Yangyang Liu  Zhiyong U. Wang  Hong‐Cai Zhou 《Greenhouse Gases: Science and Technology》2012,2(4):239-259

Uncontrolled massive release of the primary greenhouse gas carbon dioxide (CO₂) into atmosphere from anthropogenic activities poses a big threat and adversely affects our global climate and natural environment. One promising approach to mitigate CO₂ emission is carbon capture and storage (CCS), in which ideal adsorbent materials with high storage capacity and excellent adsorption selectivity over other gases are urgently needed. For practical applications in CO₂ capture from flue gas of power plants, the biggest single contributor of anthropogenic CO₂ emission, the adsorbent materials must also be chemically stable, be easy to regenerate with minimal energy input, and be easily synthesized with low capital cost. Metal‐organic frameworks (MOFs), highly crystalline porous materials constructed by metal ions and organic ligands, have emerged as a class of excellent adsorbent materials for carbon capture. Great progress in MOF materials for CO₂ capture has been made in the past and reviewed accordingly, but new discoveries are constantly being made as the field quickly grows. In this paper, we provide a short review on the most recent advances in using MOFs for CO₂ adsorption, storage, and separation that are directly related to CO₂ capture. Some of the important properties of MOF adsorbents which are crucial for practical applications but are largely overlooked in research carried out so far are discussed. © 2012 Society of Chemical Industry and John Wiley & Sons, Ltd  相似文献   

    

Hao Zhang  Abdel El‐Shaarawi 《Environmetrics》2010,21(1):33-47

In many applications, observed spatial variables have skewed distributions. It is often of interest to model the shape of the skewed marginal distributions as well as the spatial correlations. We propose a class of stationary processes that have skewed marginal distributions. The covariance function of the process can be given explicitly. We study maximum likelihood inference through a Monte Carlo EM algorithm, and develop a method for the minimum mean‐square error prediction. We also present two applications of the process. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

    

Hae‐Kyung Im  Paul J. Rathouz  John E. Frederick 《Environmetrics》2009,20(5):494-511

We analyze 20 years of daily minimum and maximum air temperature data in the Chicago metropolitan region and propose a parsimonious model that describes their mean function and the space–time covariance structure. The mean function contains a long‐term trend, annual and semiannual harmonics, and physical covariates such as latitude, distance to the Lake Michigan, and winds, each interacted with the harmonic terms, thus allowing the effects of physical covariates to vary smoothly over time. The temporal correlation at a given location is described using an ARMA(1,2) model. The residuals (innovations) from this models are treated as independent replications of a spatial process with covariance structure in the Matérn class. The space–time covariance structure parameters are allowed to vary seasonally. Using the estimated covariance structure, we interpolate the temperature to a fine grid in the Chicago metropolitan region. This procedure borrows information from temporally and spatially adjacent data. The methods presented in this paper should be useful to approach other environmental problems where the data are discrete and regular in time but irregular in space. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

    

Noriah M. Al‐Kandari  Ian T. Jolliffe 《Environmetrics》2005,16(6):659-672

Principal component analysis (PCA) is a dimension‐reducing tool that replaces the variables in a multivariate data set by a smaller number of derived variables. Dimension reduction is often undertaken to help in interpreting the data set but, as each principal component usually involves all the original variables, interpretation of a PCA can still be difficult. One way to overcome this difficulty is to select a subset of the original variables and use this subset to approximate the principal components. This article reviews a number of techniques for choosing subsets of the variables and examines their merits in terms of preserving the information in the PCA, and in aiding interpretation of the main sources of variation in the data. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

    

Chung‐Kung Lee  Ding‐Shun Ho  Chung‐Chin Yu  Cheng‐Cai Wang  Yun‐Hua Hsiao 《Environmetrics》2003,14(3):255-269

A simple two‐scale Cantor set with unequal scales and weights was presented for the APC time series. The validity of this multifractal cascade model was examined with a one‐year length of hourly average CO, NO, NO₂, O₃, PM10 and SO₂ observations. This model fits remarkably well the entire spectrum of scaling exponents for the examined APC time series. It was found that the multifractal characteristics of the examined APC time series were closely related to both scale and weight parameters. Moreover, the weight parameter could be used to distinguish the degree of right‐skewness of APC frequency distribution. However, the relationship between the long‐range dependence and model parameters still requires further investigation. Some problems concerning the applicability of multifractal models on air pollution are also discussed. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

    

