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Search Results: 1 - 10 of 224731 matches for " R. Gama "
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Calibration of Numerical Model Applied to a Shear Zone Located on a Slope in an Open Pit Mine—Case History  [PDF]
Evandro Moraes da Gama, Bruno C. R. da Silva
Geomaterials (GM) , 2012, DOI: 10.4236/gm.2012.21002
Abstract: The instability of a pit mine slope diagnostic caused by the slipping of a localized deep shear zone is described. The slope was designed on ultra basic, serpentine and metabasite rock formations with an angle varying from 40 to 45 de- grees. The perturbed slope zone was classified as RMR 12 and the non-perturbed zone as RMR 75. The boundary of these zones is defined as the shear zone. The pit slope was field mapped in detail and the mechanical properties of the rock were obtained through a laboratory test. The lab data were further processed using the RMR mechanical classifi- cation system. The Distinct Elements Code numerical modeling and simulation software was used to design the pit slope. The model was calibrated through topographic mapping of the points on the ground. The task of calibrating a numerical model is far from simple. Exhaustive attempts to find points of reference are required. The mechanical be- havior in function of the time factor is a problem that has yet to be solved. The instant deformation generated in the numerical model generated functions that can be compared with the deformations of quick shifts acquired in the topog- raphic monitoring. SMR is indeed more often recommended for Pit Slopes, though the fact that we have used RMR does not invalidate the classification for the modeling effect. The main parameters such as spacing, filling, diving direc- tion and continuity allow for compartmentalization of the modeled area. The objective of the modeling was not to pro- ject slopes because this massif was undergoing a progressive slow rupture. The objective of the modeling was to study the movement of the mass of rock and its progressive rupture caused by a shear zone.
Simulation of Steady-State Nonlinear Heat Transfer Problems Through the Minimization of Quadratic Functionals
Gama, R. M. S. da;
Journal of the Brazilian Society of Mechanical Sciences , 2002, DOI: 10.1590/S0100-73862002000100003
Abstract: in this work it is presented a systematic procedure for constructing the solution of a large class of nonlinear conduction heat transfer problems through the minimization of quadratic functionals like the ones usually employed for linear descriptions. the proposed procedure gives rise to an efficient and easy way for carrying out numerical simulations of nonlinear heat transfer problems by means of finite elements. to illustrate the procedure a particular problem is simulated by means of a finite element approximation.
Simulation of Steady-State Nonlinear Heat Transfer Problems Through the Minimization of Quadratic Functionals
Gama R. M. S. da
Journal of the Brazilian Society of Mechanical Sciences , 2002,
Abstract: In this work it is presented a systematic procedure for constructing the solution of a large class of nonlinear conduction heat transfer problems through the minimization of quadratic functionals like the ones usually employed for linear descriptions. The proposed procedure gives rise to an efficient and easy way for carrying out numerical simulations of nonlinear heat transfer problems by means of finite elements. To illustrate the procedure a particular problem is simulated by means of a finite element approximation.
Two-Dimensional Simulation of the Navier-Stokes Equations for Laminar and Turbulent Flow around a Heated Square Cylinder with Forced Convection  [PDF]
R?mulo D. C. Santos, Sílvio M. A. Gama, Ramiro G. R. Camacho
Applied Mathematics (AM) , 2018, DOI: 10.4236/am.2018.93023
Few studies jointly investigate thermal and turbulent effects. In general, these subjects are treated separately. The purpose of this paper is to use the Immersed Boundary Method (IBM) coupled with the Virtual Physical Model (VPM) to investigate incompressible two-dimensional Newtonian flow around a heated square cylinder at constant temperature on its surface with forced convection and turbulence. The VPM model dynamically evaluates the force that the fluid exerts on the immersed surface and the thermal exchange between both in the Reynolds numbers (Re) window 40 ≤ Re ≤ 5×103 . For simulations of turbulence the Smagorinsky and Spalart-Allmaras models are used. The first model uses the Large Eddy Simulation (LES) methodology and is based on the local equilibrium hypothesis for small scales associated with the Boussinesq hypothesis, such that the energy injected into the spectrum of the turbulence balances the energy dissipated by convective effects. The second model uses the concept Unsteady Reynolds Averaged Navier-Stokes Equations (URANS), with only one transport equation for turbulent viscosity, being calibrated in pressure gradient layers. The goal of this work is to analyse the combination of the heat-transfer phenomena with the turbulence for the thermo-fluid-structure interaction in a square cylinder. For this, it was developed a C/C++ code that requires low computational costs in regards to memory and computer facilities. It is observed that, with the increase of the Reynolds number, an increase of the drag coefficient occurs, as well as reinforces the influence of the pressure distribution downstream of the cylinder, which is strongly influenced by the formation and detachment of vortices on the upper and lower sides of the square cylinder.
