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Search Results: 1 - 10 of 278486 matches for " H. V. Ribeiro "
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Heat flux canals (HFC) technique: an alternative to cool down stereolithography moulds
Ahrens, C. H.;Ribeiro Jr, A. S.;Beal, V. E.;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2003, DOI: 10.1590/S1678-58782003000300006
Abstract: the design of injection mould inserts obtained by stereolithography (sl) has various recommendations that are based on experimental work done by researchers over the last decade. there are no final conclusions about the best cooling technique for sl inserts. moreover, no criteria are presented concerning structural and thermal designs based on stress-strain analysis, although a number of researchers consider ejection forces as the main failure effect of the sl tool. this work presents an alternative technique to cool down sl inserts, based on heat flux canals that are strategically positioned on hot areas along the cavity walls. using this approach it is possible to keep direct contact between the back metal filling of the stereolithography insert and the injected thermoplastic material. this paper shows the results of aspects such as thermal evaluation in a fem analysis, where the heat flux canals, solid sl moulds and the traditional direct aim? process performances have been compared. the results indicate that this evolution of the direct aim? process may improve the average life of sl inserts while keeping the traditional one-week development for the tool.
Chaetognatha species distribution in the continental shelf off Sergipe and Alagoas States. Distribui o das espécies de chaetognatha na plataforma continental de Sergipe e Alagoas
H. M. P. Araújo,V. A. Ribeiro
Brazilian Journal of Aquatic Science and Technology , 2005,
Abstract: The present study investigated the Chaetognatha species distribution in the continental shelf off Sergipe and Alagoas States and its relation to the abiotic variables. Samples were collected at eighteen stations along six transects, perpendicular to the coast line in December (2001 and 2002) and June (2002 and 2003), corresponding to the dry and rainy seasons, respectively. Oblique hauls were done with plankton net, mesh size 200 μm. Temperature, salinity, pH, dissolved oxygen and nutrients were measured in three levels of the water column. Subsamples were taken using a Stempel pippette. Correlations analysis between Chaetognatha distribution and environmental parameters were studied using canonical correspondence analysis. Sagitta tenuis and S. enflata were the most adundant species, following by S. hispida, Sagitta spp., Krohnitta pacifica, Pterosagitta draco and S. bipunctata. Density values ranged between 9 ind.m-3 , in December 2002, and 4,473 ind.m-3 in June 2002, when Sagitta tenuis and S. enflata were more abundant. Density average values decreased from stations located at 10 meters to that located at 30 meters depth. Temperature, phosphate, salinity and water transparence were correlated (p<0,05) to the Chaetognatha species distribution. The present study investigated the Chaetognatha species distribution in the continental shelf off Sergipe and Alagoas States and its relation to the abiotic variables. Samples were collected at eighteen stations along six transects, perpendicular to the coast line in December (2001 and 2002) and June (2002 and 2003), corresponding to the dry and rainy seasons, respectively. Oblique hauls were done with plankton net, mesh size 200 μm. Temperature, salinity, pH, dissolved oxygen and nutrients were measured in three levels of the water column. Subsamples were taken using a Stempel pippette. Correlations analysis between Chaetognatha distribution and environmental parameters were studied using canonical correspondence analysis. Sagitta tenuis and S. enflata were the most adundant species, following by S. hispida, Sagitta spp., Krohnitta pacifica, Pterosagitta draco and S. bipunctata. Density values ranged between 9 ind.m-3 , in December 2002, and 4,473 ind.m-3 in June 2002, when Sagitta tenuis and S. enflata were more abundant. Density average values decreased from stations located at 10 meters to that located at 30 meters depth. Temperature, phosphate, salinity and water transparence were correlated (p<0,05) to the Chaetognatha species distribution.
Heat flux canals (HFC) technique: an alternative to cool down stereolithography moulds
Ahrens C. H.,Ribeiro Jr A. S.,Beal V. E.
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2003,
Abstract: The design of injection mould inserts obtained by stereolithography (SL) has various recommendations that are based on experimental work done by researchers over the last decade. There are no final conclusions about the best cooling technique for SL inserts. Moreover, no criteria are presented concerning structural and thermal designs based on stress-strain analysis, although a number of researchers consider ejection forces as the main failure effect of the SL tool. This work presents an alternative technique to cool down SL inserts, based on heat flux canals that are strategically positioned on hot areas along the cavity walls. Using this approach it is possible to keep direct contact between the back metal filling of the stereolithography insert and the injected thermoplastic material. This paper shows the results of aspects such as thermal evaluation in a FEM analysis, where the heat flux canals, solid SL moulds and the traditional Direct AIM[tm] process performances have been compared. The results indicate that this evolution of the Direct AIM[tm] process may improve the average life of SL inserts while keeping the traditional one-week development for the tool.
