Polarizablity of 2D and 3D conducting objects using method of moments

Fundamental antenna limits of the gain-bandwidth product are derived from polarizability calculations. This electrostatic technique has significant value in many antenna evaluations. Polarizability is not available in closed form for most antenna shapes and no commercial electromagnetic packages have this facility. Numerical computation of the polarizability for arbitrary conducting bodies was undertaken using an unstructured triangular mesh over the surface of 2D and 3D objects. Numerical results compare favourably with analytical solutions and can be implemented efficiently for large structures of arbitrary shape.Comment: Peer-reviewed articl

An investigation into the Gustafsson limit for small planar antennas using optimisation

The fundamental limit for small antennas provides a guide to the effectiveness of designs. Gustafsson et al, Yaghjian et al, and Mohammadpour-Aghdam et al independently deduced a variation of the Chu-Harrington limit for planar antennas in different forms. Using a multi-parameter optimisation technique based on the ant colony algorithm, planar, meander dipole antenna designs were selected on the basis of lowest resonant frequency and maximum radiation efficiency. The optimal antenna designs across the spectrum from 570 to 1750 MHz occupying an area of $56mm \times 25mm$ were compared with these limits calculated using the polarizability tensor. The results were compared with Sievenpiper's comparison of published planar antenna properties. The optimised antennas have greater than 90% polarizability compared to the containing conductive box in the range $0.3<ka<1.1$, so verifying the optimisation algorithm. The generalized absorption efficiency of the small meander line antennas is less than 50%, and results are the same for both PEC and copper designs.Comment: 6 pages, 10 figures, in press article. IEEE Transactions on Antennas and Propagation (2014

Point Contacts in Modeling Conducting 2D Planar Structures

Use of an optimization algorithm to improve performance of antennas and electromagnetic structures usually ends up in planar unusual shapes. Using rectangular conducting elements the proposed structures sometimes have connections with only one single point in common between two neighboring areas. The single point connections (point crossing) can affect the electromagnetic performance of the structure. In this letter, we illustrate the influence of point crossing on dipole and loop antennas using MoM, FDTD, and FEM solvers. Current distribution, radiation pattern, and impedance properties for different junctions are different. These solvers do not agree in the modeling of the point crossing junctions which is a warning about uncertainty in using such junctions. However, solvers agree that a negligible change in the junction would significantly change the antenna performance. We propose that one should consider both bridging and chamfering of the conflicting cells to find optimized structures. This reduces the simulation time by 40% using FDTD modeling, however no significant reduction is obtained using the MoM and FEM methods.Comment: 4 pages, 10 figures, 1 table, accepted for publication in IEEE Antennas Wireless Propag. Let

Research Methods for Engineers

Learn how to plan for success with this hands-on guide to conducting high-quality engineering research. Plan and implement your next project for maximum impact Step-by-step instructions that cover every stage in engineering research, from the identification of an appropriate research topic through to the successful presentation of results. Improve your research outcomes Discover essential tools and methods for producing high-quality, rigorous research, including statistical analysis, survey design and optimization techniques. Research with purpose and direction Clear explanations, real-world examples and over 50 customizable end-of-chapter exercises, all written with the practical and ethical considerations of engineering in mind. A unique engineering perspective Written especially for engineers, and relevant across all engineering disciplines, this is the ideal book for graduate students, undergraduates, and new academics looking to launch their research careers

Front crawl swimming analysis using accelerometers:A preliminary comparison between pool and flume

AbstractBiomechanical characteristics such as stroke rate and stroke length can be used to determine the velocity of a swimmer and can be analysed in both a swimming pool and a flume. The aim of the present preliminary study was to investigate the differences between the acceleration data collected from a swimming pool with that collected from a flume, as a function of the swimmer's stroke rate and stroke count, with the objective of identifying the impact on the swimmer's performance. The differences were determined by the analysis of the stroke's features, comparing several strokes normalized to one stroke count from an elite swimmer. Triaxial accelerometer logging using a sensor located in an arm band positioned immediately in the wrist was used to record the swimmer's stroke. There is statistical evidence that show that there are small differences between the pool and flume on medio-lateral wrist movements (0.64 < r < 0.75). The correlation coefficients are (0.75 < r < 0.83) and (0.82 < r < 0.89) for the other two axes

Novel Methodology for Measuring the Coefficient of Restitution from Various Types of Balls and Surfaces

Abstract The determination of the coefficient of restitution is of major interest in the design of balls and surfaces. Tennis courts are required to be resurfaced every five years. Players that slide on the court trust the surface to be uniform. Tennis court surfaces change as the ball fluff builds up, the heavily used playing areas are compacted more, the surface on clay is scuffed, and the sun and rain degrades the surface. Injuries can be caused by a player losing footing because of surface variability. With bouncing balls, the ball type and pressure are variable and depend on temperature and age. An investigation on the bounce of various balls (diameter less than 150 mm) from surfaces using an accelerometer on a novel, low cost, portable apparatus is presented. The mechanical structure holds both the moving ball and an inertial sensor. The quality and age of balls and the wear on playing surfaces is particularly important for reflex actions of elite athletes. Courts, pitches and other sports surfaces can be routinely quantified using sport specific balls and this simple, low cost method. Good agreement was observed between the coefficient of restitution using the portable device and a vertical drop test using a high speed camera. The error obtained using the portable device on various types of sports balls with the variation in CoR ≤ 0.01 which falls within the standards of the International Tennis Federation. There is a significant difference ( p = 0.0003) between a hardcourt tennis CoR and a synthetic grass tennis court

Triaxial accelerometer sensor trials for bat swing interpretation in cricket

AbstractAnalysis of bat swing is important to the assessment and understanding of effective batting in cricket. The key features of a bat swing include the spatio-temporal position of the bat before contact with the ball and the bat velocity. The current methods of bat swing analysis such as video tracking and coach observation are labor intensive and expensive. This work examined the use of small, low-cost, three dimensional motion sensors as a replacement to existing methods. Using two bat-mounted accelerometer sensors, two experiments were conducted: a set of ball-free, straight drives by an amateur batter at nominal constant speed, and a set of straight drives at different speeds by the same batter accompanied by video tracking. In all cases the bat swing was in the x-z plane of the sensors placed on the reverse face of the bat. The bat face remains in the z direction. The objective was to minimize accelerations perpendicular to the swing plane. Data analysis revealed consistent acceleration profiles with minimal acceleration perpendicular to the plane of the swing (x-z plane). The time lag between the z acceleration peak and the x acceleration peak is related to the speed of the bat. The highest peak in x acceleration results from the higher centrifugal force with minimum radius of gyration while the bat was close to the batter (confirmed by the video footage). This is the dominant rotational component plus an additional gravitational force in the x direction when the bat is aligned to gravity. The sensor attached to the on-side edge of the bat showed higher peak magnitude in x acceleration compared to that from the off-side edge, which indicated variation between the two edges of the bat during swing. The tilted position of the stationary bat at the start of each swing was determined from the x and z axis profiles from minus one g and zero respectively. Different peak accelerations were evident for different swing intensities. This study indicated that the accelerometer sensors can provide reliable bat swing information