According to turbulent theory and characteristics of beam blank continuous casting, 3-D model to represent the flow of beam blank mould is established. The predicted results indicate that the exit obliquity of up 15&#...According to turbulent theory and characteristics of beam blank continuous casting, 3-D model to represent the flow of beam blank mould is established. The predicted results indicate that the exit obliquity of up 15°(+15°) should be adopted, which will benefit the floatation of non-metallic inclusion and purification of the molten steel. When the nozzle angle is 120°, the flow pattern is reasonable. Proper nozzle depth can be 200mm. Turbulent kinetic of meniscus can be reduced by adopting the square nozzle and suitable area of side outlet when casting speed increases. The results are consistent with those of water model experiment, so the model is exact and reasonable. The model can provide important information for design of SEN and defining of immersion depth.展开更多
在气候变化和人类活动的综合影响下,青海省生态环境发生了明显变化。在此背景下,以GIMMS NDVI 3g.v1为数据源,采用Sen+Mann-Kendal方法研究青海省1982-2015年植被覆盖区域NDVI时空变化,将趋势分析和R/S(rescaled range analysis)分析叠...在气候变化和人类活动的综合影响下,青海省生态环境发生了明显变化。在此背景下,以GIMMS NDVI 3g.v1为数据源,采用Sen+Mann-Kendal方法研究青海省1982-2015年植被覆盖区域NDVI时空变化,将趋势分析和R/S(rescaled range analysis)分析叠加,研究植被生长季NDVI变化的持续性特征,并揭示植被对气候变化及人类活动的响应规律。结果表明:1)近34年青海省植被NDVI整体呈从西北到东南的增加趋势;且变异系数显示,波动性较大地区集中在柴达木盆地周边和青南牧区西北部等植被NDVI较低的区域,波动性较小地区集中在祁连山东部、东部农业区和青南牧区东南部等植被NDVI较高的区域。2)近34年青海省植被NDVI整体呈增加趋势,增长率为0.38%·10a^(-1);且NDVI变化具有明显的阶段性,存在1994年和2000年两个突变点。3)近34年青海省植被改善区域(75.4%)远大于退化区域(24.6%),其中显著改善面积占植被覆盖区域面积的40.9%,退化区随时间变化在空间上表现出明显的转移现象。4)Hurst指数表明,青海省植被变化反持续性较强,趋势分析与Hurst指数叠加得出,由退化转为改善的区域占植被覆盖区面积的13.7%,由改善转为退化的区域占植被覆盖区面积的44.3%,另41.5%的区域无法确定未来变化趋势。5)青海省植被生长季NDVI受气候变化和人类活动的双重影响,且不同植被类型对气候变化的响应存在较大差异。展开更多
Remote sensing,geographic information system and GPS(3S)technology have been well recognized as comprehensive,accurate and up-to-date information collection methods,which are increasingly adopted in biodiversity conse...Remote sensing,geographic information system and GPS(3S)technology have been well recognized as comprehensive,accurate and up-to-date information collection methods,which are increasingly adopted in biodiversity conservation.This review summarizes the application of object-oriented classification methods on biodiversity monitoring projects based on high-resolution remote sensing imagines in China.Biodiversity conservation research based on GIS technology in China is also discussed,with emphasis on the advantages of GIS analysis and modeling function.展开更多
Three cadmium(II) metal-organic frameworks(MOFs) based on tetracarboxylate ligands, namely[Cd_2(TTTA)(DMF)_3]·2 DMF(1),[Cd_2(TB)(H_2O)_4]·3DMF·H_2O(2)and [Cd(TEB)_(0.5)].2 DMF.4 H_2O(3) have been design...Three cadmium(II) metal-organic frameworks(MOFs) based on tetracarboxylate ligands, namely[Cd_2(TTTA)(DMF)_3]·2 DMF(1),[Cd_2(TB)(H_2O)_4]·3DMF·H_2O(2)and [Cd(TEB)_(0.5)].2 DMF.4 H_2O(3) have been designed and synthesized. Complex 1 is a 2-dimensional(2 D) 3,4-connected network with 3,4 L13 topology, complex 2 features a 3-dimensional(3D) 3,4-connected tfa topology with a 2-fold interpenetrating structure and complex 3 has a 3D 4-connected dia topology with a 4-fold interpenetrating structure. Interestingly, 2 exhibits permanent pores and selective adsorption of CO_2 over CH_4. In addition, 2 shows fluorescence sensing of Fe^(3+) ion and rapid detection of nitroaromatic compounds(NACs) through fluorescence quenching.展开更多
Fatigue crack growth tests were carried out on the SEN B3 precracked specimens, with dimensions in accordance with ISO 12108 requirements. The specimens were made of martensitic stainless steel, X17CrNi15-2, and some ...Fatigue crack growth tests were carried out on the SEN B3 precracked specimens, with dimensions in accordance with ISO 12108 requirements. The specimens were made of martensitic stainless steel, X17CrNi15-2, and some of them were modified by the ceramic coating deposition surface treatment. The effects of ceramic coating, on the fatigue crack growth behaviour of hollow shaft specimens, were experimentally investigated. Fatigue crack growth rates, da/dN, were characterised, using the power law relationship between da/dN (in mm/cycle) and the stress intensity factor range, ΔK (in MPa∙m0.5). The two constants of the correlation are 7.9768 × 10−9 and 2.8107 for the parent material, and those for the coated material are 2.4391 × 10−9 and 3.1990, respectively. Microstructural analyses were carried out on the tested specimens, which shows that the maximum hardness of the ceramic coating is higher than that of substrate by a factor of ~3.2. The dimple fracture dominates the final fracture mechanism for the parent material, and the combination of fatigue, ductile fracture and cleavage dominates the final fracture mechanism for the coated material, based on the SEM analyses. EDS tests’ results reveal that the parent material specimen shows higher levels of C at matrix regions along with Fe- and O-rich regions, compared with the coated material specimen.展开更多
