3,095,336 research outputs found
Cooling system for high speed aircraft
The system eliminates the necessity of shielding an aircraft airframe constructed of material such as aluminum. Cooling is accomplished by passing a coolant through the aircraft airframe, the coolant acting as a carrier to remove heat from the airframe. The coolant is circulated through a heat pump and a heat exchanger which together extract essentially all of the added heat from the coolant. The heat is transferred to the aircraft fuel system via the heat exchanger and the heat pump. The heat extracted from the coolant is utilized to power the heat pump. The heat pump has associated therewith power turbine mechanism which is also driven by the extracted heat. The power turbines are utilized to drive various aircraft subsystems, the compressor of the heat pump, and provide engine cooling
Cooper Pairs with Broken Parity and Time-Reversal Symmetries in D-wave Superconductors
Paramagnetic effects are shown to result in the appearance of a triplet
component of order parameter in a vortex phase of a d-wave superconductor in
the absence of impurities. This component, which breaks both parity and
time-reversal symmetries of Cooper pairs, is expected to be of the order of
unity in a number of modern superconductors such as organic, high-Tc, and some
others. A generic phase diagram of such type-IV superconductors, which are
singlet ones at H=0 and characterized by singlet-triplet mixed Copper pairs
with broken time-reversal symmetry in a vortex phase, is discussed.Comment: 10 pages, 1 figures, Phys. Rev. Lett., submitted (July 25 2005
The cosmological evolution of p-brane networks
In this paper we derive, directly from the Nambu-Goto action, the relevant
components of the acceleration of cosmological featureless -branes,
extending previous analysis based on the field theory equations in the
thin-brane limit. The component of the acceleration parallel to the velocity is
at the core of the velocity-dependent one-scale model for the evolution of
-brane networks. We use this model to show that, in a decelerating expanding
universe in which the -branes are relevant cosmologically, interactions
cannot lead to frustration, except for fine-tuned non-relativistic networks
with a dimensionless curvature parameter . We discuss the implications
of our findings for the cosmological evolution of -brane networks.Comment: 6 page
Cosmological Perturbations of Quantum-Mechanical Origin and Anisotropy of the Microwave Background
Cosmological perturbations generated quantum-mechanically (as a particular
case, during inflation) possess statistical properties of squeezed quantum
states. The power spectra of the perturbations are modulated and the angular
distribution of the produced temperature fluctuations of the CMBR is quite
specific. An exact formula is derived for the angular correlation function of
the temperature fluctuations caused by squeezed gravitational waves. The
predicted angular pattern can, in principle, be revealed by the COBE-type
observations.Comment: 9 pages, WUGRAV-92-17 Accepted for Publication in Phys. Rev. Letters
(1993
Relic Gravitational Waves and Cosmology
This is an expanded version of my talk given at the international conference
"Zeldovich-90". I start with a brief recollection of interactions with
Zeldovich in the context of the study of relic gravitational waves. I then
summarise the principles and early results on the quantum-mechanical generation
of cosmological perturbations. The expected amplitudes of relic gravitational
waves are different in different frequency windows, and therefore the
techniques and prospects of their detection are different. One section of the
paper describes the present state of efforts in direct detection of relic
gravitational waves. Another section is devoted to indirect detection via the
anisotropy and polarisation measurements of the cosmic microwave background
radiation (CMB). It is emphasized throughout the paper that the conclusions on
the existence and expected amount of relic gravitational waves are based on a
solid theoretical foundation and the best available cosmological observations.
I also explain in great detail what went wrong with the so-called `inflationary
gravitational waves', whose amount is predicted by inflationary theorists to be
negligibly small, thus depriving them of any observational significance.Comment: 36 pages including 8 figures; expanded version of a talk at the
international conference `Zeldovich-90', Moscow, December 2004;
http://hea.iki.rssi.ru/Z-90; v.2: additional formulas and explanations in
response to remarks of anonymous referee; v.3: extra details about 'scalar'
perturbations and T/S ratio, scheduled to appear in Uspekhi Fiz. Nauk v.176
(2006); v.4: matches published paper: Physics-Uspekhi, 48(12) 1235-1247
(2005) [Russian version: Uspekhi Fiz. Nauk, 175(12) 1289-1303 (2005)
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