Numerical challenges,incorporating non-uniqueness,non-convexity,undefined gradients,and high curvature,of the positive level sets of yield function are encountered in stress integration when utilizing the return-mappi...Numerical challenges,incorporating non-uniqueness,non-convexity,undefined gradients,and high curvature,of the positive level sets of yield function are encountered in stress integration when utilizing the return-mapping algorithm family.These phenomena are illustrated by an assessment of four typical yield functions:modified spatially mobilized plane criterion,Lade criterion,Bigoni-Piccolroaz criterion,and micromechanics-based upscaled Drucker-Prager criterion.One remedy to these issues,named the"Hop-to-Hug"(H2H)algorithm,is proposed via a convexification enhancement upon the classical cutting-plane algorithm(CPA).The improved robustness of the H2H algorithm is demonstrated through a series of integration tests in one single material point.Furthermore,a constitutive model is implemented with the H2H algorithm into the Abaqus/Standard finite-element platform.Element-level and structure-level analyses are carried out to validate the effectiveness of the H2H algorithm in convergence.All validation analyses manifest that the proposed H2H algorithm can offer enhanced stability over the classical CPA method while maintaining the ease of implementation,in which evaluations of the second-order derivatives of yield function and plastic potential function are circumvented.展开更多
A novel Al-14.1 Mg-0.47 Si-0.31 Sc-0.17 Zr alloy was applied in the printing process of selective laser melting(SLM),and the corresponding microstructural feature,phase identification,tensile properties and corrosion ...A novel Al-14.1 Mg-0.47 Si-0.31 Sc-0.17 Zr alloy was applied in the printing process of selective laser melting(SLM),and the corresponding microstructural feature,phase identification,tensile properties and corrosion behavior of the Al Mg Si Sc Zr alloy were studied in detail.As fabricated at 160 W and 200 mm/s,the Mg content of bulk sample decreased to 11.7 wt%due to the element vaporization at high energy density,and the density of this additively manufactured Al Mg Si Sc Zr alloy was 2.538 g/cm^(3),which is4.2%8.5%lighter than that of other SLM-processed Al alloys.After heat-treated(HT)at 325℃and 6 h,the microstructure was almost unchanged with an alternate distribution of fine equiaxed crystals and coarse columnar crystals.Nano-sized Al3(Sc,Zr)and Mg_(2)Si phases precipitated dispersedly in the Al matrix,and the tensile strength increased from 487.6 MPa to 578.4 MPa for precipitation strengthening and fine grain strengthening.With a fine grain size of 2.53μm,an excellent corrosion resistance was obtained for the as-printed(AP)Al Mg Si Sc Zr alloy.While the corrosion resistance of HT sample decreased slightly for the formation of non-dense oxide layer and pitting corrosion induced by diffuse precipitation distribution.This SLM-printed Al Mg Si Sc Zr alloy with high specific strength,good thermal stability and excellent corrosion resistance has broad prospects for the aerospace and automotive applications.展开更多
The new generation of Sc and Zr modified Al alloys has been attracted wide concerns in aerospace industry,owing to the excellent mechanical performances and superior thermal stability than other normal Al alloys.By mi...The new generation of Sc and Zr modified Al alloys has been attracted wide concerns in aerospace industry,owing to the excellent mechanical performances and superior thermal stability than other normal Al alloys.By microalloying with Sc and Zr,the Al3(Sc,Zr)particle forms as the grain refiner during the solidification,which is extremely beneficial for the laser powder bed fusion(LPBF)processed Al alloys.In this study,a new type Al-14.1 Mg-0.47 Si-0.31 Sc-0.17 Zr alloy was additively manufactured by LPBF,and the microstructure,tensile properties and thermal stability were studied in detail.By using a single melt-67°scanning strategy,the LPBF-processed specimen with a relative density of 99.4%and tensile strength of 487.7 MPa was obtained at 160 W-200 mm/s.And this AlMgSiScZr alloy can still exhibit an excellent tensile strength of 393.9 MPa at a moderate temperature of 473 K.After the aging treatment,the tensile properties further increased due to the precipitate hardening of Mg2Si and Al3(Sc,Zr),and the maximum value(580 MPa)was reached at an aging time of 10 h.The average crystal size was almost unchanged after aging treated at 325℃and 24 h,indicating this AlMgSiScZr alloy has an improved thermal stability.The AlMgSiScZr alloy is recommended to substitute some particular titanium alloys in aerospace field afterwards.展开更多
