Dissertations / Theses on the topic 'Guide star'
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1
Booth, H. J. "Guide star lasers." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300872.
2
Roberts, William Thomas. "Guide star lasers for adaptive optics." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/290501.
Abstract:
Exploitation of the imaging capabilities of the new generation of ground-based astronomical telescopes relies heavily on Adaptive Optics (AO). Current AO system designs call for sodium guide star lasers capable of producing at least eight Watts of power tuned to the peak of the sodium D₂ line, with a high duty cycle to avoid saturation, and with 0.5-1.0 GHz spectral broadening. This work comprises development and testing of six candidate laser systems and materials which may afford a path to achieving these goals. An end-pumped CW dye laser producing 4.0 Watts of tuned output power was developed and used to obtain the first accurate measurement of sodium layer scattering efficiency. Methods of optimizing the laser output through improving pump overlap efficiency and reducing the number of intracavity scattering surfaces are covered. The 1181 nm fluorescence peak of Mn⁵⁺ ion in Ba₅(PO₄)₃Cl could be tuned and doubled to reach 589 nm. While efforts to grow this crystal were under way, the Mn⁵⁺ ion in natural apatite (Ca₅(PO₄)₃F) was studied as a potential laser material. Fluorescence saturation measurements and transmission saturation are presented, as well as efforts to obtain CW lasing in natural apatite. A Q-switched laser color-center laser in LiF : F⁻₂ was developed and successfully tuned and doubled to the sodium D₂ line. Broad-band lasing of 80 mW and tuned narrow-band lasing of 35 mW at 1178 nm were obtained with 275 mW of input pump power at 1064 nm. The measured thermal properties of this material indicate its potential for scaling to much higher power. A Q-switched intracavity Raman laser was developed in which CaWO₄ was used to shift a Nd:YAG laser, the frequency-doubled output of which was centered at 589.3 nm. To obtain light at 589.0 nm, a compositionally tuned pump laser of Nd : Y₃Ga₁.₁Al₃.₉O₁₂ was produced which generated the desired shift, but was inhomogeneous broadened, limiting the tunable power of the material. Finally, temperature tuning of a Nd:YAG laser was demonstrated in which the laser emitted up to 8.6 Watts at a temperature of -21.5 C, bringing the wavelength into a regime favorable for efficient Raman shifting by CaWO₄.
3
Sereni, Giulia. "Optical design of MAORY Laser Guide Star Objective." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14069/.
Abstract:
The turbulence affects the angular resolution of images. Single Conjugate Adaptive optics, SCAO, is the simplest way to correct the atmospheric turbulence using a Natural Guide Star, but it has some limitations such as the anisoplanatism. Multi Conjugate Adaptive Optics is a technique which overcomes this issue by using as many NGSs, as Wavefront Sensors. In order to increase the sky coverage, Laser Guide Stars, LGSs, are also used. One of the first light instrument of the 40 meter European Extremely Large Telescope is MICADO, or the Multi-Adaptive Optics Imaging Camera for Deep Observations. It works with the post-focal MCAO relay, called MAORY, which uses six LGSs. A description of MAORY optical design is provided in this thesis. These LGSs suffer from aberrations and thus, after separating the light by a dichroic, an objective is designed to reduce these aberrations. In fact, since during sky tracking the zenith angle changes, the six LGSs launched at the Sodium layer vary their distances from the telescope primary mirror. As a consequence, the LGSs at different distances will focus on different positions along the optical axis. Through the procedure of optimization one can improve or modify the design in order to reduce or remove aberrations. Since no component can be perfectly manufactured and aligned, a tolerance analysis is important to ensure that the final, assembled instrument meets the requested performance. All in all, the goal of this thesis is to optimize and perform the tolerance analysis for the LGS Objective of MAORY and show the results. The mechanical constraints and the variations of the aberrations with the zenith and azimuthal angle are taken into account. The number of optical surfaces has been minimized keeping the LGS Objective requirements satisfied. Moreover, the residual aberrations of the LGSs have been kept as small as possible in order to reach the performance requirements of MAORY. The software Zemax has been used.
4
Hart, Michael, Stuart Jefferies, and Neil Murphy. "Daylight operation of a sodium laser guide star." SPIE-INT SOC OPTICAL ENGINEERING, 2016. http://hdl.handle.net/10150/622016.
Abstract:
We report photometric measurements of a sodium resonance guide star against the daylight sky when observed through a tuned magneto-optical filter (MOF). The MOF comprises a sodium vapor cell in a kilogauss-level magnetic field between crossed polarizers and has a very narrow transmission profile at the sodium D-2 resonance of approximately 0.008 nm. Our observations were made with the 1.5 m Kuiper telescope on Mt. Bigelow, AZ, which has a separately mounted guide star laser projecting a circularly polarized single-frequency beam of approximately 6.5 W at 589.16 nm. Both the beam projector and the 1.5 m telescope were pointed close to zenith; the baseline between them is approximately 5 m. Measurements of the guide star were made on the morning of 2016 March 24 using an imaging camera focused on the beacon and looking through the full aperture of the telescope. The guide star flux was estimated at 1.20x10(6) photon/m(2)/s while at approximately 45 minutes after sunrise, the sky background through the MOF was 1100 photon/m(2)/s/arcsec(2). We interpret our results in terms of thermal infrared observations with adaptive optics on the next generation of extremely large telescopes now being built.
5
Jacobsen, Bruce Paul 1964. "Sodium laser guide star projection for adaptive optics." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/288754.
Abstract:
In order to increase sky coverage, adaptive optics (AO) systems for large telescopes will require laser systems to provide artificial reference beacons. The most prominent method for creating an artificial beacon is to project laser light tuned to the 589nm, D2 line of sodium onto the mesospheric sodium atoms at an altitude of 90km. When correcting with AO, the best wavefront measurements are obtained when the image of the sodium beacon is as bright and sharp as possible. Blurring occurs due to spot elongation, as a result of sub-aperture displacement from the projector axis, and from diffraction and seeing effects on the projected beam. Mounting the projector in the center of the telescope minimizes the effect of elongation. Simulations were conducted that show that matching the beam waist to ∼2 times the atmospheric turbulence parameter r₀ minimizes the beacon size. For r₀ = 15cm and a 48cm projector, calculations show the optimum projected waist is 29cm. A prototype projector has been built and operated. Recent experiments have shown that this projector is capable of producing 0.75arcsec beacons under good seeing. In addition, spot elongation of 0.5arcsec was observed corresponding to a sodium layer thickness of 10km. The first experimental evidence for optical pumping in the mesospheric layer were obtained. They show a non-thermal profile for the sodium hyperfine structure (3.5:1 line ratio as opposed to 5:3) when projecting circularly polarized light. This profile indicates that the maximum return per watt is obtained by pumping the F = 2 level with a narrow bandwidth compared with pumping both F = 2 and F = 1 with a broad bandwidth. In addition, evidence shows a 30% increase in beacon brightness when pumping the sodium layer with circularly polarized light over linear. A projector for the 6.5m MMT conversion has been designed based on experience gained with the prototype. Analysis of the Strehl reduction due to wavefront reconstruction error shows a reduction in Strehl of < 1% for the optimal operating parameters at the MMT. This less than the fundamental limit of 0.79 for focus anisoplanatism.
6
Reeves, Andrew Paul. "Laser Guide Star only adaptive optics : the development of tools and algorithms for the determination of Laser Guide Star tip-tilt." Thesis, Durham University, 2015. http://etheses.dur.ac.uk/11199/.
Abstract:
Adaptive Optics (AO) is a technology which corrects for the effects of the atmosphere and so improves the optical quality of ground based astronomical observations. The bright “guide stars” required for correction are not available across the entire sky, so Laser Guide Stars (LGSs) are created. A Natural Guide Star (NGS) is still required to correct for tip-tilt as the LGS encounters turbulence on the uplink path resulting in unpredictable “jitter”, hence limiting corrected sky coverage. In this thesis an original method is proposed and investigated that promises to improve the correction performance for tomographic AO systems using only LGSs, and no NGS, by retrieving the LGS uplink tip-tilt. To investigate the viability of this method, two unique tools have been developed. A new AO simulation has been written in the Python programming language which has been designed to facilitate the rapid development of new AO concepts. It features realistic LGS simulation, ideal to test the method of LGS uplink tip-tilt retrieval. The Durham Real-Time Adaptive Optics Generalised Optical Nexus (DRAGON) is a laboratory AO test bench nearing completion, which features multiple LGS and NGS Wavefront Sensors (WFSs) intended to further improve tomographic AO. A novel method of LGS emulation has been designed, which re-creates focus anisoplanatism, elongation and uplink turbulence. Once complete, DRAGON will be the ideal test bench for further development of LGS uplink tip-tilt retrieval. Performance estimates from simulation of the LGS uplink tip-tilt retrieval method are presented. Performance is improved over tomographic LGS AO systems which do not correct for tip-tilt, giving a modest improvement in image quality over the entire night sky. Correction performance is found to be dependent on the atmospheric turbulence profile. If combined with ground layer adaptive optics, higher correction performance with a very high sky coverage may be achieved.
7
Hart, Michael, Stuart Jefferies, and Douglas Hope. "Tomographic wave-front sensing with a single guide star." SPIE-INT SOC OPTICAL ENGINEERING, 2016. http://hdl.handle.net/10150/622717.
