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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Washboarding of Corrugated Cardboard

Wendler, Sven Dieter, not supplied January 2006 (has links)
The aims of the thesis were to study how washboarding (the undulations present on the surface of corrugated cardboard used to manufacture boxes) relates to the mechanical properties of paper and the board manufacturing conditions and to examine the impact of washboarding upon the structural integrity and printability of corrugated cardboard packaging. A digital image profilometry technique was developed to measure the washboarding profiles of corrugated board. This technique was used to measure the washboarding depth and profiles for a range of corrugated boards, some constructed manually and some machine manufactured. This enabled a study into how a change in the mechanical properties of paper and glue affect washboarding depth. The effect that the speed of machine manufacturing had upon the degree of washboarding was also determined. A study of how environmental conditions affect washboarding geometry was undertaken. The effects of the extent of washboarding upon a range of board performance measures were tested empirically and modelled using Finite Element Analysis. These were edgewise compression testing (ECT), three-point bend, and MD-Shear (an Amcor Ltd. proprietary test). A method was developed to measure full-tone print coverage of corrugated board and was used to study how washboarding affects the printing quality of corrugated board.
22

Inspection to 3-D deformation of a dynamic object using fringe projection techniques

Ko, Wei-Ting 18 July 2012 (has links)
A projected fringe profilometry (PFP) is a wide optical measurement technology to gauge the three dimensional appearance of object.Because of non-contact type , the short retrieve time and low environmental effect,PFP was usually used in many fields.PFP has become rather efficient and precise on gauging the three dimensional appearance of the static obiect because of its persistent development in recent years.However,it is still not mature yet to gauge the dynamic object. If we could develop a gauging way in the dynamic object , the application would be more widespread. First of all,using PFP as the gauging principle and utilzing the math algorithm for analyzing the changes between the dynamic measured object and the blurred fringes.Secondly,reconstructed the inspected object's three dimensional appearance and the velocity. Finally,found out the deformation of the measured object. The technology of this thesis broke through the typical measurement of velocity.We could analyze the velocities of three dimentional dirtions by only single optic imformation.
23

SUPER RESOLUTION 3D SCANNING USING SPATIAL LIGHT MODULATOR AND BAND CORRECTION

Pethe, Akshay 01 January 2008 (has links)
Multi Frequency Phase Measuring Profilometry is the most popular lateral contact 3-D Scanning technique. The Phase Measuring Profilometry is limited in resolution by the projector and cameras used. Conventional signal projectors have a maximum of 2000 to 4000 scan lines limiting the projector resolution. To obtain greater detail with higher resolution the PMP technique is applied to a Spatial Light Modulator (SLM) having 12000 lines, very large as compared to conventional projectors. This technology can achieve super resolution scans having varied applications. Scans achieved from PMP suffer from a certain type of artifact called “banding” which are periodic bands across the captured target. This leads to incorrect measurement of surfaces. Banding is the most limiting noise source in PMP because it increases with lower frequency and decrease in number of patterns. The requirement for lager number of patterns increases the possibility of motion banding. The requirement for higher frequency leads to the necessity for multifrequency PMP which, again leads to more patterns and longer scan times. We aim to reduce the banding by correcting the phase of the captured data.
24

Motion Correction Structured Light using Pattern Interleaving Technique

Cavaturu, Raja Kalyan Ram 01 January 2008 (has links)
Phase Measuring Profilometry (PMP) is the most robust scanning technique for static 3D data acquisition. To make this technique robust to the target objects which are in motion during the scan interval a novel algorithm called ‘Pattern Interleaving’ is used to get a high density single scan image and making Phase Measuring Profilometry insensitive to ‘z’ motion and prevent motion banding which is predominant in 3D reconstruction when the object is in motion during the scan time
25

Análise in situ da irradiação com laser de Er:YAG no controle da progressão de lesões de erosão e abrasão do esmalte dental / In situ analysis of Er:YAG laser irradiation to control the progression of erosive and abrasive lesions on tooth enamel

