We report the observation for the pz electron band and the band inversion in Fe1+yTexSe1-xwith angleresolved photoemission spectroscopy. Furthermore, we found that excess Fe(y>0) inhibits the topological band inver...We report the observation for the pz electron band and the band inversion in Fe1+yTexSe1-xwith angleresolved photoemission spectroscopy. Furthermore, we found that excess Fe(y>0) inhibits the topological band inversion in Fe1+yTexSe1-x,which explains the absence of Majorana zero modes in previous reports for Fe1+yTexSe1-xwith excess Fe. Based on our analysis of different amounts of Te doping and excess Fe, we propose a delicate topological phase in this material. Thanks to this delicate phase, one may be able to tune the topological transition via applying lattice strain or carrier doping.展开更多
By using angle-resolvea photoemission spectroscopy(ARPES) combined with the first-principies electronic structure calculations,we report the quantized states at the surface of a single crystal 2 H-TaSe_(2).We have obs...By using angle-resolvea photoemission spectroscopy(ARPES) combined with the first-principies electronic structure calculations,we report the quantized states at the surface of a single crystal 2 H-TaSe_(2).We have observed sub-bands of quantized states at the three-dimensional Brillouin zone center due to a highly dispersive band with light effective mass along k_(z) direction.The quantized sub-bands shift upward towards E_(F) while the bulk band at Γ shifts downward with the decrease of temperature across charge density wave(CDW) formation.The band shifts could be intimately related to the CDW.While neither the two-dimensional Fermi-surface nesting nor purely strong electron-phonon coupling can explain the mechanism of CDW in 2 H-TaSe_(2),our experiment may ignite the interest in understanding the CDW mechanism in this family.展开更多
In this paper, an analytical and numerical study of strain fields, stress fields and displacements in a rotating hollow cylinder, whose walls were completely made in Functionally Graded Materials (FGM), was conducted....In this paper, an analytical and numerical study of strain fields, stress fields and displacements in a rotating hollow cylinder, whose walls were completely made in Functionally Graded Materials (FGM), was conducted. We have considered the rotating hollow cylinder submitted to an asymmetric radial loading. It is assumed that, because of the functional graduation of the material, the mechanical properties such as Young elastic modulus and the density varies in the radial direction, in accordance with a the power law function. The inhomogeneity parameter was selected between -1 and 1. On the basis of the second law of Newton, Hooke’s law and the strain-stress relationship, we established the differential equation which governs the equilibrium for a rotating hollow cylinder. We found the analytical solution and compared to the numerical solution obtained by using the shooting method and the fourth order Runge-Kutta algorithm. The analytical and numerical results lead to the conclusion that the magnitude of the tangential stresses is greater than that of the radial stresses. The changes due to the graduation of FGM does not produce consistent variations in the distribution of radial stresses, but strongly affects the distribution of tangential stresses. The tangential stresses, tangential strains and displacements are much higher at the inner surface of the cylinder wall. The internal radial pressure intensely affects the radial stresses and the radial strain.展开更多
Naphthenic acids,NAs,are a major contaminant of concern and a focus of much research around remediation of oil sand process affected waters,OSPW.Using activated carbon adsorbents are an attractive option given their l...Naphthenic acids,NAs,are a major contaminant of concern and a focus of much research around remediation of oil sand process affected waters,OSPW.Using activated carbon adsorbents are an attractive option given their low cost of fabrication and implementation.A deeper evaluation of the effect NA structural differences have on uptake affinity is warranted.Here we provide an in-depth exploration of NA adsorption including many more model NA species than have been assessed previously with evaluation of adsorption kinetics and isotherms at the relevant alkaline pH of OSPW using several different carbon adsorbents with pH buffering to simulate the behaviour of real OSPW.Uptake for the NA varied considerably regardless of the activated carbon used,ranging from 350 mg/g to near zero highlighting recalcitrant NAs.The equilibrium data was explored to identify structural features of these species and key physiochemical properties that influence adsorption.We found that certainNAwill be resistant to adsorptionwhen hydrophobic adsorbents are used.Adsorption isotherm modelling helped explore interactions occurring at the interface between NA and adsorbent surfaces.We identified the importance of NA hydrophobicity for activated carbon uptake.Evidence is also presented that indicates favorable hydrogen bonding between certain NA and surface site hydroxyl groups,demonstrating the importance of adsorbent surface functionality for NA uptake.This research highlights the challenges associated with removing NAs from OSPW through adsorption and also identifies howadsorbent surface chemistry modification can be used to increase the removal efficiency of recalcitrant NA species.展开更多
