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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

A method for the characterization of off-road terrain severity /

Malmedahl, Grant Anders, January 2006 (has links)
Thesis (M.S.)--Ohio State University, 2006. / Includes bibliographical references (leaves 99-109). Available online via OhioLINK's ETD Center
22

Modeling effects of random rough surface on conductor loss at microwave frequencies /

Gu, Xiaoxiong, January 2006 (has links)
Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 82-88).
23

Bacterial attachment to micro- and nano- structured surfaces

Mitik-Dineva, Natasa. January 2009 (has links)
Thesis (PhD) - Environment and Biotechnology Centre, Faculty of Life and Social Sciences, Swinburne University of Technology, 2009. / Submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy, Environment and Biotechnology Centre, Faculty of Life and Social Sciences, Swinburne University of Technology, 2009. Typescript. Bibliography: p. 223-240.
24

Quantitative Multiscale Analysis of Topographical Anisotropy on Biological and Engineering Surfaces

Bergstrom, Torbjorn S. 17 April 2019 (has links)
Surfaces cover everything, and since the first standards for the measurement and characterization of surface texture were written researchers, scientists, and engineers have known that all surfaces have a directional property. This property is either an alignment of features or roughness on the surface (anisotropy), a lack of such an alignment (isotropy), or in most cases something in between. In the earliest standards written, this anisotropy of surfaces was characterized visually and referred to as “Lay.” This lay is almost always caused by the process that created the surface of question and can have significant impact on the surfaces performance when interacting with other surfaces in cases where fluids or partials are flowing over the surface. By the late 1900s researchers began to quantify surface anisotropy and by the year 2000 it had been established that surface anisotropy is a multi-scale phenomenon. In this work I look at and expand the state of the art in the characterization of surface anisotropy with examples from both biological and engineering surfaces.
25

The opposition effect in optical scattering from rough surfaces /

Puskar, Robert J. January 1983 (has links)
No description available.
26

Error Mitigation in Roughness Measurements

Wang, Zhuosong 13 August 2014 (has links)
Road roughness is an important factor in determining the quality of a stretch of road. The International Roughness Index, a specific measure of road roughness, is widely used metric. However, in order to measure roughness, an accurate road profile must exist. To measure the roads, terrain profiling systems are commonly used. Modern systems based on laser scanners and inertial navigation systems (INS) are able to measure thousands of data points per seconds over a wide path. However, because of the subsystems in the profiling systems, they are susceptible to errors that reduce the accuracy of the measurements. Thus, both major subsystems - the laser and the navigation system - must be accurate and synchronized for the road to be correctly scanned. The sensors' mounting was investigated to ensure that the vehicle motion is accurately captured and accounted for, demonstrated in the Vehicle Terrain Performance Lab's (VTPL) Ford Explorer profilometer. Next, INS errors were addressed. These may include drift in the inertial measurement unit or errors due to poor reception with the global navigation satellite system. The solution to these errors was demonstrated through the VTPL's HMMWV profilometer. / Master of Science
27

Colloid Detachment from Rough Surfaces in the Environment

Neyland, Ryan P. 05 May 2005 (has links)
Colloid detachment and mobilization can be of significant interest to those studying colloid behavior in the environment. The transport of pathogens such as viruses, bacteria, and protozoa can cause health problems in animals and humans. The transport of organics, radionuclides, and other hydrophobic contaminants can be enhanced by adsorption to mobilized colloid surfaces. Research has been done by others quantifying the detachment of colloids from smooth porous media. Real surfaces in the environment and engineered systems are rough. Glass beads were chemically roughened by procedures similar to those from Shellenberger and Logan (2002) and It et al. (2001) using chromic acid and a citric acid/ammonium fluoride solution. Surface asperities were measured using Atomic Force Microscopy (AFM), and the roughness was defined by three parameters: Root Mean Square (RMS) roughness, peak to valley height (P/V height), and peak to peak distance (λ). Detachment from the chemically etched porous media was measured in column tests. The controlling roughness parameter between the two batches of beads was found to be λ. A theoretical model to predict the effect of roughness on detachment was developed. Using a moment balance around the downstream point of contact, the parameters incorporated into the model were particle diameter, P/V height, and λ. The model predicted the shear required for colloid detachment in column tests. Surface roughness was found to significantly inhibit colloid detachment.
28

