Vol. 59 No. 3 (2013): Revista Mexicana de Física.

Published: 2013-01-01

Articles

  • Evaluación de la estructura y microestructura de óxidos de Ni$_{x}$Mg$_{1 - x}$O, obtenidos por co-precipitación

    G. Martínez-Lozano, T. Kr, shtab., M. Hesiquio-Garduño, A. Kr, vko.
    186-0
    Abstract:
    Ni$_{x}$Mg$_{1 - x}$O oxides were prepared by thermal treatment at temperatures of 400$^{\circ}$C, 600$^{\circ}$C and 800$^{\circ}$C from a hydrotalcite-like precursor obtained by co-precipitation at constant pH. The oxides obtained were characterized by X-ray diffraction methods. From the obtained results we concluded that the oxides calcined at temperatures of 400$^{\circ}$C and 600$^{\circ}$C are unstable that means that there exists the effect of memory and with a time they return to the precursor. Presence of Ni in Mg oxide provides stability of the compounds thermally treated at 800$^{\circ}$C. In order to analyze the structure and microstructure, the reflections 111, 200 and 220 were used. The positions of the maxima of the diffraction peaks are shifted with respect to the simulated ones for MgO and NiO. This result reveals that in solid solutions studied compressive strains or vacation are present. The parameters of the microstructure (coherent domain size and microdeformations) were evaluated. The coherent domain size was found to be in the range of 8 - 10 nm and the presence of residual strains of microdeformation can be associated with the existence of extended defects.
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  • Time-resolved microwave conductivity (TRMC) a useful characterization tool for charge carrier transfer in photocatalysis: a short review

    C. Colbeau-Justin, M. A
    191-0
    Abstract:
    We provide a brief introduction about photocatalysis and the reaction mechanism for charge-carrier dynamics focusing in the situation and application of Time Resolved Microwave Conductivity (TRMC) as a useful characterization technique of irradiated semiconductors.
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  • Scale-free growing networks and gravity

    J. A
    201-0
    Abstract:
    We propose a possible relation between complex networks and gravity. Our guide in our proposal is the power-law distribution of the node degree in network theory and the information approach to gravity. The established bridge may allow us to carry geometric mathematical structures, which are considered in gravitational theories, to probabilistic aspects studied in the framework of complex networks and vice versa.
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  • The study of electro-optical properties of nanocomposite ITO thin films prepared by e-beam evaporation

    M. Farahamndjou
    205-0
    Abstract:
    Indium-tin oxide thin films are deposited on sods lime glass substrates using e-beam evaporation system. In order to improve the structural, electrical and optical properties of the films, these films were annealed in vacuum and different temperature. The structure, sheet resistance and optical transmission of the films were systematically investigated as function of post annealing temperature. It has been observed that the films take its maximum transmission and conductivity at annealing temperature 400$^{\circ}$C. The XRD and AFM analysis reveals that the amorphous films were oriented to $\langle 222 \rangle$ crystal texture direction with size of grains about 35-40 nm.
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  • Desarrollo de un microscopio electroquímico basado en servomecanismos

    J. Guillén Rodríguez, E. Valaguez - Velázquez, A. Zapata-Navarro, A. Márquez-Herrera, M. Melendez-Lira, M. Zapata-Torres
    208-0
    Abstract:
    An electrochemical microscope was developed using novel instrumentation based on a nanopositioning stage (containing servomotors) and controlled through a motion controller card. Even though a movement specialized hardware offers advantages doing scanning microelectrochemical experimentation, it has not been previously reported. The whole system was controlled through a personal computer using a data acquisition card and the serial RS232 port. The complete software for controlling the system was developed~ and tested through typical scanning electrochemical microscopy experiments. As a result, approach curves, chemical maps, morphology and~ interpolated movements over dielectric and conductor samples using the constant height technique, were obtained.
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  • Solución general de la ecuación de Navier-Stokes para describir la dinámica de un fluido viscoso homogéneo en una tubería abierta

