Advanced Materials Research Vol. 701

Abstract: This paper addresses optimization of the flexible job-shop problem (FJSP) by using real-coded genetic algorithms (RCGA) that use an array of real numbers as chromosome representation. The first part of the papers has detailed the modelling of the problems and showed how the novel chromosome representation can be decoded into solution. This second part discusses the effectiveness of each genetic operator and how to determine proper values of the RCGAs parameters. These parameters are used by the RCGA to solve several test bed problems. The experimental results show that by using only simple genetic operators and random initial population, the proposed RCGA can produce promising results comparable to those achieved by other best-known approaches in the literatures. These results demonstrate the robustness of the RCGA.

Abstract: Ti6Al4V alloy are among the most widely used materials in engineering applications. This is because their relatively beneficial properties. However, inadequate wear properties of Ti6Al4V alloy have largely constrained the application for this material. In this study, Plasma nitriding of the Ti6Al4V was performed using microwave plasma technique at 600°C for 1hour, 3 hours and 5 hours then followed with deposition of CrN on plasma nitrided samples for duplex coating purposes. Microstructural analysis and hardness measurement revealed that formation of Ti₂N and TiN phases indicating the formation of compound layer is observed for substrate nitrided at temperature as low as 600°C 1 hour and a substantial increase on the surface hardness of plasma nitrided Ti6Al4V is observed with an increase of process time. The duplex coating obtained in this study has significant surface hardness property and superior as compared with CrN coatings deposited on as received Ti6Al4V.

Abstract: Malaysia plans to become a regional hub for aircraft maintenance and repairs. The country was currently ranked fifth in Asia and tenth in the world in terms of aircraft maintenance, repair and overhaul.It show a positive sign for aviation industry in Malaysia.Maintenance or repair technique play a major role in increasing useful life of the aerospace part and it increase the confident level of the user. This paper is an outcome to discuss Cold spray process as potential repair technique which is widely acclaimed for its ability to perfom a bonding with the underlying material without the creation of heat affected zones which are typical of other deposition processes (thermal spray) and are undesirable in many structural applications. One of potential application for Cold spray process is dimensional restoration or tooling repair like chipped area, if the defect exceed repairable limit that provided by OEM, that part considered scrap. Cold spray can provided environmental friendly solution to thick deposit for dimensional restoration or tooling repair without creation heat affected zone.There is no application yet of this repair technology in Malaysia and on top of that,re-use of material will contribute to cost saving and in-haze the environmet.

Abstract: Friction Stir Welding (FSW) is a simple process involving a rotating tool (with an extended pin) traversing on the joining line of the two work pieces leaving behind the required weld. Tool geometry (pin and shoulder), rotational speed, traverse speed, and tilt angle are important parameters which determine the resultant properties of weld. Milling machines due to rotating tool and traversing can be used as a method of doing laboratory scale FSW experiment. In cases where milling machines have a fixed head, limitation of zero degree tool tilt angle results in substantial defects (e.g. tunnel defect) in weldments. In this study a new approach is developed and adopted for overcoming this limitation of a fixed head vertical milling machine to incorporate the flexibility of tool tilt. The results for welding with and without this approach are presented along with discussion and conclusion.

Abstract: Welding fumes are known as hazard that can cause acute health effects. Welders exposures to welding fumes are oftentimes difficult to evaluate due to the different parameters settings exist in their workplace. Therefore, this experimental study focused on welding fumes exposure towards aluminum metal inert gas (MIG) welders. The experimental set-up was done by using a dummy welder and a welding machine attached to Computer Numerical Control (CNC) workbench for programmable welding route. This preliminary experiment aims at comparing results between scanning electron microscope with energy dispersive spectroscopy (SEM-EDS), inductively coupled mass spectroscopy (ICP-MS) and atomic absorption spectrometry (AAS) analysis method. New insight on the consistency of the SEM-EDS experimental results, comparison of element detected by using SEM-EDS and ICP-MS result analysis and the different elements detected between standing and sitting welding position were recognized through this preliminary experimental study. It is concluded that SEM-EDS analysis are not suitable to be used as a preliminary analysis to shortlist the metal elements exists in the welding fumes sample due to the misleading results if compared to the elemental characterization measure proportional to the atomic number such as ICP-MS.

