Molecular dynamics is a technique in which the trajectories of a group of particles are calculated as a function of time by integrating the equations of motion. In this thesis we study the use of molecular dynamics for atoms in a crystal. A model is introduced which describes interactions of a physical system with an external heat reservoir in molecular dynamics simulations. This is accomplished by the addition of a "virtual variable" to the Hamiltonian which is used to scale time. Aspects of this model are discussed and examples are presented for a simple system. Similarly, a constant pressure model is introduced in which additional virtual volume variables are added to the Hamiltonian. The volume and shape of the molecular dynamics cell are now free to vary. Simple examples are discussed. Aspects of the computer programs and the algorithms are explained. Particular attention is focused on the methods used to integrate the equations of motion and to calculate the coulomb interactions. Examples of simulations using a zirconium oxide crystal are presented. We study the effects of heat bath and pressure bath simulations, both separately and in combination. Various features of the behavior are investigated with the primary focus on phase changes, numerical errors, and parameters describing the heat and pressure baths. / Graduation date: 1996

Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Ludovice, Pete; Committee Member: Chen, Rachel; Committee Member: Harvey, Steve; Committee Member: Sambanis, Athanassios; Committee Member: Wartell, Roger. Part of the SMARTech Electronic Thesis and Dissertation Collection.

No description available.

A project report submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg in partial fulfillment of the requirements for the degree of Master of Science in Engineering. / Urban stormwater drainage designers and planners are having to deal with the dramatic effect that urbanization has on the hydrological regime. To cope economically with the increases in runoff volumes and peaks due to urbanization, more sophisticated approaches are required for the design and planning of stormwater drainage systems. [Abbreviated abstract. Open document to view full version] / AC2017

This thesis presents a discussion of motion of a six-legged walking machine following removal of one leg constraint. To take a step, one leg must be lifted and placed at some other position. As soon as the constraint provided by the leg is removed, however the machine begins to fall. This falling motion can be represented as screw motion of the body center of mass and of body-leg attachments. First a study of body workspace of the machine was done with all six feet on the ground. Body workspace is the intersection of kinematic and force workspaces. Kinematic workspace is the volume in space where the center of mass can be placed such that all joint angles of legs are within specified limits; and force workspace is the volume in space where the force in all legs is compressive. The affect of various foot positions, pitches and heights of the center of mass were investigated to find a set of three symmetric foot positions that might constitute acceptable intermediate positions in a walking sequence. Motion of the center of mass in the forward direction is limited in the force workspace by two points at which the force on a pair of legs goes to zero. With the center of mass at each of these two positions, the screw parameters resulting from the release of force on one leg (front, middle and hind individually) could be determined. Dynamic simulation of these body and foot positions used the commercial software SD/FAST. Code was written in C to do both static and dynamic simulation of machine and merged with code generated by SD/FAST. Code was also written in Auto Lisp to plot the falling motion of machine. Screw parameters found in this study were such that sustained forward motion of the body could not be achieved using the falling motion alone. Other measures such as extending one or more of the remaining five legs would be needed for effective forward body motion. / Graduation date: 1994

Thesis (M.S.)--Mississippi State University. Department of Computational Engineering. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--Mississippi State University. Department of Computational Engineering. / Title from title screen. Includes bibliographical references.

No description available.

Significant reductions in the number of defects in parts produced by investment casting can be obtained by improving the flow of the molten metal during pouring. Studies have been done at Oregon State University with simulated casting techniques to determine optimal mold configurations. Better mold layouts have been shown to improve this flow. The purpose of this project was to develop a computer imaging system that would aid in reliably evaluating these experiments. The completed system consisted of a computer, a frame grabber, video equipment and operating software. Videotapes made of the fluid flow in the mold during the pouring process were replayed into the computer and evaluated. Custom software reduced the collected data to a representative evaluation number. Results show that the computer evaluations are reliable and reproducible, but applications are limited because of the cost, speed and power of available computer systems. / Graduation date: 1994

This research focuses on the computational fluid dynamics modelling and simulation of the existing reactors and mixing tanks employed by the Australian Defence Industries to manufacture military propellants for gun projectiles and small rockets; high explosives for naval gun projectiles and aerial bombs. The main objective of this research is to gain a thorough understanding of these process vessels via research and to provide recommendations to improve their performance. Reactors and mixing tanks were chosen as the test unit operations because although they contribute significantly to the manufacturing process, reactors have frequently been poorly understood or in the case of mixing tanks, taken for granted. Consequently, there is a lack of comprehensive knowledge to support successful operations of these process vessels. In addition, this research also recommends using photocatalysis technology to destroy liquid wastes produced from such manufacturing activities. For each product, a full characterisation was provided that included detailed theoretical analyses that presents a unique insight into the hydrodynamics occurring in these process vessels. The credibility of theoretical predictions was demonstrated via qualitative and quantitative validation using particle image velocimetry. Results from characterisation showed that the reactors and mixing tanks employed in the manufacture of military propellants, high explosives or aerial bombs were operating at sub-optimum conditions. To tackle this shortcoming, four ideal geometrical configurations that promised optimum performance were proposed for each of the test studies. These included a designer reactor for the manufacture of military propellants and effective mixing tanks for suspending high explosive particles, blending different high explosives and for manufacturing aerial bombs. The correct implementation of these recommendations will provide an optimum operation that achieves high product throughput and concurrently reduces reject rate. Research was also conducted to formulate a set of multipurpose design guidelines for a suspension mixing tank. The design template created from the results will provide valuable information to researchers across industries in their quest to optimise any unit suspension mixing tank operated on the principle of mechanical agitation. Finally, modelling of reactive species was conducted on a laboratory-scale photoreactor, involving physical experiments to destroy toxic effluent aqueous phase.