The interface properties in two-dimensional(2D)layered materials and their van der Waals(vdW)homo-/heterostructures are of importance in both uncovering novel physical phenomena and optimizing device performance.Despi...The interface properties in two-dimensional(2D)layered materials and their van der Waals(vdW)homo-/heterostructures are of importance in both uncovering novel physical phenomena and optimizing device performance.Despite considerable research interest and enthusiasm direct toward the interlayer coupling in 2D homo-and heterostructures,there is limited research on the coupling at the 2D layered material-substrate interface.This limitation is due to the challenges in achieving direct detection.Currently,the coupling mechanisms at the 2D layered material-substrate interface is ambiguous,which needs greater attention.In this study,we have systematically investigated the interface coupling between monolayer WS_(2)and its supported substrates using high-temperature and high-vacuum in-situ Raman spectroscopy through monitoring the low-frequency Raman mode of monolayer WS_(2).Our findings reveal that both interfacial spacing and strain can significantly affect the coupling strength between the monolayer WS_(2)and the supported substrate.More notably,we found that the strategic introduction of appropriate interfacial strain can effectively enhance the interface coupling.Consequently,we have succeeded in achieving effective regulation of the sample-substrate coupling via a convenient way of controlling the cooling process during annealing.Our findings contribute to a deeper understanding of the coupling correlation between 2D layered materials and substrates,which is of great significance for the design and optimization of high-performance devices based on 2D layered semiconductors.展开更多
Since the first demonstrations of radio-frequency(RF)circuits,the physics of the electromagnetic(EM)field and its regulation and control with codesigned circuits,have become essential competencies of RF circuit design...Since the first demonstrations of radio-frequency(RF)circuits,the physics of the electromagnetic(EM)field and its regulation and control with codesigned circuits,have become essential competencies of RF circuit designers.Leveraging advanced regulation or control methods,numerous high-performance circuits have been developed at RF and millimeter-wave(mm-wave)frequencies.Three main methods of electromagnetic regulation have been widely utilized,namely,the separation of electric and magnetic coupling paths,the manipulation of electromagnetic energy through the coupling of multiple tanks or multiple resonators,and the regulation of electromagnetic fields in air cavities or meta-substrates.The separated coupling paths of electric and magnetic fields provide guidance for designing a high-performance filter topology with a quasielliptical response through additional zeros.The manipulation of the EM field through electrical and magnetic intercouplings of multitanks or multiresonators,such as are used in oscillators,power amplifiers(PAs),etc.,results in remarkable power efficiency,size reduction,and wide bandwidth.The regulation of electromagnetism through an air cavity,patterned substrate,or metasubstrate reduces dielectric losses and size,especially when using a substrate integrated suspended line(SISL)platform.Many excellent circuits have been reported based on SISL with low loss,high integration,and self-packaging.Here,we present state-of-the-art cases that demonstrate the benefits of EM field regulation and control.展开更多
Single-atom catalysts(SACs)have emerged as one of the most competitive catalysts toward a variety of important electrochemical reactions,thanks to their maximum atom economy,unique electronic and geometric structures....Single-atom catalysts(SACs)have emerged as one of the most competitive catalysts toward a variety of important electrochemical reactions,thanks to their maximum atom economy,unique electronic and geometric structures.However,the role of SACs supports on the catalytic performance does not receive enough research attentions.Here,we report an efficient route for synthesis of single atom Zn loading on the N-doped carbon nano-onions(ZnN/CNO).ZnN/CNO catalysts show an excellent high selectivity for CO_(2) electro-reduction to CO with a Faradaic efficiency of CO(FECO)up to 97%at -0.47 V(vs.reversible hydrogen electrode,RHE)and remarkable durability without activity decay.To our knowledge,ZnN/CNO is the best activity for the Zn based catalysts up to now,and superior to single atom Zn loading on the two-dimensional planar and porous structure of graphene substrate,although the graphene with larger surface area.The exact role of such carbon nano-onions(CNO)support is studied systematically by coupling characterizations and electrochemistry with density functional theory(DFT)calculations,which have attributed such good performance to the increased curvature.Such increased curvature modifies the surface charge,which then changes the adsorption energies of key intermediates,and improves the selectivity for CO generation accordingly.展开更多
A wideband rectangular patch antenna resonat- ing at 3.5 GHz and 8 GHz frequencies is developed on a flexible substrate, which can be used for wearable applications. The proposed antenna gives a wide impe- dance bandw...A wideband rectangular patch antenna resonat- ing at 3.5 GHz and 8 GHz frequencies is developed on a flexible substrate, which can be used for wearable applications. The proposed antenna gives a wide impe- dance bandwidth of 116%, operating from 2.SGHz to 9.5 GHz, covering most of the ultra-wideband （UWB） operating frequency range. A two-element multiple-input multiple-output （MIMO） system is developed using the proposed antenna, and the mutual coupling between the two antennas for various separations and frequencies is analyzed by using artificial neural networks （ANNs）. The neural structure is trained by using different ANN algorithms and a comparative study is made between them. It is shown that, quasi-Newton （QN） and quasi- Newton multi layer perceptron （QN-MLP） algorithms are better in terms of training, testing errors, and correlation coefficient.展开更多
