Mg-rare earth(RE)based systems provide several important commercial alloys and many alloy development opportunities for high strength applications,especially in aerospace and defense industries.The phase diagrams,micr...Mg-rare earth(RE)based systems provide several important commercial alloys and many alloy development opportunities for high strength applications,especially in aerospace and defense industries.The phase diagrams,microstructure,and strengthening mechanisms of these multicomponent systems are very complex and often not well understood in literature.We have calculated phase diagrams of important binary,ternary,and multicomponent RE-containing alloy systems,using CALPHAD(CALculation of PHAse Diagrams).Based on these phase diagrams,this paper offers a critical overview on phase equilibria and strengthening mechanisms in these alloy systems,including precipitation,long period stacking order(LPSO),and other intermetallic phases.This review also summarized several promising Mg-RE based cast alloys in comparison with commercial WE54 and WE43 alloys;and explored new strategies for future alloy development for high strength applications.It is pointed out that the combination of precipitation and LPSO phases can lead to superior strength and ductility in Mg-RE based cast alloys.The precipitates and LPSO phases can form a complex three-dimensional network that effectively impedes dislocation motion on the basal and non-basal planes.The LPSO phases can also prevent the coarsening of precipitates when they interact,thus providing good thermal stability at elevated temperatures.Future research is needed to determine how the combination of these two types of phases can be used in alloy design and industrial scale applications.展开更多
The field of topological photonic crystals has attracted growing interest since the inception of optical analog of quantum Hall effect proposed in 2008.Photonic band structures embraced topological phases of matter,ha...The field of topological photonic crystals has attracted growing interest since the inception of optical analog of quantum Hall effect proposed in 2008.Photonic band structures embraced topological phases of matter,have spawned a novel platform for studying topological phase transitions and designing topological optical devices.Here,we present a brief review of topological photonic crystals based on different material platforms,including all-dielectric systems,metallic materials,optical resonators,coupled waveguide systems,and other platforms.Furthermore,this review summarizes recent progress on topological photonic crystals,such as higherorder topological photonic crystals,non-Hermitian photonic crystals,and nonlinear photonic crystals.These studies indicate that topological photonic crystals as versatile platforms have enormous potential applications in maneuvering the flow of light.展开更多
The Fe-Pt based intermetallic compounds exhibit good chemical stability and unique magnetic proper-ties,where Ni is an important additional element to optimize the magnetic properties or obtain the outstanding catalyt...The Fe-Pt based intermetallic compounds exhibit good chemical stability and unique magnetic proper-ties,where Ni is an important additional element to optimize the magnetic properties or obtain the outstanding catalytic performances of the Fe-Pt based alloys.Knowledge of how Ni addition affects the order-disorder transitions of the Fe-Pt intermetallics is thus necessary;however,the related information is limited.Therefore,in this work,the phase diagrams of the Fe-Ni-Pt system were experimentally in-vestigated,and as a result,the isothermal sections of the Fe-Ni-Pt system at 600 and 900℃,as well as the vertical sections of Fe_(80)Ni_(20)-Pt_(80)Ni_(20)and Fe_(50)Pt_(50)-Ni_(50)Pt_(50)were constructed.Based on these re-sults,the influences of Ni addition on the crystal stabilities and phase transformations of the ordered Fe-Pt intermetallics have been well described.The results show that the L1_(0)-FePt and L1_(0)-NiPt phases form a ternary continuous solid solution of L1_(0)-(Fe,Ni)Pt,whereas Ni can dissolve in the L1_(2)-Fe_(3)Pt and L1_(2)-FePt_(3)phases as high as 57.0 at.%and 26.0 at.%at 600℃,respectively.The selective occupancy of Ni atoms has been predicted,which should depend on the alloy composition.For both the L1_(0)-(Fe,Ni)Pt and L1_(2)-FePt_(3)phases,when Pt contents are less than their stoichiometric values,Ni atoms will preferentially occupy the Pt sublattice,forming as many nearest-neighbor Fe-Pt bonds as possible.All these results can correlate the alloy compositions,annealing temperatures and crystal structures to both magnetic and catalytic properties,thus providing a basis for optimizing the Fe-Ni-Pt alloys towards enhanced magnetic or catalytic performances.展开更多
In this work,we introduce a kind of new structured radial grating,which is named the even-type sinusoidal amplitude radial(ETASR)grating.Based on diffraction theory and the principle of stationary phase,a comprehensiv...In this work,we introduce a kind of new structured radial grating,which is named the even-type sinusoidal amplitude radial(ETASR)grating.Based on diffraction theory and the principle of stationary phase,a comprehensive theoretical investigation on the diffraction patterns of ETASR gratings is conducted.Theoretical results show that novel carpet beams with beautiful optical structures and distinctive characteristics have been constructed on the basics of the ETASR grating.Their diffraction patterns are independent of propagation distance,that is,the new carpet beams have diffraction-free propagating characteristics.The non-diffracting carpet beams are divided into two types by beam characteristics:non-diffracting integer-order and half-integer-order carpet beams.Subsequently,we experimentally generate these carpet beams using the ETASR grating.Finally,their particularly interesting optical morphology and features are explored through numerical simulations and experiments.展开更多
