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Dynamic stress concentration in an infinitely long cylindrical cavity due to a point spherical source embedded within a fluid-saturated poroelastic formation of infinite extent

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Applied Mathematics and Mechanics(English Edition) 2025年第1期46卷 139-156页

作者： h.hosseini O.BALILAShAKI Department of Mechanical Engineering Faculty of EngineeringGolestan University

The effects of a harmonically exciting monopole source on an infinitely long cylindrical cavity embedded entirely within a fluid-saturated poroelastic formation of infinite extent are examined theoretically. It is assumed that the source is located outside the cavity at a specified distance from the borehole axis. The magnitudes of the hoop and radial stresses beside the pore pressures exerted on the interface and inside the porous medium surrounding the borehole are calculated and discussed. Biot's poroelastic modeling along with three types of boundary conditions for the cylindrical interface including the ideal fluid, empty borehole, and rigid inclusion with a hard boundary is employed for the analysis. Utilizing a proper translational addition theorem for expressing the incident spherical wave in terms of cylindrical wave expansions, the proposed boundary conditions at the interface are satisfied. Stresses are formulated by means of wave potential functions in a three-dimensional(3D) manner. The effects of the frequency and the radial distance between the source and borehole on the induced stresses are examined for the first cylindrical modes over frequency spectra. Two permeability conditions for the interface and three types of soils for the porous formation are considered throughout the analysis. To give an overall outline of the study, a numerical example is presented. The results clearly indicate that the distance is a key parameter and has considerable effects on the induced stress values. In addition, the interface permeability condition and soil characteristics play an important role in determining the dynamic response of the borehole. Finally,the obtained results are compared with the relevant analyses existing in the literature for some limit cases, and good agreement is achieved.

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Nonlinear beam formulation incorporating surface energy and size effect:application in nano-bridges

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Applied Mathematics and Mechanics(English Edition) 2016年第5期37卷 583-600页

作者： A.KOOChI h.hosseini-TOUDEShKY M.ABADYAN Department of Aerospace Engineering Amirkabir University of TechnologyTehran 15875-4413Iran Mechanical Engineering Group Shahrekord BranchIslamic Azad UniversityShahrekord ***Iran

A nonlinear beam formulation is presented based on the Gurtin-Murdoch surface elasticity and the modified couple stress theory. The developed model theoretically takes into account coupled effects of the energy of surface layer and microstructures size- dependency. The mid-plane stretching of a beam is incorporated using von-Karman nonlinear strains. hamilton＇s principle is used to determine the nonlinear governing equation of motion and the corresponding boundary conditions. As a case study, pull-in instability of an electromechanical nano-bridge structure is studied using the proposed formulation. The nonlinear governing equation is solved by the analytical reduced order method （ROM） as well as the numerical solution. Effects of various parameters including surface layer, size dependency, dispersion forces, and structural damping on the pull- in parameters of the nano-bridges are discussed. Comparison of the results with the literature reveals capability of the present model in demonstrating the impact of nano- scale phenomena on the pull-in threshold of the nano-bridges.

关键词： surface energy size effect nonlinear beam formulation electromechanicalnano-bridge pull-in instability

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Gamma ray and neutron shielding capacity of and dosimetry of composite compounds with diagnostic and therapeutic energies

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Radiation Detection Technology and Methods 2024年第2期8卷 1217-1228页

作者： h.hosseini Sarteshnizi M.Eshghi Department of Physics Imam Hossein Comprehensive UniversityTehranIran

Purpose Ionizing radiation protection is one of the most fundamental research and application fields in reducing the absorbed dose of sensitive internal *** presence of lead as the first radiation shield with a series of good features,such as high density and having some flexibility,and a series of features such as toxicity,low physical and chemical stability and high weight has been thinking about replacing it for a long ***,in this research,we have investigated features of the ionizing radiation shielding of composite compounds without lead in the photon energy range of 15 keV to 15 *** To extract such features,it is necessary to use a computational *** this research,we have done all our calculations based on the Geant4 tool based on the Monte Carlo *** tool is a multi-purpose tool that can be used for particle transport calculations such as electrons,protons,neutrons,heavy charged particles and photons in different environments such as human *** We have calculated mass attenuation coefficient(MAC)by using the Monte Carlo simulations such as Geant4 tool,XMuDat and XCOM *** the continuation of the investigation of the protection feature,four laboratory energies have been selected and *** fact,the performance of shields against 60 keV,662 keV and 1.2 MeV sources has been *** this case,we have obtained the passing flux of photons,half-value layer(hVL),tenth-value layer(TVL)and mean free path(MFP).Then,the image of the passing photon flux of 241 Am(60 keV),^(137)Cs(662 keV)and^(60)Co(1.2 MeV)sources for a shielding sample is *** the aim is to examine the overall protection characteristics of the samples,we have considered the source as a neutron-gamma mixture and made of *** this case,the passing fux of photons and the ratio of neutrons passing through the shields are *** the continuation of the work,MIRD phantom has been used to check the performance of the shields in

