27,817 research outputs found
Energy efficient engine preliminary design and integration studies
The characteristics and systems benefits of an energy efficient engine (E3) suitable for use on advanced subsonic transport aircraft were determined. Relative to a current CF6-50C engine, the following benefits were estimated: 14.4% reduction in installed cruise specific fuel consumption, and a reduction in direct operating cost of more than 5%. The advanced technology E3 system would also permit: compliance with FAR 36 (1977) noise limits, and compliance with 1981 EPA emission standards
Decorating Random Quadrangulations
On various regular lattices (simple cubic, body centred cubic..) decorating
an edge with an Ising spin coupled by bonds of strength L to the original
vertex spins and competing with a direct anti-ferromagnetic bond of strength
alpha L can give rise to three transition temperatures for suitable alpha. The
system passes through ferromagnetic, paramagnetic, anti-ferromagnetic and
paramagnetic phases respectively as the temperature is increased.
For the square lattice on the other hand multiple decoration is required to
see this effect. We note here that a single decoration suffices for the Ising
model on planar random quadrangulations (coupled to 2D quantum gravity). Other
random bipartite lattices such as the Penrose tiling are more akin to the
regular square lattice and require multiple decoration to have any affect.Comment: 6 pages + 5 figure
Preparation of monotectic alloys having a controlled microstructure by directional solidification under dopant-induced interface breakdown
Monotectic alloys having aligned spherical particles of rods of the minor component dispersed in a matrix of the major component are prepared by forming a melt containing predetermined amounts of the major and minor components of a chosen monotectic system, providing in the melt a dopant capable of breaking down the liquid solid interface for the chosen alloy, and directionally solidfying the melt at a selected temperature gradient and a selected rate of movement of the liquid-solid interface (growth rate). Shaping of the minor component into spheres or rods and the spacing between them are controlled by the amount of dopant and the temperature gradient and growth rate values. Specific alloy systems include Al Bi, Al Pb and Zn Bi, using a transition element such as iron
Potts Models with (17) Invisible States on Thin Graphs
The order of a phase transition is usually determined by the nature of the
symmetry breaking at the phase transition point and the dimension of the model
under consideration. For instance, q-state Potts models in two dimensions
display a second order, continuous transition for q = 2,3,4 and first order for
higher q.
Tamura et al recently introduced Potts models with "invisible" states which
contribute to the entropy but not the internal energy and noted that adding
such invisible states could transmute continuous transitions into first order
transitions. This was observed both in a Bragg-Williams type mean-field
calculation and 2D Monte-Carlo simulations. It was suggested that the invisible
state mechanism for transmuting the order of a transition might play a role
where transition orders inconsistent with the usual scheme had been observed.
In this paper we note that an alternative mean-field approach employing
3-regular random ("thin") graphs also displays this change in the order of the
transition as the number of invisible states is varied, although the number of
states required to effect the transmutation, 17 invisible states when there are
2 visible states, is much higher than in the Bragg-Williams case. The
calculation proceeds by using the equivalence of the Potts model with 2 visible
and r invisible states to the Blume-Emery-Griffiths (BEG) model, so a
by-product is the solution of the BEG model on thin random graphs.Comment: (2) Minor typos corrected, references update
Active clearance control system for a turbomachine
An axial compressor is provided with a cooling air manifold surrounding a portion of the shroud, and means for bleeding air from the compressor to the manifold for selectively flowing it in a modulating manner axially along the outer side of the stator/shroud to cool and shrink it during steady state operating conditions so as to obtain minimum shroud/rotor clearance conditions. Provision is also made to selectively divert the flow of cooling air from the manifold during transient periods of operation so as to alter the thermal growth or shrink rate of the stator/shroud and result in adequate clearance with the compressor rotor
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