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Wavelet analysis, being a popular time-frequency analysis method has been applied in various fields to analyze a wide range of signals covering biological signals, vibration signals, acoustic and ultrasonic signals, to name a few. With the capability to provide both time and frequency domains information, wavelet analysis is mainly for time-frequency analysis of signals, signal compression, signal denoising, singularity analysis and features extraction. The main challenge in using wavelet transform is to select the most optimum mother wavelet for the given tasks, as different mother wavelet applied on to the same signal may produces different results. This paper reviews on the mother wavelet selection methods with particular emphasis on the quantitative approaches. A brief description of the proposed new technique to determine the optimum mother wavelet specifically for machinery faults diagnosis is also presented in this paper.

This review provides a brief discussion about how additive manufacturing works, together with its strength and limitations. Fundamental aspects of FDM including the working mechanism, processing parameters have been reported. This study emphasizes on the progress of Polylactic acid (PLA) utilizing FDM and looks at the opportunity it offers as an advance material when integrated with filler compounds forming potential composites. A summary on the recent developments of PLA composites have been included, also elaborating the preparation technique and the relevance of the composite developed. Mechanical properties of pure PLA have been presented highlighting the processing parameter used, types of mechanical tests done and the resulting values from those conducted experiments.

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