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Geometrical transition properties of vortex cavitation and associated flow-choking characteristics in poppet valves

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第6期25卷 455-469页

作者： liang lu Zhongdong liang Yuming LIU Zhipeng WANG Shohei RYU School of Mechanical Engineering Tongji UniversityShanghai 201804China Frontiers Science Center for Intelligent Autonomous Systems Tongji UniversityShanghai 201210China Technical Research Laboratory Hitachi Construction Machinery Co.Ltd.Tsuchiura 300-0013Japan

Poppet valves have become increasingly significant in ensuring precise digital flow rate and pressure control in hydraulic systems,necessitating a more profound understanding of the geometrical properties of cavitation in them,as well as associated flow-choking conditions.Through a comparative analysis with experimentally observed cavity images,we found that large eddy simulation(LES)turbulence modeling effectively replicates the geometrical properties of cavitation in these valves.The analysis demonstrated that cavitation is generated from vortices that result from the interaction between the notch contracta flow and the surrounding fluid structure.Variations in the internal or external vena contracta conditions result in fixed or discrete cavities,and the length-to-diameter ratio serves as a measure of the transition between internal and external vena contracta flow properties.This study establishes a threshold length-to-diameter ratio of approximately 2 for the tested poppet valves.More specifically,in notch structures with a smaller valve opening,longer sealing length,and smaller throttling angle(corresponding to a larger length-to-diameter ratio),the liquid-to-vapor transfer process is more evident than that in the reverse direction.A long-standing vapor cavity becomes fixed inside the notch,leading to a more pronounced flow-choking phenomenon.In contrast,for structures with a smaller length-to-diameter ratio,the cavitation process for discrete vapor cavities is more complete,ensuring fluid flow continuity and significantly reducing the occurrence of the flow-choking phenomenon.

关键词： Poppet valves Vena contracta Vortex flow Vapor cavity Flow-choking

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A Degree Condition for Graphs Having All(a,b)-parity Factors

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Acta Mathematicae Applicatae Sinica 2024年第3期40卷 656-664页

作者： Hao-dong LIU Hong-liang lu School of Mathematics and Statistics Xi'an Jiaotong UniversityXi'an 710049China

Let a and b be positive integers such that a≤b and a≡b(mod 2).We say that G has all(a,b)-parity factors if G has an h-factor for every function h:V(G)→{a,a+2,…,b-2,b} with b|V(G)| even and h(v)≡b(mod 2) for all v∈V(G).In this paper,we prove that every graph G with n≥2(b+1)(a+b) vertices has all(a,b)-parity factors if δ(G)≥(b^(2)-b)/a,and for any two nonadjacent vertices u,v ∈V(G),max{d_(G)(u),d_(G)(v)}≥bn/a+b.Moreover,we show that this result is best possible in some sense.

关键词： degree condition all(a,b)-factors

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Stochastic programming based coordinated expansion planning of generation,transmission,demand side resources,and energy storage considering the DC transmission system

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Global Energy Interconnection 2024年第1期7卷 25-37页

作者： liang lu Mingkui Wei Yuxuan Tao Qing Wang Yuxiao Yang Chuan He Haonan Zhang Southwest Branch of State Grid Corporation of China Chengdu 610065P.R.China College of Electrical Engineering Sichuan UniversityChengdu 610065P.R.China

With the increasing penetration of wind and solar energies,the accompanying uncertainty that propagates in the system places higher requirements on the expansion planning of power systems.A source-grid-load-storage coordinated expansion planning model based on stochastic programming was proposed to suppress the impact of wind and solar energy fluctuations.Multiple types of system components,including demand response service entities,converter stations,DC transmission systems,cascade hydropower stations,and other traditional components,have been extensively modeled.Moreover,energy storage systems are considered to improve the accommodation level of renewable energy and alleviate the influence of intermittence.Demand-response service entities from the load side are used to reduce and move the demand during peak load periods.The uncertainties in wind,solar energy,and loads were simulated using stochastic programming.Finally,the effectiveness of the proposed model is verified through numerical simulations.

