To see the other types of publications on this topic, follow the link: Doppler effect.
Dissertations / Theses on the topic 'Doppler effect'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Doppler effect.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Bouras, Bouhafs. "Traitement du signal adapté aux signaux GPS." Valenciennes, 1994. https://ged.uphf.fr/nuxeo/site/esupversions/357ad253-2be4-452d-ad4e-eb2a9e8ef7b6.
Full textAbstract:
Parmi les systèmes de radionavigation existants, GPS est sans doute le plus complet et le plus précis. Il est conçu pour fournir des mesures précises des trois coordonnées d'un navigateur partout dans le monde, et de corriger son horloge dans un repère référentiel. Compare aux autres systèmes de navigation, il fait appel à des traitements du signal plus sophistiques, et qui font des récepteurs GPS plus complexes que d'autres. Notre objectif est de rendre ces récepteurs compétitifs en termes de cout et d'utilisation sans compromettre leurs hautes performances. Dans notre travail sur une unité de traitement GPS, prototype réalisé dans notre laboratoire, de très bonnes performances étaient obtenues sur un signal GPS simule. Des signaux fortement noyés dans le bruit (avec un rapport signal a bruit inferieur a 23 dB) et affectes par le doppler, étaient traites avec succès et la reconnaissance des codes correspondants était établie. Parmi les aspects les plus importants du système réalisé, la haute immunité au bruit des signaux d'asservissement, permettait une opération stable en présence d'un bruit intense, permettant l'acquisition des données de navigation dans de bonnes conditions
2
Ridgway, Andrea Janina. "Ultrasound doppler evaluation of mechanical aortic heart valves." Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/10213.
Full text
3
Ah-Thew, George Patrick. "Doppler compensation for LEO satellite communication systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0005/NQ42831.pdf.
Full text
4
Thomas, Nicholas. "On the application of the Doppler effect in pulsed Doppler flowmeters and the effect of certain propagation and scattering artifacts." Thesis, King's College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297092.
Full text
5
How, Whye Keong. "Automated detection of a crossing contact based on its Doppler shift." Thesis, Monterey, Calif. : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Mar/09Mar%5FHow.pdf.
Full textAbstract:
Thesis (M.S. in Engineering Acoustics)--Naval Postgraduate School, March 2009.Thesis Advisor(s): Kapolka, Daphne ; Rice, Joseph. "March 2009." Description based on title screen as viewed on April 23, 2009. Author(s) subject terms: Automated passive contact detection, Doppler shift, cross correlation, matched filter, velocity estimation, CPA range estimation Includes bibliographical references (p. 99). Also available in print.
6
Newton, Bradley Scot. "Blood flow evaluation using an intracoronary doppler catheter." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/16404.
Full text
7
Moore, Alan D. "Reproducibility and sensitivity of Doppler echocardiographic indices of left ventricular function during exercise." Diss., Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/53648.
Full textAbstract:
The two most common methods used for the assessment of left ventricular function (LVF) are two-dimensional echocardiography and nuclear ventriculography. Recent technological advances have led to the development of an inexpensive, noninvasive alternative: the stand-alone continuous wave Doppler echocardiograph. The purposes cf this study were twofold: 1) to examine the repeatability of three Doppler measured indices of LVF during repeated exercise trials, and 2) to determine if induced changes in myocardial contractility would be reflected by changes in the Doppler indices. The Doppler indices of LVF were the peak acceleration of ascending aortic blood (pkA), peak Velocity of ascending aortic blood (pkV), and the integral of the Velocity-time waveform (SVI). The study was conducted in two phases. In the first phase, 44 young, healthy males performed similar graded cycle exercise tasks on two separate days. Exercise levels were increased by 50 W every three minutes. PkA, pkV, SVI, blood pressure, heart rate and oxygen consumption were recorded every stage. The test was continued until the subject reached symptom-limited maximum. Pearson product-moment correlation coefficients were used to determine the reproducibility of the dependent measures between the two tests.
The second phase involved the testing of a subset of the original 44 subjects (N=18) under a placebo (control) condition, acute beta-blockade, and oral hyperhydration states. Hematocrit was measured as a means to assess blood volume changes. The subjects exercised at levels requiring 20, 40 and 60% of their maximum oxygen consumption. Each stage lasted six minutes. PkA, pkV, SVI, heart rate, blood pressure, cardiac output, and stroke volume were measured. The latter two were determined by a carbon dioxide rebreathing technique. This was a split-plot design with multiple dependent measures. The statistical analysis was a multivariate analysis of variance (MANOVA) with repeated measures. Appropriate univariate tests were utilized as post-hoc procedures.
With respect to the first phase, the correlation coefficients for pkA ranged from 0.54-0.81, for pkV, 0.65-0.77, and for SVI, 0.40-0.71. The results of the second phase indicated that alterations in contractile status by beta-blockade was reflected by changes in the Doppler measures, but the hyperhydration state did not produce a change in cardiac contractile response that was detectable. There were no documented changes in plasma volume as measured by change in hematocrit, therefore, the effectiveness of the hyperhydration procedure was judged ineffective. PkA and pkV were significantly reduced (p<.01) at all stages of exercise in the beta-blocked state as compared to the placebo values. Cardiac output and heart rate were significantly lower in the beta-blocked state, and stroke volume was significantly higher.
The results of this experiment indicates that continuous wave Doppler echocardiographic estimates of LVF are reproducible (r=0.40-0.81) and reflect changes in myocardial contractility induced by acute beta-blockade.Ph. D.
8
Messer, Matthias. "Pulsed ultrasonic doppler velocimetry for measurement of velocity profiles in small channels and capplilaries." Thesis, Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-09022005-131744/.
Full textAbstract:
Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2006.Cyrus K. Aidun, Committee Member ; Farrokh Mistree, Committee Member ; Yves H. Berthelot, Committee Member ; Philip J. W. Roberts, Committee Member. Includes bibliographical references.
9
Hewitt, Charles R. Jr. "Technique for calculating the effect of line doppler shifting on transmitted infrared radiation." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/16620.
Full text
10
Dilsaver, Benjamin Walter. "Experiments with GMTI Radar using Micro-Doppler." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3678.
Full textAbstract:
As objects move, their changing shape produces a signature that can be measured by a radar system. That signature is called the micro-Doppler signature. The micro-Doppler signature of an object is a distinguishing characteristic for certain classes of objects. In this thesis features are extracted from the micro-Doppler signature and are used to classify objects. The scope of the objects is limited to humans walking and traveling vehicles. The micro-Doppler features are able to distinguish the two classes of objects. With a sufficient amount of training data, the micro-Doppler features may be used with learning algorithms to predict unknown objects detected by the radar with high accuracy.
11
de, Paula Abdon B. "An introduction to Doppler effect and fading in mobile communication." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23709.
Full text
12
Zajaczkowski, Maciej. "Fast reactor design with enhanced Doppler Effect : Core design, computer scheme design, uncertainty evaluation." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALI054.
