The China high speed railway vehicles of type CRH2 and type CRH3, modeled on Japanese high speed Electric Multiple Units (EMU) E2 series and Euro high speed EMU ICE3 series possess different stability behaviors due to...The China high speed railway vehicles of type CRH2 and type CRH3, modeled on Japanese high speed Electric Multiple Units (EMU) E2 series and Euro high speed EMU ICE3 series possess different stability behaviors due to the different matching re-lations between bogie parameters and wheel profiles. It is known from the field tests and roller rig tests that, the former has a higher critical speed while large limit cycle oscillation appears if instability occurs, and the latter has lower critical speed while small limit cycle appears if instability occurs. The dynamic model of the vehicle system including a semi-carbody and a bogie is established in this paper. The bifurcation diagrams of the two types of high speed vehicles are extensively studied. By using the method of normal form of Hopf bifurcation, it is found that the subcritical and supercritical bifurcations exist in the two types of vehicle systems. The influence of parameter variation on the exported function Rec1(0) in Hopf normal form is studied and numerical shooting method is also used for mutual verification. Furthermore, the bifurcation situation, subcritical or supercritical, is also discussed. The study shows that the sign of Re(λ) determinates the stability of linear system, and the sign of Rec1(0) determines the property of Hopf bifurcation with Rec1(0)】0 for supercritical and Rec1(0)【0 for subcritical.展开更多
目的探讨育龄期正常乳腺组织在不同月经周期下磁共振体素内不相干运动（IVIM）、扩散张量成像（DTI）及扩散加权成像（DWI）各参数值变化情况。方法共搜集26名健康女性志愿者,年龄22~30岁,平均26岁,规律月经周期,无口服避孕药史,未育。...目的探讨育龄期正常乳腺组织在不同月经周期下磁共振体素内不相干运动（IVIM）、扩散张量成像（DTI）及扩散加权成像（DWI）各参数值变化情况。方法共搜集26名健康女性志愿者,年龄22~30岁,平均26岁,规律月经周期,无口服避孕药史,未育。分别在月经期（第2天）、增生期（第7天）、卵泡期（第14天）、黄体期（第21天）、分泌期（第27天）进行了1个月经周期的MRI扫描,扫描序列包括T1WI、T2WI、DTI、DWI及IVIM。基于感兴趣区（ROI）的方法,由2名观察者分别在不同时间测量相同区域正常乳腺组织的真实扩散系数（D）、灌注相关扩散系数（D^＊）、血管容积分数（f）、各向异性分数（FA）及表观扩散系数（ADC）。结果采用3.0 T MR获得的IVIM、DTI、DWI乳腺图像具有较高的图像质量和分辨率,其参数图无严重伪影,图像质量较好,能满足参数测量要求。2名观察者分别所测得（观察者间）D值、D^＊值、FA值及ADC值可重复性好（ICC值〉0.8）,f值可重复性较差。正常乳腺的D^＊值显示随月经周期规律波动,在黄体期最高,与月经期和增殖期对比,有显著性差异（P〈0.01）;f值在卵泡期高于其他阶段,但是对比没有显著差异。D值和ADC值随月经周期有相似趋势,D值在黄体期和增殖期对比,差异具有统计学意义（P=0.005）;ADC值的差异在月经周期中无统计学意义。FA值在月经期与分泌期对比差异有统计学意义（P=0.034）。结论乳腺D值、D^＊值、FA值及ADC值可重复性好,可以敏感地反映乳腺组织随月经周期激素调节的变化特点。展开更多
Reciprocal translocation is a chromosomal structural abnormal- ity that arises when two non-homologous chromosomes rearrange and attach with each other, an incidence that occurs in about 1/500 to 1/625 newborns （Mack...Reciprocal translocation is a chromosomal structural abnormal- ity that arises when two non-homologous chromosomes rearrange and attach with each other, an incidence that occurs in about 1/500 to 1/625 newborns （Mackie and Scriven, 2002）. This event typically does not lead to any significant loss of genetic material, thus recip- rocal translocation carriers do not exhibit any severe abnormal phenotypes （Scriven et al., 1998; Zhang et al., 2016）.展开更多
