Submitted by Caroline Xavier (caroline.xavier@pucrs.br) on 2017-07-26T12:28:46Z No. of bitstreams: 1 TES_MARCOS_WERNER_COMPLETO.pdf: 4983787 bytes, checksum: c225e563acba72bee8aa18ccf79172cd (MD5) / Made available in DSpace on 2017-07-26T12:28:46Z (GMT). No. of bitstreams: 1 TES_MARCOS_WERNER_COMPLETO.pdf: 4983787 bytes, checksum: c225e563acba72bee8aa18ccf79172cd (MD5) Previous issue date: 2017-04-26 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / This paper aims to elaborate and develop an elastomeric compound able to be used in an industrial complex system as a grain harvester machine in order to reduce the grain breakage (seed) and/or mechanical damage in self-propelled harvesters through its energy absorption capabilities, energy produced by the material loading and transportation within the machine system. The compound was developed with Ethylene-Propylene-Diene Monomer (EPDM) and natural rubber (NR), loaded with silica (S), carbon black (CB) and multi-walled carbon nanotubes (MWCNT) in predefined proportions. From the evaluated compounds, three samples were chosen based on tear resistance, abrasion resistance and rubber hardness tests results, and then shaped in its original format (metallic geometry) for performance field tests and a more detailed material analysis. Field tests were done in two steps, one material assessment, and another one to assess the material performance in normal harvest conditions in two different crops (edible beans and soybeans), these tests also were used to evaluate the harvested grain quality in relation to the rubber compound used for harvesting and, therefore, the conclusions attained from the material usage. At the end of the tests, a significant improvement in grain quality was evidenced, and the differences in the compositions were noticed in the laboratory tests, and the application was the most critical to the materials in terms of resistance. / Este trabalho tem por objetivo elaborar e desenvolver uma composi??o elastom?rica apta a ser aplicada no sistema industrial de uma m?quina colheitadeira de gr?o visando reduzir a quebra de gr?o (semente) e ou dano mec?nico em colhedoras automotrizes atrav?s da sua capacidade de absor??o de energia, gerada pelo carregamento do trilhamento de material no sistema da m?quina. Foi trabalhado com matrizes de Etileno-Propileno-Dieno (EPDM) e borracha natural (NR), carregadas com s?lica (S), negro de fumo (CB) e nanotubos de carbono de paredes m?ltiplas (MWCNT) em propor??es predefinidas. A partir das composi??es analisadas, foram escolhidas tr?s formula??es com base nos resultados de resist?ncia ao rasgamento, resist?ncia ? abras?o e dureza, e ent?o elaboradas em seu formato original (geometria met?lica) para testes de desempenho em campo e an?lises mais detalhadas do material. Os testes de campo foram elaborados em duas etapas, uma de avalia??o do material em si, e outra para avaliar a performance do material em condi??es normais de colheita em duas culturas diferentes (feij?o e soja), onde a partir do mesmo, foi mensurada qualidade da semente colhida em rela??o ao material proposto, e obtidas as conclus?es da utiliza??o do mesmo. Ao final do teste foi evidenciada uma melhora significativa na qualidade de gr?o, e percebida as diferen?as nas composi??es nos ensaios laboratoriais, e a aplica??o foi a que exigiu mais dos materiais em termos de resist?ncia.

Submitted by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2016-01-12T17:16:00Z No. of bitstreams: 2 license_rdf: 22974 bytes, checksum: 99c771d9f0b9c46790009b9874d49253 (MD5) juliao_ribeiro_lessa_couto.pdf: 304364 bytes, checksum: 8f02ddbb4cf99ed8ffdcea725d7c4170 (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2016-01-12T17:16:49Z (GMT) No. of bitstreams: 2 license_rdf: 22974 bytes, checksum: 99c771d9f0b9c46790009b9874d49253 (MD5) juliao_ribeiro_lessa_couto.pdf: 304364 bytes, checksum: 8f02ddbb4cf99ed8ffdcea725d7c4170 (MD5) / Made available in DSpace on 2016-01-12T17:16:49Z (GMT). No. of bitstreams: 2 license_rdf: 22974 bytes, checksum: 99c771d9f0b9c46790009b9874d49253 (MD5) juliao_ribeiro_lessa_couto.pdf: 304364 bytes, checksum: 8f02ddbb4cf99ed8ffdcea725d7c4170 (MD5) Previous issue date: 2014 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Objetivou-se avaliar o desempenho produtivo e econ?mico de bovinos alimentados com diferentes n?veis de ponta de cana de a??car, em substitui??o ? cana de a??car, recebendo uma dieta de alto concentrado. Dezesseis bovinos machos, n?o castrados, da ra?a Nelore, com idade m?dia de 24 ? 