Laser machining is a commonly used method for materials processing. Focusing laser energy onto a sample can lead to material modifications and achieve feature sizes on the order of micrometres. However, designing a machining platform capable of producing high quality, repeatable, and accurate results is a key challenge because the final outcome can be variable, even when using fixed laser parameters. Therefore, in order to understand and monitor the process, real-time in situ metrology is required. In this work, a coherent imaging technique analogous to spectral domain optical coherence tomography (SD-OCT) was applied inline with a machining laser in order to monitor the cut development of various materials for industrial and biomedical applications. Such inline coherent imaging (ICI) provides axial resolution on the order of ones to tens of micrometers as well as temporal resolution on the order of microseconds. In stainless steel, the machining front was observed to have very different responses to pulsed lasers operating in different ablation regimes. Applying shorter pulse duration with higher peak intensity led to more deterministic material removal with little relaxation between pulses, while longer pulses revealed periodic melting and refilling behaviour. In addition, improvement of depth sensitivity to nanometre scales was explored by accessing phase information for Doppler processing techniques. For poorly absorbing materials, ICI provides the ability to observe structures below the surface. This is a very important characteristic for biomedical applications, such as guiding ablation in biological tissue. By monitoring the ablation of bone tissue in real-time using ICI, the operator was able to terminate exposure from the machining laser 50 μm before perforation into a natural inclusion in the tissue. ICI was able to anticipate the inclusion 176 ± 8 μm below the ablation front with signal intensity 9 ± 2 dB above the noise floor. With added real-time depth control, many applications will benefit whether it is achieving higher precision cuts in industrial materials, or limiting the possibility of damaging organs at risk below the cutting surface in surgical intervention. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2010-10-29 16:01:38.048

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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Degertekin, Levent; Committee Co-Chair: Kurfess, Thomas; Committee Member: Adibi, Ali; Committee Member: Danyluk, Steven; Committee Member: Hesketh, Peter.

Recently, structured surfaces, consisting of deterministic features designed to produce a particular effect, have shown promise in providing superior functional performance for a range of applications including: low friction surfaces, hydrophobic surfaces and optical effects. Methods have been developed to characterise such structured surfaces. The most widely used characterisation methods are based on segmenting the surface in feature and background regions and then determining the geometrical properties of those features. However, further work is needed to refine these characterisation techniques and provide associated uncertainties. This thesis considers the effect of various segmentation control parameters such as thresholds on the final geometric parameters. The effect of varying filter size is also considered. These considerations should help in selecting a suitable characterisation method for future projects. Additionally, uncertainty in the characterisation should be estimated in order to give an indication of the accuracy of the assessment. However, no previous work has assessed uncertainty in the dimensional properties of structured surfaces. Therefore, this thesis presents two methods to characterise the uncertainty in the geometric characteristics of structured surfaces. First, the measurement reproducibility is used, which can be determined by repeated measurement of a feature. However, measurement reproducibility cannot account for all sources of uncertainty and cannot assess any bias in the measurements. Therefore, a second method based on assessment of the metrological characteristics of the instrument is considered. The metrological characteristics estimate errors produced by the instrument in a way that can easily be measured. Monte Carlo techniques are then used to propagate the effects of the metrological characteristics and their uncertainties into the final measurement uncertainty. For the example used, it was found that the results using the metrological characteristics were in good agreement with the reproducibility results. From these results, it is concluded that the choice of segmentation method, control parameters and filtering can all significantly effect the characterisation of features on a structured surface, often in unexpected ways. Therefore, care must be taken when selecting these values for a specific application. Additionally, two methods of determining the uncertainty of the structured surfaces were considered. Both methods are valid and produce similar results. Using the measurement reproducibility is simple to perform, but requires many measurements and cannot account for some uncertainty sources such as those due to the instrument amplification factors. On the other hand, the use of metrological characteristics can account for all significant sources of uncertainty in a measurement, but is mathematically more complex, requiring Monte Carlo simulations to propagate the uncertainties into the final characteristics. Additionally, other artefacts than the sample being measured are required to determine the metrological characteristics, which may be an issue in some cases.

