Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
12
3
1999
08
01
an Efficient Drive Circuit for Switched Reluctance Motor
137
143
EN
M.
Fallah
hasnomail@ije.ir
E.
Afjei
Department of Electrical Engineering, Shahid Beheshti University
afjei@yahoo.com
The purpose of this paper is to present an efficient converter circuit used to drive switched reluctance motors. It uses the C-dump topology in which the trapped energy in the phase windings is returned to the supply capacitor to be used in the following strokes. In addition to the C-dump topology, it uses two extra feedbacks. One comes from a governor mounted on the shaft of motor which controls the proper advancement of the firing time for each power transistor in different speeds, and the other, gets pulses from the shaft sensors in order to keep the motor speed constant under different loads. A Spice simulation has been performed on the drive circuit to see the current waveforms under different firing time advancements. Finally the test results of the converter circuit driving an isolated phase reluctance motor are presented.
Switched Reluctance Motor Drive and Converter Drive for Reluctance Motor,SRM Drive Circuit
http://www.ije.ir/article_71232.html
http://www.ije.ir/article_71232_a38d68890db13d711135f786310c6712.pdf
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
12
3
1999
08
01
Combination of Approximation and Simulation Approaches for Distribution Functions in Stochastic Networks
145
154
EN
fariborz
jolai
Industrial Engineering, University of Tehran
fjolai@ut.ac.ir
S. M. T.
Fatemi Ghomi
Orcid.org/0000-00034
Industrial Engineering, Amirkabir University of Technology
fatemi@aut.ac.ir
This paper deals with the fundamental problem of estimating the distribution function (df) of the duration of the longest path in the stochastic activity network such as PERT network. First a technique is introduced to reduce variance in Conditional Monte Carlo Sampling (CMCS). Second, based on this technique a new procedure is developed for CMCS. Third, a combined approach of simulation and approximation procedures is introduced for the networks with activity discrete distribution function to enhance the accuracy of the approximation procedures. Application of the new approach proves that the error is drastically reduced in comparison with the best existing approximation approach.
PERT Network,completion time,distribution function,Discrete,Simulation,approximation,Combination
http://www.ije.ir/article_71233.html
http://www.ije.ir/article_71233_7f78dab8bb031adb24613b86635f1cfe.pdf
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
12
3
1999
08
01
Reliability of Repairable System with Removable Multi-Repairmen
155
164
EN
R. P.
Ghimire
, S. N. Multiple Campus
hasnomail@ije.ir
Madhu
Jain
Department Of Mathematics, IIT Roorkee,Roorkee,India
drmadhujain@yahoo.co.in
In this investigation, the explicit expressions for reliability function and mean time to failure (MTTF) of a repairable system with provision of spares and removable multi-repair facility have been established. In removable repairmen strategy, the repairmen turn on when there are N or more than N failed units and turn-off when system is empty. The failure times of operating/spare units and repair time of failed units are exponentially distributed.
Reliability,Repairable,Removable Servers,Spare Units,MTTF,Transient Analysis
http://www.ije.ir/article_71234.html
http://www.ije.ir/article_71234_6ddacc3c9f419e65fb52c90755b80df0.pdf
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
12
3
1999
08
01
Flow Analysis Heat and Mass Transfer in a Room
165
178
EN
A. R.
Azimian
, Isfahan University of Technology
azimian@cc.iut.ac.ir
This reports the study on the flow behaviour, heat transfer and contamination distribution in a room. For this purpose the 3-D incompressible Navier-Stokes equations, energy equation and a mass transfer equation which model the concentration of contamination have been applied. For turbulence simulation the two equation standard k- turbulence model was employed. By means of SIMPLE algorithm the system of eight equations are solved. From the flow field solution the velocity vector plots, temperature and contamination contour plots were obtained and the results are compared with the calculated and published results. Agreement is reasonable enough and the results of such a study would help in much better use of indoor areas. Also it would be possible to estimate the heat load and the contamination removal from a room more accurately.