3 meses e peso m?dio inicial de 360 ? 14,7 kg, foram mantidos em confinamento por 84 dias, recebendo uma dieta de alto concentrado. A rela??o concentrado:volumoso foi de 80:20. Quatro n?veis de substitui??o foram avaliados: T0 = sem adi??o de ponta de cana; T33 = substitui??o de 33% da cana de a??car por ponta de cana; T66 = substitui??o de 66% da cana de a??car por ponta de cana; e T100 = substitui??o total da cana de a??car por ponta de cana. O delineamento experimental empregado foi em blocos casualizados, com quatro repeti??es em cada tratamento. Um modelo linear contemplando os efeitos fixos de bloco (peso vivo inicial) e tratamento (dieta) foi usado nas an?lises. Os consumos de mat?ria seca, mat?ria org?nica, mat?ria mineral, prote?na bruta, fibra em detergente neutro, ganho de peso, convers?o alimentar e efici?ncia alimentar foram avaliados como indicadores de desempenho produtivo, e como indicadores econ?micos, a receita total, custo operacional total, custo operacional efetivo, margem bruta e margem l?quida. N?o houve efeito (P>0,05) de dieta para nenhuma das vari?veis estudadas. Os valores m?dios de ganho de peso total, ganho m?dio di?rio, convers?o e efici?ncia alimentar foram 102 ? 10,0 kg/animal, 1,2 ? 0,12 kg/dia, 8,6 ? 0,72 e 0,12 ? 0,010, respectivamente. Ao contr?rio dos demais tratamentos, a margem l?quida do T100 foi positiva, devido ao menor custo de aquisi??o da ponta de cana em rela??o ? cana de a??car. A substitui??o parcial ou total de cana de a??car por ponta de cana em dietas de alto concentrado n?o afetou o desempenho de bovinos confinados. No entanto, a inclus?o da ponta de cana diminuiu os custos de produ??o, apresentando margem l?quida positiva quando substituiu totalmente a cana de a??car. Assim, a ponta de cana pode ser utilizada pela ind?stria sucroalcooleira e por produtores artesanais de cacha?a como fonte de volumoso de baixo custo na alimenta??o de bovinos de corte. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Zootecnia, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2014. / ABSTRACT The objective was to evaluate the productive and economic performances of beef bulls fed different levels of sugarcane tops, as a substitute of sugarcane, provided with a high-concentrate diet. Sixteen Nellore bulls, with average age of 24 ? 3 months and initial weight of 360 ? 14.7 kg, were kept in a feedlot for 84 days, receiving a high-concentrate diet. The concentrate:roughage ratio was 80:20. Four levels of substitution were evaluated: T0 = no addition of sugarcane tops; T33 = 33% substitution of sugarcane by sugarcane tops; T66 = 66% substitution of sugarcane by sugarcane tops; and T100 = total substitution of sugarcane by sugarcane tops. The experimental design was a randomized block with four replications for each treatment. A linear model considering fixed effects as block (initial weight) and treatment (diet) was utilized in analyzes. Dry matter, organic matter, mineral matter, crude protein and neutral detergent fiber intake, body weight gain, feed conversion and feed efficiency were evaluated as productive performance parameters, and as economic indicators, total revenue, total operating expenses, gross margin, and net margin. No effect (P>0.05) of diet was found for the studied variables. Average values of total body weight gain, average daily gain, feed conversion, and feed efficiency were 102 ? 10.0 kg/animal, 1.2 ? 0.12 kg/day, 8.6 ? 0.72 and 0.12 ? 0.010, respectively. Unlike other treatments, the T100 net margin was positive, due to the lower cost of acquiring sugarcane tops compared with sugarcane. Partial or total substitution of sugarcane by sugarcane tops in high-concentrate diets did not affect performance of feedlot bulls. However, the inclusion of sugarcane tops reduced production costs, with positive net margin when totally substituting sugarcane. Therefore, sugarcane tops can be utilized by the ethanol industry and producers of handicraft sugarcane-rum as a low-cost roughage source in diets for beef bulls.