Space exploration has become a major focus in the field of technology,with gear transmissions in aerospace equipment playing a crucial role.In the extreme environment of space,gear transmissions face challenges like l...Space exploration has become a major focus in the field of technology,with gear transmissions in aerospace equipment playing a crucial role.In the extreme environment of space,gear transmissions face challenges like large temperature differentials,deformation and maintenance difficulties,which will severely impact transmission accuracy and service life.To meet the growing demands for high-performance gear transmissions with high transmission efficiency and error adaptability in the aerospace field,this paper proposes a novel curve-surface conjugate internal gear drive consisting of an involute internal gear and a curve-surface gear.The fundamental theory of curve-surface conjugation is introduced,and the construction method for curve-surface gear based on a selected contact path and meshing tube is presented.The analysis models including induced curvature,sliding ratio and tooth contact analysis with errors(ETCA)are simulated to evaluate the meshing characteristics.Additionally,prototypes are manufactured and experimental setups are established to validate the transmission performance.These results indicate that as the rotational speed increases,the transmission efficiency of the curve-surface conjugate internal gear drive improves,which is contrary to the trend observed in involute gear drives.And the transmission efficiency of the curve-surface conjugate internal gear drive surpasses that of the involute gear drive at higher rotational speeds.Moreover,this novel gear drive exhibits excellent error adaptability,maintaining intact contact paths and high transmission efficiency even in the presence of assembly errors.This study provides new ideas for the design and manufacture of high-performance gear transmissions from the perspective of spatial geometric elements.展开更多
Cadmium （Cd） entering the human body via the food chain is of increasing concern. This study investigates the effects of soil type and genotype on variations in the Cd concentrations of different organs of nine rice...Cadmium （Cd） entering the human body via the food chain is of increasing concern. This study investigates the effects of soil type and genotype on variations in the Cd concentrations of different organs of nine rice plants grown on two types of soils with two Cd levels. Cd concentrations in nine rice cultivars varied significantly with genotype and soil type （P 〈 0.01）. The Cd concentration was higher in red paddy soil （RP） than in yellow clayey paddy soil （YP）. The average Cd concentrations of different organs in three rice types were indica 〉 hybrid 〉 japonica for the Cd treatments and controls. The polished grain concentration in YP and RP soils had a range of 0.055--0.23 mg/kg and 0.13-0.36 mg/kg in the Cd treatment, respectively. Two rice cultivars in YP soil and five rice cultivars in RP soil exceeded the concentration limits in the Chinese Food Hygiene Standard （0.2 mg/kg）. The Cd concentrations in roots, stems, and leaves were all significantly and positively correlated to that in polished grain in a single test. The Cd concentrations in polished grain were positively and significantly （P 〈 0.01） correlated with the calculated transfer factors of stem to grain and leaf to grain Cd transfer. The results indicated that the variations of Cd concentration in grain were related to Cd uptake and the remobilization of Cd from stem and leaf to grain. Also, the cultivars with a strong tendency for Cd-accumulation should be avoided in paddy soil with low soil pH and low organic matter content to reduce the risks to human health from high Cd levels in rice.展开更多
Hydroxyapatite（HAP） has been widely used to immobilize many cationic metals in water and soils. The specific reason why an increase in the surface area of HAP enhances cadmium（Cd） uptake, but has no effect on lead...Hydroxyapatite（HAP） has been widely used to immobilize many cationic metals in water and soils. The specific reason why an increase in the surface area of HAP enhances cadmium（Cd） uptake, but has no effect on lead（Pb） uptake, is not clear. The aim of this study was to determine the factors causing the differences in sorption behavior between Cd and Pb by evaluating HAPs with different surface areas. We synthesized HAPs with two different surface areas, which were characterized by X-ray diffraction, N2 adsorption, and scanning electron microscopy, and then evaluated them as sorbents for Cd and Pb removal by testing in single and binary systems. The sorption capacity of large surface area HAP（1.85 mmol/g） for Cd in the single-metal system was