The 2D sandwich model serves as a potent tool in exploring the influence of surface geometry on the combustion attributes of Ammonium perchlorate/Hydroxyl-terminated polybutadiene(AP/HTPB)propellant under rapid pressu...The 2D sandwich model serves as a potent tool in exploring the influence of surface geometry on the combustion attributes of Ammonium perchlorate/Hydroxyl-terminated polybutadiene(AP/HTPB)propellant under rapid pressure decay.The thickness of the sandwich propellant is derived from slicing the 3D random particle packing,an approach that enables a more effective examination of the micro-flame structure.Comparative analysis of the predicted burning characteristics has been performed with experimental studies.The findings demonstrate a reasonable agreement,thereby validating the precision and soundness of the model.Based on the typical rapid depressurization environment of solid rocket motor(initial combustion pressure is 3 MPa and the maximum depressurization rate is 1000 MPa/s).A-type(a flatter surface),B-type(AP recesses from the combustion surface),and C-type(AP protrudes from the combustion surface)propellant combustion processes are numerically simulated.Upon comparison of the evolution of gas-phase flame between 0.1 and 1 ms,it is discerned that the flame strength and form created by the three sandwich models differ significantly at the beginning stage of depressurization,with the flame structures gradually becoming harmonized over time.Conclusions are drawn by comparison extinction times:the surface geometry plays a pivotal role in the combustion process,with AP protrusion favoring combustion the most.展开更多
Textured magnesium alloys usually exhibit anisotropic mechanical behavior due to the asymmetric activation of different twinning and slipping modes.This work focuses on the pyramidal slip responses of rolled AZ31 magn...Textured magnesium alloys usually exhibit anisotropic mechanical behavior due to the asymmetric activation of different twinning and slipping modes.This work focuses on the pyramidal slip responses of rolled AZ31 magnesium alloy under two loading conditions,compressive and tensile loading along the normal direction.Under the condition where the compressive loading direction is closely parallel to the c-axis of the unit cell,tensile twinning and basal slips are prohibited, dislocations then active and tend to accumulate at grain boundaries and form dislocation walls.Meanwhile,these dislocations exhibit zigzag morphologies,which result from the cross-slip from {10■1} first-order pyramidal plane to {11■2} second-order pyramidal plane,then back to {10■1} first-order pyramidal plane.Under the condition where tensile twins are prevalent,{10■1} first-order and {11■2} second-order pyramidal dislocations are favorable to be activated.Both types of dislocations behave climb-like dissociations onto the basal plane,forming zigzag dislocations.展开更多
Multi-lane integrated transmitter chips are key components in future compact optical modules to realize high-speed optical interconnects.Thin-film lithium niobate(TFLN)photonics have emerged as a promising platform fo...Multi-lane integrated transmitter chips are key components in future compact optical modules to realize high-speed optical interconnects.Thin-film lithium niobate(TFLN)photonics have emerged as a promising platform for achieving high-performance chip-scale optical systems.Combining a coarse wavelength-division multiplexing(CWDM)devices using fabrication-tolerant angled multimode interferometer structure and high-performance electro-optical modulators,we demonstrate monolithic on-chip four-channel CWDM transmitter on the TFLN platform for the first time.The four-channel CWDM transmitter enables high-speed transmissions of 100 Gb/s data rate per wavelength channel(i.e.,an aggregated date rate of 400 Gb/s).展开更多
Movement intention recognition paves the path to developing Brain-Computer Interface(BCI)applications.Current research mostly focuses on questions like“which hand is intended to move”.While answering questions like...Movement intention recognition paves the path to developing Brain-Computer Interface(BCI)applications.Current research mostly focuses on questions like“which hand is intended to move”.While answering questions like“whether a hand is intended to move”is more desirable for widely real-world applications,because we cannot continuously perform intention tasks during usage,and the gap periods may cause unintended operation resulting in system failures.However,this kind of intention detection task is more difficult,since for a“whether”problem,it is hard to know what the“not”situation is and consequently to acquire training samples for the“not”situation.Furthermore,the occurrence of genuine intentions is comparatively scarce and unexpected,making the intention detection task hard and computation-consuming.To tackle this problem,we propose a Reconstruction-based Intention Detection(RID)framework,which utilises a reconstruction model to represent a high-level abstraction of EEG signals and leverages the reconstruction errors to determine“whether”there is a movement intention.Our framework is not only theoretically flexible and robust to any sophisticated real-world scenarios but also hand-crafted feature and domain knowledge free.Comprehensive experiments on detecting movement intention tasks with different reconstruction models demonstrate the promising performance of the proposed reconstruction intention detection framework.展开更多
