改性SiO2载体对邻菲咯啉钌荧光特性及氧敏感荧光膜性能的影响

为提高极性荧光指示剂Ru(dpp)₃Cl₂在非极性硅橡胶中的分散性,以沉淀白炭黑、气相白炭黑和甲基MQ树脂,载负荧光指示剂Ru(dpp)₃Cl₂,再填充到二甲基硅橡胶(PDMS)中,制备氧敏感荧光膜.以分光光度计和荧光光谱仪,研究载体种类对Ru(dpp)₃Cl₂的吸附性、荧光特性及氧敏感荧光膜性能的影响.白炭黑载负Ru(dpp)₃Cl₂的荧光发射光谱相对其稀溶液约红移20 nm.载体表面的甲基可减弱SiO₂载体对Ru(dpp)₃Cl₂分子的吸附性和相互作用,减少荧光发射光谱的红移12 nm,提高荧光强度近10倍.白炭黑有助改善Ru(dpp)₃Cl₂在PDMS中的分散性和氧敏感荧光膜的荧光输出和猝灭比,尤以MQ树脂的效果最为显著.     

Coherent structures in trailing-edge cooling and the challenge for turbulent heat transfer modelling

The present paper tests the capability of a standard Reynolds-Averaged Navier–Stokes (RANS) turbulence model for predicting the turbulent heat transfer in a generic trailing-edge situation with a cutback on the pressure side of the blade. The model investigated uses a gradient-diffusion assumption with a scalar turbulent-diffusivity and constant turbulent Prandtl number. High-fidelity Large-Eddy Simulations (LES) were performed for three blowing ratios to provide reliable target data and the mean velocity and eddy viscosity as input for the heat transfer model testing. Reasonably good agreement between the LES and recent experiments was achieved for mean flow and turbulence statistics. The LES yielded coherent structures which were analysed, in particular with respect to their effect on the turbulent heat transfer. For increasing blowing ratio, the LES replicated an also experimentally observed counter-intuitive decrease of the cooling effectiveness caused by the coherent structures becoming stronger. In contrast, the RANS turbulent heat transfer model failed in predicting this behaviour and yielded significantly too high cooling effectiveness. It is shown that the model cannot predict the strong upstream and wall-directed turbulent heat fluxes caused by large coherent structures, which were found to be responsible for the counter-intuitive decrease of the cooling effectiveness.     

Numerical simulation of flow over an airfoil in heavy rain via a two-way coupled Eulerian–Lagrangian approach

Airfoil performance degradation in heavy rain has attracted many aeronautical researchers’ eyes. In this work, a two-way momentum coupled Eulerian–Lagrangian approach is developed to study the aerodynamic performance of a NACA 0012 airfoil in heavy rain environment. Scaling laws are implemented for raindrop particles. A random walk dispersion approach is adopted to simulate raindrop dispersion due to turbulence in the airflow. Raindrop impacts, splashback and formed water film are modeled with the use of a thin liquid film model. The steady-state incompressible air flow field and the raindrop trajectory are calculated alternately through a curvilinear body-fitted grid surrounding the airfoil by incorporating an interphase momentum coupling term. Our simulation results of aerodynamic force coefficients agree well with the experimental results and show significant aerodynamic penalties at low angles of attack for the airfoil in heavy rain. An about 3° rain-induced increase in stall angle of attack is predicted. The loss of boundary momentum by raindrop splashback and the effective roughening of the airfoil surface due to an uneven water film are testified to account for the degradation of airfoil aerodynamic efficiency in heavy rain environment.     

基于粗对准与精对准信号分开探测的对准系统

提出了一种用于光刻装置的对准系统。该对准系统所用的标记包含多个相位子光栅。其中,标记±1级衍射光的光强信息用于产生粗对准信号。在粗对准信号上,通过峰值检测和信号拟合获得最大峰值点,该峰值点即为粗对准位置。同时,在另一光路中,精细子光栅的±1级衍射光的光强信息用于产生精对准信号。利用余弦或正弦曲线对该精对准信号进行拟合,得到一系列的波峰点。距离粗对准位置最近的波峰点即为精对准位置。当精细子光栅的周期足够小时,该对准系统可获得5nm级的重复精度。     

