硅整流二极管组件低温性能测试

为了验证硅整流二极管组件在低温下能否正常工作,利用电流表、温度计和数据采集卡结合LabVIEW虚拟仪器软件组建的测试系统测试了组件在284K和77K下的伏安特性。实验结果表明组件在低温下依然呈现出二极管的各项性能,可以用于超导磁铁的失超保护系统。     

基于PWM整流器双闭环控制的超导电磁储能功率调节器的研究

本文基于电压型超导电磁储能系统(Superconducting Magnet Energy Storage,简称SMES)的基本结构和工作原理,结合脉冲宽度调制(Pulse Width Modulation,简称PWM)整流器的应用,建立了三相电压型PWM整流器控制的超导电磁储能系统的数学模型.设计了具有前馈解耦控制的PWM整流器双闭环控制系统,并运用Mat-lab/Simulink仿真分析软件对基于PWM整流器的超导电磁储能双闭环控制系统进行了仿真研究.仿真结果表明PWM整流器双闭环控制策略应用于SMES电压型SMES功率控制器比直接电流控制等传统的控制策略反应速度更快,向电网注入谐波电流更小,有利于提高了电网的稳定性.     

14T核磁共振成像超导磁体电源拓扑设计及纹波抑制

根据14T 核磁共振成像(MRI)大电感超导体磁体(电感307H、连接阻抗2mΩ)负载纹波的需求(低压为3V、电流为1500A、电流纹波小于1ppm)，基于常见拓扑结构出现的问题，提出了一种适用于这种大电感超导磁体运行电源的拓扑结构。此拓扑结构采用多级处理、无源滤波和有源滤波相结合的思想来设计。介绍了电源的输入级、中间变换级及输出级三个部分的拓扑，并阐述了各部分拓扑设计对负载电流纹波抑制的作用。通过 Matlab 仿真分析，验证了拓扑设计的合理性。     

冷却储存环主环注入线四极磁铁测量

 介绍了兰州重离子加速器冷却储存环工程主环注入线四极磁铁谐波测磁系统和谐波磁场测量结果。分析了磁铁误差产生的原因以及磁铁加工存在的问题和注意事项。     

单分子磁体中交换常数计算的新方法

采用基于密度泛函理论(DFT)的第一性原理计算方法,在现有的单分子磁体交换耦合常数计算方法的基础上提出了一种新的计算方法.采用新方法计算两个原子之间的交换耦合常数时,首先分别设置这两个原子的自旋取向,然后再同时设置两个原子的自旋取向,计算出总能即可,而不用选取不同的自旋组态并求解线性方程组.方法特别适合含有数目很大的磁性原子的单分子磁体交换耦合常数的计算.采用新方法计算了Fe7和Fe20配合物分子的交换耦合常数.结果表明,Fe7和Fe20分子中的交换常数都为负,即反铁磁耦合时能量更低,这与类似分子的相关研究相一致.     

Manganese(II)-phenanthroline-azide compounds: Versatile Precursors as Ligands in Designing Heteropolymetallic Systems

Two novel manganese(II) complexes, [Mn(phen)₂N₃·H₂O]ClO₄·H₂O and Mn(phen)₂(N₃)₂ have been synthesized by the reaction of Mn(ClO₄)₂·6H₂O and Mn(CH₃CO₂)₂·4H₂O with NaN₃ and phen in EtOH/H₂O solution, respectively (where phen = 1,10-phenanthroline). Their crystal structures have been determined by X-ray diffraction. Both complex molecules have distorted octahedral geometry and two 1,10-phenanthroline molecules chelate to a Mn(II) atom with a cis-configuration. To [Mn(phen)₂N₃·H₂O]ClO₄·H₂O, one nitrogen atom from an azide anion and one oxygen atom from a water molecule cis-coordinate to the Mn(II) atom while two nitrogen atoms occupy cis positions in Mn(phen)₂(N₃)₂. These complexes are versatile precursors for the design of heteropolymetallic systems.     

