Electrostatic forces and shadow effects in planetary dust rings     

Ove Havnes 《Astrophysics and Space Science》1986,122(1):97-107

The vertical dust distribution of dust clouds around planets, resulting from electrostatic forces, is calculated as a function of dust and plasma parameters. Photoelectric charging is included and differences between clouds on the illuminated side and in the shadow zone are examined. We compute ring structures for conditions which may apply in the spoke-forming regions and study at what dust and plasma conditions the shadow has a significant effect on the vertical dust cloud structure.  相似文献   

Bacteria in the gut of juvenile cod Gadus morhua fed live feed enriched with four different commercial diets     

Korsnes  Kjetil; Nicolaisen  Ove; Skar  Cecilie K.; Nerland  Audun H.; Bergh  Oivind 《ICES Journal of Marine Science》2006,63(2):296-301

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The use of catch statistics to monitor the abundance of escaped farmed Atlantic salmon and rainbow trout in the sea     

Skilbrei  Ove T.; Wennevik  Vidar 《ICES Journal of Marine Science》2006,63(7):1190-1200

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瑞典爱斯泼硬岩实验场地应力研究     

苏生瑞  STEPHANSSON Ove  王士天 《工程地质学报》2001,9(1):100-106

爱斯泼 (A..sp o..)硬岩实验场 (HRL)是瑞典拟建的永久储放核废料的场地。实测地应力结果表明, 应力的大小和方位变化较为复杂。通过初步分析认为, 场地附近地应力的变化与断裂构造的发育有关。应用离散元方法, 分别选择平面模型和剖面模型模拟了应力场。模拟结果表明, 地应力的量值和方位在断裂附近均发生明显变化, 且与实测结果较吻合。主应力在断裂附近发生不同程度的偏转, 偏转的幅度与断裂走向和区域应力方向之间的夹角有关。应力的量值在断裂附近也有明显变化。在剖面模型中, 较缓倾角断裂模型的模拟结果最接近实测结果。文中还探讨了断裂带法向刚度和切向刚度的计算方法。  相似文献   

Using the pseudospectral technique on curved grids for 2D acoustic forward modelling1     

Per Nielsen  Flemming If  Per Berg  Ove Skovgaard 《Geophysical Prospecting》1994,42(4):321-341

The Fourier pseudospectral method has been widely accepted for seismic forward modelling because of its high accuracy compared to other numerical techniques. Conventionally, the modelling is performed on Cartesian grids. This means that curved interfaces are represented in a ‘staircase fashion‘causing spurious diffractions. It is the aim of this work to eliminate these non-physical diffractions by using curved grids that generally follow the interfaces. A further advantage of using curved grids is that the local grid density can be adjusted according to the velocity of the individual layers, i.e. the overall grid density is not restricted by the lowest velocity in the subsurface. This means that considerable savings in computer storage can be obtained and thus larger computational models can be handled. One of the major problems in using the curved grid approach has been the generation of a suitable grid that fits all the interfaces. However, as a new approach, we adopt techniques originally developed for computational fluid dynamics (CFD) applications. This allows us to put the curved grid technique into a general framework, enabling the grid to follow all interfaces. In principle, a separate grid is generated for each geological layer, patching the grid lines across the interfaces to obtain a globally continuous grid (the so-called multiblock strategy). The curved grid is taken to constitute a generalised curvilinear coordinate system, where each grid line corresponds to a constant value of one of the curvilinear coordinates. That means that the forward modelling equations have to be written in curvilinear coordinates, resulting in additional terms in the equations. However, the subsurface geometry is much simpler in the curvilinear space. The advantages of the curved grid technique are demonstrated for the 2D acoustic wave equation. This includes a verification of the method against an analytic reference solution for wedge diffraction and a comparison with the pseudospectral method on Cartesian grids. The results demonstrate that high accuracies are obtained with few grid points and without extra computational costs as compared with Cartesian methods.  相似文献   

