ARJ 2017 Vol 108 No 1

A Ranking Method for Rating the Performances of Permutation Codes
by K. Ogunyanda and T.G. Swart
Abstract: Abstract: Minimum Hamming distance, dm, has been widely used as the yard-stick for the performance of permutation codes (PCs). However, a number of PCs with the same dm and cardinality can have different performances, even if they have the same distance optimality. Since PC is a robust channel coding scheme in power line communications applications, we present a simple and fast ranking method that predicts the relative performance of PCs, by using the information extracted from their Hamming distance distributions. This tool is useful for selecting an ef?cient PC codebook out of a number of similar ones.
A Technical and Economic Comparison Between Traditionally Employed and Emerging Fault Level Management Solutions at Distribution Voltages
by M.F. Khan, A.L.L. Jarvis, E.A. Young, R.G. Stephen
Abstract: Abstract: Network fault levels are reported to be increasing and this is often attributed to an increase in network interconnectivity and localised generation. When the fault level at a substation increases beyond the rated value of the installed equipment, a power utility traditionally responded by either (i) replacing the equipment with higher rated equipment or, (ii) installing series reactors or, (iii) replacing the existing transformers with high impedance transformers. Using a South African case study, this paper compares both the effectiveness and financial viability of a superconducting fault current limiter (SFCL) against the traditional three options. When one also considers the operational or ‘energy’ cost associated with all these options it was found that a high capital cost was sometimes offset by lower energy costs over a 25 year service life. Regional prices of electricity and tariffs therefore have a significant impact on a utility’s choice of fault management solutions.
Design and Optimisation of a PCB Eddy Current Displacement Sensor
by A.J. Grobler, G. van Schoor and E.O. Ranft
Abstract: Abstract: Position sensing is one of the crucial parts of many systems, speci?cally in an active magnetic bearing. The position is used to control the magnetic forces within an active magnetic bearing to keep a rotor levitated. Sensors used in these systems must be very sensitive and are usually very expensive. In this paper a low cost printed circuit board position sensor is analysed. The sensor uses an excitation coil to establish a magnetic ?eld. Four sensing coils are then used to measure the in?uence a conducting target has on the magnetic ?eld to enable position sensing. The sensor’s magnetic operation is analysed using ?nite element methods and very good correlation is found with measured results. The effects of the target material and the number of PCB layers are analysed. It is shown that a two layer sensor can produce acceptable sensitivity and linearity.
The Modified Soft Inpout Parity Check Transformation Algorithm for Reed Solomon Codes
by Y. Genga, D.J.J. Versfeld
Abstract: Abstract: In this paper, we propose a modi?cation to the recently developed Parity check Transformation Algorithm (PTA) used in the decoding of Reed Solomon codes. This extension of the PTA is referred to as the Modi?ed Parity check Transformation Algorithm (MPTA). The MPTA is developed with the aim of reducing the number of iterations run by the algorithm during the decoding process, and also to improve on the SER performance of the algorithm. Three version of the MPTA are developed in this paper to achieve this goal.