Electrodynamic tether for scientific mission in low Jovian orbit

An electrodynamic bare tether is shown to allow carrying out scientific observations very close to Jupiter, for exploration of its surface and subsurface, and ionospheric and atmospheric in-situ measurements. Starting at a circular equatorial orbit of radius about 1.3/1.4 times the Jovian radius, continuous propellantless Lorentz drag on a thin-tape tether in the 1-5 km length range would make a spacecraft many times as heavy as the tape slowly spiral in, over a period of many months, while generating power at a load plugged in the tether circuit for powering instruments in science data acquisition and transmission. Lying under the Jovian radiation belts, the tape would avoid the most severe problem facing tethers in Jupiter, which are capable of producing both power and propulsion but, operating slowly, could otherwise accumulate too high a radiation dose . The tether would be made to spin in its orbit to keep taut; how to balance the Lorentz torque is discussed. Constraints on heating and bowing are also discussed, comparing conditions for prograde versus retrograde orbits. The system adapts well to the moderate changes in plasma density and motional electric field through the limited radial range in their steep gradients near Jupiter.

A proposed bare-tether experiment on board a sounding rocket

A mission on board a sounding rocket to carry out two bare-tether experiments is proposed: a test of orbital-motion-limited (OML) collection and the proof-of-flight of a technique to determine the (neutral) density vertical profile in the critical E-layer. Since full bias from the motional field will be small (~ 20V), corresponding to a tape 1 km long and V rocket <8 km/s, a power source with a range of supply voltages of few kV would be used. First, the negative terminal of the supply would be connected to the tape, and the positive terminal to a round, conductive boom of length 10 - 20 m; electrons collected by the boom cross the supply into the tape, where they leak out at the rate of ion impact plus secondary emission. Determination of the density profile from measurements of auroral emissions observed from the rocket, as secondaries racing down the magnetic field reach an E-layer footprint, are discussed. Next the positive terminal of the voltage supply is connected to the tape, and the negative terminal to a Hollow Cathode (HC); electrons now collected by the tape cross the supply, and are ejected at the HC. The opposite connections, with current collection operated by tape and boom, and operating on electrons and ions, and through partial switching in the supply, allow testing OML collection in almost all respects it depends on.

Floating Bare Tether as Upper Atmosphere Probe

Use of a (bare) conductive tape electrically floating in LEO as an effective e-beam source that produces artificial auroras, and is free of problems that have marred standard beams, is considered. Ambient ions impacting the tape with KeV energies over most of its length liberate secondary electrons, which race down the magnetic field and excite neutrals in the E-layer, resulting in auroral emissions. The tether would operate at night-time with both a power supply and a plasma contactor off; power and contactor would be on at daytime for reboost. The optimal tape thickness yielding a minimum mass for an autonomous system is determined; the alternative use of an electric thruster for day reboost, depending on mission duration, is discussed. Measurements of emission brightness from the spacecraft could allow determination of the (neutral) density vertical profile in the critical E-layer; the flux and energy in the beam, varying along the tether, allow imaging line-of-sight integrated emissions that mix effects with altitude-dependent neutral density and lead to a brightness peak in the beam footprint at the E-layer. Difficulties in tomographic inversion, to determine the density profile, result from beam broadening, due to elastic collisions, which flattens the peak, and to the highly nonlinear functional dependency of line-of-sight brightness. Some dynamical issues are discussed.

Conductive-tether design for de-orbiting from given altitude and inclination

A bare tether with thin-tape cross section is both i) the most effective electrodinamic tether for given length and mass, and ii) capable of effective design for an arbitrary mission through its three disparate dimensions. It handily beats the fully insulated tether that exchanges current at both ends, a result resting in advantages of 2D current collection as against 3D collection; it has much greater perimeter than the round bare tether and much lower fatal debris-impact rate, leading to greatly faster de-orbiting and greatly higher probability of survival; and it only allows multi-line tethers reaching a few hundred lines to stand competitive. In selecting the disparate values of length L, width w, and thickness h for a de-orbit mission, performance involves three criteria: a) tether-tospacecraft mass ratio must be small; b) probability of survival against the debris environment must be high; and c) de-orbiting must be fast to reduce manoeuvres for avoiding catastrophic collisions with big active/passive satellites around. Beyond determining tether mass through the product Lwh, main dimension parameters affecting performance are L/h2li characterizing ohmic effects, and w determining electron collection. An algorithm for optimal selection of tape dimensions is elaborated.

