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黄土丘陵区林草地枯落层盖度遥感估算研究 被引量:4
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作者 谢小燕 刘咏梅 +2 位作者 李京忠 常伟 王玲 《光谱学与光谱分析》 SCIE EI CAS CSCD 北大核心 2016年第7期2217-2223,共7页
枯落层盖度的定量估算对于植被防蚀功效的评价具有重要作用。在陕北黄土丘陵沟壑区选取典型落叶林和退耕草地作为光谱测试样地,通过室内和野外实验分析枯落层—土壤混合场景的光谱变化规律,研究高光谱指数NDLI(normalized difference li... 枯落层盖度的定量估算对于植被防蚀功效的评价具有重要作用。在陕北黄土丘陵沟壑区选取典型落叶林和退耕草地作为光谱测试样地,通过室内和野外实验分析枯落层—土壤混合场景的光谱变化规律,研究高光谱指数NDLI(normalized difference lignin index)和CAI(cellulose absorption index)估算枯落层盖度的有效性。结果表明,受颜色及含水量等因素的影响,不同盖度枯落层—土壤混合场景的光谱反射率呈现不同的变化规律。干和湿状态下,随着枯落层盖度的增加混合场景的NDLI、CAI指数值均呈现增大的趋势,CAI与枯落层盖度的相关性高于NDLI,R^2最高为0.98(阔叶林和退耕草地干的混合场景),CAI能够更有效地估算枯落层盖度。野外实测验证了室内实验结果,退耕草地混合场景的CAI值与枯落层盖度相关性最高(R^2=0.90),野外条件下两种高光谱指数估算枯落层盖度的有效性均有一定程度的降低。该研究为枯落层盖度的遥感定量反演提供了基础与依据。 展开更多
关键词 枯落层盖度 土壤 混合场景 植被指数 黄土丘陵沟壑区
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利用半球图像反演祁连山区青海云杉(Picea crassifolia)林盖度 被引量:9
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作者 赵传燕 齐家国 +1 位作者 沈卫华 邹松兵 《生态学报》 CAS CSCD 北大核心 2009年第8期4196-4205,共10页
青海云杉是祁连山森林生态系统的主要建群种,具有重要的生态水文功能。冠层盖度是评估生态环境的一个重要参数,但目前缺乏有效评估手段。半球摄影技术在估算林冠盖度方面已显示出潜在优势,但它受到环境条件例如天气的影响仍然没有报道... 青海云杉是祁连山森林生态系统的主要建群种,具有重要的生态水文功能。冠层盖度是评估生态环境的一个重要参数,但目前缺乏有效评估手段。半球摄影技术在估算林冠盖度方面已显示出潜在优势,但它受到环境条件例如天气的影响仍然没有报道。在祁连山排露沟流域利用半球摄影技术反演冠层盖度,界定不同天气条件对阈值的影响,评估与传统方法估算林冠盖度的差别,结果表明:分类阈值受天气状况的影响较大,阴天的最佳阈值为118,晴天的最佳阈值为149;另外传统观测与半球图像法获得的林冠盖度有一定的差异,其中最大差值17.88%,最小差值5.34%。该项研究对青海云杉林盖度估算提供新的方法,为生态水文过程模型提供有价值的输入参数。 展开更多
关键词 祁连山区 青海云杉林 半球图像 层盖度
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珙桐群落学特征及群落环境分析 被引量:10
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作者 林洁 沈泽昊 +1 位作者 贺金生 陈伟烈 《植物学报》 CAS CSCD 1995年第S2期71-78,共8页
珙桐群落学特征及群落环境分析林洁,沈泽昊,贺金生,陈伟烈(中国科学院植物研究所,北京100044)(中国科学院武汉植物研究所,武昌430074)ENVIRONMENTEDANALYSISFORTHEDAVIDIAIN... 珙桐群落学特征及群落环境分析林洁,沈泽昊,贺金生,陈伟烈(中国科学院植物研究所,北京100044)(中国科学院武汉植物研究所,武昌430074)ENVIRONMENTEDANALYSISFORTHEDAVIDIAINVOLUCRATACIMMUNIT... 展开更多
关键词 珙桐群落 群落学特征 主要种类 层盖度 群落环境 后河自然保护区 分布区类型 残遗植物群落 群落分布 重要值
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焦岗湖沉水植被对水体反射光谱的影响
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作者 王杰 崔玉环 +2 位作者 李健 王旦 王晟 《遥感信息》 CSCD 北大核心 2019年第6期50-55,共6页
针对沉水植被冠层对光学浅水区离水辐射信号影响不清楚的问题,以浅水湖泊焦岗湖为研究区,根据水面光谱实测资料探究了沉水植物菹草生长对湖泊光学浅水区水体反射光谱特征的影响。结果表明,草型与淤泥底质在可见光波段对水中光均具有吸... 针对沉水植被冠层对光学浅水区离水辐射信号影响不清楚的问题,以浅水湖泊焦岗湖为研究区,根据水面光谱实测资料探究了沉水植物菹草生长对湖泊光学浅水区水体反射光谱特征的影响。结果表明,草型与淤泥底质在可见光波段对水中光均具有吸收作用,但草型底质的吸收作用明显强于淤泥底质;在近红外波段,2种类型底质对水中光都具有一定的反射作用,而淤泥底质的反射作用要强于草型底质;对于同一种草型底质,随着植被盖度增加、冠层水下深度减小,沉水植被冠层对湖泊水体反射光谱的贡献度逐渐增加,其中0.65~0.75um、0.7~0.9um分别为水体反射光谱对冠层盖度、冠层水下深度的光学敏感波段。该研究可为提高湖泊水质参数反演精度、改进沉水植物信息提取方法提供科学参考。 展开更多
关键词 光学浅水区 菹草 反射光谱 层盖度 水深
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河南草场资源的类型及其开发
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作者 李和平 张天义 王德甫 《地域研究与开发》 CSSCI 北大核心 1989年第S1期29-30,共2页
