117,961 research outputs found
Subsonic pitch-up alleviation on a 74 deg delta wing
Fixed leading-edge devices were investigated for alleviating the low speed pitch-up and longitudinal instability of a 74 deg delta wing model. In wind-tunnel tests, Pylon Vortex Generators were shown to be highly effective, compared to leading-edge fences and slots, in raising the pitch-up angle of attack from 8 deg to 28 deg. The subsonic drag penalty was negligible
Experimental study of delta wing leading-edge devices for drag reduction at high lift
The drag reduction devices selected for evaluation were the fence, slot, pylon-type vortex generator, and sharp leading-edge extension. These devices were tested on a 60 degree flatplate delta (with blunt leading edges) in the Langley Research Center 7- by 10-foot high-speed tunnel at low speed and to angles of attack of 28 degrees. Balance and static pressure measurements were taken. The results indicate that all the devices had significant drag reduction capability and improved longitudinal stability while a slight loss of lift and increased cruise drag occurred
What is a quantum simulator?
Quantum simulators are devices that actively use quantum effects to answer
questions about model systems and, through them, real systems. Here we expand
on this definition by answering several fundamental questions about the nature
and use of quantum simulators. Our answers address two important areas. First,
the difference between an operation termed simulation and another termed
computation. This distinction is related to the purpose of an operation, as
well as our confidence in and expectation of its accuracy. Second, the
threshold between quantum and classical simulations. Throughout, we provide a
perspective on the achievements and directions of the field of quantum
simulation.Comment: 13 pages, 2 figure
Atomic resolution STM imaging of a twisted single-wall carbon nanotube
We present atomically-resolved STM images of single-wall carbon nanotubes
(SWNTs) embedded in a crystalline nanotube rope. Although they may be
interpreted as of a chiral nanotube, the images are more consistently explained
a an achiral armchair tube with a quenched twist distortion. The existence of
quenched twists in SWNTs in ropes might explain the fact that both as-grown
bulk nanotube material and individual ropes have insulator-like conductivity at
low temperature.Comment: preprint, 4 pages, and 4 gif figure
Chebychev trajectory optimization program /CHEBYTOP 2/ Final report
Computer program for electric propelled spacecraft interplanetary, flyby, and rendezvous trajectory optimization based on Chebyshev approximation and polynomial representation
Development of approach control system requirements with applications to a jet transport
The development of requirements for an approach control system and example applications to a jet transport aircraft are presented. The material is divided into a general discussion of approach control requirements, and a specific application resulting in the design of three alternative longitudinal controllers. The point of view taken is that the essential features of the system structure are the feedbacks themselves, their equalization, and their combinations to create control commands. Use is made of the fact that for sucessful systems the possible feedback structures are very limited. They derive primarily from guidance, control, and regulation demands; and secondarily from dynamic response characteristics desired by the pilot. From the systems view it is the satisfaction of these requirements that is important rather than the means automatic, manual, or hygrid manual/automatic approach systems
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