Ni-rich layered cathode is regarded as one of the most promising candidates to achieve lithium-ion batteries (LIBs) with high energy density. However, due to the irreversible phase transformation (IPT) and its eventua...Ni-rich layered cathode is regarded as one of the most promising candidates to achieve lithium-ion batteries (LIBs) with high energy density. However, due to the irreversible phase transformation (IPT) and its eventual propagation from surface to the bulk of the material, Ni-rich layered cathode typically suffers from severe capacity fading, structure failure, and thermal instability, which greatly hinders its mass adoption. Hence, achieving an in-depth understanding of the IPT propagation mechanism in Ni-rich layered cathode is crucial in addressing these issues. Herein, the triggering factor of IPT propagation in Ni-rich cathode is verified to be the initial surface disordered cation mixing domain covered by a thin rock-salt phase, instead of the rock-salt phase itself. According to the density functional theory (DFT) results, it is further illustrated that the metastable cation mixing domain possesses a lower Ni migration energy barrier, which facilitates the migration of Ni ions towards the Li slab, and thus driving the propagation of IPT from surface to the bulk of the material. This finding clarifies a prevailing debate regarding the surface impurity phases of Ni-rich cathode material and reveals the origin of IPT propagation, which implies the principle and its effectiveness of tuning the surface microstructure to address the structural and thermal instability issue of Ni-rich layered cathode materials.展开更多
Nickel-rich transition-metal oxides are widely regarded as promising cathode materials for high-energydensity lithium-ion batteries for emerging electric vehicles. However, achieving high energy density in Ni-rich cat...Nickel-rich transition-metal oxides are widely regarded as promising cathode materials for high-energydensity lithium-ion batteries for emerging electric vehicles. However, achieving high energy density in Ni-rich cathodes is accompanied by substantial safety and cycle-life obstacles. The major issues of Ni-rich cathodes at high working potentials are originated from the unstable cathode-electrolyte interface, while the underlying mechanism of parasitic reactions towards surface reconstructions of cathode materials is not well understood. In this work, we controlled the Li_(2)CO_(3) impurity content on LiNi_(0.83)Mn_(0.1)Co_(0.07)O_(2) cathodes using air, tank-air, and O_(2) synthesis environments. Home-built high-precision leakage current and on-line electrochemical mass spectroscopy experiments verify that Li_(2)CO_(3) impurity is a significant promoter of parasitic reactions on Ni-rich cathodes. The rate of parasitic reactions is strongly correlated to Li_(2)CO_(3) content and severe performance deterioration of Ni83 cathodes.The post-mortem characterizations via high-resolution transition electron microscope and X-ray photoelectron spectroscopy depth profiles reveal that parasitic reactions promote more Ni reduction and O deficiency and even rock-salt phase transformation at the surface of cathode materials. Our observation suggests that surface reconstructions have a strong affiliation to parasitic reactions that create chemically acidic environment to etch away the lattice oxygen and offer the electrical charge to reduce the valence state of transition metal. Thus, this study advances our understanding on surface reconstructions of Nirich cathodes and prepares us for searching for rational strategies.展开更多
Background The aim of this experiment was to investigate the effect of different levels of betaine(Bet)inclusion in the diet on the intestinal health of growing rabbits under summer heat.A total of 100 weaned Qixing m...Background The aim of this experiment was to investigate the effect of different levels of betaine(Bet)inclusion in the diet on the intestinal health of growing rabbits under summer heat.A total of 100 weaned Qixing meat rabbits aged 35 d with body weight of 748.61±38.59 g were randomly divided into 5 treatment groups:control group(basal diet)and Bet groups(basal diet+0.75,1.0,1.5 or 2.0 g/kg Bet).The average daily temperature in the rabbitry during the experiment was 30.48°C and the relative humidity was 69.44%.Results Dietary addition of Bet had no significant effect on growth performance and health status of growing rabbits(P>0.05),but it increased ileal secretory immunoglobulin A content compared to the control under summer heat(P<0.05).Addition of 0.75 g/kg Bet up-regulated jejunal IL-4,down-regulated ileal TNF-αexpression(P<0.05).The addition of 1.0 g/kg Bet increased the villi height(VH)in the jejunum(P<0.05).Serum glucose levels were reduced,and the expression of SLC6A20 was up-regulated in jejunum and ileum of rabbits fed with 1.5 g/kg Bet(P<0.05).When added at 2.0 g/kg,Bet reduced serum HSP70 content,increased jejunal VH,and up-regulated duodenal SLC7A6,SLC38A2,mTOR and 4EBP-2 expression(P<0.05).Correlation analysis revealed that intestinal mTOR expression was significantly and positively correlated with SLC7A6,SLC38A2,SLC36A1 and IL-4 expression(P<0.05).Conclusions Dietary addition of Bet can up-regulate the expression of anti-inflammatory factors through the AAT/mTOR pathway,improve the intestinal immune function,alleviate intestinal damage in growing rabbits caused by summer heat,and improve intestinal health.展开更多
