865 resultados para Cipher and telegraph codes
Resumo:
The thesis deals with channel coding theory applied to upper layers in the protocol stack of a communication link and it is the outcome of four year research activity. A specific aspect of this activity has been the continuous interaction between the natural curiosity related to the academic blue-sky research and the system oriented design deriving from the collaboration with European industry in the framework of European funded research projects. In this dissertation, the classical channel coding techniques, that are traditionally applied at physical layer, find their application at upper layers where the encoding units (symbols) are packets of bits and not just single bits, thus explaining why such upper layer coding techniques are usually referred to as packet layer coding. The rationale behind the adoption of packet layer techniques is in that physical layer channel coding is a suitable countermeasure to cope with small-scale fading, while it is less efficient against large-scale fading. This is mainly due to the limitation of the time diversity inherent in the necessity of adopting a physical layer interleaver of a reasonable size so as to avoid increasing the modem complexity and the latency of all services. Packet layer techniques, thanks to the longer codeword duration (each codeword is composed of several packets of bits), have an intrinsic longer protection against long fading events. Furthermore, being they are implemented at upper layer, Packet layer techniques have the indisputable advantages of simpler implementations (very close to software implementation) and of a selective applicability to different services, thus enabling a better matching with the service requirements (e.g. latency constraints). Packet coding technique improvement has been largely recognized in the recent communication standards as a viable and efficient coding solution: Digital Video Broadcasting standards, like DVB-H, DVB-SH, and DVB-RCS mobile, and 3GPP standards (MBMS) employ packet coding techniques working at layers higher than the physical one. In this framework, the aim of the research work has been the study of the state-of-the-art coding techniques working at upper layer, the performance evaluation of these techniques in realistic propagation scenario, and the design of new coding schemes for upper layer applications. After a review of the most important packet layer codes, i.e. Reed Solomon, LDPC and Fountain codes, in the thesis focus our attention on the performance evaluation of ideal codes (i.e. Maximum Distance Separable codes) working at UL. In particular, we analyze the performance of UL-FEC techniques in Land Mobile Satellite channels. We derive an analytical framework which is a useful tool for system design allowing to foresee the performance of the upper layer decoder. We also analyze a system in which upper layer and physical layer codes work together, and we derive the optimal splitting of redundancy when a frequency non-selective slowly varying fading channel is taken into account. The whole analysis is supported and validated through computer simulation. In the last part of the dissertation, we propose LDPC Convolutional Codes (LDPCCC) as possible coding scheme for future UL-FEC application. Since one of the main drawbacks related to the adoption of packet layer codes is the large decoding latency, we introduce a latency-constrained decoder for LDPCCC (called windowed erasure decoder). We analyze the performance of the state-of-the-art LDPCCC when our decoder is adopted. Finally, we propose a design rule which allows to trade-off performance and latency.
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A study was conducted to empirically determine the degradation of survey-grade GPS horizontal position measurements due to the effects of broadleaf forest canopies. The measurements were taken using GPS/GLONASS-capable receivers measuring C/A and P-codes, and carrier phase. Fourteen survey markers were chosen in central Connecticut to serve as reference markers for the study. These markers had varying degrees of sky obstruction due to overhanging tree canopies. Sky obstruction was measured by photographing the sky with a 35mm reflex camera fitted with a hemispherical lens. The negative was scanned and the image mapped using an equal- area projection to remove the distortion caused by the lens. The resulting digital image was thresholded to produce a black-and-white image in which a count of the black pixels is a measure of sky-area obstruction. The locations of the markers were determined independently before the study. During the study, each marker was occupied for four 20-minute sessions over the period of one week in mid-July, 1999. The location of the study markers produced relatively long baselines, as compared with similar studies. We compared the accuracy of GPS-only vs. GPS&GLONASS as a function of sky obstruction. Based on our results, GLONASS observations did not improve or degrade the accuracy of the position measurements. There is a loss of 2mm of accuracy per percent of sky obstruction for both GPS only and GPS&GLONASS.
