Emulating bearing faults : a novel approach

The relation between evolving mechanical faults in rotating electrical machines and their reflection in the machines’ electrical parameters still requires a lot of research. This implies serious obstructions in the evolution of e.g. Motor Current Signature Analysis as a complete and reliable condition monitoring technology. This paper presents the translation of common bearing faults into specific rotor-stator movements using finite element modeling. Subsequently, a novel method to elucidate the complex relation between rotor movements and the electrical parameters of an induction machine using an experimental test setup is described, dimensioned and simulated. Replacing one of the induction machine’s bearings with an Active Magnetic Bearing will give the opportunity to create specific rotor movements and consequently evaluate different programmable mechanical faults and their reflection in the stator current and/or voltage with high relevance and reproducibility

Impact of the Sectoral Determination for Farm Workers on the South African Sugar Industry: Case Study of the KwaZulu-Natal North and South Coasts

A survey of 103 sugarcane farmers on the KwaZulu-Natal coast was conducted in order to analyse the impact of the Sectoral Determination for Farm Workers (2002) on South African agriculture. The sample was separated into a high wage paying North Coast and lower wage paying South Coast. Typically farmers were unable to distinguish between the impact of the Sectoral Determination and other labour laws. Results indicate that the impact of the legislation is similar in each region. No respondents reported mass retrenchment, but job shedding is disguised by not replacing workers (especially unskilled workers) that leave the farm. A sizeable number of growers (17 per cent on the South Coast and 44 per cent on the North Coast) have reduced the working week to 27 hours (or 36 hours in the Felixton Mill Group Area) enabling them to pay wages on an hourly, rather than a weekly basis. This strategy reduces the effective wage. About 40 per cent of growers have reduced the in-kind benefits to their workers. About half of respondents indicated that they are likely to increase their use of seasonal and contract labour in future. Although a majority of respondents indicated that they considered mechanisation of the harvesting process, cost and topographical factors currently does not make this a serious alternative to manual harvesting. However, because of increased wage costs and the relatively strong currency in recent years, chemical weed control has become an attractive alternative to manual weed control.Crop Production/Industries, Labor and Human Capital,

Hybridizing Non-dominated Sorting Algorithms: Divide-and-Conquer Meets Best Order Sort

Many production-grade algorithms benefit from combining an asymptotically efficient algorithm for solving big problem instances, by splitting them into smaller ones, and an asymptotically inefficient algorithm with a very small implementation constant for solving small subproblems. A well-known example is stable sorting, where mergesort is often combined with insertion sort to achieve a constant but noticeable speed-up. We apply this idea to non-dominated sorting. Namely, we combine the divide-and-conquer algorithm, which has the currently best known asymptotic runtime of $O(N (\log N)^{M - 1})$, with the Best Order Sort algorithm, which has the runtime of $O(N^2 M)$ but demonstrates the best practical performance out of quadratic algorithms. Empirical evaluation shows that the hybrid's running time is typically not worse than of both original algorithms, while for large numbers of points it outperforms them by at least 20%. For smaller numbers of objectives, the speedup can be as large as four times.Comment: A two-page abstract of this paper will appear in the proceedings companion of the 2017 Genetic and Evolutionary Computation Conference (GECCO 2017