多孔涂层横向抽吸效应强化膜状凝结换热的研究

研究多孔涂层界面抽吸效应对强化膜状凝结换热的影响。考察了多孔涂层的特性参数对凝液膜厚度和换热系数的影响。与Nusselt理论预示值对照表明,多孔涂层界面抽吸效应是强化膜状凝结换热的重要因素。     

High mobility In2O3:H transparent conductive oxides prepared by atomic layer deposition and solid phase crystallization

The preparation of high‐quality In₂O₃:H, as transparent conductive oxide (TCO), is demonstrated at low temperatures. Amorphous In₂O₃:H films were deposited by atomic layer deposition at 100 °C, after which they underwent solid phase crystallization by a short anneal at 200 °C. TEM analysis has shown that this approach can yield films with a lateral grain size of a few hundred nm, resulting in electron mobility values as high as 138 cm²/V s at a device‐relevant carrier density of 1.8 × 10²⁰ cm^–3. Due to the extremely high electron mobility, the crystallized films simultaneously exhibit a very low resistivity (0.27 mΩ cm) and a negligible free carrier absorption. In conjunction with the low temperature processing, this renders these films ideal candidates for front TCO layers in for example silicon heterojunction solar cells and other sensitive optoelectronic applications. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

紫外成像器件光电阴极封接焊料熔层缺陷对气密性的影响

为解决紫外成像器件光电阴极与管体封接漏气问题,对管体InSn合金熔化过程中出现的质量问题进行了深入分析,找出焊料熔层缺陷主要来源于对焊料除气不彻底和基底表面氧化及设备油污染。通过优化工艺参数,改进工艺质量和把化铟设备管体搁置焊料熔化改为浇铸熔化,使管体焊料熔化合格率达到了100%,光电阴极与管体封接气密性成品率达到98%。     

亚单分子层三聚氰胺的便携式拉曼检测

通过改进Lee和Meisel法,制备了两种银胶。以三聚氰胺分子为探针分子,银胶为SERS基底,使用便携式拉曼光谱仪进行拉曼测试。拉曼光谱表明银纳米粒子和三聚氰胺发生的吸附作用明显,三聚氰胺的四个较强振动峰有4～9cm-1的频移和强度比变化较大。由于SERS基底的表面增强作用,三聚氰胺的便携式拉曼光谱仪最小检测量达到了6×10-12g,实现了三聚氰胺的亚单分子层检测水平。该检测方法快捷、简便,如果结合奶粉或食品中三聚氰胺的固相萃取技术,将可以应用于三聚氰胺的现场、快速、半定量检测。     

A first-order system approach for diffusion equation. II: Unification of advection and diffusion

In this paper, we unify advection and diffusion into a single hyperbolic system by extending the first-order system approach introduced for the diffusion equation [J. Comput. Phys., 227 (2007) 315–352] to the advection–diffusion equation. Specifically, we construct a unified hyperbolic advection–diffusion system by expressing the diffusion term as a first-order hyperbolic system and simply adding the advection term to it. Naturally then, we develop upwind schemes for this entire   system; there is thus no need to develop two different schemes, i.e., advection and diffusion schemes. We show that numerical schemes constructed in this way can be automatically uniformly accurate, allow O(h)$O(h)$ time step, and compute the solution gradients (viscous stresses/heat fluxes for the Navier–Stokes equations) simultaneously to the same order of accuracy as the main variable, for all Reynolds numbers. We present numerical results for boundary-layer type problems on non-uniform grids in one dimension and irregular triangular grids in two dimensions to demonstrate various remarkable advantages of the proposed approach. In particular, we show that the schemes solving the first-order advection–diffusion system give a tremendous speed-up in CPU time over traditional scalar schemes despite the additional cost of carrying extra variables and solving equations for them. We conclude the paper with discussions on further developments to come.     