Full textAbstract:
Afin d'améliorer la sûreté passive des réacteurs rapides refroidis au sodium (SFR) en cas de transitoires non protégés, tels que la perte de débit non protégée (ULOF) ou une insertion de réactivité (UTOP), le CEA a proposé le concept CADOR - une nouvelle conception du cœur SFR avec un effet Doppler renforcé. L'une des caractéristiques de conception la plus importante est l’implantation de modérateur dans chaque assemblage combustible pour diminuer l'énergie moyenne des neutrons d'environ 40%. La solution conduit à un effet Doppler environ trois fois plus élevé en raison de l'augmentation de la population de neutrons dans les résonances. D'autre part, le spectre neutronique adouci modifie d'autres propriétés du cœur. Par exemple, le placement hétérogène du modérateur dans l'assemblage peut entraîner une distribution inégale de la vitesse de réaction et un risque de pics de puissance non observés dans les SFR standard. Pour démontrer la sûreté du concept CADOR, il est essentiel d'évaluer d'abord la fiabilité des outils de calcul, à la suite d'un processus de vérification, validation et quantification d'incertitude (VVQI). Les modifications du bilan neutronique remettent en question l'applicabilité des schémas de calcul standards du transport neutronique dans le cadre de ce concept CADOR. Par conséquent, le but de cette thèse est d'établir un schéma de calcul de neutronique précis, conforme aux principes de la VVQI, prenant en compte tous les phénomènes physiques pertinents liés aux propriétés atypiques de CADOR.Un schéma de calcul du code neutronique déterministe APOLLO3 a été défini comme base de l'analyse. Les cœurs CADOR avec deux types de modérateurs différents, beryllium (Be) et hydrure de zirconium (ZrH2), ont été utilisés. Les éléments du schéma et leurs améliorations possibles ont été étudiés par comparaison directe avec le code Monte Carlo de référence TRIPOLI-4. Les biais systématiques des modèles numériques (différentes approches d'homogénéisation spatiale ou de traitement de résonance ascendante, différentes définitions d'énergie et de maillage spatial) ont été étudiés pour la précision de keff, l'effet Doppler et les taux de réactions. Les sources d'incertitudes les plus importantes ont été identifiées et quantifiées. Enfin, comme première estimation de la sensibilité du schéma de calcul multi-physique, l'impact des incertitudes sur les simulations des transitoires UTOP et ULOF a été évalué par couplage avec MACARENa, un code de calcul pour l'analyse transitoire en SFR.Les résultats indiquent que la précision du schéma de calcul peut être améliorée en appliquant un traitement de diffusion exact, notamment en cas de cœur avec ZrH2 où l'utilisation d'un modelé de diffusion simplifié conduit à une sous-estimation de l'effet Doppler jusqu'à 5,2%. Avec un traitement de diffusion exact, le biais global du schéma de calcul d'APOLLO3 a été estimé à environ 500 pcm pour le cœur avec le modérateur Be et 460 pcm pour le cœur avec le modérateur ZrH2. Les biais dans le cas de CADOR sont du même ordre de grandeur que pour les cœurs SFR conventionnels. En conservant une description plus hétérogène de la zone fissile pendant le processus d'homogénéisation, le biais global peut être encore réduit de 110-280 pcm en fonction du niveau d'hétérogénéité étudié ; cependant, cette approche présente l'inconvénient d'une complexité de calcul nettement plus élevée. L'analyse de sensibilité réalisée dans MACARENa suggère que les incertitudes des calculs neutroniques ont un impact mineur sur la progression des transitoires simulés. Ce travail montre que les méthodes disponibles dans APOLLO3 fournissent une bonne précision de calcul des SFR, même dans le cas de conceptions moins conventionnelles. Les faibles incertitudes du schéma de calcul indiquent la robustesse des modèles numériques utilisés; le schéma de calcul offre une précision suffisante pour être appliqué dans la conception des réacteurs rapides et leurs études de sûretéIn order to improve passive safety of Sodium-cooled Fast Reactors (SFR) in case of unprotected transients such as Unprotected Loss of Flow (ULOF) or Unprotected Transient Overpower (UTOP), The French Alternative Energies and Atomic Energy Commission proposed a CADOR concept – a new design of SFR core with enhanced Doppler effect. One of the most important design features is the addition of moderating materials inside fuel assemblies to decrease the average neutron energy by around 40%. The solution leads to roughly three times higher magnitude of Doppler effect due to the increase of resonance neutron population. On the other hand, the softened neutron spectrum changes other core properties. It increases the importance of low-energy neutron scattering and absorption. Moreover, the heterogeneous moderator placement in the assembly may cause an uneven reaction rate distribution and a risk of power peaks not observed in standard SFRs. To demonstrate the safety of CADOR design, it is essential to first evaluate the performance of calculation tools following a Verification, Validation and Uncertainty Quantification (VVUQ) - a process that must be applied to calculation codes and methods to show their reliability. The aforementioned changes in the neutron balance put into question the applicability of standard fast reactor neutronic calculation schemes to the case of CADOR. The purpose of this thesis, therefore, is to establish an accurate neutron transport calculation scheme, in line with VVUQ principles, that takes into account all relevant physical phenomena related to atypical properties of the CADOR core.A two-step calculation scheme of deterministic neutron transport code APOLLO3 was defined as a basis for the analysis. The CADOR cores with two different moderator types, Be and ZrH2, were used. The elements of the scheme and their possible improvements were studied through direct comparison with the reference Monte Carlo code TRIPOLI-4. The systematic biases of numerical models, such as: different spatial homogenization approaches or resonance upscattering treatment, different energy and spatial mesh definitions, were studied with respect to accuracy of multiplication factor, Doppler effect and reaction rates. The most important sources of uncertainties were identified and quantified. Finally, as a first estimation of the sensitivity of the multiphysics calculation scheme, the impact of the uncertainties on simulations UTOP and ULOF transients was evaluated via coupling with MACARENa, a calculation code for transient analysis in SFRs.The results indicate that the accuracy of calculation scheme can be improved by applying exact scattering treatment, notably in case of core with ZrH2 moderator where utilization of simplified scattering kernel leads to underestimation of Doppler effect of up to 5.2 %. With exact scattering treatment the global bias of the calculation scheme of APOLLO3 was estimated at approximately 500 pcm for core with Be moderator and 460 pcm for core with ZrH2 moderator. The biases in case of CADOR are of the same order of magnitude as for conventional SFR designs. By preserving more heterogeneous description of the fissile zone during homogenization process the global bias can be further reduced by 110-280 pcm depending on the studied level of heterogeneity; however this approach has a drawback of significantly higher computational complexity. The sensitivity analysis performed in MACARENa suggests that the uncertainties of neutronic calculations have minor impact on the progression of simulated transients. This work shows that the methods available in APOLLO3 provide a good accuracy of calculation of SFRs, even in case of less conventional designs. The low uncertainties of the calculation scheme indicate robustness of the numerical models used; the calculation scheme provides sufficient accuracy to be applied in fast reactor design and safety studies
13
Mojžíš, Karel. "Ultrazvukový měřič rychlosti toku krve." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-242030.
Full textAbstract:
This master's thesis is concerned with the basis of ultra-acoustics and it explains the application of Doppler effect in medicine as a diagnostic method used for measuring blood flow velocity in blood vessels. The thesis also presents Doppler systems used for diagnostic purposes. It describes the principles of these systems, shows accompanying flowcharts and explains the function of these systems. There is also included the system design of the whole ultrasonic blood flow velocity meter. The system has been designed for the specified parameters with continuous 4 MHz operating frequency, generated intensity of ultrasound 100 mW/cm^2 and diameter D-shaped transmitting transducer 8 mm. In the design of personal solution there are described all the function blocks of the ultrasonic meter. There is also described the choice of appropriate components and designed all the required supply voltages. All the function blocks of the system are experimentally verified. The system has been designed with acoustic intercept and the resultant velocity curves are displayed on software oscilloscope on PC.
14
Michalski, Marcin [Verfasser]. "The rotational Doppler effect and the rotational frequency shift / Marcin Michalski." Ulm : Universität Ulm. Fakultät für Naturwissenschaften, 2004. http://d-nb.info/1015439160/34.
Full text
15
Ruo, Jeanny Bin-chin. "In vitro continuous monitoring of cardiac output using ultrasound doppler in pulsatile flow." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/10224.
Full text
16
Ferreira, Neto Pedro Pires. "Analise da dopplervelocimetria feto-placentaria em gestantes hipertensas e resultados perinatais segundo a idade gestacional." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/308231.
