Multi-Region Boundary Element Analysis for Coupled Thermal-Fracturing Processes in Geomaterials     

Baotang Shen  Hyung-Mok Kim  Eui-Seob Park  Taek-Kon Kim  Manfred W. Wuttke  Mikael Rinne  Tobias Backers  Ove Stephansson 《Rock Mechanics and Rock Engineering》2013,46(1):135-151

This paper describes a boundary element code development on coupled thermal–mechanical processes of rock fracture propagation. The code development was based on the fracture mechanics code FRACOD that has previously been developed by Shen and Stephansson (Int J Eng Fracture Mech 47:177–189, 1993) and FRACOM (A fracture propagation code—FRACOD, User’s manual. FRACOM Ltd. 2002) and simulates complex fracture propagation in rocks governed by both tensile and shear mechanisms. For the coupled thermal-fracturing analysis, an indirect boundary element method, namely the fictitious heat source method, was implemented in FRACOD to simulate the temperature change and thermal stresses in rocks. This indirect method is particularly suitable for the thermal-fracturing coupling in FRACOD where the displacement discontinuity method is used for mechanical simulation. The coupled code was also extended to simulate multiple region problems in which rock mass, concrete linings and insulation layers with different thermal and mechanical properties were present. Both verification and application cases were presented where a point heat source in a 2D infinite medium and a pilot LNG underground cavern were solved and studied using the coupled code. Good agreement was observed between the simulation results, analytical solutions and in situ measurements which validates an applicability of the developed coupled code.  相似文献   

Galactic spiral arms formed by central explosions     

Ove Havnes 《Astrophysics and Space Science》1978,57(2):401-408

We have made calculations of spiral arm formation due to central explosions in a nucleus surrounded by a disc containing most of the galactic mass with the purpose of obtaining estimates on lifetimes of arms and the requirements on the energy involved in the process. The ejected gas is taken to be a few percent, or less, of the central nucleus and is ejected with velocities of the order of 1000 km s^–1. The gas, considered to be in forms of blods, moves under the gravitational force from the disc and the nucleus and the drag force by the gas in the disc. The orbits of the blobs evolve towards the circular orbits of the disc due to this drag force and the velocities in the arms will therefore, after some time, approach those of a normal rotation curve.A relatively open structure will last 5×10⁸ years. Stable ring structures with longer lifetimes may be formed by some explosions. With an energy of 5×10⁵⁷ erg in the initial gas-blod motion and a duration of the explosion of 10⁷ years, the energy output in such explosions has to be >10⁴³ erg s^–1.  相似文献   

In situ stress determination from breakouts in the Tornquist Fan, Denmark     

Maria V.S. Ask  Birgit Müller  Ove Stephansson 《地学学报》1996,8(6):575-584

The Tornquist Fan, a fan-shaped region in Denmark and Western Baltic, is situated in the transition zone between the Western and Northern European Stress Provinces. Breakout data from 20 wells (0.3–3.6 km) were analysed. The fan can be divided into three stress provinces: (i) The area south of the Rømø Fracture Zone is part of the Western European Stress Province and has NNW-SSE orientation of the maximum horizontal stress, (ii) The sediment cover in the Nonvegian-Danish Basin is dominated by ENE-WSW orientated maximum horizontal stress, (iii) The maximum horizontal stress is sub-parallel to the strike of the Sorgenfrei-Tornquist Zone. Deviations from the regional stress field were observed in wells close to faults and salt diapirs. In wells south of the Sorgenfrei-Tornquist Zone, breakout occurrence decreases with increasing age of the stratigraphic units. The downhole breakout distribution seems to correlate with lithology and thickness of the sediment layer.  相似文献   

Danske provinsbyers indre differentiering og differentieringen mellem danske provinsbyer     

Poul Ove Pedersen  Civilingeniør Peter Rasmussen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):49-56

Pedersen, P. O. & Rasmussen, P., 1973: Danske provinsbyers indre differentiering og differentieringen mellem danske provinsbyer. Geografisk Tidsskrift, 72, 49–56. København, September 30., 1973.

