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Search Results: 1 - 10 of 408405 matches for " Léo F.;Mello "
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Normal force calculations for rocket-like configurations
Bigarella, E. D. V.;Azevedo, J. L. F.;Mello, O. A. F.;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2004, DOI: 10.1590/S1678-58782004000300005
Abstract: transonic and supersonic flow simulations over typical launch vehicle configurations are presented. a 3-d finite difference numerical code, written for general, curvilinear, body-conforming coordinate systems, is used. the code solves the thin-layer approximation for the laminar navier-stokes equations. simulations are performed for a launcher and a sounding rocket configurations, currently under development at instituto de aeronáutica e espa?o. calculations consider cases at angle of attack and at various freestream mach numbers. normal force coefficients are obtained such that the loads required for the design phase can be determined. computational results are compared to available experimental data. in general, good results within engineering error margins are obtained.
Porosidade de aera??o de solos para a máxima produ??o de gr?os de feijoeiro, em casa de vegeta??o
Primavesi, O.;Mello, F.A.F. de;Libardi, P.L.;
Anais da Escola Superior de Agricultura Luiz de Queiroz , 1988, DOI: 10.1590/S0071-12761988000100024
Abstract: experiments were carried out in greenhouse, at esalq/usp, in piracicaba, state of s?o paulo, brazil, with soil samples of the a1 or ap and b2 horizon of an oxisol (lr) and an alfisol (pvp) , without and with mineral fertilizer and lime , to verify the optimum aeration porosity, between 3 and 24%, for the maximal yield of common bean, cv. aroana 80. the water content in the 2,5 1 of the soil sample in the pot was maintained between 100 and 70% of the field capacity. a preferential range (9 - 16%) of macropores or aeration pores (diameter greater than 0,05 mm) could be verified. and deslocated to a range between 24 and 29% of macropores, when a higher dry matter accumalation rate occur, besides a probably lower oxygen supply to the growth points of the roots in soils with small aggregates extremely water stable and with a higher water content.
Sele??o preliminar de parametros físicos mais adequados para estudar o efeito da compacta??o de amostras de solo sobre a produ??o de matéria seca vegetal de feijoeiro (Phaseolue vulgaris L.)
Primavesi, O.;Mello, F.A.F.;Llbardi, P.L.;
Anais da Escola Superior de Agricultura Luiz de Queiroz , 1984, DOI: 10.1590/S0071-12761984000100026
Abstract: soil samples of the a and b2 horizons of an oxisol (lr) and.an alfisol (pvp) were subjected to compaction, to offer resistance to cone penetrograph penetration of 0 - 8,8 - 17,6 kg/cm2. the soil samples were cultivated with common bean, cultivar rico pardo 896, during 67 days, in 3,8 liter pots in geenhouse, with the soil water content between the tension levels of 100 to 300 mbars. it could be verified, considering the different soil samples, that the dry matter production seems to correlate better with the efective aeration porosity. so it seems to be the better indicator for the plant dry matter production tendency in different soils, with different compaction degrees. the parameters soil bulk density, saturated hydraulic conductivity an mechanical resistance to penetro-graph did not seem good general indicators.
Influência da compacta??o em características químicas e propriedades físicas de amostras de solo cultivadas com feijoeiro (Phaseolus vulgaris L.)
Primavesi, O.;Mello, F.A.F.;Libardi, P.L.;
Anais da Escola Superior de Agricultura Luiz de Queiroz , 1984, DOI: 10.1590/S0071-12761984000100027
Abstract: soil samples of an orthic haplacrox (lr) and an ochrultic typustalf (pvp) were used in this experiments, including the a and b2 horizon, subject to compaction. they were confined in 3,8 1 pots, and incubated during 80 days (cultivated with beans during 67 days), with a soil water tension between 100 to 300 mbars. the physical determinations showed an increase of the soil bulk density, and a decrease of the total porosity and the saturated hydraulic conductivity. the micropores and bloqued pores increased in lr an decreased in pvp. the soil samples of the lr-b2 were less susceptible to changes due compaction, while of the pvp-b2 were the most susceptible, followed by those of the lr-a1 and the pvp-ap. the chemical data showed tendencies of increase of the carbon level in the a horizon without fertilizer, and decrease with fertilizer, on lr and pvp with compaction increase. they also showed decrease of the available p and increase of the exchangeable al with fertilizer, and reduction of the exchangeable mg without and with fertilizer in the a horizon of both soils, as the compaction was increased.
Comparison of Pavlovian serial conditional discrimination in rats and hamsters in the same experimental situation
Bueno, J.L.O.;Figueiredo, T.H.;Mello, F.M.C.;
Brazilian Journal of Medical and Biological Research , 2001, DOI: 10.1590/S0100-879X2001001200012
Abstract: the present study compares behavioral changes between two distinct rodent groups, hamsters (mesocricetus auratus) and wistar rats, when submitted in the same homogeneous experimental situations to a serial conditional discrimination procedure which involves water deprivation and the processing of temporal variables. both hamsters and rats acquired serial positive conditional discrimination as indicated by higher frequencies of magazine-oriented behavior during the tone followed by reinforcement (t+) and preceded by the feature stimulus light (l) and during the empty interval, than during the tone alone not followed by reinforcement (t-). rats' frequencies of magazine-oriented behavior were high during t+ and t-, initially during training, and decreased during t- as the training progressed. however, the hamsters' frequencies of magazine-oriented behavior started very low and increased only during t+ as the training progressed. comparison of the frequencies of magazine-oriented behavior during the empty interval in relation to the frequencies during the preceding l period showed that rats' frequencies remained very high and hamsters' frequencies increased during training. these results suggest that rats and hamsters have different behavioral strategies for the acquisition of a conditional discrimination. the results of the comparisons made in these experiments support the view of the importance of an ecological psychology approach to the understanding of complex learning in animals.
