No description available.

Laser welding was investigated as a potential joining technology for alumina ceramic substrates. The objective of this study was to develop a method to preheat the ceramic using a single defocused laser beam prior to welding. Engineering ceramics are employed in a variety of systems and environments due to their unique properties. Joining technologies must be developed to facilitate the manufacture of complex or large ceramic components. Laser welding is advantageous as it forms joints rapidly, and does not introduce intermediate materials to form the bond, which can have deleterious effects. The Laser Machining System (LMS) at Queen’s University was adapted for this study. A defocused far-infrared (FIR) laser beam was positioned to overlay a focused near-infrared (NIR) laser beam; the defocused FIR beam preheated the ceramic substrate and the focused NIR beam formed the weld. A finite element model was developed in COMSOL MultiPhysics to simulate the preheating processes and to develop a preheating protocol. The protocol was implemented using the FIR beam and adjusted to achieve preheating temperatures of 1450, 1525, and 1600degC. Welds were performed on 1 mm thick alumina plates using the preheating protocols and NIR beam powers of 25, 50, and 75 W. Weld speed was held constant throughout the study at 0.5 mm/s. The preheating protocols were successful at achieving near-constant preheating temperatures, with standard deviations below 32 degrees. Partially penetrating welds were formed with the NIR beam at 25 W, and fully penetrating welds at 50 and 75 W. Large pores were present in the 25 W and 50 W welds. Minimal porosity was observed in the welds formed at 75 W. All of the welded plates experienced a transverse fracture that extended perpendicular to weld, and a longitudinal fracture extending parallel to the weld. This study shows that a fixed defocused laser beam can successfully preheat alumina substrates to the high temperatures required for welding; however, non-homogenous cooling results in fracture. Increasing the preheating beam diameter or introducing an auxiliary means to provide a controlled cool-down cycle may mitigate these effects. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-04-29 17:59:57.43

Today it is possible to create veneers that are aesthetically and functionally satisfying, but there are some factors that may compromise the aesthetic results.  The aim of this study was to investigate influence of cement shades and ceramic thickness on the colour of ceramic veneers, but also to study how well try-in pastes match with their corresponding cements. PubMed was used to search for papers using MeSH-terms and keywords. 144 titles and abstracts were read, 29 full texts were read and 24 papers were used in the analysis. All of the studies were in vitro. In 20 studies, it was found that the cement shade influences the colour of the ceramic veneer. Two studies reported that the cement shade had no influence on the colour of ceramic veneers, and two did not draw any conclusions regarding the influence of cement shade. Twelve studies compared different thicknesses of the veneers; all of them found that the thicknesses had an influence on the colour of the veneers. Two out of four studies found no compatibility between try-in pastes and their corresponding cements, while two studies found compatibility for some try-in pastes. The shades of cement and thicknesses of ceramic veneers can influence the colour of the ceramics. The colour of try-in pastes does not always show a similarity with their corresponding cement.

Approved for public release; distribution is unlimited / A simple low-noise hydrophone design with internal preamplifier is presented. This design is similar to published designs and is a variation of the design developed in the NPS thesis by Miguel Alvarado [2003], except that several improvement features are included. These include a simplification of the structure and its modes of vibration, a large reduction in package diameter and the effect its acoustic diffraction has on the sensitivity, and an extended upper frequency response of 42 kHz resulting from the simplified structure and reduced diameter. Furthermore, the modified geometry along with its orientation in the water should produce a very omni-directional response in the horizontal plane at the higher frequencies. Finally, an new feedback preamplifier design developed by Hofler and Alvarado was discovered to have some subtle but serious performance problems. These problems were resolved in this research and the resulting preamplifier performance was tested and documented herein. / Lieutenant, Hellenic Navy

