It is one concern of the researchers how magnesium(Mg)alloys solidify under different conditions and how their microstructure evolves during solidification,and what are the relationship between the macroscopic propert...It is one concern of the researchers how magnesium(Mg)alloys solidify under different conditions and how their microstructure evolves during solidification,and what are the relationship between the macroscopic properties and various microstructures.Such issues are difficult to be revealed through experiments only,especially for the newly developed Mg alloys,for which there is a lack of more systematic and mature system.However,multi-scale modeling and simulation can promote and deepen our understanding of the microstructure and its deformation mechanism.In this paper,we review and summarize the recent research progress of numerical simulation of Mg alloys in forming and microstructure,namely casting,extrusion,rolling,and welding,using crystal plasticity finite element(CPFEM)and molecular dynamics(DM)methods.Besides,the methods and innovations of modeling are also summarized.Lastly,the paper discusses the development prospects and challenges of the numerical simulation in the field of Mg alloys.展开更多
A ring-shaped Mg?8.5 Gd?4 Y?1 Zn?0.4 Zr(wt%) alloy was manufactured via centrifugal casting and ring-rolling process. The effects of accumulative ring-rolling reduction amount on the microstructure, texture, and tensi...A ring-shaped Mg?8.5 Gd?4 Y?1 Zn?0.4 Zr(wt%) alloy was manufactured via centrifugal casting and ring-rolling process. The effects of accumulative ring-rolling reduction amount on the microstructure, texture, and tensile properties of the alloy were investigated. The results indicate that the microstructure of centrifugal cast alloy consists of equiaxed grains and network-like eutectic structure present at grain boundaries. The ring-rolled alloy exhibits a characteristic bimodal microstructure composed of fine dynamic recrystallized(DRXed) grains with weak basal texture and coarse un-DRXed grains with strong basal texture, along with the presence of LPSO phase. With increasing amount of accumulative ring-rolling reduction, the coarse un-DRXed grains are refined via the formation of increasing amount of fine DRXed grains. Meanwhile, the dynamic precipitation of Mg5 RE phase occurs, generating a dispersion strengthening effect. A superior combination of strength and ductility is achieved in the ring-rolled alloy after an accumulative rolling reduction of 80%. The tensile strength of this ring-rolled alloy after peak aging is further enhanced, reaching 511 MPa, while keeping a reasonable ductility. The salient strengthening mechanisms identified include the grain boundary strengthening of fine DRXed grains, dispersion strengthening of dynamic precipitated Mg;RE phase, short fiber strengthening of LPSO lamellae/rods, and precipitation strengthening of nano-sized prismatic β precipitates and basal γ precipitates.展开更多
An efficient preparation of imidazolines from nitriles and aziridines in the presence of TfOH via Ritter reaction is described. It indicates that different kinds of nitriles can undergo the process. Among the nitriles...An efficient preparation of imidazolines from nitriles and aziridines in the presence of TfOH via Ritter reaction is described. It indicates that different kinds of nitriles can undergo the process. Among the nitriles, pivalonitrile is proven to be better than acetonitrile. The reaction is performed at room temperature and the yields are excellent.展开更多
Language transfer plays a critical role in second language acquisition. It has been proved that language transfer occurs in all the aspects of L2 learning. This paper,with a focus on lexical collocations,adopts a corp...Language transfer plays a critical role in second language acquisition. It has been proved that language transfer occurs in all the aspects of L2 learning. This paper,with a focus on lexical collocations,adopts a corpus approach and attempts to address the long-standing issue from different perspectives. On the face of it,the result from the research shows clearly that not just negative transfer,positive transfer also takes place in the collocation. But actually,it is the conceptual metaphor rooted in experiences of cultures that acts as a major factor in language transfer in second language acquisition. Finally,a few suggestions of collocations are offered to benefit English Chinese learners in their L2 learning.展开更多
