Beta flecks are one of the most common defects occur in someα+βandβtitanium alloys.In this study,formation of beta flecks in Ti-17 alloy was investigated by directional solidification experiments.Samples were direc...Beta flecks are one of the most common defects occur in someα+βandβtitanium alloys.In this study,formation of beta flecks in Ti-17 alloy was investigated by directional solidification experiments.Samples were directionally solidified under a constant temperature gradient of 2×10^4 K/m and a wide range of withdrawal rates(R)from 3 mm/h to 150 mm/h.We find that macrostructure of the directionally solidified Ti-17 samples can be characterized by"four zones and two lines"after the heat treatment.Profile of the solid-liquid interface transits from planar to cellular to dendritic shape with solidification rate increasing from 3 mm/h to 150 mm/h.The critical rates for planar to cellular(Rc1)transition and cellular to dendritic(Rc2)transition can be well predicted based on the traditional solidification theory.Dark and light contrast areas in macrostructure are directly related to elemental segregation.Dark contrast areas are rich of Cr,Zr but lean of Mo,while no apparent segregation is found in light contrast areas and the mean level of Cr,Zr is lower and Mo is higher in this area than that in dark contrast areas.We conclude thatβ-flecks in Ti-17 titanium alloy are induced by segregation of alloying elements with k<1 and their shape and size are determined by solidification conditions.Based on the findings of the present article and other literatures,three types ofβ-flecks are proposed and their formation mechanisms are discussed.展开更多
Vitis vinifera 87-1 plants infected by grapevine fleck virus(GFkV) and grapevine rupestris stem pitting-associated virus(GRSPaV) were used as the plant materials for virus elimination treatment. This study evaluated t...Vitis vinifera 87-1 plants infected by grapevine fleck virus(GFkV) and grapevine rupestris stem pitting-associated virus(GRSPaV) were used as the plant materials for virus elimination treatment. This study evaluated the effects of ribavirin at different concentrations(15 and 25 μg mL^(–1);R15 and R25, respectively), thermotherapy(37°C;T), and the combination of ribavirin and thermotherapy(R15+T and R25+T) on eliminating viruses from grapevine plants in vitro. Both R15 and R25 had phytotoxic effects and weakened plant growth. Thermotherapy positively affected the growth of grapevine plants. Plant height was significantly greater in T, R15+T, and R25+T than in CK, R15 and R25. The proportion of dead plants after T, R15+T, and R25+T was 51.4, 11.4, and 8.6%, respectively. The survival rates of regenerated plants after all treatments were >68.0%. Ribavirin concentration and treatment time were related to the regeneration of shoot tips and elimination efficiencies of the two viruses. The survival rates of plants after R15+T for 30, 40, and 50 days were 97.3, 90.7, and 74.4%, respectively. The elimination rates of GRSPaV from plants in the three time quantum were 55.6, 84.6, and 93.8%, respectively. The elimination rate of GFkV was 23.9% higher in R25(35/44) than in R15(25/45), and that of GRSPaV was 7.0% higher in R25 than in R15. The combination of thermotherapy and chemotherapy was found to have a positive effect on the eradication of GFkV and GRSPaV, and R25+T for 50 days was able to completely eliminate the two viruses from in vitro grapevines.展开更多
Effect of β-flecks on properties of tensile elongation and low cycle.fatigue life at room tern. perature for Ti-10V-2Fe-3Al alloy has been investigated.The cracks along initial β-grain boundaries in the β-fleck reg...Effect of β-flecks on properties of tensile elongation and low cycle.fatigue life at room tern. perature for Ti-10V-2Fe-3Al alloy has been investigated.The cracks along initial β-grain boundaries in the β-fleck region may propagate to form intergranular brittle fracture.Under alternating load,the β-fleck often becomes a fatigue origin.While under higher strain,the cracks initiate and propagate to fracture early at the original β-grain boundaries in β-fleck region and at α-grain boundaries.展开更多
以杏树为试材，为了解杏树冠层内透光率随树龄和叶面积指数的变化，采用LP-80型冠层分析仪测定了光合有效辐射PAR（Photosynthetically Active Radiation）在不同树龄杏树冠层三维空间上的分布情况，研究了杏树冠层内透光率随树龄（2-6...以杏树为试材，为了解杏树冠层内透光率随树龄和叶面积指数的变化，采用LP-80型冠层分析仪测定了光合有效辐射PAR（Photosynthetically Active Radiation）在不同树龄杏树冠层三维空间上的分布情况，研究了杏树冠层内透光率随树龄（2-6a）和叶面积指数的变化。结果表明，杏树冠层内部平均PAR的垂直分布具有随着向下累计叶面积指数的增加而递减的趋势，在冠层中上部，透光率较高，PAR递减很明显，冠层下部则维持较低水平，变化不大，在相同的天气和时间条件下不同树龄冠层内PAR同一相对高度的透光率有随树龄增加而递减的趋势，但在不同时刻不同天气条件下，即使同一棵树相同高度同一方位冠层内也具有不同的消光系数，影响杏树冠内光分布的因素是多样的，它们之间存在着复杂的关系；2～6年生杏树冠层中部的全天平均透光率分别为49．5％、30．0％、27．5％、13．4％和7．8％，冠层下部的平均透光率分别为29．1％、12．1％、10．9％、6．4％和5．9％；杏树冠层叶面积指数LAI（kaf Area Index）与透光率呈极显著指数相关关系，其表达式为Y=131．39e^-0．8963X（R^2=0．907^＊＊）；试验结果也可为果树冠层内PAR三维空间分布的模拟研究及冠层结构的优化提供试验方法和理论验证上的参考。展开更多
