This computational study reveals the primacy of language contact in the variation of language (Sarah Grey Thomason 2003). The visualization and further analysis confirm the reconceptualization of Chinese linguistic history with the theory of Horizontal Transmission (Shen 2016). Horizontal Transmission situates the development of Mandarin and other Chinese dialects in a sociopolitical landscape as a cultural complex and introduces imperfect learning to the time-capsulated process of Language Shift as an inevitable social phenomenon. The nature of language largely determines how it can change(Janda and Joseph 2003). We have to ruminate on the fact that the grammar of language is a symbolic system of representation while living language is a complex adaptive system generated and regenerated by individuals (Shen 2015). The descriptive capacity of Shen’s theory is compatible with the nature of language being dynamic idiolects alongside a real linguistic history embodied by individual speakers in time and space. The descriptive capacity of Shen’s theory is compatible with the nature of language being dynamic idiolects alongside a real linguistic history embodied by individual speakers in time and space. Only by understanding the change mechanism of Chinese from the perspective of language contact and through the lens of language shift, the variation of Mandarin and emergence of Chinese dialects find their explanations in a salient chain of logic to create a holistic account of Chinese evolution where the intertwined influence of languages finds its manifestation.

Much of the recent work in the area of implicit contract theory hypothesizes that firms and workers differ in their attitudes towards risk. The optimal wage and employment contract calls for shifting some of the risk associated with a randomly fluctuating marginal product of labor from the more risk averse party to the less risk averse party. The purpose of this dissertation is to explore the empirical implications of this risk shifting hypothesis. In particular, the following question is addressed: "How can we empirically identify whether risk shifting is occurring in the labor market?” Chapter 2 explores this question in the context of an implicit contract model with nominal variables and a randomly fluctuating price level. Under the usual assumption of risk neutral firms and risk averse workers the implications of the model are refuted by the industry level nominal wage stylized facts. Under the assumption that risk neutral workers insure risk averse firms the model is capable of explaining the stylized facts about the co-movements in nominal wages and employment. Chapter 3 explores this question in the context of a long-term implicit contract model with bankruptcy constraints. It is shown that if risk neutral firms insure risk averse workers then the real wage will respond asymmetrically to permanent and temporary revenue function disturbances. In particular, the real wage will respond more to a given permanent shock than to a temporary shock of the same size. Chapter 4 empirically tests this asymmetric wage response implication. A frequency domain technique is developed for decomposing a measure of revenue function disturbances into its permanent and temporary components and the real wage is regressed on each component. A sample of 12 4-digit SIC code industries are tested. The industry wage responses are estimated separately and as a system of seemingly unrelated regressions. Estimated separately, the results support the asymmetric response implication for 7 of the 12 industries at the .10 level of significance and 6 of the 12 industries at the .05 level. Estimated as a system the joint asymmetric response hypothesis is supported at the .01 level of significance for the 12 industries. / Ph. D. / incomplete_metadata

This dissertation is primarily concerned with studying the invariant subspaces of left-invertible, weighted shifts, with generalizations to left-invertible operators where applicable. The two main problems that are researched can be stated together as When does a weighted shift have the one-dimensional wandering subspace property for all of its closed, invariant subspaces? This can fail either by having a subspace that is not generated by its wandering subspace, or by having a subspace with an index greater than one. For the former we show that every left-invertible, weighted shift is similar to another weighted shift with a residual space, with respect to being generated by the wandering subspace, of dimension $n$, where $n$ is any finite number. For the latter we derive necessary and sufficient conditions for a pure, left-invertible operator with an index of one to have a closed, invariant subspace with an index greater than one. We use these conditions to show that if a closed, invariant subspace for an operator in a class of weighted shifts has a vector in $l^1$, then it must have an index equal to one, and to produce closed, invariant subspaces with an index of two for operators in another class of weighted shifts. / Ph. D.

