The process of laser cladding consists of depositing successive layers of molten metallic powder to create a near-net shape. A high-power laser is used to melt incoming metallic powder, which forms a melt pool on the surface. As the latter moves beneath the laser, this newly created melt pool solidifies. By properly controlling the trajectory of deposition tracks, one can create a diverse range of shapes with varying complexities. However, the process is very sensitive to parameters, requiring constant attention from technicians. This lends itself perfectly to the addition of automatic controllers whereby supervision is minimal. <br /><br /> In this thesis, an optical sensor is developed to monitor the process zone. The sensor will output a measurement of the height of solidified clad, which in turn can be used by a controller to adjust this geometrical feature. The thesis is divided into three main parts, each contributing to the final algorithm. <br /><br /> First, in Chapter 3 an analysis is performed on the light irradiating from the interaction zone (or melt pool). It is stated that the dominating source of light is governed by blackbody radiation from this molten metal. This is confirmed by analyzing a series of images captured through a digital camera, where various narrow bandpass filters were utilized to selectively view a portion of the CCD-sensor's spectrum. This investigation also leads to the selection of bandpass filter such that a stable, relatively intense melt pool is captured through the digital camera's CCD-sensor. <br /><br /> Second, in Chapter 4 the captured images are taken through a pair of image processing techniques, outputting a series of coordinates representating the melt pool's boundary. The image is first analyzed to calculate an optimal threshold level based on the minimization of fuzzy entropy. With this threshold selected, the grayscale image is converted into black-and-white, where the white pixels represent the melt pool. After this step, the melt pool's boundary is extracted through an 8-connectivity border tracing algorithm. This technique outputs a series of coordinates (in pixels) as though one were traveling along the melt pool in a clockwise rotation. <br /><br /> Last, Chapter 5 analyzes these pixel coordinates to extract the melt pool's height. The coordinates are first transformed into real-world coordinates, by use of a perspective transformation. This transformation essentially yields the melt pool's shadow, as created by a light-source coincident with the camera. As a result, the melt pool's height is estimated based upon a right-angle triangle, where the camera's angle is known, and the projected coordinates represent the shadow length (triangle's base). <br /><br /> The result of applying this series of steps to the estimation of clad heights is found at the end of Chapter 5. Results varied dramatically, from 4% error to 393%. Although the errors are large at times, they are mainly caused by a bias in the estimate. That is, the dynamics of the true clad formation are very well predicted by the algorithm, however, shifting by a certain amount. This amount varies both with substrate velocity, and the clad's direction of travel, relative to the camera. A partial explanation is given such that the clad's height is offset from the laser center-point, which is a function of both these parameters. However, the specific relationship requires further experimentation.

The objective of this research is the statistical study of space weather e ects on im- age detectors in Low Earth Orbit. The Hubble Space Telescope is used as a resource for acquiring proton a ected images for statistical analysis. For the purpose of the present work, the space weather environment will consist of cosmic as well as solar proton particles. The proton occurrences evident in images from the Hubble Charge Coupled Device (CCD) have been used to calculate the probability of proton events, which is related to the local space weather particle ux. The proton particles transfer energy to the CCD silicon, which ultimately results in measured signal that is not originating from photon illumination. The signal due to the proton interactions is rst separated from the noise contribution and subsequently used in the determi- nation of a pulse height probability distribution. Separation of the noise from the proton events also leads to the measurement of proton streak lengths and orientations along with the associated probability distributions. The directionality of the space weather environment in Low Earth Orbit is examined using the distribution of proton streak angles. Statistics found from the Hubble are also used as a starting point for simulations that create synthetic proton signal images. The distributions resulting from the Hubble CCD analysis give the probability of the: number of proton events, which is related to the ux of the space weather protons; energy of proton events, which allows estimates of damaging proton interactions; length of proton streaks on the CCD, which shows the relative probability of a long traversing proton event; angle of proton event, which indicates the directionality of the space weather environment.

