Ice krill is the keystone species in the neritic ecosystem in the Southern Ocean,where it replaces the more oceanic Antarctic krill. It is essential to understand the variation of target strength(TS in d B re 1 m 2) w...Ice krill is the keystone species in the neritic ecosystem in the Southern Ocean,where it replaces the more oceanic Antarctic krill. It is essential to understand the variation of target strength(TS in d B re 1 m 2) with the different body size to accurately estimate ice krill stocks. However,there is comparatively little knowledge of the acoustic backscatter of ice krill. The TS of individual,formalin-preserved,tethered ice krill was measured in a freshwater test tank at 38,120,and 200 k Hz with a calibrated split-beam echo sounder system. Mean TS was obtained from 21 individual ice krill with a broad range of body lengths(L :13–36 mm). The length( L,mm) to wet weight( W; mg) relationship for ice krill was W =0.001 218×103 × L 3.53( R 2= 0.96). The mean TS-to-length relationship were TS3 8 k Hz =-177.4+57log 10( L),( R 2 = 0.86); TS 120 k Hz =-129.9+31.56 log 10( L),( R 2 =0.87); and TS 200 k Hz =-117.6+24.66log1 0( L),( R 2 =0.84). Empirical estimates of the relationship between the TS and body length of ice krill were established at 38,120,and 200 k Hz and compared with predictions obtained from both the linear regression model of Greene et al.(1991) and the Stochastic Distorted Wave Born Approximation(SDWBA) model. This result might be applied to improve acoustic detection and density estimation of ice krill in the Southern Ocean. Further comparative studies are needed with in situ target strength including various body lengths of ice krill.展开更多
94Zr的中子谱因子可用于研究93Zr(n,γ)94Zr直接辐射俘获反应的激发函数和天体物理反应率,对研究s-过程的核合成有重要意义。现有的94Zr中子谱因子实验结果仍存在较大的差异。本工作在北京HI-13串列加速器Q3D磁谱仪上测量了12C+94Zr、13...94Zr的中子谱因子可用于研究93Zr(n,γ)94Zr直接辐射俘获反应的激发函数和天体物理反应率,对研究s-过程的核合成有重要意义。现有的94Zr中子谱因子实验结果仍存在较大的差异。本工作在北京HI-13串列加速器Q3D磁谱仪上测量了12C+94Zr、13C+94Zr弹性散射反应及94Zr(12C,13C)93Zr单中子转移反应的角分布。通过对弹性散射角分布的仔细分析,拟合出了入射道和出射道的光学势参数,并结合扭曲波玻恩近似(Distorted wave Born approximation,DWBA)理论对转移反应的微分截面进行了理论分析,提取出94Zr的中子谱因子为2.60±0.20。展开更多
基金Supported by the Korea Polar Research Institute(No.PP14020)the Korea Institute of Ocean Science and Technology(No.PN65250)
文摘Ice krill is the keystone species in the neritic ecosystem in the Southern Ocean,where it replaces the more oceanic Antarctic krill. It is essential to understand the variation of target strength(TS in d B re 1 m 2) with the different body size to accurately estimate ice krill stocks. However,there is comparatively little knowledge of the acoustic backscatter of ice krill. The TS of individual,formalin-preserved,tethered ice krill was measured in a freshwater test tank at 38,120,and 200 k Hz with a calibrated split-beam echo sounder system. Mean TS was obtained from 21 individual ice krill with a broad range of body lengths(L :13–36 mm). The length( L,mm) to wet weight( W; mg) relationship for ice krill was W =0.001 218×103 × L 3.53( R 2= 0.96). The mean TS-to-length relationship were TS3 8 k Hz =-177.4+57log 10( L),( R 2 = 0.86); TS 120 k Hz =-129.9+31.56 log 10( L),( R 2 =0.87); and TS 200 k Hz =-117.6+24.66log1 0( L),( R 2 =0.84). Empirical estimates of the relationship between the TS and body length of ice krill were established at 38,120,and 200 k Hz and compared with predictions obtained from both the linear regression model of Greene et al.(1991) and the Stochastic Distorted Wave Born Approximation(SDWBA) model. This result might be applied to improve acoustic detection and density estimation of ice krill in the Southern Ocean. Further comparative studies are needed with in situ target strength including various body lengths of ice krill.
文摘94Zr的中子谱因子可用于研究93Zr(n,γ)94Zr直接辐射俘获反应的激发函数和天体物理反应率,对研究s-过程的核合成有重要意义。现有的94Zr中子谱因子实验结果仍存在较大的差异。本工作在北京HI-13串列加速器Q3D磁谱仪上测量了12C+94Zr、13C+94Zr弹性散射反应及94Zr(12C,13C)93Zr单中子转移反应的角分布。通过对弹性散射角分布的仔细分析,拟合出了入射道和出射道的光学势参数,并结合扭曲波玻恩近似(Distorted wave Born approximation,DWBA)理论对转移反应的微分截面进行了理论分析,提取出94Zr的中子谱因子为2.60±0.20。
