Mn-Zn ferrites doped with different contents of Sm^（3＋） and Gd^（3＋） ions were prepared by sol-gel auto-combustion method and characterized by Fourier transform infrared spectroscopy（FTIR）, thermogravimetric an...Mn-Zn ferrites doped with different contents of Sm^（3＋） and Gd^（3＋） ions were prepared by sol-gel auto-combustion method and characterized by Fourier transform infrared spectroscopy（FTIR）, thermogravimetric analysis（TG）, X-ray diffraction（XRD）, scanning electron microscopy（SEM） and vibrating sample magnetometer（VSM）. When samples were calcined in a relatively low temperature below 1100 °C, secondary phases（α-Fe_2O_3） could be identified. Therefore, in order to acquire pure and better crystallinity, the suitable calcining temperature of powders was selected at 1200 °C. It was also found that all the samples consisting of ferrite phases of typical spinel cubic structure and average crystallite sizes between 31.5 and 38.2 nm were obtained after calcining at 1200 oC for 4 h. The lattice parameters increased almost linearly with increasing Sm content. A dense microstructure was obtained after sintering at 1250 °C for 4 h. Through the analysis of magnetic properties, hysteresis loops for all the samples were narrow with low values of coercivity and retentivity, indicating the paramagnetic nature of these samples. And saturation magnetization Ms strongly depended on the type of additive to reach a maximum of 47.99 emu/g for x=0.015, which showed a great promise for hyperthermia applications.展开更多
Stabilizing pile is a kind of earth shoring structure frequently used in slope engineering. When the piles have cantilever segments above the ground,laggings are usually installed to avoid collapse of soil between pil...Stabilizing pile is a kind of earth shoring structure frequently used in slope engineering. When the piles have cantilever segments above the ground,laggings are usually installed to avoid collapse of soil between piles. Evaluating the earth pressure acting on laggings is of great importance in design process.Since laggings are usually less stiff than piles,the lateral pressure on lagging is much closer to active earth pressure. In order to estimate the lateral earth pressure on lagging more accurately,first,a model test of cantilever stabilizing pile and lagging systems was carried out. Then,basing the experimental results a three-dimensional sliding wedge model was established. Last,the calculation process of the total active force on lagging is presented based on the kinematic approach of limit analysis. A comparison is made between the total active force on lagging calculated by the formula presented in this study and the force on a same-size rigid retaining wall obtained from Rankine's theory. It is found that the proposed method fits well with the experimental results.Parametric studies show that the total active force on lagging increases with the growth of the lagging height and the lagging clear span; while decreases asthe soil internal friction angle and soil cohesion increase.展开更多
Regarding the rapid compensation of the influence of the Earth＇ s disturbing gravity field upon trajectory calculation,the key point lies in how to derive the analytical solutions to the partial derivatives of the st...Regarding the rapid compensation of the influence of the Earth＇ s disturbing gravity field upon trajectory calculation,the key point lies in how to derive the analytical solutions to the partial derivatives of the state of burnout point with respect to the launch data.In view of this,this paper mainly expounds on two issues：one is based on the approximate analytical solution to the motion equation for the vacuum flight section of a long-range rocket,deriving the analytical solutions to the partial derivatives of the state of burnout point with respect to the changing rate of the finalstage pitch program;the other is based on the initial positioning and orientation error propagation mechanism,proposing the analytical calculation formula for the partial derivatives of the state of burnout point with respect to the launch azimuth.The calculation results of correction data are simulated and verified under different circumstances.The simulation results are as follows：（1） the accuracy of approximation between the analytical solutions and the results attained via the difference method is higher than 90%,and the ratio of calculation time between them is lower than 0.2%,thus demonstrating the accuracy of calculation of data corrections and advantages in calculation speed;（2） after the analytical solutions are compensated,the longitudinal landing deviation of the rocket is less than 20 m and the lateral landing deviation of the rocket is less than 10 m,demonstrating that the corrected data can meet the requirements for the hit accuracy of a long-range rocket.展开更多
