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Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Title: 
Author(s): 

Journal: 

امیرکبیر

Issue Info: 
  • Year: 

    0
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    -
Measures: 
  • Citations: 

    0
  • Views: 

    1053
  • Downloads: 

    0
Keywords: 
Abstract: 

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Title: 
Author(s): 

Journal: 

امیرکبیر

Issue Info: 
  • Year: 

    0
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    -
Measures: 
  • Citations: 

    0
  • Views: 

    1368
  • Downloads: 

    0
Keywords: 
Abstract: 

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Journal: 

امیرکبیر

Issue Info: 
  • Year: 

    1381
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    491-498
Measures: 
  • Citations: 

    0
  • Views: 

    462
  • Downloads: 

    0
Keywords: 
Abstract: 

مناسب ترین روش برای مطالعات حالات گذرای سیم پیچ ترانسفورماتور استفاده از مدل مشروح (Detailed) است. مدل مشروح اثرات سلفی حلقه ها، اثرات خازنی بین حلقه ها و تلفات در هادیها و عایق سیم پیچ را به صورت المانهای فشرده در نظر می گیرد. تلفات این مدل در میرائی نوسانات حالت های گذرا نقش بسیار بسزایی دارد و در واقع دامنه اضافه ولتاژها را تعیین می کنند. بنابراین لازم است که این پارامتر وابسته به فرکانس با دقت بیشتری مدل شود. در این مقاله تلفات ناشی از جریانهای گردابی در هادیهای سیم پیچ به کمک ماتریس تلفات ارائه می گردد. ابتدا عناصر این ماتریس در فرکانس پایین به کمک روش اجزا محدود (FEM) محاسبه شده و سپس به فرکانس های بالا تعیم داده می شوند. عناصر این ماتریس از جنس مقاومت بوده و پدیده های همجواری و پوسته را در بر می گیرند. مقایسه نتایج به دست آمده از محاسبات مستقیم و محاسبات بر مبنای روش پیشنهادی نشان می دهند که روش ارائه شده از تقریب خوبی جهت تعمیم فرکانس بالای ماتریس تلفات برخوردار است.

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Author(s): 

KHALOU A.R. | TARIVERDILOU S.

Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    105-115
Measures: 
  • Citations: 

    0
  • Views: 

    197
  • Downloads: 

    0
Abstract: 

This paper studies the possibility of localizations for frame structures in static and dynamic analysis. A finite element model is used in which the sections resisting force is calculated using an introduced differential hysteretic model. A microplane constitutive law for concrete and bi-linear elasto-plastic material model for reinforcements evaluates parameters of the differential hysteretic model in sections. The sensitivity to probable changes in ground motion characteristics is assessed by a nonstationary ground motion generation process to obtain excitations with approximately the same amplitude and frequency content evolution as those of a base ground motion. The procedure is applied in two case studies and possibility of localization in response is investigated. A measure for the probability of occurrence of this behavior in code-designed structures is obtained. This study indicates that localization and resulting early collapse of structure is possible. It is concluded that some modifications in design code provisions are required.

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Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    319-330
Measures: 
  • Citations: 

    0
  • Views: 

    1475
  • Downloads: 

    0
Abstract: 

Neural Networks (NNs) are one of the meta-heuristics methods to solve complex problems. NNs have been able to solve combinatorial optimization problems in many cases successfully. Quadratic Assignment Problem (QAP) is an NP-hard combinatorial optimization problem. Some of QAP applications are: layout design, keyboard design, VLSI design and etc. Many approaches, so far, have been used to solve this kind of problems and one of them is NNs approach. In this study we suggest an algorithm based on Mean Field Theory (MFT), a kind of NNs with patts neurons. Computational results indicate that this algorithm produces better solutions in comparison with two previous NNs algorithms.

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Author(s): 

HAERI S.M. | KHAVAS M.H. | NASR M.

Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    331-338
Measures: 
  • Citations: 

    0
  • Views: 

    3788
  • Downloads: 

    0
Abstract: 

Filter in earth and rock fill dams are very important elements in controlling the safety against piping affine materials. Therefore, design and construction of filters are very important. According to the literature, very little research has been done on design of filters for cores of gap graded material. Thus in this research we have concentrated on such material to find a criteria for design of filters for earth and rock fill dams of gap graded core material. In this investigation 207 No Erosion Filter (NEF) tests were performed on four types of soils with 15-50% fine conrent as base soil and clean sands as filter. Three types of materials have been selected for filters such as very uniform filters (C=2.5), well graded filters (C=11 -14) and boundary condition (C=5-6). Tests were performed under very high hydraulic gradient of 400-600. The NEF tests resulted in a criteria for design of filters for such material. also 99 permeability tests were conducted on sandy filters and relationship was suggested for design purposes.

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Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    339-351
Measures: 
  • Citations: 

    1
  • Views: 

    699
  • Downloads: 

    0
Abstract: 

In this paper, analysis of column base plates have been done by using the methods of contact problem. The result of this analysis on different Specimens, have been compared with the results of current method with is done by presuming uniform stress under plate.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    352-360
Measures: 
  • Citations: 

    0
  • Views: 

    2457
  • Downloads: 

    0
Abstract: 

Capacity Requirements Planning (CRP) model is applied to control the output plant of Material Requirements Planning (MRP) model. These models have deeply investigated in deterministic circumstances. However there are a few models for uncertain conditions. This paper develops a CRP model for a probabilistic case. The case is an overhaul center in which the repairing aredone on the disassembled parts. The case is an overhaul center in which the repairing operations are done on the disassembled parts. The disassembled parts may he in one of three situations: workable, repairable and salvage. Therefore the classic CRP model cannot be used to check the required capacity. EXplaining the algorithm of classic CRP model, the paper expands its concept to develop a special CRP model. Using an example, the capability of new model is indicated.

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Author(s): 

ASGHARPOUR M.J. | GHASEMI K.

Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    361-381
Measures: 
  • Citations: 

    0
  • Views: 

    1521
  • Downloads: 

    0
Abstract: 

Permutation method is one of the MADM techniques. This method can find and determine the best linear ordering of the alternatives on the basis of maximizing a test called "T" test. Unfortunately, to reach the final result by PM, needs tremendous amount of CPU-time and increases exponentially as the number of the alternatives increases. Therefore it can be categorized as NP-Hard. There are many heuristic methods in literatures which try to find local solutions of the permutation method. The following new combination method applies to optimization conditions during the calculating process (by defining two main rules). It reduces the searching space continuously and computes the final global optimal solutions with respect to value functions properties. The new combination method is about 120,000 times faster than permutation method with the same conditions and 10 alternatives and based on empirical data. Combination method can be developed for other linear ordering problems such as traveling salesman, one machine or one job scheduling and preferential voting system.

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Author(s): 

VAHIDI B. | MOHAMMADZADEH A.

Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    382-390
Measures: 
  • Citations: 

    0
  • Views: 

    800
  • Downloads: 

    0
Abstract: 

The main aim of this paper is analyzing design of guard electrodes of high voltage insulators chain. These electrodes are used for making the distribution of uniform potential across the insulators chain, reducing leakage current and preventing the degradation of insulators. if the design is not corrector in the case of insulators chain without guard electrodes, the potential distribution will not uniform. Thus the voltage drops on the insulators adjacent to conductors will be more than maximum voltage that can be tolerated by the insulators. Therefore these voltage drops can damage the insulators. In this paper A new method is introduced for analyzing and design of gurad electrodes of high voltage insulators chain.

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Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    391-397
Measures: 
  • Citations: 

    0
  • Views: 

    875
  • Downloads: 

    0
Abstract: 

This paper discusses a fuzzy variance analysis model with interaction between explanatory variables using Tanakas model. Based on Tanakas model, a linear programming model has been formulated for measuring the value of response factors. This model measures both values of the response factors, as well as their interactions.

