921 research outputs found
The Petrocarb pneumatic feeding system: A proven method for feeding particulate solids at controlled rates
An outline of the principal features of the Petrocarb Pneumatic Feeding System is given. Early development and various commercial applications are included. It is concluded that the Petrocarb Injection System is capable of feeding dry solids into most of the processes being developed for utilizing coal
"Regularity Singularities" and the Scattering of Gravity Waves in Approximate Locally Inertial Frames
It is an open question whether solutions of the Einstein-Euler equations are
smooth enough to admit locally inertial coordinates at points of shock wave
interaction, or whether "regularity singularities" can exist at such points.
The term {\it regularity singularity} was proposed by the authors as a point in
spacetime where the gravitational metric tensor is Lipschitz continuous
(), but no smoother, in any coordinate system of the atlas.
An existence theory for shock wave solutions in admitting arbitrary
interactions has been proven for the Einstein-Euler equations in spherically
symmetric spacetimes, but is the requisite smoothness required for
space-time to be locally flat. Thus the open problem of regularity
singularities is the problem as to whether locally inertial coordinate systems
exist at shock waves within the larger atlas. To clarify this open
problem, we identify new "Coriolis type" effects in the geometry of
shock wave metrics and prove they are essential in the sense that they can
never be made to vanish within the atlas of {\it smooth} coordinate
transformations, the atlas usually assumed in classical differential geometry.
Thus the problem of existence of regularity singularities is equivalent to the
question as to whether or not these Coriolis type effects are essentially
non-removable and `real', or merely coordinate effects that can be removed, (in
analogy to classical Coriolis forces), by going to the less regular atlas of
transformations. If essentially non-removable, it would argue
strongly for a `real' new physical effect for General Relativity, providing a
physical context to the open problem of regularity singularities.Comment: 29 pages. Version 2: Corrections of some typographical errors and
improvements of wording. Results are unchange
A Non-Perturbative Construction of the Fermionic Projector on Globally Hyperbolic Manifolds II - Space-Times of Infinite Lifetime
The previous functional analytic construction of the fermionic projector on
globally hyperbolic Lorentzian manifolds is extended to space-times of infinite
lifetime. The construction is based on an analysis of families of solutions of
the Dirac equation with a varying mass parameter. It makes use of the so-called
mass oscillation property which implies that integrating over the mass
parameter generates decay of the Dirac wave functions at infinity. We obtain a
canonical decomposition of the solution space of the massive Dirac equation
into two subspaces, independent of observers or the choice of coordinates. The
constructions are illustrated in the examples of ultrastatic space-times and de
Sitter space-time.Comment: 29 pages, LaTeX, minor improvements (published version
Channelization architecture for wide-band slow light in atomic vapors
We propose a ``channelization'' architecture to achieve wide-band
electromagnetically induced transparency (EIT) and ultra-slow light propagation
in atomic Rb-87 vapors. EIT and slow light are achieved by shining a strong,
resonant ``pump'' laser on the atomic medium, which allows slow and
unattenuated propagation of a weaker ``signal'' beam, but only when a
two-photon resonance condition is satisfied. Our wideband architecture is
accomplished by dispersing a wideband signal spatially, transverse to the
propagation direction, prior to entering the atomic cell. When particular
Zeeman sub-levels are used in the EIT system, then one can introduce a magnetic
field with a linear gradient such that the two-photon resonance condition is
satisfied for each individual frequency component. Because slow light is a
group velocity effect, utilizing differential phase shifts across the spectrum
of a light pulse, one must then introduce a slight mismatch from perfect
resonance to induce a delay. We present a model which accounts for diffusion of
the atoms in the varying magnetic field as well as interaction with levels
outside the ideal three-level system on which EIT is based. We find the maximum
delay-bandwidth product decreases with bandwidth, and that delay-bandwidth
product ~1 should be achievable with bandwidth ~50 MHz (~5 ns delay). This is a
large improvement over the ~1 MHz bandwidths in conventional slow light systems
and could be of use in signal processing applications.Comment: Published in SPIE Proceedings, Photonics West 2005 (San Jose, CA,
Jan. 22-27, 2005
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