Threshold Study of Phase Lock Loop Systems Interim Technical Report
Threshold studies of phase lock loop systems - effect of phase comparator on overall performance and threshold phenomena
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Constant-current regulator improves tunnel diode threshold-detector performance
Grounded-base transistor is placed in a tunnel diode threshold detector circuit, and a bias voltage is applied to the tunnel diode. This provides the threshold detector with maximum voltage output and overload protection.
Cancro, C. A.↗
The effect on cosmic rays of a variation in the geomagnetic thresholds
Geomagnetic threshold effects on cosmic ray intensity during geomagnetic storm, and daily lunar tidal variation effect on geomagnetic threshold
GEOMAGNETIC STORM↗
Radiographic threshold detection levels of aluminum weld defects
Test program is used in the design and fabrication of special graduated aluminum penetrometers. The program evaluates the threshold detection capabilities of a fixed radiographic technique in detecting surface and subsurface cracks in one-quarter inch aluminum welds. The radiographic films were evaluated and the threshold detection capabilities defined.
Tryon, R. W.↗
Effect of duration of stimulus presentation on the angular acceleration threshold
Human oculogyral illusion thresholds determined on Ames Man-Carrying Rotation Device to establish stimulus duration effect on angular acceleration thresholds
Doty, R. L.↗
Comparison of cupulometric and psychophysical thresholds for perception of rotation and the oculogyral illusion
Thresholds comparison for angular acceleration derived by subjective cupulometry and by staircase method, determining thresholds for rotation perception and oculogyral illusion
Dockstader, S. L.↗
Results of FM-TV threshold reduction investigation for the ATS F trust experiment
An investigation of threshold effects in FM TV was initiated to determine if any simple, low cost techniques were available which can reduce the subjective video threshold, applicable to low cost community TV reception via satellite. Two methods of eliminating these effects were examined: the use of standard video pre-emphasis, and the use of an additional circuit to blank the picture tube during the retrace period.
Brown, J. P.↗
Bandwidth and threshold calculations for angle-tuned parametric oscillators.
The bandwidth of angle-tuned optical parametric oscillators, in some cases, is limited by the noncolinear interaction of the pump, signal, and idler beams, which results when the nonlinear material is rotated relative to the pump beam. To determine this bandwidth, a theoretical expression for the pump power threshold is derived in the near field limit taking into account double refraction for a noncolinear interaction. Angle tuning can be done by (1) rotating the crystal and mirrors as a unit, or by (2) rotating the crystal only. Expressions for determining the tuning rate and threshold increase for both tuning methods are derived.
Basu, R.↗
Reciprocal - MSE and SNR as distinct performance measures in below-threshold communication.
The possible advantages of using algorithms that are minimum mean-square-error (MSE) optimal, or other averaging-type demodulators with frequency position modulation (FPM), are investigated. An attempt is made to describe the performance of the optimal and various suboptimal demodulators in terms of three parameters which depend on SNR and bandwidth expansion. The performance measures investigated are the reciprocal of the normalized mean-square error and the output SNR, which are different in the below-threshold region. The former is compared to the rate-distortion bound. The possible advantage of averaging-type discriminators from the point of view of the threshold is discussed.
Bar-David, I.↗
Digital slope-threshold data compressor
Slope-threshold compression scheme for telemetered video data is efficient, and its principle of operation is as follows: when slope of raw data exceeds threshold decision reference, previous sample is transmitted. All-digital design is more economical than analog system. It exhibits well-defined accuracy, provides unlimited storage time, and is convenient and reliable.
Anderson, T. O.↗
Calculation of photoionization cross section near auto-ionizing lines and magnesium photoionization cross section near threshold
The research performed is briefly reviewed. A simple method was developed for the calculation of continuum states of atoms when autoionization is present. The method was employed to give the first theoretical cross section for beryllium and magnesium; the results indicate that the values used previously at threshold were sometimes seriously in error. These threshold values have potential applications in astrophysical abundance estimates.
