二冷强度和两种断面对82B钢铸坯中心碳偏析的影响

研究了240mm×180Fnrn的82B钢矩形坯和150mm×150mm的82B钢小方坯的二次枝晶臂间距和中心碳偏析情况,结果表明：相同二冷比水量下气雾冷却的冷却强度较喷水冷却的冷却强度提高1倍;对于小方坯,增加二冷比水量,二次枝晶臂间距减小,能够改善中心碳偏析;小方坯采用末端电磁搅拌,增加等轴晶改善中心碳偏析的效果优于减小二次枝晶臂间距。较大断面矩形坯比小方坯中心碳偏析明显严重,增加二冷强度对改善矩形坯中心碳偏析无明显影响,末端电磁搅拌可减少矩形坯中心碳偏析,但其偏析指数仍高于小方坯。     

连铸参数对高碳钢小方坯二次枝晶间距的影响

通过研究高碳钢小方坯连铸参数对铸坯二次枝晶臂间距的影响发现:采用结晶器电磁搅拌、加大二冷比水量,二次枝晶臂间距减小;过热度升高、拉速增大,二次枝晶臂间距增大.无M-EMS的铸坯接近中心的区域,仍然是枝晶臂发达的柱状晶组织;采用结晶器电磁搅拌,促使铸坯中心区域形成粒状等轴晶组织;随搅拌电流增大,二次枝晶间距明显减小.随二次枝晶臂间距增大,渗透率增加,造成铸坯中心碳偏析加重.     

M-EMS 对中碳钢连铸方坯碳偏析的影响

180 mm×180 nm 方坯结晶器电磁搅拌电流强度对中碳钢铸坯碳偏析及显微凝固组织的研究结果表明:结晶器电磁搅拌电流强度增大,铸坯等轴晶比例增加,二次枝晶间距减小,连铸坯中心碳偏析减小,但铸坯中间碳偏析增大,因此中碳钢方坯的电磁搅拌电流强度不宜过大.中碳钢方坯中间碳偏析与坯壳处出现白亮带有关.     

改善弹簧钢小方坯中心碳偏析的实践

结合中天钢铁第三炼钢厂3#连铸机的生产实际,分析二冷比水量和结晶器电磁搅拌电流强度对60Si2Mn A弹簧钢160 mm×160 mm方坯中心碳偏析的影响,结果表明:二冷比水量增加,中心碳偏析指数先降低后增加;结晶器电磁搅拌强度增加,铸坯中心碳偏析指数降低。比水量为1.0 L/kg、结晶器电磁搅拌强度为300 A/3 Hz时,中心碳偏析指数达到最小值1.04,且铸坯的中心偏析指数波动更小。     

连铸方坯拉坯方向凝固行为与偏析控制研究进展

连铸方坯是棒线类钢铁产品的主要母材,其宏观/半宏观偏析等缺陷,一定程度反映了铸坯成分分布和组织性能的不均匀,是影响高端钢材质量提升的重要因素。从二维横断面入手对铸坯内部低倍组织进行表征、分析与优化是目前铸坯内部偏析缺陷调控的主要手段;然而,铸坯内部凝固枝晶和中心偏析均具有三维空间形貌和分布特征,导致仅通过二维横断面进行研究可能会存在一定误差;同时,连铸拉坯方向（垂直于横断面）上凝固枝晶与偏析的波动特征能够更直观地反映连铸坯内部组织性能和质量沿长度方向的波动,这也是影响高品质钢连铸坯及后续产品质量稳定性的关键之一。从凝固行为特点、组织波动变化规律、中心偏析控制等3个方面总结讨论近年来连铸方坯拉坯方向的凝固行为与偏析控制研究进展。CET转变是铸坯凝固组织调控的重点,其判定依据及其与偏析相关性的研究表明,拉坯方向上CET位置存在波动性且与中心偏析形貌特征相关。液相穴内非对称流场及温度变化会造成拉坯方向凝固枝晶的波动特征以及凝固终点的周期性波动;同时,实际铸坯以及相关定性定量模型也表明了拉坯方向偏析元素的分布具有波动特征,并可以利用时间序列技术等方法展开解析。中心偏析控制技术的发展明显提升了连...     

