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Journal of Rare Earths 2014年第10期32卷 965-972页

作者： m.Eshraghi P.Kameli F.Khalili m.h.Ehsani h.Salamati Department of Physics Payame Noor University Department of Physics Isfahan University of Technology Department of Physics Semnan University

Structural, magnetic and electrical properties of the La0.7Ca0.3Co1–xmnxO3（x=0, 0.7 and 1） samples prepared by a simple method were systematically studied and it was found that the crystal structure was transformed from rhombohedral for La0.7Ca0.3CoO3（LCCO） and La0.7Ca0.3Co0.3mn0.7O3（LCCmO） samples to orthorhombic for La0.7Ca0.3mnO3（LCmO） sample. The AC magnetic susceptibility measurements showed that LCCO sample underwent a transition from paramagnetic（Pm） to ferromagnetic（Fm） phase at Curie temperature, TC^155 K and below Curie temperature, the glassy ferromagnetism nature was observed. In LCCmO sample,clear evidence of spin glass（SG） state was observed at low temperature. Pm-Fm phase transition at about TC^260 K and long range Fm order at low temperatures were observed in LCmO sample. Both the LCCO and LCCmO samples exhibited insulating behavior in the whole range of measuring temperature whereas the LCmO sample underwent a clear metal-insulator（mI） transition at about TmI^263 K, corresponding to Curie temperature. metallic region of ρ（T） curve of the LCmO sample was fitted to the model of electron-electron and electron-magnon scattering. The charge carrier transport behavior in all the samples was compared based on polaronic models.

关键词： cobaltite spin glass manganites rare earths

Experimental Study of Wave Attenuation in Trapezoidal Floating Breakwaters

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China Ocean Engineering 2019年第1期33卷 103-113页

作者： A.h.Nikpour m.N.moghim m.A.Badri Department of Civil Engineering Isfahan University of Technology Research Institute for Subsea Science and Technology Isfahan University of Technology

A comprehensive experimental study was carried out on the regular wave attenuation with a trapezoidal pontoontype floating breakwater(FB) in deep water. The functionalities of two simple FB geometries consist of a rectangle and a trapezoid with the slope of 60° were investigated under the wave attack. A two-dimensional wave flume was used in the experiment; the incident, transmitted waves, mooring line forces and motion responses of the floating breakwaters were measured. Also the influence of the sea state conditions(incident wave height and wave period)and structural parameters(draught of the structure) were investigated using the trapezoidal FB. Our experimental results indicated that the trapezoidal FB significantly reduced the wave transmission and mooring line force when compared with rectangular FBs. A new formula was developed in order to predict the value of the transmission coefficient in trapezoidal FBs with the slope of 60°. Experimental data showed to be consistent with the results of the formula.

关键词： regular waves floating breakwater(FB) wave flume trapezoid mooring line force transmission

mechanism of fracture in macro- and micro-scales in hollow centre cracked disc specimen

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Journal of Central South University 2015年第11期22卷 4426-4433页

作者： m.Eftekhari A.Baghbanan h.hashemolhosseini h.Amrollahi Department of mining Engineering Isfahan University of Technology (IUT)

The hollow centre cracked disc(hCCD) specimen is one of the suggested alternative methods for determining the fracture toughness of rock. This work aims to investigate the fracture mechanism in hCCD in macro- and micro-scales using numerical methods, extended finite element method(X-FEm) and particle flow code(PFC) modeling, respectively. In the X-FEm, heaviside and near-tip enrichment functions are employed to consider the presence of the crack in the model. In PFC modeling the movement and interaction of stressed assemblies of rigid spherical particles are modeled using the distinct element method(DEm). A numerical code called mEX-FEm based on XFEm has been developed to simulate the problems involving crack. The models of pure modes I and Ⅱ in macro-scale are simulated in micro-scale. The results show that dimensionless stress intensity factors(YI, YⅡ) for pure modes I and Ⅱ increase by increasing the crack length ratio. The angle at which the pure mode Ⅱ occurs decreases by increasing the crack length ratio. In mixed mode I-Ⅱ, The value of YI decreases by increasing the crack angle, while the value of YⅡ increases to a given crack angle and then it decreases. moreover, the fracture in micro-scale, unlike the macro-scale, includes a combination of different modes of fracturing.

