Saturated Domain Research Articles

Large anisotropy of fracture toughness in mechanically poled/depoled ferroelectric ceramics

We observed large anisotropy of indentation fracture toughness in both mechanically poled and depoled lead titanate zirconate (PZT) ceramics under uniaxial compression up to 400 MPa. The fracture toughness anisotropy can reach as much as 3.82 in the former and 3.63 in the latter, which are both considerably larger than that of 2.62 in electrically poled PZT ceramics. This phenomenon is thought to be caused by ferroelastic domain switching during indentation and by the existence of more saturated domain orientation textures under compression than under electrical poling.

Three dimensional modelling of interaction between surface and Darcy flow regimes through soils

The present paper deals with the impact of surface flow on hydrodynamic conditions in saturated underground domains. A three dimensional finite element scheme has been used to simulate underground flow resulting from the flow of water over a saturated land. The results clearly show the effects of the surface flow on the hydrodynamic conditions of the subsurface porous regions. This analysis is an important prerequisite for the prediction of contaminant mobility in soils and hence provides a convenient tool for the prediction of interaction between surface and subsurface flow processes. For low permeability cases, considered here, the governing equations consist of water continuity and Darcy equations. These equations are solved using a robust and reliable finite element procedure.

Classical solutions of many-dimensional elliptic–parabolic free boundary problems

We consider a free boundary problem modeling fluid flow in a partially saturated porous media. In that context an unknown function represents the pressure and satisfies an elliptic equation in the saturated domain and a quasilinear parabolic equation in the unsaturated domain. The principal part of this work is the investigation of the smoothness properties of an unknown (free) boundary between domains of ellipticity and parabolicity.

Topic XP-nun and intervention effects

This squib explores the behavior of so called contrastive topic phrases (i.e. XP-nun phrases) in relation to other A-phrases. XP-nun phrases exhibit dual nature in that they sometimes induce intervention effects but not in other cases. The usual assumption that the contrastive topic phrases are licensed by a higher head Top is questioned in this paper because it doesnt provide any account for this asymmetry in intervention effects. Instead an alternative proposal is considered such that XP-nun is not the target of licensing but forms a kind of self saturated domain in which both the licenser(=nun) and the licensee(=a focus target within XP) are contained. It is shown that this proposal can not only account for the asymmetry in the intervention effects, but can accommodate unexpected saving effects in some focus constructions.

Stochastic analysis of transport in a combined heterogeneous vadose zone–groundwater flow system

First‐order analysis was used to investigate the effect of a few characteristics of the vadose zone and the solute source at the soil surface on the expected breakthrough curves (BTCs) of tracer solutes in a combined unsaturated‐saturated spatially heterogeneous formation with a three‐dimensional, statistically anisotropic structure. The analysis is based on a stochastic continuum representation of the stationary and nonstationary Eulerian velocity vectors in the unsaturated and saturated domains, respectively, and a general Lagrangian description of the solute mass flux in steady state flow. Results of the present analysis suggest that the length scales and the flow characteristics of the spatially heterogeneous, unsaturated zone that affect the travel time probability density function between the soil surface and the water table also affect the expected solute BTC at a control plane located downstream in the groundwater. The flow in the unsaturated zone might enhance the early arrival time and the spreading of the expected solute BTC in the groundwater, especially when the vertical extent of the unsaturated zone is relatively large; when the unsaturated zone consists of relatively dry, coarse‐textured, stratified soil material; and when the horizontal extent of the solute source in the direction of the mean groundwater flow is relatively large. The effect of the characteristics of the vadose zone and the solute source at the soil surface on the expected solute BTC in the groundwater decreases as the distance to the control plane increases and as the process of the solute breakthrough is more advanced. The relatively good agreement between the results of the present first‐order, stochastic analysis with the results of detailed, numerical analyses of flow and transport in a three‐dimensional heterogeneous, combined vadose zone–groundwater flow domain suggests that the first‐order stochastic analyses may be sufficiently reliable to show appropriate trends which might occur in realistic combined vadose zone–groundwater flow systems.

Comportement thermo-hydro-mécanique d'une argile sableuse non saturée sur chemin de cisaillement triaxial

ABSTRACT A new experimental device has been designed to study the THM behavior of a soil on triaxial paths. The material is a laboratory sandy clay with a liquid limit wL = 38 and a plasticity index Ip = 19. Three initial states of samples have been studied: (1) normally consolidated NC (2) overconsolidated OC (3) compacted to Proctor optimum water content and maximum density. Saturated triaxial tests under controlled temperature conditions and unsaturated triaxial tests under controlled temperature and suction conditions were performed on the material in the different initial states. In the saturated domain, the results show the influence of temperature and initial state on the secant modulus, maximum strength and pore pressure changes during the undrained deviatoric loading. In the unsaturated domain, the coupled effect of suction and temperature on the evolution of the secant modulus and maximum strength is highlighted.

