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Vegetation change in the Mt. Qomolangma Nature Reserve from 1981 to 2001

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Journal of Geographical Sciences 2007年第2期17卷 152-164页

作者： ZHANG Wei ZHANG Yili WANG Zhaofeng DING Mingjun YANG Xuchao lin xuedong LIU linshan Institute of Geographic Sciences and Natural Resources Research CAS Beijing 100101 China Graduate School of the Chinese Academy of Sciences Beijing 100039 China Institute of Tibetan Plateau Research CAS Beijing 100085 China

Based on the NOAA AVHRR-NDVI data from 1981 to 2001, the digitalized China Vegetation Map （1：1,000,000）, DEM, temperature and precipitation data, and field investigation, the spatial patterns and vertical characteristics of natural vegetation changes and their influencing factors in the Mt. Qomolangma Nature Reserve have been studied. The results show that：（1） There is remarkable spatial difference of natural vegetation changes in the Mt. Qomolangma Nature Reserve and stability is the most common status. There are 5.04% of the whole area being seriously degraded, 13.19% slightly degraded, 26.39% slightly improved, 0.97% significantly improved and 54.41% keeping stable. The seriously and slightly degraded areas, which mostly lie in the south of the reserve, are along the national boundaries. The areas of improved vegetation lie in the north of the reserve and the south side of the Yarlung Zangbo River. The stable areas lie between the improved and degraded areas. Degradation decreases with elevation. （2） Degeneration in the Mt. Qomolangma Nature Reserve mostly affects shrubs, needle-leaved forests and mixed forests. （3） The temperature change affects the natural vegetation changes spatially while the integration of temperature changes, slopes and aspects affects the natural vegetation change along the altitude gradients. （4） It is the overuse of resources that leads to the vegetation degeneration in some parts of the Mt. Qomolangma Nature Reserve.

关键词： Mt. Qomolangma (Everest) nature reserve AVHRR vegetation degradation Himalayas

表面腐蚀对离心铸造铝基复合材料耐磨性的影响

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特种铸造及有色合金 2013年第4期33卷 365-369页

作者：林雪冬重庆工程职业技术学院机械工程学院

采用离心铸造制备了Al-10Si-15Mg2Si复合材料。检测了该复合材料内层颗粒增强层在未经过腐蚀处理以及经过10%的NaOH溶液在常温下不同时间的腐蚀预处理后的耐磨性能。结果表明,复合材料增强层的磨损量随着腐蚀时间的延长呈现先降低后增... 详细信息

采用离心铸造制备了Al-10Si-15Mg2Si复合材料。检测了该复合材料内层颗粒增强层在未经过腐蚀处理以及经过10%的NaOH溶液在常温下不同时间的腐蚀预处理后的耐磨性能。结果表明,复合材料增强层的磨损量随着腐蚀时间的延长呈现先降低后增加的变化趋势。讨论了腐蚀预处理对复合材料颗粒增强层耐磨性能的影响机制。

关键词：腐蚀预处理耐磨性能 Mg2Si Al复合材料离心铸造

Study of the Effect of Combustion Chamber Shape on the Mixture Formation and Combustion Characteristic on CNG-di Engine

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Study of the Effect of Combustion Chamber Shape on the Mixtu...

The trend on runoff variations in the Lhasa River Basin

2016中国汽车工程学会年会暨展览会

作者： Jiang Tao lin xuedong Yang Miao State Key Laboratory of Automotive Simulation and Control Jilin University

A combustion system model of CNG- DI engine which was modified from a 2.0L diesel engine was built with software FIRE,the turbulence combustion model of CNG- DI engine was verified with the experimental result of CNG- DI optical engine,on the condition of unchanged 4 valves structure of original engine and the jet location,the spark plug was arranged between the two exhaust valves,the effect of different combustion chamber shapes on the microscopic physical fields such as turbulence characteristic in cylinder was simulated and studied,based on which the effect of combustion chamber shapes on the formation and combustion of mixture and the formation rule of NO was *** result shows that he combustion shape has a tremendous influence on the turbulence characteristic of cylinder and distribution characteristics of concentration fields especially besides the spark plug,which plays a decisive role on the whole process of combustion;Not only the production of NO can be inhibited and the combustion propagation speed which is in favour of lean burn can be controlled effectively when the straight mouth combustion chamber was used at the bottom of which has a proper *** amount of NO is closely related to the size of the reaction area and the duration of reaction besides the reaction rate of NO when the CNG fuel is injected into cylinder directly and burned thin,which can be controlled by the rational design of the structure of combustion chamber.

