The multi-resonant technique, a novel concept in dc/dc power conversion, is proposed. The essence of the multi-resonant power conversion is the effective utilization of the major parasitic reactive components of the power stage, including the leakage inductance of the power transformer, output capacitance of the power MOSFET, and junction capacitance of the rectifier. The multi-resonant operation is achieved by addition of a resonant switching network around the semiconductor switching devices. Zero-voltage-switched multi-resonant converters (ZVS-MRCs) are proposed for high-frequency power conversion applications. ZVS-MRCs use a resonant network with one resonant inductor and two resonant capacitors. The resonant inductor is in series with the leakage inductance of the power transformer. One of the resonant capacitors is effectively in parallel with the power MOSFET, while the other resonant capacitor is effectively in parallel with the rectifier. As a result of the arrangement of the multi-resonant network, the major parasitic reactances of the power stage are utilized in the circuit. In addition, all semiconductor devices operate with zero-voltage switching, which substantially reduces the switching losses and permits efficient operation in multi-megahertz range, with moderate transistor voltage stress and wide load range. A dc analysis is presented for the basic converter topologies: buck, boost, buck-boost, Cuk, Zeta, and SEPIC. The analysis is performed using a generalized multi-resonant switch concept. The forward ZVS-MRC topology is employed to develop a state-of-the-art, high-density, on-board dc/dc power converter. The converter operates with a nominal input of 50 V and an output of 5 V at 10 A. The nominal switching frequency is 2.7 MHz. The complete hybridized converter has a power density of 50 W/in³ and a nominal efficiency of 83%. The feasibility of increasing conversion efficiency at several megahertz by means of resonant synchronous rectification is investigated using circuit analysis with nonlinear-capacitance MOSFET and Schottky diode models. / Ph. D.

Rapid increases in poultry litter production in concentrated areas has caused litter to be overapplied to nearby cropland at higher rates than the agronomic requirements of crops. Surface and ground water pollution has resulted due to leaching and runoff of nutrients in the litter. One solution to this litter disposal problem is to move litter from areas of concentrated poultry production (litter-surplus areas) to adjoining areas that have the capacity to absorb more litter for fertilizer and animal feed (litter-deficit areas). A linear programming feed cost minimization model was used to estimate the value of litter as a feed for beef stockers and beef cows. The value of litter in beef and stocker rations were estimated by determining the value of alternative feeds replaced by litter. The value of litter for use as fertilizer was estimated by determining the value of commercial fertilizer replaced by litter in selected crop rotations. The services and costs required to make litter available for fertilizer and feed were estimated. A linear programming cost minimization model was used to estimate the costs of moving varying amounts of litter from surplus to deficit counties in Virginia for use as fertilizer. Results indicated that it is economically feasible to establish a poultry litter handling industry. Results indicated more profit potential in moving litter for fertilizer than for feed. The profit potential to a litter handling firm is affected by several factors including the price of commercial fertilizer, waste management requirements, and litter storage subsidies. In order to increase the use of poultry litter for use as fertilizer and feed, it is necessary to educate farmers and the public about the nutritive and economic value of litter as a fertilizer and animal feed. / Ph. D.

The use of fractals in fields such as molecular biology, epidemiology, landscape, ecology, geology, physics, etc., is becoming more common. In order to use fractals to model many phenomena, the researcher requires the knowledge of the fractal, or Hausdorff-Besicovitch, dimension. However, no statistical properties of the usual estimator, the entropy estimator, are known. In addition, the entropy estimator is biased high when an inefficient net is used. This dissertation develops a new estimator, the relative entropy estimator, which is asymptotically unbiased and is consistent. The estimator is asymptotically normal, and asymptotic confidence intervals are presented. An estimate of the variance of the estimator is given which does not depend on the dimension, or its estimate, using an occupancy model. The exact distribution of the estimator is also derived. Applications of the theory to various fields are presented. For example, I find that from the point of view of dimension, the logarithms of stock prices behave consistently with the classical Brownian function. Also, the relative entropy estimator gives a more realistic estimate of the dimension of surface terrain than an ad hoc estimate found in the literature. The Hausdorff dimensions of nursery-grown tree roots were estimated, and it was found that the dimension is related to the probability of the tree’s survival when the tree is planted in the wild. The dimensions of Julia sets and of the Hénon attractor were also investigated. A computer program for calculating the estimates is included. / Ph. D.

