Browsing by Subject "Speed"
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Item A Multivariate Analysis of Freeway Speed and Headway Data(2013-11-11) Zou, YajieThe knowledge of speed and headway distributions is essential in microscopic traffic flow studies because speed and headway are both fundamental microscopic characteristics of traffic flow. For microscopic simulation models, one key process is the generation of entry vehicle speeds and vehicle arrival times. It is helpful to find desirable mathematical distributions to model individual speed and headway values, because the individual vehicle speed and arrival time in microscopic simulations are usually generated based on some form of mathematical models. Traditionally, distributions for speed and headway are investigated separately and independent of each other. However, this traditional approach ignores the possible dependence between speed and headway. To address this issue, the dissertation presents two different methodologies to construct bivariate distributions to describe the characteristics of speed and headway. Based on the investigation of freeway speed and headway data measured from the loop detector data on IH-35 in Austin, it is shown that there exists a weak dependence between speed and headway and the correlation structure can vary depending on the traffic condition. The dissertation first proposes skew-t mixture models to capture the heterogeneity in speed distribution. Finite mixture of skew-t distributions can significantly improve the goodness of fit of speed data. To develop a bivariate distribution to capture the dependence and describe the characteristics of speed and headway, finite mixtures of multivariate skew-t distributions are applied to the 24-hour speed and headway data. The bivariate skew-t mixture model can provide a satisfactory fit to the multimodal speed and headway distribution and this modeling approach can accommodate the varying correlation structure between speed and headway. To avoid the restriction of the bivariate skew-t distributions that individual behavior of speed and headway is described by the same univariate distributions, this research proposes copulas as an alternative method for constructing the multivariate distribution of traffic variables. Copula models can adequately represent the multivariate distributions of microscopic traffic data and accurately reproduce the dependence structure revealed by the speed and headway observations. This dissertation compares the advantages and disadvantages of copula models and finite mixtures of multivariate distributions. Overall, the proposed methodologies in this dissertation can be used to generate more accurate vehicle speeds and vehicle arrival times by considering their dependence on each other when developing microscopic traffic simulation models.Item Adhesion of particles on indoor flooring materials(2007-12) Lohaus, James Harold, 1968-; Siegel, Jeffrey A.This dissertation involved a theoretical and experimental investigation of the adhesive forces between spherical particles of four different diameters and two selected flooring materials under different air velocities. Previous theoretical work and experiments described in the literature tended to be conducted with idealized surfaces, and therefore have limited applicability to indoor environments. Controlled experiments were designed, constructed and executed to measure the air velocity required to overcome adhesion forces. The diameters of the particles investigated were 0.5, 3.0, 5.0 and 9.9 [mu]m, and the flooring materials were linoleum and wooden flooring. The critical velocity, the flow at which 50% of the particles detached, is presented as a function of particle diameter for each surface. The measured values were then compared to empirical and theoretical models as well as to a scaling analysis that considers component forces that act on a particle-surface system. The results suggest that critical velocity decreases with increasing particle diameter and that existing models have limited applicability to resuspension from flooring materials.Item Andy Warhol's cinema beyond the lens(2013-05) Weathers, Chelsea Lea; Reynolds, Ann MorrisThis dissertation examines a small selection of the hundreds of films made by Andy Warhol and his collaborators between 1963 and 1968. Each chapter contextualizes a particular aspect of Warhol's filmmaking in terms of the artistic and cultural circumstances that informed it. Through an analysis of the content of specific films, rather than just their formal or stylistic tendencies, I discuss how the filmmaking process might have functioned for those involved in the films' production, as well as how those films might have functioned for specific spectators. The first chapter is a speculation on how Warhol might have understood filmmaking as a method for creating concrete connections between feelings and things -- for collecting imagery with his camera in order to create a historical catalog of people and their emotions. This first chapter also considers how some art critics in the 1960s used Warhol's early silent films as exemplars for their own anti-formalist art-historical and critical discourses. The second chapter examines the relationship between Warhol's films and the proliferation of amphetamine use amongst his collaborators. Amphetamines functioned to perpetuate for its users a way of life based on an alternative conception of time, and often involved a continued engagement with bad feelings, which fueled much of the creativity of the artistic community whose locus was Warhol's Factory in the mid-1960s. As such, many of Warhol's films from this period exhibit what I term an "amphetamine aesthetic" -- visual clues that suggest the effects of long-term amphetamine use by its participants. The third chapter is an analysis of a single film, Lonesome Cowboys. Participants in the film's production used the conventions