表面微放电等离子体特性参数计算及介质片性质的影响

表面微放电(SMD)在不同的领域有着越来越广泛的应用。为了深入理解其放电特性及介质片性质的影响,基于放电物理过程及SMD特有的放电结构,建立了等效电路模型,并联立Boltzmann方程求解器求解电子连续性方程,得到气隙电压、等离子体电阻及电子密度等特性参数。结果表明,对于同一种类不同厚度的介质片,功率相同时的放电面积及各特性参数一致,对于不同种类的介质片,介电常数较大的介质片下SMD的放电功率、气隙电压、等离子体电阻及电子密度随外加电压的变化率较大。在电压相似的情况下,相同厚度下介电常数较大的介质片放电功率及气隙电压更大,等离子体电阻更小。最后通过比较计算功率和测量功率,验证了模型及仿真计算的正确性。

On the evolution and formation of discharge morphology in pulsed dielectric barrier discharge

The discharge morphology of pulsed dielectric barrier discharge(PDBD) plays important roles in its applications. Here, we systematically investigated the effects of the voltage amplitude,discharge gap, and O_(2)content on the PDBD morphology, and revealed the possible underlying mechanism of the U-shaped formation. First, the morphological evolution under different conditions was recorded. A unique U-shaped region appears in the middle edge region when the gap is larger than 2 mm, while the entire discharge region remains columnar under a 2 mm gap in He PDBD. The width of the discharge and the U-shaped region increase with the increase in voltage, and decrease with the increase of the gap and O_(2)content. To explain this phenomenon,a two-dimensional symmetric model was developed to simulate the spatiotemporal evolution of different species and calculate the electric thrust. The discharge morphology evolution directly corresponds to the excited-state atomic reduction process. The electric thrust on the charged particles mainly determines the reaction region and strongly influences the U-shaped formation.When the gap is less than 2 mm, the electric thrust is homogeneous throughout the entire region,resulting in a columnar shape. However, when the gap is larger than 2 mm or O_(2)is added, the electric thrust in the edge region becomes greater than that in the middle, leading to the U-shaped formation. Furthermore, in He PDBD, the charged particles generating electric thrust are mainly electrons and helium ions, while in He/O_(2)PDBD those that generate electric thrust at the outer edge of the electrode surface are mainly various oxygen-containing ions.

Study on characteristics of acoustic signals generated by different DC discharge modes

Acoustic signals contain rich discharge information.In this study,the acoustic signal characteristics of transient glow,spark,and glow discharges generated through DC pin–pin discharge were investigated.The signals were analyzed in the time,frequency,and time–frequency domains,and the correlation between the electric and the acoustic signal was studied statistically.The results show that glow discharge does not produce measurable sound signals.For the other modes,with a decrease in the discharge gap,the amplitude of the acoustic signal increases sharply with mode transformation,the short-time average energy becomes higher,and the frequency components are more abundant.Meanwhile,the current pulse and sound pressure pulse have a one-to-one relationship in the transient glow and spark regimes,and they are positively correlated in amplitude.A brief theoretical analysis of the mechanism of plasma sound and the trends of signals in different modes is presented.Essentially,the change in the discharge energy is closely related to the sound generation of the plasma.

华中科技大学电气与电子工程学院70周年院庆纪念专刊 序言

七十载栉风沐雨,七十载薪火相传。金秋十月,华中科技大学电气与电子工程学院即将喜迎建院(系)70周年华诞。作为华中科技大学(原华中工学院)的创始专业之一,学院在新中国的朝阳中诞生,在共和国的旗帜下成长,在改革开放中腾飞,在新时代迈向世界一流。“厚积薄发、担当致远”,华中大电气人的精神随着学院的诞生、成长、发展而生生不息,融入了每一位华中大电气人的血液,打造出中国高等教育史上电气工程学科院系建设与发展的典范。

一起换流变压器油箱局部过热分析与维修

对一起换流变压器油箱局部过热现象进行了分析,详细介绍了故障概况、试验结果及分析过程,通过有限元仿真换流变压器的漏磁场分布情况,验证了故障分析的正确性,并提供了改进方案。

Bacterial-killing Effect of Atmospheric Pressure Non-equilibrium Plasma Jet and Oral Mucosa Response

