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82.
Spatio-temporal modeling of particulate matter concentration through the SPDE approach 总被引:3,自引:0,他引:3
Michela Cameletti Finn Lindgren Daniel Simpson Håvard Rue 《AStA Advances in Statistical Analysis》2013,97(2):109-131
In this work, we consider a hierarchical spatio-temporal model for particulate matter (PM) concentration in the North-Italian region Piemonte. The model involves a Gaussian Field (GF), affected by a measurement error, and a state process characterized by a first order autoregressive dynamic model and spatially correlated innovations. This kind of model is well discussed and widely used in the air quality literature thanks to its flexibility in modelling the effect of relevant covariates (i.e. meteorological and geographical variables) as well as time and space dependence. However, Bayesian inference—through Markov chain Monte Carlo (MCMC) techniques—can be a challenge due to convergence problems and heavy computational loads. In particular, the computational issue refers to the infeasibility of linear algebra operations involving the big dense covariance matrices which occur when large spatio-temporal datasets are present. The main goal of this work is to present an effective estimating and spatial prediction strategy for the considered spatio-temporal model. This proposal consists in representing a GF with Matérn covariance function as a Gaussian Markov Random Field (GMRF) through the Stochastic Partial Differential Equations (SPDE) approach. The main advantage of moving from a GF to a GMRF stems from the good computational properties that the latter enjoys. In fact, GMRFs are defined by sparse matrices that allow for computationally effective numerical methods. Moreover, when dealing with Bayesian inference for GMRFs, it is possible to adopt the Integrated Nested Laplace Approximation (INLA) algorithm as an alternative to MCMC methods giving rise to additional computational advantages. The implementation of the SPDE approach through the R-library INLA (www.r-inla.org) is illustrated with reference to the Piemonte PM data. In particular, providing the step-by-step R-code, we show how it is easy to get prediction and probability of exceedance maps in a reasonable computing time. 相似文献
83.
This article compares behavioral health service use and cost for foster care versus nonfoster care children; children before, during, and after foster care placement; and successfully reunified versus nonsuccessfully reunified foster care children. Behavioral health service costs for children in foster care were higher than for children not in foster care. Children in foster care used more services during their foster care placement than before placement and after discharge. Nonsuccessfully reunified children received a significantly larger quantity of services than those successfully reunified. 相似文献
84.
We present a maximum likelihood estimation procedure for the multivariate frailty model. The estimation is based on a Monte Carlo EM algorithm. The expectation step is approximated by averaging over random samples drawn from the posterior distribution of the frailties using rejection sampling. The maximization step reduces to a standard partial likelihood maximization. We also propose a simple rule based on the relative change in the parameter estimates to decide on sample size in each iteration and a stopping time for the algorithm. An important new concept is acquiring absolute convergence of the algorithm through sample size determination and an efficient sampling technique. The method is illustrated using a rat carcinogenesis dataset and data on vase lifetimes of cut roses. The estimation results are compared with approximate inference based on penalized partial likelihood using these two examples. Unlike the penalized partial likelihood estimation, the proposed full maximum likelihood estimation method accounts for all the uncertainty while estimating standard errors for the parameters. 相似文献
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T. Andrew Finn 《Information, Communication & Society》1999,2(2):174-200
This article examines two components of temporality that have implications for electronically mediated communication. One is the dichotomy of simultaneous/non-simultaneous communication and then the varying degrees of non-simultaneity that are possible. The other is the fundamental difference between timed and untimed communication. Timed communication is temporally based and sequential, while untimed communication, such as print and still image content, is spatially based. The article argues that there are two fundamental types of mediated communication: communication mediated across time and communication mediated across space. The implications of temporality for both forms of mediated communication are examined in detail. The implications of temporality and mediated communication for multimedia, technology convergence, and research are discussed. 相似文献
88.
Mathias Herup Nielsen Morten Frederiksen Christian Albrekt Larsen 《The British journal of sociology》2020,71(1):112-126
The increased comparative research on perceptions of public welfare deservingness studies the extent to which different subgroups of citizens are deemed worthy or unworthy of receiving help from the welfare state. The concept of deservingness criteria plays a crucial role in this research, as it theorizes a universal heuristic that citizens apply to rank people in terms of their welfare deservingness. Due to the mainly quantitative nature of the research and despite the indisputable progress it has made, the subjective existence and actual application of these deservingness criteria remain a bit of a black box. What criteria of deservingness do citizens actually apply, and how do they apply them? This article opens the black box of welfare deservingness and sheds light on the nature and practice of deservingness criteria. Empirically, the paper explores how the deservingness of immigrants is discussed and established within 20 focus groups conducted in Slovenia, Denmark, UK, and Norway in 2016 with a total of 160 participants. All 20 focus groups discussed the welfare deservingness of immigrants based on similar vignette stimuli. Our analysis shows that (1) deservingness criteria are used both to construct images of target groups and as normative yardsticks; (2) deservingness criteria do not work independently of each other, but rather co-function in specific hybridized discourses; and (3) the moral logic of deservingness is supplemented by alternative moral logics, at least in the case of migrants. 相似文献
89.
Alison E. Baroody Charlotte Ferretti Ross Larsen 《Journal of Children and Poverty》2018,24(2):123-143
The aim of the study is to evaluate the effects of a language-rich math content text message intervention as a way to promote child literacy outcomes for children enrolled in 15 Head Start centers participating in Jumpstart. Two-hundred and fifty-eight families were randomly assigned to treatment (language-rich math text) or control (information about kindergarten enrollment) conditions. Families received text messages in English, Spanish, or written Chinese. Parents reported on children’s fall entry skills and family demography. Teachers reported on children’s interest in math and literacy. Children were directly assessed on literacy skills to determine if the language-rich math content increased literacy skills. Structural equation models reveal no main effects for the sample of 258, but subgroup analyses by language show intervention effectiveness. For families receiving text messages in English, effectiveness depended on children’s fall letter and shape knowledge for increasing phonological awareness (English). The intervention appears most effective for Spanish-speaking families by increasing children’s math and literacy interest, definitional vocabulary, and print knowledge. Limitations and finding implications are discussed. 相似文献
90.
This research examines whether the exogamy effect on the divorce risk varies over marital duration. Registry data from 1970 to 2003 allow us to observe couples in exogamous and endogamous ethno-linguistic marriages (Finnish speakers and Swedish speakers in Finland). We find that an elevated divorce risk of exogamous couples, which has been observed in numerous studies, is not typical of recently initiated marriages only, because it does not attenuate over marital duration. Marital problems that lead to divorce seem to be more common among exogamous couples than among endogamous couples. We argue that these patterns are likely due to group-specific differences in attitudes toward marriage. The argument is supported by a persistent difference in the divorce risk across endogamous Finnish- and Swedish-speaking marriages, and by the variation in divorce risk by ethno-linguistic composition of the couples in a regional context where minority group behaviors are more likely absorbed into majority group behaviors. 相似文献