Coercivity enhancement of Nd2Fe14B/α-Fe nanocomposite magnets through neodymium diffusion under annealing

The coercivity enhancement of ball-milled Nd2Fe14B/α-Fe nanocomposite magnets was investigated. It was found that the coercivity could be enhanced through mixing a small amount of Nd powder with as-milled Fe-rich Nd-Fe-B powders. The annealed samples were investigated by means of X-ray diffraction, scanning electron microscopy and magnetic measurement systems. Under annealing, some of Nd powders promoted the formation of hard magnetic phase Nd2Fe14B. On the other hand, a few of Nd would diffuse into the interface of Nd2Fe14B/α-Fe nanocomposite to compensate for the loss of the interfacial magnetic anisotropy. These two features are all beneficial to the coercivity.     

Performance of EDAB-HCl acid blended system as fracturing fluids in oil fields简

Due to the high price and formation damage of the guargum fracturing fluid, many oilfields are more and more interested in surfactant based fracturing fluids. The rheological properties of erucicamide dimethyl amidopropyl betaine （EDAB）-HC1 acid blended system and its suitability as fracturing fluid were investigated in this work. The effects of pH, concentration of EDAB, and temperature on the rheological properties of the blended system were studied. The results show that addition of EDAB improved the viscosity of the system from less than 10 mPa. s to about 400 mPa. s, which could retard the acid-rock reaction to about one half at 60℃ and one quarter at 90℃ comparing to straight HC1 acid, suggesting that there is sufficient time for the blended fluid to react with formation rock when it is used as fracturing fluid in an oil field. Core flow tests demonstrated that the EDAB-acid blended fluid could divert itself from high permeability formation core to low permeability one, thus ensuring proper acid placement in the target reservoirs.     

江西省社会化养老问题与对策研究

正根据1956年联合国《人口老龄化及其社会经济后果》确定的划分标准,当一个国家或地区65岁及以上老年人口数量占总人口比例超过7%时,则意味着这个国家或地区进入老龄化。国际上通常把60岁以上的人口占总人口比例达到10%,或65岁以上人口占总人口的比重达到7%作为国家或地区进入老龄化社会的标准。老龄化在人口结构上表现为劳动年龄人口比重下降,赡养人口比重上升;实质上触及国民经济和社会生活的方方面面,引发诸如财政支出、医疗、社会保障、税收等方面的变化。因此,随着全球老龄化趋势日益严峻,老龄化问题引起全球各方的高度关注。     

竹炭改性泡沫炭材料制备及铜离子吸附性能研究

以酚醛树脂为基体前躯体,竹炭为添加剂,通过发泡、固化及炭化工艺制备出竹炭改性酚醛树脂基泡沫炭材料,研究了其对Cu2+的吸附性能,探究了竹炭含量、吸附时间和溶液pH值对泡沫炭材料吸附Cu2+效果的影响。结果表明:在竹炭含量为7%~10%、吸附时间45 min、溶液pH值为9的条件下,Cu2+的吸附效果最好,并且从微观结构上解释了其对Cu2+吸附能力曲线的变化趋势,解决了泡沫炭因孔径大而难以吸附重金属离子的问题,降低了制备成本,扩大了泡沫炭材料的应用范围。     

以学习者为中心的学习支持服务系统的现状与对策研究

通过期刊网查阅了关于学习支持服务系统的论文,发现从以学习者为中心进行探讨的论文不多。该文是从以学习者为中心的学习支持服务系统中存在的问题进行阐述,并提出了相应的对策。     

浅谈火电厂土建结构抗震设计

火力发电厂土建结构设计涉及到的方面非常的多,其中最为重要的当属抗震设计,其中的意义深远。科学合理的抗震设计极大地提高了火电厂的可靠性、稳定性,有力的削弱地震水平荷载对于火电厂土建结构的作用,使得火电厂在地震作用下的经济损失降低到最低点。本文首先阐述了火电厂钢筋混凝土框架排架的震害问题,随后相应的对火电厂土建结构设计要点分条说明,同时提出了相关的优化措施,以求为相关专业人士提供可靠地指导。     

同沟敷设中热油管道停输过程模拟分析

管内油流的传热与土壤中导热的耦合由管道内流体换热量和土壤中导热量的平衡关系建立联系.用分段法对鄯兰线停输温降进行数值计算,油品的物性参数及周围环境参数是根据实验数据、西部管道勘察设计数据以及历史资料来分段确定.数值计算结果表明,对于西部管道的土质环境及敷设方案,2月份停输72 h内无输送危险;沿线加热站布置合理,加热设施选配得当;同沟敷设间距为1.2 m时,成品油管道对原油管道停输温降的影响比较小.     

稀土和镍含量对Al-Gd-Er-Ni金属玻璃初晶化的影响

通过调节稀土和镍含量研究Al88Gd6Er2Ni4和Al88Gd3Er1Ni8金属玻璃的初晶化行为.结果表明,降低稀土含量、升高Ni含量有利于获得淬火晶核,降低了Al-Gd-Er-Ni金属玻璃的初晶化温度;有利于得到高密度小尺寸的α-Al纳米晶;加大了初晶、第二晶化反应之间的温度差,有助于避免稀土金属间化合物的析出,在较宽的温度范围内获得高纯α-Al纳米晶镶嵌在非晶基体的复合结构.     

大孔吸附树脂分离富集水皂角多酚

运用静态吸附与解吸实验对大孔树脂进行筛选,然后,通过单因素实验、正交实验以及方差分析确定了水皂角多酚分离富集的最佳操作条件。结果表明,S-8大孔树脂表现出最好的吸附性能与良好的解吸效果。确定的最佳吸附条件为A3B2C3,即上柱速度为2.5BV/h,料液浓度为4mg/ml,料液pH值为6.5,最佳洗脱条件为A2B3C2D1,即乙醇浓度为75%,洗脱流速为2BV/h,洗脱液pH值为8,洗脱体积为3.5BV。     

明胶在组织工程支架材料中的应用

本文对明胶在组织工程支架材料中的应用进行了评述,表明明胶作为种子细胞的载体具有广阔的应用前景。