Temperature dependence of viscosity for more than ten kinds of metallic melts is analysed based on viscosity measurements. An obvious turning point is observed on the Arrhenius curves. Since viscosity is one of the ph...Temperature dependence of viscosity for more than ten kinds of metallic melts is analysed based on viscosity measurements. An obvious turning point is observed on the Arrhenius curves. Since viscosity is one of the physical properties sensitive to structure, its discontinuous change with temperature reveals the possible liquidliquid structure transition in the metallic melts. Furthermore, an integrated liquid structure transition diagram of the Sn-Bi system is presented. The universality of liquid-liquid structure transition is also discussed simply.展开更多
While non-Hermiticity provokes intriguing phenomena without Hermitian counterparts, e.g., the skin effect and the breakdown of bulk-boundary correspondence, attracting extensive attention both in fundamental physics a...While non-Hermiticity provokes intriguing phenomena without Hermitian counterparts, e.g., the skin effect and the breakdown of bulk-boundary correspondence, attracting extensive attention both in fundamental physics and device engineering, the role of finite sizes therein remains elusive. Here, we propose a class of finite-size-induced non-Hermitian phase transitions, relying upon higher-order topological invariants associated with real-space wave functions. The phase diagrams for general non-Hermitian chiral models are further acquired to demonstrate our topological definition. Such phase transitions are elucidated qualitatively by an effective intercell coupling alteration that depends on finite sizes in respective directions. Besides, we mimic these phenomena by analogizing the circuit Laplacian in finite-size electric circuits with nonreciprocal couplings. The resultant admittance spectra agree with our theoretical predictions. Our findings shed light on the finite-size mechanism of non-Hermitian topological phase transitions and pave the way for applications in switching and sensing.展开更多
To improve the accuracy of the conventional finite-difference method, finitedifference numerical modeling methods of any even-order accuracy are recommended. We introduce any even-order accuracy difference schemes of ...To improve the accuracy of the conventional finite-difference method, finitedifference numerical modeling methods of any even-order accuracy are recommended. We introduce any even-order accuracy difference schemes of any-order derivatives derived from Taylor series expansion. Then, a finite-difference numerical modeling method with any evenorder accuracy is utilized to simulate seismic wave propagation in two-phase anisotropic media. Results indicate that modeling accuracy improves with the increase of difference accuracy order number. It is essential to find the optimal order number, grid size, and time step to balance modeling precision and computational complexity. Four kinds of waves, static mode in the source point, SV wave cusps, reflection and transmission waves are observed in two-phase anisotropic media through modeling.展开更多
Due to the coupling between the hydrodynamic equation and the phase-field equation in two-phase incompressible flows,it is desirable to develop efficient and high-order accurate numerical schemes that can decouple the...Due to the coupling between the hydrodynamic equation and the phase-field equation in two-phase incompressible flows,it is desirable to develop efficient and high-order accurate numerical schemes that can decouple these two equations.One popular and efficient strategy is to add an explicit stabilizing term to the convective velocity in the phase-field equation to decouple them.The resulting schemes are only first-order accurate in time,and it seems extremely difficult to generalize the idea of stabilization to the second-order or higher version.In this paper,we employ the spectral deferred correction method to improve the temporal accuracy,based on the first-order decoupled and energy-stable scheme constructed by the stabilization idea.The novelty lies in how the decoupling and linear implicit properties are maintained to improve the efficiency.Within the framework of the spatially discretized local discontinuous Galerkin method,the resulting numerical schemes are fully decoupled,efficient,and high-order accurate in both time and space.Numerical experiments are performed to validate the high-order accuracy and efficiency of the methods for solving phase-field models of two-phase incompressible flows.展开更多
基金partially funded by the United States Army Research Laboratory (ARL)Terves LLC。
文摘Mg-rare earth(RE)based systems provide several important commercial alloys and many alloy development opportunities for high strength applications,especially in aerospace and defense industries.The phase diagrams,microstructure,and strengthening mechanisms of these multicomponent systems are very complex and often not well understood in literature.We have calculated phase diagrams of important binary,ternary,and multicomponent RE-containing alloy systems,using CALPHAD(CALculation of PHAse Diagrams).Based on these phase diagrams,this paper offers a critical overview on phase equilibria and strengthening mechanisms in these alloy systems,including precipitation,long period stacking order(LPSO),and other intermetallic phases.This review also summarized several promising Mg-RE based cast alloys in comparison with commercial WE54 and WE43 alloys;and explored new strategies for future alloy development for high strength applications.It is pointed out that the combination of precipitation and LPSO phases can lead to superior strength and ductility in Mg-RE based cast alloys.The precipitates and LPSO phases can form a complex three-dimensional network that effectively impedes dislocation motion on the basal and non-basal planes.The LPSO phases can also prevent the coarsening of precipitates when they interact,thus providing good thermal stability at elevated temperatures.Future research is needed to determine how the combination of these two types of phases can be used in alloy design and industrial scale applications.
