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Conception and achievement of an interferometric device of shearography. Application through scattering media / Conception et réalisation d'un dispositif interférométrique de shearographie. Application en milieu diffusant.Rosso, Vanessa 10 December 2007 (has links)
Lobjectif de cette thèse était de concevoir et développer un dispositif expérimental réalisant des mesures dans la gamme micrométrique, qui soit compact, transportable et le plus stable possible pour la réalisation de mesures in-situ. Ce projet a donc contribué à la conception et à la réalisation dun dispositif interférométrique de shearographie qui constituera une base pour de futurs développements.
Un interféromètre original de shearographie à chemins optiques quasi-communs et utilisant la technique du décalage de phase temporel a été présenté dans ce travail. Lélément clef du montage expérimental de shearographie est le dispositif de cisaillement (« shearing device », en anglais) : il sagit dun prisme qui sépare les états de polarisation TE et TM grâce à une couche mince polarisante et une fine lame de verre qui lui est accolée. Cet élément de cisaillement ainsi que lutilisation dune caméra CMOS et dune cellule à cristaux liquide pour modulateur de phase, ont permis la réalisation dun interféromètre compact, en ligne, relativement bon marché et à chemins optiques quasi-communs, lui conférant ainsi une grande stabilité par rapport aux perturbations extérieures. De plus, la sensibilité de cet interféromètre peut être ajustée pour différentes applications en modifiant la distance de cisaillement, par exemple en utilisant une lame de verre dépaisseur différente accolée au prisme séparateur de polarisation. Des logiciels pour lacquisition et le traitement des images ont également été développés afin de rendre le système simple dutilisation et convivial.
Lefficacité de cet interféromètre de shearographie a été prouvée dans le domaine mécanique et une application originale a été développée dans le domaine de la biophotonique.
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Contribution à l'étude des transferts de matière gaz-liquide en présence de réactions chimiques/Contribution to the gas-liquid mass transfer study coupled with chemical reactionsWylock, Christophe E M 29 September 2009 (has links)
Le bicarbonate de soude raffiné, produit industriellement par la société Solvay, est fabriqué dans des colonnes à bulles de grande taille, appelées les colonnes BIR.
Dans ces colonnes, une phase gazeuse contenant un mélange d’air et dioxyde de carbone (CO2) est dispersée sous forme de bulles dans une solution aqueuse de carbonate et de bicarbonate de sodium (respectivement Na2CO3 et NaHCO3). Cette dispersion donne lieu à un transfert de CO2 des bulles vers la phase liquide. Au sein des colonnes, la phase gazeuse se répartit dans deux populations de bulles : des petites bulles (diamètre de quelques mm) et des grandes bulles (diamètre de quelques cm). Le transfert bulle-liquide de CO2 est couplé à des réactions chimiques prenant place en phase liquide, qui conduisent à la conversion du Na2CO3 en NaHCO3. Une fois la concentration de saturation dépassée, le NaHCO3 précipite sous forme de cristaux et un mélange liquide-solide est recueilli à la sortie de ces colonnes.
Ce travail, réalisé en collaboration avec la société Solvay, porte sur l’étude et la modélisation mathématique des phénomènes de transfert de matière entre phases, couplés à des réactions chimiques, prenant place au sein d’une colonne BIR. L’association d’études sur des colonnes à bulles à l’échelle industrielle ou réduite (pilote) et d’études plus fondamentales sur des dispositifs de laboratoire permet de développer une meilleure compréhension du fonctionnement des colonnes BIR et d’en construire un modèle mathématique détaillé.
L’objectif appliqué de ce travail est la mise au point d’un modèle mathématique
complet et opérationnel d’une colonne BIR. Cet objectif est supporté par trois blocs
de travail, dans lesquels différents outils sont développés et exploités.
Le premier bloc est consacré à la modélisation mathématique du transfert bulle-liquide de CO2 dans une solution aqueuse de NaHCO3 et de Na2CO3. Ce transfert est couplé à des réactions chimiques en phase liquide qui influencent sa vitesse.
