Metal-nitrogen doped carbon catalysts(M-N/C) with abundantly accessible M-Nxsites, particularly single metal atom M-N/C(SAM-N/C), have been developed as a substitute for expensive Pt-based catalysts.These catalysts ar...Metal-nitrogen doped carbon catalysts(M-N/C) with abundantly accessible M-Nxsites, particularly single metal atom M-N/C(SAM-N/C), have been developed as a substitute for expensive Pt-based catalysts.These catalysts are used to increase the efficiency of otherwise sluggish oxygen reduction reactions(ORR) and hydrogen evolution reactions(HER). However, although the agglomerated metal nanoparticles are usually easy to form, they are very difficult to remove due to the protective surface-coating carbon layers, a factor that significantly hampers SAM-N/C fabrication. Herein, we report a one-step pyrolysis approach to successfully fabricate single cobalt atom Co-N/C(SACo-N/C) by using a Co2+-SCN-coordination compound as the metal precursor. Thanks to the decomposition of Co2+-SCN-compound at lower temperature than that of carbon layer deposition, Co-rich particles grow up to larger ones before carbon layers formation. Even though encapsulated by the carbon layers, it is difficult for the large Co-rich particle to be completely sealed. And thus, it makes the Co atoms possible to escape from incomplete carbon layer, to coordinate with nitrogen atoms, and to form SACo-N/C catalysts. This SACo-N/C exhibits excellent performances for both ORR(half-wave potential of 0.878 V) and HER(overpotential at 10 mA/cm2 of178 m V), and is thus a potential replacement for Pt-based catalysts. When SACo-N/C is integrated into a Zn-O2 battery, battery with high open-circuit voltage(1.536 V) has high peak power density(266 mW/cm2)and large gravimetric energy density(755 mA h/gZn) at current densities of 100 mA/cm2. Thus, we believe that this strategy may offer a new direction for the effective generation of SAM-N/C catalysts.展开更多
A mathematic model has been presented to predict the decarburization kinetics of grain-oriented silicon steel sheet in the gas mixture of N2–H2–H2O during annealing.This model is based on the carbon flux balance bet...A mathematic model has been presented to predict the decarburization kinetics of grain-oriented silicon steel sheet in the gas mixture of N2–H2–H2O during annealing.This model is based on the carbon flux balance between the oxidation reaction at the surface and the carbon diffusion inside the steel sheet.It can be numerically solved to quantify the influences of annealing temperature and atmosphere on decarburization kinetics when the boundary conditions are properly determined.In case that a humid gas mixture is employed during annealing,the most influential process parameter is temperature rather than compositions of the gas mixture,because the diffusion of carbon in ferrite is the rate-limiting step.Therefore,a higher temperature is required for the efficient decarburization of the thicker silicon steel sheet using the industrial continuous annealing production line.展开更多
This paper examines the effects of CFO narcissism on audit fees in China.Using the size of CFO signatures in annual audit reports to measure individual narcissism,we find that CFO narcissism is associated with higher ...This paper examines the effects of CFO narcissism on audit fees in China.Using the size of CFO signatures in annual audit reports to measure individual narcissism,we find that CFO narcissism is associated with higher audit fees.We find empirical evidence that CFO narcissism significantly increases the audit fees of listed companies,and this effect is stronger in state-owned enterprises.This paper also explores the mediating effects of financial information and the engagement of prestigious Big-4 and Big-10 firms.The results show that companies with narcissistic CFOs have lower quality financial information and prefer more prestigious firms,which leads to higher audit fees.This research highlights the importance of CFO narcissism in corporate performance and provides new evidence that will be useful for listed companies that plan to hire senior executives.展开更多
Pelleting is the most extensively used thermal processing method in feed industry.In this article,a single pellet press device was developed to investigate the pelleting processing of animal feed.Effects of moisture c...Pelleting is the most extensively used thermal processing method in feed industry.In this article,a single pellet press device was developed to investigate the pelleting processing of animal feed.Effects of moisture content(10%-18%w.b.),preheating temperature(60°C-100°C)and maximum compression force(0.2-0.6 kN)on feed pellet were determined and analyzed,as well as energy consumption.The results showed that unit density,pellet hardness and energy consumption were 0.87-2.92 g/cm3,1.08-4.55 kg,and 3.27-12.66 J/g,respectively.Unit density was found to increase with the increase of preheating temperature and maximum compression force,but decrease with the increase of moisture content.Pellet hardness showed a first ascending then descending trend with the increase of moisture content,but exhibited a positive relationship with both preheating temperature and maximum compression force.Energy consumption increased with the increase of maximum compression force,but exhibited descending trends with the increase of moisture content and preheating temperature.Due to its features of low cost,high efficiency and easy control,the single pellet press device has a wide application prospect in feed processing.展开更多
