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Home range variation of two different-sized groups of golden snub-nosed monkeys (Rhinopithecus roxellana) in Shennongjia,China:implications for feeding competition
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作者 Peng-Lai Fan Yi-Ming Li +4 位作者 Craig B.Stanford Fang Li Ze-Tian Liu Kai-Hua Yang Xue-Cong Liu 《动物学研究》 CAS CSCD 2019年第2期121-128,共8页
Knowledge on the home range size of a species or population is important for understanding its behavioral and social ecology and improving the effectiveness of conservation strategies.We studied the home range size of... Knowledge on the home range size of a species or population is important for understanding its behavioral and social ecology and improving the effectiveness of conservation strategies.We studied the home range size of two different-sized groups of golden snub-nosed monkeys (Rhinopithecus roxellana)in Shennongjia,China.The larger group (236 individuals) had a home range of 22.5 km^2 from September 2007 to July 2008,whereas the smaller group (62 individuals)occupied a home range of 12.4 km^2 from November 2008 to July 2009.Both groups exhibited considerable seasonal variation in their home range size,which was likely due to seasonal changes in food availability and distribution.The home range in any given season (winter,spring,summer,or winter+spring+summer)of the larger group was larger than that of the smaller group.As the two groups were studied in the same area,with the confounding effects of food availability thus minimized,the positive relationship between home range size and group size suggested that scramble feeding competition increased within the larger group. 展开更多
关键词 RHINOPITHECUS ROXELLANA Home range SIZE Group SIZE FEEDING competition
Age factor affects reading acuity and reading speed in attaining text information
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作者 Ai-Hong Chen Nursyairah Mohd Khalid Noor Halilah Buari 《国际眼科杂志:英文版》 SCIE CAS 2019年第7期1170-1176,共7页
AIM: To investigate the effect of age on reading acuity and reading speed in attaining text information in healthy eyes.METHODS: Reading acuity, critical print size, reading speed and maximum reading speed were measur... AIM: To investigate the effect of age on reading acuity and reading speed in attaining text information in healthy eyes.METHODS: Reading acuity, critical print size, reading speed and maximum reading speed were measured in groups of 40 children (8 to 12 years old), 40 teenagers (13 to 19 years old), 40 young adults (20 to 39 years old), and 40 adults (40 years old and above) using the Buari-Chen Malay Reading Chart [contextual sentences (CS) set and random words (RW) set] in a cross-sectional study design.RESULTS: Reading acuity was significantly improved by 0.04 logMAR for both CS set and RW set from children to teenagers, then gradually worsened from young adults to adults (CS set: 0.06 logMAR;RW set: 0.08 logMAR). Critical print size for children showed a significant improvement in teenagers (CS set: 0.14 logMAR;RW set: 0.07 logMAR), then deteriorated from young adults to adults by 0.09 logMAR only for CS set. Reading speed significantly increased from children to teenagers,[CS set: 46.20 words per minute (wpm);RW set: 42.06 wpm], then stabilized from teenagers to young adults, and significantly reduced from young adults to adults (CS set: 28.58 wpm;RW set: 24.44 wpm). Increment and decrement in maximum reading speed measurement were revealed from children to teenagers (CS set: 39.38 wpm;RW set: 43.38 wpm) and from young adults to adults (CS set: 22.26 wpm;RW set: 26.31 wpm) respectively.CONCLUSION: The reference of age-related findings in term of acuity and speed of reading should be incorporated in clinical practice to enhance reading assessment among healthy eyes population. 展开更多
关键词 READING ACUITY CRITICAL print size readingspeed MAXIMUM READING SPEED age effect
Effect of Particle Size on Gasification Reactivity of Different Rank Coal Chars 预览
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作者 Li Wenxiu Rong Ling Kun Jia Feng Jun 《环境科学前沿:中英文版》 2019年第1期8-12,共5页