In the context of climate variability resulting in a decrease in rainfall with a severe drought, a spatio-temporal study of this phenomenon remains imperative for the efficient management of water resources. This pape...In the context of climate variability resulting in a decrease in rainfall with a severe drought, a spatio-temporal study of this phenomenon remains imperative for the efficient management of water resources. This paper aims to assess the long-term rainfall drought trend and breakpoints within the Comoe River watershed. From monthly rainfall data series (1960-2000), Standardized Precipitation Index (SPI) values were calculated for a time scale of 3 months (SPI.3). Statistical tests for breaks (CUSUM, and t-Student) and trends (Man-Kendall and Linear Regression) as well as the Sen’ slope method for estimating the magnitude of trends w<span style="font-family:Verdana;">as</span><span style="font-family:Verdana;"> applied. The breaks dates observed are mostly located after the 1970s. Based on SPI.3 values below the threshold of 0.84 chosen as an indicator of drought, rarely has more than half of the catchment area been affected by drought. The average watershed affected is about 20% over the study period (1960-2000). The most representative years, in terms of spatial expansion of the drought, in decreasing order of importance are: 1983, 1992, 1972 and 1982. The years 1982 and 1983 stand out for their exceptional condition, as the drought-affected 50% to 90% of the total catchment area. SPI.3 series from 1960 to the various break dates recorded slopes between </span><span style="font-family:Verdana;"><span style="white-space:nowrap;">-</span>0.01 and 0.00 with a slight drought trend for most of the catchment. After the break periods, almost the entire northern part of the basin is characterized by slight moisture with Sen’s slopes between 0.000 and 0.005. The southern part will remain slightly subject to normal rainfall conditions.</span>展开更多
文摘According to turbulent theory and characteristics of beam blank continuous casting, 3-D model to represent the flow of beam blank mould is established. The predicted results indicate that the exit obliquity of up 15°(+15°) should be adopted, which will benefit the floatation of non-metallic inclusion and purification of the molten steel. When the nozzle angle is 120°, the flow pattern is reasonable. Proper nozzle depth can be 200mm. Turbulent kinetic of meniscus can be reduced by adopting the square nozzle and suitable area of side outlet when casting speed increases. The results are consistent with those of water model experiment, so the model is exact and reasonable. The model can provide important information for design of SEN and defining of immersion depth.
文摘在气候变化和人类活动的综合影响下,青海省生态环境发生了明显变化。在此背景下,以GIMMS NDVI 3g.v1为数据源,采用Sen+Mann-Kendal方法研究青海省1982-2015年植被覆盖区域NDVI时空变化,将趋势分析和R/S(rescaled range analysis)分析叠加,研究植被生长季NDVI变化的持续性特征,并揭示植被对气候变化及人类活动的响应规律。结果表明:1)近34年青海省植被NDVI整体呈从西北到东南的增加趋势;且变异系数显示,波动性较大地区集中在柴达木盆地周边和青南牧区西北部等植被NDVI较低的区域,波动性较小地区集中在祁连山东部、东部农业区和青南牧区东南部等植被NDVI较高的区域。2)近34年青海省植被NDVI整体呈增加趋势,增长率为0.38%·10a^(-1);且NDVI变化具有明显的阶段性,存在1994年和2000年两个突变点。3)近34年青海省植被改善区域(75.4%)远大于退化区域(24.6%),其中显著改善面积占植被覆盖区域面积的40.9%,退化区随时间变化在空间上表现出明显的转移现象。4)Hurst指数表明,青海省植被变化反持续性较强,趋势分析与Hurst指数叠加得出,由退化转为改善的区域占植被覆盖区面积的13.7%,由改善转为退化的区域占植被覆盖区面积的44.3%,另41.5%的区域无法确定未来变化趋势。5)青海省植被生长季NDVI受气候变化和人类活动的双重影响,且不同植被类型对气候变化的响应存在较大差异。
文摘Remote sensing,geographic information system and GPS(3S)technology have been well recognized as comprehensive,accurate and up-to-date information collection methods,which are increasingly adopted in biodiversity conservation.This review summarizes the application of object-oriented classification methods on biodiversity monitoring projects based on high-resolution remote sensing imagines in China.Biodiversity conservation research based on GIS technology in China is also discussed,with emphasis on the advantages of GIS analysis and modeling function.
