Vol. 60 No. 1 Jan-Feb (2014): Revista Mexicana de Física.

Published: 2014-01-01

Articles

  • Improved spatial resolution in time-resolved transillumination imaging using temporal extrapolation with the cumulant expansion solution to the transport equation

    E. Ortiz-Rascón, N. C, A. A, J. Garduño-Mejía, R. Ortega-Martínez
    1-0
    Abstract:
    This paper presents results of a time-resolved transillumination imaging method using temporal extrapolation. The temporal extrapolation is performed with the cumulant expansion solution to the transport equation. The results obtained are compared to results of the same method but using the diffusion approximation solution. It is found that the results are consistent but that the cumulant expansion method gives better resolution, by a factor of approximately 3, for the imaging process, because it gives a better estimation of the photon contribution for shorter integration times.
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  • Experimental accelerated method for determining fatigue in aluminum 2024 alloy

    V. A, P. A, o Meza., I. N, J. M, oval Pineda., L. A, G. J
    8-0
    Abstract:
    The time of developing a main fatigue crack resulting in a fracture represents only 10 to 30% of the life of a specimen. The method proposed by Paris and Erdorgan analyzes the kinetics of developing a main fatigue crack based on the theoretical framework of fracture mechanics. However, this method cannot be applied to fully analyze the crack incubation process stage, which is a fundamental part of the specimen life time according to this theory. Therefore we propose to solve this problem of fracture mechanics approach by means of a high resolution photometric and phase analysis for structure images (PHASI), evaluating the life of the material by analyzing structural damage of the specimen surface fragments by PHASI, experimentally constructing fatigue curves using 2--4 specimens and photometrically analyzing the specimen surfaces before and after the tests.
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  • One pot synthesis of PbS/Cu$_{2}$S core-shell nanoparticles and their optical properties

    T. Serrano, I. Gómez
    14-0
    Abstract:
    The synthesis of PbS/Cu$_{2}$S core-shell nanoparticles with emission on the visible range and with improved luminescence properties was carried out by the colloidal solution-phase growth method by using simple stabilizers such as trisodium citrate and 3-mercaptopropionic acid. The core shell arrangement for particles with different crystalline structure was achieved, in addition this is the first report related to the synthesis PbS/Cu$_{2}$S core-shell system. The data obtained from absorption spectra, PL spectra, and HRTEM image provided direct proof of the formation of PbS core with size around 11 nm and Cu$_{2}$S shell of 5 nm thickness. According to the UV-vis absorption and PL spectrum, the optical characteristics observed in the synthesized material correspond to a PbS/Cu$_{2}$S system that has a higher confinement effect than the pure PbS nanoparticles. The QY was improved in 15 % from PbS to PbS/Cu$_{2}$S nanoparticles. The estimated band (HOMO-LUMO) alignment determined by CV measurements corresponds to a type-I core shell arrangement.
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  • Propiedades de transporte en el transistor $\delta$-FET

    O. Oubram, L. Cisneros-Villalobos, L. M, M. Abatal
    22-0
    Abstract:
    Electron transport in the $\delta$-FET transistor has been studied in GaAs. A theoretical model of transport based on the electronic structure is used to calculate mobility and conductivity. Results show that the electrical properties of $\delta$-FET depend on device intrinsic parameters (position of delta-doped quantum well, background density) and the magnitude of the voltage contact. Such results are useful in applications in temperature-insensitive devices.
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  • Aluminum-doped ZnO polycrystalline films prepared by co-sputtering of a ZnO-Al target

