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Shape-influenced non-reciprocal transport of magnetic skyrmions in nanoscale channel
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作者 陈杰尧 罗佳 +8 位作者 胡更新 王君林 李冠祺 陈振东 陆显扬 赵国平 刘远 吴竞 徐永兵 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第7期605-611,共7页
Skyrmions, with their vortex-like structures and inherent topological protection, play a pivotal role in developing innovative low-power memory and logic devices. The efficient generation and control of skyrmions in g... Skyrmions, with their vortex-like structures and inherent topological protection, play a pivotal role in developing innovative low-power memory and logic devices. The efficient generation and control of skyrmions in geometrically confined systems are crucial for the development of skyrmion-based spintronic devices. In this study, we focus on investigating the non-reciprocal transport behavior of skyrmions and their interactions with boundaries of various shapes. The shape of the notch structure in the nanotrack significantly affects the dynamic behavior of magnetic skyrmions. Through micromagnetic simulation, the non-reciprocal transport properties of skyrmions in nanowires with different notch structures are investigated in this work. 展开更多
关键词 SKYRMION micromagnetic simulation racetrack memory
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Does community-based health insurance affect lifestyle and timing of treatment seeking behavior?Evidence from Ethiopia
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作者 Zecharias Fetene Anteneh Anagaw D.Mebratie +2 位作者 Zemzem Shigute Getnet Alemu Arjun S.Bedi 《Global Health Journal》 2024年第2期83-90,共8页
Objectives This paper aims to investigate the effects of enrollment in the Ethiopian community-based health insurance(CBHI)scheme on household preventive care activities and the timing of treatment-seeking behavior fo... Objectives This paper aims to investigate the effects of enrollment in the Ethiopian community-based health insurance(CBHI)scheme on household preventive care activities and the timing of treatment-seeking behavior for illness symptoms.There is growing concern about the financial sustainability of CBHI schemes in developing countries.However,few empirical studies have identified potential contributors,including ex-ante and ex-post moral hazards.Methods We implement a household fixed-effect panel data regression model,drawing on three rounds of household survey data collected face to face in districts where CBHI scheme is operational and in districts where it is not operational in Ethiopia.Results The findings show that enrolment in CBHI does not significantly influence household behaviour regarding preventive care activities such as water treatment before drinking and handwashing before meals.However,CBHI significantly increases delay in treatment-seeking behaviour for diseases symptoms.Particularly,on average,we estimate about 4-6 h delay for malaria symptoms,a little above 4 h for tetanus,and 10-11 h for tuberculosis among the insured households.Conclusions While there is evidence that CBHI improve the utilization of outpatient or primary care services,our study suggests that insured members may wait longer before visiting health facilities.This delay could be partly due to moral hazard problems,as insured households,particularly those from rural areas,may consider the opportunity costs associated with visiting health facilities for minor symptoms.Overall,it is essential to identify the primary causes of delays in seeking medical services and implement appropriate interventions to encourage insured individuals to seek early medical attention. 展开更多
关键词 Community-based health insurance Financial sustainability Preventive care Treatment-seeking behavior Household fixed effect Ethiopia
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Analysis of community question-answering issues via machine learning and deep learning:State-of-the-art review 被引量:3
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作者 Pradeep Kumar Roy Sunil Saumya +2 位作者 Jyoti Prakash Singh Snehasish Banerjee Adnan Gutub 《CAAI Transactions on Intelligence Technology》 SCIE EI 2023年第1期95-117,共23页
Over the last couple of decades,community question-answering sites(CQAs)have been a topic of much academic interest.Scholars have often leveraged traditional machine learning(ML)and deep learning(DL)to explore the eve... Over the last couple of decades,community question-answering sites(CQAs)have been a topic of much academic interest.Scholars have often leveraged traditional machine learning(ML)and deep learning(DL)to explore the ever-growing volume of content that CQAs engender.To clarify the current state of the CQA literature that has used ML and DL,this paper reports a systematic literature review.The goal is to summarise and synthesise the major themes of CQA research related to(i)questions,(ii)answers and(iii)users.The final review included 133 articles.Dominant research themes include question quality,answer quality,and expert identification.In terms of dataset,some of the most widely studied platforms include Yahoo!Answers,Stack Exchange and Stack Overflow.The scope of most articles was confined to just one platform with few cross-platform investigations.Articles with ML outnumber those with DL.Nonetheless,the use of DL in CQA research is on an upward trajectory.A number of research directions are proposed. 展开更多