基金supported by the National Natural Science Foundation of China(NSFC, No. 21771191)the Shandong Natural Science Fund (No. ZR2017QB012)+2 种基金the Applied Basic Research Projects of Qingdao (No.16-5-1-95-jch)the Fundamental Research Funds for the Central Universities (Nos.16CX05015A,18CX06003A, YCX2018071)the Foundation of State Key Laboratory of Structural Chemistry (No. 20160006)
文摘Three cadmium(II) metal-organic frameworks(MOFs) based on tetracarboxylate ligands, namely[Cd_2(TTTA)(DMF)_3]·2 DMF(1),[Cd_2(TB)(H_2O)_4]·3DMF·H_2O(2)and [Cd(TEB)_(0.5)].2 DMF.4 H_2O(3) have been designed and synthesized. Complex 1 is a 2-dimensional(2 D) 3,4-connected network with 3,4 L13 topology, complex 2 features a 3-dimensional(3D) 3,4-connected tfa topology with a 2-fold interpenetrating structure and complex 3 has a 3D 4-connected dia topology with a 4-fold interpenetrating structure. Interestingly, 2 exhibits permanent pores and selective adsorption of CO_2 over CH_4. In addition, 2 shows fluorescence sensing of Fe^(3+) ion and rapid detection of nitroaromatic compounds(NACs) through fluorescence quenching.
文摘Fatigue crack growth tests were carried out on the SEN B3 precracked specimens, with dimensions in accordance with ISO 12108 requirements. The specimens were made of martensitic stainless steel, X17CrNi15-2, and some of them were modified by the ceramic coating deposition surface treatment. The effects of ceramic coating, on the fatigue crack growth behaviour of hollow shaft specimens, were experimentally investigated. Fatigue crack growth rates, da/dN, were characterised, using the power law relationship between da/dN (in mm/cycle) and the stress intensity factor range, ΔK (in MPa∙m0.5). The two constants of the correlation are 7.9768 × 10−9 and 2.8107 for the parent material, and those for the coated material are 2.4391 × 10−9 and 3.1990, respectively. Microstructural analyses were carried out on the tested specimens, which shows that the maximum hardness of the ceramic coating is higher than that of substrate by a factor of ~3.2. The dimple fracture dominates the final fracture mechanism for the parent material, and the combination of fatigue, ductile fracture and cleavage dominates the final fracture mechanism for the coated material, based on the SEM analyses. EDS tests’ results reveal that the parent material specimen shows higher levels of C at matrix regions along with Fe- and O-rich regions, compared with the coated material specimen.
文摘In the context of climate variability resulting in a decrease in rainfall with a severe drought, a spatio-temporal study of this phenomenon remains imperative for the efficient management of water resources. This paper aims to assess the long-term rainfall drought trend and breakpoints within the Comoe River watershed. From monthly rainfall data series (1960-2000), Standardized Precipitation Index (SPI) values were calculated for a time scale of 3 months (SPI.3). Statistical tests for breaks (CUSUM, and t-Student) and trends (Man-Kendall and Linear Regression) as well as the Sen’ slope method for estimating the magnitude of trends w<span style="font-family:Verdana;">as</span><span style="font-family:Verdana;"> applied. The breaks dates observed are mostly located after the 1970s. Based on SPI.3 values below the threshold of 0.84 chosen as an indicator of drought, rarely has more than half of the catchment area been affected by drought. The average watershed affected is about 20% over the study period (1960-2000). The most representative years, in terms of spatial expansion of the drought, in decreasing order of importance are: 1983, 1992, 1972 and 1982. The years 1982 and 1983 stand out for their exceptional condition, as the drought-affected 50% to 90% of the total catchment area. SPI.3 series from 1960 to the various break dates recorded slopes between </span><span style="font-family:Verdana;"><span style="white-space:nowrap;">-</span>0.01 and 0.00 with a slight drought trend for most of the catchment. After the break periods, almost the entire northern part of the basin is characterized by slight moisture with Sen’s slopes between 0.000 and 0.005. The southern part will remain slightly subject to normal rainfall conditions.</span>
