Based on test data from the hot forge experiments on Gleeble 1500, a Kumar type constitutive equation for 33Mn2V steel is established. Applying this constitutive equation in commercial FEM software of MSC/SuperForm 20...Based on test data from the hot forge experiments on Gleeble 1500, a Kumar type constitutive equation for 33Mn2V steel is established. Applying this constitutive equation in commercial FEM software of MSC/SuperForm 2005, the piercing process of 33Mn2V steel in Mannesmann mill is then simulated. The modeling results visualized the dynamic evolution of equivalent stress, especially inside the workpieee. It is shown that the non-uniform distribu- tion of stress on the internal and external surface of the workpiece is a distinct characteristic of processing tube pierc- ing. The numerical model was verified by comparing the values of calculated force parameters of the piercing process with those measured in laboratory eonditions. And it shows that the Kumar-type constitutive relationship meets the practical needs.展开更多
The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 t...The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.展开更多
We study the electronic structures of LiMn2O4 by x-ray and ultraviolet photoelectron spectroscopy （XPS, UPS） and resonant photoelectron spectroscopy （RPES）. XPS data suggest that the average oxidation state of Mn ...We study the electronic structures of LiMn2O4 by x-ray and ultraviolet photoelectron spectroscopy （XPS, UPS） and resonant photoelectron spectroscopy （RPES）. XPS data suggest that the average oxidation state of Mn ions is 3.55, probably due to the small amount of lithium oxides on the surface. UPS and RPES data imply that Mn ions are in a high spin state, and RPES results show strong Mn3d-O2p hybridization in the LiMn2O4 valence band.展开更多
The optical properties and electronic structure of marokite-type CaMn2O4 are investigated by using UV−vis spectroscopy and the local-spin-density approximation plus the Hubbard-U(LSDA+U)method.Four absorption bands ar...The optical properties and electronic structure of marokite-type CaMn2O4 are investigated by using UV−vis spectroscopy and the local-spin-density approximation plus the Hubbard-U(LSDA+U)method.Four absorption bands are observed at 638 nm(1.94 eV),512 nm(2.42 eV),377 nm(3.29 eV)and 248 nm(5.00 eV),which are ascribed to the charge transfer transitions O2p↑→Mn3d eg↑,O2p↓→Mn3d eg↑,Mn3d eg↑→Mn3d t2g↓and O2p↑→Mn3d t2g↓,respectively.We further use CaMn2O4 as a photocatalyst to decompose an azo-dye acid orange 7(AO7)under irradiation of visible light and find that the decomposition ratio of AO7 reaches 15.9%under the irradiation of visible light for two hours.展开更多
The changes of antioxidant enzyme activities and related genes expression of tomato seedlings were evaluated under hypoxia stress with different levels of Mn2+. Activities of superoxide dismutase (SOD), peroxidase (PO...The changes of antioxidant enzyme activities and related genes expression of tomato seedlings were evaluated under hypoxia stress with different levels of Mn2+. Activities of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxide (APX), glutathione reductase (GR), catalase (CAT), the contents of H2O2, ascorbic (AsA) and malondialdehyde (MDA) were studied to investigate how active oxygen damaged the membrane lipid under hypoxia stress. With 10-200 μmol?L-1 Mn2+, the activities of SOD, POD, APX, GR and the contents of H2O2, AsA, MDA of leaves and roots increased significantly, which indicated that low Mn2+ could eliminate the active oxygen and protect the membrane lipid from hurt. But the activities of catalase (CAT) decreased evidently in the root. When the concentration of Mn2+ reached 400-600 μmol?L-1 under hypoxia stress, the activities of SOD, POD, APX, GR and ASA content decreased remarkably. However, the contents of H2O2 and MDA increased contrarily. A series of resistance genes level achieved peak value with 10 μmol?L-1 Mn2+. The expression level of SOD, CAT, APX, POD, GR were 6.28, 2.19, 5.66, 5.21 and 6.79 times compared to control respectively. These results illustrated appropriate amount of Mn2+ could reduce the damage of active oxygen under hypoxia stress, but reversely, high level of Mn2+ just aggravated the already serious damage to the tomato seedlings.展开更多
White light-emitting diodes(WLEDs)fabricated by single-phase full color emitting phosphor are an emerging solution for health lighting.The crystallographic site occupation of activators in a proper host lattice is cru...White light-emitting diodes(WLEDs)fabricated by single-phase full color emitting phosphor are an emerging solution for health lighting.The crystallographic site occupation of activators in a proper host lattice is crucial for sophisticated design of such phosphor.Here,we report a high quality white lightemitting phosphor Ba_(2)Ca(BO_(3))_(2):Ce^(3+)(K^(+)),Eu^(2+),Mn^(2+)with spectral distribution covering whole visible region.Blue light emission originates from Ce3+ions occupying preferentially Ba^(2+)site by controlling synthesis conditions.Green and red lights are obtained from Eu^(2+)occupying Ba2+(and Ca)site and Mn2+occupying Casite,respectively.In this triple-doped phosphor,strong red emission with a low concentration of Mn2+is realized by the efficient energy transfer from Ce3+and Euto Mn.Furthermore,high quality white light is accomplished by properly tuning the relative doping amount of Ce^(3+)(K^(+))/Eu^(2+)/Mn^(2+)based on efficient simultaneous energy transfer.The results indicate that Ba_(2)Ca(BO_(3))_(2):Ce^(3+)(K^(+)),Eu^(2+),Mn^(2+)is a promising white light-emitting phosphor in WLEDs application.展开更多
基金Item Sponsored by Tianjin Natural Science Foundation of China(06YFJ MJC02200,11JCZDJC22600)
文摘Based on test data from the hot forge experiments on Gleeble 1500, a Kumar type constitutive equation for 33Mn2V steel is established. Applying this constitutive equation in commercial FEM software of MSC/SuperForm 2005, the piercing process of 33Mn2V steel in Mannesmann mill is then simulated. The modeling results visualized the dynamic evolution of equivalent stress, especially inside the workpieee. It is shown that the non-uniform distribu- tion of stress on the internal and external surface of the workpiece is a distinct characteristic of processing tube pierc- ing. The numerical model was verified by comparing the values of calculated force parameters of the piercing process with those measured in laboratory eonditions. And it shows that the Kumar-type constitutive relationship meets the practical needs.
