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Odelstad, Elias. "Noise sources in the electric field antenna on the ESA JUICE satellite." Thesis, Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-208411.
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The noise in the Langmuir Probe and Plasma Wave Instrument (LP-PWI) on board ESA:s future Jupiter satellite JUICE (Jupiter ICy Moons Explorer) was investigated. Thermal Johnson-Nyquist noise and shot noise, caused by fluctuations in the probe-plasma currents, were combined with the quasi-thermal noise (QTN) due to thermal fluctuations in the electric field in the plasma, using a small signal equivalent circuit model. The contributions and effects of each of the considered noise sources were examined and compared for a number of representative space plasma conditions, including the cold dense plasma of Ganymede's ionosphere and the hot tenuous plasma out in the Jovian magnetosphere. The results showed that in the cold dense plasma of Ganymede's ionosphere, the antenna was long compared to the Debye length and the quasi-thermal noise had a clearly pronounced peak and a steep high-frequency cut-off. For an antenna biased to 1 V with respect to the plasma, the shot noise due to the ambient plasma was the dominant source of noise. For a an antenna at the floating potential the photoelectron shot noise coalesced with the shot and Nyquist noises of the ambient plasma to form almost a single curve. In the hot tenuous plasma out in Jupiter's magnetosphere, the antenna was short compared to the Debye length and the QTN spectrum was much flatter, with little or no peak at the plasma frequency and a very weak high-frequency cut-off. For an antenna biased to 1 V, the shot noise due to photoelectron emission dominated at Callisto's orbital position whereas at Ganymede's and Europa's orbital positions the Nyquist and shot noises of the ambient plasma particles were the dominant noise components. For an antenna at the floating potential, the shot and Nyquist noises of the ambient plasma also dominated the output noise, except at Europa's orbital position, where the quasi-thermal noise was the largest noise component for frequencies at and above the plasma frequency. The numerical calculations were performed using MATLAB. The code was made available in a Git repository at https://github.com/eliasodelstad/irfuproj_JUICE_noise.
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Husák, Marek. "Využití šumové diagnostiky k analýze vlastností solárních článků." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217922.
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The master’s thesis deals with the noise diagnostic in the solar cells. Describes the main kinds of noises. The samples were quality and reliability screened using noise reliability indicators. The samples were surveyed by measuring the I-V characteristics, the noise spectral density as a function of forward voltage and frequency. It was calculated the noise spectral density as a function of forward current.
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Mostovov, Andrey. "Quantum Shot Noise in Graphene." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2014. http://tel.archives-ouvertes.fr/tel-01023003.
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We have conducted an experimental study of the quantum shot noise in a mono-layer graphene device. Conductance of the device and the quantum Hall effect were also investigated. A theoretical model, describing conductance and quantum shot noise in ideal (ballistic) graphene was proposed by Tworzydlo et al., 2006. In diffusive graphene, that is much easier achievable experimentally, shot noise was investigated numerically by several authors (San-Jose et al., 2007, Lewenkopf et al., 2008, Logoteta et al., 2013). Conclusions of the first experimental works (DiCarlo et al., 2008 and Danneau et al., 2008), addressing this problem, didn't lead to an enough broad understanding of it and a further investigation was required. In our experiment we intended to maximally reduce the contributions of the measurement system to the detected signal by performing four-point voltage noise measurement as well as by using cross-correlation detection. In addition to that, our measurement system include home-made cryogenic low-noise amplifiers combined with band-pass filters, while our experimental device carries a constriction in the center of graphene layer and side-gates are used instead of back-gate. First, using the results of the conductance and of the quantum Hall effect measurements we determined the mean free path in our sample and concluded that it was in diffusive regime. The extracted values of the Fano factor show a good agreement with the above-mentioned simulations for this regime, in particular, the peak at Dirac point, predicted by Lewenkopf et al., was observed. Moreover our results are consistent with those of Danneau et al. and DiCarlo et al.
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Brock, Scott E. "Device Shot Noise and Saturation Effects on Oscillator Phase Noise." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/35099.
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Oscillator phase noise is an important factor in designing radio frequency (RF) communications hardware. Phase noise directly contributes to adjacent-channel interference and an increase in bit error rate (BER).
Understanding the operation of an oscillator can help with the oscillator design process. Also, the understanding of the noise processes within an oscillator can add insight to the design process, allowing an intelligent low-noise design. It will be shown that although simulation software can be helpful, the understanding of the oscillator operation is a valuable tool in the design process.
Oscillator design will be discussed, and then the noise processes of the oscillator will be investigated. A new method of decomposing shot noise into in-phase and quadrature components will be discussed. The noise processes discussed for a non-saturating bipolar junction transistor (BJT) Colpitts oscillator will be extended to the case of a saturating BJT Colpitts oscillator. This new method gives insight into the design of low-noise oscillators, and provides guidelines for design of low-noise oscillators. Example oscillators will support the theory and low-noise design guidelines. It will be seen that although designing an oscillator to saturate can provide a stable output level over a wide bandwidth, the added noise production may degrade the performance of the oscillator through both a lower effective Q and restricted signal level compared to the noise.
Master of Science
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DeMino, Kenneth William. "Shot noise approach to stochastic resonance." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/27968.
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Strass, Michael. "Shot noise control in coherent nanoscale conductors." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=979705819.
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Kovalik, Joseph Michael. "A study of thermal noise." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/28121.
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Pedurand, Richard. "Instrumentation for Thermal Noise Spectroscopy." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1356.
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La résolution des interféromètres gravitationnels est limitée par le mouvement Brownien - ou bruit thermique - de leurs miroirs dans la partie centrale de leur bande de détection, entre 10Hz et 1kHz. La répartition en fréquence de ce bruit thermique est dictée par les mécanismes de dissipation d'énergie mécanique à l'origine de cette vibration aléatoire, en accord avec le théorème fluctuation-dissipation. Cette dissipation provient principalement des revêtements optiques déposés sur les miroirs pour leur donner leur réflectivité. Dans le but de réduire le bruit thermique, une nouvelle génération de détecteurs d'ondes gravitationnelles employant des miroirs refroidis à température cryogénique a été proposée. Le développement de nouveaux matériaux optiques en couche mince à faible dissipation mécanique, opérant à la fois à température ambiante et température cryogénique, demande donc de nouveaux outils expérimentaux. L'objet principal de cette thèse est la construction d'un nouvel instrument, le CryoQPDI, qui consiste en l'association d'un interféromètre haute résolution et d'un cryostat basé sur un refroidisseur pulse tube. Il est capable de mesurer directement le mouvement Brownien d'un microlevier entre 300 K et 7 K. En combinant des mesures effectuées sur un microlevier avant et après le dépôt d'une couche mince, il est possible de caractériser la dissipation mécanique interne de cette couche mince. Cet instrument participera ainsi à l'optimisation des revêtements optiques des futurs interféromètres gravitationnels, dans le but de minimiser les nuisances dues au bruit thermiqueThe resolution limit of gravitational wave interferometers is set by their mirrors' Brownian motion – or thermal noise - in the central part of their detection band, from 10Hz to 1kHz. This thermal noise frequency distribution is given by the mechanical energy dissipation mechanisms it originates from, in agreement with the fluctuation-dissipation theorem. This dissipation mainly derives from the optical coatings deposited on the mirrors to give them their reflectivity. To reduce this thermal noise, a new generation of gravitational wave detectors employing mirrors cooled to cryogenic temperature has been suggested. The development of new optical thin-film materials with low mechanical dissipation, operating at both room and cryogenic temperatures, therefore requires new experimental tools. The main object of this thesis is the construction of a new instrument, the CryoQPDI, which is an association between a high-resolution interferometer and a cryostat based on a pulse tube cooler. It can directly measure the Brownian motion of a microcantilever between 300 K and 7 K. By combining measurements made on a microcantilever before and after the deposition of a thin film, it is possible to characterize the internal mechanical dissipation of this thin film. This instrument will eventually contribute to the optimisation of optical coatings of future gravitational wave detectors, aiming at minimizing the limitations due to thermal noise
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Dragomirova, Ralitsa L. "Spin-dependent shot noise in semiconductor and graphene nanostructures." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 140 p, 2009. http://proquest.umi.com/pqdweb?did=1674099571&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Silva, José Felix Estanislau da. "Shot Noise e corrente dependentes de spin: modelo quântico." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-08032017-091450/.
