Synthesis and properties of polystyrene/graphite nanocomposites

In this paper, graphite/polystyrene nanocomposite is synthesized by in situ polymerization of styrene in a tetrahydrofuran (THF) solution system of potassium (K)-THF-graphite intercalation compound (GIC). K-THF-GIC has proved to initiate polymerization of styrene by the anionic mechanism. Due to the interfacial interaction between the graphite nanolayers and the polymer, the composites exhibit higher glass transition temperature and higher thermal stability when compared to polystyrene. The percolation threshold in the conductivity of the composites is lesser than 8.2 wt% and the dielectric constant can reach as high as 136.     

Radio wave propagation over finite size plateau

The problem of radio wave propagation over a perfectly conducting, infinitely wide rectangular plateau of finite length has previously been solved. (see Electron. Lett., vol.25, p.707-9, 1989). This solution is now extended to deal with a perfectly conducting, rectangular plateau of finite size along all three coordinate axes. When the infinite width is reduced to a finite size the additional diffraction round the two sides of the plateau will produce a more complicated expression for the overall attenuation. The authors quantify the new attenuation and derive an approximate analytic expression for the attenuation function in closed form. Experimental confirmation of the calculated result both as a function of distance along the propagation path and as a function of transverse displacement of the plateau perpendicular to the propagation path is presented     

3D非织造物生产的新技术

许多技术的应用如固定的过滤层和复合形式都需要 3D形状的非织造产品 ,现在它是由平网构成的。加入高费用的转化过程 ,由于接合问题 ,不均匀就不可避免地产生在最终产品上。有一些方法试图直接产生 3D形状的纤维结构 ,但这些技术都没有在商业上成功过。Thomas开发的技术只限于坚硬的结构和简单的几何形式。Miura和Hosokawa描述的方法只能用于非常短的非织造物纤维。我们开发的制作法能用各种纤维制成复杂的 3D形状。这里描述了设计这一工艺的关键因素 ,特别集中在工艺参数对 3D产品性能的影响方面。1　工艺设计生产过程将空气层原理用于…     

艺术建筑设计的探索

通过徐州一中艺术楼的设计实践，寻求优美而独特的艺术形象，并用纯几何形体的组合来达到功能与形式的完美统一。     

透过第四届亚洲印刷大奖赛看亚洲的印刷质量

业内人士翘首以待的一年一度的第四届亚洲印刷大奖Asian Print Awards 2006，已经于11月11日在上海揭晓并举行了盛大的颁奖仪式。亚洲印刷大赛的颁奖仪式设在中国的上海，盟然是对于我国印刷业发展成就的重视。虽然亚洲印刷大奖只举办了4届，但在亚洲地区已经享有良好的声誉，并为众多有志于开拓国外市场的亚洲印刷企业所看重，其影响力不亚于美国Premier Print Awards印刷大奖赛。     

Preparation of brush-like crystals of poly[2,6-(1,4-phenylene)-benzobisimidazole]

Poly[2,6-(1,4-phenylene)-benzobisimidazole] (PPBI) crystals were prepared by using reaction-induced crystallization of oligomers during solution polymerization of 1,2,4,5-tetraaminobenzene and diphenyl terephthalate. Polymerizations were carried out at a monomer concentration of 4.3 × 10⁻² mol L⁻¹ at 350 °C for 6 h. Brush-like PPBI crystals were obtained in a mixture of structural isomers of dibenzyltoluene, in which many needle-like crystals came out vertically from the surface of the ribbon-like crystals. Average width and thickness of the ribbon-like crystals were 0.75 μm and 0.11 μm, respectively. And average length and diameter of the needle-like crystals were 0.36 μm and 50 nm, respectively. The brush-like crystals possessed high crystallinity and exhibited good thermal resistance. The ribbon-like crystals were formed by the crystallization of imidazole oligomers at an initial stage of polymerization, and then the needle-like crystals grew from the surface of the ribbon-like crystals. Polymerization occurred on the crystals when the oligomers were crystallized, leading to the high molecular weight PPBI crystals.     

Global practical tracking of a class of nonlinear systems by output feedback

In this paper we address the practical tracking problem for a class of nonlinear systems by dynamic output feedback control. Unlike most of the existing results where the unmeasurable states in the nonlinear vector field can only grow linearly, we allow higher-order growth of unmeasurable states. The proposed controller makes the tracking error arbitrarily small and demonstrates nice properties such as robustness to disturbances and universal property to reference signals.     

A note on global output regulation of nonlinear systems in the output feedback form

This note shows how the adaptive control method developed recently for nonlinearly parameterized systems can be used to solve the problem of global output regulation, for nonlinear systems in the so-called output-feedback form with unknown parameters and exogenous signals belonging to a compact set whose bound is also unknown.     

激光束偏转法检测金属表面层的缺陷

本文编程计算了由激光光热应产业的金属表面的温度分布和泵浦光的调制频率、金属层厚度等的关系，预言检测浓度缺陷的能力。用激光光束偏转法检测到表面下不同深处的缺陷，并把面扫描幅值信号以三维象和灰度象显示。     

The base current degradation of poly-emitter BJTs under AC stress

A simple model for the analysis of the ac stress effect in poly-emitter bipolar transistors is presented. Apart from the reverse-bias induced hot-carrier effects, the forward-bias recovery effect is a key factor under ac stress, it obviously suppresses the base current degradation of the device which is caused during the reverse-bias periods. In this work, we derived the relationship between the excess base current and the stress time for different ac stress conditions. This model is verified with experimental results.<>