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Muscular contraction is associated with low frequency transverse mechanical waves called acoustic myograph (AMG). It can be recorded by microphones and accelerometer. The origin of AMG is thought to be due to the lateral movement of the muscle as a whole. The signal is implicated in many reports as having great potential as force indicator during muscular contraction and could be use clinically in distinguishing healthy and disease, and evaluate force in muscles normally with little clinical access. The aim of this series of investigation was to assess the feasibility of using AMG as a force indicator, especially in situations where direct force measurement is not practical and in FES applications as fatigue indicator. Attempts were made to clarify AMG signal characteristics and assess the possible parameters which could be deployed to describe the AMG signal. Two series of experiments were carried out: one on voluntary contractions of human quadriceps and the other on stimulated contractions of rabbit anterior tibialis. Strain gauges were used to measure force and accelerometers were used to record AMG signal from the skin surface of the thigh on human and from the muscle surface of rabbit anterior tibialis. The AMG signal was recorded between 0.5Hz and wideband frequency and sampled at 512Hz. AMG signal amplitude was calculated by both the rectify-integrated and room-mean-square methods. Frequency content of AMG signal was analyzed by Fast-Fourier-Transform method. The studies carried out on human quadriceps were to: 1) Locate the possible optimal recording site for AMG. 2) Investigate the relationship between AMG and force production during isometric constant force and varying force contractions. 3) Study the AMG-force relationship during sustained and intermittent contractions till fatigue. The study performed on rabbit anterior tibialis were to: 1) Investigate the AMG signal characteristic with changing muscle length both under twitch and tetanic contractions. 2) Examine the AMG signal change with stimulation frequencies both at fixed and varied muscle lengths. 3) Assess the possible association between force and AMG in stimulated contraction till fatigue by both continuous and intermittent stimulation. 4) Study the influence of fatigue on AMG-force relationship under different stimulation frequencies. Results shown that there is no single optimal position for AMG recording on human quadriceps. But high AMG signal intensity were recorded at the mid and proximal-lateral region. The data presented in this report collaborated a linear relationship between AMG and force level in isometric contractions of human quadriceps muscle. This close link between AMG signal intensity and force production is also present in fatigue induced by sustained muscle contractions but not by intermittent contractions. The data obtained from rabbit tibialis anterior muscle showed less systemic relationships between AMG and force production. AMG signal intensity did not display a close relationship with force under condition of changing muscle length, stimulation frequency and fatigue. There were no significant change in AMG signal median frequency during voluntary contractions and AMG signal recorded during stimulated contractions were dominated by stimulation frequency. The good correlation between AMG and force in voluntary contractions, shows promise as an indicator of voluntary force from isometric contractions and fatigue by sustained contractions. The possible clinical use of AMG could be in the area of assessing force output from muscles with limited access, such as paraspinal muscle and facial muscles. It could also be used in conjunction with EMG to assess the state of the muscle function in health and disease and muscle mechanic in training. The use of AMG as force indicator in stimulated contractions, such as FES applications, requires further investigation. It did not appear to relate strongly to force output under conditions investigated. Alternative properties of AMG signal, such as power content in specific frequency range, should be investigated further for FES applications. The AMG median frequency certainly is not a good force indicator under all conditions tested in the experiment.

Free boundary problems can be reformulated as shape optimization problems with partial differential equation (PDE) constraints, making them solvable through numerical shape optimization algorithms. The Smooth Extension Embedding Method (SEEM), a novel approach for solving PDEs, leverages straightforward discretization of complex domains and achieves a high degree of convergence for problems with smooth solutions. This makes SEEM a viable alternative to the finite element methods used in traditional numerical shape optimization algorithms, effectively overcoming key challenges such as mesh degeneration and low-order convergence. To enhance the stability of SEEM while maintaining its high-order accuracy for boundary value problems on non-smooth numerical representations of inherently smooth boundaries, we employ a regularized level set boundary approximation technique. This enhancement broadens the applicability of SEEM to the class of free boundary problems with a shape optimization approach. Through theoretical and practical examples, experiments show that our improved SEEM-based algorithm maintains high-order accuracy in shape gradient approximation and circumvents computational pitfalls like mesh degeneration that can arise during shape evolution. This makes the direct use of a simple shape gradient formula and an explicit gradient descent flow possible. The resulting algorithm employs straightforward domain grids throughout the shape optimization process, resulting in significant computational savings and ease of implementation.

This dissertation uses economic theory, in tandem with experiments and other empirical methods, to better understand the role of information – for instance, missing information, conflicting information, and information overload – in determining outcomes in decision settings characterized by risk and uncertainty. In my first chapter, I use theory and experiments to compare market outcomes in a setting where the seller has better information on product quality than the buyer, and examine the effects of introducing a third-party who can credibly relay information on product quality. Under a range of conditions, I find market efficiency is higher when the information intermediaries interact with buyers instead of sellers. Moreover, market outcomes depend on many other factors, including the accuracy of the certification process and the level of competition in the certification market. My other dissertation chapters examine decision making in settings characterized by ambiguity, where agents may not form unique beliefs about the probabilities associated with potential outcomes either because there is too little information, or too much conflicting information is provided. In the second chapter, I design a novel experiment that takes advantage of information updating to test the predictive power of two popular classes of ambiguity aversion models, and the experimental results suggest that the “kinked” rather than “smooth” specification better predict subjects’ behavior. In the third chapter, I conduct MATLAB simulations to study the timing of technology adoption in response to climate change when predictions from multiple climate models are available. Using the data from California’s Central Valley, my simulation results show that an increase in the confliction between projections accelerates the adaption speed of new technology, while an increase in the volatility of projections delay the procedure.

