Paulo Laerte Natti

Local calibration of coliforms parameters of water quality problem at Igapó I Lake, Londrina, Paraná, Brazil

The calibration of a model refers to the process by which one can estimate some parameters by comparisons with observed data. Due to the dynamical nature of the environment, variations between predicted and observed values occur. Thus, the environmental parameters may vary due to random temperature changes, time of discharge flow, time of the day, and other conditions. Such variations can be minimized by identifying and optimizing some parameters of the transport model, like the values of diffusion coefficients in x and y directions and the kinetic parameter that describes the process of removing pollutants. This paper presents results concerning the calibration of transport parameters for two-dimensional problems of water quality (fecal coliform control) at Igapo I Lake, located in Londrina, Parana, Brazil. Thus, the convection-diffusion-reaction equation, which describes mathematically the process studied in this work, is resolved by a semidiscrete finite element method (SUPG) which combines finite differences in time and finite elements in space.

On the equivalence principle and gravitational and inertial mass relation of classical charged particles

We show that the locally constant force necessary to get a stable hyperbolic motion regime for classical charged point particles, actually, is a combination of an applied external force and of the electromagnetic radiation reaction force. It implies, as the strong equivalence principle is valid, that the passive gravitational mass of a charged point particle should be slightly greater than its inertial mass. An interesting new feature that emerges from the unexpected behavior of the gravitational and inertial mass relation, for classical charged particles, at a very strong gravitational field, is the existence of a critical, particle-dependent, gravitational field value that signs the validity domain of the strong equivalence principle. For electrons and protons, these critical field values are gc � 4.8 × 10 31 ms −2 and gc � 8.8 × 10 34 ms −2 , respectively.

Ondas do tipo sóliton em guias dielétricos

In this work we study a coupled differential equations system, which describes the propagation of a wave packet, composed of two waves with frequencies w0 (fundamental wave) and 2w0 (second-harmonic wave), in a quadratic nonlinear dieletric waveguide. Asymptotically, we show that these equations reduce to the nonlinear Schr¨odinger equation (NLSE). Solving the coupled differential equations system, we obtain soliton solutions for the time evolution of the packet in the dielectric waveguide. Finally, we discuss the property of soliton solutions, in particular the necessary conditions for their existence.

A transport modeling of the carbon-nitrogen cycle at Igapó I Lake - Londrina, Paraná State, Brazil

This work is a contribution to better understand the effect that domestic sewage discharges may cause in a water body, specifically Igapo I Lake, in Londrina, Parana, Brazil. The simulation of the dynamics of pollutant concentrations all over the water body is conducted by means of structured discretization of the geometry of Igapo I Lake, together with the finite differences and the finite elements methods. Firstly, the hydrodynamic flow (without the pollutants), modeled by Navier-Stokes and pressure equations, is numerically resolved by the finite differences method, and associated with the fourth order Runge-Kutta procedure. After that, by using the hydrodynamic field velocity, the flow of the reactive species (pollutants) is described through a transport model, which considers advective and diffusive processes, as well as through a reactions model, restricted to the carbon-nitrogen cycle. The transport and reactions model is numerically resolved by the stabilized finite elements method, by means of a semidiscrete formulation. A qualitative analysis of the numerical simulations conducted in function of the diffusion coefficient provided better understanding of the dynamics of the processes involved in the flow of the reactive species, such as the dynamics of the nitrification process, of the biochemical requirement of oxygen and of the level of oxygen dissolved in the water body at Igapo I Lake.

A modeling of the carbon-nitrogen cycle transport at Igap\'o I Lake - Londrina, Paran\'a, Brazil

This work is a contribution to better understand the effect that domestic sewage discharges may cause in a water body, specifically Igapo I Lake, in Londrina, Parana, Brazil. The simulation of the dynamics of pollutant concentrations all over the water body is conducted by means of structured discretization of the geometry of Igapo I Lake, together with the finite differences and the finite elements methods. Firstly, the hydrodynamic flow (without the pollutants), modeled by Navier-Stokes and pressure equations, is numerically resolved by the finite differences method, and associated with the fourth order Runge-Kutta procedure. After that, by using the hydrodynamic field velocity, the flow of the reactive species (pollutants) is described through a transport model, which considers advective and diffusive processes, as well as through a reactions model, restricted to the carbon-nitrogen cycle. The transport and reactions model is numerically resolved by the stabilized finite elements method, by means of a semidiscrete formulation. A qualitative analysis of the numerical simulations conducted in function of the diffusion coefficient provided better understanding of the dynamics of the processes involved in the flow of the reactive species, such as the dynamics of the nitrification process, of the biochemical requirement of oxygen and of the level of oxygen dissolved in the water body at Igapo I Lake.