higher than that of small surface area HAP（0.64 mmol/g）, but there were no differences between single- and binary-metal solutions containing Pb. After the Cd experiments, the HAP retained a stable structure and intact morphology, which promotes the accessibility of reactive sites for Cd. However, a newly formed precipitate covered the surface and blocked the channels in the presence of Pb, which reduced the number of potential adsorption sites on HAP for Cd and Pb.Remediation experiments using Cd- and Pb-contaminated soil produced similar results to the solution tests. These results indicate that alterations of the structure and morphology during the reaction is an important factor influencing metal sorption to HAP.展开更多
Combining the H2 production with brine remediation is regarded as a sustainable approach to achieving clean H2 energy. However, designing stable Cl− oxidation reaction (COR) electrocatalyst is the key to realize this ...Combining the H2 production with brine remediation is regarded as a sustainable approach to achieving clean H2 energy. However, designing stable Cl− oxidation reaction (COR) electrocatalyst is the key to realize this route. Herein, a type of oxygen-modified Co nanoparticles anchored graphitic carbon nanofibers catalyst (Co/GCFs) was synthesized through a two-step strategy of adsorption and pyrolysis. The Co/GCFs-2.4 exhibits high selectivity and stability for COR at neutral electrolyte. It is worth noting that unlike the water oxidation, the chemical valence of cobalt has not changed during the COR. Further results demonstrated that the oxygen-modified Co nanoparticles provide active sites for selective COR, meanwhile, the graphitic carbon gives rise to strong catalytic stability. Thanks to the superior COR and H2 production activity of Co/GCFs-2.4, a two-electrode brine electrocatalysis system employing Co/GCFs-2.4 as both cathode and anode for H2 production exhibited robust stability, efficient and high Faraday efficiency (98%-100%). We propose that this work provides a novel strategy for designing efficient and stable catalysts with electrocatalytic COR and HER activities at neutral brine water for practically coupling with H2 production by water electrolysis and brine water remediation.展开更多
Herein,a Fe^(3+)-loaded aminated polypropylene fiber has been reported as an efficient phosphate adsorbent.The remarkable phosphate removal ability of the fiber is due to Fe^(3+)immobilization,and it demonstrates a ma...Herein,a Fe^(3+)-loaded aminated polypropylene fiber has been reported as an efficient phosphate adsorbent.The remarkable phosphate removal ability of the fiber is due to Fe^(3+)immobilization,and it demonstrates a maximum adsorption capacity of 33.94 mg·P·g^(–1).Adsorption experiments showed that the fiber is applicable over a wide pH range from 2 to 9.Furthermore,the adsorption kinetics and isotherm data were consistent with the pseudo-second-order and Langmuir adsorption models,respectively.The adsorption equilibrium of the fiber for phosphate was reached within 60 min,indicating an efficient monolayer chemisorption process.Moreover,the adsorbent maintained prominent phosphate removal in the presence of competitive ions such as NO_(3)^(–)and Cl^(–),exhibiting high selectivity.More importantly,the fiber demonstrated excellent reusability(5 times)and low adsorption limit below 0.02 mg·P·g^(–1).In addition,the phosphate removal efficiency of the fiber can exceed 99%under continuous flow conditions.The adsorption mechanism was studied by X-ray photoelectron spectroscopy,showing that the adsorption of phosphate on the fiber mainly depended on the chemical adsorption of the modified Fe^(3+).Overall,this study proves that the fiber possesses many advantages for phosphate removal,including high adsorption efficiency,lower treatment limit,good recyclability,and environmental friendliness.展开更多
A facile method for preparing hollow mesoporous carbon nitride microspheres(HMCNMs)has been developed.A cya namide/ethanol solution was used as a precursor,with ethanol acting as both a solve nt and a porogen,to prepa...A facile method for preparing hollow mesoporous carbon nitride microspheres(HMCNMs)has been developed.A cya namide/ethanol solution was used as a precursor,with ethanol acting as both a solve nt and a porogen,to prepare HMCNMs with a high surface area of 112 m^2/g.It was demonstrated that the HMCNM microstructure and surface morphology can be controlled by adjusting the proportion of ethanol in the precursor solution.The resulting HMCNMs exhibited much higher visible light photocatalytic degradative activity toward methylene blue than bulk graphitic carbon nitride.展开更多
基金Supported by Major Projects in Aviation Engines and Gas Turbines(Grant No.J2019-IV-0001-0068).