Made available in DSpace on 2014-06-11T19:29:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-12-21Bitstream added on 2014-06-13T19:58:47Z : No. of bitstreams: 1 carvalho_gc_me_araiq.pdf: 2780066 bytes, checksum: 373166ff1df7c9a7a4eec770d434e0a1 (MD5) / Este trabalho teve como objetivos a validação do método analítico para determinação do pH em águas, o levantamento das fontes prováveis de incerteza e a estimativa da incerteza associada ao resultado da medição. A abordagem foi desenvolvida com vistas à melhoria do processo analítico e à adoção de medidas preventivas, buscando-se, ao final desta etapa, repassar o conhecimento obtido, para o corpo técnico da empresa OIKOS: Controle Ambiental Ltda., e atender aos requisitos da norma ABNT NBR ISO/IEC 17025: 2005. Durante os experimentos o sistema de medição foi calibrado / ajustado utilizando-se: pH 7,00 e pH 4,00 (para leitura na faixa ácida) ou pH 7,00 e pH 10,00 (para leitura na faixa alcalina); e utilizou-se padrões rastreáveis ao NIST para a comparação. Foram obtidos os parâmetros: 1- precisão por repetitividade; precisão intermediária variando-se dias, equipamento e analista; a reprodutibilidade foi avaliada a partir da participação em ensaios de proficiência (EP) promovidos pelo INMETRO: pH 4,00 e pH 6,86. O laboratório apresentou desempenho satisfatório nestes ensaios, apresentando bom índice z em ambos, sendo que no segundo EP a precisão pôde ser melhorada. O método em estudo também apresentou 2- exatidão, obtida por meio da comparação entre o valor médio determinado e o valor aceito como verdadeiro, neste caso, o pHnominal disponibilizado no certificado do material de referência (MRC); 3- linearidade (Y-Yo); e 4- sensibilidade, em função da pendente de Nerst, considerando a temperatura média no dia de trabalho. Para a estimativa da incerteza foram consideradas as fontes de incerteza: i- precisão por repetitividade (maior valor de sr); ii- determinação do pH, obtida da regressão linear; iii- do potenciômetro; e iv- dos materiais de referência certificados utilizados... / This work aims the validation, the survey of likely sources of uncertainty, its estimate, the calculation of uncertainty and expanded uncertainty of quantitative analytical methods related to measures of pH in waters. This approach was developed to improve the analytical process, seeking the fitness of methods for use, recognizing the possible adoption of preventive measures, as well as the adequacy of the laboratory and analytical methods in compliance with the requirements of ABNT ISO/IEC 17025:2005. This work was undertaken in partnership with the company OIKOS Environmental Control Ltda. seeking, at the end of this step, pass on the knowledge obtained for the company's technical team. During the experiments, the calibration / adjustment of the measuring system were done using: pH 7.00 and pH 4.00 (for reading in the acid range) or pH 7.00 and pH 10.00 (for reading in the alkaline range); and traceable to NIST standards were used for comparison. The performance parameters obtained were: the: 1- repeatability; intermediate precision varying the conditions: day, equipment and analyst; and finally, reproducibility was evaluated from the participation in proficiency testing (EP) pH 4.00 and pH 6.86 promoted by INMETRO. The laboratory showed satisfactory performance in these trials, showing good z-index in both tests, but in the second EP, the “precision” was improved... (Complete abstract click electronic access below)

<p>Quantitative imaging is important in medical imaging. Physical phantoms are used. There is reason to believe that anthropomorphic physical phatoms are better than uniform phantoms. To investigate this question, we develop a novel imaging metrology with a phatient-based phantom and apply its use to several digital breast tomosytneshis machines. At the same time, we use the traditional means of assessing image quality. Our results show a strong dependence on image performance with the type of phantom used. Furthermore, we demonstrate the feasibility of this metrology in real, clinical applications.</p> / Dissertation