The objective of the proposed research is to answer the question of how to provide verification and redactability to medical documents at a manageable computation cost to all parties involved. The approach for this solution examines the use of Merkle Hash Trees to provide the redaction and verification characteristics required. Using the Merkle Hash Tree, various Continuity of Care Documents will have their various elements extracted for storage in the signature scheme. An analysis of the approach and the various characteristics that made this approach a likely candidate for success are provided within. A description of a framework implementation and a sample application are provided to demonstrate potential uses of the system. Finally, results seen from various experiments with the framework are included to provide concrete evidence of a solution to the question which was the focus of this research.

Cette thèse, effectuée à l'Institut de Physique Nucléaire de Lyon (IPNL), s'inscrit dans le cadre de l'expérience SNfactory, dédiée à l'observation précise d'un grand nombre de supernovae de type Ia. Ces explosions thermonucléaires de naines blanches, très lumineuses, sont aujourd'hui les meilleures chandelles standards connues et ont de ce fait un grand intérêt pour la cosmologie.<br />Les travaux exposés ici contribuent à l'étalonnage de SNIFS, le spectrographe à champ intégral utilisé par SNfactory pour l'observation des supernovae de type Ia. Une étude des CCD a été effectuée ainsi que la collection de spectres d'étoiles de référence pour l'étalonnage en flux de l'instrument. La contribution principale a consisté en la réalisation d'un code complet pour l'extraction du spectre d'une source ponctuelle à partir du cube pré-étalonné de données. Le procédé choisi est la photométrie de PSF (Point Spread Function), nécessaire ici du fait de la petite taille du champ observé. Le flux perdu peut ainsi être évalué, et l'on atteint une qualité de mesure du flux de l'ordre du pourcent, objectif de l'expérience.

This thesis will present the design, implementation, and testing of a high voltage Charge-Coupled Device (CCD) controller ASIC for the Large Synoptic Survey Telescope (LSST), which will be used to study dark energy and dark matter. The LSST observatory, which includes a 3.2-gigapixel camera, will cover the entire sky every three nights by taking continuous 15-second exposures. The CCD controller ASIC, or Sensor Control Chip (SCC), will provide five CCD driver channels that are capable of generating serial or parallel clock signals for the LSST’s imaging sensors during readout mode. The SCC will also provide three programmable bias voltages for the CCDs along with eight supplementary programmable voltages and currents for the CCD’s output drain terminals. Additionally, the controller ASIC includes eight control signals for a separate Analog Signal Processing Integrated Circuit (ASPIC) that is designed as the readout chip for LSST. The SCC is designed to operate down to 153 K. Fabricated in a commercially available 0.8-micron Bipolar-CMOS-DMOS Silicon-On-Insulator (BCD-SOI) process, the SCC has been verified to meet all design requirements.

System zur berührungslosen Drahtvorschubgeschwindigkeitsmessung mittels CCD-Kameramodul. Die Auswertung der Daten wird mittels Wavelet-Algorithmen durchgeführt.

Cette thèse porte sur le développement du DosiMap, un nouvel instrument de dosimétrie pour le contrôle des faisceaux de radiothérapie. Ce dispositif est basé sur l'utilisation d'un scintillateur plastique plan placé au sein d'un fantôme de polystyrène. La distribution lumineuse produite par le DosiMap sous irradiation, composée de scintillation et de rayonnement Čerenkov, est mesurée par une caméra CCD, puis analysée afin d'en déduire la distribution de dose déposée dans le scintillateur.<br />Ce dispositif possède un certain nombre d'avantages. Il est équivalent tissus, présente une bonne résolution spatiale et une réponse linéaire en énergie. Il permet également d'effectuer des mesures de dose immédiates, ce qui rend son utilisation adaptée à une utilisation clinique.<br />Après une introduction des notions de base de la radiothérapie, les différentes étapes du développement de cet instrument sont exposées dans ce mémoire. Différents scintillateurs plastiques ont, dans un premier temps, été testés afin de déterminer le mieux adapté à cette application. Seule la scintillation étant proportionnelle à la dose, la déconvolution de la scintillation et du rayonnement Čerenkov a ensuite été réalisée. Enfin, la caméra se trouvant en salle d'irradiation, il a été nécessaire de mettre au point un blindage afin de la protéger. La calibration en dose du dispositif ainsi que sa réponse dosimétrique sont alors exposées.<br />Ce travail a permis de mesurer des distributions de dose avec une incertitude inférieure à 2 % pour des faisceaux de photons homogènes. D'excellents résultats ont également été obtenus dans le cas de faisceaux modulés en intensité.

