Opportunistic and systematic screening for chlamydia: a study of consultations by young adults in general practice

BACKGROUND: Opportunistic screening for genital chlamydia infection is being introduced in England, but evidence for the effectiveness of this approach is lacking. There are insufficient data about young peoples' use of primary care services to determine the potential coverage of opportunistic screening in comparison with a systematic population-based approach. AIM: To estimate use of primary care services by young men and women; to compare potential coverage of opportunistic chlamydia screening with a systematic postal approach. DESIGN OF STUDY: Population based cross-sectional study. SETTING: Twenty-seven general practices around Bristol and Birmingham. METHOD: A random sample of patients aged 16-24 years were posted a chlamydia screening pack. We collected details of face-to-face consultations from general practice records. Survival and person-time methods were used to estimate the cumulative probability of attending general practice in 1 year and the coverage achieved by opportunistic and systematic postal chlamydia screening. RESULTS: Of 12 973 eligible patients, an estimated 60.4% (95% confidence interval [CI] = 58.3 to 62.5%) of men and 75.3% (73.7 to 76.9%) of women aged 16-24 years attended their practice at least once in a 1-year period. During this period, an estimated 21.3% of patients would not attend their general practice but would be reached by postal screening, 9.2% would not receive a postal invitation but would attend their practice, and 11.8% would be missed by both methods. CONCLUSIONS: Opportunistic and population-based approaches to chlamydia screening would both fail to contact a substantial minority of the target group, if used alone. A pragmatic approach combining both strategies might achieve higher coverage.

Brief Report: How Adolescents with ASD Process Social Information in Complex Scenes. Combining Evidence from Eye Movements and Verbal Descriptions

We investigated attention, encoding and processing of social aspects of complex photographic scenes. Twenty-four high-functioning adolescents (aged 11���16) with ASD and 24 typically developing matched control participants viewed and then described a series of scenes, each containing a person. Analyses of eye movements and verbal descriptions provided converging evidence that both groups displayed general interest in the person in each scene but the salience of the person was reduced for the ASD participants. Nevertheless, the verbal descriptions revealed that participants with ASD frequently processed the observed person���s emotion or mental state without prompting. They also often mentioned eye-gaze direction, and there was evidence from eye movements and verbal descriptions that gaze was followed accurately. The combination of evidence from eye movements and verbal descriptions provides a rich insight into the way stimuli are processed overall. The merits of using these methods within the same paradigm are discussed.

BrainCheck - a very brief tool to detect incipient cognitive decline: optimized case-finding combining patient- and informant-based data.

INTRODUCTION Optimal identification of subtle cognitive impairment in the primary care setting requires a very brief tool combining (a) patients' subjective impairments, (b) cognitive testing, and (c) information from informants. The present study developed a new, very quick and easily administered case-finding tool combining these assessments ('BrainCheck') and tested the feasibility and validity of this instrument in two independent studies. METHODS We developed a case-finding tool comprised of patient-directed (a) questions about memory and depression and (b) clock drawing, and (c) the informant-directed 7-item version of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE). Feasibility study: 52 general practitioners rated the feasibility and acceptance of the patient-directed tool. Validation study: An independent group of 288 Memory Clinic patients (mean��������SD age���=���76.6��������7.9, education���=���12.0��������2.6; 53.8% female) with diagnoses of mild cognitive impairment (n���=���80), probable Alzheimer's disease (n���=���185), or major depression (n���=���23) and 126 demographically matched, cognitively healthy volunteer participants (age���=���75.2��������8.8, education���=���12.5��������2.7; 40% female) partook. All patient and healthy control participants were administered the patient-directed tool, and informants of 113 patient and 70 healthy control participants completed the very short IQCODE. RESULTS Feasibility study: General practitioners rated the patient-directed tool as highly feasible and acceptable. Validation study: A Classification and Regression Tree analysis generated an algorithm to categorize patient-directed data which resulted in a correct classification rate (CCR) of 81.2% (sensitivity���=���83.0%, specificity���=���79.4%). Critically, the CCR of the combined patient- and informant-directed instruments (BrainCheck) reached nearly 90% (that is 89.4%; sensitivity���=���97.4%, specificity���=���81.6%). CONCLUSION A new and very brief instrument for general practitioners, 'BrainCheck', combined three sources of information deemed critical for effective case-finding (that is, patients' subject impairments, cognitive testing, informant information) and resulted in a nearly 90% CCR. Thus, it provides a very efficient and valid tool to aid general practitioners in deciding whether patients with suspected cognitive impairments should be further evaluated or not ('watchful waiting').

A hybrid method in combining treatment effects from matched and unmatched studies

In the biomedical studies, the general data structures have been the matched (paired) and unmatched designs. Recently, many researchers are interested in Meta-Analysis to obtain a better understanding from several clinical data of a medical treatment. The hybrid design, which is combined two data structures, may create the fundamental question for statistical methods and the challenges for statistical inferences. The applied methods are depending on the underlying distribution. If the outcomes are normally distributed, we would use the classic paired and two independent sample T-tests on the matched and unmatched cases. If not, we can apply Wilcoxon signed rank and rank sum test on each case. ^ To assess an overall treatment effect on a hybrid design, we can apply the inverse variance weight method used in Meta-Analysis. On the nonparametric case, we can use a test statistic which is combined on two Wilcoxon test statistics. However, these two test statistics are not in same scale. We propose the Hybrid Test Statistic based on the Hodges-Lehmann estimates of the treatment effects, which are medians in the same scale.^ To compare the proposed method, we use the classic meta-analysis T-test statistic on the combined the estimates of the treatment effects from two T-test statistics. Theoretically, the efficiency of two unbiased estimators of a parameter is the ratio of their variances. With the concept of Asymptotic Relative Efficiency (ARE) developed by Pitman, we show ARE of the hybrid test statistic relative to classic meta-analysis T-test statistic using the Hodges-Lemann estimators associated with two test statistics.^ From several simulation studies, we calculate the empirical type I error rate and power of the test statistics. The proposed statistic would provide effective tool to evaluate and understand the treatment effect in various public health studies as well as clinical trials.^

