm) for stars spanning the most different types, from M to O, from A-peculiar to Emission lines to White Dwarfs, and (b) the implementation of those libraries in our SSP code (Tantalo in The Initial Mass Function 50 Years Later, 327:235 2005), exploring different stellar evolution models.  相似文献   

Water Discharges Determined From Sediment Distributions: A Palaeohydrological Method   总被引：2，自引：0，他引：2  

Åke Sundborg  & Bengt Calles 《Geografiska Annaler: Series A, Physical Geography》2001,83(1-2):39-54

The article presents a simple sediment deposition model, based on current knowledge of the processes of transport and deposition of suspended material. It indicates possibilities of interpreting flow conditions from grain-size distributions at two localities, situated along the water flowline. The model reveals new information on ancient hydrological and sedimentological processes and events. Previously the model has been applied to forecast trap efficiency of reservoirs and predict reservoir sedimentation. In this study the model is used as a palaeohydrological method in studies of annual varves.
In varve geochronology a major attention has been paid to varve correlations and varve thickness variations, whereas other sedimentological data have been more or less disregarded. In this article new information on the spatial distribution of particle sizes demonstrate that further knowledge can be gained by careful studies of the patterns of grain-size distributions.
Annual variations in water discharges during late glacial time were studied in the Indalsälven and Dalälven valleys in Sweden. Water discharges during the deglaciation seem to have been of the same order of magnitude as in present-day rivers during normal years. During some years catastrophic events occurred, resulting in exceptional water discharges. The magnitudes of these discharges were estimated, and drainage directions were established. It appears from the studies that there are promising prospects of finding out both the magnitude and frequency of processes that until now have been described only in qualitative terms.  相似文献   

Effects on ground water caused by excavation of rock store caverns     

Ingemar Larsson  Akiva Flexer  Bengt Rosen 《Engineering Geology》1977,11(4):279-294

Unlined rock caverns for oil storage are very common in Sweden. Most of them are excavated in hard rocks (compact, non-carbonate, non-volcanic rocks). The fundamental idea of underground oil storage is that the rock caverns are located below the natural ground water level. Hereby the ground water keeps the oil inside the caverns and prevents products migration.

During the excavating period the water seeping through the fractures of a cavern is pumped up to avoid flooding. This discharge causes a local drop in the ground-water level around the cavern and a cone of depression develops.

A local study of the development of such a cone of depression has been made by means of a network of observation holes around the cavern. On enlargement of an oil storage (by constructing new caverns close to the old ones), the cone of depression moves according to the progress of the new excavations. This process has been studied and described in two cases.

Underground storages in Sweden are very often closely spaced in order to use common facilities such as entrance tunnel, pumping station, housing etc. Therefore an artificial ground-water divide sometimes must be arranged between different caverns in order to prevent products migration. This paper describes how such an artificial recharge of water between some caverns is made. The control of its effectiveness is shown as well as the method for sealing off undesirable leakage.  相似文献   

Changes in benthos following the clean-up of a severely metalpolluted cove in the Hudson River estuary: Environmental restoration or ecological disturbance?     

Brendan?P.?Kelaher  Jeffrey?S.?LevintonEmail author  Jamina?Oomen  Bengt?J.?Allen  Wai?Hing?Wong 《Estuaries and Coasts》2003,26(6):1505-1516

We studied changes in macrobenthic communities following the environmental clean-up of metal-polluted (cadmium, nickel, and cobalt) sediments in Foundry Cove, a small inlet within the Hudson River estuary of New York. We used a BACI-style experiment to test the hypotheses that high levels of cadmium in sediments change macrobenthic assemblages relative to unpolluted areas, and removal of metals (especially cadmium) by dredging will restore the benthos, such that benthic fauna in Foundry Cove are not different from unpolluted areas. In 1984, prior to the restoration work, there were no significant differneces between macrobenthic assemblages in polluted and unpolluted locations, indicating that cadmium had little effect on community structure. The lack of an observed toxicity effect may have been caused by the compensatory evolution of resistance to cadmium in dominant organisms. Six years after the restoration work and despite a substantial reduction in metal pollution, there were lower abundances of oligochaetes, nematodes, and chironomids and a higher abundance of polychaetes at Foundry Cove relative to reference locations. Correlative analyses identified greater sediment compaction caused by dredging at Foundry, Cove as a possible cause of faunal differences. The results demonstrate that it is difficult to accurately predict, the effects of anthropogenic disturbances and restorations in complex natural systems and that unforeseen side effects are inevitable. Documenting these unpredicted effects and experimentally understanding their causes in past restorations will greatly improve the success and cost-effectiveness of future projects of a similar type.  相似文献   

The production of lithium in the solar chromosphere and photosphere during white light flares     

Lennart Hultqvist 《Solar physics》1977,52(1):101-106

Recently new values of the lithium formation rate in low energy flares have been reported in the literature. These values are applied to the white light flare phenomenon on the Sun. It is found that the formation rate in the chromosphere is much larger than in the upper photosphere and that the ratio between the time integrated flare created abundance and the initial photospheric abundance is modest in the chromosphere and small in the upper photosphere. The yield of Li⁶ in the upper photosphere is, however, comparable to the upper limit of Li⁶ there.  相似文献