1,720,955 research outputs found
Application of denoising techniques to micro-tomographic images
No full textMicrocomputed tomography (microCT) is a particular version of computerized axial tomography commonly used by radiologists which reaches resolutions of the order of a few micrometers.
In biology, this technique is especially useful for the study of hard tissues, such as calcified bone and dental matrices, because of their high linear attenuation coefficient.
MicroCT images, though, are affected by a strong noise component, neither Gaussian nor white, caused by the characteristics of the acquisition system itself.
In this paper we consider the problem of microCT image denoising, and compare the performance of two well-known denoising techniques and of BM3D, a recent technique based on the nonlocal approach.
Although for the time being the performance analysis is mostly qualitative, results speak clearly in favor of BM3D
Le frane d’Ischia (Italia): un approccio integrato finalizzato alla protezione ambientale
No full textUn approccio integrato (chimico, idrologico, mineralogico e microtomografico) è stato usato per studiare i suoli delle frane (colate rapide di fango) avvenute ad Ischia nell’aprile del 2006. Lo studio è stato condotto su campioni di suolo prelevati da tre profili pedologici rappresentativi descritti nelle nicchie di distacco delle frane. Il principale risultato indica: (i) presenza di suoli vulcanici, molto ricchi di vetro primario, caratterizzati dalla presenza di caolinite a basso ordine cristallino in tutti gli orizzonti e minerali argillosi a reticolo espandibile negli orizzonti più profondi (2CB e 2C), (ii) elevata capacità di ritenzione idrica in tutti gli orizzonti del suolo, (iii) una discontinuità verticale delle proprietà fisiche del suolo. In termini di processi pedogenetici, i suoli del versante nord del M. Vezzi sono molto diversi da quelli descritti per le altre frane catastrofiche della regione Campania (Sarno, Quindici, ecc), ma hanno in comune la presenza, lungo il profilo del suolo, di una marcata discontinuità fisica che certamente contribuisce ai meccanismi di innesco delle frane
Porous Media Characterization by Micro-Tomographic Image Processing
No full textIn this thesis, we have focused our attention on the characterization of porous media through micro-tomographic image processing.
A porous medium can be simply seen as a solid material with "holes" in it, which, connected or isolated, may or may not eventually allow the flow of one or more fluids. They have various applications in common practice and are widely used in many disciplines, both scientific and industrial. Porous media are strongly characterized by their internal microstructure, which needs to be accurately described in order to determine their performance and macroscopic properties. Despite recent technological advances and the introduction of imaging techniques such as X-ray micro-tomography, methods to characterize quantitatively the porous media internal structure are still few and related to some specific applications.
To this regards, we propose new algorithms for the analysis of the 3D micro-architecture of porous media based on image processing and the mathematical morphology theory. In particular, the opening operator properties have been exploited in the "successive opening" algorithm which represents the starting point for the construction of three morphological synthetic indicators. They are the dimensional curves, Pore Size Distribution (PoSD) and Trabecular Size Distribution (TrSD), which provide information about the pores or solid phase structure, the connectivity curves, which allow to identify how the structural elements are interconnected, and the effective porosity, which represents the porous fraction concerned with the transport of fluids. Experimental results show that the proposed indicators together represent an effective tool for the porous media internal structure characterization.
Since noise is a primary cause of reduced image analysis capability in micro-CT, we have dedicated a part of our research to the reduction of the strong noise that corrupts tomographic images. After evaluating experimentally the characteristics of noise, we propose a filtering technique for correlate noise based on the Block-Matching 3D (BM3D) algorithm. Experimental results prove the proposed technique effectiveness and its potential to improve the performance of the algorithms proposed in the first part.
Although micro-tomographic image processing presents considerable difficulties, both for the intrinsic characteristics of the images, and for the nature of analyzed objects, this thesis proves that reliable and useful indications about the structure of porous media can be obtained through the use of the mathematical morphology theory
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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