Development of closed loop roll control for magnetic balance systems

This research was undertaken with the goal of demonstrating closed loop control of the roll degree of freedom on the NASA prototype magnetic suspension and balance system at the MIT Aerophysics Laboratory, thus, showing feasibility for a roll control system for any large magnetic balance system which might be built in the future. During the research under this grant, study was directed toward the several areas of torque generation, position sensing, model construction and control system design. These effects were then integrated to produce successful closed loop operation of the analogue roll control system. This experience indicated the desirability of microprocessor control for the angular degrees of freedom

Application of digital control to a magnetic model suspension and balance model

The feasibility of using a digital computer for performing the automatic control functions for a magnetic suspension and balance system (MSBS) for use with wind tunnel models was investigated. Modeling was done using both a prototype MSBS and a one dimensional magnetic balance. A microcomputer using the Intel 8080 microprocessor is described and results are given using this microprocessor to control the one dimensional balance. Hybrid simulations for one degree of freedom of the MSBS were also performed and are reported. It is concluded that use of a digital computer to control the MSBS is eminently feasible and should extend both the accuracy and utility of the system

Application of superconducting coils to the NASA prototype magnetic balance

Application of superconducting coils to a general purpose magnetic balance was studied. The most suitable currently available superconducting cable for coils appears to be a bundle of many fine wires which are transposed and are mechanically confined. Sample coils were tested at central fields up to .5 Tesla, slewing rates up to 53 Tesla/ sec and frequencies up to 30 Hz. The ac losses were measured from helium boil-off and were approximately 20% higher than those calculated. Losses were dominated by hysteresis and a model for loss calculation which appears suitable for design purposes is presented along with computer listings. Combinations of two coils were also tested and interaction losses are reported. Two feasible geometries are also presented for prototype magnetic balance using superconductors

The effect of airfoil scaling on the predicted unsteady loading onthe blade of a 1 and 1/2 stage transonic turbine and a comparison with experimental results

ABSTRACT In this study, two time-accurate Navier-Stokes analyses were obtained to predict the first-vane/first-blade interaction in a 1 and 1/2-stage turbine rig for comparison with measurements. In the first computation, airfoil scaling was applied to the turbine blade to achieve periodicity in the circumferential direction while modeling 1/18 of the annulus. In the second, 1/4 of the wheel was modeled without the use of airfoil scaling. For both simulations the predicted unsteady pressures on the blade were similar in terms of time-averaged pressure distributions and peak-peak unsteady pressure envelopes. However, closer inspection of the predictions in the frequency domain revealed significant differences in the magnitudes of unsteadiness at twice vane-passing frequency (and the vane-passing frequency itself, to a lesser extent). The results of both computations were compared to measurements of the vane-blade interaction in a full-scale turbine rig representative of an early design iteration of the PW6000 engine. These measurements were made in the short-duration turbine-test facility at The Ohio State University Gas Turbine Laboratory. The experimentally determined, time-resolved pressures were in good agreement with those predicted with the 1/4-wheel simulation

Injuries at a Canadian National Taekwondo Championships: a prospective study

BACKGROUND: The purpose of this prospective study was to assess the injury rates in male and female adult Canadian Taekwondo athletes relative to total number of injuries, type and body part injured. METHODS: Subjects (219 males, 99 females) participated in the 1997 Canadian National Taekwondo Championships in Toronto, Canada. Injuries were recorded on an injury form to documents any injury seen and treatment provided by the health care team. These data were later used for this study. The injury form describes the athlete and nature, site, severity and mechanism of the injury. RESULTS: The overall rate of injuries was 62.9/1,000 athlete-exposures (A-E). The males (79.9/1,000 A-E) sustained significantly more injuries than the females (25.3/1,000 A-E). The lower extremities were the most commonly injured body region in the men (32.0 /1,000 A-E), followed by the head and neck (18.3/1,000 A-E). Injuries to the spine (neck, upper back, low back and coccyx) were the third most often injured body region in males (13.8/1,000 A-E). All injuries to the women were sustained to the lower extremities. The most common type of injury in women was the contusion (15.2/1,000 A-E). However, men's most common type of injury was the sprain (22.8/1,000 A-E) followed by joint dysfunction (13.7/1,000A-E). Concussions were only reported in males (6.9/1,000 A-E). Compared to international counterparts, the Canadian men and women recorded lower total injury rates. However, the males incurred more cerebral concussions than their American colleagues (4.7/1,000 A-E). CONCLUSIONS: Similar to what was found in previous studies, the current investigation seems to suggest that areas of particular concern for preventive measures involve the head and neck as well as the lower extremities. This is the first paper to identify spinal joint dysfunction

