Volume Volume 11 No.1 2002

ABSTRACT: The study was done to quantify elements in diluted deammoniation latex effluent sludge through EDS (energy dispersive spectroscopy). A reduction in percentage weight and percentage atomic weight was observed for the carbon (C) element, however an increase of oxygen (0) at both percentages was seen. It also found that the spec ific exogenous bacteria (inoculum), Bacillus sp. was a short rod shape as seen under TEM and it attached and penetrate on the diluted deammoniation latex effluent sludge surface as seen under scanning electron microscope (SEM). The effectiveness of using specific exogenous bacteria to enhance the reduction of the organic and inorganic pollutants was done through the pilot scale latex effluent treatment by extended aeration and bioaugmentation . The results showed BOD3 , COD and SS were removed up to 91 .8%, 89.7% and 88.6 ± 0.4 at 24 h HAT and 22 mg/I inoculum. KEYWORDS: Extended aeration, scanning electron microscope, transmission electron microscope, energy dispersive spectroscopy, inoculum, bioaugmentation. Author: Mohd Omar A.K., Norli lsmai, Nik Fuaad N.A. and Nik Norulaini N.A.

ABSTRACT: Online adaptation of a PID control system is required in most chemical process systems to compensate for changes in process parameters and conditions. One approach is to perform offline regression of the changing parameter with the PID tuning parameters which is however not robust. Another approach is to perform online optimisation to obtain the necessary PID parameters which, on the other hand is time consuming. To obtain the advantages of both approaches, we have combined them in a hybrid strategy called REOP (Regression and Optimisation) method. This method has been tested to control an isothermal reactor and a level-in-tank system and the results obtained for the controlled system is very promising. KEYWORDS: regression, optimization, PID, online, adaptive. Author: M.A. Hussain, H.S. Ching and C.E. Weei

ABSTRACT: Lipases from Candida rugosa (type VII), Candida rugosa (type AYS), Pseudomonas cepacia, Aspergillus nigerand Mucormieheiwere immobilised on to mullite powder by physical adsorption method . The activity of the immobilised lipases, determined by carrying out the esterification of 0.1 M propionic acid and 0 .1 M n-butanol in n-hexane, were compared with those of their tree counterpart. The lipase from Mucor miehei was able to retain 97% of its activity when immobilised on to mullite powder as compared to 80% retention in activity with celite. Repeated usage of mullite immobilised Mucor miehei lipase showed that the enzyme preparation retained more than 90% of activity after 240 hours of operation. In comparison, the preparation from celite lost 94% of its activity upon immobilisation. The mullite support when tested for its suitability for conducting enantioselective esterification reaction using the kinetic resolution of (±) 2- (4- chlorophenoxy) propionic acid with n-butanol, retained 85% of its activity with enantiomeric excess of 32% for the S-acid. The results obtained suggest that mullite is suitable for use as an enzyme support. KEYWORDS: Lipase, immobilisation, mullite, physical adsorption, esterification.

ABSTRACT: Growth and sporulation of Bacillus thuringiensis in a two-stage continuous culture at steady-state conditions using a defined medium was investigated. The effect of dilution rate ratio (D1/D2) in reactor 1 {K1) and reactor 2 (K2) and initial pH in K2 which gives the highest value for total viable cell count (TVCC) in K1 and spore percentage in K2 was ascertained. Result showed that spore percentage in K2 was higher than in K1 whereas the total viable cell count in K2 was lower than in K1. The following operating conditions, namely, dilution rate= 0.45 h-1 and the ratio of dilution rate D1/D2= 4 gave the highest value for total viable cell count (TVCC) of 32x109 CFU/ml in K1 and a spore percentage of 50% in K2. The effect of pH (5.5 - 8.5) in K2 on spore percentage, TVCC and spore count (SC) are also reported. Our results showed that medium in K2 with initial pH 7 .5 gave the highest spore percentage of 65%. This was achieved with TVCC of 6x109 CFU/ml and spore count of 4x109 CFU/ml. Whilst in another experiment, the highest spore percentage recorded in K1 was only 46%, with TVCC of 24x109 CFU/ml and spore count of 11x109 CFU/ml. Our result supports the idea that a two-stage continuous culture could be easily operated at steady-state conditions to optimize growth in the first reactor and then to optimize sporulation in the second reactor. KEYWORDS: Bioinsecticide, B. thuringiensis, two-stage continuous culture. Author: Wan Mohtar Wan Yusoff, Mohd. Mazmira Mohd. Masri, Bhavani, U. and Rusni Maruan