By using scanning tunneling microscopy,we investigated the electronic evolution of T_(d)-WTe_(2) via in-situ surface alkali K atoms deposition.The T_(d)-WTe_(2) surface is electron doped upon K deposition,and as the K...By using scanning tunneling microscopy,we investigated the electronic evolution of T_(d)-WTe_(2) via in-situ surface alkali K atoms deposition.The T_(d)-WTe_(2) surface is electron doped upon K deposition,and as the K coverage increases,two gaps are sequentially opened near Fermi energy,which probably indicates that two phase transitions concomitantly occur during electron doping.The two gaps both show a dome-like dependence on the K coverage.While the bigger gap shows no prominent dependence on the magnetic field,the smaller one can be well suppressed and thus possibly corresponds to the superconducting transition.This work indicates that T_(d)-WTe_(2) exhibits rich quantum states closely related to the carrier concentration.展开更多
Population density functions have long been used to describe the spatial structure of regional population distributions.Several studies have been conducted to examine the population distribution in Shandong Province,C...Population density functions have long been used to describe the spatial structure of regional population distributions.Several studies have been conducted to examine the population distribution in Shandong Province,China,but few have applied regional density functions to the analysis.Therefore,based on the 2000,2010,and 2020 population censuses,this study used monocentric and polycentric regional density functions to study the characteristics of population agglomeration and diffusion in Shandong.This is followed by an in-depth discussion based on population growth rate data and hot-and cold-spot analyses.The results showed that the Shandong Province population was spatially unevenly distributed.Population growth rates were higher in urban centers and counties,with more significant changes in population size in the eastern coastal areas than in the inland areas.As verified in this study,the logarithmic form of the single-center regional density function R2 was greater than 0.8,which was in line with the population spatial structure of Shandong Province.During the study period,the estimated population density of the regional center and the absolute value of the regional population density gradient both increased,indicating a clear and increasing trend of centripetal agglomeration of regional centers over the study period.Overall,the R2 value of the multicenter region density function was higher than that of the single-center region density function.The polycentric regional density function showed that the population density gradient of some centers had a downward trend,which reflected the spatial development trend of outward diffusion in these centers.Meanwhile,the variation in the estimated population density and the population density gradient exhibited differences in the central population distribution patterns at different levels.展开更多
Developing new linkages by means of new reversible bonds is essential towards expanding the scope of covalent organic frameworks(COFs),which has become one of the major research targets in this area.Herein,the solvoth...Developing new linkages by means of new reversible bonds is essential towards expanding the scope of covalent organic frameworks(COFs),which has become one of the major research targets in this area.Herein,the solvothermal reaction of octahydroxylphthalocyaninato metal complexes MPc(OH)8 with SiO_(2)under the catalysis of methanolic lithium affords a series of two-dimension(2D)COFs,PT-Si-COF-M(M=Co,Ni,and Zn).The planar-square tetracoordinated SiO_(4)-moiety connected 2D network nature of PT-Si-COFs has been demonstrated by powder X-ray diffraction,transmission electron microscopy,29Si nuclear magnetic resonance,and X-ray absorption fine structure spectroscopy.Theoretical calculations reveal that effective interlayerπ-πinteraction countervails the energy disadvantage of the parallel arranged Pc macrocycles connected by unprecedented planar-square coordination rather than the well-known tetrahedrally coordinated SiO_(4)moiety.This,in combination with the tightly hindered rotation of Pc unit in bulky frameworks once formed due to the extremely narrow interlayer spacing of ca.bonds is essential towards expanding the scope of covalent organic frameworks(COFs),which has become one of the major research targets in this area.Herein,the solvothermal reaction of octahydroxylphthalocyaninato metal complexes MPc(OH)8 with SiO_(2)under the catalysis of methanolic lithium affords a series of two-dimension(2D)COFs,PT-Si-COF-M(M=Co,Ni,and Zn).The planar-square tetracoordinated SiO_(4)-moiety connected 2D network nature of PT-Si-COFs has been demonstrated by powder X-ray diffraction,transmission electron microscopy,29Si nuclear magnetic resonance,and X-ray absorption fine structure spectroscopy.Theoretical calculations reveal that effective interlayerπ-πinteraction countervails the energy disadvantage of the parallel arranged Pc macrocycles connected by unprecedented planar-square coordination rather than the well-known tetrahedrally coordinated SiO_(4)moiety.This,in combination with the tightly hindered rotation of Pc unit in bulky frameworks once formed due to the extremely narrow interlayer spacing of ca.3.2Å,allows the isolation of Pc-based 2D COFs.PT-Si-COF-M possess conjugated,N/O-rich,and ordered porous frameworks,endowing them with remarkable anodic K+storage performancewith a high specific capacity(384-386 mA h g^(-1)at 40 mA g^(-1)),outstanding rate performance,and excellent cycling stability.展开更多
