In this paper, We show that the simple K\-3-groups can be characterized by the orders of their maximal abelian subgroups. That is, we have Theorem Let G be a finite group and M a simple K \-3-group. Then ...In this paper, We show that the simple K\-3-groups can be characterized by the orders of their maximal abelian subgroups. That is, we have Theorem Let G be a finite group and M a simple K \-3-group. Then G is isomorphic to M if and only if the set of the orders of the maximal abelian subgoups of G is the same as that of M .展开更多
北斗三号全球卫星导航系统(BDS-3)于2020年7月31日正式开通,其空间段服务能力是决定系统整体性能表现的重要因素.本文对广播轨道、广播钟差、空间信号测距误差、广播电离层精度的评估计算方法进行了分析,分别以GFZ(German Research Cent...北斗三号全球卫星导航系统(BDS-3)于2020年7月31日正式开通,其空间段服务能力是决定系统整体性能表现的重要因素.本文对广播轨道、广播钟差、空间信号测距误差、广播电离层精度的评估计算方法进行了分析,分别以GFZ(German Research Centre for Geosciences)和iGMAS(International GNSS Monitoring and Assessment System)的最终产品为参考基准,对系统从2020年正式开通至2025年的变化情况进行了评估分析.研究表明, BDS-3广播轨道精度呈现明显的卫星类型相关性, MEO卫星高于IGSO卫星,与GFZ产品和iGMAS产品相比,径向、切向、法向95%的RMS值均得到不同程度地改善;广播钟差误差与SISRE(Signal-InSpace Range Error) 95%的RMS值则提升了分米级的精度;电离层模型误差方面,在评估周期内, Klobuchar模型的VTEC值分布范围相对较广,低VTEC区间BDGIM模型的频次分布更为集中;与CODE和iGMAS电离层产品相比,在太阳活动极小期的2020年BDGIM(Beidou Global Lonospheric Delay Correction Model)模型VTEC平均RMS值优于Klobuchar模型,而在太阳活动极大期的2025年两模型的VTEC平均RMS值均呈上升的趋势,且BDGIM模型的稳定性更强.展开更多
Ti-6 Al-4 V alloy powder was processed by electrode induction melting gas atomization(EIGA)at high gas pressure(5.5-7.0 MPa).The effects of atomizing gas pressure on the powder characteristics and the microstructure,a...Ti-6 Al-4 V alloy powder was processed by electrode induction melting gas atomization(EIGA)at high gas pressure(5.5-7.0 MPa).The effects of atomizing gas pressure on the powder characteristics and the microstructure,along with the mechanical properties of the as-fabricated block by laser melting deposition(LMD),were investigated.The results indicate that the diameters of powders are distributed in a wide range of sizes from 1 to 400μm,and the median powder size(d50)decreases with increasing gas pressure.The powders with a size fraction of 100-150μm obtained at gas pressures of 6.0 and 6.5 MPa have better flowability.The oxygen content is consistent with the change trend of gas pressure within a low range of 0.06%-0.20%.Specimens fabricated by LMD are mainly composed ofα+βgrains with a fine lamellar Widmanstatten structures and have the ultimate tensile strength(UTS)and yield strength of approximately 1100 and 1000 MPa,respectively.Furthermore,the atomized powders have a favorable 3 D printing capability,and the mechanical properties of Ti-6 Al-4 V alloys manufactured by LMD typically exceed those of their cast or wrought counterparts.展开更多
The effect of acidity and redox capability over sulfuric acid-modified CeO_2 catalysts were studied for the selective catalytic reduction of NO_x with NH_3(NH_3-SCR). The deposition of sulfate significantly enhanced t...The effect of acidity and redox capability over sulfuric acid-modified CeO_2 catalysts were studied for the selective catalytic reduction of NO_x with NH_3(NH_3-SCR). The deposition of sulfate significantly enhanced the catalytic performance over CeO_2. NO_x conversion over4H_2SO_4/CeO_2 at 230–440 °C was higher than 90%. The strong redox capability of CeO_2 could result in unselective NH_3 oxidation and decrease high temperatures catalytic activity and N_2 selectivity. The deposition of sulfate increased the acidity and weakened the redox capability, and then increased the high temperature NO_x conversion and N_2 selectivity. An appropriate level of acidity also promoted the activity at 190–250 °C over ceria-based catalysts, and with further increase in the acidity, the SCR activity decreased slightly. Weak redox capability lowered the low-temperature catalytic activity. Excellent SCR activity requires a balance of acidity and redox capability on the catalysts.展开更多