关键词 answer quality community question answering deep learning expert user machine learning question quality
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Tuning the selectivity of natural oils and fatty acids/esters deoxygenation to biofuels and fatty alcohols:A review 被引量:3
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作者 Yingdong Zhou Javier Remon +2 位作者 Zhicheng Jiang Avtar S.Matharu Changwei Hu 《Green Energy & Environment》 SCIE EI CAS CSCD 2023年第3期722-743,共22页
The chemical transformation of natural oils provides alternatives to limited fossil fuels and produces compounds with added value for the chemical industries.The selective deoxygenation of natural oils to diesel-range... The chemical transformation of natural oils provides alternatives to limited fossil fuels and produces compounds with added value for the chemical industries.The selective deoxygenation of natural oils to diesel-ranged hydrocarbons,bio-jet fuels,or fatty alcohols with controllable selectivity is especially attractive in natural oil feedstock biorefineries.This review presents recent progress in catalytic deoxygenation of natural oils or related model compounds(e.g.,fatty acids)to renewable liquid fuels(green diesel and bio-jet fuels)and valuable fatty alcohols(unsaturated and saturated fatty alcohols).Besides,it discusses and compares the existing and potential strategies to control the product selectivity over heterogeneous catalysts.Most research conducted and reviewed has only addressed the production of one category;therefore,a new integrative vision exploring how to direct the process toward fuel and/or chemicals is urgently needed.Thus,work conducted to date addressing the development of new catalysts and studying the influence of the reaction parameters(e.g.,temperature,time and hydrogen pressure)is summarized and critically discussed from a green and sustainable perspective using efficiency indicators(e.g.,yields,selectivity,turnover frequencies and catalysts lifetime).Special attention has been given to the chemical transformations occurring to identify key descriptors to tune the selectivity toward target products by manipulating the reaction conditions and the structures of the catalysts.Finally,the challenges and future research goals to develop novel and holistic natural oil biorefineries are proposed.As a result,this critical review provides the readership with appropriate information to selectively control the transformation of natural oils into either biofuels and/or value-added chemicals.This new flexible vision can help pave the wave to suit the present and future market needs. 展开更多
关键词 Natural oil DEOXYGENATION Controllable selectivity Biofuels Fatty alcohols
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Tuning Surface Spin Polarization of CoFeB by Boron Diffusion Detected by Spin Resolved Photoemission
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作者 Qi Liu Xianyang Lu +15 位作者 Chengrui Fu Jiarui Chen Zhe Zhang Yuting Gong Xinyue Wang Yu Yan Qinwu Gao Hui Li Xuezhong Ruan Yao Li Jun Du Jing Wu Liang He Bo Liu Rong Zhang Yongbing Xu 《Chinese Physics Letters》 SCIE EI CAS CSCD 2023年第8期86-91,共6页
Research of spin polarization of magnetic CoFeB thin films is of practical importance in spintronic applications.Here,using a direct characterization technique of spin-resolved photoemission spectroscopy,we obtain the... Research of spin polarization of magnetic CoFeB thin films is of practical importance in spintronic applications.Here,using a direct characterization technique of spin-resolved photoemission spectroscopy,we obtain the surface spin polarization of amorphous Co_(40)Fe_(40)B_(20)thin films with different annealing temperatures from 100℃to 500℃prepared by magnetron sputtering.After high annealing temperature,a quasi-semiconductor state is gradually formed at the CoFeB surface due to the boron diffusion.While the global magnetization remains almost constant,the secondary electrons’spin polarization,average valence band spin polarization and the spin polarization at Fermi level from spin-resolved photoemission spectroscopy show a general trend of decreasing with the increasing annealing temperature above 100℃.These distinct surface properties are attributed to the enhanced Fe-B bonding due to the boron segregation upon surface after annealing as confirmed by x-ray photoelectron spectroscopy and scanning transmission electron microscopy with energy dispersive spectroscopy.Our findings provide insight into the surface spin-resolved electronic structure of the CoFeB thin films,which should be important for development of high-performance magnetic random-access memories. 展开更多
关键词 SPECTROSCOPY ANNEALING BORON
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A Study of the Self-efficacy of Viola Majors in Chinese Universities Regarding Career Choice