Due to the continuous development of science and technology,China has stepped into the stage of rapid development of network information technology.Internet technology products come out in an unending flow,such as tab...Due to the continuous development of science and technology,China has stepped into the stage of rapid development of network information technology.Internet technology products come out in an unending flow,such as tablets and mobile phones,which are representative.In order to meet the needs of economic and social development,“micromedia”has become the mainstream of current social development,including:QQ,WeChat,Tik Tok and Weibo,which have become indispensable platforms for people to get information and communicate with each other in daily life.We have ushered in the“micromedia era”.On the one hand,it has injected new impetus into China’s social economy;on the other hand,it has opened up a new horizon for China’s education.The focus and difficulty of this paper is how to effectively combine the teaching ideas of vocational colleges with“micromedia”and elaborate its transformation strategy and policy.展开更多
Reading is always regarded as a solitary process of decoding the text.People think that they are able to understand as long as they are good at linguistic knowledge.In fact,Reading is a both linguistic and cognitive p...Reading is always regarded as a solitary process of decoding the text.People think that they are able to understand as long as they are good at linguistic knowledge.In fact,Reading is a both linguistic and cognitive process.This paper intends to deal with the schema theory and its application to teaching practice of second language reading.展开更多
Waterlogging is frequently stressed rapeseed growth. Under this stress, plant is in state of hypoxia which limits aerobic respiration and energy metabolism. Promoting root growth is an adaptive strategy of terrestria...Waterlogging is frequently stressed rapeseed growth. Under this stress, plant is in state of hypoxia which limits aerobic respiration and energy metabolism. Promoting root growth is an adaptive strategy of terrestrial plants in response to waterlogging stress. Auxin plays important roles in root growth. However, the effects of auxin on rapeseed root growth under waterlogging stress remain largely unknown. In this study, we investigated endoge-nous IAA levels and root growth of rapeseed under hypoxia stress （H）, hypoxia treatment with IAA（HI）f PCIB （an auxin action inhibitor, HP） or TIBA（an auxin polar-transport inhibi-tor, HT） through hydroponic experiment. Pot experiment was further employed to evaluate effects of exogenous IAA on growth of rapeseed under waterlogging stress by foliar spray-ing. Results from hydroponic showed that compared with control （CK）, hypoxia significantly decreased rapeseed growth after 48 hours treatment, while HI dramatically alleviated the depression. In contrast, HP and HT aggravated growth depression by hypoxia stress, as indicated by obvious decrease in root and shoot dry weight. Under hypoxia stress, alter-ation in root growth, especially for lateral roots with a diameter 〈1.5 mm was positively related with IAA levels in roots. Pot experiment further proved those findings. These results suggested that endogenous IAA might be involved in root growth of rapeseed response to waterlogging stress. Furthermore, foliar spraying with moderate IAA increased rapeseed growth underwaterlogging stress through promoting endogenous lAA-caused root growth. This work provided an available method to improve rapeseed tolerance to waterlogging in soil.展开更多
Regulation of gas–solid flow is crucial for optimizing the operation efficiency of dual-circulating fluidized beds that are considered to be the most appropriate type of chemical-looping reactors. Herein, a computati...Regulation of gas–solid flow is crucial for optimizing the operation efficiency of dual-circulating fluidized beds that are considered to be the most appropriate type of chemical-looping reactors. Herein, a computational particle fluid dynamics method was employed to simulate the gas–solid flow in a 3-MWth dual-circulating fluidized bed used for chemical-looping combustion and gasification. The influence of structural difference between units on particle residence time was determined. The multi-parameter control mechanism of pressure, particle circulation, and particle residence time in a whole-loop system was investigated. Results revealed that under stable particle circulation, the particle residence time in the fuel reactor is much longer than that in the air reactor. The axial forces on the particles are reduced upon increasing particle density and size, leading to particle accumulation in the dense-phase zone. When the particle properties are stable, increasing the fluidizing gas flow rates by the same proportion leads to identical pressure drops on the involved two loop seals, which cause symmetrical alterations in the particle circulation rate between the air and fuel reactors. The dual-circulating fluidized bed exhibits certain multi-condition adaptability, which is limited by the stock bin volume. Overall, this study is beneficial for effective and economical optimization of the operation of chemical-looping dual-circulating fluidized beds.展开更多
基金supported by the National Natural Science Foundation of China(No.52271091)Natural Science Foundation Project of Ningxia Province(No.2023AAC03324)the National Key Research and Development Program of China(No.2021YFB3701100).