This paper analyses the inner differentiation in the three largest provincial towns in Denmark by means of a factor analysis of 25 variables characterizing the population and the housing in 40 zones, 14 in Århus (187,000 inh.), 14 in Odense (133,000 inh.), and 12 in Ålborg (123,000 inh.). The paper especially focuses on the differences in inner differentiation between the three towns.  相似文献   

Nye kandidater udgået fra Københavns Universitets Geografiske Institut     

Poul Ove Pedersen  Viggo Hansen  lektor  dr. scient. Christian Wichmann Matthiessen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):71-79

Danish Journal of Geography: 71–82, 1995.

This paper presents two mega events as tools in the strategic planning of the Copenhagen area. Due to growing inter-metropolitan competition, increasingly offensive and complex means are applied. This demands strong leadership, stable longterm planning and willingness to accept the costs in order to reach the objectives. Marketing versus strategic planning is discussed. The general position of Copenhagen in the European urban system gives perspective to a potential change on the South Scandinavian urban scene. New instruments of strategic planning in Greater Copenhagen are introduced. The competitive level of Copenhagen is analyzed in relation to Stockholm, Berlin and Hamburg. Two examples of mega events are discussed that represent typical elements in urban competition: cultural events and infrastructure improvements. 1) Copenhagen as ‘The cultural City of Europe’ in 1996 represents a temporary mega event. 2) The planned bridge between Copenhagen and the south Swedish city of Malmö, combined with Swedish entrance into EU, opens up for development of the first cross-national integrated large-city region outside the European centre. This is an example of a mega event which will alter the scene permanently. Both events are important issues used in developing a growth strategy for Greater Copenhagen. But neither the cultural city nor the bridge may by themselves guarantee any advantages. It depends upon the ability of local actors to develop and promote the quality of their city. The paper represents a continuation and elaboration on earlier papers, see Matthiessen (1990, 1992) and Andersen &; Jørgensen (1994).  相似文献   

Studying interactions between excavating sponges and massive corals by the use of hybrid cores          下载免费PDF全文

James K. H. Fang  Robert A. B. Mason  Christine H. L. Schönberg  Ove Hoegh‐Guldberg  Sophie Dove 《Marine Ecology》2017,38(1)

Excavating sponges often compete with reef‐building corals. To study sponge–coral interactions, we devised a design of hybrid cores that allows sponges and corals to be arranged side by side with similar size and shape, mimicking the situation of neighbouring organisms. Compared to earlier methods that attached sponge cores onto coral surfaces, hybrid cores provide an opportunity to study organism interactions under conditions more equal to the interacting partners. The use of hybrid cores was demonstrated for the excavating sponge Cliona orientalis and the massive coral Porites, which commonly interact on the Great Barrier Reef. Cliona orientalis and massive Porites were cut into half‐moon shaped explants and combined as hybrid cores under replicate conditions. After 90 days in an aquarium setting, positive growth of Cl. orientalis along with net bioerosion were observed in sponge control cores that combined Cl. orientalis with blank substrate. However, when Cl. orientalis and massive Porites were in contact in interaction cores, the sponge displayed negative growth and undetectable bioerosion, and was slightly overgrown by the coral. Cliona orientalis may have developed tissue extension beneath the living coral tissue, but growth and net calcification rates of massive Porites were apparently not affected by Cl. orientalis when comparing the interaction cores to coral control cores that combined massive Porites with blank substrate. Overall, the present work demonstrated that hybrid cores can be used to generate conditions suitable for studying sponge–coral interactions in the laboratory, which can also be applied in the field.  相似文献   

Methods to quantify components of the excavating sponge Cliona orientalis Thiele, 1900     

James K. H. Fang  Christine H. L. Schönberg  David I. Kline  Ove Hoegh‐Guldberg  Sophie Dove 《Marine Ecology》2013,34(2):193-206

