Analysis of house prices to assess economic impacts of new public transport infrastructure: Madrid metro line 12.

Transportation infrastructure is known to affect the value of real estate property by virtue of changes in accessibility. The impact of transportation facilities is highly localized as well, and it is possible that spillover effects result from the capitalization of accessibility. The objective of this study was to review the theoretical background related to spatial hedonic models and the opportunities that they provided to evaluate the effect of new transportation infrastructure. An empirical case study is presented: the Madrid Metro Line 12, known as Metrosur, in the region of Madrid, Spain. The effect of proximity to metro stations on housing prices was evaluated. The analysis took into account a host of variables, including structure, location, and neighborhood and made use of three modeling approaches: linear regression estimation with ordinary least squares, spatial error, and spatial lag. The results indicated that better accessibility to Metrosur stations had a positive impact on real estate values and that the effect was marked in cases in which a house was for sale. The results also showed the presence of submarkets, which were well defined by geographic boundaries, and transport fares, which implied that the economic benefits differed across municipalities.

Electronic property analysis of O-doped Cu3SbS3

The ternary Cu-Sb-S semiconductors are considered to be sustainable and potential alternative absorber materials in thin film photovoltaic applications. In these compounds, several phases may coexist, albeit in different proportions depending on experimental growth conditions. Additionally, the photovoltaic efficiency could be increased with isoelectronic doping. In this work we analyze the electronic properties of O-doped Cu3SbS3 in two structures: the wittichenite and the skinnerite. We use first-principles within the density functional formalism with two different exchange-correlation potentials. In addition, we estimate the potential of these compounds for photovoltaic applications.

Analysis of the Iberian Power Forward Price Formation

The price formation of the Iberian Energy Derivatives Market-the power futures market-starting in July 2006, is assessed until November 2011, through the evolution of the difference between forward and spot prices in the delivery period (“ex-post forward risk premium”) and the comparison with the forward generation costs from natural gas (“clean spark spread”). The premium tends to be positive in all existing mechanisms (futures, Over-the-Counter and auctions for catering part of the last resort supplies). Since year 2011, the values are smaller due to regulatorily recognized prices for coal power plants. The power futures are strongly correlated with European gas prices. The spreads built with prompt contracts tend also to be positive. The biggest ones are for the month contract, followed by the quarter contract and then by the year contract. Therefore, gas fired generation companies can maximize profits trading with contracts of shorter maturity.

An Empirical Analysis of the Spanish Gas Price Structure

We can say without hesitation that in energy markets a throughout data analysis is crucial when designing sophisticated models that are able to capture most of the critical market drivers. In this study we will attempt to investigate into Spanish natural gas prices structure to improve understanding of the role they play in the determination of electricity prices and decide in the future about price modelling aspects. To further understand the potential for modelling, this study will focus on the nature and characteristics of the different gas price data available. The fact that the existing gas market in Spain does not incorporate enough liquidity of trade makes it even more critical to analyze in detail available gas price data information that in the end will provide relevant information to understand how electricity prices are affected by natural gas markets. In this sense representative Spanish gas prices are typically difficult to explore given the fact that there is not a transparent gas market yet and all the gas imported in the country is negotiated and purchased by private companies at confidential terms.

Optoelectronic property analysis of MCrO4 (M=Ba, Sr) with a response to visible light irradiation

Ternary MCrO4 (M = Ba, Sr) semiconductors are materials with a variety of photocatalyst and optoelectronic applications. We present detailed microscopic analyses based on first principles of the structure, the electronic properties and the optical absorption in which the difference between symmetrically non-equivalent atoms has been considered. The high absorption coefficients of these materials are split into chemical species contributions in accordance with the symmetry. The high optical absorption in these materials is mainly because of the Cr–O inter-species transitions.

Desarrollo de un modelo de formación del valor inmobiliario en áreas de crecimiento suburbano. Aplicación a la comarca de la Vega Baja del Segura en el litoral alicantino

