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Vibration and wave propagation analysis of twisted micro-beam using strain gradient theory

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Applied mathematics and mechanics(English Edition) 2016年第10期37卷 1375-1392页

作者： m.mOHAmmADImEHR m.j.FARAHI S.ALImIRZAEI Department of Solid mechanics Faculty of Mechanical Engineering University of Kashan

In this research, vibration and wave propagation analysis of a twisted micro- beam on Pasternak foundation is investigated. The strain-displacement relations （kine-matic equations） are calculated by the displacement fields of the twisted micro-beam. The strain gradient theory （SGT） is used to implement the size dependent effect at micro-scale. Finally, using an energy method and Hamilton＇s principle, the governing equations of motion for the twisted micro-beam are derived. Natural frequencies and the wave prop- agation speed of the twisted micro-beam are calculated with an analytical method. Also, the natural frequency, the phase speed, the cut-off frequency, and the wave number of the twisted micro-beam are obtained by considering three material length scale parameters, the rate of twist angle, the thickness, the length of twisted micro-beam, and the elastic medium. The results of this work indicate that the phase speed in a twisted micro-beam increases with an increase in the rate of twist angle. moreover, the wave number is in- versely related with the thickness of micro-beam. meanwhile, it is directly related to the wave propagation frequency. Increasing the rate of twist angle causes the increase in the natural frequency especially with higher thickness. The effect of the twist angle rate on the group velocity is observed at a lower wave propagation frequency.

关键词： vibration and wave propagation analysis twisted micro-beam strain gradient theory (SGT) rate of twist angle

Effects of Ni doping on the structural properties and collapse of magnetic ordering in NdFe_(1-x)Ni_xO_3(0.1 ≤x≤ 0.7) orthoferrites

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Chinese Physics B 2016年第2期25卷 496-503页

作者： I.Ahmad m.j.Akhtar m.Siddique Department of metallurgy and materials Engineering PIEAS Physics Division PINSTECH

Nd Fe_（1-x）Ni_xO_3（0.1 ≤ x ≤ 0.7） orthoferrites are synthesized by solid state reaction method, and the structural properties of these materials are investigated by employing x-ray diffraction（XRD）, scanning electron microscopy（SEm） and m o¨ssbauer spectroscopy. The orthorhombic structure is observed in all systems; however, with the increase in Ni doping,the increase in tolerance factor and the decrease in the cell volume are observed. Orthorhombic distortion decreases with Ni content increasing up to 50%, while above 50% Ni doping it increases. SEm examination indicates the increases in grain size and intermixing of grains with increase in Ni concentration. Comparison between bulk and theoretical densities shows that in each of all samples porosity is less than 2%. m？ssbauer spectroscopic investigations are performed to explain local structure, Fe oxidation states and collapse of the magnetic ordering. In these samples the Fe oxidation state remains＋3 and there is no considerable increase in hole states observed; however due to mismatch of the ionic radii between Fe^（3＋） and Ni^（3＋）, octahedral distortions, sagging and distribution of hyperfine parameters increase with increase in Ni concentration. The major factors behind the collapse of magnetic ordering in the Ni-doped systems are the weakening of the super-exchange interactions, decrease in the Neel temperature, increase in spin–spin relaxation frequency and high spin to low spin transition.

关键词： ceramic crystal structure electron microscopy mossbauer spectroscopy

Nonlinear Quantum Optical Springs and Their Nonclassical Properties

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Communications in Theoretical Physics 2011年第8期56卷 327-332页

作者： m.j.Faghihi m.K.Tavassoly Atomic and molecular Group Faculty of PhysicsYazd University

The original idea of quantum optical spring arises from the requirement of quantization of the frequency of oscillations in the Hamiltonian of harmonic oscillator. This purpose is achieved by considering a spring whose constant （and so its frequency） depends on the quantum states ofanother system. Recently, it is realized that by the assumption of frequency modulation of ω to ω √1＋ μα＋α the mentioned idea can be established. In the present paper, we generalize the approach of quantum optical spring with particular attention to the dependence or trequency to the intensity of radiation field that naturally observes in the nonlinear coherent states, from which we arrive at a physical system has been called by us as nonlinear quantum optical spring. Then, after the introduction of the generalized tlamiltonian of nonlinear quantum optical spring and it＇s solution, we will investigate the nonclassical properties of the obtained states. Specially, typical collapse and revival in the distribution functions and squeezing parameters, as particular quantum features, will be revealed.

