5,342 research outputs found
Economic considerations in coverting from oil/gas firing to coal
Economic considerations involved in fuel conversion such as from oil and/or gas firing to coal are discussed including investments costs for new facilities and equipment (including air pollution control equipment), operation and maintenance costs, and purchased fuel costs. An analytical approach to assessing the cost effectiveness of fuel conversion in terms of the annual net cost of conversion, the equivalent annual number of barrels of oil saved, and the integral rate of return of the conversion investment is presented. Illustrative numerical examples are presented for typical utility boilers and industrial boiler facilities. A further consideration addressed deals with the impacts of these costs on the overall financial structure of the firm and the ability of the firm to raise the necessary investment captial
Non-Hermitian topology of spontaneous magnon decay
Spontaneous magnon decay is a generic feature of the magnetic excitations of
anisotropic magnets and isotropic magnets with non-collinear order. In this
paper, we argue that the effect of interactions on one-magnon states can, under
many circumstances, be treated in terms of an effective, energy independent,
non-Hermitian Hamiltonian for the magnons. In the vicinity of Dirac or Weyl
touching points, we show that the spectral function has a characteristic
anisotropy arising from topologically protected exceptional points or lines in
the non-Hermitian spectrum. Such features can, in principle, be detected using
inelastic neutron scattering or other spectroscopic probes. We illustrate this
physics through a concrete example: a honeycomb ferromagnet with
Dzyaloshinskii-Moriya exchange. We perform interacting spin wave calculations
of the structure factor and spectral function of this model, showing good
agreement with results from a simple effective non-Hermitian model for the
splitting of the Dirac point. Finally, we argue that the zoo of known
topological protected magnon band structures may serve as a nearly ideal
platform for realizing and exploring non-Hermitian physics in solid-state
systems.Comment: 4+epsilon page
Hidden and antiferromagnetic order as a rank-5 superspin in URu2Si2
We propose a candidate for the hidden order in URu2Si2: a rank-5 E type spin
density wave between Uranium 5f crystal field doublets breaking time reversal
and lattice tetragonal symmetry in a manner consistent with recent torque
measurements [R. Okazaki et al, Science 331, 439 (2011)]. We argue that
coupling of this order parameter to magnetic probes can be hidden by crystal
field effects, while still having significant effects on transport,
thermodynamics and magnetic susceptibilities. In a simple tight-binding model
for the heavy quasiparticles, we show the connection between the hidden order
and antiferromagnetic phases arises since they form different components of
this single rank-5 pseudo-spin vector. Using a phenomenological theory, we show
the experimental pressure-temperature phase diagram can be qualitatively
reproduced by tuning terms which break pseudo-spin rotational symmetry. As a
test of our proposal, we predict the presence of small magnetic moments in the
basal plane oriented in the [110] direction ordered at the wave-vector (0,0,1).Comment: 5 page
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