Showing papers by "Iran University of Science and Technology published in 1995"

Real-time image processing approach to measure traffic queue parameters

Abstract: The real-time measurement of various traffic parameters including queue parameters is required in many traffic situations such as accident and congestion monitoring and adjusting the timings of the traffic lights. In case of the queue detection, at least two algorithms have been proposed by previous researchers. Those algorithms are used for queue detection and are unable to measure queue parameters. The authors propose a method based on applying the combination of noise insensitive and simple algorithms on a number of sub-profiles (a one-pixel-wide key-region) along the road. The proposed queue detection algorithm consists of motion detection and vehicle detection operations, both based on extracting edges of the scene, to reduce the effects of variation of lighting conditions. To reduce the computation time, the motion detection operation continuously operates on all the sub-profiles, but the vehicle detection is only applied to the tail of the queue. The proposed algorithms have been implemented on an 80386-based microcomputer system and the whole system works in real-time.

On the Performance of a Cascade of Turbine Rotor Tip Section Blading in Nucleating Steam: Part 2: Wake Traverses

Abstract: During the course of expansion of steam in turbines the fluid first supercools and then nucleates to become a two-phase mixture. To reproduce turbine two-phase flow conditions requires a supply of supercooled vapour which can be achieved under blow-down conditions by the equipment employed. This paper is the second of a set describing an investigation into the performance of a cascade of rotor tip section profiles in nucleating steam and presents the results of the wake traverses and droplet measurements.

A Window-based Edge Detection Technique for Measuring Road Traffic Parameters in Real-Time

Abstract: The real-time measurement and analysis of various traffic parameters such as volume, speed and types of vehicles are increasingly required for traffic control and management. Image processing technique is now considered as an attractive and flexible method for automatic analysis and data collections in traffic engineering. Various algorithms based on background differencing techniques have been applied to vehicle detection. However, these techniques have not yielded good results due to inefficiency of background updating techniques. This paper describes a new method for vehicle detection based on edge detection techniques. This method eliminates the background updating and has been implemented in real-time on a low-cost 80386 based microcomputer system. This new vehicle detection algorithm works under various lighting and weather conditions and measures other traffic parameters in real-time as well.

Effects of composition changes on the crystallization behaviour and properties of SiO2-Al2O3-CaO-MgO (Fe2O3-Na2O-K2O) glass-ceramics

Abstract: Several glass-ceramic materials located in the SiO 2 -Al 2 O 3 -CaO-MgO(Fe 2 O 3 -Na 2 O-K 2 O) system were formulated by using naturally occurring materials and 1 wt% chromite ore as a nucleant. The crystallization behaviour of specimens was investigated by using dilatometric, DTA and XRD techniques. It was found that the replacement of CaO by MgO has a profound effect on the crystallization behaviour of specimens and some of them show almost complete crystallization. After a two stage heat treatment, an aluminium dioxide phase was identified as the sole crystallization product in all specimens. The microstructures were investigated by SEM. It was found that phase separation occurs prior to nucleation of dioxide and the latter phase grows into a fibrous shape. The bending strength of crystallized specimens which range from 31 to 76 MPa depends on the degree of crystallinity and on the porosity of specimens. The hardness and chemical durability values depend only on the amount of crystalline phase.

Time domain analysis of transmission lines

Abstract: A simple numerical method is developed for the determination of the transient response of lossy transmission lines with a general impedance loading to a general voltage excitation. First, the transient response of the lossless transmission line with a load impedance to a voltage excitation is formulated. The steady state response of the line is then derived from its transient response. A recursive relation for determining the transient response is also given. Reflection coefficient at the load is determined by deriving differential equations directly and also by the use of the Thevenin's equivalent circuits. A computer program for the implementation of the numerical method together with several examples of the transient response of lossless/lossy transmission lines with passive/reactive loadings are presented. This numerical method has both practical engineering applications and pedagogical value.

