2024-03-29T10:37:39Z
https://www.ije.ir/?_action=export&rf=summon&issue=11379
International Journal of Engineering
IJE
1025-2495
1025-2495
2000
13
4
Power Supply and Current Modulation Circuits for Semiconductor Lasers
H.
Golnabi
Design and construction of a stable current supply with protection circuits are described. The reported circuit provides a high-stable and high-level current variable from 0.5-1.2 A with the protect ion circuits to prevent over load current, voltage and off-range temperature operation. A detailed analysis of the circuit parameters is given and the time behaviors of the load voltage/current and shut-off voltage/current are presented. Theoretical analysis shows a turn-on time of about 20 ns for the load current and a shut-off time of about 150 ns. The proposed scheme is verified both by simulation and by constructing a prototype. The prototype version of this circuit shows a good stability in load current, and the laser diode temperature can be monitored with an accuracy of about 1 degree. In addition, design and analysis of the current modulator and switching circuit s for laser diodes are reported. Modulation process and different modulation techniques are explained in detail. Drive circuits for positive and negative intensity modulation are presented. Transient analysis for the proposed drivers is performed by using PSPICE software and the results are reported here. Evaluation of the results indicates that the reported modulators can be used successfully for direct current modulations.
power supply
Modulation
Current
Voltage
Semiconductor Laser
2000
11
01
1
16
https://www.ije.ir/article_71272_a9fe242c73f47e1e18ecf8d66a74d6ee.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2000
13
4
Reliability of Repairable Multicomponent Redundant System
Madhu
Jain
C. J.
Singh
This investigation deals with transient analysis of cold standby system with n units . Chapman-Kolmogorov equations are developed for repair facility with two repairmen and solved by using matrix technique. Availability and reliability factors have been obtained with probability of the system. A particular case has also been discussed.
transient
Standby
Availability
Reliability
2000
11
01
17
22
https://www.ije.ir/article_71273_4d7fd6df947d9df70ab2b42bf1e5aabd.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2000
13
4
Analytic Solution for Hypersonic Flow Past a Slender Elliptic Cone Using Second-Order Perturbation Approximations
A.
Baradaran Rahimi
A.
Omehtalb
An approximate analytical solution is obtained for hypersonic flow past a slender elliptic cone using second-order perturbation techniques in spherical coordinate systems. The analysis is based on perturbations of hypersonic flow past a circular cone aligned with the free stream, the perturbations stemming from the small cross-section eccentricity. By means of hypersonic approximations for the basic cone problem, closed-form second-order approximate solutions for the perturbation equations are obtained within the framework of hypersonic small-disturbance theory. Results for the shock shape, shock-layer structure, and surface pressure are presented for all ranges of Mach number s, together with comparisons with experimental data. Also a complete vortical layer analysis is presented to prove the suitability of the surface boundary conditions.
Hypersonic
Elliptic Cone
Second
Order Perturbation
Surface Pressure
Vortical Layer
2000
11
01
23
34
https://www.ije.ir/article_71274_db58fece261b650a1a4a65045ad87cd7.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2000
13
4
On Interaction of T S Waves and 3 D Localized Disturbance in a Divergent Flow Under Zero Pressure Gradient
Mohsen
Jahanmiri
To simulate the effect of free st ream turbulence on turbulent spot formation, experiments were conducted on the interaction of localized three-dimensional disturbances with the harmonic waves in a laminar boundary layer on a flat plate. Experiments conducted in three-dimensional diverging flow (but zero pressure gradient) show, while individually the disturbances decay downstream, their interaction leads to amplification of three-dimensional disturbance leading to formation of the turbulent spot. Also flow divergence show the least effect in the interaction process.
T
S Waves
3
D Flow
Turbulence Spot
Transitional Boundary Layer
2000
11
01
35
42
https://www.ije.ir/article_71275_57d0c9391a00e397fc02d0c0d45238c1.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2000
13
4
Adaptive Unstructured Grid Generation Scheme for Solution of the Heat Equation
S.A.
seyed-reyhani
A.
Banai
Kiumars
Mazaheri Body
An adaptive unstructured grid generation scheme is introduced to use finite volume (FV) and finite element (FE) formulation to solve the heat equation with singular boundary conditions. Regular grids could not acheive accurate solution to this problem. The grid generation scheme uses an optimal time complexity frontal method for the automatic generation and delaunay triangulation of the grid points. The algorithm is incremental, so it is the most appropriate for an adaptive solver. Using adaptive grids, the solution is refined to get enough accuracy in all grid points. Two schemes are applied for the solution of the equations to show the flexibility of the adaptive grid scheme. First a cell-vertex finite volume formulation is used. Then, for the FE scheme, using linear shape functions, a set of linear equations are solved explicitly, with overrelaxation. A sequence of adaptation is applied and appropriate number of grid points are introduced in finite predetermined formats to the existent elements, till convergence in the solution is observed. A postprocess is used to smooth the distribution of the set of nodes. This procedure is applied to a few study cases to show that the method is convergent, and produces accurate solution even in the case of singular boundary conditions.
