A spatiotemporal evolution model of a short-circuit arc to a secondary arc based on the improved charge simulation method

The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical.In this study,an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc.The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc.A secondary arc evolution model was developed based on this model.Moreover,the accuracy of the model was evaluated by comparison with physical experimental results.When the secondary arc current increased,the arcing time and dispersion increased.There is an overall trend of increasing arc length with increasing arcing time.Nevertheless,there is a reduction in arc length during arc ignition due to short circuits between the arc columns.Furthermore,the arcing time decreased in the range of 0°-90°as the angle between the wind direction and the x-axis increased.This work investigated the method by which short-circuit arcs evolve into secondary arcs.The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.

Effect of contact materials on the transient characteristics of vacuum arc plasma and anode erosion

In this study, the mechanisms of the anode phenomena and anode erosion with various contact materials were investigated. Arc parameters were calculated, and the anode temperature was predicted with a transient self-consistent model. The simulation results predicted a constricted arc column and obvious anode phenomena in Cu–Cr alloy contacts than in W–Cu alloy contacts.This observation could be the reason for the concentrated anode erosion in Cu–Cr alloys. For the contacts made by pure tungsten(W) and W–Cu alloy, the anode temperature increased rapidly because of the low specific heat of W. However, the maximum energy flux from the arc column to the anode surface was lower than in other cases. The simulation results were compared with experimental results.

Synthesis of NO by rotating sliding arc discharge reactor with conical-spiral electrodes

The present work investigates the potential applications of nitrogen oxides(NO_(x)),particularly nitric oxide(NO)and nitrogen dioxide(NO_(2)),generated through discharge plasma in diverse sectors such as medicine,nitrogen fixation,energy,and environmental protection.In this study,a rotating sliding arc discharge reactor was initially employed to produce high concentrations of gaseous NO_(x),followed by the utilization of a molybdenum wire redox reactor for NO_(2)-to-NO conversion.The outcomes reveal that the discharge states and generations of NO_(x) are affected by varying parameters,including the applied energies,frequencies and airflow states(1.3-2.6 m/s are the laminar flow,2.6-5.2 m/s are the transition state,5.2-6.5 m/s are the turbulent flow),and the concentrations of NO_(x) within the arc discharge are higher than that in the spark discharge.Moreover,the concentrations of NO,NO_(2) and NO_(x) gradually increased,and the concentration ratios of NO/NO_(2) and NO_(x)/NO_(2) decreased with increasing the applied energy for one cycle from 14.8 mJ to 24.3 mJ.Meanwhile,the concentrations of NO,NO_(2) and NO_(x) gradually decreased,and the concentration ratios of NO/NO_(2) and NO_(x)/NO_(2) first decreased and then increased with increasing the applied frequencies from 5.0 kHz to 9.0 kHz.Further,the concentrations of NO,NO_(2) and NO_(x) gradually decreased,and the concentration ratios of NO/NO_(2) and NO_(x)/NO_(2) first increased and then decreased with increasing the air flow speeds from 1.3 m/s to 6.5 m/s.Lastly,the concentrations of NO increased and NO_(2) decreased with increasing temperature from 25℃ to 400℃ using molybdenum converted.These findings provide experimental support for the application of plasma in the fields of medicine,nitrogen fixation,energy and environmental protection.

Geochemistry of island arc assemblage in the Eastern Desert of Egypt and the role of Pan-African magmatism in crustal growth of the Arabian–Nubian Shield:A review

Neoproterozoic island arc assemblage of the Arabian–Nubian Shield(ANS)in the Eastern Desert(ED)of Egypt comprises juvenile suites of metavolcanics(MV),large amounts of meta-sedimentary rocks(MS),and voluminous metagabbros-diorites(MGD)and syn-tectonic intrusions of older granitoids(OG).We report here the updates of these four rock units in terms of classification,distribution,chemical characteristics,geodynamic evolution,metamorphism,and ages.In addition,we discuss these integrated data to elucidate a reasonable and reliable model for crustal evolution in the ANS.The main features of these rock units indicate their relation to each other and the geodynamic environment dominated by early immature oceanic island arcs to primitive continental arcs.Integrated information of the island arc metavolcanic and plutonic rocks(gabbros,diorites,tonalites,and granodiorites)furnish evidence of the genetic relationships.These include proximity and a coeval nature in the field;all protolith magmas are subalkaline in nature following calc-alkaline series with minor tholeiitic affinities;common geochemical signature of the arc rocks and subduction-related magmatism;their similar enrichment in LREEs;and similar major element compositions with mafic melts derived from metasomatized mantle wedge.The volcano-sedimentary and the OG rocks underwent multiphase deformation events whereas the MGD complexes deformed slightly.Based on the magmatic,sedimentological,and metamorphic evolutions constrained by geochronological data as well as the progressive evolutionary trend from extensional to compressional regimes,a possible gradual decrease in the subducted slab dip angle is the most infl uential in any geodynamic model for arc assemblage in the ED of Egypt.

