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Sequential Calibration Of Computer ModelsKumar, Arun 11 September 2008 (has links)
No description available.
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Técnicas adesivas de obturação - Avaliação microscópica quantitativa da reparação apical e periapical pós-tratamento de canais radiculares de dentes de cães com lesão periapical / Adhesive root canal filling techniques A quantitative microscopic evaluation of apical and periapical repair after root canal treatment of dog\'s teeth with periapical lesionKleber Cortes Bonifacio 19 September 2013 (has links)
O objetivo deste estudo foi avaliar quantitativamente, in vivo, a resposta dos tecidos apicais e periapicais de dentes de cães com lesão periapical crônica, induzida experimentalmente, após tratamento de canal radicular e obturação endodôntica empregando os seguintes cimentos: EndoREZ, Real Seal e Sealapex. Canais radiculares não obturados (curativo de demora) foram utilizados como controle. Após a obtenção de lesões periapicais experimentalmente induzidas, os dentes foram submetidos à abertura coronária, neutralização do conteúdo necrótico, preparo biomecânico, curativo de demora com uma pasta à base de hidróxido de cálcio (Calen) e obturação dos canais radiculares com os diferentes cimentos obturadores citados. Decorridos os períodos de 30 e 90 dias, os animais foram mortos e o material submetido ao processamento histotécnico. A análise microscópica pelo método quantitativo de avaliação foi realizada em microscópio Axio Imager.M1 (Zeiss), acoplado a uma câmera AxioCam MRc5 (Zeiss). Foi registrada a descrição completa das características dos tecidos apicais e periapicais e efetuada a quantificação do número de células inflamatórias e das extensões das áreas da lesão periapical em mm2, a presença de reabsorção óssea e a presença de selamento biológico apical, em imagens microscópicas obtidas de cortes histológicos corados por hematoxilina e eosina, utilizando o Software AxioVision Rel.4.6 (Automatic Measurements Programs Program Wizard). Os valores obtidos foram avaliados quanto ao tipo de distribuição e comparados por meio da análise de variância (ANOVA), seguido pelo pós-teste de Tukey, com nível de significância de 5%. A presença e extensão do infiltrado inflamatório além da metade do ligamento periodontal foi observada em todos os cimentos avaliados, tanto no período de 30 quanto 90 dias, sendo predominantemente mononuclear. Não houve modulação do infiltrado inflamatório em nenhum dos cimentos, pois a quantidade de células inflamatórias foi semelhante em ambos os períodos, 30 e 90 dias (p>0,05). Em relação as áreas de reabsorções óssea e radicular, nos cimentos EndoREZ e Real Seal, a presença foi de aproximadamente 50% dos casos aos 90 dias; enquanto no cimento Sealapex, as mesmas estiveram presentes em 30% dos casos tanto aos 30 quanto aos 90 dias. A extensão da lesão periapical foi semelhante em ambos períodos experimentais (30 e 90 dias), em todos os cimentos avaliados. Por fim, selamento biológico foi observado aos 90 dias, em, aproximadamente, 20%, 30% e 50% dos casos nos cimentos EndoREZ, Real Seal e Sealapex, respectivamente; e em 15% dos casos, no período de 30 dias, apenas no cimento do Sealapex. Dentro das limitações deste experimento, pode-se concluir que os cimentos resinosos EndoREZ e Real Seal, não foram bem tolerados pelos tecidos apicais e periapicais. Ainda, reparo dos tecidos apicais, com deposição de cemento, foi encontrado nos dentes obturados com o cimento Sealapex, embora não tenha sido observado reparo total das lesões periapicais. / The aim of this study was to evaluate quantitatively, in vivo, the response of apical and periapical tissues of dog\'s teeth with experimentally induced chronic periapical lesion, after endodontic treatment and root canal filling using the following sealers: EndoREZ, Real Seal and Sealapex. Non-filled root canals (intracanal dressing) were used as control. After induction of the experimental periapical lesions, the teeth were subjected to coronal access, neutralization of the necrotic content, biomechanical preparation, placement of an intracanal dressing with a calcium hydroxide paste (Calen), and root canal filling with the different endodontic sealers mentioned above. After 30 and 90 days, the animals were euthanized and the material was subjected to histotechnical processing. A quantitative microscopic analysis was performed using an Axio Imager.M1 (Zeiss) microscope coupled to an AxioCam MRc5 (Zeiss) camera. A complete description of the characteristics of the apical and periapical tissues was performed and the number of inflammatory cells, size of the periapical lesions (in mm2), presence of bone resorption and presence of sealing of the apical opening with mineralized tissue deposition was determined on microscopic images obtained from hematoxylin and eosin-stained histological sections, using the Software AxioVision Rel.4.6 (Automatic Measurements Programs Program Wizard). Data were examined for their distribution and the compared using analysis of variance (ANOVA) followed by Tukeys post-test with a 5% significance level. Presence and extension of an inflammatory infiltrate, predominantly