超声乳化法制备纳米Fe3O4磁性颗粒及壳聚糖表面改性

采用超声乳化法制备纳米Fe3O4磁性颗粒,以壳聚糖作为表面活性剂,制备具有生物亲和性的水基Fe3O4磁流体.研究了Fe2+/Fe3+摩尔比、超声时间和表面活性剂用量对磁流体性能的影响.结果表明:当Fe2+/Fe3+摩尔比为1:1·5,滴加氨水时反应温度为70℃时,可制备理想纳米Fe3O4磁性颗粒;超声时间为7·5min左右,质量分数1%的壳聚糖溶液体积占FeO溶液总体积的50%时,有利于壳聚糖分子的包覆,使磁流体具有较高的比饱和磁化强度及稳定性.     

Nd~(3+)的稳定能与晶场参数及磁交换作用的关系

基于单离子模型,通过对Nd3+磁晶各向异性哈密顿数值的求解,研究了温度趋于0 K时,Nd3+离子稳定能与晶场参数及磁交换作用的关系.结果表明,对于强磁物质(如NdCo5,Nd2Co17,Nd2Fe14B等),Nd3+贡献的稳定能与晶场参数B20近似成正比,而对磁交换作用的变化不敏感.     

基于巨磁阻抗效应表征材料磁结构的模型

研究了一种可用于磁结构表征的基于巨磁阻抗效应分析材料磁结构的模型.在建立巨磁阻抗效应与简化磁结构对应关系模型的基础上,结合磁化矢量正交分解手段,通过调节巨磁阻抗效应与简化磁结构对应关系模型特征参量的方法,获得了各种形状的巨磁阻抗曲线,根据拟合得到的解叠子谱特征,可获知材料内部磁结构的组成和特征.研究结果对于磁性材料内部磁结构的新型表征方法及其内部结构的控制具有重要的意义.     

Enhanced anti-sunward flow near local noon during a period of horizontal IMF and high solar wind velocity <Emphasis Type="Italic">V</Emphasis><Subscript><Emphasis Type="Italic">Y</Emphasis></Subscript>

It is believed that a southward interplanetary magnetic field (IMF) is mainly responsible for the energy input from solar wind into the magnetosphere. This paper presents an unusual case of strong anti-sunward plasma flow (up to 2 km/s) in the polar cap ionosphere and large cross-polar cap potential (CPCP) during a period of horizontal IMF (|B _Z | < 2 nT) observed by both ACE (at the L1 point) and Geotail (on the dusk flank of the magnetosheath). The CPCP is even higher than that under preceding B _Z ≈ −23 nT. Furthermore, GOES8 observed that the magnetosheath field turns northward as the anti-sunward plasma flow and CPCP start to increase, which implies that the magnetosheath field interacting with the Earth’s magnetopause has significantly rotated and differs from the IMF observed by ACE and Geotail. In accordance with previous theoretical work, we suggest that the magnetic field line draping produces a southward magnetosheath field and enhances anti-sunward plasma flow and the CPCP.     

The effects of the guide field on the structures of electron density depletions in collisionless magnetic reconnection

Two-dimensional particle-in-cell simulations are performed to investigate the formation of electron density depletions in collisionless magnetic reconnection.In anti-parallel reconnection,the quadrupole structures of the out-of-plane magnetic field are formed,and four symmetric electron density depletion layers can be found along the separatrices due to the effects of magetic mirror.With the increase of the initial guide field,the symmetry of both the out-of-plane magnetic field and electron density depletion layers is distorted.When the initial guide field is sufficiently large,the electron density depletion layers along the lower left and upper right separatrices disappear.The parallel electric field in guide field reconnection is found to play an important role in forming such structures of the electron density depletion layers.The structures of the out-of-plane magnetic field By and electron depletion layers in anti-parallel and guide field reconnection are found to be related to electron flow or in-plane currents in the separatrix regions.In anti-parallel reconnection,electrons flow towards the X line along the separatrices,and are directed away from the X line along the magnetic field lines just inside the separatrices.In guide field reconnection,electrons can only flow towards the X line along the upper left and lower right separatrices due to the existence of the parallel electric field in these regions.     

表面等离子共振检测葡萄糖浓度的数据处理方法

根据表面等离子共振(SPR)检测葡萄糖浓度时信号和噪声的特点,研究了寻找曲线最低点算法和基线动态调整方法等SPR数据后处理方法.采用加权质心法精确地捕获到了表面等离子共振曲线的最低点,采用固定计算点数的动态基线法调整基线位置,消除了基线附近点值的波动对测量结果的影响.模拟仿真及实验验证结果表明,采用固定点数的动态基线法和加权质心法处理SPR数据,能显著提高SPR检测葡萄糖的分辨率,在葡萄糖浓度检测技术中有很好的应用前景.     

一种基于声-地震耦合的室内声波探雷实验系统

为了研究声波探雷机理,设计了一个基于声-地震耦合原理的室内声波探雷实验系统.首先,简述声波探雷技术的基本原理;然后,详细介绍室内声波探雷实验系统的硬件组成及实验方案;最后,用一种反坦克塑料教练地雷进行实验,重点讨论实验系统的可重复性.实验结果显示,在相同实验条件下,测得的3条地表振动曲线基本重合,表明所设计的实验系统的可重复性良好,满足测试要求,可用于实验室条件下声波探雷机理的研究.     

锶锆共掺杂对钛酸钡陶瓷结构和介电性质的影响

采用固相反应法制备了(Ba0.85 Sr0.15)(Ti1-xZrx)O3(x=0.10,0.15,0.20,0.25)陶瓷.通过X射线粉末衍射、介电温谱测试和电子顺磁共振技术对其进行了结构表征、介电性能评价和杂质定性检测.结果表明:(Ba0.85 Sr0.15)(Ti1-xZrx)O3陶瓷显示平均立方钙钛矿结构,随着...     

微波辅助磁记录技术研究

颗粒磁矩反转场的大小和反转速度是衡量磁记录写入效率的主要指标.利用LL方程描述在微波场下颗粒磁矩的动力学行为,考虑了颗粒磁矩各向异性场之间存在一定夹角,计算了颗粒磁矩之间相互作用对反转场大小以及反转速度的影响,对于单个颗粒磁矩提出了能够有效提高磁矩反转速度,同时降低磁矩反转场的方法.     

电磁场对固定化活性污泥磁性微球处理污水的影响

设计了带电磁场的污水处理装置,通过测定污水CODcr的去除率考察装置的运行效果,并获得初步的污水处理工艺参数.固定化活性污泥磁性微球在磁场中进行污水处理实验结果表明:当磁场强度为8.50 m T时,处理污水的CODcr去除率可达87.57%;当磁场强度为80.7mT时,处理污水的CODcr去除率可达98.42%.