934 resultados para spontaneously generated coherence


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On 22nd February '96, the space mission STS 75 started ,from the NASA facilities at Cape Canaveral. Such a mission consists in the launch of the shuttle Columbia in order to carry out two experiments in the space: the TSS 1R (Tethered Satellite Sistem 1 Refliight) and the USMP (United States Microgravity Payload). The TSS 1R is a replica of a similar mission TSS 1 '92. The TSS space programme is a bilateral scientific cooperation between the USA space agency NASA (National Aeronautics and Space Agency) and the ASI (Italian Space Agency. The TSS 1R system consists on the shuttle Columbia which deploys, up-ward, by means a conducting tether 20 km long, a spherical satellite (1.5 mt diameter) containing scientific instrumentation. This system, orbiting at about 300 km from the Earth's surface, represents, presently, the largest experimental space structure, Due to its dimensions, flexibility and conducting properties of the tether, the system interacts, in a quite complex manner, wih the earth magnetic field and the ionospheric plasma, in a way that the total system behaves as an electromagnetic radiating antenna as well as an electric power generator. Twelve scientific experiments have been assessed by US and Italian scientists in order to study the electro dynamic behaviour of the structure orbiting in the ionos phere. Two experiments have been prepared in the attempt to receive on the Earth's surface possible electromagnetic events radiated by the TSS 1R. The project EMET (Electro Magnetic Emissions from Tether),USA and the project OESEE (Observations on the Earth Surface of Electromagnetic Emissions) Italy, consist in a coordinated programme of passive detection of such possible EM emissions. This detection will supply the verification of some thoretical hypotheses on the electrodynamic interactions between the orbiting system, the Earth's magnetic field and the ionospheric plasma with two principal aims as the technological assesment of the system concept as well as a deeper knowledge of the ionosphere properties for future space applications. A theoretical model that keeps the peculiarities of tether emissionsis being developed for signal prediction at constant tether current. As a step previous to the calculation of the expected ground signal , the Alfven-wave signature left by the tether far back in the ionosphere has been determined. The scientific expectations from the combined effort to measure the entity of those perturbations will be outlined taking in to account the used ground track sensor systems.

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Una de las principales causas del ruido en nuestras ciudades es el tráfico rodado. El ruido generado por los vehículos no es sólo debido al motor, sino que existen diversas fuentes de ruido en los mismos, entre las que se puede destacar el ruido de rodadura. Para localizar las causas del ruido e identificar las principales fuentes del mismo se han utilizado en diversos estudios las técnicas de coherencia y las técnicas basadas en arrays. Sin embargo, en la bibliografía existente, no es habitual encontrar el uso de estas técnicas en el sector automovilístico. En esta tesis se parte de la premisa de la posibilidad de usar estas técnicas de medida en coches, para demostrar a la largo de la misma su factibilidad y su bondad para evaluar las fuentes de ruido en dos condiciones distintas: cuando el coche está parado y cuando está en movimiento. Como técnica de coherencia se elige la de Intensidad Selectiva, utilizándose la misma para evaluar la coherencia existente entre el ruido que llega a los oídos del conductor y la intensidad radiada por distintos puntos del motor. Para la localización de fuentes de ruido, las técnicas basadas en array son las que mejores resultados ofrecen. Statistically Optimized Near-field Acoustical Holography (SONAH) es la técnica elegida para la localización y caracterización de las fuentes de ruido en el motor a baja frecuencia. En cambio, Beamforming es la técnica seleccionada para el caso de media-alta frecuencia y para la evaluación de las fuentes de ruido cuando el coche se encuentra en movimiento. Las técnicas propuestas no sólo pueden utilizarse en medidas reales, sino que además proporcionan abundante información y frecen una gran versatilidad a la hora de caracterizar fuentes de ruido. ABSTRACT One of the most important noise causes in our cities is the traffic. The noise generated by the vehicles is not only due to the engine, but there are some other noise sources. Among them the tyre/road noise can be highlighted. Coherence and array based techniques have been used in some research to locate the noise causes and identify the main noise sources. Nevertheless, it is not usual in the literature to find the application of this kind of techniques in the car sector. This Thesis starts taking into account the possibility of using this kind of measurement techniques in cars, to demonstrate their feasability and their quality to evaluate the noise sources under two different conditions: when the car is stopped and when it is in movement. Selective Intensity was chosen as coherence technique, evaluating the coherence between the noise in the driver’s ears and the intensity radiated in different points of the engine. Array based techniques carry out the best results to noise source location. Statistically Optimized Near-field Acoustical Holography (SONAH) is the measurement technique chosen for noise source location and characterization in the engine at low frequency. On the other hand, Beamforming is the technique chosen in the case of medium-high frequency and to characterize the noise sources when the car is in movement. The proposed techniques not only can be used in actual measurements, but also provide a lot of information and are very versatile to noise source characterization.

