Ammonia and nitric acid,versatile industrial feedstocks,and burgeoning clean energy vectors hold immense promise for sustainable development.However,Haber–Bosch and Ostwald processes,which generates carbon dioxide as...Ammonia and nitric acid,versatile industrial feedstocks,and burgeoning clean energy vectors hold immense promise for sustainable development.However,Haber–Bosch and Ostwald processes,which generates carbon dioxide as massive by-product,contribute to greenhouse effects and pose environmental challenges.Thus,the pursuit of nitrogen fixation through carbon–neutral pathways under benign conditions is a frontier of scientific topics,with the harnessing of solar energy emerging as an enticing and viable option.This review delves into the refinement strategies for scale-up mild photocatalytic nitrogen fixation,fields ripe with potential for innovation.The narrative is centered on enhancing the intrinsic capabilities of catalysts to surmount current efficiency barriers.Key focus areas include the in-depth exploration of fundamental mechanisms underpinning photocatalytic procedures,rational element selection,and functional planning,state-of-the-art experimental protocols for understanding photo-fixation processes,valid photocatalytic activity evaluation,and the rational design of catalysts.Furthermore,the review offers a suite of forward-looking recommendations aimed at propelling the advancement of mild nitrogen photo-fixation.It scrutinizes the existing challenges and prospects within this burgeoning domain,aspiring to equip researchers with insightful perspectives that can catalyze the evolution of cutting-edge nitrogen fixation methodologies and steer the development of next-generation photocatalytic systems.展开更多
Depth maps play a crucial role in various practical applications such as computer vision,augmented reality,and autonomous driving.How to obtain clear and accurate depth information in video depth estimation is a signi...Depth maps play a crucial role in various practical applications such as computer vision,augmented reality,and autonomous driving.How to obtain clear and accurate depth information in video depth estimation is a significant challenge faced in the field of computer vision.However,existing monocular video depth estimation models tend to produce blurred or inaccurate depth information in regions with object edges and low texture.To address this issue,we propose a monocular depth estimation model architecture guided by semantic segmentation masks,which introduces semantic information into the model to correct the ambiguous depth regions.We have evaluated the proposed method,and experimental results show that our method improves the accuracy of edge depth,demonstrating the effectiveness of our approach.展开更多
In this article,we first establish an asymptotically sharp result on the higher order Fréchet derivatives for bounded holomorphic mappings f(x)=f(0)+∞∑s=1Dskf(0)(x^(sk))/(sk)!:B_(X)→B_(Y),where B_X is the unit...In this article,we first establish an asymptotically sharp result on the higher order Fréchet derivatives for bounded holomorphic mappings f(x)=f(0)+∞∑s=1Dskf(0)(x^(sk))/(sk)!:B_(X)→B_(Y),where B_X is the unit ball of X.We next give a sharp result on the first order Fréchet derivative for bounded holomorphic mappings F(X)=F(0+)∞∑s=KD^(s)f(0)(x^(8)/s!):B_(X)→B_(Y),where B_(X)is the unit ball of X.The results that we derive include some results in several complex variables,and extend the classical result in one complex variable to several complex variables.展开更多
1 The need to refine journal subject classification systems Journal subject classification systems are fundamental to journal evaluation,research assessments and information retrieval.Previous studies(e.g.,Wang&Wa...1 The need to refine journal subject classification systems Journal subject classification systems are fundamental to journal evaluation,research assessments and information retrieval.Previous studies(e.g.,Wang&Waltman,2016)have identified accuracy issues in major classification systems such as the Subject Categories in the Web of Science and ASJC in Scopus.展开更多
An h-adaptive method is developed for high-order discontinuous Galerkin methods(DGM)to solve the laminar compressible Navier-Stokes(N-S)equations on unstructured mesh.The vorticity is regarded as the indicator of adap...An h-adaptive method is developed for high-order discontinuous Galerkin methods(DGM)to solve the laminar compressible Navier-Stokes(N-S)equations on unstructured mesh.The vorticity is regarded as the indicator of adaptivity.The elements where the vorticity is larger than a pre-defined upper limit are refined,and those where the vorticity is smaller than a pre-defined lower limit are coarsened if they have been refined.A high-order geometric approximation of curved boundaries is adopted to ensure the accuracy.Numerical results indicate that highly accurate numerical results can be obtained with the adaptive method at relatively low expense.展开更多
