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  1. The role of carbon chain length in the attachment between microbubbles and aqueous solutions of ionic liquid
    Chew EK, Lee KY, Lau EV
    J Colloid Interface Sci, 2017 Nov 15;506:452-459.
    PMID: 28755640 DOI: 10.1016/j.jcis.2017.07.078
    HYPOTHESIS: The effects of varying carbon chain lengths (CCLs) and concentrations of aqueous solutions of imidazolium based ionic liquids on bubble particle attachment (BPA) will provide a better understanding in catering for the varying degrees of surface activities in the application of the flotation technology. The general trends of this study should also be applicable to homologous series of other cationic surfactants and ionic liquids.

    EXPERIMENTS: Zeta potentials of small air bubbles and bunker oil drops dispersed in aqueous solutions of n-methylimidazolium chloride ionic liquids (n=0, 2, 3, 6, 8, 10, 12) of concentrations ranging from 1000PPM to 8000PPM, as were interfacial tensions of these solutions with bunker oil (180cst) and contact angles made by air bubbles at interfaces between these solutions and thin layers of bunker oil on flat solid surfaces were investigated. Finally, interparticle forces analysis using the Derjaguin-Landau, Verwey-Overbeek (DLVO) theory is also included.

    FINDINGS: Analysis using the DLVO theory showed attractive forces between the oil particles and micro-bubbles are significantly more prevalent in short CCLs solutions of imidazolium-based ILs in low concentrations, namely [C0mim][Cl] and [C2mim][Cl] at a maximum zeta potential difference of 75.3mV. The results from CA measurements follows similarly whereby low concentrations of ILs with short CCLs were in favor for the bubble-particle attachment process with angles ranging between 93.95° for [C0mim][Cl] and 97.28° for [C2mim][Cl]. IFT which is important in reducing coalescence for the preferential BPA process to occur in flotation decreases with an increase of CCL and concentration of IL.

  2. Post partum splenic artery aneurysm rupture
    Asokan S, Chew EK, Ng KY, Thanaletchimy N, Asmiati A, Kong NM
    J Obstet Gynaecol Res, 2000 Jun;26(3):199-201.
    PMID: 10932982
    Ruptured splenic artery aneurysm during pregnancy is a rare event with high maternal and fetal mortality rate. A case of ruptured splenic artery aneurysm in the post partum period is presented. The literature is reviewed on pathophysiology, clinical presentation and management of this rare and potentially fatal entity.
  3. Fulltext Optimal Computing Budget Allocation for Particle Swarm Optimization in Stochastic Optimization
    Zhang S, Xu J, Lee LH, Chew EP, Wong WP, Chen CH
    IEEE Trans Evol Comput, 2017 Apr;21(2):206-219.
    PMID: 29170617 DOI: 10.1109/TEVC.2016.2592185
    Particle Swarm Optimization (PSO) is a popular metaheuristic for deterministic optimization. Originated in the interpretations of the movement of individuals in a bird flock or fish school, PSO introduces the concept of personal best and global best to simulate the pattern of searching for food by flocking and successfully translate the natural phenomena to the optimization of complex functions. Many real-life applications of PSO cope with stochastic problems. To solve a stochastic problem using PSO, a straightforward approach is to equally allocate computational effort among all particles and obtain the same number of samples of fitness values. This is not an efficient use of computational budget and leaves considerable room for improvement. This paper proposes a seamless integration of the concept of optimal computing budget allocation (OCBA) into PSO to improve the computational efficiency of PSO for stochastic optimization problems. We derive an asymptotically optimal allocation rule to intelligently determine the number of samples for all particles such that the PSO algorithm can efficiently select the personal best and global best when there is stochastic estimation noise in fitness values. We also propose an easy-to-implement sequential procedure. Numerical tests show that our new approach can obtain much better results using the same amount of computational effort.
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