Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 99-108. / by Marvin Stuart Keshner. / Sc.D.

The topic of this thesis is the design of an automatic preanodizer to be used to preadjust precision tantalum resistors by anodizing their surfaces. The purpose of the preanodizer is to generate a controllable voltage ramp to be applied to a set of tantalum resistors which are immersed in a suitable electrolyte. The slope and maximum value of the voltage ramp are set to produce the current required for proper anodization of the resistors. The rate of anodization determines the rate of change of the resistor value. This thesis covers the design of an electronic device to meet a set of requirements specified by the Western Electric Company. The primary tasks the device has to perform are the generation of a linear voltage ramp of adjustable slope and maximum voltage and the supply of a given maximum current. Metering circuits are provided to measure, store and display the current and the maximum value reached by the ramp voltage.

Το θέμα της διπλωματικής μεταπτυχιακής εργασίας είναι οι συνήθεις μη γραμμικότητες και οι εφαρμογές τους. Σχεδιάζονται, εξομοιώνονται και υλοποιούνται στην πράξη απλοί και σύνθετοι μη γραμμικοί αντιστάτες τμηματικής γραμμικότητας (PieceWise-Linear – PWL). Ιδιαίτερη προσοχή δίνεται στην υλοποίηση της διόδου Chua καθώς και στο σχεδιασμό και υλοποίηση του ίδιου του χαοτικού κυκλώματος Chua. Ταυτόχρονα δίνονται συνοπτικά στοιχεία θεωρίας χάους. Επιπλέον, μελετάται και υλοποιείται υπερχαοτικός ταλαντωτής κατάλληλος για συγχρονισμό και εφαρμογή σε ασφαλείς επικοινωνίες. Αυτός ο υπερχαοτικός ταλαντωτής βασίζεται σε έναν LC ταλαντωτή και το γνωστό Deliyannis SAB συζευγμένα μέσω μιας διόδου. Σε όλα τα παραπάνω πρέπει να προστεθεί η συγκέντρωση όλης της σχετικής βιβλιογραφίας. / The subject of this diploma thesis is to study usual nonlinearities and their applications. Simple and composite nonlinear piecewise-linear resistors have been designed, simulated and implemented. A great care is shown towards implementing the Chua’s diode and designing and implementing the chaotic Chua’s circuit itself. At the same time some basics of chaos theory are given. Moreover, a hyperchaotic oscillator is studied which is suitable for synchronization and application in secure communications. This hyperchaotic oscillator is based on a LC oscillator and the well-known Deliyannis SAB coupled by means of a diode. To all above, one should add the very rich bibliography, which has now been accumulated for the benefit of all concerned in the Electronics Laboratory.

This work introduces fundamental knowledge of EMI, and presents three basic features correlated to EMI susceptibility: nonlinear distortion, asymmetric slew rate (SR) and parasitic capacitance. Different existing EMI-resisting techniques are analyzed and compared to each other in terms of EMI-Induced input offset voltage and other important specifications such as current consumption. In this work, EMI-robust analog circuits are proposed, of which the architecture is based on source-buffered differential pair in the previous publications. The EMI performance of the proposed topologies has been verified within a test IC which was fabricated in NCSU 0.5um CMOS technology. Experimental results are presented when an EMI disturbance signal of 400mV and 800mV amplitude was injected at the input terminals, and compared with a conventional and an existing topology. The tested maximal EMI-induced input offset voltage corresponds to -222mV for the new structure, which is compared to -712mV for the conventional one and -368mV for the one using existing source-buffered technique in literature. Furthermore the overall performances of the circuits such as current consumption or input referred noise are also provided with the corresponding simulation results.

