期刊文献+
共找到13篇文章
< 1 >
每页显示 20 50 100
高中地理概念的深度学习模式构建与实施——以高三地理一轮复习“陆地水体”单元中的“含沙量”概念为例
1
作者 陈萍 《教育信息化论坛》 2024年第18期3-5,共3页
地理概念是地理知识的组成部分,也是理解与掌握地理原理和基本规律的关键。将以高阶思维发展为目标的深度学习模式引入高中地理概念教学中,能深化学生对地理概念内涵的理解,提升学生解决地理问题的能力。以高三地理一轮复习“陆地水体... 地理概念是地理知识的组成部分,也是理解与掌握地理原理和基本规律的关键。将以高阶思维发展为目标的深度学习模式引入高中地理概念教学中,能深化学生对地理概念内涵的理解,提升学生解决地理问题的能力。以高三地理一轮复习“陆地水体”单元中的“含沙量”概念为例,基于深度学习理论,提出“概念解读—概念建构—概念迁移—概念变式”的学习模式,剖析地理事象的本质特征,探索有效的高中地理概念教学实施路径。 展开更多
关键词 地理概念 深度学习 “含沙量” 学科素养
下载PDF
A study of impact of the reclamation and artificial island projects on tidal currents and sediment concentration in radial sand ridge field of the South Yellow Sea 被引量:3
2
作者 赵强 何琴燕 +1 位作者 杨耀芳 黄秀清 《Marine Science Bulletin》 CAS 2015年第1期71-85,共15页
The two-dimensional hydrodynamic model, MIKE21, is applied to simulate the tidal currents and sediment concentration in the radial sand ridges of the South Yellow Sea. Results are in accordance with in situ observatio... The two-dimensional hydrodynamic model, MIKE21, is applied to simulate the tidal currents and sediment concentration in the radial sand ridges of the South Yellow Sea. Results are in accordance with in situ observations. Then the variations of tidal currents and suspended sediment concentration caused by reclamation and artificial islands projects are simulated. The results show that the impacts are limited around the project areas. After the projects, the fan-shaped, Jianggang centered tidal current pattern would be replaced by a pattern which is formed by two tidal paths. One locates at the Xiyang channel in north-south direction, and the other locates at the Huangshayang channel in east-west direction. The reclamation of Tiaozini separates the waters into south portion and north portion. The changes of sediment concentrations coincide with those of currents. Both the sediment concentrations and tidal currents increase at the northwest of Dongsha and the south of Gaoni, while both decrease at the north and south of Tiaozini, and the east and southwest of Dongsha. 展开更多
关键词 radial sand ridges RECLAMATION artificial island tidal currents suspended sediment concentration numerical modeling
下载PDF
The Suitability of Using Leaf Area Index to Quantify Soil Loss under Vegetation Cover 被引量:7
3
作者 ZHANG Wentai YU Dongsheng +4 位作者 SHI Xuezheng WANG Hongjie GU Zhujun ZHANG Xiangyan TAN Manzhi 《Journal of Mountain Science》 SCIE CSCD 2011年第4期564-570,共7页
Soil erosion by water under forest cover is a serious problem in southern China.A comparative study was carried out on the use of leaf area index(LAI) and vegetation fractional coverage(VFC) in quantifying soil loss u... Soil erosion by water under forest cover is a serious problem in southern China.A comparative study was carried out on the use of leaf area index(LAI) and vegetation fractional coverage(VFC) in quantifying soil loss under vegetation cover.Five types of vegetation with varied LAI and VFC under field conditions were exposed to two rainfall rates(40 mm h-1 and 54 mm h-1) using a portable rainfall simulator.Runoff rate,sediment concentration and soil loss rate were measured at relatively runoff stable state.Significant negative exponential relationship(p < 0.05,R2 = 0.83) and linear relationship(p < 0.05,R2 = 0.84) were obtained between LAI and sediment concentration,while no significant relationship existed between VFC and sediment concentration.The mechanism by which vegetation canopy prevents soil loss was by reducing rainfall kinetic energy and sediment concentration.LAI could better quantify such a role than VFC.However,neither LAI nor VFC could explain runoff rate or soil loss rate.Caution must be taken when using LAI to quantify the role of certain vegetation in soil and water conservation. 展开更多
关键词 Leaf area index(LAI) Runoff steady state Sediment concentration Simulated rainfall
下载PDF
Vertical distribution of sediment concentration 被引量:3
4
作者 Sai-hua HUANG Zhi-lin SUN +1 位作者 Dan XU Shan-shan XIA 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2008年第11期1560-1566,共7页
