Laboratory experiments were carried out to investigate the effect of freezing and thawing processes on wet aggregate stability （WAS） of black soil. Wet aggregate stability was determined by different aggregate size ...Laboratory experiments were carried out to investigate the effect of freezing and thawing processes on wet aggregate stability （WAS） of black soil. Wet aggregate stability was determined by different aggregate size groups, different water contents, various freeze-thaw cycles, and various freezing temperatures. The results showed that, when at suitable water content, aggregate stability was enhanced, aggregate sta-bility will be disrupted when moisture content is too high or too low, especially higher water content. Temperature also had a significant ef-fect, but moisture content determined the suitable freezing temperatures for a given soil. Water-stable aggregate （WSA〉0.5）, the total aggre-gate content, and mean weight diameter decreasing with the freeze-thaw cycles increase, reached to 5 percent significance level. The reason for crumbing aggregates is the water and air conflict, thus raising the hypothesis that water content affects the aggregate stability in the process of freezing and thawing.展开更多
Taking Scotland Rural Priority Scheme as an example, experiences of EU rural eco-compensation policy were discussed to enlighten China. The implementing objectives and processing program of Scottish policy were respec...Taking Scotland Rural Priority Scheme as an example, experiences of EU rural eco-compensation policy were discussed to enlighten China. The implementing objectives and processing program of Scottish policy were respectively set forth,including 6 steps of statement of Intent, proposal, assessment, contract signing, claims and inspections, breaches and penalties.Therein 3 meaningful aspects for the construction of current compensation mechanism in China were as following: keeping consistency between national and local policies to establish close connection in eco-goal and funding subsidy, setting both improved assessment procedure and scientific compensation system to promote the lasting implementation of environmental-friendly measures, making correspondent check and monitor mechanism together with breach and penalty mechanism to secure the payment execution.展开更多
The dissemination of antibiotic resistance genes(ARGs)in soil has become a global environmental issue.Vermicomposting is gaining prominence in agricultural practices as a soil amendment to improve soil quality.However...The dissemination of antibiotic resistance genes(ARGs)in soil has become a global environmental issue.Vermicomposting is gaining prominence in agricultural practices as a soil amendment to improve soil quality.However,its impact on soil ARGs remains unclear when it occurs in farmland.We comprehensively explored the evolution and fate of ARGs and their hosts in the field soil profiles under vermicompost application for more than 3years.Vermicompost application increased several ARG loads in soil environment but decreased the high-risk bla-ARGs(bla_(ampC),bla_(NDM),and bla_(GES-1))by log(0.04-0.43).ARGs in soil amended with vermicompost primarily occurred in topsoil(approximately 1.04-fold of unfertilized soil),but it is worth noting that their levels in the 40-60 cm soil layer were the same or even less than in the unfertilized soil.The microbial community structure changed in soil profiles after vermicompost application.Vermicompost application altered the microbial community structure in soil profiles,showing that the dominant bacteria(i.e.,Proteobacteria,Actinobacteriota,Firmicutes)were decreased 2.62%-5.48%with the increase of soil depth.A network analysis further revealed that most of ARG dominant host bacteria did not migrate from surface soil to deep soil.In particular,those host bacteria harboring high-risk bla-ARGs were primarily concentrated in the surface soil.This study highlights a lower risk of the propagation of ARGs caused by vermicompost application and provides a novel approach to reduce and relieve the dissemination of ARGs derived from animals in agricultural production.展开更多
Hydroxyapatite(HA)bioceramic scaffolds were fabricated by using digital light processing(DLP)based additive manufacturing.Key issues on the HA bioceramic scaffolds,including dispersion,DLP fabrication,sintering,mechan...Hydroxyapatite(HA)bioceramic scaffolds were fabricated by using digital light processing(DLP)based additive manufacturing.Key issues on the HA bioceramic scaffolds,including dispersion,DLP fabrication,sintering,mechanical properties,and biocompatibility were discussed in detail.Firstly,the ffects of dispersant dosage,solid loading,and sintering temperature were studied.The optimal dispersant dosage,solid loading,and sintering temperature were 2wt%,50vol%,and 1250℃,respectively.Then,the mechanical properties and biocompatibility of the HA bioceramic scaffolds were investigated.The DLP-prepared porous HA bioceramic scaffold was found to exhibit excellent mechanical properties and degradation behavior.From this study,DLP technique shows good potential for manufacturing HA bioceramic scaffolds.展开更多
