53,612 research outputs found
Interplay of Fulde-Ferrell-Larkin-Ovchinnikov and Vortex states in two-dimensional Superconductors
Clean superconductors with weakly coupled conducting planes have been
suggested as promising candidates for observing the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. We consider here a layered
superconductor in a magnetic field of arbitrary orientation with respect to the
conducting plane. In this case there is competition of spin-pair-breaking and
orbital-pair-breaking effects. In previous work, phase boundaries characterized
by Landau quantum numbers n > 0 have been predicted. Here, we calculate the
actual structure of the stable states below Hc2 by minimizing the free energy.
We find several new order parameter structures differing from both the
traditional Abrikosov and FFLO solutions. Some interesting unsolved questions
appear in the limit of large n.Comment: 13 pages, 3 figure
Tritiated alumina serves as reagent for self-labeling analysis
Tritiated alumina, prepared by exchange of the surface hydroxyl groups with tritiated water, is a suitable reagent for exchange-labeling of specific compounds in low concentrations prior to chromatographic analysis. In a chromatographic column, it detects and measures submicrogram quantities of material
Principles for the design of advanced flight director systems based on the theory of manual control displays
Design and development of flight director systems based on theory of manual control display
Controlled Ecological Life Support System. Life Support Systems in Space Travel
Life support systems in space travel, in closed ecological systems were studied. Topics discussed include: (1) problems of life support and the fundamental concepts of bioregeneration; (2) technology associated with physical/chemical regenerative life support; (3) projection of the break even points for various life support techniques; (4) problems of controlling a bioregenerative life support system; (5) data on the operation of an experimental algal/mouse life support system; (6) industrial concepts of bioregenerative life support; and (7) Japanese concepts of bioregenerative life support and associated biological experiments to be conducted in the space station
25 kHz narrow spectral bandwidth of a wavelength tunable diode laser with a short waveguide-based external cavity
We report on the spectral properties of a diode laser with a tunable external
cavity in integrated optics. Even though the external cavity is short compared
to other small-bandwidth external cavity lasers, the spectral bandwidth of this
tunable laser is as small as 25 kHz (FWHM), at a side-mode suppression ratio
(SMSR) of 50 dB. Our laser is also able to access preset wavelengths in as
little as 200 us and able to tune over the full telecom C-band (1530 nm - 1565
nm).Comment: 8 pages, 7 figure
Manual and automatic flight control during severe turbulence penetration
An analytical and experimental investigation of possible contributing factors in jet aircraft turbulence upsets was conducted. Major contributing factors identified included autopilot and display deficiencies, the large aircraft inertia and associated long response time, and excessive pilot workload. An integrated flight and thrust energy management director system was synthesized. The system was incorporated in a moving-base simulation and evaluated using highly experienced airline pilots. The evaluation included comparison of pilot workload and flight performance during severe turbulence penetration utilizing four control/display concepts: manual control with conventional full panel display, conventional autopilot (A/P-A) with conventional full panel display, improved autopilot (A/P-B) with conventional full panel display plus thrust director display, and longitudinal flight director with conventional full panel display plus thrust director display. Simulation results show improved performance, reduced pilot workload, and a pilot preference for the autopilot system controlling to the flight director command and manual control of thrust following the trim thrust director
Exobiology in Earth orbit: The results of science workshops held at NASA, Ames Research Center
The Workshops on Exobiology in Earth Orbit were held to explore concepts for orbital experiments of exobiological interest and make recommendations on which classes of experiments should be carried out. Various observational and experimental opportunities in Earth orbit are described including those associated with the Space Shuttle laboratories, spacecraft deployed from the Space Shuttle and expendable launch vehicles, the Space Station, and lunar bases. Specific science issues and technology needs are summarized. Finally, a list of recommended experiments in the areas of observational exobiology, cosmic dust collection, and in situ experiments is presented
Analytical design and simulation evaluation of an approach flight director system for a jet STOL aircraft
A program was undertaken to develop design criteria and operational procedures for STOL transport aircraft. As part of that program, a series of flight tests shall be performed in an Augmentor Wing Jet STOL Aircraft. In preparation for the flight test programs, an analytical study was conducted to gain an understanding of the characteristics of the vehicle for manual control, to assess the relative merits of the variety of manual control techniques available with attitude and thrust vector controllers, and to determine what improvements can be made over manual control of the bare airframe by providing the pilot with suitable command guidance information and by augmentation of the bare airframe dynamics. The objective of the study is to apply closed-loop pilot/vehicle analysis techniques to the analysis of manual flight control of powered-lift STOL aircraft in the landing approach and to the design and experimental verification of an advanced flight director display
Influence of quark boundary conditions on the pion mass in finite volume
We calculate the mass shift for the pion in a finite volume with
renormalization group (RG) methods in the framework of the quark-mesons model.
In particular, we investigate the importance of the quark effects on the pion
mass. As in lattice gauge theory, the choice of quark boundary conditions has a
noticeable effect on the pion mass shift in small volumes, in addition to the
shift due to pion interactions. We compare our results to chiral perturbation
theory calculations and find differences due to the fact that chiral
perturbation theory only considers pion effects in the finite volume.Comment: 24 pages, 5 figures, RevTex4, published version, discussion of
lattice results extende
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