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1
NAKAGAWA, Seiichi, Souta HAMAGUCHI, and Norihide KITAOKA. "Noisy Speech Recognition Based on Integration/Selection of Multiple Noise Suppression Methods Using Noise GMMs." Institute of Electronics, Information and Communication Engineers, 2008. http://hdl.handle.net/2237/14965.
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Toro, Clemente. "Improved 1/f noise measurements for microwave transistors." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000371.
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Toro, Clemente Jr. "Improved 1/f Noise Measurements for Microwave Transistors." Scholar Commons, 2004. https://scholarcommons.usf.edu/etd/1271.
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Minimizing electrical noise is an increasingly important topic. New systems and modulation techniques require a lower noise threshold. Therefore, the design of RF and microwave systems using low noise devices is a consideration that the circuit design engineer must take into account. Properly measuring noise for a given device is also vital for proper characterization and modeling of device noise. In the case of an oscillator, a vital part of a wireless receiver, the phase noise that it produces affects the overall noise of the system. Factors such as biasing, selectivity of the input and output networks, and selectivity of the active device (e.g. a transistor) affect the phase noise performance of the oscillator. Thus, properly selecting a device that produces low noise is vital to low noise design. In an oscillator, 1/f noise that is present in transistors at low frequencies is upconverted and added to the phase noise around the carrier signal. Hence, proper characterization of 1/f noise and its effects on phase noise is an important topic of research.
This thesis focuses on the design of a microwave transistor 1/f noise (flicker noise) measurement system. Ultra-low noise operational amplifier circuits are constructed and used as part of a system designed to measure 1/f noise over a broad frequency range. The system directly measures the 1/f noise current sources generated by transistors with the use of a transimpedance (current) amplifier. Voltage amplifiers are used to provide the additional gain. The system was designed to provide a wide frequency response in order to determine corner frequencies for various devices. Problems such as biasing filter networks, and load resistances are examined as they have an effect on the measured data; and, solutions to these problems are provided. Proper representation of measured 1/f noise data is also presented. Measured and modeled data are compared in order to validate the accuracy of the measurements. As a result, 1/f noise modeling parameters extracted from the measured 1/f noise data are used to provide improved prediction of oscillator phase noise.
4
Sanders, Barry Cyril. "Phase noise in quantum physics." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/11624.
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The nature of phase noise in quantum optics is analyzed. In an experiment involving the measurement of the electromagnetic field the two quantities of interest are the energy and phase of the field. However, measurements of the quantities produce quantum fluctuations. The quantum fluctuations are regarded as noise in the treatment presented here. The quantum system is represented by a probability distribution, the Wigner function, and the quantum fluctuations are treated as stochastic noise associated with the quantity being measured. The difficulties of associating a quantum operator with the phase of the system are reviewed and the related energy-phase uncertainty relation is discussed. The alternate interpretation of the phase noise of a quantum system as being the classical phase noise of the Wigner function is presented. In particular the energy and phase noise of the vacuum state, the coherent state, the squeezed state and the squeezed vacuum are discussed in this way. The squeezed states of light are minimum uncertainty states with respect to the quadrature operators and exhibit noise of one quadrature below the noise level associated with the vacuum. The reduced noise level in one quadrature of the field underlies the importance of squeezed states in many practical applications where there is a need to reduce the quantum noise of one quadrature of coherent light. The periodic phase operator eliminates the difficulties associated with the multivalued nature of phase. The analysis of the vacuum and intense coherent state of Carruthers and Nieto by employing periodic phase operators is reviewed, particularly with respect to the energy-phase uncertainty relations and we generalize the approach to develop a phase operator analysis of the squeezed state in the intense field and vacuum limits. We demonstrate here for the first time that the phase operator is simply related to the phase of the squeezed state in the intense field limit and that the squeezed state is approximately an energy-phase minimum uncertainty state in the low-squeezing limit. Also we enlarge on previous work to demonstrate that the phase operator corresponds simply and unambiguously to the phase of the squeeze parameter for the strongly squeezed vacuum and the intensely squeezed vacuum is an energy-phase minimum uncertainty state for some values of phase. The occurrence of squeezing for the case of two coupled quantum oscillators is presented. The system consisting of one mode of the electromagnetic field coupled to a spinless nonrelativistic electron subjected to an harmonic potential is represented by two coupled harmonic oscillators. The dynamics are compared for the case that the rotating wave approximation is employed and for the case that the counter-rotating terms are included. These calculations have not been performed before. The parametric amplifier Hamiltonian with a nonresonant coupling is also studied in order to provide insight into the effects of the counter-rotating terms. Squeezing of the field produced by the electron is a consequence of the inclusion of the counter-rotating terms. The case of a spinless nonrelativistic electron subject to an harmonic potential and coupled to a continuum of electromagnetic field modes is also considered. The case of two coupled oscillators discussed above is generalized by replacing the oscillator which represents the single-mode field by a bath of oscillators. The effects of including counter-rotating terms and of ignoring the counter - rotating terms in the Hamiltonian are compared. The interaction is assumed to produce a frequency shift and an exponential damping term for the oscillating electron. The frequency shift is assumed to be small in either case and so the Wigner-Weisskopff approximation is employed to solve the equations of motion. We demonstrate the new results that dissipation-induced phase-dependent noise is a consequence of including the counter-rotating terms and that the noise is phase-independent for the case that the counterrotating terms are excluded. The relation between these results and recent work on quantum tunnelling in superconducting quantum interference devices is discussed. We conclude by suggesting further research related to the work in this thesis.
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Gesley, Mark Alan. "Spectral analysis of field emission flicker (1/f) noise." Full text open access at:, 1985. http://content.ohsu.edu/u?/etd,85.
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Haigh, Mary K. "1/f noise in mercury cadmium telluride semiconductor diodes." Thesis, Heriot-Watt University, 2005. http://hdl.handle.net/10399/200.
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Jong, Yeung-dong. "Fiber-optic interferometer for high 1/f noise environments /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Gross, Blaine Jeffrey. "1/f noise in MOSFETs with ultrathin gate dielectrics." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13192.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1992.Includes bibliographical references (p. 176-184).
by Blaine Jeffrey Gross.