A simple formula is proposed to predict the vertical distribution of a suspended load concentration in a 2D steady turbulent flow. The proposed formula significantly improves the well-known Rouse formula where sedimen... A simple formula is proposed to predict the vertical distribution of a suspended load concentration in a 2D steady turbulent flow. The proposed formula significantly improves the well-known Rouse formula where sediment concentration has an infinitely large value at the channel bottom and a zero value at the water surface. Based on this formula and the logarithmic ve- locity profile, a theoretical elementary function for the transport rate of a suspended load is developed. This equation improves the Einstein equation in which the unit-width suspended sediment discharge must be solved by numerical integration and a contra- diction between the lower limit of the integral and that of velocity distribution exists. 展开更多
关键词 Sediment concentration Vertical distribution Suspended load Sediment discharge
下载PDF
Landslides & Debris Flows Formation from Gravelly Soil Surface Erosion and Particle Losses in Jiangjia Ravine 被引量:3
5
作者 HU Ming-jian PAN Hua-li +2 位作者 WEI Hou-zhen WANG Ren A Ying 《Journal of Mountain Science》 SCIE CSCD 2013年第6期987-995,共9页
Gravelly soils are made up of gravel, sand, silt and clay. They are widely used in engineering applications such as rock-fill dams with clay cores, which are the main researches at present. The strength and mechanical... Gravelly soils are made up of gravel, sand, silt and clay. They are widely used in engineering applications such as rock-fill dams with clay cores, which are the main researches at present. The strength and mechanical properties of the gravelly soils are affected by the content of coarse grain, fine particles, and their adhesive states. These Properties can be verified by laboratory unconsolidated undrained triaxial tests with grain size less than 5 mm and by large scale direct-shear tests with original grain content. Fine particles of the loose gravelly slopes are released under rainfalls, alternated the structures and mechanical properties, even affected the slope stability. There are a series of large scale direct-shear tests with different coarse grain contents to study the influence of fine particles releasing and migration, results showed the strength behavior of the gravelly soils were affected by the coarse grain content (5) and the inflection coarse grain contents. In order to study the erosion features of the gravelly soil slopes on rainfall conditions and the slopes stability alteration, we had carried out one sort of artificial rainfall local and model experiments, the runoff sediment contents were monitored during the experiments. Result showed that the shapes of the slopes surface transformed periodically, runoff sediment contents were divided into five phases according to the experiment phenomena, runoff sediment contents maintained downtrend during the rain time and the downtrend was obviouslyinterpreted by one descend belt no matter the rainfall intensity and the slope angels. Particle size analysis released the deposit on the slope surface lost almost all of the clay, most of the silt and sand after the experiments, this meant the fine particles releasing, migration and accumulation process on condition of rainfall resulted in the instability factor of the slopes even induced landslide or debris flow. 展开更多
关键词 Gravelly soils Erosion process Particlelosses Runoff sediment content JiangJia Ravine
下载PDF
Application of Wenner Configuration to Estimate Soil Water Content in Pine Plantations on Sandy Land 被引量:8
6
作者 ZHU Jiao-Jun KANG Hong-Zhang Y. GONDA 《Pedosphere》 SCIE CAS CSCD 2007年第6期801-812,共12页
To estimate the mean value of surface soil water content rapidly,accurately,and nonintrusively,field investigations on soil electrical resistivity(SER)with the Yokogawa 324400 earth resistivity meter and the surface(0... To estimate the mean value of surface soil water content rapidly,accurately,and nonintrusively,field investigations on soil electrical resistivity(SER)with the Yokogawa 324400 earth resistivity meter and the surface(0-150 cm)soil water content(SWC)with time domain reflectometry(TDR),together with the abiotic factors including soil texture,structure. and salinity concentrations were conducted in the Mongolian pine(Pinus sylvestris var.mongolica)plantations on a sandy land.The measurement of SER was based on the 4-probe Wenner configuration method.Relationships between the