铸型涂层对熔体过冷度和凝固组织的影响

利用溶胶－凝胶方法,在铸型内表面玻璃涂层上制备ＳｉＯ２晶态和非晶态薄膜涂层,将深过冷的Ｃｕ７０Ｎｉ３０合金熔体浇入两种涂层铸型中,分别获得９０Ｋ和１９８Ｋ的过冷度。提出了用重合密度和重合原子中心偏离度分析涂层结构对合金熔体形核惰性影响的模型。用ＢＣＴ模型分析过冷熔体凝固过程中枝晶生长与过冷度的关系,结果表明,８０Ｋ为临界冷度,△Ｔ〈８０Ｋ时,枝晶生长受成分过冷控制;△Ｔ〉８０Ｋ时,受热过冷控制。在深过冷范围内,凝固组织为细密挺直枝晶。     

高温熔体在碳材料表面润湿性研究进展

理解高温熔体(熔盐、液态金属及合金)在碳材料表面的润湿行为对发展高温能源储存与转换、材料铸造与加工、电解冶金、熔盐制备碳等技术十分关键,而目前对这一主题的系统评述还很罕见.本文首先结合实际应用,对常见典型碳材料/高温熔体固?液界面润湿性特点进行了梳理,评述比较了目前常用的三种高温接触角测定方法,随后重点对两类润湿机理进...     

电磁搅拌下稀土在铝合金熔体中的分布规律

应用Ansys软件中电磁场模拟模块Ansoft以及流场模块Fluent,研究在单一低频旋转电磁场作用下A356-1.2 %La熔体中稀土La的运动规律以及分布规律. 通过对单一低频且搅拌时间短暂电磁搅拌情况下的A356-1.2 %La熔体进行建模仿真,并着重对电磁搅拌频率分别为f=5 Hz、15 Hz、30 Hz时稀土La的分布情况进行对比分析,最终得出当电磁搅拌频率f=30 Hz时熔体内稀土La分布相对均匀;且一定条件下随着电磁搅拌时间以及频率的增加,稀土La在A356-1.2 %La熔体内的分布也越均匀;并证实通过Ansys软件中电磁场模块Ansoft以及流场模块Fluent可以较好地对旋转电磁场内铝-稀土多相熔体中稀土的运动情况进行数值仿真.      

A SYSTEMATIC COMPARISON OF CURRENT KINETIC THEORIES FOR POLYMER MELT RHEOLOGY

The internal consistency of two recent kinetic theories is investigated. Rheologically simple experiments, such as step strain stress relaxation and small angle oscillatory shear, are used to assess model parameters in the Doi-Edwards and Curtiss-Bird reptation theories. These parameters are then used to predict the results of shear stress growth, shear stress decay and interrupted steady shear experiments. Inconsistencies are found in the cases of η*and the early stages of stress growth when nonzero values for the “link tension coefficient” are employed. Neither theory predicts stress overshoot at the shear rates where it is observed nor the extremely long recovery times required to reproduce stress overshoot.     

Survey of polyurethane adhesives

Polyurethane chemistry provides a means to ‘tailor’ adhesives to specific needs. This is being achieved by polyurethane technology at a cost of more sophisticated application/bonding equipment and a need for better control of raw materials and adhesive processing conditions.     

Enthalpies of Mixing in Liquid Alloys of Copper with Hafnium

Enthalpies of mixing of liquid alloys of copper with hafnium were measured at 1650 K in the concentration range 0 < x _Hf < 0.50 by high-temperature isoperibolic calorimetry. The experimental data obtained indicates exothermic effects upon alloy formation, which confirm a strong interaction of the components in copper hafnium melts.     

一种自动读取指针式仪表读数的方法

为解决变电站中自动化监控仪表读数的问题,提出基于机器学习和图像处理算法的指针式仪表自动读数方法,由仪表检测和指针识别两个阶段组成。使用全卷积网络(fully convolutional networks,FCN)对输入图像进行语义分割,以检测仪表的位置并提取仪表部分的图像。利用直方图均衡化、中值滤波和双边滤波减小光照和阴影对指针识别的干扰,并利用仿射变换矫正拍摄时的倾斜,再结合改进的霍夫变换识别仪表中指针的位置,从而计算指针角度获取读数。结果表明,对于自然场景中变电站中的指针式仪表,本研究能很好地检测出仪表并识别出指针的读数,对于光照和阴影等干扰具有良好的鲁棒性,可以显著减少变电站巡检人员的工作量,提高工作效率。     

APPLICABILITY OF THE MASS ACTION LAW IN COMBINATION WITH THE COEXISTENCE THEORY OF METALLIC MELTS INVOLVING COMPOUND TO BINARY METALLIC MELTS

Based on the atomicity and rnolecularity as well as the consistency of thermodynamic properties and activities of metallic melts with their structures, the coexistence theory of metallic melts structure involving compound has been suggested. According to this theory, the calculating models of mass action concentrations for different binary metallic melts have been formulated. The calculated mass action concentrations agree well with corresponding measured activities, which confirms that the suggested theory can reflect the structural characteristics of metallic melts involving compound and that the mass action law is widely applicable to this kind of metallic melts.