Is Menopause Optimal?

Various theories have been put forward to explain the fact that humans experience menopause while virtually no animals do. This paper aims to investigate one such theory: children provide a savings technology into old age, but as human babies are usually large and have long gestation periods, a substantial risk of death exists for the mother as she bears children. It seems therefore appropriate to impose a stopping rule for fertility. Given an objective (support for old age) and demographics (mortality of mother and children), an optimal age for menopause can be calculated. Using demographic data from populations that have seen little influence from modern medicine, this optimal age is compared to empirical evidence.

The impact of 1995--1996 health sector reforms in the effectiveness of malaria control program in the state of Orissa, India

Malaria poses a significant public health problem worldwide. The World Health Organization indicates that approximately 40% of the world's population and almost 85% of the population from the South–East Asian region is at risk of contracting malaria. India being the most populous country in the region, contributes the highest number of malaria cases and deaths attributed to malaria. Orissa is the state that has the highest number of malaria cases and deaths attributable to malaria. A secondary data analysis was carried out to evaluate the effectiveness of the World bank-assisted Malaria Action Program in the state of Orissa under the health sector reforms of 1995-96. The secondary analysis utilized the government of India's National Anti Malaria Management Information System's (NAMMIS) surveillance data and the National Family Health Survey (NFHS–I and NFHS–II) datasets to compare the malaria mortality and morbidity in the state between 1992-93 and 1998-99. Results revealed no effect of the intervention and indicated an increase of 2.18 times in malaria mortality between 1992-1999 and an increase of 1.53 times in malaria morbidity between 1992-93 and 1998-99 in the state. The difference in the age-adjusted malaria morbidity in the state between the time periods of 1992-93 and 1998-99 proved to be highly significant (t = 4.29 df=16, p<. 0005) whereas the difference between the increase of age-adjusted malaria morbidity during 1992-93 and 1998-99 between Orissa (with intervention) and Bihar (no intervention) proved to be non significant (t=.0471 df=16, p<.50). Factors such as underutilization of World Bank funds for the malaria control program, inadequate health care infrastructure, structural adjustment problems, poor management, poor financial management, parasite resistance to anti-malarial drugs, inadequate supply of drugs and staff shortages may have contributed to the failure of the program in the state.^

Control of the master virulence regulatory gene atxA in Bacillus anthracis

Transcription of the Bacillus anthracis structural genes for the anthrax toxin proteins and biosynthetic operon for capsule are positively regulated by AtxA, a transcription regulator with unique properties. Consistent with the role of atxA in virulence factor expression, a B. anthracis atxA-null mutant is avirulent in a murine model for anthrax. In batch culture, multiple signals impact atxA transcript levels, and the timing and steady state level of atxA expression is critical for optimal toxin and capsule synthesis. Despite the apparent complex control of atxA transcription, only one trans-acting protein, the transition state regulator AbrB, has been demonstrated to directly interact with the atxA promoter. The AbrB-binding site has been described, but additional cis-acting control sequences have not been defined. Using transcriptional lacZ fusions, electrophoretic mobility shift assays, and Western blot analysis, the cis-acting elements and trans-acting factors involved in regulation of atxA in B. anthracis strains containing either both virulence plasmids, pXO1 and pXO2, or only one plasmid, pXO1, were studied. This work demonstrates that atxA transcription from the major start site P1 is dependent upon a consensus sequence for the housekeeping sigma factor SigA, and an A+T-rich upstream element (UP-element) for RNA polymerase (RNAP). In addition, the data show that a trans-acting protein(s) other than AbrB negatively impacts atxA transcription when it binds specifically to a 9-bp palindrome within atxA promoter sequences located downstream of P1. Mutation of the palindrome prevents binding of the trans-acting protein(s) and results in a corresponding increase in AtxA and anthrax toxin production in a strain- and culture-dependent manner. The identity of the trans-acting repressor protein(s) remains elusive; however, phenotypes associated with mutation of the repressor binding site have revealed that the trans-acting repressor protein(s) indirectly controls B. anthracis development. Mutation of the repressor binding site results in misregulation and overexpression of AtxA in conditions conducive for development, leading to a marked sporulation defect that is both atxA- and pXO2-61-dependent. pXO2-61 is homologous to the sensor domain of sporulation sensor histidine kinases and is proposed to titrate an activating signal away from the sporulation phosphorelay when overexpressed by AtxA. These results indicate that AtxA is not only a master virulence regulator, but also a modulator of proper B. anthracis development. Also demonstrated in this work is the impact of the developmental regulators AbrB, Spo0A, and SigH on atxA expression and anthrax toxin production in a genetically incomplete (pXO1+, pXO2-) and genetically complete (pXO1+, pXO2+) strain background. AtxA and anthrax toxin production resulting from deletion of the developmental regulators are strain-dependent suggesting that factors on pXO2 are involved in control of atxA. The only developmental deletion mutant that resulted in a prominent and consistent strain-independent increase in AtxA protein levels was an abrB-null mutant. As a result of increased AtxA levels, there is early and increased production of anthrax toxins in an abrB-null mutant. In addition, the abrB-null mutant exhibited an increase in virulence in a murine model for anthrax. In contrast, virulence of the atxA promoter mutant was unaffected in a murine model for anthrax despite the production of 5-fold more AtxA than the abrB-null mutant. These results imply that AtxA is not the only factor impacting pathogenesis in an abrB-null mutant. Overall, this work highlights the complex regulatory network that governs expression of atxA and provides an additional role for AtxA in B. anthracis development.