In this paper,a Fe-based Mn-Ni–Cr–Mo high strength low alloy(HSLA)steel was prepared by using Vacuum melting,following by hot rolling with 78%deformation and various heat treatment processes.Microstructure were char...In this paper,a Fe-based Mn-Ni–Cr–Mo high strength low alloy(HSLA)steel was prepared by using Vacuum melting,following by hot rolling with 78%deformation and various heat treatment processes.Microstructure were characterized by optical microscope(OM),scanning electron microscope(SEM)equipped with energy dispersive spectrometer.Tensile tests were performed.After direct quenching(Q)from 860℃,the samples were subjected to secondary quenching(L)at different intercritical temperatures within the two-phase region and various tempering temperatures(T).Results show that QLT treatment increases elongation and decreases yield ratio compared with conventional quenching and tempering process(QT).The optimum QLT heat treatment parameter in terms of temperature are determined as Q:860℃,L:700℃,and T:600℃,resulting in the better combined properties with yield strength of 756MPa,tensile strength of 820MPa,tensile elongation of 16.76%and yield ratio of 0.923.展开更多
The Ni-based Udemit720Li superalloy tends to form largeγ/γ'eutectic on grain boundaries(GBs)during solidification due to the addition of excessive Al and Ti elements,which provides convenience to study the effec...The Ni-based Udemit720Li superalloy tends to form largeγ/γ'eutectic on grain boundaries(GBs)during solidification due to the addition of excessive Al and Ti elements,which provides convenience to study the effect of carbide andγ/γ'eutectic on crack initiation and propagation during tensile process.In this paper,Udemit720Li superalloy samples were prepared by induction melting casting method,arc melting and suction casting method.The microstructure,tensile properties and mechanism of crack initiation and propagation in Ni-based superalloy fabricated by two methods are investigated.The results exhibitγ/γ'eutectic accelerates the stress concentration at GB and thus leads to premature fracture failure.The samples with grain-boundary eutectic have higher strain hardening rate,but their cumulative and local misorientations are lower.For samples without eutectic at GB,the primary crack initiates at grain-boundary carbide along GB and extends along GB or into grain matrix,and exhibits better deformation performance and dislocation storage capacity within grains.展开更多
A compact and high-performance coarse wavelength-division multiplexing(CWDM) device is introduced with a footprint of 2.1 mm × 0.02 mm using an angled multimode interferometer structure based on a thin-film lithi...A compact and high-performance coarse wavelength-division multiplexing(CWDM) device is introduced with a footprint of 2.1 mm × 0.02 mm using an angled multimode interferometer structure based on a thin-film lithium niobate(TFLN) platform.The demonstrated device built on a 400 nm thick x-cut TFLN shows ultra-low insertion losses of <0.72 dB.Measured 3 dB bandwidths are 12.1 nm for all channels,and cross talks from adjacent channels are better than 18 dB.Its peak wavelength positions comply with the CWDM standard with a channel spacing of 20 nm.The filter bandwidth of the proposed CWDM device can be tuned by adjusting the structural parameters.This demonstrated CWDM device will promote future realization of multi-channel and multi-wavelength transmitter chips on TFLN.展开更多
Fast electro-optic modulators with an ultracompact footprint and low power consumption are always highly desired for optical interconnects.Here we propose and demonstrate a high-performance lithium niobate electro-opt...Fast electro-optic modulators with an ultracompact footprint and low power consumption are always highly desired for optical interconnects.Here we propose and demonstrate a high-performance lithium niobate electro-optic modulator based on a new 2×2 Fabry–Perot cavity.In this structure,the input and reflected beams are separated by introducing asymmetric multimode-waveguide gratings,enabling TE_(0)−TE_(1)mode conversion.The measured results indicate that the fabricated modulator features a low excess loss of∼0.9dB,a high extinction ratio of∼21dB,a compact footprint of∼2120μm^(2),and high modulation speeds of 40 Gbps OOK and 80 Gbps PAM4 signals.The demonstrated modulator is promising for high-speed data transmission and signal processing.展开更多
