四极透镜电流对CT法测束流发射度的影响

利用CT法测量束流发射度是近年来出现的高能强流速束流发射度高精度测量诊断技术。主要就四极透镜电流变化带来的角度分布不同对束流发射度重建精度的影响进行了研究,选取了系列不同的重建角度分布进行模拟计算。研究结果表明,不同的角度分布对重建精度有很大影响,当角度均匀取值时,重建精度最佳。     

双凸极永磁电机控制方式II的两种通电原则比较

以12/8极双凸极永磁电机为研究对象,介绍了其在控制方式下的两种通电原则,对二者进行了分析比较,并对其稳态运行过程进行了仿真模拟,最后在一台原理样机上进行了实验验证。结果表明:双凸极电机在控制方式下的两种通电原则,其工作模式间存在着本质的差别,因而在实际运用中只能采用通电原则。     

零电流零电压开关PWM Boost全桥变换器

提出一种新颖的零电流零电压开关PWM Boost全桥变换器。超前管串联电感，并利用输出滤波电容的能量，可以在很宽的负载范围内实现ZCS。滞后管利用其寄生电容和与变压器原边并联的辅助电感，可以在任何负载下实现ZVS。与ZCS PWM Boost全桥变换器相比，所提出的变换器没有电流占空比丢失的问题。本文详细分析了该变换器的工作原理，参数设计原则。通过一个480W的原理样机，验证了分析结果。     

稀土永磁方波无刷直流电动机调速系统的实验研究

稀土永磁方波无刷直流电动机是静止功率变换器和电机设计相结合的产物，本文分析了稀土永磁方波无刷直流电动机的控制性能，指出它具有电机磁定向控制简化为磁极位置控制的特点，从而控制简单又提高控制性能，为此在稀土永磁方波无刷直流电动机调速系统中，采用了两态稳频电流调节器，ＰＷＭ电子换向器，电流分时反馈等具有特色的线路设计，实验结果表明，该调速系统体现了静止功率变换器与电机配合运行的特点，验证了稀土永磁方波无     

矩形栅格波导阵列单元的阵中特性

根据等效原理,用矩量法(MOM)导出求解仅激励中心单元条件下矩形栅格开口波导阵列各单元口面等效磁流的模型,在此基础上给出了激励单元的内部场、耦合场、反射系数、驻波系数,激励波导与阵中其他波导的耦合系数,以及远区场等阵中特性的计算公式。在不同工作频率下计算了一7单元×7单元开口波导矩形栅格阵中激励单元的等效磁流和阵中方向图,以及激励单元与阵中其他单元的耦合系数。研究表明:互耦对单元的阵中特性影响明显,阵中驻波系数明显大于孤立单元,单元间的耦合随工作频率增大而减弱。     

mA级恒流源逆向建模高准确度测量

通过对I/V -ADC过程的逆向建模 ,补偿了I/V -ADC过程的非线性和受温度等环境因素影响产生的测量误差 ,提高了对高准确度恒流源的测量准确度。建模过程简单 ,易于实现。     

Numerical study of magnetic reconnection possibly occurring near heliospheric current sheet

The third-order accurate upwind compact difference scheme has been applied for the numerical study of the magnetic reconnection driven by a plasma blob impacting the heliospheric current sheet, under the framework of the two-dimensional compressible magnetohydrodynamics. The results show that the driven reconnection near the current sheet could occur in about 10–30 min for the interplanetary high magnetic Reynolds number, R_M = 2000–10,000, a stable magnetic reconnection structure can be formed in hour order of magnitude, and there appear some basic properties such as the multiple X-line reconnections, vortex structures, filament current systems, splitting and collapse of the high-density plasma blob. These results are helpful in understanding and identifying the magnetic reconnection phenomena possibly occurring near the heliospheric current sheets.     

用经验模式参数研究电离层发电机效应

本文利用MSIS-86和IRI-86模式的基本参数,求得热层风系和电导率的三维分布;继而从发电机理论得到了电离层电位及层电流密度在北半球的分布和变化。本研究将大量数据统计平均的大气模式参数与热层、电离层理论研究联系了起来。     

Storm-time formation of a relativistic electron belt and some relevant phenomena in other magnetospheric plasma domains

An empirical formula relating the strength of a storm given by its |Dst|_max with the L-coordinate of the peak of storm-injected relativistic electrons is one of a few well-confirmed quantitative relations found in the magneto-spheric physics. We successively extended a dataset of the formula’s basic storms with several events of high Dst-amplitude up to the highest observed |Dst|_max = 600 nT. Possible applying of the formula to the predicting of the ring-current plasma-pressure distribution and the lowest westward electrojet position for a storm are discussed. We have also analyzed the 2000–2001 years’ data on relativistic electrons from our instruments installed on EXPRESS-A (geosynchronous orbit; E_e = 0.8–6 MeV), Molniya-3 (h = 500 × 40 000 km, i = 63°; E_e = 0.8–5.5 MeV) and GLONASS (h = 20 000 km, i = 64°; E_e  l MeV) along with other correlated measurements: GOES series (E_e > 2 MeV), geomagnetic indices (Dst, AE, AL) and interplanetary parameters (solar wind, IMF). The goal is to investigate which outer conditions are most responsible for the high/low output of the storm-injected relativistic electrons. For the geosynchronous orbit, two factors are found as the necessary condition of the highest electron output: high and long-lasting substorm activity on a storm recovery phase and high velocity of solar wind. On the contrary, extremely low substorm activity surely observed during whole the storm recovery phase constitutes a sufficient condition of the non-increased after-storm electron intensity. For the first time found cases of the increased after-storm electron intensity observed at the inner L-shells with no simultaneously seen increase in the geosynchronous distances are presented.