Tether radiation in Juno-type and circular-equatorial Jovian orbits

Wave radiation by a conductor carrying a steady current in both a polar, highly eccentric, low perijove orbit, as in NASA's planned Juno mission, and an equatorial low Jovian orbit (LJO) mission below the intense radiation belts, is considered. Both missions will need electric power generation for scientific instruments and communication systems. Tethers generate power more efficiently than solar panels or radioisotope power systems (RPS). The radiation impedance is required to determine the current in the overall tether circuit. In a cold plasma model, radiation occurs mainly in the Alfven and fast magnetosonic modes, exhibiting a large refraction index. The radiation impedance of insulated tethers is determined for both modes and either mission. Unlike the Earth ionospheric case, the low-density, highly magnetized Jovian plasma makes the electron gyrofrequency much larger than the plasma frequency; this substantially modifies the power spectrum for either mode by increasing the Alfven velocity. Finally, an estimation of the radiation impedance of bare tethers is considered. In LJO, a spacecraft orbiting in a slow downward spiral under the radiation belts would allow determining magnetic field structure and atmospheric composition for understanding the formation, evolution, and structure of Jupiter. Additionally, if the cathodic contactor is switched off, a tether floats electrically, allowing e-beam emission that generate auroras. On/off switching produces bias/current pulses and signal emission, which might be used for Jovian plasma diagnostics.

Application of a Bayesian/Generalised Least-Squares method to generate correlations between independent neutron fission yield data

Fission product yields are fundamental parameters for several nuclear engineering calculations and in particular for burn-up/activation problems. The impact of their uncertainties was widely studied in the past and valuations were released, although still incomplete. Recently, the nuclear community expressed the need for full fission yield covariance matrices to produce inventory calculation results that take into account the complete uncertainty data. In this work, we studied and applied a Bayesian/generalised least-squares method for covariance generation, and compared the generated uncertainties to the original data stored in the JEFF-3.1.2 library. Then, we focused on the effect of fission yield covariance information on fission pulse decay heat results for thermal fission of 235U. Calculations were carried out using different codes (ACAB and ALEPH-2) after introducing the new covariance values. Results were compared with those obtained with the uncertainty data currently provided by the library. The uncertainty quantification was performed with the Monte Carlo sampling technique. Indeed, correlations between fission yields strongly affect the statistics of decay heat. Introduction Nowadays, any engineering calculation performed in the nuclear field should be accompanied by an uncertainty analysis. In such an analysis, different sources of uncertainties are taken into account. Works such as those performed under the UAM project (Ivanov, et al., 2013) treat nuclear data as a source of uncertainty, in particular cross-section data for which uncertainties given in the form of covariance matrices are already provided in the major nuclear data libraries. Meanwhile, fission yield uncertainties were often neglected or treated shallowly, because their effects were considered of second order compared to cross-sections (Garcia-Herranz, et al., 2010). However, the Working Party on International Nuclear Data Evaluation Co-operation (WPEC)

Mechanical behavior and residual stress field of dissimilar laser welded joints

The present investigation addresses the mechanical behavior and residual stress field of dissimilar joints produced by laser welding. Microstructure characterization and residual strain scanning, carried out by neutron diffraction, were used to assess the joints features. It was found that the heat source position influences the base metals dilution and the residual stress field associated to the welding process. The tensile behavior of the joint, different zones achieved by using a video-image based system (VIC-2D) reveals that the residual stress field, together with the positive difference in yield between the weld metal and the base materials protects the joint from being plastically deformed.

High-accuracy adaptive simulations of a Petri dish exposed to electromagnetic radiation

This paper analyses numerically the electric field distribution of a liquid contained in a Petri dish when exposed to electromagnetic waves excited in a rectangular waveguide. Solutions exhibit high-gradients due to the presence of the dielectric liquid contained in the dish. Furthermore, electromagnetic fields within the dielectric have a dramatically lower value than on the remaining part of the domain, which difficults its simulation. Additionally, various singularities of different intensity appear along the boundary of the Petri dish. To properly reproduce and numerically study those effects, we employ a highly-accurate hp-adaptive finite element method. Results of this study demonstrate that the electric field generated within the circular Petri dish is non-homogeneous, and thus, a better shape, size, or location of the dish is needed to achieve an equally distributed radiation enabling the uniform growth of cell cultives.

Terasense WP03 radiation and sensor measurement lab workpackage

This paper explains the progress accomplished in the WP03 of the Terasense Project (TERAHERTZ TECHNOLOGY FOR ELECTROMAGNETIC SENSING APPLICATIONS) approved in the 2008 CONSOLIDERINGENIO program (project CSD2008-0068). The Radiation and Sensor Measurement Lab (RSMLab) is a laboratory based in the existing antenna measurement laboratories at UPM, UC3 and UNiOvi and the new capacities to extend the measurement range from the millimetre wave to the THz region. This laboratory is intended to be shared in more than one place and with more than one institution, in such a way that we could take advantage of other research financial sources and contributions from other institutions with interest in the same field of measurements. One important task will be the international links between the RSMLab and other European and international institutions dedicated to the antenna and sensor measurement in the same frequency range.

A bankable method for the field testingor a CPV plant

The bankability of CPV projects is an important issue to pave the way toward a swift and sustained growth in this technology. The bankability of a PV plant is generally addressed through the modeling of its energy yield under a b aseline loss scenario, followed by an on-site measurement campaign aimed at verifying its energetic behavior. The main difference between PV and CPV resides in the proper CPV modules, in particular in the inclusion of optical lements and III-V multijunction cells that are much more sensitive to spectral variations than xSi cells, while the rest of the system behaves in a way that possesses many common points with xSi technology. The modeling of the DC power output of a CPV system thus requires several impo rtant second order parameters to be considered, mainly related to optics, spectral direct solar radiation, wind speed, tracker accuracy and heat dissipation of cells.

