Showing 13 results for Hosseini
S. H. Mansouri, S. M. Hosseini Sarvari, A. Keshavarz and M. Rahnama,
Volume 16, Issue 1 (7-1997)
Abstract
In this paper, a Schwarz-Christoffel method for generating two-dimensional grids for a variety of complex internal and external flow configurations based on the numerical integration procedure of the Schwarz-Christoffel transformation has been developed by using Mathematica, which is a general purpose symbolic-numerical-graphical mathematics software. This method is highly accurate (fifth order) with mesh size, and is highly flexible for treatment of complex internal flow geometries, for a high degree of control of mesh spacing, and for generation of either orthogonal or non-orthogonal grids. In addition, this method directly generates two-dimensional incompressible potential flow solutions for internal flow, and simply or symmetrical multiply connected external flows: it generates a C type grid for a general multiply connected two-dimensional external flow. The capabilities of this method has been shown by sample cases including external flow over symmetric and antisymmetric airfoils, a car profile, and internal flows with arbitrary shapes. To facilitate further applications, a computer program using Mathematica software has been developed.
H. Izadan and S. A. Hosseini Ravandi,
Volume 19, Issue 1 (7-2000)
Abstract
In this study, a relationship between scanner response (RGB) and CIE tristimulus values (XYZ) is established by regression technique with different polynomials for colored polyester fabrics. The results showed that the transformation process is material dependent and higher order polynomials will fit the experimental data better than lower polynomials. The results also showed that the way the colors are chosen for primary calibration samples is more important than the number of samples. Using calibration samples with color characteristics closer to unknown samples leads to better results.
M.r. Bannazadeh, A. A. Bidokhti, M. Kherandish and H. F. Hosseini,
Volume 21, Issue 1 (7-2002)
Abstract
Observations of the Caspian Sea during August-September 1995 are used to develop a three-dimensional numerical model to be used in calculating temperature and current. The model has variable grid resolution and horizontal smoothing that filters out small scale vertical motion. Data from the meteorological buoy network on the Caspian Sea are combined with routine observations at first-order synoptic station around the lake to obtain hourly values of wind stress and pressure fields. The hydrodynamic model of the Caspian Sea has 6 vertical levels and a uniform horizontal grid size of 50 km. The model is driven with surface fluxes of heat and momentum derived from observed meteorological data. The model was able to reproduce all the basic features of the thermal structure in the Caspian Sea and larger-scale circulation patterns tended to be anticyclone, with anticyclone circulation within each sub-basin. The results matched observation data.
Keywords: Circulation, Temperature, Numerical model, Vorticity, wind stress
S. M. Hosseini and E. Sonei,
Volume 22, Issue 1 (7-2003)
Abstract
In this paper, Forchheimer equation is used as the constitutive equation for flow through rockfill, and the non-linear two-dimensional governing equation with free surface is solved by a new finite element method in a fixed grid. The model is verified by applying it to different flow conditions. The first scenario, which is assumed to be one-dimensional with analytical solution available for it, is used to verify the developed code. Other scenarios, which are two-dimensional free surface tests on a laboratory rockfill, are used to verify the model. The model shows satisfactory performance in this regard. For example, on average, a mean absolute relative error of about 2.3%, in terms of pressure head was found to exist between modelling results and observed values. Further capabilities of the model are discussed by simulating overflow through self– spillway rockfill dams.
Keywords: Finite element, Method, Fixed grid, Non-Darcy flow, Non-linear flow, Rock fill dam
H. Izadan, S. A. Hosseini, and M. Ashori,
Volume 22, Issue 2 (1-2004)
Abstract
In this study, colorimetric calibration of scanner has been done via perceptron neural network with three or four layers by back propagation algorithm for colored polyester fabrics. The results obtained for random training samples are not satisfactory but application of selective training samples for L*a*b* or RGB leads to good results, with better results obtained for the L*a*b* method. On the other hand, the color differences between calculation XYZ and real XYZ for unknown samples, are not only in agreement with the results of polynomials and regression methods, but are also better than the results obtained in previous studies where neural networkhad been used for colorimetric calibration of scanner.
S. A. Hosseini, G. Afkhami, A. Tabibi and A. Sadeghi,
Volume 23, Issue 1 (7-2004)
Abstract
Physical properties of cotton yarns are affected by the characteristics of cotton fibers such as fineness, length, maturity and strength. This relationship has been worked out by means of multivariable regression and stepwise method for an open-end spun (NeC 20) cotton yarn. Moreover, with the help of linear programming, it was made possible to determine the percentage of different cottons in the blend with the aim of reducing the yarn price to a minimum while keeping the yarn quality to a certain level.
S. H. Hosseini, H. Seifi, M. Parsa, M. R. Omidkhah, M. Farmad and M. Gaznavi,
Volume 24, Issue 1 (7-2005)
Abstract
Generation Expansion Planning (GEP) is one of major modules of power system planning studies, normally performed for the nex 10-30 years horizon. The current industrial practices are to find the generation requirements based on a
nodal analysis. In this way, the allocations are not determined and subequent studies are required to find the exact locations
which as decomposed from the earlier stage, may result in non-optimum solution. A new approach is proposed in this paper in which, based on dynamic programming and sensitivity factors, GEP is performed with due to consideration of transmission
system effects. In this way, the allocations of justified generation plants are also determined. The results for Iranian Power Grid for the years 2011 to 2021 are demonstracted.