In the current research process of coal rank char gasification reaction in China, it is found that particle size has different influence on the gasification reactivity of coal char of different ranks. Therefore, monod... In the current research process of coal rank char gasification reaction in China, it is found that particle size has different influence on the gasification reactivity of coal char of different ranks. Therefore, monodisperse pulverized coal was prepared from eight kinds of coal chars of different ranks in entrained-flow gasifier. The particle size and gasification temperature of coal char were analyzed for these samples. The degree of influence of carbon dioxide gasification reaction. Through research and analysis, the performance differences of these samples under different carbon conversion rates were compared, and the sample reaction under high carbon conversion rates was discussed. The experimental results show that the orderliness of the microcrystalline structure of coal char is directly proportional to the rank of coal, while the gasification activity of coal char is inversely proportional to the rank of coal. Therefore, for different coal ranks, the influence of coal char particle size on coal char gasification reaction is different. According to the experiments, smaller coal char size and higher gasification temperature can promote the reactivity of higher-order coal gasification. In order to clarify the correlation between particle size and gasification reactivity of coal chars with different ranks, this paper discussed this issue. 展开更多
关键词 Particle Size DIFFERENT RANKS of COAL GASIFICATION Activity of COAL CHAR
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Remote Sensing Monitoring of Surface Characteristics in the Badain Jaran, Tengger, and Ulan Buh Deserts of China 预览
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作者 LIU Qingsheng LIU Gaohuan +1 位作者 HUANG Chong LI He 《中国地理科学:英文版》 SCIE CSCD 2019年第1期151-165,共15页
Deserts and sandy land in northern China are very susceptible to sandy desertification and are the main source of sand-dust storms of Asian dust. However, because of the complex factors involved, descriptions of the r... Deserts and sandy land in northern China are very susceptible to sandy desertification and are the main source of sand-dust storms of Asian dust. However, because of the complex factors involved, descriptions of the relationship between sandy desertification and surface characteristics in these regions are lacking. We monitored the surface characteristics and their changes in time using information about soil, vegetation, and landforms in the Badain Jaran Desert(BJD), Tengger Desert(TD), and Ulan Buh Desert(UBD) in the northern China. The monitoring was done using tasseled cap angle(TCA), disturbance index(DI), and topsoil grain size index(TGSI) from Moderate Resolution Imaging Spectroradiometer(MODIS) images combined with a decision tree classification. Results showed that the TD had higher topsoil fine sand content, and the ratio of non-vegetated to vegetated areas was similar with that in the UBD. Northeast-southwest coarse sand dunes with thin interdune(NECTI) dominated the BD, fine sand dunes(FSD) dominated the TD, and a combination of northeast-southwest coarse sand dunes with wide interdune(NECWI) and northwest-southeast coarse sand dunes with wide interdune(NWCWI) dominated the UBD. From 2000 to 2015, in the BJD the area of the NECTI, non-sand dune(Non) and potential sand sources(PSS) increased, whereas the area of the NECWI, FSD and NWCWI decreased, indicating a improve process in the BJD. In the TD, the area covered by Non increased, whereas the area covered by PSS, NECWI, NECTI, FSD, and NWCWI decreased from 2000 to 2015. The area covered by the various surface characteristic types fluctuated annually in the UBD from 2000 to 2015. Changes in surface characteristics reflect the combined effects of natural conditions and human activity. The findings of our study will assist scientists and policy makers in proposing different management techniques to combat sandy desertification for the different surface characteristics of these regions. 展开更多
关键词 surface characteristics MODIS DESERT tasseled CAP angle DISTURBANCE INDEX TOPSOIL GRAIN size INDEX