A preliminary study on anisotropic polishing behaviors of hydrodynamic polishing process

Chiu, Yi-hung 15 July 2004 (has links)
This study is to investigate that the polishing behavior will be independent of or dependent on the direction of particle motion by the anisotropic polishing phenomenon of hydrodynamic polishing process under the semi-contact lubricating condition. There are two types of experiments to be examined to get to the objectives. First, taking polishing on the work surface which possesses the isotropic surface roughness, to discuss the variation of the smoothing efficiency of the surface irregularities in the five different directions on the work surface. Second, taking three kinds of polishing, ¡§longitudinal, transverse, and oblique roughness polishing¡¨, on the work surface which possesses the anisotropic surface roughness. Then to discuss the variation of the smoothing efficiency of the surface irregularities on the work surface. Both the results of two types experiments should be take to distinguish the difference between one smoothing efficiency and the others from using the hypothesis testing. All hypothesis tests about the experiment results of the work piece which possesses the isotropic surface roughness are accepting . But, most hypothesis tests about the experiment results of the work piece which possesses the anisotropic surface roughness are rejecting . The theory analysis about the smoothing efficiency is discussing. The discussion about the smoothing efficiency can explain the phenomenon due to taking polishing on the work surface which possesses the anisotropic surface roughness. The reason why the phenomenon happened is possible the effects of different lubrication condition. Last, from the lubrication theory, the effects of different lubrication condition due to different surface texture can be employed to verify the explanation about the phenomenon is suitable. The conclusion from the experiment results and the theory analysis is: the polishing behavior is possible independent of the direction of particle motion by the anisotropic polishing phenomenon of hydro- dynamic polishing process under the semi-contact lubricating condition.
29

Development of Basin Factor Methodology for the Pima County Hydrology Procedures

Stewart, Dave January 2008 (has links)
The basin factor is a hydrologic parameter that represents the overall impedance to flow of a watershed in the PC-Hydro peak discharge model for small ( < 10 mi2) semi-arid watersheds in Pima County, Arizona. To improve peak discharge estimates and provide validation of the basin factor as a physically-based parameter, basin factor values were "back-calculated" for return period and observed events on six undeveloped rangeland watersheds and correlated with Manning's n roughness coefficients, rainfall intensities, and hydraulic radii. Observed basin factor values displayed a positive trend with observed peak discharge. The results suggest that the correlated variables can predict the basin factor on small undeveloped sub-basins in Pima County and the basin factor is measurable as a physical parameter. Empirical models for basin factor prediction are proposed. The study may also be useful for estimating hydraulic roughness in hydrologic methods such as the kinematic wave time of concentration equation.
30

Influence of surface roughness on thermography measurement

Zhang, Cheng January 2014 (has links)
This university Bachelor's Thesis was performed to explore the influence of surface roughness on the thermography measurement. Thermography is a non-destructive testing method which can be used to detect cracks. However, it is hard to define how the surface roughness influences the emissivity and the result of a thermography measurement, as well as how the angle of the excitation source influences the result. Therefore, this work aims to define how the heating angle and surface roughness influence the thermography measurement, define the relationship between surface roughness and emissivity for the same crack, and define the influence of the angles which composed of the heating source, the direction of crack and the direction of surface roughness on thermography measurement. In this report, the theories of radiation and Signal-to-noise ratio (SNR) were explained, clearly. Also, two kinds of experiments were set up. One is focus on how the heating angle influence the thermography measurement, the other is focus on how the angle of the heating source, in relation to the crack direction and the direction of surface roughness, influence the SNR value. The conclusions of these experiments are that the heating of a crack increases as the angle decreases (from wide side to narrow side) and the angle ofincreases (from horizontal to vertical). Moreover, the SNR value decreases as the surface roughness increases. For the same surface roughness, the SNR value increases with increased crack angle (0°, 45° or 90°) and with decreased sample position angle (horizontal, 45°or vertical). What is more, the higher surface roughness, the larger the influence of the crack angle and the sample position angle. Finally, when the surface is polish, the crack angle and the sample position angle does not have any influence.

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