The textures and microstructures of hot-and cold-rolled sheets of an AA 5454 aluminium alloy were studied,with special attention paid to comparing the texture development for the symmetric and asymmetric cold rolling....The textures and microstructures of hot-and cold-rolled sheets of an AA 5454 aluminium alloy were studied,with special attention paid to comparing the texture development for the symmetric and asymmetric cold rolling.Scanning electron microscopy with electron-backscatter diffraction was used to monitor the development of the microstructure in the differently deformed and additionally annealed samples.Details of the formations and transformations of individual texture components occurring during the rolling processes were observed and discussed.The average grain sizes,textures and mechanical properties were correlated and explained for the symmetric and asymmetric cold-rolled samples.The asymmetric rolling is beneficial in terms of deep drawability because it reduces the planar anisotropy of the annealed material due to the decrease of the Cube,Goss,rotated-Cube and η-fibre texture components and at the same time strengthens X1-and X2-fibre texture components which are shear texture components and improve deep drawability.During the asymmetric cold rolling,the temperature increases due to friction,triggering recrystallisation processes and leading to larger grains.It is also confirmed that asymmetric cold rolling uses less rolling force and consequently less energy to produce a final material with better formability,particularly earing.展开更多
Analysis and design of linear periodic control systems are closely related to the periodic matrix equations.The biconjugate residual method(BCR for short)have been introduced by Vespucci and Broyden for efficiently so...Analysis and design of linear periodic control systems are closely related to the periodic matrix equations.The biconjugate residual method(BCR for short)have been introduced by Vespucci and Broyden for efficiently solving linear systems Aα=b.The objective of this paper is to provide one new iterative algorithm based on BCR method to find the symmetric periodic solutions of linear periodic matrix equations.This kind of periodic matrix equations has not been dealt with yet.This iterative method is guaranteed to converge in a finite number of steps in the absence of round-off errors.Some numerical results are performed to illustrate the efficiency and feasibility of new method.展开更多
The aim of the present paper is to study 2-complex symmetric bounded weighted composition operators on the Fock space of C^(N) with the conjugations J and J_(t,A,b) defined by ■ respectively,where k(z_(1),...,z_N)=(...The aim of the present paper is to study 2-complex symmetric bounded weighted composition operators on the Fock space of C^(N) with the conjugations J and J_(t,A,b) defined by ■ respectively,where k(z_(1),...,z_N)=(■,...,■),t∈C,b∈C^(N) and A is a linear operator on C^(N).An example of 2-complex symmetric bounded weighted composition operator with the conjugation J_(t,A,b) is given.展开更多
In this paper,we propose a symmetric difference data enhancement physics-informed neural network(SDE-PINN)to study soliton solutions for discrete nonlinear lattice equations(NLEs).By considering known and unknown symm...In this paper,we propose a symmetric difference data enhancement physics-informed neural network(SDE-PINN)to study soliton solutions for discrete nonlinear lattice equations(NLEs).By considering known and unknown symmetric points,numerical simulations are conducted to one-soliton and two-soliton solutions of a discrete KdV equation,as well as a one-soliton solution of a discrete Toda lattice equation.Compared with the existing discrete deep learning approach,the numerical results reveal that within the specified spatiotemporal domain,the prediction accuracy by SDE-PINN is excellent regardless of the interior or extrapolation prediction,with a significant reduction in training time.The proposed data enhancement technique and symmetric structure development provides a new perspective for the deep learning approach to solve discrete NLEs.The newly proposed SDE-PINN can also be applied to solve continuous nonlinear equations and other discrete NLEs numerically.展开更多