An Overview on the Composition and Age of Upper Crust of Proto-Tethyan Lajishan Intra-oceanic Arc,NE Tibet Plateau

Identification and anatomy of oceanic arcs within ancient orogenic belt are significant for better understanding the tectonic framework and closure process of paleo-ocean basin.This article summarizes the geological,geochemical,and geochronological characteristics of upper crust of Proto-Tethyan Lajishan intra-oceanic arc and provides new data to constrain the subduction evolution of the South Qilian Ocean.The intra-oceanic arc volcanic rocks,including intermediate-mafic lava,breccia,tuff,and minor felsic rocks,are distributed along southern part of the Lajishan ophiolite belt.Geochemical and isotopic compositions indicate that the intermediate-mafic lava were originated from depleted mantle contaminated by sediment melts or hydrous fluids,whereas the felsic rocks were likely generated by partial melting of juvenile mafic crust in intra-oceanic arc setting.Zircons from felsic rocks yield consistent and concordant ages ranging from 506 to 523 Ma,suggesting these volcanic rocks represent the relicts of upper crust of the Cambrian intra-oceanic arc.Combined with the Cambrian forearc ophiolite and accretionary complex,we suggest that the Cambrian intra-oceanic arc in the Lajishan ophiolite belt is belonging to the intra-oceanic arc system which was generated by south-directed subduction in the South Qilian Ocean at a relatively short interval between approximately 530 and 480 Ma.

Arc Grounding Fault Identification Using Integrated Characteristics in the Power Grid

Arc grounding faults occur frequently in the power grid with small resistance grounding neutral points.The existing arc fault identification technology only uses the fault line signal characteristics to set the identification index,which leads to detection failure when the arc zero-off characteristic is short.To solve this problem,this paper presents an arc fault identification method by utilizing integrated signal characteristics of both the fault line and sound lines.Firstly,the waveform characteristics of the fault line and sound lines under an arc grounding fault are studied.After that,the convex hull,gradient product,and correlation coefficient index are used as the basic characteristic parameters to establish fault identification criteria.Then,the logistic regression algorithm is employed to deal with the reference samples,establish the machine discrimination model,and realize the discrimination of fault types.Finally,simulation test results and experimental results verify the accuracy of the proposed method.The comparison analysis shows that the proposed method has higher recognition accuracy,especially when the arc dissipation power is smaller than 2×10^(3) W,the zero-off period is not obvious.In conclusion,the proposed method expands the arc fault identification theory.

The Origins of the Arc-Shaped Langshan Uplift and Linhe Trench

In the northern part of the Ordos Basin, there is a 325 km long arc-shaped Langshan uplift and a 15 km-deep Linhe Trench in front of Langshan, which are rare geological phenomena for which origins no one has explained. This article comprehensively analyzes the research achievements over the past 40 years of geology, geomorphology, seismic exploration, paleogeography, and oil and gas exploration in the Ordos Basin and Langshan. It recognizes that the northern part of the Ordos Basin experienced a meteorite impact in the Late Cretaceous period. The impact pushed the block northwest ward, subducting after colliding with igneous rocks in the north. This sudden event formed a clear arc-shaped mountain zone in the north and a wedge-shaped trench in front of the mountain. The chaotic layers, prolonged and continuous faults, and numerous thrust layers in the Langshan, a negative anomaly area in the center of the northern Ordos, abnormal orientation of crystalline basement structures in the north of Ordos, Moho uplift, and distribution of meteorite fragments in the northwest of Langshan, all of these geological phenomena support the occurrence of the meteorite impact event, forming the arc-shaped Langshan and the Trench.

