The cast Al-Si alloy was fabricated using the Additive Pressure Casting(APC)method.The effects of holding pressure from 50 to 400 k Pa on the density,cooling rate,and mechanical properties of the alloy,and the corresp...The cast Al-Si alloy was fabricated using the Additive Pressure Casting(APC)method.The effects of holding pressure from 50 to 400 k Pa on the density,cooling rate,and mechanical properties of the alloy,and the corresponding mechanism were discussed.The results indicate that the application of high holding pressure(300 k Pa)enhances the feeding ability of the alloy,leading to an increase of the density.Meanwhile,the cooling rate of the alloy is increased by 100%.In addition,the tensile testing results show that the increase of holding pressure from 50 to 300 k Pa improves the tensile strength and elongation of the alloy by 6.2%and 81.3%,respectively.However,excessive holding pressure(400 k Pa)might lower the density and cooling rate of the alloy due to the feeding channels being blocked.展开更多
The decomposition rate and the water-holding capacity of 6 kinds of grass litters were studied in the Jinshajiang river dry-hot valley. The results showed that the dry weight remains reduced with time but did not have...The decomposition rate and the water-holding capacity of 6 kinds of grass litters were studied in the Jinshajiang river dry-hot valley. The results showed that the dry weight remains reduced with time but did not have a direct correlation with time. The decomposition litters were affected by climate, character of litter, animalcule and soil animal. The climate factors of temperature and humidity were important especially. The water-holding capacity was in the sequence ofN. wightii （336%）, P. notatum Flugge （248%）, H. contortus （L.） Beauv （209%）, B. pertusa （L.） A. Camus（206%）, L endecaphylla Jacq （174%）, D. annulatum （Forsk.） Stapf （168%）. After 24 months decomposition the remaining dry weight of the litter was in the sequence as follows： 15.12% for N. wightii, 26.38% for I. endecaphylla Jacq, 27.23% for B. pertusa （L.） A. Camus, 30.78% for P. notatum Flugge, 39.72% for H. contortus （L.） Beauv and 39.76% for D. annulatum （Forsk.） Stapf. The decomposition rate and water-holding capacity ofN. wightii are at the highest level. It is important for the development, improvement and conservation of the grassland soil.展开更多
The use of superabsorbent polymers or hydrogels could increase the water holding capacity (WHC) of sandy soil and reduce water loss by deep percolation.However,hydrogels' retained water availability to plants migh...The use of superabsorbent polymers or hydrogels could increase the water holding capacity (WHC) of sandy soil and reduce water loss by deep percolation.However,hydrogels' retained water availability to plants might be overestimated without taking into consideration the hydrogel particles size.Therefore,the ultimate objective of this study was to address the impacts of hydrogel particles size on hydrogel's retained water availability (plant available water,PAW),daily water consumption (DWC) and survival of Guava seedlings subjected to drought.Moreover,some soil physical properties,i.e.,WHC,water retention properties,and hydraulic conductivity (Ksat) were investigated.Hydrogel (WaterSorb,'WS') application,particularly the WS of small particles,significantly reduced Ksat,and increased WHC and PAW.Therefore,seedlings grown in soil amended with WS fine (0.8-1.0 mm),WS medium (1.0-2.0 mm) and WS large (2-4 mm) survived for 27.0 ± 1.3,24.0 ± 1.1 and 17.0 ± 0.7 days,respectively,compared to 13.0 ± 1.0 days for the control.The water stored in the WS of large particles was less readily available for plant roots.Interestingly,hydrogels,had no effect on the DWC of the seedlings.Utilizing hydrogels as a soil amendment increases WHC PAW,growth and survival of Guava seedlings,while the effect was less pronounced for the large hydrogel particles which had lower specific surface area and swelling rate.展开更多
The microstructure changes of Ti-6Al-2V-1.5Mo-0.5Zr-0.3Si alloy manufactured by laser additive manufacturing （LAM） are systematically investigated with statistical analysis of primary α phase （αp） and secondary ...The microstructure changes of Ti-6Al-2V-1.5Mo-0.5Zr-0.3Si alloy manufactured by laser additive manufacturing （LAM） are systematically investigated with statistical analysis of primary α phase （αp） and secondary α phase （αs） under different annealing conditions. Results indicate that, with the increase in holding temperature, the content of αp lamellas decreases with the increasing αs content, maintaining the total α phases concentration stabilized. The width of αp lamellas and the nominal specific surface area of α phase both exhibit positive correlation with the temperature, while the increment of αp and the widths of αs lamellas show an increase-decrease tendency. Besides, with the decrease in cooling rate, the total content of α and the width of αp lamellas increase, while the nominal specific surface area of α phase shows no significant change. The results indicate that, in the annealing process, the holding temperature determines the surplus and growth interfaces of % lamellas, and the cooling rate influences the nucleation quantity of c^s in unit time. During the cooling stage, the αp lamellas grow initially, and then, the nucleation and crab-like structure growth occur followed by those of the αs lamellas. The time intervals among them are influenced by cooling rate. The mechanism of microstructure formation of the LAMed titanium alloy during annealing stage was discussed, which would guide for the heat treatment method to achieve required microstructure.展开更多
基金National Key Research Project of China(No.2016YFB0300901).