Wireless communication enhancement methods for mobile robots in radiation environments

En entornos hostiles tales como aquellas instalaciones cient��ficas donde la radiaci��n ionizante es el principal peligro, el hecho de reducir las intervenciones humanas mediante el incremento de las operaciones robotizadas est�� siendo cada vez m��s de especial inter��s. CERN, la Organizaci��n Europea para la Investigaci��n Nuclear, tiene alrededor de unos 50 km de superficie subterr��nea donde robots m��viles controlador de forma remota podr��an ayudar en su funcionamiento, por ejemplo, a la hora de llevar a cabo inspecciones remotas sobre radiaci��n en los diferentes ��reas destinados al efecto. No solo es preciso considerar que los robots deben ser capaces de recorrer largas distancias y operar durante largos periodos de tiempo, sino que deben saber desenvolverse en los correspondientes t��neles subterr��neos, tener en cuenta la presencia de campos electromagn��ticos, radiaci��n ionizante, etc. y finalmente, el hecho de que los robots no deben interrumpir el funcionamiento de los aceleradores. El hecho de disponer de un sistema de comunicaciones inal��mbrico fiable y robusto es esencial para la correcta ejecuci��n de las misiones que los robots deben afrontar y por supuesto, para evitar tales situaciones en las que es necesario la recuperaci��n manual de los robots al agotarse su energ��a o al perder el enlace de comunicaciones. El objetivo de esta Tesis es proveer de las directrices y los medios necesarios para reducir el riesgo de fallo en la misi��n y maximizar las capacidades de los robots m��viles inal��mbricos los cuales disponen de almacenamiento finito de energ��a al trabajar en entornos peligrosos donde no se dispone de l��nea de vista directa. Para ello se proponen y muestran diferentes estrategias y m��todos de comunicaci��n inal��mbrica. Teniendo esto en cuenta, se presentan a continuaci��n los objetivos de investigaci��n a seguir a lo largo de la Tesis: predecir la cobertura de comunicaciones antes y durante las misiones robotizadas; optimizar la capacidad de red inal��mbrica de los robots m��viles con respecto a su posici��n; y mejorar el rango operacional de esta clase de robots. Por su parte, las contribuciones a la Tesis se citan m��s abajo. El primer conjunto de contribuciones son m��todos novedosos para predecir el consumo de energ��a y la autonom��a en la comunicaci��n antes y despu��s de disponer de los robots en el entorno seleccionado. Esto es importante para proporcionar conciencia de la situaci��n del robot y evitar fallos en la misi��n. El consumo de energ��a se predice usando una estrategia propuesta la cual usa modelos de consumo provenientes de diferentes componentes en un robot. La predicci��n para la cobertura de comunicaciones se desarrolla usando un nuevo filtro de RSS (Radio Signal Strength) y t��cnicas de estimaci��n con la ayuda de Filtros de Kalman. El segundo conjunto de contribuciones son m��todos para optimizar el rango de comunicaciones usando novedosas t��cnicas basadas en muestreo espacial que son robustas frente a ruidos de campos de detecci��n y radio y que proporcionan redundancia. Se emplean m��todos de diferencia central finitos para determinar los gradientes 2D RSS y se usa la movilidad del robot para optimizar el rango de comunicaciones y la capacidad de red. Este m��todo tambi��n se valida con un caso de estudio centrado en la teleoperaci��n h��ptica de robots m��viles inal��mbricos. La tercera contribuci��n es un algoritmo robusto y estoc��stico descentralizado para la optimizaci��n de la posici��n al considerar m��ltiples robots aut��nomos usados principalmente para extender el rango de comunicaciones desde la estaci��n de control al robot que est�� desarrollando la tarea. Todos los m��todos y algoritmos propuestos se verifican y validan usando simulaciones y experimentos de campo con variedad de robots m��viles disponibles en CERN. En resumen, esta Tesis ofrece m��todos novedosos y demuestra su uso para: predecir RSS; optimizar la posici��n del robot; extender el rango de las comunicaciones inal��mbricas; y mejorar las capacidades de red de los robots m��viles inal��mbricos para su uso en aplicaciones dentro de entornos peligrosos, que como ya se mencion�� anteriormente, se destacan las instalaciones cient��ficas con emisi��n de radiaci��n ionizante. En otros t��rminos, se ha desarrollado un conjunto de herramientas para mejorar, facilitar y hacer m��s seguras las misiones de los robots en entornos hostiles. Esta Tesis demuestra tanto en teor��a como en pr��ctica que los robots m��viles pueden mejorar la calidad de las comunicaciones inal��mbricas mediante la profundizaci��n en el estudio de su movilidad para optimizar din��micamente sus posiciones y mantener conectividad incluso cuando no existe l��nea de vista. Los m��todos desarrollados en la Tesis son especialmente adecuados para su f��cil integraci��n en robots m��viles y pueden ser aplicados directamente en la capa de aplicaci��n de la red inal��mbrica. ABSTRACT In hostile environments such as in scientific facilities where ionising radiation is a dominant hazard, reducing human interventions by increasing robotic operations are desirable. CERN, the European Organization for Nuclear Research, has around 50 km of underground scientific facilities, where wireless mobile robots could help in the operation of the accelerator complex, e.g. in conducting remote inspections and radiation surveys in different areas. The main challenges to be considered here are not only that the robots should be able to go over long distances and operate for relatively long periods, but also the underground tunnel environment, the possible presence of electromagnetic fields, radiation effects, and the fact that the robots shall in no way interrupt the operation of the accelerators. Having a reliable and robust wireless communication system is essential for successful execution of such robotic missions and to avoid situations of manual recovery of the robots in the event that the robot runs out of energy or when the robot loses its communication link. The goal of this thesis is to provide means to reduce risk of mission failure and maximise mission capabilities of wireless mobile robots with finite energy storage capacity working in a radiation environment with non-line-of-sight (NLOS) communications by employing enhanced wireless communication methods. Towards this goal, the following research objectives are addressed in this thesis: predict the communication range before and during robotic missions; optimise and enhance wireless communication qualities of mobile robots by using robot mobility and employing multi-robot network. This thesis provides introductory information on the infrastructures where mobile robots will need to operate, the tasks to be carried out by mobile robots and the problems encountered in these environments. The reporting of research work carried out to improve wireless communication comprises an introduction to the relevant radio signal propagation theory and technology followed by explanation of the research in the following stages: An analysis of the wireless communication requirements for mobile robot for different tasks in a selection of CERN facilities; predictions of energy and communication autonomies (in terms of distance and time) to reduce risk of energy and communication related failures during missions; autonomous navigation of a mobile robot to find zone(s) of maximum radio signal strength to improve communication coverage area; and autonomous navigation of one or more mobile robots acting as mobile wireless relay (repeater) points in order to provide a tethered wireless connection to a teleoperated mobile robot carrying out inspection or radiation monitoring activities in a challenging radio environment. The specific contributions of this thesis are outlined below. The first sets of contributions are novel methods for predicting the energy autonomy and communication range(s) before and after deployment of the mobile robots in the intended environments. This is important in order to provide situational awareness and avoid mission failures. The energy consumption is predicted by using power consumption models of different components in a mobile robot. This energy prediction model will pave the way for choosing energy-efficient wireless communication strategies. The communication range prediction is performed using radio signal propagation models and applies radio signal strength (RSS) filtering and estimation techniques with the help of Kalman filters and Gaussian process models. The second set of contributions are methods to optimise the wireless communication qualities by using novel spatial sampling based techniques that are robust to sensing and radio field noises and provide redundancy features. Central finite difference (CFD) methods are employed to determine the 2-D RSS gradients and use robot mobility to optimise the communication quality and the network throughput. This method is also validated with a case study application involving superior haptic teleoperation of wireless mobile robots where an operator from a remote location can smoothly navigate a mobile robot in an environment with low-wireless signals. The third contribution is a robust stochastic position optimisation algorithm for multiple autonomous relay robots which are used for wireless tethering of radio signals and thereby to enhance the wireless communication qualities. All the proposed methods and algorithms are verified and validated using simulations and field experiments with a variety of mobile robots available at CERN. In summary, this thesis offers novel methods and demonstrates their use to predict energy autonomy and wireless communication range, optimise robots position to improve communication quality and enhance communication range and wireless network qualities of mobile robots for use in applications in hostile environmental characteristics such as scientific facilities emitting ionising radiations. In simpler terms, a set of tools are developed in this thesis for improving, easing and making safer robotic missions in hostile environments. This thesis validates both in theory and experiments that mobile robots can improve wireless communication quality by exploiting robots mobility to dynamically optimise their positions and maintain connectivity even when the (radio signal) environment possess non-line-of-sight characteristics. The methods developed in this thesis are well-suited for easier integration in mobile robots and can be applied directly at the application layer of the wireless network. The results of the proposed methods have outperformed other comparable state-of-the-art methods.

