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Due to the importance of acoustic response control of submerged vibrating structures, in this study,the optimization of acoustic power radiation from a square stiffened plate under harmonic loading was investigated.Since one face of the plate is in contact with water, a fully coupled analysis was used. The effect of fluid in the analysis was considered via added mass matrix. The added mass matrix was obtained based on both Rayleigh integral and the boundary element approaches.The obtained added mass matrix was then added to the mass matrix of the structure calculated from the finite element discretization of plate. Several variables such as acoustic pressure at specific points and also radiated power were calculated. Results show good agreement between obtained results from the Rayleigh integral and the boundary element. To reduce the radiation power, dynamic absorbers in the form of lumped mass and mass-springs in specific locations on the plate surface were considered. Because optimization procedure requires several evaluation of cost function in the design variable space, model reduction can save a great amount of computation efforts. Therefore, the truncated modal matrix was employed and its effectiveness and precision on the obtained results was studied. Finally, Genetic Algorithm (GA) was used for minimizing the appropriate goal function in three case studies: concentrated mass on cross-points, dynamic absorbers on cross-points and combination of two former cases.All the studied cases resulted on significant reduction in the goal function index.

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In this paper, the design of predictive functional controller based on Laguerre functions to track the load changes in Pressurized Water Reactor (PWR) nuclear power stations has been considered. Since, despite of out-performance of predictive controllers in industrial applications, their implementation implies high computational complexity for constrained large scale systems, in this paper, the design of model predictive controller with low computational complexity was considered. For this purpose, at first, the order of PWR model was reduced via Balanced Truncation method. Then, due to low computational complexity and high performance of predictive functional controllers, we dealt with the design of predictive functional controllers based on Laguerre functions. In this context, the Laguerre polynomial scaling parameter was determined by minimizing integral square error. Then, due to mechanical constraints, some specific constraints were applied to the control effort and its changes, and the Quadratic Programming method was used for solving the constrained model predictive control problem and consequently, designing the control effort signal. Also, in order to show the efficiency of the proposed core power control method, the system response in the presence of disturbance is investigated. It is shown that, by using predictive functional controller on a reduced order model, in addition to the decrease of the computation volume, the performance of the core power control to track load changes in presence of external disturbance is well done.

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The main approach in the study of fluid flow instabilities is the theory of linear stability, which is based on linearizing the governing equations and finding unstable eigenvalues. In many flows, like shear flows, the results of linear stability theory fail to match most experiments. In a linear system, even if all the eigenvalues are stable, the perturbations can lead to instability, if the eigenfunctions are not orthogonal. The transient features of these non-normal dynamical systems, can be described with low-dimensional structures, i.e. a few modes. It is possible to suppress the asymptotic and transient growth by identification of time-dependent modes. In this paper, a method of order reduction based on optimally time-dependent modes has been implemented. This method identifies the growth behavior of disturbances in short and long times. Also, a control algorithm based on the above method has been implemented to stabilize the growth of disturbances. The DNS solution of the flow and the implementation of the reduction and control algorithms is based on the NEKTAR++ open-source solver. At first problem, to validate the solution method, the order reduction and control algorithm has been implemented on the flow over a cylinder with Re=50. At second problem, for the first time, the control algorithm is implemented on the flow over a cylinder subjected to persistent time-varying disturbances. The results show that by applying a control force, the Von-Karman vortices are stabilized and a constant lift is obtained and body vibrations are cancelled.