Taking China’s 2018 value-added tax(VAT)credit refund reform as an exogenous shock to improve VAT neutrality,we use a difference-in-differences approach to explore how the reform affected corporate social responsibil...Taking China’s 2018 value-added tax(VAT)credit refund reform as an exogenous shock to improve VAT neutrality,we use a difference-in-differences approach to explore how the reform affected corporate social responsibility(CSR).We find that the reform motivated firms to improve CSR performance.The reform has a“resource”effect,increasing internal funds and reducing financing costs,thereby enhancing firms’ability to undertake CSR.The reform also has a“reputation”effect,stimulating firms’willingness to engage in CSR to improve their reputations.CSR following the reform increases firm values and reduces bankruptcy risk.Our study provides fresh insights into VAT neutrality theory and is a reference for tax reform in emerging economies.展开更多
Vat photopolymerization(VPP)3D printing is an optimized technology for complex-shaped ceramic cores,in which the solid loading of ceramic slurries greatly infiuences the microstructure and property of the final cerami...Vat photopolymerization(VPP)3D printing is an optimized technology for complex-shaped ceramic cores,in which the solid loading of ceramic slurries greatly infiuences the microstructure and property of the final ceramic parts.However,the high solid loading of slurries is highly limited by the high viscosity.In this study,silica-based ceramic core slurries with solid loading up to 68vol.%were achieved by the composition design to optimize the performance,considering the curing,rheological,and double bond conversion rate.The slurries demonstrate superior curing and rheological performance with mass ratio of monomers being 3:2 and mass fraction of BYK111 being 4wt.%.Afterwards,the impact of solid loading on the morphology and mechanical properties was investigated.As the solid loading increases,the microstructure becomes gradually dense,leading to an improved flexural strength of 19.5 MPa.Additionally,the sintering shrinkage becomes more uniform,satisfying the casting requirements effectively.This work serves as a guide for the preparation of ceramic slurries with a high solid loading.展开更多
As a key process in the manufacturing of hollow turbine blades for aeroengines,ceramic-core stereolithography(SL)is vital for the structural design and precise performance control of hollow turbine blades for aeroengi...As a key process in the manufacturing of hollow turbine blades for aeroengines,ceramic-core stereolithography(SL)is vital for the structural design and precise performance control of hollow turbine blades for aeroengines.Based on SL and digital light processing(DLP),ceramic SL has technical advantages such as high flexibility,short process flow,and integrated structure-performance manufacturing,making it ideal for manufacturing complex hollow ceramic cores.Currently,ceramic cores produced using this technology still encounter several challenges such as low bending strength,low dimensional accuracy,significant sintering shrinkage,and poor surface quality,which limit the innovative development and engineering applications of the additive manufacturing of UV-cured ceramics.This paper reviews the development of additive manufacturing technology and equipment for the vat polymerization of ceramic cores used in aeroengine blades and summarizes the principles and characteristics of vat polymerization for manufacturing ceramic cores.It also highlights research progress in lightweight structural design methods for ceramic cores,ceramic slurry preparation processes,SL processes,debinding and sintering processes,integration of forming system equipment,and verification of aeroengine blade casting.A comprehensive performance control strategy for the SL of ceramic cores is proposed,and future development directions and trends in ceramic-core fabrication using SL technology are discussed.展开更多
To meet the evolving demands of aeroengine development,the structural and performance requirements for ceramic cores have become increasingly stringent.Vat photopolymerization 3D printing,owing to its moldless,fiexibl...To meet the evolving demands of aeroengine development,the structural and performance requirements for ceramic cores have become increasingly stringent.Vat photopolymerization 3D printing,owing to its moldless,fiexible manufacturing,and other advantages,demonstrates significant potential in the preparation of ceramic cores with intricate structures.However,its practical application still faces multiple challenges,including layered structures and property anisotropy,defects such as cracks and collapse during printing and sintering,forming inaccuracies,and difficulties in controlling surface roughness.Recent advances have focused on optimizing slurry formulation and rheology,improving curing behavior,introducing auxiliary powders and additives,tailoring forming parameters,and optimizing the sintering process.Nevertheless,effectively suppressing lamellar defects,achieving superior dimensional accuracy,and maintaining high surface quality in complex structures remain the core scientific and technical issues to be solved.Future research should concentrate on refining curing mechanisms,advancing powder design and organic system optimization,and regulating the coupled processes of forming,debinding,and sintering to accelerate the application of VPP 3D printed ceramic cores in aerospace manufacturing.展开更多
