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Alguns aspectos do conceito de razão em Voltaire
(Universidade Estadual de Campinas, 2000-03-21) DIAS, Elizabeth de Assis; SILVA, Roberto Romano da; http://lattes.cnpq.br/7540974264149909
Acesso aberto (Open Access)
O ambiente deposicional da Formação Carajás e uma proposta de modelo evolutivo para a Bacia Grão Pará
(Universidade Estadual de Campinas, 2003-08-20) MACAMBIRA, Joel Buenano; SCHRANK, Alfonso; http://lattes.cnpq.br/5381945062567191
The large Carajás iron ores belongs to the Carajás fonnation, which is a 1 00-400m thick banded and laminated iron formation Gaspilite ), located at Pará state in North Brazil. This almost continuous formation outcrops for at least 260km, in 60 ore deposits, distributed in three main ridges, São Felix, Leste and Carajás. The last one is a sinformal structure sub-divided in South and North ridges. This work was carried out on detailed mapping, stratigraphic raising and petrographic, geochemical, isotopic and geochronological sampling of the North ridge, where the mining activity is currently running and bench and drill-core are available. Leveis ( 4 J.Ul1 to 3 cm) composed by chert or jasper alternated with magnetite-maghemite-hematite was deposed between 2,754 and 2,744 Ma (22m/Ma) at depths of 100-200m, locally affected by bottom currents. This hydroplastic chemical sediments precipitated by supersaturation (Si) and oxidation (Fe) from upwelling waters where the base was richer in hydrothermal source waters (LREE=6,66; Eu*=3,54; (La/Yb),=l,52) than the top (I:REE= 3,89; Eu*=3,18; (La/Yb),==,66). Besides, the major elements content have more variability at base than top. The Carajás jaspilite have twice Ga (2lppm), Bi (6ppm), Pb (18ppm) and seven times Sb (7ppm) than the world average for similar rocks. The Fe oxidation may have be promoted by organic activity, attested by delicate double wall spherulites and kerogen preservation in siltstones of a light younger unit. Local hydrothermal carbonatization has affected the jaspilite producing 813C mean of -4.3%opoa and two groups of 8180 (+24,9 to +15,4 and +12,8 to +6,6%osMow ). Otherwise, metamorphic imprints on this rocks are minimal. Regional work, bibliographic compilation and correlations of the Carajás formation with overlying units ofBahia and Azul mines leaves to propose a evolutionary model for the Grão Pará Basin, initiated as a intracontinental rifting stage, marked by crusta! contaminated tholeiitic basalt volcanism (2.76 Ga- U-Pb zircon ages). The second stage was the deposition ofthe Carajás formation over a wide, quiet marine continental she1f, in:fluenced by upwelling of Fe-Si rich waters. In a third stage, the last was recovered by volcanics associated with clastic sedimentation (2.74 Ga- Pb-Pb zircon ages). The fourth stage comprises the installation of another continental shelf environment, where clastics and carbonate rocks has deposed (2.68 Ga - U-Pb zircon ages). Basin inversion and fluvial deposition closes the evolution.
Acesso aberto (Open Access)
Análise comparativa da alteração dimensional de materiais de moldagem elastoméricos, através da técnica do casquete
(Universidade Estadual de Campinas, 2000-09-18) ANDRADE, Cícero Almeida de; SILVA, Frederico Andrade e; http://lattes.cnpq.br/2282864112869742
The present study assessed comparatively the dimensional change of four fluid-consistence elastomeric impression materiais (one addition silicone, two condensation silicones and one mercaptan) using the headcap technique. A metal cast (pattern) was made, enclosing two teeth with metal-crown preparation. On this cast, with a 0,3-mm metal relief, were obtained the headcaps using Neelon's technique (brush method). The impressions were carried out with a static-weight press, where a strength of 39.2 N (newton) was pressing the trays over the metal cast. The occlusal surfaces of the prepared teeth had cross-wise grooves. In the extreme of each groove there were small points where the reading started. The linear reading, in a comparing microscope, was initially done at the occlusal surface of each teeth distinctly, so following it was read matching the points between the two teeth. The results were statistically analysed and it followed that there were no statistically significant differences.
