Abstract: The scope of this study is to investigate linear viscoelastic vibration response of conical and hyperboloidal helices having an elliptical hollow section. A mixed finite element formulation based on the Timoshenko beam theory is implemented, where the numerical analysis are performed in the Laplace domain. Noncylindrical helix geometry is spatially discretized by the finite elements where nodes are placed on the exact geometry. The curvatures are approximated by shape functions over each element. The material constants are replaced with their complex counterparts in the Laplace domain in accordance to the correspondence principle. For the step type loading, results from the solutions performed in the Laplace domain are transformed back to the time domain numerically by employing the Modified Durbin’s transformation procedure. Numerical results are presented as benchmark examples investigating the viscolelastic dynamic behavior of noncylindrical helices with elliptical hollow sections.

• Publication Date: 26-Oct-2014
• DOI: 10.15224/978-1-63248-030-9-13
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Abstract: This paper presents the multiscale spectral analysis of four water quality time series data from an Indian river. First, the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) is employed for multiscale decomposition and the resulted orthogonal modes namely Intrinsic Mode Functions (IMFs) are subsequently subjected to the Normalized Hilbert Transform (NHT). The spectral representation clearly depicts the nonlinearity and non-stationarity of the datasets and the time varying behavior of dominant frequency. The marginal Hilbert spectrum of different parameters shows that the dominant frequency of most of the pollutants is at high frequency range which indicates the significant anthropogenic impacts in the study area. Also the trend analysis performed upon the instantaneous amplitudes show that the high frequency components are responsible for overall trend of the four time series during the study period under consideration. The multiscale decomposition process a

• Publication Date: 26-Oct-2014
• DOI: 10.15224/978-1-63248-030-9-14
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