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Search Results: 1 - 10 of 11079 matches for " Renato Mendes; "
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Forma o de professores em Educa o Física: o lugar da prática...
Renato Mendes
Pensar a Prática , 2006, DOI: 19806183/rpp.v3i0.40
Avalia??o da qualidade de sementes sucupira-preta (Bowdichia virgilioides Kunth.) pelo teste de raios X
Albuquerque, Keline Sousa;Guimar?es, Renato Mendes;
Ciência e Agrotecnologia , 2008, DOI: 10.1590/S1413-70542008000600005
Abstract: injuries represent a limitng factor for the seed viability. depending on their intensity, the injuries might reduce seed vigour, produce weak seedlings. consequently, they might be more susceptible to adverse conditions. in this research, the efficiency of x ray test was verifie to evaluate damage in seeds of black sucupira and its relation with germination test. initially, seeds were exposed to different intensities of radiation for different periods. next, seeds were separated in three categories according to the images obtained in radiographs: seeds without damage, seeds with little damage and seeds with severe damage. the experiment was conducted in factorial system 3x3, corresponding to three lots and three categories of seeds. the variable analyzed were percentage and germination speed index. it was verified that the intensity of 30 kv per 45 seconds allowed better visualization of damages in seeds of black sucupira. damages affect wich severely seed germination.
CERNE , 2007,
Abstract: This research verified the influence of the temperature and light on seed germination of Bowdichia virgilioides. The experiment was conducted in factorial system 3x5x2, correspoding to three lots of seeds, five temperatures and two light condictions. The germination test was conducted in thermo gradiente table regulated in temperatures of 20°C, 25°C, 30°C and 35°C under constant light and BOD adjusted in temperature 20-30°C with photoperiod of 12 hours. In order to simulate the light absence the gerbox were involved with alluminium paper. There were evaluated the percentage of germination, index speed of germination and dry weight of seedlings. The tempeatures of 25°C and 20-30°C result in higher percentage. In relation to photoblastism, the seeds are indifferent to light conditions.
Strongly nonnegative curvature
Renato G. Bettiol,Ricardo A. E. Mendes
Mathematics , 2015,
Abstract: We prove that all currently known examples of manifolds with nonnegative sectional curvature satisfy a stronger condition: their curvature operator can be modified with a 4-form to become positive-semidefinite.
Flag manifolds with strongly positive curvature
Renato G. Bettiol,Ricardo A. E. Mendes
Mathematics , 2014, DOI: 10.1007/s00209-015-1464-1
Abstract: We obtain a complete description of the moduli spaces of homogeneous metrics with strongly positive curvature on the Wallach flag manifolds $W^6$, $W^{12}$ and $W^{24}$, which are respectively the manifolds of complete flags in $\mathbb C^3$, $\mathbb H^3$ and $\mathbb{Ca}^3$. Together with our earlier work, this concludes the classification of simply-connected homogeneous spaces that admit a homogeneous metric with strongly positive curvature.
Strongly positive curvature
Renato G. Bettiol,Ricardo A. E. Mendes
Mathematics , 2014,
Abstract: We begin a systematic study of a curvature condition (strongly positive curvature) which lies strictly between positive curvature operator and positive sectional curvature, and stems from the work of Thorpe in the 1970s. We prove that this condition is preserved under Riemannian submersions and Cheeger deformations, and that most compact homogeneous spaces with positive sectional curvature satisfy it.
Florística e estrutura de comunidades vegetais em uma cronoseqüência de Floresta Atlantica no Estado do Paraná, Brasil
Liebsch, Dieter;Goldenberg, Renato;Marques, Márcia Cristina Mendes;
Acta Botanica Brasilica , 2007, DOI: 10.1590/S0102-33062007000400023
Abstract: we describe the tree structure of three atlantic forest fragments on the coast of paraná, in order to detect differences in community structure throughout the succession process and to support future vegetation restoration projects. the study area was the reserva natural rio cachoeira, where three sites were chosen based on length of time since the last manmade disturbance (mostly agriculture and lodging); these were, respectively, 20-, 80- and 120-year-old forests. the 20-year-old forest had the lowest richness, diversity, basal area and volume. the 80-year-old forest had the highest density and richness. the 120-year-old forest had the highest diversity, equitability and volume. diversity, basal area and volume were significantly different among the three sites. there were no important differences among structures of populations of species shared by the three areas. on the other hand, structural characteristics of exclusive species were important to determine differences among sites.