The emergence of Y6-type nonfullerene acceptors has greatly enhanced the power conversion efficiency(PCE)of organic solar cells(OSCs).However,which structural feature is responsible for the excellent photovoltaic perf...The emergence of Y6-type nonfullerene acceptors has greatly enhanced the power conversion efficiency(PCE)of organic solar cells(OSCs).However,which structural feature is responsible for the excellent photovoltaic performance is still under debate.In this study,two Y6-like acceptors BDOTP-1 and BDOTP-2 were designed.Different from previous Y6-type acceptors featuring an A–D–Aʹ–D–A structure,BDOTP-1,and BDOTP-2 have no electron-deficient Aʹfragment in the core unit.Instead,there is an electron-rich dibenzodioxine fragment in the core.Although this modification leads to a marked change in the molecular dipole moment,electrostatic potential,frontier orbitals,and energy levels,BDOTP acceptors retain similar three-dimensional packing capability as Y6-type acceptors due to the similar banana-shaped molecular configuration.BDOTP acceptors show good performance in OSCs.High PCEs of up to 18.51%(certified 17.9%)are achieved.This study suggests that the banana-shaped configuration instead of the A–D–Aʹ–D–A structure is likely to be the determining factor in realizing high photovoltaic performance.展开更多
LiNi1/3Co1/3Mn1/3O2 was coated with uniform nano-sized AlF3 layer by chemical precipitation method to improve its rate capability.The samples were characterized by X-ray diffractometry (XRD),transmission electron micr...LiNi1/3Co1/3Mn1/3O2 was coated with uniform nano-sized AlF3 layer by chemical precipitation method to improve its rate capability.The samples were characterized by X-ray diffractometry (XRD),transmission electron microscopy (TEM),energy dispersive spectroscopy (EDS),charge-discharge cycling,cyclic voltammetry (CV),and electrochemical impedance spectroscopy (EIS).Uniform coated layer with a thickness of about 3 nm was observed on the surface of LiNi1/3Co1/3Mn1/3O2 particle by TEM.At 0.5C and 2C rates,1.5% (mass fraction) AlF3-coated LiNi1/3Co1/3Mn1/3O2/Li in 2.8-4.3 V versus Li/Li+ after 80 cycles showed less than 3% of capacity fading,while those of the bare one were 16.5% and 45.9%,respectively.At 5C rate,the capacity retention of the coated sample after 50 cycles maintained 91.4% of the initial discharge capacity,while that of the bare one decreased to 52.6%.EIS result showed that a little change of charge transfer resistance of the coated sample resulting from uniform thin AlF3 layer was proposed as the main reason why its rate capability was improved obviously.CV result further indicated a greater reversibility for the electrode processes and better electrochemical performance of AlF3-coated layer.展开更多
NiMnO3 perovskite catalysts supported on cordierite modified by CexZr（1-x）O2 coatings were prepared using impregnation and sol-gel methods for catalytic combustion of single/double component VOCs at different concen...NiMnO3 perovskite catalysts supported on cordierite modified by CexZr（1-x）O2 coatings were prepared using impregnation and sol-gel methods for catalytic combustion of single/double component VOCs at different concentrations and GHSV of 15,000 h^（-1）, which were characterized by BET, XRD, SEM, FT-IR, H2-TPR and O2-TPD. After coating modification, the specific surface area of catalysts is improved obviously.Among the catalysts, the Ce（0.75）Zr（0.25）O2 coating modified NiMnO3 catalyst exhibits the best catalytic activity for VOCs combustion with 95.6% conversion at 275 ℃ and has stable activity when catalyst is embalmed at 800 ℃. In addition, the catalyst also presents the excellent water-resistant and conversion stability over time-on-stream condition. The reason is that Ce（0.75）Zr（0.25）O2 coating can promote more lattice distortion and defects and smaller crystal size, which improve oxygen transfer capability and dispersion of active component.展开更多