One of the most critical processes in CdTe device production is the activation process induced by cadmium chloride (CdCl2). In this thesis, the CdCl2 treatment has been optimized using both wet and thermal evaporation methods for close-spaced sublimated (CSS) devices. Maximum cell efficiencies of η=7.24% and η=9.37% respectively have been measured without the use of copper in the back contact. A clear link has been established between treatment conditions, electrical measurements and microstructure, where parameters such as the dwell annealing temperature for evaporated CdCl2 and the concentration of the solution for the wet treatment are varied. It has been shown that a certain concentration of chlorine is necessary to remove high densities of planar defects present in the as-deposited material. The CSS CdTe is deposited in a dual layer structure with smaller grains at the CdS interface and with larger grains developing towards the surface. The defects are initially removed in the smaller grains at the CdS interface. When the temperature and concentration increase, more grains recrystallize with the total removal of stacking faults. At a critical temperature and Cl concentration, the entire CdTe film recrystallizes into large grains with no stacking faults. The CdS grains and the interface with the CdTe also changes with sulphur migration into the CdTe. The results indicate that the recrystallization actually initiates at the CdS/CdTe junction. This has been observed clearly for both sputtered and electrodeposited CdTe. The recrystallization process gradually propagates towards the surface as the concentration of the CdCl2 solution in methanol is increased. This observation is not intuitive because the solution is initially in contact with the outer surface of the CdTe. Finally, the use of different chlorine containing compounds has been used as an alternative to CdCl2 and to further understand the role of chlorine in the process. All the samples treated with Cl containing compounds have shown the elimination of the dual layer structure and the recrystallization of the small grains at the interface. Tellurium tetrachloride (TeCl4) and zinc chloride (ZnCl2) have shown the most promising increase in conversion efficiency. The maximum efficiencies measured using these two solutions were 4.58% and 5.05% respectively. TeCl4 has shown an encouraging open circuit voltage of 594 mV, while the open circuit voltage using ZnCl2 was 494 mV. However, TeCl4 has shunting issues and low current density (17.9 mA/cm2), whereas ZnCl2 has the promising current density of 20.8 mA/cm2. This work has shown that alternatives to CdCl2 treatment exist, however further work is required to optimize the performance of these treatments to enable them to be competitive. Advanced materials characterization techniques are essential to understand and then enhance photovoltaic cell and module performance. New and improved tools are being developed to deliver fast, accurate and non-destructive characterization. One of these tools is coherence correlation interferometry (CCI) which has been developed by Taylor Hobson Ltd. This is a particular variant of scanning white light interferometry used for surface metrology with a high vertical resolution. In this thesis, it has been shown that the capability of the CCI can be extended to perform accurate thin film thickness measurements using the Helix Complex Field (HFC) function. The main attraction of this technique for thin film PV applications is that it allows surface metrology and thin film thickness measurements to be obtained simultaneously from the same area of the sample in the same system. The results obtained from CCI on a variety of materials, used in thin film PV, correlate very well the results obtained from other techniques such as ellipsometry, electron microscopy and atomic force microscopy. The CCI has also been used in the optimization of a new one-step interconnect process (OSI) for thin film PV module interconnects.

Speckle noise is an integral part of any laser projection display because it is the nature of laser (coherent) illumination to form interference patterns with high visibility. The granularity of the image due to the speckle formed on the viewer's retina degrades the image quality, thus stimulating the need for speckle reduction techniques applied to laser displays. An instrument to measure image plane speckle contrast was built based on a linear CCD detector array interfaced to an LSI-11 microcomputer. Speckle reduction techniques were then evaluated by comparing the contrast obtained with each method. The effect of the spatial frequency response (MTF) on the measured contrast was studied, along with the statistical significance of the measurement which is limited by the finite sample space of 1024 detector pixels per CCD frame. The lowering of the contrast due to the array MTF can be minimized by working at extremely high F numbers (> 100). The sample space can be widened by taking more than one frame of data and treating all the frames as a single data set. Techniques to reduce speckle noise in laser displays fall into two broad categories: reducing the coherence of light forming the speckle, and incoherently adding multiple uncorrelated (or partially correlated) speckle patterns. The first technique (effective only for monochromatic displays) was implemented by coating a screen with various dyes, phosphors, or fluorescent paints. Using the 514 nm line from an Argon laser, the contrast can be reduced by almost 30% by spraying a thin layer of fluorescent paint on the screen. More speckle reduction can be achieved with an accompanying loss in image brightness. The second technique involved creating a multiplicity of partially correlated speckle patterns that appear from the same position on the screen over the integration period of the eye. The different speckle patterns are produced by changing the angle of illumination while keeping a portion of the laser spot focused on the same point on the screen. The scan angle method (applicable to multi-color displays), can be implemented by properly synchronizing an acousto-optic modulator with the scan optics, and imaging the modulator on the screen. Using a beaded screen and a reasonable laser dither of 10 millirads, the contrast can be reduced by half.