Decomposition d'une Bioapatite Phosphocalcique en Milieu Dit Physiologique: Effet de la Sursaturation

The effect of saturation of the solution on transformations of a synthetic calcium phosphate was investigated. The solution was shown to have some physicochemical properties equivalent to those of physiological fluid. The Bioapatite is the apatitic octacalcium phosphate (OCPa); it has a low Ca/P atomic ratio identical to that of triclinic octacalcium phosphate (OCPtr). Results of solid analysis coupled with calculations of the degree of saturation of the solution enable us to delimit two saturation domains. In the first domain (low saturation degree), the calcium phosphate evolves only towards an apatitic phase with appreciable improvement of crystallization state. In the second domain (high saturation degree) a monotonous decomposition of the calcium phosphate gives a mixture of an apatitic solide phase and monetite (DCPA). The mechanism of evolution or decomposition process of the OCPa during this in vitro test is discussed.

Half-cycle slip activity of persistent slip bands at different stages of fatigue life of polycrystalline nickel

The slip activity of persistent slip bands (PSBs) in polycrystalline nickel was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The half-cycle slip activity as well as the local shear strain amplitudes was investigated after half-cycle deformation at different numbers of cycles in the domain of stress saturation. Moreover, the fraction of grains containing cumulated PSBs and the accumulated volume fraction of PSBs was estimated depending on the number of cycles during fatigue life. The volume fraction of active PSBs during half-cycle deformation is significantly lower than the cumulated PSB volume and decreases with increasing number of cycles. Additionally, an increasing localization of cyclic plastic strain within the PSBs was observed. However, with increasing number of cycles the average local shear strain amplitude remains almost unchanged. Thus, PSBs in polycrystals are subjected to a life history which is characterized by active and inactive periods of their half-cycle slip activity during cyclic deformation at different stages of the saturation state.

Validated Leverett Approach for Multiphase Flow in PEFC Diffusion Media: I. Hydrophobicity Effect

This is the first in a series of papers in which we introduce a validated Leverett function appropriate for SGL 24 series carbon paper fuel cell diffusion media (DM) that describes the capillary pressure as a function of liquid saturation and hydrophobic additive content. The presented relationship was derived based on the benchmark data gathered from direct measurements of drainage capillary pressure-saturation of differently engineered DM (coated with a microporous layer) tailored with various poly(tetrafluoroethylene) content (ranging from 5 to ) at room temperature under no compression. A key feature of the relationship is that the contact angle is implicitly embedded into the hydrophobicity parameter, thereby eliminating any ambiguity regarding the selection of a representative surface contact angle. A detailed comparative analysis of the present Leverett function and the standard Leverett function with the experimental data was performed. The standard Leverett function is found to exhibit significant deviation from the experimental data, whereas the present empirical function successfully predicts the capillary pressure over the entire saturation domain. Finally, additional spontaneous capillary imbibition experiments were performed to obtain estimates for the water retention capacity of a typical fuel cell DM as a function of the hydrophobicity of bilayered DM.

Validated Leverett Approach for Multiphase Flow in PEFC Diffusion Media: III. Temperature Effect and Unified Approach

The final paper in this series is devoted to delineating the effects of temperature on the multiphase transport characteristics of thin-film polymer electrolyte fuel cell (PEFC) diffusion media (DM). Direct measurements of capillary pressure-saturation of various commercial DM coated with a wide range of poly(tetrafluoroethylene) (PTFE) loadings (from 5 to PTFE) were performed at different operating temperatures (20, 50, and ). The benchmark data gathered from these experiments (available upon request) were compiled into the existing database generated from the first and second phase of this study, which examined the hydrophobicity and compression effects. The expanded database was then utilized to deduce a unified form of an empirical correlation appropriate for the tested DM. This semiempirical approach can predict capillary pressure of the tested DM as a function of liquid saturation, hydrophobic additive content, uncompressed porosity, compression pressure, and operating temperature within an uncertainty of of the measured capillary pressure over the entire saturation domain, showing considerable improvement over the traditional Leverett approach.

The laminar flow field at the interface of a Sierpinski carpet configuration

The problem of laminar flow in a combined free and saturated porous domain was investigated using a Sierpinski carpet configuration. The three‐dimensional steady state microscale velocities were measured using a particle image velocimeter and computed numerically. The macroscale velocity profiles were then obtained by averaging the microscale velocities. A comparison between the measured and computed velocities showed a good fit. The macroscale velocity profile was calculated using the modified Brinkman equation (MBE), which was recently derived for two‐dimensional brush configurations. The MBE was developed for unidirectional, laminar flows, assuming that the porous medium planar porosity follows a step function. A new analytical solution of the MBE was developed and applied using no calibration or curve fitting. It was shown that although the MBE was originally derived for a unidirectional microscopic flow field, the macroscopic representation of the complex microscopic flow in the Sierpinski configuration can be well described by the solutions of the MBE.

