In this study,the discrete element method was combined with physical experiments to examine the capsule filling practice in the hot-isostatic-pressing process and to study the densification of spherical particles in a...In this study,the discrete element method was combined with physical experiments to examine the capsule filling practice in the hot-isostatic-pressing process and to study the densification of spherical particles in a three-way pipe capsule for offshore engineering under mechanical vibration conditions.The effects of vibration parameters—such as the vibration time,vibration frequency,vibration amplitude,rolling friction coefficient,sliding friction coefficient,recovery coefficient,and other particle properties—on the filling density were analyzed.The results showed that the packing density in the three-way capsule could be increased considerably using a vibration frequency of 40 Hz and a vibration amplitude of 2.5 mm.The contact form between particles in the vibration-assisted mold-filling process was determined and the particle velocity field,compression force,and coordination number under a single harmonic vibration period were analyzed.The real-time motion of the particles at the micro level was visualized,and the mechanism of the mechanical vibration effect on mold filling and densification was explored.The distribution and evolution of the coordination number indicated that the distribution of the filling density was uneven,and that the change in the coordination number of particles at the bottom exhibited no major response to the vibration.展开更多
Semi-autogenous grinding(SAG)mill is widely used in the grinding process of coal and ores because of its strong applicability,large capacity and low consumption of grinding media.Therefore,the research of SAG mill is ...Semi-autogenous grinding(SAG)mill is widely used in the grinding process of coal and ores because of its strong applicability,large capacity and low consumption of grinding media.Therefore,the research of SAG mill is still of great important practical significance.Among those parameters of the SAG mill,the flling level is very important for it is not only directly related to the processing capacity of the mill,but also affects the operation cost and stability of mill.In this paper,combined with shear impact energy model(SIEM)and discrete element method(DEM),the particle collision energy spectrum was applied to analyze the influence of ore flling level and media flling level on the power draw of the mill,the impact energy on ore,and the wear of liner and media in a slice of an industrial SAG mill.It was found that increasing the ore flling level would increase energy consumption and reduce the energy efficiency and the wear of liner and grinding media.Furthermore,the vibration of mill was explored from the collision energy on liner.The results showed that the low frequency but high energy ollision between grinding media and liner was the main reason for liner wear and mill vibration.展开更多
Arranging heat exchanger in filling body to extract geothermal energy is an effective way to alleviate the problems of high ground pressure and high ground temperature in deep resource exploitation.Filling body with c...Arranging heat exchanger in filling body to extract geothermal energy is an effective way to alleviate the problems of high ground pressure and high ground temperature in deep resource exploitation.Filling body with casing heat exchanger was acted as research object,encapsulating phase change materials(PCMs)in annular space.During heat storage and heat release process,the effects of different PCMs on temperature distribution,phase-change process and heat transfer performance were studied.The result indicates:During heat storage process,the temperature increases rapidly and the melting process is accelerated for the position closer surrounding rock.CaCl_(2)·6H_(2)O/EG can make filling body complete heat storage process in the shortest time because of its good thermal diffusivity.The heat storage capacity of PCMs backfill is significantly higher than that of ordinary backfill;it increases by 36.6%-67.3%at heat storage of 10 h.During heat release process,the closer to the heat exchange tube,the greater the temperature drop in filling body.The maximum value of heat release rate and heat release capacity is in CaCl_(2)·6H_(2)O/EG backfill,it can release 116.4%more heat than RT35backfill after heat release of 12 h,the maximum value of effectiveness and its heat transfer rate also is in CaCl_(2)·6H_(2)O/EG backfill.This paper provides the basic data for the selection of PCMs in phase-change thermal storage filling body.展开更多
Inverted perovskite solar cells(PSCs)have attracted increasing attention in recent years owing to their low-temperature fabrication proces s.However,they suffer from a limited number of electron transport materials av...Inverted perovskite solar cells(PSCs)have attracted increasing attention in recent years owing to their low-temperature fabrication proces s.However,they suffer from a limited number of electron transport materials available with[6,6]-phenyl C61 butyric acid methyl ester(PCBM)to be the most widely studied based on its appropriate energy levels and high electron mobility.The low relative permittivity and aggregation tendency upon illumination of PCBM,however,compromises the solar cell efficiency whereas its modest hydrophobicity negatively impacts on the device stability.Alternative electron transport materials with desired properties and appropriate degree of hydrophobicity are thus desirable for further developments in inverted PSCs.Herein,we synthesize a triethyleneglycol C60 mono-adduct derivative(termed as EPF03)and test it as a novel electron transport material to replace PCBM in inverted PSCs based on a quadruple cation(RbCsMAFA)perovskite.We also compare this derivative with two novel fullerenes decorated with two(EPF01)or one dodecyl(EPF02)long side chains.The latter two fail to perform efficiently in inverted PSCs whereas the former enabled a power conversion efficiency of 18.43%,which represents a 9%improvement compared to the reference device using PCBM(17.21%).The enhanced performance mainly stems from improved electron extraction and reduced recombination enabled by the insertion of the large relative permittivity amongst other properties of EPF03.Furthermore,our results indicate that triethylene glycol side chains can also passivate perovskite trap states,suppress ion migration and enhance photostability and long-term stability of EPF03 based perovskite solar cells.展开更多
