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Teses / dissertações sobre o tema "Doppler"
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1
Killich, Markus. "Tissue Doppler Imaging". Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-67089.
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2
Searle, Stephen. "Matched doppler processing /". Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09AS/09ass439.pdf.
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3
Pawelka, Robert H. "Digitized Doppler Signal Processor". International Foundation for Telemetering, 1989. http://hdl.handle.net/10150/614677.
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International Telemetering Conference Proceedings / October 30-November 02, 1989 / Town & Country Hotel & Convention Center, San Diego, CaliforniaAt the present time there is a requirement for developing an airborne approach for processing radar doppler video data into digital PCM format compatible with current IRIG standards. Techniques for digitizing the doppler video presently exist, but have limitations due to the fact that the data is processed and represented in the time domain. These limitations can be mainly attributed to the high bit rates required for quantizing the dynamic nature of the doppler signal. Therefore, an alternate approach was selected by which the video doppler data is converted and represented in the frequency domain. The time to frequency domain conversion is accomplished with a digital Part Fourier Transform (FFT) implemented in conjunction with a quadrature translator. This method will provide a means by which the doppler signal can be represented as a quasi-static spectrum. The advantage in this application is that only the spectral data which contains relevant engineering information will be processed. The resultant system will thereby minimize the transmission bit rate and maximize the dynamic range for the purpose of signal analysis. The paper will describe the implementation and work performed on the digitized doppler signal processor along with the potential application in PCM systems requiring spectral signal analysis.
4
Fredriksson, Ingemar. "Quantitative Laser Doppler Flowmetry". Doctoral thesis, Linköpings universitet, Biomedicinsk instrumentteknik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-19947.
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Laser Doppler flowmetry (LDF) is virtually the only non-invasive technique, except for other laser speckle based techniques, that enables estimation of the microcirculatory blood flow. The technique was introduced into the field of biomedical engineering in the 1970s, and a rapid evolvement followed during the 1980s with fiber based systems and improved signal analysis. The first imaging systems were presented in the beginning of the 1990s. Conventional LDF, although unique in many aspects and elegant as a method, is accompanied by a number of limitations that may have reduced the clinical impact of the technique. The analysis model published by Bonner and Nossal in 1981, which is the basis for conventional LDF, is limited to measurements given in arbitrary and relative units, unknown and non-constant measurement volume, non-linearities at increased blood tissue fractions, and a relative average velocity estimate. In this thesis a new LDF analysis method, quantitative LDF, is presented. The method is based on recent models for light-tissue interaction, comprising the current knowledge of tissue structure and optical properties, making it fundamentally different from the Bonner and Nossal model. Furthermore and most importantly, the method eliminates or highly reduces the limitations mentioned above. Central to quantitative LDF is Monte Carlo (MC) simulations of light transport in tissue models, including multiple Doppler shifts by red blood cells (RBC). MC was used in the first proof-of-concept study where the principles of the quantitative LDF were tested using plastic flow phantoms. An optically and physiologically relevant skin model suitable for MC was then developed. MC simulations of that model as well as of homogeneous tissue relevant models were used to evaluate the measurement depth and volume of conventional LDF systems. Moreover, a variance reduction technique enabling the reduction of simulation times in orders of magnitudes for imaging based MC setups was presented. The principle of the quantitative LDF method is to solve the reverse engineering problem of matching measured and calculated Doppler power spectra at two different source-detector separations. The forward problem of calculating the Doppler power spectra from a model is solved by mixing optical Doppler spectra, based on the scattering phase functions and the velocity distribution of the RBC, from various layers in the model and for various amounts of Doppler shifts. The Doppler shift distribution is calculated based on the scattering coefficient of the RBC:s and the path length distribution of the photons in the model, where the latter is given from a few basal MC simulations. When a proper spectral matching is found, via iterative model parameters updates, the absolute measurement data are given directly from the model. The concentration is given in g RBC/100 g tissue, velocities in mm/s, and perfusion in g RBC/100 g tissue × mm/s. The RBC perfusion is separated into three velocity regions, below 1 mm/s, between 1 and 10 mm/s, and above 10 mm/s. Furthermore, the measures are given for a constant output volume of a 3 mm3 half sphere, i.e. within 1.13 mm from the light emitting fiber of the measurement probe. The quantitative LDF method was used in a study on microcirculatory changes in type 2 diabetes. It was concluded that the perfusion response to a local increase in skin temperature, a response that is reduced in diabetes, is a process involving only intermediate and high flow velocities and thus relatively large vessels in the microcirculation. The increased flow in higher velocities was expected, but could not previously be demonstrated with conventional LDF. The lack of increase in low velocity flow indicates a normal metabolic demand during heating. Furthermore, a correlation between the perfusion at low and intermediate flow velocities and diabetes duration was found. Interestingly, these correlations were opposites (negative for the low velocity region and positive for the mediate velocity region). This finding is well in line with the increased shunt flow and reduced nutritive capillary flow that has previously been observed in diabetes.
5
Barba, Alessandra. "Effetto Doppler in astrofisica". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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Questo elaborato espone le caratteristiche principali dell'effetto Doppler e l'applicazione del suddetto in vari ambiti del settore astrofisico.
La derivazione della formule è divisa nel caso classico in cui si studia il fenomeno rispetto alle onde acustiche, e il nel caso relativistico nel quale si studia l'effetto sulle onde elettromagnetiche.
Le applicazioni astrofisiche prese in considerazione sono le seguenti: Redshift e Legge di Hubble nell'ambito cosmologico; allargamento Doppler delle linee spettrali nell'ambito della spettroscopia astronomica; stelle binarie spettroscopiche e MASER nell'ambito del calcolo di grandezze fisiche attraverso la determinazione della velocità radiale tramite lo shift delle righe spettrali.
6
Cuoghi, Lorenzo. "Effetto Doppler e applicazioni astrofisiche". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/12830/.
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Nel corso del secolo XIX il fisico James Clerk Maxwell riassunse le leggi sull'elettromagnetismo nelle note equazioni che portano il suo nome, dalle quali è stato possibile estrapolare la natura ondulatoria della luce. Questa importantissima caratteristica, per la quale la luce è definita come onda elettromagnetica, implica una grande vastità di fenomeni di origine ondulatoria, tra i quali l'Effetto Doppler, il quale ha importantissime applicazioni nell'ambito astrofisico e cosmologico.
