Host (nanopores of zeolite Y)-guest (oxovanadium(IV) tetradentate schiff-base complexes) nanocomposite materials: synthesis,characterization and liquid phase hydroxylation of phenol with hydrogen peroxide

Oxovanadium(IV) tetradentate Schiff-base complexes; [VO(X₂-haacac)] (X = H, Cl, CH₃ and NO₂), X₂-haacac = substituted bis(2-hydroxyanil)acetylacetone; and encapsulated in the nanopores of zeolite NaY; [VO(X₂-haacac)]-NaY; have been synthesized and characterized. The host-guest nanocomposite materials; [VO(X₂-haacac)]-NaY; was characterized by chemical analysis and spectroscopic methods (FT-IR, UV/VIS, XRD, BET and DRS). The analytical data indicated a composition corresponding to the mononuclear complex of Schiff-base ligand. The characterization data showed the absence of extraneous complexes, retention of zeolite crystalline structure and encapsulation in the nanopores. Substitution of the aromatic hydrogen atoms of the Schiff-base ligand by electron withdrawing groups like −Cl, and −NO₂ has two major effects: (1) retention and concentration of the oxovanadium(IV) complex in the zeolite cavities is enhanced (due to the larger size of the substituents) and (2) the electronic and spectral properties of the encapsulated complex are modified. Liquid-phase selective hydroxylation of phenol with H₂O₂ to a mixture of catechol and hydroquinone in CH₃CN has been reported using oxovanadium(IV) Schiff-base complexes encapsulated in zeolite-Y as catalysts. Reaction conditions have been optimized by considering the concentration of substrate and oxidant, amount of catalyst, effect of time, volume of solvent and temperature. Under the optimized reaction conditions, [VO((NO₂)₂-haacac)]-NaY has shown the highest conversion of 42.3% after 6 h. All these catalysts are more selective toward catechol formation. Encapsulated oxovanadium(IV) complex is catalytically very efficient as compared to other neat complexes for the hydroxylation of phenol and is stable to be recycled without much deterioration.     

In Pursuit of Excellence and Gender Equality: Engineering Education at Kuwait University

The multi‐dimensional effort in the pursuit of excellence in engineering education at Kuwait University is described. The engineering program curricula have continuously been modified to provide engineering students with an intellectual foundation that is broad, well‐rounded, and multi‐disciplinary. He pursuit of excellence in engineering education has earned the College ABET's “substantial equivalency” rating for six of its programs. Women constitute more than forty percent of the incoming engineering student body in recent years. A comprehensive questionnaire survey of the alumni of the College of Engineering was performed. Nearly all of engineering women alumnae are presently employed and a majority feel that the education and training, which they received from the engineering programs, were excellent and responsive to the needs of their jobs. A clear majority of women alumnae also feel equal (or even superior), to their male counterparts with regard to job‐related factors. The feeling of equality is positively and significantly correlated with GPA, field of specialization, and years of experience.     

Flexible multibody simulation using hybrid integration scheme

One issue in the dynamic simulation of flexible multibody system is poor computation efficiency, which is due to high frequency components in the solution associated with a deformable body. Standard explicit numerical methods should take very small time steps in order to satisfy the absolute stability condition for the high frequency components and, in turn, the computational efficiency deteriorates. In this study, a hybrid integration scheme is applied to solve the equations of motion of a flexible multibody system for achieving better computational efficiency. The computation times and simulation results are compared between the hybrid scheme and conventional methods. The results demonstrate that the efficiency of a flexible multibody simulation can be improved by using the hybrid scheme.     

Polymer-stabilized graphene dispersions at high concentrations in organic solvents for composite production

We demonstrate a simple and effective technique for dispersing pristine (unfunctionalized) graphene at high concentrations in a wide range of organic solvents by use of a stabilizing polymer (polyvinylpyrrolidone, PVP). These polymer-stabilized graphene dispersions are shown to be highly stable and readily redispersible even after freeze-drying. This technique yields significantly higher graphene concentrations compared to prior studies. An excellent increase in the thermal conductivity of the fluid by the addition of pristine graphene is also demonstrated. These well-dispersed pristine graphene sheets were then used as a strong and conductive nano-filler for polymer composites. Graphene/PVP composites were produced by the bulk polymerization of N-vinylpyrrolidone loaded with dispersed graphene, resulting in excellent load transfer and improved mechanical and electrical properties.     