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The spatial distribution of major and trace elements of surface sediments in the northeastern Beibu Gulf of the South China Sea 预览
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作者 Qian Ge George Z Xue +3 位作者 Liming Ye Dong Xu Jianru Zhao Fengyou Chu 《海洋学报:英文版》 SCIE CAS CSCD 2019年第3期93-102,共10页
A multi-index analysis including grain size, major and trace elements is performed on the surface sediments from the northeastern Beibu Gulf to trace the sources of the sediments and to understand the controlling fact... A multi-index analysis including grain size, major and trace elements is performed on the surface sediments from the northeastern Beibu Gulf to trace the sources of the sediments and to understand the controlling factors for elements distribution. The mean grain size exhibits a wide variation ranging from 0.09Φ to 8.05Φ with an average value of 5.33Φ. The average contents of major elements descend in an order of c(SiO2)>c(Al2O3)>c(Fe2O3)>c(CaO)>c(MgO)>c(K2O)>c(Na2O)>c(TiO2)>c(P2O5)>c(MnO), while those of trace elements exhibit a descending order of c(Sr)>c(Rb)>c(V)>c(Zn)>c(Cr)>c(Pb)>c(Ni)>c(Cu)>c(As). On the basis of elementary distribution characteristics and statistical analyses, the study area is divided into the four zones: Zone I is located in the northeastern coastal area of the gulf, which receives large amount of fluvial materials from local rivers in Guangxi and Guangdong, China, and the Qiongzhou Strait;Zone Ⅱ is located in the center of the study area, where surface sediments exhibits a multiple source;Zone Ⅲ is located in the Qiongzhou Strait, where surface sediments are dominated by materials from the Zhujiang River and Hainan;Zone IV is located in the southwest of the study area, where surface sediments are mainly originated from the Red River and Hainan. The statistical analyses of sediment geochemical characteristics reveal that the grain size, which is mainly influenced by hydrodynamics and mineral composition of terrigenous materials, is the leading factor controlling the elementary distribution.Meanwhile, impacts from anthropogenic activities and marine biogenic process will also be taken into consideration. 展开更多
关键词 GRAIN size major and TRACE elements Beibu GULF spatial distribution sediment source
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基于复杂网络构建的系统重要性银行评估研究 预览
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作者 邢春娜 《金融发展研究》 北大核心 2019年第1期19-25,共7页
复杂网络为分析系统性金融风险和系统重要性机构提供了全局性视角,但由于数据获取上的局限,我国银行系统网络构建存在困难。利用贝叶斯方法和2013—2015年银行资产负债数据构建银行系统网络,在此基础上建立系统性损失测度指标,并讨论规... 复杂网络为分析系统性金融风险和系统重要性机构提供了全局性视角,但由于数据获取上的局限,我国银行系统网络构建存在困难。利用贝叶斯方法和2013—2015年银行资产负债数据构建银行系统网络,在此基础上建立系统性损失测度指标,并讨论规模与网络中心性在系统重要性银行评估中的作用。研究发现:国有大型商业银行处于银行系统的枢纽位置;同业负债和入度对银行个体风险造成的系统性损失有显著正向影响,而资本缓冲和出度增大能够降低局部危机造成的整体损失。因此,规模仍是影响银行系统重要性的主要因素,而银行之间的关联性也发挥着越来越重要的作用。 展开更多
关键词 复杂网络 系统重要性银行 规模 网络中心性 关联性
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Scale-Dependent Nature of Porosity and Pore Size Distribution in Lacustrine Shales: An Investigation by BIB-SEM and X-Ray CT Methods
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作者 Junqian Li Pengfei Zhang +4 位作者 Shuangfang Lu Chen Chen Haitao Xue Siyuan Wang Wenbiao Li 《地球科学学刊:英文版》 SCIE CAS CSCD 2019年第4期823-833,共11页
Due to heterogeneous pore distributions within shales,petrophysical properties of shales determined by scanning electron microscopy(SEM) and X-ray computed tomography(CT) methods strongly depend on the observed domain... Due to heterogeneous pore distributions within shales,petrophysical properties of shales determined by scanning electron microscopy(SEM) and X-ray computed tomography(CT) methods strongly depend on the observed domain size(analysis scale). In this paper,the influence of the analysis scale on areal and bulk porosities and pore size distribution(PSD) for lacustrine shales from the Dongying sag of Bohai Bay Basin,China were investigated using broad ion beam(BIB)-SEM and X-ray CT methods.The BIB-SEM cross-sections with high imaging resolution(10 nm/pixel) and a large field of view(>1 mm2)mainly describe the 2 D nanoscale pore system in the two shales(samples F41#-2 and Y556#-1),while CTbased 3 D reconstructions with resolutions of 0.42(F41#-1) and 0.5 μm/pixel(H172#-1) reflect the 3 D submicron pore system. The results indicate that