Water movement in melting snow

The mathematical model of water movement in melting snow is studied in neglect of deformation of the porous medium. As the mathematical model of the problem, the mass conservation equations for water, air and stationary porous skeleton of snow are used along with an analogue of Darcy’s law for water and air. Water and air are considered to be individual phases with its own filtration rate determined in solving the problem. This assumption allows constructing the closed model. The numerical test calculations are carried out. The mathematical model under study is verified using experimental data.

Liquid Migration in the Paste as the Result of Consolidation

The processing of various powder materials is often done by an extrusion process; the powders being formed into a paste by the addition of a liquid substance. During extrusion, by reason of the extrusion pressure, some properties of the paste are changing, which affect its rheology and thus the extrusion itself. One of the phenomena is the movement of the liquid phase. This paper is focused on monitoring this phenomenon using model material in a simple test device. Its design simulates the effect of pressure in the extruder. The results of the measurements provide a picture of the movement of the liquid phase under the influence of the pressure in the porous skeleton formed by the powder material.

On the Poroelastic Biot Coefficient for a Granitic Rock

The Biot coefficient is a parameter that is encountered in the theory of classical poroelasticity, dealing with the mechanics of a fluid-saturated porous medium with elastic grains and an elastic skeletal structure. In particular, the coefficient plays an important role in the partitioning of externally applied stresses between the pore fluid and the porous skeleton. The conventional approach for estimating the Biot coefficient relies on the mechanical testing of the poroelastic solid, in both a completely dry and a fully saturated state. The former type of tests to determine the skeletal compressibility of the rock can be performed quite conveniently. The latter tests, which determine the compressibility of the solid material constituting the porous skeleton, involve the mechanical testing of the fully saturated rock. These tests are challenging when the rock has a low permeability, since any unsaturated regions of the rock can influence the interpretation of the compressibility of the solid phase composing the porous rock. An alternative approach to the estimation of the solid grain compressibility considers the application of the multi-phasic theories for the elasticity of composite materials, to estimate the solid grain compressibility. This approach requires the accurate determination of the mineralogical composition of the rock using XRD, and the estimation of the elasticity characteristics of the minerals by appealing to published literature. This procedure is used to estimate the Biot coefficient for the Lac du Bonnet granite obtained from the western region of the Canadian Shield.

Enhanced Tribological Properties of an Advanced Al–Al2O3 Composite Infiltrated With a Tin-Based Alloy

In this article, a new hybrid material is elaborated, which combines the advantages of the mechanically more resistive alloy-based composites and the effective lubricating properties of tin-based alloys with the purpose of enhancing the tribological properties and especially to enhance resistance under extreme and transient operating conditions for the application of sliding bearings. The hybrid material consists of an aluminum composite skeleton obtained via a replication method with NaCl particles as spacers and a tin-based alloy that is infiltrated into the composite skeleton. The hybrid material is characterized in respect to its microstructure and tribological parameters, such as the wear-rate and coefficient of friction. Data from the conducted tribological tests using the pin-on-disk method under dry friction conditions are obtained and compared with the results of the same tribological tests for the Al alloy, Al alloy-based porous skeleton, Al alloy-based porous composite skeleton, and tin-based alloy. It is concluded that the new hybrid material possesses superior tribological properties in comparison with the tin-based alloy, Al alloy, Al alloy-based porous skeleton, and Al alloy-based porous composite skeleton.

Experimental Investigation of Water–Sand Mixed Fluid Initiation and Migration in Porous Skeleton during Water and Sand Inrush

Water–sand inrush is one of the most serious disasters for mining in China. The evaluation of the occurrence and development of a high-concentration water and sand mixed fluid is an important issue for mining in China. In this study, contraposing to the 3 phases of water–sand inrush, three kinds of experiments are designed for the investigation of initiation, development, and occurrence of the disaster. A new sand–water transport testing system is setup to perform the tests. The results show that there are two key points in the disaster: (1) sand particle incipient motion and (2) porous skeleton structural instability. The incipient motion of sand grains is accompanied with the phenomena of volumetric dilatation and granular fluidization. The critical velocity of the incipient motion of the water–sand mixed fluid is significantly affected by the particle size and external stress. The interaction between water and sand grains is the key factor affecting the motion characteristics of water–sand mixture. When the hydraulic conditions exceed the threshold, the water and sand grains are mutually promoted, and the aquifer skeleton becomes unstable. Furthermore, during the water–sand inrush, the curves of volumetric flow rates of sand and water, respectively, for different samples manifest as two distinct waveforms.

A novel porous egg-white (EW)/titania composite photocatalytic material for efficient photodegradation applications

A novel porous egg-white (EW)/titania composite material was prepared via a facile nonaqueous precipitation method with EW as the porous skeleton.

3D lithiophilic–lithiophobic–lithiophilic dual-gradient porous skeleton for highly stable lithium metal anode

A 3D porous lithiophilic–lithiophobic–lithiophilic dual-gradient CAZPZ current collector is designed to regulate homogeneous Li deposition, and the CAZPZ–Li hybrid anode has superb practical applications in different full cells.