Browsing by Subject "Hysteresis"
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Item Adaptive inverse modeling of a shape memory alloy wire actuator and tracking control with the model(2009-06-02) Koh, Bong SuIt is well known that the Preisach model is useful to approximate the effect of hysteresis behavior in smart materials, such as piezoactuators and Shape Memory Alloy(SMA) wire actuators. For tracking control, many researchers estimate a Preisach model and then compute its inverse model for hysteresis compensation. However, the inverse of its hysteresis behavior also shows hysteresis behavior. From this idea, the inverse model with Kransnoselskii-Pokrovskii(KP) model, a developed version of Preisach model, can be used directly for SMA position control and avoid the inverse operation. Also, we propose another method for the tracking control by approximating the inverse model using an orthogonal polynomial network. To estimate and update the weight parameters in both inverse models, a gradient-based learning algorithm is used. Finally, for the SMA position control, PID controller, adaptive controllers with KP model and adaptive nonlinear inverse model controller are compared experimentally.Item Development of compositional three-phase relative permeability and hysteresis models and their application to EOR processes(2016-12) Mohammad Reza Beygi, Mohammad Reza; Delshad, Mojdeh; Wheeler, Mary F. (Mary Fanett); Pope, Gary A; Sepehrnoori, Kamy; Mohanty, Kishory K.; Arbogast, ToddEnhanced oil recovery (EOR) techniques have the potential to improve hydrocarbon recovery and project economics substantially. Characterizing fluid displacement and the relevant multiphase flow properties are essential to modeling EOR processes to reliably forecast the performance and economics. The spatial-temporal distribution of fluids spans a broad spectrum of composition and saturation spaces. In addition, a fundamental understanding of characteristic parameters of interphase mass-transfer in various EOR applications is crucial to capture and model fluid displacement. Relative permeability is a critical characteristic petrophysical property for modeling fluid displacement in porous media. Also, hysteresis phenomena govern physics of fluid flow in many subsurface applications such as multicyclic EOR processes, geological CO2 sequestration, and natural gas storage. Capillary trapping is the essence of hysteresis to trap fluids. In this research, we developed a high-fidelity computational tool for integrating compositional three-phase relative permeability and hysteresis to assist in accurate modeling of multicycle and compositional EOR methods. This viable tool can be implemented into general-purpose reservoir simulators to model field-scale projects. It consists of an integrated compositionally-consistent three-phase relative permeability and three-phase hysteresis models. The developed three-phase relative permeability model is valid on entire saturation and composition spaces, is simple with one free parameter for each phase, and is versatile for all phases and wettability states. The general model is saturation-path dependent and adopts a linear saturation-weighted interpolation scheme for calculation of relative permeability parameters. For the compositional relative permeability modeling, we developed a general framework applicable to hydrocarbon and non-hydrocarbon phases. The developed framework provides a pragmatic approach for adding the direct impact of composition, pressure, and temperature and is independent of the conventional phase-labeling method. The proposed framework unifies thermodynamics, petrophysics, and geochemistry to enhanced relative permeability modeling. Relative permeability parameters are calculated based on a mapping scheme of current-state bulk and interphase Gibbs free energy onto corresponding initial-state values. We applied the developed framework to modeling lowsalinity waterflood and complex fluid displacement of near-critical fluids. The three-phase hysteresis model provides a general and straightforward approach for calculation of capillary trapping in multicyclic processes. The developed hysteresis model provides a set of cycle-dependent relative permeability curves and applies to any three-phase relative permeability model by incorporating the free-saturation concept. We implemented the developed toolbox into two in-house compositional reservoir simulators (i.e., IPARS and UT-DOECO2). Several synthetic field cases are discussed to validate the implemented models conceptually. Using the enhanced simulators, we demonstrated accurate modeling of multiphase fluid displacement and trapping in EOR processes such as water-alternate-gas injection scheme, low-tension gas flood (i.e., foam), and carbon capture, utilization, and storage (CCUS).Item Energy intensity ratios as net energy measures for selected countries 1978-2010(2013-12) Maxwell, John Paul; King, Carey Wayne, 1974-; Zarnikau, Jay William, 1959-Stated simply, this thesis focuses on the relationship between energy and the economy. Using the foundation of King 2010, this analysis expands the scholarship from a U.S. focus to perform Energy Intensity Ratio analysis on forty-four countries for the time period 1978-2010. There are four fuels examined: coal, natural gas, crude oil and electricity. Using both the price and expenditures based Energy Intensity Ratio methods, outputs for each fuel in any applicable sector was determined. In addition, this work compiles an estimate of the total energy expenditures for the majority of the world. By examining the overall expenditures of gross domestic product spent on energy, the data showed two points in time where energy appears to become a constraint on growth. Though this thesis does not answer the question directly as to whether an increase in energy expenditures “causes” an increase in economic growth, or whether an increase in economic growth “causes” an increase in energy expenditures, the research shows that vi there may be a “threshold” effect whereby as energy expenditures become a greater share of output, the ability of economic growth to take place is affected.Item Essays on international trade(2010-05) French, Scott Thomas; Corbae, Dean; Abrevaya, Jason; Freitas, Kripa; Ramondo, Natalia; Ruhl, KimThis dissertation consists of three essays pertaining to the causes of the levels and composition of the international trade flows of nations, and the consequential implications for the levels of per capita income and welfare of their populations. The first of these documents a pattern of comparative advantage in product level, bilateral trade data that conventional quantitative trade models have difficulty explaining. It goes on to develop a theory of product level productivity differences based on endogenous differences in the allocation of research and development into product and process innovation across countries over time, and it