Sonochemical synthesis of polyaniline nanofibers

Conventionally, micro-sized irregular polyaniline (PANI) particles were synthesized by dropwise addition of the ammonium persulfate (APS) solution into the aniline (ANI) solution with mechanical stirring. By replacing the mechanical stirring with an ultrasonic irradiation, PANI nanofibers in diameters of approximately 50 nm and lengths of 200 nm to several micrometers were prepared. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that at the early stage of polymerization, the polymers formed in both the mechanical stirred and ultrasonicated systems are in the form of nanofiber. However, with continuing of the reaction, these primary nanofibers grow and agglomerate into irregular shaped PANI particles in the mechanical stirred system, while in the case of the ultrasonic irradiation, the growth and agglomeration are effectively prevented, preserving thus the PANI nanofibers in the final product. By increasing the APS/ANI molar ratio from 0.5 to 2.5, the aspect ratios of the PANI nanofibers decreased. The PANI nanofibers exhibit higher solubility than the irregular shaped PANI particles. Although the yield, as well as the conductivity of the ultrasonic synthesized PANI nanofibers, was slightly lower than the irregular shaped PANI particles, the ultrasonic synthesis approach is one of the facile and scalable approaches in synthesizing PANI nanofibers in comparison with other ones without use of templates (e.g., the interfacial polymerization and rapid mixing polymerization). UV-Vis and Fourier transformed infrared (FTIR) spectra indicated ultrasound had no significant effect on the chemical structure of the PANI.     

分担集合的亚纯函数的正规性*

本文研究了亚纯函数及其 k 阶导数分担两个不同集合的亚纯函数族的正规性问题.证明了如下结论: 设 F 是平面区域 D上的亚纯函数族, 其中函数的零点重数至少为 k+1. 设S₁, S₂是两个集合,且|S₁|=m, |S₂|=n, S₂ ≠ 0, 这里m, n是正整数. 如果任意f(z) ∈ F,满足f(z) ∈ S₁?f^(k)(z) ∈ S₂, z ∈ D, 则 F 在区域 D 上正规.本文的研究结果是对刘晓俊和庞学诚[刘晓俊, 庞学诚. 分担值与正规族 [J].数学学报(中文版),2007, 50(2):409--412] 2007年研究结果的改进.     

B型套筒角焊缝缺陷相控阵超声检测定量方法

B型套筒修复作为油气管道修复的主要方式之一,在其修复的焊接过程中,该结构的环形角焊缝内部常常出现以气孔、夹渣为代表的孔型缺陷。这类缺陷由于角焊缝特殊的结构,在利用相控阵超声无损检测技术对其检测时,难以对其进行定量分析。通过数值模拟和实验,发现通过相控阵超声扇扫得到缺陷回波信号峰值与孔型缺陷直径呈正相关,为孔型缺陷的定量分析提供了一种可靠的手段。     

惯性辅助电光测距技术研究与误差分析

将目标物上的某一点在两幅图像上的对应点之间的灰度值和坐标值进行比较，结合惯性导航系统的输出信号，可得到运载体与目标物间的距离。对惯性辅助电光测距方法进行了理论分析、测距仿真及误差分析。仿真结果与真实值之间的误差小于5%，表明了该算法的可行性和整个设计的可用性。     

用于先进半导体制程的光刻反向计算技术(ILT)

此篇论文将介绍一个用于半导体光罩上图样设计以及可用于实际生产的光刻反向计算技术（ILT）。在论文中将讨论有关ILT的最新发展，包括在超成像极限协助图样（SRAF）的生成，可增加制程宽容度的ILT，以及如何生成满足光罩生产标准的图样等方面。从内部的研究结果和客户的使用结果可以看出，ILT已经不再只是一种用于研究的工具，而是已经可以用于先进半导体制程的大规模生产。在对各个环节优化之后，ILT可以增加制程的宽容度，同时将光罩的成本控制在可以接受的水平。     

Review on underwater sound absorption materials and mechanisms

随着我国加速实施海洋强国战略,对先进水下吸声材料的需求日益迫切.与空气吸声不同,水下的高静水压力和复杂的海洋环境对水下吸声材料提出了更为苛刻的要求.吸声问题的本质是如何将弹性能高效地转化为热能或其他形式能量.本文综述了主要以聚合物分子内摩擦机制及界面耗能机制为基础的传统水下吸声材料.传统水下吸声材料面临的主要是其在低频及高静水压力下吸声性能差的问题.这是因为：一方面受质量密度定律的限制,有限厚度的水下吸声材料无法有效吸收水中传来的低频声波;另一方面,在高静水压力下,弹性材料如高分子聚合物会变“硬”,从而大大降低了声波弹性能的转换效率.随着局域共振理论及超材料概念的提出,发展出了一系列新型水下吸声材料,为解决水下吸声材料遇到的难题提供了新思路.局域共振理论的特点是可以用小尺度结构控制长波声波的传播,从而可以解决低频吸声问题.本文重点综述了局域共振理论,以及由此发展出的声子木堆、声子玻璃等新型水下吸声材料.声子玻璃材料在局域共振理论基础上,通过引入多孔金属骨架结构提高了材料的抗压性能,从而解决了高静水压力下材料吸声性能变差的问题.本文最后对水下吸声材料未来发展方向进行了展望.     

4106航空润滑油拖动特性研究

采用高速球-盘式拖动力试验装置测定了4106航空润滑油在不同载荷、滚动速度、入口油温及滑滚比下的拖动系数,分析了润滑油的拖动特性,建立了拖动系数的简单计算公式.结果表明:4106航空润滑油的拖动系数随着载荷变化出现转折;在高速和高压条件下,4106航空润滑油呈现非牛顿特性;当入口油温较低时润滑油的热效应较显著;随着载荷增大,入口油温和滚动速度对拖动系数的影响减小;理论计算结果同实测值吻合良好.     

THE IMPACT MECHANICAL PROPERTIES OF COAL CONTAINING GAS1)

为得出含瓦斯煤体的冲击力学特性,采用类单轴压缩试验方法,对吸附瓦斯压力在0 MPa, 2 MPa, 4 MPa, 6 MPa等情况下的煤样力学特性进行了研究。研究得出：随着吸附瓦斯压力的增大,煤样的抗压强度、弹性模量、冲击能指数均近似线性降低,峰值应变近似线性增大。随着吸附瓦斯压力的增大,煤体的破坏类型由脆性向延性破坏转变,破坏的分选性增强。吸附瓦斯的作用加速了煤体失稳破坏的进程,并使煤岩瓦斯动力灾害类型呈现由冲击地压主导型向煤与瓦斯突出主导型转变的趋势。     

A New Low-Reynolds-Number One-Equation Model of Turbulence

In this study, we propose a new Low-Reynolds-Number (LRN)one-equation model, which is derived from an LRN two-equation(k-ε) model. The derivation of the transport equation, in principle, is based on the assumption that the turbulent structure parameter remains constant. However, the relation for the turbulent structure parameter a ₁(=|− |/k) is modified to account for near-wall turbulence. As a result, the present one-equation model contains a term which takes the near-wall limiting behavior explicitly into account. Thus, the present model provides the correct wall-limiting behavior of turbulence in the vicinity of the wall and can be applied to the analysis of heat transfer. The validity of the present model is tested in channel flows, boundary layer flows with and without pressure gradient, plane wall jet, and flow with separation and reattachment. The calculated results showed good agreement with the direct numerical simulation (DNS) and experimental data. This revised version was published online in July 2006 with corrections to the Cover Date.