A novel model reduction method based on balanced truncation

The main goal of this paper is to construct an efficient reduced-order model (ROM) for unsteady aerodynamic force modeling. Balanced truncation (BT) is presented to address the problem. For conventional BT method, it is necessary to compute exact controllability and observability grammians. Although it is relatively straightforward to compute these matrices in a control setting where the system order is moderate, the technique does not extend easily to high order systems. In response to the challenge, snapshots-BT (S-BT) method is introduced for high order system ROM construction. The outline idea of the S-BT method is that snapshots of primary and dual system approximate the controllability and observability matrices in the frequency domain. The method has been demonstrated for 3 high order systems: (1) unsteady motion of a two-dimensional airfoil in response to gust, (2) AGARD 445.6 wing aeroelastic system, and (3) BACT (benchmark active control technology) standard aeroservoelastic system. All the results indicate that S-BT based ROM is efficient and accurate enough to provide a powerful tool for unsteady aerodynamic force modeling.     

Hybrids perfluorosulfonic acid ionomer and silicon oxide membrane for application in ion-exchange polymer-metal composite actuators

This paper reports a new technique to fabricate an ion-exchange polymer-metal composite (IPMC) actuator. This technique is based on a hybrid organic-inorganic composite membrane. In the fabrication course, silica oxide particles, prepared from hydrolysis of tetraethyl orthosilicate in situ with sol-gel reaction, co-crystallize with perfluorosulfonate acid (PFSA) ionomer. Attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) analyses demonstrate that a highly water-saving hybrid mem...     

Flux pinning effect of cubic equiaxed morphology and its Ti stabilizing in Nb<Subscript>3</Subscript>Sn superconductors

Two sets of internal-Sn Nb3Sn superconducting strands were fabricated through RRP method, one with 2 wt% of Ti alloyed in Sn core and the other just pure Sn. Four reaction temperatures of 650℃, 675℃, 700℃ and 725℃ and 128 h duration were applied for A15 phase formation heat treatment after Cu-Sn alloying procedure of 210℃/50 h + 340℃/25 h. For the heat-treated coil samples, transport non-Cu JC was examined through standard 4-probe technique and phase microstructure was observed by means of Field Emission Sc...     

Composite silicone rubber of high piezoresistance repeatability filled with nanoparticles

The ruthenium oxide nanoparticles with size less than 20 nm were fabricated by annealing the metallic ruthenium nanoparticles in air, which were synthesized by using the thermal reduction in the polyol solution. The rutile structure of the ruthenium oxide was proved by using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The oxide has good electron conductivity. The surface of the ruthenium oxide was modified by a vinyl silane coupling agent. The assembling of the silane to the oxide surface was proved by Infrared (IR) absorption spectroscopy. By mixing the nanoparticles with poly(methylvinylsiloxane) (PMVS) silicone rubber, a composite filled with dispersive conducting phase was fabricated. The temperature dependent conductivity shows that the electron transportation through composite is mainly dominated by tunneling. The measurement of piezoresistance shows that the composite at low strain has high piezoresistance repeatability. The 3D reconstruction images of the composite filled with carbon black or ruthenium oxide show that the aggregation of the nanoparticles differs much for two composites. The narrow distribution range of the particle size was thought to be the main factor for the high piezoresistance recurrence.     

模糊变机构控制在蛇型弯管机中的应用

基于弯管工艺的要求,对控制系统采用速度与位置双重控制策略;针对电液伺服系统非线性、慢时变的特性,在常规的变结构控制中引入模糊控制,有效地削弱滑模切换控制所产生的抖振,而不牺牲滑模控制系统对参数变化和外干扰不确定的强鲁棒性,实现了系统快速、准确的定位要求.该控制策略在实践中取得了良好的控制效果.     

区域对接的多目标决策模型研究

在系统目标分析的基础上,提出了系统的模型体系结构,确定了区域对接模型的目标、决策变量,及约束条件;根据模型要达到的不同日标,分别建立了3种发展方案.该模型可较好地反映局部与整体协调发展的制衡关系,为区域对接的定量研究提供了基础.     

含给电子Z-N催化剂催化乙烯/1-丁烯共聚的研究

研究了两种含有给电子体分别为对硝基苯胺、乙二醇二甲醚的Ziegler-Natta催化剂催化乙烯与1-丁烯高压的共聚反应性能,主要考察了反应条件对聚合活性、聚合物物理性质的影响,同时采用红外光谱法测定了聚合物的支化度.研究表明,给电子体为乙二醇二甲醚的催化剂催化活性高于对硝基苯胺.反应条件如反应压力、温度、铝钛比对聚合活性、丁烯的插入率以及聚合物性质都有明显影响.高的反应压力有利于1-丁烯插入和聚合物堆密度的提高;反应温度在50℃时的聚合活性最大,聚合物的支化度较高,聚合物熔点较低;铝钛比为500时聚合活性高于低铝钛比的聚合活性.     

Examining the use of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles to enhance the NH<Subscript>3</Subscript> sensitivity of polypyrrole films

Summary Polypyrrole (PPy) composite films with different contents of Fe₃O₄ were prepared by in-situ polymerization of pyrrole in aqueous solutions. The dependence of dc current changes on the response of the samples exposure to NH₃ vapor has been investigated. The results shows the composite films are more stable than the pristine ones after being exposed to NH₃ vapor. Meanwhile, the response time was reduced with increasing the Fe₃O₄ content in the films. The results might be originated from the structural changes in the PPy films caused by the addition of Fe₃O₄.     

Fabrication of a gradient refractive index preform using laminar shear mixing

A gradient refractive index rod was successfully prepared by a new fabrication method using laminar shear mixing, and a graded index polymer optical fiber that satisfied IEEE1394b was obtained from the method. To fabricate the gradient refractive index rod, a liquid monomer mixture with a relatively low refractive index was placed in a prepared cylindrical glass reactor and a transparent polymer rod with a higher refractive index was introduced at the center of the reactor. The reactor and the polymer rod were then rotated concurrently with a small rotating speed difference to generate a Couette flow in the liquid phase. The centrifugal force generated by rotation and the polymer diffusion into the liquid monomer mixture developed a graded concentration profile in a radial direction. The Couette flow could reduce the concentration fluctuation in a tangential direction. In addition, the graded index profile could be controlled by the copolymer composition of the rod and its diameter. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1100–1104, 2005     

顶空固相微萃取-气相色谱法测定苯胺类化合物

应用自制羟基-二苯并冠醚(OH-DB14C4/OH-TSO)为涂层的固相微萃取探头,采用气相色谱法测定苯胺(A)、间甲苯胺(MT)、N,N-二乙基苯胺(NNDEA)、N-乙基间甲苯胺(NEMT)和3,4-二甲基苯胺(3,4-DMA).并对固相微萃取的最佳条件进行了优化.顶空固相微萃取-气相色谱法的检测限(LOD)为0.17～0.98 ng·ml-1,相对标准偏差(RSD)为3.23%～6.20%,线性范围(LR)为0.11～29 μg·ml-1.对药厂废水的3,4-DMA进行了分析,其回收率为86%～90%.