An as-cast bainite ductile iron with excellent mechanical properties and wear resistance was fabricated by alloying and centrifugal casting method, and the alloyed chemical composition was optimized by using the therm...An as-cast bainite ductile iron with excellent mechanical properties and wear resistance was fabricated by alloying and centrifugal casting method, and the alloyed chemical composition was optimized by using the thermodynamic software Thermo-Calc. By using optical microscopy, transmission electron microscopy, scanning electron microscopy, and X-ray diffraction, the microstructure of the as-fabricated bainite ductile cast iron was characterized pertinent to the elements distribution in matrix and features of ferrite and retained austenite. The results of mechanical properties test show that the hardness and compressive strength of this alloyed ductile iron are 52 HRC and 2,200 MPa, respectively. The as- cast bainite ductile iron possesses highly abrasive wear resistance and the reason can be ascribed to the solid solution of the elements Si, Ni, Cu, and Mn in the austenite and the formation of carbides of elements Cr and Mo. The strength of bainite ductile iron is increased by the acicular bainitic ferrite in the matrix.展开更多
The roller is one of the main parts of a high-pressure grinding roller, which is a type of highly efficient ore crushing equipment. Its working life is strongly affected by the materials used. In this paper, a new kin...The roller is one of the main parts of a high-pressure grinding roller, which is a type of highly efficient ore crushing equipment. Its working life is strongly affected by the materials used. In this paper, a new kind of roller material, the high-vanadium alloy steel （HVAS）, was investigated. The results showed that the as-cast microstructures of the HVAS roller contained martensite, residual austenite, and alloy carbides. The HVAS sample quenched at 1,080 ℃ had a high hardness, and it had much higher compressive strength and abrasive wear resistance after tempering at 560 ℃ for 30 rain. The mechanical properties of the HVAS are more sufficient than the existing roller materials, which are feasible for larger machine design.展开更多
To further improve the mechanical performance of a new alloyed austempered ductile iron（ADI）, deep cryogenic treatment（DCT） has been adopted to investigate the effect of DCT time on the microstructure and mechanic...To further improve the mechanical performance of a new alloyed austempered ductile iron（ADI）, deep cryogenic treatment（DCT） has been adopted to investigate the effect of DCT time on the microstructure and mechanical behaviors of the alloyed ADI Fe-3.55 C-1.97 Si-3.79 Ni-0.71 Cu-0.92 Mo-0.64 Cr-0.36 Mn-0.30 V（in wt.%）. With increasing the DCT time, more austenite transformed to martensite and very fine carbides precipitated in martensite in the extended period of DCT. The amount of austenite decreased in alloyed ductile irons, while that of martensite and carbide precipitation increased. The alloyed ADI after DCT for 6 h had the highest hardness and compressive strength, which can be attributed to the formation of more plate-like martensite and the finely precipitated carbides. There was a gradual decrease in hardness and compressive strength with increasing the DCT time to 12 h because of the dissolution of M3 C carbide. After tempering, there was a decrease in mechanical properties compared to the direct DCT sample, which was caused by the occurrence of Ostwald ripening of precipitated carbides. The optimum wear resistance was achieved for the alloyed ADI after DCT for 6 h. The wear mechanism of the alloyed ADI in associating with DCT is mainly consisted of micro-cutting wear and some plastic deformation wear.展开更多
Collaborative f iltering, as one of the most popular techniques, plays an important role in recommendation systems. However,when the user-item rating matrix is sparse,its performance will be degenerate. Recently,domai...Collaborative f iltering, as one of the most popular techniques, plays an important role in recommendation systems. However,when the user-item rating matrix is sparse,its performance will be degenerate. Recently,domain-specific recommendation approaches have been developed to address this problem.The basic idea is to partition the users and items into overlapping domains, and then perform recommendation in each domain independently. Here, a domain means a group of users having similar preference to a group of products. However, these domain-specific methods