1,721,001 research outputs found
Aerosol extinction coefficient profile retrieval in the oxygen A-band considering multiple scattering atmosphere.Test case: SCIAMACHY nadir simulated measurements.
No full textA multiple scattering inversion procedure for the aerosol extinction coefficient profile retrieval and error assessment in the oxygen A-band, for passive remote sensing instruments, has been developed. The
procedure has been applied to SCIAMACHY nadir simulated measurements to investigate its effectiveness in the troposphere.
The inversion procedure consists of a multiple scattering Forward Model, an inversion method and a complete sensitivity and error assessment tool. The Forward Model is based on LIDORT code; the inversion method, the sensitivity study and the complete error assessment are based on Optimal Estimation. The sensitivity and error analysis has been derived to investigate the profile retrieval errors due to the uncertainty of different aerosol optical properties, molecular and surface parameters.
The analysis confirms that the profile retrieval accuracy and vertical resolution are strongly dependent on the oxygen A-band spectral resolution. The moderately high SCIAMACHY spectral resolution (0.4 nm in
the oxygen A-band) results in distinguishing a maximum of three aerosol layers in troposphere. The SCIAMACHY tropospheric aerosol profile retrieval is shown to be highly sensitive to aerosol optical
properties as phase function and single scattering albedo. The sensitivity study reveals an improvement of information content increasing the solar zenith angle and decreasing the surface albedo. As regards the
forward model, negligible errors occur as the number of streams exceeds 6.Published354-3801.10. TTC - TelerilevamentoJCR Journalreserve
Intraurban air pollution variability in industrialised towns and its potential impact on population exposure assessment
No full textEpidemiological studies often use air pollution monitored data from a single station or as averaged data from a few stations to estimate exposure (Serinelli et al., 2010). Indeed, in industrialised urban areas, this approach may present critical issues, e.g. i) missing intraurban exposure variability (Wilson et al., 2005) due to relationship among emissions and meteorology with respect to different intraurban areas; ii) loosing information about different health effects due to (mix of) not measured chemicals, "hidden" in even homogeneous concentration spatial distribution of measured pollutants, as may be the case for toxics adhering on particulate, originated from different sources (Amodio et al., 2010). Such issues seem to occur in two coastal industrialised towns (Brindisi and Taranto, Southern Italy) characterized by huge industrial emissions and high environmental risk. The aims of this work are to refine population exposure assessment and consequent health effects by studying time-space variability of pollutants. Time series of meteorological and pollution data (SO2, NO2, TSP and PM10) measured simultaneously in different sites are analysed. Concentration spatial variations were investigated by means of statistical indexes. Some meteorological variables, in particular the prevailing wind direction and speed are crucial in determining the areas with different exposure. Overall analysis evidence how various parts of both towns are affected by the industrial and harbour sites. Such influence may be primarily identified with SO2 concentration data, showing higher concentration values and positive correlation with wind intensity downwind the industrial site. These results suggest the model that links air pollution exposure to health effects may take into account both intraurban variability for directly monitored pollutants, and the consequent "wind effect" for harmful substances emitted by local sources, transported in atmosphere but not routinely measured. The approach and methodology is potentially applicable to other industrialised cities
Physics-based Residual Kriging for dynamically evolving functional random fields
Full text linkWe present a novel approach named Physics-based Residual Kriging for the statistical prediction of spatially dependent functional data. It incorporates a physical model—expressed by a partial differential equation—within a Universal Kriging setting through a geostatistical modelization of the residuals with respect to the physical model. The approach is extended to deal with sequential problems, where samples of functional data become available along consecutive time intervals, in a context where the physical and stochastic processes generating them evolve, as time intervals succeed one another. An incremental modeling is used to account for both these dynamics and the misfit between previous predictions and actual observations. We apply Physics-based Residual Kriging to forecast production rates of wells operating in a mature reservoir according to a given drilling schedule. We evaluate the predictive errors of the method in two different case studies. The first deals with a single-phase reservoir where production is supported by fluid injection, while the second considers again a single-phase reservoir but the production is driven by rock compaction
Variabilità intraurbana dell'inquinamento in città industrializzate e potenziale impatto sulla esposizione della popolazione
No full textIntroduzione. Per valutare l'esposizione della popolazione, gli studi epidemiologici usano solitamente lamedia dei valori di inquinamento dell'aria registrati dalle stazioni urbane di monitoraggio. Ma, in aree industrializzate, questo approccio può presentare criticità perché porta a trascurare: _ le variazioni intraurbane di esposizione dovute alla dinamica tra emissioni e meteorologia; _ le informazioni che possono emergere dal confronto della disomogeneità spaziale fra traccianti locali come SO2 eNO2 e inquinanti più omogenei come la concentrazione di PM10, che potrebbe presentare però differente composizione chimica (non misurata) più sensibile alle sorgenti locali. Questo lavoro è incentrato su due città industrializzate (Brindisi e Taranto) caratterizzate dalla presenza di importanti emissioni industriali, e ad alto rischio ambientale. Obiettivi. Approfondire la valutazione dell'esposizione della popolazione, e conseguente associazione eventuale ai dati di esiti sanitari, attraverso lo studio della variabilità spazio-temporale degli inquinanti valutata nell'anno 2006 a Taranto e Brindisi. Metodi. Sono state analizzate serie di dati meteorologici (direzione e intensità del vento) e di inquinamento (concentrazioni medie giornaliere) misurate in diversi siti nelle due città. Le va riazioni di concentrazione sono state studiate permezzo di indici statistici: il coefficiente di correlazione di Pearson, il 90° percentile delle differenze tra le concentrazioni giornaliere, e un coefficiente di divergenza normalizzato. Risultati. La direzione prevalente del vento è fondamentale nel determinare le aree delle città interessate da esposizione differente. Gli esiti generali dell’analisi mostrano come in entrambe le città si possano individuare zone influenzate da siti industriali e portuali.Tale influenza può essere in primo luogo identificata con i dati di concentrazione di SO2: sottovento a siti industriali, si registrano valori di concentrazione superiori, e correlazione positiva con l'intensità del vento. Maggiore omogeneità spaziale emerge per il particolato, del quale però non si registra una probabile differente composizione chimica in relazione alla presenza di grosse sorgenti locali. Conclusioni.Questi risultati indicano la necessità di cambiare lo schema usuale con cui si sperimenta la relazione tra l'esposizione all'inquinamento dell'aria e gli esiti sanitari, suggerendo di considerare la variabilità intraurbana per gli inquinanti monitorati direttamente, senzamediare assieme valori rappresentativi di differenti esposizioni. Inoltremettono in evidenza come il c.d. tracciante industriale SO2 può surrogare la presenza di sostanze non misurate routinariamente ed emesse da fonti locali, trasportate dal vento locale, adese al particolato. Mentre i risultati specifici hanno diretta applicazione nelle due aree considerate, l'approccio e la metodologia sono potenzialmente applicabili ad altre città industrializzat
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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