Characterizing the nature of the rigidity transition

Rahbari, S. H. E.,Vollmer, J.,Park, Hyunggyu American Physical Society 2018 Physical review. E Vol.98 No.5

Structural identification of Humber Bridge for performance prognosis

Rahbari, R.,Niu, J.,Brownjohn, J.M.W.,Koo, K.Y. Techno-Press 2015 Smart Structures and Systems, An International Jou Vol.15 No.3

Structural identification or St-Id is 'the parametric correlation of structural response characteristics predicted by a mathematical model with analogous characteristics derived from experimental measurements'. This paper describes a St-Id exercise on Humber Bridge that adopted a novel two-stage approach to first calibrate and then validate a mathematical model. This model was then used to predict effects of wind and temperature loads on global static deformation that would be practically impossible to observe. The first stage of the process was an ambient vibration survey in 2008 that used operational modal analysis to estimate a set of modes classified as vertical, torsional or lateral. In the more recent second stage a finite element model (FEM) was developed with an appropriate level of refinement to provide a corresponding set of modal properties. A series of manual adjustments to modal parameters such as cable tension and bearing stiffness resulted in a FEM that produced excellent correspondence for vertical and torsional modes, along with correspondence for the lower frequency lateral modes. In the third stage traffic, wind and temperature data along with deformation measurements from a sparse structural health monitoring system installed in 2011 were compared with equivalent predictions from the partially validated FEM. The match of static response between FEM and SHM data proved good enough for the FEM to be used to predict the un-measurable global deformed shape of the bridge due to vehicle and temperature effects but the FEM had limited capability to reproduce static effects of wind. In addition the FEM was used to show internal forces due to a heavy vehicle to to estimate the worst-case bearing movements under extreme combinations of wind, traffic and temperature loads. The paper shows that in this case, but with limitations, such a two-stage FEM calibration/validation process can be an effective tool for performance prognosis.

A two-dimensional analytical model of laminar flame in lycopodium dust particles

Alireza Rahbari,Ashkan Shakibi,Mehdi Bidabadi 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.9

A two-dimensional analytical model is presented to determine the flame speed and temperature distribution of micro-sized lycopodium dust particles. This model is based on the assumptions that the particle burning rate in the flame front is controlled by the process of oxygen diffusion and the flame structure consists of preheat, reaction and post flame zones. In the first step, the energy conservation equations for fuel-lean condition are expressed in twodimensions, and then these differential equations are solved using the required boundary condition and matching the temperature and heat flux at the interfacial boundaries. Consequently, the obtained flame temperature and flame speed distributions in terms of different particle diameters and equivalence ratio for lean mixture are compared with the corresponding experimental data for lycopodium dust particles. Consequently, it is shown that this two-dimensional model demonstrates better agreement with the experimental results compared to the previous models.

Status of Haemaphysalis tick infestation in domestic ruminants in Iran

Sadegh RAHBARI,Sedigheh NABIAN,Parviz SHAYAN,Hamid Reza HADDADZADEH 대한기생충학열대의학회 2007 The Korean Journal of Parasitology Vol.45 No.2

Structural identification of Humber Bridge for performance prognosis

R. Rahbari,J. Niu,J.M.W. Brownjohn,K.Y. Koo 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.15 No.3

Structural identification or St-Id is ‘the parametric correlation of structural responsecharacteristics predicted by a mathematical model with analogous characteristics derived from experimentalmeasurements’. This paper describes a St-Id exercise on Humber Bridge that adopted a novel two-stageapproach to first calibrate and then validate a mathematical model. This model was then used to predicteffects of wind and temperature loads on global static deformation that would be practically impossible toobserve. The first stage of the process was an ambient vibration survey in 2008 that used operational modalanalysis to estimate a set of modes classified as vertical, torsional or lateral. In the more recent second stagea finite element model (FEM) was developed with an appropriate level of refinement to provide acorresponding set of modal properties. A series of manual adjustments to modal parameters such as cabletension and bearing stiffness resulted in a FEM that produced excellent correspondence for vertical andtorsional modes, along with correspondence for the lower frequency lateral modes. In the third stage traffic,wind and temperature data along with deformation measurements from a sparse structural health monitoringsystem installed in 2011 were compared with equivalent predictions from the partially validated FEM. Thematch of static response between FEM and SHM data proved good enough for the FEM to be used topredict the un-measurable global deformed shape of the bridge due to vehicle and temperature effects but theFEM had limited capability to reproduce static effects of wind. In addition the FEM was used to showinternal forces due to a heavy vehicle to to estimate the worst-case bearing movements under extremecombinations of wind, traffic and temperature loads. The paper shows that in this case, but with limitations,such a two-stage FEM calibration/validation process can be an effective tool for performance prognosis.

