Projeto e controle de um sistema de aquecimento no Laboratório de Avaliação de Medição em Petróleo

The Oil Measurement Evaluation Laboratory (LAMP), located in the Federal University of Rio Grande do Norte (UFRN), has as main goal to evaluate flow and BS&W meters, where the simulation of a bigger number of operation variable in field, guarantees a less uncertain evaluation. The objective of this work is to purpose a heating system design and implementation, which will control the temperature safely and efficiently in order to evaluate and measure it. Temperature is one of the variables which influence the flow and BS&W accurate measurement, directly affecting the fluid viscosity and density in the experiment. To project the heating system it is of great importance to take the laboratory requirements, conditions and current restrictions into consideration. Three alternatives were evaluated: heat exchanger, internal resistance and external resistance. After the analyses are made in order to choose the best alternative for the heating system in the laboratory, control strategies were determined for it, PID control methods in combination with fuzzy logic were used. Results showed a better performance with fuzzy logic than with classic PID

Distribuição da carga hidráulica em linhas de derivação otimizadas por programação linear

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A method for plotting the complementary root locus using the root-locus (positive gain) rules

The root-locus method is a well-known and commonly used tool in control system analysis and design. It is an important topic in introductory undergraduate engineering control disciplines. Although complementary root locus (plant with negative gain) is not as common as root locus (plant with positive gain) and in many introductory textbooks for control systems is not presented, it has been shown a valuable tool in control system design. This paper shows that complementary root locus can be plotted using only the well-known construction rules to plot root locus. It can offer for the students a better comprehension on this subject. These results present a procedure to avoid problems that appear in root-locus plots for plants with the same number of poles and zeros.

Garantia literária: elementos para uma revisão crítica após um século

This study contributes to a critical synthesis of the principle of literary warrant, initially formulated by Hulme in 1911. Hulme proposed that the terms of a classification system should be derived from the literature to be classified, rather than based on purely theoretical considerations. Founding literary warrant on literature which is actually documented rather than on scientific or philosophical classifications or on the supposed authority of the first classificationists implied a clear departure from the conceptions of Harris and Dewey, who had used the classifications of Bacon and Leibniz as models. The validity of this principle over the past century is studied by means of diverse documental data (entries in dictionaries, retrieval by Google, etc.), as it is recognized as a main methodological element for classification standards and systems. This study also discusses the situation with respect to the top-down or bottom-up methodologies of system design. Three traditional applications of literary warrant are described as well as three new applications are suggested, in light of its methodological potential. It is possible to conclude that this principle will find increasing applications in other contexts, within and beyond Information Science.

Sistema especialista fuzzy para dimensionamento de bombeio mecânico

Despite the emergence of other forms of artificial lift, sucker rod pumping systems remains hegemonic because of its flexibility of operation and lower investment cost compared to other lifting techniques developed. A successful rod pumping sizing necessarily passes through the supply of estimated flow and the controlled wear of pumping equipment used in the mounted configuration. However, the mediation of these elements is particularly challenging, especially for most designers dealing with this work, which still lack the experience needed to get good projects pumping in time. Even with the existence of various computer applications on the market in order to facilitate this task, they must face a grueling process of trial and error until you get the most appropriate combination of equipment for installation in the well. This thesis proposes the creation of an expert system in the design of sucker rod pumping systems. Its mission is to guide a petroleum engineer in the task of selecting a range of equipment appropriate to the context provided by the characteristics of the oil that will be raised to the surface. Features such as the level of gas separation, presence of corrosive elements, possibility of production of sand and waxing are taken into account in selecting the pumping unit, sucker-rod strings and subsurface pump and their operation mode. It is able to approximate the inferente process in the way of human reasoning, which leads to results closer to those obtained by a specialist. For this, their production rules were based on the theory of fuzzy sets, able to model vague concepts typically present in human reasoning. The calculations of operating parameters of the pumping system are made by the API RP 11L method. Based on information input, the system is able to return to the user a set of pumping configurations that meet a given design flow, but without subjecting the selected equipment to an effort beyond that which can bear

Spectrophotometric flow-injection determination of sulphite in white wines involving gas diffusion through a concentric tubular membrane

A flow-injection system is proposed for the spectrophotometric determination of sulphite in white wines. The method involves analyte conversion to SO2, gas diffusion through a Teflon® semi-permeable membrane, collection into an alkaline stream (pH 8), reaction with Malachite green (MG) and monitoring at 620 nm. With a concentric tubular membrane, the system design was simplified. Influence of reagent concentrations, pH of donor and acceptor streams, temperature, timing, surfactant addition and presence of potential interfering species of the wine matrix were investigated. A pronounced (ca. 100%) enhancement in sensitivity was noted by adding cetylpyridinium chloride (CPC). The proposed system is robust and baseline drift is not observed during 4 h operating periods. Only 400 μL of sample and 0.32 mg MG are required per determination. The system handles 30 samples per hour, yielding precise results (r.s.d. < 0.015 for 1.0 - 20.0 mg L-1 SO2) in agreement with those obtained by an alternative procedure.