Theoretical calculations were carried out using the DFT/B3LYP/6-31+G(d) methodology in an attempt to predict the preferred interaction site of a polyfunctional heterocyclic base 3-methyl-4- pyrimidone molecule with a ...Theoretical calculations were carried out using the DFT/B3LYP/6-31+G(d) methodology in an attempt to predict the preferred interaction site of a polyfunctional heterocyclic base 3-methyl-4- pyrimidone molecule with a series of proton donors of different acidic strength, i.e. water, methanol, phenol, 1-naphtol, 2,4,5 trichlorophenol, pentachlorophenol, picric acid and hydrogen chlordide. Computed H-bond interaction energies (ΔEc), internuclear and intermolecular distances r(O…H) and r(O…O), infrared frequency shifts Δv(C=O) and (Δv(OH) are proved to be reliable parameters for predicting the preferred interaction site of 3-methyl-4-pyrimidone. These computational data suggest that the O-H…O=C complex is preferred with water, methanol, phenol, 1-naphtol, 2,4,5 trichlorophenol and pentachlorophenol. However, for H-bonding with stronger acids such as picric acid or hydrochloric acid, the computational data suggest that the H-bonding occurs at the N1 ring atom of 3-methyl-4-pyrimidone. In the O-H…O=C com- plex, where the H-bond at the carbonyl O-atom can be oriented “anti” (Ha) and “syn” (Hb) with respect to the N3 atom, the same computational data suggest a higher stability of the “anti-O” compared to the “syn-O” orientation.展开更多
Manganese oxides are regarded as one of the most promising cathode materials in rechargeable aqueous Zn-ion batteries(ZIBs)because of the low price and high security.However,the practical application of Mn2O3 in ZIBs ...Manganese oxides are regarded as one of the most promising cathode materials in rechargeable aqueous Zn-ion batteries(ZIBs)because of the low price and high security.However,the practical application of Mn2O3 in ZIBs is still plagued by the low specific capacity and poor rate capability.Herein,highly crystalline Mn2O3 materials with interconnected mesostructures and controllable pore sizes are obtained via a ligand-assisted self-assembly process and used as high-performance electrode materials for reversible aqueous ZIBs.The coordination degree between Mn2+and citric acid ligand plays a crucial role in the formation of the mesostructure,and the pore sizes can be easily tuned from 3.2 to 7.3 nm.Ascribed to the unique feature of nanoporous architectures,excellent zinc-storage performance can be achieved in ZIBs during charge/discharge processes.The Mn2O3 electrode exhibits high reversible capacity(233 mAh g−1 at 0.3 A g−1),superior rate capability(162 mAh g−1 retains at 3.08 A g−1)and remarkable cycling durability over 3000 cycles at a high current rate of 3.08 A g−1.Moreover,the corresponding electrode reaction mechanism is studied in depth according to a series of analytical methods.These results suggest that rational design of the nanoporous architecture for electrode materials can effectively improve the battery performance.展开更多
Organic substance such as solvent and resin's effect on luminescent capability of SrAl2O4:Eu2+ , Dy3+ phosphor was studied. Some organic solvents and resins were selected for experimentation. The results indicate ...Organic substance such as solvent and resin's effect on luminescent capability of SrAl2O4:Eu2+ , Dy3+ phosphor was studied. Some organic solvents and resins were selected for experimentation. The results indicate that those organic solvents will not have negative effect on the applied capability of SrAl2O4:Eu2+ , Dy3+ phosphor. Adopting the organic resins and covering method, the afterglow luminance of SrAl2O4:Eu2+ , Dy3+ phosphor was increased by 85.01% and 82.51%.展开更多
文摘In this paper, We show that the simple K\-3-groups can be characterized by the orders of their maximal abelian subgroups. That is, we have Theorem Let G be a finite group and M a simple K \-3-group. Then G is isomorphic to M if and only if the set of the orders of the maximal abelian subgoups of G is the same as that of M .