Renewable energy and distributed generation are getting more and more popular, including photovoltaic modules (PV), wind turbines, and fuel cells. The renewable energy sources need the power electronics interface to the utility grid because of different characteristics between the sources and the grid. No matter what renewable energy source is utilized, inverters are essential in the microgrid system. Thanks to flexible modular design, transformerless connection, extended voltage and power output, less maintenance and higher fault tolerance, the cascade inverters are good candidates for utility interface of various renewable energy sources. This dissertation proposes a new type of cascade inverters based on dual-buck topology and phase-shift control scheme. Compared to traditional cascade inverters, they have enhanced system reliability thanks to no shoot-through problems and lower switching loss with the help of using power MOSFETs. With phase-shift control, it theoretically eliminates the inherent current zero-crossing distortion of the single-unit dual-buck type inverter. In addition, phase-shift control can greatly reduce the ripple current or cut down the size of passive components by increasing the equivalent switching frequency. An asymmetrical half-cycle unipolar (AHCU) PWM technique is proposed for dual-buck full-bridge inverter. The proposed approach is to cut down the switching loss of power MOSFETs by half. At the same time, this AHCU PWM leads to current ripple reduction, and thus reducing ripple-related loss in filter components. Therefore, the proposed PWM strategy results in significant efficiency improvement. Additionally, the AHCU PWM also compensates for the zero-crossing distortion problem of dual-buck full-bridge inverter. Several PWM techniques are analyzed and compared, including bipolar PWM, unipolar PWM and phase-shifted PWM, when applied to the proposed cascade dual-buck full-bridge inverter. It has been found out that a PWM combination technique with the use of two out of the three PWMs leads to better performance in terms of less output current ripple and harmonics, no zero-crossing distortion, and higher efficiency. A grid-tie control system is proposed for cascade dual-buck inverter with both active and reactive power flow capability in a wide range under two types of renewable energy and distributed generation sources. Fuel cell power conditioning system (PCS) is Type I system with active power command generated by balance of plant (BOP) of each unit; and photovoltaic or wind PCS is Type II system with active power harvested by each front-end unit through maximum power point tracking (MPPT). Reactive power command is generated by distributed generation (DG) control site for both systems. Selective harmonic proportional resonant (PR) controller and admittance compensation controller are first introduced to cascade inverter grid-tie control to achieve better steady-state and dynamic performances. / Ph. D.

Analyses are performed on the potential of using radio-frequency signals from massive LEO satellite constellations. This work aids in the creation of a navigation system independent of current GNSS. A tightly-coupled carrier Doppler shift/INS filter is developed to determine the feasibility of using signals of opportunity from LEO satellites for navigation purposes. This portion of the work makes two major contributions to the field of satellite-based radio-navigation systems. The first contribution is an analysis that shows GNSS-like position accuracy is possible using only INS measurements and carrier Doppler shift from LEO communication constellations. The second contribution is that INS quality, signal availability, and constellation design can significantly impact the navigation accuracy of a carrier Doppler shift/INS Kalman filter. An analysis of the costs and benefits of using model replacement over a Markov model in the dynamic propagation step of a tightly-coupled carrier Doppler shift/INS Kalman filter is performed in the next part of this work. This portion of the work makes contributions to the field of satellite-based radio-navigation systems. The main contribution is an analysis that shows Gauss-Markov models can be used instead of model replacement without increasing navigation error. Next, a DOP analysis is developed for systems using pseudorange and carrier Doppler shift measurements in point-solution batch filters that do not rely on INS data or dynamic propagation. This section's contributions to the field of satellite-based radio-navigation systems include a combined pseudorange and carrier Doppler shift DOP analysis using a novel DOP metric and an example of how to use the DOP analysis to identify the constellation characteristics, such as alternating ascending and descending nodes, that the OneWeb constellation could change to increase navigation accuracy. / Doctor of Philosophy / This dissertation presents research on using large communication satellite constellations as an independent backup to GPS. Simulated data are used to study the feasibility and navigation accuracy of such a system. Also investigated are different implementations of the algorithms used to navigate. Finally, a general analysis is developed to quickly approximate the navigation accuracy of a system that uses multiple measurement types.