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A novel method for generating patient-specific high quality conforming hexahedral meshes is presented. The meshes are directly obtained from the segmentation of patient magnetic resonance (MR) images of abdominal aortic aneu-rysms (AAA). The MRI permits distinguishing between struc-tures of interest in soft tissue. Being so, the contours of the lumen, the aortic wall and the intraluminal thrombus (ILT) are available and thus the meshes represent the actual anato-my of the patient?s aneurysm, including the layered morpholo-gies of these structures. Most AAAs are located in the lower part of the aorta and the upper section of the iliac arteries, where the inherent tortuosity of the anatomy and the presence of the ILT makes the generation of high-quality elements at the bifurcation is a challenging task. In this work we propose a novel approach for building quadrilateral meshes for each surface of the sectioned geometry, and generating conforming hexahedral meshes by combining the quadrilateral meshes. Conforming hexahedral meshes are created for the wall and the ILT. The resulting elements are evaluated on four patients? datasets using the Scaled Jacobian metric. Hexahedral meshes of 25,000 elements with 94.8% of elements well-suited for FE analysis are generated.

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In hybrid and electric vehicles, passengers sit very close to an electric system of significant power, which means that they may be subjected to high electromagnetic fields. The hazards of long-term exposure to these fields must be taken into account when designing electric vehicles and their components. Among all the electric devices present in the power train, the electronic converter is the most difficult to analyze, given that it works with different frequencies. In this paper, a methodology to evaluate the magnetic field created by a power electronics converter is proposed. After a brief overview of the recommendations of electromagnetic fields exposure, the magnetic field produced by an inverter is analyzed using finite element techniques. The results obtained are compared to laboratory measurements, taken from a real inverter, in order to validate the model. Finally, results are used to draw some conclusions regarding vehicle design criteria and magnetic shielding efficiency.

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The type-I intermittency route to (or out of) chaos is investigated within the horizontal visibility (HV) graph theory. For that purpose, we address the trajectories generated by unimodal maps close to an inverse tangent bifurcation and construct their associatedHVgraphs.We showhowthe alternation of laminar episodes and chaotic bursts imprints a fingerprint in the resulting graph structure. Accordingly, we derive a phenomenological theory that predicts quantitative values for several network parameters. In particular, we predict that the characteristic power-law scaling of the mean length of laminar trend sizes is fully inherited by the variance of the graph degree distribution, in good agreement with the numerics. We also report numerical evidence on how the characteristic power-law scaling of the Lyapunov exponent as a function of the distance to the tangent bifurcation is inherited in the graph by an analogous scaling of block entropy functionals defined on the graph. Furthermore, we are able to recast the full set of HV graphs generated by intermittent dynamics into a renormalization-group framework, where the fixed points of its graph-theoretical renormalization-group flow account for the different types of dynamics.We also establish that the nontrivial fixed point of this flow coincides with the tangency condition and that the corresponding invariant graph exhibits extremal entropic properties.

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In this paper we propose an innovative approach to tackle the problem of traffic sign detection using a computer vision algorithm and taking into account real-time operation constraints, trying to establish intelligent strategies to simplify as much as possible the algorithm complexity and to speed up the process. Firstly, a set of candidates is generated according to a color segmentation stage, followed by a region analysis strategy, where spatial characteristic of previously detected objects are taken into account. Finally, temporal coherence is introduced by means of a tracking scheme, performed using a Kalman filter for each potential candidate. Taking into consideration time constraints, efficiency is achieved two-fold: on the one side, a multi-resolution strategy is adopted for segmentation, where global operation will be applied only to low-resolution images, increasing the resolution to the maximum only when a potential road sign is being tracked. On the other side, we take advantage of the expected spacing between traffic signs. Namely, the tracking of objects of interest allows to generate inhibition areas, which are those ones where no new traffic signs are expected to appear due to the existence of a TS in the neighborhood. The proposed solution has been tested with real sequences in both urban areas and highways, and proved to achieve higher computational efficiency, especially as a result of the multi-resolution approach.