文摘北斗三号全球卫星导航系统(BDS-3)于2020年7月31日正式开通,其空间段服务能力是决定系统整体性能表现的重要因素.本文对广播轨道、广播钟差、空间信号测距误差、广播电离层精度的评估计算方法进行了分析,分别以GFZ(German Research Centre for Geosciences)和iGMAS(International GNSS Monitoring and Assessment System)的最终产品为参考基准,对系统从2020年正式开通至2025年的变化情况进行了评估分析.研究表明, BDS-3广播轨道精度呈现明显的卫星类型相关性, MEO卫星高于IGSO卫星,与GFZ产品和iGMAS产品相比,径向、切向、法向95%的RMS值均得到不同程度地改善;广播钟差误差与SISRE(Signal-InSpace Range Error) 95%的RMS值则提升了分米级的精度;电离层模型误差方面,在评估周期内, Klobuchar模型的VTEC值分布范围相对较广,低VTEC区间BDGIM模型的频次分布更为集中;与CODE和iGMAS电离层产品相比,在太阳活动极小期的2020年BDGIM(Beidou Global Lonospheric Delay Correction Model)模型VTEC平均RMS值优于Klobuchar模型,而在太阳活动极大期的2025年两模型的VTEC平均RMS值均呈上升的趋势,且BDGIM模型的稳定性更强.
基金Project(2017YFB0305801)supported by the National Key R&D Program of ChinaProject(U1508213)supported by the Joint-Fund of NSFC-Liaoning,ChinaProject(51771051)supported by the National Natural Science Foundation of China.
文摘Ti-6 Al-4 V alloy powder was processed by electrode induction melting gas atomization(EIGA)at high gas pressure(5.5-7.0 MPa).The effects of atomizing gas pressure on the powder characteristics and the microstructure,along with the mechanical properties of the as-fabricated block by laser melting deposition(LMD),were investigated.The results indicate that the diameters of powders are distributed in a wide range of sizes from 1 to 400μm,and the median powder size(d50)decreases with increasing gas pressure.The powders with a size fraction of 100-150μm obtained at gas pressures of 6.0 and 6.5 MPa have better flowability.The oxygen content is consistent with the change trend of gas pressure within a low range of 0.06%-0.20%.Specimens fabricated by LMD are mainly composed ofα+βgrains with a fine lamellar Widmanstatten structures and have the ultimate tensile strength(UTS)and yield strength of approximately 1100 and 1000 MPa,respectively.Furthermore,the atomized powders have a favorable 3 D printing capability,and the mechanical properties of Ti-6 Al-4 V alloys manufactured by LMD typically exceed those of their cast or wrought counterparts.