Dans un premier temps, des modèles sont développés selon des approches unidimensionnelles
classiquement rencontrées dans la littérature. Ces approches passent par une idéalisation de l’écoulement du liquide autour des bulles. Une expression simplifiée de la vitesse du transfert
bulle-liquide de CO2, est également développée et validée pour le modèle de colonne BIR.
Dans un second temps, une modélisation complète des phénomènes de transport (convection
et diffusion), couplés à des réactions chimiques, est réalisée en suivant une approche
bidimensionnelle axisymétrique. L’influence de la vitesse de réactions sur la vitesse de transfert
est étudiée et les résultats des deux approches sont également comparés.
Le deuxième bloc est consacré à l’étude expérimentale du transfert gaz-liquide de
CO2 dans des solutions aqueuses de NaHCO3 et de Na2CO3. A cette fin, un dispositif
expérimental est développé et présenté. Du CO2 est mis en contact avec des solutions aqueuses
de NaHCO3 et de Na2CO3 dans une cellule transparente. Les phénomènes provoqués en phase
liquide par le transfert de CO2 sont observés à l’aide d’un interféromètre de Mach-Zehnder.
Les résultats expérimentaux sont comparés à des résultats de simulation obtenus avec un des
modèles unidimensionnels développés dans le premier bloc. De cette comparaison, il apparaît
qu’une mauvaise estimation de la valeur de certains paramètres physico-chimiques apparaissant
dans les équations de ce modèle conduit à des écarts significatifs entre les grandeurs observées
expérimentalement et les grandeurs estimées par simulation des équations du modèle.
C’est pourquoi une méthode d’estimation paramétrique est également développée afin
d’identifier les valeurs numériques de ces paramètres physico-chimiques sur base des résultats expérimentaux. Ces dernières sont également discutées.
Dans le troisième bloc, nous apportons une contribution à l’étude des cinétiques de
précipitation du NaHCO3 dans un cristallisoir à cuve agitée. Cette partie du travail est réalisée en collaboration avec Vanessa Gutierrez (du service Matières et Matériaux de l’ULB).
Nous contribuons à cette étude par le développement de trois outils : une table de calcul Excel permettant de synthétiser les résultats expérimentaux, un ensemble de simulations de l’écoulement au sein du cristallisoir par mécanique des fluides numérique et une nouvelle méthode d’extraction des cinétiques de précipitation du NaHCO3 à partir des résultats expérimentaux. Ces trois outils sont également utilisés de façon combinée pour estimer les influences de la fraction massique de solide et de l’agitation sur la cinétique de germination secondaire du NaHCO3.
Enfin, la synthèse de l’ensemble des résultats de ces études est réalisée. Le résultat final est le développement d’un modèle mathématique complet et opérationnel des colonnes BIR. Ce modèle est développé en suivant l’approche de modélisation en compartiments, développée au cours du travail de Benoît Haut. Ce modèle synthétise les trois blocs d’études réalisées dans ce travail, ainsi que les travaux d’Aurélie Larcy (du service Transferts, Interfaces et Procédés de l’ULB) et de Vanessa Gutierrez. Les équations modélisant les différents phénomènes sont présentées, ainsi que la méthode utilisée pour résoudre ces équations. Des simulations des équations du modèle sont réalisées et discutées. Les résultats de simulation sont également comparés à des mesures effectuées sur une colonne BIR. Un accord raisonnable est observé.
A l’issue de ce travail, nous disposons donc d’un modèle opérationnel de colonne BIR. Bien que ce modèle doive encore être optimisé et validé, il peut déjà être utilisé pour étudier l’effet des caractéristiques géométriques des colonnes BIR et des conditions appliquées à ces colonnes sur le comportement des simulations des équations du modèle et pour identifier des tendances.
//
The refined sodium bicarbonate is produced by the Solvay company using large size bubble columns, called the BIR columns.
In these columns, a gaseous phase containing an air-carbon dioxyde mixture (CO2) is dispersed under the form of bubbles in an aqueous solution of sodium carbonate and sodium bicarbonate (Na2CO3 and NaHCO3, respectively). This dispersion leads to a CO2 transfer from the bubbles to the liquid phase. Inside these columns, the gaseous phase is distributed in two bubbles populations : small bubbles (a few mm of diameter) and large bubbles (a few cm of diameter).
