Thèse (M. ATDR) -- Université Laval, 1997. / Bibliogr.: f. [169]-171. Publié aussi en version électronique.

Cette thèse présente l'étude et le développement de méthodes numériques pour la résolution d'équations de transport, en particulier d'une méthode de remapping bidimensionnel dont un avantage important par rapport aux algorithmes existants est la propriété de conservation de la masse. De nombreux cas-tests permettront de comparer ces approches entre elles ainsi qu'à des méthodes de référence. On s'intéressera en particulier aux équations dites de Vlasov-Poisson et du Centre-Guide, qui apparaissent très classiquement dans le cadre de la physique des plasmas. / This PhD thesis presents the study and development of numerical methods for the resolution of transport equations, in particular a bidimensional remapping method whose main advantage over existing algorithms is the property of mass conservation. Numerous test cases are presented in order to compare these approaches with regard to the others and with reference methods. Focus is made on the so-called Vlasov-Poisson and Center-Guide equations, that appear very classically in the domain of plasma physics.

The thesis focuses on creating point cloud and mesh model of chosen intersections and their applications in forensic-engineering praxis. In the first part, we describe a workflow for creating point cloud and mesh model of intersection by digital photogrammetry. In the second part, we applied these at chosen intersections. Which leads us to the comparison of three digital photogrammetric programs which we used to make point clouds and mesh models. At the end of thesis, we use our mesh models in forensic-engineering praxis and we decide about barriers in sign conditions at intersections.

This thesis widens the application of intersectionality into the study of visual media. This study examines representational patterns on GQ magazine covers issued in the US with specific regards to gender-race-sexuality intersections. Also, this study seeks to grasp what meaning is conveyed via those representational patterns in conjunction with the visual and linguistic modes, and what social effect it imparts. The study employs a mixed-method approach combining the quantitative content analysis with the social semiotics, and the inter-categorical methodological approach to intersectionality. The findings show that GQ magazine employs the same representational patterns acknowledged in culture and the magazines’ market. Those patterns manifest in the sexual objectification of women, racial exclusion, and emphasis on white heterosexual maleness. Additionally, the intersectional analysis revealed that women of colour and sexual minorities are in the least favourable position regarding representational patterns on GQ magazine.

Improving intersection safety and efficiency are the primary goals of alternative intersection designs. These designs seek to improve on traditional traffic control methods, often by reducing intersection conflict points, reducing or eliminating time-wasting signal phases, or both. However, public opposition to these new designs can be a large barrier to implementation of alternative intersections despite their known safety and efficiency benefits.<br><br>This study evaluated current public perception and factors influencing that perception for four alternative intersection designs - the roundabout, the restricted crossing U-turn (also known as J-turn and reduced conflict intersection), the displaced left turn (also known as the continuous flow intersection), and the diverging diamond interchange (also known as the double crossover diamond interchange). <br><br>To achieve this objective, a survey instrument was designed and distributed to a target sample of 1,000 adults residing in the State of Indiana. The survey solicited participant awareness of these designs, acceptance of a potential implementation of the design in their community, and driver confidence using the design along with participant socio-demographic data. Descriptive and inferential statistical analysis was then conducted. <br><br>The survey results indicate that residents of Indiana are not aware of designs not currently widely implemented in the state, that opposition to these rarer designs is prominent, and that drivers were generally less confident in their ability to safely navigate these unfamiliar designs. Younger respondents, male respondents, more highly educated respondents, respondents who travel more often or for farther distances, and respondents who rate their own driving ability highly are more likely to be aware, accepting, and confident using alternative designs. <br><br>The results of this study will inform future outreach efforts pertaining to alternative intersections by improving transportation agency understanding of public opinions and primary concerns regarding these designs and provide potential paths for improving public perception. <br>

