In the hyperbolic research community,there exists the strong belief that a continuous Galerkin scheme is notoriously unstable and additional stabilization terms have to be added to guarantee stability.In the first par...In the hyperbolic research community,there exists the strong belief that a continuous Galerkin scheme is notoriously unstable and additional stabilization terms have to be added to guarantee stability.In the first part of the series[6],the application of simultaneous approximation terms for linear problems is investigated where the boundary conditions are imposed weakly.By applying this technique,the authors demonstrate that a pure continu-ous Galerkin scheme is indeed linearly stable if the boundary conditions are imposed in the correct way.In this work,we extend this investigation to the nonlinear case and focus on entropy conservation.By switching to entropy variables,we provide an estimation of the boundary operators also for nonlinear problems,that guarantee conservation.In numerical simulations,we verify our theoretical analysis.展开更多
Reversible solid oxide cell(RSOC)is a new energy conversion device with significant applications,especially for power grid peaking shaving.However,the reversible conversion process of power generation/energy storage p...Reversible solid oxide cell(RSOC)is a new energy conversion device with significant applications,especially for power grid peaking shaving.However,the reversible conversion process of power generation/energy storage poses challenges for the performance and stability of air electrodes.In this work,a novel high-entropy perovskite oxide La_(0.2)Pr_(0.2)Gd_(0.2)Sm_(0.2)Sr_(0.2)Co_(0.8)Fe_(0.2)O_(3−δ)(HE-LSCF)is proposed and investigated as an air electrode in RSOC.The electrochemical behavior of HE-LSCF was studied as an air electrode in both fuel cell and electrolysis modes.The polarization impedance(Rp)of the HE-LSCF electrode is only 0.25Ω·cm^(2) at 800℃ in an air atmosphere.Notably,at an electrolytic voltage of 2 V and a temperature of 800℃,the current density reaches up to 1.68 A/cm^(2).The HE-LSCF air electrode exhibited excellent reversibility and stability,and its electrochemical performance remains stable after 100 h of reversible operation.With these advantages,HE-LSCF is shown to be an excellent air electrode for RSOC.展开更多
Lithium-ion batteries(LIBs)currently occupy an important position in the energy storage market,and the development of advanced LIBs with higher energy density and power density,better cycle life and safety is a hot to...Lithium-ion batteries(LIBs)currently occupy an important position in the energy storage market,and the development of advanced LIBs with higher energy density and power density,better cycle life and safety is a hot topic for both academia and industry.In recent years,high-entropy materials(HEMs)with complex stoichiometric ratios have attracted great attention in the field of LIBs due to their various promising functional properties.The adjustability and synergistic effects of multiple elements in HEMs make them possible to break through the bottleneck of traditional electrode materials and electrolytes,providing new opportunities for the development of high-performance LIBs.This article provides an overview of the opportunities and challenges of HEMs in LIBs,including cathodes,anodes and electrolytes.The progress of HEMs in LIBs is first summarized and analyzed,then the potential advantages and limitations of HEMs used in LIBs are concluded,finally some envisioned solutions are proposed to develop more advanced LIBs through HEMs.展开更多
The eutectic CoFeNi2V0.5Nb0.75 high entropy alloys （HEAs） were heated at 500, 600, 700, 800 and 1000 ℃, respectively for 6 h and subsequently quenched in the water to investigate their thermal stability and phase t...The eutectic CoFeNi2V0.5Nb0.75 high entropy alloys （HEAs） were heated at 500, 600, 700, 800 and 1000 ℃, respectively for 6 h and subsequently quenched in the water to investigate their thermal stability and phase transformation at high temperature. The microstructure and mechanical properties of the samples were investigated by scanning electron microscopy, X-ray diffraction, compressive and hardness tests. It was found that the as-cast CoFeNi2V0.5Nb0.75 HEAs showed a eutectic microstructure with alternating fcc solid solution phase and Fe2Nb-type Laves phase. The NbNi4-type intermetallic phase appeared when the heat-treated temperature was higher than 600 ℃. With increasing quenching temperature, the volume fraction of the NbNi4-type intermetallic phase increased while that of the eutectic regions decreased. The sample quenched at 800 ℃ showed the most excellent comprehensive mechanical properties; its fracture strength, yield strength and plastic strain were as high as 2586.76 MPa, 2075.18 MPa and 16.73%, respectively. Moreover, the eutectic CoFeNi2V0.5Nb0.75 HEAs exhibited apparent age hardening, especially quenched at 700 ℃, the hardness reached up to the maximum value of HV 727.52.展开更多