Silicon carbide(SiC)ceramic and related materials are widely used in various military and engineering fields.The emergence of additive manufacturing(AM)technologies provides a new approach for the fabrication of SiC c...Silicon carbide(SiC)ceramic and related materials are widely used in various military and engineering fields.The emergence of additive manufacturing(AM)technologies provides a new approach for the fabrication of SiC ceramic products.This article systematically reviews the additive manufacturing technologies of SiC ceramic developed in recent years,including Indirect Additive Manufacturing(Indirect AM)and Direct Additive Manufacturing(Direct AM)technologies.This review also summarizes the key scientific and technological challenges for the additive manufacturing of SiC ceramic,and also forecasts its possible future opportunities.This paper aims to provide a helpful guidance for the additive manufacturing of SiC ceramic and other structural ceramics.展开更多
Ceramics have been widely fabricated by additive manufacturing(AM).Compared to conventional technologies,the strength of additive manufactured ceramic is relatively low owing to the formation of defects during manufac...Ceramics have been widely fabricated by additive manufacturing(AM).Compared to conventional technologies,the strength of additive manufactured ceramic is relatively low owing to the formation of defects during manufacturing process.These defects have significant effects on the microstructure and mechanical properties of additive manufactured ceramics.However,systematic research on defects,including defect geometrical features,quantitative statistics,and formation mechanism,as well as the intrinsic relationship with mechanical properties,need to be studied in depth.In this work,Al2 O3 ceramics were prepared from photosensitive slurries with different solid loadings by using stereolithographic(SL)additive manufacturing.The defects,including their sizes and distributions,in both green and sintered bodies were investigated by using scanning electron microscopy(SEM)and X-ray computed tomography(X-CT).Geometrical features and quantitative statistics of the defects were evaluated and discussed to reveal their formation mechanism.Moreover,the intrinsic relationship between defects and mechanical properties of the additive manufactured ceramic was revealed.This study can give some fundamental understanding of the defects in additive manufactured ceramics.展开更多
Cellular ceramic structures(CCSs)are promising candidates for structural components in aerospace and modern industry because of their extraordinary physical and chemical properties.Herein,the CCSs with different struc...Cellular ceramic structures(CCSs)are promising candidates for structural components in aerospace and modern industry because of their extraordinary physical and chemical properties.Herein,the CCSs with different structural parameters,i.e.,relative density,layer,size of unit cells,and structural configuration,were designed and prepared by digital light processing(DLP)-based additive manufacturing(AM)technology to investigate their responses under compressive loading systematically.It was demonstrated that as the relative density increased and the size of the unit cells decreased,the mechanical properties of one-layer CCSs increased.The mechanical properties of three-layer CCSs were more outstanding than those of the CCSs with one and two layers.In addition,structural configurations also played a vital role in the mechanical properties of the CCSs.Overall,the mechanical properties of the CCSs from superior to inferior were that with the structural configurations of modified body-centered cubic(MBCC),Octet,SchwarzP,IWP,and body-centered cubic(BCC).Furthermore,structural parameters also had significant impacts on the failure mode of the CCSs under compressive loading.As the relative density increased,the failure mode of the one-layer CCSs changed from parallel-vertical-inclined mode to parallel-vertical mode.It was worth noting that the size of the unit cells did not alter the failure mode.Inclined fracture took a greater proportion in the failure mode of the multi-layer CCSs.But it could be suppressed by the increased relative density.Similarly,the proportions of the parallel-vertical mode and the fracture along a specific plane always changed with the variation of the structural configurations.This study will serve as the base for investigating the mechanical properties of the CCSs.展开更多
基金National Basic Research Program of China (2005CB121101, 2005CB121103)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-407)
文摘Laboratory experiments were carried out to investigate the effect of freezing and thawing processes on wet aggregate stability （WAS） of black soil. Wet aggregate stability was determined by different aggregate size groups, different water contents, various freeze-thaw cycles, and various freezing temperatures. The results showed that, when at suitable water content, aggregate stability was enhanced, aggregate sta-bility will be disrupted when moisture content is too high or too low, especially higher water content. Temperature also had a significant ef-fect, but moisture content determined the suitable freezing temperatures for a given soil. Water-stable aggregate （WSA〉0.5）, the total aggre-gate content, and mean weight diameter decreasing with the freeze-thaw cycles increase, reached to 5 percent significance level. The reason for crumbing aggregates is the water and air conflict, thus raising the hypothesis that water content affects the aggregate stability in the process of freezing and thawing.
