Currently,applications accessing remote computing resources through cloud data centers is the main mode of operation,but this mode of operation greatly increases communication latency and reduces overall quality of se...Currently,applications accessing remote computing resources through cloud data centers is the main mode of operation,but this mode of operation greatly increases communication latency and reduces overall quality of service(QoS)and quality of experience(QoE).Edge computing technology extends cloud service functionality to the edge of the mobile network,closer to the task execution end,and can effectivelymitigate the communication latency problem.However,the massive and heterogeneous nature of servers in edge computing systems brings new challenges to task scheduling and resource management,and the booming development of artificial neural networks provides us withmore powerfulmethods to alleviate this limitation.Therefore,in this paper,we proposed a time series forecasting model incorporating Conv1D,LSTM and GRU for edge computing device resource scheduling,trained and tested the forecasting model using a small self-built dataset,and achieved competitive experimental results.展开更多
One of the most primary challenges to achieve large-scale hydrogen generation from water electrolysis is the sluggish kinetics and noble metal dependence of cathodic hydrogen evolution reaction(HER).By considering the...One of the most primary challenges to achieve large-scale hydrogen generation from water electrolysis is the sluggish kinetics and noble metal dependence of cathodic hydrogen evolution reaction(HER).By considering the excellent water dissociation catalytic activity of Mo2C, abundant Pt/Mo2C interfaces were facilely engineered via galvanic replacement(gr) by using Mo/Mo2C nanosheets as self-sacrificed templates to alter the alkaline HER mechanism on Pt based catalyst. The rational designed interface-rich gr-Pt/Mo2C catalyst exhibited excellent activity with the overpotential to drive 10 mA/cm2 current density decreased by 18.5 mV compared with the commercial Pt/C catalyst. 34.3 mV/dec Tafel slope confirms the Volmer-Tafel HER route on gr-Pt/Mo2C in alkaline condition. Platinum utilization is calculated to be improved by 9.7 times by considered the low Pt loading in the gr-Pt/Mo2C catalyst. With its satisfied stability, the scalable gr-Pt/Mo2C catalyst shows promising application potential in industrial electrolysis systems.展开更多
In the smart logistics industry,unmanned forklifts that intelligently identify logistics pallets can improve work efficiency in warehousing and transportation and are better than traditional manual forklifts driven by...In the smart logistics industry,unmanned forklifts that intelligently identify logistics pallets can improve work efficiency in warehousing and transportation and are better than traditional manual forklifts driven by humans.Therefore,they play a critical role in smart warehousing,and semantics segmentation is an effective method to realize the intelligent identification of logistics pallets.However,most current recognition algorithms are ineffective due to the diverse types of pallets,their complex shapes,frequent blockades in production environments,and changing lighting conditions.This paper proposes a novel multi-feature fusion-guided multiscale bidirectional attention(MFMBA)neural network for logistics pallet segmentation.To better predict the foreground category(the pallet)and the background category(the cargo)of a pallet image,our approach extracts three types of features(grayscale,texture,and Hue,Saturation,Value features)and fuses them.The multiscale architecture deals with the problem that the size and shape of the pallet may appear different in the image in the actual,complex environment,which usually makes feature extraction difficult.Our study proposes a multiscale architecture that can extract additional semantic features.Also,since a traditional attention mechanism only assigns attention rights from a single direction,we designed a bidirectional attention mechanism that assigns cross-attention weights to each feature from two directions,horizontally and vertically,significantly improving segmentation.Finally,comparative experimental results show that the precision of the proposed algorithm is 0.53%–8.77%better than that of other methods we compared.展开更多
A facile strategy is introduced to upgrade thermomechanical stability of the cesium pentahydrogen diphosphate(CPD), which is the most efficient inorganic electrolyte among all solid proton conductors,by constructing P...A facile strategy is introduced to upgrade thermomechanical stability of the cesium pentahydrogen diphosphate(CPD), which is the most efficient inorganic electrolyte among all solid proton conductors,by constructing P–OH···F hydrogen bonds with lanthanum fluoride(LaF_3). The optimal combination of the LaF_3–CPD composite electrolyte is found to be 1:2 in a molar ratio(LaF_3–CPD-2). LaF_3–CPD-2 composite maintains robust solid state, even at a temperature up to 200 °C, which is 50 °C higher than the melting temperature of CPD. Meanwhile, the considerable proton conductivity of CPD is achieved in the LaF_3–CPD-2 composite electrolyte due to the synergistic effect of the P–OH···F hydrogen bonds and the intrinsic proton conductive property of CPD. Last but not least, the LaF_3–CPD-2 composite manifests excellent conductivity durability at 150 °C and low humidity condition with sizeable proton conductivity of0.0262 S cm^(-1) after 60 h operation, implying that the LaF_3–CPD composite could be a promising candidate for intermediate temperature proton conductors.展开更多
The grain boundaries of graphene are disordered topological defects,which would strongly affect the physical and chemical properties of graphene.In this paper,the spectral characteristics and photoresponse of MoS2/gra...The grain boundaries of graphene are disordered topological defects,which would strongly affect the physical and chemical properties of graphene.In this paper,the spectral characteristics and photoresponse of MoS2/graphene heterostructures are studied.It is found that the blueshift of the G and 2D peaks of graphene in Raman spectrum is due to doping.The lattice mismatch at the graphene boundaries results in a blueshift of MoS2 features in the photoluminescence spectra,comparing to the MoS2 grown on SiO2.In addition,the photocurrent signal in MoS2/hexagonal single-crystal graphene heterostructures is successfully captured without bias,but not in MoS2/polycrystalline graphene heterostructures.The electron scattering at graphene grain boundaries affects the optical response of MoS2/graphene heterostructures.The photoresponse of the device is attributed to the optical absorption and response of MoS2 and the high carrier mobility of graphene.These findings offer a new approach to develop optoelectronic devices based on two-dimensional material heterostructures.展开更多
