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Acta Mechanica Sinica 2019年第1期35卷 129-143,I0004页

作者： Milad Saadatmand alireza shooshtari Department of Electrical Engineering Technical University of DenmarkKgs.LyngbyDenmark Department of Mechanical Engineering Bu-Ali Sina UniversityHamedanIran

In this study, forced nonlinear vibration of a circular micro-plate under two-sided electrostatic, two-sided Casimir and external harmonic forces is investigated analytically. For this purpose, at first, von Karman plate theory including geometrical nonlinearity is used to obtain the deflection of the micro-plate. Galerkin decomposition method is then employed, and nonlinear ordinary differential equations (ODEs) of motion are determined. A harmonic balance method (HBM) is applied to equations and analytical relation for nonlineaT frequency response (F-R) curves are derived for two categories (including and neglecting Casimir force) separately. The analytical results for three cases:(1) semi-linear vibration;(2) weakly nonlinear vibration;(3) highly non linear vibration, are validated by comparing with the numerical solutio ns. After validation, the effects of the voltage and Casimir force on the natural frequency of two-sided capacitor system are investigated. It is shown that by assuming Casimir force in small gap distances, reduction of the natural frequency is considerable. The influences of the applied voltage, damping, micro-plate thickness and Casimir force on the frequency response curves have been presented too. The results of this study can be useful for modeling circular parallel-plates in nano /microelectromechanical transducers such as microphones and pressure sensors.

关键词： Nonlinear vibration Two-sided MEMS capacitor Circular plate Harmonic balance method

Joint slip investigation based on finite element modelling verified by experimental results on wind turbine lattice towers

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Frontiers of Structural and Civil Engineering 2018年第3期12卷 341-351页

作者： Saleh YAGHOOBI Ahmad shooshtari Civil Engineering Department Ferdowsi University of Mashhad Mashhad Iran

Slippage corresponds to the relative displacement of a bolted joint subjected to shear loads since the construction clearance between the bolt shank and the bolthole at assembly can cause joint slip. Deflections of towers with joint slippage effects is up to 1.9 times greater than the displacements obtained by linear analytical methods. In this study, 8 different types of joints are modelled and studied in the finite element program, and the results are verified by the experimental results which have been done in the laboratory. Moreover, several types of joints have been modelled and studied and load-deformation curves have also been presented. Finally, joint slip data for different types of angles, bolt diameter and bolt arrangements are generated. Thereupon, damping ratios （ζ） for different types of connections are reported. The study can be useful to help in designing of wind turbine towers with a higher level of accuracy and safety.

关键词： Joint slip cyclic loading Finite element modelling Experimental joint behavior damping ratios (ζ)

A new approach for correlating of H_(2)S solubility in[emim][Lac],[bmim][ac]and[emim][pro]ionic liquids using two-parts combined models

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Chinese Journal of Chemical Engineering 2022年第4期35卷 521-527页

作者： alireza Afsharpour Faculty of Chemical and Materials Engineering Shahrood University of TechnologyShahroodIran

Two bi-part combined models containing reaction equilibrium thermodynamic model and an equation of state(EoS)including cubic plus association(CPA)or modified Soave-Redlich-Kwong(SRK),were employed to correlate H_(2)S solubility in ionic liquids[emim][Lac],[bmim][Ac]and[emim][Pro].RETM and CPA/mSRK are responsible for chemical and phase equilibria calculations,*** RETM defines a complex formation reaction between an H_(2)S and two IL molecules into the liquid phase so that a complex in the form of H_(2)S(IL)_(2)is probable to *** the other side,CPA/mSRK EoSs perform phase equilibria computations to find pressure and vapor phase *** the case of CPA,both of H_(2)S and the ionic liquids were considered as self-associating components which pursue 4 C and 2 B schemes,*** model computes the pure IL parameters using experimental density *** this work,critical properties were estimated through the modified Lydersen-Joback-Reid method,Eotvos and Guggenheim ***,the binary systems were investigated by applying *** presents average absolute deviations(AADs)equal to 2.41%,13.42%and 3.52%for[emim][Lac],[bmim][Ac],and[emim][Pro],***,the AADs obtained by mSRK are 3.75%,5.07%,and 6.06%,*** it is evident from the results,the combination of RETM with both CPA and m SRK EoSs will result in good correlation accuracy.

