International Journal of Modeling, Simulation, and Scientific Computing

In this paper, we have formulated mathematical models to optimize the bouncing transmissibility of the sprung mass of the half car system with passengers' seat suspensions considering different road conditions. The corresponding problem has been solved with the help of advanced real coded Genetic Algorithm (GA). The nonlinearity of suspension spring and damper, which are the most important characteristics of the suspension, has been taken into account in order to validate the model to real applications. The nonlinear cubic polynomial has been used to describe the spring characteristic and a quadratic polynomial has been used to describe the damper characteristic. The coefficients of each polynomial represent the design parameters of the suspension system and are to be determined. To find these parameters we have formulated a nonlinear optimization problem in which the bouncing transmissibility of the sprung mass at the center of mass has been minimized with respect to technological constraints and the constraints which satisfy the performance as per ISO 2631 standards. The advanced real coded GA has been used to solve this problem in time domain and the results obtained have been compared to those obtained using the existing design parameters. The objective function and the constraints have been evaluated by simulating the vehicle model over two roads with multiple bumps at uniform velocity.

Present study proposes a method for fuzzy time series forecasting based on difference parameters. The developed method has been presented in a form of simple computational algorithm. It utilizes various difference parameters being implemented on current state for forecasting the next state values to accommodate the possible vagueness in the data in an efficient way. The developed model has been simulated on the historical student enrollments data of University of Alabama and the obtained forecasted values have been compared with the existing methods to show its superiority. Further, the developed model has also been implemented in forecasting the movement of market prices of share of State Bank of India (SBI) at Bombay Stock Exchange (BSE), India.

Elastic interactions, arising from a difference of lattice spacing between two coherent phases in eutectic alloys with misfit stresses, can have an influence on microstructural pattern formation of eutectic colonies during solidification process. From a thermodynamic point of view the elastic energy contributes to the free energy of the phases and modifies their mutual stability. Therefore, the elastic stresses will have an effect on stability of lamellae, lamellae spacing and growth modes. In this paper, a phase-field model is employed to investigate the influence of elastic misfits in eutectic growth. The model reduces to the traditional sharp-interface model in a thin-interface limit, where the microscopic interface width is small but finite. An elastic model is designed, based on linear microelasticity theory, to incorporate the elastic energy in the phase-field model. Theoretical and numerical approaches, required to model elastic effects, are formulated and the stress distributions in eutectic solidification structures are evaluated. The two-dimensional simulations are performed for directed eutectic growth and the simulation results for different values of the misfit stresses are illustrated.

It is important to calculate the electric field at the surface of high voltage direct current power transmission lines, since it is this field which governs the onset of corona discharge and the power loss arising therefrom. A method is presented here to calculate the electric field based on an implementation of the boundary element method for conductors of strictly circular cross section. Given the circular geometry it is possible to resolve all integrals involved analytically. A Galerkin approach is adopted, giving the solution in the spatial frequency domain. That allows a controlled truncation of the system matrix by choice of which frequency components to keep. It transpires that the low frequency components are the most important ones. Two test cases are used to quantify the accuracy of the solution with respect to truncation and distance from the surface. It is found that the accuracy increases with distance from the surface, but for all distances can be controlled by choosing an appropriate level of truncation.

Multi-agent systems for a certain application area can be modeled at multiple levels of abstraction. Interlevel relations are a means to relate models from different abstraction levels. Three dimensions of abstraction often occurring are the process abstraction, temporal abstraction, and agent cluster abstraction dimension. In this paper a unifying formalization is presented that can be used as a framework to specify interlevel relations for any of such dimensions. The approach is illustrated by showing how a variety of different types of abstraction relations between multi-agent system models can be formally specified in a unified manner.

Wireless technology is now an integral part of communication network infrastructure. From their first beginnings, such as connection-oriented General System Mobile networks for voice traffic only and connectionless wireless local area networks for data traffic, new generation wireless networks are connection-oriented and provide differentiated services to the user. With the arrival of more sophisticated services and mobility, have arisen the need for Connection Admission Control and traffic scheduling in the network to enhance the quality of experience (QoE) of the user and optimizing the revenue in dynamic workload environments. A great deal of research effort has gone into the study of the performance of one such network standard, namely the IEEE 802.16 networks. Most optimization studies focus on scheduling (a very mature subject in computing) and ignore connection admission (a very mature subject in telephone engineering) or vice versa. In this paper we claim that one should not study the two in isolation and provide empirical evidence to prove our claim.

Unlike the traditional independent component analysis (ICA) algorithms and some recently emerging linear ICA algorithms that search for solutions in the space of general matrices or orthogonal matrices, in this paper we propose two new methods which only search for solutions in the space of the matrices with unitary determinant and without whitening. The new algorithms are based on the special linear group SL(n). In order to achieve our target, we first provide a representation theory for any matrix in SL(n), which only simply uses the product of multiple exponentials of traceless matrices. Based on the matrix representation theory, two novel ICA algorithms are developed along with simple analysis on their equilibrium points. Moreover, we apply our methods to the classical problem of signal separation. The experimental results indicate that the superior convergence of our proposed algorithms, which can be expected as two viable alternatives to the ICA algorithms available in publications.

We investigate the practical implementation of a high-order explicit time-stepping method based on polynomial approximations, for possible application to large-scale problems in electromagnetics. After the spatial discretization by a high-order discontinuous Galerkin method, we obtain a linear system of differential equations of the form, , where is a matrix containing the spatial derivatives and t is the time variable. The formal solution can be written in terms of the matrix exponential, , acting on some vectors. We introduce a general family of time-integrators based on the approximation of by Jacobi polynomial expansions. We discuss the efficient implementation of this technique, and based on some test problems, we compare the virtues and shortcomings of the algorithm. We also demonstrate how these schemes provide an efficient alternative to standard explicit integrators for computing solutions over long time intervals.