Proton exchange membrane fuel cells(PEMFCs)constitute a promising avenue for environmentally friendly power generation.However,the reliance on unsustainable platinum-based electrocatalysts used at the electrodes poses...Proton exchange membrane fuel cells(PEMFCs)constitute a promising avenue for environmentally friendly power generation.However,the reliance on unsustainable platinum-based electrocatalysts used at the electrodes poses challenges to the commercial viability of PEMFCs.Non-platinum group metal(non-PGM)alternatives,like nitrogen-coordinated transition metals in atomic dispersion(M–N–C catalysts),show significant potential.This work presents a comparative study of two distinct sets of Fe–N–C materials,prepared by pyrolyzing hybrid composites of polyaniline(PANI)and iron(Ⅱ)chloride on a hard template.One set uses bipyridine(BPy)as an additional nitrogen source and iron ligand,offering an innovative approach.The findings reveal that the choice of pyrolysis temperature and atmosphere influences the catalyst properties.The use of ammonia in pyrolysis emerges as a crucial parameter for promoting atomic dispersion of iron,as well as increasing surface area and porosity.The optimal catalyst,prepared using BPy and ammonia,exhibits a half-wave potential of 0.834 V in 0.5 M H_(2)SO_(4)(catalyst loading of 0.6 mg cm^(-2)),a mass activity exceeding 3 A g^(-1)and high stability in acidic electrolyte,positioning it as a promising non-PGM structure in the field.展开更多
The variations in the mechanical and magnetic properties of cold-rolled 20Mn23AlV non-magnetic structural steel after annealing at different temperatures were investigated.The microstructure and precipitation changes ...The variations in the mechanical and magnetic properties of cold-rolled 20Mn23AlV non-magnetic structural steel after annealing at different temperatures were investigated.The microstructure and precipitation changes during annealing were studied by optical microscopy,scanning electron microscopy,and transmission electron microscopy.The results show that recrystallization completed after annealing at 620℃,resulting in grain sizes of approximately 800 nm and the best combination of strength and plasticity.The yield-to-tensile ratio of the non-magnetic structural steel after cold rolling continuously decreases from low to high temperatures after annealing,with the highest value being 0.89 and the lowest value being 0.43,indicating a wide range of yield-to-tensile ratio adjustment.The introduction of numerous dislocations during cold rolling provided favorable nucleation sites for precipitation,leading to abundant precipitation of the fine second-phase V(C,N).The phase composition of the samples remained unchanged as single-phase austenite after annealing,and the relative permeability values were calculated to be less than 1.002,meeting the requirements for non-magnetic steel in terms of magnetic properties.展开更多
研究了微肋管内R407C和R22的流动沸腾换热特性,采用威尔逊图解法对实验数据进行处理,主要分析实验工况、制冷剂物性、微肋管结构等变量的影响。结果表明:制冷剂R407C与R22与换热壁面之间的换热热阻均随热流密度、质流密度、干度、肋片...研究了微肋管内R407C和R22的流动沸腾换热特性,采用威尔逊图解法对实验数据进行处理,主要分析实验工况、制冷剂物性、微肋管结构等变量的影响。结果表明:制冷剂R407C与R22与换热壁面之间的换热热阻均随热流密度、质流密度、干度、肋片螺旋角等的增加而减小;由于制冷剂气液相密度比的差异性,R22传热系数比与R407C的高约18.5%—21.4%。选用关联式对微肋管内R407C流动沸腾换热特性进行预测评估,并对关联式预测精度随干度、质流密度等的变化趋势进行分析。在所选关联式内,Yu and Koyama关联式表现出最佳预测效果,其平均预测误差在±6.5%以内,且干度、质流密度对其预测精度的影响相近;而对于其它关联式,干度对关联式预测精度的影响比重普遍高于质流密度。展开更多
