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401.
Abstract: We proposed a step‐by‐step approach to quantify the sensitivity of ground‐water discharge by evapotranspiration (ET) to three categories of independent input variables. To illustrate the approach, we adopt a basic ground‐water discharge estimation model, in which the volume of ground water lost to ET was computed as the product of the ground‐water discharge rate and the associated area. The ground‐water discharge rate was assumed to equal the ET rate minus local precipitation. The objective of this study is to outline a step‐by‐step procedure to quantify the contributions from individual independent variable uncertainties to the uncertainty of total ground‐water discharge estimates; the independent variables include ET rates of individual ET units, areas associated with the ET units, and precipitation in each subbasin. The specific goal is to guide future characterization efforts by better targeting data collection for those variables most responsible for uncertainty in ground‐water discharge estimates. The influential independent variables to be included in the sensitivity analysis are first selected based on the physical characteristics and model structure. Both regression coefficients and standardized regression coefficients for the selected independent variables are calculated using the results from sampling‐based Monte Carlo simulations. Results illustrate that, while as many as 630 independent variables potentially contribute to the calculation of the total annual ground‐water discharge for the case study area, a selection of seven independent variables could be used to develop an accurate regression model, accounting for more than 96% of the total variance in ground‐water discharge. Results indicate that the variability of ET rate for moderately dense desert shrubland contributes to about 75% of the variance in the total ground‐water discharge estimates. These results point to a need to better quantify ET rates for moderately dense shrubland to reduce overall uncertainty in estimates of ground‐water discharge. While the approach proposed here uses a basic ground‐water discharge model taken from an earlier study, the procedure of quantifying uncertainty and sensitivity can be generalized to handle other types of environmental models involving large numbers of independent variables.  相似文献   
402.
    
We used distance sampling (line transects) and mark‐resight to estimate habitat and local area (area size, range: 3.9–44.5 ha) population density of ungulates. The distance sampling study was performed on fallow deer (Dama dama), roe deer (Capreolus capreolus) and wild boar (Sus scrofa) in a mediterranean forest. The mark‐resight study was performed on a roe deer population in a hilly area of the Apennines. The first study allowed us to estimate the animal density into four different habitats (deciduous oak wood, evergreen oak wood, maquis and open areas with domestic‐pine woods). The between habitat differences of population density are large for the three species: fallow deer are more abundant in the open areas (22.22 heads/km2, c.i. 12.42–39.74), roe deer in the deciduous oak wood (14.50 heads/km2, c.i. 7.01–30.10) and wild boar in both the open areas (11.29 heads/km2, c.i. 4.86–26.20) and evergreen oak wood (10.42 heads/km2, c.i. 6.78–16.02). The roe deer population in the Apennines is characterized by large between‐zone variations of population density (range: 1997: 13.25–131.31, 1998: 29.06–78.01, 1999: 10.67–88.58). Moreover, trends of local zones may be quite different with respect to the average trend of a wider study area, suggesting a well‐defined short‐scale spatial structure for this population. We conclude that both survey methods may be very useful in population assessment, but they need intense field effort and careful statistical design. Care needs to be taken to satisfy the assumptions of the statistical models. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
403.
    
This article is concerned with the estimation of the mean μ and standard deviation σ utilizing a singly‐left‐censored sample of normally distributed data having a known detection limit (DL). A new computer algorithm for obtaining the Cohen ( 1959 ) maximum likelihood estimates of μ and σ is provided which does not require auxiliary tables. The algorithm utilizes S‐PLUS or R languages. Closed form estimates of the mean and standard deviation obtained under a new replacement method are given for normally distributed left‐censored samples, which appear to be superior to existing replacement method estimates. The replacement method estimates are based on replacing the left‐censored observations by a non‐constant value. The performances of these methods are compared utilizing many simulated data sets. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
404.
    
In the context of geologic carbon dioxide (CO2) sequestration, the storage effectiveness of a caprock–reservoir system is a function of the properties of both the caprock and reservoir – namely, the ability of the caprock to prevent upward leakage of CO2 (caprock sealing capability), the mechanical response of the reservoir and caprock (by evaluating in situ stress changes), and the extent and degree to which CO2 can be trapped over long periods of time. In this work, all three parameters were considered to evaluate the storage effectiveness of the Cambrian–Ordovician sequence of the Northern Appalachian Basin. We constructed a series of hydro‐mechanical models to investigate interactions between CO2 flow and geomechanical processes and to evaluate the three aspects of storage performance. Models were built to evaluate two scenarios: (1) single reservoirs with a single overlying caprock, and (2) systems comprising multiple reservoirs and multiple intermediate caprock units in addition to the primary (uppermost) caprock unit. The overall conclusion of the work is that focusing only on one aspect of storage effectiveness might not necessarily warrant long‐term CO2 storage. Results of the sensitivity analysis for the single caprock–reservoir system show that each storage effectiveness metric has its own control parameters. A comparison among three stacked caprock–reservoir systems in different parts of the study area shows that each location in the study area could be appropriate for one of the storage effectiveness metrics. Therefore, we conclude that the screening process to select the best site for CO2 sequestration should be based on an evaluation of all three metrics. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.  相似文献   
405.
    
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406.
    