The bubble-liquid CO2 transfer is coupled with chemical reactions taking places in the liquid
phase that leads to the conversion of Na2CO3 to NaHCO3. When the solution is supersaturated in NaHCO3, the NaHCO3 precipitates under the form of crystals and a liquid-solid mixture is extracted at the outlet of the BIR columns.
This work, realized in collaboration with Solvay, aims to study and to model mathematically the mass transport phenomena between the phases, coupled with chemical reactions, taking
places inside a BIR column. Study of bubble columns at the industrial and the pilot scale is
combined to a more fundamental study at laboratory scale to improve the understanding of
the BIR columns functioning and to develop a detailed mathematical modeling.
The applied objective of this work is to develop a complete and operational mathematical modeling of a BIR column. This objective is supported by three blocks of work. In each block, several tools are developed and used.
The first block is devoted to the mathematical modeling of the bubble-liquid CO2 transfer in an NaHCO3 and Na2CO3 aqueous solution. This transfer is coupled with chemical reactions in liquid phase, which affect the transfer rate.
In a first time, mathematical models are developed following the classical one-dimensional
approaches of the literature. These approaches idealize the liquid flow around the bubbles. A
simplified expression of the bubble-liquid CO2 transfer rate is equally developed and validated
for the BIR column model.
In a second time, a complete modeling of the transport phenomena (convection and diffusion) coupled with chemical reactions is developed, following an axisymmetrical twodimensional approach. The chemical reaction rate influence on the bubble-liquid transfer rate is studied and the results of the two approaches are then compared.
The second block is devoted to the experimental study of the gas-liquid CO2 transfer to NaHCO3 and Na2CO3 aqueous solutions. An experimental set-up is developed and presented. CO2 is put in contact with NaHCO3 and Na2CO3 aqueous solutions in a transparent cell. The phenomena induced in liquid phase by the CO2 transfer are observed using a Mach-Zehnder interferometer.
The experimental results are compared to simulation results that are obtained using one of
the one-dimensional model developed in the first block. From this comparison, it appears that
a wrong estimation of some physico-chemical parameter values leads to significative differences between the experimentally observed quantities and those estimated by simulation of the model equations. Therefore, a parametric estimation method is developed in order to estimate those parameters numerical values from the experimental results. The found values are then discussed.
In the third block is presented a contribution to the NaHCO3 precipitation kinetic study in a stirred-tank crystallizer. This part of the work is realized in collaboration with Vanessa Gutierrez (Chemicals and Materials Department of ULB).
Three tools are developed : tables in Excel sheet to synthetize the experimental results, a set of simulations of the flow inside the crystallizer by Computational Fluid Dynamic (CFD) and a new method to extract the NaHCO3 precipitation kinetics from the experimental measurements.
These three tools are combined to estimate the influences of the solid mass fraction and the flow on the NaHCO3 secondary nucleation rate.
Finally, the synthesis of all these results is realized. The final result is the development of a complete and operational mathematical model of BIR columns. This model is developed following the compartmental modeling approach, developed in the PhD thesis of Benoît Haut. This model synthetizes the three block of study realized in this work and the studies of Aurélie Larcy (Transfers, Interfaces and Processes Department of ULB) and those of Vanessa Gutierrez. The equations modeling the phenomena taking place in a BIR column are presented as the used method to solve these equations. The equations of the model are simulated and the results are discussed. The results are equally compared to experimental measurement realized on a BIR column. A reasonable agreement is observed.
At the end of this work, an operational model of a BIR column is thus developed. Although this model have to be optimized and validated, it can already be used to study the influences of the geometrical characteristics of the BIR columns and of the conditions applied to these columns on the behaviour of the model equation simulations and to identity tendencies.