Full textAbstract:
Orientador: Anibal FaundesTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas
Made available in DSpace on 2018-08-08T03:02:55Z (GMT). No. of bitstreams: 1 FerreiraNeto_PedroPires_D.pdf: 756822 bytes, checksum: 391b94a37ae61d1eb12c2c4f4b8aeacb (MD5) Previous issue date: 2006
Resumo: Objetivo: Avaliar a capacidade dos índices de pulsatilidade das artérias umbilical e cerebral média e a relação do índice de pulsatilidade umbilico-cerebral em fetos de gestantes hipertensas de predizer risco de resultados perinatais adversos de acordo com a idade gestacional. Métodos: No período de janeiro de 2000 a agosto de 2004 foi realizada a avaliação dopplervelocimétrica dos índices de pulsatilidade da artéria umbilical (IPAU), da artéria cerebral média (IPACM) e da relação do índice de pulsatilidade umbilical/cerebral (IPAU/IPACM) de 289 gestantes com hipertensão artérial, com idade gestacional entre 24 a 41 semanas de gestação. Os resultados doplervelocimétricos que apresentaram IPAU acima do percentil 95 ou fluxo diastólico ausente ou reverso, IPACM abaixo do percentil 5 e relação IPAU/IPACM acima do percentil 95, foram avaliados quanto à capacidade de prever resultados perinatais adversos (Apgar do 5º minuto < 7, recém-nascido pequeno para a idade gestacional (RN PIG), ocorrência da doença da síndrome do desconforto respiratório (SDR), ocorrência da síndrome hipóxico-isquêmica (SHI) e óbito perinatal. Estes resultados foram comparados entre si sem ajuste e com ajuste pela idade gestacional no parto. Resultados: Os resultados alterados da dopplervelocimetria não estiveram associados ao risco de Apgar do 5º minuto < 7, antes de ajustar por idade gestacional. Com o ajuste, o risco aumentou. Entretanto, apenas a associação com alteração do IPAU alcançou significação estatística. O risco de ocorrência de recém-nascido PIG aumentou entre cinco e sete vezes na análise sem ajuste e em torno de três vezes na análise ajustada, e foi estatisticamente significativa para todos os parâmetros da dopplervelocimetria estudados. O risco de SHI aumentou entre duas e cinco vezes antes do ajuste. O aumento do risco ajustado foi significativo apenas para IPAU e relação IPAU/IPACM. Quanto ao risco da SDR houve aumento de duas a seis vezes na análise sem ajuste, mas na análise ajustada não houve aumento. Na análise da mortalidade perinatal o risco não ajustado foi entre três e dez vezes maior, nos casos com alteração do IPAU, IPACM e na relação IPAU/IPACM. Na análise ajustada apenas o IPAU alterado apresentou associação com risco quase três vezes maior e foi estatisticamente significativo. Conclusão: Neste grupo selecionado de gestantes hipertensas, a análise isolada do IPAU apresentou melhor correlação com os resultados perinatais do que a análise do IPACM ou da relação IPAU/IPACM, particularmente quando a análise foi feita com o ajuste da idade gestacional
Abstract: Objetive: To evaluate the capacity of the pulsatility Index of the umbilical artery and of the median cerebral artery and of the umbilical/cerebral ratio to predict adverse perinatla outcomes. Métodos: Dopplervelocimetric evaluation of the pulsatility Index of the umbilical artery (IPAU) and of the Median cerebral artery (IPACM) and of the umbilical/cerebral ratio (IPAU/IPACM) was carried out 289 pregnant women with hypertension at 24 through 41 weeks of gestation. Abscent or reverse diastolic flux and, IPAU above the 95 percentil, IPACM below percentil 10 and IPAU/IPACM ratio over the 95 percentil were evaluated in relation to its associasaion with adverse perinatal outcomes (5 minutes Apgar score < 7, small for gestational age (PIG), hialine membrane disease (DMH), hipoxic ischemic syndrome (SHI) and perinatal death. These results were compare before and after adjustment by gestational age at birth. Results: Abnormal Doppler results were not associated with the risk of 5 minutes Apgar score < 7 before adjustment by gestational age. After adjustment the risk increased, but only adnormal IPAU was significantly associated with. 5 minutes Apgar score < 7. The risk of PIG was 5 to 7 times higher before adjustment and arround 3 times and significantly higher after adjustment in cases with alterations in any of the three Doppler indicators studied. The risk of SHI was increased between 2 and 5 times before adjustment, but after adjustment the risk was significantly higher when the IPAU and the IPAU/IPACM ratio were adnormal. The risk DMH appeared to be between 2 and 6 times higher before adjustment, but became insignificant for the three indicators after adjustment. The risk of perinatal death before adjustment was between 3 and 10 times higher in cases with alteration in the IPAU, IPACM and the IPAU/IPACM ratio. After adjustment, only adnormal IPAU was associated with a three folds increase risk, that was statistiocally significant. Conclusion: In this selected group of preganat women with hypertension the isolated analysys of IPAU showed the best correlation with adverse perinatal outcomes, particularly after adjustment by gestational age
Doutorado
Tocoginecologia
Doutor em Tocoginecologia
17
Rana, Shaikh Masud. "A Study of Multipath Propagation and Doppler Effect at 24GHz ISM band." Thesis, Högskolan i Gävle, Elektronik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-34066.
Full textAbstract:
The wideband channel has been analyzed at the University of Gävle by using millimeter-wave (mm-Wave) frequency for improving the fifth-generation (5G) in Radio-frequency (RF) characterization. The proposed mm-Wave frequency is 24GHz, which is carried out from measurement testbed at the Robotics Lab. To explore the channel behaviors of the ISM band and mobile radio, three typically environments have been created inside of the Robotics Lab at the University of Gävle in which are Higher reflection (HR), natural reflection (NR), and Ultra reflection (UR). The relative motion of the transmitter (Tx) is carried out by adjoining the omnidirectional antenna to a KUKA robot's arm inside the Robotics lab at the University of Gävle, Sweden. The radio channel behavior is observed at different circumstances with two different movements of KUKA’s arm e.g., higher speed (2m/s) and slower speed (1m/s) for the Line of sight (LOS) and Non-Line of sight (NLOS) condition. We then achieve the time-varying power delay profile (PDP) and frequency-varying Doppler spectral density (DSD) from scattering components of the experiment environment. The Wide-band channel characteristics have been based on the (PDP) and (DSD), we analyze the root-mean-square of the (RMS) delay spread, RMS Doppler spread, Coherence time, Coherence bandwidth, and mean delay, Doppler shift from 24 different scenarios for behaviors of the mobile radio channels and indoor wireless application.Actually, My thesis title is '' A Study of Multipath Propagation and Doppler Effect at 24GHz ISM band''. I have generated mm-wave frequency from my testbed which is 24GHz. For better analysis, i was designed and created a Multipath environment inside of the Robotics Lab at University of Gävle, I also used KUKA Robot and designed two diffrient motion for the Transmitter,such as ''C'' type and '' inverse ''type .
18
Ramos-Orosco, Elizabeth J. "Comment on first trimester maternal serum analytes and second trimester uterine artery doppler in the prediction of preeclampsia and fetal growth restriction." Taiwan Association of Obstetrics and Gynecology, 2018. http://hdl.handle.net/10757/622873.
Full text
19
Jimoh, Abdulganiyu A. "In vitro assessment of pressure gradient across infundibular pulmonary and sub-aortic stenoses using doppler ultrasound." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/11241.
Full text
20
Amiryan, Arevik. "Formation of narrow optical resonances in thin atomic vapor layers of Cs, Rb, K and applications." Thesis, Bourgogne Franche-Comté, 2019. http://www.theses.fr/2019UBFCK028/document.
Full textAbstract:
Cette thèse présente l'étude de l'interaction de lumière cohérente avec une couche sub-longueur d'onde de vapeur alcaline atomique confinée en nano-cellule et applications pour la formation de résonances optiques étroites.Nous développons un modèle théorique décrivant l'interaction résonante de lumière laser avec la couche mince de vapeur alcaline en présence d'un champ magnétique. Nous montrons qu'en raison d'un régime transitoire d'interaction, seuls les atomes lents contribuent au signal et leur spectre de transmission est essentiellement sans effet Doppler. La nature des spectres obtenus fait de la spectroscopie de transmission, en nano-cellule, une technique pratique pour l'étude de transitions très rapprochées et l'évolution de leur comportement dans un champ magnétique. Des expériences réalisées pour des champs magnétiques jusqu'à 7000 G montrent un excellent accord entre théorie et expérience.Nous explorons aussi la rotation Faraday du plan de polarisation de la lumière lors de sa propagation dans la couche mince atomique. Bien que l'angle de rotation soit très faible, nous observons que les résonances des spectres de rotation Faraday sont plus étroites que celles de transmission. Enfin, nous étudions de nouvelles possibilités pour former des résonances optiques étroites et montrons qu'un traitement par deuxième dérivée des spectres de transmission donne le meilleur rétrécissement de raies parmi toutes les méthodes étudiées dans cette thèseThis thesis presents the study of coherent light interaction with a sub-wavelength atomic alkali vapor layer confined in a nano-cell and applications for the formation of narrow optical resonances.We develop a theoretical model describing the resonant interaction of the laser light with the thin alkali vapor layer in the presence of an external static magnetic field. We show that due to a transient regime of interaction, only slow atoms contribute to the signal and their transmission spectrum is essentially Doppler-free. The nature of the obtained spectra makes the transmission spectroscopy from a nano-cell a convenient technique to perform studies of closely-spaced atomic transitions and investigate their behavior in magnetic fields. Experimental realizations for magnetic field up to 7000~G show an excellent agreement between theory and experiment.We also explore the Faraday rotation of the plane polarization of light with the propagation through the thin atomic slab. We see that despite a small angle of rotation, Faraday rotation spectra exhibit resonances narrower than that for transmission. At last, we investigate new possibilities to form narrow optical resonances in nano-cells and show that second derivation processing of transmission spectra yields the strongest line narrowing among all methods studied in this thesis
21
Glova, Michael A. "Experimental verification of the flow around compressor blades in cascade at stall with initial numerical simulations." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Mar%5FGlova.pdf.
Full textAbstract:
Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, March 2006.Thesis Advisor(s): Garth V. Hobson. "March 2006." Includes bibliographical references (p. 69-70). Also available online.
22
Cohen, Joseph P. "Digital calculation of real time velocity profiles using ultrasonics." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/17977.
Full text
23
Seet, Siong Leng Henry. "Analysis of noncoherent orthogonal modulation for mobile computing." Thesis, Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/55206.