mononuclear, beyond half of the periodontal ligament was observed for all sealers, at both 30-day and 90-day periods. There was no modulation of the inflammatory infiltrate for any of the sealers because the number of inflammatory cells was similar at both 30-day and 90-day periods (p>0.05). Bone and radicular resorption areas were found in approximately 50% of the cases at 90 days for EndoREZ and Real Seal, and in 30% of the cases at the 30-day and 90-day periods for Sealapex. The periapical lesion size was similar at both experimental periods (30 and 90 days) for all evaluated sealers. Finally, sealing of the apical opening with mineralized tissue deposition was observed at 90 days in approximately 20%, 30% and 50% of the cases for EndoREZ, Real Seal and Sealapex, respectively; and in 15% dos cases, at the 30-day period, only for Sealapex. Within the limitations of this experiment, it may be concluded that the resin-based sealers EndoREZ and Real Seal were not well tolerated by the apical and periapical tissues. Periapical tissue repair, with cementum deposition, was found in the teeth filled with Sealapex, although complete repair of the periapical lesions was not observed.
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Técnicas adesivas de obturação - Avaliação microscópica quantitativa da reparação apical e periapical pós-tratamento de canais radiculares de dentes de cães com lesão periapical / Adhesive root canal filling techniques A quantitative microscopic evaluation of apical and periapical repair after root canal treatment of dog\'s teeth with periapical lesionBonifacio, Kleber Cortes 19 September 2013 (has links)
O objetivo deste estudo foi avaliar quantitativamente, in vivo, a resposta dos tecidos apicais e periapicais de dentes de cães com lesão periapical crônica, induzida experimentalmente, após tratamento de canal radicular e obturação endodôntica empregando os seguintes cimentos: EndoREZ, Real Seal e Sealapex. Canais radiculares não obturados (curativo de demora) foram utilizados como controle. Após a obtenção de lesões periapicais experimentalmente induzidas, os dentes foram submetidos à abertura coronária, neutralização do conteúdo necrótico, preparo biomecânico, curativo de demora com uma pasta à base de hidróxido de cálcio (Calen) e obturação dos canais radiculares com os diferentes cimentos obturadores citados. Decorridos os períodos de 30 e 90 dias, os animais foram mortos e o material submetido ao processamento histotécnico. A análise microscópica pelo método quantitativo de avaliação foi realizada em microscópio Axio Imager.M1 (Zeiss), acoplado a uma câmera AxioCam MRc5 (Zeiss). Foi registrada a descrição completa das características dos tecidos apicais e periapicais e efetuada a quantificação do número de células inflamatórias e das extensões das áreas da lesão periapical em mm2, a presença de reabsorção óssea e a presença de selamento biológico apical, em imagens microscópicas obtidas de cortes histológicos corados por hematoxilina e eosina, utilizando o Software AxioVision Rel.4.6 (Automatic Measurements Programs Program Wizard). Os valores obtidos foram avaliados quanto ao tipo de distribuição e comparados por meio da análise de variância (ANOVA), seguido pelo pós-teste de Tukey, com nível de significância de 5%. A presença e extensão do infiltrado inflamatório além da metade do ligamento periodontal foi observada em todos os cimentos avaliados, tanto no período de 30 quanto 90 dias, sendo predominantemente mononuclear. Não houve modulação do infiltrado inflamatório em nenhum dos cimentos, pois a quantidade de células inflamatórias foi semelhante em ambos os períodos, 30 e 90 dias (p>0,05). Em relação as áreas de reabsorções óssea e radicular, nos cimentos EndoREZ e Real Seal, a presença foi de aproximadamente 50% dos casos aos 90 dias; enquanto no cimento Sealapex, as mesmas estiveram presentes em 30% dos casos tanto aos 30 quanto aos 90 dias. A extensão da lesão periapical foi semelhante em ambos períodos experimentais (30 e 90 dias), em todos os cimentos avaliados. Por fim, selamento biológico foi observado aos 90 dias, em, aproximadamente, 20%, 30% e 50% dos casos nos cimentos EndoREZ, Real Seal e Sealapex, respectivamente; e em 15% dos casos, no período de 30 dias, apenas no cimento do Sealapex. Dentro das limitações deste experimento, pode-se concluir que os cimentos resinosos EndoREZ e Real Seal, não foram bem tolerados pelos tecidos apicais e periapicais. Ainda, reparo dos tecidos apicais, com deposição de cemento, foi encontrado nos dentes obturados com o cimento Sealapex, embora não tenha sido observado reparo total das lesões periapicais. / The aim of this study was to evaluate quantitatively, in vivo, the response of apical and periapical tissues of dog\'s teeth with experimentally induced chronic periapical lesion, after endodontic treatment and root canal filling using the following sealers: EndoREZ, Real Seal and Sealapex. Non-filled root canals (intracanal dressing) were used as control. After induction of the experimental periapical lesions, the teeth were subjected to coronal access, neutralization of the necrotic content, biomechanical preparation, placement of an intracanal dressing with a calcium hydroxide