Ph.D.
9
Rodda, Lasya. "Baseband Noise Suppression in Ofdm Using Kalman Filter." Thesis, University of North Texas, 2012. https://digital.library.unt.edu/ark:/67531/metadc115147/.
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As the technology is advances the reduced size of hardware gives rise to an additive 1/f baseband noise. This additive 1/f noise is a system noise generated due to miniaturization of hardware and affects the lower frequencies. Though 1/f noise does not show much effect in wide band channels because of its nature to affect only certain frequencies, 1/f noise becomes a prominent in OFDM communication systems where narrow band channels are used. in this thesis, I study the effects of 1/f noise on the OFDM systems and implement algorithms for estimation and suppression of the noise using Kalman filter. Suppression of the noise is achieved by subtracting the estimated noise from the received noise. I show that the performance of the system is considerably improved by applying the 1/f noise suppression.
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Aitha, Venkat Ramana, and Mohammad Kawsar Imam. "Low Noise Amplifier for radio telescope at 1 : 42 GHz." Thesis, Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-997.
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This is a part of the project “Radio telescope system” working at 1.42 GHz, which includes designing of patch antenna and LNA. The main objective of this thesis is to design a two stage low noise amplifier for a radio telescope system, working at the frequency 1.42 GHz. Finally our aim is to design a two stage LNA, match, connect and test together with patch antenna to reduce
the system complexity and signal loss.
The requirements to design a two stage low noise amplifier (LNA) were well studied, topics including RF basic theory, layout and fabrication of RF circuits. A number of tools are available to design and simulate low noise amplifiers but our simulation work was done using advanced design system (ADS 2004 A). The design process includes selection of a proper device, stability check of the device, biasing, designing of matching networks and layout of total design and fabrication. A lot of time has been
spent on designing of impedance matching network, fabrication and testing of the design circuits and finally a two stage low noise amplifier (LNA) was designed. After the fabrication work, the circuits were tested by the spectrum analyzer in between 9 KHz to 25 GHz frequency range. Finally the resulting noise figure 0.299 dB and gain 24.25 dB are obtained from the simulation.
While measuring the values from the fabricated circuit board, we found that bias point is not stable due to self oscillations in the amplifier stages at lower frequencies like 149 MHz for first stage and 355 MHz for second stage.
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Tobias, David Andrew. "1/f noise and Luttinger liquid phenomena in carbon nanotubes." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/7334.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Siabi-Shahrivar, Nasser. "A study of 1/f noise in polysilicon emitter transistors." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314728.
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Timpe, Jason T. (Jason Thomas) 1977. "Measurement and analysis of 1/f noise in uncooled microbolometers." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86827.
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Kuhler, Kent A. (Kent Alan). "Design of a high speed 1/f noise test station." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43300.
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Bathaei, F. Z. "Electrical noise measurements in amorphous silicon films." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/37937.
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Ge, Ming. "Noise covariance identification for filtering and prediction." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/31434.
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In this thesis, we introduce two different methods for determining noise covariance matrices in order to improve the stability and accuracy in state estimation and output prediction of discrete-time linear time varying (LTV) and nonlinear state space systems. The first method is based on the auto-covariance least squares (ALS) method, where the noise covariance matrices can be estimated by establishing a linear relationship between noise covariances and correlations of innovation sequence, hence solving a linear least squares problem. For LTV systems, we propose a new ALS algorithm that does not involve any approximations in the formulation. Our new ALS algorithm has fewer parameters to determine and can provide more accurate noise covariance estimation even when the historical output measurement window is not sufficiently long, comparing to an existing method. In addition to the noise covariance estimates, our ALS algorithm can also provide the estimate of the initial state error covariance, which is required by most state estimation methods. For higher-order systems, we also provide a much faster and less memory demanding formulation by splitting large Kronecker products with sums of smaller Kronecker or Schur products. For nonlinear systems, we have to approximate nonlinear parts as time-varying matrices by linearizing the nonlinear function around current state estimates. In addition to the extended Kalman Filter (EKF), our ALS algorithm also uses moving horizon estimation (MHE) to estimate the system state. MHE guarantees stability, is able to add state constraints and provides more accurate state estimates and local linearizations around the current state than the EKF. The second method is based on expectation maximization (EM), where the noise covariance matrices are determined by recursively maximizing the likelihood of covariance matrices, given output measurements. In our method, the noise covariance matrices are estimated using a semi-definite programming (SDP) solver, so that the results are more accurate and guaranteed to be positive definite. We propose a new EM algorithm that, combined with MHE and full information estimation (FIE) rather than a Kalman-based filter/smoother, allows the addition of state constraints, provides stable and more accurate estimates, so that the performance of noise covariance estimation can be significantly improved. Finally, we apply our noise covariance estimation methods to ocean wave prediction for the control of a wave energy converter (WEC), in order to approach optimal efficiency of wave energy extraction. We use a state space model representation for an autoregressive (AR) process, combined with noise covariance estimation, to simulate wave height forecasting based on data recorded at Galway Bay, Ireland. The simulation returns good wave predictions. Compared to existing wave prediction methods, our model has fewer parameters to tune and is able to provide more stable and accurate wave predictions by using a Kalman-based filter combined with the ALS or EM method.
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Liu, Chengxin. "Jitter in oscillators with 1/f noise sources and application to true RNG for cryptography." Link to electronic dissertation, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-011006-221104/.
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Matharoo, Rishi. "1/f Additive Phase Noise Analysis for One-Port Injection Locked Oscillators." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1430772754.
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Zhang, Hengsong. "Excess Noise in the Superconducting Transition of Tin Films." Scholarly Repository, 2007. http://scholarlyrepository.miami.edu/oa_dissertations/1.
