Columnar to equiaxial crystal transition(CET)is an important technological feature in many casting processes.This work investigated the CET during the solidification of Mg-Gd-Zn alloys by combining synchrotron radiati...Columnar to equiaxial crystal transition(CET)is an important technological feature in many casting processes.This work investigated the CET during the solidification of Mg-Gd-Zn alloys by combining synchrotron radiation in-situ imaging and phase-field method.Results show that the grain size,dendrite tip radius,and secondary dendrite arm spacing(SDAS)all exponentially decrease with an increase in cooling rate(Vc).The variation in the radius of the dendritic tip is similar to the prediction of the Hunt model,while the variation in the SDAS is close to the Bouchard-Kirkaldy model.It is worth noting that the CET is promoted by a decrease in the temperature gradient(G)and an increase in the cooling rate(Vc).In both equiaxed and columnar crystal regions,the dendrite tip growth rate and solid phase volume fraction increase with increasing G and Vc.In addition,the CET process has been predicted by simulation.The results are consistent with the predictions of the GTK model,which is important for the in-depth study of the dendrite morphology in different crystallization regions.In the final stage,the effects of different critical subcooling degrees and nucleation densities on the CET were explored.The results show that increasing the critical nucleation supercooling degree can inhibit the generation of equiaxial crystals,while increasing the nucleation density helps to promote the CET.展开更多
The sliding friction and wear behaviors of Mg-11Y-5Gd-2Zn-0.5Zr （wt%） alloy were investigated under oil lubricant condition by pin-on-disk configuration with a constant sliding distance of 1,000 m in the temperature...The sliding friction and wear behaviors of Mg-11Y-5Gd-2Zn-0.5Zr （wt%） alloy were investigated under oil lubricant condition by pin-on-disk configuration with a constant sliding distance of 1,000 m in the temperature range of 25-200℃. Results indicate that the volumetric wear rates and average friction coefficients decrease with the increase of sliding speeds, and increase with the increase of test temperature below 150℃. The hard and thermally stable Mg12（Y,Gd）Zn phase with long-period stacking order structure in the alloy presents significant wear resistance, The wear mechanism below 100℃ is abrasive wear as a result of plastic extrusion deformation. The corporate effects of severe abrasive, oxidative, and delaminating wear result in the tribological mechanism above 100℃.展开更多
Liquid phase epitaxy （LPE） is a mature technology. Early experiments on single magnetic crystal films fabricated by LPE were focused mainly on thick films for microwave and magneto-optical devices. The LPE is an exc...Liquid phase epitaxy （LPE） is a mature technology. Early experiments on single magnetic crystal films fabricated by LPE were focused mainly on thick films for microwave and magneto-optical devices. The LPE is an excellent way to make a thick film, low damping magnetic garnet film and high-quality magneto-optical material. Today, the principal challenge in the applied material is to create sub-micrometer devices by using modern photolithography technique. Until now the magnetic garnet films fabricated by LPE still show the best quality even on a nanoscale （about 100 nm）, which was considered to be impossible for LPE method.展开更多
A quantitative multi-phase-field model for non-isothermal and polycrystalline solidification was developed and applied to dilute multicomponent alloys with hexagonal close-packed structures.The effects of Lewis coeffi...A quantitative multi-phase-field model for non-isothermal and polycrystalline solidification was developed and applied to dilute multicomponent alloys with hexagonal close-packed structures.The effects of Lewis coefficient and undercooling on dendrite growth were investigated systematically.Results show that large Lewis coefficients facilitate the release of the latent heat,which can accelerate the dendrite growth while suppress the dendrite tip radius.The greater the initial undercooling,the stronger the driving force for dendrite growth,the faster the growth rate of dendrites,the higher the solid fraction,and the more serious the solute microsegregation.The simulated dendrite growth dynamics are consistent with predictions from the phenomenological theory but significantly deviate from the classical JMAK theory which neglects the soft collision effect and mutual blocking among dendrites.Finally,taking the Mg-6Gd-2Zn(wt.%)alloy as an example,the simulated dendrite morphology shows good agreement with experimental results.展开更多
