996 resultados para acousto-optical Q-swithed


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The rigorous and transparent treatment of the effects of nuclear vibrational motion in two-photon absorption (TPA) was discussed. Perturbation formula for diatomic molecules were developed and applied to the X¹Σ+–A¹Π transition in CO. The analysis showed that the vibrations played an important role in TPA, just as their role in the calculation of conventional nonlinear optical (NLO) hyperpolarizabilities

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In the static field limit, the vibrational hyperpolarizability consists of two contributions due to: (1) the shift in the equilibrium geometry (known as nuclear relaxation), and (2) the change in the shape of the potential energy surface (known as curvature). Simple finite field methods have previously been developed for evaluating these static field contributions and also for determining the effect of nuclear relaxation on dynamic vibrational hyperpolarizabilities in the infinite frequency approximation. In this paper the finite field approach is extended to include, within the infinite frequency approximation, the effect of curvature on the major dynamic nonlinear optical processes

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Large scale image mosaicing methods are in great demand among scientists who study different aspects of the seabed, and have been fostered by impressive advances in the capabilities of underwater robots in gathering optical data from the seafloor. Cost and weight constraints mean that lowcost Remotely operated vehicles (ROVs) usually have a very limited number of sensors. When a low-cost robot carries out a seafloor survey using a down-looking camera, it usually follows a predetermined trajectory that provides several non time-consecutive overlapping image pairs. Finding these pairs (a process known as topology estimation) is indispensable to obtaining globally consistent mosaics and accurate trajectory estimates, which are necessary for a global view of the surveyed area, especially when optical sensors are the only data source. This thesis presents a set of consistent methods aimed at creating large area image mosaics from optical data obtained during surveys with low-cost underwater vehicles. First, a global alignment method developed within a Feature-based image mosaicing (FIM) framework, where nonlinear minimisation is substituted by two linear steps, is discussed. Then, a simple four-point mosaic rectifying method is proposed to reduce distortions that might occur due to lens distortions, error accumulation and the difficulties of optical imaging in an underwater medium. The topology estimation problem is addressed by means of an augmented state and extended Kalman filter combined framework, aimed at minimising the total number of matching attempts and simultaneously obtaining the best possible trajectory. Potential image pairs are predicted by taking into account the uncertainty in the trajectory. The contribution of matching an image pair is investigated using information theory principles. Lastly, a different solution to the topology estimation problem is proposed in a bundle adjustment framework. Innovative aspects include the use of fast image similarity criterion combined with a Minimum spanning tree (MST) solution, to obtain a tentative topology. This topology is improved by attempting image matching with the pairs for which there is the most overlap evidence. Unlike previous approaches for large-area mosaicing, our framework is able to deal naturally with cases where time-consecutive images cannot be matched successfully, such as completely unordered sets. Finally, the efficiency of the proposed methods is discussed and a comparison made with other state-of-the-art approaches, using a series of challenging datasets in underwater scenarios

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All-Optical Label Swapping (AOLS) es una tecnología clave para la implementación de nodos de conmutación completamente óptica de paquetes. Sin embargo, el costo de su desarrollo es proporcional al tamaño del espacio de etiquetas (label space). Debido a que los principios de funcionamiento de AOLS son casos particulares de los del MultiProtocol Label Switching (MPLS), esta tesis estudia métodos generales, aplicables a ambos, con el propósito de reducir el espacio de etiquetas tanto como sea posible. Modelos de programación lineal entera y heurísticas son propuestos para el caso en el que se permite apilar una etiqueta extra. Encontramos que cerca del 50% del espacio de etiquetas puede ser reducido, si se permite colocar una etiqueta extra en la pila. Además, particularmente para AOLS, encontramos que se puede reducir el espacio de etiquetas cerca al 25% si se duplica la capacidad de los enlaces y se permite re-encaminar el tráfico.

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This paper is a review of the literature regarding design of classrooms for hearing impaired children.

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This paper reviews a study that was done with hearing and hearing impaired children to test the effectiveness of self-instructional programs and whether the results can be correlated with Educational Quotient and Intelligence Quotient.

