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Asymmetrical Fault Current Calculation Method and Influencing Factors Analysis of Droop-Controlled Inverters

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 562-573页

作者： Huimin Zhao Zhikang Shuai jun ge An Luo Weimin Wu Z.John Shen College of Electrical and Information Engineering Hunan UniversityChangsha 410006China Electrical Engineering Department Shanghai Maritime UniversityShanghai 201306China Department of Electrical and Computer Engineering Ilinois Institute of TechnologyChicagoIL 60616 USA

Since the fault dynamic of droop-controlled inverter is different from synchronous generators (SGs), protection devices may become invalid, and the fault overcurrent may damage power electronic devices and threaten the safety of the microgrid. Therefore, it is imperative to conduct a comprehensive fault analysis of the inverter to guide the design of protection schemes. However, due to the complexity of droop control strategy, existing literatures have simplified asymmetric fault analysis of droop-controlled inverters to varying degrees. Therefore, accurate fault analysis of a droop-controlled inverter is needed. In this paper, by analyzing the control system, an accurate fault model is established. Based on this, a calculation method for instantaneous asymmetrical fault current is proposed. In addition, the current components and current characteristics are analyzed. It was determined that fault currents are affected by control loops, fault types, fault distance and nonlinear limiters. In particular, the influences of limiters on the fault model, fault current calculation and fault current characteristics were analyzed. Through detailed analysis, it was found that dynamics of the control loop cannot be ignored, the fault type and fault distance determine fault current level, and part of the limiters will totally change the fault current trend. Finally, calculation and experimental results verify the correctness of the proposed method.

关键词： Asymmetrical fault analysis droop control fault current calculation method limiter transient fault characteristics

Enantioselective Synthesis of Benzimidazole Atropisomers Featuring a N-N Axis

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Chinese Journal of Chemistry 2024年第7期42卷 711-718页

作者： Fang-Bei ge Qi-Kun Yin Chuan-jun Lu Xuan Xuan Jia Feng Ren-Rong Liu College of Chemistry and Chemical Engineering Qingdao UniversityQingdaoShandong 266071China School of Pharmacy Key Laboratory of Mlecular Pharmacoogy and Drug EvaluationMinistry of EducationYantai Universit YantaiShandong 264005China

Atroposelective synthesis of N-N atropisomers is an emerging area but remains underexplored;in particular,the synthesis of N-N benzimidazole atropisomers is still unprecedented.Herein,the first enantioselective synthesis of N-N benzimidazole atropisomers via the palladium-catalyzed de novo construction of benzimidazole skeleton is presented.With readily available palladium catalyst and biphosphine ligand,a broad range of nonbiaryl benzimidazole and indole-benzimidazole atropisomers were conveniently ac-cessed in high yields and with excellent enantioselectivities.Significantly,these N-N benzimidazole atropisomers showed great anti-tumor activity and selectivity to breast cancer MCF-7 cells.The simple catalytic system,broad substrate scope,high enantioselectivi-ty,and good bioactivity make this approach highly attractive.

关键词： Asymmetric synthesis Atropisomerism Palladium Benzimidazole Antitumor

Diffusion process in enzyme-metal hybrid catalysts

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Frontiers of Chemical Science and Engineering 2022年第6期16卷 921-929页

作者： Shitong Cui jun ge Key Lab for Industrial Biocatalysis Ministry of EducationDepartment of Chemical EngineeringTsinghua UniversityBeijing 100084China Institute of Biopharmaceutical and Health Engineering Tsinghua Shenzhen International Graduate SchoolShenzhen 518055China

Enzyme-metal hybrid catalysts bridge the gap between enzymatic and heterogeneous catalysis,which is significant for expanding biocatalysis to a broader scope.Previous studies have demonstrated that the enzyme-metal hybrid catalysts exhibited considerably higher catalytic efficiency in cascade reactions,compared with that of the combination of separated enzyme and metal catalysts.However,the precise mechanism of this phenomenon remains unclear.Here,we investigated the diffusion process in enzyme-metal hybrid catalysts using Pd/lipase-Pluronic conjugates and the combination of immobilized lipase(Novozyme 435)and Pd/C as models.With reference to experimental data in previous studies,the Weisz-Prater parameter and efficiency factor of internal diffusion were calculated to evaluate the internal diffusion limitations in these catalysts.Thereafter,a kinetic model was developed and fitted to describe the proximity effect in hybrid catalysts.Results indicated that the enhanced catalytic efficiency of hybrid catalysts may arise from the decreased internal diffusion limitation,size effect of Pd clusters and proximity of the enzyme and metal active sites,which provides a theoretical foundation for the rational design of enzyme-metal hybrid catalysts.

