Predictive permeability variations in a Hermod sand reservoir,Stine Segments,Siri Field,Danish North Sea     

Jesper Stokkendal  Henrik Friis  Johan B. Svendsen  Mette Lise K. Poulsen  Lars Hamberg 《Marine and Petroleum Geology》2009

The Hermod sand of the Stine Segments, Siri Field, Danish North Sea, displays large permeability variations (1–600 mD). These permeability variations represent horizontal layering in the reservoir, largely formed by diagenetic processes. They have a significant impact on reservoir performance, because horizontal producers in fairly thin reservoirs (∼30 m) are protected against bottom-water influx and can produce water-free for long periods of time.  相似文献   

Glacial history of the Greenland Ice Sheet and a local ice cap in Qaanaaq,northwest Greenland     

Anne Sofie Sndergaard  Nicolaj Krog Larsen  Jesper Olsen  Astrid Strunk  Sarah Woodroffe 《第四纪科学杂志》2019,34(7):536-547

In this study, we present new information on the glacial history of the Greenland Ice Sheet (GrIS) and a local ice cap in Qaanaaq, northwest Greenland. We use geomorphological mapping, ¹⁰Be exposure dating of boulders, analysis of lake cores, and ¹⁴C dating of reworked marine molluscs and subfossil plants to constrain the glacial history. Our ¹⁴C ages of reworked marine molluscs reveal that the ice extent in the area was at or behind its present‐day position from 42.2 ± 0.4 to 30.6 ± 0.3k cal a BP after which the GrIS expanded to its maximum position during the Last Glacial Maximum. We find evidence of early ice retreat in the deep fjord (Inglefield Bredning) at 11.9 ± 0.6 ka whereas the Taserssuit Valley was deglaciated ~4 ka later at 7.8 ± 0.1k cal a BP. A proglacial lake record suggests that the local ice cap survived the Holocene Thermal Maximum but moss kill‐dates reveal that it was smaller than present for a period of time before 3.3 ± 0.1k until 0.9 ± 0.1k cal a BP, following which the ice in the area expanded towards its Little Ice Age extent. Copyright © 2019 John Wiley & Sons, Ltd.  相似文献   

Kinematics and Dynamics of the Galactic Stellar Halo     

Jesper Sommer-Larsen 《Astrophysics and Space Science》1999,265(1-4):123-131

The structure, kinematics and dynamics of the Galactic stellar halo are reviewed including evidence of substructure in the spatial distribution and kinematics of halo stars. Implications for galaxy formation theory are subsequently discussed; in particular it is argued that the observed kinematics of stars in the outer Galactic halo can be used as an important constraint on viable galaxy formation scenarios. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Automated rainfall simulator for variable rainfall on urban green areas   总被引：1，自引：0，他引：1  

Kristoffer T. Nielsen  Per Moldrup  Sren Thorndahl  Jesper E. Nielsen  Lene B. Duus  Sren H. Rasmussen  Mads Uggerby  Michael R. Rasmussen 《水文研究》2019,33(26):3364-3377

Rainfall simulators can enhance our understanding of the hydrologic processes affecting the total runoff to urban drainage systems. This knowledge can be used to improve urban drainage designs. In this study, a rainfall simulator is developed to simulate rainfall on urban green surfaces. The rainfall simulator is controlled by a microcomputer programmed to replicate the temporal variations in rainfall intensity of both historical and synthetic rainfall events with constant rainfall intensity on an area of 1 m². The performance of the rainfall simulator is tested under laboratory conditions with regard to spatial uniformity of the rainfall, the kinetic energy of the raindrops, and the ability to replicate historical and synthetic rainfall events with temporally varying intensity. The rainfall simulator is applied in the field to evaluate its functionality under field conditions and the influence of wind on simulated rainfall. Finally, a field study is carried out on the relationship between runoff, soil volumetric water content, and surface slope. Performance and field tests show that the simulated rainfall has a uniform spatial distribution, whereas the kinetic energy of the raindrops is slightly higher than that of other comparable rainfall simulators. The rainfall simulator performs best in low wind speed conditions. The simulator performs well in replicating historical and synthetic rainfall events by matching both intensity variations and accumulated rainfall depth. The field study shows good correlation between rainfall, runoff, infiltration, soil water content, and surface slope.  相似文献   

Statistical analysis of temperature extremes in long-time series from Uppsala     

Jesper Ryd��n 《Theoretical and Applied Climatology》2011,105(1-2):193-197

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Integration of European habitat monitoring based on plant life form composition as an indicator of environmental change and change in biodiversity     

Margit Bloch-Petersen  Jesper Brandt  Martin Olsen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):61-74

Geografisk Tidsskrift, Danish Journal of Geography 106(2): 61–74, 2006

During the last 25 years a number of European countries have developed general landscape monitoring systems. In the agricultural landscapes of Denmark the Small Biotope Monitoring Program (SBMP). which focuses on the dynamics of small biotopes and their relation to changes in agricultural technology and structural characteristics, has been developed since 1981. Erom 2007, the SBMP will continue as part of the Danish nature monitoring program, NOVANA.

