by D.A. Huffman. / "January 10, 1954." "Reprinted from Journal of the Franklin Institute, vol. 257, no.3, March, 1954." / Includes bibliographical references. / Army Signal Corps Contract No. DA36-039 sc-100, Project 8-102B-0. Dept. of the Army Project No. 3-99-10-022.

Two different types of switching mechanism are considered in this thesis; one is featured with abrupt/sudden switching while the other one shows gradual changing behavior in its dynamics. It is shown that, through the comparison of the identification results from the proposed method and a benchmark method, the proposed robust identification method can achieve better performance when dealing with the data set mixed with outliers. To model the switched systems exhibiting gradual or smooth transition among different local models, in addition to estimating the local sub-systems parameters, a smooth validity (an exponential function) function is introduced to combine all the local models so that throughout the working range of the gradual switched system, the dynamics of the nonlinear process can be appropriately approximated. Verification results on a simulated numerical example and CSTR process confirm the effectiveness of the proposed Linear Parameter Varying (LPV) identification algorithm. / Process Control

Wireless micro-sensors can enjoy popularity in biomedical drug-delivery treatments and tire-pressure monitoring systems because they offer in-situ, real-time, non-intrusive processing capabilities. However, miniaturized platforms severely limit the energy of onboard batteries and shorten the lifespan of electronic systems. Ambient energy is an attractive alternative because the energy from light, heat, radio-frequency (RF) radiation, and motion can potentially be used to continuously replenish an exhaustible reservoir. Of these sources, solar light produces the highest power density, except when supplied from indoor lighting, under which conditions the available power decreases drastically. Harnessing thermal energy is viable, but micro-scale dimensions severely limit temperature gradients, the fundamental mechanism from which thermo piles draw power. Mobile electronic devices today radiate plenty of RF energy, but still, the available power rapidly drops with distance. Harvesting kinetic energy may not compete with solar power, but in contrast to indoor lighting, thermal, and RF sources, moderate and consistent vibration power across a vast range of applications is typical. Although operating conditions ultimately determine which kinetic energy-harvesting method is optimal, piezoelectric transducers are relatively mature and produce comparatively more power than their counterparts such as electrostatic and electromagnetic kinetic energy transducers. The presented research objective is to develop, design, simulate, fabricate, prototype, test, and evaluate CMOS ICs that harvest ambient kinetic energy in periodic and non-periodic vibrations using a small piezoelectric transducer to continually replenish an energy-storage device like a capacitor or a rechargeable battery. Although vibrations in surrounding environment produce abundant energy over time, tiny transducers can harness only limited power from the energy sources, especially when mechanical stimulation is weak. To overcome this challenge, the presented piezoelectric harvesters eliminate the need for a rectifier which necessarily imposes threshold limits and additional losses in the system. More fundamentally, the presented harvesting circuits condition the transducer to convert more electrical energy for a given mechanical input by increasing the electromechanical damping force of the piezoelectric transducer. The overall aim is to acquire more power by widening the input range and improving the efficiency of the IC as well as the transducer. The presented technique in essence augments the energy density of micro-scale electronic systems by scavenging the ambient kinetic energy and extends their operational lifetime. This dissertation reports the findings acquired throughout the investigation. The first chapter introduces the applications and challenges of micro-scale energy harvesting and also reviews the fundamental mechanisms and recent developments of various energy-converting transducers that can harness ambient energy in light, heat, RF radiation, and vibrations. Chapter 2 examines various existing piezoelectric harvesting circuits, which mostly adopt bridge rectifiers as their core. Chapter 3 then introduces a bridge-free piezoelectric harvester circuit that employs a switched-inductor power stage to eliminate the need for a bridge rectifier and its drawbacks. More importantly, the harvester strengthens the electrical damping force of the piezoelectric device and increases the output power of the harvester. The chapter also presents the details of the integrated-circuit (IC) implementation and the experimental results of the prototyped harvester to corroborate and clarify the bridge-free harvester operation. One of the major discoveries from the first harvester prototype is the fact that the harvester circuit can condition the piezoelectric transducer to strengthen its electrical damping force and increase the output power of the harvester. As such, Chapter 4 discusses various energy-investment strategies that increase the electrical damping force of the transducer. The chapter presents, evaluates, and compares several switched-inductor harvester circuits against each other. Based on the investigation in Chapter 4, an energy-investing piezoelectric harvester was designed and experimentally evaluated to confirm the effectiveness of the investing scheme. Chapter 5 explains the details of the IC design and the measurement results of the prototyped energy-investing piezoelectric harvester. Finally, Chapter 6 concludes the dissertation by revisiting the challenges of miniaturized piezoelectric energy harvesters and by summarizing the fundamental contributions of the research. With the same importance as with the achievements of the investigation, the last chapter lists the technological limits that bound the performance of the proposed harvesters and briefly presents perspectives from the other side of the research boundary for future investigations of micro-scale piezoelectric energy harvesting.