The role of walking in the development of healthy, livable communities is being increasingly recognized. In urban areas, intersections represent locations where different modes converge, and are often viewed as deterrents to walking. This is due to the unwarranted and often unnecessary delays imposed by signal timing policies for pedestrians and increased potential for conflicts. Traditional signal timing design prioritizes vehicles over pedestrians leading to undesirable consequences such as large delays and risky pedestrian behaviors. Pedestrians are accommodated in a manner that is designed to cause least interruption to the flow of motor vehicles. This lack of pedestrian accommodation at signalized intersections is the focus of this dissertation. Understanding pedestrian attitudes and perceptions is important because it offers insights into actual crossing behavior at signalized intersections. An intercept survey of 367 crossing pedestrians was undertaken at four signalized intersections in Portland, Oregon, and binary logistic regression models were constructed to quantify the impacts of demographics, trip characteristics and type of infrastructure on pedestrian perceptions and attitudes regarding delay, crossing time and motivators for crossing decisions. Safety was found to have a larger effect than compliance on the decision to cross the street. Pedestrians at recall intersections expressed higher satisfaction with delay than at actuated intersections. Novel methods to measure pedestrian delay using 2070 signal controllers and Voyage software were developed. These methods have been adopted by the City of Portland to record actuation trends and delays at various intersections. In the absence of demand data, pedestrian push button actuations can be considered as a proxy for crossing demand. The micro-simulation software VISSIM was used to analyze delays resulting from varying pedestrian and vehicle volumes on a network of three intersections in Portland, Oregon. From a pedestrian perspective, free operation was found to be always beneficial due to lower pedestrian delays. However, from a system wide perspective, free operation was found to be beneficial only under low-medium traffic conditions from an overall delay reduction viewpoint, while coordinated operation showed benefits under heavy traffic conditions, irrespective of the volume of pedestrians. Control strategies were developed to identify the best mode of signal controller operation that produced the lowest overall average delay per user. A procedure to identify the optimal control strategy based on user inputs (major street volume to capacity ratios and rate of pedestrian phase serviced for the minor street) was developed. The procedure was applied to a network of three intersections in east Portland, OR and the findings were verified. This research offers significant contributions in the field of pedestrian research. The findings related to attitudes and perceptions of crossing pedestrians offer greater insights into pedestrian crossing behavior and add to the body of existing literature. The methods developed to obtain pedestrian actuations and delay data from signal controllers represent an easy and cost-effective way to characterize pedestrian service at intersections. The results pertaining to signal timing strategies represent an important step towards incorporating pedestrian needs at intersections and demonstrate how control strategies employed to benefit pedestrians could benefit the entire system.

Light or photons can excite electrons in a molecule, leading to creation of electronically excited states. Such processes are ubiquitous in nature, such as, vision, photo-protection of DNA/RNA nucleobases, light harvesting, energy and charger transfer etc. This photoexcitation induces nuclear motion on the excited states, leading the excess energy to dissipate either non-radiatively via internal conversion back down to the ground state, isomerization, and dissociation, or radiatively via fluorescence and phosphorescence. In this dissertation, we investigate the non-radiative processes in organic chromophores that ensue in an ultrafast manner, mediated via conical intersections (CoIn). Description of such excited state processes generally require multi-reference treatment because of quasi-degeneracy near CoIns. Hence, most insight about these processes is typically gained by constructing potential energy surface (PES) using multi-reference electronic structure methods along important reaction coordinates. Nonetheless, the aforementioned static treatment fails to provide any dynamical information, such as, excited state lifetime, state populations, branching ratio, quantum yield etc. In this dissertation, we have gone beyond the static treatment by undertaking computationally expensive non-adiabatic excited state molecular dynamics simulations employing trajectory surface hopping (TSH) methodology on PESs created on-the-fly using multi-reference electronic structure methods. This allows us to compare theoretical results to experimental observables, when possible, strengthening the explanations underlying those processes. Our goal is to examine the effect of structure, and of electronic structure methods on the excited state dynamics. We have examined the non-adiabatic excited state dynamics of cis,cis-1,3-cyclooctadiene (cc-COD), a cyclic diene, in an effort to systematically compare and contrast the dynamics of cc-COD to that of other well studied conjugated molecules. Such exploration is very significant, since the majority of the molecules involved in natural photoexcited processes, include an ethylenic double bond or alternating double bonds creating conjugation. Our calculations have revealed ultrafast sub-ps decay for cc-COD, and have illustrated that the internal conversion dynamics is facilitated by CoIns, dominated by twisting of one of the double bonds and pyramidalization of one of the carbons of that double bond, similar to trans-1,3-butadiene and unlike 1,3-cyclohexadiene (CHD). Our high-level electronic structure calculations have also explained the features in the experimental time-resolved photoelectron spectrum of cc-COD. Another molecule of biological importance, uracil, was also investigated using TSH simulations, by systematically increasing dynamical correlation. We have found that the inclusion of dynamical correlation for uracil leads to an almost barrierless PES on S2, leading to a faster decay and no population trap on this state. Uracil also contains a double bond and the simulations have revealed that the ultrafast relaxation is dominated by an ethylenic twist and pyramidalization of a carbon of that bond, increasing importance of such nuclear motion in photoexcited molecular dynamics. A comparison of the molecules studied have illustrated that the rigid molecules, such as uracil, CHD, have a very local CoIn seam space, whereas cc-COD, which is flexible having many low frequency degrees of freedom, has a non-local or extended CoIn seam space. Overall, the work performed in this dissertation, elucidates the significance of structure and conjugation, in the photoinduced coupled electron-nuclear dynamics in organic molecules. / Chemistry