The complex ceramic core used for hollow turbine blades requires a high porosity and a high fiexural strength. For a better balance between porosity and fiexural strength, ceramic materials with porous structures are ...The complex ceramic core used for hollow turbine blades requires a high porosity and a high fiexural strength. For a better balance between porosity and fiexural strength, ceramic materials with porous structures are preferred. In order to achieve the transition from disordered pore formation to ordered pore formation, Al_(2)O_(3) ceramic cores with triply periodic minimal surface(TPMS) micro lattice structures with different structural configurations(gyroid, diamond, and neovius) and different volume fractions of lattice structures(30, 40, and 50, vol.%) were designed and prepared by vat photopolymerization 3D printing. The effects of structural configuration and volume fraction of the lattice structure on the following structural shrinkage, microstructure, and flexural strength were investigated. The shrinkage relationship of the three lattice configurations is: neovius>diamond>gyroid. Besides, it is found that with an increase in the volume fraction of the 3D printed Al_(2)O_(3) ceramic micro lattice structures, their fiexural strength correspondingly increases ranging from 54.95 MPa to 139.1 MPa. The maximum average fiexural strength of the 3D printed Al_(2)O_(3) ceramic micro lattice structures is obtained when the structural configuration is diamond and with a volume fraction of 50vol.%, which is 139.1 MPa. Even when the volume fraction of the lattice structure is 30vol.%, that is to say the porosity is 70%, the fiexural strength is as high as 50-70 MPa, which can still be maintained at a high level. In addition, when the volume fraction of the lattice structure is a certain value, the sample with diamond configuration has a higher strength. The internal pore morphology, pore size, and porosity of the cores are precisely controlled, achieving both a high porosity and a high strength. Therefore, this study maintains high porosity and high strength simultaneously, providing a new lattice structure design idea for 3D printed ceramic cores.展开更多
目的通过研究Ⅲ度房室传导阻滞患者高位右室间隔部起搏(HRVS)时,VAT与DDD模式对心功能的影响,探讨心房的生理收缩和舒张对左心功能的作用。方法 32例Ⅲ度房室传导阻滞患者,在HRVS时,分别给予DDD模式或VAT模式工作,于调控即刻通过超声心...目的通过研究Ⅲ度房室传导阻滞患者高位右室间隔部起搏(HRVS)时,VAT与DDD模式对心功能的影响,探讨心房的生理收缩和舒张对左心功能的作用。方法 32例Ⅲ度房室传导阻滞患者,在HRVS时,分别给予DDD模式或VAT模式工作,于调控即刻通过超声心动图测定二尖瓣口快速充盈期峰值血流速度(Ep),二尖瓣口左房收缩期峰值血流速度(Ap),二尖瓣环后壁处收缩期脉冲组织多普勒峰值速度平均值(Vs),二尖瓣环后壁处舒张早期脉冲组织多普勒峰值速度平均值(Ve),二尖瓣环后壁处舒张晚期脉冲组织多普勒峰值速度平均值(Va),二尖瓣血流频谱等容舒张时间(IVRT),通过Ep/Ap,Ve/Va,Ep/Ve和IVRT评价左室舒张功能,通过Vs,LVEF和LVFS评价收缩功能。结果 HRVS时DDD较VAT模式Ep/Ap、Ve/Va、Ep/Ve,IVRT差异有显著性(0.97±0.11 vs 1.01±0.11,0.89±0.09 vs 0.97±0.07,6.00±0.45 vs 6.24±0.36,100.4±14.32 vs 89.99±7.94;P均<0.01),Vs、左室射血分数和左室短轴缩短率无显著性差异。结论Ⅲ度房室传导阻滞时,HRVS起搏时,DDD模式较VAT模式使左室舒张功能下降,收缩功能无影响,表明了心房生理性起搏的重要性。展开更多
基金Scientific Research Project of Higher Education Institutions in Hebei Province in 2025“Research on Government Procurement-Driven Green Governance of Hebei’s Manufacturing Industry”(Project No.:QN2025662)Social Science Fund of Hebei Province in 2024“Research on Informal Environmental Regulation Promoting Green Development of Hebei’s Manufacturing Industry”(Project No.:HB24GL036)Hebei Provincial Social Science Development Research Project,“Study on the Constraints and Implementation Paths of the Transformation from Dual Control of Energy Consumption to Dual Control of Carbon Emissions in Hebei Province”(Project No.:HBSKFZ25QN199)。
文摘Taking China’s 2018 value-added tax(VAT)credit refund reform as an exogenous shock to improve VAT neutrality,we use a difference-in-differences approach to explore how the reform affected corporate social responsibility(CSR).We find that the reform motivated firms to improve CSR performance.The reform has a“resource”effect,increasing internal funds and reducing financing costs,thereby enhancing firms’ability to undertake CSR.The reform also has a“reputation”effect,stimulating firms’willingness to engage in CSR to improve their reputations.CSR following the reform increases firm values and reduces bankruptcy risk.Our study provides fresh insights into VAT neutrality theory and is a reference for tax reform in emerging economies.