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Nesta dissertação, fazemos a primeira investigação sobre flutuações em corrente e corrente média dependentes de spin em potenciais duplo e simples da estrutura Zn1-xMnxSe. Consideramos efeitos de campos magnético e elétrico externos à temperatura nula. Na presença de um campo magnético, a interação dos íons de Mn com elétrons de condução e valência (interação de troca sp-d) origina potenciais dependentes de spin para o transporte em Zn1-xMnxSe. Aqui, flutuações em corrente (\"shot noise\") e a corrente média são calculados usando o modelo quântico de transporte através do potencial dependente de spin é descrito por uma matriz s de espalhamento. Os elementos da matriz de espalhamento, i.e., as amplitudes de transmissão e reflexão, são determinados pelo método da matriz transferência. Nossos resultados indicam que estruturas de potenciais simples e duplos Zn1-xMnxSe agem como se fossem \"filtros de spin\" para corrente. Em determinadas faixas de parâmetros do sistema, \"shot noise\" pode complementar informações obtidas da corrente médiaIn this dissertation we investigation for the first time spin dependent-current and its fluctuations in double and single barrier potentials of the Zn1-xMn xSe structure sandwiched between ZnSe layers. We consider effects of external magnetic field, the interaction of the Mn ions with thew conduction and valence electrons (sp-d exchange interation) give rises to spin-dependent potentials for transport across the Zn1-xMn xSe layer. Here, the average current and its fluctuations are calculated using the quantum transport model in which transport across the spin-dependent potential is described via scattering matrix s. The elements of the scattering matrix, i.e., the transmission and reflection amplitudes, are determined through the transfer-matrix method. Our results indicate date single and double potentials of the Zn1-xMn xSe structure act as \"spin filters\" for the current. Within some system parameter range, shot noise can supplement the information contained in the average current
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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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Chen, Yuanzhen. "Searching for entangled electron spin states with shot noise detection." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2519.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.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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Camarota, Benedetta. "Towards shot noise-limited detection of a single-electron transistor." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7844.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of 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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Landström, Julia. "The Hawkes process – a self-exciting Poisson shot noise model." Thesis, Uppsala universitet, Tillämpad matematik och statistik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-396673.
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Gretarsson, Andri Marcus. "Thermal noise in low loss flexures." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2002. http://wwwlib.umi.com/cr/syr/main.
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Thielmann, Axel. "Co-tunneling current and shot noise in molecules and quantum dots." Karlsruhe : FZKA, 2005. http://bibliothek.fzk.de/zb/berichte/FZKA7167.pdf.
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Loh, Huanqian. "Applications of correlated photon pairs : sub-shot noise interferometry and entanglement." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36126.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.Includes bibliographical references (p. 89-95).
Using cesium atoms weakly coupled to a low-finesse cavity, we have generated photon pairs that are highly correlated in a non-classical way, as demonstrated by a large violation of the Cauchy-Schwartz inequality G = 760 +2100 -320 for a bin width T = 60 ns. Biphoton interferometry of the correlated pairs via the Holland-Burnett scheme holds promise to demonstrate precision beyond the shot noise limit, although the current interference fringe visibility of [beta]= 0.84 ± 0.04 only translates to a shot noise limited phase uncertainty. Polarization-time entangled pairs can also be directly generated, by optically pumping the atoms to both F = 3, mF = ±3 ground states. The degree of entanglement, expressed by the calculated fidelity f = 0.81 ± 0.09 and calculated Bell state parameter S = 2.3 ± 0.2, is estimated to be finite but not maximal.
by Huanqian Loh.
S.B.
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Brito, Fernando Graciano de. "Shot Noise dependente de spin em sistemas com tunelamento: modelo semiclássico." Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-19092013-110033/.
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Neste trabalho investigamos pela primeira vez flutuações dependentes de spin em correntes eletrônicas polarizadas através de estruturas magnéticas. Nosso sistema físico consiste de uma heteroestrutura com tunelamento ressonante formada por um poço ou \"ponto\" quântico contendo Mn, confinado entre duas barreiras de potencial. Usamos um modelo semiclássico baseado em equações de taxa para calcular as ocupações dos estados ressonantes up e down. Estas equações são derivadas de uma equação mestra que descreve a probabilidade de ocupação dos estados de spin em um dado tempo. Funções correlação corrente-corrente são expressas em termos das funções correlação hop-hop (associadas à transições entre os níveis ressonantes up e down) e o shot noise dependente de spin é determinado em termos da matriz variância do sistema, também derivada da equação mestra. Quando consideramos um feixe polarizado e tempos distintos (τ ↑ ↓ ≠ τ ↓ ↑), podemos obter ambas \"correlações positivas\" (‹ Δ ↑ Δ ↓ › ≥ 0) e/ou \"negativas\" (‹ Δ ↑ Δ ↓ › ≤ 0) no nosso modelo. A generalização e reinterpretação do modelo de ilhas nos possibilitou (i) investigar flutuações dependentes de spin em correntes polarizadas; (ii) observar aumento e atenuação do shot noise; (iii) verificar que processos de \"spin-flip\" com (τ ↑ ↓ ≠ τ ↓ ↑) são relevantes na atenuação do shot noise e (iv) verificar que o ruído contém informações sobre o processo de \"spin-flip\"In this work we investigate for the first time spin-dependent fluctuations in spin-polarized electronic currents through magnetic structures. Our physical model consists of a resonant-tunneling heterostructure formed by a Mn-based quantum well or \"point\", confined between a double-barrier potential. We used a semiclassical model based on rate equations to calculate the occupations of the spin-up and spindown resonant states. These equations are derived from a master equation describing the probability of occupation of the spin states at a given time. Current-current correlation functions are expressed in terms of hop-hop correlation functions (for hops between islands representing the up and down states) and the spin-dependent shoi noise is determined in terms of the variance matrix of the system; also derived from the master equation. When we consider a polarized beam and distinctive times (τ ↑ ↓ ≠ τ ↓ ↑), we can obtain both \"positive correlations\" (‹ Δ ↑ Δ ↓ › ≥ 0) and \"negative correlations\" (‹ Δ ↑ Δ ↓ › ≤ 0) in our model. The generalization and reinterpretation of the island model allowed us (i) to investigate spin-dependent fluctuations in spinpolarized electronic currents; (ii) to observe enhancement and suppression of shot noise; (iii) to verify that spin-flip processes with (τ ↑ ↓ ≠ τ ↓ ↑) are relevant to shotnoise suppression and (iv) to verify that noise contains information about spin-flip processes
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Weatherall, Nicholas Owen. "Quantum Stochastic Calculus for Thermal (squeezed)Noise." Thesis, Lancaster University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518151.
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Gillespie, Aaron D. Raab Frederick J. Raab Frederick J. "Thermal noise in the initial LIGO interferometers /." Diss., Pasadena, Calif. : California Institute of Technology, 1995. http://resolver.caltech.edu/CaltechETD:etd-10032007-142542.
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Souza, Fabricio Macedo de. "Transporte quântico em spintrônica: corrente e shot noise via funções de Green de não equilíbrio." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-26112008-143946/.
