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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
221

Computational Reconstruction of the Physical Eye Using a New Gradient Index of Refraction Model

Dube, Zack January 2016 (has links)
This thesis proposes and tests an individually customizable model of the human crystalline lens. This model will be crucial in developing both research on the human eye and driving diagnostic tools to help plan and treat optical issues, such as those requiring refractive surgery. This thesis attempts to meet two goals: first, it will determine whether this new lens model can reproduce the major aberrations of real human eyes using a computational framework. Second, it will use clinical information to measure how well this model is able to predict post-operation results in refractive surgery, attempting to meet clinical standards of error. The model of the crystalline lens proposed within this thesis is shown to be valid, as it is able to both reproduce individual patient's optical information, and correctly predicts the optical results of a refractive surgery of an individual human eye within clinical standards of error.
222

Modelling and experimental study of millimetre wave refractive systems

Ozturk, Fahri January 2014 (has links)
Astronomical instruments dedicated to the study of Cosmic Microwave Background polarization are in need of optics with very low systematic effects such as beam shape and cross-polarization in an optical configuration. With the demand for millimetre wave larger focal planes comprising thousands of pixels, these systematic effects have to be minimal across the whole focal surface. In order to reach the instrument requirements such as resolution, cross-polarization and beam ellipticity, new optical configurations with well-understood components have to be studied. Refractive configurations are of great importance amongst the potential candidates. The aim is to bring the required technology to the same level of maturity that has been achieved with well-understood existing ones. This thesis is focused on the study of such optical components for the W-band spectral domain. Using optical modelling with various software packages, combined with the manufacture and accurate experimental characterization of some prototype components, a better understanding of their performance has been reached. To do so, several test set-ups have been developed. Thanks to these new results, full Radio-Frequency refractive systems can be more reliably conceived.
223

Élaboration d'optiques infrarouges par combinaison de la mécanosynthèse et du frittage SPS / Elaboration of infrared optics by combining mechanosynthesis with SPS sintering

Novikova, Anna 12 December 2018 (has links)
En 2010, une nouvelle méthode de production de verres de chalcogénure transparents dans l'infrarouge a été brevetée, alliant la mécanosynthèse au frittage Spark Plasma Sintering. Ce travail de thèse intègre le transfert de technologie vers la société Diafir dans le cadre d'un projet RAPID, financé par la DGA. Il a pour but un travail d'optimisation des procédés de synthèse et de mise en forme a été mené afin de permettre d'adapter cette technologie innovante à un volume industriel. Les verres de composition Ge28Sb12Se60, 80GeSe2-20Ga2Se3, Te20As30Se50, As2Se3 et As2S3 ont été synthétisés par fusion-trempe, broyés finement puis frittés par SPS. Des disques avec des transmissions comparables au verre obtenu par voie classique ont été obtenus. Des traitements antireflets ont été déposés avec succès à leur surface. Le développement de moules spécifiques au SPS a conduit à la production de lentilles sphériques adaptables à des dispositifs optiques. Ces compositions vitreuses ont ensuite été synthétisées par mécanosynthèse puis frittées par SPS. Les disques obtenus présentant des phénomènes de diffusion récurrents. Les principales causes de diffusion ont été analysées afin d'optimiser le procédé de synthèse par voie mécanique. / In 2010, a new method of production of chalcogenide glasses, transparent in the infrared, has been patented. It combines mechanosynthesis to Spark Plasma Sintering. In this thesis work, there is the technology transfer to the Diafir society included in the RAPID project, founded by the DGA. The aim is to optimize the processes of synthesis and forming in order to adapt this innovating technology to an industrial scale. The glasses of composition Ge28Sb12Se60, 80GeSe2-20Ga2Se3, Te20As30Se50, As2Se3 and As2S3 have been synthetized by melt-quench method then crushedfinely before to be sintered by SPS.
224

Everyday Decay

Jacobs, Abageal 01 May 2020 (has links)
The medium format photographs created in conjunction with my senior thesis exhibit, Everyday Decay, use texture, line, intimate framing, warm color palettes, and layering to explore an aspect of the everyday landscape that we interact with often but generally ignore. The choice of medium and subject of decay creates a sense of the past, aided by the warm tones that imply affinity and nostalgia.
225

