Linear microstrip surface coil for MR imaging of the rat spinal cord at 4.7 T

A new design of RF coil based on a quasi-transverse electromagnetic field is described. The coil was developed for the acquisition of MR images of the rat spinal cord at 4.7 T. Different materials for the construction of the coil were tested, and the best results were obtained with Teflon. The design of the microstrip coil enables the investigator to change the length of the coil in a longitudinal direction and yields a relatively high signal-to-noise ratio due to the restricted field of view. Low RF field penetration depth also helps in suppressing motion artifacts generated by, e.g., breathing or heartbeats.     

Chemical Processing of Nanostructured Cemented Carbide

Chemical processing is becoming a vital component in the economic development of advanced engineering materials. Our research group on chemical processing has been focussed on the development of process to produce nanophase cemented carbide. It is a much more direct route for making WC/Co than traditional processing methods, and offers the potential for lower cost production of novel materials with homogeneous nanophase microstructures and improved properties. This paper addresses the scientific and technical issues relating to the chemical processing of nanophase WC/Co composite powder and their sintering.     

氮化铝一维纳米结构制备方法和物性研究的最新进展

全面总结了近年来氮化铝一维纳米结构的各种制备方法及物理性能等研究的最新进展,并提出了有待进一步深入研究的一些发展方向。     

NiCuZn ferrite flakes prepared using a sol-gel bubble method and its magnetic properties

Ni_0.23Cu_0.11Zn_0.66Fe₂O₄ ferrite flakes, with thickness of about 8 μm and average diameter of 20-35 μm, were prepared using a sol-gel bubble method. Morphology, phase evolution, static and dynamic magnetic properties of the flakes and their composites were studied. Magnetic measurements showed that easy magnetization direction of the flaky filler composite was parallel to its sample plane. Composites made of silicone resins and flakes had higher complex permeability, which can be attributed to the reduction in demagnetization factor due to their flaky shapes. This sol-gel bubble method should be also applicable to fabricating flakes of other multi-component oxides.     

Cobalt-iron cyanide hollow cubes: Three-dimensional self-assembly and magnetic properties

Cobalt-iron cyanide hollow cubes have been synthesized via a poly(vinylpyrrolidone) assisted solvothermal route. A unique formation process: self-assembly followed by Ostwald ripening process, has been put forward to take account for the construction of hollow cubes. The rod-like nanocrystals first assemble as porous cubes via an oriented attachment process. Then, the porous cubes undergo an Ostwald-ripening process, which create interior spaces and result in the formation of hollow cubes. The magnetic property investigation reveals that K_0.22Co_0.58Fe_2.2(CN)₆ hollow cubes exhibit a ferromagnetic behavior.     

Modeling radiative properties of nanoscale patterned wafers

Temperature nonuniformity in rapid thermal processing of wafers is a critical problem facing the semiconductor industry. One cause of the problem is the nonuniform absorption of thermal radiation in patterned wafers where the optical properties vary across the wafer surface. This paper presents a parametric study of the radiative properties of patterned wafers, considering the effect of temperature, wavelength, and polarization. The finite-difference time-domain (FDTD) method is employed to examine the effe...     

5KW全数字控制单级隔离型功率因数校正变换器的研究

针对当前工业界某些应用场合对高功率等级、严格的谐波标准以及输入输出隔离等要求,本文提出了一种新的结合主电路拓扑和全数字控制技术的解决方案。文章采用单级隔离型全桥结构结合传统BOOST型PFC的输入电感和RCD钳位作为主电路,并融合数字控制方案,对中大功率单级隔离型PFC进行研究。分析了主电路工作原理,建立了小信号动态模型,并详细分析了基于该模型的数字控制设计方法。提供输入输出电气隔离的变压器,允许输出可以在较大范围内调整,既可以高于输出电压也可以低于输出电压,此外允许多路输出方案。因此,变压器的加主大大拓展了此类PFC变换器的使用场合。采用的数字控制方案,同时具有良好的动态响应特性和稳态调节特性。优异的动态调节特性可成功解决模拟控制引入的变压器偏磁现象。基于本文所提出的拓扑以及控制方案,制作了5kW输出功率且开关频率为55kHz的样机,验证了该变换器的优良性能,满载功率因数达到0．994,效率超过92％。     

Rapid detection of Listeria monocytogenes in food by biofunctionalized magnetic nanoparticle based on nuclear magnetic resonance

In order to ensure the safety of food, particularly ready-to-eat (RTE) food, a sensitive and rapid method for the detection of foodborne pathogenic bacteria is always in high demand. An accurate and reliable detection method for Listeria monocytogenes has been developed based on the aggregation of biofunctionalized magnetic nanoparticles induced by specific binding between L. monocytogenes and antibody-modified nanoparticles, which results in the change of the transverse relaxation time (T2) of surrounding water protons of nanoparticles detected by nuclear magnetic resonance. The detection limit of this method is 3 MPN (using the most-probable-number (MPN) assay) and the functionalized Fe/Fe₃O₄ nanoparticles exhibit a high specificity with the existence of other interfering bacteria. Furthermore, this detection method is successfully applied to detect L. monocytogenes in milk powder and lettuce. This method could be a useful tool for sensitive and rapid detection of foodborne pathogenic bacteria.     

外延单晶(YNd)_3Fe_5O_(12)磁光薄膜性能分析

对钇钕铁石榴石单晶薄膜材料进行了大量的性能研究,发现了过冷度与错配度、光损耗的关系,并提出了改善其磁光性能的可行途径。同时作出了XPS能谱图,比较氧化前后能谱图的差别,对实验结果给出了明晰的解释。