Una de las principales líneas de investigación de la economía urbana es el comportamiento del mercado inmobiliario y sus relaciones con la estructura territorial. Dentro de este contexto, la reflexión sobre el significado del valor urbano, y abordar su variabilidad, constituye un tema de especial importancia, dada la relevancia que ha supuesto y supone la actividad inmobiliaria en España. El presente estudio ha planteado como principal objetivo la identificación de aquellos factores, ligados a la localización que explican la formación del valor inmobiliario y justifican su variabilidad. Definir este proceso precisa de una evaluación a escala territorial estableciendo aquellos factores de carácter socioeconómico, medioambiental y urbanístico que estructuran el desarrollo urbano, condicionan la demanda de inmuebles y, por tanto, los procesos de formación de su valor. El análisis se centra en valores inmobiliarios residenciales localizados en áreas litorales donde la presión del sector turístico ha impulsado un amplio. Para ello, el ámbito territorial seleccionado como objeto de estudio se sitúa en la costa mediterránea española, al sur de la provincia de Alicante, la comarca de la Vega Baja del Segura. La zona, con una amplia diversidad ecológica y paisajística, ha mantenido históricamente una clara distinción entre espacio urbano y espacio rural. Esta dicotomía ha cambiado drásticamente en las últimas décadas, experimentándose un fuerte crecimiento demográfico y económico ligado a los sectores turístico e inmobiliario, aspectos que han tenido un claro reflejo en los valores inmobiliarios. Este desarrollo de la comarca es un claro ejemplo de la política expansionista de los mercados de suelo que ha tenido lugar en la costa española en las dos últimas décadas y que derivado en la regeneración de un amplio tejido suburbano. El conocimiento del marco territorial ha posibilitado realizar un análisis de variabilidad espacial mediante un tratamiento masivo de datos, así como un análisis econométrico que determina los factores que se valoran positivamente y negativamente por el potencial comprador. Estas relaciones permiten establecer diferentes estructuras matemáticas basadas en los modelos de precios hedónicos, que permiten identificar rasgos diferenciales en los ámbitos económico, social y espacial y su incidencia en el valor inmobiliario. También se ha sistematizado un proceso de valoración territorial a través del análisis del concepto de vulnerabilidad estructural, entendido como una situación de fragilidad debida a circunstancias tanto sociales como económicas, tanto actual como de tendencia en el futuro. Actualmente, esta estructura de demanda de segunda residencia y servicios ha mostrado su fragilidad y ha bloqueado el desarrollo económico de la zona al caer drásticamente la inversión en el sector inmobiliario por la crisis global de la deuda. El proceso se ha agravado al existir un tejido industrial marginal al que no se ha derivado inversiones importantes y un abandono progresivo de las explotaciones agropecuarias. El modelo turístico no sería en sí mismo la causa del bloqueo del desarrollo económico comarcal, sino la forma en que se ha implantado en la Costa Blanca, con un consumo del territorio basado en el corto plazo, poco respetuoso con aspectos paisajísticos y medioambientales, y sin una organización territorial global. Se observa cómo la vinculación entre índices de vulnerabilidad y valor inmobiliario no es especialmente significativa, lo que denota que las tendencias futuras de fragilidad no han sido incorporadas a la hora de establecer los precios de venta del producto inmobiliario analizado. El valor muestra una clara dependencia del sistema de asentamiento y conservación de las áreas medioambientales y un claro reconocimiento de tipologías propias del medio rural aunque vinculadas al sector turístico. En la actualidad, el continuo descenso de la demanda turística ha provocado una clara modificación en la estructura poblacional y económica. Al incorporar estas modificaciones a los modelos especificados podemos comprobar un verdadero desmoronamiento de los valores. Es posible que el remanente de vivienda construida actualmente vaya dirigido a un potencial comprador que se encuentra en retroceso y que se vincula a unos rasgos territoriales ya no existentes. Encontrar soluciones adaptables a la oferta existente, implica la viabilidad de renovación del sistema poblacional o modificaciones a nivel económico. La búsqueda de respuestas a estas cuestiones señala la necesidad de recanalizar el desarrollo, sin obviar la potencialidad del ámbito. SUMMARY One of the main lines of research regarding the urban economy focuses on the behavior of the real estate market and its relationship to territorial structure. Within this context, one of the most important themes involves considering the significance of urban property value and dealing with its variability, particularly given the significant role of the real estate market in Spain, both in the past and present. The main objective of this study is to identify those factors linked to location, which explain the formation of property values and justify their variability. Defining this process requires carrying out an evaluation on a territorial scale, establishing the socioeconomic, environmental and urban planning factors that constitute urban development and influence the demand for housing, thereby defining the processes by which their value is established. The analysis targets residential real estate values in coastal areas where pressure from the tourism industry has prompted large-scale transformations. Therefore, the focal point of this study is an area known as Vega Baja del Segura, which is located on the Spanish Mediterranean coast in southern Alicante (province). Characterized by its scenic and ecological diversity, this area has historically maintained a clear distinction between urban and rural spaces. This dichotomy has drastically changed in past decades due to the large increase in population attributed to the tourism and real estate markets – factors which have had a direct effect on property values. The development of this area provides a clear example of the expansionary policies which have affected the housing market on the coast of Spain during the past two decades, resulting in a large increase in suburban development. Understanding the territorial framework has made it possible to carry out a spatial variability analysis through massive data processing, as well as an econometric analysis that determines the factors that are evaluated positively and negatively by potential buyers. These relationships enable us to establish different mathematical systems based on hedonic pricing models that facilitate the identification of differential features in the economic, social and spatial spheres, and their impact on property values. Additionally, a process for land valuation was established through an analysis of the concept of structural vulnerability, which is understood to be a fragile situation resulting from either social or economic circumstances. Currently, this demand structure for second homes and services has demonstrated its fragility and has inhibited the area’s economic development as a result of the drastic fall in investment in the real estate market, due to the global debt crisis. This process has been worsened by the existence of a marginal industrial base into which no important investments have been channeled, combined with the progressive abandonment of agricultural and fishing operations. In and of itself, the tourism model did not inhibit the area’s economic development, rather it is the result of the manner in which it was implemented on the Costa Brava, with a land consumption based on the short-term, lacking respect for landscape and environmental aspects and without a comprehensive organization of the territory. It is clear that the link between vulnerability indexes and property values is not particularly significant, thereby indicating that future fragility trends have not been incorporated into the problem in terms of establishing the sale prices of the analyzed real estate product in question. Urban property values are clearly dependent on the system of development and environmental conservation, as well as on a clear recognition of the typologies that characterize rural areas, even those linked to the tourism industry. Today, the continued drop in tourism demand has provoked an obvious modification in the populational and economic structures. By incorporating these changes into the specified models, we can confirm a real collapse in values. It’s possible that the surplus of already-built homes is currently being marketed to a potential buyer who is in recession and linked to certain territorial characteristics that no longer exist. Finding solutions that can be adapted to the existing offer implies the viability of renewing the population system or carrying out modifications on an economic level. The search for answers to these questions suggests the need to reform the development model, without leaving out an area’s potentiality.

