Showing 590 results for Subject: General
M.a. Golozar, A. Najafi- Zadeh,
Volume 13, Issue 1 (7-1993)
Abstract
A. Abrishamchi, A. Afshar,
Volume 13, Issue 1 (7-1993)
Abstract
M.e. Eslimi, M.m. Saadatpour, M. Vafaeian,
Volume 13, Issue 1 (7-1993)
Abstract
M.a. Golozar,
Volume 14, Issue 1 (1-1994)
Abstract
Kiani Rashid, A. Najafi- Zadeh, M.a. Golozar,
Volume 14, Issue 1 (1-1994)
Abstract
Saatchi, A. Najafi- Zadeh, M. R. Rahimipour,
Volume 14, Issue 1 (1-1994)
Abstract
M. M. Saadatpour, N. Fallah,
Volume 14, Issue 1 (1-1994)
Abstract
R. Khoee, A. M. Keynia,
Volume 14, Issue 1 (1-1994)
Abstract
M. Chalkosh Amiri,
Volume 14, Issue 1 (1-1994)
Abstract
G. Aryanpour, M. H. Abbasi,
Volume 14, Issue 1 (1-1994)
Abstract
A.r. Khoee and A.m. Kaynia,
Volume 14, Issue 1 (1-1994)
Abstract
M. Farzin and M Shariaty,
Volume 14, Issue 1 (1-1994)
Abstract
Stretching process of sheet metals in both cases of axisymmetric and non-axisymmetric is analyzed. A rigid-plastic, normal anisotrop material is assumed and large strain formulation is applied. Triangular elements are used and stiffness equations of elements are obtained from virtual work principle. These nonlinear equations are linearized by Newton-Raphson's method and are solved by Gaussian elimination technique. Punch displacement is applied incrementally and deformation of sheet specimen is obtained by calculation of displacement of nodes at each increment. After convergence of calculations at each increment, results which include nodes displacements, strains and stresses at elements, nodal forces and total punch force, etc., are saved and initial guesses are updated. This procedure is continued up to an obtainable or desired punch stroke. Results of this analysis are presented and their comparison with other available theoretical and experimental works are very satisfactory.
S. Talebi and A.a. Rostami,
Volume 14, Issue 1 (1-1994)
Abstract
Refrigerants that are used in refrigeration systems, cause environmental difficulties such as depletion of ozone layer and greenhouse effect. Thus, we must find substitutes for such refrigerants, in this paper, the effect of refrigerant on the thermodynamics performance of refrigeration cycles are studied. To do this, a refrigerator that has designed for R12, is simulated. Results show that pure refrigerant R134a and mixture R32/R132b are convenient substitutes for R12.
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.
S. H. Amirshahi,
Volume 14, Issue 2 (1-1996)
Abstract
An algorithm is suggested for implementation of unlimited primaries in two-constants Kubelka-Munk color matching attempt. Allen's method for tristimulus color matching which was limited to four colorants in two constant theory, dealt with inversable matrices. By application of the pseudo-inverse, it is not necessary to limit the number of primary colors to four as Allen suggested. The suggested method is programmed to a color matching attempt with five pre-colored fibers.
V. Kalantar and M. Abbaspour,
Volume 14, Issue 2 (1-1996)
Abstract
A computer program was developed to predict the dispersion of gas pollutant in the atmosphere. This program relies on puff method, and in order to consider the wind shear effects, the program has the ability to consider the complete dynamic and unsteady atmospheric conditions. Plume rise of hot pollutants due to buoyancy effects was also considered. The program has the capacity to perform the realtime calculations and uses on-line data of atmospheric conditions that are measured by an anemometer and a thermometer. In order to consider the effects of presence of building and other obstacles or sudden change in surface roughness on dispersion of released materials, a model was added to evaluate the dispersion coefficients in the wake of obstacles. Using this relatively complete simulation, we analyzed the effects of above parameters on the dispersion of gas pollutants in atmosphere and the interpretation of the results is presented.
Mojtaba Rajaee,
Volume 14, Issue 2 (1-1996)
Abstract
Flow visualization techniques using tracer markers such as die, smoke, hydrogen bubbles, etc., have been widely used in experimental investigations of large scale structures of a variety of flow fields. They have played an important role in understanding the physics of the coherent structures' formation and evolution in the transitional as well as the turbulent regions of the flow fields. However, they lack to provide detailed quantitative information about the flow. Here, a new approach is taken in obtaining quantitative flow field snapshots from a region of a two-dimensional free shear flow mixing layer. A single cross-wire probe is used to make measurements of the flow in a time frame phase locked with the coherent flow structures which facilitates reconstructed flow snapshots from the hot-wire measurements in a very long run experiment. A new detailed calibration updating scheme is developed to resolve the problem of calibration validity encountering very long time hot-wire measurements. This is a key factor in facilitating reconstructed flow snapshots that satisfy the continuity equation with a very high accuracy.
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. R. Zamani and M. S. Saidi,
Volume 14, Issue 2 (1-1996)
Abstract
In dynamic analysis of floating structures, the designer needs to know the wave forces due to incident and scattered waves on the structure. In this work, the flow field around the body is solved based on the potential theory with considering the free surface and sea bed effects. Using this theory, the wave forces exerted on two typical sea buoys with spherical and disc-type bodies are determined. Comparison of these results with the one obtained using Haskind method shows good accuracy of the present method.
