基于改进Deformable DETR模型的多源局部放电识别方法及其应用

基于图像的局部放电识别方法大部分仅对单源局部放电谱图有效,无法识别多源局部放电谱图。为实现对多源局部放电谱图的识别,该文提出一种基于Transformer架构的局部放电Deformable DETR目标检测模型,收集典型单源局部放电和多源局部放电数据,生成局部放电相位角解析和极坐标相位分布解析谱图数据集。在Deformable DETR模型中引入去噪训练任务和贝叶斯优化算法,优化了局部放电目标检测模型;编写局部放电谱图采集和识别程序,并使用优化后的局部放电Deformable DETR模型对单源和多源局部放电谱图进行识别。结果表明:局部放电Deformable DETR模型不仅可有效识别出单源和多源局部放电的类型,而且大幅提升了局部放电类型识别的收敛速度和精度等性能。在对真实绝缘缺陷电动机的局部放电谱图识别中,局部放电Deformable DETR模型的识别准确率达到91%,证明该模型在实际应用中的有效性。

Efficient activation of the Co/SBA-15catalyst by high-frequency AC-DBD plasma thermal effects for toluene removal

Dielectric barrier discharge(DBD)plasma excited by a high-frequency alternating-current(AC)power supply is widely employed for the degradation of volatile organic compounds(VOCs).However,the thermal effect generated during the discharge process leads to energy waste and low energy utilization efficiency.In this work,an innovative DBD thermally-conducted catalysis(DBD-TCC)system,integrating high-frequency AC-DBD plasma and its generated thermal effects to activate the Co/SBA-15 catalyst,was employed for toluene removal.Specifically,Co/SBA-15 catalysts are closely positioned to the ground electrode of the plasma zone and can be heated and activated by the thermal effect when the voltage exceeds 10 k V.At12.4 k V,the temperature in the catalyst zone reached 261℃ in the DBD-TCC system,resulting in an increase in toluene degradation efficiency of 17%,CO_(2)selectivity of 21.2%,and energy efficiency of 27%,respectively,compared to the DBD system alone.In contrast,the DBD thermally-unconducted catalysis(DBD-TUC)system fails to enhance toluene degradation due to insufficient heat absorption and catalytic activation,highlighting the crucial role of AC-DBD generated heat in the activation of the catalyst.Furthermore,the degradation pathway and mechanism of toluene in the DBD-TCC system were hypothesized.This work is expected to provide an energy-efficient approach for high-frequency AC-DBD plasma removal of VOCs.

平行磁场对脉冲针–板介质阻挡放电物理化学特性的影响

为在大气压下产生高强度的介质阻挡放电(dielectric barrier discharge,DBD)等离子体,该文利用永磁铁产生平行于电场方向的磁场,用于增强纳秒脉冲针–板DBD等离子体的物理化学活性,并探究不同脉冲参数下磁场对等离子体特性的影响规律和机制。考察平行磁场辅助脉冲针–板DBD等离子体的动态演化特性,并从电学、光学和臭氧生成特性等方面研究了脉冲电压幅值、上升沿时间和下降沿时间等参数对平行磁场辅助脉冲针–板DBD特性的影响规律。实验结果表明:平行磁场通过磁化电子改变DBD等离子体特性;施加平行磁场后,针–板DBD中空间流光放电及介质表面流光放电强度增强;不同脉冲放电参数下,施加平行磁场对放电强度及臭氧产量均显示出增强效果,在短脉冲上升沿时间条件下平行磁场的增强效果尤为显著。

三电极脉冲沿面介质阻挡放电等离子体特性及除冰研究

风力发电机和飞机在低温潮湿环境下运行时存在表面覆冰问题,进而影响装备的正常工作,严重时甚至危害人身财产安全。已有文献发现两电极沿面介质阻挡放电(surface dielectric barrier discharge,SDBD)在除冰方面有潜在的应用前景,但仍存在温升小和效率低等问题。为有效提高SDBD表面温度和除冰效率,该文将一接地电极安装在高压电极同侧,构成三电极SDBD结构,研究三电极脉冲SDBD等离子体特性及除冰过程与效果。结果表明:在相同的放电条件下,与两电极脉冲SDBD相比,三电极脉冲SDBD在放电能量、表面温度、发射光谱强度和除冰效果等方面表现出更为优异的能力。在20kV脉冲电压作用下,13mm间隙的三电极SDBD比两电极SDBD的放电能量增加了约1.95倍,最高温度提高了8℃。数值模拟结果也进一步表明:通过脉冲快速加热,三电极SDBD温升范围广和热量空间分布均匀,在除冰方面有很大的潜力。研究结果可为脉冲放电等离子体除冰及相关应用提供参考。

