The task of modeling and analyzing intercepted multifunction radars(MFRs)pulse trains is vital for cognitive electronic reconnaissance.Existing methodologies predominantly rely on prior information or heavily constrai...The task of modeling and analyzing intercepted multifunction radars(MFRs)pulse trains is vital for cognitive electronic reconnaissance.Existing methodologies predominantly rely on prior information or heavily constrained models,posing challenges for non-cooperative applications.This paper introduces a novel approach to model MFRs using a Bayesian network,where the conditional probability density function is approximated by an autoregressive kernel mixture network(ARKMN).Utilizing the estimated probability density function,a dynamic programming algorithm is proposed for denoising and detecting change points in the intercepted MFRs pulse trains.Simulation results affirm the proposed method's efficacy in modeling MFRs,outperforming the state-of-the-art in pulse train denoising and change point detection.展开更多
二氧化碳(CO_(2))虽然被视为破坏生态环境的温室气体,但也是储量最丰富的碳资源,对其进行转化和利用将对社会环境和能源结构产生深远影响.电化学还原CO_(2)(CO_(2)RR)不仅转化效率高,而且成本较低,有望实现规模化生产.在众多催化剂中,...二氧化碳(CO_(2))虽然被视为破坏生态环境的温室气体,但也是储量最丰富的碳资源,对其进行转化和利用将对社会环境和能源结构产生深远影响.电化学还原CO_(2)(CO_(2)RR)不仅转化效率高,而且成本较低,有望实现规模化生产.在众多催化剂中,廉价易得的铜基催化剂被认为是电化学催化还原CO_(2)生成高附加值产物的理想催化剂之一,其中铜氧化物的存在是CO_(2)RR生成高附加值产物的关键.然而,CO_(2)RR过程是在负电位下进行的,当施加电位低于‒0.1 VRHE时,铜氧化物很容易被还原为金属态铜.因此,催化剂稳定氧化态铜的能力在保持连续、高效和稳定的CO_(2)RR产多碳产物性能中至关重要.本文将简单的O_(2)等离子体处理技术与静电纺丝技术相结合,合成了多孔碳纳米纤维负载的Cu/Cu_(x)O异质结催化剂,并考察了其催化CO_(2)RR的性能.在静电纺丝过程中,Cu-ZIF-8前驱体的加入使得热处理后的原丝纤维中形成了丰富的网络贯穿多孔结构,该结构有效地实现了铜纳米颗粒的均匀分散;随后,通过O_(2)等离子体处理技术,在碳纳米纤维中构建了大量的开放介孔,为CO_(2)的吸附和反应提供了有利环境,并使Cu/Cu_(x)O异质结位点暴露于反应界面.电化学性能测试结果表明,在400 mA cm^(‒2)电流密度下,独特的Cu/Cu_(x)O异质结活性位点电催化还原CO_(2)生成乙醇的法拉第效率可达70.7%,该性能优于未经O_(2)等离子体处理的多孔铜纳米纤维.此外,高暴露的Cu/Cu_(x)O异质结活性位点显著地增加实际参与反应的活性位点数量,经计算Cu/Cu_(x)O异质结CO_(2)RR产乙醇的质量活性高达8.4 A mg^(‒1),是目前报道生产乙醇的较高质量活性.多孔碳纳米纤维衬底不仅具有协同电子输运能力,而且在CO_(2)RR测试中施加的负电压有助于维持Cu/Cu_(x)O异质结构的稳定性,使其在高电流密度下能够保持长时间的催化稳定性.此外,本文利用原位拉曼光谱和红外光谱、有限元模拟及密度泛函理论计算等方法深入研究了Cu/Cu_(x)O异质结的催化机理.原位拉曼光谱和红外光谱表征结果证实了在CO_(2)RR过程中Cu_(x)O的动态稳定状态以及关键信号*CO和C‒C键的存在;理论计算表明,Cu/Cu_(x)O异质结的存在促进了关键中间体*CO的溢流,降低了C‒C耦合过程的反应能垒,从而提高了还原产物乙醇的产率.综上,本文成功地在多孔铜纳米纤维中引入氧化物物种,并优化了纤维孔结构.其表现出了较好的电催化还原CO_(2)性能,可高选择性生成乙醇,其独特的多孔碳纤维结构充分暴露了活性位点,实现了较高的质量活性.本文所采用的催化剂组分和微观结构的调控策略为提升电催化中催化剂稳定性和催化活性提供了有益的借鉴.展开更多
With the development of green data centers,a large number of Uninterruptible Power Supply(UPS)resources in Internet Data Center(IDC)are becoming idle assets owing to their low utilization rate.The revitalization of th...With the development of green data centers,a large number of Uninterruptible Power Supply(UPS)resources in Internet Data Center(IDC)are becoming idle assets owing to their low utilization rate.The revitalization of these idle UPS resources is an urgent problem that must be addressed.Based on the energy storage type of the UPS(EUPS)and using renewable sources,a solution for IDCs is proposed in this study.Subsequently,an EUPS cluster classification method based on the concept of shared mechanism niche(CSMN)was proposed to effectively solve the EUPS control problem.Accordingly,the classified EUPS aggregation unit was used to determine the optimal operation of the IDC.An IDC cost minimization optimization model was established,and the Quantum Particle Swarm Optimization(QPSO)algorithm was adopted.Finally,the economy and effectiveness of the three-tier optimization framework and model were verified through three case studies.展开更多
Owing to the rapid development of microgrids(MGs)and growing applications of renewable energy resources,multiobjective optimal dispatch of MGs need to be studied in detail.In this study,a multiobjective optimal dispat...Owing to the rapid development of microgrids(MGs)and growing applications of renewable energy resources,multiobjective optimal dispatch of MGs need to be studied in detail.In this study,a multiobjective optimal dispatch model is developed for a standalone MG composed of wind turbines,photovoltaics,diesel engine unit,load,and battery energy storage system.The economic cost,environmental concerns,and power supply consistency are expressed via subobjectives with varying priorities.Then,the analytic hierarchy process algorithm is employed to reasonably specify the weight coefficients of the subobjectives.The quantum particle swarm optimization algorithm is thereafter employed as a solution to achieve optimal dispatch of the MG.Finally,the validity of the proposed model and solution methodology are con firmed by case studies.This study provides refere nee for mathematical model of multiojective optimizati on of MG and can be widely used in current research field.展开更多
This paper presents an improved approach based on the equivalent-weights particle filter(EWPF)that uses the proposal density to effectively improve the traditional particle filter.The proposed approach uses historical...This paper presents an improved approach based on the equivalent-weights particle filter(EWPF)that uses the proposal density to effectively improve the traditional particle filter.The proposed approach uses historical data to calculate statistical observations instead of the future observations used in the EWPF’s proposal density and draws on the localization scheme used in the localized PF(LPF)to construct the localized EWPF.The new approach is called the statistical observation localized EWPF(LEWPF-Sobs);it uses statistical observations that are better adapted to the requirements of real-time assimilation and the localization function is used to calculate weights to reduce the effect of missing observations on the weights.This approach not only retains the advantages of the EWPF,but also improves the assimilation quality when using sparse observations.Numerical experiments performed with the Lorenz 96 model show that the statistical observation EWPF is better than the EWPF and EAKF when the model uses standard distribution observations.Comparisons of the statistical observation localized EWPF and LPF reveal the advantages of the new method,with fewer particles giving better results.In particular,the new improved filter performs better than the traditional algorithms when the observation network contains densely spaced measurements associated with model state nonlinearities.展开更多
