Nonequilibrium work theorems, such as the Jarzynski equality and the Crooks fluctuation theorem, allow one to use nonequilibrium measurements to determine equilibrium free energies. For example, it has been demonstrated that the Crooks fluctuation theorem can be used to determine RNA folding energies. We used single-molecule manipulation with an atomic force microscope to measure the work done on poly(dA) as it was stretched and relaxed. This single-stranded nucleic acid exhibits unique base-stacking transitions in its force-extension curve due to the strong interactions among A bases, as well as multiple pathways. Here we showed that free energy curves can be determined by using the Crooks fluctuation theorem. The nonequilibrium work theorem can be used to determine free energy curves even when there are multiple pathways.

The stride interval of typical human gait is correlated over thousands of strides. This statistical persistence diminishes with age, disease, and pace-constrained walking. Considering the widespread use of treadmills in rehabilitation and research, it is important to understand the effect of this speed-constrained locomotor modality on stride interval dynamics. To this end, and given that the dynamics of children have been largely unexplored, this study investigated the impact of treadmill walking, both with and without handrail use, on paediatric stride interval dynamics. An initial stationarity analysis of stride interval time series identified both non-stationary and stationary signals during all walking conditions. Subsequent scaling analysis revealed diminished stride interval persistence during unsupported treadmill walking compared to overground walking. Finally, while the correlation between stride interval dynamics and gross energy expenditure was investigated in an effort to elucidate the clinical meaning of persistence, no simple linear correlation was found.

The stride interval of typical human gait is correlated over thousands of strides. This statistical persistence diminishes with age, disease, and pace-constrained walking. Considering the widespread use of treadmills in rehabilitation and research, it is important to understand the effect of this speed-constrained locomotor modality on stride interval dynamics. To this end, and given that the dynamics of children have been largely unexplored, this study investigated the impact of treadmill walking, both with and without handrail use, on paediatric stride interval dynamics. An initial stationarity analysis of stride interval time series identified both non-stationary and stationary signals during all walking conditions. Subsequent scaling analysis revealed diminished stride interval persistence during unsupported treadmill walking compared to overground walking. Finally, while the correlation between stride interval dynamics and gross energy expenditure was investigated in an effort to elucidate the clinical meaning of persistence, no simple linear correlation was found.

Cet ouvrage présente une analyse d'un système de demande dans le domaine énergétique. Il concerne le marché résidentiel québécois. Le but est de déterminer les facteurs importants qui causent des perturbations dans la demande énergétique. L'Enquête des dépenses des ménages de Statistique Canada servira de source de données afin d'analyser les comportements de ceux-ci. Ce système de demande permettra de comprendre les réactions des ménages à ces perturbations du marché. De plus, il servira à mesurer le niveau de sensibilité des ménages aux prix d'électricité et des autres combustibles. Un modèle économétrique de la forme AIDS sera utilisé pour arriver à trouver ces variables déterminantes pour bien expliquer la demande énergétique. L'explication de ce modèle sera présentée pour bien démontrer le respect de la théorie économique. La résolution de ce système permet d'établir une liste de variables importantes ayant un impact dans la demande des ménages. Notre étude permet également d'expliquer de façon précise les réactions des ménages à des fluctuations de prix du marché. Nos résultats démontrent que la sensibilité des ménages aux prix d'électricité n'est pas inexistante et n'est pas similaire pour tous les ménages. Ce résultat est expliqué en fonction des différentes carctéristiques des ménages. Certaines carctéristiques des ménages influencent plus que d'autres le niveau de sensibilité aux prix d'électricité. Le degré d'importance des différentes caractéristiques est établi afin d'expliquer les résultats obtenus. Finalement, notre étude permet de faire des suggestions aux différentes institutions impliquées dans ce marché. Ces conseils poursuivent comme but l'amélioration de leurs objectifs personnels.

<p>This thesis focuses on the fluctuation in the switching current $I_s$ of superconducting Al nanowires. We discovered that the maximum current which nanowires can support is limited by a single phase slip at low temperature. </p><p>Al superconducting nanowires less than 10 nm wide were fabricated based on a MBE grown InP ridge template in an edge-on geometry. The method utilizes a special substrate featuring a high standing 8nm-wide InP ridge. A thin layer of Al was evaporated on the substrate and Al on the ridge formed nanowires.</p><p>The fluctuation effects starts to dominate in the nanowire due to reduced energy barrier. One of such effects is the phase slip. The phase slip is a topological event, during which the superconducting phase between two superconducting electrodes changes by $2\pi$. The phase slip broadens the normal-superconducting transition. Part of the nanowire becomes normal during the phase slip and forms a normal core. The normal core generates heat and causes the premature switching in superconducting nanowires.</p><p></p><p>The nanowire becomes superconducting below the critical temperature $T_c$. The superconducting-normal transition was studied in the thesis. The transition of nanowires with superconducting leads qualitatively fits the thermally activated phase slip (TAPS) theory. On the other hand, the transition of the nanowires with normal leads showed a resistive tail due to the inverse-proximity effect.</p><p>The nanowire switches from the superconducting state to the normal state as the current is increased. Ideally, the maximum current is set by a pair-breaking mechanism, by which the kinetic energy of quasi-particles exceeds the bonding energy of Cooper pairs. This is called the critical current, $I_c$. In practice, the measured maximum current, called the switching current $I_s$, cannot reach $I_c$ because of the phase slip.</p><p>$I_s$ shows stochasticity due to the phase slip. For the nanowires with superconducting leads, the average $I_s$ approximately follows but falls below $I_c$. The fluctuation in $I_s$ shows non-monotonic behavior, in contrast to other studies. The fluctuation first increases and then decreases rapidly with increasing temperature. The fluctuation behavior is consistent with a scenario where the switch is triggered by a single phase slip at low temperature while by multiple phase slips at higher temperature. Thermal activation of phase slips appears dominant at most temperatures. However, in the thinnest nanowire, the saturation of the fluctuation at low temperature indicates that the phase slips by macroscopic quantum tunneling.</p><p>The superconducting nanowires with normal leads were also studied. One of the distinctive properties of our nanowire (the critical field of 1D nanowire is 10 times larger than that of a 2D superconducting film) allowed us to study the same nanowire with different leads (superconducting or normal). Both the average $I_s$ and the fluctuation in $I_s$ differed qualitatively depending on whether the leads were superconducting or normal. The temperature dependence of the average $I_s$ followed the $I_c$ of the Josephson junction instead of the phenomenological pair-breaking $I_c$. The difference was found to depend on both the temperature (close to $T_c$ or 0) and the length (shorter or longer than the charge imbalance length). Our study also showed that nonlinear current-voltage (IV) curves were observed due to the inverse-proximity effect.</p> / Dissertation