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Se analiza la función de las definiciones en los textos científicos como elemento esencial para crear coherencia y dotar de comprensibilidad al texto. Se presentan varios ejemplos en textos de divulgación y en artículos dirigidos a pares.

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The dielectrophoretic potential generated near the surface of a z-cut LiNbO3 by photovoltaic charge transport has been calculated for first time. The procedure and results are compared with the ones corresponding to x-cut. Diferences in the position, sharpness and time evolution are reported, and their implication on particle trapping are discussed.

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This paper presents a mechanism to generate virtual buildings considering designer constraints and guidelines. This mechanism is implemented as a pipeline of different Variable Neighborhood Search (VNS) optimization processes in which several subproblems are tackled (1) rooms locations, (2) connectivity graph, and (3) element placement. The core VNS algorithm includes some variants to improve its performance, such as, for example constraint handling and biased operator selection. The optimization process uses a toolkit of construction primitives implemented as "smart objects" providing basic elements such as rooms, doors, staircases and other connectors. The paper also shows experimental results of the application of different designer constraints to a wide range of buildings from small houses to a large castle with several underground levels.

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It is known that some orthogonal systems are mapped onto other orthogonal systems by the Fourier transform. In this article we introduce a finite class of orthogonal functions, which is the Fourier transform of Routh-Romanovski orthogonal polynomials, and obtain its orthogonality relation using Parseval identity.