Objective: To evaluate the efficacy and feasibility of the transradial approach for primary percutaneous coronary intervention (PCI) in patients with acute myocardial infarction(AMI). Methods: 195 patients with ...Objective: To evaluate the efficacy and feasibility of the transradial approach for primary percutaneous coronary intervention (PCI) in patients with acute myocardial infarction(AMI). Methods: 195 patients with acute myocardial infarction were randomly divided into two groups according to the different PCI operation pathways. 105 cases were assigned to the transfemoral artery group and 90 cases to the transradial artery group. We analyzed the data from the two groups, including the achievement ratio of paracentesis, cannulation time, the time from local anesthesia to the first time balloon inflation, the time of the total procedure, achievement ratio of PCI, incidence rate of vascular complications, total duration of hospitalization, and the six-month follow-up results in both groups. Results: Our results showed that the achier ement ratio of arteriopuncture, cannulafion time and the time from local anesthesia to the first time balloon inflation in the transradial and transfemoral groups were 98.9% vs. 100%, 3.15 ± 1.56min vs. 2.86 ± 0.97 min, and 18.56 ± 4.37 min vs. 17.75 ± 3.21 min, respectively. These differences between the two groups were not statistically significant. The total operating time was 29.75 ± 4.38 rain for the transradial group and 27.89 ± 3.95 min(P 〈 0.05) for the transfemoral group. The operation achievement ratio in the transradial group was 96.7%, and 96.2% in the transfemoral group. The incidence of puncture point complications was 2.2% in the transradial group and 11.4% in the transfemoral group, and this difference was significant. The duration of hospitalization was 10.56 ± 2.85 days for the transradial group and 13.78 ± 3.15 days(P 〈 0.05) for the transfemoral group. At the six-month follow-up, the rate of survival without cardiac event was 86.1% vs. 86.4% respectively in the transradial and transfemoral groups(P 〉 0.05). Conclusion: The transradial approach was as effective as the transfemoral approach, and there were fewer puncture point complications as well as a shorter span of hospitalization in the transradial group. PCI via the transradial approach is safe, effective and feasible in patients with AMI.展开更多
With the deepening reform and education system, teacher development is increasingly being taken seriously. Teachers' professional development ability is related to the overall level of higher education. For science a...With the deepening reform and education system, teacher development is increasingly being taken seriously. Teachers' professional development ability is related to the overall level of higher education. For science and engineering colleges, the traditional light text is serious on a weight management, science and engineering university foreign language teacher development is severely limited. In this view, I try to start from the theory of teacher development, combined with the actual characteristics of the University of Science and Engineering, University of Science and Engineering is to expLore the implementation of foreign language teachers' professional development path.展开更多
Designing high efficacy photocatalysts is a promising way to improve solar fuel production efficiency.In this work,we prepared a core/shell composite of loose ZnCr layered double hydroxide nanosheets modified CdS nano...Designing high efficacy photocatalysts is a promising way to improve solar fuel production efficiency.In this work,we prepared a core/shell composite of loose ZnCr layered double hydroxide nanosheets modified CdS nanorods for efficient visible light driven photocatalytic hydrogen production.The highest hydrogen production rate achieved 425.8μmol·h^(−1) without adding any noble metal cocatalyst under the visible light stimulus,which is 22.4 times that of 1 wt.%Pt-modified CdS.The corresponding apparent quantum yield is 13.9%at 420 nm.It is revealed that the synergistic actions of the interfacial redox shuttle of Cr^(3+)/Cr^(δ+)and the interfacial electric field enable the efficient separation of photoinduced charge carriers between two components via a Z-scheme energy band configuration.Meanwhile,with the hydrogen evolution contribution of Zn^(2+),a remarkable improvement in photocatalytic performance was achieved in contrast to bare CdS.This work provides an effective methodology to construct highly efficient and economically viable photocatalysts for solar H_(2)production and mechanistic study.展开更多
The spatial order of architecture has been significantly impacted by digital architectural design and production,creating a dynamic uncertainty.This study aims to explore digital architecture from the perspective of s...The spatial order of architecture has been significantly impacted by digital architectural design and production,creating a dynamic uncertainty.This study aims to explore digital architecture from the perspective of spatial order,discussing the antidote/poison effect caused by digital technologies in architectural practice and the cultural digital changes in digital architectures.The study selected four digital architecture cases,including the(W)rapper at Los Angeles by Eric Owen Moss,Beijing Daxing International Airport by Zaha Hadid,3D Print Niaokan Bridge by Xu Weiguo,and World Internet Conference Center by Yuan Feng.This study is hypothesising that the future special order of digital architectures will be a dynamic and balanced new spatial order.This new order includes the symbiosis of a human-machine and virtual-real hierarchy;the interactive co-existence between nature,humanity and technology;and the creative multi-immersive sharing of parametric information,built-environment resources and cultural artistic information.The evolution of spatial order of future digital architecture will be discussed in connection with the idea of the metaverse.The value of this work is its ability to inspire a broader examination of the new order of digital architectural space.展开更多