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2018-08-22T18:12:38Z No. of bitstreams: 1 2017 - Helio Jos? de Ara?jo Filho.pdf: 1260983 bytes, checksum: 99a5ebc69e0f2db8e73b43a3fbf3d09d (MD5) / Made available in DSpace on 2018-08-22T18:12:38Z (GMT). No. of bitstreams: 1 2017 - Helio Jos? de Ara?jo Filho.pdf: 1260983 bytes, checksum: 99a5ebc69e0f2db8e73b43a3fbf3d09d (MD5) Previous issue date: 2017-02-22 / FAPERJ / CNPq / The growth of the world population has increased the demand for food, this implies in reduction of the available areas for animal production, which makes imperative the development, evaluation and application of techniques that propitiate the increase of the productivity of Brazilian livestock. Thus, the objective of this study was to evaluate and compare the productive and economic performance of beef cattle finishing under three management and feeding systems, namely: at pasture with mineral supplementation (PSM); at pasture with protein-energy supplementation (SPE); And raised at feedlot with high concentrate diet (AG). For this purpose, 60 castrated male bovines, crossbreed Nelore x Angus, which were distributed in a design Completely randomized, with three systems and twenty animals in each. The study was conducted at Fazenda Tr?s Morros, in the city of Casimiro de Abreu. The means of the studied variables were estimated by LSMEANS and compared by PDIFF, at 5% of probability (p<0.05%), of SAS?. The feedlot (AG) presented shorter finishing time (76 days) and higher weight gain (102.2 kg), total daily average gain (1.35 kg.animal-1.day-1) and average daily gain of carcass (1.02 kg.animal-1.day-1), followed by SPE and PSM, respectively, in relation to the finishing time and the average daily gain of carcass. Regarding weight gain and average daily gain, there was no significant difference (p <0.05) between SPE and PSM. In turn, the average carcass weights (ACW), carcass yields (CY), and carcass gains (CG) of AG (ACW 298.3 kg or 19.9@, CY 55.1% and CG 78.3 kg) and SPE (ACW 288.2 kg or 19.2@, CY 56.1% and CG 68.1 kg) were similar to each other and higher (p<0.05) to PSM. The system PSM had the lowest production costs (effective operational cost R$ 2,277, total operational cost R$ 2,323 and total cost R$ 2,466), while the highest effective operational cost was AG (R$ 2,598) and the highest total operational cost (TOC) and total cost (TC) of SPE (TOC of R$ 2,632 and R$ 2,668). The highest gross margin (R$ 341.1) and net margin (R$ 295.9), net result (R$ 153.0), profitability (5.84%) and simple rentability (4.54%) were obtained by PSM, followed by SPE and AG, in that order. However, when the cash flows were corrected by the general price index - domestic availability (GPI-DA), the gross margins (R$ 199.6) and net margin (R$ 152.2) of PSM remained the highest and followed by SPE and AG (respectively), but the other economic indicators were the lowest among the systems. In this way, the highest net result (R$ 70.7), profitability (2.43%) and simple rentability (1.81%) were observed in SPE. Therefore, the feedlot provided the smallest production cycle and increased animal productivity, the pasture system with mineral supplementation allowed the reduction of production costs, while the concentrate supplementation presented better economic result during the dry season of the year 2015. According to the information obtained, both confinement and supplementation with whole maize diet have the potential to be strategic alternatives to the finishing cattle at exclusively pasture, provided satisfactory market conditions. / O crescimento da popula??o mundial tem elevado a demanda por alimento, isso implica em redu??o das ?reas dispon?veis para produ??o animal, o que torna imperativo o desenvolvimento, avalia??o e aplica??o de t?cnicas que propiciem o aumento da produtividade da pecu?ria brasileira. Desta forma, o objetivo deste estudo foi avaliar e comparar o desempenho produtivo e econ?mico da termina??o de bovinos sob tr?s sistemas de manejo e alimenta??o, a