The tortuosity factor is the most critical parameter for the pore characteristic of porous materials. The tortuosity factor for porous FeAl intermetallics was studied based on the Darcy law and Hagen-Poiseuille equati...The tortuosity factor is the most critical parameter for the pore characteristic of porous materials. The tortuosity factor for porous FeAl intermetallics was studied based on the Darcy law and Hagen-Poiseuille equation. Porous stainless steel with the same pore structure parameter as porous FeAl was fabricated by powder metallurgy method for comparison. The results show that the tortuosity factor of porous FeAl intermetallics is smaller than that of porous stainless steel when their pore structure parameters are the same. The average tortuosity factor is 2.26 for the porous FeAl material and 2.92 for the porous stainless steel, calculated by Hagen-Poiseuille equation. The reason of the different tortuosity factors for porous FeAl and porous stainless steel was also explored through studying the pore formation mechanisms of the two types of porous materials.展开更多
The pore constitution and tortuosity factor of porous TiAl intermetallic were studied on the basis of the variation behavior of pore structure parameters and the discrete particle model. The pore formation mechanism o...The pore constitution and tortuosity factor of porous TiAl intermetallic were studied on the basis of the variation behavior of pore structure parameters and the discrete particle model. The pore formation mechanism of porous TiAl is mainly ascribed to three aspects: the clearance space in green compact, the diffusive pores in the reaction process and the phase transition pores, resulting in the open porosities of 5.6%, 42.9% and 1.3%, respectively. According to the Hagen-Poiseuille equation, the tortuosity factor of porous TiAl is determined in the range of 1.3-2.2. Based on the discrete particle model and the variation rule of the tortuosity factor, the tortuosity factor depends mainly on the parameters of fabrication constant, particle shape factor, clearance distance and powder particle size. The quantitative relationships among them have been established, which can be used as the basis for adjusting the pore structure of porous intermetallics.展开更多
Objective： To observe the therapeutic effect of absorbable screw in medial malleolus fracture and discuss its clinical application in orthopedics. Methods： A total of 129 patients with simple medial malleolus fract...Objective： To observe the therapeutic effect of absorbable screw in medial malleolus fracture and discuss its clinical application in orthopedics. Methods： A total of 129 patients with simple medial malleolus fracture were studied. Among them, 64 patients were treated with poly-D, L-lactic acid （PDLLA） absorbable screws, while the others were treated with metal screws. All the patients were followed up for 12-20 months （averaged 18.4 months） and the therapeutic effect was evaluated according to the American Orthopaedic Foot and Ankle Society clinical rating systems. Results： In absorbable screw group, we obtained excel- lent and good results in 62 cases （96.88%）; in steel screw group, 61 cases （93.85%） achieved excellent and good results. There was no significant difference between the two groups. Conclusion： In the treatment of malleolus fracture, absorbable screw can achieve the same result compared with metal screw fixation. Absorbable screw is preferred due to its advantages of safety, cleanliness and avoiding the removal procedure associated with metallic implants.展开更多
Exploration of new infrared(IR) nonlinear optical(NLO) materials is still in urgency owing to the indispensable roles in optoelectronic devices, resource exploration, and long-distance laser communication. The formida...Exploration of new infrared(IR) nonlinear optical(NLO) materials is still in urgency owing to the indispensable roles in optoelectronic devices, resource exploration, and long-distance laser communication. The formidable challenge is to balance the contradiction between wide band gaps and large second harmonic generation(SHG) effects in IR NLO materials. In the present work, we proposed new kinds of NLO active units, d^0 transition metal fluorooxofunctional groups for designing mid-IR NLO materials. By studying a series of d^0 transition metal oxyfluorides(TMOFs),the influences of fluorooxo-functional groups with different d^0 configuration cations on the band gap and SHG responses were explored. The results reveal that the fluorooxo-functional groups with different d^0 configuration cations can enlarge band gaps in mid-IR NLO materials. The first-principles calculations demonstrate that the nine alkali/alkaline earth metals d^0 TMOFs exhibit wide band gaps(all the band gaps >3.0 e V), large birefringence Δn(> 0.07), and two W/Mo TMOFs also exhibit large SHG responses. Moreover, by comparing with other fluorooxo-functional groups, it is found that introducing fluorine into building units is an effective way to enhance optical performance. These d^0 TMOFs with superior fluorooxo-functional groups represent a new exploration family of the mid-IR region, which sheds light on the design of mid-IR NLO materials possessing large band gap.展开更多
Objective: To sutdy the mechanical properties and the clinical results of minimum-contact plate in the treatment of fractures. Methods: Four-point bending and torsion tests were conducted to compare the new minimum co...Objective: To sutdy the mechanical properties and the clinical results of minimum-contact plate in the treatment of fractures. Methods: Four-point bending and torsion tests were conducted to compare the new minimum contact plate (MCP) with dynamic compression plate (DCP) and limited contact dynamic compression plate (LC-DCP). The fracture healing time and growth of bony callus were observed in 29 cases of long bone fracture fixed with MCP to evaluate the advantages of this kind of plate. Results: The 29 patients who underwent MCP were followed up from 6 to 14 months. The average healing time for femoral, tibial and humeral fractures was 12, 13 and 10 weeks, respectively. All fractures were healed. No displacement of fracture, screw pullout, deformation or break of the plate were found. Conclusions: The bending stiffness of MCP is significantly greater than that of DCP and LC-DCP (P< 0.05). MCP can protect the periosteal blood supply against avascular osseous necrosis and accelerate bone healing. It is a kind of reliable and effective plate in treatment of fractures.展开更多
基金Project (2009CB623406) supported by the National Basic Research Program of ChinaProjects (50825102, 50721003, 51071178) supported by the National Natural Science Foundation of China+1 种基金Project (11JJ4036) supported by the Natural Science Foundation of Hunan Province, ChinaProject supported by the Central South University Free Exploring Project, China
文摘The tortuosity factor is the most critical parameter for the pore characteristic of porous materials. The tortuosity factor for porous FeAl intermetallics was studied based on the Darcy law and Hagen-Poiseuille equation. Porous stainless steel with the same pore structure parameter as porous FeAl was fabricated by powder metallurgy method for comparison. The results show that the tortuosity factor of porous FeAl intermetallics is smaller than that of porous stainless steel when their pore structure parameters are the same. The average tortuosity factor is 2.26 for the porous FeAl material and 2.92 for the porous stainless steel, calculated by Hagen-Poiseuille equation. The reason of the different tortuosity factors for porous FeAl and porous stainless steel was also explored through studying the pore formation mechanisms of the two types of porous materials.