基金supported by the National Key R&D Program of China(Nos.2018YFA0306200,and 2017YFA0303702)the National Natural Science Foundation of China(Grant Nos.11625418,51732006,and 11890700)as well as the Academic Program Development of Jiangsu Higher Education(PAPD).
文摘The field of topological photonic crystals has attracted growing interest since the inception of optical analog of quantum Hall effect proposed in 2008.Photonic band structures embraced topological phases of matter,have spawned a novel platform for studying topological phase transitions and designing topological optical devices.Here,we present a brief review of topological photonic crystals based on different material platforms,including all-dielectric systems,metallic materials,optical resonators,coupled waveguide systems,and other platforms.Furthermore,this review summarizes recent progress on topological photonic crystals,such as higherorder topological photonic crystals,non-Hermitian photonic crystals,and nonlinear photonic crystals.These studies indicate that topological photonic crystals as versatile platforms have enormous potential applications in maneuvering the flow of light.
基金supported by the Major Scientific and Technological Projects in Yunnan Province(No.202002AB080001-1)the National Natural Science Foundation of China(Nos.U1602275 and 51971059).Special thanks are due to the instrumen-tal data analysis from the Analytical and Testing Center,Northeast-ern University。
文摘The Fe-Pt based intermetallic compounds exhibit good chemical stability and unique magnetic proper-ties,where Ni is an important additional element to optimize the magnetic properties or obtain the outstanding catalytic performances of the Fe-Pt based alloys.Knowledge of how Ni addition affects the order-disorder transitions of the Fe-Pt intermetallics is thus necessary;however,the related information is limited.Therefore,in this work,the phase diagrams of the Fe-Ni-Pt system were experimentally in-vestigated,and as a result,the isothermal sections of the Fe-Ni-Pt system at 600 and 900℃,as well as the vertical sections of Fe_(80)Ni_(20)-Pt_(80)Ni_(20)and Fe_(50)Pt_(50)-Ni_(50)Pt_(50)were constructed.Based on these re-sults,the influences of Ni addition on the crystal stabilities and phase transformations of the ordered Fe-Pt intermetallics have been well described.The results show that the L1_(0)-FePt and L1_(0)-NiPt phases form a ternary continuous solid solution of L1_(0)-(Fe,Ni)Pt,whereas Ni can dissolve in the L1_(2)-Fe_(3)Pt and L1_(2)-FePt_(3)phases as high as 57.0 at.%and 26.0 at.%at 600℃,respectively.The selective occupancy of Ni atoms has been predicted,which should depend on the alloy composition.For both the L1_(0)-(Fe,Ni)Pt and L1_(2)-FePt_(3)phases,when Pt contents are less than their stoichiometric values,Ni atoms will preferentially occupy the Pt sublattice,forming as many nearest-neighbor Fe-Pt bonds as possible.All these results can correlate the alloy compositions,annealing temperatures and crystal structures to both magnetic and catalytic properties,thus providing a basis for optimizing the Fe-Ni-Pt alloys towards enhanced magnetic or catalytic performances.
基金supported by the National Natural Science Foundation of China(Nos.11974314 and 11674288).