A review of electrodynamic tethers for science applications

A bare electrodynamic tether (EDT) is a conductive thin wire or tape tens of kilometres long, which is kept taut in space by gravity gradient or spinning, and is left bare of insulation to collect (and carry) current as a cylindrical Langmuir probe in an ambient magnetized plasma. An EDT is a probe in mesothermal flow at highly positive (or negative) bias, with a large or extremely large 2D sheath, which may show effects from the magnetic self-field of its current and have electrons adiabatically trapped in its ram front. Beyond technical applications ranging from propellantless propulsion to power generation in orbit, EDTs allow broad scientific uses such as generating electron beams and artificial auroras; exciting Alfven waves and whistlers; odifying the radiation belts; and exploring interplanetary space and the Jovian magnetosphere. Asymptotic analysis, numerical simulations, laboratory tests, and planned missions on EDTs are reviewed

Effect of composition, sonication and pressure on the rate capability of 5 V-LiNi0.5Mn1.5O4 composite cathodes

Positive composite electrodes having LiNi0.5Mn1.5O4 spinel as active material, a blend of graphite and carbon black for increasing the electrode electrical conductivity and either polyvinyldenefluoride (PVDF) or a blend of PVDF with a small amount of Teflon® (1 wt%) for building up the electrode. They have been processed by tape casting on an aluminum foil as current collector using the doctor blade technique. Additionally, the component blends were either sonicated or not, and the processed electrodes were compacted or not under subsequent cold pressing. Composites electrodes with high weight, up to 17 mg/cm2, were prepared and studied as positive electrodes for lithium-ion batteries. The addition of Teflon® and the application of the sonication treatment lead to uniform electrodes that are well-adhered to the aluminum foil. Both parameters contribute to improve the capacity drained at high rates (5C). Additional compaction of the electrode/aluminum assemblies remarkably enhances the electrode rate capabilities. At 5C rate, remarkable capacity retentions between 80% and 90% are found for electrodes with weights in the range 3–17 mg/cm2, having Teflon® in their formulation, prepared after sonication of their component blends and compacted under 2 tonnes/cm2.

Mechanical behavior of 2G REBCO HTS at 77 and 300 K

El gran esfuerzo realizado durante la última década con el fin de integrar los diferentes materiales superconductores en el campo de los sistemas eléctricos y en otras aplicaciones tecnológicas ha dado lugar a un campo de investigación amplio y prometedor. El comportamiento eléctrico de los Superconductores de Alta Temperatura (SAT) crítica (masivo y cintas) depende de diferentes parámetros desde su fabricación hasta la aplicación final con imanes o cables. Sin embargo, las aplicaciones prácticas de estos materiales están fuertemente vinculadas con su comportamiento mecánico tanto a temperatura ambiente (manipulación durante fabricación o instalación) como a temperaturas criogénicas (condiciones de servicio). En esta tesis se ha estudiado el comportamiento mecánico de materiales masivos y cintas de alta temperatura crítica a 300 y 77 K (utilizando nitrógeno líquido). Se han obtenido la resistencia en flexión, la tenacidad de fractura y la resistencia a tracción a la temperatura de servicio y a 300 K. Adicionalmente, se ha medido la dureza mediante el ensayo Vickers y nanoindentación. El módulo Young se midió mediante tres métodos diferentes: 1) nanoindentación, 2) ensayos de flexión en tres puntos y 3) resonancia vibracional mediante grindosonic. Para cada condición de ensayo, se han analizado detalladamente las superficies de fractura y los micromecanismos de fallo. Las propiedades mecánicas de los materiales se han comparado con el fin de entender la influencia de las técnicas de procesado y de las características microestructurales de los monocristales en su comportamiento mecánico. Se ha estudiado el comportamiento electromecánico de cintas comerciales superconductoras de YBCO mediante ensayos de tracción y fatiga a 77 y 300 K. El campo completo de deformaciones en la superficie del material se ha obtenido utilizando