High-entropy materials(HEMs)have attracted extensive attention in the field of electrochemical catal-ysis due to their unique properties.However,the preparation of high-entropy catalysts typically relies on high-tempe...High-entropy materials(HEMs)have attracted extensive attention in the field of electrochemical catal-ysis due to their unique properties.However,the preparation of high-entropy catalysts typically relies on high-temperature,energy-intensive,and time-consuming synthesis methods due to their compositional complexity.In this study,a facile low-temperature electrochemical reconstruction approach is adopted to synthesize Ag-decorated septenary Co-Cu-Fe-Mo-Zn-Ag-Ru high-entropy(oxy)hydroxide electro-catalysts for oxygen evolution reaction(OER).By introducing Ag and Ru elements and implanting Ag nanoparticles to co-regulate the electronic structure of the catalysts,the as-prepared catalyst achieves remarkable OER performance with a low overpotential of 298 mV at 100 mA/cm^(2)and a small Tafel slope of 30.1 mV/dec in 1 mol/L KOH.This work offers a valuable strategy for developing high-performance high-entropy OER electrocatalysts.展开更多
Nucleophile oxidation reaction(NOR),represented by ethanol oxidation reaction(EOR),is a promising pathway to replace oxygen evolution reaction(OER).EOR can effectively reduce the driving voltage of hydrogen production...Nucleophile oxidation reaction(NOR),represented by ethanol oxidation reaction(EOR),is a promising pathway to replace oxygen evolution reaction(OER).EOR can effectively reduce the driving voltage of hydrogen production in direct water splitting.In this work,large current and high efficiency of EOR on a Ni,Fe layered double hydroxide(NiFe-LDH)catalyst were simultaneously achieved by a facile fluorination strategy.F in NiFe-LDH can reduce the activation energy of the dehydrogenation reaction,thus promoting the deprotonation process of NiFe-LDH to achieve a lower EOR onset potential.It also weakens the absorption of OH-and nucleophile electrooxidation products on the surface of NiFe-LDH at a higher potential,achieving a high current density and EOR selectivity,according to density functional theory calculations.Based on our experiment results,the optimized fluorinated NiFe-LDH catalyst achieves a low potential of 1.386 V to deliver a 10 mA cm^(-2)EOR.Moreover,the Faraday efficiency is greater than 95%,with a current density ranging from 10 to 250 mA cm^(-2).This work provides a promising pathway for an efficient and cost-effective NOR catalyst design for economic hydrogen production.展开更多
Developing highly active oxygen evolution reaction(OER)electrocatalysts with robust durability is essential in producing high-purity hydrogen through water electrolysis.Layered double hydroxide(LDH)based catalysts hav...Developing highly active oxygen evolution reaction(OER)electrocatalysts with robust durability is essential in producing high-purity hydrogen through water electrolysis.Layered double hydroxide(LDH)based catalysts have demonstrated efficient catalytic performance toward the relatively sluggish OER.By considering the promotion effect of phosphate(Pi)on proton transfer,herein,a facile phosphate acid(PA)surface-neutralization strategy is developed to in-situ construct NiCo-LDH/NiCoPi hetero-sheets toward OER catalysis.OER activity of NiCoLDH is significantly boosted due to the proton promotion effect and the electronic modulation effect of NiCoPi.As a result,the facilely prepared NiCo-LDH/NiCoPi catalyst displays superior OER catalytic activity with a low overpotential of 300 mV to deliver 100 mA cm^(-2)OER and a Tafel slope of 73 mV dec^(-1).Furthermore,no visible activity decay is detected after a 200-h continuous OER operation.The present work,therefore,provides a promising strategy to exploit robust OER electrocatalysts for commercial water electrolysers.展开更多
Sluggish kinetics of methanol oxidation reaction(MOR)and alkaline hydrogen evolution reaction(HER)even on precious Pt catalyst impede the large-scale commercialization of direct methanol fuel cell(DMFC)and water elect...Sluggish kinetics of methanol oxidation reaction(MOR)and alkaline hydrogen evolution reaction(HER)even on precious Pt catalyst impede the large-scale commercialization of direct methanol fuel cell(DMFC)and water electrolysis technologies.Since both of MOR and alkaline HER are related to water dissociation reaction(WDR),it is reasonable to invite secondary active sites toward WDR to pair with Pt for boosted MOR and alkaline HER activity on Pt.Mo_(2)C and Ni species are therefore employed to engineer NiPt-Mo_(2)C active site pairs,which can be encapsulated in carbon cages,via an in-situ self-confinement strategy.Mass activity of Pt in NiPt-Mo_(2)C@C toward HER is boosted to11.3 A mg_(pt)^(-1),33 times higher than that of Pt/C.Similarly,MOR catalytic activity of Pt in NiPt-Mo_(2)C@C is also improved by 10.5 times and the DMFC maximum power density is hence improved by 9-fold.By considering the great stability,NiPt-Mo_(2)C@C exhibits great practical application potential in DMFCs and water electrolysers.展开更多
The development of cost-effective,robust,and durable electrocatalysts to replace the expensive Pt-based catalysts towards oxygen reduction reaction(ORR)is the trending frontier research topic in renewable energy and e...The development of cost-effective,robust,and durable electrocatalysts to replace the expensive Pt-based catalysts towards oxygen reduction reaction(ORR)is the trending frontier research topic in renewable energy and electrocatalysis.Particular attention has been paid to metal-nitrogen-carbon(M-N-C)single atom catalysts(SACs)due to their maximized atom utilization efficiency,biomimetic active site,and distinct electronic structure.More importantly,their catalytic properties can be further tailored by rationally regulating the microenvironment of active sites(i.e.,M-N coordination number,heteroatom doping and substitution.Herein,we present a comprehensive summary of the recent advancement in the microenvironment regulation of MN-C SACs towards improved ORR performance.The coordination environment manipulation regarding central metal and coordinated atoms is first discussed,focusing on the structure-function relationship.Apart from the near-range coordination,longrange substrate modulation including heteroatom doping,defect engineering is discussed as well.Besides,the synergy mechanism of nanoparticles and single atom sites to tune the electron cloud density at the active sites is summarized.Finally,we provide the challenges and outlook of the development of M-N-C SACs.展开更多
We report on the direct generation of passively mode-locked vortex lasers in the visible spectral region, for the first time to the best of our knowledge, using a Pr :Li YF4(Pr:YLF) crystal as the gain medium. A stabl...We report on the direct generation of passively mode-locked vortex lasers in the visible spectral region, for the first time to the best of our knowledge, using a Pr :Li YF4(Pr:YLF) crystal as the gain medium. A stable mode-locked TEM00 mode has been achieved with a maximum average output power of 75 m W using a graphene saturable absorber mirror. The mode-locked pulse width is measured to be as short as about 73.4 ps at a repetition rate of about 140 MHz, and the laser wavelength is at about 721 nm with spectral width of about 0.5 nm. By slightly misaligning the laser resonator, a first-order Laguerre-Gaussian mode(LG0,1) has also been obtained with output power reduced to about 22 m W. The achieved LG0,1 mode has been verified via a home made improved Fizeau interferometer. This work provides a simple and universal method for direct generation of an ultrafast vortex laser,which can be readily extended to other spectral regions by using different laser gain mediums.展开更多
