低作用应力引起的溶质在晶界非平衡偏聚或贫化

提出了关于应力时效（高温及作用应力）引起溶质原子的晶界非平衡偏聚或贫化机理的一个新模型。此模型基于如下假设：晶界相对于完整晶体而言在强度上是弱化区。当多晶体受到一个在弹性范围内的作用应力时,晶界优先变形。若压应力作用时,晶界作为激发射空位;若拉应力作用时,晶界作为阱吸收空位,应力引起的过饱和空位与溶质原子形成复合体,此复合体在基体中的扩散速率远高于溶质原子。作用应力对晶界溶质偏聚或贫化的影响,是由复合体的扩散和溶质原子的反向扩散之间的平衡所决定。根据此模型,应力时效过程中存在一个临界时间,在此时间,应力引起的晶界偏聚或贫化程度将达到一个极大值。此模型已由ShinodaT等所作的磷在钢中的应力时效实验和MisraR D K所作的硫在钢中的应力时效实验结果所证实。     

Nb的非平衡晶界偏聚动力学模拟与实验研究

Nb是现代高性能钢铁材料中重要的微合金化元素,其在晶界有强偏聚特性。采用3种Nb-空位复合体扩散系数分别对非平衡晶界偏聚进行拟合,根据铁-铌二元合金中Nb在晶界偏聚实验的EPMA测量结果筛选出最终的复合体扩散系数,并据此讨论了低温恒温温度,基体Nb含量,原奥氏体晶粒尺寸对非平衡晶界偏聚动力学的影响,得出了最符合实验结果的铌-空位复合体扩散系数公式。结果表明,在1 000℃恒温过程,Nb非平衡晶界偏聚的临界时间在15 min左右,临界时间常数为6.57×10⁵。从1 200℃固溶态冷却至某低温等温时,随着等温温度的升高临界时间迅速减小,Nb在晶界的最大偏聚量逐渐越小;随着基体Nb含量增加晶界Nb的最大偏聚量线性增加;随着原奥晶粒尺寸的增加临界时间逐渐增大。     

高温和低张应力引起的非平衡晶界偏聚动力学(Ⅱ)--实验结果的动力学模拟

以文献[1]建立的张应力引起的非平衡晶界偏聚动力学方程模拟了Shinoda T等的磷在钢中的应力时效实验结果和Misra R D K的硫在钢中的应力时效实验结果，模拟结果与实验结果互相吻合。通过模拟发现，张应力使磷-空位复合体以及硫-空位复合体在钢中的扩散系数均增加3个数量级，且磷原子和硫原子的扩散系数分别降低3个和5个数量级。     

一个强韧化钢的新概念--非平衡晶界共偏聚

基于固溶体中溶质原子间及溶质原子与过饱和空位的交互作用,提出了非平衡晶共偏聚的概念。在一个由溶质２和溶剂３组成的固溶体中,若溶质２与空位的结合能超过适于发生非平衡晶界偏聚的范围时,极少或没有溶质２的非平衡晶界偏聚在２－３固溶体中发生。     

Al/Mg异质金属FSpW过程热-力耦合扩散机制

文章构建了原子扩散计算模型用于摩擦焊条件下金属基体原子扩散系数的数值计算,以铝/镁异质金属回填式搅拌摩擦点焊(FSpW)连接为例,从理论上分析了动态再结晶过程中的原子扩散机制,定量评价了形变诱导的过饱和空位增强扩散效应和位错管道扩散效应。探索了快速扩散通道(晶界、位错、空位)对原子扩散的影响,结合焊点热变形计算,建立了原子扩散与热变形之间的定量关系,从而明确了Al/Mg异质金属搅拌摩擦焊过程原子热-力耦合超扩散机制。在FSpW界面Al原子和Mg原子扩散层厚度测量的基础上,基于Fick定律反推获得界面处原子扩散系数。经过对比发现,采用原子扩散系数模型计算结果与根据扩散层获得界面原子扩散系数拥有相同数量级。     

溶质原子晶界偏聚动力学过程的数值模拟

建立了溶质原子在晶界的平衡偏聚、非平衡偏聚、晶界偏聚溶质向沉淀析出转化以及冷却速度等因素的晶界偏聚物理模型和数学模型.模型考虑了晶界及晶界附近扩展畸变区对溶质的吸附作用和吸附能力.对含硼0.0010%的Fe-40%Ni-B合金体系从1150℃连续冷却到640℃的过程中硼的晶界偏聚状态进行了模拟计算.计算表明,晶界区域硼富集因子在降温初期增加较快,随后增幅变缓,模拟数据显示过程中有晶界区域硼原子向晶内的反向扩散;当晶界上偏聚的硼转化为析出物时,晶界区域富集因子的增加再次变快.模拟计算结果与已发表的实验结果吻合较好.     

