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Träfflista för sökning "WFRF:(Johnson Peter W) srt2:(2000-2004)"

Sökning: WFRF:(Johnson Peter W) > (2000-2004)

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1.
  • Derevianko, A, et al. (författare)
  • Electric-octupole and pure-electric-quadrupole effects in soft-X-ray photoemission
  • 2000
  • Ingår i: Physical Review Letters. - 0031-9007. ; 84:10, s. 2116-2119
  • Tidskriftsartikel (refereegranskat)abstract
    • Second-order [O(k(2)), k = omega/c] nondipole effects in soft-x-ray photoemission are demonstrated via an experimental and a theoretical study of angular distributions of neon valence photoelectrons in the 100-1200 eV photon-energy range. A newly derived theoretical expression for nondipolar angular distributions characterizes the second-order effects using four new parameters with primary contributions from pure-quadrupole and octupole-dipole interference terms;Independent-particle calculations of these parameters account for a significant portion of the existing discrepancy between experiment and theory for Ne 2p first-order nondipole parameters.
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2.
  • Johnson, Peter W, et al. (författare)
  • Comparison of measurement accuracy between two wrist goniometer systems during pronation and supination.
  • 2002
  • Ingår i: Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology. - 1050-6411. ; 12:5, s. 413-20
  • Tidskriftsartikel (refereegranskat)abstract
    • Pronation and supination have been shown to affect wrist goniometer measurement accuracy. The purpose of this study was to compare differences in measurement accuracy between a commonly used biaxial, single transducer wrist goniometer (System A) and a biaxial, two-transducer wrist goniometer (System B) over a wide range of pronation and supination (P/S) positions. Eight subjects moved their wrist between -40 and 40 degrees of flexion/extension (F/E) and -10 and 20 degrees of radial/ulnar (R/U) deviation in four different P/S positions: 90 degrees pronation; 45 degrees pronation; 0 degrees neutral and 45 degrees supination. System A was prone to more R/U crosstalk than System B and the amount of crosstalk was dependent on the P/S position. F/E crosstalk was present with both goniometer systems and was also shown to be dependent on P/S. When moving from pronation to supination, both systems experienced a similar extension offset error; however R/U offset errors were roughly equal in magnitude but opposite in direction. The calibration position will affect wrist angle measurements and the magnitude and direction of measurement errors. To minimize offset errors, the goniometer systems should be calibrated in the P/S posture most likely to be encountered during measurement. Differences in goniometer design and application accounted for the performance differences.
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