849 resultados para Meta heuristics


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El objetivo de este artículo es estimar, mediante un meta-análisis, el valor promedio de las elasticidades ingreso y precio de la demanda de gasolinas y analizar las causas de la variación en las elasticidades reportadas en la literatura. Los resultados muestran que existe un sesgo de publicación, que la volatilidad de las estimaciones de las elasticidades no se debe exclusivamente a errores de muestreo y que existen factores sistemáticos que explican estas diferencias. Las elasticidades ingreso y precio de la demanda de gasolinas son distintas en el corto y largo plazo, por regiones, y son susceptibles de incluirse en la estimación la flota vehicular y el precio de bienes substitutos, los tipos de datos y métodos de estimación utilizados. La presencia de una baja elasticidad precio sugiere que un impuesto a los combustibles, en un entorno de rápido crecimiento económico, será insuficiente para controlar el aumento del consumo.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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By means of a meta-analysis, this article sets out to estimate average values for the income and price elasticities of gasoline demand and to analyse the reasons for the variations in the elasticities reported by the literature. The findings show that there is publication bias, that the volatility of elasticity estimates is not due to sampling errors alone, and that there are systematic factors explaining these differences. The income and price elasticities of gasoline demand differ between the short and long run and by region, and the estimation can appropriately include the vehicle fleet and the prices of substitute goods, the data types and the estimation methods used. The presence of a low price elasticity suggests that a fuel tax will be inadequate to control rising consumption in a context of rapid economic growth.

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Em muitos problemas de otimização há dificuldades em alcançar um resultado ótimo ou mesmo um resultado próximo ao valor ótimo em um tempo viável, principalmente quando se trabalha em grande escala. Por isso muitos desses problemas são abordados por heurísticas ou metaheurísticas que executam buscas por melhores soluções dentro do espaço de busca definido. Dentro da computação natural estão os Algoritmos Culturais e os Algoritmos Genéticos, que são considerados metaheurísticas evolutivas que se complementam devido ao mecanismo dual de herança cultura/genética. A proposta do presente trabalho é estudar e utilizar tais mecanismos acrescentando tanto heurísticas de busca local como multipopulações aplicados em problemas de otimização combinatória (caixeiro viajante e mochila), funções multimodais e em problemas restritos. Serão executados alguns experimentos para efetuar uma avaliação em relação ao desempenho desses mecanismos híbridos e multipopulacionais com outros mecanismos dispostos na literatura de acordo com cada problema de otimização aqui abordado.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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PURPOSE: Systematic reviews are criticized for frequently offering inconsistent evidences and absence of straightforward recommendations. Their value seems to be depreciated when the conclusions are uncertain. To describe an alternative approach of evaluating case series studies in health care when there is absence of clinical trials. METHODS: We provide illustrations from recent experiences. Proportional meta-analysis was performed on surgical outcomes: (a) case series studies, (b) use of cryoablation or radiofrequency ablation, and (c) patients with small renal cell carcinoma. The statistically significant difference between both interventions studied was defined if their combined 95% confidential interval (CI) did not overlap. RESULTS: As demonstrated by the example, this analysis is an alternative approach to provide some evidence of the intervention´s effects under evaluation and plotting all available case series in the absence of clinical trials for the health field. CONCLUSIONS: Although we are leading to a low level of evidence to determine efficacy, effectiveness and safety of interventions this alternative approach can help surgeons, physicians and health professionals for a provisionally decision in health care along with their clinical expertise and the patient´s wishes and circumstances in the absence of high-quality primary studies. It´s not a replacement for the gold standard randomized clinical trial, but an alternative analysis for clinical research.