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In medicine, the vast majority of conscientious objection (CO) is exercised within the reproductive healthcare field – particularly for abortion and contraception. Current laws and practices in various countries around CO in reproductive healthcare show that it is unworkable and frequently abused, with harmful impacts on women's healthcare and rights. CO in medicine is supposedly analogous to CO in the military, but in fact the two have little in common. This paper argues that CO in reproductive health is not actually Conscientious Objection, but Dishonourable Disobedience (DD) to laws and ethical codes. Healthcare professionals who exercise CO are using their position of trust and authority to impose their personal beliefs on patients, who are completely dependent on them for essential healthcare. Health systems and institutions that prohibit staff from providing abortion or contraception services are being discriminatory by systematically denying healthcare services to a vulnerable population and disregarding conscience rights for abortion providers. CO in reproductive healthcare should be dealt with like any other failure to perform one's professional duty, through enforcement and disciplinary measures. Counteracting institutional CO may require governmental or even international intervention.
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El protagonista de la novela de Aquiles Tacio Leucipa y Clitofonte incurre en dos tipos de transgresiones de la moral sexual: seducción de una joven virgen y adulterio. Analizaremos aquí el modo en que ambas faltas aparecen representadas en la novela, su definición, las reacciones sociales ante ellas y las penas que pueden aplicárseles, y compararemos esa representación con las caracterizaciones de estos delitos en las leyes griegas y romanas que interactuaban en el complejo panorama cultural del período imperial. Postulamos que este análisis puede aportar datos que contribuyan a la comprensión de la historia social y de los códigos morales y legales que delimitaban las relaciones lícitas e ilícitas entre los sexos, pues a pesar de que la ficción novelesca no refleja en forma directa la realidad histórica, afloran en ella elementos propios del contexto socio-cultural en que autor y público están inmersos
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La escena del campo de batalla tras el enfrentamiento entre pompeyanos y cesarianos en el libro VII del Bellum Ciuile de Lucano (786-846) deja al descubierto el proceso de refuncionalización del tópico tradicional del día después de la lucha. Desde una perspectiva estilística mostramos que la intersección entre los códigos historiográfico, épico y trágico y la manipulación de diversos motivos literarios y culturales en dicho relato pueden leerse como uno de los principales mecanismos de la poética lucaniana del ciuile nefas.
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La escena del campo de batalla tras el enfrentamiento entre pompeyanos y cesarianos en el libro VII del Bellum Ciuile de Lucano (786-846) deja al descubierto el proceso de refuncionalización del tópico tradicional del día después de la lucha. Desde una perspectiva estilística mostramos que la intersección entre los códigos historiográfico, épico y trágico y la manipulación de diversos motivos literarios y culturales en dicho relato pueden leerse como uno de los principales mecanismos de la poética lucaniana del ciuile nefas.
Resumo:
El protagonista de la novela de Aquiles Tacio Leucipa y Clitofonte incurre en dos tipos de transgresiones de la moral sexual: seducción de una joven virgen y adulterio. Analizaremos aquí el modo en que ambas faltas aparecen representadas en la novela, su definición, las reacciones sociales ante ellas y las penas que pueden aplicárseles, y compararemos esa representación con las caracterizaciones de estos delitos en las leyes griegas y romanas que interactuaban en el complejo panorama cultural del período imperial. Postulamos que este análisis puede aportar datos que contribuyan a la comprensión de la historia social y de los códigos morales y legales que delimitaban las relaciones lícitas e ilícitas entre los sexos, pues a pesar de que la ficción novelesca no refleja en forma directa la realidad histórica, afloran en ella elementos propios del contexto socio-cultural en que autor y público están inmersos
Resumo:
La escena del campo de batalla tras el enfrentamiento entre pompeyanos y cesarianos en el libro VII del Bellum Ciuile de Lucano (786-846) deja al descubierto el proceso de refuncionalización del tópico tradicional del día después de la lucha. Desde una perspectiva estilística mostramos que la intersección entre los códigos historiográfico, épico y trágico y la manipulación de diversos motivos literarios y culturales en dicho relato pueden leerse como uno de los principales mecanismos de la poética lucaniana del ciuile nefas.
