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High Voltage 2023年第6期8卷 1264-1274页

作者： Xiaotong Zhang Zhuolin Cheng Xing Sun kangning wu Jianying Li State Key Laboratory of Electrical Insulation and Power Equipment Xi'an Jiaotong UniversityXi'anChina

The direct bonding copper(DBC)substrates of insulated gate bipolar transistor(IGBT)modules degrade inevitably under cycling thermo‐mechanical stress,causing potential threat to the reliability of IGBT modules.However,little attention has been paid to monitoring their degradation.This paper proposes a DBC degradation monitoring method for IGBT modules,which combines boundary‐dependent thermal network and feedback control.A thermal network is employed to describe the internal material degradation of IGBT modules and can be extracted from a finite‐element method model.The boundary conditions including power losses and DBC degradation are considered,enabling the thermal network suitable for various working conditions and different DBC degradation conditions of IGBT modules.The DBC degradation is characterised by its equivalent thermal conductivities measured in the thermal cycling ageing experiments.On the basis of the boundary‐dependent thermal network,feedback control is applied to monitor DBC degradation by regulating boundary‐dependent thermal impedances.Finally,the proposed model is verified from the effectiveness and accuracy of DBC degradation monitoring and junction temperature calculation.This method casts new light on thermal network modelling and could provide a feasible method for the monitoring of DBC degradation.

关键词： network bipolar transistor

Significantly enhanced varistor properties of CaCu_(3)Ti_(4)O_(12) based ceramics by designing superior grain boundary:Deepening and broadening interface states

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Journal of Materials Science & Technology 2022年第13期108卷 82-89页

作者： Zhuang Tang Kai Ning Zhiyao Fu Ze Lian kangning wu Shoudao Huang State Key Laboratory of Disaster Prevention and Reduction for Power Grid Transmission and Distribution Equipment SGCC(State Grid Corporation of China)Changsha 410000China College of Electrical and Information Engineering Hunan UniversityChangsha 410082China State Grid Shanxi Electric Power Research Institute Taiyuan 030001China State Key Laboratory of Electrical Insulation and Power Equipment Xi'an Jiaotong UniversityXi’an 710049China

Significantly enhanced varistor properties via tailoring interface states were obtained in Ca_(1-2x/3)Y_(x)Cu_(3)Ti_(4)O_(12)-SrCu_(3)Ti_(4)O_(12) composite ceramics.The breakdown field was improved to 35.8 kV cm^(-1) and the nonlinear coefficient in 0.1-1 mA cm^(-2) was enhanced to 14.6 for Ca_(0.67)Y_(0.5)Cu_(3)Ti_(4)O_(12)-SrCu_(3)Ti_(4)O_(12).Noticeably,the withstand voltage of single grain boundary reached up to 24 V while the reported ones were constant to about 3 V.Greatly improved properties were attributed to the formation of superior grain boundary rather than the reduced grain size.Surprisingly,with distinct discrepancy of nonlinear performance in the composites,the resistance and activation energy of grain boundary exhibited little differences.Based on the double Schottky barrier at grain boundary and the field-assisted thermal emission model,it was found that the excellent electrical nonlinearity arose from the formation of deeper and broader interface states at grain boundary.In this case,interface states were not easily entirely filled and the barrier could maintain its height under applied voltage.This work provides a novel routine for enhancing the varistor properties of CaCu_(3)Ti_(4)O_(12) based ceramics by manipulating interface states at grain boundary.

关键词： Schottky barrier Grain boundary Varistor ceramics Interface states

Power loss transition of stable ZnO varistor ceramics: Role of oxygen adsorption on the stability of interface states at the grain boundary

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Journal of Advanced Ceramics 2023年第5期12卷 972-983页

作者： Zhuolin Cheng Rou Li Yiwei Long Jianying Li Shengtao Li kangning wu State Key Laboratory of Electrical Insulation and Power Equipment Xi’an Jiaotong UniversityXi’an 710049China Department of Thermal and Fluid Engineering University of TwenteEnschede 7500AEthe Netherlands

Highly stable ZnO varistor ceramics with steadily decreasing power loss have been put into applications in electrical and electronic systems for overvoltage protections, even with the absence of general understandings on their aging behaviors. In this paper, we investigated their aging nature via conducting comparative direct current (DC) aging experiments both in air and in nitrogen, during which variations of electrical properties and interface properties were measured and analyzed. Notably, continuously increasing power loss with severe electrical degradation was observed for the sample aged in nitrogen. The power loss transition was discovered to be closely related to the consumption of oxygen adsorption at the grain boundary (GB), which could, however, remain constant for the sample aged in air. The interface density of states (DOS) Ni, which is crucial for pinning the potential barrier, was proved to decrease in nitrogen, but keep stable in air. Therefore, it is concluded that the oxygen adsorption at the GB is significant for the stability of interface states, which further correlates to the long-term stability of modern stable ZnO varistor ceramics.