文摘It is one concern of the researchers how magnesium(Mg)alloys solidify under different conditions and how their microstructure evolves during solidification,and what are the relationship between the macroscopic properties and various microstructures.Such issues are difficult to be revealed through experiments only,especially for the newly developed Mg alloys,for which there is a lack of more systematic and mature system.However,multi-scale modeling and simulation can promote and deepen our understanding of the microstructure and its deformation mechanism.In this paper,we review and summarize the recent research progress of numerical simulation of Mg alloys in forming and microstructure,namely casting,extrusion,rolling,and welding,using crystal plasticity finite element(CPFEM)and molecular dynamics(DM)methods.Besides,the methods and innovations of modeling are also summarized.Lastly,the paper discusses the development prospects and challenges of the numerical simulation in the field of Mg alloys.
基金financial support by Fundamental Research Funds for the National Key Research and Development Program of China(Project No.2016YFB0700403)the Venture&Innovation Support Program for Chongqing Overseas Returnees(Project No.cx2018057)+1 种基金the Chongqing Research Program of Basic Research and Frontier Technology(Project Nos.cstc2019jcyjmsxm0548 and cstc2019jcyj-msxm X0306)the Fundamental Research Funds for the Central Universities(Project No.2021CDJJMRH-001)。
文摘A ring-shaped Mg?8.5 Gd?4 Y?1 Zn?0.4 Zr(wt%) alloy was manufactured via centrifugal casting and ring-rolling process. The effects of accumulative ring-rolling reduction amount on the microstructure, texture, and tensile properties of the alloy were investigated. The results indicate that the microstructure of centrifugal cast alloy consists of equiaxed grains and network-like eutectic structure present at grain boundaries. The ring-rolled alloy exhibits a characteristic bimodal microstructure composed of fine dynamic recrystallized(DRXed) grains with weak basal texture and coarse un-DRXed grains with strong basal texture, along with the presence of LPSO phase. With increasing amount of accumulative ring-rolling reduction, the coarse un-DRXed grains are refined via the formation of increasing amount of fine DRXed grains. Meanwhile, the dynamic precipitation of Mg5 RE phase occurs, generating a dispersion strengthening effect. A superior combination of strength and ductility is achieved in the ring-rolled alloy after an accumulative rolling reduction of 80%. The tensile strength of this ring-rolled alloy after peak aging is further enhanced, reaching 511 MPa, while keeping a reasonable ductility. The salient strengthening mechanisms identified include the grain boundary strengthening of fine DRXed grains, dispersion strengthening of dynamic precipitated Mg;RE phase, short fiber strengthening of LPSO lamellae/rods, and precipitation strengthening of nano-sized prismatic β precipitates and basal γ precipitates.
基金supported by the National Natural Science Foundation of China(Nos.21262024,21062014)the Key Project of Chinese Ministry of Education(No.211193)+3 种基金the Scientific Research Foundation for Returned Scholars(Ministry of Education of China)the Natural Science Foundation of Ningxia(No.NZ1165)the Key Project of Department of Education in Ningxia(2010 Preparation of Capsaicin)the 100 Talents Program of Ningxia,and the"211"Project in Ningxia University
文摘An efficient preparation of imidazolines from nitriles and aziridines in the presence of TfOH via Ritter reaction is described. It indicates that different kinds of nitriles can undergo the process. Among the nitriles, pivalonitrile is proven to be better than acetonitrile. The reaction is performed at room temperature and the yields are excellent.
文摘Language transfer plays a critical role in second language acquisition. It has been proved that language transfer occurs in all the aspects of L2 learning. This paper,with a focus on lexical collocations,adopts a corpus approach and attempts to address the long-standing issue from different perspectives. On the face of it,the result from the research shows clearly that not just negative transfer,positive transfer also takes place in the collocation. But actually,it is the conceptual metaphor rooted in experiences of cultures that acts as a major factor in language transfer in second language acquisition. Finally,a few suggestions of collocations are offered to benefit English Chinese learners in their L2 learning.
