1,720,958 research outputs found
Model-oriented review and multi-body simulation of the ossicular chain of the human middle ear
No full textThe ossicular chain of the human middle ear has a key role in sound conduction since it transfers vibrations from the tympanic membrane to the cochlea, connecting the outer and the inner part of the hearing organ. This study reports firstly a description of the main anatomical features of the middle ear to introduce a detailed survey of its biomechanics, focused on model development, with a collection of geometric, inertial and mechanical/material parameters. The joint issues are particularly discussed from the perspective of developing a model of the middle ear both explanatory and predictive. Such a survey underlines the remarkable dispersion of data, due also to the lack of a standardization of the experimental techniques and conditions. Subsequently, a 3D multi-body model of the ossicular chain and other structures of the middle ear is described. Such an approach is justified as the ossicles were proven to behave as rigid bodies in the human hearing range and was preferred to the more widely used finite element one as it simplifies the model development and improves joint modeling. The displacement of the umbo (a reference point of the tympanic membrane) in the 0.3-6. kHz frequency range was defined as input of the model, while the stapes footplate displacement as output. A parameter identification procedure was used to find parameter values for reproducing experimental and numerical reference curves taken from the literature. This simple model might represent a valid alternative to more complex models and might provide a useful tool to simulate pathological/post-surgical/post-traumatic conditions and evaluate ossicular replacement prostheses. © 2012 IPEM
Studio di fattibilità di un orecchio virtuale
No full textLa ricerca intrapresa dagli autori ha come obiettivo la realizzazione di un “orecchio virtuale”, ovvero di un modello “completo” psico-acustico della percezione uditiva umana, che tenga conto di contributi alternativi alla via aerea normale quali contributi derivanti da vie tissutali (in particolare ossee) e fluide e contributi a frequenze ultrasoniche ed infrasoniche. Dato che risulta necessario studiare tecniche specifiche di modellazione e simulazione per ciascuna parte anatomica, nel presente lavoro sono stati approfonditi ed applicati a geometrie semplificate bidimensionali e tridimensionali dell’orecchio esterno, alcuni metodi (principalmente metodo ad elementi finiti spettrali (SFE), metodo ad elementi finiti generalizzato (GFEM)) di generalizzazione ed estensione del metodo agli elementi finiti classico (FEM) (principalmente metodo ad elementi finiti spettrali (SFE), metodo ad elementi finiti generalizzato (GFEM)). Tali metodi permettono di ottenere un’elevata accuratezza dei risultati delle simulazioni di trasmissione acustica con numero inferiore di nodi della meshdiscretizzazione rispetto alla regola convenzionalmente accettata per il FEM di dieci punti per lunghezza d’ondaun costo computazionale inferiore rispetto ai metodi tradizionali
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
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
An image formation model for Secondary Ion Mass Spectrometry imaging of biological tissue samples RID A-6953-2008
No full textSecondary Ion Mass Spectrometry (SIMS) can provide distribution images of elements and molecular fragments with high sensitivity and spatial resolution. This study aims to exploit the potential of this modality as an imaging technique for biomedical applications. A model of image generation was developed and validated on experimental SIMS images. The model allowed for the selection of standard distance deviation (SDD) and nearest neighbor index (NNI) as suitable indices for the characterization of SIMS images, as they have been associated with sample morphology. Two regression models were proposed to correlate the SDD index and NNI with an index of effectiveness and acquisition parameters. The SDD index, due to its linear relationship with the image noise parameter, was less sensitive to noise. The model was then applied to study the effect of instrumental and analytical parameters, such as pre-sputtering time, on image generation. (C) 2010 Elsevier B. V. All rights reserved
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