Abstract:
Adaptive optics or numerical restoration algorithms that restore high resolution imaging through atmospheric turbulence are subject to isoplanatic wave-front errors. Mitigating those errors requires that the wave-front aberrations be estimated within the 3D volume of the atmosphere. Present techniques rely on multiple beacons, either natural stars or laser guide stars, to probe the atmospheric aberration along different lines of sight, followed by tomographic projection of the measurements onto layers at defined ranges. In this paper we show that a three-dimensional estimate of the wave-front aberration can be recovered from measurements by a single guide star in the case where the aberration is stratified, provided that the telescope tracks across the sky with non-uniform angular velocity. This is generally the case for observations of artificial earth-orbiting satellites, and the new method is likely to find application in ground based telescopes used for space situational awareness.
8
Czarske, J., H. Radner, and L. Büttner. "Adaptive interferometric velocity measurements using a laser guide star." SPIE, 2015. https://tud.qucosa.de/id/qucosa%3A35038.
Abstract:
We have harnessed the power of programmable photonics devices for an interferometric measurement technique. Laser interferometers are widely used for flow velocity measurements, since they offer high temporal and spatial resolutions. However, often optical wavefront distortions deteriorate the measurement properties. In principle, adaptive optics enables the correction of these disturbances. One challenge is to generate a suitable reference signal for the closed loop operation of the adaptive optics. An adaptive Mach Zehnder interferometer is presented to measure through a dynamic liquid-gas phase boundary, which can lead to a misalignment of the interfering laser beams. In order to generate the reference signal for the closed loop control, the Fresnel reflex of the phase boundary is used as Laser Guide Star (LGS) for the first time to the best of the authors’ knowledge. The concept is related to the generation of artificial stars in astronomy, where the light transmitted by the atmosphere is evaluated. However, the adaptive interferometric flow velocity measurements at real world experiments require a different concept, since only the reflected light can be evaluated. The used LGS allows to measure the wavefront distortions induced by the dynamic phase boundary. Two biaxial electromagnetically driven steering mirrors are employed to correct the wavefront distortions. This opens up the possibility for accurate flow measurements through a dynamic phase boundary using only one optical access. Our work represents a paradigm shift in interferometric velocity measurement techniques from using static to dynamic optical elements.
9
Ge, Jian 1966. "Sodium laser guide star technique, spectroscopy and imaging with adaptive optics." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282740.
Abstract:
A sodium laser guide star (LGS) adaptive optics (AO) system developed at Stewart Observatory is to be used at the 6.5m MMT. Annual measurements at Kitt Peak show that the mean mesospheric sodium column density varies from ∼2x10⁹cm⁻² (summer) to ∼5x10⁹cm⁻² (winter). The sodium column density also varies by a factor of two during a one hour period. The first simultaneous measurements of sodium LGS brightness, sodium column density and laser power were obtained. The absolute sodium return for a continuous wave circularly polarized beam is 1.2(±0.3)x10⁶ photons s⁻¹m⁻²W⁻¹ for the sodium column density of 3.7x10⁹cm⁻². Theoretical studies demonstrate that the 6.5m MMT LGS AO can provide Strehl ratios better than 0.15 and about 50% flux concentration within 0.2" aperture for 1-5.5μm under median seeing. This correction will be available for the full sky. Better Strehl and higher flux concentration can be achieved with natural guide stars, but limited sky coverage. The AO corrected field-of-view is about 60". The Arizona IR Imager and Echelle Spectrograph (ARIES) was designed to match the 6.5m MMT AO. Detection limits of more than 2 magnitude fainter can be reached with the AO over without the AO. A pre-ARIES wide field near-IR camera was designed, built and tested. The camera provides 1" images in the near-IR over an 8.5 x 8.5arcmin² field. The 10-σ detection limit with one minute exposures is 17.9 mag. in the K band. A prototype very high resolution cross-dispersed optical echelle spectrograph was designed and built to match the Starfire Optical Range 1.5m AO images. Interstellar KI 7698Å absorption lines have been detected in the spectra of αCyg and ζPer. The spectral resolution is 250.000. About 300Å wavelengths were covered in a single exposure. Total detection efficiency of 1% has been achieved. For the first time, a near-single-mode fiber with 10μm core size was applied to transmit the Mt. Wilson 100inch AO corrected beams to a spectrograph. The coupling efficiency of the fiber reached up to 70%. Spectra of αOri were recorded. The spectral resolution is 200,000. The total wavelength coverage is about 650Å per exposure.
10
Moldovan, Ioana Cristina. "Étude photométrique de l’atome de sodium : application aux étoiles lasers (LGS ET PLGS)." Grenoble 1, 2008. http://www.theses.fr/2008GRE10060.
Abstract:
Pour corriger la dégradation des images astronomiques due aux turbulences atmosphériques, les astronomes ont proposé de créer une étoile laser dans la haute atmosphère. Cette thèse a pour objectif l'étude théorique et expérimentale au laboratoire des différents processus d'excitation du sodium mésosphérique pour obtenir une source monochromatique et polychromatique, afin d'estimer avec précision le flux retourné d'une expérience sur le ciel. Les deux premières parties sont consacrées au contexte scientifique à l'interface entre la physique et l'astronomie, et à la description de diverses propriétés de l'atome de sodium, ainsi qu'à deux études portant sur les propriétés de polarisation de la fluorescence de Na. L'étude du laser sans mode UV, développé au LSP, est ensuite réalisée. La partie suivante décrit en détail l'expérience de photométrie ainsi que la mesure des paramètres nécessaires comme les profils spatiaux, temporels et spectraux du laser, ainsi que la densité de sodium. Enfin, on présente le développement d'un modèle cinétique (REM) de l'excitation du sodium utilisant des équations de taux dans plusieurs cas: excitation à un photon à 589 nm, excitation à un photon à 330 nm et excitation à deux photons résonants ou non résonants. Un très bo accord avec le code BEA CON et les résultats expérimentaux confirme la validité de ce modèle. A l'aide du code REM, les différentes méthodes sont comparées et l'efficacité de l'excitation du sodium mésosphérique est calculée. Ce travail montre que, dans les meilleures conditions et pour les puissances laser envisagées dans le projet ELPOA actuel, le flux retourné à 330 nm ne dépassera pas 5x104 photons/m2/sLn order to correct the astronomical images degradation due to the atmospheric turbulences, the astronomers propose to create a laser guide star in the high atmosphere. The purpose of this thesis is to study experimentally and theoretically in the laboratory different mesospheric sodium excitation methods to obtain a monochromatic and a polychromatic source, to choose the most appropriate solution, and to estimate accurately the returned flux of an experiment to the sky. The first two parts of this report describe respectively the scientific context which is at the interface of physics and astronomy, and several properties of the sodium atom as weIl as two theoretical and experimental studies about the polarisation properties of the Na fluorescence. The study of the UV modeless laser developed at LSP is presented. The next part explains precisely the photometry experiment and also the measurement of the needed parameters, such as spatial, temporal and spectral laser profiles and the atomic density. At last, we present the development of a kinetic model (called REM) of the sodium excitation via the rate equations in several cases: one photon excitation at 589 nm, one photon excitation at 330 nm, and two-resonant-or-non-resonant-photons excitation. A very good agreement with the BEACON code and the experimental results confirms the validity of this model. Thanks to REM code, the different methods are compared and the mesospheric sodium excitation efficiency is calculated. This work shows that in the best case and for the present ELP-OA project lasers power, the returned flux at 330 nm is around 5 x 104 photons/m2/s
11
Hart, Michael, Stuart M. Jefferies, and Neil Murphy. "Daylight operation of a sodium laser guide star for adaptive optics wavefront sensing." SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2016. http://hdl.handle.net/10150/624361.
Abstract:
We report contrast measurements of a sodium resonance guide star against the daylight sky when observed through a tuned magneto-optical filter (MOF). The guide star was created by projection of a laser beam at 589.16 nm into the mesospheric sodium layer and the observations were made with a collocated 1.5-m telescope. While MOFs are used with sodium light detecting and ranging systems during the day to improve the signalto- noise ratio of the measurements, they have not so far been employed with laser guide stars to drive adaptive optics (AO) systems to correct atmospherically induced image blur. We interpret our results in terms of the performance of AO systems for astronomy, with particular emphasis on thermal infrared observations at the next generation of extremely large telescopes now being built. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)
12
Christou, J. C., G. Brusa, A. Conrad, S. Esposito, T. Herbst, P. Hinz, J. M. Hill, et al. "Adaptive optics capabilities at the Large Binocular Telescope Observatory." SPIE-INT SOC OPTICAL ENGINEERING, 2016. http://hdl.handle.net/10150/622008.
Abstract:
We present an overview of the current and future adaptive optics systems at the LBTO along with the current and planned science instruments they feed. All the AO systems make use of the two 672 actuator adaptive secondary mirrors. They are (1) FLAO (NGS/SCAO) feeding the LUCI NIR imagers/spectrographs; (2) LBTI/AO (NGS/SCAO) feeding the NIR/MIR imagers and LBTI beam combiner; (3) the ARGOS LGS GLAO system feeding LUCIs; and (4) LINO-NIRVANA - an NGS/MCAO imager and interferometer system. AO performance of the current systems is presented along with proposed performances for the newer systems taking into account the future instrumentation.