Geotubes are heterogeneous structures composed of filling sand and bag material,and its pemeability characteristics are different from that of flling sand.The uncertainty of geotubes permeability characteristics resul...Geotubes are heterogeneous structures composed of filling sand and bag material,and its pemeability characteristics are different from that of flling sand.The uncertainty of geotubes permeability characteristics results in the failure of seepage analysis of geotube dams,which restricts the safety assessment of the dams.As the basis of the study on the seepage mechanism of the geotubes,the influence of particle grading on pemeability cofficient of flling sand and sand covered with geotextiles were explored by the pemmeability tests of flling sand with different particle grading under the condition of sand covered with or without geotextiles.And the infuence of geotextiles on the permeability coefficient was analyzed by comparing permeability coefficient of sand covered with and without geotextiles.The test results show that the influence of single particle size content on permeability coe ficient is consistent under the condition of sand covered with and without geotextiles.The content of powder,fine,medium and coarse particles is linearly related to their respective permeability cofficients.And the content of powder,fine,medium particles is negatively correlated with their permeability coefficients,while the content of coarse particles is positively correlated with the permeability coefficient.But the pemeability coefficient of sand covered with geotextiles is smaller than that of flling sand under the same conditions.Finally,the parameter d2 50 Cc/Cu was selected as a variable representing the particle grading to fit the empirical formula of permeability coefficient of flling sand and sand covered with geotextiles.展开更多
Event extraction is one of the most challenging tasks in information extraction.It is a common phenomenon where multiple events exist in the same sentence.However,extracting multiple events is more difficult than extr...Event extraction is one of the most challenging tasks in information extraction.It is a common phenomenon where multiple events exist in the same sentence.However,extracting multiple events is more difficult than extracting a single event.Existing event extraction methods based on sequence models ignore the interrelated information between events because the sequence is too long.In addition,the current argument extraction relies on the results of syntactic dependency analysis,which is complicated and prone to error trans-mission.In order to solve the above problems,a joint event extraction method based on global event-type guidance and attention enhancement was proposed in this work.Specifically,for multiple event detection,we propose a global-type guidance method that can detect event types in the candidate sequence in advance to enhance the correlation information between events.For argument extraction,we converted it into a table-flling problem,and proposed a table-flling method of the attention mechanism,that is simple and can enhance the correlation between trigger words and arguments.The experimental results based on the ACE 2005 dataset showed that the proposed method achieved 1.6%improvement in the task of event detection,and obtained state-of-the-art results in the argument extraction task,which proved the effectiveness of the method.展开更多
基金financial support of Beijing Nova Program(grant No.2022139).
文摘In this study,the discrete element method was combined with physical experiments to examine the capsule filling practice in the hot-isostatic-pressing process and to study the densification of spherical particles in a three-way pipe capsule for offshore engineering under mechanical vibration conditions.The effects of vibration parameters—such as the vibration time,vibration frequency,vibration amplitude,rolling friction coefficient,sliding friction coefficient,recovery coefficient,and other particle properties—on the filling density were analyzed.The results showed that the packing density in the three-way capsule could be increased considerably using a vibration frequency of 40 Hz and a vibration amplitude of 2.5 mm.The contact form between particles in the vibration-assisted mold-filling process was determined and the particle velocity field,compression force,and coordination number under a single harmonic vibration period were analyzed.The real-time motion of the particles at the micro level was visualized,and the mechanism of the mechanical vibration effect on mold filling and densification was explored.The distribution and evolution of the coordination number indicated that the distribution of the filling density was uneven,and that the change in the coordination number of particles at the bottom exhibited no major response to the vibration.