Resumo:
El protagonista de la novela de Aquiles Tacio Leucipa y Clitofonte incurre en dos tipos de transgresiones de la moral sexual: seducción de una joven virgen y adulterio. Analizaremos aquí el modo en que ambas faltas aparecen representadas en la novela, su definición, las reacciones sociales ante ellas y las penas que pueden aplicárseles, y compararemos esa representación con las caracterizaciones de estos delitos en las leyes griegas y romanas que interactuaban en el complejo panorama cultural del período imperial. Postulamos que este análisis puede aportar datos que contribuyan a la comprensión de la historia social y de los códigos morales y legales que delimitaban las relaciones lícitas e ilícitas entre los sexos, pues a pesar de que la ficción novelesca no refleja en forma directa la realidad histórica, afloran en ella elementos propios del contexto socio-cultural en que autor y público están inmersos
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The aim of this paper is to study the importance of nuclear data uncertainties in the prediction of the uncertainties in keff for LWR (Light Water Reactor) unit-cells. The first part of this work is focused on the comparison of different sensitivity/uncertainty propagation methodologies based on TSUNAMI and MCNP codes; this study is undertaken for a fresh-fuel at different operational conditions. The second part of this work studies the burnup effect where the indirect contribution due to the uncertainty of the isotopic evolution is also analyzed.
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In this chapter we are going to develop some aspects of the implementation of the boundary element method (BEM)in microcomputers. At the moment the BEM is established as a powerful tool for problem-solving and several codes have been developed and maintained on an industrial basis for large computers. It is also well known that one of the more attractive features of the BEM is the reduction of the discretization to the boundary of the domain under study. As drawbacks, we found the non-bandedness of the final matrix, wich is a full asymmetric one, and the computational difficulties related to obtaining the integrals which appear in the influence coefficients. Te reduction in dimensionality is crucial from the point of view of microcomputers, and we believe that it can be used to obtain competitive results against other domain methods. We shall discuss two applications in this chapter. The first one is related to plane linear elastostatic situations, and the second refers to plane potential problems. In the first case we shall present the classical isoparametric BEM approach, using linear elements to represent both the geometry and the variables. The second case shows how to implement a p-adaptive procedure using the BEM. This latter case has not been studied until recently, and we think that the future of the BEM will be related to its development and to the judicious exploitation of the graphics capabilities of modern micros. Some examples will be included to demonstrate the kind of results that can be expected and sections of printouts will show useful details of implementation. In order to broaden their applicability, these printouts have been prepared in Basic, although no doubt other languages may be more appropiate for effective implementation.
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Fuel cycles are designed with the aim of obtaining the highest amount of energy possible. Since higher burnup values are reached, it is necessary to improve our disposal designs, traditionally based on the conservative assumption that they contain fresh fuel. The criticality calculations involved must consider burnup by making the most of the experimental and computational capabilities developed, respectively, to measure and predict the isotopic content of the spent nuclear fuel. These high burnup scenarios encourage a review of the computational tools to find out possible weaknesses in the nuclear data libraries, in the methodologies applied and their applicability range. Experimental measurements of the spent nuclear fuel provide the perfect framework to benchmark the most well-known and established codes, both in the industry and academic research activity. For the present paper, SCALE 6.0/TRITON and MONTEBURNS 2.0 have been chosen to follow the isotopic content of four samples irradiated in the Spanish Vandellós-II pressurized water reactor up to burnup values ranging from 40 GWd/MTU to 75 GWd/MTU. By comparison with the experimental data reported for these samples, we can probe the applicability of these codes to deal with high burnup problems. We have developed new computational tools within MONTENBURNS 2.0. They make possible to handle an irradiation history that includes geometrical and positional changes of the samples within the reactor core. This paper describes the irradiation scenario against which the mentioned codes and our capabilities are to be benchmarked.