values of SWC and SER were obtained based on analysis of the abiotic factors of the research site,which play a key role in affecting the soil electrical resistivity.Results indicate that the SER meter could be used to estimate the mean value of SWC in the Mongolian pine plantations on the sandy land during the growing seasons.The bulky nature of the equipment simplified the cumbersome measurements of soil water content with the general methods.It must be noted that the Wenner configuration method could only provide the mean values of the SWC,and the soil texture,structure, temperature,and solute concentrations influenced the SER and further affected the estimation of the SWC by the SER meter.Therefore,the results of this study could be applied on a sandy land during the growing seasons only.However, the SWC of other soil types also may be obtained according to the individual soil types using the procedures of this study. 展开更多
关键词 Mongolian pine plantation sandy land soil electrical resistivity soil water content Wenner configuration method
下载PDF
Paleoclimatic record from Chumbur-Kosa section in Sea of Azov region since Marine Isotope Stage 11 被引量:1
7
作者 LIANG Ye YANG Tai-bao +6 位作者 Andrey Aleksevitch VELICHKO ZENG Biao SHI Pei-hong WANG Lin-dong HE Yi CHEN Jie CHEN Yu 《Journal of Mountain Science》 SCIE CSCD 2016年第6期985-999,共15页
Abstract: Loess-paleosol sequences preserve records of climatic change during the Quaternary, which is important for paleoclimate study. In this study, a loess-palaeosol sequence from the Chumbur- Kosa (CK) site in... Abstract: Loess-paleosol sequences preserve records of climatic change during the Quaternary, which is important for paleoclimate study. In this study, a loess-palaeosol sequence from the Chumbur- Kosa (CK) site in the Sea of Azov region was investigated to reconstruct climatic variability during the Marine Isotope Stage (MIS)11- MIS 1, using proxies of grain size (GS), magnetic susceptibility (xlf and Xfd(%)), carbonate content (CaCO3%) and soil color The results enabled formulation of a detailed description of the climatic characteristics related to each individual layer. The sequence indicates that the paleoclimate shifted progressively towards increasingly cooler, somewhat drier conditions. The CK section may thus be ideal for reconstructing climatie eondifions during the Middle and Late Pleistocene in the Sea of Azov region. However, the )Of value of paleosol $2 in the CK profile indicates different characteristics from the other paleosol layers, dilution of carbonate resulting from carbonate leaching in L2 may be the main reason for the decrease in magnetic susceptibility. Furthermore, through simple analysis part of the environmental evolution process in the Sea of Azov region and Serbia during Middle and Late Pleistocene cycles. The climate cycle expressed by Xfd(%) and Xlf variations show similar patterns, with rapidly alternating cold and warm intervals. Nevertheless, although the two areas had different climatic regimes, geographical settings, and loess source areas, both exhibited similar climate change trends since the MIS 11. 展开更多
关键词 LOESS PALEOSOL Magnetic susceptibility PALEOCLIMATE Sea of Azov
下载PDF
Assessment of Selected Heavy Metals in Street Dust Samples from Jazan City, KSA (Kingdom of Saudi Arabia)
8
作者 Mohammad Kamal Harb 《Journal of Environmental Science and Engineering(A)》 2014年第4期211-218,共8页
In this work, Jazan province (Saudi Arabia) was examined for its heavy metals content. Therefore, 15 street dust samples were collected, digested and analyzed in order to investigate the levels of selected heavy met... In this work, Jazan province (Saudi Arabia) was examined for its heavy metals content. Therefore, 15 street dust samples were collected, digested and analyzed in order to investigate the levels of selected heavy metals and propose the causes for the presence of these metals. All collected samples were digested using Leeds Public Analyst method. The concentrations of heavy metals (Fe, Cu, Mn, Zn, Cd, Co and Pb) were analyzed using atomic absorption spectroscopy. Six heavy metals (Fe, Cu, Mn, Zn, Co and Pb) were measured in all samples; the concentration of Cd was not detected in Jazan dust by atomic absorption spectroscopy. The heavy metals levels in Jazan street dust increase according to the following sequence: Fe 〉 Mn 〉 Zn 〉 Cu 〉 Pb 〉 Co. The correlation coefficients and enrichment factors relative to earth crust abundances of heavy metals were calculated in order to predict the possible sources in dust. 展开更多
