The present study is concerned with the vibration analysis of symmetric composite beams with a variable fiber volume fraction through thickness. First-order shear deformation and rotary inertia have been included in t...The present study is concerned with the vibration analysis of symmetric composite beams with a variable fiber volume fraction through thickness. First-order shear deformation and rotary inertia have been included in the analysis. The solution procedure is applicable to arbitrary boundary conditions. Continuous gradation of the fiber volume fraction is modeled in the form of an m-th power polynomial of the coordinate axis in the thickness direction of the beam. By varying the fiber volume fraction within the symmetric composite beam to create a functionally graded material （FGM）, certain vibration characteristics are affected. Results are presented to demonstrate the effects of shear deformation, fiber volume fraction, and boundary conditions on the natural frequencies and mode shapes of composite beams.展开更多
Concentrations of Fe, Cu, Pb, Zn, Cd and Ni were determined in the red alga Corallina officinalis (Linnaeus, 1758), the green alga Ulva lactuca (Linnaeus, 1753) and sediment sampled in four stations of the coastline o...Concentrations of Fe, Cu, Pb, Zn, Cd and Ni were determined in the red alga Corallina officinalis (Linnaeus, 1758), the green alga Ulva lactuca (Linnaeus, 1753) and sediment sampled in four stations of the coastline of Hona?ne (extreme Western Algeria). The abundance of metal concentrations in algae and sediment samples, is in the following order: Fe > Zn > Pb > Ni > Cu > Cd. The schematic representation by PCA reflects a strong correlation of the corallina with Cd and Pb, the ulva with Zn and Ni and sediment with Cu and Fe, in addition, to homogeneity of rehearsals in each matrix. The results of this study validate the use of these species as reliable tools for biomonitoring of metal pollution of coastal ecosystems, even if the levels of heavy metals in sediment and algae from the coastline of Hona?ne are in general, very low compared with those from other geographic areas and by guidelines.展开更多
文摘The present study is concerned with the vibration analysis of symmetric composite beams with a variable fiber volume fraction through thickness. First-order shear deformation and rotary inertia have been included in the analysis. The solution procedure is applicable to arbitrary boundary conditions. Continuous gradation of the fiber volume fraction is modeled in the form of an m-th power polynomial of the coordinate axis in the thickness direction of the beam. By varying the fiber volume fraction within the symmetric composite beam to create a functionally graded material （FGM）, certain vibration characteristics are affected. Results are presented to demonstrate the effects of shear deformation, fiber volume fraction, and boundary conditions on the natural frequencies and mode shapes of composite beams.
文摘Concentrations of Fe, Cu, Pb, Zn, Cd and Ni were determined in the red alga Corallina officinalis (Linnaeus, 1758), the green alga Ulva lactuca (Linnaeus, 1753) and sediment sampled in four stations of the coastline of Hona?ne (extreme Western Algeria). The abundance of metal concentrations in algae and sediment samples, is in the following order: Fe > Zn > Pb > Ni > Cu > Cd. The schematic representation by PCA reflects a strong correlation of the corallina with Cd and Pb, the ulva with Zn and Ni and sediment with Cu and Fe, in addition, to homogeneity of rehearsals in each matrix. The results of this study validate the use of these species as reliable tools for biomonitoring of metal pollution of coastal ecosystems, even if the levels of heavy metals in sediment and algae from the coastline of Hona?ne are in general, very low compared with those from other geographic areas and by guidelines.