基金The authors would like to acknowledge the support provided by the National Key Research and Development Program of China(2019YFC1805600)the support provided by the State Key Laboratory of Process Automation in Mining&Metallurgy and Beijing Key Laboratory of Process Automation in Mining(KY20192069000002).
文摘Semi-autogenous grinding(SAG)mill is widely used in the grinding process of coal and ores because of its strong applicability,large capacity and low consumption of grinding media.Therefore,the research of SAG mill is still of great important practical significance.Among those parameters of the SAG mill,the flling level is very important for it is not only directly related to the processing capacity of the mill,but also affects the operation cost and stability of mill.In this paper,combined with shear impact energy model(SIEM)and discrete element method(DEM),the particle collision energy spectrum was applied to analyze the influence of ore flling level and media flling level on the power draw of the mill,the impact energy on ore,and the wear of liner and media in a slice of an industrial SAG mill.It was found that increasing the ore flling level would increase energy consumption and reduce the energy efficiency and the wear of liner and grinding media.Furthermore,the vibration of mill was explored from the collision energy on liner.The results showed that the low frequency but high energy ollision between grinding media and liner was the main reason for liner wear and mill vibration.
基金supported by the National Natural Science Foundation of China(Nos.51974225,51674188,51874229,51504182,51904224,51904225,51704229)Shaanxi Innovative Talents Cultivate Program-New-star Plan of Science and Technology(No.2018KJXX-083)+4 种基金Natural Science Basic Research Plan of Shaanxi Province of China(Nos.2018JM5161,2018JQ5183,2015JQ5187,2019JM-074)Scientific Research Program funded by the Shaanxi Provincial Education Department(Nos.15JK1466,19JK0543)China Postdoctoral Science Foundation(No.2015M582685)Outstanding Youth Science Fund of Xi’an University of Science and Technology(No.2018YQ2-01)the Scientific Research Program funded by Xi’an Science and Technology Bureau(No.201805036YD14CG20)。
文摘Arranging heat exchanger in filling body to extract geothermal energy is an effective way to alleviate the problems of high ground pressure and high ground temperature in deep resource exploitation.Filling body with casing heat exchanger was acted as research object,encapsulating phase change materials(PCMs)in annular space.During heat storage and heat release process,the effects of different PCMs on temperature distribution,phase-change process and heat transfer performance were studied.The result indicates:During heat storage process,the temperature increases rapidly and the melting process is accelerated for the position closer surrounding rock.CaCl_(2)·6H_(2)O/EG can make filling body complete heat storage process in the shortest time because of its good thermal diffusivity.The heat storage capacity of PCMs backfill is significantly higher than that of ordinary backfill;it increases by 36.6%-67.3%at heat storage of 10 h.During heat release process,the closer to the heat exchange tube,the greater the temperature drop in filling body.The maximum value of heat release rate and heat release capacity is in CaCl_(2)·6H_(2)O/EG backfill,it can release 116.4%more heat than RT35backfill after heat release of 12 h,the maximum value of effectiveness and its heat transfer rate also is in CaCl_(2)·6H_(2)O/EG backfill.This paper provides the basic data for the selection of PCMs in phase-change thermal storage filling body.
基金T.S.and E.R.S acknowledge funding from the DFG in the frame of the SPP2196(project numbers 424156582 and 423660474)G.C.V.and L.P.Z.acknowledge funding provided by the Special Account for Research Grants of the National and Kapodistrian University of Athens(research projects 14872,16294,16598,17168,and 17784)+2 种基金Dr.Eleftherios K.Pefkianakis and Anastasios Misichronis are acknowledged for some initial contributions in the synthesis of the fullerene derivatives.This work was also supported by the research project"HELIOKERAMOs"-MIS 5066858funded by the Operational Programme(EPAnEK)"Competitiveness,Entrepreneurship and Innovation"(NSRF2014-2020)under the special action"lndustrial Materials"and co-financed by Greece and the European Union(European Regional Development Fund).