Acesso aberto (Open Access)
Análise da interferência de dois procedimentos na aprendizagem operatória
(Universidade Estadual de Campinas, 1995-11-04) SILVA, Francisco Hermes Santos da; SISTO, Fermino Fernandes; http://lattes.cnpq.br/8719624962833123
The objective of this study was to analyze two processes of intervention with a view toward operatory learning. In the first, the technique of cognitive conflict was applied and in the second, cognitive conflict associated with the formation of possibles. Our hypothesis was that the second process would present better results than the first, having seen that Piaget affirmed that the formation of possibles preceeds concrete operations. We worked with 20 children between the ages of 6 and 7 applying 10 sessions in two groups of 10 children. Comparative analyses of the data collected in the two interventions were made by taking into consideration five aspects: 1. a study of the interventions in terms of the acquisition of conservation of mass; 2. a study of the differences between IGC (Intervention Groups with Cognitive Conflict) and IGCP (Mixed Intervention Groups of Cognitive Conflict and Formation of Possibles) in terms of the indices and stability of operatory conduct; 3. a study of the differences between IGC and IGCP in terms of the types of operative arguments presented by the subjects; 4. analysis of the period of transition between non-operativeness and operativeness; and 5. studies of the differences between IGC and IGCP in terms of the operative arguments in function of the number of sessions with intermediary conducts. Our hypothesis was not confirmed from a quantitative point of view. However, while the intervention with conflict associated with the formation of possibles was not quantitatively demonstrated better than cognitive conflict, the technique was demonstrated valid as a pedagogical instrument in the acquisition of operativeness, since it presented satisfactory results with differences in relation to other groups being in terms of velocity of this acquisition and lesser production of operative arguments.
Acesso aberto (Open Access)
Análise da resistência a corrosão do aço carbono revestido com Al55-Zn após deformação mecânica e tratamento térmico
(Universidade Estadual de Campinas, 2001-01-12) BESERRA, Antonio Adelmo Freire; FREIRE, Célia Marina de Alvarenga; http://lattes.cnpq.br/6392994144210466
Analysis of the corrosion resistance of the 55AI-Zn coating on carbon steel after mechanical deformation and heat treatment The atmospheric corrosion resistance of 55%Al-Zn alloy coating on average is twelve times that of an equal thickness of galvanized coating. However, it has been shown that microcracks were observed at all levels of strain under simple uniaxial tension. Our research has been focused on determining the degree of corrosion experienced by these coatings after deformation under simple tension or bending and how much the heat treatment at '200 DEGREES' or '360 DEGREES' for 16h can influence the corrosion resistance of the coating. The coated sheet samples were strained to 10% or 15% engineering strain while another group of samples was bent to bend angles of '90 DEGREES' or '180 DEGREES'. The corrosion resistance of the samples was evaluated trhough Tafel extrapolation and electrochemical impedance spectroscopy methods. As a result, it was observed that both the straining and the bending of the coating reduces its corrosion resistance. After the heat treatment at '360 DEGREES' the samples strained to 10% or 15% recover their corrosion resistance, but the specimens bended to '90 DEGREES' or '180 DEGREES' recuperate only partially the corrosion resistance after the heat treatments.
Acesso aberto (Open Access)
Análise de três técnicas de moldagem utilizando-se duas siliconas por condensação e uma silicona por adição
(Universidade Estadual de Campinas, 1999-02-25) ANDRADE, Cícero Almeida de; SILVA, Frederico Andrade e; http://lattes.cnpq.br/2282864112869742
The procedure ín the constructíon of a fixed brídged has always been long, dífficult and tedíous" New equípament and materiais has appered to facílítate this procedure, however a question sti!! remains: conciliate techniques and materiais with an suitab!e cost-benefit In thís way, lhe aím of this study was: evaluated 3 impressíon techiniques (unitary tray, double impression and simultaneous impression ) using addition and condensatíon sílícon materiais ( Express, 3M and Optosii/Xantopren )" Over a comparative mensuraments from complet arch model cast, we could conclude: consídering the techniques, the unítary tray technique had better results: the 3M material (condensatíon) showed statístically the most satisfactory results when the unitary tray was used.
