Vol. 54 No. 5 (2008): Revista Mexicana de Física.

Published: 2008-01-01

Articles

  • La infiltración no asistida como una técnica de procesamiento de compósitos Al-Mg-Si/SiC

    J.A. Aguilar-Martínez, M.B. Hernández
    336-0
    Abstract:
    This work intends to describe the technique of pressureless infiltration as a alternative route in the composite processing Al-Mg-Si/SiC. Also some parameters are discussed that should be controlled adequately, like the formation of undesirable products, wettability, processing atmosphere, alloys elements, etc. Likewise it intends to give a brief description about the metal matrix composites for, this way, to know the importance that has this class of materials in our society nowadays.
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  • Boundary element analysis for primary and secondary creep problems

    E. Pineda León, M.H. Aliabadi, M. Ortiz-Dominguez
    341-0
    Abstract:
    This paper presents the application of the Boundary Element Method to primary and secondary creep problems in a two{}-dimensional analysis. The domain, where the creep phenomena takes place, is discretized into quadratic, quadrilateral, continuous internal cells. The creep analysis is basically applied to metals, that are capable of modeling secondary and primary creep behaviour. This is confined to standard power law creep equations. Constant applied loads are used to demonstrate time effects. Numerical results are compared with solutions obtained from the Finite Element Method (FEM) and references.
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  • Frustración local en la red arquimediana (3,4,6,4)

    W. Lebrecht, J.F. Valdés
    349-0
    Abstract:
    By means of Ising model with mixed interactions $\pm J$ to nearest neighbors and null temperature, is described the behavior of physical and topological parameters of the fundamental level associated to (3,4,6,4) lattices in notation of Grünbaum and Shephard, NL for simplicity. It is used for it, two canonical descriptions determined by distributions of probabilities $\phi$ and $\psi$ that they are established through a local analysis of frustration on a representative cell of the lattice. The results obtained for average energy per bond, average frustration segment and fraction of unfrustrated bonds in both descriptions are compared with numerical simulations based on method of multireplicas of quick descent over a set of 10000 samples randomly generated including periodic boundary conditions. It observes a good agreement between analytical and numerical results, especially at antiferromagnetic and spin glass phases.
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  • Thermally assisted NO$_{2}$ and NH$_{3}$ gas desorption process in a polyaniline thin film based optochemical sensor

    J.Elizalde-Torres., Hailin Hu., A. Guadarrama-Santana, A.García-Valenzuela., J.M.Saniger.
    358-0
    Abstract:
    NO$_{2}$ gas is a strong electron acceptor that can oxidize the chemically deposited semiconductor polyaniline (PANI) at room temperature under atmospheric pressure. Since each redox state of this polymer is associated with a specific electronic structure, an oxidized PANI thin film undergoes a color change that can be detected in a sensitive optochemical sensor. But the strongly absorbed NO$_{2}$ molecules cannot be removed at room temperature from the polymer material during the purging process with a dried N$_{2}$ gas flux. We report in this work that a heating element can be integrated into the optochemical sensor to elevate the sensing sample temperature during the desorption process. At temperatures higher than 50$^{\circ}$C, the optical signal of the NO$_{2}$ absorbed PANI samples starts to return to its original value during the purging process, suggesting the desorption of the NO$_{2}$ species from the PANI samples. The higher the heating temperature, the greater the activation energy for desorption, and consequently the faster the desorption speed. Similar results are also obtained for the NH$_{3}$ desorption process occurring in the same polymer.
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  • A resonant nuclear reaction analysis of fluorine in thin CdO films

    R. Ferro, J.A. Rodríguez, J. Rickards, J. Cañetas-Ortega, R. Trejo-Luna
    364-0
    Abstract:
    The resonant nuclear reaction (RNR) technique has been used for determining the fluorine content in CdO thin films prepared by spray pyrolysis. The gamma rays observed were from the nuclear reaction $^{19}$F(p,$\alpha \gamma )^{16}$O, which presents a resonance at 340 keV bombarding energy. From the excitation curves the dependence of the fluorine content in the films on the wt % of NH$_{4}$F in the starting solution was observed. In order to understand the doping process, the RNR study was complemented with the other techniques of chemical and electrical analysis such as energy dispersive spectroscopy and the Hall effect.
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  • Optically pumped generation of multi-pulse three-wave coupled states in a two-mode waveguide with a square-law nonlinearity and digital modulation of light