关键词： Solubility Thermodynamics Ionic liquids CPA RETM mSRK

Progressive collapse resisting capacity of reinforced concrete load bearing wall structures

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Journal of Central South University 2015年第7期22卷 2730-2738页

作者： alireza Rahai alireza Shahin Farzad Hatami Department of Civil Engineering Amirkabir University of Technology (Tehran Polytechnic) No.424 Structural & Earthquake Research Center (SERC) Amirkabir University of Technology No.424

Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the "load factor" parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.

关键词： reinforced concrete(RC) load bearing wall structure progressive collapse fiber sections nonlinear analysis load factor method

A Numerical Approach for Multicomponent Vapor Solid Equilibrium Calculations in Gas Hydrate Formation

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Journal of Natural Gas Chemistry 2007年第1期16卷 16-21页

作者： alireza Bahadori Department of Petroleum Engineering National Iranian South Oil Co.AhwazP.O.Box 61735-1338Iran

A new numerical approach has been developed for vapor solid equilibrium calculations and for predicting vapor solid equilibrium constant and composition of vapor and solid phases in gas hydrate formation. Equation of state methods generally do a good job of determining vapor phase properties, but for solid phase it is much more difficult and inaccurate. This proposed new model calculates vapor solid equilibrium constant and vapor and solid phase composition as a function of temperature and partial pressure. The results of this proposed numerical approach, for vapor solid equilibrium, have a good agreement with the available reported data. This new numerical model also has an advantage to tune coefficients, to cover different sets of experimental data accurately.

关键词： numerical model vapor solid equilibrium hydrate multicomponent system

Effect of inlet temperature and equivalence ratio on HCCI engine performance fuelled with ethanol:Numerical investigation

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Journal of Central South University 2016年第1期23卷 122-129页

作者： alireza Rahbari Department of Mechanical Engineering Shahid Rajaee Teacher Training University (SRTTU)

A numerical model is presented to investigate the performance of homogeneous charge compression ignition(HCCI) engines fueled with ethanol. Two approaches are studied. On one hand, two-step reaction mechanisms with Arrhenius reaction rates are implemented in combustion chemistry modeling. On the other hand, a reduced mechanism containing important reactions of ethanol involving heat release rate and reaction rates compatible with experimental data is employed. Since controls of combustion phenomenon and ignition timing are the main issues of these engines, the effects of inlet temperature and equivalence ratio as the controlling factors on the operating parameters such as ignition timing, burn duration, in-cylinder temperature and pressure of HCCI engines are explored. The results show that the maximum predicted pressures for thermodynamic model are about 71.3×10~5 Pa and 79.79×10~5 Pa, and for chemical kinetic model, they are about 71.48×10~5 Pa and 78.123×10~5 Pa, fairly comparable with corresponding experimental values of 72×10~5 Pa and 78.7×10~5 Pa. It is observed that increasing the initial temperature advances the ignition timing, decreases the burn duration and increases the peak temperature and pressure. Moreover, the maximum temperature and pressure are associated with richer mixtures.

关键词： HCCI engine ethanol two-step reaction mechanism model chemical kinetic model

A new artificial bee swarm algorithm for optimization of proton exchange membrane fuel cell model parameters

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Journal of Zhejiang University-Science C(Computers and Electronics) 2011年第8期12卷 638-646页

作者： alireza ASKARZADEH alireza REZAZADEH Faculty of Electrical and Computer Engineering Shahid Beheshti University

An appropriate mathematical model can help researchers to simulate,evaluate,and control a proton exchange membrane fuel cell (PEMFC) stack *** a PEMFC is a nonlinear and strongly coupled system,many assumptions and approximations are considered during ***,some differences are found between model results and the real performance of *** increase the precision of the models so that they can describe better the actual performance,opti-mization of PEMFC model parameters is *** this paper,an artificial bee swarm optimization algorithm,called ABSO,is proposed for optimizing the parameters of a steady-state PEMFC stack model suitable for electrical engineering *** studying the usefulness of the proposed algorithm,ABSO-based results are compared with the results from a genetic algo-rithm (GA) and particle swarm optimization (PSO).The results show that the ABSO algorithm outperforms the other algorithms.