Aqueous rechargeable magnesium ion batteries(ARMBs) have obtained more attention due to the twoelectrons transfer nature, low cost and safety. However, the scarcity of cathode materials seriously hinders the developme...Aqueous rechargeable magnesium ion batteries(ARMBs) have obtained more attention due to the twoelectrons transfer nature, low cost and safety. However, the scarcity of cathode materials seriously hinders the development of ARMBs because of the unfavorable strong interaction between Mg^(2+) and cathode material. Herein, we choose a pre-treated spinel Mn_(3)O_(4) cathode for aqueous Mg^(2+) storage. The pretreatment in Na_(2)SO_(4) solution induces the grain refinement decorated with tortuous amorphous ion diffusion channels, facilitating the production of electrochemical reaction active sites and the diffusion of Mg^(2+), respectively, which achieve a(sub-)surface pseudocapacitance reaction between Mn(Ⅱ) and Mn(Ⅲ). As a result, the pre-treated Mn_(3)O_(4) cathode exhibits a package of optimal performances, i.e., a capacity of 98.9 m Ah g^(-1) and a high capacity retention rate of 99.4% after 2000 cycles. To the best of our knowledge, our work not only provides a new reaction mechanism of spinelMn_(3)O_(4) in aqueous batteries system,but also affords a high cycle stability electrode material for rechargeable Mg^(2+) energy storage.展开更多
Polymer injectivity is an important factor for evaluating the project economics of chemical flood,which is highly related to the polymer viscosity.Because the flow rate varies rapidly near injectors and significantly ...Polymer injectivity is an important factor for evaluating the project economics of chemical flood,which is highly related to the polymer viscosity.Because the flow rate varies rapidly near injectors and significantly changes the polymer viscosity due to the non-Newtonian rheological behavior,the polymer viscosity near the wellbore is difficult to estimate accurately with the practical gridblock size in reservoir simulation.To reduce the impact of polymer rheology upon chemical EOR simulations,we used an efficient multilevel local grid refinement（LGR）method that provides a higher resolution of the flows in the near-wellbore region.An efficient numerical scheme was proposed to accurately solve the pressure equation and concentration equations on the multilevel grid for both homogeneous and heterogeneous reservoir cases.The block list and connections of the multilevel grid are generated via an efficient and extensible algorithm.Field case simulation results indicate that the proposed LGR is consistent with the analytical injectivity model and achieves the closest results to the full grid refinement,which considerably improves the accuracy of solutions compared with the original grid.In addition,the method was validated by comparing it with the LGR module of CMG_STARS.Besides polymer injectivity calculations,the LGR method is applicable for other problems in need of near-wellbore treatment,such as fractures near wells.展开更多
Tin (Sn) metal foil is a promising anode for next-generation high-energy–density lithium-ion batteries (LIBs) due to its high capacity and easy processibility. However, the pristine Sn foil anode suffers nonuniform a...Tin (Sn) metal foil is a promising anode for next-generation high-energy–density lithium-ion batteries (LIBs) due to its high capacity and easy processibility. However, the pristine Sn foil anode suffers nonuniform alloying/dealloying reaction with lithium (Li) and huge volume variation, leading to electrode pulverization and inferior electrochemical performance. Herein, we proposed that reduced grain size and elaborate porosity design of Sn foil can circumvent the nonuniform alloy reaction and buffer the volume change during the lithiation/delithiation cycling. Experimentally, we designed a three-dimensional interconnected porous Sn (3DIP-Sn) foil by a facile chemical alloying/dealloying approach, which showed improved electrochemical performance. The enhanced structure stability of the as-fabricated 3DIP-Sn foil was verified by chemo-mechanical simulations and experimental investigation. As expected, the 3DIP-Sn foil anode revealed a long cycle lifespan of 4400 h at 0.5 mA cm^(−2) and 1 mAh cm^(−2) in Sn||Li half cells. A 3DIP-Sn||LiFePO_(4) full cell with LiFePO_(4) loading of 7.1 mg cm^(−2) exhibited stable cycling for 500 cycles with 80% capacity retention at 70 mA g^(−1). Pairing with high-loading commercial LiNi0.6Co0.2Mn0.2O_(2) (NCM622, 18.4 mg cm^(−2)) cathode, a 3DIP-Sn||NCM622 full cell delivered a high reversible capacity of 3.2 mAh cm^(−2). These results demonstrated the important role of regulating the uniform alloying/dealloying reaction and circumventing the localized strain/stress in improving the electrochemical performance of Sn foil anodes for advanced LIBs.展开更多
In the case of lid-driven deep cavity flow, the effects of different resolutions of local grid refinement have been studied in the frame of multiple relaxation times (MRT) lattice Boltzmann method (LBM). In all the ca...In the case of lid-driven deep cavity flow, the effects of different resolutions of local grid refinement have been studied in the frame of multiple relaxation times (MRT) lattice Boltzmann method (LBM). In all the cases, the aspect ratio and Reynolds number are set as 1.5 and 3.200, respectively. First, the applied method is validated by comparing it with two reported works, with which agreements are reached. Then, six separate degrees of local grid refinement at the upper left corner, i.e. purely coarse grid, including 1/64, 1/32, 1/16, 1/8, 1/4 refinements of the lattice number in the width direction have been studied in detail. The results give the following indications:① The refinement degrees lower than 1/8 produce similar results;② For single corner refinement, 1/4 refinement is adequate for clearing the noises in the singularity zone to a large extent;③ New noise around the interface between coarse and fine zones are introduced by local grid refinement. Finally, refinement of entire subzone neighboring the lid is examined to avoid introducing new noises and it has been found effective.展开更多