The fundamental problems associated with structural inhomogeneities of hydrogen-bonded organic frameworks(HOFs),such as surface terminations and host-vip heterostructures that govern their functionalities and growth...The fundamental problems associated with structural inhomogeneities of hydrogen-bonded organic frameworks(HOFs),such as surface terminations and host-vip heterostructures that govern their functionalities and growth mechanisms,remain a critical gap in knowledge.This arises from the lack of advanced real-space structural characterization tools with molecular precision.By leveraging state-of-the-art cryogenic low-dose electron microscopy,this work overcomes the beam damage limitations of traditional techniques and elucidates the crystal structures,surface terminations,and host-vip structures of HOFs at molecular-level.Real-space observations confirm lateral crystal growth consistent with the terrace-ledge-kink(TLK)model,but deviate from the classical monomer-addition mechanism.Instead,we propose a nonclassical cooperative multisite monomer-addition mechanism,where simultaneous monomer addition at both framework and vip sites eventually drives crystal faceting.展开更多
The controlled growth of perovskite nanowires along predefined orientations offers significant advantages over traditional post-growth assembly strategies,facilitating their integration into compact functional devices...The controlled growth of perovskite nanowires along predefined orientations offers significant advantages over traditional post-growth assembly strategies,facilitating their integration into compact functional devices.In this study,a nanogroove-confined recrystallization process is designed for the precise and scalable growth of oriented perovskite nanowires with millimeter lengths and high crystallinity.The process involves annealing a perovskite-containing solution sandwiched between a hydrophobic flat silicon wafer and a hydrophilic faceted sapphire wafer featuring parallel nanogrooves at 90℃under ambient conditions.By customizing the electrode design,the nanowire arrays can be seamlessly integrated into monolithic photodetectors with large detection areas or into photodetector arrays with multiple microscale detector cells on their growth substrate.This in-situ integration strategy eliminates the need for complex post-growth processing steps.The photodetectors exhibit exceptional responsivity(38.4 A·W^(−1)),detectivity(4.35×10^(13)Jones),and response times in tens of microseconds across the ultraviolet-visible-near infrared ray(UV-vis-NIR)spectrum.The seamless integration of the nanowire photodetectors opens avenues for practical applications,including high-contrast optical imaging and efficient data transmission through Morse code encoding,leveraging their high on-off current ratios and rapid response.This innovative approach streamlines the growth of highly oriented perovskite nanowires,facilitating their integration into compact optoelectronic devices.展开更多
The Chinese government intends to upgrade its current provincial carbon emission trading pilots to a nationwide scheme by 2015. This study investigates two of scenarios： separated provincial markets and a linked inte...The Chinese government intends to upgrade its current provincial carbon emission trading pilots to a nationwide scheme by 2015. This study investigates two of scenarios： separated provincial markets and a linked inter- provincial market. The carbon abatement effects of separated and linked markets are compared using two pilot provinces of Hubei and Guangdong based on a computable general equilibrium model termed Sino- TERMCo2. Simulation results show that the linked market can improve social welfare and reduce carbon emission intensity for the nation as well as for the Hubei-Guangdong bloc compared to the separated market. However, the combined system also distributes welfare more unevenly and thus increases social inequity. On the policy ground, the current results suggest that a well-constructed, nation- wide carbon market complemented with adequate welfare transfer policies can be employed to replace the current top-down abatement target disaggregation practice.展开更多
In this study we successfully intercalated potassium(K) atoms into single ZrTe_5 crystals by liquid ammonia method, and found a semimetal-to-semiconductor transition at low temperatures in K-intercalated ZrTe_5. As th...In this study we successfully intercalated potassium(K) atoms into single ZrTe_5 crystals by liquid ammonia method, and found a semimetal-to-semiconductor transition at low temperatures in K-intercalated ZrTe_5. As the K concentration increased, the resistance anomalous peak was gradually suppressed until finally disappearing. Whilst, the corresponding Hall resistance measurements consistently showed a sign reversal. The semimetal-to-semiconductor transition can be attributed to a lattice expansion induced by atom intercalation, leading to a larger energy band gap.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.12372376 and U22A20596).