2.25Cr-1Mo合金钢回火脆化过时效现象的研究

研究了2.25Cr-1Mo合金钢在回火温度下时效处理时,发生回火脆化和回火脆化的过时效反偏聚现象。应用非平衡偏聚的动力学理论,确定了成分(%)为0.15C、2.32Cr、0.95Mo、0.009P的2.25Cr-1Mo合金钢在650℃140 h回火时钢中磷的非平衡晶界偏聚规律。试验得出,2.25Cr-1Mo合金钢650℃磷非平衡偏聚的临界时间t_c为20 h,晶界磷的原子浓度,由初始状态的0.016%提高至最大值2.79%。根据试验数据进行的动力学计算,得出的计算曲线与试验结果吻合,验证了非平衡晶界偏聚空位-复合体模型的扩散机制。     

La在Fe基合金铁素体区的晶界扩散行为研究

以Fe-La合金为研究对象,研究了La元素在纯铁中的铁素体晶界的扩散行为。借助Gleeble-1500D热模拟实验机完成了Fe-La系合金的扩散连接,采用QUANTA 400环境扫描电子显微镜及能谱仪,观察并分析了稀土镧元素在纯铁晶界上的扩散情况。在此基础上,根据扩散浓度,利用相关扩散系数公式计算了镧在纯铁中沿晶界扩散的扩散系数,再通过不同温度下的扩散系数拟合出扩散常数。结果表明,稀土元素在纯铁中扩散时,扩散沿着晶界进行,扩散深度随着加热温度等因素的变化而不同,稀土镧在纯铁铁素体晶界中780℃、810℃、840℃、880℃时的扩散系数分别为6. 32×10-15m2/s、1. 06×10-14m2/s、1. 45×10-14m2/s和2. 13×10-14m2/s,并得出在780℃到880℃之间镧原子在α-Fe中的晶界扩散激活能为68. 277 k J/mol,扩散系数的表达式为D=2. 49×10-10(-68277/RT) m2/s。     

经验原子势下铝镁合金中溶质原子向位错芯迁移的最低能量路径

铝镁合金在制造业中应用广泛, 但其在特定应变率下的塑性失稳不利于加工应用. 溶质原子与位错的交互作用是塑性失稳的微观机理. 本文采用势能曲面过渡态搜索技术计算了铝镁合金中替代型溶质镁原子向位错芯迁移的过渡态, 确认了溶质原子与位错芯的交互作用范围, 并采用过渡态理论估算了迁移扩散所需的时间, 且区分了无空位及有空位参与迁移两种情况. 结果表明, 位错压应力区内的溶质原子迁移无明显规律, 而在位错拉应力区内, 随着溶质原子与位错间距的缩短, 迁移势能垒和系统总能量均逐渐降低. 说明目前广泛采用的经验原子势可以很好地反映溶质原子易朝位错拉应力区偏聚这一现象. 溶质原子迁移的过渡态证实迁移过程中的微观结构变化因溶质原子所处位置不同而各异, 而交互作用范围不超过约2 nm. 空位参与对迁移的辅助作用被量化为迁移热激活时间的缩短, 并得出其可在微秒量级. 当溶质原子完成迁移稳定至位错芯附近, 并不倾向于沿位错线密集分布.      

Gleeble模拟热轧工艺对磷非平衡晶界偏聚的影响

 采用Gleeble 3500热模拟试验机研究了轧制和卷取温度下磷元素晶界偏聚与热轧板高温热塑性的关联机制。研究结果表明,含磷钢中磷元素晶界偏聚符合空位-磷原子复合体非平衡共偏聚理论,800 ℃以上轧制温度对磷元素晶界偏聚引起的钢板脆性影响较小,而在500～650 ℃温度范围存在磷元素偏聚导致的热塑性低谷区,且在该温度区施加1%拉伸预应变将加剧磷元素晶界偏聚和钢板脆性。因此,本试验成分含磷钢热轧生产中卷取温度设定应避免550 ℃塑性低谷。     

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。     

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。     

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.     

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。     

Effect of antibiotics of chemotaxis of human leukocytes

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.