In this paper,we study the Cauchy problem of three-dimensional incompressible magnetohydrodynamics with almost symmetrical initial values in the cylindrical coordinates.Here the almost axisymmetric means that(■θu_(0...In this paper,we study the Cauchy problem of three-dimensional incompressible magnetohydrodynamics with almost symmetrical initial values in the cylindrical coordinates.Here the almost axisymmetric means that(■θu_(0)^(r),■θeu_(0)^(θ),■θeu_(θ)^(z))is small.With additional smallness assumption on(u_(0)^(θ),b_(0)^(θ)),we prove the global existence of a unique strong solution(u,b),which keeps close to some axisymmetric vector fields.Moreover,we give the initial data with some special symmetric structures that will persist for all time.展开更多
Kármán vortex street not only exists in nature,but also widely appears in engineering practice,which is of great significance for understanding superfluid.Parity-time(PT)symmetric potential provides a good p...Kármán vortex street not only exists in nature,but also widely appears in engineering practice,which is of great significance for understanding superfluid.Parity-time(PT)symmetric potential provides a good platform for the study of Kármán vortex streets.In this paper,different patterns of vortex shedding formed behind PT symmetric potential in Bose-Einstein condensate(BEC)are simulated numerically.Kármán vortex streets and others are discovered to emerge in the wake of a moving obstacle with appropriate parameters.Compared with BEC without PT symmetric potential,the frequency and amplitude of the drag force are more complex.The parametric regions of the combined modes are scattered around the Kármán vortex street.Numerical simulations indicate that the imaginary part of the PT symmetric potential affects the vortex structure patterns.Finally,we proposed an experimental protocol that may observe a Kármán vortex street.展开更多
As environmental concerns from fossil fuel consumption intensify,large-scale energy storage becomes imperative for the integration of renewable sources like wind,hydro,and solar with the electrical grid.Redox flow bat...As environmental concerns from fossil fuel consumption intensify,large-scale energy storage becomes imperative for the integration of renewable sources like wind,hydro,and solar with the electrical grid.Redox flow batteries,particularly those employing organic molecules,are positioned as a key technology for this purpose.This review explores the growing field of symmetric organic redox flow batteries(ORFBs)within this context.Unlike traditional asymmetric designs based on unique active materials for each electrode,symmetric ORFBs involve a single bipolar species for both electrodes.This review highlights the benefits of a symmetric design,and categorizes five distinct classes of organic bipolar molecules used in both aqueous and non-aqueous solvents.By providing a comprehensive overview of their cell cycling and performance characteristics,the strengths and weaknesses of the diverse categories of bipolar molecules are highlighted for both solvent systems,as are opportunities for future development.This should guide new research directions and advance the development of practical symmetric ORFBs.展开更多
Symmetric encryption algorithms learned by the previous proposed end-to-end adversarial network encryption communication systems are deterministic.With the same key and same plaintext,the deterministic algorithm will ...Symmetric encryption algorithms learned by the previous proposed end-to-end adversarial network encryption communication systems are deterministic.With the same key and same plaintext,the deterministic algorithm will lead to the same ciphertext.This means that the key in the deterministic encryption algorithm can only be used once,thus the encryption is not practical.To solve this problem,a nondeterministic symmetric encryption end-to-end communication system based on generative adversarial networks is proposed.We design a nonce-based adversarial neural network model,where a“nonce”standing for“number used only once”is passed to communication participants,and does not need to be secret.Moreover,we optimize the network structure through adding Batch Normalization(BN)to the CNNs(Convolutional Neural Networks),selecting the appropriate activation functions,and setting appropriate CNNs parameters.Results of experiments and analysis show that our system can achieve non-deterministic symmetric encryption,where Alice encrypting the same plaintext with the key twice will generate different ciphertexts,and Bob can decrypt all these different ciphertexts of the same plaintext to the correct plaintext.And our proposed system has fast convergence and the correct rate of decryption when the plaintext length is 256 or even longer.展开更多
