5,156 research outputs found
Optimum outgassing cycles for aluminum and stainless steel
Outgassing rates were measured for a modified 7075T6 aluminum and 304L stainless steel, for two degrees of finish, at temperatures of 285 deg F to 392 deg F, for times of 0.5 to 72 hours. The results were analyzed to determine optimum time and temperature cycles for outgassing. Optimum cycles were determined with and without the limitations of a graph. The graph related allowable time at temperature to a 5 percent or less reduction in room temperature properties of 7075T6 aluminum. For aluminum, within the limits set by reduction in mechanical properties, the optimum cycle tested was 40 hours at 285 deg F. Disregarding the limits, optimum outgassing was achieved at the highest temperatures and longest times tested, for both aluminum and stainless steel
Evaluation of a pulsed quasi-steady MPD thruster and associated subsystems
The performance of quasi-steady magnetoplasmadynamic (MPD) thrusters at high power levels is discussed. An axisymmetric configuration is used for the MPD thruster, with various cathode and anode sizes, over a wide range of experimental conditions. Thrust is determined from impulse measurements with current waveforms, while instantaneous measurements are made for all other variables. It is demonstrated that the thrust produced has a predominately self-magnetic origin and is directly proportional to the square of the current. The complete set of impulse measurement data is presented
Partial breakdown of quantum thermalization in a Hubbard-like model
We study the possible breakdown of quantum thermalization in a model of
itinerant electrons on a one-dimensional chain without disorder, with both spin
and charge degrees of freedom. The eigenstates of this model exhibit peculiar
properties in the entanglement entropy, the apparent scaling of which is
modified from a "volume law" to an "area law" after performing a partial,
site-wise measurement on the system. These properties and others suggest that
this model realizes a new, non-thermal phase of matter, known as a quantum
disentangled liquid (QDL). The putative existence of this phase has striking
implications for the foundations of quantum statistical mechanics.Comment: As accepted to PR
Quasi-steady MPD propulsion at high power Final technical report
Quasi-steady MPD propulsion at power levels in range 1 to 10 megawatt
On the physical association of the peculiar emission: Line stars HD 122669 and HD 122691
Spectroscopic and photometric observations indicate a physical association between the peculiar early-type emission-line stars HD 122669 and HD 122691. The latter has undergone a drastic change in the strength of its emission lines during the past twenty years. There is some indication that both stars vary with shorter time scales
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