A random walk description of individual animal movement accounting for periods of rest

Animals do not move all the time but alternate the period of actual movement (foraging) with periods of rest (e.g. eating or sleeping). Although the existence of rest times is widely acknowledged in the literature and has even become a focus of increased attention recently, the theoretical approaches to describe animal movement by calculating the dispersal kernel and/or the mean squared displacement (MSD) rarely take rests into account. In this study, we aim to bridge this gap. We consider a composite stochastic process where the periods of active dispersal or ‘bouts’ (described by a certain baseline probability density function (pdf) of animal dispersal) alternate with periods of immobility. For this process, we derive a general equation that determines the pdf of this composite movement. The equation is analysed in detail in two special but important cases such as the standard Brownian motion described by a Gaussian kernel and the Levy flight described by a Cauchy distribution. For the Brownian motion, we show that in the large-time asymptotics the effect of rests results in a rescaling of the diffusion coefficient. The movement occurs as a subdiffusive transition between the two diffusive asymptotics. Interestingly, the Levy flight case shows similar properties, which indicates a certain universality of our findings.

O bóson de Higgs

The Higgs boson was predicted in 1964 by British physicist Peter Higgs. The Higgs is the key to explain the origin of the mass of other elementary particles of Nature. However, only with the coming into operation of the LHC, in 2008, there were technological conditions to search for the Higgs boson. Recently, a major international effort conducted at CERN, by means of ATLAS and CMS experiments, has enabled the observation of a new bosonic particle in the region of 125 GeVs. In this paper, by means of known mechanisms of symmetry breaking that occur in the BCS theory of superconductivity and in the theory of nuclear pairing, we discuss the Higgs mechanism in the standard model. Finally, we present the current state of research looking for the Higgs boson and the alternative theories and extensions of the standard model for the elementary particle physics.The Higgs boson was predicted in 1964 by British physicist Peter Higgs. The Higgs is the key to explain the origin of the mass of other elementary particles of Nature. However, only with the coming into operation of the LHC, in 2008, there were technological conditions to search for the Higgs boson. Recently, a major international effort conducted at CERN, by means of ATLAS and CMS experiments, has enabled the observation of a new bosonic particle in the region of 125 GeVs. In this paper, by means of known mechanisms of symmetry breaking that occur in the BCS theory of superconductivity and in the theory of nuclear pairing, we discuss the Higgs mechanism in the Standard Model. Finally, we present the current state of research looking for the Higgs boson and the alternative theories and extensions of the Standard Model for the elementary particle physics. nKeywords: Higgs boson, BCS theory, nuclear pairing, Higgs mechanism, Standard Model.

Avaliação computacional de esquemas convectivos em problemas de dinâmica dos fluidos

This article provides a computational evaluation of the popular high resolution upwind WACEB, CUBISTA and ADBQUICKEST schemes for solving non-linear fluid dynamics problems. By using the finite difference methodology, the schemes are analyzed and implemented in the context of normalized variables of Leonard. In order to access the performance of the schemes, Riemann problems for 1D Burgers, Euler and shallow water equations are considered. From the numerical results, the schemes are ranked according to their performance in solving these non-linear equations. The best scheme is then applied in the numerical simulation of tridimensional incompressible moving free surface flows.

Fermion pairing dynamics in the relativistic scalar plasma

Using many-body techniques we obtain the time-dependent Gaussian approximation for interacting fermion-scalar field models. This method is applied to an uniform system of relativistic spin-1/2 fermion field coupled, through a Yukawa term, to a scalar field in 3+1 dimensions, the so-called quantum scalar plasma model. The renormalization for the resulting Gaussian mean-field equations, both static and dynamical, are examined and initial conditions discussed. We also investigate solutions for the gap equation and show that the energy density has a single minimum.

Simulação numérica da dinâmica de DBO5 no lago Igapó I, Londrina, Paraná, Brasil: Medição experimental e modelagem matemática

The concentration of biochemical oxygen demand, BOD5, was studied in order to evaluate the water quality of the Igapo I Lake, in Londrina, Parana State, Brazil. The simulation was conducted by means of the discretization in curvilinear coordinates of the geometry of Igapo I Lake, together with finite difference and finite element methods. The evaluation of the proposed numerical model for water quality was performed by comparing the experimental values of BOD5 with the numerical results. The evaluation of the model showed quantitative results compatible with the actual behavior of Igapo I Lake in relation to the simulated parameter. The qualitative analysis of the numerical simulations provided a better understanding of the dynamics of the BOD5 concentration at Igapo I Lake, showing that such concentrations in the central regions of the lake have values above those allowed by Brazilian law. The results can help to guide choices by public officials, as: (i) improve the identification mechanisms of pollutant emitters on Lake Igapo I, (ii) contribute to the optimal treatment of the recovery of the polluted environment and (iii) provide a better quality of life for the regulars of the lake as well as for the residents living on the lakeside.