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

A study on the effect of a metallic ring worn on human fingers using a simple scannable block hand phantom

A simple geometrical representation of a human hand has been constructed which allow a metallic ring to be placed on the finger. The electric field magnitude within an isolated finger is measured and compared with the cases when the ring is worn. The ring has been found to significantly alter the electric field magnitude within the finger at 1800 MHz. This effect can also be found within the adjacent fingers at both 900 MHz and 1800 MHz

A study on the effect of loop-like jewellery items worn on human hand on specific absorption rate (SAR) at 1900 MHz

Abstract: This paper presents simulation results that evaluate the effect of loop-like jewellery items (rings and bangles) worn on human fingers and wrist on SAR in the human head and the hand. The jewellery items were modelled as conducting objects with the typical commercial sizes available. Rings were placed on different fingers in a computer model for comparison purposes. The amount of energy absorbed in the head/hand and the effect brought about by the jewellery are shown to vary for different antennas. In this study, a monopole and a PIFA antenna have been employed. The results obtained indicated that: (i) by using a monopole antenna, the peak and average 1g SAR in the head are slightly decreased by the introduction of the ring and bangle, (ii) by using a PIFA, the peak and average 1g SAR in the head are increase by more than 12% and 11% respectively by the metallic rings

Planar electromagnetic bandgap structures based on polar curves and mapping functions

A type of electromagnetic bandgap structure is described that is easily parameterized and can produce a range of square and spiral geometries. Individual electromagnetic bandgap (EBG) geometries are defined on a cell-by-cell basis in terms of their convolution factor , which defines the extent to which the elements are interleaved and controls the coupling slot length between adjacent elements. Polar equations are used to define the slot locus which also incorporate a transformation which ensures the slot extends into the corners of the square unit cell and hence extends the maximum slot length achievable. The electromagnetic properties of the so-called polar EBG are evaluated by means of numerical simulation and measurements and dispersion diagrams are presented. Finally, the performance is compared with other similar miniaturized EBG cell geometries. It is shown that the polar EBG has better angular stability than the equivalent square patch design and is comparable in terms of performance to other low frequency EBG elements. At the same time it retains the ability to fine tune the response by adjusting

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)

A study on the effect of loop-like jewellery items worn on human hand on specific absorption rate (SAR) at 1900 MHz

Abstract: This paper presents simulation results that evaluate the effect of loop-like jewellery items (rings and bangles) worn on human fingers and wrist on SAR in the human head and the hand. The jewellery items were modelled as conducting objects with the typical commercial sizes available. Rings were placed on different fingers in a computer model for comparison purposes. The amount of energy absorbed in the head/hand and the effect brought about by the jewellery are shown to vary for different antennas. In this study, a monopole and a PIFA antenna have been employed. The results obtained indicated that: (i) by using a monopole antenna, the peak and average 1g SAR in the head are slightly decreased by the introduction of the ring and bangle, (ii) by using a PIFA, the peak and average 1g SAR in the head are increase by more than 12% and 11% respectively by the metallic rings

A study on the effect of a metallic ring worn on human fingers using a simple scannable block hand phantom

A simple geometrical representation of a human hand has been constructed which allow a metallic ring to be placed on the finger. The electric field magnitude within an isolated finger is measured and compared with the cases when the ring is worn. The ring has been found to significantly alter the electric field magnitude within the finger at 1800 MHz. This effect can also be found within the adjacent fingers at both 900 MHz and 1800 MHz

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