关键词： CNG-DI engine lean burn Injection mode mixture formation mechanism flame propagation characteristic NOx formation rule

来源： cnki会议评论

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Journal of Geographical Sciences 2008年第1期18卷 95-106页

作者： lin xuedong ZHANG Yili YAO Zhijun GONG Tongliang WANG Hong CHU Duo LIU linshan ZHANG Fei Institute of Geographic Sciences and Natural Resources Research CAS Beijing 100101 China Institute of Tibetan Plateau Research CAS Beijing 100085 China Tibet Hydroelectric Investigation Designed Research Institute Lhasa 850000 China Department of Hydraulic Engineering Tsinghua University Beijing 100084 China Tibet Hydrographic and Water Resources Survey Bureau Lhasa 850000 China Institute of Xizang-Plateau Atmosphere Environment Sciences Lhasa 850000 China

Taking the Lhasa River Basin above Lhasa hydrological station in Tibetan Plateau as a study area, the characteristics of the annual and monthly mean runoff during 1956-2003 were analyzed, based on the hydro-data of the two hydrological stations （Lhasa and Tanggya） and the meteorological data of the three meteorological stations （Damxung, Lhasa and Tanggya）. The trends and the change points of runoff and climate from 1956 to 2003 were detected using the nonparametric Mann-Kendall test and Pettitt-Mann-Whitney change-point statistics. The correlations between runoff and climate change were analyzed using multiple linear regression. The major results could be summarized as follows：（1） The annual mean runoff during the last 50 years is characterized by a great fluctuation and a positive trend with two change points （around 1970 and the early 1980s）, after which the runoff tended to increase and was increasing intensively in the last 20 years. Besides, the monthly mean runoff with a positive trend is centralized in winter half-year （November to April） and some other months （May, July and September）. （2） The trends of the climate change in the study area are generally consistent with the trend of the runoff, but the leading climate factors which aroused the runoff variation are distinct. Precipitation is the dominant factor influencing the annual and monthly mean runoff in summer half year, while temperature is the primary factor in winter season.

关键词： Lhasa River Basin trend of runoff variation Pettitt change-point test Mann-Kendall trend analysis multiple linear regressions

A l15-W Ytterbium-Doped Fibre Laser

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Chinese Physics Letters 2004年第6期21卷 1083-1085页

作者： ZHOUJun LOUQi-Hong KONGling-Feng WUZhong-lin xuedong DONGJing-Xing WEIYun-Rong YEZhen-Huan ZHUJian-Qiang WANGZhi-Jiang ShanghaiInstituteofOpticsandFineMechanics ChineseAcademyofSciencesShanghai201800

全球化下的经济赶超路径探索——基于D-S框架

维普期刊数据库评论

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南开经济研究 2014年第4期 32-49页

作者：朱廷珺林薛栋兰州商学院国际经济与贸易学院 730020 北京师范大学经济与工商管理学院 100875

本文通过构建具有产品差异性、厂商垄断性和规模报酬递增的两国模型,运用修正的D-S分析框架,证明了在全球化下一国经济赶超可分为两步:初期建立与要素禀赋相符的产业结构;当要素禀赋与产业结构发生背离时进入加速期,此时应确保技术进步... 详细信息

本文通过构建具有产品差异性、厂商垄断性和规模报酬递增的两国模型,运用修正的D-S分析框架,证明了在全球化下一国经济赶超可分为两步:初期建立与要素禀赋相符的产业结构;当要素禀赋与产业结构发生背离时进入加速期,此时应确保技术进步与要素禀赋变动同步,进行产业升级。基于韩国数据,本文实证研究发现固定产业结构对经济赶超有倒U型影响,证实了上述结论。其后依据全球化下技术进步的不同方式,给出了赶超国在加速期面临的三种不同赶超路径,认为我国当前可以选择"吸收主动技术溢出—吸收被动技术溢出—自主研发"的赶超路径。