CRISPR-based tran-scription regulators(CRISPR-TRs)have revolutionized the field of synthetic biol-ogy by enabling tar-geted activation or repression of any de-sired gene.However,the majority of exist-ing inducible CRI...CRISPR-based tran-scription regulators(CRISPR-TRs)have revolutionized the field of synthetic biol-ogy by enabling tar-geted activation or repression of any de-sired gene.However,the majority of exist-ing inducible CRISPR-TRs are limited by their dependence on specific sequences,which restricts their flex-ibility and controllability in genetic engineering applications.In this study,we proposed a novel strategy to construct sequence-independent inducible CRISPR-TRs,which is achieved by the design of stem loop 2 in the single guide RNA(sgRNA).Under this strategy,by utiliz-ing toehold-mediated strand displacement(TMSD)reactions between small endogenous molecules(miR-20a and TK1 mRNA)and bridge RNA(bRNA)to link bRNA with sgRNA,we achieved synergistic transcriptional activation of VP64 and p65-HSF1 in response to en-dogenous molecules.To enable response to exogenous molecules,we added response se-quences and bRNA sequences to the 5'end of sgRNA to block sgRNA activity,and achieved activation of sgRNA by shearing the response sequence,called sequential unlimited interlock-ing(SUI).Compared with conventional sequence-restricted interlocking(spacer-blocking hairpin(SBH)),the transcriptional activation ratio between response and non-response to the Cas6A protein using our approach was increased by 2.28-fold.Our work presents a modular and versatile framework for endogenous and exogenous molecule-responsive CRISPR-TRs in mammalian cells,without limitations imposed by sequence dependence.展开更多
Cleanliness control of advanced steels is of vital importance for quality control of the products.In order to understand and control the inclusion removal during refining process in molten steel,its motion behaviors a...Cleanliness control of advanced steels is of vital importance for quality control of the products.In order to understand and control the inclusion removal during refining process in molten steel,its motion behaviors at the multiple steel/gas/slag interfaces have attracted the attention much of metallurgical community.The recent development of the agglomeration of non-metallic inclusions at the steel/Ar and steel/slag interfaces has been summarized,and both the experimental as well as theoretical works have been surveyed.In terms of in situ observation of high-temperature interfacial phenomena in the molten steel,researchers utilized high-temperature confocal laser scanning microscopy to observe the movement of more types of inclusions at the interface,i.e.,the investigated inclusion is no longer limited to Al_(2)O_(3)-based inclusions but moves forward to rare earth oxides,MgO-based oxides,etc.In terms of theoretical models,especially the model of inclusions at the steel/slag interface,the recent development has overcome the limitations of the assumptions of Kralchevsky-Paunov model and verified the possible errors caused by the model assumptions by combining the water model and the physical model.Last but not least,the future work in this topic has been suggested,which could be in combination of thermal physical properties of steels and slag,as well as utilize the artificial intelligence-based methodology to implement a comprehensive inclusion motion behaviors during a comprehensive metallurgical process.展开更多
Temperature programmed reduction (TPR) study was carried out for CeO 2/Al 2O 3 and CeO 2/ZrO 2 catalysts to evaluate oxygen storage property induced by a facile redox cycling of Ce ion. The CeO 2/ZrO 2 catalyst...Temperature programmed reduction (TPR) study was carried out for CeO 2/Al 2O 3 and CeO 2/ZrO 2 catalysts to evaluate oxygen storage property induced by a facile redox cycling of Ce ion. The CeO 2/ZrO 2 catalyst possesses excellent oxygen storage activity at 373 K after reduction above 1173 K although the oxygen storage of CeO 2/Al 2O 3 catalyst after reduction above 1173 K is poor because of the formation of CeAlO 3. Consequently, the oxygen storage on the CeO 2/ZrO 2 catalyst smoothly occurs from low temperatures when the catalyst is reduced even at high temperatures.展开更多
