Based on the nonlocal continuum theory, the nonlinear vibration of an embedded single-walled carbon nanotube （SWCNT） subjected to a harmonic load is in- vestigated. In the present study, the SWCNT is assumed to be a...Based on the nonlocal continuum theory, the nonlinear vibration of an embedded single-walled carbon nanotube （SWCNT） subjected to a harmonic load is in- vestigated. In the present study, the SWCNT is assumed to be a curved beam, which is unlike previous similar work. Firstly, the governing equations of motion are derived by the Hamilton principle, meanwhile, the Galerkin approach is carried out to convert the nonlinear integral-differential equation into a second-order nonlinear ordinary differ- ential equation. Then, the precise integration method based on the local linearzation is appropriately designed for solving the above dynamic equations. Besides, the numerical example is presented, the effects of the nonlocal parameters, the elastic medium constants, the waviness ratios, and the material lengths on the dynamic response are analyzed. The results show that the above mentioned effects have influences on the dynamic behavior of the SWCNT.展开更多
Electrical properties of C/Ni films are studied using four mosaic targets made of pure graphite and stripes of nickel with the surface areas of 1.78,3.21,3.92 and 4.64%.The conductivity data in the temperature range o...Electrical properties of C/Ni films are studied using four mosaic targets made of pure graphite and stripes of nickel with the surface areas of 1.78,3.21,3.92 and 4.64%.The conductivity data in the temperature range of400-500 K shows the extended state conduction.The conductivity data in the temperature range of 150-300 K shows the multi-phonon hopping conduction.The Berthelot-type conduction dominates in the temperature range of 50-150 K.The conductivity of the films in the temperature range about 〈 50 K is described in terms of variable-range hopping conduction.In low temperatures,the localized density of state around Fermi level（F）for the film deposition with 3.92% nickel has a maximum value of about 56.2×10^（17）cm^（-3）eV^（-1） with the minimum average hopping distance of about 3.43 × 10^（-6） cm.展开更多
Although currently,a large part of the existing buildings is considered inefficient in terms of energy,the ability to save energy consumption up to 80%has been proven in residential and commercial buildings.Also,carbo...Although currently,a large part of the existing buildings is considered inefficient in terms of energy,the ability to save energy consumption up to 80%has been proven in residential and commercial buildings.Also,carbon dioxide is one of the most important greenhouse gases contributing to climate change and is responsible for 60%of global warming.The facade of the building,as the main intermediary between the interior and exterior spaces,plays a significant role in adjusting the weather conditions and providing thermal comfort to the residents.In this research,715 different scenarios were defined with the combination of various types of construction materials,and the effect of each of these scenarios on the process of energy loss from the surface of the external walls of the building during the operation period was determined.In the end,these scenarios were compared during a one-year operation period,and the amount of energy consumption in each of these scenarios was calculated.Also,bymeasuring the amount of carbon emissions in buildings during the operation period and before that,let’s look at practical methods to reduce the effects of the construction industry on the environment.By comparing the research findings,it can be seen that the ranking of each scenario in terms of total energy consumption is not necessarily the same as the ranking of energy consumption for gas consumption or electricity consumption for the same scenario.That is,choosing the optimal scenario depends on the type of energy consumed in the building.Finally,we determined the scenarios with the lowest and highest amounts of embodied and operational carbon.In the end,we obtained the latent carbon compensation period for each scenario.This article can help designers and construction engineers optimize the energy consumption of buildings by deciding on the right materials.展开更多
