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- Genre: Academic theses
- Creators: Arizona State University
- Creators: Chakraborty, Bijeta
- Member of: ASU Electronic Theses and Dissertations
- Status: Published
Description
Research has shown that the ability to smell is the most direct sense an individual can experience. With every breath a person takes, the brain recognizes thousands of molecules and makes connections with our memories to determine their composition. With the amount of research looking into how and why we smell, researchers still have little understanding of how the nose and brain process an aroma, and how emotional and physical behavior is impacted. This research focused on the affects smell has on a caregiver in a simulated Emergency Department setting located in the SimET of Banner Good Samaritan Medical Center in Phoenix, Arizona. The study asked each participant to care for a programmed mannequin, or "patient", while performing simple computer-based tasks, including memory and recall, multi-tasking, and mood-mapping to gauge physical and mental performance. Three different aromatic environments were then introduced through diffusion and indirect inhalation near the participants' task space: 1) a control (no smell), 2) an odor (simulated dirty feet), and 3) an aroma (one of four true essential oils plus a current odor-eliminating compound used in many U.S. Emergency Departments). This study was meant to produce a stressful environment by leading the caregiver to stay in constant movement throughout the study through timed tasks, uncooperative equipment, and a needy "patient". The goal of this research was to determine if smells, and of what form of pleasantness and repulsiveness, can have an effect on the physical and mental performance of emergency caregivers. Findings from this study indicated that the "odor eliminating" method currently used in typical Emergency Departments, coffee grounds, is more problematic than helpful, and the introduction of true essential oils may not only reduce stress, but increase efficiency and, in turn, job satisfaction.
ContributorsClark, Carina M (Author) / Bernardi, Jose (Thesis advisor) / Heywood, William (Committee member) / Watts, Richard (Committee member) / Rosso, Rachel (Committee member) / Arizona State University (Publisher)
Created2013
Description
Switch mode DC/DC converters are suited for battery powered applications, due to their high efficiency, which help in conserving the battery lifetime. Fixed Frequency PWM based converters, which are generally used for these applications offer good voltage regulation, low ripple and excellent efficiency at high load currents. However at light load currents, fixed frequency PWM converters suffer from poor efficiencies The PFM control offers higher efficiency at light loads at the cost of a higher ripple. The PWM has a poor efficiency at light loads but good voltage ripple characteristics, due to a high switching frequency. To get the best of both control modes, both loops are used together with the control switched from one loop to another based on the load current. Such architectures are referred to as hybrid converters. While transition from PFM to PWM loop can be made by estimating the average load current, transition from PFM to PWM requires voltage or peak current sensing. This theses implements a hysteretic PFM solution for a synchronous buck converter with external MOSFET's, to achieve efficiencies of about 80% at light loads. As the PFM loop operates independently of the PWM loop, a transition circuit for automatically transitioning from PFM to PWM is implemented. The transition circuit is implemented digitally without needing any external voltage or current sensing circuit.
ContributorsVivek, Parasuram (Author) / Bakkaloglu, Bertan (Thesis advisor) / Ogras, Umit Y. (Committee member) / Song, Hongjiang (Committee member) / Arizona State University (Publisher)
Created2014
Description
Efficiency of components is an ever increasing area of importance to portable applications, where a finite battery means finite operating time. Higher efficiency devices need to be designed that don't compromise on the performance that the consumer has come to expect. Class D amplifiers deliver on the goal of increased efficiency, but at the cost of distortion. Class AB amplifiers have low efficiency, but high linearity. By modulating the supply voltage of a Class AB amplifier to make a Class H amplifier, the efficiency can increase while still maintaining the Class AB level of linearity. A 92dB Power Supply Rejection Ratio (PSRR) Class AB amplifier and a Class H amplifier were designed in a 0.24um process for portable audio applications. Using a multiphase buck converter increased the efficiency of the Class H amplifier while still maintaining a fast response time to respond to audio frequencies. The Class H amplifier had an efficiency above the Class AB amplifier by 5-7% from 5-30mW of output power without affecting the total harmonic distortion (THD) at the design specifications. The Class H amplifier design met all design specifications and showed performance comparable to the designed Class AB amplifier across 1kHz-20kHz and 0.01mW-30mW. The Class H design was able to output 30mW into 16Ohms without any increase in THD. This design shows that Class H amplifiers merit more research into their potential for increasing efficiency of audio amplifiers and that even simple designs can give significant increases in efficiency without compromising linearity.
