Thesis (M. Phil.)--University of Hong Kong, 1993.

Zugl.: Kassel, Univ., Diss., 2007 / Download lizenzpflichtig

Thesis (M.S.)--Rochester Institute of Technology, 2005. / Typescript. Includes bibliographical references (leaves 81-83).

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Simulated Annealing is a general purpose combinatorial optimization technique which has been applied to many problems in VLSI design. In essence, simulated annealing is Monte Carlo iterative improvement with the ability to conditionally accept uphill moves. The notion of a cooling schedule is common to all simulated annealing implementations. A cooling schedule can be thought of as simulated annealing's control mechanisms. Experiential work has been done on estimating the cost of an optimal solution to some combinatorial optimization problem instances. Such an estimate can be used to determine termination criteria for general purpose optimization techniques such as iterative improvement or simulated annealing. We have extended this idea and designed a complete simulated annealing general cooling schedule based on the cost of an optimal solution to a problem instance. We call the resultant schedule an extended goal-directed general cooling schedule. One of the major problems with simulated annealing is its long computation times. This problem can be addressed by first using a fast heuristic to find a good initial configuration and then applying simulated annealing. This approach is called Simulated Sintering. To exploit the potential of simulated sintering one needs an appropriate general cooling schedule. The extended goal-directed cooling schedule is equally applicable to simulated annealing and simulated sintering. To date, no one cooling schedule has proven suitable for all optimization problem instances. In our view, no such cooling schedule exits. Consequently, we have attempted to identify the type of problem best suited to optimization by simulated annealing and simulated sintering using the extended goal-directed schedule. We have applied the extended goal-directed schedule to standard-cell placement and floorplanning problems using both simulated annealing and simulated sintering. Within this context, we have compared the performance of the extended goal-directed schedule to other published schedules. Our results indicate that in terms of layout quality, the extended goal-directed schedule performs as well or better than the other schedules. In this dissertation, we have developed a new general cooling schedule. Our evaluation of the extended goal-directed schedule suggests that it is a useful research contribution in the area of simulated annealing algorithms. / Graduate

This thesis investigates the effect of neighborhood structure on simulated annealing, a random search algorithm that has the ability to search through a sequence of local optimal solutions and return the globally optimal solution. Neighborhood sizes of one, two, three, four and N (equal to the size of the problem) decision variable alterations have been experimentally tested on the following problem types: Quadratic Assignment problem; Quadratic Selection problem; Stochastic Optimization problem; and Traveling Salesman problem. Empirical results indicate that a smaller neighborhood size is better. However, for some instances, a neighborhood size of one larger than the smallest defined neighborhood size performed best.

For years, electron beam induced deposition has been used to fabricate electrical contacts for micro and nanostructures. The role of the contact resistance is key to achieve high performance and efficiency in electrical devices. The present thesis reports on the electrical, structural and chemical characterization of electron beam deposited platinum electrodes that are exposed to different steps of thermal annealing and how they are used in four-probe devices of ultrathin graphite (uG) flakes (<100nm thickness). The device integration of liquid phase exfoliated uG is demonstrated, and its performance compared to devices made with analogous mechanically exfoliated uG. For both devices, similar contact resistances of ~2kΩ were obtained. The electrical measurements confirm a 99.5% reduction in contact resistance after vacuum thermal annealing at 300 °C. Parallel to this, Raman characterization confirms the formation of a nanocrystalline carbon structure over the electrode. While this could suggest an enhancement of the electrical transport in the device, an additional thermal annealing step in air at 300 °C, promoted the oxidation and removal of the carbon shell and confirmed that the contact resistance remained the same. Overall this shows that the carbon shell along the electrode has no significant role in the contact resistance. Finally, the challenges based on topographical analysis of the deposited electrodes are discussed. Reduction of the electrode’s height down to one-third of the initial value, increased surface roughness, formation of voids along the electrodes and the onset of platinum nanoparticles near the area of deposition, represent a challenge for future work.

We present a new method for predicting the secondary structure of RNA sequences. Using our method, each RNA nucleotide of an RNA Sequence is represented as a point on a 3D triangular lattice. Using the Simulated Annealing technique, we manipulate the location of the points on the lattice. We explore various scoring functions for judging the relative quality of the structures created by these manipulations. After near optimal configurations on the lattice have been found, we describe how the lattice locations of the nucleotides can be used to predict a secondary structure for the sequence. This prediction can be further improved by using a greedy, 2-interval post-processing step to find the maximum independent set of the helices predicted by the lattice. The complete method, DeltaIS, is then compared with HotKnot, a popular secondary structure prediction program. We evaluate the relative effectiveness of DeltaIS and HotKnot by predicting 252 sequences from the Pseudobase Database. The predictions of each method are then scored against the true structures. We show DeltaIS to be superior to HotKnot for shorter RNA sequences, and in the number of perfectly predicted structures.

No description available.

Pages 154 and 155 were not included in the thesis. / <p> The post-irradiation annealing of highly converted styrene-polystyrene systems was explored. Experimental conditions necessary for the entrapment of high concentrations of free radicals in such systems were investigated. They were found to bear a relation to the glass transition temperature of the system.</p> <p> The concentration of free radicals formed by subjecting the polymer-monomer systems to Gamma rays, at room temperature, was measured, and the subsequent GM and GP values were calculated. The structure of the formed radical was found to be in agreement with that suggested by previous investigators. The free radicals decay was examined at varied temperatures above and below Tgs, and was found to follow a second order mechanism. The activation energy of decay was found to increase by raising the temperature above Tgs.</p> <p> When irradiation was executed at temperatures below Tgs, post-irradiation annealing led to high rates of polymerization when carried out at temperatures above Tgs. </p> <p> The number average molecular weight was practically unchanged during the polymerization of the last few percent monomer.</p> / Thesis / Master of Engineering (MEngr)