纳米稀土铁氧体磁性颗粒的制备研究

采用湿化学方法研究制备纳米稀土铁氧体磁性颗粒，研究纳米稀土铁氧体颗粒制备过程中主要影响因素，如pH和RE^3＋等对纳米稀土铁氧体颗粒粒径及磁性能的影响；同时对纳米Dy铁氧体颗粒的形貌、粒度分布、晶型结构及磁性能进行了分析和研究。研究发现轻稀土对Fe3O4颗粒的磁性有削弱作用，不宜掺杂；重稀土元素掺杂是提高铁氧体磁性颗粒磁性能的有效途径，改善磁性能的强弱顺序为Dy^3＋〉Gd^3＋〉Er^3＋。制备的Dy铁氧体颗粒的平均粒径为9．6nm，比饱和磁化强度98．27A·m^2·kg^-1，具有超顺磁特性。同时讨论了Dy^3＋在Fe3O4的晶体结构中取代Fe离子增强磁性能的可能形式。     

纳米晶复合Nd2Fe14B/α-Fe永磁合金磁性能研究

采用快淬和晶化退火法制备了成分为Nd8.5Fe74.5Co5Cu1Nb1Zr3Cr0.5B6.5的纳米晶复合永磁合金.研究了制备过程中快淬速度和退火温度对合金磁性能和组织结构的影响.结果表明,快淬速度为16.7m/s,合金样品经690℃/4min的晶化处理后,制成的粘结磁体可得到较优异的综合磁性能Br=0.65T,JHc=708.4kA/m,(BH)max=72.0kJ/m3.     

稳定性油基纳米Fe3O4磁性流体的制备与性能研究

采用化学共沉淀法制备纳米Fe3O4磁性颗粒,在强超声振荡下将其分散在煤油中。采用正交试验设计技术,研究不同用量表面活性剂对Fe3O4磁性颗粒分散的状况以及对饱和磁化强度的影响,通过X射线衍射、红外光谱、VSM振动磁强计对纳米磁流体颗粒的分散稳定性、饱和磁化强度、纯度等进行表征。结果表明:在Fe3+与Fe2+摩尔比约为3∶2、最佳反应温度40～45℃,表面活性剂油酸用量为0.6～0.9ml/g(Fe3O4)的条件下合成的油基磁流体分散均匀、性能稳定;测得的Fe3O4比饱和磁化强度为83.33 A.m2.kg-1,矫顽力为3.40 kA.m-1,具有超顺磁性。     

负载纳米铁颗粒的碳纳米球的制备及磁性能研究

采用喷雾催化热解法制备出负载纳米铁颗粒的碳纳米球,研究了氢气流量对其微观结构、晶体结构和磁性能的影响.当氢气流量为3.0L/min时,所制备的碳纳米球具有洋葱状结构,外表面不光滑,其石墨层间距为0.342nm,球体中散布着直径为几个纳米到30 nm的纳米铁颗粒;当氢气流量提高到5.4 L/min后,所制备的碳纳米球具有光滑的表面,其石墨层间距增大到0.360 nm;随着氢气流量的增大,碳纳米球的矫顽力逐渐增大,饱和磁场强度和剩余磁场强度则逐渐降低.     

制备工艺对Nd8Fe82Co3Nb1B6纳米晶双相复合永磁体的影响

采用直接制备纳米晶和非晶晶化法获得了Nd8Fe82Co3Nb1B6纳米晶双相复合永磁合金,并借助XRD、VSM等分析手段比较了两种方法制备的永磁合金的显微结构及磁性能.结果表明,与非晶晶化方法相比,当辊速为20m/s时,可获得适当的过冷度,直接制备出晶粒尺寸较小的纳米晶双相永磁合金,获得较好的磁性能,其中,Br＝1.12T,Hcj＝381kA/m,(BH)max＝110.5kJ/m3.     