草场草地是河南的一项重要农业资源。省农牧厅畜牧局1980~1984年完成了全省草场资源调查和编图工作。1988年,我们采用TM卫星影像对原1∶50万河南草场资源类型图进行修编,对适宜营建人工草场的区域进行了评价。查明全省草场总面积约4433... 草场草地是河南的一项重要农业资源。省农牧厅畜牧局1980~1984年完成了全省草场资源调查和编图工作。1988年,我们采用TM卫星影像对原1∶50万河南草场资源类型图进行修编,对适宜营建人工草场的区域进行了评价。查明全省草场总面积约44338平方公里,占全省总面积的27%。 一、草场资源分布的地带性及类型 河南位于我国南北自然地带的过渡区。自然条件复杂,给形成各类自然草场提供了环境基础,自然草场的分布具有水平和垂直地带性的规律。 展开更多
关键词 草场资源 河南 平方 灌木 鲜草 层盖度 黄荆 总面积 疏林 草场畜牧业
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西樵山景观林改造——宫胁法的成功应用 被引量:5
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作者 方卓林 《中国城市林业》 2005年第6期33-36,共4页
Forest resources is limited inNanhai District of Foshan city. Since theimplementation of classified forestmanagement, the forests have not producedthe best ecological benefit, due to itsweakness in resistance to disea... Forest resources is limited inNanhai District of Foshan city. Since theimplementation of classified forestmanagement, the forests have not producedthe best ecological benefit, due to itsweakness in resistance to diseases andpests, forest fire and air pollution resultingfrom the simple species composition of theforests. Starting from 1997, XijiaoMountain in Nanhai District has been takenas an emphasis for forest standimprovement using the close-to-naturemanagement method, following the naturallaw of succession of forest community.Significant outcome have been achieved. 展开更多
关键词 林分改造 西樵山 近自然林 树种 森林群落 生物群落 层盖度 南海区 假苹婆 苹婆属 林地 农业用地 牛矢果 米锥 马尾松毛虫 松毛虫属 山牡荆 狗骨柴 对叶榕 罗伞树
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山丹县戈壁类型与灌木林封育成效
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作者 司健 《甘肃林业科技》 2021年第2期35-39,共5页
戈壁生态系统脆弱,一旦破坏很难恢复。山丹县北部戈壁灌木林是县域南部绿洲农牧区重要的生态屏障,规划为生态公益林区。样线样方结合法调查山丹县北部戈壁灌木林封育成效。结果表明,山丹县北部戈壁分布有11种灌木;分布有7种灌木群丛,珍... 戈壁生态系统脆弱,一旦破坏很难恢复。山丹县北部戈壁灌木林是县域南部绿洲农牧区重要的生态屏障,规划为生态公益林区。样线样方结合法调查山丹县北部戈壁灌木林封育成效。结果表明,山丹县北部戈壁分布有11种灌木;分布有7种灌木群丛,珍珠猪毛菜群丛为典型戈壁灌木林的基本群落,随着局域性盐碱化、沙化或向山地过渡被盐爪爪、蒙古扁桃、鲜黄小檗群丛代替,或组成双优群丛;灌木层盖度与戈壁类型、地形和坡度关系密切,而与海拔相关不大;超过半数灌木群落达到成林标准,基本分布于典型戈壁。总之,山丹县北部公益林区戈壁灌木林封育成效比较显著。 展开更多
关键词 戈壁类型 灌木林 封育 灌木层盖度
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Changes in Lake Ice Cover on the Morskie Oko Lake in Poland(1971-2007) 被引量:4
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作者 Adam Choiński Leszek Kolendowicz +1 位作者 Joanna Pociask-Karteczka Leszek Sobkowiak 《Advances in Climate Change Research》 SCIE 2010年第2期71-75,共5页
On the basis of data from the period 1971-2007, and by applying trend analysis, a study on formation, disappearance and duration of lake ice cover on the Morskie Oko Lake in the Tatra Mountains in southern Poland was ... On the basis of data from the period 1971-2007, and by applying trend analysis, a study on formation, disappearance and duration of lake ice cover on the Morskie Oko Lake in the Tatra Mountains in southern Poland was carried out. The results show decreasing trends in the maximum thickness of winter lake ice cover and in duration of lake ice phenomena, while air temperature recorded at the same period at the foot of the Tatra Mountains shows increasing trend. There are strong relationships between the course of lake ice phenomena and air temperature. 展开更多