文摘Inverted perovskite solar cells(PSCs)have attracted increasing attention in recent years owing to their low-temperature fabrication proces s.However,they suffer from a limited number of electron transport materials available with[6,6]-phenyl C61 butyric acid methyl ester(PCBM)to be the most widely studied based on its appropriate energy levels and high electron mobility.The low relative permittivity and aggregation tendency upon illumination of PCBM,however,compromises the solar cell efficiency whereas its modest hydrophobicity negatively impacts on the device stability.Alternative electron transport materials with desired properties and appropriate degree of hydrophobicity are thus desirable for further developments in inverted PSCs.Herein,we synthesize a triethyleneglycol C60 mono-adduct derivative(termed as EPF03)and test it as a novel electron transport material to replace PCBM in inverted PSCs based on a quadruple cation(RbCsMAFA)perovskite.We also compare this derivative with two novel fullerenes decorated with two(EPF01)or one dodecyl(EPF02)long side chains.The latter two fail to perform efficiently in inverted PSCs whereas the former enabled a power conversion efficiency of 18.43%,which represents a 9%improvement compared to the reference device using PCBM(17.21%).The enhanced performance mainly stems from improved electron extraction and reduced recombination enabled by the insertion of the large relative permittivity amongst other properties of EPF03.Furthermore,our results indicate that triethylene glycol side chains can also passivate perovskite trap states,suppress ion migration and enhance photostability and long-term stability of EPF03 based perovskite solar cells.
基金The author(s)received funding for this study from Key Research Project of Natural Science in Colleges and Universities of Anhui Province(KJ2019A0640)and(KJ2018B09).
文摘Geotubes are heterogeneous structures composed of filling sand and bag material,and its pemeability characteristics are different from that of flling sand.The uncertainty of geotubes permeability characteristics results in the failure of seepage analysis of geotube dams,which restricts the safety assessment of the dams.As the basis of the study on the seepage mechanism of the geotubes,the influence of particle grading on pemeability cofficient of flling sand and sand covered with geotextiles were explored by the pemmeability tests of flling sand with different particle grading under the condition of sand covered with or without geotextiles.And the infuence of geotextiles on the permeability coefficient was analyzed by comparing permeability coefficient of sand covered with and without geotextiles.The test results show that the influence of single particle size content on permeability coe ficient is consistent under the condition of sand covered with and without geotextiles.The content of powder,fine,medium and coarse particles is linearly related to their respective permeability cofficients.And the content of powder,fine,medium particles is negatively correlated with their permeability coefficients,while the content of coarse particles is positively correlated with the permeability coefficient.But the pemeability coefficient of sand covered with geotextiles is smaller than that of flling sand under the same conditions.Finally,the parameter d2 50 Cc/Cu was selected as a variable representing the particle grading to fit the empirical formula of permeability coefficient of flling sand and sand covered with geotextiles.
基金This work was supported by the Hunan Provincial Natural Science Foundation of China(Grant No.2020JJ4624,2019JJ50655)the Scientific Research Fund of Hunan Provincial Education Department(Grant No.19A020)the National Social Science Fund of China(Grant No.20&ZD047)。
文摘Event extraction is one of the most challenging tasks in information extraction.It is a common phenomenon where multiple events exist in the same sentence.However,extracting multiple events is more difficult than extracting a single event.Existing event extraction methods based on sequence models ignore the interrelated information between events because the sequence is too long.In addition,the current argument extraction relies on the results of syntactic dependency analysis,which is complicated and prone to error trans-mission.In order to solve the above problems,a joint event extraction method based on global event-type guidance and attention enhancement was proposed in this work.Specifically,for multiple event detection,we propose a global-type guidance method that can detect event types in the candidate sequence in advance to enhance the correlation information between events.For argument extraction,we converted it into a table-flling problem,and proposed a table-flling method of the attention mechanism,that is simple and can enhance the correlation between trigger words and arguments.The experimental results based on the ACE 2005 dataset showed that the proposed method achieved 1.6%improvement in the task of event detection,and obtained state-of-the-art results in the argument extraction task,which proved the effectiveness of the method.
