Quasi-isotropic bending responses of metallic sandwich plates with bi-directionally corrugated cores

In order to reduce anisotropic behaviors of sandwich plates with open channel cores under the bending load, bi-directionally corrugated cores were introduced. Bi-directionally corrugated core has two additional design parameters related with a corrugation pass than uni-directionally corrugated core, so that its properties with respect to core orientations can be controlled. Sandwich plate with bi-directionally corrugated core is designed optimally so that beam buckling of face sheets is reduced drastically and anisotropic buckling behavior in the face sheets is minimized. The cores fabricated by a sectional forming process were bonded with face sheets by adhesive bonding. Three-point bending experiments were carried out with respect to core orientations. It has been shown from the experiments that sandwich plates with bi-directionally corrugated cores exhibit quasi-isotopic bending behaviors and structural performances in sandwich plates.     

Spray jet penetration and distribution of modulated liquid jets in subsonic cross-flows

Modulated liquid jets injected into subsonic cross-flows are empirically studied by using a mechanical liquid jet modulation apparatus. Experimental investigations were conducted using water over a range of cross-flow velocities from 5 m/s to 143 m/s and with modulated liquid jet frequencies from 35.7 Hz to 166.2 Hz and so on. PDPA(phase Doppler particle anemometry) was employed to measure droplet diameter and velocity with various spray cross-sections from Z/d=20 to Z/d=60. The spray structure, penetration depth, SMD(Sauter mean diameter), volume flux and velocity characteristics of modulated liquid jets injected into cross-flows were examined. As oscillation of the periodic pressure that could make liquid jet moved up and down in cross-flow field, the mixing process was facilitated. This phenomenon has the advantage of mixing the spray concentration from the center area to the outer area. Also, a bulk liquid jet puff was detected in the upper field of the liquid jet surface. The modulation effect appears significant in the extent of the spray oscillation. The correlation equations for the liquid jet boundary of the upper and lower regions which related to the Strouhal number have been presented to predict the spray structure under modulation conditions. Because of the modulation frequency, an inclination of averaged SMD for the structured layer was evanescent which contributed to the promotion of the macroscopic spray mixing process. Cross-sectional characteristics of SMD had the same tendency over a range of various modulation frequencies. As the modulation frequency increased, the region of volume flux distribution also increased.     

Fabrication of Al matrix composite reinforced with submicrometer-sized Al<Subscript>2</Subscript>O<Subscript>3</Subscript> particles formed by combustion reaction between HEMM Al and V<Subscript>2</Subscript>O<Subscript>5</Subscript> composite particles during sintering

To fabricate an Al-V matrix composite reinforced with submicron-sized Al₂O₃ and Al_xV_y (Al₃V, Al₁₀V) phases, high energy mechanical milling (HEMM) and sintering were employed. By increasing the milling time, the size of mechanically milled powder was significantly reduced. In this study, the average powder size of 59 μm for Al, and 178 μm for V₂O₅ decreased with the formation of a new product, Al-Al₂O₃-Al_xV_y, with a size range from 1.3 μm to 2.6 μm formed by the in-situ combustion reaction during sintering of HEM milled Al and V₂O₅ composite powders. The in-situ reaction between Al and V₂O₅ during the HEMM and sintering transformed the Al₂O₃ and Al_xV_y (Al₃V, Al₁₀V) phases. Most of the reduced V reacted with excess the Al to form Al_xV_y (Al₃V, Al₁₀V) with very little V dissolved into Al matrix. By increasing the milling time and weight percentage of V₂O₅, the hardness of the Al-Al₂O₃-Al_xV_y composite sintered at 1173 K increased. The composite fabricated with the HEMM Al-20wt.%V₂O₅ composite powder and sintering at 1173 K for 2 h had the highest hardness.     

Prediction of thermal deformation considering the residual stresses for the PMMA-TSP laminated structure

The use of polymethylmethacrylate (PMMA) plates is limited by some of their typical features, particularly the tendency to be deformed when conjugated with other materials, while remaining stable if it becomes homogeneous. This paper describes PMMA deformation caused by injection molding at high temperature. The relocation of the injection gate in order to minimize the deformation is also studied. Results rule out residual stresses as the main cause of the deformation, which are predicted by inverse engineering as described in the paper. Further study of residual stresses among different injection gates is made, and deformations of the PMMA-touch screen panel (TSP) laminated plate based on the locations of the injection gates are measured. In conclusion, one of the ways by which to reduce deformation at high temperature is to locate the injection gate at a symmetrical position of the plate.     

Effects of bimetallic catalyst composition and growth parameters on the growth density and diameter of carbon nanotubes

Multi-wall carbon nanotubes (MWNTs) were synthesized by catalytic decomposition of acetylene over Fe, Ni and Fe-Ni bimetallic catalysts supported on alumina under various controlled conditions. The growth density and diameter of CNTs were markedly dependent on the activation time of catalysts in H₂ atmosphere, reaction time, reaction temperature, flow rate of acetylene, and catalyst composition. Bimetallic catalysts were apt to produce narrower diameter of CNTs than single metal catalysts. For the growth of CNTs at 600 ‡C under 10/100 seem flow of C₂H₂/H₂ mixture, the narrowest diameter about 20 nm was observed at the reaction time of 1 h for 20Fe : 20Ni : 60Al₂O₃ catalyst, but at that of 1.5 h for 10Fe : 30Ni : 60Al₂O₃ catalyst. It was considered that the diameter and density of CNTs decreased with the increase of the growth time mainly due to hydrogen etching. The growth of CNTs followed the tip growth mode.     

Recent advances of nanolead-free solder material for low processing temperature interconnect applications

Recent advances of nanolead-free solder materials for microelectronic packaging is presented. The syntheses of Sn, SnAg and SnAgCu nanoparticles and their size dependent melting temperature are discussed. Capping nanoparticle surfaces with organic molecules for antioxidation and particle size control is studied as well. An in-house made nanosolder pastes is formulated and its metallurgical joint onto a Cu substrate is demonstrated.     

Book reviews

Australian Environmental Policy 2: Studies in Decline and Devolution

Ken Walker and Kate Crowley (eds) UNSW Press, Sydney, 1999 ISBN 0868406732 (paperback) 323 pp.; bibliography and index RRP $35.00

Beyond Meltdown: The Global Battle for Sustained Growth.

Peter Brain. Scribe, Melbourne, 1999 ISBN 0908011369 (paperback) 273 pp.; bibliography and index RRP $26.95

Cities Back from the Edge: New Life for Downtown

Roberta Brandes Gratz with Norman Mintz John Wiley & Sons, New York, 1998 ISBN 0471144177 (hardback) 347 pp.; index RRP $59.95

Evaluation in Planning: Facing the Challenge of Complexity

Nathaniel Lichfield, Angela Barbanente, Dino Bori, Abdul Khakee and Anna. Prat (eds). Kluwer, Dordrecht, 1998. ISBN 0792351770 (hardback). 383 pp.; index. RRP $254.00

Gritty Cities: Images of the Urban

Lyaranette Finch and Chris McConville (eds). Pluto, Sydney, 1999. ISBN 1864030631 (paperback). 250 pp.; bibliography and index. RRP $24.95

Setting the Stage for Systainability: A Citizen's Handbook

Chris Maser, Russ Beaton and Kevin Smith Lewis Publishers, Boca Raton, 1998 ISBN 1574441876 (hardback) 269 pp.; index RRP $47.50

The Australian Metropolis: A Planning History

Stephen Hamnett and Robert Freestone (eds) Allen & Unwin, Sydney, 1999 ISBN 1865080535 (paperback) 229 pp.; index RRP $35.00