Proposal of a Transmission Line Model Based on Lumped Elements: An Analytic Solution

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Esquemas alternativos para o passo de parametrização do método da continuação baseados em parâmetros físicos

O método de fluxo de carga convencional é considerado inadequado para se obter o ponto de máximo carregamento (PMC) de sistemas de potência, devido à singularidade da matriz Jacobiana neste ponto. Os métodos da continuação são ferramentas eficientes para a solução deste tipo de problema, visto que técnicas de parametrização podem ser utilizadas para evitar a singularidade da matriz Jacobiana. Neste trabalho, novas opções para a etapa de parametrização do método da continuação são apresentadas. Mostra-se que variáveis com claro significado físico podem ser utilizadas na etapa de parametrização. As seguintes variáveis foram testadas: perda total de potência ativa e reativa, potência ativa e reativa na barra de referência, potência reativa das barras de geração, e as perdas de potência ativa e reativa nas linhas de transmissão (LT). Além de facilitar a implementação computacional do método de continuação, as técnicas de parametrização apresentadas simplificam a definição matemática e o entendimento do método por parte de engenheiros de potência, visto que os métodos de continuação existentes na literatura sempre utilizam técnicas de parametrização complexas, e de interpretação puramente geométrica. Resultados obtidos com a nova metodologia para os sistemas testes do IEEE (14, 30, 57 e 118 barras) mostram que as características de convergência do método de fluxo de carga convencional são melhoradas na região do PMC. Além disso, durante o traçado das curvas PV, as diversas técnicas de parametrização podem ser comutadas entre si possibilitando o cálculo de todos os pontos da curva com um número reduzido de iterações. Diversos testes são realizados para proporcionar a comparação do desempenho dos esquemas de parametrização propostos.

Cultura de condrócitos em arcabouço tridimensional: hidrogel de alginato

OBJETIVOS: O presente estudo teve como objetivo cultivar condrócitos retirados da articulação do joelho de coelhos encapsulados em hidrogel de alginato (HA) e caracterizar a produção de matriz extracelular (ECM). MÉTODOS: A cartilagem articular foi removida do joelho de coelhos, com três a seis meses, fragmentada em pedaços de 1mm e submetida à digestão enzimática. Uma concentração de 1x106 céls/mL foram ressuspensas em uma solução de alginato de sódio a 1,5% (w/v), em seguida fez-se o processo de gelatinização em CaCl2 (102 mM), permitindo a formação do HA e cultivo em meio DMEM-F12 durante quatro semanas. A distribuição das células e a ECM foram acessadas através das secções histológicas coradas com e azul de toluidina hematoxilina e eosina (HE). RESULTADOS: Houve um aumento no número e na viabilidade dos condrócitos durante as quatro semanas de cultura. Através das análises histológicas dos HAs corados com azul de toluidina e HE foi possível observar a distribuição definida dos condrócitos no hidrogel, assemelhando-se a grupos isógenos e formação de matriz territorial. CONCLUSÃO: Este estudo demonstrou a eficiência do HA como arcabouço para ser usado na cultura de condrócitos, constituindo uma alternativa no reparo de lesões na cartilagem articular.

Study of alternative schemes for the parameterization step of the continuation power flow method based on physical parameters, part I: Mathematical modeling

The conventional power flow method is considered to be inadequate to obtain the maximum loading point because of the singularity of Jacobian matrix. Continuation methods are efficient tools for solving this kind of problem since different parameterization schemes can be used to avoid such ill-conditioning problems. This paper presents the details of new schemes for the parameterization step of the continuation power flow method. The new parameterization options are based on physical parameters, namely, the total power losses (real and reactive), the power at the slack bus (real or reactive), the reactive power at generation buses, and transmission line power losses (real and reactive). The simulation results obtained with the new approach for the IEEE test systems (14, 30, 57, and 118 buses) are presented and discussed in the companion paper. The results show that the characteristics of the conventional method are not only preserved but also improved.

Estudo da biodegradação de corantes azóicos por inóculo proveniente de biodigestor anaeróbio de alimentos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Desenvolvimento de métodos para determinação de sulfonamidas, dipirona e citrato de sildenafil em matrizes diversas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

SPECT (Single photon emission tomography): Gama câmara, reconstrução tomográfica e características funcional

The SPECT (Single Photon Emission Computed Tomography) systems are part of a medical image acquisition technology which has been outstanding, because the resultant images are functional images complementary to those that give anatomic information, such as X-Ray CT, presenting a high diagnostic value. These equipments acquire, in a non-invasive way, images from the interior of the human body through tomographic mapping of radioactive material administered to the patient. The SPECT systems are based on the Gamma Camera detection system, and one of them being set on a rotational gantry is enough to obtain the necessary data for a tomographic image. The images obtained from the SPECT system consist in a group of flat images that describe the radioactive distribution on the patient. The trans-axial cuts are obtained from the tomographic reconstruction techniques. There are analytic and iterative methods to obtain the tomographic reconstruction. The analytic methods are based on the Fourier Cut Theorem (FCT), while the iterative methods search for numeric solutions to solve the equations from the projections. Within the analytic methods, the filtered backprojection (FBP) method maybe is the simplest of all the tomographic reconstruction techniques. This paper's goal is to present the operation of the SPECT system, the Gamma Camera detection system, some tomographic reconstruction techniques and the requisites for the implementation of this system in a Nuclear Medicine service

A emergência do pluralismo teórico-metodológico na alfabetização: em busca de uma prática pedagógica para formar escritores

