Nonlinear phenomena in dielectric barrier discharges: pattern, striation and chaos

The nonlinear phenomenon is very popular in dielectric barrier discharge （DBD） plasmas. There are at least three kinds of spatial and temporal nonlinear phenomena appearing synchronously or asynchronously in DBDs, i.e. self-organized patterns, striations and chaos. This paper describes the recent research and progress in understanding the nature of these nonlinear phenomena. Patterns are macroscopic structures with certain spatial and/or temporal periodicities generated through self- organization of microscopic parameters. The physics of patterns in DBDs is mainly associated with lateral dynamic behaviors or the lateral non-local effect of charged particles resulting in the lateral development or non-uniformity of discharge. Striations are ionization waves with unique properties determined by transport phenomena, ionization processes and electron kinetics in current-carrying plasmas. The physics of striations in DBDs is mainly associated with the advances in non-local electron kinetics in spatially inhomogeneous plasmas. Chaos is a kind of random and non-periodic phenomenon occunfng in a determined dynamic system, following a series of certain rules while exhibiting random locomotion, and is regarded as an intrinsic and ubiquitous phenomenon in a nonlinear dynamic system. An evolution trajectory including period-doubling bifurcation to chaos was observed in DBDs or DBD-derived plasmas. In a common sense, it is believed that the formation of all the three nonlinear phenomena in a DBD system should be related to the non-local transversal and/or longitudinal dynamics of space charges （i.e. non-local effect） or the localized electric field interaction. Future work is still needed on the underlying physics and should be directed to pursuing the unification of these nonlinear phenomena in DBD.

Investigation of Anode Striation in 34”VGA Shadow Mask PDP

A macro-cell was used to study the phenomenon of anode striation on a 34 VGA Shadow Mask Plasma Display Panel （SMPDP）. The breakdown process in the sustaining period of the macro-cell was taken by an Intensified Charge Coupled Device（ICCD） with narrow band filters. The mechanism of formation and evolution of the anode striation on SMPDP were investigated. The influence of the width of the electrode, the sustaining voltage, sustaining frequency and the voltage of the shadow mask on the anode striation was also studied. The results showed that the width of the electrodes, the sustaining voltage and frequency had a strong influence on the anode striation. The voltage of the shadow mask, however, hardly affected the anode striation, the firing voltage or the sustaining voltage.

Evolution of Striation in Pulsed Glow Discharges

In this work,striations in pulsed glow discharges are studied by experiments and Particle-In-Cell/Monte Carlo Collision（PIC/MCC）simulation.The spatio-temporal evolution of the potential and the electron energy during the discharge are analyzed.The processes of striation formation in pulsed glow discharges and dielectric barrier discharges（DBD）are compared.The results show that the mechanisms of striation in pulsed DC discharge and DBD are similar to each other.The evolution of electron energy distribution function before and after the striation formation indicates that the striation results from the potential well of the space charge.During a pulsed breakdown,the striations are formed one by one towards the anode in a weak field channel.This indicates that the formation of striations in a pulsed discharge depends on the flow of modulated electrons.

A Statistical Model of Quantitative Relationship between Striation Spacings and Fatigue Crack Growth Rates

Fatigue crack growth experiments were per- formed on A1 alloy LD 10 and Ti-6A1-4V alloy. Fatigue striation spacings and the deviation angles between the direction of micro-crack growth and that of macro-crack growth were quanti- tatively measured on fracture surface using scanning electron microscope. A statistical model of the relationship between striation spacings and fatigue crack propagation rates was developed on the basis of a statistical analysis of the deviation angles, Good agreement between experimental results and theoretical results calculated with the present model was obtained.

Effect of Wall Charge on Striation in Plasma Display Cells

Different configurations and driving voltages have been employed to investigate the effect of the wall charge on the striations in macroscopic plasma display panel （PDP） cells. The experimental results show that a discharge channel near the dielectric layer is indispensable to striation occurring in the anode area during a discharge, while the pre-accumulated charge on the dielectric layer and the surface state are not important. The origin of the striation is related only to the physical process in the cell. The dielectric layer acts as a charge collector during a PDP discharge.

