Numerical simulation of a radial diffuser turbulent airflow

In the present work are presented results from numerical simulations performed with the ANSYS-CFX (R) code. We have studied a radial diffuser flow case, which is the main academic problem used to study the flow behavior on flat plate valves. The radial flow inside the diffuser has important behavior such as the turbulence decay downstream and recirculation regions inside the valve flow channel due to boundary layer detachment. These flow structures are present in compressor reed valve configurations, influencing to a greater extent the compressor efficiency. The main target of the present paper was finding the simulation set-up (computational domain, boundary conditions and turbulence model) that better fits with experimental data published by Tabatabai and Pollard. The local flow turbulence and velocity profiles were investigated using four different turbulence models, two different boundary conditions set-up, two different computational domains and three different flow conditions (Re-in - Reynolds number at the diffuser inlet). We used the Reynolds stress (BSL); the k-epsilon; the RNG k-epsilon; and the shear stress transport (SST) k-omega turbulence models. The performed analysis and comparison of the computational results with experimental data show that the choice of the turbulence model, as well as the choice of the other computational conditions, plays an important role in the results physical quality and accuracy. (c) 2007 Elsevier B.V. All rights reserved.

Blocking Radial Diffusion in a Double-Waved Hamiltonian Model

A non-twist Hamiltonian system perturbed by two waves with particular wave numbers can present Robust Tori, barriers created by the vanishing of the perturbing Hamiltonian at some defined positions. When Robust Tori exist, any trajectory in phase space passing close to them is blocked by emergent invariant curves that prevent the chaotic transport. We analyze the breaking up of the RT as well the transport dependence on the wave numbers and on the wave amplitudes. Moreover, we report the chaotic web formation in the phase space and how this pattern influences the transport.

Introduction to Focus Issue: Statistical mechanics and billiard-type dynamical systems

Dynamical systems of the billiard type are of fundamental importance for the description of numerous phenomena observed in many different fields of research, including statistical mechanics, Hamiltonian dynamics, nonlinear physics, and many others. This Focus Issue presents the recent progress in this area with contributions from the mathematical as well as physical stand point. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4730155]

SECAGEM DE SEMENTES DE SOJA em SILO COM DISTRIBUI����O RADIAL do FLUXO DE AR: I. MONITORAMENTO F��SICO

O trabalho foi desenvolvido com o objetivo de avaliar a evolu����o f��sica do processo de remo����o de ��gua das sementes em secador estacion��rio, com cilindro central perfurado e distribui����o radical de ar. A pesquisa foi conduzida com sementes de soja, variando o fluxo (26,9, 28,4 e 33,2 m��/minuto/t) e a temperatura do ar insuflado (42, 46 e 50��C), considerando a posi����o das sementes (17, 34 e 51 cm em rela����o ao cilindro de insufla����o) e o tempo de secagem (zero a doze horas, com intervalos de duas horas). Foram caracterizados o ar ambiente, o ar insuflado, as temperaturas e os teores de ��gua da massa, as velocidades e curvas de secagem. As avalia����es realizadas destacaram vantagens f��sicas operacionais da combina����o de 28,4 m��/minuto/t com 46��C e o contr��rio, com a combina����o de 26,9 m��/minuto/t com 42��C.

SECAGEM DE SEMENTES DE SOJA em SILO COM DISTRIBUI����O RADIAL do FLUXO DE AR: II. EFEITOS SOBRE A QUALIDADE DAS SEMENTES

O trabalho avaliou, em sementes de soja, as conseq����ncias qualitativas provenientes da secagem estacion��ria com distribui����o radial de ar, variando o fluxo (26,9, 28,4 e 33,2 m��/minuto/t) e a temperatura do ar insuflado (42, 46 e 50��C), considerando a posi����o das sementes na massa (17, 34 e 51 cm em rela����o ao cilindro de insufla����o) e o tempo de secagem (0 a 12 horas, com intervalos de quatro horas). Para tanto, al��m das determina����es das temperaturas e dos teores de ��gua da massa, foi avaliado o desempenho fisiol��gico das sementes no in��cio e ao final de seis meses de armazenamento. Apesar das vantagens f��sicas operacionais resultantes da combina����o entre o fluxo e a temperatura intermedi��rios (28,4 m��/minuto/t e 46��C), a qualidade fisiol��gica foi menos prejudicada nas combina����es dos menores fluxos (26,9 e 28,4 m��/minuto/t) com a maior temperatura (50��C) e do maior fluxo (33,2 m��/minuto/t) com as menores temperaturas (42 e 46��C); entre estas, levando em conta os aspectos f��sico-operacionais, a associa����o de 28,4 m��/minuto/t com 50��C foi a mais eficiente na retirada de ��gua das sementes. Assim, admitindo os intervalos de fluxo (26,9 a 33,2 m��/minuto/t) e de temperatura (42 a 50��C) estudados, conclui-se que a eleva����o na temperatura demanda redu����o no fluxo e, inversamente, o aumento no fluxo demanda redu����o na temperatura.