Optimal, minimax, and Bayesian two-stage designs in two-dose phase II clinical trials

Background: For most cytotoxic and biologic anti-cancer agents, the response rate of the drug is commonly assumed to be non-decreasing with an increasing dose. However, an increasing dose does not always result in an appreciable increase in the response rate. This may especially be true at high doses for a biologic agent. Therefore, in a phase II trial the investigators may be interested in testing the anti-tumor activity of a drug at more than one (often two) doses, instead of only at the maximum tolerated dose (MTD). This way, when the lower dose appears equally effective, this dose can be recommended for further confirmatory testing in a phase III trial under potential long-term toxicity and cost considerations. A common approach to designing such a phase II trial has been to use an independent (e.g., Simon's two-stage) design at each dose ignoring the prior knowledge about the ordering of the response probabilities at the different doses. However, failure to account for this ordering constraint in estimating the response probabilities may result in an inefficient design. In this dissertation, we developed extensions of Simon's optimal and minimax two-stage designs, including both frequentist and Bayesian methods, for two doses that assume ordered response rates between doses. ^ Methods: Optimal and minimax two-stage designs are proposed for phase II clinical trials in settings where the true response rates at two dose levels are ordered. We borrow strength between doses using isotonic regression and control the joint and/or marginal error probabilities. Bayesian two-stage designs are also proposed under a stochastic ordering constraint. ^ Results: Compared to Simon's designs, when controlling the power and type I error at the same levels, the proposed frequentist and Bayesian designs reduce the maximum and expected sample sizes. Most of the proposed designs also increase the probability of early termination when the true response rates are poor. ^ Conclusion: Proposed frequentist and Bayesian designs are superior to Simon's designs in terms of operating characteristics (expected sample size and probability of early termination, when the response rates are poor) Thus, the proposed designs lead to more cost-efficient and ethical trials, and may consequently improve and expedite the drug discovery process. The proposed designs may be extended to designs of multiple group trials and drug combination trials.^

Separation of Control and Cash-Flow Rights of State Owned Listed Enterprises: Channels of Expropriation after the Discriminated Share Reform in China

Literature on agency problems arising between controlling and minority owners claim that separation of cash flow and control rights allows controllers to expropriate listed firms, and further that separation emerges when dual class shares or pyramiding corporate structures exist. Dual class share and pyramiding coexisted in listed companies of China until discriminated share reform was implemented in 2005. This paper presents a model of controller to expropriate behavior as well as empirical tests of expropriation via particular accounting items and pyramiding generated expropriation. Results show that expropriation is apparent for state controlled listed companies. While reforms have weakened the power to expropriate, separation remains and still generates expropriation. Size of expropriation is estimated to be 7 to 8 per cent of total asset at mean. If the "one share, one vote" principle were to be realized, asset inflation could be reduced by 13 percent.