The Zero-Removing Property and Lagrange-Type Interpolation Series

The classical Kramer sampling theorem, which provides a method for obtaining orthogonal sampling formulas, can be formulated in a more general nonorthogonal setting. In this setting, a challenging problem is to characterize the situations when the obtained nonorthogonal sampling formulas can be expressed as Lagrange-type interpolation series. In this article a necessary and sufficient condition is given in terms of the zero removing property. Roughly speaking, this property concerns the stability of the sampled functions on removing a finite number of their zeros.

Normalización del análisis de la piedra y conservación del patrimonio cultural. The Standardization of Stone Analysis and Conservation of Cultural Heritage

La normalización de los métodos de análisis y de los principales aspectos relacionados con la conservación de los bienes culturales ha empezado en 2004 con la creación del comité europeo de normalización, CEN/TC 346 Conservation of Cultural Property, que tiene la responsabilidad no solamente de redactar protocolos de ensayos en laboratorio, sino también proponer las recomendaciones más adecuadas para designarlos de forma consensual y conservarlos de la forma más apropiada. Se comentan los aspectos relacionados con el origen de estas normas, el trabajo desarrollado y que muchas de ellas, aunque no estén dirigidas específicamente a la piedra, tienen en cuenta la presencia de este material en objetos arqueológicos, obras de arte, estructuras de fábricas y elementos ornamentales.

An efficient, parametric fixpoint algorithm for analysis of java bytecode

Abstract interpretation has been widely used for the analysis of object-oriented languages and, in particular, Java source and bytecode. However, while most existing work deals with the problem of flnding expressive abstract domains that track accurately the characteristics of a particular concrete property, the underlying flxpoint algorithms have received comparatively less attention. In fact, many existing (abstract interpretation based—) flxpoint algorithms rely on relatively inefHcient techniques for solving inter-procedural caligraphs or are speciflc and tied to particular analyses. We also argüe that the design of an efficient fixpoint algorithm is pivotal to supporting the analysis of large programs. In this paper we introduce a novel algorithm for analysis of Java bytecode which includes a number of optimizations in order to reduce the number of iterations. The algorithm is parametric -in the sense that it is independent of the abstract domain used and it can be applied to different domains as "plug-ins"-, multivariant, and flow-sensitive. Also, is based on a program transformation, prior to the analysis, that results in a highly uniform representation of all the features in the language and therefore simplifies analysis. Detailed descriptions of decompilation solutions are given and discussed with an example. We also provide some performance data from a preliminary implementation of the analysis.

Las decisiones de proyecto y los costes de construcción en la vivienda rural, aplicado al estudio de la vivienda autopromovida en la provincia de Cáceres

