Efficient automotive electromagnetic modelling

The Transmission Line Modelling (TLM) method is applied to the electromagnetic modelling of vehicles. Implications of increasing frequencies in computer models of electromagnetic compatibility (EMC) studies are discussed. Efficient algorithms and resource management strategies are developed With a view to producing accurate results m a realistic computational run time. Theoretical aspects covered are: (1) the development and accuracy of the TLM method; (2) an improved Partial Huygens' surface for plane wave excitation; (3) an evaluation of high-performance local and global absorbing boundary conditions. Implementation aspects of TLM addressed include: (1) the effects of arithmetic precision on link line voltage and stub impedance calculations; (2) the development of an object-oriented computer code using the Object Modelling Technique; (3) methods for estimating and managing the memory requirement and run lime of simulations. It is shown that by optimizing algorithms and carefully managing resources, sufficient improvement can be made to allow relatively sophisticated models to be run on a modest desktop computer

Experimental evidence of bandgap structures in the lower jaw of the bottlenose dolphin (tursiops truncatus)

Previous studies using the TLM numerical modelling technique have demonstrated the potential existence of bandgap structures within the lower jawbone of the Atlantic Bottlenose dolphin (Tursiops truncatus). The study presented here shows experimental evidence of the existence of these bandgaps within a 2-D structure that mimics the prinnciple dimensions of the lower teeth and jawbone of the Bottlenose dolphin. The bandgap present is due to the tooth structure in the lower jaw forming a periodic array of scattering elements, which results in the formation of an acoustic stop band that is angular dependent

Ultrasonic noise emissions from wind turbines: potential effects on bat species

The impact that wind turbines have on the environment, particularly with respect to wildlife such as bat species, has generated increasing concern over the last decade. Although the harnessing of wind power is becoming much more widespread as a clean, renewable energy resource, the increasing global turbine mortality rates for bats are thought to be significantly detrimental to susceptible species. Much research is still needed to fully understand the ways in which turbines affect bats, since they rely on echolocation and audible cues to hunt and navigate, therefore having a unique acoustic perspective of objects in their vicinity. Here we present an overview of what is currently known regarding ultrasonic emissions from operational wind turbine structures, including noise generated from the gearing mechanism, rotor, or through blade defects, and how such noise may be perceptible to some bat species in the local turbine habitat

'Rock Guitar': optimising concrete properties for the manufacture of a concrete guitar

There is potential for cement-based materials to be used in making high-value customised musical instruments. This paper considers the properties (modulus, density, strength, and damping ratio) that a cement-based material requires to replicate traditional materials currently used in instrument production. Results are presented which demonstrate sound interaction with cementitious materials. A selection of mixes incorporating PVA, Lytag lightweight aggregate and normal sand mix with PVA were produced and tested with an impact hammer using the roving hammer technique and modal analysis in order to obtain the natural frequencies and damping ratio of the specimens. Lytag based mortars with PVA was determined as the optimum mix from the tests which was subsequently used to cast a workable full-size solid-bodied electric guitar, due to its lower elastic modulus and lower density compared to the normal compared mix, and its damping ratio in the region of wood (pine)

Wind turbines and bat mortality: interactions of bat echolocation pulses with moving turbine rotor blades.

Wind power is a rapidly growing energy technology, popular for being a clean, reliable and cost-efficient renewable energy source. However, recently concern has been growing over the impact of wind turbines on flying wildlife, with both birds and bats found dead around turbine bases and observed collisions with moving turbine rotors. This phenomenon is widespread and has received enough attention to warrant investigation into how and why these collisions occur. In this paper we investigate the acoustic interaction of bats with wind turbines, in particular the interpretation of reflected sound pulses (echolocation) used by bats to navigate. This paper focuses on the effects of moving turbine rotor blades on reflected acoustic pulses, analogous to what might be presented to an echolocating bat approaching an operational turbine at rotor height. High frequency, simulated FM bat pulses were used to assess reflected echo properties from microturbines (experimentally and in simulation) in order to investigate what interaction rotor movements had with incoming pulses and the potential consequences for an echolocating bat near a moving wind turbine

Acoustic emission monitoring in geotechnical element tests

Acoustic emission (AE) is high-frequency noise (>10kHz) generated by deforming materials. AE is widely used in many industries for non-destructive testing and evaluation; however, it is seldom used in geotechnical engineering, despite evidence of the benefits, because AE generated by particulate materials is highly complex and difficult to measure and interpret. This paper demonstrates that innovative AE instrumentation and measurement can enhance insights into geotechnical element tests. Results from a programme of triaxial compression and shear, large direct-shear and large permeameter experiments show that AE can be used to characterise mechanical and hydromechanical behaviour of soils and soil-structure interaction, including: dilative shear behaviour; transitions from pre- to post-peak shear strength; changes in strain rates; isotropic compression; unload-reload cycles of compression and shear; and seepage-induced internal instability phenomena