El cambio en la designaci��n general de material (DGM) de las AACR a las RDA : Definici��n de los atributos tipo de contenido, tipo de medio y tipo de soporte

Se aborda el estudio de los atributos tipo de contenido, tipo de medio y tipo de soporte definidos por el c��digo de catalogaci��n Resource Description and Access (RDA) para solucionar los problemas que presentaba la lista de t��rminos utilizadas para registrar la designaci��n general de material (DGM) en las Anglo American Cataloging Rules (AACR). Los t��rminos eran ambiguos combinando aspectos referidos al contenido y clase de material del recurso. Se parte de una exhaustiva revisi��n bibliogr��fica y del estudio de los documentos que se generaron en el proceso de elaboraci��n del nuevo c��digo. Se menciona el trabajo conjunto entre el Joint Steering Committee (JSC) y el est��ndar ONIX para el establecimiento de criterios que permitieron definir estos tres atributos, as�� como el aporte del modelo FRBR en la definici��n de los mismos. Se presentan ejemplos de registros bibliogr��ficos donde se utilizan estos tres atributos en formato MARC21, ISBD consolidada a partir de la definici��n del ��rea 0 y en el esquema de metadatos Dublin Core. Se finaliza destacando la necesidad de continuar con investigaciones que permitan concluir sobre la adecuaci��n de estos tres atributos a las necesidades de los catalogadores, usuarios y a la realidad tecnol��gica

El cambio en la designaci��n general de material (DGM) de las AACR a las RDA : Definici��n de los atributos tipo de contenido, tipo de medio y tipo de soporte

Se aborda el estudio de los atributos tipo de contenido, tipo de medio y tipo de soporte definidos por el c��digo de catalogaci��n Resource Description and Access (RDA) para solucionar los problemas que presentaba la lista de t��rminos utilizadas para registrar la designaci��n general de material (DGM) en las Anglo American Cataloging Rules (AACR). Los t��rminos eran ambiguos combinando aspectos referidos al contenido y clase de material del recurso. Se parte de una exhaustiva revisi��n bibliogr��fica y del estudio de los documentos que se generaron en el proceso de elaboraci��n del nuevo c��digo. Se menciona el trabajo conjunto entre el Joint Steering Committee (JSC) y el est��ndar ONIX para el establecimiento de criterios que permitieron definir estos tres atributos, as�� como el aporte del modelo FRBR en la definici��n de los mismos. Se presentan ejemplos de registros bibliogr��ficos donde se utilizan estos tres atributos en formato MARC21, ISBD consolidada a partir de la definici��n del ��rea 0 y en el esquema de metadatos Dublin Core. Se finaliza destacando la necesidad de continuar con investigaciones que permitan concluir sobre la adecuaci��n de estos tres atributos a las necesidades de los catalogadores, usuarios y a la realidad tecnol��gica

El cambio en la designaci��n general de material (DGM) de las AACR a las RDA : Definici��n de los atributos tipo de contenido, tipo de medio y tipo de soporte

Se aborda el estudio de los atributos tipo de contenido, tipo de medio y tipo de soporte definidos por el c��digo de catalogaci��n Resource Description and Access (RDA) para solucionar los problemas que presentaba la lista de t��rminos utilizadas para registrar la designaci��n general de material (DGM) en las Anglo American Cataloging Rules (AACR). Los t��rminos eran ambiguos combinando aspectos referidos al contenido y clase de material del recurso. Se parte de una exhaustiva revisi��n bibliogr��fica y del estudio de los documentos que se generaron en el proceso de elaboraci��n del nuevo c��digo. Se menciona el trabajo conjunto entre el Joint Steering Committee (JSC) y el est��ndar ONIX para el establecimiento de criterios que permitieron definir estos tres atributos, as�� como el aporte del modelo FRBR en la definici��n de los mismos. Se presentan ejemplos de registros bibliogr��ficos donde se utilizan estos tres atributos en formato MARC21, ISBD consolidada a partir de la definici��n del ��rea 0 y en el esquema de metadatos Dublin Core. Se finaliza destacando la necesidad de continuar con investigaciones que permitan concluir sobre la adecuaci��n de estos tres atributos a las necesidades de los catalogadores, usuarios y a la realidad tecnol��gica

A syntactic approach to combining functional notation, lazy evaluation, and higher-order in LP systems

Nondeterminism and partially instantiated data structures give logic programming expressive power beyond that of functional programming. However, functional programming often provides convenient syntactic features, such as having a designated implicit output argument, which allow function cali nesting and sometimes results in more compact code. Functional programming also sometimes allows a more direct encoding of lazy evaluation, with its ability to deal with infinite data structures. We present a syntactic functional extensi��n, used in the Ciao system, which can be implemented in ISO-standard Prolog systems and covers function application, predefined evaluable functors, functional definitions, quoting, and lazy evaluation. The extensi��n is also composable with higher-order features and can be combined with other extensions to ISO-Prolog such as constraints. We also highlight the features of the Ciao system which help implementation and present some data on the overhead of using lazy evaluation with respect to eager evaluation.

Combining a Similar Coefficient Identification Algorithm with the Boundary Element Method

The boundary element method (BEM) has been applied successfully to many engineering problems during the last decades. Compared with domain type methods like the finite element method (FEM) or the finite difference method (FDM) the BEM can handle problems where the medium extends to infinity much easier than domain type methods as there is no need to develop special boundary conditions (quiet or absorbing boundaries) or infinite elements at the boundaries introduced to limit the domain studied. The determination of the dynamic stiffness of arbitrarily shaped footings is just one of these fields where the BEM has been the method of choice, especially in the 1980s. With the continuous development of computer technology and the available hardware equipment the size of the problems under study grew and, as the flop count for solving the resulting linear system of equations grows with the third power of the number of equations, there was a need for the development of iterative methods with better performance. In [1] the GMRES algorithm was presented which is now widely used for implementations of the collocation BEM. While the FEM results in sparsely populated coefficient matrices, the BEM leads, in general, to fully or densely populated ones, depending on the number of subregions, posing a serious memory problem even for todays computers. If the geometry of the problem permits the surface of the domain to be meshed with equally shaped elements a lot of the resulting coefficients will be calculated and stored repeatedly. The present paper shows how these unnecessary operations can be avoided reducing the calculation time as well as the storage requirement. To this end a similar coefficient identification algorithm (SCIA), has been developed and implemented in a program written in Fortran 90. The vertical dynamic stiffness of a single pile in layered soil has been chosen to test the performance of the implementation. The results obtained with the 3-d model may be compared with those obtained with an axisymmetric formulation which are considered to be the reference values as the mesh quality is much better. The entire 3D model comprises more than 35000 dofs being a soil region with 21168 dofs the biggest single region. Note that the memory necessary to store all coefficients of this single region is about 6.8 GB, an amount which is usually not available with personal computers. In the problem under study the interface zone between the two adjacent soil regions as well as the surface of the top layer may be meshed with equally sized elements. In this case the application of the SCIA leads to an important reduction in memory requirements. The maximum memory used during the calculation has been reduced to 1.2 GB. The application of the SCIA thus permits problems to be solved on personal computers which otherwise would require much more powerful hardware.