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Estudamos transporte quântico dependente de spin em sistemas de ponto e de poço quântico acoplados a contatos magnéticos. O primeiro passo do nosso estudo foi a dedução de fórmulas originais para a corrente e para o ruído em sistemas com tunelamento dependente de spin, através do formalismo de funções de Green de mão equilíbrio. As equações deduzidas reproduzem casos limites da literatura - em particular as fórmulas de Landauer-Buttiker. Posteriormente aplicamos essas fórmulas para estudar três sistemas distintos: (1) ponto quântico acoplado a contatos ferromagnéticos, (2) um ponto quântico acoplado a múltiplos terminais ferromagnéticos, e (3) um poço quântico acoplado a terminais de semicondutor magnético diluído (DMS). No sistema (1) consideramos os alinhamentos paralelo (P) e anti-paralelo (AP) entre as magnetizações dos terminais. Nesse sistema levamos em conta interação de Coulomb e espalhamento de spin no ponto quântico. Com as fórmulas para corrente e ruído deduzidas aqui, encontramos, por exemplo, que a interação de Coulomb, combinada com o magnetismo dos eletrodos, leva a um bloqueio de Coulomb dependente de spin. Esse efeito por sua vez leva a uma polarização da corrente que pode ser modulada (intensidade e sinal) através de uma tens~ao externa. Também encontramos que o espalhamento de spin leva a comportamentos contrastantes entre corrente e ruído. Enquanto a corrente na configuração AP aumenta com a taxa de espalhamento de spin R, o ruído nessa mesma configuração é suprimido para uma certa faixa de valores de R. Um outro efeito interessante que observamos foi a possibilidade de se suprimir o ruído térmico através de uma tensão de porta. Para o sistema (2) mostramos que é possível injetar corrente ↑-polarizada no ponto quântico e coletar simultaneamente correntes ↑ e ↓ polarizadas em terminais diferentes. Além disso, a corrente ao passar do reservatório emissor para um dos reservatórios coletores tem a sua polarização intensificada. Portanto esse sistema pode operar como inversor e amplificador de polarização de corrente. Por último, analisamos os efeitos de terminais DMS e quantização de Landau (na presença de um campo magnético externo) sobre a corrente e o ruído no sistema (3). Encontramos que o efeito Zeeman gigante nos terminais DMS, gerado pela interação de troca s-d, leva a uma polarização da corrente. Em particular, para uma certa faixa de tensão o efeito Zeeman gigante resulta na completa supressão de uma dada componente de spin no transporte. Com isso é possível controlar a polarização da corrente através de uma tensão externa. Também observamos oscilações na corrente, no ruído e no fator de Fano como função do campo magnético.We study spin dependent quantum transport in quantum dots and quantum well devices attached to magnetic leads. We first derive general formulas, including electron-electron interaction and spin flip, for both current and noise, using the no equilibrium Green function technique (Keldysh). From our equations we regain limiting cases in the literature - in particular the Landauer-Buttiker formula when we neglect electron-electron interaction. We apply these formulas to study three distinct systems: (1) a quantum dot attached to two ferromagnetic leads, (2) a quantum dot linked to many ferromagnetic leads, and (3) a quantum well coupled to dilute magnetic semiconductor (DMS) terminals. In the first system we consider both parallel (P) and anti-parallel (AP) ferromagnetic alignments of the leads. Coulomb interaction and spin flip scattering are also taken into account. With the formulas for the current and the noise derived here, we find, for instance, that the Coulomb interaction, combined with the magnetism of the electrodes, gives rise to a spin-dependent Coulomb blockade. This effect allows the control (intensity and sign) of the current polarization via the bias voltage. We also observe that spin flip scattering yields contrasting behavior between current and shot noise. While the current in the AP configuration increases with the spin flip, the shot noise becomes suppressed for a range of spin flip rates. Another interesting finding is the possibility to suppress the thermal noise via a gate voltage. For the dot coupled to three magnetic leads, we show that it is possible to inject current ↑-polarized into the dot from the FM emitter, detect simultaneously ↑ and ↓ - polarized currents at distinct collectors. In addition, we find that the current has its polarization amplified when going from the emitter to one of the collectors. Therefore we have a device that operates as both as current polarization inverter and amplifier. Finally, we analyze the effects of DMS leads and Landau quantization on the current and noise of system (3). We and that the giant Zeeman effect in the DMS leads, due to the it s-d exchange interaction, gives rise to a spin polarized current, and for a particular bias voltage range, full suppression of one spin component. This gives rise to the possibility of tuning the current polarization via the bias voltage. We also observe oscillations in the current, the noise and the Fano factor as a function of the magnetic field.
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Deschênes, Jean-Daniel. "Non-stationary photodetection shot noise in frequency combs: a signal processing perspective." Thesis, Université Laval, 2014. http://www.theses.ulaval.ca/2014/30510/30510.pdf.
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Cette thèse examine le bruit de photon lors de la détection d’impulsions provenant d’un peigne de fréquences. En premier lieu, nous faisons abstraction du mécanisme physique produisant le bruit de photon, réduisant son effet à celui d’une source de bruit additif non-stationnaire (avec des statistiques variables dans le temps). Ce modèle de traitement de signal est ensuite utilisé dans l’analyse de deux expériences importantes pour l’utilisation d’un peigne de fréquence comme mécanisme de compteur de fréquence dans une horloge optique : la conversion du train d’impulsions optiques en un train d’impulsions électriques, et le battement hétérodyne entre un peigne de fréquences et un laser à onde continue. Nous démontrons en premier lieu que le bruit de photon lié à la photodétection produit principalement du bruit d’amplitude, et une quantité presque négligeable de jigue aléatoire de temps sur le signal électrique détecté. Des résultats expérimentaux viennent confirmer nos prédictions théoriques. Nous explorons ensuite les limites de ce mécanisme en considérant la physique de la photodétection, ce qui révèle un étalement du temps de transit qui peut affecter la jigue aléatoire produite par cette conversion. Dans un deuxième temps, nous démontrons que la nature pulsée du peigne de fréquences peut être utilisée pour donner un rapport signal-sur-bruit plus élevé que celui qui est prédit en considérant seulement le battement d’un seul mode du peigne avec le laser à onde continue. La première technique développée, le GATOR, rejette une grande partie du bruit de photon produit par le laser à onde continue afin d’améliorer le rapport signal-sur-bruit lorsque la puissance du peigne est faible. Avec cette technique, nous démontrons un rapport signal-sur-bruit 100 fois plus élevé que la limite en admettant l’utilisation d’un seul mode. Nous démontrons ensuite un raffinement de cette technique qui utilise le glissement de fréquence de l’impulsion optique afin d’utiliser efficacement tous les photons du peigne dans une bande passante déterminée. Cette technique nous a permis de produire un battement avec le plus grand rapport signal-sur-bruit parmi les résultats dans la littérature, 68.3 dB, obtenu en normalisant dans une bande passante commune de 100 kHz.This thesis is a study of shot noise in the photodetection of pulses from a frequency comb. We first make abstraction of the physical mechanism of shot noise to reduce its effects to that of an additive, non-stationary (meaning with time-varying statistics) noise source. This signal processing model is then used to analyze two experiments of importance for the operation of optical clockwork based on frequency combs: the conversion of the optical pulse train into an electrical pulse train by a photodetector, and the heterodyne (or beating) experiment between a frequency comb and a continuous wave laser. For the detection of the optical pulse train, we show that photodetection shot noise yields mostly amplitude noise and vanishingly low timing jitter on the electrical signal. Experimental results confirm our theoretical predictions. We then explore the limits of this jitter when considering practical photodetection physics. This reveals a transit time spread parameter that can affect the jitter produced by this conversion. Next, we turn our attention to the heterodyne experiment. We show that the pulsed nature of the frequency comb can be exploited in different schemes to yield higher signal-to-noise ratio (SNR) that is predicted by the use of the beating of a single comb mode with the continuous wave laser. The first technique that we develop, the GATOR, gates out shot noise from the continuous wave, and improves the SNR in the case of low comb power. Using this technique, we have demonstrated a factor of 100 higher SNR than the single-mode limit. We then show a further refinement of the technique which uses chirping of the optical pulse to effectively use all the available photons from the comb in a given bandwidth. This technique enabled us to produce the beating with the highest SNR reported in the literature of 68.3 dB, when normalizing to the common detection bandwidth of 100 kHz.
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Deschênes, Jean-Daniel, and Jean-Daniel Deschênes. "Non-stationary photodetection shot noise in frequency combs: a signal processing perspective." Doctoral thesis, Université Laval, 2014. http://hdl.handle.net/20.500.11794/25158.
