This study investigates seismic interferometry in which the Green＇s function is estimated between two receiv- ers by cross-correlation and integration over sources. For smoothly varying source strengths, the dominant...This study investigates seismic interferometry in which the Green＇s function is estimated between two receiv- ers by cross-correlation and integration over sources. For smoothly varying source strengths, the dominant contributions of the correlation integral come from the stationary phase directions in the forward and backward directions from the alignment of the two receivers. Gaussian beams can be used to evaluate the correlation integral and concentrate the amplitudes in a vicinity of the stationary phase regions instead of completely relying on phase interference. Several numerical examples are shown to illustrate how this process works. The use of Gaussian beams for the evaluation of the correlation integral results in stable estimates, and also provides physical insight into the estimation of the Green＇s function based on seismic interferometry.展开更多
Within the framework of the Ultra-relativistic Quantum Molecular Dynamics model,the effects of resonance decay widths,inmedium nucleon-nucleon(in)elastic cross sections,and potentials on the pion Hanbury-Brown-Twiss(H...Within the framework of the Ultra-relativistic Quantum Molecular Dynamics model,the effects of resonance decay widths,inmedium nucleon-nucleon(in)elastic cross sections,and potentials on the pion Hanbury-Brown-Twiss(HBT)intensity interferometry in central Au+Au collisions at Ebeam=1.23 GeV/nucleon are investigated.The results show that the pion emission source is visibly influenced by theΔparticles with small invariant masses,i.e.,with long resonance lifetimes.Furthermore,the pion HBT radii are found to be insensitive to the nucleon-nucleon(in)elastic cross sections,while the measured rapidity distributions of the charged pions are sensitive to the nucleon-nucleon(in)elastic cross sections and can be much better reproduced by considering a reduction factor on the nucleon-nucleon inelastic cross sections.The observed charge-sign difference of the source radii,especially in outward and sideward directions,can be qualitatively explained by simulations with the potential contributions,especially including the Coulomb potential of mesons.The present work demonstrates that the potential updates play important roles in describing the measured HBT radii and duration-time-related radii ratios when understanding the dynamics in relativistic heavy-ion collisions at~GeV beam energies.展开更多
G/T是天线的一项重要技术指标,在综合考虑测地VLBI(Very Long Baseline Interferometry,甚长基线干涉测量)和航天器VLBI观测两者需求的基础上,提出了深空干涉测量天线的G/T指标设计方法。首先根据射电源的空间分布以及流量密度特性,确...G/T是天线的一项重要技术指标,在综合考虑测地VLBI(Very Long Baseline Interferometry,甚长基线干涉测量)和航天器VLBI观测两者需求的基础上,提出了深空干涉测量天线的G/T指标设计方法。首先根据射电源的空间分布以及流量密度特性,确定了测地VLBI和航天器VLBI观测模式下射电源流量密度的要求。在此基础上建立了2种观测模式下时延误差与深空干涉测量天线G/T之间的关系模型。最后参考目前国际国内测地VLBI观测中的通用参数设置以及月球探测任务中航天器VLBI观测的参数设置,对不同观测任务、不同观测模式下的G/T要求进行仿真分析。综合测地VLBI和航天器VLBI观测仿真分析的结果,S频段G/T建议不小于32dB/K,X频段G/T建议不小于43dB/K。仿真分析结果可以作为后续深空干涉测量天线G/T设计的参考。展开更多
基金supported by U.S. National Science Foundation EAR06-35611U.S. Air Force contract FA8718-08-C-002the members of the Geo-Mathematical Imaging Group (GMIG) at Purdue University
文摘This study investigates seismic interferometry in which the Green＇s function is estimated between two receiv- ers by cross-correlation and integration over sources. For smoothly varying source strengths, the dominant contributions of the correlation integral come from the stationary phase directions in the forward and backward directions from the alignment of the two receivers. Gaussian beams can be used to evaluate the correlation integral and concentrate the amplitudes in a vicinity of the stationary phase regions instead of completely relying on phase interference. Several numerical examples are shown to illustrate how this process works. The use of Gaussian beams for the evaluation of the correlation integral results in stable estimates, and also provides physical insight into the estimation of the Green＇s function based on seismic interferometry.
基金supported by the National Natural Science Foundation of China(Grant Nos.11875125,12075085,U2032145,12175170,and12147219)the National Key Research and Development Program of China(Grant No.2020YFE0202002)the financial support from China Scholarship Council(Grant No.202106180053)。
文摘Within the framework of the Ultra-relativistic Quantum Molecular Dynamics model,the effects of resonance decay widths,inmedium nucleon-nucleon(in)elastic cross sections,and potentials on the pion Hanbury-Brown-Twiss(HBT)intensity interferometry in central Au+Au collisions at Ebeam=1.23 GeV/nucleon are investigated.The results show that the pion emission source is visibly influenced by theΔparticles with small invariant masses,i.e.,with long resonance lifetimes.Furthermore,the pion HBT radii are found to be insensitive to the nucleon-nucleon(in)elastic cross sections,while the measured rapidity distributions of the charged pions are sensitive to the nucleon-nucleon(in)elastic cross sections and can be much better reproduced by considering a reduction factor on the nucleon-nucleon inelastic cross sections.The observed charge-sign difference of the source radii,especially in outward and sideward directions,can be qualitatively explained by simulations with the potential contributions,especially including the Coulomb potential of mesons.The present work demonstrates that the potential updates play important roles in describing the measured HBT radii and duration-time-related radii ratios when understanding the dynamics in relativistic heavy-ion collisions at~GeV beam energies.
文摘G/T是天线的一项重要技术指标,在综合考虑测地VLBI(Very Long Baseline Interferometry,甚长基线干涉测量)和航天器VLBI观测两者需求的基础上,提出了深空干涉测量天线的G/T指标设计方法。首先根据射电源的空间分布以及流量密度特性,确定了测地VLBI和航天器VLBI观测模式下射电源流量密度的要求。在此基础上建立了2种观测模式下时延误差与深空干涉测量天线G/T之间的关系模型。最后参考目前国际国内测地VLBI观测中的通用参数设置以及月球探测任务中航天器VLBI观测的参数设置,对不同观测任务、不同观测模式下的G/T要求进行仿真分析。综合测地VLBI和航天器VLBI观测仿真分析的结果,S频段G/T建议不小于32dB/K,X频段G/T建议不小于43dB/K。仿真分析结果可以作为后续深空干涉测量天线G/T设计的参考。