Delaunay Grid
Unstructured
Heat Equation
2000
11
01
43
54
https://www.ije.ir/article_71276_8e34eb7c0c68c84432cd53395eee7292.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2000
13
4
Robust Hybrid Motion Force Control Algorithm for Robot Manipulators
B.
Kuchen
V. A.
Mut
In this paper we present a robust hybrid motion/force controller for rigid robot manipulators. The main contribution of this paper is that the proposed hybrid control system is able to accomplish motion objectives in free directions and force objectives in constrained directions under parametric uncertainty both in robot dynamics and stiffness constraint constant. Also, the given scheme is proved globally stable in the sense that the control objectives are achieved asymptotically, when a signum function is used in the control law, though giving rise to chattering effects. To avoid this problem a saturation function is used. In this case the motion and force errors are proved to be bounded functions. Using the proposed control structure there is no need to measure the derivative of the interaction forces. Some simulation results are given to illustrate the control system performance.
Robot Manipulators
Nonlinear systems
Hybrid Motion
Force Control
Robust Control
2000
11
01
55
64
https://www.ije.ir/article_71277_812dff5396a8a500a7bcc942427812be.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2000
13
4
Compressive Strength Freeze and Thow Durability Correlation in Soil Cement Design (RESEARCH NOTE)
Jamshid
Sadr Karimi
This paper explains the procedure and results of an experiment on the relationship between the unconfined compressive strength and percent weight loss due to freeze and thaw durability test of laboratory compacted soil-cement specimens. The tests were carried out on soil cement mixtures of 10 different soil types. It was shown that the percent weight loss due to freeze and thaw durability test (F&T) and the 28-day compressive strength (UCS) may be correlated with some error. However, using the graph given in this paper, the designer may estimate the percent weight loss with an error in the order of 2 percent. The 28-day UCS values are linearly correlated with the UCS values of the similar specimens subjected to the F & T durability tests with a regression factor of o.96.
Soil
cement
Compressive strength
Freeze and Thaw Test
Slope Protection
2000
11
01
65
72
https://www.ije.ir/article_71278_14375ec554bcabc363b3371e8afe541c.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2000
13
4
Earthquake Induced Permanent Displacement of Slopes: a Numerical Study (TECHNICAL NOTE)
M.J.
moosavi
A. A.
Fakhimi
The conventional method to evaluate earthquake induced permanent deformations of slopes is the one proposed by Newmark. In this paper, permanent displacement of slopes is studied using a combination of distinct element and finite difference methods and the results of these numerical evaluations are compared with those of the Newmark's approach. Several parameters involved, including peak ground acceleration, period of excitation, friction and cohesion of the sliding surface, are considered in this study. The results show that the period of excitation is an important parameter in finding the displacements of slopes. In addition, it is shown that in resonance condition, the permanent displacement of a slope, derived by Newmark's method, can be twice the one predicted by the distinct element method. Finally, It is realized that, in frictional materials, permanent displacements of slopes obtained by the distinct element and Newmark's methods are in better agreement compared with the corresponding results in cohesive materials.
Slopes
Permanent Displacement
Distinct Element Method
Newmark
s Method
Earthquake
Numerical Study
2000
11
01
73
80
https://www.ije.ir/article_71279_07c626252de0f292cfd8f046cc322da0.pdf
International Journal of Engineering
IJE
1025-2495
1025-2495
2000
13
4
Using 2D Lerchs and Grossmann Algorithm to Design Final Pit Limits of Sungun Copper Deposit of Iran (TECHNICAL NOTE)
M.
Osanloo
Mohammad
Ataei
The Sungun copper deposit is located in about 40km north west of Ahar city in the east Azarbaigan province of Iran. The total geological ore deposit is estimated to be 740 million tons. In this study using all information from exploration and geotechnical studies of the area, final pit limits of Sungun copper deposit is designed by the 2-D Lerchs & Grossmann Algorithm. By this method, from 740 million tons of geological ore reserve, 411 million tons can be mined by open-pit method with overall stripping ratio of 2.14:1. Cut off grade is found to be 0.32% Cu. The average ore grade is found to be 0.665% Cu.
Open Pit
Final Pit Limits
Lerchs
Grossmann Algorithm
Economic value
2000
11
01
81
89
https://www.ije.ir/article_71280_4eca680eb71f23a61ebaeae5b981f1f4.pdf