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Literature Models (literature + models)
Selected Abstracts4432: Comparison of the two domains of visual optics: the aberrometric domain and the straylight domainACTA OPHTHALMOLOGICA, Issue 2010TJTP VAN DEN BERG Purpose The ocular point-spread-function defines the functional problem originating from optical defects in the eye. Aberrations as well as scatter degrade the psf. How do these two types of defect differ with respect to their effect on the psf, and on functional measures? Methods Literature models for different aspects of the optical irregularities in the eye media, in particular Thibos et al. JOSA A 2002 for the aberration structure and Van den Berg et al. VR 1999 for small particle scattering, were used to delineate their effects on the psf. The Thibos et al. model was extrapolated to allow inclusion of the high orders of aberration not normally included in aberrometry, but potentially visible with double pass. With respect to the visual function counterparts, straylight (C-Quant from Oculus) outcomes were compared to visual acuity and contrast sensitivity in 2400 subjects. Results As a reference the full scale psf standard model of Vos et al. CIE 1999 was used. The modeled aberration structures of the eye proved to predict the central part of the psf up till about 0.3 degrees if extreme high orders were included. For angles >1 degree predicted values were far below the actual values of the psf. Small particle scattering was essential to predict the psf for angles above 1 degree. Conclusion In the assessment of disturbances to the optical media two domains must be discriminated: the aberration domain and the small particle domain, with corresponding parts (small angle vs large angle) to the psf. Straylight typically originates from irregularities of size 10 micrometer and below, as opposed to aberrations originating from refractile humps and bumps extending over 100 micrometer and more. Straylight has independent value. [source] The Tank Drainage Problem Revisited: Do These Equations Actually Work?THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2003Donald D. Joye Abstract The tank drainage problem with pipeline attached is studied in this work. Laminar and turbulent formulations of this unsteady-state flow problem are derived and evaluated by experimental data. Additional literature models are also evaluated for comparison. Several experimental configurations were used including a small tank with a vertical tube, the same with various- sized orifices, a large tank with a horizontal pipe, and a large tank including a piping system with elbows, vertical drop and horizontal extension. Not all the models performed well under all conditions. Limitations of the models are discussed. The model derived by Loiacono and the model we derived (an exact equivalent) showed the best for both laminar and turbulent flow, predicting drainage times to better than ± 8%, on average. On a étudié dans ce travail le problème du drainage des réservoirs munis de conduites. Les formulations laminaires et turbulentes de ce problème d'écoulement en régime non permanent ont été calculées et évaluées à l'aide de données expérimentales. D'autres modèles venant de la littérature scientifique ont également été évalués à des fins de comparaison. Plusieurs configurations expérimentales ont été utilisées, notamment : un petit réservoir muni d'un tube vertical, le même réservoir comprenant des orifices de tailles diverses, un grand réservoir muni d'une conduite horizontale, un grand réservoir équipé d'un système de conduites ayant des coudes, une chute verticale et une extension horizontale. Tous les modèles n'ont pas donné de bons résultats dans toutes les conditions. Les limites des modèles sont analysées. Le modèle établi par Loiacono et le modèle que nous avons calculé (un équivalent strict) montrent le meilleur potentiel autant pour l'écoulement laminaire que turbulent, prédisant des temps de drainage jusqu'à plus ± 8% en moyenne. [source] Morphology in Immiscible Polymer Blends During Solidification of an Amorphous Dispersed Phase under ShearingTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2002Yves Deyrail Abstract Solidification under shear of dispersed polycarbonate (PC) fibers in copolymer polyethylene-methyl acrylate matrix (EMA) was investigated using a hot optical shear device. First, the deformation of PC droplets and its modeling under isothermal conditions were studied for comprehension purposes. Overall agreement with literature models was found and the main influence of the viscosity ratio has been stressed. Second, the morphology control through dynamic quenching was experimented. It consists of solidifying the amorphous PC dispersed phase under shear flow. Break-up times of PC fibers were taken into account. Shear rate and quenching-time balance was demonstrated. Thus, during dynamic solidification, a fibrillar morphology could be obtained through rapid quenching. Long quenching times allow nodular morphology, whose size depends on the shear rate used. PC rods can be obtained by adjusting the shear rate during dynamic quenching. La solidification sous cisaillement du polycarbonate (PC) dispersé dans une matrice copolymère éthylène-acétate de vinyle (EMA) a été suivie à l'aide d'un microscope et d'une platine de cisaillement chauffante. Dans un premier temps la déformation isotherme de billes de PC pour différentes températures a été étudiée, ainsi que sa modélisation. Une bonne corrélation avec les modèles issus de la littérature a été obtenue. L'importance du rapport des viscosités a été ainsi soulignée. Dans un second temps le contrôle de la morphologie par le procédé de « refroidissement dynamique » a été expérimenté. Celui-ci consiste à solidifier le PC sous cisaillement pendant le refroidissement. Les temps de rupture des fibres de PC ont été considérés et l'importance du couple gradient de cisaillement-temps de refroidissement sur le contrôle de la morphologie a été mis en évidence. Pendant la solidification, un refroidissement rapide permet d'obtenir une morphologie fibrillaire. [source] Turbulence Transfer Processes in Adiabatic and Condensing Film Flow in an Inclined TubeCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2003R. Würfel Abstract For the description of transfer processes in separated turbulent two-phase flow, knowledge is necessary about interactions at the interface. Particularly experimental studies were performed of the two-phase-friction coefficient, film thickness, entrainment and heat transfer for adiabatic and condensing conditions. Working systems were n-heptane/air, water/air and condensing n-heptane. The measurement of the liquid film thickness was successful with the ultrasonic method and the entrainment was measured with an isokinetic technique. Quantitative connections between hydrodynamic parameters were discussed and compared with literature models. Based on experimental data, special models are proposed. Partly the influence of the mass transfer intensity cannot be neglected for calculation of the two-phase-friction coefficient. For the description of the heat transfer for film condensation in turbulent flow the interface shear stress and the inclination angle of the tube have proved useful. [source] | ||||||||||