CAPES / A tomografia por resistência elétrica (ERT) é uma técnica destinada a estimar a distribuição interna de condutividade de um corpo através de medições na periferia. Em aplicações médicas, o objetivo é detectar algum distúrbio de saúde em diferentes diagnósticos comumente utilizados para exames médicos. Em aplicações industriais, a ERT se destina a levantar características internas do objeto para detectar alguma anomalia em variação de alguma grandeza. Uma aplicação industrial notável é a medição de temperatura de gases, porque consegue pode monitorar processos industriais. Neste trabalho, foi proposta uma abordagem alternativa para estimar condutâncias numa rede ou grade de resistências, na qual apenas os elementos periféricos são acessíveis para medições. Diferente das abordagens existentes, onde o meio é considerado contínuo, propõe-se discretizar o meio em elementos de resistência. O princípio de medição baseia-se na injeção de corrente elétrica conhecida em determinados pontos e posterior estimava de todas as condutâncias da rede apenas através medições de tensões periféricas. O sensor para prova de conceito é composto por resistências soldadas entre si. Com o intuito de modelar o comportamento do sensor, foram feitas simulações elétricas. Para validar o desenvolvimento, foi construída uma fonte de corrente e um software onde é possível salvar os dados adquiridos. A montagem completa também inclui uma placa de aquisição de sinais e um algoritmo de reconstrução. Uma vez que a relação entre os valores de condutância e de medição de tensão é não linear, a solução para o problema inverso inclui linearização iterativa, sendo necessário à atualização da matriz de sensibilidade a cada iteração. Possíveis aplicações da técnica desenvolvida incluem qualquer sensoriamento distribuído composto por transdutores que tenha a sua resistência elétrica variada em função de outra grandeza (temperatura, pressão, etc.). As principais vantagens em relação a sensores de temperatura é a capacidade de se desenvolver sensores robustos e a simplicidade de medição. / Electrical Resistance Tomography is a technique aimed at estimating the inner conductivity distribution of a phantom from boundary measurements. In medical applications, the goal is to detect any medical condition. In industrial applications, the objective is to detect any anomalous condition. A notable application is the determination of gas temperature distribution. This work proposes an alternative approach to determine all conductances in a resistor network or grid where only boundary elements are accessible for measurements. Differently from most existing approaches, where the medium is considered continuum, this work proposes to discretize the medium in resistive elements. The basic principle is to inject a known electrical current in certain points and estimate all conductances in the network from only boundary voltage measurements. The proof-of-concept sensor is composed by inter-welded resistors. For modeling purposes, simulations were performed in Proteus. To validate the development, a current source and a LabView software were developed. The complete setup includes a reconstruction algorithm developed in Matlab. Since the relationship between conductance values and voltage measurements is nonlinear, the inverse problem requires an iterative linearization step, where a sensitivity matrix is calculated at each iteration. The main applications of the developed technique include any distributed sensor based on resistive transducers such as temperature, pressure, etc. The advantages of the proposed technique are the ability of design robust sensors as well as the simplicity of measurements.

No description available.