关键词： enzyme-metal hybrid catalyst internal diffusion proximity effect kinetic model

Enzyme-metal nanocomposites for antibacterial applications

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Particuology 2022年第5期20卷 134-139页

作者： Jiarong Xiong Xinyi cai jun ge Key Lab for Industrial Biocatalysis Ministry of EducationDepartment of Chemical EngineeringTsinghua UniversityBeijing 100084China Institute of Biopharmaceutical and Health Engineering Tsinghua Shenzhen International Graduate SchoolShenzhen 518055China

Metal nanoparticles have been used as antibacterial agents widely,and the combined use of enzymes and metal nanoparticles promotes antibacterial activity,achieving a synergistic effect.Additionally,enzymes decrease the amounts of metals and increase biocompatibility,thereby reducing toxicity of metals.However,the efficiency of enzymes is hindered when coupled with metals,which causes deactivation in the function of enzymes.How can a balance be struck between metals and enzymes?Although the antibacterial mechanism of metal nanoparticles is relatively clear,how enzyme-metal nanocomposites work against bacteria is not conclusive.Here,we describe several examples on the synthesis of enzyme-metal nanocomposites via co-immobilization or in situ reduction and summarize how enzyme-metal nanocomposites combat microorganisms.

关键词： Enzyme-metal nanocomposites Applications Preparations Antibacterial mechanisms

Design study of charge-stripping scheme of heavy ion beams for HIAF-BRing

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Nuclear Science and Techniques 2024年第5期35卷 30-41页

作者： jun-Jie Zhang Zhi-You Xu Jin-Quan Zhang Wen-Wen ge Liang-Ting Sun Huan-Yu Zhao Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China

Charge strippers play an essential role in heavy-ion accelerators by stripping the projectile ions to higher charge states to enhance the acceleration efficiency downstream of the stripper.In the high-energy mode of the booster ring(BRing)of the high-intensity heavy-ion accelerator facility,the pre-accelerated ions from the iLinac will be stripped by a carbon foil to higher charge states and then injected into the BRing.The key parameters of the stripper and stripped ions were calculated,and the influence of stripping on the beam quality was discussed.To get high stripping efficiencies,the foil thicknesses and resultant charge state distributions for the typical ions were determined by the code ETACHA.The equilibrium thickness was obtained for the U beam,while the stripper thicknesses for the Xe and Kr beams were determined based on a compromise between the stripped charge states and the stripping efficiency.The energy loss,energy straggling,and emittance growth due to stripping have a non-negligible impact on the transport of the stripped beams and the injection of the ring.Therefore,these parameters were simulated by geANT4.In addition,the foil’s temperature evolution,which greatly affects the foil lifetime,was simulated by ANSYS.The maximum temperature of the foil bombarded by the U and Xe beams with the nominal parameters will exceed the safe value in terms of the impact of evaporation on the foil’s lifetime.Given the foil temperature constraint,the highest tolerable beam intensity and the injected ion number into the ring were derived for different beam sizes.The results of this paper will present important reference data for the optimization design and commissioning of the beamline and injection to the BRing for the stripped ions.

