Journal of Computational Methods In Engineering
http://jcme.iut.ac.ir
Computational Methods in Engineering - Journal articles for year 2009, Volume 27, Number 2Yektaweb Collection - http://www.yektaweb.comen2009/1/12A Novel Method for Impedance Calculation of Distance Relays Using Third Order Interpolation
http://jcme.iut.ac.ir/browse.php?a_id=448&sid=1&slc_lang=en
All algorithms for impedance calculation use an analog-to-digital converter. The high accuracy of the impedance seen by a distance relay is an important factor in the correct isolation of the faulty part of power systems. To achieve this, a novel
technique based on third order interpolation is used in this paper. According to this technique, the times and the values of the obtained samples are changed to real ones. To evaluate the new technique, it is applied to six digital distance algorithms, namely, Discrete Fourier Transform (DFT), Half-cycle Discrete Fourier Transform, Least Square, Mann-Morrison, Least Square with Delete Dc, and Prodar70. The technique is found to be capable of accurately computing the impedance in the algorithms mentioned. Comparisons are made among the results to show the efficiency of the new technique for decreasing errors in all algorithms.
H.A. AbyanehA New Inventory Model for Deteriorating Items with Price-dependent Demand, Time-value of money, and Shortages
http://jcme.iut.ac.ir/browse.php?a_id=449&sid=1&slc_lang=en
This paper presents a discounted cash-flow approach to an inventory model for deteriorating items with the
two-parameter Weibull distribution. According to our proposed model, two shortages are considered: back-orders and lost-sales,
in which the back-order rate is a varying function of the time when the shortage happens. In general, the demand rate is a linear function of the selling price. The objective of this model is to determine the optimal pricing policy and the optimal throughput time in such a way that the total net present value of profits is maximized in the given planning horizon. Finally, a numerical example is provided to solve the model presented using our proposed three-stage approach.
M. RabbaniApplication of Fuzzy Decision-Making to Facility Layout Planning
http://jcme.iut.ac.ir/browse.php?a_id=450&sid=1&slc_lang=en
This research proposes a vigorous methodology based on the fuzzy set theory to improve the facility layout process. Using natural language, the fuzzy set theory is an appropriate tool for controlling complex systems such as facility planning. The closeness rating between departments in a plant depends on qualitative and quantitative factors. Some of these factors may have a greater effect on the closeness rating. Thus, analytical hierarchy process (AHP) is used to find the weight of these factors. In this paper, a computer program, called FDARC, is developed to generate quantitative activity relationship charts. These charts are used by FLAYOUT to develop the layouts. The procedure is compared with two other recent methods. Computational results are used to demonstrate the effectiveness and efficiency of the method proposed.
H.R. KhazakiNet Present Value of Cash Flows in Single Machine and Flow Shop Scheduling Problems
http://jcme.iut.ac.ir/browse.php?a_id=451&sid=1&slc_lang=en
While a great portion of the scheduling literature focuses on time-based criteria, the most important goal of management is maximizing the profitability of the firm. In this paper, the net preset value criterion is studied taking account of linear time-dependent cash flows in single machine and flow shop scheduling problems. First, a heuristic method is presented for the single machine scheduling problem with NPV criterion. Second, the permutation flow shop scheduling problem is studied with NPV criterion. An efficient Branch & Bound algorithm is accordingly presented using strong lower and upper bounds and dominace rules which are expanded for this problem. Finally, three heuristic methods are presented and compared to find
appropriate solutions over short periods. By generating random problems of different sizes, it has been shown that the Branch & Bound method is efficient in solving small and medium sized problems, and also that the presented heuristic algorithm is efficient in tackling problems of any size.
G. Moslehi and M. MahnamCoordinating Orders in Three-echelon Supply Chain using price adjustment mechanism
http://jcme.iut.ac.ir/browse.php?a_id=452&sid=1&slc_lang=en
Supply chain coordination has become a critical success factor for supply chain management (SCM). In the past few years, the researchers have widely emphasized that cooperation among supply chain (SC) firms is a key source of competitive advantage. This paper is focused on supply chain coordination from the perspective of inventory management. Li and Liu [1] developed a model for illustrating how to use quantity discount policy by price adjustment mechanism to achieve supply chain coordination. We extend this mechanism to three echelon supply chain and consider variable lead time which has more
representation of the real world situation. For this purpose, we will develop a model with benefit objective function for the problem. We will then analyze the model with and without coordination. By solving the proposed model, proper order quantities will be obtained. Finally, the advantages of the proposed mechanism will be explored and a surplus benefit dividing method will be designed.