Mo_(2)C is an excellent electrocatalyst for hydrogen evolution reaction(HER).However,Mo_(2)C is a poor electrocatalyst for oxygen evolution reaction(OER).Herein,two different elements,namely Co and Fe,are incorporated...Mo_(2)C is an excellent electrocatalyst for hydrogen evolution reaction(HER).However,Mo_(2)C is a poor electrocatalyst for oxygen evolution reaction(OER).Herein,two different elements,namely Co and Fe,are incorporated in Mo_(2)C that,therefore,has a finely tuned electronic structure,which is not achievable by incorporation of any one of the metals.Consequently,the resulting electrocatalyst Co_(0.8)Fe_(0.2)-Mo_(2)C-80 displayed excellent OER catalytic performance,which is evidenced by a low overpotential of 214.0(and 246.5)mV to attain a current density of 10(and 50)mA cm^(-2),an ultralow Tafel slope of 38.4 mV dec^(-1),and longterm stability in alkaline medium.Theoretical data demonstrates that Co_(0.8)Fe_(0.2)-Mo_(2)C-80 requires the lowest overpotential(1.00 V)for OER and Co centers to be the active sites.The ultrahigh catalytic performance of the electrocatalyst is attributed to the excellent intrinsic catalytic activity due to high Brunauer-Emmett-Teller specific surface area,large electrochemically active surface area,small Tafel slope,and low chargetransfer resistance.展开更多
Intensive management is known to markedly alter soil carbon(C)storage and turnover in Moso bamboo forests compared with extensive management.However,the effects of intensive management on soil respiration(RS)component...Intensive management is known to markedly alter soil carbon(C)storage and turnover in Moso bamboo forests compared with extensive management.However,the effects of intensive management on soil respiration(RS)components remain unclear.This study aimed to evaluate the changes in different RScomponents(root,mycorrhizal,and free-living microorganism respiration)in Moso bamboo forests under extensive and intensive management practices.A1-year in-situ microcosm experiment was conducted to quantify the RScomponents in Moso bamboo forests under the two management practices using mesh screens of varying sizes.The results showed that the total RSand its components exhibited similar seasonal variability between the two management practices.Compared with extensive management,intensive management significantly increased cumulative respiration from mycorrhizal fungi by 36.73%,while decreased cumulative respiration from free-living soil microorganisms by 8.97%.Moreover,the abundance of arbuscular mycorrhizal fungi(AMF)increased by 43.38%,but bacterial and fungal abundances decreased by 21.65%and 33.30%,respectively,under intensive management.Both management practices significantly changed the bacterial community composition,which could be mainly explained by soil pH and available potassium.Mycorrhizal fungi and intensive management affected the interrelationships between bacterial members.Structural equation modeling indicated that intensive management changed the cumulative RSby elevating AMF abundance and lowering bacterial abundance.We concluded that intensive management reduced the microbial respiration-derived C loss,but increased mycorrhizal respiration-derived C loss.展开更多
Soybean(Glycine max)is a globally important crop that serves as a primary source of edible oil and protein for both humans and animals.Cultivated soybean varieties exhibit considerable genetic diversity depending on t...Soybean(Glycine max)is a globally important crop that serves as a primary source of edible oil and protein for both humans and animals.Cultivated soybean varieties exhibit considerable genetic diversity depending on their geographical origin.Heinong 531(HN531)is an elite cultivar that was released in China in June 2021 with 22.34%seed oil,high resistance to soybean cyst nematode(SCN)race 3,and enhanced yield.However,the genetic basis for these desirable agronomic traits is unclear.In this study,we generated a high-quality genome assembly for HN531 and used it to systematically analyze genes related to agronomic traits such as resistance to SCN.The assembled genome spans 981.20 Mb,featuring a contig N50 of 19.47 Mb,and contains 58,151 predicted gene models.Pan-genomic comparison with 27 previously reported soybean genomes revealed 95,071 structural variants(SVs)of>50 bp,of which 602 were HN531-specific.Furthermore,we identified a copy number variation at rhg1 that underlies resistance to SCN,and we found elite alleles of functional genes underlying important agronomic traits such as seed oil content,adaptability,and yield.This high-quality HN531 genome can be used to explore the genetic basis for the excellent agronomic traits of this cultivar,and is a valuable resource for breeders aiming to improve HN531 and related cultivars.展开更多