Recently,inspired by a modified generalized shift-splitting iteration method for complex symmetric linear systems,we propose two variants of the modified generalized shift-splitting iteration(MGSS)methods for solving ...Recently,inspired by a modified generalized shift-splitting iteration method for complex symmetric linear systems,we propose two variants of the modified generalized shift-splitting iteration(MGSS)methods for solving com-plex symmetric linear systems.One is a parameterized MGSS iteration method and the other is a modified parameterized MGSS iteration method.We prove that the proposed methods are convergent under appropriate constraints on the parameters.In addition,we also give the eigenvalue distributions of differ-ent preconditioned matrices to verify the effectiveness of the preconditioners proposed in this paper.展开更多
Copper–carbon(Cu–C)composites have achieved great success in various fields owing to the greatly improved electrical properties compared to pure Cu,for example,a two-order-of-magnitude increase in current-carrying c...Copper–carbon(Cu–C)composites have achieved great success in various fields owing to the greatly improved electrical properties compared to pure Cu,for example,a two-order-of-magnitude increase in current-carrying capacity(ampacity).However,the frequent fuse failure caused by the poor thermal transport at the Cu–C heterointerface is still the main factor affecting the ampacity.In this study,we unconventionally leverage atomic distortion at Cu grain boundaries to alter the local atomic environments,thereby placing a premium on noticeable enhancement of phonon coupling at the Cu–C heterointerface.Without introducing any additional materials,interfacial thermal transport can be regulated solely through rational microstructural design.This new strategy effectively improves the interfacial thermal conductance by three-fold,reaching the state-of-the-art level in van der Waals(vdW)interface regulation.It can be an innovative strategy for interfacial thermal management by turning the detrimental grain boundaries into a beneficial thermal transport accelerator.展开更多
Symmetric secondary batteries are expected to become promising storage devices on account of their low cost,environmentally friendly and high safety.Nevertheless,the further development of symmetric batteries needs to...Symmetric secondary batteries are expected to become promising storage devices on account of their low cost,environmentally friendly and high safety.Nevertheless,the further development of symmetric batteries needs to rely on bipolar electrodes with superior performance.Cation-disordered rocksalt(DRX)Li_(2)FeTiO_(4)shows promising properties as symmetric electrodes,based on the ability of iron to undergo multiple electrochemical reactions over a wide voltage window.Unfortunately,this cation-disordered structure would not provide a cross-path for the rapid migration of Li^(+),ultimately resulting in inferior electrochemical dynamics and cycle stability.Herein,Li_(2)FeTiO_(4)nanoparticles assembled by ultrafine nanocrystals are synthesized via a sol-gel method through an orderly reaction regulation strategy of precursor reactants.Such ultrafine nanocrystals increase the active sites to promote the reversibility of multi-cationic(e.g.,stable Fe^(2+)/Fe^(3+),Ti^(3+)/Ti^(4+)and moderated Fe^(3+)/Fe^(4+))and anionic redox,and maintain the DRX structure well during the cycling process.The half cells with nano-sized Li_(2)FeTiO_(4)as the cathode/anode exhibit a high reversible capacity of 127.8/500.8 mAh/g,respectively.Besides,the Li_(2)FeTiO_(4)//Li_(2)FeTiO_(4)symmetric full cell could provide a reversible capacity of 95.4 mAh/g at 0.1 A/g after 200 cycles.This hierarchical self-assembly by nanocrystal strategy could offer effective guidance for high-performance electrode design for rechargeable secondary batteries.展开更多