    M. Becerril, H. Silva-López, A. Guillén-Cervantes, O. Zela, a-Ángel.
    27-0
    Abstract:
    Aluminum-doped Zinc oxide polycrystalline thin films (AZO) were grown on 7059 Corning glass substrates at room temperature by co-sputtering from a ZnO-Al target. The target was designed as follows, high purity elemental Aluminum was evaporated onto a ZnO target covering small areas. The structural, optical, and electrical properties were analyzed as a function of Al content. The Al doped ZnO polycrystalline films showed an n-type conductivity. It was found that the electrical resistivity drops and the carrier concentration increases as a consequence of Al incorporation within the ZnO lattice. In both cases the changes are of several orders of magnitude. From the results, we conclude that, using these ZnO-Al targets, n-type Al doped ZnO polycrystalline films with high transmittance and low resistivity can be obtained.
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  • A physical interpretation of fractional calculus in observables terms: analysis of the fractional time constant and the transitory response

    J.F. Gómez-Aguilar, R. Razo-Hernández, D. Granados-Lieberman.
    32-0
    Abstract:
    This work presents the analysis of the fractional time constant and the transitory response (delay, rise, and settling times) of a RC circuit as a physical interpretation of fractional calculus in observables terms, the definition of Caputo fractional derivative is applied. The physical interpretation of these observables allows a clearer understanding of the concept of fractional derivative.
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  • First-principles study of electronic structure of Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10}$

    J. A, Diego Espitia., R. Baquero
    39-0
    Abstract:
    We present for the first time the electronic structure calculation of Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10}$ compound in the tetragonal structure (space group $I4/mmm$). We used the Local Density Approximation (LDA) as in the Wien2k code. We analyze in detail the band structure, density of states, and Fermi surface (FS) for this compound. The FS calculated shows the feature known as the Bi-O pocket problem which we associate with the interaction of the Cu2-O2 and Bi-O4 planes through O3 atoms. However, our FS in the nodal direction is in very good agreement with the FS measured using angle-resolved photo-emission spectroscopy (ARPES). This calculation is useful, since Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10}$ compound show a transition to the superconducting state at $\sim110$ K and to date there are no reports in the literature of its electronic structure known to us.
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  • Geophysical exploration to estimate conductivity and permittivity model of an excavated soil block

    F. Uribe, P. Zúñiga, P. Gómez
    46-0
    Abstract:
    An electrical model for a real stratified soil block is proposed in this paper. The model is suitable to estimate the physical properties of electrical conductivity and permittivity, as well as the thickness of each of the layers of the subsoil. For the estimation, we implement a methodology based on the efficient numerical solution of the Takahashi et al. infinite integrals for calculating the vector potentials at the soil surface. For the truncation of the infinite integrals, a new exponential based truncation criterion is proposed. Subsequently, to evaluate a more accurate fitting of the apparent resistivity curves obtained by measurements and by the Takahashi et al., integrals, two numerical optimization techniques based on genetic algorithms, and least squares method are implemented for accuracy assessment. Finally, a formal quantitative validation methodology is presented in this paper based on the comparison of the numerical optimization results with respect to a data set obtained by direct measurements of the electrical resistivity on the vertical excavation profiles on each subsurface layer down the experimental workstations named Site-1, 2, \ldots 4.
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  • Láser de Brillouin con cavidad corta de fibra estabilizado pasivamente en la resonancia de bombeo por fenómeno de auto-encadenamiento por inyección óptica

    C. A, V. V, Patrice Mégret., A. A
    53-0
    Abstract:
    We demonstrate a short cavity Brillouin fiber ring laser, which is passively stabilized at pump resonance frequency by using self-injection locking phenomena. Simple and efficient algorithm for the adjusting of the double resonance in short cavity Brillouin fiber laser is offered. Locked Brillouin laser exhibited stable single frequency operation at pump wavelength up to 3 minutes and Stokes radiation with linewidth less than 1.2 kHz.
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  • Thermodynamic response functions and Maxwell relations for a Kerr black hole

    L. Escamilla, J. Torres-Arenas
    59-0
    Abstract:
    Assuming the existence of a fundamental thermodynamic relation, the classical thermodynamics of a black hole with mass and angular momentum is given. New definitions of the response functions and $TdS$ equations are introduced and mathematical analogous of the Euler equation and Gibbs-Duhem relation are founded. Thermodynamic stability is studied from concavity conditions, resulting in an unstable equilibrium at all the domain except for a region of local stable equilibrium. The Maxwell relations are written, allowing to build the thermodynamic squares. Our results shown an interesting analogy between thermodynamics of gravitational and magnetic systems.
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  • Right- and left-handed twist in optical fibers

