2,038 research outputs found

    Politics and political determinants of health policy and systems research funding in Latin America and the Caribbean

    Get PDF
    Objectives and importance of study: The importance of health policy and systems research (HPSR) has been acknowledged since 2004 and was recognised by the United Nations World Health Assembly in 2005. However, many factors influence its development. This paper aims to analyse the impact of politics and political determinants on HPSR funding in selected countries of Latin America and the Caribbean. Methods: Using a standardised protocol, we performed an analysis of available data and financing structures for health research and HPSR based on research in eight countries, including interviews with key stakeholders (n = 42). Results: Dollar depreciation and gross national product growth in the region may play a role in how governments fund research. There have been shifts in the political spectrum in governments, which have affected research coordination and funding in positive and negative ways. HPSR funding in some countries was dependent on budget decisions and although some have improved funding, others have regressed by decreasing funding or have completely cancelled financing mechanisms. Caribbean countries rely mainly on institutional funding. HPSR is recognised as important but remains underfunded; stakeholders believed it should be used more in decision making. Conclusion: Although HPSR is recognised as valuable for decision making and policy development it does not have the financial support required to flourish in Latin America and the Carribean. Data on health research financing were not easy to access. There was little or no evidence of published reports or papers about research financing, health research funding, and HPSR funding in particular in the studied countries Because of the fragility of health systems highlighted by the coronavirus disease 2019 (COVID-19) pandemic, HPSR should be of great relevance and value to both policy makers and funders