Acesso aberto (Open Access)
Análise de um modelo matemático de condução-convecção do tipo campo de fases para solidificação
(Universidade Estadual de Campinas, 2000-02-28) VAZ, Cristina Lúcia Dias; BOLDRINI, José Luiz; http://lattes.cnpq.br/6706768152701754
In this work we present results on existence and regularity of solutions of some conduction-convection models of phase-field type for solidification of either pure or impure (alloy) materiaIs. The essential characteristic of this models is that the solid fraction has a functional relation only with the phase field. For binary alloy solidification we are able to prove the existence of solutions only when the initial solute concentration is sufficiently small (that is, for dopant materiaIs.). The governing equations of the model are the phase field equation, the heat equation and/or solute equation coupled with a modified Navier-Stokes equations whose source term simulates the mushy region as a porous medium. Existence and regularity of the corresponding solutions are obtained as follows: firstly, the problem is adequately regularized and a sequence of regularized solutions is obtained using the Leray-Schauder's fixed point theorem. Then, by using compactness arguments, one proves that this sequence has a limit point which is a solution of the original problem. The corresponding regularity is obtained using bootstraping arguments.
Acesso aberto (Open Access)
Análise de um processo de recobrimento de comprimidos em um sistema vibro-jorrado bidimensional
(Universidade Estadual de Campinas, 1997) SOUZA, Célio Augusto Gomes de; KIECKBUSCH, Theo Guenter; http://lattes.cnpq.br/8568010039715375
An experimental set up for the study of tablets coating in a two-dimensional spouted bed that uses vibration of the perforated base to enhance the circulation of the particles was developed. An acrylic rectangular upper section (4x32 cm) with fixed 4x4 cm draft plates was adjusted over 3 different convergent sections (inclination 50') with 4x4 cm, 4x6 cm or 4x8 cm bases and contained 800g, 1100g or 1300g of tablets, Air (0,8 to 1,6 m3/min) forced by a 7,5 cv blower, was cooled down to 55°C and spouted this bed. The lenticular tablets (0,12g; 0,25g., 0,44g) were coated with a polymeric aqueous solution (11% solids). A two-fluid atomizer (air pressure 82,7 1kPa) was used, inserted laterally, near the bed base, and showed no influence on the movement of the particles. The experimental characterization of the tablets circulation rates was emphasized, using a magnet (0,4062 g) that followed the particles, activating a bobbin located at the upper end of the draft plates. The electric pulses were processed by a data acquisition sistem and the cicle time distribution curves were adjusted by the Modified Spline fit technique. The mean of the cicle time distribution creased with are increase of the bed load and the size of the tablets in all comparative tests. The vibration (10 Hz, 8 mm amplitude) reduced the mean of the cicle time distribution by more than 10%, and also decreased its variance. The vibration also affected the maximum pressure drop (40% reduction) and the minimum spouting velocity. The vibro spouted bed showed higher- adhesion efficency (73 to 88%) than the non-vibrated spouted bed (66 to 79%) in all equivalent situations and the complete coating of the smaller tablets demanded less processing time due to higher surface area circulation rate.
Acesso aberto (Open Access)
Análise do processo de difusão atômica no estado sólido em sistemas unidirecionais e radiais
(Universidade Estadual de Campinas, 1991-03-14) MOREIRA, Antonio Luciano Seabra; SANTOS, Rezende Gomes dos; http://lattes.cnpq.br/8824197696621614
In this work an analytical method is proposed to study diffusion pro¬cess in the solid state in binary systems consisting of only one phase with unidirectional, cylindrical and spherical atomic fluxo Initially a literature survey is carried out regarding some of the most important methods applied to diffusion process in these systems. The method is developed from the differential equation which treats this process in systems with unidirectional atomic flux, that is modified by geometric correlation and convenient changes of variables. The modified differential equation is solved by using a well known exact solution based on the error function and equations are obtained to analyse both the position of the diffusion interface as a function of time and the concentration profiles as a function of the position and time. The predictions furnished by the analytical method are compared with numerical results. A comparative study of diffusion process in planar, cylindrical and spherical geometries is ais o presented. Finally possible applications of the proposed method to the solution of practical problems are discussed.