Objective:To study the influence of human albumin combined with low-dose heparin on disease condition, serology and placental blood flow of severe preeclampsia patients. Methods:A total of 78 patients with severe pree...Objective:To study the influence of human albumin combined with low-dose heparin on disease condition, serology and placental blood flow of severe preeclampsia patients. Methods:A total of 78 patients with severe preeclampsia in our hospital between May 2011 and February 2017 were chosen as study subjects, treatment methods were reviewed and all patients were divided into control group (n=37) who underwent low-dose heparin plus conventional treatment and observation group (n=41) who underwent human albumin combined with low-dose heparin plus conventional treatment, both lasting for 7 d. Before and after treatment, mean arterial pressure (MAP) and 24 h urinary protein were measured, serum markers of disease were measured by enzyme-linked immunosorbent assay (ELISA), and umbilical artery hemodynamics were detected by color Doppler ultrasound.Results:Before treatment, there was no significant difference between the two groups in MAP, 24 h urine protein, serum disease-related indexes or umbilical artery hemodynamic indexes. 7 d after treatment, MAP and 24 h urine protein levels in observation group were lower than those in control group;serum disease-related indexes TGF-β1 and VEGF contents in observation group were higher than those in control group whereas VCAM-1 and sFlt-1 contents were lower than those in control group;umbilical artery hemodynamic indexes PI, RI and S/D levels in observation group were lower than those in control group.Conclusion: Human albumin combined with low-dose heparin can optimize the disease condition, promote the angiogenesis of placenta and increase the blood supply of placenta in patients with severe preeclampsia.展开更多
基金financially supported by the Postdoctoral Research Project of Henan Province(No.202101003)the Key Research Programs of Higher Education Institutions in Henan Province(Nos.24A450003,23A460016)+2 种基金the Henan Provincial Key Laboratory of Intelligent Manufacturing of Machinery and Equipment Open Subjects(No.IM202308)the Zhengzhou University of Light Industry Doctoral Research Initiation Fund(No.2019BSJJ005)the Henan Provincial Science and Technology Tackling Project(No.23A460016).
文摘Columnar to equiaxial crystal transition(CET)is an important technological feature in many casting processes.This work investigated the CET during the solidification of Mg-Gd-Zn alloys by combining synchrotron radiation in-situ imaging and phase-field method.Results show that the grain size,dendrite tip radius,and secondary dendrite arm spacing(SDAS)all exponentially decrease with an increase in cooling rate(Vc).The variation in the radius of the dendritic tip is similar to the prediction of the Hunt model,while the variation in the SDAS is close to the Bouchard-Kirkaldy model.It is worth noting that the CET is promoted by a decrease in the temperature gradient(G)and an increase in the cooling rate(Vc).In both equiaxed and columnar crystal regions,the dendrite tip growth rate and solid phase volume fraction increase with increasing G and Vc.In addition,the CET process has been predicted by simulation.The results are consistent with the predictions of the GTK model,which is important for the in-depth study of the dendrite morphology in different crystallization regions.In the final stage,the effects of different critical subcooling degrees and nucleation densities on the CET were explored.The results show that increasing the critical nucleation supercooling degree can inhibit the generation of equiaxial crystals,while increasing the nucleation density helps to promote the CET.
