Altermagnets,a new type of collinear antiferromagnet,exhibiting non-degenerate electron and magnon dispersion in momentum space have attracted intensive research attention.We theoretically analyze the origin and featu...Altermagnets,a new type of collinear antiferromagnet,exhibiting non-degenerate electron and magnon dispersion in momentum space have attracted intensive research attention.We theoretically analyze the origin and feature of chiral magnon splitting in representative altermagnets including tetragonal RuO_(2),hexagonal MnTe,and orthorhombic LaMnO_(3).The magnon spin transport properties including spin Seebeck and spin Nernst coefcients have been investigated.Through these materials,we demonstrate the diference of chiral splitting in d-wave and g-wave antiferromagnet on magnon transport.RuO2with planar magnon splitting exhibits signifcant magnon spin Nernst and magnon spin Seebeck anisotropy in(110)and(001)planes,whereas MnTe,due to its bulk-like magnon splitting,is incapable of producing magnon spin Nernst efect.Our work may provide in-depth understanding on the mechanisms of nonrelativistic magnon splitting and thermal spin transport in altermagnets.展开更多
In this paper,a second-order fnite-diference scheme is investigated for time-dependent space fractional difusion equations with variable coefcients.In the presented scheme,the Crank-Nicolson temporal discretization an...In this paper,a second-order fnite-diference scheme is investigated for time-dependent space fractional difusion equations with variable coefcients.In the presented scheme,the Crank-Nicolson temporal discretization and a second-order weighted-and-shifted Grünwald-Letnikov spatial discretization are employed.Theoretically,the unconditional stability and the second-order convergence in time and space of the proposed scheme are established under some conditions on the variable coefcients.Moreover,a Toeplitz preconditioner is proposed for linear systems arising from the proposed scheme.The condition number of the preconditioned matrix is proven to be bounded by a constant independent of the discretization step-sizes,so that the Krylov subspace solver for the preconditioned linear systems converges linearly.Numerical results are reported to show the convergence rate and the efciency of the proposed scheme.展开更多
Compared with ordinary graphite anode,SnO_(2) possesses higher theoretical specifc capacity,rich raw materials and low price.While the severe volume expansion of SnO_(2) during lithium-ion extraction/intercalation lim...Compared with ordinary graphite anode,SnO_(2) possesses higher theoretical specifc capacity,rich raw materials and low price.While the severe volume expansion of SnO_(2) during lithium-ion extraction/intercalation limits its further application.To solve this problem,in this work the reduced graphene oxide(rGO)was introduced as volume bufer matrix of SnO_(2).Herein,SnO_(2)/rGO composite is obtained through one-step hydrothermal method.Three-dimensional structure of rGO could efectively hinder the polymerization of SnO_(2) nanoparticles and provide more lithium storage sites attributed to high specifc surface area and density defects.The initial discharge capacity of the composite cathode is 959 mA·h·g^(-1) and the capacity remained at 300 mA·h·g^(-1) after 1000 cycles at 1 C.It proved that the rGO added in the anode has a capacity contribution to the lithium-ion battery.It changes the capacity contribution mechanism from difusion process dominance to surface driven capacitive contribution.Due to the addition of rGO,the anode material gains stable structure and great conductivity.展开更多
Anomalous diffusion is a phenomenon that cannot be modeled accurately by second-order diffusion equations,but is better described by fractional diffusion models.The nonlocal nature of the fractional diffusion operator...Anomalous diffusion is a phenomenon that cannot be modeled accurately by second-order diffusion equations,but is better described by fractional diffusion models.The nonlocal nature of the fractional diffusion operators makes substantially more difficult the mathemati-cal analysis of these models and the establishment of suitable numerical schemes.This paper proposes and analyzes the first finite difference method for solving variable-coefficient one-dimensional(steady state)fractional differential equations(DEs)with two-sided fractional derivatives(FDs).The proposed scheme combines first-order forward and backward Euler methods for approximating the left-sided FD when the right-sided FD is approximated by two consecutive applications of the first-order backward Euler method.Our scheme reduces to the standard second-order central difference in the absence of FDs.The existence and uniqueness of the numerical solution are proved,and truncation errors of order h are demonstrated(h denotes the maximum space step size).The numerical tests illustrate the global 0(h)accu-racy,except for nonsmooth cases which,as expected,have deteriorated convergence rates.展开更多