Catastrophic Regime Shift in Water Reservoirs and S?o Paulo Water Supply Crisis
Renato Mendes Coutinho,Paulo Inácio Prado,Roberto André Kraenkel
Physics , 2015,
Abstract: The relation between rainfall and water accumulated in reservoirs comprises nonlinear feedbacks. Here we show that they may generate alternative equilibrium regimes, one of high water-volume, the other of low water-volume. Reservoirs can be seen as socio-environmental systems at risk of regime shifts, characteristic of tipping point transitions. We analyze data from stored water, rainfall, and water inflow and outflow in the main reservoir serving the metropolitan area of S\~ao Paulo, Brazil, by means of indicators of critical regime shifts, and find a strong signal of a transition. We furthermore build a mathematical model that gives a mechanistic view of the dynamics and demonstrates that alternative stable states are an expected property of water reservoirs. We also build a stochastic version of this model that fits well to the data. These results highlight the broader aspect that reservoir management must account for their intrinsic bistability, and should benefit from dynamical systems theory. Our case study illustrates the catastrophic consequences of failing to do so.
Dynamic Tracking with Zero Variation and Disturbance Rejection Applied to Discrete-Time Systems
Renato de Aguiar Teixeira Mendes,Edvaldo Assun??o,Marcelo C. M. Teixeira,Cristiano Q. Andrea
Mathematical Problems in Engineering , 2010, DOI: 10.1155/2010/842896
Abstract: The problem of signal tracking in discrete linear time invariant systems, in the presence of a disturbance signal in the plant, is solved using a new zero-variation methodology. A discrete-time dynamic output feedback controller is designed in order to minimize the norm between the exogen input and the output signal of the system, such that the effect of the disturbance is attenuated. Then, the zeros modification is used to minimize the norm from the reference input signal to the error signal. The error is taken as the difference between the reference and the output signal. The proposed design is formulated in linear matrix inequalities (LMIs) framework, such that the optimal solution of the stated problem is obtained. The method can be applied to plants with delay. The control of a delayed system illustrates the effectiveness of the proposed method. 1. Introduction In a control systems theory, the design of controller using pole placement of closed loop discrete-time systems can be easily done. In [1] a controller using pole placement is used to obtain an exact plot of complementary root locus, of biproper open-loop transfer functions, using only well-known root locus rules. However, the problem of zero placement is not very much studied by the control researchers. In [2] a discrete-time pole placement is obtained by a control design technique that uses simple and multirate sample. The methodology proposed in [3] preserves the state feedback controller optimality by pole placement in a plain region specified in design. In the field of discrete-time systems pole placement we find [4], where discrete adaptative controllers are designed considering arbitrary zero location. Also, in [5] a class of nonmodeled dynamics is controlled using a zero placement. In [6] a methodology is proposed using zero and pole placement for discrete-time systems, to obtain the signal tracking and disturbance rejection, respectively. However, for the signal tracking problem, when a state feedback estimator is proposed, a modification occurs in -norm value obtained with the initial controller that provides the disturbance rejection. The methodology proposed in this paper has the advantage of maintaining the -norm value obtained with the initial controller for the signal tracking problem. The problem of signal tracking, in the presence of disturbance signal for continuous-time plant, was solved in [7], using a zero variation methodology. A methodology with a simpler mathematic formulation is proposed in [8]. The signal tracking problem with disturbance rejection in discrete-time
Efeito da secagem, do armazenamento e da germina??o sobre a micromorfologia de sementes de Eugenia pyriformis Camb
Justo, Cristina Filomena;Alvarenga, Amauri Alves de;Alves, Eduardo;Guimar?es, Renato Mendes;Strassburg, Rosali Constantino;
Acta Botanica Brasilica , 2007, DOI: 10.1590/S0102-33062007000300004
Abstract: eugenia pyriformis camb. is a tree species of medium height that produces savory fruits with large thin-coated seeds. these seeds quickly lose viability when submitted to desiccation. our aim was to investigate embryo structure in e. pyriformis seeds and the ultra-structural changes that result from drying, germination and storage. the axis was less than 1.0 mm long, while the fleshy cotyledons varied from 1.0 to 2.0 cm. the apical and radicular meristem lie in opposing positions. there is a procambium and a medulla of parenchymatous nature, rich in starch grains. leafy primordia were identified around the stem meristem and there were unicellular trichomes and stomata on the adaxial epidermis of the cotyledons. the gradual desiccation of the seeds provoked cellular structure disarrangement, which also occurred as the seeds aged. apical meristem form changed from concave to conical during germination and the radicular hypocotyl axis became elongated, with root protrusion. in this phase, the cells have structured content and hydrolysis of reserves. seed water content variation was evaluated and the physiological consequences of this change are discussed.
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