Estrategias para el control microclimático del espacio entre edificaciones en clima cálido – húmedo

La presente investigación parte del problema en las zonas de clima cálido - húmedo en las cuales se producen impactos asociados a la incomodidad térmica producto de la intensa radiación solar, altas temperaturas y elevada humedad. Estos factores reducen la calidad de los espacios abiertos y desarrollan en la población una actitud de rechazo hacia el uso del microespacio urbano entre edificaciones en los desarrollos urbanos - conjuntos urbanos - , los mismos frecuentemente admiten soluciones que al parecer no contribuyen a la realización de las actividades comunes de esparcimiento de la población residente. Por lo tanto, el objetivo de la investigación es profundizar en la temática urbano - ambiental - social y el diseño urbano vinculada a la particularidad morfológica local, las condiciones microclimáticas, el uso del microespacio y los requerimientos de los usuarios. La finalidad de desarrollar estrategias de control microclimático del microespacio entre edificios en clima cálido - húmedo en búsqueda de soluciones óptimas que satisfagan las necesidades de los usuarios de los espacios exteriores en estas áreas residenciales. La investigación se centra en el estudio de las particularidades contextuales relacionadas con el microclima y las características urbanas - morfotipológicas, básicamente los factores microclimáticos (soleamiento y ventilación), los morfológicos y edificatorios y las características de las superficies (pavimentos). En coherencia con el objetivo propuesto el trabajo se desarrolla en cuatro fases: la primera aborda la revisión documental, literatura relevante e investigaciones relativas a la calidad ambiental, medio social, medio físico, el microespacio urbano, control y diseño sostenible, modelización proyectual y estrategias sostenibles; la segunda fase se refiere al marco contextual, características urbanas, datos climáticos locales, planes y procesos urbanos, tipologías y conformación urbana. En esta fase se describe el proceso de selección, análisis y evaluación urbano - ambiental de los casos de estudio (conjuntos residenciales). En la tercera fase se aborda el marco evaluativo y estudio de casos, consideraciones físicas, climáticas y valoración térmico - ambiental de los conjuntos residenciales seleccionados. En esta fase se aplican Técnicas Estadísticas y de Simulación Computacional y se analizan los resultados obtenidos. Finalmente, la cuarta fase propositiva incluye el establecimiento de Estrategias, Principios y Lineamientos de optimación térmica y se exponen las Conclusiones parciales de la tesis, alcances y perspectivas futuras. Finalmente, los resultados obtenidos en la investigación demuestran que el análisis en las experiencias de la realidad permiten comprobar que las situaciones y alteraciones ambientales sustanciales, los niveles de afectación térmica y las condiciones de confortabilidad e impacto derivan de las características urbanas, los componentes del microespacio y de las condiciones climáticas las cuales afectan el desarrollo de las actividades y el uso efectivo del microespacio entre edificios. El análisis de los factores morfo - climáticos incidentes y el estudio de los efectos de interacción contribuyen al establecimiento de Principios y Lineamientos para la evaluación y diseño sostenible del microespacio entre edificios y el uso correcto de los elementos del clima en estas áreas urbanas destinadas a la actividad social y al esparcimiento de la población residente. ABSTRACT This research starts from the problem of hot - humid climate zones where impacts related to thermal discomfort are produced as a result from the intense solar radiation and high temperatures and humidity. These factors reduce the quality of open spaces and people develop an attitude of rejection towards the use of urban microspace among buildings within urban developments - urban complexes - . Usually, these complexes admit solutions that apparently do not contribute to the achievement of common leisure activities in the resident dwellers. Therefore, the main purpose of this research is to deepen in the urban - environmental - social issue and urban design linked to the local morphological particularity, microclimate conditions, use of microspace and users’ requirements. In order to develop microclimate control strategies of microspace among buildings in hot - humid climate to look for optimal solutions that satisfy users’ needs of outdoors spaces in these residential areas. The research focuses in the study of contextual particularities related to microclimate and urban - morphotypological characteristics. Basically, microclimate (sunlight and ventilation), morphological and building factors as well as road surface characteristics. According to the proposed objective, this research is developed in four phases: the first one considers documentary review, relevant literature and researches related to environmental quality, social environment, physical environment, urban microspace, control and sustainable design, project modelling and sustainable strategies; while the second phase refers to contextual framework, urban characteristics, local climate data, plans and urban processes, typologies and urban structure. In this phase, the process of selection, analysis and urban - environmental evaluation of case studies (residential complexes) is described. The third phase approaches the assessment framework and case studies, physical and climate considerations as well as environmental - thermal evaluation of selected residential complexes. In this phase, statistical techniques and computational simulations are applied. Likewise, results obtained are analysed. Similarly, fourth and proposing phase includes the establishment of strategies, principles and guidelines of thermal optimization and partial conclusions of the thesis, scopes and future perspectives are exposed. Finally, from the results obtained, it is demonstrated that the analysis on reality experiences allow proving that situations and substantial environmental changes, levels of thermal affectations, comfort conditions and impact derive from urban characteristics, microspace components and from climate conditions which affect the development of activities and the effective use of microspace among buildings. The analysis of incidental morpho - climate factors and the study of interaction effects contribute to the establishment of principles and guidelines for the assessment and sustainable design of microspace among buildings as well as the correct use of climate elements in these urban areas oriented to social and leisure activities of resident population.