Modeling Temporal Bias of Uplift Events in Recommender Systems

Altaf, Basmah 08 May 2013 (has links)
Today, commercial industry spends huge amount of resources in advertisement campaigns, new marketing strategies, and promotional deals to introduce their product to public and attract a large number of customers. These massive investments by a company are worthwhile because marketing tactics greatly influence the consumer behavior. Alternatively, these advertising campaigns have a discernible impact on recommendation systems which tend to promote popular items by ranking them at the top, resulting in biased and unfair decision making and loss of customers’ trust. The biasing impact of popularity of items on recommendations, however, is not fixed, and varies with time. Therefore, it is important to build a bias-aware recommendation system that can rank or predict items based on their true merit at given time frame. This thesis proposes a framework that can model the temporal bias of individual items defined by their characteristic contents, and provides a simple process for bias correction. Bias correction is done either by cleaning the bias from historical training data that is used for building predictive model, or by ignoring the estimated bias from the predictions of a standard predictor. Evaluated on two real world datasets, NetFlix and MovieLens, our framework is shown to be able to estimate and remove the bias as a result of adopted marketing techniques from the predicted popularity of items at a given time.
226

Development of a Sensor Readout Integrated Circuit Towards a Contact Lens for Wireless Intraocular Pressure Monitoring

Tran, Sung 01 June 2017 (has links)
This design covers the design of an integrated circuit (IC) in support of the active contact lens project at Cal Poly. The project aims to monitor intraocular eye pressure (IOP) to help diagnose and treat glaucoma, which is expected affect 6.3 million Americans by 2050. The IC is designed using IBM’s 130 nm 8RF process, is powered by an on-lens thin film 3.8 V rechargeable battery, and will be fabricated at no cost through MOSIS. The IC features a low-power linear regulator that powers a current-starved voltage-controlled oscillator (CSVCO) used for establishing a backscatter communication link. Additional circuitry is included to regulate power to and from the battery. An undervoltage lockout circuit protects the battery from deep discharge damage. When recharging, a rectifier and a voltage regulator provides overvoltage protection. These circuit blocks are biased primarily using a 696 mV subthreshold voltage reference that consumes 110.5 nA.
227

Studium sférické vady optické čočky / Study of spherical aberration

Fojtík, Tomáš January 2013 (has links)
This thesis deals with the theoretical analysis of rays passing through lenses. Emphasis on optical defects, particularly focusing on spherical aberration lenses. It also includes the preparation of a workplace and the measurement of spherical aberration and evaluate the quality of different lenses. Furthermore, a program for simulation of spherical aberration lens.
228

Raman Spectroscopic Investigation of Porcine Lens Proteins Before and After Ultraviolet Radiation

Brandt, Samuel TC January 2020 (has links)
No description available.
229

Systems Engineering of the Global L-Band Observatory for Water Cycle Studies

Smith, James Nathan 12 April 2022 (has links)
The Global L-band Observatory for Water Cycle Studies (GLOWS) is designed as a follow-on to the Soil Moisture Active Passive (SMAP) observatory launched in 2015. While GLOWS is essentially copying many aspects of the SMAP mission, a key change has been made in the antenna technology. SMAP uses a reflector antenna and to reduce mission costs GLOWS uses a metamaterial lens antenna. This type of antenna is less efficient, so it must be proven that GLOWS can achieve the same uncertainty levels in soil moisture measurements as SMAP. In this work, a unified framework for modeling and analyzing GLOWS' ability to meet all mission and measurement requirements is developed. A model for the uncertainty effects of the lens antenna is developed and used to show that so long as the lens efficiency is above a threshold determined by the accuracy of the lens physical temperature knowledge, GLOWS will also be able to achieve all measurement requirements. It is shown that GLOWS is able to copy the design parameters of SMAP and achieve the same mission requirements.
230

Elevers reflektioner om subtraktionsstrategier : En intervjustudie med elever i årskurs 4-6 / Students' reflections on subtraction strategies : An interview study with students in grades 4 and 6

Mattsson, Ellinore January 2021 (has links)
Under mina verksamhetsförlagda utbildningar har jag uppmärksammat att flera elever endast behärskar en huvudräkningsstrategi och att de därav inte anpassar strategin utefter uppgiftens utformning. Således är syftet med den här studien att bidra med insikt om elevers subtraktionsstrategier vid huvudräkning. Det här syftet avser jag att uppfylla genom att karaktärisera elevernas reflektioner om subtraktionsstrategier i förhållande till olika aspekter inom det teoretiska ramverket six-lens framework. Studien bygger på en kvalitativ metod. Datainsamlingsmetoden har bestått av intervjuer som har inletts med att eleverna har fått lösa en subtraktionsuppgift med hjälp av en huvudräkningsstrategi. Vid intervjuerna har studien inte fokuserat på huruvida eleverna svarar rätt eller fel på uppgiften, inte heller om eleverna väljer rätt eller fel huvudräkningsstrategi. Istället inriktar sig studien på hur eleverna reflekterar och tänker. Studiens resultat visar att en övervägande del av eleverna inte tillämpar en lämplig huvudräkningsstrategi, de värderar inte heller den valda strategins relevans utifrån hur uppgiften är utformad. Det här innebär att de inte uppnår två av de totalt fem förmågorna inom matematikämnet.

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