等离子体羟基化改性纳米SiO_(2)粒子对绝缘纸绝缘特性的影响

在绝缘纸中掺杂纳米粒子,可通过其对载流子的限制来提高绝缘纸的绝缘特性。然而,纳米粒子的高比表面积和表面活性易形成“团聚”,导致纳米粒子聚集处易产生局部放电和击穿。为了有效抑制纳米粒子团聚、进一步提高绝缘纸的绝缘特性,利用介质阻挡放电(DBD)等离子体对纳米SiO_(2)粒子进行羟基化改性,增加纳米粒子表面羟基数,并通过氢键与硅烷偶联剂分子发生偶联作用从而桥接在绝缘纸基体上,改善了纳米粒子和绝缘纸的兼容性,从而改善其团聚,并采用原位聚合法制备了掺杂纳米SiO_(2)粒子的纤维素绝缘纸。利用X射线光电子能谱仪(XPS)、扫描电子显微镜(SEM)、傅里叶红外光谱仪(FTIR)、比表面及孔隙度分析仪(BET)结合滴定法等手段表征了等离子体改性前后纳米SiO_(2)粒子表面化学组分、微观形貌、官能团及接枝羟基数目的变化规律。并考察了等离子体处理条件及改性步骤对绝缘纸击穿场强和体积电阻率的影响。研究结果表明,纳米SiO_(2)粒子经等离子体羟基化改性后表面氧元素含量及羟基吸收峰显著增强,其在绝缘纸中的分散性得到明显改善。当等离子体改性时间为5 min、空气相对湿度为75%时,纳米SiO_(2)粒子表面接枝的羟基数目达到最高。掺杂了3wt%等离子体羟基化改性的纳米SiO_(2)后,绝缘纸的直流击穿场强和体积电阻率达到18.35 kV/mm和17.45×10^(9)Ω·m,较掺杂了未改性纳米SiO_(2)的绝缘纸分别提高了10.7%和19.4%,较未掺杂纳米SiO_(2)粒子的绝缘纸提高了52.3%和106.2%。

试论茶叶栽培田间管理技术

栽培茶叶能给茶农带来一定的经济收益,带动农村经济发展。但要想确保茶业栽培能够获得高产、稳产,推动茶业种植业的持续稳步发展,还需要深入实际,进一步强化茶树栽培田间管理技术的研究。基于此,本文结合茶叶栽培实践,总结了一些茶叶栽培的田间管理技术措施,以期能对推动茶叶栽培业的健康发展提供一些借鉴与参考。

毛细管共面介质阻挡放电等离子体特性

共面介质阻挡放电(coplanar dielectric barrier discharge,CDBD)因高压电极和接地电极掩埋在绝缘介质中而具有较长的使用寿命和广泛的应用前景。然而,传统CDBD起始电压高、制作较为复杂,这会限制其应用的进一步发展。因此提出了一种新型的毛细管CDBD结构,即用填充铜粉的毛细管作为高/低压电极,并利用两电极间的紧密接触缩短放电气隙以降低起始放电电压。该研究从流光发展过程、光学特性、电学特性以及活性粒子生成角度对毛细管CDBD进行了系统性的研究,并探究了脉冲电压幅值、上升时间、下降时间、峰值平顶宽度、电极直径以及介质的相对介电常数对等离子体特性的影响。结果表明,毛细管CDBD在单次脉冲作用下存在一次放电和二次放电,分别对应电流极性为正和为负的部分。在脉冲上升沿阶段,流光从相邻高/低压毛细管间的“V型”区域底部产生,然后主要沿着高压电极表面爬升并达到最高点。而在脉冲下降沿阶段,流光则主要沿着接地电极表面发展。高的脉冲电压、短的脉冲上升时间和下降时间有利于放电的增强和活性粒子的生成。同时脉冲上升时间的增加还会使得放电均匀性变差,而脉冲峰值平顶宽度的影响则较为有限。相对介电常数的增加能够增强放电强度和降低起始放电电压,而电极直径的增加虽能增加放电面积,但也会使得放电强度变差。