关键词： Hydro-wind-solar complementary Expansion planning Demand response Energy storage system Source-network-demand-storage coordination

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Spatial Heterogeneity and Influencing Factors of HFRS Epidemics in Rural and Urban Areas:A Study in Guanzhong Plain of Shaanxi Province,China

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Biomedical and Environmental Sciences 2022年第11期35卷 1012-1024页

作者： ZHU Ling Li LI Yan Ping lu liang LI Shu Juan REN Hong Yan National Institute for Nutrition and Health Chinese Center for Disease Control and PreventionBeijing 100050China State Key Laboratory of Resources and Environmental Information System Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China Xi’an Eighth Hospital Xi’an 710061ShaanxiChina State Key Laboratory of Infectious Disease Prevention and Control National Institute for Communicable Disease Control and PreventionChinese Center for Disease Control and PreventionBeijing 102206China

Objective The Guanzhong Plain of Shaanxi Province is a severely afflicted hemorrhagic fever with renal syndrome(HFRS)epidemic area,while HFRS prevalence has decreased in most epidemic areas in China.Little information is available regarding the leading fine-scale influencing factors in this highly HFRSconcentrated area and the roles of natural environmental and socioeconomic factors.To investigate this,two regions in the Guanzhong Plain,that is,the Chang’an District and Hu County,with similar geographical environments,different levels of economic development,and high epidemic prevalence,were chosen as representative areas of the HFRS epidemic.Methods Maximum entropy models were constructed based on HFRS cases and fine-scale influencing factors,including meteorological,natural environmental,and socioeconomic factors,from 2014 to 2016.Results More than 95% of the HFRS cases in the study area were located in the northern plains,which has an altitude of less than 800 m,with topography contributed 84.1% of the impact on the spatial differentiation of the HFRS epidemic.In the northern plains,precipitation and population density jointly affected the spatial differentiation of the HFRS epidemic,with contribution rates of 60.7% and 28.0%,respectively.By comparing the influencing factors of the northern plains of Chang’an District and Hu County,we found that precipitation and the normalized difference vegetation index(NDVI)dominated the HFRS epidemic in the relatively developed Chang’an District,while land-use type,temperature,precipitation and population density dominated the HFRS epidemic in the relatively undeveloped Hu County.Conclusion Topography was the primary key factor for HFRS prevalence in the Chang’an District and Hu County,and the spatial differentiation of HFRS was dominated by precipitation and population density in the northern plains.Compared with the influencing factors of the relatively developed Chang’an District,the developing Hu County was more affected by socioeconomic factors.When formulating target

关键词： Hemorrhagic fever with renal syndrome(HFRS) Spatial heterogeneity Influencing factors Economic development stages Fine scale Maximum Entropy model

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Structure,electronic,and nonlinear optical properties of superalkaline M_(3)O(M=Li,Na)doped cyclo[18]carbon

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Chinese Physics B 2024年第2期33卷 311-317页

作者：刘晓东卢其亮罗其全 School of Physics and Material Science Anhui UniversityHefei 230601China Institute of Physical Science and Information Technology Anhui UniversityHefei 230601China Department of Chemical Physics University of Science and Technology of ChinaHefei 230026China

Cyclo[18]carbon has received considerable attention thanks to its novel geometric configuration and special electronic structure.Superalkalis have low ionization energy.Doping a superalkali in cyclo[18]carbon is an effective method to improve the optical properties of the system because considerable electron transfer occurs.In this paper,the geometry,bonding properties,electronic structure,absorption spectrum,and nonlinear optical(NLO)properties of superalkaline M_(3)O(M=Li,Na)-doped cyclo[18]carbon were studied by using density functional theory.M_(3)O and the C_(18) rings are not coplanar.The C_(18) ring still exhibits alternating long and short bonds.The charge transfer between M_(3)O and C_(18) forms stable[M_(3)O]+[C_(18)]-ionic complexes.C_(18)M_(3)O(M=Li,Na)shows striking optical nonlinearity,i.e.,their first-and second-order hyperpolarizability(βvec andγ||)increase considerably atλ=1907 nm and 1460 nm.