The catalytic reductive amination of biomass-derived carbonyl compounds into value-added primary amines has attracted significant attention in renewable biomass upgrading.Herein,highly dispersed Ru cluster-embedded ni...The catalytic reductive amination of biomass-derived carbonyl compounds into value-added primary amines has attracted significant attention in renewable biomass upgrading.Herein,highly dispersed Ru cluster-embedded nitrogen-doped hollow carbon sphere(Ru@NHCS)catalysts were constructed,which achieved a 100%furfurylamine(FUA)yield,and exhibited a superior initial reaction rate of 3745.7 mmol gRu−1 h^(−1)and a turnover frequency of 378.58 h^(−1)in the reductive amination of biomass-derived furfural.Systematic structural characterization indicated that the presence of abundant N species promoted the uniform dispersion of Ru clusters and induced electronic metal-support interaction(EMSI)between Ru and the NHCS support,thus leading to the formation of bifunctional Ru^(0)and Ru^(δ+)active sites.The structure-activity relationship study demonstrated that the synergistic catalysis of Ru^(0)and Ru^(δ+)active sites effectively promoted the adsorption and activation of H_(2)and NH_(3)molecules,and accelerated the hydrogenation of imines and the ammonolysis of Schiff base intermediates,thereby achieving the highly selective synthesis of FUA under mild reaction conditions.Moreover,the Ru@NHCS catalyst exhibited excellent catalytic stability over five consecutive cycles and showed wide substrate applicability for the synthesis of valuable primary amines.This work not only unveils rational design strategies for developing efficient and stable metal catalysts to achieve the highly selective synthesis of value-added primary amines but also provides essential theoretical guidance for efficient biomass conversion.展开更多
In order to enhance performance of pre-cast shapes of alumina based castables, the present work explored the approach of forming in-situ bonding phases by incorporating Si powders and then heating in carbon, embedded ...In order to enhance performance of pre-cast shapes of alumina based castables, the present work explored the approach of forming in-situ bonding phases by incorporating Si powders and then heating in carbon, embedded atmosphere. Using tabular alumina as aggregates, tabular alumina, SiC powders, Si powders, calcium aluminate cenwnt, microsilica and ultrafine α-A12 03 powders as matrix, alumina based ultra low cement （ULC） castables were prepared. Influences of Si powder addition at O, 4% , 6% , 8% alul 10% （in nutss ） on regular properties, cold modulus of rupture （CMOR）, hot modulus of rupture （HMOR）, thermal shock resistance （TSR） and microstructure of the castables after carbonization were investigated. After incorporation of Si powders and carbon embedded heating, the in-situ mullite and nonoxide phases such as SiAION and SiC can be fornwd by oxidation, nitridation or carbomlzation reaction. HMOR and TSR of the castables with in-situ nonoxides bonding are obviously improted. After carbon embedded heating, the HMOR at 1 400 ℃ increases from 1.6 MPa to 8. 3 MPa, and the residual CMOR ratio after thermal shock increases from 64. 9% to 137. 9% when Si addition increases from 0 to 10%.展开更多
Molybdenum sulfide(MoS_(2))with a high theoretical capacity and large interlayer distance has triggered extensive attention as a promising alternative anode for lithium ion batteries(LIBs)and sodium ion batteries(SIBs...Molybdenum sulfide(MoS_(2))with a high theoretical capacity and large interlayer distance has triggered extensive attention as a promising alternative anode for lithium ion batteries(LIBs)and sodium ion batteries(SIBs).However,the sluggish kinetics and structural collapse induced by its poor conductivity usually lead to unsatisfactory rate capability and poor cycling performance.Herein,few-layered MoS_(2) with abundant S vacancies were anchored on V_(2)C-MXene and embedded in carbon via an in situ assembly and carbonization strategy.The V_(2)C-MXene substrate suppressed the agglomeration and stacking of MoS_(2) nanosheets,facilitated the efficient exposure of MoS_(2) and shortened the diffusion pathways,which favored ion accessibility and induced a strong capacitive-controlled charge storage behavior.Experimental results and theoretical calculations revealed that the electronic coupling between MoS_(2) and V_(2)C-MXene not only induced abundant S vacancies and modulated the charge distribution but also promoted Li/Na adsorption and lowered the ion diffusion energy barrier.Consequently,the V_(2)C-MXene coupled MoS_(2)@C electrode delivered high capacities of 732.8 and 337.3 mA h g^(-1) at 1 A g^(-1) in LIBs and SIBs,respectively.This work provided a new insight into the rational design of stable and advanced electrode materials for energy storage and conversion.展开更多