We report the synthesis of isotopically-labeled graphite films on nickel substrates by using cold-wall chemical vapor deposition(CVD).During the synthesis,carbon from^(12)C-and^(13)C-methane was deposited on,and disso...We report the synthesis of isotopically-labeled graphite films on nickel substrates by using cold-wall chemical vapor deposition(CVD).During the synthesis,carbon from^(12)C-and^(13)C-methane was deposited on,and dissolved in,a nickel foil at high temperature,and a uniform graphite film was segregated from the nickel surface by cooling the sample to room temperature.Scanning and transmission electron microscopy,micro-Raman spectroscopy,and X-ray diffraction prove the presence of a graphite film.Monolayer graphene films obtained from such isotopically-labeled graphite films by mechanical methods have electron mobility values greater than 5000 cm^(2)·V^(-1)·s^(-1)at low temperatures.Furthermore,such films exhibit the half-integer quantum Hall effect over a wide temperature range from 2 K to 200 K,implying that the graphite grown by this cold-wall CVD approach has a quality as high as highly oriented pyrolytic graphite(HOPG).The results from transport measurements indicate that^(13)C-labeling does not significantly affect the electrical transport properties of graphene.展开更多
Multi-user collaborative editors are useful computer-aided tools to support human-to-human collaboration.For multi-user collaborative editors,selective undo is an essential utility enabling users to undo any editing o...Multi-user collaborative editors are useful computer-aided tools to support human-to-human collaboration.For multi-user collaborative editors,selective undo is an essential utility enabling users to undo any editing operations at any time.Collaborative editors usually adopt operational transformation(OT)to address concurrency and consistency issues.However,it is still a great challenge to design an efficient and correct OT algorithm capable of handling both normal do operations and user-initiated undo operations because these two kinds of operations can interfere with each other in various forms.In this paper,we propose a semi-transparent selective undo algorithm that handles both do and undo in a unified framework,which separates the processing part of do operations from the processing part of undo operations.Formal proofs are provided to prove the proposed algorithm under the well-established criteria.Theoretical analysis and experimental evaluation are conducted to show that the proposed algorithm outperforms the prior OT-based selective undo algorithms.展开更多
Thermal interface materials(TIMs)with high through-plane thermal conductivity are urgently desired to avoid overheating of high-power density electronics.Introducing and aligning fillers in polymer matrixes via magnet...Thermal interface materials(TIMs)with high through-plane thermal conductivity are urgently desired to avoid overheating of high-power density electronics.Introducing and aligning fillers in polymer matrixes via magnetic field is a promising method to improve the thermal conductivity of the polymer.However,either the fillers need to be modified with magnetic particles or a strong magnetic field is needed for good alignment in high filler content.This prevents further improvement of the through-plane thermal conductivity.Herein,mesophase pitch-based carbon fibers(MPCFs)with a content as high as 76 wt.%are aligned vertically in water-soluble polyvinyl alcohol(PVA)under a low magnetic field(~0.4 T),forming a vertically aligned MPCF(VAMPCF)/PVA composite with an extraordinary through-plane thermal conductivity of 86 W/(m·K),which is higher than that of many alloys.In addition,both theoretical and experimental results demonstrate that the critical intensity of the magnetic field needed for good alignment of the fillers depends on their size and magnetic susceptibility.Furthermore,the water solubility of PVA makes it easy to recycle MPCFs.This study offers an inspired venue to develop excellent and eco-friendly TIMs to meet ever increasing demand in heat dissipation for electronics.展开更多
Energy dissipation has always been an attention-getting issue in modern electronics and the emerging low-symmetry two-dimensional(2D)materials are considered to have broad prospects in solving the energy dissipation p...Energy dissipation has always been an attention-getting issue in modern electronics and the emerging low-symmetry two-dimensional(2D)materials are considered to have broad prospects in solving the energy dissipation problem.Herein the thermal transport of a typical 2D ternary chalcogenide Ta_(2)NiS_(5) is investigated.For the first time we have observed strongly anisotropic in-plane thermal conductivity towards armchair and zigzag axes of suspended few-layer Ta_(2)NiS_(5) flakes through Raman thermometry.For 7-nm-thick Ta_(2)NiS_(5) flakes,theκz i g z a g is 4.76 W·m^(−1)·K^(−1) andκa r m c h a i r is 7.79 W·m^(−1)·K^(−1),with a large anisotropic ratio(κa r m c h a i r/κz i g z a g)of 1.64 mainly ascribed to different phonon mean-free-paths along armchair and zigzag axes.Moreover,the thickness dependence of thermal anisotropy is also discussed.As the flake thickness increases,theκa r m c h a i r/κz i g z a g reduces sharply from 1.64 to 1.07.This could be attributed to the diversity in phonon boundary scattering,which decreases faster in zigzag direction than in armchair direction.Such anisotropic property enables heat flow manipulation in Ta_(2)NiS_(5) based devices to improve thermal management and device performance.Our work helps reveal the anisotropy physics of ternary transition metal chalcogenides,along with significant guidance to develop energy-efficient next generation nanodevices.展开更多
With the packing density growing continuously in integrated electronic devices,sufficient heat dissipation becomes a serious challenge.Recently,dielectric materials with high thermal conductivity have brought insight ...With the packing density growing continuously in integrated electronic devices,sufficient heat dissipation becomes a serious challenge.Recently,dielectric materials with high thermal conductivity have brought insight into effective dissipation of waste heat in electronic devices to prevent them from overheating and guarantee the performance stability.Layered CrOCl,an antiferromagnetic insulator with low-symmetry crystal structure and atomic level flatness,might be a promising solution to the thermal challenge.Herein,we have systematically studied the thermal transport of suspended few-layer CrOCl flakes by microRaman thermometry.The CrOCl flakes exhibit high thermal conductivities along zigzag direction,from~392±33 to~1,017±46 W·m^(−1)·K^(−1) with flake thickness from 2 to 50 nm.Besides,pronounced thickness-dependent thermal conductivity ratio(/from~2.8±0.24 to~4.3±0.25)has been observed in the CrOCl flakes,attributed to the discrepancy of phonon dispersion and phonon surface scattering.As a demonstration to the heat sink application of layered CrOCl,we then investigate the energy dissipation in graphene devices on CrOCl,SiO_(2) and hexagonal boron nitride(h-BN)substrates,respectively.The graphene device temperature rise on CrOCl is only 15.4%of that on SiO_(2) and 30%on h-BN upon the same electric power density,indicating the efficient heat dissipation of graphene device on CrOCl.Our study provides new insights into two-dimentional(2D)dielectric material with high thermal conductivity and strong anisotropy for the application of thermal management in electronic devices.展开更多