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Cette thèse examine le bruit de photon lors de la détection d’impulsions provenant d’un peigne de fréquences. En premier lieu, nous faisons abstraction du mécanisme physique produisant le bruit de photon, réduisant son effet à celui d’une source de bruit additif non-stationnaire (avec des statistiques variables dans le temps). Ce modèle de traitement de signal est ensuite utilisé dans l’analyse de deux expériences importantes pour l’utilisation d’un peigne de fréquence comme mécanisme de compteur de fréquence dans une horloge optique : la conversion du train d’impulsions optiques en un train d’impulsions électriques, et le battement hétérodyne entre un peigne de fréquences et un laser à onde continue. Nous démontrons en premier lieu que le bruit de photon lié à la photodétection produit principalement du bruit d’amplitude, et une quantité presque négligeable de jigue aléatoire de temps sur le signal électrique détecté. Des résultats expérimentaux viennent confirmer nos prédictions théoriques. Nous explorons ensuite les limites de ce mécanisme en considérant la physique de la photodétection, ce qui révèle un étalement du temps de transit qui peut affecter la jigue aléatoire produite par cette conversion. Dans un deuxième temps, nous démontrons que la nature pulsée du peigne de fréquences peut être utilisée pour donner un rapport signal-sur-bruit plus élevé que celui qui est prédit en considérant seulement le battement d’un seul mode du peigne avec le laser à onde continue. La première technique développée, le GATOR, rejette une grande partie du bruit de photon produit par le laser à onde continue afin d’améliorer le rapport signal-sur-bruit lorsque la puissance du peigne est faible. Avec cette technique, nous démontrons un rapport signal-sur-bruit 100 fois plus élevé que la limite en admettant l’utilisation d’un seul mode. Nous démontrons ensuite un raffinement de cette technique qui utilise le glissement de fréquence de l’impulsion optique afin d’utiliser efficacement tous les photons du peigne dans une bande passante déterminée. Cette technique nous a permis de produire un battement avec le plus grand rapport signal-sur-bruit parmi les résultats dans la littérature, 68.3 dB, obtenu en normalisant dans une bande passante commune de 100 kHz.Cette thèse examine le bruit de photon lors de la détection d’impulsions provenant d’un peigne de fréquences. En premier lieu, nous faisons abstraction du mécanisme physique produisant le bruit de photon, réduisant son effet à celui d’une source de bruit additif non-stationnaire (avec des statistiques variables dans le temps). Ce modèle de traitement de signal est ensuite utilisé dans l’analyse de deux expériences importantes pour l’utilisation d’un peigne de fréquence comme mécanisme de compteur de fréquence dans une horloge optique : la conversion du train d’impulsions optiques en un train d’impulsions électriques, et le battement hétérodyne entre un peigne de fréquences et un laser à onde continue. Nous démontrons en premier lieu que le bruit de photon lié à la photodétection produit principalement du bruit d’amplitude, et une quantité presque négligeable de jigue aléatoire de temps sur le signal électrique détecté. Des résultats expérimentaux viennent confirmer nos prédictions théoriques. Nous explorons ensuite les limites de ce mécanisme en considérant la physique de la photodétection, ce qui révèle un étalement du temps de transit qui peut affecter la jigue aléatoire produite par cette conversion. Dans un deuxième temps, nous démontrons que la nature pulsée du peigne de fréquences peut être utilisée pour donner un rapport signal-sur-bruit plus élevé que celui qui est prédit en considérant seulement le battement d’un seul mode du peigne avec le laser à onde continue. La première technique développée, le GATOR, rejette une grande partie du bruit de photon produit par le laser à onde continue afin d’améliorer le rapport signal-sur-bruit lorsque la puissance du peigne est faible. Avec cette technique, nous démontrons un rapport signal-sur-bruit 100 fois plus élevé que la limite en admettant l’utilisation d’un seul mode. Nous démontrons ensuite un raffinement de cette technique qui utilise le glissement de fréquence de l’impulsion optique afin d’utiliser efficacement tous les photons du peigne dans une bande passante déterminée. Cette technique nous a permis de produire un battement avec le plus grand rapport signal-sur-bruit parmi les résultats dans la littérature, 68.3 dB, obtenu en normalisant dans une bande passante commune de 100 kHz.
This thesis is a study of shot noise in the photodetection of pulses from a frequency comb. We first make abstraction of the physical mechanism of shot noise to reduce its effects to that of an additive, non-stationary (meaning with time-varying statistics) noise source. This signal processing model is then used to analyze two experiments of importance for the operation of optical clockwork based on frequency combs: the conversion of the optical pulse train into an electrical pulse train by a photodetector, and the heterodyne (or beating) experiment between a frequency comb and a continuous wave laser. For the detection of the optical pulse train, we show that photodetection shot noise yields mostly amplitude noise and vanishingly low timing jitter on the electrical signal. Experimental results confirm our theoretical predictions. We then explore the limits of this jitter when considering practical photodetection physics. This reveals a transit time spread parameter that can affect the jitter produced by this conversion. Next, we turn our attention to the heterodyne experiment. We show that the pulsed nature of the frequency comb can be exploited in different schemes to yield higher signal-to-noise ratio (SNR) that is predicted by the use of the beating of a single comb mode with the continuous wave laser. The first technique that we develop, the GATOR, gates out shot noise from the continuous wave, and improves the SNR in the case of low comb power. Using this technique, we have demonstrated a factor of 100 higher SNR than the single-mode limit. We then show a further refinement of the technique which uses chirping of the optical pulse to effectively use all the available photons from the comb in a given bandwidth. This technique enabled us to produce the beating with the highest SNR reported in the literature of 68.3 dB, when normalizing to the common detection bandwidth of 100 kHz.
This thesis is a study of shot noise in the photodetection of pulses from a frequency comb. We first make abstraction of the physical mechanism of shot noise to reduce its effects to that of an additive, non-stationary (meaning with time-varying statistics) noise source. This signal processing model is then used to analyze two experiments of importance for the operation of optical clockwork based on frequency combs: the conversion of the optical pulse train into an electrical pulse train by a photodetector, and the heterodyne (or beating) experiment between a frequency comb and a continuous wave laser. For the detection of the optical pulse train, we show that photodetection shot noise yields mostly amplitude noise and vanishingly low timing jitter on the electrical signal. Experimental results confirm our theoretical predictions. We then explore the limits of this jitter when considering practical photodetection physics. This reveals a transit time spread parameter that can affect the jitter produced by this conversion. Next, we turn our attention to the heterodyne experiment. We show that the pulsed nature of the frequency comb can be exploited in different schemes to yield higher signal-to-noise ratio (SNR) that is predicted by the use of the beating of a single comb mode with the continuous wave laser. The first technique that we develop, the GATOR, gates out shot noise from the continuous wave, and improves the SNR in the case of low comb power. Using this technique, we have demonstrated a factor of 100 higher SNR than the single-mode limit. We then show a further refinement of the technique which uses chirping of the optical pulse to effectively use all the available photons from the comb in a given bandwidth. This technique enabled us to produce the beating with the highest SNR reported in the literature of 68.3 dB, when normalizing to the common detection bandwidth of 100 kHz.
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Rao, Shanti Raja Libbrecht Kenneth George. "Mirror thermal noise in interferometric gravitational wave detectors /." Diss., Pasadena, Calif. : California Institute of Technology, 2003. http://resolver.caltech.edu/CaltechETD:etd-05092003-153759.
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Mercier, Bertrand. "Développement d'une méthode de mesure de la masse volumique par diffusion Rayleigh appliquée à l'étude du bruit de jets, et contribution à l'étude du screech dans les jets supersoniques sous détendus." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC061/document.