IgG Avidity ELISA Test for Diagnosis of Acute Toxoplasmosis in Humans

Amir Hossien Rahbari,Hossien Keshavarz,Saeedeh Shojaee,Mehdi Mohebali,Mostafa Rezaeian 대한기생충학열대의학회 2012 The Korean Journal of Parasitology Vol.50 No.2

Aharonov-Casher effect and quantum transport in graphene based nano rings: A self-consistent Born approximation

Ghaderzadeh, A.,Rahbari, S.H. Ebrahimnazhad,Phirouznia, A. Elsevier 2018 Journal of magnetism and magnetic materials Vol.449 No.-

<P><B>Abstract</B></P> <P>In this study, Rashba coupling induced Aharonov-Casher effect in a graphene based nano ring is investigated theoretically. The graphene based nano ring is considered as a central device connected to semi-infinite graphene nano ribbons. In the presence of the Rashba spin-orbit interaction, two armchair shaped edge nano ribbons are considered as semi-infinite leads. The non-equilibrium Green’s function approach is utilized to obtain the quantum transport characteristics of the system. The relaxation and dephasing mechanisms within the self-consistent Born approximation is scrutinized. The Lopez-Sancho method is also applied to obtain the self-energy of the leads. We unveil that the non-equilibrium current of the system possesses measurable Aharonov-Casher oscillations with respect to the Rashba coupling strength. In addition, we have observed the same oscillations in dilute impurity regimes in which amplitude of the oscillations is shown to be suppressed as a result of the relaxations.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Rashba coupling induced Aharonov-Casher effect in graphene. </LI> <LI> Manipulation of Aharonov-Casher phase by Rashba interaction. </LI> <LI> The effect of the relaxations within the self-consistent Born Approximation. </LI> </UL> </P>

Novel analytical model for predicting the combustion characteristics of premixed flame propagation in lycopodium dust particles

Mehdi Bidabadi,Alireza Rahbari 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.9

This paper presents the effects of the temperature difference between gas and particle, different Lewis numbers, and heat loss from the walls in the structure of premixed flames propagation in a combustible system containing uniformly distributed volatile fuel particles in an oxidizing gas mixture. It is assumed that the fuel particles vaporize first to yield a gaseous fuel, which is oxidized in a gas phase. The analysis is performed in the asymptotic limit, where the value of the characteristic Zeldovich number is large. The structure of the flame is composed of a preheat zone, reaction zone, and convection zone. The governing equations and required boundary conditions are applied in each zone, and an analytical method is used for solving these equations. The obtained results illustrate the effects of the above parameters on the variations of the dimensionless temperature, particle mass friction, flame temperature, and burning velocity for gas and particle.

Nanofluid thin film flow and heat transfer over an unsteady stretching elastic sheet by LSM

Mehdi Fakour,Alireza Rahbari,Erfan Khodabandeh,Davood Domiri Ganji 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.1

This study is carried out on the unsteady flow and heat transfer of a nanofluid in a stretching flat plate. Least square method is implemented for solving the governing equations. It also attempts to demonstrate the accuracy of the aforementioned method compared with a numerical one, Runge-Kutta fourth order. Furthermore, the impact of some physical parameters like unsteadiness parameter (S), Prandtl number (Pr) and the nanoparticles volume fraction ( f ) on the temperature and velocity profiles is scrutinized carefully. Accordingly, the results obtained from this study reveal that the temperature enhances by means of augmenting the nanoparticles volume fraction. At η ∈ {0, 0.5}, the velocity decreases as a result of a rise in nanoparticles volume fraction and at η ∈ {0.5, 1}, an opposite treatment takes place. Moreover, velocity distribution augments by raising the S value, however an inverse trend is observed in temperature values. Moreover, the local skin friction coefficient indicated a notable rise by increasing the S parameter as well as a steady decrease by risingf . Finally, water-Alumina nanofluid demonstrated better heat transfer enhancement compared to other types of nanofluids.

A New Hybrid Optimization Algorithm for Recognition of Hysteretic Non-linear Systems

S. Talatahari,N. Mohajer Rahbari,A. Kaveh 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.5

In this article, a new two-stage hybrid optimization method based on the Particle Swarm Optimization and the Big Bang-Big Crunch algorithm (BB-BC) is introduced for identification of highly non-linear systems. In this hybrid algorithm, the term of the center of mass from the BB-BC algorithm is incorporated into the standard particle swarm optimizer to markedly improve its searching abilities. In order to investigate the effectiveness of the newly formed optimization algorithm in identification of non-linear and hysteretic systems,it is utilized to optimally find the Bouc-Wen model’s parameters for a sample MR damper in which the damper’s force is related to its piston’s motion through a non-linear differential equation. The obtained results indicate that the proposed optimization method is highly robust and accurate and can be utilized successfully in such intricate non-linear identification problems.