Flow pattern characterization for R-245fa in minichannels: Optical measurement technique and experimental results

An optical measurement method using image processing for two-phase flow pattern characterization in minichannel is developed. The bubble frequency, the percentage of small bubbles as well as their velocity are measured. A high-speed high-definition video camera is used to measure these parameters and to identify the flow regimes and their transitions. The tests are performed in a 3.0 mm glass channel using saturated R-245fa at 60 °C (4.6 bar). The mass velocity is ranging from 100 to 1500 kg/m² s, the heat flux is varying from 10 to 90 kW/m² and the inlet vapor quality from 0 to 1. Four flow patterns (bubbly flow, bubbly–slug flow, slug flow and annular flow) are recognized. The comparison between the present experimental intermittent/annular transition lines and five transition lines from macroscale and microscale flow pattern maps available in the literature is presented. Finally, the influence of the flow pattern on the heat transfer coefficient is highlighted.     

Finite Element Error Analysis Approach for Three-Dimensional Incompressible Viscous Fluid Flow Analysis

In our previous research, the modified Galerkin method was proposed as one of the most efficient methods for the analyses of convection-diffusion problems and two-dimensional viscous fluid flow problems. In this modified Galerkin method, the inertia term is considered explicitly, so only the symmetrical matrixes appear. Then an artificial viscosity is introduced through an error analysis approach to improve its accuracy and stability. In this paper, we proposed a new finite element formulation for three-dimensional incompressible viscous fluid flow analysis. This formulation (‘MS’ algorithm and ‘MSR’ algorithm) is based on the modified Galerkin method coupled with the Semi-Implicit Method for Pressure-Linked Equations. The cubic cavity flow problems were investigated for the Reynolds number of 400, 1,000, 2,000 and 3,200 using non-uniform meshes. Finally, we confirmed the effectiveness of our proposed method through the comparison with other research works.     

基于高光谱成像技术的番茄叶片灰霉病早期检测研究

提出了独立软模式法(SIMCA)的番茄叶片灰霉病特征波段图像的提取,并通过多元线性回归法(MLR)提取波段融合图像,通过最小距离法获取番茄灰霉病患病信息的技术路线。利用680～740 nm波段的方差图像和建模能力参数提取的特征波段,并作为输入变量进行MLR分析,在0.5准确率阈值下,准确率均大于99%,说明特征波段可以实现番茄叶片灰霉病的检测,并利用MLR回归系数提取波段融合图像,通过最小距离法获取番茄灰霉病患病信息,结果表明所提出的方法具有很好的预测能力,为番茄灰霉病的早期检测提供了一种新方法,且大大降低了高光谱图像的数据处理时间。     

New formulas for normalizing photon-added（-subtracted） two-mode squeezed thermal states

For the first time,we derive the compact forms of normalization factors for photon-added(-subtracted) two-mode squeezed thermal states by using the P-representation and the integration within an ordered product of operators(IWOP) technique.It is found that these two factors are related to the Jacobi polynomials.In addition,some new relationships for Jacobi polynomials are presented.     

基于层流动能湍流模型的数值模拟方法

从层流动能出发提出数值模拟原则;综合考虑自然、旁路和分离流转捩的因素构建实用的层流动能湍流模型,结合预处理和基本求解技术发展出适于转捩流动的数值模拟方法和程序.针对预处理技术,以Weiss-Smith矩阵为基础,考虑湍流粘性的影响;针对基本离散格式和边界条件,结合模型方程进行对角占优强化等特殊处理.最后通过平板边界层和典型翼型,特别是低雷诺数翼型的数值模拟,验证数值方法的有效性和鲁棒性.算例表明本文的方法能够为求解更复杂的流动提供参考.     

PPLN晶体差频测量飞秒激光脉冲的载波包络相移

在飞秒激光频率梳系统中，通常采用自参考技术测量飞秒激光脉冲的载波包络相移，但该技术需要采用光子晶体光纤进行光谱扩展从而增加了系统的不稳定性，这种技术已经制约了高稳定度的飞秒激光频率梳的发展.采用PPLN晶体差频法测量了宽谱钛宝石振荡器输出的7fs激光脉冲的载波包络频移，得到了大于30dB的拍频信号，为研制无光纤的新一代高稳定度光学频率梳奠定了基础.     

基于应变计观测数据的混凝土温度应力解析

混凝土温度应力测定一直是人们致力解决的科学难题.本文根据振弦式混凝土应变计的工作原理,提出了基于混凝土应变计观测数据的温度应力计算公式,并采用电热带给试件直接施加温度作用的方法,模拟弹性约束条件进行了温度应力试验测定,确定了计算公式中温度应力修正系数与温度变化的关系.研究结果表明,振弦式混凝土应变计可以用来测定均匀温度作用产生的温度应力,根据本文提出的计算公式得到的温度应力计算值与实测值吻合良好.     

基于信息扩散的海洋稀疏资料插值算法-概率模型

针对海洋观测资料零散、稀少等问题,提出了基于信息扩散思想的插值方法-信息扩散插值算法。该方法基于模糊映射思想,通过对稀疏数据点信息进行模糊扩散和插值映射,进而实现有限数据点信息向其邻近区域点的概率插值。针对正态扩散函数在表现广义非对称结构数据资料时存在的局限性,发展了一类非均匀信息扩散插值算法-概率模型,进行了海温资料插值试验和对比分析。     

Direct Synthesis of High Purity Silicon Wires by Electrorefining in Molten KF-NaF Eutectic

The electrochemical synthesis silicon wires by electrorefining metallurgical grade silicon in thermally dried and pre-electrolyzed molten KF-NaF eutectic were studied at temperatures 800-900 oC using cyclic voltammetry and ac impedance. One oxidation peak at -0.14 V could be attributed to the reaction of Si to Si⁴⁺. A cathodic peak occurred at -0.56 V in the cyclic voltammogram and one response semicircle in the ac impedance spectrum was observed, supporting a one-step electrochemical reduction process of Si⁴⁺→Si. The electrochemical reaction of silicon was controlled by the diffusion process. The purity of electrorefined silicon wires was up to 99.999% by ICP-MS analysis.