Recursos de colección

Archivo Digital UPM (109.118 recursos)

This is an institutional repository providing access to the research output of the institution. Primarily contains thesis.

Materia = Física

Mostrando recursos 1 - 20 de 1.578

  1. Libro de Actas del IX Congreso de estudiantes universitarios de Ciencia, Tecnología e Ingeniería Agronómica

    Compendio de 26 trabajos presentados por estudiantes de la ETSIAAB.

  2. Monte Carlo simulation of circular grain growth

    Morón Fernández, Carlos; Maganto Suárez, Fernando José; Tremps Guerra, Enrique; Ramírez Fernández, M. Puerto; García García, Alfonso
    Monte Carlo simulations have been carried out to study the effect of temperature on the growth kinetics of a circular grain. This work demonstrates the importance of roughening fluctuations on the growth dynamics. Since the effect of thermal fluctuations is stronger in d =2 than in d =3, as predicted by d =3 theories of domain kinetics, the circular domain shrinks linearly with time as A (t)=A(0)-αt, where A (0) and A(t) are the initial and instantaneous areas, respectively. However, in contrast to d =3, the slope α is strongly temperature dependent for T≥0.6TC. An analytical theory which considers the...

  3. Material properties of evolutionary diverse spider silks described by variation in a single structural parameter

    Madurga, Rodrigo; Plaza Baonza, Gustavo Ramon; Blackledge, Todd A; Guinea Tortuero, Gustavo Víctor; Elices Calafat, Manuel; Pérez Rigueiro, José
    Spider major ampullate gland silks (MAS) vary greatly in material properties among species but, this variation is shown here to be confined to evolutionary shifts along a single universal performance trajectory. This reveals an underlying design principle that is maintained across large changes in both spider ecology and silk chemistry. Persistence of this design principle becomes apparent after the material properties are defined relative to the true alignment parameter, which describes the orientation and stretching of the protein chains in the silk fiber. Our results show that the mechanical behavior of all Entelegynae major ampullate silk fibers, under any conditions,...

  4. Modeling of thermal effect on the electronic properties of photovoltaic perovskite CH3NH3PbI3: the case of tetragonal phase

    Montero Alejo, Ana L.; Menéndez-Proupin, E.; Hidalgo-Rojas, D.; Palacios Clemente, Pablo; Wahnon Benarroch, Perla; Conesa, J.C.
    Hybrid organic-inorganic perovskites are semiconductors with disordered structures and remarkable properties for photovoltaic applications. Many theoretical investigations have attempted to obtain structural models of the high-temperature phases, but most of them are focused on the mobility of organic components and their implications in material properties. Herein we propose a set of geometric variables to evaluate the conformation of the inorganic framework at each phase of methylammonium lead iodide perovskite. We show that the analysis of these variables is required to ensure consistent structural models of the tetragonal phase. We explore the theoretical ingredients needed to achieve good models of this...

  5. Electronic band alignment at CuGaS2 chalcopyrite interfaces

    Palacios Clemente, Pablo; Wahnon Benarroch, Perla; Castellanos Aguila, J.e.; Conesa, J.c.; Arriaga, J.
    Cu-chalcopyrite semiconductors are commonly used as light absorbing materials on solar cell devices. The study of the heterointerfaces between the absorbent and the contact materials is crucial to understand their operation. In this study, band alignments of the heterojunctions between CuGaS2 chalcopyrite and different semiconductors have been theoretically obtained using density functional theory and more advanced techniques. Band alignments have been determined using the average electrostatic potential as reference level. We have found that the strain in the heterointerfaces plays an important role in the electronic properties of the semiconductors employed here. In this work CuAlSe2/CuGaS2 and CuGaS2/ZnSe heterointerfaces show...

  6. Enhanced mechanical energy extraction from transverse galloping using a dual mass system

    Vicente-Ludlam, David; Barrero Gil, Antonio; Velázquez, A.
    This paper offers a theoretical study of energy extraction through transverse galloping using a dual-mass system. To this end, a two-degree-of-freedom model is developed where fluid forces on the galloping body are described resorting to quasi-steady hypothesis; the model is solved approximately by using the Harmonic Balance Method. Three possible configurations of the dual-mass system have been analyzed. Two of them show an improvement in the efficiency of energy extraction with respect to that of the single mass configuration when the mechanical properties of the dual-mass system are appropriately chosen. In addition, the dual-mass system promotes a broadening of the...

  7. Neutron area monitor with passive detector

    Valero-Luna, Claudia; Guzmán-García, Karen Arlete; Borja-Hernández, Candy Gretel; Hernández-Dávila, Víctor Manuel; Vega-Carrillo, Héctor René
    Using Monte Carlo methods the responses of a passive neutron monitor area has been calculated. To detect thermal neutrons the monitor has a gold foil that is located at the center of a polyethylene cylinder. Impinging neutrons are moderated by polyethylene nuclei reaching the gold foil with the energy to induce activation through the reaction 197Au (n,γ) 198Au. The198Au decays emitting 0.411 MeV gamma rays with a half life of 2.7 days. The induced activity is intended to be measured with a gamma-ray spectrometer with a 3”Ø×3” NaI(Tl) scintillator and the saturation activity is correlated to the ambient dose equivalent....