Breast cancer positions as the most well-known threat and the main source of malignant growth-related morbidity and mortality throughout the world.It is apical of all new cancer incidences analyzed among females.Two f...Breast cancer positions as the most well-known threat and the main source of malignant growth-related morbidity and mortality throughout the world.It is apical of all new cancer incidences analyzed among females.Two features substantially inuence the classication accuracy of malignancy and benignity in automated cancer diagnostics.These are the precision of tumor segmentation and appropriateness of extracted attributes required for the diagnosis.In this research,the authors have proposed a ResU-Net(Residual U-Network)model for breast tumor segmentation.The proposed methodology renders augmented,and precise identication of tumor regions and produces accurate breast tumor segmentation in contrast-enhanced MR images.Furthermore,the proposed framework also encompasses the residual network technique,which subsequently enhances the performance and displays the improved training process.Over and above,the performance of ResU-Net has experimentally been analyzed with conventional U-Net,FCN8,FCN32.Algorithm performance is evaluated in the form of dice coefcient and MIoU(Mean Intersection of Union),accuracy,loss,sensitivity,specicity,F1score.Experimental results show that ResU-Net achieved validation accuracy&dice coefcient value of 73.22%&85.32%respectively on the Rider Breast MRI dataset and outperformed as compared to the other algorithms used in experimentation.展开更多
An airship named ＂Zhiyuan-l＂ was designed/fabricated/flied as a technical demonstration for stratospheric airship during 2007--2009 by Shanghai Jiaotong University. The calculation method and procedure of aerodynami...An airship named ＂Zhiyuan-l＂ was designed/fabricated/flied as a technical demonstration for stratospheric airship during 2007--2009 by Shanghai Jiaotong University. The calculation method and procedure of aerodynamic parameters were introduced, and the optimized configuration of the hull and the aerodynamic layout were given in this paper. Wind tunnel tests with different configurations, different pitch angles and different yaw angles were performed to study the wind load characteristics of the rigid model of the airship ＂Zhiyuan-1＂ in the φ3.2 m wind tunnel at China Aerodynamics Research ＆ Development Center. Also the numerical calculation about the test model was carried out to investigate the aerodynamic behavior. According to the results of wind test and numerical calculation, the excellent hull configuration of the airship ＂Zhiyuan-1＂ with lower drag characteristic was confirmed, which is based on optimism of the Michel transition law. And the phenomena of pressure coefficient distribution were discussed according to the results of wind tunnel test and numerical calculation at different flight attitudes.展开更多
To solve large-scale optimization problems,Fragrance coefficient and variant Particle Swarm local search Butterfly Optimization Algorithm(FPSBOA)is proposed.In the position update stage of Butterfly Optimization Algor...To solve large-scale optimization problems,Fragrance coefficient and variant Particle Swarm local search Butterfly Optimization Algorithm(FPSBOA)is proposed.In the position update stage of Butterfly Optimization Algorithm(BOA),the fragrance coefficient is designed to balance the exploration and exploitation of BOA.The variant particle swarm local search strategy is proposed to improve the local search ability of the current optimal butterfly and prevent the algorithm from falling into local optimality.192000-dimensional functions and 201000-dimensional CEC 2010 large-scale functions are used to verify FPSBOA for complex large-scale optimization problems.The experimental results are statistically analyzed by Friedman test and Wilcoxon rank-sum test.All attained results demonstrated that FPSBOA can better solve more challenging scientific and industrial real-world problems with thousands of variables.Finally,four mechanical engineering problems and one ten-dimensional process synthesis and design problem are applied to FPSBOA,which shows FPSBOA has the feasibility and effectiveness in real-world application problems.展开更多
Wave reflection is one of the key problems affecting wave simulation quality in ocean engineering basin. The deep ocean engineering basin is equipped with two-sided segmented wavemakers and two wave absorbing beaches,...Wave reflection is one of the key problems affecting wave simulation quality in ocean engineering basin. The deep ocean engineering basin is equipped with two-sided segmented wavemakers and two wave absorbing beaches, which are located opposite to wave generators to reduce wave reflection effects. When an oblique longcrested wave is made by two-sided segmented wavemakers in a wave basin, two bi-directional reflected waves with the same azimuth but opposite propagation directions are generated. According to this feature, based on the two-point approach developed by Goda, a method to separate an incident regular wave from two bi-directional reflected waves using three wave gauges is proposed. The validity of this method is proved by numerical composite waves. The results indicate that the method can separate incident wave from reflected waves effectively. The method can be used to determine the reflection coefficient and verify the capacity of wave absorbing beaches in deep ocean engineering basin.展开更多
