A study of probability distributions of DCT coefficients in JPEG compression

The Discrete Cosine Transform (DCT) used in JPEG compression has shown excellent energy compaction properties that rival that of the ideal Karhunen-Loève Transform. Lossy compression in JPEG is achieved by distorting 8x8 block DCT coefficients through quantization. It has been shown in literature that DC block DCT coefficients are Gaussian probability distributed and AC block DCT coefficients are Generalized Normal probability distributed. In this investigation, three probability density models for individual modes of non- quantized AC block DCT coefficients are evaluated and are used as basis for the derivation of probability distributions for quantized block DCT coefficients. The suitability of each of the three derived models is evaluated using the Kolmogorov-Smirnov and χ2 goodness-of-fit tests, and the moments of the best-fit model are derived. The best-fit model is applied to detect the presence and extent of JPEG compression history in bitmap images. A model for all quantized AC block DCT coefficients is derived using mixtures of individual quantized block DCT modes, and the model hence developed is used to validate the Generalized Benford\u27s Law for leading digit distributions of quantized AC block DCT coefficients

Constructing a \u27good death\u27 : news media framing of the euthanasia debate from 1975 to 1997

Social and legal acceptance of euthanasia—including physician-assisted suicide has picked up considerable momentum in the 20th century. Among the most important chroniclers and shapers of cultural attitudes, beliefs, and values about issues such as euthanasia are the mainstream news media. The purpose of this study is to examine the national, print news media\u27s role in conditioning public knowledge abouteuthanasia and its consequences. To accomplish this task, news framing analysis wasconducted of all Time and Newsweek euthanasia articles published in the roughlytwo-decade period between the two major United States Supreme Court cases thatencase this controversial issue (the 1976 Quinlan case and the Court\u27s 1997 decisionupholding state laws prohibiting physician-assisted suicide). Using a variety of framing strategies advanced by framing theorists, 57 stories were analyzed according to their dominant frames and ideological positions. In order to explore the dynamic between the\u27 news media and social change processes, shifts in framing stages overtime were also charted, and special attention was devoted to assessing some of the factors triggering these changes.Results showed dominant frames to reflect pro-euthanasia views in air but a few of the stories analyzed, a phenomenon that held true throughout the two decades of research. Moreover, journalists represented this highly complex and emotionally laden issue through two basic frames: medicine and law. Given the broad spectrum of topics euthanasia encompasses—including metaphysics, philosophy, ethics, sociology,psychology, and religion—such narrow coverage raises troubling questions. Unliketheir forebears, whose exposure to death was intimate and commonplace, individuals in late 20th-century America know about death primarily through the mass media. Yet news consumers relying on the mainstream news publications in this study for information on euthanasia were offered a meager selection of perspectives and positions from which to assess this critically important issue