Renata Siqueira Scatolin 06 February 2015 (has links)
Este estudo, composto por 2 experimentos in situ, teve como objetivo avaliar o efeito do laser de Er:YAG no controle da progressão de lesões de erosão e abrasão no esmalte dental. Incisivos bovinos foram seccionados (5x3x2,5mm), planificados e polidos. Os fragmentos de esmalte (KHN=330±10%) tiveram parte da superfície coberta com resina composta (área de referência), e posteriormente foram submetidos à formação de lesões erosivas com ácido cítrico 1% (pH = 2,3), 5 minutos, 2x/dia, durante 2 dias. No primeiro experimento, 56 espécimes foram divididos em dois grupos de acordo com o tratamento de superfície: irradiados com laser de Er:YAG (5,2J/cm2, 2Hz, 85mJ, 10s) e não irradiados, e subdivididos de acordo com o tipo de desgaste: erosivos (ácido cítrico) e não erosivos (água deionizada). A realização dos desafios foi realizada através da imersão dos dispositivos em 100mL de ácido cítrico ou água deionizada, 3x/dia, de maneira alternada e independente. O desgaste do esmalte foi determinado por um perfilômetro óptico 3D após: formação inicial da lesão erosiva, tratamento da superfície e fase intraoral. A avaliação de desgaste foi verificada por meio de três leituras de cada área em relação a área de referência. Os dados foram analizados através da análise de variância (ANOVA) e do teste Tukey. No primeiro experimento quando utilizou-se água deionizada (desafios não erosivos) na fase intraoral, os espécimes apresentaram menores valores de desgaste comparados aos grupos que foram erodidos, independentemente de terem sido irradiados ou não com laser de Er:YAG. No entanto, quando erodidos na fase intraoral, o grupo irradiado com laser de Er:YAG não diferiu do grupo não irradiado. O desgaste do esmalte foi avaliado qualitativamente por microscopia eletrônica de varredura em 3 espécimes de cada grupo. No segundo experimento, 48 espécimes foram divididos em dois grupos de acordo com o tratamento de superfície: irradiados com laser de Er:YAG (5,2 J/cm2, 2Hz, 85mJ, 10s) e não irradiados, e subdivididos de acordo com o tipo de desgaste: erosivos (ácido cítrico) e erosivos associado a abrasão (ácido cítrico e escovação). A realização dos desafios, foi realizada através da imersão dos dispositivos em 100mL de ácido cítrico e imersão em ácido cítrico+escovação, de cada um dos lados do dispositivo, 3x/dia. A análises de perfilometria e microscopia eletrônica de varredura foram realizadas como descritas nos procedimentos do primeiro experimento. Os dados obtidos no segundo experimento foram submetidos à análise estatística de forma separada e independente do primeiro experimento, utilizando o teste Kruskal- Wallis e o teste Mann-Whitney. Os resultados deste segundo experimento mostraram que após os desafios erosivos e abrasivos, o grupo que foi irradiado com laser de Er:YAG apresentou menores valores de desgaste quando comparados com o grupo que não foi irradiado. O grupo que sofreu apenas erosão e foi irradiado com laser de Er:YAG não diferiu significativamente quanto aos valores de desgaste do grupo não irradiado. Assim, pode-se