Indole alkaloids have attracted considerable attention from synthetic chemists and biochemists for their structural diversity and important biological activities.Compared with traditional organic synthesis methods,the...Indole alkaloids have attracted considerable attention from synthetic chemists and biochemists for their structural diversity and important biological activities.Compared with traditional organic synthesis methods,the strategy of using cytochrome P450s'extraordinary abilities to selectively activate carbon-hydrogen bonds to assist in the synthesis of various indole alkaloids has the characteristics of short synthetic route,mild conditions and high atomic economy.Here,we utilized P450 monooxygenases HinD and TleB to synthesize a novel 6/5/8 tricyclic product from(S)-N-((S)-1-(4-fluoro-1H-indol-3-yl)-3-hydroxypropan-2-yl)-2-mercapto-3-methylbutanamide through the substrate structure-directed strategy.TleB was more effective in catalyzing C–S coupling,and was used to synthesize a series of 6/5/8 tricyclic indololactam derivatives to provide drug candidates.Interestingly,the S–S coupling product was observed in HinD catalysis,which was a minor product in the wild-type TleB catalysis.With the help of protein engineering,we accurately regulated the catalytic flow and reversed the selectivity of TleB to obtain the S–S coupling product.At the same time,the reaction mechanism was reasonably speculated by means of site blocking and protein-substrate complex analysis.展开更多
For three-dimensional(3D)mono-layer molecular thin-film lubrication,the elasticity of the substrate affects the tribological behaviors of a thin fluid film confined by two solid substrates.To account for the elastic e...For three-dimensional(3D)mono-layer molecular thin-film lubrication,the elasticity of the substrate affects the tribological behaviors of a thin fluid film confined by two solid substrates.To account for the elastic effects,this study establishes a multi-scale method that combines an atomistic description of the near region with a coarse-grained description of the far region of the solid substrate to simulate the thin-film lubrication.It is demonstrated that for a given temperature range and film-substrate coupling strength,the multi-scale method is in excellent agreement with the fully atomistic simulation.This study reveals that the elastic response of the substrate can be effectively rendered in the hybrid scheme.In the application of the multi-scale method to investigate the tribological properties of the multi-layer molecular thin-film lubrication,it is determined that the systematic static friction coefficient monotonously decreases as the molecular layer thickness in the fluid film increases.In comparison to the mono-layer molecular thin-film lubrication,the multi-layer molecular thin-film lubrication plays a role in reducing the friction and wear of the system.展开更多
基金supported by the National Key R&D Program of China(2018YFA0703700)the National Natural Science Foundation of China(62374037)+1 种基金Shanghai Municipal Natural Science Foundation(20ZR1403200)the National Young 1000 Talent Plan of China。
文摘The interface properties in two-dimensional(2D)layered materials and their van der Waals(vdW)homo-/heterostructures are of importance in both uncovering novel physical phenomena and optimizing device performance.Despite considerable research interest and enthusiasm direct toward the interlayer coupling in 2D homo-and heterostructures,there is limited research on the coupling at the 2D layered material-substrate interface.This limitation is due to the challenges in achieving direct detection.Currently,the coupling mechanisms at the 2D layered material-substrate interface is ambiguous,which needs greater attention.In this study,we have systematically investigated the interface coupling between monolayer WS_(2)and its supported substrates using high-temperature and high-vacuum in-situ Raman spectroscopy through monitoring the low-frequency Raman mode of monolayer WS_(2).Our findings reveal that both interfacial spacing and strain can significantly affect the coupling strength between the monolayer WS_(2)and the supported substrate.More notably,we found that the strategic introduction of appropriate interfacial strain can effectively enhance the interface coupling.Consequently,we have succeeded in achieving effective regulation of the sample-substrate coupling via a convenient way of controlling the cooling process during annealing.Our findings contribute to a deeper understanding of the coupling correlation between 2D layered materials and substrates,which is of great significance for the design and optimization of high-performance devices based on 2D layered semiconductors.
文摘Since the first demonstrations of radio-frequency(RF)circuits,the physics of the electromagnetic(EM)field and its regulation and control with codesigned circuits,have become essential competencies of RF circuit designers.Leveraging advanced regulation or control methods,numerous high-performance circuits have been developed at RF and millimeter-wave(mm-wave)frequencies.Three main methods of electromagnetic regulation have been widely utilized,namely,the separation of electric and magnetic coupling paths,the manipulation of electromagnetic energy through the coupling of multiple tanks or multiple resonators,and the regulation of electromagnetic fields in air cavities or meta-substrates.The separated coupling paths of electric and magnetic fields provide guidance for designing a high-performance filter topology with a quasielliptical response through additional zeros.The manipulation of the EM field through electrical and magnetic intercouplings of multitanks or multiresonators,such as are used in oscillators,power amplifiers(PAs),etc.,results in remarkable power efficiency,size reduction,and wide bandwidth.The regulation of electromagnetism through an air cavity,patterned substrate,or metasubstrate reduces dielectric losses and size,especially when using a substrate integrated suspended line(SISL)platform.Many excellent circuits have been reported based on SISL with low loss,high integration,and self-packaging.Here,we present state-of-the-art cases that demonstrate the benefits of EM field regulation and control.