Nickel is typically used as one of the main components in electrical contact devices or connectors.Nickel oxide(NiO)is usually formed on the surfaces of electrodes and can negatively impact system performance by intro...Nickel is typically used as one of the main components in electrical contact devices or connectors.Nickel oxide(NiO)is usually formed on the surfaces of electrodes and can negatively impact system performance by introducing electrical contact resistance.The thermal,electrical,and transport properties of NiO,as a Mott insulator or a p-type semiconductor,can be altered by operating and environmental conditions such as temperature and stress/strain by contact.In this study,we inves-tigate the fundamental material properties of NiO through the first-principle calculations.First,we obtain and compare the lattice parameter,magnetic moment,and electronic structure for NiO via the WIEN2K simulations with four different poten-tials(i.e.,GGA,GGA+U,LSDA,and LSDA+U).Then,using the WIEN2K simulation results with LSDA+U potential that produces a highly accurate bandgap for NiO,we calculate the electrical conductivity and electrical part of the thermal conductivity of nickel and NiO as a function of temperature and carrier concentration through the BoltzTraP simulations.Systematic simulation results revealed that the electrical conductivity relative to the relaxation time for NiO increases with the carrier concentration,while it shows a slightly decreasing trend with temperature under a fixed carrier concentration.By contrast,the electrical part of the thermal conductivity shows an increasing trend considering carrier concentration and temperature.展开更多
This paper is concerned with a singular second-order nonlinear boundary value problem with a time depending on derivative operator and posed on the positive half-line. The nonlinearity is derivative-dependent, which h...This paper is concerned with a singular second-order nonlinear boundary value problem with a time depending on derivative operator and posed on the positive half-line. The nonlinearity is derivative-dependent, which has singularities at t=0 and/or x=0, and may change sign. The method of the upper and lower solutions on unbounded domains combined with the topological degree theory are employed to prove the existence and multiplicity of solutions.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12174129,T2394475,and T2394470)。
文摘Altermagnets,a new type of collinear antiferromagnet,exhibiting non-degenerate electron and magnon dispersion in momentum space have attracted intensive research attention.We theoretically analyze the origin and feature of chiral magnon splitting in representative altermagnets including tetragonal RuO_(2),hexagonal MnTe,and orthorhombic LaMnO_(3).The magnon spin transport properties including spin Seebeck and spin Nernst coefcients have been investigated.Through these materials,we demonstrate the diference of chiral splitting in d-wave and g-wave antiferromagnet on magnon transport.RuO2with planar magnon splitting exhibits signifcant magnon spin Nernst and magnon spin Seebeck anisotropy in(110)and(001)planes,whereas MnTe,due to its bulk-like magnon splitting,is incapable of producing magnon spin Nernst efect.Our work may provide in-depth understanding on the mechanisms of nonrelativistic magnon splitting and thermal spin transport in altermagnets.
基金This research was supported by research Grants,12306616,12200317,12300519,12300218 from HKRGC GRF,11801479 from NSFC,MYRG2018-00015-FST from University of Macao,and 0118/2018/A3 from FDCT of Macao,Macao Science and Technology Development Fund 0005/2019/A,050/2017/Athe Grant MYRG2017-00098-FST and MYRG2018-00047-FST from University of Macao.S。
文摘In this paper,a second-order fnite-diference scheme is investigated for time-dependent space fractional difusion equations with variable coefcients.In the presented scheme,the Crank-Nicolson temporal discretization and a second-order weighted-and-shifted Grünwald-Letnikov spatial discretization are employed.Theoretically,the unconditional stability and the second-order convergence in time and space of the proposed scheme are established under some conditions on the variable coefcients.Moreover,a Toeplitz preconditioner is proposed for linear systems arising from the proposed scheme.The condition number of the preconditioned matrix is proven to be bounded by a constant independent of the discretization step-sizes,so that the Krylov subspace solver for the preconditioned linear systems converges linearly.Numerical results are reported to show the convergence rate and the efciency of the proposed scheme.