the areal(bulk) porosity exhibits a multiple power-law distribution with increasing analysis area(volume),which can be used to extrapolate the porosity of a given area(volume). Based on SEM and CT investigations,the sizes of the minimum representative elementary areas(REAs) and volumes(REVs) were determined respectively,which are closely associated with the heterogeneousness of the pore system. Minimum REAs are proposed to be 2.93×10~4(F41#-2) and 0.91×10~4μm2(Y556#-1),and minimum REVs are 0.016(F41#-1) and 0.027 mm~3(H172#-1). As the analyzed areas(volumes) are larger than the minimum REA(REV),obtained 2 D(3 D) PSDs are comparable to each other and can be considered to reflect the shale PSD. These results provide insights into the porosity and PSD characterization of shales by SEM and X-ray CT methods. 展开更多
关键词 LACUSTRINE SHALE POROSITY PORE size distribution BIB-SEM X-ray CT
Grain Size-Dependent Mechanical Properties of a High-Manganese Austenitic Steel
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作者 Xiao-Jiang Wang Xin-Jun Sun +4 位作者 Cheng Song Huan Chen Shuai Tong Wei Han Feng Pan 《金属学报:英文版》 SCIE EI CAS CSCD 2019年第6期746-754,共9页
The effect of grain size on the mechanical properties of a high-manganese(Mn)austenitic steel was investigated via electron-backscattered diffraction,transmission electron microscope,X-ray diffraction,and tensile and ... The effect of grain size on the mechanical properties of a high-manganese(Mn)austenitic steel was investigated via electron-backscattered diffraction,transmission electron microscope,X-ray diffraction,and tensile and impact tests at 25°C and-196°C.The Hall–Petch strengthening coefficients for the yield strength of the high-Mn austenitic steels were 7.08 MPa mm 0.5 at 25°C,which increased to 14 MPa mm 0.5 at-196°C.The effect that the grain boundary strengthening had on improving the yield strength at-196°C was better than that at 25°C.The impact absorbed energies and the tensile elongations were enhanced with the increased grain size at 25°C,while they remained nearly unchanged at-196°C.The unchanged impact absorbed energies and the tensile elongations were primarily attributed to the emergence of the micro-twin at-196°C,which promoted the cleavage fracture in the steels with large-sized grains.Refining the grain size could improve the strength of the high-Mn austenitic steels without impairing their ductility and toughness at low temperature. 展开更多
关键词 High-Mn steel Grain size LOW-TEMPERATURE TOUGHNESS Hall–Petch Micro-twin
城市快递末端节点规模影响因素探讨 被引量:1
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作者 晏雪 石小法 《综合运输》 2019年第2期111-115,126共6页
电子商务的发展使得快递末端节点数量不断增加,但是在规划末端节点上大多按照经验设置,造成许多末端节点的规模并不合理。为了明确影响城市末端节点规模的因素,为合理规划末端节点提供依据,本文通过实际调查收集了城市快递末端节点的一... 电子商务的发展使得快递末端节点数量不断增加,但是在规划末端节点上大多按照经验设置,造成许多末端节点的规模并不合理。为了明确影响城市末端节点规模的因素,为合理规划末端节点提供依据,本文通过实际调查收集了城市快递末端节点的一手数据,并采用灰色关联度法确定了影响末端节点规模分拣暂存区的主要因素。根据分析结果显示,派件量、快递员数量、快递配送频率和快递到达频率为主要影响因素。根据主要影响因素提出了确定末端节点规模的一般流程和通过将末端节点部分功能转移至上级节点以此降低末端节点成本的建议。 展开更多
关键词 快递 灰色关联分析 影响因素 末端节点 规模
Recent Progress in Dual-Polarization Radar Research and Applications in China 预览
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作者 Kun ZHAO Hao HUANG +11 位作者 Mingjun WANG Wen-Chau LEE Gang CHEN Long WEN Jing WEN Guifu ZHANG Ming XUE Zhengwei YANG Liping LIU Chong WU Zhiqun HU Sheng CHEN 《大气科学进展:英文版》 SCIE CAS CSCD 2019年第9期961-974,共14页
Dual-polarization(dual-pol)radar can measure additional parameters that provide more microphysical information of precipitation systems than those provided by conventional Doppler radar.The dual-pol parameters have be... Dual-polarization(dual-pol)radar can measure additional parameters that provide more microphysical information of precipitation systems than those provided by conventional Doppler radar.The dual-pol parameters have been successfully utilized to investigate precipitation microphysics and improve radar quantitative precipitation estimation(QPE).The recent progress in dual-pol radar research and applications in China is summarized in four aspects.Firstly,the characteristics of several representative dual-pol radars are reviewed.Various approaches have been developed for radar data quality control,including calibration,attenuation correction,calculation of specific differential