consisting of two sequential steps ignore the mutual benefi t of domain segmentation and recommendation. Hence, a unified framework is presented to simultaneously realize recommendation and make use of the domain information underlying the rating matrix in this paper. Based on matrix factorization,the proposed model learns both user preferences of multiple domains and preference selection vectors to select relevant features for each group of products. Besides, local context information is utilized from the user-item rating matrix to enhance the new framework.Experimental results on two widely used datasets, e.g., Ciao and Epinions, demonstrate the effectiveness of our proposed model.展开更多
While crop yields have historically increased,drought resistance has become a major concern in the context of global climate change.The trade-off between crop yield and drought resistance is a common phenomenon;howeve...While crop yields have historically increased,drought resistance has become a major concern in the context of global climate change.The trade-off between crop yield and drought resistance is a common phenomenon;however,the underlying molecular modulators remain undetermined.Through genome-wide association study,we revealed that three non-synonymous variants in a drought-resistant allele of ZmSRO1d-R resulted in plasma membrane localization and enhanced mono-ADP-ribosyltransferase activity of ZmSRO1d toward ZmRBOHC,which increased reactive oxygen species(ROS)levels in guard cells and promoted stomatal closure.ZmSRO1d-R enhanced plant drought resilience and protected grain yields under drought conditions,but it led to yield drag under favorable conditions.In contrast,loss-of-function mutants of ZmRBOHC showed remarkably increased yields under well-watered conditions,whereas they showed compromised drought resistance.Interestingly,by analyzing 189 teosinte accessions,we found that the ZmSRO1d-R allele was present in teosinte but was selected against during maize domestication and modern breeding.Collectively,our work suggests that the allele frequency reduction of ZmSRO1d-R in breeding programs may have compromised maize drought resistance while increased yields.Therefore,introduction of the ZmSRO1d-R allele into modern maize cultivars would contribute to food security under drought stress caused by global climate change.展开更多
基金supported by the National High Technology Research and Development Program (No.2012AA03A508)the National Natural Science Foundation of China (No. 51271051)
文摘An as-cast bainite ductile iron with excellent mechanical properties and wear resistance was fabricated by alloying and centrifugal casting method, and the alloyed chemical composition was optimized by using the thermodynamic software Thermo-Calc. By using optical microscopy, transmission electron microscopy, scanning electron microscopy, and X-ray diffraction, the microstructure of the as-fabricated bainite ductile cast iron was characterized pertinent to the elements distribution in matrix and features of ferrite and retained austenite. The results of mechanical properties test show that the hardness and compressive strength of this alloyed ductile iron are 52 HRC and 2,200 MPa, respectively. The as- cast bainite ductile iron possesses highly abrasive wear resistance and the reason can be ascribed to the solid solution of the elements Si, Ni, Cu, and Mn in the austenite and the formation of carbides of elements Cr and Mo. The strength of bainite ductile iron is increased by the acicular bainitic ferrite in the matrix.
基金supported by the National High Technology Research and Development Program (No. 2012AA03A508)Project of Science and Technology Plan of Shenyang City (No. F12-027-2-00)Project of Science and Technology Plan of Liaoning Province (No. LNSBQ4-2010921055)
文摘The roller is one of the main parts of a high-pressure grinding roller, which is a type of highly efficient ore crushing equipment. Its working life is strongly affected by the materials used. In this paper, a new kind of roller material, the high-vanadium alloy steel （HVAS）, was investigated. The results showed that the as-cast microstructures of the HVAS roller contained martensite, residual austenite, and alloy carbides. The HVAS sample quenched at 1,080 ℃ had a high hardness, and it had much higher compressive strength and abrasive wear resistance after tempering at 560 ℃ for 30 rain. The mechanical properties of the HVAS are more sufficient than the existing roller materials, which are feasible for larger machine design.