基金supported by the National Key Research and Development Program of China(2016YFB0101202)the National Natural Science Foundation of China(21761162015,91534205,21436003)the Fundamental Research Funds for the Central Universities
文摘Metal-nitrogen doped carbon catalysts(M-N/C) with abundantly accessible M-Nxsites, particularly single metal atom M-N/C(SAM-N/C), have been developed as a substitute for expensive Pt-based catalysts.These catalysts are used to increase the efficiency of otherwise sluggish oxygen reduction reactions(ORR) and hydrogen evolution reactions(HER). However, although the agglomerated metal nanoparticles are usually easy to form, they are very difficult to remove due to the protective surface-coating carbon layers, a factor that significantly hampers SAM-N/C fabrication. Herein, we report a one-step pyrolysis approach to successfully fabricate single cobalt atom Co-N/C(SACo-N/C) by using a Co2+-SCN-coordination compound as the metal precursor. Thanks to the decomposition of Co2+-SCN-compound at lower temperature than that of carbon layer deposition, Co-rich particles grow up to larger ones before carbon layers formation. Even though encapsulated by the carbon layers, it is difficult for the large Co-rich particle to be completely sealed. And thus, it makes the Co atoms possible to escape from incomplete carbon layer, to coordinate with nitrogen atoms, and to form SACo-N/C catalysts. This SACo-N/C exhibits excellent performances for both ORR(half-wave potential of 0.878 V) and HER(overpotential at 10 mA/cm2 of178 m V), and is thus a potential replacement for Pt-based catalysts. When SACo-N/C is integrated into a Zn-O2 battery, battery with high open-circuit voltage(1.536 V) has high peak power density(266 mW/cm2)and large gravimetric energy density(755 mA h/gZn) at current densities of 100 mA/cm2. Thus, we believe that this strategy may offer a new direction for the effective generation of SAM-N/C catalysts.
文摘A mathematic model has been presented to predict the decarburization kinetics of grain-oriented silicon steel sheet in the gas mixture of N2–H2–H2O during annealing.This model is based on the carbon flux balance between the oxidation reaction at the surface and the carbon diffusion inside the steel sheet.It can be numerically solved to quantify the influences of annealing temperature and atmosphere on decarburization kinetics when the boundary conditions are properly determined.In case that a humid gas mixture is employed during annealing,the most influential process parameter is temperature rather than compositions of the gas mixture,because the diffusion of carbon in ferrite is the rate-limiting step.Therefore,a higher temperature is required for the efficient decarburization of the thicker silicon steel sheet using the industrial continuous annealing production line.
文摘This paper examines the effects of CFO narcissism on audit fees in China.Using the size of CFO signatures in annual audit reports to measure individual narcissism,we find that CFO narcissism is associated with higher audit fees.We find empirical evidence that CFO narcissism significantly increases the audit fees of listed companies,and this effect is stronger in state-owned enterprises.This paper also explores the mediating effects of financial information and the engagement of prestigious Big-4 and Big-10 firms.The results show that companies with narcissistic CFOs have lower quality financial information and prefer more prestigious firms,which leads to higher audit fees.This research highlights the importance of CFO narcissism in corporate performance and provides new evidence that will be useful for listed companies that plan to hire senior executives.
基金The authors acknowledge that this work was financially supported by the National Natural Science Foundation of China(Grant No.52005012)the Key Laboratory of Environment Controlled Aquaculture(Dalian Ocean University)Ministry of Education(Grant No.202222).
文摘Pelleting is the most extensively used thermal processing method in feed industry.In this article,a single pellet press device was developed to investigate the pelleting processing of animal feed.Effects of moisture content(10%-18%w.b.),preheating temperature(60°C-100°C)and maximum compression force(0.2-0.6 kN)on feed pellet were determined and analyzed,as well as energy consumption.The results showed that unit density,pellet hardness and energy consumption were 0.87-2.92 g/cm3,1.08-4.55 kg,and 3.27-12.66 J/g,respectively.Unit density was found to increase with the increase of preheating temperature and maximum compression force,but decrease with the increase of moisture content.Pellet hardness showed a first ascending then descending trend with the increase of moisture content,but exhibited a positive relationship with both preheating temperature and maximum compression force.Energy consumption increased with the increase of maximum compression force,but exhibited descending trends with the increase of moisture content and preheating temperature.Due to its features of low cost,high efficiency and easy control,the single pellet press device has a wide application prospect in feed processing.