Full textAbstract:
Approved for public release; distribution is unlimited.Wireless communication is employed to connect mobile computers in a networked environment for information exchange. In a tactical space, sensors and computers typically need to operate on-the-move while transmitting data over both short and long distances in different terrain and conditions. The wireless communication is thus susceptible to effects of Doppler shift and channel fading. In addition, when security and anti jamming features are required, such as frequency-hopping techniques, then coherent signal detection is difficult and noncoherent modulation is used instead. Our study will focus on the bit error rate (BER) performance analysis of noncoherent orthogonal modulation, specifically M-ary frequency-shift keying (MFSK) and code-shift keying (CSK) modulation, in both additive white Gaussian noise (AWGN) and for a Rayleigh fading channel with Doppler shift. The potential applications include communications between mobile computer-sensor devices, such as a mobile ground control station maintaining a datalink with UAV.
Civilian
24
Ramírez, Miquet Evelio Esteban. "Implementation of optical feedback interferometry for sensing applications in fluidic systems." Thesis, Toulouse, INPT, 2016. http://www.theses.fr/2016INPT0068/document.
Full textAbstract:
L'interférométrie par réinjection optique est une technique de mesure dont l'implémentation pour l'interrogation de systèmes fluidiques est assez récente. Le principe de mesure est basé sur la perturbation des paramètres d'émission du laser induite par la réinjection dans la cavité laser de lumière rétro-diffusée par une cible distante. La technique permet le développement de capteurs compact et non-invasifs qui mesurent différents paramètres liés aux déplacements de la cible. En particulier, les interféromètres par réinjection optique prennent avantage de l'effet Doppler pour mesurer la vitesses de traceurs dans les liquides en écoulement. Cet aspect important de la technique de réinjection optique la rend adaptée à une grande variété d'applications dans les domaines du génie chimique et du biomédical où un contrôle des écoulements est requis. Cette thèse présente l'implémentation de capteur basés sur la réinjection optique pour différents systèmes fluidiques où la vitesse locale d'écoulement ou le débit sont directement mesurés. Nous présentons une étude centrée sur les applications où la réinjection optique est utilisée pour la mesure du débit à la micro-échelle avec en particulier une analyse de la robustesse des méthodes de traitement du signal propres aux régimes de diffusion simple et de diffusion multiple. Par ailleurs, nous présentons des résultats expérimentaux de mesures ex vivo où le capteur par réinjection optique est proposé comme alternative pour la myographie. Nous présentons également une implémentation temps réel pour l’estimation du débit instantané d'écoulements dynamiques dans une configuration milli-fluidique. Un système semi-automatisé de détection de particule unique dans un micro-canal est proposé et démontré. Enfin, un capteur basé sur la réinjection optique est implémenté pour la caractérisation des interactions entre deux fluides immiscibles en écoulement à micro-échelle et les mesures réalisées sont comparées à un modèle développé afin de décrire le comportement hydrodynamique des deux fluides dans un micro-réacteur. Le manuscrit décrit une contribution importante pour l'implémentation de capteur par réinjection optique pour des applications fluidiques et en particulier micro-fluidiques. Il présente également des résultats expérimentaux remarquables qui ouvrent de nouveaux horizons pour l'interférométrie à réinjection optiqueOptical feedback interferometry is a sensing technique with relative recent implementation for the interrogation of fluidic systems. The sensing principle is based on the perturbation of the laser emission parameters induced by the reinjection in the laser cavity of light back-scattered from a distant target. The technique allows for the development of compact and noninvasive sensors that measure various parameters related to the motion of moving targets. In particular, optical feedback interferometers take advantage of the Doppler effect to measure the velocity of tracers in flowing liquids. These important features of the optical feedback interferometry technique make it wellsuited for a variety of applications in chemical engineering and biomedical fields, where accurate monitoring of the flows is needed. This thesis presents the implementation of optical feedback interferometry based sensors in multiple fluidic systems where local velocity or flow rate are directly measured. We present an application-centered study of the optical feedback sensing technique used for flow measurement at the microscale with focus on the reliability of the signal processing methods for flows in the single and the multiple scattering regimes. Further, we present experimental results of ex vivo measurements where the optical feedback sensor is proposed as an alternative system for myography. In addition we present a real-time implementation for the assessment of non-steady flows in a millifluidic configuration. A semi-automatized system for single particle detection in a microchannel is proposed and demonstrated. Finally, an optical feedback based laser sensor is implemented for the characterization of the interactions between two immiscible liquid-liquid flowing at the microscale, and the measurement is compared to a theoretical model developed to describe the hydrodynamics of both fluids in a chemical microreactor. The present manuscript describes an important contribution to the implementation of optical feedback sensors for fluidic and microfluidic applications. It also presents remarkable experimental results that open new horizons to the optical feedback interferometry
25
Kharchakdjian, Raffi. "Modelling the structure of the tumour vasculature and its effect on Doppler ultrasound signals." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq58834.pdf.
Full text
26
An, Youngwon Kim. "Multiple targets detection and tracking with Doppler effect in noisy acoustic wireless sensor networks." Thesis, The University of Alabama in Huntsville, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3558526.
Full textAbstract:
This dissertation presents a new detection algorithm and high speed/accuracy tracker for tracking a single and multiple ground vehicles in noisy acoustic wireless sensor networks (WSNs). For tracking ground vehicles, acoustic WSNs have been regarded to be useful and increasingly available due to recent advancement of micro sensors technology with low cost. Requirements for WSNs applications are low computational and communication load to each sensor node as each sensor node runs with a low-power battery.
The new detection algorithm of this dissertation naturally accounts for the Doppler effect which is an important consideration for tracking higher-speed targets. The tracking system used in this study employs Kalman Filtering (KF) with the weighted sensor position centroid being used as the target position measurement. The weighted centroid makes the tracker to be independent of the detection model and changes the tracker to be near optimal, at least within the detection parameters used in the study of single target.
The new approach for a single target tracking contrasts with the previous approaches that employed more sophisticated tracking algorithms with higher computational complexity and used a power law detection model. The power law detection model, neglecting Doppler effect, is valid only for low speed targets and is susceptible to mismatch with detection by the sensors in the field. The tracking model also makes it possible to uniquely study various environmental effects on track accuracy, such as the Doppler effect, signal collision, signal delay, and different sampling time. The tracking model is shown to be highly accurate for a moving single target in both linear and accelerated motions. The computing speed is estimated to be 50∼100 times faster than the previous more sophisticated methods and track accuracy compares very favorably.
As the WSN systems face multiple targets in the real world, the study has been expanded to the multiple targets tracking including the environmental noise mitigation. Localization and tracking multiple targets which undergo merging and split in the noisy acoustic WSNs require a new approach for detection and tracking. Doppler effect is included in the detection model and an efficient noise mitigation algorithm is developed. A new rule-based tracking algorithm is also developed, which guarantees reliable tracking of multiple targets in noisy acoustic WSNs with very low computational complexity and high track accuracy. The tracking system guarantees much lower computational complexity and comparable track accuracy to more sophisticated algorithms of the previous work.
27
Steel, Robin. "An experimental and theoretical investigation of the wall-effect in doppler ultrasound flow phantoms." Thesis, Bangor University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263969.
Full text
28
Землянський, Володимир Михайлович, and М. О. Гусєв. "Independence of doppler effect from wave-length at the multiwave concerted sounding and reception." Thesis, Національний авіаційний університет, 2014. http://er.nau.edu.ua/handle/NAU/11684.
Full text
29
Hoechstetter, Ronald S. "Effect of anthropometric factors on the reproducibility of Doppler echocardiographic measurements during stationary bicycle exercise in healthy males." Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/45806.
Full textAbstract:
The effect of selected anthropometric indices on the reproducibility of
continuous wave (CW) Doppler echocardiographic recordings in exercise were
studied in 42 healthy males between 18 and 43 years of age. Each subject was
measured and rank ordered in reference to four anthropometric Indices: sum
of 3 skinfolds (SK); chest girth-waist girth ratio (CW); biacromial width-chest
depth ratio (WD); and peak exercise ventilationâ forced vital capacity ratio (VV).
Each subject then performed two maximal bicycle exercise tolerance tests on
nonconsecutive days wherein the CW Doppler variables of peak acceleration
(pKA), peak velocity (pKV) and stroke velocity integral (SVI) were measured
along with heart rate (HR), blood pressure (BP) and respiratory gas analysis
data including oxygen consumption (V02). Statistical analyses were then
conducted to determine if subject groups with high vs. low values on any
anthropometric index differentiated with regard to testâ retest reliability
between bicycle exercise test trials. Statistical differences were noted between (
the high and a low groups for each index at the .05 alpha level. Pearson's Product
Moment correlational analyses revealed that across all subjects the
highest test-retest reliability occurred during the moderate intensity of
exercise. The average test-retest correlation coefficients for the high and low
groups within each index are as follows: SKH, = .52, SKL = 62, CWH = .64,
CWL = .60, WDH. = 62,WDL = 58, VVh. = 61, VVL = .67. Inspection of
test-retest correlations between the high vs. low groups for the anthropometric
indicies revealed a trend in the skinfold index. For each dependent measure
at all levels of exercise intensity, the low group exhibited higher correlation
coefficients than the high group except for pKA at the peak level of exercise.