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Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    398-412
Measures: 
  • Citations: 

    0
  • Views: 

    1069
  • Downloads: 

    0
Abstract: 

BP algorithm has been used for wide range of applications. One of the most important limitations of this algorithm, is the low rate of convergence. The important reason behind this, is the saturation property of its activation functions. Once the output of a unit lies in the saturation area, the corresponding decent gradient would take a very small value. This will result in very little progress in the weight adjustment, if one takes affixed small learning rate parameter. To avoid this undesired phenomenon, one may consider a relative large learning rate. Unfortunately this would be dangerous, because it may take the algorithm diverges especially when the weight adjustment happens to fall into the surface regions with a large steepness. So, we require algorithms capable of tuning dynamically learning rate according to changes of gradient values. In this paper, different methos of dynamic changing of learning rate has been considered. Variable Learning Rate (VLR) algorithm and learning automata based learning rate adaptation algorithms are considered and compared with each other. Because the VLR parameters have important influence in its performance, so we use learning automata for adjusting them. In the proposed algorithm called Adaptive Variable Learning Rate (AVLR) algorithm, VLR parameters are adapted dynamically by learning automata according to error changes. Simulation results on various problems highlight better the merit of the proposed AVLR.

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Author(s): 

GHAZANFARI M. | AHMADVAND A.

Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    413-425
Measures: 
  • Citations: 

    0
  • Views: 

    993
  • Downloads: 

    0
Abstract: 

This paper investigates to extend the Material Requirements Planning (MRP) model for situations in which lead times for procurement the raw materials and for operations on parts are fuzzy. Reviewing the classical MRP, we address the main weaknesses of MRP in crisp conditions. The MRP models developed in uncertainty situations are also reviewed. Finally, a fuzzy MRP model is developed using fuzzy lead times. Considering an example, the proposed model is described.

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Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    426-438
Measures: 
  • Citations: 

    0
  • Views: 

    1041
  • Downloads: 

    0
Abstract: 

A sloding mode controller may be employed to improve the perfromance in response to variations an induction motor mechanical porameters and load torque. In this paper, a new sliding @ mode controller is propased for an jndirect-vector controlled induction motor in which high frequency switching problem is avoided and sliding variables are reduced. A fuzzy controller in employed to adaptively enhance convergence speed. Test studies shows the acceptable. performance the proposed algorithm.

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Author(s): 

MADADY A. | SHAFIEE M.

Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    439-452
Measures: 
  • Citations: 

    1
  • Views: 

    1010
  • Downloads: 

    0
Abstract: 

In this paper an adaptive algorithm based on I-D representation of 2-D systems(Wave Advanced Model) is presented for estimating the parameters of 2-D systems in state-space form. The convergence (stability) of the algorithm is analyzed using the lyaponov approach and also its asymptotic stability conditions are derived in terms of the system properties (locally controllability) and the generality of system input (persistent excitation conditions). The effectiveness of proposed procedure is illustrated by simulation.

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Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    453-466
Measures: 
  • Citations: 

    0
  • Views: 

    1375
  • Downloads: 

    0
Abstract: 

Rock abutments of arch dam consist of jointed rock mass whose strength is based on strike, dip, spacing and behavior of rock joints. Behavior of rock joints depends on spacing, friction, wall strength of joint, joint filling amount and water pressure. Abutments are the most important and sensitive parts of arch dam sites. In fact the stability of dam depends directly on the stability of it:" abutments. Therefore in this research jointed rock mass of abutment is modeled by using a multilaminate model. The stability of abutment is studied in diffrent cases of bedding and joint sets. The constitutive model for joint sets is a nonlinear viscoplastic lnaterial. The multilaminate model is based on an equivalent material approach and is obtained hy integrating of mechanical response of intact rock and joints. It is capable of modeling sliding/opening/ closing of multiple joint sets in the rock mass and any yield function of joint can be incorporated in it. Here we take use of this model for predicting the sliding in abutments of dam under hydrostatic force, rock weight and uplift loads using Bartons criterion.

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Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    467-474
Measures: 
  • Citations: 

    0
  • Views: 

    1004
  • Downloads: 

    0
Abstract: 

One of important problems in interconnected power systems is the proper co-ordination of relays. Also one of the most important part of a co-ordination program is break point de- termination based on graph theory [1, 2, 3]. These methods consider system configurations only, however many other parameters in- flouence break points. Expert persons can realize how these parameters affect the break points. In this paper a comprehensive analysis for specification of effective parameter such as type of protective relays, short circuit levels, number of relays related to each other etc is taken into account. A computer program based on an expert system has been dveloped. The program has been tested on some power system examples and the results were com- pared with graph theory method.