Near-surface turbulence in the atmospheric boundary layer

Measurements of the near-surface turbulence in the atmospheric boundary layer have been made using hot-wire probes above the salt flats of northwestern Utah, where the momentum thickness Reynolds number, R_θ, is O(10⁶), and the surface is smooth and nearly devoid of flow obstructions. The measurements were made with arrays of up to 24 parallel straight sensors and with a modular 12-sensor probe capable of measuring all of the components of the instantaneous velocity vector and velocity gradient tensor. Measurements were also made in a laboratory wind tunnel at R_θ=1730 using 22 straight sensors. The data analysis focuses on the effects of the Reynolds number on turbulence properties and on the physics of the dissipation rate of turbulent kinetic energy.Some properties are found to be dependent on the Reynolds number when normalized with inner variables, while others are not. Among those that show the significant Reynolds number dependence are the rms and the skewness factor of the streamwise velocity fluctuations.Significant differences in flow structure, particularly those related to high rates of dissipation, are implied by the data. The joint PDF and covariance integrand of streamwise and wall normal vorticity fluctuations show less preferred orientation of the vorticity vector in the buffer layer at R_θ of O(10⁶) than at R_θ=1070. The largest contribution to the dissipation rate, at O(10⁶) is by the ∂w/∂z velocity gradient, while this term makes a quite small contribution to the dissipation rate at low R_θ. Here w and z are the spanwise velocity fluctuations and direction, respectively. Conditional analysis in the streamwise-wall normal (x−y) plane based on high instantaneous dissipation rate shows that the typical high dissipation rate events are generally similar at high and low Reynolds numbers, but display some significant differences.     

Bioactivity of SiO2-CaO-P2O5-Na2O glasses containing zinc-iron oxide

Glasses with composition x(ZnO,Fe₂O₃)(65 − x)SiO₂20(CaO,P₂O₅)15Na₂O (6 ≤ x ≤ 21 mol%) were prepared by melt-quenching technique. Bioactivity of the glasses was investigated in vitro by examining apatite formation on the surface of glasses treated in acellular simulated body fluid (SBF) with ion concentrations nearly equal to those in human blood plasma. Formation of bioactive apatite layer on the samples treated in SBF was confirmed by using Fourier transform infrared reflection (FTIR) spectroscopy, grazing incidence X-ray diffraction (GI-XRD) and scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer. Development of an apatite structure on the surface of the SBF treated glass samples as functions of composition and time could be established using the GI-XRD data. FTIR spectra of the glasses treated in SBF show features at characteristic vibration frequencies of apatite after 1-day of immersion in SBF. SEM observations revealed that the spherical particles formed on the glass surface were made of calcium and phosphorus with the Ca/P molar ratio being close to 1.67, corresponding to the value in crystalline apatite. Increase in bioactivity with increasing zinc-iron oxide content was observed. The results have been used to understand the evolution of the apatite surface layer as a function of glass composition and immersion time in SBF.     

Reflection absorption infrared spectroscopy during atomic layer deposition of HfO2 films from tetrakis(ethylmethylamido)hafnium and water

Tetrakis(ethylmethylamido)hafnium and water are commonly used precursors for atomic layer deposition of HfO₂. Using reflection absorption infrared spectroscopy with a buried-metal-layer substrate, we probe surface species present during typical deposition conditions. We observe evidence for thermal decomposition of alkylamido ligands at 320 °C. Additionally, we find that complete saturation of the SiO₂ substrate occurs in the first cycle at ≈100 °C whereas incomplete coverage is apparent even after many cycles at higher temperatures. The use of this technique as an in situ diagnostic useful for process optimization is demonstrated.     

Growth of b-axis oriented VO2 thin films on glass substrates using ZnO buffer layer

VO₂ thin films are grown on glass substrates by pulsed laser deposition using vanadium metal as a target. In this study, a ZnO thin film was used as a buffer layer for the growth of VO₂ thin films on glass substrates. X-ray diffraction studies showed that the VO₂ thin film had b-axis preferential orientation on a c-axis oriented ZnO buffer layer. The thickness of the ZnO buffer layer and the oxygen pressure during VO₂ deposition were optimized to grow highly b-axis oriented VO₂ thin films. The metal-insulator transition properties of the VO₂ film samples were investigated in terms of infrared reflectance and electrical resistance with varying temperatures.     

Double atmospheric gravity wave frequency oscillations of sporadic E formed in a horizontal shear flow

The new theory of sporadic E density oscillation with double atmospheric gravity wave (AGW) frequency in two-dimensional case taking into account ions ambipolar diffusion is presented. It is found that densities of multi-layered sporadic E, formed under the influence of atmospheric vortical perturbation (with vertical wavelength λz≠0) evolving in the horizontal shear flow (shear wave), can oscillate with up to double Brunt-Väisälä frequency under the action of short-period AGW, in which shear wave is transformed. The formation of multi-layered sporadic E (inside regions with vertical thickness about λz/2) and its density changes in every half AGW period close to ions convergence region occur by combined action of ion-neutral collision and Lorentz forcing and can cause additional accumulation of ions responsible for sporadic E density oscillation with double AGW frequency.