We investigate the behavior of non-Hermitian birefringent Dirac fermions by examining their interaction with electromagnetic fields through renormalization group analysis. Our research reveals that the interplay betwe...We investigate the behavior of non-Hermitian birefringent Dirac fermions by examining their interaction with electromagnetic fields through renormalization group analysis. Our research reveals that the interplay between non-Hermiticity and birefringence leads to distinct behaviors in two and three dimensions, where the system exhibits different fixed points and scaling properties due to dimension-dependent charge renormalization effects. In two dimensions, where the electronic charge remains unrenormalized, the system flows in the deep infrared limit from non-Hermitian birefringent spin-3/2fermions to two copies of non-Hermitian spin-1/2 Dirac fermions, demonstrating a crossover of relativistic liquid and nonrelativistic liquid. In three dimensions, dynamic screening of electromagnetic interactions modifies the logarithmic growth of Fermi velocity, leading to richer quantum corrections while maintaining similar suppression of birefringence in the infrared limit. Our findings provide theoretical insights into the emergence of Lorentz symmetry in non-Hermitian systems,laying theoretical foundations for studying low-energy behavior in other non-Hermitian models.展开更多
The system consisting of(2+1)-dimensional quasirelativistic birefringent Dirac fermions with Coulomb interactions and retarded current–current interactions is described by a quantum field theory similar to reduced qu...The system consisting of(2+1)-dimensional quasirelativistic birefringent Dirac fermions with Coulomb interactions and retarded current–current interactions is described by a quantum field theory similar to reduced quantum electrodynamics.We used the perturbative renormalization group method to study the low-energy behavior of the system and found that it flows to a fixed point of the non-Fermi liquid composed of relativistic pseudospin-1/2 Dirac fermions in the deep infrared limit.At the fixed point,the fermion Green function exhibits a finite anomalous dimension,and the residue of the quasiparticle pole vanishes in a power-law fashion.Our research provides new theoretical perspectives for understanding the origin of spin-1/2 fermions in the standard model.展开更多
Renormalization group analysis has been proposed to eliminate secular terms in perturbation solutions of differential equations and thus expand the domain of their validity.Here we extend the method to treat periodic ...Renormalization group analysis has been proposed to eliminate secular terms in perturbation solutions of differential equations and thus expand the domain of their validity.Here we extend the method to treat periodic orbits or limit cycles.Interesting normal forms could be derived through a generalization of the concept'resonance',which offers nontrivial analytic approximations.Compared with traditional techniques such as multi-scale methods,the current scheme proceeds in a very straightforward and simple way,delivering not only the period and the amplitude but also the transient path to limit cycles.The method is demonstrated with several examples including the Duffing oscillator,van der Pol equation and Lorenz equation.The obtained solutions match well with numerical results and with those derived by traditional analytic methods.展开更多
Accurate evaluation of elec-tron correlations is essential for the reliable quantitative de-scription of electronic struc-tures in strongly correlated sys-tems,including bond-dissociat-ing molecules,polyradicals,large...Accurate evaluation of elec-tron correlations is essential for the reliable quantitative de-scription of electronic struc-tures in strongly correlated sys-tems,including bond-dissociat-ing molecules,polyradicals,large conjugated molecules,and transition metal complex-es.To provide a user-friendly tool for studying such challeng-ing systems,our team developed Kylin 1.0[J.Comput.Chem.44,1316(2023)],an ab initio quantum chemistry program designed for efficient density matrix renormalization group(DMRG)and post-DMRG methods,enabling high-accuracy calculations with large active spaces.We have now further advanced the software with the release of Kylin 1.3,featuring optimized DMRG algorithms and an improved tensor contraction scheme in the diagonaliza-tion step.Benchmark calculations on the Mn_(4)CaO_(5)cluster demonstrate a remarkable speed-up of up to 16 fater than Kylin 1.0.Moreover,a more user-friendly and efficient algorithm[J.Chem.Theory Comput.17,3414(2021)]for sampling configurations from DMRG wavefunc-tion is implemented as well.Additionally,we have also implemented a spin-adapted version of the externally contracted multi-reference configuration interaction(EC-MRCI)method[J.Phys.Chem.A 128,958(2024)],further enhancing the program’s efficiency and accuracy for electron correlation calculations.展开更多
Generally,referring to the stability of perovskite,the most studied perovskite material has been MA-free mixed-cationperovskite.The precise role of MA in the light-thermal-humid stability of perovskite solar cells sti...Generally,referring to the stability of perovskite,the most studied perovskite material has been MA-free mixed-cationperovskite.The precise role of MA in the light-thermal-humid stability of perovskite solar cells still lacks ofa systematically understanding.In this work,the evolution of crystallographic structures,intermediate phase,ultrafast dynamics,and thermal decomposition behavior of MA-mixed perovskite FA_(1-x)MA_(x)PbI_(3)(x=0–100%)areinvestigated.The influence of MA on the stability of devices under heat,light,and humidity exposure arerevealed.In the investigated compositional space(x=0–100%),device efficiencies vary from 19.5%to 22.8%,andthe light,thermal,and humidity exposure stability of the related devices are obviously improved forFA1-xMAxPbI_(3)(x=20%–30%).Incorporation 20%–30%of MA cations lowers nucleation barrier and causes asignificant volume shrinkage,which enhances the interaction between FA and I,thus improving crystallizationand stability of the FA_(1-x)MA_(x)PbI_(3).Thermal behavior analysis reveals that the decomposition temperature of FA_(0.8)MA_(0.2)PbI_(3)reaches 247℃(FAPbI_(3),233℃)and trace amounts of MA cations enhance the thermal stability ofthe perovskite.Remarkably,we observe lattice shrinkage using spherical aberration corrected transmissionelectron microscope(AC-TEM).This work implies that stabilizing perovskites will be realized by incorporatingtrace amounts of MA,which improve the crystallization and carrier transport,leading to improved stability andperformances.展开更多
