
محمدرضا
میبدی
author
حمید
بیگی
author
text
article
2001
per
The goal of neural network engineering (NNE) is to study the advantages and disadvantages of neural networks and also providing methods to increase their performance. One of the problems in NNE is determination of optimal topology of neural networks for solving a given problem. There is no method to determine the optimal topology of multilayer neural networks for a given problem. Usually, the designer selects a
topology for neural networks and then trains it. The selected topology remains fixed during the training period. The performance of neural network depends on its size(number of hidden layers and hidden units). Determination of the optimal topology of neural network is an intractable problem. Therefore, most of
algorithms for determination of the
topology of neural ne1twork are
approximate algorithms. These algorithms
could be classified into five main groups: pruning algorithms, constructive algorithms, hybrid algorithms, evolutionary algorithms, and learning automata based algorithms. The only learning automata(LA) based algorithms, called survival algorithm, has been proposed by Beigy and Meybodi. This algorithm uses an object migrating learning automata and error backpropagation (BP) algorithm and determines the number of hidden units of
three layers neural networks, as training proceeds. In this paper, we propose three
algorithms which are based on LA and BP. These algorithms determine a near optimal topology with low time complexity and high generalization capability for a given training set. These algorithms: have two parts: determination of number of hidden units and determination of the number of
hidden weights. One of the proposed algorithms uses the survival algorithm to determine the number of hidden units. A new algorithm based on LA is proposed to determine the number of hidden weights. This algorithm deletes weights with small effect, which leads to lower time complexity and higher generalization rate. Two other algorithms do not omit the hidden units explicitly; a hidden unit is omitted when all its input weights are deleted. Most of the reported algorithms in the literature for determination of topology of neural networks use hillclimbing method and may stuck at local minima.
The proposed algorithms use global search
method which results in increasing the probability of escaping from local minima. The proposed algorithms have been tested on several problems such as: recognition of Farsi and English digits. Simulation results show that the produced networks have good performance. The proposed algorithms are compared with Karnin pruning algorithm.
University College of Engineering
دانشکده فنی
08031026
34
v.
4
no.
2001
https://jfe.ut.ac.ir/article_15244_9c080f4a4484402bfabcd873e9e985f4.pdf

پیمان
بدیعی
author
text
article
2001
per
In this paper the effects of grains on near shore hydrodynamic processes are studied by applying physical models. The experiments were conducted in a wave basin with fixed bed. Both regular and irregular waves were used in the tests. Wave induced currents were measured using bidirectional electromagnetic current meters and waves heights were measured using capacitance wave height meters. Twelve tests were conducted on straight beach with no grains and a single grain. The wave height and current patterns are discussed. The significance of wavecurrent interaction in the near shore region was shown in the results of
the experiments, especially in the presence of grains. The data provided by
this series of tests could be applied to the calibration and verification of two and three dimensional numerical models.
University College of Engineering
دانشکده فنی
08031026
34
v.
4
no.
2001
https://jfe.ut.ac.ir/article_15245_a349bdcbaa20c561e127141409781a36.pdf

امیر
تائبی
author
مجید
وشتانی
author
text
article
2001
per
University College of Engineering
دانشکده فنی
08031026
34
v.
4
no.
2001
https://jfe.ut.ac.ir/article_15246_014c777e1720396c08cdd1a10187567b.pdf

علی اصغر
میرقاسمی
author
سید رضا موسوی
نیک
author
احمدرضا محبوبی
اردکانی
author
text
article
2001
per
Using OEM (Discrete Element Method), a model is presented for simulation of breakage of twodimensional polygonshaped particles. In this model, shapes of the particles generated after breakage are predefined and each uniform (uncracked) particle is replaced with some smaller interconnected subparticles.
If the bond between these subparticles break, breakage will happen.
With the help of this model, it is possible to study the influence of particle
breakage on internal angle of friction and deformability of granular materials. For this purpose, two series of biaxial test simulations (breakage is enabled and
disabled) are conducted on assemblies of twodimensional polygonshaped particles with different confining pressures and the results are compared. It was found that the
simulation results are in good agreement with observations obtained from experimental tests.
University College of Engineering
دانشکده فنی
08031026
34
v.
4
no.
2001
https://jfe.ut.ac.ir/article_15247_77652670ed262f2ac009a9075c82e428.pdf

حسین
بهمنیار
author
محمدعلی
موسویان
author
محمد قنادی
مراغه
author
حسین
ابوالقاسمی
author
محمدعلی
سائلی
author
text
article
2001
per
University College of Engineering
دانشکده فنی
08031026
34
v.
4
no.
2001
https://jfe.ut.ac.ir/article_15248_0dd41aa9150eb06d1da3b977b8079476.pdf