基金financially supported by National Key R&D Program of China(No.2016YFC0205301)the Key Project of National Natural Science Foundation(No.21637005)+1 种基金the National Natural Science Foundation of China(No.21607149)the Natural Science Foundation of Fujian Province,China(No.2016J05142)
文摘The effect of acidity and redox capability over sulfuric acid-modified CeO_2 catalysts were studied for the selective catalytic reduction of NO_x with NH_3(NH_3-SCR). The deposition of sulfate significantly enhanced the catalytic performance over CeO_2. NO_x conversion over4H_2SO_4/CeO_2 at 230–440 °C was higher than 90%. The strong redox capability of CeO_2 could result in unselective NH_3 oxidation and decrease high temperatures catalytic activity and N_2 selectivity. The deposition of sulfate increased the acidity and weakened the redox capability, and then increased the high temperature NO_x conversion and N_2 selectivity. An appropriate level of acidity also promoted the activity at 190–250 °C over ceria-based catalysts, and with further increase in the acidity, the SCR activity decreased slightly. Weak redox capability lowered the low-temperature catalytic activity. Excellent SCR activity requires a balance of acidity and redox capability on the catalysts.
基金the open research fund of the Songshan Lake Materials Laboratory(2021SLABFK02)the National Key Research and Development Program of China(2017YFA0206600)the National Natural Science Foundation of China(51922032 and 21961160720).
文摘The emergence of Y6-type nonfullerene acceptors has greatly enhanced the power conversion efficiency(PCE)of organic solar cells(OSCs).However,which structural feature is responsible for the excellent photovoltaic performance is still under debate.In this study,two Y6-like acceptors BDOTP-1 and BDOTP-2 were designed.Different from previous Y6-type acceptors featuring an A–D–Aʹ–D–A structure,BDOTP-1,and BDOTP-2 have no electron-deficient Aʹfragment in the core unit.Instead,there is an electron-rich dibenzodioxine fragment in the core.Although this modification leads to a marked change in the molecular dipole moment,electrostatic potential,frontier orbitals,and energy levels,BDOTP acceptors retain similar three-dimensional packing capability as Y6-type acceptors due to the similar banana-shaped molecular configuration.BDOTP acceptors show good performance in OSCs.High PCEs of up to 18.51%(certified 17.9%)are achieved.This study suggests that the banana-shaped configuration instead of the A–D–Aʹ–D–A structure is likely to be the determining factor in realizing high photovoltaic performance.
基金Project(50542004) supported by the National Natural Science Foundation of ChinaProject(1960-71131100017) supported by Graduate Degree Thesis Innovation Foundation of Central South University,China
文摘LiNi1/3Co1/3Mn1/3O2 was coated with uniform nano-sized AlF3 layer by chemical precipitation method to improve its rate capability.The samples were characterized by X-ray diffractometry (XRD),transmission electron microscopy (TEM),energy dispersive spectroscopy (EDS),charge-discharge cycling,cyclic voltammetry (CV),and electrochemical impedance spectroscopy (EIS).Uniform coated layer with a thickness of about 3 nm was observed on the surface of LiNi1/3Co1/3Mn1/3O2 particle by TEM.At 0.5C and 2C rates,1.5% (mass fraction) AlF3-coated LiNi1/3Co1/3Mn1/3O2/Li in 2.8-4.3 V versus Li/Li+ after 80 cycles showed less than 3% of capacity fading,while those of the bare one were 16.5% and 45.9%,respectively.At 5C rate,the capacity retention of the coated sample after 50 cycles maintained 91.4% of the initial discharge capacity,while that of the bare one decreased to 52.6%.EIS result showed that a little change of charge transfer resistance of the coated sample resulting from uniform thin AlF3 layer was proposed as the main reason why its rate capability was improved obviously.CV result further indicated a greater reversibility for the electrode processes and better electrochemical performance of AlF3-coated layer.