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Optical and Raman Spectroscopic Studies on H2O at High PressureSundberg, Sara Nanna Kristina January 2005 (has links)
In this thesis, volumetric, optical and vibrational properties of H2O were studied at high pressures by combining techniques of Raman spectroscopy, interferometry and optical imaging. Pressures up to 7 GPa were generated in the diamond anvil cell (DAC), entering the stability fields of liquid water and ices VI, VII and VIII. A new integrated system for Raman, interferometric and optical-imaging studies has been built up. Utilizing the interferometric patterns formed between closely-spaced diamond anvils, the system allowed the complete monitoring and control of pVT-conditions of studied ices, as well as the determination of their dispersive properties in the visible range using the Airy equation and Cauchy formulation. This setup and technique thus represent a novel tool for the precise determination of equations of state (EOSs) of transparent materials, including fluids and low-Z materials. Data-sets on thermal pressure were obtained from heating/cooling experiments carried out on the liquid water and used for checking the mutual consistency between published EOSs. A pVT-EOS for ice VIII and room temperature isotherms for ices VI and VII at 300 K were derived by combined methods of interferometry and imaging. While the agreement with the available EOSs of ices VII and VIII is very good, some inconsistent EOSs of ice VI were identified in the present study. The technique of micro-Raman spectroscopy was applied for the monitoring of phase transformations, identification of various ice phases and for studying the response of vibrational symmetry modes to varying conditions. Analysis based on the combination of the pT-dependencies of the vibrational frequencies with the pVT-EOSs showed that, in the studied ices, the implicit volume-driven contributions dominate over the explicit phonon effects in the total temperature-induced changes in vibrational frequencies. The results provide valuable insight on the anharmonic effects and interactions in these molecular solids.
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Quantum Holonomies : Concepts and Applications to Quantum Computing and InterferometryKult, David January 2007 (has links)
Quantum holonomies are investigated in different contexts. A geometric phase is proposed for decomposition dependent evolution, where each component of a given decomposition of a mixed state evolves independently. It is shown that this geometric phase only depends on the path traversed in the space of decompositions. A holonomy is associated to general paths of subspaces of a Hilbert space, both discrete and continuous. This opens up the possibility of constructing quantum holonomic gates in the open path setting. In the discrete case it is shown that it is possible to associate two distinct holonomies to a given path. Interferometric setups for measuring both holonomies are provided. It is further shown that there are cases when the holonomy is only partially defined. This has no counterpart in the Abelian setting. An operational interpretation of amplitudes of density operators is provided. This allows for a direct interferometric realization of Uhlmann's parallelity condition, and the possibility of measuring the Uhlmann holonomy for sequences of density operators. Off-diagonal geometric phases are generalized to the non-Abelian case. These off-diagonal holonomies are undefined for cyclic evolution, but must contain members of non-zero rank if all standard holonomies are undefined. Experimental setups for measuring the off-diagonal holonomies are proposed. The concept of nodal free geometric phases is introduced. These are constructed from gauge invariant quantities, but do not share the nodal point structure of geometric phases and off-diagonal geometric phases. An interferometric setup for measuring nodal free geometric phases is provided, and it is shown that these phases could be useful in geometric quantum computation. A holonomy associated to a sequence of quantum maps is introduced. It is shown that this holonomy is related to the Uhlmann holonomy. Explicit examples are provided to illustrate the general idea.
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Deformation measurement and monitoring with Ground-Based SARMonserrat Hernández, Oriol 15 March 2012 (has links)
The Ground-Based Synthetic Aperture Radar (GB-SAR) is a relatively new technique,
which in the last ten years has gained interest as deformation measurement and
monitoring tool. The GB-SAR technique is based on an imaging radar-based sensor, which
o ers high sensitivity to small displacements, in the region of sub-millimetres to
millimetres, long-range measurements, which can work up to some kilometres, and massive
deformation measurement capability. These features confer to the GB-SAR technique
interesting advantages with respect to other point-wise deformation measurement
techniques.
The process of estimating deformation from the GB-SAR data is not straightforward:
it requires complex data processing and analysis tools. This dissertation is focused on
these tools, covering the whole deformation estimation process. This thesis collects the
main research results achieved on this topic during my work at the Active Remote Sensing
Unit of the Institute of Geomatics. Two di erent approaches for measuring deformation
with GB-SAR data are described and discussed. The irst one is the interferometric
approach, based on the exploitation of the phase component of the GB-SAR data, which
is the commonly used GB-SAR method. The second one is a non-interferometric approach,
which exploits the amplitude component of the GB-SAR data, o ering an interesting
alternative way to exploit the GB-SAR data.