关键词： ZnO varistor ceramics aging power loss oxygen adsorption interface states

Correlation between antioxidant depletion kinetic model and ageing behaviour of cross-linked polyethylene cable insulation

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High Voltage 2023年第2期8卷 231-238页

作者： Yingying Zheng Yiwei Long Delun Yi Haoran Zhang Jian Gao kangning wu Jianying Li State Key Laboratory of Electrical Insulation and Power Equipment Xi'an Jiaotong UniversityXi'anShaanxiChina

A concise kinetic model catering for the antioxidant reaction of thermally aged crosslinked polyethylene(XLPE)cable insulation before its abrupt performance deterioration is proposed for life prediction and condition assessment.The alternating current breakdown strength,elongation at break,carbonyl index,and pyrolysis activation energy of XLPE insulation are found to consistently display an abrupt change at a certain point of ageing time.This is strongly correlated to the depletion of the antioxidant whose content gradually decreases with ageing time and drops to a critical value,after which the abrupt degradation of the above macroscopic performances happens.Based on the simplified chain reactions of XLPE during thermal-oxidative ageing,a concise kinetic model about antioxidant prediction is accordingly established by solving the chemical kinetics equations.It indicates that the antioxidant content decays with the reciprocal of time before the abrupt degradation occurs.Results of antioxidant content predicted by the kinetic model at different temperatures matches well with the experimental results,and its reliability can also be proved by the Arrhenius relationship of the obtained results.The kinetic model proposed herein demonstrates satisfying conciseness and thus can be highly feasible in ageing condition assessment and life predicting of XLPE insulation.

关键词： kinetic insulation depletion

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究竟什么样的人可称为“教育家”

教育发展研究 2024年第4期44卷 1-8页

作者：吴康宁南京师范大学中国教育改革与发展研究院南京师范大学教育社会学研究中心南京210097

区别于“教育工作者”这一概念,汉语中的“教育家”是对极小部分教育工作者的一种尊称。教育本身是一种实践,而不是一种理论。教育家说到底必须是教育实践方面而不必是教育理论方面的“家”。单纯的教育理论工作者、单纯的教育学者很难... 详细信息

区别于“教育工作者”这一概念,汉语中的“教育家”是对极小部分教育工作者的一种尊称。教育本身是一种实践,而不是一种理论。教育家说到底必须是教育实践方面而不必是教育理论方面的“家”。单纯的教育理论工作者、单纯的教育学者很难称得上教育家。教育家应该是教育实践领域中有创见、有贡献、有影响的杰出人物。不论官方授予称号还是民间赋予称谓,都需要考虑人们心中的那杆秤,需要顾及现实语境中占主导地位的“接受心理”,不宜过于随意,门槛不宜过低。真正意义上的教育家不是“培养”出来的,而是具有“教育家天赋”的人在良好的制度与文化土壤中通过长期教育实践的滋养、锤炼乃至考验“生长”出来的。作为教育实践人才金字塔之塔尖部分的“教育家队伍”的规模十分有限,“我们需要成千上万的教育家”这样的说法有罔顾可能、用力过猛之嫌。在认识、判断乃至推动教育家队伍的形成与发展问题上需要有足够的理性。

关键词：教育家教育实践卓尔不凡教育家型教师

重提一个命题:国家课程的实践命运——以“校长对国家课程的地位赋予”为例

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当代教育科学 2024年第2期 3-8页

作者：吴康宁南京师范大学中国教育改革与发展研究院、教育社会学研究中心

研究国家课程,不仅要研究国家课程本身(课程方案、课程标准、教材等),而且要研究国家课程的“实践命运”,审视国家课程在学校中究竟得到怎样的实施、实施效果究竟如何、倘若实施效果不佳乃至较差则究竟是何原因等。笔者近三十年前曾提... 详细信息