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Dans ce travail de recherche, on présente des développements spécifiques de diagnostiques optiques et leur application à l’étude aéroacoustique des jets rapides à haut nombre de Reynolds. Les résultats expérimentaux présentés ici résultent de visualisation par strioscopie et, de manière prépondérante dans ce manuscrit, de mesure de masse volumique par diffusion Rayleigh. Ces méthodes de caractérisation d’écoulement, appliquées aux jets subsoniques ou supersoniques, ont été associées à des mesures de bruit en champ lointain. La mesure par diffusion Rayleigh, qui repose sur la lumière diffusée par les molécules constituantes du gaz, et n’est donc pas intrusive. Des difficultés apparaissent néanmoins pour exploiter les résultats lorsque le milieu diffusant contient des poussières. Bien que l’air des écoulements obtenu en soufflerie soit filtré, la quantité résiduelle de poussières a rendu nécessaire le développement d’une méthode de nettoyage du signal en post-traitement. Le niveau des signaux obtenus par diffusion Rayleigh est très faible, et dominé par du bruit appelé shot noise. Un gain significatif sur le niveau de ce bruit a été obtenu en optimisant la chaîne d’acquisition après analyse des systèmes existants. De plus une méthode de traitement du signal dérivée d’une méthode existante a permis de calculer des spectres de masse volumique malgré le shot noise avec un seul capteur, là où il en fallait deux auparavant. Les profils de p obtenus par cette technique ont montré qu’il existe une loi de similarité permettant de superposer les profils mesurés à différentes positions axiales. Cette loi est identique pour les jets issus de trois tuyères aux géométries différentes, et à des nombres de Mach de 0.7 et 0.9. Une loi de similarité est également observée pour p’rms si les profils sont mesurés suffisamment loin de la tuyère. L’étude des spectres dans la couche de mélange a mis en évidence un maximum faiblement marqué autour d’une fréquence centrale comprise entre St = 0:2 et St = 2 dans les régions mesurées, plus marqué que dans les spectres de vitesse, et dont le comportement diffère selon l’état initialement laminaire ou turbulent du jet. L’évolution de la forme des spectres en fonction de la différence de masse volumique entre le jet et le milieu ambiant, ainsi qu’en fonction du nombre de Mach, a également été étudiée. Une loi permettant de superposer les spectres a été définie empiriquement sur la plage de variation des différents paramètres. Des mesures simultanées entre l’acoustique en champ lointain et la masse volumique dans l’écoulement ont été réalisées pour un jet à Mj = 0:9 et un jet à Mj = 1:32. Ces résultats ont permis l’estimation de cohérences spectrales et de moyennes conditionnelles. Les résultats obtenus mettent en évidence la présence de structures liées au rayonnement acoustique dans une région située proche de l’axe du jet en aval du cône potentiel. Pour finir, une étude a été réalisée sur le screech dans les jets supersoniques sous-détendus. Elle a permis d’identifier la position de la source de la rétroaction acoustique pour les modes A1, A2, et B, ainsi que la structure du cycle de la boucle qui détermine les changements de fréquences observés aux sauts de modesIn this research study, developments of optical diagnosis techniques are presented, and are put into practice in an aeroacoustics study of high speed and high Reynolds jets. The results described here are obtained from Schlieren visualization, and in the majority from density measurements through Rayleigh scattering. These measurement methods are applied for subsonic and supersonic jets, and associated with far field acoustics measurements. Rayleigh scattering measurements rely on laser light scattered by the molecules constituting the flow, thus they are non-intrusive. However, some difficulties in interpreting the results arise when the flow contains dust particles. This problem is partly solved by using air filters in the wind tunnel, but some residual dust particles remain, thus a software based signal cleaning method has been developed and is applied to the signals during post-processing. Besides, the signals obtained from Rayleigh scattering are very weak, and dominated by a shot noise. The noise level has been significantly reduced following the optimization of the chain of acquisition in comparison with actual apparatus. Moreover, a method to compute spectra despite the shot noise level has been adapted from a classic method to be usable with a single sensor instead of two. The analysis of radial profiles of density measured with the Rayleigh scattering apparatus shows that a similarity law allows to superimpose radial profiles measured in jets exhausted from three different nozzles at Mach 0.9 and Mach 0.7. Another similarity law is observed for radial profiles of 0 rms when they are measured far enough form the nozzle. The analysis of density spectra in the mixing layer points out the presence of a local maximum of central frequency found between St = 0:2 and St = 2 depending on the probed location, which is not as clearly observed in velocity spectra. The spatial evolution of this maximum is found different whether the flow is initially laminar or turbulent at the nozzle exit. The dependence of spectra to the Mach number, and to the difference of density between the jet and the surrounding is also studied. A scaling law is empirically determined for the scope of the study. Simultaneous measurements of density and farfield acoustic acquired in a Mach 0.9, and a supersonic ideally expanded Mach 1.32 jets are processed to obtain coherence, and conditional averaging. The results emphasis the role of large structures downstream the end of the potential core in acoustic radiations. Finally, the screech in underexpended jets is studied. This work results in the identification of the acoustic feedback source location for A1, A2 and B modes, and in the characterization of the changes in the loop structure associated with mode switching
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Steininger, Daniel [Verfasser], and Christoph [Akademischer Betreuer] Strunk. "Shot Noise Detection in Carbon Nanotube Quantum Dots / Daniel Steininger ; Betreuer: Christoph Strunk." Regensburg : Universitätsbibliothek Regensburg, 2017. http://d-nb.info/113281328X/34.
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McKenzie, Kirk. "Experimental demonstration of a gravitational wave detector configuration below the shot noise limit." View electronic text, 2002. http://eprints.anu.edu.au/documents/disk0/00/00/04/63/index.html.
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Thesis (BSc. (Hons))--Australian National University, 2002.Title from title screen (viewed July 31, 2002). Available via the Australian National University Library Electronic Pre and Post Print Repository.
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Hutton, Jane Louise. "Non-negative time series and shot noise processes as models for dry rivers." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38044.
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Steininger, Daniel Verfasser], and Christoph [Akademischer Betreuer] [Strunk. "Shot Noise Detection in Carbon Nanotube Quantum Dots / Daniel Steininger ; Betreuer: Christoph Strunk." Regensburg : Universitätsbibliothek Regensburg, 2017. http://nbn-resolving.de/urn:nbn:de:bvb:355-epub-356719.
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Slagmolen, Bram Johannes Jozef, and BRAM SLAGMOLEN@ANU EDU AU. "Direct Measurement of the Spectral Distribution of Thermal Noise." The Australian National University. Faculty of Science, 2005. http://thesis.anu.edu.au./public/adt-ANU20051128.104552.
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This thesis investigates the direct measurement of the thermal noise spectral distribution.
Long base line gravitational wave detectors, being commissioned around
the world, are limited in sensitivity in the intermediate frequencies by the thermal
noise. These detectors are utilising suspended test mirrors for the detection of gravitational
waves by measuring their relative displacement. One of the fundamental
noise sources in these detectors is the thermally induced displacement of the suspension
onto and within the mirrors. This thermally induced motion of the test mirrors
limits the displacement sensitivity of the gravitational wave detectors. Knowledge
of the spectral behavior of thermal noise over a wide frequency range will improve
predictions and understanding of the behavior of the suspension and test mirrors.¶
In this thesis the direct measurement of the thermal noise spectral distribution
of a mechanical flexure resonator is described. The mechanical flexure resonator is
an unidirectional ’wobbly table’ made from copper-beryllium, which hinges around
four thin flexures 15 mm wide, 1 mm high and ~116 µm thick. The mechanical
flexure resonator has a resonant frequency of 192 Hz, with a quality factor of ~3000.¶
The thermal noise induced displacement of the mechanical flexure resonator was
measured using an optical cavity. The end mirror of a two mirror optical cavity was
mounted on the mechanical flexure resonator. A laser was made resonant with the
test cavity by use of a locking control system. Thermal noise induced displacement
moved the test cavity away from resonance. By measuring the error-signal in the
control system, the equivalent thermal noise displacement was obtained.¶
The thermal noise induced displacement of the mechanical flexure resonator was
predicted to be in the order of 10^(−12) to 10^(−17) m/sqrtHz over a frequency range of
10 Hz to 10 kHz. All other external noise sources needed to be suppressed to below
this level. A major noise source was the laser frequency fluctuations. When the
test cavity was locked to the laser, the laser frequency fluctuations dominated the
read out signal. To suppress the frequency fluctuations, the laser was locked to a
rigid long optical reference cavity. This allowed the frequency fluctuations to be
suppressed to below the equivalent thermal noise displacement of the test cavity
over the frequency range of interest.¶
Acoustic noise was suppressed by placing the whole experiment inside a vacuum
chamber, and evacuating the air inside the chamber down to a pressure level of
10^(−4) mbar. A seismic vibration isolation system was used to suppress the seismic
noise in the laboratory to below 10^(−14) m/sqrtHz at frequencies above 4 Hz.¶
With the experimental set up, the thermal noise displacement of the mechanical
flexure resonator has been measured. Due to the degradation of the isolator performance,
measurement of the thermal noise behavior over a wide frequency range of
the mechanical flexure resonator was unsuccessful. By using an analytical curve fitting
routine around the fundamental and first order resonant modes of the resonator,
a loss factor of (3.5 ± 1.5 − 3.7 ± 1.5) × 10^(−4) for the copper-beryllium mechanical
flexure resonator was obtained and structural damping was inferred.
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Slagmolen, Bram Johannes Jozef. "Direct measurement of the spectral distribution of thermal noise /." View thesis entry in Australian Digital Theses Program, 2004. http://thesis.anu.edu.au/public/adt-ANU20051128.104552/index.html.