关键词： superalkaline doped cyclocarbon structure and electronic properties nonlinear optical properties density functional theory(DFT)

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面向现代化的政府运行保障体系建构

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行政管理改革 2024年第5期5卷 50-58页

作者：卢亮国管局北戴河接待服务中心协调办公室

新时代政府运行保障体系需要转变传统机关事务发挥作用的路径依赖,建立系统高效的运行保障机制。这是推进国家治理体系和治理能力现代化的必然要求,对于破解政府内部治理难题,推动党政机关高质量发展具有重要意义。鉴于当前政府运行保... 详细信息

新时代政府运行保障体系需要转变传统机关事务发挥作用的路径依赖,建立系统高效的运行保障机制。这是推进国家治理体系和治理能力现代化的必然要求,对于破解政府内部治理难题,推动党政机关高质量发展具有重要意义。鉴于当前政府运行保障面临的实践困境,基于集中统一、节俭高效的目标,构建政府运行保障体系的分析框架,从坚持节俭高效导向、创新体制机制、加强资源统筹协调、深化开放多元四个维度构建政府运行保障的系统性治理模式,提升政府运行保障的效能性、专业性、协同性和示范性。

关键词：政府运行保障机关事务治理现代化

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基于Pushover方法的耗能自复位铰节点框架结构抗震性能分析

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东南大学学报（自然科学版） 2024年第3期54卷 608-615页

作者：鲁亮颜浩天叶雨立同济大学土木工程学院上海200092 华东建筑设计研究院有限公司上海200002

基于Pushover分析方法研究设置耗能自复位铰节点(EDSC-HJ)的钢筋混凝土框架结构的抗震性能.首先介绍EDSC-HJ框架的结构形式,并建立了EDSC-HJ框架结构的有限元模型,通过与振动台试验结果对比验证数值模拟的正确性;其次使用Pushover方法计... 详细信息

基于Pushover分析方法研究设置耗能自复位铰节点(EDSC-HJ)的钢筋混凝土框架结构的抗震性能.首先介绍EDSC-HJ框架的结构形式,并建立了EDSC-HJ框架结构的有限元模型,通过与振动台试验结果对比验证数值模拟的正确性;其次使用Pushover方法计算EDSC-HJ框架有控结构与无控结构的抗震性能并设计节点弹性恢复装置和耗能装置的力学参数.结果表明:EDSC-HJ框架结构节点相对转动刚度比的合理取值区间为0.05~0.5;设置节点阻尼器的EDSC-HJ有控结构的层间位移响应下降了76%,且满足限值要求;由于节点阻尼器的设置提高了结构的附加抗侧刚度,有控结构的基底剪力响应提高了23%.EDSC-HJ框架结构的抗震性能明显优于钢筋混凝土框架(RCF)结构,具有良好的韧性结构特征.

关键词： Pushover分析抗震性能耗能自复位铰节点有限元模型阻尼器

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人文地理方法论视角下的乡村聚落景观流派进展及展望

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地理科学进展 2024年第1期43卷 163-178页

作者：杨阳房艳刚梁璐东北师范大学地理科学学院长春130024 东北师范大学长白山地理过程与生态安全教育部重点实验室长春130024 西安外国语大学旅游学院/人文地理研究所西安710128

人文地理学方法论在经历了实证主义、人文主义、结构主义三种主要流派的过程探索之后逐渐趋向体系化、完整化,构成了整个现代地理学的思想轮廓和学术分期。论文在人文地理学哲学思潮的基础上,对国内外地理学视角下的乡村聚落景观流派成... 详细信息

