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Effect of streamlined nose length on aerodynamic performance of high-speed train with a speed of 400 km/h

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第7期25卷 525-540页

作者： nianxun li Tian li Zhiyuan DAI Deng QIN Jiye ZHANG State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong UniversityChengdu 610031China

The streamlined nose length(SNL)plays a crucial role in determining the aerodynamic performance of high-speed *** appropriate SNL can not only effectively reduce the magnitude of aerodynamic drag and lift forces,but also improve the performance of the high-speed train in tunnel passing and crosswind *** this study,a numerical simulation of the aerodynamic performance of high-speed trains at a speed of 400 km/h,with varying SNLs,is conducted using the k-ωshear stress transport(SST)turbulence *** different SNLs include 6.0,7.0,8.0,9.0,9.8,12.0,15.0,and 18.0 *** order to validate the accuracy of the numerical simulation,its results are compared with wind tunnel test data obtained from the *** simulation is carried out using compressible and incompressible gases to determine the effect of gas compressibility on *** impact of SNL on the aerodynamic performance of the trains is analyzed in terms of aerodynamic forces,velocity,and pressure *** comparison to the original train,the train with a 6.0 m SNL experienced a 10.8%increase in overall aerodynamic ***,the lift forces on the head and tail cars increased by 35.7%and 75.5%,*** the other hand,the train with an 18.0 m SNL exhibited a 16.5%decrease in aerodynamic ***,the lift forces on the head and tail cars decreased by 21.9%and 49.7%,*** aerodynamic drag force of the entire train varies linearly with the SNL,while the aerodynamic lift of the tail car follows a quadratic function in relation to the SNL.

关键词： Streamlined nose length(SNL) High-speed train Aerodynamic performance Numerical simulation Flow structures

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Species abundance is jointly determined by functional traits and negative density dependence in a subtropical forest in southern China

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Journal of Plant Ecology 2021年第3期14卷 491-503页

作者： Weitao Wang Yun Jiang Buhang li nianxun Xi Yongfa Chen Dong He Jiayi Feng Chengjin Chu Department of Ecology State Key Laboratory of BiocontrolSchool of Life SciencesSun Yat-sen UniversityGuangzhou 510275China School of Ecological and Environmental Sciences East China Normal UniversityShanghai 200241China

Aims The factors affecting species abundance are a subject of ongoing debates in community *** studies have demonstrated that tree abundance is affected by plant functional traits and negative density dependence(NDD).However,few studies have focused on the combined effects of NDD and plant functional traits on species *** In this study,we used tree functional traits and two census data from a 50-ha forest dynamic plot in the Heishiding(HSD)Nature Reserve to explore the combined effects of functional traits and NDD on species *** hierarchical Bayesian models,we analyzed how neighbor densities affected the survival of saplings from 130 species and extracted posterior means of the coefficients to represent *** structural equation modeling(SEM)analysis was then applied to investigate the causal relationships among species functional traits,NDD and species *** Findings SEM showed that tree functional traits,including specific leaf area(SLA),leaf area(LA),leaf dry matter content(LDMC),leaf N content(LNC),maximum electron transport rate(ETRmax)and conspecific adult negative density dependence(CNDDadult),together explained 20%of the total variation in tree ***,SLA affected tree abundance both directly and indirectly via CNDDadult,with a totally negative influence on *** and LNC had only indirect effects mediated by CNDDadult on tree *** and LA had directly negative effects on abundance,but their direct connections with CNDDaduIt were not *** addition,CNDDadult was negatively correlated with species abundance,indicating that abundant species are under stronger *** these investigated traits,SLA contributed the most to the variation in CNDDaduIt and *** argued that our findings of trait-CNDDadult-abundance relationships can improve our understanding of the determinants of species commonness and rarity in forests.

关键词： tree abundance negative density dependence functional traits common species rare species

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根系竞争对两个不同年代春小麦品种生长及资源分配的影响

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中国生态农业学报（中英文） 2020年第7期28卷 945-953页

作者：朱莉席念勋张大勇黄冈师范学院生物与农业资源学院/经济林木种质改良与资源综合利用湖北省重点实验室黄冈438000 北京师范大学生命科学学院/生物多样性与生态工程教育部重点实验室北京100875 中山大学生命科学学院/有害生物控制与资源利用国家重点实验室广州510275

植物相同基因型个体之间竞争地下资源会导致根系增生,这被称为根系竞争的“公地悲剧”现象。减少或者消除作物的根系增生有望提高种子产量。但人工育种是否已经无意识地影响了作物的根系竞争效应,目前研究尚不足。本研究选取春小麦古老... 详细信息

植物相同基因型个体之间竞争地下资源会导致根系增生,这被称为根系竞争的“公地悲剧”现象。减少或者消除作物的根系增生有望提高种子产量。但人工育种是否已经无意识地影响了作物的根系竞争效应,目前研究尚不足。本研究选取春小麦古老品种‘和尚头’和现代品种‘92-46’开展温室盆栽试验,通过设置尼龙隔离、无竞争塑料隔离和有竞争塑料隔离,并设置1倍营养和2倍营养两个营养水平,分析根系竞争对春小麦各器官生物量的影响,并采用标准化主轴回归(SMA)方法分析根系竞争对资源分配的影响。结果表明,与无竞争塑料隔离相比,尼龙隔离的根系生物量无显著变化,但茎叶生物量和总生物量显著提高。尼龙隔离的古老品种‘和尚头’种子生物量与无竞争塑料隔离无显著差异,而现代品种‘92-46’的种子生物量显著高于无竞争塑料隔离。2倍营养-有竞争塑料隔离与1倍营养-无竞争塑料隔离相比,根系生物量和种子生物量无显著差异,但茎叶生物量和总生物量显著降低。标准化主轴回归(SMA)分析发现,根系竞争对‘和尚头’的根系资源分配无显著影响,根系竞争显著降低了‘92-46’的根系资源分配但降低程度较小(尼龙隔离相比无竞争塑料隔离);根系竞争对两个品种的茎叶资源分配和种子资源分配均无显著影响。另外,本研究还发现:‘和尚头’的根系生物量和茎叶生物量大于‘92-46’,而种子生物量小于‘92-46’。除1倍营养-无竞争塑料隔离处理,其他隔离处理下‘和尚头’的根系资源分配与‘92-46’无显著差异;且‘和尚头’的茎叶资源分配大于‘92-46’,种子资源分配小于‘92-46’。总之,现代品种‘92-46’可能发展出一定程度的合作行为,通过根系分泌物介导识别邻株根系并减少根系资源分配;现代品种‘92-46’资源更多分配到繁殖生长,而古老品种‘和尚头’更多分配到茎叶生长。

关键词：达尔文农学 “公地悲剧” 根系竞争合作行为春小麦品种生物量资源分配

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