No description available.

Materials Science has in recent years become a high priority research area, having been identified as a growth sector for the UK economy over the next decade. Breakthroughs in this field are likely to have a significant impact on every area of our lives. There has recently been a trend toward automation at beamlines which is driven by rapid technology advancement. This technology advancement has improved the quality of experiment data and has allowed data collection times to improve exponentially. The Materials Science Research Group in the Institute of Mathematics, Physics and Computer Science, at Aberystwyth University have achieved international recognition for their research on materials under extreme conditions. They have a rich history in the development and use of specialist instruments to conduct real time surface analysis. Their custom made instrumentation has allowed them to greatly improve experiment throughput. Automation of the group's ultra high vacuum chambers is therefore a further enhancement that is advantageous, important, necessary and inevitable. This thesis presents the research undertaken to study what is required to provide automated sample positioning inside vacuum chambers that are operated under ultra high vacuum conditions, as the first step towards automation. As part of the research, a prototype automated positioning system that employs state of the art model based visual tracking techniques was developed to gain an understanding of the challenges the ultra high vacuum environment presents. Experimentation was carried out to assess the effects of different lighting conditions on tracking, evaluate the tracking library, extract suitable extrinsic parameters for tracker initialisation, and evaluate both monocular and stereo mode tracking. Key findings were that the model based tracking is a suitable approach for an automated positioning system but that performance depends on having suitable port placement for the cameras. Stereo tracking provided the best performance but was still prone to divergence at certain relative positions of the manipulator. On linear runs the average error was 0.06mm. On rotational runs, anti-clockwise runs proved better with an average error of 2^o to 3^o. The high errors of mixed rotational and linear tracking runs did not match the visual outputs indicating that there were inherent errors in the data evaluation. Tracking output video footage is available at [8]. More work is needed to take the system forward and close the tracking loop. Recommendations for improvements were provided.

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Thesis (M.S. in Systems Engineering)--Naval Postgraduate School, Sept. 2004. / Thesis advisor(s): David C. Jenn. Includes bibliographical references (p. 81). Also available online.

Thesis (M.S.)--University of Michigan, 1958.

Thesis (M.S.)--University of Michigan, 1962.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1971. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S)--University of Maryland, College Park, 2004.

In radiotherapy, half value layer has been accepted as a practical specification of the quality of primary x-rays. For the degraded radiation in a scattering medium, however, it is neither an applicable nor an adequate specification of the quality. This thesis describes a practical method of investigating the radiation quality in an irradiated medium. The method is based essentially on differences in emission and on differences in absorption of different materials. Two ratios were measured: (a) the ratio of the ionization current in a copper-lined ionization chamber to the ionization current in a lucite-wall chamber, (b) the ratio of the ionization current in the copper-lined chamber to the ionization current in the same lucite-wall chamber with the latter shielded by a copper absorber. These ratios, which depend on the spectrum of the x-radiation to which the chambers are exposed, change differently with change in spectrum and, therefore, give two indices of quality. For calibration purposes, the above ratios were measured for primary x-rays generated at different kilovoltages and with different filters. To investigate the quality of radiation in a scattering medium, the same ratios were measured and were compared with the results obtained for primary spectra. Radiation quality at different depths in water exposed to different qualities of primary x-rays was investigated. The results are in qualitative agreement with those obtained by previous workers. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The efficiency of a He³ filled ionization chamber for detecting neutrons via the He³ (n,p)T reaction was investigated to see if it would be feasible to use the instrument for measuring neutron flux. Calculations of wall loss showed that such measurements would in all probability not be very precise. Using neutrons with an energy of 2.76 Mev derived from the D(d,n)He³ reaction these calculations were born out. The efficiency of the detector was found to be ~0.9 x 10ˉ² % at 2.76 Mev, including the correction for the wall loss which amounted to 64% of the detected flux. / Science, Faculty of / Physics and Astronomy, Department of / Graduate