With financial liberalization and economic globalization, international trade and capital transactions result in larger exchange rate fluctuations than in the past. Besides, it can¡¦t be ignored that the change of exchange rate influences the economics and real exchange rate which be regarded as the indicator of external competitiveness becomes more important than before, so my paper aims to know not only whether there is stochastic segmented trend in their fluctuation but also the factors which are closely related to regime switches. As we all know that it is significant to forecast the volatility of exchange rate in the global society. A number of previous studies discussed the relationship between exchange rate and fundamentals under the monetary models, however many people found that these models are handicapped in out-of sample forecasting. Therefore, I compare the forecasting performance of the real interest differential monetary (RID) model of Frankel (1979) with the models which I built in the paper. By using the market share of the top ten currencies in 2010 which is published by Bank for International Settlements (BIS) and the fundamentals. The empirical results indicate that fundamentals do not only matter for real exchange rate, but are also related to the switches between the regimes. Besides, the real exchange rates are highly persistent in each regime and the effect of fundamentals is different in different countries. At last, my result suggest that the models which I built in the paper provide better forecast in the yen, pound sterling and New Zealand dollar than the RID model.

Fluorescent lamps are in general driven by ac ballasting currents. The cyclic variation in arc discharging power results in light fluctuation at twice the frequency of the ac current. Light fluctuation may be intolerable when a steady light output is required in some particular applications. To eliminate light fluctuation, an electronic ballast with dc current is proposed to operate the fluorescent lamp at a constant power. The main power conversion of the electronic ballast employs the single-stage high-power-factor inverter, which is originated from a combination of the half-bridge resonant inverter and the buck-boost converter. With such a circuit configuration, the output power can be regulated by asymmetrical pulse-width-modulation. The ac output of the inverter is then rectified and filtered to provide the dc ballasting current. Driven by dc current, however, the fluorescent lamp emits electrons unilaterally from one end leading to wearing out of emission material on the cathode filament. To solve this problem, an inverter is integrated for commutation of the lamp electrodes. Furthermore, a preheating control is included to start the fluorescent lamps with zero glow-current. A prototype is designed and built for the OSRAM T5-80W fluorescent lamp. The dc operating characteristics of starting transient, light fluctuation, lighting spectra, color temperature as well as the light fluctuation are investigated from experiments. Experimental results also show that the electronic ballast is capable of high-power-factor, dimming capability and zero glow-current preheating.

In markets with cyclical fluctuations, firms may have different dynamic decision rules facing upturns and downturns of industry cycles. This paper extends the dynamic factor demand model to consider industry cycles. Because investment behavior could be endogenous uncertainty involved on industry dynamics, the current industry dynamic models with state-of-the-art would not appropriately interpret industry dynamics. In order to solve the uncertain problem, we utilize the idea of transfer probability in Markov switching model to catch the industry cyclical behavior. Explicitly incorporating the Markov regime switching mechanism based on Nelson and Kim (2000), this paper measures the firm¡¦s dynamic adjustments when facing upturns and downturns of industry cycles. The empirical work is based on firm level data of Taiwan high-technology industries. The empirical results show that the expansionary strategy in labor and capital usage may not have positive impacts on output when considering uncertainty that may be casued by business cycles. To have correct prediction in cyclical fluctuation becomes important task for high-technology firms. However, the positive contribution of exogenous technology to output growth is so significant. This proves why every industry tries to impel technology in recent years. The industry dynamic model integrated with cyclical fluctuation and demand uncertainty allows us to examine how sharp changes in financial factors might affect investment behavior, technological nature and adjustment effects for industries in facing demand and investment shocks.

This thesis study is focused on experimentally investigating pump noise at design and off-design operations and its relations with pressure fluctuations. Small size pumps are placed in a semi-anechoic chamber and operated at various system conditions and various rotational pump speeds. Pump operational data, noise data and time dependent pressure data are recorded. Fast Fourier Transform spectra of noise and pressure data are compared. Coherence spectrum between sound pressure level and hydraulic pressures are obtained. Data processing, Fast Fourier Transform and cross correlation are conducted with specific software Soundbook SAMURAI. The experiments have indicated that system characteristics or pump size do not have any influence on the noise of pump. On the other hand, pump characteristics are found to be distinguishable by means of peak frequencies on the sound spectra which are proportional to blade passing frequency. Results of cross correlations also show that, pump outlet pressure is a more significant source of noise than pump inlet pressure.

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