paste (Calen), and root canal filling with the different endodontic sealers mentioned above. After 30 and 90 days, the animals were euthanized and the material was subjected to histotechnical processing. A quantitative microscopic analysis was performed using an Axio Imager.M1 (Zeiss) microscope coupled to an AxioCam MRc5 (Zeiss) camera. A complete description of the characteristics of the apical and periapical tissues was performed and the number of inflammatory cells, size of the periapical lesions (in mm2), presence of bone resorption and presence of sealing of the apical opening with mineralized tissue deposition was determined on microscopic images obtained from hematoxylin and eosin-stained histological sections, using the Software AxioVision Rel.4.6 (Automatic Measurements Programs Program Wizard). Data were examined for their distribution and the compared using analysis of variance (ANOVA) followed by Tukeys post-test with a 5% significance level. Presence and extension of an inflammatory infiltrate, predominantly mononuclear, beyond half of the periodontal ligament was observed for all sealers, at both 30-day and 90-day periods. There was no modulation of the inflammatory infiltrate for any of the sealers because the number of inflammatory cells was similar at both 30-day and 90-day periods (p>0.05). Bone and radicular resorption areas were found in approximately 50% of the cases at 90 days for EndoREZ and Real Seal, and in 30% of the cases at the 30-day and 90-day periods for Sealapex. The periapical lesion size was similar at both experimental periods (30 and 90 days) for all evaluated sealers. Finally, sealing of the apical opening with mineralized tissue deposition was observed at 90 days in approximately 20%, 30% and 50% of the cases for EndoREZ, Real Seal and Sealapex, respectively; and in 15% dos cases, at the 30-day period, only for Sealapex. Within the limitations of this experiment, it may be concluded that the resin-based sealers EndoREZ and Real Seal were not well tolerated by the apical and periapical tissues. Periapical tissue repair, with cementum deposition, was found in the teeth filled with Sealapex, although complete repair of the periapical lesions was not observed.
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Free View Rendering for 3D Video : Edge-Aided Rendering and Depth-Based Image InpaintingMuddala, Suryanarayana Murthy January 2015 (has links)
Three Dimensional Video (3DV) has become increasingly popular with the success of 3D cinema. Moreover, emerging display technology offers an immersive experience to the viewer without the necessity of any visual aids such as 3D glasses. 3DV applications, Three Dimensional Television (3DTV) and Free Viewpoint Television (FTV) are auspicious technologies for living room environments by providing immersive experience and look around facilities. In order to provide such an experience, these technologies require a number of camera views captured from different viewpoints. However, the capture and transmission of the required number of views is not a feasible solution, and thus view rendering is employed as an efficient solution to produce the necessary number of views. Depth-image-based rendering (DIBR) is a commonly used rendering method. Although DIBR is a simple approach that can produce the desired number of views, inherent artifacts are major issues in the view rendering. Despite much effort to tackle the rendering artifacts over the years, rendered views still contain visible artifacts. This dissertation addresses three problems in order to improve 3DV quality: 1) How to improve the rendered view quality using a direct approach without dealing each artifact specifically. 2) How to handle disocclusions (a.k.a. holes) in the rendered views in a visually plausible manner using inpainting. 3) How to reduce spatial inconsistencies in the rendered view. The first problem is tackled by an edge-aided rendering method that uses a direct approach with one-dimensional interpolation, which is applicable when the virtual camera distance is small. The second problem is addressed by using a depth-based inpainting method in the virtual view, which reconstructs the missing texture with background data at the disocclusions. The third problem is undertaken by a rendering method that firstly inpaint occlusions as a layered depth image (LDI) in the original view, and then renders a spatially consistent virtual view. Objective assessments of proposed methods show improvements over the state-of-the-art rendering methods. Visual inspection shows slight improvements for intermediate views rendered from multiview videos-plus-depth, and the proposed methods outperforms other view rendering methods in the case of rendering from single view video-plus-depth. Results confirm that the proposed methods are capable of reducing rendering artifacts and producing spatially consistent virtual views. In conclusion, the view rendering methods proposed in this dissertation can support the production of high quality virtual views based on a limited number of input views. When used to create a multi-scopic presentation, the outcome of this dissertation can benefit 3DV technologies to improve the immersive experience.
