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Published document discusses devices which are based on weak-link Josephson elements that join superconductors. Links can take numerous forms, and circuitry utilizing links can perform many varied functions with unprecedented sensitivity. Theoretical review of Josephson's junctions include tunneling junctions, point contact devices, microbridges, and proximity-effect devices.
Miniaturized transducers are fabricated from commercially available four-arm semiconductor gages; transducers are connected as bridge circuit and mounted on internal face of small diaphragm. Jacket made of conductive plastic may be needed to avoid buildup or static charges.
An experimental aerodynamic investigation was conducted in the NASA/ARC 6- by 6-foot supersonic wind tunnel on an 0.015-scale configuration 140A/B SSV Orbiter model. The primary objective was to determine the extent aerodynamic simulation is compromised by sting base mounting with MPS nozzles removed. Both a conventional sting (through the base) and an alternate model mounting system were utilized. The alternate mounting system consisted of a non-metric blade strut, which approximated the vertical tail and entered the model through the upper aft section of its fuselage. The model was tested both in and out of the presence of a dummy sting with and without MPS nozzles when on the alternate mounting system. Data were obtained at Mach numbers from 0.6 through 2.0, a Reynolds number of 2.5 million per foot, angles of attack from -4 through 14 degrees, angles of sideslip from -15 through 15 degrees, elevon deflections of 0 and 15 degrees, and bodyflap deflections of -11.7, 0, and 16.3 degrees.
The purpose is to update the RFI estimates in the 136- to 138-MHz VHF band and to make estimates for the first time for the 400.5- to 401.5-MHz UHF band. These preliminary predictions are based on primarily ITU frequency-registration data, with missing data bridged by engineering judgement.
A receiving system for automatically selecting a desired one of two approximately orthogonally polarized signals occupying the same bandwidth, is described. Received signals are provided by any orthomode antenna system at a pair of output ports, i.e., right hand and left hand circular polarizations or two linear polarizations. The received signals are then applied to the inputs of a hybrid junction to produce sum and difference signals. The resulting sum signal at one output port comprises components of the undesired one of two orthogonally polarized signals and is used to coherently detect and dynamically balance out the undesired signal components that are included at the difference signal port. The desired one of two orthogonally polarized signals is thereby provided at the difference port of the hybrid junction. Feedback loops are used to effect dynamic balancing.
Recent investigations of propulsion-induced aerodynamics are reviewed. Experimental and analytical studies of the fundamental properties of lifting jet wakes and wind-tunnel investigations of VTOL configuration variables are discussed. The jet-wake flow studies will provide the data base for evaluating theoretical performance prediction methods; while the configuration studies will provide guidance for optimizing airframe/propulsion system integration. The influence of results to date on high-performance VTOL designs emphasizing minimum jet-induced losses and improved thrust vectoring in forward flight (VIFF) capability is illustrated.
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It is known that electron beams are easily deflected by magnetic and electrostatic fields. Therefore, to prevent weld defects, stray electromagnetic fields are avoided in electron beam welding chambers if at all possible. The successful results of tests conducted at MSFC to evaluate a simple magnetic shield made from steel tubing are reported. Tests indicate that this shield was up to 85 percent effective in reducing magnetic effects on the electron beam of a welding machine. In addition, residual magnetic fields within the shield were so nearly uniform that the net effect on the beam alignment was negligible. It is concluded that the shield, with the addition of a tungsten liner, could be used in production welding.
The adaptive-wall or self-correcting wind tunnel has been proposed for such regimes as transonic and V/STOL where wall effects are large and cannot be corrected for. The power and generality of the concept are pointed out. In a two-dimensional transonic embodiment in the Calspan One-Foot Tunnel, the scheme has been shown to work at lower transonic Mach numbers. Several practical problems are cited, including instrumentation, the nature of the wall modification, and convergence of the iterative procedure. Moreover, questions of shock-wave neutralization at the wall and probable configuration of three-dimensional embodiments are discussed.
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The possibility that drugs administered to Skylab 3 and 4 crewmen for space motion sickness may have interfered with their biomedical evaluation in space is investigated. The mixture of scopolamine and dextroamphetamine produced changes which allow a more valid interpretation of the early biomedical changes ocurring in weightlessness. There is no doubt that the dramatic increase in aldosterone excretion is not attributable to the drug, while the drug could have contributed to the in-flight changes observed in cortisol, epinephrine, heart rate and possibly urine volume.
Field strength measurements on a single row of panels indicates that the operational mode of the array as configured presents no radiated EMI problems. Only one relatively significant frequency band near 200 kHz showed any degree of intensity (9 muV/m including a background level of 5 muV/m). The level was measured very near the array (at 20 ft distance) while Federal Communications Commission (FCC) regulations limit spurious emissions to 15 muV/m at 1,000 ft. No field strength readings could be obtained even at 35 ft distant.
A theory concerning the problem of fringe interpretation reported by Hecht et al. (1973) is extended and a simpler semiquantitative method for the assessment of the fringes is developed. According to the new method, the fringe contrast between any two points on an object, is determined on the basis of the difference of the path-length changes at each point. The theoretical development of the method is discussed and a description of experimental results is given.