A.J. Silva Neto

Solution of inverse radiative transfer problems in two-layer participating media with differential evolution

In the present work the differential evolution approach (DE) is used for the estimation of radiative properties in two-layer participating media. This physical phenomenon is modelled by an integro-differential equation known as the Boltzmann equation. A review of the optimization technique used is presented. The direct radiative transfer problem is solved by using the collocation method. Then, case studies are presented aimed at illustrating the efficiency of the methodology used in the treatment of an inverse problem of radiative transfer. The results obtained from the solution of the inverse problem are compared with those obtained from a hybridization of simulated annealing and Levenberg–Marquardt methods. The preliminary results indicate that the proposed approach characterizes a promising methodology for the present type of inverse problem.

Application of the generalized extremal optimization algorithm to an inverse radiative transfer problem

The recently developed generalized extremal optimization (GEO) algorithm is applied for the solution of an inverse problem of radiative properties estimation. A comparison with two other stochastic methods, simulated annealing and genetic algorithms, is also performed, demonstrating that GEO is competitive. From the test case results we could also infer that a hybridization of GEO with gradient-based methods is very promising.

A regularized solution with weighted Bregman distances for the inverse problem of photoacoustic spectroscopy

In the present work we propose the use of weighted Bregman distances in the construction of regularization terms for the Tikhonov functional applied for the formulation and solution of the inverse problem of photoacoustic spectroscopy. Test case results demonstrate that better estimates were obtained for the simultaneous estimation of the thermal diffusivity and optical absorption coefficient using, as synthetic experimental data, the information on both the amplitude and phase-lag of the temperature at the interface sample-gas between the material under analysis and the air chamber of the closed photoacoustic cell.

Estimation of space-dependent single scattering albedo in a radiative transfer problem using differential evolution

This work presents the differential evolution algorithm applied to an inverse radiative transfer problem formulated as a finite dimensional optimization problem. It is considered a one-dimensional isotropically-scattering medium with finite optical thickness, space-dependent scattering albedo and plane-parallel geometry. The direct radiative transfer problem models the transmission of radiation through this medium by a linear version of the Boltzmann equation with azimuthal symmetry. The direct radiative transfer problem solution, which is required for the optimization techniques, is obtained by using the collocation method. Some test cases are presented, aiming at illustrating the efficiency of the methodologies used in the treatment of an inverse problem of radiative transfer. The results are compared with other approaches and indicate that the proposed methodology characterizes a promising methodology for dealing with this type of inverse problem.

A novel fault diagnosis scheme applying fuzzy clustering algorithms

Abstract In this paper an approach to design data driven based fault diagnosis systems using fuzzy clustering techniques is presented. In this proposal, as a first part of the classification process, the data was pre-processed to eliminate outliers and reduce the confusion. To achieve this, the Noise Clustering and Density Oriented Fuzzy C-Means algorithms were used. Secondly, the Kernel Fuzzy C-Means algorithm was used to achieve greater separability among the classes, and reduce the classification errors. Finally, a third step is developed to optimize the two parameters used in the algorithms in the training stage using the Differential Evolution algorithm. The proposed approach was validated using the nonlinear continuous stirred-tank reactor. The obtained results indicate the feasibility of the proposal.

Stochastic and hybrid methods for the identification in the Bouc-Wen model for magneto – rheological dampers

Magneto-rheological (MR) dampers are semi-active control devices that require low power input and are considered fail-safe, i.e. in case of control hardware failure they become passive dampers. In the present work we consider a sensitivity analysis and use the deterministic gradient based Levenberg-Marquardt method, the stochastic methods Simulated Arnealing and Genetic Algorithms, as well as hybridizations of these methods, for the estimation of parameters in the Bouc-Wen model, which is used to describe the dynamic behavior of MR dampers. The parameters associated with the histeretic displacement evolution equation are the most difficult to be estimated, and therefore we use a strategy for estimating such parameters separately from other parameters of the model.

An inverse problem for thermal diffusivity estimation with the photoacoustic spectroscopy

In the present work we investigate the estimation of the thermal diffusivity with an inverse problem approach for photoacoustic spectroscopy (PAS). The direct problem is solved analytically using Rosencwaig-Gersho (RG) theory and the inverse problem is solved using the method of Levenberg-Marquardt. A sensitivity analysis is presented. We used real experimental data for the amplitude and phase-lag of the photoacoustic signal, acquired with a PAS experimental apparatus. A discussion is presented on the results obtained for the thermal diffusivity of a glass sample.

An inverse analysis of the radiative transfer in a two-layer heterogeneous medium

The radiative transfer in multi-layer composite media has numerous applications, for example, in regional and global climate models, Solar System bodies research, Earth remote sensing, and multi-layer clouds studies, among others. In this study, we focus on the inverse analysis of the radiative transfer problem in a two-layer plane-parallel medium. For the direct problem solution, we use the well-known Chandrasekhars discrete ordinates method combined with the finite difference method. We are interested in the estimation of the scattering and absorbing coefficients using the measured data of the emerging radiation at both boundary surfaces of the medium and also at the interface between the two layers. The inverse problem is implicitly formulated and the minimization of the defined objective function is achieved with the Levenberg–Marquardt method. The solutions obtained are investigated in the face of the sensitivity analysis.

Parallel Computation Approach for the Restoration of AFM Images based on the Tikhonov Regularization Method

This work proposes a parallel implementation for image restoration, applied to biological images, obtained from an Atomic Force Microscope (AFM) [1]. Depending on the scanning dimensions, any image obtained from this technique can present either poor signal/noise ratios and blurred contents. In order to restore or, at least, decrease the effects of such degradations, image restoration methods are usually employed. The algorithm of restoration is based on the use of the Tikhonov methodology, described elsewhere, known here as the serial approach [2].

Comparing 3d and 2d computational modeling of an oil well blowout using MOHID platform - A case study in the Campos Basin

The oil well blowout releases hydrocarbons into the marine environment as an oil droplets and gas bubbles dispersion. The oil trajectory is strongly influenced by physical, chemical and biological processes. In general, the ocean oil drift studies are based on a two-dimensional approach, whereas the whole oil from a well blowout can be represented by a surface oil leak in the same geographical coordinates. This work is a case study, where MOHID software is used at the Campos Basin region, in which the Lagrangian results of the surface oil leaks were confronted to their well blowout scenarios in different conditions of depth, seasonality (summer and winter), and use of dispersants at the source of the leak. The research results reinforced the importance of the three-dimensional approach to the scenario of deep and ultra-deep waters, especially for cases in which the dispersant injection into the source of the leak was considered.