低覆盖度CO分子在 Ni（110）面的吸附研究

利用密度泛函理论研究了低覆盖度下CO分子在Ni（110）表面的吸附结构和电子态。研究结果表明：在低覆盖度情况下, CO分子优先垂直吸附在短桥位,其次是顶位和长桥位。垂直短桥位吸附、顶位吸附相应的振动频率分别是1850.52 cm-1、1998.08cm-1。态密度的研究结果表明：CO分子和Ni原子在-10 eV -8 eV,-8 eV—-6 eV及1 eV -5 eV能量范围内发生了杂化作用。-10ev -8ev能量范围内的杂化主要来源于C、O原子的s轨道、pz轨道与Ni原子s、p、d轨道的杂化作用。-8ev—-6ev能量范围内的杂化作用主要来源于C、O原子的py、 px轨道与Ni原子d、s轨道的杂化作用。轨道间的杂化作用是吸附作用的主要来源。 我们计算的吸附位置与相应的振动频率与相关实验结果基本一致。     

Numerical study of a thin liquid film flowing down an inclined wavy plane

We investigate the stability of a thin liquid film flowing down an inclined wavy plane using a direct numerical solver based on a finite element/arbitrary Lagrangian Eulerian approximation of the free-surface Navier-Stokes equations. We study the dependence of the critical Reynolds number for the onset of surface wave instabilities on the inclination angle, the waviness parameter, and the wavelength parameter, focusing in particular on mild inclinations and relatively large waviness so that the bottom does not fall monotonously. In the present parameter range, shorter wavelengths and higher amplitude for the bottom undulation stabilize the flow. The dependence of the critical Reynolds number evaluated with the Nusselt flow rate on the inclination angle is more complex than the classical relation (5/6 times the cotangent of the inclination angle), but this dependence can be recovered if the actual flow rate at critical conditions is used instead.     

Rivulet flow on the outer surface of an inclined cylinder

A study of the three-dimensional flow of a liquid film (rivulet) over the external part of an inclined cylinder was conducted for liquids with various physical properties. Patterns of the flow regimes were constructed. Good agreement is observed between the experimental data on the thickness and wall friction with the calculation with an asymptotic model in the case of a waveless rivulet. A comparison of the evolution of natural waves on rivulets with the theory of waves of maximal growth shows good agreement for small Re numbers. During the experiments, the wave characteristics of excited waves on a rivulet were investigated. The thickness, amplitude, frequency, and phase velocity of the waves over a wide range of variable parameters are given. Phase velocity integrated functions of the amplitude are constructed for various liquids. The friction on the cylinder wall is measured in the presence of natural and excited waves. The effects of wave regimes on the average values and RMS (root-mean-square) friction pulsations are studied.     

On the dynamics of moving single bubble sonoluminescence

It is well known that the primary Bjerknes force is the origin of the trapping of sonoluminescing bubble in the sound field in liquid. In the present Letter, the quantitative investigation of the behavior of hydrodynamic force on the moving sonoluminescing (SL) bubble introduces the new role of stabilizing the trajectory motion of the bubble for primary Bjerknes force. Using a complete force balanced radial-translational dynamics, it is analytically discussed that by increasing the bubble distance from the antinode of the sound field the increase of the magnitude of inward Bjerknes force, controls the size of the domain of the bubble trajectory. At this time the wake produced by the rapid variation of the bubble's relative translational velocity to the surrounding liquid, changes the bubble direction of motion through the effect of history force. The required momentum for accelerating the SL bubble around the central antinode is produced by the added mass force at the bubble collapse. It is revealed in a re-examination of the coupled radial-translational dynamics for a trapping bubble that because of the bubble lower translational acceleration caused due to the lower added mass force and the bubble attraction towards the acoustic antinodes in presence of inward Bjerknes force, the small bubble will be trapped at the antinode of the sound field.     

Adsorption behavior of weak hydrophilic substances on low-energy surface in aqueous medium

Through the methods such as measurements of contact angle and surface tension, calculations of surface energy and interfacial interaction free energy, and four weak hydrophilic substances (WHS) were taken as research objects, some interesting conclusions were obtained as follow. In aqueous medium, the WHS give priority to adsorb on low-energy surface that is low polar or particularly non-polar. There is a clear corresponding relationship between the free energy and Lewis base component γ⁻ or the hydrophile index of low-energy surface, and the specific relationship is obtained. Finally, we find hydrophobic attractive force of the Lewis acid-base interaction is mainly responsible for the absorption of WHS on low-energy surface. In short, an initial insight into adsorption behavior of WHS on low-energy surface is demonstrated in this paper.     