关键词 Heavy metals POLLUTION street dust Saudi Arabia atomic absorption
下载PDF
Characteristics of vibration liquefaction of saturated medium sandy soil with silt
9
作者 HUANG Rui ZHANG Yanjun GONG Liliang 《Global Geology》 2010年第2期90-93,共4页
In order to understand and master the dynamic characteristics of sandy soil with different silt contents, the authors carried out many indoor dynamic triaxial tests for five groups of sandy with silt which took from P... In order to understand and master the dynamic characteristics of sandy soil with different silt contents, the authors carried out many indoor dynamic triaxial tests for five groups of sandy with silt which took from Panjin and Xiamen. Under the conditions of consolidation pressure of 100 kPa, 200 kPa, 300 kPa, stationary vibration frequency H=1 and cyclic loading, the authors found that the effective cohesion increases and the effective internal friction angle decreases with the increase of the silt contents. During the liquefied scope, the cementation and the strength have been increased with the increase of the silt contents. 展开更多
关键词 sandy soil dynamic characteristics vibration liquefaction
下载PDF
Nematode Community Structure and Diversity Pattern in Sandy Beaches of Qingdao,China 被引量:2
10
作者 HUA Er MU Fanghong +3 位作者 ZHANG Zhinan YANG Shichao ZHANG Ting LI Jia 《Journal of Ocean University of China》 SCIE CAS 2016年第1期33-40,共8页
We investigated the diversity and structure of free-living marine nematode communities at three sandy beaches representing typical intertidal environments of a temperate zone in Qingdao,Shandong Province,China.Average... We investigated the diversity and structure of free-living marine nematode communities at three sandy beaches representing typical intertidal environments of a temperate zone in Qingdao,Shandong Province,China.Average nematode abundance ranged from 1006 to 2170 ind.10 cm-2,and a total of 34 nematode genera were recorded,of which only 8 were common in all the studied beaches.Pielou's evenness and Shannon-Wiener diversity index were the lowest at the second beach where nematode abundance was the highest.The highest species diversity index coincided with the lowest nematode abundance at Shilaoren beach.Sediment median grain size,sorting coefficient,and chlorophyll-a content were essential for differentiation in nematode abundance and species diversity,whereas taxonomic diversity of nematode was homogeneous across the three beaches.In 0–20 cm sediment profile,nematode abundance declined abruptly with depth,whereas nematode diversity changed gently with obvious difference in 16–20 cm layer.Sediment granulometry and chlorophyll-a content were the two foremost factors which influenced the vertical distribution pattern of nematode generic diversity.Non-selective deposit feeders constituted the most dominant trophic group,followed by epistratum feeders.Bathylaimus(family:Tripyloididae) dominated at the second and Yangkou beach,while Theristus(family:Xyalidae) prevailed at Shilaoren beach.Omnivores and predators became important at Shilaoren beach because of the high proportion of Enoplolaimus.Even though,nematode community of the studied beaches did not differ significantly from each other. 展开更多
关键词 vertical distribution BIODIVERSITY taxonomic diversity index trophic structure
下载PDF
Correlations between Mineral Nitrogen Contents and Vertical Distribution of N20 Emission Potentials in Tropical Peat Soils Transformed into Oil Palm Plantations in Sarawak, Malaysia
11
作者 Sharon Yu Ling Lau Yasuyuki Hashidoko +2 位作者 Naoki Takahashi Ryusuke Hatano Lulie Melling 《Journal of Agricultural Science and Technology(B)》 2014年第9期691-700,共10页