关键词 lake ice cover thickness duration of lake ice phenomena air temperature
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Evaluation of parameters affecting reflection cracking in geogrid-reinforced overlay 被引量:3
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作者 Shahab Fallah Ali Khodaii 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第3期1016-1025,共10页
The influence of the most important parameters on the service life of reinforced asphalt overlay with geogrid materials in bending mode was examined by employing the Taguchi method and analysis of variance techniques.... The influence of the most important parameters on the service life of reinforced asphalt overlay with geogrid materials in bending mode was examined by employing the Taguchi method and analysis of variance techniques. The objectives of this experiment was to investigate the effects of grid stiffness, tensile strength, coating type, amount of tack coat, overlay thickness, crack width and stiffnesses of asphalt overlay and existing asphalt concrete on propagation of the reflection cracking. Results indicate that the stiffnesses of cracked layer and overlay are the main significant factors that can directly improve the service life of an overlay against the reflection cracking. Generally, glass grid is more effective in reinforced overlay than polyester grid. Effect of crack width of the existing layer is significant when its magnitude increases from 6 to 9 mm. 展开更多
关键词 reflection cracking geogrid bituminous mixture pavement overlay bending mode Taguchi method
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An Assessment of the Groundwater Potential of Bayero University Kano Permanent Site Using Induced Polarization and Self-potential Methods
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作者 Shehu Sani Jamaluddeen Abdulrahim Ali Bunawa Muhammad Saleh 《Journal of Earth Science and Engineering》 2014年第10期587-596,共10页
This paper centers on the investigation of the subsurface condition of Bayero University Kano Permanent Site with the aim of understanding the lithology and also mapping out the groundwater patterns within the area. T... This paper centers on the investigation of the subsurface condition of Bayero University Kano Permanent Site with the aim of understanding the lithology and also mapping out the groundwater patterns within the area. To achieve this, time domain IP (induced polarization) and SP (self-potential) methods were adopted using VES (vertical electrical sounding) technique with 49 stations sounded. The result of the interpreted and analyzed measured data shows that the area is underlain by two to five subsurface layers. These layers are top soil, laterite, weathered basement