文摘Space exploration has become a major focus in the field of technology,with gear transmissions in aerospace equipment playing a crucial role.In the extreme environment of space,gear transmissions face challenges like large temperature differentials,deformation and maintenance difficulties,which will severely impact transmission accuracy and service life.To meet the growing demands for high-performance gear transmissions with high transmission efficiency and error adaptability in the aerospace field,this paper proposes a novel curve-surface conjugate internal gear drive consisting of an involute internal gear and a curve-surface gear.The fundamental theory of curve-surface conjugation is introduced,and the construction method for curve-surface gear based on a selected contact path and meshing tube is presented.The analysis models including induced curvature,sliding ratio and tooth contact analysis with errors(ETCA)are simulated to evaluate the meshing characteristics.Additionally,prototypes are manufactured and experimental setups are established to validate the transmission performance.These results indicate that as the rotational speed increases,the transmission efficiency of the curve-surface conjugate internal gear drive improves,which is contrary to the trend observed in involute gear drives.And the transmission efficiency of the curve-surface conjugate internal gear drive surpasses that of the involute gear drive at higher rotational speeds.Moreover,this novel gear drive exhibits excellent error adaptability,maintaining intact contact paths and high transmission efficiency even in the presence of assembly errors.This study provides new ideas for the design and manufacture of high-performance gear transmissions from the perspective of spatial geometric elements.
基金supported by the Special Funds for Agroscientific Research (No. 200903015)the Quality Supervision Scientific Research (No. 200910201) in the public interest
文摘Cadmium （Cd） entering the human body via the food chain is of increasing concern. This study investigates the effects of soil type and genotype on variations in the Cd concentrations of different organs of nine rice plants grown on two types of soils with two Cd levels. Cd concentrations in nine rice cultivars varied significantly with genotype and soil type （P 〈 0.01）. The Cd concentration was higher in red paddy soil （RP） than in yellow clayey paddy soil （YP）. The average Cd concentrations of different organs in three rice types were indica 〉 hybrid 〉 japonica for the Cd treatments and controls. The polished grain concentration in YP and RP soils had a range of 0.055--0.23 mg/kg and 0.13-0.36 mg/kg in the Cd treatment, respectively. Two rice cultivars in YP soil and five rice cultivars in RP soil exceeded the concentration limits in the Chinese Food Hygiene Standard （0.2 mg/kg）. The Cd concentrations in roots, stems, and leaves were all significantly and positively correlated to that in polished grain in a single test. The Cd concentrations in polished grain were positively and significantly （P 〈 0.01） correlated with the calculated transfer factors of stem to grain and leaf to grain Cd transfer. The results indicated that the variations of Cd concentration in grain were related to Cd uptake and the remobilization of Cd from stem and leaf to grain. Also, the cultivars with a strong tendency for Cd-accumulation should be avoided in paddy soil with low soil pH and low organic matter content to reduce the risks to human health from high Cd levels in rice.
基金supported by the National Natural Science Foundation of China(No.41301347)the Anhui Provincial Natural Science Foundation(No.1408085MKL61)+1 种基金the Scientific and Technical Key Research Program of Auhui(No.1501031088)the Natural Science Foundation of Anhui Academy of Agricultural Sciences(No.16A1029)
文摘Hydroxyapatite（HAP） has been widely used to immobilize many cationic metals in water and soils. The specific reason why an increase in the surface area of HAP enhances cadmium（Cd） uptake, but has no effect on lead（Pb） uptake, is not clear. The aim of this study was to determine the factors causing the differences in sorption behavior between Cd and Pb by evaluating HAPs with different surface areas. We synthesized HAPs with two different surface areas, which were characterized by X-ray diffraction, N2 adsorption, and scanning electron microscopy, and then evaluated them as sorbents for Cd and Pb removal by testing in single and binary systems. The sorption capacity of large surface area HAP（1.85 mmol/g） for Cd in the single-metal system was higher than that of small surface area HAP（0.64 mmol/g）, but there were no differences between single- and binary-metal solutions containing Pb. After the Cd experiments, the HAP retained a stable structure and intact morphology, which promotes the accessibility of reactive sites for Cd. However, a newly formed precipitate covered the surface and blocked the channels in the presence of Pb, which reduced the number of potential adsorption sites on HAP for Cd and Pb.Remediation experiments using Cd- and Pb-contaminated soil produced similar results to the solution tests. These results indicate that alterations of the structure and morphology during the reaction is an important factor influencing metal sorption to HAP.