基金Ting-ting FENG acknowledges the financial support from Professor Paul V.BRAUN at Department of Materials Science and Engineering,University of Illinois at Urbana-Champaign,the support from Chinese Scholarship Council during her visit to University of Illinois at Urbana-Champaign,partial financial supports from Department of Science and Technology of Sichuan Province,China(2019YFH0002,2019YFG0222 and 2019YFG0526).The research was partly carried out in the Frederick Seitz Materials Research Laboratory Central Research Facilities,University of Illinois at Urbana-Champaign.
文摘The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.
文摘We study the electronic structures of LiMn2O4 by x-ray and ultraviolet photoelectron spectroscopy （XPS, UPS） and resonant photoelectron spectroscopy （RPES）. XPS data suggest that the average oxidation state of Mn ions is 3.55, probably due to the small amount of lithium oxides on the surface. UPS and RPES data imply that Mn ions are in a high spin state, and RPES results show strong Mn3d-O2p hybridization in the LiMn2O4 valence band.
基金Supported by the National Natural Science Foundation of China under Grant Nos,10874087,11074124 and 11174113Jiangsu Provincial Natural Science Foundation under Grant No.200921555.
文摘The optical properties and electronic structure of marokite-type CaMn2O4 are investigated by using UV−vis spectroscopy and the local-spin-density approximation plus the Hubbard-U(LSDA+U)method.Four absorption bands are observed at 638 nm(1.94 eV),512 nm(2.42 eV),377 nm(3.29 eV)and 248 nm(5.00 eV),which are ascribed to the charge transfer transitions O2p↑→Mn3d eg↑,O2p↓→Mn3d eg↑,Mn3d eg↑→Mn3d t2g↓and O2p↑→Mn3d t2g↓,respectively.We further use CaMn2O4 as a photocatalyst to decompose an azo-dye acid orange 7(AO7)under irradiation of visible light and find that the decomposition ratio of AO7 reaches 15.9%under the irradiation of visible light for two hours.
文摘The changes of antioxidant enzyme activities and related genes expression of tomato seedlings were evaluated under hypoxia stress with different levels of Mn2+. Activities of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxide (APX), glutathione reductase (GR), catalase (CAT), the contents of H2O2, ascorbic (AsA) and malondialdehyde (MDA) were studied to investigate how active oxygen damaged the membrane lipid under hypoxia stress. With 10-200 μmol?L-1 Mn2+, the activities of SOD, POD, APX, GR and the contents of H2O2, AsA, MDA of leaves and roots increased significantly, which indicated that low Mn2+ could eliminate the active oxygen and protect the membrane lipid from hurt. But the activities of catalase (CAT) decreased evidently in the root. When the concentration of Mn2+ reached 400-600 μmol?L-1 under hypoxia stress, the activities of SOD, POD, APX, GR and ASA content decreased remarkably. However, the contents of H2O2 and MDA increased contrarily. A series of resistance genes level achieved peak value with 10 μmol?L-1 Mn2+. The expression level of SOD, CAT, APX, POD, GR were 6.28, 2.19, 5.66, 5.21 and 6.79 times compared to control respectively. These results illustrated appropriate amount of Mn2+ could reduce the damage of active oxygen under hypoxia stress, but reversely, high level of Mn2+ just aggravated the already serious damage to the tomato seedlings.
基金Project supported by the National Key Research and Development Plan of China(2019YFE0107200)the Natural Science Foundation of Hubei Province(2020CFB700)+4 种基金the Doctoral Researchof Hubei University of Arts and Science(kyqdf2020023)Innovation Research Team Project of Hubei University of Arts and Science(2020kypytd001)the Project of Hubei University of Arts and Science(XK2021027)the National Natural Science Foundation of China(10804099)Natural Science Foundation of Zhejiang Province(LZ18B050002)。
文摘White light-emitting diodes(WLEDs)fabricated by single-phase full color emitting phosphor are an emerging solution for health lighting.The crystallographic site occupation of activators in a proper host lattice is crucial for sophisticated design of such phosphor.Here,we report a high quality white lightemitting phosphor Ba_(2)Ca(BO_(3))_(2):Ce^(3+)(K^(+)),Eu^(2+),Mn^(2+)with spectral distribution covering whole visible region.Blue light emission originates from Ce3+ions occupying preferentially Ba^(2+)site by controlling synthesis conditions.Green and red lights are obtained from Eu^(2+)occupying Ba2+(and Ca)site and Mn2+occupying Casite,respectively.In this triple-doped phosphor,strong red emission with a low concentration of Mn2+is realized by the efficient energy transfer from Ce3+and Euto Mn.Furthermore,high quality white light is accomplished by properly tuning the relative doping amount of Ce^(3+)(K^(+))/Eu^(2+)/Mn^(2+)based on efficient simultaneous energy transfer.The results indicate that Ba_(2)Ca(BO_(3))_(2):Ce^(3+)(K^(+)),Eu^(2+),Mn^(2+)is a promising white light-emitting phosphor in WLEDs application.
