Astigmatism and Pseudoaccommodation in Pseudophakic Eyes

noAdvanced IOLs with circumferential zones of different power provide pseudoaccommodation. We investigated the potential for power variation with meridian, namely astigmatism, to provide pseudo-accommodation. With appropriate power and axis orientations, acceptable pseudo-accommodation can be achieved

Gravitational Lensing by Spinning Black Holes in Astrophysics, and in the Movie Interstellar

Interstellar is the first Hollywood movie to attempt depicting a black hole as it would actually be seen by somebody nearby. For this we developed a code called DNGR (Double Negative Gravitational Renderer) to solve the equations for ray-bundle (light-beam) propagation through the curved spacetime of a spinning (Kerr) black hole, and to render IMAX-quality, rapidly changing images. Our ray-bundle techniques were crucial for achieving IMAX-quality smoothness without flickering. This paper has four purposes: (i) To describe DNGR for physicists and CGI practitioners . (ii) To present the equations we use, when the camera is in arbitrary motion at an arbitrary location near a Kerr black hole, for mapping light sources to camera images via elliptical ray bundles. (iii) To describe new insights, from DNGR, into gravitational lensing when the camera is near the spinning black hole, rather than far away as in almost all prior studies. (iv) To describe how the images of the black hole Gargantua and its accretion disk, in the movie \emph{Interstellar}, were generated with DNGR. There are no new astrophysical insights in this accretion-disk section of the paper, but disk novices may find it pedagogically interesting, and movie buffs may find its discussions of Interstellar interesting.Comment: 46 pages, 17 figure

Near infrared flares of Sagittarius A*: Importance of near infrared polarimetry

We report on the results of new simulations of near-infrared (NIR) observations of the Sagittarius A* (Sgr A*) counterpart associated with the super-massive black hole at the Galactic Center. The observations have been carried out using the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope and CIAO NIR camera on the Subaru telescope (13 June 2004, 30 July 2005, 1 June 2006, 15 May 2007, 17 May 2007 and 28 May 2008). We used a model of synchrotron emission from relativistic electrons in the inner parts of an accretion disk. The relativistic simulations have been carried out using the Karas-Yaqoob (KY) ray-tracing code. We probe the existence of a correlation between the modulations of the observed flux density light curves and changes in polarimetric data. Furthermore, we confirm that the same correlation is also predicted by the hot spot model. Correlations between intensity and polarimetric parameters of the observed light curves as well as a comparison of predicted and observed light curve features through a pattern recognition algorithm result in the detection of a signature of orbiting matter under the influence of strong gravity. This pattern is detected statistically significant against randomly polarized red noise. Expected results from future observations of VLT interferometry like GRAVITY experiment are also discussed.Comment: 26 pages, 38 figures, accepted for publication by A&

Optimized auxiliary oscillators for the simulation of general open quantum systems

A method for the systematic construction of few-body damped harmonic oscillator networks accurately reproducing the effect of general bosonic environments in open quantum systems is presented. Under the sole assumptions of a Gaussian environment and regardless of the system coupled to it, an algorithm to determine the parameters of an equivalent set of interacting damped oscillators obeying a Markovian quantum master equation is introduced. By choosing a suitable coupling to the system and minimizing an appropriate distance between the two-time correlation function of this effective bath and that of the target environment, the error induced in the reduced dynamics of the system is brought under rigorous control. The interactions among the effective modes provide remarkable flexibility in replicating non-Markovian effects on the system even with a small number of oscillators, and the resulting Lindblad equation may therefore be integrated at a very reasonable computational cost using standard methods for Markovian problems, even in strongly non-perturbative coupling regimes and at arbitrary temperatures including zero. We apply the method to an exactly solvable problem in order to demonstrate its accuracy, and present a study based on current research in the context of coherent transport in biological aggregates as a more realistic example of its use; performance and versatility are highlighted, and theoretical and numerical advantages over existing methods, as well as possible future improvements, are discussed.Comment: 23 + 9 pages, 11 + 2 figures. No changes from previous version except publication info and updated author affiliation