The past few years have delivered a great deal of development in the area of Layered Manufacturing. The challenge is to apply the existing technologies to existing and/or new manufacturing systems, thereby adding value to these systems. The advances in the field of Layered Manufacturing range from the process of slicing to the actual building process. The main achievements in the arena of slicing have been in the advances of Adaptive Slicing. By not using a uniform slice thickness, not only is the stair stepping effect minimized, but the build time is also shortened. Many advances have been made in terms of the actual materials used and the process of building, thereby expanding the range of uses for the technology as a whole. With the extension in the variety of materials available for use with the technology, new uses become more than mere possibility and actually become viable. The use of Layered Manufacturing in the case of the CSIR was not the focus of the original experiment, but was a method to test the results of their main experiments – namely, research into the properties of ceramic materials and their use in the realm of medicine. The research of the CSIR focuses on the use of ceramic materials for the purpose of bone implants, which is a problem area in medicine. The machine they built in order to test the properties of the new materials they invent, uses Layered Manufacturing as a building process. What the CSIR lacks are the backend systems to enable the building of more complex experimental parts, as they have no way of going from design to a full build. This research project focuses on proving that the technologies involved in Layered Manufacturing will add value to the CSIR’s research. By implementing a system that takes advantage of existing software, and by using custom software to make it applicable to the environment the CSIR is currently operating in, their research could be speeded up tremendously without putting too much strain on their budget. What has been achieved is a simple system which employs the use of available technologies and software packages, and which requires no changes to the hardware of the current process used, such as the Rapid Prototyping machine. / Ehlers, E.M., Prof.

M.Tech. (Industrial Design) / The research project entitled: The Analysis of Clay Materials for use in a Ceramic Studio was undertaken in order to give a quantitative base to the understanding of clay materials and their role in clay bodies. The project consists of analysing the clay materials as they are supplied, using technically sophisticated equipment. A set of data for each of the nine chosen clays was assembled and then correlated for easier comparison. The clay materials were then mixed into clay bodies using a set proportion in order that a comparison of the nine clay bodies could be made and related to the data assembled for the clay materials. The data collected, as well as the ceramic calculations used in the research project were entered into the "Insight" Ceramic software programme for use in the studio. This data base will be the foundation for ongoing research into ceramic materials.

This project analyzes a database of 118 ceramic sherds that were excavated from the Late Intermediate Period site of Yanaorco, located in the Cajamarca region of the north highlands in present-day Peru, for vessel form, style, and imagery. Through the placement of these sherds within the context of inter-community feasting events that took place at Yanaorco, fineware ceramic vessels are interpreted as prestige items that were utilized by the elite to further differentiate themselves from other community citizens. By examining key examples of representational and non-representational imagery depicted on the sherds, an understanding of the social agency of the vessel and the esoteric knowledge that the imagery communicated to feasting participants is explored. The use of fineware ceramic vessels during feasting events at the site of Yanaorco served to ideologically reinforce or manipulate social, political, and economic stratification.

No description available.

