http://hdl.handle.net/1957/88 Wed, 22 May 2013 21:02:22 GMT 2013-05-22T21:02:22Z http://hdl.handle.net/1957/38709 Linearizing techniques for voltage controlled oscillator based analog to digital converters Rao, Sachin B. Voltage controlled oscillator (VCO) based ADC is an important class of time-domain ADC that has gained widespread acceptance due to their several desirable properties. VCO-based ADCs behave like an open-loop continuous time ΔΣ modulator and achieve excellent resolution by first order noise shaping the quantization error. However, the SNDR of an open-loop VCO-based ADC is severely distortion limited by the voltage-to-frequency tuning characteristics of the VCO. This work examines various techniques that have already been proposed to overcome the VCO tuning non-linearity problem. Two new VCO-based ADC architectures, that overcome the limitations of the conventional approaches, are proposed. In the first approach, the ADC is linearized by forcing the VCO to operate at only two operating points using a front-end two level modulator. With this technique, the linearity is improved without using either a multi-bit feedback DAC or calibration. Fabricated in a 90 nm CMOS process, the prototype ADC achieves better than 71 dB SFDR and 59.1 dB SNDR in 8 MHz signal bandwidth while consuming 4.3 mW power. The ADC achieves a figure of merit of 366 fJ/conv-step, which is comparable with other state of the art time based ADCs. In the second approach, the need for a front-end two level modulator is obviated using linearizers, which introduce an inverse of VCO’s voltage to frequency characteristics in the signal path. A deterministic digital calibration unit runs continuously in the background and builds the inverse voltage to frequency transfer function. Implemented in a 90nm CMOS process, this on-chip calibration improves SFDR of the prototype ADC from 46 dB to more than 83 dB. The ADC consumes 4.1 mW power and achieves 73.9 dB SNDR in 5 MHz signal bandwidth resulting in an excellent figure of merit of 101 fJ/conv-step. Graduation date: 2013; Access restricted to the OSU Community at author's request from May 22, 2013 - May 22, 2015 Mon, 13 May 2013 00:00:00 GMT http://hdl.handle.net/1957/38709 2013-05-13T00:00:00Z http://hdl.handle.net/1957/38702 Photochemical reduction of carbon dioxide in aqueous and ionic liquid solutions in a microreactor with TiO₂ catalyst; experiment and modeling Campbell, Travis J. (Travis James) Microtechnology was used to study the chemical reduction of dissolved carbon dioxide into useful products. A novel TiO₂ photocatalyst was used to activate the reaction under ultraviolet irradiation. CO₂ was dissolved in aqueous and 50% BMIM-BF₄ (ionic liquid) solutions. The introduction of an ionic liquid increased the solubility of CO₂ by 60%. Both solutions were pumped through a continuous photochemical microreactor and analyzed for products. The aqueous photochemical microreactor process produced 5x10⁻⁸-1x10⁻⁶ moles of methane per liter of solution processed. These values vary with mean residence time within the 0.016 mL microreactor volume. Serial reduction intermediates are likely present in solution below the detection limits of our analytical instruments. The 50% ionic liquid process produced 4x10⁻⁸-1x10⁻⁷ moles of methane per liter of solution processed. Similarly, no intermediates were measured. Mathematical models for the kinetic mechanism, momentum transfer, and mass transfer within the reactor were developed. These models were added to a numerical simulation and compared to experimental values. An optimization scheme was executed to extract meaningful reaction rate constants from the simulation that best fit the experimental data. Reaction rate constants reflect the feasibility of operating these processes and the numerical models can be used as design tools. Graduation date: 2013 Tue, 14 May 2013 00:00:00 GMT http://hdl.handle.net/1957/38702 2013-05-14T00:00:00Z http://hdl.handle.net/1957/38669 Interactions of Amphorophora agathonica Hottes with raspberry viruses and resistant red and black raspberry Lightle, Danielle In recent years, red raspberry production in Washington and British Columbia has been severely limited by a newly emerged virus complex that causes symptoms of crumbly fruit. The complex is comprised of three viruses: Raspberry bushy dwarf virus (RBDV), Raspberry leaf mottle virus (RLMV) and Raspberry latent virus (RpLV). Both RLMV and RpLV are transmitted by the aphid Amphorophora agathonica Hottes. The objectives of this work were to monitor seasonal phenology of A. agathonica and study the aphids' behavior on infected plants as well as resistant red and black raspberry cultivars. The lower developmental threshold of A. agathonica