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The cellular particle swarm optimization algorithm
Get PDFThis work presents a variant of the Particle Swarm Optimization (PSO) original algorithm, the Cellular-PSO.
Inspired by the cellular Genetic Algorithm (GA), particles in Cellular-PSO are arranged into a matrix of cells
interconnected according to a given topology. Such topology defines particle’s neighborhood, inside which
social adaptation may occur. As a consequence, population diversity is increased and the optimization process becomes more efficient and robust. The proposed Cellular-PSO has been applied to the nuclear reactor core design optimization problem and comparative experiments demonstrated that it is superior to the standard PSO
A potencialidade de ferramentas interativas de comunicação disponíveis em ambientes virtuais de aprendizagem para a avaliação formativa
Get PDFAs novas tecnologias da informação e comunicação, por sua influência radical em diferentes dimensões da sociedade, estabelecem um novo paradigma sociocultural. Esse fato tem alterado significativamente as práticas educativas, principalmente por colocar em xeque as concepções de aprendizagem e o novo papel dos sujeitos envolvidos nesse processo. Os ambientes virtuais de aprendizagem (AVA) surgem, então, como realidade emergente no novo contexto da Educação On-line, enquanto espaço de interação e de construção coletiva do conhecimento. Entende-se também que esse novo cenário educacional passa a demandar uma discussão crítica sobre conceitos e práticas pedagógicas que possam responder às necessidades de alunos e professores que atuam nessa modalidade de ensino. Nesse sentido, o objetivo aqui é situar a função pedagógica das ferramentas interativas de comunicação presentes nos AVA (diário de bordo, Chat, fórum de discussão, portfólio e correio eletrônico) e descrever de que forma elas podem favorecer o acompanhamento e a orientação dos alunos na construção social de novos significados a partir de uma proposta de avaliação formativa. Trata-se, portanto, de refletir sobre a qualidade e a eficácia da aprendizagem através da problematização desse novo campo de ação, para que se possa pensar na Educação On-line como uma modalidade educativa realmente preocupada com o pedagógico do “mundo virtual”
Modificação no método do Thorin para determinação quantitativa rápida de tório em minérios brasileiros
Get PDFThe minerals controlled by CNEN have in its composition, moreover than uranium and thorium, other elements, as rare earths, bismuth, tantalum, niobium and iron. Most of these elements are a great obstacle to the analytical quantitative determination of Thorium, when modern and non-destructive techniques as Energy Dispersive X Ray Fluorescence – EDXRF, cannot be used. The present work is successful in satisfying all the CNEN parameters, and executing the job in a secure and optimized way. Through the planned and studied modifications, executed in well-know and consecrated analytical methods we hit the objective to reduce the total time of the analysis process to 3 hours. The new procedure is also versatile: it can be used in all the brazilian minerals which is responsibility to CNEN such as: ilmenite, anatase, columbite, tantalite, caldasite, zirconite, thorianite, monazite and pirochlorine with the same accurate and fast results although they have diverse chemical compositions. The foremost, modifications included in the process was the fusion with ammonium and potassium bifluorides, promoting the quantitative precipitation of thorium and allowing it's separation from uranium. So, the slowly step of precipitation with oxalate used in former processes can be eliminated. The results of the separation can be confirmed by FRX analysis. After, the thorium is separated from the rare-earth using mesytilium oxide. The thorium quantifying can be done just after, by epectrophotometry in 545 nm using thorin in a 0,24 mol L-1 HCl medium. The methodology developed and presented in this writing was compared with the classic method using the statistical test of the t pair used in the determination of Th in certified material of reference (monazite), not having been found difference between the two methodologies. The new methodology also was applied to some ores with values of concentration of Th certified presenting compatible agreement enters the results for a reliable level of 95%.Os minérios controlados pela Comissão Nacional de Energia Nuclear - CNEN possuem em sua composição, além do urânio e do tório, outros elementos como terras raras, zircônio, bismuto, tântalo, nióbio e ferro. Muitos desses elementos representam um grande obstáculo à determinação analítica quantitativa do tório, especialmente quando não se pode recorrer a técnicas mais sofisticadas e não destrutivas, como a Fluorescência de Raios X por Energia Dispersiva - EDXRF. Neste trabalho, através de alterações planejadas, estudadas e executadas tendo como base o método analítico do thorin, já consagrado para determinação quantitativa do tório, atingiu-se o objetivo de reduzir para cerca de 3 horas