Electrocatalytic CO2 reduction is a promising way to mitigate the urgent energy and environmental issues, but how to increase the selectivity for desired product among multiple competi ng reaction pathways remains a b...Electrocatalytic CO2 reduction is a promising way to mitigate the urgent energy and environmental issues, but how to increase the selectivity for desired product among multiple competi ng reaction pathways remains a bottle neck. Here, we demonstrate that engineering the gas-liquid-solid contact interface on the electrode surface could tailor the selectivity of CO2 reducti on and meanwhile suppress H2 production through regulated reacti on kin etics. Specifically, polytetrafl uoroethyle ne (PTFE) was utilized to modify a Cu nano array electrode as an example, which is able to cha nge the electrode surface from aerophobic to aerophilic state. The en riched nano-tunnels of the Cu nano array electrode can facilitate CO2 transportation and pin gaseous products on the electrode surface. The latter is believed to be the reason that boosts the Faradaic efficie ncy of liquid products by 67% and limits the H2 producti on to less than half of before. This in terface engin eeri ng strategy also lowered H2O (proton) affinity, therefore promoting CO and HCOOH production. Engineering the electrode contact interface controls the reaction kinetics and the selectivity of products, which should be inspiring for other electrochemical reactions.展开更多
PtTe2 and PtSe2 with trigonal structure have attracted extensive research interests since the discovery of type-II Dirac fermions in the bulk crystals. The evolution of the electronic structure from bulk 3D topologica...PtTe2 and PtSe2 with trigonal structure have attracted extensive research interests since the discovery of type-II Dirac fermions in the bulk crystals. The evolution of the electronic structure from bulk 3D topological semimetal to 2D atomic thin films is an important scientific question. While a transition from 3D type-II Dirac semimetal in the bulk to 2D semiconductor in monolayer(ML) film has been reported for PtSe2, so far the evolution of electronic structure of atomically thin PtTe2 films still remains unexplored.Here we report a systematic angle-resolved photoemission spectroscopy(ARPES) study of the electronic structure of high quality PtTe2 films grown by molecular beam epitaxy with thickness from 2 ML to 6 ML.ARPES measurements show that PtTe2 films still remain metallic even down to 2 ML thickness, which is in sharp contrast to the semiconducting property of few layer PtSe2 films. Moreover, a transition from 2D metal to 3D type-II Dirac semimetal occurs at film thickness of 4–6 ML. In addition, Spin-ARPES measurements reveal helical spin textures induced by local Rashba effect in the bulk PtTe2 crystal, suggesting that similar hidden spin is also expected in few monolayer PtTe2 films. Our work reveals the transition from2D metal to 3D topological semimetal and provides new opportunities for investigating metallic 2D films with local Rashba effect.展开更多
With the possibility of large-area processing, the ZIF-8-coated mesh membranes with rough micro-/nanostructures and underwater superoleophobic properties were successfully fabricated at ambient temperature and pressur...With the possibility of large-area processing, the ZIF-8-coated mesh membranes with rough micro-/nanostructures and underwater superoleophobic properties were successfully fabricated at ambient temperature and pressure.These membranes exhibited excellent separation efficiency over 99.99% for various oil-water mixtures with the residual oil content in the collected water less than 4 ppm, and high water flux of 10.2×104 L m-2 h-1. Furthermore, the ZIF-8-coated mesh membrane displayed outstanding stability towards high temperature and various organic solvents immersion. More importantly, based on its facile fabrication method, this kind of ZIF-8-coated mesh membrane can be easily enlarged, which is critical for the practical oil-water separation applications.展开更多
The careful design of nano-architectures and smart hybridization of expected active materials can lead to more advanced properties. Here we have engineered a novel hierarchical branching Cu/Cu2O/CuO heteronanostructur...The careful design of nano-architectures and smart hybridization of expected active materials can lead to more advanced properties. Here we have engineered a novel hierarchical branching Cu/Cu2O/CuO heteronanostructure by combining a facile hydrothermal method and subsequent controlled oxidation process. The fine structure and epitaxial relationship between the branches and backbone are investigated by high-resolution transmission electron microscopy. Moreover, the evolution of the branch growth has also been observed during the gradual oxidation of the Cu nanowire surface. The experimental results suggest that the surface oxidation needs to be performed via a two-step exposure process to varying humidity in order to achieve optimized formation of a core-shell structured branching architecture. Finally, a proof-of-concept of the function of such a hierarchical framework as the anode material in lithium-ion batteries is demonstrated. The branching core-shell heterostructure improves battery performance by several means: (i) The epitaxially grown branches provide a high surface area for enhanced electrolyte accessibility and high resistance to volume change induced by Li^+ intercalation/extraction; (ii) the core-shell structure with its well-defined heterojunction increases the contact area which facilitates effective charge transport during lithiation; (iii) the copper core acts as a current collector as well as providing structural reinforcement.展开更多