7
Lauretta, Francesco. "Effetto doppler ed applicazioni astrofisiche". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14767/.
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L’effetto doppler fu scoperto dall'austriaco Christian Johann Doppler che nel 1842 fece una pubblicazione, affermando che un oggetto luminoso deve cambiare colore se posto in moto rispetto ad un osservatore. Infatti notò, sfruttando un vagone con alcuni musicisti sopra, come il suono variasse in base al moto relativo tra vagone ed osservatore. Un'analisi più dettagliata mostrò che un ascoltatore in moto verso una sorgente sonora ferma rispetto al mezzo di trasmissione, riceve un suono di frequenza maggiore rispetto a quello che ascolterebbe se anche lui fosse a riposo. Viceversa la frequenza è minore se l'ascoltatore si allontana dalla sorgente. Fenomeni analoghi si manifestano se la sorgente
si muove rispetto al mezzo di trasmissione mentre l’ascoltatore resta fermo. Oggi sappiamo che questo fenomeno è verificato per qualsiasi tipo di onda meccanica.
8
Di, Benedetto Andrea. "Effetto Doppler e applicazioni astrofisiche". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/15821/.
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In questo trattato si parlerà dell'effetto doppler e di alcune delle sue applicazioni in astrofisica. Si distingueranno due casi a seconda delle velocità in gioco (relativistiche o meno) e si applicheranno le rispettive formule a diversi casi specifici per darne una spiegazione.
9
Politi, Marialudovica. "Effetto Doppler e applicazioni astrofisiche". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16160/.
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In questo elaborato si analizza l'Effetto Doppler e le sue applicazioni in astronomia. Nella prima parte viene analizzato il fenomeno tramite qualche passaggio prettamente matematico e fisico per arrivare ad una corretta formulazione generale del fenomeno.
Nella seconda parte vi è l'applicazione vera e propria dell'effetto Doppler in ambito astrofisico.
10
Maranzano, Matteo. "Effetto Doppler e applicazioni astrofisiche". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/17068/.
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Viene trattato l'effetto Doppler nell'ambito classico, analizzando in che modo variano le caratteristiche di un'onda quando la sua sorgente e l'osservatore che la rileva si muovono uno rispetto all'altro.
Una breve appendice tratterà,poi, dello stesso effetto nel regime relativistico.
In seguito, si analizza come l'effetto Doppler venga utilizzato per determinare la massa delle stelle componenti un sistema binario spettroscopico, e come lo si utilizzi come scala di distanza cosmica sfruttando il così detto Redshift Cosmologico.
11
Casavecchia, Benedetta. "Effetto Doppler e applicazioni astrofisiche". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18767/.
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L’Effetto Doppler è il fenomeno fisico che descrive la variazione della frequenza osservata di un’onda quando la sorgente emittente e l’osservatore sono in moto relativo fra di loro. Esso può essere trattato in maniera classica, se l'onda ha una velocità di propagazione inferiore a quella della luce, o in maniera relativistica. In ambito astrofisico l'Effetto Doppler viene applicato alla radiazione elettromagnetica, unico segnale che ci giunge dai corpi celesti. Esso viene studiato tramite lo spostamento delle righe spettrali verso il rosso (redshift) o il blu (blueshift). Un'importante conseguenza di questo fenomeno è l'allargamento delle righe a causa dell'agitazione termica delle particelle in una nube di gas o dei moti di rotazione dei corpi. Inoltre, grazie alla misura delle velocità radiali con il metodo Doppler si possono ricercare esopianeti, sistemi di stelle binarie/multiple e si possono stimare le masse degli oggetti in esame. Infine, si parlerà di come il fenomeno è stato utile per il calcolo del tasso di espansione dell’Universo e di come il reshift cosmologico venga impiegato nella misura del look back time.
12
Girolamodibari, Andrea. "Effetto Doppler e applicazioni astrofisiche". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21208/.
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Una breve trattazione riguardante l'effetto Doppler. Prima verranno affrontati gli aspetti matematici e fisici del fenomeno, nella casistica delle onde sonore, poi tenendo in considerazione gli effetti relativistici, mediante l'utilizzo di formule e grafici. In seguito si proverà ad analizzare i svariati ambiti di applicazione dell'effetto, e mediante il suo utilizzo, si è arrivati e si arrivi a risultati concreti nel mondo della ricerca astrofisica e cosmologica.
13
Chua, Cheng Lock Charles. "Doppler-only synthetic aperture radar". Thesis, Monterey, Calif. : Naval Postgraduate School, 2006. http://bosun.nps.edu/uhtbin/hyperion.exe/06Dec%5FChua.pdf.
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Thesis (M.S. in Combat Systems Sciences and Technology)--Naval Postgraduate School, December 2006.Thesis Advisor(s): Brett Borden, Donald Walters. "December 2006." Includes bibliographical references (p. 69-70). Also available in print.
14
Walker, Andrew. "Testing of Doppler Ultrasound Systems". Doctoral thesis, Linköpings universitet, Fysiologisk mätteknik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-51213.
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Blood and tissue velocities are measured and analyzed in cardiac, vascular, and other applications of diagnostic ultrasound. Errors in system performance might give invalid measurements. We developed two moving string test targets and a rotating cylinder phantom (Doppler phantoms) to characterize Doppler ultrasound systems. These phantoms were initially used to measure such variables as sample volume dimensions, location of the sample volume, and the performance of the spectral analysis. Later, specific tests were designed and performed to detect errors in signal processing, causing time delays and inaccurate velocity estimation in all Doppler modes. In cardiac motion pattern even time delays as short as 30 ms may have clinical relevance. These delays can be obtained with echocardiography by using flow and tissue Doppler and M-mode techniques together with external signals (e.g., electrocardiography (ECG) and phonocardiography). If one or more of these signals are asynchronous in relation to the other signals, an incorrect definition of cardiac time intervals may occur. To determine if such time delays in signal processing are a serious problem, we tested four commercial ultrasound systems. We used the Doppler string phantom and the rotating cylinder phantom to obtain test signals. We found time delays of up to 90 ms in one system, whereas delays were mostly short in the other systems. Further, the time delays varied relative to system settings. In two-dimensional (2D) Doppler the delays were closely related to frame rate. To determine the accuracy in velocity calibration, we tested the same four ultrasound systems using the Doppler phantoms to obtain test signals for flow (PW) and tissue (T-PW) pulse Doppler and for continuous wave (CW) Doppler. The ultrasound systems were tested with settings and transducers commonly used in cardiac applications. In two systems, the observed errors were mostly close to zero, whereas one system systematically overestimated velocity by an average of 4.6%. The detected errors are mostly negliable in clinical practice but might be significant in certain cases and research applications.