Optimal load of robotic manipulator with joint elasticity using accuracy and actuator constraints

Abstract: A computational technique for obtaining the maximum load-carrying capacity for a robotic manipulator with joint elasticity, subject to accuracy and actuator constraints, is described. Full load motions and increased productivity are linked in the industrial applications of many robotic manipulators; the maximum load carrying capacity which can be achieved by a manipulator during a given trajectory is limited by a number of factors. The dynamic properties of a manipulator, its actuator limitations, and joint elasticity (transmissions, reducers, and servo drive system) are probably the most important factors. This paper presents a strategy for determining dynamic load carrying capacity (DLCC), subject to both accuracy and actuator constraints, where a series of cubical bounds centred at the desired trajectory is used in the end-effector oscillation constraint while a typical d.c. motor speed-torque characteristics curve is used in the actuator constraint. The technique which considers the full nonlinear manipulator dynamics, actuator constraints, and accuracy constraints permits the manipulator user to specify the trajectory completely. Finally, a numerical example involving a two-link manipulator with joint flexibility using this method is presented and the results are discussed.

Application of sorted codebook vector quantization to spectral coding of speech

Abstract: A new vector quantization method, namely sorted codebook vector quantization (SCVQ) is presented in this article. The paper explains the principles of this method, including training and optimization of the associated codebook. It is shown that this quantizer can be implemented efficiently with almost similar computational complexity to tree-searched vector quantization (TSVQ) and the storage cost of that is the same as unstructured VQ (i.e less than TSVQ). Application of SCVQ to quantization of Line Spectral Frequencies (LSFs), which are the most popular parameters for spectrum quantization in speech coders using linear prediction model, is described. Superior performance of the new method is verified through experimental simulations.

Optimal Trajectory of Flexible Manipulator with Maximum Load Carrying Capacity

Abstract: In this paper, a new formulation along with numerical solution for the problem of finding a point-to-point trajectory with maximum load carrying capacities for flexible manipulators is proposed. For rigid manipulators, the major limiting factor in determining the Dynamic Load Carrying Capacity (DLCC) is the joint actuator capacity. The flexibility exhibited by light weight robots or by robots operating at a higher speed dictates the need for an additional constraint to be imposed for situations where precision tracking i. e., the allowable deformation at the end effector is required. An Iterative Linear Programming (ILP) method is used to optimise the load (load mass and load moment of inertia) of elastic robot subject to both constraints. A general computational procedure for the multiple-link case is presented in detail. Simulation is carried out for a two-link planer robot. The results confirm the necessity of the dual constraints.

Object recognition using simulated annealing and Fourier descriptors

Abstract: In this paper a method for object recognition is proposed. This method combines some local characteristics of the image, such as the location and intensity of the edges with some priory information about the possible shape of the object in order to recognize objects in a noisy or faded image. Finding objects in an aerial photograph could be considered as a good example of such images. The method implements the above idea by defining a function which includes a number of measures of some properties of the image as its terms. Each of these measures is defined so as to take its minimum value when the corresponding property is best met. This function is called the objective function. In our approach the object recognition problem is defined as a minimization of an objective function with terms which include the sharpness of the edges of the object, the smoothness of the object and its level of similarity with the predefined models. Simulated annealing has been employed for the minimization of this objective function. Fourier descriptors have been used to represent the shape of the objects which, with some modifications, can result in a rotation, scale, and translation invariant recognition system. The results obtained by applying the method to aerial photographs indicate its good ability to locate and recognize complex regions.

Fabrication of reflection gratings by contact copying of amplitude holographic gratings on a metal surface

Abstract: This paper describes the contact copying of amplitude transmission holographic gratings. Master gratings (MG) are written in silver halide sensitized gelatine. A smooth and flat sheet is coated with a layer of negative photoresist constituted from a combination of polyvinyl alcohol, ammonium dichromate and Arabic gum, then the MG is put in contact with the metal surface and exposed by a mercury lamp. After processing with deionized water at (35 degree(s)C), a reflection grating is obtained. For a MG with 117 l/mm of spatial frequency and 10% of diffraction efficiency (DE), we have obtained a DE of 12%.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Non-parallel plane Rayleigh Benard convection in cylindrical geometry

Abstract: This paper considers the effect of a perturbed wall in regard to the classical Benard convection problem in which the lower rigid surface is of the form z = eg(s), s = er, in axisymmetric cylindrical polar coordinates (r, φ, z). The boundary conditions at s = 0 for the linear amplitude equation are found and it is shown that these conditions are different from those which apply to the nonlinear problem investigated by Brown and Stewartson [1], representing the distribution of convection cells near the center.