Dissipative solitons in pattern-forming nonlinear optical systems : cavity solitons and feedback solitons

Many dissipative optical systems support patterns. Dissipative solitons are generally found where a pattern coexists with a stable unpatterned state. We consider such phenomena in driven optical cavities containing a nonlinear medium (cavity solitons) and rather similar phenomena (feedback solitons) where a driven nonlinear optical medium is in front of a single feedback mirror. The history, theory, experimental status, and potential application of such solitons is reviewed

Fluids real-time rendering

In this thesis the existing methods for realistic visualization of uids in real-time are reviewed. The correct handling of the interaction of light with a uid surface can highly increase the realism of the rendering, therefore method for physically accurate rendering of re ections and refractions will be used. The light- uid interaction does not stop at the surface, but continues inside the uid volume, causing caustics and beams of light. The simulation of uids require extremely time-consuming processes to achieve physical accuracy and will not be explored, although the main concepts will be given. Therefore, the main goals of this work are: Study and review the existing methods for rendering uids in realtime. Find a simpli ed physical model of light interaction, because a complete physically correct model would not achieve real-time. Develop an application that uses the found methods and the light interaction model

Wave modelling - the state of the art

This paper is the product of the wave modelling community and it tries to make a picture of the present situation in this branch of science, exploring the previous and the most recent results and looking ahead towards the solution of the problems we presently face. Both theory and applications are considered. The many faces of the subject imply separate discussions. This is reflected into the single sections, seven of them, each dealing with a specific topic, the whole providing a broad and solid overview of the present state of the art. After an introduction framing the problem and the approach we followed, we deal in sequence with the following subjects: (Section) 2, generation by wind; 3, nonlinear interactions in deep water; 4, white-capping dissipation; 5, nonlinear interactions in shallow water; 6, dissipation at the sea bottom; 7, wave propagation; 8, numerics. The two final sections, 9 and 10, summarize the present situation from a general point of view and try to look at the future developments

Study on the general applicability of the collector efficiency model to solar process heat collectors