Improving thermal transport between substrate and transistors has become a vital solution to the thermal challenge in nanoelectronics.Recently 2D WTe_(2) has sparked extensive interest because of heavy atomic mass and...Improving thermal transport between substrate and transistors has become a vital solution to the thermal challenge in nanoelectronics.Recently 2D WTe_(2) has sparked extensive interest because of heavy atomic mass and low Debye temperature.Here,the thermal transport of supported WTe_(2) was studied via Raman thermometry with electrical heating.The supported 30 nm WTe2 encased with 70 nm Al_(2)O_(3) delivered 4.8 W·m^(-1)·K^(-1)in-plane thermal conductivity along zigzag direction at room temperature,which was almost 1.6 times larger than that along armchair direction(3.0 W·m^(-1)·K^(-1)).Interestingly,the superior and inferior directions for thermal transport are just opposite of those for electrical transport.Hence,a heat manipulation model in WTe_(2) FET device was proposed.Within the designed configuration,waste heat in WTe_(2) would be mostly dissipated to metal contacts located along zigzag,relieving the local temperature discrepancy in the channel effectively and preventing degradation or breakdown.Our study provides new insight into thermal transport of anisotropic 2D materials,which might inspire energy-efficient nanodevices in the future.展开更多
Monolayer graphene has attracted enormous attention owing to its unique electronic and optical properties.However,achieving an effective approach without applying electrical bias for manipulating the charge transfer b...Monolayer graphene has attracted enormous attention owing to its unique electronic and optical properties.However,achieving an effective approach without applying electrical bias for manipulating the charge transfer based on graphene is elusive to date.Herein,we realized the manipulation of excitons’transition from emitter to the graphene surface with plasmonic engineering nanostructures and firstly obtained large enhancements for photon emission on the graphene surface.The localized plasmons generated from the plasmonic nanostructures of shell-isolated nanoparticle coupling to ultra-flat Au substrate would dictate a consistent junction geometry while enhancing the optical field and dominating the electron transition pathways,which may cause obvious perturbations for molecular radiation behaviors.Additionally,the three-dimensional finite-difference time-domain and time-dependent density functional theory were also carried out to simulate the distributions of electromagnetic field and energy levels of hybrid nanostructure respectively and the results agreed well with the experimental data.Therefore,this work paves a novel approach for tunning graphene charge/energy transfer processes,which may hold great potential for applications in photonic devices based on graphene.展开更多
Developing efficient platinum(Pt)-based electrocatalysts is enormously significant for fuel cells.Herein,we report an integrated electrocatalyst of ultralow-Pt alloy encapsulated into nitrogen-doped nanocarbon archite...Developing efficient platinum(Pt)-based electrocatalysts is enormously significant for fuel cells.Herein,we report an integrated electrocatalyst of ultralow-Pt alloy encapsulated into nitrogen-doped nanocarbon architecture for efficient oxygen reduction reaction.This hybrid Pt-based catalyst achieves a mass activity of 3.46 A mg^(-1)_(pt)the potential of 0.9 V vs.RHE with a negligible stability decay after 10,000 cycles.More importantly,this half-cell activity can be expressed at full cell level with a high Pt utilization of 10.22 W mg^(-1)_(Pt cathode)and remarkable durability after 30,000 cycles in single-cell.Experimental and theoretical investigations reveal that a highly strained Pt structure with an optimal Pt-0 binding energy is induced by the incorporation of Co/Ni into Pt lattice,which would account for the improved reaction kinetics.The synergistic catalysis due to nitrogen-doped nanocarbon architecture and active Pt component is responsible for the enhanced catalytic activity.Meanwhile,the strong metal-support interaction and optimized hydrophilic properties of nanocarbon matrix facilitate efficient mass transport and water management.This work may provide significant insights in designing the low-Pt integrated electrocatalysts for fuel cells and beyond.展开更多
The control of combustion is a hot and classical topic.Among the combustion technologies,electric-field assisted combustion is an advanced technology that enjoys major advantages such as fast response and low power co...The control of combustion is a hot and classical topic.Among the combustion technologies,electric-field assisted combustion is an advanced technology that enjoys major advantages such as fast response and low power consumption compared with thermal power.However,its fundamental principle and impacts on the flames are complicated due to the coupling between physics,chemistry,and electromagnetics.In the last two decades,tremendous efforts have been made to understand electric-field assisted combustion.New observations have been reported based on different combustion systems and improved diagnostics.The main impacts,including flame stabilization,emission reduction,and flame propagation,have been revealed by both simulative and experimental studies.These findings significantly facilitate the application of electric-field assisted combustion.This brief review is intended to provide a comprehensive overview of the recent progress of this combustion technology and further point out research opportunities worth investigation.展开更多
基金supported in part by the National Natural Science Foundation of China under Grant 62172192,U20A20228,and 62171203in part by the Science and Technology Demonstration Project of Social Development of Jiangsu Province under Grant BE2019631。
文摘Currently,applications accessing remote computing resources through cloud data centers is the main mode of operation,but this mode of operation greatly increases communication latency and reduces overall quality of service(QoS)and quality of experience(QoE).Edge computing technology extends cloud service functionality to the edge of the mobile network,closer to the task execution end,and can effectivelymitigate the communication latency problem.However,the massive and heterogeneous nature of servers in edge computing systems brings new challenges to task scheduling and resource management,and the booming development of artificial neural networks provides us withmore powerfulmethods to alleviate this limitation.Therefore,in this paper,we proposed a time series forecasting model incorporating Conv1D,LSTM and GRU for edge computing device resource scheduling,trained and tested the forecasting model using a small self-built dataset,and achieved competitive experimental results.