N-doped ZnO films were radio frequency(RF)sputtered on glass substrates and studied as a function of oxygen partial pressure(OPP)ranging from 3.0×10-4 to 9.5×10-3 Pa.X-ray diffraction patters confirmed the p...N-doped ZnO films were radio frequency(RF)sputtered on glass substrates and studied as a function of oxygen partial pressure(OPP)ranging from 3.0×10-4 to 9.5×10-3 Pa.X-ray diffraction patters confirmed the polycrystalline nature of the deposited films.The crystalline structure is influenced by the variation of OPP.Atomic force microscopy analysis confirmed the agglomeration of the neighboring spherical grains with a sharp increase of root mean square(RMS)roughness when the OPP is increased above 1.4×10-3 Pa.X-ray photoelectron spectroscopy analysis revealed that the incorporation of N content into the film is decreased with the increase of OPP,noticeably N 1s XPS peaks are hardly identified at 9.5×10-3 Pa.The average visible transmittance(380-700 nm) is increased with the increase of OPP(from～17%to 70%),and the optical absorption edge shifts towards the shorter wavelength.The films deposited with low OPP(≤3.0×10-4 Pa)show n-type conductivity and those deposited with high OPP(≥9.0×10-4 Pa)are highly resistive(>105Ω·cm)展开更多
In this paper numerical analysis of underground structures, taking account the transverse isotropy system of rocks, was done using CAST 3M code by varying the shape of excavation and the coefficient of earth pressure ...In this paper numerical analysis of underground structures, taking account the transverse isotropy system of rocks, was done using CAST 3M code by varying the shape of excavation and the coefficient of earth pressure k. Numerical results reveal that the anisotropy behavior, the shape of hole and the coefficient of earth pressure k have significant influence to the mining induced stress field and rock deformations which directly control the stability of underground excavation design. The magnitude of horizontal stress obtained for the horse shoe shape excavation(25.2 MPa for k = 1; 52.7 MPa for k = 2)is lower than the magnitude obtained for circular hole(26.4 MPa for k = 1; 59.5 MPa for k = 2).Therefore, we have concluded that the horse shoe shape offers the best stability and the best design for engineer. The anisotropy system presented by rock mass can also influence the redistribution of stresses around hole opened. Numerical results have revealed that the magnitude of redistribution of horizontal stresses obtained for transverse isotropic rock(12.1 MPa for k = 0.5; 25.2 MPa for k = 1 and52.7 MPa for k = 2) is less than those obtained in the case of isotropic rock(27.6 MPa for k = 1;48.6 MPa for k = 2 and 90.81 MPa for k = 2). The more the rock has the anisotropic behavior, the more the mass of rock around the tunnel is stable.展开更多
The density, cell size and structure of closed-cell aluminum foam were measured by optical microscopy and image analysis. The properties and the mechanism of compressive deformation that occur in closed-cell aluminum ...The density, cell size and structure of closed-cell aluminum foam were measured by optical microscopy and image analysis. The properties and the mechanism of compressive deformation that occur in closed-cell aluminum foam were measured and discussed. The results show that the cell size of foam with density of 0.37 mg/m^3 is distributed in the range of 0.5 4.0 mm. The cell size of foam with density of 0.33 mg/m^3 is distributed in the range of 0.55.0 mm. The cell wall thickness of both types is 0.10.3 mm. The closed-cell aluminum foam almost belongs to isotropic one, with a variation of ±15% in elastic modulus and yield strength in longitudinal and transverse direction. Under compressive loading, foam materials show inhomogeneous macroscopic deformation. The site of the onset of local plastic deformation depends on the cell structure. The shape of cell is more important than size in determining the yielding susceptibility of the cells. At early stage of deformation,the deformation is localized in narrow bands having width of one cells diameter, and outside the bands the cell still remains the original shape. The cells within bands experience large permanent deformation. The band normals are usually within 20° of the loading axis.展开更多
Hybrid density functional theory was used to investigate the structural,electronic,magnetic and elastic properties of the Laves phase binary intermetallics RFe_(2)(R=La,Ce,Pr and Nd) in C_(15) crystal structure.The ca...Hybrid density functional theory was used to investigate the structural,electronic,magnetic and elastic properties of the Laves phase binary intermetallics RFe_(2)(R=La,Ce,Pr and Nd) in C_(15) crystal structure.The calculated lattice constants of these materials are found in good agreement with the experiments.The band structures and density of states distribution confirm the metallic nature of all these intermetallics.The optimized energies in different magnetic phases and magnetic susceptibilities by postDFT treatments confirm that all the understudy compounds are ferromagnetic in nature.Elastic parameters were calculated from the cubic elastic coefficients C_(11),C_(12) and C_(44).The elastic properties reveal that these intermetallics are incompressible,ductile,elastically anisotropic and mechanically stable.Based on the metallic nature and ferromagnetic properties,it is expected that these intermetallics are suitable materials for spintronic technology.展开更多