En la coyuntura actual, en la que existe por un lado, exceso en la oferta de vivienda (de alto precio o de segunda residencia), y aparece por otro demanda de vivienda (de bajo precio y/o social), el mercado inmobiliario se encuentra paradójicamente bloqueado. Así, surge esta investigación como fruto de este momento histórico, en el cual se somete a debate económico el producto vivienda, no solo como consecuencia de la profunda crisis económica, sino también para la correcta gestión de los recursos desde el punto de vista de lo eficiente y sostenible. Se parte de la hipótesis de que es necesario determinar un estimador de costes de construcción de vivienda autopromovida como una de las soluciones a la habitación en el medio rural de Extremadura, para lo cual se ha tomado como modelo de análisis concretamente la Vivienda Autopromovida subvencionada por la Junta de Extremadura en el marco de la provincia de Cáceres. Con esta investigación se pretende establecer una herramienta matemática precisa que permita determinar la inversión a los promotores, el posible margen de beneficios a los contratistas y el valor real de la garantía en el préstamo a las entidades financieras. Pero el objetivo de mayor proyección social de esta investigación consiste en facilitar una herramienta sencilla a la Junta de Extremadura para que pueda establecer las ayudas de una manera proporcional. De este modo se ayuda a optimizar los recursos, lo cual en época de crisis resulta aun más acuciante, ya que conociendo previamente y con bastante exactitud el importe de las obras se pueden dirigir las ayudas de forma proporcional a las necesidades reales de la ejecución. De hecho, ciertas características difíciles de cuantificar para determinar las ayudas en materia de vivienda, como la influencia del número de miembros familiares o la atención a la discapacidad, se verían contempladas de forma indirecta en el coste estimado con el método aquí propuesto, ya que suponen siempre un aumento de las superficies construidas y útiles, de los huecos de fachadas o del tamaño de locales húmedos y por tanto se contemplan en la ecuación del modelo determinado. Por último, contar con un estimador de costes potencia la forma de asentamiento de la construcción mediante autopromocion de viviendas ya que ayuda a la toma de decisiones al particular, subvencionado o no. En efecto, la herramienta es valida en cierta medida para cualquier autopromocion, constituye un sistema de construcción con las menores posibilidades especulativas y lo más sostenible, es abundante en toda Extremadura, y consigue que el sector de la construcción sea un sistema más eficiente al optimizar su proceso económico de producción. SUMMARY Under the present circumstances, in which there is, on one hand, an excess in the supply of housing (high-price or second-home), and on the other hand a demand for housing (low cost and/or social), paradoxically the property market is at a standstill. This research has come about as a result of this moment in time, in which the product: housing, is undergoing economic debate, not only on account of this serious economic crisis, but for the proper management of resources from the point of view of efficiency and sustainability. A building-costs estimator for owner-developed housing is deemed necessary as one of the solutions for the rural environment that is Extremadura. To this end, it is the Owner-Developed House which has been taken as analysis model. It is subsidized by the Extremadura Regional Government in Caceres Province. This research establishes an accurate mathematical tool to work out the developers’ investment, the builder’s potential profit margin and the reality of the loan for the Financial Institution. But the result of most social relevance in this research is to provide the Extremadura Regional Government with a simple tool, so that it can draw up the Subventions proportionally. Thus, the resources are optimized, an even more vital matter in times of economic slump, due to the fact that if the cost of the building works is known with some accuracy beforehand, the subventions can be allocated in a way that is proportional to the real needs of execution. In fact certain elements related to housing subventions which are hard to quantify, such as the influence of number of family members or disability support, would be covered indirectly in cost estimate with the proposed method, since they inevitably involve an increase in built area, exterior wall openings and the size of plumbed rooms. As such they are covered in the determined model equation. Lastly, the availability of a cost-estimator reinforces the ownerdeveloped building model, since it assists decision-making by the individual, whether subsidized or not. This is because the tool is valid to some extent in any owner-development, and this building scheme, which is common in Extremadura, is the most sustainable, and the least liable to speculation. It makes the building sector more efficient by optimizing the economic production process.

An efficient, parametric fixpoint algorithm for incremental analysis of java bytecode

Abstract interpretation has been widely used for the analysis of object-oriented languages and, more precisely, Java source and bytecode. However, while most of the existing work deals with the problem of finding expressive abstract domains that track accurately the characteristics of a particular concrete property, the underlying fixpoint algorithms have received comparatively less attention. In fact, many existing (abstract interpretation based) fixpoint algorithms rely on relatively inefficient techniques to solve inter-procedural call graphs or are specific and tied to particular analyses. We argue that the design of an efficient fixpoint algorithm is pivotal to support the analysis of large programs. In this paper we introduce a novel algorithm for analysis of Java bytecode which includes a number of optimizations in order to reduce the number of iterations. Also, the algorithm is parametric in the sense that it is independent of the abstract domain used and it can be applied to different domains as "plug-ins". It is also incremental in the sense that, if desired, analysis data can be saved so that only a reduced amount of reanalysis is needed after a small program change, which can be instrumental for large programs. The algorithm is also multivariant and flowsensitive. Finally, another interesting characteristic of the algorithm is that it is based on a program transformation, prior to the analysis, that results in a highly uniform representation of all the features in the language and therefore simplifies analysis. Detailed descriptions of decompilation solutions are provided and discussed with an example.