Increasing mechanical flexibility without sacrificing electrochemical performance of the electrode material is highly desired in the design of flexible electrochemical energy storage devices.In metal-related materials...Increasing mechanical flexibility without sacrificing electrochemical performance of the electrode material is highly desired in the design of flexible electrochemical energy storage devices.In metal-related materials science,decreasing the grain size introduces more grain boundaries;this stops dislocations and crack propagation under deformation,and results in increased strength and toughness.However,such a size refinement effect has not been considered in the mechanical properties,particle stacking,wetting,and electrochemical performances of flexible supercapacitor electrodes.In this paper,MXene was used as an electrode material to study the size refinement effect of flexible supercapacitors.Size refinement improved the strength and toughness of the MXene electrodes,and this resulted in increased flexibility.Finite elemental analysis provided a theoretical understanding of size refinement-increased flexibility.Moreover,the size refinement also improved the specific surface area,electric conductance,ion transportation,and water wetting properties of the electrode,and the size refinement provided highly increased energy density and power density of the MXene supercapacitors.A highly flexible,water-proof supercapacitor was fabricated using size-refined MXene.The current study provides a new viewpoint for designing tough and flexible energy storage electrodes.The size refinement effect may also be applicable for metal ion batteries and electronic and photo devices composed of MXene and other nanoparticles.展开更多
In this article, we show that the generalized logarithmic mean is strictly Schurconvex function for p 〉 2 and strictly Schur-concave function for p 〈 2 on R_＋^2. And then we give a refinement of an inequality for t...In this article, we show that the generalized logarithmic mean is strictly Schurconvex function for p 〉 2 and strictly Schur-concave function for p 〈 2 on R_＋^2. And then we give a refinement of an inequality for the generalized logarithmic mean inequality using a simple majoricotion relation of the vector.展开更多
In this paper,the spectral estimation algorithm is extended to the detection of human vi-tal signs by mm-wave frequency modulated continuous wave(FMCW)radar,and a comprehensive algorithm based on spectrum refinement a...In this paper,the spectral estimation algorithm is extended to the detection of human vi-tal signs by mm-wave frequency modulated continuous wave(FMCW)radar,and a comprehensive algorithm based on spectrum refinement and the extended differentiate and cross multiply al-gorithm(DCMA)has been proposed.Firstly,the improved DFT algorithm is used to accurately obtain the distance window of human body.Secondly,phase ambiguity in phase extraction is avoided based on extended DCMA algorithm.Then,the spectrum range of refinement is determ-ined according to the peak position of the spectrum,and the respiratory and heartbeat frequency information is obtained by using chirp z-transform(CZT)algorithm to perform local spectrum re-finement.For verification,this paper has simulated the radar echo signal modulated by the simu-lated cardiopulmonary signal according to the proposed algorithm.By recovering the simulated car-diopulmonary signal,the high-precision respiratory and heartbeat frequency have been obtained.The results show that the proposed algorithm can effectively restore human breathing and heart-beat signals,and the relative error of frequency estimation is basically kept below 1.5%.展开更多
Road Side Units(RSUs)are the essential component of vehicular communication for the objective of improving safety and mobility in the road transportation.RSUs are generally deployed at the roadside and more specifical...Road Side Units(RSUs)are the essential component of vehicular communication for the objective of improving safety and mobility in the road transportation.RSUs are generally deployed at the roadside and more specifically at the intersections in order to collect traffic information from the vehicles and disseminate alarms and messages in emergency situations to the neighborhood vehicles cooperating with the network.However,the development of a predominant RSUs placement algorithm for ensuring competent communication in VANETs is a challenging issue due to the hindrance of obstacles like water bodies,trees and buildings.In this paper,Ruppert’s Delaunay Triangulation Refinement Scheme(RDTRS)for optimal RSUs placement is proposed for accurately estimating the optimal number of RSUs that has the possibility of enhancing the area of coverage during data communication.This RDTRS is proposed by considering the maximum number of factors such as global coverage,intersection popularity,vehicle density and obstacles present in the map for optimal RSUs placement,which is considered as the core improvement over the existing RSUs optimal placement strategies.It is contributed for deploying requisite RSUs with essential transmission range for maximal coverage in the convex map such that each position of the map could be effectively covered by at least one RSU in the presence of obstacles.The simulation experiments of the proposed RDTRS are conducted with complex road traffic environments.The results of this proposed RDTRS confirmed its predominance in reducing the end-to-end delay by 21.32%,packet loss by 9.38%with improved packet delivery rate of 10.68%,compared to the benchmarked schemes.展开更多