phase shift,and identification and removal of non-meteorological echoes.Using dual-pol radar measurements,the microphysical characteristics derived from raindrop size distribution retrieval,hydrometeor classification,and QPE is better understood in China.The limited number of studies in China that have sought to use dual-pol radar data to validate the microphysical parameterization and initialization of numerical models and assimilate dual-pol data into numerical models are summarized.The challenges of applying dual-pol data in numerical models and emerging technologies that may make significant impacts on the field of radar meteorology are discussed. 展开更多
关键词 DUAL-POLARIZATION RADAR QUANTITATIVE PRECIPITATION estimation PRECIPITATION MICROPHYSICS DROP size distribution numerical model
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Characteristics of size distributions and sources of water-soluble ions in Lhasa during monsoon and non-monsoon seasons
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作者 Nannan Wei Zhiyou Xu +5 位作者 Junwen Liu Guanghua Wang Wei Liu Deqing Zhuoga Detao Xiao Jian Yao 《环境科学学报:英文版》 SCIE EI CAS CSCD 2019年第8期155-168,共14页
To understand the physical and chemical characteristics, particle size distribution and sources of size-separated aerosols in Lhasa, which is located on the Tibetan Plateau(TP), six sizes of aerosol samples were colle... To understand the physical and chemical characteristics, particle size distribution and sources of size-separated aerosols in Lhasa, which is located on the Tibetan Plateau(TP), six sizes of aerosol samples were collected in Lhasa in 2014. Ca^2+, NH4^+, NO3^-,SO4^2-and Cl^-were the dominant ions. The ratio of cation equivalents(CE) to anion equivalents(AE) for each particle size segment indicated that the atmospheric aerosols in Lhasa were alkaline. SO4^2-and NO3-could be neutralized by Ca^2+, but could not be neutralized by NH4^+, according to the [NH4^+]/[NO3^-+ SO4^2-] and [Ca^2+]/[NO3^-+ SO4^2-] ratios. Mobile sources were dominant in PM0.95-1.5,PM1.5-3 and PM3-7.2, while stationary sources were dominant in the other three size fractions according to the [NO3^-]/[SO4^2-] ratios. The particle size distribution of all watersoluble ions during monsoon and non-monsoon periods was characterized by a bimodal distribution due to the different sources and formation mechanisms, and it was revealed that different ions had different sources in different seasons and different particle size segments by combining particle size distribution with correlation analysis. Source analysis of aerosols in Lhasa was performed using the Principal component analysis(PCA) for the first time, which revealed that combustion sources, motor vehicle exhaust, photochemical reaction sources and various types of dust were the main sources of Lhasa aerosols.Furthermore, Lhasa’s air quality was also affected by long-distance transmission, expressed as pollutants from South Asia and West Asia, which were transmitted to Lhasa according to backward trajectory analysis. 展开更多
关键词 Atmospheric AEROSOLS WATER-SOLUBLE ions(WSIs) Size distribution Principal component analysis(PCA) BACKWARD trajectory
The effect of pore size and porosity of Ti6Al4V scaffolds on MC3T3-E1 cells and tissue in rabbits
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作者 LUAN HuiQin WANG LiTing +4 位作者 REN WeiYan CHU Zhao Wei HUANG YunFei LU ChengLin FAN YuBo 《中国科学:技术科学英文版》 SCIE EI CAS CSCD 2019年第7期1160-1168,共9页
Electron beam melting(EBM) allows the fabrication of specific porous titanium implants, whereas their in vitro and in vivo biological performance should be further investigated. In this study, we examined the porous T... Electron beam melting(EBM) allows the fabrication of specific porous titanium implants, whereas their in vitro and in vivo biological performance should be further investigated. In this study, we examined the porous Ti6 Al4 V scaffolds(low, 334.1 μm pore size with 55.4% porosity;middle, 383.2 μm pore size with 65.2% porosity;and high, 401.6 μm pore size with 78.1%porosity) fabricated through EBM. The structural characterization and mechanical properties of porous Ti6 Al4 V scaffolds were measured through micro-computed tomography(micro-CT), scanning electron