Formation and destruction of striation plasmas in helium glow discharge at medium pressures

The striation plasmas are usually generated within a positive column of glow discharge,where rich and complex physical interactions are involved,especially,in the medium or high pressures.Along these lines,our work aims to thoroughly investigate the formation and destruction of helium striation plasmas at kPa level pressures.The characteristics of the helium striation plasmas,and especially the optical emission properties are explored.The emission lines of 706.52 nm and391.44 nm related to the energetic electrons and the high-energy metastable helium atoms respectively,were focused on in this work.The formation of striation plasmas in a helium glow discharge,is mainly associated with the instability originating from the stepwise ionization of high-energy metastable state atoms,Maxwellization of the electron distribution functions and gas heating.Additionally,the destruction effect of helium striation plasmas is of great significance when a small amount of nitrogen or oxygen is mixed into the discharge plasmas.The reduction of the mean electron energy and the consumption of the high-energy metastable helium atoms are considered as the underlying reasons for the destruction of striation plasmas.

Analysis of Striation Formation and Suppression Strategy on Upper Edge of Cutting Surface in Laser Cutting

Metal laser cutting belongs to mature laser material processing technologies in industry applications. However, without understanding of the mechanism underlying the overall process, the improvement of the cutting quality is restricted. In this paper, an instantaneous melt removal model is presented to describe the process of material removal and striation formation. In the temperature field calculation, melted metal layer is removed when it grows to an assumed thickness. The effects of cutting parameters including cutting speed, gas pressure and laser power on the shape of striation are discussed. A novel method of getting striation free cutting surface is presented. Finally, laser cutting experiments of mild steel is conducted to validate the model. The striation variation trend can be well predicted by the model presented here and the disagreement may be caused by the coupling effect of cutting speed and critical thickness value.

A Study on Application of Fractal Theory in Examination of Striation Marks

Use scissors and cutting pliers to produce some striation marks. The data collection apparatus is used to collect the surface data of such marks produced by scissors and cutting pliers, and then get the profile curve that is vertical to the surface of striation marks. In tha application of fractal theory, the fractal dimension of such a profile curve is then calculated, and further studies are made on its fractal characteristics. As an exploration on tool types and individual identification, this is aimed to provide a new theory and approach to examination and identification of striation tool marks.

磷酸二氢铵对甲烷爆炸火焰结构影响的抑爆试验研究

本研究旨在探讨磷酸二氢铵对甲烷/空气爆炸火焰传播和结构的直观影响。基于能量守恒和化学动力学原理,在60L定容燃烧弹中进行甲烷抑爆试验,利用纹影技术获取爆炸火焰传播图像并进行分析。试验结果表明,磷酸二氢铵对爆炸火焰有减弱作用,并且随着其浓度增加,火焰传播速度下降显著,火焰半径缩小,在接近最佳甲烷气体爆炸浓度时,效果更加明显。其中,150 g/m 3磷酸二氢铵抑制9.5%、8.0%浓度甲烷爆炸体现出高效性。此外,磷酸二氢铵使甲烷爆炸反应时间延长,表现为流场中自发光时间的显著增加。从热力学角度来看,磷酸二氢铵的分解吸热效应降低了火焰温度,不仅减缓火焰传播速度,也导致火焰边界呈现出片状和变薄的特征。这种现象在甲烷浓度为11%时表现得尤为突出,进一步证实了磷酸二氢铵作为抑爆添加剂的潜在效能。

汽车后悬架纵臂开裂原因分析

某汽车在试验场行驶2796 km后发现其QSTE420TM钢后悬架纵臂断裂。对断裂的纵臂进行了宏观检验、化学成分分析、金相检验、硬度检测及有限元模拟。结果表明:后悬架纵臂是多源疲劳断裂,裂纹始于纵臂与轮毂支架的安装面;汽车在运行中紧固螺栓发生了松动,裂纹源处产生应力集中,应力接近材料的屈服强度,从而导致后悬架纵臂开裂。

