Heat capacities and magnetic moments of potential regenerator materials at low temperatures

Several samples of rare-earth oxides of perovskite structure were developed and investigated between 1.5 and 10 K. The measurements have shown, that these materials have large magnetic moments and most of them exhibit a magnetic phase transition below 4 K. The heat capacities of the samples have been measured with the adiabatic heat-pulse method. The dependence of the heat capacity on the preparation temperature of the samples has been studied. The results of the measurements are presented in this paper. The possibility of using these materials as regenerator materials in cryocoolers, e.g. pulse-tube refrigerators, is discussed.     

冷量计量仪表的选型

首先介绍了冷量计量方法,然后以盐水为例介绍了在冷量计量方面应该注意的问题,并对参与冷量计量的仪表在选择时应注意的事项作了详细说明。     

Effect of a magnetic field on the conduction mechanism in Silicon PN junctions

The influence of a weak magnetic field on the electric current across silicon P⁺N junctions has been studied. The theoretical analysis considers two types of diodes: diodes with short base and diodes with long base and the magnetic field is assumed to be perpendicular to the direction of the electric current across the junction. The results show that the variation of the current is directly related to the variation of the hole diffusion coefficient, which is then calculated in the approximation of a P-type silicon material. The relative variation of the diffusion coefficient was found B² dependent. Experimental investigations have then been carried out in order to validate the theoretical calculations. The experimental results were in good agreement with the theoretical development when taking into account the two types of holes in the diffusion mechanism in silicon.     

System modeling and robust control of an AMB spindle : part II a robust controller design and its implementation

This paper discusses an entire procedure for a robust controller design and its implementation of an AMB (active magnetic bearing) spindle, which is part II of the papers presenting details of system modeling and robust control of an AMB spindle. Since there are various uncertainties in an AMB system and reliability is the most important factor for applications, robust control naturally gains attentions in this field. However, tight evaluations of various uncertainties based on experimental data and appropriate performance weightings for an AMB spindle are still ongoing research topics. In addition, there are few publications on experimental justification of a designed robust controller. In this paper, uncertainties for the AMB spindle are classified and described based on the measurement and identification results of part I, and an appropriate performance weighting scheme for the AMB spindle is developed. Then, a robust control is designed through the mixedμ synthesis based on the validated accurate nominal model of part I, and the robust controller is reduced considering its closed loop performance. The reduced robust controller is implemented and confirmed with measurements of closed-loop responses. The AMB spindle is operated up to 57,600 rpm and performance of the designed controller is compared with a benchmark PID controller through experiments. Experiments show that the robust controller offers higher stiffness and more efficient control of rigid modes than the benchmark PID controller.     

Al^3＋对高频大功率NiZn铁氧体性能的影响

研究了用Al^3 代替Fe^3 ，对高频大功率NiZn铁氧体性能的影响，它有效抑制了Fe^2 的产生，使铁氧体电阻率增加，介电损耗和磁损耗下降，且有较大的摆幅磁感，是提高高频大功率NiZn铁氧体性能的有效方法。     

磁刺激作用下哺乳动物有髓神经强度-时间关系的研究

磁刺激是一种利用强磁场激活神经的方法。本文将功能电刺激广泛使用的哺乳动物有髓神经纤维CRRSS模型用于磁刺激，利用该模型计算了传播跨膜动作电位沿神经的分布和时间历程，以及用电容初始充电电压表示的给定脉冲宽度的阈值刺激强度，并通过引入一组可变宽度的放电电流脉冲，确定了强度－时间关系曲线。该模型在磁刺激作用下的结果如时值得与电刺激作用下得出的结果是一致的。     

精细陶瓷高温疲劳性能测试方法研究

对平面弯曲型的三点弯曲试样，采用共振法研究并测定了两类Ｓｉ３Ｎ４陶瓷的高温疲劳性能曲线。研究结果表明：所用陶瓷材料的高温疲劳数据位于两个极端；即：起始阶段就破断或超过指定寿命不破坏。经疲劳试验未破断的样品在高温下的弯曲强度明显地高于原邕样品的高温弯曲强度。