稀土区质子滴线核~(142)Ho的β缓发质子衰变

通过重离子引起的核反应106Cd(40Ca,p3n)合成了新的β缓发质子先驱核142Ho,并且配合氦喷嘴快速带传输系统用“p-γ”符合方法对它进行了首次鉴别.观测了142Ho的β缓发质子衰变,测定其半衰期为(0.4±0.1)s.利用统计模型拟合实验估计的对质子女儿核141Tb中末态的相对分支比和缓发质子能谱,142Ho的基态自旋被指认为5,6或7.用Woods-Xason Strutinsky方法计算了142Ho的核位能面,其结果支持指认142Ho的基态自旋宇称为7-.作为副产品,还首次观测到了来自先驱核139Gd,140Tb,142Tb和143Dy的β缓发质子衰变产生的质子女儿核中的一些γ跃迁.

~(142)Ce的新激发态及其经验壳模型研究

利用 42 0MeV　82 Se轰击1 39La引起的深部非弹反应和在束γ谱学方法研究了1 4 2 Ce的中高自旋激发态 .识别出了激发能为 2 62 5,2 995和 3 83 4keV的 3个新能级 ,自旋、宇称分别被指定为 8+,9(- ) 和 1 1 (- ) .发现这些能级非常好地符合N=84偶偶核转晕能级的系统性 .利用经验壳模型计算了1 4 2 Ce的中高自旋激发态的激发能 ,计算结果比较好地重现了实验值 .对它们的结构进行了讨论 ,表明在1 4 2 Ce的中高自旋激发态中以单粒子激发为主

双奇核~(142)Pm高自旋态能级纲图

利用能量为 75— 95MeV19F束流 ,通过反应12 8Te( 19F ,5nγ) 142 Pm研究了双奇核142 Pm的高自旋态能级结构 .实验中进行了γ射线的激发函数、γ射线单谱和γ γ符合测量 .建立了激发能达 70 3 0 .0keV的142 Pm的能级纲图 ,其中包括新发现的 2 5条γ射线和 1 3个新能级 .基于实验测量的γ跃迁各向异性度 ,建议了142 Pm能级的自旋值

高产抗病春小麦新品种-高原142

小麦新品种高原142是由中国科学院西北高原生物研究所1999年从国际玉米小麦改良中心引进的高代品系筛选而来，组合为：BABAX/4/BOBWHITE/CROWN//BUCBUC/PAVON/3/VEERY#10/5/BABAX。经在该研究所平安育种试验站筛选与鉴定，

Material response and failure mechanism of unidirectional metal matrix composites under impulsive shear loading

The material response and failure mechanism of unidirectional metal matrix composite under impulsive shear loading are investigated in this paper. Both experimental and analytical studies were performed. The shear strength of unidirectional C-f/A356.0 composite and A356.0 aluminum alloy at high strain rate were measured with a modified split Hopkinson torsional bar technique. The results indicated that the carbon fibers did not improve the shear strength of aluminum matrix if the fiber orientation aligned with the shear loading axis. The microscopic inspection of the fractured surface showed a multi-scale zigzag feature which implied a complicated shear failure mechanism in the composite. In addition to testing, the micromechanical stress field in the composite was analyzed by the generalized Eshelby equivalent method (GEEM). The influence of cracking in matrix on the micromechanical stress field was investigated as well. The results showed that the stress distribution in the composite is quite nonhomogeneous and very high shear stress concentrations are found in some regions in the matrix. The high shear stress concentration in the matrix induces tensile cracking at 45 degrees to the shear direction. This in turn aggravates the stress concentration at the fiber/matrix interface and finally leads to a catastrophic failure in the composite. From the correlation between the analysis and experimental results, the shear failure mechanism of unidirectional C-f/A356.0 composite can be elucidated qualitatively.