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Tchomeni B.X.,VUT | Masu L.M.,VUT | Alugongo A.A.,VUT | Tengen T.,VUT
Proceedings of the 10th South African Conference on Computational and Applied Mechanics, SACAM 2016 | Year: 2016

A 4-DOF nonlinear model of a cracked de Laval rotor-stator system derived using Energy Principles is presented in this paper. The model has been used to simulate the system response under the parametric excitations; rotor-stator-rub, a breathing transverse crack, eccentric mass and an axial force by Wavelet Transform (WT). CWT and DWT reveal the signal aspects; trends, breakdown points, discontinuities of the non-stationary waveform under the parametric excitations. Presented results provide a useful tool for on-line monitoring of rotor-stator-rub, transverse crack and eccentric mass.

Tchomeni B.X.,VUT | Alugongo A.A.,VUT | Tengen T.,VUT
Proceedings of the 10th South African Conference on Computational and Applied Mechanics, SACAM 2016 | Year: 2016

This paper provides a technique to identify the characteristics of vibration responses of strong nonlinear rotor system, generated by multiple excitations during low and high acceleration by means of the time-frequency plots. A cracked de Laval rotor system characterized by a hinge model for a small crack, Mayes' modified function for a deep crack, and rotor-stator rub-impact are numerically simulated. The effects of the non-linear disturbances due to oil film forces, rotor stator rub forces, and a breathing crack on the rotor shaft is numerically analysed by Fast Fourier Transform (FFT) and Wavelet Transform (WT). An attempt for fault detection based on different factors such as unbalance eccentricity, rub, crack and oil film force with the influence of low and high acceleration vibration are investigated. Simulation results presented show that, the nonlinear phenomena are well observed at low acceleration, through the orbits at the start-up period. However at high acceleration several nonlinear phenomena including chaotic features behaviour are observed and analysis become complicated, and could only be observed through wavelet transform features. The observed frequency spectra and time-frequency features are unique and could serve as identification criteria of rotor faults.

Burdikova Z.,Teagasc | Svindrych Z.,University of Virginia | Hickey C.,Teagasc | Wilkinson M.G.,University of Limerick | And 6 more authors.
Dairy Science and Technology | Year: 2015

Despite considerable advances in confocal microscopy and related technologies, advanced light microscopy techniques have been rarely used to study the microstructure of cheese matrices. Here, we demonstrate the potential of advanced microscopic techniques, namely fluorescence lifetime imaging (FLIM), confocal Raman spectroscopy and non-linear microscopy (two-photon excitation and second harmonic generation microscopy), to study localized physicochemical properties of cheese matrices. These methods allow for precise localization of individual chemical components and help to determine their spatial organization in three dimensions. We discuss both fluorescent labelling and label-free methods that provide valuable information about the localized environment. Overall, these new technologies will enable a greater understanding of the influence of manufacturing processes on cheese quality and consistency. © 2015, INRA and Springer-Verlag France.

Sonriera N.,VUT | Kritzinger E.,University of South Africa | Loock M.,University of South Africa
ACM International Conference Proceeding Series | Year: 2012

In South Africa, there is a lack of structure or guidance for schools on how to deal with cyber threats. There are no clear procedures that are consistently followed by schools, governing boards and educators, and the cyber threat process is not widely known and understood by educators, learners and their parents/guardians. As a result, many learners remain vulnerable to the negative effects of cyber threats. An example is a Krugersdorp High School girl who was attacked after a cyberthreat ordeal, (The Star 9 February 2012:1). In this paper a framework is therefore proposed that schools can implement to assist learners with cyber threat incidents. The methodology that will be followed in this article is, firstly, to determine from the literature how a victim of cyber threat can be helped, secondly, to develop an incident handling structure that will assist learners in reporting cyber threats, and thirdly, to develop a framework which will address the lack of structure, guidance or procedures when dealing with cyber threats in schools. The gap which exists now deters learners from reporting cyber threat incidents. To fill this gap, the authors propose an incident handling structure which will assist learners to report and receive protection against online threats. It is hoped that, in the end, learners will know what to do when they are threatened online. In addition, cyber threat policies and procedures are proposed to protect and inform learners and their parents about cyber threats. These procedures collate, outline legislation and the policies of the Department of Basic Education. The aim is to give schools rights and responsibilities in addressing cyber threat incidents. Practical considerations such as time and costs limit the study to a sample of schools in South Africa. The framework for intervention in cyber threat incidents as part of school policies in South Africa is merely a proposal to the rightful stake holders, since policies for schools are determined by the Department of Basic Education which the authors are not members of. Copyright 2012 ACM.

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