Ethylene(C_(2)H_(4))is conventionally produced by a high energy-consumption process based on the steam cracking of ethane(C_(2)H_(6)).In contrast,we presented a novel symmetrical solid oxide fuel cell(SOFC)to coproduc...Ethylene(C_(2)H_(4))is conventionally produced by a high energy-consumption process based on the steam cracking of ethane(C_(2)H_(6)).In contrast,we presented a novel symmetrical solid oxide fuel cell(SOFC)to coproduce electricity and C_(2)H_(4)through C_(2)H_(6)dehydrogenation.The symmetrical cell contains a thin Ba Zr_(0.1)Ce_(0.7)Y_(0.2)O_(3)(BZCY)electrolyte sandwiched between two thicker(PrBa)_(0.95)(Fe_(0.7)Ni_(0.2)Cu_(0.1))_(1.8)Mo_(0.2)O_(6-δ)impregnated BZCY(PBFNCM-BZCY)electrodes.The as-synthesized reduced-PBFNCM(R-PBFNCM)contained Fe-Ni-Cu alloy particles embedded on a double-perovskite matrix uniformly,while the electrode showed high oxygen vacancy concentration,electronic conductivity,redox stability,and activity for C_(2)H_(6)dehydrogenation with improved ethylene selectivity.The symmetrical cell demonstrated a peak power density of 409 mW cm^(-2)using C_(2)H_(6)as fuel,accompanying with a C_(2)H_(6)conversion of 51.2%,a C_(2)H_(4)selectivity of 92.5%,and a C_(2)H_(4)yield of 47.4%at 750℃and 750 mA cm^(-2).Despite carbon deposition occurred slowly in the anode,the deposited carbon was removed by simply switching C_(2)H_(6)and air between electrodes.Consequently,the cell voltage and C_(2)H_(4)yield recover by 91.4%and 98.1%,respectively,after three switches with an interval of 48 h,suggesting that the symmetrical SOFC is a promising solution for long-term continuous electricity and C_(2)H_(4)co-production by C_(2)H_(6)dehydrogenation.展开更多
A voltage controlled oscillator (VCO) which can generate 2 4GHz quadrature local oscillating (LO) signals is reported.It combines a LC VCO,realized by on chip symmetrical spiral inductors and differential diodes,an...A voltage controlled oscillator (VCO) which can generate 2 4GHz quadrature local oscillating (LO) signals is reported.It combines a LC VCO,realized by on chip symmetrical spiral inductors and differential diodes,and a two stage ring VCO.The principle of this VCO is demonstrated and further the phase noise is discussed in detail.The fabrication of prototype is demonstrated using 0 25μm single poly five metal N well salicide CMOS digital process.The reports show that the novel VCO is can generate quadrature LO signals with a tuning range of more than 300MHz as well as the phase noise--104 33dBc/Hz at 600KHz offset at 2 41GHz (when measuring only one port of differential outputs).In addition,this VCO can work in low power supply voltage and dissipate low power,thus it can be used in many integrated transceivers.展开更多
In the present paper we obtain the following result: Theorem Let M^R be a compact submanifold with parallel mean curvature vector in a locally symmetric and conformally flat Riemannian manifold N^(n+p)(p>1). If the...In the present paper we obtain the following result: Theorem Let M^R be a compact submanifold with parallel mean curvature vector in a locally symmetric and conformally flat Riemannian manifold N^(n+p)(p>1). If then M^n lies in a totally geodesic submanifold N^(n+1).展开更多
Using the variable transformation method,the formulae of the axial symmetrical wall temperature distribution during steady heat conduction of a hollow cylinder are derived in this paper.The wall temperature distributi...Using the variable transformation method,the formulae of the axial symmetrical wall temperature distribution during steady heat conduction of a hollow cylinder are derived in this paper.The wall temperature distribution and the wall heat flux distribution in both axial and radial direction can be calculated by the temperature distribution of the liquid medium both inside and outside the cylinder with temperature changing in axial direction.The calculation results are almost consistent with the experience results.The applicative condition of the formulae in this paper consists with most of practice.They can be applied to the engineering calculation of the steady heat conduction.The calculation is simple and accurate.展开更多
The symmetric positive definite solutions of matrix equations (AX,XB)=(C,D) and AXB=C are considered in this paper. Necessary and sufficient conditions for the matrix equations to have symmetric positive de...The symmetric positive definite solutions of matrix equations (AX,XB)=(C,D) and AXB=C are considered in this paper. Necessary and sufficient conditions for the matrix equations to have symmetric positive definite solutions are derived using the singular value and the generalized singular value decompositions. The expressions for the general symmetric positive definite solutions are given when certain conditions hold.展开更多