Narrowband microwave generation with tuneable frequency is demonstrated by illuminating a photoconductive semiconductor switch(PCSS)with a burst-mode fibre laser.The whole system is composed of a high-power linearly p...Narrowband microwave generation with tuneable frequency is demonstrated by illuminating a photoconductive semiconductor switch(PCSS)with a burst-mode fibre laser.The whole system is composed of a high-power linearly polarized burst-mode pulsed fibre laser and a linear-state PCSS.To obtain a high-performance microwave signal,a desired envelope of burst is necessary and a pulse pre-compensation technique is adopted to avoid envelope distortion induced by the gain-saturation effect.Resulting from the technique,homogenous peak power distribution in each burst is ensured.The maximum energy of the laser burst pulse reaches 200μJ with a burst duration of 100 ns at the average power of 10 W,corresponding to a peak power of 4 kW.When the PCSS is illuminated by the burst-mode fibre laser,narrowband microwave generation with tuneable frequency(0.80-1.12 GHz)is obtained with a power up to 300 W.To the best of the authors’knowledge,it is the first demonstration of frequency-tuneable narrowband microwave generation based on a fibre laser.The high-power burst-mode fibre laser reported here has great potential for generating high-power arbitrary microwave signals for a great deal of applicable demands such as smart adaptive radar and intelligent high-power microwave systems.展开更多
The methanol oxidation reaction(MOR)is the limiting half-reaction in direct methanol fuel cell(DMFC).Although Pt is the most active single-metal electrocatalyst for MOR,it is hampered by high cost and CO poisoning.Con...The methanol oxidation reaction(MOR)is the limiting half-reaction in direct methanol fuel cell(DMFC).Although Pt is the most active single-metal electrocatalyst for MOR,it is hampered by high cost and CO poisoning.Constructing a Pt or Ru monolayer on a second metal substrate by means of galvanic replacement of underpotentially deposited(UPD)Cu monolayer has been shown as an efficient catalyst design strategy for the electrocatalysis of MOR because of the presumed 100%utilization of atoms and resistance to CO poisoning.Herein,we prepared one-dimensional surface-alloyed electrocatalyst from predominantly(111)faceted Au nanowires with high aspect ratio as the substrate of under-potential deposition.The electrocatalyst comprises a core of the Au nanowire and a shell of catalytically active Pt coated by Ru.Coverage-dependent electro-catalytic activity and stability is demonstrated on the Pt/Ru submonolayers on Au wires for MOR.Among all these catalysts,Au@Pt_(ML)@Ru_(ML)exhibits the best electrocatalytic activity and poisoning tolerance to CO.This presents a viable method for the rational catalyst design for achieving high noble-metal utilization efficiency and high catalytic performance.展开更多
The addition of yttrium chloride(YCl) to an activated carbon-supported Au catalyst(Au/AC) can markedly promote the catalytic performance of acetylene hydrochlorination to the vinyl chloride monomer(VCM), The structure...The addition of yttrium chloride(YCl) to an activated carbon-supported Au catalyst(Au/AC) can markedly promote the catalytic performance of acetylene hydrochlorination to the vinyl chloride monomer(VCM), The structure and physicochemical features of the YCl-modified catalysts(Y-Au/AC)were measured by X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction, CH-temperature programmed desorption, and scanning transmission electron microscopy.The presence of YClwas found suppressing the reduction of highly oxidized Au(δ=1,3) to metallic Au~0 dependently and thus retard the agglomeration of Au nanoparticles during the reaction. In addition,the additive of YClto the Au/AC catalyst greatly inhibits the coke deposition on the catalyst surface. The optimized catalyst with an atomic ratio of Y/Au = 5(1 wt% Au loading weight) yields an 87.8% acetylene conversion and almost 100% selectivity for VCM under the reaction of GHSV(CH) = 800 hat 180 ℃.The durability test indicates that the 5 Y-1 Au/AC catalyst maintains high catalytic activity for more than2300 h at 30 hGHSV(CH) and 180 ℃, indicating great promise as a non-mercury catalyst for PVC manufacture.展开更多
Pillararene/calixarene-based functional materials have garnered significant attention for their unique topological/chemical structures and physicochemical properties,and their extended applications in electro-chemistr...Pillararene/calixarene-based functional materials have garnered significant attention for their unique topological/chemical structures and physicochemical properties,and their extended applications in electro-chemistry have given rise to a promising area of research.This review details current advance in developing electrochemical energy materials based on pillararene/calixarene systems from the viewpoint of both fundamental theoretical simulations and research on practical applications.First,we discuss the underlying mechanisms of applying pillararene/calixarene-based systems for electrochemical energy applications.Second,we summarize simulation studies on pillarquinone and calixquinone with intrinsic structures for applications in batteries.In addition,state-of-the-art applications of pillararene/calixarene-based systems in electrochemical energy storage devices such as lithium/sodium-ion batteries and supercapacitors are highlighted.The diverse roles they play and the various design strategies that have been investigated for high-performance pillararene/calixarene-based batteries are analyzed.Finally,we discuss the prospects for further developments in this emerging field.This review not only describes recent advances in pillararene/calixarene-based batteries and supercapacitors but also lays a firm groundwork for their further application in electrochemical energy engineering.展开更多
基金supported by the National Natural Science Foundation of China under Grant 62301119。
文摘The task of modeling and analyzing intercepted multifunction radars(MFRs)pulse trains is vital for cognitive electronic reconnaissance.Existing methodologies predominantly rely on prior information or heavily constrained models,posing challenges for non-cooperative applications.This paper introduces a novel approach to model MFRs using a Bayesian network,where the conditional probability density function is approximated by an autoregressive kernel mixture network(ARKMN).Utilizing the estimated probability density function,a dynamic programming algorithm is proposed for denoising and detecting change points in the intercepted MFRs pulse trains.Simulation results affirm the proposed method's efficacy in modeling MFRs,outperforming the state-of-the-art in pulse train denoising and change point detection.