This qualitative research was performed with the goal of investigating the contributions of theoretical and methodological perspectives in the alphabetization process, aiming to train proficient writers of texts with communicative function. Hence, such were the goals established for this research: giving a retrospective look on the synthetic and analytic methods of teaching literacy; verifying the possibilities and limits of theoretical and methodological approaches of acquiring the ability to write and identifying the teachers’ ideas concerning basic concepts (such as literacy, text and textual genres) imbued in the teaching of writing; and establishing which activities they develop in the course of teaching whether the pedagogical practices of the teacher observed contributed to the formation of students who were capable of producing significant texts of diverse genres, suitable to the objectives, to the readers, and to the context of the circulation of texts. The research was done in a public elementary school, in a 2nd grade class of the city of Jaú. Subjects of the research were four teachers and twenty-eight children. For this work, two instruments were used for data collecting: a questionnaire and direct observation, registered in research diaries. Among the observations made were that, although there are many studies on literacy, the practices actually adopted in class are empirical in nature and do not contribute to the process of developing individual writing or reading skills at all; rather, it is only valued the ability of establishing relations between phonemes and graphemes; literacy teachers do not have adequate knowledge of concepts of literacy, teaching, text and textual genres, valuing only one methodological theory and disregarding other contributions on the field of text production

Ensino da leitura no método intuitivo: as palavras como unidade de compreensão e sentido

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Desenvolvimento de sistema de análise para valerato de estradiol baseado em polímeros biomiméticos

Abstracts : The development of analytic methods more selective and sensitive is of great importance for a better quality in the determination of chemical species, therefore increasing the reliability of the results. In this way, the optimization of separation/concentration is still necessary. The use of Molecularly Imprinted Polymers - MIPs have demonstrated to be an efficient tool of analysis with a great potential in minimizing limitations of separation/concentration techniques traditionally employed. In general, the MIPs are obtained by polymerization in the presence of a template to be imprinted so that a polymeric skeleton is formed around the future analyte. In the present work, the template used is Estradiol Valerate (EV), compound used in the hormone replacement therapy (HRT) during climacteric. After the polymerization in bulk and in an anaerobic environment using MAA, EGDMA, AIBN, acetonitrile and VE, the obtained MIP was powdered, sifted (<120 μm) and placed in a soxhlet system containing ethanol at 60 °C, in order to remove the imprinted molecule through six successive washes in periods of 24 hours. The water used in the washings was analyzed using HPLC and spectrophotometry UV/Vis. Then, the obtained MIP was dried at room temperature and 150 mg was inset in SPE cartridges in order to evaluate the polymer's efficiency in the analyte pre-concentration and extraction. To do so, 100,0 mL of VE standard solution (2mg L-1) were pre-concentrated at 4,0 mL min-1 and eluted with 10,0 mL ethanol at 1,0 mL min-1, obtaining recoveries of 53%. Additionally, a NIP (non-imprinting polymer) was prepared to compare the obtained results, in which the recovery was 80%. In the same way, studies were conducted using commercial Strata™-X cartridges, obtaining 53% recovery. Since, the results did not reflect that than was expected, in relation with the MIP efficiency in the recovery, a computational ...

Comparison between Two Methods to Calculate the Transition Matrix of Orbit Motion

Two methods to evaluate the state transition matrix are implemented and analyzed to verify the computational cost and the accuracy of both methods. This evaluation represents one of the highest computational costs on the artificial satellite orbit determination task. The first method is an approximation of the Keplerian motion, providing an analytical solution which is then calculated numerically by solving Kepler's equation. The second one is a local numerical approximation that includes the effect of J(2). The analysis is performed comparing these two methods with a reference generated by a numerical integrator. For small intervals of time (1 to 10s) and when one needs more accuracy, it is recommended to use the second method, since the CPU time does not excessively overload the computer during the orbit determination procedure. For larger intervals of time and when one expects more stability on the calculation, it is recommended to use the first method.

Expression of matrix metalloproteinases, type IV collagen, and interleukin-10 in rabbits treated with morphine after lamellar keratectomy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Short communication: Principal components and factor analytic models for test-day milk yield in Brazilian Holstein cattle

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evaluation of an average numerator relationship matrix model and a Bayesian hierarchical model for growth traits in Nellore cattle with uncertain paternity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Parameterized fast decoupled power flow methods for obtaining the maximum loading point of power systems. Part I. Mathematical modeling

The conventional Newton and fast decoupled power flow (FDPF) methods have been considered inadequate to obtain the maximum loading point of power systems due to ill-conditioning problems at and near this critical point. It is well known that the PV and Q-theta decoupling assumptions of the fast decoupled power flow formulation no longer hold in the vicinity of the critical point. Moreover, the Jacobian matrix of the Newton method becomes singular at this point. However, the maximum loading point can be efficiently computed through parameterization techniques of continuation methods. In this paper it is shown that by using either theta or V as a parameter, the new fast decoupled power flow versions (XB and BX) become adequate for the computation of the maximum loading point only with a few small modifications. The possible use of reactive power injection in a selected PV bus (Q(PV)) as continuation parameter (mu) for the computation of the maximum loading point is also shown. A trivial secant predictor, the modified zero-order polynomial which uses the current solution and a fixed increment in the parameter (V, theta, or mu) as an estimate for the next solution, is used in predictor step. These new versions are compared to each other with the purpose of pointing out their features, as well as the influence of reactive power and transformer tap limits. The results obtained with the new approach for the IEEE test systems (14, 30, 57 and 118 buses) are presented and discussed in the companion paper. The results show that the characteristics of the conventional method are enhanced and the region of convergence around the singular solution is enlarged. In addition, it is shown that parameters can be switched during the tracing process in order to efficiently determine all the PV curve points with few iterations. (C) 2003 Elsevier B.V. All rights reserved.