The International Temperature Scale of 1990 (ITS-90) defines the present S.I.(“System International”) means of measuring temperature. The ITS-90 uses the freezing points of metals to define temperature fixed points. It also uses long-stemplatinum resistance thermometers to interpolate between the fixed points from 660 °Cdown to 84 K (if one includes the Argon triple point). Impurities are a major source of uncertainty in the fixed point temperature (of the order of 1 mK). And a better understanding of the impurity effect is required to improve top-level metrologicalthermometry. Most historical experiments with impurities have worked at a muchhigher levels of impurities – say of the order of 100ppm - and in arrangements that are not used on a day-to-day basis in a metrology laboratory. This thesis describes the deliberate doping of tin and aluminium, each with three different impurities and the effects of these on the temperature of the tin and aluminium liquid-solid phase transitions. The impurities, of the order of 1-30 ppm,were Co, Pb and Sb in the tin and Cu, Si and Ti in the aluminium. The tin and aluminium samples were in the form of ~0.3 kg ingots that would normally be used to realise an ITS-90 fixed point. Measurements were made using equipment normally available in a metrological thermometry laboratory, rather than using specially prepared samples. The samples were chemically analysed (by Glow Discharge Mass Spectrometry(GD-MS)) before and after the doping. Using the amount of dopants introduced,and/or the chemical analysis data, the measured temperature changes were compared with those interpolated from the standard text. The experimental undoped liquid-solid transition curves were also compared against theoretical curves (calculated from atheoretical model MTDATA). The results obtained did not disagree with the Hansen interpolated values (though there was considerable uncertainty in some of the measurements (e.g. a factor of 2 ormore) due to the measurement of small changes. Within these uncertainties it indicatesthat the Sum of Individual Estimates (SIE) method of correcting for, at least, metal impurities in otherwise high purity metals remain valid. However the results also showed considerable discrepancies between the initial measured and calculated temperature shifts (based on the pre-existing impurities prior to doping) suggesting that there may be impurities that are not (separately) detected by the GD-MS method. There was evidence that the thermal history of the metal phase transitions can cause considerable segregation of some impurities, particularly those likely to increase the phase transition temperature through a peritectic (“positive” impurities), and that the effects of this segregation can be clearly seen on the shape of the melting curves of thetin doped with Sb. Some of the aluminium doped with Ti freezing curves may also show evidence of a“concave up” shape at the start of the freezing curve, as previously calculated by MTDATA, though the effect is not as pronounced. All individual phase transition measurements - made over tens of hours – were repeated at least three times and found to be reproducible, hence providing a real dataset that can be used for comparison with theoretical models still under development.

Abstract This research report details the design, construction, implementation and optimization of a quantitative movable flow visualization technique named Electronic Speckle Pattern Interferometry (ESPI). ESPI is a powerful visualisation technique that can allow for full flowfield analysis. It is thus possible to quantitatively determine the refractive index variation and hence the density variation in a compressible gas flow. Complementary results between previous work done and the current work shows the integrity of ESPI results Flowfields that were investigated included – candle flame, axis symmetric and nonaxis symmetric nozzles. Due to advanced CCD technology, there have been improvements in the overall image quality. Post processing of the images produced clearer images and hence better results. The technique was applied on multiple test rigs, proving its versatility