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.

Passive neutron area monitor with pairs of TLDs as neutron detector

A passive neutron area monitor has been designed using Monte Carlo methods; the monitor is a polyethylene cylinder with pairs of thermoluminescent dosimeters (TLD600 and TLD700) as thermal neutron detector. The monitor was calibrated with a bare and a thermalzed 241AmBe neutron sources and its performance was evaluated measuring the ambient dose equivalent due to photoneutrons produced by a 15 MV linear accelerator for radiotherapy and the neutrons in the output of a TRIGA Mark III radial beam port.

AlGaAs/GaAs photovoltaic converters for high power narrowband radiation

AlGaAs/GaAs-based laser power PV converters intended for operation with high-power (up to 100 W/cm(2)) radiation were fabricated by LPE and MOCVD techniques. Monochromatic (lambda = 809 nm) conversion efficiency up to 60% was measured at cells with back surface field and low (x = 0.2) Al concentration 'window'. Modules with a voltage of 4 V and the efficiency of 56% were designed and fabricated.

Effects of a bifenthrin-treated net on the natural enemies Aphidius colemani (Haliday) and Adalia bipunctata L. in a cucumber crop in Central Spain. Semi-field experiments

Pest management practices that rely on pesticides are growing increasingly less effective and environmentally inappropriate in many cases and the search of alternatives is under focus nowadays. Exclusion of pests from the crop by means of pesticide-treated screens can be an eco-friendly method to protect crops, especially if pests are vectors of important diseases. The mesh size of nets is crucial to determine if insects can eventually cross the barrier or exclude them because there is a great variation in insect size depending on the species. Long-lasting insecticide-treated (LLITN) nets, factory pre-treated, have been used since years to fight against mosquitoes vector of malaria and are able to retain their biological efficacy under field for 3 years. In agriculture, treated nets with different insecticides have shown efficacy in controlling some insects and mites, so they seem to be a good tool in helping to solve some pest problems. However, treated nets must be carefully evaluated because can diminish air flow, increase temperature and humidity and decrease light transmission, which may affect plant growth, pests and natural enemies. As biological control is considered a key factor in IPM nowadays, the potential negative effects of treated nets on natural enemies need to be studied carefully. In this work, the effects of a bifentrhin-treated net (3 g/Kg) (supplied by the company Intelligent Insect Control, IIC) on natural enemies of aphids were tested on a cucumber crop in Central Spain in autumn 2011. The crop was sown in 8x6.5 m tunnels divided in 2 sealed compartments with control or treated nets, which were simple yellow netting with 25 mesh (10 x 10 threads/cm2; 1 x 1 mm hole size). Pieces of 2 m high of the treated-net were placed along the lateral sides of one of the two tunnel compartments in each of the 3 available tunnels (replicates); the rest was covered by a commercial untreated net of a similar mesh. The pest, Aphis gossypii Glover (Aphidae), the parasitoid Aphidius colemani (Haliday) (Braconidae) and the predator Adalia bipunctata L. (Coccinellidae) were artificially introduced in the crop. Weekly sampling was done determining the presence or absence of the pest and the natural enemies (NE) in the 42 plants/compartment as well as the number of insects in 11 marked plants. Environmental conditions (temperature, relative humidity, UV and PAR radiation) were recorded. Results show that when aphids were artificially released inside the tunnels, neither its number/plant nor their distribution was affected by the treated net. A lack of negative effect of the insecticide-treated net on natural enemies was also observed. Adalia bipunctata did not establish in the crop and only a short term control of aphids was observed one week after release. On the other hand, A. colemani did establish in the crop and a more long-term effect on the numbers of aphids/plant was detected irrespective of the type of net. KEY WORDS: bifenthrin-treated net, Adalia bipunctata, Aphidius colemani, Aphis gossypii, semi-field