Folding: A House is a study of the continuity of floor, wall and ceiling within the context of a house. With this method of continuity through folding, a strong directionality occurs within the spaces. The relationship among the different folds and between the folds and their enclosures is a syntactical relationship. Each fold slips in and past the previous fold. The forty-five degree rotation of the house on the forty-five degree sloped hill site allows for four fundamentally different relationships of house to ground and the surrounding views. The closed and open spaces inherently created within the folds directly relate to these differentiated views. / Master of Architecture

Over 20% of the American work force is employed on shifts other than the typical 9 a.m. to 5 p.m.. The effects of shift work can be many and varied. Perceptions of health as well as the eating patterns of shiftworkers were investigated in this study. The methodology used yielded a small, statistically insignificant sample population of both fixed and rotating shiftworkers; yet, after analysis, certain trends of the population were revealed. The rotating shiftworker consumed fewer meals and snacks than the fixed shiftworker. Meals and snacks were defined based on a food taxonomy developed to describe food intake. Additionally, the rotating shiftworker ate less often than the fixed worker. Consuming a meal in the 6 p.m. to 11 p.m. not affected by shift among rotating shiftworkers. Caffeine containing beverages comprised a large part of the diet of shiftworkers. Coffee was consumed more by the older group, and caffeinated soft drinks were preferred by the younger employees. The health status perception of the shiftworker could be labeled as"good". There may be a positive correlation between the regular occurrence of nervous stomach and coffee consumption among the rotating shiftworkers. Nervous stomach may also be related to days taken due to sickness for the rotators. Shift work is a disruption for employees. The nature and frequency of these disruptions are as of yet, not fully realized. Findings from this study warrant further investigation on this topic. / M.S.

purpose of this study was to determine if there are differences in dietary intakes and meal patterns, schedule satisfaction, and health satisfaction between nurses who work a permanent day shift (controls), and nurses who work alternate schedules. Subjects were selected from four hospitals: a large urban military hospital, a small military hospital located on a southern army base, a large southern community hospital, and a large southern university teaching hospital. One hundred and eighty full-time nurses were assigned to four schedule groups: Day, Evening, Night, and Rotating. Subjects completed a detailed survey regarding their work history, schedule and health satisfaction, meal patterns, and background, as well as a 24-hour dietary recall. Nurses who worked permanent days were the most satisfied with their schedules, followed, in order of priority, by the Night, Evening, and Rotating shift groups. Day shift nurses were also the most satisfied with the way their schedule affected their health, followed by nurses in the Evening, Night, and Rotating shift groups. There were no significant differences among the groups in nutrient intake although there were some differences in eating patterns. Nurses working the day shift ate more meals each day and more meals with their families. Rotating shift group nurses were more likely to skip meals. Nurses working the night shift ate more snacks per day and more snacks while at work. Nutrient analysis revealed that all four groups had intakes deficient in Vitamin D according to the RDA. Intakes were below the RDA for calcium, but only the Evening shift group was deficient. / Master of Science

This thesis shows the implementation of a novel control scheme DC-DC converter. The converter is a phase-shifted full-bridge PWM converter that is designed to operate as a front stage of a power conversion system where the input is a variable low voltage high current source. The converter is designed to step-up the low voltage input to an acceptable level that can be inverted to a 120/240 VAC 60Hz voltage for residential power. A DSP based adaptive control model is developed, taking into account line variations introduced by the input source while providing very good load dynamics for the converter in both discontinuous and continuous conduction modes. The adaptive controller is implemented using two voltage sensors that read the input and the output voltages of the converter. The controller's bandwidth is comparable to current mode control, without the need for an expensive current sensor, yet providing the noise immunity seen in voltage mode controllers. The intended input source was a fuel cell but in its absence a DC supply is utilized instead. The system is simulated for both discontinuous and continuous conduction modes and implemented and demonstrated for the continuous conduction mode. The test results are shown to match the simulation results very closely. / Master of Science

Research on unit load stability aids manufacturing facilities in selecting the most efficient load stabilizer when shipping their products to market. This study's objective was to compare the performance a variety of different commonly used load stabilizers to stretch hooding. Stretch hooding is a method of load stabilization in which a tubular film is heat sealed at the top, stretched by four mechanical arms to a desired width, pulled down over the unit load. The film is slowly released as the arms descend, and is released under the pallet. 400ga stretch hooding, 80ga and 63ga stretch wrap and strapping were tested. Twenty unit loads for both vibration and impact testing were used, with 5 replications per load stabilizer. Container displacement and pallet-container displacement were measured, and the number of tares in the load stabilizer film, on the corners of the test units, after testing, was noted. Container displacement was significantly greater during impact testing than in vibration testing. Strapping was the most effective stabilizer during vibration testing because of its ability to restrict vertical displacement. The stretch hooding was the most effective stabilizer during impact testing because of its ability to restrict horizontal displacement. / Master of Science