Anomalous Diffusion and Long-range Correlations in the Score Evolution of the Game of Cricket
H. V. Ribeiro,Satyam Mukherjee,Xiao Han T. Zeng
Physics , 2012, DOI: 10.1103/PhysRevE.86.022102
Abstract: We investigate the time evolution of the scores of the second most popular sport in world: the game of cricket. By analyzing the scores event-by-event of more than two thousand matches, we point out that the score dynamics is an anomalous diffusive process. Our analysis reveals that the variance of the process is described by a power-law dependence with a super-diffusive exponent, that the scores are statistically self-similar following a universal Gaussian distribution, and that there are long-range correlations in the score evolution. We employ a generalized Langevin equation with a power-law correlated noise that describe all the empirical findings very well. These observations suggest that competition among agents may be a mechanism leading to anomalous diffusion and long-range correlation.
Functional groups of forest succession as dissipative structures: an applied study
Souza, G. M.;Ribeiro, R. V.;Santos, M. G.;Ribeiro, H. L.;Oliveira, R. F.;
Brazilian Journal of Biology , 2004, DOI: 10.1590/S1519-69842004000400020
Abstract: this study tested the hypothesis that dissipative efficiency of tropical tree species could be an ecological advantage in the forest succession process. daily leaf gas exchanges of a pioneer species (guazuma ulmifolia) and a late successional species (cariniana legalis) were evaluated under well-irrigated conditions and by withholding irrigation. analyses of network connectance (cg) and plant autonomy (at) were carried out in order to assess metabolic network changes in response to environmental perturbation. as a global estimation of latent heat dissipation, the capacity to both maintain and cool leaf temperature in response to air temperature changes (dt = tocair - tocleaf) was evaluated. the changes observed in both the systemic parameters (cg and at) and the physiological ones brought about by water deficit, associated with discrepant growth rates between both species, suggested that the initial formation of gap canopies composed by pioneer species could simply be a result of the higher photosynthetic rates of these species, and not necessarily because late successional species cannot cope with such a heterogeneous environment as that of a gap. our results indicate that, in the absence of water constraints, the highest co2 assimilation rates of pioneer species are supported by the efficiency of the whole dissipative structure, involving both degradation and dissipative processes. as a practical result, our study suggests the dt analysis in order to evaluate the efficiency of dissipative structures and as a aid in characterizing functional groups.
Scaling laws and universality in the choice of election candidates
M. C. Mantovani,H. V. Ribeiro,M. V. Moro,S. Picoli Jr.,R. S. Mendes
Physics , 2011, DOI: 10.1209/0295-5075/96/48001
Abstract: Nowadays there is an increasing interest of physicists in finding regularities related to social phenomena. This interest is clearly motivated by applications that a statistical mechanical description of the human behavior may have in our society. By using this framework, we address this work to cover an open question related to elections: the choice of elections candidates (candidature process). Our analysis reveals that, apart from the social motivations, this system displays features of traditional out-of-equilibrium physical phenomena such as scale-free statistics and universality. Basically, we found a non-linear (power law) mean correspondence between the number of candidates and the size of the electorate (number of voters), and also that this choice has a multiplicative underlying process (lognormal behavior). The universality of our findings is supported by data from 16 elections from 5 countries. In addition, we show that aspects of network scale-free can be connected to this universal behavior.
