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RISS 인기검색어
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- 저자 : Heydari, Akbar (검색결과 86 건)
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Exact solution for transverse bending analysis of embedded laminated Mindlin plate
Heydari, Mohammad Mehdi,Kolahchi, Reza,Heydari, Morteza,Abbasi, Ali Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.5
Laminated Rectangular plates embedded in elastic foundations are used in many mechanical structures. This study presents an analytical approach for transverse bending analysis of an embedded symmetric laminated rectangular plate using Mindlin plate theory. The surrounding elastic medium is simulated using Pasternak foundation. Adopting the Mindlin plate theory, the governing equations are derived based on strain-displacement relation, energy method and Hamilton's principle. The exact analysis is performed for this case when all four ends are simply supported. The effects of the plate length, elastic medium and applied force on the plate transverse bending are shown. Results indicate that the maximum deflection of the laminated plate decreases when considering an elastic medium. In addition, the deflection of the laminated plate increases with increasing the plate width and length.
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Robust Model Predictive Control of Biped Robots with Adaptive On-line Gait Generation
Reza Heydari,Reza Heydari 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.1
In this paper, an on-line gait control scheme is proposed for the biped robots for walking up and down thestairs. In the proposed strategy, the nonlinear model predictive control approach is used for the trajectory planningand as well as for the control of the robot. The motion of the robot is expressed in the form of a cost functionand some constraints that are related to the stable walking of the robot. The main feature of this method is that itdoes not need any off-line trajectory planning and the walking gait is formulated such that the environmental andstability constraints of the robot are satisfied. This on-line trajectory planning gives the important ability to therobot to adjust its gait lengths. In this way, the robot is able to ascend and descend the stairs without knowing theheight and depth of the stairs in advance. In the control algorithm, the Radial-Basis Function (RBF) neural networkwith on-line training method is used to model the behavior of the robot over the prediction horizon. The stabilityanalysis of the closed-loop system is performed using the Lyapunov method as well as the Poincaré map. Theproposed method is applied to a 5-DOF biped robot in the sagittal plane. The simulation results show effectivenessof the proposed method.
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Exact solution for transverse bending analysis of embedded laminated Mindlin plate
Mohammad Mehdi Heydari,Reza Kolahchi,Morteza Heydari,Ali Abbasi 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.5
Laminated Rectangular plates embedded in elastic foundations are used in many mechanical structures. This study presents an analytical approach for transverse bending analysis of an embedded symmetric laminated rectangular plate using Mindlin plate theory. The surrounding elastic medium is simulated using Pasternak foundation. Adopting the Mindlin plate theory, the governing equations are derived based on strain-displacement relation, energy method and Hamilton’s principle. The exact analysis is performed for this case when all four ends are simply supported. The effects of the plate length, elastic medium and applied force on the plate transverse bending are shown. Results indicate that the maximum deflection of the laminated plate decreases when considering an elastic medium. In addition, the deflectionof the laminated plate increases with increasing the plate width and length.
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Heydari, Abbas Techno-Press 2020 Advances in computational design Vol.5 No.4
Functionally graded material (FGM) illustrates a novel class of composites that consists of a graded pattern of material composition. FGM is engineered to have a continuously varying spatial composition profile. Current work focused on buckling analysis of beam made of stepwise linear and quadratic graded material in axial direction subjected to axial span-load with piecewise function and rested on shear layer based on classical beam theory. The various boundary and natural conditions including simply supported (S-S), pinned - clamped (P-C), axial hinge - pinned (AH-P), axial hinge - clamped (AH-C), pinned - shear hinge (P-SHH), pinned - shear force released (P-SHR), axial hinge - shear force released (AH-SHR) and axial hinge - shear hinge (AH-SHH) are considered. To the best of the author's knowledge, buckling behavior of this kind of Euler-Bernoulli beams has not been studied yet. The equilibrium differential equation is derived by minimizing total potential energy via variational calculus and solved analytically. The boundary conditions, natural conditions and deformation continuity at concentrated load insertion point are expressed in matrix form and nontrivial solution is employed to calculate first buckling loads and corresponding mode shapes. By increasing truncation order, the relative error reduction and convergence of solution are observed. Fast convergence and good compatibility with various conditions are advantages of the proposed method. A MATLAB code is provided in appendix to employ the numerical procedure based on proposed method.
