In the context of global emission reduction, the low-carbon sustainable development of the construction industry has become an important research content. With the vigorous development of new industrial technologies, ...In the context of global emission reduction, the low-carbon sustainable development of the construction industry has become an important research content. With the vigorous development of new industrial technologies, the application of prefabrication technology to buildings had become a mainstream. However, the research on the role of prefabricated technology in reducing building carbon emissions was not yet comprehensive, and the research on the relationship between prefabricated structure types and carbon emissions in the construction stage was not yet thorough. Guided by life cycle assessment (LCA), this paper used the scenario analysis method to set different working conditions for five different structural systems, and used SimaPro software to evaluate the carbon emissions of prefabricated buildings in order to clarify the carbon emissions of prefabricated buildings under different structural systems, and explore their impact mechanisms in depth. Finally, take the existing buildings in China as an empirical study, the results showed that: 1) The carbon emissions produced by the four common prefabricated structural systems were almost the same. Different structures had different requirements for the combination of components. The carbon emissions of individual buildings would be superimposed according to the carbon emission characteristics of various individual components to form the final total carbon emissions. 2) When the building structure system requires more combinations of components, the greater the amount of transportation invested in the transportation process, the more carbon emissions would be caused. In the calculation of all individual building construction stages, the carbon emissions generated by tower cranes almost exceed the sum of the carbon emissions of all mobile machinery. 3) Prefabricated shear wall structures and prefabricated frame-shear wall structures require a large amount of hoisting of prefabricated shear walls, so the carbon emissions of their mechanical equipment were also the highest.展开更多
This paper extends the classical covariant deriva tive to the generalized covariant derivative on curved sur faces. The basement for the extension is similar to the pre vious paper, i.e., the axiom of the covariant fo...This paper extends the classical covariant deriva tive to the generalized covariant derivative on curved sur faces. The basement for the extension is similar to the pre vious paper, i.e., the axiom of the covariant form invariabil ity. Based on the generalized covariant derivative, a covari ant differential transformation group with orthogonal duality is set up. Through such orthogonal duality, tensor analy sis on curved surfaces is simplified intensively. Under the covariant differential transformation group, the differential invariabilities and integral invariabilities are constructed on curved surfaces.展开更多
Nitrogen-15 isotope-modified compounds are widely used in medicine, pharmacology, agriculture and various fields of science and their nomenclature is gradually increasing. Their widespread use depends on the availabil...Nitrogen-15 isotope-modified compounds are widely used in medicine, pharmacology, agriculture and various fields of science and their nomenclature is gradually increasing. Their widespread use depends on the availability of inexpensive and simple isotope analysis methods. The present article is an attempt to determine the nitrogen-15 isotope content directly in organic compounds without their conversion. The general principle of possibility of determination of the isotopes of nitrogen directly in organic compounds is proposed. Based on the study of mass-spectra of Carbamide Carbonyldiamide, isocyanic acid and nitrobenzene the mass peaks are selected, by which it is possible to determine the atomic fraction of the isotopes of nitrogen. The respective formulas are proposed.展开更多
Potassium-ion batteries(PIBs)are considered promising alternatives to lithium-ion batteries owing to cost-effective potassium resources and a suitable redox potential of-2.93 V(vs.-3.04 V for Li+/Li).However,the explo...Potassium-ion batteries(PIBs)are considered promising alternatives to lithium-ion batteries owing to cost-effective potassium resources and a suitable redox potential of-2.93 V(vs.-3.04 V for Li+/Li).However,the exploration of appro-priate electrode materials with the correct size for reversibly accommodating large K+ions presents a significant challenge.In addition,the reaction mecha-nisms and origins of enhanced performance remain elusive.Here,tetragonal FeSe nanoflakes of different sizes are designed to serve as an anode for PIBs,and their live and atomic-scale potassiation/depotassiation mechanisms are revealed for the first time through in situ high-resolution transmission electron micros-copy.We found that FeSe undergoes two distinct structural evolutions,sequen-tially characterized by intercalation and conversion reactions,and the initial intercalation behavior is size-dependent.Apparent expansion induced by the intercalation of K+ions is observed in small-sized FeSe nanoflakes,whereas unexpected cracks are formed along the direction of ionic diffusion in large-sized nanoflakes.The significant stress generation and crack extension originating from the combined effect of mechanical and electrochemical interactions are elucidated by geometric phase analysis and finite-element analysis.Despite the different intercalation behaviors,the formed products of Fe and K_(2)Se after full potassiation can be converted back into the original FeSe phase upon depotassiation.In particular,small-sized nanoflakes exhibit better cycling perfor-mance with well-maintained structural integrity.This article presents the first successful demonstration of atomic-scale visualization that can reveal size-dependent potassiation dynamics.Moreover,it provides valuable guidelines for optimizing the dimensions of electrode materials for advanced PIBs.展开更多