Monitoring x-ray beam damage on lipid films by an integrated Brewster angle microscope/x-ray diffractometer

We describe an integrated Brewster angle microscope (BAM), Langmuir trough, and grazing incidence x-ray diffraction assembly. The integration of these three techniques allows for the direct observation of radiative beam damage to a lipid monolayer at the air-water interface. Although beam damage has been seen in x-ray measurements, it has not been directly observed in situ at the micron scale. Using this integrated assembly, we examined the effects of radiative beam damage on Langmuir monolayers of 1,2-dimyristoyl-sn-glycero-3-[phospho-L-serine] (DMPS), 1:1 DMPS:1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, and 1:1 DMPS:1,2-dioleoyl-sn-glycero-3-phosphocholine held at a constant surface pressure. For constant surface pressure experiments, we observed a marked decrease in the surface area of the film upon exposure to the beam due to photodissociation. For a condensed lipid film, a change in refractive index of the film was observed post-beam-exposure, indicating areas of damage. For DMPS in an oxygenated environment, the Bragg peak intensity decreased with beam exposure. In mixed monolayer systems, with saturated and unsaturated lipids, an increase in the number of small saturated lipid domains was seen as the unsaturated lipid was preferentially damaged and lost from the monolayer. We show that BAM is a highly effective technique for in situ observation of the effects of radiative damage at the air/water interface during a synchrotron experiment.

Flux-Based Alternative Formulation for Variably Saturated Subsurface Flow

Finite-element and finite-difference solutions to different forms of the Richards equation can exhibit stability problems as well as mass balance errors. These problems are more pronounced for sharp wetting fronts in soils with very dry initial conditions and at material interfaces for layered soil profiles. The pressure head form can suffer from large mass balance errors while the moisture content form conserves mass perfectly but has difficulty handling material boundaries in layered soil profiles and near saturation conditions. This paper presents a conservative mixed formulation for the solution of the Richards equation of unsaturated flow by the finite-element method in which the discharge velocity (volumetric flux) and pressure head are the primary field variables. Solution techniques for various boundary conditions including prescribed constant pressure head and constant flux are also presented. The ability of the formulation to handle variably saturated domain and material heterogeneity is also established. Example solutions for infiltration into homogeneous and heterogeneous unsaturated and variably saturated soil profiles are compared with finite-element and finite-difference solutions of pressure head and mixed form of Richards equation. Results indicate that the alternative formulation is mass conservative, stable, and can better handle heterogeneous boundaries and variably saturated flow domains.

Dynamic effects for two‐phase flow in porous media: Fluid property effects

AbstractTraditional descriptions of multiphase flow in porous media rely on an extension of Darcy's law along with relationships between capillary pressure (Pc), saturation (S), and relative permeability (Kr). New theories have been proposed which suggest that Pc relationships should include a dynamic coefficient (τ) (Hassanizadeh and Gray, Water Resour Res. 1993;29:3389–3405) to indicate how “quickly” or “slowly” flow equilibrium is reached. While validity of these theories must be examined, it is also necessary to determine the significance of τ and its range of values. In this article, we analyze the significance of τ depending on fluid properties. We address the ways in which they cause nonuniqueness of dynamic two‐phase flow in porous media and, hence, dynamic effect. Simulations are conducted for quasi‐static and dynamic flow of perchloroethylene (PCE) in water saturated domains. The data are then fitted to the dynamic Pc relationships to obtain values of τ. The effects of flow directions and, viscosity and density ratios are discussed. To consider the lumped effects of various fluid properties, τ–S relationships are examined for silicone oils. The results are interpreted by examining the correlation between τ and a mobility coefficient, m. We discuss a scaling relationship that shows the dependence of τ on fluid and material properties. © 2007 American Institute of Chemical Engineers AIChE J, 2007

SATURATION PHYSICS AND THE ELECTRON-ION COLLIDER

Using an extension of the Iancu-Itakura-Munier model to nuclear targets we look for saturation effects in electron-ion collisions. In previous publications we have made definite predictions. Here we try to compare our results with already existing experimental data on structure functions and on total and diffractive cross sections. Strictly speaking such a comparison is not well justified because the present data are not yet in the saturation domain. Nevertheless our results agree qualitatively with data and, in some cases, even quantitatively.