    A.S. Shcherbakov, A. Aguirre Lopez
    368-0
    Abstract:
    We study the process of sculpturing three-wave weakly coupled states under the action of the pulsed optical pump in a two-mode square-law nonlinear waveguide within the collinear regime of propagating the interacting waves. The analytical model for this process with slightly mismatched wave numbers predicts the sculpturing of multi-pulse optical components inherent in three-wave coupled states. Reasoning from the developed approach, we discuss an opportunity for the digital modulation of light, because those potentially three-wave coupled states under consideration can be binary encoded. The performed analysis of sculpturing multi-pulse coupled states in a non-stationary regime was experimentally examined during our studies of collinear acousto-optical interaction in a two-mode lithium niobate waveguiding structure exhibiting a square-law nonlinearity.
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  • Difracción de Bragg de ondas ópticas guiadas por ondas de dipolo de spin en guías de onda ferromagnéticas de doble capa

    O. Cortés-Pérez, C.L. Ordoñez-Romero, R. Ortega-Martínez, O.V. Kolokoltsev, A. Grishin
    376-0
    Abstract:
    The peculiarities of the Bragg diffraction of optical guided waves (OGWs) by spin-dipole waves (SDWs) in a new ferrite heterostructure, based on Bi$_{3}$Fe$_{5}$O$_{12 }$(BIG) thin film deposited on a standard YIG/GGG (a Yttrium Iron Garnet thin film over a Galium Gadolinum Garnet substrate) sample, is presented. It is shown that the efficiency of waveguide magnetooptic interaction between OGWs and SDWs in BIG/YIG/GGG can be 4-14 times larger than in the standard YIG/GGG waveguide, even in the case when the interacting waves are localized in YIG waveguide layer.
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  • Estudio de una onda lenta de gran amplitud en el sistema chorro - plasma por ondas de prueba

    J. Ruiz-Camacho
    382-0
    Abstract:
    A theoretical and experimental study of the potential well that takes place behind the shock wave excited in an ion-beam plasma system was performed. The space distribution of the potential well was calculated with the fluid theory where, in addition to the two ionic species, two electronic species with different temperatures and densities were included. The width and depth of the well, which were measured experimentally, were compared with the theoretical results. Amplification of locally excited test waves within the plasma was measured, allowing us to calculate the ion beam acceleration in the potential well. From these measurements we calculated the space variation of ion beam velocity within the well.
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  • Photovoltage and J-V features of porous silicon

    MC. Arenas, Hailin Hu., J. Antonio del Río, Oscar H. Salinas
    391-0
    Abstract:
    In this paper we present a systematic study into the influence of the electrical, structural and optical properties of the porous silicon (PS) layers on the photovoltage and J --V responses of devices prepared from this semiconductor material. Electronic devices were prepared forming a p- or n-type PS (pPS and nPS, respectively) layer on crystalline silicon c-Si (p- or n-type, pSi and nSi, respectively) substrate. Two different metals were deposited as contact electrodes. The devices' electrical responses analyzed were their current density versus voltage (J-V) and photovoltaic. It was found that the presence of the pPS layer significantly modifies the electrical responses mentioned above of the pSi material. It means the optoelectronics properties of the pSi are modified by the presence of the pPS layer; it can be understood in terms of the optical absorption spectra of PS. The nPS does not modify the optoelectronic properties of the nSi material. We propose an energy band diagram in order to explain the different behavior of these two different PS layers.
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  • Medición la función de Wigner para campos electromagnéticos en cavidades

    J.L. Escudero Jiménez, H. Mo, a-Cessa.
    397-0
    Abstract:
    We show how the Wigner function may be measured for a quantum state of light. For this we show a form to displace fields inside cavities. Displacement of quantum fields is a key ingredient in quasiprobability reconstruction processes, i.e. the measurement of quantum states of light.
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  • Encadenamiento por inyección óptica de un láser DFB con la dispersión de brillouin

    M. Castro Muñoz, V.V. Spirin
    400-0
    Abstract:
    We reported novel optical injection locking (OIL) configurations to generate a frequency and intensity stable Stokes signal without microwave generator and optic modulator. The first configuration based on OIL of DFB laser on Brillouin fiber ring laser radiation and second one on self-injection locking on Brillouin amplified radiation. Comparing the noise level of both configurations we found that second provides significantly more intensity and frequency stable Stokes signal. These configurations can advantageously be utilized in probe Stokes signal generation for distributed fiber optical Brillouin sensing.
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