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The I-V characteristics of Tin films in the superconducting transition have been measured when ac current was applied. The experimental results suggest that the electrical response in ac is not satisfied with the I-V equation in dc. A new equation was suggested to describe the vortex motion and the vortex pair separation in the two dimensional superconducting transition with ac current, which is satisfied with our experimental results. The excess noises of Tin films in the superconducting transition have been found to depend strongly on the temperature and ac current. An empirical expression of voltage noise density in term of resistance has been used to fit the data. The peak of voltage noise density follows closely but always shifted down from dR/dT. Comparison with the dc noise measurement shows the voltage noise density with ac current is much larger than with dc current. The excess noises with ac appear earlier than the noises with dc. The difference of excess noises between ac and dc can be explained by the fluctuation of vortex pair separation process which dominates the noises generation in ac. I-V characteristics and voltage noises are measured simultaneously to reveal the nature of the excess noises. The coincidence of the excess noise and the third harmonic voltage suggests that the fluctuation of vortex pair separation process is one of the main contributions to excess noises in the two dimensional superconducting transition.
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Bai, Jiongjun. "Adaptive hidden Markov noise modelling for speech enhancement." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/11158.
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A robust and reliable noise estimation algorithm is required in many speech enhancement systems. The aim of this thesis is to propose and evaluate a robust noise estimation algorithm for highly non-stationary noisy environments. In this work, we model the non-stationary noise using a set of discrete states with each state representing a distinct noise power spectrum. In this approach, the state sequence over time is conveniently represented by a Hidden Markov Model (HMM). In this thesis, we first present an online HMM re-estimation framework that models time-varying noise using a Hidden Markov Model and tracks changes in noise characteristics by a sequential model update procedure that tracks the noise characteristics during the absence of speech. In addition the algorithm will when necessary create new model states to represent novel noise spectra and will merge existing states that have similar characteristics. We then extend our work in robust noise estimation during speech activity by incorporating a speech model into our existing noise model. The noise characteristics within each state are updated based on a speech presence probability which is derived from a modified Minima controlled recursive averaging method. We have demonstrated the effectiveness of our noise HMM in tracking both stationary and highly non-stationary noise, and shown that it gives improved performance over other conventional noise estimation methods when it is incorporated into a standard speech enhancement algorithm.
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Can, Ozgun. "Noise Assessment Of Shipyard Workers." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609538/index.pdf.
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ABSTRACT
NOISE ASSESSMENT OF SHIPYARD WORKERS
Can,Özgü
n M.Sc.,Department of Engineering Sciences Supervisor : Prof.Dr.Gü
lin Birlik May 2008,139 pages Noise is one of the most important health risks in workplaces worldwide and NIOSH identified noise as one of the 10 important occupational problems. In OSHA'
s hearing conservation amendment it is stated that in U.S., more than 5 million workers are exposed to potentially hazardous levels of noise in manufacturing and utilities. In 1981 OSHA estimated that, at least one million workers in industry had undergone occupational hearing loss. Ship building has been one of the most promising and rapidly growing industries in Turkey in the recent years. It comprises many production techniques and activities, requires qualified personnel and compliance with several class institutions making the job interesting for the enthusiastic engineers and workers. However shipyard workers are subject to high levels of noise besides other health risks. The aim of this study is to figure out the effect of noise on shipyard workers. For this purpose 2 factories, namely Factory 1 and Factory 2 in a shipyard were chosen and two methods were adopted. The first method was the subjective evaluation of the workers through questionnaires distributed to them, whereas the second method involved the noise level measurement during their work hours. At all the points in Factory 1 where noise level measurements have been done, higher A-weighted values of noise than the limits stated in the legal regulations were found. In Factory 2, noise levels were all below the action value of 85 dBA .Dose measurements of the workers displayed the extremely variable acoustical conditions that the workers encountered. According to the &ldquo
Noise Regulation&rdquo
of Ministry of Labour and Social Security and &ldquo
The European Noise Directive&rdquo
, the employer seems to be obliged to measure periodically and to assess the level of noise exposure of workers in Factory 1 and take immediately the necessary precautions. Ear plug performance and speech interference conditions were also examined.
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Wang, Xiawa. "On the 1/f noise of atomic-layer-deposition metal films." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77000.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2012."February 2011." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 77-81).
This thesis presents the measurement techniques and results of low-frequency noise for atomic-layer-deposition Pt films. Atomic-layer-deposition has been developed as an approach to make ultra-thin and conformal films. It has been employed to make detectors of bolometers. 1/f noise is a fundamental limit to the resolution. The experiments are designed to characterize the 1/f noise of the ALD fabricated Pt films. The measurement results show that for 7nm and 13nm ALD fabricated Pt films, 1/f noise is about two orders of magnitude larger than reported for continuous Pt films in literature. The thin film is also very likely to suffer from electromigration damage.
by Xiawa Wang.
M.Eng.
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SANTOS, DEBORA ANDREA DE OLIVEIRA. "SPEECH RECOGNITION IN NOISE ENVIRONMENT." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2001. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1987@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOREste trabalho apresenta um estudo comparativo de três técnicas de melhoria das taxas de reconhecimento de voz em ambiente adverso, a saber: Normalização da Média Cepestral (CMN), Subtração Espectral e Regressão Linear no Sentido da Máxima Verossimilhança (MLLR), aplicadas isoladamente e em concomitância, duas a duas. Os testes são realizados usando um sistema simples: reconhecimento de palavras isoladas (dígitos de zero a nove, e meia), modo dependente do locutor, modelos ocultos de Markov do tipo contínuo, e vetores de atributos com doze coeficientes cepestrais derivados da análise de predição linear. São adotados três tipos de ruído (gaussiano branco, falatório e de fábrica) em nove razões sinal-ruído diferentes. Os resultados experimentais demonstram que o emprego isolado das técnicas de reconhecimento robusto é, em geral, vantajoso, pois nas diversas razões sinal-ruído para as quais os testes são efetuados, quando as taxas de reconhecimento não sofrem um acréscimo, mantém-se as mesmas obtidas quando não se aplica nenhum método de aumento da robustez. Analisando-se comparativamente as implementações isoladas e simultânea das técnicas, constata-se que a simultânea nem sempre é atraente, dependendo da dupla empregada. Apresentam-se, ainda, os resultados decorrentes do uso de modelos ruidosos, observando-se que, embora sejam inegavelmente melhores, sua utilização é inviável na prática. Das técnicas implementadas, a que representa resultados mais próximos ao emprego de modelos ruidosos é a MLLR, seguida pela CMN, e por último pela Subtração Espectral. Estas últimas, embora percam em desempenho para a primeira, apresentam como vantagem a simplicidade e a generalidade. No que concerne as técnicas usadas concomitantemente, a dupla Subtração Espectral e MLLR é a considerada de melhor performance, pois mostra-se conveniente em relação ao emprego isolado de ambos os métodos, o que nem sempre ocorre com o uso de outras combinações das técnicas individuais.
