有限元法在表面波等离子体中的数值模拟应用

工业用平板型表面波等离子体（SWP）源具有大面积、高密度、高活性等优良性能,其建造之前必须进行结构优化,而对表面电磁波的数值模拟,可以辅助其优化设计。基于有限元法（FEM）,采用AnsoftHFSS模拟软件,数值仿真了大面积矩形SWP源的电磁场空间分布。研究了开槽天线激发表面波场的特性,得出了表面波场的空间分布,与理论分析和实验结果进行了对比,解释了表面波放电的实验现象。研究结果表明在石英-等离子体界面有表面电磁波存在,且分布均匀。研究成果为大面积高效等离子体工艺的产业应用提供建议,也为下一代超大面积SWP源的成功建造提供了有益借鉴。     

Character Diagnosis for Surface-Wave Plasmas Excited by Surface Plasmon Polaritons

The plasma parameters of planar-type surface-wave plasmas (SWPs) are diagnosed based on the resonant excitation of surface plasmon polaritons (SPPs).The plasma parameter distributions are obtained by changing the discharge conditions of gas pressure and incident power.The measured experimental results show that the plasma near the heating layer is excited by surface waves of SPPs while the plasma located downstream originates from diffusion Moreover,the influence of high-frequency oscillations plays a significant role in producing the proposed SWPs with bi-Maxwellian electron energy distributions.     

基于随机森林的电能质量综合评估

电能质量的准确合理评估对建立公平的电力市场有着重要意义。针对目前电能质量评估中受人为因素影响较大的问题,借助随机森林处理分类问题的高度准确性,建立了基于随机森林的电能质量综合评估模型。以电能质量的6项评估指标为特征值将电能质量划分为5个等级,并以此生成随机森林的样本集,利用样本集生成多个电能质量综合评估树形分类器,通过投票的方式对电能质量所属等级进行划分。通过两例电网电能质量数据的分析计算,验证了评估模型的有效性。该模型避免了评估过程中的人为干扰,具有很强的泛化和抗噪能力,在电网电能质量综合评估中具有很好的应用前景。     

Si/SiC混合开关最优门极延时及其在逆变器中的应用

由大电流硅绝缘栅双极型晶体管（Silicon Insulated-Gate Bipolar Transistor,Si IGBT）和小电流碳化硅金属-氧化物-半导体场效应晶体管（Silicon Carbon Metal-Oxide-Semiconductor Field-Effect Transistor,SiC MOSFET）并联构成的Si/SiC混合开关具有低成本、高效率的特点. Si/SiC混合开关门极关断延时的控制是提高混合开关效率的关键因素.本文首先研究了在不同工作电流下Si/SiC混合开关关断损耗随门极关断延时的变化,结果表明,Si/SiC混合开关有一个最优的关断延时,此时混合开关的关断损耗最低,并且最优门极关断延时随混合开关工作电流的增大而减小.将所得到的Si/SiC混合开关最优门极关断延时应用在单相全桥逆变器中,实验结果表明,逆变器的转换效率比同等条件下固定关断延时的最高转换效率提高了0.67%.     

基于DSP的非隔离型光伏并网逆变器设计

基于TMS320F28035芯片,设计了一种两级式非隔离型单相光伏并网逆变器.前级采用Boost型DC/DC电路,后级采用改进的DC/AC逆变桥电路.给出了主电路拓扑,详细分析了改进的DC/AC电路.在扰动观察法的基础上,提出了变步长扰动观察法,使最大功率跟踪（MPPT）的快速性及稳定性得到增强.运用无差拍电流控制策略,实现了网侧电流正弦化且功率因数为l.仿真分析及试验结果表明了设计的正确性与可行性.     

Ionization process and distinctive characteristic of atmospheric pressure cold plasma jet driven resonantly by microwave pulses

In the present study, a coaxial transmission line resonator is constructed, which is always capable of generating cold microwave plasma jet plumes in ambient air in spite of using argon, nitrogen, or even air, respectively. Although the different kinds of working gas induce the different discharge performance, their ionization processes all indicate that the ionization enhancement has taken place twice in each pulsed periods, and the electron densities measured by the method of microwave Rayleigh scattering are higher than the amplitude order of 10¹⁸ m⁻³. The tail region of plasma jets all contain a large number of active particles, like NO, O, emitted photons, etc, but without O3. The formation mechanism and the distinctive characteristics are attributed to the resonance excitation of the locally enhanced electric fields, the ionization wave propulsion, and the temporal and spatial distribution of different particles in the pulsed microwave plasma jets. The parameters of plasma jet could be modulated by adjusting microwave power, modulation pulse parameters (modulation frequency and duty ratio), gas type and its flow rate, according to the requirements of application scenarios.     

Development of an atmospheric fluorocarbon plasma jet generated by pulse modulated microwave discharge

Atmospheric fluorocarbon plasma plays an important role in the surface modification of insulating materials like polymers. The existing fluorocarbon plasma is usually generated by dielectric barrier discharge, which has a low concentration of reactive species and may cause insufficient surface fluorination. This work attempts to develop an atmospheric fluorocarbon plasma jet using a coaxial transmission line resonator by microwave discharge with locally enhanced electric field and high density. ...     

矿用锂电池组并联均流电路的设计

介绍了矿用锂电池组并联均流电路的设计.通过对环流现象和电流的不均衡现象的研究,设计了并联均流电路,并用单片机对其进行控制,以达到均衡电流的目的.实验结果表明该均流电路工作稳定可靠,能够很好地投入煤矿井下电机车使用.     

An edge-adaptive demosaicking method based on image correlation

To reduce the cost, size and complexity, a consumer digital camera usually uses a single sensor overlaid with a color filter array(CFA) to sample one of the red-green-blue primary color values, and uses demosaicking algorithm to estimate the missing color values at each pixel. A novel image correlation and support vector machine(SVM) based edge-adaptive algorithm was proposed, which can reduce edge artifacts and false color artifacts, effectively. Firstly, image pixels were separated into edge region and smooth region with an edge detection algorithm. Then, a hybrid approach switching between a simple demosaicking algorithm on the smooth region and SVM based demosaicking algorithm on the edge region was performed. Image spatial and spectral correlations were employed to create middle planes for the interpolation. Experimental result shows that the proposed approach produced visually pleasing full-color result images and obtained higher CPSNR and smaller S-CIELAB*ab?E than other conventional demosaicking algorithms.