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。     

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。     

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。     

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.     

方坯连铸结晶器电磁搅拌磁场的数值模拟

对方坯连铸结晶器电磁搅拌磁场进行了数值模拟,分析了不同电流强度、电流频率、结晶器铜管以及结晶器内水套对电磁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,模拟结果与实测结果一致;并得出采用合适的电磁搅拌参数可以在结晶器内获得合理有效地电磁搅拌强度,从而可以更有效地改善铸坯的质量.     

160 mm x 160 mm连铸坯结晶器电磁搅拌对钢液流场影响的数值模拟

采用数值模拟方法对比研究了160 mm×160 mm铸坯电磁搅拌参数对钢液搅动和结晶器内流场的影响。结果表明,在频率(1.0～5.0 Hz)条件下,磁感应强度随着频率的增大而减小,且变化量较大。钢液内电磁力沿圆周方向对称分布。在电流(200～500 A)条件下,磁感应强度随着电流的增大而增大。结晶器内半径方向上电磁力波动较大,存在多个波峰,波峰最大的位置都在距结晶器铜管15 mm处,与搅拌电流的大小无关,电磁力随电流的增大而增大。小方坯结晶器电磁搅拌频率应控制在3～4.5 Hz,电流大小应控制在300～500 A。     

双流低频电磁连铸过程中磁场分布的数值模拟

采用数值模拟的方法研究了双流低频电磁连铸过程中磁场分布规律.建立了单、双流低频电磁连铸中包括铸锭、结晶器、线圈和屏蔽罩的二维轴对称有限元模型.利用ANSYS软件包进行划分网格及计算,模拟出了磁场在连铸结晶器区域的分布.研究了电流频率、电流强度、电流方向和线圈距离对金属熔体内磁感应强度的影响.计算结果表明:单流时,电流频率升高,磁感应强度降低;电流强度增大,磁感应强度升高.双流时,无论电流方向是同向还是反向,同一铸锭的远端磁场强度要大于其近端磁场强度,相邻线圈电流方向为反向时,铸锭内磁场强度高于相邻线圈电流方向为同向的情况;增大线圈之间的距离时,铸锭远端和近端的磁感应强度的差值降低.     

圆坯中频电磁软接触结晶器内磁场分布实验研究

为了研究中频电磁软接触连铸结晶器内磁场分布,通过实验的方法测量出不同电参数和工艺参数下圆坯中频电磁软接触连铸结晶器内磁感应强度的分布情况。实验结果表明:结晶器内磁感应强度随着功率和感应线圈电流的增加而增加;相同功率时随着电源频率的增加先增大后减小,相同电流时随着频率的增加而增加,但是增幅却在减小;在本实验中,相同功率下频率为2500 Hz时产生的磁感应强度最大;随着自由液面的下降,结晶器内磁感应强度先增大后减小,并且当自由液面位于感应线圈的中心高度时磁感应强度达到最大。     

380mm×280mm大方坯连铸结晶器电磁搅拌的数值模拟

利用有限元分析软件,建立了380 mm×280 mm大方坯结晶器电磁搅拌的三维数学模型,系统研究了电磁搅拌工艺参数(电流250～500 A,频率1.5～3.0 Hz,结晶器铜板厚度34～40 mm)对结晶器内电磁场的分布影响。结果表明,结晶器内磁感应强度沿铸流轴向呈"两端小、中间大"分布;电流从350 A增大到500 A,搅拌器中心的磁感应强度呈线性递增;频率由1.5Hz增大到3.0Hz,搅拌器中心磁感应强度仅减小0.001 5 T;随着结晶器铜板厚度的增大,铸坯宽面、窄面和角部的磁感应强度都减小。在实际连铸U71Mn重轨钢中,电流应该维持在400 A以上。     

转炉炉壳热应力分析

根据实际转炉建立实体模型。以有限元为手段,考虑了炉衬和炉壳材料的物性参数随温度变化的特点和炉衬与炉壳之间膨胀间隙,计算了转炉炉壳在温度载荷和炉衬膨胀压力同时作用下的热应力。所得结果可为转炉炉壳设计提供依据。     

The effect of amount of possession of the trait of hostility on accuracy of perception of hostility in others.

