Ab initio modeling of dynamic structure factors(DSF)and related density response properties in the warm dense matter(WDM)regime is a challenging computational task.The DSF,convolved with a probing X-ray beam and instr...Ab initio modeling of dynamic structure factors(DSF)and related density response properties in the warm dense matter(WDM)regime is a challenging computational task.The DSF,convolved with a probing X-ray beam and instrument function,is measured in X-ray Thom-son scattering(XRTS)experiments,which allow the study of electronic structure properties at the microscopic level.Among the various ab initio methods,linear-response time-dependent density-functional theory(LR-TDDFT)is a key framework for simulating the DSF.The standard approach in LR-TDDFT for computing the DSF relies on the orbital representation.A significant drawback of this method is the unfavorable scaling of the number of required empty bands as the wavenumber increases,making LR-TDDFT impractical for modeling XRTS measurements over large energy scales,such as in backward scattering geometry.In this work,we consider and test an alternative approach to LR-TDDFT that employs the Liouville–Lanczos(LL)method for simulating the DSF of WDM.This approach does not require empty states and allows the DSF at large momentum transfer values and over a broad frequency range to be accessed.We compare the results obtained from the LL method with those from the solution of Dyson’s equation using the standard LR-TDDFT within the projector augmented-wave formalism for isochorically heated aluminum and warm dense hydrogen.Additionally,we utilize exact path integral Monte Carlo results for the imaginary-time density-density correlation function(ITCF)of warm dense hydrogen to rigorously benchmark the LL approach.We discuss the application of the LL method for calculating DSFs and ITCFs at different wavenumbers,the effects of pseudopotentials,and the role of Lorentzian smearing.The successful validation of the LL method under WDM conditions makes it a valuable addition to the ab initio simulation landscape,supporting experimental efforts and advancing WDM theory.展开更多
Volterra series is a powerful mathematical tool for nonlinear system analysis,and there is a wide range of nonlinear engineering systems and structures that can be represented by a Volterra series model.In the present...Volterra series is a powerful mathematical tool for nonlinear system analysis,and there is a wide range of nonlinear engineering systems and structures that can be represented by a Volterra series model.In the present study,the random vibration of nonlinear systems is investigated using Volterra series.Analytical expressions were derived for the calculation of the output power spectral density（PSD） and input-output cross-PSD for nonlinear systems subjected to Gaussian excitation.Based on these expressions,it was revealed that both the output PSD and the input-output crossPSD can be expressed as polynomial functions of the nonlinear characteristic parameters or the input intensity.Numerical studies were carried out to verify the theoretical analysis result and to demonstrate the effectiveness of the derived relationship.The results reached in this study are of significance to the analysis and design of the nonlinear engineering systems and structures which can be represented by a Volterra series model.展开更多
Traditional computing method is inefficient for getting key dynamical parameters of complicated structure.Pseudo Excitation Method（PEM）is an effective method for calculation of random vibration.Due to complicated an...Traditional computing method is inefficient for getting key dynamical parameters of complicated structure.Pseudo Excitation Method（PEM）is an effective method for calculation of random vibration.Due to complicated and coupling random vibration in rocket or shuttle launching,the new staging white noise mathematical model is deduced according to the practical launch environment.This deduced model is applied for PEM to calculate the specific structure of Time of Flight Counter（ToFC）.The responses of power spectral density and the relevant dynamic characteristic parameters of ToFC are obtained in terms of the flight acceptance test level.Considering stiffness of fixture structure,the random vibration experiments are conducted in three directions to compare with the revised PEM.The experimental results show the structure can bear the random vibration caused by launch without any damage and key dynamical parameters of ToFC are obtained.The revised PEM is similar with random vibration experiment in dynamical parameters and responses are proved by comparative results.The maximum error is within 9%.The reasons of errors are analyzed to improve reliability of calculation.This research provides an effective method for solutions of computing dynamical characteristic parameters of complicated structure in the process of rocket or shuttle launching.展开更多