ABSTRACT: This paper describes a study of fatigue crack growth (FCG) characteristics and mechanisms in Al-Si-Mg eutectic casting alloys containing 0.35wt% magnesium and O to 0.02wt% strontium as a function of stress ratio (R}, stress-intensity factor range (AK}, and silicon (Si) particle size. Experimental data for fatigue crack growth rates of commercial aluminum casting alloy A356 are also presented and compared graphically against the Al-Si alloys. At the same applied AK level, the crack growth rate was found to increase with increasing stress ratio and Si particle size. Modified (fine Si morphology) and A356 alloys showed better FCG resistance than the unmodified (coarse Si morphology) alloys, for a constant applied AK, due to increased closure. The fatigue crack propagation path is found to be dependent on the Si particle characteristics. The results also indicated that the fatigue crack growth behaviour of the alloys showed a strong dependence upon the stress ratio, applied stress intensity level and the size, shape and distribution of the eutectic silicon particles. The silicon particle characteristics also determine the fracture mode of the alloy. Fracture characteristics observed include decohesion of the silicon particles from the aluminum matrix; silicon particle cleavage cracking and striations in the aluminum phase, particularly at high stress ratios. KEYWORDS: Fracture, fatigue crack growth, stress ratio, Si partical, stress-intensity, factor range (?K), fatigue mechanisms, microstructures. Author: Lee Fui Tong

ABSTRACT: Results show that when end milling of aerospace material Ti-62428 with the off-center ball end mill made of alloyed uncoated carbide (W-Ti/Ta/Nb)C-Co under green environment, localised flank wear at the tool leading edge was found as the dominant tool rejection criterion. Attrition and diffusion-dissolution were observed as the wear mechanisms on both tool's flank and rake faces. When tool life data from trials at cutting speeds of 100-150 m/min were plotted in V-Tcurve, Taylor equations for feeds of 0.1 and 0.15 mm/tooth were sequentially given by VT 0·2905 =316.51 and VT 0·2113 = 190.01, while the modified Taylor equations for volume of material removed (VMR) were given by V(VMR)0.4009 = 820.38 and V(VMR) 0·2708 = 357.87. Based on tool life up to cutting speed of 125 m/min, it was concluded that uncoated alloyed carbide used in this study was much better than the one used by Konig (1979) and Dearnley and Grearson (1986) due to some principal reasons such as tool geometry, carbide grain size and the absence of cutting fluid. It seems keeping the tool hot is beneficial. KEYWORDS: Alloyed uncoated carbide, end milling, tool life, Taylor equation, Ti-62428. Author: Armansyah Ginting and Che Hassan Che Haron

ABSTRACT: Solubilisation of methanol and ethanol in palm olein and red palm oil were studied using mixed fatty alcohol/alkanol as solubiliser. Ternary phase diagrams were constructed to determine the solubilisation (isotropic) regions. Results showed that methanol and ethanol were readily solubilised in palm olein and red palm oil in the presence of mixed fatty alcohol/alkanol. Large isotropic regions were formed with mixtures containing long-chain alkanols (decanol, octanol and octa-2-ol). The order of increasing isotropic region in both fatty alcohol systems was butanol oC. KEYWORDS: Palm oil, solubilisation, isotropic, fatty alcohol. Author: Dzulkefly, K., Lim, W.H., Norsilah, S. and Norlizah, K.