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El reto de los sistemas educativos debe centrar en ofrecer la calidad que la sociedad exige: primero por la atención a la diversidad, que demanda de una oferta educativa de atención definida, que cada alumno requiere en términos de equidad y segundo por una permanente evaluación que es el medio de disposición de elementos de juicio fiables y válidos, para tomar medidas inmediatas de mejora de los diferentes componentes del sistema educativo, con mayor convencimiento de que la educación intercultural sigue siendo una de las prioridades centrales de la humanidad, sustentada en la equidad, pertinencia, eficacia y eficiencia característica, de la excelencia. En este contexto el trabajo que se presenta en esta tesis, es un intento por entregar una visión representada como un proceso de investigación, análisis e interrelación de reformas educativas de los sistemas, con la historia de los procesos de lucha de los pueblos indígenas exteriorizado en experiencias educativas previas y las sugerencias de las concepciones técnico-científicas de la educación vinculado con el siglo XXI la sociedad del conocimiento y de la información, un interés por comprender en educación la realidad socio-lingüística, político-económica y socio-cultural de los pueblos indígenas. Sin embargo en el esfuerzo de realizar esta investigación, sobre la “Aplicación del Rediseño Curricular de EIB., en el sexto y séptimo nivel de Educación Básica del CEDEIB-Q” de San Roque, Quito, Pichincha, a pesar de que las experiencias previas antes de la creación de la DINEIB han sido exitosas, el sistema de EIB., no ha contribuido a fortalecer estas expectativas, puesto que según los resultados, existiendo un instrumento curricular, no ha apoyado a su real aplicación: las “clases” se realizan en español, no existen materiales de consistencia en LM., no se evidencia la presencia de los factores asociados al proceso, se demuestra un descuido total del sistema en los procesos de reconceptualización del currículo, capacitación, acompañamiento y evaluación continua.

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La presencia, en Bolivia de un katarismo radical, promovido por los más recientes movimientos indigenistas, nos obliga a repensar las políticas de conocimiento criollo-mestizas. En este sentido, el presente artículo ubica la propuesta de "indianizar al q'ara" como una "pedagogía al revés" con la cual la ideología katarista radical de Felipe Quispe, alias "el Mallku", cuestiona desde abajo el mestizaje que los grupos dominantes promueven desde principios de siglo.

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North African dust is important for climate through its direct radiative effect on solar and terrestrial radiation and its role in the biogeochemical system. The Dust Outflow and Deposition to the Ocean project (DODO) aimed to characterize the physical and optical properties of airborne North African dust in two seasons and to use these observations to constrain model simulations, with the ultimate aim of being able to quantify the deposition of iron to the North Atlantic Ocean. The in situ properties of dust from airborne campaigns measured during February and August 2006, based at Dakar, Senegal, are presented here. Average values of the single scattering albedo (0.99, 0.98), mass specific extinction (0.85 m^2 g^-1 , 1.14 m^2 g^-1 ), asymmetry parameter (0.68, 0.68), and refractive index (1.53--0.0005i,1.53--0.0014i) for the accumulation mode were found to differ by varying degrees between the dry and wet season, respectively. It is hypothesized that these differences are due to different source regions and transport processes which also differ between the DODO campaigns. Elemental ratios of Ca/Al were found to differ between the dry and wet season (1.1 and 0.5, respectively). Differences in vertical profiles are found between seasons and between land and ocean locations and reflect the different dynamics of the seasons. Using measurements of the coarse mode size distribution and illustrative Mie calculations, the optical properties are found to be very sensitive to the presence and amount of coarse mode of mineral dust, and the importance of accurate measurements of the coarse mode of dust is highlighted.

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An operational dust forecasting model is developed by including the Met Office Hadley Centre climate model dust parameterization scheme, within a Met Office regional numerical weather prediction (NWP) model. The model includes parameterizations for dust uplift, dust transport, and dust deposition in six discrete size bins and provides diagnostics such as the aerosol optical depth. The results are compared against surface and satellite remote sensing measurements and against in situ measurements from the Facility for Atmospheric Airborne Measurements for a case study when a strong dust event was forecast. Comparisons are also performed against satellite and surface instrumentation for the entire month of August. The case study shows that this Saharan dust NWP model can provide very good guidance of dust events, as much as 42 h ahead. The analysis of monthly data suggests that the mean and variability in the dust model is also well represented.