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Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    475-490
Measures: 
  • Citations: 

    2
  • Views: 

    1542
  • Downloads: 

    0
Abstract: 

Mathematical analysis is one of the methods to evaluate inventory system, in this approach, we should make a mathematical model for the system then study the properties of the model. Because it is impossible to represent the real world entirely, some approximations and assumptions are necessary when building the mathematical model. This paper develops a model for two-echelon inventory control structure with stochastic demand and constant lead time. This model actually determines the optimal policy (Q,r) for each ware house. An recursive algorithm has been designed to solve the model. Also it considers emergency transshipments between local warehouses to reduce the holding and shortage costs of total system in manner of using the extra inventory of warehouses for those warehouses encountering the shortage. A numerical analysis has been done for, the model.

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Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    491-498
Measures: 
  • Citations: 

    0
  • Views: 

    233
  • Downloads: 

    0
Abstract: 

The known measuring techniques are difficult to apply for determining the power loss of transformer windings at high frequencies. None of them can be used to obtain the distribution of the power loss among and within the layers or discs. Analytical methods use simplification on the geometry of problems, therefore applicable in special cases. In this paper a finite element technique is introduced for calculating the ac losses of disc windings at high frequencies. This includes a method to calculate the ac resistance of windings which not only applicable for any winding with arbitrary shape of conductors, but also gives more accurate answers than analytical methods.

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Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    491-498
Measures: 
  • Citations: 

    0
  • Views: 

    231
  • Downloads: 

    0
Keywords: 
Abstract: 

One of the most suitable models for studing the electromagnetic transient behavior of the high voltage winding of the power transformers is the detailed model. This model consists of inductive and capacitive effects as well as the eddy current and dielectric losses in the form of lumped parameters. The losses have significant effects on the damping of transient over voltages. In this paper, the eddy current losses are expressed by a matrix which its elements satisfy the proximity effects and skin effects precisely. The matrix is calculated at low frequency by the finite element method (FEM) and then generalized to the high frequencies. simulation are presented for illustration and validation.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

View 231

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesDownload 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesCitation 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesRefrence 0
Author(s): 

AFANDIZADEH S. | AFUNIAN M.R.

Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    499-511
Measures: 
  • Citations: 

    1
  • Views: 

    1440
  • Downloads: 

    0
Keywords: 
Abstract: 

urban bus route network design involves determining a route configuration with a set of transit routes and associated frequencies that archives the desired objective. This can be formulated as an optimization problem of minimizing the overall cost (both the users and the operators) incurred. In this paper, the use of genetic algorithms (Gas), a search and optimization method based on natural genetics and selection, in solving the route network design problem is reported. The design is done in two phases. First, a set of candidate routes competing for the optimum solution is generated. Second, the optimum set is selected using a GA. This method assumes a solution route set size, and tries to find that many best routes from the candidate route set, using a GA. The routes set size is varied interactively to find the optimum solution. The model is applied to a case study network, and results are presented.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

View 1440

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesDownload 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesCitation 1 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesRefrence 0
Journal: 

AMIRKABIR

Issue Info: 
  • Year: 

    2002
  • Volume: 

    13
  • Issue: 

    51
  • Pages: 

    511-524
Measures: 
  • Citations: 

    0
  • Views: 

    1793
  • Downloads: 

    0
Abstract: 

In the past decade, there is some concern as to how systems of the style of MRP can be integrated and the adequacy of such systems compared with alternative philosophies such as Just In Time (JIT) and proprietary techniques such as Optimized Production Technology (Fox 1985).Question are being raised regarding the effectiveness of MRP, as managers see the extent of the effort required to implement such systems and the all too frequent failure to realize the promised benefits.In this article, the starting and finishing time of production for the batch of each item has been determined, based on the Theory Of Constraints rules. In this regard, the capacity limitation of facilities have also been considered. Then a mathematical model for the integration of material requirement planning and theory of constraint have been developed.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

View 1793

مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesDownload 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesCitation 0 مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic ResourcesRefrence 0
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