Carbon dioxide emissions to the atmosphere lead to global warming and unpredictable climate change via the greenhouse effect. Carbon dioxide from industrial sources can be captured by the membrane separation technique to mitigate the greenhouse effect. In this research, a polymer solution was prepared by blending a cellulose triacetate (CTA) polymer with a tri‐n‐butyl phosphate (TBP) additive. The polymer solution was coated on an alumina (α‐Al2O3) tube, which acted as a support material, to prepare a composite membrane for the CO2 separation. The composite membrane that was prepared was characterized by Fourier‐transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermo‐gravimetric analysis (TGA), and differential scanning calorimetry (DSC) analyses. The CO2 permeance and the selectivity for the prepared composite membrane were evaluated using a constant pressure‐variable volume method. The influence of the concentration of CTA and TBP, polymer solution preparation time, number of sequential dip coating, and the feed gas pressure on the CO2, N2, and CH4 gas separation performances was examined. The highest CO2 permeance of 129 GPU and the selectivity of 19.9 versus N2 and 10.6 against CH4 were obtained for the pure gases, and a CO2 permeance of 116 GPU and selectivity of 17.1 against N2 were obtained for a mixture of gases (15% CO2/85% N2). © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.  相似文献   
407.
    
When CO2 is injected into saline aquifers, salt precipitation will occur near the injection well. To investigate the effects of temperature on salt precipitation, a series of non‐isothermal numerical models were conducted by simulating the injection of cold CO2 into the aquifers with relatively high temperature. Some thermal processes, the evolution of CO2 plume, salt precipitation, the effects of gravity, and permeability reduction were analyzed. Furthermore, the deviance of the isothermal model was evaluated. The results show that the heat exchange between cold CO2 and hot rock significantly affects the formation temperature. The injection of colder CO2 can obviously decrease the extent of salt precipitation. A localized region with very large solid saturation occurs near the upper portion of the dry‐out front. Furthermore, another localized region with larger solid saturation emerges near the lower portion of the dry‐out front when the CO2 injection rate is low. This region seems to move upward because of dissolution and reprecipitation of salt caused by capillary‐driven backflow of the aqueous phase. Salt precipitation can result in a significant decrease in permeability. Temperature‐induced change of CO2 viscosity seems to have greater impact on the pressure evolution in the formation than precipitation‐induced change of permeability. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.  相似文献   
408.
    
Understanding the dynamic response of coal to carbon dioxide sorption is crucial for optimizing carbon dioxide sequestration in unmineable coal seams and enhanced coalbed methane recovery. In order to explore the adsorption kinetics of carbon dioxide in coal, 15 isothermal adsorption tests were conducted on bituminous and sub‐bituminous coals at 50°C for increasing equilibrium pressures (up to 4 MPa). The pseudo‐second order (PSO) model is introduced to approximate the carbon dioxide sorption kinetics in coal, and the kinetics properties are then investigated via the PSO model. The linear relationship between (t/q) and (t) is validated and confirmed with a high correlation coefficient (>99%). The kinetics parameter, k2, decreases with both increasing equilibrium sorption pressure and increasing pressure difference. The sorption equilibrium content, Qe, in each sorption stage depends on both the final equilibrium pressure and the pressure difference. Based on the relationship between sorption content and time, the sorption content for different pressure ranges is predicted using different time intervals. The analysis indicates that the adsorption process for carbon dioxide in coal is a combination of both bulk diffusion‐controlled and surface interaction‐controlled processes; the former dominates the initial stage while the latter controls the majority of the overall process. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd  相似文献   
409.
    
Partial differential equations (PDEs) are a useful tool for modeling spatiotemporal dynamics of ecological processes. However, as an ecological process evolves, we need statistical models that can adapt to changing dynamics as new data are collected. We developed a model that combines an ecological diffusion equation and logistic growth to characterize colonization processes of a population that establishes long‐term equilibrium over a heterogeneous environment. We also developed a homogenization strategy to statistically upscale the PDE for faster computation and adopted a hierarchical framework to accommodate multiple data sources collected at different spatial scales. We highlighted the advantages of using a logistic reaction component instead of a Malthusian component when population growth demonstrates asymptotic behavior. As a case study, we demonstrated that our model improves spatiotemporal abundance forecasts of sea otters in Glacier Bay, Alaska. Furthermore, we predicted spatially varying local equilibrium abundances as a result of environmentally driven diffusion and density‐regulated growth. Integrating equilibrium abundances over the study area in our application enabled us to infer the overall carrying capacity of sea otters in Glacier Bay, Alaska.  相似文献   
410.
    
Elevated levels of particulate matter (PM) in the ambient air have been shown to be associated with certain adverse human health effects. As a result, monitoring networks that track PM levels have been established across the United States. Some of the older monitors measure PM less than 10 µm in diameter (PM10), while the newer monitors track PM levels less than 2.5 µm in diameter (PM2.5); it is now believed that this fine component of PM is more likely to be related to the negative health effects associated with PM. We propose a bivariate dynamic process convolution model for PM2.5 and PM10 concentrations. Our aim is to extract information about PM2.5 from PM10 monitor readings using a latent variable approach and to provide better space‐time interpolations of PM2.5 concentrations compared to interpolations made using only PM2.5 monitoring information. We illustrate the approach using PM2.5 and PM10 readings taken across the state of Ohio in 2000. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
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