关键词：比较优势竞争优势经济赶超技术进步

进出口产品质量测度方法的比较与中国事实——基于微观产品和企业数据的实证分析

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财经研究 2017年第5期43卷 89-101页

作者：魏浩林薛栋北京师范大学经济与工商管理学院北京100875

如何科学合理地测算贸易产品质量是研究企业产品质量异质性的一个关键问题,但目前仍缺乏一个被广泛认可的方法,也没有相关研究对不同方法的结果进行比较和检验。文章基于国家层面的进口质量、企业层面的出口质量和企业层面的进口质量三... 详细信息

如何科学合理地测算贸易产品质量是研究企业产品质量异质性的一个关键问题,但目前仍缺乏一个被广泛认可的方法,也没有相关研究对不同方法的结果进行比较和检验。文章基于国家层面的进口质量、企业层面的出口质量和企业层面的进口质量三个视角,将已有研究方法进行归类,并利用中国数据进行测算和检验,力求找到不同视角下最符合中国现实的测算方法。研究表明:(1)国家层面的进口质量测算使用KHW方法,而企业层面的出口质量测算则使用SHIBZ方法更加符合中国现实;(2)对于企业层面的进口质量测算,通过引入运输成本和汇率作为产品价格的工具变量对现有方法加以改进,可以克服其存在的样本选择偏差等问题;(3)对贸易产品质量测算方法在国家层面与企业层面、进口方面和出口方面进行划分,其测算结果能够合理地解释我国近年来的进出口产品质量变动趋势,且国家层面与企业层面的一般贸易进口产品质量的变动趋势一致。文章不仅为今后研究中国进出口产品质量问题提供了测算依据,而且有助于我们廓清我国进出口产品质量的现实情况及其变动趋势。

关键词：进口产品质量出口产品质量国家层面企业层面

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进口产品质量与中国企业创新

统计研究 2017年第6期34卷 16-26页

作者：魏浩林薛栋北京师范大学经济与工商管理学院

本文基于2000—2007年工业企业数据库和海关数据库,通过对已有企业层面进口产品质量测算方法的改进,从进口产品质量角度研究了我国进口促进政策与创新驱动发展战略之间的关系及其内在传导机制。研究发现:从一般贸易的进口来看,进口中间... 详细信息

本文基于2000—2007年工业企业数据库和海关数据库,通过对已有企业层面进口产品质量测算方法的改进,从进口产品质量角度研究了我国进口促进政策与创新驱动发展战略之间的关系及其内在传导机制。研究发现:从一般贸易的进口来看,进口中间品质量的提升显著促进了企业创新,进口资本品质量的提升对企业创新的影响表现为倒U型;技术溢出和市场扩大是企业进口产品质量促进创新的两个显著性路径,但是,降低生产成本路径不是影响企业创新的显著性路径;进口产品质量的提升显著增加了企业持续创新的时间。本文的政策启示是:中国实施进口促进政策具有合理性,实施积极的进口贸易政策对国家创新驱动发展战略具有积极的促进作用。

关键词：进口产品质量企业创新持续创新

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润滑脂管道流动阻力的测试研究

机械工程学报 2005年第10期41卷 185-192页

作者：张晓光徐健键林学栋中国矿业大学机电工程学院徐州221008 南京大学应用物理研究所南京210093

分析了存在壁滑移时的流动阻力测试原理,对测试系统和阻力计算进行了研究。为了测试润滑脂的阻力特性,去除壁滑移流动的影响,根据Mooney方法建立了扣除壁滑移后适应任一管径的流动方程;润滑脂的粘弹性、触变性等其他因素会使流动曲线不... 详细信息

分析了存在壁滑移时的流动阻力测试原理,对测试系统和阻力计算进行了研究。为了测试润滑脂的阻力特性,去除壁滑移流动的影响,根据Mooney方法建立了扣除壁滑移后适应任一管径的流动方程;润滑脂的粘弹性、触变性等其他因素会使流动曲线不重合,研制了管流流变仪测试系统,并制定了合理的试验方法,达到使这些因素的影响降到最低和分离壁滑移流动的试验效果。通过试验验证了所建立的适应任一管径的流动方程,求解了流动方程的阻力近似解,并通过三维优化计算降低了近似解与精确解的偏差。润滑脂流动阻力的测试研究,为集中润滑系统的管路输送提供了理论和试验依据。

关键词：润滑脂管道流动壁滑移阻力特性测试系统