A series of CeO2-Co3O4 mixed oxide catalysts with different Co/（Co＋Ce） atomic ratios were synthesized by citric acid sol-gel method and used for catalytic oxidation of formaldehyde（HCHO）. Many techniques such as ...A series of CeO2-Co3O4 mixed oxide catalysts with different Co/（Co＋Ce） atomic ratios were synthesized by citric acid sol-gel method and used for catalytic oxidation of formaldehyde（HCHO）. Many techniques such as Brumauer-Emmett-Teller（BET）, X-ray diffraction（XRD）, scanning electron microscopy（FE-SEM）, temperature programmed reduction（H_2-TPR）, temperature-programmed desorption（O_2-TPD） and X-ray photoelectron spectroscopy（XPS） were used to characterize catalysts. The results of catalytic performance tests showed that the catalyst CeO_2-Co_3O_4 with Co/（Co＋Ce） ratio of 0.95 exhibited the best performance, and the temperature of complete oxidation of HCHO was 80 oC. The analytical results indicated that the addition of CeO_2 enhanced the specific surface area of Co_3O_4 and the fine dispersion of both of them. Moreover, the strong interaction between CeO_2 and Co_3O_4 resulted in the unique redox properties, which enhanced the available surface active oxygen and led to high valence state of cobalt oxide species. All those effects played crucial roles in the excellent performance of CeO_2-Co_3O_4 for the HCHO oxidation.展开更多
To investigate the seismic passive earth thrust with two-dimensional steady seepage, a general pseudo-dynamic solution was established based on the limit equilibrium analysis. This solution was purposefully applied to...To investigate the seismic passive earth thrust with two-dimensional steady seepage, a general pseudo-dynamic solution was established based on the limit equilibrium analysis. This solution was purposefully applied to a waterfront gravity wall, which retains a submerged backfill with a drainage system along the backfill-structure interface. The wall was assumed to move towards the backfill to the passive failure state. And the theoretical derivation considered the pore pressures induced by the seepage, the excess pore pressures generated by the earthquake and the seismic inertial forces. Thereinto, the hydrostatic and hydrodynamic pressures were calculated by the analytical formulas, while the seismic forces were obtained by the pseudo-dynamic method. In the parametric study, the results indicate that the velocity of shear wave has a more prominent impact on the seismic passive earth thrust than that of primary wave. Both the horizontal and vertical seismic actions decrease the passive earth pressure, but the horizontal one affects the amplitude of the earth pressure coefficient more significantly. Moreover, the soil friction and the wall friction distinctly increase the seismic passive earth pressure just like the static situation. The comparison shows that the results are consistent with the previous work, which verifies its validity.展开更多
Ti/SnO2–Sb electrode has a good effect on the removal of organic pollutants. But its short service life limits its large-scale application in industry. Electro-catalytic degradation performances and service life of t...Ti/SnO2–Sb electrode has a good effect on the removal of organic pollutants. But its short service life limits its large-scale application in industry. Electro-catalytic degradation performances and service life of the electrode can be significantly improved by doping rare earth（RE） ions into the oxide coating of Ti/SnO2–Sb electrode. Ti/SnO2–Sb electrodes doped with different RE elements（Ce, Dy, La, and Eu） were prepared by the thermal decomposition method at 550 ℃. Electro-catalytic degradation performances of electrodes doped with different RE elements were evaluated by linear sweep voltammetry（LSV） and Tafel curves. During the electrolysis,the conversion of p-nitrophenol was performed with these electrodes as anodes under galvanostatic control. The structures and morphologies of the surface coating of the electrodes were characterized by scanning electron microscope（SEM）. The results demonstrate that the electro-catalytic degradation performances of Ti/SnO2–Sb electrodes are improved to different levels by doping different RE ions. Improved Ti/SnO2–Sb electrodes by the introduction of different RE have higher oxygen evolution potential, better electro-catalysis ability, better coverage,and longer electrode life.展开更多