Tropical peat swamp forest beds that have been reclaimed for agricultural use are generally an active source of nitrous oxide (N2O) efflux, however, the mechanism by which reclaimed tropical peat soils promote the e... Tropical peat swamp forest beds that have been reclaimed for agricultural use are generally an active source of nitrous oxide (N2O) efflux, however, the mechanism by which reclaimed tropical peat soils promote the emergence of N2O emitters in soil microbial communities remains unclear. The purpose of this study was to reveal the vertical distribution of N2O emission potential and its correlation with mineral nitrogen contents in reclaimed soils. Using a culture-based N2O emission assay, the N2O emission potentials of soil at various depths (0-450 cm) were investigated in two oil palm plantations in Sarawak, Malaysia, which had elapsed times of two years (E2Y) and 10 years (El 0Y) after deforestation, respectively. On the basis of the relationship between the vertical profiles of N2O emission potentials and the contents of mineralized nitrogen in the peat soils at various depths, the impact of land management on soil microbial communities was discussed. The peat soil at plantation site E2Y showed a trend of high N2O production in deep layers (200-400 cm), whereas the older plantation site E10Y showed considerably more active N2O emission in shallow soil (10-50 cm). N2O emission potentials among the soil microbial communities at different soil depths at the E10Y site showed positive correlations with NO3- and NH4+ contents, whereas, soils obtained from the E2Y site had N2O emission potentials that were inversely proportional to the contents of NO3-. This contrasting vertical correlation between N2O-emitting potentials and mineralized nitrogen contents in bulk soils suggests that active N2O emission in deep soil at the E2Y site has maintained the original carbon-nitrogen (C/N) ratio of the peat soil, whereas at EIOY, such a regulatory system has been lost due to advanced soil degradation, leading to dynamic changes in the nitrogen cycle in shallow soil. 展开更多
关键词 N2O emitters tropical peat soil vertical N20 emission potential C/N ratio oil palm plantation.
下载PDF
Elemental Content in Wheat Products of Asir Region, Saudi Arabia
12
作者 Omar Abdulrahman Fahad A1-Dayel Saad Ali. AlKahtani 《Journal of Chemistry and Chemical Engineering》 2010年第5期8-13,共6页
Wheat is one of the most grown crops in Saudi Arabia. Accurate knowledge of the various elemental concentrations in wheat and its products (bran and flower) is of great importance from nutrition point of view. Wheat... Wheat is one of the most grown crops in Saudi Arabia. Accurate knowledge of the various elemental concentrations in wheat and its products (bran and flower) is of great importance from nutrition point of view. Wheat samples were obtained from Asir region, 900 Km southern of Riyadh, and analyzed. Up to 50 elements in wheat products were determined. It was observed that the mineral content of bran was much higher than white flour. 展开更多
关键词 WHEAT BRAN SEMOLINA neutron activation analysis (NAA).
下载PDF
Hyperconcentration Based on Projection Measurements
13
作者 陈晓 曾志 李熙涵 《Communications in Theoretical Physics》 SCIE CAS CSCD 2014年第3期322-328,共7页
We propose an efficient hyperconcentration protocol for distilling maximally hyperentangled state from partially entangled pure state, resorting to the projection measurement on an auxiliary photon. In our scheme, two... We propose an efficient hyperconcentration protocol for distilling maximally hyperentangled state from partially entangled pure state, resorting to the projection measurement on an auxiliary photon. In our scheme, two photons simultaneously entangled in polarization states and spatial modes are considered. One party performs quantum nondemolition detections on his photon and an additional photon to produce three photon hyperentangled state, then he projects the assistant photon into an orthogonal basis composed of both the polarization and spatial degree of freedom.Then the state of the left two photons collapses into maximally hyperentangled state with a certain probability. In the rest cases, some less-entangled states are obtained, which can be used as resource for the next round concentration. By repeating the concentration process for several rounds, a higher success probability can be obtained, which makes our scheme useful in practical quantum information applications. 展开更多
关键词 entanglement concentration hyperentanglement POLARIZATION spatial modes
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部