文摘In the context of global emission reduction, the low-carbon sustainable development of the construction industry has become an important research content. With the vigorous development of new industrial technologies, the application of prefabrication technology to buildings had become a mainstream. However, the research on the role of prefabricated technology in reducing building carbon emissions was not yet comprehensive, and the research on the relationship between prefabricated structure types and carbon emissions in the construction stage was not yet thorough. Guided by life cycle assessment (LCA), this paper used the scenario analysis method to set different working conditions for five different structural systems, and used SimaPro software to evaluate the carbon emissions of prefabricated buildings in order to clarify the carbon emissions of prefabricated buildings under different structural systems, and explore their impact mechanisms in depth. Finally, take the existing buildings in China as an empirical study, the results showed that: 1) The carbon emissions produced by the four common prefabricated structural systems were almost the same. Different structures had different requirements for the combination of components. The carbon emissions of individual buildings would be superimposed according to the carbon emission characteristics of various individual components to form the final total carbon emissions. 2) When the building structure system requires more combinations of components, the greater the amount of transportation invested in the transportation process, the more carbon emissions would be caused. In the calculation of all individual building construction stages, the carbon emissions generated by tower cranes almost exceed the sum of the carbon emissions of all mobile machinery. 3) Prefabricated shear wall structures and prefabricated frame-shear wall structures require a large amount of hoisting of prefabricated shear walls, so the carbon emissions of their mechanical equipment were also the highest.
基金supported by the NSFC(11072125 and 11272175)the NSF of Jiangsu Province(SBK201140044)the Specialized Research Fund for Doctoral Program of Higher Education(20130002110044)
文摘This paper extends the classical covariant deriva tive to the generalized covariant derivative on curved sur faces. The basement for the extension is similar to the pre vious paper, i.e., the axiom of the covariant form invariabil ity. Based on the generalized covariant derivative, a covari ant differential transformation group with orthogonal duality is set up. Through such orthogonal duality, tensor analy sis on curved surfaces is simplified intensively. Under the covariant differential transformation group, the differential invariabilities and integral invariabilities are constructed on curved surfaces.
文摘Nitrogen-15 isotope-modified compounds are widely used in medicine, pharmacology, agriculture and various fields of science and their nomenclature is gradually increasing. Their widespread use depends on the availability of inexpensive and simple isotope analysis methods. The present article is an attempt to determine the nitrogen-15 isotope content directly in organic compounds without their conversion. The general principle of possibility of determination of the isotopes of nitrogen directly in organic compounds is proposed. Based on the study of mass-spectra of Carbamide Carbonyldiamide, isocyanic acid and nitrobenzene the mass peaks are selected, by which it is possible to determine the atomic fraction of the isotopes of nitrogen. The respective formulas are proposed.
基金This work was supported by the National Key R&D Program of China(Grant No.2018YFB1304902)the National Natural Science Foundation of China(Grant Nos.12004034,U1813211,22005247,11904372,51502007,52072323,52122211,12174019,and 51972058)+1 种基金the Gen-eral Research Fund of Hong Kong(Project No.11217221)China Postdoctoral Science Foundation Funded Project(Grant No.2021M690386).
文摘Potassium-ion batteries(PIBs)are considered promising alternatives to lithium-ion batteries owing to cost-effective potassium resources and a suitable redox potential of-2.93 V(vs.-3.04 V for Li+/Li).However,the exploration of appro-priate electrode materials with the correct size for reversibly accommodating large K+ions presents a significant challenge.In addition,the reaction mecha-nisms and origins of enhanced performance remain elusive.Here,tetragonal FeSe nanoflakes of different sizes are designed to serve as an anode for PIBs,and their live and atomic-scale potassiation/depotassiation mechanisms are revealed for the first time through in situ high-resolution transmission electron micros-copy.We found that FeSe undergoes two distinct structural evolutions,sequen-tially characterized by intercalation and conversion reactions,and the initial intercalation behavior is size-dependent.Apparent expansion induced by the intercalation of K+ions is observed in small-sized FeSe nanoflakes,whereas unexpected cracks are formed along the direction of ionic diffusion in large-sized nanoflakes.The significant stress generation and crack extension originating from the combined effect of mechanical and electrochemical interactions are elucidated by geometric phase analysis and finite-element analysis.Despite the different intercalation behaviors,the formed products of Fe and K_(2)Se after full potassiation can be converted back into the original FeSe phase upon depotassiation.In particular,small-sized nanoflakes exhibit better cycling perfor-mance with well-maintained structural integrity.This article presents the first successful demonstration of atomic-scale visualization that can reveal size-dependent potassiation dynamics.Moreover,it provides valuable guidelines for optimizing the dimensions of electrode materials for advanced PIBs.