A general implementation framework for tabled CLP

This paper describes a framework to combine tabling evalua- tion and constraint logic programming (TCLP). While this combination has been studied previously from a theoretical point of view and some implementations exist, they either suffer from a lack of efficiency, flex- ibility, or generality, or have inherent limitations with respect to the programs they can execute to completion (either with success or fail- ure). Our framework addresses these issues directly, including the ability to check for answer / call entailment, which allows it to terminate in more cases than other approaches. The proposed framework is experimentally compared with existing solutions in order to provide evidence of the mentioned advantages.

Combining Text and Graphics for Interactive Exploration of Behavior Datasets

Modern sensor technologies and simulators applied to large and complex dynamic systems (such as road traffic networks, sets of river channels, etc.) produce large amounts of behavior data that are difficult for users to interpret and analyze. Software tools that generate presentations combining text and graphics can help users understand this data. In this paper we describe the results of our research on automatic multimedia presentation generation (including text, graphics, maps, images, etc.) for interactive exploration of behavior datasets. We designed a novel user interface that combines automatically generated text and graphical resources. We describe the general knowledge-based design of our presentation generation tool. We also present applications that we developed to validate the method, and a comparison with related work.

Bayesian scene analysis for multi-camera 3D tracking and camera positioning

Los sistemas de seguimiento mono-c��mara han demostrado su notable capacidad para el an��lisis de trajectorias de objectos m��viles y para monitorizaci��n de escenas de inter��s; sin embargo, tanto su robustez como sus posibilidades en cuanto a comprensi��n sem��ntica de la escena est��n fuertemente limitadas por su naturaleza local y monocular, lo que los hace insuficientes para aplicaciones realistas de videovigilancia. El objetivo de esta tesis es la extensi��n de las posibilidades de los sistemas de seguimiento de objetos m��viles para lograr un mayor grado de robustez y comprensi��n de la escena. La extensi��n propuesta se divide en dos direcciones separadas. La primera puede considerarse local, ya que est�� orientada a la mejora y enriquecimiento de las posiciones estimadas para los objetos m��viles observados directamente por las c��maras del sistema; dicha extensi��n se logra mediante el desarrollo de un sistema multi-c��mara de seguimiento 3D, capaz de proporcionar consistentemente las posiciones 3D de m��ltiples objetos a partir de las observaciones capturadas por un conjunto de sensores calibrados y con campos de visi��n solapados. La segunda extensi��n puede considerarse global, dado que su objetivo consiste en proporcionar un contexto global para relacionar las observaciones locales realizadas por una c��mara con una escena de mucho mayor tama��o; para ello se propone un sistema autom��tico de localizaci��n de c��maras basado en las trayectorias observadas de varios objetos m��viles y en un mapa esquem��tico de la escena global monitorizada. Ambas l��neas de investigaci��n se tratan utilizando, como marco com��n, t��cnicas de estimaci��n bayesiana: esta elecci��n est�� justificada por la versatilidad y flexibilidad proporcionada por dicho marco estad��stico, que permite la combinaci��n natural de m��ltiples fuentes de informaci��n sobre los par��metros a estimar, as�� como un tratamiento riguroso de la incertidumbre asociada a las mismas mediante la inclusi��n de modelos de observaci��n espec��ficamente dise��ados. Adem��s, el marco seleccionado abre grandes posibilidades operacionales, puesto que permite la creaci��n de diferentes m��todos num��ricos adaptados a las necesidades y caracter��sticas espec��ficas de distintos problemas tratados. El sistema de seguimiento 3D con m��ltiples c��maras propuesto est�� espec��ficamente dise��ado para permitir descripciones esquem��ticas de las medidas realizadas individualmente por cada una de las c��maras del sistema: esta elecci��n de dise��o, por tanto, no asume ning��n algoritmo espec��fico de detecci��n o seguimiento 2D en ninguno de los sensores de la red, y hace que el sistema propuesto sea aplicable a redes reales de vigilancia con capacidades limitadas tanto en t��rminos de procesamiento como de transmision. La combinaci��n robusta de las observaciones capturadas individualmente por las c��maras, ruidosas, incompletas y probablemente contaminadas por falsas detecciones, se basa en un metodo de asociaci��n bayesiana basado en geometr��a y color: los resultados de dicha asociaci��n permiten el seguimiento 3D de los objetos de la escena mediante el uso de un filtro de part��culas. El sistema de fusi��n de observaciones propuesto tiene, como principales caracter��sticas, una gran precisi��n en t��rminos de localizaci��n 3D de objetos, y una destacable capacidad de recuperaci��n tras eventuales errores debidos a un n��mero insuficiente de datos de entrada. El sistema autom��tico de localizaci��n de c��maras se basa en la observaci��n de m��ltiples objetos m��viles y un mapa esquem��tico de las ��reas transitables del entorno monitorizado para inferir la posici��n absoluta de dicho sensor. Para este prop��sito, se propone un novedoso marco bayesiano que combina modelos din��micos inducidos por el mapa en los objetos m��viles presentes en la escena con las trayectorias observadas por la c��mara, lo que representa un enfoque nunca utilizado en la literatura existente. El sistema de localizaci��n se divide en dos sub-tareas diferenciadas, debido a que cada una de estas tareas requiere del dise��o de algoritmos espec��ficos de muestreo para explotar en profundidad las caracter��sticas del marco desarrollado: por un lado, an��lisis de la ambig��edad del caso espec��ficamente tratado y estimaci��n aproximada de la localizaci��n de la c��mara, y por otro, refinado de la localizaci��n de la c��mara. El sistema completo, dise��ado y probado para el caso espec��fico de localizaci��n de c��maras en entornos de tr��fico urbano, podr��a tener aplicaci��n tambi��n en otros entornos y sensores de diferentes modalidades tras ciertas adaptaciones. ABSTRACT Mono-camera tracking systems have proved their capabilities for moving object trajectory analysis and scene monitoring, but their robustness and semantic possibilities are strongly limited by their local and monocular nature and are often insufficient for realistic surveillance applications. This thesis is aimed at extending the possibilities of moving object tracking systems to a higher level of scene understanding. The proposed extension comprises two separate directions. The first one is local, since is aimed at enriching the inferred positions of the moving objects within the area of the monitored scene directly covered by the cameras of the system; this task is achieved through the development of a multi-camera system for robust 3D tracking, able to provide 3D tracking information of multiple simultaneous moving objects from the observations reported by a set of calibrated cameras with semi-overlapping fields of view. The second extension is global, as is aimed at providing local observations performed within the field of view of one camera with a global context relating them to a much larger scene; to this end, an automatic camera positioning system relying only on observed object trajectories and a scene map is designed. The two lines of research in this thesis are addressed using Bayesian estimation as a general unifying framework. Its suitability for these two applications is justified by the flexibility and versatility of that stochastic framework, which allows the combination of multiple sources of information about the parameters to estimate in a natural and elegant way, addressing at the same time the uncertainty associated to those sources through the inclusion of models designed to this end. In addition, it opens multiple possibilities for the creation of different numerical methods for achieving satisfactory and efficient practical solutions to each addressed application. The proposed multi-camera 3D tracking method is specifically designed to work on schematic descriptions of the observations performed by each camera of the system: this choice allows the use of unspecific off-the-shelf 2D detection and/or tracking subsystems running independently at each sensor, and makes the proposal suitable for real surveillance networks with moderate computational and transmission capabilities. The robust combination of such noisy, incomplete and possibly unreliable schematic descriptors relies on a Bayesian association method, based on geometry and color, whose results allow the tracking of the targets in the scene with a particle filter. The main features exhibited by the proposal are, first, a remarkable accuracy in terms of target 3D positioning, and second, a great recovery ability after tracking losses due to insufficient input data. The proposed system for visual-based camera self-positioning uses the observations of moving objects and a schematic map of the passable areas of the environment to infer the absolute sensor position. To this end, a new Bayesian framework combining trajectory observations and map-induced dynamic models for moving objects is designed, which represents an approach to camera positioning never addressed before in the literature. This task is divided into two different sub-tasks, setting ambiguity analysis and approximate position estimation, on the one hand, and position refining, on the other, since they require the design of specific sampling algorithms to correctly exploit the discriminative features of the developed framework. This system, designed for camera positioning and demonstrated in urban traffic environments, can also be applied to different environments and sensors of other modalities after certain required adaptations.