文摘Beta flecks are one of the most common defects occur in someα+βandβtitanium alloys.In this study,formation of beta flecks in Ti-17 alloy was investigated by directional solidification experiments.Samples were directionally solidified under a constant temperature gradient of 2×10^4 K/m and a wide range of withdrawal rates(R)from 3 mm/h to 150 mm/h.We find that macrostructure of the directionally solidified Ti-17 samples can be characterized by"four zones and two lines"after the heat treatment.Profile of the solid-liquid interface transits from planar to cellular to dendritic shape with solidification rate increasing from 3 mm/h to 150 mm/h.The critical rates for planar to cellular(Rc1)transition and cellular to dendritic(Rc2)transition can be well predicted based on the traditional solidification theory.Dark and light contrast areas in macrostructure are directly related to elemental segregation.Dark contrast areas are rich of Cr,Zr but lean of Mo,while no apparent segregation is found in light contrast areas and the mean level of Cr,Zr is lower and Mo is higher in this area than that in dark contrast areas.We conclude thatβ-flecks in Ti-17 titanium alloy are induced by segregation of alloying elements with k<1 and their shape and size are determined by solidification conditions.Based on the findings of the present article and other literatures,three types ofβ-flecks are proposed and their formation mechanisms are discussed.
基金supported by the National Key R&D Program of China (2019YFD1001800)the China Agricultural Research System of MOF and MARA (CARS-29)。
文摘Vitis vinifera 87-1 plants infected by grapevine fleck virus(GFkV) and grapevine rupestris stem pitting-associated virus(GRSPaV) were used as the plant materials for virus elimination treatment. This study evaluated the effects of ribavirin at different concentrations(15 and 25 μg mL^(–1);R15 and R25, respectively), thermotherapy(37°C;T), and the combination of ribavirin and thermotherapy(R15+T and R25+T) on eliminating viruses from grapevine plants in vitro. Both R15 and R25 had phytotoxic effects and weakened plant growth. Thermotherapy positively affected the growth of grapevine plants. Plant height was significantly greater in T, R15+T, and R25+T than in CK, R15 and R25. The proportion of dead plants after T, R15+T, and R25+T was 51.4, 11.4, and 8.6%, respectively. The survival rates of regenerated plants after all treatments were >68.0%. Ribavirin concentration and treatment time were related to the regeneration of shoot tips and elimination efficiencies of the two viruses. The survival rates of plants after R15+T for 30, 40, and 50 days were 97.3, 90.7, and 74.4%, respectively. The elimination rates of GRSPaV from plants in the three time quantum were 55.6, 84.6, and 93.8%, respectively. The elimination rate of GFkV was 23.9% higher in R25(35/44) than in R15(25/45), and that of GRSPaV was 7.0% higher in R25 than in R15. The combination of thermotherapy and chemotherapy was found to have a positive effect on the eradication of GFkV and GRSPaV, and R25+T for 50 days was able to completely eliminate the two viruses from in vitro grapevines.
文摘Effect of β-flecks on properties of tensile elongation and low cycle.fatigue life at room tern. perature for Ti-10V-2Fe-3Al alloy has been investigated.The cracks along initial β-grain boundaries in the β-fleck region may propagate to form intergranular brittle fracture.Under alternating load,the β-fleck often becomes a fatigue origin.While under higher strain,the cracks initiate and propagate to fracture early at the original β-grain boundaries in β-fleck region and at α-grain boundaries.
文摘以杏树为试材，为了解杏树冠层内透光率随树龄和叶面积指数的变化，采用LP-80型冠层分析仪测定了光合有效辐射PAR（Photosynthetically Active Radiation）在不同树龄杏树冠层三维空间上的分布情况，研究了杏树冠层内透光率随树龄（2-6a）和叶面积指数的变化。结果表明，杏树冠层内部平均PAR的垂直分布具有随着向下累计叶面积指数的增加而递减的趋势，在冠层中上部，透光率较高，PAR递减很明显，冠层下部则维持较低水平，变化不大，在相同的天气和时间条件下不同树龄冠层内PAR同一相对高度的透光率有随树龄增加而递减的趋势，但在不同时刻不同天气条件下，即使同一棵树相同高度同一方位冠层内也具有不同的消光系数，影响杏树冠内光分布的因素是多样的，它们之间存在着复杂的关系；2～6年生杏树冠层中部的全天平均透光率分别为49．5％、30．0％、27．5％、13．4％和7．8％，冠层下部的平均透光率分别为29．1％、12．1％、10．9％、6．4％和5．9％；杏树冠层叶面积指数LAI（kaf Area Index）与透光率呈极显著指数相关关系，其表达式为Y=131．39e^-0．8963X（R^2=0．907^＊＊）；试验结果也可为果树冠层内PAR三维空间分布的模拟研究及冠层结构的优化提供试验方法和理论验证上的参考。