CaMoO_4：Pr^（3＋）/Yb^（3＋） powder was successfully synthesized by a facile hydrothermal method. X-ray diffraction（XRD） patterns of samples confirmed tetragonal structure and morphology and sizes were confirmed b...CaMoO_4：Pr^（3＋）/Yb^（3＋） powder was successfully synthesized by a facile hydrothermal method. X-ray diffraction（XRD） patterns of samples confirmed tetragonal structure and morphology and sizes were confirmed by scanning electron microscopy（SEM） analyses. Particles consisted of regular micro-spheres with uniform sizes, the diameter of each sphere lay in the range of 3 to 4 μm. The up-conversion photoluminescence emission and its concentration dependence were investigated under infrared excitation at 980 nm. All the UC micro-particles exhibited the typical blue, green and red emissions. Dominant blue emissions originated from ~3P_0→~3H_4 and intense red emissions originated from ~3P0→~3F_2 transitions, and they both belonged to two-photon excitation processes in CaMoO_4： Yb^（3＋）/Pr^（3＋） powder. The optimum doping concentrations of Pr^（3＋） and Yb^（3＋） for the highest UC luminescence were 0.1 mol.% and 16 mol.%, respectively. The possible up-conversion mechanisms were discussed in detail. It was found that the UC emission could be well controlled from blue to green to white color by adjusting the concentration of Pr^（3＋） ions in CaMoO_4：Pr^（3＋）/Yb^（3＋） microcrystal. So it is a candidate material for solid-state lasers, biological imaging, solar cells, and optical communications.展开更多
γ-LiAlO2：Eu3＋（Eu3＋：LAO） phosphor was obtained by gel combustion method using LiNO3,Al（NO3）3·9H2O,Eu（NO3）3·6H2O and citric acid as raw materials.The structure,morphology and luminescence were chara...γ-LiAlO2：Eu3＋（Eu3＋：LAO） phosphor was obtained by gel combustion method using LiNO3,Al（NO3）3·9H2O,Eu（NO3）3·6H2O and citric acid as raw materials.The structure,morphology and luminescence were characterized by means of X-ray diffraction （XRD）,scanning electron microscopy （SEM）,photoluminescence （PL）.The results demonstrated that the phosphor was pure-phase of flaky tetragonal crystal system with a mean size of around 1 μm.The strongest excitation peak was at 254 nm,belonging to the broadband excitation and the maximum emission peak was at 613 nm,corresponding to the 5D0→7F2 transition of Eu3＋.Luminous intensity is closely related to the calcination temperature and doping concentration of Eu3＋.展开更多
The Extreme Ultraviolet Camera （EUVC） onboard the Chang＇e-3 （CE-3） lander is used to observe the structure and dynamics of Earth＇s plasmasphere from the Moon. By detecting the resonance line emission of helium i...The Extreme Ultraviolet Camera （EUVC） onboard the Chang＇e-3 （CE-3） lander is used to observe the structure and dynamics of Earth＇s plasmasphere from the Moon. By detecting the resonance line emission of helium ions （He＋） at 30.4 nm, the EUVC images the entire plasmasphere with a time resolution of 10 min and a spatial resolution of about 0.1 Earth radius （RE） in a single frame. We first present details about the data processing from EUVC and the data acquisition in the commissioning phase, and then report some initial results, which reflect the basic features of the plas- masphere well. The photon count and emission intensity of EUVC are consistent with previous observations and models, which indicate that the EUVC works normally and can provide high quality data for future studies.展开更多
In this study, ultrafine Ce0.8La0.2–x Y x O1.9（for x=0, 0.05, 0.10, 0.15, 0.20） powders were successfully prepared by the sol-gel method.The samples were characterized by fourier transform infrared（FTIR）, thermog...In this study, ultrafine Ce0.8La0.2–x Y x O1.9（for x=0, 0.05, 0.10, 0.15, 0.20） powders were successfully prepared by the sol-gel method.The samples were characterized by fourier transform infrared（FTIR）, thermogravimetric and differential scanning calorimetry（TG-DSC）, X-ray diffraction（XRD）, scanning electron microscopy（SEM）, AC impedance and thermal expansion measurements.Experimental results indicated that highly phase-pure cubic fluorite electrolyte Ce0.8La0.2–x Y x O1.9 powders were obtained after calcining at 600 °C.The as-synthesized powders exhibited high sintering activity, the Ce0.8La0.2–x Y x O1.9 series electrolytes which have higher relative densities over 96% could be obtained after sintered at 1400 °C for 4 h.Ce0.8La0.15Y0.05O1.9 electrolyte sintered at 1400 °C for 4 h exhibited higher oxide ionic conductivity（σ800 oC=0.057 S/cm）, lower electrical activation energy（E a=0.87 e V） and moderate thermal expansion coefficient（TEC=15.5×10-6 K-1, temperature range 25–800 °C）.展开更多