The other three indicies exhibited no such trends. lt was concluded that since The other three indicies exhibited no such trends. lt was concluded that since
the overall correlation coefficients (average = .65) were within the ranges of
those computed for HR. BP and VO2; (average = .50) the test-retest reliability
with the CW Doppler was acceptable; but only during moderate levels of
exercise. It was also determined from the correlation coefficients generated
by the skinfold index data that measures obtained on lean individuals may be
moree reproducible than measures obtained from obese individuals (See Table
2).Master of Science
30
Zhang, Jianjun, and j3029709 zhang@gmail com. "Precise Velocity and Acceleration Determination Using a Standalone GPS Receiver in Real Time." RMIT University. Mathematical and Geospatial Sciences, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080121.142357.
Full textAbstract:
Precise velocity and acceleration information is required for many real time applications. A standalone GPS receiver can be used to derive such information; however, there are many unsolved problems in this regard. This thesis establishes the theoretical basis for precise velocity and acceleration determination using a standalone GPS receiver in real time. An intensive investigation has been conducted into the Doppler effect in GPS. A highly accurate Doppler shift one-way observation equation is developed based on a comprehensive error analysis of each contributing factor including relativistic effects. Various error mitigation/elimination methods have been developed to improve the measurement accuracy of both the Doppler and Doppler-rate. Algorithms and formulae are presented to obtain real-time satellite velocity and acceleration in the ECEF system from the broadcast ephemeris. Low order IIR differentiators are designed to derive Doppler and Doppler-rate measurements from the raw GPS data for real-time applications. Abnormalities and their corresponding treatments in real-time operations are also discussed. In addition to the velocity and acceleration determination, this thesis offers a good tool for GPS measurement modelling and for design of interpolators, differentiators, as well as Kalman filters. The relativistic terms presented by this thesis suggest that it is possible to measure the geopotential directly using Doppler shift measurements. This may lead to a foundation for the development of a next generation satellite system for geodesy in the future.
31
Tezeren, Serdar U. "Reed-Muller codes in error correction in wireless adhoc networks." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Mar%5FTezeren.pdf.
Full textAbstract:
Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, March 2004.Thesis advisor(s): Murali Tummala, Roberto Cristi. Includes bibliographical references (p. 133-134). Also available online.
32
Raszka, Aleš. "Klasifikace vozidel s použitím radaru." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2017. http://www.nusl.cz/ntk/nusl-363896.
Full textAbstract:
This Master thesis deals with usage of radar signal for vehicle classification. The thesis uses radar modules with continuous wave based on Doppler effect. Radar signal is processed by a series of signal processing method finished by Fourier transform. Data produced by FFT is used to create SVM and AdaBoost classifier which can be used to classify vehicles into groups.
33
Luo, Ruichen. "Wi-Fi Based Microwave GI Surveillance for Indoor Scenarios." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/18564.
Full textAbstract:
This thesis focuses on a novel design of Wi-Fi based microwave ghost imaging scheme for surveillance applications. The first research focus is demonstrating the feasibility of applying Wi-Fi signals into microwave ghost imaging. To meet the time-space independent requirements of microwave ghost imaging, the applied Wi-Fi signal source should be random and group-orthogonal. However, the preamble sequence of a Wi-Fi signal is full of repeating elements and the preamble sequences from different access points are the same. Based on a further analysis of Wi-Fi frame structures, I propose a detection time window to avoid using any preamble sequence for achieving a better performance of microwave ghost imaging. In addition, the performance of the Wi-Fi based microwave ghost imaging scheme for stationary objects has been numerically simulated. The second research focus is modifying the imaging reconstruction procedure in microwave ghost imaging scheme for surveillance in practical indoor scenarios where both stationary and moving targets appear. If the moving object appears, the reconstructed imaging will be blurred. To eliminate the blur caused by motion, the method of refocusing to compensate motion of the object has been proposed. The effectiveness of refocusing is validated in relative numerical simulations. Further, I investigate the proposed scheme in the scenario that contains both stationary and moving targets. The receiving signal should be processed to distinguish various reflecting signals from different targets before refocusing. Thus, the object reconstruction procedure of microwave GI is also modified to fit this scenario for surveillance purpose. Numerical simulation shows that the proposed modification can effectively isolate reflections from targets with different velocities and obtain focused images.
34
Michel, Guillaume. "Parois et ondes de surface : dissipation, effet Doppler et interactions non linéaires." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEE038/document.
Full textAbstract:
Dans cette thèse, nous étudions comment la présence de parois affecte les ondes de surface. La dissipation associée au mouillage, objet central des premiers chapitres, est abordée expérimentalement. Nous mesurons son évolution avec la taille du ménisque et montrons qu’en mouillage total des non-linéarités apparaissent dès que l’oscillation du ménisque atteint l’épaisseur des couches limites. Dans un deuxième temps, nous quantifions les échanges d’énergie ayant lieu lors de laréflexion d’une onde de surface sur une paroi oscillante, appelés effet Doppler généralisé. Après une mise en évidence expérimentale, une approche théorique les évalue et illustre comment leurs effets cumulatifs peuvent mener à des spectres en compétition avec ceux de la turbulence d’ondes. Finalement, nous traitons les interactions entre paquets d’ondes. En géométrie confinée, nous montrons que des résonances à trois ondes gravitaires sont autorisées. Dépassant la problématique des parois, nous caractérisons les interactions entre ondes gravitaires en milieu infini, puis décrivons les grandes échelles de la turbulence d’ondes capillaireIn this thesis, we study the impact of solid boudaries on surface waves. We first consider the dissipation caused by dynamical wetting. We experimentally show how the damping of surface waves evolves with the size of the meniscus and demonstrate that in perfect wetting it leads to a nonlinear behavior as soon as the meniscus oscillation amplitude compares to the thickness of the boundary layer. Secondly, we investigate energy exchanges through scales occuring when a surface wave reflects on an oscillating wall, the so-called generalized Doppler effect. We evidence the creation of Doppler-shifted waves, compute their amplitudes and illustrate how the continuous bouncing of surface waves on wavemakers may lead to self-similar spectra competing with the ones of wave turbulence. Finally, we focus on nonlinear interaction between surface waves. We prove that gravity waves can undergo triad resonances in confined geometry. Going beyond the consequencies of solid boundaries, we perform experiments on four-wave interactions in the gravity regime and describe large scales in capillary wave turbulence
35
Zhao, Yu. "Optical feedback sensing in microfluidics : design and characterization of VCSEL-based compact systems." Thesis, Toulouse, INSA, 2017. http://www.theses.fr/2017ISAT0008/document.
Full textAbstract:
L’interférométrie par retro-injection optique (OFI) est une technique de détection émergente pour les systèmes fluidiques. Son principe est basé sur la modulation de la puissance et/ou de la tension de polarisation d’une diode laser induites par interférence entre le faisceau propre de la cavité laser et la lumière réfléchie ou rétro-diffusée par une cible distante. Grâce à l’effet Doppler, cette technique permet de mesurer précisément la vitesse de particules en mouvement dans un fluide, et de répondre aux besoins croissants de mesure de débit dans les systèmes d’analyse biomédicale ou chimique.Dans cette thèse, les performances de la vélocimétrie par rétro-injection optique sont étudiées théoriquement et expérimentalement pour le cas de micro-canaux fluidiques. Un nouveau modèle numérique multi-physique (optique, optoélectronique et fluidique) est développé pour reproduire les spectres Doppler expérimentaux. En particulier, les effets de la concentration en particules, de la distribution angulaire de la diffusion du laser par les particules, ainsi que du profil d’écoulement dans le canal sont pris en compte. Un bon accord est obtenu entre les vitesses d’écoulement théoriques et expérimentales. Ce modèle est également appliqué avec succès à la mesure de la vitesse locale dans un micro-canal et à l’analyse de l’impact sur le signal des configurations particulières de canal. Enfin, la conception d’un capteur OFI tirant parti des avantages des Lasers à Cavité Verticale à Emission par la Surface (VCSEL) est proposée. Grâce au développement de techniques de microfabrication à base de matériaux polymères, un premier démonstrateur composé d’un VCSEL à lentille intégrée est réalisé et testé sans aucune optique macroscopique additionnelle. Les résultats obtenus en termes de mesure de flux sur des canaux micro-fluidiques de tailles différentes valident l’intérêt de cette approche et ouvrent la voie vers la réalisation de capteurs OFI ultra-compactsOptical feedback interferometry (OFI) is an emerging sensing technique which has been studied in fluidic systems. This sensing scheme is based on the modulation of the laser emission output power and/or the junction voltage induced by the interaction between the back-scattered light from a distant target and the laser inner cavity light. Thanks to the Doppler Effect, OFI can precisely measure the velocity of seeding particles in flowing liquids which is much required in chemical engineering and biomedical fields. In the present thesis, optical feedback interferometry performance for microscale flow sensing is studied theoretically and experimentally. A new numerical modeling approach based on multi-physics numerical simulations for OFI signal simulation in the micro-scale flowmetry configuration is presented that highlight the sensor performances. In this model, many factors are involved such as particle concentration and laser-particle scattering angle distribution and flow velocity distribution. The flow rate measurement shows good agreement with the modeling. The implementation of OFI based sensors in multiple fluidic systems, investigating the impact of the fluidic chip specific configuration on the sensor signal.Finally, a compact OFI flowmetry sensor based on Vertical-Cavity Surface-Emitting Lasers (VCSELs) using micro optical fabrication techniques is demonstrated as well. The simulation method for the design and the microfabrication procedures are detailed. After an evaluation of the experimental results, the capabilities of this new OFI sensor in microfluidic measurements are emphasized, thus demonstrating an open path towards ultra-compact microfluidic systems based on the OFI sensing technique
36
Aftel, Robert. "Effect of atomization gas properties on droplet atomization in an "air-assist" atomizer." Master's thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/32599.
