Traditional tribology is based on the surface with random micro structures due to limitations of manufacturing technology. The modern manufacturing technology now promises to fabricate surfaces with regular micro structures (or asperities). The word asperity refers to a single physical entity on the surface of a material, contributing to a concept called roughness in traditional tribology. Regular asperity surfaces imply that all asperities on the surface of a material have the same shape and size, and a deterministic distribution over the surface. The emergence of regular asperity surfaces will have a transformative impact to the discipline of tribology.<p> The overall objective of this thesis is to study how the regular asperity would affect the tribological behavior. Specifically, this thesis develops a computational model to demonstrate and characterize the effect of the surface with regular anisotropic asperities (RAA) on the directional friction behavior when the surface is in a fully lubricated state. By directional friction, it is meant that friction force changes its magnitude with the change of the relative motion direction. By anisotropic asperity, it is meant that the geometry of the asperity is not symmetrical along the motion direction.<p> This thesis presents a detailed development of the computational model by employing computational fluid dynamics (CFD) techniques. In particular, the model takes the Navier-Stokes (NS) equation as a governing equation and the Half-Sommerfeld Condition (HSC) to represent fluid behavior in the cavitation region; as such the model is named NS-HSC for short. Verification of the NS-HSC model is conducted with the information available in literature. A theory is proposed to explain the relationship between directional friction behavior and specific RAA structures. The thesis concludes: (1) the NS-HSC model is more accurate than the existing model in the literature and can be used to predict directional friction behavior and to design RAA surfaces, and (2) the proposed theory is excellent consistent with the NS-HSC model and thus useful to analysis and design of RAA surfaces for directional friction.<p> The major contributions of this thesis are: (1) the first model in the field of tribology to predict the directional friction behavior for RAA surfaces under a fully lubricated status, (2) the first investigation, in the field of CFD, into combining the NS and HSC for modeling a laminar flow with cavitation, and (3) the first theory in the field of tribology for directional friction on fully lubricated RAA surfaces.

Thesis (Ph. D.)--University of Oregon, 2002. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 127-139). Also available for download via the World Wide Web; free to University of Oregon users. Address: http://wwwlib.umi.com/cr/uoregon/fullcit?p3045096.

Principal neurons of the medial superior olive (MSO) encode low-frequency sound localization cues by comparing the relative arrival time of sound to the two ears. In mammals, MSO neurons display biophysical specializations, such as voltage-gated sodium (Na[subscript v]) and potassium (K[subscript v]) channels that enable them to detect these cues with microsecond precision. In this dissertation electrophysiological techniques were used to examine the specific channel properties and functional role these channels play in MSO neurons following hearing onset. In addition, computational models that incorporated these physiological data were used to further study how the specific properties of these channels facilitate MSO function. Experiments in this dissertation showed that Na[subscript v] channels are heavily expressed in the persisomatic region of MSO neurons, but unlike those expressed in other neurons they minimally contribute to action potential generation. This is likely due to the low percentage of channels available for activation at the resting membrane potential. Current clamp recordings determined that Na[subscript v] channels counterbalance K[subscript v] channels voltage rectification by boosting near action potential threshold excitatory post-synaptic potentials (EPSPs). Further, computational modeling revealed that synaptic inputs are larger at the soma with Na[subscript v] channels restricted to the soma than when they are evenly distributed throughout the soma and dendrites. During the first few weeks after hearing onset current clamp experiments showed EPSP duration decreased while the temporal resolution for detecting the arrival time of synaptic inputs increased. These changes in EPSP duration are due in part to both the development of faster membrane response properties and increases in the expression of low voltage-activated K[subscript v] channels (K[subscript LVA]). Further investigation determined these channels display a somatically enriched distribution and act to counterbalance the distortions that result from dendritic cable filtering. This is accomplished by K[subscript LVA] actively decreasing the duration of EPSPs in a voltage dependent manner. Computational modeling confirmed these results as well as illustrating their effects on the integration of mono- versus bilateral excitation. Together these findings indicate that the expression of specialized Na[subscript v] and K[subscript v] channels facilitate the neuron’s computational task, detecting and comparing the relative timing of synaptic inputs used in low frequency sound localization. / text

