In this study, a superhydrophobic surface on polydimethylsiloxane (PDMS) substrate was constructed via the proposed vapor-liquid sol-gel process in conjunction with spin coating of dodecyltrichlorosilane (DTS). Unlike the conventional sol-gel process where the reaction takes place in the liquid phase, layers of silica (SiO(2)) particles were formed through the reaction between the reactant spin-coated on the PDMS surface and vapor of the acid solution. This led to the SiO(2) particles inlaid on the PDMS surface. Followed by subsequent spin coating of DTS solution, the wrinkle-like structure was formed, and the static contact angle of the water droplet on the surface could reach 162 degrees with 2 degrees sliding angle and less than 5 degrees contact angle hysteresis. The effect of layers of SiO(2) particles, concentrations of DTS solution and surface topography on superhydrophobicity of the surface is discussed.
The main objective of this paper is to evaluate the capabilities of non-destructive test (NDT) methods by using transient loading, i.e. the sonic echo (SE) method in the time domain and the impulse response (IR) method in the frequency domain, in detecting the pile length in the foundations of bridges. Methods such as these, which are based on transient elastic waves, have been used for many years. However, several drawbacks have been described in the literature, including difficulties with the installation of the testing devices. In this paper, several experimental studies were carried out on existing scoured bridge pile foundations. In order to overcome environmental limitations, the Ultrasonic Pulse Velocity method was adopted, and the installation procedure for the testing devices was modified. Moreover, a recently developed numerical signal processing tool, the Wavelet Transform (WT), was adopted to interpret the testing signal in the time-frequency domain. The results indicate that the modified testing procedure is feasible for in-service pile integrity tests. The processed signal clearly and visually illustrates the temporal changes, and the pile tip can be highlighted in the timefrequency domain. The depth of the scour pile tips can be detected precisely with the proposed modified device installation and the improved numerical signal processing. The results in the time-frequency domain are also consistent with traditional SE/IR testing methods.
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