Purpose:In this paper,we attempt to use query refinements to identify users' search intents and seek a method for intent clustering based on real world query data.Design/methodology/approach:An experiment has been...Purpose:In this paper,we attempt to use query refinements to identify users' search intents and seek a method for intent clustering based on real world query data.Design/methodology/approach:An experiment has been conducted to analyze selected search sessions from the American Online(AOL) query logs with a two-stage approach.The first stage is to identify underlying intent by combining query co-occurrence information with query expression similarity.The work in the second stage is to cluster identified results by constructing query vectors through performing random walks on a Markov graph.Findings:Average correctness for identifying search intent is 0.74.Precision,recall,F-score values for intent clustering are 0.73,0.72 and 0.71,respectively.The results indicate that combining session co-occurrence information and query expression similarity can further filter noises and our clustering method is more suitable for sparse data.Research limitations:We use the time-out threshold(15-minutc) method to group queries in one session,but a user may have multiple search goals at the same time and the multi-task behavior of a user is hard to capture in a session defined based on time notions.Practical implications:This study provides insights into the ways of understanding users' search intents by analyzing their queries and refinements from a new perspective.The results will help search engine developers to identify user intents.Originality/value:We propose a new method to identify users' search intents by combining session co-occurrence information and query expression similarity,and a new method for clustering sparse data.展开更多
Using current Embedded Discrete Fracture Models(EDFM) to predict the productivity of fractured wells has some drawbacks, such as not supporting corner grid, low precision in the near wellbore zone, and disregarding th...Using current Embedded Discrete Fracture Models(EDFM) to predict the productivity of fractured wells has some drawbacks, such as not supporting corner grid, low precision in the near wellbore zone, and disregarding the heterogeneity of conductivity brought by non-uniform sand concentration. An EDFM is developed based on the corner grid, which enables high efficient calculation of the transmissibility between the embedded fractures and matrix grids, and calculation of the permeability of each polygon in the embedded fractures by the lattice data of the artificial fracture aperture. On this basis, a coupling method of local grid refinement(LGR) and embedded discrete fracture model is designed, which is verified by comparing the calculation results with the Discrete Fracture Network(DFN) method and fitting the actual production data of the first hydraulically fractured well in Iraq. By using this method and orthogonal experimental design, the optimization of the parameters of the first multi-stage fractured horizontal well in the same block is completed. The results show the proposed method has theoretical and practical significance for improving the adaptability of EDFM and the accuracy of productivity prediction of fractured wells, and enables the coupling of fracture modeling and numerical productivity simulation at reservoir scale.展开更多
Over the past decade,China’s refined oil market has experienced considerable growth and fluctuations.Gasoline consumption has generally followed the growth rate of vehicle equipment,with fluctuations influenced by tr...Over the past decade,China’s refined oil market has experienced considerable growth and fluctuations.Gasoline consumption has generally followed the growth rate of vehicle equipment,with fluctuations influenced by travel frequency;aviation fuel consumption has seen stable growth following the end of COVID-19,while diesel consumption has been affected by multiple factors including demand and policy.With the rapid development of new energy vehicles and alternative fuels,the gasoline and diesel market has essentially peaked,yet domestic production of refined oil continues to grow,leading to an increasingly prominent oversupply issue.To achieve the dual carbon goals,the Chinese government has introduced a series of policies that have a profound impact on the refined oil market.Facing resource surplus and market demand changes,the refining industry needs to optimize production capacity structure,and oil products retail companies face transformation pressure.The article aims to provide market analysis and recommendations,serving as a reference for relevant enterprises and policymakers.展开更多
基金financially supported by the National Natural Science Foundation of China(No.21675131)the Volkswagen Foundation(Freigeist Fellowship No.89592)+1 种基金the Natural Science Foundation of Chongqing(No.2020jcyj-zdxmX0003,CSTB2023NSCQ-MSX0924)the National Research Foundation,Singapore,and A*STAR(Agency for Science Technology and Research)under its LCER Phase 2 Programme Hydrogen&Emerging Technologies FI,Directed Hydrogen Programme(Award No.U2305D4003).