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La Organización de Estados Iberoamericanos para la Educación, la Ciencia y la Cultura (OEI) pretende llevar energía solar y acceso a internet a más de 66.000 escuelas en Iberoamérica, la mayor parte de ellas ubicadas en zonas rurales y de difícil acceso. Con el proyecto “Luces para aprender” se quiere reducir la brecha digital y poner fin al aislamiento de las comunidades rurales, facilitando su acceso a las tecnologías de la comunicación, con el fin de favorecer su desarrollo educativo, económico, social y cultural. La OEI que coordina el proyecto “Luces para Aprender” se dirigió a TEDECO (Tecnología para el Desarrollo y la Cooperación), que es un grupo de cooperación al desarrollo de la Facultad de Informática de la UPM, para solicitar asesoramiento en la parte software a instalar en el proyecto. Surge la necesidad de dotar de sistema operativo a los computadores que tendrán las escuelas beneficiarias de este proyecto. Por lo tanto, se ha decido crear un sistema operativo que consiste en una distribución GNU/Linux que se adapte a las necesidades de dicho proyecto. Esta distribución va acompañada de un manual de usuario y una guía de instalación para facilitar la implantación en los respectivos centros. Se pretende que la distribución esté disponible en un repositorio web y además esté basada en la filosofía de código libre y abierto. ---ABSTRACT---The OEI (Organization of Ibero-American States for Education, Science and Culture) hopes to provide solar energy and Internet access to more than 66.000 schools in Ibero-America, most of them, located in rural zones and of difficult access. With the project “Luces para aprender” (lights to learn), they would like to reduce the digital gap and put an end to the deprivation of the rural communities, supplying access to the Information Technologies, with the aim of contributing to its educative, economic, social and cultural development. The OEI that coordinates "Luces para Apreder" project, requested TEDECO (Technology for Development and Cooperation), which is a group of development cooperation of Facultad de Informática of the UPM, to advice in the part of software installation in the project. There is a need for an operative system that the computers will have in schools that will benefit from that project. Therefore, it has been decided to create an operative system that consists of a GNU/Linux distribution adapted to the needs of the project. That distribution will be accompanied by a user’s manual and an installation guide to help the implementing in the centres. The distribution is supposed to be available in a web, and moreover, will be based on the philosophy of free and opened codes.
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Este trabajo trata de la aplicación de los códigos detectores y correctores de error al diseño de los Computadores Tolerantes a Fallos, planteando varias estrategias óptimas de detección y corrección para algunos subsistemas. En primer lugar,"se justifica la necesidad de aplicar técnicas de Tolerancia a Fallos. A continuación se hacen previsiones de evolución de la tecnología de Integración, así como una tipificación de los fallos en circuitos Integrados. Partiendo de una recopilación y revisión de la teoría de códigos, se hace un desarrollo teórico cuya aplicación permite obligar a que algunos de estos códigos sean cerrados respecto de las operaciones elementales que se ejecutan en un computador. Se plantean estrategias óptimas de detección y corrección de error para sus subsistemas mas Importantes, culminando en el diseño, realización y prueba de una unidad de memoria y una unidad de proceso de datos con amplias posibilidades de detección y corrección de errores.---ABSTRACT---The present work deals with the application of error detecting and correctíng codes to the désign of Fault Tolerant Computers. Several óptimo» detection and correction strategies are presented to be applied in some subsystems. First of all, the necessity of applying Fault Tolerant techniques is explained. Later, a study on íntegration technology evolution and typification of Integrated circuit faults 1s developed. Based on a compilation and revisión of Coding Theory, a theoretical study is carried out. It allows us to force some of these codes to be closed over elementary operations. Optimum detection and correction techniques are presented for the raost important subsystems. Flnally, the design, building and testing of a memory unit and a processing unit provided with wlde error detection and correction posibilities 1s shown.