TiO2-hydroxyapatite （HA） nanostructured coatings were produced by atmospheric plasma spray method. The effects of starting powder composition and grain size on their mechanical properties were investigated. The micr...TiO2-hydroxyapatite （HA） nanostructured coatings were produced by atmospheric plasma spray method. The effects of starting powder composition and grain size on their mechanical properties were investigated. The microstructure and morphology were characterized by X-ray diffraction and scanning electron microscopy （SEM）. It is found that the coating with 10% HA has the best mechanical properties. Based on Rietveld refinement method, the mean grain size of the as-received powder （212 nm） extensively decreases to 66.4 nm after 20 h of high-energy ball milling. In spite of grain growth, the deposited coatings maintain their nanostructures with the mean grain size of 112 nm. SEM images show that there is a lower porosity in the coating with a higher HA content. Optical microscopy images show that uniform thickness is obtained for all the coatings.展开更多
In this work,CuFe_(2)O_(4) hollow microspheres assembled with nanosheets(CuFe_(2)O_(4) HMANs)were synthesized using a solvothermal method followed by an annealing treatment.The effects of annealing temperature on micr...In this work,CuFe_(2)O_(4) hollow microspheres assembled with nanosheets(CuFe_(2)O_(4) HMANs)were synthesized using a solvothermal method followed by an annealing treatment.The effects of annealing temperature on microstructure,chemical composition and gas sensing characteristics of as-prepared samples were investigated.The results showed that annealing treatment played a crucial role in the final products.All samples demonstrated hollow spherical morphology assembled with nanosheets or nanoparticles.The CuFe_(2)O_(4) HMANs annealed at400℃exhibited the best n-type conductometric sensing properties toward low-concentration NH3 at 100℃and49%RH.The sensor response to 10×10^(-6)NH_(3) was 4.0 with a rapid response time of 32 s,and it even showed a response of 1.2 toward 1×10^(-6)NH3 at the same condition,while a response of 3.95 to trimethylamine(TMA).The CuFe_(2)O_(4) HMANs-based NH_(3) sensor also exhibited good selectivity and excellent reproducibility.Therefore,this work provided a novel promised sensing material of low-concentration NH_(3) and TMA for real-time monitoring.展开更多
The coating of ZnS∶Mn by Sb-doped SnO2 using an co-precipitation process was reported. ZnS∶Mn phosphor particles were prepared by solid reaction with ZnS and MnCl2·4H2O. Surface modification of the ZnS∶Mn powd...The coating of ZnS∶Mn by Sb-doped SnO2 using an co-precipitation process was reported. ZnS∶Mn phosphor particles were prepared by solid reaction with ZnS and MnCl2·4H2O. Surface modification of the ZnS∶Mn powders was carried out by coating transparent conductive films of Sb-doped tin oxides which were formed by co-precipitation and heat treatment process. Tin tetrachloride and antimony trichloride were used as the precursor materials for the co-precipitation. The influences of coating molar ratio, Sb concentration in the coatings, annealing temperature and time on the resistivity of coated ZnS∶Mn phosphors were investigated. The optimum co-precipitation processing parameters and annealing conditions were determined. The phosphors were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence(PL) observation and conductance measurements. An improvement in phosphors conductivity was observed while the respective photoluminescence intensity is analogous to the as-prepared ZnS∶Mn phosphors.展开更多
Currently, lithium–sulfur batteries su er from several critical limitations that hinder their practical application, such as the large volumetric expansion of electrode, poor conductivity and lower sulfur utilization...Currently, lithium–sulfur batteries su er from several critical limitations that hinder their practical application, such as the large volumetric expansion of electrode, poor conductivity and lower sulfur utilization. In this work, TiO2 nanofibers with mesoporous structure have been synthesized by electrospinning and heat treating. As the host material of cathode for Li–S battery, the as prepared samples with novelty structure could enhance the conductivity of cathode composite, promote the utilization of sulfur, and relieve volume expansion for improving the electrochemical property. The initial discharge capacity of TiO2/S composite cathode is 703 mAh/g and the capacity remained at 652 mAh/g after 200 cycles at 0.1 C, whose the capacity retention remains is at 92.7%, demonstrating great prospect for application in high-performance Li–S batteries.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11888101 and U1832202)the Chinese Academy of Sciences(Grant Nos.QYZDB-SSW-SLH043,XDB28000000,and XDB33000000)+3 种基金the K.C.Wong Education Foundation(Grant No.GJTD-2018-01)the Informatization Plan of Chinese Academy of Sciences(Grant No.CAS-WX2021SF-0102)supported by the Synergetic Extreme Condition User Facility(SECUF)supported by US DOE(Grant Nos.DESC0010526 and DE-SC0012704)。