Correlación Digital de Imágenes (DIC, por sus siglas en inglés) a 300 K. Además, se realizaron ensayos de fragmentación in situ dentro de un microscopio electrónico con el fin de estudiar la fractura de la capa superconductora y determinar la resistencia a cortante de la intercara entre el substrato y la capa cerámica. Se ha conseguido ver el proceso de la fragmentación aplicando tensión axial y finalmente, se han implementado simulaciones mediante elementos finitos para reproducir la delaminación y el fenómeno de la fragmentación. Por último, se han preparado uniones soldadas entre las capas de cobre de dos cintas superconductoras. Se ha medido la resistencia eléctrica de las uniones con el fin de evaluar el metal de soldadura y el proceso. Asimismo, se ha llevado a cabo la caracterización mecánica de las uniones mediante ensayos "single lap shear" a 300 y 77 K. El efecto del campo magnético se ha estudiado aplicando campo externo hasta 1 T perpendicular o paralelo a la cinta-unión a la temperatura de servicio (77 K). Finalmente, la distribución de tensiones en cada una de las capas de la cinta se estudió mediante simulaciones de elementos finitos, teniendo en cuenta las capas de la cinta mecánicamente más representativas (Cu-Hastelloy-Cu) que influyen en su comportamiento mecánico. The strong effort that has been made in the last years to integrate the different superconducting materials in the field of electrical power systems and other technological applications led to a wide and promising research field. The electrical behavior of High Temperature Superconducting (HTS) materials (bulk and coated conductors) depends on different parameters since their processing until their final application as magnets or cables. However, practical applications of such materials are strongly related with their mechanical performance at room temperature (handling) as well as at cryogenic temperatures (service conditions). In this thesis, the mechanical behavior of HTS bulk and coated conductors was investigated at 300 and 77 K (by immersion in liquid nitrogen). The flexural strength, the fracture toughness and the tensile strength were obtained at service temperature as well as at 300 K. Furthermore, their hardness was determined by Vickers measurements and nanoindentation and the Young's modulus was measured by three different techniques: 1) nanoindentation, 2) three-point bending tests and 3) vibrational resonance with a grindosonic device. The fracture and deformation micromechanics have been also carefully analyzed for each testing condition. The comparison between the studied materials has been performed in order to understand the influence of the main sintering methods and the microstructural characteristics of the single grains on the macroscopic mechanical behavior. The electromechanical behavior of commercial YBCO coated conductors was studied. The mechanical behavior of the tapes was studied under tensile and fatigue tests at 77 and 300 K. The complete strain field on the surface of the sample was obtained by applying Digital Image Correlation (DIC) at 300 K. Addionally, in situ fragmentation tests inside a Scanning Electron Microscope (SEM) were carried out in order to study the fragmentation of the superconducting layer and determine the interfacial shear strength between substrate and ceramic layer. The fragmentation process upon loading of the YBCO layer has been observed and finally, Finite Element Simulations were employed to reproduce delamination and fragmentation phenomena. Finally, joints between the stabilizing Cu sides of two coated conductors have been prepared. The electrical resistivity of the joints was measured for the purpose of qualifying the soldering material and evaluating the soldering process. Additionally, mechanical characterization under single lap shear tests at 300 and 77 K has been carried out. The effect of the applied magnetic field has been studied by applying external magnetic field up to 1 T perpendicular and parallel to the tape-joint at service temperature (77 K). Finally, finite element simulations were employed to study the distribution of the stresses in earch layer, taking into account the three mechanically relevant layers of the coated conductor (Cu-Hastelloy-Cu) that affect its mechanical behavior