文摘二氧化碳(CO_(2))虽然被视为破坏生态环境的温室气体,但也是储量最丰富的碳资源,对其进行转化和利用将对社会环境和能源结构产生深远影响.电化学还原CO_(2)(CO_(2)RR)不仅转化效率高,而且成本较低,有望实现规模化生产.在众多催化剂中,廉价易得的铜基催化剂被认为是电化学催化还原CO_(2)生成高附加值产物的理想催化剂之一,其中铜氧化物的存在是CO_(2)RR生成高附加值产物的关键.然而,CO_(2)RR过程是在负电位下进行的,当施加电位低于‒0.1 VRHE时,铜氧化物很容易被还原为金属态铜.因此,催化剂稳定氧化态铜的能力在保持连续、高效和稳定的CO_(2)RR产多碳产物性能中至关重要.本文将简单的O_(2)等离子体处理技术与静电纺丝技术相结合,合成了多孔碳纳米纤维负载的Cu/Cu_(x)O异质结催化剂,并考察了其催化CO_(2)RR的性能.在静电纺丝过程中,Cu-ZIF-8前驱体的加入使得热处理后的原丝纤维中形成了丰富的网络贯穿多孔结构,该结构有效地实现了铜纳米颗粒的均匀分散;随后,通过O_(2)等离子体处理技术,在碳纳米纤维中构建了大量的开放介孔,为CO_(2)的吸附和反应提供了有利环境,并使Cu/Cu_(x)O异质结位点暴露于反应界面.电化学性能测试结果表明,在400 mA cm^(‒2)电流密度下,独特的Cu/Cu_(x)O异质结活性位点电催化还原CO_(2)生成乙醇的法拉第效率可达70.7%,该性能优于未经O_(2)等离子体处理的多孔铜纳米纤维.此外,高暴露的Cu/Cu_(x)O异质结活性位点显著地增加实际参与反应的活性位点数量,经计算Cu/Cu_(x)O异质结CO_(2)RR产乙醇的质量活性高达8.4 A mg^(‒1),是目前报道生产乙醇的较高质量活性.多孔碳纳米纤维衬底不仅具有协同电子输运能力,而且在CO_(2)RR测试中施加的负电压有助于维持Cu/Cu_(x)O异质结构的稳定性,使其在高电流密度下能够保持长时间的催化稳定性.此外,本文利用原位拉曼光谱和红外光谱、有限元模拟及密度泛函理论计算等方法深入研究了Cu/Cu_(x)O异质结的催化机理.原位拉曼光谱和红外光谱表征结果证实了在CO_(2)RR过程中Cu_(x)O的动态稳定状态以及关键信号*CO和C‒C键的存在;理论计算表明,Cu/Cu_(x)O异质结的存在促进了关键中间体*CO的溢流,降低了C‒C耦合过程的反应能垒,从而提高了还原产物乙醇的产率.综上,本文成功地在多孔铜纳米纤维中引入氧化物物种,并优化了纤维孔结构.其表现出了较好的电催化还原CO_(2)性能,可高选择性生成乙醇,其独特的多孔碳纤维结构充分暴露了活性位点,实现了较高的质量活性.本文所采用的催化剂组分和微观结构的调控策略为提升电催化中催化剂稳定性和催化活性提供了有益的借鉴.
基金supported by the Key Technology Projects of the China Southern Power Grid Corporation(STKJXM20200059)the Key Support Project of the Joint Fund of the National Natural Science Foundation of China(U22B20123)。
文摘With the development of green data centers,a large number of Uninterruptible Power Supply(UPS)resources in Internet Data Center(IDC)are becoming idle assets owing to their low utilization rate.The revitalization of these idle UPS resources is an urgent problem that must be addressed.Based on the energy storage type of the UPS(EUPS)and using renewable sources,a solution for IDCs is proposed in this study.Subsequently,an EUPS cluster classification method based on the concept of shared mechanism niche(CSMN)was proposed to effectively solve the EUPS control problem.Accordingly,the classified EUPS aggregation unit was used to determine the optimal operation of the IDC.An IDC cost minimization optimization model was established,and the Quantum Particle Swarm Optimization(QPSO)algorithm was adopted.Finally,the economy and effectiveness of the three-tier optimization framework and model were verified through three case studies.
基金State Grid Corporation Science and Technology Project(520605190010).
文摘Owing to the rapid development of microgrids(MGs)and growing applications of renewable energy resources,multiobjective optimal dispatch of MGs need to be studied in detail.In this study,a multiobjective optimal dispatch model is developed for a standalone MG composed of wind turbines,photovoltaics,diesel engine unit,load,and battery energy storage system.The economic cost,environmental concerns,and power supply consistency are expressed via subobjectives with varying priorities.Then,the analytic hierarchy process algorithm is employed to reasonably specify the weight coefficients of the subobjectives.The quantum particle swarm optimization algorithm is thereafter employed as a solution to achieve optimal dispatch of the MG.Finally,the validity of the proposed model and solution methodology are con firmed by case studies.This study provides refere nee for mathematical model of multiojective optimizati on of MG and can be widely used in current research field.
