The rotary lip seal is the most widely used dynamic seal. It is used extensively in the automotive and appliance industries. Experimentally, it is well known that the microasperities on the shaft surface can significantly affect the performance of a lip seal, even though the shaft roughness, after run-in, is much smaller than the lip roughness. In the present study, several deterministic numerical models are developed to investigate the effect of shaft surface finish on rotary lip seal behavior, through an understanding of the basic physics of lip seal operation. This project is performed in a step by step manner with gradually increasing complexity. Four models are included in this study: hydrodynamic analysis, elastohydrodynamic analysis for full film lubrication, mixed-EHL model for mixed lubrication with asperity contact, and transient dynamic mixed-EHL model for startup and shutdown processes. Those analyses allow the examination of some important seal characteristics, such as the load support sharing between hydrodynamic and contact pressure, contact and cavitation area ratio, reverse pumping rate, liftoff speed for tracing the liftoff process and average film thickness. The development of fluid, contact and cavitation areas as a result of the changing operation condition is also examined. The results of the present deterministic modeling indicate that shaft surface roughness can produce significant desirable effects on lip seal behavior. An appropriate shaft surface profile could improve the sealing ability and prevent seal failure.

In the first part of this dissertation we explore the consequences of high frequency operation of Josephson junction arrays. At high frequencies these systems are no longer well modeled by Kirchhoffs laws, and new dynamical equations are derived directly from Maxwells equations. From these equations we derive a reduced set of averaged equations which greatly simplify the analysis of high frequency arrays. The averaged equations allow us to examine experimental strategies for obtaining higher power outputs from arrays. These strategies rely on resonant architectures that place the junctions near antinodes of a desired standing wave mode of the fluctuating current. Simple, heuristic rules are derived for the proper placement of junctions. The second part of the dissertation is devoted to stochastic resonance. A new theory is proposed to explain both two-state and excitable stochastic resonance. Previous theories explaining the two types of stochastic resonance yield similar results while using different analytic strategies. A constrained asymmetric rate model is derived that in one limit produces the proper result for the two-state system, while in another limit models the excitable system. The result that the constrained asymmetric rate model gives in the excitable limit is off by a factor of two, and this discrepancy is examined. Furthermore, we study the consequences of adding a colored noise source to the classic two-state model of stochastic resonance. We will find that when both white and colored noise sources are present, stochastic resonance will occur as a function of colored noise strength only if the correlation time of the colored noise source is small enough. Two theories are proposed to explain this phenomenon and both are examined in detail.

¡@¡@This paper uses the unemployment rate in quarterly data from 1987 to 2011, empirical exploration whether unemployment rate of with Taiwan¡¦s frequent trading countries has a hysteresis effect, as government policy on the basis. ¡@¡@In general circumstances, there are different results by using traditional unit root tests (ADF, PP, KPSS, the DF-of GLS and NP). And the possible reasons are getting the lower power of individual series because of the small simples and without considering about the structural break results in the series with problem of type I error. Therefore, in order to solve the problem, Kyung So, Im, Junsoo Lee, and the Margie Tieslau (2010) constructed an unit root test of panel data which needs to consider the structural break of level and trend. Moreover, the correlation between the inter-individual series by using the cross-sectionally augmented (CA) method from Pesaran (2007) also needs to be considered. ¡@¡@As the results of panel data unit root tests, series of unemployment rate do not reject the null hypothesis, that is, with hysteresis effect which breaks natural unemployment rate continuously. In this case, the government must set up policies to intervene to recover the unemployment rate.

With the possibility of imitation, we discuss the pricing strategy of an inventor and the piracy-deterrence policy of a government. When inventor and imitator have asymmetric manufacturing costs, piracy may not be deterred by the government. When the inventor¡¦s cost of production is low enough, the inventor always stays in the market and the piracy only occurs if the social welfare is enhanced by the competition. When the inventor¡¦s cost of production is high, a monopoly market emerges and the identity of the monopolist, which can be the inventor or the imitator, is determined by the government through the piracy-deterrence policy such that the social welfare is maximized.