提高霍山黄芽品质的相关措施分析

近年来,霍山黄芽从茶园发展、优良品种选择、采摘和加工技术等各方面都有了一定程度的发展,茶叶品质得到大幅提高。结合生产实际,从鲜叶质量要素、鲜叶质量指标、鲜叶采摘基本要求、鲜叶处理等方面总结了提高鲜叶质量及采摘保管规范的相关措施;提出杀青、理条、初烘、摊凉、足烘、拣剔复火等各道工序技术要点及注意事项。

Pulsed gas–liquid discharge plasma catalytic degradation of bisphenol A over graphene/Cd S:process parameters optimization and O_(3)activation mechanism analysis

In the present work,pulsed gas–liquid hybrid discharge plasma coupled with graphene/Cd S catalyst was evaluated to eliminate bisphenol A(BPA)in wastewater.The optimization of a series of process parameters was performed in terms of BPA degradation performance.The experimental results demonstrated that nearly 90%of BPA(20 mg l^(-1))in the synthetic wastewater(p H=7.5,σ=10μS m^(-1))was degraded by the plasma catalytic system over 0.2 g l^(-1)graphene/Cd S at 19k V with a 4 l min^(-1)air flow rate and 10 mm electrode gap within 60 min.The BPA removal rate increased with increasing the discharge voltage and decreasing the initial BPA concentration or solution conductivity.Nevertheless,either too high or too low an air flow rate,electrode gap,catalyst dosage or initial solution p H would lead to a decrease in BPA degradation.Moreover,optical emission spectroscopy was used to gain information on short-lived reactive species formed from the pulsed gas–liquid hybrid discharge plasma system.The results indicated the existence of several highly oxidative free radicals such as·O and·OH.Finally,the activation pathway of O_(3)on the catalyst surface was analyzed by density functional theory.

Generation of air discharge plasma in the cavities of porous catalysts:a modeling study

A study of the behaviors of air discharge plasma inside a catalyst’s pores is important to understand the plasma catalysis mechanism;however,few articles have reported the generation characteristics of air plasma in the pores of catalysts.The production of air microdischarge in a pore was studied by a two-dimensional fluid model,mainly focusing on the effect of pore size and applied voltage.The results show that an increase in the pore size in the range of 20–100μm facilitates the occurrence of microdischarge in the pore.In addition,at an applied voltage of 9 kV,the ionization of air mainly occurs near the topside of the pore when the pore diameter is less than 20μm,leading to a low plasma density in the pore,but the time-averaged plasma density in the pore reaches a maximum value at a 70μm pore diameter.Moreover,the applied voltage also has an important effect on the production of air microdischarge in the pore.The existence of a pore of 80μm diameter on the dielectric has no obvious influence on the plasma density in the pore at 2 kV applied voltage,but the plasma density in the pore begins to sharply rise when the voltage exceeds 3 kV due to the enhanced air ionization at higher applied voltage.The study indicates that microdischarge can be generated in a pore with a size of tens of micrometers,and the microdischarge in porous catalysts will affect the catalytic degradation efficacy of gaseous pollutants.

中国茶叶品质危害因素分析及对策研究进展

近年来中国茶产业发展迅速,但因受不完善茶业体制和机制等因素影响,中国茶业一直未能完全摆脱来自农药残留、重金属、微生物及生物毒素等方面的安全危害,造成茶叶出口量和出口产值与国内茶叶资源在国际茶叶市场占有额不对称。本文围绕茶场生态环境、茶园管理、茶叶加工及贮运等方面阐述当前中国茶业发展中所面临的一些品质危害问题,并通过对茶叶质量安全法律体系、标准体系、危害评估和风险预警体系、质量控制体系、监管机制及人才培养等宏观体制、机制方面建设阐述解决目前存在问题的几点建议,旨在为未来中国茶业良性、快速、可持续发展提供一定理论参考依据。

