60,420 research outputs found
Energy and Economic Trade Offs for Advanced Technology Subsonic Aircraft
Changes in future aircraft technology which conserve energy are studied, along with the effect of these changes on economic performance. Among the new technologies considered are laminar-flow control, composite materials with and without laminar-flow control, and advanced airfoils. Aircraft design features studied include high-aspect-ratio wings, thickness ratio, and range. Engine technology is held constant at the JT9D level. It is concluded that wing aspect ratios of future aircraft are likely to significantly increase as a result of new technology and the push of higher fuel prices. Composite materials may raise aspect radio to about 11 to 12 and practical laminar flow-control systems may further increase aspect ratio to 14 or more. Advanced technology provides significant reductions in aircraft take-off gross weight, energy consumption, and direct operating cost
Hot-wire anemometry in hypersonic helium flow
Hot-wire anemometry techniques are described that have been developed and used for hypersonic-helium-flow studies. The short run time available dictated certain innovations in applying conventional hot-wire techniques. Some examples are given to show the application of the techniques used. Modifications to conventional equipment are described, including probe modifications and probe heating controls
How the Liquid-Liquid Transition Affects Hydrophobic Hydration in Deeply Supercooled Water
We determine the phase diagram of liquid supercooled water by extensive
computer simulations using the TIP5P-E model [J. Chem. Phys. {\bf 120}, 6085
(2004)]. We find that the transformation of water into a low density liquid in
the supercooled range strongly enhances the solubility of hydrophobic
particles. The transformation of water into a tetrahedrally structured liquid
is accompanied by a minimum in the hydration entropy and enthalpy. The
corresponding change in sign of the solvation heat capacity indicates a loss of
one characteristic signature of hydrophobic hydration. The observed behavior is
found to be qualitatively in accordance with the predictions of the information
theory model of Garde et al. [Phys. Rev. Lett. {\bf 77}, 4966 (1996)].Comment: 4 pages, 4 figures, twocolumn Revtex, modified text applied changes
to figure 1, 2d, 3,
The drive system of the Major Atmospheric Gamma-ray Imaging Cherenkov Telescope
The MAGIC telescope is an imaging atmospheric Cherenkov telescope, designed
to observe very high energy gamma-rays while achieving a low energy threshold.
One of the key science goals is fast follow-up of the enigmatic and short lived
gamma-ray bursts. The drive system for the telescope has to meet two basic
demands: (1) During normal observations, the 72-ton telescope has to be
positioned accurately, and has to track a given sky position with high
precision at a typical rotational speed in the order of one revolution per day.
(2) For successfully observing GRB prompt emission and afterglows, it has to be
powerful enough to position to an arbitrary point on the sky within a few ten
seconds and commence normal tracking immediately thereafter. To meet these
requirements, the implementation and realization of the drive system relies
strongly on standard industry components to ensure robustness and reliability.
In this paper, we describe the mechanical setup, the drive control and the
calibration of the pointing, as well as present measurements of the accuracy of
the system. We show that the drive system is mechanically able to operate the
motors with an accuracy even better than the feedback values from the axes. In
the context of future projects, envisaging telescope arrays comprising about
100 individual instruments, the robustness and scalability of the concept is
emphasized.Comment: 15 pages, 12 (10) figures, submitted to Astroparticle Physics, a high
resolution version of the paper (particularly fig. 1) is available at
http://publications.mppmu.mpg.de/2008/MPP-2008-101/FullText.pd
Analysis of supersonic conical flows
Method of characteristics analytical technique for flow predictions of supersonic cross flows over conical bodie
A conceptual design of an advanced 23 m diameter IACT of 50 tons for ground-based gamma-ray astronomy
A conceptual design of an advanced Imaging Air Cherenkov Telescope with a 23
m diameter mirror and of 50 tons weight will be presented. A system photon
detection efficiency of 15-17%, averaged over 300-600 nm, is aimed at to lower
the threshold to 10-20 GeV. Prospects for a second generation camera with
Geiger-mode Avalanche Photo Diodes will be discussed.Comment: 4 pages, 1 figure, to appear in the proceedings of the 31th
International Cosmic Ray Conference, Lodz, Poland, 200
Gauge-Higgs Unification and Radiative Electroweak Symmetry Breaking in Warped Extra Dimensions
We compute the Coleman Weinberg effective potential for the Higgs field in RS
Gauge-Higgs unification scenarios based on a bulk SO(5) x U(1)_X gauge
symmetry, with gauge and fermion fields propagating in the bulk and a custodial
symmetry protecting the generation of large corrections to the T parameter and
the coupling of the Z to the bottom quark. We demonstrate that electroweak
symmetry breaking may be realized, with proper generation of the top and bottom
quark masses for the same region of bulk mass parameters that lead to good
agreement with precision electroweak data in the presence of a light Higgs. We
compute the Higgs mass and demonstrate that for the range of parameters for
which the Higgs boson has Standard Model-like properties, the Higgs mass is
naturally in a range that varies between values close to the LEP experimental
limit and about 160 GeV. This mass range may be probed at the Tevatron and at
the LHC. We analyze the KK spectrum and briefly discuss the phenomenology of
the light resonances arising in our model.Comment: 31 pages, 9 figures. Corrected typo in boundary condition for gauge
bosons and top mass equation. To appear in PR
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