15
Hawkes, Graham S. "Three-dimensional doppler global velocimetry". Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427619.
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16
Pannell, C. N. "Fibre-optic laser Doppler velocimetry". Thesis, University of Kent, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383370.
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17
Comani, Alice. "Effetto Doppler e applicazioni astrofisiche". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24850/.
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18
Mary, Delphine Armengol Valérie. "Laser Doppler et diagnostic pulpaire". [S.l.] : [s.n.], 2006. http://theses.univ-nantes.fr/thesemed/CDmary.pdf.
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19
Bättig, Rainer. "Fiber optic Doppler velocimeter probes /". [S.l.] : [s.n.], 1988. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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20
Giannella, Giovanni. "Effetto doppler e applicazioni astrofisiche". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7149/.
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21
Guidotti, Simone. "Effetto doppler e applicazioni astrofisiche". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7390/.
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22
Liu, Zenghai. "Interferometric filter planar Doppler velocimetry". Thesis, Cranfield University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539402.
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This thesis describes the development of a Mach-Zehnder interferometric filter based planar Doppler velocimetry (MZI-PDV) flow measurement technique. The technique uses an entirely new optical system, an unbalanced MZI incorporating glass blocks for wavefront-matching, to replace the iodine cell currently used in conventional PDV. The free spectral range of the interferometric filter can be selected by adjusting the optical path difference of the MZI. This allows the velocity measurement range, sensitivity and resolution to be varied. This system offers no restricts to the choice of laser wavelength of operation which is not the case with most techniques. Two techniques to process the interference fringe images are presented. The first uses the shift of the fringe pattern to determine the Doppler frequency shift along profiles. The second provides a full-field measurement by normalising the received light intensity at each pixel in the image. With the single camera MZI-PDV scheme, exact alignment of the two output images on the active area of the camera is automatic. This eliminates the pixel-matching problem in conventional two camera PDV systems. The technique allows the measurement of up to three components of the flow velocity across a plane defined by a laser light sheet. The construction of a single velocity component MZI-PDV system that incorporates a phase-locking system designed to stabilise the filter is described. Measurements are made on the velocity field of a rotating disc with maximum velocities of ~±70ms-1 and an axis-symmetric air jet (with a nozzle diameter of 20mm) with an exit velocity of ~85ms-1. Standard deviations in the measured velocities were found to be about 2.9 and 2ms-1 for the two processing methods respectively. The system was then modified to make 3-component velocity measurements using imaging fibre bundles to port multiple views to a single detector head, and the standard deviation of the velocity error is around ±3ms-1 for a maximum velocity of ~±30ms-1 in the field of view. The factors that will affect the quality of the interference fringe image are investigated including polarisation sensitivity of the two beam splitters and flatness of the optical components. The inclination angle and the optical path deviation have little effect on the contrast of the interference fringes since collimated light beams, rather than divergent ones, are used in the interferometer.
23
Simonpietri, Caroline. "Techniques modernes en écho Doppler". Paris 5, 1997. http://www.theses.fr/1997PA05P158.
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24
Greil, Oliver. "Strömungsuntersuchung in Modellen humaner Karotisbifurkationen nach Stentimplantation mittels Laser-Doppler-Anemometrie und endoluminaler Doppler-Sonographie". [S.l.] : [s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=962787213.
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25
Lindqvist, Per. "Right heart function in health and disease : a Doppler echocardiography and Doppler tissue imaging study /". Doctoral thesis, Umeå : Department of Public Health and Clinical Medicine, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-392.
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26
Walker, Andrew. "Performance testing of ultrasound Doppler equipment". Licentiate thesis, Linköping University, Linköping University, The Institute of Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-29499.
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Blood and tissue velocities are measured and analysed in cardiac, vascular and other applications of diagnostic ultrasound. Errors in system performance might give invalid measurements.
We developed two moving string test targets (“Doppler phantoms”) to characterise ultrasound Doppler systems. These phantoms were initially used to measure such variables as sample volume dimensions, location of the sample volume, and the performance of the spectral analysis. Specific tests were done to detect errors in signal processing causing time delays and inaccurate velocity estimation.
Even time delays as short as 30 ms in cardiac motion pattern may have clinical relevance. These delays can be measured with echocardiography, by using techniques such as flow and tissue Doppler and M-mode together with external signals (e.g., ECG and phonocardiography). If one or more of these signals are delayed in relation to the other signals (asynchronous), an incorrect definition of cardiac time intervals can occur. To determine if this time delay in signal processing is a problem, we tested three commercial ultrasound systems. We used a digital ECG simulator and a Doppler string phantom to obtain test signals. We found time delays of up to 90 ms in one system, whereas delays were mostly short in the other two systems. Further, the time delays varied relative to system settings.
To determine the accuracy in velocity calibration, we tested the same three ultrasound systems using the Doppler phantom to obtain test signals for flow and tissue pulsed Doppler and for continuous wave Doppler. The ultrasound systems were tested with settings and transducers commonly used in cardiac applications. In two systems the observed errors were mostly close to zero, whereas one system systematically overestimated velocity by an average of 4.6%. The detected errors can be considered small in clinical applications but might be serious in certain research applications. It is important to know the velocity error of the used ultrasound system and to judge it in relation to the application in which it is used.
27
Joncour, Isabelle. "Imagerie Doppler des étoiles T Tauri". Phd thesis, Université Paris-Diderot - Paris VII, 1994. http://tel.archives-ouvertes.fr/tel-00725018.