This dissertation has two main objectives. The first one is presenting, step by step, a
complete interferometric GB-SAR procedure for deformation measuring and monitoring.
The second one is presenting two new algorithms, which represent the most innovative
part of this thesis. The first algorithm faces the phase unwrapping problem, providing an
automatic solution for detecting and correcting unwrapping errors, which is called 2+1D
phase unwrapping. The second algorithm is the base of the above mentioned non-
interferometric approach, which overcomes some of the most critical limitation of GB-SAR
interferometry, at the expense of getting less precise deformation estimates.
The dissertation is divided in 6 chapters. The first one is the introduction, while the
second one provides an overview of GB-SAR interferometry, introducing the main aspects
that are the basics of the subsequent chapters. Chapter 3 describes a complete GB-SAR
processing chain. Chapters 4 and 5 contain the most original part of the dissertation, i.e.
the 2D+1 phase unwrapping algorithm, and the non-interferometric approach. Finally, in
Chapter 6 the conclusions are discussed and further research is proposed. / El radar terrestre d’obertura sintètica (GB-SAR) és una tècnica relativament nova
que, en els últims deu anys, ha guanyat interès com a eina per a mesurar i monitorar
deformacions. La tècnica GB-SAR es basa en un sistema radar amb capacitat per
proporcionar imatges, que ofereix una alta sensibilitat a petits desplaçaments, d’ordre
mil·limètric o submil·limètric, que és capaç de mesurar a llargues distàncies (alguns km)
i que té una alta capacitat per fer mesures massives. Aquestes característiques donen a la
tècnica interessants avantatges respecte a altres tècniques clàssiques de mesura de
deformacions, típicament basades en mesures puntuals.
Derivar mesures de deformació a partir de dades GB-SAR no és un procés senzill, ja
que requereix uns procediments complexos de processat i anàlisi de dades. Aquesta tesi es
centra en aquests processos. Aquesta tesi recull alguns dels resultats més destacats de la
investigació que he desenvolupat sobre aquest tema a la unitat de Teledetecció Activa de
l'Institut de Geomàtica. Al llarg del document es descriuen dues aproximacions diferents
per mesurar deformacions amb GB-SAR. Una es basa en la explotació de la tècnica de la
interferometria, és a dir explotant la component de la fase de les imatges GB-SAR: és la
tècnica GB-SAR usada habitualment. La segona, anomenada tècnica no-interferomètrica,
es basa en la component de l’amplitud de les dades GB-SAR i ofereix una interessant
alternativa a la primera.
La tesi acompleix dos objectius principals. En primer lloc presenta un procediment
complet per la mesura i monitoratge de deformacions mitjançant interferometria GB-SAR.
En segon lloc, descriu dos nous algorismes que resolen problemes específics de la
interferometria clàssica aplicada al GB-SAR i que representen la part més innovadora
d’aquesta tesi. El primer algorisme aborda un dels problemes oberts de la interferometria,
el phase unwrapping, proposant un mètode automàtic per detectar-ne i corregir-ne els
errors. El segon algorisme proposa un nou mètode per a l'explotació de les dades GB-SAR
per mesurar deformacions sense utilitzar la interferometria.
La estructura de la tesi consisteix en sis capítols. Després de la introducció, el Capítol
2 proporciona una visió general de la interferometria GB-SAR, introduint els conceptes
principals utilitzats en la tesi. En el tercer capítol es descriu una cadena de processament
basada en GB-SAR interferomètric. Els capítols quart i cinquè contenen la part més
original de la tesi: l'algorisme de phase unwrapping i el mètode no-interferomètric per la
mesura de deformacions. Finalment, es discuteixen les conclusions principals i es proposen
futures línies d’investigació.
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An Experimental Technique for the Study of the Mechanical Behavior of Thin Film Materials at Micro- and Nano-ScaleTajik, Arash January 2008 (has links)
An experimental technique has been presented to probe the mechanical behavior of thin film materials. The method is capable of tensile testing thin films on substrate and free-standing thin film specimens. A mechanical gripper was designed to address the current challenges in gripping thin film specimens. In order to measure the strain field across the gage section, the moire interferometry technique was used and the respective optical setup was designed.