Moore, E. N.↗
Correlation of new hypervelocity impact data by threshold penetration relations
Threshold penetration data are established by impacting spherical projectiles onto 2024 aluminum single-wall targets. Nylon and cadmium projectiles were used at impacting velocities from 3.0 to 6.8 km/s and 7.9 to 8.5 km/s respectively. These data are combined with existing data and compared with three threshold relations to assess their respective validities over a wide range of projectile densities. Two of these relations were validated over the extended range of projectile densities.
Hayduk, R. J.↗
The photodetachment cross-section and threshold energy of negative ions in carbon dioxide
Threshold energy and sunlight photodetachment measurements on negative carbon dioxide ions, using a 2.5 kw light pressure xenon lamp, show that: (1) Electron affinity of CO3(+) is larger than 2.7 e.V. and that an isomeric form of CO3(+) is likely an error; (2) The photodetachment cross section of CO3(-) will roughly be like a step function across the range of 4250 to 2500A, having its threshold energy at 4250A; (3) Sunlight photodetachment rate for CO3(-) is probably much smaller than elsewhere reported; and (4) The probability of having photodetached electrons re-attach to form negative ions is less than 1%. Mass identifying drift tube tests confirm that the slower ion is CO3(-), formed through the O(-) + 2CO2 yields CO3(-) + CO2 reaction.
Helmy, E. M.↗
On the performance of digital phase locked loops in the threshold region
Extended Kalman filter algorithms are used to obtain a digital phase lock loop structure for demodulation of angle modulated signals. It is shown that the error variance equations obtained directly from this structure enable one to predict threshold if one retains higher frequency terms. This is in sharp contrast to the similar analysis of the analog phase lock loop, where the higher frequency terms are filtered out because of the low pass filter in the loop. Results are compared to actual simulation results and threshold region results obtained previously.
Hurst, G. T.↗
Computer simulation of the threshold sensitivity determinations
A computer simulation study was carried out to evaluate various methods for determining threshold stimulus levels for impact sensitivity tests. In addition, the influence of a number of variables (initial stimulus level, particular stimulus response curve, and increment size) on the apparent threshold values and on the corresponding population response levels was determined. Finally, a critical review of previous assumptions regarding the stimulus response curve for impact testing is presented in the light of the simulation results.
Gayle, J. B.↗
Effect of threshold rigidity variations on the electron production rate in the atmosphere
Current systems formed during magnetic disturbances cause threshold energy variations of cosmic ray particles. The latter, in turn, are a source of electron production in the terrestrial atmosphere. The paper gives the calculations of the electron production rate with the count of threshold variations during magnetic disturbances.
Dorman, L. I.↗
Estimates of saltation threshold and erosion rates on Mars
The Mariner 9 photographs of the Martian surface include many which show crater-associated streaks caused by atmospheric winds. Due to the low density atmosphere of Mars, the wind speeds necessary to move surface particles and thus cause the streaks are apparently very high. The atmospheric-boundary-layer wind tunnel has been used to determine threshold speeds for particles of varying density and diameter and the results for small particles have been extrapolated to estimate somewhat lower threshold speeds on Mars than previous estimates. A series of streak modeling tests is used to derive an erosion-rate correlation function, which is in turn used to estimate erosion rates to the lee of some of the craters on Mars which exhibited time-dependent streak behavior during the mission.
Iversen, J. D.↗
Difference thresholds for judgments of sink rate during the flare
Past studies have shown that touchdown rates of descent (sink rates) are higher in aircraft simulators than in aircraft under similar conditions. The objective of this paper was to use a psychophysical technique to investigate a pilot's ability to distinguish between two different sink rates close to the ground. The pilots observed a collimated computer graphics display of a typical runway with edge, zone, and centerline lights. The results showed that with a forward velocity of 120 knots, pilots could reliably distinguish between a sink rate of 0.5 m/sec (1.7 ft/sec) and 0.9 m/sec (2.9 ft/sec). The results also showed that the absolute rate of sink did not significantly affect the perception of sink rate. Time of sink and total height drop during the sink did affect the minimum detectable difference between sink rates (the differential threshold). The effects were such that a greater time of sink and greater height drop produced lower thresholds
Palmer, E.↗