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Thyristor-inserted MMC Sub-module Topology with DC Fault Blocking Capability

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CSEE Journal of Power and Energy Systems 2024年第5期10卷 2221-2229页

作者： cheng peng Rui li Xu Cai Key Laboratory of Control of Power Transmission and Conversion Shanghai Jiao Tong UniversityMinistry of EducationShanghai Jiao Tong UniversityShanghai 200240China.

Modular multilevel converter(MMC)is increasingly being applied to high voltage direct current(HVDC)***,dc short circuit situations restrain the application of a conventional half bridge MMC *** this paper,a new sub-module topology with inserted thyristor can help the MMC system clear a dc side *** states and devices voltage stress of the proposed topology are analyzed and the conduction loss comparison between the proposed topology with several existing topologies with dc fault blocking capability is carried *** show the proposed topology is superior to other topologies in terms of conduction loss while using the same voltage rating ***,compared with traditional half bridge topology,only thyristors and diodes are added in the proposed ***,cost of the proposed topology can be lower than conventional hybrid MMC *** last,the fault blocking capability of the proposed topology is verified in the simulation.

关键词： Fault current limiting high voltage direct current(HVDC)transmission modular multilevel converter(MMC)

Autism spectrum disorders: autistic phenotypes and complicated mechanisms

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World Journal of Pediatrics 2019年第1期15卷 17-25页

作者： Xi-cheng Zhang li-Qi Shu xing-Sen Zhao Xue-Kun li Children's Hospital Zhejiang University School of MedicineHangzhou 310003China Institute of Translational Medicine School of MedicineZhejiang UniversityHangzhou 310029China School of Medicine and Health Sciences George Washington UniversityWashingtonDCUSA

Background Autism spectrum disorder (ASD),a pervasive developmental neurological disorder,is characterized by impairments in social interaction and communication,and stereotyped,repetitive patterns of interests or *** mechanism of ASDs is complex,and genetic components and epigenetic modifications play important *** this review,we summarized the recent progresses of ASDs focusing on the genetic and epigenetic *** also briefly discussed current animal models of ASD and the application of high-throughput sequencing technologies in studying *** sources Original research articles and literature reviews published in PubMed-indexed *** Individuals with ASDs exhibit a set of phenotypes including neurological *** components including gene mutation,copy-number variations,and epigenetic modifications play important and diverse roles in *** establishment of animal models and development of new-generation sequencing technologies have contributed to reveal the complicated mechanisms underlying autistic *** Dramatic progress has been made for understanding the roles of genetic and epigenetic components in *** basic and translational studies should be carried out towards those candidate therapeutic targets.

关键词： Autism spectrum disorders Genetics Epigenetics CNV Next-generation sequencing

Radio recombination line observations at 1.0-1.5 GHz with FAST

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Research in Astronomy and Astrophysics 2021年第8期21卷 269-274页

作者： Chuan-peng Zhang Jin-Long Xu Guang-xing li li-Gang Hou Nai-Ping Yu peng Jiang National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China CAS Key Laboratory of FAST National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China South-Western Institute for Astronomy Research Yunnan UniversityKunming 650500China

H Ⅱ regions made of gas ionized by radiations from young massive stars,are widely distributed in the Milky *** are tracers for star formation,and their distributions are correlated with the Galactic spiral *** recombination lines(RRLs) of hydrogen and other atoms allow for the most precise determination of physical parameters such as temperature and ***,RRLs at around 1.4 GHz from HⅡ regions are weak and their detections are *** a result,only a limited number of detections have been obtained *** 19-beam receiver on board of the Five-hundred-meter Aperture Spherical radio Telescope(FAST) can simultaneously cover 23 RRLs for Hnα,Henα,and Cnα(n=164-186),***,combined with its unparalleled collecting area,makes FAST the most powerful telescope to detect weak *** this pilot survey,we use FAST to observe nine HⅡ regions at L *** allocate20 minutes pointing time for each source to achieve a sensitivity of around 9 mK in a velocity resolution of2.0 km s^(-1).In total,21 RRLs for Hnα and Cnα at 1.0-1.5 GHz have been simultaneously detected with strong emission ***,the detection rates for the H167α and C167α RRLs are 100%,while that for the He167α RRL is 33.3%.Using hydrogen and helium RRLs,we measure the electron density,electron temperature,and pressure for three HⅡ *** pilot survey demonstrates the capability of FAST in RRL measurements,and a statistically meaningful sample with RRL detection,through which knowledge about Galactic spiral structure and evolution can be obtained,is expected in the future.

