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Implantable electrode holds itself in place until body tissue grows around it and retains it. Sheath covers electrode during implantation. Partially retracted after implantation and completely retracted after growth of tissue onto electrode. Intended to provide electrical stimuli to muscles having become inactive through accident or disease. Helps paraplegics and others to exercise voluntary control over arms and legs.
Report describes experiments to test two algorithms being considered for use in automatic control of robots and remote manipulators. One algorithm based on quadrangle-projection method, which involves use of four target points lying at corners of quadrangle. Other algorithm based on elastic-matching ("rubber-mask") approach, in which reference image warped to conform to actual image. Both algorithms determine position and orientation of target with accuracy sufficient for consistent and efficient acquisition by telerobot.
Plasmaspheric density profiles and their cold plasma boundaries observed by the retarding ion mass spectrometer aboard the DE-1 satellite were classified using the results of a statistical study. Six different categories of the plasmasphere density profiles were identified: 'featureless', featureless with enhancement near left, multiple-plateau, featureless with trough, multiple-plateau with trough, and other complex structure profiles. An explanation for the occurrence of these different profiles is presented.
Computational experiments have been performed for a few configurations in order to investigate the effects of external flow disturbances on the extent of laminar flow and wake drag. Theoretical results have been compared with experimental data for the AEDC cone, for Mach numbers from subsonic to supersonic, and for both free flight and wind tunnel environments. The comparisons have been found to be very satisfactory, thus establishing the utility of the present method for the design and development of laminar flow configurations and for the assessment of wind tunnel data. In addition, results of calculations concerning the effects of unit Reynolds numbers on transition are presented. In addition to the AEDC cone, computations have been performed for an ogive body of revolution at zero angle of attack and supersonic Mach numbers. Results are presented for transition Reynolds number and wake drag for external disturbances corresponding to free air and the test section of the AEDC-VKF tunnel. These results have been found to compare quite well with wind tunnel data for cases when surface suction is applied as well as when suction is absent.
The Venus terminator bow shock position is monitored and it is shown that the shock radius increases as the solar cycle approaches a new maximum. It is also shown that the subsolar bow shock changes with the solar cycle, and that these positions are correlated with each other and with solar activity. It is hypothesized that, at solar minimum, the magnetic barrier is weak, and that some absorption of solar wind is to be expected.
An analysis was conducted of current ELT problems and potential improvements that could be made by employing the TSO-C91a ELTs to replace the current TSO-C91 ELTs. The scope of the study included the following: (1) validate the problems; (2) determine specific failure causes; (3) determine false alarm causes; (4) estimate improvements from TSO-C91a; (5) estimate benefits from replacement of the current ELTs; and (6) determine need and benefits for improved ELT inspection and maintenance. A detailed comparison between the two requirements documents (TSO-C91 and -91a) was made to assess improved performance of the ELT in each category of failure cause and each cause of false alarms. The comparison and analysis resulted in projecting a success of operation rate approximately 3 times the current rate and a reduction in false alarms to 0.25 of those generated by TSO-C91 ELTs. These improvements led to a projection of benefits of approximately 25 additional lives to be saved each year with TSO-C91a ELTs and an improved inspection and maintenance program.
There is significant industry demand for a method of analyzing the shear buckling of composite plates with cutouts. This method should be able to easily accommodate frequent changes in model design; inflexibility being the major drawback to current finite element methods. The approach taken here is broken into two problems, prebuckling and buckling. To solve for the prebuckling stresses, complex variable equations are used in conjunction with boundary collocation. The least squares approach is utilized to improve the accuracy of the results. The buckling problem is solved using the Ritz method. A product of the Ritz method is a complicated integral equation which is solved using numerical integration. To date, the aforementioned method of determining the prebuckling stresses was verified against infinite plate theory and finite elements. Recent efforts have focused on reducing run time, improving accuracy and adding more boundary condition choices.
The concept being designed by the Leningrad Scientific Research Radio Technical Institute (LSRRI) of united positioning and timing service on the basis of the utilization of long-range and global radionavigation and common time systems and aids for different users is described. The estimate of its utilization on the national as well as on international scale is given.