Acesso aberto (Open Access)
Análise dos parâmetros de influência na qualidade superficial de lingotes
(Universidade Estadual de Campinas, 1992) QUARESMA, José Maria do Vale; GARCIA, Amauri; http://lattes.cnpq.br/1721691084829002
Acesso aberto (Open Access)
Análise experimental do processo de secagem de urucum (Bixa orellana L.) em leito fixo
(Universidade Estadual de Campinas, 1998-12-18) FARIA, Lênio José Guerreiro de; ROCHA, Sandra Cristina dos Santos; http://lattes.cnpq.br/3173533801776868
The drying of annatto seeds (Bixa orellana L.), type Red Piave, was studied in a fixed bed dryer. The optimal conditions were obtained to minimize the bixin losses and to obtain the final moisture content of seeds in the adequate lovels for conservation and quality maintenance. The bixix and the final moisture contents were studied as a function of the operational variables of the drying process. The termodynamic behavior of the seeds during the process of moisture desorption was verified by the static gravimetric method, using saturated salt solutions to maintain atmospheres with relative humidities in the range from 7 to 75%, at temperatures between 15 and 80ºC. GAB medel was used to fit the experimental data and the three parameters of GAB equation were evaluated. The Clausisus-Clapeyron equations was applied to obtain the net isosteric heats of sorption, using the desorption isotherm¿s data. It was verified that the annatto seeds can be conserved with higher stability in atmospheres with relative humidity of 60% in the range of temperatures studied. The quantification of the influences of the inlet variables of the process in the final moisture and bixin contents of the seeds and the identification of the optimal point for the process was accomplished by techniques of fractional factorial design, response surface methodology, canonical analysis and desirability function. Its was verified that the final moisture content of the seeds can be estimated by a second order polynomial model as a function of the is temperature and mass flow rate and of the dryng time, and that final bixin content is significantly influenced only by the process time, being described appropriately by linear model.
Acesso aberto (Open Access)
A arte de narrar: da constituição das estórias e dos saberes dos narradores da Amazônia paraense
(Universidade Estadual de Campinas, 2000-12-13) BENTES, Anna Christina; ALKMIM, Tânia Maria; http://lattes.cnpq.br/8437404856512094; KOCH, Ingedore Grunfeld Villaça; http://lattes.cnpq.br/9851642920435372
Taking into account that the act of narrating presents a necessary meta-discoursive reflexion about what is being narrated and that narrative presents a patteming or a "schematism" responsible for maintaining the narrative paradigm order, this study describes how narrators from Brazilian Amazon region configurate narrative tradition in two different ways. The first way called "folk-tale" is characterized considering the fact that narrators, when telling their stories, choose (i) to present frxed plots, which are commonshared, (ii) to construct a high degree of distance from what is being narrated, (iii) to necessarily present narrative structured in tenns of "conflict/resolutionn and {iv) to inscribe narrative sequences in a wondering discoursive domain. Narrators choose to configurate oral tradition in a way called "oral story" when they (i) do not present a frxed plot, reconstructing oral traditional narrativas in a personal way (ii) express their evaluations about what is been narrated, (iii) structure narrativa not necessarily in tenns of "conflict/resolution", but in a way that "resolution" category is not obrigatory, (iv) present the characters through a subjective perspectiva, showing their internai processes (feelings, thoughts etc.) and (v) inscribe the narrative sequences in other fictional domains. The narrativas analysed in this thesis were collected by a group of researchers from Universidade Federal do Pará and were published in three volumes. The analysis of thirty narrativas allows us to conclude that narrators can linguistically configurate narrative tradition in two ways: the first one, characterized by the fact that narrators privilege when telling their stories the dimensions of repetition and stability; the second one, characterized by the fact that narrators privilege when telling their stories the dimensions of difference and instability.