The TMT Detailed Science Case describes the transformational science that the Thirty Meter Telescope will enable. Planned to begin science operations in 2024, TMT will open up opportunities for revolutionary discoveri...The TMT Detailed Science Case describes the transformational science that the Thirty Meter Telescope will enable. Planned to begin science operations in 2024, TMT will open up opportunities for revolutionary discoveries in essen- tially every field of astronomy, astrophysics and cosmology, seeing much fainter objects much more clearly than existing telescopes. Per this capability, TMT＇s sci- ence agenda fills all of space and time, from nearby comets and asteroids, to exo- planets, to the most distant galaxies, and all the way back to the very first sources of light in the universe. More than 150 astronomers from within the TMT partner- ship and beyond offered input in compiling the new 2015 Detailed Science Case. The contributing astronomers represent the entire TMT partnership, including the California Institute of Technology （Caltech）, the Indian Institute of Astrophysics （HA）, the National Astronomical Observatories of the Chinese Academy of Sciences （NAOC）, the National Astronomical Observatory of Japan （NAOJ）, the University of California, the Association of Canadian Universities for Research in Astronomy （ACURA） and US associate partner, the Association of Universities for Research in Astronomy （AURA）.展开更多
In this paper we reported the preparation and extensive characterization of La9.83–x Sr x Si6O26＋δ（0≤x≤0.50） precursors, intermediate and final products. The sintering reactions, the phase formation, the struct...In this paper we reported the preparation and extensive characterization of La9.83–x Sr x Si6O26＋δ（0≤x≤0.50） precursors, intermediate and final products. The sintering reactions, the phase formation, the structure as well as the powders＇ morphology were studied by means of thermogravimetric analysis, X-ray diffraction（XRD）, Fourier-transform infrared spectroscopy（FTIR） and scanning electron microscopy（SEM）. Moreover, the effect of stoichiometry on precursor＇s structure and morphology as well as on intermediate and final products was reported. As was concluded pure La9.83Si6O26＋δ, La9.38Sr0.45Si6O26＋δ and La9.33Sr0.50Si6O26＋δ could be prepared after sintering at 1400 °C for 20 h while La9.68Sr0.15Si6O26＋δ and La9.53Sr0.30Si6O26＋δ compounds contained minor traces（〈3.5%） of La2Si2O7 secondary phase. Concerning the synthesis, there have been no previous reports on the preparation of pure La9.83Si6O26＋δ, La9.38Sr0.45Si6O26＋δ and La9.33Sr0.50Si6O26＋δ compounds. The final powders consisted of spherical particles and an increase of Sr content seemed to inhibit sintering phenomena. The existence of interstitial oxygen at intermediate crystallographic positions of apatite structure had great effect on Si O4 sub-structure distortion. The increase of Sr content led to a major reduction of interstitial oxygen quantity and the refutation of silicon tetrahedron distortion.展开更多
The factor of safety of mechanically stabilized earth(MSE) structures can be analyzed either using limit equilibrium method(LEM) or strength reduction method(SRM) in finite element/difference method. In LEM, the stren...The factor of safety of mechanically stabilized earth(MSE) structures can be analyzed either using limit equilibrium method(LEM) or strength reduction method(SRM) in finite element/difference method. In LEM, the strengths of the reinforcement members and soils are reduced with the same factor. While using the SRM, only soil strength is reduced during the calculation of the factor of safety. This causes inconsistence in calculating the factor of safety of the MSE structures. To overcome this, an iteration method is proposed to consider the strength reduction of the reinforcements in SRM. The method is demonstrated by using PLAXIS, a finite element software. The results show that the factor of safety converges after a few iterations. The reduction of strength has different effects on the factor of safety depending on the properties of the reinforcements and the soil, and failure modes.展开更多