This study applied the loss after combustion (LAC) method and the acid decalcification (ADC) method to quantify different components of an excavating sponge. Samples of dried coral skeleton of Favia sp. invaded by the Indo‐Pacific excavating sponge Cliona orientalis Thiele, 1900 were used. The sponge tissue penetrated the 12‐mm‐thick samples to approximately 10 mm. The average proportional weight of organic matter, siliceous spicules, calcareous substrate and salts in the entire samples was found to be respectively 2.5%, 4.4%, 90.5% and 2.5% of dry weight applying the LAC method, and 2.9%, 5.9%, 89.0% and 2.3% of dry weight applying the ADC method. Respective volumetric proportions of the organic matter, spicules, substrate and salts were then calculated to be 6.4%, 5.5%, 85.2% and 3.0% of volume with the LAC method, and 7.4%, 7.2%, 82.7% and 2.7% of volume with the ADC method. The LAC method showed low variability of data and is simple and fast and therefore is recommended. The ADC method generated very similar results to the LAC method. However, due to the handling involved in the ADC method, more than half of the spicules may be lost and the method is therefore not recommended unless careful data corrections are considered. In addition, the buoyant weight method was used to quantify actual substrate weight in the fresh sponge‐substrate samples. This method was found to be at least 97% effective, revealing that buoyant weights can potentially be used to quantify bioerosion rates of excavating sponges. To our knowledge, this is the first study to systemically quantify organic and inorganic components of an excavating sponge and its calcareous substrate, providing improved standard methods for future studies.  相似文献   

Glacial mass balance of Austre Brøggerbreen (Spitsbergen), 1971–1999, modelled with a precipitation-run-off model     

Oddbjørn Bruland  Jon Ove Hagen 《Polar research》2002,21(1):109-121

An energy balance based HBV model was calibrated to the run-off from Bayelva catchment in western Spitsbergen, Svalbard. The model simulated the glacier mass balance, and the results were compared to observations at Austre Brøggerbreen for the period 1971-1997. Even though the model was optimized to observed run-off from a catchment in which the glaciers constitute 50% of the area, and not to the observation of glacier mass balance, the model was able to reconstruct the trends and values of the mass balance found through observations. On average the simulation gave a negative net balance of 696 mm. The observed average is 442 mm. The simulated winter accumulation was in average for the same period 9% lower and the summer ablation 17% higher than the observed. The years 1994-96 show deviations between simulated and observed winter accumulation up to 160%. This can probably be accounted for by extreme rainfall during the winter, leading to thick ice layers which make accurate observations difficult. The higher simulated summer ablation might indicate that the glaciers in the catchment as a whole have a larger negative mass balance than Austre Brøggerbreen. The simulations showed that the glacier mass-balance would be in equilibrium with a summer temperature 1.2°C lower than the average over the last decades or with a 100% increase in the winter (snow) precipitation. These are higher values than former estimates. A combined change of temperature and precipitation showed a synergic effect and thereby less extreme values.  相似文献   

The distribution of snow accumulation across the Austfonna ice cap, Svalbard: direct measurements and modelling     

Andrea Taurisano  Thomas V. Schuler  Jon Ove Hagen  Trond Eiken  Even Loe  Kjetil Melvold  & Jack Kohler 《Polar research》2007,26(1):7-13

  相似文献   

Dealing with climate science denialism: experiences from confrontations with other forms of pseudoscience     

Sven Ove Hansson 《Climate Policy》2018,18(9):1094-1102

Climate science denialism is a form of pseudoscience. This contribution provides proposals for how to counter it, based on previous research on the demarcation between science and pseudoscience and on the author’s experience of tackling other forms of pseudoscience. Science denialism has much in common with other variants of pseudoscience, but it also has characteristics of its own. In particular, it is much more prone than other forms of pseudoscience to seek conflicts with genuine science. Like other science denialists, those attacking climate science have fabricated a large number of fake controversies in issues where there is no authentic scientific controversy. The defence of climate science against science denial has to take this into account. There is no reason to accept the denialists’ agenda or to treat their claims as legitimate alternatives to science. Climate science should primarily be presented to the public in ways that are independent of denialist activities, rather than reactively in response to those activities. Disclosures of the strategies, motives and funding of denialism are important contributions to the public understanding of the fake controversies. It is also important to document the scientific consensus and make it known. The public defence of climate science is an important and urgent undertaking, and active contributions by as many scientists as possible are needed.

Key policy insights

• Climate science denialism is a form of pseudoscience, and much can be learned from confrontations with other types of pseudoscience.

• The creation of fake controversies is a key strategy of climate science denialism. It is important to expose this strategy and not to accept denialists’ choice of an agenda.

• ‘Equal time’ arrangements should be rejected since they put the truthful side at a disadvantage. It takes more time to refute a single lie than to deliver ten new ones.

• The experience from fighting tobacco science denialism shows that it is highly efficient to expose the hidden operations, funding and motives behind denialism.

• As many scientists as possible should take part in the public defence of climate science. This is one of the best ways to show our consensus.

  相似文献