@article { author = {Sharma, Sudheer and Sharma, G. C. and Jain, M.}, title = {Mathematical Modeling of the Temperature-Dependent Growth of Living Systems}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {319-328}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {In this investigation a non-equilibrium thermodynamic model of the temperature dependent biological growth of a living systems has been analyzed. The results are derived on the basis of Gompertzian growth equation. In this model, we have considered the temperature dependent growth rate and development parameter. The non-equilibrium thermodynamic model is also considered for exploring the variation of growth rate with temperature. The biological growth process of a living system near the threshold temperature has been studied. The growth rate has been taken as general function of temperature. The analytical solution has been obtained by solving differential equation governing the model. The solution of non linear equation provides an expression for biomass of the living systems at a time t, which is valid for a temperature near the threshold temperature. The numerical experiment has been conducted to exhibit the effects of various parameters on growth. The physical conditions of a living systems for different value of activated constant energy and gas, has been examined.}, keywords = {Temperature Dependent Growth,Threshold Temperature,Gompertz Growth,Non,Equilibrium Thermodynamic Model,Living Systems}, url = {https://www.ije.ir/article_71735.html}, eprint = {https://www.ije.ir/article_71735_36e502d09c937931474c5d65ea73e389.pdf} } @article { author = {Sadrnejad, S. A. and Khosroshahi, A.A.}, title = {Substructure Model for Concrete Behavior Simulation under Cyclic Multiaxial Loading}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {329-346}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {This paper proposes a framework for the constitutive model based on the semi-micromechanical aspects of plasticity, including damage progress for simulating behavior of concrete under multiaxial loading. This model is aimed to be used in plastic and fracture analysis of both regular and reinforced concrete structures, for the framework of sample plane crack approach. This model uses multilaminated framework with sub-loading surface to provide isotropic and kinematics hardening/softening in the ascending/descending branches of loading. In multilaminated framework a relation between stress/strain and yield function on planes of various orientation is defined and stress/strain path history for each plane is kept for a sequence of future analysis. Four basic stress states including compression-shear with increase/decrease in the compression/shear ratio,tension-shear and pure compression are defined and the constitutive law for each plane is derived from the most influenced combination of stress states. With using sub-loading aspect of the surface, the kinematics and isotropic hardening are applied to the model to make it capable of simulating the behavior under any stress path, such as cyclic loading in the ascending/descending branch of loading. Based on the experimental results of the literature, the model parameters are calibrated. The model results under monotonic loading and also different states of cyclic loadings such as uniaxial compression, tension, alternate compression tension, shear and triaxial compression are compared with experimental results that shows the capability of the model.}, keywords = {Concrete,Multilaminate,Microplane,Elastoplastic,FEM,Substructure,fracture}, url = {https://www.ije.ir/article_71737.html}, eprint = {https://www.ije.ir/article_71737_b07ca22332680f2df4e34d0e4dbde345.pdf} } @article { author = {Tavakkoli-Moghaddam, Reza and Seifi, M.}, title = {A New Bi-Objective Model for a Multi-Mode Resource-Constrained Project Scheduling Problem with Discounted Cash Flows and four Payment Models}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {347-360}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {The aim of a multi-mode resource-constrained project scheduling problem (MRCPSP) is to assign resource(s) with the restricted capacity to an execution mode of activities by considering relationship constraints, to achieve pre-determined objective(s). These goals vary with managers or decision makers of any organization who should determine suitable objective(s) considering organization strategies. In this paper, we present a new bi-objective model for the MRCPSP that maximizes the net present value (NPV) and minimizes the holding cost of activities completed by the projects’ completion time. For better adoption with real conditions, we consider four different payment models for positive cash flow. To verify the proposed model, a number of numerical examples are solved in small sizes and the related computational results are illustrated in terms of schedules. Finally, a meta-heuristic algorithm based on simulated annealing (SA) is utilized to solve our four payment proposed models in various sizes and the obtained results were analyzed.}, keywords = {Project scheduling,Net Present Value,resource constraint,Execution Mode,Payment Model}, url = {https://www.ije.ir/article_71740.html}, eprint = {https://www.ije.ir/article_71740_fe0721c45af802b4981d5801e47e0ca4.pdf} } @article { author = {Jenabi, M. and Torabi, S. A.}, title = {A Basic Period Approach for Solving the Economic Lot and Delivery Scheduling in Flexible Flow Lines}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {361-374}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {In this paper, the problem of lot sizing, scheduling and delivery of several items in a two-stage supply chain over a finite planning horizon is studied. Single supplier via a flexible flow line production system (FFL), produces several items and delivers them directly to an assembly facility. Based on basic period (BP) strategy, a new mixed zero-one nonlinear programming model has been developed with the objective of minimizing the average setup, inventory-holding and delivery costs per unit time in the supply chain without any stock-out. The problem is very complex and it can not be optimaly solved, especially in real-sized problems. So, an efficient hybrid genetic algorithm (HGA) has been proposed based on applying, the most applied BP approach i.e. power-of-two policy. Based on some problem instances, the solution quality of the algorithm has been evaluated and also compared with the common cycle approach. Numerical experiments demonstrate the effectiveness of the proposed HGA.