Current Mode with RMS Voltage and Offset Control Loops for a Single-Phase Aircraft Inverter Suitable for Parallel and 3-Phase Operation Modes

Rms voltage regulation may be an attractive possibility for controlling power inverters. Combined with a Hall Effect sensor for current control, it keeps its parallel operation capability while increasing its noise immunity, which may lead to a reduction of the Total Harmonic Distortion (THD). Besides, as voltage regulation is designed in DC, a simple PI regulator can provide accurate voltage tracking. Nevertheless, this approach does not lack drawbacks. Its narrow voltage bandwidth makes transients last longer and it increases the voltage THD when feeding non-linear loads, such as rectifying stages. On the other hand, the implementation can fall into offset voltage error. Furthermore, the information of the output voltage phase is hidden for the control as well, making the synchronization of a 3-phase setup not trivial. This paper explains the concept, design and implementation of the whole control scheme, in an on board inverter able to run in parallel and within a 3-phase setup. Special attention is paid to solve the problems foreseen at implementation level: a third analog loop accounts for the offset level is added and a digital algorithm guarantees 3-phase voltage synchronization.

Automatic lateral control for unmanned vehicles via genetic algorithms

It is known that the techniques under the topic of Soft Computing have a strong capability of learning and cognition, as well as a good tolerance to uncertainty and imprecision. Due to these properties they can be applied successfully to Intelligent Vehicle Systems; ITS is a broad range of technologies and techniques that hold answers to many transportation problems. The unmannedcontrol of the steering wheel of a vehicle is one of the most important challenges facing researchers in this area. This paper presents a method to adjust automatically a fuzzy controller to manage the steering wheel of a mass-produced vehicle; to reach it, information about the car state while a human driver is handling the car is taken and used to adjust, via iterative geneticalgorithms an appropriated fuzzy controller. To evaluate the obtained controllers, it will be considered the performance obtained in the track following task, as well as the smoothness of the driving carried out.