concluir que o laser de Er:YAG não controlou o desgaste do esmalte quando submetidos apenas a desafios erosivos, porém, foi capaz de controlar o desgaste do esmalte quando submetidos a processos abrasivos subsequentes. / This study, composed of two in situ experiment, evaluated the effect of Er:YAG laser irradiation to control the progression of erosive and abrasive lesions on enamel. Bovine incisors were sectioned (5x3x2.5mm), flattened and polished. The enamel slabs (KHN = 330 ± 10%) with one fourth of the surface covered with resin composite (reference area) were submitted to initial erosion-like lesion formation with 1% citric acid (pH 2,3), 5 min, 2x/day for 2 days. In the first experiment, 56 slabs were divided into two groups according to the surface treatment: irradiated with Er:YAG laser (5,2 J / cm2, 2 Hz, 85 mJ, 10 s) and non-irradiated, and subdivided according to the type of wear: erosive (citric acid) and non-erosive (deionized water). The challenges were performed by immersing the devices in 100 mL citric acid or deionized water, 3x/day, randomly and independently. Enamel loss was determined by an optical 3D profilometer after: initial erosion, surface treatment and intraoral phase. The average of structure loss was verified by three readings of each experimental area comparing with reference area. Data was analyzed using the analysis of variance (ANOVA) and Tukeys test. In the first experiment, when used deionized water (non-erosive challenges) in intraoral phase, the specimens showed lower values of wear compared with the groups that were eroded with citric acid, whether irradiated or non-irradiated with Er:YAG laser. When erosion with citric acid was performed, Er:YAG laser didnt differ from non-irradiated group. The enamel wear was assessed qualitatively by scanning electron microscopy in 3 specimens of each group. In the second experiment, 48 slabs were divided into two groups according to the surface treatment: irradiated with Er:YAG laser (5,2 J/cm2, 2 Hz, 85 mJ, 10 s) and nonirradiated and subdivided according to the type of wear: erosive (citric acid) and erosive associated with abrasive (citric acid + brushing). The challenges were performed by immersing the devices in 100 mL citric acid and citric acid+brushing on each side of the device. The profilometry and scanning electronic microscopy analysis were performed as described in the procedures of the first experiment. The data from the second study were statistically analyzed separately and independently of the first experiment, using the Kruskal-Wallis test and the Mann-Whitney test.The results of the second experiment showed that after erosive and abrasive challenges, the group irradiated with Er:YAG laser showed lower structure loss than nonirradiated group. The group that suffered erosion and was irradiated, did not differ significantly from the non-irradiated group. Thus, it can be concluded the Er:YAG laser irradiation didnt control the enamel loss when submitted to erosive challenges, however, was able to control the enamel loss when submitted to abrasive challenges.
26

