1,721,045 research outputs found
Empirical Distribution of Good Channel Codes With Nonvanishing Error Probability
Get PDFAbstract—This paper studies several properties of channel codes that approach the fundamental limits of a given (discrete or Gaussian) memoryless channel with a nonvanishing probability of error. The output distribution induced by an-capacity-achieving code is shown to be close in a strong sense to the capacity achieving output distribution. Relying on the concentration of measure (isoperimetry) property enjoyed by the latter, it is shown that regular (Lipschitz) functions of channel outputs can be precisely estimated and turn out to be essentially nonrandom and independent of the actual code. It is also shown that the output distribution of a good code and the capacity achieving one cannot be distinguished with exponential reliability. The random process produced at the output of the channel is shown to satisfy the asymptotic equipartition property. Index Terms—Additive white Gaussian noise, asymptotic equipartition property, concentration of measure, discrete memoryless channels, empirical output statistics, relative entropy, Shannon theory. To approximate this limiting rate of transmission the transmitted signals must approximate, in statistical properties, a white noise. A general and formal statement of this property of optimal codes was put forward by Han and Verdú [2, Th. 15]: Theorem 1: Fixanarbitrary. For any channel with finite input alphabet and capacity that satisfies the strong converse, and sufficiently large, where is the maximal mutual information output distribution and is the output distribution induced by the codebook (assuming equiprobable codewords) of any code such that as,and (1) I
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
Prime-sized multilevel flash memory with non-binary LDPC
No full textThesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 65-67).Flash memory companies are increasing the number of bits per cell to obtain higher information capacity per cell, starting from 1 bit/cell and going to 4 bits/cell recently. This scaling is enabled by the advancements in flash semiconductor technology, specifically the Bit Cost Scalable (BiCS) technology. However, capacity per cell scaling comes with performance, reliability, and endurance challenges. The industry has only used integer number of bits per cell, which makes the tradeoff between the capacity and the other system features less flexible than using fractional bits. This project explores programming 13 levels of charge ( 3.7 bits) into a QLC flash cell that normally carries 16 levels of charge (4 bits). We evaluate the 13-ary scheme against the 16-ary one and we show that the 13-ary has the same reliability at a lower SNR as the 16-ary, or the 13-ary has higher reliability than the 16-ary at the same SNR. We design binary and non-binary Quasi-Cyclic LDPC codes and implement Belief Propagation decoders for them.by Mohammed Al Ai Baky.M. Eng
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