http://ir.library.oregonstate.edu/dspace The ScholarsArchive digital repository system captures, stores, indexes, preserves, and distributes digital research material. Search the Channel search http://ir.library.oregonstate.edu/dspace/simple-search http://hdl.handle.net/1957/9094 Title: Development of a decision support system for pond aquaculture / by Shree S. Nath <br/> <br/>Abstract: Decision support systems (DSS) have been used to a very limited extent in pond aquaculture. This study documents the development of a DSS (POND) which allows representation of an entire pond aquaculture facility, and provides analysis capabilities in the form of simulation models and an economics package. Simulation tools in POND include temperature, water budget, fertilization, and fish bioenergetics models. Verification of the water temperature model at sites in Thailand, Honduras and Rwanda indicated that it would accurately predict daily temperatures over entire seasons or diurnal temperatures over one day intervals if complete input weather datasets are available. Similarly, adequate estimates of water requirements can be obtained from the water budget model. Sensitivity analysis with the former model, and results obtained from the latter, indicate that input weather datasets should include air temperature, relative humidity, short-wave solar radiation, precipitation and wind speed measurements. The fertilization model estimates fertilizer application rates on the basis of nutrient concentrations, gross primary productivity and nutrient recycling processes. Model output was more conservative compared to rates used in Honduras, Thailand and the Philippines, suggesting that responsive fertilization strategies which account for ambient pond water conditions are more efficient than fixed input strategies. The bioenergetics model accounts for the effects of size, water temperature, photoperiod, dissolved oxygen and unionized ammonia on fish growth. The model was calibrated and validated for Nile tilapia (Oreochromis niloticus), tambaqui (Colossoma macropomum), pacu (Piaractus mesopotamicus), common carp (Cyprinus carpio), and channel catfish (Ictalurus punctatus). Model experiments generated useful information regarding supplemental feed initiation and fish feeding rates. A resource substitution function was also used in this model to analyze the consumption of endogenous and exogenous food resources by Nile tilapia. This function suggests that adding supplemental feed to tilapia ponds may increase phytoplankton biomass because feed is preferentially consumed. A genetic algorithm-based technique was developed to automatically calibrate the bioenergetics model. This technique generates best-fit parameters by comparing results of multiple model runs to observed data. In general, results obtained from all the models suggest that POND should be a useful tool for managers, planners and researchers involved with pond aquaculture. <br/> <br/>Description: Graduation date: 1997 Mon, 02 Dec 1996 22:58:59 GMT http://hdl.handle.net/1957/9093 Title: "I'm the best of both worlds" : factors influencing the racial identities of biracial youth <br/> <br/>Abstract: This study examined the social and contextual factors that lead to differences in the way biracial adolescents interpret their racial identity. Using 11 interviews with a sample of biracial youth between the ages of 14 and 17-years-old, this study also explores the strategies these individuals use to achieve social validation for their preferred racial self-understanding. Theoretically, the factors shaping identity construction and the strategies used to negotiate identity are studied through both a bioecological model and a symbolic interactionist framework. The findings from this study provide new insights into adolescent biracial identity that involve issues ranging from cultural racism to the impact of video media on adolescent development. The main themes emerging from youth narratives suggest that four primary factors shape how biracial youth understand and reconcile their racial identities. First, community messages about race define the parameters of adolescents' racial identity options. Secondly, social meanings attached to physical appearance play a pivotal role in how racial identities are understood by self and others. Thirdly, peer endorsements of color-based stereotypes, especially those derived from popular media images of Black entertainers, are crucial to how these adolescents frame their racial identity options. Lastly, racial socialization in the familial context provides an important, though often ambiguous, piece to biracial identity formation. As well, four strategies surfaced in this study that biracial adolescents appear to use when negotiating identity claims in interactions with others. These strategies include compromise, evoking mixed parentage, emotion regulation, and using humor. <br/> <br/>Description: Graduation date: 2009 Fri, 25 Jul 2008 20:18:24 GMT http://hdl.handle.net/1957/9092 Title: Performance of wood frame wall with thin shell ECC shear panel <br/> <br/>Abstract: The overall goal of this study was to evaluate an alternative to traditional wood framed shear wall construction. This study introduced the innovative idea of using a water and seismic damage resistant, wood-concrete- composite (WCC) construction instead of an all-wood design. The WCC design consisted of a thin shell of engineered cementitious composite (ECC) cast in composite with a traditional wood frame. The WCC wall was evaluated with regards to structural performance during lateral loading, cost and damage sustained during lateral loading. The WCC test results were compared to a traditional wood frame wall with OSB sheathing. Data from the monotonic tests of the WCC walls show that the average maximum load was 47.5 kN (10700 lb), average elastic shear stiffness was 1.78 kN/mm (10200 lb/in) and the average energy absorbed was 4810 J (42600 lb-in). Overall, the test results indicate that the WCC is comparable with or superior to the OSB wall in regards to shear strength, shear stiffness, energy absorption and ductility. During lateral loading tests the WCC wall appeared to sustain less damage than the OSB wall. Panelized construction of the WCC system may increase overall project cost but could provide many additional benefits such as decreased construction time and greater durability. The WCC design appears to be a viable shear wall system that should be refined and fully tested for building code compliance. <br/> <br/>Description: Graduation date: 2009 Fri, 25 Jul 2008 17:54:49 GMT http://hdl.handle.net/1957/9090 Title: Long-term fertilizer input influences total and bioavailable metal in agricultural soils and crops <br/> <br/>Abstract: Protection of the quality and integrity of food supplies is of global concern. Crops can accumulate non-nutritive and sometimes toxic metals and metalloids. Accumulated metals/metalloids can come in part, from fertilizers, which may contain variable levels of non-nutritive metals or metalloids such as arsenic (As), cadmium (Cd), lead (Pb), nickel (Ni), and mercury (Hg). Metal bioavailability measurements can estimate crop metal accumulation and potential offsite movement. Diffusive Gradients in Thin Films (DGT) are used to measure labile, considered to be bioavailable, metal in soil solution. The DGT technique was applied in diverse agricultural soils receiving various applications of phosphate fertilizers. DGT was found to be marginally predictive of Cd accumulated in the edible portion of wheat (Triticum aestivum L.) and potato crops (Solanum tuberosum). A distinct approach was developed to estimate short and long-term changes to total and labile metal concentrations using a uniquely calculated distribution coefficient (Kd-BIO). Kd-BIO values for Cd and Ni did not decrease over the study period, indicating that soils may serve as a long-term contaminant sink. For As and Pb, there was a tendency for the Kd (As) and Kd-BIO (Pb) values to decrease with treatment and with yearly applications. If these tendencies were to continue, they may have long term implication for human health risk assessment. In general, total recoverable As, Pb, and Hg did not increase with fertilizer treatment level or over time in agricultural soils. Labile As and Pb dose response with fertilizer treatment was site specific. As and Pb were not detected in either crop throughout the study. Cd, Ni, and Hg were measured in wheat and potato. Kd-BIO was found to be a strong indicator of Ni and Cd accumulation in crops. Transfer coefficients (Tc) for Hg were calculated and determined to increase with time. Finally, the use of chemical profiling techniques to identify the geographic growing region of three fruits strawberry (Fragaria x ananassa), blueberry (Vaccinium caesariense/ corymbosum, and pear (Pyrus communis) was considered. The data were modeled with successful regional, sub-regional, and varietal classification ranging from 70 to 100% depending on commodity and model. <br/> <br/>Description: Graduation date: 2009 Thu, 24 Jul 2008 22:40:46 GMT