文摘We report the observation for the pz electron band and the band inversion in Fe1+yTexSe1-xwith angleresolved photoemission spectroscopy. Furthermore, we found that excess Fe(y>0) inhibits the topological band inversion in Fe1+yTexSe1-x,which explains the absence of Majorana zero modes in previous reports for Fe1+yTexSe1-xwith excess Fe. Based on our analysis of different amounts of Te doping and excess Fe, we propose a delicate topological phase in this material. Thanks to this delicate phase, one may be able to tune the topological transition via applying lattice strain or carrier doping.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11774421,11774424,11574394,11774423,11822412,and 11874047)the National Key R&D Program of China(Grant Nos.2016YFA0401002,2018YFA0307000,2016YFA0300504,and 2018FYA0305800)the Fundamental Research Funds for the Central Universities,China(Grant No.2042018kf-0030)。
文摘By using angle-resolvea photoemission spectroscopy(ARPES) combined with the first-principies electronic structure calculations,we report the quantized states at the surface of a single crystal 2 H-TaSe_(2).We have observed sub-bands of quantized states at the three-dimensional Brillouin zone center due to a highly dispersive band with light effective mass along k_(z) direction.The quantized sub-bands shift upward towards E_(F) while the bulk band at Γ shifts downward with the decrease of temperature across charge density wave(CDW) formation.The band shifts could be intimately related to the CDW.While neither the two-dimensional Fermi-surface nesting nor purely strong electron-phonon coupling can explain the mechanism of CDW in 2 H-TaSe_(2),our experiment may ignite the interest in understanding the CDW mechanism in this family.
文摘In this paper, an analytical and numerical study of strain fields, stress fields and displacements in a rotating hollow cylinder, whose walls were completely made in Functionally Graded Materials (FGM), was conducted. We have considered the rotating hollow cylinder submitted to an asymmetric radial loading. It is assumed that, because of the functional graduation of the material, the mechanical properties such as Young elastic modulus and the density varies in the radial direction, in accordance with a the power law function. The inhomogeneity parameter was selected between -1 and 1. On the basis of the second law of Newton, Hooke’s law and the strain-stress relationship, we established the differential equation which governs the equilibrium for a rotating hollow cylinder. We found the analytical solution and compared to the numerical solution obtained by using the shooting method and the fourth order Runge-Kutta algorithm. The analytical and numerical results lead to the conclusion that the magnitude of the tangential stresses is greater than that of the radial stresses. The changes due to the graduation of FGM does not produce consistent variations in the distribution of radial stresses, but strongly affects the distribution of tangential stresses. The tangential stresses, tangential strains and displacements are much higher at the inner surface of the cylinder wall. The internal radial pressure intensely affects the radial stresses and the radial strain.
文摘Naphthenic acids,NAs,are a major contaminant of concern and a focus of much research around remediation of oil sand process affected waters,OSPW.Using activated carbon adsorbents are an attractive option given their low cost of fabrication and implementation.A deeper evaluation of the effect NA structural differences have on uptake affinity is warranted.Here we provide an in-depth exploration of NA adsorption including many more model NA species than have been assessed previously with evaluation of adsorption kinetics and isotherms at the relevant alkaline pH of OSPW using several different carbon adsorbents with pH buffering to simulate the behaviour of real OSPW.Uptake for the NA varied considerably regardless of the activated carbon used,ranging from 350 mg/g to near zero highlighting recalcitrant NAs.The equilibrium data was explored to identify structural features of these species and key physiochemical properties that influence adsorption.We found that certainNAwill be resistant to adsorptionwhen hydrophobic adsorbents are used.Adsorption isotherm modelling helped explore interactions occurring at the interface between NA and adsorbent surfaces.We identified the importance of NA hydrophobicity for activated carbon uptake.Evidence is also presented that indicates favorable hydrogen bonding between certain NA and surface site hydroxyl groups,demonstrating the importance of adsorbent surface functionality for NA uptake.This research highlights the challenges associated with removing NAs from OSPW through adsorption and also identifies howadsorbent surface chemistry modification can be used to increase the removal efficiency of recalcitrant NA species.