Q195镀锌带钢表面横纹的原因与控制

镀锌生产线上,Q195带钢经过塔顶辊后表面出现横纹。对显示横纹的带钢进行了宏观检验、金相检验、拉伸试验和力学性能的理论计算。结果表明:该镀锌线能生产的最大带钢厚度为1.975 mm,超过该厚度的带钢受到的弯曲应力小于屈服极限,从而仅发生弹性变形。通过提高运行速度、降低退火温度,从而提高带钢强度,厚规格带钢已经不再显示因塑性变形而产生的横纹。

腕横纹桡动脉掌浅支游离皮瓣移植修复手指软组织缺损的疗效观察

目的 探究腕横纹桡动脉掌浅支游离皮瓣移植修复手指软组织缺损的疗效。方法 34例手指软组织缺损患者,以1:1分为观察组和对照组,每组17例。对照组采用局部带蒂转移皮瓣修复治疗,观察组采用腕横纹桡动脉掌浅支游离皮瓣移植治疗。对比两组术后并发症发生情况、手术操作时间、创面愈合时间、术中出血量、皮瓣成活率、手指皮瓣外形恢复美观优良率、血运状态恢复优良率、浅感觉恢复优良率、满意度评分、心理健康评分。结果 观察组术后并发症发生率低于对照组,但对比无差异(P>0.05)。观察组手术操作时间(104.65±10.28)min长于对照组的(92.21±10.18)min,创面愈合时间(19.35±2.22)d短于对照组的(24.18±2.81)d(P<0.05)。两组术中出血量对比无差异(P>0.05)。观察组皮瓣成活率100.00%高于对照组的64.71%(P<0.05)。观察组手指皮瓣外形恢复美观优良率94.12%高于对照组的58.82%(P<0.05)。观察组血运状态恢复优良率94.12%高于对照组的58.82%(P<0.05)。观察组浅感觉恢复优良率94.12%高于对照组的58.82%(P<0.05)。观察组满意度评分(95.32±2.26)分、心理健康评分(23.32±5.26)分均优于对照组的(82.33±2.18)、(49.66±5.20)分(P<0.05)。结论 腕横纹桡动脉掌浅支游离皮瓣移植修复手指软组织缺损的疗效显著,能够取得满意疗效,患者恢复快,且预后显著,建议临床推广。

A frequency-adapted optimal-weighted method of array interference striations

Considering the filter properties of the long horizontal line array （HLA） to the sound field modes, we established an adaptive optimal method to design HLA weights, which can change the filter pass band with the frequency. Using the normal modes theory and combining with the feature of the sound field HLA beamformer, and analyzing the differences of definition and slope in the LOFAR （Low Frequency Analysis Recording） spectrogram between the single-hydrophone and the beamformer, a frequency-adapted optimal-weighted （FAOW） estimate method was obtained by solving a quadratic optimization model with linear equality constraints. The numerical simulation and the experimental data analysis indicated that we can obtain the beamformer signal with the designed optimal array weight which was made up by the Surface-Reflected Bottom-Reflected modes or Non-Surface-Reflected Bottom-Reflected modes. The slope of striations in the signal spectrogram fitted well with the theoretical analysis.

Ion resonance causes striations in electronegative rf glow discharges

With the support by the National Natural Science Foundation of China,Dr Liu Yongxin(刘永新)and his coworkers at the Key Laboratory of Materials Modification by Laser,Ion,and Electron Beams(Ministry of Education),School of Physics and Optoelectronic Technology,Dalian University of Technology,observed,for the first time,the self-organized striated structures of the plasma emission in