Full textAbstract:
Air, nitrogen, argon and carbon dioxide were used as the atomizing gas in an 'air-assist' spray nozzle to determine the effect of these gases on mean droplet size, number density, velocity and their distributions in kerosene fuel spays and spray flames using a two dimensional phase Doppler interferometer. Data have been obtained with these atomizing gases using a base, air assisted case as a reference, since this is the most commonly used atomizing fluid in almost all applications. Comparisons were made between the gases on a mass and momentum flux basis. Both burning and nonburning sprays were investigated. The results show significant differences in atomization characteristics from the atomizer with different gases and under conditions of constant mass and momentum flux of the gas. The results also show that the presence of oxygen in the air atomized sprays assists in the combustion process, since it produces smaller and faster moving droplets, especially at locations near to the nozzle exit. In nonburning sprays, droplets had similar size and velocity. Lighter gases such as nitrogen more effectively atomized the fuel in comparison to the denser gases. Argon and carbon dioxide produced larger, slower moving droplets than air and nitrogen assisted cases in both the burning and nonburning sprays. Flame photographs revealed the argon and carbon dioxide atomized flames to have greater luminosity than air or nitrogen atomized flames.
Master of Science
37
Gasperini, David. "A multi-harmonic finite element method for the micro-Doppler effect, with an application to radar sensing." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0026.
Full textAbstract:
Nous proposons une méthode de résolution par éléments finis et en domaine fréquentiel de problèmes de diffraction d'ondes au sein de domaines dont les frontières se déforment au cours du temps. Le problème original est exprimé sous forme faible, puis approché par une formulation simplifiée basée sur des développements asymptotiques valides lorsque l'amplitude des déformations est faible. Nous introduisons alors des développements en séries de Fourier de certaines grandeurs géométriques, ainsi que de la solution dans le cas de mouvements périodiques. Cela permet ainsi d'obtenir une formulation multi-harmonique couplée du problème de diffraction initial. Une méthode de résolution standard par éléments finis, couplée avec un solveur itératif, est alors appliquée afin de résoudre le système résultant. En vue d'accélérer la solution du système linéaire, définie sur des sous-espaces de Krylov, nous proposons un préconditionneur diagonal par bloc, indispensable à la convergence de la méthode pour les problèmes hautes fréquences. L'efficacité de la méthode présentée est enfin illustrée à travers une application à la détection radar pour l'industrie automobileA finite element method in the frequency domain is proposed for solving wave scattering problems with moving or, more generally, deforming boundaries. First, the original problem is rewritten as an equivalent weak formulation set in a fixeddomain. Next, this formulation is approximated as a simpler weak form based on asymptotic expansions when the amplitude of the movements or the deformations is small. Fourier series expansions of some geometrical quantities under the assumption that the movement is periodic, and of the solution are next introduced to obtain a coupled multi-harmonic frequency domain formulation. Standard finite element methods can then be applied to solve the resulting problem and a block diagonal preconditioner is proposed to acceleratethe Krylov subspace solution of the linear system for high frequency problems.The efficiency of the resulting method is demonstrated on a radar sensing application for the automotive industry.A finite element method in the frequency domain is proposed for solving wave scattering problems with moving or, more generally, deforming boundaries. First, the original problem is rewritten as an equivalent weak formulation set in a fixeddomain. Next, this formulation is approximated as a simpler weak form based on asymptotic expansions when the amplitude of the movements or the deformations is small. Fourier series expansions of some geometrical quantities under the assumption that the movement is periodic, and of the solution are next introduced to obtain a coupled multi-harmonic frequency domain formulation. Standard finite element methods can then be applied to solve the resulting problem and a block diagonal preconditioner is proposed to acceleratethe Krylov subspace solution of the linear system for high frequency problems.The efficiency of the resulting method is demonstrated on a radar sensing application for the automotive industry
38
Maršík, Lukáš. "Algoritmy zpracování signálu v FPGA." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2010. http://www.nusl.cz/ntk/nusl-237152.
Full textAbstract:
This master's thesis describes ways of signal processing via digital devices. Major field of interest is an analysis of Doppler radar response and then mining of informations about detected object (e.g. speed, movement direction, length, ...). There was realized too little research, that's why borrowing some procedures from different branches not too much related to the IT is necessary. In case of using very complex methods that are easy to parallel, hardware implementation on the FPGA is supposed. With transceiver there is created a very powerful on-line system able to process most of tasks real-time. Then processed and transformed data are sent to the output so visualization and display can be made.
39
Lendínez, Escudero Sergi. "Magnetization dynamics at the nanoscale in nanoparticles and thin films: single-molecule magnets, magnetic vortices, and magnetic droplet solutions." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/395194.
Full textAbstract:
Research in magnetic materials leads to new devices and technologies. As the technology progresses, the devices become smaller and this miniaturization allows more storage capacity and lower costs in the production of new technologies. As new and smaller materials are fabricated, new phenomena appear and thus new physics is needed to describe them. Nanomaterials meet characteristics of both the microscopic quantum world and the macroscopic classic world. This intermediate length scale is known as mesoscale. Nanomaterials can be obtained in a variety of forms, being nanoparticles and magnetic ultra-thin films some of the most used. These magnetic systems are very different in their composition: nanoparticles are grown with chemical reactions, and thin films are grown on a substrate by nanofabrication techniques such as sputtering or electron-beam evaporation. The magnetization might not be uniform in a magnetic thin film or in a large magnetic nanoparticle leading to the formation of magnetic domains. Magnetic domains are static structures that appear due to competition of the different magnetic energies and can be used to store and transport information.
In all these systems, the magnetization dynamics gives rise to new behavior not visible in static measurements: quantum steps of the magnetization in molecular magnets; characteristic resonant frequencies that can be used to control the magnetic state of vortices; and formation of magnetic droplet solitons in thin films with perpendicular magnetic anisotropy.
Understanding the dynamics of nanomaterials and the evolution of the magnetization is a key process to develop faster devices and technologies. The early studies of molecular magnets showed quantum effects at the macroscopic scale, which have allowed a better understanding of spin. Magnetic vortices have been proposed for multiple applications, from magnetic storage of information to cancer cell destruction. The recently discovered magnetic droplet soliton is also a very good candidate for technological applications due to the low current and magnetic field needed for its generation, and it is now a system with a growing interest in spintronics.