Mapeamento da precipita??o mínima provável para o sul de Minas Gerais
ávila, Léo F.;Mello, Carlos R. de;Viola, Marcelo R.;
Revista Brasileira de Engenharia Agrícola e Ambiental , 2009, DOI: 10.1590/S1415-43662009000700013
Abstract: the probable minimum precipitation associated to the period, location and frequency of occurrence represents an important tool to support agricultural practices. the objective of this work was to map the probable minimum monthly and fortnightly precipitation for southern minas gerais state, applying geostatistical procedures. the probability level considered was 75% and the period evaluated was the rainy season. the values of probable minimum precipitation were estimated by log-normal probability distribution, following kolmogorov-smirnov adequacy test and using long-term daily precipitation data set of 69 pluviometric stations in the region and its surroundings. exponential and spherical semi-variogram models, adjusted by maximum likelihood (ml) and minimum weighted square (mws), were modelled to choose the best to represent the experimental semi-variogram. based on spatial dependence degree and cross-validation, the exponential model adjusted by mws presented better performance. the probable minimum precipitation maps have shown considerable variability during the rainy season. the greatest values were estimated for the region close to mantiqueira and canastra ranges.
Continuidade e distribui??o espacial da umidade do solo em bacia hidrográfica da Serra da Mantiqueira
ávila, Léo F.;Mello, Carlos R. de;Silva, Ant?nio M. da;
Revista Brasileira de Engenharia Agrícola e Ambiental , 2010, DOI: 10.1590/S1415-43662010001200002
Abstract: the knowledge related to the spatial continuity of the soil moisture is essential for understanding and prediction of the hydrological processes. the geostatistical methodology has often been applied in such studies. in this context, the semi-variogram is used to model the spatial continuity of a specific variable for its mapping. this work aimed to model the spatial continuity of soil moisture in an experimental watershed located in mantiqueira range, mg, and then to generate map of soil moisture through the year. exponential, spherical and gaussian semi-variogram models were fitted applying the ordinary least square, weighted minimum square and maximum likelihood methodologies, testing their adherence based on the spatial dependence degree and database from cross-validation procedure. the exponential model presented better performance in 59% of the situations. the mean spatial dependence degree was 88%, showing a strong dependence degree to the spatial continuity structure. the soil moisture mapping demonstrated behavior strongly associated to the land use and topographical conditions.
Comparison of Pavlovian serial conditional discrimination in rats and hamsters in the same experimental situation
Bueno J.L.O.,Figueiredo T.H.,Mello F.M.C.
Brazilian Journal of Medical and Biological Research , 2001,
Abstract: The present study compares behavioral changes between two distinct rodent groups, hamsters (Mesocricetus auratus) and Wistar rats, when submitted in the same homogeneous experimental situations to a serial conditional discrimination procedure which involves water deprivation and the processing of temporal variables. Both hamsters and rats acquired serial positive conditional discrimination as indicated by higher frequencies of magazine-oriented behavior during the tone followed by reinforcement (T+) and preceded by the feature stimulus light (L) and during the empty interval, than during the tone alone not followed by reinforcement (T-). Rats' frequencies of magazine-oriented behavior were high during T+ and T-, initially during training, and decreased during T- as the training progressed. However, the hamsters' frequencies of magazine-oriented behavior started very low and increased only during T+ as the training progressed. Comparison of the frequencies of magazine-oriented behavior during the empty interval in relation to the frequencies during the preceding L period showed that rats' frequencies remained very high and hamsters' frequencies increased during training. These results suggest that rats and hamsters have different behavioral strategies for the acquisition of a conditional discrimination. The results of the comparisons made in these experiments support the view of the importance of an ecological psychology approach to the understanding of complex learning in animals.
Preparation and electrochemical characterization of Pt nanoparticles dispersed on niobium oxide
Mello, R. L. S.;Mattos-Costa, F. I.;Villullas, H. de las M.;Bulh?es, L. O. de S.;
Eclética Química , 2003, DOI: 10.1590/S0100-46702003000200009
Abstract: electrodes consisting of pt nanoparticles dispersed on thin films of niobium oxide were prepared onto titanium substrates by a sol-gel method. the physical characterization of these electrodes was carried out by x-ray diffraction, scanning electron microscopy and energy dispersive x-ray analysis. the mean size of the pt particles was found to be 10.7 nm. the general aspects of the electrochemical behavior were studied by cyclic voltammetry in 1 mol l-1 hclo4 aqueous solution. the response of these electrodes in relation to the oxidation of formaldehyde and methanol in acidic media was also studied.
Magnetic vortex chirality switching in Permalloy nanowires with asymmetric notches
J. Brand?o,R. L. Novak,H. Lozano,P. R. Soledade,A. Mello,F. Garcia,L. C. Sampaio
Physics , 2014, DOI: 10.1063/1.4902008
Abstract: We have investigated the motion of vortex domain walls passing across non symmetric triangular notches in single Permalloy nanowires. We have measured hysteresis cycles using the focused magneto-optical Kerr effect before and beyond the notch, which allowed to probe beyond the notch the occurrence probability of clockwise (CW) and counter-clockwise (CCW) walls in tail-to-tail (TT) and head-to-head (HH) configurations. We present experimental evidence of chirality flipping provided by the vortex -- notch interaction. With a low exit angle the probability of chirality flipping increases and here with the lowest angle of 15$^o$ the probability of propagation of the energetically favored domain wall configuration (CCW for TT or CW for HH walls) is $\approx 75\%$. Micromagnetic simulations reveal details of the chirality reversal dynamics.
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