液相还原法制备纳米Ag粉的研究

分别以聚乙烯吡咯烷酮(PVP)和一种复合物作表面保护剂、水合肼作还原剂,通过液相还原法制备出Ag粉,考察了保护剂的品种、用量以及还原条件等对所制备的Ag粉粒度及形貌的影响。结果表明:采用本试验的液相还原法,可以制备出具有纳米粒度的Ag颗粒,且复合保护剂的使用可以减小Ag颗粒的粒度;当复合保护剂与Ag离子摩尔比为1∶1时,所得的纳米Ag粉形状接近球形、平均粒度约为16nm,且粒度分布范围窄。通过控制工艺,可以获得纯度高、分散性好的纳米Ag粉。     

离子束混合过程中Au/Fe磁性膜的巨磁电阻效应在线研究

在离子柬混合和强磁场条件下，在线研究了Au/Fe磁性膜的巨磁电阻效应，发现了不同磁场强度下的离子柬混合对巨磁电阻效应影响的规律，以及不同注入条件对样品饱和磁场的影响。讨论了样品由磁性多层膜逐渐向磁性纳米颗粒膜的转变，以及与此相关的纳米磁性颗粒在磁场作用下的非各向同性生长，并通过高分辨透射电镜(TEM)观察证实了磁性膜样品中磁性纳米Fe颗粒存在各向异性生长现象。通过对室温放置了一年以上的磁性纳米颗粒膜样品的电磁物性测量，证明利用离子柬混合技术制备的纳米颗粒膜在室温具有良好的热稳定性和时间稳定性。     

碳包覆磁性金属纳米胶囊的制备及表征

采用直流电弧等离子体法制备出表面包覆碳膜的金属纳米颗粒,这种纳米颗粒通常被称为“纳米胶囊”。其表面包覆气密的碳膜,具有良好的抗氧化性和稳定性。在甲烷气氛中蒸发各种磁性金属可获得具有良好物理化学性能的磁性纳米胶囊。对这种纳米胶囊进行了Ｘ射线衍射、Ｘ光电子谱、俄歇能谱、氧含量测定及ＨＲＴＥＭ、磁性分析等研究,提供了确定纳米颗粒新型壳－核结构的可靠实验依据。     

纳米磁性颗粒防伪条码

英国研究人员用磁性纳米颗粒制作条码中的线，创造了一种防伪安全系统。印刷条码使用的“墨水”含有铁与镍的纳米颗粒。所产生的每一种磁性结构都是独一无二的，由一套自然出现的铁陷构成。这些铁陷形成了该磁性结构的独一无二的“指纹”，具有它自己的特定磁性特征，可以测量出来，并可储存于通用数据库中，这是一种新的防伪途径，目前尚无人可以预测这种磁性材料自然产生的这种无序性，即使制造者自己也不能预测。因而几乎不可能进行伪造。     

低温燃烧合成法制备粒径相近的MnO、Mn3O4和Mn2O3纳米颗粒

通过控制硝酸盐(硝酸锰) 与有机燃料(尿素) 的摩尔比, 采用低温燃烧合成法制备了粒径相近、形貌不同的单相MnO、Mn₃O₄和Mn₂O₃纳米粒子。扫描电子显微形貌观察结果显示, 三种纳米粒子尺寸约为100 nm, 依据Mn离子价态的不同, 三种纳米粒子的形貌分别为链状、马铃薯状和球状; 热重-差热分析表明, 样品粒径大小主要取决于有机燃料的着火点; 磁性测量结果显示, 低温时MnO和Mn₂O₃粒子表现出弱铁磁性, 这主要归因于纳米颗粒表面存在未补偿的自旋。本文为制备不同价态高纯锰氧化物纳米颗粒提供了一种环境友好、工业稳定的途径。     

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。     

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。     

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.     

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。     

参与式农业基地建设行动方案设计

为了编制实用性强的基地建设行动方案,首先,确定参与式发展的主体,搭建一个"决策框架";其次,针对行动目标,提出不同参与主体,如管理者、农民、消费者等团队与个人的目标及行动内容;最后,工作应向重塑伙伴式合作关系,挖掘农民自我发展潜力,完成三大角色的转换,打造农业基地文化等方向推进.