基金Supported by National Natural Science Foundation of China(Grant No.61774022)Natural Science Foundation of Guangdong Province(Grant No.2022A1515011449)+2 种基金Special Program for Science Research Foundation of the Higher Education Institutions of Guangdong Providence(Grant No.2020ZDZX2052)2020 Li Ka Shing Foundation Cross-Disciplinary Research Grant(Grant No.2020LKSFG01A)Research.Start-up Foundation of Shantou University(Grant No.NTF20024).
文摘Compared with ordinary graphite anode,SnO_(2) possesses higher theoretical specifc capacity,rich raw materials and low price.While the severe volume expansion of SnO_(2) during lithium-ion extraction/intercalation limits its further application.To solve this problem,in this work the reduced graphene oxide(rGO)was introduced as volume bufer matrix of SnO_(2).Herein,SnO_(2)/rGO composite is obtained through one-step hydrothermal method.Three-dimensional structure of rGO could efectively hinder the polymerization of SnO_(2) nanoparticles and provide more lithium storage sites attributed to high specifc surface area and density defects.The initial discharge capacity of the composite cathode is 959 mA·h·g^(-1) and the capacity remained at 300 mA·h·g^(-1) after 1000 cycles at 1 C.It proved that the rGO added in the anode has a capacity contribution to the lithium-ion battery.It changes the capacity contribution mechanism from difusion process dominance to surface driven capacitive contribution.Due to the addition of rGO,the anode material gains stable structure and great conductivity.
基金The support of the King Fahd University of Petroleum and Minerals(KFUPM)through the project No.KAUST0O5 is gratefully acknowledgedResearch reported in this publication was also sup-ported by the research funding from the King Abdullah University of Science and Technology(KAUST).
文摘Anomalous diffusion is a phenomenon that cannot be modeled accurately by second-order diffusion equations,but is better described by fractional diffusion models.The nonlocal nature of the fractional diffusion operators makes substantially more difficult the mathemati-cal analysis of these models and the establishment of suitable numerical schemes.This paper proposes and analyzes the first finite difference method for solving variable-coefficient one-dimensional(steady state)fractional differential equations(DEs)with two-sided fractional derivatives(FDs).The proposed scheme combines first-order forward and backward Euler methods for approximating the left-sided FD when the right-sided FD is approximated by two consecutive applications of the first-order backward Euler method.Our scheme reduces to the standard second-order central difference in the absence of FDs.The existence and uniqueness of the numerical solution are proved,and truncation errors of order h are demonstrated(h denotes the maximum space step size).The numerical tests illustrate the global 0(h)accu-racy,except for nonsmooth cases which,as expected,have deteriorated convergence rates.
文摘Breast cancer positions as the most well-known threat and the main source of malignant growth-related morbidity and mortality throughout the world.It is apical of all new cancer incidences analyzed among females.Two features substantially inuence the classication accuracy of malignancy and benignity in automated cancer diagnostics.These are the precision of tumor segmentation and appropriateness of extracted attributes required for the diagnosis.In this research,the authors have proposed a ResU-Net(Residual U-Network)model for breast tumor segmentation.The proposed methodology renders augmented,and precise identication of tumor regions and produces accurate breast tumor segmentation in contrast-enhanced MR images.Furthermore,the proposed framework also encompasses the residual network technique,which subsequently enhances the performance and displays the improved training process.Over and above,the performance of ResU-Net has experimentally been analyzed with conventional U-Net,FCN8,FCN32.Algorithm performance is evaluated in the form of dice coefcient and MIoU(Mean Intersection of Union),accuracy,loss,sensitivity,specicity,F1score.Experimental results show that ResU-Net achieved validation accuracy&dice coefcient value of 73.22%&85.32%respectively on the Rider Breast MRI dataset and outperformed as compared to the other algorithms used in experimentation.