Reproductive performance of Dorset ewes in the Cornell University STAR accelerated lambing program was evaluated. This program consists of five 30-d concurrent breeding and lambing periods per year beginning on January 1 (Sl), March 15 (S2), May 27 (S3), August 8 (S4) and October 20 (S5). Optimally, a ewe could lamb every 7.2 mo beginning at 1 yr of age, Records on 1,084 ewes over 7 yr beginning S1, 1982 Reproductive traits considered were ewe fertility, prolificacy, days to first lambing (DFL) and days between lambing (DBL). Fertility and prolificacy differed (P < .001) by exposure seasons. Exposure during favorable seasons (S1, S4, S5) increased fertility (P < .001) and prolificacy (P < .01) over that observed in unfavorable seasons (S2, S3). On average, first lambing occurred at 476 ± 5 d with ewe lambs first exposed during S1, S4 and S5 lambing at younger ages (P < .001). Ewes had more DBL (P < .001) if initial exposure following lambing occurred during an unfavorable season. A curvilinear relationship of ewe age with fertility (P < .001) , prolificacy (P < .01) and DBL (P < .05) was observed in ewes less than 4 yr old. At first exposure following lambing, fertility was lower (P < .001) than at subsequent exposures and ewes that had nursed lambs were less prolific (P < .01) than those that had not. Prolificacy and nursing status had little effect on fertility or DBL (P > .10). Fertility was transformed to an underlying liability scale based on the expected fertility of ewes of a given age and reproductive history. Variance components were estimated by least-squares (LS) and restricted maximum likelihood (REML) procedures. First-exposure fertility was not heritable. heritabilities for fertility at first post-lambing exposure, first-lambing prolificacy, and second-lambing prolificacy were .191 ± .088 (LS) and .200 ± .132 (REML), .914 ± .091 (LS) and .158 ± .144 (REML), and .168 ± .082 (LS) and .210 ± .137 (REML), respectively. Genetic variation in DFL (P < .01) and DBL (P < .001) was found. Although intrasire ewe variation was detected for prolificacy (P < .001) and DBL (P < .01), repeatability estimates were low and smaller than heritability. / Ph. D.

As the use of computers in the workplace becomes more commonplace, the levels of interconnection and interoperability increases. The desire to pass large amounts of data almost instantaneously is the basis of the high speed local area network (LAN). To meet the needs of these LANs, the American National Standards Institute has developed the Fiber Distributed Data Interface (FDDI) standard. This new LAN can provides high speed fiber optic based communication between computers. In meeting the computer/LAN interface requirements, new methods for data transfer will be required. Trade-offs between the reliability, architecture and buffer sizes must be developed. These concepts must include variables of data transfer widths, protocol processing, transfer architecture and packet length distributions. This dissertation addresses these hardware requirements in using the high speed computer interface known as the Fiber Data Distributed Interface. / Ph. D.

This investigation was concerned with the development of a fiber optic evanescent sensor. Such a sensor is based upon the lateral regions of the waveguide and their interaction with a chemical environment. The basic principles and concepts involved in the construction of a fiber optic spectroscopic evanescent field sensor are developed. From this fundamental knowledge a series of sensors were constructed to characterize their responses. First, the response to simple refractive index changes and angle launch conditions were explored. This demonstrated the light interaction with the measurement environment. What followed was the use of these sensors to make spectrochemical absorption measurements suitable for a calibration curve of 1.25 x 10⁻² to 1.22 x 10⁻⁹ M concentrations for various dye systems. As a consequence of the spectrochemical studies the unique interaction between the chemical environment and the silica surface was observed. This response is based upon the chemical reactivity of the silica surface and the chemical environment. This prompted the investigation of the ion exchange characteristics of the silica waveguide surface and the chemical environment. In this investigation the exchange selectivities of the alkali, alkali earth and lanthanide metals were determined. Finally, a series of innovative fiber optic sensors base upon interferometric and refractometric measurements were investigated. These designs were based upon the fabrication characteristics of glass and plastic fiber optic waveguides. / Ph. D.

A stability theory for lyophobic colloids was put forth in the 1940’s by Derjaguin, Landau, Verwey, and Overbeek. This theory, known as DLVO theory, has gone through the test of time and survived as a pillar of colloid science. In the present work, this theory has been used for describing the behavior of fine coal and silica particles in aqueous media. It has been found, however, that the classical DLVO theory is applicable only to weakly hydrophobic solids but not to very hydrophobic ones. The coagulation experiments conducted with very hydrophobic particles suggest that there exists a strong attractive force that has not been considered in the theory. This non-DLVO force has been estimated in the present work based on the data obtained from coagulation experiments. Contributions from the non-DLVO force, which is referred to as hydrophobic interaction energy (V_H), have been related to the nondispersion component of work of adhesion of water on solids (W^nd_a). An expression for V_H which is now a function of W^nd_a, has been added as a third term in the DLVO equation in order to better describe the stability of colloidal suspensions regardless of the hydrophobicity of the particles involved. A population balance model for a system of isotropic turbulent flow has been developed. Both aggregate growth and breakage have been considered in the model and their rate constants have been derived from a phenomenological approach. Numerical procedures have been proposed for solving the coagulation kinetic equations. Computer simulations show that the model is fairly flexible and the results are in reasonable agreement with experiment. / Ph. D.

