小方坯连铸结晶器电磁搅拌工艺参数优化

通过不同电磁搅拌参数条件下结晶器内轴向和径向磁感应强度的测定,得到电流为510 A、频率为3 Hz时结晶器内的磁感应强度值相对较大,结晶器内在径向上的磁感应强度变化较一致,磁场的分布均匀.方坯断面的低倍照片等轴晶测定结果表明,频率为3 Hz及电流为510 A时,铸坯等轴晶率也最大.     

圆坯连铸机结晶器电磁搅拌的研究与实践

对圆坯连铸机结晶器内磁感应强度分布特征和结晶器电磁搅拌对GCr15钢碳偏析的影响进行了研究。研究表明:结晶器的磁感应强度随电流的增强而增大直至趋于平稳,随搅拌频率的增大而降低;结晶器内磁感应强度轴向最大位置在距结晶器上口900mm位置,向两侧陡降;径向分布不均匀,由搅拌器内表面向中心逐渐减小;高频率经结晶器铜管后衰减更大。当M-EMS参数在(450A/3.0Hz),改善了铸坯的C偏析,获得良好的工艺效果。     

大圆坯结晶器电磁搅拌器磁场的数值模拟

基于有限元方法,利用ANSYS软件模拟计算了大圆坯连铸结晶器电磁搅拌(M-EMS)器内三维磁场分布,分析了铜管厚度、断面和搅拌电流、频率对磁场分布的定量影响,并通过磁场的实验测定对数学模型进行了验证.研究表明,磁场模拟结果与实测结果吻合得较好;结晶器铜管对磁场具有较强的屏蔽作用,铜管越厚,屏蔽作用越强;小断面结晶器内磁感应强度大于大断面的情况;磁感应强度随着频率的增大而减小,随电流的增大而增大.     

350 mm×470 mm大方坯结晶器电磁搅拌参数优化

对350 mm×470 mm大方坯结晶器电磁搅拌的空载磁场进行了在线测量,获得了结晶器内磁感应强度分布规律。根据磁场测量结果计算了凝固前沿的电磁力及钢水流动速度,并分析了电磁搅拌参数对钢水流动速度的影响,确定了搅拌电流和频率的范围。由42CrMo钢现场实验的结果得出,当结晶器电磁搅拌电流为150 A,频率为2.5 Hz时,铸坯横断面的最大碳含量的偏差为±0.01%,带状偏析基本消除,铸坯内部质量明显改进。     

结晶器内磁感应强度分布研究

采用CST—11A型数字特斯拉计对圆坯连铸机结晶器内磁感应强度进行了研究,研究表明:结晶器的磁感应强度随电流的增加而增大,随频率的增大而降低;结晶器内磁感应强度轴向最大位置在距结晶器上口900 mm位置,向两侧陡降;径向分布不均匀,由搅拌器内表面向中心逐渐减小;高频率经结晶器铜管后衰减更大.研究结果对合理制定及优化电磁搅拌工艺参数提供了理论依据.     

大方坯连铸M-EMS参数对磁场和流场分布的影响

采用数值模拟与现场实测相结合的方法,对大方坯结晶器电磁搅拌(M-EMS)过程进行了耦合数值模拟,研究了电磁搅拌参数及结晶器铜管厚度对钢液磁场和流场分布的影响。结果表明:当其他参数不变时,磁感应强度、电磁力和流速随着电流的增大而增加。磁感应强度随频率增加而减小,电磁力和流速随频率的增加而增大;且随着频率的增加,最大磁感应强度、电磁力和流速的变化值减小。对于连铸470mm×350mm大方坯,电磁搅拌电流和频率分别为550A和2Hz,结晶器铜板厚度为35mm时,能起到良好的电磁搅拌效果。     

方坯连铸结晶器电磁搅拌的数值模拟

根据麦克斯韦电磁理论,利用有限元分析软件ANSYS对240 mm×280 mm方坯结晶器电磁搅拌的磁场进行数值模拟。分析电流强度、电流频率及结晶器铜管等对搅拌器内磁场分布的影响,得到了磁场特性与电磁搅拌参数的关系。研究结果表明:旋转磁场在结晶器搅拌区域内产生旋转电磁力,使钢液在水平方向形成旋转流动;磁感应强度随电流强度的增大呈线性递增;在低频搅拌条件下频率对电磁搅拌强度的影响较小,而铜管厚度对磁场强度影响较大;模拟结果与实测结果基本吻合。     