Design of a new neutron delivery system for high flux source

La construcci��n en la actualidad de nuevas fuentes para el uso de haces de neutrones as�� como los programas de renovaci��n en curso en algunas de las instalaciones experimentales existentes han evidenciado la necesidad urgente de desarrollar la tecnolog��a empleada para la construcci��n de gu��as de neutrones con objeto de hacerlas mas eficientes y duraderas. Esto viene motivado por el hecho de que varias instalaciones de experimentaci��n con haces de neutrones han reportado un n��mero de incidentes mec��nicos con tales gu��as, lo que hace urgente el progresar en nuestro conocimiento de los susbtratos v��treos sobre los cuales se depositan los espejos que permiten la reflexi��n total de los neutrones y como aquellos se degradan con la radiaci��n. La presente tesis se inscribe en un acuerdo de colaboraci��n establecido entre el Institut Max von Laue - Paul Langevin (ILL) de Grenoble y el Consorcio ESS-Bilbao con objeto de mejorar el rendimiento y sostenibilidad de los sistemas futuros de guiado de neutrones. El caso de la Fuente Europea de Espalaci��n en construcci��n en Lund sirve como ejemplo ya que se contempla la instalaci��n de gu��as de neutrones de m��s de 100 metros en algunos de los instrumentos. Por otro lado, instalaciones como el ILL prev��n tambi��n dentro del programa Endurance de rejuvenecimiento la reconstrucci��n de varias l��neas de transporte de haz. Para el presente estudio se seleccionaron cuatro tipos de vidrios borosilicatados que fueron el Borofloat, N-ZK7, N-BK7 y SBSL7. Los tres primeros son bien conocidos por los especialistas en instrumentaci��n neutr��nica ya que se han empleado en la construcci��n de varias instalaciones mientras que el ��ltimo es un candidato potencial en la fabricaci��n de substratos para espejos neutr��nicos en un futuro. Los cuatro vidrios tiene un contenido en ��xido de Boro muy similar, approximadamente un 10 mol.%. Tal hecho que obedece a las regulaciones para la fabricaci��n de estos dispositivos hace que tales substratos operen como protecci��n radiol��gica absorbiendo los neutrones transmitidos a trav��s del espejo de neutrones. Como contrapartida a tal beneficio, la reacci��n de captura 10B(n,_)7Li puede degradar el substrato v��treo debido a los 2.5 MeV de energ��a cin��tica depositados por la part��cula _ y los n��cleos en retroceso y de hecho la fragilidad de tales vidrios bajo radiaci��n ha sido atribuida desde hace ya tiempo a los efectos de esta reacci��n. La metodolog��a empleada en esta tesis se ha centrado en el estudio de la estructura de estos vidrios borosilicatados y como esta se comporta bajo condiciones de radiaci��n. Los materiales en cuesti��n presentan estructuras que dependen de su composici��n qu��mica y en particular del ratio entre formadores y modificadores de la red iono-covalente. Para ello se han empleado un conjunto de t��cnicas de caracterizaci��n tanto macro- como microsc��picas tales como estudios de dureza, TEM, Raman, SANS etc. que se han empleado tambi��n para determinar el comportamiento de estos materiales bajo radiaci��n. En particular, algunas propiedades macrosc��picas relacionadas con la resistencia de estos vidrios como elementos estructurales de las gu��as de neutrones han sido estudiadas as�� como tambi��n los cambios en la estructura v��trea consecuencia de la radiaci��n. Para este prop��sito se ha dise��ado y fabricado por el ILL un aparato para irradiaci��n de muestras con neutrones t��rmicos en el reactor del ILL que permite controlar la temperatura alcanzada por la muestra a menos de 100 ��C. Tal equipo en comparaci��n con otros ya existences permite en cuesti��n de dias acumular las dosis recibidas por una gu��a en operaci��n a lo largo de varios a��os. El uso conjunto de varias t��cnicas de caracterizaci��n ha llevado a revelar que los vidrios aqui estudiados son significativamente diferentes en cuanto a su estructura y que tales diferencias afectan a sus propiedades macrosc��picas asi como a su comportamiento bajo radiaci��n. Tal resultado ha sido sorprendente ya que, como se ha mencionado antes, algunos de estos vidrios eran bien conocidos por los fabricantes de gu��as de neutrones y hasta el momento eran considerados pr��cticamente similares debido a su contenido comparable en ��xido de Boro. Sin embargo, los materiales N-BK7 and S-BSL7 muetran gran homogeneidad a todas las escalas de longitud, y m��s espec��ficamente, a escalas nanom��tricas las subredes de S��lice y ��xido de Boro se mezclan dando logar a estructuras locales que recuerdan a la del cristal de Reedmergnerita. Por el contrario, N-ZK7 y Borofloat muestran dominios separados ricos en S��lice o Boro. Como era de esperar, las importantes diferencias arriba mencionadas se traducen en comportamientos dispares de estos materiales bajo un haz de neutrones t��rmicos. Los resultados muestran que el N-BK7 y el S-BSL7 son los m��s estables bajo radiaci��n, lo que macrosc��picamente hace que estos materiales muestren un comportamiento similar expandi��ndose lentamente en funci��n de la dosis recibida. Por el contario, los otros dos materiales muestran un comportamiento mucho m��s reactivo, que hace que inicialmente se compacten con la dosis recibida