Towards cost reduction in concentrating solar power: innovative design for an efficient fresnel based solar field

Energ��a termosolar (de concentraci��n) es uno de los nombres que hacen referencia en espa��ol al t��rmino ingl��s ���concentrating solar power���. Se trata de una tecnolog��a basada en la captura de la potencia t��rmica de la radiaci��n solar, de forma que permita alcanzar temperaturas capaces de alimentar un ciclo termodin��mico convencional (o avanzado); el futuro de esta tecnolog��a depende principalmente de su capacidad para concentrar la radiaci��n solar de manera eficiente y econ��mica. La presente tesis est�� orientada hacia la resoluci��n de ciertos problemas importantes relacionados con este objetivo. La mencionada necesidad de reducir costes en la concentraci��n de radiaci��n solar directa, asegurando el objetivo termodin��mico de calentar un fluido hasta una determinada temperatura, es de vital importancia. Los colectores lineales Fresnel han sido identificados en la literatura cient��fica como una tecnolog��a con gran potencial para alcanzar esta reducci��n de costes. Dicha tecnolog��a ha sido seleccionada por numerosas razones, entre las que destacan su gran libertad de dise��o y su actual estado inmaduro. Con el objetivo de responder a este desaf��o se desarrollado un detallado estudio de las propiedades ��pticas de los colectores lineales Fresnel, para lo cual se han utilizado m��todos anal��ticos y num��ricos de manera combinada. En primer lugar, se han usado unos modelos para la predicci��n de la localizaci��n y la irradiaci��n normal directa del sol junto a unas relaciones anal��ticas desarrolladas para estudiar el efecto de m��ltiples variables de dise��o en la energ��a incidente sobre los espejos. Del mismo modo, se han obtenido anal��ticamente los errores debidos al llamado ���off-axis aberration���, a la apertura de los rayos reflejados en los espejos y a las sombras y bloqueos entre espejos. Esto ha permitido la comparaci��n de diferentes formas de espejo ���planos, circulares o parab��licos���, as�� como el dise��o preliminar de la localizaci��n y anchura de los espejos y receptor sin necesidad de costosos m��todos num��ricos. En segundo lugar, se ha desarrollado un modelo de trazado de rayos de Monte Carlo con el objetivo de comprobar la validez del estudio anal��tico, pero sobre todo porque este no es preciso en el estudio de la reflexi��n en espejos. El c��digo desarrollado est�� espec��ficamente ideado para colectores lineales Fresnel, lo que ha permitido la reducci��n del tiempo de c��lculo en varios ��rdenes de magnitud en comparaci��n con un programa comercial m��s general. Esto justifica el desarrollo de un nuevo c��digo en lugar de la compra de una licencia de otro programa. El modelo ha sido usado primeramente para comparar la intensidad de flujo t��rmico y rendimiento de colectores Fresnel, con y sin reflector secundario, con los colectores cil��ndrico parab��licos. Finalmente, la conjunci��n de los resultados obtenidos en el estudio anal��tico con el programa num��rico ha sido usada para optimizar el campo solar para diferentes orientaciones ���Norte-Sur y Este-Oeste���, diferentes localizaciones ���Almer��a y Aswan���, diferentes inclinaciones hacia el Tr��pico ���desde 0 deg hasta 32 deg��� y diferentes m��nimos de intensidad del flujo en el centro del receptor ���10 kW/m2 y 25 kW/m2���. La presente tesis ha conducido a importantes descubrimientos que deben ser considerados a la hora de dise��ar un campo solar Fresnel. En primer lugar, los espejos utilizados no deben ser plano, sino cil��ndricos o parab��licos, ya que los espejos curvos implican mayores concentraciones y rendimiento. Por otro lado, se ha llegado a la conclusi��n de que la orientaci��n Este-Oeste es m��s propicia para localizaciones con altas latitudes, como Almer��a, mientras que en zonas m��s cercanas a los tr��picos como Aswan los campos Norte-Sur conducen a mayores rendimientos. Es de destacar que la orientaci��n Este-Oeste requiere aproximadamente la mitad de espejos que los campos Norte-Sur, puediendo estar inclinados hacia los Tr��picos para mejorar el rendimiento, y que alcanzan parecidos valores de intensidad t��rmica en el receptor todos los d��as a mediod��a. Sin embargo, los campos con orientaci��n Norte-Sur permiten un flujo m��s constante a lo largo de un d��a. Por ��ltimo, ha sido demostrado que el uso de dise��os pre-optimizados anal��ticamente, con anchura de espejos y espaciado entre espejos variables a lo ancho del campo, pueden implicar aumentos de la energ��a generada por metro cuadrado de espejos de hasta el 6%. El rendimiento ��ptico anual de los colectores cil��ndrico parab��licos es 23 % mayor que el rendimiento de los campos Fresnel en Almer��a, mientras que la diferencia es de solo 9 % en Aswan. Ello implica que, para alcanzar el mismo precio de electricidad que la tecnolog��a de referencia, la reducci��n de costes de instalaci��n por metro cuadrado de espejo debe estar entre el 10 % y el 25 %, y que los colectores lineales Fresnel tienen m��s posibilidades de ser desarrollados en zonas de bajas latitudes. Como consecuencia de los estudios desarrollados en esta tesis se ha patentado un