文摘Numerical challenges,incorporating non-uniqueness,non-convexity,undefined gradients,and high curvature,of the positive level sets of yield function are encountered in stress integration when utilizing the return-mapping algorithm family.These phenomena are illustrated by an assessment of four typical yield functions:modified spatially mobilized plane criterion,Lade criterion,Bigoni-Piccolroaz criterion,and micromechanics-based upscaled Drucker-Prager criterion.One remedy to these issues,named the"Hop-to-Hug"(H2H)algorithm,is proposed via a convexification enhancement upon the classical cutting-plane algorithm(CPA).The improved robustness of the H2H algorithm is demonstrated through a series of integration tests in one single material point.Furthermore,a constitutive model is implemented with the H2H algorithm into the Abaqus/Standard finite-element platform.Element-level and structure-level analyses are carried out to validate the effectiveness of the H2H algorithm in convergence.All validation analyses manifest that the proposed H2H algorithm can offer enhanced stability over the classical CPA method while maintaining the ease of implementation,in which evaluations of the second-order derivatives of yield function and plastic potential function are circumvented.
文摘A novel Al-14.1 Mg-0.47 Si-0.31 Sc-0.17 Zr alloy was applied in the printing process of selective laser melting(SLM),and the corresponding microstructural feature,phase identification,tensile properties and corrosion behavior of the Al Mg Si Sc Zr alloy were studied in detail.As fabricated at 160 W and 200 mm/s,the Mg content of bulk sample decreased to 11.7 wt%due to the element vaporization at high energy density,and the density of this additively manufactured Al Mg Si Sc Zr alloy was 2.538 g/cm^(3),which is4.2%8.5%lighter than that of other SLM-processed Al alloys.After heat-treated(HT)at 325℃and 6 h,the microstructure was almost unchanged with an alternate distribution of fine equiaxed crystals and coarse columnar crystals.Nano-sized Al3(Sc,Zr)and Mg_(2)Si phases precipitated dispersedly in the Al matrix,and the tensile strength increased from 487.6 MPa to 578.4 MPa for precipitation strengthening and fine grain strengthening.With a fine grain size of 2.53μm,an excellent corrosion resistance was obtained for the as-printed(AP)Al Mg Si Sc Zr alloy.While the corrosion resistance of HT sample decreased slightly for the formation of non-dense oxide layer and pitting corrosion induced by diffuse precipitation distribution.This SLM-printed Al Mg Si Sc Zr alloy with high specific strength,good thermal stability and excellent corrosion resistance has broad prospects for the aerospace and automotive applications.
文摘The new generation of Sc and Zr modified Al alloys has been attracted wide concerns in aerospace industry,owing to the excellent mechanical performances and superior thermal stability than other normal Al alloys.By microalloying with Sc and Zr,the Al3(Sc,Zr)particle forms as the grain refiner during the solidification,which is extremely beneficial for the laser powder bed fusion(LPBF)processed Al alloys.In this study,a new type Al-14.1 Mg-0.47 Si-0.31 Sc-0.17 Zr alloy was additively manufactured by LPBF,and the microstructure,tensile properties and thermal stability were studied in detail.By using a single melt-67°scanning strategy,the LPBF-processed specimen with a relative density of 99.4%and tensile strength of 487.7 MPa was obtained at 160 W-200 mm/s.And this AlMgSiScZr alloy can still exhibit an excellent tensile strength of 393.9 MPa at a moderate temperature of 473 K.After the aging treatment,the tensile properties further increased due to the precipitate hardening of Mg2Si and Al3(Sc,Zr),and the maximum value(580 MPa)was reached at an aging time of 10 h.The average crystal size was almost unchanged after aging treated at 325℃and 24 h,indicating this AlMgSiScZr alloy has an improved thermal stability.The AlMgSiScZr alloy is recommended to substitute some particular titanium alloys in aerospace field afterwards.
基金This work was supported by the National Key R&D Program of China(2016YFB0100301)National Natural Science Foundation of China(21875022,51802020)+2 种基金the Natural Science Foundation of Chongqing,China(cstc2020jcyj-msxmX0654,cstc2020jcyj-msxm X0589)the Science and Technology Innovation Foundation of Beijing Institute of Technology Chongqing Innovation Center(2020CX5100006)the Young Elite Scientists Sponsorship Program by CAST(2018QNRC001).L.Chen,N.Li and D.Y.Cao acknowledge the support from Beijing Institute of Technology Research Fund Program for Young Scholars.