The impedance matching of absorbers is a vital factor affecting their microwave absorption(MA)properties.In this work,we controllably synthesized Material of Institute Lavoisier 88C(MIL-88C)with varying aspect ratios(...The impedance matching of absorbers is a vital factor affecting their microwave absorption(MA)properties.In this work,we controllably synthesized Material of Institute Lavoisier 88C(MIL-88C)with varying aspect ratios(AR)as a precursor by regulating oil bath conditions,followed by one-step thermal decomposition to obtain carbon-coated iron-based composites.Modifying the precursor MIL-88C(Fe)preparation conditions,such as the molar ratio between metal ions and organic ligands(M/O),oil bath temperature,and oil bath time,influenced the phases,graphitization degree,and AR of the derivatives,enabling low filler loading,achieving well-matched impedance,and ensuring outstanding MA properties.The MOF-derivatives 2(MD_(2))/polyvinylidene Difluoride(PVDF),MD_(3)/PVDF,and MD4/PVDF absorbers all exhibited excellent MA properties with optimal filler loadings below 20 wt%and as low as 5 wt%.The MD_(2)/PVDF(5 wt%)achieved a maximum effective absorption bandwidth(EAB)of 5.52 GHz(1.90 mm).The MD_(3)/PVDF(10 wt%)possessed a minimum reflection loss(RL_(min))value of−67.4 at 12.56 GHz(2.13 mm).A symmetric gradient honeycomb structure(SGHS)was constructed utilizing the high-frequency structure simulator(HFSS)to further extend the EAB,achieving an EAB of 14.6 GHz and a RL_(min) of−59.0 dB.This research offers a viable inspiration to creating structures or materials with high-efficiency MA properties.展开更多
基金funding from the Hellenic Foundation for Research and Innovation(HFRI)under grant agreement No 3655.
文摘Proton exchange membrane fuel cells(PEMFCs)constitute a promising avenue for environmentally friendly power generation.However,the reliance on unsustainable platinum-based electrocatalysts used at the electrodes poses challenges to the commercial viability of PEMFCs.Non-platinum group metal(non-PGM)alternatives,like nitrogen-coordinated transition metals in atomic dispersion(M–N–C catalysts),show significant potential.This work presents a comparative study of two distinct sets of Fe–N–C materials,prepared by pyrolyzing hybrid composites of polyaniline(PANI)and iron(Ⅱ)chloride on a hard template.One set uses bipyridine(BPy)as an additional nitrogen source and iron ligand,offering an innovative approach.The findings reveal that the choice of pyrolysis temperature and atmosphere influences the catalyst properties.The use of ammonia in pyrolysis emerges as a crucial parameter for promoting atomic dispersion of iron,as well as increasing surface area and porosity.The optimal catalyst,prepared using BPy and ammonia,exhibits a half-wave potential of 0.834 V in 0.5 M H_(2)SO_(4)(catalyst loading of 0.6 mg cm^(-2)),a mass activity exceeding 3 A g^(-1)and high stability in acidic electrolyte,positioning it as a promising non-PGM structure in the field.
基金support from the Gansu Province Science and Technology Major Project(22ZD6GA008)Commissioner for Science,Technology Program of China Gansu Province(23CXA0013)+1 种基金National Natural Science Foundation of China(NSFC)(52061022)Jiayuguan City Science and Technology Major Project of China Gansu Province(22-02).
