Showing papers in "Mathematical & Computational Applications in 2006"
TL;DR: An optimal design method to optimize three-phase induction motor in manufacturing process is presented and the optimally designed motor is compared with an existing motor having the same ratings.
Abstract: This paper presents an optimal design method to optimize three-phase induction motor in manufacturing process. The optimally designed motor is compared with an existing motor having the same ratings. The Genetic Algorithm is used for optimization and three objective functions namely torque, efficiency, and cost are considered. The motor design procedure consists of a system of non-linear equations, which imposes induction motor characteristics, motor performance, magnetic stresses and thermal limits. Computer simulation results are given to show the effectiveness of the proposed design process.
60 citations
TL;DR: In this paper, a tuned absorber is added to an externally excited pendulum, in the longitudinal direction, and the stability of the system is investigated by applying both frequency response equations and phase plane methods.
Abstract: In part I [1] we dealt with a tuned absorber, which can move in the transversally direction, where it is added to an externally excited pendulum. Active control is applied to the system via negative velocity feedback or its square or cubic value. The multiple time scale perturbation technique is applied throughout. An approximate solution is derived up to second order approximation. The stability of the system is investigated applying both frequency response equations and phase plane methods. The effects of the absorber on system behavior are studied numerically. Optimum working conditions of the system are obtained applying passive and active control methods. Both control methods are demonstrated numerically. In this paper, a tuned absorber, in the longitudinal direction, is added to an externally excited pendulum. Active control is applied to the system via negative acceleration feedback or via negative angular displacement or its square or cubic value. An approximate solution is derived up to the second order approximation for the system with absorber. The stability of the system is investigated applying both frequency response equations and phase plane methods. The effects of the absorber on system behavior are studied numerically. Optimum working conditions of the system are extracted when applying both passive and active control methods.
45 citations
TL;DR: In this article, a tuned absorber is added to an externally excited pendulum, which is simulated by a second order non-linear differential equation having both quadratic and cubic non-linearties, subjected to harmonic excitation.
Abstract: Vibrations and dynamic chaos should be controlled in structures and machines The most famous method of vibration control is using absorbers or tuned dampers or neutralizers The main aim is to improve the system behavior at different resonance conditions Two main strategies are used They are passive and active control methods In this paper, a tuned absorber, in the transversally direction, is added to an externally excited pendulum, which is simulated by a second order non-linear differential equation having both quadratic and cubic non-linearties, subjected to harmonic excitation The absorber is usually designed to control one frequency at primary resonance where system damage is probable The quenching efficiency of the system is studied Active control is applied to the system via negative velocity feedback or its square or cubic value The multiple time scale perturbation technique is applied throughout An approximate solution is derived up to the second order approximation The stability of the system is investigated applying both frequency response equations and phase plane methods The effects of the absorber on system behavior are studied numerically Optimum working conditions of the system are extracted when applying both passive and active control methods
43 citations
TL;DR: In this article, a backpropagation neural network that uses gradient descent learning algorithm was used to predict microhardness values of Al/SiCp metal matrix composite material couples.
Abstract: In this study, modelling of microhardness values by means of artificial neural networks of Al/SiCp metal matrix composite material couples with diffusion method and manufactured by powder metallurgy process, were obtained using a backpropagation neural network that uses gradient descent learning algorithm. After diffusion bonding and relevant test, to prepare the training and test (checking) set of the network, results were recorded in a file on a computer. Then, the neural network was trained using the prepared training set. At the end of the training process, the test data were used to check the system accuracy. As a result the neural network was found successful in the prediction of modelling of microhardness values of Al/SiCp metal matrix composite material couples processed with diffusion method and behavior.
20 citations
TL;DR: It is proved that the expected overall costs for an imperfect EPQ model with backlogging permitted is less than or equal to that of the one without backlogging, and the relationship between “imputed backorder cost” and maximal shortage level is derived.