In modern electromagnetic environment, radar emitter signal recognition is an important research topic. On the basis of multi-resolution wavelet analysis, an adaptive radar emitter signal recognition method based on m...In modern electromagnetic environment, radar emitter signal recognition is an important research topic. On the basis of multi-resolution wavelet analysis, an adaptive radar emitter signal recognition method based on multi-scale wavelet entropy feature extraction and feature weighting was proposed. With the only priori knowledge of signal to noise ratio(SNR), the method of extracting multi-scale wavelet entropy features of wavelet coefficients from different received signals were combined with calculating uneven weight factor and stability weight factor of the extracted multi-dimensional characteristics. Radar emitter signals of different modulation types and different parameters modulated were recognized through feature weighting and feature fusion. Theoretical analysis and simulation results show that the presented algorithm has a high recognition rate. Additionally, when the SNR is greater than-4 d B, the correct recognition rate is higher than 93%. Hence, the proposed algorithm has great application value.展开更多
In this paper,we study the convergence of a second-order finite volume approximation of the scalar conservation law.This scheme is based on the generalized Riemann problem(GRP)solver.We first investigate the stability...In this paper,we study the convergence of a second-order finite volume approximation of the scalar conservation law.This scheme is based on the generalized Riemann problem(GRP)solver.We first investigate the stability of the GRP scheme and find that it might be entropy-unstable when the shock wave is generated.By adding an artificial viscosity,we propose a new stabilized GRP scheme.Under the assumption that numerical solutions are uniformly bounded,we prove the consistency and convergence of this new GRP method.展开更多
Although Pt and other noble metals are the state-of-the-art catalysts for various energy conversion applications,their low reserve,high cost,and instability limit their large-scale utilization.Herein,we report a hybri...Although Pt and other noble metals are the state-of-the-art catalysts for various energy conversion applications,their low reserve,high cost,and instability limit their large-scale utilization.Herein,we report a hybrid catalysts design featuring noble metal clusters(e.g.,Pt)uniformly dispersed and stabilized on high-entropy alloy nanoparticles(HEA,e.g.,FeCoNiCu),denoted as HEA@Pt,which is prepared via ultra-fast shock synthesis(∼300 ms)for HEA alloying combined with Pt galvanic replacement for surface anchoring.In our design,the HEA core critically ensures high dispersity,stability,and tunability of the surface Pt clusters through high entropy stabilization and core-shell interactions.As an example in the hydrogen evolution reaction,HEA@Pt achieved a significant mass activity of 235 A/gPt,which is 9.4,3.6,and 1.9-times higher compared to that of homogeneous FeCoNiCuPt(HEA-Pt),Pt,and commercial Pt/C,respectively.We also demonstrated noble Ir stabilized on FeCoNiCrMn nanoparticles(HEA-5@Ir),achieving excellent anodic oxygen evolution performance and highly efficient overall water splitting when combined with the cathodic HEA@Pt.Therefore,our work developed a general catalysts design strategies by using high entropy nanoparticles for effective dispersion,stabilization,and modulation of surface active sites,achieving a harmonious combination of high activity,stability,and low cost.展开更多
基金funded by the SNF Grant(Number 200021175784)the UZH Postdoc grant+1 种基金funded by an SNF Grant 200021_153604The Los Alamos unlimited release number is LA-UR-19-32411.