On the practical uselessness of structural designs derived from some theoretical optimal solutions

A recent study by Pichugin et al. recall the Hemp’s solution for uniform load of 1974, showing that if allowable tensile and compressive stresses are unequal then the Hemp’s arch is optimal provided the ratio of stresses falls within a certain interval. This work is undoubtedly an important pass forward to find an optimal solution for the mathematical problem stated by Hemp. Furthermore, the Authors suggest that their optimal solutions are potentially reasonable from a practical perspective for materials with more allowable compressive stress than tensile one, as this kind of materials used to be not too much expensive. In this paper we profoundly analyse the solutions of the Authors from this practical perspective finding that the original Hemp’s solution —albeit sub-optimal for the mathematical problem— leads to real designs that are more efficient than the theoretic optimal solutions of the Authors.We show that the reasons for this shocking fact has to do with the class of problems considered by Hemp and the Authors.

The Optimal combination: Grammatical Swarm, Particle Swarm Optimization and Neural Networks.

Social behaviour is mainly based on swarm colonies, in which each individual shares its knowledge about the environment with other individuals to get optimal solutions. Such co-operative model differs from competitive models in the way that individuals die and are born by combining information of alive ones. This paper presents the particle swarm optimization with differential evolution algorithm in order to train a neural network instead the classic back propagation algorithm. The performance of a neural network for particular problems is critically dependant on the choice of the processing elements, the net architecture and the learning algorithm. This work is focused in the development of methods for the evolutionary design of artificial neural networks. This paper focuses in optimizing the topology and structure of connectivity for these networks.

Analysis of the geometric altimetry to support aircraft optimal profiles within future 4D trajectory management

The use of barometric altimetry is to some extent a limiting factor on safety, predictability and efficiency of aircraft operations, and reduces the potential of the trajectory based operations capabilities. However, geometric altimetry could be used to improve all of these aspects. Nowadays aircraft altitude is estimated by applying the International Standard Atmosphere which differs from real altitude. At different temperatures for an assigned barometric altitude, aerodynamic forces are different and this has a direct relationship with time, fuel consumption and range of the flight. The study explores the feasibility of using sensors providing geometric reference altitude, in particular, to supply capabilities for the optimization of vertical profiles and also, their impact on the vertical Air Traffic Management separation assurance processes. One of the aims of the thesis is to assess if geometric altitude fulfils the aeronautical requirements through existing sensors. Also the thesis will elaborate on the advantages of geometric altitude over the barometric altitude in terms of efficiency for vertical navigation. The evidence that geometric altitude is the best choice to improve the efficiency in vertical profile and aircraft capacity by reducing vertical uncertainties will also be shown. In this paper, an atmospheric study is presented, as well as the impact of temperature deviation from International Standard Atmosphere model is analyzed in order to obtain relationship between geometric and barometric altitude. Furthermore, an aircraft model to study aircraft vertical profile is provided to analyse trajectories based on geometric altitudes.

Goal-oriented self-adaptive hp-strategies for finite element analysis of electromagnetic scattering and radiation problems

In this paper, a fully automatic goal-oriented hp-adaptive finite element strategy for open region electromagnetic problems (radiation and scattering) is presented. The methodology leads to exponential rates of convergence in terms of an upper bound of an user-prescribed quantity of interest. Thus, the adaptivity may be guided to provide an optimal error, not globally for the field in the whole finite element domain, but for specific parameters of engineering interest. For instance, the error on the numerical computation of the S-parameters of an antenna array, the field radiated by an antenna, or the Radar Cross Section on given directions, can be minimized. The efficiency of the approach is illustrated with several numerical simulations with two dimensional problem domains. Results include the comparison with the previously developed energy-norm based hp-adaptivity.