文摘Ammonia and nitric acid,versatile industrial feedstocks,and burgeoning clean energy vectors hold immense promise for sustainable development.However,Haber–Bosch and Ostwald processes,which generates carbon dioxide as massive by-product,contribute to greenhouse effects and pose environmental challenges.Thus,the pursuit of nitrogen fixation through carbon–neutral pathways under benign conditions is a frontier of scientific topics,with the harnessing of solar energy emerging as an enticing and viable option.This review delves into the refinement strategies for scale-up mild photocatalytic nitrogen fixation,fields ripe with potential for innovation.The narrative is centered on enhancing the intrinsic capabilities of catalysts to surmount current efficiency barriers.Key focus areas include the in-depth exploration of fundamental mechanisms underpinning photocatalytic procedures,rational element selection,and functional planning,state-of-the-art experimental protocols for understanding photo-fixation processes,valid photocatalytic activity evaluation,and the rational design of catalysts.Furthermore,the review offers a suite of forward-looking recommendations aimed at propelling the advancement of mild nitrogen photo-fixation.It scrutinizes the existing challenges and prospects within this burgeoning domain,aspiring to equip researchers with insightful perspectives that can catalyze the evolution of cutting-edge nitrogen fixation methodologies and steer the development of next-generation photocatalytic systems.
文摘Depth maps play a crucial role in various practical applications such as computer vision,augmented reality,and autonomous driving.How to obtain clear and accurate depth information in video depth estimation is a significant challenge faced in the field of computer vision.However,existing monocular video depth estimation models tend to produce blurred or inaccurate depth information in regions with object edges and low texture.To address this issue,we propose a monocular depth estimation model architecture guided by semantic segmentation masks,which introduces semantic information into the model to correct the ambiguous depth regions.We have evaluated the proposed method,and experimental results show that our method improves the accuracy of edge depth,demonstrating the effectiveness of our approach.
基金supported by the NSFC(11871257,12071130)supported by the NSFC(11971165)。
文摘In this article,we first establish an asymptotically sharp result on the higher order Fréchet derivatives for bounded holomorphic mappings f(x)=f(0)+∞∑s=1Dskf(0)(x^(sk))/(sk)!:B_(X)→B_(Y),where B_X is the unit ball of X.We next give a sharp result on the first order Fréchet derivative for bounded holomorphic mappings F(X)=F(0+)∞∑s=KD^(s)f(0)(x^(8)/s!):B_(X)→B_(Y),where B_(X)is the unit ball of X.The results that we derive include some results in several complex variables,and extend the classical result in one complex variable to several complex variables.
文摘1 The need to refine journal subject classification systems Journal subject classification systems are fundamental to journal evaluation,research assessments and information retrieval.Previous studies(e.g.,Wang&Waltman,2016)have identified accuracy issues in major classification systems such as the Subject Categories in the Web of Science and ASJC in Scopus.
基金supported by the National Natural Science Foundation of China(11272152)
文摘An h-adaptive method is developed for high-order discontinuous Galerkin methods(DGM)to solve the laminar compressible Navier-Stokes(N-S)equations on unstructured mesh.The vorticity is regarded as the indicator of adaptivity.The elements where the vorticity is larger than a pre-defined upper limit are refined,and those where the vorticity is smaller than a pre-defined lower limit are coarsened if they have been refined.A high-order geometric approximation of curved boundaries is adopted to ensure the accuracy.Numerical results indicate that highly accurate numerical results can be obtained with the adaptive method at relatively low expense.