Background:High liver fat content(LFC)induces increased risks of both hepatic and extrahepatic progression in metabolic dysfunction-associated steatotic liver disease(MASLD),while maintaining a significant decline in ...Background:High liver fat content(LFC)induces increased risks of both hepatic and extrahepatic progression in metabolic dysfunction-associated steatotic liver disease(MASLD),while maintaining a significant decline in magnetic resonance imaging-based proton density fat fraction(MRI-PDFF)(≥30%decline relative to baseline)without worsening fibrosis results in improved histological severity and prognosis.However,the factors associated with the loss of sustained responses to treatment remain unclear,and we aim to identify them.Methods:Consecutive treatment-naïve MASLD patients between January 2015 and February 2022,with follow-up until April 2023,were included in this prospective cohort study.LFC quantified by MRI-PDFF and liver stiffness measurements(LSM)determined by two-dimensional shear wave elastography(2D-SWE)were evaluated at weeks 0,24 and 48.MRI-PDFF response was defined as a≥30%relative decline in PDFF values,and LSM response was defined as a≥1 stage decline from baseline.Results:A total of 602 MASLD patients were enrolled.Of the 303 patients with a 24-week MRI-PDFF response and complete follow-up of 48 weeks,the rate of loss of MRI-PDFF response was 29.4%,and multivariable logistic regression analyses showed that 24-week insulin resistance(IR),still regular exercise and caloric restriction after 24 weeks,and the relative decline in LFC were risk factors for loss of MRI-PDFF response.Loss of LSM response at 48 weeks occurred in 15.9%of patients,and multivariable analysis confirmed 24-week serum total bile acid(TBA)levels and the relative decline in TBA from baseline as independent predictors.No significant association was found at 48 weeks between loss of MRI-PDFF response and loss of LSM response.Conclusions:MASLD patients with IR and high TBA levels are at higher risks of subsequent diminished sustained improvements of steatosis and fibrosis,respectively.展开更多
基金supported by the Center for Advanced Systems Understanding(CASUS),financed by Germany’s Federal Ministry of Education and Research(BMBF)and the Saxon State Government out of the State Budget approved by the Saxon State Parliamentfunding from the European Research Council(ERC)under the European Union’s Horizon 2022 research and innovation programme(Grant Agreement No.101076233,“PREXTREME”)funding from the European Union’s Just Transition Fund(JTF)within the project Röntgenlaser-Optimierung der Laserfusion(ROLF),Contract No.5086999001,co-financed by the Saxon State Government out of the State Budget approved by the Saxon State Parliament.
文摘Ab initio modeling of dynamic structure factors(DSF)and related density response properties in the warm dense matter(WDM)regime is a challenging computational task.The DSF,convolved with a probing X-ray beam and instrument function,is measured in X-ray Thom-son scattering(XRTS)experiments,which allow the study of electronic structure properties at the microscopic level.Among the various ab initio methods,linear-response time-dependent density-functional theory(LR-TDDFT)is a key framework for simulating the DSF.The standard approach in LR-TDDFT for computing the DSF relies on the orbital representation.A significant drawback of this method is the unfavorable scaling of the number of required empty bands as the wavenumber increases,making LR-TDDFT impractical for modeling XRTS measurements over large energy scales,such as in backward scattering geometry.In this work,we consider and test an alternative approach to LR-TDDFT that employs the Liouville–Lanczos(LL)method for simulating the DSF of WDM.This approach does not require empty states and allows the DSF at large momentum transfer values and over a broad frequency range to be accessed.We compare the results obtained from the LL method with those from the solution of Dyson’s equation using the standard LR-TDDFT within the projector augmented-wave formalism for isochorically heated aluminum and warm dense hydrogen.Additionally,we utilize exact path integral Monte Carlo results for the imaginary-time density-density correlation function(ITCF)of warm dense hydrogen to rigorously benchmark the LL approach.We discuss the application of the LL method for calculating DSFs and ITCFs at different wavenumbers,the effects of pseudopotentials,and the role of Lorentzian smearing.The successful validation of the LL method under WDM conditions makes it a valuable addition to the ab initio simulation landscape,supporting experimental efforts and advancing WDM theory.