In this dissertation we show some new dynamic phenomena. In the first part of the thesis we study systems that allow a macroscopic-spin model where spatial variations of magnetization are neglected. We develop a theory that sets the requirements for the observation of the rotational Doppler effect in a ferromagnetic system and we measure quantum effects in randomly oriented nanoparticles of a single-molecule magnet, which might be a good candidate for the observation of the Doppler effect. In the second part of the thesis, we study the magnetization dynamics in macroscopic systems that require a spatial dependence of the magnetic moment. We generate and control the dynamic states of the magnetic domains with oscillating fields, in the case of magnetic vortices, and with electrical currents, in the case of droplet solitons.La investigación en materiales magnéticos ha dado lugar a nuevos dispositivos y tecnologías. A medida que la tecnología progresa, los dispositivos se hacen más pequeños. Esto permite una mayor capacidad de almacenamiento y reducir los costes de producción. A medida que se fabrican materiales más pequeños, surgen nuevos comportamientos. Los nanomateriales reúnen características tanto del mundo cuántico microscópico como del mundo clásico macroscópico. Esta escala de longitud se conoce como mesoescala. Existen variedad de forms de nanomateriales, entre las cuales nanopartículas y capas magnéticas ultrafinas. La composición de estos sistemas es diversa: las nanopartículas se obtienen a partir de reacciones químicas y las capas finas se crecen en un sustrato mediante técnicas de nanofabricación. La magnetización en las capas finas o en nanopartículas magnéticas grandes puede no ser uniforme, lo que lleva a la formación de dominios magnéticos. En todos estos sistemas, la dinámica de la magnetización da lugar a un nuevo comportamiento que no es visible en las mediciones estáticas: fenómenos cuánticas de la magnetización en imanes moleculares; frecuencias de resonancia características que se pueden utilizar para controlar el estado magnético de los vórtices; y la formación de solitones “droplet” magnéticos en capas finas con anisotropía magnética perpendicular. La comprensión de la dinámica de los nanomateriales y la evolución de la magnetización es un proceso clave para el desarrollo de dispositivos y tecnologías más rápidas. Los primeros estudios de imanes moleculares mostraron efectos cuánticos a escala macroscópica, que han permitido una mejor comprensión del espín. Los vórtices magnéticos se han propuesto para múltiples aplicaciones, desde el almacenamiento magnético de la información a la destrucción de células de cáncer. El solitón “droplet” magnético, descubierto recientemente, es también muy buen candidato para aplicaciones tecnológicas debido al bajo campo magnético y baja corriente necesarios para su generación. En esta tesis se muestran algunos nuevos fenómenos dinámicos. En la primera parte de la tesis, estudiamos sistemas que permite un modelo de macroespín, en el que no hay variaciones espaciales de la magnetización. En la segunda parte estudiamos la dinámica en sistemas con dominios magnéticos, lo cual requiere una dependencia espacial de la magnetización.
40
CHO, DOO-YEARN. "Mesure du champ des vitesses de melanges solide-liquide par anemometrie laser a effet doppler." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13150.
Full textAbstract:
Un circuit logique incorpore dans la chaine de mesure permet de distinguer les signaux provenant des particules et du traceur visualisant le liquide porteur. L'association de l'anemometrie laser a effet doppler et d'un oscilloscope numerique rend possible l'echantillonnage du signal doppler. Un logiciel de traitement du signal permet de determiner les vitesses moyennes locales des particules solides spheriques en suspension et du liquide porteur. On peut obtenir ainsi simultanement les deux vitesses et la vitesse de glissement particule-liquide
41
Thierry, Gilles. "Etude des problemes lies a l'interferometrie acoustique appliquee a la trajectographie sous-marine passive." Toulon, 1988. http://www.theses.fr/1988TOUL0002.
Full textAbstract:
Developpement d'algorithmes permettant de realiser la poursuite automatique d'un mobile a partir des bruits qu'il rayonne. La localisation s'effectue grace a la connaissance des retards de perception d'un meme signal relativement aux paires d'hydrophones. L'estimation de ces retards est obtenue par interferometrie
42
Krohová, Lucie. "Ultrazvukový průtokoměr pro dialyzační monitor." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-220873.
Full textAbstract:
The main objective of this thesis is to get know about introduce the principles of hemodialysis, blood flow measurement methods and the creation the system and peripheral design of blood flow meter. The thesis contains an introduction to hemodialysis, a description of the dialysis monitor, the distribution of ultrasonic flow meters and system design of blood flow meter with a brief description of each function block, circuit diagram of a flow meter and experimental verification of the circuit. There are also the list of components, printed circuit board drawing and technical drawing of the sensor included.
43
Steinberg, Gary. "Relative Reality." Ohio University / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1016207660.
Full text
44
Prost, Emilien. "Optique ultra-rapide dans des rotors moléculaires synchrones." Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCK009.
Full textAbstract:
Cette thèse porte sur l'étude de la rotation unidirectionnelle de molécules et en particulier de l'effet Doppler rotationnel en génération de troisième harmonique dans des rotors moléculaires synchrones. L'effet Doppler rotationnel apparaît lors de l'interaction entre une onde polarisée circulairement et un objet anisotrope en rotation. Lors de cette interaction, il y a échange de moment angulaire entre l'onde et l'objet induisant, par conservation de l'énergie et du moment angulaire, un décalage en fréquence de l'onde après l'interaction. Une observation du décalage en fréquence de la troisième harmonique générée dans des molécules en mouvement de rotation unidirectionnelle est présentée. Un modèle analytique décrit dans ce manuscrit permet de prévoir quatre décalages en fréquences dépendant du sens des polarisations circulaires fondamentale et harmonique ainsi que du sens de rotation des molécules. Ces quatre décalages en fréquences ont été observés expérimentalement lors de la génération de troisième harmonique dans des molécules de O2, N2 et CO2 en rotation unidirectionnelle. Une étude minutieuse de l'effet Doppler rotationnel et de la physique sous-jacente à ce phénomène a ensuite été conduite. Une analyse de l'état de polarisation de la troisième harmonique produite dans des rotors moléculaires synchrones a également été réalisée permettant de mettre en avant le haut degré d'ellipticité de l'harmonique produite. À partir de cette analyse en polarisation, l'orientation de l'axe moléculaire peut être retrouvée, offrant une méthode de mesure de la fréquence angulaire des molécules en rotationThis thesis reports on the study of unidirectional rotation of molecules and focuses on the rotational Doppler effect occuring in the course of third-harmonic generation in coherently spinning molecules.The rotational Doppler effect appears when a circularly polarized wave interacts with an anisotropic rotating object. During the interaction, an exchange of angular momentum and energy between the field and the object occurs, leading to a frequency shift of the wave. In this work, the frequency shift of the third-harmonic generated in unidirectionaly rotating molecules has been observed. An anlytical model developped in the mansucript forsees four kinds of frequency shifts depending on the mutual handedness of the circular polarization of the fundamental and harmonic fields and the handedness of the rotating molecules. The four shifts have been measured in third-harmonic generation in unidirectionaly rotating molecules of O2, N2, and CO2. A thorough study of the rotational Doppler effect and the underlying physics has been conducted. A polarization analysis of the third-harmonic produced in coherently spinning molecules has also been done, showing the high degree of ellipticty of the harmonic. From this polarization analysis, the orientation of the molecular axis can be retrieved, providing a new way to measure the angular frequency of rotating molecules
45
Wetherill, Lindsay D. "Reproducibility of a continuous-wave Doppler ultrasound system for assessment of ascending aortic blood flow responses during graded exercise testing with healthy individuals." Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/80102.
Full textAbstract:
Continuous-wave (CW) Doppler recordings of ascending aortic maximal blood flow acceleration (PkA), maximal velocity (PkV) and systolic velocity integral (SVI) were taken at each stage of a graded exercise treadmill test on two separate days with 30 physically active adult males. Signals were measured (Quinton Exerdop) for all cardiac cycles in the 3rd minute of each stage using a hand-held probe positioned at the suprasternal notch. A dedicated microcomputer, programmed to select "valid" beats on the basis of value consistency in the sample set, determined the acceptability of signals. No significant differences were found between the three trial means within each stage on either day for PkA, PkV or SVI. Significant (p <.01) intraclass reliability estimates ranged from r = 0.89 to 0.97 (Pk.A), r = 0.90 to 0.98 (PkV) and r = 0.85 to 0.95 (SVI) . Coefficients of variation were calculated at each stage to estimate the relative consistency of each measure. A gradual reduction of the coefficient of variation was observed for each blood flow measure between stages one and four. The test-retest (between days) reliability coefficients for PkA, PkV and SVI for stages one to four ranged between r = 0.51 to 0.78 (P <.004), but correlations for the pre-exercise baseline and stages five and six were lower. These results indicate that (1) PkA, PkV and SVI demonstrate greater measurement stability within each stage of a graded exercise test than is the case between separate days of measurement at the same stage; and (2) there is modest day-to-day response stability for clinical testing with the Doppler parameter of PkV. Reliability/stability was best in exercise stages which encompass the speed and grade range of 45.0 m•min⁻¹/10%. - 111.7 m•min⁻¹/14%, i.e., those in which all subjects can walk.Master of Science
46
Lyonnet, Bastien. "Diversité spatiale et compensation Doppler en communication sous-marine sur signaux large-bandes." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00664710.
Full textAbstract:
Le milieu sous-marin est doublement dispersif, en temps et en fréquence. L'utilisation récente de signaux de communication multi-porteuses offre une solution pour lutter contre la sélectivité fréquentielle. Mais ce type de signaux reste très sensible à la dispersivité fréquentielle. Cette thèse se concentre sur le problème de la dispersivité fréquentielle qu'est l'effet Doppler. Des méthodes d'estimation du paramètre Doppler sont développées pour des signaux multi-porteuses DMT. Est également abordé le problème de la compensation Doppler dans les cas mono et multitrajets. Une méthode générale et une méthode spéci que au signaux multiporteuses sont présentées et testées sur simulation. Cette thèse se distingue par son modèle du canal sous-marin qui considère un paramètre Doppler différent sur chaque trajet. Ceci résulte de la géométrie du problème et des vitesses émetteur/récepteur considérées. Nous présentons nalement des méthodes pour séparer les différents trajets arrivant sur une antenne a n de pouvoir considérer un paramètre Doppler unique sur chacun.