Servicio de seguridad combinable mediante técnicas de orquestación de servicios

En los últimos años, la seguridad en redes y servicios ha evolucionado de manera exponencial debido al crecimiento de dispositivos conectados a Internet. Con el avance de las nuevas tecnologías es imprescindible dotar a cualquier servicio o dispositivo de la seguridad adecuada dado que éstos se pueden ver afectados por diversas amenazas tales como la accesibilidad, la integridad, la identidad del usuario, la disponibilidad y la confidencialidad de los datos. Cuando se trata de comunicaciones, la seguridad cobra especial importancia dado que los datos enviados a través de la red pueden ser interceptados por un agente no autorizado y utilizarlos para su propio beneficio o alterar su contenido. Para contrarrestar estos ataques, se han definido unos servicios de seguridad como son, por ejemplo, la confidencialidad y la integridad de los datos. Existen diversos mecanismos de seguridad que implementan estos servicios los cuales se apoyan en técnicas criptográficas. Desde el comienzo de las primeras comunicaciones se han desarrollado diferentes técnicas criptográficas que han ido evolucionando a la vez que éstas. La primera de estas técnicas conocida fue escítala lacedemonia en el siglo V a.C. Los éforos espartanos, que eran los que utilizaban dicha técnica, escribían el mensaje en una cinta de cuero o papiro enrollada en una vara de grosor variable. A continuación desenrollaban la cinta y la enviaban al receptor. Sí el mensaje era interceptado solo podrían leer una pila de letras sin sentido. Sí el mensaje llegaba al receptor, éste enrollaría de nuevo la cinta en una vara del mismo grosor que lo hizo el emisor y leería el mensaje. En este proyecto de fin de grado se va a realizar un estudio del estado de arte sobre mecanismos de seguridad para posteriormente diseñar e implementar un componente de seguridad que ofrecerá los servicios citados. Dicho componente se integrará en el sistema del proyecto Europeo I3RES como un servicio más de los definidos dentro del propio proyecto. Los servicios de seguridad que requiere el proyecto I3RES, y por tanto los que ofrecerá el componente, son los de autenticación, integridad, no repudio y confidencialidad. El proyecto I3RES basa su sistema en una arquitectura distribuida por lo que es necesario realizar un estudio del estado del arte sobre dichas arquitecturas para el correcto despliegue del componente en el sistema. Actualmente, la mayoría de los sistemas mantienen una arquitectura distribuida. Este tipo de arquitectura conecta distintos equipos y dispositivos que están separados físicamente mediante una red llamada middleware. Estos equipos trabajan conjuntamente para implementar un conjunto de servicios. En el documento presente se tratan todos los temas anteriormente citados y se detalla el componente a desarrollar así como las correspondientes pruebas de validación y las conclusiones obtenidas. ABSTRACT. Security in networks and services have been extensively developed in last decades due to the arising of multiple devices connected to Internet. Advances in new technologies enhanced the necessity of security requirements to in order to avoid several warnings such as accessibility, integrity, user identity, availability, and confidentiality of our data. In terms of communications, security is crucial due to data could be intercepted on Internet by non-authorised agents which could use them or even alter their content. In order to avoid this warnings, security services have been defined such as data confidentiality and integrity. There is several security mechanism which implement this services based on cryptographic techniques. In parallel to the evolution of communication, cryptographic technics have been also developed with. The most ancient of technics was described in s. V b.C called escitala lacedemonia. Spartan ephorts, which extensively used this method, were used to write messages on the surface of a leather tape or papyri which were rolled on a rod. Next, they unrolled the tape and they sent to the receptor. Whether the message was intercepted they just would be able to read a mess of letters without sense. On the other hand, if the message arrive to the proper receptor, he roll the tape again in a rod with similar anchor of the transmitter one which leads to the adequate read. This Degree Project is focused on an analysis of the state of art about security mechanism together with a design and implement of a security component which offered the services mentioned. This component will be integrated within the European project I3RES as one of the security elements defined inside the project. The security components required in project I3REs are authentication, integrity and non-repudiation will be offered by the designed component as well. Nowadays, the most of the systems maintain a distributed architecture. This type of architecture connect several devices which are physically separated by a network called middleware. This equipment work altogether to implement a set of services. This document is focused on all the topics mentioned as well as the details of the component developed together with the validation tests required and the conclusions obtained.

Propellantless deorbiting of space debris by bare electrodynamic tethers : final report

A Space tether is a thin, multi-kilometers long conductive wire, joining a satellite and some opposite end mass, and keeping vertical in orbit by the gravity-gradient. The ambient plasma, being highly conductive, is equipotential in its own co-moving frame. In the tether frame, in relative motion however, there is in the plasma a motional electric field of order of 100 V/km, product of (near) orbital velocity and geomagnetic field. The electromotive force established over the tether length allows plasma contactor devices to collect electrons at one polarized-positive (anodic) end and eject electrons at the opposite end, setting up a current along a standard, fully insulated tether. The Lorentz force exerted on the current by the geomagnetic field itself is always drag; this relies on just thermodynamics, like air drag. The bare tether concept, introduced in 1992 at the Universidad Politécnica de Madrid (UPM), takes away the insulation and has electrons collected over the tether segment coming out polarized positive; the concept rests on 2D (Langmuir probe) current-collection in plasmas being greatly more efficient than 3D collection. A Plasma Contactor ejects electrons at the cathodic end. A bare tether with a thin-tape cross section has much greater perimeter and de-orbits much faster than a (corresponding) round bare tether of equal length and mass. Further, tethers being long and thin, they are prone to cuts by abundant small space debris, but BETs has shown that the tape has a probability of being cut per unit time smaller by more than one order of magnitude than the corresponding round tether (debris comparable to its width are much less abundant than debris comparable to the radius of the corresponding round tether). Also, the tape collects much more current, and de-orbits much faster, than a corresponding multi-line “tape” made of thin round wires cross-connected to survive debris cuts. Tethers use a dissipative mechanism quite different from air drag and can de-orbit in just a few months; also, tape tethers are much lighter than round tethers of equal length and perimeter, which can capture equal current. The 3 disparate tape dimensions allow easily scalable design. Switching the cathodic Contactor off-on allows maneuvering to avoid catastrophic collisions with big tracked debris. Lorentz braking is as reliable as air drag. Tethers are still reasonably effective at high inclinations, where the motional field is small, because the geomagnetic field is not just a dipole along the Earth polar axis. BETs is the EC FP7/Space Project 262972, financed in about 1.8 million euros, from 1 November 2010 to 31 January 2014, and carrying out RTD work on de-orbiting space debris. Coordinated by UPM, it has partners Università di Padova, ONERA-Toulouse, Colorado State University, SME Emxys, DLR–Bremen, and Fundación Tecnalia. BETs work involves 1) Designing, building, and ground-testing basic hardware subsystems Cathodic Plasma Contactor, Tether Deployment Mechanism, Power Control Module, and Tape with crosswise and lengthwise structure. 2) Testing current collection and verifying tether dynamical stability. 3) Preliminary design of tape dimensions for a generic mission, conducive to low system-to-satellite mass ratio and probability of cut by small debris, and ohmic-effects regime of tether current for fast de-orbiting. Reaching TRL 4-5, BETs appears ready for in-orbit demostration.

