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The sigma-delta modulator is a popular signal amplitude quantization error (or noise) shaper used in oversampling analogue-to-digital and digital-to-analogue converter systems. The shaping of the noise frequency spectrum is performed by feeding back the quantization errors through a time delay element filter and feedback loop in the circuit, and by the addition of a possible stochastic dither signal at the quantizer. The aim in audio systems is to limit audible noise and distortions in the reconverted analogue signal. The formulation of the sigma-delta modulator as a discrete dynamical system provides a useful framework for the mathematical analysis of such a complex nonlinear system, as well as a unifying basis from which to consider other systems, from pseudorandom number generators to stochastic resonance processes, that yield equivalent formulations. The study of chaos and other complementary aspects of internal dynamical behaviour in previous research has left important issues unresolved. Advancement of this study is naturally facilitated by the dynamical systems approach. In this thesis, the general order feedback/feedforward sigma-delta modulator with multi-bit quantizer (no overload) and general input, is modelled and studied mathematically as a dynamical system. This study employs pertinent topological methods and relationships, which follow centrally from the symmetry of the circle map interpretation of the error state space dynamcis. The main approach taken is to reduce the nonlinear system into local or special case linear systems. Systems of sufficient structure are shown to often possess structured random, or random-like behaviour. An adaptation of Devaney's definition of chaos is applied to the model, and an extensive investigation of the conditions under which the associated chaos conditions hold or do not hold is carried out. This seeks, in part, to address the unresolved research issues. Chaos is shown to hold if all zeros of the noise transfer function lie outside the unit circle of radius two, provided the input is either periodic or persistently random (mod delta). When the filter satisfies a certain continuity condition, the conditions for chaos are extended, and more clear cut classifications emerge. Other specific chaos classifications are established. A study of the statistical properties of the error in dithered quantizers and sigma-delta modulators is pursued using the same state space model. A general treatment of the steady state error probability distribution is introduced, and results for predicting uniform steady state errors under various conditions are found. The uniformity results are applied to RPDF dithered systems to give conditions for a steady state error variance of delta squared over six. Numerical simulations support predictions of the analysis for the first-order case with constant input. An analysis of conditions on the model to obtain bounded internal stability or instability is conducted. The overall investigation of this thesis provides a theoretical approach upon which to orient future work, and initial steps of inquiry that can be advanced more extensively in the future.

Although most organisations want to improve quality and reduce costs, the deployment and implementation of continuous improvement methodologies is commonly viewed as a daunting journey. Many organisations fail to properly structure and/or support continuous improvement initiatives, which ultimately doom them to failure. South African Banks are not adopting Lean and/or Six-sigma to the point where it is going to make any sort of significant difference to the bottom line over a significantly meaningful period of time. So where are they going wrong? Often it comes down to key issues that are not addressed effectively as part of the deployment. The research objectives are: • The primary objective is to establish what the mission critical success factors for Lean and/or Six-sigma implementation in South African Banking are. • The secondary objective is to define a list of the sources of benefits for Lean and/or Six-sigma implementations in South African Banking. The research questions/problems to be addressed are: • What are the mission critical success factors for Lean and/or Six-sigma implementations in South African Banking? • How do South African Banks prioritise these critical success factors? • How do South African Banks that are already on the Lean and/or Six-sigma journey perform against these critical success factors? • What are the gaps between the importance’s of the critical success factors versus the banks actual performance against these, and how is this gap impacting on the benefits that the banks are experiencing? • What sources of benefits are South African Banks experiencing? • Can generic guidelines be provided to the South African Banks for successful Lean and/or Six-sigma implementation?

Studien går ut på att se om metoden DMAIC (Define, measure, analyze, improve och control) är ett bra sätt att minska kvalitetsbristkostnader hos ett kontrakts tillverkande företag. Aktuell forskning på Six Sigma, som är en metodik för förbättringsprojekt, och DMAIC har legat som bas för den teori som applicerats.  Produktfamiljen som har att undersökts heter STB och består av två olika processer, montering av motor och montering av strömmodul. För att avgränsa studien ytterligare kommer endast montering av motor att arbetas med och analyseras för att identifiera vilken är fyra stycken olika komponenter där modellen DMAIC kommer att appliceras som förbättringsmetod, för att finna vilken av dem som bidrar till höga kvalitetsbristkostnader.   Under arbetets gång har det framkommit att verksamheter inom samma bransch till sin fördel, bör logga testresultat för att underlätta framtida förbättringsarbeten. Det grundar sig i att många förbättringsarbeten med DMAIC som fokus, använder sig av statistiska metoder. Med det sagt har det visat sig att det går att utföra ett DMAIC projekt utan den typen av statistik, men att det är en fördel ifall den finns tillhanda. / The study is about whether the DMAIC (Define, measure, analyze, improve and control) method is a good way to reduce cost of poor quality in a contract manufacturing company. Current research of Six Sigma, which is a method applied for improvement projects, and DMAIC has been the basis for the theory applied.  The product family that has been examined is called STB and contains two different processes, mounting of engine and mounting of the power module. For further delineation the study will only focus on the mounting of the engine to analyse and identify which one of the four different components where the DMAIC method will be applied as an improvement method, could be the source of the high cost of poor quality.   During this study it has been found that activities in the same industry, to their advantage, should log test results to facilitate future improvements. This is based on the fact that many improvements, with DMAIC as a tool, focuses on using statistical methods. With that, it has been found that it is possible to perform a DMAIC project without statistics but for future state there will be an advantage for the company if it would be available.