    UAV perception for safe flight under physical interaction

    Get PDF
    Aplicat embargament des de la data de defensa fins al maig 2020The control of autonomous flying vehicles with navigation purposes is a challenging task. Complexity arises mainly due to the non-linearity and uncertainty inherently present in the flight mechanics and aircraft-air interactions. Recently, interest has grown for equipping unmanned vehicles with the capacity to interact with their environment, other vehicles or humans. This will enable interesting applications such as autonomous load carrying, aerial refueling or parcel delivering. Having measured the interaction wrenches ease the control problem which can be configured to reject disturbances or to take profit of them to fulfill mission objectives. This thesis will contribute to this area by providing perception solutions which use limited and low cost sensors that enable state and disturbance estimation for possible, but not restricted to, interaction scenarios. This thesis contain three parts. The first part, introduces basic concepts related to the navigation state, aircraft dynamics, and sensor models. In addition, the platform under study is presented and mathematical models associated to it are calibrated. The second part is devoted to the observability analysis and the design of state observers. Linear and non-linear observability analysis techniques are used to unveil that the state of quadrotors equipped with GPS, magnetometers an IMU sensors cannot be uniquely identified in some specific flight configurations. Results of this section are relevant because the conflicting flight configurations contain hover, a flight maneuverer central in many unmanned aerial missions of VtoL vehicles. For many possible singular configurations, insightful descriptions and interpretations of the solution space known as indistinguishable region is provided. Findings are verified in simulation scenarios where it can be seen how a filter fails to recover the true state of an aircraft when imposing the hover flight condition. We discuss then the design of Extended Kalman Filters for state estimation that considers the available sensors. Issues that are typically not reported in the literature, such as when to update or propagate in the estimator algorithm or which coordinate frame should be used to represent each state variable are discussed. This leads to the formulation of four potentially equivalent but different discrete event-based filters for which precise algorithmic expressions are given. We compare the results of the four filters in simulation under known favorable conditions for observability. In order to diminish the effect of flying in the conflicting observability configurations, we provide an alternative filter based on the Schmidt Kalman Filter (SKF). The proposed filter shares the structure of the EKF, behaves better in the instants that the EKF fails and provides similar results in the remaining conditions. The last part of the thesis deals with the estimation of external disturbances. Disturbance estimation results are based on the derivation of a linear model for the aircraft dynamics which then extended with a high order disturbance model to enable the estimation of fast varying disturbances. Two external disturbance estimators from the literature are reviewed and adapted to the new model. Also, two Kalman observers that exploit the linearity of the derived model are presented. A simulation comparison is provided demonstrating that the KF disturbance estimators outperform the other. In addition, this part presents a design methodology of generic quadratic bounded observers for linear systems with ellipsoidal bounded uncertainty. The derived observers maximize a user tunable compromise between the estimation convergence speed and the final volume containing the estimation error. An observer for disturbances acting on a flying platform is derived considering the high order disturbance model above mentioned. Finally, an analysis of the estimation performance with respect to the design parameters is presented.Esta tesis, contribuye en este área formulando soluciones de percepción que permiten la estimación del estado y perturbaciones externas en condiciones normales de vuelos así como casos de interacción para UAVs equipados con sensores limitados y de bajo coste. La tesis se estructura en tres partes. La primera de ellas introduce los conceptos básicos relacionados con el estado de navegación, la dinámica de la aeronave y modelos de sensores. Además, se presenta la plataforma de estudio así como los modelos matemáticos asociados a ella y su calibración. La segunda parte está destinada al análisis de observabilidad y el diseño de observadores de estado. Los resultados de esta sección son importantes porque dentro de las condiciones de vuelo conflictivas se encuentra el vuelo a punto fijo, una maniobra de vuelo central en muchas misiones de vehículos VToL. Se analizan estas condiciones críticas de vuelo y para ellas se deriva y describe el espacio de soluciones posible conocido como región indistinguible. Los resultados son verificados en simulación dónde se puede apreciar como un estimador de estado falla al intentar realizar su tarea cuando la aeronave está en vuelo a punto fijo. Seguidamente se presenta el diseño de filtros extendidos de Kalman (EKF) que proveen estimaciones del estado con la información limitada de los sensores disponibles. Se discuten conceptos que habitualmente no se presentan en la literatura como cuando actualizar o propagar en el algoritmo de estimación o que sistema de referencia se debe utilizar para representar adecuadamente las variables de estado. Esto lleva a la formulación algorítmica de cuatro filtros discretos basados en eventos, diferentes, pero en esencia equivalentes. Se derivan rutinas de inicialización para los filtros y se comparan los resultados en simulación bajo condiciones favorables de estimación. Con la idea de disminuir el efecto de volar en configuraciones de observabilidad conflictivas, se deriva un filtro alternativo basado en el filtro de Schmidt Kalman (SKF). El filtro propuesto comparte estructura con el EKF, tiene un mejor comportamiento allí dónde le EKF falla y una respuesta similar en el resto de condiciones de vuelo. La última parte de la tesis trata con la estimación de perturbaciones externas. Para ello se deriva un modelo lineal que relaciona fuerzas y momentos con velocidades junto a un modelo de alto orden para las perturbaciones. Se estudia su aplicación a dos modelos para la estimación de perturbaciones ya presentes en la literatura. Además, se proponen dos nuevos filtros de Kalman que se aprovechan de la linealidad del modelo. Se presenta una comparativa basada en la simulación de escenarios ideales así como realistas que demuestra que los filtros KF superan al resto. Esta misma parte de la tesis presenta el diseño genérico de estimadores "quadratic bounded" para sistemas dinámicos lineales cuya incertidumbre se encuentra acotada dentro de elipsoides. Estos estimadores maximizan un compromiso, ajustable por el usuario que contempla la velocidad de convergencia así como el volumen de la solución final que contiene el error de estimación. Se deriva un observador de perturbaciones para plataformas aéreas basado en el modelo de alto orden arriba mencionado. Finalmente, se presenta un análisis del desempeño de estimación en función de los parámetros de diseño del filtro.Postprint (published version