基金The National Basic Research Program of China under contract Nos 2017YFC1404100,2017YFC1404103 and 2017YFC1404104the National Natural Science Foundation of China under contract No.41676088。
文摘This paper presents an improved approach based on the equivalent-weights particle filter(EWPF)that uses the proposal density to effectively improve the traditional particle filter.The proposed approach uses historical data to calculate statistical observations instead of the future observations used in the EWPF’s proposal density and draws on the localization scheme used in the localized PF(LPF)to construct the localized EWPF.The new approach is called the statistical observation localized EWPF(LEWPF-Sobs);it uses statistical observations that are better adapted to the requirements of real-time assimilation and the localization function is used to calculate weights to reduce the effect of missing observations on the weights.This approach not only retains the advantages of the EWPF,but also improves the assimilation quality when using sparse observations.Numerical experiments performed with the Lorenz 96 model show that the statistical observation EWPF is better than the EWPF and EAKF when the model uses standard distribution observations.Comparisons of the statistical observation localized EWPF and LPF reveal the advantages of the new method,with fewer particles giving better results.In particular,the new improved filter performs better than the traditional algorithms when the observation network contains densely spaced measurements associated with model state nonlinearities.
基金support from the Editorial Department of the Journal of Nanjing Medical Univrsity
文摘Objective: To evaluate the efficacy and feasibility of the transradial approach for primary percutaneous coronary intervention (PCI) in patients with acute myocardial infarction(AMI). Methods: 195 patients with acute myocardial infarction were randomly divided into two groups according to the different PCI operation pathways. 105 cases were assigned to the transfemoral artery group and 90 cases to the transradial artery group. We analyzed the data from the two groups, including the achievement ratio of paracentesis, cannulation time, the time from local anesthesia to the first time balloon inflation, the time of the total procedure, achievement ratio of PCI, incidence rate of vascular complications, total duration of hospitalization, and the six-month follow-up results in both groups. Results: Our results showed that the achier ement ratio of arteriopuncture, cannulafion time and the time from local anesthesia to the first time balloon inflation in the transradial and transfemoral groups were 98.9% vs. 100%, 3.15 ± 1.56min vs. 2.86 ± 0.97 min, and 18.56 ± 4.37 min vs. 17.75 ± 3.21 min, respectively. These differences between the two groups were not statistically significant. The total operating time was 29.75 ± 4.38 rain for the transradial group and 27.89 ± 3.95 min(P 〈 0.05) for the transfemoral group. The operation achievement ratio in the transradial group was 96.7%, and 96.2% in the transfemoral group. The incidence of puncture point complications was 2.2% in the transradial group and 11.4% in the transfemoral group, and this difference was significant. The duration of hospitalization was 10.56 ± 2.85 days for the transradial group and 13.78 ± 3.15 days(P 〈 0.05) for the transfemoral group. At the six-month follow-up, the rate of survival without cardiac event was 86.1% vs. 86.4% respectively in the transradial and transfemoral groups(P 〉 0.05). Conclusion: The transradial approach was as effective as the transfemoral approach, and there were fewer puncture point complications as well as a shorter span of hospitalization in the transradial group. PCI via the transradial approach is safe, effective and feasible in patients with AMI.
文摘With the deepening reform and education system, teacher development is increasingly being taken seriously. Teachers' professional development ability is related to the overall level of higher education. For science and engineering colleges, the traditional light text is serious on a weight management, science and engineering university foreign language teacher development is severely limited. In this view, I try to start from the theory of teacher development, combined with the actual characteristics of the University of Science and Engineering, University of Science and Engineering is to expLore the implementation of foreign language teachers' professional development path.
基金This work was financially supported by the National Key Research and Development Program of China(No.2018YFB1502000)the National Natural Science Foundation of China(Nos,62074123 and 52106270)+3 种基金the PetroChina Innovation Foundation(No.2019D-5007-0410)the Young Talent Support Plan of Xi'an Jiaotong University(No.7121191202)the Natural Science Foundation of Shaanxi Province(No.2021JQ-040)the China Postdoctoral Science Foundation(No.2020M683472).
文摘Designing high efficacy photocatalysts is a promising way to improve solar fuel production efficiency.In this work,we prepared a core/shell composite of loose ZnCr layered double hydroxide nanosheets modified CdS nanorods for efficient visible light driven photocatalytic hydrogen production.The highest hydrogen production rate achieved 425.8μmol·h^(−1) without adding any noble metal cocatalyst under the visible light stimulus,which is 22.4 times that of 1 wt.%Pt-modified CdS.The corresponding apparent quantum yield is 13.9%at 420 nm.It is revealed that the synergistic actions of the interfacial redox shuttle of Cr^(3+)/Cr^(δ+)and the interfacial electric field enable the efficient separation of photoinduced charge carriers between two components via a Z-scheme energy band configuration.Meanwhile,with the hydrogen evolution contribution of Zn^(2+),a remarkable improvement in photocatalytic performance was achieved in contrast to bare CdS.This work provides an effective methodology to construct highly efficient and economically viable photocatalysts for solar H_(2)production and mechanistic study.
文摘The spatial order of architecture has been significantly impacted by digital architectural design and production,creating a dynamic uncertainty.This study aims to explore digital architecture from the perspective of spatial order,discussing the antidote/poison effect caused by digital technologies in architectural practice and the cultural digital changes in digital architectures.The study selected four digital architecture cases,including the(W)rapper at Los Angeles by Eric Owen Moss,Beijing Daxing International Airport by Zaha Hadid,3D Print Niaokan Bridge by Xu Weiguo,and World Internet Conference Center by Yuan Feng.This study is hypothesising that the future special order of digital architectures will be a dynamic and balanced new spatial order.This new order includes the symbiosis of a human-machine and virtual-real hierarchy;the interactive co-existence between nature,humanity and technology;and the creative multi-immersive sharing of parametric information,built-environment resources and cultural artistic information.The evolution of spatial order of future digital architecture will be discussed in connection with the idea of the metaverse.The value of this work is its ability to inspire a broader examination of the new order of digital architectural space.