Over the last decade,nuclear theory has made dramatic progress in few-body and ab initio many-body calculations.These great advances stem from chiral efective feld theory(xEFT),which provides an efcient expansion and ...Over the last decade,nuclear theory has made dramatic progress in few-body and ab initio many-body calculations.These great advances stem from chiral efective feld theory(xEFT),which provides an efcient expansion and consistent treatment of nuclear forces as inputs of modern many-body calculations,among which the in-medium similarity renormalization group(IMSRG)and its variants play a vital role.On the other hand,signifcant eforts have been made to provide a unifed description of the structure,decay,and reactions of the nuclei as open quantum systems.While a fully comprehensive and microscopic model has yet to be realized,substantial progress over recent decades has enhanced our understanding of open quantum systems around the dripline,which are often characterized by exotic structures and decay modes.To study these interesting phenomena,Gamow coupled-channel(GCC)method,in which the open quantum nature of few-body valence nucleons coupled to a deformed core,has been developed.This review focuses on the developments of the advanced IMSRG and GCC and their applications to nuclear structure and reactions.展开更多
The purpose of this paper is to present the results of investigations on quasi-one-dimensional organic crystals of tetrathiotetracene-tetracyanoquinodi- methane (TTT(TCNQ)<sub>2</sub>) from the prospective...The purpose of this paper is to present the results of investigations on quasi-one-dimensional organic crystals of tetrathiotetracene-tetracyanoquinodi- methane (TTT(TCNQ)<sub>2</sub>) from the prospective of thermoelectric applications. The calculations were performed after analytical expressions, obtained in the frame of a physical model, more detailed than the model presented earlier by authors. The main Hamiltonian of the model includes the electronic and phonon part, electron-phonon interactions and the impurity scattering term. In order to estimate the electric charge transport between the molecular chains, the physical model was upgraded to the so-called three-dimen- sional (3D) physical model. Numeric computations were performed to determine the electrical conductivity, Seebeck coefficient, thermal conductivity, thermoelectric power factor and thermoelectric figure-of-merit as a function on charge carrier concentrations, temperatures and impurity concentrations. A detailed analysis of charge-lattice interaction, consisting of the exploration of the Peierls structural transition in TCNQ molecular chains of TTT(TCNQ)<sub>2</sub> was performed. As result, the critical transition temperature was determined. The dispersion of renormalized phonons was examined in detail.展开更多
We consider the AB-(Bernal) stacking for the bi-layer graphene (BLG) system and assume that a perpendicular electric field is created by the external gates deposited on the BLG surface. In the basis (A1, B2, A2, B1) f...We consider the AB-(Bernal) stacking for the bi-layer graphene (BLG) system and assume that a perpendicular electric field is created by the external gates deposited on the BLG surface. In the basis (A1, B2, A2, B1) for the valleyKand the basis (B2, A1, B1, A2) for the valley K′, we show the occurrence of trigonal warping [1], that is, splitting of the energy bands or the density of states on the kx - ky plane into four pockets comprising of the central part and three legs due to a (skew) interlayer hopping between A1 and B2. The hopping between A1 - B2 leads to a concurrent velocity v3 in addition to the Fermi velocity vF. Our noteworthy outcome is that the above-mentioned topological change, referred to as the Lifshitz transition [2, 3], is entirely bias-tunable. Furthermore, the many-body effects, which is known to yield logarithmic renormalizations [4] in the band dispersions of monolayer graphene, is found to have significant effect on the bias-tunability of this transition. We also consider a variant of the system where the A atoms of the two layers are over each other and the B atoms of the layers are displaced with respect to each other. The Fermi energy density of statesfor zero bias corresponds to the inverted sombrero-like structure. The structure is found to get deformed due to the increase in the bias.展开更多
Using a field equation with a phase factor, a universal analytic potential-energy function applied to the interactions between diatoms or molecules is derived, and five kinds of potential curves of common shapes are o...Using a field equation with a phase factor, a universal analytic potential-energy function applied to the interactions between diatoms or molecules is derived, and five kinds of potential curves of common shapes are obtained adjusting the phase factors. The linear thermal expansion coefficients and Young's moduli of eleven kinds of face-centered cubic (fcc) metals - Al, Cu, Ag, etc. are calculated using the potential-energy function; the computational results are quite consistent with experimental values. Moreover, an analytic relation between the linear thermal expansion coefficients and Young's moduli of fcc metals is given using the potential-energy function. Finally, the force constants of fifty-five kinds of diatomic moleculars with low excitation state are computed using this theory, and they are quite consistent with RKR (Rydberg-Klein-Rees) experimental values.展开更多
