Reliability improvement of gas discharge tube by suppressing the formation of short-circuit pathways

After cumulative discharge of gas discharge tube(GDT),it is easy to form a short circuit pathway between the two electrodes,which increases the failure risk and causes severe influences on the protected object.To reduce the failure risk of GDT and improve cumulative discharge times before failure,this work aims to suppress the formation of two short-circuit pathways by optimizing the tube wall structure,the electrode materials and the electrode structure.A total of five improved GDT samples are designed by focusing on the insulation resistance change that occurs after the improvement;then,by combining these designs with the microscopic morphology changes inside the cavity and the differences in deposition composition,the reasons for the differences in the GDT failure risk are also analyzed.The experimental results show that compared with GDT of traditional structure and material,the method of adding grooves at both ends of the tube wall can effectively block the deposition pathway of the tube wall,and the cumulative discharge time before device failure is increased by 149%.On this basis,when the iron-nickel electrode is replaced with a tungsten-copper electrode,the difference in the electrode’s surface splash characteristics further extends the discharge time before failure by 183%.In addition,when compared with the traditional electrode structure,the method of adding an annular structure at the electrode edge to block the splashing pathway for the particles on the electrode surface shows no positive effect,and the cumulative discharge time before the failure of the two structures is reduced by 22.8%and 49.7%,respectively.Among these improved structures,the samples with grooves at both ends of the tube wall and tungsten-copper as their electrode material have the lowest failure risk.

Full-Spectrum Fluoromethyl Sulfonation via Modularized Multicomponent Coupling

Modular free-assembly construction of mono-,di-,and tri-fluoromethyl sulfones was comprehensively achieved by a combination of halides,a sulfur dioxide surrogate,and halofluorocarbons.The industrial raw material thiourea dioxide served as the sulfur dioxide source,combined with readily available fluorocarbon sources such as 2-bromo-2-fluoroacetate and chlorodifluoromethane(ClCF_(2)H,Freon)employed as fluoromethyl reagents.Notably,four methyl sulfone-containing pharmaceuticals were modified into three types of fluoromethyl sulfones,displaying their great potential for drug discovery via the current strategy.Mechanistic studies further demonstrated that C-F…H-N interactions between thiourea dioxide and halofluorocarbons play a key role in stabilizing monofluoromethyl electrophiles and difluorocarbene species.

Analysis of Conducted Disturbance via Current Transformer Due to Switch Operation of GIS Disconnector in UHV Substation

The characteristics of conducted disturbances via current transformer(CT)caused by switch operations in 1000 kV UHV substations are studied in this paper.Since the broadband circuit models might have limitations on the stability and accuracy for CT conducted disturbance simulation,a frequencydomain simulation method without circuit synthesis is proposed based on VFTC spectrum and CT transfer characteristics.To improve VFTC simulation accuracy,both the bushing radiation loss and frequency-dependent earth impedance are taken into consideration.Transfer characteristics of three types of windings for the 1000 kV GIS CT are ingeniously measured from a combination of fast and slow impulse tests.Through conducted disturbances simulations in UHV Wuhu substation,bushing radiation loss is found to have a suppression effect on the highfrequency response but the effect of frequency-dependent earth impedance can be ignored.As a result,the maximum amplitude of 84.5 A for the conducted disturbance is obtained,thus a fast damped oscillatory wave immunity test with no lower than Level 4 from IEC standard is suggested to test the anti-interference performance of the secondary equipment in UHV substation.

Dispersion characteristics of switching transients from large‐scale experiments in a 1100 kV gas insulated switchgear circuit

The switching operation of gas insulated switchgear(GIS)disconnector will produce multiple random spark discharges between the gas gaps of the disconnector.Each spark discharge can be affected by various random factors,such as trapped charge on the load side,the initial operating phase,gap distance and operating speed of the disconnector,leading to dispersion characteristics.At present,some studies have mentioned this dispersion,but its impact is still unclear due to the lack of experimental data,resulting in a deviation between the simulation results and the measured results.In this study,thousands of switching operations were carried out based on the 1100 kV full‐scale GIS circuit in Wuhan ultra‐high voltage alternating current Test Base.The maximal information coeffi-cient analysis,linear regression fitting and other statistical methods were used to discuss the dispersion characteristics of very fast transient overvoltage(VFTO)and transient enclosure voltage(TEV)from large‐scale experimental data.The results show that the dispersion of VFTO and TEV in amplitude aspects both increase gradually as the breakdown voltage increases,with the maximum difference of five times of TEV amplitude at normalised breakdown voltage.In terms of frequency characteristics,the dispersion of different fre-quency components in TEV is always greater than that of VFTO,especially for the high‐frequency components.Moreover,by comparing the frequency characteristics of TEV at different positions,we notice that the dispersion is almost independent of the spatial po-sition but only determined by the randomness of spark discharges.These discoveries reveal the importance of the dispersion in switching transients and make up for the lack of theoretical understanding of the correlation among them.

家蚕CRISPR/Cpf1基因编辑系统建立

自CRISPR/Cas9基因编辑系统成功应用于模式生物以来,因其快速、高效、便捷等特点,广泛应用于基因功能研究、基因治疗和基因工程等研究领域。与此同时,CRISPR/Cas系统不断在微生物界的发现也加速了新的基因编辑工具的不断涌现。CRISPR/Cpf1是第二类(Ⅴ型)能够编辑哺乳动物基因组的CRISPR系统,相比于CRISPR/Cas9基因编辑系统,能够利用5′T-PAM富集区增加基因组覆盖率,具有其切割位点为粘性末端和更不易同源重组修复等诸多优势。基于此,本研究构建了能够在家蚕细胞表达的3个不同来源的CRISPR/Cpf1 (AsCpf1、FnCpf1和LbCpf1)表达载体,选择高度保守的家蚕热休克蛋白基因BmHSP60和家蚕ATP酶家族BmATAD3A基因分别设计靶标gRNA,构建gHSP60-266R和gATAD3A-346R基因编辑载体。通过T7E1酶切分析和T克隆测序,鉴定3个Cpf1基因编辑系统AsCpf1、FnCpf1和LbCpf1对靶标基因BmHSP60和BmATAD3A的编辑效率。同时,利用Western blotting分析不同基因编辑系统敲除靶基因后对其BmATAD3A和BmHSP60蛋白翻译的影响。本研究成功构建了家蚕CRISPR/Cpf1基因编辑系统,能够在家蚕细胞中有效编辑家蚕基因组,为家蚕基因功能研究、基因工程和遗传育种开发了新技术与新方法。