47
Noblett, S. E. "A randomised clinical trial assessing the effect of oesophageal Doppler guided perioperative fluid optimisation on outcome following elective colorectal resection." Thesis, University of Newcastle upon Tyne, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437253.
Full text
48
Oliveira, Sergio Ferreira de. "Sensor de presença para semáforo inteligente de baixo custo." Universidade de Taubaté, 2012. http://www.bdtd.unitau.br/tedesimplificado/tde_busca/arquivo.php?codArquivo=588.
Full textAbstract:
Este trabalho destina-se a especificar, analisar e ensaiar um sensor de presença para um semáforo inteligente de baixo custo. O sensor tem por finalidade a redução dos custos de implantação e manutenção nos sistemas de controles dos semáforos inteligentes, quando comparado a outros sensores, tais como, por imagem, ultrassom, laser, infravermelho, pneumático ou indutivo. O princípio de funcionamento tem por base a detecção de veículos na região de aproximação das vias de uma interseção por meio de um sensor que gera um sinal elétrico para o sistema de controle de tráfego. Utilizando sensores de micro-ondas de efeito Doppler e um circuito detecção o sistema torna-se de fácil implantação nos cruzamentos das vias públicas, por possuir tamanho reduzido, facilidade de programação e baixo consumo de energia, atendendo, portanto a necessidade de sistemas sustentáveis. Por motivo de segurança, ao ser iniciado ou reiniciado devido a falta de energia elétrica, o sistema funciona de forma temporizada por dois ciclos completos, tempo suficiente para que seja possível a detecção de veículos pelos sensores.This work aims to specify, analyze and test a presence sensor for an intelligent traffic light at low cost. The sensor is intended to reduce the costs of deployment and maintenance of control systems in intelligent traffic lights, when compared to other sensors such as imaging, ultrasound, laser, infrared, pneumatic or inductive. The operating principle is based on the detection of approaching vehicles in the region of an intersection roads by means of a sensor which generates an electrical signal to the control system traffic. Using sensors microwave Doppler Effect and a loop detection system becomes easy to deploy in the crossings of public roads, for having reduced size, ease of programming and low power consumption, light, therefore the need for sustainable systems. For security reasons, to be started or restarted due to power outages, the system works timed by two complete cycles, enough time to be able to detect vehicles by sensors.
49
Kallala, Haithem. "Massively parallel algorithms for realistic PIC simulations of ultra high intensity laser-plasma interaction, application to attosecond pulses separation of Doppler harmonics." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS052.
Full textAbstract:
La complexité des mécanismes physiques mis en jeu lors de l'interaction laser-plasma à ultra-haute intensité nécessite de recourir à des simulations PIC particulièrement lourdes. Au cœur de ces codes de calcul, les solveurs de Maxwell pseudo-spectraux d'ordre élevé présentent de nombreux avantages en termes de précision numérique. Néanmoins, ces solveurs ont un coût élevé en termes de ressources nécessaires. En effet, les techniques de parallélisation existantes pour ces solveurs sont peu performantes au-delà de quelques milliers de coeurs, ou induisent un important usage mémoire, ce qui limite leur scalabilité à large échelle. Dans cette thèse, nous avons développé une toute nouvelle approche de parallélisation qui combine les avantages des méthodes existantes. Cette méthode a été testée à très large échelle et montre un scaling significativement meilleur que les précédentes techniques, tout en garantissant un usage mémoire réduit.En capitalisant sur ce travail numérique, nous avons réalisé une étude numérique/théorique approfondie dans le cadre de la génération d'harmoniques d'ordres élevés sur cible solide. Lorsqu'une impulsion laser ultra-intense (I>10¹⁶W.cm⁻² ) et ultra-courte (de quelques dizaines de femtosecondes) est focalisée sur une cible solide, elle génère un plasma sur-dense, appelé miroir plasma, qui réfléchit non-linéairement le laser incident. La réflexion de l'impulsion laser est accompagnée par l'émission cohérente d'harmoniques d'ordres élevées, sous forme d'impulsions X-UV attosecondes (1 attosecond = 10⁻¹⁸s). Pour des intensités laser relativistes (I>10¹⁹ W.cm⁻²), la surface du plasma est incurvée sous l'effet de la pression de radiation du laser. De ce fait, les harmoniques rayonnées par la surface du plasma sont focalisées. Dans cette thèse, j'ai étudié la possibilité de produire des impulsions attosecondes isolées en régime relativiste sur miroir plasma, grâce au mécanisme de phare attoseconde. Celui-ci consiste à introduire une rotation des fronts d'onde du laser incident de façon à séparer angulairement les différentes impulsions attosecondes produites à chaque cycle optique. En régime relativiste, la courbure du miroir plasma augmente considérablement la divergence du faisceau harmonique, ce qui rend le mécanisme phare attoseconde inefficace. Pour y remédier, j'ai développé deux techniques de réduction de divergence harmonique afin de mitiger l'effet de focalisation induit par la courbure du miroir plasma et permettre de générer des impulsions attosecondes isolées à partir d’harmoniques Doppler. Ces deux techniques sont basées sur la mise en forme en amplitude et en phase du faisceau laser. Par ailleurs, j'ai développé un modèle théorique pour déterminer les régimes optimaux d'interaction afin de maximiser la séparation angulaire des impulsions attosecondes. Ce modèle a été validé par des simulations numériques PIC en géométries 2D et 3D et sur une large gamme de paramètres laser et plasma. Finalement, on montre qu'en ajustant des paramètres laser et plasma réalistes, il est possible de séparer efficacement les impulsions attosecondes en régime relativisteThe complexity of the physical mechanisms involved in ultra-high intensity laser-plasma interaction requires the use of particularly heavy PIC simulations. At the heart of these computational codes, high-order pseudo-spectral Maxwell solvers have many advantages in terms of numerical accuracy. This numerical approach comes however with an expensive computational cost. Indeed, existing parallelization methods for pseudo-spectral solvers are only scalable to few tens of thousands of cores, or induce an important memory footprint, which also hinders the scaling of the method at large scales. In this thesis, we developed a novel, arbitrarily scalable, parallelization strategy for pseudo-spectral Maxwell's equations solvers which combines the advantages of existing parallelization techniques. This method proved to be more scalable than previously proposed approaches, while ensuring a significant drop in the total memory use.By capitalizing on this computational work, we conducted an extensive numerical and theoretical study in the field of high order harmonics generation on solid targets. In this context, when an ultra-intense (I>10¹⁶W.cm⁻²) ultra-short (few tens of femtoseconds) laser pulse irradiates a solid target, a reflective overdense plasma mirror is formed at the target-vacuum interface. The subsequent laser pulse non linear reflection is accompanied with the emission of coherent high order laser harmonics, in the form of attosecond X-UV light pulses (1 attosecond = 10⁻¹⁸s). For relativistic laser intensities (I>10¹⁹ W.cm⁻²), the plasma surface is curved under the laser radiation pressure. And the plasma mirror acts as a focusing optics for the radiated harmonic beam. In this thesis, we investigated feasible ways for producing isolated attosecond light pulses from relativistic plasma-mirror harmonics, with the so called attosecond lighthouse effect. This effect relies introducing a wavefront rotation on the driving laser pulse in order to send attosecond pulses emitted during different laser optical cycles along different directions. In the case of high order harmonics generated in the relativistic regime, the plasma mirror curvature significantly increases the attosecond pulses divergence and prevents their separation with the attosecond lighthouse scheme. For this matter, we developed two harmonic divergence reduction techniques, based on tailoring the laser pulse phase or amplitude profiles in order to significantly inhibit the plasma mirror focusing effect and allow for a clear separation of attosecond light pulses by reducing the harmonic beam divergence. Furthermore, we developed an analytical model to predict optimal interaction conditions favoring attosecond pulses separation. This model was fully validated with 2D and 3D PIC simulations over a broad range of laser and plasma parameters. In the end, we show that under realistic laser and plasma conditions, it is possible to produce isolated attosecond pulses from Doppler harmonics
50
NUNEZ, SILVIA C. "Efeito do laser de helio neonio sobre a microcirculacao sanguinea durante a reparacao tecidual: estudo in vivo por meio de fluxometria laser Doppler." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11055.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:47:34Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:10:10Z (GMT). No. of bitstreams: 1 08989.pdf: 4487879 bytes, checksum: e80261387f79b3fc70c007567515777d (MD5)
Dissertacao (Mestrado Profissionalizante em Lasers em Odontologia)
IPEN/D-MPLO
Instituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP; Faculdade de Odontologia, Universidade de Sao Paulo