Three-dimensional convection regimes in a cubical cavity

Nonlinear three-dimensional convection regimes in a cubical cavity heated from below are studied numerically for small and moderate supercriticalities and different values of the Prandtl number Pr. The cases of adiabatic and perfectly heat-conducting lateral cavity boundaries are considered. The structure of different supercritical motions and their stability are investigated. The existence of different kinds of convective structures is detected over a wide range of governing parameters.     

The Influence of Film Coating on the Surface Roughness and Specific Surface Area of Pellets

The aim of this paper was to study the surface roughness of pellets after the application of a film coat. In total eight batches of pellets were examined of which four were considered to be round, whereas the other four deviated from the spherical shape by various degrees. The determination of the specific surface area of the coated pellets suggested that, although the film appeared to have filled the pores, the final film structure still mirrored the original surface structure of the pellets. However, profilometry was able to evaluate these gross results in more detail. From the latter measurements it appeared as though the pellet shape was another major influence factor on the final surface texture of the film coating. Pellets with a more elongated and irregular shape such as dumbbells provided more possibilities for interparticulate contact during the coating process, whereby film forming material was ripped off the pellet surfaces making these appear more rough due to surface defects. The use of alcoholic binder solutions during the pellet production might have resulted in surfaces with slightly changed surface free energy, which allowed a better spreading and adhesion of the polymer film and resulted in less textured film surfaces.     

Preparation and Crystal Structure of Sarcosine 5-Nitrosalicylic Acid Organic Adduct

1 INTRODUCTION Nonlinear optical second harmonic generation(SHG) material is one important embranchment ofnonlinear optical materials. The main advantages oforganic nonlinear optical materials over the inor-ganic ones are as follows: bigger nonline…     

MEASUREMENT IN TENSILE TEST OF TRUE STRESS-STRAIN CURVES FOR LOW-CARBON STEEL1)

针对低碳钢拉伸的真应力-应变曲线测量问题,开发了基于单相机三维数字图像相关的实验教学系统。该系统可测量低碳钢拉伸过程中的表面三维形貌和表面应变,并由此获得低碳钢拉伸的真应力-应变曲线。该实验有助于学生深入理解塑性金属材料的力学性能,培养其科研兴趣。     

三维花状铜基复合物及其低温煅烧衍生物用于高效析氧反应

采用一种简单易行的方法来制备铜基电化学催化剂,该催化剂用于析氧反应。利用沸石咪唑酯骨架-67(ZIF-67)为前驱体,通过铜离子刻蚀合成新型铜基复合物(命名为Cu-NF)。它具有特殊的三维花状形貌和中孔结构,其形貌受铜离子与ZIF-67的质量比的影响。随后,Cu-NF经过低温煅烧处理,得到了不同温度下的衍生物,而煅烧过程并未改变其原始形貌。煅烧温度决定了活性物种的组成及含量,并增强了材料的多孔性。其中,300℃煅烧得到的产物Cu-NF-300具有最好的析氧反应性能：在1.0 mol·L^-1 KOH溶液中,过电位低达347 mV,塔菲尔斜率为93 mV·dec^-1。该材料电化学性能的提高归因于其三维结构以及低温煅烧所带来的活化作用。     

基于傅里叶变换轮廓术的动态液膜测量

动态液膜三维形貌的高速测量及重建,对于能源动力领域的工业过程优化十分重要。基于傅里叶变换轮廓术,对缓变表面和非缓变表面分别进行了模拟仿真,研究了物体表面形貌重建精度的影响因素,包括物体表面高度变化率、环境随机噪声以及条纹频率。并根据模拟结果对实验参数进行了优化,研发构建了高速三维结构光测量系统,对竖直壁面下降液膜表面形貌进行了动态测量。实验结果表明:随着液膜沿竖直壁面向下流动,液膜厚度呈现先增大后减小的趋势,高度方向的平均误差为0.1 mm,傅里叶变换轮廓术能够精确地应用于动态液膜高速测量。     

钢-混凝土组合梁桥徐变的三维虚拟层合元分析

采用三参数粘弹性模型,对钢-混凝土组合梁桥在长期荷载作用下的徐变性能进行了研究,并采用三维虚拟层合单元法研究这种效应以及截面由不同材料组成时结构的受力特点。在实验研究的基础上,拟合了粘弹性模型中的参数,并对钢-混凝土组合梁桥在长期荷载作用下的竖向变形和轴向应变进行了研究,通过对计算和试验结果进行对比分析验证了该法的准确性。     

多源光谱信息融合在水质分析中的应用

为解决现有单一光谱法用于水质有机污染综合指标分析精度较低的问题,提出一种基于多源光谱信息融合的水质分析新方法。本方法采用改进的参考独立成分分析方法分别提取紫外吸收光谱和三维荧光光谱对检测水样的多种有效信息特征,去除与水质分析无关的干扰信号;然后采用最小二乘支持向量机进行特征信息融合建模。采用总有机碳指标覆盖范围在3.4~125.3 mg/L内的32个城市地表水和生活污水样本为研究对象,对其紫外光谱、荧光光谱数据进行了信息融合分析实验。结果表明:采用融合分析方法后,对总有机碳指标的分析误差均方根比单一紫外光谱分析法和单一荧光光谱分析法分别下降36.1%和34.7%。     

数字三色条纹相移形貌投影栅线法

基于投影栅线的三色条纹相移算法与投影栅线法相结合,提出一种数字三色条纹相移形貌投影栅线法.此法是对时间相移法的改进,只需一幅三色条纹图,就可利用简单的三光强相移算法完成物体表面的形貌重建;不需要相移装置而误差较小,成本较低,简易实用,将有利于推广到动态实时分析.实验证明,此法是正确可行的.     

基于傅里叶条纹分析的多摄像机标定方法

提出一种新的摄像机标定方法,该方法基于2D共面参照物摄像机标定方法和傅里叶条纹分析方法.将已知相位分布的平面二维正弦灰度调制条纹图作为平面标定靶,通过傅里叶条纹分析方法计算出两个截断正交相位分布,利用截断正交相位分布并结合二维正弦条纹图特点提取相应的图像特征点,建立像素坐标与2D平面坐标的对应关系.将该二维平面靶在摄像机成像空间中放置不同的位置,并完成相应的特征点提取,根据2D共面参照物摄像机标定方法即可完成摄像机标定.该方法利用平面相位测量的高准确度来提高标定特征点的提取准确度,从而提高标定准确度.实验对双摄像机系统进行了标定,标定后该系统对标定靶进行测量,标准偏差达到0.010 mm.