关键词： telescopes:FAST HⅡregions radio lines:ISM galaxies:star formation

Effects of sequential decay on collective flows and nuclear stopping power in heavy-ion collisions at intermediate energies

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Nuclear Science and Techniques 2023年第4期34卷 175-184页

作者： Kui Xiao peng-cheng li Yong-Jia Wang Fu-Hu liu Qing-Feng li State Key Laboratory of Quantum Optics and Quantum Optics devices and Collaborative Innovation Center of Extreme Optics Institute of Theoretical PhysicsShanxi UniversityTaiyuan 030006China School of Science Huzhou UniversityHuzhou 313000China School of Nuclear Science and Technology Lanzhou UniversityLanzhou 730000China Institut für Theoretische Physik Goethe Universität FrankfurtFrankfurt am Main 60438Germany Institute of Modern Physics Chinese Academy of ScienceLanzhou 730000China

In this study, the rapidity distribution, collective flows, and nuclear stopping power in ^(197)Au+^(197)Au collisions at intermediate energies were investigated using the ultrarelativistic quantum molecular dynamics(UrQMD) model with GEMINI++ code. The UrQMD model was adopted to simulate the dynamic evolution of heavy-ion collisions, whereas the GEMINI++ code was used to simulate the decay of primary fragments produced by UrQMD. The calculated results were compared with the INDRA and FOPI experimental data. It was found that the rapidity distribution, collective flows, and nuclear stopping power were affected to a certain extent by the decay of primary fragments, especially at lower beam energies. Furthermore, the experimental data of the collective flows and nuclear stopping power at the investigated beam energies were better reproduced when the sequential decay effect was included.

关键词： Heavy-ion collisions Sequential decay effect Collective flow Nuclear stopping power

Effects of urban grass coverage on rainfall-induced runoff in Xi'an loess region in China

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Water Science and Engineering 2017年第4期10卷 320-325页

作者： Jing li, Zhan-bin li Meng-jing Guo peng li Sheng-dong cheng State Key Laboratory Base of Eco-Hydraulic Engineering in Arid Areas Xi'an University of TechnologyXi'an 710048China

In this study, laboratory rainfall simulation experiments were conducted to investigate the regulatory effects of grass coverage on rainfallrunoff processes. A total of 80 grass blocks planted with well-grown manilagrass, together with their root systems, were sampled from an eastern suburban area of Xi'an City in the northwest arid area of China and sent to a laboratory for rainfall simulation experiments. The runoff and infiltration processes of a slope with different grass coverage ratios and vegetation patterns were analyzed. The results show that the runoff coefficient decreases with the increase of the grass coverage ratio, and the influence of grass coverage on the reduction of runoff shows a high degree of spatial variation. At a constant grass coverage ratio, as the area of grass coverage moves downward, the runoff coefficient, total runoff,and flood peak discharge gradually decrease, and the flood peak occurs later. With the increase of the grass coverage ratio, the flood peak discharge gradually decreases, and the flood peak occurs later as well. In conclusion, a high grass coverage ratio with the area of grass coverage located at the lower part of the slope will lead to satisfactory regulatory effects on rainfall-induced runoff.

关键词： Rainfall simulation Urban vegetation in arid area Rainfall-runoff process Regulatory effect Xi'an loess region

An adaptive data-driven method for accurate prediction of remaining useful life of rolling bearings

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Frontiers of Mechanical Engineering 2018年第2期13卷 301-310页

作者： Yanfeng peng Junsheng cheng Yanfei liU Xuejun li Zhihua peng State Key Laboratory of Advanced design and Manufacturing for Vehicle Body Hunan University Changsha 410082 China College of Mechanical and Vehicle Engineering Hunan UniversityChangsha 410082 China Hunan-Provincial Key Laboratory of Health Maintenance for Mechanical Equipment Hunan University of Science and Technology Xiangtan 411201 China School of Mathematics and Physics University of South ChinaHengyang 421001 China

A novel data-driven method based on Gaussian mixture model （GMM） and distance evaluation technique （deT） is proposed to predict the remaining useful life （RUL） of rolling bearings. The data sets are clustered by GMM to divide all data sets into several health states adaptively and reasonably. The number of clusters is determined by the minimum description length principle. Thus, either the health state of the data sets or the number of the states is obtained automatically. Meanwhile, the abnormal data sets can be recognized during the clustering process and removed from the training data sets. After obtaining the health states, appropriate features are selected by deT for increasing the classification and prediction accuracy. In the prediction process, each vibration signal is decomposed into several components by empirical mode decomposition. Some common statis- tical parameters of the components are calculated first and then the features are clustered using GMM to divide the data sets into several health states and remove the abnormal data sets. Thereafter, appropriate statistical parameters of the generated components are selected using deT. Finally, least squares support vector machine is utilized to predict the RUL of rolling *** results indicate that the proposed method reliably predicts the RUL of rolling bearings.

