Vibration analysis of laminated plates using a refined shear deformation-theory

A previously published discrete-layer shear deformation theory is used to analyze free vibration of laminated plates. The theory includes the assumption that the transverse shear strains across any two layers are linearly dependent on each other. The theory has the same dependent variables as first order shear deformation theory, but the set of governing differential equations is of twelfth order. No shear correction factors are required. Free vibration of simply supported symmetric and antisymmetric cross-ply plates is calculated. The numerical results are in good agreement with those from three-dimensional elasticity theory.

扁担塘螺类生产力的研究Ⅱ.纹沼螺的周年生产量

采用四种方法对扁担塘纹沼螺的周年生产量进行了测算 ,结果表明 ,四种方法得到的生产量吻合极好。生产量的去壳干重和带壳湿重分别是 :体长频度法 ,1 78.0 7mg·m- 2 ·a- 1 ,4998.40mg·m- 2 ·a- 1 ;减员累计法 ,1 74.50mg·m- 2 ·a- 1 ,4898.2 0mg·m- 2 ·a- 1 ;Allen曲线法 ,1 74 50mg·m- 2 ·a- 1 ,4898.2 0m- 2 ·a- 1 ;瞬时生长率法 ,1 78.1 4mg·m- 2 ·a- 1 ,50

漫谈团头鲂

<正> 团头鲂又名武昌鱼,即产于湖北省鄂城县梁子湖樊口镇的鳊鱼。中国科学院水生生物研究所易伯鲁先生发现,鳊鱼和鲂鱼都是身体高而两侧扁平的较大型的鱼类。从外部形态来看,它们之间主要的区别在于鳊鱼腹部中央的角质棱是从胸部腹面一直延到肛门之前;而鲂鱼的则仅仅局限于鳍基部至肛门之间,鲂鱼身体的高度也是显著大于鳊鱼的。