13
Stalcup, Thomas Eugene. "Design and Construction of a Multiple Beam Laser Projector and Dynamically Refocused Wavefront Sensor." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/194836.
Abstract:
Adaptive optics using natural guide stars can produce images of amazing quality, but is limited to a small fraction of the sky due to the need for a relatively bright guidestar. Adaptive optics systems using a laser generated artifical reference can be used over a majority of the sky, but these systems have some attendant problems. These problems can be reduced by increasing the altitude of the laser return, and indeed a simple, single laser source focused at an altitude of 95 km on a layer of atmospheric sodium performs well for the current generation of 8-10 m telescopes. For future giant telescopes in the 20-30 m class, however, the errors due to incorrect atmospheric sampling and spot elongation will prohibit such a simple system from working.The system presented in this dissertation provides a solution to these problems. Not only does it provide the 6.5m MMT with a relatively inexpensive laser guide star system with unique capabilities, it allows research into solving many of the problems faced by laser guide star systems on future giant telescopes.The MMT laser guidestar system projects a constellation of five doubled Nd:YAG laser beams focused at a mean height of 25 km, with a dynamic refocus system that corrects for spot elongation and allows integrating the return from a 10 km long range gate. It has produced seeing limited spot sizes in ~1 arcsecond seeing conditions, and has enabled the first on-sky results of Ground Layer Adaptive Optics (GLAO).
14
Figlewski, Nathan Michael. "Laser Guide Star Design Project for the USAF John Bryan State Park Quad Axis Observatory." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1453240229.
15
Morris, T. J. "An experimental Rayleigh laser guide star ground layer adaptive optics system for the William Herschel telescope." Thesis, Durham University, 2005. http://etheses.dur.ac.uk/2717/.
Abstract:
The design of an experimental ground layer adaptive optics (GLAO) system that uses a low altitude Rayleigh laser guide star as a wavefront reference source is presented. GLAO is a technique for achieving wide-field partial adaptive optics correction of the aberrations in a wavefront due to the effects of propagation through a turbulent atmosphere. The theoretical performance of the GLAO sub-systems, such as the laser launch system, wavefront sensor and optical train are analysed and compared, where possible, to measurements taken both under laboratory conditions and on-sky at the William Herschel Telescope.
16
Radner, Hannes, Lars Büttner, and Jürgen Czarske. "Interferometric velocity measurements through a fluctuating interface using a Fresnel guide star-based wavefront correction system." SPIE, 2018. https://tud.qucosa.de/id/qucosa%3A71762.
Abstract:
To improve optical measurements, which are degraded by optical distortions, wavefront correction systems can be used. Generally, these systems evaluate a guide star in transmission. The guide star emits wellknown wavefronts, which sample the distortion by propagating through it. The system is able to directly measure the distortion and correct it. There are setups, where it is not possible to generate a guide star behind the distortion. Here, we consider a liquid jet with a radially open surface. A Mach–Zehnder interferometer is presented where both beams are stabilized through a fluctuating liquid jet surface with the Fresnel guide star (FGS) technique. The wavefront correction system estimates the beam path behind the surface by evaluating the incident beam angle and reflected beam angle of the Fresnel reflex with an observer to control the incident angle for the desired beam path. With this approach, only one optical access through the phase boundary is needed for the measurement, which can be traversed over a range of 250 μm with a significantly increased rate of valid signals. The experiment demonstrates the potential of the FGS technique for measurements through fluctuating phase boundaries, such as film flows or jets.
17
Bardou, Lisa. "Analyse de front d'onde sur étoile laser allongée pour l'optique adaptative de l'ELT." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC036/document.
Abstract:
L’ELT (Extremely Large Telescope), est un télescope de diamètre 39 m en cours de réalisation par l’Observatoire Européen Austral (ESO). Pour pouvoir tirer pleinement parti de sa taille, ses instruments seront équipés de systèmes d’Optique Adaptative (OA) qui compenseront la turbulence atmosphérique. Ces systèmes d’OA requièrent l’utilisation d’étoiles guides laser afin de maximiser la couverture du ciel. Les étoiles guides laser sont générées par laser accordé sur une résonance d’atome de sodium présents dans une couche d’une épaisseur de 10 km et située à environ 90 km d’altitude. Une étoile laser est donc un cylindre lumineux dans la haute atmosphère, allumé par la relaxation des atomes. L’analyse de front d’onde à l’aide de ces étoiles artificielles souffrent de limitations connues. De plus, sur un télescope de la taille de l’ELT, leur utilisation est compliquée par l’effet de perspective qui provoque un allongement de l’étoile guide lorsqu’elle est vue d’un point éloigné de son point de lancement au sol : le cylindre n’est plus vu par une section circulaire, mais sur le côté. Sur un télescope de 39m, l’élongation de l’étoile peut alors atteindre jusqu’à 20 secondes d’arc, à comparer avec le diamètre du cylindre qui est déterminé par la turbulence, soit de l’ordre d’une seconde d’arc. La variabilité de l’épaisseur, de l’altitude et de la distribution de densité de la couche de sodium ont alors un impact sur la mesure du front d’onde.L’étude de ce problème, qui porte à la fois sur les algorithmes de mesure et le design des analyseurs de front d’onde, a donné lieu à de nombreux travaux s’appuyant sur des simulations et des tests en laboratoire. Le but de cette thèse a été d’étudier cette question à l’aide de données expérimentales obtenues sur le ciel. Ces données ont été enregistrées grâce au démonstrateur d’OA CANARY, situé sur le télescope William Herschel sur l’île de la Palma aux Canaries. CANARY a été développé par le LESIA, en collaboration avec l’Université de Durham; le laser et son télescope d’émission ont été fournis et opéré par l’ESO. Lors de cette expérience, l'allongement extrême des étoiles laser qui sera observé sur l'ELT a été reproduit en plaçant le télescope d’émission à environ 40m du télescope William Herschel. Le front d'onde a ensuite été mesuré sur l’étoile laser allongée ainsi crée.Les travaux effectués pendant cette thèse ont consisté en la préparation de l’instrument et en particulier de l’analyseur de front d’onde de l’étoile laser, la réalisation des observations et le traitement des données résultant de ces dernières. L’analyse de ces données a permis de construire un budget d’erreur de la mesure de front d’onde sur étoile laser allongée. Grâce à ce budget d’erreur, les performances de différents algorithmes de mesure ont été comparées, ainsi que leur comportement face à la variabilité du profil de sodium et des conditions de turbulence. Enfin, différentes configurations d’analyseurs ont été extrapolées, ce qui a permis d’établir des limites sur leur design dans le cadre de l’ELTThe ELT (Extremely Large Telescope) is a telescope whose diameter is 39 m currently under construction by the European Southern Observatory (ESO). In order to fully benefit from its size, ELT instruments will be equipped with Adaptive Optics (AO) systems to compensate the atmospheric turbulence. These AO systems require the use of Laser Guides Stars (LGS) in order to have as large a sky coverage as possible. LGS are generated using a laser tuned on a resonant frequency of sodium atoms contained in a layer approximately 90km high and 10 km thick. Therefore, a LGS is a luminous cylinder in the high atmosphere, lighted by sodium atoms relaxation. Wavefront sensing on these artificial stars suffers from known limitations. On a telescope the size of the ELT, their use is further complicated by the perspective effect which causes an elongation of the LGS when it is seen from a point distant from its launch position : the cylinder is no longer seen by its circular section, but on the side. On a 39m telescope, the elongation can reach up to 20 arcseconds, which is large compared to to the diameter of the cylinder determined by the turbulence, that is about 1 arcsecond. Variability of the thickness, height and density distribution of the sodium layer then have an impact on wavefront sensing. The study of this problem, which concerns both sensing algorithms and wavefront sensor design, has already been the subject of many work relying on simulations and laboratory experiments. This thesis aims at studying this question using experimental data obtained on sky. These data were acquired using the AO demonstrator CANARY, placed on the William Herschel Telescope (WHT) on the island of La Palma in the Canaries Island. CANARY was developed by LESIA in collaboration with Durham University; the laser and its launch telescope were supplied and operated by ESO. In this experiment, the extreme elongation of LGS as will be seen on the ELT was reproduced by placing the launch telescope 40 m away from the William Herschel Telescope. The wavefront was the measured on the elongated LGS thus created. The studies led during this thesis consisted in the preparation of the instrument and in particular the LGS Wavefront Sensor (WFS), the realisation of the observations and processing on the data obtained. Analysis of these data allowed to build an error breakdown of wavefront sensing on the elongated LGS. Thanks to this error breakdown, performances of different measurement algorithms where compared, as well as their behaviour according to the variability of the sodium profile and the turbulence conditions. Finally, different wavefront sensor designs were extrapolated which allowed to establish limits on their designs for the ELT
18
Williams, Anthony R. "The nursing home five star rating: How does it compare to resident and family views of care?" Miami University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=miami1348673081.
19
Girard, Julien. "Validation sur le ciel du concept d'étoile laser polychromatique." Lyon 1, 2005. http://tel.archives-ouvertes.fr/docs/00/10/96/00/PDF/these_girard.pdf.