    J. de Jesús Rubio, G. Ordaz, M. Jiménez-Lizárraga, R. Iván Cabrera
    217-0
    Abstract:
    This paper presents a particle analysis of the unidimentional solution of the Navier-Stokes equation with border conditions which lets to describe a fluid on a petroleum industry pipe.
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  • Monodisperse magnetic nanoparticles: Effects of surfactants on the reaction between iron acetylacetonate and platinum acetylacetonate

    K. Chokprasombat, C. Sirisathitkul, P. Harding, S. Ch, arak., R. Yimnirun
    224-0
    Abstract:
    Magnetic properties of monodisperse nanoparticles for ultrahigh density recording and biomedical applications are sensitive to their shape and size distributions. These attributes are, in turns, dictated by several parameters during the synthesis and heat treatments. In this work, monodisperse FePt-based magnetic nanoparticles around 5 nm in diameter were synthesized by the reaction between iron acetylacetonate (Fe(acac)$_{3})$ and platinum acetylacetonate (Pt(acac)$_{2}$) in benzyl ether. X-ray absorption near-edge structure (XANES) spectra agreed with transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) that as-synthesized nanoparticles were composed of Pt-rich nuclei and iron oxides. Whereas their composition and size was not sensitive to the variation in the amount of surfactants (oleic acid and oleylamine), the nanoparticles exhibited a larger variation in shape with the increase in each surfactant from 1.5 to 4.5 mmol. After annealing in argon atmosphere at 650$^{\circ}$C for 1 hour, the nanoparticles tended to agglomerate. Higher amounts of surfactants surrounded the nanoparticles apparently allowed more sintering because the decomposed carbon from the excess surfactants facilitated the reduction of iron oxides. More Fe in the large annealed particles then resulted in ferromagnetic properties. By contrast, the ferromagnetic behavior and the highest coercivity were obtained without such agglomeration in the case of annealed particles synthesized by using the minimum surfactants.
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  • Bound state solutions of deformed generalized Deng-Fan potential plus deformed Eckart potential in D-dimensions

    O. A, A. N, J. B
    229-0
    Abstract:
    In this article,we present the approximate solution of the D-dimensional Schrödinger equation for deformed generalized Deng-Fan plus deformed Eckart potential using parametric Nikiforov-Uvarov method. We obtain the bound state energy eigenvalues and the corresponding wave function for arbitrary $l$ state. Special cases of this potential are also discussed.
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  • Mean field theory of inhomogeneous fluid mixtures

    J. G.~Segovia-López, A. Zamora, J. Antonio~Santiago
    236-0
    Abstract:
    By using density functional theory, we analyze an inhomogeneous fluid mixture composed of an arbitrary number of species within mean field approximation. Under the assumption that the interfacial region behaves as an elastic continuous medium, we calculate the stress tensor and the equilibrium grand potential of the system for different surfaces. It is found that, unlike the single component system, there exist multiple coexistence regions induced by the diversity of interaction potentials between the different species. Surface properties are calculated for a step-like density profile and consistency with the monocomponent system is verified for both the same formalism and other approaches at the level of surface tension.
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  • A generating function for the spherical harmonics in $p$ dimensions

    G.F. Torres del Castillo
    248-0
    Abstract:
    A generating function for the spherical harmonics in three or more dimensions is given. This function allows us to find in a simple manner the explicit expressions for the spherical harmonics in three dimensions. The generating functions for the spherical harmonics given here are analogous to certain well-known generating functions for solutions of the wave equation.
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  • State space second order filter estimation

    J. J, M. T
    254-0
    Abstract:
    The second order stochastic filter is based on difference models with uncorrelated innovation conditions structured in state space having stationary properties through a surface with bounded drift around the mean value. This allows building recursive estimation without generality lost and basic properties over the stochastic state space surface with unknown gains viewed as a black-box scheme. The spatial region generated gave an approximation to real parametres set with a sufficient convergence rate in a probability sense. The results were applied in adaptive identification states with a high convergence rate, observed in the functional error described illustratively in simulations. This technique was developed over the smooth slide surface having advantages over other traditional filters.
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  • Simulation of breakthrough curves of selenium absorbed in two biomass filters using a dispersion and sorption model. Use for a hypothetical case

