氢气泡动态模板电沉积和电势脉冲氧化还原法制备多孔铋膜

分别用氢气泡动态模板电沉积法和电势脉冲氧化还原法制备了三维微/纳米多孔铋薄膜和纳米多孔铋膜.利用扫描电子显微镜(SEM)和X射线粉末衍射(XRD)对其表面形貌和结构组成进行了表征.两种多孔铋膜对4-硝基酚的电还原有较高活性.     

阴极电沉积高c轴取向ZnO薄膜及其光学性能的研究

以硝酸锌水溶液为电沉积液,采用两步法电沉积技术在ITO导电玻璃上电沉积出透明致密的ZnO薄膜.利用电势-pH计算和循环伏安实验得到适宜的溶液pH值和电沉积电势,采用X射线衍射、热重-差热、光致发光谱和透射光谱对ZnO薄膜的结构、组成和光学性能进行了表征.结果表明,所制备的ZnO薄膜在c轴方向上具有高度的择优取向性质,平均粒径为纳米级,性能稳定、单一,发光性能良好,可见光区透射率较高.此类产品在太阳能电池和光电子器件等光学材料方面具有很高的应用价值.     

CoSnS2薄膜的制备及性能研究

采用两种方法制备了CoSnS2薄膜。在两步电沉积法中，先沉积SnS薄膜，再在其上制备CoS沉积薄膜，最后进行退火处理形成厚度约为1250nm的CoSnS2薄膜。在三元共沉积法中，加入EDTA(乙二胺四乙酸二钠)配合剂来调整Sn、Co、S的沉积电势以实现这三种元素的共沉积，从而一步形成厚约620nm的CoSnS2薄膜。探讨了薄膜的制备机理和制备条件对薄膜结构特性和光学特性的影响。得到的薄膜为多晶γ-Co6S2(立方晶系)和SnS(斜方晶系)结构，其直接光学带隙和间接光学带隙分别在1．05～1．25eV和0．11～0．71eV之间可调。     

基于能量动量方法的空间薄膜结构的展开分析

基于能量、动量以及动量矩(角动量)守恒定律,该文对传统的拉格朗日方程进行了修正,将能量动量法应用于空间薄膜结构的展开分析中,该方法不仅保证了计算的精度和数值积分的稳定,而且在薄膜的非线性变形分析中,将小刚度模型引入薄膜的褶皱松弛分析,同时考虑了气体的热力学性能、气体与薄膜的耦合作用以及薄膜的自接触等问题.通过对充气管的...     

ITO玻璃电致化学发光微流控芯片的低温键合

研究了一种利用商品化的氧化铟锡ITO）玻璃制作一次性电致化学发光微流控芯片的方法．采用光刻和湿法腐蚀ITO（氧化铟锡）层制作微电极;利用同样的方法,在另一片Cr板玻璃上湿法腐蚀微沟道．在玻璃之间夹入PE薄膜作为间质实现芯片的低温键合,采用开孔和预压处理PE薄膜,解决了键合气泡和储液池边缘变形问题．该方法解决了ITO玻璃不耐高温的问题,在120～125℃实现了微通道的有效封接,芯片的键合强度达到0．7MPa．     

压电功能梯度层合梁的力-电-热耦合梁单元及最优振动控制

给出了一个压电功能梯度层合梁振动分析的两节点力-电-热耦合梁单元,并将其用于功能梯度层合梁的振动最优控制。在这个多场耦合梁单元中,功能梯度材料的等效力学性能用Voigt或Mori-Tanaka模型表征;梁的位移场用Shi改进的三阶剪切变形板理论描述;压电层的电势场用Layer-wise理论分层表征,且呈高阶非线性电势场的压电层可离散成数个子层。用Hamilton原理推导了压电功能梯度梁的力-电-热耦合单元列式,用拟协调元法给出了多场耦合梁单元的高计算效率的显式单元刚度矩阵,以及采用线性二次型(LQR)最优控制算法进行压电功能梯度层合梁的最优振动控制。使用所得力-电-热耦合梁单元进行了压电功能梯度层合梁的静力和动力分析。数值算例表明,所得力-电-热耦合梁单元可靠、准确和高效,LQR最优控制算法得到最优控制电压可有效抑制功能梯度梁的振动且实现控制系统能量的优化。     

