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.

Transverse striation needling for 30 cases of cervical spondylosis

Objective To observe the clinical efficacy of transverse striation needling in treatment of cervical spondylosis.Method Thirty patients were diagnosed with cervical spondylosis in Guoyitang Clinic,Yanwu Branch of Zhongshan Hospital,Xiamen University from July,2013 to March,2015,and were included into this study.Transverse striation needling,i.e.transverse insertion into the transverse striation of the cervical vertebra,was adopted for the 30 patients,and conventional acupuncture at Fēngchí（风池 GB 20,bilateral）,Jiānj？ng（肩井 GB 21,bilateral） and Jiānzhōngshù（肩中俞 SI 15,bilateral） was combined.The treatment was conducted for once a day,twice a week,and 6 times were needed in total.Follow-up visit was performed two months after the treatment.Result Among the 30 patients,the markedly effective rate was 70.0%（21/30）,effective rate was 30.0%（9/30）,and the total effective rate was 100.0%.There was no relapse during two months after the treatment.Conclusion The therapeutic effect of transverse striation needling in treatment of cervical spondylosis was good.

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

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。

地黄总黄酮提取工艺优化及其抗氧化活性研究

试验通过响应面法优化地黄总黄酮的提取工艺,评价QH-1、金九两种质地黄菊花心、非菊花心、整体块根部位总黄酮含量及抗氧化能力。结果显示,地黄总黄酮的最佳提取工艺为液料比30 mL/g、乙醇体积分数50%、提取温度50℃、提取时间40 min,此时地黄总黄酮提取率为0.1302%。两种质地黄总黄酮含量均表现为非菊花心>菊花心,QH-1地黄菊花心、非菊花心、整体块根清除1,1-二苯基-2-三硝基苯肼(DPPH)自由基的IC50值分别为0.016、0.009、0.009 g/L,金九地黄菊花心、非菊花心、整体块根清除DPPH自由基的IC50值分别为0.006、0.009、0.010 g/L;QH-1地黄菊花心、非菊花心、整体块根的清除羟自由基的IC50值分别为0.054、0.035、0.047 g/L,金九地黄菊花心、非菊花心、整体块根清除羟自由基的IC50值分别为0.024、0.032、0.034 g/L。研究表明,地黄总黄酮的抗氧化活性较强,可以作为天然绿色抗氧化剂在动物生产中应用。

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。

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。

TC11钛合金叶片锻件暗条纹的成因

批量生产的TC11钛合金叶片锻件上发现有暗黑色条纹。为此,对锻件上显示条纹和正常部位进行了金相检验,对锻造工艺进行了数值模拟,对锻件显示条纹的区域进行了能谱分析。结果表明:叶片锻件上产生暗黑色条纹的原因是原材料存在微区成分偏析,导致锻件局部区域相变温度较低,并在相变点附近温度锻造变形。

断口反推疲劳应力及其在叶片断裂分析中的应用

介绍了断口反推疲劳应力的分类与方法 ,给出了疲劳条带间距反推疲劳应力的基本原理和方法 ,并着重研究了其在叶片断裂失效分析中的应用。结果表明 ,可采用疲劳条带间距对工程实际应用中叶片疲劳断裂时的应力进行断口反推 ,且该方法简单易行。

大巴山前陆北西向褶皱的厘定及其意义

大巴山位于南秦岭造山带与上扬子前陆交接部位,其西北缘地区发育规模大、方向各异、叠加特征明显的褶皱构造体系。通过关键地区的褶皱及其叠加变形的几何学、运动学及时空序列的研究鉴别出至少是三期褶皱构造,包括北东—近东西向、近南北—北北西向和北西向褶皱。本文详细介绍北西向褶皱的厘定依据和空间构造要素,研究其对晚侏罗世形成的大巴山弧形褶皱带的叠加改造及过程。根据区域变形的特征分析,以及下白垩统地层卷入北西向褶皱变形的事实,推测这组褶皱形成与早白垩世晚期或其后的收缩变形事件有关,但其地球动力学背景仍需进一步探讨。大巴山地区北西—南东向褶皱的厘定有助于完善和深化大巴山西缘地区构造演化及地壳变形历史的认识。