基金supported by the National Natural Science Foundation of China (No. 51074106)Key HiTech Research and Development Program of China (No. 2009AA033501)National Key Technology R&D Program of China (No. 2011BAE22B01-5)
文摘The sliding friction and wear behaviors of Mg-11Y-5Gd-2Zn-0.5Zr （wt%） alloy were investigated under oil lubricant condition by pin-on-disk configuration with a constant sliding distance of 1,000 m in the temperature range of 25-200℃. Results indicate that the volumetric wear rates and average friction coefficients decrease with the increase of sliding speeds, and increase with the increase of test temperature below 150℃. The hard and thermally stable Mg12（Y,Gd）Zn phase with long-period stacking order structure in the alloy presents significant wear resistance, The wear mechanism below 100℃ is abrasive wear as a result of plastic extrusion deformation. The corporate effects of severe abrasive, oxidative, and delaminating wear result in the tribological mechanism above 100℃.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFA0300801)the National Natural Science Foundation of China(Grant Nos.51702042,61734002,61571079,51572042,and 61471096)+1 种基金the International Science&Technology Cooperation Program of China(Grant No.2015DFR50870)the Sichuan Science and Technology Support Project,China(Grant Nos.2016GZ0250 and 2017JY0002)
文摘Liquid phase epitaxy （LPE） is a mature technology. Early experiments on single magnetic crystal films fabricated by LPE were focused mainly on thick films for microwave and magneto-optical devices. The LPE is an excellent way to make a thick film, low damping magnetic garnet film and high-quality magneto-optical material. Today, the principal challenge in the applied material is to create sub-micrometer devices by using modern photolithography technique. Until now the magnetic garnet films fabricated by LPE still show the best quality even on a nanoscale （about 100 nm）, which was considered to be impossible for LPE method.
基金the National Natural Science Foundation-Youth Science Foundation Project(No.51901208)the Henan University Key Scientific Research Project(No.20B430020)+1 种基金the Key Scientific and Technological Projects in Henan Province(Nos.202102210016,202102210272)the Major Innovation Project of Zhengzhou City(No.23101000010).
文摘A quantitative multi-phase-field model for non-isothermal and polycrystalline solidification was developed and applied to dilute multicomponent alloys with hexagonal close-packed structures.The effects of Lewis coefficient and undercooling on dendrite growth were investigated systematically.Results show that large Lewis coefficients facilitate the release of the latent heat,which can accelerate the dendrite growth while suppress the dendrite tip radius.The greater the initial undercooling,the stronger the driving force for dendrite growth,the faster the growth rate of dendrites,the higher the solid fraction,and the more serious the solute microsegregation.The simulated dendrite growth dynamics are consistent with predictions from the phenomenological theory but significantly deviate from the classical JMAK theory which neglects the soft collision effect and mutual blocking among dendrites.Finally,taking the Mg-6Gd-2Zn(wt.%)alloy as an example,the simulated dendrite morphology shows good agreement with experimental results.
文摘Objective:To study the influence of human albumin combined with low-dose heparin on disease condition, serology and placental blood flow of severe preeclampsia patients. Methods:A total of 78 patients with severe preeclampsia in our hospital between May 2011 and February 2017 were chosen as study subjects, treatment methods were reviewed and all patients were divided into control group (n=37) who underwent low-dose heparin plus conventional treatment and observation group (n=41) who underwent human albumin combined with low-dose heparin plus conventional treatment, both lasting for 7 d. Before and after treatment, mean arterial pressure (MAP) and 24 h urinary protein were measured, serum markers of disease were measured by enzyme-linked immunosorbent assay (ELISA), and umbilical artery hemodynamics were detected by color Doppler ultrasound.Results:Before treatment, there was no significant difference between the two groups in MAP, 24 h urine protein, serum disease-related indexes or umbilical artery hemodynamic indexes. 7 d after treatment, MAP and 24 h urine protein levels in observation group were lower than those in control group;serum disease-related indexes TGF-β1 and VEGF contents in observation group were higher than those in control group whereas VCAM-1 and sFlt-1 contents were lower than those in control group;umbilical artery hemodynamic indexes PI, RI and S/D levels in observation group were lower than those in control group.Conclusion: Human albumin combined with low-dose heparin can optimize the disease condition, promote the angiogenesis of placenta and increase the blood supply of placenta in patients with severe preeclampsia.
