41 research outputs found
Global solutions to the three-dimensional full compressible magnetohydrodynamic flows
The equations of the three-dimensional viscous, compressible, and heat
conducting magnetohydrodynamic flows are considered in a bounded domain. The
viscosity coefficients and heat conductivity can depend on the temperature. A
solution to the initial-boundary value problem is constructed through an
approximation scheme and a weak convergence method. The existence of a global
variational weak solution to the three-dimensional full magnetohydrodynamic
equations with large data is established
Global Existence and Large-Time Behavior of Solutions to the Three-Dimensional Equations of Compressible Magnetohydrodynamic Flows
The three-dimensional equations of compressible magnetohydrodynamic
isentropic flows are considered. An initial-boundary value problem is studied
in a bounded domain with large data. The existence and large-time behavior of
global weak solutions are established through a three-level approximation,
energy estimates, and weak convergence for the adiabatic exponent
and constant viscosity coefficients
Isometric Immersions and Compensated Compactness
A fundamental problem in differential geometry is to characterize intrinsic
metrics on a two-dimensional Riemannian manifold which can be
realized as isometric immersions into . This problem can be formulated as
initial and/or boundary value problems for a system of nonlinear partial
differential equations of mixed elliptic-hyperbolic type whose mathematical
theory is largely incomplete. In this paper, we develop a general approach,
which combines a fluid dynamic formulation of balance laws for the
Gauss-Codazzi system with a compensated compactness framework, to deal with the
initial and/or boundary value problems for isometric immersions in . The
compensated compactness framework formed here is a natural formulation to
ensure the weak continuity of the Gauss-Codazzi system for approximate
solutions, which yields the isometric realization of two-dimensional surfaces
in . As a first application of this approach, we study the isometric
immersion problem for two-dimensional Riemannian manifolds with strictly
negative Gauss curvature. We prove that there exists a isometric
immersion of the two-dimensional manifold in satisfying our prescribed
initial conditions. TComment: 25 pages, 6 figue
Composite cathode La0.4Sr0.4TiO3-[delta]- Ce0.8Sm0.2O2-[delta] impregnated with Ni for high-temperature steam electrolysis
Composite Ni–SDC (Samaria doped Ceria) cathodes are able to operate in strong reducing atmospheres for steam electrolysis, and composite cathodes based on redox-stable La0.4Sr0.4TiO3 (LSTO) have demonstrated promising performances without the reducing gas flow. However, the electro-catalytic activity of cathodes based on LSTO is insufficient for the efficient electrochemical reduction of steam or carbon oxide. In this work, catalytic-active Ni nanoparticles were loaded on a La0.4Sr0.4TiO3−δ–Ce0.8Sm0.2O2−δ cathode (Ni-loaded LSTO–SDC) via an impregnation method to improve the electrode performances for direct steam electrolysis. The synergetic effect of catalytically-active Ni nanoparticles and the redox-stable LSTO–SDC skeleton contributed to the improved performances and the excellent stability of the cathode for direct steam electrolysis. The current efficiency with a Ni-loaded cathode was enhanced by 3% and 17% compared to the values with a bare LSTO–SDC cathode under 2.0 V of applied voltage at 800 °C with a flow of 3% H2O/5% H2/Ar and 3% H2O/Ar to cathodes, respectively