高职院校学生ARCS学习动机模型的探索与实践

本研究利用发放调查问卷、查阅文献和现场访谈等方法,结合ARCS学习动机模型,对现阶段高职院校学生学习现状进行调查研究。结合调查分析结果,借助ARCS学习动机模型进行教学设计并实施教学,调动学生学习的积极性,激发学生的学习动机,提高了学生的学习兴趣和学习能力。

OBE-ARCS导向的化学工程专业学位研究生课程体系建设和课堂教学模式创新

立足学校理工交叉学科特色,化学工程专业以OBE理念为指导,融合产学研用多要素,对专业学位研究生的核心课程体系进行重构;基于ARCS动机模型,创新研究生课程教学模式;协同专业、课程和教材思政,构建一体化育人机制;依托工程实践基地建设,强化理论与工程实践的结合。基于以上举措构建的“四维一体”育人模式将研究生的知识学习、能力培养、意识强化、专业素养提升紧密融合,在培养高质量应用型人才方面取得了显著成效。

基于ARCS模型的翻转课堂教学设计

以“取样定理”为例,提出采用ARCS模型进行翻转课堂教学设计的案例。教学内容设计注重核心价值观的传播,从取样定理形成的历史脉络引出课程思政;运用多种教学手段,提升学生注意力;重视学习内容的关联设计,学生端倚重信息技术应用,及时反馈,提升学生自信度;学习评价注重应用性,提升学习满意度。教学实施结果表明,该教学设计能调动学生的课堂热情,师生满意度高。

ARCS动机模型混合学习造纸英语听力App设计与开发

ARCS动机模型是1987年美国学者研究并提出的。信息技术的迅速发展,促使该动机模型在多媒体产品开发、课件设计及教育App领域得以广泛应用,并以此来调动学习者的积极性。依托ARCS动机模型对造纸英语听力App进行设计的主要目的是提升学习者对时间的利用率和学习满意度。基于此,针对用户对造纸英语听力App的学习需求,与现有技术相结合,对当前只限于“速记”“跟读”的学习英语听力App进行创新,提供新的研发思路与方向。

基于ARCS激励模型的老年健步走运动产品设计研究

为提高老年群体参与健步走运动锻炼的积极性,文章从运动激励的角度出发开展老年健步走运动相关的产品设计研究,并利用计算机化行为研究的E-Prime软件,建立SAM情绪测试实验程序。同时,通过对实验所得的情感体验数据进行单因素方差分析,证实引入ARCS模型的健步走运动对于激发老年人积极情绪价值的有效性,并得出ARCS模型激励要素的优先性,基于此提出老年健步走产品设计的策略,以期为老年运动相关产品设计提供新的思路。

ARCS模型视角下高职英语教学资源建设与应用研究

基于ARCS模型视角的高职英语教学资源平台建设和应用,坚持以学习者为中心,以整体化、系统化、标准化、科学化、合作性、共享性、循环性改进为原则,围绕高职学生岗位英语语言技能和职业素养目标,构建高职英语课程教学资源库和教学资源共享平台,完善学习成果考核评价体系,建立质量评估和诊改机制,多举措提升教改能力,促进数字化技术与教学改革实践深度融合与双向赋能。

基于ARCS模型设计的VR实训课程教学效果分析

以基站运行与维护实训课程为例,基于ARCS模型进行教学设计,关注学生学习感受的四个方面:注意、关联、信心、满足感。同时结合情境认知理论和建构主义理论,通过VR实训课程教学,激发学生学习的兴趣和动机,分析实训课程教学设计,增强课程教学效果。

Effect of grain refinement induced by wire and arc additive manufacture (WAAM) on the corrosion behaviors of AZ31 magnesium alloy in NaCl solution

Additive manufacturing(AM)of Mg alloys has become a promising strategy for producing complex structures,but the corrosion performance of AM Mg components remains unexploited.In this study,wire and arc additive manufacturing(WAAM)was employed to produce single AZ31 layer.The results revealed that the WAAM AZ31 was characterized by significant grain refinement with non-textured crystallographic orientation,similar phase composition and stabilized corrosion performance comparing to the cast AZ31.These varied corrosion behaviors were principally ascribed to the size of grain,where cast AZ31 and WAAM AZ31 were featured by micro galvanic corrosion and intergranular corrosion,respectively.