关键词： Proton exchange membrane fuel cell stack model Parameter optimization Artificial bee swarm optimization algorithm

Simultaneous effects of mesh refinement, grid configuration and wall boundary condition on prediction of pressure gradients and velocity profiles of microparticles in a conical fluidized bed

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Particuology 2019年第2期17卷 123-136页

作者： alireza Bahramian Department of Chemical Engineering Ha med an University of Technology P.O. Box 65155 Hamedan Iran

The reliability and accuracy of numerical results of microparticle fluidization in a conical bed, affected simultaneously by mesh refinement, the grid configuration and the wall boundary condition (BC), are analyzed. Specifically, pressure gradients and velocity profiles of titania powder are studied for a conical bed. The Gidaspow drag correlation and different wall BCs are considered using a Eulerian-Eulerian two-fluid model. Predictions of the pressure fluctuation, power spectra of the corresponding pressure fluctuations, bed pressure drop, minimum fluidizati on veloc ity, axial solid velocity, bed expansi on ratio, and particle size distribution are compared with experimental data. Mesh sensitivity analysis using hexahedral and tetrahedral cells with a un iform mesh and n ear-wall mesh refineme nr is con ducted to inv estigate the effects of mesh configurations in estimating particle flow patterns. Simulations show that significant savings in terms of computational time are realized by choosing a uniform mesh while the hexahedral structure, the near-wall mesh refinement, and the free-slip BC give the closest fit to the experimental data.

关键词： Conical fluidized bed Mesh configuration Grid refinement Velocity field Pressure gradie nt

Modeling of a Silicon Nanowire pH Sensor with Nanoscale Side Gate Voltage

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Chinese Physics Letters 2009年第6期26卷 73-76页

作者： alireza Kargar Department of Electrical and Computer Engineering Shiraz University Shiraz *** Iran

A silicon nanowire （Si-NW） sensor for pH detection is presented. The conductance of the device is analytically obtained, demonstrating that the conductance increases with decreasing oxide thickness. To calculate the electrical conductance of the sensor, the diffusion-drift model and nonlinear Poisson-Boltzmann equation are applied. To improve the conductance and sensitivity, a Si-NW sensor with nanoscaie side gate voltage is offered and its characteristics are theoretically achieved. It is revealed that the conductance and sensor sensitivity can be enhanced by adding appropriate side gate voltages. This effect is compared to a similar fabricated structure in the literature, which has a wire with a rectangular cross section. Finally, the effect of NW length on sensor performance is investigated and an inverse relation between sensor sensitivity and NW length is achieved.

关键词： gamma-ray bursts gamma-rays relativity

Numerical and experimental study of twin-fluid two-phase internal-mixing atomizer to develop maximum entropy method

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Chinese Journal of Aeronautics 2020年第9期33卷 2281-2294页

作者： alireza MOHAMMADI Fathollah OMMI Department of Mechanical Engineering.Tarbiat Modares University Tehran 14115-111Iran

This paper presents an analytical, numerical, and experimental study on atomization characteristics and droplet distribution of a twin-fluid two-phase internal mixing atomizer to develop a Maximum Entropy Method(MEM). A two-phase Eulerian-Lagrangian method is utilized for atomization modeling of the inside and outside atomizer. In order to modify energy and momentum sources in the MEM, parametric studies are performed, and experimental tests are carried out to verify the results by applying the shadowgraph method. An advanced test stand is developed to prepare a wide range of changes in atomization characteristics and mixing ratios. A high degree of consistency is found between numerical results from the developed MEM and experimental tests with different gas-phase pressures and liquid flow rates. The droplet diameter and velocity distribution are reviewed based on various Weber numbers, sources of energy, and momentum. Turbulence modeling assists to estimate the breakup length and time scale precisely in the developed MEM, and distribution ranges with mean values are achieved. With reference to a strong correlation between upstream turbulence flow and the developed MEM verified by experimental tests, an ideal droplet size and velocity distribution prediction is observed.

关键词： Atomization Droplet distribution Internal-mixing atomizer Maximum entropy method Shadowgraph technique Test stand