1,721,036 research outputs found
Small area estimation via m-quantile geographically weighted regression
No full textThe effective use of spatial information, that is the geographic locations of population units, in a regression model-based approach to small area estimation is an important practical issue. One approach for incorporating such spatial information in a small area regression model is via Geographically Weighted Regression (GWR). In GWR the relationship between the outcome variable and the covariates is characterised by local rather than global parameters, where local is defined spatially. In this paper we investigate GWR-based small area estimation under the M-quantile modelling approach. In particular, we specify an M-quantile GWR model that is a local model for the M-quantiles of the conditional distribution of the outcome variable given the covariates. This model is then used to define a bias-robust predictor of the small area characteristic of interest that also accounts for spatial association in the data. An important spin-off from applying the M-quantile GWR small area model is that it can potentially offer more efficient synthetic estimation for out of sample areas. We demonstrate the usefulness of this framework through both model-based as well as design-based simulations, with the latter based on a realistic survey data set. The paper concludes with an illustrative application that focuses on estimation of average levels of Acid Neutralizing Capacity for lakes in the north-east of the USA.<br/
Second Order Statistics of Mixed RF-FSO Relay Systems and Its Application to Vehicular Networks
No full textThis paper considers channel modeling and evaluation of second-order outage statistics of mixed radio frequency/free space optical (RF/FSO) relay systems over mixed turbulence induced fading (TIF) and non-turbulence induced fading (non-TIF) channels. The derived statistics are directly related to the performance measures. In particular, we derive fast computing closed form expressions for relevant statistics such as cumulative-distribution-function (CDF), level-crossing-rate (LCR), and average-fade-duration (AFD). Approximation through Laplace integration of the products of random processes modeled as Gamma-Gamma (G-G) and Nakagami-m (N-m) are exploited. The proposed framework is then applied to two different scenarios for vehicular networks: i) I2I (infrastructure-to-infrastructure) direct communications enabled by FSO link, ii) V2V (vehicle-to-vehicle) communications enabled by RF/FSO/RF AaF (amplify-and-forward) relay link. Moreover, we provide numerical results for various settings of RF/FSO system model parameters
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Improving small area estimates of households’ share of food consumption expenditure in Italy by means of Twitter data
No full textIn this work we use emotional data coming from Twitter as auxiliary variable in a small area model to estimate Italian households’ share of food consumption expenditure (the proportion of food consumption expenditure on the total consumpion expenditure) at the provincial level. We show that the use of Twitter data has a potential in predicting our target variable, reducing the estimated mean squared error with respect to what obtained by the same working model without the Twitter data
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
L’impiego delle variabili ausiliarie per la costruzione degli stimatori
No full textL’opera si propone di illustrare in modo sintetico e sistematico le tecniche di stima dei parametri di una popolazione finita che fanno uso delle informazioni ausiliarie disponibili, al fine di affrontare i problemi che emergono nelle indagini reali. In queste infatti ci si trova a dover fronteggiare gli effetti delle imperfezioni nelle basi di campionamento, della mancata osservazione di tutte le variabili da rilevare o di una parte di esse nelle unità designate a far parte del campione, degli errori di misura. Il volume si propone di rendere il lettore conscio di tali effetti e capace di farvi fronte con le tecniche che vengono descritte sottolineandone le potenzialità e i limiti al fine di una scelta consapevole
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