Physiological response of common bean (Phaseolus vulgaris L.) seedlings to salinity stress
PBS Gama, S Inanaga, K Tanaka, R Nakazawa
African Journal of Biotechnology , 2007,
Abstract: The effect of salinity stress on five cultivars of common bean: Bassbeer, Beladi, Giza 3, HRS 516 and RO21 were evaluated on a sand/peat medium with different salinity levels (0, 50 and 100 mM NaCl) applied 3 weeks after germination for duration of 10 days. Salinity had adverse effects not only on the biomass yield and relative growth rate (RGRt), but also on other morphological parameters such as plant height, number of leaves, root length and shoot/root weight ratio. Photosynthesis, transpiration rate and stomatal conductance were adversely affected in all cultivars. Leaf osmotic potential and leaf turgor varied significantly among cultivars and salt levels. The interaction between cultivars and salt levels for photosynthesis, leaf osmotic potential and leaf turgor was highly significant at day 10 of salt treatment. The Na uptake among the cultivars varied in the order: HRS 516 highest survival rate and no symptoms of salt stress. RO21 was the most susceptible to salinity as it showed severe symptoms of salt stress and very low survival rate.
Complete rupture of the hamstring origin in a road accident: 5-year follow-up
V. Sansone,A. De Ponti,M. da Gama Malchèr
Journal of Orthopaedics and Traumatology , 2002, DOI: 10.1007/s101950200008
Abstract: A rare case of posttraumatic rupture of the hamstring muscles at their origin in a young adult is reported. Lesional mechanisms, epidemiology and diagnostic tools are described. A conservative treatment was adopted because of the presence of other more severe pathologies, but functional results at the 5-year follow-up are unsatisfactory. We suggest surgical treatment of this uncommon lesion.
Dependence of magnetic field generation by thermal convection on the rotation rate: a case study
R. Chertovskih,S. M. A. Gama,O. Podvigina,V. Zheligovsky
Physics , 2009, DOI: 10.1016/j.physd.2010.03.008
Abstract: Dependence of magnetic field generation on the rotation rate is explored by direct numerical simulation of magnetohydrodynamic convective attractors in a plane layer of conducting fluid with square periodicity cells for the Taylor number varied from zero to 2000, for which the convective fluid motion halts (other parameters of the system are fixed). We observe 5 types of hydrodynamic (amagnetic) attractors: two families of two-dimensional (i.e. depending on two spatial variables) rolls parallel to sides of periodicity boxes of different widths and parallel to the diagonal, travelling waves and three-dimensional "wavy" rolls. All types of attractors, except for one family of rolls, are capable of kinematic magnetic field generation. We have found 21 distinct nonlinear convective MHD attractors (13 steady states and 8 periodic regimes) and identified bifurcations in which they emerge. In addition, we have observed a family of periodic, two-frequency quasiperiodic and chaotic regimes, as well as an incomplete Feigenbaum period doubling sequence of bifurcations of a torus followed by a chaotic regime and subsequently by a torus with 1/3 of the cascade frequency. The system is highly symmetric. We have found two novel global bifurcations reminiscent of the SNIC bifurcation, which are only possible in the presence of symmetries. The universally accepted paradigm, whereby an increase of the rotation rate below a certain level is beneficial for magnetic field generation, while a further increase inhibits it (and halts the motion of fluid on continuing the increase) remains unaltered, but we demonstrate that this "large-scale" picture lacks many significant details.