基金supported by the National Science Fund for Distinguished Young Scholars (11125209)the National Natural Science Foundation of China (10902068,51121063 and 10702039)+1 种基金the Shanghai Pujiang Program (10PJ1406000)the Opening Project of State Key Laboratory of Mechanical System and Vibration (MSV201103)
文摘Volterra series is a powerful mathematical tool for nonlinear system analysis,and there is a wide range of nonlinear engineering systems and structures that can be represented by a Volterra series model.In the present study,the random vibration of nonlinear systems is investigated using Volterra series.Analytical expressions were derived for the calculation of the output power spectral density（PSD） and input-output cross-PSD for nonlinear systems subjected to Gaussian excitation.Based on these expressions,it was revealed that both the output PSD and the input-output crossPSD can be expressed as polynomial functions of the nonlinear characteristic parameters or the input intensity.Numerical studies were carried out to verify the theoretical analysis result and to demonstrate the effectiveness of the derived relationship.The results reached in this study are of significance to the analysis and design of the nonlinear engineering systems and structures which can be represented by a Volterra series model.
基金Supported by National Natural Science Foundation of China(Grant No.51105025)International Science & Technology Cooperation Program of China(Grant No.2013DFB70110)
文摘Traditional computing method is inefficient for getting key dynamical parameters of complicated structure.Pseudo Excitation Method（PEM）is an effective method for calculation of random vibration.Due to complicated and coupling random vibration in rocket or shuttle launching,the new staging white noise mathematical model is deduced according to the practical launch environment.This deduced model is applied for PEM to calculate the specific structure of Time of Flight Counter（ToFC）.The responses of power spectral density and the relevant dynamic characteristic parameters of ToFC are obtained in terms of the flight acceptance test level.Considering stiffness of fixture structure,the random vibration experiments are conducted in three directions to compare with the revised PEM.The experimental results show the structure can bear the random vibration caused by launch without any damage and key dynamical parameters of ToFC are obtained.The revised PEM is similar with random vibration experiment in dynamical parameters and responses are proved by comparative results.The maximum error is within 9%.The reasons of errors are analyzed to improve reliability of calculation.This research provides an effective method for solutions of computing dynamical characteristic parameters of complicated structure in the process of rocket or shuttle launching.
基金National Natural Science Foundation of China(grant Nos.81870404 and 82100648)Natural Science Foundation of Guangdong Province,China(grant Nos.2021A1515011442 and 2022A1515012369)China Postdoctoral Science Foundation(grant No.2020M683128).
文摘Background:High liver fat content(LFC)induces increased risks of both hepatic and extrahepatic progression in metabolic dysfunction-associated steatotic liver disease(MASLD),while maintaining a significant decline in magnetic resonance imaging-based proton density fat fraction(MRI-PDFF)(≥30%decline relative to baseline)without worsening fibrosis results in improved histological severity and prognosis.However,the factors associated with the loss of sustained responses to treatment remain unclear,and we aim to identify them.Methods:Consecutive treatment-naïve MASLD patients between January 2015 and February 2022,with follow-up until April 2023,were included in this prospective cohort study.LFC quantified by MRI-PDFF and liver stiffness measurements(LSM)determined by two-dimensional shear wave elastography(2D-SWE)were evaluated at weeks 0,24 and 48.MRI-PDFF response was defined as a≥30%relative decline in PDFF values,and LSM response was defined as a≥1 stage decline from baseline.Results:A total of 602 MASLD patients were enrolled.Of the 303 patients with a 24-week MRI-PDFF response and complete follow-up of 48 weeks,the rate of loss of MRI-PDFF response was 29.4%,and multivariable logistic regression analyses showed that 24-week insulin resistance(IR),still regular exercise and caloric restriction after 24 weeks,and the relative decline in LFC were risk factors for loss of MRI-PDFF response.Loss of LSM response at 48 weeks occurred in 15.9%of patients,and multivariable analysis confirmed 24-week serum total bile acid(TBA)levels and the relative decline in TBA from baseline as independent predictors.No significant association was found at 48 weeks between loss of MRI-PDFF response and loss of LSM response.Conclusions:MASLD patients with IR and high TBA levels are at higher risks of subsequent diminished sustained improvements of steatosis and fibrosis,respectively.
