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Applied mathematics and mechanics(English Edition) 2025年第1期46卷 101-122页

作者： m.GHOLAmI m.eftekhari Department of mechanical Engineering Shahid Bahonar University of Kerman

This study examines the nonlinear behaviors of a clamped-clamped porous pipe made of a functionally graded material(FGm) that conveys fluids and is equipped with a retaining clip, focusing on primary resonance and subcritical dynamics. The nonlinear governing equations for the FGm pipe are derived by the extended Hamilton's principle, and subsequently discretized through the application of the Galerkin *** direct method of multi-scales is then used to solve the derived equations. A thorough analysis of various parameters, including the clip stiffness, the power-law index, the porosity, and the clip location, is conducted to gain a comprehensive understanding of the system's nonlinear dynamics. Through the analysis of the first natural frequency, the study highlights the influence of the flow velocity and the clip stiffness, while the comparisons with metallic pipes emphasize the role of FGm composition. The examination of the forced response curves reveals saddle-node bifurcations and their dependence on parameters such as the detuning parameter and the power-law index, offering valuable insights into the system's nonlinear resonant behavior. Furthermore, the frequency-response curves illustrate the hardening nonlinearities influenced by factors such as the porosity and the clip stiffness, revealing nuanced effects on the system response and resonance characteristics. This comprehensive analysis enhances the understanding of nonlinear behaviors in FGm porous pipes with a retaining clip, providing key insights for practical engineering applications in system design and optimization.

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magnetic field effects on the nonlinear vibration of a rotor

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Applied mathematics and mechanics(English Edition) 2020年第2期41卷 289-312页

作者： m.eftekhari A.DASHTI-RAHmATABADI A.mAZIDI Department of mechanical Engineering Yazd UniversityYazd 89195-741Iran

The nonlinear vibration of a rotor operated in a magnetic field with geometric and inertia nonlinearity is investigated. An asymmetric magnetic flux density is generated,resulting in the production of a load on the rotor since the air-gap distribution between the rotor and the stator is not uniform. This electromagnetic load is a nonlinear function of the distance between the geometric centers of the rotor and the stator. The nonlinear equation of motion is obtained by the inclusion of the nonlinearity in the inertia, the curvature, and the electromagnetic load. After discretization of the governing partial differential equations by the Galerkin method, the multiple-scale perturbation method is used to derive the approximate solutions to the equations. In the numerical results, the effects of the electromagnetic parameter load, the damping coefficient, the amplitude of the initial displacement, the mass moment of inertia, and the rotation speed on the linear and nonlinear backward and forward frequencies are investigated. The results show that the magnetic field has significant effects on the nonlinear frequency of oscillation.

关键词： nonlinear vibration in-extensional rotor nonlinear curvature gyroscopic effect magnetic field

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

Techno-economic review on storage of petroleum products in abandoned underground salt mines:A case study on underground salt mines of Sardareh region,Garmsar,Iran

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International Journal of mining Science and Technology 2013年第6期23卷 931-936页

作者： H.mohammadi m.Noroozi m.eftekhari Department of mining Engineering Shahrood BranchIslamic Azad University Faculty of mining Engineering.Petroleum and Geophysics Shahrood University of Technology Department of mining Engineering.South Tehran Branch Islamic Azad University

During the past few decades,along with creation of new needs,large spaces of underground mines(especially abandoned mines)have found new applications,e.g.,storage of petroleum *** of empty spaces of these mines as hydrocarbons storage facilities decreases the costs of construction of underground spaces,which can be very expensive and *** the other hand,crude oil and other hydrocarbons nowadays are one of the most important factors affecting political and a major part of the domestic economy is achieved through ***,in this paper,a feasibility study has been performed on the application of underground salt mines near the city of Garmsar on the southern edge of Alborz mountains and on the north of the central desert of *** studies of documentaries,field observations and considering technical,geometrical and defensive criterion,the most suitable abandoned underground mine for reutilization as a storage facility is selected and presented.

