Showing 5 results for Alizadeh
M. A. Massoumnia, Gh, Alizadeh and H. R. Momeni,
Volume 17, Issue 2 (4-1998)
Abstract
In this paper, a new guidance method for surface to surface ballistic missiles without mandatory engine cut-off will be presented. The complexity of solid fuel engine cut-off demands a comprehensive method for guiding these missiles. In the method presented in this paper, a certain guidance law is applied such that by transmitting appropriate commands to the control system, by changing the missiles path and also through wasting additional fuel energy, the missile velocity will be equal to the desired one at the end of the burning time. The results of the simulation indicate that the aforementioned guidance method is quite effective and practical with long-range missiles having thrust vector control.
M. Alizadeh and H. Edriss,
Volume 21, Issue 2 (1-2003)
Abstract
In recent years many different ways have been investigated by steel producers to increase ductility, impact strength and formability of steels. More important ways are steels with very low amounts of inclusion, small size inclusions and modified inclusions. In this study, experiments have been performed on the API-X42 steel produced by the electric arc furnace in Mobarekeh Steel Co. After the preparation of the melt in the electric arc furnace, it is taped in a 200-ton ladle and ladle treatment was preformed in a ladle furnace (LF) in the steelmaking shop. In this study the effects of amount and the rate of CaSi wire addition on the shape and structure of inclusion were investigated. The optimum conditions for adding CaSi for inclusion shape control were also determined. Scanning electron microscope (SEM) and chemical energy analysis dispersive system (EDS) showed that adding calcium to the melt affects the chemical composition of inclusions present in steel melt. The effects of CaSi wire injection treatment, injection amount and inclusion shape control on the impact property and formability of steel were shown using charpy impact test.
Keywords: Inclusion shape control, calcium treatment, ladle furnace and inclusion modification
M. Alizadeh, H. Edris, and A. Shafyei,
Volume 27, Issue 2 (1-2009)
Abstract
K. Shakeri, M. Mohebbi, G. Alizadeh ,
Volume 34, Issue 1 (7-2015)
Abstract
Since there is no closed-form formula for designing TMD (Tuned Mass Damper) for nonlinear structures, some researchers have proposed numerical optimization procedures such as a genetic algorithm to obtain the optimal values of TMD parameters for nonlinear structures. These methods are based on determining the optimal values of TMD parameters to minimize the maximum response (e.g. inter story drift) of the controlled structure subjected to a specific earthquake record. Therefore, the performance of TMD that has been designed using a specific record strongly depends on the characteristics of the earthquake record. By changing the characteristics of the input earthquake record, the efficiency of TMD is changed and in some cases, it is possible that the response of the controlled structure is increased. To overcome the shortcomings of the previous researches, in this paper, an efficient method for designing optimal TMD on nonlinear structures is proposed, in which the effect of different ground motion records is considered in the design procedure. In the proposed method, the optimal value of the TMD parameters are determined so that the average maximum response (e.g. inter story drift) resulting from different records in the controlled structure is minimized. To illustrate the procedure of the propose method, the method is used to design optimal TMD for a sample structure. The results of numerical simulations show that the average maximum response of controlled structure resulting from different records is reduced significantly. Hence, it can be concluded that the proposed method for designing optimal TMD under different earthquakes is effective.
Z. Z. Ahangari Sisi, M. Mirzaei, S. Rafatnia, B. Alizadeh,
Volume 39, Issue 2 (2-2021)
Abstract
Active vehicle suspension system is designed to increase the ride comfort and road holding of vehicles. Due to limitations in the external force produced by actuator, the design problem encounters the constraint on the control input. In this paper, a novel nonlinear controller with the input constraint is designed for the active suspension system. In the proposed method, at first, a constrained multi-objective optimization problem is defined. In this problem, a performance index is defined as a weighted combination of the predicted responses of the nonlinear suspension system and control input. Then, this problem is solved by the modified firefly optimization algorithm to find the constrained optimal control input. To evaluate the performance of the proposed method, the results of the unconstrained and constrained controllers are provided and discussed for various road excitations. The results show a remarkable increase in the ride comfort with the limited force, while other suspension outputs including the suspension travel and tire deflection being in the acceptable ranges. In addition, these controllers are compared with Sliding Mode Control (SMC) and Nonlinear Model Predictive Control (NMPC) in the presence of model uncertainty.