关键词： hollow centre cracked disc(hCCD) extended finite e

Numerical Analysis of mhD Accelerator with Non-Equilibrium Air Plasma

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Plasma Science and Technology 2012年第12期14卷 1110-1115页

作者： m.ANWARI h.h.QAZI SUKARSAN N.hARADA Electrical Engineering Department Umm Al-Qura University Faculty of Electrical Engineering Universiti Teknologi Malaysia Faculty of Electrical Engineering Universitas Islam "45" Bekasi Department of Electrical Engineering Nagaoka University of Technology

magnetohydrodynamic （mhD） accelerator is proposed as a next generation propulsion system. It can be used to increase the performance of a propulsion system. The objective of this study is to investigate the performance of mhD accelerator using non-equilibrium air plasma as working gas. In this study, the fundamental performance of mhD accelerator such as flow performance and electrical performance is evaluated at different levels of applied magnetic field using I-D numerical simulation. The numerical simulation is developed based on a set of differential equations with mhD approximation. To solve this set of differential equations the macCormack scheme is used. A specified channel designed and developed at NASA marshall Space Flight Centre is used in the numerical simulation. The composition of the simulated air plasma consists of seven species, namely, N2, N, O2, O, NO, NO＋, and e-. The performance of the non-equilibrium mhD accelerator is also compared with the equilibrium mhD accelerator.

关键词： mhD accelerator Faraday type connection non-equilibrium air plasma

Feasibility study of symmetric solution of molecular argon flow inside microscale nozzles

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Applied mathematics and mechanics(English Edition) 2018年第4期39卷 489-500页

作者： S.m.h.KARImIAN A.AmANI m.SEYEDNIA Department of Aerospace Engineering Amirkabir University of Technology Faculty of New Sciences and Technologies University of Tehran

The computational cost of numerical methods in microscopic-scales such as molecular dynamics(mD) is a deterrent factor that limits simulations with a large number of particles. hence, it is desirable to decrease the computational cost and run time of simulations, especially for problems with a symmetrical domain. however, in microscopic-scales, implementation of symmetric boundary conditions is not straightforward. Previously, the present authors have successfully used a symmetry boundary condition to solve molecular flows in constant-area channels. The results obtained with this approach agree well with the benchmark cases. Therefore, it has provided us with a sound ground to further explore feasibility of applying symmetric solutions of micro-fluid flows in other geometries such as variable-area ducts. molecular flows are solved for the whole domain with and without the symmetric boundary condition. Good agreement has been reached between the results of the symmetric solution and the whole domain solution. To investigate robustness of the proposed method, simulations are conducted for different values of affecting parameters including an external force, a flow density, and a domain length. The results indicate that the symmetric solution is also applicable to variable-area ducts such as micro-nozzles.

关键词： molecular dynamics(mD) symmetric boundary condition computational cost nozzle argon flow

Level-direction decomposition analysis with a focus on image watermarking framework

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Frontiers of Information Technology & Electronic Engineering 2016年第11期17卷 1199-1217页

作者： m.F.KAZEmI m.A.POURmINA A.h.mAZINAN Department of Electrical and Computer Engineering Science and Research Branch Islamic Azad University Department of Control Engineering Faculty of Electrical Engineering South Tehran Branch Islamic Azad University

This research addresses the new level-direction decomposition in the area of image watermarking as the further development of investigations. The main process of realizing a watermarking framework is to generate a watermarked image with a focus on contourlet embedding representation. The approach performance is evaluated through several indices including the peak signal-to-noise ratio and structural similarity, whereby a set of attacks are carried out using a module of simulated attacks. The obtained information is analyzed through a set of images, using different color models, to enable the calculation of normal correlation. The module of the inverse of contourlet embedding representation is correspondingly employed to obtain the present watermarked image, as long as a number of original images are applied to a scrambling module, to represent the information in disorder. This allows us to evaluate the performance of the proposed approach by analyzing a complicated system, where a decision making system is designed to find the best level and the corresponding direction regarding contourlet embedding representation. The results are illustrated in appropriate level-direction decomposition. The key contribution lies in using a new integration of a set of subsystems, employed based upon the novel mechanism in contourlet embedding representation, in association with the decision making system. The presented approach is efficient compared with state-of-the-art approaches, under a number of serious attacks. A number of benchmarks are obtained and considered along with the proposed framework outcomes. The results support our ideas.

关键词： Level-direction decomposition analysis Watermarking framework Contourlet embedding representation Scrambling module Simulated attacks

Exact solution for the unsteady flow of a semi-infinite micropolar fluid

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Acta mechanica Sinica 2011年第3期27卷 354-359页

作者： h.h. Sherief m.S. Faltas E.A. Ashmawy Department of mathematics Faculty of ScienceAlexandria University

The unsteady motion of an incompressible micropolar fluid filling a half-space bounded by a horizontal infinite plate that started to move suddenly is considered. Laplace transform techniques are used. The solution in the Laplace transform domain is obtained by using a direct approach. The inverse Laplace transforms are obtained in an exact manner using the complex inversion formula of the transform together with contour integration techniques. The solution in the case of classical viscous fluids is recovered as a special case of this work when the micropolarity coecient is assumed to be zero. Numerical computations are carried out and represented graphically.

