Part A of two parts. Part B titled: "Xenon Transient Studies For a CANDU Reactor". / <p> In CANDU reactors, mechanical devices called shutoff rods are used to shutdown the reactor if required. These rods are made of high thermal neutron absorbing material such as cadmium. The number and the locations of the shutoff rods are optimized for a given reactor configuration. Optimization here means minimizing the number of rods and maximizing their reactivity depth or effectiveness. </p> <p> Optimization may be studied in various ways but the method selected is both simple and basic. It is apparent that if the interaction effects between the individual shutoff rods are reduced, their worths will increase. The optimum distance between two rods was determined to be 130 cm. Also, the best location of a third rod with respect to two already placed at an optimum separation was studied. Finally, these results were used in order to determine the optimum distance between banks of shutoff rods. These banks of rods were arranged in such a way as to achieve maximum flux flattening with all the rods inserted in the core. A 22 shutoff rod configuration for an adjuster flattened CANDU reactor gave a total change of 5.6% in keff. </p> / Thesis / Master of Engineering (MEngr)

I have explored the combination of sound, textile and space. How can one create textiles to use as sound dampening material in an arts and craft practice? To enhance the architectural aspect of textile as one of the five building materials I have chosen to weave walls. Walls don´t have to be straight or go from floor to ceiling but they should somehow create room and divide the space. I felt the need of walls working within Konstfack because of the distraction of fellow students in the open space classroom. Torn walls tells a story, we see the left traces. These traces I wanted to convert into woven textile. Sounds of people and objects in public spaces bounces between hard surfaces often without dampening, this creates an environment that causes stress and distraction. In Virginia Wolf´s essay “A room of Ones Own” (1929) she points at how important it is to create a workspace for the professional you, to take place and be part of the public realm. A big part of this master project has been making the actual materials to build with and executing fibre. Does the material do the job of sound absorption? Wool and silk both have a fibrous cell, which is suitable for sound absorption they also have low flammability and is biodegradable; therefore I chose to work mainly with these fibres. I share my knowledge through the experience of the space I create. How to create o Room of one´s own in an open office.

Two-periodic random walks are models for the one-dimensional motion of particles in which the jump probabilities depend on the parity of the currently occupied state. Such processes have interesting applications, for instance in chemical physics where they arise as embedded random walk of a special queueing problem. In this paper we discuss in some detail first passage time problems of two-periodic walks, the distribution of their maximum and the transition functions when the motion of the particle is restricted by one or two absorbing boundaries. As particular applications we show how our results can be used to derive the distribution of the busy period of a chemical queue and give an analysis of a somewhat weird coin tossing game. / Series: Research Report Series / Department of Statistics and Mathematics

As optical microscopy techniques continue to improve, most notably the development of super-resolution optical microscopy which garnered the Nobel Prize in Chemistry in 2014, renewed emphasis has been placed on the development and use of fluorescence microscopy techniques. Of particular note is a renewed interest in multiphoton excitation due to a number of inherent properties of the technique including simplified optical filtering, increased sample penetration, and inherently confocal operation. With this renewed interest in multiphoton fluorescence microscopy, comes an increased demand for robust non-linear fluorescent markers, and characterization of the associated tool set. These factors have led to an experimental setup to allow a systematized approach for identifying and characterizing properties of fluorescent probes in the hopes that the tool set will provide researchers with additional information to guide their efforts in developing novel fluorophores suitable for use in advanced optical microscopy techniques as well as identifying trends for their synthesis. Hardware was setup around a software control system previously developed [1]. Three experimental tool sets were set up, characterized, and applied over the course of this work. These tools include scanning multiphoton fluorescence microscope with single molecule sensitivity, an interferometric autocorrelator for precise determination of the bandwidth and pulse width of the ultrafast Titanium Sapphire excitation source, and a simplified fluorescence microscope for the measurement of two-photon absorption cross sections. Resulting values for two-photon absorption cross sections and two-photon absorption action cross sections for two standardized fluorophores, four commercially available fluorophores, and ten novel fluorophores are presented as well as absorption and emission spectra.

Bridges with low clearance are vulnerable to collision with overheight vehicles. Collisions of overheight vehicles can cause fatalities and injuries to the drivers and passengers of the overheight vehicles, and damage to bridge girders. The repair of the damaged bridges can be costly and time consuming. This research investigates the feasibility of developing a bridge bumper that minimizes the physical injuries and the likelihood of fatalities and protects the structural elements of bridges by absorbing the impact energy. The thesis describes a small-scale impact experiment using the proposed bridge bumper with several options of energy absorbing materials to protect a reinforced concrete beam. A finite element analysis is done to simulate the small-scale impact experiments. Optimization of the finite element model is carried out for the response quantities of interest with respect to the geometrical parameters and the material properties of the proposed bridge bumper. Such analysis can guide the design of an optimal bridge bumper that maximizes the energy dissipation and minimizes the damage to the bridge girder and the likelihood of fatalities and injuries.

