1,720,955 research outputs found
LAWS OF LARGE NUMBERS AND CENTRAL LIMIT THEOREMS FOR RANDOM GEOMETRIC MEASURES. A COMPUTATIONAL APPROACH
No full textThe aim of this thesis is to produce computational experiments related to
a Central Limit Theorem (CLT) for random measures proved by Penrose in [4]. In particular we analyze some random measures associated with a segment process, a Voronoi tessellation and a Johnson-Mehl tessellation constructed on an underlying 2-dimensional point process. In the result by Penrose, this point process is supposed to be Poisson non-homogeneous (or Binomial, but we are
not going to study this case). In this thesis, we also consider the case of an
underlying Neyman-Scott cluster process.
The main references are [4] and references therein; before this CLT, in [5] Penrose
obtained a Law of Large Numbers for random measures. These results are an extension of [1], where Baryshnikov and Yukich proved similar theorems under stricter assumptions on the radius of stabilization of the considered random measure. There are also other results concerning CLTs on random measures(for example in [2]), but processes are always assumed to be homogeneous; through Baryshnikov, Yukich and Penrose’s approach it is possible to relax the
homogeneity conditions, so that their hypotheses are more likely to be true for
applications. The main difference between other CLTs for random measures and this new approach is that the limit is not considered as the window of observation increases (which is a problem, because we should have homogeneity conditions of the random process on the whole space), but as the intensity of the process increases (just one realization of a process with sufficiently large intensity gives information on the typical features of the process). In Baryshnikov, Yukich and Penrose’s works new theoretical results and some examples are presented, but
simulations are not included; moreover, the hypothesis of Poisson distribution of the underlying point process is extended only to the case of a Binomial point process. This thesis is a computational approach to the theorem, which may lead to possible future generalizations from a theoretical point of view, including more general point processes, such as the cluster ones.
In our work we analyze the behaviour of some particular random measures as the intensity of the underlying point process increases. We find some advantages and disadvantages of Penrose’s approach; we have a validation of the theorem through our simulations by observing a Gaussian trend of our data (and by 2 performing some Lilliefors tests), and we also obtain some Laws of Large Numbers.
Our computational approach has been carried out for measures depending on homogeneous Poisson point processes, non-homogeneous ones and Neyman-Scott ones. References
[1] Yu Baryshnikov, J.E.Yukich, Gaussian limits for random measures in geometric
probability. Ann. Appl. Probab. 15, 2005, 213-253. [2] V. Benes, J. Rataj, Stochastic Geometry: Selected Topics. Kluwer Academic
Publishers, Boston, 2004.[3] V.Capasso, M.Burger, A.Micheletti, C.Salani, Mathematical models for polymer crystallization processes. In Mathematical Modelling for Polymer Processing (V. Capasso, Ed). Springer, Heidelberg, 2000, 167-242. [4] M. D. Penrose, Gaussian limits for random geometric measures. Electronic
Journal of Probability 12, 2007, 989-1035.
[5] M. D. Penrose, Laws of large numbers in stochastic geometry with statistical
applications. Bernoulli 13, 2007, 1124-1150.
Statistical identification of epidemics for rare events point processes. A case of listeriosis in Lombardy
No full textThe aim of this work is to present a MP test for extreme monotone randomized models. In particular it tests whether the extreme event of a sample comes from the same distribution as the other data. The application we present concerns the detection of epidemics of listeriosis in Lombardy from 2005 to 2011
A randomized most powerful test to detect a cheater's action. Applicaton to identification of listeriosis in Lombardy
Full text linkThis article presents a new randomized non-parametric test based on a sample of independent but not identically distributed variables; this test detects if a cheater replaces one of the distributions of the sample with a convex-dominating one. The presented test is the uniformely most powerful, in the sense that it is the most powerful for any change of the cheater. We show that this test may be applied when we have variables with distribution satisfying the monotone likelihood ratio property and we need to check whether a parameter of a variable has been changed. The application we present concerns the detection of epidemics of listeriosis in Lombardy from 2005 to 2011
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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