This work presents a comparative study of three techniques for improving the speech recognition rates in adverse environment, namely: Cepstral Mean Normalization (CMN), Spectral Subtraction and Maximum Likelihood Linear Regression (MLLR). They are implemented in two ways: separately and in pairs. The tests are carried out on a simple system: recognition of isolated words (digits from zero to nine, and the word half), speaker-dependent mode, continuous hidden Markov models, and speech feature vectors with twelve cepstral coefficients derived from linear predictive analysis. Three types of noise are considered (the white one, voice babble and from factory) at nine different signal-to-noise ratios. Experimental result demonstrate that it is worth using separately the techniques of robust recognition. This is because for all signal-to-noise conditions when the recognition accuracy is not improved it is the same one obtained when no method for increasing the robustness is applied. Analyzing comparatively the isolated and simultaneous applications of the techniques, it is verified that the later is not always more attractive than the former one. This depends on the pair of techniques. The use of noisy models is also considered. Although it presents better results, it is not feasible to implement in pratical situations. Among the implemented techniques, MLLR presents closer results to the ones obtaneid with noisy models, followed by CMN, and, at last, by Spectral Subtraction. Although the two later ones are beaten by the first, in terms of recognition accuracy, their advantages are the simplicity and the generality. The use of simultaneous techniques reveals that the pair Spectral Subtraction and MLLR is the one with the best performance because it is superior in comparison with the individual use of both methods. This does not happen with other combination of techniques.
Este trabajo presenta un estudio comparativo de tres técnicas de mejoría de las tasas de reconocimiento de voz en ambiente adverso, a saber: Normalización de la Media Cepextral (CMN), Substracción Espectral y Regresión Lineal en el Sentido de la Máxima Verosimilitud (MLLR), aplicadas separada y conjuntamente, dos a dos. Las pruebas son realizados usando un sistema simple: reconocimiento de palabras aisladas (dígitos de cero al nueve, y media), de modo dependiente del locutor, modelos ocultos de Markov de tipo contínuo, y vectores de atributos con doce coeficientes cepextrales derivados del análisis de predicción lineal. Se adoptan tres tipos de ruido (gausiano blanco, parlatorio y de fábrica) en nueve razones señal- ruido diferentes. Los resultados experimentales demuestran que el empleo aislado de las técnicas de reconocimiento robusto es, en general, ventajoso, pues en las diversas relaciones señal ruido para las cuales las pruebas son efetuadas, cuando la tasa de reconocimiento no aumenta, manteniendo las mismas tasas cuando no se aplica ningún método de aumento de robustez. Analizando comparativamente las implementaciones aisladas y simultáneas de las técnicas, se constata que no siempre la simultánea resulta atractiva, dependiendo de la dupla utilizada. Se presentan además los resultados al utilizar modelos ruidosos, observando que, aunque resultan mejores, su utilización em la práctica resulta inviable. De las técnicas implementadas, la que presenta resultados más próximos al empleo de modelos ruidosos es la MLLR, seguida por la CMN, y por último por la Substracción Espectral. Estas últimas, aunque tienen desempeño peor que la primera, tienen como ventaja la simplicidad y la generalidad. En lo que se refiere a las técnicas usadas concomitantemente, la dupla Substracción Espectral y MLLR es la de mejor performance, pues se muestra conveniente en relación al empleo aislado de ambos métodos, lo que no siempre ocurre con el uso de otras combinaciones de las técnicas individuales.
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Floud, Sarah Katherine. "Cardiovascular disease and medication use associated with exposure to aircraft noise, road traffic noise and air pollution in populations living near airports." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/39137.
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Noise is a significant environmental problem; epidemiological evidence that noise from road traffic and aircraft may be damaging to health has been increasing. This thesis uses data from the HYENA (HYpertension and Exposure to Noise near Airports) multi-centre study. Earlier HYENA studies suggested that noise exposure increased the risk of hypertension and other risk factors for cardiovascular disease, through blood pressure spikes, reduced night-time dipping of blood pressure and raised morning salivary cortisol. This thesis found that long-term exposure to aircraft noise was associated with increased prevalence of cardiovascular disease and with the use of anti-hypertensive and anxiolytic medication. Road traffic noise was also associated with cardiovascular disease and additionally with antacid use in men. These are new findings with significant implications for public policy. Airports generate road traffic, with associated air pollution increasing the risk of cardiovascular disease. An analysis was therefore undertaken into whether the association between cardiovascular disease and road traffic noise was confounded by air pollution or if there was interaction between the exposures. Mutual confounding by noise and air pollution was found in separate analyses of three countries within HYENA. It is possible that aspects of the home environment, insulation, open windows and room orientation, affect exposure to noise and thus modify health risks. Associations between cardiovascular disease and road traffic noise were found for participants whose rooms faced the road and for those who had sound proofing installed in their home, suggesting the latter is a marker for higher exposure and/or sensitivity to noise. The effect of opening windows on the association between cardiovascular disease and noise was less clear, with an association with aircraft noise but not with road traffic noise.
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Rabey, Isabel. "Improved shot noise limit of the YbF EDM experiment." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/45291.
