Pion structure function within the instanton model

The leading-twist valence-quark distribution function in the pion is obtained at a low normalization scale of an order of the inverse average size of an instanton pc. The momentum dependent quark mass and the quark-pion vertex are constructed in the framework of the instanton liquid model, using a gauge invariant approach. The parameters of instanton vacuum, the effective instanton radius and quark mass, are related to the vacuum expectation values of the lowest dimension quark-gluon operators and to the pion low energy observables. An analytic expression for the quark distribution function in the pion for a general vertex function is derived. The results are QCD evolved to higher momentum-transfer values, and reasonable agreement with phenomenological analyses of the data on parton distributions for the pion is found. ©2000 The American Physical Society.

Reliability of timber bridges using nailed plywood box beams

The Nailed Box Beam structural efficiency is directly dependent of the flange-web joint behavior, which determines the partial composition of the section, as the displacement between elements reduces the effective rigidity of the section and changes the stress distribution and the total displacement of the section. This work discusses the use of Nailed Plywood Box Beams in small span timber bridges, focusing on the reliability of the beam element. It is presented the results of tests carried out in 21 full scale Nailed Plywood Box Beams. The analysis of maximum load tests results shows that it presents a normal distribution, permitting the characteristic values calculation as the normal distribution theory specifies. The reliability of those elements was analyzed focusing on a timber bridge design, to estimate the failure probability in function of the load level.

The small x behavior of the gluon structure function from total cross-sections

Within a QCD-based eikonal model with a dynamical infrared gluon mass scale we discuss how the small x behavior of the gluon distribution function at moderate Q 2 is directly related to the rise of total hadronic cross-sections. In this model the rise of total cross-sections is driven by gluon-gluon semihard scattering processes, where the behavior of the small x gluon distribution function exhibits the power law xg(x, Q 2) = h(Q 2)x( -∈). Assuming that the Q 2 scale is proportional to the dynamical gluon mass one, we show that the values of h(Q 2) obtained in this model are compatible with an earlier result based on a specific nonperturbative Pomeron model. We discuss the implications of this picture for the behavior of input valence-like gluon distributions at low resolution scales. © 2008 World Scientific Publishing Company.

Modelagem do crescimento e produção em povoamentos desbastados de Eucalyptus grandis

The aim of the study was to develop a system of growth and yield models for thinned stands of Eucalyptus spp.; and to assess the behavior of the growth in scenarios with 10% decrease or increase in rainfall. The probability distribution functions Weibull 2 and 3 parameters and Johnson SB for different methods were fitted. Correlation between the fitted parameters with age was evaluated. Dominant height growth behavior was evaluated to check if thinned stand changes its growth when compared to a non-thinned stands. The stand variables dominant height and basal area were projected and simultaneously predicted and projected, respectively. Individual tree equations were fitted, which were fitted as functions of stand level variables in order to decrease the error propagation. R software was used to fit all the proposed models and consequently all the fitted models were evaluated by their parameters significance (F-test) and graphs of predicted values in relation to the observed values around the 1:1 line. Thus, the prognosis system was made by two ways, first one using the full data set, and for the second one the dataset was restricted at age 7.5. Increase and decrease in 20% of rainfall were assessed by updating the site index function. Method of moments was the most precise to describe the diameter distribution for every age in eucalyptus stands for Johnson SB and Weibull 2 parameters pdfs. When observed for each pdf the correlation for their fitted parameters with age, we noticed that shape parameters for a thinned stand were no longer correlated with age, differently of non-thinned stands. Thus, thinning effect was accounted in the basal area prediction and projection modeling. This result emphasized the necessity of applying the Parameter Recovery method in order to assess differences and capture the right pattern for thinned and non-thinned stands in the future. Dominant height was not influenced by thinning intensity. Therefore the fitted Chapman-Richards model did not account for a stand being thinned or not. All the fitted equations behaved with good precision, no matter using full or precocious dataset. The prognosis system using full and/or precocious date set was evaluated for when using Parameter Recovery method for Sb and Weibull pdfs, and by then, graphical analysis and precision statistics showed appropriated results. Finally, the increase or decrease in rainfall regime were observed for eucalyptus stand yields and we may notice how important is to observe this effect, since the growth pattern is strictly affected by water.

Probabilidade de atendimento da demanda hídrica das culturas do arroz de terras altas, milho e soja, como subsídio para a definição de épocas de semeadura na região de Ilha Solteira-SP

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação de um escarificador em função dos tipos de haste e profundidades de trabalho

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Rentabilidade e risco da produção de milho safrinha geneticamente modificado na região de Guaíra-SP

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

A new sampling strategy to reduce the effect of autocorrelation on a control chart

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The Fokker-Planck equation for a bistable potential

The Fokker-Planck equation is studied through its relation to a Schrodinger-type equation. The advantage of this combination is that we can construct the probability distribution of the Fokker-Planck equation by using well-known solutions of the Schrodinger equation. By making use of such a combination, we present the solution of the Fokker-Planck equation for a bistable potential related to a double oscillator. Thus, we can observe the temporal evolution of the system describing its dynamic properties such as the time tau to overcome the barrier. By calculating the rates k = 1/tau as a function of the inverse scaled temperature 1/D, where D is the diffusion coefficient, we compare the aspect of the curve k x 1/D, with the ones obtained from other studies related to four different kinds of activated process. We notice that there are similarities in some ranges of the scaled temperatures, where the different processes follow the Arrhenius behavior. We propose that the type of bistable potential used in this study may be used, qualitatively, as a simple model, whose rates share common features with the rates of some single rate-limited thermally activated processes. (C) 2014 Elsevier B.V. All rights reserved.