Doctor of Philosophy (PhD) / This thesis is an enquiry into the social and political role, in Australia, of practices that have attracted such labels as ‘community arts’, ‘cultural animation’, ‘cultural action’, or ‘community cultural development’ (CCD). It is often argued that such practices offer an effective means to bring about social and political change for people and communities who participate in them. Looking specifically at theatre-based approaches to CCD in Australia, this thesis examines an alternative hypothesis, namely that such projects and programs can contribute to the continued marginalisation of those who take part in them. Using a combination of Pierre Bourdieu’s theoretical approach to field analysis, Don Handelman’s analytical framework of special events and Baz Kershaw’s theory of potential efficacy, I carry out an ethnographic and performance-based analysis of a particular project called The Longest Night (TLN), which was devised in collaboration with young people from The Parks, a cluster of suburbs north west of Adelaide, South Australia, and in collaboration between Urban Theatre Projects, a small Sydney-based theatre company with a reputation for doing socially and politically challenging work, young people living in The Parks and local partner organisations, for the 2002 Adelaide Festival. I find that in some instances participation in CCD projects and programs is an enabling factor, creating change opportunities in cultural, economic and/or political spheres in the lives of those who take part, whilst at other times it is a constraining factor. Participation in CCD projects and programs creates possibilities because the practices are potentially subversive and foster elements of learning and change in some participants. It also creates limitations because CCD practitioners operate within a subfield of social and cultural practices where the mechanisms and structures in place, indirectly, tend to help reproduce legitimised social and cultural values and norms.

Doctor of Philosophy (PhD) / This thesis is an enquiry into the social and political role, in Australia, of practices that have attracted such labels as ‘community arts’, ‘cultural animation’, ‘cultural action’, or ‘community cultural development’ (CCD). It is often argued that such practices offer an effective means to bring about social and political change for people and communities who participate in them. Looking specifically at theatre-based approaches to CCD in Australia, this thesis examines an alternative hypothesis, namely that such projects and programs can contribute to the continued marginalisation of those who take part in them. Using a combination of Pierre Bourdieu’s theoretical approach to field analysis, Don Handelman’s analytical framework of special events and Baz Kershaw’s theory of potential efficacy, I carry out an ethnographic and performance-based analysis of a particular project called The Longest Night (TLN), which was devised in collaboration with young people from The Parks, a cluster of suburbs north west of Adelaide, South Australia, and in collaboration between Urban Theatre Projects, a small Sydney-based theatre company with a reputation for doing socially and politically challenging work, young people living in The Parks and local partner organisations, for the 2002 Adelaide Festival. I find that in some instances participation in CCD projects and programs is an enabling factor, creating change opportunities in cultural, economic and/or political spheres in the lives of those who take part, whilst at other times it is a constraining factor. Participation in CCD projects and programs creates possibilities because the practices are potentially subversive and foster elements of learning and change in some participants. It also creates limitations because CCD practitioners operate within a subfield of social and cultural practices where the mechanisms and structures in place, indirectly, tend to help reproduce legitimised social and cultural values and norms.

Universiẗat, Diss., 2002--Bremen.