轴承钢大方坯二次枝晶臂间距数值模拟

针对某钢厂GCr15钢连铸坯质量问题,利用实验室试验和Pro CAST模拟软件对连铸坯二次枝晶臂间距进行研究,分析过热度、拉速和二冷水量对二次枝晶臂间距的影响,并进一步探究碳偏析与二次枝晶臂间距的关系。结果表明,铸坯二次枝晶臂间距从铸坯表面到中心呈先增大后减小的趋势,与Pro CAST模拟结果基本一致。降低过热度和拉速、增大二冷水量均有助于减小二次枝晶臂间距;为了提高连铸坯质量,建议将过热度、拉速和二冷水量分别控制在20℃、0.45 m/min、0.32 L/kg左右。铸坯碳偏析最大值位于柱状晶向等轴晶转变区域(CET)。     

?450mm圆坯碳偏析影响因素及改进措施

研究了?450mm连铸圆坯横断面上沿直径方向碳元素分布情况,结合连铸圆坯的工艺特点和设备条件分析讨论了生产过程中连铸工艺参数对碳元素偏析的影响。结果表明:过热度、二冷比水量及电磁搅拌强度等是影响铸坯横断面碳偏析的主要因素。过热度越高越促进于偏析的形成。比水量较低不利于偏析控制,而较高的比水量对偏析影响不明显。电磁搅拌的位置和强度均对偏析有影响。采用合适的过热度、二冷比水量及电磁搅拌方式是控制铸坯碳偏析的有效措施。     

20CrMnTiH齿轮钢铸坯内部质量控制研究

针对20CrMnTiH齿轮钢质量要求,分析了连铸过程拉速、结晶器电磁搅拌电流强度以及二冷强度等关键参数对铸坯内部质量的影响。试验结果表明:拉速控制在1.2~1.4 m/min有利于中心疏松和中心偏析的控制;结晶器电磁搅拌电流强度为380 A时,铸坯中心疏松控制在1.0级以内,碳偏析指数≤1.08,等辅晶率平均达到34.9%;二冷控制模式采用弱冷更有利于减轻该钢种的铸坯中心疏松和偏析。根据研究结果生产的20CrMnTiH齿轮钢棒材低倍组织和淬透性良好。     

无取向电工钢XG800WR连铸电磁搅拌试验研究

采用铸坯低倍组织检验和化学分析的方法,研究板坏连铸机二冷区电磁搅拌器电流和频率参数对无取向电工钢XG800WR板坯中心偏析和等轴晶率的影响,结果表明:铸坯等轴晶率随着搅拌器电流强度和电流频率的增大而增加.采用二冷区电磁搅拌可减小中心易偏析元素S的偏析,试验得出:减小铸坯S偏析效果最好的电磁搅拌参数为电流380～400A...     

高强度二冷对高碳钢小方坯凝固组织和中心碳偏析的影响

试验了250A/5Hz电磁搅拌连铸150 mm×150 mm方坯时二冷比水量对0．64％-0．82％C钢铸坯冷却速度、凝固组织和中心碳偏析的影响。结果表明,当二冷比水量由0．83 L/kg增加至1．55 L/kg时,距铸坯边缘46 mm处的一次枝晶臂间距由380μm降至300μm,平均中心碳偏析指数由1．15降至1．10,同时等轴晶比例由45％降至40％,二次强冷工艺适合于小方坯连铸。     

Benzimidazole resistance in cyathostomes in horses in the Ukraine

The efficacy of treatment with cambendazole was tested in 1-year-old horses on a farm in Dubrovka, Ukraine. Thirty-five horses were treated. Their egg output was compared on the day of treatment and 14 days later with that of 33 untreated horses. Before treatment the mean number of eggs g-1 faeces was 614 in the controls and 766 in horses that had been treated. After 14 days the mean egg output in the controls was 580 and in the treated horses 369. This means a reduction of 54.5%. Only cyathostome larvae could be cultured from faeces collected after treatment. It can be concluded that benzimidazole resistance in cyathostomes is present in the Ukraine.     