内置式结晶器电磁搅拌器磁感应强度的测量与分析

在空载条件下测量电磁搅拌结晶器的磁感应强度,通过对测量数据进行分析,得出了磁感应强度在电磁搅拌结晶器内的分布规律及影响磁感应强度的因素。     

小方坯连铸结晶器电磁搅拌的数值模拟

借助有限元分析软件ANSYS,对150mm×150mm小方坯连铸结晶器电磁搅拌在电流为150A,频率变化情况下的钢液内部磁感应强度和电磁力进行了数值分析,并分析了结晶器厚度对钢液内部磁场的影响以及不同时刻钢液内部电磁力的分布。模拟结果表明,在结晶器电磁搅拌时,同一个断面上,4个角部的磁感应强度最大;随着频率的增加,钢液内部磁感应强度降低,钢液边部电磁力在4~5Hz时最大;钢液内部的电磁力在1个周期的不同时刻,形成了同一个方向的力偶,在这个力偶的作用下,完成了对钢液的搅拌;结晶器厚度对钢液内部磁场影响很大,厚度增加,钢液内部磁感应强度降低。     

小方坯结晶器电磁搅拌磁场测试与分析

对重钢小方坯结晶器电磁搅拌磁场进行了测试,分析了其磁场特性,总结了磁场随电流与频率的变化规律及磁场的空间位置分布特点.并计算出工作温度下理论最佳搅拌频率为4 Hz.分析结果对结晶器电磁搅拌工艺参数优化具有指导意义.     

论从实践理解世界的物质性和自然世界的先在性

马克思主义唯物论是一种物本主义形态的唯物论,还是一种超越物本主义形态、从实践理解世界的本质相关问题的实践的唯物主义的唯物论?这是一个我们必须搞清楚的有关马克思主义唯物论的本质规定性和精神实质的重大问题.在考察物本主义的唯物论及其思维方式的局限性的基础上,揭示了马克思主义唯物论是现代的、实践的唯物主义,并重点研讨了马克思主义唯物论关于从实践理解世界的物质性和自然世界的先在性的原理,以期为马克思主义唯物论进一步阐明人类世界的实践性原理奠定基础.     

Effect of cyproheptadine on the ultrastructure of the neurons of the arcuate nucleus in the hypothalamus of the rat

The data are presented on changes in the rat arcuate nuclear neuron ultrastructure after using cyproheptadine (peritol, Egyt Pharmaceutical Works, Hungary) in a water suspension at a dose of 20 mg/kg once daily during 7 successive days and twice a day within 10 days. It was shown that cyproheptadine decreases the functional activity of the arcuate nuclear neurons, depending on the total amount of the drug used. Cyproheptadine-induced inhibition of the forming neurohormone release from neurons is likely to be one of the mechanisms of its therapeutic effect in Itsenko-Cushing's disease.     

Characteristics of the sympathetic innervation of the nictitating membrane and of the vasculature of the nose and tongue of the cat

Vasomotor responses from the nasal mucosa and tongue, and contractions of the nictitating membrane, were recorded on stimulation of the cervical sympathetic or internal carotid nerves. Preganglionic sympathetic nerve fibres which elicited a membrane response possessed a lower threshold than those which evoked nasal vasoconstriction, while the latter displayed a lower threshold than fibres which evoked tongue vasoconstriction. The sympathetic vasodilator fibres to the tongue whose activity was revealed after alpha-receptor blockade, had a similar threshold to the vasoconstrictor fibres. Membrane contraction, nasal vasoconstriction and occasionally tongue vasoconstriction could be evoked by stimulating the internal carotid nerve. The postganglionic fibres innervating the nasal mucosa had a similar threshold to those of the nictitating membrane, which may indicate that there are small myelinated fibres innervating the mucosa. The preganglionic compound nerve action potential had four major components, S1-S4. S1, S2 and usually S3 fibres were associated with membrane contraction; S2, S3 and sometimes S1 fibres were associated with nasal vasoconstriction; and S3, usually S2 and occasionally S1 fibres were associated with vasoconstriction in the tongue. It is concluded that each of these three groups of nerve fibres, but not S4 fibres, may include fibres associated functionally with the three effectors. There was a considerable difference between the relative amplitude of the responses of the three effectors elicited by stimulation of the cervical sympathetic nerve at frequencies between 0.2 and 2 Hz. Vasoconstrictor responses were relatively larger than membrane contractions suggesting differences in the mechanisms of neurotransmission at the neuroeffector junctions.