超高韧性水泥基复合材料在受弯构件中应用研究

超高韧性水泥基复合材料(UHTCC)具有出色的非线性变形能力、能量吸收能力和裂缝控制能力,针对该材料在受弯构件中的应用问题,开展了钢筋增强UHTCC受弯构件和UHTCC取代受拉区纵向钢筋周围部分混凝土而作为钢筋保护层受弯构件的试验研究。结果发现,UHTCC与钢筋能够协同工作,提高构件的承载能力和延性,裂缝宽度也得到良好的控制效果。     

高三阶光学非线性Cd/CdS-SiO2复合薄膜的电化学–溶胶凝胶制备及表征

以硝酸镉、硫脲和正硅酸乙酯为前驱体, 采用电化学-溶胶凝胶法, 以ITO玻璃为基底制备了透明薄膜。扫描电子显微镜(SEM)表征表明薄膜为纳米束结构。X射线能谱(EDX)表征表明薄膜由Si、O、Cd、S元素组成, Cd/S(原子比)＞1。EDX表征结合循环伏安(CV)实验确定薄膜为Cd/CdS-SiO₂复合薄膜。Z扫描表征表明, 薄膜在1064 nm处表现出自散焦特性的非线性折射效应和饱和吸收特性的非线性吸收特性。薄膜的三阶非线性极化率(χ(3))较高, 达到了1.18×10^-14~1.39×10^-13 (m/V)², 表明薄膜具有优良的三阶光学非线性。分析认为薄膜中CdS的含量对薄膜的光学性非线性起主要作用。     

导电玻片上氧化亚铜膜的电沉积和表征

研究了用简单铜盐通过阴极还原氧化亚铜的电化学行为，讨论了一些工艺因素对在导电玻片上电沉积Cu2O薄膜的影响，并对所制备的Cu2O薄膜分别用台阶仪、X射线衍射仪(XRD)、扫描电镜(SEM)、X射线光电子能谱(XPS)进行表征．得到的较佳工艺条件为：电势-0．22～-0．45V(vs SCE)，温度为60℃，pH值为5．5～6．0，(CH3COO)2Cu浓度为0．015—0．04mol／L．表征结果发现，随池温的升高，晶粒尺寸从0.2μm增加到0．4μm，60。C沉积的Cu2O薄膜开始具有(111)面择优取向，Cu2O膜纯度高，薄膜表面呈网络多孔结构     

单壁碳纳米管-DNA复合物的微观结构和电化学性质

对单壁碳纳米管-DNA复合物(SWCNT-DNA)的微观结构和电化学性质进行了研究.TEM观察表明:通过DNA辅助超声,绝大多数成束单壁管离散为单根分散的碳管.AFM结果进一步证明DNA均匀缠绕在单根离散的碳纳米管外壁,形成稳定的SWCNT-DNA复合物.这一自组装过程同时也是碳管的纯化过程,催化剂颗粒在超声过程中被除去.初步探讨了SWCNT-DNA复合物的电化学电容性质,结果显示:通过与单链DNA(ss-DNA)的杂化作用,SWCNTs的电化学性质得到改善.与SWCNTs相比,SWCNT-DNA复合物的比电容提高了117.9%.     

Microfluidic DNA fragmentation for on-chip genomic analysis

We report a high-throughput clog-free microfluidic deoxyribonucleic acid (DNA) fragmentation chip that is based on hydrodynamic shearing. Salmon sperm DNA has been reproducibly fragmented down to ～ 5k?bp fragment lengths by applying low hydraulic pressures (≤1?bar) across micromachined constrictions positioned in larger microfluidic channels that create point-sink flow with large velocity gradients near the constriction entrance. Long constrictions (100?μm) produce shorter fragment lengths compared to shorter constrictions (10?μm), while increasing the hydrodynamic pressure requirement. Sample recirculation (10 ×) in short constrictions reduces the mean fragment length and fragment length variation, and improves yield compared to single-pass experiments without increasing the hydrodynamic pressure.     