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作者 YANG Qiming 《Psychology Research》 2023年第7期319-323,共5页
This study examined and analysed the impact of self-efficacy on the career decisions of 52 viola students enrolled in Chinese universities.According to the findings,the level of self-efficacy influences the learning a... This study examined and analysed the impact of self-efficacy on the career decisions of 52 viola students enrolled in Chinese universities.According to the findings,the level of self-efficacy influences the learning and career decisions of students directly.Higher self-efficacy can positively affect how individuals perceive their past experiences and those of others.Therefore,a high degree of self-efficacy can be advantageous.Self-efficacy is primarily influenced by a person’s prior experiences,alternative experiences,verbal persuasion,and physical and emotional state during work-based learning.Schools may offer courses that foster and improve the development of self-efficacy in order to help viola majors in improving their self-efficacy effectively. 展开更多
关键词 VIOLA SELF-EFFICACY career choice
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Characterization of hot electrons generated by laser-plasma interaction at shock ignition intensities
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作者 E.D.Filippov M.Khan +17 位作者 A.Tentori P.Gajdos A.S.Martynenko R.Dudzak P.Koester G.Zeraouli D.Mancelli F.Baffigi L.A.Gizzi S.A.Pikuz Ph.D.Nicolaï N.C.Woolsey R.Fedosejevs M.Krus L.Juha D.Batani O.Renner G.Cristoforetti 《Matter and Radiation at Extremes》 SCIE EI CSCD 2023年第6期74-89,共16页
In an experiment carried out at the Prague Asterix Laser System at laser intensities relevant to shock ignition conditions(I>10^(16) W/cm^(2)),the heating and transport of hot electrons were studied by using severa... In an experiment carried out at the Prague Asterix Laser System at laser intensities relevant to shock ignition conditions(I>10^(16) W/cm^(2)),the heating and transport of hot electrons were studied by using several complementary diagnostics,i.e.,K_(α)time-resolved imaging,hard x-ray filtering(a bremsstrahlung cannon),and electron spectroscopy.Ablators with differing composition from low Z(parylene N)to high Z(nickel)were used in multilayer planar targets to produce plasmas with different coronal temperature and collisionality and modify the conditions of hot-electron generation.The variety of available diagnostics allowed full characterization of the population of hot electrons,retrieving their conversion efficiency,time generation and duration,temperature,and angular divergence.The obtained results are shown to be consistent with those from detailed simulations and similar inertial confinement fusion experiments.Based on the measured data,the advantages,reliability,and complementarity of the experimental diagnostics are discussed. 展开更多
关键词 SPECTROSCOPY shock allowed
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Research on the Value and Strategy of Integrating Music Education and National Music Culture
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作者 Liangyihui Chen 《Journal of Contemporary Educational Research》 2023年第9期14-19,共6页
China’s traditional national music is an art form formed by the working people and art pioneers to express their emotions during thousands of years of productive labor.National music not only contains emotional stori... China’s traditional national music is an art form formed by the working people and art pioneers to express their emotions during thousands of years of productive labor.National music not only contains emotional stories that are capable of evoking praises and tears,but also has a profound understanding of the lives of sages.In summary,integrating college music education with national music culture can allow students to deeply discover music,thereby stimulating students’enthusiasm for learning music,improving students’learning quality,mastering the core parts of music learning,and helping students to go a long way in music.This article mainly focuses on the characteristics and educational value of national music culture,and its effective integration with music education in colleges and universities.This article can help relevant workers in college music education and promote the sustainable development of music education in colleges and universities in China. 展开更多
关键词 Music education in colleges and universities National music culture Effective integration Teaching value
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“思政课的本质是讲道理”的研究现状及其深化
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作者 王佳颖 梁百川 《潍坊工程职业学院学报》 2024年第3期5-10,共6页
习近平总书记关于“思政课的本质是讲道理”的重要论述为新时代思政课改革创新提供了理论遵循。围绕这一重要论述,学界从何谓“讲道理”、讲何“道理”等层面分析了“思政课的本质是讲道理”的内在蕴涵;从学科依据、理论依据和现实依据... 习近平总书记关于“思政课的本质是讲道理”的重要论述为新时代思政课改革创新提供了理论遵循。围绕这一重要论述,学界从何谓“讲道理”、讲何“道理”等层面分析了“思政课的本质是讲道理”的内在蕴涵;从学科依据、理论依据和现实依据等层面考察了“思政课的本质是讲道理”的价值渊源;从创新方法、误区辨明以及教学逻辑等角度探讨了“思政课的本质是讲道理”的实践路径。但综合而言,学界对思政课本质的本体性价值、系统化实现路径以及跨学科方法研究等方面还需进一步深化。 展开更多
关键词 思政课 本质 讲道理 研究综述 未来展望