基金This work was financially supported by the National Natural Science Foundation of China(No.51902312)Natural Science Foundation of Anhui Province(Nos.1908085QC139 and 1908085QB83)+4 种基金the Youth Science Fund of Anhui Agricultural University(No.2018zd25)the Science Foundation for Distinguished Young Scholars of Anhui Province(No.2008085J13)the Key research and development Project of Anhui Province(No.1804h07020148)the Fundamental Research Funds for the Central Universities(Nos.JZ2019HGBH0204 and PA2019GDPK0061)The authors thank the 1W1B station for XAFS measurement in Beijing Synchrotron Radiation Facility.
文摘Combining the H2 production with brine remediation is regarded as a sustainable approach to achieving clean H2 energy. However, designing stable Cl− oxidation reaction (COR) electrocatalyst is the key to realize this route. Herein, a type of oxygen-modified Co nanoparticles anchored graphitic carbon nanofibers catalyst (Co/GCFs) was synthesized through a two-step strategy of adsorption and pyrolysis. The Co/GCFs-2.4 exhibits high selectivity and stability for COR at neutral electrolyte. It is worth noting that unlike the water oxidation, the chemical valence of cobalt has not changed during the COR. Further results demonstrated that the oxygen-modified Co nanoparticles provide active sites for selective COR, meanwhile, the graphitic carbon gives rise to strong catalytic stability. Thanks to the superior COR and H2 production activity of Co/GCFs-2.4, a two-electrode brine electrocatalysis system employing Co/GCFs-2.4 as both cathode and anode for H2 production exhibited robust stability, efficient and high Faraday efficiency (98%-100%). We propose that this work provides a novel strategy for designing efficient and stable catalysts with electrocatalytic COR and HER activities at neutral brine water for practically coupling with H2 production by water electrolysis and brine water remediation.
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.22208003)Natural Science Foundation of Anhui Province(No.1908085QB87)Major Science and Technology Projects in Anhui Province(No.202103a06020012).
文摘Herein,a Fe^(3+)-loaded aminated polypropylene fiber has been reported as an efficient phosphate adsorbent.The remarkable phosphate removal ability of the fiber is due to Fe^(3+)immobilization,and it demonstrates a maximum adsorption capacity of 33.94 mg·P·g^(–1).Adsorption experiments showed that the fiber is applicable over a wide pH range from 2 to 9.Furthermore,the adsorption kinetics and isotherm data were consistent with the pseudo-second-order and Langmuir adsorption models,respectively.The adsorption equilibrium of the fiber for phosphate was reached within 60 min,indicating an efficient monolayer chemisorption process.Moreover,the adsorbent maintained prominent phosphate removal in the presence of competitive ions such as NO_(3)^(–)and Cl^(–),exhibiting high selectivity.More importantly,the fiber demonstrated excellent reusability(5 times)and low adsorption limit below 0.02 mg·P·g^(–1).In addition,the phosphate removal efficiency of the fiber can exceed 99%under continuous flow conditions.The adsorption mechanism was studied by X-ray photoelectron spectroscopy,showing that the adsorption of phosphate on the fiber mainly depended on the chemical adsorption of the modified Fe^(3+).Overall,this study proves that the fiber possesses many advantages for phosphate removal,including high adsorption efficiency,lower treatment limit,good recyclability,and environmental friendliness.
基金the Natural Science Foundation of Tianjin(18JCYBJC89200)the PetroChina Innovation Foundation(2018D-5007-0502,2016D-5007-0502)the Project from Tianjin Education Commission(2017KJ018,2017KJ017).
文摘A facile method for preparing hollow mesoporous carbon nitride microspheres(HMCNMs)has been developed.A cya namide/ethanol solution was used as a precursor,with ethanol acting as both a solve nt and a porogen,to prepare HMCNMs with a high surface area of 112 m^2/g.It was demonstrated that the HMCNM microstructure and surface morphology can be controlled by adjusting the proportion of ethanol in the precursor solution.The resulting HMCNMs exhibited much higher visible light photocatalytic degradative activity toward methylene blue than bulk graphitic carbon nitride.