文摘The cast Al-Si alloy was fabricated using the Additive Pressure Casting(APC)method.The effects of holding pressure from 50 to 400 k Pa on the density,cooling rate,and mechanical properties of the alloy,and the corresponding mechanism were discussed.The results indicate that the application of high holding pressure(300 k Pa)enhances the feeding ability of the alloy,leading to an increase of the density.Meanwhile,the cooling rate of the alloy is increased by 100%.In addition,the tensile testing results show that the increase of holding pressure from 50 to 300 k Pa improves the tensile strength and elongation of the alloy by 6.2%and 81.3%,respectively.However,excessive holding pressure(400 k Pa)might lower the density and cooling rate of the alloy due to the feeding channels being blocked.
基金Supported by the National Science and Technology Sup-porting Program in the Eleventh Five-Year Plan of China (2006BAC01A11)
文摘The decomposition rate and the water-holding capacity of 6 kinds of grass litters were studied in the Jinshajiang river dry-hot valley. The results showed that the dry weight remains reduced with time but did not have a direct correlation with time. The decomposition litters were affected by climate, character of litter, animalcule and soil animal. The climate factors of temperature and humidity were important especially. The water-holding capacity was in the sequence ofN. wightii （336%）, P. notatum Flugge （248%）, H. contortus （L.） Beauv （209%）, B. pertusa （L.） A. Camus（206%）, L endecaphylla Jacq （174%）, D. annulatum （Forsk.） Stapf （168%）. After 24 months decomposition the remaining dry weight of the litter was in the sequence as follows： 15.12% for N. wightii, 26.38% for I. endecaphylla Jacq, 27.23% for B. pertusa （L.） A. Camus, 30.78% for P. notatum Flugge, 39.72% for H. contortus （L.） Beauv and 39.76% for D. annulatum （Forsk.） Stapf. The decomposition rate and water-holding capacity ofN. wightii are at the highest level. It is important for the development, improvement and conservation of the grassland soil.
文摘The use of superabsorbent polymers or hydrogels could increase the water holding capacity (WHC) of sandy soil and reduce water loss by deep percolation.However,hydrogels' retained water availability to plants might be overestimated without taking into consideration the hydrogel particles size.Therefore,the ultimate objective of this study was to address the impacts of hydrogel particles size on hydrogel's retained water availability (plant available water,PAW),daily water consumption (DWC) and survival of Guava seedlings subjected to drought.Moreover,some soil physical properties,i.e.,WHC,water retention properties,and hydraulic conductivity (Ksat) were investigated.Hydrogel (WaterSorb,'WS') application,particularly the WS of small particles,significantly reduced Ksat,and increased WHC and PAW.Therefore,seedlings grown in soil amended with WS fine (0.8-1.0 mm),WS medium (1.0-2.0 mm) and WS large (2-4 mm) survived for 27.0 ± 1.3,24.0 ± 1.1 and 17.0 ± 0.7 days,respectively,compared to 13.0 ± 1.0 days for the control.The water stored in the WS of large particles was less readily available for plant roots.Interestingly,hydrogels,had no effect on the DWC of the seedlings.Utilizing hydrogels as a soil amendment increases WHC PAW,growth and survival of Guava seedlings,while the effect was less pronounced for the large hydrogel particles which had lower specific surface area and swelling rate.
基金This work was supported by the Beijing Natural Science Foundation （Grant No. Z140002）,
文摘The microstructure changes of Ti-6Al-2V-1.5Mo-0.5Zr-0.3Si alloy manufactured by laser additive manufacturing （LAM） are systematically investigated with statistical analysis of primary α phase （αp） and secondary α phase （αs） under different annealing conditions. Results indicate that, with the increase in holding temperature, the content of αp lamellas decreases with the increasing αs content, maintaining the total α phases concentration stabilized. The width of αp lamellas and the nominal specific surface area of α phase both exhibit positive correlation with the temperature, while the increment of αp and the widths of αs lamellas show an increase-decrease tendency. Besides, with the decrease in cooling rate, the total content of α and the width of αp lamellas increase, while the nominal specific surface area of α phase shows no significant change. The results indicate that, in the annealing process, the holding temperature determines the surplus and growth interfaces of % lamellas, and the cooling rate influences the nucleation quantity of c^s in unit time. During the cooling stage, the αp lamellas grow initially, and then, the nucleation and crab-like structure growth occur followed by those of the αs lamellas. The time intervals among them are influenced by cooling rate. The mechanism of microstructure formation of the LAMed titanium alloy during annealing stage was discussed, which would guide for the heat treatment method to achieve required microstructure.