Abstract:
La turbulence atmosphérique baisse considérablement la résolution angulaire au foyer des grands télescopes terrestres. L'optique adaptative (OA) corrige les distorsions de front d'onde mesurées à l'aide d'une source de référence brillante à proximité de la ligne de visée. Dans le domaine du visible, la probabilité de disposer d'une étoile naturelle de référence est infime. L'étoile laser remédie à ce problème sauf pour la pente du front d'onde (ou tilt) qui demeure non corrigée. L'étoile laser polychromatique permettra l'utilisation de l'OA avec une couverture totale du ciel. Basée sur le chromaticité du tilt, il s'agit de créer une référence multicolore dans l'atmosphère et de mesurer le tilt différentiel à deux longueurs d'onde distinctes pour remonter au tilt lui-même. Dans cette thèse, je décris l'expérience ATTILA, conçue pour prouver la faisabilité de ce concept en conditions astronomiques. Des observations menées à l'Observatoire de Haute-Provence sur des étoiles naturelles ont permis d'établir la relation de proportionnalité entre le tilt et le tilt différentiel pour la première fois. Un suivi en temps réel montre une bonne corrélation entre les deux signaux. La précision de mesure obtenue sur la pente (environ une tache d'Airy) ouvre la voie pour le futur démonstrateur ELP-OA avec lasers. Ce travail a nécessité une caractérisation approfondie d'un détecteur pourvu de la récente technologie EMCCD ainsi que le développement et les tests de sismomètres pendulaires dédiés à la mesure des vibrations angulaires de télescopeThe atmospheric turbulence affects image quality and causes angular resolution losses at the focus of large ground based optical telescopes. Real time adaptive optics (AO) corrects wave front distortions measured with at least one bright reference source located within a tiny isoplanatic angle from the science object. At visible wavelengths, the probability to find one such natural star is ridiculously small. The laser guide star (LGS) solves the problem but the overall wavefront slope (referred here as tilt) remains undetermined. The Polychromatic Laser Guide Star will allow the use of AO with full sky coverage. Based on the tilt chromaticity, a multicolor reference spot is created in the upper atmosphere and the differential tilt is measured between two wavelengths to retrieve the tilt itself. In the present thesis, I describe ATTILA, an experiment designed to prove the feasibility of the concept in astronomical conditions. Observations carried on at Observatoire de HauteProvence on natural stars allowed us to establish the proportionality law that links the tilt and the differential tilt for the first time. A temporal monitoring of the two signals shows a good correlation. The accuracy obtained on the slope (about one Airy disk ) let us be optimistic for the future full ELP-OA demonstrator with lasers. This work required an in-depth characterization of a detector featuring the novel EMCCD technology as well as the implementation and tests of pendular seismometers dedicated to measure telescope angular vibrations
20
Gagné, Ronald C. "Measuring the return flux from laser guide stars." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44593.
Abstract:
For future extremely-large telescopes (ELT), operation at or near diffraction limited resolutions will be the norm, rather than the exception. Thus, adaptive optics systems and laser guide star facilities will be a critical component of the ELTs. The UBC Large Zenith Telescope (LZT) has conducted lidar observations to monitor the vertical distribution of sodium atoms with the goal of understanding both the abundance and evolution of sodium in the mesosphere to aid in both AO and laser guide star (LGS) return flux simulations. Access to the LZT's high resolution lidar experiment has lead to a joint collaboration between UBC, Thirty Meter Telescope (TMT), and the Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences (TIPC), to conduct upgrades of at the LZT site for sodium laser characterization tests, specifically TIPC's prototype pulsed sodium laser. The additional facilities and instrumentation at the LZT site include: 1) a new building to be used as a laser room to house visiting groups' lasers, corresponding control equipment and power systems, 2) optical equipment (scanning Fabry-Pérot interferometer, fast photodiode sensor, and miscellaneous optical filters) to measure the characteristics of the laser spectral format and pulse-shapes of pulsed lasers, and finally, 3) the site is now capable of directly imaging both natural stars and the LGS sodium spot with a 30 cm Ritchey-Chrétien equipped with a SBIG CCD camera to help determine the e ciency of LGS lasers. This document describes the new ancillary equipment for sodium laser characterization tests as well as a successful campaign conducted in the summer of 2012 on the UBC lidar laser. The summer campaign measured the laser pulse profile and spectral profile as well as LGS sodium spot measurements. The combined measurements which subsequently lead to an estimated sodium column density ranging from 5.1 × 10¹³ atoms/m² to 1.1 × 10¹³ − 1.5 × 10¹³ atoms/m² depending on the number of laser spectral modes used in the model.
21
Lombini, Matteo <1977>. "Laser guide stars wavefront sensors for the EELT." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3706/.
Abstract:
The Adaptive Optics is the measurement and correction in real time of the wavefront aberration of the star light caused by the atmospheric turbulence, that limits the angular resolution of ground based telescopes and thus their capabilities to deep explore faint and crowded astronomical objects. The lack of natural stars enough bright to be used as reference sources for the Adaptive Optics, over a relevant fraction of the sky, led to the introduction of artificial reference stars. The so-called Laser Guide Stars are produced by exciting the Sodium atoms in a layer laying at 90km of altitude, by a powerful laser beam projected toward the sky. The possibility to turn on a reference star close to the scientific targets of interest has the drawback in an increased difficulty in the wavefront measuring, mainly due to the time instability of the Sodium layer density. These issues are increased with the telescope diameter. In view of the construction of the 42m diameter European Extremely Large Telescope a detailed investigation of the achievable performances of Adaptive Optics becomes mandatory to exploit its unique angular resolution .
The goal of this Thesis was to present a complete description of a laboratory Prototype development simulating a Shack-Hartmann wavefront sensor using Laser Guide Stars as references, in the expected conditions for a 42m telescope. From the conceptual design, through the opto-mechanical design, to the Assembly, Integration and Test, all the phases of the Prototype construction are explained. The tests carried out shown the reliability of the images produced by the Prototype that agreed with the numerical simulations. For this reason some possible upgrades regarding the opto-mechanical design are presented, to extend the system functionalities and let the Prototype become a more complete test bench to simulate the performances and drive the future Adaptive Optics modules design.
22
Baranec, Christoph James. "Astronomical Adaptive Optics using Multiple Laser Guide Stars." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/193876.
Abstract:
Over the past several years, experiments in adaptive optics involving multiple natural and laser guide stars have been carried out at the 1.55 m Kuiper telescope and the 6.5 m MMT telescope. The astronomical imaging improvement anticipated from both ground-layer and tomographic adaptive optics has been calculated. Ground-layer adaptive optics will reduce the effects of atmospheric seeing, increasing the resolution and sensitivity of astronomical observations over wide fields. Tomographic adaptive optics will provide diffraction-limited imaging along a single line of sight, increasing the amount of sky coverage available to adaptive optics correction.A new facility class wavefront sensor has been deployed at the MMT which will support closed-loop adaptive optics correction using a constellation of five Rayleigh laser guide stars and the deformable F/15 secondary mirror. The adaptive optics control loop was closed for the first time around the focus signal from all five laser signals in July of 2007, demonstrating that the system is working properly. It is anticipated that the full high-order ground-layer adaptive optics loop, controlled by the laser signals in conjunction with a tip/tilt natural guide star, will be closed in September 2007, with the imaging performance delivered by the system optimized and evaluated.The work here is intended to be both its own productive scientific endeavor for the MMT, but also as a proof of concept for the advanced adaptive optics systems designed to support observing at the Large Binocular Telescope and future extremely large telescopes such as the Giant Magellan Telescope.
23
Butterley, Timothy. "Laser guide stars and turbulence profiling for extremely large telescopes." Thesis, Durham University, 2006. http://etheses.dur.ac.uk/2397/.
Abstract:
The next generation of ground based telescopes, the so-called extremely large telescopes, will offer a significant leap in sensitivity and resolution compared to current telescopes. They also present a range of technical challenges. This thesis presents work on two important problems in implementing laser guide star adaptive optics on extremely large telescopes: focal anisoplanatism and turbulence profiling. The SPLASH (Sky-Projected Laser Array Shack-Hartmann) laser guide star wavefront sensing technique is described. The technique is shown to offer reduced focal anisoplanatism compared to a conventional laser guide star for large telescopes. The technique may also offer advantages for larger apertures, including extremely large telescopes, but simulations were limited to 8 metre apertures by currently available computing capabilities. A calibration method is presented for the SLODAR (Slope Detection and Ranging) turbulence profiling technique, along with an analysis of the effects of scintillation on SLODAR when the technique is applied on a small (~ 40 cm diameter)' telescope. A new variation on the SLODAR technique, SLOTDAR (Slope Detection and Ranging through a slot), is introduced, in which the spatial sampling can be optimised based on the brightness of the available reference stars.
24
Milton, Norman Mark. "Tomographic Reconstruction of Wavefront Aberrations using Multiple Laser Guide Stars." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/194080.
Abstract:
Tomographic reconstruction using multiple laser guide stars (MLGS) will be required by the next generation of extremely large (30 m class) telescopes (ELT). Modal decomposition of wavefront phase using Zernike polynomials is a widely used technique in adaptive optics (AO) research. However, this approach breaks down with the large number of degrees of freedom required by ELTs.This research proposes the use of an alternative basis, the disk harmonic functions, to overcome the disadvantages of the Zernike basis at high spatial resolution. A method of fast, analytic, modal tomographic modeling is developed and used for fast calculation of reconstruction matrices used on-sky at the MMT telescope.The specific reconstruction techniques of ground layer adaptive optics and laser tomography adaptive optics using MLGS are presented along with the results of on-sky experiments at the MMT. In addition to developing a laser AO instrument for the MMT, these experiments provide a test bed for validating the reconstruction techniques that will be critical to the success of ELTs.An approach to using real-time wavefront sensor and deformable mirror telemetry from the MLGS system to estimate the vertical distribution of turbulence in the atmosphere is also presented.