研究国家课程,不仅要研究国家课程本身(课程方案、课程标准、教材等),而且要研究国家课程的“实践命运”,审视国家课程在学校中究竟得到怎样的实施、实施效果究竟如何、倘若实施效果不佳乃至较差则究竟是何原因等。笔者近三十年前曾提出“课程的实践命运”这一命题(其确切表达即为“国家课程的实践命运”),并对影响国家课程实践命运的教师因素与学生因素进行了初步探讨。本文现在重提这一命题,认为影响国家课程实践命运的学校内部因素主要有三个,即作为课程实施主体的校长、作为课程施教主体的教师及作为课程学习主体的学生;其影响分别体现为校长对国家课程的“地位赋予”、教师对国家课程的“内容重组”、学生对国家课程的“文化反应”。在三十年前探讨的基础上,本文聚焦于作为课程实施主体的校长,指出不论在“积极”的意义上,还是在“消极”的意义上,校长都对国家课程在本校课程系统中的实际地位进行着事实上的“赋予”。这是我们认识、审视及反思国家课程实施乃至国家课程本身时不可忽略的一个基本常识。这意味着,国家课程在学校中安身立命并非易事,国家课程在学校中的地位充满不确定性,对于国家课程本身需要边实施、边反思。

关键词：国家课程主体地位实践命运本校课程系统地位赋予

Cobalt doping amount determines dominant reactive species in peroxymonosulfate activation via porous carbon catalysts co-doped by cobalt and nitrogen

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Journal of Environmental Sciences 2024年第4期138卷 212-226页

作者： Xiang Li Limeng wu Aiqin Zhang Shaohua wu Yan Lin Chunping Yang Key Laboratory of Jiangxi Province for Persistent Pollutants Control and Resources Recycle Nanchang Hangkong UniversityNanchang 330063China Academy of Environmental and Resource Sciences School of Environmental Science and EngineeringGuangdong University of Petrochemical TechnologyMaoming 525000China College of Environmental Science and Engineering Hunan University and Key Laboratory of Environmental Biology and Pollution Control(Hunan University)Ministry of EducationChangsha 410082China

Switching the reaction routes in peroxymonosulfate(PMS)-based advanced oxidation processes have attracted much attention but remain challenging.Herein,a series of Co-N/C catalysts with different compositions and structures were prepared by using bimetallic zeolitic imidazolate frameworks based on ZIF-8 and ZIF-67(x Zn/Co-ZIFs).Results show that Co doping amount could mediate the transformation of the activation pathway of PMS over CoN/C.When Co doping amount was less than 10%,the constructed x Co-N/C/PMS system(x≤10%)was singlet oxygen-dominated reaction;however further increasing Co doping amount would lead to the generation and coexistence of sulfate radicals and high-valent cobalt,besides singlet oxygen.Furthermore,the nitrogen-coordinated Co(Co-NX)sites could serve as main catalytically active sites to generate singlet oxygen.While excess Co doping amount caused the formation of Co nanoparticles from which leached Co ions were responsible for the generation of sulfate radicals and high-valent cobalt.Compared to undoped N/C,Co doping could significantly enhance the catalytic performance.The 0.5%Co-N/C could achieve the optimum degradation(0.488 min^(-1))and mineralization abilities(78.4%)of sulfamethoxazole among the investigated Co-N/C catalysts,which was superior to most of previously reported catalysts.In addition,the application prospects of the two systems in different environmental scenarios(pH,inorganic anions and natural organic matter)were assessed and showed different degradation behaviors.This study provides a strategy to regulate the reactive species in PMS-based advanced oxidation process.

关键词： Peroxymonosulfate Sulfate radical Singlet oxygen Cobalt Zeolitic imidazolate framework Advanced oxidation process

The physiological role of the unfolded protein response in the nervous system

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Neural Regeneration Research 2024年第11期19卷 2411-2420页

作者： Shuangchan wu Wensheng Lin Department of Neuroscience University of MinnesotaMinneapolisMNUSA Institute for Translational Neuroscience University of MinnesotaMinneapolisMNUSA

The unfolded protein response(UPR)is a cellular stress response pathway activated when the endoplasmic reticulum,a crucial organelle for protein folding and modification,encounters an accumulation of unfolded or misfolded proteins.The UPR aims to restore endoplasmic reticulum homeostasis by enhancing protein folding capacity,reducing protein biosynthesis,and promoting protein degradation.It also plays a pivotal role in coordinating signaling cascades to determine cell fate and function in response to endoplasmic reticulum stress.Recent research has highlighted the significance of the UPR not only in maintaining endoplasmic reticulum homeostasis but also in influencing various physiological processes in the nervous system.Here,we provide an overview of recent findings that underscore the UPR’s involvement in preserving the function and viability of neuronal and myelinating cells under physiological conditions,and highlight the critical role of the UPR in brain development,memory storage,retinal cone development,myelination,and maintenance of myelin thickness.