During the microstructural analysis of weakly cemented sandstone,the granule components and ductile structural parts of the sandstone are typically generalized.Considering the contact between granules in the microstru...During the microstructural analysis of weakly cemented sandstone,the granule components and ductile structural parts of the sandstone are typically generalized.Considering the contact between granules in the microstructure of weakly cemented sandstone,three basic units can be determined:regular tetrahedra,regular hexahedra,and regular octahedra.Renormalization group models with granule-and pore-centered weakly cemented sandstone were established,and,according to the renormalization group transformation rule,the critical stress threshold of damage was calculated.The results show that the renormalization model using regular octahedra as the basic units has the highest critical stress threshold.The threshold obtained by iterative calculations of the granule-centered model is smaller than that obtained by the pore-centered model.The granule-centered calculation provides the lower limit(18.12%),and the pore-centered model provides the upper limit(36.36%).Within this range,the weakly cemented sandstone is in a phase-like critical state.That is,the state of granule aggregation transforms from continuous to discrete.In the relative stress range of 18.12%-36.36%,the weakly cemented sandstone exhibits an increased proportion of high-frequency signals(by 83.3%)and a decreased proportion of low-frequency signals(by 23.6%).The renormalization calculation results for weakly cemented sandstone explain the high-low frequency conversion of acoustic emission signals during loading.The research reported in this paper has important significance for elucidating the damage mechanism of weakly cemented sandstone.展开更多
The mechanism of local scour around submarine pipelines is studied numerically based on a renormalized group （RNG） turbulence model. To validate the numerical model, the equilibrium profiles of local scour for two c...The mechanism of local scour around submarine pipelines is studied numerically based on a renormalized group （RNG） turbulence model. To validate the numerical model, the equilibrium profiles of local scour for two cases are simulated and compared with the experimental data. It shows that the RNG turbulence model can give an appropriate prediction for the configuration of equilibrium scour hole, and it is applicable to this situation. The local scour mechanism around submarine pipelines including the flow structure, shear stress distribution and pressure field is then analyzed and compared with experiments. For further comparison and validation, especially for the flow structure, a numerical calculation employing the large eddy simulation （LES） is also conducted. The numerical results of RNG demonstrate that the critical factor governing the equilibrium profile is the seabed shear stress distribution in the case of bed load sediment transport, and the two-equation RNG turbulence model coupled with the law of wall is capable of giving a satisfying estimation for the bed shear stress. Moreover, the piping phenomena due to the great difference of pressure between the upstream and downstream parts of pipelines and the vortex structure around submarine pipelines are also simulated successfully, which are believed to be the important factor that lead to the onset of local scour.展开更多
Stochastic dynamic analysis of the nonlinear system is an open research question which has drawn many scholars'attention for its importance and challenge.Fokker–Planck–Kolmogorov(FPK)equation is of great signifi...Stochastic dynamic analysis of the nonlinear system is an open research question which has drawn many scholars'attention for its importance and challenge.Fokker–Planck–Kolmogorov(FPK)equation is of great significance because of its theoretical strictness and computational accuracy.However,practical difficulties with the FPK method appear when the analysis of multi-degree-offreedom(MDOF)with more general nonlinearity is required.In the present paper,by invoking the idea of equivalence of probability flux,the general high-dimensional FPK equation related to MDOF system is reduced to one-dimensional FPK equation.Then a cell renormalized method(CRM)which is based on the numerical reconstruction of the derived moments of FPK equation is introduced by coarsening the continuous state space into a discretized region of cells.Then the cell renormalized FPK(CR-FPK)equation is solved by difference method.Three numerical examples are illustrated and the effectiveness of proposed method is assessed and verified.展开更多
In this paper,we present an overview on recent progress in studies of QCD at finite temperature and densities within the functional renormalization group(fRG)approach.The f RG is a nonperturbative continuum field appr...In this paper,we present an overview on recent progress in studies of QCD at finite temperature and densities within the functional renormalization group(fRG)approach.The f RG is a nonperturbative continuum field approach,in which quantum,thermal and density fluctuations are integrated successively with the evolution of the renormalization group(RG)scale.The f RG results for the QCD phase structure and the location of the critical end point(CEP),the QCD equation of state(EoS),the magnetic EoS,baryon number fluctuations confronted with recent experimental measurements,various critical exponents,spectral functions in the critical region,the dynamical critical exponent,etc,are presented.Recent estimates of the location of the CEP from first-principle QCD calculations within f RG and Dyson-Schwinger equations,which pass through lattice benchmark tests at small baryon chemical potentials,converge in a rather small region at baryon chemical potentials of about 600 MeV.A region of inhomogeneous instability indicated by a negative wave function renormalization is found withμ_(B)■420 MeV.It is found that the non-monotonic dependence of the kurtosis of the net-proton number distributions on the beam collision energy observed in experiments could arise from the increasingly sharp crossover in the regime of low collision energy.展开更多
