Tailoring Supramolecular Nanotubes by Bile Salt Based Surfactant Mixtures

An approach for tailoring self‐assembled tubular structures is described. By controlling the relative composition of a two‐component surfactant mixture comprising the natural bile salt lithocholate and its bolamphiphilic derivative, it was possible to finely tune the nanotube cross‐section of the mixed tubular aggregates that self‐associated spontaneously in aqueous solution at pH 12. The diameter was found to vary up to 50 % when the stoichiometric ratio of the two bile salts was changed. The tuning of supramolecular nanochannels with such remarkable precision is of significant interest for technological applications of these materials.     

CdSe/HgSe/CdSe量子点量子阱(QDQW)晶粒的光学性质和电子结构

以CdSe纳米晶体为核,用胶体化学的方法,通过化学替代反应,获得了不同阱层或不同垒层的CdSeHgSeCdSe量子点量子阱(QDQW)晶体.紫外可见光吸收谱研究表明,通过调节QDQW中间HgSe阱层的厚度从0.9nm至0,可以调节QDQW颗粒的带隙从1.8变化至2.1eV,实现QDQW纳米晶体的剪裁.光致荧光(PL)谱研究显示,QDQW形成后,CdSeHgSe纳米颗粒表面态得到钝化,显现出发光强度加强的带边荧光峰.利用有效质量近似模型,对QDQW晶粒内部电子的1s—1s态进行了估算,估算结果总体趋势与实验数据相符 关键词： 量子点量子阱晶体 能带剪裁 加强的带边荧光峰     

Porous panels with fixed ends lose stability by divergence

The aeroelastic stability of one-dimensional porous panels with a Darcy boundary condition on its surface is examined theoretically. Analytical and numerical analyses demonstrate that a porous panel in a uniform, single-sided, incompressible flow becomes aeroelastically unstable via divergence. This primary route of instability is identical to the well-known mechanism for non-porous panels. However, the divergence speed of a porous panel is always greater than the non-porous limit and increases with a dimensionless porosity parameter formed by the aeroelastic system. Various chordwise porosity distributions along the panel are also investigated, where the uniformly-porous panel is shown to be the most stable configuration. The generality and robustness of the primary divergence instability for porous panels is established analytically using a simple but general flutter analysis approach based on the Routh–Hurwitz stability criterion.     

Aeroelastic tailoring of a plate wing with functionally graded materials

A functionally graded material (FGM) provides a spatial blend of material properties throughout a structure. This paper studies the efficacy of FGM for the aeroelastic tailoring of a metallic cantilever plate-like wing, wherein a genetic algorithm provides Pareto trade-off curves between static and dynamic aeroelastic metrics. A key comparison is between the effectiveness of material grading, geometric grading (i.e. plate thickness variations), and using both simultaneously. The introduction of material grading does, in some cases, improve the aeroelastic performance. This improvement, and the physical mechanism upon which it is based, depends on numerous factors: the two sets of metallic material parameters used for grading; the sweep of the plate; the aspect ratio of the plate; and whether the material is graded continuously or discretely.     

The Effect of the Reducing Sugars in the Synthesis of Visible-Light-Active Copper(I) Oxide Photocatalyst

In the present work, shape tailored Cu₂O microparticles were synthesized by changing the nature of the reducing agent and studied subsequently. d-(+)-glucose, d-(+)-fructose, d-(+)xylose, d-(+)-galactose, and d-(+)-arabinose were chosen as reducing agents due to their different reducing abilities. The morpho-structural characteristics were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS), while their photocatalytic activity was evaluated by methyl orange degradation under visible light (120 min). The results show that the number of carbon atoms in the sugars affect the morphology and particle size (from 250 nm to 1.2 µm), and differences in their degree of crystallinity and photocatalytic activity were also found. The highest activity was observed when glucose was used as the reducing agent.     

合成条件对硅胶整体柱中孔结构的影响

硅胶整体柱是目前备受关注的液相色谱固定相。本文考察了合成条件对硅胶整体柱中孔结构的影响,包括反应体系的pH值、聚乙二醇(PEG)含量及分子量。实验表明,反应体系的pH值能有效地调控硅胶整体柱的中孔孔径及孔结构,当pH值为2或5时,整体柱中孔孔径较小;而当pH值为3或9时,孔径较大,孔结构趋于圆筒状。整体柱的中孔平均孔径随着PEG含量和分子量的增加而增加,其孔径分布也逐渐变宽。     

模板法制备介孔材料的研究进展

从微孔到中孔或介孔材料的制备过程中．离子模板、乳液模板、液晶模板及至细菌模板得到广泛的应用．具有空间规整性的介孔材料就其介观结构所具有的空间群而言，有P6mm，P6 3／mmc，Pm3n，Ia3d；就其介观结构的形态而言．有二维六方，三维六方，双连续立方，La层状相，多层囊泡等．本文对MCM系列，SBA-n系列、MSU系列，以及那些较为单一的硅基品种FMS-16、HMS等的制备体系及其特点进行了综述．对介孔分子筛合成中常用的表面活性剂分子类型进行了归纳．本文针对的是单一表面活性剂作模板的类型，对那些混合型模板则未予详细介绍．     

Modeling and computational simulation for supersonic flutter prediction of polymer/GNP/fiber laminated composite joined conical-conical shells

This paper is presented to study the supersonic flutter characteristics of laminated joined conical-conical shells made of epoxy as the matrix and fibers and graphene nanoplatelets (GNPs) as the reinforcements. The mathematical modeling of the shell and the aerodynamic pressure are performed sequentially using the first-order shear deformation theory (FSDT) and the supersonic piston theory incorporating the aerodynamic damping coefficient. The effective elasticity and shear modulus, Poisson’s ratios, and density are estimated using the rule of mixture, Halpin-Tsai model, and micromechanical relations. The governing equations and associated boundary and compatibility conditions are derived utilizing Hamilton’s principle and are solved in the circumferential direction and numerically in the meridional direction via the differential quadrature method (DQM). The natural frequencies and mode shapes are obtained, and the influences of various parameters on the flutter boundaries are examined including the geometrical characteristics of the shell segments, boundary conditions, circumferential wave number, and weight fractions of the GNPs and fibers. It is concluded that by increasing the weight fractions of the fibers and the GNPs, the natural frequencies grow and the aeroelastic stability improves.     

Design of active flutter suppression and wind-tunnel tests of a wing model involving a control delay

In this study, a delayed controller was designed for active flutter suppression of a three-dimensional wing model. The design of controller can be divided into two steps. At the first step, a short time delay was artificially introduced into the control loop and the dynamic equations of the aeroelastic system with delayed control were converted into a set of delay-free state-space equations by using a state transformation. At the second step, the control law was synthesized by using the theory of optimal control for the delay-free state-space equations. To demonstrate the performance of the delayed controller, the margin of time delay was studied. The numerical results showed that the delayed controller had good robustness with respect to the time delay. Moreover, the delayed controller was digitally implemented and tested for the three-dimensional wing model in NH-2 subsonic wind-tunnel. The experimental results illustrated that the critical flow speed of flutter instability of the wing model could be effectively increased from 36.5 m/s to 39 m/s.