基金Project supported by the National Basic Research Program of China (No. 2011CB610300)the National Natural Science Foundation of China (Nos. 10972182, 11172239, and 10902089)+3 种基金the 111 Project of China (No. B07050)the Ph. D. Programs Foundation of Ministry of Education of China (No. 20106102110019)the Open Foundation of State Key Laboratory of Structural Analysis of Industrial Equipment (No. GZ0802)the Doctorate Foundation of Northwestern Polytechnical University (No. CX201224)
文摘Based on the nonlocal continuum theory, the nonlinear vibration of an embedded single-walled carbon nanotube （SWCNT） subjected to a harmonic load is in- vestigated. In the present study, the SWCNT is assumed to be a curved beam, which is unlike previous similar work. Firstly, the governing equations of motion are derived by the Hamilton principle, meanwhile, the Galerkin approach is carried out to convert the nonlinear integral-differential equation into a second-order nonlinear ordinary differ- ential equation. Then, the precise integration method based on the local linearzation is appropriately designed for solving the above dynamic equations. Besides, the numerical example is presented, the effects of the nonlocal parameters, the elastic medium constants, the waviness ratios, and the material lengths on the dynamic response are analyzed. The results show that the above mentioned effects have influences on the dynamic behavior of the SWCNT.
文摘Electrical properties of C/Ni films are studied using four mosaic targets made of pure graphite and stripes of nickel with the surface areas of 1.78,3.21,3.92 and 4.64%.The conductivity data in the temperature range of400-500 K shows the extended state conduction.The conductivity data in the temperature range of 150-300 K shows the multi-phonon hopping conduction.The Berthelot-type conduction dominates in the temperature range of 50-150 K.The conductivity of the films in the temperature range about 〈 50 K is described in terms of variable-range hopping conduction.In low temperatures,the localized density of state around Fermi level（F）for the film deposition with 3.92% nickel has a maximum value of about 56.2×10^（17）cm^（-3）eV^（-1） with the minimum average hopping distance of about 3.43 × 10^（-6） cm.
文摘Although currently,a large part of the existing buildings is considered inefficient in terms of energy,the ability to save energy consumption up to 80%has been proven in residential and commercial buildings.Also,carbon dioxide is one of the most important greenhouse gases contributing to climate change and is responsible for 60%of global warming.The facade of the building,as the main intermediary between the interior and exterior spaces,plays a significant role in adjusting the weather conditions and providing thermal comfort to the residents.In this research,715 different scenarios were defined with the combination of various types of construction materials,and the effect of each of these scenarios on the process of energy loss from the surface of the external walls of the building during the operation period was determined.In the end,these scenarios were compared during a one-year operation period,and the amount of energy consumption in each of these scenarios was calculated.Also,bymeasuring the amount of carbon emissions in buildings during the operation period and before that,let’s look at practical methods to reduce the effects of the construction industry on the environment.By comparing the research findings,it can be seen that the ranking of each scenario in terms of total energy consumption is not necessarily the same as the ranking of energy consumption for gas consumption or electricity consumption for the same scenario.That is,choosing the optimal scenario depends on the type of energy consumed in the building.Finally,we determined the scenarios with the lowest and highest amounts of embodied and operational carbon.In the end,we obtained the latent carbon compensation period for each scenario.This article can help designers and construction engineers optimize the energy consumption of buildings by deciding on the right materials.
基金supported by the National Natural Science Foundation of China(21902094)the China Postdoctoral Science Foundation(2020M683405)the Natural Science Foundation of Shaanxi Province(2023-JC-QN-0103).