Simultaneous effects of polymer concentration,jet-stretching,and hot-drawing on microstructural development of wet-spun poly(acrylonitrile) fibers

Investigation of structural development of acrylic fibers during the early stages of the wet-spinning process has great importance both in carbon fiber and textile industries. The simultaneous effects of increasing polymer concentration, jet-stretching and hot-drawing on porosity, morphology, and mechanical properties of wet-spun poly(acrylonitrile) fibers were studied. The detailed microstructure of the voids was characterized by electron microscopy, porosimetry, and thermoporometry. The effects of jet-stretching/hot-drawing on the overall porosity of the fibers were negligible below a threshold polymer concentration. Increasing polymer concentration from 10 to 20 vol.% reduced the total porosity. Hot-drawing was more effective in reducing the overall porosity of the fibers in comparison with jet-stretching. Stretching and drawing replaced the macrovoids by dense ligaments but did not change the volume fraction of nanovoids, however, shifted nanovoids size distribution toward smaller values. In general, Young’s modulus and elongation at break increased by decreasing overall porosity, however, they depended also on the distribution of voids size and chain orientation along the fiber axis. Strength–diameter correlation showed a good agreement with the Griffith’s theory.     

Neutral N,N′-bis(2-pyridinecarboxamide)-1,2-ethane as sensing material for determination of lutetium(III) ions in biological and environmental samples

The biological properties of the lutetium as well as other lanthanide ions, primarily based on their similarity to calcium, have been the bases for research into potential therapeutic applications of lanthanide series since the early part of the twentieth century. In this research, a Lu(III) potentiometric membrane sensor based on N,N′-bis(2-pyridinecarboxamide)-1,2-ethane (PCAE) is described. The sensor exhibits a Nernstian response over a concentration range of 1.0 × 10^? 6 mol L^? 1–1.0 × 10^? 1 mol L^? 1, with a detection limit of 6.0 × 10^? 7 mol L^? 1. The best performance was achieved with a membrane composition, consisting of 30% PVC, 63% o-nitrophenyl octyl ether (NPOE), 5% PCAE and 2% sodium tetraphenylborate (NaTPB). It was found that at the pH range of 4.0–9.0, the potential response of the sensor was not affected by the pH. Furthermore, the electrode presents satisfactory reproducibility, very fast response time (5 s) and relatively good discriminating ability for Lu(III) ions with respect to many common cations and other lanthanide ions. The sensor has been applied to the determination of Lu(III) in human serum and in some soil samples where domestic devices were stored.     

PRELIMINARY PHASE DIAGRAMS FOR BITUMEN/ HEAVY OILS AND RELATED MIXTURES

ABSTRACT

The phase behaviour of heavy oil mixtures was studied using an X-ray imaging system. Batch phase experiments were performed at temperatures and pressures up to 725 K and 7 MPa. Complex phase behaviour such as liquid-liquid-vapour and solid-liquid-liquid-vapour were observed and preliminary experimental phase diagrams were constructed. This observed complex phase behaviour is consistent with thermodynamic theory and such phase behaviour can be modelled using the Peng-Robinson equation of state and the tangent plane criterion. These latter points are illustrated through the phase diagram for a model reservoir fluid (ethane + propane + n-butane + phenanthrene) which exhibits solid-liquid-liquid-vapour phase behaviour. Example predicted and experimental phase diagrams are presented for this model system.     

Influence of Aging Treatment on In-Situ Electrical Resistance Variation During Aging of Nickel-Rich NiTi Shape Memory Wires

Electrical resistance variations of Ni_50.9Ti_49.1 shape memory wires were studied during aging treatment at different temperatures via in-situ electrical resistance measurement. The results showed that during aging treatment, a cyclic behavior was observed in the electrical resistance variations, which could be related to the precipitation process. The evaluation of transition temperatures was conducted, after aging, using differential scanning calorimetry (DSC) analysis. The precipitation process is found to occur in four different stages. The results show that depending on the stress level around precipitates, two-, three-, or four-step martensitic transformation could be observed in DSC curves. In the points with maximum stress level (during precipitation process), four-step martensitic transformation is observed.