基金supported by the National Natural Science Foundation of China(No.22073090,No.21991132,No.52021002)the National Key R&D Program of China(No.2020YFA0710700)the Funds of Youth Innovation Promotion Association,and the Fundamental Research Funds for the Central Universities(WK3450000009).
文摘CRISPR-based tran-scription regulators(CRISPR-TRs)have revolutionized the field of synthetic biol-ogy by enabling tar-geted activation or repression of any de-sired gene.However,the majority of exist-ing inducible CRISPR-TRs are limited by their dependence on specific sequences,which restricts their flex-ibility and controllability in genetic engineering applications.In this study,we proposed a novel strategy to construct sequence-independent inducible CRISPR-TRs,which is achieved by the design of stem loop 2 in the single guide RNA(sgRNA).Under this strategy,by utiliz-ing toehold-mediated strand displacement(TMSD)reactions between small endogenous molecules(miR-20a and TK1 mRNA)and bridge RNA(bRNA)to link bRNA with sgRNA,we achieved synergistic transcriptional activation of VP64 and p65-HSF1 in response to en-dogenous molecules.To enable response to exogenous molecules,we added response se-quences and bRNA sequences to the 5'end of sgRNA to block sgRNA activity,and achieved activation of sgRNA by shearing the response sequence,called sequential unlimited interlock-ing(SUI).Compared with conventional sequence-restricted interlocking(spacer-blocking hairpin(SBH)),the transcriptional activation ratio between response and non-response to the Cas6A protein using our approach was increased by 2.28-fold.Our work presents a modular and versatile framework for endogenous and exogenous molecule-responsive CRISPR-TRs in mammalian cells,without limitations imposed by sequence dependence.
基金the National Natural Science Foundation of China(Grant No.52074179)for the financial supportNational Key Research and Development Program of China(2024YFB3713705)is also acknowledged.
文摘Cleanliness control of advanced steels is of vital importance for quality control of the products.In order to understand and control the inclusion removal during refining process in molten steel,its motion behaviors at the multiple steel/gas/slag interfaces have attracted the attention much of metallurgical community.The recent development of the agglomeration of non-metallic inclusions at the steel/Ar and steel/slag interfaces has been summarized,and both the experimental as well as theoretical works have been surveyed.In terms of in situ observation of high-temperature interfacial phenomena in the molten steel,researchers utilized high-temperature confocal laser scanning microscopy to observe the movement of more types of inclusions at the interface,i.e.,the investigated inclusion is no longer limited to Al_(2)O_(3)-based inclusions but moves forward to rare earth oxides,MgO-based oxides,etc.In terms of theoretical models,especially the model of inclusions at the steel/slag interface,the recent development has overcome the limitations of the assumptions of Kralchevsky-Paunov model and verified the possible errors caused by the model assumptions by combining the water model and the physical model.Last but not least,the future work in this topic has been suggested,which could be in combination of thermal physical properties of steels and slag,as well as utilize the artificial intelligence-based methodology to implement a comprehensive inclusion motion behaviors during a comprehensive metallurgical process.
基金the financial supports from the Natural Science Foundation of Hunan Province, China (Nos. 2020JJ4114, 2016JJ3151)the National Natural Science Foundation of China (No. 51601229)+2 种基金the Young Elite Scientist Sponsorship Program by CAST, China (No. 2015QNRC001)the Hunan Province Innovation Platform and Talent Plan Project, China (No. 2015RS4001)the Open-end Fund for the Valuable and Precision Instruments of Central South University, China (No. CSUZC201815)。
基金financially supported by the Natural Science Foundation of Hunan Province,China(Nos.2020JJ4114,2016JJ3151)the National Natural Science Foundation of China(No.51601229)+2 种基金the Young Elite Scientist Sponsorship Program by CAST,China(No.2015QNRC001)the Hunan Province Innovation Platform and Talent Plan,China(No.2015RS4001)the Open-End Fund for the Valuable and Precision Instruments of Central South University,China(No.CSUZC201815)。
文摘Temperature programmed reduction (TPR) study was carried out for CeO 2/Al 2O 3 and CeO 2/ZrO 2 catalysts to evaluate oxygen storage property induced by a facile redox cycling of Ce ion. The CeO 2/ZrO 2 catalyst possesses excellent oxygen storage activity at 373 K after reduction above 1173 K although the oxygen storage of CeO 2/Al 2O 3 catalyst after reduction above 1173 K is poor because of the formation of CeAlO 3. Consequently, the oxygen storage on the CeO 2/ZrO 2 catalyst smoothly occurs from low temperatures when the catalyst is reduced even at high temperatures.