    UAV perception for safe flight under physical interaction

    Get PDF
    The control of autonomous flying vehicles with navigation purposes is a challenging task. Complexity arises mainly due to the non-linearity and uncertainty inherently present in the flight mechanics and aircraft-air interactions. Recently, interest has grown for equipping unmanned vehicles with the capacity to interact with their environment, other vehicles or humans. This will enable interesting applications such as autonomous load carrying, aerial refueling or parcel delivering. Having measured the interaction wrenches ease the control problem which can be configured to reject disturbances or to take profit of them to fulfill mission objectives. This thesis will contribute to this area by providing perception solutions which use limited and low cost sensors that enable state and disturbance estimation for possible, but not restricted to, interaction scenarios. This thesis contain three parts. The first part, introduces basic concepts related to the navigation state, aircraft dynamics, and sensor models. In addition, the platform under study is presented and mathematical models associated to it are calibrated. The second part is devoted to the observability analysis and the design of state observers. Linear and non-linear observability analysis techniques are used to unveil that the state of quadrotors equipped with GPS, magnetometers an IMU sensors cannot be uniquely identified in some specific flight configurations. Results of this section are relevant because the conflicting flight configurations contain hover, a flight maneuverer central in many unmanned aerial missions of VtoL vehicles. For many possible singular configurations, insightful descriptions and interpretations of the solution space known as indistinguishable region is provided. Findings are verified in simulation scenarios where it can be seen how a filter fails to recover the true state of an aircraft when imposing the hover flight condition. We discuss then the design of Extended Kalman Filters for state estimation that considers the available sensors. Issues that are typically not reported in the literature, such as when to update or propagate in the estimator algorithm or which coordinate frame should be used to represent each state variable are discussed. This leads to the formulation of four potentially equivalent but different discrete event-based filters for which precise algorithmic expressions are given. We compare the results of the four filters in simulation under known favorable conditions for observability. In order to diminish the effect of flying in the conflicting observability configurations, we provide an alternative filter based on the Schmidt Kalman Filter (SKF). The proposed filter shares the structure of the EKF, behaves better in the instants that the EKF fails and provides similar results in the remaining conditions. The last part of the thesis deals with the estimation of external disturbances. Disturbance estimation results are based on the derivation of a linear model for the aircraft dynamics which then extended with a high order disturbance model to enable the estimation of fast varying disturbances. Two external disturbance estimators from the literature are reviewed and adapted to the new model. Also, two Kalman observers that exploit the linearity of the derived model are presented. A simulation comparison is provided demonstrating that the KF disturbance estimators outperform the other. In addition, this part presents a design methodology of generic quadratic bounded observers for linear systems with ellipsoidal bounded uncertainty. The derived observers maximize a user tunable compromise between the estimation convergence speed and the final volume containing the estimation error. An observer for disturbances acting on a flying platform is derived considering the high order disturbance model above mentioned. Finally, an analysis of the estimation performance with respect to the design parameters is presented.Esta tesis, contribuye en este área formulando soluciones de percepción que permiten la estimación del estado y perturbaciones externas en condiciones normales de vuelos así como casos de interacción para UAVs equipados con sensores limitados y de bajo coste. La tesis se estructura en tres partes. La primera de ellas introduce los conceptos básicos relacionados con el estado de navegación, la dinámica de la aeronave y modelos de sensores. Además, se presenta la plataforma de estudio así como los modelos matemáticos asociados a ella y su calibración. La segunda parte está destinada al análisis de observabilidad y el diseño de observadores de estado. Los resultados de esta sección son importantes porque dentro de las condiciones de vuelo conflictivas se encuentra el vuelo a punto fijo, una maniobra de vuelo central en muchas misiones de vehículos VToL. Se analizan estas condiciones críticas de vuelo y para ellas se deriva y describe el espacio de soluciones posible conocido como región indistinguible. Los resultados son verificados en simulación dónde se puede apreciar como un estimador de estado falla al intentar realizar su tarea cuando la aeronave está en vuelo a punto fijo. Seguidamente se presenta el diseño de filtros extendidos de Kalman (EKF) que proveen estimaciones del estado con la información limitada de los sensores disponibles. Se discuten conceptos que habitualmente no se presentan en la literatura como cuando actualizar o propagar en el algoritmo de estimación o que sistema de referencia se debe utilizar para representar adecuadamente las variables de estado. Esto lleva a la formulación algorítmica de cuatro filtros discretos basados en eventos, diferentes, pero en esencia equivalentes. Se derivan rutinas de inicialización para los filtros y se comparan los resultados en simulación bajo condiciones favorables de estimación. Con la idea de disminuir el efecto de volar en configuraciones de observabilidad conflictivas, se deriva un filtro alternativo basado en el filtro de Schmidt Kalman (SKF). El filtro propuesto comparte estructura con el EKF, tiene un mejor comportamiento allí dónde le EKF falla y una respuesta similar en el resto de condiciones de vuelo. La última parte de la tesis trata con la estimación de perturbaciones externas. Para ello se deriva un modelo lineal que relaciona fuerzas y momentos con velocidades junto a un modelo de alto orden para las perturbaciones. Se estudia su aplicación a dos modelos para la estimación de perturbaciones ya presentes en la literatura. Además, se proponen dos nuevos filtros de Kalman que se aprovechan de la linealidad del modelo. Se presenta una comparativa basada en la simulación de escenarios ideales así como realistas que demuestra que los filtros KF superan al resto. Esta misma parte de la tesis presenta el diseño genérico de estimadores "quadratic bounded" para sistemas dinámicos lineales cuya incertidumbre se encuentra acotada dentro de elipsoides. Estos estimadores maximizan un compromiso, ajustable por el usuario que contempla la velocidad de convergencia así como el volumen de la solución final que contiene el error de estimación. Se deriva un observador de perturbaciones para plataformas aéreas basado en el modelo de alto orden arriba mencionado. Finalmente, se presenta un análisis del desempeño de estimación en función de los parámetros de diseño del filtro