shows that, when fitted to cross-country manufacturing wage data, the predicted product level technology distribution is consistent with the observed trade pattern. The second essay shows that the distribution of technology levels inferred in the first essay can help explain the inability of both ad-hoc and theoretically based gravity models of trade to account for the observed positive correlation between the percentage of manufacturing output that is traded and countries' per capita income. It derives a modified gravity equation based on a Ricardian model of trade with deterministic product level technology differences across countries. It then uses estimates from a product level gravity estimation to compute the component of this equation that differs from a conventional gravity equation in order to determine the extent to which the observed concentration of comparative advantage in a common set of products for low-income countries explains the small percentage of their output that is exported. The final essay shows that a simple model of firm profit maximization in the presence of sunk costs of entering the export market is broadly consistent with the observed persistence of exporting behavior in firm level data. It uses this simple model and moments from data on US manufacturing firms to estimate the value of the sunk export entry costs faced by these firms using an indirect inference strategy. These costs are shown to be substantial relative the revenue stream of a typical firm.Item High performance pulse width modulated CMOS class D power amplifiers(2012-12) Lu, Jingxue; Gharpurey, RanjitThe objective of this research is to explore circuit techniques and architectures suitable for implementation in digital technologies, that can be used to enhance the efficiency of power stages. Specifically, the use of switching power stages with pulse-width modulation techniques is considered. Switching power stages, such as Class D amplifiers, are inherently well-suited for implementation in deep-submicron CMOS. Pulse-width modulation (PWM) employs discrete amplitude levels and encodes signal information in local time-based averages, and as such can also benefit from such technologies. Additionally PWM does not suffer from quantization noise, and is well-suited for low noise applications. PWM designs, that can be applied for a range of signal bandwidth requirements, spanning several tens to hundreds of kHz are proposed. Applications for these architectures include audio systems, powerline communications and wireless communications. Design challenges and requirements that can arise in different application contexts are considered in the specification of the architectures. A common goal in the definition of the architectures is to minimize complexity of the designs. In the first part of the dissertation, a third-order self-oscillating PWM class-D amplifier for audio applications, that utilizes a hysteretic comparator is described. The design is analyzed and its THD is theoretically determined by employing an equivalent model, that relates the approach to natural sampling pulse-width modulation. The architecture eliminates the requirement for a high-quality carrier generator. A low-cost hysteresis compensation technique is utilized to enhance distortion performance at high output power levels. An implementation is presented in a 0.7um CMOS process. The design achieves a dynamic range (DR) of 116.5 dB, and a THD+N of 0.0012%, while delivering a power of 125 mW into an 8[Omega] load at 1 kHz. The THD+N is under 0.006% up to 90% of the maximum output power. The amplifier can deliver 1.45 W into the load with a THD of 5% with a 5 V power supply. The efficiency is greater than 84% for output power larger than 1 W. The area of the amplifier is 6 mm². The achieved performance indicates that the design is well-suited for high-performance audio applications. A class D line driver that utilizes a phase-locked loop (PLL) based PWM generation technique is presented next. The principle of operation, and implementation details relating to loop stability, linearity and noise performance are analyzed. An implementation is presented in a 130nm CMOS process. The amplifier can deliver 1.2 W into an 6.8[Omega] load with a 4.8 V power supply. The architecture eliminates the requirement for a high-quality carrier generator and a fast, continuous voltage comparator that are often required in PWM implementations. The design can achieve a THD of -65 dB, with a switching frequency that can be as high as 20 MHz. The peak efficiency is 83% for output power larger than 1 W, for a switching frequency of 10 MHz. The area of the amplifier is 2.25 mm². This architecture is potentially suitable for powerline applications. Finally, a phase-locked loop based PWM Cartesian transmitter with the capability to drive switched power amplifiers, such as a Class D power amplifier, is proposed. A phase-locked loop based technique is employed to generate a high-frequency PWM pulse stream centered at 1.28 GHz. The prototype is simulated in a 130 nm CMOS process, and achieves 35% peak efficiency for 17 dBm output power with a carrier frequency of 900 MHz. Operation of the architecture with non-constant envelope modulation, such as that employed in the WCDMA standard, is verified in simulation.Item The investigation of MOSFET transistors at low temperature(Texas Tech University, 1980-12) Fang, Bo-shungNot availableItem Thermostatted models for hysteresis in magnetic nanoparticles(2002-12) Robb, Daniel Thomas; Reichl, L. E.Item Item Watercut Measurement Method by Using High Speed Impedance Sensor(2014-08-20) Erdogan, BurakOil and water mixtures are present in many applications, specifically in upstream oil production. To investigate oil-water that utilizes an electrical impedance measurement method. In this method, watercut is measured by using a newly developed algorithm that uses multiple frequencies to enhance the accuracy of the watercut measurements and to identify the mixture dispersion type. Electrical characteristics of the mixture were investigated by studying the effect of three factors, the emulsion properties, hysteresis effect, and temperature effect. The dependency of the watercut meter response to the influencing factors was reduced by implementing this developed novel method. Using this method, the uncertainty in watercut measurement from 0 to 1 watercuts was obtained to be about ?3% regardless of phase distribution. The effect of the shear forces on emulsion properties was investigated for all watercuts separately. The hysteresis effect was investigated by testing from 1 to 0.3 watercuts and 0 to 0.7 watercuts. The temperature effect was investigated by testing from 29.44 ?C (85 ?F) to 23.88 ?C (75 ?F) for 1 watercut. The shear forces have significant effect on emulsion properties in ambivalent range. The hysteresis and temperature do not have significant effect on the watercut measurement method.