This article presents an adaptive attitude tracking controller with external disturbances and unknown inertia parameters. The similar skew-symmetric structure is extended from the autonomous case to the non-autonomous...This article presents an adaptive attitude tracking controller with external disturbances and unknown inertia parameters. The similar skew-symmetric structure is extended from the autonomous case to the non-autonomous case. The non-autonomous similar skew-symmetric is chosen as the desired structure of the closed loop system for attitude controller design. Based on this structure, a novel adaptive backstepping scheme is proposed to design the attitude controller by taking full advantage of the symmetry and the positive definiteness of the inertia matrix. The attitude tracking precision is enhanced by employing the linear parameterized form of the external disturbance torques. Simulation results demonstrate the effectiveness of the proposed attitude controller.展开更多
文摘The textures and microstructures of hot-and cold-rolled sheets of an AA 5454 aluminium alloy were studied,with special attention paid to comparing the texture development for the symmetric and asymmetric cold rolling.Scanning electron microscopy with electron-backscatter diffraction was used to monitor the development of the microstructure in the differently deformed and additionally annealed samples.Details of the formations and transformations of individual texture components occurring during the rolling processes were observed and discussed.The average grain sizes,textures and mechanical properties were correlated and explained for the symmetric and asymmetric cold-rolled samples.The asymmetric rolling is beneficial in terms of deep drawability because it reduces the planar anisotropy of the annealed material due to the decrease of the Cube,Goss,rotated-Cube and η-fibre texture components and at the same time strengthens X1-and X2-fibre texture components which are shear texture components and improve deep drawability.During the asymmetric cold rolling,the temperature increases due to friction,triggering recrystallisation processes and leading to larger grains.It is also confirmed that asymmetric cold rolling uses less rolling force and consequently less energy to produce a final material with better formability,particularly earing.
基金Supported by NSFC (No.12371378)NSF of Fujian Province (Nos.2024J01980,2023J01955)。
文摘Analysis and design of linear periodic control systems are closely related to the periodic matrix equations.The biconjugate residual method(BCR for short)have been introduced by Vespucci and Broyden for efficiently solving linear systems Aα=b.The objective of this paper is to provide one new iterative algorithm based on BCR method to find the symmetric periodic solutions of linear periodic matrix equations.This kind of periodic matrix equations has not been dealt with yet.This iterative method is guaranteed to converge in a finite number of steps in the absence of round-off errors.Some numerical results are performed to illustrate the efficiency and feasibility of new method.
基金Supported by Sichuan Science and Technology Program (No.2022ZYD0010)。
文摘The aim of the present paper is to study 2-complex symmetric bounded weighted composition operators on the Fock space of C^(N) with the conjugations J and J_(t,A,b) defined by ■ respectively,where k(z_(1),...,z_N)=(■,...,■),t∈C,b∈C^(N) and A is a linear operator on C^(N).An example of 2-complex symmetric bounded weighted composition operator with the conjugation J_(t,A,b) is given.
基金supported by the National Natural Science Foundation of China(Grant No.12071042)the Beijing Natural Science Foundation(Grant No.1202004)Promoting the Development of University Classification-Student Innovation and Entrepreneurship Training Programme(Grant No.5112410857)。
文摘In this paper,we propose a symmetric difference data enhancement physics-informed neural network(SDE-PINN)to study soliton solutions for discrete nonlinear lattice equations(NLEs).By considering known and unknown symmetric points,numerical simulations are conducted to one-soliton and two-soliton solutions of a discrete KdV equation,as well as a one-soliton solution of a discrete Toda lattice equation.Compared with the existing discrete deep learning approach,the numerical results reveal that within the specified spatiotemporal domain,the prediction accuracy by SDE-PINN is excellent regardless of the interior or extrapolation prediction,with a significant reduction in training time.The proposed data enhancement technique and symmetric structure development provides a new perspective for the deep learning approach to solve discrete NLEs.The newly proposed SDE-PINN can also be applied to solve continuous nonlinear equations and other discrete NLEs numerically.