lo que hace que las redes de Silicio y Boro se mezclen resultando en un incremento en densidad hasta alcanzar un valor l��mite, seguido por un proceso de expansi��n lenta que resulta comparable al observado para N-BK7 y SBSL7. Estos resultados nos han permitido explicar el origen de las notorias diferencias observadas en cuanto a las dosis l��mite a partir de las cuales estos materiales desarrollan procesos de fragmentaci��n en superficie. ABSTRACT The building of new experimental neutron beam facilities as well as the renewal programmes under development at some of the already existing installations have pinpointed the urgent need to develop the neutron guide technology in order to make such neutron transport devices more efficient and durable. In fact, a number of mechanical failures of neutron guides have been reported by several research centres. It is therefore important to understand the behaviour of the glass substrates on top of which the neutron optics mirrors are deposited and how these materials degrade under radiation conditions. The case of the European Spallation Source (ESS) at present under construction at Lund is a good example. It previews the deployment of neutron guides having more than 100 metres of length for most of the instruments. Also, the future renovation programme of the ILL, called Endurance, foresees the refurbishment of several beam lines. This Ph.D. thesis was the result of a collaboration agreement between the ILL and ESS-Bilbao aiming to improve the performance and sustainability of future neutron delivery systems. Four different industrially produced alkali-borosilicate glasses were selected for this study: Borofloat, N-ZK7, N-BK7 and SBSL7. The first three are well known within the neutron instrumentation community as they have already been used in several installations whereas the last one is at present considered as a candidate for making future mirror substrates. All four glasses have a comparable content of boron oxide of about 10 mol.%. The presence of such a strong neutron absorption element is in fact a mandatory component for the manufacturing of neutron guides because it provides a radiological shielding for the environment. This benefit is however somewhat counterbalanced since the resulting 10B(n,_)7Li reactions degrade the glass due to the deposited energy of 2.5 MeV by the _ particle and the recoil nuclei. In fact, the brittleness of some of these materials has been ascribed to this reaction. The methodology employed by this study consisted in understanding the general structure of borosilicates and how they behave under irradiation. Such materials have a microscopic structure strongly dependent upon their chemical content and particularly on the ratios between network formers and modifiers. The materials have been characterized by a suite of macroscopic and structural techniques such as hardness, TEM, Raman, SANS, etc. and their behaviour under irradiation was analysed. Some macroscopic properties related to their resistance when used as guide structural elements were monitored. Also, changes in the vitreous structure due to radiation were observed by means of several experimental tools. For such a purpose, an irradiation apparatus has been designed and manufactured to enable irradiation with thermal neutrons within the ILL reactor while keeping the samples below 100 ��C. The main advantage of this equipment if compared to others previously available was that it allowed to reach in just some days an equivalent neutron dose to that accumulated by guides after several years of use. The concurrent use of complementary characterization techniques lead to the discovery that the studied glasses were deeply different in terms of their glass network. This had a strong impact on their macroscopic properties and their behaviour under irradiation. This result was a surprise since, as stated above, some of these materials were well known by the neutron guide manufacturers, and were considered to be almost equivalent because of their similar boron oxide content. The N-BK7 and S-BSL7 materials appear to be fairly homogeneous glasses at different length scales. More specifically, at nanometre scales, silicon and boron oxide units seem to mix and generate larger structures somewhat resembling crystalline Reedmergnerite. In contrast, N-ZK7 and Borofloat are characterized by either silicon or boron rich domains. As one could expect, these drastic differences lead to their behaviour under thermal neutron flux. The results show that N-BK7 and S-BSL7 are structurally the most stable under radiation. Macroscopically, such stability results in the fact that these two materials show very slow swelling as a function or radiation dose. In contrast, the two other glasses are much more reactive. The whole glass structure compacts upon radiation. Specifically, the silica network, and the boron units tend to blend leading to an increase in density up to some saturation, followed by a very slow expansion which comes to be of the same order than that shown by N-BK7 and S-BSL7. Such findings allowed us to explain the drastic differences in the radiation limits for macroscopic surface splintering for these materials when they are used in neutron guides.