On the potential of mean force of a sterically stabilized dispersion
R. Catarino Centeno,E. Perez,A. Gama Goicochea
Physics , 2014,
Abstract: The potential of mean force (PMF) of a colloidal dispersion under various circumstances of current interest, such as varying solvent quality, polymer coating thickness, and addition of electrostatic interaction is obtained from radial distribution functions available from the literature. They are based on an implicit solvent, molecular dynamics simulation study of a model titania dispersion that takes into account three major components to the interaction between colloidal particles, namely van der Waals attraction, repulsion between polymer coating layers, and a hard core particle repulsion. Additionally, a screened form of the electrostatic interaction was included also. It is argued that optimal conditions for dispersion stability can be derived from a comparative analysis of the PMF under the different situations under study. This thermodynamics based analysis is believed to be more accessible to specialists working on the development of improved titania formulations than that based on the more abstract, radial distribution functions.
Métodos de preserva??o e crescimento de Xanthomonas campestris pv. viticola em meio de cultura variando temperatura, pH e concentra??o de NaCl
Nascimento, Ana R. P.;Mariano, Rosa L. R.;Gama, Marco A. S.;
Fitopatologia Brasileira , 2005, DOI: 10.1590/S0100-41582005000600014
Abstract: the phytopathogenic bacterium xanthomonas campestris pv. viticola (xcv) induces grapevine (vitis vinifera) bacterial canker, causing severe losses in brazil. four preservation methods [dried paper strips (dps), periodic transfer (pt), sterile distiled water (sdw) and dried leaves (dl)] were compared for storing two xcv strains over a 12-month periods. viability and pathogenicity were evaluated every month and estimated by bacterial growth and area under the disease incidence curve (audic). both the dps and sdw methods maintained 100% of cell viability to and showed higher audic values for 11 months. the pt did not permit growth at 30 days while dl maintained cell viability for up to five months. the growth of two xcv strains in liquid culture medium at varying temperatures (0, 5, 10, 15, 20, 25, 27, 28, 29, 30, 35, 40 and 45°c), ph (5.0; 5.,5; 6.0; 6.5; 7.0; 7.5; 8.0; 8.5 and 9.0) and nacl concentration (1, 2, 3, 4, 5, 6 and 7%) was evaluated with spectrophotometer. the xcv growth was observed from 5 to 35 °c, with optimum growth from 27 to 29 °c. the xcv did not grow at zero and 40 °c. the optimum ph for xcv growth was 7.5. the pathogen growth declined from 3.0% nacl and was null at 6.0%.
Field experimental evaluation of secondary metabolites from marine invertebrates as antifoulants
Brazilian Journal of Biology , 2002, DOI: 10.1590/S1519-69842002000200015
Abstract: the crude organic extracts of the endemic gorgonian phyllogorgia dilatata and two sponge species aplysina fulva and mycale microsigmatosa were evaluated for anti-fouling properties through field experiments. to investigate this property in ecologically meaningful conditions, crude extracts from these invertebrates were incorporated at concentrations naturally found in these marine organisms into a stable gel used as a substratum for fouling settlement. crude extract from a. fulva showed no significant anti-fouling property at the natural concentrations used in the field experiments. in fact, fouling organisms settled significantly more on gels treated with a. fulva extract than on the control gel. on the other hand, both m. microsigmatosa and p. dilatata yielded crude extracts that exhibited a selective action inhibiting only the settlement of barnacles. the evidences obtained here by means of field experiments can provide a basis for future development of one kind of natural antifoulant technology to prevent marine biofouling.
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