Optical analysis of parabolic dish concentrators for solar dynamic power systems in space

An optical analysis of a parabolic solar collection system operating in Earth orbit was performed using ray tracing techniques. The analysis included the effects of: (1) solar limb darkening, (2) parametric variation of mirror surface error, (3) parametric variation of mirror rim angle, and (4) parametric variation of alignment and pointing error. This ray tracing technique used numerical integration to combine the effects of rays emanating from different parts of the sun at different intensities with the effects of normally distributed mirror-surface errors to compute the angular intensity distribution of rays leaving the mirror surface. A second numerical integration was then performed over the surface of the parabolic mirror to compute the radial distribution of brightness at the mirror focus. Major results of the analysis included: (1) solar energy can be collected at high temperatures with high efficiency, (2) higher absorber temperatures can be achieved at lower efficiencies, or higher efficiencies can be achieved at lower temperatures, and (3) collection efficiency is near its maximum level across a broad plateau of rim angles from 40 deg to 70 deg

A theoretical comparison of the near-optimum design and predicted performance of n/p and p/n indium phosphide homojunction solar cells

Using a detailed simulation model of p(+)nn(+) and n(+)pp(+) indium phosphide (InP) homojunction solar cells, extensive parametric variation computer simulation runs were performed to aid in making near-optimum designs for these two solar cell configurations. The values of all the geometrical and material parameters corresponding to the near-optimal designs of both these configurations are presented. The results of parametric variation runs are presented for each configuration showing how the performance parameters J(sub sc), V(sub oc), and eta vary with each of the cell design parameters for the near-optimally designed cell. Finally, the theoretically obtained results are discussed, and the relative merits and drawbacks of the two configurations are compared

Phase theory and parametric variation

El objetivo de esta tesis es explorar la Teoría de Fases de Chomsky (cf. Chomsky 2000; 2001; 2004; 2005; 2007; en preparación) y sus conexiones con la variación paramétrica. El estudio considera la hipótesis de que la computación sintáctica opera a través de pequeñas etapas derivacionales (las fases), prestando especial atención a los sistemas de Caso y concordancia, y al papel que desempeña la morfología en relación con la variación lingüística. El Capítulo I presenta las bases generales del marco teórico que se asume a lo largo de la tesis (el llamado Programa Minimista; cf. Chomsky 1993a hasta el presente), concentrándose tanto en las operaciones computacionales centrales (Fusión y Acuerdo) como en la naturaleza cíclica del sistema. El Capítulo II se dedica a la noción de fase, cuyos criterios de identificación son considerados con detenimiento. Se adopta la hipótesis de Pesetsky & Torrego (2001) de que lo que normalmente se llama 'Caso' es en realidad un rasgo no interpretable de 'aspecto'/'tiempo' codificado en la categoría D y se explora la idea (presente en el sistema de Chomsky, así como en el de Pesetsky & Torrego) de que la morfología no interpretable puede usarse para procesos sintácticos solo durante un breve período de tiempo, que precisamente coincide con las fases. Junto con Uriagereka (1999b), también se propone que las Lenguas de Sujeto Nulo (LSNs) recurren a un proceso adicional de Transferencia que es responsable de un macro-parámetro desencadenado por el movimiento del verbo, denominado aquí Corrimiento de Fase. Plausiblemente, este mecanismo explica el status particular de los sujetos en las LSNs (e.g., extracción, borrado del complementante, inversión obligatoria, etc.), además de otros fenómenos que previamente habían sido analizados en términos de nudos frontera, marcaje-L, rección o la distinción A/A-barra. En el Capítulo III, la atención se centra en un micro-parámetro relacionado con la arista de los núcleos de fase (su Periferia Izquierda). Se discute un corte paramétrico que implica a lo que Uriagereka (1995a; 1995b; 2002b) llama «FP», una proyección relacionada con la semántica de corte discursivo (anteriormente, «interpretación superficial»). Se defiende que la actividad sintáctica 'caliente' de la F de Uriagereka no se limita a la capa SC, extendiéndose también al Sv*, de una manera paralela (de hecho, tal y como predice el análisis de Uriagereka 2002b, el patrón se extiende a entornos nominales): aquellas lenguas con un SC más activo tienen un Sv* más activo. Esta 'activación' del margen periférico se relaciona con la morfología explícita, una idea tradicional que se refina y relaciona con la morfología temporal y el movimiento de núcleos. La segunda parte del capítulo aborda las estructuras VOS en las LSNs, para cuya formación se arguye que hay dos estrategias: batido de objeto o topicalización de SV (cf. Belletti 2004, Cardinaletti 2001b y Ordóñez 1997; 1998b). Con Ordóñez (1997; 1998b), se asume que el VOS del español se deriva mediante batido de objeto, se consideran las consecuencias para la asignación de Caso nominativo en términos de minimidad y, finalmente, se recupera un análisis basado en la equidistancia de Chomsky (1993a). El Capítulo IV se dedica a la (sub-)extracción. En él se sostiene que una aproximación a las islas en términos estructurales (cf. Chomsky 1986a; 2004; en preparación) no es totalmente satisfactorio, siendo más adecuado tratar este fenómeno como una consecuencia de los efectos de paralización que surgen de la interacción entre el Caso y la concordancia (cf. Boeckx 2003a).The goal of this dissertation is to explore Chomsky's Phase Theory (see Chomsky 2000; 2001; 2004; 2005; 2007; to appear) and its connections with parametric variation. The study considers the hypothesis that syntactic computation operates through small derivational leaps (the phases), paying special attention to the Case/agreement systems, and the role of overt morphology for linguistic variation. Chapter I presents the general guidelines of the framework that shall be assumed throughout the dissertation (the so-called Minimalist Program; see Chomsky 1993a through the present), concentrating on both the core computational operations (Merge and Agree) and the cyclic nature of the system. Chapter II is devoted to the notion of phase, whose identification criteria are considered at length. I adopt Pesetsky & Torrego's (2001) hypothesis that what is normally referred to as 'Case' is actually an uninterpretable 'aspect'/'tense' feature on D heads, and entertain the idea (present in Chomsky's system, as well as in Pesetsky & Torrego's) that uninterpretable morphology can be used for syntactic processes only within a short, phase-based, time span. In line with Uriagereka (1999b), I further propose that Null Subject Languages (NSLs) resort to an additional process of Transfer that is responsible for a macro-parameter triggered by verb movement, which I call Phase Sliding. Plausibly, this mechanism explains the particular status of subjects in NSLs (e.g., subject extraction, that-deletion, obligatory inversion, etc.) and additional empirical facts, previously framed in terms of bounding nodes, L-marking, government, or the A/A-bar distinction. In chapter III, attention is shifted to a micro-parameter related to the edge of phase heads (their Left Periphery). I argue for a parametric cut that concerns what Uriagereka (1995a; 1995b; 2002b) calls «FP,» a projection related to discourse-oriented semantics (formerly, «surface interpretation»). I claim that the 'hot' syntactic activity of Uriagereka's F is not limited to the CP layer, but is actually found in the v*P too, in a parallel fashion (actually, as predicted by Uriagereka 2002b, the pattern extends to nominal environments): those languages with a more active CP, have a more active v*P. I relate this peripheral boost to overt morphology, a traditional idea that is sharpened and connected to tense morphology and head movement. The second part of the chapter focuses on VOS structures in NSLs, for which I argue that there are two strategies: object scrambling and VP topicalization (see Belletti 2004, Cardinaletti 2001b, and Ordóñez 1997; 1998b). With Ordóñez (1997; 1998b), I take Spanish VOS to be derived through object scrambling, consider its consequences for nominative Case assignment in minimality terms, and eventually revamp an equidistance-based analysis, in the sense of Chomsky (1993a). Chapter IV is dedicated to (sub-)extraction. I argue that islandhood cannot be entirely accounted for in structural terms (see Chomsky 1986a; 2004; to appear), being better understood if related to freezing effects that emerge from the interaction between Case and agreement (see Boeckx 2003a)