文摘Ni-rich layered cathode is regarded as one of the most promising candidates to achieve lithium-ion batteries (LIBs) with high energy density. However, due to the irreversible phase transformation (IPT) and its eventual propagation from surface to the bulk of the material, Ni-rich layered cathode typically suffers from severe capacity fading, structure failure, and thermal instability, which greatly hinders its mass adoption. Hence, achieving an in-depth understanding of the IPT propagation mechanism in Ni-rich layered cathode is crucial in addressing these issues. Herein, the triggering factor of IPT propagation in Ni-rich cathode is verified to be the initial surface disordered cation mixing domain covered by a thin rock-salt phase, instead of the rock-salt phase itself. According to the density functional theory (DFT) results, it is further illustrated that the metastable cation mixing domain possesses a lower Ni migration energy barrier, which facilitates the migration of Ni ions towards the Li slab, and thus driving the propagation of IPT from surface to the bulk of the material. This finding clarifies a prevailing debate regarding the surface impurity phases of Ni-rich cathode material and reveals the origin of IPT propagation, which implies the principle and its effectiveness of tuning the surface microstructure to address the structural and thermal instability issue of Ni-rich layered cathode materials.
基金supported by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Officesupported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office, under Contract No. DE-SC0012704+1 种基金supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract DE-AC02-06CH11357supported by the Vehicle Technologies Office of the U.S. Department of Energy。
文摘Nickel-rich transition-metal oxides are widely regarded as promising cathode materials for high-energydensity lithium-ion batteries for emerging electric vehicles. However, achieving high energy density in Ni-rich cathodes is accompanied by substantial safety and cycle-life obstacles. The major issues of Ni-rich cathodes at high working potentials are originated from the unstable cathode-electrolyte interface, while the underlying mechanism of parasitic reactions towards surface reconstructions of cathode materials is not well understood. In this work, we controlled the Li_(2)CO_(3) impurity content on LiNi_(0.83)Mn_(0.1)Co_(0.07)O_(2) cathodes using air, tank-air, and O_(2) synthesis environments. Home-built high-precision leakage current and on-line electrochemical mass spectroscopy experiments verify that Li_(2)CO_(3) impurity is a significant promoter of parasitic reactions on Ni-rich cathodes. The rate of parasitic reactions is strongly correlated to Li_(2)CO_(3) content and severe performance deterioration of Ni83 cathodes.The post-mortem characterizations via high-resolution transition electron microscope and X-ray photoelectron spectroscopy depth profiles reveal that parasitic reactions promote more Ni reduction and O deficiency and even rock-salt phase transformation at the surface of cathode materials. Our observation suggests that surface reconstructions have a strong affiliation to parasitic reactions that create chemically acidic environment to etch away the lattice oxygen and offer the electrical charge to reduce the valence state of transition metal. Thus, this study advances our understanding on surface reconstructions of Nirich cathodes and prepares us for searching for rational strategies.
文摘Background The aim of this experiment was to investigate the effect of different levels of betaine(Bet)inclusion in the diet on the intestinal health of growing rabbits under summer heat.A total of 100 weaned Qixing meat rabbits aged 35 d with body weight of 748.61±38.59 g were randomly divided into 5 treatment groups:control group(basal diet)and Bet groups(basal diet+0.75,1.0,1.5 or 2.0 g/kg Bet).The average daily temperature in the rabbitry during the experiment was 30.48°C and the relative humidity was 69.44%.Results Dietary addition of Bet had no significant effect on growth performance and health status of growing rabbits(P>0.05),but it increased ileal secretory immunoglobulin A content compared to the control under summer heat(P<0.05).Addition of 0.75 g/kg Bet up-regulated jejunal IL-4,down-regulated ileal TNF-αexpression(P<0.05).The addition of 1.0 g/kg Bet increased the villi height(VH)in the jejunum(P<0.05).Serum glucose levels were reduced,and the expression of SLC6A20 was up-regulated in jejunum and ileum of rabbits fed with 1.5 g/kg Bet(P<0.05).When added at 2.0 g/kg,Bet reduced serum HSP70 content,increased jejunal VH,and up-regulated duodenal SLC7A6,SLC38A2,mTOR and 4EBP-2 expression(P<0.05).Correlation analysis revealed that intestinal mTOR expression was significantly and positively correlated with SLC7A6,SLC38A2,SLC36A1 and IL-4 expression(P<0.05).Conclusions Dietary addition of Bet can up-regulate the expression of anti-inflammatory factors through the AAT/mTOR pathway,improve the intestinal immune function,alleviate intestinal damage in growing rabbits caused by summer heat,and improve intestinal health.