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Effectiveness of Adherence to Standardized Hypertension Management by Primary Health Care Workers in China:a Cross-sectional Survey 3 Years after the Healthcare Reform 被引量:6
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作者 LI Yuan WANG Jing Lei +4 位作者 ZHANG Xiao Chang LIU Dan SHI Wen Hui LIANG Xiao Feng WU Jing 《Biomedical and Environmental Sciences》 SCIE CAS CSCD 2016年第12期915-921,共7页
The standardized hypertension management provided by primary health care workers is an important part of China's recent health care reform efforts. Investigating 5,116 hypertensive patients from a cross-sectional sur... The standardized hypertension management provided by primary health care workers is an important part of China's recent health care reform efforts. Investigating 5,116 hypertensive patients from a cross-sectional survey conducted by the Chinese Center for Disease Control and Prevention in 2012, this study found that adherence to standardized hypertension management is associated with positive effects on hypertension- related knowledge, healthy lifestyle behavior, antihypertensive medical treatments, and blood pressure control. It will be necessary to provide primary health care workers with sufficient training and reasonable incentives to ensure the implementation and effectiveness of hypertension management. 展开更多
关键词 HYPERTENSION Primary health care Community health workers China
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Low temperature microwave-assisted vs conventional pyrolysis of various biomass feedstocks 被引量:7
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作者 Peter Shuttleworth Vitaliy Budarin +2 位作者 Mark Gronnow James H.Clark Rafael Luque 《Journal of Natural Gas Chemistry》 EI CAS CSCD 2012年第3期270-274,共5页
A comparison between conventional pyrolysis and a novel developed low-temperature microwave-assisted pyrolysis methodology has been performed for the valorisation of a range of biomass feedstocks including waste resid... A comparison between conventional pyrolysis and a novel developed low-temperature microwave-assisted pyrolysis methodology has been performed for the valorisation of a range of biomass feedstocks including waste residues. Microwave pyrolysis was found to efficiently deliver comparable evolution of bio-gases in the system as compared with conventional pyrolysis at significantly reduced temperatures (120-180 ℃vs 250-400 ℃). The gas obtained from microwave-assisted pyrolysis was found to contain CO2, CH4 and CO as major components as well 展开更多
关键词 microwave-assisted pyrolysis biomass valorisation gas production
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Risk stratification for ST segment elevation myocardial infarction in the era of primary percutaneous coronary intervention 被引量:6
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作者 Richard A Brogan Christopher J Malkin +3 位作者 Philip D Batin Alexander D Simms James M McLenachan Christopher P Gale 《World Journal of Cardiology》 CAS 2014年第8期865-872,共8页
Acute coronary syndromes presenting with ST elevation are usually treated with emergency reperfusion/revascularisation therapy. In contrast current evidence and national guidelines recommend risk stratification for no... Acute coronary syndromes presenting with ST elevation are usually treated with emergency reperfusion/revascularisation therapy. In contrast current evidence and national guidelines recommend risk stratification for non ST segment elevation myocardial infarction(NSTEMI) with the decision on revascularisation dependent on perceived clinical risk. Risk stratification for STEMI has no recommendation. Statistical risk scoring techniques in NSTEMI have been demonstrated to improve outcomes however their uptake has been poor perhaps due to questions over their discrimination and concern for application to individuals who may not have been adequately represented in clinical trials. STEMI is perceived to carry sufficient risk to warrant emergency coronary intervention [by primary percutaneous coronary intervention(PPCI)] even if this results in a delay to reperfusion with immediate thrombolysis. Immediate thrombolysis may be as effective in patients presenting early, or at low risk, but physicians are poor at assessing clinical and procedural risks and currently are not required to consider this. Inadequate data on risk stratification in STEMI inhibits the option of immediate fibrinolysis, which may be cost-effective. Currently the mode of reperfusion for STEMI defaults to emergency angiography and percutaneous coronary intervention ignoring alternative strategies. This review article examines the current risk scores and evidence base for risk stratification for STEMI patients. The requirements for an ideal STEMI risk score are discussed. 展开更多
关键词 ST segment elevation myocardial INFARCTION RISK STRATIFICATION Primary PERCUTANEOUS coronary intervention HARM RISK SCORES
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Ultrastructural characters of a Physarum melleum on living leaves of Dendrobium candidum in China 被引量:2
