Abstract— Metallographic cooling rates have been calculated for all five members of the iron meteorites group IIF using two different techniques. We have determined cooling rates of ～5 °C/Ma based on Ni profiles through the taenite rim enclosing kamacite spindles. Ni profiles through the kamacite phase are less precise cooling rate indicators, but suggest a cooling rate of ～1 °C/Ma within an order of magnitude at lower temperatures (360–400 °C). Based on the kamacite bandwidth and the Ni profiles through the taenite, we estimate that the kamacite nucleated 130–200 °C below the temperature predicted from the phase diagram. The size of and the distance between the large kamacite spindles is found to be consistent with the thermal history that we have determined on the basis of Ni profiles in kamacite and taenite. We find that previously published kamacite bandwidth cooling rates for the five group IIF members are most likely in error because of the presence of large schreibersite spindles in some kamacite spindles and because undercooling of kamacite was ignored. Contrary to previous workers we find that the metallographic cooling rates are consistent with cooling in a common core. 相似文献
We present here simulations of extrasolar planets detections obtained using a combination of extreme adaptive optics and integral field spectroscopy. The simulation code, written for IDL, provides images and, in particular, spectra, taking into account realistic Speckle Noise, AO correction effects and specific instrumental features. A detailed study has been done for ESO VLT telescopes (8.2 m), within the Phase A of the CHEOPS project, but the code is particularly flexible and can be updated for larger telescope diameters (ELTs) in order to give a realistic estimate of the detection limits, for giant telescopes, in standard conditions of seeing. 相似文献
Bennekou, G., Rand, P., & Schroll, H. 1974: Energiforhold I den Danske landbrugsproduktion. Geografisk Tidsskrift 73: 36–48. København, juni 1, 1974. The increasing supply of energy in Danish agricultural production has reached a level where the energy lost on its way through the food chain in animal production only just balances with the gain of energy obtained by vegetable production. 相似文献
This article presents some advantages using a shape-preserving total variation diminishing (TVD) advection scheme in an ecosystem model. The superbee flux-limiter has been used to the second-order Lax–Wendroff advection scheme to make it TVD. We performed simulations for three shelf sea regions with different characteristic time scales, namely, the North Sea, the Barents Sea, and the Baltic Sea. To explore the advantages, we also performed reference runs with the much simpler and computationally cheaper upwind advection scheme. Frontal structures are much better resolved with the TVD scheme. The bottom salinity in the Baltic Sea stays at realistic values throughout the 10-year simulation with the TVD scheme, while with the upwind scheme, it drifts towards lower values and the permanent haline stratification in the Baltic is almost completely eroded within one seasonal cycle. Only when applying TVD for both the vertical and horizontal advections the model succeeded to preserve haline stratification in the decadal simulation. Lower trophic level patterns are far better reproduced with the TVD scheme, and for the estimated cod larval survival, the advantages seem to be even stronger. Simulations using the TVD-derived prey fields identified distinct regions such as Dogger Bank to favor potential larvae survival (PLS), which did not appear as particularly favorable in the upstream simulations. The TVD scheme needs about 25 % more time on the central processing unit (CPU) in case of a pure hydrodynamic setup with only two scalar state variables (Barents Sea application). The additional CPU time cost increases for a coupled physical–biological model application with a large number of state variables. However, this is more than compensated by all the advantages found, and, hence, we conclude that it is worthwhile to use the TVD scheme in our ecosystem model.
Climate change will affect the regional ability to achieve the poverty reduction and sustainable development (SD) objectives. Thus, any action plans to achieve these objectives should make climate change policies an integral part of the development planning process. The best practices and measures of climate change policies should be implemented to ensure regional or community sustainability. In this paper, a case study that promotes the integration of carbon sequestration into sustainable forest management and rural development plan with multi-stakeholders participation is introduced. To achieve SD goals, appropriate tools and methods are required to address impacts of alternative forest land uses on carbon sequestration and rural sustainability, and to prioritise land use options. A range of forest land use scenarios that address various aspects of the forest carbon sequestration rate and rural sustainability are evaluated against a SD indicator system. Planting vegetation is one of the practical approaches in mitigating global warming by sequestrating carbon from the atmosphere to plant matter and soil. In order to protect environment, reduce excessive soil erosion, and decrease the propensity and frequency of flooding and other natural disasters, China has initiated nationwide pivotal projects such as “Grain for Green” to mitigate exacerbated environmental deterioration and degradation. Such ecological programs may affect the socio-economic livelihoods of peasants and the economic activities of the whole region. The impact and economic uncertainty associated with such projects urge policy makers to include all stakeholders in the decision making process so that an agreeable solution towards sustainable rural development can be identified. This study uses Liping County in Guizhou province as a case study to identify a consensus among peasants regarding planting selected tree-species. Analytic hierarchy process (AHP) is used as a multicriteria decision making tool to rank sustainability criteria and determine the priority of options. The method helps policy makers to understand what the peasants want to achieve by participating in a Grain for Green program and what their priorities are with respect to particular types of vegetation. The case study finds that economic and financial concerns are the most important drivers of the decision of which trees to plant among the peasants who took part in the implementation of the Grain for Green program. As a result of this, Gingko, redpine, and Chinese chestnut were the predominant trees planted under the program. The integrated assessment based on the AHP method provides an effective tool to help understand how economic, social and environmental factors are related to each other in affecting the nature of rural sustainability. 相似文献