A novel platinum-catalyzed asymmetric ring-opening reaction of oxabenzonorbornadiene with terminal alkynes is described.The reaction affords optically active cis-2-alkynyl-1,2-dihydronaphthalen-1-ols in moderate yield...A novel platinum-catalyzed asymmetric ring-opening reaction of oxabenzonorbornadiene with terminal alkynes is described.The reaction affords optically active cis-2-alkynyl-1,2-dihydronaphthalen-1-ols in moderate yields with good enantioselectivity in the presence of catalytic amounts of Pt(COD)Cl_(2)/(S)-BINAP and an excess of zinc powder.The products were obtained exclusively with the relative cis-configuration of the ring substituents and the prevalent(1R,2S)-configuration of the stereocenters,as determined by single crystal X-ray diffraction analysis.展开更多
The recently reported non-fullerene acceptor(NFA)Y6 has been extensively investigated for high-performance organic solar cells.However,its charge transport property and physics have not been fully studied.In this work...The recently reported non-fullerene acceptor(NFA)Y6 has been extensively investigated for high-performance organic solar cells.However,its charge transport property and physics have not been fully studied.In this work,we acquired a deeper understanding of the charge transport in Y6 by fabricating and characterizing thin-film transistors(TFTs),and found that the electron mobility of Y6 is over 0.3-0.4 cm^(2)/(V⋅s)in top-gate bottom-contact devices,which is at least one order of magnitude higher than that of another well-known NFA ITIC.More importantly,we observed band-like transport in Y6 spin-coated films through temperature-dependent measurements on TFTs.This is particularly amazing since such transport behavior is rarely seen in polycrystalline organic semiconductor films.Further morphology characterization and discussions indicate that the band-like transport originates from the unique molecule packing motif of Y6 and the special phase of the film.As such,this work not only demonstrates the superior charge transport property of Y6,but also suggests the great potential of developing high-mobility n-type organic semiconductors,on the basis of Y6.展开更多
A porous polymeric ligand(PPL)has been synthesized and complexed with copper to generate a heterogeneous catalyst(Cu@PPL)that has facilitated the efficient C-N coupling with various(hetero)aryl chlorides under mild co...A porous polymeric ligand(PPL)has been synthesized and complexed with copper to generate a heterogeneous catalyst(Cu@PPL)that has facilitated the efficient C-N coupling with various(hetero)aryl chlorides under mild conditions of visiblelight irradiation at 80°C(58 examples,up to 99%yields).This method could be applied to both aqueous ammonia and substituted amines,and is compatible to a variety of functional groups and heterocycles,as well as allows tandem C-N couplings with conjunctive dihalides.Furthermore,the heterogeneous characteristic of Cu@PPL has enabled a straightforward catalyst separation in multiple times of recycling with negligible catalytic efficiency loss by simple filtration,affording reaction mixtures containing less than 1 ppm of Cu residue.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51176076)。
文摘The 2D sandwich model serves as a potent tool in exploring the influence of surface geometry on the combustion attributes of Ammonium perchlorate/Hydroxyl-terminated polybutadiene(AP/HTPB)propellant under rapid pressure decay.The thickness of the sandwich propellant is derived from slicing the 3D random particle packing,an approach that enables a more effective examination of the micro-flame structure.Comparative analysis of the predicted burning characteristics has been performed with experimental studies.The findings demonstrate a reasonable agreement,thereby validating the precision and soundness of the model.Based on the typical rapid depressurization environment of solid rocket motor(initial combustion pressure is 3 MPa and the maximum depressurization rate is 1000 MPa/s).A-type(a flatter surface),B-type(AP recesses from the combustion surface),and C-type(AP protrudes from the combustion surface)propellant combustion processes are numerically simulated.Upon comparison of the evolution of gas-phase flame between 0.1 and 1 ms,it is discerned that the flame strength and form created by the three sandwich models differ significantly at the beginning stage of depressurization,with the flame structures gradually becoming harmonized over time.Conclusions are drawn by comparison extinction times:the surface geometry plays a pivotal role in the combustion process,with AP protrusion favoring combustion the most.
