Texte remanié de: Dissertation--Fachbereich III--Universität Trier, 1996. / Notes bibliogr.

Thesis (M.S. in E.S.M.)--School of Civil and Environmental Engineering, Georgia Institute of Technology, 2004. Directed by Laurence Jacobs. / Includes bibliographical references (leaves 111-114).

Thesis (M.S. in M.E.)--School of Mechanical Engineering, Georgia Institute of Technology, 2004. Directed by Marc K. Smith. / Includes bibliographical references (leaves 63-64).

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Civil and Environmental Engineering." Includes bibliographical references (p. 194-197).

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 105-108). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains viii, 69 p. : ill. (some col.), col. maps. Includes abstract. Includes bibliographical references (p. 55-58).

Not available / text

Urban VANET (Vehicular Ad hoc NETworks) performance optimization concerns the improvement of wireless signal quality between two arbitrary selected nodes moving within along city streets. It includes three procedures: VANET architecture modeling; wireless signal simulation; and signal quality optimization techniques. The first procedure converts real-world map data into a network graph according to the requirement of the optimization algorithm. The second step analyzes a communication route between two network nodes and calculates received signal quality with the information provided by the network model. The final operation optimizes the signal quality to an expected level by choosing appropriate communication route between two wireless nodes. In this thesis, three optimization techniques are presented: EP (Evolutionary Programming), SG (Stochastic Geometry) and SW (Small World). EP is a widely applied optimization strategy based on Darwin’s natural selection and evolution theory. It is effective with an enormous number of data support, and it can provide detailed route information. However, it requires enough time to evolve to an optimal solution. SG is a statistical tool to analyze points’ distribution within a multi-dimensional space, and it was recently applied on wireless network analysis. Given the distribution characteristics of an urban area, SG can calculate average data loss rate of a communication route. However, it cannot provide detailed route information. SW is a widely accepted model to represent people’s relationship in social networks, and it can be used in VANET analysis. SW provides a simplified network architecture compared with EP an SG. However, it requests additional long-range communication equipment and consumes more energy. The thesis is divided into three parts. Chapter 1 introduces the history of VANET and its architecture (in this research, it is a combination of Ad hoc network and WSN (Wireless Sensor Network)). Chapter 2 and 3 presents literature review of EP and SG. Chapter 4, 5, and 6 discusses how to implement EP, SG and SW on Boston VANET. At the end of each chapter, a conclusion is presented and a discussion on the author’s contribution is given.

This thesis investigates the use of Discrete Element Modelling (DEM) to simulate the elastic and viscoelastic deformation behaviour of an asphalt mixture. A numerical specimen preparation procedure has been developed to produce specimens with an isotropic stress and correct volumetrics. Stone mastic asphalt has been chosen in this project because of its high content of coarse aggregate and binder-rich mortar. A range of uniaxial compression tests have been undertaken in the laboratory under various loading speeds and stresses. The axial stress, axial strain and radial strain were recorded during the tests. The peak stress is found to be as a power-law function of the strain rates for the asphaltic material. Elastic contact properties have been used to investigate the effect of particle number and location, loading speed, normal and shear contact stiffness. The Poisson's ratio was found to increase with the ratio of normal to shear contact stiffness but was independent of the stiffnesses. The Young's modulus was found to be dependent on both normal and shear stiffnesses, in agreement with previous work on idealised asphalt mixtures. The Burger's model was introduced to give time-dependent stiffness for the viscoelastic modelling. The Burger's model was implemented to give moment and torsional resistance as well as in direct tension and compression. To reduce the computational time in the creep simulations, the effect of scaling both viscosities in the Burger's model to simulate a shorter time, have been investigated. The effects of each parameter on the deformation of asphalt mixture were also investigated. The stress-strain response for the laboratory tests and the simulations were recorded. The results show good agreement when the bond strengths in the model are made to be a function of strain rate for both constant strain rate and creep conditions. Both normal and Weibull distributions have been used for the bond strengths between the aggregate particles. The constant strain rate tests results were proved to be independent of the bond strength variability and position of particles, while the creep tests results were dependent on the hand strength variability and position of particles. This is in good agreement with experimental tests: different specimens at the same stress level gave variability in the creep behaviour, at higher stress levels. Bond breakages were recorded during the simulations to investigate the micromechanical deformation behaviour of asphalt mixtures. It was found that a well-defined rupture at higher stress levels coincided with the maximum rate of bond breakage. The modified Burger's model has therefore proven to be a useful tool in modelling the moment and torsional resistance at particle contacts in an asphalt mixtures, in order to correctly predict observed behaviour.

No description available.