http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Strong Law of Large Numbers for Fuzzy Random Variables in Fuzzy Metric Space
Reza Ghasemi,Mohammad Reza Rabiei,Ahmad Nezakati 한국지능시스템학회 2020 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.20 No.4
Despite uncertainty in fuzzy random variables, crisp metrics have always been used. In this study, we attempt to introduce the concept of fuzzy metric space and fuzzy normed space for fuzzy sets and some of its properties, and we investigate the strong law of large numbers. The embedded theorem for fuzzy compact sets in fuzzy normed space and the generalized Hukuhara difference are the most important tools used to prove this theorem. In addition, as a result and application, we use the strong law of large numbers for fuzzy random variables in the fuzzy metric space for the bootstrap mean.
Numerical and analytical study of aeroelastic characteristics of wind turbine composite blades
Ahmad Reza Ghasemi,Arezu Jahanshir,Mohammad Hassan Tarighat 한국풍공학회 2014 한국풍공학회지 Vol.18 No.2
Aeroelasticity is the main source of instability in structures which are subjected to aerodynamic forces. One of the major reasons of instability is the coupling of bending and torsional vibration of the flexible bodies, which is known as flutter. The presented investigation aims to study the aeroelastic stability of composite blades of wind turbine. Geometry, layup, and loading of the turbine blades made of laminated composites were calculated and evaluated. To study the flutter phenomenon of the blades, two numerical and analytical methods were selected. The finite element method (FEM), and JAR-23 standard were used to perform the numerical studies. In the analytical method, two degree freedom flutter and Lagrange\'s equations were employed to study the flutter phenomena analytically and estimate the flutter speed.
Numerical and analytical study of aeroelastic characteristics of wind turbine composite blades
Ghasemi, Ahmad Reza,Jahanshir, Arezu,Tarighat, Mohammad Hassan Techno-Press 2014 Wind and Structures, An International Journal (WAS Vol.18 No.2
Aeroelasticity is the main source of instability in structures which are subjected to aerodynamic forces. One of the major reasons of instability is the coupling of bending and torsional vibration of the flexible bodies, which is known as flutter. The presented investigation aims to study the aeroelastic stability of composite blades of wind turbine. Geometry, layup, and loading of the turbine blades made of laminated composites were calculated and evaluated. To study the flutter phenomenon of the blades, two numerical and analytical methods were selected. The finite element method (FEM), and JAR-23 standard were used to perform the numerical studies. In the analytical method, two degree freedom flutter and Lagrange's equations were employed to study the flutter phenomena analytically and estimate the flutter speed.
Ghasemi, Ahmad Reza,Mohandes, Masood Techno-Press 2016 Advances in aircraft and spacecraft science Vol.3 No.4
In this manuscript, free vibrations of a unidirectional composite orthotropic Timoshenko beam based on finite strain have been studied. Using Green-Lagrange strain tensor and comprising all of the nonlinear terms of the tensor and also applying Hamilton's principle, equations of motion and boundary conditions of the beam are obtained. Using separation method in single-harmonic state, time and locative variables are separated from each other and finally, the equations of motion and boundary conditions are gained according to locative variable. To solve the equations, generalized differential quadrature method (GDQM) is applied and then, deflection and cross-section rotation of the beam in linear and nonlinear states are drawn and compared with each other. Also, frequencies of carbon/epoxy and glass/epoxy composite beams for different boundary conditions on the basis of the finite strain are calculated. The calculated frequencies of the nonlinear free vibration of the beam utilizing finite strain assumption for various geometries have been compared to von Karman one.
An analytical approach for aeroelastic analysis of tail flutter
Gharaei, Amin,Rabieyan-Najafabadi, Hamid,Nejatbakhsh, Hossein,Ghasemi, Ahmad Reza Techno-Press 2022 Advances in computational design Vol.7 No.1
In this research, the aeroelastic instability of a tail section manufactured from aluminum isotropic material with different shell thickness investigated. For this purpose, the two degrees of freedom flutter analytical approach are used, which is accompanied with simulation by finite element analysis. Using finite element analysis, the geometry parameters such as the center of mass, the aerodynamic center and the shear center are determined. Also, by simulation of finite element method, the bending and torsional stiffnesses for various thickness of the airfoil section are determined. Furthermore, using Lagrange's methods the equations of motion are derived and modal frequency and critical torsional/bending modes are discussed. The results show that with increasing the thickness of the isotropic airfoil section, the flutter and divergence speeds increased. Compared of the obtained results with other research, indicates a good agreement and reliability of this method.