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Dans ce travail de thèse, nous analysons pour la première fois à l'aide de la technique d'imagerie doppler, les raies photosphériques de deux étoiles T Ttauri à faibles raies d'émission, pour cartographier leur brillance de surface et localiser ainsi les inhomogenéités en température, qui signent la présence de forts champs magnétiques. Pour ce faire, nous avons développé une méthode numerique fondée sur la paramétrisation de taches, dont les caractéristiques sont déterminées lors de la minimisation, de type moindres carrés, des différences entre les modèles de raie calculés et l'ensemble des raies (issues de divers éléments chimiques) observées à plusieurs phases rotationnelles. Nous étudions le type et l'amplitude de déformations engendrées par la présence de taches froides, ce qui nous permet d'en déduire les conditions optimales d'application de l'imagerie doppler. Nous etudions par ailleurs les limitations intrinséques de cette technique déterminées par la qualité des données (résolution instrumentale et rapport signal sur bruit). L'application à des étoiles T Tauri, jeunes étoiles en fin de formation, similaires au soleil dans sa jeunesse, nous permet de mettre en évidence la présence de larges taches froides, préférentiellement localisées aux latitudes élevées. La position de ces taches suggère une géometrie de type dipolaire pour le champ magnétique. Seule une étude exhaustive pourra déterminer si cette géometrie est commune à toute cette classe d'étoiles, ou si elle est liée à des caractéristiques particulières (fort taux de rotation 70km/s ; 80 km/s). cette réponse est cruciale pour déterminer l'origine du champ magnétique : fossile, engendré par un mecanisme particulier de type dynamo, peut-etre les deux à la fois. L'application future de cette technique aux etoiles T Tauri classiques, supposées etre entourées d'un disque d'accrétion, sera determinante pour comprendre l'interaction entre l'environnement circumstellaire et l'objet central.
28
Agirman, Handan. "Waveform Design For Pulse Doppler Radar". Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/2/12606840/index.pdf.
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ABSTRACT
WAVEFORM DESIGN FOR PULSE DOPPLER RADAR
AgIRMAN, Handan
M.S., Department of Electrical and Electronics Engineering
Supervisor: Prof. Dr. Mete Severcan
December 2005, 100 pages
This study is committed to the investigation of optimum waveforms for a pulse doppler radar which uses a non linear high power amplifier in the transmitter. The optimum waveform is defined as the waveform with the lowest peak and integrated side lobe level, the narrowest main lobe in its autocorrelation and the narrowest bandwidth in its spectrum.
The Pulse Compression method is used in radar systems since it is more advantageous in terms of the resolution. Among all pulse compression methods, the main focus of this study is on Phase Coding. Two types of radar waveforms assessed throughout this study are Discrete Phase Modulated Waveforms and Continuous Phase Modulated Waveforms. The continuous phase modulated waveforms are arranged under two titles: the memoryless phase modulated waveform and the waveform modulated with memory.
In order to form memoryless continuous phase waveforms, initially, discrete phase codes are obtained by using Genetic Algorithm. Following this process, a new phase shaping pulse is defined and applied on the discrete phase waveforms.
Among the applicable modulation with memory techniques, Continuous Phase Modulation maintains to be the most appropriate. The genetic algorithm is used to find different lengths of optimum data sequences which form the continuous phase scheme.
29
Aygar, Alper. "Doppler Radar Data Processing And Classification". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609890/index.pdf.
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In this thesis, improving the performance of the automatic recognition of the Doppler radar targets is studied. The radar used in this study is a ground-surveillance doppler radar. Target types are car, truck, bus, tank, helicopter, moving man and running man. The input of this thesis is the output of the real doppler radar signals which are normalized and preprocessed (TRP vectors: Target Recognition Pattern vectors) in the doctorate thesis by Erdogan (2002). TRP vectors are normalized and homogenized doppler radar target signals with respect to target speed, target aspect angle and target range. Some target classes have repetitions in time in their TRPs. By the use of these repetitions, improvement of the target type classification performance is studied. K-Nearest Neighbor (KNN) and Support Vector Machine (SVM) algorithms are used for doppler radar target classification and the results are evaluated. Before classification PCA (Principal Component Analysis), LDA (Linear Discriminant Analysis), NMF (Nonnegative Matrix Factorization) and ICA (Independent Component Analysis) are implemented and applied to normalized doppler radar signals for feature extraction and dimension reduction in an efficient way. These techniques transform the input vectors, which are the normalized doppler radar signals, to another space. The effects of the implementation of these feature extraction algoritms and the use of the repetitions in doppler radar target signals on the doppler radar target classification performance are studied.
30
Halimi, Abderrahim. "From conventional to delay/Doppler altimetry". Phd thesis, Toulouse, INPT, 2013. http://oatao.univ-toulouse.fr/10444/1/halimi.pdf.
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For more than twenty years, conventional altimeters like Topex, Poseidon-2 or Poseidon-3, have been delivering waveforms that are used to estimate many parameters such as the range between the satellite and the observed scene, the wave height and the wind speed. Several waveform models and estimation processing have been developed for the oceanic data in order to improve the quality of the estimated altimetric parameters. Moreover, a great effort has been devoted to process coastal echoes in order to move the altimetric measurements closer to the coast. In this thesis, we are interested in resolving these two problems, i.e., processing coastal waveforms and improving the quality of the estimated oceanic parameters. The first part of the study considers the problem of coastal waveforms and proposes a new altimetric model taking into account the possible presence of peaks affecting altimetric echoes. In a second part of our work, we have been interested in the delay/Doppler altimetry. This new technology aims at reducing the measurement noise and increasing the alongtrack resolution when compared to conventional altimetry. Two altimetric models have been developed in order to estimate the resulting delay/Doppler echoes. These models allow a clear improvement in parameter estimation when compared to conventional altimetry.
31
Lange, Marcos Christiano. "Embolia paradoxal avaliada pelo Doppler Transcraniano". reponame:Repositório Institucional da UFPR, 2011. http://hdl.handle.net/1884/26288.
