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191.
Manef Chtourou Rami Abdelhdi Mohamed Hdi Frikha Mahmoud Trabelsi 《Ultrasonics sonochemistry》2010,17(1):246-249
This paper presents a novel solvent free method of synthesis of trans-chalcones. The method was based on ultrasound irradiation of the reagents (aryl methyl ketones and aryl aldehydes) in presence of commercial acid-montmorillonites as catalysts. The trans-chalcones were synthesized in high yields (85–95%) and excellent selectivity in a short reaction time. 相似文献
192.
The ground state properties of the spherical nucleus ^40Ca have been investigated by using constrained spherical Hartree Fock (CSHF) approximation at equilibrium and under high radial compression in a six major shells. The effective baryon-baryon interaction that includes the △(1236) resonance freedom degrees to calculate nuclear properties is used. The nucleon-nucleon (N-N) interaction is based on Reid soft core (RSC) potential. The results of calculations show that much of increase in the nuclear energy generated under compression is used to create the massive △ particles. The number of △ 's can be increased to about 2.1% of constituents of nucleus when nuclear density reaches about 1.34 times of normal density. The single particle energy levels are calculated and their behavior under compression is also examined. △ good agreement has been found between current calculations and phenomenological shell model for low lying single-particle spectra. The gap between shells is very clear and L-S coupling become stronger as increasing the static load on the nucleus. The results show a considerable reduction in compressibility when freedom degrees of △'s are taken into account. It has been found that the total nuclear radial density becomes denser in the interior and less dense in the exterior region of nucleus. The surface of nucleus becomes more and more responsive to compression than outer region. 相似文献
193.
n-Type indium antimonide-Au hybrid macro-structure was successfully fabricated on p-GaAs substrate by a simple and economic
flash evaporation technique. The elemental composition of the prepared InSb film was confirmed by energy dispersive X-ray
spectroscopy microanalysis (EDX). The surface topography and crystal structure of the InSb film was characterized by scanning
electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The magnetoresistance of the prepared hybrid macro-structure
was measured and discussed in terms of the model of current redistribution. 相似文献
194.
195.
We study poissonized triangular (reducible) urns on two colors, which we take to be white and blue. We analyze the number of white and blue balls after a certain period of time has elapsed. We show that for balanced processes in this class, a different scaling is needed for each color to produce nontrivial limits, contrary to the distributions in the usual irreducible urns which only require the same scaling for both colors. The limit distributions (of the scaled variables) underlying triangular urns are Gamma. The technique we use couples partial differential equations with the method of moments applied in a bootstrapped manner to produce exact and asymptotic moments. For the dominant color, we get exact moments, while relaxing the balance condition. The exact moments include alternating signs and Stirling numbers of the second kind. 相似文献
196.
In this research paper, we examine a novel method called the Natural Decomposition Method (NDM). We use the NDM to obtain exact solutions for three different types of nonlinear ordinary differential equations (NLODEs). The NDM is based on the Natural transform method (NTM) and the Adomian decomposition method (ADM). By using the new method, we successfully handle some class of nonlinear ordinary differential equations in a simple and elegant way. The proposed method gives exact solutions in the form of a rapid convergence series. Hence, the Natural Decomposition Method (NDM) is an excellent mathematical tool for solving linear and nonlinear differential equation. One can conclude that the NDM is efficient and easy to use. 相似文献
197.
Ali Y. Al-Rayyah Magdi S. Mahmoud 《Journal of Optimization Theory and Applications》2010,147(2):318-336
In this paper, we study the problem of designing decentralized reliable feedback control methods under a class of control
failures for a class of linear interconnected continuous-time systems having internal subsystem time-delays and additional
time-delay couplings. These failures are described by a model that takes into consideration possible outages or partial failures
in every single actuator of each decentralized controller. The decentralized control design is performed through two steps.
First, a decentralized stabilizing reliable feedback control set is derived at the subsystem level through the construction
of appropriate Lyapunov-Krasovskii functional and, second, a feasible linear matrix inequalities procedure is then established
for the effective construction of the control set under different feedback schemes. Two schemes are considered: the first
is based on state-measurement and the second utilizes static output-feedback. The decentralized feedback gains in both schemes
are determined by convex optimization over linear matrix inequalities. We characterize decentralized linear matrix inequality-based
feasibility conditions such that every local closed-loop subsystem of the linear interconnected delay system is delay-dependent
robustly asymptotically stable with an γ-level ℒ2-gain. The developed results are tested on a representative example. 相似文献
198.
Hosam M. Mahmoud 《Methodology and Computing in Applied Probability》2010,12(4):763-773
The power of choice is known to change the character of random structures and produce desirable optimization effects. We discuss
generalizations of random recursive trees, grown under the choice to meet optimization criteria. Specifically, we discuss
the random k-minimal (k-maximal) label recursive tree, where a set of k candidate parents, instead of one as in the usual recursive tree, is selected and the node with minimal (maximal) label among
them is assigned as parent for the next node. These models are proposed as alternatives for D’Souza et al. (Eur Phys J B59:535–543,
2007) minimal and maximal depth models. The advantage of the label models is that they are tractable and at the same time provide
approximations and bounds for the depth models. For the depth of nodes in label models we give the average behavior and exact
distributions involving Stirling’s numbers and derive Gaussian limit laws. 相似文献
199.
In this paper, we investigate the problem of robust global exponential stability analysis for a class of neutral-type neural networks. The interval time-varying delays allow for both slow and fast time-varying delays. The values of the time-varying uncertain parameters are assumed to be bounded within given compact sets. Improved global exponential stability condition is derived by employing new Lyapunov-Krasovskii functional and the integral inequality. The developed nominal and robust stability criteria is delay-dependent and characterized by linear-matrix inequalities (LMIs). The developed results are less conservative than previous published ones in the literature, which are illustrated by representative numerical examples. 相似文献
200.
ABSTRACTNonlinear propagation of dust-ion-acoustic shock waves in an unmagnetized, collisionless four-component quantum plasma containing electrons, positrons, ions and negatively charged dust grains affected by dust charge variations and viscosity of ions is studied using quantum hydrodynamic model. Considering dust charge variation give rise to calculating of charging currents of the plasma particles. These currents have been calculated with orbit limited motion theory and using Fermi-distribution functions or Boltzmann–Maxwell distribution depending on quantum or classical particles, respectively. The basic characteristics of quantum dust-ion-acoustic shock waves are investigated by deriving Korteweg–de Vries–Burgers equation under the reductive perturbation method. Depending on the relative values of the dispersive and dissipative coefficients, oscillatory and monotonic shock waves can propagate in the plasma model. The effect of chemical potential and density of dust particles on the shock wave’s height and thickness is investigated. In addition, the critical value of H (Hc) is calculated and it is shown that for R?>?0 compressive shock waves and for R?<?0 rarefactive ones can exist. The present study is applicable to researchers on quantum nonlinear structures in dense astrophysical objects and ultra-small micro- and nano-electronic devices. 相似文献