Major crossroads are designed to facilitate the conflicting movements of numerous vehicles in a manner that is both safe and efficient. Accesses located within the functional areas of major crossroads add complication to intersection activity due to additional conflicts arising from ingressing and egressing movements at the accesses. In this research, the impact of accesses on crashes within major crossroad functional areas was analyzed. Specifically, the effects of access spacing within functional areas and access setback from intersections were addressed. In order to conduct the analysis, the functional areas of 159 signalized major arterial crossroads across the state of Utah were examined. A database was built containing the frequency, type, and severity of functional area crashes as well as the intersection and roadway characteristics within the functional area. Statistical analyses were conducted to determine the influence of accesses in intersection functional areas on functional area crashes. The statistical analyses show that the existence of accesses within the functional areas was correlated with increased crashes and crash severity costs. In particular, an increase in commercial access density was associated with increases in crash totals, crash rates, and rear end crashes in intersection functional areas. The analyses also showed that study site intersections meeting Utah Department of Transportation (UDOT) corner clearance standards exhibited fewer right angle crashes and lower crash severity costs. Finally, intersections that prohibited all unsignalized access had lower crash totals, crash rates, right angle crash totals, and rear end crash totals than intersections that allowed some unsignalized access.

Since its inception in 1965, the Level-of-Service (LOS) has proved to be an important and practical "quality of service" indicator for transportation facilities around the world, widely used in the transportation and planning fields. The LOS rates these facilities' traffic operating conditions through the following delay-based indicators (ordered from best to worst conditions): A, B, C, D, E and F. This LOS rating has its foundation on quantifiable measures of effectiveness (MOEs) and on road users' perceptions; altogether, these measures define a LOS based on acceptable traffic operating conditions for the road user, implying that traffic safety is inherent to this definition. However, since 1994 safety has been excluded from the LOS definition since it cannot be quantified nor explicitly defined. The latter has been the motivation for research based on the LOS-Safety relationship, conducted at the University of Central Florida (UCF). Using data from two of the most studied transportation facility types within the field of traffic safety, signalized intersections and multilane high-speed arterial corridors, the research conducted has the following main objectives: to incorporate the LOS as a parameter in several traffic safety models, to extend the methodology adopted in previous studies to the subject matter, and to provide a platform for future transportation-related research on the LOS-Safety relationship. A meticulous data collection and preparation process was performed for the two LOS-Safety studies comprising this research. Apart from signalized intersections' and multilane-high speed arterial corridors' data, the other required types of information corresponded to crashes and road features, both obtained from FDOT's respective databases. In addition, the Highway Capacity Software (HCS) and the ArcGIS software package were extensively used for the data preparation. The result was a representative and robust dataset for each LOS-Safety study, to be later tested and analyzed with appropriate statistical methods. Regarding the LOS-Safety study for signalized intersections, two statistical techniques were used. The Generalized Estimating Equations (GEEs), the first technique, was used for the analyses considering all periods of a regular weekday (i.e. Monday through Friday): Early Morning, A.M. Peak, Midday, P.M. Peak and Late Evening; the second technique considered was the Negative Binomial, which was used for performing an individual analysis per period of the day. On the other hand, the LOS-Safety study for multilane high-speed arterial corridors made exclusive use of the Negative Binomial technique. An appropriate variable selection process was required for the respective model building and calibration procedures; the resulting models were built upon the six following response variables: total crashes, severe crashes, as well as rear-end, sideswipe, head-on and angle plus left-turn crashes. The final results proved to be meaningful for the understanding of traffic congestion effects on road safety, and on how they could be useful within the transportation planning scope. Overall, it was found that the risk for crash occurrence at signalized intersections and multilane high-speed arterial corridors is quite high between stable and unacceptable operating conditions; it was also found that this risk increases as it becomes later in the day. Among the significant factors within the signalized intersection-related models were LOS for the intersection as a whole, cycle length, lighting conditions, land use, traffic volume (major and minor roads), left-turn traffic volume (major road only), posted speed limit (major and minor roads), total number of through lanes (major and minor roads), overall total and total number of left-turn lanes (major road only), as well as county and period of the day (dummy variables). For multilane-high speed arterial corridors, the final models included LOS for the road section, average daily traffic (ADT), total number of through lanes in a single direction, total length of the road section, pavement surface type, as well as median and inside shoulder widths. A summary of the overall results per study, model implications and each LOS indicator is presented. Some of the final recommendations are to develop models for other crash types, to perform a LOS-Safety analysis at the approach-level for signalized intersections, as well as one that incorporates intersections within the arterial corridors' framework.

The description logic ALCQI extends the 'standard' description logic ALC by qualifying number restrictions and converse roles. We show that conept satisfiability for this DL is still decidable in polynomial space. The presented algorithm combines techniques from [Tob99a] to deal with qualifying number restrictions and from [HST99] to deal with converse roles. Additionally, we extend the result to ALCQIR, which extends ALCQI by role intersections. This solves an open problem from [DLNN97]. The result for ALCQI has already been presented in the seperate technical report [Tob99b]. In this report we use the same techniques to obtain the stronger result for ALCQIR.