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Archivo Digital UPM (49,666 recursos)
This is an institutional repository providing access to the research output of the institution. Primarily contains thesis.

Materia = Electrónica

Mostrando recursos 301 - 320 de 858

301. Atlas-free Brain Tissue Segmentation Using a Single T1-weighted MRI Acquisition - Kober, Tobias; Roche, Alexis; Esteban Sanz-Dranguet, Oscar; Gorthi, Subrahmanyam; Rives, Delphine; Bach-Cuadra, Meritxell; Meuli, Reto; Krueger, Gunnar
Many studies investigating the aging brain or disease-induced brain alterations rely on accurate and reproducible brain tissue segmentation. Being a preliminary processing step prior to the segmentation, reliableskull-stripping the removal ofnon-brain tissue is also crucial for all later image assessment. Typically, segmentation algorithms rely on an atlas i.e. pre-segmented template data. Brain morphology, however, differs considerably depending on age, sex and race. In addition, diseased brains may deviate significantly from the atlas information typically gained from healthy volunteers. The imposed prior atlas information can thus lead to degradation of segmentation results. The recently introduced MP2RAGE sequence provides a bias-free T1...

302. Estructura electrónica de fotocatalizadores compuestos ZnO-TiO2 - Conesa, Jose Carlos
Recientes publicaciones han mostrado propiedades fotocatalíticas interesantes en sistemas basados en TiO2 y ZnO. En unos casos hay presentes fases de ambos óxidos binarios en íntimo contacto [1] y en otros se tienen óxidos mixtos (titanatos de Zn) de distintas estequiometrías [2]; estos últimos, además, se han podido dopar con nitrógeno para obtener actividad con luz visible [3]. Las características electrónicas relevantes de estos sistemas (posición relativa de los niveles de ambas fases en el primero, estructura de bandas para los titanatos con o sin N) se conocen muy poco. Aquí se realiza un estudio teórico cuántico de estos materiales,...

303. Study of the Electrical Behavior in Intermediate Band-Si Junctions - Pastor Pastor, David; Olea Ariza, Javier; Prado Millán, Alvaro del; García Hemme, Eric; García Hernansanz, Rodrigo; González Pariente, L.; Mártil de la Plaza, Ignacio; González Díaz, Germán
In this study we analyze the electrical behavior of a junction formed by an ultraheavily Ti implanted Si layer processed by a Pulsed Laser Melting (PLM) and the non implanted Si substrate. This electrical behavior exhibits an electrical decoupling effect in this bilayer that we have associated to an Intermediate Band (IB) formation in the Ti supersaturated Si layer. Time-of-flight secondary ion mass spectrometry (ToFSIMS) measurements show a Ti depth profile with concentrations well above the theoretical limit required to the IB formation. Sheet resistance and Hall mobility measurements in the van der Pauw configuration of these bilayers exhibit a...

304. Effect of concentration on the performance of quantum dot intermediate-band solar cells - Okada, Y.; Yoshida, Katsuhisa; Shoji, Y.; Ogura , A.; García-Linares Fontes, Pablo; Martí Vega, Antonio; Luque López, Antonio
Implementation of a high-efficiency quantum dot intermediate-band solar cell (QD-IBSC) must accompany a sufficient photocurrent generation via IB states. The demonstration of a QD-IBSC is presently undergoing two stages. The first is to develop a technology to fabricate high-density QD stacks or a superlattice of low defect density placed within the active region of a p-i-n SC, and the second is to realize half-filled IB states to maximize the photocurrent generation by two-step absorption of sub-bandgap photons. For this, we have investigated the effect of light concentration on the characteristics of QDSCs comprised of multi-layer stacks of self-organized InAs/GaNAs QDs...

