Thermodynamics of fluid-saturated porous media with a phase change

Summary In the present paper some aspects of the thermodynamics of a fluid-saturated porous solid, taking into account the phase change of liquid into gas, are discussed. Based on the principles of the thermodynamics of irreversible processes, restrictions for the constitutive equations of the constituents are developed, in particular for the phase transition. The porous body is assumed to be incompressible and elastically deformed, and the pore space is filled with an immiscible liquid-gas mixture (moisture). The theory presented here provides some background that can be found suitable, e.g., for drying aspects.Dedicated to Professor Franz Kollmann on the occasion of his 60th birthday     

Steady convection in a porous layer with translational flow

Summary We prove that if in a porous layer there is a translational flow in a horizontal direction, then the only stationary convection which may occur, in the presence of a small transversal gradient of temperature, is a helical motion with axes parallel to the translational flow. The stability analysis of this finite-amplitude steady solution is investigated, in the vicinity of the critical point.     

Improved ITO thin films with a thin ZnO buffer layer by sputtering

In this paper, we report a buffering method of improving the quality of ITO thin films on glass by r.f. magnetron sputtering. By applying a ZnO buffer before the ITO deposition in the same run of sputtering, ITO films showed single (111)-oriented highly textured structure, while ITO films showed mixed-oriented polycrystalline structure on bare glass. A design of experiment was taken out to minimize the resistivity of ITO films in the deposition parameter space (oxygen ratio, total gas pressure, and temperature). Resistance measurements showed that the ITO films with ZnO buffers had a remarkable 50% decrease of resistivity comparing to those without ZnO buffers at optimized deposition condition. Room-temperature Hall effect measurements showed that the decrease in resistivity comes from a large increase of mobility and a slight increase of carrier density after forming gas annealing. The ZnO/glass may be a good alternative substrate to bare glass for producing high quality ITO films for advanced electro-optic applications.     

Jet flow in a porous layer

The problem of fluid (gas) flow originating during jet injection in a cylindrical apparatus filled with a porous layer of finite height is solved. Pressure and velocity distributions in the layer are obtained. The influence of the walls of the pipe containing a granular layer on the velocity profile of a one-dimensional filtration layer is investigated.     

Penetrative ferroconvection in a porous layer

Penetrative convection in a horizontal ferrofluid-saturated porous layer in the presence of a uniform applied vertical magnetic field has been investigated via the internal heating model using the Brinkman-extended Darcy equation. The rigid-isothermal boundaries of the porous layer are considered to be either paramagnetic or ferromagnetic. The eigenvalue problem is solved numerically using the Galerkin method with either thermal or magnetic Rayleigh number as the eigenvalue. The stability of the system is significantly affected by the internal heating in the porous layer. It is noted that the paramagnetic boundaries with large magnetic susceptibility delay the onset of penetrative ferroconvection the most when compared to very low magnetic susceptibility as well as ferromagnetic boundaries. An increase in the value of magnetic Rayleigh number (R _m ), heat source strength (N _S ) and non-linearity of magnetization (M ₃) is to hasten the onset of ferroconvection. In addition, the stability of the system when heated from above and also in the absence of thermal buoyancy has been discussed in detail.     

Mass transfer coefficient and concentration boundary layer thickness for a dissolving NAPL pool in porous media

Analytical expressions for the time invariant, average mass transfer coefficient and the concentration boundary layer thickness applicable to dissolving single-component nonaqueous phase liquid (NAPL) pools in two-dimensional, saturated, homogeneous and isotropic porous formations are derived. Good agreement between predicted and experimentally determined time invariant average mass transfer coefficients is observed.     

Electroosmotic dispersion in microchannels with a thin double layer

Dispersion of a nonelectrolyte solute due to the electroosmotic flow in long straight microchannels was analyzed theoretically. A version of the Aris-Taylor procedure was employed to predict the dispersion coefficient for arbitrary geometry of the microchannel cross section. The analysis was conducted using a thin double-layer approximation, which is valid when the Debye length is much smaller than the characteristic dimensions of the cross section. For thin double layers, the obtained results describe the electroosmotic dispersion for arbitrary surface potential, electrolyte type, and cross-section geometry. Dispersion for several cases of the cross-section geometries was discussed. It was shown that, for given values of the surface potential and the Debye length, both the cross-section geometry and the electrolyte content of the driven solution substantially affect the dispersion of a nonelectrolyte solute. In the relevant particular cases, the obtained results agree with predictions of the previous theories.     