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RANGASWAMY, KASTURIRANGAN. "INFLUENCE OF IMAGE FORCE POTENTIAL ON THE SHOT NOISE PROPERTIES OF PLANAR COLD CATHODES." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1113877019.
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Amato, Alex. "Low Thermal Noise Coating for New Generation Gravitational-Wave Detectors." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1245.
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Le travail de thèse consiste en l'étude des propriétés mécaniques et optiques de couches minces (principalement déposées par IBS au LMA), dans le but de réduire le bruit thermique des miroirs des détecteurs des ondes gravitationnelles (GWDs) actuels et futurs. La caractérisation mécanique effectuée au LMA concerne les mesures de frottement interne et de constantes élastiques par la méthode de "ring-down" utilisant un système de suspension nodale (GeNS). La caractérisation optique a été réalisée à l'aide de l'ellipsométrie spectroscopique (SE). Grâce à une collaboration avec l'OPTMATLAB de l'Université de Gênes, j'ai pu caractériser les échantillons par SE pour une large gamme d'énergie (des NIR aux UV). Les premiers échantillons analysés sont les couches actuellement utilisées dans les GWDs: SiO2, Ta2O5 et Ti:Ta2O5. Ensuite, Nb2O5, Nb:TiO2, Zr:Ta2O5, SiC et SiNx ont été caractérisés en tant que matériaux à haute indice de réfraction, tandis que MgF2 et AlF3 ont été étudiés pour remplacer le matériau à bas indice afin de réduire l'épaisseur totale du revêtement et donc le bruit thermique. Parmi les couches étudiées, Zr:Ta2O5 et SiNx ont fourni les résultats les plus prometteurs en terme de dissipation. Des résultats importants ont été obtenus concernant la théorie de la dissipation dans les oxydes et lors de la caractérisation optique et mécanique des échantillonsThe work of this thesis is the study of mechanical and optical properties of coatings (mainly deposited by IBS technique at LMA), with the purpose of finding a new possible material with the aim of reduce the coating thermal noise in current and in future gravitational-wave detectors (GWDs). The mechanical characterization done at LMA regards measurements of internal friction and elastic constants by the ring-down method using a Gentle Nodal Suspension (GeNS) system. The optical characterization has been done using spectroscopic ellipsometry (SE). Thanks to a collaboration with the OPTMATLAB of the University of Genova, I was able to characterize the samples using SE in a wide-range energy region (from UV to NIR). The first analysed samples are the coatings currently used in GWDs, SiO2, Ta2O5 and Ti:Ta2O5. Then, Nb2O5, Nb:TiO2, Zr:Ta2O5, SiC and SiNx have been characterize as high-refractive index coatings, whereas MgF2 and AlF3 have been studied with the purpose of replace the low-refractive index, reducing the total coating thickness, hence the coating thermal noise. Among the investigated coatings, Zr:Ta2O5 and SiNx provided the most promising results in term of internal friction. Important finding have been achieved regarding the theory of the internal friction of amorphous oxides and the optical and mechanical characterization of the samples
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Silva, Erick Rodrigues. "Simetrias de paridade e de reversão temporal no Efeito Hanbury Broen-Twiss." Universidade Federal da Paraíba, 2015. http://tede.biblioteca.ufpb.br:8080/handle/tede/8164.
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The Hanbury Brown-Twiss experiment is very well established in quantum optics literature, so we devoted this dissertation in order to embed the parity and temporal reversal symmetry in the former experiment. Therefore, we developed the scattering matrix formalism which allow us use some techniques such as the scattering matrices' concatenation of di erent sections in terms of one matrix and the scattering problem of a parity and temporal reverse symmetric system. In this manner, we could derive the scattering matrix of a parity and temporal reverse symmetric Hanbury Brown- Twiss experiment(HBT-PT). With the possession of this matrix, we proposed a theoretical model which provides how to measure the symmetry of this system, which we called correlation functions formalism. In order to stablish the former formalism, we studied B uttiker formalism, which we veri ed how the correlation between 2 incident particles in a system relates to the noise due transport of this particles and what kind of noise we are treating in a given regime which the system is operating. Then, we found the input states in terms of the output states of two particles inciding in a multiterminal system, which we used it's scattering matrix to stablish the relation between the states. Thereat, we derived all the possibles correlations(therefore, the noise) of two incident particles in the former system. Thereby, we analysed the extreme cases of a barrier coupled to the HBT-PT experiment for the purpose of stablish which regime the experiment is symmetric adjusted, so, demonstrating the Hanbury Brown-Twiss E ect with parity and temporal reverse symmetries.
Sendo o experimento Hanbury Brown-Twiss bem estabelecido na literatura da otica quântica, dedicamos esta dissertação a embutir no mesmo experimento a questão da simetria por paridade e reversão temporal. Para tanto, abrimos mão do formalismo da matriz de espalhamento que permitiu nos utilizar tecnicas como a concatenação de matrizes de espalhamento de sec ções diferentes em termos de apenas uma matriz e o problema do espalhamento em um sistema simétrico por paridade e reversão temporal. Dessa forma, pudemos derivar a matriz de espalhamento para o experimento Hanbury Brown-Twiss com simetria de paridade e revers~ao temporal(HBT-PT). De posse dessa matriz, propusemos um modelo teórico que propicia a medição experimental a simetria desse sistema, o qual chamamos de formalismo das fun c~oes de correla c~ao. Para estabelecermos o formalismo supracitado, estudamos o formalismo de Buttiker, onde veri case como a correlaçãao entre 2 partículas incidentes em um sistema relaciona-se com o ru do devido ao transporte dessas part culas e que tipo de ru do estamos tratando, dado o regime em que o sistema está operando. Em seguida, encontramos os estados de entrada em termos dos estados de saída de 2 partículas incidindo em um sistema multiterminal, onde utilizamos a sua matriz de espalhamento para estabelecer a rela c~ao entre os estados. Com isso, derivamos todas as possíveis correlações (e, por conseguinte, o ruído) de 2 partículas incidentes nesse sistema. Assim, analisamos os casos extremos de uma barreira acoplada ao experimento HBT-PT, a m de estabelecer o regime em que o experimento está simetricamente ajustado e demonstramos o Efeito Hanbury Brown-Twiss por paridade e reversão temporal.
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Cornwell, William David. "On the characterisation of interferometric noise in optical networks." Thesis, University of Strathclyde, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327304.
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Leonhardt, Volker. "Displacement measurements on suspended mirrors for off-resonant thermal noise detection." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=971220948.
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Burtzlaff, Andreas [Verfasser]. "Shot noise measurements at single atom contacts in a low-temperature scanning tunnelling microscope / Andreas Burtzlaff." Kiel : Universitätsbibliothek Kiel, 2017. http://d-nb.info/1136903283/34.
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Mohrmann, Jens [Verfasser], and H. von [Akademischer Betreuer] Löhneysen. "Quantum Transport and Shot Noise in Graphene-Boron Nitride Heterostructures / Jens Mohrmann ; Betreuer: H. von Löhneysen." Karlsruhe : KIT-Bibliothek, 2016. http://d-nb.info/1114273538/34.
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Savas, Serdar. "Monitoring Variation Of Surface Residual Stresses In The Shot Peened Steel Components By Magnetic Barkhausen Noise Method." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612183/index.pdf.
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Shot peening is a cold-working process by which residual compressive stresses are being induced in the surface region to increase the fatigue strength and the resistance to stress-corrosion cracking. This study covers non-destructive measurement of surface residual stresses in the shot-peened steel components by a micro-magnetic technique, named as Magnetic Barkhausen Noise (MBN) method. For this purpose, various low alloy steel specimens were prepared by a controlled shot peening process with different intensity, impact angle and coverage values. The measurements showed that a clear relationship exists between residual stresses and the MBN signals. Residual stress values determined by MBN technique were also verified by X-ray diffraction measurements.
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Thielmann, Axel [Verfasser]. "Co-tunneling current and shot noise in molecules and quantum dots / Forschungszentrum Karlsruhe GmbH, Karlsruhe. Axel Thielmann." Karlsruhe : FZKA, 2005. http://d-nb.info/977173488/34.
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Rolf, Daniela [Verfasser]. "Fundamental Properties of Atoms and Molecules on Surfaces : a Combined STM and Shot-Noise Study / Daniela Rolf." Berlin : Freie Universität Berlin, 2019. http://d-nb.info/1176637126/34.