关键词： nonlinear coherent states quantum optical spring nonclassical states

Parameters for Cold Collisions of Lithium and Caesium Atoms

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Chinese Physics Letters 2011年第6期28卷 56-58页

作者： jamieson m.j Ouerdane H School of Computing Science University of GlasgowGlasgow G128QQUK mediterranean Institute of Fundamental Physics Via Appia Nuova 3100040 MarinoRomeItaly CNRT matériaux UmS CNRS 3318 6 Boulevard Maréchal Juin14050 Caen CedexFrance

We calculate the s-wave scattering length and effective range and the p-wave scattering volume for 7Li atoms interacting with 133Cs atoms via the X1Σ+molecular *** length and volume are found by fitting the log-derivative of the zero energy wave function evaluated at short range to a long range expression that accounts for the leading van der Waals dispersion potential and then incorporating the remaining long range dispersion contributions to first *** effective range is evaluated from a quadrature *** calculated parameters are checked from the zero energy limits of the scattering phase *** comment on ill-conditioning in the calculated s-wave scattering length.

关键词： potential dispersion checked

Lattice Boltzmann method formulation for simulation of thermal radiation effects on non-Newtonian Al_(2)O_(3) free convection in entropy determination

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Applied mathematics and mechanics(English Edition) 2024年第6期45卷 1085-1106页

作者： m.NEmATI m.SEFID A.KARImIPOUR A.j.CHAmKHA Faculty of mechanical Engineering Yazd UniversityYazd ***Iran Department of mechanical Engineering Najafabad BranchIslamic Azad UniversityNajafabad ***Iran Faculty of Engineering Kuwait College of Science and TechnologyDoha 35004Kuwait

The simultaneous investigation on the parameters affecting the flow of electrically conductive fluids such as volumetric radiation,heat absorption,heat generation,and magnetic field(mF)is very vital due to its existence in various sectors of industry and *** present research focuses on mathematical modeling to simulate the cooling of a hot component through power-law(PL)nanofluid convection *** temperature reduction of the hot component inside a two-dimensional(2D)inclined chamber with two different cold wall shapes is *** formulation of the problem is derived with the lattice Boltzmann method(LBm)by code writing via the FORTRAN *** variables such as the radiation parameter(0–1),the Hartmann number(0–75),the heat absorption/generation coefficient(−5–5),the fluid behavioral index(0.8–1.2),the Rayleigh number(103–105),the imposed mF angle(0°–90°),the chamber inclination angle(−90°–90°),and the cavity cold wall shape(smooth and curved)are *** findings indicate that the presence of radiation increases the mean Nusselt number value for the shear-thickening,Newtonian,and shear thinning fluids by about 6.2%,4%,and 2%,*** most cases,the presence of nanoparticles improves the heat transfer(HT)rate,especially in the cases where thermal conduction dominates *** is the lowest cooling performance index and mF effect for the cavity placed at an angle of 90°.The application in the design of electronic coolers and solar collectors is one of the practical cases of this numerical research.

关键词： thermal performance analysis heat absorption/generation power-law(PL)Al_(2)O_(3)nanofluid magnetohydrodynamics natural convection volumetric radiation inclined cavity

Simulation and calibration of granules using the discrete element method

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Particuology 2014年第1期12卷 40-43页

作者： Peter müller jürgen Tomas Institute of Process Engineering Mechanical Process EngineeringOtto-von-Guericke University MagdeburgUniversitätsplatz 239106 MagdeburgGermany

The discrete element method （DEm）, developed by Cundall and 5track to solve geomecnamcai problems, is used to simulate the mechanical behavior of granules. According to the DEm, an individ ual granule can be modeled as a realistic mechanical system consisting of primary particles bonded by interaction forces. Cranulometric properties of the model material, zeolite 4A, have been measured to determine their macro properties. To investigate the compression behavior, a compression test was performed using a strength tester on single granules between two pistons. A modeled granule consisting of more than 22,000 primary particles was generated. The micro properties of the modeled granule have been precisely set to allow its macro properties to be equivalent to the macro properties of zeolite 4A granules. To calibrate the mechanical properties, diametrical compression was simulated using two rigid walls stressed at a constant stressing velocity, The force-displacement curve of the modeled granule at compression has been calibrated by the experimental curve of zeolite 4A.