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Invariantes del pensamiento en los arquitectos de Madrid. Primera década del siglo XXI. Una historia de transmisión oral es una Tesis Doctoral que parte de la elaboración de un archivo documental inédito, archivo que aglutina los testimonios de los más importantes arquitectos de Madrid presentes durante los primeros diez años del siglo XXI. Estos testimonios se recogen ordenadamente a modo de conversaciones transcritas, reflexiones puntuales y audios. La incorporación de los audios al trabajo documental permite comprobar a futuros investigadores, de manera directa, la certeza de las conclusiones o, incluso, establecer interpretaciones distintas. Los documentos sonoros son el germen de este trabajo. La Tesis Doctoral ordena e interpreta los testimonios en su apartado de ANÁLISIS/ DESARROLLO permitiendo entender a través de constantes demostraciones un hilo conductor del pensamiento en los arquitectos de Madrid. Se trata de una Tesis Doctoral que se entiende como un documento vivo, abierto y que gracias a su carácter inédito descubre matices y reflexiones de los arquitectos nunca antes recogidos en otros trabajos. Se ha conseguido reunir y ordenar por primera vez la voz y el pensamiento de los más importantes arquitectos de Madrid, muchos de ellos ya fallecidos. Se ha establecido un árbol genealógico ordenado y completo de los arquitectos de referencia indiscutibles desde el año 1939. Se ha conseguido reunir en un solo documento a los arquitectos y personajes más citados y recurrentes en el discurso de los arquitectos de Madrid, pudiendo constatar así sus referentes culturales más utilizados. Se ha descubierto y argumentado un pensamiento común dividido en cuatro conceptos: Oportunidad, Orden, Compromiso y Contención. Se produce una aproximación al arquitecto y a su pensamiento de la manera más natural y espontánea. Las grabaciones nos permitirán introducirnos, sin imposturas, no solo en el fondo, sino también en la forma de lo que se comunica, en el cómo. Una vez seleccionados los documentos sonoros más adecuados para el objetivo de este trabajo se ha procedido a su transcripción al papel. En este proceso se depura el lenguaje y se liman defectos de forma, al mismo tiempo se resumen las conversaciones y se recogen solo los comentarios más interesantes. En el proceso de transcripción, así como en la elección de las preguntas, existe una labor editorial, la aplicación de un criterio a la hora de seleccionar, resumir, corregir, completar, etc. Para abordar las conversaciones se ha recurrido a la bibliografía de referencia de cada uno de los arquitectos. Una vez transcritas las entrevistas, se establece una valoración crítica, una aproximación teórica al tema principal de la conversación. Bien puede tratarse de una reflexión sobre el arquitecto y su trabajo o sobre algunas de las opiniones o temas vertidos durante la charla. Para situar a cada uno de los arquitectos que se citan, se ha establecido un apartado genealógico completo donde cada uno se coloca en su lugar correspondiente conforme a sus apariciones en los textos principales de la historiografía reciente desde Carlos Flores hasta el año 2010. Esta Tesis Doctoral es un testigo de la diversidad de pensamientos y actitudes así como de las coincidencias. Las conversaciones mantenidas, las reflexiones y las opiniones vertidas al respecto han tocado reiteradamente muchos temas que aparecerán ordenados en el ANÁLISIS/DESARROLLO y en el apartado DESCRIPTORES. A partir de estos y otros temas genéricos, los pensamientos se aglutinan en torno a cuatro puntos que resumen las actitudes y los planteamientos conceptuales más recurrentes y coincidentes. Estos cuatro puntos definen de una manera concreta al arquitecto de Madrid. Oportunidad, Orden, Compromiso y Contención. Identidad generada a través de una historia de transmisión oral, desde los arquitectos de las primeras generaciones de posguerra hasta hoy. ABSTRACT Invariable thought in the architects of Madrid. First decade of the XXI century. A history of oral transmission is a Doctoral Thesis that starts with the development of a new documentary file, a file which brings together the testimonies of the most important architects of Madrid present during the first ten years of this century. These testimonies include conversations, punctual reflections and audio bites. Incorporating audio allows future researchers to check certain conclusions directly or even to have different interpretations. Sound bites are the seed of this work. This Doctoral Thesis orders and interprets the testimonies in the ANALYSIS / DEVELOPMENT section, through which a common thread of thought in Madrid architects can be ascertained. This doctoral thesis is meant as a living, open document, which, thanks to its unprecedented nature, discovers nuances and reflections of architects that had never been collected in previous studies. It has brought together and sorted for the first time the voice and thoughts of the most important architects of Madrid, many of them already deceased. It has established an orderly and comprehensive reference guide to the most important architects since 1939. It has brought together in one document the most cited and recurring architects and characters in the discourse of the architects of Madrid, which enables us to observe the cultural references they used the most. We have discovered and put forward a common thought divided into four concepts: Opportunity, Order, Commitment and Containment. The architect and his thoughts are revealed as naturally and spontaneously as possible. The recordings allow us to ascertain, without impositions, not only the substance but also the form of what is communicated. After selecting the most appropriate sound bites for the purpose of this work, we have proceeded to transcribe them to paper. In this process the language has been purified and formal defects have been dealt with, and at the same time the conversations have been summarized and only the most interesting comments have been kept. The transcription process and the choice of questions entails editorial work, applying a criterion when selecting, summarizing, amending, supplementing, etc. To address the conversations, the bibliographic reference of each of the architects has been used. Once the interviews have been transcribed, a critical appraisal and a theoretical approach to the main topic of conversation are established. It may be a reflection on the architect and his work or some of the views or issues discussed during the talk. In order to place each of the cited architects, a complete family tree has been devised in which each architect is situated according to his appearances in the main text of recent historiography, from Carlos Flores until 2010. This Doctoral Thesis is a witness to the diversity of thoughts, attitudes and coincidences. The conversations, reflections and opinions expressed in this regard have repeatedly touched many issues that will be sorted in the ANALYSIS/DEVELOPMENT and the KEYWORDS section. From these and other generic issues, thoughts coalesce around four points which summarize the attitudes and the most recurrent and similar conceptual approaches. These four points define the architect of Madrid in a concrete way. Opportunity, order, engagement and containment. An identity generated by a history of oral transmission, from the architects of the first post-war generations until today.

