Computational Methods in Engineering

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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.

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Manual fingerprint classification algorithms are very time consuming, and usually not accurate. Fast and accurate fingerprint classification is essential to each AFIS (Automatic Fingerprint Identification System). This paper investigates a fingerprint classification algorithm that reduces the complexity and costs associated with the fingerprint identification procedure. A new structural algorithm for classification of fingerprints is described. This algorithm is based on structural features: core and delta, and their orientation. The accuracy and speed of the proposed method is tested for a large number of fingerprint images with different initial qualities. The results are independent of image orientation and, show a significant classification performance.

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There are several sources for pressure oscillations in solid propellant rocket motors. Oscillatory flow field is one of them. Free shear layers in motor flow field cause vortex shedding. End edges of propellant grains and baffle edge in two-segmented motors are samples of such zones. These vortices move from their forming points and strike the field walls. The kinetic energy of vortices change to pressure, forming acoustical pressure oscillations. Acoustical characteristics of pressure oscillations such as frequency and amplitude change with the gradual change in the internal geometry of the motor. In this paper, the interaction between mean flow and acoustic field in a solid propellant rocket motor is studied numerically. Roe’s flux function in an unstructured grid strategy for solving compressible viscous flow equations show large changes in frequency of pressure oscillations in motor. Six different motor geometries are used for simulation of motor internal geometry at different burning times and grain configurations. Using this methodology, the frequency and intensity of pressure waves are well predicted. It is also shown that frequency jump from second longitudinal mode to the first is formed as a result of changes in the internal geometry.

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The main objective of this paper is to provide an applied algorithm for analyzing propeller-shaft vibrations in marine vessels. Firstly an underwater marine vehicle has been analyzed at different speed in unsteady condition using the finite volume method. Based on the results of this analysis, flow field of marine vehicle (wake of stern) and velocity inlet to the marine propeller  is extracted at different times. Propeller inlet flow field is applied in the boundary element code and using this code, marine propeller has been analyzed in unsteady state. In continue, main / lateral forces and moments over the propeller are extracted. Then the data obtained from the boundary element code alongwith exact geometry of the propeller and shaft have been studied, using finite element code. Natural and forced frequency of the propeller have been determined in various modes of vibration. According to obtained data from Finite Element Method (FEM) numerical analysis, maximum displacement of propeller is for displacement of the propeller tip in forced vibration state