New methods for the synthesis of radiation patterns of coupled antenna arrays = Nuevos m��todos de s��ntesis de diagramas de radiaci��n de agrupaciones de antenas acopladas

El principal objetivo de esta tesis es el desarrollo de m��todos de s��ntesis de diagramas de radiaci��n de agrupaciones de antenas, en donde se realiza una caracterizaci��n electromagn��tica rigurosa de los elementos radiantes y de los acoplos mutuos existentes. Esta caracterizaci��n no se realiza habitualmente en la gran mayor��a de m��todos de s��ntesis encontrados en la literatura, debido fundamentalmente a dos razones. Por un lado, se considera que el diagrama de radiaci��n de un array de antenas se puede aproximar con el factor de array que ��nicamente tiene en cuenta la posici��n de los elementos y las excitaciones aplicadas a los mismos. Sin embargo, como se mostrar�� en esta tesis, en m��ltiples ocasiones un riguroso an��lisis de los elementos radiantes y del acoplo mutuo entre ellos es importante ya que los resultados obtenidos pueden ser notablemente diferentes. Por otro lado, no es sencillo combinar un m��todo de an��lisis electromagn��tico con un proceso de s��ntesis de diagramas de radiaci��n. Los m��todos de an��lisis de agrupaciones de antenas suelen ser costosos computacionalmente, ya que son estructuras grandes en t��rminos de longitudes de onda. Generalmente, un dise��o de un problema electromagn��tico suele comprender varios an��lisis de la estructura, dependiendo de las variaciones de las caracter��sticas, lo que hace este proceso muy costoso. Dos m��todos se utilizan en esta tesis para el an��lisis de los arrays acoplados. Ambos est��n basados en el m��todo de los elementos finitos, la descomposici��n de dominio y el an��lisis modal para analizar la estructura radiante y han sido desarrollados en el grupo de investigaci��n donde se engloba esta tesis. El primero de ellos es una t��cnica de an��lisis de arrays finitos basado en la aproximaci��n de array infinito. Su uso es indicado para arrays planos de grandes dimensiones con elementos equiespaciados. El segundo caracteriza el array y el acoplo mutuo entre elementos a partir de una expansi��n en modos esf��ricos del campo radiado por cada uno de los elementos. Este m��todo calcula los acoplos entre los diferentes elementos del array usando las propiedades de traslaci��n y rotaci��n de los modos esf��ricos. Es capaz de analizar agrupaciones de elementos distribuidos de forma arbitraria. Ambas t��cnicas utilizan una formulaci��n matricial que caracteriza de forma rigurosa el campo radiado por el array. Esto las hace muy apropiadas para su posterior uso en una herramienta de dise��o, como los m��todos de s��ntesis desarrollados en esta tesis. Los resultados obtenidos por estas t��cnicas de s��ntesis, que incluyen m��todos rigurosos de an��lisis, son consecuentemente m��s precisos. La s��ntesis de arrays consiste en modificar uno o varios par��metros de las agrupaciones de antenas buscando unas determinadas especificaciones de las caracter��sticas de radiaci��n. Los par��metros utilizados como variables de optimizaci��n pueden ser varios. Los m��s utilizados son las excitaciones aplicadas a los elementos, pero tambi��n es posible modificar otros par��metros de dise��o como son las posiciones de los elementos o las rotaciones de estos. Los objetivos de las s��ntesis pueden ser dirigir el haz o haces en una determinada direcci��n o conformar el haz con formas arbitrarias. Adem��s, es posible minimizar el nivel de los l��bulos secundarios o del rizado en las regiones deseadas, imponer nulos que evitan posibles interferencias o reducir el nivel de la componente contrapolar. El m��todo para el an��lisis de arrays finitos basado en la aproximaci��n de array infinito considera un array finito como un array infinito con un n��mero finito de elementos excitados. Los elementos no excitados est��n f��sicamente presentes y pueden presentar tres diferentes terminaciones, corto-circuito, circuito abierto y adaptados. Cada una de estas terminaciones simular�� mejor el entorno real en el que el array se encuentre. Este m��todo de an��lisis se integra en la tesis con dos m��todos diferentes de s��ntesis de diagramas de radiaci��n. En el primero de ellos se presenta un m��todo basado en programaci��n lineal en donde es posible dirigir el haz o haces, en la direcci��n deseada, adem��s de ejercer un control sobre los l��bulos secundarios o imponer nulos. Este m��todo es muy eficiente y obtiene soluciones ��ptimas. El mismo m��todo de an��lisis es tambi��n aplicado a un m��todo de conformaci��n de haz, en donde un problema originalmente no convexo (y de dif��cil soluci��n) es transformado en un problema convexo imponiendo restricciones de simetr��a, resolviendo de este modo eficientemente un problema complejo. Con este m��todo es posible dise��ar diagramas de radiaci��n con haces de forma arbitraria, ejerciendo un control en el rizado del l��bulo principal, as�� como en el nivel de los l��bulos secundarios. El m��todo de an��lisis de arrays basado en la expansi��n en modos esf��ricos se integra en la tesis con tres t��cnicas de s��ntesis de diagramas de radiaci��n. Se propone inicialmente una s��ntesis de conformaci��n del haz basado en el m��todo de la recuperaci��n de fase resuelta de forma iterativa mediante m��todos convexos, en donde relajando las restricciones del problema original se consiguen unas soluciones cercanas a las ��ptimas de manera eficiente. Dos m��todos de s��ntesis se han propuesto, donde las variables de optimizaci��n son las posiciones y las rotaciones de los elementos respectivamente. Se define una funci��n de coste basada en la intensidad de radiaci��n, la cual es minimizada de forma iterativa con el m��todo del gradiente. Ambos m��todos reducen el nivel de los l��bulos secundarios minimizando una funci��n de coste. El gradiente de la funci��n de coste es obtenido en t��rminos de la variable de optimizaci��n en cada m��todo. Esta funci��n de coste est�� formada por la expresi��n rigurosa de la intensidad de radiaci��n y por una funci��n de peso definida por el usuario para imponer prioridades sobre las diferentes regiones de radiaci��n, si as�� se desea. Por ��ltimo, se presenta un m��todo en el cual, mediante t��cnicas de programaci��n entera, se buscan las fases discretas que generan un diagrama de radiaci��n