Abstract: This paper examines an economic production quantity (EPQ) model with rework and service level constraint. First, we prove that the expected overall costs for an imperfect EPQ model with backlogging permitted is less than or equal to that of the one without backlogging. Secondly, the relationship between “imputed backorder cost” and maximal shortage level is derived for decision-making on whether the required service level is achievable. Then an equation for calculating the intangible backorder cost is proposed for situation when the required service level is not attainable. By including this intangible backorder cost in mathematical analysis, one can derive a new optimal lot-size policy that minimizes expected total costs as well as satisfies the maximal shortage level constraint for the EPQ model with rework. Numerical example is provided to demonstrate its practical usage.
19 citations
TL;DR: In this paper, artificial neural networks (ANNs) were used to determine the effects of injection pressure on smoke emissions and engine performance in a diesel engine, and the best results were obtained from Levenberg-Marquardt (LM) and Scaled Conjugate Gradient (SCG) algorithms with 11 neurons.
Abstract: The fuel injection pressure is one of the significant operating parameters affects atomization of fuel and mixture formation; therefore, it determines the performance and emissions of a diesel engine. Increasing the fuel injection pressure decrease the particle diameter and caused the diesel fuel spray to vaporize quickly. However, with decreasing fuel particles their inertia will also decrease and for this reason fuel can not penetrate deeply into the combustion chamber. In this study, artificial neural-networks (ANNs) are used to determine the effects of injection pressure on smoke emissions and engine performance in a diesel engine. Experimental studies were used to obtain training and test data. Injection pressure was changed from 100bar to 300bar in experiment (standard injection pressure of test engine is 150bar). Injection pressure and engine speed have been used as the input layer; smoke emission, engine torque and specific fuel consumption have been used as the output layer. Two different training algorithms were studied. The best results were obtained from Levenberg-Marquardt (LM) and Scaled Conjugate gradient (SCG) algorithms with 11 neurons. However, The LM algorithm is faster than the SCG algorithm, and its error values are smaller than those of the SCGs. For the torque with LM algorithm, fraction of variance (R2) and mean absolute percentage error (MAPE) were found to be 0.9927 and 7.2108%, respectively. Similarly, for the specific fuel consumption (SFC), R2 and MAPE were calculated as 0.9872 and 6.0261%, respectively. For the torque with SCG algorithm, R2 and MAPE were found to be 0.9879 and 9.0026%, respectively. Similarly, for the specific fuel consumption (SFC), R2 and MAPE were calculated as 0.9793 and 8.7974%, respectively. So, these ANN predicted results can be considered within acceptable limits and the results show good agreement between predicted and experimental values.
17 citations
TL;DR: In this paper, the in-plane vibrations of cracked circular curved beams are investigated using FEM and the curvature is in a single plane, and the analysis, elongation, bending and rotary inertia effects are included.
Abstract: In this study, the in plane vibrations of cracked circular curved beams is investigated. The beam is an Euler-Bernoulli beam. Only bending and extension effects are included. The curvature is in a single plane. In plane vibrations is analyzed using FEM. In the analysis, elongation, bending and rotary inertia effects are included. Four degrees of freedom for in-plane vibrations is assumed. Natural frequencies of the beam with a crack in different locations and depths are calculated using FEM. Comparisons are made for different angles.
17 citations
TL;DR: In this article, the authors investigated elasto-plastic thermal stresses in a thermoplastic composite disc that is reinforced by steel fibers, curvilinearly, using the Finite Element Method (FEM) to calculate the thermal stress distribution in the model of composite disc.
Abstract: The aim of this study was to investigate elasto-plastic thermal stresses in a thermoplastic composite disc that is reinforced by steel fibers, curvilinearly. Finite element method (FEM) was used to calculate the thermal stress distribution in the model of composite disc. The solution was performed by ANSYS software code. In order to evaluate the effects of uniform temperature, different values of it were carried out on the model of composite disc, uniformly. Radial and tangential stresses were calculated under a uniform temperature distribution which was selected from 60 C to 120 C. Because of the composite disc having different thermal expansions in radial and tangential directions, thermal stresses were produced in it by the applied uniform temperature values. The magnitude of the tangential stress component for elastic and elasto-plastic solutions was higher than the radial stress component. The radial stress components were obtained as compressive on the inner and outer surfaces. Besides the tangential stress components were calculated as compressive and tensile on the inner and outer surfaces, respectively. The absolute values of it were the highest on the inner surface both radial and tangential directions. The residual stress components also were calculated using elastic and elasto-plastic solution results. The obtained results showed that the positions of the improved thermal stresses and residual stresses were considerably affected increasing uniform temperature value.