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(51971251,51774336).
文摘The pore constitution and tortuosity factor of porous TiAl intermetallic were studied on the basis of the variation behavior of pore structure parameters and the discrete particle model. The pore formation mechanism of porous TiAl is mainly ascribed to three aspects: the clearance space in green compact, the diffusive pores in the reaction process and the phase transition pores, resulting in the open porosities of 5.6%, 42.9% and 1.3%, respectively. According to the Hagen-Poiseuille equation, the tortuosity factor of porous TiAl is determined in the range of 1.3-2.2. Based on the discrete particle model and the variation rule of the tortuosity factor, the tortuosity factor depends mainly on the parameters of fabrication constant, particle shape factor, clearance distance and powder particle size. The quantitative relationships among them have been established, which can be used as the basis for adjusting the pore structure of porous intermetallics.
文摘Objective： To observe the therapeutic effect of absorbable screw in medial malleolus fracture and discuss its clinical application in orthopedics. Methods： A total of 129 patients with simple medial malleolus fracture were studied. Among them, 64 patients were treated with poly-D, L-lactic acid （PDLLA） absorbable screws, while the others were treated with metal screws. All the patients were followed up for 12-20 months （averaged 18.4 months） and the therapeutic effect was evaluated according to the American Orthopaedic Foot and Ankle Society clinical rating systems. Results： In absorbable screw group, we obtained excel- lent and good results in 62 cases （96.88%）; in steel screw group, 61 cases （93.85%） achieved excellent and good results. There was no significant difference between the two groups. Conclusion： In the treatment of malleolus fracture, absorbable screw can achieve the same result compared with metal screw fixation. Absorbable screw is preferred due to its advantages of safety, cleanliness and avoiding the removal procedure associated with metallic implants.
基金supported by Tianshan Innovation Team Program (2018D14001)the National Natural Science Foundation of China (51922014 and 11774414)+2 种基金Shanghai Cooperation Organization Science and Technology Partnership Program (2017E01013)Xinjiang Program of Introducing High-Level Talents, Fujian Institute of Innovation, Chinese Academy of Sciences (FJCXY18010202)the Western Light Foundation of CAS (2017-XBQNXZ-B-006 and 2016QNXZ-B-9)
文摘Exploration of new infrared(IR) nonlinear optical(NLO) materials is still in urgency owing to the indispensable roles in optoelectronic devices, resource exploration, and long-distance laser communication. The formidable challenge is to balance the contradiction between wide band gaps and large second harmonic generation(SHG) effects in IR NLO materials. In the present work, we proposed new kinds of NLO active units, d^0 transition metal fluorooxofunctional groups for designing mid-IR NLO materials. By studying a series of d^0 transition metal oxyfluorides(TMOFs),the influences of fluorooxo-functional groups with different d^0 configuration cations on the band gap and SHG responses were explored. The results reveal that the fluorooxo-functional groups with different d^0 configuration cations can enlarge band gaps in mid-IR NLO materials. The first-principles calculations demonstrate that the nine alkali/alkaline earth metals d^0 TMOFs exhibit wide band gaps(all the band gaps >3.0 e V), large birefringence Δn(> 0.07), and two W/Mo TMOFs also exhibit large SHG responses. Moreover, by comparing with other fluorooxo-functional groups, it is found that introducing fluorine into building units is an effective way to enhance optical performance. These d^0 TMOFs with superior fluorooxo-functional groups represent a new exploration family of the mid-IR region, which sheds light on the design of mid-IR NLO materials possessing large band gap.
文摘Objective: To sutdy the mechanical properties and the clinical results of minimum-contact plate in the treatment of fractures. Methods: Four-point bending and torsion tests were conducted to compare the new minimum contact plate (MCP) with dynamic compression plate (DCP) and limited contact dynamic compression plate (LC-DCP). The fracture healing time and growth of bony callus were observed in 29 cases of long bone fracture fixed with MCP to evaluate the advantages of this kind of plate. Results: The 29 patients who underwent MCP were followed up from 6 to 14 months. The average healing time for femoral, tibial and humeral fractures was 12, 13 and 10 weeks, respectively. All fractures were healed. No displacement of fracture, screw pullout, deformation or break of the plate were found. Conclusions: The bending stiffness of MCP is significantly greater than that of DCP and LC-DCP (P< 0.05). MCP can protect the periosteal blood supply against avascular osseous necrosis and accelerate bone healing. It is a kind of reliable and effective plate in treatment of fractures.