基金Project supported by the National Natural Science Foundation of China(51102073)the Natural Science Foundation of Education Department of Anhui Province of China(KJ2015A232,KJ2015B1105906)+3 种基金the Natural Science Foundation of Anhui Province of China(1308085QB35)the research fund of State Key Laboratory of Structural Chemistry(20110012)Anhui Province Outstanding Young Teachers Visit Abroad Training Projects(gxfxZD2016220)the Outstanding Young Talent Project in Colleges and Universities of Anhui Province
文摘Mn-Zn ferrites doped with different contents of Sm^（3＋） and Gd^（3＋） ions were prepared by sol-gel auto-combustion method and characterized by Fourier transform infrared spectroscopy（FTIR）, thermogravimetric analysis（TG）, X-ray diffraction（XRD）, scanning electron microscopy（SEM） and vibrating sample magnetometer（VSM）. When samples were calcined in a relatively low temperature below 1100 °C, secondary phases（α-Fe_2O_3） could be identified. Therefore, in order to acquire pure and better crystallinity, the suitable calcining temperature of powders was selected at 1200 °C. It was also found that all the samples consisting of ferrite phases of typical spinel cubic structure and average crystallite sizes between 31.5 and 38.2 nm were obtained after calcining at 1200 oC for 4 h. The lattice parameters increased almost linearly with increasing Sm content. A dense microstructure was obtained after sintering at 1250 °C for 4 h. Through the analysis of magnetic properties, hysteresis loops for all the samples were narrow with low values of coercivity and retentivity, indicating the paramagnetic nature of these samples. And saturation magnetization Ms strongly depended on the type of additive to reach a maximum of 47.99 emu/g for x=0.015, which showed a great promise for hyperthermia applications.
基金financially supported by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China under Grant No. 2012BAJ22B06
文摘Stabilizing pile is a kind of earth shoring structure frequently used in slope engineering. When the piles have cantilever segments above the ground,laggings are usually installed to avoid collapse of soil between piles. Evaluating the earth pressure acting on laggings is of great importance in design process.Since laggings are usually less stiff than piles,the lateral pressure on lagging is much closer to active earth pressure. In order to estimate the lateral earth pressure on lagging more accurately,first,a model test of cantilever stabilizing pile and lagging systems was carried out. Then,basing the experimental results a three-dimensional sliding wedge model was established. Last,the calculation process of the total active force on lagging is presented based on the kinematic approach of limit analysis. A comparison is made between the total active force on lagging calculated by the formula presented in this study and the force on a same-size rigid retaining wall obtained from Rankine's theory. It is found that the proposed method fits well with the experimental results.Parametric studies show that the total active force on lagging increases with the growth of the lagging height and the lagging clear span; while decreases asthe soil internal friction angle and soil cohesion increase.
文摘Regarding the rapid compensation of the influence of the Earth＇ s disturbing gravity field upon trajectory calculation,the key point lies in how to derive the analytical solutions to the partial derivatives of the state of burnout point with respect to the launch data.In view of this,this paper mainly expounds on two issues：one is based on the approximate analytical solution to the motion equation for the vacuum flight section of a long-range rocket,deriving the analytical solutions to the partial derivatives of the state of burnout point with respect to the changing rate of the finalstage pitch program;the other is based on the initial positioning and orientation error propagation mechanism,proposing the analytical calculation formula for the partial derivatives of the state of burnout point with respect to the launch azimuth.The calculation results of correction data are simulated and verified under different circumstances.The simulation results are as follows：（1） the accuracy of approximation between the analytical solutions and the results attained via the difference method is higher than 90%,and the ratio of calculation time between them is lower than 0.2%,thus demonstrating the accuracy of calculation of data corrections and advantages in calculation speed;（2） after the analytical solutions are compensated,the longitudinal landing deviation of the rocket is less than 20 m and the lateral landing deviation of the rocket is less than 10 m,demonstrating that the corrected data can meet the requirements for the hit accuracy of a long-range rocket.