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Resumo: O Doppler transcraniano contrastado (DTCc) é um método diagnóstico utilizado com frequência na investigação da embolia paradoxal (EP) e do forame oval patente (FOP). Apesar da padronização do método, inúmeros questionamentos existem em relação a metodologia utilizada, entre as quais, a solução contrastante ideal, o momento de realização da manobra de Valsalva (MV) durante o exame sensibilizado e marcadores que diferenciem entre a EP devido o FOP e outras EPs, preferencialmente as extracardíacas. Este estudo teve como objetivos: 1) comparar a positividade de EP pelo DTCc com o uso de duas soluções contrastantes, a solução salina agitada (SSA) e a solução salina agitada com sangue (SSAs); 2) comparar dois momentos da MV com o uso da SSAs; e 3) identificar possíveis marcadores de EP pelo DTCc que possam estar correlacionados com a presença de FOP pelo ecocardiograma. Material e Métodos: Foram analisados 42 pacientes em acompanhamento no Ambulatório de Doenças Cerebrovasculares do Serviço de Neurologia do Hospital de Clínicas da UFPR entre primeiro de outubro de 2007 e 31 de agosto de 2008 com indicação para investigação de EP ou FOP. Todos os pacientes foram submetidos a exame de DTCc padronizado, com uso das duas soluções contrastantes: SSA composta por 9ml de solução salina e 1ml de ar e SSAs, composta por 8ml de solução salina, 1ml de sangue do próprio paciente e 1ml de ar. Foram realizadas três metodologias: exame em repouso; sensibilizado previamente pela MV (MV-Pré), caracterizado por MV 5 segundos antes da injeção da solução contrastante e sensibilizado posteriormente pela MV (MV-Pós), caracterizado por MV 5 segundos após a injeção da solução contrastante. Resultados: Foi observada diferença na positividade da EP comparando as duas soluções utilizadas com a presença de maior duração da passagem de sinais de microembolia (MES) com a SSAs. Ao serem avaliados dois momentos distintos para a MV com o uso de SSAs, não foi observada diferença nos resultados de exames positivos, número e duração de MES. Nos pacientes com AVEi e DTCc positivo submetidos a ecocardiograma transesofágico contrastado (ETEc) para o diagnóstico de FOP, os exames com passagem de EP com número acima de 9 MES e início da passagem de MES antes de 9 segundos após a injeção da SSAs foram observados somente em pacientes com FOP pelo ETEc (31%). Conclusão: O uso de SSAs aumenta os graus e a duração da EP comparada a SSA, porém não existe diferença quanto a positividade de EP com SSAs quando comparados dois momentos distintos da MV. A presença de mais de 9 MES e início da passagem destes com menos de 9 segundos após a injeção da SSAs é um ponto de corte para identificar, com alta especificidade, os pacientes com FOP pelo ETEc.
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Kamiya, Carla Priscila [UNESP]. "Estudo Power Doppler das lesões mamárias". Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/99244.
Texto completo da fonteResumo:
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A ultra-sonografia mamária tem sido um método padrão complementar à mamografia há mais de dez anos. Permite o detalhamento da morfologia capaz de diferenciar lesões benignas de malignas. A angiogênese tumoral é crítica para o crescimento autônomo e desenvolvimento do câncer de mama. A alteração hemodinâmica que acompanha tal angiogênese fornece base para o estudo das lesões no Doppler US O estudo Doppler US permite a análise de parâmetros objetivos do fluxo como sinais de fluxo, velocidade máxima sistólica (Vmax), índice de resistência (RI) e índice de pulsatilidade (PI). Avaliar o papel do Power Doppler estudando tais variáveis de fluxo. O estudo foi realizado no Setor de Diagnóstico e Imagem do Centro de Avaliação em Mastologia (CAM) do Departamento de Ginecologia, Obstetrícia e Mastologia da Faculdade de Medicina de Botucatu – UNESP, de dezembro de 2004 a dezembro de 2007. Este estudo é retrospectivo, analítico e observacional. Resultados: Foram estudadas 613 lesões mamárias, avaliadas por Power Doppler e citologia aspirativa ou biópsia percutânea. Pelo estudo, 462 lesões não apresentaram vascularização: 340 benignas (26,41%) e 122 malignas (73,59%). Observou-se vascularização em 151 lesões: 98 malignas (64,90%) e 53 benignas (35,10%). As benignas apresentaram média de 1,79 vasos por lesão; Vmax de 15,86cm/s; IP de 0,99 e IR de 0,61. Já as malignas com fluxo Doppler, observou-se média de 5,6 vasos por lesão; Vmax de 21,0cm/s; IP de 1,45 e IR de 0,74. Pela curva ROC, para predizer malignidade, observou-se sensibilidade e especificidade respectivos de 64,3% e 73,6% para 1,5 vasos por lesão; 61,3% e 56,6% para Vmax de 16,50 cm/s ; 72,8% e 66,7% para IP de 1,08 e 70,6% e 68,0% para IR de 0,66. O estudo Power Doppler das lesões mamárias consegue determinar limites que auxiliam na diferenciação entre lesões benignas e malignas.
has been a standard complementary procedure to mammography for more than 10 years. It gives morphological details which enable differentiation between benign and malignant lesions. Tumor angiogenesis is critical for the autonomous growth and spread of breast cancers. The altered hemodynamics that accompany tumor angiogenesis provide a basis for discriminating between malignant and benign breast masses at color Doppler US. The Doppler Sonographic study of vascularity includes assessment of parameters like number of flow signals, peak flow velocity (Vmax), resistivity index (RI), and pulsatility index (PI). Objective: The aim is to evaluate the role of Power Doppler at breast lesions, studying flow variables. Methods: The study was conducted in Setor de Diagnóstico e Imagem of Centro de Avaliação em Mastologia (CAM), Department of Gynecology, Obstetrics and Mastology - Faculty of Medicine of Botucatu - UNESP in the period of December 2004 to December 2007. This study is retrospective, observational and analytical. Results: We studied 613 breast lesions, evaluated by Power Doppler and percutaneous biopsy or aspiration cytology. By PD study, 462 lesions showed no vascularity: 340 benign (26.41%) and 122 malignant (73.59%). Vascularization was observed in 151 lesions: 98 malignant lesions (64.90%) and 53 benign lesions (35.10%). Benign lesions has an average of 1.79 vessels per lesion; Vmax of 15.86 cm / s; PI of 0.99 and RI of 0.61. Already the malignant lesions with Doppler flow, it was observed an avaerage of 5.6 vessels per lesion; Vmax of 21.0 cm / s; PI of 1.45 and RI of 0.74. For the ROC curve, to predict malignancy, was observed a sensitivity and specificity of 64,3% and 73,6% for the presence of 1.5 vessels per lesion; 61,3% and 56,6% for Vmax of 16.50 cm / s, 72,8% and 66,7% for PI of 1.08 and 70,6% and 68,0% for RI of 0.66. Has been a standard complementary procedure to mammography for more than 10 years.
