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Multiple discharges before leader inception in long air gaps under positive switching impulses

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High Voltage 2023年第1期8卷 111-118页

作者： Xiangen Zhao Juhyeong Lee Gang Liu Lei Jia Yang Liu Junjia He Yaping Du Department of Building Environment and Energy Engineering The Hong Kong Polytechnic UniversityHung HomHong KongChina Department of Mechanical and Aerospace Engineering Utah State UniversityLoganUtahUSA State Key Laboratory of HVDC Transmissions Technology Electric Power Research InstituteChina Southern Power GridGuangzhouChina State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and TechnologyWuhanChina

There are multiple corona bursts before leader inception when the rising rate of the applied voltage or electric field is not sufficiently high enough in long positive sparks.In existing studies,no attention has been paid to whether these corona bursts occur in the same location,and they are mostly considered directly as belonging to the same discharge.However,this paper presents that in a typical rod-plate long air gap,the multiple corona bursts before leader inception are distributed in at least two different locations,and the highest probability of three discharges occurs.Also,the discharge occurs with the highest probability in the time sequence‘tip-tip-side-tip-other side’of the electrode in the first five corona bursts.For each discharge,the first corona current is a single,double exponential pulse,while the following corona currents are mostly a superposition of multiple pulses.The above findings are mainly based on experiments in a 1.4 m air gap under positive switching impulses,in which the voltage,current,and high-speed images were recorded simultaneously.Finally,based on the experimental results,this paper discusses the effects brought by ignoring the multiple discharges on key parameters of leader inception and makes some suggestions to optimise long spark experiments.

关键词： positive exponential superposition

Influence of positive DC electric field on rime icing on the insulator and its experimental verification in the natural environment

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High Voltage 2023年第5期8卷 954-966页

作者： Zongyuan Liu Yuyao Hu Xingliang Jiang Lei Chen Mingchen Chi Feiyan Han Chong Zhao College of Electrical and Electronic Engineering Shandong University of TechnologyZiboChina State Key Laboratory of Power Transmission Equipment&System Security and New Technology Chongqing UniversityChongqingChina

The electric field imposes a significant effect on ice accretion on the insulator.The impact of an AC electric field on insulator icing in an artificial climate chamber has been addressed.Compared with AC,DC electric field exerts an attraction on supercooled water droplets,which is more detrimental to the power system.Moreover,the icing on energised insulators is rarely studied in the natural environment.In the present research,an electrical,fluid coupled‐field simulation was carried out on the insulator.The force characteristics and motion deviation features of water droplets at different positive DC electric field strengths were studied.On this basis,rime icing on the insulator energised with different positive DC voltages was investigated in the field.Results show that the charged droplet shifts along the electric field line under a positive DC voltage.The deviation degree of the droplet increases with the increment of the voltage and droplet size and decreases with an increase in wind speed.As the voltage rises,the surface roughness,icing amount and icing length of rime ice‐covered insulator increase.Consequently,compared with that without energisation,the local collision coefficient,icing amount and icing length increase by 17.6%,46.4%and 63.9%,respectively,under a 40 kV DC voltage.

关键词： insulator field positive

Urbanization: positive and negative effects

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Science Bulletin 2019年第5期64卷 281-283页

作者： Chaolin Gu School of Architecture Tsinghua University

Urbanization is a sign of modernization,and both developed and developing countries attach great importance to this issue.It is also a process in which the population continues to flow in urban areas,the non-agricultural industries(manufacturing and seivice industries)concentrate and develop,and the structure of human society gradually transforms.Urbanization drives economic development.changes the urban form,and in fluences production technologies,citizen lifestyles,and societal values.However,urbanization can have negative impacts on social equity,public health,and the natural environment.Leveraging the positive effects of urbanization while mitigating the negative effects is necessary for sustaining urban progress and improving human settlements.Otherwise,the"urban disease"and regional inequalities caused by urbanization will become increasingly severe,especially in rapidly urbanizing countries.

关键词： Urbanization positive negative effects

Effect of High positive Acceleration(+Gz) Environment on Dental Implant Osseointegration:A Preliminary Animal Study

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Biomedical and Environmental Sciences 2019年第9期32卷 687-698页

作者： ZHU Xiao Ru DENG Tian Zheng PANG Jian Liang LIU Bing KE Jie Department of Stomatology Air Force Medical Center PLA

