Sharif Digital Repository

This study provides a stochastic dynamic programming model with a Markov chain that explicitly focuses on the customer as well as a new model for valuing the customers in the banking industry. The proposed framework calculates individual customer’s lifetime value dynamically. The study follows a stochastic dynamic programming model that is based on the Markov chain. The deduced findings are illustrated with supplementary context from an outstanding case study. The findings underline the importance of the stochastic model for calculating customer lifetime value based on customer behavior. The presented framework provides a beneficial way for future research and valuable insight for allocating... 

Twitter as one of the most important microblogging online social networks has attracted more than 200 million users in recent years. Although there have been several attempts on characterizing the Twitter by using incomplete sampled data, they have not been very successful to estimate the characteristics of the whole network. In this paper, we characterize Twitter by sampling from its social graph and user behaviors through a random walk based sampling technique called Respondent-Driven Sampling (RDS). To the best of our knowledge, for the first time RDS method and its estimator are used in order to obtain uniform unbiased estimation of several key structural and behavioral properties of... 

At present, corrugated plates have numerous applications such as web of plate girders and aerospace applications. Higher out-of-plane stiffness and initial elastic strength of the corrugated plates compared with flat plates are reasons for consideration. This study investigates the behavior of trapezoidally corrugated steel plate shear walls (TCSPSWs) under monotonic and cyclic loadings. Finite element analyses that include both material and geometric nonlinearities are employed for the examination. The results from finite element analysis are verified through tested specimen findings. Moreover, the behavior of the steel shear walls with the flat infill panels and the corrugated plate infill... 

In this paper, Plate Frame Interaction (PFI) developed by other researches for modeling Steel Plate Shear Wall (SPSW) is applied for designing a half-scale, single bay and one story SPSW. After designing of SPSW, one specimen is constructed accordingly. In order to determine the mechanical properties of steel, coupon test is performed; and then again theoretical relations based on PFI is re-checked. In this study, gravity loads are neglected and only seismic resistance of SPSW is considered. With cyclic lateral loading as quasi-static load, according to Acceptance Criteria for Cyclic Racking Shear Tests For Metal-Sheathed Shear Walls with Steel Framing (AC154) and obtaining its hysteretic... 

Design and performance of two-stage optical beam shaping system based on a plastic fiberbundle, prism coupled waveguide, is described in this study. Such systems offer practical means to modify and change the output beam shape at two stages and also provide quantitative information concerning the output beam intensity. It is possible to investigate output power and image transmittance data by using a light source for illumination and image analysis by a CCD/digital camera. The photograph picture of the illuminating LED beam shows a circular shape with a diameter of about 10 mm at its output point. Picture of the fiber-bundle output beam is also taken, which shows a rectangular shape with a... 

Structural engineers have recognized unstiffened Steel Plate Shear Wall (SPSW) as an economical lateral resisting system due to the post-buckling capacity, energy dissipation, and deformability. This study investigates practical application of an added Energy Absorbent Element (EAE), subjoined to the SPSW in order to improve seismic behavior of the SPSW. The EAE is an aluminum shear panel with or without bracings and surrounding frame. Furthermore, a series of parametric studies are implemented to examine the effect of dimensions, position, and formation of the EAE. It is assumed that the lateral loading is applied as quasi-static loading. Further, nonlinearity of the material and the... 

This research deals with developing an intelligent trajectory tracking control approach for an aircraft in the presence of internal and external disturbances. Internal disturbances including actuators faults, unmodeled dynamics, and model uncertainties as well as the external disturbances such as wind turbulence significantly affect the performance of the common trajectory tracking control approaches. There are several fault-tolerant control approaches in the literature to overcome the effects of specific actuator or sensor faults during the flight. However, trajectory tracking control of an air vehicle in the presence of unexpected faults and simultaneous presence of wind turbulence is... 

In this paper, a multiple model-based nonlinear identification approach is introduced for a conventional aircraft in the presence of different types of actuator faults. Occurrence of actuator faults can obviously reduce the validity of a predetermined dynamic model of nonlinear systems. In such cases, use of multi-model structures can be an effective choice. However, determining the optimal validity functions of the local models in a multi-model structure is still a challenging problem. This problem becomes even more challenging in case of unpredictable faults, which are not considered in training the local models. In this paper, two effective techniques are proposed for online determination... 

Variable speed wind turbines are widely used in the modern power industry. These turbines that are usually driven by doubly fed induction generators (DFIG) contain two groups of controlling variables; mechanical variables like pitch angle, and electrical variables like rotor voltage. During the turbine operation, with variable wind speed, power must be managed in two different regimes; power optimization and power limitation. In the current research, initially a non-linear simulation, based on the general wind turbine dynamic model is presented. Then, the desired controllers for both pitch angle and generator voltage components are constructed. To validate turbine behavior and controller... 

Variable speed wind turbines are widely used in the modern power industry. These turbines that are usually driven by doubly fed induction generators (DFIGs) contain two groups of controlling variables; mechanical variables like pitch angle and electrical variables like rotor voltage. During the turbine operation, with variable wind velocity, power must be managed in two regimes; power optimisation and power limitation. In the current research, initially a non-linear simulation, based on the general wind turbine dynamic model is presented. Then, the desired controllers for both pitch angle and generator voltage components are constructed. After designing the controller, in order to... 

A comparison of three common controllers for stabilising a vertical take-off and landing air vehicle is presented. RMIT is a small sized tail-sitter ducted fan air vehicle with a particular configuration layout, multiple control surfaces, low weight, and high-speed flight capability. The main problem here is control effectiveness at low flight speeds and transition manoeuvres because of the inherent instability. In the current study, a comprehensive nonlinear model is firstly developed for RMIT, followed by a validation process. Subsequently, linear, adaptive and model predictive controllers are designed in vertical flight. Based on the simulation results, it is shown that the linear... 

A novel adaptive model-based predictive controller for attitude and trajectory tracking of a vertical take-off and landing(VTOL) aircraft in the simultaneous presence of model uncertainties and external disturbances is introduced in this study. Animportant challenge of designing the model-based controllers is developing an accurate model, especially in the presence ofmodel uncertainties. In this study, first, the nominal model of a ducted-fan air vehicle, which is a multi-input multi-outputnonlinear system with non-minimum phase behaviour, is given as the test case of this research. After that, two modified robustand adaptive model predictive controllers are proposed for tracking a... 

The development of a multiple model-based identification algorithm is addressed in this paper for nonlinear modeling of a conventional aircraft in the entire flight envelope. The dynamic model of an aircraft varies significantly depending on changes in the flight condition of the air vehicle including the altitude and the equivalent air speed. Therefore, the conventional identification approaches for generating a single nonlinear model with time-invariant parameters cannot be used in the entire flight envelope of an aircraft. Accordingly, a multiple model-based approach using nonlinear autoregressive exogenous neural networks is introduced in this paper as a powerful tool in identifying... 

A novel fault-tolerant model predictive control (MPC)-based trajectory tracking approach for an aerial vehicle is presented in this study. A generalised online sequential extreme learning machine is introduced first to identify the corresponding coefficients of actuator faults. Subsequently, a robust trajectory tracking control is developed based on MPC, where the system constraints can be effectively considered in the designed control scheme. Trajectory tracking control is achieved by controlling only the acceleration of the aerial robot in the MPC structure. This leads to less computational burden and faster closed-loop dynamics. In addition, an effective disturbance observer is employed,...