基金National Natural Science Foundation of Chinathe National Key Research and Development Program of China (Nos. 2016YFC0801302 and 2016YFF0204402)+3 种基金the Program for Changjiang Scholars and Innovative Research Team in the Universitythe Fundamental Research Funds for the Central Universitiesthe longterm subsidy mechanism from the Ministry of Finance and the Ministry of Education of PRCthe National Natural Science Foundation of China (No. 61701543) for the financial support.
文摘Electrocatalytic CO2 reduction is a promising way to mitigate the urgent energy and environmental issues, but how to increase the selectivity for desired product among multiple competi ng reaction pathways remains a bottle neck. Here, we demonstrate that engineering the gas-liquid-solid contact interface on the electrode surface could tailor the selectivity of CO2 reducti on and meanwhile suppress H2 production through regulated reacti on kin etics. Specifically, polytetrafl uoroethyle ne (PTFE) was utilized to modify a Cu nano array electrode as an example, which is able to cha nge the electrode surface from aerophobic to aerophilic state. The en riched nano-tunnels of the Cu nano array electrode can facilitate CO2 transportation and pin gaseous products on the electrode surface. The latter is believed to be the reason that boosts the Faradaic efficie ncy of liquid products by 67% and limits the H2 producti on to less than half of before. This in terface engin eeri ng strategy also lowered H2O (proton) affinity, therefore promoting CO and HCOOH production. Engineering the electrode contact interface controls the reaction kinetics and the selectivity of products, which should be inspiring for other electrochemical reactions.
基金supported by the National Natural Science Foundation of China(11725418 and 11334006)the National Basic Research Program of China(2016YFA0301004,2016YFA0301001,and 2015CB921001)+1 种基金Science Challenge Project(TZ2016004)Beijing Advanced Innovation Center for Future Chip(ICFC)
文摘PtTe2 and PtSe2 with trigonal structure have attracted extensive research interests since the discovery of type-II Dirac fermions in the bulk crystals. The evolution of the electronic structure from bulk 3D topological semimetal to 2D atomic thin films is an important scientific question. While a transition from 3D type-II Dirac semimetal in the bulk to 2D semiconductor in monolayer(ML) film has been reported for PtSe2, so far the evolution of electronic structure of atomically thin PtTe2 films still remains unexplored.Here we report a systematic angle-resolved photoemission spectroscopy(ARPES) study of the electronic structure of high quality PtTe2 films grown by molecular beam epitaxy with thickness from 2 ML to 6 ML.ARPES measurements show that PtTe2 films still remain metallic even down to 2 ML thickness, which is in sharp contrast to the semiconducting property of few layer PtSe2 films. Moreover, a transition from 2D metal to 3D type-II Dirac semimetal occurs at film thickness of 4–6 ML. In addition, Spin-ARPES measurements reveal helical spin textures induced by local Rashba effect in the bulk PtTe2 crystal, suggesting that similar hidden spin is also expected in few monolayer PtTe2 films. Our work reveals the transition from2D metal to 3D topological semimetal and provides new opportunities for investigating metallic 2D films with local Rashba effect.
基金financially supported by the National Natural Science Foundation of China (21571076, 21390394, 21571079 and 61701543)"111" project (B07016)+1 种基金the Ministry of Science and Technology of SINOPEC (A381)Open Projects of State Key Laboratory of Safety and Control for Chemicals (SKL-038)
文摘With the possibility of large-area processing, the ZIF-8-coated mesh membranes with rough micro-/nanostructures and underwater superoleophobic properties were successfully fabricated at ambient temperature and pressure.These membranes exhibited excellent separation efficiency over 99.99% for various oil-water mixtures with the residual oil content in the collected water less than 4 ppm, and high water flux of 10.2×104 L m-2 h-1. Furthermore, the ZIF-8-coated mesh membrane displayed outstanding stability towards high temperature and various organic solvents immersion. More importantly, based on its facile fabrication method, this kind of ZIF-8-coated mesh membrane can be easily enlarged, which is critical for the practical oil-water separation applications.
基金We thank Prof. Mingbo Wu (State Key Laboratory of Heavy Oil Processing, China University of Petroleum) for his help in experiments. This work was finandally supported by the Key Joint Foundation of PetroChina, the National Natural Science Foundation of China (Nos. 51271215, U1362202, and 21106185) and the PetroChina Key Programs on Oil Refinery Catalysts (No. 2010E-1908 and 2010E-1903).
文摘The careful design of nano-architectures and smart hybridization of expected active materials can lead to more advanced properties. Here we have engineered a novel hierarchical branching Cu/Cu2O/CuO heteronanostructure by combining a facile hydrothermal method and subsequent controlled oxidation process. The fine structure and epitaxial relationship between the branches and backbone are investigated by high-resolution transmission electron microscopy. Moreover, the evolution of the branch growth has also been observed during the gradual oxidation of the Cu nanowire surface. The experimental results suggest that the surface oxidation needs to be performed via a two-step exposure process to varying humidity in order to achieve optimized formation of a core-shell structured branching architecture. Finally, a proof-of-concept of the function of such a hierarchical framework as the anode material in lithium-ion batteries is demonstrated. The branching core-shell heterostructure improves battery performance by several means: (i) The epitaxially grown branches provide a high surface area for enhanced electrolyte accessibility and high resistance to volume change induced by Li^+ intercalation/extraction; (ii) the core-shell structure with its well-defined heterojunction increases the contact area which facilitates effective charge transport during lithiation; (iii) the copper core acts as a current collector as well as providing structural reinforcement.