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The electron is predicted to have a small electric dipole moment (EDM). This fundamental property characterises the distortion of the electron's almost perfectly spherical charge distribution. The size of this distortion (de) is intimately connected to the breaking of time reversal symmetry (T) in nature. The Standard Model of particle physics, which contains a small amount of T-asymmetry, predicts a tiny, non-zero value of the electron EDM, |de| ≃ 10^-38 e.cm. However, many extensions to the Standard Model, which naturally include additional T-violating effects, also predict much larger values of de that should be detectable using current experimental techniques. Measurements of the electron's EDM constrains these theories, making these experiments a powerful tool in the search for physics beyond the Standard Model. The most precise measurements of the electron EDM have been made using paramagnetic atoms and moleules. This thesis describes the progress made towards a new measurement of the electron EDM using the polar, paramagnetic molecule, YbF. A new state preparation technique is described that optically pumps most of the population from the first and second rotationally excited states into a single hyper fine component of the ground state. This increases the number of molecules entering the experiment by a factor of 6. A new state-selective detection scheme is also described, where multiple laser frequencies are used so that each molecule scatters many photons. This has increased detection efficiency by a factor of 20. In order to reduce magnetic noise in the experiment, new electric field plates have been introduced into the interaction region which have reduced the magnetic Johnson noise by a factor of 100. Together, these improvements increase statistical sensitivity by a factor of 11.4 over the last EDM measurement made using YbF. With an enhanced sensitivity of (5x10^-27/sqrt(Nb)) e.cm, we can expect to measure the electron's EDM more precisely than ever before, constraining T-violating physics at a higher energy scale.
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Dimino, Ignazio. "Smart panels for active noise control in aircraft cabin." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/14605.
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Active noise control is a key technology to enhance aircraft cabin comfort. This reflects the view of a vast amount of research aimed at reducing cabin noise levels by tackling structural vibration of the fuselage sidewalls. Aircraft interior trim panels and windows are characterized by poor sound transmission loss behaviour at low frequencies as a result of the mass-air-mass resonance phenomena. For next-generation transport aircraft, their impact on the cabin vibroacoustic environment is expected to become increasingly important with the upcoming use of larger passive windows providing a weak link in protecting aircraft interior from outside noise. This thesis presents a novel active structural acoustic control (ASAC) concept to reduce sound transmission through aircraft-type windows at low frequencies. The structural control inputs are achieved by piezoelectric actuators applied to the structure while the radiating pressure field is minimized. The control concept is developed by means of numerical and experimental investigations. A theoretical analysis of the fluid-structure interaction of vibrating structures is presented. A simulation procedure for the numerical evaluation of the sound transmission loss behaviour of plate-like multi wall structures is developed. The method is based on a hybrid FEM/Rayleigh methodology and utilises numerically calculated sound transmission loss of flat multi panel partitions and box like cavities with idealized boundary conditions. Several examples are presented to demonstrate the accuracy of the proposed technique. A suitable control algorithm based on an adaptive feed-forward Multi-Input Multi- Output control strategy is developed and implemented on a real-time Digital Signal Processing control board. The control strategy is based on the minimization of the sum of square outputs of a number of field microphones. Active noise control experiments are conducted for tonal and narrowband excitations by mounting the structure on a reference test suite. The sound power transmitted through the structure is determined by intensity measurements in anechoic chamber. Focus is finally given to the potential impact of active noise and vibration reduction on passengers from the point of view of comfort perception.
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Claubnitzer, Diana. "Bacterial chemotaxis: sensory adaptation, noise filtering, and information transmission." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/6918.
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Chemotaxis is a fundamental cellular process by which cells sense and navigate in theirenvironment. The molecular signalling pathway in the bacterium Escherichia coli is experimentallywell-characterised and, hence, ideal for quantitative analysis and modelling.Chemoreceptors sense gradients of a multitude of substances and regulate an intracellularsignalling pathway, which modulates the swimming behaviour. We studied the chemotaxispathway in E. coli (i) to quantitatively understand molecular interactions in the signallingnetwork, (ii) to gain a systems view of the workings of the pathway, including the effectsof noise generated by biomolecular reactions during signalling, and (iii) to understandgeneral design principles relevant for many sensory systems. Specifically, we investigatedthe adaptation dynamics due to covalent chemoreceptor modification, which includes numerouslayers of feedback regulation. In collaboration with an experimental group, weundertook quantitative experiments using wild-type cells and mutants for proteins involvedin adaptation using in vivo fluorescence resonance transfer (FRET). We developeda dynamical model for chemotactic signalling based on cooperative chemoreceptors andadaptation of the sensory response. This model quantitatively explains an interestingasymmetry of the response to favourable and unfavourable stimuli observed in the experiments.In a whole-pathway description, we further studied the response to controlledconcentration stimuli, as well as how fluctuations from the environment and due to intracellularsignalling affect the detection of input signals. Finally, the chemotaxis pathwayis characterised by high sensitivity, a wide dynamic range and the need for informationtransmission, properties shared with many other sensory systems. Based on FRET data,we investigated the emergence, limits and biological significance of Weber?s law which predictsthat the system detects stimuli relative to the background stimulus. Furthermore, westudied the information transmission from input concentrations into intracellular signals.We connect Weber?s law, as well as information transmission, to swimming bacteria andpredict typically encountered chemical inputs.
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Kalyoncu, Ozden. "Noise Reduction In Time-frequency Domain." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608768/index.pdf.
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In this thesis work, time-frequency filtering of nonstationary signals in noise using Wigner-Ville Distribution is investigated. Continuous-time, discrete-time and discrete Wigner Ville Distribution definitions, their relations, and properties are given.
Time-Frequency Peak Filtering Method is presented. The effects of different parameters on the performance of the method are investigated, and the results are presented.
Time-Varying Wiener Filter is presented. Using simulations it is shown that the performance of the filter is good at SNR levels down to -5 dB. It is proposed and shown that the performance of the filter improves by using Support Vector Machines.
The presented time-frequency filtering techniques are applied on test signals and on a real world signal. The results obtained by the two methods and also by classical zero-phase low-pass filtering are compared. It is observed that for low sampling rates Time-Varying Wiener Filter, and for high sampling rates Time-Frequency Peak Filter performs better.
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Klegová, Hana. "Nízkošumové zesilovače pro pásmo 1-3 GHz." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-316424.
