1,720,958 research outputs found
Measuring the shape of time-varying objects
No full textThis thesis describes the first implementation of a colour encoded structured light (CESL) range-finder capable of measuring the shape of time-varying or moving surfaces. The system is shown to have mean square accuracies of better than 0.5mm when measuring the shape of the human mouth during continuous speech sampled at 50Hz, and better than 0.2mm when measuring static objects of similar dimensions. In order to sample range at video-rates, the images of the scene to be digitised are stored on video tape. This allows the image processing to be performed off-line so the sampling rate of the system only depends on the frame-rate of the video equipment used. The work was motivated by the need to acquire information on mouth shape for acoustics of speech experiments so that the results presented are for measurements of mouth shape and objects relating to the field. The reasons for producing a new system, and the choice of CESL are discussed. The work covers the entire implementation of the range-finder, including code and slide design, feature extraction, feature interpretation, calibration and 3D reconstruction, and performance evaluation. A modification on the Blackman and Tukey classical power density spectrum (PDS) estimator was used for feature extraction which was shown to perform better than other techniques evaluated. The accuracy of detected features and the probability that they were not spurious was determined, based on the feature confidence output by the PDS estimator. Detected features were tracked to produce segments, and encoded as a directed acyclic graph (DAG) which was then matched with the original code sequence using a fast but sub-optimal technique. An existing camera calibration technique was used which was extended to include a second step for projector calibration. The projector model used was linear, had the correct number of degrees of freedom, and was particular to our stripe system
Depth Measurement of Face and Palate by Structured Light
No full textIn order to model speech production for purposes such as articulatory synthesis, articulatory data must be acquired, preferably in a way that does not impede the speaker's ability to speak. A variety of techniques has been used, many of them, such as ultrasound, X-rays, or MRI, adapted from medical imaging. For externally accessible articulators such techniques are not appropriate, but the task of measuring the shape of a complex three-dimensional object is still difficult. For a static object such as a dental impression manual methods such as slicing a mold of the impression and measuring the slices with calipers can be quite accurate, though time-consuming. For a dynamic object such as the face shape during speech such manual methods cannot be used. A workable alternative has been developed at Grenoble that instead uses simultaneous video pictures of front and profile face. Blue lipstick is used on the subject's lips to provide a definite outline and provide maximum contrast with the teeth and tongue. The images must then be post-processed before parameters such as mouth area are extracted. In this paper we present a structured light system which uses a slide projector and a single video camera to acquire depth coordinates of a static or moving object. We discuss pilot experiments aimed at optimising its output and establishing its accuracy, and make some preliminary comparisons with the Grenoble double-video system. In the next section the structured light technique is summarised, focusing on the experimental constraints it imposes. The technique is described in more detail elsewhere. In Static measurements' its use on the static object of an EPG palate is described. In 'Dynamic measurements' its use in acquiring dynamic face shape data is described, focusing on methodology issues that arose in an extended recording session with a human speaker. In the discussion we describe the calibration procedure and the related tradeoffs, and finally we make some initial comparisons to the double-video system
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
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