Determina����o da velocidade de condu����o nervosa motora dos nervos radial e ulnar de c��es clinicamente sadios

O presente trabalho teve como objetivo a padroniza����o dos valores de refer��ncia de velocidade de condu����o nervosa motora dos nervos radial e ulnar em c��es clinicamente sadios. Para tanto, foram utilizados 30 c��es, 11 machos e 19 f��meas, sem ra��a definida, com idade entre dois e seis anos. Os valores m��dios das medidas do potencial muscular produzidos por meio de estimula����o proximal e distal do nervo radial foram, respectivamente: lat��ncia inicial, 2,46+0,72ms e 1,58+0,62ms, amplitude de pico a pico, 8,79+2,26mV e 9,52+2,42mV e dura����o, 2,85+0,76ms e 2,71+0,75ms. Os respectivos valores do nervo ulnar foram: lat��ncia inicial, 4,17+0,53ms e 2,67+0,38ms; amplitude de pico a pico, 10,72+2,60mV e 11,72+2,81mV e dura����o, 2,23+0,38ms e 2,04+0,35ms. Os valores m��dios das medidas de velocidade de condu����o nervosa motora dos nervos radial e ulnar foram, respectivamente, 66,18+7,26m/s e 60,50+7,86m/s.

Aprendizado n��o-supervisionado em redes neurais pulsadas de base radial: um estudo da capacidade de agrupamento para a classifica����o de pixels

Redes neurais pulsadas - redes que utilizam uma codifica����o temporal da informa����o - t��m despontado como uma promissora abordagem dentro do paradigma conexionista, emergente da ci��ncia cognitiva. Um desses novos modelos �� a rede neural pulsada com fun����o de base radial, que �� capaz de armazenar informa����o nos tempos de atraso axonais dos neur��nios. Um algoritmo de aprendizado foi aplicado com sucesso nesta rede pulsada, que se mostrou capaz de mapear uma seq����ncia de pulsos de entrada em uma seq����ncia de pulsos de sa��da. Mais recentemente, um m��todo baseado no uso de campos receptivos gaussianos foi proposto para codificar dados constantes em uma seq����ncia de pulsos temporais. Este m��todo tornou poss��vel a essa rede lidar com dados computacionais. O processo de aprendizado desta nova rede n��o se encontra plenamente compreendido e investiga����es mais profundas s��o necess��rias para situar este modelo dentro do contexto do aprendizado de m��quinas e tamb��m para estabelecer as habilidades e limita����es desta rede. Este trabalho apresenta uma investiga����o desse novo classificador e um estudo de sua capacidade de agrupar dados em tr��s dimens��es, particularmente procurando estabelecer seus dom��nios de aplica����o e horizontes no campo da vis��o computacional.

Radiographic study of distal radial physeal closure in thoroughbred horses

Monthly radiography was performed to study distal radial physeal closure in ten male and ten female Throughbred horses. The height, thoracic circumference and metacarpus circumference were also measured, Distal radial physeal closure time was sooner in females than males, and took 701 +/- 37 and 748 +/- 55 days respectively.