25
Meilard, Nicolas. "Etoile Laser Polychromatique pour l’Optique Adaptative : modélisation de bout-en-bout, concepts et étude des systèmes optiques." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10107/document.
Abstract:
L’étoile laser polychromatique (ELP) fournit la référence de phase à une optique adaptative (OA)pour corriger les surfaces d’onde turbulentes, y compris leur pente. L’ELP, générée dans la mésosphère parune excitation résonnante à deux photons du sodium, repose sur la déviation chromatique des images. Uneimagerie dans le visible devient possible, et est indispensable pour 80% des programmes astrophysiquesprioritaires de l'E-ELT.L’ELP requiert un écart-type des mesures de position 26 fois inférieur au cas classique. Cela m’a amené àétudier le projecteur laser interférométrique. J’ai mis au point un correcteur de base polychromatique pourégaliser la période des franges et un correcteur de phase pour compenser la réfraction atmosphérique. J’aiétudié l'optique de mesure des franges, et de séparation entre l'ELP et l’objet observé.La précision requise m’a conduit à étudier dans quelles conditions l’algorithme du maximum devraisemblance tend vers la borne de Cramér-Rao.J’ai également développé un modèle numérique de bout en bout pour simuler l’ELP depuis les lasersjusqu’à la mesure du rapport de Strehl. Je montre que pour un VLT, les rapports de Strehl sont supérieurs à40% à 500 nm sans étoile de référence, en prenant une OA qui aurait donné 50% instantané (Strehl depente : 80%). Une approche analytique valide ces résultats.Enfin, j’aborde l’application de l’ELP aux télécommunications interplanétaires et à la destruction des débrisorbitauxThe polychromatic laser guide star (PLGS) provides adaptive optics (AO) with a phase referenceto correct corrugated wavefronts, including tip tilt. It relies on the chromatic dispersion of light returnedfrom the 2-photon resonant excitation of sodium in the mesosphere. Diffraction limited imaging in thevisible then becomes possible. This is mandatory for 80% of the prominent astrophysical cases for the EELT.A PLGS requires standard deviations of position measurements 26 times less than in classical cases. Thus Ihave studied the interferometric laser projector. I have designed a polychromatic base corrector to equalizethe fringe periods, a phase corrector to compensate atmospheric refraction and the optics for fringemeasurements and for keeping apart the PLGS from the science target images.The required accuracy leads me to study how the maximum likelihood algorithm approaches the Cramer-Rao bound.I have written an end-to-end code for numerical simulations of the PLGS, from the lasers to the Strehlmeasurement. I get for the VLT Strehl ratios larger than 40% at 500 nm if one uses an AO providing us a50% instantaneous Strehl (tip tilt Strehl : 80%). An analytical model validates these results.Finally I address the application of the PLGS to deep space communications and to space debris clearing
26
Raphoto, Katleho. "Fintech Start-ups in South Africa : A Conceptual Framework to Guide Technology Entrepreneurs." Diss., University of Pretoria, 2021. http://hdl.handle.net/2263/78920.
Abstract:
Owing to the lack of information and guidelines currently available for technology entrepreneurs, establishing Fintech start-ups in South Africa is challenging. The current literature on Fintech does not provide information highlighting ways in which technology entrepreneurs can establish and sustain Fintech start-ups, nor does it discuss the relevant skills required or the potential entry barriers for Fintech start-ups in the South African context. The purpose of this research is to investigate the factors that make Fintech startups successful, highlight the barriers faced by Fintech startups, elaborate on the skills required, and create a conceptual framework based on the research, that will guide technology entrepreneurs towards successful venture creation. A qualitative research methodology was used in this study using a semi-structured interview with open-ended questions as a research instrument. Financial Capital, Adherence to Regulation and Customer Centric Platform Development were some of the key findings related to establishing and sustaining Fintech start-ups in South Africa. Costly and scarce skilled resources and regulation barriers were some of the contributors to the failure of Fintech start-ups in South Africa. The government needs to assist where they can from a regulation perspective and provide more support to Fintech start-ups. Tax rebates for Fintech start-ups would also help these start-ups survive in South Africa.Dissertation (MCom)--University of Pretoria, 2021.
Informatics
MCom
Unrestricted
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Jones, Neville Thomas. "Simulating the use of multiple laser guide stars in ground-based astronomical adaptive optics." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392354.
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Saab, Mohamad Yehia. "Photochimie organique guidée par pulses laser : Applications : Benzopyrane et Pyrazine." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20014/document.
Abstract:
La photo-isomérisation par ouverture de cycle du benzopyrane a été étudiée à l'aide de la méthode MCTDH (Multi-Configuration Time-Dependent Hartree). Nous avons introduit différentes stratégies pour contrôler la conversion du benzopyrane en mérocyanine à l'aide d'impulsions laser. Nous avons utilisé un modèle pour le potentiel électronique à six dimensions développé dans le cadre d'un travail antérieur. Le modèle repose sur une généralisation des Hamiltoniens modèles standards pour les couplages vibroniques et utilise les six coordonnées les plus importantes pour le processus. Le principal objectif est de fournir des stratégies de contrôle qui pourront être utilisées par les expérimentateurs par la suite. Plus précisément, nous avons proposé: (i) une technique de type pompe-sonde pour contrôler la photostabilité, (ii) une stratégie en deux étape avec une préexcitation vibrationnel du système,(iii) une stratégie reposant sur un contrôle par effet Stark induit par un laser non-résonantThe ring-opening photoisomerization of benzopyran, which occurs via a photochemical route involving a conical intersection,has been studied with quantum dynamics calculations using the multi-configuration time-dependent Hartree method (MCTDH). We introduce a mechanistic strategy to control the conversion of benzopyran to merocyanine with laser pulses. We use asix-dimensional model developed in a previous work for the potential energy surfaces (PES) based on an extension of thevibronic-coupling Hamiltonian model (diabatization method by ansatz), which depends on the most active degrees of freedom. The main objective of these quantum dynamics simulations is to provide a set of strategies that could help experimentalists tocontrol the photoreactivity vs. photostability ratio (selectivity). In this work we present:(i) a pump-dump technique used tocontrol the photostability, (ii) a two-step strategy to enhance the reactivity of the system: first, a pure vibrational excitation inthe electronic ground state that prepares the system and, second, an ultraviolet excitation that brings the system to the firstadiabatic electronic state; (iii) finally the effect of a non-resonant pulse (Stark effect) on the dynamics
29
Bendek, Eduardo A. "High-Precision Astrometry Using a Diffractive Pupil and Advancements in Multi-Laser Adaptive Optics." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/238675.
Abstract:
Detection of earth-size exoplanets using the astrometric signal of the host star requires sub-microarcsecond measurement precision. One major challenge in achieving this precision using a medium-size (< 2-m) space telescope is the calibration of dynamic distortions. A diffractive pupil can be used to generate polychromatic diffraction spikes in the focal plane, which encode the distortions in the optical system and may be used to calibrate astrometric measurements. The first half of this dissertation discusses the design and construction of a laboratory to test this concept. The main components of the system are a high stability star simulator, a diffraction limited off-axis optical system, and the data reduction algorithms to obtain the distortion map calibration. Currently, the laboratory is operational and first tests of distortion measurements have been done validating this concept to improve the astrometric accuracy of a telescope. The second part of this dissertation describes the use of the multi-laser guide star (LGS) system available at the 6.5 m MMT telescope to characterize GLAO performance and advance Laser Tomography Adaptive Optics (LTAO) technology. The system uses five range-gated and dynamically refocused Rayleigh laser beacons to sense the atmospheric wavefront aberration. Corrections are then applied to the wavefront using the 336-actuator adaptive secondary mirror of the telescope. So far, the system has demonstrated successful control of ground-layer aberration over a field of view (FoV) substantially wider than is delivered by conventional adaptive optics, yielding reduction in the width of the on-axis point-spread function from 1.07" to < 0.2" in H band. Both techniques can be combined to improve the astrometric accuracy of ground based telescopes, especially when using Multi-Conjugated Adaptive Optics (MCAO). A diffractive pupil can be used to calibrate the distortions induced by multiple Deformable Mirrors (DM), which is the main limitation to use this kind of AO system for high precision astrometric measurements.
30
Wiles, Bradford Broyhill. "Shared Reading, Scaffolding, Guided Participation, and Mind-mindedness in Appalachian Head Start Families: Building the Construct of Mindful-mindedness." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/50640.
