The solidified structure of the thin-walled and complicated Ti-6AI-4V castings produced by the vertical centrifugal casting process was studied in the present work. The results show that the wall thickness of the sect...The solidified structure of the thin-walled and complicated Ti-6AI-4V castings produced by the vertical centrifugal casting process was studied in the present work. The results show that the wall thickness of the section is featured with homogeneously distributed fine equiaxial grains, compared with the microstructure of the thick-walled section. The grain size of the castings has a tendency to decrease gradually with the increasing of the centrifugal radius. The inter-lamellar space in thick-walled casting parts is bigger than that of the thin-walled parts, and the profile of inter-lamellar space is not susceptible to the centrifugal radius.展开更多
Two japonica rice varieties, Longjing 20 （more tillers and curved panicle type, MCP） and Longjing 21 （few tillers and half erect panicle type, FEP）, were used to study the effects of row-spacing on canopy structur...Two japonica rice varieties, Longjing 20 （more tillers and curved panicle type, MCP） and Longjing 21 （few tillers and half erect panicle type, FEP）, were used to study the effects of row-spacing on canopy structure, morphological characteristics and yield. The results showed that the percentage of productive tiller reduced first, and increased afterwards as row-spacing increasing. The relationship between row spacing and the percentage of productive tiller fitted a quadratic regression. The effects of row spacing on leaf area index （LAI） at later tillering stage and the highest stem number per square meter also followed a quadratic regression relationship with increasing first and then reducing. The effects of row-spacing on primary branch were larger than the secondary branch in Longjing 20. However, the trend in Longjing 21 was opposite. The relationship between row spacing and seed setting rate of the secondary branch or panicle was negatively correlated. An extreme significant negative correlation was obtained between seed setting rate of secondary branch in Longjing 20. There was no significant positive correlation between row-spacing and yield in Longjing 20 （R2=0.68）. However, the negative correlation between row-spacing and yield of Longjing 21 was extremely significant （R2=–0.96＊＊）. The canopy structure of MCP was more sensitive to row-spacing. The positive correlation between row spacing and the length of the flag leaf （R2=0.89＊＊）, the width of the flag leaf （R2=0.85＊）, the length of the last internode （R2=0.85＊）, the length of the last 2nd internode （R2=0.96＊＊） or the length of the panicle （R2=0.91＊＊） was significant or extremely significant in Longjing 20, but not in Longjing 21. The wider row-spacing promoted the accumulation of the dry matter of panicle, stem and leaf and the yield formation in MCP. The best row-spacing in Longjing 20 was 30 cm. For Longjing 21, the narrower row-spacing was better. The best row-spacing of it was 21 cm. These results suggested that improved the population environment of MCP or the utilization of the free space in the field of FEP could be reached either by wider row-spacing or narrow row-spacing.展开更多
基金by the National Natural Science Foundation of China under grant No. 50775050the State Key Laboratory of Solidif ication Processing in NWPU (200702)
文摘The solidified structure of the thin-walled and complicated Ti-6AI-4V castings produced by the vertical centrifugal casting process was studied in the present work. The results show that the wall thickness of the section is featured with homogeneously distributed fine equiaxial grains, compared with the microstructure of the thick-walled section. The grain size of the castings has a tendency to decrease gradually with the increasing of the centrifugal radius. The inter-lamellar space in thick-walled casting parts is bigger than that of the thin-walled parts, and the profile of inter-lamellar space is not susceptible to the centrifugal radius.
基金Supported by the National Key Technology R&D Program (2007BAD65B01-4)Science and Technology Development Plan of Heilongjiang Province in China (GB06B104-1-5)Key Technology R&D Program of Heilongjiang Province in China (GA09B102-3)
文摘Two japonica rice varieties, Longjing 20 （more tillers and curved panicle type, MCP） and Longjing 21 （few tillers and half erect panicle type, FEP）, were used to study the effects of row-spacing on canopy structure, morphological characteristics and yield. The results showed that the percentage of productive tiller reduced first, and increased afterwards as row-spacing increasing. The relationship between row spacing and the percentage of productive tiller fitted a quadratic regression. The effects of row spacing on leaf area index （LAI） at later tillering stage and the highest stem number per square meter also followed a quadratic regression relationship with increasing first and then reducing. The effects of row-spacing on primary branch were larger than the secondary branch in Longjing 20. However, the trend in Longjing 21 was opposite. The relationship between row spacing and seed setting rate of the secondary branch or panicle was negatively correlated. An extreme significant negative correlation was obtained between seed setting rate of secondary branch in Longjing 20. There was no significant positive correlation between row-spacing and yield in Longjing 20 （R2=0.68）. However, the negative correlation between row-spacing and yield of Longjing 21 was extremely significant （R2=–0.96＊＊）. The canopy structure of MCP was more sensitive to row-spacing. The positive correlation between row spacing and the length of the flag leaf （R2=0.89＊＊）, the width of the flag leaf （R2=0.85＊）, the length of the last internode （R2=0.85＊）, the length of the last 2nd internode （R2=0.96＊＊） or the length of the panicle （R2=0.91＊＊） was significant or extremely significant in Longjing 20, but not in Longjing 21. The wider row-spacing promoted the accumulation of the dry matter of panicle, stem and leaf and the yield formation in MCP. The best row-spacing in Longjing 20 was 30 cm. For Longjing 21, the narrower row-spacing was better. The best row-spacing of it was 21 cm. These results suggested that improved the population environment of MCP or the utilization of the free space in the field of FEP could be reached either by wider row-spacing or narrow row-spacing.