文摘The catalytic reductive amination of biomass-derived carbonyl compounds into value-added primary amines has attracted significant attention in renewable biomass upgrading.Herein,highly dispersed Ru cluster-embedded nitrogen-doped hollow carbon sphere(Ru@NHCS)catalysts were constructed,which achieved a 100%furfurylamine(FUA)yield,and exhibited a superior initial reaction rate of 3745.7 mmol gRu−1 h^(−1)and a turnover frequency of 378.58 h^(−1)in the reductive amination of biomass-derived furfural.Systematic structural characterization indicated that the presence of abundant N species promoted the uniform dispersion of Ru clusters and induced electronic metal-support interaction(EMSI)between Ru and the NHCS support,thus leading to the formation of bifunctional Ru^(0)and Ru^(δ+)active sites.The structure-activity relationship study demonstrated that the synergistic catalysis of Ru^(0)and Ru^(δ+)active sites effectively promoted the adsorption and activation of H_(2)and NH_(3)molecules,and accelerated the hydrogenation of imines and the ammonolysis of Schiff base intermediates,thereby achieving the highly selective synthesis of FUA under mild reaction conditions.Moreover,the Ru@NHCS catalyst exhibited excellent catalytic stability over five consecutive cycles and showed wide substrate applicability for the synthesis of valuable primary amines.This work not only unveils rational design strategies for developing efficient and stable metal catalysts to achieve the highly selective synthesis of value-added primary amines but also provides essential theoretical guidance for efficient biomass conversion.
文摘In order to enhance performance of pre-cast shapes of alumina based castables, the present work explored the approach of forming in-situ bonding phases by incorporating Si powders and then heating in carbon, embedded atmosphere. Using tabular alumina as aggregates, tabular alumina, SiC powders, Si powders, calcium aluminate cenwnt, microsilica and ultrafine α-A12 03 powders as matrix, alumina based ultra low cement （ULC） castables were prepared. Influences of Si powder addition at O, 4% , 6% , 8% alul 10% （in nutss ） on regular properties, cold modulus of rupture （CMOR）, hot modulus of rupture （HMOR）, thermal shock resistance （TSR） and microstructure of the castables after carbonization were investigated. After incorporation of Si powders and carbon embedded heating, the in-situ mullite and nonoxide phases such as SiAION and SiC can be fornwd by oxidation, nitridation or carbomlzation reaction. HMOR and TSR of the castables with in-situ nonoxides bonding are obviously improted. After carbon embedded heating, the HMOR at 1 400 ℃ increases from 1.6 MPa to 8. 3 MPa, and the residual CMOR ratio after thermal shock increases from 64. 9% to 137. 9% when Si addition increases from 0 to 10%.
基金supported by the Natural Science Foundation of China[Grant Number 51904152 and 42002040]the Program for Science&Technology Innovation Talents in Universities of Henan Province[Grant Number 20HASTIT020]+2 种基金the Young Backbone Teachers Training Plan of Henan Province,the Natural Science Foundation of Henan Province[Grant Number 222300420502]the Key Science and Technology Program of Henan Province[Grant Number 222102240044]the Key Scientific Research Projects in Colleges and Universities of Henan Province[Grant Number 21B610010].
文摘Molybdenum sulfide(MoS_(2))with a high theoretical capacity and large interlayer distance has triggered extensive attention as a promising alternative anode for lithium ion batteries(LIBs)and sodium ion batteries(SIBs).However,the sluggish kinetics and structural collapse induced by its poor conductivity usually lead to unsatisfactory rate capability and poor cycling performance.Herein,few-layered MoS_(2) with abundant S vacancies were anchored on V_(2)C-MXene and embedded in carbon via an in situ assembly and carbonization strategy.The V_(2)C-MXene substrate suppressed the agglomeration and stacking of MoS_(2) nanosheets,facilitated the efficient exposure of MoS_(2) and shortened the diffusion pathways,which favored ion accessibility and induced a strong capacitive-controlled charge storage behavior.Experimental results and theoretical calculations revealed that the electronic coupling between MoS_(2) and V_(2)C-MXene not only induced abundant S vacancies and modulated the charge distribution but also promoted Li/Na adsorption and lowered the ion diffusion energy barrier.Consequently,the V_(2)C-MXene coupled MoS_(2)@C electrode delivered high capacities of 732.8 and 337.3 mA h g^(-1) at 1 A g^(-1) in LIBs and SIBs,respectively.This work provided a new insight into the rational design of stable and advanced electrode materials for energy storage and conversion.
