111,811 research outputs found
Analytical fuel property effects, small combustors, phase 1
The effects of nonstandard aviation fuels on a typical small gas turbine combustor was analyzed. The T700/CT7 engine family was chosen as being representative of the class of aircraft power plants desired. Fuel properties, as specified by NASA, are characterized by low hydrogen content and high aromatics levels. Higher than normal smoke output and flame radiation intensity for the current T700 combustor which serves as a baseline were anticipated. It is, therefore, predicted that out of specification smoke visibility and higher than normal shell temperatures will exist when using NASA ERBS fuels with a consequence of severe reduction in cyclic life. Three new designs are proposed to compensate for the deficiencies expected with the existing design. They have emerged as the best of the eight originally proposed redesigns or combinations thereof. After the five choices that were originally made by NASA on the basis of competing performance factors, General Electric narrowed the field to the three proposed
Diffractive energy spreading and its semiclassical limit
We consider driven systems where the driving induces jumps in energy space:
(1) particles pulsed by a step potential; (2) particles in a box with a moving
wall; (3) particles in a ring driven by an electro-motive-force. In all these
cases the route towards quantum-classical correspondence is highly non-trivial.
Some insight is gained by observing that the dynamics in energy space, where
is the level index, is essentially the same as that of Bloch electrons in a
tight binding model, where is the site index. The mean level spacing is
like a constant electric field and the driving induces long range hopping
1/(n-m).Comment: 19 pages, 11 figs, published version with some improved figure
The total nucleon-nucleon cross section at large N_c
It is shown that at sufficiently large for incident momenta which are
much larger than the QCD, the total nucleon-nucleon cross section is
independent of incident momentum and given by . This result is valid in the extreme large
regime of and has corrections of relative order . A possible connection of this result to the
Froissart-Martin bound is discussed.Comment: 4 page
Constrained Molecular Dynamics Simulations of Atomic Ground-States
Constrained molecular dynamics(CoMD) model, previously introduced for nuclear
dynamics, has been extended to the atomic structure and collision calculations.
Quantum effects corresponding to the Pauli and Heisenberg principle are
enforced by constraints, in a parameter-free way. Our calculations for small
atomic system, H, He, Li, Be, F reproduce the ground-state binding energies
within 3%, compared with the results of quantum mechanical Hartree-Fock
calculations.Comment: 3 pages, 2 figure
A pseudo-matched filter for chaos
A matched filter maximizes the signal-to-noise ratio of a signal. In the
recent work of Corron et al. [Chaos 20, 023123 (2010)], a matched filter is
derived for the chaotic waveforms produced by a piecewise-linear system.
Motivated by these results, we describe a pseudo-matched filter, which removes
noise from the same chaotic signal. It consists of a notch filter followed by a
first-order, low-pass filter. We compare quantitatively the matched filter's
performance to that of our pseudo-matched filter using correlation functions in
a simulated radar application. On average, the pseudo-matched filter performs
with a correlation signal-to-noise ratio that is 2.0 dB below that of the
matched filter. Our pseudo-matched filter, though somewhat inferior in
comparison to the matched filter, is easily realizable at high speed (> 1 GHz)
for potential radar applications
N-body Monte Carlo simulation of specific lunar orbiter missions
N-body Monte Carlo simulation of specific lunar orbiter mission
Model Independent Tests of Skyrmions and Their Holographic Cousins
We describe a new exact relation for large QCD for the long-distance
behavior of baryon form factors in the chiral limit. This model-independent
relation is used to test the consistency of the structure of several baryon
models. All 4D semiclassical chiral soliton models satisfy the relation, as
does the Pomarol-Wulzer holographic model of baryons as 5D Skyrmions. However,
remarkably, we find that the holographic model treating baryons as instantons
in the Sakai-Sugimoto model does not satisfy the relation.Comment: v2. Added references, corrected typo
Comparing the Weighted Density Approximation with the LDA and GGA for Ground State Properties of Ferroelectric Perovskites
First-principles calculations within the weighted density approximation (WDA)
were performed for ground state properties of ferroelectric perovskites
PbTiO, BaTiO, SrTiO, KNbO and KTaO. We used the plane-wave
pseudopotential method, a pair distribution function based on the uniform
electron gas, and shell partitioning. Comparing with the local density
approximation (LDA) and the general gradient approximation (GGA), we found that
the WDA significantly improves the equilibrium volume of these materials in
cubic symmetry over both the LDA and GGA; Ferroelectric instabilities
calculated by the WDA agree with the LDA and GGA very well; At the experimental
ferroelectric lattice, optimized atom positions by the WDA are in good
agreement with measured data; However the WDA overestimates the strain of
tetragonal PbTiO at experimental volume; The WDA overestimates the volume
of fully relaxed structures, but the GGA results are even worse. Some
calculations were also done with other models for . It is found that a
with longer range behavior yields improved relaxed structures. Possible avenues
for improving the WDA are discussed.Comment: 19 pages, 3 figures, submitted to PR
Introduction to the themed issue - Corporate power : agency, communication, influence and social policy
This paper introduces this themed issue of Critical Social Policy on the question of corporate power. Corporate power is recognized as an important agent in social policy making and delivery. However, to date there has been comparatively little attention to the crucial role that lobbying and corporate 'spin' play in helping to shape policy making contexts. This special issue of Critical Social Policy is concerned to bring such issues to the mainstream of social policy analysis. It is argued here that the rise of spin and public relations is a key feature of neoliberalism in the past two decades. These have worked to reshape policy making, resulting in pronounced changes in the content and process of policy making and it is argued that these have tended to marginalize or undermine democratic processes
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