A. ArkanEffects of Transverse and Longitudinal Steel Ratios and Shear Span on the Behavior of RC Beams under Shear Using Modified Compression Field Theory
http://jcme.iut.ac.ir/browse.php?a_id=453&sid=1&slc_lang=en
Although studies on RC beams under shear have a history record of more than 100 years, many important
issues in this context still remain that have evaded attention. The aim of the current study is to study a number of these less investigated aspects of the behavior of RC beams under shear. For this purpose, and based on the modified compression field theory, a computer program has been written to study the effects of transverse and longitudinal steel reinforcement and shear span, a/d, on the behavior of RC beams under shear. The results show that the shear capacity of the beam cannot be increased beyond an optimum amount of transverse steel ratio. This paper will try to provide a precise definition of this optimum transverse steel ratio. Another finding of the present study is that increasing tensile longitudinal steel ratio increases the amount of the optimum transverse steel ratio, while increasing a/d decreases the optimum transverse steel ratio.
D. Mostofinejad and M. NoormohamadiModified Fixed Grid Finite Element Method in the Analysis of 2D Linear Elastic Problems
http://jcme.iut.ac.ir/browse.php?a_id=454&sid=1&slc_lang=en
In this paper, a modification on the fixed grid finite element method is presented and used in the solution of 2D linear elastic problems. This method uses non-boundary-fitted meshes for the numerical solution of partial differential equations. Special techniques are required to apply boundary conditions on the intersection of domain boundaries and non-boundary-fitted elements. Hence, a new method is also presented for the computation of stiffness matrix of boundary intersecting elements and boundary conditions of higher accuracy are applied. In order to examine the applicability of the proposed method, some
numerical examples are solved and the results are compared with those obtaioned from both fixed grid finite element and standard finite element methods.
F. DaneshmandCombination of Adaptive-Grid Embedding and Redistribution Methods on Semi Structured Grids for two-dimensional invisid flows
http://jcme.iut.ac.ir/browse.php?a_id=455&sid=1&slc_lang=en
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.
M.S. HosseiniStudy of Reinforced Slopes Safety Factor Using the Inclined Slices Method
http://jcme.iut.ac.ir/browse.php?a_id=456&sid=1&slc_lang=en
Stability of reinforced slopes is almost always carried out using limit equilibrium methods and controlled by the shear strengths of the slope materials and the extension force of reinforcements. According to limit equilibrium methods, the stability of slopes is assessed by dividing the whole failure wedge into several vertical elements. In order to determine the safety
factor of the reinforced slopes, a new approach is proposed based on the inclined slices method. According to this approach, a 4n formulation is introduced which uses fewer unknowns and a simpler formulation to calculate the extension forces of reinforcements and safety factors of the slopes. Additionally, moment and forces equilibrium in all slices are taken into account while the tensile force of each reinforcing element is independently calculated. Comparisons revealed differences at 5 to 10 percent level between analytical results obtained from this method and those of ReSSA software.
S. ShekarianModeling the Vertical Falling Life Chute
http://jcme.iut.ac.ir/browse.php?a_id=457&sid=1&slc_lang=en
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. L. SaidiProduction of Titanium Carbide via Mechanochemical Process
http://jcme.iut.ac.ir/browse.php?a_id=458&sid=1&slc_lang=en
N. SetoudehIntermix Modeling of Grade Change Operations in Steel Slab Continuous Casting Process
http://jcme.iut.ac.ir/browse.php?a_id=459&sid=1&slc_lang=en
M. AlizadehProduction of A356/SiCp Composite using EPS/SiCp/CMC Mortar
http://jcme.iut.ac.ir/browse.php?a_id=460&sid=1&slc_lang=en
S. SookhtehsaraeeAnnealing Effects on Microstructure and Microwave Properties of CuO-Doped (Zr0.8Sn0.2)TiO4
http://jcme.iut.ac.ir/browse.php?a_id=461&sid=1&slc_lang=en
S. VahabzadehEffects of Substrate Solution pH, Incubation Temperature, and Calcination Temperature on Bacterial Synthesis of Nano-Crystalline Hydroxyapatite
http://jcme.iut.ac.ir/browse.php?a_id=462&sid=1&slc_lang=en
B. Mostaghaci