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SARS疫情分析及对北京疫情走势的预测 总被引:5,自引:0,他引:5
在考虑每个SARS病人每日平均传染概率和他的直接传染的平均期限的基础上,建立了一个统计分析模型.分析表明,每个病人可以造成直接感染他人的期限平均在20天左右,这个值在不同地区和不同疫情阶段似乎变化不大.病人的平均每天感染率与社会状况有关,在疫情爆发期较大,在疫情控制期要小很多.北京后期如果控制在香港后期的感染率水平上,则有望在6月上中旬下降到日增几例.然后再经过约一个月,即7月上中旬达到日增0病例,而累积总病例数将达到3100多.但如果北京的新病例下降速度与广东类似的话,则要再多花至少一个月,才能达到上述的效果,且累积总病例数会达到3800左右. 相似文献
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Measurement of One— and Two—Neutron Transfers in Reaction of ^6He+^9Be at 25MeV/u 总被引:1,自引:0,他引:1 下载免费PDF全文
葛愉成叶沿林 郑涛王全进 李智焕李湘庆 江栋兴A.Ozawa Y.Yamaguchi C.Wu R.Kanungo D.Fang I.Tanihata 《中国物理快报》2003,20(7):1034-1037
The cross sections one-and two-neutron transfers induced by 6He at 25MeV/u on a^9Be target were measured in RIKEN.Clear identification of the recoiled Be isotopes was achieved.In total five 11Be and 371 ^10Be events,the corresponding two-and one-neutron transfers were obtained and analysed for transfer reaction cross sections.The results are useful to determine the spectroscopic factors of the internal halo structure of the 6He nucleus. 相似文献
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段芳芳 杨彦云 庞丹阳 胡碧涛 王建松 王康 杨过 Valdir Guimar?es 马朋 许世伟 刘星泉 马军兵 白真 胡强 金树亚 孙欣欣 姚佳盛 齐航凯 孙志宇 《中国物理C(英文版)》2020,(2):72-79
Elastic scattering of 10Be on a 208Pb target was measured at ELab=127 MeV,which corresponds to three times the Coulomb barrier.The secondary 10Be beam was produced at the Radioactive Ion Beam Line in Lanzhou of the Heavy-Ion Research Facility in Lanzhou.The angular distribution of elastic scattering in the 10 Be+208Pb system shows a typical Fresnel diffraction peak.Optical model analysis of the angular distribution was performed using the Woods-Saxon,double-folding and global potentials.With the global potential,different density distributions were used.The results indicate that different density distributions for the projectile induce distinct effects in the angular distribution. 相似文献
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张高龙 叶沿林 江栋兴 郑涛 李智焕 李湘庆 吴翠娥 陈志强 胡青元 庞丹阳 王佳 A.Ozawa Y.Yamaguchi R.Kanungo D.Fang I.Tanihata 《中国物理 C》2005,29(10):940-943
在25MeV/u 6He轰击9Be靶的反应中,用探测器望远镜测得氚碎片,得到了5个角度的能谱,经过仔细的分析取得了高能直接破碎成分的角分布.利用Serber模型进行了破碎反应的理论计算,证实了实验中高能成分的t来自于6He的直接破碎反应.利用Fermi破碎模型计算了6He中各破碎反应道基于相空间的百分比产额,进而估算出6He初态中t+t结构的概率约占1/3, 而4He核心加价中子的组态约占2/3. 相似文献
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One resistive plate chamber made of Chinese materials and one Italian resistive plate chamber have been tested in the Gamma
Irradiation Facility (GIF) at CERN on a high intensity muon beam together with a137Cs source to give a uniform photon background, and simulating conditions close to those expected for an LHC muon detector.
The results are analyzed. Good space and time resolutions are obtained which satisfy the future CMS experiment requirements.
The detection efficiency is different between two RPCs against a high irradiation background. The reason is discussed. 相似文献
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The nuclear potentials between protons and different target nuclei are calculated by using the single folding model with the density-dependent nucleon-nucleon interaction.The fusion barrier heights and positions for proton projectiles fusing with different target nuclei with masses from 51 amu to 139 amu are systematically shown,with charge numbers and root-mean-square radii of the interacting nuclei.The parameterized formulas for the fusion barrier height and position are obtained for proton projectile fusing with the different nuclei.The calculated results of parameterized formulas are compared to empirical values,as well as those of the proximity potential and AkyüzWinther(AW) potential.It is shown that the calculated results agree perfectly with theirs.The parameterized formulas can reproduce the exact barrier heights and positions for proton fusion systems. 相似文献