The performance of two innovative collector-loop heat exchangers used in pumped circulation solar water heaters was investigated experimentally and numerically, and TRNSYS simulation models were developed for evaluating long-term performance. The heat exchangers evaluated are a narrow gap mantle on a vertical tank and a falling film system in a standard gas hot water tank. The falling film system is based on minor changes to a mass produced tank and does not require the addition of a special purpose heat exchanger. The heat exchangers were assessed for a range of operating conditions to quantify the overall heat exchanger UAhx value and the effect of thermal stratification in the tank. Flow visualisation experiments and CFD modelling were also performed to provide detailed understanding of the operation characteristics of the heat exchangers. For each heat exchanger, the measured and computed collector loop side heat transfer coefficients were correlated by developing new Nusselt number versus Reynolds and Prandtl number functions. New heat transfer correlations were developed for both types of heat exchanger and have been implemented into full solar water heater simulation models in TRNSYS. Predictions of tank stratification conditions in each heat exchanger were in good agreement with experimental data. Compared to a standard direct circulation system, the annual performance of the mantle system and falling film system are 8% and 18% less respectively. The decrease in system performance is due to the heat exchanger penalty and reduced thermal stratification in the storage tank, however they have the added features of freeze protection and suitability for hard water areas. They are also cheaper to manufacture than convectional heat exchange systems. The annual performance of a falling film solar water heater was shown to be affected by de-stratification if an in-tank electric booster was used. However, improved performance can be achieved if an advanced switching controller is used to modulate the flow rate such that the collector return temperature is always higher than the temperature in the top of the tank.

Algorithms and simulators comprised of SPICE3 as a circuit level simulator and two device simulators EOFLOW and PROPHET for accurate simulation of new types of devices are presented in this thesis. An integration of EOFLOW with SPICE3 creates a capability for efficient simulation of a system containing interconnected electroosmotic flow channels together with control electronics. Using this simulator, an accurate simulation of a complex interconnection of channels has been performed. In addition, various flow control schemes have been evaluated for their effectiveness. Coupling of PROPHET and SPTCE3 allows for the simulation of accurate semiconductor device models. This capability is necessary for critical RF and analog applications. The coupled SPICE3-HB-PROPHET simulator incorporates the harmonic balance algorithm for large-signal frequency domain analysis. Applications of this analysis are demonstrated in the noise coupling between devices sharing the same silicon substrate. / Graduation date: 2003

The harmonic problem in power systems is gaining more attention as incidences correlated with harmonics increase. Conventional passive filtering techniques for harmonic mitigation have inherent problems, and purely active filters have the disadvantages of higher costs and ratings. Hybrid active filters inherit the efficiency of passive filters and the improved performance of active filters, and thus constitute a viable improved approach for harmonic compensation. To date, there have been several literature works comparing passive and active filters for harmonic mitigation. However, there are currently no comparisons of possible hybrid active filters. This thesis presents an assessment and comparison of hybrid active filters, including their topologies and control algorithms. Three different topologies of hybrid active filters are simulated in PSpice version 9.0 to verify their feasibility for harmonic compensation. From the simulations, all three topologies have better performance over passive filters for harmonic compensation and are insensitive to parameter variations. In addition, the simulated hybrid active filter ratings are lower than can be achieved with purely active filters. A modified "p-q" theory is introduced for control strategy, which is more feasible for extracting harmonic components for distorted load voltages. This thesis concludes with a comprehensive comparison of the hybrid active filter characteristics. / Graduation date: 2001