Acesso aberto (Open Access)
Aspectos bioquímicos e morfológicos da matriz extracelular das cartilagens septal e alares do nariz suíno
(Universidade Estadual de Campinas, 1999-07-02) MESSIAS JÚNIOR, Nazário de Souza; GOMES, Laurecir; http://lattes.cnpq.br/0032653238117133
The objective of the present study was to characterize some aspects of the extracellular matrix components of the alar and septal cartilage of the nose of swine and to examine the histological and histochemical aspects of the two types of cartilage. The kaotropic agent Gu-HCl was used to extract the matrix components. The predominant glycosaminoglycan in the two caitilages was chondroitin sulfate. After ultracentrifugation, the D4 fraction of the septal and alar cartilages was fractioned on DEAE-Sephacel using na NaCl gradient. SDS-PAGE analysiys showed similarities between the two cartilages, with the presence of fíbromodulin, decorin and binding proteins. Only the septal cartilage presented the 115 kDa component, which possibly appears as 30 kDa subunits after the action of the reducing agent. The glycosaminoglycan populations were determined by fractionation on Sepharose CL-6B followed by analysis of the samples on the agarosepolyacrilamide gel. The two cartilages presented a strongly polydispersed population, which was less uniformly polydispersed in the septal than in the alar cartilage. AD2 fractionation on DEAE-Sephacel and sample analysis by SDS-PAGE and agarosepolyacrylamide electrophoresis showed the presence of the small proteoglycans biglycan and decorin, possible associated with the large proteoglycans. The septal cartilage presents chondrocytes roughly arranged in rows accompanyng the widest axis of the cartilage, whereas the alar cartilage presents chondrocytes characteristically arranged in isogenic groups. Histhochemistry was performed usisng Xylidine Ponceau for total proteins, Picrosirius-Hematoxylin for collagen, Toluidine Blue for total glycosaminoglycans. And alcian blues, pH 2.5 and pH 1.0, for sulfated and carboxylated glycosaminoglycans. Total glycosaminoglycans are more cleary visible in the territorial matrix, whereas total proteins are more cleary visible in the interterritorial matrix. The collagen of the septal cartilage is roughly organized along the longitudinal axis of the specimens between the chondrocytes rows.
Acesso aberto (Open Access)
Aspectos computacionais da resolução de um modelo em educação
(Universidade Estadual de Campinas, 1983-12-16) ESPIRITO SANTO, Adilson Oliveira do; MARTÍNEZ PÉREZ, José Mário; http://lattes.cnpq.br/8543703316798123
Acesso aberto (Open Access)
Avaliação cefalométrica do perfil tegumentar e esquelético inicial e final de tratamento ortodôntico
(Universidade Estadual de Campinas, 1999-07-06) ALMEIDA, Haroldo Amorim de; ALMEIDA, Maria Helena Castro de; http://lattes.cnpq.br/0770202080280415
Was accomplished a study in 114 telerradiography of the head in lateral norm, of 57 Brazilian individuais, white, with Class 11, division 1 malocclusion (An.gle), submitted to orthodontic treatment according to the Tweed philosophy, with the purpose of evaluating the alterations to levei of the bony and soft-profile . The results demonstrated that among the angle Z and FMA an inverse correlation exists; when modifying the values of FMIA, Âng. Z suffers alterations of same degree and direction; altering the angle of the occlusal plan, they happen variations of similar value in FMA; any modification in ANB is accomplished by an alteration in AO-BO, of same magnitude and direction.