人文地理学方法论在经历了实证主义、人文主义、结构主义三种主要流派的过程探索之后逐渐趋向体系化、完整化,构成了整个现代地理学的思想轮廓和学术分期。论文在人文地理学哲学思潮的基础上,对国内外地理学视角下的乡村聚落景观流派成果开展整合性归纳与总结,研究发现三种流派范式下的乡村聚落景观研究内涵各有侧重,呈现出“传统—批判—整合—超越”的更新路径,相互之间兼收并蓄,并行不悖。其中,实证主义地理学主要以刻画乡村聚落景观的空间性、区域性为主,表现为“空间化秩序特征描述”;人文主义地理学热衷于对景观地方性、象征性意义的探索,充满了“多元化人文情感关怀”;结构主义地理学注重景观的阶级性和社会性,关注景观背后的“因果化博弈机制解释”。总体来看,乡村聚落景观框架下的流派研究成果微观多于宏观、静态多于动态、物质空间多于社会经济空间,对指导中国乡村振兴实践各有所长,各有所短。未来应从人文地理方法论的视角创建中国特色乡村聚落景观研究的“中国范式”,针对不同类型乡村的聚落景观有所侧重地强化“短板研究”,以综合并充分发挥各个流派的优长。

关键词：乡村聚落景观人文地理学方法论流派进展研究展望

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孕妇环境暴露致使胎儿出生缺陷的无知责任审视

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医学与哲学 2024年第10期45卷 33-38页

作者：梁璐张欣中南大学人文学院湖南长沙410012 中南大学湘雅医院湖南长沙410008

环境暴露是造成胎儿出生缺陷的重要生殖风险,无知通常是孕妇环境暴露无责的借口。无知能否免责,则需要在知识论的立场上审视无知的责任归属问题。标准观点主张无知是知识的缺乏或缺失,蕴含着真值无知、信念无知和正当性无知三种可能。... 详细信息

环境暴露是造成胎儿出生缺陷的重要生殖风险,无知通常是孕妇环境暴露无责的借口。无知能否免责,则需要在知识论的立场上审视无知的责任归属问题。标准观点主张无知是知识的缺乏或缺失,蕴含着真值无知、信念无知和正当性无知三种可能。对等论认为仅当主体存在疏忽、故意、偏见、鲁莽、轻信或消极态度等理智恶习时,所造成的无知才是有责的。修正出于理智恶习的无知需要主体自我改善,通过个人自主原因和关系自主原因的动机干预,能够为维护母胎健康和公共卫生安全提供行动保障。

关键词：无知无知责任环境暴露出生缺陷理智恶习

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Evaluation of global land cover maps for cropland area estimation in the conterminous United States

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International Journal of Digital Earth 2015年第2期8卷 102-117页

作者： lu liang Peng Gong Department of Environmental Science Policy and ManagementUniversity of CaliforniaBerkeleyCAUSA Ministry of Education Key Laboratory for Earth System Modeling Center for Earth System ScienceTsinghua UniversityBeijingChina

Global land cover data could provide continuously updated cropland acreage and distribution information,which is essential to a wide range of applications over large geographical regions.Cropland area estimates were evaluated in the conterminous USA from four recent global land cover products:MODIS land cover(MODISLC)at 500-m resolution in 2010,GlobCover at 300-m resolution in 2009,FROM-GLC and FROM-GLC-agg at 30-m resolution based on Landsat imagery circa 2010 against the US Department of Agriculture survey data.Ratio estimators derived from the 30-m resolution Cropland Data Layer were applied to MODIS and GlobCover land cover products,which greatly improved the estimation accuracy of MODISLC by enhancing the correlation and decreasing mean deviation(MDev)and RMSE,but were less effective on GlobCover product.We found that,in the USA,the CDL adjusted MODISLC was more suitable for applications that concern about the aggregated county cropland acreage,while FROM-GLC-agg gave the least deviation from the survey at the state level.Correlation between land cover map estimates and survey estimates is significant,but stronger at the state level than at the county level.In regions where most mismatches happen at the county level,MODIS tends to underestimate,whereas MERIS and Landsat images incline to overestimate.Those uncertainties should be taken into consideration in relevant applications.Excluding interannual and seasonal effects,R 2 of the FROM-GLC regression model increased from 0.1 to 0.4,and the slope is much closer to one.Our analysis shows that images acquired in growing season are most suitable for Landsat-based cropland mapping in the conterminous USA.

关键词： cropland area global land cover FROM-GLC area estimation NASS survey

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