文摘The variations in the mechanical and magnetic properties of cold-rolled 20Mn23AlV non-magnetic structural steel after annealing at different temperatures were investigated.The microstructure and precipitation changes during annealing were studied by optical microscopy,scanning electron microscopy,and transmission electron microscopy.The results show that recrystallization completed after annealing at 620℃,resulting in grain sizes of approximately 800 nm and the best combination of strength and plasticity.The yield-to-tensile ratio of the non-magnetic structural steel after cold rolling continuously decreases from low to high temperatures after annealing,with the highest value being 0.89 and the lowest value being 0.43,indicating a wide range of yield-to-tensile ratio adjustment.The introduction of numerous dislocations during cold rolling provided favorable nucleation sites for precipitation,leading to abundant precipitation of the fine second-phase V(C,N).The phase composition of the samples remained unchanged as single-phase austenite after annealing,and the relative permeability values were calculated to be less than 1.002,meeting the requirements for non-magnetic steel in terms of magnetic properties.
文摘研究了微肋管内R407C和R22的流动沸腾换热特性,采用威尔逊图解法对实验数据进行处理,主要分析实验工况、制冷剂物性、微肋管结构等变量的影响。结果表明:制冷剂R407C与R22与换热壁面之间的换热热阻均随热流密度、质流密度、干度、肋片螺旋角等的增加而减小;由于制冷剂气液相密度比的差异性,R22传热系数比与R407C的高约18.5%—21.4%。选用关联式对微肋管内R407C流动沸腾换热特性进行预测评估,并对关联式预测精度随干度、质流密度等的变化趋势进行分析。在所选关联式内,Yu and Koyama关联式表现出最佳预测效果,其平均预测误差在±6.5%以内,且干度、质流密度对其预测精度的影响相近;而对于其它关联式,干度对关联式预测精度的影响比重普遍高于质流密度。
基金financial support from the SERB-SURE under file number of SUR/2022/003129Jong Hyeok Park acknowledges the support of the National Research Foundation of Korea (NRF)funded by the Ministry of Science and ICT (RS-2023-00302697,RS-2023-00268523).
文摘Mo_(2)C is an excellent electrocatalyst for hydrogen evolution reaction(HER).However,Mo_(2)C is a poor electrocatalyst for oxygen evolution reaction(OER).Herein,two different elements,namely Co and Fe,are incorporated in Mo_(2)C that,therefore,has a finely tuned electronic structure,which is not achievable by incorporation of any one of the metals.Consequently,the resulting electrocatalyst Co_(0.8)Fe_(0.2)-Mo_(2)C-80 displayed excellent OER catalytic performance,which is evidenced by a low overpotential of 214.0(and 246.5)mV to attain a current density of 10(and 50)mA cm^(-2),an ultralow Tafel slope of 38.4 mV dec^(-1),and longterm stability in alkaline medium.Theoretical data demonstrates that Co_(0.8)Fe_(0.2)-Mo_(2)C-80 requires the lowest overpotential(1.00 V)for OER and Co centers to be the active sites.The ultrahigh catalytic performance of the electrocatalyst is attributed to the excellent intrinsic catalytic activity due to high Brunauer-Emmett-Teller specific surface area,large electrochemically active surface area,small Tafel slope,and low chargetransfer resistance.
基金financially supported by the National Natural Science Foundation of China(Nos.31971631,41977083,and 41671252)。
文摘Intensive management is known to markedly alter soil carbon(C)storage and turnover in Moso bamboo forests compared with extensive management.However,the effects of intensive management on soil respiration(RS)components remain unclear.This study aimed to evaluate the changes in different RScomponents(root,mycorrhizal,and free-living microorganism respiration)in Moso bamboo forests under extensive and intensive management practices.A1-year in-situ microcosm experiment was conducted to quantify the RScomponents in Moso bamboo forests under the two management practices using mesh screens of varying sizes.The results showed that the total RSand its components exhibited similar seasonal variability between the two management practices.Compared with extensive management,intensive management significantly increased cumulative respiration from mycorrhizal fungi by 36.73%,while decreased cumulative respiration from free-living soil microorganisms by 8.97%.Moreover,the abundance of arbuscular mycorrhizal fungi(AMF)increased by 43.38%,but bacterial and fungal abundances decreased by 21.65%and 33.30%,respectively,under intensive management.Both management practices significantly changed the bacterial community composition,which could be mainly explained by soil pH and available potassium.Mycorrhizal fungi and intensive management affected the interrelationships between bacterial members.Structural equation modeling indicated that intensive management changed the cumulative RSby elevating AMF abundance and lowering bacterial abundance.We concluded that intensive management reduced the microbial respiration-derived C loss,but increased mycorrhizal respiration-derived C loss.