Graduation date: 1999

The study critically analyzes the implication of various agricultural development policies on urban unemployment and income distribution. More specifically it focuses on the evaluation of agricultural policies at the macro-economic Level in the Nigerian economy. A system science and simulation approach is used to build and test a ten sector macro-economic model of the Nigerian economy to investigate the problem. The model simulates consumption, investment, employment and production endogenously. Validation of the model shows that it is capable of describing the major trends in the Nigerian economy for recent history. By interacting with a detailed agricultural sector model, the macro-model enables evaluation of agricultural policies in the context of the total economy after taking account of the important interactions between the agricultural and nonagricultural economies. In particular the model enables some measures of income distribution and employment to be included as targets of economic development planning together with the conventional target of growth. The model predicts that if current agricultural policies are continued, urban unemployment and income disparities will become increasingly more serious in Nigeria. Furthermore, the income differential between agriculture and nonagriculture is predicted to widen leading to a continuing increase in the rate of labor migration out of agriculture. The evaluation of two sets of agricultural policies, export crop modernization and food crop modernization, leads to a serious questioning of the present emphasis among development economists on agricultural development as a means of steadying the flow of rural-urban migration and reducing urban unemployment and rural-urban income inequities. Because of the considerable multiplier effects of increased agricultural incomes on nonagricultural incomes, both agricultural policies produced a wider differential between agricultural and nonagricultural incomes stimulating further labor migration out of agriculture. This effect was particularly acute in the case of the food modernization policy where the terms of trade turned against agriculture. Nevertheless both sets of policies and particularly the export modernization policy improved the disparity in self-employed earnings and wage earnings and produced a steady rise in nonagricultural self-employed earnings which, under current policies, were predicted to stagnate because of rising urban unemployment. Other policies to restrain wages and increase government employment demonstrated the considerable trade-off between various groups of the population arising out of the complexity of interactions between the agricultural and nonagricultural sectors. The macroeconomic simulation model is suggested as a useful approach to development planning where there is need to consider interactions between sectors and trade-offs between targets of development. / Graduation date: 1972

The objectives of this study are to revise and reformulate a previous simulation model of the Calapooia River and proposed Holley Dam project and to critically investigate the anadromous fish enhancement function of the project. The Corps of Engineers proposes a 145,000 acre-foot reservoir for the Calapooia River at Holley, Oregon. Previously, a 97,000 acre-foot reservoir was proposed. The larger project's justification is based mainly on anadromous fish enhancement. Investigation revealed that there is a great deal of uncertainty and lack of information about: (1) temperature requirements of anadromous fish in the Calapooia River and whether they can be met, (2) the affects of high streamflow discharges on spawning, incubation, and rearing of anadromous fish in the Calapooia River, (3) the affects of variability in food supply due to fluctuations in the level of the water in the reservoir, and (4) the survival rates of salmon eggs to fry, fry to smolts, and ocean survival. A simulation model in DYNAMO computer language is formulated and includes the following components: (1) hydrology generator, (2) reservoir regulation and flood control procedures, (3) freshwater life cycle of Spring Chinook and Fall Chinook Salmon, (4) supply of recreation user days, (5) supply of resident fishing angler days, and (6) supply of irrigation water. The model calculates the daily, monthly, and yearly variability of various physical, economic, and intangible outcomes. The simulation of floods and their regulation corresponds to historical data and regulation hypothesized by the Corps of Engineers. The dynamic nature of the Spring and Fall Chinook Salmon populations are modeled and computer results indicate that the likelihood of conservation and enhancement is not great enough to justify the 145,000 acre-foot reservoir. Due to the fluctuations in the reservoir level which accompany flood control regulation and reflect the variability in the hydrology, the recreational use and resident fishing angler use is highly variable and the average use is unlikely to reach the estimated supply potential. The reservoir, as simulated by the model, has sufficient capacity to supply water for the proposed irrigation project. However, it appears that uncertainty remains concerning the dollar benefits that are obtainable from irrigating soils along the Calapooia River. Further study is necessary to determine whether the 97,000 acre-foot reservoir is a feasible alternative to the proposed 145,000 acre-foot reservoir. The computer model is general in formulation and can be utilized to provide information to decision makers in determining the feasibility of further dam and reservoir construction. / Graduation date: 1972

Thesis (M.S.)--Rochester Institute of Technology, 2009. / Typescript. Includes bibliographical references (leaves 108-110).

Thesis (M.S. in Modeling, Virtual Environments, and Simulation (MOVES))--Naval Postgraduate School, December 2009. / Thesis Advisor(s): Buss, Arnold. Second Reader: Meyer, David. "December 2009." Description based on title screen as viewed on January 28, 2010. Author(s) subject terms: Discrete Event Simulation, airlift operation. Includes bibliographical references (p. 145-147). Also available in print.

Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): Eugene P. Paulo, Sergio Posadas, Susan M. Sanchez. Includes bibliographical references (p. 63-64). Also available online.

Thesis (M.S.)--University of Kentucky, 2002. / Title from document title page. Document formatted into pages; contains viii, 66 p. : ill. Includes abstract. Includes bibliographical references (p. 64-65).