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薄板坯连铸中间包内抑湍器的模拟研究 总被引:3,自引:0,他引:3
控制中间包内钢液的合理流动对夹杂物的排除有重要影响,为此建立了模拟薄板坯连铸中间包流动情况的水模型。通过测定停留时间分布(RTD)曲线,研究了不同组合控流装置对中间包流体流动特性的影响。结果表明,结构及尺寸合理的抑湍器能延长水口响应时间及平均停留时间、提高活塞流区体积分数及降低死区体积分数;抑湍器与单坝组合的控流装置在控制流体流动方面效果极佳,而抑湍器与单墙单坝、单墙双坝组合的控流装置的控流效果不太理想。 相似文献
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根据国内某钢厂两流板坯连铸80 t中间包现场工艺及结构,在分析了其控流装置下的中包流场的基础上,研究了双层湍流抑制器下,挡墙位置和高度对中间包内流体流动特性的影响.结果表明:双层湍流抑制器下,挡坝距长水口2 000 mm,高400 mm时中包流场最合理,且抑湍器和坝组合控流装置结构简单,避免了钢水对堰等其他中包控流装置冲刷而污染钢水影响铸坯洁净度.对比优化前后的包内流体流动特性,平均停留时间由292 s提高到380 s,死区比例由37.3%降低至18.5%,活塞区与死区比值由0.35增大至0.65,有利于钢液温度和成分的均匀,增大了夹杂物上浮去除的几率,有助于提高铸坯洁净度. 相似文献
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结合某钢厂八流大方坯连铸中间包生产现状,基于物理模拟与数值模拟方法,对中间包内钢水流动特性及温度场进行了研究.物理模拟结果表明:原中间包因各流水口距长水口冲击点距离不等,导致各流响应时间及停留时间差别增大,各流钢水温差扩大,死区体积分率偏高,影响了铸坯质量和生产顺行.此外,原中间包稳流器因内腔体积小,注流过程中存在包壁冲刷严重等问题.采用优化控流方式后,死区体积比率由优化前的37.5%减小至19.0%,各流响应时间标准差由58降至15,各流停留时间标准差由185降至68,流动一致性得到显著改善.同时,中间包内最大温差降低至4 K,各水口间最大温差降至1 K,包内温度分布更趋均匀.此外,扩大稳流器内腔容积减小了对包壁的冲刷. 相似文献
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为了解决经典组合方法处理多流中间包停留时间分布(RTD)曲线过程中出现的负死区体积分率问题,利用总体分析法对多流中间包各流的RTD曲线进行合成预处理,得到特征RTD曲线.然后利用经典组合方法处理特征RTD曲线,获得评价多流中间包流体流动的整体评价参数.非对称两流中间包水模型实验结果表明,Sahai修正方法仍会出现负死区体积分率现象;各流的流体平均停留时间是评价多流中间包各流一致性的特征参数;各流流体平均停留时间的最小值是评价多流中间包流体流动特性的关键参数. 相似文献
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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。 相似文献
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K Ohta M Nishi M Ueda S Ohyama T Matsubara T Takahashi T Nakajima 《Canadian Metallurgical Quarterly》1998,99(9):589-594
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. 相似文献
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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) 相似文献
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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. 相似文献
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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". 相似文献
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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。 相似文献
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The effect of 20 different antibiotics on chemotaxis by human neutrophils was studied. Human leukocytes incubated with chloramphenicol, rifampin, sodium fusidate, and tetracyclines in vitro showed markedly depressed migration. The mechanisms by which these antibiotics affect leukotaxis are discussed. 相似文献