Contact angle hysteresis of liquid drops as means to measure adhesive energy of zein on solid substrates

Adhesion of zein to solid substrates has been studied using surface energy profiles as indices and by adhesion mapping using atomic force microscopy (AFM). Different plasticizers like glycerol and sorbitol have been used to form mixed films with zein and properties of these films are studied using surface energy profiles. Comparison of the results from the different mixed samples with those from the pure zein films showed that force mapping could identify areas rich in protein. The adhesion maps produced were deconvoluted from sample topography and contrasted with the data obtained from contact angle measurements. A comparison of the two methods shows that the extent of contact angle hysteresis is indicative of both hydrophobicity of the surface as well as the force of adhesion. Mechanical properties and microstructure of zein films prepared by casting from solutions and using Langmuir-Blodgett film technique have been investigated. Pure zein seemed brittle and exhibited an essentially linear relationship between stress and strain. Films with plasticizer were tougher than these films. In general, mixed films showed better mechanical properties than pure films and had higher ultimate tensile strength and increased per cent elongation. Further, the mixed films of zein showed a higher force of adhesion compared to the pure films.     

转动传能中的量子干涉--干涉角和转动量子数的关系

沙国河等人在CO(A1∏(v=0)~e3∑-(v=1))体系与He,Ne和Ar碰撞诱导转动传能中首次观测到了量子干涉效应,并测量了干涉度。从理论上进一步研究原子-双原子分子体系碰撞诱导转动传能中量子干涉效应与转动量子数以及能量间隔的关系是十分必要的。我们考虑长程相互作用势,应用一级玻恩近似和直线轨迹近似,分别计算了CO(A1∏(v=0)~e3∑-(v=1))体系和He,Ne,Ar碰撞诱导转动传能中不同转动量子数以及不同能量间隔下的干涉角,得到了干涉角随转动量子数和能量间隔的变化趋势。这些结果对设计、分析这种类型的实验有一定的指导意义。     

飞机机体表面声压及舱内降噪优化设计

本文以某型客机为研究对象,从飞行试验数据分析和声学建模两方面研究机体表面声压分布及其对舱内壁板近场辐射声压的影响。首先根据试飞数据分析了机体表面声压分布,然后利用统计能量法建立飞机客舱中后段的声学模型,以试飞数据作为声源输入,研究机体表面声压分布对客舱内部壁板附近声压分布的影响,并在此基础上提出优化设计方案,通过模型验证优化方案的有效性。试飞数据表明：机体表面声压在后应急门前方、靠近地板处最大;巡航速度升高,声压级较大区域的面积随之增加;巡航高度和发动机N1N2频率变化对机体表面声压级分布无明显影响。仿真数据表明：仅蒙皮结构无法有效降低客舱噪声;对声学降噪包进行优化能增加壁板隔声量,降低舱内声压。     

缓蚀剂在铜表面吸附行为的研究

采用密度泛函理论计算了缓蚀分子苯并三氮唑(BTA)和二巯基噻二唑(DMTD)的全局反应活性和局部反应活性. 采用分子动力学方法模拟了不同含量的BTA和DMTD对其热力学性质的影响. 同时通过腐蚀试验研究了缓蚀剂复配体系的缓蚀效果. 结果表明: 两种缓蚀分子的缓蚀效率关系为BTA小于DMTD, 活性主要集中于N和S原子上, 有多个活性位点, 因此, 缓蚀剂分子平卧式吸附在铜表面; 铜表面吸附单个缓蚀剂分子BTA和DMTD后, 室温下比热容基本相同, 但随缓蚀剂含量的增加, 比热容呈增大趋势. 这为铜箔轧制油缓蚀剂的选择提供理论指导. 通过腐蚀试验研究, 复配体系缓蚀具有很好的缓蚀效果, BTA和DMTD 的复配比例为1:1时最佳. 关键词： 密度泛函理论 分子动力学方法 反应活性 热力学性质     

人为扰动的模型势函数及其动力学特征

目前,结合高精度从头算方法和全维量子动力学计算,对四原子气相反应,理论计算可以获得与实验结果完全一致的结果。一般情况下,一个精确的量子动力学模拟需要一个精确的势能面,但是在实际的计算当中,势能面的拟合误差是不可避免的。在本文中,我们考察了在模型势能面外加各种扰动时的动力学反应行为,在2维的势能面上进行了量子动力学计算。反应速率常数对近反应能垒区域或最小能量反应路径上的干预是较为敏感的,但是在势能面上的其它地方加入的外加干扰对反应速率影响不大。本文给出一个比较重要的和比较简单的结论,在量子动力学模拟中,在精确的势能面上增加相关的扰动,会帮助我们更深入地理解给定类型的反应,对于一个特定体系,其精确势能面上可以作为一个模型体系研究。     

Polymer and surface roughness effects on the drag crisis for falling spheres

We make time resolved velocity measurements of steel spheres in free fall through liquid using a continuous ultrasound technique. We explore two different ways to induce large changes in drag on the spheres: 1) a small quantity of viscoelastic polymer added to water and 2) altering the surface of the sphere. Low concentration polymer solutions and/or a pattern of grooves in the sphere surface induce an early drag crisis, which may reduce drag by more than 50% compared to smooth spheres in pure water. On the other hand, random surface roughness and/or high concentration polymer solutions reduce drag progressively and suppress the drag crisis. We also present a qualititative argument which ties the drag reduction observed in low concentration polymer solutions to the Weissenberg number and normal stress difference.     