Many bridges are handling heavier loads than those expected at design, making it increasingly necessary to strengthen existing members or conduct repairs on damaged structural members. Carbon Fiber Reinforced Polymer (CFRP) materials have been broadly used to repair and strengthen reinforced concrete structures. Using CFRP materials as the strengthening material is an excellent solution because of their mechanical properties. CFRP has properties of high strength, corrosion resistance, and light weight. CFRP materials are being widely used for shear and flexural strengthening. Most studies have focused on uni-directional layout of CFRP strips in high shear regions of beams. Recent shear tests on full-scale I-girders have shown that the use of bi-directional CFRP layouts with CFRP anchors led to much higher shear strength increases than when using uni-directional layouts. The objective of the study is to determine the mechanism that governs shear strengthening of bridge girders using bi-directional CFRP and, in doing so, demonstrate the feasibility of using bi-directional CFRP for shear strengthening of large bridge I- and U-beams. Small-scale panel tests have been conducted to investigate parameters that influence the shear strength provided by bi-directional CFRP layouts. Panels were tested under compressive forces to simulate the compression struts that develop in the webs of I-beams. The applied loads generated bottle-shaped compressive struts. CFRP anchors were used to prevent early failure due to CFRP strip delamination from the panel surface. The panels, while not fully reproducing the boundary condition of girder webs, were tested ahead of full-scale girders to investigate a wide range of parameters in a cost-effective manner. The variables considered include the amount of CFRP and steel reinforcement, the inclination of CFRP fibers, and the layout and spacing of CFRP strips. The panel tests provide qualitative comparisons between the influence of the various parameters. The relative strength contributions of CFRP strips, steel stirrups, and concrete were evaluated. / text

No description available.

Crickets rely on binaural comparisons of intensity to locate sound. Intensity can be encoded by response magnitude as well as response latency. The effects of sound intensity and pulse repetition rate on the auditory responses of the tympanal nerve were investigated. Adaptation, a decline in the response due to repeated stimulation, is greater for higher pulse rates and higher intensities. Since sound intensity is louder at the ear closer to the sound source, adaptation is more pronounced in the ipsilateral ear. As a result, the interaural difference in response magnitude decreases. Therefore response magnitude cannot be a reliable cue for sound location. I found that response latency also adapts: it increases over time. However, this change is not intensity dependent. So interaural latency difference is stable over time. The results show that interaural latency difference is a more reliable cue than interaural magnitude difference to locate sound.

This thesis examines the properties of spatial (i.e., locational and directional) Ps within the minimalist framework (Chomsky 1995,1998,1999), which has put an ultimate emphasis on economy in terms of derivation and representation. The principal goals of this thesis are (i) to investigate how the syntax of such nature derives PPs in accordance with the properties of Ps and (ii) to show how the internal PP structure interacts with the external syntax of PP. Chomsky's minimalist framework assumes two syntactic operations, i.e.. Merge and Move, and two different types of outcome of the operations, depending on the properties of lexical items involved in each operation executed. One outcome results from a merger of two items, of which one selects the other. The other results from a merger of two items, neither of which selects the other. I propose that there are three heads involved in deriving a layered PP structure: functional p, lexical P and locative N. This analysis is shown to be empirically supported from languages such as Dutch, English, Hungarian, Japanese and K'ekchi. I also claim that there are also intransitive Ps that adjoin to either or pP. The internal structure of PP interacts with its external syntax. One apparent area of grammar that shows desirable consequences for the layered PP analysis is P-to-V incorporation. For instance, the incorporability versus the unincorporability of Ps in Dutch can be accounted for by the principle (i.e.. Minimal Link Condition) that forbids skipping over an intermediate head, thus supporting the layered structure of PP. Another area offering support is locative inversion: the presence versus the absence of locative N head in PP can account for a contrast observed in locative inversion facts. Provided that an EPP-feature of T is category-specific, a contrast between PPs that can undergo movement to [Spec, T] and those that cannot stems from their respective internal structures.

Thesis (Ph.D.)--University of Tulsa, 1986. / Bibliography: l. 104-116.

Thesis (Ph. D.)--Discipline of Physiology, Faculty of Medicine, University of Sydney, 2004. / Includes list of published articles: leaf iv. Bibliography: leaves [188]-203.

Thesis (Ph. D.)--University of Sydney, 2004. / Title from title screen (viewed 14 May 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Discipline of Physiology, Faculty of Medicine. Includes bibliographical references. Also available in print form.