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作者 ZHANG Jing-ze LIU Lu-ning +1 位作者 FIORE-DONNO Anna-Maria XU Tong 《Journal of Zhejiang University-Science B(Biomedicine & Biotechnology)》 SCIE CAS CSCD 2007年第12期896-899,共4页
A known species, Physarum melleum, was found fruiting on living leaves of Dendrobium candidum, which was collected in China in 2004. Its morphological characters were revealed by light microscopy (LM), environmental s... A known species, Physarum melleum, was found fruiting on living leaves of Dendrobium candidum, which was collected in China in 2004. Its morphological characters were revealed by light microscopy (LM), environmental scanning elec- tron microscopy (ESEM) and scanning electron microscopy (SEM). Character variations were distinguished by its olive-yellow peridium and its always thinner capillitium containing globulose granular material between the large calcareous nodes. The cal- cium carbonate granules, deposited on stalks, peridium and hypothallus as well as within stalks, were globose and smooth. 展开更多
关键词 MYXOMYCETE PHYSARUM ULTRASTRUCTURE Fruiting site Peridium
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Encyclopedia of Autographa californica Nucleopolyhedrovirus Genes 被引量:2
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作者 David P. A. Cohen Martin Marek +2 位作者 Bryn G. Davies Just M. Vlak Monique M. van Oers 《Virologica Sinica》 SCIE CAS CSCD 2009年第5期359-414,共56页
The Autographa californica multiple capsid nucleopolyhedrovirus (AcMNPV) was the first baculovirus for which the complete nucleotide sequence became known. Since then 15 years lapsed and much research has been perform... The Autographa californica multiple capsid nucleopolyhedrovirus (AcMNPV) was the first baculovirus for which the complete nucleotide sequence became known. Since then 15 years lapsed and much research has been performed to elucidate putative functions of the annotated open reading frames of this virus and this endeavour is still ongoing. AcMNPV is the most well-known and well-studied baculovirus species, not in the least for its application as a vector for the high-level expression of foreign genes in insect cells. This article is the first monograph of a single baculovirus and gives a current overview of what is known about the 151 AcMNPV ORFs, including (putative) function and temporal and spatial presence of transcripts and protein. To date 60 ORFs have a proven function, another 19 ORFs have homologs for which functions are known in other baculoviruses and 72 ORFs are still enigmatic. This paper should assist the reader in quickly finding the essentials of AcMNPV. 展开更多
关键词 BACULOVIRUS Autographa californica multiple capsid nucleopolyhedrovirus(AcMNPV) Functional genomics Review
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Industrial layout reconstruction, the role of local government and variation of pollution distribution in China 被引量:1
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作者 Liming Ge Bingtao Qin Shang Li 《Chinese Journal of Population,Resources and Environment》 2018年第4期314-328,共15页
In recent years, high-polluting industries have been gradually shifted from the eastern developed regions to the central and western underdeveloped regions in China. Certain environmental regulations have been in plac... In recent years, high-polluting industries have been gradually shifted from the eastern developed regions to the central and western underdeveloped regions in China. Certain environmental regulations have been in place accordingly in various regions, but the pollution in the central and western regions has risen sharply. Based on the data of interprovincial panel in China from 2006 to 2015, this paper calculates high-pollution industry dynamic agglomeration index, environmental pollution agglomeration index and relative environmental regulation intensity index, and uses Generalized Method of Moments to carry out the regression analyses of the whole samples,regional heterogeneity and temporal heterogeneity. The results show that there is an inverted Ushaped relationship between relative environmental regulation and environmental pollution concentration in China. The concentration degrees of industrial wastewater pollution and industrial waste gas pollution are deepened, which are mainly caused by the transfer of highly polluting industries. However, the concentration of industrial solid waste pollution caused by the transfer is not obvious. Furthermore, the deepening of industrialization intensifies the concentration of regional environmental pollution. Environmental Kuznets Curve does exist in China,but it is not significant. The increase of labor cost and quality will reduce the concentration of environmental pollution. 展开更多
关键词 High-pollution industry transfer RELATIVE environmental regulation intensity POLLUTION AGGLOMERATION
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Parameter Deviation Effect Study of the Power Generation Unit on a Doubly-Fed Induction Machine-based Shipboard Propulsion System 被引量:2