The fragmentation test of granite subjected to strain rate of 10~010~2s~ -1 was carried out using split Hopkinson pressure bar(SHPB) whose diameter is 75 mm, where half-sine loading waveform was performed. The sieving...The fragmentation test of granite subjected to strain rate of 10~010~2s~ -1 was carried out using split Hopkinson pressure bar(SHPB) whose diameter is 75 mm, where half-sine loading waveform was performed. The sieving statistics results of the fragments show that the distribution of the fragments is a fractal, and the fractal dimension values fall into the range of 1.22.4. The correlation analysis between the fractal dimension and the logarithm of the energy density shows that they have approximately linear relation. Finally, based on damage theory and scale invariant principle, the fragmentation model with renormalization method was put forward, and the fractal dimension value predicted with the model was compared with the test results. It is found that the fractal dimension value obtained from the improved fragmentation model is more reasonable.展开更多
Adopted the fractal tree-like failure model, and established the renormalization group transform function of fractured fault, and investigated the mechanism of water-inrush from fault, and found out the critical proba...Adopted the fractal tree-like failure model, and established the renormalization group transform function of fractured fault, and investigated the mechanism of water-inrush from fault, and found out the critical probability of water-inrush from fault caused by fault fracture. The results indicate： when the failure rate P is less than the critical failure rate Pc=0.206 3, the failure of the system is just partial. When P is more than the critical failure rate Pc=0.206 3, the random distributed crannies concentrate to certain domain of attraction （such as the maximum shear stress face in the fault） gradually. The process will continue until the crannies run-through, forming conductivity channel, and cause water-inrush from fault.展开更多
Liquid sloshing is a common phenomenon in the transportation of liquid-cargo tanks.Liquid waves lead to fluctuating forces on the tank walls.If these fluctuations are not predicted or controlled,for example,by using b...Liquid sloshing is a common phenomenon in the transportation of liquid-cargo tanks.Liquid waves lead to fluctuating forces on the tank walls.If these fluctuations are not predicted or controlled,for example,by using baffles,they can lead to large forces and momentums.The volume of fluid(VOF)two-phase numerical model in Open FOAM open-source software has been widely used to model the liquid sloshing.However,a big challenge for modeling the sloshing phenomenon is selecting a suitable turbulence model.Therefore,in the present study,different turbulence models were studied to determine their sloshing phenomenon prediction accuracies.The predictions of these models were validated using experimental data.The turbulence models were ranked by their mean error in predicting the free surface behaviors.The renormalization group(RNG)k-ε and the standard k–ω models were found to be the best and worst turbulence models for modeling the sloshing phenomena,respectively;moreover,the SST k-ω model and v2-f k-ε results were very close to the RNG k-εmodel result.展开更多
The quantum gravity is formulated based on the principle of local gauge invariance. The model discussedin this paper has local gravitational gauge symmetry, and gravitational field is represented by gauge field. In th...The quantum gravity is formulated based on the principle of local gauge invariance. The model discussedin this paper has local gravitational gauge symmetry, and gravitational field is represented by gauge field. In the leading-order approximation, it gives out classical Newton's theory of gravity. In the first-order approximation and for vacuum,it gives out Einstein's general theory of relativity. This quantum gauge theory of gravity is a renormalizable quantumtheory.展开更多
The anomalous dimensions of the quantum fields are the Hausdorff dimensiongrad. The present candidate of the renormalization constant is the generalized Cantor discontinuum. The Hausdorff dimensiongrad of the Minkowsk...The anomalous dimensions of the quantum fields are the Hausdorff dimensiongrad. The present candidate of the renormalization constant is the generalized Cantor discontinuum. The Hausdorff dimensiongrad of the Minkowski space time is based upon the point set with σ-length on light cone.展开更多