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In this work we have realized plasma diagnosis produced by Laser (LPP), by means of emission spectroscopy in a Laser Shock Processing (LSP). The LSP has been proposed as an alternative technology, competitive with classical surface treatments. The ionic species present in the plasma together with electron density and its temperature provide significant indicators of the degree of surface effect of the treated material. In order to analyze these indicators, we have realized spectroscopic studies of optical emission in the laser-generated plasmas in different situations. We have worked focusing on an aluminum sample (Al2024) in air and/or in LSP conditions (water flow) a Q-switched laser of Nd:YAG (λ = 1.06 μm, 10 ns of pulse duration, running at 10 Hz repetition rate). The pulse energy was set at 2,5 J per pulse. The electron density has been measured using, in every case, the Stark broadening of H Balmer α line (656.27 nm). In the case of the air, this measure has been contrasted with the value obtained with the line of 281.62 nm of Al II. Special attention has been paid to the self-absorption of the spectral lines used. The measures were realized with different delay times after the pulse of the laser (1–8 μs) and with a time window of 1 μs. In LSP the electron density obtained was between 1017 cm−3 for the shortest delays (4–6 μs), and 1016 cm−3 for the greatest delays (7,8 μs).

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We present temporal information obtained by mass spectrometry techniques about the evolution of plasmas generated by laser filamentation in air. The experimental setup used in this work allowed us to study not only the dynamics of the filament core but also of the energy reservoir that surrounds it. Furthermore, valuable insights about the chemistry of such systems like the photofragmentation and/or formation of molecules were obtained. The interpretation of the experimental results are supported by PIC simulations.

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Recent evidence in vivo indicates that spontaneously hypertensive rats (SHR) exhibit an increase in oxyradical production in and around microvascular endothelium. This study is aimed to examine whether xanthine oxidase plays a role in overproduction of oxidants and thereby may contribute to hypertensive states as a consequence of the increasing microvascular tone. The xanthine oxidase activity in SHR was inhibited by dietary supplement of tungsten (0.7 g/kg) that depletes molybdenum as a cofactor for the enzyme activity as well as by administration of (−)BOF4272 [(−)-8-(3-methoxy-4-phenylsulfinylphenyl)pyrazolo(1,5-α)-1,3,5-triazine-4-monohydrate], a synthetic inhibitor of the enzyme. The characteristic elevation of mean arterial pressure in SHR was normalized by the tungsten diet, whereas Wistar Koto (WKY) rats displayed no significant alteration in the pressure. Multifunctional intravital videomicroscopy in mesentery microvessels with hydroethidine, an oxidant-sensitive fluoroprobe, showed that SHR endothelium exhibited overproduction of oxyradicals that coincided with the elevated arteriolar tone as compared with WKY rats. The tungsten diet significantly repressed these changes toward the levels observed in WKY rats. The activity of oxyradical-producing form of xanthine oxidase in the mesenteric tissue of SHR was ≈3-fold greater than that of WKY rats, and pretreatment with the tungsten diet eliminated detectable levels of the enzyme activity. The inhibitory effects of the tungsten diet on the increasing blood pressure and arteriolar tone in SHR were also reproducible by administration of (−)BOF4272. These results suggest that xanthine oxidase accounts for a putative source of oxyradical generation that is associated with an increasing arteriolar tone in this form of hypertension.

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The 1,3–1,4-β-glucanase from Bacillus macerans (wtGLU) and the 1,4-β-xylanase from Bacillus subtilis (wtXYN) are both single-domain jellyroll proteins catalyzing similar enzymatic reactions. In the fusion protein GluXyn-1, the two proteins are joined by insertion of the entire XYN domain into a surface loop of cpMAC-57, a circularly permuted variant of wtGLU. GluXyn-1 was generated by protein engineering methods, produced in Escherichia coli and shown to fold spontaneously and have both enzymatic activities at wild-type level. The crystal structure of GluXyn-1 was determined at 2.1 Å resolution and refined to R = 17.7% and R(free) = 22.4%. It shows nearly ideal, native-like folding of both protein domains and a small, but significant hinge bending between the domains. The active sites are independent and accessible explaining the observed enzymatic activity. Because in GluXyn-1 the complete XYN domain is inserted into the compact folding unit of GLU, the wild-type-like activity and tertiary structure of the latter proves that the folding process of GLU does not depend on intramolecular interactions that are short-ranged in the sequence. Insertion fusions of the GluXyn-1 type may prove to be an easy route toward more stable bifunctional proteins in which the two parts are more closely associated than in linear end-to-end protein fusions.