11 citations
TL;DR: In this article, the dynamic treatment of one-dimensional generalized thermoelastic problem of heat conduction is made for a layered thin plate, which is exposed, to a uniform thermal shock.
Abstract: The dynamic treatment of one-dimensional generalized thermoelastic problem of heat conduction is made for a layered thin plate, which is exposed, to a uniform thermal shock The basic equations are transformed by Laplace transform and solved by a direct method The solution was applied for a plate of sandwich structure The inverses of Laplace transforms are obtained numerically The temperature, the stress and the displacement distributions are represented in graphs, which show the coupled and the generalized cases
10 citations
TL;DR: In this article, color information is used to classify color textures to gray-level ones and classifying them using gray level random field models, which is shown to be significantly more accurate than its grey-level counterpart.
Abstract: A large number of texture classification approaches have been developed in the past but most of these studies target gray-level textures. In this paper, supervised classification of color textures is considered. Several different Multispectral Random Field models are used to characterize the texture. The classifying features are based on the estimated parameters of these model and functions defined on them. The approach is tested on a database of sixteen different color textures. A near 100% classification accuracy is achieved. The advantage of utilizing color information is demonstrated by converting color textures to gray-level ones and classifying them using gray-level random field models. It is shown that color based classification is significantly more accurate than its gray-level counterpart.
9 citations
TL;DR: In this paper, the Navier-Stokes equations are solved explicitly for the velocity field using the explicit marching procedure, the continuity equation is implied at each grid point in the solution of pressure equation, while the SOR method is used for the Neumann problem for pressure.
Abstract: In this paper presents a new model procedure for the solution of the incompressible Navier-Stokes equations in primitive variables, using grid generation techniques. The time dependent momentum equations are solved explicitly for the velocity field using the explicit marching procedure, the continuity equation is implied at each grid point in the solution of pressure equation, while the SOR method is used for the Neumann problem for pressure. Results obtained for the model problem of driven flow in a square cavity demonstrate that the method yields accurate solutions. The results of the numerical computations in a driven cavity, which are presented for the history of the residues at several Reynolds numbers Re=100,1000,4000 and 5000 all the computed results are obtained without any artificial dissipation. This feature of the present procedure demonstrates its excellent convergence and stability characteristics. Numerically results obtained for the steady state static pressure in the driven cavity are presented for the first time at Re=4000 and 5000 using non-staggered grid.
TL;DR: In this article, a self-similar theoretical model of propagation of cylindrical shock wave in a magneto- gas dynamic rotating non-uniform atmosphere in the presence of monochromatic radiation and gravitation is considered.
Abstract: A self-similar, theoretical model of propagation of cylindrical shock wave in a magneto- gas dynamic rotating non-uniform atmosphere in the presence of monochromatic radiation and gravitation, is considered. The result discussed depends upon the variations of the flow variables behind the shock, which are displayed graphically. A special case is considered in presence and absence of gravitation along with rotation to observe the influence of gravitation.
TL;DR: In this article, an infinitely wide slider bearing consisting of connected surfaces with thirtd grade fluid as lubricant is analyzed under the assumptions of the order of magnitudes of the variables, and the results are presented both analytically and graphically.
Abstract: An infinitely wide lubricated slider bearing consisting of connected surfaces with thirtd grade fluid as lubricant is analyzed in the present study. Under the assumptions of the order of magnitudes of the variables, it is seen that only viscous and non-Newtonian terms have significant contributions, whereas inertia terms are negligible. Choosing non-Newtonian effects to be smaller than the viscous effects, analytical and numerical solutions are constructed. To illustrate the mathematical model, the set of equations is to used calculate the pressure for two special forms of the slider bearings, namely inclined and parabolic slider bearings. In these two cases, the variation of pressure, for a range of fluid and bearing parameters is presented. The results are presented both analytically and graphically.
TL;DR: The results show that the artificial neural network is powerful an alternate method in temperature estimations in Denizli, Turkey.