基金financially supported by the National Natural Science Foundation of China(No.52102062)the Xi’an Science and Technology Plan Project(No.23LLRH0004)the Key Research and Development Project of Shaanxi Province of China(2024GX-YBXM-352)。
文摘Vat photopolymerization(VPP)3D printing is an optimized technology for complex-shaped ceramic cores,in which the solid loading of ceramic slurries greatly infiuences the microstructure and property of the final ceramic parts.However,the high solid loading of slurries is highly limited by the high viscosity.In this study,silica-based ceramic core slurries with solid loading up to 68vol.%were achieved by the composition design to optimize the performance,considering the curing,rheological,and double bond conversion rate.The slurries demonstrate superior curing and rheological performance with mass ratio of monomers being 3:2 and mass fraction of BYK111 being 4wt.%.Afterwards,the impact of solid loading on the morphology and mechanical properties was investigated.As the solid loading increases,the microstructure becomes gradually dense,leading to an improved flexural strength of 19.5 MPa.Additionally,the sintering shrinkage becomes more uniform,satisfying the casting requirements effectively.This work serves as a guide for the preparation of ceramic slurries with a high solid loading.
基金supported by Jiangsu Provincial Basic Research Program(Natural Science Foundation)Youth Fund(Grant No.BK20230885)International Joint Laboratory of Sustainable Manufacturing,Ministry of Education,Fundamental Research Funds for Central Universities(Grant No.NG2024012)+1 种基金Basic Research Project for Major Special Programs of Aero-Engine and Gas Turbine(Grant No.J2022-Ⅶ-0006-0048)High-Quality Development Special Project of the Ministry of Industry and Information Technology.
文摘As a key process in the manufacturing of hollow turbine blades for aeroengines,ceramic-core stereolithography(SL)is vital for the structural design and precise performance control of hollow turbine blades for aeroengines.Based on SL and digital light processing(DLP),ceramic SL has technical advantages such as high flexibility,short process flow,and integrated structure-performance manufacturing,making it ideal for manufacturing complex hollow ceramic cores.Currently,ceramic cores produced using this technology still encounter several challenges such as low bending strength,low dimensional accuracy,significant sintering shrinkage,and poor surface quality,which limit the innovative development and engineering applications of the additive manufacturing of UV-cured ceramics.This paper reviews the development of additive manufacturing technology and equipment for the vat polymerization of ceramic cores used in aeroengine blades and summarizes the principles and characteristics of vat polymerization for manufacturing ceramic cores.It also highlights research progress in lightweight structural design methods for ceramic cores,ceramic slurry preparation processes,SL processes,debinding and sintering processes,integration of forming system equipment,and verification of aeroengine blade casting.A comprehensive performance control strategy for the SL of ceramic cores is proposed,and future development directions and trends in ceramic-core fabrication using SL technology are discussed.