基金supported by the Doctoral Program of Xi'an Shiyou University(134010155)Shaanxi Provincial College Students'Inno vative Entrepreneurial Training Program(No.2016107051360 and 201610705046)
文摘A series of CeO2-Co3O4 mixed oxide catalysts with different Co/（Co＋Ce） atomic ratios were synthesized by citric acid sol-gel method and used for catalytic oxidation of formaldehyde（HCHO）. Many techniques such as Brumauer-Emmett-Teller（BET）, X-ray diffraction（XRD）, scanning electron microscopy（FE-SEM）, temperature programmed reduction（H_2-TPR）, temperature-programmed desorption（O_2-TPD） and X-ray photoelectron spectroscopy（XPS） were used to characterize catalysts. The results of catalytic performance tests showed that the catalyst CeO_2-Co_3O_4 with Co/（Co＋Ce） ratio of 0.95 exhibited the best performance, and the temperature of complete oxidation of HCHO was 80 oC. The analytical results indicated that the addition of CeO_2 enhanced the specific surface area of Co_3O_4 and the fine dispersion of both of them. Moreover, the strong interaction between CeO_2 and Co_3O_4 resulted in the unique redox properties, which enhanced the available surface active oxygen and led to high valence state of cobalt oxide species. All those effects played crucial roles in the excellent performance of CeO_2-Co_3O_4 for the HCHO oxidation.
基金Projects(U1234204,51378463) supported by the National Natural Science Foundation of China
文摘To investigate the seismic passive earth thrust with two-dimensional steady seepage, a general pseudo-dynamic solution was established based on the limit equilibrium analysis. This solution was purposefully applied to a waterfront gravity wall, which retains a submerged backfill with a drainage system along the backfill-structure interface. The wall was assumed to move towards the backfill to the passive failure state. And the theoretical derivation considered the pore pressures induced by the seepage, the excess pore pressures generated by the earthquake and the seismic inertial forces. Thereinto, the hydrostatic and hydrodynamic pressures were calculated by the analytical formulas, while the seismic forces were obtained by the pseudo-dynamic method. In the parametric study, the results indicate that the velocity of shear wave has a more prominent impact on the seismic passive earth thrust than that of primary wave. Both the horizontal and vertical seismic actions decrease the passive earth pressure, but the horizontal one affects the amplitude of the earth pressure coefficient more significantly. Moreover, the soil friction and the wall friction distinctly increase the seismic passive earth pressure just like the static situation. The comparison shows that the results are consistent with the previous work, which verifies its validity.
基金financially supported by the National Natural Science Foundation of China (No. 51364024 and 51404124)Gansu Province Department of Education Fund (No. 2013A-029)the Foundation of State Key Laboratory of Gansu Advanced Nonferrous Metal Materials (Nos. SKL 1316 and SKL 1314)
文摘Ti/SnO2–Sb electrode has a good effect on the removal of organic pollutants. But its short service life limits its large-scale application in industry. Electro-catalytic degradation performances and service life of the electrode can be significantly improved by doping rare earth（RE） ions into the oxide coating of Ti/SnO2–Sb electrode. Ti/SnO2–Sb electrodes doped with different RE elements（Ce, Dy, La, and Eu） were prepared by the thermal decomposition method at 550 ℃. Electro-catalytic degradation performances of electrodes doped with different RE elements were evaluated by linear sweep voltammetry（LSV） and Tafel curves. During the electrolysis,the conversion of p-nitrophenol was performed with these electrodes as anodes under galvanostatic control. The structures and morphologies of the surface coating of the electrodes were characterized by scanning electron microscope（SEM）. The results demonstrate that the electro-catalytic degradation performances of Ti/SnO2–Sb electrodes are improved to different levels by doping different RE ions. Improved Ti/SnO2–Sb electrodes by the introduction of different RE have higher oxygen evolution potential, better electro-catalysis ability, better coverage,and longer electrode life.