脉冲参数对脉冲介质阻挡放电臭氧产生影响的数值模拟

在脉冲介质阻挡放电产生臭氧的过程中,脉冲参数至关重要。为研究脉冲参数对其流光传播速度和臭氧分子浓度的影响,构建了1个由流体动力学模型和包含11种粒子、29个反应的反应模型组成的准2维动力学模型并进行了数值模拟。模拟结果表明：流光传播速度和臭氧分子浓度均随脉冲峰值电压的增大而增大,随脉冲上升时间的减小而增大,在模拟工况所得流光速度范围为4.2×104~3.57×105 m/s;脉冲宽度的变化对流光传播速度与臭氧分子浓度基本无影响,但减小脉冲宽度有利于提高臭氧产率;随着脉冲上升率的增大,在流光出现后并经历相同时间时对应的电场强度更大,流光的传播速度随之加快,同时臭氧分子浓度也由于氧原子产生速率的增大而增大。该研究可以为脉冲电源的选择和优化提供参考。

气液混合脉冲放电再生吸附苯酚的活性炭

采用多针-板鼓泡气液混合纳秒脉冲放电等离子体系统对吸附苯酚饱和的活性炭进行再生。考察了外加电压、初始溶液电导率、初始溶液pH以及活性炭与高压电极之间的距离对活性炭再生效果的影响,表征了放电处理后活性炭表面官能团的变化。实验结果表明:在高低压电极间距25 mm、初始溶液电导率5 μS/cm、初始溶液pH=6、活性炭与高压电极之间距离0 mm的条件下,活性炭再生效果最好,再生率为126%,能量效率为15.1 kg/(kW·h)。表征结果显示,再生炭表面的O—H、C=C、C=O、C—O等官能团的含量均增加。

霍山黄芽采摘加工技术

介绍了霍山黄芽鲜叶采摘、手工制作及机械炒制技术。

悬浮导体电极电晕放电凝并亚微米颗粒物研究

为提升亚微米颗粒物的凝并效果,提出在针-针高低压电极之间引入悬浮导体电极的结构,采用单极性直流高压电源供电,在悬浮导体电极两侧分别产生正、负电晕放电,实现对气体中亚微米颗粒物的荷电和凝并。研究了电极系统放电特性、颗粒物荷电量和凝并效果,以及电流体动力学模拟。研究结果表明:引入悬浮导体电极后,起晕电压、火花击穿电压略有增加,且在相同供电电压下电晕电流下降;在供电电压为15 kV的条件下,采用悬浮导体电极结构使颗粒物荷电量增加了10%,0.3μm和0.5μm粒径颗粒物的凝并效率分别增加了20%和35%;悬浮导体电极板开孔时凝并效果低于无开孔的悬浮电极板凝并效果,且随着悬浮导体电极开孔率增加亚微米颗粒物凝并效果下降。仿真结果表明引入悬浮导体电极后,增强了针尖区域内的离子风,增加了单个亚微米颗粒荷元电荷数,颗粒粒径越大荷元电荷数量提升越多;对于0.3μm的颗粒物,引入悬浮导体电极后荷电数量由195e提升至243e,荷电量提升了24%。

Experimental and simulated investigation of microdischarge characteristics in a pin-to-pin dielectric barrier discharge(DBD)reactor

Both experimental and simulated studies of microdischarge(MD)are carried out in a dielectric barrier discharge with a pin-to-pin gap of 3.5 mm,ignited by a sinusoidal voltage with a peak voltage of 10 kV and a driving frequency of 5 kHz.Statistical results have shown that the probability of the single current pulse in the positive half-period(HP)reaches 73.6%under these conditions.Experimental results show that great luminous intensity is concentrated on the dielectric surface and the tip of the metal electrode.A 1D plasma fluid model is implemented by coupling the species continuity equations,electron energy density equations,Poisson equation,and Helmholtz equations to analyze the MD dynamics on the microscale.The simulated results are in good qualitative agreement with the experimental results.The simulated results show that the MD dynamics can be divided into three phases:the Townsend phase,the streamer propagation phase,and the discharge decay phase.During the streamer propagation phase,the electric field and electron density increase with the streamer propagation from the anode to the cathode,and their maximal values reach 625.48 Td and 2.31×10^(19)m^(-3),as well as 790.13 Td and 3.58×10^(19)m^(-3)in the positive and negative HP,respectively.Furthermore,a transient glow-like discharge is detected around the anode during the same period of streamer propagation.The formation of transient glow-like discharge is attributed to electrons drifting back to the anode,which is driven by the residual voltage in the air gap.