基金supported by the National Key R&D Program of China(Grant Nos.2024YFB3714502,2024YFB3714501,2024YFB3714504)the National Natural Science Foundation of China(Grant Nos.52130204,52174376)+5 种基金the TQ Innovation Foundation(Grant No.23-TQ09-02-ZT-01-005)the Aeronautical Science Foundation of China(Grant No.20220042053001)the Ningbo Science and Technology Plan Project(Grant No.2025Z070)the Key R&D Project of Shaanxi Province(Grant Nos2024GX-YBXM-220,2024CY-GJHX-29,2024GX-ZDCYL-03-03,2024GX-YBXM-400)the National Advanced Rare Metal Materials Innovation Center Project[Grant No.2024 ZG-GCZX-01(1)-01]the Foundation of China Scholarship Council(Grant No.202406290136)。
文摘To meet the evolving demands of aeroengine development,the structural and performance requirements for ceramic cores have become increasingly stringent.Vat photopolymerization 3D printing,owing to its moldless,fiexible manufacturing,and other advantages,demonstrates significant potential in the preparation of ceramic cores with intricate structures.However,its practical application still faces multiple challenges,including layered structures and property anisotropy,defects such as cracks and collapse during printing and sintering,forming inaccuracies,and difficulties in controlling surface roughness.Recent advances have focused on optimizing slurry formulation and rheology,improving curing behavior,introducing auxiliary powders and additives,tailoring forming parameters,and optimizing the sintering process.Nevertheless,effectively suppressing lamellar defects,achieving superior dimensional accuracy,and maintaining high surface quality in complex structures remain the core scientific and technical issues to be solved.Future research should concentrate on refining curing mechanisms,advancing powder design and organic system optimization,and regulating the coupled processes of forming,debinding,and sintering to accelerate the application of VPP 3D printed ceramic cores in aerospace manufacturing.
基金supported by the National Natural Science Foundation of China (Grant No. 52275310)。
文摘The complex ceramic core used for hollow turbine blades requires a high porosity and a high fiexural strength. For a better balance between porosity and fiexural strength, ceramic materials with porous structures are preferred. In order to achieve the transition from disordered pore formation to ordered pore formation, Al_(2)O_(3) ceramic cores with triply periodic minimal surface(TPMS) micro lattice structures with different structural configurations(gyroid, diamond, and neovius) and different volume fractions of lattice structures(30, 40, and 50, vol.%) were designed and prepared by vat photopolymerization 3D printing. The effects of structural configuration and volume fraction of the lattice structure on the following structural shrinkage, microstructure, and flexural strength were investigated. The shrinkage relationship of the three lattice configurations is: neovius>diamond>gyroid. Besides, it is found that with an increase in the volume fraction of the 3D printed Al_(2)O_(3) ceramic micro lattice structures, their fiexural strength correspondingly increases ranging from 54.95 MPa to 139.1 MPa. The maximum average fiexural strength of the 3D printed Al_(2)O_(3) ceramic micro lattice structures is obtained when the structural configuration is diamond and with a volume fraction of 50vol.%, which is 139.1 MPa. Even when the volume fraction of the lattice structure is 30vol.%, that is to say the porosity is 70%, the fiexural strength is as high as 50-70 MPa, which can still be maintained at a high level. In addition, when the volume fraction of the lattice structure is a certain value, the sample with diamond configuration has a higher strength. The internal pore morphology, pore size, and porosity of the cores are precisely controlled, achieving both a high porosity and a high strength. Therefore, this study maintains high porosity and high strength simultaneously, providing a new lattice structure design idea for 3D printed ceramic cores.
文摘目的通过研究Ⅲ度房室传导阻滞患者高位右室间隔部起搏(HRVS)时,VAT与DDD模式对心功能的影响,探讨心房的生理收缩和舒张对左心功能的作用。方法 32例Ⅲ度房室传导阻滞患者,在HRVS时,分别给予DDD模式或VAT模式工作,于调控即刻通过超声心动图测定二尖瓣口快速充盈期峰值血流速度(Ep),二尖瓣口左房收缩期峰值血流速度(Ap),二尖瓣环后壁处收缩期脉冲组织多普勒峰值速度平均值(Vs),二尖瓣环后壁处舒张早期脉冲组织多普勒峰值速度平均值(Ve),二尖瓣环后壁处舒张晚期脉冲组织多普勒峰值速度平均值(Va),二尖瓣血流频谱等容舒张时间(IVRT),通过Ep/Ap,Ve/Va,Ep/Ve和IVRT评价左室舒张功能,通过Vs,LVEF和LVFS评价收缩功能。结果 HRVS时DDD较VAT模式Ep/Ap、Ve/Va、Ep/Ve,IVRT差异有显著性(0.97±0.11 vs 1.01±0.11,0.89±0.09 vs 0.97±0.07,6.00±0.45 vs 6.24±0.36,100.4±14.32 vs 89.99±7.94;P均<0.01),Vs、左室射血分数和左室短轴缩短率无显著性差异。结论Ⅲ度房室传导阻滞时,HRVS起搏时,DDD模式较VAT模式使左室舒张功能下降,收缩功能无影响,表明了心房生理性起搏的重要性。
