不同退火的纳米晶Fe_(73.1)Cu_(1.2)Nb_(3.2)Si_(12.5)B_(10)合金的结构和磁化率的温度关系

在室温下，用Ｍ¨ｏｓｂａｕｅｒ谱和透射电子显微镜考查了纳米晶Ｆｅ７３．１Ｃｕ１．２Ｎｂ３．２Ｓｉ１２．５Ｂ１０合金的显微组织，给出了αＦｅ（Ｓｉ）晶粒的体积分数、平均直径以及非晶基体粒间层的平均厚度的数值。仔细地考查了不同退火态样品加热时交流起始磁化率的温度关系。结果表明，在非晶相Ｃｕｒｉｅ温度以上，随温度上升磁化率近似线性减小，在明显高于非晶Ｃｕｒｉｅ温度情况下达到极小值，而后再增大。用Ｈｒｅｎａｎｄｏ等提出的双相结构唯象理论定性地解释了这种温度行为。     

Influence of spin orbit coupling and lanthanide contraction on the exchange interaction in rare earth garnets

The exchange constants observed in the rare earth iron garnets, obtained from fitting magnetization and paramagnetic susceptibility as a function of temperature have been analysed in terms of Anderson’s theory of superexchange. The transfer integrals and covalency parameters have been obtained for various rare earth ions overlapping with oxygen.     

Multidimensional NMR diffusion studies in microporous materials

The diffusional behavior of selected hydrocarbons adsorbed in NaX zeolites were investigated with pulsed magnetic field gradient (PFG) NMR methods in two different ways. First, the exchange time τ_exch of n-pentane between the interior and the exterior of the zeolite crystals was determined by two-dimensional diffusion exchange spectroscopy. The results were compared to the mean life time τ_intra as obtained by fast NMR tracer desorption method. Second, the diffusion of a propylene–propane mixture adsorbed in the zeolite was studied by Fourier transform PFG NMR, thus employing the chemical shift of the individual organic constituents as a second dimension for a selective evaluation of the PFG NMR signal decays and the subsequent extraction of corresponding diffusion coefficients. Modifications of NMR pulse sequences necessary for the application of ultra-high pulsed magnetic field gradients of up to in microporous materials are briefly discussed for both kind of experiments.     

边界：从对峙到交流——浅议高速公路服务区场所设计

作为高速公路的附属设施,服务区处于功能的边界,存在着建设和营运中的矛盾。该文结合具体的项目实例,对由此引发的问题进行了分析,探讨了从人的需求、环境因子等不同层面中搜寻共同性交集,以消除边界对峙的设计策略。     

MPLS的原理与应用

MPLS是一个可以在多种第二层媒质上进行标记交换的网络技术.本文主要介绍了MPLS的工作流程,在实践中的应用,MPLS技术的意义,最后指出了MPLS还存在的一些问题.     

逆变电路能量交换的仿真分析

本文通过MATLAB仿真和博立叶分析,分析了PWM逆变电路的有功功率和能量交换过程,推导出能量交换的计算公式,通过对实际例题的计算,验证了逆变电路交直流两侧的能量守恒关系。逆变电路交流侧的能量交换,使得直流侧的电流出现了波动,由于能量交换的频率是基波频率的两倍,所以在逆变电路的直流侧就出现了2次谐波电流。搞清楚这些过程和关系将有利于更好地理解交流电路的无功功率。     

基于SOA架构运用SAP XI实现卷烟工业企业一体化信息集成平台的应用研究

为有效集成卷烟工业企业的众多管理信息系统、整合现有信息资源,以浙江中烟工业有限责任公司信息系统建设为例,基于SOA架构运用SAP XI(Exchange Infrastructure,XI)构建了卷烟工业企业一体化信息集成平台.该集成体系将所有需要连接的系统,建立以SAP XI为中心Hub的星形连接,简化了多系统集成时的复杂度;SAP XI将所有由源系统传来的数据格式进行转换处理.实现了异构系统之间的通信集成;SAP XI服务总线将国家局、省级公司、制造部不同信息系统互相衔接,实现了不同层级多个业务系统之间的无缝集成.信息集成平台应用后,实现了多套应用系统之间的总线式信息交互,从架构层面确保了企业各应用系统之间进行灵活、有序、可控的信息交互,解决了信息孤岛、数据质量、流程整合等问题,对卷烟工业企业开展信息化建设提供了借鉴和参考.     