关键词： myelin neuron oligodendrocyte Schwann cell unfolded protein response

LONP1 ameliorates liver injury and improves gluconeogenesis dysfunction in acute-on-chronic liver failure

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Chinese Medical Journal 2024年第2期137卷 190-199页

作者： Muchen wu Jing wu Kai Liu Minjie Jiang Fang Xie Xuehong Yin Jushan wu Qinghua Meng Department of Liver Disease Beijing You-An HospitalCapital Medical UniversityBeijing 100069China Beijing Institute of Hepatology Beijing You-An HospitalCapital Medical UniversityBeijing 100069China Department of General Surgery Beijing You-An HospitalCapital Medical UniversityBeijing 100069China

Background:Acute-on-chronic liver failure(ACLF)is a severe liver disease with complex pathogenesis.Clinical hypoglycemia is common in patients with ACLF and often predicts a worse prognosis.Accumulating evidence suggests that glucose metabolic disturbance,especially gluconeogenesis dysfunction,plays a critical role in the disease progression of ACLF.Lon protease-1(LONP1)is a novel mediator of energy and glucose metabolism.However,whether gluconeogenesis is a potential mechanism through which LONP1 modulates ACLF remains unknown.Methods:In this study,we collected liver tissues from ACLF patients,established an ACLF mouse model with carbon tetrachloride(CCl 4),lipopolysaccharide(LPS),and D-galactose(D-gal),and constructed an in vitro hypoxia and hyperammonemia-triggered hepatocyte injury model.LONP1 overexpression and knockdown adenovirus were used to assess the protective effect of LONP1 on liver injury and gluconeogenesis regulation.Liver histopathology,biochemical index,mitochondrial morphology,cell viability and apoptosis,and the expression and activity of key gluconeogenic enzymes were detected to explore the underlying protective mechanisms of LONP1 in ACLF.Results:We found that LONP1 and the expressions of gluconeogenic enzymes were downregulated in clinical ACLF liver tissues.Furthermore,LONP1 overexpression remarkably attenuated liver injury,which was characterized by improved liver histopathological lesions and decreased serum alanine aminotransferase(ALT)and aspartate aminotransferase(AST)in ACLF mice.Moreover,mitochondrial morphology was improved upon overexpression of LONP1.Meanwhile,the expression and activity of the key gluconeogenic enzymes were restored by LONP1 overexpression.Similarly,the hepatoprotective effect was also observed in the hepatocyte injury model,as evidenced by improved cell viability,reduced cell apoptosis,and improved gluconeogenesis level and activity,while LONP1 knockdown worsened liver injury and gluconeogenesis disorders.Conclusion:We demonstrated that gluconeogenesis dysfunc

关键词： Acute-on-chronic liver failure Lon protease-1 Gluconeogenesis disturbance Mitochondrial dysfunction Metabolism

Ballistic performances of the hourglass lattice sandwich structures under high-velocity fragments

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Defence Technology（防务技术） 2024年第1期31卷 312-325页

作者： He-xiang wu Jia Qu Lin-zhi wu Key Laboratory of Advanced Ship Materials and Mechanics College of Aerospace and Civil EngineeringHarbin Engineering UniversityHarbin150001China School of Civil Engineering Northeast Forestry UniversityHarbin150040China

In this paper,the numerical simulation method is used to study the ballistic performances of hourglass lattice sandwich structures with the same mass under the vertical incidence of fragments.Attention is paid to elucidating the influences of rod cross-section dimensions,structure height,structure layer,and rod inclination angle on the deformation mode,ballistic performances,and ability to change the ballistic direction of fragments.The results show that the ballistic performances of hourglass lattice sandwich structures are mainly affected by their structural parameters.In this respect,structural parameters optimization of the hourglass lattice sandwich structures enable one to effectively improve their ballistic limit velocity and,consequently,ballistic performances.

关键词： Hourglass lattice sandwich structures Ballistic performances high-velocity Finite element analysis