Tether-mission design for multiple flybys of moon Europa

Electrodynamic tape-tethers are shown to allow a cheap, light, fast mission to Jupiter for multiple flybys of moon Europa and close exploration of the Jovian interior. As regards flybys, this mission is similar to the Clipper mission presently considered by NASA, the basic difference (periapsis location) arising from mission-challenge metrics.

Estudio acústico de la sala 8 de los cines Kinépolis de Ciudad de la Imagen

Este proyecto consistira en la realization de un estudio aciistico sobre la sala 8 de los cines Kinepolis de Ciudad de la Imagen, que dispone de 408 butacas. Los cines Kinepolis es uno de los mayores complejos multisala de Europa. Cuenta con mas de 9.200 butacas en total distribuidas en 25 salas a las que se accede mediante dos grandes pasillos conectados por el hall. En 1998, ano de su apertura, el complejo recibio el Record Guinness a la sala cinematografica mas grande del mundo, que dispone de 996 butacas. El objetivo de este proyecto es conseguir caracterizar acusticamente una sala de cine a traves de la medicion de parametros acusticos de la sala y de un modelo virtual de la misma. Para llevar a cabo el proyecto, primero se van a realizar tanto una medicion geometrica como acustica de la sala mediante el sistema de medida DIRAC. Los resultados de estas mediciones nos serviran para construir y validar un modelo virtual de la sala real con el software de simulacion EASE. La medicion acustica se va a realizar con el sistema de medicion DIRAC. Este sistema nos dara information sobre una amplia variedad de parametros acusticos. En este proyecto no se va a trabajar con todos ellos, solo con los mas significativos. Estos se describen a continuacion en la introduccion teorica. La medicion geometrica nos va a servir para construir un modelo virtual que tenga las mismas dimensiones que la sala original. Esta medicion la realizaremos mediante un medidor laser y una cinta metrica. Una vez construido el modelo virtual, se procedera a su validacion. Este proceso se realiza ajustando el tiempo de reverberacion del modelo mediante la introduccion de distintos materiales acusticos en las superficies del mismo, de manera que, variando la absorcion de la sala, el tiempo de reverberacion promedio del modelo se asemeje lo mas posible al medido en la sala real. Este proceso tiene como objetivo comprobar que el modelo virtual tiene un comportamiento acustico similar al de la sala real. Es necesario validar adecuadamente el modelo para que las comparaciones y conclusiones sean fiables. Por ultimo, tras la simulacion acustica del modelo, se compararan los resultados simulados con los medidos en la sala. En este proceso se contrastaran algunos de los parametros que guardan relation con el tiempo de reverberacion. De esta manera se verificara si el tiempo de reverberacion es o no un parametro acustico fiable para la validacion de un modelo virtual de una sala de cine. Anteriormente se han realizado proyectos iguales de otras salas de diferente tamano de Kinepolis. El objetivo de realizar el mismo estudio en distintas salas, es comprobar si el tamano de la sala influye en la validacion de los modelos virtuales mediante el tiempo de reverberacion. ABSTRACT. This Project consists on the development of an acoustic research of the movie theater 8 of the Kinepolis complex in Ciudad de la Imagen, Madrid. This room has 408 spots. Kinepolis is one of the biggest multiplex complexes in Europe. It has 9,200 locations disposed in 25 rooms. There are two large corridors which give access to all of theaters. In the middle of the structure, there is the main hall that connects these corridors. In 1998, at the time when the complex was open, it was awarded with the Record Guinness for the biggest theater in the world, which has 996 locations. The target of this project is to successfully characterize the acoustics of a movie theater through reverberation time and a virtual model. In order to reach this goal, in the first place, we are going to perform both, an acoustic and a geometric measurement of the room using DIRAC measurement system. The results of these measures will allow us to build and validate a virtual model of the room, using the simulation software EASE. We are going to use the DIRAC system in order to accomplish the acoustic measure. This operation gives us a huge variety of acoustic parameters. Not all of these are going to be used for this research, only the most significant ones. These are described in the theoretical introduction. The geometric measure is essential to help us to build the virtual model, because the model has to be exactly equal as the real room. This measurement will be performed with an electronic distance meter and a measuring tape. Once the virtual model is finished, it will be proved. This validation process will be realized by adjusting the reverberation time in the model. We will change the walls materials, therefore, the overall absorption of the room will change. We want the model reverberation time resemble to the real one. This practice is going to ensure that the model acoustic performance is close to the real one. In addition, it has to be successfully validate of we want the future comparisons to be reliable. Finally, after the model virtual simulation, we will compare the simulated results with the measure in the room. In this process, we will compare not only the reverberation time, but others parameters that keep relation with the reverberation time. We will verify this way, if the reverberation time is or is not an appropriate acoustic parameter to validate a virtual model of a movie theater. There have been done others similar acoustic researches in different theaters with different sizes. The aim of performing similar researches in different rooms is to determine if the size of the room infers in the validation process.