关键词： Unsteady motion . Laplace transform . microp-olar fluid

Fundamental solutions for axi-symmetric translational motionof a microstretch fluid

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Acta mechanica Sinica 2012年第3期28卷 605-611页

作者： h.h.Sherief m.S.Faltas E.A.Ashmawy Department of mathematics Faculty of ScienceAlexandria University

The fundamental solution for the axi-symmetric translational motion of a microstretch fluid due to a concen- trated point body force is obtained. A general formula for the drag force exerted by the fluid on an axi-symmetric rigid par- ticle translating in it is then deduced. As an application to the obtained drag formula, this paper has discussed the problem of creeping translational motion of a rigid sphere in a mi- crostretch fluid. The slip boundary condition on the surface of the spherical particle is applied. The drag force and the other physical quantities are obtained and represented graph- ically for various values of the micropolarity and slip param- eters.

关键词： Drag force Fundamental solution mi-crostretch fluid Slip condition

A new image watermarking framework based on levels-directions decomposition in contourlet representation

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Journal of Central South University 2017年第3期24卷 521-532页

作者： m.F.Kazemi m.A.Pourmina A.h.mazinan Department of Electrical and Computer Engineering Science and Research BranchIslamic Azad University(IAU)TehranIran Department of Control Engineering Faculty of Electrical EngineeringSouth Tehran BranchIslamic Azad University(IAU)TehranIran

With the development of digital information technologies,robust watermarking framework is taken into real consideration as a challenging issue in the area of image processing,due to the large applicabilities and its utilities in a number of academic and real *** are a wide range of solutions to provide image watermarking frameworks,while each one of them is attempted to address an efficient and applicable *** reality,the traditional techniques do not have sufficient merit to realize an accurate *** to the fact that the main idea behind the approach is organized based on contourlet representation,the only state-of-the-art materials that are investigated along with an integration of the aforementioned contourlet representation in line with watermarking framework are concentrated to be able to propose the novel and skilled *** a word,the main process of the proposed robust watermarking framework is organized to deal with both new embedding and de-embedding processes in the area of contourlet transform to generate watermarked image and the corresponding extracted logo image with high *** fact,the motivation of the approach is that the suggested complexity can be of novelty,which consists of the contourlet representation,the embedding and the corresponding de-embedding modules and the performance monitoring including an analysis of the watermarked image as well as the extracted logo *** is also a scrambling module that is working in association with levels-directions decomposition in contourlet embedding mechanism,while a decision maker system is designed to deal with the appropriate number of sub-bands to be embedded in the presence of a series of simulated *** required performance is tangibly considered through an integration of the peak signal-to-noise ratio and the structural similarity indices that are related to watermarked *** the bit error rate and the normal correlation are considered that are

关键词： contourlet based watermarking framework levels-directions decomposition embedding process de-embedding process peak signal-to-noise ratio structural similarity indices normal correlation bit error rate

Barrier height and ideality factor dependency on identically produced small Au/p-Si Schottky barrier diodes

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Journal of Semiconductors 2010年第7期31卷 16-21页

作者： m.A.Yeganeh S.h.Rahmatollahpur Faculty of Physics Baku State UniversityAcademic Zahid X■lilov ksi-23AZ 1148BakuAzerbaijan Departments of Physics Sharif University of Technology11365-9567TehranIran

Small high-quality Au/P-Si Schottky barrier diodes（SBDs） with an extremely low reverse leakage current using wet lithography were *** effective barrier heights（Bhs） and ideality factors from current-voltage （Ⅰ-Ⅴ） characteristics were measured by a conducting probe atomic force microscope（C-AFm）.In spite of the identical preparation of the diodes there was a diode-to-diode variation in ideality factor and barrier height *** extrapolating the plots the built in potential of the Au /p-Si contact was obtained as V_（bi）=0.5425 V and the barrier height valueΦ_（b（c-V）） was calculated to beΦ_（B（C-V））=0.7145 V for Au/*** is found that for the diodes with diameters smaller than 100μm,the diode barrier height and ideality factor dependency to their diameters and correlation between the diode barrier height and its ideality factor are nonlinear,where similar to the earlier reported different metal semiconductor diodes in the literature,these parameters for the here manufactured diodes with diameters more than 100μm are also *** on the very obvious sub-nanometer C-AFm produced pictures the scientific evidence behind this controversy is also explained.

关键词： Schottky barrier diodes conducting probe-atomic force microscope barrier height and ideality factor