A versatile microfabrication process has been developed to fabricate free-standing dog-bone specimens. Aluminum was used as the model material; however, any other metallization material can be integrated in the process. Thin film specimens have been characterized using SEM, AFM, and TEM. A process has been developed to fabrication diffraction gratings on the specimen by FIB milling. Different grating geometries were fabricated and the diffraction efficiency of the gratings was characterized. The structural damage induced by the Ga+ ions during the FIB milling of the specimens was partially characterized using STEM and EDS.
In order to extract the strain field information from the moire interferogram data, a numerical postprocessing technique was developed based on continuous wavelet transforms (CWT). The method was applied on simulated uniform and nonuniform strain fields and the wavelet parameters were tuned to achieve the best spatial localization and strain accuracy.
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Inspection and Characterization of Exoplanet Using the CHARA ArrayBaines, Ellyn K 07 August 2007 (has links)
Until the last decade or so, our entire knowledge of planets around Sun-like stars consisted of those in our own Solar System. This is no longer the case. Over 200 planets have been discovered through radial velocity surveys and photometric studies, both of which depend on observing the planet's effects on its host star. Much of our knowledge of the planets orbiting these stars is uncertain, based on assumptions about the stars' masses and the planets' orbital inclinations. This dissertation is comprised of two main sections. The first involves measuring the angular diameters for a sample of exoplanet host stars using Georgia State University's CHARA Array in order to learn more about the nature of these stars. These direct angular measurements are not dependent on the exoplanet systems' inclinations or the masses of the stars. Improved angular diameters lead to linear diameters when combined with HIPPARCOS parallax measurements, which in turn tell us of the stars' ages and masses. Of the 82 exoplanet systems observable with the CHARA Array, 31 host stars were observed and stellar angular diameters were measured for 26 systems. In the special case of an exoplanet system with a transiting planet, this direct measurement of the star's angular diameter leads to a direct measurement of the planet's diameter, when the planet-to-star-radii ratio is known from photometric studies. This was done for HD 189733. The star's angular diameter is 0.377 +/- 0.024 mas, which produces a stellar linear radius of 0.779 +/- 0.052 R_Sun and a planetary diameter of 1.19 +/- 0.08 R_Jupiter. The second part of this project involved the inspection of the exoplanet systems for stellar companions masquerading as planets. From radial velocity studies alone, it is impossible to distinguish between a planet in a high-inclination orbit and a low-mass stellar companion in a low-inclination orbit. Using the CHARA Array, it was possible to rule out certain secondary spectral types for each exoplanet system observed by studying the errors in the diameter fit and searching for separated fringe packets. While no definitive stellar companions were found, two expolanet systems, upsilon Andromedae and rho Coronae Borealis, exhibited behavior that were not consistent with the host star being a simple limb-darkened disk.
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The Separated Fringe Packet Survey: Updating Multiplicity of Solar-Type Stars within 22 ParsecsFarrington, Christopher Donald 18 November 2008 (has links)
Over the past half century, multiplicity studies have provided a foundation for the theories of stellar formation and evolution through understanding how likely it is that stars form alone or with companions. If spectroscopic orbits are combined with techniques that can determine visual orbits, we can access the most fundamental parameter of stellar evolution, stellar mass. This dissertation is composed of two main sections. The first involves the investigation of the seminal multiplicity study of Duquennoy & Mayor (1991b) which has been the ``gold standard" for solar-type stars for nearly 20 years. Improvements in technology in the intervening years have improved the measurement accuracy for radial velocities and distances on which the study was based. Using Georgia State University's CHARA Array to search the systems in Duquennoy & Mayor's multiplicity survey for overlooked companions along with a literature search covering regimes unreachable by the CHARA Array, we have found that more than 40% of the Duquennoy & Mayor's sample was further than originally believed and the uncorrected multiplicity percentages change from 57:38:4:1:0% (single:double:triple:quad:quint%) to 48:42.5:7.5:1:1% with the discoveries of multiple previously undiscovered companions. The second part of this project describes the application of separated fringe packets for resolving the astrometric position of secondaries with small angular separations on long-baseline optical interferometers. The longest baselines of the CHARA Array allow access to a previously inaccessible range of separations compared with other techniques (<40 milliarcseconds) and the ability to very accurately angularly resolve a large number of single- and double-lined spectroscopic binaries. Combining astrometric and spectroscopic orbits provides assumption-free stellar masses and using the CHARA Array allows access to many previously unreachable systems available for high-accuracy mass determinations. We report the first angular separation measurements of seven spectroscopic binary systems, five additional separated fringe packet detections, ten systems with probably overlapping fringe packets, four systems with new data on pre-existing orbits, one completely new visual orbit for a SB2 system previously unresolved, and the detection of two previously unknown companions.