ContributorsPeterson, Cory (Author) / Bakkaloglu, Bertan (Thesis advisor) / Barnaby, Hugh (Committee member) / Kiaei, Sayfe (Committee member) / Arizona State University (Publisher)
Created2013
Description
Class D Amplifiers are widely used in portable systems such as mobile phones to achieve high efficiency. The demands of portable electronics for low power consumption to extend battery life and reduce heat dissipation mandate efficient, high-performance audio amplifiers. The high efficiency of Class D amplifiers (CDAs) makes them particularly attractive for portable applications. The Digital class D amplifier is an interesting solution to increase the efficiency of embedded systems. However, this solution is not good enough in terms of PWM stage linearity and power supply rejection. An efficient control is needed to correct the error sources in order to get a high fidelity sound quality in the whole audio range of frequencies. A fundamental analysis on various error sources due to non idealities in the power stage have been discussed here with key focus on Power supply perturbations driving the Power stage of a Class D Audio Amplifier. Two types of closed loop Digital Class D architecture for PSRR improvement have been proposed and modeled. Double sided uniform sampling modulation has been used. One of the architecture uses feedback around the power stage and the second architecture uses feedback into digital domain. Simulation & experimental results confirm that the closed loop PSRR & PS-IMD improve by around 30-40 dB and 25 dB respectively.
ContributorsChakraborty, Bijeta (Author) / Bakkaloglu, Bertan (Thesis advisor) / Garrity, Douglas (Committee member) / Ozev, Sule (Committee member) / Arizona State University (Publisher)
Created2012
Description
The continuing advancement of modulation standards with newer generations of cellular technology, promises ever increasing data rate and bandwidth efficiency. However, these modulation schemes present high peak to average power ratio (PAPR) even after applying crest factor reduction. Being the most power-hungry component in the radio frequency (RF) transmitter, power amplifiers (PA) for infrastructure applications, need to operate efficiently at the presence of these high PAPR signals while maintaining reasonable linearity performance which could be improved by moderate digital pre-distortion (DPD) techniques. This strict requirement of operating efficiently at average power level while being capable of delivering the peak power, made the load modulated PAs such as Doherty PA, Outphasing PA, various Envelope Tracking PAs, Polar transmitters and most recently the load modulated balanced PA, the prime candidates for such application. However, due to its simpler architecture and ability to deliver RF power efficiently with good linearity performance has made Doherty PA (DPA) the most popular solution and has been deployed almost exclusively for wireless infrastructure application all over the world.
Although DPAs has been very successful at amplifying the high PAPR signals, most recent advancements in cellular technology has opted for higher PAPR based signals at wider bandwidth. This lead to increased research and development work to innovate advanced Doherty architectures which are more efficient at back-off (BO) power levels compared to traditional DPAs. In this dissertation, three such advanced Doherty architectures and/or techniques are proposed to achieve high efficiency at further BO power level compared to traditional architecture using symmetrical devices for carrier and peaking PAs. Gallium Nitride (GaN) based high-electron-mobility (HEMT) technology has been used to design and fabricate the DPAs to validate the proposed advanced techniques for higher efficiency with good linearity performance at BO power levels.
Although DPAs has been very successful at amplifying the high PAPR signals, most recent advancements in cellular technology has opted for higher PAPR based signals at wider bandwidth. This lead to increased research and development work to innovate advanced Doherty architectures which are more efficient at back-off (BO) power levels compared to traditional DPAs. In this dissertation, three such advanced Doherty architectures and/or techniques are proposed to achieve high efficiency at further BO power level compared to traditional architecture using symmetrical devices for carrier and peaking PAs. Gallium Nitride (GaN) based high-electron-mobility (HEMT) technology has been used to design and fabricate the DPAs to validate the proposed advanced techniques for higher efficiency with good linearity performance at BO power levels.