Love type waves in a porous layer with irregular interface

The dispersion equation is derived relating to the frequency and the phase velocity of propagation of Love waves in a nondissipative liquid filled porous solid underlain by an isotropic and homogeneous half space. The rectangular irregularity in the interface between the upper porous layer and the lower semi-infinite medium with a source in it is studied herein. The modified dispersion equation of Mal and the standard dispersion equation of Love waves are deduced as particular cases. In the present study, the frequency equation is obtained by applying the method of perturbation and the phase velocity curves have been drawn for different irregularities by using the numerical parameteric values as suggested by Biot.     

Elastic modulus determination of a thin layer

The titanium alloy TA6V was nitrogen implanted to improve its wear resistance. In order to extract the value of the elastic modulus of the thin layer that is formed by ion implantation of this titanium alloy, a modelling taking into account different features occurring during implantation is considered, namely erosion, concentration profile and nature of the layer. Then, the elastic modulus of the thin layer is deduced. The estimated value is shown to be consistent with the formation of a TiN rich layer about 0.2 μm thick. In this paper, a procedure based on the resonance frequency of a cantilever is presented leading to the optimisation of the measurement. Then the actual modelling proposed above is described and reliability of calculated values is discussed.     

带薄层的板反射波谱分析

1引言 粘接结构广泛应用于航空航天等高技术产业及国防工业.一方面,因粘接层间脱粘而引发的各种灾难性事故时有发生,脱粘缺陷的超声检测一直是无损检测领域一个极其重要的研究课题;另一方面,在一些高技术领域常常遇到带薄层的板的结构,需要检测薄层的厚度或性状变化.     

Thermal loading of a thin layer with circular debonding over a substrate

By using techniques appropriate to mixed boundary value problems, this study addresses the determination of stress intensity factors for a circular interface debonding between a thin layer and a substrate subjected to nearly uniform temperature change. The solution method involves three-dimensional equilibrium equations of thermo-elasticity under axisymmetry conditions. The stress intensity factors are obtained by solving the resulting pair of coupled singular integral equations numerically. This revised version was published online in August 2006 with corrections to the Cover Date.     

High-performance antireflective coatings with a porous nanoparticle layer for visible wavelengths

Ghosts and flares are well-known problems that are caused by reflections from lens surfaces when we take photographs. It is more difficult to prevent such stray light in a digital camera than in a film camera because of high reflectance from the low-pass filter and diffraction from the image sensor. To prevent such stray light, we introduce an ultralow refractive index layer into the antireflective (AR) coatings. We used the solgel method to form porous fluoride layers with ultralow refractive indices, and we succeeded in developing a unique process to form AR coatings with superior performance.     

The boundary layer on a regular droplet chain in controlled motion

The retardation of a droplet chain by air resistance has been examined. Lee's method gives nomograms for the boundary-layer thickness, velocity distribution near the chain, and chain retardation. Experiments show that the model is applicable to important cases.Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 60, No. 4, pp. 661–668, April, 1991.     

Spherical indentation of a transversely isotropic elastic half-space reinforced with a thin layer

The frictionless spherical indentation test is considered for a transversely isotropic elastic half-space reinforced with a thin layer whose flexural stiffness is negligible compared to its tensile stiffness. It is assumed that the deformation of the reinforcing layer can be treated as the generalized plane stress state. Closed-form analytical approximate equations for the maximum contact pressure, contact radius, and contact force are presented. The isotropic case is considered in detail.     

Radiation slip in a highly porous material layer

Expressions are obtained for the coefficient of radiant heat conductivity and the temperature jumps in the radiation slip mode in a highly porous material layer.Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 59, No. 4, pp. 606–609, October, 1990.