Abnormal response of left ventricular systolic function to submaximal exercise in post-partial left ventriculotomy patients
Herdy, A.H.;Moritz, P.;Assis, A.V.;Ribeiro, F.;Colla?o, J.;Ribeiro, J.P.;
Brazilian Journal of Medical and Biological Research , 2007, DOI: 10.1590/S0100-879X2006005000052
Abstract: patients with heart failure who have undergone partial left ventriculotomy improve resting left ventricular systolic function, but have limited functional capacity. we studied systolic and diastolic left ventricular function at rest and during submaximal exercise in patients with previous partial left ventriculotomy and in patients with heart failure who had not been operated, matched for maximal and submaximal exercise capacity. nine patients with heart failure previously submitted to partial left ventriculotomy were compared with 9 patients with heart failure who had not been operated. all patients performed a cardiopulmonary exercise test with measurement of peak oxygen uptake and anaerobic threshold. radionuclide left ventriculography was performed to analyze ejection fraction and peak filling rate at rest and during exercise at the intensity corresponding to the anaerobic threshold. groups presented similar exercise capacity evaluated by peak oxygen uptake and at anaerobic threshold. maximal heart rate was lower in the partial ventriculotomy group compared to the heart failure group (119 ± 20 vs 149 ± 21 bpm; p < 0.05). ejection fraction at rest was higher in the partial ventriculotomy group as compared to the heart failure group (41 ± 12 vs 32 ± 9%; p < 0.0125); however, ejection fraction increased from rest to anaerobic threshold only in the heart failure group (partial ventriculotomy = 44 ± 17%; p = non-significant vs rest; heart failure = 39 ± 11%; p < 0.0125 vs rest; p < 0.0125 vs change in the partial ventriculotomy group). peak filling rate was similar at rest and increased similarly in both groups at the anaerobic threshold intensity (partial ventriculotomy = 2.28 ± 0.55 edv/s; heart failure = 2.52 ± 1.07 edv/s; p < 0.0125; p > 0.05 vs change in partial ventriculotomy group). the abnormal responses demonstrated here may contribute to the limited exercise capacity of patients with partial left ventriculotomy despite the improvement in resting left ventri
Three new Pimelodus species (Siluriformes: Pimelodidae) from the rio Tocantins drainage, Brazil
Ribeiro, Frank R.V.;Lucena, Carlos A. S.;Lucinda, Paulo H. F.;
Neotropical Ichthyology , 2008, DOI: 10.1590/S1679-62252008000300019
Abstract: three new species of siluriformes from the rio tocantins drainage of brazil are placed in the genus pimelodus, p. stewarti, p. joannis, and p. halisodous. pimelodus halisodous differs from the sympatric p. joannis and p. stewarti by the number of premaxillary tooth rows (13-16 vs. 5-9). pimelodus joannis differs from p. stewarti by the presence of two dark blotches on the base of the caudal fin. the three new species differ from all other species of pimelodus by the possession of a uniform gray coloration along flanks; the relatively short distance between the posterior nostril and the anterior orbital border; a short maxillary barbel, that only slightly surpasses the caudal-fin base.
Ageneiosus uranophthalmus, a new species of auchenipterid catfish (Osteichthyes: Siluriformes) from river channels of the central Amazon basin, Brazil
Ribeiro, Frank Raynner V;Py-Daniel, Lúcia H. Rapp;
Neotropical Ichthyology , 2010, DOI: 10.1590/S1679-62252010000100012
Abstract: ageneiosus uranophthalmus is described from river channels of the central amazon basin, brazil. the new species is widely distributed in the amazon and is distinguished from its congeners by the v-shape snout and eye laterally placed and dorsally oriented, more visible in dorsal view than in ventral view. ageneiosus uranophthalmus shows a range of variation on color pattern when compared with its congeners. this and other differences are described and discussed herein.
Reevaluation of ethanol as organic modifier for use in HPLS-RP mobile phases
Ribeiro, Ricardo L. V.;Bottoli, Carla B. G.;Collins, Kenneth E.;Collins, Carol H.;
Journal of the Brazilian Chemical Society , 2004, DOI: 10.1590/S0103-50532004000200022
Abstract: ethanol:water mixtures have been reevaluated for use as reversed phase mobile phases. optimization of the chromatographic conditions for both c8 and c18 columns was carried out through a factorial design which evaluates temperature, ethanol concentration and mobile phase flow rate. with the c8 stationary phase, peak asymmetries were not significantly altered at the different points in the factorial design while the retention factors and resolutions were somewhat lower at higher temperatures, where the viscosity of etoh is lower. similar observations were obtained with the c18 phase. the efficiency of the ethanol:water mobile phase for the separation of mixtures containing neutral and basic compounds was compared with those obtained using methanol:water and acetonitrile:water mobile phases. ethanol was shown to be a good organic modifier for rp-hplc, with good chromatographic properties. this, considering the much lower toxicity of ethanol, the facility of its disposal, and its favorable cost, should make ethanol:h2o the mobile phase of choice for many rp-hplc applications.
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