Relationship between residual stresses and mechanical behavior in ceramic composites

En este trabajo, materiales de tipo alúmina/Y-TZP (ZrO2 tetragonal, estabilizada con 3 mol. % Y2O3), como sistema cerámico popular por sus mejoradas propiedades mecánicas en comparación con las cerámicas de alúmina puras, han sido estudiados en términos de propiedades mecánicas y tensiones residuales. El novedoso método de colado en cinta, consistente en el apilamiento de cintas de cerámica verde a temperatura ambiente y el uso de bajas presiones, se ha escogido para la presente investigación con el fin de poder aprovechar al máximo el futuro desarrollo de materiales laminados de alúmina-óxido de circonio. Se han determinado las propiedades de los materiales obtenidos por este nuevo método de procesamiento comparándolas con las de los materiales obtenidos por “slip casting”, con el fin de analizar si el método propuesto afecta a la microestructura y, por tanto, a las propiedades mecánicas y tensiones residuales propias de estos materiales. Para analizar la idoneidad del proceso de fabricación, utilizado para evitar la presencia de discontinuidades en las intercaras entre las láminas así como otros fenómenos que puedan interferir con las propiedades mecánicas, se estudiaron materiales cerámicos con la misma composición en cintas. Por otra parte también se analizó el efecto de la adición de óxido de circonio sobre la aparición de tensiónes residuales en cerámicas Al2O3/Y-TZP, teniendo en cuenta su notable influencia sobre las propiedades microestructurales y mecánicas de los materiales, así como el requisito de co-sinterización de capas con diferentes materiales compuestos en materiales laminados. La caracterización del material incluye la determinación de la densidad, el análisis de la microestructura, la obtención de las propiedades mecánicas (módulo de elasticidad, dureza, resistencia a la flexión y tenacidad de fractura) así como de las tensiones residuales. En combinación con otros métodos de medida tradicionales, la nanoindentación también se empleó como una técnica adicional para la medida del módulo de elasticidad y de la dureza. Por otro lado, diferentes técnicas de difracción con neutrones, tanto las basadas en longitud de onda constante (CW) como en tiempo de vuelo (TOF), han sido empleadas para la medición fiable de la deformación residual a través del grosor en muestras a granel. Las tensiones residuales fueron determinadas con elevada precisión, aplicando además métodos de análisis apropiados, como por ejemplo el refinamiento de Rietveld. Las diferentes fases en cerámicas sinterizadas, especialmente las de zirconia, se examinaron con detalle mediante el análisis de Rietveld, teniendo en cuenta el complicado polimorfismo del Óxido de Zirconio (ZrO2) así como las posibles transformaciones de fase durante el proceso de fabricación. Los efectos del contenido de Y-TZP en combinación con el nuevo método de procesamiento sobre la microestructura, el rendimiento mecánico y las tensiones residuales de los materiales estudiados (Al2O3/Y-TZP) se resumen en el presente trabajo. Finalmente, los mecanismos de endurecimiento, especialmente los relacionados con las tensiones residuales, son igualmente discutidos. In present work, Alumina/Y-TZP (tetragonal ZrO2 stabilized with 3 mol% Y2O3) materials, as an popular ceramic system with improved mechanical properties compared with the pure alumina ceramics, have been studied in terms of mechanical properties and residual stresses. The novel tape casting method, which involved the stacking of green ceramics tapes at room temperature and using low pressures, is selected for manufacturing and investigation, in order to take full advantage of the future development of alumina-zirconia laminated materials. Features of materials obtained by the new processing method are determined and compared with those of materials obtained by conventional slip casting in a plaster mold, in order to study whether the proposed method of processing affects microstructure and thereby the mechanical properties and residual stresses characteristics of materials. To analyse the adequacy of the manufacturing process used to avoid the presence of discontinuities at the interfaces between the sheets and other phenomena that interfere with the mechanical properties, ceramic materials with the same composition in tapes were investigated. Moreover, the effect of addition of zirconia on residual stress development of Al2O3/Y-TZP ceramics were taken into investigations, considering its significantly influence on the microstructure and mechanical properties of materials as well as the requirement of co-sintering of layers with different composites in laminated materials. The characterization includes density, microstructure, mechanical properties (elastic modulus, hardness, flexure strength and fracture toughness) and residual stresses. Except of the traditional measurement methods, nanoindentation technique was also used as an additional measurement of the elastic modulus and hardness. Neutron diffraction, both the constant-wavelength (CW) and time-of-flight (TOF) neutron diffraction techniques, has been used for reliable through-thickness residual strain measurement in bulk samples. Residual stresses were precisely determined combined with appropriate analysis methods, e.g. the Rietveld refinement. The phase compositions in sintered ceramics especially the ones of zirconia were accurately examined by Rietveld analysis, considering the complex polymorph of ZrO2 and the possible phase transformation during manufacturing process. Effects of Y-TZP content and the new processing method on the microstructure, mechanical performance and residual stresses were finally summarized in present studied Al2O3/Y-TZP materials. The toughening mechanisms, especially the residual stresses related toughening, were theoretically discussed.