基金supported by the National Natural Science Foundation of China (51932003, 51872115)the 2020 International Cooperation Project of the Department of Science and Technology of Jilin Province (20200801001GH)+4 种基金the Program for the Development of Science and Technology of Jilin Province(20190201309JC)the Jilin Province/Jilin University coConstruction Project-Funds for New Materials (SXGJSF2017-3,Branch-2/440050316A36)the Project for Self-innovation Capability Construction of Jilin Province Development and Reform Commission (2021C026)the Program for JLU Science and Technology Innovative Research Team (JLUSTIRT, 2017TD-09)the Fundamental Research Funds for the Central Universities JLU, and “DoubleFirst Class” Discipline for Materials Science&Engineering。
文摘Aqueous rechargeable magnesium ion batteries(ARMBs) have obtained more attention due to the twoelectrons transfer nature, low cost and safety. However, the scarcity of cathode materials seriously hinders the development of ARMBs because of the unfavorable strong interaction between Mg^(2+) and cathode material. Herein, we choose a pre-treated spinel Mn_(3)O_(4) cathode for aqueous Mg^(2+) storage. The pretreatment in Na_(2)SO_(4) solution induces the grain refinement decorated with tortuous amorphous ion diffusion channels, facilitating the production of electrochemical reaction active sites and the diffusion of Mg^(2+), respectively, which achieve a(sub-)surface pseudocapacitance reaction between Mn(Ⅱ) and Mn(Ⅲ). As a result, the pre-treated Mn_(3)O_(4) cathode exhibits a package of optimal performances, i.e., a capacity of 98.9 m Ah g^(-1) and a high capacity retention rate of 99.4% after 2000 cycles. To the best of our knowledge, our work not only provides a new reaction mechanism of spinelMn_(3)O_(4) in aqueous batteries system,but also affords a high cycle stability electrode material for rechargeable Mg^(2+) energy storage.
文摘Polymer injectivity is an important factor for evaluating the project economics of chemical flood,which is highly related to the polymer viscosity.Because the flow rate varies rapidly near injectors and significantly changes the polymer viscosity due to the non-Newtonian rheological behavior,the polymer viscosity near the wellbore is difficult to estimate accurately with the practical gridblock size in reservoir simulation.To reduce the impact of polymer rheology upon chemical EOR simulations,we used an efficient multilevel local grid refinement（LGR）method that provides a higher resolution of the flows in the near-wellbore region.An efficient numerical scheme was proposed to accurately solve the pressure equation and concentration equations on the multilevel grid for both homogeneous and heterogeneous reservoir cases.The block list and connections of the multilevel grid are generated via an efficient and extensible algorithm.Field case simulation results indicate that the proposed LGR is consistent with the analytical injectivity model and achieves the closest results to the full grid refinement,which considerably improves the accuracy of solutions compared with the original grid.In addition,the method was validated by comparing it with the LGR module of CMG_STARS.Besides polymer injectivity calculations,the LGR method is applicable for other problems in need of near-wellbore treatment,such as fractures near wells.
基金This work is financially supported by the National Natural Science Foundation of China(Grant Nos.52072137,51802105).
文摘Tin (Sn) metal foil is a promising anode for next-generation high-energy–density lithium-ion batteries (LIBs) due to its high capacity and easy processibility. However, the pristine Sn foil anode suffers nonuniform alloying/dealloying reaction with lithium (Li) and huge volume variation, leading to electrode pulverization and inferior electrochemical performance. Herein, we proposed that reduced grain size and elaborate porosity design of Sn foil can circumvent the nonuniform alloy reaction and buffer the volume change during the lithiation/delithiation cycling. Experimentally, we designed a three-dimensional interconnected porous Sn (3DIP-Sn) foil by a facile chemical alloying/dealloying approach, which showed improved electrochemical performance. The enhanced structure stability of the as-fabricated 3DIP-Sn foil was verified by chemo-mechanical simulations and experimental investigation. As expected, the 3DIP-Sn foil anode revealed a long cycle lifespan of 4400 h at 0.5 mA cm^(−2) and 1 mAh cm^(−2) in Sn||Li half cells. A 3DIP-Sn||LiFePO_(4) full cell with LiFePO_(4) loading of 7.1 mg cm^(−2) exhibited stable cycling for 500 cycles with 80% capacity retention at 70 mA g^(−1). Pairing with high-loading commercial LiNi0.6Co0.2Mn0.2O_(2) (NCM622, 18.4 mg cm^(−2)) cathode, a 3DIP-Sn||NCM622 full cell delivered a high reversible capacity of 3.2 mAh cm^(−2). These results demonstrated the important role of regulating the uniform alloying/dealloying reaction and circumventing the localized strain/stress in improving the electrochemical performance of Sn foil anodes for advanced LIBs.