33
Rajan, Vinayakrishnan. "Speckles in laser doppler perfusion imaging". Enschede : University of Twente [Host], 2007. http://doc.utwente.nl/58017.
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Lu, Zenghai. "Interferometric filter-based planar Doppler velocimetry". Thesis, Cranfield University, 2008. http://dspace.lib.cranfield.ac.uk/handle/1826/7151.
Texto completo da fonteResumo:
This thesis describes the development of a Mach-Zehnder interferometric filter based
planar Doppler velocimetry (MZI-PDV) flow measurement technique. The technique
uses an entirely new optical system, an unbalanced MZI incorporating glass blocks for
wavefront-matching, to replace the iodine cell currently used in conventional PDV. The
free spectral range of the interferometric filter can be selected by adjusting the optical
path difference of the MZI. This allows the velocity measurement range, sensitivity and
resolution to be varied. This system offers no restricts to the choice of laser wavelength
of operation which is not the case with most techniques. Two techniques to process the
interference fringe images are presented. The first uses the shift of the fringe pattern to
determine the Doppler frequency shift along profiles. The second provides a full-field
measurement by normalising the received light intensity at each pixel in the image.
With the single camera MZI-PDV scheme, exact alignment of the two output images on
the active area of the camera is automatic. This eliminates the pixel-matching problem
in conventional two camera PDV systems. The technique allows the measurement of up
to three components of the flow velocity across a plane defined by a laser light sheet.
The construction of a single velocity component MZI-PDV system that incorporates a
phase-locking system designed to stabilise the filter is described. Measurements are
made on the velocity field of a rotating disc with maximum velocities of ~±70ms-1 and
an axis-symmetric air jet (with a nozzle diameter of 20mm) with an exit velocity of
~85ms-1. Standard deviations in the measured velocities were found to be about 2.9 and
2ms-1 for the two processing methods respectively. The system was then modified to
make 3-component velocity measurements using imaging fibre bundles to port multiple
views to a single detector head, and the standard deviation of the velocity error is
around ±3ms-1 for a maximum velocity of ~±30ms-1 in the field of view.
The factors that will affect the quality of the interference fringe image are investigated
including polarisation sensitivity of the two beam splitters and flatness of the optical
components. The inclination angle and the optical path deviation have little effect on the
contrast of the interference fringes since collimated light beams, rather than divergent
ones, are used in the interferometer.
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Fredriksen, Tonje Dobrowen. "Quantitative Doppler Methods in Cardiovascular Imaging". Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for sirkulasjon og bildediagnostikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-27300.
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Ultrasound imaging of blood flow in the heart and blood vessels has become an essential part of diagnosing diseases related to the circulatory system. By using different Doppler methods, the blood flow may be visualized or quantified. In this work we take advantage of the opportunities given by the introduction of parallel processing of ultrasound data to develop new quantitative Doppler methods. Pulsed wave (PW) Doppler is a technique for measuring blood velocities, providing the full velocity spectrum in a specific region of interest. The maximum velocities may be found by delineation of the spectral envelope, and may be used to estimate the severity of stenoses or valve leakages. However, PW Doppler suffers from several challenges, which makes quantitative analysis problematic. To limit spectral broadening, we created a new method called 2-D tracking Doppler, which incorporates information from several parallel receive beams. Spectra with improved resolution and signal-to-noise ratio were produced for a large span of beam-to-flow angles. The new method was tested using in vitro and in vivo recordings. A signal model was derived and the expected Doppler power spectra were calculated, showing good agreement with experimental data. Experiments were performed to investigate how the 2-D tracking Doppler method depends on the tracking angle. It was shown that the spectra have lowest bandwidth and maximum power when the tracking angle is equal to the beam-to-flow angle. This may facilitate new techniques for velocity calibration. It was shown that the velocity calibration errors may be lower for the 2-D tracking Doppler method than for a conventional PW Doppler approach, and especially for large beam-to-flow angles. In heart disease, the quantification of valve regurgitation is a remaining challenge. In this thesis, we have investigated a new technique to estimate the size of regurgitant jets using spectral Doppler and parallel beamforming. A modality that uses high pulse repetition frequency 3-D Doppler was devised, to isolate the backscattered signal power from the vena contracta, that is the narrowest flow region of a regurgitant jet. A simulation study was performed to test and optimize the new method, suggesting a feasible setup for the transmit- and receive beams. Cross-sectional power Doppler images of simulated regurgitations of various sizes were generated, and the regurgitant volumes were accurately estimated. Since the velocity-time integral and the orifice area are extracted from a single recording, the proposed method may give more robust volume estimates than methods where the velocities and the area are measured from separate recordings.
36
McConnell, B. A. "Neurodevelopmental outcome and prenatal Doppler performance". Thesis, Queen's University Belfast, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390885.
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Christensen, John Kenneth. "Doppler signatures from canonical rotating targets". Thesis, University of Surrey, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411384.
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Dooley, Saul. "Subsample time delay and Doppler estimation". Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248768.
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Heine, Matthew K. "Doppler shifts in the KATRIN experiment". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44462.
Texto completo da fonteResumo:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2008."June 2008."
Includes bibliographical references (p. 83-84).
In the past few decades, neutrinos, which are predicted to be massless particles by the Standard Model of Particle Physics, have been shown to have non-zero mass. The absolute scale of this neutrino mass has significant implications in particle physics, astrophysics, and cosmology. The KATRIN experiment is designed to measure this absolute scale by examining the beta decay spectrum of molecular, gaseous tritium source. In this thesis, the beta decay of this molecular tritium is simulated to study the effects of "Doppler shifts" in the energy of the emitted electrons due to the random thermal motion and fluid flow velocity of the differentially pumped tritium gas. Simulated spectra are presented for three different neutrino masses and the relative effects of the thermal and flow velocities are discussed.
by Matthew K. Heine.
S.B.
40
Smith, G. E. "Radar target micro-Doppler signature classification". Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/18688/.