305. NGCPV: A new generation of concentrator photovoltaic cells, modules and systems - Cristóbal López, Ana Belén; Martí Vega, Antonio; Sala Pano, Gabriel; Bett, Andreas W.; Ekins-Daukes, Ned; Roca, Franco; Luque Heredia, Ignacio; Warmuth, Werner; Merten, Jens; Okada, Y.; Hishikawa, Y.; Takamoto, Tatsuya; Araki, Kenji; Fukuyama, A.; Kuze, N.; Kita, T.; Kotagiri, Akira; Yamaguchi, M.; Luque López, Antonio
This work introduces the lines of research that the NGCPV project is pursuing and some of the first results obtained. Sponsored by the European Commission under the 7th Framework Program and NEDO (Japan) within the first collaborative call launched by both Bodies in the field of energy, NGCPV project aims at approaching the cost of the photovoltaic kWh to competitive prices in the framework of high concentration photovoltaics (CPV) by exploring the development and assessment of concentrator photovoltaic solar cells and modules, novel materials and new solar cell structures as well as methods and procedures to standardize measurement technology for...

306. Nano-imprinted rear-side diffraction gratings for absorption enhancement in solar cells - Mellor Null, Alexander Virgil; Hauser, Hubert; Guttowski, Aron; Wellens, Christine; Bläsi, Benedikt; Tobías Galicia, Ignacio; Martí Vega, Antonio; Luque López, Antonio
As wafer-based solar cells become thinner, light-trapping textures for absorption enhancement will gain in importance. In this work, crystalline silicon wafers were textured with wavelength-scale diffraction grating surface textures by nanoimprint lithography using interference lithography as a mastering technology. This technique allows fine-tailored nanostructures to be realized on large areas with high throughput. Solar cell precursors were fabricated, with the surface textures on the rear side, for optical absorption measurements. Large absorption enhancements are observed in the wavelength range in which the silicon wafer absorbs weakly. It is shown experimentally that bi-periodic crossed gratings perform better than uni-periodic linear gratings....

307. Guide to intermediate band solar cell research - Martí Vega, Antonio; Antolín Fernández, Elisa; García-Linares Fontes, Pablo; Hernández Martín, Estela; Ramiro Gonzalez, Iñigo; Moura Dias Mendes, Manuel Joao de; Mellor Null, Alexander Virgil; Artacho Huertas, Irene; López Estrada, Esther; Tobías Galicia, Ignacio; Fuertes Marrón, David; Tablero Crespo, César; Cristóbal López, Ana Belén; Luque López, Antonio
The intermediate band solar cell (IBSC) is a solar cell that, in order to increase its efficiency over that of single gap solar cells, takes advantage of the absorption of below-bandgap energy photons by means of an intermediate band (IB) located in the semiconductor bandgap. For this process to improve the solar cell performance, the belowbandgap photon absorption has to be effective and the IB cannot limit the open-circuit voltage of the cell. In this paper we provide a guide to the new researcher interested in the idea in order he can quickly become familiar with the concept and updated...

308. Sulfuros fotocatalizadores que utilizan ampliamente el espectro de luz visible - Conesa, Jose Carlos; Lucena, Raquel; Fresno, Fernando; Wahnón Benarroch, Perla; Palacios Clemente, Pablo; Seminóvski Pérez, Yohanna
Cuando se usa fotocatálisis, tanto para procesos de descontaminación como para síntesis química específica y (especialmente) para aprovechamiento de energía solar, importa aprovechar un rango muy amplio de luz visible. Para ello se estudian hoy principalmente óxidos (con o sin adición de aniones que disminuyen el gap como el nitrógeno); los sulfuros, como el bien conocido CdS, tienen estabilidad limitada, sobre todo para procesos de fotooxidación en presencia de agua en los que sufren corrosión. Aquí se presentan estudios sobre sulfuros como el In2S3 y el SnS2 (con bandgaps respectivos de 2.0 y 2.2 eV [1]) cuyos metales tienen mayor...

