Aluminium oxide optical film fabricated with ion-assisted deposition using sulphur hexafluoride and oxygen working gases

Al₂O₃ thin films fabricated by electron-beam evaporation with ion-assisted deposition at room temperature using O₂ or SF₆, or their mixture as a working gas were investigated. A significant 20% packing density increase and a low extinction coefficient were obtained when only SF₆ was used.     

Surface modification on a glass surface with a combination technique of sol-gel and air brushing processes

This study fabricated the large area and optically transparent superhydrophobic silica based films on glass surface with optimized hardness. A silane coupling agent, tetraethoxysilane (TEOS), effectively bonds silica particles onto the glass substrate. Desired surface roughness was obtained by adjusting nano silica particles concentration of the precursors prepared by the sol-gel process. Silica suspension was coated onto the glass substrate by the air brushing methods. This method can deposit a uniform, transparent coating on the glass substrate efficiently. Diluting the precursor by adding ethanol or a mixture of D.I. water and ethanol further improved the transmittance and superhydrophobicity efficiency. The results showed that as the silica particle concentration and the thickness of the coating were increased, the surface roughness was enhanced. Rougher surface displayed a higher superhydrophobicity and lower transmittance. Therefore, the concentration of silica particle, volume of coatings, and the ratio of ethanol and D.I. water are of great importance to deposit a transparent, superhydrophobic coating on glass.     

A meshless numerical method for solving slow mixed convections in containers with discontinuous boundary data

This paper describes the formulations of the method of fundamental solutions (MFS), which is a famous meshless numerical method representing a sought solution by a series of fundamental solutions to solve slow mixed convections in containers with discontinuous boundary data. In the derivations, the fundamental solutions were obtained by using the Hörmander operator decomposition technique. All the velocities, temperatures, pressures, stresses and thermal fluxes corresponding to the fundamental solutions were addressed explicitly in tensor forms. Although the MFS is highly accurate for smooth boundary data, its convergence becomes poor when it is applied to problems with discontinuous boundary data. To compensate for this drawback, we enriched the MFS by adding the local discontinuous solutions to the series of fundamental solutions. This enriched MFS was applied to solve the benchmark problems of a lid‐driven cavity and natural convection in rectangular containers. In addition, the numerical solutions were compared with the analytical solutions. Then, the meshless numerical method was further utilized to solve mixed convections in a triangular cavity and a cavity with a cosine‐shaped bottom. These numerical results demonstrated the applicability of the enriched MFS to two‐dimensional mixed convections in containers with discontinuous boundary data. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of 3,3‐Dimethylglutamic Acid Derivatives as DPP‐IV Inhibitors and Evaluation of Their Chemical Stability

A novel five‐step synthesis of Boc‐3,3‐dimethylglutamic acid α‐ethyl ester 11 is reported. All the steps are high yielding and simple to carry out. By use of the 3,3‐dimethylglutamic acid building block, we successfully discovered a novel class of DPP‐IV inhibitors, Glu‐Pro‐Nitrile dipeptide mimics 2 , with high potency (IC₅₀ < 40 nM). The consequence of 3,3‐dimethyl substituent on the rate of intramolecular cyclization between N‐terminal amine and 5‐position amide bond in different buffer solutions was also evaluated.     

Computer-aided photoelastic analysis of orthogonal 3D textile composites: Part 1. Whole-field determination of isochromatics and isoclinics

Two correlative methods are developed for the computer-aided photoelastic analysis of orthogonal 3D textile composites comprising 6 mm×6 mm highly heterogeneous unit cells in-plane. The first method, presented in Part 1, is used for the whole-field determination of isochromatics and isoclinics; the second method, presented in Part 2, is applied for subsequent photoelastic stress analysis. Part 1 delineates precisely how one circular polariscope and two plane polariscope photoelastic images are implemented to extract the isochromatic parameterR and isoclinic parameter α using the digital image processing technique. The photoelastic experiments were performed with orthogonal 3D textile composite as well as aluminum plates containing a hole under the uniaxial tension loading. The obtained values ofR and α, for the case of the aluminum plate, are smoothly distributed over the field and show consistent agreement with those computed from finite element analysis (FEM). In the case of the composite plate, the global distribution ofR and α also agree well with FEM results employing the homogenized composite properties. However, bothR and α exhibit local variations according to the 3D fabric structure, and the varying amplitude of α is relatively larger than that ofR.     

Mixed convection film condensation from downward flowing vapors onto a sphere with uniform wall heat flux

A model is developed for the study of mixed convection film condensation from downward flowing vapors onto a sphere with uniform wall heat flux. The model combined natural convection dominated and forced convection dominated film condensation, including effects of pressure gradient and interfacial vapor shear drag has been investigated and solved numerically. The separation angle of the condensate film layer, φ _s is also obtained for various pressure gradient parameters, P ^* and their corresponding dimensionless Grashof?'s parameters, Gr ^*. Besides, the effect of P ^* on the dimensionless mean heat transfer, will remain almost uniform with increasing P ^* until for various corresponding available values of Gr ^*. Meanwhile, the dimensionless mean heat transfer, is increasing significantly with Gr ^* for its corresponding available values of P ^*. For pure natural-convection film condensation, is obtained.