Fourth-order method for solving the Navier-Stokes equations in a constricting channel

A fourth-order numerical method for solving the Navier-Stokes equations in streamfunction/vorticity formulation on a two-dimensional non-uniform orthogonal grid has been tested on the fluid flow in a constricted symmetric channel. The family of grids is generated algebraically using a conformal transformation followed by a non-uniform stretching of the mesh cells in which the shape of the channel boundary can vary from a smooth constriction to one which one possesses a very sharp but smooth corner. The generality of the grids allows the use of long channels upstream and downstream as well as having a refined grid near the sharp corner. Derivatives in the governing equations are replaced by fourth-order central differences and the vorticity is eliminated, either before or after the discretization, to form a wide difference molecule for the streamfunction. Extra boundary conditions, necessary for wide-molecule methods, are supplied by a procedure proposed by Henshaw et al. The ensuing set of non-linear equations is solved using Newton iteration. Results have been obtained for Reynolds numbers up to 250 for three constrictions, the first being smooth, the second having a moderately sharp corner and the third with a very sharp corner. Estimates of the error incurred show that the results are very accurate and substantially better than those of the corresponding second-order method. The observed order of the method has been shown to be close to four, demonstrating that the method is genuinely fourth-order. © 1977 John Wiley & Sons, Ltd.

Concept of Matching Parallelepiped and its use in the correspondence problem

In this paper, the concept of Matching Parallelepiped (MP) is presented. It is shown that the volume of the MP can be used as an additional measure of `distance' between a pair of candidate points in a matching algorithm by Relaxation Labeling (RL). The volume of the MP is related with the Epipolar Geometry and the use of this measure works as an epipolar constraint in a RL process, decreasing the efforts in the matching algorithm since it is not necessary to explicitly determine the equations of the epipolar lines and to compute the distance of a candidate point to each epipolar line. As at the beginning of the process the Relative Orientation (RO) parameters are unknown, a initial matching based on gradient, intensities and correlation is obtained. Based on this set of labeled points the RO is determined and the epipolar constraint included in the algorithm. The obtained results shown that the proposed approach is suitable to determine feature-point matching with simultaneous estimation of camera orientation parameters even for the cases where the pair of optical axes are not parallel.

On the regular-geometric-figure solution to the N-body problem

The regular-geometric-figure solution to the N-body problem is presented in a very simple way. The Newtonian formalism is used without resorting to a more involved rotating coordinate system. Those configurations occur for other kinds of interactions beyond the gravitational ones for some special values of the parameters of the forces. For the harmonic oscillator, in particular, it is shown that the N-body problem is reduced to N one-body problems.

Global optimization for the ℋ∞-norm model reduction problem

A branch and bound algorithm is proposed to solve the [image omitted]-norm model reduction problem for continuous and discrete-time linear systems, with convergence to the global optimum in a finite time. The lower and upper bounds in the optimization procedure are described by linear matrix inequalities (LMI). Also proposed are two methods with which to reduce the convergence time of the branch and bound algorithm: the first one uses the Hankel singular values as a sufficient condition to stop the algorithm, providing to the method a fast convergence to the global optimum. The second one assumes that the reduced model is in the controllable or observable canonical form. The [image omitted]-norm of the error between the original model and the reduced model is considered. Examples illustrate the application of the proposed method.

Meta-heuristic approaches for a soft drink industry problem

The present paper evaluates meta-heuristic approaches to solve a soft drink industry problem. This problem is motivated by a real situation found in soft drink companies, where the lot sizing and scheduling of raw materials in tanks and products in lines must be simultaneously determined. Tabu search, threshold accepting and genetic algorithms are used as procedures to solve the problem at hand. The methods are evaluated with a set of instance already available for this problem. This paper also proposes a new set of complex instances. The computational results comparing these approaches are reported. © 2008 IEEE.

Problem of assignment cells to switches in a cellular mobile network via beam search method

The problem of assigning cells to switches in a cellular mobile network is an NP-hard optimization problem. So, real size mobile networks could not be solved by using exact methods. The alternative is the use of the heuristic methods, because they allow us to find a good quality solution in a quite satisfactory computational time. This paper proposes a Beam Search method to solve the problem of assignment cell in cellular mobile networks. Some modifications in this algorithm are also presented, which allows its parallel application. Computational results obtained from several tests confirm the effectiveness of this approach to provide good solutions for medium- and large-sized cellular mobile network.