基金Project supported by the Science and Technology Department of Jiangsu Province(BE2016769)the Natural Science Foundation of China(51172107)+2 种基金Natural Science Foundation of the Jiangsu Higher Education Institutions of China(14KJB430014)Open fund by Jiangsu Engineering Technology Research Center of Environmental Cleaning Materials(KFK1503)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘NiMnO3 perovskite catalysts supported on cordierite modified by CexZr（1-x）O2 coatings were prepared using impregnation and sol-gel methods for catalytic combustion of single/double component VOCs at different concentrations and GHSV of 15,000 h^（-1）, which were characterized by BET, XRD, SEM, FT-IR, H2-TPR and O2-TPD. After coating modification, the specific surface area of catalysts is improved obviously.Among the catalysts, the Ce（0.75）Zr（0.25）O2 coating modified NiMnO3 catalyst exhibits the best catalytic activity for VOCs combustion with 95.6% conversion at 275 ℃ and has stable activity when catalyst is embalmed at 800 ℃. In addition, the catalyst also presents the excellent water-resistant and conversion stability over time-on-stream condition. The reason is that Ce（0.75）Zr（0.25）O2 coating can promote more lattice distortion and defects and smaller crystal size, which improve oxygen transfer capability and dispersion of active component.
文摘Theoretical calculations were carried out using the DFT/B3LYP/6-31+G(d) methodology in an attempt to predict the preferred interaction site of a polyfunctional heterocyclic base 3-methyl-4- pyrimidone molecule with a series of proton donors of different acidic strength, i.e. water, methanol, phenol, 1-naphtol, 2,4,5 trichlorophenol, pentachlorophenol, picric acid and hydrogen chlordide. Computed H-bond interaction energies (ΔEc), internuclear and intermolecular distances r(O…H) and r(O…O), infrared frequency shifts Δv(C=O) and (Δv(OH) are proved to be reliable parameters for predicting the preferred interaction site of 3-methyl-4-pyrimidone. These computational data suggest that the O-H…O=C complex is preferred with water, methanol, phenol, 1-naphtol, 2,4,5 trichlorophenol and pentachlorophenol. However, for H-bonding with stronger acids such as picric acid or hydrochloric acid, the computational data suggest that the H-bonding occurs at the N1 ring atom of 3-methyl-4-pyrimidone. In the O-H…O=C com- plex, where the H-bond at the carbonyl O-atom can be oriented “anti” (Ha) and “syn” (Hb) with respect to the N3 atom, the same computational data suggest a higher stability of the “anti-O” compared to the “syn-O” orientation.
基金the Young Thousand Talented Program and the National Natural Science Foundation of China (21671073 and 21621001)the “111” Project of the Ministry of Education of China (B17020)Program for JLU Science and Technology Innovative Research Team
文摘Manganese oxides are regarded as one of the most promising cathode materials in rechargeable aqueous Zn-ion batteries(ZIBs)because of the low price and high security.However,the practical application of Mn2O3 in ZIBs is still plagued by the low specific capacity and poor rate capability.Herein,highly crystalline Mn2O3 materials with interconnected mesostructures and controllable pore sizes are obtained via a ligand-assisted self-assembly process and used as high-performance electrode materials for reversible aqueous ZIBs.The coordination degree between Mn2+and citric acid ligand plays a crucial role in the formation of the mesostructure,and the pore sizes can be easily tuned from 3.2 to 7.3 nm.Ascribed to the unique feature of nanoporous architectures,excellent zinc-storage performance can be achieved in ZIBs during charge/discharge processes.The Mn2O3 electrode exhibits high reversible capacity(233 mAh g−1 at 0.3 A g−1),superior rate capability(162 mAh g−1 retains at 3.08 A g−1)and remarkable cycling durability over 3000 cycles at a high current rate of 3.08 A g−1.Moreover,the corresponding electrode reaction mechanism is studied in depth according to a series of analytical methods.These results suggest that rational design of the nanoporous architecture for electrode materials can effectively improve the battery performance.
文摘Organic substance such as solvent and resin's effect on luminescent capability of SrAl2O4:Eu2+ , Dy3+ phosphor was studied. Some organic solvents and resins were selected for experimentation. The results indicate that those organic solvents will not have negative effect on the applied capability of SrAl2O4:Eu2+ , Dy3+ phosphor. Adopting the organic resins and covering method, the afterglow luminance of SrAl2O4:Eu2+ , Dy3+ phosphor was increased by 85.01% and 82.51%.