基金supported by the National Natural Science Foundation of China(11871305).
文摘In this paper,we study the Cauchy problem of three-dimensional incompressible magnetohydrodynamics with almost symmetrical initial values in the cylindrical coordinates.Here the almost axisymmetric means that(■θu_(0)^(r),■θeu_(0)^(θ),■θeu_(θ)^(z))is small.With additional smallness assumption on(u_(0)^(θ),b_(0)^(θ)),we prove the global existence of a unique strong solution(u,b),which keeps close to some axisymmetric vector fields.Moreover,we give the initial data with some special symmetric structures that will persist for all time.
基金supported by the National Natural Science Foundation of China under Grant Nos.12065022,12147213。
文摘Kármán vortex street not only exists in nature,but also widely appears in engineering practice,which is of great significance for understanding superfluid.Parity-time(PT)symmetric potential provides a good platform for the study of Kármán vortex streets.In this paper,different patterns of vortex shedding formed behind PT symmetric potential in Bose-Einstein condensate(BEC)are simulated numerically.Kármán vortex streets and others are discovered to emerge in the wake of a moving obstacle with appropriate parameters.Compared with BEC without PT symmetric potential,the frequency and amplitude of the drag force are more complex.The parametric regions of the combined modes are scattered around the Kármán vortex street.Numerical simulations indicate that the imaginary part of the PT symmetric potential affects the vortex structure patterns.Finally,we proposed an experimental protocol that may observe a Kármán vortex street.
基金Natural Sciences and Engineering Research Council(NSERC)of Canada(RGPIN-2022-03488)New Brunswick Innovation Foundation(NBIF)。
文摘As environmental concerns from fossil fuel consumption intensify,large-scale energy storage becomes imperative for the integration of renewable sources like wind,hydro,and solar with the electrical grid.Redox flow batteries,particularly those employing organic molecules,are positioned as a key technology for this purpose.This review explores the growing field of symmetric organic redox flow batteries(ORFBs)within this context.Unlike traditional asymmetric designs based on unique active materials for each electrode,symmetric ORFBs involve a single bipolar species for both electrodes.This review highlights the benefits of a symmetric design,and categorizes five distinct classes of organic bipolar molecules used in both aqueous and non-aqueous solvents.By providing a comprehensive overview of their cell cycling and performance characteristics,the strengths and weaknesses of the diverse categories of bipolar molecules are highlighted for both solvent systems,as are opportunities for future development.This should guide new research directions and advance the development of practical symmetric ORFBs.
基金supported by The National Defense Innovation Project(No.ZZKY20222411)Natural Science Basic Research Plan in Shaanxi Province of China(No.2024JC-YBMS-546).
文摘Symmetric encryption algorithms learned by the previous proposed end-to-end adversarial network encryption communication systems are deterministic.With the same key and same plaintext,the deterministic algorithm will lead to the same ciphertext.This means that the key in the deterministic encryption algorithm can only be used once,thus the encryption is not practical.To solve this problem,a nondeterministic symmetric encryption end-to-end communication system based on generative adversarial networks is proposed.We design a nonce-based adversarial neural network model,where a“nonce”standing for“number used only once”is passed to communication participants,and does not need to be secret.Moreover,we optimize the network structure through adding Batch Normalization(BN)to the CNNs(Convolutional Neural Networks),selecting the appropriate activation functions,and setting appropriate CNNs parameters.Results of experiments and analysis show that our system can achieve non-deterministic symmetric encryption,where Alice encrypting the same plaintext with the key twice will generate different ciphertexts,and Bob can decrypt all these different ciphertexts of the same plaintext to the correct plaintext.And our proposed system has fast convergence and the correct rate of decryption when the plaintext length is 256 or even longer.
基金supported by the National Natural Science Foundation of China(Grant No.12371378)by the Natural Science Foundation of Fujian Province(Grant Nos.2024J01980,2024J08242).
