Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 141-153).

Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2006. / Zhang, Zhuomin, Committee Chair ; Joshi, Yogendra, Committee Member ; Lee, Kok-Meng, Committee Member ; Gallivan, Martha, Committee Member ; Zhao, Yiping, Committee Member.

No description available.

Numerous studies have addressed the role of stream geomorphology on vegetation distribution. These studies have shown that channel morphology, including depositional and erosional processes, influence vegetation colonization. However, few studies have addressed the impact of vegetation on the geomorphic processes of streams. Vegetation has the ability to stabilize channel banks and alter stream hydrology and stream power. Little research has addressed the impact of invasive vegetation and its ability to change river channel processes. My research addresses the impact of the highly invasive Phalaris arundinacea and quantifies its influence on the stream channel form of the Sprague River, Oregon. I conducted field research that included root density and root strength surveys to determine the below ground influences of vegetation in terms of added bank cohesion provided by the invasive and two similar native species: Eleocharis palustris and Carex vesicaria. To ascertain differences between the species above ground characteristics and influences, I measured stem density and elasticity to calculate their roughness (Manning's n) and determine their potential impact on stream velocity. Finally, I used these vegetation characteristics to model stream velocity, water depth, and bed shear stress within the 2-D model MD-SWMS. Differences in root size were significant with C. vesicaria having the largest root diameters, largest root area ratio, and largest bank cohesion provided by roots. This was followed by the invasive and then E. palustris. E. palustris had the highest stem density, followed by C. vesicaria and P. arundinacea. The invasive had the highest stem stiffness. E. palustris was associated with the highest roughness value, closely followed by the invasive and C. vesicaria. Using modeling I found the presence of the invasive increased velocity compared to E. palustris and increased bed shear stress compared to C. vesicaria. Therefore, changes in species composition, such as a shift from either of the natives to the invasive, could affect channel morphology over time. By comparing the impact of this invasive to that of native grasses and sedges, this research provides insight into how further spread of the invasive may affect the Sprague River and other riparian ecotones. / 2015-10-03

abstract: The dissolution of metal layers such as silver into chalcogenide glass layers such as germanium selenide changes the resistivity of the metal and chalcogenide films by a great extent. It is known that the incorporation of the metal can be achieved by ultra violet light exposure or thermal processes. In this work, the use of metal dissolution by exposure to gamma radiation has been explored for radiation sensor applications. Test structures were designed and a process flow was developed for prototype sensor fabrication. The test structures were designed such that sensitivity to radiation could be studied. The focus is on the effect of gamma rays as well as ultra violet light on silver dissolution in germanium selenide (Ge30Se70) chalcogenide glass. Ultra violet radiation testing was used prior to gamma exposure to assess the basic mechanism. The test structures were electrically characterized prior to and post irradiation to assess resistance change due to metal dissolution. A change in resistance was observed post irradiation and was found to be dependent on the radiation dose. The structures were also characterized using atomic force microscopy and roughness measurements were made prior to and post irradiation. A change in roughness of the silver films on Ge30Se70 was observed following exposure. This indicated the loss of continuity of the film which causes the increase in silver film resistance following irradiation. Recovery of initial resistance in the structures was also observed after the radiation stress was removed. This recovery was explained with photo-stimulated deposition of silver from the chalcogenide at room temperature confirmed with the re-appearance of silver dendrites on the chalcogenide surface. The results demonstrate that it is possible to use the metal dissolution effect in radiation sensing applications. / Dissertation/Thesis / M.S. Electrical Engineering 2012

