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Noise barriers have been widely used to decrease the transportation noise. How to utilize limited structure and material to achieve the environmental requirements for noise control is an important research topic. This research combines the use of boundary element method and SIMP to generate an acoustic topology optimization method and applies this optimization method to optimization distribution of absorbing material installed on the noise barrier’s edges. Optimality criteria method is used to update the design variables and look for the final optimal solution. A new material interpolation scheme for acoustic problems based on SIMP is given, where the interpolation variable is not real structural density used in conventional SIMP, but fictitious material density deciding the normalized surface admittance. It is noteworthy that gray elements exist in the acoustic optimization analysis based on SIMP. However, a modified method based on a smoothed Heaviside function is applied to eliminate the gray elements. In order to demonstrate the validity and efficiency of the proposed algorithm in this paper, vertical barrier and T-shaped barrier with two wells are used for the numerical analysis, respectively. [ABSTRACT FROM AUTHOR]

The Late Cenozoic strata are 313 m thick, revealed by the drilling core PD-99 in the south Changjiang delta. Monazite chemical dating shows that 350--500-Ma monazites predominate in the Pliocene and 100--275-Ma monazites in the Quaternary, indicating a great change of their provenance. The first presence horizon of monazites younger than 25 Ma is just above the Matruyama/Gauss boundary (2.58 Ma), whch is exactly when uplift of the Tibetan Plateau began to influence deposition in the East China Sea. Variations in contents of monazites younger than 25 Ma can be divided into two sections. The Early-Middle Pleistocene with less <25 Ma monazites corresponds with rapid uplift of the Tibetan Plateau, and the Late Pleistocene with more <25 Ma monazites parallels the peak uplift of the Tibetan Plateau. This study demonstrates that chemical dating of monazites in the river-mouth strata is a useful method to explore changes of river drainage basins, and deconvolute multistage tectonic and magmatic activity histories in the provenance areas. [ABSTRACT FROM AUTHOR]