Abstract: In this study, the artificial neural networks have been used for the estimation of hourly ambient temperature in Denizli, Turkey. The model was trained and tested with four years (2002-2005) of hourly mean temperature values. The hourly temperature values for the years 2002-2004 were used in training phase, the values for the year 2005 were used to test the model. The architecture of the ANN model was the multi-layer feedforward architecture and has three layers. Inputs of the network were month, day, hour, and two hourly mean temperatures at the previous hours, and the output was the mean temperature at the hour specified in the input. In the model, Levenberg-Marquardt learning algorithm which is a variant of backpropagation was used. With the software developed in Matlab, an ANN was constructed, trained, and tested for a different number of neurons in its hidden layer. The best result was obtained for 27 neurons, where R2, RMSE and MAPE values were found to be 0.99999, 0.92024 and 0.20900% for training, and 0.9999, 0.91301 and 0.20907% for test. The results show that the artificial neural network is powerful an alternate method in temperature estimations.
TL;DR: Because the system characteristics are expressed and governed by the membership functions, the fuzzy batch-arrival queues with multiple servers are represented more accurately and the analytic results are more useful for system designers and practitioners.
Abstract: This work constructs the membership functions of the system characteristics of a batch-arrival queuing system with multiple servers, in which the batch-arrival rate and customer service rate are all fuzzy numbers. The α-cut approach is used to transform a fuzzy queue into a family of conventional crisp queues in this context. By means of the membership functions of the system characteristics, a set of parametric nonlinear programs is developed to describe the family of crisp batch-arrival queues with multiple servers. A numerical example is solved successfully to illustrate the validity of the proposed approach. Because the system characteristics are expressed and governed by the membership functions, the fuzzy batch-arrival queues with multiple servers are represented more accurately and the analytic results are more useful for system designers and practitioners.
TL;DR: In this paper, a random flow generation (RFG) algorithm for a previously established large eddy simulation (LES) code is successfully incorporated into a finite element fluid flow solver to generate the required inflow/initial turbulence boundary conditions for the LES computations of viscous incompressible turbulent flow over a nominally two-dimensional circular cylinder at Reynolds number of 140,000.
Abstract: A random flow generation (RFG) algorithm for a previously established large eddy simulation (LES) code is successfully incorporated into a finite element fluid flow solver to generate the required inflow/initial turbulence boundary conditions for the LES computations of viscous incompressible turbulent flow over a nominally twodimensional circular cylinder at Reynolds number of 140,000. The effect of generated turbulent inflow boundary conditions on the near wake flow and the shear layer and on the prediction of integral flow parameters is studied based on long time average results. No-slip velocity boundary function is used but wall effects are taken into consideration with a near wall modelling methodology based on van Driest Damping approach. The numerical results obtained from simulations are compared with each other and with the experimental data for different turbulent inflow boundary conditions to assess the functionality of the RFG algorithm for the present LES code and hence its influence on the vortex shedding mechanism and the resulting flow field predictions.
TL;DR: In this article, scaling transformation is applied to the equations to determine the specific forms of these functions for which the equation admits such type of transformation, and the resulting equation is solved numerically and temperature distribution is determined for various heat conductivity parameters.
Abstract: A nonlinear fin equation in which thermal conductivity is an arbitrary function of temperature and, heat transfer coefficient is an arbitrary function of spatial variable is considered Scaling transformation is applied to the equations to determine the specific forms of these functions for which the equation admits such type of transformation It is found that for arbitrary heat conduction function, scaling transformation exists for an inverse square heat transfer coefficient Selecting also the conductivity as an exponential function, the partial differential equation is transferred to an ordinary differential equation via similarity transformations The resulting equation is solved numerically and temperature distribution is determined for various heat conductivity parameters
TL;DR: The properties of a special function which is defined by an integral is presented in this article, where the numerical values of this function are tabulated correct to twenty decimal places and the curves of the function and its complementary are plotted.
Abstract: The properties of a special function which is defined by an integral is presented. The numerical values of this function are tabulated correct to twenty decimal places. The curves of this function and its complementary are plotted. Some properties of this function are investigated.
