Surface layer coatings, which are thin films in the range of micrometer and nanometer are of utmost importance. These layers have many applications and control processes like corrosion, friction, wearing and adhesion. Therefore the search for layers with satisfactory surface properties for different applications is needed. Thickness measurements were evaluated in this study using PIXE in conjunction with RBS. Different samples were evaluated using both the solid-state chamber and the nuclear microprobe. The energies of 2.0 MeV alpha particles, 2.5 MeV and 3.0 MeV protons were used in this study. RBS when compared to PIXE showed low sensitivity towards light elements. The High purity Germanium detector also found it difficult to resolve peaks of elements (Magnesium and. Aluminum) that were close to one another. The GeoPIXE software showed inconsistent results for all the measurements. However the results showed good agreement between the two techniques. The overall observation of the study was that PIXE has shown its ability to measure thickness and that the inconsistency in the results from GeoPIXE software makes it difficult to trust the software for analysis of the results. / MSc (ARST) North-West University, Mafikeng Campus, 2003

This study is concerned with flow and stability of thin liquid films flowing over the surface of a disc rotating about a vertical axis. The work consists of a theoretical and experimental investigation into the flow of the steady-state film, and the waves which occur on it. The theoretical model is investigated in its steady-state form (no waves present) using both asymptotic and numerical techniques. The unsteady problem is also examined, using asymptotic methods, for the inception and propagation of waves of small amplitude with respect to the mean film thickness. The experimental investigation employs a light absorption technique to obtain accurate film thickness measurements across individual three dimensional wave profiles. The results are used to test the validity of the small amplitude assumption of the theoretical model, which is found to be restrictive, and to give both qualitative and quantitative data about the large amplitude waves that are often observed.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 113-116).

No description available.

Thesis (M.S.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 17, 2009) Vita. Includes bibliographical references.

No description available.

The cerebral cortex is gray matter tissue which covers cerebral hemispheres. In recent years, many studies reported that abnormal cortical thickness was found in several diseases of central neural system, such as multiple sclerosis, Alzheimer's diseases, and schizophrenia. Therefore, the whole-brain measurement of cortical thickness using the non-invasive magnetic resonance imaging becomes important. However, not many algorithms were reported in the past due to the extremely complex folding structure of human cortex. In this thesis, a voxel-based cortical thickness method proposed by Hutton et al was implemented using MATLAB to achieve automated measurement. Several crucial factors, including the definition of boundary condition, interpolation method, the step size of developing each streamline, and spatial resolution of imaging space, in the implementation were discussed. In addition, the analysis of stability, or precision, of our self-developed program was evaluated . Sixteen experiments of reproducibility were performed in two months on the same 24-year-old healthy volunteer repeatedly to obtain whole-brain 3D T1WI. Cortical thickness map was calculated independently and normalized to the same coordination. Mean, standard deviation, and normalized standard deviation of 16 measurements were calculated on every cortical voxel, along with whole-brain mean cortical thickness. Various sizes of 3D smoothing kernel were applied, and the results showed stronger smoothing might help higher precision by the cost of spatial resolution.

The pipeline is playing an important role in industry nowadays. However, the inner wall of pipeline may suffer corrosion after a long service time. When excessive corrosion occurred, not only the transported material inside the pipe will let out but also serious accident may be induced. So, it¡¦s necessary to monitor pipeline thickness regularly. Conventionally, since most piping systems were subjected to high-temperature working environments, hence if an operator intend to examine the thickness of a pipeline, the whole piping system need to be shutdown and resulted in financial losses. Therefore, to develop on-line thickness measurement technique for pipelines subjected to high-temperature working environment is indispensable. ¡@¡@In this study, low-cost PZT sensors (Pb(ZrxTi1-x)O3), which can sustain high-temperature working environment, were used to execute the thickness measurements. A single PZT, which was bonded on the surface of a pipe as an actuator and a receiver simultaneously. Then, by utilizing the GUI(Graphic User Interface) system, which was designed in this study, the echo signal can be analyzed and the thickness of the pipe can be determined on-line and automatically. It is noted that the wave speed changed as environmental temperature increased. So, in this study, by using A36 steel plates and steel tubes as a specimens, a modified temperature versus wave velocity curve was proposed.. The experimental results showed that non-conservative thickness measurements will be obtained if modified wave speed was not adopted when working temperature increased. keywords¡GThickness measurement, PZT sensor, GUI system, Modified wave velocity curve.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [197]-201).

Cerebral cortex, classified as gray matter, is the superficial layer of the cerebrum. In recent years, many studies have shown the abnormality of cortical thickness is possibly correlated to the disease or disorder in central nervous system, such as Alzheimer¡¦s disease and lissencephaly. Therefore, this purpose of this work is to implement the measurement of the cortical thickness. In general, two approaches, surface-based and voxel-based methods, have been proposed to measure the cortical thickness. In this thesis, a procedure of the voxel-based method using Laplace¡¦s equation was developed on the basis of a 2008 publication reported by Chloe Hutton et al to obtain voxel-based cortical thickness (VBCT) map. The result of our home-made program was further compared with those calculated by Hutton¡¦s program, whic h was generously provided by the author. The difference between two implementations was consisted of four main parts. First of all, different strategies of the tissue classification were used to define boundary condition of Laplace¡¦s equation. When grey matter, white matter, and cerebrospinal fluid were classified by maximizing the tissue probability, Hutton¡¦s program tends to search more voxels of cerebrospinal fluid in sulci by skeletonizing the non-parenchyma area. Second, the algorithm of layer growing also differs. The single layer obtained by the 26-neighborhood algorithm in our program would be obviously thicker than that provided by Hutton¡¦s program using 6-neighborhood. Third, compared with a fixed step size (usually 0.5 mm) porposed in the main reference to track cortical streamline, we designed a variable step size, reducing the underestimation of cortical thickness. The last but not the least, the connecting points of the cortical streamline usually are not grid points, thus requiring interpolation to estimate the stepping gradient. We adapted the linear interpolation for better accuracy when Hutton et al searched for the closest grid point for replacement to achieve faster computation.