文摘Narrowband microwave generation with tuneable frequency is demonstrated by illuminating a photoconductive semiconductor switch(PCSS)with a burst-mode fibre laser.The whole system is composed of a high-power linearly polarized burst-mode pulsed fibre laser and a linear-state PCSS.To obtain a high-performance microwave signal,a desired envelope of burst is necessary and a pulse pre-compensation technique is adopted to avoid envelope distortion induced by the gain-saturation effect.Resulting from the technique,homogenous peak power distribution in each burst is ensured.The maximum energy of the laser burst pulse reaches 200μJ with a burst duration of 100 ns at the average power of 10 W,corresponding to a peak power of 4 kW.When the PCSS is illuminated by the burst-mode fibre laser,narrowband microwave generation with tuneable frequency(0.80-1.12 GHz)is obtained with a power up to 300 W.To the best of the authors’knowledge,it is the first demonstration of frequency-tuneable narrowband microwave generation based on a fibre laser.The high-power burst-mode fibre laser reported here has great potential for generating high-power arbitrary microwave signals for a great deal of applicable demands such as smart adaptive radar and intelligent high-power microwave systems.
基金financially supported by the Natural Science Foundation of Tianjin,China(No.18JCYBJC20600)the National Natural Science Foundation of China(Nos.62074123,61701543)Institute of Energy,Hefei Comprehensive National Science Center(No.19KZS207)。
文摘The methanol oxidation reaction(MOR)is the limiting half-reaction in direct methanol fuel cell(DMFC).Although Pt is the most active single-metal electrocatalyst for MOR,it is hampered by high cost and CO poisoning.Constructing a Pt or Ru monolayer on a second metal substrate by means of galvanic replacement of underpotentially deposited(UPD)Cu monolayer has been shown as an efficient catalyst design strategy for the electrocatalysis of MOR because of the presumed 100%utilization of atoms and resistance to CO poisoning.Herein,we prepared one-dimensional surface-alloyed electrocatalyst from predominantly(111)faceted Au nanowires with high aspect ratio as the substrate of under-potential deposition.The electrocatalyst comprises a core of the Au nanowire and a shell of catalytically active Pt coated by Ru.Coverage-dependent electro-catalytic activity and stability is demonstrated on the Pt/Ru submonolayers on Au wires for MOR.Among all these catalysts,Au@Pt_(ML)@Ru_(ML)exhibits the best electrocatalytic activity and poisoning tolerance to CO.This presents a viable method for the rational catalyst design for achieving high noble-metal utilization efficiency and high catalytic performance.
基金Project supported by the Natural Science Foundation of China(91545115,21403178,and 21503278)the Program for Innovative Research Team in Chinese Universities(IRT_14R31)+1 种基金the Scientific Program of Fujian Province for Young College Teachers(JA15002)Fundamental Research Funds for the Central Universities(20720170024)
文摘The addition of yttrium chloride(YCl) to an activated carbon-supported Au catalyst(Au/AC) can markedly promote the catalytic performance of acetylene hydrochlorination to the vinyl chloride monomer(VCM), The structure and physicochemical features of the YCl-modified catalysts(Y-Au/AC)were measured by X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction, CH-temperature programmed desorption, and scanning transmission electron microscopy.The presence of YClwas found suppressing the reduction of highly oxidized Au(δ=1,3) to metallic Au~0 dependently and thus retard the agglomeration of Au nanoparticles during the reaction. In addition,the additive of YClto the Au/AC catalyst greatly inhibits the coke deposition on the catalyst surface. The optimized catalyst with an atomic ratio of Y/Au = 5(1 wt% Au loading weight) yields an 87.8% acetylene conversion and almost 100% selectivity for VCM under the reaction of GHSV(CH) = 800 hat 180 ℃.The durability test indicates that the 5 Y-1 Au/AC catalyst maintains high catalytic activity for more than2300 h at 30 hGHSV(CH) and 180 ℃, indicating great promise as a non-mercury catalyst for PVC manufacture.
基金The authors acknowledge the financial support from the Young Talent Support Plan(No.010600-11301291010702,010600-71211201010715 and 050700-71240000000046)of Xi’an Jiaotong Universitythe Natural Science Foundation of Shaanxi Province(No.2021JM-006)+3 种基金the National Natural Science Foundation of China(No.62074123 and 61701543)the PetroChina Innovation Foundation(No.2019D-5007-0410)This research is also supported by the Singapore National Research Foundation Investigator Ship(No.NRF-NRFI2018-03)the Singapore Academic Research Fund(No.TR12/19).
文摘Pillararene/calixarene-based functional materials have garnered significant attention for their unique topological/chemical structures and physicochemical properties,and their extended applications in electro-chemistry have given rise to a promising area of research.This review details current advance in developing electrochemical energy materials based on pillararene/calixarene systems from the viewpoint of both fundamental theoretical simulations and research on practical applications.First,we discuss the underlying mechanisms of applying pillararene/calixarene-based systems for electrochemical energy applications.Second,we summarize simulation studies on pillarquinone and calixquinone with intrinsic structures for applications in batteries.In addition,state-of-the-art applications of pillararene/calixarene-based systems in electrochemical energy storage devices such as lithium/sodium-ion batteries and supercapacitors are highlighted.The diverse roles they play and the various design strategies that have been investigated for high-performance pillararene/calixarene-based batteries are analyzed.Finally,we discuss the prospects for further developments in this emerging field.This review not only describes recent advances in pillararene/calixarene-based batteries and supercapacitors but also lays a firm groundwork for their further application in electrochemical energy engineering.