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OBJECTIVE: To assess whether the Brazilian Driving Dry Law reached its goal after the three years following its enactment. METHODS: We onnducted a retrospective study of patients with craniofacial fractures who underwent surgery at a university hospital in two periods: before the Law (2005 to 2008) and after the Law (2008 to 2011). RESULTS: 265 patients (220 men and 45 women) were operated on during this period, 149 (56%) before and 116 (44%) after the Law, which indicates a reduction in the number of traumatisms (p=0.04). The age range between 19 and 40 years predominated in both periods. The main causes of traumas were car accidents, physical aggression and falls. Alcohol abuse was identified in 15.4% patients before and 19% patients after the enactment. The jaw and the maxillo-zygomatic complex were the most affected bones. CONCLUSION: The drop in the number of polytraumatized patients operated on at this institution in the three years following the Driving Dry Law was 22%, which is below the expected and desired percentage. These results must be compared to those of different services offering the same attendance type in order to compile data and enlarge statistics. The low index of reduction in the number of traumatisms and the report of alcohol abuse by several patients at the moment of trauma, even after the law, evidence the need of adopting stricter measures to control and punish violators.

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Pós-graduação em Engenharia Elétrica - FEIS

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Pós-graduação em Engenharia Elétrica - FEIS

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A data set based on 50 studies including feed intake and utilization traits was used to perform a meta-analysis to obtain pooled estimates using the variance between studies of genetic parameters for average daily gain (ADG); residual feed intake (RFI); metabolic body weight (MBW); feed conversion ratio (FCR); and daily dry matter intake (DMI) in beef cattle. The total data set included 128 heritability and 122 genetic correlation estimates published in the literature from 1961 to 2012. The meta-analysis was performed using a random effects model where the restricted maximum likelihood estimator was used to evaluate variances among clusters. Also, a meta-analysis using the method of cluster analysis was used to group the heritability estimates. Two clusters were obtained for each trait by different variables. It was observed, for all traits, that the heterogeneity of variance was significant between clusters and studies for genetic correlation estimates. The pooled estimates, adding the variance between clusters, for direct heritability estimates for ADG, DMI, RFI, MBW and FCR were 0.32 +/- 0.04, 0.39 +/- 0.03, 0.31 +/- 0.02, 0.31 +/- 0.03 and 0.26 +/- 0.03, respectively. Pooled genetic correlation estimates ranged from -0.15 to 0.67 among ADG, DMI, RFI, MBW and FCR. These pooled estimates of genetic parameters could be used to solve genetic prediction equations in populations where data is insufficient for variance component estimation. Cluster analysis is recommended as a statistical procedure to combine results from different studies to account for heterogeneity.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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BACKGROUND AND OBJECTIVES: Gross motor (GM) deficits are often reported in children with prenatal alcohol exposure (PAE), but their prevalence and the domains affected are not clear. The objective of this review was to characterize GM impairment in children with a diagnosis of fetal alcohol spectrum disorder (FASD) or moderate to heavy maternal alcohol intake.METHODS: A systematic review with meta-analysis was conducted. Medline, Embase, Allied and Complementary Medicine Database, Cumulative Index to Nursing and Allied Health Literature, PsycINFO, PEDro, and Google Scholar databases were searched. Published observational studies including children aged 0 to <= 18 years with (1) an FASD diagnosis or moderate to heavy PAE, or a mother with confirmed alcohol dependency or binge drinking during pregnancy, and (2) GM outcomes obtained by using a standardized assessment tool. Data were extracted regarding participants, exposure, diagnosis, and outcomes by using a standardized protocol. Methodological quality was evaluated by using Strengthening the Reporting of Observational Studies in Epidemiology guidelines.RESULTS: The search recovered 2881 articles of which 14 met the systematic review inclusion criteria. The subjects' mean age ranged from 3 days to 13 years. Study limitations included failure to report cutoffs for impairment, nonstandardized reporting of PAE, and small sample sizes. The meta-analysis pooled results (n = 10) revealed a significant association between a diagnosis of FASD or moderate to heavy PAE and GM impairment (odds ratio: 2.9; 95% confidence interval: 2.1-4.0). GM deficits were found in balance, coordination, and ball skills. There was insufficient data to determine prevalence.CONCLUSIONS: The significant results suggest evaluation of GM proficiency should be a standard component of multidisciplinary FASD diagnostic services.

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This work presents a framework for full-time education in Brazil, analyzing the levels of proximity and distance of the Brazilian regions in relation to achieving target paragraph 06 of the bill of the new National Education Plan, which establishes the offer of full-time education in at least fifty percent of public schools, and at least twenty-five percent of students in basic education. It aims to determine the contribution of the “Mais Educação” (More Education) Program of the federal government in fulfilling this goal.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)