文摘Due to the continuous development of science and technology,China has stepped into the stage of rapid development of network information technology.Internet technology products come out in an unending flow,such as tablets and mobile phones,which are representative.In order to meet the needs of economic and social development,“micromedia”has become the mainstream of current social development,including:QQ,WeChat,Tik Tok and Weibo,which have become indispensable platforms for people to get information and communicate with each other in daily life.We have ushered in the“micromedia era”.On the one hand,it has injected new impetus into China’s social economy;on the other hand,it has opened up a new horizon for China’s education.The focus and difficulty of this paper is how to effectively combine the teaching ideas of vocational colleges with“micromedia”and elaborate its transformation strategy and policy.
文摘Reading is always regarded as a solitary process of decoding the text.People think that they are able to understand as long as they are good at linguistic knowledge.In fact,Reading is a both linguistic and cognitive process.This paper intends to deal with the schema theory and its application to teaching practice of second language reading.
文摘Waterlogging is frequently stressed rapeseed growth. Under this stress, plant is in state of hypoxia which limits aerobic respiration and energy metabolism. Promoting root growth is an adaptive strategy of terrestrial plants in response to waterlogging stress. Auxin plays important roles in root growth. However, the effects of auxin on rapeseed root growth under waterlogging stress remain largely unknown. In this study, we investigated endoge-nous IAA levels and root growth of rapeseed under hypoxia stress （H）, hypoxia treatment with IAA（HI）f PCIB （an auxin action inhibitor, HP） or TIBA（an auxin polar-transport inhibi-tor, HT） through hydroponic experiment. Pot experiment was further employed to evaluate effects of exogenous IAA on growth of rapeseed under waterlogging stress by foliar spray-ing. Results from hydroponic showed that compared with control （CK）, hypoxia significantly decreased rapeseed growth after 48 hours treatment, while HI dramatically alleviated the depression. In contrast, HP and HT aggravated growth depression by hypoxia stress, as indicated by obvious decrease in root and shoot dry weight. Under hypoxia stress, alter-ation in root growth, especially for lateral roots with a diameter 〈1.5 mm was positively related with IAA levels in roots. Pot experiment further proved those findings. These results suggested that endogenous IAA might be involved in root growth of rapeseed response to waterlogging stress. Furthermore, foliar spraying with moderate IAA increased rapeseed growth underwaterlogging stress through promoting endogenous lAA-caused root growth. This work provided an available method to improve rapeseed tolerance to waterlogging in soil.
基金supported by the key research and development program of Ningxia province of China(No.2018BCE01002)the national key research and development program of China(No.2018YFB0605401)+1 种基金the national natural science foundation of China(No.U20A20124)the innovation group project of Ningxia(No.2022AAC01001).
文摘Regulation of gas–solid flow is crucial for optimizing the operation efficiency of dual-circulating fluidized beds that are considered to be the most appropriate type of chemical-looping reactors. Herein, a computational particle fluid dynamics method was employed to simulate the gas–solid flow in a 3-MWth dual-circulating fluidized bed used for chemical-looping combustion and gasification. The influence of structural difference between units on particle residence time was determined. The multi-parameter control mechanism of pressure, particle circulation, and particle residence time in a whole-loop system was investigated. Results revealed that under stable particle circulation, the particle residence time in the fuel reactor is much longer than that in the air reactor. The axial forces on the particles are reduced upon increasing particle density and size, leading to particle accumulation in the dense-phase zone. When the particle properties are stable, increasing the fluidizing gas flow rates by the same proportion leads to identical pressure drops on the involved two loop seals, which cause symmetrical alterations in the particle circulation rate between the air and fuel reactors. The dual-circulating fluidized bed exhibits certain multi-condition adaptability, which is limited by the stock bin volume. Overall, this study is beneficial for effective and economical optimization of the operation of chemical-looping dual-circulating fluidized beds.