ContributorsRuhul Hasin, Muhammad (Author) / Kitchen, Jennifer (Thesis advisor) / Aberle, James T., 1961- (Committee member) / Bakkaloglu, Bertan (Committee member) / Kiaei, Sayfe (Committee member) / Arizona State University (Publisher)
Created2018
Description
In this thesis, a digital input class D audio amplifier system which has the ability
to reject the power supply noise and nonlinearly of the output stage is presented. The main digital class D feed-forward path is using the fully-digital sigma-delta PWM open loop topology. Feedback loop is used to suppress the power supply noise and harmonic distortions. The design is using global foundry 0.18um technology.
Based on simulation, the power supply rejection at 200Hz is about -49dB with
81dB dynamic range and -70dB THD+N. The full scale output power can reach as high as 27mW and still keep minimum -68dB THD+N. The system efficiency at full scale is about 82%.
to reject the power supply noise and nonlinearly of the output stage is presented. The main digital class D feed-forward path is using the fully-digital sigma-delta PWM open loop topology. Feedback loop is used to suppress the power supply noise and harmonic distortions. The design is using global foundry 0.18um technology.
Based on simulation, the power supply rejection at 200Hz is about -49dB with
81dB dynamic range and -70dB THD+N. The full scale output power can reach as high as 27mW and still keep minimum -68dB THD+N. The system efficiency at full scale is about 82%.
ContributorsBai, Jing (Author) / Bakkaloglu, Bertan (Thesis advisor) / Arizona State University (Publisher)
Created2015
Description
This thesis describes the design process used in the creation of a two stage cellular power amplifier. A background for understanding amplifier linearity, device properties, and ACLR estimation is provided. An outline of the design goals is given with a focus on linearity with high efficiency. The full design is broken into smaller elements which are discussed in detail. The main contribution of this thesis is the description of a novel interstage matching network topology for increasing efficiency. Ultimately the full amplifier design is simulated and compared to the measured results and design goals. It was concluded that the design was successful, and used in a commercially available product.
ContributorsSpivey, Erin (Author) / Aberle, James T., 1961- (Thesis advisor) / Kitchen, Jennifer (Committee member) / Ozev, Sule (Committee member) / Arizona State University (Publisher)
Created2012
Description
Voltage Source Inverter (VSI) is an integral component that converts DC voltage to AC voltage suitable for driving the electric motor in Electric Vehicles/Hybrid Electric Vehicles (EVs/HEVs) and integration with electric grid in grid-connected photovoltaic (PV) converter. Performance of VSI is significantly impacted by the type of Pulse Width Modulation (PWM) method used.In this work, a new PWM method called 240° Clamped Space Vector PWM (240CPWM) is studied extensively. 240CPWM method has the major advantages of clamping a phase to the positive or negative rail for 240° in a fundamental period, clamping of two phases simultaneously at any given instant, and use of only active states, completely eliminating the zero states. These characteristics lead to a significant reduction in switching losses of the inverter and lower DC link capacitor current stress as compared to Conventional Space Vector PWM. A unique six pulse dynamically varying DC link voltage is required for 240CPWM instead of constant DC link voltage to maintain sinusoidal output voltage. Voltage mode control of DC-DC stage with Smith predictor is developed for shaping the dynamic DC link voltage that meets the requirements for fast control.
Experimental results from a 10 kW hardware prototype with 10 kHz switching frequency validate the superior performance of 240CPWM in EV/HEV traction inverters focusing on loss reduction and DC link capacitor currents. Full load efficiency with the proposed 240CPWM for the DC-AC stage even with conventional Silicon devices exceeds 99%.
