Effective thermal conductivity as a function of domain structure is studied by solving the heat conduction equation using a spectral iterative perturbation algorithm in materials with inhomogeneous thermal conductivity distribution. Using this proposed algorithm, the experimentally measured effective thermal conductivities of domain-engineered {001} p-BiFeO 3 thin films are quantitatively reproduced. In conjunction with two other testing examples, this proposed algorithm is proven to be an efficient tool for interpreting the relationship between the effective thermal conductivity and micro-/domain-structures. By combining this algorithm with the phase-field model of ferroelectric thin films, the effective thermal conductivity for PbZr 1x Ti x O 3 films under different composition, thickness, strain, and working conditions is predicted. It is shown that the chemical composition, misfit strain, film thickness, film orientation, and a Piezoresponse Force Microscopy tip can be used to engineer the domain structures and tune the effective thermal conductivity. Therefore, we expect our findings will stimulate future theoretical, experimental and engineering efforts on developing devices based on the tunable effective thermal conductivity in ferroelectric nanostructures.

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Anisotropic pore structure affects fluid storage and transport behaviors in rock matrix. In this study, we quantitatively investigate the anisotropic pore structure properties of coal and shale through small-angle neutron scattering associated with contrast-matching method. Experimental 2D scattering profiles from the samples cut parallel and perpendicular to the bedding indicate isotropic 3D spherical scattering profile for Hazleton coal and anisotropic 3D ellipsoidal scattering profile for Marcellus shale. Apparent porosity and surface area of total pores are similar between the samples cut parallel and perpendicular to the bedding for Hazleton coal but are higher for the sample cut perpendicular to the bedding than the sample cut parallel to the bedding for Marcellus shale. Apparent pore accessibility follows the trend powder sample > sample cut perpendicular to the bedding > sample cut parallel to the bedding for both the measured coal and shale, indicating nanopores near the surface of granular particles have higher pore accessibility than those inside granular particles. It was captured that the measured coal has less porosity, surface area, and pore accessibility than the measured shale for each type of sample. In addition, based on the apparent pore properties of accessible pores, microscopic transport mechanism could be that fluid preferably diffuses along the bedding direction in coalbed methane and shale gas reservoirs.

This paper is concerned with theoretical analysis of a heat and moisture transfer model arising from textile industries, which is described by a degenerate and strongly coupled parabolic system. We prove the global (in time) existence of weak solution by constructing an approximate solution with some standard smoothing. The proof is based on the physical nature of gas convection, in which the heat (energy) flux in convection is determined by the mass (vapor) flux in convection.

Reduced-order modeling approaches for gas flow in dual-porosity dual-permeability porous media are studied based on the proper orthogonal decomposition (POD) method combined with Galerkin projection. The typical modeling approach for non-porous-medium liquid flow problems is not appropriate for this compressible gas flow in a dual-continuum porous media. The reason is that non-zero mass transfer for the dual-continuum system can be generated artificially via the typical POD projection, violating the mass-conservation nature and causing the failure of the POD modeling. A new POD modeling approach is proposed considering the mass conservation of the whole matrix fracture system. Computation can be accelerated as much as 720 times with high precision (reconstruction errors as slow as 7.69 × 10 −4 %~3.87% for the matrix and 8.27 × 10 −4 %~2.84% for the fracture).