Coherence characteristics of random lasing in a dye doped hybrid powder

The photon statistics of the random laser emission of a Rhodamine B doped di-ureasil hybrid powder is investigated to evaluate its degree of coherence above threshold. Although the random laser emission is a weighted average of spatially uncorrelated radiation emitted at different positions in the sample, a spatial coherence control was achieved due to an improved detection configuration based on spatial filtering. By using this experimental approach, which also allows for fine mode discrimination and timeresolved analysis of uncoupled modes from mode competition, an area not larger than the expected coherence size of the random laser is probed. Once the spectral and temporal behavior of nonoverlapping modes is characterized, an assessment of the photon-number probability distribution and the resulting second-order correlation coefficient as a function of time delay and wavelength was performed. The outcome of our single photon counting measurements revealed a high degree of temporal coherence at the time of maximum pump intensity and at wavelengths around the Rhodamine B gain maximum.

Equação de Fokker-Planck e enovelamento de proteínas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Rentabilidade e Risco da Produção de Milho Safrinha Geneticamente Modificado e Convencional na Região de Guaíra/sp

The objective of this study was to dimension the economic risks and returns on adopters of genetically modified (GM) maize in one of the major corn producing regions of São Paulo state. We performed analysis of variation of the quantities and prices of insecticides used, productivity gains, and variation in the price differentials between GM maize and conventional hybrids seeds, according to account to the maize prices oscillation during the period studied. The net benefits methodology was used, in other words, the economic gains minus the costs of GM technology under risk conditions were calculated. The net benefits was calculated as a function of four critical variables: 1) GM maize productivity; 2) costs of pest control; 3) maize price; 4) GM seeds cost. The probability distribution functions of these critical variables were estimated and included in the net benefit equation. Using the Monte Carlo simulation methodology, the following indicator sets were estimated: central tendency measurements, variability in net benefits (total benefits minus total costs), sensitivity analysis of the net benefits in relation to the critical variables, and finally, a map of the risk to GM technology adopters. These indicators allow one to design economic scenarios associated with their probability of occurring. The results showed probability of 85% to positive gains to the farmers who adopted the transgenic maize seed cultivation. The variable with the greatest impact on the farmers' income was the reduction in productivity loss, that means, as higher is the maize productivity, higher will be the net income. The average gain was US$ 137,41 (R$ 2.45/US$)per hectare with the adoption of transgenic maize seed when compared to conventional maize seed.

Classificação climática de Thornthwaite e sua aplicabilidade agroclimatológica nos diferentes regimes de precipitação em Pernambuco

Knowing the annual climatic conditions is of great importance for appropriate planning in agriculture. However, the systems of climatic classification are not widely used in agricultural studies because of the wide range of scales in which they are used. A series with data from 20 years of observations from 45 climatological stations in all over the state of Pernambuco was used. The probability density function of the incomplete gamma distribution was used to evaluate the occurrence of dry, regular and rainy years. The monthly climatic water balance was estimated using the Thornthwaite and Mather method (1955), and based on those findings, the climatic classifications were performed using the Thornthwaite (1948) and Thornthwaite and Mather (1955) for each site. The method of Kriging interpolation was used for the spatialization of the results. The study classifications were very sensitive to the local reliefs, to the amount of rainfall, and to the temperatures of the regions resulting in a wide number of climatic types. The climatic classification system of Thornthwaite and Mather (1955) allowed efficient classification of climates and a clearer summary of the information provided. In so doing, it demonstrated its capability to determine agro climatic zones.

Universality in bibliometrics

Many discussions have enlarged the literature in Bibliometrics since the Hirsch proposal, the so called h-index. Ranking papers according to their citations, this index quantifies a researcher only by its greatest possible number of papers that are cited at least h times. A closed formula for h-index distribution that can be applied for distinct databases is not yet known. In fact, to obtain such distribution, the knowledge of citation distribution of the authors and its specificities are required. Instead of dealing with researchers randomly chosen, here we address different groups based on distinct databases. The first group is composed of physicists and biologists, with data extracted from Institute of Scientific Information (IS!). The second group is composed of computer scientists, in which data were extracted from Google-Scholar system. In this paper, we obtain a general formula for the h-index probability density function (pdf) for groups of authors by using generalized exponentials in the context of escort probability. Our analysis includes the use of several statistical methods to estimate the necessary parameters. Also an exhaustive comparison among the possible candidate distributions are used to describe the way the citations are distributed among authors. The h-index pdf should be used to classify groups of researchers from a quantitative point of view, which is meaningfully interesting to eliminate obscure qualitative methods. (C) 2011 Elsevier B.V. All rights reserved.

A Bayesian nonparametric model for Taguchi's on-line quality monitoring procedure for attributes

A Bayesian nonparametric model for Taguchi's on-line quality monitoring procedure for attributes is introduced. The proposed model may accommodate the original single shift setting to the more realistic situation of gradual quality deterioration and allows the incorporation of an expert's opinion on the production process. Based on the number of inspections to be carried out until a defective item is found, the Bayesian operation for the distribution function that represents the increasing sequence of defective fractions during a cycle considering a mixture of Dirichlet processes as prior distribution is performed. Bayes estimates for relevant quantities are also obtained. (C) 2012 Elsevier B.V. All rights reserved.