309. Novel Gravity Distortion Evaluation on Large Antenna Array for Deep Space Communication - Salas Natera, Miguel Alejandro; Martínez Rodríguez-Osorio, Ramón; Haro Ariet, Leandro de; Calvo Ramón, Miguel
This paper presents a simple gravity evaluation model for large reflector antennas and the experimental example for a case study of one uplink array of 4x35-m antennas at X and Ka band. This model can be used to evaluate the gain reduction as a function of the maximum gravity distortion, and also to specify this at system designer level. The case study consists of one array of 35-m antennas for deep space missions. Main issues due to the gravity effect have been explored with Monte Carlo based simulation analysis.

310. 3D Determination of Area-at-Risk in Acute Myocardial Infarction - Ding, Haiyan; Fernández de Manuel, Laura; Shär, Michael; McVeigh, Elliot R.; Halperin, Henry; Zviman, Menekhem Muz; Herzka, Daniel A.
MRI methods for acute myocardial infarction

311. An Interleaved EPE-Immune PA-DPL Structure for Resisting Concentrated EM Side Channel Attacks on FPGA Implementation - He, Wei; Torre Arnanz, Eduardo de la; Riesgo Alcaide, Teresa
Early propagation effect (EPE) is a critical problem in conventional dual-rail logic implementations against Side Channel Attacks (SCAs). Among previous EPE-resistant architectures, PA-DPL logic offers EPE-free capability at relatively low cost. However, its separate dual core structure is a weakness when facing concentrated EM attacks where a tiny EM probe can be precisely positioned closer to one of the two cores. In this paper, we present an PA-DPL dual-core interleaved structure to strengthen resistance against sophisticated EM attacks on Xilinx FPGA implementations. The main merit of the proposed structure is that every two routing in each signal pair are kept...

312. A Novel Method for Radio Propagation Simulation Based on Automatic 3D Environment Reconstruction - He, Danping; Liang, Guixuan; Portilla Berrueco, Jorge; Riesgo Alcaide, Teresa
In this paper, a novel method to simulate radio propagation is presented. The method consists of two steps: automatic 3D scenario reconstruction and propagation modeling. For 3D reconstruction, a machine learning algorithm is adopted and improved to automatically recognize objects in pictures taken from target regions, and 3D models are generated based on the recognized objects. The propagation model employs a ray tracing algorithm to compute signal strength for each point on the constructed 3D map. Our proposition reduces, or even eliminates, infrastructure cost and human efforts during the construction of realistic 3D scenes used in radio propagation modeling. In...

313. Low losses power distribution network at X band in stripline - Inclan Alonso, Jose Manuel; Fernández González , José Manuel; Sierra Pérez, Manuel
An asymmetric stripline is proposed in this paper. The main aim of this line is to distribute the power among subarrays in an array with minimum losses. Several vertical transitions to subarrays are shown besides some network designs at X band for a square array for satellite communications.

314. The NACIR Project: New Applications for CPV'S: A fast way to improve reliability and Technology progress - Sala Pano, Gabriel
The main goal of this proposal is to join together the owners of the most advanced CPV technology, with respect to the state of the art, in order to research from its leading position new applications for CPV systems. In addition to opening up new markets, it will unveil possible sources of failure in new environments outside Europe, in order to assure component reliability. The proposed project will also try to improve the current technology of the industrial partners (ISOFOTON and CONCENTRIX) by accelerating the learning curve that CPV must follow in order to reach the competitive market, and lowering...

315. Renewable energies Driven by Feed-on Tariffs. Photovoltaic vs Wind Energy Development in Spain - Victoria Pérez, Marta; Anton Hernandez, Ignacio; Sala Pano, Gabriel
Although others regulations regarding feed-in tariffs for photovoltaics (PV) existed in Spain previously, the one that meant a paradigm change was the introduction in 2007 of law R.D.661/2007 which established a feed-in tariff of 41,75 cents/kWh if the installed capacity was greater than 100KWp and 44,04 cents/kWh if it was smaller. The high level of the subsidies together with the lack of a limit for the total installed capacity originates the well-known Spanish photovoltaic boom. In September 2008 the installed PV capacity accounted for 3.2GWp (while the official objective stated in the national renewable roadmap was only 400MWp). To avoid...