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El riesgo de caída por deslizamiento en los edificios es un riesgo muy importante ya que supone numerosas muertes, perdida de días laborales y secuelas, así como importantes costes económicos. Se trata de accidentes difíciles de predecir debido al número de factores que intervienen para que se produzcan, muchos de los cuales son difícilmente controlables, como el calzado del usuario o su comportamiento. Para evitar un resbalón es necesario que la fricción del conjunto pavimento/calzado/contaminante supere el coeficiente de fricción requerido para la estabilidad y que depende de la forma de caminar, la longitud del paso, etc. Por ello, es necesario medir la contribución del pavimento al riesgo de deslizamiento y limitarla adecuadamente. A lo largo de la historia reciente se han diseñado y desarrollado multitud de aparatos con la intención de medir esta contribución en la forma de coeficientes de fricción —dinámicos, estáticos, de transición— sin llegar a un acuerdo sobre cuál es el método más apropiado. La reglamentación española de edificación, que ha sufrido un importante cambio recientemente con la adopción de un nuevo código basado en prestaciones, ha sido innovadora en este campo introduciendo por primera vez una medida contrastable de la contribución del pavimento al riesgo de deslizamiento mediante el ensayo del péndulo de fricción en húmedo. Sin embargo, el desacuerdo a nivel europeo sobre un ensayo único y las limitaciones en las normas de ensayo existentes derivadas de esta falta de consenso, han sido la causa de que la solución aportada por el Código Técnico de la Edificación (CTE) se cimentara en normas que no contemplaban todas las modalidades de ensayo. Esto ha generado algunos problemas de aplicación que han afectado fundamentalmente a los pavimentos pulidos, que han visto prácticamente vetada su utilización en los edificios incluso en las zonas donde, por no existir presencia de agua, el riesgo es menor. El objetivo de esta tesis es analizar estos problemas de aplicación, ligados al ensayo del péndulo de fricción, y tratar de resolverlos optimizando el procedimiento de ensayo empleado, modificando sus condiciones, para representar de forma mucho más adecuada el riesgo que se pretende limitar. Para ello se ha estudiado de forma exhaustiva la literatura científica y las normas y reglamentaciones, tanto españolas como extranjeras. Se han detectado los posibles problemas que podría plantear la introducción del ensayo del péndulo de fricción en seco y se ha diseñado una campaña de ensayos, tanto de coeficiente de fricción con el péndulo, como de la rugosidad superficial, para confirmarlos o desecharlos. El análisis de los resultados de la campaña de ensayos ha permitido validar la modalidad de ensayo planteada y proponer una medida complementaria de la rugosidad superficial que resulte útil para facilitar la evaluación de este riesgo no poco importante. Los resultados de esta tesis han permitido desarrollar una modificación del CTE de próxima aparición y un documento de apoyo que ya la adelanta, y con ello, resolver el problema de aplicación del CTE a los pavimentos pulidos. ABSTRACT Slipping accidents in building environments are a serious problem involving numerous fatal accidents, loss of work days, incapacity and great costs. Prediction of such accidents is difficult due to the number of factors involved, many of which are not controllable, like footwear or users behavior. To prevent a slip the coefficient of friction provided by the combination floor-footwear-contaminant must be greater than the required coefficient of friction for stability, that depends on the step length and the walking speed among other factors. It is then necessary to measure the contribution of the floor to the slipping risk so it can be limited to an adequate extent. In the recent history many apparatuses have been developed in order to measure this contribution in the form of friction coefficients —dynamic, static or even transition COFs— but none of them seems to be internationally accepted as sufficiently valid. The Spanish Building Code, which has recently undergone a big change to a performance based code, has been innovative in this area, introducing for the first time a measurement of this contribution by means of the friction pendulum test. However, due to the European disagreement about an unique test for slip resistance, and to the limitations of the European standards derived from it, the Spanish Building Code relies on standards that do not take into account all possible methods. As a consequence, smooth floors have been seriously affected and cannot be installed in almost any place, not even in dry areas where the risk of slipping is much lower. The aim of this research is to analyze these problems associated with the pendulum test and resolve them proposing some changes to the test conditions in order to represent in a proper manner the real risk that is to be considered: the slip in dry conditions. Relevant scientific literature has been studied as well as Spanish and foreign codes and standards. Potential problems of the pendulum test in dry conditions have been detected and an experiment has been designed to confirm or discard them, testing both friction coefficient and surface roughness. The results of the experiment have permitted to validate the pendulum test in dry conditions and to suggest a complementary measurement of the surface roughness to help evaluate the slip resistance of a floor. These results have also permitted to develop an amendment to the building code that will appear soon. In the meanwhile it has been included in a support document issued by the administration to resolve this urgent problem.
