386,119 research outputs found
Installing fiber insulation
A method for installing fragile, high temperature insulation batting in an elongated cavity or in a resilient wire sleeve to form a resilient seal. The batting is preformed to rough dimensions and wrapped in a plastic film, the film being of a material which is fugitive at a high temperature. The film is heat sealed and trimmed to form a snugly fit skin which overlaps at least at one end to permit attachment of a pull cord. The film absorbs the tensile force of pulling the film enclosed batting through the cavity or wire mesh sleeve and is subsequently driven off by high temperature baking, leaving only the insulation in the cavity or wire mesh sleeve
Spin-orbit field switching of magnetization in ferromagnetic films with perpendicular anisotropy
As an alternative to conventional magnetic field, the effective spin-orbit
field in transition metals, derived from the Rashba field experienced by
itinerant electrons confined in a spatial inversion asymmetric plane through
the s-d exchange interaction, is proposed for the manipulation of
magnetization. Magnetization switching in ferromagnetic thin films with
perpendicular magnetocrystalline anisotropy can be achieved by current induced
spin-orbit field, with small in-plane applied magnetic field. Spin-orbit field
induced by current pulses as short as 10 ps can initiate ultrafast
magnetization switching effectively, with experimentally achievable current
densities. The whole switching process completes in about 100 ps.Comment: 4 pages, 3 figure
Parity-locking effect in a strongly-correlated ring
Orbital magnetism in an integrable model of a multichannel ring with
long-ranged electron-electron interactions is investigated. In a noninteracting
multichannel system, the response to an external magnetic flux is the sum of
many diamagnetic and paramagnetic contributions, but we find that for
sufficiently strong correlations, the contributions of all channels add
constructively, leading to a parity (diamagnetic or paramagnetic) which depends
only on the total number of electrons. Numerical results confirm that this
parity-locking effect is robust with respect to subband mixing due to disorder.Comment: part of lecture presented in the conference ``Unconventional quantum
liquids", appearing in Z. Phy
Figure of Merit for Dark Energy Constraints from Current Observational Data
Choosing the appropriate figure of merit (FoM) for dark energy (DE)
constraints is key in comparing different DE experiments. Here we show that for
a set of DE parameters {f_i}, it is most intuitive to define FoM =
1/\sqrt{Cov(f1,f2,f3,...)}, where Cov(f1,f2,f3,...) is the covariance matrix of
{f_i}. The {f_i} should be minimally correlated. We demonstrate two useful
choices of {f_i} using 182 SNe Ia (compiled by Riess et al. 2007), [R(z_*),
l_a(z_*), \Omega_b h^2] from the five year Wilkinson Microwave Anisotropy Probe
(WMAP) observations, and SDSS measurement of the baryon acoustic oscillation
(BAO) scale, assuming the HST prior of H_0=72+/-8 km/s Mpc^{-1} and without
assuming spatial flatness. We find that the correlation of (w_0,w_{0.5})
[w_0=w_X(z=0), w_{0.5}=w_X(z=0.5), w_X(a) = 3w_{0.5}-2w_0+3(w_0-w_{0.5})a] is
significantly smaller than that of (w_0,w_a) [w_X(a)=w_0+(1-a)w_a]. In order to
obtain model-independent constraints on DE, we parametrize the DE density
function X(z)=\rho_X(z)/\rho_X(0) as a free function with X_{0.5}, X_{1.0}, and
X_{1.5} [values of X(z) at z=0.5, 1.0, and 1.5] as free parameters estimated
from data. If one assumes a linear DE equation of state, current data are
consistent with a cosmological constant at 68% C.L. If one assumes X(z) to be a
free function parametrized by (X_{0.5}, X_{1.0}, X_{1.5}), current data deviate
from a cosmological constant at z=1 at 68% C.L., but are consistent with a
cosmological constant at 95% C.L.. Future DE experiments will allow us to
dramatically increase the FoM of constraints on (w_0,w_{0.5}) and of (X_{0.5},
X_{1.0}, X_{1.5}). This will significantly shrink the DE parameter space to
enable the discovery of DE evolution, or the conclusive evidence for a
cosmological constant.Comment: 7 pages, 3 color figures. Submitte
Anomalous magneto-structural behavior of MnBi explained: a path towards an improved permanent magnet
Low-temperature MnBi (hexagonal NiAs phase) exhibits anomalies in the lattice
constants (a, c) and bulk elastic modulus (B) below 100 K, spin reorientation
and magnetic susceptibility maximum near 90 K, and, importantly for
high-temperature magnetic applications, an increasing coercivity (unique to
MnBi) above 180 K. We calculate the total energy and magneto-anisotropy energy
(MAE) versus (a, c) using DFT+U methods. We reproduce and explain all the above
anomalies. We predict that coercivity and MAE increase due to increasing a,
suggesting means to improve MnBi permanent magnets.Comment: 4 pages, 5 figure
Spin squeezing in nonlinear spin coherent states
We introduce the nonlinear spin coherent state via its ladder operator
formalism and propose a type of nonlinear spin coherent state by the nonlinear
time evolution of spin coherent states. By a new version of spectroscopic
squeezing criteria we study the spin squeezing in both the spin coherent state
and nonlinear spin coherent state. The results show that the spin coherent
state is not squeezed in the x, y, and z directions, and the nonlinear spin
coherent state may be squeezed in the x and y directions.Comment: 4 pages, 2 figs, revised version submitted to J. Opt.
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