Abstract:
The purpose of this study was to provide an intervention to Appalachian Head Start families that provided novel ways of thinking about their children\'s development, while also arming them with effective strategies and tools they could use to build engaging and enriched interactions. The intervention curriculum was developed based on a theory of mentoring in the zone of proximal development (Vygotsky, 1978; Wiles, 2008). This research effort sought to answer the following research questions: (a) Do adults\' descriptions of their children as mental beings and perceptions about their children as individuals with minds of their own change due to participation in the intervention condition as compared to those in the control condition?; (b) What are the effects of this intervention on adults\' use of scaffolding and guided participation strategies in the shared reading activity over time?; (c) Does participation in the intervention condition affect the child\'s outcomes on standardized tests?; and (d) What qualitative differences in the way adults and children interact in the shared reading activity can occur as a result of the intervention? A randomized controlled trial including 50 parent-child dyads, were videotaped answering a mind-mindedness interview question and reading with their children at three time points over the Head Start school year. A Mixed-methods approach was implemented in the study\'s design, implementation, data collection, and analyses. Quantitative analyses revealed significant differences in both mental descriptions of participants\' children and the type and frequency of scaffolding techniques as a result of participation in the intervention. Triangulation of the qualitative and quantitative analyses indicated the need for a new theoretical construct to explain what occurs in optimally functioning interactions. Mindful-mindedness describes and explains adults\' metastrategic scaffolding technique selection in a mindful and mind-minded style, and then their application of these techniques in a serial process creates a multiplier effect on the efficacy of scaffolding. Implications for policy and practice, limitations of the current study, and directions for future research are also provided.Ph. D.
31
Ramson, Ryan R. "VLBI observations of the candidate guide stars and the reference sources for the spaceborne NASA/Stanford gyroscope relativity mission, Gravity Probe B." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq27373.pdf.
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Kellner, Stephan [Verfasser], and Reinhardt [Akademischer Betreuer] Mundt. "Novel Adaptive Optics Concepts : Wavefront Sensing with Sodium Laer Guide Stars at Extemely Large Telescopes and Simultaneous Differential Imaging / Stephan Kellner ; Betreuer: Reinhardt Mundt." Heidelberg : Universitätsbibliothek Heidelberg, 2005. http://d-nb.info/1177808838/34.
33
Yu, Suhnah. "A Pedagogical Guide: Using Sassmannshaus’s Early Start on the Violin, Volumes 1 and 2 as a supplement to the Suzuki Violin School, Volume 1." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342106257.
34
Herlemont, François. "Contribution à des études de spectroscopie haute résolution par laser à C02 guide d'onde." Lille 1, 1985. http://www.theses.fr/1985LIL10095.
Abstract:
La spectroscopie haute résolution dans la cavité d'un laser à C02 est une méthode de spectroscopie utilisée maintenant dans divers laboratoires. La mise au point de laser à C02 guide d'onde ayant des caractéristiques fort différentes des lasers à onde libre nous a conduit à exploiter ses spécificités en spectroscopie intracavité haute résolution. Deux types de spectroscopie subDoppler ont ainsi été développés: - La spectroscopie de saturation. Dans ce cas, c'est la gamme d'accord importante du laser à C02 guide d'onde qui est exploitée. Le Bromure de Methyle a servi de gaz test. Les nombreuses observations ont permis une analyse détaillée de la bande de vibration v6 des deux espèces isotopiques. - La spectroscopie à deux photons à effet Doppler compensé. Cette technique de spectroscopie haute résolution est surtout utilisée dans le domaine visible. Son extension au domaine infrarouge n'est pas sans poser de problèmes. Nous montrons comment la disposition intracavité du gaz absorbant associée à l'utilisation d'un amplificateur à C02 guide d'onde réalise un compromis entre les différents paramètres intervenant dans le processus d'absorption à deux photons (densité de puissance gamme d'accord, résolution). Nous avons appliqué cette méthode de spectroscopie à l'étude de la bande de vibration v3 = 0 + v3 = 2 de SF6, molécule type pour les expériences d'excitation multiphotonique. Par ailleurs, une nouvelle voie de recherche permettant 1'étude d'absorption à deux photons a été mise au point : le gaz absorbant est placé dans une cavité passive en dehors de cette cavité laser. Cette configuration originale fournit une phénoménologie riche dont les principaux aspects sont abordés. Au cours de ces études, de nombreux effets ont été observés et analysés: régime de Q-switch (automodulation de la puissance laser), régime de bistabilité d'absorption, de bistabilité dispersive, dispersion à deux photons.
35
O'Hara, Karen Mary. "An Internship at Miami University Libraries Center for Information Management." Miami University / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=miami1101996292.
36
Chebbo, Manal. "Simulation fine d'optique adaptative à très grand champ pour des grands et futurs très grands télescopes." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4733/document.
Abstract:
La simulation fine de systèmes d'OA à grand champ de type MOAO ou LTAO pour l'ELT se heurte à deux problématiques: l'augmentation du nombre de degrés de liberté du système. Cette augmentation rend les codes de simulation classiques peu utilisables, en particulier en ce qui concerne les processus d'inversion et de calcul matriciel. La complexité des systèmes, combinant EGL et EGN, grands miroirs déformables couvrant tout le champs et des miroirs dédiés dans les instruments eux mêmes, des rotations différentielles de pupille et ou de champs. Cette complexité conduit aux développements de procédures nouvelles d'étalonnage, de filtrage et fusion de données, de commande distribuée ou globale. Ces procédures doivent être simulées finement, comparées et quantifiées en termes de performances, avant d'être implantées dans de futurs systèmes. Pour répondre à ces deux besoins, le LAM développe en collaboration avec l'ONERA un code de simulation complet, basé sur une approche de résolution itérative de systèmes linéaires à grand nombre de paramètres (matrices creuses). Sur cette base, il incorpore de nouveaux concepts de filtrage et de fusion de données pour gérer efficacement les modes de tip/tilt/defocus dans le processus complet de reconstruction tomographique. Il permettra aussi, de développer et tester des lois de commandes complexes ayant à gérer un la combinaison du télescope adaptatif et d'instrument post-focaux comportant eux aussi des miroirs déformables dédiés.La première application de cet outil se fait naturellement dans le cadre du projet EAGLE, un des instruments phares du futur E-ELT, qui, du point de vue de l'OA combinera l'ensemble de ces problématiquesRefined simulation tools for wide field AO systems on ELTs present new challenges. Increasing the number of degrees of freedom makes the standard simulation's codes useless due to the huge number of operations to be performed at each step of the AO loop process. The classical matrix inversion and the VMM have to be replaced by a cleverer iterative resolution of the Least Square or Minimum Mean Square Error criterion. For this new generation of AO systems, concepts themselves will become more complex: data fusion coming from multiple LGS and NGS will have to be optimized, mirrors covering all the field of view associated to dedicated mirrors inside the scientific instrument itself will have to be coupled using split or integrated tomography schemes, differential pupil or/and field rotations will have to be considered.All these new entries should be carefully simulated, analysed and quantified in terms of performance before any implementation in AO systems. For those reasons i developed, in collaboration with the ONERA, a full simulation code, based on iterative solution of linear systems with many parameters (sparse matrices). On this basis, I introduced new concepts of filtering and data fusion to effectively manage modes such as tip, tilt and defoc in the entire process of tomographic reconstruction. The code will also eventually help to develop and test complex control laws who have to manage a combination of adaptive telescope and post-focal instrument including dedicated DM
37
Рябова, Світлана Олександрівна. "Гідродинамічне удосконалення поворотно-лопатевої гідротурбіни на основі використання просторового профілювання лопатей робочого колеса." Thesis, НТУ "ХПІ", 2017. http://repository.kpi.kharkov.ua/handle/KhPI-Press/29700.
Abstract:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.05.17 – гідравлічні машини та гідропневмоагрегати. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2017.
Дисертацію присвячено вирішенню важливої науково-технічної задачі покращення енергетичних характеристик проточної частини низьконапірної осьової гідротурбіни. Виконано огляд науково-технічних джерел щодо методів досліджень гідродинамічних процесів у проточних частинах поворотно-лопатевих гідротурбін. За результатами чисельних досліджень просторової течії в'язкої нестисливої рідини в проточній частині вертикальної поворотно-лопатевої осьової гідротурбіни ПЛ20/3271у Кременчуцької ГЕС отримано детальну інформацію про структуру потоку у всіх елементах проточної частини в широкому діапазоні режимів роботи за допомогою програмного комплексу IPMflow, розробленого в ІПМаш НАН України. Досліджено вплив параметрів потоку на вході в розрахункову область на характеристики проточної частини, встановлено діапазон режимів роботи низьконапірної вертикальної осьової турбіни, при яких забезпечується рівномірний розподіл гідродинамічних величин в окружному напрямку на вході в робоче колесо. Запропоновано підхід до просторового профілювання лопатей робочих коліс осьових гідротурбін, заснований на застосуванні складних навалів в осьовому й окружному напрямках, який дозволяє підвищити ефективність проточної частини. Встановлено закономірності впливу складних осьових і окружних навалів робочих коліс на структуру потоку та інтегральні енергетичні показники, що використовуватимуться при проектуванні та модернізації проточних частин осьових гідротурбін. Розроблено робоче колесо з комбінованим периферійним навалом сучасної високоефективної низьконапірної осьової гідротурбіни ПЛ20/3271у Кременчуцької ГЕС з покращеними енергетичними показниками.The dissertation for the degree of Candidate of Technical Sciences in the specialty 05.05.17 – hydraulic machines and hydropneumatic units. – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2017. The thesis is devoted to solving of important scientific and technical problem of improving the energy characteristics of the flow part of Kaplan turbine. A review of the scientific and technical literatures on the methods of testing of hydrodynamic processes in flow parts of the Kaplan turbines has been carried out. According to the results of numerical investigations of the spatial flow of a viscous incompressible fluid in the flow part of the Kaplan turbine PL 20/3271у of the Kremenchug HPP detailed information on the structure of flow in all elements of the flow part in a wide range of operating modes has been received using software complex IPMflow developed at IPMash NAS of Ukraine. The influence of flow parameters at the inlet to the computational domain on the characteristics of the flow part has been investigated, a range of operation modes of Kaplan turbine that provide uniform distribution of the hydrodynamic values in circular direction at the inlet to the runner has been established. The approach to spatial profiling of the runner blades of Kaplan turbines based on the use of complex offsets in the axial and circular directions, which allows improving the energy characteristics of a flow part has been proposed. The influence of complex axial and circular offsets of the runners on flow structure and integral energy parameters that can be used in the design and modernization of the flow parts of Kaplan turbines have been established. The runner with combined peripheral offset of the modern high-performance Kaplan turbine ПЛ20/3271у Kremenchug HPP with improved energy performance has been developed.