K. Krishnamoorthy  Luis Len‐Novelo 《Environmetrics》2014,25(2):107-126

Signed‐likelihood ratio tests (SLRTs) are derived for testing the shape and scale parameters and the mean of a gamma distribution. The properties of the proposed tests are evaluated by Monte Carlo simulation and compared with the other tests available in the literature. SLRTs are also developed for two‐sample problems of comparing two shape parameters, two scale parameters and two means, and their merits are evaluated by Monte Carlo simulation. Evaluation studies indicate that the SLRTs are accurate even for small samples and are comparable with or better than other tests. Furthermore, simple parametric bootstrap (PB) methods based on the maximum likelihood estimates are proposed for interval estimation. The PB confidence intervals are satisfactory even for small samples. The methods are illustrated and compared using two examples. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

    

Issis C. Romero‐Ibarra  Fernando Durn‐Muoz  Heriberto Pfeiffer 《Greenhouse Gases: Science and Technology》2014,4(1):145-154

Lithium oxosilicate (Li₈SiO₆) was synthesized and mechanically mixed with potassium carbonate, sodium carbonate, or a mixture of both. While the product sample composition was characterized using X‐ray diffraction, the CO₂ chemisorption was evaluated using dynamic (30–800 °C), isothermal (350–650 °C) and cyclic thermogravimetric analyses. The presence of the K, Na, or K‐Na‐carbonates in Li₈SiO₆ changes the sorption properties in a wide temperature range. K‐, Na‐, K‐Na‐Li₈SiO₆ samples captured a maximum weight of 32 wt% at 400 °C, 42 wt% at 550 °C, and 38 wt% at 600 °C, respectively. The results revealed that the weight gained on Li₈SiO₆ mixed with K‐, Na‐ and K‐Na‐carbonates was attributed to the formation of the eutectic phases. These materials would be suitable for CO₂ capture over a wide temperature range depending on the application process. Nevertheless, the cyclic experiments showed important variations in their respective efficiencies, depending on the temperature.  相似文献   

    

Dang Viet Quang  Abdallah Dindi  Aravind V Rayer  Nabil El Hadri  Abdurahim Abdulkadir  Mohammad R.M. Abu‐Zahra 《Greenhouse Gases: Science and Technology》2015,5(1):91-101

In this study, we report the effect of the moisture of polyethylenimine (PEI) impregnated mesoporous precipitated silica used for CO₂ adsorption on the heat capacity and the heat required to regenerate the adsorbent. The results indicate that the heat capacity of the absorbent increases as its moisture content increases. The increase in moisture results in the rise of the vaporization heat of water and the elevated heat capacity results in higher sensible heat. For these reasons, the total regeneration heat required for CO₂ capture process increases significantly. The adsorbent has a maximum CO₂ adsorption capacity at 75 °C. CO₂ capture process using PEI impregnated mesoporous precipitated silica requires a minimum energy to regenerate the adsorbent; it reduces 46% of the energy compared to a process using an aqueous MEA 30 wt%, as the process operates at 75 °C.  相似文献   

    

Kung‐Jong Lui 《Environmetrics》2001,12(6):539-546

To increase the efficiency of a study and to eliminate the effects of some nuisance confounders, we may consider employing a matched‐pair design. Under the commonly assumed quadrinomial sampling, in which the total number of matched‐pairs is fixed, we note that the maximum likelihood estimator (MLE) of rate ratio (RR) has an infinitely large bias and no finite variance, and so does the MLE of relative difference (RD). To avoid this theoretical concern, this paper suggests use of an inverse sampling and notes that the MLEs of these parameters, which are actually of the same forms as those under the quadrinomial sampling, are also the uniformly minimum variance estimators (UMVUEs) under the proposed samplings. This paper further derives the exact variances of these MLEs and the corresponding UMVUEs of these variances. Finally, this paper includes a discussion on interval estimation of the RR and RD using these results as well. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

    

A. Carbonez  A. H. El‐Shaarawi  J. L. Teugels 《Environmetrics》1999,10(1):79-86

Microbiological monitoring of drinking water for fecal contamination is a legal requirement in most countries. The objective is to protect the users from water borne disease. We expressed The United States Drinking Water Regulations (DWR) in statistical terms and examined their probabilistic characteristics both analytically and by simulations. The DWR set upper limits on the mean coliform count and on the individual counts of all samples examined per month. Our results show that only an upper limit on the mean coliform count is basically sufficient for DWR. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献