was calculated to be 2.7°C and field populations in northern Washington began increasing rapidly at approximately 800 growing degree days and peaked at approximately 1000 degree days. Evaluations of aphid performance on infected plants revealed that single infection plants (RLMV or RpLV) and co-infected plants (RLMV+RpLV) significantly increased aphid longevity over the healthy controls, while the co-infected plants also significantly increased aphid fecundity. Electrical penetration graph (EPG) studies of A. agathonica feeding behavior showed no differences in feeding between healthy and infected plants. However, EPG studies revealed two distinct mechanisms of resistance against A. agathonica in red and black raspberry. The red raspberry resistance gene Ag₁ results in extended periods of salivation in the phloem sieve elements with little subsequent phloem ingestion, a behavior commonly associated with plant defense mechanisms related to a phloem recognition factor. Three novel aphid-resistant black raspberry selections were also studied. Aphids feeding on the resistant black raspberries were unlikely to salivate in the phloem sieve elements, which may point to a mechanism that causes aphids to be unable to recognize when they have punctured the sieve elements. Overall, this research discovered new information about A. agathonica biology, feeding behavior, and interactions with viruses that can be incorporated into future management strategies. Graduation date: 2013 Thu, 09 May 2013 00:00:00 GMT http://hdl.handle.net/1957/38669 2013-05-09T00:00:00Z http://hdl.handle.net/1957/38666 Parental beliefs and practices : influences of parenting in Latino/a and Caucasian children's behavioral regulation Diaz, Guadalupe The transition to kindergarten can be challenging for many children who do not have the necessary skills to meet the demands of classroom settings such as paying attention, remembering instructions, and demonstrating self-control. Children who lack the necessary behavioral regulation skills to meet the demands in the classroom environment are at risk of lower academic achievement (Blair and Razza, 2007; Galindo & Fuller, 2010; McClelland et al., 2006). Previous research has documented that disadvantaged children are at higher risk for having poor behavioral regulation and lower academic achievement (Galindo and Fuller, 2010; Wanless, McClelland, Tominey, & Acock, 2010). Moreover, parental beliefs and practices such as the discipline strategies, parent interaction, and parents beliefs about their children have been recognized as an important influence on children's behavioral regulation, but very little is known about the parental beliefs and practices of Latino/a parents and their influence on children's behavioral regulation. Therefore, it is important to explore the parenting styles and behaviors of Latino/a parents and their influence on children's behavioral regulation, as well as examine how factors such as acculturation influence the parental beliefs and practices of Latino/a parents. Using principal component analysis, regressions, and qualitative interviews, this study examined the reliability of the Parenting Questionnaire (Morrison & Cooney, 2002) for Latino/a and Caucasian parents. It also explored if parenting dimensions differently influence Latino/a and Caucasian children's behavioral regulation. In addition, the study explored how acculturation levels among Latino/a parents may influence parenting styles and behaviors. Using a modified Parenting Questionnaire, results indicated that for Latino/a parents, the quality of the family learning environment had a significant positive relation to children's behavioral regulation. For Caucasian parents, parental beliefs had a marginally significant and negative relation to behavioral regulation. The acculturation levels of Latino parents were not significantly correlated and did not significantly relate to the parenting dimensions. The qualitative interviews indicated that Latino/a parents face constant struggles to provide additional educational materials to enrich the home learning environment of their children. In addition, parent control and parent beliefs, which include respect and being well educated, emerged as key factors that guide parents' expectations of children's behaviors and discipline. Understanding the influence of parenting dimensions on Latino/a and Caucasian children's behavioral regulation provides important empirical evidence to further understand how parenting dimensions may differently relate to the behavioral regulation and academic achievement of Latino/a and Caucasian children. Graduation date: 2013 Thu, 04 Apr 2013 00:00:00 GMT http://hdl.handle.net/1957/38666 2013-04-04T00:00:00Z