Texto completo da fonteResumo:
This thesis reports on research into the field of Micro-Doppler Signature (μ-DS) based radar Automatic Target Recognition (ATR) with additional contributions to general radar ATR methodology. The μ-DS based part of the research contributes to three distinct areas: time domain classification; frequency domain classification; and multiperspective μ-DS classification that includes the development of a theory for the multistatic μ-DS. The contribution to general radar ATR is the proposal of a methodology to allow better evaluation of potential approaches and to allow comparison between different studies. The proposed methodology is based around a “black box” model of a radar ATR system that, critically, includes a threshold to detect inputs that are previously unknown to the system. From this model a set of five evaluation metrics are defined. The metrics increase the understanding of the classifier’s performance from the common probability of correct classification, that reports how often the classifier correctly identifies an input, to understanding how reliable it is, how capable it is of generalizing from the reference data, and how effective its unknown input detection is. Additionally, the significance of performance prediction is discussed and a preliminary method to estimate how well a classifier should perform is developed. The proposed methodology is then used to evaluate the μ-DS based radar ATR approaches considered. The time domain classification investigation is based around using Dynamic Time Warping (DTW) to identify radar targets based on their μ-DS. DTW is a speech processing technique that classifies data series by comparing them with a pre-classified reference dataset. This is comparable to the common k-Nearest Neighbour (k-NN) algorithm, so k-NN is used as a benchmark against which to evaluate DTW’s performance. The DTW approach is observed to work well. It achieved high probability of correct classification and reliability as well as being able to detect inputs of unknown class. However, the classifier’s ability to generalize from the reference data is less impressive and it performed only slightly better than a random selection from the possible output classes. Difficulties in classifying the μ-DS in the time domain are identified from the k-NN results prompting a change to the frequency domain. Processing the μ-DS in the frequency domain permitted the development of an advanced feature extraction routine to maximize the separation of the target classes and therefore reduce the effort required to classify them. The frequency domain also permitted the use of the performance prediction method developed as part of the radar ATR methodology and the introduction of a na¨ıve Bayesian approach to classification. The results for the DTW and k-NN classifiers in the frequency domain were comparable to the time domain, an unexpected result since it was anticipated that the μ-DS would be easier to classify in the frequency domain. However, the naıve Bayesian classifier produced excellent results that matched with the predicted performance suggesting it could not be bettered. With a successful classifier, that would be suitable for real-world use, developed attention turned to the possibilities offered by the multistatic μ-DS. Multiperspective radar ATR uses data collected from different target aspects simultaneously to improve classification rates. It has been demonstrated successful for some of the alternatives to μ-DS based ATR and it was therefore speculated that it might improve the performance of μ-DS ATR solutions. The multiple perspectives required for the classifier were gathered using a multistatic radar developed at University College London (UCL). The production of a dataset, and its subsequent analysis, resulted in the first reported findings in the novel field of the multistatic μ-DS theory. Unfortunately, the nature of the radar used resulted in limited micro-Doppler being observed in the collected data and this reduced its value for classification testing. An attempt to use DTW to perform multiperspective μ-DS ATR was made but the results were inconclusive. However, consideration of the improvements offered by multiperspective processing in alternative forms of ATR mean it is still expected that μ-DS based ATR would benefit from this processing.
41
Carpenter, James. "Low bandwidth laser Doppler blood flowmetry". Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14267/.
Texto completo da fonteResumo:
Laser Doppler Blood Flowmetry (LDBF) has for several decades been applied to measure the flow of red blood cells in living tissue. Laser Doppler Perfusion Imaging (LDPI), a recent advancement which enables full-field blood flow visualisation, is gaining clinical acceptance in fields such as burn diagnostics. However, video-rate full-field imagers with appropriate sensor and processing capability require large financial and physical resources and this has prompted the development of under-specified systems. These systems may reduce the bandwidth and processing complexity but the question of how they perform compared to their fully specified counterparts remains. The advantages of these cheaper and often highly reconfigurable systems are recognised and so it is beneficial to ask whether any novel processing schemes can reduce the resultant error. Here a reduced bandwidth LDBF signal processing system has been modelled. Bayesian Inference has been used to show that the Pareto distribution is a likely model for the LDBF power spectrum, despite often being cited as exponential. Methods of evaluating microvascular blood flow have been described and compared. Additionally, one fast algorithm's effectiveness has been explained, and a novel and accurate method using the Hilbert transform has been presented. By understanding how aliasing modifies the frequency distribution, Bayesian Inference has been used to correct the blood flow output towards gold-standard values. The technique has been shown to correct the output of a low bandwidth CMOS camera imaging a rotating diffuser. Low bandwidth LDPI systems may be suitable for certain clinical applications where sensitivity to high flow is not required. However, where sensitivity to higher flow than baseline is required, e.g. in burn diagnostics, low bandwidth systems may underestimate the true blood flow leading to misdiagnosis. Nevertheless, low bandwidth systems could be used in this scenario if reliable post-processing is employed, such as that suggested by this thesis.
42
Tannergren, Tomas. "Determining Orbits through Doppler Shift Observation". Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-200515.
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43
Kamiya, Carla Priscila. "Estudo Power Doppler das lesões mamárias /". Botucatu : [s.n.], 2009. http://hdl.handle.net/11449/99244.
Texto completo da fonteResumo:
Orientador: Gilberto UemuraBanca: José Ricardo P. Rodrigues
Banca: Ivo Carelli Filho
Resumo: A ultra-sonografia mamária tem sido um método padrão complementar à mamografia há mais de dez anos. Permite o detalhamento da morfologia capaz de diferenciar lesões benignas de malignas. A angiogênese tumoral é crítica para o crescimento autônomo e desenvolvimento do câncer de mama. A alteração hemodinâmica que acompanha tal angiogênese fornece base para o estudo das lesões no Doppler US O estudo Doppler US permite a análise de parâmetros objetivos do fluxo como sinais de fluxo, velocidade máxima sistólica (Vmax), índice de resistência (RI) e índice de pulsatilidade (PI). Avaliar o papel do Power Doppler estudando tais variáveis de fluxo. O estudo foi realizado no Setor de Diagnóstico e Imagem do Centro de Avaliação em Mastologia (CAM) do Departamento de Ginecologia, Obstetrícia e Mastologia da Faculdade de Medicina de Botucatu - UNESP, de dezembro de 2004 a dezembro de 2007. Este estudo é retrospectivo, analítico e observacional. Resultados: Foram estudadas 613 lesões mamárias, avaliadas por Power Doppler e citologia aspirativa ou biópsia percutânea. Pelo estudo, 462 lesões não apresentaram vascularização: 340 benignas (26,41%) e 122 malignas (73,59%). Observou-se vascularização em 151 lesões: 98 malignas (64,90%) e 53 benignas (35,10%). As benignas apresentaram média de 1,79 vasos por lesão; Vmax de 15,86cm/s; IP de 0,99 e IR de 0,61. Já as malignas com fluxo Doppler, observou-se média de 5,6 vasos por lesão; Vmax de 21,0cm/s; IP de 1,45 e IR de 0,74. Pela curva ROC, para predizer malignidade, observou-se sensibilidade e especificidade respectivos de 64,3% e 73,6% para 1,5 vasos por lesão; 61,3% e 56,6% para Vmax de 16,50 cm/s ; 72,8% e 66,7% para IP de 1,08 e 70,6% e 68,0% para IR de 0,66. O estudo Power Doppler das lesões mamárias consegue determinar limites que auxiliam na diferenciação entre lesões benignas e malignas.