关键词： High-intensity heavy-ion accelerator facility Charge stripper Energy spread Thermal analysis Emittance growth Injection turns

Targeting ASIC1a Promotes Neural Progenitor Cell Migration and Neurogenesis in Ischemic Stroke

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Research 2024年第1期2023卷 369-387页

作者： Hongfei ge Tengyuan Zhou Chao Zhang Yupeng Cun Weixiang Chen Yang Yang Qian Zhang Huanhuan Li jun Zhong Xuyang Zhang Hua Feng Rong Hu Department of Neurosurgery and Key Laboratory of Neurotrauma Southwest HospitalThird Military Medical University(Army Medical University)400038 ChongqingChina Medical Research Center Southwest HospitalThird Military Medical University(Army Medical University)400038 ChongqingChina Pediatric Research Institute Ministry of Education Key Laboratory of Child Development and DisordersNational Clinical Research Center for Child Health and DisordersChildren’s Hospital of Chongqing Medical University400014 ChongqingChina

Cell replacement therapy using neural progenitor cells(NPCs)has been shown to be an effective treatment for ischemic stroke.However,the therapeutic effect is unsatisfactory due to the imbalanced homeostasis of the local microenvironment after ischemia.Microenvironmental acidosis is a common imbalanced homeostasis in the penumbra and could activate acid-sensing ion channels 1a(ASIC1a),a subunit of proton-gated cation channels following ischemic stroke.However,the role of ASIC1a in NPCs post-ischemia remains elusive.Here,our results indicated that ASIC1a was expressed in NPCs with channel functionality,which could be activated by extracellular acidification.Further evidence revealed that ASIC1a activation inhibited NPC migration and neurogenesis through RhoA signaling-mediated reorganization of filopodia formation,which could be primarily reversed by pharmacological or genetic disruption of ASIC1a.In vivo data showed that the knockout of the ASIC1a gene facilitated NPC migration and neurogenesis in the penumbra to improve behavioral recovery after stroke.

关键词： ASIC1a homeostasis inhibited

Mortality from cerebrovascular diseases in China:Exploration of recent and future trends

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Chinese Medical Journal 2024年第5期137卷 588-595页

作者： Bin Lv ge Song Feng Jing Mingyu Li Hua Zhou Wanjun Li Jiacai Lin Shengyuan Yu jun Wang Xiangyu Cao Chenglin Tian Department of Neurology The First Medical CenterChinese PLA General HospitalBeijing 100853China Department of Neurology the 305 Hospital of Chinese PLABeijing 100017China Department of Internal Medicine Gucheng County Hospital of Traditional Chinese MedicineHengshuiHebei 253800China Department of Neurology Tangshan Hospital of Traditional Chinese MedicineTangshanHebei 063000China Department of Neurology Hainan Hospital of Chinese PLA General HospitalSanyaHainan 572013China

Background:Cerebrovascular disease(CVD)ranks among the foremost factors responsible for mortality on a global scale.The mortality patterns of CVDs and temporal trends in China need to be well-illustrated and updated.Methods:We collected mortality data on patients with CVD from Chinese Center for Disease Control and Prevention’s Disease Surveillance Points(CDC-DSP)system.The mortality of CVD in 2020 was described by age,sex,residence,and region.The temporal trend from 2013 to 2019 was evaluated using joinpoint regression,and estimated rates of decline were extrapolated until 2030 using time series models.Results:In 2019,the age-standardized mortality in China(ASMRC)per 100,000 individuals was 113.2.The ASMRC for males(137.7/10^(5))and rural areas(123.0/10^(5))were both higher when stratified by gender and urban/rural residence.The central region had the highest mortality(126.5/10^(5)),the western region had a slightly lower mortality(123.5/10^(5)),and the eastern region had the lowest mortality(97.3/10^(5)).The age-specific mortality showed an accelerated upward trend from aged 55-59 years,with maximum mortality observed in individuals over 85 years of age.The age-standardized mortality of CVD decreased by 2.43%(95%confidence interval,1.02-3.81%)annually from 2013 to 2019.Notably,the age-specific mortality of CVD increased from 2013 to 2019 for the age group of over 85 years.In 2020,both the absolute number of CVD cases and the crude mortality of CVD have increased compared to their values in 2019.The estimated total deaths due to CVD were estimated to reach 2.3 million in 2025 and 2.4 million in 2030.Conclusion:The heightened focus on the burden of CVD among males,rural areas,the central and western of China,and individuals aged 75 years and above has emerged as a pivotal determinant in further decreasing mortalities,consequently presenting novel challenges to strategies for disease prevention and control.