In this dissertation, two important current mode circuit design subjects have been explored. In the first part, the switched-current circuit technique has been investigated. The fundamental performance and limitations of this technique are explored. One of the major limitations, the signal distortion caused by clock feedthrough has been substantially reduced by a newly developed clock feedthrough cancellation technique. In addition, a filter synthesis technique has been developed by directly simulating the structure of digital filter. Several experimental CMOS prototypes have been designed and fabricated. The measured frequency and phase responses demonstrated the feasibility of this synthesis technique. In the second part, a new logic family called current-steering logic has been developed. The fundamental performance and characteristics of this technique have been discussed including the basic inverter and NOR gate with DC analysis, transient analysis and power-delay product. It has been shown that the current-steering logic has, a much smaller current spike than conventional CMOS logic circuits, which is especially desirable in mixed-mode applications. Several experimental prototypes have verified the functionality and performance of this new technique. / Graduation date: 1991

The relationship in a bilingual conversation between language choice and identity has been the subject of research in different disciplines such as sociolinguistics, psycholinguistics, and second language acquisition among others. The purpose of this research was to understand why and how language alternation occurs in bilingual interviews and its potential connection with identity. The data analyzed was from interviews from Proyecto Latino@, a previous research on Latin@ high school students’ experiences in schools and their academic engagement and/or disengagement. Participants’ narratives of their experiences indicated that code-switching is a result and a process of cultural adaptation. Code-switching in this research presented ways in which participants re-created their own concept of identity. Bilinguals of the Proyecto Latin@ portrayed a multiple identities construction –Spanish- English – when code-switching.

The relationship in a bilingual conversation between language choice and identity has been the subject of research in different disciplines such as sociolinguistics, psycholinguistics, and second language acquisition among others. The purpose of this research was to understand why and how language alternation occurs in bilingual interviews and its potential connection with identity. The data analyzed was from interviews from Proyecto Latino@, a previous research on Latin@ high school students’ experiences in schools and their academic engagement and/or disengagement. Participants’ narratives of their experiences indicated that code-switching is a result and a process of cultural adaptation. Code-switching in this research presented ways in which participants re-created their own concept of identity. Bilinguals of the Proyecto Latin@ portrayed a multiple identities construction –Spanish- English – when code-switching.

This dissertation study the effectiveness of antenna switching diversity for orthogonal frequency division multiplexing (OFDM) systems such as in IEEE 802.11. One of the ways to exploit the multiple antenna configurations is to use antenna switching diversity. Antenna switching diversity is used in wireless systems to combat the effect of fading, as we can combine multiple independent copies of the same signal into a total signal with high quality. In this work, we implement and compare the performance of two systems, antenna switching diversity system and single-input single-output (SISO) system. We firstly study the performance of the antenna switching diversity system as we increases the number of antennas compared to the performance of signal-to-noise ratio (SNR) or gain of the system. The performance of antenna switching diversity is studied on several difference configurations such as receive diversity where there are multiple receive antennas, and transmit diversity where the there are multiple transmit antennas. The study is performed on eight (8) antenna switching, on either the transmit or receive side. The implementation of antenna switching diversity system shows that there are definite improvement on signal-to-noise ratio (gain) value compared to single-input single-output system signal-to-noise ratio (gain).

