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Impact of finite-range tensor terms in the Gogny force on theβ-decay of magic nuclei

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Nuclear Science and Techniques 2021年第7期32卷 83-89页

作者： Da-Zhuang Chen dong-liang fang Chun-Lin Bai College of Physics Sichuan UniversityChengdu 610065China Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China

Effects of finite-range tensor force onβ-decay of magic and semimagic nuclei of^(34)Si,^(68,78)Ni,and^(132)Sn have been investigated using the self-consistent Hartree–Fock plus random-phase approximation *** tensor force shifts the low-lying Gamow–Teller states downward and systematically improves the calculations of Q and logft ***,it systematically reduces the deviations between the theoretical and experimental data and significantly improves the calculation ofβ-decay *** effect is similar to that of zero-range tensor force.

关键词： tensor decay finite

2νββ-decay to first 2^+states with partial isospin symmetry restoration from spherical QRPA calculations

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Chinese Physics C 2020年第8期44卷 139-146页

作者： dong-liang fang Amand Faessler Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China Center for Theoretical Physics Jilin UniversityChangchun 130012China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China Institute for Theoretical Physics Tuebingen UniversityD-72076Germany

Using partially restored isospin symmetry,we calculate the nuclear matrix elements for a special decay mode of a two-neutrino double beta decay–the decay to the first 2+excited *** the realistic CD–Bonn nuclear force,we analyze the dependence of the nuclear matrix elements on the isovector and isoscalar parts of proton–neutron particle–particle *** dependence on the different nuclear matrix elements is observed,and the results are *** also provide the phase space factors using numerical electron wavefunctions and properly chosen excitation ***,we present our results for the half-lives of this decay mode for different nuclei.

关键词： double beta decay quasi-particle random phase approximation nuclear matrix element

Calculation of microscopic nuclear level densities based on covariant density functional theory

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Nuclear Science and Techniques 2023年第9期34卷 118-127页

作者： Kun-Peng Geng Peng-Xiang Du Jian Li dong-liang fang College of Physics Jilin UniversityChangchun 130012China Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China

In this study,a microscopic method for calculating the nuclear level density(NLD)based on the covariant density functional theory(CDFT)is *** particle-hole state density is calculated by a combinatorial method using single-particle level schemes obtained from the CDFT,and the level densities are then obtained by considering collective effects such as vibration and *** results are compared with those of other NLD models,including phenomenological,microstatisti-cal and nonrelativistic Hartree–Fock–Bogoliubov combinatorial *** comparison suggests that the general trends among these models are essentially the same,except for some deviations among the different NLD *** addition,the NLDs obtained using the CDFT combinatorial method with normalization are compared with experimental data,including the observed cumulative number of levels at low excitation energies and the measured *** CDFT combinatorial method yields results that are in reasonable agreement with the existing experimental data.

关键词： Nuclear level density Covariant density functional theory Combinatorial method

Experimental investigation of turbulent flows around high-rise structure foundations and implications on scour

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Water Science and Engineering 2022年第1期15卷 47-56页

作者： dong-fang liang Hao Jia Yang Xiao Sai-yu Yuan Department of Engineering University of CambridgeCambridge CB21PZUK State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai UniversityNanjing 210098China Yangtze Institute for Conservation and Development Hohai UniversityNanjing 210098China

Many studies have been undertaken to predict local scour around offshore high-rise structure foundations(HRSFs),which have been used in constructing the donghai Wind Farm in ***,there have been few works on the turbulent flow that drives the scour *** this study,the characteristics of the turbulent flow fields around an HRSF were investigated using the particle image velocimetry *** mean flow,vorticity,and turbulence intensity were analyzed in *** relationship between the flow feature and scour development around an HRSF was *** results showed that the flow velocity increased to its maximum value near the third row of the pile *** shear layer and wake vortices could not be fully developed downstream of the last row of the piles at small Reynolds *** strong flow and turbulent fluctuation near the third piles explained the existence of a longtail scour pattern starting from the HRSF shoulders and a trapezoidal deposition region directly downstream of *** laboratory experiment gains insight into the mechanism of the turbulent flow around HRSFs and provides a rare dataset for numerical model verifications.

