Rock Porous Structure Characterization: A Critical Assessment of Various State-of-the-Art Techniques

Transport in Porous Media - The porous structure of geomaterials is of utmost importance for various industrial and natural processes. In this study, various conventional porous structure...     

A Capillary Water-Retention Framework for the Effective Stress Parameter Considering Hydraulic Hysteresis

Transport in Porous Media - The establishment of the representative elementary volume (REV) in studies of porous media is crucial for linking microscopic structure and pore-scale fluid...     

Creeping flow analysis of slightly non-Newtonian fluid in a uniformly porous slit

This paper provides the analysis of the steady, creeping flow of a special class of slightly viscoelastic, incompressible fluid through a slit having porous walls with uniform porosity. The governing two dimensional flow equations along with non-homogeneous boundary conditions are non-dimensionalized. Recursive approach is used to solve the resulting equations. Expressions for stream function, velocity components, volumetric flow rate, pressure distribution, shear and normal stresses in general and on the walls of the slit, fractional absorption and leakage flux are derived. Points of maximum velocity components are also identified. A graphical study is carried out to show the effect of porosity and non-Newtonian parameter on above mentioned resulting expressions. It is observed that axial velocity of the fluid decreases with the increase in porosity and non-Newtonian parameter. The outcome of this theoretical study has significant importance both in industry and biosciences.     

A Simplified Novel Technique for Solving Fully Fuzzy Linear Programming Problems

This study proposes a novel technique for solving Linear Programming Problems in a fully fuzzy environment. A modified version of the well-known simplex method is used for solving fuzzy linear programming problems. The use of a ranking function together with the Gaussian elimination process helps in solving linear programming problems in a fully uncertain environment. The proposed algorithm is flexible, easy and reasonable.     

Spectral characterization of the quadratic variation of mixed Brownian–fractional Brownian motion

Dzhaparidze and Spreij (Stoch Process Appl, 54:165–174, 1994) showed that the quadratic variation of a semimartingale can be approximated using a randomized periodogram. We show that the same approximation is valid for a special class of continuous stochastic processes. This class contains both semimartingales and non-semimartingales. The motivation comes partially from the recent work by Bender et al. (Finance Stoch, 12:441–468, 2008), where it is shown that the quadratic variation of the log-returns determines the hedging strategy.     

Preparation of highly efficient Al-doped ZnO photocatalyst by combustion synthesis

Novel Al-doped ZnO (AZO) photocatalysts with different Al concentrations (0.5–6.0 mol%) were prepared through a facile combustion method and followed by calcination at 500 °C for 3 h. The obtained nanopowders were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM) combined with EDX, transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy and photoluminescence spectroscopy. The XRD patterns of AZO nanopowders were assigned to wurtzite structure of ZnO with the smallest crystallite size about 11 nm consistent with the results from TEM. The doping of Al in ZnO crystal structure successfully suppressed the growth of ZnO nanoparticles confirmed by XRD patterns. The absorption spectra analysis showed that the optical band gap energy (E_g) for the AZO nanopowders were in the range of 3.12–3.21 eV and decreased with increasing of Al dopant. The photocatalytic activities of the samples were evaluated by photocatalytic degradation of methyl orange under visible light (λ ≥ 420 nm) and sunlight irradiation. The results showed that the AZO photocatalyst doped with 4.0 mol% Al exhibited five times enhanced photocatalytic activity compared to pure ZnO. The enhanced photocatalytic activity could be attributed to extended visible light absorption, inhibition of the electron–hole pair's recombination and enhanced adsorptivity of MO dye molecule on the surface of AZO nanopowders.     

Algebraic Characterization of Dense-Separability Among Compact Spaces

In this note, we show that a compact Hausdorff space X is dense-separable if and only if every family of ideals of C(X) with zero intersection has a countable subfamily with zero intersection. As a consequence of this characterization we observe that every compact dense-separable space whith Soc(C(X)) = 0 has a countable dense and co-dense subset.     

2D Poly(arylene vinylene) Covalent Organic Frameworks via Aldol Condensation of Trimethyltriazine

Designing structural order in electronically active organic solids remains a great challenge in the field of materials chemistry. Now, 2D poly(arylene vinylene)s prepared as highly crystalline covalent organic frameworks (COFs) by base‐catalyzed aldol condensation of trimethyltriazine with aromatic dialdehydes are reported. The synthesized polymers are highly emissive (quantum yield of up to 50 %), as commonly observed in their 1D analogues poly(phenylene vinylene)s. The inherent well‐defined porosity (surface area ca. 1000 m² g^?1, pore diameter ca. 11 Å for the terephthaldehyde derived COF‐1) and 2D structure of these COFs also present a new set of properties and are likely responsible for the emission color, which is sensitive to the environment. COF‐1 is highly hydrophilic and reveals a dramatic macroscopic structural reorganization that has not been previously observed in framework materials.