基金supported by National Natural Science Foundation of China(32201759,32172002)Inner Mongolia Innovation Center of Biological Breeding Technology,National Key Research and Development Program of China(2021YFD1201600)+1 种基金Earmarked Fund for CARS(CARS-04-PS01)Agricultural Science and Technology Innovation Program(ASTIP).
文摘Soybean(Glycine max)is a globally important crop that serves as a primary source of edible oil and protein for both humans and animals.Cultivated soybean varieties exhibit considerable genetic diversity depending on their geographical origin.Heinong 531(HN531)is an elite cultivar that was released in China in June 2021 with 22.34%seed oil,high resistance to soybean cyst nematode(SCN)race 3,and enhanced yield.However,the genetic basis for these desirable agronomic traits is unclear.In this study,we generated a high-quality genome assembly for HN531 and used it to systematically analyze genes related to agronomic traits such as resistance to SCN.The assembled genome spans 981.20 Mb,featuring a contig N50 of 19.47 Mb,and contains 58,151 predicted gene models.Pan-genomic comparison with 27 previously reported soybean genomes revealed 95,071 structural variants(SVs)of>50 bp,of which 602 were HN531-specific.Furthermore,we identified a copy number variation at rhg1 that underlies resistance to SCN,and we found elite alleles of functional genes underlying important agronomic traits such as seed oil content,adaptability,and yield.This high-quality HN531 genome can be used to explore the genetic basis for the excellent agronomic traits of this cultivar,and is a valuable resource for breeders aiming to improve HN531 and related cultivars.
基金financially supported by the National Natural Science Foundation of China(51972049,52073010,and 52373259)the Projects of the Science and Technology Department of Jilin Province(20230201132GX)the Projects of the Education Department of Jilin Province(JJKH20220123KJ)。
文摘The impedance matching of absorbers is a vital factor affecting their microwave absorption(MA)properties.In this work,we controllably synthesized Material of Institute Lavoisier 88C(MIL-88C)with varying aspect ratios(AR)as a precursor by regulating oil bath conditions,followed by one-step thermal decomposition to obtain carbon-coated iron-based composites.Modifying the precursor MIL-88C(Fe)preparation conditions,such as the molar ratio between metal ions and organic ligands(M/O),oil bath temperature,and oil bath time,influenced the phases,graphitization degree,and AR of the derivatives,enabling low filler loading,achieving well-matched impedance,and ensuring outstanding MA properties.The MOF-derivatives 2(MD_(2))/polyvinylidene Difluoride(PVDF),MD_(3)/PVDF,and MD4/PVDF absorbers all exhibited excellent MA properties with optimal filler loadings below 20 wt%and as low as 5 wt%.The MD_(2)/PVDF(5 wt%)achieved a maximum effective absorption bandwidth(EAB)of 5.52 GHz(1.90 mm).The MD_(3)/PVDF(10 wt%)possessed a minimum reflection loss(RL_(min))value of−67.4 at 12.56 GHz(2.13 mm).A symmetric gradient honeycomb structure(SGHS)was constructed utilizing the high-frequency structure simulator(HFSS)to further extend the EAB,achieving an EAB of 14.6 GHz and a RL_(min) of−59.0 dB.This research offers a viable inspiration to creating structures or materials with high-efficiency MA properties.