38
Рябова, Світлана Олександрівна. "Гідродинамічне удосконалення поворотно-лопатевої гідротурбіни на основі використання просторового профілювання лопатей робочого колеса." Thesis, НТУ "ХПІ", 2017. http://repository.kpi.kharkov.ua/handle/KhPI-Press/29696.
Abstract:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.05.17 – гідравлічні машини та гідропневмоагрегати. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2017.
Дисертацію присвячено вирішенню важливої науково-технічної задачі покращення енергетичних характеристик проточної частини низьконапірної осьової гідротурбіни. Виконано огляд науково-технічних джерел щодо методів досліджень гідродинамічних процесів у проточних частинах поворотно-лопатевих гідротурбін. За результатами чисельних досліджень просторової течії в'язкої нестисливої рідини в проточній частині вертикальної поворотно-лопатевої осьової гідротурбіни ПЛ20/3271у Кременчуцької ГЕС отримано детальну інформацію про структуру потоку у всіх елементах проточної частини в широкому діапазоні режимів роботи за допомогою програмного комплексу IPMflow, розробленого в ІПМаш НАН України. Досліджено вплив параметрів потоку на вході в розрахункову область на характеристики проточної частини, встановлено діапазон режимів роботи низьконапірної вертикальної осьової турбіни, при яких забезпечується рівномірний розподіл гідродинамічних величин в окружному напрямку на вході в робоче колесо. Запропоновано підхід до просторового профілювання лопатей робочих коліс осьових гідротурбін, заснований на застосуванні складних навалів в осьовому й окружному напрямках, який дозволяє підвищити ефективність проточної частини. Встановлено закономірності впливу складних осьових і окружних навалів робочих коліс на структуру потоку та інтегральні енергетичні показники, що використовуватимуться при проектуванні та модернізації проточних частин осьових гідротурбін. Розроблено робоче колесо з комбінованим периферійним навалом сучасної високоефективної низьконапірної осьової гідротурбіни ПЛ20/3271у Кременчуцької ГЕС з покращеними енергетичними показниками.The dissertation for the degree of Candidate of Technical Sciences in the specialty 05.05.17 – hydraulic machines and hydropneumatic units. – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2017. The thesis is devoted to solving of important scientific and technical problem of improving the energy characteristics of the flow part of Kaplan turbine. A review of the scientific and technical literatures on the methods of testing of hydrodynamic processes in flow parts of the Kaplan turbines has been carried out. According to the results of numerical investigations of the spatial flow of a viscous incompressible fluid in the flow part of the Kaplan turbine PL 20/3271у of the Kremenchug HPP detailed information on the structure of flow in all elements of the flow part in a wide range of operating modes has been received using software complex IPMflow developed at IPMash NAS of Ukraine. The influence of flow parameters at the inlet to the computational domain on the characteristics of the flow part has been investigated, a range of operation modes of Kaplan turbine that provide uniform distribution of the hydrodynamic values in circular direction at the inlet to the runner has been established. The approach to spatial profiling of the runner blades of Kaplan turbines based on the use of complex offsets in the axial and circular directions, which allows improving the energy characteristics of a flow part has been proposed. The influence of complex axial and circular offsets of the runners on flow structure and integral energy parameters that can be used in the design and modernization of the flow parts of Kaplan turbines have been established. The runner with combined peripheral offset of the modern high-performance Kaplan turbine ПЛ20/3271у Kremenchug HPP with improved energy performance has been developed.
39
Tecklenburg, Gerhard. "Design of body assemblies with distributed tasks under the support of parametric associative design (PAD)." Thesis, University of Hertfordshire, 2011. http://hdl.handle.net/2299/5809.
Abstract:
This investigation identifies how CAD models of typical automotive body assemblies could be defined to allow a continuous optimisation of the number of iterations required for the final design and the number of variants on the basis of Parametric Associative Design (PAD) and how methodologies for the development of surfaces, parts and assemblies of the automotive body can be represented and structured for a multiple re-use in a collaborative environment of concept phase of a Product Evolution (Formation) Process (PEP). The standardisation of optimised processes and methodologies and the enhanced interaction between all parties involved in product development could lead to improve product quality and reduce development time and hence expenses. The fundamental principles of PAD, the particular methodologies used in automotive body design and the principles of methodical development and design in general are investigated. The role which automotive body engineers play throughout the activities of the PEP is also investigated. The distribution of design work in concept teams of automotive body development and important methodologies for the design of prismatic profile areas is critically analysed. To address the role and distribution of work, 25 group work projects were carried out in cooperation with the automotive industry. Large assemblies of the automotive bodies were developed. The requirements for distributed design work have been identified and improved. The results of the investigation point towards a file based, well structured administration of a concept design, with a zone based approach. The investigation was extended to the process chain of sections, which are used for development of surfaces, parts and assemblies. Important methods were developed, optimised and validated with regard to an update safe re-use of 3D zone based CAD models instead of 2D sections. The thesis presents a thorough description of the research undertaken, details the experimental results and provides a comprehensive analysis of them. Finally it proposes a unique methodology to a zone based approach with a clearly defined process chain of sections for an update-safe re-use of design models.
40
Vu, K. "Sodium line guide star laser using optical parametric oscillator." Thesis, 2003. http://hdl.handle.net/1885/41345.
Abstract:
The aim of this project is to develop a novel, high average power source of highly coherent radiation at the 589nm sodium D2 resonance line for use in creating a laser guide star for use with adaptive optics systems such as astronomical telescopes and satellite ranging. Adaptive optics is used to improve the resolution of ground base telescope by compensating the atmospheric turbulence. To achieve this it is necessary to measure and correct the distortions caused by the atmosphere on the beam. A laser guide star provides a beacon which combined with a wavefront sensor allows the effect of the atmosphere to be quantified and mechanical corrections made to the adaptive optics in the telescope to cancel those distortions. Whilst laser guide stars have been demonstrated as effective in a number of astronomical observatories, at present there is no laser technology that dominates this application. This project will demonstrate a novel approach to the creation of high average power optical sources for guide star applications. The aim of the project is to build a prototype of high average power, synchronously pumped optical parametric oscillators pumped by novel high power solid state laser technology. The Magnesium Oxide doped periodically poled Lithium Niobate was used as the nonlinear crystal for the 532nm pumped singly resonant parametric oscillator. The oscillator was pumped by 1.4W of 532nm light which was created from a 3.5W mode-locked Nd:YVO4 laser by a Lithium Triborate second harmonic generator. With a grating period of 12.05µm, the signal at the wavelength of 594nm was obtained at 150C. There was unexpected green absorption of the crystal, which undermined the performance of the oscillator. However, from the experimental results of a Potassium Titanyl Phosphate optical parametric oscillator, it was demonstrated that highly efficient parametric oscillator can be built despite the idler absorption.
41
Jackson, Kate. "Modeling of laser guide star wavefront sensing for extremely large telescopes." Thesis, 2009. http://hdl.handle.net/1828/1992.
Abstract:
This thesis presents a simulation of the control system for Laser Guide Star (LGS)
wavefront sensing of the Narrow Field Infrared Adaptive Optics System (NFIRAOS)
which will be the Adaptive Optics (AO) system on the Thirty Meter Telescope. The
control system is multirate and combines data from multiple sources, both natural
and artificial, to provide wavefront correction. Artificial guide stars are generated by
exciting atoms in the mesospheric sodium (Na) layer.
The characteristics of the Na layer have been examined; its variability, altitude
and thickness will lead to false atmospheric turbulence measurements by AO systems
integrated with Extremely Large Telescopes. A periodically updated constrained
matched filter algorithm has been implemented in the control system simulation in
order to gauge its ability to mitigate these effects.
The control system has also been implemented on the University of Victoria LGS
Test Bench which reproduces wavefront measurements as they will be made by several
of the wavefront sensors of NFIRAOS. The simulation has provided insight into the
stability of the proposed control system and allowed necessary improvements to be
made. It has been shown to meet the requirements of stability over long term with
fast convergence. The matched filter algorithm has been shown to effectively reject
the Na layer fluctuations both in simulation and on the test bench.
42
Schwab, Christian [Verfasser]. "A calibration system for a Rayleigh laser guide star constellation & a planet around a giant star / put forward by Christian Schwab." 2010. http://d-nb.info/1006942173/34.
43
Cross, Garnett B. "Investigation of a laser-induced breakdown spark as a near field guide star for aero-optic measurements." 2009. http://etd.nd.edu/ETD-db/theses/available/etd-12072009-130933/.