This thesis contains both Parts A and B. / <p> Xenon induced flux oscillations are possible in large thermal reactors operating at high powers because of the inter-play between the xenon concentration, reactivity, and thermal flux, and the fact that xenon is produced mainly by radioactive decay of I-135, which has a half-life of 6.7 hours. Due to these nuclear characteristics along with size and operating conditions of the Pickering and Bruce cores, these oscillations in flux are inherently unstable with respect to xenon. That is, a local perturbation in reactivity will result in a divergent and cyclic time and space variation in the thermal flux distribution in the core.</p> <p> One group diffusion theory and a simple perturbation analysis yield for a bare thermal reactor, a threshold in the average flux level ∅ which satisfies (1) M^2λij^2 / αxe - αT/αxe ∅ = 1/1+λxe/σxe∅ - μxe / 1+(λxe + λ1)/σxe∅ for oscillations in ijth mode of the flux distribution (see Figure 1) M^2 is the migration area in cm^2, αxe is the reactivity load of Xe-135 at high flux levels; αT is the fuel temperature coefficient expressed in terms of reactivity change per unit flux. The function f(∅) depends only upon the decay constants λxe of Xe-135 and λ1 of I-135; μxe is the fraction of Xe-135 produced directly from the fission of the fuel rather than through iodine decay (which fraction is denoted by μ1). The dimensionless parameter λij^2 depends only upon the shape of the flux distribution and is equal to the difference between the bulking of the ijth mode and the fundamental model.</p> <p> The Bruce and Pickering reactors are used as models in this study to determine the threshold power level at which xenon instability is possible and in which mode this instability occurs.</p> <p> Bruce is found to be unstable in the fundamental and first azimuthal mode for fresh and equilibrium fuel conditions, and stable for the radial, axial and higher azimuthal modes.</p> <p> Pickering, on the other hand, is unstable for the equilibrium fuel condition in the fundamental and first azimuthal modes only and is stable in every mode except the fundamental in the fresh fuel condition.</p> (Part A of Thesis)-------------------------------------------------------------------------------------------------------(Part B of Thesis) </p> Trimming of thin-film resistor components by an electrical arc is investigated in this report as an inexpensive and simple alternative to the laser trim and mechanical scribe methods. A multitude of tests were effected on Garrett Manufacturing Limited production circuits containing nichrome thin film resistors. These tests included Temperature Coefficient of Resistivity, resistance stability, substrate damage, noise performance, dynamic trim with active devices operating, width of cut as compared to mechanical scribe and laser trim techniques, and optimum parameters for trimming. In all cases the trimmed circuits were within the design specifications of the resistor properties under test. It is the conclusion of the author that the obvious attributes of the arc-trim method as well as its outstanding performance in the above tests, warrants its serious consideration as a viable alternative to the laser trim and mechanical scribe methods of altering resistance levels.</p> / Thesis / Master of Engineering (MEngr)

Since the development of thick film hybrid microelectronic processing, there has been a need for methods to adjust for tighter tolerances for electrical components through a trimming process. Components/elements, as produced, show a tolerance of the order of ±10% due to the variability of the screen printing process associated with film curing conditions. The methods that have arisen from this need encompass a variety of technologies and techniques. The usefulness of each method is based on its operation, flexibility, repeatability, and post-trim effects on the resistor's reliability. The work in this thesis concerns the laser trimming of resistor components to a tight tolerance. It is the objective of this thesis to address the performance of an Nd:YAG laser operation and interface with a computer. The first task involves a computer hardware system to be interfaced to the laser control system, this task includes both design and implementation. The second task consists of a software operating environment to be flowcharted, written, and tested. The third task involves the computer interface driving the laser in the process of trimming resistor components using different types of cuts. The trimmed resistor performance is evaluated as part of the study. / Master of Science

This thesis reports the development of Vanadium Tungsten Oxide (VWO) film as an active detector material for uncooled infrared detectors by using the reactive DC magnetron co-sputtering method. VWO is a doped form of the Vanadium Oxide (VOx) which is known as a prominent material for uncooled infrared detectors with its high TCR, low resistivity, and low noise properties. VOx is a widely preferred material for commercialized uncooled infrared detectors along with its drawbacks. Fabrication is fairly difficult due to its unstable material properties and the need for low process temperatures for a monolithic, CMOS compatible surface micromachining process. Hence, a new material with high performance and easier fabrication is needed. This thesis is the first study at METU on the development of high-performance VWO as an active detector material for uncooled infrared detectors. Deposition studies of VWO primarily started by measuring the effects of deposition parameters upon the magnetron sputtering system. Because the high effectiveness of the tungsten doping has been obtained for the doping level below 10% according to literary information, maximum vanadium (V) deposition rate together with minimum tungsten (W) deposition rate has been initially aimed. TCR of the VWO films has been measured between -2.48 %/K and -3.31 %/K, and the variation of noise corner frequency from 0.6 kHz to 8 kHz has been observed. In addition to these results of VWO, a favorable VOx recipe which has the highest performance done at METU in terms of resistance, TCR, noise and uniformity has also attained during the studies. Structural characterization of VWO is achieved using XPS, XRD, and AFM characterization techniques. Other than the sputtering parameters, post-annealing process and oxygen plasma exposure was examined as well. A general observation of the post-annealing is that it decreases not merely the TCR but also the noise of the deposited film. A short-period oxygen plasma exposure has a constructive effect on the noise behavior. Fabricated vanadium tungsten oxide with sandwich type resistor structure shows very close but better bolometric properties when compared with the yttrium barium copper oxide (YBCO), which is another material being studied in scope of other theses at METU. XPS, XRD and AFM characterization methods have been used for the structural characterization of vanadium-tungsten-oxide.