基金Project supported by the National Science Foundation of China(11574190)the Fundamental Research Funds for the Central Universities(GK201503024)
文摘CaMoO_4：Pr^（3＋）/Yb^（3＋） powder was successfully synthesized by a facile hydrothermal method. X-ray diffraction（XRD） patterns of samples confirmed tetragonal structure and morphology and sizes were confirmed by scanning electron microscopy（SEM） analyses. Particles consisted of regular micro-spheres with uniform sizes, the diameter of each sphere lay in the range of 3 to 4 μm. The up-conversion photoluminescence emission and its concentration dependence were investigated under infrared excitation at 980 nm. All the UC micro-particles exhibited the typical blue, green and red emissions. Dominant blue emissions originated from ~3P_0→~3H_4 and intense red emissions originated from ~3P0→~3F_2 transitions, and they both belonged to two-photon excitation processes in CaMoO_4： Yb^（3＋）/Pr^（3＋） powder. The optimum doping concentrations of Pr^（3＋） and Yb^（3＋） for the highest UC luminescence were 0.1 mol.% and 16 mol.%, respectively. The possible up-conversion mechanisms were discussed in detail. It was found that the UC emission could be well controlled from blue to green to white color by adjusting the concentration of Pr^（3＋） ions in CaMoO_4：Pr^（3＋）/Yb^（3＋） microcrystal. So it is a candidate material for solid-state lasers, biological imaging, solar cells, and optical communications.
基金Funded by Southwest University of Technology (No.08zx0103)
文摘γ-LiAlO2：Eu3＋（Eu3＋：LAO） phosphor was obtained by gel combustion method using LiNO3,Al（NO3）3·9H2O,Eu（NO3）3·6H2O and citric acid as raw materials.The structure,morphology and luminescence were characterized by means of X-ray diffraction （XRD）,scanning electron microscopy （SEM）,photoluminescence （PL）.The results demonstrated that the phosphor was pure-phase of flaky tetragonal crystal system with a mean size of around 1 μm.The strongest excitation peak was at 254 nm,belonging to the broadband excitation and the maximum emission peak was at 613 nm,corresponding to the 5D0→7F2 transition of Eu3＋.Luminous intensity is closely related to the calcination temperature and doping concentration of Eu3＋.
文摘The Extreme Ultraviolet Camera （EUVC） onboard the Chang＇e-3 （CE-3） lander is used to observe the structure and dynamics of Earth＇s plasmasphere from the Moon. By detecting the resonance line emission of helium ions （He＋） at 30.4 nm, the EUVC images the entire plasmasphere with a time resolution of 10 min and a spatial resolution of about 0.1 Earth radius （RE） in a single frame. We first present details about the data processing from EUVC and the data acquisition in the commissioning phase, and then report some initial results, which reflect the basic features of the plas- masphere well. The photon count and emission intensity of EUVC are consistent with previous observations and models, which indicate that the EUVC works normally and can provide high quality data for future studies.
基金Project supported by National Natural Science Foundation of China(51102073)the research fund of Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province(AE201361)+1 种基金Natural Science Foundation of Anhui Province of China(10040606Q53,1308085QB35)the Outstanding Young Talent Project in Colleges and Universities of Anhui Province
文摘In this study, ultrafine Ce0.8La0.2–x Y x O1.9（for x=0, 0.05, 0.10, 0.15, 0.20） powders were successfully prepared by the sol-gel method.The samples were characterized by fourier transform infrared（FTIR）, thermogravimetric and differential scanning calorimetry（TG-DSC）, X-ray diffraction（XRD）, scanning electron microscopy（SEM）, AC impedance and thermal expansion measurements.Experimental results indicated that highly phase-pure cubic fluorite electrolyte Ce0.8La0.2–x Y x O1.9 powders were obtained after calcining at 600 °C.The as-synthesized powders exhibited high sintering activity, the Ce0.8La0.2–x Y x O1.9 series electrolytes which have higher relative densities over 96% could be obtained after sintered at 1400 °C for 4 h.Ce0.8La0.15Y0.05O1.9 electrolyte sintered at 1400 °C for 4 h exhibited higher oxide ionic conductivity（σ800 oC=0.057 S/cm）, lower electrical activation energy（E a=0.87 e V） and moderate thermal expansion coefficient（TEC=15.5×10-6 K-1, temperature range 25–800 °C）.