microscopy, and a material testing system.MC3 T3-E1 cells were used to assess the proliferation and differentiation of the cells on different scaffolds at day 7 and day 14 based on the expression levels of genes, including alkaline phosphatase, bone morphogenetic protein-2, osteopontin and runtrelated transcription factor-2. Rabbits with distal femoral defects were utilized to evaluate bone ingrowth in the porous titanium.All of the samples were subjected to micro-CT and histological analysis after 12 weeks. Results showed that compressive Young’s modulus of 0.3–1.1 GPa was similar to the trabecular bone. The three types of porous Ti6 Al4 V scaffolds were inclined to promote cell proliferation, whereas cell differentiation and bone ingrowth into the porous scaffolds were biased to the porous titanium with relatively large pores and porosity(middle and high). This study implied that the present porous implant design,which had the combined advantages of different pore sizes and porosity, might be meaningful and promising for trabecular bone defect restoration. 展开更多
关键词 PORE size POROSITY porous titanium alloy scaffolds OSTEOGENESIS bone DEFECT
Effect of Spherical Particle Size on the Electrochemical Properties of Lithium Iron Phosphate
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作者 刘远远 LIU Hao +2 位作者 ZHAO Xinxin WANG Li 梁广川 《武汉理工大学学报:材料科学英文版》 SCIE EI CAS 2019年第3期549-557,共9页
The effect of spherical particle size on the surface morphology, electrochemical property and processability of lithium iron phosphate was systematically studied. Spherical lithium iron phosphate with different partic... The effect of spherical particle size on the surface morphology, electrochemical property and processability of lithium iron phosphate was systematically studied. Spherical lithium iron phosphate with different particle size distributions controlled with ball time of precursor slurry was prepared by spray drying method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), charge and discharge measurements and EIS. The electrochemical performances of the sample materials were measured by coin cells and 14500 batteries. XRD shows that the spherical lithium iron phosphate with different particle sizes all have good crystal structure due to the perfect mixing of the raw materials and rapid drying. The lithium iron phosphate microsphere with different particle sizes self-assembled with submicron primary particles has a core-shell structure. The longer ball time the precursors are, the smaller the active material particles are prepared. The electrode material with 6 h ball time of precursor slurry has the best physical properties and the processability. The composite has a uniform particle size and higher tap density of 1.46 g/cm3, which delivers a discharge capacity of 167.6 mAh/g at a discharge rate of 0.5 C. The results were confirmed by the 14 500 mA h cylindrical batteries, which delivers a discharge capacity of 579 mAh at 0.5 C. And low-temperature performance with capacity of 458.5 mA h at -20 °C under a discharge rate of 0.5 C is the 79.2% of the same discharge rate at 25 °C. Otherwise, the 14500 batteries also exhibit excellent cycling performance and the capacity maintains 93% after 2 000 cycles. 展开更多
关键词 LITHIUM ion battery micro-spherical structure PARTICLE size SPRAY DRYING
基础实验:金纳米粒子的制备及其光学性质 预览
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作者 南彩云 张宇 +1 位作者 李玉峰 赵云岺 《大学化学》 CAS 2019年第1期58-63,共6页
围绕金纳米粒子前沿内容,设计了一个简易的本科生基础实验,利用柠檬酸钠还原氯金酸法制备分散性好的金纳米粒子溶液,讨论了其尺寸与颜色的关系,探究了不同电解质和非电解质对金纳米粒子团聚及其颜色的影响,初步了解金纳米粒子的光学特... 围绕金纳米粒子前沿内容,设计了一个简易的本科生基础实验,利用柠檬酸钠还原氯金酸法制备分散性好的金纳米粒子溶液,讨论了其尺寸与颜色的关系,探究了不同电解质和非电解质对金纳米粒子团聚及其颜色的影响,初步了解金纳米粒子的光学特性和探针效应基本原理。 展开更多
关键词 金纳米粒子 光学性质 尺寸 基础实验
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The combined effects of grain and sample sizes on the mechanical properties and fracture modes of gold microwires
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作者 H.K.Yang K.Cao +5 位作者 Y.Han M.Wen J.M.Guo Z.L.Tan J.Lu Y.Lu 《材料科学技术学报:英文版》 SCIE EI CAS CSCD 2019年第1期76-83,共8页