Blind estimation of unknown channel parameters and data symbol detection represent major open problems in non-cooperative communication systems such as automatic modulation classification (AMC). This thesis focuses on estimating the symbol rate and detecting the data symbols. A blind oversampling-based signal detector under the circumstance of unknown symbol period is proposed. The thesis consists of two parts: a symbol rate estimator and a symbol detector. First, the symbol rate is estimated using the EM algorithm. In the EM algorithm, it is difficult to obtain the closed form of the log-likelihood function and the density function. Therefore, both functions are approximated by using the Particle Filter (PF) technique. In addition, the symbol rate estimator based on cyclic correlation is proposed as an initialization estimator since the EM algorithm requires initial estimates. To take advantage of the cyclostationary property of the received signal, there is a requirement that the sampling period should be at least four times less than the symbol period on the receiver side. Second, the blind data symbol detector based on the PF algorithm is designed. Since the signal is oversampled at the receiver side, a delayed multi-sampling PF detector is proposed to manage inter-symbol interference, which is caused by over- sampling, and to improve the demodulation performance of the data symbols. In the PF algorithm, the hybrid importance function is used to generate both data samples and channel model coe±cients, and the Mixture Kalman Filter (MKF) algorithm is used to marginalize out the fading channel coe±cients. At the end, two resampling schemes are adopted.

Because of an ever-increasing threat of foreign animal disease outbreaks in the United States, there is a desire to develop strategies to prevent the occurrence of a foreign animal disease and control an outbreak if it does occur. Infectious disease models have been developed and are being used to determine reasonable mitigation strategies. However, little information is available concerning premises characteristics and movement of animals in extensively managed livestock areas. Hence adaptation of these models to areas where there is low livestock density is not easy. We collected empirical data, via mail out surveys, from an extensively managed livestock area. This will aid in improving the results of infectious disease models in these areas. In contrast to the intensively managed livestock that have previously been modeled, this study has shown that in areas of low livestock density, multiple livestock types often are managed on the same premises. Direct contacts, facilitated through the planned movement of animals, appear to have a greater seasonality in extensively managed areas as compared to intensively managed areas. Furthermore, wildlife contacts are likely and of potential importance. The results of this study add to the knowledge base used to model the spread of infectious disease in extensively managed livestock populations. Seasonal changes in animal densities and contact rates may impact the results of the models. Additionally, the effect of multiple livestock types on premises should be considered when the expected spread of disease is modeled in extensive livestock areas.

Body shape affects the capacity and efficiency of swimming in fishes, and places constraints on foraging and reproductive performance. Hence, fitness components, such as aerobic swimming capacity and efficiency, can be determined from analysis of swimming energetics using active respirometry. In particular, body shape adaptations, such as streamlining, aim at reducing hydrodynamic drag (resistance), thereby increasing swimming efficiency in the presence of water flow, which is a principal contributor to resistance for fish inhabiting rivers. For two populations of bluegill sunfish, one from the Brazos River and the other from Moelman’s Slough (a Brazos River oxbow lake), the metabolic transport rate (MTR) was determined to evaluate differences in swimming efficiency. The standard cost of swimming (SCOS) was also determined to evaluate differences in swimming capacity, which represents the overall capacity of the skeletal muscles to generate mechanical power to overcome hydrodynamic resistance. The MTR and the SCOS describe holistic swimming performance, where the MTR specifies the hydrodynamic response due to swimming, and the SCOS specifies the physiologic response due to swimming. The differences in swimming performance are mainly attributed to factors affecting hydrodynamic resistance and could be predicted by morphology; because body shape, like water flow, is also a principal contributor to resistance. Multivariate body shape, from generalized Procrustes analysis, was used to assess the influence of multiple shape traits on swimming costs. This measure of shape related to swimming performance using partial least-squares analysis showed the two bluegill populations to be significantly different. The results were as follows: the shallow-bodied condition in bluegills was highly correlated with efficient swimming and low swimming capacities; whereas, deep-bodied bluegills were highly correlated with inefficient swimming and high swimming capacities. This is an empirical case of divergent natural selection. For convergence, however, the position of the caudal peduncle is consistent with optimal swimming speed (Um), which depends on standard metabolic rate (SMR), or metabolic maintenance. Bluegills with erect caudal peduncles have a high range of swimming speeds without suffering much cost of swimming ability compared to bluegills with prone caudal peduncles. The adaptive physiological response to high Um is due to a low SCOS because swimming efficiency is low and metabolic maintenance is high. In other words, bluegills that are inefficient swimmers and require a high energy intake cannot survive unless they gain the ability to increase their foraging capacity by thrust or metabolic power reduction. This is perhaps one of the most remarkable adaptive physiological responses due to the joint effects of shape and SMR.

