Active rc networks of low sensitivity for integrated circuit transfer function

Active RC network is capable of extremely high Q performance with exceptional stability and has independently adjustable zeros and poles. The circuit consists of two integrators and two summers that are interconnected to produce a complete second-order numerator and a second-order denominator

CHANGES IN SPLIT VELOCITIES DURING SPRINT PERFORMANCE DEVELOPMENT

Sprint times and split velocities are invaluable measures for coaches and athletes monitoring sprint training and performance development. This study analysed sprint times and 10 m split velocities as performance of three developing athletes developed over a five week training period. All significantly improved their 60 m sprint times over the training period (p < 0.05). Sprint performance developed individually with a tendency for maximal velocities to increase early in the training period and start and acceleration velocities later. All athletes’ performances fluctuated between weeks, possibly due to a period of experimental learning in their process of skill development. This study will inform further analysis of the kinematic and kinetic parameters determining velocity, with the aim of identifying the key variables responsible for these changes

BIOMECHANICS OF LONGSWINGS PRECEDING TKACHEV ON UNEVEN BARS

Changes in the rules governing the separation of uneven bars have allowed female gymnasts to perform the Tkachev in both directions. The aim of this study was to compare the similarities in the preparatory longswing during the outward (O) and inward (I) Tkachevs. Video recordings of the Tkachevs (O=5, I=5) were collected from the 2000 Sydney Olympic Games. A 37° greater range of movement was found at the hips during the I Tkachev. In the more conventional O technique changes in the hip angle were smaller (23°) and occurred over a greater circle angle. This study has identified differences in what appear to be very similar skills. Further inter-segmental coordination and joint kinetic analyses may provide insight into the performance of these release and regrasp skills

Development of integrated thermionic circuits for high-temperature applications

Integrated thermionic circuits (ITC) capable of extended operation in ambient temperatures up to 500 C are studied. A set of practical design and performance equations is demonstrated. Experimental results are discussed in which both devices and simple circuits were successfully operated in 5000 C environments for extended periods. It is suggested that ITC's may become an important technology for high temperature instrumentation and control systems in geothermal and other high temperature environments

LOWER LIMB JOINT KINETICS IN THE SPRINT START PUSH-OFF

Previous studies have analysed lower limb joint kinetics during sprint performance, but not addressed the earliest contact out of the blocks. The aim of this study was to report lower limb joint moments and powers during the first stance phase of the sprint push-off. One competitive male sprinter performed 10 maximal sprint starts. An automatic motion analysis system (CODA, 200 Hz) with synchronised force plate data (1000 Hz) were used to collect kinematic profiles at the hip, knee and ankle and ground reaction forces for the first stance phase. Cluster markers defined the orientation of the lower limb segments in 3D. Knee and hip kinetics differed to the later phases of sprint, whereas similarities were found at the ankle. This study highlights the need for the push-off phase to be considered separately from both research and practical perspectives

LOWER LIMB LANDING BIOMECHANICS ON NATURAL AND FOOTBALL TURF

The aim of the study was to investigate variation in lower limb kinematics during jump landings on natural (NT) and artificial Football Turf (FT). One footballer performed 30 single leg jump landings, following a ball heading movement on NT and FT and immediately continued into a two-step forward run. Landing limb kinematics were recorded (200Hz) using CODA™ and cluster markers. There were similar knee and ankle touchdown kinematics and differing joint angle profiles throughout. FT landings showed greater knee flexion, adduction and internal rotation and reduced ankle eversion. During early impact, the ankle showed a tendency for greater plantar-flexion and inversion using FT compared to NT. These observations highlight a potential for altered lower limb kinematics on NT and FT which may be exaggerated during more demanding tasks and warrant further investigation

DOUBLE KNEE BEND IN THE POWER CLEAN

The power clean is well established as the “gold standard” exercise for the development of lower extremity propulsive forces (Garhammer, 1982). The power clean has become a sprint specific strength and conditioning exercise, which is incorporated into periodised training programmes (Siff, 1992). Specifically the occurrence of a double knee bend (DKB) provides a mechanism to elicit a sprint specific stretch shortening cycle (SSC), maximising power output (Enoka, 1979). The aim of this exploratory study was to investigate whether the DKB occurred in power cleans as relative load increased

Functional phases and angular momentum characteristics of Tkatchev and Kovacs

Understanding the technical requirements and underlying biomechanics of complex release and re-grasp skills on high bar allows coaches and scientists to develop safe and effective training programmes. The aim of this study was to examine the differences in the functional phases between the Tkatchev and Kovacs skills and to explain how the angular momentum demands are addressed. Images of 18 gymnasts performing 10 Tkatchevs and 8 Kovacs at the Olympic Games were recorded (50 Hz), digitised and reconstructed (3D Direct Linear Transformation). Orientation of the functional phase action, defined by the rapid flexion to extension of the shoulders and extension to flexion of the hips as the performer passed through the lower vertical, along with shoulder and hip angular kinematics, angular momentum and key release parameters (body angle, mass centre velocity and angular momentum about the mass centre and bar) were compared between skills. Expected differences in the release parameters of angle, angular momentum and velocity were observed and the specific mechanical requirement of each skill were highlighted. Whilst there were no differences in joint kinematics, hip and shoulder functional phase were significantly earlier in the circle for the Tkatchev. These findings highlight the importance of the orientation of the functional phase in the preceding giant swing and provide coaches with further understanding of the critical timing in this key phase

Influence of longswing technique on the kinematics and key release parameters of the straddle Tkachev on uneven bars

Tkachev on uneven bars is a release and re-grasp skill performed using variations of preparatory longswing techniques; the reasons why different techniques are chosen remains unclear. This study examined kinematic and key release parameters specific to three distinct techniques with the aim of understanding the relative benefits of each. During two international artistic gymnastics competitions six arch, straddle and pike longswings preceding the straddle Tkachev were recorded using twin video cameras. Calibration and movement images were digitised and reconstructed using 3D DLT. Shoulder and hip angular kinematics, angular momentum and key release parameters were compared between techniques. In the arch longswing, the first and second hip functional phases began significantly earlier than the straddle or pike. No significant differences were established for release parameters although large effect sizes for horizontal release velocity and angular momenta about the mass centre and bar were reported between the arch and other two variants. Therefore, the arch variant may provide the opportunity to develop more complex combinations following the Tkachev. Providing insight into mechanical advantages of specific longswing techniques, and highlighting those that elicit desirable characteristics offers the potential to provide coaches with objective data on technique selection and ultimately skill development

TOWARDS AN AUTOMATED FEEDBACK COACHING SUPPORT SYSTEM FOR SPRINT PERFORMANCE MONITORING

The purpose of this study was to investigate the feasibility of developing a cost-effective, automated performance feedback system to support sprint coaching. The proposed system is designed to deliver step length, step frequency, contact time and 10 m split time information of multiple athletes training on an indoor track. An integrated systems approach was chosen combining the novel Pisa Light-Gate (PLG) and Step Information Monitoring Systems (SIMS). Current results indicate data accuracy of RMS 1.662 cm for step length, RMS 0.977 ms for foot contact time and a split time detection accuracy of 8.45 ± 6.85 ms. These results suggest that the proposed integrated system, using off-the-shelf equipment, would go beyond currently available coaching tools by providing automated and highly accurate sprint performance information for multiple athletes