This dissertation offers a new narrative on the history of public debt in late Qing and Republican-era China (1850 – 1914), highlighting its links with late Qing and Republican political economy. A history of economic ideas and institutions, the dissertation draws from official and diplomatic communications, contemporary newspapers and journals, academic studies and private letters to explore the process of its embedment into Chinese fiscal system and its evolution in China as a set of discourses and practice, including its reception by officials, merchants and general public, and its adjustment to established discourses of political economy in late Qing and Republican China.Adopting an expansive conception of public debt to include related public credit mechanisms and discourses, the dissertation traces the impact of pre-1850 official debates on late 19th Century Chinese officials’ ambivalence towards modern public debt. It argues that a domestic intellectual and policy reorientation in favour of growth was needed and mostly achieved before Qing’s military defeat in 1895, paving the way for large-scale borrowing that in turn reconfigured state-society relations in late Qing. The dissertation also investigates how mid-Victorian liberal discourses on public debt were co-opted by Chinese reformists, which in their modified form of political and fiscal accountability, proved to be effective in dominating late Qing and Republican discourses on public debt.This dissertation is one of the first English-language studies discussing the evolution of economic ideas surrounding Chinese public debt. Recounting China’s historical experiences with public debt, and discourses on political economy that resulted from these experiences would promote a more layered understanding of public debt’s role for peripheral economies in the late 19th and 20th Century.

The single-phase uncontrolled rectifier supplying a constant power load (CPL) is common in a power system, especially for digital devices such as telecommunication equipment. The characteristics of CPLs may de-stabilize the system and cause the output voltage collapse if the initial capacitor voltage is too low. Based on a mathematical model of the rectifier-CPL circuit, a method is proposed to estimate the minimum initial voltage. Also, some non-linear factors including the source impedance and the inertia of the CPL. When the rectifier operates in steady states, a high load power may cause the bifurcation phenomenon. Some analysis is made for the bifurcation and its negative effects on the power grid.

Grassland ecosystems occupy approximately 40% of the earth’s terrestrial area and represent one of most important ecosystems on Earth in terms of its impacts on global food supply, carbon sequestration and maintaining biodiversity. Grassland ecosystems are very sensitive to disturbances caused by either climatic or anthropogenic changes such as changes in precipitation regimes or management practices. The objective of this dissertation is to investigate the impacts imposed by grassland restoration activities and changes in precipitation anomalies on the steppe in China’s Loess Plateau and the mixed-grass prairie in southwest Oklahoma. In chapter two, I analyzed how large-scale vegetation conservation programs affected the grassland dynamics in China’s Loess Plateau by combining remotely sensed data with socio-economic statistics. The results of this study showed that the impact of vegetation conservation programs on vegetation change in the Loess Plateau is twofold. On the one hand, vegetation conservation programs target marginal lands. Thus, significant vegetation increases due to cropland conversion and afforestation can be found in these regions. On the other hand, intensified agricultural production can be found in croplands with suitable topography and well-established irrigation systems which were not enrolled in conservation programs to offset the agricultural production loss caused by vegetation conservation programs elsewhere. In chapter three, I demonstrated a new methodology on mapping the historical distribution of grassland species in southwest Oklahoma based on the Random Forest classification algorithm. In this study, elevation, soil pH and soil clay content were found to be significant variables for predicting the distribution of C3 and C4 grassland species. With the mapped distribution of grassland species between 1981 and 2010, in chapter four, I examined the relationship between changes in precipitation anomalies and the dynamics of relative abundance of C3 and C4 grassland species in southwest Oklahoma. In this study, significant decreases of C3/C4 ratio were identified in pasture/hay fields due to the increases in C4 abundance resulting from the decreases of sparsely vegetated area between 2005 and 2010. I suspect that the increase in C4 abundance was a drought adaptation strategy adopted by ranchers. Because C4 species are more tolerant of drought conditions and thus can help to maintain stable forage/hay production when negative precipitation anomalies prevailed during the growing season of C3 species.

Heparan sulfate proteoglycans (HSPGs) are cell-surface and extracellular matrix macromolecules that comprise a core protein to which a number of heparan sulfate (HS) glycosaminoglycan (GAG) chains are attached. Current evidence suggests that HSPGs participate in many different signaling pathways during development. However, it is largely unknown what specific HSPG molecules are involved in these processes. My work demonstrates that two Drosophila glypicans, Dally and Dally-like (Dlp), are the major HSPGs involved in Wg, Hh and FGF signaling. Furthermore, I analyzed the mechanisms of HSPG function in different signaling pathways by combining genetic, molecular and biochemical experiments. My work argues that much of the specific activities of Dlp in Hh and Wg signaling come from its core protein, rather than the attached HS GAG chains. Importantly, the new results from my studies allowed me to propose a novel model to explain the biphasic activity of Dlp in Wg morphogen signaling. Such a biphasic co-receptor is likely a general component in other morphogen systems, because I also found that another Hh co-receptor, Inteference hedgehog (Ihog), also has biphasic activity in Hh morphogen signaling. Thus, the dissertation work will shed light on the mechanisms of how the morphogen system is organized at the level of ligand binding.