电针神庭、百会穴通过ARC/GluR2/NMDAR2B调节海马突触可塑性改善MCAO/R大鼠学习记忆的机制研究

目的观察电针神庭、百会穴对大脑中动脉闭塞再灌注(MCAO/R)大鼠学习记忆功能改善的作用机制。方法线栓法制备MCAO/R大鼠模型。24只雄性SD大鼠随机分为模型组(n=6)、电针组(n=6)、非穴组(n=6)和假手术组(n=6)。电针组大鼠选取百会、神庭穴,非穴组选取双侧胁下非经非穴,共电针7 d。ZeaLonga评分法对各组大鼠进行神经功能缺损评分,新物体识别评估大鼠的学习记忆能力,小动物磁共振T2WI系列扫描梗死面积,HE染色观察缺血侧海马病理形态,波谱(1HMRS)比较各组海马区N-乙酰天冬氨酸(NAA)、肌酸(Cr)和谷氨酸(Glu)代谢物含量,Western blotting检测缺血侧海马ARC/GluR2/NMDAR2B的表达情况。结果干预7 d后,与模型组及非穴组比较,电针组大鼠神经功能缺损评分显著降低(P<0.05),电针组大鼠新物体识别指数较模型及非穴组升高(P<0.05)。磁共振T2WI显示电针组的梗死面积较模型组、非穴组明显减小(P<0.05),波谱显示电针组较模型和非穴组海马区NAA/Cr比值明显增高(P<0.001),GLU/Cr降低(P<0.01)。Western blotting结果表明电针组大鼠缺血侧海马中NMDAR2B含量明显低于模型组和非穴组(P<0.01),ARC及GluR2含量高于模型及非穴组(P<0.05)。结论电针神庭、百会穴能够改善MCAO/R大鼠的神经缺损情况,提高学习记忆能力,降低缺血侧梗死面积,改善病理形态,提高神经元兴奋性,降低膜后谷氨酸累积,其机制可能与促进MCAO/R大鼠海马区ARC、GluR2,抑制NMDAR2B的表达,进而改善卒中后海马突触可塑性损伤有关。

Tri-Arc双丝焊“Γ”形电弧及其促进方法

Tri-Arc双丝三电弧焊通过中间第3弧的M弧重新分配焊接热输入,实现高熔覆率低热输入焊接.M弧与主电弧耦合,在整个动态周期表现为“Γ”形和“μ”形及其镜像形态.该文研究“Γ”形电弧的形成机理和热输入调控机制,结果表明,“Γ”形态由“μ”形态转变而来,熔滴振荡引起焊丝末端间距的变化,从而促进耦合电弧“Γ”形态的形成,此时M弧不作用于母材,比“μ”形电弧焊接热输入更低.为提高Tri-Arc双丝焊接低热输入效果,在维持导电嘴末端到工件距离不变的前提下,提高焊枪枪体抬升距离从而改变焊丝末端间距.当导电嘴长度由30 mm增加至35 mm时,随着焊枪抬升,“Γ”形电弧作用时间逐渐增加,能更好地促进电弧热分配,降低Tri-Arc双丝焊接热输入,从而降低熔池最高温度,获得更小宽高比和更小熔深的焊缝.

基于ARCS动机模型的“中药鉴定实习”实践教学设计与应用

ARCS动机模型在实践教学中被广泛应用,对激发和维持学生学习动机起着重要的作用。文章以ARCS动机模型为基础对“中药鉴定实习”进行课堂教学设计,进而提升学生的学习动力。同时,该课程依托内蒙古医科大学位于河北安国的实习基地进行为期一周的实践教学,以期让学生对中药学专业有一个全新的认识,深入了解中药学相关工作。该课程的实践教学设计与应用,不仅有效地激发了学生的学习兴趣,调动了学生的学习热情,而且为其今后的学习深造和工作奠定了良好的基础,同时也为学生的职业生涯规划提供了良好的帮助。

Drift characteristics and the multi-field coupling stress mechanism of the pantograph-catenary arc under low air pressure

The fault caused by a pantograph-catenary arc is the main factor that threatens the stability of high-speed railway energy transmission.Pantograph-catenary arc vertical drift is more severe than the case under normal pressure,as it is easy to develop the rigid busbar,which may lead to the flashover occurring around the support insulators.We establish a pantograph-catenary arc experiment and diagnosis platform to simulate low pressure and strong airflow environment.Meanwhile,the variation law of arc drift height with time under different air pressures and airflow velocities is analyzed.Moreover,arc drift characteristics and influencing factors are explored.The physical process of the arc column drifting to the rigid busbar with the jumping mechanism of the arc root on the rigid busbar is summarized.In order to further explore the mechanism of the above physical process,a multi-field stress coupling model is built,as the multi-stress variation law of arc is quantitatively evaluated.The dynamic action mechanism of multi-field stress on arc drifting characteristics is explored,as the physical mechanism of arc drifting under low pressure is theoretically explained.The research results provide theoretical support for arc suppression in high-altitude areas.

基于TARGET融合ARCS动机模型的应用统计学课程教学改革研究

学生的学习动机直接关系到课程教学目标的达成,激发学习动机是推动课程教学改革的应有之义。将TARGET和ARCS学习动机模型引入应用统计学课程教学,分析当前教学中存在的动机问题,提出有效激发学生动机的教学方案和实践策略,结果既可促进应用统计学课程教学质量提升,也可为其他相似课程教学设计提供参考借鉴。