Showing 238 results for Gh
C. Dehghanian,
Volume 6, Issue 1 (1-1988)
Abstract
C. Dehghanian,
Volume 6, Issue 1 (1-1988)
Abstract
H. Mir- Mohamad-Sadeghi, A. M. Kaynia,
Volume 7, Issue 1 (7-1989)
Abstract
M. Azhari, R. Mirghaderi,
Volume 7, Issue 1 (7-1989)
Abstract
M.m Saadatpour and B. Haghighi,
Volume 14, Issue 1 (1-1994)
Abstract
A. Meghdari, G. Vosoughi and A. Sekhavat,
Volume 14, Issue 1 (1-1994)
Abstract
– One of the important applications of robots is in material handling and transport of various shaped objects. In cases where an object cannot be directly grasped by the robot gripper, and must be carried by a hook, it may be subject to undesirable swings during transport. This paper presents an analytical method for minimizing the oscillation of a suspended object during transport. This method has been experimentally tested on a laboratory robot manipulator "TQ – MA3000", which is neither a path controlled robot nor features the path defining ability. The results indicate a reduction in the amplitude of oscillation of the suspended object to about 1.5 to 3 percent of the initial values.
F.ghassemi and R.safari,
Volume 14, Issue 2 (1-1996)
Abstract
Distance relays are used to protect EHV and HV Transmission lines. Over the past decades many algorithms have emerged for digital distance relays. These are based on the calculation of the transmission line impedance from the relaying to fault points. In this paper a novel method for digital distance relaying is proposed. In the method the tracking procedure is implemented. The method uses the calculus of variations for optimization of functionals. The method tracks the fundamental component of the waveforms and at the same time calculates the fault loop impedance. This eliminates the need for a pre-algorithm filtering which in turn improves the speed of the relay. Comparison with other algorithms has shown that the proposed method has a faster response and improved accuracy, in particular when a long line is considered.
A. Meghdari,
Volume 15, Issue 1 (7-1994)
Abstract
Recent developments in the area of smart structures indicate that variable geometry / stiffness truss network is of fundamental importance in designing smart transformable structures and systems for space applications. This paper presents the conceptual design and dynamic modeling of a cooperative re-configurabel dual-arm robotic structure called Dual-Arm Cam-Lock Manipulator. The Manipulator is designed to be capable of performing a wide variety of tasks by automatically reconfiguring itself to form a variable geometry, stiffness, and workspace robotic structure. Hence, it may also be referred to as a Variable Geometry Robot Manipulator (VGRM).
N.najaf- Zadeh, M.ghorbani,
Volume 15, Issue 1 (7-1994)
Abstract
The effects of carbon content on the dynamic and static softening mechanisms of Ti microalloy steels were investigated both in ferrite and austenite regions.
The results obtained showed that recrystallization rate decreased as the percentage of carbon content was increased from 0.0035 to 0.110. This is due to the Ti(CN) and TiC precipitates and also the free carbon content. In the ferrite region, the main obstacles for dynamic recrystallization are interstitial elements such as C and N. The interrupted compression tests also showed that increasing temperature leads to the increasing rate of static recovery and recrystallization in both ferrite and austenite regions.
B. Gholizadeh,
Volume 15, Issue 1 (7-1994)
Abstract
This paper proposes a triangulation method for a digitized surface whose points are located on a regular lattice. The method relies on an iterative and adaptive splitting of triangular faces of an initial polyhedral surface. Assuming a bijection between the digitized surface and its approximation, a partition of the data base is performed. The method allows the measurement of the local quality of the approximation and avoids the generation of triangles with sharp corners. Its low computational complexity permits the approximation of very large sets of points.
M. Monir-Vaghefi, A Saatchi and J.hejazi,
Volume 15, Issue 1 (7-1994)
Abstract
In this work the effects of various methods of agitation on the properties of electroless Ni-P-MoS2 composite coatings were investigated. Magnetic stirring as well as purging the solution with gas (Air, Oxygen, Nitrogen) were used. Plating rate, chemical composition, MoS2 distribution, and hardness of the deposit were measured. Topography of coating was studied with metallography and scanning electron microscopy. It was concluded that purging the solution with air produced optimum results, i.e. high rate of deposition, uniform distribution of MoS2 particles and appropriate surface morphology.
M. Rezaiee-Pajand and H. Asghari,
Volume 15, Issue 2 (1-1997)
Abstract
This paper is on the elasto-plastic analysis of plane stress problems. A five-parameter yield surface is presented. This yield criterion uses associate flow along with mixed hardening rule. The analytical formulations are written and related computer program for non-linear analysis is prepared. Finally, based on the formulations, numerical examples are solved.
S.m. Saghaian and F.farahmand,
Volume 15, Issue 2 (1-1997)
Abstract
In this article our objective is to obtain steady state characteristics of shunt, series, and separately excited DC motors coupled with a centrifugal water pump supplied through a step-up, step-down, and cuk converter from photovoltaic generator. We assume that there are no storage batteries and, of course, the system must operate on maximum utilization i.e. maximum water must be pumped. It is proven that if maximum utilization is obtained by duty ratio tuning, system utilization maximization and generator peak power tracking will be equal. Thus, a DC/DC converter is used as a peak power tracker. However, a single exception exists in the case of separately excited motors operated in constant converter duty ratio and tuned excitation for maximum utilization. In this case, system utilization maximization and generator peak power tracking will be different. In addition, with the assumption of generator peak power tracking, as in the case of shunt and series motors, system efficiency relative to generator terminals will also be maximized.