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This masters thesis deals with low noise amplifier design for frequency range 1 GHz - 3 GHz. There is a short theoretical introduction in the first part of the thesis. There are described parameters and properties of transistors and general two-ports. Description of the noise characteristics two-ports follows. The next capture contains design of two-stage amplifiers. One of them is with a microstrip filter between stages and the second one is with combline filter on input of the amplifier. The amplifiers and the microstrip filter were designed in program ANSOFT Designer. The design of combline filter was realised in program CST Microwave Studio. Both amplifiers ware made and their properties ware compared with simulations.
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Blaschke, Peter Gerhard. "Vibro-acoustic design tool for noise optimization of rotating machines." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/7355.
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Pathak, Khanindra. "Modelling and prediction of environmental noise levels near mechanised surface mines and quarries." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/8776.
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Jin, Heng. "A 1-V, CMOS on SOI, 1.9-GHz CDMA low noise amplifier." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0015/MQ53435.pdf.
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Mayorov, Alexander. "Tunnelling and noise in GaAs and graphene nanostructures." Thesis, University of Exeter, 2008. http://hdl.handle.net/10036/46914.
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Experimental studies presented in this thesis have shown the first realisation of resonant tunnelling transport through two impurities in a vertical double-barrier tunnelling diode; have proved the chiral nature of charge carriers in graphene by studying ballistic transport through graphene $p$-$n$ junctions; have demonstrated significant differences of $1/f$ noise in graphene compared with conventional two-dimensional systems. Magnetic field parallel to the current has been used to investigate resonant tunnelling through a double impurity in a vertical double-barrier resonant tunnelling diode, by measuring the current-voltage and differential conductance-voltage characteristics of the structure. It is shown that such experiments allow one to obtain the energy levels, the effective electron mass and spatial positions of the impurities. The chiral nature of the carriers in graphene has been demonstrated by comparing measurements of the conductance of a graphene $p$-$n$-$p$ structure with the predictions of diffusive models. This allowed us to find, unambiguously, the contribution of ballistic resistance of graphene $p$-$n$ junctions to the total resistance of the $p$-$n$-$p$ structure. In order to do this, the band profile of the $p$-$n$-$p$ structure has been calculated using the realistic density of states in graphene. It has been shown that the developed models of diffusive transport can be applied to explain the main features of the magnetoresistance of $p$-$n$-$p$ structures. It was shown that $1/f$ noise in graphene has much more complicated concentration and temperature dependences near the Dirac point than in usual metallic systems, possibly due to the existence of the electron-hole puddles in the electro-neutrality region. In the regions of high carrier concentration where no inhomogeneity is expected, the noise has an inverse square root dependence on the concentration, which is also in contradiction with the Hooge relation.
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Doire, Clément. "Single-channel enhancement of speech corrupted by reverberation and noise." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/43932.
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When capturing speech signals using a distant microphone within a confined acoustic space, the recordings are often degraded by reverberation. This can have a detrimental impact on the quality and intelligibility of speech, especially when combined with acoustic noise. In recent years, there has been increasing demand for effective ways of combating the damaging effects of reverberation in applications such as hands-free telephony or hearing-aids technology. However, the task of providing a blind single-channel dereverberation method robust to high levels of noise and suitable for real-time processing remains a challenge. An important prerequisite for many single-channel dereverberation algorithms is the estimation of the acoustic parameters governing reverberation. In this thesis, a novel online method of estimating these parameters jointly with the interfering signal powers is proposed that is based on a combination of Voice Activity Detection and Extended Kalman Filters. This method is then extended to take into account the spectral structure of clean speech signals and to perform dereverberation by applying a time-frequency gain to the degraded speech spectrogram. The estimation of this gain is formulated as a Bayesian filtering problem conditioned on a Hidden Markov Model. In order to evaluate the proposed algorithm in terms of speech intelligibility, a novel algorithm for measuring Psychometric Functions efficiently in listening experiments is presented. The algorithms developed are evaluated on both simulated and real recordings and are compared with existing state-of-the art alternatives.
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Tanrikulu, Oguz. "Adaptive signal processing algorithms with accelerated convergence and noise immunity." Thesis, Imperial College London, 1995. http://hdl.handle.net/10044/1/7877.
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SANTOS, BRUNO PALHARES DOS. "PHASE NOISE OPTIMIZATION OF MICROWAVE OSCILLATORS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2005. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=7590@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORNesta dissertação foram projetados e desenvolvidos osciladores apresentando ruído de fase otimizado. Em virtude das limitações dos equipamentos analisadores de espectro na precisa medição do ruído de fase dos osciladores desenvolvidos nos laboratórios do CETUC, foi implementada a técnica de medição Método do Detector de Fase. Esta técnica consiste no desenvolvimento de um segundo oscilador com as mesmas características do existente, e com auxílio de misturadores, realizar o batimento dos mesmos para freqüências próximas a DC, onde nesta região a medição do ruído de fase torna-se viável. Entretanto, em aplicações dedicadas, verificou-se que o batimento entre dois osciladores operando em torno de 10 GHz produz uma freqüência intermediária instável, variando de 10 kHz à 50 kHz. Para evitar a realização de uma medição extremamente instável, utilizou-se o método de sincronização de freqüências (Injection Locking) entre os osciladores. Foi também destacada a influência do ruído de cintilação (Flicker Noise) na medida final do ruído de fase. A melhor medida aferida foi em torno de -100 dBc/Hz @ 3,25 kHz. Foi verificado através de diversas simulações que a freqüência de cintilação int c f , situada em 10 MHz, apresenta grande influência sobre as medições do ruído de fase realizadas à 3,25 kHz da portadora, degradando-o em cerca de 30dB.
