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Tensegrities are a kind of spatial structural system composed of cable (in tension) and strut (in compression). Stability of this system is provided by the self stress state between tensioned and compressed elements. In this paper, co-rotational method is used for study geometrical nonlinear analysis of tensegrity structure and analysis of the effect of pre-stress on it. This approach unlike other available approach in nonlinear static analysis, the major part of geometric non-linearity is treated by a co-rotational filter. The function of CR formulation is to extract relevant deformation quantities free or almost free from any rigid body motion in a given displacement field. One of advantage of the co-rotational approach is the fact that linear models can be easily used in the local coordinate system for modeling of nonlinear problems. The geometric non-linearity is incorporated in the transformation matrices relating local and global internal force vectors and tangent stiffness matrices. Three different numerical examples are studied using this approach. Results demonstrate that the deformations of tensegrity system are dependent on the value of pre-stress in tensegrity systems. The displacements of tensegrity system are decreased for fixed external tensile loading and increasing pre-tension force, however, for fixed pre-tension force and increasing external loading the displacements of tensegrity system are increased.

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Tensegrity is a kind of spatial structural system composed of cable (in tension) and strut (in compression). Stability is provided by the self-stress state between tensioned and compressed elements. When this structure is subjected to external dynamic loading, it may become unstable due to low structural damping. In this study, the proportional damping is considered and dynamical equations of the tensegrity structure are derived based on the equilibrium configuration. In addition the mass of cable element is taken into account. In general, linearized dynamic model provides a good approximation for analyzing the nonlinear behavior of tensegrity structures around an equilibrium configuration. So, state space method is implemented to obtain the dynamic response of the tensegrity system. Two different tensegrity structures are numerically evaluated using this approach in order to show its efficiency. Results reveal how the dynamic analysis of a tensegrity structure is essential. When resonance occurs, the compressive and in-tension members of a tensegrity system may dynamically buckle and slack respectively. In addition, the results show that the computational time to evaluate a tensegrity structure using the state space method is shorter than that of Newmark algorithm.

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In this paper, the longitudinal vibration of nanorod based on Eringen’s nonlocal elasticity theory was studied using Rayleigh-Ritz method. A non-uniform nano-rod with variable cross-sectional area, density and Young’s modulus were considered. In the present work, boundary polynomials with orthogonal polynomials were used as shape functions in the Rayleigh-Ritz method which causes the vibrational analysis to be computationally efficient and imposing of boundary conditions to be easier. Using the mentioned polynomials the convergence rate of the obtained results was increased. All of the equations used in this study were made to have no dimensional to reduce the number of effective parameters in the solution. The influence of the nonlocal and in-homogeneity parameters on the vibrational behavior of nanorod was investigated. The results were compared to available results in the literature and a good agreement has been achieved. The results showed that nanorod frequencies were depended to the small scale effect, non-uniformity, and boundary conditions. For instance, an increase in frequency ratio causes the scale coefficient in all vibration modes to be increased, especially in higher modes. In addition, the frequencies were increased by increasing in the length of the nanorod.

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This study aimed at investigating and comparing the expenditure of cognitive effort in translating various text types. The text typology of Reiss (1971, 2014) including informative, expressive, and operative text types was used as the theoretical framework. A mixed-method approach involving the use of screen recording, keystroke logging, think-aloud protocols, and retrospective interviews was adopted for the investigation. To pursue the research aims, 22 senior translation students were recruited to participate in the study and perform three translation tasks: translating informative, expressive, and operative texts. By using think-aloud protocols, the participants were instructed to speak out during the execution of the tasks. The amount of time spent by each participant and the number of pauses taken by them on each translation task were measured and compared as indicators of cognitive effort. Additionally, time and pause analyses were triangulated using technical operation analysis to have a better perception and obtain more reliable results. The findings of this study showed a significant difference in the cognitive effort required to translate informative, expressive, and operative texts. The findings also revealed a higher level of cognitive effort in translating expressive text compared with informative and operative ones

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In this research dynamic instability and nonlinear vibration of a clamped-clamped micro-beam sandwiched with piezoelectric layers based on parametric excitation in sub-harmonic region is investigated. The equation of motion is derived based on Hamiltonian principle, and non-dimensionalized using appropriate non-dimensional parameters. Applying a harmonic AC voltage to the piezoelectric layers results in the time varying of the linear stiffness of the micro-beam. The resultant motion equation in non-dimensional form is discretized to single degree of freedom model using Galerkin technique. The governing equation is a nonlinear Mathieu type ODE, and the periodic attractors are captured based on the shooting technique. The nonlinearity of governing equation is due to the geometric nonlinearity which originates from the clamped-clamped boundary conditions. The effect of various parameters including, magnitude of the nonlinear stiffness, damping coefficient, the frequency and the amplitude of the harmonic excitation on the parametric resonance region is investigated. The results depict that increased damping coefficient leads to the decreased aria of the parametric resonance region. It is concluded that the magnitude of the nonlinear stiffness, does not affect on the area of the resonance region, however it considerably influences on the amplitude of the parametric resonance.

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In this work, axial vibration of nanorod was analyzed based on two phase integro-differential nonlocal elasticity theory using isogeometric method. Two phase integro-differential nonlocal elasticity theory not only shows the nonlocal property in an integrated manner based on kernel weight function, but also combines local and nonlocal linear curvature for a two phase nonlocal elastic material. The new isogeometric approach combines finite element method with computational geometry and can present an accurate geometric model for the problem. Also, using b-spline basis functions with arbitrary continuity order, it can be a better alternative for classical finite element methods. The obtained results indicated that isogeometric approach was superior to finite element method in term of speed and convergence quality. Moreover, in this model, the effects of phase and nonlocal parameters on the natural frequencies of the nanorod were investigated and it was shown that increase of parameters of local phase and nonlocal length scale, respectively, increased and decreased the values of natural frequencies of nanorods. Finally, for two special cases, asymptotic frequencies for a single type of nonlocal rod, two phase integro-differential was obtained and the results were compared with corresponding available differential Eringen results.

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