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Rätten till naturaprestation : Bortfaller rätten efter det att ett långvarigt embargo har lyfts?Aziz, Diden January 2013 (has links)
Export is a top priority for Sweden's economy but for Swedish companies it may involve uncomfortable risks of exporting without sincere consideration. When the United Nations Security Council puts an embargo against a country, this often mean an import and export restriction. The thought is to push undemocratic regimes into respecting human rights. When the embargo is in force, however, the parties are not able to fulfill their contractual obligations, which practically means that the agreement will be suspended. The problem is what happens when an embargo is in force for a longer period of time. After the embargo is withdrawn, the price on the market may have changed significantly, which indicates a financial sacrifice for a seller if he has to provide specific performance to the buyer. The question thus is whether the seller, after a prolonged economic sanctions is withdrawn, still is obliged to provide specific performance? The United Nations Convention on Contracts for the International Sale of Goods (CISG) is applicable where both parties are signatories to CISG or by rules of international private law. To require performance as a buyer is a general right in Article 46 CISG, but there are exceptions to this rule in Article 28 CISG. Article 28 CISG states that if one party is entitled to require performance of any obligation by the other party, a court is not bound to enter a judgment for specific performance unless the court would do so under its own law in respect of similar contracts of sale not governed by this Convention. Since CISG advocates a harmonized application of international trade, the right to specific performance cannot be waived just on the basis of Article 28 CISG alone. With regard to good faith in international trade in Article 7 (1) CISG, the principle of reasonableness, which is a general principle that the CISG is based upon in accordance with Article 7 (2) CISG and 7.2.2 (b) UPICC, and with the support of international usage regularity observed in the trade concerned in Article 9 CISG, the right to specific performance does not exist anymore after a prolonged embargo has been withdrawn. / Export är högprioriterat för Sveriges ekonomi men för svenska företag kan det inne-bära obekväma risker med att exportera utan eftertanke. När Förenta Nationernas säkerhetsråd går in och lägger ett embargo mot en stat innebär detta ofta en import- och export restriktion. Tanken är att pressa odemokratiska regimer att respektera mänskliga rättigheter. När embargot är i kraft kan dock parterna inte uppfylla sina avtalsförpliktelser vilket innebär att avtalet blir suspenderat. Det problematiska är vad som händer då ett embargo är i kraft under en längre tid. Efter det att ett embargo lyfts kan priset på marknaden ändrats avsevärt vilket innebär en ekonomisk uppoffring för en säljare att tvingas fullgöra i natura. Frågan blir då om säljare efter det att en långvarig ekonomisk sanktion lyfts, fortfarande är tvingen att fullgöra i natura? Lag (1987:822) om internationella köp(CISG) blir tillämplig i det fall då båda parters stater är signatärer eller genom privaträttsliga regler. Att kräva fullgörelse som köpare är en generell rätt i artikel 46 CISG men det finns ett explicit undantag till denna regel i artikel 28 CISG. Artikel 28 CISG stadgar att domstol som ska lösa tvisten, inte är skyldig att meddela dom på fullgörelse om domstol enligt egen forumlandets egen lagstiftning inte skulle ha gjort detta. Skulle tvisten lösas i Svensk domstol blir 23 § köplag (1990:931) tillämplig. Eftersom CISG förespråkar en harmoniserad tillämpning inom internationell handel är det inte tillförlitligt att mena på att rätten till fullgörelse bortfaller med stöd av endast artikel 28 CISG. Med beaktande av god sed i internationell handel i artikel 7(1) CISG, principen om rimlighet/förnuftig person som är en generell princip som CISG är baserat på i enlighet med artikel 7(2) CISG och 7.2.2 (b) UPICC, samt med stöd av handelsbruk i artikel 9 CISG, bortfaller rätten till fullgörelse i natura efter det att ett långvarigt embargo har lyfts.