This dissertation is a study of two basic questions involving irreducible elements in algebraic number fields. The first question is: Given an algebraic integer β in a field with class number greater than two, how many different lengths of factorizations into irreducibles exist? The distribution into ideal classes of the prime ideals whose product is the principal ideal (β) determines the possible length of the factorizations into irreducibles. Chapter 2 gives precise answers when the field has class number 3 or 4, as well as when the class group is an elementary 2-group of order 8. The second question is: In a normal extension, when are there rational primes which split completely and remain irreducible? Chapter 3 focusses on the bicyclic bi-quadratic fields. The imaginary bicyclic biquadratic fields which contain such primes are completely determined. / Ph. D.

Methods of co-optimizing resolution and detection in Capillary Zone Electrophoresis (CZE) and Micellar Electrokinetic Chromatography (MEKC) are examined by deriving mathematical expressions which illustrate the relative importance of various experimental parameters. For CZE, expressions are derived to show the interrelationship between efficiency, capillary dimensions and sample size. The interrelationship shows that resolution and detectability cannot be optimized simultaneously. Efficiency and, therefore, resolution are maximized when small sample sizes and capillaries with small internal diameters are employed. Detection is more favorable when large sample sizes and capillaries with large internal diameters are used. To achieve a favorable compromise between resolution and detection, the Influence of pH, electrolyte concentration and forced air convection are examined. A decrease in pH or an increase in electrolyte concentration reduces electroosmotic flow. This increases the relative velocity difference between two zones and, thereby, minimizes the efficiency required for unit resolution. Forced air convection minimizes the loss in efficiency observed as capillaries with larger internal diameters are employed. In MEKC, the importance of efficiency is minimized by employing a micellar phase which provides adequate selectivity for the separation. The separation of ASTM test mix LC-79-2 obtained in sodium dodecyl sulfate, sodium decyl sulfate, and sodium dodecyl sulfate modified with Brij 35 indicates that selectivity is governed by the nature of the surfactant's polar head group. Beyond selectivity optimization, resolution may be improved by increasing efficiency or decreasing electroosmotic flow. Of these approaches, increasing capillary length, to improve efficiency, is more time effective. Using the guidelines described herein, several practical applications were developed. The methods are examined with respect to migration time and quantitative reproducibility. / Ph. D.

Studies of log truck speeds and fuel consumption were made at four location in the southeastern United States. Execution of the study necessitated the development and testing of a microprocessor based data logger capable of withstanding the harsh operating environment found in forest harvesting and transport equipment. The first study investigated the normal operating pattern for a truck in a logging contractors flect. The truck was found to be highly utilized and to incur considerable distances of unloaded running to service the contractor's widely separated operations. A second study highlighted the fucl and speed penalties associated with operations on sand and gravel roads. The third study documented significant performance differences between routes delivering to one location even where road surface differences were minimal. A fourth, detailed study illustrated speed and fuel consumption differences between urban and mural operations. Tests on a group of five experienced drivers demonstrated considerable differences in speed and fuel usage. Some drivers appeared to have a driving style which delivered higher speed with low fuel consumption. A detailed analysis of individual speed profiles indicated that as much as 1/3 to 1/2 of the recorded fuel consumption on one section was associated with air resistance. In conclusion the studies noted that for the trucks and conditions evaluated: (1) there are significant performance losses and increased costs associated with operations on low standard road sections. Road roughness was a significant factor determining speed. (2) performance and cost differences between routes were demonstrated even for roads of comparable road surface type. This indicated that inter-route costs differences may be pervasive. These differences would require acknowledgement and evaluation if equitable route payment schedules were to be constructed. (3) All the trucks studied operated for at least part of the time at high speeds and may be incurring unnecessary fuel and maintenance expenses. Application of aerodynamic deflectors might be beneficial and their applicability should be tested. (4) Some driving styles appear more efficient and deserve further investigation and documentation. Changing driver behavior might present the most cost effective means of improvement in fleet performance. / Ph. D.