Call number: LD2668 .T4 1986 B62 / Master of Science / Biological and Agricultural Engineering

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Nursing Studies / Master / Master of Nursing

published_or_final_version / Nursing Studies / Master / Master of Nursing

This Thesis presents the development of an empirical and simple computer model for a voltage response of a ZnO element The derived model consists of a linear capacitor and atime-varying resistance. The data necessary for the derivation of the model is collected from testing on three ZnO elements with three different linear circuits. The front times of the voltage responses of the ZnO elements range from nanoseconds to submicroseconds. The front times of the current impulses being used to produce the voltage impulses varies from nanoseconds to microseconds. The voltages having nanosecond front times are measured with attenuators and the voltages with sub-microsecond-front time with a capacitor divider. Currents associated with the nanosecond-front-time voltages are measured with a technique founded on transmission line concepts. Currents associated with the submicrosecond-front-time voltages are obtained with a current shunt The response time of the capacitor divider and of the current shunt fall outside the ranges of the ratios of front time to response times specified in the IEC standard. Distortion introduced by the measuring devices into the measured signals is investigated with computer simulation. Conical transmission lines were constructed to test the voltage response of a toroidal ZnO element to the nanosecond-front-time current impulses. Analysis of the voltage response to the current impulses with sub-and-microsecond-front times indicates that at the beginning of the response, of a ZnO element it behaves as an approximately linear capacitor and subsequently as a capacitor in parallel with a timevarying resistance. The turn-on of the resistive behaviour occurs at approximately the first current peak The discrete voltage relating to the first current peak is named here the threshold voltage. This discrete voltage also denotes the tum-off of the resistive behaviour on the wave tail. The values of the apparent capacitances and permittivities of the ZnO elements are obtained. The apparent permittivities of the three ZnO elements are similar. The computed and measured variations of the resistance show good agreement The simulated and computed voltage responses of a ZnO element also show good agreement Atoroidal ZnO element is tested with the nanosecond-front-time current impulses. Analysis of the voltage response and the current-impulse shape by q-v curves and comparison of the measured responses to those of lumped linear capacitors show that a)the response of the ZnO element is capacitive and b) the capacitor characteristic is quasilinear. The simulated and computed voltage responses show good agreement The deviation from linearity originates from both the limited response of the attenuators and mismatches between the conical transmission lines and the section of the coaxial cable of the used current generator. The voltage response of miniature ZnO elements (also tested with the nanosecond-front time current impulses) show resistive behaviour. This Thesis also presents the design, construction and operation of a measuring system based on Rogowski coils. The model used for the analysis of the measuring system is an extended version of an existing model of a Rogowski coil. The model being introduced here can account for the interaction of the Rogowski coil with the remainder of the measuring system. This is applied successfully to the measurement of an impulse current flowing through a ZnO element

Experiments were conducted with 180 m long T-tape and Agrifim emitter lateral lines in the laboratory and field to determine the effects of water temperature and sediment concentration on the hydraulics of drip irrigation laterals. The flow regime was laminar through the T-tape emitter and turbulent through the Agrifim emitter. Water temperature decreased along the lateral line in the laboratory where the inlet water temperature was higher than ambient air. In contrast, temperatures increased along a lateral line exposed to the sun in the field with an inlet temperature lower or slightly higher than that of air. The rate of increase or decrease was more pronounced towards the end of the line. The effect of temperature was highly significant on emitter flow rates obtained for a T-tape emitter as opposed to those recorded for the Agrifim emitter in the laboratory; however, the increase of emitter flow rates due to temperature was reduced by plugging in the field. Discharges of T-tape emitters were dominated by the hydraulic pressure for the first half of the line with the water temperature being more important for the second half of the line in both the laboratory and field. Measured discharges of Agrifim emitters were dominated by the hydraulic pressure for the entire lateral length especially in the laboratory. The Darcy-Weisbach friction factor, as opposed to the Blasius friction factor, is recommended for design because it accounts for the wall roughness of the pipe. The Hazen-Williams roughness coefficient was related to Reynolds number to improve the drip system design. Total friction losses, as a result of water viscosity changes and lateral discharge variations due to temperature, increased significantly for the T-tape emitter lateral in the laboratory and field for different inlet water temperatures and inlet-outlet temperature variations. In contrast, total friction losses decreased for the Agrifim emitter lateral primarily because of water viscosity changes with temperature. The sediment concentration along an Agrifim emitter lateral in the laboratory decreased sharply in the second half of the line when the flow velocity dropped below 0.29 ms⁻¹ . Also friction losses increased for an Agrifim emitter lateral in the laboratory as the inlet concentration increased from 200 to 650 mg/l.

This thesis describes a multi-channel millimeter wave radiometer control system that will be used for atmospheric water vapor and temperature profile retrievals. The system consists of four subsystems which provide a total of nine frequency channels, a steerable reflector to permit slant-path measurements at different zenith angles, and a host computer for analyzing the data. The nine channels span the water vapor and oxygen absorption lines in the 20 to 60 GHz range. A distributed processing architecture is implemented to control the system. Each of the subsystems employs a signal processor and a microcontroller, which are configurable from the host. The signal processor filters the receiver's output, while the microcontroller oversees the radiometer, accepts data from the signal processor and communicates with the host. The host executes a custom shell that allows it to concurrently accept data from the subsystems, position the reflector and execute user analysis programs.

The Naval Construction Force (NCF) performs construction projects in all areas of the world during both peacetime and war. While some of these projects occur in populated areas where project materials are readily available, many of these projects occur in remote areas or war zones, where project materials must be procured from the United States or elsewhere and shipped to the unit performing the construction. The construction scopes also vary from projects as small as concrete sidewalks to projects as large as full utility system installations, or complete facility and base construction. As a result of the diverse locations and project types that the Naval Construction Force experiences, the logistics of providing project material and construction equipment to multiple global locations is a major challenge. The Naval Construction Force still experiences delays and inefficiencies in supplying construction materials to its various projects and units deployed throughout the world, which in turn reduces the overall productivity of the deployed Construction Battalions. This research explores the current supply chain that the NCF has in place for obtaining construction project materials. It also explores the latest initiatives in information technology and construction supply chain management that are being applied in the commercial sector. The two systems are compared to determine what private practices and technologies can be applied to the Navy system to make it more efficient. Since the Navy is restricted by Federal Acquisition Regulations, and has unique funding streams authorized by Congress, it will not have the ability to fully operate as a private construction company, and these restrictions are addressed. The issue of outsourcing and privatization is also studied, and the feasibility of outsourcing the entire construction material process is considered.

The purpose of this research is to determine the impacts of utilizing radio frequency identification (RFID) technology in order to implement intransit visibility (ITV) into the Marine Corps' Supply Process. I interviewed experts and users of the LTMITV/W2W at the Supply Management Unit (SMU), 1st Combat Logistics Regiment, 1st Marine Logistics Group on the operational implementation of the system as well as benefits and opportunities for improvement. With the information I recovered and data I collected, I was able to create a small simulation of the supply process. I used the simulation to create various scenarios that have been encountered in the past including possible negative impacts of the lack of ITV at certain portions of the supply process. I made recommendations on how to improve the current supply process as well as recommendations for future research.

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