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Mohammad Hossein Ghadiri Rad,Farzad Shahabian,Seyed Mahmoud Hosseini 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.1
The present paper outlined a procedure for geometrically nonlinear dynamic analysis of functionally graded graphene platelets-reinforced (GPLR-FG) nanocomposite cylinder subjected to mechanical shock loading. The governing equation of motion for large deformation problems is derived using meshless local Petrov-Galerkin (MLPG) method based on total lagrangian approach. In the MLPG method, the radial point interpolation technique is employed to construct the shape functions. A micromechanical model based on the Halpin-Tsai model and rule of mixture is used for formulation the nonlinear functionally graded distribution of GPLs in polymer matrix of composites. Energy dissipation in analyses of the structure responding to dynamic loads is considered using the Rayleigh damping. The Newmark-Newton/Raphson method which is an incremental-iterative approach is implemented to solve the nonlinear dynamic equations. The results of the proposed method for homogenous material are compared with the finite element ones. A very good agreement is achieved between the MLPG and FEM with very fine meshing. In addition, the results have demonstrated that the MLPG method is more effective method compared with the FEM for very large deformation problems due to avoiding mesh distortion issues. Finally, the effect of GPLs distribution on strength, stiffness and dynamic characteristics of the cylinder are discussed in details. The obtained results show that the distribution of GPLs changed the mechanical properties, so a classification of different types and volume fraction exponent is established. Indeed by comparing the obtained results, the best compromise of nanocomposite cylinder is determined in terms of mechanical and dynamic properties for different load patterns. All these applications have shown that the present MLPG method is very effective for geometrically nonlinear analyses of GPLR-FG nanocomposite cylinder because of vanishing mesh distortion issue in large deformation problems. In addition, since in proposed method the distributed nodes are used for discretization the problem domain (rather than the meshing), modeling the functionally graded media yields to more accurate results.
Nonlocal geometrically nonlinear dynamic analysis of nanobeam using a meshless method
Mohammad Hossein Ghadiri Rad,Farzad Shahabian,Seyed Mahmoud Hosseini 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.32 No.3
In the present paper, the element free Galerkin (EFG) method is developed for geometrically nonlinear analysis of deep beams considering small scale effect. To interpret the behavior of structure at the nano scale, the higher-order gradient elasticity nonlocal theory is taken into account. The radial point interpolation method with high order of continuity is used to construct the shape functions. The nonlinear equation of motion is derived using the principle of the minimization of total potential energy based on total Lagrangian approach. The Newmark method with the small time steps is used to solve the time dependent equations. At each time step, the iterative Newton-Raphson technique is applied to minimize the residential forces caused by the nonlinearity of the equations. The effects of nonlocal parameter and aspect ratio on stiffness and dynamic parameters are discussed by numerical examples. This paper furnishes a ground to develop the EFG method for large deformation analysis of structures considering small scale effects.
Dynamic analysis of magnetorheological elastomer sandwich MEMS sensor under magnetic field
Hossein Akhavan,Javad Ehyaei,Majid Ghadiri 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.5
In this paper, the effect of magnetic field on the vibration behavior of a Magnetorheological elastomer (MRE) sandwich MEMS actuated by electrostatic actuation with conductive skins are examined within the multiple scales (MMS) perturbation method. Magnetorheological smart materials have been widely used in vibration control of various systems due to their mechanical properties change under the influence of different magnetic fields. To investigate the vibrational behavior of the movable electrode, the Euler-Bernoulli beam theory, as well as Hamilton's principle is used to derive the equations and the related boundary conditions governing the dynamic behavior of the system are applied. The results of this study show that by placing the Magnetorheological elastomer core in the movable electrode and applying different magnetic fields on it, its natural vibrational frequency can be affected so that by increasing the applied magnetic field, the system's natural frequency increases. Also, the effect of various factors such as the electric potential difference between two electrodes, changes in the thickness of the core and the skins, electrode length, the distance between two electrodes and also change in vibration modes of the system on natural frequencies have been investigated.
THE EFFECT OF NUMBER OF VIRTUAL CHANNELS ON NOC EDP
Mahdieh Nadi Senejani,Mahdiar Hossein Ghadiry,Mohamad Khalily Dermany 한국전산응용수학회 2010 Journal of applied mathematics & informatics Vol.28 No.1
Low scalability and power efficiency of the shared bus in SoCs is a motivation to use on chip networks instead of traditional buses. In this paper we have modified the Orion power model to reach an analytical model to estimate the average message energy in K-Ary n-Cubes with focus on the number of virtual channels. Afterward by using the power model and also the performance model proposed in [11] the effect of number of virtual channels on Energy-Delay product have been analyzed. In addition a cycle accurate power and performance simulator have been implemented in VHDL to verify the results.
THE EFFECT OF NUMBER OF VIRTUAL CHANNELS ON NOC EDP
Senejani, Mahdieh Nadi,Ghadiry, Mahdiar Hossein,Dermany, Mohamad Khalily The Korean Society for Computational and Applied M 2010 Journal of applied mathematics & informatics Vol.28 No.1
Low scalability and power efficiency of the shared bus in SoCs is a motivation to use on chip networks instead of traditional buses. In this paper we have modified the Orion power model to reach an analytical model to estimate the average message energy in K-Ary n-Cubes with focus on the number of virtual channels. Afterward by using the power model and also the performance model proposed in [11] the effect of number of virtual channels on Energy-Delay product have been analyzed. In addition a cycle accurate power and performance simulator have been implemented in VHDL to verify the results.
The role of noninvasive penile cuff test in patients with bladder outlet obstruction
Seyed Mohamad Kazemeyni,Ehsan Otroj,Darab Mehraban,Gholam Hossein Naderi,Afsoon Ghadiri,Mahdi Jafari 대한비뇨의학회 2015 Investigative and Clinical Urology Vol.56 No.10
Purpose: The aim of this study was to compare the penile cuff test (PCT) and standard pressure-flow study (PFS) in patients with bladder outlet obstruction. Materials and Methods: A total of 58 male patients with moderate to severe lower urinary tract symptoms (LUTS) were selected. Seven patients were excluded; thus, 51 patients were finally enrolled. Each of the patients underwent a PCT and a subsequent PFS. The sensitivity (SE), specificity (SP), positive predictive value (PPV), negative predictive value (NPV), and likelihood ratio were calculated. Chi-square and Fisher exact test were used to evaluate relationships between PCT results and maximal urine flow (Qmax); a p<0.05 was considered statistically significant. Results: The mean (±standard deviation) age of the study group was 65.5±10.4 years. Overall, by use of the PCT, 24 patients were diagnosed as being obstructed and 27 patients as unobstructed. At the subsequent PFS, 16 of the 24 patients diagnosed as obstructed by the PCT were confirmed to be obstructed, 4 were diagnosed as unobstructed, and the remaining 4 patients appeared equivocal. Of the 27 patients shown to be unobstructed by the PCT, 25 were confirmed to not be obstructed by PFS, with 13 equivocal and 12 unobstructed. Two patients were diagnosed as being obstructed. For detecting obstruction, the PCT showed an SE of 88.9% and an SP of 75.7%. The PPV was 66.7% and the NPV was 93%. Conclusions: The PCT is a beneficial test for evaluating patients with LUTS. In particular, this instrument has an acceptable ability to reject obstruction caused by benign prostatic hyperplasia.