Showing 7 results for Modeling
S. Yaghmaei, A. A. Seifkordi and H. Shirzadi,
Volume 21, Issue 1 (7-2002)
Abstract
A mathematical model has been analyzed for in-situ bioremediation with the purpose of remediating organic contaminated soil. Oxygen rich water when passed through the porous media of soil activates the aerobic microorganisms, leading to the biodegradation of the organic content. The model equations comprise three convection-dispersion partial differential solution of these equations has been conducted using the finite difference method. The effects of insufficient oxygen supply, growth of biomass and resistance to contaminant migration on the rate of biodegradation have been analyzed by numerically solving the equations.
The results from the numerical simulation indicate that the rate of biodegradation of contaminants in soil may be constrained not only by insufficient oxygen supply, but also by resistance to contaminant migration within the pore network.
Keywords: Bioremediation, Soil, Porous media, modeling
A. Gholami and M. Mirzai,
Volume 22, Issue 1 (7-2003)
Abstract
Overhead transmission lines are influenced by different factors which are mostly electrical and mechanical. These factors can cause problems for lines, distortions in network and outage of line. In designing transmission lines mechanical properties are evaluated after selecting a suitable conductor and clearance with regard to electrical properties. In lines designing, an important mechanical parameter for estimating of phase distance is oscillations. Strong wind or ice fall from conductor surfaces or simultaneous presence of ice and wind may cause different oscillations. These oscillations are classified to aeoliane, galloping, and swing. Aeoliane is of high frequency (5-100Hz) and low amplitude (about a few centimeters), galloping is of low frequency (0.1 to 0.3Hz) and high amplitude (about of span sagging), also swing is of horizontal oscillation. In this paper, the mechanism of conductor galloping oscillation and its different types are described. Also these oscillations are simulated on the typical span by personal computer.
Keywords: Galloping, Overhead transmission lines, Single conductors, Modeling
S. Roushanbin, M.r. Maheri and A Rangbaran,
Volume 24, Issue 1 (7-2005)
Abstract
There are a number of parameters influencing the dynamic and seismic response of bridges. Of these, two important parameters warranting special notice include: the properties of the neoperenes in the state of connection between girders and columns and the shear stiffness of underlying soil in the level of bridge substructure’s connectivity to the ground. In
this paper, the effects of these two parameters on the dynamic and seismic response of Ghadir Bridge in Isfahan are investigated. The main conclusions drawn from these investigations include: the sensitivity of the bridge’s lateral modes of vibration to the horizontal shear stiffness of the neoperenes and the substantial effects of the soil’s shear rigidity on the longitudinal modes. Based on the findings, it is recommended tha a thorough geotechnical site investigation of the soil be conducted and the properties of the underlying soil be accurately established in order to correctly identify the dynamic behaviour of a bridge.
S. A. A. Moosavian and A. Mirani,
Volume 24, Issue 2 (1-2006)
Abstract
Mobile robotic systems, which include a mobile platform with one or more manipulators, mounted at specific locations on the mobile base, are of great interest in a number of applications. In this paper, after thorough kinematic studies on the platform and manipulator motions, a systematic methodology will be presented to obtain the dynamic equations for such systems without violating the base nonholonomic constraints. Combining the kinematic model with the initial dynamic equations and eliminating Lagrange multiplier with natural orthogonal complement technique lead to the comprehensive dynamic model. The variables of this model include the path of a reference point of the base and the position and orientation of the end-effector. The proposed approach will be applied on a car-like platform and a manipulator with 5 degrees-of freedom. The calculations for deriving such a model will be implemented by a program in Maple which can be used for control design and simulation purposes. The validity of the methodology is demonstrated using a second model and comparing the elements of these two models with each other. With trajectory generation for platform and manipulator generalized coordinates separately, set points for control system design will be provided. Motion generation for the platform, which due to the nonholonomic constraint has more sensitivity, will be dealt with by two motion modes. Inverting the model in terms of joint space variables, strict control of the work space variables is accomplished. Introducing state space variables and inverting the system into first order equations, the necessary preliminaries for control system design will be provided. Based on two simulation programs in Matlab, two controllers are designed with model-based algorithm (MBA) and Transposed Jacobian (TJ) control. Simulating different external conditions such as parameter perturbation, disturbances and noise, the robotic system behavior in the vicinity of real conditions will be examined. The results obtained show the merits of the TJ algorithm in controlling highly nonlinear and complex systems with multiple degrees- of freedom (DOF), without requiring a priori knowledge of plant dynamics, and with reduced computational burden which motivates further work on this algorithm
S. Farahani and A. Assempour,
Volume 26, Issue 1 (7-2007)
Abstract
In this paper, an analytical method for noncircular shape extrusion is presented. Using this method, non-linear deformation field can be described with Hermit cubic spline which is prescribed by the boundary conditions of the die at its entryand exit. The upper bound method has been used to obtain optimum coefficient of the tangential boundary conditions. The results show that the optimum tangential parameter and the extrusion force determined by this method have good agreement with those obtained from other established methods. Also physical modeling tests show that optimum non-linear die could reduce extrusion force and strain variation compared with those in a linear die.
M. Reza Afshar, M. R. Aboutalebi, M. Isac, R.i.l. Guthrie,
Volume 28, Issue 1 (6-2009)
Abstract
In this research, a 3-D mathematical model is developed for simulating electromagnetic continuous removal of inclusions from molten metals. The model includes the computation of electromagnetic force field and fluid flow in the presence of electromagnetic forces. The results of flow field together with electromagnetic force field were further used for calculating the trajectory of inclusions in the molten metal. Parametric studies were performed to evaluate the effects of various parameters such as magnetic field intensity, inclusion size, and fluid velocity on inclusion removal efficiency in molten magnesium. In order to verify the mathematical model and visualize the trajectories of particles in the melt flow under electromagnetic force, a physical model was constructed. The predicted particle trajectories and separation in the physical model were compared with those obtained from experiments, which showed a relatively good agreement.
S. R. Hosseini, M. Barati, E. Maghsoudi,
Volume 36, Issue 1 (6-2017)
Abstract
The aim of the present research is calculation and determination of the temperature distribution in the oxy-gas source line heating process for application in the steel plates. Analytical method was used to calculate the temperature distribution by solving mathematical equations. The temperature distribution was determined with numerical method using MATLAB software. A computerized numerical control line heating apparatus was used for carrying out the processes. ITI thermograph camera was used to measure the temperature. The effect of torch distance, gas flow and torch speed on the temperature distribution at the upper and lower surfaces of plate were evaluated. The changes of temperature distribution were achieved at torch speeds of 120, 200 and 300 mm/min, gas flow of 10, 9 and 8 lit/min and torch distances of 30, 40 and 50 mm. Calculated and measured maximum temperatures reached to 900, 810 and 720 K, and 885, 785, 690 K, at torch speeds of 120, 200, 300 mm/min, respectively. The calculated and measured maximum temperatures at gas flow of 10, 9, 8 lit/min are attained to be 900, 810 and 750 K, and 885, 795 and 740 K, respectively. Maximum calculated and measured temperatures at torch distance of 30, 40 and 50 mm are accomplished to be 900, 880 and 810 K and 885, 840 and 790 K, respectively.