文摘In the hyperbolic research community,there exists the strong belief that a continuous Galerkin scheme is notoriously unstable and additional stabilization terms have to be added to guarantee stability.In the first part of the series[6],the application of simultaneous approximation terms for linear problems is investigated where the boundary conditions are imposed weakly.By applying this technique,the authors demonstrate that a pure continu-ous Galerkin scheme is indeed linearly stable if the boundary conditions are imposed in the correct way.In this work,we extend this investigation to the nonlinear case and focus on entropy conservation.By switching to entropy variables,we provide an estimation of the boundary operators also for nonlinear problems,that guarantee conservation.In numerical simulations,we verify our theoretical analysis.
基金supported by Fundamental Research Funds for the Central Universities(2023KYJD1008)the Science Research Projects of the Anhui Higher Education Institutions of China(2022AH051582).
文摘Reversible solid oxide cell(RSOC)is a new energy conversion device with significant applications,especially for power grid peaking shaving.However,the reversible conversion process of power generation/energy storage poses challenges for the performance and stability of air electrodes.In this work,a novel high-entropy perovskite oxide La_(0.2)Pr_(0.2)Gd_(0.2)Sm_(0.2)Sr_(0.2)Co_(0.8)Fe_(0.2)O_(3−δ)(HE-LSCF)is proposed and investigated as an air electrode in RSOC.The electrochemical behavior of HE-LSCF was studied as an air electrode in both fuel cell and electrolysis modes.The polarization impedance(Rp)of the HE-LSCF electrode is only 0.25Ω·cm^(2) at 800℃ in an air atmosphere.Notably,at an electrolytic voltage of 2 V and a temperature of 800℃,the current density reaches up to 1.68 A/cm^(2).The HE-LSCF air electrode exhibited excellent reversibility and stability,and its electrochemical performance remains stable after 100 h of reversible operation.With these advantages,HE-LSCF is shown to be an excellent air electrode for RSOC.
基金financially supported by the funding of the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.BK20230067)the National Natural Science Foundation of China(Nos.22109112 and 22179090)Jiangsu Students’Innovation and Entrepreneurship Training Program(No.202310285120Y)。
文摘Lithium-ion batteries(LIBs)currently occupy an important position in the energy storage market,and the development of advanced LIBs with higher energy density and power density,better cycle life and safety is a hot topic for both academia and industry.In recent years,high-entropy materials(HEMs)with complex stoichiometric ratios have attracted great attention in the field of LIBs due to their various promising functional properties.The adjustability and synergistic effects of multiple elements in HEMs make them possible to break through the bottleneck of traditional electrode materials and electrolytes,providing new opportunities for the development of high-performance LIBs.This article provides an overview of the opportunities and challenges of HEMs in LIBs,including cathodes,anodes and electrolytes.The progress of HEMs in LIBs is first summarized and analyzed,then the potential advantages and limitations of HEMs used in LIBs are concluded,finally some envisioned solutions are proposed to develop more advanced LIBs through HEMs.
基金supported by the National Natural Science Foundation of China (Nos. 51104029, 51134013, 51471044, 51104029 and 51375070)the Fundamental Research Funds for the Central Universitiesthe Natural Science Foundation of Liaoning Province (No. 2014028013)
文摘The eutectic CoFeNi2V0.5Nb0.75 high entropy alloys （HEAs） were heated at 500, 600, 700, 800 and 1000 ℃, respectively for 6 h and subsequently quenched in the water to investigate their thermal stability and phase transformation at high temperature. The microstructure and mechanical properties of the samples were investigated by scanning electron microscopy, X-ray diffraction, compressive and hardness tests. It was found that the as-cast CoFeNi2V0.5Nb0.75 HEAs showed a eutectic microstructure with alternating fcc solid solution phase and Fe2Nb-type Laves phase. The NbNi4-type intermetallic phase appeared when the heat-treated temperature was higher than 600 ℃. With increasing quenching temperature, the volume fraction of the NbNi4-type intermetallic phase increased while that of the eutectic regions decreased. The sample quenched at 800 ℃ showed the most excellent comprehensive mechanical properties; its fracture strength, yield strength and plastic strain were as high as 2586.76 MPa, 2075.18 MPa and 16.73%, respectively. Moreover, the eutectic CoFeNi2V0.5Nb0.75 HEAs exhibited apparent age hardening, especially quenched at 700 ℃, the hardness reached up to the maximum value of HV 727.52.