In this dissertation, oscillators presenting optimized phase noise had been projected and develloped. Because of the limitation of the specter analyzer devices in the accurate measurements of the oscillators phase noise developed in the CETUC laboratories, it was implemented the measurement technique called Phase Detector Method. This technique consists on the development of a second oscillator with the same characteristics of the already existent one and, with aid of mixers, multiplies these signals together and provides the difference of the two signals next to DC, where, in this region, the measurement of the phase noise becomes viable. However, in dedicated applications, it was verified that the beating between two oscillators operating around 10GHz produces instable intermediate frequency, varying between 10kHz to 50kHz. To prevent the accomplishment of an extremely unstable measurement, the method of synchronization of frequency (Injection Locking) between the oscillators was used. Also the influence of the Flicker Noise in the final measure of the phase noise was detached. The best measure was around -100dBc/Hz@3,25kHz. It was verified through lots of simulations that the flicker corner frequency int c f , situated in 10MHz, presents great influence on the measures of the phase noise carried through to the 3,25kHz of the carrier, degrading it in about 30dB.
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Viklund, Jonas. "Developing of an ultra low noise bolometer biasing circuit." Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-296698.
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Noise in electronic circuits can sometimes cause problems. It is especially problematic in for example high sensitive sensors and high end audio and video equipment. In audio and video equipment the noise will make its way into the sound and picture reducing the overall quality. Sensors that are constructed to sense extremely small changes can only pick up changes larger than the noise floor of the circuit. By lowering the noise, sensors can achieve higher accuracy. This thesis presents an ultra low noise solution of the biasing circuitry to the bolometer used in one of FLIR Systems high end cameras. The bolometer uses different adjustable direct current voltage sources and is extremely sensitive to noise. The purpose is to improve the picture quality and the thermal measurement resolution. A prototype circuit was constructed and in the end of the thesis a final circuit with successful result will be presented.
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Both, Thiago Hanna. "Autocorrelation analysis in frequency domain as a tool for MOSFET low frequency noise characterization." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/174487.
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O ruído de baixa frequência é um limitador de desempenho em circuitos analógicos, digitais e de radiofrequência, introduzindo ruído de fase em osciladores e reduzindo a estabilidade de células SRAM, por exemplo. Transistores de efeito de campo de metalóxido- semicondutor (MOSFETs) são conhecidos pelos elevados níveis de ruído 1= f e telegráfico, cuja potência pode ser ordens de magnitude maior do que a observada para ruído térmico para frequências de até dezenas de kHz. Além disso, com o avanço da tecnologia, a frequência de corner —isto é, a frequência na qual as contribuições dos ruídos térmico e shot superam a contribuição do ruído 1= f — aumenta, tornando os ruídos 1= f e telegráfico os mecanismos dominantes de ruído na tecnologia CMOS para frequências de até centenas de MHz. Mais ainda, o ruído de baixa frequência em transistores nanométricos pode variar significativamente de dispositivo para dispositivo, o que torna a variabilidade de ruído um aspecto importante para tecnologias MOS modernas. Para assegurar o projeto adequado de circuitos do ponto de vista de ruído, é necessário, portanto, identificar os mecanismos fundamentais responsáveis pelo ruído de baixa frequência em MOSFETs e desenvolver modelos capazes de considerar as dependências do ruído com geometria, polarização e temperatura. Neste trabalho é proposta uma técnica para análise de ruído de baixa frequência baseada na autocorrelação dos espectros de ruído em função de parâmetros como frequência, polarização e temperatura. A metodologia apresentada revela informações importantes sobre os mecanismos responsáveis pelo ruído 1= f que são difíceis de obter de outras formas. As análises de correlação realizadas em três tecnologias CMOS comerciais (140 nm, 65 nm e 45 nm) fornecem evidências contundentes de que o ruído de baixa frequência em transistores MOS tipo-n e tipo-p é composto por um somatório de sinais telegráficos termicamente ativados.Low-frequency noise (LFN) is a performance limiter for analog, digital and RF circuits, introducing phase noise in oscillators and reducing the stability of SRAM cells, for example. Metal-oxide-semiconductor field-effect-transistors (MOSFETs) are known for their particularly high 1= f and random telegraph noise levels, whose power may be orders of magnitude larger than thermal noise for frequencies up to dozens of kHz. With the technology scaling, the corner frequency — i.e. the frequency at which the contributions of thermal and shot noises to noise power overshadow that of the 1= f noise — is increased, making 1= f and random telegraph signal (RTS) the dominant noise mechanism in CMOS technologies for frequencies up to several MHz. Additionally, the LFN levels from device-to-device can vary several orders of magnitude in deeply-scaled devices, making LFN variability a major concern in advanced MOS technologies. Therefore, to assure proper circuit design in this scenario, it is necessary to identify the fundamental mechanisms responsible for MOSFET LFN, in order to provide accurate LFN models that account not only for the average noise power, but also for its variability and dependences on geometry, bias and temperature. In this work, a new variability-based LFN analysis technique is introduced, employing the autocorrelation of multiple LFN spectra in terms of parameters such as frequency, bias and temperature. This technique reveals information about the mechanisms responsible for the 1= f noise that is difficult to obtain otherwise. The correlation analyses performed on three different commercial mixed-signal CMOS technologies (140-nm, 65-nm and 40-nm) provide strong evidence that the LFN of both n- and p-type MOS transistors is primarily composed of the superposition of thermally activated random telegraph signals (RTS).
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Younan, Hany Reffat. "Energy consumption and noise generation in the impact cutting of polymers." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38203.
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Johnson, Robert Andrew. "Probabilistic modelling of noise as a driving force in biological systems." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/45356.
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Systems biology takes a mechanistic, relational approach to the study of biological processes, commonly finding expression in mathematical models. Hypotheses about systems can be tested when formulated as models, and promising avenues for further study identified. A model sufficiently faithful to the system under study can be used to guide experiments, to probe the system in silico, and to learn about emergent features not evident from the static picture of the system. In this work, three contributions to the modelling community are proffered. First, a computational package is presented that implements an algorithm for the validation and parametrisation of a model. In validation, we are asking how likely we were to make some observation, given the model, or, equivalently, how able the model is to explain the data. The subsequent two contributions concern noise in biological systems. Biological systems display inherent variability, or noise, due to the stochastic mechanisms through which biochemical processes occur. This variability can be critical to the behaviour of a system and to the fates of individual cells. With this in mind, the second contribution is the development of a methodology to model protein-dependent population dynamics. The idea is to model cell population dynamics that result of noisy intracellular protein dynamics. The method's application is demonstrated in population-level models of a protein-dependent cell cycle and yeast antibiotic resistance. Given an appreciation of the pivotal effects of noise, the third and final contribution is a study of the mechanism of noise propagation. I present an analysis of the contributions of biochemical reaction motifs to the creation and transmission of noise that ultimately manifest in observations of biological systems. This study points to specific processes that enhance or attenuate noise, with the aim of beginning to unravel the flow of noise through a system.
