1,720,982 research outputs found
Minimum-Error Splitting Algorithm for a Dual Layer LCD Display—Part II: Implementation and Results
No full textA dual layer LCD display is able to achieve a high dynamic range by stacking two liquid crystal panels one on top of the other over an enhanced backlight unit. However, the finite distance between the two panels inevitably introduces a parallax error when the display is observed off-axis, and the dynamic range limitations of the individual panels introduce a reconstruction error near sharp edges in the input image. In Part I, we have formulated the image splitting as a constrained optimization problem in which a joint minimization of the parallax error and the visibility of the reconstruction error is performed.
In this Part II, we describe one possible numerical method which solves the optimization problem at a low computational cost. We also describe in more detail the characteristics of the prototype display which has been built by FIMI-Philips. We finally present some results and an evaluation of the errors introduced by the proposed splitting algorithm
Minimum-Error Splitting Algorithm for a Dual Layer LCD Display—Part I: Background and Theory
No full textA Dual Layer high dynamic range LCD display can be built by stacking two panels one on top of the other. In this way, the dynamic range is theoretically squared and the bit depth is also increased. Dedicated splitting algorithms are however needed to generate the two images which drive the panels, in order to minimize the parallax and reconstruction errors.
In this paper we present an algorithm, based on variational techniques, which seeks the joint minimization of both errors. We propose a simplified visible difference metric that exploits some limitations of the human visual system and can be easily incorporated into an optimization algorithm. The image splitting task is formulated as a quadratic programming problem, which can be efficiently solved by means of appropriate numerical methods.
Preliminary tests on medical images showed that the algorithm has good performances and appears robust with respect to the parameter adjustment
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
Quantization in Medical Imaging Displays — Initial Observer Results for a High-Luminance-Range, Dual-Layer LCD
No full textWe studied the effect of image quantization by comparing observer detection performance with 8-and 16-bit grayscale presentation. Eight readers evaluated 532 image pairs using a two-alternative forced choice experimental design. The image set consisted of synthetic backgrounds generated using the mammography-like cluster lumpy background (CLB) technique with a dual-layer approach with parameter values that have been shown to replicate the correlation structure found in digital mammography. The image pairs were reviewed in a display device prototype with one million pixels capable of processing and displaying 16-bit images (up to 65536 luminance values). These image pairs were presented either as non-quantized (full range) images in a 16-bit presentation scale, or as quantized, 8-bit images, with a perceptual mapping of gray levels to luminance. The difference in reader performance between reads on quantized image pairs and reads on non-quantized image pairs were derived using fraction of correct decisions. The variance of our measurements was estimated using a multi-reader, multi-case analysis. Average reader performance difference between 16-and 8-bit quantization was 0.065 with an associated standard deviation of 0.048. Our study showed that image quantization is an important factor in visual detection task, that is, a quantization from 16-to 8-bit significantly reduces reader detection performance
A quantitative assessment of non specific pinocytosis by human endothelial cells surviving in vitro.
No full textHuman umbilical vein endothelial cells have been assayed in vitro, 24 hrs. after plating, for non specific pinocytic activity. The culture conditions were designed to minimize the exogenous stimulations of pinocytosis, such as those possibly coming from mitotic induction and chemical and contact-dependent signaling. Two different markers were used: Lucifer Yellow CH (LY), and three different preparations of horseradish peroxidase, a multiple form (type II) composed of five different isoenzymes, and two purified acidic (type VIII) and basic (type IX) isoenzymes. The uptake of LY appears to depend on both fluid-phase incorporation and non specific adsorption to the cell surface, and it shows a linear monophasic dependence on time and a linear diphasic dependence on concentration. This probe is actively chased from the cells to an extent proportional to the amount incorporated. Therefore, the endocytic index obtained from the LY incorporation data is not a reliable estimate of extracellular fluid incorporation. The three different forms of HRP share an incorporation pattern linearly dependent on both time and concentration, consistent with the classical interpretation of a simple fluid-phase mechanism of intracellular uptake; however, the rates of uptake and chase activity of the pure isoenzymes are clearly different from that of the multiple form. The observed differences are related to possible local variations in the physicochemical properties of the cell surface, which may restrict the cell surface area suitable for fluid-phase uptake of differently charged macromolecular probes
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
Effect of case variability on the measurement of reader performance when comparing medical display technologies: application to the study of high-luminance-range displays
No full textImage-splitting techniques for a dual-layer high dynamic range LCD display
No full textLiquid crystal displays (LCDs) are replacing analog film in radiology and reducing diagnosis times. Their typical dynamic range, however, can be too low for some applications, and their poor ability to reproduce low-luminance areas represents a critical drawback. The black level of an LCD can be drastically improved by stacking two liquid crystal panels in series. In this way the global transmittance is the pointwise product of the transmittances of the two panels and the theoretical dynamic range is squared. Such a high dynamic range (HDR) display also permits the reproduction of a larger number of gray levels, increasing the bit depth of the device. The two panels, however, are placed at a small distance from each other due to mechanical constraints, and this introduces a parallax error when the display is observed off-axis. A complex, spatially adaptive algorithm is therefore necessary to generate the images used to drive the two panels. We describe the characteristics of a prototype dual-layer HDR display and discuss the issues involved in the image-splitting algorithms. We propose some solutions and analyze their performance, giving a measure of the capabilities and limitations of the device
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