The development of cable force during hammer-throw turns is crucial to the throw distance. In this paper, we present a method that is capable of measuring cable force in real time and, as it does not interfere with technique, it is capable of providing immediate feedback to coaches and athletes during training. A strain gauge was mounted on the wires of three hammers to measure the tension in the wire and an elite male hammer thrower executed three throws with each hammer. The output from the gauges was recorded by a data logger positioned on the lower back of the thrower. The throws were captured by three high-speed video cameras and the three-dimensional position of the hammer's head was determined by digitizing the images manually. The five best throws were analysed. The force acting on the hammer's head was calculated from Newton's second law of motion and this was compared with the force measured via the strain gauge. Qualitatively the time dependence of the two forces was essentially the same, although the measured force showed more detail in the troughs of the force-time curves. Quantitatively the average difference between the measured and calculated forces over the five throws was 76 N, which corresponds to a difference of 3.8% for a cable force of 2000 N.

The National Aeronautics and Space Administration (NASA) has flight-tested a flush airdata sensing (FADS) system on the Hyper-X Research Vehicle (X-43A) at hypersonic speeds during the course of two successful flights. For this series of tests, the FADS system was calibrated to operate between Mach 3 and Mach 8, and flight test data was collected between Mach 1 and Mach 10. The FADS system acquired pressure data from surfacemounted ports and generated a real-time angle-of-attack ( ! ) estimate on board the X-43A. The collected data were primarily intended to evaluate the FADS system performance, and the estimated ! was used by the flight control algorithms on the X-43A for only a portion of the first successful flight. This paper provides an overview of the FADS system and ! = port 2 pressure reading, psf P 3 = port 3 pressure reading, psf P 4 = port 4 pressure reading, psf P 5 = port 5 pressure reading, psf psf = pounds per square foot scramjet = supersonic combustion ramjet TPS = thermal protection system X/L = fraction of reference length q = dynamic pressure, psf ! = angle of attack, deg ! = angle of sideslip, deg

No abstract

The second flight of the Hyper-X program afforded a unique opportunity to determine the aerodynamic force and moment characteristics of an airframe-integrated scramjet-powered aircraft in hypersonic flight. These data were gathered via a repeated series of pitch, yaw, and roll doublets, frequency sweeps, and pushover-pullup maneuvers performed throughout the X-43A cowl-closed descent. Maneuvers were conducted at Mach numbers of 6.80-0.95 and at altitudes from 92,000 ft mean sea level to sea level. The dynamic pressure varied from 1300 to 400 psf with the angle of attack ranging from 0 to 14 deg. The flight-extracted aerodynamics were compared with preflight predictions based on wind-tunnel test data. The X-43A flight-derived axial force was found to be 10-15% higher than prediction. Underpredictions of similar magnitude were observed for the normal force. For Mach numbers above 4.0, the flight-derived stability and control characteristics resulted in larger-than-predicted static margins, with the largest discrepancy approximately 5 in. forward along the x-axis center of gravity at Mach 6.0. This condition would result in less static margin in pitch. The predicted lateral-directional stability and control characteristics matched well with flight data when allowance was made for the high uncertainty in angle of sideslip.

An economic analysis of a private commercial magnetic resonance (MR) imaging service was carried out. At an expected case-load of 2000 per year, a mid-field MR unit was predicted to cost $470 per case using teleradiology and $544 per case using film and a courier service. Routine and emergency MR services were provided to two communities in Maryland. In a two-year study period, 8083 teleradiology examinations were performed. Digital images were acquired and transmitted without data compression via ISDN at 128 kbit/s to a central diagnostic workstation for interpretation by a team of radiologists. The average transmission time for a typical case of 50 images was 6-8 min. Preliminary interpretations were normally available within 2 h and the final transcribed reports were usually faxed to the physicians' offices within 24 h. The results of a survey indicated that the system was well received by both referring physicians and patients. Costs per case in practice were similar to those predicted.