O objetivo deste trabalho compreende o estudo dos mecanismos e da cinética formação de fases intermetálicas no aço UNS S31803 envelhecido a entre 700 e 950C. Para este estudo foram conduzidos envelhecimentos isotérmicos por até 360 horas entre 700 e 950C. A identificação das fases foi realizada utilizando-se microscopia óptica, microscopia eletrônica de varredura (MEV), análises por Espectroscopia por Energia Dispersiva (EDS), e difração de raios X. Já sua quantificação foi realizada por análise quantitativa a partir de imagens obtidas pela técnica de elétrons retroespalhados e medidas magnéticas. No início do envelhecimento entre 700 e 950 C, anteriormente à formação intensa de sigma, foi observado o reequilíbrio das frações de ferrita e austenita, mostrando que a formação de sigma ocorre quando as frações de ferrita e austenita atingem respectivamente 41,451,7% de ferrita e 56,961,7% de austenita. A análise das imagens obtidas pela técnica de elétrons retroespalhados permite a distinção entre as fases chi e sigma, e o estudo mais preciso dos mecanismos de formação de fase sigma. Evidências mostram que a nucleação e crescimento de sigma para as temperaturas de 700 e 750 C ocorre por precipitação descontínua a partir da ferrita, formando sigma e ferrita secundária, empobrecida em cromo e molibdênio em relação à matriz. Já para as temperaturas de envelhecimento entre 800 e 950 C a nucleação e crescimento de sigma ocorrem por decomposição eutetóide da ferrita gerando sigma e austenita secundária. Após a saturação dos sítios de nucleação heterogênea de sigma, provavelmente o crescimento de sigma ocorre a partir da austenita, gerando fase sigma e austenita empobrecida, à exceção da temperatura de 950 C onde o crescimento a partir da austenita não é observado devido à alta fração de ferrita disponível ao final do envelhecimento. Em todas as temperaturas de envelhecimento estudadas não existe evidência de que o sistema esteja em equilíbrio até 360 h de envelhecimento, e o consumo de chi nos estágios finais de envelhecimento indica que esta fase não é de equilíbrio. O estudo da cinética de formação de sigma a partir do modelo de J-M-A-K mostra a mudança no mecanismo principal de formação de sigma entre 700 e 900 C com o aumento do tempo de envelhecimento. Para a temperatura de 950C o comportamento distinto, já que provavelmente, nesta temperatura a taxa de nucleação de sigma é muito baixa e o mecanismo preponderante seja o crescimento dos núcleos de sigma formados. Foi observado ainda que o aumento da temperatura de envelhecimento reduz o tempo para a transformação do mecanismo de nucleação para crescimento das partículas de sigma formadas provavelmente devido ao aumento das taxas de difusão dos elementos formadores de sigma a altas temperaturas. O estudo cinético permitiu ainda estimar que para temperaturas entre 700 e 850C a energia de ativação necessária para a nucleação de sigma é maior em relação à energia necessária para o crescimento de sigma, mostrando que uma vez nucleada a fase sigma, seu crescimento se daria com mais facilidade devido às altas taxas de difusão propiciadas pelas elevadas temperaturas de envelhecimento. Além disso, os valores estimados neste trabalho para a energia de ativação para a formação de sigma são bastante próximos aos valores relacionados à difusão de molibdênio na ferrita. Esta evidência mostra que possivelmente a difusão de molibdênio, controlaria a nucleação e crescimento de sigma. O diagrama Tempo-Temperatura-Precipitação elaborado prevê o início da formação de sigma e mostra que a máxima cinética de formação de sigma para o aço UNS S31803 ocorre a 850 C.