Abstract: has been a standard complementary procedure to mammography for more than 10 years. It gives morphological details which enable differentiation between benign and malignant lesions. Tumor angiogenesis is critical for the autonomous growth and spread of breast cancers. The altered hemodynamics that accompany tumor angiogenesis provide a basis for discriminating between malignant and benign breast masses at color Doppler US. The Doppler Sonographic study of vascularity includes assessment of parameters like number of flow signals, peak flow velocity (Vmax), resistivity index (RI), and pulsatility index (PI). Objective: The aim is to evaluate the role of Power Doppler at breast lesions, studying flow variables. Methods: The study was conducted in Setor de Diagnóstico e Imagem of Centro de Avaliação em Mastologia (CAM), Department of Gynecology, Obstetrics and Mastology - Faculty of Medicine of Botucatu - UNESP in the period of December 2004 to December 2007. This study is retrospective, observational and analytical. Results: We studied 613 breast lesions, evaluated by Power Doppler and percutaneous biopsy or aspiration cytology. By PD study, 462 lesions showed no vascularity: 340 benign (26.41%) and 122 malignant (73.59%). Vascularization was observed in 151 lesions: 98 malignant lesions (64.90%) and 53 benign lesions (35.10%). Benign lesions has an average of 1.79 vessels per lesion; Vmax of 15.86 cm / s; PI of 0.99 and RI of 0.61. Already the malignant lesions with Doppler flow, it was observed an avaerage of 5.6 vessels per lesion; Vmax of 21.0 cm / s; PI of 1.45 and RI of 0.74. For the ROC curve, to predict malignancy, was observed a sensitivity and specificity of 64,3% and 73,6% for the presence of 1.5 vessels per lesion; 61,3% and 56,6% for Vmax of 16.50 cm / s, 72,8% and 66,7% for PI of 1.08 and 70,6% and 68,0% for RI of 0.66. Has been a standard complementary procedure to mammography for more than 10 years.
Mestre
44
Maillard, André. "Le doppler trans-cranien en neurochirurgie". Toulouse 3, 1992. http://www.theses.fr/1992TOU31508.
Texto completo da fonte
45
JONCOUR, ISABELLE. "Imagerie doppler des etoiles t tauri". Paris 7, 1994. http://www.theses.fr/1994PA077352.
Texto completo da fonteResumo:
Dans ce travail de these, nous analysons pour la premiere fois a l'aide de la technique d'imagerie doppler, les raies photospheriques de deux etoiles t tauri a faibles raies d'emission, pour cartographier leur brillance de surface et localiser ainsi les inhomogeneites en temperature, qui signent la presence de forts champs magnetiques. Pour ce faire, nous avons developpe une methode numeriaue fondee sur la parametrisation de taches, dont les caracteristiques sont determinees lors de la minimisation, de type moindres carres, des differences entre les modeles de raie calcules et l'ensemble des raies (issues de divers elements chimiques) observees a plusieurs phases rotationnelles. Nous etudions le type et l'amplitude de deformations engendrees par la presence de taches froides, ce qui nous permet d'en deduire les conditions optimales d'application de l'imagerie doppler. Nous etudions par ailleurs les limitations intrinseques de cette technique determinees par la qualite des donnees (resolution instrumentale et rapport signal sur bruit). L'application a des etoiles t tauri, jeunes etoiles en fin de formation, similaires au soleil dans sa jeunesse, nous permet de mettre en evidence la presence de larges taches froides, preferentiellement localisees aux latitudes elevees. La position de ces taches suggere une geometrie de type dipolaire pour le champ magnetique. Seule une etude exhaustive pourra determiner si cette geometrie est commune a toute cette classe d'etoiles, ou si elle est liee a des caracteristiques particulieres (fort taux de rotation 70km/s ; 80 km/s). Cette reponse est cruciale pour determiner l'origine du champ magnetique : fossile, engendre par un mecanisme particulier de type dynamo, peut-etre les deux a la fois. L'application future de cette technique aux etoiles t tauri classiques, supposees etre entourees d'un disque d'accretion, sera determinante pour comprendre l'interaction entre l'environnement circumstellaire et l'objet central.
46
Hong, Xichun. "Doppler Shifted Fourier Transform Emission Spectroscopy /". The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487929745336654.
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Iverson, Thomas Z. "Signature Stability in Laser Doppler Vibrometry". University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1497386740815576.
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48
Unruh, Yvonne Christine. "Doppler imaging of late-type stars". Thesis, University of Sussex, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260022.
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49
Yang, Jie. "Doppler and acceleration invariant pulse compression". Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2007. http://wwwlib.umi.com/cr/syr/main.
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Chester, David B. "A Parameterized Simulation of Doppler Lidar". DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6794.
Texto completo da fonteResumo:
Upcoming missions to explore planetary bodies in the solar system will require accurate position and velocity data during descent in order to land safely at a predesignated site. A Doppler lidar instrument could provide measurements of the altitude, attitude, and velocity of the landing vehicle to supplement the data collected by other instruments. A flexible simulation tool would aid the tasks of designing and testing the functionality of such an instrument.
LadarSIM is a robust parameterized simulation tool developed for time of flight lidar at Utah State University's Center for Advanced Imaging Ladar. This thesis outlines how LadarSIM was modified to include a simulation of Doppler lidar. A study is performed using LadarSIM to determine the effects of varying certain parameters of a Doppler lidar system. Point clouds of landing scenarios generated by the simulation with different scanning patterns are shown.