Enhancement of convective heat transfer by electrically-induced swirling effect in laminar and fully-developed internal flows

A computational and experimental approach is undertaken to study the enhancement of convective heat transfer in fully-developed internal flows by an electrically-induced secondary flow field. Using longitudinal flat electrodes along a parallel-plate configuration, the corona discharge is employed to generate an electrically induced secondary flow on the cross section of the flow passage. The electrically-induced secondary flow forms a swirling flow field in the fully-developed condition and enhances the heat transfer significantly. The flow field was solved computationally and the results were verified and validated by grid refinement study and computational error analysis.     

Pulsed laser ablation in liquid of sp-carbon chains: Status and recent advances

This review provides a discussion of the current state of research on sp-carbon chains synthesized by pulsed laser ablation in liquid. In recent years, pulsed laser ablation in liquid (PLAL) has been widely employed for polyynes synthesis thanks to its flexibility with varying laser parameters, solvents, and targets. This allows the control of sp-carbon chains properties as yield, length, termination and stability. Although many reviews related to PLAL have been published, a comprehensive work reporting the current status and advances related to the synthesis of sp-carbon chains by PLAL is still missing. Here we first review the principle of PLAL and the mechanisms of formation of sp-carbon chains. Then we discuss the role of laser fluence (i.e. energy density), solvent, and target for sp-carbon chains synthesis. Lastly, we report the progress related to the prolonged stability of sp-carbon chains by PLAL encapsulated in polymeric matrices. This review will be a helpful guide for researchers interested in synthesizing sp-carbon chains by PLAL.     

Doppler spectroscopy of hydrogen Balmer lines in a hollow cathode glow discharge in argon–methane and argon–acetylene mixture

The results of Doppler spectroscopy of hydrogen Balmer lines emitted from a stainless steel (SS) and copper (Cu) hollow cathode (HC) low-pressure glow discharge in argon–methane and argon–acetylene mixtures are reported. The role of dissociative excitation and dissociative ionization and excitation of hydrocarbon molecules in Balmer line shape formation is studied and discussed in relation to earlier electron beam interaction experiments with CH₄ and C₂H₂. Experimental results of excessive Doppler broadening (EDB) of Balmer lines are reported also.     

Development and fundamental investigation of Laser Ablation Glow Discharge Time-Of-Flight Mass Spectrometry (LA-GD-TOFMS)

Glow Discharge (GD) spectroscopy is a well known and accepted technique for the bulk and surface composition analysis, while laser ablation (LA) provides analysis with high spatial-resolution analysis in LIBS (laser-induced breakdown spectroscopy) or when coupled to inductively coupled plasma spectrometry (ICP-OES or ICP-MS). This work concerns the construction of a Laser Ablation Glow Discharge Time-Of-Flight Mass Spectrometry (LA-GD-TOFMS) instrument to study the analytical capabilities resulting from the interaction of a laser-generated sample plume with a pulsed glow discharge. Two ablation configurations were studied in detail. In a first approach, the laser-generated plume was introduced directly into the GD, while the second approach generated the plume inside the GD. The ablated material was introduced at different times with respect to the discharge pulse in order to exploit the efficient ionization in the GD plasma. For both LA-GD configurations, direct ablation into the afterglow of the pulsed glow discharge leads to an ion signal enhancement of up to a factor of 7, as compared to the ablation process alone under the same experimental conditions. The LA-GD enhancement was found to occur exclusively in the GD afterglow, with a maximum ablation S/N occurring in a few hundred microseconds after the termination of the glow discharge. The duration of the enhanced signal is about two milliseconds. Both the laser pulse energy and the position of the ablation plume (with respect to the sampling orifice) were found to affect the amount of mass entering the afterglow region and consequently, the enhancement factor of ionization.     

Pulsed Corona Discharge-Induced Reactions of Acetophenone in Water

The reactions of acetophenone in water by pulsed corona discharges have been investigated to provide fundamental information concerning the reactions of acetophenone in water. Experimental results indicated that photolysis of acetophenone did not involve a hydroxyl radical mechanism and the majority flux of hydroxyl radicals originated from the dissociation of gas-phase oxygen in the plasma channels. The rate constants for photolysis and pyrolysis were determined to be 1.5×10^–7 M-s^–1, 2.2×10^–4 s^–1, respectively. The rate constant for the oxidative reactions was measured as 1.2×10^–7 M-s^–1. Results from this study support the proposal that acetophenone degradation reaction proceed through the oxidative reaction pathway, where molecular oxygen accelerates acetophenone degradation, photolysis, and pyrolysis pathways.     

