L. Barabesi  M. Marcheselli 《Environmetrics》2005,16(8):803-817

When a continuous population is sampled, the spatial mean is often the target parameter if the design‐based approach is assumed. In this case, auxiliary information may be suitably used to increase the accuracy of the spatial mean estimators. To this end, regression models are usually considered at the estimation stage in order to implement regression estimators. Since the spatial mean may be obviously represented as a bivariate integral, the strategies for placing the sampling locations are actually Monte Carlo integration methods. Hence, the regression‐based estimation is equivalent to the control‐variate integration method. In this setting, we suggest more refined Monte Carlo integration strategies which may drastically increase the regression estimator accuracy. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

    

S. Mukhopadhyay  S. Bhattacharya 《Environmetrics》2013,24(8):550-568

Fossil‐based palaeoclimate reconstruction is an important area of ecological science that has gained momentum in the backdrop of the global climate change debate. The hierarchical Bayesian paradigm provides an interesting platform for studying such important scientific issue. However, our cross‐validation based assessment of the existing Bayesian hierarchical models with respect to two modern proxy data sets based on chironomid and pollen, respectively, revealed that the models are inadequate for the data sets. In this paper, we model the species assemblages (compositional data) by the zero‐inflated multinomial distribution while modelling the species response functions using Dirichlet process‐based Gaussian mixtures. This modelling strategy yielded significantly improved performances, and a formal Bayesian test of model adequacy, developed recently, showed that our new model is adequate for both the modern data sets. Furthermore, combining together the zero‐inflated assumption, Importance Resampling Markov Chain Monte Carlo (IRMCMC) and the recently developed Transformation‐based Markov Chain Monte Carlo (TMCMC), we develop a powerful and efficient computational methodology. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

    

Michela Cameletti  Rosaria Ignaccolo  Stefano Bande 《Environmetrics》2011,22(8):985-996

In the last two decades, increasing attention has been given to air pollution around the world, mainly because of its impact on human health and on the environment. In the Po valley (northern Italy), one of the most troublesome pollutant is PM₁₀ (particulate matter with an aerodynamic diameter of less than 10 μm). In order to assess PM₁₀ concentration over an entire region, environmental agencies need models to predict PM₁₀ at unmonitored sites. To choose among possible predictive models and then meet the agencies' request, we focus on the class of Bayesian hierarchical models as they provide a flexible framework for incorporating relevant covariates as well as spatio‐temporal interactions. We consider six alternative models for PM₁₀ concentration in Piemonte region (north‐western Po Valley), during the winter season October 2005–March 2006. Our aim is to choose a model that is satisfactory in terms of goodness of fit, interpretability, parsimony, prediction capability and computational costs. In order to support this choice, we propose a comparison approach based on a set of criteria summarized in a table that can be easily communicated to non‐statisticians. The comparison findings allow to provide Piemonte environmental agencies with an effective statistical model for building reliable PM₁₀ concentration maps, equipped with the corresponding uncertainty measure. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

    

Phillip Cassey  Robert A. R. King 《Environmetrics》2001,12(7):691-698

We present a Monte Carlo test to distinguish among a general class of stochastic resource apportionment models using replicated species abundance data. In this test, the stochastic nature of resource apportionment models is used to carry out a large number of simulations and thus calculate a p‐value describing how well the model fits the data. We clarify an existing method and present a necessary modification to reduce the computing time required without affecting the reliability of the test. The use of the method is demonstrated with regional data from the North American Breeding Bird Survey (BBS). The example we present shows that the method provides a good level of discrimination between models that match the data and those that don't. An algorithm to implement our test, written for the application SAS, is freely available from the authors upon request. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

    

G. Caramanna  Y. Wei  M. M. Maroto‐Valer  Paul Nathanail  M. Steven 《Greenhouse Gases: Science and Technology》2012,2(2):136-143

In sub‐seabed storage, CO₂ is injected under the seafloor in geological structures that are able to trap and retain it. Even if the overall procedure is considered safe, the effects of potential seepage must be addressed in order to develop a reliable risk assessment of the process. This study focuses on the effects of CO₂ seepage on the chemistry of sediments and on the overlying water column in shallow‐water environments. To study these effects, an experimental rig was designed, fabricated, and tested. The main unit of the rig is a transparent Plexiglas vertical cylindrical vessel that can be filled with sediment in the bottom section and water in the upper part. CO₂ is injected as gas from the bottom through nozzles fed by a CO₂ cylinder. Sensors are used to monitor the variation of the main physical and chemical properties of water and sediments. Gas, water, and sediment samples can be collected for further analysis. The results highlight a fast response of the system to the injected CO₂ with a sharp reduction of the pH values of the interstitial water inside the sediments; once the injection stops, a recovery toward the initial values is recorded. The water above the sediment is also affected by the presence of CO₂; in this case the gas‐water interaction is controlled by the water movements induced by the rising bubble column. © 2012 Society of Chemical Industry and John Wiley & Sons, Ltd  相似文献   

    

Jun Li  Xiaochun Li 《Greenhouse Gases: Science and Technology》2015,5(2):152-168

When CO₂ is injected into aquifers in a hydrocarbon basin, either for CO₂ geological storage or enhanced oil recovery (EOR), these aquifers are most likely saturated with CH₄. Dissolving CO₂ into the aqueous phase will cause CH₄ to come out of the aqueous phase and partitioning into the CO₂‐rich non‐aqueous phase under static conditions. It is not well understood how this process develops under flow conditions, which is the subject of this paper. Although CH₄ solubility in brine is low under the subsurface conditions, the effects of CH₄ dissolved in saline aquifers cannot be ignored for CO₂ sequestration projects. This is due to the changes of the phase behavior, capillary pressure, and relative permeability which has already been recognized by previous studies. This work couples a recently developed thermodynamic model of CO₂‐CH₄‐brine system with an industrial reservoir simulator and applies it in the simulation of CO₂ injection into a CH₄ saturated aquifer. Simulation results are compared to field observations from U‐tube sampling and used to provide reasonable explanations. From the simulations, the compositions in U‐tube samples are influenced by U‐tube inlet position, perforation and the reservoir (geological) properties. With the explanations, the U‐tube observations of gas samples can be well matched by numerical simulation results.© 2014 Society of Chemical Industry and John Wiley & Sons, Ltd  相似文献   