    D. Tentori, A. Garcia-Weidner
    69-0
    Abstract:
    The effect of twist-induced variation of the output state of polarization on clockwise and counterclockwise torsion was measured in two standard optical fibers made by different manufacturers. It was found that standard fiber samples may exhibit a different twist-induced polarization performance for right- and left-handed twists. In this work we compare the results obtained for two commercial fibers using linearly polarized input signals with azimuth angles between 0 and 150$^{\circ}$, within the 1520-1570 nm spectral range. In all cases these results could be described using the same theoretical model. We demonstrate that the different behavior observed for right- and left-handed twists for one of the samples can be explained by the presence of a residual torsion.
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  • Generation of solutions of the Hamilton--Jacobi equation

    G.F. Torres del Castillo
    75-0
    Abstract:
    It is shown that any function $G(q_{i}, p_{i}, t)$, defined on the extended phase space, defines a one-parameter group of canonical transformations which act on any function $f(q_{i}, t)$, in such a way that if $G$ is a constant of motion then from a solution of the Hamilton--Jacobi (HJ) equation one obtains a one-parameter family of solutions of the same HJ equation. It is also shown that any complete solution of the HJ equation can be obtained in this manner by means of the transformations generated by $n$ constants of motion in involution.
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  • Estimación de parámetros concentrados de un proceso estocástico de segundo orden

    J. J, R. Urbieta P., J. C
    80-0
    Abstract:
    In this paper develops a stochastic digital filter as identification with estimation technique considering the second probability moment, with respect to a second order model applied on stochastic physics such as Van der Pol, Schrödinger and Bernulli equation with perturbations. The mathematical design considered the Martingale form and mathematical expectation into state space model with stationary conditions and bounded output. The variance and covariance are used for internal parametres description model and its recursive form allows implementing into a digital system with minimum computational resources. The parametres estimation results are included into model proving that the convergence answer tends to reference signal, and in consequence, the error tends to cero. The graphical results were obtained using the MatLab software as a platform simulation.
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  • Graphite thin film characterization using a simplified resonant near field scanning microwave microscope

    G. López-Maldonado, N. Qureshi, O. V, H. Vargas-Hernández, C. L
    88-0
    Abstract:
    We describe a highly simplified design for a coaxial resonant near field scanning microwave microscope operating at 7.4 GHz configured to measure surface resistance and obtain topographic images with micrometer resolution. This design for a resonant probe tip combined with a highly stable mechanical system developed to rapidly tune the resonant frequency enables a simplified and effective approach to implementing near field microwave microscopy. We present images and measurements performed on a non-uniform granular graphite film sample and the surface resistance results agree with data in the literature.
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  • Black holes from Myers-Perry solution

    L. A
    95-0
    Abstract:
    From the five dimensional Myers-Perry solution and consider that de metric MP corresponding to the Kaluza-Klein ansatz (zero mode), we obtained $4D$ solution with non-minimally coupled scalar and electromagnetic fields, characterized by three parameters, $r_{0},a,b$, related to the mass, angular momentum and electromagnetic field, respectively and proposing that the $4D$ solution is a solution type black hole. Then for $a\neq 0$, $b=0$ the electromagnetic field vanishes and the black hole is stationary. For $a=0$, $b\neq 0$ the solution is static with electric field. If $a\neq 0$, $b\neq 0$ the solution is stationary with electric field and, due to the rotation, a magnetic field appears. The scalar field that arises from the dimensional reduction is present in all cases. At infinity the solution is asymptotically flat and the trace of the scalar field get lost, turning out that this solution is in agreement with the no hair conjecture.
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