o tempo total de análise. O novo procedimento desenvolvido tem também a vantagem de ser versátil, pois, como ficou evidenciado, foi aplicado em minérios brasileiros sob a fiscalização da CNEN tais como: ilmenita, anatásio, tantalita columbita, caldasito zirconita, torianita, monazita, pirocloro com excelentes resultados, apesar de todos eles possuírem composições químicas bem diferentes. As principais características introduzidas no método foram a abertura do minério e a precipitação do tório. A abertura dos minérios por fusão com misturas de bifluoretos de amônia e potássio promove ao mesmo tempo a precipitação quantitativa do tório como fluoreto insolúvel, permitindo dessa forma a sua separação do urânio, assim, a longa etapa de precipitação com oxalato, usada em métodos mais antigos, torna-se desnecessária. Os resultados dessa separação são confirmados por análises qualitativa e quantitativa por FRX. Em continuidade, o tório é totalmente separado das terras raras por extração com óxido de mesitilo e determinado, em seguida por espectrofotometria em 545 nm com thorin em meio de HCl 0,24 mol L-1. A metodologia desenvolvida e apresentada nesta dissertação foi comparada ao método clássico utilizando-se o teste estatístico do t emparelhado na determinação de Th em material de referência certificado (monazita), não tendo sido encontrada diferença entre as duas metodologias. A nova metodologia foi também aplicada a vários minérios com valores de concentração de Th certificados, apresentando concordância compatível entre os resultados para um nível de confiança de 95%
A new software to increase ultrasound signals resolution for internal stresses measurements in metallic materials
No full textThe phenomenon of ultrasonic velocity change has been successfully used for the verification of internal
stresses in metallic materials at IEN during last years. It is possible to know the ultrasonic velocity change by
the measurement of the time elapsed between echoes of ultrasonic signals. Since the ultrasonic time of flight
changes on the nanosecond order, it is requested high resolution to the assessment of internal stresses. A
method for the measurement of this time using ultrasonic signal processing techniques was developed and
tested. The method uses cross correlation and multirate techniques to increase the measure resolution. This
paper describes the software developed to improve the application of this method. The software, developed in
C++ and Labview, processes the ultrasonic signal with high resolution and performs this task in few milliseconds, allowing the development of portable equipment to assess internal stresses in metallic materials
in the field, with direct time of flight measurement. The software developed was implemented in two portable
data acquisition systems in use at IEN laboratories and can be adapted for different types of data acquisition
systems with few modifications
Acessment of intermittent two-phase flow using a high-speed visualization technique
No full textThe intermittent two-phase horizontal flow is recognized by many authors to be one of the most highly complex inherently unsteady flow pattern. Great efforts have been made in recent years to develop theoretical models to predict the intermittent flow interfacial parameters. However, as far as the flow structure itself is concerned, these models are not capable to predicting them yet. The liquid slug and gas bubble velocity, length and evolution along the flow are examples of structural parameters that require experimental specialized work to their evaluation. In this paper, we describe the application of a visualization technique to assess the intermittent two-phase air-water horizontal flow. The technique consists in employing a high-speed digital camera to take a series of pictures of the bubbles moving in the upper side of a horizontal pipe, where a gas-liquid mixture flows. From the images obtained the bubbles can be tracked along. Analyzing frame by frame it is possible to extract the gas bubbles lengths and velocities. This investigation in restricted to liquid superficial velocities ranging from 0.3 to 2.0 m/s and to gas superficial velocities ranging from 0.0 to 1.6 m/s
A strategy to reuse the radioactive sources storage at radioactive waste depositories
No full textUntil now, all the Brazilian’s Radioactives Wastes depositories were only able to insurance the care of
radioactives sources that were useless. To do that, a management policy is applied that recommend the waste
treatment trying to reduce it’s size, if it is possible, so that waste can be storage inside the depository. However,
what we are seeing in the last few years, even in the field of industries as much as in the field of medicine is an
increase of the radioactive materials´ use. So one can understand that the waste collection is increasing at the
same proportion, forcing the institutions that have Radioactive Waste depositories build new facilities, biggers
than the old ones. Most of the time, when those facilities are completed, their capabilities are restricted. At that