The artificial reefs placed on the seabed with different layouts and disposal spaces will produce variational flow field. The intensity and scale of the combined three-tube artificial reefs with different layouts at f...The artificial reefs placed on the seabed with different layouts and disposal spaces will produce variational flow field. The intensity and scale of the combined three-tube artificial reefs with different layouts at five Reynolds numbers（Re） are numerically investigated by use of the RNG k-ε turbulent model and SIMPLEC algorithm. A stationary no-slip boundary condition is used on the models and the bottoms, and the free surface is treated as a ＂moving wall＂ with zero shear force and the same velocity with inflow. In order to validate the simulation results, a particle image velocimetry（PIV） experiment is carried out to analyze the flow field. The numerical simulation results are consistent with the data obtained from experiment. The corresponding errors are all below 20%. Based on the validation, the effects of disposal space on flow field are simulated and analyzed. According to the simulation, in a parallel combination, a better artificial reef effect is obtained when the disposal space between two parallel reefs is 1.0L（L is the length of the combined three-tube reef model）. In a vertical combination, when the disposal space between two vertical reefs is 1.0L to 2.0L, the artificial reef effect is better.展开更多
基金Project supported by the National Key Research and Development Program of China (Grants Nos. 2021YFA1400900,2021YFA0718300, and 2021YFA1400243)the National Natural Science Foundation of China (Grant Nos. 61835013,12174461, and 12234012)the Fund from the Space Application System of China Manned Space Program。
文摘We investigate the behavior of non-Hermitian birefringent Dirac fermions by examining their interaction with electromagnetic fields through renormalization group analysis. Our research reveals that the interplay between non-Hermiticity and birefringence leads to distinct behaviors in two and three dimensions, where the system exhibits different fixed points and scaling properties due to dimension-dependent charge renormalization effects. In two dimensions, where the electronic charge remains unrenormalized, the system flows in the deep infrared limit from non-Hermitian birefringent spin-3/2fermions to two copies of non-Hermitian spin-1/2 Dirac fermions, demonstrating a crossover of relativistic liquid and nonrelativistic liquid. In three dimensions, dynamic screening of electromagnetic interactions modifies the logarithmic growth of Fermi velocity, leading to richer quantum corrections while maintaining similar suppression of birefringence in the infrared limit. Our findings provide theoretical insights into the emergence of Lorentz symmetry in non-Hermitian systems,laying theoretical foundations for studying low-energy behavior in other non-Hermitian models.
基金supported by the National Key Research and Development Program of China(Grant Nos.2021YFA1400900,2021YFA0718300,and 2021YFA1400243)the National Natural Science Foundation of China(Grant Nos.61835013,12174461,and 12234012)Space Application System of China Manned Space Program.
文摘The system consisting of(2+1)-dimensional quasirelativistic birefringent Dirac fermions with Coulomb interactions and retarded current–current interactions is described by a quantum field theory similar to reduced quantum electrodynamics.We used the perturbative renormalization group method to study the low-energy behavior of the system and found that it flows to a fixed point of the non-Fermi liquid composed of relativistic pseudospin-1/2 Dirac fermions in the deep infrared limit.At the fixed point,the fermion Green function exhibits a finite anomalous dimension,and the residue of the quasiparticle pole vanishes in a power-law fashion.Our research provides new theoretical perspectives for understanding the origin of spin-1/2 fermions in the standard model.
文摘Renormalization group analysis has been proposed to eliminate secular terms in perturbation solutions of differential equations and thus expand the domain of their validity.Here we extend the method to treat periodic orbits or limit cycles.Interesting normal forms could be derived through a generalization of the concept'resonance',which offers nontrivial analytic approximations.Compared with traditional techniques such as multi-scale methods,the current scheme proceeds in a very straightforward and simple way,delivering not only the period and the amplitude but also the transient path to limit cycles.The method is demonstrated with several examples including the Duffing oscillator,van der Pol equation and Lorenz equation.The obtained solutions match well with numerical results and with those derived by traditional analytic methods.
基金supported by Shandong Provincial Nat-ural Science Foundation(ZR2024ZD30)the National Natural Science Foundation of China(Nos.22325302 and 22403100).
文摘Accurate evaluation of elec-tron correlations is essential for the reliable quantitative de-scription of electronic struc-tures in strongly correlated sys-tems,including bond-dissociat-ing molecules,polyradicals,large conjugated molecules,and transition metal complex-es.To provide a user-friendly tool for studying such challeng-ing systems,our team developed Kylin 1.0[J.Comput.Chem.44,1316(2023)],an ab initio quantum chemistry program designed for efficient density matrix renormalization group(DMRG)and post-DMRG methods,enabling high-accuracy calculations with large active spaces.We have now further advanced the software with the release of Kylin 1.3,featuring optimized DMRG algorithms and an improved tensor contraction scheme in the diagonaliza-tion step.Benchmark calculations on the Mn_(4)CaO_(5)cluster demonstrate a remarkable speed-up of up to 16 fater than Kylin 1.0.Moreover,a more user-friendly and efficient algorithm[J.Chem.Theory Comput.17,3414(2021)]for sampling configurations from DMRG wavefunc-tion is implemented as well.Additionally,we have also implemented a spin-adapted version of the externally contracted multi-reference configuration interaction(EC-MRCI)method[J.Phys.Chem.A 128,958(2024)],further enhancing the program’s efficiency and accuracy for electron correlation calculations.
基金supported by the Nation Key R&D Program of China(Grant Numbers:2023YFC3906103)the Natural Science Foundation of Hunan Province(No.2022JJ30757)+1 种基金Entrepreneurship Research Team Project(No.1053320220430)Guangdong Science and Technology Planning Project(2018B030323010).