Bridges with low clearance are vulnerable to collision with overheight vehicles. Collisions of overheight vehicles can cause fatalities and injuries to the drivers and passengers of the overheight vehicles, and damage to bridge girders. The repair of the damaged bridges can be costly and time consuming. This research investigates the feasibility of developing a bridge bumper that minimizes the physical injuries and the likelihood of fatalities and protects the structural elements of bridges by absorbing the impact energy. The thesis describes a small-scale impact experiment using the proposed bridge bumper with several options of energy absorbing materials to protect a reinforced concrete beam. A finite element analysis is done to simulate the small-scale impact experiments. Optimization of the finite element model is carried out for the response quantities of interest with respect to the geometrical parameters and the material properties of the proposed bridge bumper. Such analysis can guide the design of an optimal bridge bumper that maximizes the energy dissipation and minimizes the damage to the bridge girder and the likelihood of fatalities and injuries.

In this thesis, we demonstrated the effectiveness and the accuracy of the FD-FD method for complex optical waveguide structures such as the micro ring resonator, micro disk resonator, tapered waveguides and waveguides terminated with tilted facets. We are able to achieve the goals by deriving the following modification/extension of the original FD-FD methods. In frequency domain, we can build an accurate frequency-domain modal absorbing boundary condition (ABC) for both the homogeneous region and for the layered background. This allows us to connect the analytical modal solutions with FD solutions and thus reduce the area of the FD domain. In addition, we adopt an effective index averaging method for representing equivalent material for grid cells containing more than one kind of materials. For the TM case, for each grid cell we need to compute effective indices for all four surrounding cells (left, right, up, and down). For the TE case, we need to compute just one effective index within each grid cell. Note that we employ two different averaging schemes for the TE and the TM cases. To solve the huge block tri-diagonal matrix equation (derived from the FD-FD approximation) we modified the Thomas method and we were able to obtain the solutions of linear equations involving more than a hundred thousand variables under a few minutes. We used our method to analyze optical micro-ring waveguides, micro-disk cavities, adiabatic tapered waveguides and waveguides terminated with tilted facets. The simulated results include the reflection coefficients, transmission coefficients and field distribution.

We consider tiling problems for graphs and hypergraphs. For two graphs and , an -tiling of is a subgraph of consisting of only vertex disjoint copies of . By using the absorbing method, we give a short proof that in a balanced tripartite graph , if every vertex is adjacent to of the vertices in each of the other vertex partitions, then has a -tiling. Previously, Magyar and Martin [11] proved the same result (without ) by using the Regularity Lemma. In a 3-uniform hypergraph , let denote the minimum number of edges that contain for all pairs of vertices. We show that if , there exists a -tiling that misses at most vertices of . On the other hand, we show that there exist hypergraphs such that and does not have a perfect -tiling. These extend the results of Pikhurko [12] on -tilings.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 113-123).

Two-photon absorption and upconverted fluorescence has been utilized in a variety of applications in pure science and engineering. Multiphoton-based techniques were used in this research in order to understand photophysical and chemical characteristics of several fluorescent dyes and to demonstrate some of their key applications. Two-photon fluorescence microscopy (2PFM) has become a powerful technique in bio-photonics for non-invasive imaging in the near-infrared (NIR) region (700~1000 nm) that often results in less photobleaching. In Chapter 1, there is a brief introduction to fluorescence, examples of fluorescence materials, and a discussion of the advantages of two-photon absorption. 2PFM imaging was utilized in Chapters 2 to 4 for various applications. In Chapter 2, a new squaraine dye is introduced and its linear and nonlinear photophysical properties are characterized. This compound has very high two-photon absorption (2PA) cross sections and high photostability both in an organic solvent and when encapsulated in micelles. Based on these properties, this dye was demonstrated as a near-infrared (NIR) probe in in vitro 2PFM imaging with excitation over 800 nm wavelength. In Chapter 3, new profluorescent nitroxides are introduced. Nitroxide radicals are utilized for electron paramagnetic resonance (EPR) spectroscopy and in biological systems as some are known, in some manner, to mimic the behavior of superoxide dismutase (SOD) that detoxifies or mitigates oxidative stress by trapping free radicals. Here, two profluorescent nitroxides investigated for use as a two-photon fluorescent oxidative stress indicator in in vitro two-photon fluorescence microscopy (2PFM) imaging. In Chapter 4, two-photon excited (2PE) fluorescence of a conjugated polyelectrolyte (CPE), PPESO3, was studied in methanol and in water. The results of CPE quenching studies were comparable under both one-photon excitation conditions and two-photon excitation. CPE coated silica nanoparticles were incubated in HeLa cells and 2PFM imaging was demonstrated for this new class of fluorescent probe. Supramolecular structures based on organized assemblies/aggregation of chromophores have attracted widespread interest as molecular devices with potential applications in molecular electronics, artificial light harvesting, and pharmacology. In Chapter 5, J-aggregate formation was investigated for two porphyrin-based dyes, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS, 4) and an amino tris-sulfonate analog (5) in water via UV-vis, fluorescence, and lifetime decay studies. The effect of aggregation on two-photon absorption properties was also investigated. A functionalized norbornene-based homopolymer, synthesized by the ring opening metathesis polymerization technique was used as a J-aggregation enhancement template and had a role of polymer-templating to facilitate porphyrin aggregation and modulate 2PA. In Chapter 6, squaraine dye aggregates templated with single wall carbon nanotubes (SWCNTs) that were atomically clean were studied by using optical absorption spectroscopy, atomic force microscopy (AFM), and photoconductivity measurements. SWCNTs selectively promote the formation of squaraine dye aggregates with a head-to-head stacking arrangement, and these dye aggregates effectively photosensitize SWCNTs, demonstrating that this novel approach can yield highly photosensitized devices.