Some theories of personality hold that an individual's perception of others is influenced by his own personality characteristics; more specifically, that a trait of low social value will be projected more into others, and that insight into the possession of these characteristics reduces this distortion. These 2 hypotheses were tested by having a group of college students rate each other (including themselves) on degree of friendliness or hostility. Agreement with group rating about self yielded the insight score. In general, the hypotheses were supported; the "friendly" Ss were most accurate in their perception of others, and insight was positively associated with accurate perception. From Psyc Abstracts 36:04:4HL16M. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of rates of infection of two methods of emergency ventricular drainage

The rates of infection of two methods of external ventricular drainage in use at Atkinson Morley's Hospital--namely, (a) percutaneous drainage with Rickham reservoirs and (b) tunnelled ventriculostomies--were compared in this retrospective review. Percutaneous drainage of CSF with Rickham reservoirs was associated with a 27% rate of infection as identified by positive microbiological cultures; tunnelled ventriculostomy catheters had a 10% infection rate. The difference in the infection rate between the two methods was statistically significant (P < 0.015). Other variables examined, including the age and sex of the patients and the reasons for ventricular drainage, were not associated with an increased rate of infection. Most infections from either method were caused by a coagulase negative staphylococcus. The average duration of ventricular drainage before identification of positive cultures was 5.7 days for Rickham reservoirs and 6.0 days for ventriculostomies.     

浅析《野草》的版画特征

鲁迅先生一生热爱美术作品,对版画中木刻兴趣尤甚.<野草>作为其"写心之作",亦呈现出一些与木刻版画一致的审美特征:一是具有木刻版画的色彩特征,多对比、多冷色,有阴郁的美感;二是具有木刻版画的力度特征,环境描写、人物刻画处处刀锋毕现,遒劲有力,有一种"力之美".     

四辊破碎机车刀架的改造

针对四辊破碎机车刀架车削中存在的几个问题,详细介绍了电动车刀架的结构和工作原理,建立主要设计参数的数学表达式,并进行适当的分析。改造后,这种电动车刀架运行平稳、可靠、方便、省力,取得了预期的效果。     

Results of treatment of cancer of the cardia

Cancer of the cardia is traditionally discussed with cardiac cancer of the lower portion of the esophagus and upper gastric cancer invading the esophagus, and the specific characteristics of cancer of the cardia have never been clearly defined. We reviewed the outcome of 172 patients with adenocarcinoma of the cardia who had undergone radical surgery between 1949 and 1994 in the Division of Gastrointestinal Surgery of the Cancer Institute Hospital. The centers of the tumors were located within 2 cm above and below the boundary between the esophagus and the stomach, and their longitudinal diameter was less than 8 cm. We divided the patients into an early period (1949-1979; n = 79) and a late period (1980-1994; n = 93), and focused on the historical transition. There were no differences in patient gender or histology between the two periods. However, the late period was associated with fewer cases of esophageal invasion and shorter longitudinal diameter, as the age of the population advanced. The number of advanced cancers such as the localized and infiltrative type had decreased, and early cancer and early clinical stage had become more common, but despite the fact that the number of early cancers had increased, extended dissection, such as thoracic and paraaortic lymph node dissection, was performed more frequently. By clinical stage, the long-term outcome markedly improved in Stage I patient in the late period, and tended to improve in Stage II and III patients. This appears to have been attributable to the prevention of micrometastasis by extended dissection, although the number of early cancers is another major potential cause. There were no differences in the outcome of Stage IV patients between the two periods, and further advances in multimodality therapy must be awaited. The range of resection is basically proximal gastrectomy, and if there are adequate indications, the prognosis is favorable. In view of the status of lymphatic flow and lymph node metastasis, and long-term results, lateroaortic lymph node dissection is important. Since the number of early cancer patients has been increasing, if intraabdominal recurrence is prevented, intrathoracic lymph node dissection will contribute greatly to the outcome of such patients.     

焦炭热性能指标意义浅析

通过对焦炭在高炉内的历程及其变化规律的剖析,阐述焦炭热性能指标的意义,形象地把焦炭在高炉内的损耗分为三部分(M1,M2,M3)。指出M2对焦比及焦炭价格有一定的指导作用。     

Comparison of the results of surgical and conservative treatment of fractures of the diaphysis of the tibia

In this paper is treated the fundamental problematic of the fracture of the diaphysis of the tibia and the therapeutic results after the conservative and operative treatment are confronted. Among 518 patients with 433 open fractures and 35 with closed fractures of the diaphysis of the tibia, successful treatment of more 2/3 was obtained in the period from 1968 to 1972. Following our casuistics and literature, whose results are similar, we find out that the average total treatment of the osteosynthesis of the fracture of the diaphysis was shortened for 2,5 months depending upon the type and the localisation of the fracture. Apolied methods of the operative and conservative and conservative treatment in relation to the velocity of the medical cure as well as to the extreme anatomical-functional results are analised. We noticed that osteosynthesis, made by the intermedullary nail and the extension of the canals or by a small AO table, by the achieved stability makes conditions of immediate motions and an early rehabilitation. Because of that it gives the best functional results.