文摘The TMT Detailed Science Case describes the transformational science that the Thirty Meter Telescope will enable. Planned to begin science operations in 2024, TMT will open up opportunities for revolutionary discoveries in essen- tially every field of astronomy, astrophysics and cosmology, seeing much fainter objects much more clearly than existing telescopes. Per this capability, TMT＇s sci- ence agenda fills all of space and time, from nearby comets and asteroids, to exo- planets, to the most distant galaxies, and all the way back to the very first sources of light in the universe. More than 150 astronomers from within the TMT partner- ship and beyond offered input in compiling the new 2015 Detailed Science Case. The contributing astronomers represent the entire TMT partnership, including the California Institute of Technology （Caltech）, the Indian Institute of Astrophysics （HA）, the National Astronomical Observatories of the Chinese Academy of Sciences （NAOC）, the National Astronomical Observatory of Japan （NAOJ）, the University of California, the Association of Canadian Universities for Research in Astronomy （ACURA） and US associate partner, the Association of Universities for Research in Astronomy （AURA）.
基金funded by the Research Committee of National Technical University of Athens
文摘In this paper we reported the preparation and extensive characterization of La9.83–x Sr x Si6O26＋δ（0≤x≤0.50） precursors, intermediate and final products. The sintering reactions, the phase formation, the structure as well as the powders＇ morphology were studied by means of thermogravimetric analysis, X-ray diffraction（XRD）, Fourier-transform infrared spectroscopy（FTIR） and scanning electron microscopy（SEM）. Moreover, the effect of stoichiometry on precursor＇s structure and morphology as well as on intermediate and final products was reported. As was concluded pure La9.83Si6O26＋δ, La9.38Sr0.45Si6O26＋δ and La9.33Sr0.50Si6O26＋δ could be prepared after sintering at 1400 °C for 20 h while La9.68Sr0.15Si6O26＋δ and La9.53Sr0.30Si6O26＋δ compounds contained minor traces（〈3.5%） of La2Si2O7 secondary phase. Concerning the synthesis, there have been no previous reports on the preparation of pure La9.83Si6O26＋δ, La9.38Sr0.45Si6O26＋δ and La9.33Sr0.50Si6O26＋δ compounds. The final powders consisted of spherical particles and an increase of Sr content seemed to inhibit sintering phenomena. The existence of interstitial oxygen at intermediate crystallographic positions of apatite structure had great effect on Si O4 sub-structure distortion. The increase of Sr content led to a major reduction of interstitial oxygen quantity and the refutation of silicon tetrahedron distortion.
基金Project(41072200)supported by the National Natural Science Foundation of ChinaProject(14PJD032)supported by the Shanghai Pujiang Program,China
文摘The factor of safety of mechanically stabilized earth(MSE) structures can be analyzed either using limit equilibrium method(LEM) or strength reduction method(SRM) in finite element/difference method. In LEM, the strengths of the reinforcement members and soils are reduced with the same factor. While using the SRM, only soil strength is reduced during the calculation of the factor of safety. This causes inconsistence in calculating the factor of safety of the MSE structures. To overcome this, an iteration method is proposed to consider the strength reduction of the reinforcements in SRM. The method is demonstrated by using PLAXIS, a finite element software. The results show that the factor of safety converges after a few iterations. The reduction of strength has different effects on the factor of safety depending on the properties of the reinforcements and the soil, and failure modes.