Acesso aberto (Open Access)
Benedito Nunes e a moderna crítica literária brasileira (1946-1969)
(Universidade Estadual de Campinas, 2012-02-28) NASCIMENTO, Maria de Fátima do; KOCH, Ingedore Grunfeld Villaça
This dissertation, about the literary criticism of Benedito Nunes, divided in two parts, is based on a variety of textual genres (attempts to write novels, poems, aphorisms, chronicles on science, poetry and philosophy, interviews, criticism on poetry and novels). In other words, this study is about Nunes‟ first texts on some newspapers of Belém do Pará: “Supplement of Art and Literature”, on the newspaper Folha do Norte (1946-1951), in which the author starts his career as a literary critic, also writing on magazines such as Encontro (1948) and Norte (1952). This study is also based on Benedito Nunes‟ writings on other newspapers of Brazil, such as the “Sunday Supplement” of Jornal do Brasil and on the supplements of journals like O Estado de São Paulo and O Estado de Minas Gerais (texts containing analysis of poems, novels and philosophy); and, still, Nunes‟ first books: O mundo de Clarice Lispector (1966) and O dorso do tigre (1969). The latter causes the writer to be considered one of the exponents of modern literary criticism in the second half of the twentieth century in Brazil, mainly of the works of art of writers who published from the decade of 1940 on, namely, Clarice Lispector, Guimarães Rosa and João Cabral de Melo Neto, just to name a few. The compilation of the texts published on journals, besides enabling the identification of the main readings of Benedito Nunes, which were incorporated to the conception of his criticism, considering some Christian philosophers as Saint Thomas Aquinas, Pascal, and, particularly, a precursor of existentialism, Kierkegaard, which will be constant in the analysis of the Brazilian author, makes it possible to trace the intellectual path followed by Benedito Nunes, specially as a literary critic. The writer will, lately, add the ideas of Sartre and Heidegger to his analysis. Specifically considering Heidegger, who Nunes studies throughout his whole life, it is possible to see the ontological conception of artistic creation by verbal language, which, to the German philosopher, corresponds to the foundation of the self by the word. Regarding the division of this study, the first part contains the intellectual path Benedito Nunes followed, as well as analysis of the material compiled from the newspapers and from the two books of this Brazilian critic. The second part contains a sample of the material which was compiled.
Acesso aberto (Open Access)
Colonização, catequese e educação no Grão-Pará
(Universidade Estadual de Campinas, 2003-02-24) COLARES, Anselmo Alencar; LOMBARDI, José Claudinei; http://lattes.cnpq.br/9792876515583843
This thesis, analyzed the educational aspects with a broader approach during the Grão-Pará colonisation, which started with the foundation of the Forte do Presépio in 1616, and extended until the end of the pombalino period in 1777. The sources used for this research included written records of regional writers, including jusuit priests who were eyewitnesses to the events, and history books related to this theme. Colonisation, catecheses and education are seen as directry related to each other, articuiated in a broader process which brought the development and expansion of captaiism. Moved by the need to expand their territories and commercial networts, and at the same time by religious interests, settlers from the 'Old World' launched themselves to the seas and accomplished the so-called 'Great Discoveries'. In the 'New World' the highly unequalled cultures clashed. The settler's intentions were to modify habits and believesof the native people in order to better serve their interests. It was necessery to make them 'civilized'. Thus, the relationship between settiers and native people had an important role in the educational process. The catecheses not only served to bring the indians to the catholich faith, but also to introduce the apropriated behavior that would correspond to the econemic interests. The educational process worked like na ideologic element disaggragating the way of life of the native people, reorganizing the knowledge, the ability to do and the power, contributing for theinsertion of Brazil in the g,roup of suppliers of goods and wealth which afforded a build up of capitais by the european bourgeoisie. There was also some schooling, but limited to a few people, reproducing and reinforcing the priviledges and the social framework of that period.
Acesso aberto (Open Access)
Contribuição ao gerenciamento de recursos hídricos do Rio Piracicaba
(Universidade Estadual de Campinas, 1995-09) BARP, Ana Rosa Baganha; BARBOSA, Paulo Sérgio Franco; http://lattes.cnpq.br/9653654803297649
This work deals with a network flow optimization problem applied to the Piracicaba river system. A mathematical optimization method which gives great computational efficiency was selected. The aim is to help the management and operation of hydrografic basins geared to the control of the quality and quantity of the water. Computational mathematical models were chosen due to their speedy and efficient aid to decision making. The problem was handled by adopting the multiobjective formulation of the Weight Method and a networks flow optimization algorithm coupled with a piece-wise linear objective function. At was verified that the river system responds satisfactorily as long as the flow of a twenty-four month's period is known in advance (deterministc flows) and with due manipulation of the storages and differentiation of the storages with time. The systemic vision the models provides is an alternative approach to the traditional studies that evaluate the benefits the hydraulic structures in the punctual form
Acesso aberto (Open Access)
Contribuição para o planejamento econômico de sistemas de energias elétrica: um algoritmo para a expansão simultânea da geração e transmissão usando aproximação linear
(Universidade Estadual de Campinas, 1983) BRANCO, Tadeu da Mata Medeiros; KOO, Robert Liang; http://lattes.cnpq.br/0610628446391103
Contribution tho the eletric power systems economic planning: an algorithm for the simultaneos expansion of generation and transmission using linear approximation. Economic Planning of Generation and Transmission in Electrical Power Systems constitutes a Nonlinear Optimization Problem which has some complexity and must be treated in a global manner. Several iteractive methods has been proposed to solve problems of this nature but sometimes are unaceptable due time and large computer storage requirements. This complexity is enlarged if generation and transmission were simultaneously optimized. Linear programming has been considered as a promissing tool to solve these problems but due the linearization of nonlinear functions the results presents some loss of accuracy, even so, for planning purposes these results are aceptable. In this work we propose a Global Algorithm for the Economic Planning of Simultaneous Expansion of Generation and Transmission in Electrical Power Systems based on the application of a Linear Programming Method and Minimum Cost Flow Algorithm which permits discret addition of generation and circuits units to the system with minimum investment cost in each period. Losses and maximum capacity of the lines are included in the algorithm, some examples are shown and at the end we suggest some extensions to further works.