This thesis explores option pricing and hedging in a discrete time regime-switching environment. If the regime risk cannot be hedged away, then we cannot ignore this risk and use the Black-Scholes pricing and hedging framework to generate a unique pricing and hedging measure. We develop a risk neutral pricing measure by applying an Esscher Transform to the real world asset price process, with the focus on the issue of incompleteness of the market. The Esscher transform turns out to be a convenient and effective tool for option pricing under the discrete time regime switching models. We apply the pricing measure to both single variate European options and multivariate options. To better understand the effect of the pricing method, we also compared the results with those generated from two other risk neutral methods: the Black-Scholes model, and the natural equivalent martingale method. We further investigate the difference in hedging associated with different pricing measures. This is of interest when the choice of pricing method is uncertain under regime switching models. We compare four hedging strategies: delta hedging for the three risk neutral pricing methods under study, and mean variance hedging. We also develop a more general tool of tail ordering for hedging analysis in a general incomplete market with the uncertainty of the risk neutral measures. As a result of the analysis, we propose that pricing and hedging using the Esscher transform may be an effective strategy for a market where the regime switching process brings uncertainty.

This work has the approach for how an electric motor controller should be designed. In aircraft applications it is important that the system has a high power density, and that it is reliable. The target was to find out what is possible with technology of today, and with possibilities of tomorrow. The target is to be able to compare hydraulic systems with electrical ones. The type of controllers that was studied was controllers for permanent magnetized synchronous machines (PMSM). The reason for that choice is that PMSM has a high efficiency. Different transistor technologies were evaluated. Discrete IGBT was found to be the best option. Of the evaluated transistors has IRG4PSH71U operating with a SiC freewheeling diode the best efficiency. The benefit with discrete components is that they are easy to cool, for example if they are distributed on an aluminium heatsink with forced air cooling. To minimise losses and gain controllability on the motor should the inverter be controlled with some kind of vector control, such as DTC (Direct Torque Control). / I det här arbetet studerades hur en elmotorstyrning i ett flygplan bör konstrueras. I flygapplikationer är det viktigt att systemet är lätt i förhållande till effekten, och att det är tillförlitligt. Målet var att ta reda på vad man kan uppnå med dagens teknik, och även med kommande teknik. Syftet är att kunna jämföra hydrauliska system med elektriska. Det som undersöktes var motorstyrningar till permanentmagnetiserade synkronmaskiner (PMSM), eftersom dessa motorer har en hög verkningsgrad. Olika transistortekniker utvärderades. Diskreta IGBT fanns vara det bästa valet i en sådan applikation. Av de transistorer som jämfördes har IRG4PSH71U tillsammans med en frihjulsdiod av SiC den bästa totala verkningsgraden. Det vill säga att summan av ledningsförluster och switchförluster är lägst för den kombinationen. Fördelen med diskreta transistorer är att de har en lägre termisk resistans och kan spridas på en kylfläns, vilket underlättar kylningen, t.ex. med en aluminiumkylfläns med forcerad luft kylning. För att minimera förluster och öka styrbarheten på motorn bör växelriktaren styras med någon typ av vektor kontroll exempelvis DTC (Direct Torque Control).

MPLS is a widely used technology in the service providers and enterprise networks across the globe. MPLS-enabled infrastructure has the ability to transport any type of payload (ATM, Frame Relay and Ethernet) over it, subsequently providing a multipurpose architecture. An incoming packet is classified only once as it enters into the MPLS domain and gets assigned label information; thereafter all decision processes along a specified path is based upon the attached label rather than destination IP addresses. As network applications are becoming mission critical, the requirements for fault tolerant networks are increasing, as a basic requirement for carrying sensitive traffic. Fault tolerance mechanisms as provided by an IP/MPLS network helps in providing end to end “Quality of Service” within a domain, by better handling blackouts and brownouts. This thesis work reflects how MPLS increases the capability of deployed IP infrastructure to transport traffic in-between end devices with unexpected failures in place. It also focuses on how MPLS converts a packet switched network into a circuit switched network, while retaining the characteristics of packet switched technology. A new mechanism for MPLS fault tolerance is proposed.