    

Bo Li  Chun‐wei Gu 《Greenhouse Gases: Science and Technology》2016,6(2):232-250

This paper outlines the aerodynamic optimization for stator vane settings of multi‐stage compressors in a conceptual semi‐closed cycle with the combination of an artificial neural network (ANN) and genetic algorithm (GA). The investigation is conducted on a newly developed 5‐stage highly loaded axial flow compressor. A 3‐layer perceptron neural network is employed as the surrogate model replacing an in‐house one‐dimensional blade‐stacking computation code, and the influences of changes in physical properties of the working medium with varying ratios of exhaust CO₂ recirculation are considered in the computation. The stagger angles of the four stator vanes serve as the input data of the ANN, and the compressor aerodynamic performances are the outputs of the network. The well‐trained ANN is then incorporated into the optimization framework which is based on an improved real‐coded GA. Some advanced strategies including the elitism operator, blend crossover, non‐uniform mutation, and self‐adaption parameters are introduced into the GA to promote the searching efficiency and solution globality. A series of numerical optimization is carried out at various CO₂ contents under part‐speed conditions to achieve the maximum adiabatic efficiency with restrictions on the pressure ratio. The results show that the optimized stator vane settings can improve the adiabatic efficiency by about 1% for most cases, and a considerable reduction of the flow losses near the endwall regions is observed for the reference operating points. Regardless of the assumption of quasi‐one‐dimensional flow, the effectiveness of the optimization framework in dealing with the stage‐mismatching has been demonstrated. This research has allowed to reveal that from the compressor optimization point of view, a semi‐closed cycle is feasible using existing technology and that compressor modifications are needed according to situational requirements. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd  相似文献   

    

《Greenhouse Gases: Science and Technology》2017,7(4):613-623

Deployment of carbon capture and storage on a large scale poses many challenges. One is the availability of reservoirs with suitable characteristics (high porosity and permeability, matched large emitters, etc.). Such a challenge might lead to the selection of reservoirs with relatively low porosity. In those environments, the rock matrix is often stiff and questions arise regarding the capabilities of seismic methods to monitor injection. An illustrative modeling of seismic reflectivities within a hypothetical geological formation with physical properties equal to that of the low‐porosity reservoir in the St. Lawrence Lowlands sedimentary basin, suggests that a liquid‐water contact is a potentially good seismic reflector despite a priori unfavorable conditions. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.  相似文献   

    

Lou Yunsheng  Meng Yan  Ren Lixuan  Wu Lei  Zhang Yiwei  Zhao Shidi  Zhu Huaiwei 《Greenhouse Gases: Science and Technology》2016,6(5):662-669

A pot experiment was conducted to investigate the effects of silicate application quantity and silicate fertilizer type on rice growth and methane (CH₄) emission under elevated UV‐B radiation. The experiment was designed with two UV‐B radiation levels, i.e., reference UV‐B radiation (Ambient, A, 12.0 kJ·m⁻²·d⁻¹), and elevated UV‐B radiation (Elevated by 20%, E, 14.4 kJ·m⁻²·d⁻¹); with four silicate fertilizer levels, i.e., Si₀ (no silicate application, 0 kg SiO₂·ha⁻¹), Si₁ (sodium silicate, 100 kg SiO₂·ha⁻¹), Si₂ (sodium silicate, 200 kg SiO₂·ha⁻¹) and Si₃ (slag silicate fertilizer, 200 kg SiO₂·ha⁻¹). The results show that, silicate application could mitigate the depressive effect of elevated UV‐B radiation on rice growth and increase the tiller number, and dry weight of shoot and root biomass. Silicate application promoted rice growth, which increased with silicate application quantity (sodium silicate); slag silicate fertilizer was better than sodium silicate in promoting rice growth. Elevated UV‐B radiation could increase the emission flux and accumulative emission of CH₄ in rice soil, but silicate application significantly decreased the emission flux and accumulative emission of CH₄ and the methane emission decreased with the increase in silicate application quantity. At one silicate application quantity, slag silicate fertilizer was better than sodium silicate in respect of emission reduction effect. This indicates that application of slag silicate fertilizer in rice production can realize waste reuse and can effectively decrease the CH₄ emission in rice field under elevated UV‐B radiation. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd  相似文献   

    

Patricia Luis  Bart Van der Bruggen 《Greenhouse Gases: Science and Technology》2013,3(5):318-337

There are several technological options for post‐combustion CO₂ capture. Absorption with novel solvents, adsorption, conversion of CO₂ into chemical products, calcium looping, and membrane technology are the main alternatives to the conventional absorption process based on amines. In this review, an overview of these technologies is presented and the role that membranes play is evaluated considering two approaches: (i) processes based on selective membranes (gas permeation and supported liquid membranes), and (ii) processes based on non‐selective membranes (membrane contactors). The process performance demonstrated by recent research shows that membrane technology can fulfill the technical requirements for CO₂ capture but a closer interaction with the industrial partners and membrane manufacturers is needed to implement this technology in the industry.  相似文献