Recently, plasma sterilization has attracted increasing attention in dental community ibr the atmospheric pressure non-equilibrium plasma jet （APNPs）, which is driven by a kilohertz pulsed DC power, may be applied to the dental and oral diseases. However, it is still in doubt whether APNPs can effectively kill pathogenic bacteria in the oral cavity and produce no harmful effects on normal oral tissues, especially on normal mucosa. The aim of this study was to evaluate the bacterial-killing effect of APNPs in the biofilms containing a single breed of bacteria （Porphyromonas gingivalis, Pg.）, and the pathological changes of the oral mucosa after treatment by APNPs. P.g. was incubated to form the biofilms in vitro, and the samples were divided into three groups randomly： group A （blank control）; group B in which the biofilms were treated by APNPs （the setting of the equipment： 10 kHz, 1600 ns and 8 kV）; group C in which the biofilms were exposed only to a gas jet without ignition of the plasma. Each group had three samples and each sample was processed for up to 5 min. The biofilms were then fluorescently stained, observed and photographed under a laser scanning confocal microscope. In the animal experiment, six male Japanese white rabbits were divided into two groups randomly （n=3 in each group） in terms of the different post-treatment time （1-day group and 5-day group）. The buccal mucosa of the left side and the mucosa of the ventral surface of the tongue were treated by APNPs for 10 min in the same way as the bacterial biofilm experiment in each rabbit, and the corresponding mucosa of the other sides served as normal control. The clinical manifestations of the oral mucosa were observed and recorded every day. The rabbits were sacrificed one or five day（s） after APNPs treatment. The oral mucosa were harvested and prepared to haematoxylin and eosin-stained sections. Clinical observation and histopathological scores were used to assess mucosal changes. The results showed the obvious P.g. biofilms were formed at 10 days, and most of the bacteria in groups A and C were alive under a laser scanning confocal microscope, but the bacteria in the group B were almost all dead. In animal experiment, no ulcers, anabrosis and oral mucositis were found in both the 1-day and 5-day groups. The aver- age mucous membrane irritation index was -0.83 and -0.67 in the 1-day and 5-day groups, respectively, suggesting that no intense mucosal membrane irritation responses occurred. It was concluded that APNPs could effectively kill Pg. in the biofilms and did not cause any pathological changes in the normal mucosa, suggesting that the plasma jet （APNPs） may be applied to oral diseases as a novel sterilization device in the future.

Efficacy of Atmospheric Pressure Plasma as an Antibacterial Agent Against Enterococcus Faecalis in Vitro

Enterococcus faecalis （E. faecalis） is a microorganism that can survive extreme challenges in obturated root canals. The aim of this study was to evaluate the efficacy of a non-thermal atmospheric pressure plasma plume against E. faecalis in vitro. A non-thermal atmospheric pressure plasma jet device which could generate a cold plasma plume carrying a peak current of 300 mA was used. The antibacterial efficacy of this device against E. faecalis and its biofihn un- der different conditions was detected. The antibacterial efficacy of the plasma against E. faecalis and Staphylococcus aureus （S. aureus） was also evaluated. After plasma treatment, the average diameter of inhibition zone on S. aureus and E. faecalis was 2.62±0.26 cm and 1.06±0.30 cm, respectively （P 〈 0.05）. The diameter was increased with prolongation of the treatment dura- tion. The diameters of inhibition zone of the sealed Petri dishes were larger than those of the uncovered Petri dishes. There was significant difference in colony-forming units between plasma group and control group on E. faecalis biofilm （P 〈 0.01）. The transmission electron microscopy revealed that the ultrastructural changes eytoderm of E. faecalis were observed after treatment for 2min. It is concluded that the non-thermal atmospheric pressure plasma could serve as an effective adjunct to standard endodontie microbial treatment.

大气压低温等离子体射流及其生物医学应用

大气压低温等离子体射流是近年来学术界兴起的新型研究领域，由于其在大气压下产生，气体温度低，活性高，在众多领域尤其是生物医学方面的应用引起了人们广泛的关注。本文依据驱动电源的不同分别介绍直流电源、交流电源、射频电源、微波、直流脉冲电源驱动的大气压低温等离子体射流装置，及其各自的物理特性、杀菌效果，以及大气压低温等离子体射流在生物医学方面的应用。最后叙述了大气压低温等离子体射流应用领域的前景，以及所面临的困难和可能的解决方法。

等离子体医学

近年来,等离子体医学研究受到了极大的关注,人们尝试着使用等离子体来取代或者辅助药物和传统的医疗手段来达到更好的治疗效果,这样不仅可以避免药物对人体造成的副作用,如化疗手段等给人们带来巨大的伤害,而且更加快速高效,不会对人体产生明显伤害.国际上许多课题组在等离子体医学的诸多应用方向,如凝血、慢性伤口愈合、癌细胞处理、牙齿根管治疗等方面进行了相关研究,并取得了一定的研究成果.本文主要从等离子体医学入手,首先介绍几种典型的用于等离子体医学的大气压低温等离子体源然后简要介绍了大气压低温等离子体与生物体相互作用的机制、国际上等离子体医学的几个研究方向(病菌的灭活、癌细胞处理、正常细胞的处理、凝血等),及等离子体医学的临床应用研究情况,文章最后简要分析了等离子体医学目前的机遇和挑战,并对等离子体医学的未来研究进行了展望.