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Contribution de la planification expérimentale à la modélisation de phénomènes complexes en formulation / Experimental designs for complex phenomena in formulationGomes, Charles 20 December 2018 (has links)
Dans certains domaines de la formulation, comme la cosmétique, les phénomènes étudiés peuvent être très chaotiques avec des zones de rupture ou de non linéarité. Dans ce cas, le formulateur doit se poser de nombreuses questions avant de proposer la stratégie expérimentale optimale qui doit être adaptée au mieux à son problème. Pour de tels phénomènes, des plans d'expériences classiques, tels que les réseaux de Scheffé ou les plans D-optimaux, se révèlent insuffisants car les points expérimentaux ne couvrent pas uniformément l'espace expérimental. En effet, il est intéressant dans ces cas d'étude d'explorer l'ensemble du domaine expérimental et de répartir uniformément les points dans l'espace. Pour cela, les plans uniformes ou Space-Filling Designs (SFD), fréquemment utilisés dans le cas de variables orthogonales, mais très peu dans le cas des variables de mélange, sont particulièrement intéressants. L'objectif de cette thèse est d’adapter des algorithmes de construction de plans uniformes dans le cas de plans de mélanges, de proposer des règles simples pour aider au choix de la nature et du nombre de points du plan d'expériences de mélange / In some domains of formulation, as cosmetics, the phenomena can be very chaotic with discontinuities or not linear zones. In the cosmetic field, the formulator has to propose the optimal experimental strategy which must be well adapted to the constraints imposed by the experimenters. For such phenomena, classical designs of experiments, such as Scheffé simplexes lattices or the D-optimal designs, are proving insufficient because the experimental points do not uniformly cover the experimental space. Indeed, it is essential in these studies to explore the whole experimental domain and to uniformly distribute points in the space. For that purpose, the Space-Filling Designs (SFD), frequently used in the case of orthogonal variables, but less in the case of the mixture variables, are particularly interesting. The objective of this thesis is to adapt the algorithms for construction of uniform designs in the case of mixture designs and to propose guidelines for the choice of the nature and the number of points of the experimental design
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Hydrogen storage systems : Methodology and model development for hydrogen storage systems performance evaluation based on a transient thermodynamic approachMargaritari, Kreshnik January 2023 (has links)
The overall performance of a hydrogen storage system can be affected by various parameters, such as operation and design parameters, but also by the state of the hydrogen contained inside the storage tanks. In this work, a methodology is developed to evaluate the state of the hydrogen during the filling process and its impact on the overall system performance under variable operation conditions and design parameters. To approach as close as possible hydrogen as real gas, the thermodynamic properties of it are obtained from experimental thermodynamic tables. Based on those thermodynamic tables, a discrete database for each thermodynamic property is constructed. To minimize the error and achieve acceptable execution time, a searching method based on curve fitting techniques is developed to derive the thermodynamic properties from the discretized data. The evaluation of the hydrogen state is done based on a developed method that derives the pressure and temperature based on calculated thermodynamic properties during the filling process. The interaction between the contained hydrogen and tank during the filling process is taken into account during the methodology development. Furthermore, energy requirements for the compression system of the hydrogen storage system, including the cooling demand, are also included in the methodology. Based on the developed methodology, a transient model that can evaluate the hydrogen state condition, storage tank wall temperature condition, and energy requirement of the storage system is developed. Validation against experimental and simulation results for an actual filling event of a hydrogen storage tank is done, showing good agreement in the results. The model was used to simulate the performance of a hydrogen storage system, inspired in terms of layout by a real-world HRS storage system. The results showed that the total amount of filled hydrogen and the filling duration of the charging process are greatly affected by the compression and heat transfer phenomena occurring inside the tank. The storage tanks with lower volumes and higher operation pressure tend to be more affected by compression and heat transfer phenomena. Operation parameters such as inlet mass flow and inlet temperature, can have an impact on the system, both in terms of energy consumption and filling performance. Furthermore, based on the investigation of compression stages, the results showed that the number of stages can affect the compression ratio of each stage, resulting in lower or higher efficiency, which directly affects the energy consumption of the compression system. A parametric investigation of the upper operation pressures of the hydrogen tanks showed that the total amount of stored hydrogen is affected when the respective upper pressures vary. Last, it was shown that there is an optimal upper pressure level for each bank that can result in lower specific compression energy, indicating that the model could be used for optimization purposes.