TRICUT: a program to clip triangle meshes using the rapid and triangle libraries and the visualization toolkit

An efficient technique to cut polygonal meshes as a step in the geometric modeling of topographic and geological data has been developed. In boundary represented models of outcropping strata and faulted horizons polygonal meshes often intersect each other. TRICUT determines the line of intersection and re-triangulates the area of contact. Along this line the mesh is split in two or more parts which can be selected for removal. The user interaction takes place in the 3D-model space. The intersection, selection and removal are under graphic control. The visualization of outcropping geological structures in digital terrain models is improved by determining intersections against a slightly shifted terrain model. Thus, the outcrop line becomes a surface which overlaps the terrain in its initial position. The area of this overlapping surface changes with respect to the strike and dip of the structure, the morphology and the offset. Some applications of TRICUT on different real datasets are shown. TRICUT is implemented in C+ + using the Visualization Toolkit in conjunction with the RAPID and TRIANGLE libraries. The program runs under LINUX and UNIX using the MESA OpenGL library. This work gives an example of solving a complex 3D geometric problem by integrating available robust public domain software. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

Optimal capacitor placement in radial distribution networks

The capacitor placement (replacement) problem for radial distribution networks determines capacitor types, sizes, locations and control schemes. Optimal capacitor placement is a hard combinatorial problem that can be formulated as a mixed integer nonlinear program. Since this is a NP complete problem (Non Polynomial time) the solution approach uses a combinatorial search algorithm. The paper proposes a hybrid method drawn upon the Tabu Search approach, extended with features taken from other combinatorial approaches such as genetic algorithms and simulated annealing, and from practical heuristic approaches. The proposed method has been tested in a range of networks available in the literature with superior results regarding both quality and cost of solutions.

Coordinated views to assist exploration of spatio-temporal data: a case study

In this paper we focus on providing coordinated visual strategies to assist users in performing tasks driven by the presence of temporal and spatial attributes. We introduce temporal visualization techniques targeted at such tasks, and illustrate their use with an application involving a climate classification process. The climate classification requires extensive Processing of a database containing daily rain precipitation values collected along over fifty years at several spatial locations in the S��o Paulo state, Brazil. We identify user exploration tasks typically conducted as part of the data preparation required in this process, and then describe how such tasks may be assisted by the multiple visual techniques provided. Issues related to the use of the multiple techniques by an end-user are also discussed.

Does spatial visualization ability improve after studying technical drawing?

Two studies were carried out to analyze whether learning technical drawing improves a person's ability for spatial visualization. Visualization and inductive reasoning tests were applied at the beginning and end of a course in technical drawing in samples of first year engineering students. In both studies it was observed that a moderate percentage of students improved their Visualization test execution. The improvement was similar in men and women. There was no improvement on the inductive reasoning test. The results support the conclusion that the spatial visualization ability can be improved with training.

Tensor3D: A computer graphics program to simulate 3D real-time deformation and visualization of geometric bodies

Tensor3D is a geometric modeling program with the capacity to simulate and visualize in real-time the deformation, specified through a tensor matrix and applied to triangulated models representing geological bodies. 3D visualization allows the study of deformational processes that are traditionally conducted in 2D, such as simple and pure shears. Besides geometric objects that are immediately available in the program window, the program can read other models from disk, thus being able to import objects created with different open-source or proprietary programs. A strain ellipsoid and a bounding box are simultaneously shown and instantly deformed with the main object. The principal axes of strain are visualized as well to provide graphical information about the orientation of the tensor's normal components. The deformed models can also be saved, retrieved later and deformed again, in order to study different steps of progressive strain, or to make this data available to other programs. The shape of stress ellipsoids and the corresponding Mohr circles defined by any stress tensor can also be represented. The application was written using the Visualization ToolKit, a powerful scientific visualization library in the public domain. This development choice, allied to the use of the Tcl/Tk programming language, which is independent on the host computational platform, makes the program a useful tool for the study of geometric deformations directly in three dimensions in teaching as well as research activities. (C) 2007 Elsevier Ltd. All rights reserved.

Optimization of Radial Basis Function neural network employed for prediction of surface roughness in hard turning process using Taguchi's orthogonal arrays

Conselho Nacional de Desenvolvimento Cient��fico e Tecnol��gico (CNPq)

Performance of low/correct pressure radial ply tires

Extensive field testes were conducted using the UCD single wheel tester employing three large radial ply tractor tires in two different soils, four different soil conditions, two axle load levels, and three levels of tire inflation pressures in order to quantify the benefits of using low/correct inflation pressures. During these tests slip, net traction, gross traction, and dynamic axle load were recorded. Furthermore, soil moisture content, cone index, and dry bulk density data were obtained at test locations. The results of the analysis showed a significant increase in net traction and traction efficiency when low/correct inflation was used. Benefits of using low/correct pressure was higher in tilled soil conditions.