基金the Portuguese Ministry of Science and Technology(FCT-MCTES)for offering post-doctoral fellowships through the grants SFRH/BPD/34542/2007 and SFRH/BPD/35055/2007,respectivelyfinanced by FCT-MCTES through CENIMAT-I3N
文摘N-doped ZnO films were radio frequency(RF)sputtered on glass substrates and studied as a function of oxygen partial pressure(OPP)ranging from 3.0×10-4 to 9.5×10-3 Pa.X-ray diffraction patters confirmed the polycrystalline nature of the deposited films.The crystalline structure is influenced by the variation of OPP.Atomic force microscopy analysis confirmed the agglomeration of the neighboring spherical grains with a sharp increase of root mean square(RMS)roughness when the OPP is increased above 1.4×10-3 Pa.X-ray photoelectron spectroscopy analysis revealed that the incorporation of N content into the film is decreased with the increase of OPP,noticeably N 1s XPS peaks are hardly identified at 9.5×10-3 Pa.The average visible transmittance(380-700 nm) is increased with the increase of OPP(from～17%to 70%),and the optical absorption edge shifts towards the shorter wavelength.The films deposited with low OPP(≤3.0×10-4 Pa)show n-type conductivity and those deposited with high OPP(≥9.0×10-4 Pa)are highly resistive(>105Ω·cm)
文摘In this paper numerical analysis of underground structures, taking account the transverse isotropy system of rocks, was done using CAST 3M code by varying the shape of excavation and the coefficient of earth pressure k. Numerical results reveal that the anisotropy behavior, the shape of hole and the coefficient of earth pressure k have significant influence to the mining induced stress field and rock deformations which directly control the stability of underground excavation design. The magnitude of horizontal stress obtained for the horse shoe shape excavation(25.2 MPa for k = 1; 52.7 MPa for k = 2)is lower than the magnitude obtained for circular hole(26.4 MPa for k = 1; 59.5 MPa for k = 2).Therefore, we have concluded that the horse shoe shape offers the best stability and the best design for engineer. The anisotropy system presented by rock mass can also influence the redistribution of stresses around hole opened. Numerical results have revealed that the magnitude of redistribution of horizontal stresses obtained for transverse isotropic rock(12.1 MPa for k = 0.5; 25.2 MPa for k = 1 and52.7 MPa for k = 2) is less than those obtained in the case of isotropic rock(27.6 MPa for k = 1;48.6 MPa for k = 2 and 90.81 MPa for k = 2). The more the rock has the anisotropic behavior, the more the mass of rock around the tunnel is stable.
文摘The density, cell size and structure of closed-cell aluminum foam were measured by optical microscopy and image analysis. The properties and the mechanism of compressive deformation that occur in closed-cell aluminum foam were measured and discussed. The results show that the cell size of foam with density of 0.37 mg/m^3 is distributed in the range of 0.5 4.0 mm. The cell size of foam with density of 0.33 mg/m^3 is distributed in the range of 0.55.0 mm. The cell wall thickness of both types is 0.10.3 mm. The closed-cell aluminum foam almost belongs to isotropic one, with a variation of ±15% in elastic modulus and yield strength in longitudinal and transverse direction. Under compressive loading, foam materials show inhomogeneous macroscopic deformation. The site of the onset of local plastic deformation depends on the cell structure. The shape of cell is more important than size in determining the yielding susceptibility of the cells. At early stage of deformation,the deformation is localized in narrow bands having width of one cells diameter, and outside the bands the cell still remains the original shape. The cells within bands experience large permanent deformation. The band normals are usually within 20° of the loading axis.