}, keywords = {Flexible Flow Lines,Lot and Delivery,scheduling,Basic Period Approach,Power,of,Two Policy,Hybrid Genetic Algorithm (HGA)}, url = {https://www.ije.ir/article_71741.html}, eprint = {https://www.ije.ir/article_71741_c2dac142b2661031fcb8d0319fdc2fa9.pdf} } @article { author = {mittal, reena and Rana, U. S.}, title = {Thermal Convection of Rotating Micropolar Fluid in Hydromagnetics Saturating A Porous Medium}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {375-396}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {This paper deals with the theoretical investigation of the thermal instability of a thin layer of electrically conducting micropolar rotating fluid, heated from below in the presence of uniform vertical magnetic field in porous medium. A dispersion relation is obtained for a flat fluid layer, contained between two free boundaries using a linear stability analysis theory, and normal mode analysis method. The principle of Exchange of Stabilities (PES) is found to hold true for the micropolar fluid saturating a porous medium, heated from below in the absence of magnetic field, rotation and coupling between thermal and micropolar effects. It is also found that PES is valid in the presence of rotation and magnetic field under certain conditions. The oscillatory modes are introduced due to the presence of magnetic field and rotation, which were non-existence in their absence. The presence of coupling between thermal and micropolar effects may also introduce oscillatory modes. For the case of stationary convection, the effect of various parameters like medium permeability, rotation, magnetic field (in the presence and absence of micropolar heat conduction parameter), coupling parameter, micropolar coefficient and micropolar heat conduction parameter has been analyzed and results are depicted graphically. The sufficient conditions for the non-existence of overstability are also obtained. In this paper, an attempt is also made to apply the variational principle for the present problem and found that the said principle can be established for the present problem in the absence of coupling between spin and heat flux.}, keywords = {Thermal Convection,Medium Permeability,Rayleigh Numbers,Porous medium,Micropolar Fluids,Hydromagnetics,Rotation Effect}, url = {https://www.ije.ir/article_71743.html}, eprint = {https://www.ije.ir/article_71743_e4380b963e574c3cbbd7de969daf51a8.pdf} } @article { author = {Gandjalikhan Nassab, S.A. and Moosavi, R.}, title = {Application of the Schwarz-Christoffel Transformation in Solving Two-Dimensional Turbulent Flows in Complex Geometries}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {397-406}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {In this paper, two-dimensional turbulent flows in different and complex geometries are simulated by using an accurate grid generation method. In order to analyze the fluid flow, numerical solution of the continuity and Navier-Stokes equations are solved using CFD techniques. Considering the complexity of the physical geometry, conformal mapping is used to generate an orthogonal grid by means of the Schwarz-Christoffel transformation. The standard k-ε turbulence model is employed to simulate the mean turbulent flow field, using a linear low-Re k-ε model for near wall region. The governing equations are transformed in the computational domain and the discretized forms of these equations are obtained by the control volume method. Finite difference forms of the governing equations are solved in the computational plane and the SIMPLE algorithm is used for the pressure-velocity coupling. The important part of the present work is based on the numerical integration of Schwraz-Christoffel transformation in grid generation for simulating fluid flow in different complex geometries. To validate the computational results, the theoareticil data is compared with that of theoretical results achieved by other investigators, which are in reasonable agreement}, keywords = {Schwarz,Christoffel Transformation,Grid Generation,Turbulent Flow}, url = {https://www.ije.ir/article_71746.html}, eprint = {https://www.ije.ir/article_71746_70847b8c392dcd6e7d93736fcd0179ae.pdf} } @article { author = {Osanloo, M. and Gholamnejad, Javad and Khorram, E.}, title = {A Chance Constrained Integer Programming Model for Open Pit Long-Term Production Planning}, journal = {International Journal of Engineering}, volume = {21}, number = {4}, pages = {407-418}, year = {2008}, publisher = {Materials and Energy Research Center}, issn = {1025-2495}, eissn = {1735-9244}, doi = {}, abstract = {The mine production planning defines a sequence of block extraction to obtain the highest NPV under a number of constraints. Mathematical programming has become a widespread approach to optimize production planning, for open pit mines since the 1960s. However, the previous and existing models are found to be limited in their ability to explicitly incorporate the ore grade uncertainty into the planning process. To overcome this shortcoming, this paper presents an Integer Programming (IP) model, for long-term planning of open pit mines. This model is set up to account for grade uncertainty. The grade distribution function, in each block is used as a stochastic input, to optimize the model. The deterministic equivalent of this model is then achieved by using stochastic programming, which is a form of nonlinear in binary variables. Because of the difficulties in solving large scale nonlinear models, the model is then approximated by a linear one.This formulation will yield schedules with high chance of achieving planned production targets, while maximizes the expectation of net present value, it simultaneously minimizes the variance in function.}, keywords = {Open Pit Mine,Production Planning,Integer programming,Stochastic programming}, url = {https://www.ije.ir/article_71748.html}, eprint = {https://www.ije.ir/article_71748_cca0922d2772af7b8171a8f9abb977b2.pdf} }