基金supported by the Bejing Municipal Natural Science Foundation (No.2214072)the Interdisciplinary Research Project for Young Teachers of USTB (Fundamental Research Funds for the Central Universities) (FRF-IDRY-20-034)the Office of China Postdoctoral Council under Award No.YJ20200248。
文摘Textured magnesium alloys usually exhibit anisotropic mechanical behavior due to the asymmetric activation of different twinning and slipping modes.This work focuses on the pyramidal slip responses of rolled AZ31 magnesium alloy under two loading conditions,compressive and tensile loading along the normal direction.Under the condition where the compressive loading direction is closely parallel to the c-axis of the unit cell,tensile twinning and basal slips are prohibited, dislocations then active and tend to accumulate at grain boundaries and form dislocation walls.Meanwhile,these dislocations exhibit zigzag morphologies,which result from the cross-slip from {10■1} first-order pyramidal plane to {11■2} second-order pyramidal plane,then back to {10■1} first-order pyramidal plane.Under the condition where tensile twins are prevalent,{10■1} first-order and {11■2} second-order pyramidal dislocations are favorable to be activated.Both types of dislocations behave climb-like dissociations onto the basal plane,forming zigzag dislocations.
基金This work is supported partially by the National Major Research and Development Program(2019YFB1803902)National Natural Science Foundation of China(NSFC)(62135012,62105107)+3 种基金Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang(2021R01001)Guangdong Basic and Applied Basic Research Foundation(2021A 1515012215,2021B1515120057)Science and Technology Planning Project of Guangdong Province(2019A050510039)Fundamental Research Funds for the Central Universities(2021QNA5001).
文摘Multi-lane integrated transmitter chips are key components in future compact optical modules to realize high-speed optical interconnects.Thin-film lithium niobate(TFLN)photonics have emerged as a promising platform for achieving high-performance chip-scale optical systems.Combining a coarse wavelength-division multiplexing(CWDM)devices using fabrication-tolerant angled multimode interferometer structure and high-performance electro-optical modulators,we demonstrate monolithic on-chip four-channel CWDM transmitter on the TFLN platform for the first time.The four-channel CWDM transmitter enables high-speed transmissions of 100 Gb/s data rate per wavelength channel(i.e.,an aggregated date rate of 400 Gb/s).