سید محمد
قریشی
author
غضنفر
احسانیان
author
text
article
2001
per
In this study, the environmental condition of the Zayandehrood river was theoretically and experimentally investigated. Therefore, a dynamic mathematical model with multiple pollution sources was formulated to predict the: parameters such as BOD, DO, and temperature of water in the different locations of the river. Also, the water samples were collected from 120 kilometers of the river starting from the south Isfahan municipal wastewater
treatment plant and the BOD, DO, and
temperature of the samples were:: measured in the four seasons of the year 1377. The comparison of the obtained experimental data with the results of computer simulation revealed the extent of accuracy of the model. Using the mathematical simulation, it is possible to predict the Zayandehrood river environmental conditions in future with respect to industrial development and yearly rainfall. Thus by utilizing the model's theoretical results, one is able to make the proper decisions in order to achieve a sustainable development in the Isfahan province.
University College of Engineering
دانشکده فنی
08031026
34
v.
4
no.
2001
https://jfe.ut.ac.ir/article_15249_b798ad860d32bd5bd2d631b93481e76e.pdf

محمدعلی
موسویان
author
حسین
بهمنیار
author
پریسا
خدیوپارسی
author
text
article
2001
per
In order to investigate the effects of
drop size and its falling distance on dropinterface coalescence time, the socalled coalescence cell had been designed and built. The selected chemical materials were as follows: WaterToluene, Waternormal Heptane and 60% aqueous Glycerol Toluene. In all experiments, the oil phase was as continuous phase. Before each run, the two immiscible phases were mutually saturated by mixing and then, separated from each other. It was indicated
that, the increasing of drop diameter or
drop falling distance increases dropinterface coalescence time, separately.
These factors also cause the subsidence of
multistep coalescence phenomena in water Toluene system, which has usually occurred severely. Added to these, the vertical or horizontal fluctuations of drop on interface, causes the delaytion of drop coalescence.
University College of Engineering
دانشکده فنی
08031026
34
v.
4
no.
2001
https://jfe.ut.ac.ir/article_15250_408b56fe95edbec5fe9053d119ee4c8c.pdf

رمضانعلی مهدوی
نژاد
author
امیر
عبدالله
author
text
article
2001
per
Carbides are new ceramic materials which are growingly used as substitute for metals in modem technology. Among these, silicon carbides is more under attention. Machining of this material is very difficult due to its high hardness and resistance to wear. Among traditional
methods, grinding is the most effective one. Nonetheless, specific and expensive wheels, limits on technology parameters and shapes and low machining rate: are
still problems. Electrodischarge machining is the best nonconventional method but it shows high instability and tendency to arcing compared with
machining of steels. This paper aims to
investigate the causes and possible guidelines for instability reduction or elimination. When machining silicon carbide under different pulsetimes and number of transistors, experimental results show that, arc discharges have the
highest percentage of 60 among the other
pulse types. Open circuit pulses have the least percentage of 20 and normal discharges percentage is close to open circuit value. SEM pictures show existence of pure silicon on the machined surface which can cause instability due to
its high electrical resistance. Heat
generation within silicon carbide body especially near the discharge surface, may cause development of a thin dielectric vapor layer on the ,surface which can be a
reason for a large and fast growing
plasma channel and as a result' are
formation.
University College of Engineering
دانشکده فنی
08031026
34
v.
4
no.
2001
https://jfe.ut.ac.ir/article_15251_b2a727b5ec17605d02b81ceae90e8a24.pdf

رمضانعلی مهدوی
نژاد
author
امیر
عبدالله
author
text
article
2001
per
Tungsten carbide is one of semented carbide materials , that are known as metal carbides. Tungsten and carbon are the elements of WC, W 2C and W 5C3 that is
stable only at higher than 2535°C. Among above mentioned three combinations of Tungsten, the stability of mono Tungsten
carbide (WC) that briefly named Tungsten carbide is better, so, it is more important. The plastisity of Tungsten carbide is high and in comparision with steel its modulus
of elastisity is three times bigger. Its hardness is bigger than that of steel, even in very stream conditions, so that it doesnt's make any noticable changes at high temperature. Because of its high resistance to wear and good shockness, it is used in various kinds of carbide dies and
cutting tools. Although the machining of Tungsten carbide with conventional methods is almost successful in
comparision with machining of Silicon
carbide, but because of complexity of the shape of workpiece and high needed accuracy in machining, the conventional machining methods cannot achieve them.
Among nonconventional machining methods EDM is an especial case in machining of cemented carbides. With consideration of instability of ED
machining of Tungsten carbide process, this paper tries to give some instructions
that leads to more stable machining process. About the machining of different grades of Tungsten  carbide, open circuit pulses are more than 500/0 and Arcing are
less than 150/0 with different pulse durations. In these materials, increasing the
pulse duration, increases machining instability. In nearly all grades of
Tungsten carbide, the size of the grains on the machined surfaces become bigger and
show the gathering much more resolidified materials. The presence of cobalt nearly on everywhere of the machined surface
patterns, may be because of resolidification
of cobalt and recombination with Tungsten or Tungsten  carbide on the surface of the workpiece. The elimination of the cobalt
and Tungsten together from arcing area,
make holes which are suitable places for carbon to remain and grow and afterwards make arcing.
University College of Engineering
دانشکده فنی
08031026
34
v.
4
no.
2001
https://jfe.ut.ac.ir/article_15252_473ed1526b4a0e8afbf99512a908f816.pdf