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Sizing Up the StarsBoyajian, Tabetha Suzanne 17 July 2009 (has links)
For the main part of this dissertation, I have executed a survey of nearby, main sequence A, F, and G-type stars with the CHARA Array, successfully measuring the angular diameters of forty-four stars to better than 4% accuracy. The results of these observations also yield empirical determinations of stellar linear radii and effective temperatures for the stars observed. In addition, these CHARA-determined temperatures, radii, and luminosities are fit to Yonsei-Yale isochrones to constrain the masses and ages of the stars. These quantities are compared to the results found in Allende Prieto & Lambert (1999), Holmberg et al. (2007), and Takeda (2007), who indirectly determine these same properties by fitting models to observed photometry. I find that for most cases, the models underestimate the radius of the star by ~12%, while in turn they overestimate the effective temperature by ~ 1.5 - 4%, when compared to my directly measured values, with no apparent correlation to the star's metallicity or color index. These overestimated temperatures and underestimated radii in these works appear to cause an additional offset in the star's surface gravity measurements, which consequently yield higher masses and younger ages, in particular for stars with masses greater than ~ 1.3 M_sol. Alternatively, these quantities I measure are also compared to direct measurements from a large sample of eclipsing binary stars in Andersen (1991), and excellent agreement is seen within both data sets. Finally, a multi-parameter solution is found to fit color-temperature-metallicity values of the stars in this sample to provide a new calibration of the effective temperature scale for these types of stars. Published work in the field of stellar interferometry and optical spectroscopy of early-type stars are presented in Appendix D and E, respectively.
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The Self-Calibration Method for Multiple Systems at the CHARA ArrayO'Brien, David P 07 May 2011 (has links)
The self-calibration method, a new interferometric technique using measurements in the K′-band (2.1 μm) at the CHARA Array, has been used to derive orbits for several spectroscopic binaries. This method uses the wide component of a hierarchical triple system to calibrate visibility measurements of the triple’s close binary system through quasi-simultaneous observations of the separated fringe packets of both. Prior to the onset of this project, the reduction of separated fringe packet data had never included the goal of deriving visibilities for both fringe packets, so new data reduction software has been written. Visibilities obtained with separated fringe packet data for the target close binary are run through both Monte Carlo simulations and grid search programs in order to determine the best-fit orbital elements of the close binary.
Several targets, with spectral types ranging from O to G and luminosity classesfrom III to V, have been observed in this fashion, and orbits have been derived for the close binaries of eight targets (V819 Her B, Kappa Peg B, Eta Vir A, Eta Ori Aab, 55 UMa A, 13 Ceti A, CHARA 96 Ab, HD 129132 Aa). The derivation of an orbit has allowed for the calculation of the masses of the components in these systems. The magnitude differences between the components can also be derived, provided that the components of the close binary have a magnitude difference of Delta K < 2.5 (CHARA’s limit). Derivation of the orbit also allows for the calculation of the mutual inclination (Phi), which is the angle between the planes of the wide and close orbits. According to data from the Multiple Star Catalog, there are 34 triple systems other than the 8 studied here for which the wide and close systems both have visual orbits. Early formation scenarios for multiple systems predict coplanarity (Phi < 15 degrees), but only 6 of these 42 systems are possibly coplanar. This tendency against coplanarity may suggest that the capture method of multiple system formation is more important than previously believed.
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