基金supported by the National Basic Research Program of China ("973" Program) (Grant No. 2011CB711106)the National Key Technology R&D Program of China (Grant No. 2009BAG12A01)Southwest Jiaotong University 1st Outstanding Innovative Talents Fund and the Doctoral Student Innovation Fund of Southwest Jiaotong University
文摘The China high speed railway vehicles of type CRH2 and type CRH3, modeled on Japanese high speed Electric Multiple Units (EMU) E2 series and Euro high speed EMU ICE3 series possess different stability behaviors due to the different matching re-lations between bogie parameters and wheel profiles. It is known from the field tests and roller rig tests that, the former has a higher critical speed while large limit cycle oscillation appears if instability occurs, and the latter has lower critical speed while small limit cycle appears if instability occurs. The dynamic model of the vehicle system including a semi-carbody and a bogie is established in this paper. The bifurcation diagrams of the two types of high speed vehicles are extensively studied. By using the method of normal form of Hopf bifurcation, it is found that the subcritical and supercritical bifurcations exist in the two types of vehicle systems. The influence of parameter variation on the exported function Rec1(0) in Hopf normal form is studied and numerical shooting method is also used for mutual verification. Furthermore, the bifurcation situation, subcritical or supercritical, is also discussed. The study shows that the sign of Re(λ) determinates the stability of linear system, and the sign of Rec1(0) determines the property of Hopf bifurcation with Rec1(0)】0 for supercritical and Rec1(0)【0 for subcritical.
文摘目的探讨育龄期正常乳腺组织在不同月经周期下磁共振体素内不相干运动（IVIM）、扩散张量成像（DTI）及扩散加权成像（DWI）各参数值变化情况。方法共搜集26名健康女性志愿者,年龄22~30岁,平均26岁,规律月经周期,无口服避孕药史,未育。分别在月经期（第2天）、增生期（第7天）、卵泡期（第14天）、黄体期（第21天）、分泌期（第27天）进行了1个月经周期的MRI扫描,扫描序列包括T1WI、T2WI、DTI、DWI及IVIM。基于感兴趣区（ROI）的方法,由2名观察者分别在不同时间测量相同区域正常乳腺组织的真实扩散系数（D）、灌注相关扩散系数（D^＊）、血管容积分数（f）、各向异性分数（FA）及表观扩散系数（ADC）。结果采用3.0 T MR获得的IVIM、DTI、DWI乳腺图像具有较高的图像质量和分辨率,其参数图无严重伪影,图像质量较好,能满足参数测量要求。2名观察者分别所测得（观察者间）D值、D^＊值、FA值及ADC值可重复性好（ICC值〉0.8）,f值可重复性较差。正常乳腺的D^＊值显示随月经周期规律波动,在黄体期最高,与月经期和增殖期对比,有显著性差异（P〈0.01）;f值在卵泡期高于其他阶段,但是对比没有显著差异。D值和ADC值随月经周期有相似趋势,D值在黄体期和增殖期对比,差异具有统计学意义（P=0.005）;ADC值的差异在月经周期中无统计学意义。FA值在月经期与分泌期对比差异有统计学意义（P=0.034）。结论乳腺D值、D^＊值、FA值及ADC值可重复性好,可以敏感地反映乳腺组织随月经周期激素调节的变化特点。
基金supported by the National Natural Science Foundation of China (No. 31522034)Ministry of Science and Technology of China (2016YFC0900103)the National High Technology Research and Development Program Grant (2015AA020407)
文摘Reciprocal translocation is a chromosomal structural abnormal- ity that arises when two non-homologous chromosomes rearrange and attach with each other, an incidence that occurs in about 1/500 to 1/625 newborns （Mackie and Scriven, 2002）. This event typically does not lead to any significant loss of genetic material, thus recip- rocal translocation carriers do not exhibit any severe abnormal phenotypes （Scriven et al., 1998; Zhang et al., 2016）.