Physical stress such as the surface roughness of the implants may activate the NFkB signalling pathway in macrophages. This activation is intimately related to the mechanism(s) by which the macrophage interacts with the surface through serum proteins and/or the formation of membrane rafts. This thesis examines the role of surface topography on activation of the NFkB signalling pathway in macrophages. We examined the effect of implant surface topography on activating the NFkB signalling pathway in the RAW 264.7 macrophage cell line. We also examined the effect surface roughness had on the adhesion of the macrophages using the different media. To finish, we observed the effect the different media and the surface roughness had on the morphology of the macrophages by Scanning Electron Microscopy. Activation of the NFkB pathway was surface topography dependent. The Smooth surface showed the highest level of activation followed by the Etched then the SLA. Addition of suboptimal concentrations of LPS mildly enhanced the response by signalling through the Toll receptor. Activation of NFKB occurred in the absence of fetal calf sera, although to a lesser extent. All three surfaces had very few cells with nuclear translocation at the 5 minutes time point with no significant statistical differences between the surfaces. After 30 minutes, translocation reached comparable levels to those surfaces tested with complete medium. Disruption of the lipid rafts affected the triggering and signalling of the NFkB pathway. This inhibitory effect was concentration and time dependent. Smooth surfaces bound more macrophages in the 30 minutes assay. Fetal calf serum appeared to be very critical for adhesion and spreading of the macrophages on the various surfaces examined. Removal of cholesterol did not affect adhesion or spreading on their respective surfaces. We have clearly demonstrated that the lipid rafts along with surface topography play a role in the activation on NFKB. This in-vitro study has demonstrated that surface topography modulated activation of the NFKB signalling pathway in a time-dependent manner. However, at present, it is unclear through which receptor(s) / surface structure the signal pathway is initiated. / Dentistry, Faculty of / Graduate

No description available.

This study investigates the effect of front surface roughness on ultrasonic echo amplitude. Experiments were carried out on specimens whose front surfaces are machined by milling machine. Machining parameters were changed in milling process in order to obtain desired roughness values and milling head was tilted to a very small angle to obtain periodic rough surfaces. Experiments were performed with these specimens having roughness value of 0.5, 4.5, 11, 26.5 &micro / m. Ra. The back surface roughness of all specimens was kept constant at 1.5 &micro / m Ra by grinding operation. 1.5, 2, 3, 4 mm. holes were drilled at constant depth and to same side of each specimen to represent reference discontinuities. Ultrasonic tests, using pulse echo technique were carried out to monitor echo amplitudes corresponding to different roughness values. The tests were also repeated by using different ultrasonic probes having different frequencies. For additional comparison, different couplants were used through the tests. The results showed that there was a significant increase in the reduction of the sound pressure level with the increase in the surface roughness. Although there was no uncertainty observed about not being able to detect discontinuity because of roughness but correct couplant and frequency selection has a positive effect on correctly sizing the discontinuity and at attenuation measurements. The results obtained with this work can be used as a guide for testing rough surfaces, predicting the effect on ultrasonic examination before testing and discontinuity detecting capability under rough surface conditions.

Engineers of off-road equipment, on-road vehicles, pavement, and tires must assess the roughness of a terrain surface for the design of their products. The International Roughness Index (IRI), a standardized means of assessing longitudinal road roughness, quantifies roughness based on the average suspension travel for a particular vehicle at a prescribed speed. The Discrete Roughness Index (DRI) developed in this work address fundamental limitations of the IRI. Specifically, the DRI is calculated for each discretely measured location along a terrain surface and is applicable to vehicles traveling at varying speeds and using parameters other than the Golden Quarter-Car on which the IRI is based. The development of the DRI begins with a consistent discretization of the terrain surface, vehicle response, and the IRI. Next the Fractional Response Coefficient is developed, the properties of which are critical in the development of the DRI. The DRI is developed and its properties are discussed through theory and simulation of the ASTM E1926-08 profile. One important property of the average DRI is that it converges to the IRI as the distance between sampled points becomes smaller, for the particular case when the Golden Quarter-Car model is simulated at 80 kph. The DRI is not an alternative to the standard IRI, therefore, but a widely applicable roughness measure of which the standard IRI is a single specialized application. / Master of Science

The subject of the master thesis is to verify the possibility of application of geodetic methods to determine longitudinal and transverse pavement surface roughnesses. Geodetic techniques are compared to techniques specified in ČSN 73 6175. Subject of testing is absolute and relative accuracy of altitude measurement and accuracy of roughness parameter determination. As a result, the graphic interpretation of these parameters and deviations from reference values are presented in the current document. Practical use of the surveying methods is evaluated based on the application of the above mentioned techniques and the results of accuracy analysis.