Abstract:
Thesis (M.S. Aero. E.)--University of Notre Dame, 2009.Thesis directed by R. Mark Rennie and Eric J. Jumper for the Department of Aerospace and Mechanical Engineering. "December 2009." Includes bibliographical references (leaves 62-64).
44
Shi, Fang. "The sodium laser guide star experiment for adaptive optics and the development of a high bandwidth tracking system for the University of Chicago adaptive optics system /." 1999. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:9951838.
45
Schneider, Colleen. "Creating a community mobilization guide for Employment and Immigration Canada's "Stay in school initiative"." 1996. http://hdl.handle.net/1993/22587.
46
Ransom, Ryan R. "VLBI observations of the candidate guide stars and their reference sources for the spaceborne NASA/Stanford gyroscope relativity mission (Gravity Probe B)." 1997. http://wwwlib.umi.com/cr/yorku/fullcit?pMQ27373.
Abstract:
Thesis (M. Sc.)--York University, 1997. Graduate Programme in Physics and Astronomy.Typescript. Includes bibliographical references (leaves 137-141). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ27373.
47
Radner, Hannes. "Adaptive optische Wellenfrontkorrektur unter Einsatz des Fresnel-Leitsterns und eines hybriden Regelkreises implementiert auf einem Field-Programmable System-on-Chip." 2020. https://tud.qucosa.de/id/qucosa%3A75637.
Abstract:
Laseroptische Messsysteme werden vielseitig eingesetzt, unter anderem für die Messung der Strömung in Blasen und Tropfen. Beispielsweise ist die Messung in Tropfen von besonderem Interesse für die Brennstoffzellenforschung, da das Wasserkondensat die Leistungsfähigkeit der Zelle stark mindern kann. Bei der laseroptischen Messung durch die dynamische Phasengrenzfläche erhöht sich aufgrund der zufälligen Lichtbrechung die Messunsicherheit erheblich. Um dem entgegenzuwirken, wurde in dieser Arbeit untersucht, wie sich der in der Astronomie weitverbreitete Ansatz einer aktiven Wellenfrontkorrektur auf die laseroptische Strömungsmesstechnik für die Korrektur einer zufällig dynamisch streuenden Phasengrenzfläche mit nur einem optischen Zugang durch die Grenzfläche übertragen lässt. Als neuartiger Leitstern wurde hierfür der Fresnel-Reflex der Oberfläche als Fresnel Guide Star (FGS), welcher alle Informationen über die optische Störung enthält, untersucht und eingesetzt. Validiert wurde der neue Leitstern exemplarisch für die zwei laseroptischen Messverfahren Laser-Doppler-Velocimetrie (LDV) und Particle-Image-Velocimetrie (PIV). Für das bildgebende Messverfahren PIV wurde ein Regelsystem realisiert, welches eine adaptive optische Korrektur einer oszillierenden Wasseroberfläche durchführt. Das System besteht aus einem Hartmann-Shack-Sensor (HSS), einer Signalverarbeitungseinheit und einem 69-elementigen deformierbaren Membranspiegel. Dabei muss die Signalverarbeitungseinheit aus dem Hartmannogramm die Wellenfront des FGS rekonstruieren, die Stellgröße berechnen und den Membranspiegel ansteuern. Diese komplexe Multiple-Input-Multiple-Output(MIMO)-Regelungsaufgabe stellt besondere Anforderungen an das System, da die Wasseroberfläche mit mehreren hundert Hertz schwingt und das System für eine hinreichende Reserve somit eine Regelrate im Kilohertzbereich haben muss. Um diese Anforderungen zu erfüllen, wurde als hybride Recheneinheit ein Field- Programmable System-on-Chip (FPSoC) eingesetzt. Dieser vereint eine Central Processing Unit (CPU) und einen Field-Programmable Gate Array (FPGA) auf einem einzigen monolithischen Chip als eine sehr leistungsfähige Symbiose beider Architekturen. Das System erreicht eine Regelrate von 3,5 kHz und war in der Lage, die optische Störung mit einer Dämpfungsbandbreite von bis zu 150 Hz zu dämpfen. Bei der PIV-Messung wurde die Erhöhung der Standardunsicherheit des Geschwindigkeitsfeldes, verursacht durch die Oszillation der Phasengrenzfläche, um 67 % reduziert. Das System kann beispielsweise für die Optimierung von Brennstoffzellen eingesetzt werden, um die Tropfeninnenströmung in den auf der chemisch aktiven opaken Membran kondensierten Tropfen mit nur einem einzigen optischen Zugang durch die streuende Grenzfläche zu messen. Damit könnte der Gleitprozess des Tropfens an der Membranoberfläche verstanden werden und das Wasser effektiver abtransportiert werden, um die Leistungsfähigkeit der Zelle zu steigern. Weitere Anwendungsgebiete sind die Strömungsmessung in Taylorblasen, Regentropfen oder Flüssigkeitskühlfilmen mit offener Oberfläche. Generell hat der neue FGS zusammen mit dem Regelungssystem das Potenzial, die optische Messung durch eine dynamische oszillierende Grenzfläche zu verbessern oder überhaupt erst zu ermöglichen.Laser optical measurement systems are used in a variety of applications, e.g. the flow measurement in bubbles and droplets. The flow in droplets is of particular interest for fuel cell research, since water condensate can significantly reduce the efficiency of the cell. In laser-optical measurements the dynamic motion of the phase boundary increases the measurement uncertainty significantly because of the random refraction of light. Therefore this thesis investigates how the approach of an active wavefront correction, which is widely used in astronomy, can be applied to laser-optical flow measurement techniques for the correction of a dynamic phase boundary with only one optical access through the interface. For this purpose, the Fresnel reflection of the surface was investigated, which is called Fresnel Guide Star (FGS). It contains all information about the optical distortion. The new guide star was validated exemplarily for the two laser optical measurement techniques Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV). For PIV a control system consisting of a Hartmann-Shack-Sensor (HSS), a signal processing unit and a 69-element deformable membrane mirror was realized, which performs an adaptive optical correction of the moving water surface. Therefore the signal processing unit must reconstruct the wavefront of the FGS from the Hartmannogram, calculate the set value and control the membrane mirror. This complex Multiple-Input Multiple-Output (MIMO) control task results in extensive demands on the control system, since the water surface oscillates with several hundred hertz and the system must therefore have a control rate in the kilohertz range to ensure sufficient reserve. In order to meet these requirements, a Field- Programmable System-on-Chip (FPSoC) was used as hybrid computing unit. It combines a Central Processing Unit (CPU) and an Field-Programmable Gate Array (FPGA) on a single monolithic chip as a very powerful symbiosis of both architectures. The system achieved a control rate of 3,5 kHz and was able to attenuate the optical distortion with an attenuation bandwidth of up to 150 Hz. In the PIV measurement, the increase in the standard uncertainty of the velocity field caused by the oscillation of the phase boundary was reduced by 67 %. The system could be used for the optimization of fuel cells to measure the internal flow in the droplets condensed on the chemically active membrane with only one optical access through the fluctuating interface. This would allow the sliding process of the droplet on the membrane surface to be understood and the water to be removed more effectively in order to increase the performance of the cell. Further applications are flow measurement in bubbles, raindrops or liquid cooling films with an open surface, where the system expands the field of application for computational laser metrology. In general, the new FGS together with the low latency control system have the potential to improve the optical measurement through dynamically oscillating interfaces or to make the measurement possible at all.
48
Chieh-Hung, Li, and 李介宏. "A Study of Pain Relief and Hospital Stay Provided by Ultrasound-guided Interscalene Nerve Block with 0.25% or 0.5% Bupivacaine After Shoulder Arthroscopic Surgery." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/18165671657156362060.
Abstract:
碩士東海大學
工業工程與經營資訊學系
98
Background and Objectives: Shoulder arthroscopy is a common orthopedic surgery, and most patients report moderate to severe postoperative pain, which can delay rehabilitation and discharge. Interscalene nerve block (ISB) is considered the most efficient analgesic technique after shoulder arthroscopy. Several local anesthetics with different concentration can be applied in ISB, but the analgesic effect and the influence of hospital stay of 0.25% and 0.5% bupivacaine are unknown. Methods: in this double-blind study, 42 patients scheduled to undergo shoulder arthroscopy were randomly assigned to receive 30 ml of 0.25% or 0.5% bupivacaine before surgery. ISB was performed under the ultrasound guidance and nerve stimulator for nerve localization. Postoperative pain and muscle power scores, duration of painless period, narcotics consumption, side effects and hospital stay were recorded. Results: No neurological complication reported in this study. Postoperative pain scores and muscle power scores between each group within first 16 hours were showed no significant different. Painless duration (0.25%: 1033 min ± 487 vs. 0.5%: 833 min ± 543, P = 0.256), opioid consumption (0.25%: 95 mg ± 86 vs. 0.5%: 67 mg ± 109, P = 0.357) and postoperative hospital stay (0.25%: 4.8 day ± 2.6 vs. 0.5%: 5.6 day ± 3.4, P = 0.411) were showed no significant different. Conclusion: Ultrasound guidance ISB can provide safe and excellent postoperative pain relief after shoulder arthroscopy. We found no significant difference between 0.25% bupivacaine versus 0.5% bupivacaine with regard to postoperative analgesia, motor function influence, opioid consumptions and related side effects, and hospitalization. However, less dosage means less risk of toxicity and provides safer healthcare quality.