文摘Generally,referring to the stability of perovskite,the most studied perovskite material has been MA-free mixed-cationperovskite.The precise role of MA in the light-thermal-humid stability of perovskite solar cells still lacks ofa systematically understanding.In this work,the evolution of crystallographic structures,intermediate phase,ultrafast dynamics,and thermal decomposition behavior of MA-mixed perovskite FA_(1-x)MA_(x)PbI_(3)(x=0–100%)areinvestigated.The influence of MA on the stability of devices under heat,light,and humidity exposure arerevealed.In the investigated compositional space(x=0–100%),device efficiencies vary from 19.5%to 22.8%,andthe light,thermal,and humidity exposure stability of the related devices are obviously improved forFA1-xMAxPbI_(3)(x=20%–30%).Incorporation 20%–30%of MA cations lowers nucleation barrier and causes asignificant volume shrinkage,which enhances the interaction between FA and I,thus improving crystallizationand stability of the FA_(1-x)MA_(x)PbI_(3).Thermal behavior analysis reveals that the decomposition temperature of FA_(0.8)MA_(0.2)PbI_(3)reaches 247℃(FAPbI_(3),233℃)and trace amounts of MA cations enhance the thermal stability ofthe perovskite.Remarkably,we observe lattice shrinkage using spherical aberration corrected transmissionelectron microscope(AC-TEM).This work implies that stabilizing perovskites will be realized by incorporatingtrace amounts of MA,which improve the crystallization and carrier transport,leading to improved stability andperformances.
基金National Key R&D Program of China under Grant Nos.2023YFA1606400 and 2022YFA1602303National Natural Science Foundation of China under Grants Nos.12335007,12035001,11921006,12347106,12147101,and 12205340+1 种基金Gansu Natural Science Foundation under Grant No.22JR5RA123U.S.Department of Energy(DOE),Office of Science,under SciDAC-5(NUCLEI collaboration)。
文摘Over the last decade,nuclear theory has made dramatic progress in few-body and ab initio many-body calculations.These great advances stem from chiral efective feld theory(xEFT),which provides an efcient expansion and consistent treatment of nuclear forces as inputs of modern many-body calculations,among which the in-medium similarity renormalization group(IMSRG)and its variants play a vital role.On the other hand,signifcant eforts have been made to provide a unifed description of the structure,decay,and reactions of the nuclei as open quantum systems.While a fully comprehensive and microscopic model has yet to be realized,substantial progress over recent decades has enhanced our understanding of open quantum systems around the dripline,which are often characterized by exotic structures and decay modes.To study these interesting phenomena,Gamow coupled-channel(GCC)method,in which the open quantum nature of few-body valence nucleons coupled to a deformed core,has been developed.This review focuses on the developments of the advanced IMSRG and GCC and their applications to nuclear structure and reactions.
文摘The purpose of this paper is to present the results of investigations on quasi-one-dimensional organic crystals of tetrathiotetracene-tetracyanoquinodi- methane (TTT(TCNQ)<sub>2</sub>) from the prospective of thermoelectric applications. The calculations were performed after analytical expressions, obtained in the frame of a physical model, more detailed than the model presented earlier by authors. The main Hamiltonian of the model includes the electronic and phonon part, electron-phonon interactions and the impurity scattering term. In order to estimate the electric charge transport between the molecular chains, the physical model was upgraded to the so-called three-dimen- sional (3D) physical model. Numeric computations were performed to determine the electrical conductivity, Seebeck coefficient, thermal conductivity, thermoelectric power factor and thermoelectric figure-of-merit as a function on charge carrier concentrations, temperatures and impurity concentrations. A detailed analysis of charge-lattice interaction, consisting of the exploration of the Peierls structural transition in TCNQ molecular chains of TTT(TCNQ)<sub>2</sub> was performed. As result, the critical transition temperature was determined. The dispersion of renormalized phonons was examined in detail.
文摘We consider the AB-(Bernal) stacking for the bi-layer graphene (BLG) system and assume that a perpendicular electric field is created by the external gates deposited on the BLG surface. In the basis (A1, B2, A2, B1) for the valleyKand the basis (B2, A1, B1, A2) for the valley K′, we show the occurrence of trigonal warping [1], that is, splitting of the energy bands or the density of states on the kx - ky plane into four pockets comprising of the central part and three legs due to a (skew) interlayer hopping between A1 and B2. The hopping between A1 - B2 leads to a concurrent velocity v3 in addition to the Fermi velocity vF. Our noteworthy outcome is that the above-mentioned topological change, referred to as the Lifshitz transition [2, 3], is entirely bias-tunable. Furthermore, the many-body effects, which is known to yield logarithmic renormalizations [4] in the band dispersions of monolayer graphene, is found to have significant effect on the bias-tunability of this transition. We also consider a variant of the system where the A atoms of the two layers are over each other and the B atoms of the layers are displaced with respect to each other. The Fermi energy density of statesfor zero bias corresponds to the inverted sombrero-like structure. The structure is found to get deformed due to the increase in the bias.