关键词： Cerebrovascular diseases Mortality Epidemiology Global Burden of Disease China COVID-19 pandemic

The Mass Assembly History for Galaxies with MaNGA

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Research in Astronomy and Astrophysics 2024年第3期24卷 58-69页

作者： Xue ge Hong-Tao Wang Cheng-Long Lei Yun-jun Guo Yi-Long Jiang Xiao-Xiao Cao School of Physics and Information Engineering Jiangsu Second Normal University Jiangsu Province Engineering Research Center of Basic Education Big Data Application Jiangsu Second Normal University Key Laboratory of Modern Astronomy and Astrophysics Nanjing UniversityMinistry of Education School of Science Langfang Normal University

How galaxies assemble masses through their own star formation or interaction with the external environment is still an important topic in the field of galaxy formation and evolution.We use Value Added Catalogs with galaxy features that are spatially and temporally resolved from Sloan Digital Sky Survey Data Release 17 to investigate the mass growth histories of early-type galaxies(ETGs)and late-type galaxies(LTGs).We find that the mass growth of ETGs is earlier than that of LTGs for massive galaxies(M_(*)>10^(10)M_⊙),while low-mass(M_(*)≤10^(10)M_⊙)ETGs have statistically similar mass assembly histories as low-mass LTGs.The stellar metallicity of all massive galaxies shows a negative gradient and basically does not change with time.However,in low-mass galaxies,the stellar metallicity gradient of elliptical galaxies is negative,and the stellar metallicity gradient of lenticular and spiral galaxies evolves from positive to negative.ETGs are not all in a high-density environment,but exhibit mass dependence.As the tidal strength increases,the star formation rate of low-mass ETGs rapidly decreases.These results support a picture where massive galaxies exhibit inside-out quenching mode,while low-mass galaxies show outside-in quenching mode.Environmental effects play an important role in regulating the mass assembly histories of low-mass ETGs.

关键词： Galaxy evolution-galaxies star formation-Galaxy formation

The occurrence characteristics of oil in shales matrix from organic geochemical screening data and pore structure properties:An experimental study Author links open overlay panel

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Petroleum Science 2024年第1期21卷 1-13页

作者： Zi-Zhi Lin jun-Qian Li Shuang-Fang Lu Qin-Hong Hu Peng-Fei Zhang jun-Jie Wang Qi Zhi Hong-Sheng Huang Na Yin Yue Wang Tian-Chen ge National Key Laboratory of Deep Oil and Gas China University of Petroleum(East China)Qingdao 266580ShandongChina School of geosciences China University of Petroleum(East China)Qingdao 266580ShandongChina Sanya Offshore Oil&Gas Research Institute Northeast Petroleum UniversitySanya 572025HainanChina College of Earth Science and Engineering Shandong University of Science and TechnologyQingdao 266590ShandongChina

The occurrence characteristics of shale oil are of great significance to the movability of shale oil.In this study,the occurrence characteristics of oil in the shale matrix at Funing Formation shale in Subei Basin were quantitatively evaluated by organic geochemistry and microscopic pore structure characterization experiments.The Multiple Isothermal Stages Pyrolysis(MIS)experiment results show that the content of total oil,adsorbed oil,and free oil in the shales are 3.15-11.25 mg/g,1.41-4.95 mg/g,and 1.74-6.51 mg/g,respectively.among which the silicon-rich shale has the best oil-bearing.The relative content of free oil shows an increasing trend in pores with pore diameters greater than 3 nm.When the relative content of free oil reaches 100%,the pore size of silicon-rich shale is about 200 nm,while that of calcium-rich shale,clay-rich shale,and siliceous mixed shale is about 10 nm.The occurrence law of adsorbed oil is opposite to that of free oil,which indicates that shale oil will occur in the pores and fractures in a free state in a more extensive pore size range(>200 nm).This study also enables us to further understand the occurrence characteristics of shale oil under the interaction of occurrence state and occurrence space.

关键词： Shale oil Occurrence characteristics Sequential solvent extraction Low-temperature nitrogen adsorption Funing Formation Dongtai Depression