complex rocks, fractured basement complex rocks and fresh basement complex rocks. The aquiferous zone of the study area occurs in the weathered and fractured basements and its thickness ranges from 1.44 m to 70.157 m while the overburden thickness lies between 1.6 m and 72.104 m. SP values were plotted against depths of investigation in order to identify areas with greater depth of flow in the study area. From the analysis of the overburden thickness, aquifer thickness and SP values, the most favorable regions for groundwater exploitation were found around VES 6, 11, 13, 19, 26, 38, 44 and 48. The investigation also provides information about the subsurface condition with regards to engineering construction and safe place for refuse dumping in order to avoid groundwater contamination. 展开更多
关键词 SUBSURFACE induced polarization self-potential.
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Pricing and Permit Loads Impact on Overlay Costs for Highways in Louisiana
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作者 Saber Aziz Rasoulian Masood 《Journal of Civil Engineering and Architecture》 2012年第11期1445-1452,共8页
A methodology for the evaluation of the economic impact of overweight permitted vehicles hauling agricultural products on state highways is presented in this study. The different gross vehicle weight scenarios that ar... A methodology for the evaluation of the economic impact of overweight permitted vehicles hauling agricultural products on state highways is presented in this study. The different gross vehicle weight scenarios that are selected for this investigation range between 80,000 lb. and 100,000 lb. Uniform distribution of axle loads and lumped loads are considered in this study. This study evaluates the proposed higher truck loads and their economic impact to the highways and to the industry. The effects of adapting higher truck loads on the existing highways are evaluated using a deterministic load capacity evaluation as well as a reliability assessment. The target reliability level is derived from AASHTO (American Association of State Highway and Transportation Officials) standard design specifications to satisfy safe and adequate performance level. The overlay thickness required to carry traffic from each gross vehicle weight scenario for the overlay design period is determined. Differences in overlay life were calculated for different gross vehicle weight scenarios with uniform and lumped axle loads. The overlay thickness and costs were determined for a twenty year analysis period using statistical methods. The result showed that lumped loads with allowable axle load of 48,000 lb. produce more pavement damage than the current permitted gross vehicle weight for timber trucks with equally loaded axles. 展开更多
关键词 HIGHWAY control section OVERLAY average daily traffic PAVEMENT gross vehicle weight bridge cost.