基金Supported by Science and Technology Development Planning of Shandong Province,P.R.China(2016GGX104018)
文摘In the case of lid-driven deep cavity flow, the effects of different resolutions of local grid refinement have been studied in the frame of multiple relaxation times (MRT) lattice Boltzmann method (LBM). In all the cases, the aspect ratio and Reynolds number are set as 1.5 and 3.200, respectively. First, the applied method is validated by comparing it with two reported works, with which agreements are reached. Then, six separate degrees of local grid refinement at the upper left corner, i.e. purely coarse grid, including 1/64, 1/32, 1/16, 1/8, 1/4 refinements of the lattice number in the width direction have been studied in detail. The results give the following indications:① The refinement degrees lower than 1/8 produce similar results;② For single corner refinement, 1/4 refinement is adequate for clearing the noises in the singularity zone to a large extent;③ New noise around the interface between coarse and fine zones are introduced by local grid refinement. Finally, refinement of entire subzone neighboring the lid is examined to avoid introducing new noises and it has been found effective.
基金supported by the National Key Research and Development Program of China(grant SQ2019YFE012189,grant2017YFB0307001)the National Natural Science Foundation of China(grants 51973093,U1533122,and 51773094)+5 种基金the Natural Science Foundation of Tianjin(grant number 18JCZDJC36800)the National Special Support Plan for High-level Talents people(grant number C041800902)the Science Foundation for Distinguished Young Scholars of Tianjin(grant number 18JCJQJC46600)the Frontiers Science Center for New Organic Matter(Grant Number 63181206)the Fundamental Research Funds for the Central Universities(grant 63171219)the State Key Laboratory for Modification of Chemical Fibers and Polymer Materials,Donghua University(grant LK1704)。
文摘Increasing mechanical flexibility without sacrificing electrochemical performance of the electrode material is highly desired in the design of flexible electrochemical energy storage devices.In metal-related materials science,decreasing the grain size introduces more grain boundaries;this stops dislocations and crack propagation under deformation,and results in increased strength and toughness.However,such a size refinement effect has not been considered in the mechanical properties,particle stacking,wetting,and electrochemical performances of flexible supercapacitor electrodes.In this paper,MXene was used as an electrode material to study the size refinement effect of flexible supercapacitors.Size refinement improved the strength and toughness of the MXene electrodes,and this resulted in increased flexibility.Finite elemental analysis provided a theoretical understanding of size refinement-increased flexibility.Moreover,the size refinement also improved the specific surface area,electric conductance,ion transportation,and water wetting properties of the electrode,and the size refinement provided highly increased energy density and power density of the MXene supercapacitors.A highly flexible,water-proof supercapacitor was fabricated using size-refined MXene.The current study provides a new viewpoint for designing tough and flexible energy storage electrodes.The size refinement effect may also be applicable for metal ion batteries and electronic and photo devices composed of MXene and other nanoparticles.
基金Foundation item： Supported by the Scientific Research Common Program of Beijing Municipal Commission of Education of China（Km200611417009） Suppoted by the Natural Science Foundation of Fujian Province Education Department of China（JA05324）
文摘In this article, we show that the generalized logarithmic mean is strictly Schurconvex function for p 〉 2 and strictly Schur-concave function for p 〈 2 on R_＋^2. And then we give a refinement of an inequality for the generalized logarithmic mean inequality using a simple majoricotion relation of the vector.
文摘In this paper,the spectral estimation algorithm is extended to the detection of human vi-tal signs by mm-wave frequency modulated continuous wave(FMCW)radar,and a comprehensive algorithm based on spectrum refinement and the extended differentiate and cross multiply al-gorithm(DCMA)has been proposed.Firstly,the improved DFT algorithm is used to accurately obtain the distance window of human body.Secondly,phase ambiguity in phase extraction is avoided based on extended DCMA algorithm.Then,the spectrum range of refinement is determ-ined according to the peak position of the spectrum,and the respiratory and heartbeat frequency information is obtained by using chirp z-transform(CZT)algorithm to perform local spectrum re-finement.For verification,this paper has simulated the radar echo signal modulated by the simu-lated cardiopulmonary signal according to the proposed algorithm.By recovering the simulated car-diopulmonary signal,the high-precision respiratory and heartbeat frequency have been obtained.The results show that the proposed algorithm can effectively restore human breathing and heart-beat signals,and the relative error of frequency estimation is basically kept below 1.5%.