Packing of fine particles in an electrical field

A numerical model based on the Discrete Element Method (DEM) is developed to study the packing of fine particles in an electrical field related to the dust collection in an electrostatic precipitator (ESP). The particles are deposited to form a dust cake mainly under the electrical and van der Waals forces. It is shown that for the packing formed by mono-sized charged particles, increasing either particle size or applied electrical field strength increases packing density until reaching a limit corresponding to the density of random loose packing obtained under gravity. The corresponding structural changes are analyzed in terms of coordination number, radial distribution function and other topological and metric properties generated from the Voronoi tessellation. It is shown that these properties are similar to those for the packing under gravity. Such structural similarities result from the similar changes in the competition of the cohesive forces and the driving force in the packing. In particular, it is shown that by replacing the gravity with the electrical field force, the previous correlation between packing density and the ratio of the cohesive force to the packing-driven force can be applied to the packing of fine particles in ESP.     

Statics and dynamics of condensed DNA within phages and globules

Several controversial issues concerning the packing of linear DNA in bacteriophages and globules are discussed. Exact relations for the osmotic pressure, capsid pressure and loading force are derived in terms of the hole size inside phages under the assumption that the DNA globule has a uniform density. A new electrostatic model is introduced for computing the osmotic pressure of rod-like polyelectrolytes at very high concentrations. At intermediate packing, a reptation model is considered for DNA diffusing within a toroidal globule. Under tight-packing conditions a model of Coulomb sliding friction is proposed. A general discussion is given of our current understanding of the statics and dynamics of confined DNA in the context of the following experiments: characterization of the liquid crystalline phases, X-ray scattering by phages, osmotic-stress measurements, cyclization within globules and single-molecule determination of the loading forces.     

Detection of six single-nucleotide polymorphisms associated with rheumatoid arthritis by a loop-mediated isothermal amplification method and an electrochemical DNA chip

An electrochemical DNA chip using an electrochemically active intercalator and DNA probe immobilized on a gold electrode has been developed for genetic analysis. In this study, the six polymorphisms associated with rheumatoid arthritis (RA), N-acetyltransferase2 (NAT2) gene polymorphisms T341C, G590A, and G857A, methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms C677T and A1298C, and serum amyloid A1 (SAA1) gene promoter polymorphism C-13T were simultaneously detected by the electrochemical DNA chip and the loop-mediated isothermal amplification (LAMP) method, which is a novel technique for DNA amplification. Human genomic DNAs were extracted from blood, and the targets containing the six polymorphisms were amplified by the LAMP method. A sample containing the six LAMP products was reacted with the electrochemical DNA chip using a DNA detection system that controls hybridization reaction, washing, electrochemical detection, and data analysis automatically. A total of 31 samples were genotyped by this method, and the results were completely consistent with those determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis or the PCR direct sequence analysis. The time required for this method was only 2 h, and operations were very simple. Therefore, this method is expected to contribute to personalized medicine based on genotype.     

Fully packed capillary electrochromatographic microchip with self-assembly colloidal silica beads

A fully packed capillary electrochromatographic (CEC) microchip showing improved solution and chip handling was developed. Microchannels for the CEC microchip were patterned on a cyclic olefin copolymer substrate by injection molding and packed fully with 0.8-microm monodisperse colloidal silica beads utilizing a self-assembly packing technique. The silica packed chip substrate was covered and thermally press-bonded. After fabrication, the chip was filled with buffer solution by self-priming capillary action. The self-assembly packing at each channel served as a built-in nanofilter allowing quick loading of samples and running buffer solution without filtration. Because of a large surface area-to-volume ratio of the silica packing, reproducible control of electroosmotic flow was possible without leveling of the solutions in the reservoirs resulting 1.3% rsd in migration rate. The capillary electrophoretic separation characteristics of the chip were studied using fluorescein isothiocyanate (FITC)-derivatized amino acids as probe molecules. A mixture of FITC and four FITC-derivatized amino acids was successfully separated with 2-mm separation channel length.     