Economic analysis of drought risks: an application to irrigated agriculture in Spain

Abstract This paper describes a two-part methodology for managing the risk posed by water supply variability to irrigated agriculture. First, an econometric model is used to explain the variation in the production value of irrigated agriculture. The explanatory variables include an index of irrigation water availability (surface storage levels), a price index representative of the crops grown in each geographical unit, and a time variable. The model corrects for autocorrelation and it is applied to 16 representative Spanish provinces in terms of irrigated agriculture. In the second part, the fitted models are used for the economic evaluation of drought risk. In flow variability in the hydrological system servicing each province is used to perform ex-ante evaluations of economic output for the upcoming irrigation season. The model?s error and the probability distribution functions (PDFs) of the reservoirs? storage variations are used to generate Monte Carlo (Latin Hypercube) simulations of agricultural output 7 and 3 months prior to the irrigation season. The results of these simulations illustrate the different risk profiles of each management unit, which depend on farm productivity and on the probability distribution function of water in flow to reservoirs. The potential for ex-ante drought impact assessments is demonstrated. By complementing hydrological models, this method can assist water managers and decisionmakers in managing reservoirs.

Maximum likelihood estimation of new state space models for operational modal analysis

The modal analysis of a structural system consists on computing its vibrational modes. The experimental way to estimate these modes requires to excite the system with a measured or known input and then to measure the system output at different points using sensors. Finally, system inputs and outputs are used to compute the modes of vibration. When the system refers to large structures like buildings or bridges, the tests have to be performed in situ, so it is not possible to measure system inputs such as wind, traffic, . . .Even if a known input is applied, the procedure is usually difficult and expensive, and there are still uncontrolled disturbances acting at the time of the test. These facts led to the idea of computing the modes of vibration using only the measured vibrations and regardless of the inputs that originated them, whether they are ambient vibrations (wind, earthquakes, . . . ) or operational loads (traffic, human loading, . . . ). This procedure is usually called Operational Modal Analysis (OMA), and in general consists on to fit a mathematical model to the measured data assuming the unobserved excitations are realizations of a stationary stochastic process (usually white noise processes). Then, the modes of vibration are computed from the estimated model. The first issue investigated in this thesis is the performance of the Expectation- Maximization (EM) algorithm for the maximum likelihood estimation of the state space model in the field of OMA. The algorithm is described in detail and it is analysed how to apply it to vibration data. After that, it is compared to another well known method, the Stochastic Subspace Identification algorithm. The maximum likelihood estimate enjoys some optimal properties from a statistical point of view what makes it very attractive in practice, but the most remarkable property of the EM algorithm is that it can be used to address a wide range of situations in OMA. In this work, three additional state space models are proposed and estimated using the EM algorithm: • The first model is proposed to estimate the modes of vibration when several tests are performed in the same structural system. Instead of analyse record by record and then compute averages, the EM algorithm is extended for the joint estimation of the proposed state space model using all the available data. • The second state space model is used to estimate the modes of vibration when the number of available sensors is lower than the number of points to be tested. In these cases it is usual to perform several tests changing the position of the sensors from one test to the following (multiple setups of sensors). Here, the proposed state space model and the EM algorithm are used to estimate the modal parameters taking into account the data of all setups. • And last, a state space model is proposed to estimate the modes of vibration in the presence of unmeasured inputs that cannot be modelled as white noise processes. In these cases, the frequency components of the inputs cannot be separated from the eigenfrequencies of the system, and spurious modes are obtained in the identification process. The idea is to measure the response of the structure corresponding to different inputs; then, it is assumed that the parameters common to all the data correspond to the structure (modes of vibration), and the parameters found in a specific test correspond to the input in that test. The problem is solved using the proposed state space model and the EM algorithm. Resumen El análisis modal de un sistema estructural consiste en calcular sus modos de vibración. Para estimar estos modos experimentalmente es preciso excitar el sistema con entradas conocidas y registrar las salidas del sistema en diferentes puntos por medio de sensores. Finalmente, los modos de vibración se calculan utilizando las entradas y salidas registradas. Cuando el sistema es una gran estructura como un puente o un edificio, los experimentos tienen que realizarse in situ, por lo que no es posible registrar entradas al sistema tales como viento, tráfico, . . . Incluso si se aplica una entrada conocida, el procedimiento suele ser complicado y caro, y todavía están presentes perturbaciones no controladas que excitan el sistema durante el test. Estos hechos han llevado a la idea de calcular los modos de vibración utilizando sólo las vibraciones registradas en la estructura y sin tener en cuenta las cargas que las originan, ya sean cargas ambientales (viento, terremotos, . . . ) o cargas de explotación (tráfico, cargas humanas, . . . ). Este procedimiento se conoce en la literatura especializada como Análisis Modal Operacional, y en general consiste en ajustar un modelo matemático a los datos registrados adoptando la hipótesis de que las excitaciones no conocidas son realizaciones de un proceso estocástico estacionario (generalmente ruido blanco). Posteriormente, los modos de vibración se calculan a partir del modelo estimado. El primer problema que se ha investigado en esta tesis es la utilización de máxima verosimilitud y el algoritmo EM (Expectation-Maximization) para la estimación del modelo espacio de los estados en el ámbito del Análisis Modal Operacional. El algoritmo se describe en detalle y también se analiza como aplicarlo cuando se dispone de datos de vibraciones de una estructura. A continuación se compara con otro método muy conocido, el método de los Subespacios. Los estimadores máximo verosímiles presentan una serie de propiedades que los hacen óptimos desde un punto de vista estadístico, pero la propiedad más destacable del algoritmo EM es que puede utilizarse para resolver un amplio abanico de situaciones que se presentan en el Análisis Modal Operacional. En este trabajo se proponen y estiman tres modelos en el espacio de los estados: • El primer modelo se utiliza para estimar los modos de vibración cuando se dispone de datos correspondientes a varios experimentos realizados en la misma estructura. En lugar de analizar registro a registro y calcular promedios, se utiliza algoritmo EM para la estimación conjunta del modelo propuesto utilizando todos los datos disponibles. • El segundo modelo en el espacio de los estados propuesto se utiliza para estimar los modos de vibración cuando el número de sensores disponibles es menor que vi Resumen el número de puntos que se quieren analizar en la estructura. En estos casos es usual realizar varios ensayos cambiando la posición de los sensores de un ensayo a otro (múltiples configuraciones de sensores). En este trabajo se utiliza el algoritmo EM para estimar los parámetros modales teniendo en cuenta los datos de todas las configuraciones. • Por último, se propone otro modelo en el espacio de los estados para estimar los modos de vibración en la presencia de entradas al sistema que no pueden modelarse como procesos estocásticos de ruido blanco. En estos casos, las frecuencias de las entradas no se pueden separar de las frecuencias del sistema y se obtienen modos espurios en la fase de identificación. La idea es registrar la respuesta de la estructura correspondiente a diferentes entradas; entonces se adopta la hipótesis de que los parámetros comunes a todos los registros corresponden a la estructura (modos de vibración), y los parámetros encontrados en un registro específico corresponden a la entrada en dicho ensayo. El problema se resuelve utilizando el modelo propuesto y el algoritmo EM.