Análise da perda de estrutura dentinária após desafio abrasivo com diferentes cremes dentais contendo agentes dessensibilizantes / Analysis of loss of dentine structure after challenge with different abrasive toothpastes containing desensitizing agents

Raquel Marianna Lopes 20 January 2015 (has links)
Este estudo in vitro teve como objetivo avaliar a quantidade de perda de tecido dental após ciclos de erosão e abrasão com diferentes cremes dentais contendo ingredientes ativos para o tratamento da hipersensibilidade dentinária. Para tanto, quarenta amostras de dentina radicular (4x4x1,5 mm) foram confeccionadas a partir de terceiros molares humanos hígidos. Estes foram divididos aleatoriamente em 4 grupos (n=10): 1-controle negativo com água destilada, 2-controle positivo com Colgate Total 12, 3-Colgate Pró-Alivio e 4-Sensodyne Repair and Protect. Para o modelo de ciclagem erosiva foi utilizado o refrigerante Coca-Cola® por 5 minutos (4x/dia) a 37?C; e para a ciclagem abrasiva os espécimes foram submetidos a ciclos diários de escovação (2x/dia) com escova elétrica com pressão padronizada (15s). Os espécimes foram avaliados em Perfilometria óptica (n=10) e Microscopia Eletrônica de Varredura Ambiental (n=3) em duas fases distintas. Os dados de ambas as fases foram submetidos à análise estatística. Para a avaliação por perfilometria, a análise de variância ANOVA dois fatores para medidas repetidas mostrou que em todos os tratamentos a superfície dentinária foi afetada com o passar do tempo, havendo progressão da perda dentinária. Porém, não houve diferença estatística para cada tratamento realizado (p<0,05). Para avaliação em MEV, análises qualitativas e quantitativas foram realizadas. Para análise quantitativa, o teste Friedman demonstrou que os examinadores estavam calibrados. A análise de variância ANOVA mostrou que o Sensodyne Repair and Protect foi o creme dental mais eficaz na obliteração dos túbulos dentinários. Conclui-se que o desafio abrasivo combinado ao efeito erosivo apresenta-se como um potencial causador de lesões não cariosas e que os cremes dentais que contém dessensibilizantes apresentam comportamentos similares em termos de perda de substrato dentinário, quando comparados aos grupos controle, entretanto, mostram-se mais favoráveis para a oclusão tubular. / This in vitro study had the main objective to evaluate the amount of dental tissue loss after erosion and abrasion cycles with different toothpastes with active ingredients for the treatment of dentin hypersensitivity. Forty samples of root dentin (4x4x1.5 mm) were prepared from human third molars and randomly divided into 4 groups (n=10): 1-negative control- distilled water, 2- positive control - Colgate Total 12, 3- Colgate Pro-Relief and 4- Sensodyne Repair and Protect. For the erosion model it was used Coca-Cola® for 5 minutes (4x/day). For the abrasion model, specimens were subjected to daily brushing cycles (2x/day) with electric toothbrush with standard pressure (15s). Specimens were evaluated in Optical Profilometry (n=10) and Electron Microscopy Environmental Scan (n=3) in two distinct phases. Data from both phases were analyzed statistically. For evaluation by profilometer examination, analysis of variance for repeated measures ANOVA showed that all treatments were affected in the course of time, with progression of dentin loss. However, there was no statistical difference among treatments (p <0.05). For SEM evaluation, qualitative and quantitative analyzes were performed. For quantitative analysis, Friedman test showed that the examiners were calibrated. The ANOVA showed that Sensodyne Repair and Protect was more effective in tubules obliteration. It can be concluded that the abrasive challenge combined with the erosive effect is presented as a potential cause of non-carious lesions and toothpastes containing desensitizing agents have similar behavior in terms of loss of dentin when compared to control groups. However, it showed more favorable results to tubular occlusion.
27

Příprava vodivých struktur bezproudovým pokovením vytištěného prekurzoru / Fabrication of conducting patterns by material electroless plating of printed precursor

Kováčová, Silvia January 2021 (has links)
The subject of this diploma thesis is the preparation of conductive structures by electroless plating of an extruded precursor. The experimental part deals with the preparation of standard patterns based on the length of immersion time in a coppering bath. The precursor layers were applied with Fujifilm Dimatix to various receiver substrates. The individual substrates with the precursor layer were immersed in the copper solution within different time intervals. The structure of the layers of grown copper and their thickness was characterized by a profilometer.
28

Studium optických vlastností tenkých vrstev prekurzorů pro přípravu monokrystalů perovskitů FAPbBr3 / Study of optical properties of thin films of perovskiteFAPbBr3 precursors

Smolková, Denisa January 2021 (has links)
This thesis examines the preparation of thin layers of material for photovoltaic applications with focused on perovskites and determining their optical properties. Basic information about the photovoltaic panels, especially about the perovskites, and the preparation of thin layers is supplied in the theoretical section. This section includes description of optical properties and the main method of study of optical properties, spectroscopic ellipsometry. Experimental section is focused on the preparation of thin layers of perovskites FAPbBr3 and its precursors by spin-coating. Optical properties are evaluated using profilometry, UV VIS spectrometry and spectroscopic ellipsometry. The conclusion summarizes the results of this experiment with focused on comparison of ellipsometric spectrums of perovskites and its precursors.
29

Dissolution of fluorite type surfaces as analogues of spent nuclear fuel : Production of suitable analogues and study the effect of surface orientation on dissolution