文摘In this work,we introduce a kind of new structured radial grating,which is named the even-type sinusoidal amplitude radial(ETASR)grating.Based on diffraction theory and the principle of stationary phase,a comprehensive theoretical investigation on the diffraction patterns of ETASR gratings is conducted.Theoretical results show that novel carpet beams with beautiful optical structures and distinctive characteristics have been constructed on the basics of the ETASR grating.Their diffraction patterns are independent of propagation distance,that is,the new carpet beams have diffraction-free propagating characteristics.The non-diffracting carpet beams are divided into two types by beam characteristics:non-diffracting integer-order and half-integer-order carpet beams.Subsequently,we experimentally generate these carpet beams using the ETASR grating.Finally,their particularly interesting optical morphology and features are explored through numerical simulations and experiments.
基金Supported by the National Science Foundation of China under Grant Nos 50231040 and 50301013.
文摘Temperature dependence of viscosity for more than ten kinds of metallic melts is analysed based on viscosity measurements. An obvious turning point is observed on the Arrhenius curves. Since viscosity is one of the physical properties sensitive to structure, its discontinuous change with temperature reveals the possible liquidliquid structure transition in the metallic melts. Furthermore, an integrated liquid structure transition diagram of the Sn-Bi system is presented. The universality of liquid-liquid structure transition is also discussed simply.
基金supported by the National Natural Science Foundation of China (Grant Nos.12304340,12074241,11929401,and 52130204)the Science and Technology Commission of Shanghai Municipality (Grant Nos.20501130600,21JC1402600,and 21JC1402700)+2 种基金the Shanghai Pujiang Program (Grant No.23PJ1403200)the Key Research Project of Zhejiang Laboratory (Grant No.2021PE0AC02)the startup funding of the Chinese University of Hong Kong,Shenzhen (Grant No.UDF01002563)。
文摘While non-Hermiticity provokes intriguing phenomena without Hermitian counterparts, e.g., the skin effect and the breakdown of bulk-boundary correspondence, attracting extensive attention both in fundamental physics and device engineering, the role of finite sizes therein remains elusive. Here, we propose a class of finite-size-induced non-Hermitian phase transitions, relying upon higher-order topological invariants associated with real-space wave functions. The phase diagrams for general non-Hermitian chiral models are further acquired to demonstrate our topological definition. Such phase transitions are elucidated qualitatively by an effective intercell coupling alteration that depends on finite sizes in respective directions. Besides, we mimic these phenomena by analogizing the circuit Laplacian in finite-size electric circuits with nonreciprocal couplings. The resultant admittance spectra agree with our theoretical predictions. Our findings shed light on the finite-size mechanism of non-Hermitian topological phase transitions and pave the way for applications in switching and sensing.
文摘To improve the accuracy of the conventional finite-difference method, finitedifference numerical modeling methods of any even-order accuracy are recommended. We introduce any even-order accuracy difference schemes of any-order derivatives derived from Taylor series expansion. Then, a finite-difference numerical modeling method with any evenorder accuracy is utilized to simulate seismic wave propagation in two-phase anisotropic media. Results indicate that modeling accuracy improves with the increase of difference accuracy order number. It is essential to find the optimal order number, grid size, and time step to balance modeling precision and computational complexity. Four kinds of waves, static mode in the source point, SV wave cusps, reflection and transmission waves are observed in two-phase anisotropic media through modeling.
基金supported by the NSFC Grant no.12271492the Natural Science Foundation of Henan Province of China Grant no.222300420550+1 种基金supported by the NSFC Grant no.12271498the National Key R&D Program of China Grant no.2022YFA1005202/2022YFA1005200.
文摘Due to the coupling between the hydrodynamic equation and the phase-field equation in two-phase incompressible flows,it is desirable to develop efficient and high-order accurate numerical schemes that can decouple these two equations.One popular and efficient strategy is to add an explicit stabilizing term to the convective velocity in the phase-field equation to decouple them.The resulting schemes are only first-order accurate in time,and it seems extremely difficult to generalize the idea of stabilization to the second-order or higher version.In this paper,we employ the spectral deferred correction method to improve the temporal accuracy,based on the first-order decoupled and energy-stable scheme constructed by the stabilization idea.The novelty lies in how the decoupling and linear implicit properties are maintained to improve the efficiency.Within the framework of the spatially discretized local discontinuous Galerkin method,the resulting numerical schemes are fully decoupled,efficient,and high-order accurate in both time and space.Numerical experiments are performed to validate the high-order accuracy and efficiency of the methods for solving phase-field models of two-phase incompressible flows.