sistema de almacenamiento que tiene en cuenta la variaci��n del flujo t��rmico en el receptor a lo largo del d��a, especialmente para campos con orientaci��n Este-Oeste. Este invento permitir��a el aprovechamiento de la energ��a incidente durante m��s parte del a��o, aumentando de manera apreciable los rendimientos ��ptico y t��rmico. Abstract Concentrating solar power is the common name of a technology based on capturing the thermal power of solar radiation, in a suitable way to reach temperatures able to activate a conventional (or advanced) thermodynamic cycle to generate electricity; this quest mainly depends on our ability to concentrate solar radiation in a cheap and efficient way. The present thesis is focused to highlight and help solving some of the important issues related to this problem. The need of reducing costs in concentrating the direct solar radiation, but without jeopardizing the thermodynamic objective of heating a fluid up to the required temperature, is of prime importance. Linear Fresnel collectors have been identified in the scientific literature as a technology with high potential to reach this cost reduction. This technology has been selected because of a number of reasons, particularly the degrees of freedom of this type of concentrating configuration and its current immature state. In order to respond to this challenge, a very detailed exercise has been carried out on the optical properties of linear Fresnel collectors. This has been done combining analytic and numerical methods. First, the effect of the design variables on the ratio of energy impinging onto the reflecting surface has been studied using analytically developed equations, together with models that predict the location and direct normal irradiance of the sun at any moment. Similarly, errors due to off-axis aberration, to the aperture of the reflected energy beam and to shading and blocking effects have been obtained analytically. This has allowed the comparison of different shapes of mirrors ���flat, cylindrical or parabolic���, as well as a preliminary optimization of the location and width of mirrors and receiver with no need of time-consuming numerical models. Second, in order to prove the validity of the analytic results, but also due to the fact that the study of the reflection process is not precise enough when using analytic equations, a Monte Carlo Ray Trace model has been developed. The developed code is designed specifically for linear Fresnel collectors, which has reduced the computing time by several orders of magnitude compared to a wider commercial software. This justifies the development of the new code. The model has been first used to compare radiation flux intensities and efficiencies of linear Fresnel collectors, both multitube receiver and secondary reflector receiver technologies, with parabolic trough collectors. Finally, the results obtained in the analytic study together with the numeric model have used in order to optimize the solar field for different orientations ���North-South and East-West���, different locations ���Almer��a and Aswan���, different tilts of the field towards the Tropic ���from 0 deg to 32 deg��� and different flux intensity minimum requirements ���10 kW/m2 and 25 kW/m2. This thesis work has led to several important findings that should be considered in the design of Fresnel solar fields. First, flat mirrors should not be used in any case, as cylindrical and parabolic mirrors lead to higher flux intensities and efficiencies. Second, it has been concluded that, in locations relatively far from the Tropics such as Almer��a, East-West embodiments are more efficient, while in Aswan North- South orientation leads to a higher annual efficiency. It must be noted that East-West oriented solar fields require approximately half the number of mirrors than NS oriented fields, can be tilted towards the Equator in order to increase the efficiency and attain similar values of flux intensity at the receiver every day at midday. On the other hand, in NS embodiments the flux intensity is more even during each single day. Finally, it has been proved that the use of analytic designs with variable shift between mirrors and variable width of mirrors across the field can lead to improvements in the electricity generated per reflecting surface square meter up to 6%. The annual optical efficiency of parabolic troughs has been found to be 23% higher than the efficiency of Fresnel fields in Almer��a, but it is only around 9% higher in Aswan. This implies that, in order to attain the same levelized cost of electricity than parabolic troughs, the required reduction of installation costs per mirror square meter is in the range of 10-25%. Also, it is concluded that linear Fresnel collectors are more suitable for low latitude areas. As a consequence of the studies carried out in this thesis, an innovative storage system has been patented. This system takes into account the variation of the flux intensity along the day, especially for East-West oriented solar fields. As a result, the invention would allow to exploit the impinging radiation along longer time every day, increasing appreciably the optical and thermal efficiencies.

