@article { author = {Mehdizadeh, H. and Dickson, J. M.}, title = {Overview of Reverse Osmosis for Chemical Engineers. Part 2: Applications of Transport Models}, journal = {International Journal of Engineering}, volume = {4}, number = {3}, pages = {77-92}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {This second part of the overview of reverse osmosis investigates the ability of membrane transport models, presented in Part 1, to describe and/or predict membrane performance under different operating conditions. The problem of using the transport models to describe mixed solute systems is also discussed. The emphasis is to provide a simple, practical, and yet comprehensive summary of the most relevant information that will be needed by a chemical engineer trying to apply reverse osmosis membranes to specific applications.}, keywords = {}, url = {https://www.ije.ir/article_71044.html}, eprint = {https://www.ije.ir/article_71044_612ae57e90edc0d38a12b18041b10057.pdf} } @article { author = {Nassehi, V. and King, S.A.}, title = {Finite Element Methods for Convection Diffusion Equation}, journal = {International Journal of Engineering}, volume = {4}, number = {3}, pages = {93-100}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {This paper deals with the finite element solution of the convection diffusion equation in one and two dimensions. Two main techniques are adopted and compared. The first one includes Petrov-Galerkin based on Lagrangian tensor product elements in conjunction with streamlined upwinding. The second approach represents Bubnov/Petrov-Galerkin schemes based on a new group of exponential elements. It is shown that specially devised exponential elements can be very effective in finite element analysis of convection dominated phenomena.}, keywords = {}, url = {https://www.ije.ir/article_71045.html}, eprint = {https://www.ije.ir/article_71045_3990d9312a2a8ce09e5e9d4be13f8820.pdf} } @article { author = {Tehrani, F. T.}, title = {A Model of the Respiratory System in the Newborn Infant}, journal = {International Journal of Engineering}, volume = {4}, number = {3}, pages = {101-106}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {A dynamic mathematical model is presented which successfully simulates the respiratory control system of the newborn infant in different physiological conditions. The primary objective in constructing this model has been to provide a simulation aid in the investigation of maturation of the respiratory system, and the respiratory disorders during the newborn period, without the need for invasive measurements. The model comprises a continuous plant and a discrete controller. The controller incorporates as key elements, a non-linear multiple regression element and an energy minimization routine for the determination of ventilation and breathing frequency. The plant consists of lungs, body tissue, brain tissue, a cerebrospinal fluid compartment and central and peripheral receptors. The effect of shunt in the lungs is included in the model and the lung volume and the dead space are time varying. The effects of Hering-Breuer type reflexes are embodied to accomplish respiratory synchronization. The model is examined and simulation results of its performance for test conditions in hypoxia and hypercapnia are presented.}, keywords = {}, url = {https://www.ije.ir/article_71046.html}, eprint = {https://www.ije.ir/article_71046_fc5472b9de72313b10d4ef21714e1254.pdf} } @article { author = {Kianfar, F.}, title = {Finding the Best Coefficients in the Objective Function of a Linear Quadratic Control Problem}, journal = {International Journal of Engineering}, volume = {4}, number = {3}, pages = {107-114}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {Finding the best weights of the state variables and the control variables in the objective function of a linear-quadratic control problem is considered. The weights of these variables are considered as two diagonal matrices with appropriate size and so the objective function of the control problem becomes a function of the diagonal elements of these matrices. The optimization problem which is discussed in this paper is to minimize the objective function of the control problem as a function of these diagonal elements, when these elements are positive and the their sum in each matrix is a constant. This problem is named "the substitution between objectives in economic planning literature. In this paper, it is proved that the optimal solution of this problem is in one of the extreme points of the feasible set subject to the positive definiteness of these diagonal matrices. A method for selecting this extreme point is offered and then the unconstrained optimization problem is solved by the steepest descent method. The resulting optimal solution is the selected extreme point. Finally, the procedure is used to solve a numerical example.