基金This work was supported by the National Natural Science Foundation of China (No. 40274044).
文摘Using a field equation with a phase factor, a universal analytic potential-energy function applied to the interactions between diatoms or molecules is derived, and five kinds of potential curves of common shapes are obtained adjusting the phase factors. The linear thermal expansion coefficients and Young's moduli of eleven kinds of face-centered cubic (fcc) metals - Al, Cu, Ag, etc. are calculated using the potential-energy function; the computational results are quite consistent with experimental values. Moreover, an analytic relation between the linear thermal expansion coefficients and Young's moduli of fcc metals is given using the potential-energy function. Finally, the force constants of fifty-five kinds of diatomic moleculars with low excitation state are computed using this theory, and they are quite consistent with RKR (Rydberg-Klein-Rees) experimental values.
基金the National Natural Science Foundation of China(Grant No.51534002)the Special Funds for Technological Innovation and Entrepreneurship of China Coal Science and Engineering Group Co.Ltd.(2018-TDMS011)。
文摘During the microstructural analysis of weakly cemented sandstone,the granule components and ductile structural parts of the sandstone are typically generalized.Considering the contact between granules in the microstructure of weakly cemented sandstone,three basic units can be determined:regular tetrahedra,regular hexahedra,and regular octahedra.Renormalization group models with granule-and pore-centered weakly cemented sandstone were established,and,according to the renormalization group transformation rule,the critical stress threshold of damage was calculated.The results show that the renormalization model using regular octahedra as the basic units has the highest critical stress threshold.The threshold obtained by iterative calculations of the granule-centered model is smaller than that obtained by the pore-centered model.The granule-centered calculation provides the lower limit(18.12%),and the pore-centered model provides the upper limit(36.36%).Within this range,the weakly cemented sandstone is in a phase-like critical state.That is,the state of granule aggregation transforms from continuous to discrete.In the relative stress range of 18.12%-36.36%,the weakly cemented sandstone exhibits an increased proportion of high-frequency signals(by 83.3%)and a decreased proportion of low-frequency signals(by 23.6%).The renormalization calculation results for weakly cemented sandstone explain the high-low frequency conversion of acoustic emission signals during loading.The research reported in this paper has important significance for elucidating the damage mechanism of weakly cemented sandstone.
基金supported by the Program for Changjiang Scholars and Innovative Research Team in University of China under contract No,IRT0420the National Natural Science Foundation of China under contract No.50409015.
文摘The mechanism of local scour around submarine pipelines is studied numerically based on a renormalized group （RNG） turbulence model. To validate the numerical model, the equilibrium profiles of local scour for two cases are simulated and compared with the experimental data. It shows that the RNG turbulence model can give an appropriate prediction for the configuration of equilibrium scour hole, and it is applicable to this situation. The local scour mechanism around submarine pipelines including the flow structure, shear stress distribution and pressure field is then analyzed and compared with experiments. For further comparison and validation, especially for the flow structure, a numerical calculation employing the large eddy simulation （LES） is also conducted. The numerical results of RNG demonstrate that the critical factor governing the equilibrium profile is the seabed shear stress distribution in the case of bed load sediment transport, and the two-equation RNG turbulence model coupled with the law of wall is capable of giving a satisfying estimation for the bed shear stress. Moreover, the piping phenomena due to the great difference of pressure between the upstream and downstream parts of pipelines and the vortex structure around submarine pipelines are also simulated successfully, which are believed to be the important factor that lead to the onset of local scour.
文摘Stochastic dynamic analysis of the nonlinear system is an open research question which has drawn many scholars'attention for its importance and challenge.Fokker–Planck–Kolmogorov(FPK)equation is of great significance because of its theoretical strictness and computational accuracy.However,practical difficulties with the FPK method appear when the analysis of multi-degree-offreedom(MDOF)with more general nonlinearity is required.In the present paper,by invoking the idea of equivalence of probability flux,the general high-dimensional FPK equation related to MDOF system is reduced to one-dimensional FPK equation.Then a cell renormalized method(CRM)which is based on the numerical reconstruction of the derived moments of FPK equation is introduced by coarsening the continuous state space into a discretized region of cells.Then the cell renormalized FPK(CR-FPK)equation is solved by difference method.Three numerical examples are illustrated and the effectiveness of proposed method is assessed and verified.