[eng] According to several studies, the installed capacity of solar thermal collectors to provide heat for industrial processes is going to increase significantly during the next decades. The great variety of designs and large range of operating temperatures of solar process collectors make their performance assessment challenging. Although the quasi-dynamic testing procedure has been designed for most types of collectors, it shows limitations or vagueness when dealing with medium-scaled collectors. This thesis analyzes some limitations, focusing mainly on the optical efficiency assessment. A powerful ray-tracing algorithm has been developed for the optical analyses in this thesis. The algorithm was used to carry out a sensitivity analysis of a Fresnel collector to achieve a better understanding of the most influential parameters in ray-tracing simulations. Two observations were made: First, spectral simulations are not relevant for solar thermal applications unless mirror scattering shows a very high dependency on the wavelength. Second, defining the incidence angle dependency of optical materials is crucial to produce accurate results. In the case of biaxial concentrating collectors, the incidence angle modifier factorization model is commonly applied. This model inherently introduces errors by factorizing the underlying non-factorizable functions. The error was characterized for four different collector geometries by comparing factorization with ray-tracing simulations. Results have been presented as a function of geographical latitude. Factorization in the θi-θT -space performed best in nearly all cases. Four different collector geometries were submitted to ray-tracing simulations in order to analyze the thermal dependency of the factorization error. It is shown that the relative error generally increases with higher operating temperatures, but within the economically viable temperature range it stays fairly constant. With higher temperatures the collector gradually stops operating beginning with moments when sun angles are least favorable for factorization.[cat] Segons diversos estudis, la capacitat instal·lada de captadors solars tèrmics pel subministrament de calor en processos industrials s’incrementarà significativament en els propers anys. La gran diversitat de dissenys i temperatures de treball d’aquest tipus de captador fa difícil l’avaluació dels seus rendiments. Encara que el mètode experimental quasi dinàmic s’ha desenvolupat per la major part de models de captador, segueix tenint limitacions o imprecisions a l’hora d’avaluar captadors específics per calor de procés. Aquesta tesi analitza algunes d’aquestes limitacions, centrant-se principalment en l’avaluació de l’eficiència òptica. Per l’anàlisi òptica, en aquesta tesi s’ha desenvolupat un algoritme avançat de ray-tracing. L’algoritme ha servit per realitzar una anàlisi de sensibilitat d’un captador Fresnel, que ha permès conèixer quins son els paràmetres que tenen una major influència en la qualitat dels resultats obtinguts en les simulacions de ray-tracing. S’ha arribat a dues conclusions: En primer lloc, simulacions espectrals no son rellevants per aplicacions solars tèrmiques, a no ser que la dispersió del mirall depengui significativament de la longitud d’ona. En segon llos és imprescindible especificar al dependència de l’angle d’incidència dels materials òptics per generar resultats acurats. En el cas de captadors concentradors biaxials, s’aplica el model de factorització del modificador d’angle d’incidència. Aquesta factorització te sempre associat un cert error, ja que l’IAM no és en general factoritzable. S’ha caracteritzat l’error per quatre geometries de captadors diferents, comparant el models de factorització amb les simulacions ray-tracing. Els resultats s’han presentat en funció de la latitud geogràfica. La factorització a l’espai θi-θT es la que ofereix més bons resultats en gairebé tots els casos analitzats. Quatre geometries diferents de captador foren analitzades per determinar la dependència amb la temperatura de l’error de factorització. S’ha demostrat que a mesura que s’incrementa la temperatura de treball, s’incrementa l’error relatiu del la factorització, malgrat això, dins del rang de temperatures econòmicament viables, l’error es manté constant. Això és degut a que a mesura s’incrementa la temperatura, es redueixen les hores de treball, i per tant també les hores on el captador treballa sota els angles més desfavorables per la factorització[spa] Según varios estudios, la capacidad instalada de captadores solares térmicos para proveer calor en procesos industriales se va a incrementar significativamente a lo largo de las próximas décadas. La gran variedad de diseños y temperaturas de este tipo de captadores hace complicada la evaluación de sus rendimientos. Aunque el métdodo experimental quasi-dinámico ha sido diseñado para la mayoría de modelos de captadores, sigue teniendo limitaciones o imprecisiones a la hora de evaluar captadores de mediana escala. Esta tesis analiza algunas de dichas limitaciones, centrándose principalmente en la evaluación de la eficiencia óptica. Para el análisis óptico en esta tesis se ha desarrollado un algoritmo avanzado de raytracing. El algoritmo ha servido para realizar un análisis de sensibilidad de un captador Fresnel, para conseguir con ello un mayor conocimiento de los parámetros más influyentes en las simulaciones ray-tracing. Se ha llegado a dos conclusiones: En primer lugar, simulaciones espectrales no son relevantes para aplicaciones solares térmicas, a no ser que la dispersión del espejo dependa significativamente de la longitud de onda. En segundo lugar, es imprescindible especificar la dependencia del ángulo de incidencia de los materiales ópticos para generar resultados precisos. En el caso de captadores concentradores biaxiales, se aplica el modelo de factorización del ‘incidence angle modifier’. Por defecto, este modelo introduce errores factorizando funciones que no son factorizables. Se ha caracterizado el error para cuatro geometrías de captadores diferentes comparando el modelo de factorización con las simulaciones ray-tracing. Los resultados han sido presentados como función de la latitud geográfica. La factorización en el espacio θi-θT ha demostrado los mejores resultados para casi todos los casos. Cuatro geometrías diferentes fueron sometidas a simulaciones de ray-tracing para analizar la dependencia térmica del mismo error de factorización. Se ha demostrado que a medida que aumenta la temperatura del proceso, aumenta también el error relativo de factorización, sin embargo, dentro del rango económicamente viable de temperaturas, el error se mantiene constante. Esto se debe a que a medida se incrementa la temperatura, el captador deja de operar primero en los momentos de ángulos más desfavorables para la factorización