A second-order reduced multiscale method for nonlinear shell structures with orthogonal periodic configurations

This article develops an efficient second-order reduced multiscale (SORM) method to study the nonlinear shell structure with orthogonal periodic configurations. The heterogenous shell structure is periodically distributed in orthogonal curvilinear coordinate systems. At first, the nonlinear problems for the shell structure are introduced, and the detailed higher-order nonlinear multiscale formulas based on the asymptotic homogenization approach are given including microscale unit cell functions, effective material parameter and the homogenized equation. Also, since it requires a large number of computation cost to solve the nonlinear multiscale problems by the traditional high-order homogenization methods, the novel reduced order multiscale model is constructed. Further, according to the reduced-order multiscale models and higher-order nonlinear formulas, an effective SORM algorithm is provided for studying the nonlinear shell structures. The main characteristics of the proposed algorithm are that the novel reduced forms established to investigate the nonlinear shell structures and an efficient higher-order homogenized solution evaluated by postprocessing that does not need higher-order continuities of the homogenization solutions. Finally, according to some typical nonlinear examples including block structures, cylindrical shell and double-curved shallow shell, the availabilities of the SORM algorithm are confirmed.     

Closed-form approximation and numerical validation of the influence of van der Waals force on electrostatic cantilevers at nano-scale separations

In this paper the two-point boundary value problem (BVP) of the cantilever deflection at nano-scale separations subjected to van der Waals and electrostatic forces is investigated using analytical and numerical methods to obtain the instability point of the beam. In the analytical treatment of the BVP, the nonlinear differential equation of the model is transformed into the integral form by using the Green's function of the cantilever beam. Then, closed-form solutions are obtained by assuming an appropriate shape function for the beam deflection to evaluate the integrals. In the numerical method, the BVP is solved with the MATLAB BVP solver, which implements a collocation method for obtaining the solution of the BVP. The large deformation theory is applied in numerical simulations to study the effect of the finite kinematics on the pull-in parameters of cantilevers. The centerline of the beam under the effect of electrostatic and van der Waals forces at small deflections and at the point of instability is obtained numerically. In computing the centerline of the beam, the axial displacement due to the transverse deformation of the beam is taken into account, using the inextensibility condition. The pull-in parameters of the beam are computed analytically and numerically under the effects of electrostatic and/or van der Waals forces. The detachment length and the minimum initial gap of freestanding cantilevers, which are the basic design parameters, are determined. The results of the analytical study are compared with the numerical solutions of the BVP. The proposed methods are validated by the results published in the literature.     

Electric Field Gradient Theory with Surface Effect for Nano-Dielectrics

The electric field gradient effect is very strong for nanoscale dielectrics. In addition, neither the surface effect nor electrostatic force can be ignored. In this paper, the electric Gibbs free energy variational principle for nanosized dielectrics is established with the strain/electric field gradient effects, as well as the effects of surface and electrostatic force. As regards the surface effects both the surface stress and surface polarization are considered. From this variational principle, the governing equations and the generalized electromechanical Young-Laplace equations, which take into account the effects of strain/electric field gradient, surface and electrostatic force, are derived. The generalized bulk and surface electrostatic stress are obtained from the variational principle naturally. The form are different from those derived from the flexoelectric theory. Based on the present theory, the size-dependent electromechanical phenomenon in nano-dielectrics can be predicted.     

Computational nonlinear stochastic homogenization using a nonconcurrent multiscale approach for hyperelastic heterogeneous microstructures analysis

This paper is devoted to the computational nonlinear stochastic homogenization of a hyperelastic heterogeneous microstructure using a nonconcurrent multiscale approach. The geometry of the microstructure is random. The nonconcurrent multiscale approach for micro‐macro nonlinear mechanics is extended to the stochastic case. Because the nonconcurrent multiscale approach is based on the use of a tensorial decomposition, which is then submitted to the curse of dimensionality, we perform an analysis with respect to the stochastic dimension. The technique uses a database describing the strain energy density function (potential) in both the macroscopic Cauchy green strain space and the geometrical random parameters domain. Each value of the potential is numerically computed by means of the FEM on an elementary cell whose geometry is given by the random parameters and the corresponding macroscopic strains being prescribed as boundary conditions. An interpolation scheme is finally introduced to obtain a continuous explicit form of the potential, which, by derivation, allows to evaluate the macroscopic stress and elastic tangent tensors during the macroscopic structural computations. Two numerical examples are presented. Copyright © 2012 John Wiley & Sons, Ltd.