Dynamic Characteristics of Positive Pulsed Dielectric Barrier Discharge for Ozone Generation in Air

A comprehensive dynamic model consisting of 66 reactions and 24 species is developed to investigate the dynamic characteristics of ozone generation by positive pulsed dielectric barrier discharge（DBD） using parallel-plate reactor in air.The electron energy conservation equation is coupled to the electron continuity equation,the heavy species continuity equation,and Poisson＇s equation for a better description.The reliability of the model is experimentally confirmed.The model can be used to predict the temporal and spatial evolution of species,as well as streamer propagation.The simulation results show that electron density increases nearly exponentially in the direction to the anode at the electron avalanche.Streamer propagation velocity is about 5.26×104m/s from anode to cathode in the simulated condition.The primary positive ion,negative ion,and excited species are O_2~＋,O_3^-and O_2（1？g） in pulsed DBD in air,respectively.N_2 O has the largest density among nitrogen oxides.e and N_2~＋densities in the streamer head increase gradually to maximum values with the development of the streamer.Meanwhile,the O_2~＋,O,O_3,N_2（A^3Σ） and N_2 O densities reach maximum values in the vicinity of the anode.

Research on corona discharge suppression of high-voltage direct-current transmission lines based on dielectric-film-covered conductor

Corona discharge suppression for high-voltage direct-current(HVDC)transmission lines at line terminals such as converter stations is a subject that requires attention.In this paper,a method based on a conductor covered with dielectric film is proposed and implemented through a bench-scale setup.Compared with the bare conductor,the corona discharge suppression effect of the dielectric-film-covered conductor under positive polarity is studied from the composite field strength and ion current density using a line-plate experimental device.The influences of film thickness and film material on the corona discharge suppression effect are investigated.The charge accumulation and dissipation characteristics of different film materials are also studied.The results show that the conductor covered with dielectric film has excellent ability to inhibit corona discharge.The ground-level composite field strength of the conductor covered with dielectric film is lower than its nominal field strength,and its ion current density is at the nA m^(−2) level.The corona threshold voltage can be promoted by increasing the film thickness,but the ability to inhibit corona discharge becomes weak.The larger the surface electric field strength,the more charge accumulated,but the faster the charge dissipation rate.Compared with polyvinyl chloride film,cross-linked polyethylene film has stronger charge accumulation ability and slower charge dissipation rate,which can better restrain the corona discharge of HVDC transmission lines.

Characteristic studies on positive and negative streamers of double-sided pulsed surface dielectric barrier discharge

The mechanisms of streamer generation and propagation in double-sided pulsed surface dielectric barrier discharge(SDBD)on both sides have been analyzed and investigated by experiment and numerical simulation.The fully exposed asymmetric SDBD has two discharge processes located on the high voltage electrode(HVE)side and the ground electrode(GE)side.Discharge images of the HVE side and GE side are taken by a digital camera under continuous pulse and ICCD(Intensified Charge Coupled Device)is utilized to diagnose the generation and propagation of streamers in single pulse discharge.In order to understand the physical mechanisms of streamer evolution more deeply,we establish a 2D simulation model and analyze it from the aspects of electron density,ion density,reduced electric field and electron impact ionization source term.The results show that the primary and secondary discharges on the HVE side and the GE side of the double-sided SDBD are composed of positive streamer and negative streamer,respectively.On the HVE side,the accumulation of positive charges on the dielectric surface causes the direction of the electric field to reverse,which is the principal factor for the polarity reversal of the streamer.On the GE side,both the negative charges accumulated on the dielectric surface and the falling voltage are the key factors for the streamer polarity switch.

翘片-筒式脉冲电晕流光放电装置对二氯甲烷的降解效果及其稳定性

传统结构线-筒式电晕放电装置在降解VOCs时生成的副产物会粘附在放电区域(线电极)上,使得放电间距减小,导致降解效果不稳定。翘片-筒式脉冲电晕流光放电等离子装置的电极结构可将放电区域(翘片尖端-筒)与副产物粘附区域(连接翘片的轴线)分开,从而维持装置的放电强度和稳定性。当翘片-筒式脉冲电晕流光放电反应器相邻翘片间距/放电间距为1,在37 kV下,反应器功率为0.95 W,能量体积密度为和23.6 mJ·L-1,为最优电极配置;处理二氯甲烷2 h后的降解效率呈现小幅度下降后稳定在35%。因此,放电形成的气溶胶部分沉积在凹槽处,可维持反应器稳定的放电强度及对二氯甲烷的降解效率。本研究结果可为低温等离子体处理VOCs废气的性能提升提供参考。