文摘Recently,inspired by a modified generalized shift-splitting iteration method for complex symmetric linear systems,we propose two variants of the modified generalized shift-splitting iteration(MGSS)methods for solving com-plex symmetric linear systems.One is a parameterized MGSS iteration method and the other is a modified parameterized MGSS iteration method.We prove that the proposed methods are convergent under appropriate constraints on the parameters.In addition,we also give the eigenvalue distributions of differ-ent preconditioned matrices to verify the effectiveness of the preconditioners proposed in this paper.
基金financial support from the National Natural Science Foundation of China(Nos.52222602 and 52476052)Fundamental Research Funds for the Central Universities(FRF-TP-22-001C1 and FRF-EYIT-23-05).
文摘Copper–carbon(Cu–C)composites have achieved great success in various fields owing to the greatly improved electrical properties compared to pure Cu,for example,a two-order-of-magnitude increase in current-carrying capacity(ampacity).However,the frequent fuse failure caused by the poor thermal transport at the Cu–C heterointerface is still the main factor affecting the ampacity.In this study,we unconventionally leverage atomic distortion at Cu grain boundaries to alter the local atomic environments,thereby placing a premium on noticeable enhancement of phonon coupling at the Cu–C heterointerface.Without introducing any additional materials,interfacial thermal transport can be regulated solely through rational microstructural design.This new strategy effectively improves the interfacial thermal conductance by three-fold,reaching the state-of-the-art level in van der Waals(vdW)interface regulation.It can be an innovative strategy for interfacial thermal management by turning the detrimental grain boundaries into a beneficial thermal transport accelerator.
基金supported by the National Natural Science Foundation of China(No.22278347)the Excellent Doctoral Student Research Innovation Project of Xinjiang University of China(No.XJU2022BS048)the Postgraduate Innovation Project of Xinjiang Uygur Autonomous Region of China(No.XJ2023G027)。
文摘Symmetric secondary batteries are expected to become promising storage devices on account of their low cost,environmentally friendly and high safety.Nevertheless,the further development of symmetric batteries needs to rely on bipolar electrodes with superior performance.Cation-disordered rocksalt(DRX)Li_(2)FeTiO_(4)shows promising properties as symmetric electrodes,based on the ability of iron to undergo multiple electrochemical reactions over a wide voltage window.Unfortunately,this cation-disordered structure would not provide a cross-path for the rapid migration of Li^(+),ultimately resulting in inferior electrochemical dynamics and cycle stability.Herein,Li_(2)FeTiO_(4)nanoparticles assembled by ultrafine nanocrystals are synthesized via a sol-gel method through an orderly reaction regulation strategy of precursor reactants.Such ultrafine nanocrystals increase the active sites to promote the reversibility of multi-cationic(e.g.,stable Fe^(2+)/Fe^(3+),Ti^(3+)/Ti^(4+)and moderated Fe^(3+)/Fe^(4+))and anionic redox,and maintain the DRX structure well during the cycling process.The half cells with nano-sized Li_(2)FeTiO_(4)as the cathode/anode exhibit a high reversible capacity of 127.8/500.8 mAh/g,respectively.Besides,the Li_(2)FeTiO_(4)//Li_(2)FeTiO_(4)symmetric full cell could provide a reversible capacity of 95.4 mAh/g at 0.1 A/g after 200 cycles.This hierarchical self-assembly by nanocrystal strategy could offer effective guidance for high-performance electrode design for rechargeable secondary batteries.