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Rundström, Per. "Thermal Properties of a 5G Telecom Equipment Casing Design for Noise Suppression." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299742.
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Around the world the implementation of the 5G mobile network is under way. With this latest generation of mobile data transfer comes many advantages compared to the previous generations. One tradeoff however is the reduced range of the transmitting radios due to the higher frequencies of the signal. One way to solve this is to place smaller radios closer to where the user is. This work studies one such radio and since it is cooled by fans and meant to be placed close to where people live and reside it is favorable to be able to reduce the noise transmitted to its surrounding. This work has therefor developed a proof of concept for a noise suppressing casing that accommodates three radios in order to reduce the total A-weighted sound power level that reaches its surrounding. This was done by using ducts with micro-perforated plates (MPPs) as a sound dampening element. To assist in the design process as well as to verify that placing the radios inside the casing did not raise the temperature of the radio’s component beyond acceptable levels a CFD-simulation was performed. The results of the CFD-simulations were also verified using an experiment where the radio’s temperature was recorded during different fan speeds. When measured, the casing lowered the total A-weighted sound power level of three radios by between 11.6 dB(A) and 14.2 dB(A) depending on the fan speed. The result of the thermal experiment show that the temperature was raised by between 2.8 °C and 5.9 °C depending on the fan speed, with higher fan speeds showing less difference when compared to the radio’s standalone performance. The results are deemed to show promise for the future use of casings fitted with Micro-perforated plates being used to reduce the noise transmitted by telecom radios.Runt om i världen pågår implementeringen av 5G-mobilnätet. Med den senaste generationens mobila dataöverföring kommer många nya fördelar jämfört med tidigare generationer. En nackdel är däremot den kortare räckvidden hos signalen på grund av den högre frekvens som sänds ut av radion. Ett sätt att kringgå detta är att placera mindre radior närmare där användaren befinner sig. Detta examensarbete utgår från en sådan radio och eftersom den kyls med fläktar och ska placeras nära där människor bor och vistas är det fördelaktigt att kunna sänka ljudet som når omgivningen. Därför har ett ljudisolerande hölje utvecklats med plats för tre telekomradior med syfte att sänka den totala A-vägda ljudeffektnivån som når dess omgivning. För att åstadkomma detta användes kanaler i kombination med mikroperforerade plåtar (MPPs) tillsammans som ett ljuddämpande element. Som ett verktyg i designprocessen och för att säkerställa att radions komponenter inte blev för varma gjordes en CFD-simulering. Resultatet av simuleringen verifierades även med ett experiment där temperaturen hos radions kylflänsar mättes under olika fläktvarvtal. När den totala A-vägda ljudeffektnivån mättes för höljet tillsammans med tre radior uppstod en sänkning med mellan 11,6 dB(A) och 14,2 dB(A) beroende på aktuellt fläktvarvtal. Resultatet från experimentet visade även att temperaturen på radions kylfläns höjdes med mellan 2,8 och 5,9 °C beroende på fläktvarvtal, med mindre skillnad för högre fläktvarvtal vid jämförelse med radions temperatur vid drift utan hölje. Resultaten anses visa på den goda potentialen av att använda höljen utrustade med mikroperforerade plåtar för att minska överfört ljud från telekomradior.
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Coillet, Élodie. "Structural characterization of thin non-crystalline layers for low thermal noise optic." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1132/document.
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Prédites en 1916 par Albert Einstein, puis détectées 100 ans plus tard par les collaborations LIGO et VIRGO, les ondes gravitationnelles constituent un outil prometteur pour observer l’univers sur des échelles toujours plus grandes. Cependant, pour accéder à de plus nombreux évènements, une des principales limitations des détecteurs provient du bruit thermique des couches minces composant leurs miroirs, couches minces non cristallines de SiO2 et Ta2O5 dopé TiO2.L’objectif de ce travail est d’étudier l’origine microstructurale du bruit thermique de ces couches en utilisant les spectroscopies vibrationnelles pour, à terme, obtenir des matériaux plus performants. Il a notamment été observé que le bruit thermique diminue lorsque les miroirs sont recuits à faible température. Dans la silice, nous observons une restructuration du matériau lors du recuit qui semble suivre la diminution du bruit thermique. En particulier, un relâchement des contraintes a été constaté. En revanche, dans le Ta2O5, matériau de structure complexe et encore mal connue, l’effet du recuit sur la structure des couches apparaît plus limité, alors que celles-ci cristallisent facilement dès que la température augmente. Pour compléter la connaissance de ce matériau, des mesures in-situ hautes pressions ont été réalisées. Finalement, le rôle du dopage des couches de Ta2O5 par du TiO2 a été exploréPredicted in 1916 by Einstein, then detected one hundred year later by the VIRGO and LIGO collaborations, the gravitational waves are a promising tool to observe the universe at scales always bigger. However, to detect a larger number of events, one of the main limitation of the detectors originates in the mirrors coatings thermal noise, thin non-crystalline layers composed of SiO2 and TiO2-doped Ta2O5. The aim of this work is to study the micro-structural origin of the layers thermal noise, by using vibrational spectroscopies, in order to, ultimately, process more efficient materials. Studies show a decrease of the thermal noise when the mirrors are annealed at low temperature. In silica, a structural reorganization happens during the annealing, following the evolution of the thermal noise. Notably, a stress relaxation has been observed. However, in Ta2O5, oxide with a complex structure not much studied, the impact of the annealing seems to be more limited, while the structure crystallizes easily as soon as the temperature increases. To complete our knowledge of this structure, in-situ high pressure measurements were conducted. Finally, the TiO2-doping effect of the Ta2O5 structures was studied
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Bastos, Ivan Iuri Alves. "A MOSFET-only wideband LNA exploiting thermal noise canceling and gain optimization." Master's thesis, Faculdade de Ciências e Tecnologia, 2010. http://hdl.handle.net/10362/4867.
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Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para a obtenção do grau de Mestre em Engenharia Electrotécnica e de ComputadoresIn this thesis a MOSFET-only implementation of a balun LNA is presended. This LNA is based on the combination of a common-gate and a common-source stage with canceling of the noise of the common-gate stage. In this circuit, resistors are replaced by transistors, to reduce area and cost, and minimize the e ect of process and supply variations and mismatches. In addition we obtain a higher gain for the same voltage drop. Thus, the LNA gain is optimized, and the noise gure(NF) is reduced. We derive equations for the gain, input matching, and NF. The performance of this new topology is compared with that of a conventional LNA with resistors. Simulation results with a 130 nm CMOS technology show that we obtain a balun LNA with a peak 20.2 dB gain (about 2 dB improvement), and a spot NF lower than 2.4 dB. The total power consumption is only 4.8 mW for a bandwidth wide than 5 GHz.
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Daniel, Kyle Andreas. "Space-time Description of Supersonic Jets with Thermal Non-uniformity." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/95942.