    C. E, E. Rodríguez-Martínez, J. Klapp-Escribano, R. Duarte-Pérez, M. Teresa-Olguín, A. F, I. Cano-Aguilera, Z. González-Acevedo
    258-0
    Abstract:
    A fixed bed study was carried out using the non-living biomasses Eichhornia crassipes and Lemna minor as a biosorbent for the removal of selenium from an aqueous solution. A 3D model, capable to represent the real system, was configured using the Navier Stokes, Brinkman and mass transport equations. Experimental and numerical results were compared to validate the model. Correlation factors up to R$^{2}$=0.95 were obtained in the validation model. Using the model, different systems were simulated obtaining relations between feed concentration and sorption capacity which increases when the inlet selenium concentration increases. A serial system of columns was configured with a flow rate of 2500 L/day and an inlet selenium concentration of 100 ppm capable of keeping an outlet concentration below 10 ppb during 27 days.
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  • Geometrically-tunable self-stabilization effect in Rhodamine 6G

    J.R. Cabrera Esteves, I.V. Gur, ev., J.A. Andrade Lucio, I.A. Sukhoivanov
    266-0
    Abstract:
    This paper shows experimental results on geometrically-tunable self-stabilization effect in Rhodamine-6G dye. A crossing-laser-beams scheme has been used in the experiment in order to obtain wide-tuneability of the proposed structure. Obtained results demonstrate radiation power stabilization with up to 175 mW at the input. The proposed self-stabilization scheme can be used as a power-stabilized light source for metrology applications, and integrated circuits with nonlinear optical elements.
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  • Measurements of thermal conductivity in a crystal quartz substrate at 1.4 K

    A. Colin
    270-0
    Abstract:
    We carried out measurements of thermal conductivity in a crystal quartz substrate (900 $\mu $m thick) at temperatures of 1.4 K by using a pumped $^{4}$He cryostat. We applied a varied input power from 0.1 up to 1 mW to the heater placed at the end of the substrate, and we observed that the measured data give a temperature dependence of $k= 0.12 T^{2.7}$ W/cm$\cdot$K.
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  • Spherical aberration correction using aspheric surfaces with an analytic-numerical method

    S. Vázquez-Montiel, O. García-Liévanos
    273-0
    Abstract:
    This method is a discrete case of the E. Wolf method for the design of an aspheric surface. Using the proposed method, the designer can select how many points $(x,y)$ there will be on the entrance pupil at which the spherical aberration will be zero, by using the aspheric coefficients as degrees of freedom. For fitting the coordinates that correct the spherical aberration to an aspheric surface we solve a system of equations of the first degree. An optimisation procedure is not required because we use equations without approximations and with exact ray tracing. We obtained diffraction limited optical systems faster than the commercial programs.
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  • The diagonal Bernoulli differential estimation equation

    J. J, R. Palma
    282-0
    Abstract:
    The Bernoulli Differential Equation traditionally applies a linearization procedure instead of solving the direct form, and viewed in state space has unknown parametres, focusing all attention on it. This equation viewed in state space with unknown matrix parametres had a natural transformation and introduced a diagonal description. In this case, the problem is to know the matrix parametres. This procedure is a new technique for solving the state space Bernoulli Differential Equation without using linearization into diagonal filtering application. Diagonal filtering is a kind of quadratic estimation. This is a procedure which uses observed signals with noises and produces the best estimation for unknown matrix parametres. More formally, diagonal filtering operates recursively on streams of noisy input signals to produce an optimal estimation of the underlying state system. The recursive nature allows running in Real-time bounded temporally using the present input signal and the previously calculated state and no additional past information. From a theoretical standpoint, the diagonal filtering assumption considered that the black-box system model includes all error terms and signals having a Gaussian distribution, described as a recursive system in a Lebesgue sense. Diagonal filtering has numerous applications in science and pure solutions, but generally, the applications are in tracking and performing the stochastic system.
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