Modelling the potential impact of global warming on Ips typographus voltinism and reproductive diapause     

Anna Maria Jönsson  Susanne Harding  Paal Krokene  Holger Lange  Åke Lindelöw  Bjørn Økland  Hans Peter Ravn  Leif Martin Schroeder 《Climatic change》2011,109(3-4):695-718

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Numerical modelling of organic waste dispersion from fjord located fish farms     

Alfatih Ali  Øyvind Thiem  Jarle Berntsen 《Ocean Dynamics》2011,61(7):977-989

In this study, a three-dimensional particle tracking model coupled to a terrain following ocean model is used to investigate the dispersion and the deposition of fish farm particulate matter (uneaten food and fish faeces) on the seabed due to tidal currents. The particle tracking model uses the computed local flow field for advection of the particles and random movement to simulate the turbulent diffusion. Each particle is given a settling velocity which may be drawn from a probability distribution according to settling velocity measurements of faecal and feed pellets. The results show that the maximum concentration of organic waste for fast sinking particles is found under the fish cage and continue monotonically decreasing away from the cage area. The maximum can split into two maximum peaks located at both sides of the centre of the fish cage area in the current direction. This process depends on the sinking time (time needed for a particle to settle at the bottom), the tidal velocity and the fish cage size. If the sinking time is close to a multiple of the tidal period, the maximum concentration point will be under the fish cage irrespective of the tide strength. This is due to the nature of the tidal current first propagating the particles away and then bringing them back when the tide reverses. Increasing the cage size increases the likelihood for a maximum waste accumulation beneath the fish farm, and larger farms usually means larger biomasses which can make the local pollution even more severe. The model is validated by using an analytical model which uses an exact harmonic representation of the tidal current, and the results show an excellent agreement. This study shows that the coupled ocean and particle model can be used in more realistic applications to help estimating the local environmental impact due to fish farms.  相似文献   

Numerical simulation of internal solitary wave—induced reverse flow and associated vortices in a shallow,two-layer fluid benthic boundary layer     

Øyvind Thiem  Magda Carr  Jarle Berntsen  Peter A. Davies 《Ocean Dynamics》2011,61(6):857-872

The wave-induced velocity and pressure fields beneath a large amplitude internal solitary wave of depression propagating over a smooth, flat, horizontal, and rigid boundary in a shallow two-layer fluid are computed numerically. A numerical ocean model is utilised, the set-up of which is designed and tuned to replicate the previously published experimental results of Carr and Davies (Phys Fluids 18(1):016,601–1–016,601–10, 2006). Excellent agreement is found between the two data sets and, in particular, the numerical simulation replicates the finding of a reverse flow along the bed aft of the wave. The numerically computed velocity and pressure gradients confirm that the occurrence of the reverse flow is a consequence of boundary layer separation in the adverse pressure gradient region. In addition, vortices associated with the reverse flow are seen to form near the bed.  相似文献   

Preliminary results of the multisite time-series campaign on the sdB pulsator PG 1325+101     

R. Silvotti  A. Bonanno  A. Frasca  S. Bernabei  R. Janulis  R. Østensen  S.-L. Kim  B.-G. Park  J. Xiaojun  J. Guo  Z. Liu  M.D. Reed  R.S. Patterson  K.M. Gietzen  P.J. Clark  G.W. Wolf  Y. Lipkin  L. Formiggini  E. Leibowitz  T.D. Oswalt  M. Rudkin  K. Johnston 《Astrophysics and Space Science》2004,289(3-4):445-448

I present a model for the formation and evolution of a massive disk galaxy, within a growing dark halo whose mass evolves according to cosmological simulations of structure formation. The galactic evolution is simulated with a new 3D chemo-dynamical code, including dark matter, stars and a multi-phase ISM. We follow the evolution from redshift z = 4.85 until the present epoch. The energy release by massive stars and supernovae prevents a rapid collapse of the baryonic matter and delays the maximum star formation until redshift z ≈ 1. The galaxy forms radially from inside-out and vertically from top-to-bottom. The feedback of stars leads to turbulent motions and large-scale flows in the ISM. As one result the galactic disk is significantly enriched by chemical elements synthesized in bulge stars.  相似文献   

Radial velocity and line-profile variations in the sdBV star PG 1325+101     

Roy H. Østensen  John H. Telting 《Astrophysics and Space Science》2004,290(3-4):449-456

Historically, any newly discovered object needed to be “confirmed” with optical observations. Catalogs were published, such as the PKS (Parkes Catalog), with stamp-sized photographs that allowed us to “see” what was just found. This is still somewhat true, although far less than in the past. We are probably reaching an information overload with more efficient instruments, larger detectors, multiple wavelength coverage and an increasing number of ground and space-based facilities. At the same time, information technology is catching up and is allowing us to use the data regardless of where they reside. An increasing need of multi-wavelength observations to understand the underlying physics of the observed phenomena and the challenge to mine petabyte databases is leading to a federation of archives and cooperation among computer scientists and astronomers. These are the seeds of a virtual observatory, a cyberspace entity where the data are ready to be found and analyzed. In the United States, the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA) are funding initiatives that will lead to the creation of this entity. This paper describes these projects.  相似文献   