No description available.

A variety of functional thin films can be produced using the layer-by-layer assembly technique. In this work, assemblies of anionic clay and cationic polymer were studied with regard to film growth and gas barrier properties. A simple, yet flexible robotic dipping system, for the preparation of these thin films, was built. The robot alternately dips a substrate into aqueous mixtures with rinsing and drying in between. Thin films of sodium montmorillonite clay and cationic polymer were grown and studied on poly(ethylene terephthalate) film or a silicon wafer. After 30 clay polymer bilayers were deposited, the resulting transparent film had an oxygen transmission rate (OTR) below 0.005 cm3/m2/day/atm. This low OTR, which is unprecedented for a clay-filled polymer composite, is believed to be due to a ?brick wall? nanostructure comprised of completely exfoliated clay bricks in polymeric ?mortar?. The growth of polymer and clay assemblies is then shown to be controlled by altering the pH of polyethylenimine (PEI). Growth, oxygen permeability, and mechanical behavior of clay-PEI assemblies were studied as a function of pH in an effort to tailor the behavior of these thin films. Thicker deposition at high pH resulted in reduced oxygen permeability and lower modulus, which highlights the tailorability of this system.

This thesis evaluates the applicability of forecasting production from low permeability and layered tight gas wells using the Arps hyperbolic equation at earlier times and then switching to the exponential form of the equation at a predetermined minimum decline rate. This methodology is called the minimum terminal decline rate method. Two separate completion types have been analyzed. The first is horizontal completions with multi-stage hydraulic fractures while the second is vertical fractured wells in layered formations, completed with hydraulic fractures. For both completion types both simulated data and real world well performance histories have been evaluated using differing minimum terminal decline rates and the benefit of increasing portions of production history to make predictions. The application of the minimum terminal decline rate method to the simulated data in this study (3 percent minimum decline applied to multiple fractured horizontal wells MFHW- and 7 percent applied to vertical fractured layered wells) gave high errors for some simulations within the first two years. Once additional production data is considered in making predictions, the errors in estimated ultimate recovery and in remaining reserves is significantly reduced. This result provides a note of caution, when using the minimum decline rate method for forecasting using small quantities of production history. The evaluation of real world data using the minimum terminal decline rate method introduces other inaccuracies such as poor data quality, low data frequency, operational changes which affect the production profile and workovers / re-stimulations which require a restart of production forecasting process. Real well data for MFHW comes from the Barnett Shale completions of the type which have been widely utilized since 2004. There is insufficient production history from real wells to determine an appropriate minimum terminal decline rate. In the absence of suitable analogs for the determination of the minimum terminal decline rate it would be impossible to correctly apply this methodology. Real well data for vertical fractured layered wells from the Carthage Cotton Valley field indicate that for wells similar to Conoco operated Panola County wells a feasible decline rate is between 5 percent and 10 percent. Further if a consistent production trend and with more than 2 years of production history are used to forecast, the EUR can be predicted to within plus/minus 10 percent and remaining reserves to within plus/minus 15 percent.