saber: a pasto com suplementa??o mineral (PSM); a pasto com suplementa??o prot?ico-energ?tica (SPE); e confinamento com fornecimento de dieta alto gr?o (AG). Para tanto, foram utilizados 60 bovinos machos castrados, ? sangue Nelore x Angus, distribu?dos em um delineamento inteiramente casualizado, em tr?s sistemas e vinte animais em cada. O estudo foi conduzido na Fazenda Tr?s Morros, no munic?pio de Casimiro de Abreu/RJ. As m?dias das vari?veis estudadas foram estimadas pelo LSMEANS e comparadas pela PDIFF, a 5% de probabilidade (p<0,05), do SAS?. O confinamento (AG) apresentou menor tempo de termina??o (76 dias) e maiores ganho de peso (102,2 kg), ganho m?dio di?rio total (1,35 kg.animal-1.dia-1) e ganho m?dio di?rio de carca?a (1,02 kg.animal-1dia-1), seguido por SPE e PSM, respectivamente, em rela??o ao tempo de termina??o e ao ganho m?dio di?rio de carca?a. No que se refere ao ganho de peso e ao ganho m?dio di?rio total, n?o houve diferen?a significativa (p<0,05) entre SPE e PSM. Por sua vez, os pesos m?dios de carca?a (PMC), os rendimentos de carca?a (RC) e os ganhos de carca?a (GC) de AG (PMC de 298,3 kg ou 19,9 @, RC de 55,1% e GC de 78,3 kg) e SPE (PMC de 288,2 kg ou 19,2 @, RC de 56,1% e GC de 68,1 kg) foram semelhantes entre si e superiores (p<0,05) a PSM. J? o sistema PSM obteve os menores custos de produ??o (custo operacional efetivo de R$ 2.277, custo operacional total de R$ 2.323 e custo total de R$ 2.466), enquanto o maior custo operacional efetivo foi de AG (R$ 2.598) e os maiores custo operacional total (COT) e custo total (CT), de SPE (COT de R$ 2.632 e CT R$ 2.668). As maiores margem bruta (R$ 341,1) e l?quida (R$ 295,9), resultado l?quido (R$ 153,0), lucratividade (5,84%) e rentabilidade simples (4,54%) foram obtidas por PSM, seguidas por SPE e AG, nesta ordem. Por?m, quando os fluxos de caixa foram corrigidos pelo ?ndice geral de pre?os ? disponibilidade interna (IGP-DI), as margens bruta (R$ 199,6) e l?quida (R$ 152,2) de PSM permaneceram as mais elevadas e acompanhadas por SPE e AG (respectivamente), contudo, os demais indicadores econ?micos foram os menores entre os sistemas. Desta forma, os maiores resultado (R$ 70,7), lucratividade (2,43%) e rentabilidade simples (1,81%) foram observados em SPE. Portanto, o confinamento proporcionou o menor ciclo de produ??o e maior produtividade animal, o sistema a pasto com suplementa??o mineral possibilitou a redu??o dos custos de produ??o, enquanto a suplementa??o com concentrado apresentou melhor resultado econ?mico, durante a esta??o seca do ano de 2015. De acordo com as informa??es obtidas, tanto o confinamento quanto a suplementa??o com dieta ? base de milho inteiro possuem potencial para serem alternativas estrat?gicas ? termina??o de bovinos exclusivamente a pasto, desde que presentes condi??es satisfat?rias do mercado.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-03-09T23:06:17Z No. of bitstreams: 1 EliselmaVieiraDosSantos_DISSERT.pdf: 2170008 bytes, checksum: a21121290242fb8c43c3f7fe9a9cf8d0 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-03-11T19:37:06Z (GMT) No. of bitstreams: 1 EliselmaVieiraDosSantos_DISSERT.pdf: 2170008 bytes, checksum: a21121290242fb8c43c3f7fe9a9cf8d0 (MD5) / Made available in DSpace on 2016-03-11T19:37:06Z (GMT). No. of bitstreams: 1 EliselmaVieiraDosSantos_DISSERT.pdf: 2170008 bytes, checksum: a21121290242fb8c43c3f7fe9a9cf8d0 (MD5) Previous issue date: 2015-03-16 / A evolu??o cont?nua da tecnologia de circuitos integrados tem permitido integrar milhares de transistores em uma ?nica pastilha de sil?cio. Devido ? miniaturiza??o desta tecnologia, a redu??o do di?metro do fio e do transistor os tornaram mais fr?geis e suscet?veis a quebras, tornando o circuito mais suscept?vel a falhas permanentes tanto durante o processo de fabrica??o quanto durante seu tempo de vida ?til. As arquiteturas reconfigur?veis de gr?o grosso, tamb?m chamadas de CGRAs (Coarse Grained Reconfigurable Architectures), t?m sido utilizadas como uma alternativa ?s arquiteturas tradicionais para tentar tolerar essas falhas, devido ? sua intr?nseca redund?ncia de hardware e ao alto desempenho obtido por essas arquiteturas. Essa disserta??o prop?e um mecanismo