Development of a Uniform Theory of Diffraction for Scattered and Surface Electromagnetic Field Analysis on a Cylinder

Con esta tesis ”Desarrollo de una Teoría Uniforme de la Difracción para el Análisis de los Campos Electromagnéticos Dispersados y Superficiales sobre un Cilindro” hemos iniciado una nueva línea de investigación que trata de responder a la siguiente pregunta: ¿cuál es la impedancia de superficie que describe una estructura de conductor eléctrico perfecto (PEC) convexa recubierta por un material no conductor? Este tipo de estudios tienen interés hoy en día porque ayudan a predecir el campo electromagnético incidente, radiado o que se propaga sobre estructuras metálicas y localmente convexas que se encuentran recubiertas de algún material dieléctrico, o sobre estructuras metálicas con pérdidas, como por ejemplo se necesita en determinadas aplicaciones aeroespaciales, marítimas o automovilísticas. Además, desde un punto de vista teórico, la caracterización de la impedancia de superficie de una estructura PEC recubierta o no por un dieléctrico es una generalización de varias soluciones que tratan ambos tipos de problemas por separado. En esta tesis se desarrolla una teoría uniforme de la difracción (UTD) para analizar el problema canónico del campo electromagnético dispersado y superficial en un cilindro circular eléctricamente grande con una condición de contorno de impedancia (IBC) para frecuencias altas. Construir una solución basada en UTD para este problema canónico es crucial en el desarrollo de un método UTD para el caso más general de una superficie arbitrariamente convexa, mediante el uso del principio de localización de los campos electromagnéticos a altas frecuencias. Esta tesis doctoral se ha llevado a cabo a través de una serie de hitos que se enumeran a continuación, enfatizando las contribuciones a las que ha dado lugar. Inicialmente se realiza una revisión en profundidad del estado del arte de los métodos asintóticos con numerosas referencias. As í, cualquier lector novel puede llegar a conocer la historia de la óptica geométrica (GO) y la teoría geométrica de la difracción (GTD), que dieron lugar al desarrollo de la UTD. Después, se investiga ampliamente la UTD y los trabajos más importantes que pueden encontrarse en la literatura. As í, este capítulo, nos coloca en la posición de afirmar que, hasta donde nosotros conocemos, nadie ha intentado antes llevar a cabo una investigación rigurosa sobre la caracterización de la impedancia de superficie de una estructura PEC recubierta por un material dieléctrico, utilizando para ello la UTD. Primero, se desarrolla una UTD para el problema canónico de la dispersión electromagnética de un cilindro circular eléctricamente grande con una IBC uniforme, cuando es iluminado por una onda plana con incidencia oblicua a frecuencias altas. La solución a este problema canónico se construye a partir de una solución exacta mediante una expansión de autofunciones de propagación radial. Entonces, ésta se convierte en una nueva expansión de autofunciones de propagación circunferencial muy apropiada para cilindros grandes, a través de la transformación de Watson. De esta forma, la expresión del campo se reduce a una integral que se evalúa asintóticamente, para altas frecuencias, de manera uniforme. El resultado se expresa según el trazado de rayos descrito en la UTD. La solución es uniforme porque tiene la importante propiedad de mantenerse continua a lo largo de la región de transición, a ambos lados de la superficie del contorno de sombra. Fuera de la región de transición la solución se reduce al campo incidente y reflejado puramente ópticos en la región iluminada del cilindro, y al campo superficial difractado en la región de sombra. Debido a la IBC el campo dispersado contiene una componente contrapolar a causa de un acoplamiento entre las ondas TEz y TMz (donde z es el eje del cilindro). Esta componente contrapolar desaparece cuando la incidencia es normal al cilindro, y también en la región iluminada cuando la incidencia es oblicua donde el campo se reduce a la solución de GO. La solución UTD presenta una muy buena exactitud cuando se compara numéricamente con una solución de referencia exacta. A continuación, se desarrolla una IBC efectiva para el cálculo del campo electromagnético dispersado en un cilindro circular PEC recubierto por un dieléctrico e iluminado por una onda plana incidiendo oblicuamente. Para ello se derivan dos impedancias de superficie en relación directa con las ondas creeping y de superficie TM y TE que se excitan en un cilindro recubierto por un material no conductor. Las impedancias de superficie TM y TE están acopladas cuando la incidencia es oblicua, y dependen de la geometría del problema y de los números de onda. Además, se ha derivado una impedancia de superficie constante, aunque con diferente valor cuando el observador se encuentra en la zona iluminada o en la zona de sombra. Después, se presenta una solución UTD para el cálculo de la dispersión de una onda plana con incidencia oblicua sobre un cilindro eléctricamente grande y convexo, mediante la generalización del problema canónico correspondiente al cilindro