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[en] Comparative studies of the specific features of the composition and photoluminescence properties of porous silicon with different morphologies are carried out by infrared and photoluminescence spectroscopy. On the basis of the experimental data and commonly accepted theoretical models, the main factors that influence the photoluminescence intensity and its deterioration upon the exposure of porous silicon to directed radiation in the visible region are established. By the example of porous silicon with 50–100 nm pores, the possibility of improving the above characteristics by chemical treatment in polyacrylic acid is shown.
[en] We report increased radiation in the visible and terahertz (THz) regimes in silicon(Si)-based nanostructures. The nanostructures, Si nanowires (SiNWs) and porous Si (PSi), were synthesized via electroless and electrochemical surface modification, respectively. In particular, picosecond (ps) radiative lifetimes in the order of 250 ps were obtained from time-resolved photoluminescence (PL) measurements. The fast radiative lifetimes are associated with increased surface defect density in PSi. Reflectance measurements confirmed that optical absorption of the nanostructured Si samples increased relative to bulk Si. Both nanostructured Si exhibit THz emission, albeit weaker in PSi due to higher density of defects. An inverse relationship between PL and THz emission strength was therefore observed. Lastly, the wider bandwidth of the THz emission in SiNWs is attributed to the directionality of the transient photocurrent compared to the more disordered carrier transport in PSi.
[en] A specification is presented covering virgin hafnium metal commonly designated as sponge because of its porous, sponge-like texture; it may also be in other forms such as chunklets. The specification does not cover crystal bar
[en] The object of this invention is a heat exchanger with an anisotropic porous structure. Specifically, this invention concerns a heat exchanger for example, between a gas and a liquid that utilises, for the flow of one of the fluids, a containment at leats partly filled with a porous structure for improving the thermal exchanges between the hot primary fluid and the second fluid to be heated
[fr]La presente invention a pour objet un echangeur de chaleur a structure poreuse anisotrope. De facon plus precise, la presente invention a pour objet un echangeur de chaleur, par exemple, entre un gaz et un liquide qui utilise pour la circulation de l'un des fluides une enceinte au moins partiellement remplie par une structure poreuse pour ameliorer les echanges thermiques entre le fluide primaire chaud et le fluide secondaire a echauffer
[en] In present article author presents the method of liquids classificationin porous mediums on the base of studying of hydrodynamical particularitiesof particle movement of liquid in capillary in the area of small velocitiesof stream
[en] We address one key source of the known discrepancies between theory and experiment in poroelasticity, i.e., the fact that Gassmann's equations for the bulk and shear moduli predict that the shear modulus is independent of the saturating fluid properties, whereas it is observed on the contrary that at high enough frequencies the shear modulus can in fact depend on the fluid's elastic properties in many porous materials. One clue to understanding this behavior comes from effective medium theory, which shows that the shear modulus does depend on the fluid properties in many circumstances. In comparison to values predicted by effective medium theory, Gassmann's equations predict different, smaller values for both the effective bulk and shear moduli of porous media. Sorting through these apparent (but not actual) disagreements among theory and theory, and theory and experiment is the main thrust of the paper
[en] Highlights: • A novel porous organic cage (POC) coated chiral OT capillary column was developed. • This is a report, for the first time, that the enantioseparations are carried out by POC (CC3-R) in CEC. • Good enantioseparation for furoin, benzoin and alprenlol were achieved. • The isomers of nitrophenols, phenylenediamines, aminophenols and ionones were also separated. - Abstract: Porous organic molecular cages, as a new type of porous materials, have in recent years attracted a tremendous amount of attention for their potential applications. However, to the best of our knowledge, there has been no attempt to utilize porous organic molecular cages as stationary phases in capillary electrochromatography (CEC). We report herein the use of a homochiral porous organic cage (POC) (CC3-R) as a stationary phase in open tubular capillary electrochromatography (OT-CEC) for the separation of chiral compounds and positional isomers. The column was fabricated using CC3-R as the stationary phase by a static coating method. Separation of furoin, benzoin, and alprenlol were achieved on the CC3-R coated column, with the highest resolution value (Rs = 3.35) for the separation of benzoin. The influences of pH and buffer concentration on separation have been investigated. Besides, the CC3-R column also exhibited good selectivity for the separation of positional isomers, including those of nitrophenols, phenylenediamines, aminophenols, and ionones. The run-to-run (n = 5), day-to-day (n = 5), column-to-column (n = 3), and batch-to-batch (n = 3) relative standard deviations (RSDs) for the analyte migration time were in the range of 0.5–1.5%, 0.2–1.8%, 1.2–2.1% and 1.5–2.8%, respectively. The RSDs for the migration time and enantioselectivity of the analyte were less than 5.9% and 2.2% (inter-day, n = 5) after a week of continuous use. This work also indicates that porous organic molecular materials are promising for enantioseparation in CEC and look set to become more attractive in separation science.
[en] The flow of a viscous fluid is considered to calculate the permeability of a porous medium with granular solid phase. Under the assumption of periodicity a unit cell which contains solid phase of granular shape is selected on the microscale and the flow field is calculated by solving Stokes problem in which inertial effects are ignored. A Boundary-Vale Problem is obtained by applying the theory of homogenization to slow viscous flow through porous structure on the microscale. It is shown that the permeability is dominantly determined by the flow direction along which the pressure gradient on the macro-scale is imposed. (authors)
ConclusionA technique for replicating diffraction grating on to compliant and porous materials has been developed. The grating can be applied quickly to the specimen. It is also highly compliant and localized on the specimen surface. Three applications described illustrate replication method provides high quality fringe patterns.