Marine mammals are probably frequently exposed to floating oil but little is known about the effect oil pollution has on them. Oil stranded on the shore in Pembrokeshire, West Wales in September 1974 coincided with the start of the Grey Seal breeding season there. Observations have been made on the effect the oil had on the newborn pups and their mothers. 相似文献
Summary The paper deals with a non-linear regression model, linear in parameters. The least-squares adaptation method has been used
to determine the model parameters. The conditionality problem in solving equations, which follows from the dependent predictors,
has been suppressed by singular decomposition. This model is especially suitable for treating meteorological problems because
non-linear processes, e.g. changes of air masses, changes of circulation patterns, etc., can be treated. The model has been
tested in connection with the forecast of daily maximum and minimum temperatures. The RMS error lies in the range of 1–2°C,
if the principal PPM is supposed.
The purposes of this study are to use both field and modeling approaches to characterize the permeability of a fault and to assess the role of the fault on regional ground water flow. The study subject is the Elkhorn fault, a low-angle reverse fault that brings Precambrian crystalline rocks over the sediments of Colorado's South Park Basin. The fault is hypothesized to act as a low-permeability barrier to flow, restricting interaction between the crystalline aquifer and the basin sediments. To test this hypothesis and to better predict the permeability structure of the fault, we synthesized geologic data to create a geologic model of the fault, conducted aquifer tests to estimate the hydrogeologic properties of the fault zone, and used ground water modeling to test the influence of a range of hydraulic properties for the fault zone on ground water flow in the region. Our study suggests that the fault is a low-permeability feature. Estimated heads are best matched to observations by modeling the fault as a 10-foot-thick interval of low-permeability fault gouge. Steady-state flow models show that much of the flow in the study area is topographically driven near land surface. Flow rates decrease with depth in the aquifers. In the footwall, ground water moves updip in the Michigan-San Isabel syncline to discharge in the South Park Basin. In the hanging wall, ground water moves east to a regional ground water divide. Sensitivity analyses indicate that hydraulic heads are most sensitive to changes in hydraulic conductivity and recharge. 相似文献
Today, models are ubiquitous tools for ground water analyses. The intent of this paper is to explore philosophically the role of the conceptual model in analysis. Selection of the appropriate conceptual model is an a priori decision by the analyst. Calibration is an integral part of the modeling process. Unfortunately a wrong or incomplete conceptual model can often be adequately calibrated; good calibration of a model does not ensure a correct conceptual model. Petroleum engineers have another term for calibration; they refer to it as history matching. A caveat to the idea of history matching is that we can make a prediction with some confidence equal to the period of the history match. In other words, if we have matched a 10-year history, we can predict for 10 years with reasonable confidence; beyond 10 years the confidence in the prediction diminishes rapidly. The same rule of thumb applies to ground water model analyses. Nuclear waste disposal poses a difficult problem because the time horizon, 1000 years or longer, is well beyond the possibility of the history match (or period of calibration) in the traditional analysis. Nonetheless, numerical models appear to be the tool of choice for analyzing the safety of waste facilities. Models have a well-recognized inherent uncertainty. Performance assessment, the technique for assessing the safety of nuclear waste facilities, involves an ensemble of cascading models. Performance assessment with its ensemble of models multiplies the inherent uncertainty of the single model. The closer we can approach the idea of a long history with which to match the models, even models of nuclear waste facilities, the more confidence we will have in the analysis (and the models, including performance assessment). This thesis argues for prolonged periods of observation (perhaps as long as 300 to 1000 years) before a nuclear waste facility is finally closed. 相似文献
A study of feldspar grain size and microprobe analysis of coexisting orthopyroxene, olivine, diopside, and metal in twenty equilibrated LL-group chondrites and clasts defines the conditions of metamorphism, indicates the relative position of samples within the parent body, and suggests an accretionary-metamorphic history.
Variation of mineral chemistry indicates a range of equilibrium temperature and parallels textural variation, providing two continuous relative temperature scales, based on mean feldspar grain size and the calcium content of orthopyroxene coexisting with diopside. Maximum equilibrium temperatures range from less than 600° up to 950°C. The total Tschermak's component in orthopyroxene indicates that maximum pressure was less than 1 kbar, and a pressure gradient correlates directly with temperature. A reduction sequence, evident from systematic variation of iron in ferromagnesian silicates and metal, correlates inversely with temperature.
The maximum permissible sampling depth for the formation of surface breccias (2/10 r) also limits pressure to less than 1 kbar. The LL parent body had a minimum radius of 200 km, determined using the permissible sampling depth and published cooling rates.
The data are broadly consistent with simple reheating of colder material within a completely accreted body. This model may have problems with volatile depletion, a required lack of impact sampling during metamorphism, and the timing of the event. The data are more consistent with accretion of colder material on a hot but cooling surface. Both models apparently require a recycling process during accretion to account for the reduction sequence. 相似文献
A long-term water balance model has been developed to predict the hydrological effects of land-use change (especially forest clearing) in small experimental catchments in the south-west of Western Australia. This small catchment model has been used as the building block for the development of a large catchment-scale model, and has also formed the basis for a coupled water and salt balance model, developed to predict the changes in stream salinity resulting from land-use and climate change. The application of the coupled salt and water balance model to predict stream salinities in two small experimental catchments, and the application of the large catchment-scale model to predict changes in water yield in a medium-sized catchment that is being mined for bauxite, are presented in Parts 2 and 3, respectively, of this series of papers. The small catchment model has been designed as a simple, robust, conceptually based model of the basic daily water balance fluxes in forested catchments. The responses of the catchment to rainfall and pan evaporation are conceptualized in terms of three interdependent subsurface stores A, B and F. Store A depicts a near-stream perched aquifer system; B represents a deeper, permanent groundwater system; and F is an intermediate, unsaturated infiltration store. The responses of these stores are characterized by a set of constitutive relations which involves a number of conceptual parameters. These parameters are estimated by calibration by comparing observed and predicted runoff. The model has performed very well in simulations carried out on Salmon and Wights, two small experimental catchments in the Collie River basin in south-west Western Australia. The results from the application of the model to these small catchments are presented in this paper. 相似文献