of the Hollywood Western film genre to create a circumscribed space for transforming their everyday lives and their relationship to contemporary politics in the late 1960s. All of these chapters explore the effects of Warhol's particular approach to filmmaking, which involved Warhol's own detached style of directing, as well as his cultivation of an ultrapermissive environment in which his collaborators -- actors, directors, writers, and technicians -- felt free to experiment. This environment was predicated on the idea that the boundary between the space in front of the camera and the world beyond it was simultaneously arbitrary and deeply imbricated. Such a fluid boundary between the world inside and outside the scope of Warhol's camera is in part why some spectators, watching his films a half-century after they were made, might still find new meanings for the present in the films themselves.Item The effects of walking speed and an uneven surface on dynamic stability margins in young adult subjects with and without traumatic unilateral trans-tibial amputations(2009-12) Scott, Shawn James; Dingwell, Jonathan B.; Abraham, Larry; Jensen, Jody; Wilken, Jason M.; Childs, JohnDynamic stability is commonly defined as the ability to maintain balance through center of mass control during locomotion. Patients with locomotor impairments are especially challenged when walking over uneven surfaces (Richardson 2004). We studied dynamic stability margins in young healthy adults and in adults with unilateral traumatic trans-tibial amputations (TTA). To date, studies have not controlled for walking speed over an uneven surface in a patient population. We hypothesized that: 1) DSMs would increase over the uneven rocky surface (URS) for both groups, 2) DSMs would be greater on the involved side at faster walking speeds for subjects with TTA and, 3) DSMs would increase more for the involved limb when on the URS. 17 (4 females, 13 males) young healthy military service members (22.8 ± 6.4 years) and 12 (1 female, 11 males) service members (27.2 ± 4.7 years) with traumatic unilateral trans-tibial amputations participated in two study designs. A 15-segment model was used to estimate whole body COM motions. All subjects walked at 5 dimensionless speeds over a flat level surface (FLS) and an URS. Subjects completed 6-10 trials over each surface at each speed. Minimum frontal plane DSM values were extracted for each stride for statistical analyses. For young healthy subjects a two factor (speed x surface) ANOVA was used to test significance (p<.05). The DSMs were not greater over the URS (p=.307), but a main effect due to speed was found (p<.001) for young healthy subjects. In contrast, DSMs were significantly larger when subjects with TTA walked on the URS compared to the FLS (p = 0.011). For subjects with unilateral TTA, a three-factor ANCOVA ((amputation) side x speed x surface) with residual limb length (p=.029) and time in prosthesis (p=.741) as covariates was used for hypothesis testing. When limb length and time in prosthesis were accounted for there was no significant within subjects effect due to speed (p=.656). There were no significant differences between involved and uninvolved limbs (p = 0.211). There were no significant interaction effects. In conclusion, there was a difference in DSMs due to speed in unimpaired subjects and due to surface and residual limb length in subjects with unilateral TTAs. In subjects with unilateral TTA side-to-side symmetry was found for DSM measures, which was in contrast to an earlier study of subjects with unilateral trans-femoral amputations (Hof 2006). It appears that symmetry and dynamic stability are reasonable expectations for young adults with isolated TTAs.Item How fast is too fast? : examining the impact of speed-driven journalism on news production and audience reception(2014-08) Lee, Angela Min-Chia; Coleman, RenitaNew media technology is altering many aspects of mass communication processes. One of the most profound changes, especially in the newspaper industry, lies in the rise of speed-driven journalism, with growing emphasis on what is new or happening now. With more newspapers adopting this speed-driven news practice, the nature of its impact on journalists and audiences necessitates empirical examination, and this dissertation seeks to contribute to the professional and academic literature from a two-part, mixed method approach. Through interviews with journalists, study 1 sought to understand journalists' view of how speed-driven journalism affects their professional norms, routines and output, and how social media factors into the speed-driven online media landscape. The interviewees were also asked to discuss their view on how speed-driven journalism affects news audiences in terms of news credibility, news use, and paying intent. Based on findings from study 1, an experiment on news audiences was conducted in study 2 to assess the impact of speed-driven journalism on news credibility, future use, paying intent, readability and selective scanning. Key findings from both studies include: (1) Whereas most interviewees in study 1 believed that speed harms news credibility but boosts news use, the experiment in study 2 revealed that speed neither harms news credibility nor promotes future use. (2) Speed-driven journalism has no effect on selective scanning or audiences' paying intent. (3) In terms of readability, news stories presented in the live blog-like format are deemed harder to follow when compared to those presented in the traditional format. This dissertation advances the hierarchy of influence model by uncovering the effect of perceptual disconnect on speed-driven news practices at the social institutions level. That is, journalists are wrong at times in their assessment of how audiences engage with and are affected by new media technology, but nonetheless proceed to produce news and content based upon their mistaken judgment.