关键词： Discrete element method material behavior Granulation

Sexual dimorphism in cranial shape and size in geomyoid rodents:multivariate and evolutionary perspectives

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Current Zoology 2022年第4期68卷 469-487页

作者： jonathan j m Calede Andrew Brown Department of Evolution Ecologyand Organismal BiologyThe Ohio State University318 W.12th Ave.300 Aronoff LaboratoryColumbusOH 43210USA The Ohio State University at marion 1459 Mount Vernon AvenueMarionOH 43302USA College of Veterinary medicine Texas A&M University660 Raymond Stotzer PkwyCollege StationTX 77843USA

Geomyoid rodents provide a great study system for the analysis of sexual *** are polygynic and many inhabit harsh arid environments thought to promote sexual *** fact,there has been extensive work published on the sexual size dimorphism of individual populations and species within this rodent ***,little work has been undertaken to assess the evolutionary patterns and processes associated with this sexual *** use multivariate analyses of cranial measurements in a phylogenetic framework to determine the distribution of size and shape dimorphism among geomyoids and test for Rensch’s *** results suggest that sexual dimorphism is more common in geomyids than heteromyids,but it is not in fact *** is evidence for variation in sexual dimorphism across ***,in many taxa,geographic variation appears to overwhelm existing sexual *** find support for the repeated independent evolution of shape and size dimorphism across geomyoid taxa,but we do not find support for an association between size and shape *** is no evidence for Rensch’s rule in geomyoids,whether at the superfamily or family ***,our findings suggest that there is no single explanation for the evolution of sexual dimorphism in geomyoids and that,instead,it is the product of numerous evolutionary *** studies incorporating phylogenetic relationships will be necessary to paint a more complete picture of the evolution of sexual dimorphism in geomyoids.

关键词： Geomyidae Heteromyidae phylogenetic comparative methods morphometrics Rensch’s rule

Symmetry and Transitive Properties of monohedral f-triangulations of the Riemannian Sphere

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Acta mathematica Sinica,English Series 2009年第10期25卷 1609-1616页

作者： Ana m.BREDA j.m.SIGARRETA Department of mathematics University of Aveiro Facultad de matematicas Universidad Autonoma de Guerrero

Here we give the complete description of the symmetry group and transitive properties of the set of all of monohedral triangulations of the Riemannian sphere by f-tilings. We shall also show that each monohedral f-tiling of the Riemannian sphere can be seen, up to a spherical isometry, as the singular set of a spherical isometric folding.

关键词： isometric folding monohedral tiling graphs combinatoric

Leader-following consensus control for networked multi-teleoperator systems with interval time-varying communication delays

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Chinese Physics B 2013年第7期22卷 96-103页

作者： m. j. Park S. m. Lee j. W. Son O. m. Kwon E. j. Cha School of Electrical Engineering Chungbuk National University School of Electronic Engineering Daegu University Division of IT-Convergence Daegu Gyeongbuk Institute of Science & Technology Department of Biomedical Engineering School of MedicineChungbuk National University

We study the leader-following consensus stability and stabilization of networked multi-teleoperator systems with interval time-varying communication delays. With the construction of a suitable Lyapunov–Krasovskii functional and the utilization of the reciprocally convex approach, novel delay-dependent consensus stability and stabilization conditions for the systems are established in terms of linear matrix inequalities, which can easily be solved by various effective optimization algorithms. One illustrative example is given to illustrate the effectiveness of the proposed methods.

关键词： multi-teleoperator systems interval time-varying delay leader–following consensus problem Lyapunov method