Mathematical decomposition technique applied to the probabilistic power flow problem

In this paper a framework based on the decomposition of the first-order optimality conditions is described and applied to solve the Probabilistic Power Flow (PPF) problem in a coordinated but decentralized way in the context of multi-area power systems. The purpose of the decomposition framework is to solve the problem through a process of solving smaller subproblems, associated with each area of the power system, iteratively. This strategy allows the probabilistic analysis of the variables of interest, in a particular area, without explicit knowledge of network data of the other interconnected areas, being only necessary to exchange border information related to the tie-lines between areas. An efficient method for probabilistic analysis, considering uncertainty in n system loads, is applied. The proposal is to use a particular case of the point estimate method, known as Two-Point Estimate Method (TPM), rather than the traditional approach based on Monte Carlo simulation. The main feature of the TPM is that it only requires resolve 2n power flows for to obtain the behavior of any random variable. An iterative coordination algorithm between areas is also presented. This algorithm solves the Multi-Area PPF problem in a decentralized way, ensures the independent operation of each area and integrates the decomposition framework and the TPM appropriately. The IEEE RTS-96 system is used in order to show the operation and effectiveness of the proposed approach and the Monte Carlo simulations are used to validation of the results. © 2011 IEEE.

Domain reduction using GRASP construction phase for transmission expansion planning problem

This paper proposes a new strategy to reduce the combinatorial search space of a mixed integer linear programming (MILP) problem. The construction phase of greedy randomized adaptive search procedure (GRASP-CP) is employed to reduce the domain of the integer variables of the transportation model of the transmission expansion planning (TM-TEP) problem. This problem is a MILP and very difficult to solve specially for large scale systems. The branch and bound (BB) algorithm is used to solve the problem in both full and the reduced search space. The proposed method might be useful to reduce the search space of those kinds of MILP problems that a fast heuristic algorithm is available for finding local optimal solutions. The obtained results using some real test systems show the efficiency of the proposed method. © 2012 Springer-Verlag.

BBA: A binary bat algorithm for feature selection

Feature selection aims to find the most important information from a given set of features. As this task can be seen as an optimization problem, the combinatorial growth of the possible solutions may be in-viable for a exhaustive search. In this paper we propose a new nature-inspired feature selection technique based on the bats behaviour, which has never been applied to this context so far. The wrapper approach combines the power of exploration of the bats together with the speed of the Optimum-Path Forest classifier to find the set of features that maximizes the accuracy in a validating set. Experiments conducted in five public datasets have demonstrated that the proposed approach can outperform some well-known swarm-based techniques. © 2012 IEEE.

Teoria da formação das ações mentais por etapas, de P. Galperin, e o processo de humanização

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Investigações sobre o papel da generalização funcional em uma situação de resolução súbita de problemas (insight) em Rattus norvegicus

A psicologia da aprendizagem foi marcada pelo debate sobre se a aprendizagem seria um processo gradual ou súbito. Enquanto os associacionistas defendiam a primeira proposta, os gestaltistas afirmavam a existência de situações de aprendizagem abruptas. Dentre os principais autores a defenderem esta possibilidade estava Wolfgang Köhler. Os trabalhos deste autor têm sido apontados como evidência de que a aprendizagem seria um processo súbito. Apesar da relevância destes trabalhos em demonstrar a existência de situações em que uma forma súbita de aprendizagem ocorra, muito se tem questionado sobre as conclusões apresentadas por ele para o porquê da ocorrência deste tipo de fenômeno comportamental. Dentre as muitas críticas feitas, a que tem recebido mais atenção refere-se à ausência de controle da história dos seus sujeitos experimentais, bem como à desconsideração do papel que esta história teria nos resultados encontrados. Estudos que investigaram este papel (Epstein et al., 1984 e Epstein & Medalie 1983, 1985) demonstraram que a resposta típica de insight podia ser o resultado da junção de repertórios aprendidos previamente. Os trabalhos de Epstein foram importantes em demonstrar que o insight seria uma junção de repertórios que se combinam em situações apropriadas pelo possível envolvimento de um processo conhecido como Generalização Funcional. O presente trabalho se propôs a investigar se a Generalização Funcional era realmente responsável pela interconexão dos repertórios que culminariam na resolução da tarefa de um modo considerado como súbito. Para tal foi feita uma replicação dos experimentos de Epstein, utilizando-se ratos como sujeitos. Os resultados mostraram que a Generalização Funcional parece ser um requisito necessário, mas não suficiente para a resolução súbita de problemas, de um modo considerado como insight".