基金Supported by the Project of Intelligence import and demonstration in 2018(2018-yzzx-zr)the Project for the International Exchange and Cooperation in Agriculture in 2018(2018-gjhz-zkq)
文摘Taking Scotland Rural Priority Scheme as an example, experiences of EU rural eco-compensation policy were discussed to enlighten China. The implementing objectives and processing program of Scottish policy were respectively set forth,including 6 steps of statement of Intent, proposal, assessment, contract signing, claims and inspections, breaches and penalties.Therein 3 meaningful aspects for the construction of current compensation mechanism in China were as following: keeping consistency between national and local policies to establish close connection in eco-goal and funding subsidy, setting both improved assessment procedure and scientific compensation system to promote the lasting implementation of environmental-friendly measures, making correspondent check and monitor mechanism together with breach and penalty mechanism to secure the payment execution.
基金supported by the National Natural Science Foundation of China(Nos.42077355,42277033)the Government Purchasing Project of the Ministry of Agriculture and Rural Affairs(No.15228002)the Major Science and Technology Project of Yunnan Province(No.202102AE090011)。
文摘The dissemination of antibiotic resistance genes(ARGs)in soil has become a global environmental issue.Vermicomposting is gaining prominence in agricultural practices as a soil amendment to improve soil quality.However,its impact on soil ARGs remains unclear when it occurs in farmland.We comprehensively explored the evolution and fate of ARGs and their hosts in the field soil profiles under vermicompost application for more than 3years.Vermicompost application increased several ARG loads in soil environment but decreased the high-risk bla-ARGs(bla_(ampC),bla_(NDM),and bla_(GES-1))by log(0.04-0.43).ARGs in soil amended with vermicompost primarily occurred in topsoil(approximately 1.04-fold of unfertilized soil),but it is worth noting that their levels in the 40-60 cm soil layer were the same or even less than in the unfertilized soil.The microbial community structure changed in soil profiles after vermicompost application.Vermicompost application altered the microbial community structure in soil profiles,showing that the dominant bacteria(i.e.,Proteobacteria,Actinobacteriota,Firmicutes)were decreased 2.62%-5.48%with the increase of soil depth.A network analysis further revealed that most of ARG dominant host bacteria did not migrate from surface soil to deep soil.In particular,those host bacteria harboring high-risk bla-ARGs were primarily concentrated in the surface soil.This study highlights a lower risk of the propagation of ARGs caused by vermicompost application and provides a novel approach to reduce and relieve the dissemination of ARGs derived from animals in agricultural production.
基金This study is mainly financially supported by the Beijing Natural Science Foundation(2182064)hosted by Prof.Rujie He.Prof.Rujie He also thanks the support from the National Natural Science Foundation of China(51772028)+2 种基金Prof.M i n Xia thanks the support from the Fundamental Research Funds for the Central Universities(3052017010)Prof.Xinxin Jin thanks the support from the National Natural Science Foundation of China(51602082)Dr.Keqiang Zhang thanks the support from the Graduate Technology Innovation Project of Beijing Institute of Technology(No.2019CX10020).
