2,485 research outputs found
Support of ASTP/KOSMOS fundulus embryo development experiment
Results from the Kosmos Biosatellite 782 flight are presented. Experiments with fish hatchlings are discussed along with postflight observation and testing. The preparation of fertilized eggs for the experiments is described
Ejection mechanisms in the sublayer of a turbulent channel
A possible model for the inception of vorticity ejections in the viscous sublayer of a turbulent rectangular channel is presented. It was shown that this part of the flow is dominated by protruding strong shear layers of z-vorticity, and it was proposed as a mechanism for their maintenance and reproduction which is essentially equivalent to that responsible for the instability of 2-D Tollmien-Schlichting waves. The efforts to isolate computationally a single structure for its study have failed up to now, since it appears that single structures decay in the absence of external forcing, but a convenient computation model was identified in the form of a long and narrow periodic computational box containing at each moment only a few structures. Further work in the identification of better reduced systems is in progress
Analysis of screeching in a cold flow jet experiment
The screech phenomenon observed in a one-sixtieth scale model space shuttle test of the solid rocket booster exhaust flow noise has been investigated. A critical review is given of the cold flow test data representative of Space Shuttle launch configurations to define those parameters which contribute to screech generation. An acoustic feedback mechanism is found to be responsible for the generation of screech. A simple equation which permits prediction of screech frequency in terms of basic testing parameters such as the jet exhaust Mach number and the separating distance from nozzle exit to the surface of model launch pad is presented and is found in good agreement with the test data. Finally, techniques are recommended to eliminate or reduce the screech
High coherence hybrid superconducting qubit
We measure the coherence of a new superconducting qubit, the {\em
low-impedance flux qubit}, finding s. It is a
three-junction flux qubit, but the ratio of junction critical currents is
chosen to make the qubit's potential have a single well form. The low impedance
of its large shunting capacitance protects it from decoherence. This qubit has
a moderate anharmonicity, whose sign is reversed compared with all other
popular qubit designs. The qubit is capacitively coupled to a high-Q resonator
in a configuration, which permits the qubit's state to be read out
dispersively
A simple all-microwave entangling gate for fixed-frequency superconducting qubits
We demonstrate an all-microwave two-qubit gate on superconducting qubits
which are fixed in frequency at optimal bias points. The gate requires no
additional subcircuitry and is tunable via the amplitude of microwave
irradiation on one qubit at the transition frequency of the other. We use the
gate to generate entangled states with a maximal extracted concurrence of 0.88
and quantum process tomography reveals a gate fidelity of 81%
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