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Rational concrete cover of prestressed concrete beams and slabs for fire resistance
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作者 郑文忠 侯晓萌 许名鑫 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2009年第5期593-600,共8页
As the influence of the ratio of the characteristic value of structural resistance to that of frequent combination effect, K, on the thickness of concrete cover of prestressed concrete (PC) beams and slabs for fire ... As the influence of the ratio of the characteristic value of structural resistance to that of frequent combination effect, K, on the thickness of concrete cover of prestressed concrete (PC) beams and slabs for fire resistance is not considered sufficiently in design criteria for concrete structures in China and other countries at present, numerical analyses were carried out by ANSYS software on unbonded prestressed concrete (UPC) oneway simply-supported and continuous slabs and beams, and bonded PC simply-supported and continuous beams subjected to fire in 186 cases. In the analysis, K, section dimensions and the thickness of concrete cover are regarded as independent variables and some calculation parameters determined by trial and error based on test resuits. Calculation formula for fire endurance of UPC simply-supported and continuous slabs was proposed, and the recommended thicknesses of cover of PC beams and slabs was presented in consideration of the influence of K and section dimensions as well as fire endurance requirements. Comparison analysis of relevant design criterions in China and other countries was performed to verify the rationale of the proposed values. 展开更多
关键词 prestressed concrete (PC) beams and slabs fire resistance fire endurance COVER
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Effects of overburden, rock strength and pillar width on the safety of a three-parallel-hole tunnel 被引量:3
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作者 Shong-loong CHEN Guo-wei LI Meen-wah GUI 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2009年第11期1581-1588,共8页
During the excavation of three-parallel-hole tunnel, the tunnel might collapse due to over-stress as a result of inadequate rock pillar width. Treating the rock overburden depth, rock strength, and rock pillar width a... During the excavation of three-parallel-hole tunnel, the tunnel might collapse due to over-stress as a result of inadequate rock pillar width. Treating the rock overburden depth, rock strength, and rock pillar width as variables, a series of 3D numerical analysis was carried out to examine the effect of each variable on the safety of the tunnel, in particular the rock pillar. A stress strength ratio (SSR) was used to define whether the safety of the rock pillar was exceeded. A simple design chart for the case of three-parallel-hole tunnel, which took into account the influence of overburden depth, rock pillar width, and rock strength, was also proposed for used in the preliminary design stage. 展开更多
关键词 Three-parallel-hole tunnel Tunnels interaction Rock pillar Numerical analysis Stress strength ratio (SSR)
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Analytical investigations and fuzzy logic-based modeling of the impact resistance of aluminum-epoxy laminated composites 被引量:1
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作者 NAZARI Ali DIDEHVAR Neda 《Science China(Technological Sciences)》 SCIE EI CAS 2011年第10期2785-2794,共10页
In the present paper, Charpy impact resistance of aluminum-epoxy laminated composites in both crack divider and crack ar-rester configurations has been investigated. In both configurations, an analytical investigation... In the present paper, Charpy impact resistance of aluminum-epoxy laminated composites in both crack divider and crack ar-rester configurations has been investigated. In both configurations, an analytical investigation has been carried out to evaluate the effects of layers thickness on impact resistance of the specimens. A model based on fuzzy logic for predicting impact re-sistance of the specimens has been presented. For purpose of building the model, training and testing using experimental re-sults from 126 specimens produced from two basic composites were conducted. The data used for the input data in fuzzy logic models are arranged in a format of 7 input parameters that cover the thickness of layers, the number of layers, the adhesive type, the crack tip configuration, the content of SiC particles, the content of methacrylated butadiene-styrene particles and the number of test trial. According to these input parameters, in the fuzzy logic model, the impact resistance of each specimen was predicted. The training and testing results in the fuzzy logic model have shown a strong potential for predicting impact resis-tance of aluminum-epoxy laminated composites. 展开更多
关键词 aluminum-epoxy laminated composite Charpy impact resistance analytical investigation fuzzy logic crack divider crack arrester
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Spatio-temporal modelling of the effect of selected environmental and land-use factors on acid grassland vegetation
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作者 Christian Damgaard 《Journal of Plant Ecology》 SCIE CSCD 2022年第2期253-264,共12页