lo m��s cercano posible al deseado. Con este m��todo se obtienen dise��os que minimizan el coste de fabricaci��n. En cada uno de las diferentes t��cnicas propuestas en la tesis, se presentan resultados con elementos reales que muestran las capacidades y posibilidades que los m��todos ofrecen. Se comparan los resultados con otros m��todos disponibles en la literatura. Se muestra la importancia de tener en cuenta los diagramas de los elementos reales y los acoplos mutuos en el proceso de s��ntesis y se comparan los resultados obtenidos con herramientas de software comerciales. ABSTRACT The main objective of this thesis is the development of optimization methods for the radiation pattern synthesis of array antennas in which a rigorous electromagnetic characterization of the radiators and the mutual coupling between them is performed. The electromagnetic characterization is usually overlooked in most of the available synthesis methods in the literature, this is mainly due to two reasons. On the one hand, it is argued that the radiation pattern of an array is mainly influenced by the array factor and that the mutual coupling plays a minor role. As it is shown in this thesis, the mutual coupling and the rigorous characterization of the array antenna influences significantly in the array performance and its computation leads to differences in the results obtained. On the other hand, it is difficult to introduce an analysis procedure into a synthesis technique. The analysis of array antennas is generally expensive computationally as the structure to analyze is large in terms of wavelengths. A synthesis method requires to carry out a large number of analysis, this makes the synthesis problem very expensive computationally or intractable in some cases. Two methods have been used in this thesis for the analysis of coupled antenna arrays, both of them have been developed in the research group in which this thesis is involved. They are based on the finite element method (FEM), the domain decomposition and the modal analysis. The first one obtains a finite array characterization with the results obtained from the infinite array approach. It is specially indicated for the analysis of large arrays with equispaced elements. The second one characterizes the array elements and the mutual coupling between them with a spherical wave expansion of the radiated field by each element. The mutual coupling is computed using the properties of translation and rotation of spherical waves. This method is able to analyze arrays with elements placed on an arbitrary distribution. Both techniques provide a matrix formulation that makes them very suitable for being integrated in synthesis techniques, the results obtained from these synthesis methods will be very accurate. The array synthesis stands for the modification of one or several array parameters looking for some desired specifications of the radiation pattern. The array parameters used as optimization variables are usually the excitation weights applied to the array elements, but some other array characteristics can be used as well, such as the array elements positions or rotations. The desired specifications may be to steer the beam towards any specific direction or to generate shaped beams with arbitrary geometry. Further characteristics can be handled as well, such as minimize the side lobe level in some other radiating regions, to minimize the ripple of the shaped beam, to take control over the cross-polar component or to impose nulls on the radiation pattern to avoid possible interferences from specific directions. The analysis method based on the infinite array approach considers an infinite array with a finite number of excited elements. The infinite non-excited elements are physically present and may have three different terminations, short-circuit, open circuit and match terminated. Each of this terminations is a better simulation for the real environment of the array. This method is used in this thesis for the development of two synthesis methods. In the first one, a multi-objective radiation pattern synthesis is presented, in which it is possible to steer the beam or beams in desired directions, minimizing the side lobe level and with the possibility of imposing nulls in the radiation pattern. This method is very efficient and obtains optimal solutions as it is based on convex programming. The same analysis method is used in a shaped beam technique in which an originally non-convex problem is transformed into a convex one applying symmetry restrictions, thus solving a complex problem in an efficient way. This method allows the synthesis of shaped beam radiation patterns controlling the ripple in the mainlobe and the side lobe level. The analysis method based on the spherical wave expansion is applied for different synthesis techniques of the radiation pattern of coupled arrays. A shaped beam synthesis is presented, in which a convex formulation is proposed based on the phase retrieval method. In this technique, an originally non-convex problem is solved using a relaxation and solving a convex problems iteratively. Two methods are proposed based on the gradient method. A cost function is defined involving the radiation intensity of the coupled array and a weighting function that provides more degrees of freedom to the designer. The gradient of the cost function is computed with respect to the positions in one of them and the rotations of the elements in the second one. The elements are moved or rotated iteratively following the results of the gradient. A highly non-convex problem is solved very efficiently, obtaining very good results that are dependent on the starting point. Finally, an optimization method is presented where discrete digital phases are synthesized providing a radiation pattern as close as possible to the desired one. The problem is solved using linear integer programming procedures obtaining array designs that greatly reduce the fabrication costs. Results are provided for every method showing the capabilities that the above mentioned methods offer. The results obtained are compared with available methods in the literature. The importance of introducing a rigorous analysis into the synthesis method is emphasized and the results obtained are compared with a commercial software, showing good agreement.