de toler?ncia a falhas numa CGRA com o objetivo de aumentar a toler?ncia da arquitetura mesmo considerando uma alta taxa de falhas. O mecanismo proposto foi adicionado ao escalonador da CGRA, que consiste no mecanismo respons?vel pelo mapeamento das instru??es na arquitetura. O mapeamento das instru??es ocorre em tempo de execu??o, traduzindo o c?digo bin?rio sem a necessidade de recompila??o. Al?m disso, para permitir a acelera??o da aplica??o, o mapeamento ? realizado atrav?s de um algoritmo guloso que faz uso do modulo scheduling, que consiste em uma t?cnica em software pipeline para acelera??o de la?os. Os resultados obtidos a partir de simula??es de inje??o de falhas e de execu??o do escalonador demonstram que, mesmo com o mecanismo de toler?ncia a falhas proposto, o tempo de mapeamento das instru??es se mant?m na ordem de microssegundos. Esse resultado permite que o mapeamento das instru??es continue sendo realizado em tempo de execu??o. Al?m disso, tamb?m foi realizado um estudo de taxa de mapeamento do escalonador. Os resultados demonstram que, mesmo com taxas acima de 50% de falhas em unidades funcionas e componentes de interconex?o, o escalonador conseguiu mapear instru??es na arquitetura em parte das aplica??es testadas. / The continuous evolution of integrated circuit technology has allowed integrating thousands of transistors on a single chip. This is due to the miniaturization process, which reduces the diameter of wires and transistors. One drawback of this process is that the circuit becomes more fragile and susceptible to break, making the circuit more susceptible to permanent faults during the manufacturing process as well as during their lifetime. Coarse Grained Reconfigurable Architectures (CGRAs) have been used as an alternative to traditional architectures in an attempt to tolerate such faults due to its intrinsic hardware redundancy and high performance. This work proposes a fault tolerance mechanism in a CGRA in order to increase the architecture fault tolerance even considering a high fault rate. The proposed mechanism was added to the scheduler, which is the mechanism responsible for mapping instructions onto the architecture. The instruction mapping occurs at runtime, translating binary code without the need for recompilation. Furthermore, to allow faster implementation, instruction mapping is performed using a greedy module scheduling algorithm, which consists of a software pipeline technique for loop acceleration. The results show that, even with the proposed mechanism, the time for mapping instructions is still in order of microseconds. This result allows that instruction mapping process remains at runtime. In addition, a study was also carried out mapping scheduler rate. The results demonstrate that even at fault rates over 50% in functional units and interconnection components, the scheduler was able to map instructions onto the architecture in most of the tested applications.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-01-27T12:19:00Z No. of bitstreams: 1 EdnaldoSilvaFernandes_TESE.pdf: 4254216 bytes, checksum: cfeb3d13d5b8fd2c6bc1b1d0107dedca (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-01-27T15:58:26Z (GMT) No. of bitstreams: 1 EdnaldoSilvaFernandes_TESE.pdf: 4254216 bytes, checksum: cfeb3d13d5b8fd2c6bc1b1d0107dedca (MD5) / Made available in DSpace on 2017-01-27T15:58:26Z (GMT). No. of bitstreams: 1 EdnaldoSilvaFernandes_TESE.pdf: 4254216 bytes, checksum: cfeb3d13d5b8fd2c6bc1b1d0107dedca (MD5) Previous issue date: 2016-03-30 / P?s de c?ria dopada com 0% (CeO2); 10% (CGO10) ou 20% (CGO20) em mol de gadol?nia foram sintetizados pelo m?todo Pechini. Os p?s calcinados, como-sintetizados e mo?dos/peneirados foram caracterizados por DRX, BET, TG e DTG. Pastilhas de materiais particulados mo?dos/peneirados e como-sintetizados foram prensadas uniaxialmente com 210 MPa, e em seguida sinterizadas at? 1400 ?C com taxa de aquecimento de 5 ?C/min em dilat?metro sem e com a a??o de campo el?trico DC. Os campos el?tricos aplicados foram de 0; 10; 30 e 50 Vcm-1. Os valores da intensidade de corrente el?trica e diferen?a de potencial el?trico foram registrados em fun??o da temperatura. As densidades