文摘Movement intention recognition paves the path to developing Brain-Computer Interface(BCI)applications.Current research mostly focuses on questions like“which hand is intended to move”.While answering questions like“whether a hand is intended to move”is more desirable for widely real-world applications,because we cannot continuously perform intention tasks during usage,and the gap periods may cause unintended operation resulting in system failures.However,this kind of intention detection task is more difficult,since for a“whether”problem,it is hard to know what the“not”situation is and consequently to acquire training samples for the“not”situation.Furthermore,the occurrence of genuine intentions is comparatively scarce and unexpected,making the intention detection task hard and computation-consuming.To tackle this problem,we propose a Reconstruction-based Intention Detection(RID)framework,which utilises a reconstruction model to represent a high-level abstraction of EEG signals and leverages the reconstruction errors to determine“whether”there is a movement intention.Our framework is not only theoretically flexible and robust to any sophisticated real-world scenarios but also hand-crafted feature and domain knowledge free.Comprehensive experiments on detecting movement intention tasks with different reconstruction models demonstrate the promising performance of the proposed reconstruction intention detection framework.
基金This work was supported by the Project funded by China Postdoctoral Science Foundation,the Fundamental Research Funds for the Central Universities(No.FRF-TP-19-002A1)Domain Foundation of Equipment Advance Research of 13th Five-year Plan(No.61409220124).
文摘In this paper,a Fe-based Mn-Ni–Cr–Mo high strength low alloy(HSLA)steel was prepared by using Vacuum melting,following by hot rolling with 78%deformation and various heat treatment processes.Microstructure were characterized by optical microscope(OM),scanning electron microscope(SEM)equipped with energy dispersive spectrometer.Tensile tests were performed.After direct quenching(Q)from 860℃,the samples were subjected to secondary quenching(L)at different intercritical temperatures within the two-phase region and various tempering temperatures(T).Results show that QLT treatment increases elongation and decreases yield ratio compared with conventional quenching and tempering process(QT).The optimum QLT heat treatment parameter in terms of temperature are determined as Q:860℃,L:700℃,and T:600℃,resulting in the better combined properties with yield strength of 756MPa,tensile strength of 820MPa,tensile elongation of 16.76%and yield ratio of 0.923.
基金This work was supported by the USTB University of Science and Technology Beijing。
文摘The Ni-based Udemit720Li superalloy tends to form largeγ/γ'eutectic on grain boundaries(GBs)during solidification due to the addition of excessive Al and Ti elements,which provides convenience to study the effect of carbide andγ/γ'eutectic on crack initiation and propagation during tensile process.In this paper,Udemit720Li superalloy samples were prepared by induction melting casting method,arc melting and suction casting method.The microstructure,tensile properties and mechanism of crack initiation and propagation in Ni-based superalloy fabricated by two methods are investigated.The results exhibitγ/γ'eutectic accelerates the stress concentration at GB and thus leads to premature fracture failure.The samples with grain-boundary eutectic have higher strain hardening rate,but their cumulative and local misorientations are lower.For samples without eutectic at GB,the primary crack initiates at grain-boundary carbide along GB and extends along GB or into grain matrix,and exhibits better deformation performance and dislocation storage capacity within grains.
基金National Major Research and Development Program (2019YFB1803902)National Natural Science Foundation of China (NSFC)(61961146003, 91950205)+1 种基金Guangdong Basic and Applied Basic Research Foundation(2021A1515012215)Science and Technology Planning Project of Guangdong Province (2019A050510039)。
文摘A compact and high-performance coarse wavelength-division multiplexing(CWDM) device is introduced with a footprint of 2.1 mm × 0.02 mm using an angled multimode interferometer structure based on a thin-film lithium niobate(TFLN) platform.The demonstrated device built on a 400 nm thick x-cut TFLN shows ultra-low insertion losses of <0.72 dB.Measured 3 dB bandwidths are 12.1 nm for all channels,and cross talks from adjacent channels are better than 18 dB.Its peak wavelength positions comply with the CWDM standard with a channel spacing of 20 nm.The filter bandwidth of the proposed CWDM device can be tuned by adjusting the structural parameters.This demonstrated CWDM device will promote future realization of multi-channel and multi-wavelength transmitter chips on TFLN.