Pulsed Plasma Polymerization of Cyclic Ethers: Production of Biologically Nonfouling Surfaces

Polymerization of low molecular weight cyclic ethers was investigated under pulsed plasma conditions. Film formation conditions were adjusted to optimize retention of ethylene oxide (EO) content of the monomers in the resultant plasma generated polymers. To a large extent this goal was achieved with the 12-crown-4 and 15-crown-5 monomers, but not with dioxane. Films obtained from the 12-crown-4 monomer under ultra low power inputs are shown to be highly resistant to protein adsorption, while exhibiting good chemical compositional stability and adhesion during prolonged immersion in aqueous solutions. The dramatic differences observed in contrasting polymer film compositions from 12-crown-4 and dioxane are believed to arise from distinctive differences in the low electron impact fragmentation patterns of these two compounds, as discussed in this report.     

大气压氦氩混合气体介质阻挡放电电学和光谱特性研究

以聚对苯二甲酸乙二醇酯作为介质,在大气压下产生氦氩混合气体放电等离子体。利用电压电流探头、数字示波器和数码相机研究了聚对苯二甲酸乙二醇酯介质阻挡氦氩混合气体放电的电学特性和发光特性。发现随氩气含量增加,每半个电压周期出现一个或多个电流脉冲,放电由均匀放电转变为斑图放电。利用衍射光栅和CCD探测器组成的光谱系统测量了氩原子谱线（696.54, 763.13, 772.09, 811.17和911.81 nm）光谱强度。研究了氩气含量、峰值电压对氩原子谱线光谱强度的影响。实验结果表明：在峰值电压较低时,上述五条氩原子谱线光谱强度随氩气含量的增加均呈现先增强-后减弱-再增强的变化规律;在峰值电压较高时,波长为696.54, 763.13和772.09 nm三条谱线光谱强度增强,波长为811.17和911.81 nm谱线光谱强度减弱。上述情况表明：在低峰值电压下,上述五条氩原子谱线光谱强度的变化规律是由于在放电过程中放电模式发生了变化;而在髙峰值电压下,五条谱线强度变化与气体激发机制有关。在氩气含量低于30%或高于80%时,氩原子谱线光谱强度随峰值电压的增加先保持不变,再增强到稳定值;在氩气含量介于30%～80%之间时,氩原子谱线光谱强度随峰值电压的增加也呈现先增强-后减弱-再增强的变化规律;利用玻尔兹曼图形法计算了氩原子放电的电子激发温度,得到了不同峰值电压下电子激发温度随氦气/氩气比例变化的规律：高峰值电压下电子激发温度明显高于低峰值电压下电子激发温度;电子激发温度随氩气含量增加而减小。出现上述变化规律的原因主要是由于电子与氦原子碰撞截面小,电子与氩原子碰撞截面大,而氦气扩散系数大于氩气扩散系数。     

新型电感储能脉冲功率驱动源

提出了将传统单个储能电感利用传输线分隔成两部分的新型电感储能脉冲功率驱动源技术方案。理论分析表明,利用传输线电容的耦合延时作用,可有效对调制器输出脉冲波形进行整形,并且可以进一步提高能量转换效率,从而克服传统电感储能脉冲功率源输出波形质量差（类三角波波形）的缺点。基于该思想开展了实验研究,获得了电压约300 kV,电流约20 kA的电子束,并成功驱动S波段磁绝缘线振荡器获得了百MW量级的微波输出。     

Pulsed Laser Excited Photoacoustic Effect for Disease Diagnosis and Therapy

Pulsed laser can excite light absorber to generate photoacoustic (PA) effect, that is, when the absorber is irradiated with pulsed laser, the absorbed light energy is converted into local heat to cause rapid thermoelastic expansion and generate acoustic wave. The generated PA signal has been widely employed for the diagnosis of many diseases with superb contrast, high penetrability and sensitivity. In addition, with the increase of pulsed laser energy, the resulting PA shockwave and cavitation can promote efficient drug release at lesion sites to potentiate the resulting therapeutic efficacy. Furthermore, the PA shockwave/cavitation can mechanically inhibit disease and produce reactive species. In this Concept article, the principle and research status of pulsed laser excited disease theranostics are briefly summarized, extra suggestions are proposed to inspire extensive PA probes and photodynamic materials as well as novel methodologies.     

电荷电压法测量DBD等离子体的放电参量

在DBD应用研究中，使用电荷电压法能够测量许多重要参量，如放电功率、放电间隙等效电容、电介质层等效电容、着火电压、放电间隙等效电压及放电间隙电场强度等．同时根据电荷电压图形随工作条件及状态变化的情况还可以诊断DBD等离子体的工作稳定性．文章对相关原理、模拟实验结果及实际应用效果进行了介绍．