Analysis and Design Considerations of an Electric Vehicle Powertrain regarding Energy Efficiency and Magnetic Field Exposure

En esta tesis se analiza el sistema de tracci��n de un veh��culo el��ctrico de bater��a desde el punto de vista de la eficiencia energ��tica y de la exposici��n a campos magn��ticos por parte de los pasajeros (radiaci��n electromagn��tica). Este estudio incluye tanto el sistema de almacenamiento de energ��a como la m��quina el��ctrica, junto con la electr��nica de potencia y los sistemas de control asociados a ambos. Los an��lisis y los resultados presentados en este texto est��n basados en modelos matem��ticos, simulaciones por ordenador y ensayos experimentales a escala de laboratorio. La investigaci��n llevada a cabo durante esta tesis tuvo siempre un marcado enfoque industrial, a pesar de estar desarrollada en un entorno de considerable car��cter universitario. Las l��neas de investigaci��n acometidas tuvieron como destinatario final al dise��ador y al fabricante del veh��culo, a pesar de lo cual algunos de los resultados obtenidos son preliminares y/o excesivamente acad��micos para resultar de inter��s industrial. En el ��mbito de la eficiencia energ��tica, esta tesis estudia sistemas h��bridos de almacenamiento de energ��a basados en una combinaci��n de bater��as de litio y supercondensadores. Este tipo de sistemas son analizados desde el punto de vista de la eficiencia mediante modelos matem��ticos y simulaciones, cuantificando el impacto de ��sta en otros par��metros tales como el envejecimiento de las bater��as. Respecto a la m��quina el��ctrica, el estudio se ha centrado en m��quinas s��ncronas de imanes permanentes. El an��lisis de la eficiencia considera tanto el dise��o de la m��quina como la estrategia de control, dejando parcialmente de lado el inversor y la t��cnica de modulaci��n (que son incluidos en el estudio como fuentes adicionales de p��rdidas, pero no como potenciales fuentes de optimizaci��n de la eficiencia). En este sentido, tanto la topolog��a del inversor (trif��sico, basado en IGBTs) como la t��cnica de modulaci��n (control de corriente en banda de hist��resis) se establecen desde el principio. El segundo aspecto estudiado en esta tesis es la exposici��n a campos magn��ticos por parte de los pasajeros. Este tema se enfoca desde un punto de vista predictivo, y no desde un punto de vista de diagn��stico, puesto que se ha desarrollado una metodolog��a para estimar el campo magn��tico generado por los dispositivos de potencia de un veh��culo el��ctrico. Esta metodolog��a ha sido validada mediante ensayos de laboratorio. Otros aspectos importantes de esta contribuci��n, adem��s de la metodolog��a en s�� misma, son las consecuencias que se derivan de ella (por ejemplo, recomendaciones de dise��o) y la comprensi��n del problema proporcionada por esta. Las principales contribuciones de esta tesis se listan a continuaci��n: una recopilaci��n de modelos de p��rdidas correspondientes a la mayor��a de dispositivos de potencia presentes en un veh��culo el��ctrico de bater��a, una metodolog��a para analizar el funcionamiento de un sistema h��brido de almacenamiento de energ��a para aplicaciones de tracci��n, una explicaci��n de c��mo ponderar energ��ticamente los puntos de operaci��n par-velocidad de un veh��culo el��ctrico (de utilidad para evaluar el rendimiento de una m��quina el��ctrica, por ejemplo), una propuesta de incluir un convertidor DC-DC en el sistema de tracci��n para minimizar las p��rdidas globales del accionamiento (a pesar de las nuevas p��rdidas introducidas por el propio DC-DC), una breve comparaci��n entre dos tipos distintos de algoritmos de minimizaci��n de p��rdidas para m��quinas s��ncronas de imanes permanentes, una metodolog��a predictiva para estimar la exposici��n a campos magn��ticos por parte de los pasajeros de un veh��culo el��ctrico (debida a los equipos de potencia), y finalmente algunas conclusiones y recomendaciones de dise��o respecto a dicha exposici��n a campos magn��ticos. ABSTRACT This dissertation analyzes the powertrain of a battery electric vehicle, focusing on energy efficiency and passenger exposure to electromagnetic fields (electromagnetic radiation). This study comprises the energy storage system as well as the electric machine, along with their associated power electronics and control systems. The analysis and conclusions presented in this dissertation are based on mathematical models, computer simulations and laboratory scale tests. The research performed during this thesis was intended to be of industrial nature, despite being developed in a university. In this sense, the work described in this document was carried out thinking of both the designer and the manufacturer of the vehicle. However, some of the results obtained lack industrial readiness, and therefore they remain utterly academic. Regarding energy efficiency, hybrid energy storage systems consisting in lithium batteries, supercapacitors and up to two DC-DC power converters are considered. These kind of systems are analyzed by means of mathematical models and simulations from the energy efficiency point of view, quantifying its impact on other relevant aspects such as battery aging. Concerning the electric machine, permanent magnet synchronous machines are studied in this work. The energy efficiency analysis comprises the machine design and the control strategy, while the inverter and its modulation technique are taken into account but only as sources of further power losses, and not as potential sources for further efficiency optimization. In this sense, both the inverter topology (3-phase IGBT-based inverter) and the switching technique (hysteresis current control) are fixed from the beginning. The second aspect studied in this work is passenger exposure to magnetic fields. This topic is approached from the prediction point of view, rather than from the diagnosis point of view. In other words, a methodology to estimate the magnetic field generated by the power devices of an electric vehicle is proposed and analyzed in this dissertation. This methodology has been validated by laboratory tests. The most important aspects of this contribution, apart from the methodology itself, are the consequences (for instance, design guidelines) and the understanding of the magnetic radiation issue provided by it. The main contributions of this dissertation are listed next: a compilation of loss models for most of the power devices found in a battery electric vehicle powertrain, a simulation-based methodology to analyze hybrid energy storage performance in traction applications, an explanation of how to assign energy-based weights to different operating points in traction drives (useful when assessing electrical machine performance, for instance), a proposal to include one DC-DC converter in electric powertrains to minimize overall power losses in the system (despite the new losses added by the DC-DC), a brief comparison between two kinds of loss-minimization algorithms for permanent magnet synchronous machines in terms of adaptability and energy efficiency, a predictive methodology to estimate passenger magnetic field exposure due to power devices in an electric vehicle, and finally some useful conclusions and design guidelines concerning magnetic field exposure.

Induced radioisotopes in a linac treatment hall

When linacs operate above 8MV an undesirable neutron field is produced whose spectrum has three main components: the direct spectrum due to those neutrons leaking out from the linac head, the scattered spectrum due to neutrons produced in the head that collides with the nuclei in the head losing energy and the third spectrum due to room-return effect. The third category of spectrum has mainly epithermal and thermal neutrons being constant at any location in the treatment hall. These neutrons induce activation in the linac components, the concrete walls and in the patient body. Here the induced radioisotopes have been identified in concrete samples located in the hall and in one of the wedges. The identification has been carried out using a gamma-ray spectrometer.