关键词： High-rise structure foundations(HRSFs) Turbulent flow fields Particle image velocimetry(PIV) Scour Sediment transport

What can we learn from recent 2νββexperiments?

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Chinese Physics C 2024年第3期48卷 93-103页

作者：房栋梁 Institute of Modern Physics Chinese Academy of sciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China

Recent measurements of the two neutrino double beta decay high precision electron spectra,combined with charge exchange orβ-decay experimental data,have revealed severe constraints across current nuclear many body *** calculations show that the quasi-particle random phase approximation(QRPA)approach can adequately reproduce the measured spectra for the two open shell nuclei,^(82)Se and ^(100)*** the closed shell nucleus ^(136)Xe,QRPA can also reproduce the spectra with proper *** the high-lying state reduction,we also find that the nuclear shell model can also adequately reproduce the spectra and Gamow-Teller transition strength under a unique quenched axial-vector coupling constant *** ^(136)Xe,we find that flipping the sign for the decay strength causes the spectra to go beyond the so-called high-lying state dominance *** results call for future high precision measurements of charge-exchange reactions.

关键词： nuclear stucture double beta decay electron spectra

Wave propagation speeds and source term influences in single and integral porosity shallow water equations

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Water Science and Engineering 2017年第4期10卷 275-286页

作者： Ilhan Ozgen Jia-heng Zhao dong-fang liang Reinhard Hinkelmann Department of Civil Engineering Technische Universitat BerlinBerlin 13355Germany Department of Engineering University of CambridgeCambridge CB2 1PZUK

In urban flood modeling,so-called porosity shallow water equations(PSWEs),which conceptually account for unresolved structures, e.g.,buildings, are a promising approach to addressing high CPU times associated with state-of-the-art explicit numerical methods. The PSWE can be formulated with a single porosity term, referred to as the single porosity shallow water model(SP model), which accounts for both the reduced storage in the cell and the reduced conveyance, or with two porosity terms: one accounting for the reduced storage in the cell and another accounting for the reduced conveyance. The latter form is referred to as an integral or anisotropic porosity shallow water model(AP model). The aim of this study was to analyze the differences in wave propagation speeds of the SP model and the AP model and the implications of numerical model results. First, augmented Roe-type solutions were used to assess the influence of the source terms appearing in both models. It is shown that different source terms have different influences on the stability of the models. Second, four computational test cases were presented and the numerical models were compared. It is observed in the eigenvalue-based analysis as well as in the computational test cases that the models converge if the conveyance porosity in the AP model is close to the storage porosity. If the porosity values differ significantly, the AP model yields different wave propagation speeds and numerical fluxes from those of the BP model. In this study, the ratio between the conveyance and storage porosities was determined to be the most significant parameter.

关键词： Porosity Macroscopic modeling of urban flooding Wave propagation speed Godunov flux Single porosity shallow water model Anisotropic porosity

Comparison of depth-averaged concentration and bed load flux sediment transport models of dam-break flow

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Water Science and Engineering 2017年第4期10卷 287-294页

作者： Jia-heng Zhao Ilhan Ozgen dong-fang liang Reinhard Hinkelmann Department of Civil Engineering Technische Universitat BerlinBerlin 13355Germany Department of Engineering University of CambridgeCambridge CB2 1PZUK