On Parametric (and Non-Parametric) Variation

This article raises the issue of the correct characterization of ‘Parametric Variation’ in syntax and phonology. After specifying their theoretical commitments, the authors outline the relevant parts of the Principles–and–Parameters framework, and draw a three-way distinction among Universal Principles, Parameters, and Accidents. The core of the contribution then consists of an attempt to provide identity criteria for parametric, as opposed to non-parametric, variation. Parametric choices must be antecedently known, and it is suggested that they must also satisfy seven individually necessary and jointly sufficient criteria. These are that they be cognitively represented, systematic, dependent on the input, deterministic, discrete, mutually exclusive, and irreversible

Tunable Fano Resonances in Transport through Microwave Billiards

We present a tunable microwave scattering device that allows the controlled variation of Fano line shape parameters in transmission through quantum billiards. Transport in this device is nearly fully coherent. By comparison with quantum calculations, employing the modular recursive Green's-function method, the scattering wave function and the degree of residual decoherence can be determined. The parametric variation of Fano line shapes in terms of interacting resonances is analyzed.Comment: 5 pages, 4 figures, submitted to Phys. Rev.

Near-optimum design of the InP homojunction solar cell

Using a fairly comprehensive model, researchers have done a parametric variation study of the InP n+p homojunction solar cell for AMO, 25 C operation. The results of this study are presented. These results indicate that an efficiency of about 25 percent should be realistically possible in a shallow homojunction InP solar cell with near-optimum design

Chaotic and fractal properties of deterministic diffusion-reaction processes

We study the consequences of deterministic chaos for diffusion-controlled reaction. As an example, we analyze a diffusive-reactive deterministic multibaker and a parameter-dependent variation of it. We construct the diffusive and the reactive modes of the models as eigenstates of the Frobenius-Perron operator. The associated eigenvalues provide the dispersion relations of diffusion and reaction and, hence, they determine the reaction rate. For the simplest model we show explicitly that the reaction rate behaves as phenomenologically expected for one-dimensional diffusion-controlled reaction. Under parametric variation, we find that both the diffusion coefficient and the reaction rate have fractal-like dependences on the system parameter.Comment: 14 pages (revtex), 12 figures (postscript), to appear in CHAO

Experimental Observation of Resonance-Assisted Tunneling

We present the first experimental observation of resonance-assisted tunneling, a wave phenomenon, where regular-to-chaotic tunneling is strongly enhanced by the presence of a classical nonlinear resonance chain. For this we use a microwave cavity made of oxygen free copper with the shape of a desymmetrized cosine billiard designed with a large nonlinear resonance chain in the regular region. It is opened in a region, where only chaotic dynamics takes place, such that the tunneling rate of a regular mode to the chaotic region increases the line width of the mode. Resonance-assisted tunneling is demonstrated by (i) a parametric variation and (ii) the characteristic plateau and peak structure towards the semiclassical limit.Comment: 5 pages, 2 figure