In Europe, during the last 10 years, several national landscape surveys have cooperated to develop a European platform for consistent landscape related habitat monitoring. This has been through the BioHab Concerted Action Framework Programme of the EU (2002–2005), and the resulting publication of a handbook for recording and monitoring habitats (Bunce et al., 2005). The focus on environmentally conditioned habitat changes at a landscape level has led to the re-introduction of Raunkiaer's plant life form concept. This approach enables the indication of changes in biodiversity based on alterations in general habitat composition and quality.

Although the objectives of the SBMP and the BioHab projects have been somewhat different, the methodologies have much in common. In this paper the background and perspectives of the two approaches are discussed, and a test of the BioHab field methodology in an area previously monitored by the SBMP is presented. It was found not to be difficult to integrate the BioHab field recording methodology with the existing SBMP methods, thus permitting the SBMP to deliver an additional European perspective, with relatively little additional effort.  相似文献   

CDM, Feedback and the Hubble Sequence     

Jesper Sommer-Larsen  Martin Götz  Laura Portinari 《Astrophysics and Space Science》2002,281(1-2):519-524

We have performed TreeSPH simulations of galaxy formation in a standard ΛCDM cosmology, including effects of star formation, energetic stellar feedback processes and a meta-galactic UV field, and obtain a mix of disk, lenticular and elliptical galaxies. The disk galaxies are deficient in angular momentum by only about a factor of two compared to observed disk galaxies. The stellar disks have approximately exponential surface density profiles, and those of the bulges range from exponential to r ^1/4, as observed. The bulge-to-disk ratios of the disk galaxies are consistent with observations and likewise are their integrated B-V colours, which have been calculated using stellar population synthesis techniques. Furthermore, we can match the observed I-band Tully-Fisher (TF) relation, provided that the mass-to-light ratio of disk galaxies is (M/L _I) ≃ 0.6–0.7. The ellipticals and lenticulars have approximately r ^1/4 stellar surface density profiles, are dominated by non-disklike kinematics and flattened due to non-isotropic stellar velocity distributions, again consistent with observations. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

The mass to light ratio and the initial mass function in galactic discs     

Laura Portinari  Jesper Sommer-Larsen  Rosaria Tantalo 《Astrophysics and Space Science》2003,284(2):723-726

A low mass-to-light ratio for the baryonic component of spiral galaxies is advocated by a number of dynamical studies and by cosmological simulations of galaxy formation. We discuss the possibility of obtaining low mass-to-light ratios for the stellar component in discs, by changing the Initial Mass Function and the Star Formation History. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Multiproxy evidence for terrestrial and aquatic ecosystem responses during the 8.2 ka cold event as recorded at Højby Sø, Denmark     

Mikkel Ulfeldt Hede  Peter Rasmussen  Nanna Noe-Nygaard  Annemarie L. Clarke  Rolf D. Vinebrooke  Jesper Olsen 《Quaternary Research》2010,73(3):485-496

A sediment succession from Højby Sø, a lake in eastern Denmark, covering the time period 9400–7400 cal yr BP was studied using high-resolution geochemistry, magnetic susceptibility, pollen, macrofossil, diatom, and algal pigment analysis to investigate responses of the terrestrial and aquatic ecosystems to the 8.2 ka cold event. A reduced pollen production by thermophilous deciduous tree taxa in the period c. 8250–8000 cal yr BP reveal that the forest ecosystem was affected by low temperatures during the summer and winter/early-spring seasons. This finding is consistent with the timing of the 8.2 ka cold event as registered in the Greenland ice cores. At Højby Sø, the climate anomaly appears to have started 200–250 yr earlier than the 8.2 ka cold event as the lake proxy data provide strong evidence for a precipitation-induced distinct increase in catchment soil erosion beginning around 8500 cal yr BP. Alteration of the terrestrial environment then resulted in a major aquatic ecosystem change with nutrient enrichment of the lake and enhanced productivity, which lasted until c. 7900 cal yr BP.  相似文献   

Dynamic interpretation of grain size relations in silt     

Jesper Bartholdy 《Geo-Marine Letters》1985,5(1):67-70

In the salt marsh deposits of the Danish Wadden Sea, a separation has successfully been made of two log-normally distributed grain size populations, which make up the major part of these fine-grained sediments. The coarse population consists almost exclusively of silt and is interpreted as material either deposited as resistant flocs or as single particles. The fine population consists of approximately 50% silt and 50% clay and is interpreted as particles settled as easily destroyable flocs. These interpretations are confirned by the fact that the relative abundance of the two populations is demonstrated to be related to the degree of exposure of salt marsh areas.  相似文献