BR3: a biologically inspired fish-like robot actuated by SMA-based artificial muscles

Los peces son animales, donde en la mayor��a de los casos, son considerados como nadadores muy eficientes y con una alta capacidad de maniobra. En general los peces se caracterizan por su capacidad de maniobra, locomoci��n silencioso, giros y partidas r��pidas y viajes de larga distancia. Los estudios han identificado varios tipos de locomoci��n que los peces usan para generar maniobras y nataci��n constante. A bajas velocidades la mayor��a de los peces utilizan sus aletas pares y / o impares para su locomoci��n, que ofrecen una mayor maniobrabilidad y mejor eficiencia de propulsi��n. A altas velocidades la locomoci��n implica el cuerpo y / o aleta caudal porque esto puede lograr un mayor empuje y aceleraci��n. Estas caracter��sticas pueden inspirar el diseo y fabricaci��n de una piel muy flexible, una aleta caudal m��rfica y una espina dorsal no articulada con una gran capacidad de maniobra. Esta tesis presenta el desarrollo de un novedoso pez robot bio-inspirado y biomim��tico llamado BR3, inspirado en la capacidad de maniobra y nado constante de los peces vertebrados. Inspirado por la morfolog��a de los peces Micropterus salmoides o tambi��n conocido como lubina negra, el robot BR3 utiliza su fundamento biol��gico para desarrollar modelos y m��todos matem��ticos precisos que permiten imitar la locomoci��n de los peces reales. Los peces Largemouth Bass pueden lograr un nivel incre��ble de maniobrabilidad y eficacia de la propulsi��n mediante la combinaci��n de los movimientos ondulatorios y aletas morficas. Para imitar la locomoci��n de los peces reales en una contraparte artificial se necesita del an��lisis de tecnolog��as de actuaci��n alternativos, como arreglos de fibras musculares en lugar de servo actuadores o motores DC est��ndar, as�� como un material flexible que proporciona una estructura continua sin juntas. Las aleaciones con memoria de forma (SMAs) proveen la posibilidad de construir robots livianos, que no emiten ruido, sin motores, sin juntas y sin engranajes. Asi es como un pez robot submarino se ha desarrollado y cuyos movimientos son generados mediante SMAs. Estos actuadores son los adecuados para doblar la espina dorsal continua del pez robot, que a su vez provoca un cambio en la curvatura del cuerpo. Este tipo de arreglo estructural est�� inspirado en los m��sculos rojos del pescado, que son usados principalmente durante la nataci��n constante para la flexi��n de una estructura flexible pero casi incompresible como lo es la espina dorsal de pescado. Del mismo modo la aleta caudal se basa en SMAs y se modifica para llevar a cabo el trabajo necesario. La estructura flexible proporciona empuje y permite que el BR3 nade. Por otro lado la aleta caudal m��rfica proporciona movimientos de balanceo y guiada. Motivado por la versatilidad del BR3 para imitar todos los modos de nataci��n (anguilliforme, carangiforme, subcarangiforme y tunniforme) se propone un controlador de doblado y velocidad. La ley de control de doblado y velocidad incorpora la informaci��n del ��ngulo de curvatura y de la frecuencia para producir el modo de nataci��n deseado y a su vez controlar la velocidad de nataci��n. As�� mismo de acuerdo con el hecho biol��gico de la influencia de la forma de la aleta caudal en la maniobrabilidad durante la nataci��n constante se propone un control de actitud. Esta novedoso robot pescado es el primero de su tipo en incorporar s��lo SMAs para doblar una estructura flexible continua y sin juntas y engranajes para producir empuje e imitar todos los modos de nataci��n, as�� como la aleta caudal que es capaz de cambiar su forma. Este novedoso diseo mecatr��nico presenta un futuro muy prometedor para el diseo de veh��culos submarinos capaces de modificar su forma y nadar mas eficientemente. La nueva metodolog��a de control propuesto en esta tesis proporcionan una forma totalmente nueva de control de robots basados en SMAs, haci��ndolos energ��ticamente m��s eficientes y la incorporaci��n de una aleta caudal m��rfica permite realizar maniobras m��s eficientemente. En su conjunto, el proyecto BR3 consta de cinco grandes etapas de desarrollo: ��� Estudio y an��lisis biol��gico del nado de los peces con el prop��sito de definir criterios de dise��o y control. ��� Formulaci��n de modelos matem��ticos que describan la: i) cinem��tica del cuerpo, ii) din��mica, iii) hidrodin��mica iv) an��lisis de los modos de vibraci��n y v) actuaci��n usando SMA. Estos modelos permiten estimar la influencia de modular la aleta caudal y el doblado del cuerpo en la producci��n de fuerzas de empuje y fuerzas de rotaci��n necesarias en las maniobras y optimizaci��n del consumo de energ��a. ��� Dise��o y fabricaci��n de BR3: i) estructura esquel��tica de la columna vertebral y el cuerpo, ii) mecanismo de actuaci��n basado en SMAs para el cuerpo y la aleta caudal, iii) piel artificial, iv) electr��nica embebida y v) fusi��n sensorial. Est�� dirigido a desarrollar la plataforma de pez robot BR3 que permite probar los m��todos propuestos. ��� Controlador de nado: compuesto por: i) control de las SMA (modulaci��n de la forma de la aleta caudal y regulaci��n de la actitud) y ii) control de nado continuo (modulaci��n de la velocidad y doblado). Est�� dirigido a la formulaci��n de los m��todos de control adecuados que permiten la modulaci��n adecuada de la aleta caudal y el cuerpo del BR3. ��� Experimentos: est�� dirigido a la cuantificaci��n de los efectos de: i) la correcta modulaci��n de la aleta caudal en la producci��n de rotaci��n y su efecto hidrodin��mico durante la maniobra, ii) doblado del cuerpo para la producci��n de empuje y iii) efecto de la flexibilidad de la piel en la habilidad para doblarse del BR3. Tambi��n tiene como objetivo demostrar y validar la hip��tesis de mejora en la eficiencia de la nataci��n y las maniobras gracias a los nuevos m��todos de control presentados en esta tesis. A lo largo del desarrollo de cada una de las cinco etapas, se ir��n