O propósito deste trabalho foi avaliar, in-vitro, a alteração de cor da cerâmica de dissilicato de lítio (IPS e.max Ivoclar Vivadent AG), variando-se os seguintes aspectos: processo de confecção (cerâmica monolítica e com a infraestrutura coberta por cerâmica de revestimento), espessura da cerâmica (1,5 e 2,0mm) e substrato (resina e liga metálica), com e sem cimento. Para isso foram confeccionadas 40 pastilhas de cerâmica IPS e.max Press (Ivoclar Vivadent AG), que foram divididas em 2 grupos (n=20): LT (cerâmica de baixa translucidez na cor A2) e HO (cerâmica de alta opacidade). Neste último grupo, as pastilhas foram confeccionadas com 0,5mm de espessura revestidas com cerâmica IPS e.max Ceram na cor A2 (Ivoclar Vivadent AG) com espessuras de 1,0 e 1,5mm. Foram utilizados substratos em resina composta (n=20) e liga metálica (n=20). Para o substrato em resina foi empregada a resina Filtek® Z250 XT, na cor A2 (3M ESPE) e para o substrato em liga metálica foi utilizado a liga de cobre-alumínio (Goldent L.A,). Para a cimentação foi utilizado o cimento de polimerização dual, Variolink II, (Ivoclar Vivadent AG), na cor translúcida. A leitura da cor foi realizada em um espectrofotômetro (Minolta CM2600d), equipado com fonte de luz padrão D65 (luz do dia). A cor determinada no aparelho é expressa em coordenadas CIE L* a* b* e os valores correspondentes foram utilizados para calcular o &#x394;E. Foram feitas comparações do grupo somente com a cerâmica (controle) versus os grupos cerâmica-substrato sem e com cimento; e dos grupos cerâmica-substrato sem cimento (controle) versus cerâmica-substrato com cimento. Os dados foram submetidos a análise estatística (ANOVA e teste de Tukey, p<0,05). Quando foram comparados o grupo somente com a cerâmica (controle) versus os grupos cerâmicasubstrato sem e com cimento, os resultados mostraram que o menor valor (&#x394;E=3,0) foi o do grupo HOA2 com 2mm de espessura, substrato de metal e sem cimento; o maior valor encontrado (&#x394;E=10,0) foi do grupo LTA2 com 1,5mm de espessura, com substrato de metal e com cimento. Esta diferença foi estatisticamente significante. E quando foram comparados os grupos cerâmica-substrato sem cimento (controle) versus cerâmica-substrato com cimento os resultados apontaram que o grupo que teve menor influência do cimento foi o HOA2 com 1,5mm de espessura e substrato de resina (&#x394;E=1,1); o grupo que teve maior influência do cimento foi o LTA2 com 1,5mm de espessura e com substrato de metal (&#x394;E=6,4). Esta diferença foi estatisticamente significante. Dentro das limitações deste estudo, concluiu-se que as variáveis pesquisadas o processo de confecção e a espessura da cerâmica, a cor do substrato e a presença do cimento, influenciaram significativamente na cor da cerâmica. / The purpose of this study was to evaluate in vitro, the color change of the ceramic lithium disilicate (IPS e.max - Ivoclar Vivadent AG), varying the following aspects: manufacture process (monolithic ceramic and the infrastructure with ceramic covering), the thickness of the ceramic (1.5 and 2.0 mm) and the abutment substrate (composite resin and alloy), with and without cement. Forty discs were fabricated with ceramic IPS e.max Press (Ivoclar Vivadent AG), which were divided into two groups (n = 20): LT (low translucency, shade A2) and HO (high opacity). In the latter group, the discs were fabricated with a 0.5 mm thickness with the IPS e.max Ceram ceramic covering, shade A2 (Ivoclar Vivadent AG) with 1.0 and 1.5 mm thicknesses. The abutments substrates were composite resin (n = 20) and alloy (n = 20). The composite resin substrate was made with the Filtek Z250 XT ®, shade A2 (3M ESPE) and the metallic alloy substrate was made with aluminum-copper alloy (Goldent LA). The cementation was realized with dual cure cement Variolink II, translucent color (Ivoclar Vivadent AG). The color was measured in a spectrophotometer (Minolta CM2600d) equipped with a D65 light (daylight). The color determined on the equipment is expressed in coordinates CIE L * a * b *, and those values were used to calculate the &#x394;E. The comparisons were only made between the ceramic groups (control) versus the ceramic-substrate with and without cement; and the ceramic-substrate without cement groups (control) versus the ceramic-substrate with cement. The data were subjected to statistical analysis (ANOVA and Tukey test, p < 0.05). When the comparisons between the groups were only the ceramic (control) versus the ceramic-substrate groups, without and with cement, the results showed that the smallest value (&#x394;E=3.0) of the HOA2 group with 2 mm of thickness, metal substrate and without cement; the largest value found (&#x394;E=10.0) was that of the LTA2 group with a 1.5 mm thickness, with a metal substrate and with cement. This difference was statistically significant. When the comparisons were between the ceramic-substrate without cement groups (control) versus the ceramic-substrate with cement groups, the results showed that the group that had less influence of the cement was the HOA2 group with a 1.5 mm thickness with a composite resin substrate (&#x394;E=1.1). The group that had the greatest influence of the cement was the LTA2 with a 1.5 mm thickness and with a metal substrate (&#x394;E=6.4). This difference was statistically significant. Within the limitations of this study, it is concluded that the studied variables - the manufacture process and the thickness of ceramic, the color of the abutment substrate and the presence of the cement has a significant influence on the color of the ceramic.