Control de vibraciones en pasarelas peatonales

En los últimos años se ha construido un gran número de pasarelas peatonales como respuesta a la demanda de nuevas vías de paso en las ciudades. Estas estructuras tienen requisitos constructivos menos exigentes en comparación con otros tipos de puentes, lo cual ha facilitado el desarrollo de diseños con nuevos esquemas resistentes, complicadas geometrías y el empleo de nuevos materiales. En general estas estructuras son esbeltas, ligeras y poco amortiguadas, lo que en ocasiones ha generado problemas de vi-braciones al paso de peatones una vez puestas en servicio. Las normativas actuales son cada vez más sensibles a esta problemática, recomendando diseños cuyas frecuencias naturales deben estar alejadas de los rangos de frecuencia de paso típicos de los peatones y fijando límites de confort en forma de valores máximos de aceleración permitidos, asegurándose así un correcto comportamiento de la estructura. En el presente artículo se analiza esta problemática desde un punto de vista práctico. Para ello se muestran los puntos clave de las normativas y guías de diseño de pasarelas que se pueden encontrar actualmente en la bibliografía, se presentan las técnicas que habitualmente se emplean en el análisis dinámico experimental de estas estructuras, y se comentan las soluciones a las que generalmente se recurre para mejorar su comportamiento dinámico. Por último, se muestran los trabajos llevados a cabo por el Centro Tecnológico CARTIF en colaboración con las Universidades de Valladolid y Castilla-La Mancha en la pasarela peatonal del Museo de la Ciencia de Valladolid. Estos trabajos incluyen: (1) el estudio dinámico de los tres vanos metálicos de dicha pasarela, (2) el diseño e implementación de un amortiguador de masa sintonizado en el vano más sensible a las vibraciones, (3) la implementación de un amortiguador de masa activo utilizando un excitador electrodinámico, y (4) el desarrollo de pruebas para la verificación del estado de servicio de la pasarela. In the last years, a wide number of footbridges have been built as demand response of more direct pathways in cities. These structures have lower building requirements as compared with standard bridges. This circumstance has facilitated the development of new structural design with complex geometries and innovative materials. As a result, these structures may be slender, light and low damped, leading to vibration problems once in service. The current codes take into account this problem, and recommend designs with natural frequencies away from the typical pedestrian pacing rates and fix comfort limits to guarantee the serviceability of the structure.This paper studies this problem from a practical point of view. Thus, the key points of codes and footbridges guidelines are showed, the typical experimental dynamic analysis techniques are presented, and the usual solutions adopted to improve the dynamic performance of these structures are discussed. Finally, the works carried out on the Valladolid Science Museum Footbridge by Centro Tecnológico CARTIF in collaboration with the Universities of Valladolid and Castilla-La Mancha are showed. These works include: (1) the dynamic study of the three steel spans of the footbridge, (2) the design and implementation of a tuned mass damper in the liveliest span, (3) the implementation of an active mass damper using an electrodynamic shaker, and (4) the development of field tests to assess the serviceability of such span.

See-and-avoid quadcopter using fuzzy control optimized by cross-entropy

In this work we present an optimized fuzzy visual servoing system for obstacle avoidance using an unmanned aerial vehicle. The cross-entropy theory is used to optimise the gains of our controllers. The optimization process was made using the ROS-Gazebo 3D simulation with purposeful extensions developed for our experiments. Visual servoing is achieved through an image processing front-end that uses the Camshift algorithm to detect and track objects in the scene. Experimental flight trials using a small quadrotor were performed to validate the parameters estimated from simulation. The integration of crossentropy methods is a straightforward way to estimate optimal gains achieving excellent results when tested in real flights.