A. Meghdari and F. Fahimi,
Volume 16, Issue 2 (1-1998)
Abstract
Recently a method has been developed to decouple the equations of motion for multi-rigid body systems. In this paper, the method is first studied, then the equations of motion for a planar two degree-of-freedom robot with flexible joints are carried out using Lagarange's equations and Kane's equation with congruency transformations. Finally, the results obtained from both methods are throroughly compared.
Ch. Dehghanian and A. Shabzendeh Azari,
Volume 16, Issue 2 (1-1998)
Abstract
Effectiveness of furfural as an organic inhibitor in 5 percent hydrochloric acid which is used in acid pickling of steel was evaluated. Lungmuir, Frumkin and Flory-Huggins isotherms [1, 2] were used to determine the parameters of effective adsorption, free energy and entropy of adsorption. Furfural indicated an inhibition less than 17 percent in concentrations of 0.001 mole per liter for a duration of two hours at temperatures of 50, 60 and 70 degrees centigrade. Steel was protected up to 90 percent in concentration of 0.08 mole per liter at temperature of 70 degrees centigrade in 5 percent hydrochloric acid solution. Adsorption of furfural on the steel surface obeyed lungmuir isotherm.
S. Gh. Etemad,
Volume 17, Issue 1 (7-1998)
Abstract
The Galerkin finite element method is used to solve the three dimensional continuity, momentum and energy equations for laminar Newtonian and power-law model non-Newtonian flow through horizontal circular tube. The governing equations are non-dimensionalized with respect to specific variables and converted into algebraic equations using appropriate elements. To accelerate convergence a combination strategy of fixed iteration and Newton-Raphson methods are employed. Uniform wall temperature as well as constant wall heat flux are used as thermal boundary conditions. Apparent friction factor and incremental pressure drop and also Nusselt number are obtained for a wide range of power-law indices. The effects of thermal boundary conditions and Prandtl number on heat transfer characteristics are presented and discussed.
M. Aghdasi, F. Mokhatab Rafiei and G. Moslehi,
Volume 17, Issue 1 (7-1998)
Abstract
This paper presents a summary of the results from the simulation of a given two-stages production system which uses JIT. The system consists of an assembly line with two automated assembly cells and two assembly stock points and one manufacturing cell with three manufacturing stock points for storing reserved parts and one receiving stock. Carts with fixed capacity are used for handling the parts. A kanban is attached to each cart. The minimum number of kandbans required to operate the system without shortage in stock are estimated. The effects of changing the demand's mean and its variation on the number of carts are also investigated. Finally, a different simulation model is developed for the same production system using conventional job shop decipline and some main characteristics have been compared to the results, from the first model.
M. S. Sadeghipour and R. Razmi,
Volume 17, Issue 1 (7-1998)
Abstract
Using the highly recommended numerical techniques, a finite element computer code is developed to analyse the steady incompressible, laminar and turbulent flows in 2-D domains with complex geometry. The Petrov-Galerkin finite element formulation is adopted to avoid numerical oscillations. Turbulence is modeled using the two equation k-ω model. The discretized equations are written in the form of a set of nonlinear equations by block implicit method and are then linearized by the Newton-Raphson method. The set of linearized equations are, finally, solved Through Frontal method. This generates a full implicit solution. A few laminar and turbulent flow sample problems are solved using the code. Results obtained are in perfect agreement with those obtained from numerical and experimental works reported in the literature.
F. Ashrafizadeh, M. R. Toroghinezhad,
Volume 17, Issue 1 (7-1998)
Abstract
In this study carburizing and boronizing processes were applied to powder metallurgy steel specimens and the mechanical and tribological properties of the substrate and coatings were evaluated under various process conditions.
The specimens, made from industrial test pieces, were carburized in a powder pack for a duration of 2-5 hrs at 850-950 ˚C. Similar specimens were pack boronized for 4 hrs at 950 ˚C. The effect of austenitization-quench treatment was also investigated on some specimens. The wear tests were carried out by means of a pin-on-disc tribotester against ball bearing steel.
The results indicate that by appropriate selection of process parameters it is possible to obtain high wear resistance together with moderate toughness. Boride layers with hardness values of 1700HV are properly formed on PM samples. The wear resistance, therefore, is significantly increased with practically no reduction in impact resistance. It is concluded that boronizing treatment can be more suitable for some PM parts under tribological conditions.
M. Abedi, S. A. Taher, A. K. Sedigh and H. Seifi,
Volume 17, Issue 2 (4-1998)
Abstract
This paper deals with the design and evaluation of a robust controller for static VAR compensator (SVC) in remote industrial power systems to enhance the voltage profile for three-phase single cage induction motor (SCIM) loads. The controller design is based on H∞ theory to deal with uncertainties arising in industrial network modelling.
The performance of the H∞ controller has been evaluated extensively through non-linear time domain simulation. It is concluded that the robust controller (RSVC) enhances the voltage profile for SCIM loads compared with the optimal (OSVC) type which consists of optimal state feedback (LQR).