  8. Search via quantum walks with intermediate measurements

    García López De Lacalle, Jesús
    A modification of Tulsi's quantum search algorithm with intermediate measurements of the control qubit is presented. In order to analyze the effect of measurements in quantum searches, a different choice of the angular parameter is used. The study is performed for several values of time lapses between measurements, finding close relationships between probabilities and correlations (mutual information and cumulative correlation measure). The order of this modified algorithm is estimated, showing that for some time lapses the performance is improved, and becomes of order O(N) (classical brute-force search) when measurements are taken in every step. The results provide a possible way...

  9. Computation of the multi-chord distribution of convex and concave polygons

    Garcia-Pelayo Novo, Ricardo Angel
    Analytical expressions for the distribution of the length of chords corre- sponding to the a?ne invariant measure on the set of chords are given for convex polygons. These analytical expressions are a computational improve- ment over other expressions published in 2009 and 2011. The correlation function of convex polygons can be computed from the results obtained in this work, because it is determined by the distribution of chords. An analytical expression for the multi-chord distribution of the length of chords corresponding to the a?ne invariant measure on the set of chords is found for non convex polygons. In addition we...

  10. Action observation and motor imagery in performance of complex movements: Evidence from EEG and kinematics analysis

    Gonzalez Rosa, Javier Jesús; Natali, Fabrizio; Tettamanti, Andrea; Cursi, Marco; Velikova, Svetla; Comi, Giancarlo; Gatti, Roberto Vincenti; Leocani, Letizia
    Motor imagery (MI) and action observation (AO) are considered effective cognitive tools for motor learning, but little work directly compared their cortical activation correlate in relation with subsequent performance. We compared AO and MI in promoting early learning of a complex four-limb, hand?foot coordination task, using electroencephalographic (EEG) and kinematic analysis. Thirty healthy subjects were randomly assigned into three groups to perform a training period in which AO watched a video of the task, MI had to imagine it, and Control (C) was involved in a distracting computation task. Subjects were then asked to actually perform the motor task with...

  11. Insights into the production and characterization of electrospun fibers from regenerated silk fibroin

    Solanas Díaz, María Concepción; Herrero Galán, Sara; Dasari, Aravind; Plaza Baonza, Gustavo Ramon; Llorca Martinez, Francisco Javier; Pérez Rigueiro, José; Elices Calafat, Manuel; Guinea Tortuero, Gustavo Víctor
    Regenerated silk fibroin solutions from Bombyx mori were tested for electrospinning.Simple and reproducible tensile tests were performed on threads of aligned fibers to obtain information about their mechanical performance at the fiber level. The binary solvent formic acid/chloroform (10:1, v/v) rendered unbeaded thinner fibers with increased extensibility before failure when compared with pure formic acid. A remarkable improvement in strength was induced by immersing length-restricted fibers into ethanol for 5 min. Conformational changes of the protein chains were studied by solid-state NMR.

  12. Detecting specific oscillatory regimes in the dynamics of erbium-doped fiber laser

    Zhuravlev, Maxim O.; Koronovskii, Alexey A.; Moskalenko, Olga I.; Pisarchik, Alexander N.; Rider, D. R.; Hramov, Alexander E.
    A method for determining the oscillatory mode occurring in an erbiumdoped fiber laser with a modulated parameter is proposed. The method is based on using a continuous wavelet transform with a mother Morlet wavelet and analyzing the energy of the wavelet spectrum that corresponds to the relevant range of time scales.

  13. Deterministic coherence resonance in coupled chaotic oscillators with frequency mismatch

    Pisarchik, Alexander N.; Jaimes-Reategui, Rider
    A small mismatch between natural frequencies of unidirectionally coupled chaotic oscillators can induce coherence resonance in the slave oscillator for a certain coupling strength. This surprising phenomenon resembles “stabilization of chaos by chaos,” i.e., the chaotic driving applied to the chaotic system makes its dynamics more regular when the natural frequency of the slave oscillator is a little different than the natural frequency of the master oscillator. The coherence is characterized with the dominant component in the power spectrum of the slave oscillator, normalized standard deviations of both the peak amplitude and the interpeak interval, and Lyapunov exponents. The enhanced...

  14. Neutron absorbed dose in a pacemaker CMOS

    Borja-Hernández, Candy Gretel; Guzmán-García, Karen Arlete; Valero-Luna, Claudia; Bañuelos-Frías, Alan; Paredes-Gutiérrez, Leticia; Hernández-Dávila, Víctor Manuel; Vega-Carrillo, Héctor René
    El espectro y la dosis absorbida, debida a neutrones, por un Semiconductor de Óxido Metálico Complementario ha sido estimada utilizando métodos Monte Carlo. Eventualmente, una persona con marcapasos se convierte en un paciente oncológico que debe ser tratado en un acelerador lineal. El marcapasos contiene circuitos integrados como los CMOS que son sensibles a los campos de radiación intensos y pulsados. El haz terapéutico de un LINAC operando a voltajes mayores a 7 MV está contaminado con fotoneutrones que pueden dañar el CMOS. En este trabajo se estimó el espectro de neutrones y la dosis absorbida por un CMOS; además,...