Hall-Petch relation was widely applied to evaluate the grain size effect on mechanical properties of metallic material. However, the sample size effect on the Hall-Petch relation was always ignored. In the present stu... Hall-Petch relation was widely applied to evaluate the grain size effect on mechanical properties of metallic material. However, the sample size effect on the Hall-Petch relation was always ignored. In the present study, the mechanical test and microstructure observation were performed to investigate the combined effects of grain and sample sizes on the deformation behaviors of gold microwires. The polycrystalline gold microwires with diameter of 16 ?m were annealed at temperatures from 100°C to 600°C, leading to different ratios(t/d) of wire diameter(t) to grain size(d) from 0.9 to 16.7. When the t/d was lower than 10, the yield stress dropped fast and deviated from the Hall-Petch relation. The free-surface grains played key role in the yield stress softening, and the volume fraction of free-surface grains increased with the t/d decreasing. Furthermore, the effects of t/d on work-hardening behaviors and fracture modes were also studied. With t/d value decreasing from 17 to 3.4, the samples exhibited necking fracture and the dislocation pile-ups induced work-hardening stage was gradually activated.With the t/d value further decreasing(t/d < 3.4), the fracture mode turned into shear failure, and the work-hardening capability lost. As the gold microwire for wire bonding is commonly applied in the packaging of integrated circuit chips, and the fabrication of microwire suffers multi-pass cold-drawing and annealing treatments to control the grain size. The present study could provide instructive suggestion for gold microwire fabrication and bonding processes. 展开更多
关键词 GOLD MICROWIRE Wire BONDING Tensile testing GRAIN size HALL-PETCH relationship
合理区段煤柱尺寸与巷道支护技术研究 预览
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作者 许李龙 《山东煤炭科技》 2019年第5期58-60,66共4页
以寺河矿二号井1907工作面为研究对象,采用公式计算和数值模拟分析得出工作面巷道最佳合理煤柱尺寸为12m。采用数值模拟软件对不同支护条件下巷道变形破坏情况进行数值模拟,推出巷道采用锚索网联合支护效果最优,并分析了支护最优参数。... 以寺河矿二号井1907工作面为研究对象,采用公式计算和数值模拟分析得出工作面巷道最佳合理煤柱尺寸为12m。采用数值模拟软件对不同支护条件下巷道变形破坏情况进行数值模拟,推出巷道采用锚索网联合支护效果最优,并分析了支护最优参数。对支护效果进行检验,结果表明取得了良好的支护效果。 展开更多
关键词 煤柱 尺寸 支护
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利用表面等离子体共振效应确定金纳米棒的尺寸
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作者 陈爽 高亚臣 《光学技术》 CAS CSCD 北大核心 2019年第3期288-291,共4页
金属纳米粒子的尺寸和形状对其物理和化学性质有很大影响,通常利用昂贵的透射电子显微镜和扫描电子显微镜进行其尺寸测量。为了节约测量成本,利用时域有限差分法研究了金纳米棒的尺寸与吸收峰的对应关系得到间接的测量方法。即当金纳米... 金属纳米粒子的尺寸和形状对其物理和化学性质有很大影响,通常利用昂贵的透射电子显微镜和扫描电子显微镜进行其尺寸测量。为了节约测量成本,利用时域有限差分法研究了金纳米棒的尺寸与吸收峰的对应关系得到间接的测量方法。即当金纳米棒的纵横比增大时,横向等离子峰几乎没有变化,纵向等离子峰出现明显的红移,且红移速度随着金纳米棒半径的增大而增大。实际制备了两种不同尺寸的金纳米棒样品,通过理论模拟确定的金纳米棒的尺寸与利用透射电子显微镜测量的金纳米棒的尺寸符合的很好。 展开更多
关键词 光谱学 表面等离子体共振 时域有限差分法 金纳米棒 吸收光谱 尺寸
Understanding the need for pre-injection from permeability measurements:What is the connection? 预览
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作者 Nick Barton Eda Quadros 《岩石力学与岩土工程学报:英文版》 CSCD 2019年第3期576-597,共22页
Pre-grouting ahead of tunnels has three main functions:to control water inflow into the tunnel,to limit groundwater drawdown above the tunnel,and to make tunnelling progress more predictable since rock mass quality is... Pre-grouting ahead of tunnels has three main functions:to control water inflow into the tunnel,to limit groundwater drawdown above the tunnel,and to make tunnelling progress more predictable since rock mass quality is effectively improved.It helps to avoid settlement damage caused by consolidation of clay deposits beneath built-up areas,since towns tend to be built where terrain is more flat,due to the clay deposits.There are so many instances of settlement damage that the profession needs to take note of the need for high-pressure pre-grouting,to use micro-cements and micro-silica additives.The use of highpressure injection may cause joint jacking,but this is local in extent when the rapid pressure decay away from an injection hole is understood.This effect is variable and depends on the geometrical parameters of the joints.This pressure-decay advantage must not be violated by maintaining high pressure when grout flow from the injection hole has ceased.The latter can cause damage to the grouting already achieved.Simplified methods of estimating mean hydraulic apertures(e)from Lugeon testing are described,and from more sophisticated three-dimensional(3D)permeability