das pastilhas, a verde e sinterizada, foram calculadas pelo m?todo geom?trico. A caracteriza??o microestrutural das amostras sinterizadas foi realizada por microscopia eletr?nica de varredura (MEV), com o tamanho m?dio de gr?o avaliado por an?lise de imagem no software ImageJ. Os valores de densidades alcan?ados sugerem que a moagem/peneiramento proporciona maior taxa de sinteriza??o independentemente da composi??o e do valor do campo el?trico aplicado. Os resultados obtidos sugerem que a aplica??o de campo el?trico durante a sinteriza??o promove maior densifica??o, p? mo?do/peneirado ou p? sem moer, independentemente da composi??o, e, que quanto maior ? o valor do campo el?trico, maior ? a densifica??o do material. A dopagem da c?ria retardou o crescimento dos gr?os durante a sinteriza??o convencional no dilat?metro, pastilhas com p? mo?do/peneirado ou com p? sem moer. Este retardo no crescimento de gr?o foi atribu?do ao fen?meno ?drag solute?. A sinteriza??o das pastilhas prensadas com p? mo?do/peneirado, sob a a??o de um campo el?trico, proporcionou retardo no crescimento de gr?o para todas as composi??es. Apesar da a??o do campo el?trico retardar significativamente a taxa de crescimento de gr?o, os diferentes valores de campo el?trico n?o causaram diferen?as significativas a esta taxa. Este fen?meno n?o foi observado quando p? sem moer foi usado. Ao retardo no crescimento de gr?o, quando da sinteriza??o sob efeito do campo el?trico, foi atribu?do ? maior temperatura nos contornos de gr?o que reduz a energia livre de difus?o de contorno de gr?o. A a??o conjunta moagem/peneiramento e aplica??o de campo el?trico DC se mostrou eficiente para retardar o crescimento de gr?o das composi??es e aumentar a taxa de densifica??o, em rela??o ? sinteriza??o convencional. A sinteriza??o de p?s ? base de c?ria (mo?dos/peneirados) com aplica??o de um campo el?trico DC (em condi??es n?o isot?rmicas entre 30 e 1400 ?C) mostrou-se um alternativa bastante promissora para a obten??o de cer?micas com reduzido tamanho de gr?o e densidades relativas superiores a 90%. / Ceria powders doped with 0% (CeO2); 10% (CGO10) or 20% (CGO20) of gadolinia mol were synthesized by the Pechini method. The calcined powders, as-synthesized and ground / sieved were characterized by XRD, BET, TG and DTG. materials tablets particulate ground / sieved and as-synthesized were pressed uniaxially at 210 MPa, and then sintered to 1400 ? C with a heating rate of 5 ? C / min in dilatometer with and without DC electric field action. The applied electric fields were 0; 10; 30 and 50 Vcm-1. The values of the intensity of electric current and electric potential difference was recorded as a function of temperature. The densities of the pellets, the green and sintered, were calculated using the geometric method. Microstructural characterization of sintered samples was performed by scanning electron microscopy (SEM), with the average grain size measured by image analysis in ImageJ software. The achieved densities values suggest that the milling / sieving provides enhanced sintering rate regardless of the composition and the value of the applied electric field. The results suggest that the application of the electric field during sintering promotes greater densification, ground / sieved powder or powder without grinding, regardless of composition, and that the greater the value of the electric field, the greater the densification of the material. The delayed doping of ceria grain growth during sintering in conventional dilatometer, tablets with milled powder / or sieved powder without milling. This delay in grain growth was attributed to the phenomenon "drag solute." The sintering of pressed pellets of ground / sieved powder, under the action of an electric field, provided delayed grain growth for all compositions. Despite the electric field action significantly slow the grain growth rate, different electric field values did not cause significant differences in the rate. This phenomenon was not observed when powder without grinding was used. To delayed grain growth when sintering under the influence of the electric field, it was attributed to the higher temperature at the grain boundaries which reduces the free energy of the grain boundary diffusion. The joint action grinding / sieving and application of DC electric field was efficient for retarding grain growth of the compositions and increase the densification rate, as compared to conventional sintering. The powder sintering of ceria (ground / sieved) by applying a DC electric field (in non-isothermal conditions between 30 and 1400 ? C) proved to be a promising alternative for obtaining ceramic with reduced grain size and relative densities exceeding 90%.