A multisampling time-domain CMOS imager with synchronous readout circuit

A novel multisampling time-domain architecture for CMOS imagers with synchronous readout and wide dynamic range is proposed. The architecture was implemented in a prototype of imager with 32x32 pixel array fabricated in AMS CMOS 0.35νm and was characterized for sensitivity and color response. The pixel is composed of an n+/psub photodiode, a comparator and a D flip-flop having 16% fill-factor and 30νmx26νm dimensions. The multisampling architecture requires only a 1 bit per pixel memory instead of 8 bits which is typical for time-domain active pixel architectures. The advantage is that the number of transistors in the pixel is low, saving area and providing higher fill-factor. The maximum frame rate is analyzed as a function of number of bits and array size. The analysis shows that it is possible to achieve high frame rates and operation in video mode with 10 bits. Also, we present analysis for the impact of comparator offset voltage in the fixed pattern noise. Copyright 2007 ACM.

Radial basis function network applied to the linearization of a voltage controlled oscillator

An analog circuit that implements a radial basis function network is presented. The proposed circuit allows the adjustment of all shape parameters of the radial functions, i.e., amplitude, center and width. The implemented network was applied to the linearization of a nonlinear circuit, a voltage controlled oscillator (VCO). This application can be classified as an open-loop control in which the network plays the role of the controller. Experimental results have proved the linearization capability of the proposed circuit. Its performance can be improved by using a network with more basis functions. Copyright 2007 ACM.

Dynamics of a piecewise-linear oscillator with limited power supply

We discuss dynamics of a vibro-impact system consisting of a cart with an piecewise-linear restoring force, which vibrates under driving by a source with limited power supply. From the point of view of dynamical systems, vibro-impact systems exhibit a rich variety of phenomena, particularly chaotic motion. In our analyzes, we use bifurcation diagrams, basins of attractions, identifying several non-linear phenomena, such as chaotic regimes, crises, intermittent mechanisms, and coexistence of attractors with complex basins of attraction. © 2009 by ASME.

Modelo AC para el despacho combinado de contratos bilaterales y bolsa de energía considerando restricciones de seguridad

Reliability is a key aspect in power system design and planning. Maintaining a reliable power system is a very important issue for their design and operation. Under the new competitive framework of the electricity sector, power systems find ever more and more strained to operate near their limits. Under this new scenario, it is crucial for the system operator to use tools that facilitate an energy dispatch that minimizes possible power cuts. This paper presents a mathematical model to calculate an energy dispatch that considers security constraints (single contingencies in transmission lines and transformers). The model involves pool markets and fixed bilateral contracts. Traditional methodologies that include security constraints are usually based in multistage dispatch processes. In this case, we propose a single-stage model that avoids the economic inefficiencies which result when conventional multi-stage dispatch approaches are applied. The proposed model includes an AC representation of the transport system and allows calculating the cost overruns incurred in due to reliability restrictions. We found that complying with fixed bilateral contracts, when they go above certain levels, might lead to congestion problems in transmission lines.

O uso de dois websites de compras on-line por usuários acima de 50 anos (older users): estudo de caso

Pós-graduação em Design - FAAC

Comparação econômica entre critérios de dimensionamento de sistemas de irrigação por microaspersão utilizando modelos de programação linear

Pós-graduação em Agronomia (Irrigação e Drenagem) - FCA

Modelo para análise de negociação em projetos de sistemas em uma fábrica de software baseado em pontos de caso de uso.

A Modelagem de Sistemas vêm sendo cada vez mais aplicada nos meios de produção para as mais diversas finalidades, incluindo a área de Projeto de Sistemas, com o intuito de definir o número de pessoas na equipe, analisar o esforço, o tamanho do software e os custos totais do projeto. Este trabalho tem por finalidade desenvolver um modelo de apoio à análise baseado em Pontos de Caso de Uso (PCU). Para isso, utiliza-se de vários métodos de pesquisa entre elas a pesquisa exploratória e de laboratório para criar um modelo de apoio para a análise.

Avaliação da utilização de sistemas de alagados construídos como sistema de tratamento terciário de efluentes e para geração de biomassa da cultura de taboa (Typha sp)

Pós-graduação em Ciência Florestal - FCA

ESTUDO DA DISTRIBUIÇÃO DA EVAPOTRANSPIRAÇÃO DE REFERÊNCIA VISANDO O DIMENSIONAMENTO DE SISTEMAS DE IRRIGAÇÃO

Visando caracterizar a distribuição de freqüência da evapotranspiração de referência na região de Piracicaba, SP, e avaliar as práticas usuais de estimativa da necessidade de água para fins de dimensionamento de sistemas de irrigação, foram utilizados 30 anos de dados de evapotranspiração do mês de setembro, que foi dividido em períodos de 5, 10, 15 e 30 dias. As distribuições Beta e Normal foram aplicadas aos dados e ambas mostraram-se aptas para representá-los. Para valores de probabilidade de ocorrência iguais ou superiores a 60%, verificou-se o aumento do valor da evapotranspiração de referência com a diminuição do período. Adotando como parâmetros o período de máxima exigência hídrica de 2 a 3 semanas e a evapotranspiração de referência ao nível de 75% de probabilidade, verificou-se que o uso do valor médio mensal da evapotranspiração no dimensionamento de sistemas de irrigação conduz ao subdimensionamento, enquanto a adoção do máximo valor diário da evapotranspiração acarreta o superdimensionamento.