Leak identification in porous media by solving the Cauchy problem

We propose in this Note a method of identifying leak zones in a saturated and homogeneous porous domain by solving a Cauchy problem. The method is based on the minimisation of an energy-like error functional procedure developed in 2006 by Andrieux and Baranger. To cite this article: X. Escriva et al., C. R. Mecanique 335 (2007).

Domain observation of amorphous wire with large diameter for micro-sensor and micro-motor application

Domain structures of Fe-Si-B-Nb amorphous wires with a large diameter were investigated. A 10% increase of pulse output voltage due to large Barkhausen jumps in the Fe-Si-B-Nb wire at the diameter of 200 µm has been obtained which is less than expected due to decreased saturation and small domain size. Domain observation results indicate that the increase of the domain size in the inner core of the wire is important for high sensor output.

Numerical models for 2D free boundary analysis of groundwater in slopes stabilized by drain trenches

A numerical model for 2D free boundary analysis of groundwater in slopes stabilized by drain trenches has been developed. It consists of a front-tracking method (based on an original way of adapting the space derivatives), very effective in saving calculation time respect to classical fix-grid methods. The method analyses the trenches effect inside slopes in which the soils above the water table are partially saturated, for which a boundary can be recognized between the saturated domain (water table) and the unsaturated one (above the water table). In this case pore pressure lowering, due to trenches, can be analyzed considering the progressively reduction of the saturated domain. This approach efficiently solves the problem of fixing hydraulic boundary conditions on the sides of the trenches. Results have been compared with those obtained by a fix-grid method, observing difference less than 0.14%. Applying the method, the capability of drain trenches to control the effect of heavy rainfalls has been investigated, calculating (during the transient process of water table lowering) limit values of water recharge for which water table keeps on constant.

Analytical saturated domain orientation textures and electromechanical properties of ferroelectric ceramics due to electric/mechanical poling

Saturated domain orientation textures of three types of pseudocubic (tetragonal, rhombohedral, and orthorhombic) ferroelectric ceramics after complete electric and uniaxial tension (compression) poling is studied analytically in this paper. A one-dimensional orientation distribution function (ODF) of the domain polar vectors is explicitly derived from the uniform inverse pole figures of the poling field axes on a stereographic projection with respect to the fixed crystallite coordinates. The analytical ODF is used to obtain the analytical solutions of saturated polarization and strain after electric/mechanical poling. Based on the closed form solution of the saturated domain orientation textures, the resultant intrinsic electromechanical properties of ferroelectric ceramics, which depend only on the ODF and properties of the corresponding single crystals, are obtained. The results show how the macroscopic symmetries of ferroelectric crystals change from 4mm (tetragonal), 3m (rhombohedral), and mm2 (orthorhombic) single crystals to a ∞mm (transversely isotropic) completely poled ceramic.

Vertical porosity profile of a clay-rich marsh soil

The evolution of clay soil porosity is currently demonstrated via the shrinkage curves in a large water content domain spreading from a shrinkage limit to a liquidity limit. In fact, the parallel between in situ profiles and the shrinkage curves in such a large water content range is difficult to obtain because of the lack of earth pressure in the laboratory tests and in situ limited water contents. The vertical distribution of porosity throughout a clay-rich marsh soil profile was studied in a grassland field with samples taken from the soil surface characterized by water contents near their shrinkage limit down to 2.00 m deep saturated sediments over their liquidity limit. The depth of the plasticity limit isolates a soil in a solid state characterized by a vertical prism-like structure from a plastic to pseudo-liquid state in depth. The porosity was calculated from the measurements of the density of intact samples by double weighing and image analysis of 100 cm 2 polished sections. The initial structure of clay soil was maintained by impregnation based on water–acetone–resin exchange. An ultraviolet photo luminescent pigment added to the resin allowed the capture of images from which shrinkage cracks and microporosity of the clay matrix were easily separated. The distribution of porosity between the shrinkage crack mesoporosity and the clay matrix microporosity was evaluated after the mathematical decomposition of the grey level curves characteristic of each level. Vertical evolution of the porosity distribution from the soil surface in a solid state to the plastic and pseudo-liquid sediment in depth was presented on the shrinkage curve of the clay material. The measurements point out how the clay matrix microporosity and mesoporosity of shrinkage cracks are complementary and the role of the scale effect on the shrinkage curve. The analysis of images captured on an optical microscope under polarized and analyzed light and the SEM observation of freeze-dried samples demonstrated the isotropic arrangement of the clay particles in typical “honey-comb” architecture in the in situ plastic-to-liquid saturated domain. Eventually the distribution of porosity through the profile results from the evolution of the initial “honey-comb” microstructure of the sediment induced by the desiccation phenomenon. It is governed by the depth of plasticity limit of the clay material and by the depth of the water table.