Energization of charged particle in a time-dependent chaotic magnetic field with an implication of the production of seed particles in solar energetic particle events

We investigate the acceleration of charged particles in a time-dependent chaotic magnetic field in this work. In earlier works, it has been demonstrated that in an asymmetric wire-loop current systems (WLCSs), the magnetic field is of chaotic in nature. Furthermore, observations also showed that there exist time-varying current loops and current filaments in solar corona. It is therefore natural to conceive that the magnetic field on the solar surface is chaotic and time-dependent. Here, we develop a numerical model to study the acceleration process of charged particles in a time-varying chaotic magnetic field that is generated by an ensemble of 8 WLCSs. We found that the motion of energetic particles in the system is of diffusive in nature and a power law spectrum can quickly develop. The mechanism examined here may serve as an efficient pre-acceleration mechanism that generates the so-called seed particles for diffusive shock acceleration at a coronal mass ejection (CME) driven shock in large solar energetic particle (SEP) events.     

粉末溅射平面薄膜型SnO2/CeO2酒敏元件性能测试

给出了SnO2/10?O2(0.4mm×0.6mm×0.4mm)元件的温耗特性曲线,研究了老化的温度和时间,研究了气敏电流Ig与气体浓度C的关系,并给出了一个普遍适用的规律.     

ELID超精密镜面磨削钝化膜状态变化的研究

建立了ELID磨削系统的电解反应回路等效模型,提出用极间电流表征金属结合剂砂轮表面的钝化膜状态,分析了钝化膜在ELID超精密镜面磨削电解预修锐阶段、在线电解修整动态磨削阶段和光磨阶段的状态变化。     

Locating Current Sheets in the Solar Corona

Current sheets are essential for energy dissipation in the solar corona, in particular by enabling magnetic reconnection. Unfortunately, sufficiently thin current sheets cannot be resolved observationally and the theory of their formation is an unresolved issue as well. We consider two predictors of coronal current concentrations, both based on geometrical or even topological properties of a force-free coronal magnetic field. First, there are separatrices related to magnetic nulls. Through separatrices the magnetic connectivity changes discontinuously. Coronal magnetic nulls are, however, very rare. Second, inspired by the concept of generalized magnetic reconnection without nulls, quasi-separatrix layers (QSL) were suggested. Through QSL the magnetic connectivity changes continuously, though strongly. The strength of the connectivity change can be quantified by measuring the squashing of the flux tubes which connect the magnetically conjugated photospheres. We verify the QSL and separatrix concepts by comparing the sites of magnetic nulls and enhanced squashing with the location of current concentrations in the corona. Due to the known difficulties of their direct observation, we simulated coronal current sheets by numerically calculating the response of the corona to energy input from the photosphere, heating a simultaneously observed Extreme Ultraviolet Bright Point. We did not find coronal current sheets at separatrices but at several QSL locations. The reason is that, although the geometrical properties of force-free extrapolated magnetic fields can indeed hint at possible current concentrations, a necessary condition for current sheet formation is the local energy input into the corona.     

飞机电动机过热研究

首先从飞机防火角度，用对称分量法分析了航空电机在不对称电源下的发热情况，推导了发热电流的公式，以此作为数学模型，解释缺相时电机很快烧毁的物理现象。最后提出了防止航空三相电动机过热与起火的方法，包括采用电机在线状态监控、主动维护、增加有效的保护装置等。     

一种新型电涡流位置传感器

分析了现有位置传感器存在的问题,简要介绍了电涡流位置传感器的测量原理、性能优势和推广应用.     

Effects of space weather on high-latitude ground systems

Geomagnetically induced currents (GIC) in technological systems, such as power grids, pipelines, cables and railways, are a ground manifestation of space weather. The first GIC observations were already made in early telegraph equipment more than 150 years ago. In power networks, GIC may saturate transformers with possible harmful consequences extending even to a collapse of the whole system or to permanent damage of transformers. In pipelines, GIC and the associated pipe-to-soil voltages may enhance corrosion or disturb surveys associated with corrosion control. GIC are driven by the geoelectric field induced by a geomagnetic variation at the Earth’s surface. The electric and magnetic fields are primarily produced by ionospheric currents and secondarily affected by the ground conductivity. Of great importance is the auroral electrojet with other rapidly varying currents indicating that GIC are a particular high-latitude problem. In this paper, we summarize the GIC research done in Finland during about 25 years, and discuss the calculation of GIC in a given network. Special attention is paid to modelling a power system. It is shown that, when considering GIC at a site, it is usually sufficient to take account for a smaller grid in the vicinity of the particular site. Modelling GIC also provides a basis for developing forecasting and warning methods of GIC.     

单恒流源电流频率转换技术研究

本文设计了一种单恒流源电流频率转换电路,使电路的功耗减小一半,更加小型化,并且具有更好的对称性和精度.提出并从原理上论证了这种单恒流源I/F技术的理论依据,设计出相应的硬件电路,验证其原理的正确性和工程上的可行性.为单恒流源I/F技术的研发,拓展了思路,奠定了基础.     

V/I电路在航空发动机电子控制器上的应用

在航空发动机控制系统中,存在着大量直流驱动负载,如力矩马达、电液伺服阀等。高精度,高稳定性的直流驱动电路对发动机控制系统的性能有着至关重要的影响。针对以往采用分立元器件设计的电路,精度较低,电路设计复杂,采用集成元器件设计直流驱动电路,提高了系统精度,简化了电路设计,同时降低了设备的重量和体积。