There exist no 2-type surfaces in E 3 which are images under stereographic projection of minimal surfaces in S 3

In this paper we deal with the following particular case of a weaker conjecture by B. Y. Chen: Are there 2-type Willmore surfaces in E ³? In particular we prove that the above question has a negative answer when the surface is the image under stereographic projection of a minimal surface in S ³.     

半无限晶体中慢速运动的表面极化子

本文研究电子与体纵光学声子耦合弱、与表面光学声子耦合强的半无限晶体中的表面极化子的性质.采用改进了的线性组合算符法和微扰法导出了半无限晶体中的慢速运动极化子的有效哈密顿量.在计及电子在反冲效应中发射和吸收的不同波矢的声子之间的相互作用时,讨论了对有效哈密顿量,诱生势和有效质量的影响.对AgBr晶体进行了数值计算,结果表明反冲效应中发射和吸收的不同波矢的声子之间的相互作用对有效质量和诱生势的影响随耦合常数αt的增加而增加,对有效质量的影响随坐标z的增加而减小的更多,对诱生势的影响随z的增加而增加的更多.     

三维内肋管内插入螺旋扭带的强化传热实验

本文分别以水和乙二醇为工质，在Ｒｅ数范围为：６００～４００００，Ｐｒ数范围为：５．５～１１０之间，对四根分别插入三种不同扭率螺旋扭带的三维内助管内的换热和流阻特性进行了实验研究。结果表明：三维内肋管内加装扭带的强化传热技术适用于低Ｒｅ数下高Ｐｒ数工质的管内对流换热强化。根据实验值得到了流阻和换热关联式。     

透平级S_2流面内的反问题湍流计算

本文发展了应用湍流流函数方程计算湍流流场的方法。计算了扭曲叶片Ｓ２流面的湍流流场．在非正交曲线坐标可压湍流方程组中包含了以无量纲形式表示的能量方程，熵方程和Ｋ－ε湍流模型方程。固壁边界上采用了壁函数方程。通过计算得到了透平级内部的湍流流动合理的收敛解。此方法可以通过调节子午通道的形状及环量的大小分布来防止流动中负速度的出现，为高效透平级的设计提供了一种新的途径。     

有限深度两层流体系统中运动点源生成的内波及其与自由面的相互作用

基于水波动力学势流理论,以二流体系统中点源运动为基本模型,采用Green函数法,研究了分层流体中内部扰动诱生的内波对自由面的影响,探讨对合成孔径雷达成像起重要作用的自由面辐散场的变化规律。研究表明:当上下层流体密度跃变较大、源接近密跃层且Froude数Fr接近内波模式的临界值Fr₂时,内波模式导致的自由面辐散场强度与表面波模式的贡献相当,两者具有强烈的耦合作用,理论分析与实验结果定性一致。     

隐式曲面与参数曲面的G3过渡

通过几何过渡方法，结合重新标度连续概念，利用隐式曲面与参数曲面的各自等距曲面的交线，构成隐式曲面与参数曲面问的过渡面．用曲面的隐式与隐式、参数与参数形式，证明了所作的过渡面与给出的隐式曲面与参数曲面在连接线处是G^3连接的。     

Adsorbate motions induced by vibrational mode coupling

Adsorbate motions are discussed with a primary attention focused on the coupling between a vibrational mode excited by ultrafast laser heated hot-electrons or by inelastic tunneling electrons with scanning tunneling microscope and the reaction coordinate (RC) mode. Recent experimental results have demonstrated an efficient reaction pathways involving an indirect excitation of a frustrated translational mode, rather than its direct excitation for adsorbate hopping on surfaces. Elementary processes are briefly described for hopping of CO molecules on a laser heated stepped Pt surface, where excitation of the frustrated rotation mode has been found to plays an indispensable. Calculation of the inelastic tunneling current (ITC) for excitation of the C-O stretch mode of a CO molecule is combined with a theory of anharmonic mode coupling to activate the frustrated translation mode above the barrier. The hopping rate as a function of the bias voltage agrees with the experimental result. An unified theory of single-, and two-electron processes for ITC-induced motions induced by an indirect excitation of the RC-mode via mode coupling is also applied to reproduce a crossover from hopping to desorption of a single NH₃ molecule on Cu(1 0 0) with an increase in the tunneling current.     

Preparation of hybrid film with superhydrophobic surfaces based on irregularly structure by emulsion polymerization

A superhydrophobic surface originated from quincunx-shape composite particles was obtained by utilizing the encapsulation and graft of silica particles to control the surface chemistry and morphology of the hybrid film. The composite particles make the surface of film form a composite interface with irregular binary structure to trap air between the substrate surface and the liquid droplets which plays an essential role in obtaining high water contact angle and low water contact angle hysteresis. The water contact angle on the hybrid film is determined to be 154 ± 2° and the contact angle hysteresis is less than 5°. This is expected to be a simple and practical method for preparing self-cleaning hydrophobic surfaces on large area.     

Electron–phonon effect on the ground-state binding energy of hydrogenic impurity in quantum-well wire in presence of an electric field

The hydrogenic impurity binding energy in rectangular quantum well wire including both barriers of finite height and an applied electric field are studied. The polaron effects on the ground-state binding energy in electric field are investigated by means of Landau-Pekar variation technique. The results for the binding energy as well as polaronic correction are obtained as a function of the size of the wire, the applied electric field and the position of the impurity. Our calculations are compared with previous results in quantum wires of comparable dimensions.     

Controlling Surface Interactions with Grafted Polymers

The interactions between surfaces modified with grafted polymers is studied theoretically. The aim of this work is to find polymer surface modifications that will result in localized attractive interactions between the surfaces. The practical motivation of the work is to find means to control the distance between bilayers and solid supports in supported membranes. Two theoretical approaches are used, the analytical treatment of Alexander and a molecular theory. It is found that grafting each end of the polymer to each surface results in an interaction with a well defined minimum. The location of the minima is found to be very close to the thickness of the polymer layer when the chains are grafted to only one of the surfaces. The predictions of the analytical theory are in excellent agreement with the molecular approach in this case. It is found that increasing the surface coverage increases the strength of the interaction. However, increasing the polymer chain length at fixed surface coverage results in a decrease of the free energy cost associated with separating the surfaces from their optimal distance. For the cases in which grafting to both surfaces is not possible, the molecular theory is used to study the effect of functionalizing segments of the chain to achieve an attractive well. It is found that by functionalizing the free end-groups of the polymers with segments attracted to the membrane, the range of the attractive interaction is significantly larger than the thickness of the unperturbed layer. Functionlizing the middle segments of the chains results in a shorter range attraction but of the same strength as in the end-functionalized layers. The optimal polymer modification is found to be such that the functionlized groups are attracted to the bare surface but are not attracted to the grafting surface. The relevance of the results to the design of experimental surface modifiers is discussed.