  15. Neutron spectra and H*(10) of photoneutrons inside the vault room of an 18 MV LINAC

    Bañuelos-Frías, Alan; Borja-Hernández, Candy Gretel; Guzmán-García, Karen Arlete; Valero-Luna, Claudia; Hernández-Dávila, Víctor Manuel; Vega Carrillo, Héctor René
    Las estimaciones se llevaron a cabo utilizando métodos Monte Carlo donde una sala realista fue modelada incluyendo un fantoma de tejido equivalente. El término fuente para neutrones fue calculado usando la función de Tosi et al, la cual contabiliza los neutrones de evaporación y reacción directa. El espectro fue estimado usando dos diferentes distribuciones de energía. Los detectores fueron colocados en el plano donde se encuentra el isocentro. Dentro de la sala de tratamiento, como la distancia respecto al isocentro aumenta, la cantidad de neutrones y H*(10) se reduce, los neutrones dentro de la región de alta energía son desplazados...

  16. Passive neutron area monitor with TLD pairs

    Guzmán-García, Karen Arlete; Borja-Hernández, Candy Gretel; Valero-Luna, Claudia; Hernández-Dávila, Víctor Manuel; Vega-Carrillo, Héctor René
    The response of a passive neutron area monitor with pairs of thermoluminescent dosimeters has been calculated using the Monte Carlo code MCNP5. The response was calculated for one TLD 600 located at the center of a polyethylene moderator. The response was calculated for 47 monoenergetic neutron sources ranging from 1E(-9) to 20 MeV. Response was calculated using two irradiation geometries, one with an upper source and another with a lateral source. For both irradiation schemes the response was calculated with the TLD in two positions, one parallel to the source and another perpendicular to the source. The advantage of this passive...

  17. A review of macroscopic motion in thermodynamic equilibrium

    Sanmartín Losada, Juan Ramón
    A principle on the macroscopic motion of systems in thermodynamic equilibrium, rarely discussed in texts, is reviewed: Very small but still macroscopic parts of a fully isolated system in thermal equilibrium move as if points of a rigid body, macroscopic energy being dissipated to increase internal energy, and increase entropy along. It appears particularly important in Space physics, when dissipation involves long-range fields at Electromagnetism and Gravitation, rather than short-range contact forces. It is shown how new physics, Special Relativity as regards Electromagnetism, first Newtonian theory then General Relativity as regards Gravitation, determine different dissipative processes involved in the approach...

  18. Estudio teórico y numérico del comportamiento acústico de la disolución y crecimiento de nubes de burbujas

    Sañudo Babío, Jaime
    El proyecto trata sobre el estudio teórico y la resolución numérica de una serie de ecuaciones derivadas de las ecuaciones fundamentales de Mecánica de Fluidos. Dichas ecuaciones aplican al estudio del comportamiento o respuesta de burbujas gaseosas que se encuentran en el seno de un líquido. A lo largo del proyecto las propiedades seleccionadas para los cálculos corresponden a burbujas de CO2 sumergidas en agua, y el tamaño de las burbujas estudiado se encuentra en torno a las 100 micras. En el cuarto capítulo, se realiza una explicación teórica a modo de introducción de las ecuaciones generales de partida, a las...

  19. Demography-based adaptive network model reproduces the spatial organization of human linguistic groups

    Capitán Gómez, José Ángel; Manrubia, Susanna
    The distribution of human linguistic groups presents a number of interesting and nontrivial patterns. The distributions of the number of speakers per language and the area each group covers follow log-normal distributions, while population and area fulfill an allometric relationship. The topology of networks of spatial contacts between different linguistic groups has been recently characterized, showing atypical properties of the degree distribution and clustering, among others. Human demography, spatial conflicts, and the construction of networks of contacts between linguistic groups are mutually dependent processes. Here we introduce an adaptive network model that takes all of them into account and successfully...

  20. Analysis of thermionic bare tether operation regimes in passive mode

    Sanmartín Losada, Juan Ramón; Chen, Xin; Sánchez Arriaga, Gonzalo
    A thermionic bare tether (TBT) is a long conductor coated with a low work-function material. In drag mode, a tether segment extending from anodic end A to a zero-bias point B, with the standard Orbital-motion-limited current collection, is followed by a complex cathodic segment. In general, as bias becomes more negative in moving from B to cathodic end C, one first finds space-chargelimited (SCL) emission covering up to some intermediate point B*, then full Richardson-Dushman (RD) emission reaching from B* to end C. An approximate analytical study, which combines the current and voltage profile equations with results from asymptotic studies of the Vlasov-Poisson system for emissive...

Aviso de cookies: Usamos cookies propias y de terceros para mejorar nuestros servicios, para análisis estadístico y para mostrarle publicidad. Si continua navegando consideramos que acepta su uso en los términos establecidos en la Política de cookies.