    Hydrodynamics of a Granular Gas in a Heterogeneous Environment

    Get PDF
    We analyze the transport properties of a low density ensemble of identical macroscopic particles immersed in an active fluid. The particles are modeled as inelastic hard spheres (granular gas). The non-homogeneous active fluid is modeled by means of a non-uniform stochastic thermostat. The theoretical results are validated with a numerical solution of the corresponding the kinetic equation (direct simulation Monte Carlo method). We show a steady flow in the system that is accurately described by Navier-Stokes (NS) hydrodynamics, even for high inelasticity. Surprisingly, we find that the deviations from NS hydrodynamics for this flow are stronger as the inelasticity decreases. The active fluid action is modeled here with a non-uniform fluctuating volume force. This is a relevant result given that hydrodynamics of particles in complex environments, such as biological crowded environments, is still a question under intense debate

    Social desirability bias in the environmental economic valuation: An inferred valuation approach

    Get PDF
    Environmental economic valuation allows to derive values from individuals’ behaviour in hypothetical markets, but it is not exempt from certain biases. this work aims to evidence the existence of social desirability bias (sdb) in the use of the stated preference method for environmental valuation. sdb is due to the consideration that, when interviewed, people provide responses to match the interviewer’s expectations or to be consistent with social norms. the inferred valuation approach (iva) was used to identify and quantify the social desirability bias in a choice experiment survey conducted to estimate the benefit of protecting a coastal natura 2000 site. the results revealed the existence of a sdb that increases by 2.8-fold the benefits of the valued environmental assets. it is also found greater differences between use and non-use values when the iva is used.This work was carried out under the project AGRISERVI funded by the Spanish Ministry of Science, Innovation and Universities under the European Regional Development Fund (ERDF) [AGL2015-64411-R (MINECO/FEDER, UE)], and the 20912/PI/18 project (Fundación Séneca-Agencia de Ciencia y Tecnología de la Región de Murcia). Useful comments provided by Faustino Martínez, Ramón Ballester and Juana Guirao from OISMA are gratefully acknowledge

    High field conduction in mineral oil based zno nanofluids prior to negative streamer inception

    Get PDF
    The electric conduction under intense electric fields (up to ∼ 10 V/m) in nanofluids using surface-modified ZnO–C nanoparticles dispersed in mineral oil as host, is investigated with both experiments and numerical simulations. The measurements are used to estimate unknown parameters necessary to represent the generation and loss of electrons in an electrohydrodynamic model for mineral oil with and without ZnO–C nanoparticles in a needle-plane configuration. The model suggests that ZnO–C nanoparticles induce an enhanced field emission from negative needles, explaining the significantly larger conduction currents measured in the nanofluid compared with those in the host liquid. It is also found that the scavenging of electrons by ZnO–C nanoparticles is a process which is negligible compared with the loss of electrons due to attachment in mineral oil. It is shown that ZnO–C nanoparticles hinder the streamer initiation process by reducing the effective electric field at the tip of the needle. This electric field reduction is caused by the combined effect of enhanced electron injection through ZnO–C nanoparticles and strong electron attachment in mineral oil. Thus, the electric field on the needle tip reaches the same threshold value when the streamer is incepted in the nanofluid as in mineral oil, although at a larger voltage. Solid evidence indicating that the additional electron scavenging and the reduced electron mobility introduced by nanoparticles has no effect in the conduction currents and in the negative streamer inception in the tested ZnO–C nanofluids is shown

