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Supercontinuum fiber laser source for water quality and heavy metals detection

Teh P. C., Ho Y. H., Ong C. E., Lee S. C., Lo P. K., Lai K. C., Yeap K. H., Loh S. H., Teh P. S., Tey K. L.

Optica Applicata

2017

Vol. 47, nr 3

445--456

We report a compact, all fiber, 150 ps fiber master oscillator power amplifier operating at 1064 nm that has the ability of producing a maximum average output power of 2.16 W with peak power as high as 10 kW. The output from the master oscillator power amplifier is spliced with a highly nonlinear photonic crystal fiber, generating a supercontinuum with an average power of 250 mW at repetition rate of 1 MHz and spectrum bandwidth spanning from 600 to 1700 nm. The developed supercontinuum system is used to detect the presence of heavy metal contaminants in water by a simple light transmittance method to ensure that the water is free from heavy metal contaminants and safe for consumption. The supercontinuum laser source was shone onto a water sample with a detector placed at another end in order to measure the transmitted supercontinuum light. By measuring the amount of light attenuated at particular wavelength, the concentration of heavy metal contaminants present in the water sample could be determined.

Experimental study of water tank under impulsive loading

Wang Y., Lee S. C.

Archives of Civil and Mechanical Engineering

2015

Vol. 15, no. 4

986--996

The performance of stainless steel water tank subjected to impulsive loading was experimentally studied in this paper. The gas gun was utilized to activate the projectile with high impact velocity. The activated projectile then impinged the impact transfer plate which pressed the airbag behind it. The inflated airbag between the impact transfer plate and water tank was adopted to transfer the impulsive loading from impact transfer plate to the water tank. The ultra-thin pressure sensors were placed between the airbag and water tank to record the pressure imposed onto the water tank and the potentiometers were attached at the back of water tank to record the displacement histories. The water tanks with two different front and rear plate thicknesses were investigated. In addition, the same water tank with and without filled water was compared to study the water effects on the response of water tank under impulsive loading. Besides the experimental studies, the FE method was adopted to reproduce the experiment and improve the current test method. Finally, the experimentally verified FE models were further used to study the water effects in reducing the deformation of water tank under blast loading.

System Identification from Multiple-Trial Data Corrupted by Non-Repeating Periodic Disturbances

Phan M. Q., Longman R. W., Lee S. C., Lee J. W.

International Journal of Applied Mathematics and Computer Science

2003

Vol. 13, no 2

185-192

Iterative learning and repetitive control aim to eliminate the effect of unwanted disturbances over repeated trials or cycles. The disturbance-free system model, if known, can be used in a model-based iterative learning or repetitive control system to eliminate the unwanted disturbances. In the case of periodic disturbances, although the unknown disturbance frequencies may be the same from trial to trial, the disturbance amplitudes, phases, and biases do not necessarily repeat. Furthermore, the system may not return to the same initial state at the end of each trial before starting the next trial. In spite of these constraints, this paper shows how to identify the system disturbance-free dynamics from disturbance-corrupted input-output data collected over multiple trials without having to measure the disturbances directly. The system disturbance-free model can then be used to identify the disturbances as well, for use in learning or repetitive control. This paper represents the first extension of the interaction matrix approach to the multiple-trial environment of iterative learning control.