Abstract: Presence of chlorine in by product of degradation process from polyvinyl chloride was analysed through structural feature changes and elemental analysis. Coating samples with polyene was also tested for its wettability via contact angle. Analyzing the elimination of chlorine content from polyvinylchloride through chemical dechlorination with tetrahydrofuran (THF) has been studied via FTIR spectra, energy-dispersive x-ray spectroscopy (EDS) and static contact angle measurement. Qualitative value of decreasing chlorine content of polyene at 2 hours reaction time was found to be about 96% from supplied PVC. All treated samples at different reaction time of polyene synthesize showed good wettability properties since the contact angle value were less than 90o.

Abstract: Microbial surface active compounds (SACs) have been studied for bioremediation of non-aqueous phase liquids (NAPLs) contaminated sites where SACs reduce the surface tension and therefore improve the bioavailability of NAPLs. Hence, this study evaluates presence of microbial SACs in culture medium by detecting the surface activity of potential SAC-producing bacteria. Twenty-five strains isolated from various waste streams in Malaysia were screened for SAC production by preliminary screening tests, namely using drop collapse, oil spreading and microplate tests. Strains were further checked using complementary screening by measuring the surface tension. Four strains (P-UT4, P-UT5, P-UT6 and P-UT8) isolated from untreated palm oil mill effluent (POME) exhibited high surface active properties when tested through preliminary screening tests. These strains were also capable of reducing surface tension of water (72 mNm^-1) to below 40 mNm^-1 and thus were identified as potential SAC-producing bacteria.

Abstract: Green technology has become the primary concern of nations around the world. In-line with this concern, lignocellulosic biomass is often advocated as significant starting material for a greener production. However, the current biomass conversion cannot be considered as green due to the use of acid or alkaline during its pretreatment. An introduction of ionic liquids (ILs) as replacement of acids or alkaline for the pretreatment of lingo-cellulosic materials is gaining interest due to their minimal waste, nonvolatility and low toxicity and therefore considered green. This paper discusses the benefits of ILs as a green solvent for pretreatment of lignocellulosic biomass.

Abstract: Metaheuristic methods have become a popular tool in solving large scale optimization problem for a variety of biological systems. In this report, we present Max-Min Ant System (MMAS), a class of swarm intelligence metaheuristics approach, in computing transmembrane helical arrangement of the homotetrameric protein, the potassium channel from Streptomyces iividans (KcsA). The MMAS algorithm was employed to solve transmembrane arrangement problems through the use of an objective penalty function based on distance-violated constraints. Assembly structures of the four inner helices of the KcsA channel were computed bythe construction of probability associated with a set of translational and rotational parameters and the four-fold symmetry transformation applied to the atomic coordinates of the rigid single helix. The MMAS parameters including the number of ants, the number of iteration, weight of pheromone, weight of heuristic information, and pheromone evaporation weight were examined. We demonstrated the effectiveness of the present approach, which can correctly generate native-like structure with root-mean square deviation (RMSD) below 3 Å with respect to the x-ray structure.

Abstract: Activated carbons were prepared from rambutan seed with impregnation of zinc chloride as dehydrating agent. In order to find its characteristics, different zinc chloride to rambutan seed ratio (0.5 and 2) and activation temperature (450 and 650 °C) was employed. The carbonization occurred in a tube furnace with flow of nitrogen gas at 0.5 L/min. The results showed that at higher impregnation ratio and carbonization temperature produced a wider BET surface area of activated carbon that was 9.8761 m2/g. Total pore volume also increased with increases of these two factors. However activation yield was decreased with increasing of carbonization temperature.