Negative magnetization and exchange bias effect in Fe-doped CoCr2O4

Polycrystalline ceramics of Co(Cr_1-xFe_x)₂O₄ (0?≤?x?≤?0.12) were experimentally studied based on a series of temperature and time-dependent dc magnetic measurements using different magnetic field histories. Magnetization in field cooling process was continuously decreased for doping content x in the range of 0?≤?x?≤?0.04. Remarkable negative magnetization is observed when x reaches to 0.06 and persists up to x?=?0.1. Two-sublattice model is established and competition of the two magnetic sublattices is responsible for the phenomenon. The magnetic switching effect is realized just by changing the magnitude of the applied magnetic field and double magnetocaloric effects are obtained. These unique features under low magnetic fields show attractive for application in spintronic devices due to that the magnetic state can effectively be tuned through magnetic field or temperature. Besides, the system exhibits both positive and negative exchange bias fields which are considered to be originating from the unidirectional anisotropy of exchange coupling of antiferromagnetic/ferromagnetic phases and spin reorientation of the two sublattices magnetic moments, respectively.     

Role of exchange coupling between the hard and soft magnetic phases on the absorption of microwaves by SrFe10Al2O19/Co0.6Zn0.4Fe2O4 nanocomposite

(1-x)SrFe₁₀Al₂O₁₉/(x)Co_0.6Zn_0.4Fe₂O₄-(SFAO/CZFO) hard/soft nanocomposite ferrite materials were synthesized by ‘one-pot’ self-propagating combustion route. The co-existence of the two magnetic phases were confirmed by XRD, FESEM, EDS and VSM. The prepared nanocomposite samples were also characterized by TGA/DSC, Raman spectroscopy and VNA. Exchange coupling between the hard and the soft magnetic grains was observed by determining the switching field distribution (SFD) curve. As a result of the competing effects of exchange interaction and dipolar interaction, magnetic parameters were observed to be sensitive to the incorporation of soft magnetic phase into the nanocomposite. Results showed that with the inclusion of soft magnetic phase, exchange coupling behaviour between the hard and the soft ferrite phases had significant influence on the microwave absorption capacity of the samples. Related electromagnetic parameters and impedance matching ratio of the nanocomposite system were discussed. A minimum reflection loss of ?42.9 dB with an absorber thickness of 2.5 mm was attained by the nanocomposite (90 wt%)SrFe₁₀Al₂O₁₉/(10 wt %)Co_0.6Zn_0.4Fe₂O₄ at a matching frequency of 11.45 GHz. This assured the candidacy of SrFe₁₀Al₂O₁₉/Co_0.6Zn_0.4Fe₂O₄ nanocomposite as a promising microwave absorption material in the X-band (8–12 GHz).     

Room temperature ferromagnetic ordering of NiO films through exchange coupling

NiO films were deposited by sputtering with a relatively high oxygen partial pressure, followed by subsequent annealing in air. The as-deposited film is amorphous. The amorphous film gradually turns to crystalline structure with the increase in annealing temperature. The film annealed at 673 K shows strong ferromagnetism at room temperature, whereas, there is no room-temperature ferromagnetic ordering for the as-deposited amorphous NiO film or the film after annealed at 873 K. The ferromagnetism is due to the finite size effect and the high Curie temperature above room temperature is associated with the interaction between ferromagnetic NiO crystalline nanoclusters and antiferromagnetic amorphous matrix.