基金financially supported by the National Natural Science Foundation of China(Grants Nos.11790311,92165205,51902152,11874210,and 11774149)the National Key R&D Program of China(Grants No.2021YFA1400403)。
文摘By using scanning tunneling microscopy,we investigated the electronic evolution of T_(d)-WTe_(2) via in-situ surface alkali K atoms deposition.The T_(d)-WTe_(2) surface is electron doped upon K deposition,and as the K coverage increases,two gaps are sequentially opened near Fermi energy,which probably indicates that two phase transitions concomitantly occur during electron doping.The two gaps both show a dome-like dependence on the K coverage.While the bigger gap shows no prominent dependence on the magnetic field,the smaller one can be well suppressed and thus possibly corresponds to the superconducting transition.This work indicates that T_(d)-WTe_(2) exhibits rich quantum states closely related to the carrier concentration.
基金This research was funded by the Shandong Provincial Natural Science Foundation(grant number ZR202102240088).
文摘Population density functions have long been used to describe the spatial structure of regional population distributions.Several studies have been conducted to examine the population distribution in Shandong Province,China,but few have applied regional density functions to the analysis.Therefore,based on the 2000,2010,and 2020 population censuses,this study used monocentric and polycentric regional density functions to study the characteristics of population agglomeration and diffusion in Shandong.This is followed by an in-depth discussion based on population growth rate data and hot-and cold-spot analyses.The results showed that the Shandong Province population was spatially unevenly distributed.Population growth rates were higher in urban centers and counties,with more significant changes in population size in the eastern coastal areas than in the inland areas.As verified in this study,the logarithmic form of the single-center regional density function R2 was greater than 0.8,which was in line with the population spatial structure of Shandong Province.During the study period,the estimated population density of the regional center and the absolute value of the regional population density gradient both increased,indicating a clear and increasing trend of centripetal agglomeration of regional centers over the study period.Overall,the R2 value of the multicenter region density function was higher than that of the single-center region density function.The polycentric regional density function showed that the population density gradient of some centers had a downward trend,which reflected the spatial development trend of outward diffusion in these centers.Meanwhile,the variation in the estimated population density and the population density gradient exhibited differences in the central population distribution patterns at different levels.
基金supported by the financial support from the Natural Science Foundation of China(grant nos.22235001,22122505,22175020,and 22075250)the National Key Research and Development Program of China(grant no.2022YFE0113800).
文摘Developing new linkages by means of new reversible bonds is essential towards expanding the scope of covalent organic frameworks(COFs),which has become one of the major research targets in this area.Herein,the solvothermal reaction of octahydroxylphthalocyaninato metal complexes MPc(OH)8 with SiO_(2)under the catalysis of methanolic lithium affords a series of two-dimension(2D)COFs,PT-Si-COF-M(M=Co,Ni,and Zn).The planar-square tetracoordinated SiO_(4)-moiety connected 2D network nature of PT-Si-COFs has been demonstrated by powder X-ray diffraction,transmission electron microscopy,29Si nuclear magnetic resonance,and X-ray absorption fine structure spectroscopy.Theoretical calculations reveal that effective interlayerπ-πinteraction countervails the energy disadvantage of the parallel arranged Pc macrocycles connected by unprecedented planar-square coordination rather than the well-known tetrahedrally coordinated SiO_(4)moiety.This,in combination with the tightly hindered rotation of Pc unit in bulky frameworks once formed due to the extremely narrow interlayer spacing of ca.bonds is essential towards expanding the scope of covalent organic frameworks(COFs),which has become one of the major research targets in this area.Herein,the solvothermal reaction of octahydroxylphthalocyaninato metal complexes MPc(OH)8 with SiO_(2)under the catalysis of methanolic lithium affords a series of two-dimension(2D)COFs,PT-Si-COF-M(M=Co,Ni,and Zn).The planar-square tetracoordinated SiO_(4)-moiety connected 2D network nature of PT-Si-COFs has been demonstrated by powder X-ray diffraction,transmission electron microscopy,29Si nuclear magnetic resonance,and X-ray absorption fine structure spectroscopy.Theoretical calculations reveal that effective interlayerπ-πinteraction countervails the energy disadvantage of the parallel arranged Pc macrocycles connected by unprecedented planar-square coordination rather than the well-known tetrahedrally coordinated SiO_(4)moiety.This,in combination with the tightly hindered rotation of Pc unit in bulky frameworks once formed due to the extremely narrow interlayer spacing of ca.3.2Å,allows the isolation of Pc-based 2D COFs.PT-Si-COF-M possess conjugated,N/O-rich,and ordered porous frameworks,endowing them with remarkable anodic K+storage performancewith a high specific capacity(384-386 mA h g^(-1)at 40 mA g^(-1)),outstanding rate performance,and excellent cycling stability.