基金financial support from the National Natural Science Foundation of China (Nos.21875224 and 21703211)the Natural Science Foundation of Zhejiang Province (No.LGG19B030001)。
文摘One of the most primary challenges to achieve large-scale hydrogen generation from water electrolysis is the sluggish kinetics and noble metal dependence of cathodic hydrogen evolution reaction(HER).By considering the excellent water dissociation catalytic activity of Mo2C, abundant Pt/Mo2C interfaces were facilely engineered via galvanic replacement(gr) by using Mo/Mo2C nanosheets as self-sacrificed templates to alter the alkaline HER mechanism on Pt based catalyst. The rational designed interface-rich gr-Pt/Mo2C catalyst exhibited excellent activity with the overpotential to drive 10 mA/cm2 current density decreased by 18.5 mV compared with the commercial Pt/C catalyst. 34.3 mV/dec Tafel slope confirms the Volmer-Tafel HER route on gr-Pt/Mo2C in alkaline condition. Platinum utilization is calculated to be improved by 9.7 times by considered the low Pt loading in the gr-Pt/Mo2C catalyst. With its satisfied stability, the scalable gr-Pt/Mo2C catalyst shows promising application potential in industrial electrolysis systems.
基金supported by the Postgraduate Scientific Research Innovation Project of Hunan Province under Grant QL20210212the Scientific Innovation Fund for Postgraduates of Central South University of Forestry and Technology under Grant CX202102043.
文摘In the smart logistics industry,unmanned forklifts that intelligently identify logistics pallets can improve work efficiency in warehousing and transportation and are better than traditional manual forklifts driven by humans.Therefore,they play a critical role in smart warehousing,and semantics segmentation is an effective method to realize the intelligent identification of logistics pallets.However,most current recognition algorithms are ineffective due to the diverse types of pallets,their complex shapes,frequent blockades in production environments,and changing lighting conditions.This paper proposes a novel multi-feature fusion-guided multiscale bidirectional attention(MFMBA)neural network for logistics pallet segmentation.To better predict the foreground category(the pallet)and the background category(the cargo)of a pallet image,our approach extracts three types of features(grayscale,texture,and Hue,Saturation,Value features)and fuses them.The multiscale architecture deals with the problem that the size and shape of the pallet may appear different in the image in the actual,complex environment,which usually makes feature extraction difficult.Our study proposes a multiscale architecture that can extract additional semantic features.Also,since a traditional attention mechanism only assigns attention rights from a single direction,we designed a bidirectional attention mechanism that assigns cross-attention weights to each feature from two directions,horizontally and vertically,significantly improving segmentation.Finally,comparative experimental results show that the precision of the proposed algorithm is 0.53%–8.77%better than that of other methods we compared.
基金financially supported by the National Natural Science Foundation of China(Nos.21703211,21503197 and 21473164)Fundamental Research Funds for the Central University,China University of Geosciences(Wuhan)(Nos.CUG150615 and CUG150627)
文摘A facile strategy is introduced to upgrade thermomechanical stability of the cesium pentahydrogen diphosphate(CPD), which is the most efficient inorganic electrolyte among all solid proton conductors,by constructing P–OH···F hydrogen bonds with lanthanum fluoride(LaF_3). The optimal combination of the LaF_3–CPD composite electrolyte is found to be 1:2 in a molar ratio(LaF_3–CPD-2). LaF_3–CPD-2 composite maintains robust solid state, even at a temperature up to 200 °C, which is 50 °C higher than the melting temperature of CPD. Meanwhile, the considerable proton conductivity of CPD is achieved in the LaF_3–CPD-2 composite electrolyte due to the synergistic effect of the P–OH···F hydrogen bonds and the intrinsic proton conductive property of CPD. Last but not least, the LaF_3–CPD-2 composite manifests excellent conductivity durability at 150 °C and low humidity condition with sizeable proton conductivity of0.0262 S cm^(-1) after 60 h operation, implying that the LaF_3–CPD composite could be a promising candidate for intermediate temperature proton conductors.
基金National Natural Science Foundation of China(Grant No.11874423).
文摘The grain boundaries of graphene are disordered topological defects,which would strongly affect the physical and chemical properties of graphene.In this paper,the spectral characteristics and photoresponse of MoS2/graphene heterostructures are studied.It is found that the blueshift of the G and 2D peaks of graphene in Raman spectrum is due to doping.The lattice mismatch at the graphene boundaries results in a blueshift of MoS2 features in the photoluminescence spectra,comparing to the MoS2 grown on SiO2.In addition,the photocurrent signal in MoS2/hexagonal single-crystal graphene heterostructures is successfully captured without bias,but not in MoS2/polycrystalline graphene heterostructures.The electron scattering at graphene grain boundaries affects the optical response of MoS2/graphene heterostructures.The photoresponse of the device is attributed to the optical absorption and response of MoS2 and the high carrier mobility of graphene.These findings offer a new approach to develop optoelectronic devices based on two-dimensional material heterostructures.
基金supported by the National Key Research and Development Program of China[grant number 2020YFE0100100]the National Natural Science Foundation of China[grant number 52222103]the Fundamental Research Funds for the Central Universities and the Key Research and Development Program of Sichuan Province(Scientific and Technological Cooperation of Sichuan Province with Institutes and Universities)[grant number 2020YFSY0001].
