http://hdl.handle.net/1957/89 Search the Channel search http://ir.library.oregonstate.edu/jspui/simple-search http://hdl.handle.net/1957/13326 Title: Navigation and coordination of autonomous mobile robots with limited resources<br/><br/>Authors: Knudson, Matthew D.<br/><br/>Abstract: The use of autonomous robots in complex exploration tasks is rapidly increasing. Indeed, robots can provide speed and cost effectiveness in many tasks, as well as allow operation in environments that are hostile to humans. In this dissertation we: 1) provide two adaptive navigation algorithms; 2) develop a coordination mechanism; 3) develop a dynamic partnership formation mechanism; and 4) demonstrate the use of algorithms in a hardware implementation.The two adaptive navigation algorithms are neuro-evolution and policy gradient, where the results show that effective, adaptive navigation techniques can be developed for mobile robots in an exploration domain when the robots have limited capabilities. In addition, we show that policy gradient approaches thrive on short-term objective values, whereas neuro-evolutionary approaches provide more robust results with a time-extended objective value. Finally, we show that summing short-term values to generate a time-extended value does not capture the complexities of some real world exploration tasks.Coordinating multi-robot systems to maximize global information collection in these exploration domains presents additional challenges. In particular, in many multi-robot domains where communication is expensive, the coordination must be achieved in a passive manner. This is done in this dissertation via objective design on a hierarchical control scheme where both a navigation algorithm and coordination algorithm are operating simultaneously.We then extend results on such multi-robot coordination algorithms to domains where the robots cannot achieve the required tasks without forming teams. We investigate team formation where: i) robots must perform a task together; ii) there is an optimal number of robots; and iii) individuals vary, forming heterogeneous teams. The results show that using neuro-evolutionary robot teams with objective functions that are aligned with the global objective and locally computable significantly improve over robots using the global objective directly, particularly in dynamic environments.Finally, we develop a path to implementation of all of the coordination research done to date into robot hardware. The design represents a stable, robust robotic platform on which navigation and coordination algorithms can be run in the fashion they were developed and intricacies of real-world operation can be analyzed. Functional experiments show that the platform operates as expected and performs similarly to algorithm work done in simulation.<br/><br/>Description: Graduation date: 2010 Tue, 10 Nov 2009 21:02:09 GMT http://hdl.handle.net/1957/13295 Title: Fabrication and characterization of nanostructured surfaces for enhanced heat transfer<br/><br/>Authors: Choi, Changho<br/><br/>Abstract: This objective of this study is to investigate the capability of nanostructured surfaces on dissipating heat flux by performing pool boiling and convective flow boiling. The generation of ultra-high heat flux from high performance electric devices has motivated a number of investigations related to advanced heat transfer especially in two-phase boiling performance. It has been reported by a number of researchers that nanostructured surfaces can result in much enhanced boiling performance, compared to the conventional methods by creating desire conditions for heat transfer. In this thesis, various nanostructured surfaces having different morphology were prepared on several engineering relevant substrates and were characterized for their pool boiling performance. Microreactor-assisted-nanomaterial-deposition, MAND™ was used to fabricate a variety of different ZnO nanostructured surfaces by careful adjustment of the processing parameters. ZSM-5 zeolite was synthesized using hydrothermal reaction. ZnO nanostructures in minichannel were also successfully deposited via aflow cell for the application of flow boiling experiment. Scanning electron microscopy (SEM) and Atomic Force Microscopy (AFM) were carried out to characterize the micro- and nanostructures. Contact angle measurement was conducted to evaluate wettability and X-ray Diffraction (XRD) was used to determine the crystalline structures. The most significant enhancement of critical heat flux (CHF) and heat transfer coefficient (HTC) was observed in the flower like ZnO nanostructured surface. We observed pool boiling CHF of 80-82.5 W/cm² for nanostructured ZnO on Al surfaces versus a CHF of 23.2 W/cm² on a bare Al surface with a wall superheat reduction of 25-38°C. This new CHF values on nanostructured surfaces corresponds to a boiling heat transfer coefficient as high as ~ 23000 W/m²K. This represents an increase of almost 4X in CHF on nano-textured surfaces, which is the highest enhancement factor reported today.<br/><br/>Description: Graduation date: 2010 Mon, 09 Nov 2009 18:38:31 GMT http://hdl.handle.net/1957/13475 Title: New application of crystalline cellulose in rubber composites<br/><br/>Authors: Bai, Wen<br/><br/>Abstract: Rubber without reinforcement has limited applications. The strength of reinforced rubber composites can be ten times stronger than that of unreinforced rubbers. Therefore, rubber composites are widely used in various applications ranging from automobile tires to seals, valves, and gaskets because of their excellent mechanical elastic properties. Silica and carbon black are the two most commonly used reinforcing materials in rubber tires. They are derived from non-renewable materials and are expensive. Silica also contributes to a large amount of ash when used tires are disposed of by incineration. There is a need for a new reinforcing filler that is inexpensive, renewable and easily disposable. Cellulose is the most abundant natural polymer. Native cellulose includes crystalline regions and amorphous regions. Crystalline cellulose can be obtained by removing the amorphous regions with the acid hydrolysis of cellulose because the amorphous cellulose can be hydrolyzed faster than crystalline cellulose. We recently discovered that the partial replacement of silica with microcrystalline cellulose (MCC) provided numerous benefits: 1) low