Performance of 240CPWM is evaluated in three phase grid-connected PV converter. It is verified experimentally that 240CPWM performs well under adverse grid conditions like sag/swell and unbalance in grid voltages, and under a wide range of power factor. Undesired low frequency harmonics in inverter currents are minimized using the Harmonic Compensator that results in Total Harmonic Distortion (THD) of 3.5% with 240CPWM in compliance with grid interconnection standards. A new, combined performance index is proposed to compare the performance of different PWM schemes in terms of switching loss, THD, DC link current stress, Common Mode Voltage and leakage current. 240CPWM achieves the best value for this index among the PWM methods studied.
ContributorsQamar, Haleema (Author) / Ayyanar, Raja (Thesis advisor) / Yu, Hongbin (Committee member) / Lei, Qin (Committee member) / Weng, Yang (Committee member) / Arizona State University (Publisher)
Created2022
Description
I study split-pie bargaining problems between two agents. In chapter two, the types of both agents determine the value of outside options -- I refer to these as interdependent outside options. Since a direct mechanism stipulates outcomes as functions of agents' types, a player can update beliefs about another player’s type upon receiving a recommended outcome. I term this phenomenon as information leakage. I discuss binding arbitration, where players must stay with a recommended outcome, and non-binding arbitration, where players are not obliged to stay with an allocation. The total pie is reduced if the outcome is an outside option. With respect to efficiency, I derive a necessary and sufficient condition for first best mechanisms. These are mechanisms that assign zero probability to outside options for every report received. The condition describes balanced forces in conflict (outside options) and is the same in the cases of binding and non-binding arbitration. I also show a strong link between conflict and information: when conflict exists, information leakage occurs. Hence, non-binding arbitration may seem more restrictive than binding arbitration. To analyze why this is the case, I solve for second best mechanisms with binding arbitration and find a condition under which they can be implemented under non-binding arbitration. Thus, I show that non-binding arbitration can be as effective as binding arbitration in terms of efficiency. I also examine whether the equivalence between binding and non-binding arbitration can cease to hold, and provide analysis of why this happens. In chapter three, the bargaining problem entails no uncertainty but rather envy. Players can feel envy about the allocation of the other player. The Nash Bargaining solution is obtained in this context and some comparative statics are shown. The introduction of envy makes the more envious party a tougher negotiator.
ContributorsGonzalez Sanchez, Eric Patricio (Author) / Manelli, Alejandro (Thesis advisor) / Chade, Hector (Committee member) / Schlee, Edward (Committee member) / Arizona State University (Publisher)
Created2020
Description
About 20-50% of industrial processes energy is lost as waste heat in their operations. The thermal hydraulic engine relies on the thermodynamic properties of supercritical carbon dioxide (CO2) to efficiently perform work. Carbon dioxide possesses great properties that makes it a safe working fluid for the engine’s applications. This research aims to preliminarily investigate the actual efficiency which can be obtained through experimental data and compare that to the Carnot or theoretical maximum efficiency. The actual efficiency is investigated through three approaches. However, only the efficiency results from the second method are validated since the other approaches are based on a complete actual cycle which was not achieved for the engine. The efficiency of the thermal hydraulic engine is found to be in the range of 0.5% to 2.2% based on the second method which relies on the boundary work by the piston. The heating and cooling phases of the engine’s operation are viewed on both the T-s (temperature-entropy) and p-v (pressure-volume) diagrams. The Carnot efficiency is also found to be 13.7% from a temperature difference of 46.20C based on the measured experimental data. It is recommended that the thermodynamic cycle and efficiency investigation be repeated using an improved heat exchanger design to reduce energy losses and gains during both the heating and cooling phases. The temperature of CO2 can be measured through direct contact with the thermocouple and pressure measurements can be improved using a digital pressure transducer for the thermodynamic cycle investigation.
ContributorsManford, David (Author) / Phelan, Patrick (Thesis advisor) / Calhoun, Ronald (Thesis advisor) / Shuaib, Abdelrahman (Committee member) / Arizona State University (Publisher)
Created2020