This paper presents numerical simulations of dam-break flow over a movable bed. Two different mathematical models were compared: a fully coupled formulation of shallow water equations with erosion and deposition terms(a depth-averaged concentration flux model), and shallow water equations with a fully coupled Exner equation(a bed load flux model). Both models were discretized using the cell-centered finite volume method, and a second-order Godunov-type scheme was used to solve the equations. The numerical flux was calculated using a Harten, Lax, and van Leer approximate Riemann solver with the contact wave restored(HLLC). A novel slope source term treatment that considers the density change was introduced to the depth-averaged concentration flux model to obtain higher-order accuracy. A source term that accounts for the sediment flux was added to the bed load flux model to reflect the influence of sediment movement on the momentum of the water. In a onedimensional test case, a sensitivity study on different model parameters was carried out. For the depth-averaged concentration flux model,Manning's coefficient and sediment porosity values showed an almost linear relationship with the bottom change, and for the bed load flux model, the sediment porosity was identified as the most sensitive parameter. The capabilities and limitations of both model concepts are demonstrated in a benchmark experimental test case dealing with dam-break flow over variable bed topography.

关键词： Shallow water Sediment transport Bed load flux model Depth-averaged concentration flux model Dam break

THERMAL IMAGING STUDY OF SCALAR TRANSPORT IN SHALLOW WAKES

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Journal of Hydrodynamics 2012年第1期24卷 17-24页

作者： CHONG K.J.Y UKTHUSYANTHAN N.I. liang dong-fang TANG Hong-wu Department of Engineering University of CambridgeCambridge KW Ltd FetchamSurreyUK College of Water Conservancy and I tydropowcr Engineering Hohai University Nanjing 210098 China

The thermal imaging technique relies on the usage of infrared signal to detect the temperature *** temperature as a flow tracer,thermography is used to investigate the scalar transport in the shallow-water wake generated by an emergent circular *** imaging is demonstrated to be a good quantitative flow visualization technique for studying turbulent mixing phenomena in shallow waters.A key advantage of the thermal imaging method over other scalar measurement techniques,such as the Laser Induced Fluorescence（LIF）and Planar Concentration Analysis（PCA）methods,is that it involves a very simple experimental *** dispersion characteristics captured with this technique are found to be similar to past studies with traditional measurement techniques.

关键词： environmental hydraulics shallow wake turbulent mixing thermal imaging vortex street

Characteristics of phosphorus adsorption by sediment mineral matrices with different particle sizes

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Water Science and Engineering 2013年第3期6卷 262-271页

作者： Yang XIAO Xiao-lian ZHU Hao-ke CHENG Kai-jie LI Qi LU dong-fang liang State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University College of Water Conservancy and Hydropower Engineering Hohai University National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety Hohai University Department of Engineering Mechanics Shanghai Jiao Tong University MOE Key Laboratory of Hydrodynamics Shanghai Jiao Tong University

The particle size of sediment is one of the main factors that influence the phosphorus physical adsorption on sediment. In order to eliminate the effect of other components of sediment on the phosphorus physical adsorption, the sediment mineral matrices were obtained by removing inorganic matter, metal oxides, and organic matter from natural sediments, which were collected from the Nantong reach of the Yangtze River. The results show that an exponential relationship exists between the median particle size （Ds0） and specific surface area （Sg） of the sediment mineral matrices, and the fine sediment mineral matrix sample has a larger specific surface area and pore volume than the coarse sediment particles. The kinetic equations were used to describe the phosphorus adsorption process of the sediment mineral matrices, including the Elovich equation, quasi-first-order adsorption kinetic equation, and quasi-second-order adsorption kinetic equation. The results show that the quasi-second-order adsorption kinetic equation has the best fitting effect. Using the mass conservation and Langmuir adsorption kinetic equations, a formula was deduced to calculate the equilibrium adsorption capacity of the sediment mineral matrices. The results of this study show that the phosphorus adsorption capacity decreases with the increase of Ds0, indicating that the specific surface area and pore volume are the main factors in determining the phosphorus adsorption capacity of the sediment mineral matrices. This study will help understand the important role of sediment in the transformation of phosphorus in aquatic environments.

关键词： sediment mineral matrix " particle size " specific surface area " pore volume phosphorus adsorption