Objective To observe the effect of high positive acceleration(+Gz) environment on dental implant osseointegration in a rabbit model and to investigate its mechanism.Methods Forty-eight New Zealand white rabbits were randomly divided into 6 groups. The rabbit’s mandibular incisors were extracted and 1 implant was placed in each socket immediately. After 1 week of rest, the rabbits were exposed to a high +Gz environment, 3 times a week. The rabbits were sacrificed at 3 weeks(2 weeks +Gz exposure), 5 weeks(4 weeks +Gz exposure), and 12 weeks(4 weeks +Gz exposure and 7 weeks normal environment) after surgery, respectively. Specimens were harvested for micro-CT scanning, histological analysis, and real-time polymerase chain reaction examination.Results Compared with those in the control group, the mRNA expression levels of bone morphogenetic protein-2(BMP-2), osteopontin(OPN), and transforming growth factor-β1(TGF-β1)were significantly lower(P < 0.05), while the mRNA expression level of receptor activator of nuclear factor κB ligand(RANKL) and the RANKL/osteoprotegerin(OPG) ratio were significantly higher(P < 0.05)at 3 weeks;values of bone volume fraction, trabecular number, bone-implant contact(BIC), and TGF-β1 and OPG mRNA expression levels were significantly lower(P < 0.05), and the value of trabecular separation, RANKL mRNA expression level and RANKL/OPG ratio were significantly higher(P < 0.05) at 5 weeks;and the value of BIC was still significantly lower(P < 0.05) at 12 weeks in the experimental group.Conclusion Early exposure to the high +Gz environment after implant surgery might have an adverse effect on osseointegration, and its mechanism could be related to the inhibition of osteoblast activity and promotion of osteoclast activity.

关键词： positive acceleration Osseointegration Dental implant Micro-CT Real-time polymerase chain reaction Osteoblast

Development and validation of a preoperative nomogram for predicting positive surgical margins after laparoscopic radical prostatectomy

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Chinese Medical Journal 2019年第8期132卷 928-934页

作者： Xiao-Jun Tian Zhao-Lun Wang Geng Li Shuang-Jie Cao Hao-Ran Cui Zong-Han Li Zhuo Liu Bo-Lun Li Lu-Lin Ma Shen-Rong Zhuang Qi-Yan Xiao Department of Urology Peking University Third HospitalBeijing 100191China Peking University First Medical School Peking University First HospitalBeijing 100034China Peking University Second Medical School Peking University People's HospitalBeijing 100044China Institute of Biomedical English Peking University Health Science CenterBeijing 100191China Key Laboratory of Carcinogenesis and Translational Research(Ministry of Education) Peking University Cancer Hospital and InstituteBeijing 100142China

Background:positive surgical margins are independent risk factor for biochemical recurrence,local recurrence,and distant metastasis after radical prostatectomy.However,limited predictive tools are available.This study aimed to develop and validate a preoperative nomogram for predicting positive surgical margins after laparoscopic radical prostatectomy(LRP).Methods:From January 2010 to March 2016,a total of 418 patients who underwent LRP without receiving neoadjuvant therapy at Peking University Third Hospital were retrospectively involved in this study.Clinical and pathological results of each patient were collected for further analysis.Univariable and multivariable logistic regression(backward stepwise method)were used for the nomogram development.The concordance index(CI),calibration curve analysis and decision curve analysis were used to evaluate the performance of our model.Results:Of 418 patients involved in this study,142 patients(34.0%)had a positive surgical margin on final pathology.Based on the backward selection,four variables were included in the final multivariable regression model,including the percentage of positive cores in preoperative biopsy,clinical stage,free prostate specific antigen(fPSA)/total PSA(tPSA),and age.A nomogram was developed using these four variables.The concordance index(C-index)of the nomogram was 0.722 in the development cohort and 0.700 in the bootstrap validations.The bias-corrected calibration plot showed a limited departure from the ideal line with a mean absolute error of 2.0%.In decision curve analyses,the nomogram showed net benefits in the range from 0.2 to 0.7.Conclusion:A nomogram to predict positive surgical margins after LRP was developed and validated,which could help urologists plan surgical procedures.

关键词： Prostate cancer positive surgical margins Laparoscopic radical prostatectomy Nomogram

Improvement of the electrical resistivity of epoxy resin at elevated temperature by adding a positive temperature coefficient BaTiO3-based compound

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Plasma Science and Technology 2020年第4期22卷 15-23页

作者：滕陈源周文俊周远翔张灵张云霄周仲柳李文鹏 School of Electrical Engineering and Automation Wuhan UniversityWuhan 430072People's Republic of China China State Key Laboratory of Power System and Generation Equipment Department of Electrical EngineeringTsinghua UniversityBeijing 100084People's Republic of China School of Electrical Engineering Xinjiang UniversityUrumqi 830047People's Republic of China State Key Laboratory of Advanced Power Transmission Technology Global Energy Interconnection Research Institute CorporationBeijing 102211People’s Republic of China

The DC electrical resistivity-temperature characteristic is an important property for insulating materials to operate at a high stress level.In order to improve the DC electrical resistivity at elevated temperature in a targeted way,a positive temperature coefficient(PTC)material(Ba Ti O3-based compound(BT60))was selected as the filler in this paper,whose electrical resistivity has a PTC effect when the temperature exceeds its Curie temperature.The BT60 was treated with hydrogen peroxide and(3-Aminopropyl)triethoxysilane.Epoxy composites with different loadings of BT60 fillers(0 wt%,0.5 wt%,and 2 wt%of epoxy)were prepared,denoted as EP-0,EP-0.5,and EP-2.It was shown that BT60 was able to maintain the DC breakdown strength when its loading was less than 2 wt%of epoxy.As the temperature exceeds 60°C,BT60 will compensate for the negative temperature coefficient effect of epoxy resin to some extent.The electrical resistivity of EP-2 was improved by 55%compared with that of neat epoxy at 90°C.It was found that the potential barrier at the grain boundary of BT60 and the deep traps in the interface between BT60 and the epoxy resin hinder the migration of carriers and thus increase the electrical resistivity of epoxy composite.