甘肃金川矿区古构造应力场恢复及演化研究

金川矿区经历了复杂的构造演化历史,目前其成矿期后的构造变形特征和应力场演化阶段仍缺乏精细剖析。文章运用构造解析方法对金川矿区地表基岩中的断层进行了分期和配套,确定了构造变形序列,认为矿区存在4组重要的断层组合,包括北东向逆冲断层和北西向走滑断层、北东向走滑断层和北西向逆冲断层、北西向正断层以及北东东向走滑断层。通过研究断层破裂面及擦痕构造,利用赤平投影法恢复了断层的古构造应力场,结合区域大地构造演化历史,准确限定了金川矿区成矿期后的应力场演化阶段,对认识区域构造演化和开发新远景区具有重要意义。结果显示,金川矿区在成矿期后经历了4期古构造应力场作用,表现为多阶段不同方向的挤压和伸展过程,分别响应了区域中生代以来的一系列构造热事件,Ⅰ期表现为早—中侏罗世的北西—南东向挤压应力场,Ⅱ期为晚侏罗世的北东—南西向挤压应力场,Ⅲ期为早白垩世的北东—南西向伸展应力场,Ⅳ期为晚白垩世以来的北东—南西向挤压应力场。

“共生”视阈下线型水乡有机更新意图传导方法研究——以南沙“大稳-天益”水乡更新实践为例

线型水乡是岭南水乡的特色风貌类型之一,随着城市发展需求的日益增长,大量线型水乡参与到城市更新当中。以经济账为本的“房地产”改造逻辑,导致产生水乡特色形态丧失、水乡文化传承断裂等一系列问题。为确保将线型水乡整体性、多元性、可持续性的有机更新意图有效传导,提出一种基于“人-村-水”共生关系视阈下有机更新意图传导方法:建立运行机制和技术框架,构建共生要素谱系,提炼关键管控要素,进而实现多维有机更新意图。结合南沙实践案例,提出总体引导、小规模单元管控、地域性场景建构等有机更新路径,为我国岭南水乡高质量更新改造提供参考。

北太平洋海洋带状流的正压特性

海洋中包含着多种时空尺度的运动过程,海洋带状流是近年来发现的一种新的流动形式。这种流动现象介于地转湍流和准定常流之间。上层海洋中大尺度运动的强度远大于海洋带状流而将其遮盖,因而带状流需要借助滤波方法提取出来。本研究基于纬向速度数据,通过切比雪夫高通滤波提取了北太平洋海洋带状流的三维结构,定义了“流向稳定度”指数,量化分析了北太平洋海域带状流的正压特性,从而进一步加深了对北太平洋海洋带状流结构特征的认识。

地黄块根菊花心直径与其总苯乙醇苷成分含量相关性分析

目的:比较沁怀、1706两个种质地黄生育期内菊花心、非菊花心及整体块根中总苯乙醇苷含量变化差异,为地黄的质量评价提供科学依据。方法:以60%甲醇为提取溶剂进行超声辅助提取,并以毛蕊花糖苷作为对照品,利用紫外分光光度计于332 nm处测定样品吸光度。结果:两个种质地黄整体块根中总苯乙醇苷类成分含量随生育期延长呈缓慢增加后降低的趋势,沁怀地黄于10月31日达到高峰,1706于10月10日达到高峰;两个种质地黄生育期内菊花心部位总苯乙醇苷类成分含量均高于非菊花心部位,菊花心、非菊花心及整体块根中总苯乙醇苷类成分含量变化趋势基本相同;菊花心直径与总苯乙醇苷含量显著正相关,1706和沁怀地黄的相关系数分别为0.83和0.80。结论:菊花心相关特征可作为地黄道地性及有效成分含量的初步判断标准。

继电器底座锡青铜引脚断裂失效分析

借助光谱仪、蔡司金相显微镜、场发射电子显微镜和维氏硬度计等手段对继电器底座金属引脚失效件进行检测与观察,分析并讨论造成该试样裂纹产生的影响因素。结果表明:材料的化学成分、显微组织、硬度值、非金属夹杂物级别、晶粒度级别及镀层厚度均符合标准要求,断面未见氧化现象和其他缺陷。断面进行宏观与微观观察,呈灰色、较平整、纹路清晰呈纤维状。断面从引脚弯曲内侧分为断裂源区、扩展区、终断区,呈疲劳辉纹形貌特征,结合工作在振动条件下的工作特点,可以判断引脚断裂源于内侧弯折处的微震疲劳断裂。