重庆高校推进产学研合作的案例分析

以重庆大学、重庆邮电大学和重庆理工大学为例,剖析重庆高校推进产学研合作的基本模式,已经取得的突出成绩,分析总结其基本经验.从完善政策法规体系、强化经济调控、建立组织机构、加强中介建设及开展国际产学研合作等方面,提出了深入推进重庆高校产学研合作的对策建议.     

Fractures in childhood in Khartoum

A prospective study of fractures in 231 children received at Khartoum North Teaching Hospital(KNTH) was carried out for a period of six months. The incidence of child fracture rated as one per day, then it increased from the age of 5 years onwards in boys and between 6 and 8 years in girls. Most injuries were sustained during the day time, especially between late afternoon and sunset. 82% of injured children presented to a medical facility, while 18% were taken to native healers first. Non-road traffic accidents accounted for 84% of the fractures mainly due to sports, domestic injuries and falls; whereas road traffic accidents were 16% and occurred mainly in pedestrians. Forty three percent of the fractures needed only first aid and splintage while 42% needed closed reduction. Thirty one percent of all patients were treated as inpatients. The long bones were affected in 91% of all fractures, the commonest site being the distal end of the forearm (26%), followed by supracondylar fracture of the humerus (15.6%). In the upper limb, left-sided fractures predominated. The epiphyseal injuries were 3.5% of all fractures, mainly at the distal radial epiphysis. Boys were commonly affected between 13-15 years of age. Open fractures constituted 9.8% of the series and were mainly due to traffic accidents in town dwellers, the most vulnerable bones were those of the leg and foot. Pathological fractures accounted for 2.2% and were due to bone cysts and osteogenesis imperfecta. The problem of child safety and the preventive measures need to be more stressed.     

Apoptosis in experimental myocardial infarction in situ and in the perfused heart in vitro

We report the appearance of apoptotic cells in experimental myocardial infarction (rabbit heart) in in situ and in vitro preparations. Apoptosis was recognized by intravital staining with Hoechst 33342 (Ho342), by nick-end labeling (TUNEL) and by DNA laddering. A steady rise in the relative number of apoptotic cardiomyocytes (apoptotic index) was noted in in situ preparations. Apoptosis was first noted 6 h after the onset of ischemia with its highest value occurring after 72 h. Apoptotic nuclei were absent in remote areas of the left and right ventricles. Apoptotic nuclei within the infarcted area showed diminished intensity of Ho342 fluorescence. Three days after ischemia, a border zone adjacent to the infarcted area consisting of apoptotic macrophages was recognized. A novel finding was the appearance of apoptotic cardiomyocytes in the isolated perfused ischemic heart. Occurring as early as 50 min after the onset of ischemia, a high apoptotic index was present adjacent to the ligature placed around the coronary artery. This observation provides the opportunity to selectively examine factors leading to apoptosis in the ischemic heart under controlled experimental conditions.     

Problems in falling in love

Certain patients enter psychoanalysis because of their inability to love another person. Often they report a repetitive erotic pursuit of desired partners, without being able to experience or maintain loving feelings. Kernberg has understood such difficulties as representing effects of early narcissistic disappointments and/or of difficulties in resolving oedipal conflicts. In this paper, Lacanian concepts of the mirror phase and symbolic love are employed to develop these issues. Sexualization of problems in mirroring may be fused with oedipal conflicts in some cases. An extended vignette is presented to illustrate the technical and theoretical issues.