A transmitter generates three signals for sequential transmission. These signal are an unmodulated r.f. carrier, a r.f. carrier amplitude modulated by a first audio frequency waveform and a r.f. carrier amplitude modulated by a second audio frequency waveform which is distinguishable from the first and which may be employed as a means for identifying a particular transmitter. The composite, sequentially transmitted signal may be varied in terms of the individual signal transmission sequence, the duration of the individual signals, overall composite signal repetition rate and the frequency of the second audio waveform. Various combinations of signal variations may be employed to transmit different information.
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Zonal and meridional 60-110-km wind profiles obtained by radar measurements at Saskatoon, Adelaide, Christchurch, Puerto Rico, and Mawson are presented graphically and compared with those from the COSPAR International Reference Atmosphere (CIRA) for 1986. Good general agreement is found below about 80 km, but above 80 km the CIRA 1986 models show discrepancies, including: (1) no spring tongue of weak westward flow at latitudes 20-70 deg; (2) too strong an eastward flow at 20-52 deg in summer; (3) too great reversal heights at 35-43 deg N in summer; and (4) too strong (by a factor of 2) summer and winter jets at 65-70 deg N.
An examination of observations of the position of the terminator bow shock at Venus and Mars shows that the terminator bow shock varies with the angle between the local bow shock normal and the upstream magnetic field. The part of the shock on the quasi-parallel side is closer to the planet than the part on the quasi-perpendicular side, a result which had been suggested by an earlier computer simulation by Thomas and Winske (1990). This bow shock asymmetry is observed to be larger at Mars than at Venus.
Compact short-lived explosive events have been observed in solar transition region lines with the High-Resolution Telescope and Spectrograph (HRTS) flown by the Naval Research Laboratory on a series of rockets and on Spacelab 2. Data from Spacelab 2 are coaligned with a simultaneous magnetogram and near-simultaneous He I 10,380 -A spectroheliogram obtained at the National Solar Observatory at Kitt Peak. The comparison shows that the explosive events occur in the solar magnetic network lanes at the boundaries of supergranular convective cells. However, the events occur away from the larger concentrations of magnetic flux in the network, in contradiction to the observed tendency of the more energetic solar phenomena to be associated with the stronger magnetic fields.
The angular accuracy of gamma-ray detectors is intrinsically limited by the physical processes involved in photon detection. Although a number of pointlike sources were detected by the COS B satellite, only two have been unambiguously identified by time signature with counterparts at longer wavelengths. By taking advantage of the extended longitudinal structure of VHE gamma-ray showers, measurements in the TeV energy range can pinpoint source coordinates to arcminute accuracy. This has now been demonstrated with new data analysis procedures applied to observations of the Crab Nebula using Cherenkov air shower imaging techniques. With two telescopes in coincidence, the individual event circular probable error will be 0.13 deg. The half-cone angle of the field of view is effectively 1 deg.
The physical processes typically used in the detection of high energy gamma-rays do not permit good angular resolution, which makes difficult the unambiguous association of discrete gamma-ray sources with objects emitting at other wavelengths. This problem can be overcome by placing gamma-ray detectors on the moon and using the horizon as an occulting edge to achieve arcsec resolution. For the purpose of discussion, this concept is examined for gamma rays above about 20 MeV for which pair production dominates the detection process and locally-generated nuclear gamma rays do not contribute to the background.
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The celestial source fields of gamma ray bursts can now be determined with precision considerably greater than that provided by earlier interplanetary networks. A new burst timing array consists of the Ulysses mission and the Pioneer-Venus Orbiter at great distances and the Compton Observatory, Granat, and other burst-observing spacecraft near the Earth. With Ulysses providing a baseline approaching five astronomical units in its progress towards Jupiter, and given the timing resolution of the Compton Burst and Transient Source Experiment, source fields with dimensions as small as several arc seconds by less than one arc minute will be determined for many of the events to be studied within this network.