316. Perfect imaging of three object points with only two analytic lens surfaces in two dimensions - Duerr, Fabian; Benitez Gimenez, Pablo; Miñano Dominguez, Juan Carlos; Meuret, Youri; Thienpont, Hugo
In this work, a new two-dimensional analytic optics design method is presented that enables the coupling of three ray sets with two lens profiles. This method is particularly promising for optical systems designed for wide field of view and with clearly separated optical surfaces. However, this coupling can only be achieved if different ray sets will use different portions of the second lens profile. Based on a very basic example of a single thick lens, the Simultaneous Multiple Surfaces design method in two dimensions (SMS2D) will help to provide a better understanding of the practical implications on the design process...

317. GreenDisc: a HW/SW energy optimization framework in globally distributed computation - Zapater Sancho, Marina; Ayala Rodrigo, José Luis; Moya Fernández, José Manuel
In recent future, wireless sensor networks ({WSNs}) will experience a broad high-scale deployment (millions of nodes in the national area) with multiple information sources per node, and with very specific requirements for signal processing. In parallel, the broad range deployment of {WSNs} facilitates the definition and execution of ambitious studies, with a large input data set and high computational complexity. These computation resources, very often heterogeneous and driven on-demand, can only be satisfied by high-performance Data Centers ({DCs}). The high economical and environmental impact of the energy consumption in {DCs} requires aggressive energy optimization policies. These policies have been already...

318. Analytic free-form lens design for imaging applications with high aspect ratio - Duerr, Fabian; Benitez Gimenez, Pablo; Miñano Dominguez, Juan Carlos; Meuret, Youri; Thienpont, Hugo
A new three-dimensional analytic optics design method is presented that enables the coupling of three ray sets with only two free-form lens surfaces. Closely related to the Simultaneous Multiple Surface method in three dimensions (SMS3D), it is derived directly from Fermat?s principle, leading to multiple sets of functional differential equations. The general solution of these equations makes it possible to calculate more than 80 coefficients for each implicit surface function. Ray tracing simulations of these free-form lenses demonstrate superior imaging performance for applications with high aspect ratio, compared to conventional rotational symmetric systems.

319. New EBG solutions for mutual coupling reduction - Exposito Dominguez, Gonzalo; Fernández González, José Manuel; Padilla de La Torre, Pablo; Sierra Castañer, Manuel
Electromagnetic Band Gap (EBG) based on Frequency Selective Surfaces (FSS) [1] are one type of metamaterials [2] with electrical properties [3]. This EBG are used in mutual coupling reduction, back lobe radiation reduction, etc. In this work not only new shapes for the mushroom-type are presented, but also multilayered configurations were studied in order to reduce the patch size and the necessary number of elements.

320. Electrophoretic Deposition of Transparent ZnO Thin Films from Highly Stabilized Colloidal Suspensions - Verde Lozano, María; Peiteado, Marco; Caballero Cuesta, Amador; Villegas Gracia, Marina; Ferrari Fernández, Begoña
The parameters that control the stability of ZnO-nanoparticles suspensions and their deposition by electrophoretic deposition were studied, so as to organize the assembly and compaction of nanoparticles. The addition of cationic polyelectrolyte - Polyethylenimine (PEI) - with different molecular weights was investigated, in order to study their effectiveness and the influence of the molecular weight of the organic chain on suspensions dispersion. It was found that PEI with the highest molecular weight provided better dispersion conditions. Cathodic EPD was performed under previously optimized suspensions conditions and over electropolished stainless steel substrates. Experimental results showed that the EPD process in these...


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