基金Financial support from the National High Technology Research and Development Program of China(No.2012AA03A508)is greatly appreciated
文摘To further improve the mechanical performance of a new alloyed austempered ductile iron（ADI）, deep cryogenic treatment（DCT） has been adopted to investigate the effect of DCT time on the microstructure and mechanical behaviors of the alloyed ADI Fe-3.55 C-1.97 Si-3.79 Ni-0.71 Cu-0.92 Mo-0.64 Cr-0.36 Mn-0.30 V（in wt.%）. With increasing the DCT time, more austenite transformed to martensite and very fine carbides precipitated in martensite in the extended period of DCT. The amount of austenite decreased in alloyed ductile irons, while that of martensite and carbide precipitation increased. The alloyed ADI after DCT for 6 h had the highest hardness and compressive strength, which can be attributed to the formation of more plate-like martensite and the finely precipitated carbides. There was a gradual decrease in hardness and compressive strength with increasing the DCT time to 12 h because of the dissolution of M3 C carbide. After tempering, there was a decrease in mechanical properties compared to the direct DCT sample, which was caused by the occurrence of Ostwald ripening of precipitated carbides. The optimum wear resistance was achieved for the alloyed ADI after DCT for 6 h. The wear mechanism of the alloyed ADI in associating with DCT is mainly consisted of micro-cutting wear and some plastic deformation wear.
基金supported in part by the Humanity&Social Science general project of Ministry of Education under Grants No.14YJAZH046National Science Foundation of China under Grants No.61402304the Beijing Educational Committee Science and Technology Development Planned under Grants No.KM201610028015
文摘Collaborative f iltering, as one of the most popular techniques, plays an important role in recommendation systems. However,when the user-item rating matrix is sparse,its performance will be degenerate. Recently,domain-specific recommendation approaches have been developed to address this problem.The basic idea is to partition the users and items into overlapping domains, and then perform recommendation in each domain independently. Here, a domain means a group of users having similar preference to a group of products. However, these domain-specific methods consisting of two sequential steps ignore the mutual benefi t of domain segmentation and recommendation. Hence, a unified framework is presented to simultaneously realize recommendation and make use of the domain information underlying the rating matrix in this paper. Based on matrix factorization,the proposed model learns both user preferences of multiple domains and preference selection vectors to select relevant features for each group of products. Besides, local context information is utilized from the user-item rating matrix to enhance the new framework.Experimental results on two widely used datasets, e.g., Ciao and Epinions, demonstrate the effectiveness of our proposed model.
基金Beijing Outstanding Young Scientist Pro-gram(BJJWZYJH01201910019026)National Key Research and Devel-opment Program of China(2021YFD1200703)the National Natural Science Foundation of China(31625022,31971952).
文摘While crop yields have historically increased,drought resistance has become a major concern in the context of global climate change.The trade-off between crop yield and drought resistance is a common phenomenon;however,the underlying molecular modulators remain undetermined.Through genome-wide association study,we revealed that three non-synonymous variants in a drought-resistant allele of ZmSRO1d-R resulted in plasma membrane localization and enhanced mono-ADP-ribosyltransferase activity of ZmSRO1d toward ZmRBOHC,which increased reactive oxygen species(ROS)levels in guard cells and promoted stomatal closure.ZmSRO1d-R enhanced plant drought resilience and protected grain yields under drought conditions,but it led to yield drag under favorable conditions.In contrast,loss-of-function mutants of ZmRBOHC showed remarkably increased yields under well-watered conditions,whereas they showed compromised drought resistance.Interestingly,by analyzing 189 teosinte accessions,we found that the ZmSRO1d-R allele was present in teosinte but was selected against during maize domestication and modern breeding.Collectively,our work suggests that the allele frequency reduction of ZmSRO1d-R in breeding programs may have compromised maize drought resistance while increased yields.Therefore,introduction of the ZmSRO1d-R allele into modern maize cultivars would contribute to food security under drought stress caused by global climate change.
