This paper analyzes the effects of color quantization on standard JPEG compression. Optimized color palettes were used to quantize natural images, using dithering and chroma subsampling as optional. The resulting variations on file size and quantitative quality measures were analyzed. Preliminary results, using a small image database, show that file size suffered an average 20% increase and a concomitant loss in quality was perceived ([Formula: see text]6dB PSNR, [Formula: see text]0.16 SSIM and [Formula: see text]9.6 Butteraugli). Color quantization present itself as an ineffective tool on JPEG compression but if necessarily imposed, on high quality compressed images, it might lead to a negligible increase in data size and quality loss. In addition dithering seems to always decrease JPEG compression ratio.
<p>The present research compares multivariate models applied to the IBovespa time series analysis. Macroeconomic variables, commodities and market indices are regressors suggested by the literature. The chosen approach uses a vector error correction model (VECM) alongside unit root and cointegration tests, robust under heteroskedasticity. The impact of national and international economic instability was controlled. To accomplish this, recessive cycles, in Brazil or in the United States, and the Brazilian electoral period were taken into account. In general, the evaluated models failed to meet the estimation’s assumptions, have low explanatory power and do not present significant relationship between IBOVESPA and dependent variables. However, evidence indicates that long-term relationships could exist, although this may not imply accuracy<br />in short-term predictions.</p>
Sob a ótica da Linguística Quantitativa, este trabalho revisita a Lei de Menzerath, aplicando-a aos dados do português brasileiro, a partir das seguintes unidades de análise: palavras, sílabas e fonemas. Os dados foram extraídos do Corpus ABG. Análises estatísticas foram realizadas nos modelos propostos, as quais demonstraram uma relação de decrescimento entre o comprimento médio das palavras (em sílabas) e o comprimento médio das sílabas (em fonemas); resultados esses que corroboram a Lei de Menzerath. Alémdisso, constatou-se, de maneira geral, que melhores medições ou a existência de variáveis não consideradas no modelo poderão ser utilizadas para melhorá-lo.
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