关键词： Shielding Medical shielding Geant4 Gamma ray Radiation Dosimetry

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An Investigation on New Nonbuckling Composite Structures

An Investigation on New Nonbuckling Composite Structures

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第十三届国际复合材料会议

作者： h.hosseini-Toudeshky M.Sadeghi Aerospace Eng. Dept. Amir-Kabir University of Technology Tehran Iran h.F.Dorna Aerospace Co

＜正＞Since wing ribs and fuselage frames compose a considerable parts of the aircraft weight, it is important to make them as safety permits and be efficient relative to the cost of fabrication and assembly. In the composite flight vehicle structures, wing ribs, spar webs and fuselage frames subjected to compressive loads are usually made by sandwiched structures, e.g. Aluminum or Nomex honeycomb and P.V.C foam core. In this paper, new techniques based on the techniques already used for metallic components are studied. Three types of shear resistant, nonbuckling webs are frequently used in the metallic web design namely: a) Web with formed vertical

关键词： nonbuckllng composite structure web with beads finite element analyses

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Effect of temperature on pull-in voltage and nonlinear vibration behavior of nanoplate-based NEMS under hydrostatic and electrostatic actuations

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Acta Mechanica Solida Sinica 2017年第2期30卷 174-189页

作者： Farzad Ebrahimi S.h.S.hosseini Department of Mechanical Engineering Faculty of Engineering Imam Khomeini International University qazvinIran

This paper deals with the study of the temperature effect on the nonlinear vibration behavior of nanoplate-based nano electromechanical systems（NEMS） subjected to hydrostatic and electrostatic actuations. Using Eringen＇s nonlocal elasticity and Gurtin–Murdoch theory, the nonlocal plate model is derived through hamilton＇s principle. The governing equation which is extremely nonlinear due to the geometrical nonlinearity and electrostatic attraction forces is solved numerically using the differential quadrature method（DQM）. The accuracy of the present method is veriied by comparing the obtained results with the experimental data and those in the literature and very good agreement is obtained. Finally a comprehensive study is carried out to determine the inluence of temperature on the nonlinear vibration characteristics of NEMS made of two different materials including aluminum（Al）and silicon（Si） and some conclusions are drawn.

关键词： Small scale effect Nano electromechanical system Nonlinear vibration Temperature effect Pull-in voltage

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Effect of Gaussian size distribution width on minimum fluidization velocity in tapered gas–solid fluidized beds

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Particuology 2022年第7期20卷 71-84页

作者： Mojtaba Rasteh Goodarz Ahmadi S.h.hosseini Department of Chemical Engineering Hamedan University of TechnologyHamedanP.O.Box 65155-579Iran Department of Mechanical and Aeronautical Engineering Clarkson UniversityPotsdamNY 13699-5725USA Department of Chemical Engineering Ilam UniversityIlam 69315-516Iran

This paper investigated the effect of Gaussian distribution width,average particle diameter,particle loading,and the tapered angle on minimum fluidization velocity(U_(mf))by conducting extensive experiments in tapered fluidized *** powders with Gaussian size distribution and different distribution widths were used in the *** increase in U_(mf)with increasing the average particle diameter,particle loading,and the tapered angle was *** was also a nonmonotonic behavior of Umf as the Gaussian distribution width *** empirical correlation including dimensionless groups for predicting Umf in tapered beds was developed in which the effect of distribution width was *** proposed correlation predictions were in good agreement with the experimental data,with a maximum deviation of 16.5%and average and standard deviations of,respectively,6.4%and 7.4%.The proposed correlation was also compared with three earlier models,and their accuracy was discussed.

关键词： Tapered fluidized bed Minimum fluidization velocity Gaussian size distribution Distribution width Dimensional analysis

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Theoretical approaches to alpha decay half-lives of super-heavy nuclei

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Chinese Physics C 2017年第6期41卷 69-74页

作者： S. S. hosseini h. hassanabadi Physics Department Shahrood University of Technology Shahrood Iran

We consider the systematics of α-decay half-lives of super-heavy nuclei versus the decay energy and the total α-kinetic energy. We calculate the half-lives using the experimental Qα values. The computed half-lives are compared with the experimental data and with existing empirical estimates and are found to be in good agreement. Also, we obtain α-preformation factors from the ratio between theoretical and experimental results for some super- heavy nuclei and evaluate the standard deviation. The results indicate the acceptability of the approach.