文摘Hydroxyapatite(HA)bioceramic scaffolds were fabricated by using digital light processing(DLP)based additive manufacturing.Key issues on the HA bioceramic scaffolds,including dispersion,DLP fabrication,sintering,mechanical properties,and biocompatibility were discussed in detail.Firstly,the ffects of dispersant dosage,solid loading,and sintering temperature were studied.The optimal dispersant dosage,solid loading,and sintering temperature were 2wt%,50vol%,and 1250℃,respectively.Then,the mechanical properties and biocompatibility of the HA bioceramic scaffolds were investigated.The DLP-prepared porous HA bioceramic scaffold was found to exhibit excellent mechanical properties and degradation behavior.From this study,DLP technique shows good potential for manufacturing HA bioceramic scaffolds.
基金supported by the National Natural Science Foundation of China(No.51772028).
文摘Silicon carbide(SiC)ceramic and related materials are widely used in various military and engineering fields.The emergence of additive manufacturing(AM)technologies provides a new approach for the fabrication of SiC ceramic products.This article systematically reviews the additive manufacturing technologies of SiC ceramic developed in recent years,including Indirect Additive Manufacturing(Indirect AM)and Direct Additive Manufacturing(Direct AM)technologies.This review also summarizes the key scientific and technological challenges for the additive manufacturing of SiC ceramic,and also forecasts its possible future opportunities.This paper aims to provide a helpful guidance for the additive manufacturing of SiC ceramic and other structural ceramics.
基金financial support from the National Natural Science Foundation of China(No.51772028)the Graduate Technology Innovation Project of Beijing Institute of Technology(No.2019CX10020)。
文摘Ceramics have been widely fabricated by additive manufacturing(AM).Compared to conventional technologies,the strength of additive manufactured ceramic is relatively low owing to the formation of defects during manufacturing process.These defects have significant effects on the microstructure and mechanical properties of additive manufactured ceramics.However,systematic research on defects,including defect geometrical features,quantitative statistics,and formation mechanism,as well as the intrinsic relationship with mechanical properties,need to be studied in depth.In this work,Al2 O3 ceramics were prepared from photosensitive slurries with different solid loadings by using stereolithographic(SL)additive manufacturing.The defects,including their sizes and distributions,in both green and sintered bodies were investigated by using scanning electron microscopy(SEM)and X-ray computed tomography(X-CT).Geometrical features and quantitative statistics of the defects were evaluated and discussed to reveal their formation mechanism.Moreover,the intrinsic relationship between defects and mechanical properties of the additive manufactured ceramic was revealed.This study can give some fundamental understanding of the defects in additive manufactured ceramics.
基金supported by the National Natural Science Foundation of China(Grant No.51772028).
文摘Cellular ceramic structures(CCSs)are promising candidates for structural components in aerospace and modern industry because of their extraordinary physical and chemical properties.Herein,the CCSs with different structural parameters,i.e.,relative density,layer,size of unit cells,and structural configuration,were designed and prepared by digital light processing(DLP)-based additive manufacturing(AM)technology to investigate their responses under compressive loading systematically.It was demonstrated that as the relative density increased and the size of the unit cells decreased,the mechanical properties of one-layer CCSs increased.The mechanical properties of three-layer CCSs were more outstanding than those of the CCSs with one and two layers.In addition,structural configurations also played a vital role in the mechanical properties of the CCSs.Overall,the mechanical properties of the CCSs from superior to inferior were that with the structural configurations of modified body-centered cubic(MBCC),Octet,SchwarzP,IWP,and body-centered cubic(BCC).Furthermore,structural parameters also had significant impacts on the failure mode of the CCSs under compressive loading.As the relative density increased,the failure mode of the one-layer CCSs changed from parallel-vertical-inclined mode to parallel-vertical mode.It was worth noting that the size of the unit cells did not alter the failure mode.Inclined fracture took a greater proportion in the failure mode of the multi-layer CCSs.But it could be suppressed by the increased relative density.Similarly,the proportions of the parallel-vertical mode and the fracture along a specific plane always changed with the variation of the structural configurations.This study will serve as the base for investigating the mechanical properties of the CCSs.