基金Zhejiang Provincial Major Research and Development Program(2021CO1199)Natural Science Foundation of Zhejiang Province(LD19F050001,LZ18F050001)+3 种基金National Natural Science Foundation of China(61961146003,62105283,62135012,91950205,92150302)National Science Fund for Distinguished Young Scholars(61725503)National Key Research and Development Program of China(2018YFB2200200,2018YFB2200201)Fundamental Research Funds for the Central Universities.
文摘Fast electro-optic modulators with an ultracompact footprint and low power consumption are always highly desired for optical interconnects.Here we propose and demonstrate a high-performance lithium niobate electro-optic modulator based on a new 2×2 Fabry–Perot cavity.In this structure,the input and reflected beams are separated by introducing asymmetric multimode-waveguide gratings,enabling TE_(0)−TE_(1)mode conversion.The measured results indicate that the fabricated modulator features a low excess loss of∼0.9dB,a high extinction ratio of∼21dB,a compact footprint of∼2120μm^(2),and high modulation speeds of 40 Gbps OOK and 80 Gbps PAM4 signals.The demonstrated modulator is promising for high-speed data transmission and signal processing.
基金the National Natural Science Foundation of China(No.41376149)the Guangzhou Pearl River New Star Plan of Science and Technology Program(No.2012J2200015).
文摘A novel platinum-catalyzed asymmetric ring-opening reaction of oxabenzonorbornadiene with terminal alkynes is described.The reaction affords optically active cis-2-alkynyl-1,2-dihydronaphthalen-1-ols in moderate yields with good enantioselectivity in the presence of catalytic amounts of Pt(COD)Cl_(2)/(S)-BINAP and an excess of zinc powder.The products were obtained exclusively with the relative cis-configuration of the ring substituents and the prevalent(1R,2S)-configuration of the stereocenters,as determined by single crystal X-ray diffraction analysis.
基金The authors thank the National Key Research and Development Program(No.2021YFA1200700)the National Natural Science Foundation of China(Grant Nos.62074054 and U21A20497)+1 种基金the Natural Science Foundation of Hunan Province(Nos.2019GK2245 and 2020JJ1002)Shenzhen Science and Technology Innovation Commission(No.RCYX20200714114537036)for financial support.The work was also supported by the Fundamental Research Funds for the Central Universities.
文摘The recently reported non-fullerene acceptor(NFA)Y6 has been extensively investigated for high-performance organic solar cells.However,its charge transport property and physics have not been fully studied.In this work,we acquired a deeper understanding of the charge transport in Y6 by fabricating and characterizing thin-film transistors(TFTs),and found that the electron mobility of Y6 is over 0.3-0.4 cm^(2)/(V⋅s)in top-gate bottom-contact devices,which is at least one order of magnitude higher than that of another well-known NFA ITIC.More importantly,we observed band-like transport in Y6 spin-coated films through temperature-dependent measurements on TFTs.This is particularly amazing since such transport behavior is rarely seen in polycrystalline organic semiconductor films.Further morphology characterization and discussions indicate that the band-like transport originates from the unique molecule packing motif of Y6 and the special phase of the film.As such,this work not only demonstrates the superior charge transport property of Y6,but also suggests the great potential of developing high-mobility n-type organic semiconductors,on the basis of Y6.
基金the National Natural Science Foundation of China(21704016,21971044)。
文摘A porous polymeric ligand(PPL)has been synthesized and complexed with copper to generate a heterogeneous catalyst(Cu@PPL)that has facilitated the efficient C-N coupling with various(hetero)aryl chlorides under mild conditions of visiblelight irradiation at 80°C(58 examples,up to 99%yields).This method could be applied to both aqueous ammonia and substituted amines,and is compatible to a variety of functional groups and heterocycles,as well as allows tandem C-N couplings with conjunctive dihalides.Furthermore,the heterogeneous characteristic of Cu@PPL has enabled a straightforward catalyst separation in multiple times of recycling with negligible catalytic efficiency loss by simple filtration,affording reaction mixtures containing less than 1 ppm of Cu residue.