Acid grasslands are threatened both by agricultural intensification with nutrient addition and increased livestock densities as well as by land abandonment.In order to understand and quantify the effect of selected en... Acid grasslands are threatened both by agricultural intensification with nutrient addition and increased livestock densities as well as by land abandonment.In order to understand and quantify the effect of selected environmental and land-use factors on the observed variation and changes in the vegetation of acid grasslands,large-scale spatial and temporal pin-point plant cover monitoring data are fitted in a structural equation model.The important sources of measurement and sampling uncertainties have been included using a hierarchical model structure.Furthermore,uncertainties associated with the measurement and sampling are separated from the process uncertainty,which is important when generating ecological predictions that may feed into local conservation management decisions.Generally,increasing atmospheric nitrogen deposition led to more grass-dominated acid grassland habitats at the expense of the cover of forbs.Sandy soils were relatively more acidic,and the effects of soil type on the vegetation include both direct effects of soil type and indirect effects mediated by the effect of soil type on soil pH.Both soil type and soil pH affected the vegetation of acid grasslands.Even though only a relatively small proportion of the temporal variation in cover was explained by the model,it would still be useful to quantify the uncertainties when using the model for generating local ecological predictions and adaptive management plans. 展开更多
关键词 joint distribution of plant abundance spatial and temporal variation of cover hierarchical Bayesian models pin-point cover data structural equation modelling acid grassland vegetation
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Spatiotemporal Variations of Soil Microarthropod Communities in the Negev Desert 被引量:2
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作者 Haggai WASSERSTROM Walter G.WHITFORD Yosef STEINBERGER 《Pedosphere》 SCIE CAS CSCD 2016年第4期451-461,共11页
Desert ecosystems are characterized by sparse vegetation that affects both abiotic parameters and soil biota along the soil profile. This study was conducted in 2010-2011 in a loess plain in the northern Negev Desert ... Desert ecosystems are characterized by sparse vegetation that affects both abiotic parameters and soil biota along the soil profile. This study was conducted in 2010-2011 in a loess plain in the northern Negev Desert highlands, Israel, to test two main hypotheses: 1) the abundance and diversity of microarthropods would vary seasonally in the top 30-cm soil layer, but would be relatively stable at soil depths between 30 and 50 cm and 2) soil microarthropods would be more abundant in soils under shrubs with large litter accumulations than under shrubs with less litter or bare soil. Soil samples were collected each season from the 0-50 cm profile at 10-cm intervals under the canopies of Hammada scoparia and Zygophyllum dumosum and from the bare interspa^es between them. Soil moisture and soil organic carbon in the top 30-cm layers varied seasonally, but there was little variation in the soil layers deeper than 30 cm. Soil mites were most abundant in the top 30-cm soil layer in autumn and winter, with the highest number of families found in winter. There were no differences in soil microarthropod abundance attributable to the presence or absence of shrubs of either species. The microarthropod communities of the microhabitats studied consisted of Acari, Psocoptera, and Collembola. The Acari were mostly identified to the family level and were dominated by Oribatida (55%) and Prostigmata (41%) in all seasons and microhabitats, while the psocopterans were most abundant in summer. These results are opposite to those obtained in other studies in similar xeric environments. Moreover, our findings were not in line with our hypothesis that a better microhabitat played a major role in microarthropod community composition, diversity, and density. 展开更多
关键词 MICROHABITAT SEASONALITY SHRUB soil depth soil mites soil moisture soil organic carbon
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Effect of Catch Cup Geometry on 3D Boundary Layer Flow over the Wafer Surface in a Spin Coating
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作者 Mizue MUNEKATA Seiichi KIMURA +5 位作者 Hiroaki KURISHIMA Jinsuke TANAKA Sohei YAMAMOTO Hiroyuki YOSHIKAWA Kazuyoshi MATSUZAKI Hideki OHBA 《Journal of Thermal Science》 SCIE EI CAS CSCD 2008年第1期56-60,共5页
Recently, development of high technology has been required for the formation of thin uniform film in manufacturing processes of semiconductor as the semiconductor instruments become more sophisticated. Spin coating is... Recently, development of high technology has been required for the formation of thin uniform film in manufacturing processes of semiconductor as the semiconductor instruments become more sophisticated. Spin coating is usually used for spreading photoresist on a wafer surface. However, since rotating speed of the disk is very high in spin coating, the dropped photoresist scarers outward and reattaches on the film surface. A catch cup is set up outside the wafer in spin coating, and scattered photoresist mist is removed from the wafer edge by the exhaust flow generated at the gap between the wafer edge and the catch cup. In the dry process of a spin coating, it is a serious concern that the film thickness increases near the wafer edge in the case of low rotating speed. The purpose of this study is to make clear the effect of the catch cup geometry on the 3D boundary layer flow over the wafer surface and the drying rate of liquid film. 展开更多
关键词 Rotating disk Spin coating Boundary layer flow Laser Doppler velocimeter Infrared camera
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