Coupled Effects of Ionic Strength,Particle Size,and Flow Velocity on Transport and Deposition of Suspended Particles in Saturated Porous Media

In this study, the coupled effect of ionic strength, particle size, and flow velocity on transport and deposition of suspended particles (SP) in saturated sand was undertaken. Three polydispersive SP populations (silt particles with the median of 3.5, 9.5 and 18.3 \(\upmu \)m) were investigated using a pulse injection technique. High ionic strengths were used and vary from 0 to 600 mM (NaCl). Two high velocities were tested: 0.15 and 0.30 cm/s. Suspended particles recovery and deposition kinetics were strongly dependent on the solution chemistry, the hydrodynamics, and the suspended particles size, with greater deposition occurring for increasing ionic strength, lower flow velocity, and larger ratios of the median diameter of the SP to the median sand grain diameter. A shift between the extended Derjaguin–Landau–Verwey–Overbeek theory prediction (the particles and sand grain surfaces are considered chemically and topographically homogeneous) and the experimental results for certain ionic strength was observed. So, as reported in recent literature, effects of surface heterogeneities should be considered. The residence time of the non-captured particles is dependent on ionic strength and hydrodynamic. A relationship between the deposition kinetics, particle and grain sizes, flow velocity, and ionic strength is proposed.     

Contribution to the study of structural and elastic properties of wüstite under pressure up to 140 GPa by pseudopotential calculations

Using first-principles calculations based on the density functional theory and the generalized gradient approximations, we have studied the effect of high pressures up to 140 GPa on the structural and elastic properties of wüstite. Our results indicate that FeO undergoes a structural phase transition from NaCl-type (B1) to NiAs-type (B8) almost at the pressure of 77 GPa. The density increases across this transition by about 5%, which is a higher value than that obtained in other researches. We can clearly present the wüstite elastic properties and isotropic wave velocities which are not already studied in this range of pressure, and we could compare these results with the available experiment data, especially with that of PREM model.     

On the discrete groups of Moonshine

We characterize the 171 discrete subgroups of occurring in Monstrous Moonshine in terms of their group-theoretic properties alone.

     

Flexible electrospun PET/TiO2 nanofibrous structures: Morphology,thermal and mechanical properties

In this study, a solvothermal method was used to synthesize anatase titanium dioxide (TiO₂) nanoparticles in the presence of oleic acid (OA) and oleylamine (OM) as morphology‐directing agents. Functional nanocomposite fibers of poly(ethylene terephtalate) (PET) containing surfactants‐capped TiO₂ nanoparticles were developed by electrospinning technique. The morphology, thermal stability and mechanical properties of PET/TiO₂ nanocomposite mats were investigated as a function of TiO₂ concentration. Morphology investigation showed interesting results in terms of the level of TiO₂ dispersion inside the fibers and the improvement of the quality (smoothness) of the fibers' surface when the synthesized nanorhombic TiO₂ nanoparticles were used compared to a commercial P25 TiO₂ (AEROXIDE P25)_. The presence of OA and OM on the surface of the nanorhombic synthesized TiO₂ led to a significant improvement of TiO₂ dispersion inside the PET matrix. Furthermore, the physical interaction between the PET matrix and TiO₂ nanoparticles resulted in an enhanced thermal stability, and an increase of the Young's modulus and tensile strength for TiO₂ concentration up to 10 wt%.     

Tailoring hyper-heuristics to specific instances of a scheduling problem using affinity and competence functions

Hyper-heuristics are high level heuristics which coordinate lower level ones to solve a given problem. Low level heuristics, however, are not all as competent/good as each other at solving the given problem and some do not work together as well as others. Hence the idea of measuring how good they are (competence) at solving the problem and how well they work together (their affinity). Models of the affinity and competence properties are suggested and evaluated using previous information on the performance of the simple low level heuristics. The resulting model values are used to improve the performance of the hyper-heuristic by tailoring it not only to the specific problem but the specific instance being solved. The test case is a hard combinatorial problem, namely the Hybrid Flow Shop scheduling problem. Numerical results on randomly generated as well as real-world instances are included.     

Are closed clusters expected from the (n + 1) skeletal electron pairs rule in alanes and gallanes? A DFT structural study of AnHn + 2 (A = Al, Ga, and n = 4-6)

It has been suggested recently that the alanes Al_nH_n + 2 can be treated by the polyhedral skeletal electron pair theory (PSEPT) of Wade and Mingos (W-M) as it was successful for their borane congeners such as B_nH_n + 2, well known as the deprotonated B_nH_n²⁻. To do so, the neutral Al_nH_n + 2 have been considered as Al_nH_n²⁻ + 2H⁺. The additional hydrogens donate their electrons to the Al_nH_n polyhedral framework and according to the n + 1 electron pairs rule; these clusters should have closo-polyhedral structures. In this work the homologous gallanes, the structures and stabilities of Ga_nH_n + 2 are studied at high levels of calculational theory and we investigated the applicability of the W-M rule to the alanes and gallanes A_nH_n + 2 (n = 4-6; A = Al, Ga). It will be shown that the presence of bridging hydrogen atoms reduces the compactness of the corresponding polyhedron and so these species do not have the closed structures. The computations were performed at B3LYP/6-311+G(d,p), BPW91/6-311G(d,p) and B3LYP/6-311+G(3df,2p) levels of theory. Our interest in these compounds includes their potential use as hydrogen storage species and future clean sources of energy.     

Optical,structural, and photoelectrochemical properties of nanostructured ln-doped ZnO via electrodepositing method

Indium-doped zinc oxide nanorods were electrochemically deposited at low temperature on ITO substrates. The synthesized ZnO-arrayed layers were investigated by using X-ray diffraction, scanning electron microscopy, UV–vis transmittance, electrochemical impedance spectroscopy, and photocurrent spectroscopy. X-ray diffraction analysis demonstrates that the electrodeposited films are crystalline and present the hexagonal Würtzite ZnO phase with preferential (002) orientation. The ZnO films obtained forms aligned hexagonal nanorods, and depending on the increasing In concentration, the surface morphologies of the films are changed. The ln-doped ZnO nanorods (NRs) are well-aligned with the c-axis being perpendicular to the substrates when the ln concentration was between 0 and 2 at.%. of In, the grown films with In contents up to 4 at.%, changes in the optical band gap from 3.31 to 3.39 eV, and the blue shift in the band gap energy was attributed to the Burstein–Moss effect. The effect of In concentration on the photocurrent generated by films shows that the obtained thin films can be used as a photovoltaic material. Changes in the photocurrent response and the electronic disorder were also discussed in the light of In doping. It was found that the carrier density of IZO thin films varied between 1.06?×?10¹⁸ and 1.88?×?10¹⁸ cm^?3 when the In concentration was between 0 and 4 at.%.

Open image in new window

Graphical Abstract Photocurrent response of IZO samples

     

ChemInform Abstract: G2(MP2) Molecular Orbital Study of [H3AlXH3]‐ (X: C,Si, and Ge) and H3AlYH3 (Y: N,P, and As) Complexes.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.