2,618 research outputs found
A numerical study of fluids with pressure dependent viscosity flowing through a rigid porous medium
In this paper we consider modifications to Darcy's equation wherein the drag
coefficient is a function of pressure, which is a realistic model for
technological applications like enhanced oil recovery and geological carbon
sequestration. We first outline the approximations behind Darcy's equation and
the modifications that we propose to Darcy's equation, and derive the governing
equations through a systematic approach using mixture theory. We then propose a
stabilized mixed finite element formulation for the modified Darcy's equation.
To solve the resulting nonlinear equations we present a solution procedure
based on the consistent Newton-Raphson method. We solve representative test
problems to illustrate the performance of the proposed stabilized formulation.
One of the objectives of this paper is also to show that the dependence of
viscosity on the pressure can have a significant effect both on the qualitative
and quantitative nature of the solution
Van der Waals black hole
In the context of extended phase space, where the negative cosmological
constant is treated as a thermodynamic pressure in the first law of black hole
thermodynamics, we find an asymptotically AdS metric whose thermodynamics
matches exactly that of the Van der Waals fluid. However, we show that as a
solution of Einstein's equations, the corresponding stress energy tensor does
not obey any of the energy conditions everywhere outside of the horizon.Comment: 4 pages, 1 figure v3: corrected statements about energy condition
Broken-symmetry-adapted Green function theory of condensed matter systems:towards a vector spin-density-functional theory
The group theory framework developed by Fukutome for a systematic analysis of
the various broken symmetry types of Hartree-Fock solutions exhibiting spin
structures is here extended to the general many body context using spinor-Green
function formalism for describing magnetic systems. Consequences of this theory
are discussed for examining the magnetism of itinerant electrons in nanometric
systems of current interest as well as bulk systems where a vector spin-density
form is required, by specializing our work to spin-density-functional
formalism. We also formulate the linear response theory for such a system and
compare and contrast them with the recent results obtained for localized
electron systems. The various phenomenological treatments of itinerant magnetic
systems are here unified in this group-theoretical description.Comment: 17 page
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Life-cycle energy and climate benefits of energy recovery from wastes and biomass residues in the United States
Agricultural and forestry residues, animal manure and municipal solid waste are replenishable and widely available. However, harnessing these heterogeneous and diffuse resources for energy requires a holistic assessment of alternative conversion pathways, taking into account spatial factors. Here, we analyse, from a life-cycle assessment perspective, the potential renewable energy production, net energy gain and greenhouse gas (GHG) emission reduction for each distinct type of waste feedstock under different conversion technology pathways. The utilization of all available wastes and residues in the contiguous United States can generate 3.1–3.8 exajoules (EJ) of renewable energy, but only deliver 2.4–3.2 EJ of net energy gain, and displace 103–178 million tonnes of CO -equivalent GHG emissions. For any given waste feedstock, looking across all US counties where it is available, except in rare instances, no single conversion pathway simultaneously maximizes renewable energy production, net energy gain and GHG mitigation.
Non-Central Heavy-Ion Collisions are the Place to Look for DCC
We give two reasons why we believe that non-central ultrarelativistic heavy
ion collisions are the place to look for the disoriented chiral condensates
(DCC). First, we argue that the most probable quench scenario for the formation
of DCC requires non-central collisions. Second, we show by numerical
simulations that strong electromagnetic fields of heavy ions can exert a
surprisingly large effect on the DCC domain formation through the chiral
anomaly. The effect again requires non-central collisions. Interestingly, the
result of simulations is consistent with the formation of correlated two
domains of the chiral condensate, which are aligned in space, perpendicular to
the scattering plane, but misaligned in isospin space.Comment: 4 pages (Latex), 3 embedded ps figures, espcrc1 style, talk given at
Quark Matter 97, December 97, Tsukuba, Japa
Entanglement of Pure Two-Mode Gaussian States
The entanglement of general pure Gaussian two-mode states is examined in
terms of the coefficients of the quadrature components of the wavefunction. The
entanglement criterion and the entanglement of formation are directly evaluated
as a function of these coefficients, without the need for deriving local
unitary transformations. These reproduce the results of other methods for the
special case of symmetric pure states which employ a relation between squeezed
states and Einstein-Podolsky-Rosen correlations. The modification of the
quadrature coefficients and the corresponding entanglement due to application
of various optical elements is also derived.Comment: 12 page
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The United States can generate up to 3.2 EJ of energy annually from waste
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