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Optimal Operation of Virtual Power Plant with Considering the Demand Response and Electric Vehicles
Heydari Rana,Nikoukar Javad,Gandomkar Majid 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.5
The needs of human communities for electrical energy is increasing every day, and as a result, the price of fossil fuels is steadily increasing. Considering the trend of advances in renewable energy technologies and the support of governments and energy policymakers to make more use of these clean and inexpensive resources. Limitations such as low capacity, the uncertainty of output power and stability issues have made it costly and diffi cult to use Distributed Energy Resources (DERs). To solve these problems, a new concept known as Virtual Power Plant (VPP) has been proposed to facilitate the exploitation of DERs. The VPP is a set of DERs that are put together for market participation. Also, eff orts to reduce the amount of environmental pollution have replaced the use of Electric Vehicles (EV) instead of internal combustion engines. Regarding this paper, a new model for optimizing virtual power plant is presented. In this model, the Demand response (DR) has been used, whose modeling is based on Price-Based Demand Response for ordinary loads and incentive. To solve the problem a mixed integer linear programming model is proposed to maximize the profi t of the virtual power plant. In order to see the eff ectiveness and satisfying performance of proposed model, a case study including DERs, EV, and loads is studied as test system. The simulation results using Matlab and GAMS show the effi ciency of the proposed model and proves that simultaneous use of the price-based demand response program, smart charging, and the participation of electric vehicles in demand responses reduces operating costs
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Heydari Farhad,Azizkhani Reza,Majidinejad Saeed,Zamani Majid,Norouzian Aref 대한응급의학회 2024 Clinical and Experimental Emergency Medicine Vol.11 No.1
Objective Urolithiasis is one of the most common urological diseases worldwide, usually presenting as renal colic that leads to severe pain that requires analgesic treatment. This study aimed to compare the efficacy of ketamine and desmopressin in the pain management of renal colic patients. Methods This double-blind, randomized clinical trial was conducted on renal colic patients referred to the emergency department from June 2021 to July 2022. Patients were randomly assigned to three groups. In the desmopressin group, patients were treated with intranasal desmopressin and intravenous ketorolac. The ketamine group was treated with intranasal ketamine and ketorolac. The control group received ketorolac and an intranasal placebo. Vital signs were evaluated at baseline and 60 minutes; and pain scores were assessed at baseline, 10, 30, and 60 minutes after treatment. Results Enrollment included 135 patients, the mean (standard deviation) age was 44.1±11.4 years, and 82 (60.7%) were men. The mean visual analog scale scores were significantly lower at 10, 30, and 60 minutes in the ketamine group (5.6±1.2, 3.0±1.1, and 0.9±0.9, respectively) compared to the control (8.2±1.1, 5.1±2.0, and 2.3±2.6, respectively) and desmopressin (6.7±1.8, 4.2±2.2, and 1.3±1.4, respectively) groups (P<0.05). Although patients in the desmopressin group had lower mean pain scores than the control group at 10, 30, and 60 minutes, this difference was only significant at 10 minutes after the intervention (P<0.05). No significant differences in vital signs were found at 60 minutes after treatment. Conclusion Ketamine showed more favorable analgesic effects in renal colic patients than desmopressin, although desmopressin showed efficacy in the first minutes posttreatment.
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Heydari, Abbas 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.2
For the first time, nonlocal damped vibration and buckling analyses of arbitrary tapered bidirectional functionally graded solid circular nano-plate (BDFGSCNP) are presented by employing modified spectral Ritz method. The energy method based on Love-Kirchhoff plate theory assumptions is applied to derive neutral equilibrium equation. The Eringen's nonlocal continuum theory is taken into account to capture small-scale effects. The characteristic equations and corresponding first mode shapes are calculated by using a novel modified basis in spectral Ritz method. The modified basis is in terms of orthogonal shifted Chebyshev polynomials of the first kind to avoid employing adhesive functions in the spectral Ritz method. The fast convergence and compatibility with various conditions are advantages of the modified spectral Ritz method. A more accurate multivariable function is used to model two-directional variations of elasticity modulus and mass density. The effects of nanoscale, in-plane pre-load, distributed dashpot, arbitrary tapering, pinned and clamped boundary conditions on natural frequencies and buckling loads are investigated. Observing an excellent agreement between results of current work and outcomes of previously published works in literature, indicates the results' accuracy in current work.
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Heydari, Abbas,Shariati, Mahdi Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.6
The current study presents a new technique in the framework of the nonlocal elasticity theory for a comprehensive buckling analysis of Euler-Bernoulli nano-beams made up of bidirectional functionally graded material (BDFGM). The mechanical properties are considered by exponential and arbitrary variations for axial and transverse directions, respectively. The various circumstances including tapering, resting on two-parameter elastic foundation, step-wise or continuous variations of axial loading, various shapes of sections with various distribution laws of mechanical properties and various boundary conditions like the multi-span beams are taken into account. As far as we know, for the first time in the current work, the buckling analyses of BDFGM nano-beams are carried out under mentioned circumstances. The critical buckling loads and mode shapes are calculated by using energy method and a new technique based on calculus of variations and collocation method. Fast convergence and excellent agreement with the known data in literature, wherever possible, presents the efficiency of proposed technique. The effects of boundary conditions, material and taper constants, foundation moduli, variable axial compression and small-scale of nano-beam on the buckling loads and mode shapes are investigated. Moreover the analytical solutions, for the simpler cases are provided in appendices.
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