moment is easy to see the need of a new strategy that has to be included in the management policy that
encourage the radioactive source reuse, minimizing the increase waste collection effects. This paper describes
one kind of strategy that can be use to recycling those materials. Although it seems to be simple, it’s really a hard work process because it has to create a new routine and some times a different philosophy even among the workers and researchers in the nuclear field. But everyone can understand the importance of that new strategy because it’s straight related with the extension of the radioactive material useful life and the reduction of the time that it can spend at the depository
Contrast enhancement of tomographic images by fast fourier transform filtering
No full textComputer aided tomographic images are intrinsically affected by statistical fluctuation which degrades the
contrast, spoiling thus the density resolution, a phenomenon which precludes the differentiation between
neighbour regions of close densities. As this fluctuation involves frequencies usually high, when compared with
those associated to the inner structure of the object under inspection, a proper filtering using a kind of low-pass
filter can mitigate the problem, improving hence the density resolution. In this work, the Fast Fourier Transform
– FFT has been applied to filter high frequency components of position spectra, used as projections to
reconstruct 2D neutron tomographic images. These spectra, produced by a Position Sensitive Detector - PSD
and by a simulator, have been filtered at different frequency cut-off, in order to evaluate its impact on the quality
of the recovered images. Virtual images of a special test-object, generated by the simulator, have been used as
benchmark, to assess the capability and effectiveness of the filtering procedure. These features have been
corroborated by the contrast enhancement achieved for real images of different objects acquired with a neutron
tomographic system equipped with a PSD. The algorithm developed to perform both simulation and filtering has been written in Fortran language
Preparation of Excitation Sources to Portable X-Ray Spectrometer by Recovering 241am from Radioactive Lightning Conductor
No full textWith the prohibition of the use of radioactive lightning conductor in Brazil, this material passed to be collected
and stored as radioactive waste in the waste deposits of The Brazilian National Nuclear Energy Commission
(CNEN). The majority of these lightning conductor used as radioactive source 241Am with activity varying of 1 the 5 mCi. In this work are presented preliminary studies by recovering of 241Am through the electroplating technique, in order to posterior use as sources to portable X-rays fluorescence spectrometer. The 241Am sources have been removed from lightning conductor and dissolved in acid solution. The solution presented an activity of 0,6 Ci L-1. Small amounts of this solution were added to some electrolytes and tested in order to evaluate optimum electrolyte for deposition of 241Am. It was studied as electrolytes: HNO3 (0,2 mol L-1), NH4Cl (5,0 mol L-1) and a mixture of KCN and K2CO3 (in the rate of 2,0 g of each per liter). Yields of up to 90% were obtained applied a current density of 50 mA cm-2
Radionuclide Migration: A Numerical Study
Get PDFCrystalline rock has been considered as a potentially suitable matrix for high-level radioactive waste (HLW)
repository because it is found in very stable geological formations and may have very low permeability. A
common problem encountered in this context is the modeling of migration of radio nuclides in a fractured
medium. Generally, this consists of a large main fracture, which is surrounded by a rock matrix. Transport in the main fracture is usually assumed to obey an advection-dispersion relation, while molecular diffusion is the
assumed dominant mechanism of transport in the porous rock. In this work, a numerical study of the governing partial differential equations is done, to describe radionuclide movement in the fracture and within the rock matrix. The adopted physical system consists of the rock matrix containing a single planar fracture situated in water saturated porous rock. The initial radionuclide concentrations are assumed to be zero in both fractured and rock matrices. As inlet boundary condition, a kinetic solubility-limited dissolution model is used, in order to calculate the radionuclide concentration in the fracture. The solution of the governing partial differential equations was obtained by finite difference methods, namely: fully explicit, fully implicit and Crank-Nicolson discretization schemes. Note that the influence of the advective term was considered in the partial differential equation in the fracture, in such discretization schemes. It was shown that all numerical schemes are consistent and that the explicit method, in all configurations of the advective term, and the implicit methods and Crank-Nicolson, for the forward discretization in the advective term, presented stability conditions to be considered