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作者 Kai Ni Yihua Hu Chun Gan 《CES Transactions on Electrical Machines and Systems》 CSCD 2020年第4期339-348,共10页
To lower the difficulty of fault protection,a doubly-fed induction machine based shipboard propulsion system(DFIM-SPS)that is partially power decoupled is presented.In such an intrinsically safe SPS architecture,a syn... To lower the difficulty of fault protection,a doubly-fed induction machine based shipboard propulsion system(DFIM-SPS)that is partially power decoupled is presented.In such an intrinsically safe SPS architecture,a synchronous generator(SG)is employed for power generation,and the accuracy of the parameters of power generation unit(PGU)plays an important role in SPS stable operation.In this paper,the PGU parameter deviations are studied to evaluate the effects on system performance.The models of salient-pole SG,type DC1A excitation system(EXS)and DFIM are illustrated first.Besides,the corresponding control scheme is explained.For the 16 important parameters of PGU,up to 40%of parameter deviations are applied to implement parameter sensitivity analysis.Then,simulation studies are carried out to evaluate the parameter deviation effects on system performance in detail.By defining three parameter deviation effect indicators(PDEIs),the effects on the PGU output variables,which are the terminal voltage and output active power,are studied.Moreover,the increasing rates of PDEIs with different degrees of parameter deviations for the key parameters are analyzed.Furthermore,the overall system performance is investigated for the two most influential PGU parameters.This paper provides some vital clues on SG and EXS parameter identification for DFIM-SPS. 展开更多
关键词 shipboard propulsion system partially power decoupled doubly-fed induction machine synchronous generator parameter deviation
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Optimization of a laser plasma-based x-ray source according to WDM absorption spectroscopy requirements 被引量:1
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作者 A.S.Martynenko S.A.Pikuz +14 位作者 I.Yu.Skobelev S.N.Ryazantsev C.D.Baird N.Booth L.N.K.Dohl P.Durey A.Ya.Faenov D.Farley R.Kodama K.Lancaster P.McKenna C.D.Murphy C.Spindloe T.A.Pikuz N.Woolsey 《Matter and Radiation at Extremes》 SCIE CAS CSCD 2021年第1期37-44,共8页
X-ray absorption spectroscopy is a well-accepted diagnostic for experimental studies of warm dense matter.It requires a short-lived X-ray source of sufficiently high emissivity and without characteristic lines in the ... X-ray absorption spectroscopy is a well-accepted diagnostic for experimental studies of warm dense matter.It requires a short-lived X-ray source of sufficiently high emissivity and without characteristic lines in the spectral range of interest.In the present work,we discuss how to choose an optimum material and thickness to get a bright source in the wavelength range 2A–6A(∼2 keV to 6 keV)by considering relatively low-Z elements.We demonstrate that the highest emissivity of solid aluminum and silicon foil targets irradiated with a 1-ps high-contrast sub-kJ laser pulse is achieved when the target thickness is close to 10μm.An outer plastic layer can increase the emissivity even further. 展开更多
关键词 LASER WDM SOURCE
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Tropical forest canopies and their relationships with climate and disturbance: results from a global dataset of consistent field-based measurements 被引量:1
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作者 marion pfeifer alemu gonsamo +26 位作者 william woodgate luis cayuela andrew r.marshall alicia ledo timothy c.e.paine rob marchant andrew burt kim calders colin courtney-mustaphi aida cuni-sanchez nicolas j.deere dereje denu jose gonzalez de tanago robin hayward alvaro lau manuel j.macía pieter i.olivier petri pellikka hamidu seki deo shirima rebecca trevithick beatrice wedeux charlotte wheeler pantaleo k.t.munishi thomas martin abdul mustari philip j.platts 《Forest Ecosystems》 SCIE CSCD 2018年第1期77-90,共14页
Background: Canopy structure, defined by leaf area index (LAI), fractional vegetation cover (FCover) and fraction of absorbed photosynthetically active radiation (fAPAR), regulates a wide range of forest functi... Background: Canopy structure, defined by leaf area index (LAI), fractional vegetation cover (FCover) and fraction of absorbed photosynthetically active radiation (fAPAR), regulates a wide range of forest functions and ecosystem services. Spatially consistent field-measurements of canopy structure are however lacking, particularly for the tropics. Methods: Here, we introduce the Global LAI database: a global dataset of field-based canopy structure measurements spanning tropical forests in four continents (Africa, Asia, Australia and the Americas). We use these measurements to test for climate dependencies within and across continents, and to test for the potential of anthropogenic disturbance and forest protection to modulate those dependences. Results: Using data collected from 887 tropical forest plots, we show that maximum water deficit, defined across the most arid months of the year, is