文摘Road Side Units(RSUs)are the essential component of vehicular communication for the objective of improving safety and mobility in the road transportation.RSUs are generally deployed at the roadside and more specifically at the intersections in order to collect traffic information from the vehicles and disseminate alarms and messages in emergency situations to the neighborhood vehicles cooperating with the network.However,the development of a predominant RSUs placement algorithm for ensuring competent communication in VANETs is a challenging issue due to the hindrance of obstacles like water bodies,trees and buildings.In this paper,Ruppert’s Delaunay Triangulation Refinement Scheme(RDTRS)for optimal RSUs placement is proposed for accurately estimating the optimal number of RSUs that has the possibility of enhancing the area of coverage during data communication.This RDTRS is proposed by considering the maximum number of factors such as global coverage,intersection popularity,vehicle density and obstacles present in the map for optimal RSUs placement,which is considered as the core improvement over the existing RSUs optimal placement strategies.It is contributed for deploying requisite RSUs with essential transmission range for maximal coverage in the convex map such that each position of the map could be effectively covered by at least one RSU in the presence of obstacles.The simulation experiments of the proposed RDTRS are conducted with complex road traffic environments.The results of this proposed RDTRS confirmed its predominance in reducing the end-to-end delay by 21.32%,packet loss by 9.38%with improved packet delivery rate of 10.68%,compared to the benchmarked schemes.
基金supported by the National Natural Science Foundation of China(Grant No.:71173164)the National Key Technology R&D Program of the Ministry of Science and Technology of China(GrantNo.:2012BAH33F03)
文摘Purpose:In this paper,we attempt to use query refinements to identify users' search intents and seek a method for intent clustering based on real world query data.Design/methodology/approach:An experiment has been conducted to analyze selected search sessions from the American Online(AOL) query logs with a two-stage approach.The first stage is to identify underlying intent by combining query co-occurrence information with query expression similarity.The work in the second stage is to cluster identified results by constructing query vectors through performing random walks on a Markov graph.Findings:Average correctness for identifying search intent is 0.74.Precision,recall,F-score values for intent clustering are 0.73,0.72 and 0.71,respectively.The results indicate that combining session co-occurrence information and query expression similarity can further filter noises and our clustering method is more suitable for sparse data.Research limitations:We use the time-out threshold(15-minutc) method to group queries in one session,but a user may have multiple search goals at the same time and the multi-task behavior of a user is hard to capture in a session defined based on time notions.Practical implications:This study provides insights into the ways of understanding users' search intents by analyzing their queries and refinements from a new perspective.The results will help search engine developers to identify user intents.Originality/value:We propose a new method to identify users' search intents by combining session co-occurrence information and query expression similarity,and a new method for clustering sparse data.
基金Supported by the China National Science and Technology Major Project (2017ZX05030)
文摘Using current Embedded Discrete Fracture Models(EDFM) to predict the productivity of fractured wells has some drawbacks, such as not supporting corner grid, low precision in the near wellbore zone, and disregarding the heterogeneity of conductivity brought by non-uniform sand concentration. An EDFM is developed based on the corner grid, which enables high efficient calculation of the transmissibility between the embedded fractures and matrix grids, and calculation of the permeability of each polygon in the embedded fractures by the lattice data of the artificial fracture aperture. On this basis, a coupling method of local grid refinement(LGR) and embedded discrete fracture model is designed, which is verified by comparing the calculation results with the Discrete Fracture Network(DFN) method and fitting the actual production data of the first hydraulically fractured well in Iraq. By using this method and orthogonal experimental design, the optimization of the parameters of the first multi-stage fractured horizontal well in the same block is completed. The results show the proposed method has theoretical and practical significance for improving the adaptability of EDFM and the accuracy of productivity prediction of fractured wells, and enables the coupling of fracture modeling and numerical productivity simulation at reservoir scale.
文摘Over the past decade,China’s refined oil market has experienced considerable growth and fluctuations.Gasoline consumption has generally followed the growth rate of vehicle equipment,with fluctuations influenced by travel frequency;aviation fuel consumption has seen stable growth following the end of COVID-19,while diesel consumption has been affected by multiple factors including demand and policy.With the rapid development of new energy vehicles and alternative fuels,the gasoline and diesel market has essentially peaked,yet domestic production of refined oil continues to grow,leading to an increasingly prominent oversupply issue.To achieve the dual carbon goals,the Chinese government has introduced a series of policies that have a profound impact on the refined oil market.Facing resource surplus and market demand changes,the refining industry needs to optimize production capacity structure,and oil products retail companies face transformation pressure.The article aims to provide market analysis and recommendations,serving as a reference for relevant enterprises and policymakers.