R. Hosseini, M. Vaziri, and M. Bidi,
Volume 24, Issue 1 (7-2005)
Abstract
In this paper, the Radiation Transfer Equation(RTE) for a non-gray gas between two large parallel planes has been
solved and the temperature distribution obtained. With the RTE, solution heat fluxes are also determined. Since and are two components of most combustion products, the problem has been solved for these two gases. The results were, whenever possible, compared with data reported elsewhere. Since the simulation of exact absorbing bands has been used, it can be claimed to be relatively close to exact solution. From the results otained, it can be maintained that treating, the above mentioned gases as a gray gas could cause considerable errors in the determination of temperature distribution and heat fluxes. The error would be more for water vapour than for carbon dioxide.
A. Hosseini, M. Keshmiri, and M. J. Sadigh,
Volume 26, Issue 1 (7-2007)
Abstract
The optimal path planning of cooperative manipulators is studied in the present research. Optimal Control Theory is employed to calculate the optimal path of each joint choosing an appropriate index of the system to be minimized and taking the kinematics equations as the constraints. The formulation has been derived using Pontryagin Minimum Principle and results in a Two Point Boundary Value Problem, (TPBVP). The problem is solved for a cooperative manipulator system consisting of two 3-DOF serial robots.
M.s. Hosseini, M. Ameri and S.m. Fagheih,
Volume 27, Issue 2 (1-2009)
Abstract
Among the adaptive-grid methods, redistribution and embedding techniques have been the focus of more attention by researchers. Simultaneous or combined adaptive techniques have also been used. This paper describes a combination of adaptive-grid embedding and redistribution methods on semi-structured grids for two-dimensional invisid flows. Since the grid is semi-structured, it is possible to use different algorithms for combining adaptive-grid embedding and redistribution methods. To
evaluate the accuracy and efficiency of the method, this combination is used to solve two model problems, transonic and supersonic inviscid flows in channels with circular arc bump. The results show that combination of adaptive-grid embedding and redistribution methods on semi-structured grids remarkably increases the accuracy at the cost of a slight increase in computational time in comparison with the embedding method alone.
L. Saidi, M. Sheikhzadeh, S.a. Hosseini Ravandi, and K. Matin,
Volume 27, Issue 2 (1-2009)
Abstract
Stretchable woven chute is a safe device for falling humans from multi-story buildings in emergencies. During the fall, the elastomeric property of the fabric, in the weft direction, causes radial forces towards the human body inside .These radial forces lead to frictional forces between the chute and the body. The falling man can reduce the falling speed by exerting outward forces via stretching and contracting arms or legs. In this research, a model is developed to analyze the different forces involved in the fall based on the so-called thin sheet tank fall relations. The model is capable of determining body characteristics with respect to the real model. Finally, real-world model predictions have been made in which the effects of body weight and dimensions have been considered of.
K. Tourani, . R. Mahboubi, E. Seyedi Hosseininia,
Volume 35, Issue 1 (9-2016)
Abstract
Although a significant portion of conditions encountered in geotechnical engineering, for investigating engineering behavior of soil, involves unsaturated soils; the traditional analysis and design approach has been to assume the limiting conditions of soils being either completely dry or completely saturated. In unsaturated soils the capillary force produce attractive forces between particles. Discrete Element Method (DEM) is an appropriate tool to consider the capillary effects. The calculations performed in DEM is based on iterative application of Newton’s second law to the particles and force-displacement law at the contacts. In the present study, the behavior of unsaturated soils in pendular regime is simulated utilizing DEM. Triaxial compression tests were modeled as two-dimensional, considering capillary force effects. Finally, capillary effects on Macro parameters of a simulated granular soil (stress, axial strain, volumetric strain and void ratio) and Mohr Coulomb failure criteria parameters were studied.
R. Zardashti, S. A. Saadatdar Arani , S. M. Hosseini,
Volume 41, Issue 1 (9-2022)
Abstract
In this paper, a robust optimization method is developed to solve the Satellite Launch Vehicle (SLV) trajectory design problem in the presence of uncertainties using a powerful Particle Swarm Optimization (PSO) algorithm. Given the uncertainties such as uncertainties in the actual values of aerodynamic coefficients, engine thrust, and mass in the ascent phase of a SLV, it is important to achieve an optimal trajectory that is robust to these uncertainties; because it improves the flight performance, reduces the workload of the guidance-control system, and increases the reliability of the satellite. For this purpose, first the optimization problem is considered by using the criterion of minimizing the flight time of the SLV as a cost function, and three-dimensional equations of motion as constraints governing the problem. Then, by adding the mean parameters and the standard deviation of uncertainties in the cost function, a robust optimizer model is developed and the algorithm is used to numerically optimize the model. Monte Carlo's perspective has also been used to analyze the results of uncertainties and their continuous feedback to the optimization model. Finally, the optimal trajectory is obtained that is robust to the uncertainties. The resulting simulation results show the accuracy of this claim.