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Lucas, Patricia Havee. "Science in legislation and its enforcement : a study of neighbourhood noise." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46418.
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Legoh, Finarya. "An investigation into auditorium design using 1:50 physical scale modelling and computer modelling." Thesis, University of Salford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238916.
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Jayaraman, Rajsekhar. "Reliability and 1/f noise properties of MOSFETs with nitrided oxide gate dielectrics." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/41582.
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Wu, Qing. "Characterization of Impulse Noise and Hazard Analysis of Impulse Noise Induced Hearing Loss using AHAAH Modeling." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1467.
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Millions of people across the world are suffering from noise induced hearing loss (NIHL), especially under working conditions of either continuous Gaussian or non-Gaussian noise that might affect human's hearing function. Impulse noise is a typical non-Gaussian noise exposure in military and industry, and generates severe hearing loss problem. This study mainly focuses on characterization of impulse noise using digital signal analysis method and prediction of the auditory hazard of impulse noise induced hearing loss by the Auditory Hazard Assessment Algorithm for Humans (AHAAH) modeling. A digital noise exposure system has been developed to produce impulse noises with peak sound pressure level (SPL) up to 160 dB. The characterization of impulse noise generated by the system has been investigated and analyzed in both time and frequency domains. Furthermore, the effects of key parameters of impulse noise on auditory risk unit (ARU) are investigated using both simulated and experimental measured impulse noise signals in the AHAAH model. The results showed that the ARUs increased monotonically with the peak pressure (both P+ and P-) increasing. With increasing of the time duration, the ARUs increased first and then decreased, and the peak of ARUs appeared at about t = 0.2 ms (for both t+ and t-). In addition, the auditory hazard of experimental measured impulse noises signals demonstrated a monotonically increasing relationship between ARUs and system voltages.
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Jin, Zhenrong. "Low-Frequency Noise in Silicon-Germanium BiCMOS Technology." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4827.
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Low-frequency noise (LFN) is characterized using in-house measurement systems in a variety of SiGe HBT generations. As technology scales to improve the performance and integration level, a large low-frequency noise variation in small geometry SiGe HBTs is first observed in 90 GHz peak fT devices. The fundamental mechanism of this geometry dependent noise variation is thought to be the superposition of individual Lorentzian spectra due to the presence of G/R centers in the device. The observed noise variation is the result of a trap quantization effect, and is thus best described by number fluctuation theory rather than mobility fluctuation theory. This noise variation continues to be observed in 120 GHz and 210 GHz peak fT SiGe HBT BiCMOS technology. Interestingly, the noise variation in the 210 GHz technology generation shows anomalous scaling behavior below about 0.2-0.3um2 emitter geometry, where the noise variation rapidly decreases. Data shows that the collector current noise is no longer masked by the base current noise as it is in other technology generations, and becomes the dominant noise source in these tiny 210 GHz fT SiGe HBTs. The proton response of LFN in SiGe HBTs is also investigated in this thesis. The results show that the relative increase of LFN is minor in transistors with small emitter areas, but significant in transistors with large emitter areas after radiation. A noise degradation model is proposed to explain this observed geometry dependent LFN degradation. A 2-D LFN simulation is applied to SiGe HBTs for the first time in order to shed light on the physical mechanisms responsible for LFN. A spatial distribution of base current noise and collector current noise reveals the relevant importance of the physical locations of noise sources. The impact of LFN in SiGe HBTs on circuits is also examined. The impact of LFN variation on phase noise is demonstrated, showing VCOs with small geometry devices have relatively large phase noise variation across samples.
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Davies, John. "Studies of a novel low noise plasma source for atomic emission spectrometry." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38279.
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Erguler, Kamil. "The effect of noise on dynamics and the influence of biochemical systems." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/6071.
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Understanding a complex system requires integration and collective analysis of data from many levels of organisation. Predictive modelling of biochemical systems is particularly challenging because of the nature of data being plagued by noise operating at each and every level. Inevitably we have to decide whether we can reliably infer the structure and dynamics of biochemical systems from present data. Here we approach this problem from many fronts by analysing the interplay between deterministic and stochastic dynamics in a broad collection of biochemical models. In a classical mathematical model we first illustrate how this interplay can be described in surprisingly simple terms; we furthermore demonstrate the advantages of a statistical point of view also for more complex systems. We then investigate strategies for the integrated analysis of models characterised by different organisational levels, and trace the propagation of noise through such systems. We use this approach to uncover, for the first time, the dynamics of metabolic adaptation of a plant pathogen throughout its life cycle and discuss the ecological implications. Finally, we investigate how reliably we can infer model parameters of biochemical models. We develop a novel sensitivity/inferability analysis framework that is generally applicable to a large fraction of current mathematical models of biochemical systems. By using this framework to quantify the effect of parametric variation on system dynamics, we provide practical guidelines as to when and why certain parameters are easily estimated while others are much harder to infer. We highlight the limitations on parameter inference due to model structure and qualitative dynamical behaviour, and identify candidate elements of control in biochemical pathways most likely of being subjected to regulation.
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Guo, Ningqun. "The vibration characteristics of piezoelectric discs." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/11449.
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Lee, Wee Siang. "Exterior domain decomposition method for fluid-structure interaction problems." Thesis, Imperial College London, 1999. http://hdl.handle.net/10044/1/8533.
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Bluck, Michael John. "Integral equation methods for transient wave propagation." Thesis, Imperial College London, 1993. http://hdl.handle.net/10044/1/7973.
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