基金financially supported by the National Key R&D Program of China(No.2024YFF0506300)the National Natural Science Foundation of China(Nos.52472202 and 52272205)Hubei Province Science and Technology Program(Nos.2024EHA045,2024BCB073)
文摘Ethylene(C_(2)H_(4))is conventionally produced by a high energy-consumption process based on the steam cracking of ethane(C_(2)H_(6)).In contrast,we presented a novel symmetrical solid oxide fuel cell(SOFC)to coproduce electricity and C_(2)H_(4)through C_(2)H_(6)dehydrogenation.The symmetrical cell contains a thin Ba Zr_(0.1)Ce_(0.7)Y_(0.2)O_(3)(BZCY)electrolyte sandwiched between two thicker(PrBa)_(0.95)(Fe_(0.7)Ni_(0.2)Cu_(0.1))_(1.8)Mo_(0.2)O_(6-δ)impregnated BZCY(PBFNCM-BZCY)electrodes.The as-synthesized reduced-PBFNCM(R-PBFNCM)contained Fe-Ni-Cu alloy particles embedded on a double-perovskite matrix uniformly,while the electrode showed high oxygen vacancy concentration,electronic conductivity,redox stability,and activity for C_(2)H_(6)dehydrogenation with improved ethylene selectivity.The symmetrical cell demonstrated a peak power density of 409 mW cm^(-2)using C_(2)H_(6)as fuel,accompanying with a C_(2)H_(6)conversion of 51.2%,a C_(2)H_(4)selectivity of 92.5%,and a C_(2)H_(4)yield of 47.4%at 750℃and 750 mA cm^(-2).Despite carbon deposition occurred slowly in the anode,the deposited carbon was removed by simply switching C_(2)H_(6)and air between electrodes.Consequently,the cell voltage and C_(2)H_(4)yield recover by 91.4%and 98.1%,respectively,after three switches with an interval of 48 h,suggesting that the symmetrical SOFC is a promising solution for long-term continuous electricity and C_(2)H_(4)co-production by C_(2)H_(6)dehydrogenation.
文摘A voltage controlled oscillator (VCO) which can generate 2 4GHz quadrature local oscillating (LO) signals is reported.It combines a LC VCO,realized by on chip symmetrical spiral inductors and differential diodes,and a two stage ring VCO.The principle of this VCO is demonstrated and further the phase noise is discussed in detail.The fabrication of prototype is demonstrated using 0 25μm single poly five metal N well salicide CMOS digital process.The reports show that the novel VCO is can generate quadrature LO signals with a tuning range of more than 300MHz as well as the phase noise--104 33dBc/Hz at 600KHz offset at 2 41GHz (when measuring only one port of differential outputs).In addition,this VCO can work in low power supply voltage and dissipate low power,thus it can be used in many integrated transceivers.
文摘In the present paper we obtain the following result: Theorem Let M^R be a compact submanifold with parallel mean curvature vector in a locally symmetric and conformally flat Riemannian manifold N^(n+p)(p>1). If then M^n lies in a totally geodesic submanifold N^(n+1).
文摘Using the variable transformation method,the formulae of the axial symmetrical wall temperature distribution during steady heat conduction of a hollow cylinder are derived in this paper.The wall temperature distribution and the wall heat flux distribution in both axial and radial direction can be calculated by the temperature distribution of the liquid medium both inside and outside the cylinder with temperature changing in axial direction.The calculation results are almost consistent with the experience results.The applicative condition of the formulae in this paper consists with most of practice.They can be applied to the engineering calculation of the steady heat conduction.The calculation is simple and accurate.
文摘The symmetric positive definite solutions of matrix equations (AX,XB)=(C,D) and AXB=C are considered in this paper. Necessary and sufficient conditions for the matrix equations to have symmetric positive definite solutions are derived using the singular value and the generalized singular value decompositions. The expressions for the general symmetric positive definite solutions are given when certain conditions hold.
文摘This article presents an adaptive attitude tracking controller with external disturbances and unknown inertia parameters. The similar skew-symmetric structure is extended from the autonomous case to the non-autonomous case. The non-autonomous similar skew-symmetric is chosen as the desired structure of the closed loop system for attitude controller design. Based on this structure, a novel adaptive backstepping scheme is proposed to design the attitude controller by taking full advantage of the symmetry and the positive definiteness of the inertia matrix. The attitude tracking precision is enhanced by employing the linear parameterized form of the external disturbance torques. Simulation results demonstrate the effectiveness of the proposed attitude controller.