Este trabalho tem por objetivo o estudo e o desenvolvimento de uma solução de engenharia para o mapeamento e caracterização da oclusão dentária, não somente no âmbito de sua distribuição ao longo da arcada, mas também através da mensuração da intensidade de pressão nos pontos de contato oclusal interarco. Neste sentido, empregaram-se esforços no aprofundamento do conhecimento neste campo da Odontologia, assim como, na elaboração de um sistema experimental que, utilizando sensores de pressão/força resistivos (FSR) específicos para uso odontológico, viabilizou a análise do estado da oclusão, atuando como agente facilitador no diagnóstico de desequilíbrios oclusais. Inicialmente, são apresentados e esclarecidos os principais conceitos da esfera odontológica, os quais são tomados como base para todos os projetos deste trabalho, além da abordagem referente às formas de contato entre os dentes, aos diferentes tipos de oclusão e seus problemas. Em relação ao desenvolvimento do sistema, foram projetadas duas placas de circuito impresso para interface com os sensores e elaborados o firmware de acesso ao hardware, assim como o software de gerenciamento global do sistema. Todos os blocos do circuito de condicionamento foram avaliados e as suas funcionalidades validadas. Do mesmo modo, a caracterização da resposta dos sensores e a sua homogeneidade ao longo da extensão sensível foram analisadas, demonstrando que a resistência elétrica varia de forma análoga em todas as áreas do sensor. Através de ensaios realizados com sujeito envolvido no projeto, estabeleceu-se um comparativo entre a utilização do papel carbono e o sistema desenvolvido, mostrando as vantagens na utilização do segundo, principalmente atreladas à capacidade de avaliação da intensidade dos contatos oclusais. Por fim, ainda se valendo do uso paralelo do papel carbono, foram efetuados ensaios de análise da oclusão em sujeito envolvido no projeto utilizando placa miorrelaxante, possibilitando a utilização da capacidade do sistema desenvolvido para executar ajustes precisos na placa, com a finalidade de manter o balanço de pressões oclusais entre ambos os lados da arcada. / This essay has as objective the study and development of an engineer solution for the dental occlusion mapping and characterization, not only related to the interarch occlusal contact distribution, but also through the pressure magnitude measuring in each. In this sense, was employed effort in the Odontological knowledge increasing and also in the system elaboration allowing the occlusion state evaluation and acting as an easier agent in the occlusion disturbs diagnosing using a specific pressure/force sensing resistor (FSR) for dental use. Initially the main concepts of the Odontological sphere are presented, clarified and took as a base for all the projects in this essay. Besides this, different teeth contacts shapes are shown, as well as the occlusion’s types and its problems. In the system development, two printed circuit boards were designed for sensor interfacing. The hardware access through the firmware was elaborated, even as the global system managing software. All the conditioning circuit blocks and functionalities were evaluated and validated. In the same way, the sensor’s output and its homogeneity through all the sensible extension were evaluated, showing that the sensor’s electric resistance changes in the same form in all the sensor’s areas. In addition, it was showed the advantages of the developed system over the articulation paper through trials with a subject that is part of the project, showing the capacity of the system in the occlusion contacts magnitude evaluation. Ultimately, also in an articulation paper versus the developed system comparison, it was made occlusion analysis trials with subject using a night guard for teeth grinding (bruxism), showing the system capacity of precisely adjust the night guards for pressure balance between the both arch sides.