New Results from the Cryogenic Dark Matter Search Experiment

Using improved Ge and Si detectors, better neutron shielding, and increased counting time, the Cryogenic Dark Matter Search (CDMS) experiment has obtained stricter limits on the cross section of weakly interacting massive particles (WIMPs) elastically scattering from nuclei. Increased discrimination against electromagnetic backgrounds and reduction of neutron flux confirm WIMP-candidate events previously detected by CDMS were consistent with neutrons and give limits on spin-independent WIMP interactions which are >2X lower than previous CDMS results for high WIMP mass, and which exclude new parameter space for WIMPs with mass between 8-20 GeV/c^2.Comment: 4 pages, 4 figure

Historical influence on the practice of chiropractic radiology: part II - thematic analysis on the opinions of diplomates of the American Chiropractic College of Radiology about the future

Background: Over the past 20 years, various authors have addressed the question of the future of chiropractic. Most were positive about the future, with some advocating evidence-based practice and integration with mainstream healthcare, some advocating continued separation with an emphasis on subluxation-based care or the traditional/historical paradigm of chiropractic, and some calling for tolerance and unity. No papers were found specifically inquiring about the future of chiropractic radiology. Methods: The study population consisted of all current members of the American Chiropractic College of Radiology (ACCR), estimated at 190 people, known as chiropractic radiologists or Diplomates of the American Chiropractic Board of Radiology (DACBRs). An internet-based, anonymous survey using SurveyMonkey was implemented, supplemented by hard copies distributed at a conference. The main point of interest for this paper is the final item of the overall questionnaire. This item inquired about the future of chiropractic radiology. Thematic analysis was used on the responses, coded in both constructionist and inductive ways to extract both a general outlook and more specific themes. The inductive themes were also assigned secondarily to a SWOT (strengths, weaknesses, opportunities, and threats) analysis. Results: The overall response rate to the survey was 38% (73/190); within the group of respondents, 71 of 73 (98%) answered the item that is the subject of this paper. Opinions on the outlook for chiropractic radiology in the future were more negative than positive, with 14 respondents giving a positive outlook, 26 negative, and 14 non-committal. 28 respondents advocated integration with the wider healthcare community, 11 recommended emphasising separateness or a focus on working within chiropractic, and 15 did not express an opinion on this issue. Ten strengths were noted, 11 weaknesses, 57 opportunities, and 30 threats. Conclusions: The increasing necessity of demonstrating evidence for diagnostic and therapeutic procedures in healthcare makes it likely that chiropractic radiologists and the wider chiropractic profession will need to take a more active position on evidence-based practice. Re-evaluation of guidelines and legislation as well as enforcement policies and practices will be necessary. The consequences of failing to do so may include increased marginalisation and reduced viability as a profession

New results from the Cryogenic Dark Matter Search experiment

Using improved Ge and Si detectors, better neutron shielding, and increased counting time, the Cryogenic Dark Matter Search (CDMS) experiment has obtained stricter limits on the cross section of weakly interacting massive particles (WIMPs) elastically scattering from nuclei. Increased discrimination against electromagnetic backgrounds and reduction of the neutron flux confirm WIMP-candidate events previously detected by CDMS were consistent with neutrons and give limits on spin-independent WIMP interactions which are \u3e2× lower than previous CDMS results for high WIMP mass, and which exclude new parameter space for WIMPs with mass between 8 and 20 GeV/c2