    The websites adoption in the Spanish agrifood firms

    Get PDF
    Currently, the use of websites in the firms of the Spanish agrifood sector has not become widespread despite the possible benefits to be derived from their adequate integration and management within the firms. Among these advantages, the increase in the quality of the services offered and the improvement in the relations with their stakeholders should be highlighted. In this context, the objective of the present work is to determine to what extent websites are used by firms in the agrifood sector of Spain, analysing the background which explains why they are adopted and the consequences of introducing them. To do so, a theoretical framework is posed which allows these factors to be identified, and an empirical study is carried out with Spanish agrifood firms. The results of the work indicate that the adoption of websites will be favoured when the directors of the firm are higher qualified, the firm is bigger in size, the firm’s function is distribution, and when the relative advantage and technology compatibility is perceived, among others. Technology adoption consequences analysis suggests that the benefits of adoption are related with improving the relationships with suppliers, customers, owning partners and, in general, the quality of the services offered by the firm

    Impedance control of a planar quadrotor with an extended Kalman filter external wrench estimator

    Get PDF
    In this work we deal with the non-linear control of aerial vehicles under external disturbances. We develop a non-linear velocity controller able to accommodate estimations of the external disturbing forces and moments. To estimate the external actions and at the same time provide improvements on the state estimation we make use of the EKF approach. Finally, we present simulations comparing close loop performance of a system with the proposed methodology implemented against close loop performance of the same controller but without the estimation of the external forces.Postprint (published version

    A results-based incentive scheme to improve performance

    Get PDF
    Profesores e investigadores cualificados y motivados son un insumo clave en el éxito de cualquier esfuerzo de la educación superior como lo señala Salmi (2009). La contratación de profesores con calificaciones adecuadas es, por supuesto, parte de la respuesta para lograr esto. Sin embargo, la mejora de la competitividad de una universidad desde dentro, es una tarea mucho más difícil cuando la carrera académica se ha basado históricamente en la edad más que en el mérito. Un plan de incentivos basado en los resultados simples y transparentes puede ayudar a reestructurar el rendimiento académico. La Universidad del Pacífico, institución privada sin fines de lucro, especializada en los campos de economía y negocios, lanzó en 2007 un sistema de incentivos de estas características. Las bonificaciones monetarias y promociones están vinculadas a un conjunto de indicadores de resultados, cada uno con un peso particular que refleja las prioridades de la universidad con respecto a la enseñanza de habilidades, logros de investigación y difusión. Se describe este sistema de incentivos para discutir brevemente sobre las "políticas" internas de su aprobación e implementación, y evaluar sus posibles efectos en la producción académica después de 5 años de operación continua. Esta experiencia puede proporcionar lecciones útiles sobre cómo crear un punto de inflexión fundamental en las universidades.A qualified and motivated pool of professors and researchers is a key input in any successful higher education endeavor (Salmi, 2009). Hiring professors with adequate qualifications is, of course, part of the answer to achieve this. However, improving the competitiveness of a university from within, and when the academic career has been historically based on age rather than on merit, is a much more difficult task. We believe a simple and transparent results-based incentive scheme can help reshape academic performance. Universidad del Pacífico, a medium size not for profit private institution specialized in economics and business fields, launched in 2007, an incentive system with these characteristics (Universidad del Pacífico, 2008). Monetary bonuses and promotions are linked to a set of results indicators, each having a particular weight which reflects university’s priorities regarding teaching skills and research accomplishments and dissemination. We describe this incentive system, briefly discuss the internal “politics” of its approval and implementation, and assess its potential effects on academic performance after 5 years of continuous operation
    corecore