circular. La solución asintótica es uniforme porque se mantiene continua a lo largo de la región de transición, en las inmediaciones del contorno de sombra, y se reduce a la solución de rayos ópticos en la zona iluminada y a la contribución de las ondas de superficie dentro de la zona de sombra, lejos de la región de transición. Cuando se usa cualquier material no conductor se excita una componente contrapolar que tiende a desaparecer cuando la incidencia es normal al cilindro y en la región iluminada. Se discuten ampliamente las limitaciones de las fórmulas para la impedancia de superficie efectiva, y se compara la solución UTD con otras soluciones de referencia, donde se observa una muy buena concordancia. Y en tercer lugar, se presenta una aproximación para una impedancia de superficie efectiva para el cálculo de los campos superficiales en un cilindro circular conductor recubierto por un dieléctrico. Se discuten las principales diferencias que existen entre un cilindro PEC recubierto por un dieléctrico desde un punto de vista riguroso y un cilindro con una IBC. Mientras para un cilindro de impedancia se considera una impedancia de superficie constante o uniforme, para un cilindro conductor recubierto por un dieléctrico se derivan dos impedancias de superficie. Estas impedancias de superficie están asociadas a los modos de ondas creeping TM y TE excitadas en un cilindro, y dependen de la posición y de la orientación del observador y de la fuente. Con esto en mente, se deriva una solución UTD con IBC para los campos superficiales teniendo en cuenta las dependencias de la impedancia de superficie. La expansión asintótica se realiza, mediante la transformación de Watson, sobre la representación en serie de las funciones de Green correspondientes, evitando as í calcular las derivadas de orden superior de las integrales de tipo Fock, y dando lugar a una solución rápida y precisa. En los ejemplos numéricos realizados se observa una muy buena precisión cuando el cilindro y la separación entre el observador y la fuente son grandes. Esta solución, junto con el método de los momentos (MoM), se puede aplicar para el cálculo eficiente del acoplamiento mutuo de grandes arrays conformados de antenas de parches. Los métodos propuestos basados en UTD para el cálculo del campo electromagnético dispersado y superficial sobre un cilindro PEC recubierto de dieléctrico con una IBC efectiva suponen un primer paso hacia la generalización de una solución UTD para superficies metálicas convexas arbitrarias cubiertas por un material no conductor e iluminadas por una fuente electromagnética arbitraria. ABSTRACT With this thesis ”Development of a Uniform Theory of Diffraction for Scattered and Surface Electromagnetic Field Analysis on a Cylinder” we have initiated a line of investigation whose goal is to answer the following question: what is the surface impedance which describes a perfect electric conductor (PEC) convex structure covered by a material coating? These studies are of current and future interest for predicting the electromagnetic (EM) fields incident, radiating or propagating on locally smooth convex parts of highly metallic structures with a material coating, or by a lossy metallic surfaces, as for example in aerospace, maritime and automotive applications. Moreover, from a theoretical point of view, the surface impedance characterization of PEC surfaces with or without a material coating represents a generalization of independent solutions for both type of problems. A uniform geometrical theory of diffraction (UTD) is developed in this thesis for analyzing the canonical problem of EM scattered and surface field by an electrically large circular cylinder with an impedance boundary condition (IBC) in the high frequency regime, by means of a surface impedance characterization. The construction of a UTD solution for this canonical problem is crucial for the development of the corresponding UTD solution for the more general case of an arbitrary smooth convex surface, via the principle of the localization of high frequency EM fields. The development of the present doctoral thesis has been carried out through a series of landmarks that are enumerated as follows, emphasizing the main contributions that this work has given rise to. Initially, a profound revision is made in the state of art of asymptotic methods where numerous references are given. Thus, any reader may know the history of geometrical optics (GO) and geometrical theory of diffraction (GTD), which led to the development of UTD. Then, the UTD is deeply investigated and the main studies which are found in the literature are shown. This chapter situates us in the position to state that, as far as we know, nobody has attempted before to perform a rigorous research about the surface impedance characterization for material-coated PEC convex structures via UTD. First, a UTD solution is developed for the canonical problem of the EM scattering by an electrically large circular cylinder with a uniform IBC, when it is illuminated by an obliquely incident high frequency plane wave. A solution to this canonical problem is first constructed in terms of an exact