Made available in DSpace on 2014-12-17T14:06:51Z (GMT). No. of bitstreams: 1 AntonioEFF.pdf: 720128 bytes, checksum: febce55b295b3d3be15f1c24bf498884 (MD5) Previous issue date: 2009-02-26 / Na unfolding method of linear intercept distributions and secction ?rea distribution was implemented for structures with spherical grains. Although the unfolding routine depends on the grain shape, structures with spheroidal grains can also be treated by this routine. Grains of non-spheroidal shape can be treated only as approximation. A software was developed with two parts. The first part calculates the probability matrix. The second part uses this matrix and minimizes the chi-square. The results are presented with any number of size classes as required. The probability matrix was determined by means of the linear intercept and section area distributions created by computer simulation. Using curve fittings the probability matrix for spheres of any sizes could be determined. Two kinds of tests were carried out to prove the efficiency of the Technique. The theoretical tests represent ideal cases. The software was able to exactly find the proposed grain size distribution. In the second test, a structure was simulated in computer and images of its slices were used to produce the corresponding linear intercept the section area distributions. These distributions were then unfolded. This test simulates better reality. The results show deviations from the real size distribution. This deviations are caused by statistic fluctuation. The unfolding of the linear intercept distribution works perfectly, but the unfolding of section area distribution does not work due to a failure in the chi-square minimization. The minimization method uses a matrix inversion routine. The matrix generated by this procedure cannot be inverted. Other minimization method must be used / A rotina de desdobramento (unfolding) de distribui??es de intercepto linear e de ?rea de se??o foi implementada para gr?os de formato esf?rico. Apesar da rotina de unfolding ser fortemente dependente do formato do gr?o, estruturas que possuam gr?os com formatos esferoidais podem ser tratadas com esta rotina. Mesmo estruturas com gr?os de formatos n?o esferoidais podem ser tratadas por aproxima??o. Um programa com duas partes foi desenvolvido. Primeira parte determina a tabela de probabilidades. A segunda utiliza esta tabela e aplica o m?todo de minimiza??o do chi-quadrado. Os resultados s?o dados em qualquer n?mero de classes de tamanho de gr?o requerido pelo usu?rio. A tabela de probabilidade foi determinada a partir de distribui??es de intercepto linear e de ?rea de se??o geradas por simula??o computacional. Por meio de ajustes de curvas de distribui??o, tabelas de probabilidades para esferas de qualquer tamanho podem ser determinadas. Dois tipos de testes foram executados para verificar a efici?ncia do m?todo. Os testes te?ricos representam situa??es ideais. O programa conseguiu reproduzir com exatid?o as distribui??es de tamanho de gr?o sugeridas. Os testes simulados consistem em simular em computador distribui??es de tamanho de gr?os e executar todo o procedimento metalogr?fico usual. Este tipo de teste ? mais pr?ximo da situa??o real. Os resultados deste tipo de teste mostram que a rotina de medi??o estereol?gica introduz desvios estat?sticos, afastando o resultado encontrado do valor real. Contudo, a rotina de unfolding funciona perfeitamente para a distribui??o de intercepto linear. No caso de unfolding de ?rea de se??o, a minimiza??o do chi-quadrado pelo m?todo matricial gera matrizes n?o invers?veis e n?o pode ser aplicada. Outro m?todo de minimiza??o deve ser buscado