文摘High-entropy materials(HEMs)have attracted extensive attention in the field of electrochemical catal-ysis due to their unique properties.However,the preparation of high-entropy catalysts typically relies on high-temperature,energy-intensive,and time-consuming synthesis methods due to their compositional complexity.In this study,a facile low-temperature electrochemical reconstruction approach is adopted to synthesize Ag-decorated septenary Co-Cu-Fe-Mo-Zn-Ag-Ru high-entropy(oxy)hydroxide electro-catalysts for oxygen evolution reaction(OER).By introducing Ag and Ru elements and implanting Ag nanoparticles to co-regulate the electronic structure of the catalysts,the as-prepared catalyst achieves remarkable OER performance with a low overpotential of 298 mV at 100 mA/cm^(2)and a small Tafel slope of 30.1 mV/dec in 1 mol/L KOH.This work offers a valuable strategy for developing high-performance high-entropy OER electrocatalysts.
基金the financial support from the National Natural Science Foundation of China(22197121)Knowledge Innovation Program of Wuhan-Basic Research(2022010801010202)Research Fund Program of Guangdong Provincial Key Laboratory of Fuel Cell Technology(FC202201)。
文摘Nucleophile oxidation reaction(NOR),represented by ethanol oxidation reaction(EOR),is a promising pathway to replace oxygen evolution reaction(OER).EOR can effectively reduce the driving voltage of hydrogen production in direct water splitting.In this work,large current and high efficiency of EOR on a Ni,Fe layered double hydroxide(NiFe-LDH)catalyst were simultaneously achieved by a facile fluorination strategy.F in NiFe-LDH can reduce the activation energy of the dehydrogenation reaction,thus promoting the deprotonation process of NiFe-LDH to achieve a lower EOR onset potential.It also weakens the absorption of OH-and nucleophile electrooxidation products on the surface of NiFe-LDH at a higher potential,achieving a high current density and EOR selectivity,according to density functional theory calculations.Based on our experiment results,the optimized fluorinated NiFe-LDH catalyst achieves a low potential of 1.386 V to deliver a 10 mA cm^(-2)EOR.Moreover,the Faraday efficiency is greater than 95%,with a current density ranging from 10 to 250 mA cm^(-2).This work provides a promising pathway for an efficient and cost-effective NOR catalyst design for economic hydrogen production.
基金financial support from the National Natural Science Foundation of China(21875224 and22179121)Knowledge Innovation Program of Wuhan-Basic Research(2022010801010202)Research Fund Program of Guangdong Provincial Key Laboratory of Fuel Cell Technology(FC202201)。
文摘Developing highly active oxygen evolution reaction(OER)electrocatalysts with robust durability is essential in producing high-purity hydrogen through water electrolysis.Layered double hydroxide(LDH)based catalysts have demonstrated efficient catalytic performance toward the relatively sluggish OER.By considering the promotion effect of phosphate(Pi)on proton transfer,herein,a facile phosphate acid(PA)surface-neutralization strategy is developed to in-situ construct NiCo-LDH/NiCoPi hetero-sheets toward OER catalysis.OER activity of NiCoLDH is significantly boosted due to the proton promotion effect and the electronic modulation effect of NiCoPi.As a result,the facilely prepared NiCo-LDH/NiCoPi catalyst displays superior OER catalytic activity with a low overpotential of 300 mV to deliver 100 mA cm^(-2)OER and a Tafel slope of 73 mV dec^(-1).Furthermore,no visible activity decay is detected after a 200-h continuous OER operation.The present work,therefore,provides a promising strategy to exploit robust OER electrocatalysts for commercial water electrolysers.
基金financial support from the National Natural Science Foundation of China(Nos.21875224,22179121)the Fundamental Research Founds for National University,China University of Geosciences(Wuhan)。
文摘Sluggish kinetics of methanol oxidation reaction(MOR)and alkaline hydrogen evolution reaction(HER)even on precious Pt catalyst impede the large-scale commercialization of direct methanol fuel cell(DMFC)and water electrolysis technologies.Since both of MOR and alkaline HER are related to water dissociation reaction(WDR),it is reasonable to invite secondary active sites toward WDR to pair with Pt for boosted MOR and alkaline HER activity on Pt.Mo_(2)C and Ni species are therefore employed to engineer NiPt-Mo_(2)C active site pairs,which can be encapsulated in carbon cages,via an in-situ self-confinement strategy.Mass activity of Pt in NiPt-Mo_(2)C@C toward HER is boosted to11.3 A mg_(pt)^(-1),33 times higher than that of Pt/C.Similarly,MOR catalytic activity of Pt in NiPt-Mo_(2)C@C is also improved by 10.5 times and the DMFC maximum power density is hence improved by 9-fold.By considering the great stability,NiPt-Mo_(2)C@C exhibits great practical application potential in DMFCs and water electrolysers.
基金supported by the National Natural Science Foundation of China(No.22272161).
文摘The development of cost-effective,robust,and durable electrocatalysts to replace the expensive Pt-based catalysts towards oxygen reduction reaction(ORR)is the trending frontier research topic in renewable energy and electrocatalysis.Particular attention has been paid to metal-nitrogen-carbon(M-N-C)single atom catalysts(SACs)due to their maximized atom utilization efficiency,biomimetic active site,and distinct electronic structure.More importantly,their catalytic properties can be further tailored by rationally regulating the microenvironment of active sites(i.e.,M-N coordination number,heteroatom doping and substitution.Herein,we present a comprehensive summary of the recent advancement in the microenvironment regulation of MN-C SACs towards improved ORR performance.The coordination environment manipulation regarding central metal and coordinated atoms is first discussed,focusing on the structure-function relationship.Apart from the near-range coordination,longrange substrate modulation including heteroatom doping,defect engineering is discussed as well.Besides,the synergy mechanism of nanoparticles and single atom sites to tune the electron cloud density at the active sites is summarized.Finally,we provide the challenges and outlook of the development of M-N-C SACs.