关键词： Gaussian mixture model distance evaluation technique health state remaining useful life rolling bearing

Performance analysis of high-static-low-dynamic stiffness vibration isolator with time-delayed displacement feedback

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Journal of Central South University 2017年第10期24卷 2294-2305页

作者： cheng Chun li Shun-ming WANG Yong JIANG xing-xing College of Energy and Power Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

The displacement feedback with time delay considered is introduced in order to enhance the vibration isolation performance of a high-static-low-dynamic stiffness(HSLDS) vibration isolator. Such feedback is detailedly analyzed from the viewpoint of equivalent damping. Firstly, the primary resonance of the controlled HSLDS vibration isolator subjected to a harmonic force excitation is obtained based on the multiple scales method and further verified by numerical integration. The stability of the primary resonance is subsequently investigated. Then, the equivalent damping is defined to study the effects of feedback gain and time delay on primary resonance. The condition of jump avoidance is obtained with the purpose of eliminating the adverse effects induced by jumps. Finally, the force transmissibility of the controlled HSLDS vibration isolator is defined to evaluate its isolation performance. It is shown that an appropriate choice of feedback parameters can effectively suppress the force transmissibility in resonant region and reduce the resonance frequency. Furthermore, a wider vibration isolation frequency bandwidth can be achieved compared to the passive HSLDS vibration isolator.

关键词： vibration isolator high-static-low-dynamic stiffness piecewise nonlinear time-delayed feedback multiple scales method

Effects of residual organics in municipal wastewater on hydrogenotrophic denitrifying microbial communities

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Journal of Environmental Sciences 2018年第3期30卷 262-270页

作者： Wei xing Jinlong li peng li Chong Wang Yanan Cao desheng li Yunfeng Yang Jizhong Zhou Jiane Zuo School of Civil Engineering Beijing Jiaotong University Beijing 100044 China State Key Joint Laboratory of Environmental Simulation and Pollution Control School of Environment Tsinghua University Beijing 100084 China Beijing Key Laboratory of Aqueous Typical Pollutants Control and Water Quality Safeguard Beijing 100044 China College of Science Flunan Agricultural University Changsha 410128 China Institute for Environmental Genomics and department of Microbiology and Plant Biology University of Oklahoma Norman OK 73019 USA Earth Sciences Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA

Hydrogenotrophic denitrification is promising for tertiary nitrogen removal from municipal wastewater. To reveal the influence of residual organics in municipal wastewater on hydrogenotrophic denitrifiers, we adopted high-throughput 16 S r RNA gene amplicon sequencing to examine microbial communities in hydrogenotrophic denitrification enrichments. Using effluent from a municipal wastewater treatment plant as water source, COD,nitrate and p H were controlled the same except for a gradient of biodegradable carbon（i.e., primary effluent（PE）, secondary effluent（SE）, or combined primary and secondary effluent（CE））. Inorganic synthetic water（IW） was used as a control. Hydrogenophaga, a major facultative autotroph, accounted for 17.1%, 5.3%, 32.7% and 12.9% of the sequences in PE, CE,SE and IW, respectively, implicating that Hydrogenophaga grew well with or without ***, which contains likely obligate autotrophic denitrifiers, appeared to be the most dominant genera（23.6%） in IW and accounted for 2.5%, 4.6% and 8.9% in PE, CE and SE,respectively. Thermomonas, which is related to heterotrophic denitrification, accounted for 4.2% and 7.9% in PE and CE fed with a higher content of labile organics, *** contrast, Thermomonas was not detected in IW and accounted for only 0.6% in SE. Our results suggest that Thermomonas are more competitive than Thauera in hydrogenotrophic denitrification with biodegradable organics. Moreover, facultative autotrophic denitrifiers,Hydrogenophaga, are accommodating to residual organic in effluent wastewater, thus we propose that hydrogenotrophic denitrification is amenable for tertiary nitrogen removal.

关键词： Tertiary nitrogen removal Hydrogenotrophic denitrification Residual organics High-throughput sequencing Hydrogenophaga

Effects of combustion temperature on the optical properties of brown carbon from biomass burning

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Journal of Environmental Sciences 2024年第3期137卷 302-309页

作者： peng Gao Rule deng Song Jia Yue li Xuefei Wang Qian xing School of Chemistry Sciences University of Chinese Academy of SciencesBeijing 100049China College of Chemistry and Materials Engineering Beijing Technology and Business UniversityBeijing 100048China

Biomass burning has been known as one of main sources of Brown Carbon(BrC)in *** this study,by controlling the combustion temperature at 250℃,350℃,and 450℃,the methanol soluble organic carbon(MSOC)and methanol insoluble carbon(MISC)from pine wood burning was collected by ***–Vis,excitation emission matrix(EEM),TEM and FTIR spectra were applied to investigate the properties of BrC *** MSOC at 250℃ and 350℃,all the spectral profiles of UV–Vis absorption and excitation emission matrix are almost the same,while the EEM of MSOC at 450℃ are different from that of the other *** MISC fuorescence was observed only in the case of 450℃.In the FTIR spectra,with the temperature increasing the peaks associated to the oxygen-contained functions was weakened,indicating the formation of the fuorophores with larger conjugated system,especially aromatic *** results show that biomass combustion at low temperature produces more oxygen-riched BrC,which possesses relatively lower light absorption,while at high temperature produces more aromatics hydrocarbons with relatively strong light *** results of this work are helpful to trace the source of brown carbon and optimize biomass energy utilization.

关键词： Biomass burning Combustion temperature Methanol-soluble brown carbon EEM Impinger