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The supersonic jet plumes that exhaust from the engines of tactical aircraft produce intense noise signatures that expose the Navy personnel working on the deck of aircraft carriers to dangerously high levels of noise that often results in hearing damage. Reducing the noise radiated by these supersonic plumes is of interest to the Department of Defense and is the primary motivation of this research. Fundamentally, jet noise reduction is achieved by manipulating the nozzle boundary condition to produce changes in the turbulence development and decrease the acoustic efficiency of coherent structures. The research presented here focuses on a novel jet noise reduction technique involving a centered thermal non-uniformity that alters the base flow by introducing a temperature-driven centerline velocity deficit into a perfectly expanded Mach 1.5 jet. The results indicate $2 pm 0.5$ dB reductions in peak narrowband spectral sound pressure levels upstream of peak directivity directions for the non-uniform jet compared to a thermally uniform baseline, even for static thrust matched conditions. This reduction is hypothesized to be related to perturbations induced by the thermal non-uniformity that convect inside the irrotational core and reduce the correlation length scales of turbulence at locations far downstream. This hypothesis was evaluated by studying the coherent turbulence via its convective hydrodynamic footprint in the near-field. An indirect investigation of the near-field using a far-field-informed model of the wavenumber-frequency spectra indicate a reduction in the energy contained in the tail of the wavenumber spectra amplitude, suggesting a reduction in the size of large scale structures. A direct evaluation of the spatio-temporal behavior of the near-field was performed using temporally resolved schlieren images. Space-time correlations of the frequency-filtered near-field identified high frequency acoustic waves radiated by compactly coherent turbulent structures and low frequency Mach waves produced by large scale instabilities. In the thermally non-uniform case these features and their sources were found to be decorrelated at downstream regions. These results provide strong evidence that a centered thermal non-uniformity reduces the radiated noise compared to a uniform baseline by shortening the correlation length scales of coherent structures in regions far from the nozzle exhaust.Doctor of Philosophy
A more complete understanding of the intense noise sources present in supersonic jet plumes is of value to both government and industry, and is a necessary step towards optimizing noise reduction techniques. Tactical aircraft that operate on the deck of aircraft carriers expose Navy personnel to dangerously high levels of noise that often results in permanent hearing damage. Supersonic jet noise reduction is also of relevance to the recent efforts to revitalize supersonic air transport over land. For supersonic air transport to become a reality, the noise produced by these future aircraft during takeoff and landing must meet the increasingly stringent community noise requirements. Fundamental jet noise research is needed to guide the design of future engine architectures for these aircraft to ensure their commercial success. The research presented herein examines a novel noise reduction technique that involves a centered thermal non-uniformity consisting of a heated jet plume with a spot of locally cooler, slower moving air concentrated along the centerline of a Mach 1.5 jet. This temperature driven velocity deficit is shown to reduce the radiated noise by up to 2.5 dB at peak frequencies and at angles just outside of the peak directivity direction. The cause of the noise reduction is hypothesized be related to a reduction in the size of the coherent structures that radiate a majority of the noise produced by turbulent jets. This hypothesis is evaluated by examining the 'footprint' of the coherent structures in the ambient field directly outside of the jet shear layer in an area called the near-field. An indirect investigation of the near-field using a far-field informed analytic model suggests a reduction in the size of large scale structures. A direct evaluation of the space time structure of the near-field was performed using temporally resolved schlieren images. Statistical processing of the density gradient provided by the schlieren images revealed acoustically intense structures known as Mach waves and high frequency acoustic waves. These features and their sources, large scale instabilities and compactly coherent turbulence, were found to be decorrelated by the introduction of the thermal non-uniformity. These results provide strong evidence that the centered thermal non-uniformity produces a noise benefit by reducing the size of the turbulent structures.
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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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Vaidya, Nikhilesh Avanish. "NOISE SPECTRUM OF A QUANTUM POINT CONTACT COUPLED TO A NANO-MECHANICAL OSCILLATOR." Diss., Temple University Libraries, 2017. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/447885.
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PhysicsPh.D.
With the advance in nanotechnology, we are more interested in the "smaller worlds". One of the practical applications of this is to measure a very small displacement or the mass of a nano-mechanical object. To measure such properties, one needs a very sensitive detector. A quantum point contact (QPC) is one of the most sensitive detectors. In a QPC, electrons tunnel one by one through a tunnel junction (a "hole"). The tunnel junction in a QPC consists of a narrow constriction (nm-wide) between two conductors. To measure the properties of a nano-mechanical object (which acts as a harmonic oscillator), we couple it to a QPC. This coupling effects the electrons tunneling through the QPC junction. By measuring the transport properties of the tunneling electrons, we can infer the properties of the oscillator (i.e. the nano-mechanical object). However, this coupling introduces noise, which reduces the measurement precision. Thus, it is very important to understand this source of noise and to study how it effects the measurement process. We theoretically study the transport properties of electrons through a QPC junction, weakly coupled to a vibration mode of a nano-mechanical oscillator via both the position and the momentum of the oscillator. %We study both the position and momentum based coupling. The transport properties that we study consist of the average flow of current through the junction, given by the one-time correlation of the electron tunneling event, and the current noise given by the two-time correlation of the average current, i.e, the variance. The first comprehensive experimental study of the noise spectrum of a detector coupled to a QPC was performed by the group of Stettenheim et al. Their observed spectral features had two pronounced peaks which depict the noise produced due to the coupling of the QPC with the oscillator and in turn provide evidence of the induced feedback loop (back-action). Benatov and Blencowe theoretically studied these spectral features using the Born approximation and the Markovian approximation. In this case the Born approximation refers to second order perturbation of the interaction Hamiltonian. In this approximation, the electrons tunnel independently, i.e., one by one only, and co-tunneling is disregarded. The Markovian approximation does not take into account the past behavior of the system under time evolution. These two approximations also enable one to study the system analytically, and the noise is calculated using the MacDonald formula. Our main aim for this thesis is to find a suitable theoretical model that would replicate the experimental plots from the work of Stettenheim et al. Our work does not use the Markovian approximation. However, we do use the Born approximation. This is justified as long as the coupling between the oscillator and QPC is weak. We first obtain the non-Markovian unconditional master equation for the reduced density matrix of the system. Non-Markovian dynamics enables us to study, in principle, the full memory effects of the system. From the master equation, we then derive analytical results for the current and the current noise. Due to the non-Markovian nature of our system, the electron tunneling parameters are time-dependent. Therefore, we cannot study the system analytically. We thus numerically solve the current noise expression to obtain the noise spectrum. We then compare our noise spectrum with the experimental noise spectrum. We show that our spectral noise results agree better with the experimental evidence compared to the results obtained using the Markovian approximation. We thus conclude that one needs non-Markovian dynamics to understand the experimental noise spectrum of a QPC coupled to a nano-mechanical oscillator.
Temple University--Theses
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Putyatina, Oleksandra [Verfasser], and Jörn [Akademischer Betreuer] Sass. "Filtering, Approximation and Portfolio Optimization for Shot-Noise Models and the Heston Model / Oleksandra Putyatina. Betreuer: Jörn Sass." Kaiserslautern : Technische Universität Kaiserslautern, 2012. http://d-nb.info/102762698X/34.
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Hall, Neal Allen. "Micromachined Broadband Acoustic Transducers with Integrated Optical Displacement Detection." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4858.
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Micromachined microphones with diffraction-based optical displacement detection are presented. A compliant membrane is made part of a phase sensitive diffraction grating, and the deflection resulting from external acoustic pressure alters the intensities of the diffracted orders which are monitored with integrated photodiodes. The scheme provides the displacement sensitivity of a Michelson interferometer and can be integrated without beam splitters or critical alignment problems into volumes on the order of 1mm³. The method is implemented and characterized using microphone membranes with integrated diffraction grating back electrodes fabricated on silicon using Sandia National Laboratories' dedicated processing platform. Detailed response characterization in both air and vacuum environments is performed to extract the diaphragm properties and high frequency cutoff frequencies of the microphone. Results from a finite element model of the microphone structure are in good agreement with measured data. The sensor's internal noise is characterized with measurements performed in the anechoic acoustic test facility at Georgia Tech. While utilizing 2.4mW of laser power, an (A) weighted displacement resolution of 6×10⁻⁴Å/√Hz is measured which is limited by thermal acoustic noise caused by the microphone's back-plate flow resistance.
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Proctor, Martin J. "Ultrasound power measurement : a microprocessor based device utilising thermal expansion of a total absorber." Thesis, University of Aberdeen, 1987. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU009820.
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A new type of ultrasound power meter is described which is robust, portable, easy to operate and therefore suitable for use in the work place by non-specialist personnel. The device should be of particular value in the field of ultrasonic therapy, where a lack of suitable instrumentation has discouraged performance monitoring of ultrasound machines in the past although numerous surveys have found the calibration of such equipment generally to be poor. The mode of operation is based on absorption of the ultrasound beam within a liquid, which expands as the energy becomes degraded to heat. The rate of this thermal expansion is monitored by means of a capacitative liquid level sensor, the output signal being suitably processsed and passed to a microcomputer for analysis. Correction for interchange of heat with the surroundings is carried out automatically by the micro, by recording the 'background drift' in liquid volume for a few seconds prior to insonation and subtracting this from the expansion rate observed during input of ultrasound. Calibration is achieved by measuring the (corrected) expansion rates brought about by known powers supplied from an electrical heating coil. When using the new power meter for measurements of therapeutic ultrasound the performance compares favourably with that of other techniques: the reproducibility is on the order of 5% above about 0.5W, becoming less good below this (reaching about 20% at the minimum measurable power of 25-50mW). Design modifications which may improve performance at low power levels and possibly allow measurement of dignostic ultrasound are suggested.