}, keywords = {}, url = {https://www.ije.ir/article_71047.html}, eprint = {https://www.ije.ir/article_71047_3cb79718e43b5f1084f6ada341b43a5a.pdf} } @article { author = {Yaghoubi, M. and Taheri, M. and Karimi, G. ,}, title = {A Numerical Modeling for Natural Convection Heat Transfer in Porous Media With Generated Internal Heat Sources}, journal = {International Journal of Engineering}, volume = {4}, number = {3}, pages = {115-126}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {In this paper a numerical method is used to study the unsteady state natural convection heat transfer within a confined porous media with uniform internal heat generation. The governing equations based on the Darcy model and Bossiness approximations are solved, using the finite difference Alternating Direction Implicit (ADI) method. The developed program was used to simulate natural convection heat transfer within the grain silos, where the respiration of the grains generates heat as a result of metabolism of the products. The results of the analysis show that for short periods (up to 40 days) natural convection is not the dominant heat transfer mechanism and the maximum temperature is on the centerline. In longer periods (greater than two months), fluid recirculation enhances and a cold region near the central axis of the silo is created due to natural convection}, keywords = {}, url = {https://www.ije.ir/article_71048.html}, eprint = {https://www.ije.ir/article_71048_ee61ebe6a56e07b754c217951f72c058.pdf} } @article { author = {Liaghat, G.}, title = {Analysis of the Mechanics of Preforation by Projectiles}, journal = {International Journal of Engineering}, volume = {4}, number = {3}, pages = {127-140}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {To explain the mechanics of perforation of thick metallic target plates a modified version of the analysis suggested by Awerbuch and Bodner [2] is given by a cylindrical projectile. Although the analysis retains the basic concept of the perforation process to occur in three stages as was assumed by Awerbuch and Bodner [2] a new explanation, as to the cause and effect of the compressive force is suggested. Attention is also drawn to the force required to cause internal plastic deformation of the target material, during the passage of the projectile. In addition, the mass of the target material ahead of the projectile is modified in the manner of Tate [17]. The analysis retains the initial entrance diameter to be the same as that of the projectile, at the instant the projectile hits the target and assumes that the final length of the plug is attained at the end of the process instead of at the beginning of the second stage. The computed results using the modified analysis yield better agreement with the experiments for the perforation process especially for plates whose thicknesses are between 1 and 2.5 times the projectile diameter.}, keywords = {}, url = {https://www.ije.ir/article_71049.html}, eprint = {https://www.ije.ir/article_71049_45ab671f0e663f7d85d700a10a117c96.pdf} } @article { author = {Pirouzpanah, V. and Razavi, Seyed Esmaeil}, title = {Prediction of Physical Delay Period RiDirect Injection Diesel Engine Combustion}, journal = {International Journal of Engineering}, volume = {4}, number = {3}, pages = {141-148}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {A semi-empirical mathematical model for predicting the physical part of ignition delay period in the combustion of diesel engines with swirl is developed. This model is based on a single droplet evaporation model. The governing equations, namely, equations of droplet motion, heat and mass transfer were solved simultaneously using a Runge-Kutta step by step method. The computation was executed until somewhere in the vapor layer around the liquid droplet a near stochiometric mixture of the fuel vapor and air having at least the self-ignition temperature of the fuel formed. The predicted physical delay time for a particular Dl. diesel engine is in good agreement with engine standard data and data in the literature. Also validity of the model is examined with variation of the combustion chamber and fuel injection system data. From the parametric studies it seems that the physical delay period is particularly effected by fuel initial temperature, injection pressure, swirl level, and ambient temperature. Also from examination of the results an algebric relation for quick calculation of physical delay time is derived}, keywords = {}, url = {https://www.ije.ir/article_71050.html}, eprint = {https://www.ije.ir/article_71050_6883bacef57a2ef617beca661afbd5a9.pdf} } @article { author = {Hessam, K.}, title = {Influence of Altitude Atmospheric Pressure on Octane Requirement (RESEARCH NOTE).}, journal = {International Journal of Engineering}, volume = {4}, number = {3}, pages = {149-152}, year = {1991}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {The normal specifications of motor gasolines as well as their combustion characteristics in internal combustion engines are reviewed in this paper. The effective factors influencing the fuel performance, such as the molecular structure of the fuel constituents, the operating conditions and the atmospheric pressure and temperature are also discussed. A relationship between the optimum octane number and local altitude has been formulated and plotted for a certain range of elevations. While these studies pertain only to normal compression spark-ignition engines, it is however, possible to obtain similar correlations for high compression engines by applying a different set of data}, keywords = {}, url = {https://www.ije.ir/article_71051.html}, eprint = {https://www.ije.ir/article_71051_3a94648237c11e4d95df103079f482f4.pdf} }