O propósito deste trabalho foi avaliar, in-vitro, a alteração de cor da cerâmica de dissilicato de lítio (IPS e.max Ivoclar Vivadent AG), variando-se os seguintes aspectos: processo de confecção (cerâmica monolítica e com a infraestrutura coberta por cerâmica de revestimento), espessura da cerâmica (1,5 e 2,0mm) e substrato (resina e liga metálica), com e sem cimento. Para isso foram confeccionadas 40 pastilhas de cerâmica IPS e.max Press (Ivoclar Vivadent AG), que foram divididas em 2 grupos (n=20): LT (cerâmica de baixa translucidez na cor A2) e HO (cerâmica de alta opacidade). Neste último grupo, as pastilhas foram confeccionadas com 0,5mm de espessura revestidas com cerâmica IPS e.max Ceram na cor A2 (Ivoclar Vivadent AG) com espessuras de 1,0 e 1,5mm. Foram utilizados substratos em resina composta (n=20) e liga metálica (n=20). Para o substrato em resina foi empregada a resina Filtek® Z250 XT, na cor A2 (3M ESPE) e para o substrato em liga metálica foi utilizado a liga de cobre-alumínio (Goldent L.A,). Para a cimentação foi utilizado o cimento de polimerização dual, Variolink II, (Ivoclar Vivadent AG), na cor translúcida. A leitura da cor foi realizada em um espectrofotômetro (Minolta CM2600d), equipado com fonte de luz padrão D65 (luz do dia). A cor determinada no aparelho é expressa em coordenadas CIE L* a* b* e os valores correspondentes foram utilizados para calcular o &#x394;E. Foram feitas comparações do grupo somente com a cerâmica (controle) versus os grupos cerâmica-substrato sem e com cimento; e dos grupos cerâmica-substrato sem cimento (controle) versus cerâmica-substrato com cimento. Os dados foram submetidos a análise estatística (ANOVA e teste de Tukey, p<0,05). Quando foram comparados o grupo somente com a cerâmica (controle) versus os grupos cerâmicasubstrato sem e com cimento, os resultados mostraram que o menor valor (&#x394;E=3,0) foi o do grupo HOA2 com 2mm de espessura, substrato de metal e sem cimento; o maior valor encontrado (&#x394;E=10,0) foi do grupo LTA2 com 1,5mm de espessura, com substrato de metal e com cimento. Esta diferença foi estatisticamente significante. E quando foram comparados os grupos cerâmica-substrato sem cimento (controle) versus cerâmica-substrato com cimento os resultados apontaram que o grupo que teve menor influência do cimento foi o HOA2 com 1,5mm de espessura e substrato de resina (&#x394;E=1,1); o grupo que teve maior influência do cimento foi o LTA2 com 1,5mm de espessura e com substrato de metal (&#x394;E=6,4). Esta diferença foi estatisticamente significante. Dentro das limitações deste estudo, concluiu-se que as variáveis pesquisadas o processo de confecção e a espessura da cerâmica, a cor do substrato e a presença do cimento, influenciaram significativamente na cor da cerâmica. / The purpose of this study was to evaluate in vitro, the color change of the ceramic lithium disilicate (IPS e.max - Ivoclar Vivadent AG), varying the following aspects: manufacture process (monolithic ceramic and the infrastructure with ceramic covering), the thickness of the ceramic (1.5 and 2.0 mm) and the abutment substrate (composite resin and alloy), with and without cement. Forty discs were fabricated with ceramic IPS e.max Press (Ivoclar Vivadent AG), which were divided into two groups (n = 20): LT (low translucency, shade A2) and HO (high opacity). In the latter group, the discs were fabricated with a 0.5 mm thickness with the IPS e.max Ceram ceramic covering, shade A2 (Ivoclar Vivadent AG) with 1.0 and 1.5 mm thicknesses. The abutments substrates were composite resin (n = 20) and alloy (n = 20). The composite resin substrate was made with the Filtek Z250 XT ®, shade A2 (3M ESPE) and the metallic alloy substrate was made with aluminum-copper alloy (Goldent LA). The cementation was realized with dual cure cement Variolink II, translucent color (Ivoclar Vivadent AG). The color was measured in a spectrophotometer (Minolta CM2600d) equipped with a D65 light (daylight). The color determined on the equipment is expressed in coordinates CIE L * a * b *, and those values were used to calculate the &#x394;E. The comparisons were only made between the ceramic groups (control) versus the ceramic-substrate with and without cement; and the ceramic-substrate without cement groups (control) versus the ceramic-substrate with cement. The data were subjected to statistical analysis (ANOVA and Tukey test, p < 0.05). When the comparisons between the groups were only the ceramic (control) versus the ceramic-substrate groups, without and with cement, the results showed that the smallest value (&#x394;E=3.0) of the HOA2 group with 2 mm of thickness, metal substrate and without cement; the largest value found (&#x394;E=10.0) was that of the LTA2 group with a 1.5 mm thickness, with a metal substrate and with cement. This difference was statistically significant. When the comparisons were between the ceramic-substrate without cement groups (control) versus the ceramic-substrate with cement groups, the results showed that the group that had less influence of the cement was the HOA2 group with a 1.5 mm thickness with a composite resin substrate (&#x394;E=1.1). The group that had the greatest influence of the cement was the LTA2 with a 1.5 mm thickness and with a metal substrate (&#x394;E=6.4). This difference was statistically significant. Within the limitations of this study, it is concluded that the studied variables - the manufacture process and the thickness of ceramic, the color of the abutment substrate and the presence of the cement has a significant influence on the color of the ceramic.