基金supported by the National Key Research and Development Program of China(2022YFE0113800)Zhejiang Provincial Natural Science Foundation of China(LBMHZ25B030005)+1 种基金the National Nature Science Foundation of China(22122505)the Cultivation Fund of Zhejiang University of Technology for Excellent Doctoral Dissertation.
文摘The fundamental problems associated with structural inhomogeneities of hydrogen-bonded organic frameworks(HOFs),such as surface terminations and host-vip heterostructures that govern their functionalities and growth mechanisms,remain a critical gap in knowledge.This arises from the lack of advanced real-space structural characterization tools with molecular precision.By leveraging state-of-the-art cryogenic low-dose electron microscopy,this work overcomes the beam damage limitations of traditional techniques and elucidates the crystal structures,surface terminations,and host-vip structures of HOFs at molecular-level.Real-space observations confirm lateral crystal growth consistent with the terrace-ledge-kink(TLK)model,but deviate from the classical monomer-addition mechanism.Instead,we propose a nonclassical cooperative multisite monomer-addition mechanism,where simultaneous monomer addition at both framework and vip sites eventually drives crystal faceting.
基金financial support by the Guangdong Provincial Pearl River Talents Program(No.2019QN01C290)the Outstanding Young Scholar at South China Normal University,Guangdong Provincial Key Laboratory of Optical Information Materials and Technology under Grant(No.2023B1212060065)+1 种基金“Golden Seed”Extracurricular Scientific Research Project at South China Normal University(No.23HDKC06)National Center for International Research on Green Optoelectronics,MOE International Laboratory for Optical Information Technologies and the 111 Project(No.D16009).
文摘The controlled growth of perovskite nanowires along predefined orientations offers significant advantages over traditional post-growth assembly strategies,facilitating their integration into compact functional devices.In this study,a nanogroove-confined recrystallization process is designed for the precise and scalable growth of oriented perovskite nanowires with millimeter lengths and high crystallinity.The process involves annealing a perovskite-containing solution sandwiched between a hydrophobic flat silicon wafer and a hydrophilic faceted sapphire wafer featuring parallel nanogrooves at 90℃under ambient conditions.By customizing the electrode design,the nanowire arrays can be seamlessly integrated into monolithic photodetectors with large detection areas or into photodetector arrays with multiple microscale detector cells on their growth substrate.This in-situ integration strategy eliminates the need for complex post-growth processing steps.The photodetectors exhibit exceptional responsivity(38.4 A·W^(−1)),detectivity(4.35×10^(13)Jones),and response times in tens of microseconds across the ultraviolet-visible-near infrared ray(UV-vis-NIR)spectrum.The seamless integration of the nanowire photodetectors opens avenues for practical applications,including high-contrast optical imaging and efficient data transmission through Morse code encoding,leveraging their high on-off current ratios and rapid response.This innovative approach streamlines the growth of highly oriented perovskite nanowires,facilitating their integration into compact optoelectronic devices.
文摘The Chinese government intends to upgrade its current provincial carbon emission trading pilots to a nationwide scheme by 2015. This study investigates two of scenarios： separated provincial markets and a linked inter- provincial market. The carbon abatement effects of separated and linked markets are compared using two pilot provinces of Hubei and Guangdong based on a computable general equilibrium model termed Sino- TERMCo2. Simulation results show that the linked market can improve social welfare and reduce carbon emission intensity for the nation as well as for the Hubei-Guangdong bloc compared to the separated market. However, the combined system also distributes welfare more unevenly and thus increases social inequity. On the policy ground, the current results suggest that a well-constructed, nation- wide carbon market complemented with adequate welfare transfer policies can be employed to replace the current top-down abatement target disaggregation practice.
基金supported by the Ministry of Science and Technology of China(Grant Nos.2014CB921103,and 2015CB921203)the National Natural Science Foundation of China(Grant Nos.11774149,11790311,11674157,11674154,51032003,1171101156,11374149,and 11374140)
文摘In this study we successfully intercalated potassium(K) atoms into single ZrTe_5 crystals by liquid ammonia method, and found a semimetal-to-semiconductor transition at low temperatures in K-intercalated ZrTe_5. As the K concentration increased, the resistance anomalous peak was gradually suppressed until finally disappearing. Whilst, the corresponding Hall resistance measurements consistently showed a sign reversal. The semimetal-to-semiconductor transition can be attributed to a lattice expansion induced by atom intercalation, leading to a larger energy band gap.