energy consumption for compounding, 2) good processability, 3) strong tensile properties, 4) good heat resistance, and 5) potential for good fuel efficiency in the application of rubber tires. Strong bonding between fillers and a rubber matrix is essential for imparting rubber composites with the desired properties for many specific applications. The bonding between hydrophilic MCC and the hydrophobic rubber matrix is weak and can be improved by addition of a coupling agent or surface modifications of MCC. In this study, MCC was surface-modified with acryloyl chloride or alkenyl ketene dimer (AnKD) to form acrylated MCC (A-MCC) and AnKD-modified MCC (AnKD-MCC). The surface modifications of MCC did not change the integrity and mechanical properties of MCC, but provided functional groups that were able to form covalent linkages with the rubber matrix during the vulcanization. Both A-MCC and AnKD-MCC facilitated the process and production of rubber composites and improved tensile properties and heat resistance of the resulting rubber composites as MCC did when they were used for the partial replacement of silica in rubber composites. Furthermore, A-MCC and AnKD-MCC were superior to MCC in terms of improving tear properties of rubber composites. It has been well-established that the size and the geometrical features of reinforcing fillers play important roles in the mechanical properties of the reinforced composites. MCC was further hydrolyzed with acid to form nanocrystalline cellulose (NCC), i.e., cellulose crystals with their width of less than 100 nm. A novel differential centrifugation technique has been developed for separation of NCC mixtures into fractions with a narrow size distribution. The NCC was investigated as a filler in rubber composites through a dry blending process, but saw little success. NCC had to be dried before it could be blended with rubbers. However, NCC particles tended to aggregate after drying and could not be uniformly dispersed into the rubber matrix during the dry blending. As a result, NCC had poor reinforcing effect on rubbers. For future research, the mixing of aqueous suspension of NCC and rubber latex may improve the dispersion of NCC particles in rubbers, thus improving the reinforcing effects of NCC in rubbers.<br/><br/>Description: Graduation date: 2010 Mon, 02 Nov 2009 22:58:59 GMT http://hdl.handle.net/1957/13148 Title: The impact of Saccharomyces and non-Saccharomyces yeast on the aroma and flavor of Vitis vinifera L. cv. 'Pinot Noir' wine<br/><br/>Authors: Takush, David G.<br/><br/>Abstract: The impact of yeast on the aroma and flavor of Vitis vinifera L. cv. 'Pinot Noir' wine was investigated. Due to the presence of naturally occurring yeast and bacteria on grapes and wine equipment, and the influence these microorganisms have on wine, a means of eliminating microorganisms from grape must was explored. High Hydrostatic Pressure (HHP) processing was investigated as a means of inactivating wine microorganisms in grape must without impacting organoleptic properties. Table grape must adjusted to 23°Brix was inoculated with wine-relevant yeast and bacteria and treated for 5 and 10 minutes at 551MPa. At both 5 and 10 minutes of pressure treatment all microorganisms were reduced to below detectable numbers. Next, wine was produced from HHP treated Pinot Noir grapes and the impact of HHP on the sensory properties of the wine was investigated. Descriptive analysis of the wines using a trained panel showed minimal significant differences between wines produced from HHP treated and untreated grape must. Chemical analysis showed no significant differences in color; however, there was a 70% increase in total phenolics in the wine produced from HHP treated must. Because the sensory effects of HHP treatment on grape must appeared to be minimal, the impact of specific yeast on Pinot Noir wine was investigated. HHP treated must was fermented in sterilized red wine micro-fermentors. The yeast strains and species studied were EC1118, RC212, Assmanshausen (AMH) (Lallemand, Montréal, Canada), MERIT.ferm, and Symphony (a blend of MERIT.ferm and Kluyveromyces thermotolerans) (Chr. Hansen, Hørsholm, Denmark). All Saccharomyces yeast strains were inoculated at approximately 10⁶cfu/mL while the non-Saccharomyces yeast was inoculated at approximately 10⁵cfu/mL. Each yeast strain was inoculated in triplicate, and a total of fifteen micro-fermentors, each containing 2.75kg of HHP treated grape must, were used. Fermentation profiles were similar between yeast strains with minimal variability between replicates. However, AMH replicates finished fermentation 24 hours after other yeast strains. After fermentation, analysis showed a significant difference in color at 520nm between the AMH and EC1118 wines. There were no other significant color differences between wines. Descriptive analysis with a trained panel indicated that yeast strain had a significant effect on the sensory profile of Pinot Noir wine. Significant sensory attributes included overall fruity aroma, red fruit aroma, dark fruit aroma, and overall fruit flavor, among others. Principle Component Analysis results showed EC1118 and RC212 trending toward high overall aroma intensities and dark fruit and jammy characteristics. MERIT.ferm also produced wines with high aroma intensities; however, they trended towards red fruit and floral characteristics. The wines produced from AMH and Symphony yeasts were not distinct and resulted in low aroma and flavor intensities in several descriptor categories. The results show that HHP processing is a viable means of inactivating microorganisms from grape must without causing large alterations in the final aroma and flavor profile of wine. The data also demonstrates the feasibility of utilizing HHP processing in conjunction with autoclavable micro-fermentors to conduct experimental red wine fermentations without the influence of native yeast and bacteria. The sensory data from yeast strain trials indicate that yeast can have a significant impact on Pinot Noir wine aroma. This data could help improve control of wine aroma profiles and help improve wine quality in the Pinot Noir industry. However, more research is needed to profile a larger array of oenological yeast strains, including non-Saccharomyces species, and to examine the effects of co-inoculation.<br/><br/>Description: Graduation date: 2010 Tue, 27 Oct 2009 17:22:01 GMT