Entorno sin cinta para producción de televisión en alta definición

En este proyecto se propone un entorno de producción para televisión en alta definición donde las cintas magnéticas para la captura, modificación, gestión y transferencia de los contenidos audiovisuales, quedan sustituidas por servidores informáticos y sistemas de almacenamiento basados en las tecnologías de la información. Dicho entorno sin cintas tiene como misión la realización de la fase de la producción de los contenidos televisivos. Se trata de un centra independiente, en una ubicación remota respecto a las instalaciones centrales de la empresa emisora de televisión. La conexión del entorno sin cinta con los servicios centrales de la cadena se realiza por medio de redes de datos de alta velocidad y por enlace de radiofrecuencia. Por estos medios los sistemas de redacción comunican datos y escaletas, se reciben las señales de contribución que intervienen en los programas, se envía la serial realizada para emisión y se transfieren los materiales grabados al área de Postproducción para su elaboración final. Se plantean dos estudios de televisión dotados de servidores de video y de un almacenamiento compartido para una gestión ágil, unificada y flexible de las demandas de los programas. Además de la eliminación del lento y pesado trabajo de manipulación de las cintas, la producción resulta mucho mas ágil porque se eliminan tiempos de espera por la posibilidad de acceso simultaneo de varios usuarios a un mismo contenido. También se suprimen los tiempos de digitalización y descarga del material grabado, porque los sistemas implementados permiten la ingesta directa de las señales recibidas. Los contenidos de varias jornadas de grabación, en calidad HD, se conservan en el sistema de almacenamiento para la elaboración de materiales en el propio centra y para su transferencia al departamento central correspondiente. Mediante aplicaciones software se busca la integración del trabajo de la redacción de los programas con los procesos de producción de los estudios. El diseño que se propone para los diferentes subsistemas técnicos de los estudios esta orientado a lograr una alta fiabilidad, operatividad y adaptabilidad a las demandas técnicas de la producción audiovisual de los diferentes tipos de programas. Al tratarse de una propuesta conceptual, de manera general no se basa en equipos de marcas o fabricantes concretos sino mas bien en las metodologías concretas de trabajo. Cuando se ejemplifica algún dispositivo en particular es debido a que el concepto tecnológico del mismo es novedoso destaca de manera especial sobre la generalidad de los equipos existentes para esa funcionalidad. ABSTRACT. This project hopes to propose a television production platform that uses computers, servers and storage systems based on information technologies, rather than video tape recorders for ingesting, editing and making TV programs. This tapeless system has as its mission the production of all kind of television contents, employing IT systems, without the use of magnetic tapes. We envision an independent TV production center located in a remote location, in relation to the main broadcaster facilities, where all communications between this broadcasting center and the remote independent tapeless center would occur via high speed internet and a radiofrequency link as a back up. In this way, the Newsroom systems communicate data and rundowns; contribution feeds are received; PGM signal are codified and transmitted; and stored media are transferred to the post production area for final editing, playout and archive. Two TV studios are proposed, equipped with video servers and sharing media storage for agile, unified and flexible management of the production requirements. Apart from completely eliminating the slow and hard work resulting from handling a lot of traditional magnetic tapes, the production ends up being much quicker due to the fact that there is no waiting time between recording and viewing. This also enables several users to access and view the same material at the same time. The digitalization and downloading time is also greatly reduced due to the direct ingestion of contribution feeds to the system. The HD content of various days of recording, are stored for future use for whichever department needs the footage in the future. Through software applications, there will be complete integration between the Newsroom work and the production process of the studios. The proposed design for the various technical subsystems in the recording studio is directed towards achieving optimum reliability and operational capability: they are easily adaptable to the technical demands of the audiovisual production of the different programs. Because we are dealing with a conceptual proposal, in general terms, we are not defining the brands or manufacturers of the technical equipment, but rather we are specifying the methods which we plan to implement. When some equipment is highlighted, it's only because that specific brand exemplifies a higher performance than any other equipment in the range.