文摘An airship named ＂Zhiyuan-l＂ was designed/fabricated/flied as a technical demonstration for stratospheric airship during 2007--2009 by Shanghai Jiaotong University. The calculation method and procedure of aerodynamic parameters were introduced, and the optimized configuration of the hull and the aerodynamic layout were given in this paper. Wind tunnel tests with different configurations, different pitch angles and different yaw angles were performed to study the wind load characteristics of the rigid model of the airship ＂Zhiyuan-1＂ in the φ3.2 m wind tunnel at China Aerodynamics Research ＆ Development Center. Also the numerical calculation about the test model was carried out to investigate the aerodynamic behavior. According to the results of wind test and numerical calculation, the excellent hull configuration of the airship ＂Zhiyuan-1＂ with lower drag characteristic was confirmed, which is based on optimism of the Michel transition law. And the phenomena of pressure coefficient distribution were discussed according to the results of wind tunnel test and numerical calculation at different flight attitudes.
基金funded by the National Natural Science Foundation of China(No.72104069)the Science and Technology Department of Henan Province,China(No.182102310886 and 162102110109)the Postgraduate Meritocracy Scheme,hina(No.SYL19060145).
文摘To solve large-scale optimization problems,Fragrance coefficient and variant Particle Swarm local search Butterfly Optimization Algorithm(FPSBOA)is proposed.In the position update stage of Butterfly Optimization Algorithm(BOA),the fragrance coefficient is designed to balance the exploration and exploitation of BOA.The variant particle swarm local search strategy is proposed to improve the local search ability of the current optimal butterfly and prevent the algorithm from falling into local optimality.192000-dimensional functions and 201000-dimensional CEC 2010 large-scale functions are used to verify FPSBOA for complex large-scale optimization problems.The experimental results are statistically analyzed by Friedman test and Wilcoxon rank-sum test.All attained results demonstrated that FPSBOA can better solve more challenging scientific and industrial real-world problems with thousands of variables.Finally,four mechanical engineering problems and one ten-dimensional process synthesis and design problem are applied to FPSBOA,which shows FPSBOA has the feasibility and effectiveness in real-world application problems.
基金the National Natural Science Foundation of China(No.51239007)
文摘Wave reflection is one of the key problems affecting wave simulation quality in ocean engineering basin. The deep ocean engineering basin is equipped with two-sided segmented wavemakers and two wave absorbing beaches, which are located opposite to wave generators to reduce wave reflection effects. When an oblique longcrested wave is made by two-sided segmented wavemakers in a wave basin, two bi-directional reflected waves with the same azimuth but opposite propagation directions are generated. According to this feature, based on the two-point approach developed by Goda, a method to separate an incident regular wave from two bi-directional reflected waves using three wave gauges is proposed. The validity of this method is proved by numerical composite waves. The results indicate that the method can separate incident wave from reflected waves effectively. The method can be used to determine the reflection coefficient and verify the capacity of wave absorbing beaches in deep ocean engineering basin.
文摘Nickel is typically used as one of the main components in electrical contact devices or connectors.Nickel oxide(NiO)is usually formed on the surfaces of electrodes and can negatively impact system performance by introducing electrical contact resistance.The thermal,electrical,and transport properties of NiO,as a Mott insulator or a p-type semiconductor,can be altered by operating and environmental conditions such as temperature and stress/strain by contact.In this study,we inves-tigate the fundamental material properties of NiO through the first-principle calculations.First,we obtain and compare the lattice parameter,magnetic moment,and electronic structure for NiO via the WIEN2K simulations with four different poten-tials(i.e.,GGA,GGA+U,LSDA,and LSDA+U).Then,using the WIEN2K simulation results with LSDA+U potential that produces a highly accurate bandgap for NiO,we calculate the electrical conductivity and electrical part of the thermal conductivity of nickel and NiO as a function of temperature and carrier concentration through the BoltzTraP simulations.Systematic simulation results revealed that the electrical conductivity relative to the relaxation time for NiO increases with the carrier concentration,while it shows a slightly decreasing trend with temperature under a fixed carrier concentration.By contrast,the electrical part of the thermal conductivity shows an increasing trend considering carrier concentration and temperature.
文摘This paper is concerned with a singular second-order nonlinear boundary value problem with a time depending on derivative operator and posed on the positive half-line. The nonlinearity is derivative-dependent, which has singularities at t=0 and/or x=0, and may change sign. The method of the upper and lower solutions on unbounded domains combined with the topological degree theory are employed to prove the existence and multiplicity of solutions.