TL;DR: In this study, the fluid dynamic simulations were done in a diseased carotid bifurcation under the steady flow conditions computationally, and the location of critical flow fields such as low wall shear stress (WSS), stagnation regions and separation regions were detected near the highly stenosed region and at branching region.
Abstract: One of the leading causes for death after heart diseases and cancer in all over the world is still stroke Most strokes happen because an artery that carries blood uphill from the heart to the head is clogged Most of the time, as with heart attacks, the problem is atherosclerosis, hardening of the arteries, calcified buildup of fatty deposits on the vessel wall The primary troublemaker is the carotid artery, one on each side of the neck, the main thoroughfare for blood to the brain Only within the last twenty-five years, though, have researchers been able to put their finger on why the carotid is especially susceptible to atherosclerosis In this study, the fluid dynamic simulations were done in a diseased carotid bifurcation under the steady flow conditions computationally Reynolds numbers representing the steady flow were 300, 1020 and 1500 for diastolic, average and systolic peak flow represented by pulsatile flow waveform, respectively In vivo geometry and boundary conditions were obtained from a patient who has stenosis located at external carotid artery (ECA) and internal carotid artery (ICA) of his common carotid artery (CCA) The location of critical flow fields such as low wall shear stress (WSS), stagnation regions and separation regions were detected near the highly stenosed region and at branching region
TL;DR: Sobolev's initial value method was used to solve the Hammerstain equation of the second kind as mentioned in this paper, which was used for solving the first kind of the problem.
Abstract: Sobolev’s initial value method is used to solve the Hammerstain equation of the second kind
TL;DR: In this paper, a perturbation method, the Lindstedt-Poincare method, was used to obtain the asymptotic expansions of the solutions of a nonlinear differential equation arising in general relativity.
Abstract: A perturbation method, the Lindstedt-Poincare method, is used to obtain the asymptotic expansions of the solutions of a nonlinear differential equation arising in general relativity. The asymptotic solutions contain no secular term, which overcomes a defect in Khuri’s paper. A technique of numerical order verification is applied to demonstrate that the asymptotic solutions are uniformly valid for small parameter.
TL;DR: In this article, the steady state response of EFEF and VFVF plates is investigated using the energy-based finite difference method, where the problem is modeled by a kind of finite difference element.
Abstract: Determination of The Steady State Response of EFEF / VFVF Supported Rectangular Specially Orthotropic Plates is presented. EFEF and VFVF plates, these are rectangular plates with two opposite edges elastically or viscoelastically supported and remaining others free. Using the energy based finite difference method; the problem is modeled by a kind of finite difference element. Due to the significance of the fundamental frequency of the plate, its variation was investigated with respect to mechanical properties of plate material and translational spring coefficient of supports. The steady state response of viscoelastically supported plates was also investigated numerically for various damping coefficients. In the numerical examples, the natural frequency parameters and steady state responses to a sinusoidally varying force are assessed for the fundamental mode. Convergence studies are made. Many new results have been presented. Considered problems are solved within the frame work of Kirchhoff-Love hypothesis.
TL;DR: In this paper, the sensitivity properties of solutions of a variational inequality with respect to a parameter y were studied in the setting of Hilbert spaces, and the analysis was extended to general mixed multivalued mildly nonlinear variational inequalities.
Abstract: Dafermos [1] studied the sensitivity properties of solutions of a variational inequality with respect to a parameter y In this paper, we extend this analysis for general mixed multivalued mildly nonlinear variational inequalities in the setting of Hilbert spaces
TL;DR: In this article, the authors investigated the time dependence of large-scale nuclear shell model calculations in a parallel cluster using serial and parallel versions of DUSM code and obtained the time dependencies of these calculations on the local Cyborg Parallel Cluster at Drexel University.
Abstract: In this study, time dependence of large-scale nuclear shell model calculations in a parallel cluster is investigated Shell model calculations have been done for the light Sb isotopes by using serial and parallel versions of Drexel University Shell Model (DUSM) code and the time dependence of these calculations are obtained on the local Cyborg Parallel Cluster at Drexel University Some analyses about what kind of parallel system we need to do the calculations have been done in order to do the nuclear shell model calculations for the other nuclei