A novel method for automated grid generation of ice shapes for local‐flow analysis

Modelling a complex geometry, such as ice roughness, plays a key role for the computational flow analysis over rough surfaces. This paper presents two enhancement ideas in modelling roughness geometry for local flow analysis over an aerodynamic surface. The first enhancement is use of the leading‐edge region of an airfoil as a perturbation to the parabola surface. The reasons for using a parabola as the base geometry are: it resembles the airfoil leading edge in the vicinity of its apex and it allows the use of a lower apparent Reynolds number. The second enhancement makes use of the Fourier analysis for modelling complex ice roughness on the leading edge of airfoils. This method of modelling provides an analytical expression, which describes the roughness geometry and the corresponding derivatives. The factors affecting the performance of the Fourier analysis were also investigated. It was shown that the number of sine–cosine terms and the number of control points are of importance. Finally, these enhancements are incorporated into an automated grid generation method over the airfoil ice accretion surface. The validations for both enhancements demonstrate that they can improve the current capability of grid generation and computational flow field analysis around airfoils with ice roughness. Copyright © 2004 John Wiley & Sons, Ltd.     

An efficient algorithm for elasto-viscoplastic vibrations of multi-layered composite beams using second-order theory

An efficient time-domain algorithm for plane non-linear flexural vibrations of multi-layered composite beams, which are driven into the inelastic range by severe transverse loadings, is presented. The influence of an axial static preload is considered in the sense of the quasi-linear second-order theory of structures. The inelastic parts of strain are treated as additional sources of selfstress in the linear elastic background-structure, driving the elastic response into the inelastic one. The efficiency of this exact formulation lies in the fact that linear solution techniques can be used in their most powerful form: Rubin's useful formulation for the quasi-static second-order transfer-matrix of linear elastic structures is applied in combination with modal analysis. Having in mind multi-metal beams, the classical lamination theory is assumed to be valid. Beams with overhang composed of ideal elastic-plastic and viscoplastic layers are studied as example structures. The fictitious sources of selfstress are calculated from the different material laws of the layers in a numerical time-stepping procedure, where a generalized midpoint-rule in combination with Crisfield's secant-Newton procedure is used.     

Least‐squares finite element method on adaptive grid for PDEs with shocks

We apply the least‐squares finite element method with adaptive grid to nonlinear time‐dependent PDEs with shocks. The least‐squares finite element method is also used in applying the deformation method to generate the adaptive moving grids. The effectiveness of this method is demonstrated by solving a Burgers' equation with shocks. Computational results on uniform grids and adaptive grids are compared for the purpose of evaluation. The results show that the adaptive grids can capture the shock more sharply with significantly less computational time. For moving shock, the adaptive grid moves correctly with the shock. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006     

Synthesis of polypiperazine-amide thin-film membrane on PPESK hollow fiber UF membrane

A new interfacial polymerization (IP) procedure is developed in order to synthesize polypiperazine-amide thin-film membrane on the inner surface of poly(phthalazinone ether sulfone ketone) (PPESK) hollow fiber ultrafiltration (UF) membrane.A hollow fiber composite membrane with good performance was prepared and studied by FT-IR and scanning electron microscopy.     

泡沫铅对VRLA电池负极活性物质结构及性能影响

0引言随着36V/42V汽车电源系统的提出,新一轮汽车用电池的竞争不断加剧。从目前情况看,铅酸电池由于具有成本低廉,使用可靠,原材料来源丰富,铅回收率可高达98%等优点,因此成为电动车电源最实际的选择之一[1]。但作为电动车用电池,需要克服其比能量低、充电接受能力差和负极硫酸盐化等缺点。为此各国科学家开展了大量的研究工作。最近报道用铸造多孔体作为敞口铅酸电池的集流体,它的比表面积为14cm2·cm-3,正极活性物质利用率上升到50%,远高于传统的铸造板栅[2]。在铅酸电池集流体研究领域里另一个重大进步,就是以R V C(R etic-ulated V i…     

一个新颖三维配位聚合物Pb(1，4-napdc)(DMF)的合成、结构及热稳定性研究

A novel 3D metal-organic coordination polymer Pb(1,4-napdc)(DMF) (1,4-napdc=naphthalene-1,4-dicarboxylate) was synthesized at room temperature using slow vapor diffusion method to grow single crystal that has been analyzed by X-ray diffraction. The crystal belongs to orthorhombic with space group P2₁2₁2₁. The unit cell parameters are as fellows: a=0.701 3(2) nm, b=1.407 6(3) nm, c=1.521 5(4) nm, V=1.501 8(6) nm³ and Z=4. In the crystal structure of Pb(1,4-napdc)(DMF), the square grids constructed with paddle-wheel units of Pb(Ⅱ) and 1,4-napdc links stack over each other to generate infinite 3D network, which has square apertures (1.158×1.158 nm²) along the crystallographic a-axis. The thermal stability of compound was investigated by differential scanning calorimetry and thermogravimetric analysis. CCDC: 293617.     

SYNTHESIS, CROSSLINKING MECHANISM AND PROPERTIES OF A POLYACRYLATE/POLYURETHANE COMPOSITE COATING

A polyacrylate/polyurethane (P(A) / P(U)) composite coating has been prepared bycrosslinking an acetoacetylated polyacrylate with a vinylic group terminated polyurethaneat room temperature. A model Michael reaction between ethyl acetoacetate (EAA) andmethyl acrylate (MA) was designed to study the crosslinking mechanism. It was foundthat the two active hydrogen atoms in acetoacetyl group can both add to vinylic groupsand the yield of mono- and bis-adducts are much affected by the molar ratio of acetoacetylto vinylic groups. Higher crosslinking degree and better properties could be obtained withdecreasing the molar ratio of the two active groups from 1/1 to 0.6/1 in the compositecoatings.     

复合生物材料的研究进展

从力学性能的改善和降解速率的可调度等角度,总结了复合生物材料与单一组分的材料相比,在生物医学领域应用中所表现出的综合使用性能的优越性。综述了复合生物材料,特别是用于骨修复的各类有机／无机复合材料近年来的研究进展状况。提出将与人骨中磷灰石微晶类似的羟基磷灰石纳米粒子与可降解聚酯材料进行复合,能够得到具有优越骨诱导性能并且能够降解的新型骨修复材料。这方面的研究代表了有机／无机复合生物材料领域新的发展方向。     

LLDPE/纳米SiO_2复合材料的力学性能和光学性能研究

采用熔融共混方法制备了LLDPE 纳米SiO2 复合材料 ,并对该体系的力学性能和光学性能进行了系统研究 .结果表明 ,随着纳米SiO2 的加入 ,复合材料的弹性模量显著提高 ,冲击强度与拉伸强度呈峰形变化 ,且均在SiO2 含量为 3phr左右达到最大值 .加入少量的纳米SiO2 后 ,复合材料薄膜对长波红外线 (7～ 1 1 μm)的吸收能力较LLDPE膜有了显著提高 ,透光率略有下降但雾度提高 ,透光质量得到改善 .同时表明 ,纳米SiO2 的表面处理方法对膜的光学性能有显著影响