an important predictor of canopy structure, with all three canopy attributes declining significantly with increasing water deficit. Canopy attributes also increase with minimum temperature, and with the protection of forests according to both active (within protected areas) and passive measures (through topography). Once protection and continent effects are accounted for, other anthropogenic measures (e.g. human population) do not improve the model. Conclusions: We conclude that canopy structure in the tropics is primarily a consequence of forest adaptation to the maximum water deficits historically experienced within a given region. Climate change, and in particular changes in drought regimes may thus affect forest structure and function, but forest protection may offer some resilience against this effect. 展开更多
关键词 Leaf area index Fractional vegetation cover Fraction of absorbed photosynthetically active radiation Human population pressure Protected areas DROUGHT Climate change
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Visualization of atomic scale reaction dynamics of supported nanocatalysts during oxidation and ammonia synthesis using in-situ environmental(scanning) transmission electron microscopy
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作者 Michael R.Ward Robert W.Mitchell +1 位作者 Edward D.Boyes Pratibha L.Gai 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2021年第6期281-290,I0007,共11页
Reaction dynamics in gases at operating temperatures at the atomic level are the basis of heterogeneous gas-solid catalyst reactions and are crucial to the catalyst function.Supported noble metal nanocatalysts such as... Reaction dynamics in gases at operating temperatures at the atomic level are the basis of heterogeneous gas-solid catalyst reactions and are crucial to the catalyst function.Supported noble metal nanocatalysts such as platinum are of interest in fuel cells and as diesel oxidation catalysts for pollution control,and practical ruthenium nanocatalysts are explored for ammonia synthesis.Graphite and graphitic carbons are of interest as supports for the nanocatalysts.Despite considerable literature on the catalytic processes on graphite and graphitic supports,reaction dynamics of the nanocatalysts on the supports in different reactive gas environments and operating temperatures at the single atom level are not well understood.Here we present real time in-situ observations and analyses of reaction dynamics of Pt in oxidation,and practical Ru nanocatalysts in ammonia synthesis,on graphite and related supports under controlled reaction environments using a novel in-situ environmental(scanning) transmission electron microscope with single atom resolution.By recording snapshots of the reaction dynamics,the behaviour of the catalysts is imaged.The images reveal single metal atoms,clusters of a few atoms on the graphitic supports and the support function.These all play key roles in the mobility,sintering and growth of the catalysts.The experimental findings provide new structural insights into atomic scale reaction dynamics,morphology and stability of the nanocatalysts. 展开更多
关键词 In-situ visualization Atomic scale reaction dynamics In-situ environmental scanning transmission electron microscopy with single atom resolution Supported nanoparticles Ammonia synthesis Oxidation reactions
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Cryptanalysis and Improvement of a Chaotic Map-Control-Based and the Plain Image-Related Cryptosystem
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作者 Bin Lu Fenlin Liu +1 位作者 Xin Ge Zhenyu Li 《Computers, Materials & Continua》 SCIE EI 2019年第8期687-699,共13页
Due to the characteristics of chaotic systems,different cryptosystems based on chaos have been proposed to satisfy the security of multimedia data.A plain image-related chaotic algorithm is proposed by Luo et al.with ... Due to the characteristics of chaotic systems,different cryptosystems based on chaos have been proposed to satisfy the security of multimedia data.A plain image-related chaotic algorithm is proposed by Luo et al.with high speed and efficiency.Security weaknesses of the cryptosystem are studied in this paper.It is found that the important secret key information is leaked because an important parameter can be obtained after an inverse operation in the last step of the cryptosystems without secret key.Meanwhile,the value zero is processed improperly in quantification algorithm.Based on the weaknesses,chosen plaintext attack on the cryptosystem is proposed,by which,an important parameter,equivalent to secret key,can be calculated with a specific chosen plain image.With the obtained parameter,the plain image of any ciphered image,encrypted by the cryptosystem,can be recovered.Then,an improvement is proposed to solve the problems after modifying the quantification algorithm.It is from the experiments that chosen plaintext attack is valid and improved algorithm possesses better performance. 展开更多
关键词 Multimedia cryptosystem CRYPTANALYSIS CHAOS chosen plaintext attack
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