" Electroencephalogram (EEG), Electrocardiogram (ECG), and Electromyogram (EMG) bio-potential signals are commonly recorded in clinical practice. Typically, patients are connected to a bulky and mains-powered instrument, which reduces their mobility and creates discomfort. This limits the acquisition time, prevents the continuous monitoring of patients, and can affect the diagnosis of illness. Therefore, there is a great demand for low-power, small-size, and ambulatory bio-potential signal acquisition systems. Recent work on instrumentation amplifier design for bio-potential signals can be broadly classified as using one or both of two popular techniques: In the first, an AC-coupled signal path with a MOS-Bipolar pseudo resistor is used to obtain a low-frequency cutoff that passes the signal of interest while rejecting large dc offsets. In the second, a chopper stabilization technique is designed to reduce 1/f noise at low frequencies. However, both of these existing techniques lack control of low-frequency cutoff. This thesis presents the design of a mixed- signal integrated circuit (IC) prototype to provide complete, programmable analog signal conditioning and analog-to-digital conversion of an electrophysiologic signal. A front-end amplifier is designed with low input referred noise of 1 uVrms, and common mode rejection ratio 102 dB. A novel second order sigma-delta analog- to-digital converter (ADC) with a feedback integrator from the sigma-delta output is presented to program the low-frequency cutoff, and to enable wide input common mode range of ¡Ãƒâ€œ0.3 V. The overall system is implemented in Jazz Semiconductor 0.18 um CMOS technology with power consumption 5.8 mW from ¡Ãƒâ€œ0.9V power supplies. "

Bacteria can quickly adapt to changing environmental conditions by activating alternative sigma factors. It has been shown previously that single cell approaches can reveal hidden dynamics in sigma factor activation. Here, we investigate the single cell response dynamics of the B. subtilis extracytoplasmic function sigma factors, which are an important part of the cell envelope stress response, under their specific stresses. To do this we use transcriptional reporters of sigma factors, quantitative single cell snapshots, time-lapse microscopy, and microfluidics. By developing an improved microfluidics setup for single cell time-lapse microscopy, as well as improved single cell analysis code, we are able to observe new sigma factor dynamics. First, we observe heterogeneous entry into a higher $\sigma^{V}$ activity state in response to lysozyme, which displays a memory, as the heterogeneity is lost on removal and reapplication of the stress. Next, we observe a pulse amplitude and duration modulated sigma factor response of $\sigma^{M}$ to bacitracin. Finally, for $\sigma^{M}$ under ethanol and acidic stress, and for $\sigma^{Y}$ under ethanol stress, we observe a noisy increase in activity to a new steady state level, where the degree of variability between cells depends on the stress condition. This thesis also discusses efforts on building a single cell microfluidic device based on the ”mother machine” design, for the rod-shaped cyanobacterium, S. elongatus, which forces the cells to grow in a straight line. Growing this organism in a traditional mother machine device has, so far, proved challenging. To adapt the mother machine for cyanobacteria we modify the channel geometry using electron beam lithography, and improve the loading protocol. The research presented here reveals the range of regulatory dynamics possible for ECF sigma factors in B. subtilis, and provides improved microfluidics and analysis code that will enable easier quantification of bacterial gene circuits at the single cell level in the future.

Made available in DSpace on 2014-06-12T17:40:00Z (GMT). No. of bitstreams: 2 arquivo597_1.pdf: 3436623 bytes, checksum: 8bbb71dd0d1a5827437a026f07b7fa98 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2010 / No mundo globalizado e de intensa concorrência que vivemos hoje, fica evidente a necessidade de buscarmos forma de melhoria no desempenho competitivo das organizações, seja pela melhoria de qualidade nos processos, produtos e serviços, seja pela diminuição dos desperdícios em nossas operações, neste sentido a metodologia Lean Six Sigma tem sido preconizada como forma de atingir a excelência necessária a sobrevivência das organizações. A presente dissertação propõem um modelo de implementação da metodologia LSS nas organizações, utilizando seus elementos mais visíveis , apresentados como ferramentas do sistema e os organiza levando-se em conta os aspectos sistêmicos e subjetivos da mesma, representados pela filosofia, cultura, conceitos e questões psico-sociais necessárias para que o LSS cumpra seu papel no desenvolvimento das diferentes áreas da organização. O modelo de implementação do LSS utiliza ainda, alguns indicadores de desempenho que visam possibilitar o melhor acompanhamento do processo de implementação, da performances das ferramentas utilizadas e do próprio resultado obtido por esta metodologia para organizações, além de se preocupar em aferir o alinhamento do LSS com a própria estratégia de negócio da organização

Estágio realizado na Bosch Termotecnologia, S. A. e orientado pelo Eng.º João Pereira / Tese de mestrado integrado. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 2009