Visual Tracking, Pose Estimation, and Control for Aerial Vehicles

El principal objetivo de esta tesis es dotar a los vehículos aéreos no tripulados (UAVs, por sus siglas en inglés) de una fuente de información adicional basada en visión. Esta fuente de información proviene de cámaras ubicadas a bordo de los vehículos o en el suelo. Con ella se busca que los UAVs realicen tareas de aterrizaje o inspección guiados por visión, especialmente en aquellas situaciones en las que no haya disponibilidad de estimar la posición del vehículo con base en GPS, cuando las estimaciones de GPS no tengan la suficiente precisión requerida por las tareas a realizar, o cuando restricciones de carga de pago impidan añadir sensores a bordo de los vehículos. Esta tesis trata con tres de las principales áreas de la visión por computador: seguimiento visual y estimación visual de la pose (posición y orientación), que a su vez constituyen la base de la tercera, denominada control servo visual, que en nuestra aplicación se enfoca en el empleo de información visual para controlar los UAVs. Al respecto, esta tesis se ocupa de presentar propuestas novedosas que permitan solucionar problemas relativos al seguimiento de objetos mediante cámaras ubicadas a bordo de los UAVs, se ocupa de la estimación de la pose de los UAVs basada en información visual obtenida por cámaras ubicadas en el suelo o a bordo, y también se ocupa de la aplicación de las técnicas propuestas para solucionar diferentes problemas, como aquellos concernientes al seguimiento visual para tareas de reabastecimiento autónomo en vuelo o al aterrizaje basado en visión, entre otros. Las diversas técnicas de visión por computador presentadas en esta tesis se proponen con el fin de solucionar dificultades que suelen presentarse cuando se realizan tareas basadas en visión con UAVs, como las relativas a la obtención, en tiempo real, de estimaciones robustas, o como problemas generados por vibraciones. Los algoritmos propuestos en esta tesis han sido probados con información de imágenes reales obtenidas realizando pruebas on-line y off-line. Diversos mecanismos de evaluación han sido empleados con el propósito de analizar el desempeño de los algoritmos propuestos, entre los que se incluyen datos simulados, imágenes de vuelos reales, estimaciones precisas de posición empleando el sistema VICON y comparaciones con algoritmos del estado del arte. Los resultados obtenidos indican que los algoritmos de visión por computador propuestos tienen un desempeño que es comparable e incluso mejor al de algoritmos que se encuentran en el estado del arte. Los algoritmos propuestos permiten la obtención de estimaciones robustas en tiempo real, lo cual permite su uso en tareas de control visual. El desempeño de estos algoritmos es apropiado para las exigencias de las distintas aplicaciones examinadas: reabastecimiento autónomo en vuelo, aterrizaje y estimación del estado del UAV. Abstract The main objective of this thesis is to provide Unmanned Aerial Vehicles (UAVs) with an additional vision-based source of information extracted by cameras located either on-board or on the ground, in order to allow UAVs to develop visually guided tasks, such as landing or inspection, especially in situations where GPS information is not available, where GPS-based position estimation is not accurate enough for the task to develop, or where payload restrictions do not allow the incorporation of additional sensors on-board. This thesis covers three of the main computer vision areas: visual tracking and visual pose estimation, which are the bases the third one called visual servoing, which, in this work, focuses on using visual information to control UAVs. In this sense, the thesis focuses on presenting novel solutions for solving the tracking problem of objects when using cameras on-board UAVs, on estimating the pose of the UAVs based on the visual information collected by cameras located either on the ground or on-board, and also focuses on applying these proposed techniques for solving different problems, such as visual tracking for aerial refuelling or vision-based landing, among others. The different computer vision techniques presented in this thesis are proposed to solve some of the frequently problems found when addressing vision-based tasks in UAVs, such as obtaining robust vision-based estimations at real-time frame rates, and problems caused by vibrations, or 3D motion. All the proposed algorithms have been tested with real-image data in on-line and off-line tests. Different evaluation mechanisms have been used to analyze the performance of the proposed algorithms, such as simulated data, images from real-flight tests, publicly available datasets, manually generated ground truth data, accurate position estimations using a VICON system and a robotic cell, and comparison with state of the art algorithms. Results show that the proposed computer vision algorithms obtain performances that are comparable to, or even better than, state of the art algorithms, obtaining robust estimations at real-time frame rates. This proves that the proposed techniques are fast enough for vision-based control tasks. Therefore, the performance of the proposed vision algorithms has shown to be of a standard appropriate to the different explored applications: aerial refuelling and landing, and state estimation. It is noteworthy that they have low computational overheads for vision systems.