宽带集中元件环行器计算机辅助设计

本文从散射矩阵本征值的频率关系出发,对宽带集中元件环行器所需的设计参数作了优化计算。文中采用乘子法将约束优化问题化为无约束优化问题。计算结果与实验结果较一致并证实了为得到宽带性能实验中出现的隔离双峰的现象。     

金属间化合物Nd(Fe1-xCox)10V2的结构和磁性研究

通过 X射线衍射和磁测量等手段对金属间化合物 Nd(Fe1 - x Cox) 1 0 V2 的结构和磁性进行了研究。结果表明 ,金属间化合物 Nd(Fe1 - x Cox) 1 0 V2 (x=0 ,0 .0 5 ,0 .1,0 .15 ,0 .2 )的晶体结构均为 Th Mn1 2 型结构 ;随着 Co含量 x的增大 ,晶格常数 a、c和晶胞体积 V将单调减小 ,居里温度 Tc呈单调增大 ,饱和磁化强度 Ms逐渐增加。取向样品Nd Fe1 0 V2 的 X射线衍射和变温穆斯堡尔谱研究结果表明该化合物在 T=12 0 K条件下存在自旋重取向现象。     

钢管通孔直径对涡流检测信号的影响研究

为研究通孔直径在钢管涡流检测中对检测信号的影响,开展了不同磁化强度下钢管通孔涡流检测试验,研究了不同直径通孔随磁化电流的信号变化特征。试验结果表明:通孔直径一定时,在非饱和磁化区(6~18 A)内,信号幅值随电流的增加先增大后减小,相位角随电流的增加逐步上升,在饱和磁化区(20~22 A)内,检测信号成形较小或严重扭曲,相位变化杂乱无章;当磁化电流一定时,信号幅值随通孔直径的增大而增大,不同直径通孔间信号相位角在非饱和磁化区(6~18A)内,最大值与最小值的极值偏差在10°~18°范围内变化,差异较小,而在饱和磁化区(20~22 A)信号相位角变化起伏较大,无明显规律。试验研究结果可用于指导钢管涡流检测工程实践。     

高铁铝土矿低温磁化焙烧-磁选工艺试验研究

基于我国存在大量高铁铝土矿的现状,对高铁铝土矿进行了低温磁化焙烧-磁选工艺的研究。经过大量的试验,研究了焙烧温度、焙烧时间、煤矿比以及磁场强度、给矿时间、液固比对实验结果的影响。该工艺与高温处理高铁铝土矿的工艺相比,大大降低了能耗,节约成本,同时能综合利用此类矿中的铁和铝,取得了较理想的效果。     

载镧磁化赤泥处理含磷废水的研究

采用酒糟作为还原剂,对赤泥进行还原、磁化和焙烧,得到可磁回收的赤泥材料,然后用稀土金属镧对其进行改性得到载镧磁化赤泥,并用于水体除磷。利用X射线衍射仪、傅里叶变换红外光谱仪、振动样品磁强计和光电子能谱仪对改性前后样品进行表征,结果表明赤泥已被成功磁化和载镧,改性后赤泥磁性增加了3.85倍。在室温下,当吸附剂用量为4 g/L、磷酸盐初始质量浓度为50 mg/L时,载镧磁化赤泥对磷的平衡吸附容量达12.31 mg/g,是赤泥的6.62倍。研究结果表明,载镧磁化赤泥对水体中磷具有良好的选择性和可回收性,对磷的吸附过程遵循Langmuir等温吸附模型且属于准二阶动力学方程,是自发吸热熵增的过程。     

发电机定子铁心磁化试验

介绍了120MW发电机定子铁心磁化试验的方案和流程及结果,并对重点部分以插图进行阐述,为其它同类电站发电机定子铁心磁化试验提供一定的借鉴。目前大中型发电机组定子一般都是在现场进行组装,定子铁心磁化试验是硅钢片装压完成后必须进行的一项重要试验,其目的是检查定子铁心制造和现场装压的整体质量。     

采用饱和磁化法测定高速钢残留奥氏体

采用SJ-SM-200A磁饱和测量仪测定了丝锥用M2高速钢在不同热处理状态下的残留奥氏体含量。结果表明,经不同工艺热处理的M2高速钢的饱和磁化强度与残留奥氏体含量之间存在着对应关系。因此,根据饱和磁化强度可以精确测定高速钢中残留奥氏体的含量,准确判断高速钢产品的回火程度。     

High resolution NMR techniques in catalysis

High resolution NMR techniques are applicable to a variety of aspects of catalysis. Methods for studying homogeneously-catalyzed systems under high gas pressure are described along with approaches for obtaining mechanistic and dynamic information. Many of the same techniques may be applied to heterogeneous catalysis by following the reaction chemistry by gas phase NMR. This revised version was published online in June 2006 with corrections to the Cover Date.     

Photoinduced Magnetism in Semiconductor-Based Structures

This paper reviews the most recent progress in the studies of photocarrier-induced magnetism, phototunable magnetization reversal, as well as photoenhanced magnetization in the magnetic alloy semiconductor heterostructure (In,Mn)As/(Ga,Al)Sb and the GaAs–Fe granular structure. Emphases are given to point out that the interplay between the nonmagnetic constituents and magnetic constitutes can be mediated by carrier spins.     

Magnetic properties and phase diagram of Ni50Mn50−xGax ferromagnetic shape memory alloys

We present the magnetic properties and the magnetic phase diagram of Ni₅₀Mn_50?xGa_x ferromagnetic shape memory alloys across a wide concentration range. Martensitic transformation, intermediate transformation, B2–L2₁ order–disorder transformation, Néel and Curie temperatures are determined for the prepared samples. The martensitic transformation temperature decreases with increasing Ga concentration and bends two times when crossing the Curie temperature and the intermediate-phase transformation temperature. Spontaneous magnetization and its composition dependence were also investigated. Composition dependence of the transformation temperatures and the spontaneous magnetization in the martensite phase of Ni₅₀Mn_50?xGa_x are compared with those of Ni₅₀Mn_50?xIn_x and Ni₅₀Mn_50?xSn_x, revealing a similarity in the NiMn-based alloy systems.