关键词： Abandoned mines Salt Storage Hydrocarbons Garmsar

mechanism Based Pharmacokinetic Pharmacodynamic modeling of Vildagliptin as an Add-on to metformin for Subjects with Type 2 Diabetes

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Computer modeling in Engineering & Sciences 2018年第2期114卷 153-171页

作者： marziyeh eftekhari Omid Vahidi School of Chemical Petroleum and Gas EngineeringIran University of Science and TechnologyNarmakTehranIran

Various drugs are used to maintain normoglycemia in subjects with type 2 diabetes *** combination of the drugs from different classes in one single tablet may enhance the effectiveness of the anti-diabetic *** investigate the impact of combining drugs on the glucose regulation of subjects with type 2 diabetes,we propose a pharmacokinetic/pharmacodynamics(PK/PD)mathematical modeling approach for a combination of metformin and vildagliptin *** the proposed modeling approach,two separate PK models representing oral administration of metformin and vildagliptin for diabetic subjects are interconnected to a PD model comprising a detailed compartmental physiological model representing the regulatory effect of insulin,incretins and glucagon hormones on glucose concentration in a human *** impact of doses of individual drugs and their combination on the blood glucose concentration of a group of type 2 diabetic subjects is *** is indicated that while administration of individual drugs reduces the blood glucose levels,since they have separate mechanisms of action,combining them synergizes lowering the blood glucose levels.

关键词： Pharmacokinetics pharmacodynamics mathematical modeling anti-diabetic drugs metformin vildagliptin

Prediction of mode I fracture toughness of rock using linear multiple regression and gene expression programming

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Journal of Rock mechanics and Geotechnical Engineering 2022年第5期14卷 1421-1432页

作者： Bijan Afrasiabian mosleh eftekhari Department of mining Engineering Science and Research BranchIslamic Azad UniversityTehranIran Department of mining Engineering Faculty of EngineeringTarbiat Modares UniversityTehranIran

Prediction of mode I fracture toughness(KIC) of rock is of significant importance in rock engineering analyses. In this study, linear multiple regression(LmR) and gene expression programming(GEP)methods were used to provide a reliable relationship to determine mode I fracture toughness of rock. The presented model was developed based on 60 datasets taken from the previous literature. To predict fracture parameters, three mechanical parameters of rock mass including uniaxial compressive strength(UCS), Brazilian tensile strength(BTS), and elastic modulus(E) have been selected as the input parameters. A cluster of data was collected and divided into two random groups of training and testing ***, different statistical linear and artificial intelligence based nonlinear analyses were conducted on the training data to provide a reliable prediction model of KIC. These two predictive methods were then evaluated based on the testing data. To evaluate the efficiency of the proposed models for predicting the mode I fracture toughness of rock, various statistical indices including coefficient of determination(R2),root mean square error(RmSE), and mean absolute error(mAE) were utilized herein. In the case of testing datasets, the values of R2, RmSE, and mAE for the GEP model were 0.87, 0.188, and 0.156,respectively, while they were 0.74, 0.473, and 0.223, respectively, for the LmR model. The results indicated that the selected GEP model delivered superior performance with a higher R2value and lower errors.

关键词： mode I fracture Toughness Critical stress intensity factor Linear multiple regression(LmR) Gene expression programming(GEP)

Quantum Correlations in Ising-XYZ Diamond Chain Structure under an External magnetic Field

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Chinese Physics Letters 2015年第10期32卷 9-13页

作者： Faizi E. eftekhari H. Department of Physics Azerbaijan Shahid Madani University

We consider an entangled Ising-XY Z diamond chain structure. Quantum correlations for this model are inves- tigated by using quantum discord and trace distance discord. Quantum correlations are obtained for different values of the anisotropy parameter, magnetic field and temperature. By comparison between quantum correlations, we show that the trace distance discord is always larger than quantum discord. Finally, some novel effects such as increasing the quantum correlations with temperature and constructive role of anisotropy parameter, which may play to the quantum correlations, are observed.

关键词： TDD Quantum Correlations in Ising-XYZ Diamond Chain Structure under an External magnetic Field

mixed finite element and differential quadrature method for free and forced vibration and buckling analysis of rectangular plates

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Applied mathematics and mechanics(English Edition) 2012年第1期33卷 81-98页

作者： S. A. eftekhari A. A. JAFARI Department of mechanical Engineering K. N. Toosi University of Technology

This paper presents a combined application of the finite element method （FEm） and the differential quadrature method （DQm） to vibration and buckling problems of rectangular plates. The proposed scheme combines the geometry flexibility of the FEm and the high accuracy and efficiency of the DQm. The accuracy of the present method is demonstrated by comparing the obtained results with those available in the literature. It is shown that highly accurate results can be obtained by using a small number of finite elements and DQm sample points. The proposed method is suitable for the problems considered due to its simplicity and potential for further development.