presentando los retos, problem��ticas y soluciones a abordar. Los experimentos en canales de agua estar��n orientados a discutir y demostrar c��mo la aleta caudal y el cuerpo pueden afectar considerablemente la din��mica / hidrodin��mica de nataci��n / maniobras y c��mo tomar ventaja de la modulaci��n de curvatura que la aleta caudal m��rfica y el cuerpo permiten para cambiar correctamente la geometr��a de la aleta caudal y del cuerpo durante la nataci��n constante y maniobras. ABSTRACT Fishes are animals where in most cases are considered as highly manoeuvrable and effortless swimmers. In general fishes are characterized for his manoeuvring skills, noiseless locomotion, rapid turning, fast starting and long distance cruising. Studies have identified several types of locomotion that fish use to generate maneuvering and steady swimming. At low speeds most fishes uses median and/or paired fins for its locomotion, offering greater maneuverability and better propulsive efficiency At high speeds the locomotion involves the body and/or caudal fin because this can achieve greater thrust and accelerations. This can inspire the design and fabrication of a highly deformable soft artificial skins, morphing caudal fins and non articulated backbone with a significant maneuverability capacity. This thesis presents the development of a novel bio-inspired and biomimetic fishlike robot (BR3) inspired by the maneuverability and steady swimming ability of ray-finned fishes (Actinopterygii, bony fishes). Inspired by the morphology of the Largemouth Bass fish, the BR3 uses its biological foundation to develop accurate mathematical models and methods allowing to mimic fish locomotion. The Largemouth Bass fishes can achieve an amazing level of maneuverability and propulsive efficiency by combining undulatory movements and morphing fins. To mimic the locomotion of the real fishes on an artificial counterpart needs the analysis of alternative actuation technologies more likely muscle fiber arrays instead of standard servomotor actuators as well as a bendable material that provides a continuous structure without joins. The Shape Memory Alloys (SMAs) provide the possibility of building lightweight, joint-less, noise-less, motor-less and gear-less robots. Thus a swimming underwater fish-like robot has been developed whose movements are generated using SMAs. These actuators are suitable for bending the continuous backbone of the fish, which in turn causes a change in the curvature of the body. This type of structural arrangement is inspired by fish red muscles, which are mainly recruited during steady swimming for the bending of a flexible but nearly incompressible structure such as the fishbone. Likewise the caudal fin is based on SMAs and is customized to provide the necessary work out. The bendable structure provides thrust and allows the BR3 to swim. On the other hand the morphing caudal fin provides roll and yaw movements. Motivated by the versatility of the BR3 to mimic all the swimming modes (anguilliform, caranguiform, subcaranguiform and thunniform) a bending-speed controller is proposed. The bending-speed control law incorporates bend angle and frequency information to produce desired swimming mode and swimming speed. Likewise according to the biological fact about the influence of caudal fin shape in the maneuverability during steady swimming an attitude control is proposed. This novel fish robot is the first of its kind to incorporate only SMAs to bend a flexible continuous structure without joints and gears to produce thrust and mimic all the swimming modes as well as the caudal fin to be morphing. This novel mechatronic design is a promising way to design more efficient swimming/morphing underwater vehicles. The novel control methodology proposed in this thesis provide a totally new way of controlling robots based on SMAs, making them more energy efficient and the incorporation of a morphing caudal fin allows to perform more efficient maneuvers. As a whole, the BR3 project consists of five major stages of development: ��� Study and analysis of biological fish swimming data reported in specialized literature aimed at defining design and control criteria. ��� Formulation of mathematical models for: i) body kinematics, ii) dynamics, iii) hydrodynamics, iv) free vibration analysis and v) SMA muscle-like actuation. It is aimed at modelling the e ects of modulating caudal fin and body bend into the production of thrust forces for swimming, rotational forces for maneuvering and energy consumption optimisation. ��� Bio-inspired design and fabrication of: i) skeletal structure of backbone and body, ii) SMA muscle-like mechanisms for the body and caudal fin, iii) the artificial skin, iv) electronics onboard and v) sensor fusion. It is aimed at developing the fish-like platform (BR3) that allows for testing the methods proposed. ��� The swimming controller: i) control of SMA-muscles (morphing-caudal fin modulation and attitude regulation) and ii) steady swimming control (bend modulation and speed modulation). It is aimed at formulating the proper control methods that allow for the proper modulation of BR3���s caudal fin and body. ��� Experiments: it is aimed at quantifying the effects of: i) properly caudal fin modulation into hydrodynamics and rotation production for maneuvering, ii) body bending into thrust generation and iii) skin flexibility into BR3 bending ability. It is also aimed at demonstrating and validating the hypothesis of improving swimming and maneuvering efficiency thanks to the novel control methods presented in this thesis. This thesis introduces the challenges and methods to address these stages. Waterchannel experiments will be oriented to discuss and demonstrate how the caudal fin and body can considerably affect the dynamics/hydrodynamics of swimming/maneuvering and how to take advantage of bend modulation that the morphing-caudal fin and body enable to properly change caudal fin and body��� geometry during steady swimming and maneuvering.