斜面上任意抛射的最佳抛射角

对斜面上任意抛射的最佳抛射角和射程计算公式进行了推导.     

Density functional theory studies on the structural and physical properties of Cu-doped anatase TiO2(101) surface

Structure and physical properties of anatase TiO₂ (101) surface doped with copper have been studied by using density functional theory. Results show that Cu@Ti and Cu@O systems behave as p and n type semiconductors, respectively. Anatase TiO₂ (101) surface exhibits a blue shift in optical absorption spectra compared with pure TiO₂ bulk materials. Enhanced photocatalytic activity at wavelength around 400 nm could be contributed by the change in electronic structure.     

大气气溶胶消光特性和折射率的测量

介绍了一种综合利用能见度仪、微脉冲激光雷达和光学粒子计数器测量大气气溶胶折射率的新方法。首先使用能见度仪和激光雷达测量出大气气溶胶的消光系数和消光后向散射比,然后使用粒子计数器测量出粒子谱分布,结合气溶胶粒子折射率,根据球形粒子的米（Mie）散射理论,可以得到气溶胶消光系数和消光后向散射比。通过分析消光系数、消光后向散射比、粒子谱分布和折射率之间的关系,结合已知的消光系数和消光后向散射比,反演出大气气溶胶粒子的折射率。     

Effects of surface and interface energies on the bending behavior of nanoscale multilayered beams

A modified continuum model of the nanoscale multilayered beams is established by incorporating surface and interface energies. Through the principle of minimum potential energy, the governing equations and boundary conditions are obtained. The closed-form solutions are presented and the overall Young's modulus of the beam is studied. The surface and interface energies are found to have a major influence on the bending behavior and the overall Young's modulus of the beam. The effect of surface and interface energies on the overall Young's modulus depends on the boundary condition of the beam, the values of the surface/interface elasticity constants and the initial surface/interface energy of the system. The results can be used to guide the determinations of the surface/interface elasticity properties and the initial surface/interface energies of the nanoscale multilayered materials through nanoscale beam bending experiments.     

On an integral over the surface ofN-dimensional unit sphere

An integral which occurs in the new matrix ensembles and the width fluctuation factor is evaluated using a transformation which changes a Gaussian into an exponential. It is expressed in the form of a series whose terms are found using a simple recursion relation. It is shown that the series can be summed in closed form for the two-dimensional case.     

Sliding behavior of oil droplets on nanosphere stacking layers with different surface textures

Two facile coating techniques, gravitational sediment and spin coating, were applied for the creation of silica sphere stacking layers with different textures onto glass substrates that display various sliding abilities toward liquid drops with different surface tensions, ranged from 25.6 to 72.3 mN/m. The resulting silica surface exhibits oil repellency, long-period durability > 30 days, and oil sliding capability. The two-tier texture offers a better roll-off ability toward liquid drops with a wide range of γ_L, ranged from 30.2 to 72.3 mN/m, i.e., when the sliding angle (SA) < 15°, the oil droplet start to roll off the surface. This improvement of sliding ability can be ascribed to the fact that the two-tier texture allows for air pockets (i.e., referred to as the Cassie state), thus favoring the self-cleaning ability. Taking Young-Duprè equation into account, a linearity relationship between sine SA and work of adhesion (W_ad) appears to describe the sliding behavior within the W_ad region: 2.20-3.03 mN/m. The smaller W_ad, the easier drop sliding (i.e., the smaller SA value) takes place on the surfaces. The W_ad value ∼3.03 mN/m shows a critical kinetic barrier for drop sliding on the silica surfaces from stationary to movement states. This work proposes a mathematical model to simulate the sliding behavior of oil drops on a nanosphere stacking layer, confirming the anti-oil contamination capability.     

通道宽度对二维粗糙边界斜面颗粒流的影响

在此之前已经报道了二维斜面颗粒流在通道中的分布规律以及二维斜面粗糙边界附近的颗粒 流量密度（ξ=ρ·ν）分布.本文则主要研究通道宽度W对边界附近颗粒流量密度(ξ=ρ· ν)分布的影响.结果表明，颗粒流量密度随通道宽度的变化（ξ W）存在一临界通道宽度W c.在本实验条件下临界通道宽度Wc=70d.当通道宽度小于临界宽度Wc时 ，通道中距边界20d—30d区间内的相对颗粒流量密度随斜面倾斜角的变化可描述为ξ∝( sinθ)α，α是与通道宽度W有关的参数，其数值在032至085之间. 关键词： 二维颗粒流 颗粒物质 颗粒流量密度