ICP-AES测定铋系超导材料中各金属元素含量

建立了ICP-AES同时测定铋系超导材料中Bi、Pb、Sr、Ca、Cu5种金属元素含量的分析方法,优化了仪器的最佳工作条件。该方法无需复杂的前处理,没有谱线和基体干扰,检出限Bi为0.01699μg.mL^-1、Pb为0.02121μg.mL^-1、Sr为0.002854μg.mL^-1、Ca为0.007401μg.mL^-1、Cu为0.003726μg.mL^-1。该法相对误差均小于1.0%,RSD均小于1.0%,简便,快捷,完全满足铋系超导材料中各元素含量的测定。     

Graphitization of activated carbon under high pressures and high temperatures

Activated carbon was treated at 5.0 GPa up to 1600 ^°C and the structural evolution in the graphitization process was investigated. The graphitization temperature is reduced to 1200 ^°C at 5 GPa, as reflected by x-ray diffraction patterns. Honeycomb-like structures come into being in the high-pressure sintering temperature range of 1000–1100 ^°C and slice-like structures appear after graphitization. Raman frequency and half width drop drastically near the graphitization temperature, and the appearance of D and D′ lines indicates there are still some disorder structures in the graphitized activated carbon.     

Isobaric vapor–liquid equilibria for 1-propanol + water + lithium chloride at 100 kPa

Isobaric vapor–liquid equilibria for the ternary system 1-propanol+water+lithium chloride has been measured at 100 kPa using a recirculating still. The addition of lithium chloride to the solvent mixture produced an important salting-out effect over the alcohol and the azeotrope tended to be eliminated when the salt content increased, and two immiscible liquid phases were observed in a broad range of salt concentration. The experimental data sets were fitted with the electrolyte NRTL model and the parameters of Mock et al.’s model were estimated. This model has proved to be suitable to represent experimental data in the entire range of compositions. The effect of lithium chloride on the vapor–liquid equilibrium of the propanol+water system has been compared with that produced by other salts.     

A pressure-sensitive yield criterion under a non-associated flow rule for sheet metal forming

Spitzig and Richmond [Acta Metall. 32 (1984) 457] proposed that plastic yielding of both polycrystalline and single crystals of steel and aluminum alloys shows a significant sensitivity to hydrostatic pressure. They further showed that under the associated flow rule, this pressure sensitivity leads to a plastic dilatancy, i.e. permanent volume change, that is at least an order of magnitude larger than observed. Indeed, the plastic dilatancy for most materials is on the order of the measurement error and must be zero in the absence of phase change and significant void nucleation during plastic deformation. A non-associated flow rule based on a pressure sensitive yield criterion with isotropic hardening is proposed in this paper that is consistent with the Spitzig and Richmond data and analysis. The significance of this work is that the model distorts the shape of the yield function in tension and compression, fully accounting for the strength differential effect (SDE). This capability is important because the SDE is sometimes described through kinematic hardening models using only pressure insensitive yield criteria.     

矩形大口径激光光束质量评价光学系统设计

自适应光学校正技术可有效提升固体板条激光器的光束质量,但随着激光器输出功率的提升,输出光束口径逐渐增加,系统体积逐渐增大,自适应光学校正系统的设计难度也增加了.因此,在满足自适应光学校正系统中共轭探测等需求的前提下,统筹优化系统的尺寸参数,同时实现波前相位、光束质量评估等多参数的检测具有一定的研究意义.本文在系统整体尺...     

Surface analysis of nitride layers formed on Fe‐based alloys through plasma nitride process

Nitriding phenomena that occur on the surfaces of pure Fe and Fe? Cr alloy (16 wt% Cr) samples were investigated. An Ar + N₂ mixture‐gas glow‐discharge plasma was used so that surface nitriding could occur on a clean surface etched by Ar⁺ ion sputtering. In addition, the metal substrates were kept at a low temperature to suppress the diffusion of nitrogen. These plasma‐nitriding conditions enabled us to characterize the surface reaction between nitrogen radicals and the metal substrates. The emission characteristics of the band heads of the nitrogen molecule ion (N₂⁺) and nitrogen molecule from the glow‐discharge plasma suggest that the active nitrogen molecule is probably the major nitriding reactant. AES and angle‐resolved XPS were used to characterize the thickness of the nitride layer and the concentration of elements and chemical species in the nitride layer. The thickness of the nitride layer did not depend on the metal substrate type. An oxide layer with a thickness of a few nanometers was formed on the top of the nitride layer during the nitriding process. The oxide layer consisted of several species of N_x‐Fe_y‐O, NO⁺, and NO₂^?. In the Fe? Cr alloy sample, these oxide species could be reduced because chromium is preferentially nitrided. Copyright © 2009 John Wiley & Sons, Ltd.