Godinho, Jose January 2011 (has links)
It is accepted worldwide that the best final solution for spent nuclear fuel is to bury it in deep geological repositories. Despite the physical and chemical barriers that are supposed to isolate the nuclear waste for at least 100.000 years, some uncertainty factors may cause underground water to get in contact with the nuclear waste. Due to radioactivity and oxidation under air, dissolution experiments using UO2 pellets are difficult and frequently lead to incoherent results. Therefore, to enable a detailed study of the influence of microstructure and surface properties on the stability of spent nuclear fuel over time, it is necessary to produce analogues that closely resemble nuclear fuel in terms of crystallography and microstructure. At the same time, in-depth understanding of dissolution phenomena is crucial to geological processes such as dissolution precipitation creep and solvent mediated phase transformations. My thesis is based in two manuscripts. Paper I reports the microstructures obtained after sintering CaF2 powders at temperatures up to 1240°C. Pellets with microstructure, density and pore structure similar to that of UO2 spent nuclear fuel pellets were obtained in the temperature range between 900°C and 1000°C. Paper II reports how differences of surface chemistry and crystal symmetry, characteristics of each surface orientation, affect the topography of CaF2 pellets described in paper I during dissolution. I propose that every orientation of the fluorite structure can be decomposed in the three reference surfaces {100}, {110} and {111}. The {111} is the most stable surface with a dissolution rate of the top surface of 1,13x10-9 mol.m-2.s-1, and {112} the less stable surface with a dissolution rate 34 times faster that {111}. Surfaces that expose both Ca and F atoms in the same plan dissolve faster, possibly because the calcium is more susceptible to be solvated. The faster dissolving surfaces are replaced by the more stable {111} and {100} surfaces which causes the development of roughness on the top surface and stabilizes the surface on high energy sites; i.e. pores or grain boundaries. The main consequences of these observations are i) the increase of the total surface area; ii) the decrease of the overall surface energy. I present a dissolution model for surfaces of crystal with different surface energies. The main conclusions are: a) dissolution rates calculated from surface area are over estimated to the real dissolution rate; b) dissolution rates are faster at the beginning of dissolution and tend to diminish with time until a minimum value is reached.
30

Experiments and Simulation for 6061-T6 Aluminum Alloy Resistance Spot Welded Lap Joints

Florea, Radu Stefanel 15 December 2012 (has links)
This comprehensive study is the first to quantify the fatigue performance, failure loads, and microstructure of resistance spot welding (RSW) in 6061-T6 aluminum (Al) alloy according to welding parameters and process sensitivity. The extensive experimental, theoretical and simulated analyses will provide a framework to optimize the welding of lightweight structures for more fuel-efficient automotive and military applications. The research was executed in four primary components. The first section involved using electron back scatter diffraction (EBSD) scanning, tensile testing, laser beam profilometry (LBP) measurements, and optical microscopy(OM) images to experimentally investigate failure loads and deformation of the Al-alloy resistance spot welded joints. Three welding conditions, as well as nugget and microstructure characteristics, were quantified according to predefined process parameters. Quasi-static tensile tests were used to characterize the failure loads in specimens based upon these same process parameters. Profilometer results showed that increasing the applied welding current deepened the weld imprints. The EBSD scans revealed the strong dependency between the grain sizes and orientation function on the process parameters. For the second section, the fatigue behavior of the RSW’ed joints was experimentally investigated. The process optimization included consideration of the forces, currents, and times for both the main weld and post-heating. Load control cyclic tests were conducted on single weld lap-shear joint coupons to characterize the fatigue behavior in spot welded specimens. Results demonstrate that welding parameters do indeed significantly affect the microstructure and fatigue performance for these welds. The third section comprised residual strains of resistance spot welded joints measured in three different directions, denoted as in-plane longitudinal, in-plane transversal, and normal, and captured on the fusion zone, heat affected zone and base metal of the joints. Neutron diffraction results showed residual stresses in the weld are approximately 40% lower than the yield strength of the parent material, with maximum variation occurring in the vertical position of the specimen because of the orientation of electrode clamping forces that produce a non-uniform solidification pattern. In the final section a theoretical continuum modeling framework for 6061-T6 aluminum resistance spot welded joints is presented.

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