Selvan Pather

Vibration damping characteristics of short hemp fibre thermoplastic composites

In this project, free vibration testing and dynamic mechanical analysis methods were used to study the damping properties of noil hemp fibre-reinforced polypropylene composites with varying fibre contents (0 to 60 wt%) and compatibilizers (maleic anhydride-grafted polypropylene and maleic anhydride-grafted polyethylene octane) under applied frequencies of 1 to 200 Hz. The storage modulus of the composites was increased by the increase in hemp fibre content. However, the maximum damping ratio was obtained from the composite with 30 wt% noil hemp fibre. The addition of coupling agents reduced the damping capacity of all composites. However, 30 wt% noil hemp fibre-reinforced polypropylene coupled with 2.5 wt% anhydride-grafted poly ethylene octane revealed the highest damping ratio among coupled composites. Damping properties of the composites were relatively constant over the frequency range, except at frequencies which the material–instrument system began to resonate and peaks were observed in the curves.

The development of a robotic system for HIFU surgery applied to liver tumours

High intensity focused ultrasound is receiving increasing attention as a non-invasive method of destroying deep-seated tumours. This paper describes the early development of a novel system comprising of small multiple focused ultrasound transducers, attached to the end of a robotic manipulator, to ablate liver tumours. Small multiple transducers are proposed to minimise effects of off-focus hot spots, cavitation and to provide better access into the abdominal cavity. The design of a unique robotic manipulator is proposed to effectively scan the small combined focal region of the acoustic field throughout the volume of large tumours. This paper discusses the specification of the multiple HIFU transducers and the design of a concept robotic manipulator required for use in a surgical environment.

Depth of Anaesthesia: Measuring or guessing?

This paper is a comprehensive literature review on the Depth of Anaesthesia (DoA) monitoring problem. We first investigate the current clinical practice, then briefly introduce the DoA monitors, finally we analyse and discuss the reliability and accuracy of current DoA assessment practice. In this study we find that most of the responses suppressed by anaestheic agents are not of the central nervous system (CNS) but are responses from the peripheral nervous systems (PNS). The responses generated for drug combinations across the therapeutic ranges show considerable variations in drug concentrations that constitute adequate anaesthesia for a particular stimulus. We propose to capture the decision process of anaesthetist using neural networks as neural networks are good at finding patterns in non linear, non stationary signals.

Ground Hemp Fibers as Filler/Reinforcement for Thermoplastic Biocomposites

Mechanical properties (tensile, flexural, and impact) of ground hemp fibre polypropylene composites were investigated. Ground alkali-treated hemp fibre and noil hemp fibres with various initial fibre lengths were utilized to reinforce polypropylene matrix. Firstly, the microstructural and tensile characterizations of the two types of fibres were characterized using scanning electron microscope (SEM), Fourier transform infrared analysis (FTIR), and Dynamic Mechanical Analyser (DMA). Then, the fibres were ground into different lengths of 0.2, 0.5, 1, and 2 mm; composites containing 40 wt% short hemp fibre and 5 wt% maleic anhydride grafted polypropylene (MAPP) were fabricated by means of a twin screw extruder and an injection moulding machine. Finally, influence of hemp fibre type and initial hemp fibre length on tensile property of the composites were investigated. The results revealed that addition of either noil hemp fibre or normal treated hemp fibre into the pure polypropylene matrix increased the tensile strength almost twice and stiffness of the composites more than three times. Although noil hemp fibre composite indicated slightly lower mechanical properties than the normal alkali-treated fibre composites, the difference was not significant. The analysis of the results provided the optimum initial fibre length (powder) of 0.2 mm hemp polypropylene composite. The results can be extended to different types of natural fibres.