关键词： alpha decay super heavy nuclei (ShN) half-life preformation factor

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CFD-DEM simulation of a pseudo-two-dimensional spouted bed comprising coarse particles

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Particuology 2019年第2期17卷 171-180页

作者： B. Mahmoodi S.h. hosseini G. Ahmadi llam Gas Treating Company llam Iran Department of Chemical Engineering llam University llam 69315-516 Iran Department of Mechanical and Aeronautical Engineering Clarkson University Potsdam NY 13699-5725 USA

In the present study, computational fluid dynamics (CFD) and the discrete element method (DEM) are used in conjunction with the Eulerian-Lagrangian method to simulate a pseudo-two-dimensional spouted bed comprising coarse 6-mm particles. The open-source OpenFOAM code is used to solve the governing equations. The predicted vertical particle velocity along the bed axis, particle velocity profiles in the radial directi on, power spectral den sity, time-averaged particle velocity vectors, bed pressure drop, and solid flow pattern are evaluated and compared with existing experimental data. Good agreement is found between the CFD-DEM results and the measured data. It is also shown that the present CFD-DEM model accurately predicts the particle flow pattern throughout the bed. It is found that the drag force, solid stresses, and gravity play important roles in the CFD-DEM simulation of a spouted bed comprising coarse particles.

关键词： CFD-DEM Pseudo-2D spouted bed hydrodynamics Coarse particles

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Reproducing fling-step and forward directivity at near source site using of multi-objective particle swarm optimization and multi taper

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Earthquake Engineering and Engineering Vibration 2013年第4期12卷 529-540页

作者： A.Nicknam A.hosseini h.hamidi Jamnani M.A.Barkhordari School of Civil Engineering Iran University of Science & Technology

This paper presents a technique to reproduce compatible seismogran3s involving permanent displacen3ent effects at sites close to the fault source. A multi-objective evolutionary algorithm is used to minimize the differences between the response spectra and multi-tapered power spectral delsilies corresponding to the recorded and simulated wavelbrms. The multi-taper method is used to reduce the spectral leakage that is inherent in the Fourier rams formed form ofwavelbrms, ieading to a reduction of variance in power spectral amplitudes, thus permitting the calibration of the two sets of data. The technique is implemented using the 1998-Fandoqa （lran） earthquake data and the results are compared with the actual observed data. Additionally, a comparison is made with a SAR interfcrometry study leading to fair agreement with the reported dislocation along the main fault. The simulation procedure and results are discussed and assessed concluding that, although the technique may be associated with uncertainties, it can still be used to reproduce wavelbnns at near source sites that include permanent dislocation, and can be used for seismic pertbrmance evaluation of structures in the region under study.

关键词： near-fault simulation fling step directivity multi-taper multi-objective algorithm MO-PSO

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Surface and thermal effects on vibration of embedded alumina nanobeams based on novel Timoshenko beam model

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Applied Mathematics and Mechanics(English Edition) 2014年第7期35卷 875-886页

作者： B.AMIRIAN R.hosseini-ARA h.MOOSAVI Department of Mechanical Engineering Isfahan University of TechnologyIsfahan 84156-83111 Iran Department of Mechanical Engineering Payame Noor University Tehran 19395-3697 Iran

This paper deals with the free vibration analysis of circular alumina （Al2O3） nanobeams in the presence of surface and thermal effects resting on a Pasternak foun- dation. The system of motion equations is derived using hamilton＇s principle under the assumptions of the classical Timoshenko beam theory. The effects of the transverse shear deformation and rotary inertia are also considered within the framework of the mentioned theory. The separation of variables approach is employed to discretize the governing equa- tions which are then solved by an analytical method to obtain the natural frequencies of the alumina nanobeams. The results show that the surface effects lead to an increase in the natural frequency of nanobeams as compared with the classical Timoshenko beam model. In addition, for nanobeams with large diameters, the surface effects may increase the natural frequencies by increasing the thermal effects. Moreover, with regard to the Pasternak elastic foundation, the natural frequencies are increased slightly. The results of the present model are compared with the literature, showing that the present model can capture correctly the surface effects in thermal vibration of nanobeams.

关键词： surface effect thermal environment alumina nanobeam Pasternak foun-dation Timoshenko beam model

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