用电感耦合等离子体质谱（inductively coupled plasma mass spectrometry,ICP-MS）测量某海滨城市50例胎儿脐血中铅（Pb）质量浓度,发现Pb超标（＆gt;100μg/L）为8%.根据婴儿母体是否常食用海产品,将50例样品分为常食用海产品（A组）...用电感耦合等离子体质谱（inductively coupled plasma mass spectrometry,ICP-MS）测量某海滨城市50例胎儿脐血中铅（Pb）质量浓度,发现Pb超标（＆gt;100μg/L）为8%.根据婴儿母体是否常食用海产品,将50例样品分为常食用海产品（A组）、偶尔食用海产品（B组）和极少食用海产品（C组）,用X射线荧光光谱分析（X-ray fluorescence,XRF）测量这3组婴儿毛发中的Pb质量分数,发现婴儿毛发中Pb质量分数具有显著性差异,由高至低依次为A组＆gt;B组＆gt;C组,其相应的脐血Pb质量分数也具有相同特征.同时对婴儿中的溴（Br）质量分数也进行了测量,发现Pb质量分数高的婴儿,其Br质量分数也显著偏高,由于海产品中Br质量分数远高于淡水产品,从另一方面说明,常食用海产品组的婴儿Pb质量分数偏高与母亲食用海产品有关.此外,对同一海滨城市393例儿童（2～11岁）血液中Pb质量分数进行统计学分析,得出Pb超标（〉100μg/L）为8.9%,说明海滨城市Pb污染仍对儿童具有一定的威胁.最后,通过对环境中常见的铅源（PM2.5、大气、油漆和海产品等）及人体摄入状况进行分析比较,认为食用铅污染的海产品是造成海滨城市胎儿铅超标的主要原因之一.展开更多
A rectangular finite element for laminated plate with bonded and/or embedded piezoelectric sensors and actuators is developed based on the variational principle and the first order shear deformation theory. The elemen...A rectangular finite element for laminated plate with bonded and/or embedded piezoelectric sensors and actuators is developed based on the variational principle and the first order shear deformation theory. The element has four-node, 20-degrees-of-freedom with one potential degree of freedom for each piezoelectric layer to represent the piezoelectric behavior. The higher order derivation of deflection is obtained by using the normal rotation expressions to take the effects of transverse shear deformation into considerations. The finite element can accurately simulate the deformation of both thin and moderately thick plates. A Fortran program is written and a number of benchmark tests are exercised to verify its effectiveness. Results are compared well with the existing data. The unbalanced composite with piezoelectric layers is then analyzed by using the model. Results show that the changes of the ratio between the thickness of positive angle layers and the negative angle layers have an effect on the deformation of the structure under the same electric loading.展开更多
文摘A rectangular finite element for laminated plate with bonded and/or embedded piezoelectric sensors and actuators is developed based on the variational principle and the first order shear deformation theory. The element has four-node, 20-degrees-of-freedom with one potential degree of freedom for each piezoelectric layer to represent the piezoelectric behavior. The higher order derivation of deflection is obtained by using the normal rotation expressions to take the effects of transverse shear deformation into considerations. The finite element can accurately simulate the deformation of both thin and moderately thick plates. A Fortran program is written and a number of benchmark tests are exercised to verify its effectiveness. Results are compared well with the existing data. The unbalanced composite with piezoelectric layers is then analyzed by using the model. Results show that the changes of the ratio between the thickness of positive angle layers and the negative angle layers have an effect on the deformation of the structure under the same electric loading.