Immunomagnetic separation using carbonyl iron powder and flow cytometry for rapid detection of <Emphasis Type="Italic">Flavobacterium psychrophilum</Emphasis>

Bacterial cold water disease, caused by Flavobacterium psychrophilum, is a serious problem in the aquaculture industry worldwide. Several methods to prevent and treat cold water disease have been studied. Although detection at the early stage of F. psychrophilum infection is very important for the prevention and treatment of cold water disease, an effective detection method has not yet been developed. The use of flow cytometry (FCM) for the rapid determination of bacterial cell numbers with high sensitivity is beginning to attract attention. Immunomagnetic separation (IMS) has also been used to detect F. psychrophilum. The purpose of the present study was to develop a method to quickly determine the number of bacterial cells by combining the FCM and IMS methods. Because samples can be more effectively concentrated using smaller magnetic beads and stronger magnetism, we used carbonyl iron powder as the magnetic beads for the IMS. The detection level of F. psychrophilum using FCM combined with IMS was 5 orders lower than that using FCM without IMS. The values determined using FCM combined with IMS strongly correlated with those obtained using the colony-counting method, in the range of approximately 10–10⁸ colony-forming units per milliliter. One FCM assay could be completed within 60 s and the total assay time, including sample preparation, was less than 2 h. The combined method of FCM with IMS developed in this study can be used reliably for the rapid detection of F. psychrophilum.     

Multifunctional Helicene-Based Ytterbium Coordination Polymer Displaying Circularly Polarized Luminescence,Slow Magnetic Relaxation and Room Temperature Magneto-Chiral Dichroism**

The combination of physical properties sensitive to molecular chirality in a single system allows the observation of fascinating phenomena such as magneto-chiral dichroism (MChD) and circularly polarized luminescence (CPL) having potential applications for optical data readout and display technology. Homochiral monodimensional coordination polymers of Yb^III were designed from a 2,15-bis-ethynyl-hexahelicenic scaffold decorated with two terminal 4-pyridyl units. Thanks to the coordination of the chiral organic chromophore to Yb(hfac)₃ units (hfac⁻=1,1,1,5,5,5-hexafluoroacetylaconate), efficient NIR-CPL activity is observed. Moreover, the specific crystal field around the Yb^III induces a strong magnetic anisotropy which leads to a single-molecule magnet (SMM) behaviour and a remarkable room temperature MChD. The MChD-structural correlation is supported by computational investigations.     

Desolvation-Induced Highly Symmetrical Terbium(III) Single-Molecule Magnet Exhibiting Luminescent Self-Monitoring of Temperature

A conjunction of Single-Molecule Magnet (SMM) behavior and luminescence thermometry is an emerging research line aiming at contactless read-out of temperature in future SMM-based devices. The shared working range between slow magnetic relaxation and the thermometric response is typically narrow or absent. We report Tb^III-based emissive SMMs formed in a cyanido-bridged framework whose properties are governed by the reversible structural transformation from [Tb^III(H₂O)₂][Co^III(CN)₆] ⋅ 2.7H₂O ( 1 ) to its dehydrated phase, Tb^III[Co^III(CN)₆] ( 2 ). The 8-coordinated complexes in 1 show the moderate SMM effect but it is enhanced for trigonal-prismatic Tb^III complexes in 2 , showing the SMM features up to 42 K. They are governed by the combination of QTM, Raman, and Orbach relaxation with the energy barrier of 594(18) cm⁻¹ (854(26) K), one of the highest among the Tb^III-based molecular nanomagnets. Both systems exhibit emission related to the f–f electronic transitions, with the temperature variations resulting in the optical thermometry below 100 K. The dehydration leads to a wide temperature overlap between the SMM behavior and thermometry, from 6 K to 42 K. These functionalities are further enriched after the magnetic dilution. The role of post-synthetic formation of high-symmetry Tb^III complexes in achieving the SMM effect and hot-bands-based optical thermometry is discussed.