Granite diapirism in the Rum Jungle area,Northern Australia     

Ove Stephansson  Kevin Johnson 《Precambrian Research》1976,3(2):159-185

Early studies in the Rum Jungle area suggested an intrusive relationship between the Rum Jungle and Waterhouse “Granites”, and the overlying sediments. It was later shown that the granitic “intrusions” were Archaean basement complexes onto which Lower Proterozoic sediments had been deposited. Polyphase folding was postulated as being responsible for doming of the basement and cover rocks.This paper proposes to show that the domed structures in the Rum Jungle area, and the emplacement of Middle Proterozoic granites in the Pine Creek Geosyncline were related, and caused by diapiric intrusion of granites, in a solid state, into basement complexes and cover rocks.Structural and metamorphic evidence in support of diapiric intrusion in the Rum Jungle area includes: pebble deformation within steeply dipping beds of quartz conglomerate; disappearance of polyphase fold structures away from the basement complexes; bending of folded country-rock strata into concordance with the complex—sediment contact; and metamorphic and metasomatic alteration of sediments in contact with the basement complexes. Gravity data show mass deficiencies in the Archaean complexes which possibly coincide with young granite diapirs.  相似文献   

Theme issue on hydromechanics in geology and geotechnics     

Ove?StephanssonEmail author 《Hydrogeology Journal》2003,11(1):3-6

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The influence of microcrack density on the elastic and fracture mechanical properties of Stripa granite   总被引：1，自引：0，他引：1  

Ove Alm  Lise-Lotte Jaktlund  Kuo Shaoquan 《Physics of the Earth and Planetary Interiors》1985,40(3):161-179

Microcracks can have a strong influence on the elastic and fracture mechanical properties of rocks if they are numerous, or if they are orientated in unfavourable directions in anisotropic rocks in particular. This paper presents results from a great number of mechanical tests on Stripa granite containing various amounts of microcracks. Variations in the microcrack density were obtained by shock-heating the rock at different temperatures in the range 100–600°C for 3 h.The results presented are obtained from sound velocity measurements, uniaxial compression tests, Brazilian tests and three-point bending tests. The density of microcracks in the heated rock is studied by means of optical microscopy, SEM and differential strain analysis (DSA).Some of the calculated parameters show a maximum value for specimens heat-treated at about 100°C. The tensile strength is, for instance, substantially higher for specimens shock-heated at 100°C than for non-heated ones. Another striking feature is the initial decrease of the diameter observed in specimens heat-treated at 600°C when loaded in uniaxial compression. Both optical microscopy and DSA experiments reveal a large increase in microcracking when the heat-treatment temperature exceeds 300°C.  相似文献   

The physical environment of Kongsfjorden–Krossfjorden, an Arctic fjord system in Svalbard     

Harald Svendsen  Agnieszka Beszczynska-Møller  Jon Ove Hagen  Bernard Lefauconnier  Vigdis Tverberg  Sebastian Gerland  Jon Børre Ørbøk  Kai Bischof  Carlo Papucci  Marek Zajaczkowski  Roberto Azzolini  Oddbjørn Bruland  Christian Wiencke  Jan-Gunnar Winther  Winfried Dallmann 《Polar research》2002,21(1):133-166

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The umbral flash as a magneto-acoustic wave phenomenon     

Ove Havnes 《Solar physics》1970,13(2):323-329

The suggestion that an umbra flash may be caused by a magneto-acoustic wave phenomenon is examined. It is suggested that the flash in Ca ii lines is formed during the compressional stage in a magneto-acoustic wave. The compression which is assumed to be adiabatic will produce a rise in temperature and a corresponding increase in number of Ca ii atoms. The variations in line emission (absorption) coefficient of the Ca ii K-line are calculated on this assumption and are found to be in general agreement with the observed variations. Other observed quantities as proper motion, magnitude of line shift etc., also agree with the wave hypothesis. Further observations which may serve as tests on the wave hypothesis are suggested.  相似文献