Download the this issue (complete journal, excluding cover) (~750 kB).

Jump to:

1. Simulation of a Proton Exchange Membrane Fuel Cell Stack Using an Electronic Equivalent Circuit Model
2. The Development of a Flexible Rotor Active Magnetic Bearing System
3. An Adaptive Hybrid List Decoding and Chase-Like Algorithm for Reed-Solomon Codes
4. Effect of Characteristics of Dynamic Muscle Contraction on Crosstalk in Surface Electromyography Recordings

Simulation of a Proton Exchange Membrane Fuel Cell Stack Using an Electronic Equivalent Circuit Model by J.P. du Toit and H.C. vZ. Pienaar
Abstract: his article describes the method to calculate the parameters of an electronic equivalent circuit model of a proton exchange membrane fuel cell stack. The model is based on that of Yu and Yuvarajan, but very little detail is given by them on how to calculate the component values of the circuit model based on the experimental data of a fuel cell or fuel cell stack. Here, a method will be established in which the performance data of small fuel cell stacks can be used to simulate the behaviour of much larger stacks under the same operating conditions. It is crucial to be able to simulate a fuel cell stack using an electronic circuit equivalent model when designing power converters for fuel cells, since the fuel cell stack can then be simulated together with a power converter or any other electronic circuitry. First, a mathematical model of a small, two-cell, proton exchange membrane fuel cell was calculated based on experimental data. This model was then adapted to describe the characteristics of a much larger, 100 W, fuel cell stack. Finally, the mathematical model was used to calculate the parameters for an electronic circuit model by establishing a clear relationship between the two models.
Download Paper (~218 kB)
 

The Development of a Flexible Rotor Active Magnetic Bearing System by E.O. Ranft, G. van Schoor and J.G. Roberts
Abstract: A design process comprising aspects of modelling and analysis is developed, implemented and verified for a flexible rotor active magnetic bearing system. The system is specified to experience the first three critical frequencies up to an operating speed of 10,000 rpm. Rotor stability at critical frequencies places specific constraints on the equivalent stiffness and damping parameters of the active magnetic bearing. An iterative design process is then initiated by an electromagnetic design of the radial active magnetic bearings resulting in parameters used in the detailed modelling of the system. Stiffness and damping parameters as well as system dynamic response are verified and used to design a flexible rotor. The magnetic bearing locations, displacement sensor locations and rotordynamic response are verified using finite element analysis. The design of the rotor stands central to the iterative design process since it impacts on the forces experienced by the active magnetic bearings as well as the critical frequencies of the active magnetic bearing system. Once constructed the actual active magnetic bearing system stiffness and damping parameters as well as dynamic response are compared to modelled results. The rotordynamic response is characterised by measuring the rotor displacement at pre-defined locations as the rotor traverses the critical frequencies. These results are compared with the predicted rotordynamic response.
Download Paper (~357 kB)
 

An Adaptive Hybrid List Decoding and Chase-Like Algorithm for Reed-Solomon Codes by W. Jin, H. Xu and F. Takawira
Abstract: This paper presents an adaptive hybrid Chase-like algorithm for Reed-Solomon codes, which is based on the list decoding algorithm. The adaptive hybrid algorithm is based on the reliability threshold to exclude the more reliable bits from being processed by the list decoding algorithm and reduce the complexity of the hybrid algorithm. Simulation results show that the decoding complexities of the adaptive hybrid algorithm for both (15.7) and (31.21) Reed-Solomon codes are almost the same as those of the list decoding algorithm (without Chase algorithm) at high signal-to-noise ratios, but there is a significant improvement in FER performance.
Download Paper (~176 kB)
 

Effect of Characteristics of Dynamic Muscle Contraction on Crosstalk in Surface Electromyography Recordings by S. Viljoen, T. Hanekom and D. Farina
Abstract: An investigation into the ability of different spatial filters to reduce the amount of crosstalk in a surface electromyography measurement was conducted. A simulation model  as implemented to compare the performance of four spatial filters under dynamic muscle contractions. Two parameters of a dynamic muscle contraction, namely muscle shortening and varying contraction force, were evaluated separately. The normal double differential filter resulted in the best crosstalk rejection for varying contraction force simulations, while the double differential filter performed best when incorporating muscle shortening. It is furthermore suggested that crosstalk is influenced more by muscle shortening than by changes in the contraction force.
Download Paper (~239 kB)