Acesso aberto (Open Access)
Correlação entre condições de solidificação, microestrutura a resistência mecânica
(Universidade Estadual de Campinas, 1999-02-02) QUARESMA, José Maria do Vale; GARCIA, Amauri; http://lattes.cnpq.br/1721691084829002
Correlation among solidification conditions, microstructure and mechanical behavior / The imposition of a wide range of operational conditions in foudry and static casting generates, as a direct consequence, a diversity of solidification structures. Structural parameters such as grain size and interdendrictic spacings are highly influenced by the thermal behavior of the metal/mold system. during solidification, consequently imposing a close correlation between the described system and the resulting microstructure. The mechanical properties of an alIoy in its crude state of solidification depend on the microstructural arrangement defined in the solidification process. Under the circumstances, the mechanical behavior of the alIoy, represented by stresses and/or strains, wilI be defined by grain size, interdendritic spacings, casual porosities, segregated products and other phases. Expressions correlating the mechanical behavior with microstructural parameters are very useful in order to search for a type of previous planning of the solidification conditions in terms of a determined leveI of mechanical resistance which is intended to be attained, e.g. to settle a way of programming the microstructure and the mechanical properties as well. Particularly, the literature in this field presents relations between the yield strength of the material and the grain size, such as the renowned HalI-Petch's equation. The present work advances in that direction, in search of relations among mechanical behavior in the plastic field, secondary dendritic spacings and solidification conditions. In order to analyze an important variable of solidification in molds with good heat diffusivity, like the metal/mold heat transfer coefficient, alloys of the Sn-Pb system - with compositions Sn- 5%Pb, Sn- 10%Pb, Sn- 20%Pb, Sn- 38,1%Pb (eutectic) - besides the element tin, were chosen. The choice was made because such alloys are easily handled in laboratory and chiefly because their thermophysical properties are well known. Particularly the influences of the following operational conditions on hi were investigated: mold thickness, liquid metal superheating and magnitude of the solidification range. Experimental results related to the distribution of temperatures in metal and mold during solidification, as compared with the results of simulation with a numerical model, made it possible to attain of expressions, for each case, by relating hi in terms of time. Heat transfer from the external surface of the mold to the environment was also analyzed; in the same manner, expressions were developed correlating the mold/environment heat transfer coefficient hAmb in terms of time as well. To correlate parameters of dendritic structures and mechanical properties, the following alloys of the Al-Cu system were chosen: Al- 4,5%Cu; Al- 15%Cu. The same aforementioned analysis referring to hi and hAmb was extended to those alloys including the one of eutectic composition (Al- 33%Cu) and pure aluminum. Based upon results of standardized solidification tests, secondary dendritic spacing ( EDS ) and upon mathematical models of heat transfer and dendritic growth, expressions were developed correlating the ultimate tensile strength (σu) and specific elongation (δ) as a function of variables of the metallmold system. Thus it was a way towards the programming of the dendritic structure and the leveI of resistance as a function of preestablished operational conditions in the solidification process.