In 1964, just a few years after the invention of the laser, a fluid velocity measurement based on the frequency shift of scattered light was made and the laser Doppler technique was born. This comprehensive review paper charts advances in the development and applications of laser Doppler vibrometry (LDV) since those first pioneering experiments. Consideration is first given to the challenges that continue to be posed by laser speckle. Scanning LDV is introduced and its significant influence in the field of experimental modal analysis described. Applications in structural health

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ABSTRACT:The perception of 'feel' during a ball-implement impact is considered a significant determinant in equipment selection. Previous studies in golf have found that the perceived time for which the ball and clubface are in contact is a factor in the 'feel' of the shot. This factor appears to have become more significant with the development of the latest metal 'woods'. The purpose of this study was to investigate whether golfers' perceptions of impact duration correspond to measured values or whether the perceptions are created by other factors. A technique has been developed to measure the duration of impact by creating an electrical circuit in which the ball and clubface form a 'switch', completing the circuit whilst contact is maintained between the two bodies. Measurements were taken of the duration of impact between five different types of clubhead and two different constructions of golf ball. Further tests, also reported in this paper, investigated the effect of both clubhead speed at impact and ball compression on the impact duration. The results suggest that the ball has a greater effect on impact duration than the type of clubhead with lower compression balls producing longer impact durations than higher compression balls and two piece balls producing shorter impact durations than three piece, wound balls. It was also found that the duration of impact decreased as the clubhead speed at impact was increased. Finally, results suggest that there is no correlation between the perception of the golfer and the actual duration of impact and therefore other factors are responsible for creating this perception.

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This paper explores the use of laser vibrometry for vibration measurement directly from a rotating component. The presence of a surface velocity component due to the rotation itself is shown to create a strong measurement dependency on vibration perpendicular to the intended measurement direction. Particular ambiguity results at synchronous frequencies. A mathematical means to resolve the genuine vibration components from two simultaneous laser vibrometer measurements is presented and shown to be effective in the study of nonsynchronous rotor vibrations.

The high-speed first serve has become an increasingly dominant factor in tennis, raising concerns over the influence modern racket technology has on the game. One concern is that rackets are now too powerful and so overemphasise a player's ability to produce fast serves. This may help explain the 'penalty shootout' scenario, where match result id dictated by the relative speed and consistency of the players' first serves. There is some concern that on the faster surfaces, maximum service speeds have reached, or are approaching, the service returnee's reaction threshold, making it virtually impossible for players to return the ball. To shed light on the issue the factors relating to 'racket power', the amount a racket magnifies a player's innate ability to impart linear velocity to a tennis ball, need to be considered.Various studies have been performed that shed some light on the subject. This paper presents an overview of the published literature related to 'racket power' in the game of tennis, a review of previous research on specific and sometimes controversial issues. Areas meriting further investigation are identified to encourage future research into racket power.

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