Cirque glacier activity in arctic Norway during the last deglaciation     

yvind Paasche  Svein Olaf Dahl  Jostein Bakke  Reidar Lvlie  Atle Nesje 《Quaternary Research》2007,68(3):387-399

Numerous cirques of the Lofoten–Vesterålen archipelago in northern Norway have distinct moraine sequences that previously have been assigned to the Allerød-Younger Dryas ( 13,400 to 11,700 yr BP) interval, constraining the regional distribution of the equilibrium-line altitude (ELA) of cirque and valley glaciers. Here we present evidence from a once glacier-fed lake on southern Andøya that contests this view. Analyses of radiocarbon dated lacustrine sediments including rock magnetic parameters, grain size, organic matter, dry bulk density and visual interpretation suggest that no glacier was present in the low-lying cirque during the Younger Dryas-Allerød. The initiation of the glacial retreat commenced with the onset of the Bølling warming ( 14,700 yr BP) and was completed by the onset of Allerød Interstade ( 13,400 yr BP). The reconstructed glacier stages of the investigated cirque coincide with a cool and dry period from  17,500 to 14,700 yr BP and a somewhat larger Last Glacial Maximum (LGM) advance possibly occurring between  21,050 and 19,100 yr BP.  相似文献   

Possible Concepts for Waterproofing of Norwegian TBM Railway Tunnels   总被引：1，自引：0，他引：1  

Øyvind Dammyr  Bjørn Nilsen  Kurosch Thuro  Jørn Grøndal 《Rock Mechanics and Rock Engineering》2014,47(3):985-1002

The aim of this paper is to evaluate and compare the durability, life expectancy and maintenance needs of traditional Norwegian waterproofing concepts to the generally more rigid waterproofing concepts seen in other European countries. The focus will be on solutions for future Norwegian tunnel boring machine railway tunnels. Experiences from operation of newer and older tunnels with different waterproofing concepts have been gathered and analyzed. In the light of functional requirements for Norwegian rail tunnels, some preliminary conclusions about suitable concepts are drawn. Norwegian concepts such as polyethylene panels and lightweight concrete segments with membrane are ruled out. European concepts involving double shell draining systems (inner shell of cast concrete with membrane) and single shell undrained systems (waterproof concrete segments) are generally evaluated as favorable. Sprayable membranes and waterproof/insulating shotcrete are welcomed innovations, but more research is needed to verify their reliability and cost effectiveness compared to the typical European concepts. Increasing traffic and reliance on public transport systems in Norway result in high demand for durable and cost effective solutions.  相似文献   

Accumulation of Copper and Zinc in Danish Agricultural Soils in Intensive Pig Production Areas     

Ilse Gräber  Jørgen F. Hansen  Svend E. Olesen  Jens Petersen  Hans S. Østergaard  Lars Krogh 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):15-22

Geografisk Tidsskrift, Danish Journal of Geography 105(2):15–22, 2005

The change of Cu and Zn concentrations in Danish agricultural soils was studied in areas with intensive pig production. Cu and Zn are found in pig manure as the metals are added to pig feed as growth promoters. The changes in concentrations of total and 0.02 MEDTA extractable Cu and Zn in soils from 1986 to 1998 were determined from samples taken at two depths (0–25 cm and 25–50 cm) from 73 sites. Pig manure and mineral fertilizer was added to 60 sites whereas fertilizer only was used on 13 sites. During the survey period soil Cu concentrations increased in both depths but mostly in the sites where pig manure was added. Furthermore, the results indicated that some plant-available Cu and Zn were transported from the topsoil to the subsoil. No significant change in soil Zn concentration was found although a slight reduction was observed. Comparing soil metal concentrations observed in 1998 to the total pig manure application in a 12-year period, it was observed that application of manure caused an accumulation of Cu and of Zn in the upper 50 cm soil. The accumulation rates correspond to the Cu and Zn concentrations in the pig manure.  相似文献   

Surface wave effects on water temperature in the Baltic Sea: simulations with the coupled NEMO-WAM model   总被引：1，自引：1，他引：0  

Victor Alari  Joanna Staneva  Øyvind Breivik  Jean-Raymond Bidlot  Kristian Mogensen  Peter Janssen 《Ocean Dynamics》2016,66(8):917-930

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Numerical studies of large-amplitude internal waves shoaling and breaking at shelf slopes     

Øyvind Thiem  Jarle Berntsen 《Ocean Dynamics》2009,59(6):937-952

Hydro carbon fields beyond the shelf break are presently being explored and developed, which has increased the scientific focus in this area. Measurements from the slopes reveal large variability in temperature and velocity, and some of the observed events are due to interactions between large-amplitude oscillations of the thermocline and the topography. The present study focuses on the strong currents that are generated near the seabed during shoaling and breaking of internal waves along shelf slopes. The parameter regime used is similar to the one for the Nordic Seas. The results show that, during shoaling of large internal waves along (gentle) slopes, the energy is transferred towards smaller scales and strong velocities (over 1 m s^− 1) can be generated. To resolve all scales involved is still not feasible, and therefore, the model results are sensitive to the grid size and the subgrid scale closure.  相似文献