直下式LED黄疸灯的设计与制作

研制了一款可在接收面上实现平面光谱分布均匀的直下式LED黄疸灯。首先,按照LED数量从少到多的顺序,在同一基板上依次对4种单色LED进行排布,使其分别在同一出光面上形成大小相近且照度均匀的光斑,进而使出光面乃至接收面上实现平面光谱分布均匀。其次,对直下式LED黄疸灯仿真验证,结果表明其确实可在接收面上实现平面光谱分布均匀。最后,在出光面上分别放置扩散板和棱镜膜,对两款直下式LED黄疸灯样品进行实验测试。测试结果表明:相较而言,在出光面上放置增光膜的直下式LED黄疸灯样品可以使接收面具有较多的光能量。但无论出光面上放置的是棱镜膜还是扩散板,在600mm×300mm的接收面上,直下式LED黄疸灯都能实现99.9%以上的平面光谱分布均匀度值以及74%以上的照度均匀度值,符合国家婴幼儿光疗设备安全标准。     

Book Review:The Kinetic Theory of Gases: An Anthology of Classic Papers with Historical Commentary. S. G. Brush,World Scientific Publishing Co., River Edge,NJ, 2003

Journal of Statistical Physics -     

Preconditioning of deep snowpack for off-road vehicle mobility

This paper addresses several preconditioning techniques for strengthening a deep snowpack in order to support vehicular loadings. The criteria imposed on preconditioning a deep snowpack were: (1) only light commercially-available vehicles or equipment could be used, (2) preconditioning would only be applied to the snow surface and (3) any additives to be used should be easily acquired in remote areas. Viable preconditioning techniques were first evaluated in the laboratory using artificial snow. The techniques explored were surface loading (surcharging), heating and mixing with additives (sand and straw) followed by surcharging. The properties of the laboratory-preconditioned snow were evaluated primarily in terms of footing penetration resistance and Rammsonde hardness. Based on the laboratory results, preconditioning of a deep natural snowpack was carried out. Surcharging the snowpack was achieved by a BV206 Carrier. The preconditioning techniques studied were surcharging, heating and mixing with additives (salt and straw). Various ageing periods were imposed. The load-carrying capacity of the preconditioned snowpack was evaluated by multipasses of two wheeled vehicles (Iltis and 5/4 ton truck). The results indicated that a soft deep snowpack can be preconditioned to the extent that it can support multipasses of wheeled vehicles.     

Unprecedented syndioselectivity and syndiotactic polyolefin melting temperature: polypropylene and poly(4-methyl-1-pentene) from a highly active, sterically expanded eta1-fluorenyl-eta1-amido zirconium complex

The structurally unique, sterically expanded eta1-fluorenyl-eta1-amido single-site precatalyst, Me2Si(eta1-N-tBu)(eta1-C29H36)ZrCl2.OEt2 (3), upon activation with methylaluminoxane (MAO), is remarkably active and constitutes the most syndioselective alpha-olefin polymerization catalyst system yet reported. 3/MAO affords as-prepared syndiotactic polypropylene with [rrrr] > 99% and unprecedented melting temperatures for the unannealed (165 degrees C) and annealed (174 degrees C) polymers. The activity of this system is 4 times that of the prototypical syndioselective catalyst Me2C(eta5-C5H4)(eta5-C13H8)ZrCl2/MAO. The high activity and syndioselectivity of 3/MAO can be extended to the production of syndiotactic poly(4-methyl-1-pentene) with a record melting temperature of 215 degrees C and [rrrr] = 97%.