1,720,975 research outputs found
Assessment of site-specific wind predictions by a hidden Markov model for multivariate circular-linear data
No full textWe consider a heavy industrial district close to the city of Taranto where
winds from North-West quadrants and lack of precipitations are known to lead to a deterioration
of urban air quality in terms of PM10 concentrations. In 2012, the Apulia
Government adopted a Regional Air Quality Plan prescribing a reduction of industrial
emissions by 10% every time such meteorological conditions are forecasted 72 hours in advance.
In order to activate the appropriate safety measures, wind prediction is addressed
by the Regional Environmental Protection Agency (ARPA Puglia) using the Weather Research
and Forecasting (WRF) atmospheric simulation system. Here we investigate the
ability of the WRF system to properly predict the local wind speed and direction allowing
different performances for unknown weather regimes. Replicate observations of observed
and WRF-predicted wind speed and direction at a relevant point location within the area
of interest are jointly modeled as a multivariate 4-dimensional time series with a finite
number of states (wind regimes) characterized by homogeneous distributional behavior.
Observed and simulated wind data are made of two circular (direction) and two linear
(speed) variables, then the 4-dimensional time series is jointly modeled by a mixture
of projected-skew normal distributions with time-independent states, where the temporal
evolution of the state membership follows a first order Markov process. Parameter
estimates are obtained by a Bayesian MCMC-based method and results provide useful
insights on wind regimes corresponding to different performances of WRF predictions
A multivariate circular-linear hidden Markov model for distributions-oriented wind forecast verication
Get PDFWinds from the North-West quadrant and lack of precipitation are known to lead to an increase of PM10
concentrations in a residential neighborhood of the city of Taranto (Apulia, Italy). In 2012 the local government
prescribed a reduction of industrial emissions by 10% every time such meteorological conditions are
forecasted 72 hours in advance. Wind prediction is addressed using the Weather Research and Forecasting
(WRF) atmospheric simulation system by the Regional Environmental Protection Agency (ARPA Puglia).
In the framework of distributions-oriented forecast verication, we investigate the ability of the WRF system
to properly predict the local wind speed and direction allowing dierent performances for unknown
wind regimes. Ground-observed and WRF-predicted wind speed and direction at a relevant location are
jointly modeled as a 4-dimensional time series with a nite number of states (wind regimes) characterized by
homogeneous distributional behavior. Observed and simulated wind data are made of two circular (direction)
and two linear (speed) variables, then the 4-dimensional time series is jointly modeled by a mixture of
projected-skew normal distributions with time-independent states, where the temporal evolution of the state
membership follows a rst order Markov process. Parameter estimates are obtained by a Bayesian MCMCbased
method and results provide useful insights on wind regimes corresponding to dierent performances
of WRF predictions
Distributions-oriented wind forecast verication by a hidden Markov model for multivariate circular-linear data
Get PDFWinds from the North-West quadrant and lack of precipitation are
known to lead to an increase of PM10 concentrations over a residential neighborhood
in the city of Taranto (Italy). In 2012 the local government prescribed
a reduction of industrial emissions by 10% every time such meteorological
conditions are forecasted 72 hours in advance. Wind forecasting is addressed
using the Weather Research and Forecasting (WRF) atmospheric simulation
system by the Regional Environmental Protection Agency. In the context of
distributions-oriented forecast verification, we propose a comprehensive modelbased
inferential approach to investigate the ability of the WRF system to
forecast the local wind speed and direction allowing different performances for
unknown weather regimes. Ground-observed and WRF-forecasted wind speed
and direction at a relevant location are jointly modeled as a 4-dimensional
time series with an unknown finite number of states characterized by homogeneous
distributional behavior. The proposed model relies on a mixture of joint
projected and skew normal distributions with time-dependent states, where
the temporal evolution of the state membership follows a first order Markov
process. Parameter estimates, including the number of states, are obtained
by a Bayesian MCMC-based method. Results provide useful insights on the
performance of WRF forecasts in relation to different combinations of wind
speed and direction
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
A multivariate circular-linear hidden Markov model and site-specific assessment of wind predictions by an atmospheric simulation system
No full textWinds from the North-West quadrant and lack of precipitation are known
to lead to an increase of PM10 concentrations in the city of Taranto. In 2012 the
Apulia Government prescribed a reduction of industrial emissions by 10% every
time such meteorological conditions are forecasted 72 hours in advance. Wind
prediction is addressed using the Weather Research and Forecasting (WRF) atmospheric
simulation system by the Regional Environmental Protection Agency
(ARPA Puglia). We investigate the ability of the WRF system to properly predict
the local wind speed and direction allowing different performances for unknown
weather regimes. Observed and WRF-predicted wind speed and direction at a relevant
location are jointly modeled as a 4-dimensional time series with a finite number
of states (wind regimes) characterized by homogeneous distributional behavior. Observed
and simulated wind data are made of two circular (direction) and two linear
(speed) variables, then the 4-dimensional time series is jointly modeled by a mixture
of projected-skew normal distributions with time-dependent states, where the
temporal evolution of the state membership follows a first order Markov process.
Parameter estimates are obtained by a Bayesian MCMC-based method and results
provide useful insights on wind regimes corresponding to different performances of
WRF predictions
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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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