文摘Hybrid density functional theory was used to investigate the structural,electronic,magnetic and elastic properties of the Laves phase binary intermetallics RFe_(2)(R=La,Ce,Pr and Nd) in C_(15) crystal structure.The calculated lattice constants of these materials are found in good agreement with the experiments.The band structures and density of states distribution confirm the metallic nature of all these intermetallics.The optimized energies in different magnetic phases and magnetic susceptibilities by postDFT treatments confirm that all the understudy compounds are ferromagnetic in nature.Elastic parameters were calculated from the cubic elastic coefficients C_(11),C_(12) and C_(44).The elastic properties reveal that these intermetallics are incompressible,ductile,elastically anisotropic and mechanically stable.Based on the metallic nature and ferromagnetic properties,it is expected that these intermetallics are suitable materials for spintronic technology.
文摘TiO2-hydroxyapatite （HA） nanostructured coatings were produced by atmospheric plasma spray method. The effects of starting powder composition and grain size on their mechanical properties were investigated. The microstructure and morphology were characterized by X-ray diffraction and scanning electron microscopy （SEM）. It is found that the coating with 10% HA has the best mechanical properties. Based on Rietveld refinement method, the mean grain size of the as-received powder （212 nm） extensively decreases to 66.4 nm after 20 h of high-energy ball milling. In spite of grain growth, the deposited coatings maintain their nanostructures with the mean grain size of 112 nm. SEM images show that there is a lower porosity in the coating with a higher HA content. Optical microscopy images show that uniform thickness is obtained for all the coatings.
基金the National Natural Science Foundation of China(No.51872254)the National Key Research and Development Program of China(No.2017YFE0115900)Yangzhou City-Yangzhou University Cooperation Foundation(No.YZU201801)。
文摘In this work,CuFe_(2)O_(4) hollow microspheres assembled with nanosheets(CuFe_(2)O_(4) HMANs)were synthesized using a solvothermal method followed by an annealing treatment.The effects of annealing temperature on microstructure,chemical composition and gas sensing characteristics of as-prepared samples were investigated.The results showed that annealing treatment played a crucial role in the final products.All samples demonstrated hollow spherical morphology assembled with nanosheets or nanoparticles.The CuFe_(2)O_(4) HMANs annealed at400℃exhibited the best n-type conductometric sensing properties toward low-concentration NH3 at 100℃and49%RH.The sensor response to 10×10^(-6)NH_(3) was 4.0 with a rapid response time of 32 s,and it even showed a response of 1.2 toward 1×10^(-6)NH3 at the same condition,while a response of 3.95 to trimethylamine(TMA).The CuFe_(2)O_(4) HMANs-based NH_(3) sensor also exhibited good selectivity and excellent reproducibility.Therefore,this work provided a novel promised sensing material of low-concentration NH_(3) and TMA for real-time monitoring.
基金Project supported by the National Natural Science Foundation of China (20572064) and the Natural Science Foundation of Shandong Province (Y2002G11)
文摘The coating of ZnS∶Mn by Sb-doped SnO2 using an co-precipitation process was reported. ZnS∶Mn phosphor particles were prepared by solid reaction with ZnS and MnCl2·4H2O. Surface modification of the ZnS∶Mn powders was carried out by coating transparent conductive films of Sb-doped tin oxides which were formed by co-precipitation and heat treatment process. Tin tetrachloride and antimony trichloride were used as the precursor materials for the co-precipitation. The influences of coating molar ratio, Sb concentration in the coatings, annealing temperature and time on the resistivity of coated ZnS∶Mn phosphors were investigated. The optimum co-precipitation processing parameters and annealing conditions were determined. The phosphors were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence(PL) observation and conductance measurements. An improvement in phosphors conductivity was observed while the respective photoluminescence intensity is analogous to the as-prepared ZnS∶Mn phosphors.
基金Supported by National Nature Science Foundation of China(Grant No.61774022)Education Department of Jilin Province of China(Grant No.JJKH20181030KJ)
文摘Currently, lithium–sulfur batteries su er from several critical limitations that hinder their practical application, such as the large volumetric expansion of electrode, poor conductivity and lower sulfur utilization. In this work, TiO2 nanofibers with mesoporous structure have been synthesized by electrospinning and heat treating. As the host material of cathode for Li–S battery, the as prepared samples with novelty structure could enhance the conductivity of cathode composite, promote the utilization of sulfur, and relieve volume expansion for improving the electrochemical property. The initial discharge capacity of TiO2/S composite cathode is 703 mAh/g and the capacity remained at 652 mAh/g after 200 cycles at 0.1 C, whose the capacity retention remains is at 92.7%, demonstrating great prospect for application in high-performance Li–S batteries.