Métodos de solução para um problema de sequenciamento da produção com sincronismo de execução de tarefas

Pós-graduação em Engenharia Mecânica - FEG

Efeito de diferentes histórias de treino sobre a ocorrência de "insight" em macacos-prego (Cebus spp.)

A origem de comportamentos criativos é em grande medida pouco conhecida cientificamente. Aparentemente, trata-se de um fenômeno multifacetado que comporta muitos processos distintos. Um desses processos seria a resolução de problemas conhecida como “insight”. Tal processo pode ser explicado como resultado de uma interconexão espontânea de repertórios comportamentais previamente aprendidos. A presente pesquisa teve por objetivo produzir diferentes desempenhos de “insight”, em macacos-prego (Cebus spp.) dando-lhes diferentes histórias de treino. Em especial, pretendeu-se testar o papel da quantidade de treino de cada repertório pré-requisito. Seis sujeitos foram divididos em dois grupos de três sujeitos cada. As habilidades pré-requisitos para a resolução da tarefa foram: 1) juntar objetos (“encaixar”); e, 2) puxar uma caixa contendo alimento usando uma vareta (“pescar”). Todos os sujeitos passaram pelo treino das duas habilidades, sendo que um grupo (GS) passou por um treino simétrico (mesma quantidade de sessões) entre as duas habilidades, com critérios de aprendizagem elevados para ambas. O outro grupo (GA) passou por um treino assimétrico, no qual uma habilidade, a de encaixe, foi treinada em poucas sessões e com um baixo critério de aprendizagem. Neste grupo a habilidade de pescar teve um treino extenso, com um número de sessões de treino pelo menos duas vezes maior do que o treino da habilidade de encaixe, e um critério elevado de aprendizagem. Ao final, todos os sujeitos foram colocados frente a uma situação problema: uma caixa contendo comida fora de seu alcance, e duas ferramentas disponíveis, das quais nenhuma sozinha alcançava a caixa. Nesta situação a solução dependia da recombinação dos dois repertórios ensinados separadamente, encaixar e pescar. Apenas o terceiro participante do grupo assimétrico não resolveu a tarefa. Todos os demais participantes resolveram a tarefa consistentemente, apresentando topografias de resolução do problema de acordo com o seu treino, apontando que variáveis de quantidade de treino influenciam na forma e eficácia da resolução da tarefa.

Improving Student Engagement and Verbal Behavior Through Cooperative Learning

In this action research study of my classroom of 10th grade Algebra II students, I investigated three related areas. First, I looked at how heterogeneous cooperative groups, where students in the group are responsible to present material, increase the number of students on task and the time on task when compared to individual practice. I noticed that their time on task might have been about the same, but they were communicating with each other mathematically. The second area I examined was the effect heterogeneous cooperative groups had on the teacher’s and the students’ verbal and nonverbal problem solving skills and understanding when compared to individual practice. At the end of the action research, students were questioning each other, and the instructor was answering questions only when the entire group had a question. The third area of data collection focused on what effect heterogeneous cooperative groups had on students’ listening skills when compared to individual practice. In the research I implemented individual quizzes and individual presentations. Both of these had a positive effect on listing in the groups. As a result of this research, I plan to continue implementing the round robin style of in- class practice with heterogeneous grouping and randomly selected individual presentations. For individual accountability I will continue the practice of individual quizzes one to two times a week.

Improving Student Engagement and Verbal Behavior Through Cooperative Learning

In this action research study of my classroom of 10th grade Algebra II students, I investigated three related areas. First, I looked at how heterogeneous cooperative groups, where students in the group are responsible to present material, increase the number of students on task and the time on task when compared to individual practice. I noticed that their time on task might have been about the same, but they were communicating with each other mathematically. The second area I examined was the effect heterogeneous cooperative groups had on the teacher’s and the students’ verbal and nonverbal problem solving skills and understanding when compared to individual practice. At the end of the action research, students were questioning each other, and the instructor was answering questions only when the entire group had a question. The third area of data collection focused on what effect heterogeneous cooperative groups had on students’ listening skills when compared to individual practice. In the research I implemented individual quizzes and individual presentations. Both of these had a positive effect on listing in the groups. As a result of this research, I plan to continue implementing the round robin style of in- class practice with heterogeneous grouping and randomly selected individual presentations. For individual accountability I will continue the practice of individual quizzes one to two times a week.