On contact of curves and surfaces

Thesis (M.A.)--University of Kansas, Mathematics, 1923

A Heuristic Approach to the Theater Distribution Problem

Analysts at USTRANSCOM are tasked with providing vehicle mixtures that will support the distribution of requirements as provided in the form of TPFDD. An integer programming model exists to search for optimal solutions to these problems, but it is fairly time consuming, and produces only one of potentially several good quality solutions. This research constructs a number of heuristic approaches to solving the TDP. Two distinct shipping methods are examined and applied through both constructive and probabilistic vehicle assignment processes. Multistart metaheuristic approaches are designed and used in conjunction with the constructive and probabilistic approaches. Random TPFDDs of size 20, 100 and 1000 are tested, and solutions are compared to those obtained by the integer programming approach. The heuristic models implemented in this research develop feasible solutions to the notional TPFDDs in less time than the integer program. They can very quickly identify a number of good quality solutions to the same problem

Evidence for fault lubrication during the 1999 Chi-Chi, Taiwan, earthquake (Mw7.6)

The ground motion data of the 1999 Chi-Chi, Taiwan, earthquake exhibit a striking difference in frequency content between the north and south portions of the rupture zone. In the north, the ground motion is dominated by large low-frequency displacements with relatively small high-frequency accelerations. The pattern is opposite in the south, with smaller displacements and larger accelerations. We analyze the fault dynamics in light of a fault lubrication mechanism using near-field seismograms and a detailed rupture model. The fault zone contains viscous material (e.g., gouge), in which pressure increases following the Reynolds lubrication equation. When the displacement exceeds a threshold, lubrication pressure becomes high enough to widen the gap, thereby reducing the area of asperity contact. With less asperity contact, the fault slips more smoothly, suppressing high-frequency radiation

Childhood Trauma and Eating Psychopathology:A Mediating Role for Dissociation and Emotion Dysregulation?

The present study examined the relationship between different forms of childhood trauma and eating psychopathology using a multiple mediation model that included emotion dysregulation and dissociation as hypothesised mediators. 142 female undergraduate psychology students studying at two British Universities participated in this cross-sectional study. Participants completed measures of childhood trauma (emotional abuse, physical abuse, sexual abuse, emotional neglect and physical neglect), eating psychopathology, dissociation and emotion dysregulation. Multiple mediation analysis was conducted to investigate the study's proposed model. Results revealed that the multiple mediation model significantly predicted eating psychopathology. Additionally, both emotion dysregulation and dissociation were found to be significant mediators between childhood trauma and eating psychopathology. A specific indirect effect was observed between childhood emotional abuse and eating psychopathology through emotion dysregulation. Findings support previous research linking childhood trauma to eating psychopathology. They indicate that multiple forms of childhood trauma should be assessed for individuals with eating disorders. The possible maintaining role of emotion regulation processes should also be considered in the treatment of eating disorders

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy

Smokers' response to standardised tobacco packaging

In May 2017, the UK became the third country to fully implement standardised tobacco packaging. The requirement was phased in, with companies given 12 months from May 2016 to make the transition from fully-branded to plain, standardised cartons. The policy was introduced by the UK Government following the report of the independent review into standardised packaging of tobacco. The Review concluded that the introduction of standardised packaging, as part of a comprehensive policy of tobacco control, would be very likely over time to contribute to a modest yet important reduction in smoking prevalence. Additionally, the UK Department of Health estimates that standardised packaging will have a net benefit to government of £25 billion ten years post-implementation. However, the review also acknowledged that its conclusions were based on limited evidence. This briefing paper, summarising one of the first studies to explore how smokers responded to standardised packaging in the UK, adds to the body of evidence on the likely effect of standardised packaging on tobacco consumption. In doing so, it provides policymakers with a robust tool by which to evaluate the initial impact of the policy

Elastohydrodynamic lubrication of faults

The heat flow paradox provides evidence that a dynamic weakening mechanism may be important in understanding fault friction and rupture. We present here a specific model for dynamic velocity weakening that uses the mechanics of well-studied industrial bearings to explain fault zone processes. An elevated fluid pressure is generated in a thin film of viscous fluid that is sheared between nearly parallel surface. This lubrication pressure supports part of the load, therefore reducing the normal stress and associated friction across the gap. The pressure also elastically deforms the wall rock. The model is parameterized using the Sommerfeld number, which is a measure of the lubrication pressure normalized by the lithostatic load. For typical values of the material properties, slip distance and velocity, the Sommerfeld number suggests that lubrication is an important process. If the lubrication length scales as the slip distance in an earthquake, the frictional stress during dynamically lubricated large earthquakes is 30% less than the friction with only hydrostatic pore pressure. Elastohydrodynamic lubrication also predicts a decrease in high-frequency (>1 Hz) radiation above a critical slip distance of a few meters. This prediction is well matched by the strong motion data from the 1999 Taiwan earthquake. The observed 2 orders of magnitude variation in scaled radiated energy between small (M_w 6) is also predicted by the lubrication model