关键词： finite element method (FEm) differential quadrature method (DQm) rectangular plate free and forced vibration buckling analysis

Texture evolution and mechanical anisotropy of an ultrafine/nano-grained pure copper tube processed via hydrostatic tube cyclic expansion extrusion

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International Journal of minerals,metallurgy and materials 2022年第12期29卷 2241-2251页

作者： Seyed moien Faregh Ghader Faraji mahmoud mosavi mashhadi mohammad eftekhari School of mechanical Engineering College of EngineeringUniversity of TehranTehran 11155-4563Iran

Texture evolution and mechanical anisotropic behavior of an ultrafine-grained(UFG)pure copper tube processed by recently introduced method of hydrostatic tube cyclic expansion extrusion(HTCEE)was *** the UFG tube,different deformation behavior and a significant anisotropy in tensile properties were recorded along the longitudinal and peripheral *** HTCEE process increased the yield strength and the ultimate strength in the axial direction by 3.6 and 1.67 times,***,this process increased the yield strength and the ultimate strength in the peripheral direction by 1.15 and 1.12 times,*** ratio of ultimate tensile strength in the peripheral direction to that in the axial direction,as a criterion for mechanical anisotropy,are 1.7 and 1.16 for the as-annealed coarse-grained and the HTCEE processed UFG tube,*** results are indicative of a reducing effect of the HTCEE process on the mechanical ***,after HTCEE process,a low loss of ductility was observed in both directions,which is another advantage of HTCEE *** measurements revealed a slight increment of hardness values in the peripheral direction,which is in agreement with the trend of tensile *** analysis was conducted in order to determine the oriental distribution of the *** obtained{111}pole figures demonstrate the texture evolution and reaffirm the anisotropy observed in mechanical *** electron microscopy micrographs showed that different modes of fracture occurred after tensile testing in the two orthogonal directions.

关键词： severe plastic deformation ultrafine grained hydrostatic tube cyclic expansion extrusion anisotropy texture

Tiwari-Das nanofluid model for magnetohydrodynamics(mHD)natural-convective flow of a nanofluid adjacent to a spinning down-pointing vertical cone

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Propulsion and Power Research 2018年第1期7卷 78-90页

作者： mohammad Aghamajidi mohammad eftekhari Yazdi Saeed Dinarvand Ioan Pop mechanical Engineering Department Islamic Azad UniversityCentral Tehran BranchTehranIran Department of Applied mathematics Babeş-Bolyai UniversityCluj-Napoca 400084Romania

In this article,the natural-convective flow of an electrically conducting nanofluid adjacent to a spinning down-pointing vertical cone in the presence of transverse magnetic field is *** mathematical model has been formulated based on Tiwari-Das nanofluid *** different types of water-based nanofluid with copper,aluminum oxide(alumina)and titanium dioxide(titania)as nanoparticles are considered in this *** cases of heat transfer analysis are *** are:(i)the spinning cone with prescribed surface temperature and(ii)the spinning cone with prescribed surface heat *** appropriate transformations,the system of partial differential equations is transformed into an ordinary differential system of three equations,which is solved numerically using the fourth-order Runge-Kutta method with shooting *** current solution demonstrates very good agreement with those of the previously published studies in the especial *** effects of the three key thermophysical parameters governing the flow;the nanoparticle volume fraction,the magnetic parameter and the spin parameter on dimensionless velocity and temperature distributions,skin friction coefficient,Nusselt number and entropy generation number are presented graphically and discussed in *** results demonstrate that,the enhancement of heat transfer is a function of particle concentration,small fraction of metallic particles leading to significant changes in all three quantities of skin friction coefficient,local Nusselt number and entropy generation *** results illustrate that selecting alumina and copper as the nanoparticle leads to the minimum and maximum amounts of skin friction coefficient value,and also copper and titania nanoparticles have the largest and lowest local Nusselt ***,it is observed that the magnetic parameter has a decreasing effect on both skin friction coefficient and local Nusselt number and an increasing effect on entropy ge

关键词： Natural-convective flow Spinning verticalcone Nanofluids Entropy generation Tiwari-Das nanofluid model magnetohy drodynamics(mHD)