formulation involving a radially propagating eigenfunction expansion. The latter is converted into a circumferentially propagating eigenfunction expansion suited for large cylinders, via the Watson transformation, which is expressed as an integral that is subsequently evaluated asymptotically, for high frequencies, in a uniform manner. The resulting solution is then expressed in the desired UTD ray form. This solution is uniform in the sense that it has the important property that it remains continuous across the transition region on either side of the surface shadow boundary. Outside the shadow boundary transition region it recovers the purely ray optical incident and reflected ray fields on the deep lit side of the shadow boundary and to the modal surface diffracted ray fields on the deep shadow side. The scattered field is seen to have a cross-polarized component due to the coupling between the TEz and TMz waves (where z is the cylinder axis) resulting from the IBC. Such cross-polarization vanishes for normal incidence on the cylinder, and also in the deep lit region for oblique incidence where it properly reduces to the GO or ray optical solution. This UTD solution is shown to be very accurate by a numerical comparison with an exact reference solution. Then, an effective IBC is developed for the EM scattered field on a coated PEC circular cylinder illuminated by an obliquely incident plane wave. Two surface impedances are derived in a direct relation with the TM and TE surface and creeping wave modes excited on a coated cylinder. The TM and TE surface impedances are coupled at oblique incidence, and depend on the geometry of the problem and the wave numbers. Nevertheless, a constant surface impedance is found, although with a different value when the observation point lays in the lit or in the shadow region. Then, a UTD solution for the scattering of an obliquely incident plane wave on an electrically large smooth convex coated PEC cylinder is introduced, via a generalization of the canonical circular cylinder problem. The asymptotic solution is uniform because it remains continuous across the transition region, in the vicinity of the shadow boundary, and it recovers the ray optical solution in the deep lit region and the creeping wave formulation within the deep shadow region. When a coating is present a cross-polar field term is excited, which vanishes at normal incidence and in the deep lit region. The limitations of the effective surface impedance formulas are discussed, and the UTD solution is compared with some reference solutions where a very good agreement is met. And in third place, an effective surface impedance approach is introduced for determining surface fields on an electrically large coated metallic circular cylinder. Differences in analysis of rigorouslytreated coated metallic cylinders and cylinders with an IBC are discussed. While for the impedance cylinder case a single constant or uniform surface impedance is considered, for the coated metallic cylinder case two surface impedances are derived. These are associated with the TM and TE creeping wave modes excited on a cylinder and depend on observation and source positions and orientations. With this in mind, a UTD based method with IBC is derived for the surface fields by taking into account the surface impedance variation. The asymptotic expansion is performed, via the Watson transformation, over the appropriate series representation of the Green’s functions, thus avoiding higher-order derivatives of Fock-type integrals, and yielding a fast and an accurate solution. Numerical examples reveal a very good accuracy for large cylinders when the separation between the observation and the source point is large. Thus, this solution could be efficiently applied in mutual coupling analysis, along with the method of moments (MoM), of large conformal microstrip array antennas. The proposed UTD methods for scattered and surface EM field analysis on a coated PEC cylinder with an effective IBC are considered the first steps toward the generalization of a UTD solution for large arbitrarily convex smooth metallic surfaces covered by a material coating and illuminated by an arbitrary EM source.

Sensing colour stability and mixtures of powder paprika using optical reflectance and image analysis.

The production and industry of paprika present several problems related to quality and to production costs. One of the main difficulties is to obtain an objective and quick method for predicting quality. Quality in powder paprika involves: quantity of carotenoids and the appearance and stability of colour. The method used currently for determining quality is the measurement of absorbance at 460 nm wavelength, of an acetone extract of carotenoids, but there is no information about the appearance of the paprika or the stability of its colour with time. " Another important problem is the presence of mixtures of powdered paprika produced in the Spanish region of "La Vera", which has a peculiar way of production, with a high '' quality and price, with other products of lower quality. It is necessary to obtain methods which are able to detect the fraud.