基金Natural Science Foundation of Fujian Province of China(2018J01108)National Natural Science Foundation of China(91750115)International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology,Shenzhen University(2DMOST2018026)
文摘We report on the direct generation of passively mode-locked vortex lasers in the visible spectral region, for the first time to the best of our knowledge, using a Pr :Li YF4(Pr:YLF) crystal as the gain medium. A stable mode-locked TEM00 mode has been achieved with a maximum average output power of 75 m W using a graphene saturable absorber mirror. The mode-locked pulse width is measured to be as short as about 73.4 ps at a repetition rate of about 140 MHz, and the laser wavelength is at about 721 nm with spectral width of about 0.5 nm. By slightly misaligning the laser resonator, a first-order Laguerre-Gaussian mode(LG0,1) has also been obtained with output power reduced to about 22 m W. The achieved LG0,1 mode has been verified via a home made improved Fizeau interferometer. This work provides a simple and universal method for direct generation of an ultrafast vortex laser,which can be readily extended to other spectral regions by using different laser gain mediums.
基金This work was supported by The University of Texas at Austin and by the Texas Nanotechnology Research Superiority Initiative,Southwest Nanotechnology Institute(TNRSI)/SWAN.
文摘We report the synthesis of isotopically-labeled graphite films on nickel substrates by using cold-wall chemical vapor deposition(CVD).During the synthesis,carbon from^(12)C-and^(13)C-methane was deposited on,and dissolved in,a nickel foil at high temperature,and a uniform graphite film was segregated from the nickel surface by cooling the sample to room temperature.Scanning and transmission electron microscopy,micro-Raman spectroscopy,and X-ray diffraction prove the presence of a graphite film.Monolayer graphene films obtained from such isotopically-labeled graphite films by mechanical methods have electron mobility values greater than 5000 cm^(2)·V^(-1)·s^(-1)at low temperatures.Furthermore,such films exhibit the half-integer quantum Hall effect over a wide temperature range from 2 K to 200 K,implying that the graphite grown by this cold-wall CVD approach has a quality as high as highly oriented pyrolytic graphite(HOPG).The results from transport measurements indicate that^(13)C-labeling does not significantly affect the electrical transport properties of graphene.
基金National Key R&D Program of China(2017YFB0503004)the National Natural Science Foundation of China(Grant No.62072348)+1 种基金China Postdoctoral Science Foundation(2019M662709)Natural Science Foundation of Hubei Province(2016FC0106305 and 2019CFB627).
文摘Multi-user collaborative editors are useful computer-aided tools to support human-to-human collaboration.For multi-user collaborative editors,selective undo is an essential utility enabling users to undo any editing operations at any time.Collaborative editors usually adopt operational transformation(OT)to address concurrency and consistency issues.However,it is still a great challenge to design an efficient and correct OT algorithm capable of handling both normal do operations and user-initiated undo operations because these two kinds of operations can interfere with each other in various forms.In this paper,we propose a semi-transparent selective undo algorithm that handles both do and undo in a unified framework,which separates the processing part of do operations from the processing part of undo operations.Formal proofs are provided to prove the proposed algorithm under the well-established criteria.Theoretical analysis and experimental evaluation are conducted to show that the proposed algorithm outperforms the prior OT-based selective undo algorithms.
基金the National Natural Science Foundation of China(Nos.11874423 and 12174321)the Fundamental Research Funds for the Central Universities(No.20720190050).
文摘Thermal interface materials(TIMs)with high through-plane thermal conductivity are urgently desired to avoid overheating of high-power density electronics.Introducing and aligning fillers in polymer matrixes via magnetic field is a promising method to improve the thermal conductivity of the polymer.However,either the fillers need to be modified with magnetic particles or a strong magnetic field is needed for good alignment in high filler content.This prevents further improvement of the through-plane thermal conductivity.Herein,mesophase pitch-based carbon fibers(MPCFs)with a content as high as 76 wt.%are aligned vertically in water-soluble polyvinyl alcohol(PVA)under a low magnetic field(~0.4 T),forming a vertically aligned MPCF(VAMPCF)/PVA composite with an extraordinary through-plane thermal conductivity of 86 W/(m·K),which is higher than that of many alloys.In addition,both theoretical and experimental results demonstrate that the critical intensity of the magnetic field needed for good alignment of the fillers depends on their size and magnetic susceptibility.Furthermore,the water solubility of PVA makes it easy to recycle MPCFs.This study offers an inspired venue to develop excellent and eco-friendly TIMs to meet ever increasing demand in heat dissipation for electronics.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.11874423 and 11404399)the National Defense Science and Technology Innovation Zone,and the Scientific Researches Foundation of National University of Defense Technology(Nos.ZK20-16 and ZZKY-YX-08-06).
文摘Energy dissipation has always been an attention-getting issue in modern electronics and the emerging low-symmetry two-dimensional(2D)materials are considered to have broad prospects in solving the energy dissipation problem.Herein the thermal transport of a typical 2D ternary chalcogenide Ta_(2)NiS_(5) is investigated.For the first time we have observed strongly anisotropic in-plane thermal conductivity towards armchair and zigzag axes of suspended few-layer Ta_(2)NiS_(5) flakes through Raman thermometry.For 7-nm-thick Ta_(2)NiS_(5) flakes,theκz i g z a g is 4.76 W·m^(−1)·K^(−1) andκa r m c h a i r is 7.79 W·m^(−1)·K^(−1),with a large anisotropic ratio(κa r m c h a i r/κz i g z a g)of 1.64 mainly ascribed to different phonon mean-free-paths along armchair and zigzag axes.Moreover,the thickness dependence of thermal anisotropy is also discussed.As the flake thickness increases,theκa r m c h a i r/κz i g z a g reduces sharply from 1.64 to 1.07.This could be attributed to the diversity in phonon boundary scattering,which decreases faster in zigzag direction than in armchair direction.Such anisotropic property enables heat flow manipulation in Ta_(2)NiS_(5) based devices to improve thermal management and device performance.Our work helps reveal the anisotropy physics of ternary transition metal chalcogenides,along with significant guidance to develop energy-efficient next generation nanodevices.
基金supported by the National Natural Science Foundation of China(No.11874423).