基金This work was supported by the National Key R&D Program of China(2020YFA0710404)the Beijing Natural Science Foundation(2182077)the National Natural Science Foundation of China(21477136,51972281,and 21703250).
文摘Single-atom catalysts(SACs)have emerged as one of the most competitive catalysts toward a variety of important electrochemical reactions,thanks to their maximum atom economy,unique electronic and geometric structures.However,the role of SACs supports on the catalytic performance does not receive enough research attentions.Here,we report an efficient route for synthesis of single atom Zn loading on the N-doped carbon nano-onions(ZnN/CNO).ZnN/CNO catalysts show an excellent high selectivity for CO_(2) electro-reduction to CO with a Faradaic efficiency of CO(FECO)up to 97%at -0.47 V(vs.reversible hydrogen electrode,RHE)and remarkable durability without activity decay.To our knowledge,ZnN/CNO is the best activity for the Zn based catalysts up to now,and superior to single atom Zn loading on the two-dimensional planar and porous structure of graphene substrate,although the graphene with larger surface area.The exact role of such carbon nano-onions(CNO)support is studied systematically by coupling characterizations and electrochemistry with density functional theory(DFT)calculations,which have attributed such good performance to the increased curvature.Such increased curvature modifies the surface charge,which then changes the adsorption energies of key intermediates,and improves the selectivity for CO generation accordingly.
文摘A wideband rectangular patch antenna resonat- ing at 3.5 GHz and 8 GHz frequencies is developed on a flexible substrate, which can be used for wearable applications. The proposed antenna gives a wide impe- dance bandwidth of 116%, operating from 2.SGHz to 9.5 GHz, covering most of the ultra-wideband （UWB） operating frequency range. A two-element multiple-input multiple-output （MIMO） system is developed using the proposed antenna, and the mutual coupling between the two antennas for various separations and frequencies is analyzed by using artificial neural networks （ANNs）. The neural structure is trained by using different ANN algorithms and a comparative study is made between them. It is shown that, quasi-Newton （QN） and quasi- Newton multi layer perceptron （QN-MLP） algorithms are better in terms of training, testing errors, and correlation coefficient.
基金supported by the National Key Research and Development Program of China(2018YFA0903200 to H.S.)Wuhan University,Undergraduate Training Programs for Innovation and Entrepreneurship of Wuhan University to Y.L.+1 种基金the Science and Technology Commission of Shanghaithe National Natural Science Foundation of China(31900033,21ZR1433700)。
文摘Indole alkaloids have attracted considerable attention from synthetic chemists and biochemists for their structural diversity and important biological activities.Compared with traditional organic synthesis methods,the strategy of using cytochrome P450s'extraordinary abilities to selectively activate carbon-hydrogen bonds to assist in the synthesis of various indole alkaloids has the characteristics of short synthetic route,mild conditions and high atomic economy.Here,we utilized P450 monooxygenases HinD and TleB to synthesize a novel 6/5/8 tricyclic product from(S)-N-((S)-1-(4-fluoro-1H-indol-3-yl)-3-hydroxypropan-2-yl)-2-mercapto-3-methylbutanamide through the substrate structure-directed strategy.TleB was more effective in catalyzing C–S coupling,and was used to synthesize a series of 6/5/8 tricyclic indololactam derivatives to provide drug candidates.Interestingly,the S–S coupling product was observed in HinD catalysis,which was a minor product in the wild-type TleB catalysis.With the help of protein engineering,we accurately regulated the catalytic flow and reversed the selectivity of TleB to obtain the S–S coupling product.At the same time,the reaction mechanism was reasonably speculated by means of site blocking and protein-substrate complex analysis.
基金This research is supported by the National Natural Science Foundation of China(Grants Nos.11172310 and 11472284)the Chinese Academy of Sciences(CAS)Strategic Priority Research Program(XDB22040403).
文摘For three-dimensional(3D)mono-layer molecular thin-film lubrication,the elasticity of the substrate affects the tribological behaviors of a thin fluid film confined by two solid substrates.To account for the elastic effects,this study establishes a multi-scale method that combines an atomistic description of the near region with a coarse-grained description of the far region of the solid substrate to simulate the thin-film lubrication.It is demonstrated that for a given temperature range and film-substrate coupling strength,the multi-scale method is in excellent agreement with the fully atomistic simulation.This study reveals that the elastic response of the substrate can be effectively rendered in the hybrid scheme.In the application of the multi-scale method to investigate the tribological properties of the multi-layer molecular thin-film lubrication,it is determined that the systematic static friction coefficient monotonously decreases as the molecular layer thickness in the fluid film increases.In comparison to the mono-layer molecular thin-film lubrication,the multi-layer molecular thin-film lubrication plays a role in reducing the friction and wear of the system.