Bayesian scene analysis for multi-camera 3D tracking and camera positioning

Los sistemas de seguimiento mono-c��mara han demostrado su notable capacidad para el an��lisis de trajectorias de objectos m��viles y para monitorizaci��n de escenas de inter��s; sin embargo, tanto su robustez como sus posibilidades en cuanto a comprensi��n sem��ntica de la escena est��n fuertemente limitadas por su naturaleza local y monocular, lo que los hace insuficientes para aplicaciones realistas de videovigilancia. El objetivo de esta tesis es la extensi��n de las posibilidades de los sistemas de seguimiento de objetos m��viles para lograr un mayor grado de robustez y comprensi��n de la escena. La extensi��n propuesta se divide en dos direcciones separadas. La primera puede considerarse local, ya que est�� orientada a la mejora y enriquecimiento de las posiciones estimadas para los objetos m��viles observados directamente por las c��maras del sistema; dicha extensi��n se logra mediante el desarrollo de un sistema multi-c��mara de seguimiento 3D, capaz de proporcionar consistentemente las posiciones 3D de m��ltiples objetos a partir de las observaciones capturadas por un conjunto de sensores calibrados y con campos de visi��n solapados. La segunda extensi��n puede considerarse global, dado que su objetivo consiste en proporcionar un contexto global para relacionar las observaciones locales realizadas por una c��mara con una escena de mucho mayor tama��o; para ello se propone un sistema autom��tico de localizaci��n de c��maras basado en las trayectorias observadas de varios objetos m��viles y en un mapa esquem��tico de la escena global monitorizada. Ambas l��neas de investigaci��n se tratan utilizando, como marco com��n, t��cnicas de estimaci��n bayesiana: esta elecci��n est�� justificada por la versatilidad y flexibilidad proporcionada por dicho marco estad��stico, que permite la combinaci��n natural de m��ltiples fuentes de informaci��n sobre los par��metros a estimar, as�� como un tratamiento riguroso de la incertidumbre asociada a las mismas mediante la inclusi��n de modelos de observaci��n espec��ficamente dise��ados. Adem��s, el marco seleccionado abre grandes posibilidades operacionales, puesto que permite la creaci��n de diferentes m��todos num��ricos adaptados a las necesidades y caracter��sticas espec��ficas de distintos problemas tratados. El sistema de seguimiento 3D con m��ltiples c��maras propuesto est�� espec��ficamente dise��ado para permitir descripciones esquem��ticas de las medidas realizadas individualmente por cada una de las c��maras del sistema: esta elecci��n de dise��o, por tanto, no asume ning��n algoritmo espec��fico de detecci��n o seguimiento 2D en ninguno de los sensores de la red, y hace que el sistema propuesto sea aplicable a redes reales de vigilancia con capacidades limitadas tanto en t��rminos de procesamiento como de transmision. La combinaci��n robusta de las observaciones capturadas individualmente por las c��maras, ruidosas, incompletas y probablemente contaminadas por falsas detecciones, se basa en un metodo de asociaci��n bayesiana basado en geometr��a y color: los resultados de dicha asociaci��n permiten el seguimiento 3D de los objetos de la escena mediante el uso de un filtro de part��culas. El sistema de fusi��n de observaciones propuesto tiene, como principales caracter��sticas, una gran precisi��n en t��rminos de localizaci��n 3D de objetos, y una destacable capacidad de recuperaci��n tras eventuales errores debidos a un n��mero insuficiente de datos de entrada. El sistema autom��tico de localizaci��n de c��maras se basa en la observaci��n de m��ltiples objetos m��viles y un mapa esquem��tico de las ��reas transitables del entorno monitorizado para inferir la posici��n absoluta de dicho sensor. Para este prop��sito, se propone un novedoso marco bayesiano que combina modelos din��micos inducidos por el mapa en los objetos m��viles presentes en la escena con las trayectorias observadas por la c��mara, lo que representa un enfoque nunca utilizado en la literatura existente. El sistema de localizaci��n se divide en dos sub-tareas diferenciadas, debido a que cada una de estas tareas requiere del dise��o de algoritmos espec��ficos de muestreo para explotar en profundidad las caracter��sticas del marco desarrollado: por un lado, an��lisis de la ambig��edad del caso espec��ficamente tratado y estimaci��n aproximada de la localizaci��n de la c��mara, y por otro, refinado de la localizaci��n de la c��mara. El sistema completo, dise��ado y probado para el caso espec��fico de localizaci��n de c��maras en entornos de tr��fico urbano, podr��a tener aplicaci��n tambi��n en otros entornos y sensores de diferentes modalidades tras ciertas adaptaciones. ABSTRACT Mono-camera tracking systems have proved their capabilities for moving object trajectory analysis and scene monitoring, but their robustness and semantic possibilities are strongly limited by their local and monocular nature and are often insufficient for realistic surveillance applications. This thesis is aimed at extending the possibilities of moving object tracking systems to a higher level of scene understanding. The proposed extension comprises two separate directions. The first one is local, since is aimed at enriching the inferred positions of the moving objects within the area of the monitored scene directly covered by the cameras of the system; this task is achieved through the development of a multi-camera system for robust 3D tracking, able to provide 3D tracking information of multiple simultaneous moving objects from the observations reported by a set of calibrated cameras with semi-overlapping fields of view. The second extension is global, as is aimed at providing local observations performed within the field of view of one camera with a global context relating them to a much larger scene; to this end, an automatic camera positioning system relying only on observed object trajectories and a scene map is designed. The two lines of research in this thesis are addressed using Bayesian estimation as a general unifying framework. Its suitability for these two applications is justified by the flexibility and versatility of that stochastic framework, which allows the combination of multiple sources of information about the parameters to estimate in a natural and elegant way, addressing at the same time the uncertainty associated to those sources through the inclusion of models designed to this end. In addition, it opens multiple possibilities for the creation of different numerical methods for achieving satisfactory and efficient practical solutions to each addressed application. The proposed multi-camera 3D tracking method is specifically designed to work on schematic descriptions of the observations performed by each camera of the system: this choice allows the use of unspecific off-the-shelf 2D detection and/or tracking subsystems running independently at each sensor, and makes the proposal suitable for real surveillance networks with moderate computational and transmission capabilities. The robust combination of such noisy, incomplete and possibly unreliable schematic descriptors relies on a Bayesian association method, based on geometry and color, whose results allow the tracking of the targets in the scene with a particle filter. The main features exhibited by the proposal are, first, a remarkable accuracy in terms of target 3D positioning, and second, a great recovery ability after tracking losses due to insufficient input data. The proposed system for visual-based camera self-positioning uses the observations of moving objects and a schematic map of the passable areas of the environment to infer the absolute sensor position. To this end, a new Bayesian framework combining trajectory observations and map-induced dynamic models for moving objects is designed, which represents an approach to camera positioning never addressed before in the literature. This task is divided into two different sub-tasks, setting ambiguity analysis and approximate position estimation, on the one hand, and position refining, on the other, since they require the design of specific sampling algorithms to correctly exploit the discriminative features of the developed framework. This system, designed for camera positioning and demonstrated in urban traffic environments, can also be applied to different environments and sensors of other modalities after certain required adaptations.