文摘With the packing density growing continuously in integrated electronic devices,sufficient heat dissipation becomes a serious challenge.Recently,dielectric materials with high thermal conductivity have brought insight into effective dissipation of waste heat in electronic devices to prevent them from overheating and guarantee the performance stability.Layered CrOCl,an antiferromagnetic insulator with low-symmetry crystal structure and atomic level flatness,might be a promising solution to the thermal challenge.Herein,we have systematically studied the thermal transport of suspended few-layer CrOCl flakes by microRaman thermometry.The CrOCl flakes exhibit high thermal conductivities along zigzag direction,from~392±33 to~1,017±46 W·m^(−1)·K^(−1) with flake thickness from 2 to 50 nm.Besides,pronounced thickness-dependent thermal conductivity ratio(/from~2.8±0.24 to~4.3±0.25)has been observed in the CrOCl flakes,attributed to the discrepancy of phonon dispersion and phonon surface scattering.As a demonstration to the heat sink application of layered CrOCl,we then investigate the energy dissipation in graphene devices on CrOCl,SiO_(2) and hexagonal boron nitride(h-BN)substrates,respectively.The graphene device temperature rise on CrOCl is only 15.4%of that on SiO_(2) and 30%on h-BN upon the same electric power density,indicating the efficient heat dissipation of graphene device on CrOCl.Our study provides new insights into two-dimentional(2D)dielectric material with high thermal conductivity and strong anisotropy for the application of thermal management in electronic devices.
基金supported by the National Natural Science Foundation of China(Nos.61801498,11404399,11874423,and 51701237)the National Defense Science and Technology Innovation Zone,the Scientific Researches Foundation of National University of Defense Technology(Nos.ZK18-01-03,ZK18-03-36,ZK20-16,and ZZKY-YX-08-06)+1 种基金the China Postdoctoral Science Foundation(CPSF)(No.2019M663569)the Youth Talent Lifting Project(No.17-JCJQ-QT-004).
文摘Improving thermal transport between substrate and transistors has become a vital solution to the thermal challenge in nanoelectronics.Recently 2D WTe_(2) has sparked extensive interest because of heavy atomic mass and low Debye temperature.Here,the thermal transport of supported WTe_(2) was studied via Raman thermometry with electrical heating.The supported 30 nm WTe2 encased with 70 nm Al_(2)O_(3) delivered 4.8 W·m^(-1)·K^(-1)in-plane thermal conductivity along zigzag direction at room temperature,which was almost 1.6 times larger than that along armchair direction(3.0 W·m^(-1)·K^(-1)).Interestingly,the superior and inferior directions for thermal transport are just opposite of those for electrical transport.Hence,a heat manipulation model in WTe_(2) FET device was proposed.Within the designed configuration,waste heat in WTe_(2) would be mostly dissipated to metal contacts located along zigzag,relieving the local temperature discrepancy in the channel effectively and preventing degradation or breakdown.Our study provides new insight into thermal transport of anisotropic 2D materials,which might inspire energy-efficient nanodevices in the future.
基金supported by the National Key Research and Development Program of China(No.2019YFA0705400)the National Natural Science Foundation of China(Nos.21925404,22002128,22104135,62004095,and 22021001)Zhejiang Provincial Natural Science Foundation of China(No.LY23B050003).
文摘Monolayer graphene has attracted enormous attention owing to its unique electronic and optical properties.However,achieving an effective approach without applying electrical bias for manipulating the charge transfer based on graphene is elusive to date.Herein,we realized the manipulation of excitons’transition from emitter to the graphene surface with plasmonic engineering nanostructures and firstly obtained large enhancements for photon emission on the graphene surface.The localized plasmons generated from the plasmonic nanostructures of shell-isolated nanoparticle coupling to ultra-flat Au substrate would dictate a consistent junction geometry while enhancing the optical field and dominating the electron transition pathways,which may cause obvious perturbations for molecular radiation behaviors.Additionally,the three-dimensional finite-difference time-domain and time-dependent density functional theory were also carried out to simulate the distributions of electromagnetic field and energy levels of hybrid nanostructure respectively and the results agreed well with the experimental data.Therefore,this work paves a novel approach for tunning graphene charge/energy transfer processes,which may hold great potential for applications in photonic devices based on graphene.
基金the National Natural Science Foundation of China(22075092 and 21805104)the Program for Huazhong University of Science and Technology(HUST)Academic Frontier Youth Team(2018QYTD15)The Innovation and Talent Recruitment Base of New Energy Chemistry and Device(B21003)。
文摘Developing efficient platinum(Pt)-based electrocatalysts is enormously significant for fuel cells.Herein,we report an integrated electrocatalyst of ultralow-Pt alloy encapsulated into nitrogen-doped nanocarbon architecture for efficient oxygen reduction reaction.This hybrid Pt-based catalyst achieves a mass activity of 3.46 A mg^(-1)_(pt)the potential of 0.9 V vs.RHE with a negligible stability decay after 10,000 cycles.More importantly,this half-cell activity can be expressed at full cell level with a high Pt utilization of 10.22 W mg^(-1)_(Pt cathode)and remarkable durability after 30,000 cycles in single-cell.Experimental and theoretical investigations reveal that a highly strained Pt structure with an optimal Pt-0 binding energy is induced by the incorporation of Co/Ni into Pt lattice,which would account for the improved reaction kinetics.The synergistic catalysis due to nitrogen-doped nanocarbon architecture and active Pt component is responsible for the enhanced catalytic activity.Meanwhile,the strong metal-support interaction and optimized hydrophilic properties of nanocarbon matrix facilitate efficient mass transport and water management.This work may provide significant insights in designing the low-Pt integrated electrocatalysts for fuel cells and beyond.
基金funded by National Natural Science Foundation of China(Grant No.51976122)the Foundation of Science and Technology on Combustion and Explosion Laboratory(Grant No.6142603200508)the National Science and Technology Major Project 2017-III-0007-0033.
文摘The control of combustion is a hot and classical topic.Among the combustion technologies,electric-field assisted combustion is an advanced technology that enjoys major advantages such as fast response and low power consumption compared with thermal power.However,its fundamental principle and impacts on the flames are complicated due to the coupling between physics,chemistry,and electromagnetics.In the last two decades,tremendous efforts have been made to understand electric-field assisted combustion.New observations have been reported based on different combustion systems and improved diagnostics.The main impacts,including flame stabilization,emission reduction,and flame propagation,have been revealed by both simulative and experimental studies.These findings significantly facilitate the application of electric-field assisted combustion.This brief review is intended to provide a comprehensive overview of the recent progress of this combustion technology and further point out research opportunities worth investigation.