基金supported by the National Natural Science Foundation of China under Grant No.12175030
文摘In this paper,we present an overview on recent progress in studies of QCD at finite temperature and densities within the functional renormalization group(fRG)approach.The f RG is a nonperturbative continuum field approach,in which quantum,thermal and density fluctuations are integrated successively with the evolution of the renormalization group(RG)scale.The f RG results for the QCD phase structure and the location of the critical end point(CEP),the QCD equation of state(EoS),the magnetic EoS,baryon number fluctuations confronted with recent experimental measurements,various critical exponents,spectral functions in the critical region,the dynamical critical exponent,etc,are presented.Recent estimates of the location of the CEP from first-principle QCD calculations within f RG and Dyson-Schwinger equations,which pass through lattice benchmark tests at small baryon chemical potentials,converge in a rather small region at baryon chemical potentials of about 600 MeV.A region of inhomogeneous instability indicated by a negative wave function renormalization is found withμ_(B)■420 MeV.It is found that the non-monotonic dependence of the kurtosis of the net-proton number distributions on the beam collision energy observed in experiments could arise from the increasingly sharp crossover in the regime of low collision energy.
基金Project(10472134 ,50490274 ,50534030) supported by the National Natural Science Foundation of China
文摘The fragmentation test of granite subjected to strain rate of 10~010~2s~ -1 was carried out using split Hopkinson pressure bar(SHPB) whose diameter is 75 mm, where half-sine loading waveform was performed. The sieving statistics results of the fragments show that the distribution of the fragments is a fractal, and the fractal dimension values fall into the range of 1.22.4. The correlation analysis between the fractal dimension and the logarithm of the energy density shows that they have approximately linear relation. Finally, based on damage theory and scale invariant principle, the fragmentation model with renormalization method was put forward, and the fractal dimension value predicted with the model was compared with the test results. It is found that the fractal dimension value obtained from the improved fragmentation model is more reasonable.
基金Supported by the National Natural Science Foundation of China（50574090） the ＂973＂ Plan（2006CB202210）+1 种基金 Scientific Research Project of Ministry of Education（106084） the Foundation of Qinglan Project of Jiangsu Province
文摘Adopted the fractal tree-like failure model, and established the renormalization group transform function of fractured fault, and investigated the mechanism of water-inrush from fault, and found out the critical probability of water-inrush from fault caused by fault fracture. The results indicate： when the failure rate P is less than the critical failure rate Pc=0.206 3, the failure of the system is just partial. When P is more than the critical failure rate Pc=0.206 3, the random distributed crannies concentrate to certain domain of attraction （such as the maximum shear stress face in the fault） gradually. The process will continue until the crannies run-through, forming conductivity channel, and cause water-inrush from fault.
文摘Liquid sloshing is a common phenomenon in the transportation of liquid-cargo tanks.Liquid waves lead to fluctuating forces on the tank walls.If these fluctuations are not predicted or controlled,for example,by using baffles,they can lead to large forces and momentums.The volume of fluid(VOF)two-phase numerical model in Open FOAM open-source software has been widely used to model the liquid sloshing.However,a big challenge for modeling the sloshing phenomenon is selecting a suitable turbulence model.Therefore,in the present study,different turbulence models were studied to determine their sloshing phenomenon prediction accuracies.The predictions of these models were validated using experimental data.The turbulence models were ranked by their mean error in predicting the free surface behaviors.The renormalization group(RNG)k-ε and the standard k–ω models were found to be the best and worst turbulence models for modeling the sloshing phenomena,respectively;moreover,the SST k-ω model and v2-f k-ε results were very close to the RNG k-εmodel result.
文摘The quantum gravity is formulated based on the principle of local gauge invariance. The model discussedin this paper has local gravitational gauge symmetry, and gravitational field is represented by gauge field. In the leading-order approximation, it gives out classical Newton's theory of gravity. In the first-order approximation and for vacuum,it gives out Einstein's general theory of relativity. This quantum gauge theory of gravity is a renormalizable quantumtheory.
文摘The anomalous dimensions of the quantum fields are the Hausdorff dimensiongrad. The present candidate of the renormalization constant is the generalized Cantor discontinuum. The Hausdorff dimensiongrad of the Minkowski space time is based upon the point set with σ-length on light cone.
基金financially supported by the Special Fund for Agro-scientific Research in the Public Interest(Grant No.201003068)the Special Basic Research Fund for State Level Public Research Institutes(Grant No.20603022011006)
文摘The artificial reefs placed on the seabed with different layouts and disposal spaces will produce variational flow field. The intensity and scale of the combined three-tube artificial reefs with different layouts at five Reynolds numbers（Re） are numerically investigated by use of the RNG k-ε turbulent model and SIMPLEC algorithm. A stationary no-slip boundary condition is used on the models and the bottoms, and the free surface is treated as a ＂moving wall＂ with zero shear force and the same velocity with inflow. In order to validate the simulation results, a particle image velocimetry（PIV） experiment is carried out to analyze the flow field. The numerical simulation results are consistent with the data obtained from experiment. The corresponding errors are all below 20%. Based on the validation, the effects of disposal space on flow field are simulated and analyzed. According to the simulation, in a parallel combination, a better artificial reef effect is obtained when the disposal space between two parallel reefs is 1.0L（L is the length of the combined three-tube reef model）. In a vertical combination, when the disposal space between two vertical reefs is 1.0L to 2.0L, the artificial reef effect is better.