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Specific mold filling characteristics of highly filled phenolic injection molding compoundsScheffler, Thomas, Englich, Sascha, Gehde, Michael 08 March 2016 (has links) (PDF)
Thermosets show excellent mechanical properties and chemical resistance (for most automotive fluids) even at high temperatures up to 300 °C. Furthermore they can be highly efficient processed by injection molding. So they should be particularly suited for e.g. under the bonnet applications. However, the reality shows that thermosets are, except fiber reinforced composites, heavily underrepresented in technical applications. E.g. thermosetting components only account 0,2 % to a vehicle’s weight. Therefore reasons can be found in limited knowledge, e.g. relating mold filling behavior.
The objective of the study is to analyze the influence of the mold filling behavior during injection molding of highly filled phenolic compounds on mechanical properties. Injection molding filling studies, mechanical testing and optical microscopy were done while varying mold geometry (injection gate and cavity height), mold temperature and injection rate during injection molding a highly filled phenolic compound. It was found that the mold filling behavior varies with altered injection molding parameters as well as the mold geometry. In consequence of this the mechanical properties change according to the resulting reinforcement orientation. The results can help to improve part and mold design for optimal load transmission.
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Optimisation of the VARTM processStruzziero, Giacomo January 2014 (has links)
This study focuses on the development of a multi-objective optimisation methodology for the vacuum assisted resin transfer moulding composite processing route. Simulations of the cure and filling stages of the process have been implemented and the corresponding heat transfer and flow through porous media problems solved by means of finite element analysis. The simulations involved material sub-models to describe thermal properties, cure kinetics and viscosity evolution. A Genetic algorithm which constitutes the foundation for the development of the optimisation has been adapted, implemented and tested in terms of its effectiveness using four benchmark problems. Two methodologies suitable for multi-objective optimisation of the cure and filling stages have been specified and successfully implemented. In the case of the curing stage the optimisation aims at finding a cure profile minimising both process time and temperature overshoot within the part. In the case of the filling stage the thermal profile during filling, gate locations and initial resin temperature are optimised to minimise filling time and final degree of cure at the end of the filling stage. Investigations of the design landscape for both curing and filling stage have indicated the complex nature of the problems under investigation justifying the choice for using a Genetic algorithm. Application of the two methodologies showed that they are highly efficient in identifying appropriate process designs and significant improvements compared to standard conditions are feasible. In the cure process an overshoot temperature reduction up to 75% in the case of thick component can be achieved whilst for a thin part a 60% reduction in process time can be accomplished. In the filling process a 42% filling time reduction and 14% reduction of degree of cure at the end of the filling can be achieved using the optimisation methodology. Stability analysis of the set of solutions for the curing stage has shown that different degrees of robustness are present among the individuals in the Pareto front. The optimisation methodology has also been integrated with an existing cost model that allowed consideration of process cost in the optimisation of the cure stage. The optimisation resulted in process designs that involve 500 € reduction in process cost. An inverse scheme has been developed based on the optimisation methodology aiming at combining simulation and monitoring of the filling stage for the identification of on-line permeability during an infusion. The methodology was tested using artificial data and it was demonstrated that the methodology is able to handle levels of noise from the measurements up to 5 s per sensor without affecting the quality of the outcome.
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Physical and Chemical Properties of a New Mineral Trioxide Aggregate MaterialSpencer, David Lowell 01 January 2004 (has links)
The objective of this study was to compare the time to final set and compressive strength of the white mineral trioxide aggregate (MTA) formulation to the original grey MTA. To test compressive strength, each MTA formulation was placed into Teflon split molds for four hours at 37° Celsius (C) and 100% humidity. Compressive strength of both MTA formulations was measured at 24 hours (n=12) and 21 days (n=19) using an Instron Testing Machine. For determination of time to final set, each MTA formulation (n=6) was placed into a metal mold and maintained at 37° C and 100% humidity while setting. At five-minute time intervals, an indenter needle was lowered onto the surface of the MTA material and allowed to remain in place for five seconds before it was removed from the specimen surface. This process was repeated until the needle failed to make a complete circular indentation in the MTA specimen. Results of a two-way ANOVA indicate that white MTA had a significantly higher compressive strength (mean=32.7 MPa) than grey MTA (mean=25.2 MPa) at 24 hours and no statistically significant differences at 21 days (white mean=38.6 MPa and grey mean=38.0 MPa). Using one-way ANOVA, results indicate that grey MTA had a significantly longer time to final setting time (mean=296 min) compared to white MTA (mean=276 min). Based on this study, the results suggest that white MTA is an effective substitute for grey MTA.
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