Three,dimensional Flow,Navier,stokes Equations,heat transfer,Mass Transfer,Turbulent Flow,Air conditioning
http://www.ije.ir/article_71235.html
http://www.ije.ir/article_71235_0728a26ae1c052377c1be8b9e580d08e.pdf
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
12
3
1999
08
01
an Optimum Resource Allocation Model for Airport Passenger Terminals (RESEARCH NOTE)
179
188
EN
M.
Saffarzadeh
Civil Engineering, Tarbiat Modarres University
saffar_m@modares.ac.ir
According to the current Airport planning and design practices, for a given demand level there is a corresponding space requirement. While in practice, there are always trade-offs between cost and levels of service, labor and automation, equipment and fixed facilities, and expansion of existing facilities and the addition of new ones. In this research, the airport passenger Terminal Building (PTB) was divided into several segments (components of the PTB system). Each segment has its own set of characteristics such as; unit operational and maintenance cost, level of service standards, and variable traffic demand pattern. The optimization model which is discussed in this paper determines the optimum required resources for each segment of the PTB ro perform its activity taking into account the operational and maintenance cost involved and the level of service provided to the users.
Airport,Passenger Terminal,Resource Allocation,optimization,Over and Under Supply Cost
http://www.ije.ir/article_71236.html
http://www.ije.ir/article_71236_ea2b6263da686472b994e8b142582013.pdf
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
12
3
1999
08
01
Corrosion of Concrete in Sea Water (RESEARCH NOTE)
189
194
EN
S.
Esmaili
Materials Engineering, Shiraz University
hasnomail@ije.ir
M.
Pakshir
Materials & Metallugy Engineering, Shiraz University
pakshir@shirazu.ir
Attack and disintegration of concrete structures under the influence of aggressive fluids, wet gases, etc. are understood as corrosion of concrete. The corrosion of concrete is a chemical, colloidchemical process, yet often a physico-chemical one, while that of reinforced concrete supported oil platforms are subjected to marine environment in the Persian Gulf and therefore corroded. In the present study we have tried to investigate the time required for corrosive agents such as chloride and oxygen to penetrate through the concrete using an aerated synthetic sea water representative of Persian Gulf environment. The influence of the concrete's cover depth on corrosion rate of the rebar has also been studied.
Concrete,Reinforcement,Concrete Cover,Sea water,corrosion
http://www.ije.ir/article_71237.html
http://www.ije.ir/article_71237_93ed7dc6d699ff69b9d4022cbf385fae.pdf
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
12
3
1999
08
01
on the Elastic Stability of Sleeve Stiffened Hollow Columns; Focusing on Determination of Optimal Design Curves (TECHNICAL NOTE)
195
203
EN
H.
Shahi
A.
Sinaie
, Shahid Bahonar University of Kerman
ali_sinaie@yahoo.com
The stability analysis of sleeve stiffened pin-ended slender hollow columns of pipe or box section is performed in the present study. This is accomplished by using energy method, employing three terms in the assumed approximate deflection function. The lengthy and tedious algebraic manipulations involved in solving the relevant eigenvalue problem, necessitates employing the "MATHEMATICA" software. Nevertheless, the final result for the critical load can not be presented in a closed from equation, as it is too long and may occupy several pages. The critical loads are determined for many different box and pipe sizes. A total of 144 design curves are determined and plotted showing the critical load for different lengths and thickness of the stiffening sleeve. The curves show an increasing trend in buckling load-carrying capacity up to 90 percent. Minimizing the material volume of the sleeves, the optimal portions of the design curves are determined. It is also found that sleeve stiffening beyond 70 percent of the length of the column is a waste of material, as it does not significantly contribute to increasing the load carrying capacity. The possibility of local shell buckling is also considered.
Elastic Stability,Buckling,Stiffened Columns,Design Curves
http://www.ije.ir/article_71238.html
http://www.ije.ir/article_71238_19db4282d367aea51576523ba36fe13b.pdf