Percutaneous peptide immunization via corneum barrier-disrupted murine skin for experimental tumor immunoprophylaxis

H-2Kb-restricted tumor epitope peptides, including tyrosinase-related protein 2 residues 181–188 (TRP-2) and connexin 37 residues 52–59 (MUT1), were applied to permeability barrier-disrupted C57BL/6 (B6) mouse skin from which the stratum corneum of the epidermis had been removed by tape-stripping. This procedure primed tumor-specific cytotoxic T lymphocytes (CTLs) in the lymph nodes and spleen, protected mice against subsequent challenge with corresponding tumor cells, and suppressed the growth of established tumors. Preventive and therapeutic effectiveness was correlated with the frequency of tumor-specific CTL precursors. MHC class II Iab+ cells separated from tape-stripped skin, compared with those from intact skin, exhibited a strong antigen-presenting capacity for CTL, suggesting that CTL expansion after peptide application is primarily mediated by epidermal Langerhans cells. Thus, percutaneous peptide immunization via barrier-disrupted skin provides a simple and noninvasive means of inducing potent anti-tumor immunity which may be exploited for cancer immunotherapy.

Análise in vitro da morfologia e da resistência de união da resina composta à dentina erodida e irradiada com laser de Er:YAG com largura de pulso super curta

Lesões dentais por erosão têm sido cada vez mais presentes na prática clínica. A restauração direta com resina composta é uma das opções de tratamento para lesões severas, em que há comprometimento estético/funcional. Com o aprimoramento da tecnologia, a utilização do laser para pré-tratamento da superfície dentinária, antes do condicionamento ácido, tem sido considerada como método alternativo para melhorar a adesão das resinas compostas às superfícies erodidas. Assim, o objetivo deste estudo in vitro foi avaliar a influência da irradiação com laser de Er:YAG (2,94 ?m), de pulso super-curto, na adesão da resina composta à superfície dentinária erodida. Quarenta e seis discos de dentina foram obtidos a partir de 46 dentes terceiros molares humanos. A dentina oclusal planificada de 40 molares humanos teve metade de sua face protegida com fita UPVC (dentina hígida), enquanto na outra metade foi produzida uma lesão de erosão através da ciclagem em ácido cítrico (0,05 M, pH 2,3, 10 minutos, 6x/dia) e solução supersaturada (pH 7,0, 60 minutos entre os ataques ácidos). Metade das amostras foi irradiada com o laser de Er:YAG (50 ?s, 2 Hz, 80 mJ, 12,6 J/cm2) e a outra não (grupo controle). Em cada grupo de tratamento (laser ou controle) (n=10), um sistema adesivo autocondicionante foi utilizado e, então, confeccionados 2 cilindros de resina composta, tanto do lado erodido como no hígido (total de 4 cilindros), os quais foram submetidos à avaliação da Resistência de União através do ensaio de microcisalhamento (1 mm/min), após armazenamento em saliva artificial por 24 h. A análise do padrão de fratura foi realizada em microscópio óptico (40x). Por meio da Microscopia Eletrônica de Varredura (MEV), a morfologia das superfícies dentinárias hígida e submetida ao desafio erosivo, antes e após o tratamento com laser de Er:YAG (n=3), foi avaliada. Os valores obtidos de resistência de união (MPa) foram submetidos ao teste ANOVA e de comparações múltiplas de Tukey (p<0,05) e as análises das eletromicrografias foram feitas de forma descritiva. A análise morfológica da superfície mostrou alterações significativas na dentina hígida irradiada e na submetida à ciclagem erosiva, irradiada ou não. Quanto à resistência de união, houve diferença entre os 4 substratos analisados, sendo: dentina hígida irradiada (12,77±5,09 A), dentina hígida não irradiada (9,76±3,39 B), dentina erodida irradiada (7,62±3,39 C) e dentina erodida não irradiada (5,12±1,72 D). Houve predominância de padrão de fratura do tipo adesiva. Com base nos resultados e nos parâmetros de irradiação utilizados neste estudo, pode-se concluir que a erosão reduz a adesão em dentina e que o tratamento da superfície dentinária com laser de Er:YAG de largura de pulso super curta aumenta a adesão no substrato erodido ou hígido.