685 research outputs found

    Different intermittency for longitudinal and transversal turbulent fluctuations

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    Scaling exponents of the longitudinal and transversal velocity structure functions in numerical Navier-Stokes turbulence simulations with Taylor-Reynolds numbers up to \rel = 110 are determined by the extended self similarity method. We find significant differences in the degree of intermittency: For the sixth moments the scaling corrections to the classical Kolmogorov expectations are δξ6L=0.21±0.01\delta\xi_6^L= -0.21 \pm 0.01 and \dx_6^T= -0.43 \pm 0.01, respectively, independent of \rel. Also the generalized extended self similarity exponents \rho_{p,q} = \dx_p/\dx_q differ significantly for the longitudinal and transversal structure functions. Within the She-Leveque model this means that longitudinal and transversal fluctuations obey different types of hierarchies of the moments. Moreover, the She-Leveque model hierarchy parameters βL\beta^L and βT\beta^T show small but significant dependences on the order of the moment.Comment: 20 pages, 10 eps-figures, to appear in Physics of Fluids, December 199

    Cultivo protegido de videiras.

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    Multiscale velocity correlation in turbulence: experiments, numerical simulations, synthetic signals

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    Multiscale correlation functions in high Reynolds number experimental turbulence, numerical simulations and synthetic signals are investigated. Fusion Rules predictions as they arise from multiplicative, almost uncorrelated, random processes for the energy cascade are tested. Leading and sub-leading contribution, in the inertial range, can be explained as arising from a multiplicative random process for the energy transfer mechanisms. Two different predictions for correlations involving dissipative observable are also briefly discussed

    Radon Dose Determination and Radiological Risk in Some Mexican Caves with CR-39 Detectors

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    Radon (222Rn) is a radioactive gas, from the 238U decay chain, that contributes in large part of the natural radiation dose to which humans are exposed. Radon is the second cause of lung cancer after tobacco. The US-EPA considers a concentration of 148 Bq/m3 for homes and 400 Bq/m3 for workplaces as the reference level. Caves are closed spaces where 222Rn, which emanates from the surrounding minerals and rocks, can accumulate and reaches large concentrations that can represent a health risk for the guides, speleologists and visitors who spend time in these spaces. This work uses the previously recorded radon concentrations in 8 caves in Mexico and calculates the average dose range and the average annual dose for each of them with the “Wise” public domain program (http://www.wise-uranium.org/rdcrn.html) to determine the level of radiological risk with 2,000 1,000 and 500 working hours per year. Karmidas cave had the highest average 222Rn concentration with 27,633.3 Bq/m3 and for 2,000 working hours per year an average annual dose rate of 347.1 mSv/y. Los Riscos cave had the lowest average concentration with 384.7 Bq/m3 and for 2,000 working hours per year an average annual dose rate of 4.832 mSv/y. These results show that all the caves studied present values,with 2,000 working hours per year, that exceed 3 mSv/y for workplaces and must be considered by the people who work in these places. A casual tourist visiting the caves does not present any radiological risk, while guides and speleologists should consider it

    A new scaling property of turbulent flows

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    We discuss a possible theoretical interpretation of the self scaling property of turbulent flows (Extended Self Similarity). Our interpretation predicts that, even in cases when ESS is not observed, a generalized self scaling, must be observed. This prediction is checked on a number of laboratory experiments and direct numerical simulations.Comment: Plain Latex, 1 figure available upon request to [email protected]

    Do slower life history strategies reduce sociodemographic sex differences?

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    This study examines the relations between sociodemographic sex differences and life history strategies in the populations of Mexican States. Sex differences in anatomy and behavior was measured with traits such as educational achievement, mortality, and morbidity. The data were obtained from the Instituto Nacional de Estadística y Geografía (INEGI) and sampled from thirty-one Mexican states and the Federal District (N = 32). An extension analysis was performed selecting only the sex ratio variables that had a correlation with the slow Life History factor greater than or equal to an absolute value of .25. A unit-weighted sex ratio factor was created using these variables. Across 32 Mexican states, the correlation between latent slow life history and sex ratio was .57 (p .05). These results are consistent with our hypothesis that slower life histories favor reduced sexual dimorphism in physiology and behavior among human subnational populations. The results of the study further understanding of variations in population sex differences, male-biased behaviors toward sexual equality, and the differences among subnational (regional) populations within the United States of Mexico.   DOI:10.2458/azu_jmmss_v6i1_chavarria_miner

    Caracterização físicoquímica do mosto e do vinho de uvas Moscato Giallo cultivadas sob cobertura plástica.

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    O objetivo deste trabalho foi avaliar o efeito da cobertura plástica sobre o mosto e a qualidade do vinho da cultivar Moscato Giallo.bitstream/CNPUV-2009-09/10530/1/cot091.pd

    A Study of the Formal Architectural-Sculptural Characteristics of El Tajin

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    El Tajín was an ancient metropolis in which rituals such as the Mesoamerican ball game were carried out, later to be recorded in the sculptural bas-reliefs of its architecture. The study of its morphologies is the recognition of the ways in which an ancient civilization is expressed, thus contributing to the characterization of a culture whose past belongs to World Heritage. This paper proposes a case-sample analysis of the bas-reliefs in the South Ballcourt based on reticular geometry and fractal dimension analysis. It was found that the geometry of the RA (golden rectangle), RR2 and RR3 are prevalent, in addition to the identification of iconographic naturalist and symbolic elements; from the box-counting fractal dimension, it was found that the elements, though of different sizes or composition, show similar complexities, with a value of around 1.7

    Dust rings and filaments around the isolated young star V1331 Cygni

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    We characterize the small and large scale environment of the young star V1331 Cygni with high resolution HST/WFPC2 and Digitized Sky Survey images. In addition to a previously known outer dust ring (~30'' in diameter), the HST/WFPC2 scattered light image reveals an inner dust ring for the first time. This ring has a maximum radius of 6.5'' and is possibly related to a molecular envelope. Large-scale optical images show that V1331 Cyg is located at the tip of a long dust filament linking it to the dark cloud LDN 981. We discuss the origin of the observed dust morphology and analyze the object's relation to its parent dark cloud LDN 981. Finally, based on recent results from the literature, we investigate the properties of V1331 Cyg and conclude that in its current state the object does not show suffcient evidence to be characterized as an FU Ori object.Comment: 15 pages ApJ preprint style including 3 figures, accepted for publication in ApJ (Feb. 2007
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