measurement.The estimation of the larger mean physical joint apertures(E)is based on the joint roughness coefficient(JRC).Comparison is then made with the empirical aperture-particle size criterion E>4d95,where d95 represents almost the largest cement particle size.Depending on joint set orientations and on the available micro-cements,the decision must be made of which range of pre-injection pressure should be aimed for,using successive reductions of the water-cement ratio w/c.More simple estimation of permeability,also with depth dependence,can be made with the empirical link between a modified rock mass quality Q and permeability,which is termed QH2O.The value of this parameter can be based on core-logging or intunnel face logging.The 3D before-and-after-grouting permeability measurements have been used to justify the quantification of rock mass qua 展开更多
关键词 Pre-grouting Micro-cement Hydraulic APERTURES Physical JOINT APERTURES JOINT ROUGHNESS Particle size ANISOTROPIC PERMEABILITY
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Portable rainfall simulator for plot-scale investigation of rainfall-runoff,and transport of sediment and pollutants 预览
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作者 Julien Boulange Farag Malhat +2 位作者 Piyanuch Jaikaew Kazuki Nanko Hirozumi Watanabe 《国际泥沙研究:英文版》 SCIE 2019年第1期38-47,共10页
A low-cost,simple to use portable rainfall simulator is developed for use over a 5m2 plot.The simulator is easy to transport and assemble in the field,thereby allowing for necessary experimental replicates to be done.... A low-cost,simple to use portable rainfall simulator is developed for use over a 5m2 plot.The simulator is easy to transport and assemble in the field,thereby allowing for necessary experimental replicates to be done.It provides rainfall intensities of between 20 and 100 mm/h by changing the number and type of silicon nozzles used.The Christiansen coefficient of uniformities obtained in the field are appropriate and vary from 79 to 94%for rainfall intensities ranging from 30 to 70 mm/h.In addition,the median volumetric drop diameters measured for rainfall intensities of 30,50,and 70 mm/h are in the lower range of that of natural rainfall and equal to 1.1070.08,1.6970.21,and 1.6670.20 mm,respectively.The velocities of the raindrops with diameters less than 1.2mm reached terminal velocities,while raindrops less than 2.0mm achieved velocities reasonably close to the terminal velocity of natural rainfall.Furthermore,the average time-specific kinetic energy(KET)for rainfall intensities of 30,50,and 70 mm/h are 257.7,760.1,and 1645.2 J/m2/h,respectively accounting for about 78.0 and 86.5%of the KET of natural rainfall for 50 and 70 mm/h rainfall intensity,respectively.The applicability of the portable rainfall simulator for herbicide transport study is investigated using two herbicides(atrazine and metolachlor);herbicide losses in runoff and sediment samples are in the ranges reported in the literature.As a percentage of the amount of herbicide applied,5.29%of atrazine and 2.15%of metolachlor are lost due to combined water and sediment runoff.The results show that the portable rainfall simulator can be effectively used in studying processes such as pesticide runoff,infiltration mechanisms,and sediment generation and transport at a field plot scale with an emphasis on how surface characteristics such as slope and soil properties affect these processes. 展开更多
关键词 RAINFALL simulator RAINFALL intensity RAINDROP energy RAINDROP size distribution RAINFALL UNIFORMITY
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中国全新世人群头骨尺寸性别差异的时代比较 预览
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作者 李福明 徐瑾如 +2 位作者 李天元 李海军 戴成萍 《解剖学杂志》 CAS 2019年第3期287-291,共5页
目的:分析全新世人群头骨尺寸性别差异率的时代间变化,并对比探讨男女头骨尺寸的时代变化率。方法:以中国考古遗址520例头骨为研究材料,用SPSS18.0软件进行同一时代男女测量性状的比较、不同时代间测量性状的比较,同时计算相应的性别差... 目的:分析全新世人群头骨尺寸性别差异率的时代间变化,并对比探讨男女头骨尺寸的时代变化率。方法:以中国考古遗址520例头骨为研究材料,用SPSS18.0软件进行同一时代男女测量性状的比较、不同时代间测量性状的比较,同时计算相应的性别差异率和时代变化率。结果:性别差异率分析显示,在男女头骨尺寸差异中,头骨高度的差异相对较大,现代人群面颅尺寸的性别差异率大于脑颅。“新石器-现代”的头骨时代变化率显示,头骨尺寸随时代而缩小,眶高增大,眶宽变小,这些变化在男女中较一致,但女性头骨缩小程度大于男性。结论:相比新石器与青铜铁器时代,现代人群中头骨尺寸性别差异率最大,可能主要源于新石器时代以来,头骨趋向于缩小的微观演化中,女性随时代减小的程度更加明显。 展开更多
关键词 头骨 尺寸 性别差异
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