基金Project(61301095)supported by the National Natural Science Foundation of ChinaProject(QC2012C070)supported by Heilongjiang Provincial Natural Science Foundation for the Youth,ChinaProjects(HEUCF130807,HEUCFZ1129)supported by the Fundamental Research Funds for the Central Universities of China
文摘In modern electromagnetic environment, radar emitter signal recognition is an important research topic. On the basis of multi-resolution wavelet analysis, an adaptive radar emitter signal recognition method based on multi-scale wavelet entropy feature extraction and feature weighting was proposed. With the only priori knowledge of signal to noise ratio(SNR), the method of extracting multi-scale wavelet entropy features of wavelet coefficients from different received signals were combined with calculating uneven weight factor and stability weight factor of the extracted multi-dimensional characteristics. Radar emitter signals of different modulation types and different parameters modulated were recognized through feature weighting and feature fusion. Theoretical analysis and simulation results show that the presented algorithm has a high recognition rate. Additionally, when the SNR is greater than-4 d B, the correct recognition rate is higher than 93%. Hence, the proposed algorithm has great application value.
基金funded by the Gutenberg Research College and by Chinesisch-Deutschen Zentrum fiur Wissenschaftsforderung(中德科学中心)Sino-German Project No.GZ1465M.L.is grateful to the Mainz Institute of Multiscale Modelling and SPP 2410 Hyperbolic Balance Laws in Fluid Mechanics:Complexity,Scales,Randomness(CoScaRa)for supporting her research.
文摘In this paper,we study the convergence of a second-order finite volume approximation of the scalar conservation law.This scheme is based on the generalized Riemann problem(GRP)solver.We first investigate the stability of the GRP scheme and find that it might be entropy-unstable when the shock wave is generated.By adding an artificial viscosity,we propose a new stabilized GRP scheme.Under the assumption that numerical solutions are uniformly bounded,we prove the consistency and convergence of this new GRP method.
基金National Key R&D Program of China,Grant/Award Number:2021YFA1202300National Natural Science Foundation of China,Grant/Award Number:52101255+2 种基金the Fundamental Research Funds for the Central Universities,Grant/Award Numbers:HUST,5003110114Natural Science Foundation of China,Grant/Award Number:52002287Startup funding from Wenzhou University。
文摘Although Pt and other noble metals are the state-of-the-art catalysts for various energy conversion applications,their low reserve,high cost,and instability limit their large-scale utilization.Herein,we report a hybrid catalysts design featuring noble metal clusters(e.g.,Pt)uniformly dispersed and stabilized on high-entropy alloy nanoparticles(HEA,e.g.,FeCoNiCu),denoted as HEA@Pt,which is prepared via ultra-fast shock synthesis(∼300 ms)for HEA alloying combined with Pt galvanic replacement for surface anchoring.In our design,the HEA core critically ensures high dispersity,stability,and tunability of the surface Pt clusters through high entropy stabilization and core-shell interactions.As an example in the hydrogen evolution reaction,HEA@Pt achieved a significant mass activity of 235 A/gPt,which is 9.4,3.6,and 1.9-times higher compared to that of homogeneous FeCoNiCuPt(HEA-Pt),Pt,and commercial Pt/C,respectively.We also demonstrated noble Ir stabilized on FeCoNiCrMn nanoparticles(HEA-5@Ir),achieving excellent anodic oxygen evolution performance and highly efficient overall water splitting when combined with the cathodic HEA@Pt.Therefore,our work developed a general catalysts design strategies by using high entropy nanoparticles for effective dispersion,stabilization,and modulation of surface active sites,achieving a harmonious combination of high activity,stability,and low cost.