关键词： epoxy resin positive temperature coefficient barium titanate based compounds resistivity-temperature characteristics traps

Stability and Robust Stability of Switched positive Linear Systems With All Modes Unstable

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IEEE/CAA Journal of Automatica Sinica 2019年第1期6卷 167-176页

作者： Shaoxia Feng Juan Wang Jun Zhao Shanxi Institute of Mechanical and Electrical Engineering the College of Information Scienceand Engineering Northeastern University the Faculty of Information and Control Engineering Shenyang Jianzhu University the State Key Laboratory of Synthetical Automationfor Process Industries (Northeastern University) the Collegeof Information Science and Engineering Northeastern University

This paper is concerned with the stability and robust stability of switched positive linear systems(SPLSs) whose subsystems are all unstable. By means of the mode-dependent dwell time approach and a class of discretized co-positive Lyapunov functions, some stability conditions of switched positive linear systems with all modes unstable are derived in both the continuous-time and the discrete-time cases, respectively. The copositive Lyapunov functions constructed in this paper are timevarying during the dwell time and time-invariant afterwards. In addition, the above approach is extended to the switched interval positive systems. A numerical example is proposed to illustrate our approach.

关键词： Discretized co-positive Lyapunov functions mode-dependent dwell time robust stability switched positive linear systems (SPLSs) unstable subsystem

Discovery of a novel EGFR ligand DPBA that degrades EGFR and suppresses EGFR-positive NSCLC growth

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Signal Transduction and Targeted Therapy 2020年第1期5卷 495-507页

作者： Nan Yao Chen-Ran Wang Ming-Qun Liu Ying-Jie Li Wei-Min Chen Zheng-Qiu Li Qi Qi Jin-Jian Lu Chun-Lin Fan Min-Feng Chen Ming Qi Xiao-Bo Li Jian Hong Dong-Mei Zhang Wen-Cai Ye College of Pharmacy Jinan UniversityGuangzhouChina Guangdong Province Key Laboratory of Pharmacodynamic Constituents of Traditional Chinese Medicine and New Drugs Research Jinan UniversityGuangzhouChina School of Medicine Jinan UniversityGuangzhouChina State Key Laboratory of Quality Research in Chinese Medicine Institute of Chinese Medical SciencesUniversity of MacaoMacaoChina

Epidermal growth factor receptor(EGFR)activation plays a pivotal role in EGFR-driven non-small cell lung cancer(NSCLC)and is considered as a key target of molecular targeted therapy.EGFR tyrosine kinase inhibitors(TKIs)have been canonically used in NSCLC treatment.However,prevalent innate and acquired resistances and EGFR kinase-independent pro-survival properties limit the clinical efficacy of EGFR TKIs.Therefore,the discovery of novel EGFR degraders is a promising approach towards improving therapeutic efficacy and overcoming drug resistance.Here,we identified a 23-hydroxybetulinic acid derivative,namely DPBA,as a novel EGFR small-molecule ligand.It exerted potent in vitro and in vivo anticancer activity in both EGFR wild type and mutant NSCLC by degrading EGFR.Mechanistic studies disclosed that DPBA binds to the EGFR extracellular domain at sites differing from those of EGF and EGFR.DPBA did not induce EGFR dimerization,phosphorylation,and ubiquitination,but it significantly promoted EGFR degradation and repressed downstream survival pathways.Further analyses showed that DPBA induced clathrin-independent EGFR endocytosis mediated by flotillin-dependent lipid rafts and unaffected by EGFR TKIs.Activation of the early and late endosome markers rab5 and rab7 but not the recycling endosome marker rab11 was involved in DPBA-induced EGFR lysosomal degradation.The present study offers a new EGFR ligand for EGFR pharmacological degradation and proposes it as a potential treatment for EGFR-positive NSCLC,particularly NSCLC with innate or acquired EGFR TKI resistance.DPBA can also serve as a chemical probe in the studies on EGFR trafficking and degradation.

关键词： NSCLC EGFR positive

CHIT1-positive microglia act as culprits for spinal motor neuron aging

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Science China(Life Sciences) 2024年第4期67卷 847-848页

作者： Zhao Wang Wantong Cai Weihong Song Oujiang Laboratory(Zhejiang Lab for Regenerative Medicine Vision and Brain Health)Institute of AgingKey Laboratory of Alzheimer’s Disease of Zhejiang ProvinceThe Second Affiliated HospitalWenzhou Medical UniversityWenzhou 325035China

Aging is one of the primary factors in spinal cord-associated disorders(Roberts,1990).However,the effects of aging on the spinal cord and the age-specific mechanisms underlying this relationship remain unclear.Motor n... 详细信息

关键词： aging Roberts positive