Applied Mechanics and Materials Vols. 754-755

Abstract: A novel approach of dual lipases system was successfully carried out in improving the synthesis of ferulate esters between ethyl ferulate and olive oil. Combination of Novozym 435 and Lipozyme RMIM were used as biocatalyst to improve the reaction performance. Different reaction parameters (ratio of lipases, reaction time, lipase dosage, substrate molar ratio and reaction temperature) were analyzed systematically. A high conversion of ferulate esters (85%) was obtained after 12 hrs of reaction time at optimal conditions of 1:9 w/w (Novozym 435/Lipozyme RMIM), 80 mg of lipase and 1:4 ethyl ferulate:olive oil at 60 ^oC.

Abstract: Having the benefit of lightweight and low density makes magnesium (Mg) a good element with high potential to be used in various field of work. Yet, its application is limited for Mg is relatively low in term of strength. Hence, calcium (Ca) is chosen to be mixed with Mg as additional element for it is lightweight and non-toxic. In this research, Mg is prepared with different weight percentage (0, 1, 2 wt. %) of Ca via powder metallurgy (PM) method. The effect of sintering was investigated by focusing on the microstructure and properties of sintered sample. The samples were sintered at two sintering temperature (500 and 600 °C) in argon atmosphere. Morphological analysis carried out by optical microscope shows increase pores refinement with the increase of sintering temperature together with calcium content in Mg-Ca composites. Results show that the grain size and hardness of the samples increase as sintering temperature increase.

Abstract: This paper presents the experimental results of smoke opacity and exhaust gas measurements due to the oxidation of soot at different microwave power levels to the exhaust gas. The experiment attempts to ascertain the soot oxidation capability of using microwave in reducing smoke from the diesel engine. The exhaust gas from a diesel engine was directed into the microwave generator system which then flows through the chamber assembly that contains the soot trap. Three different microwave power levels of 0.5, 1.0 and 1.5 kW were generated and exposed to the soot at different exposure time. The results showed that when the power level of the electromagnetic waves was increased, the amount of smoke opacity reduced between 32 to 65 % depending on the microwave power levels. Due to the oxidation of the carbon particles of the soot, CO₂ gas increased in corresponding to the decreased in the smoke opacity. The experimental work also found that NOx gas was also reduced due to the breaking down of NOx at the localised high temperature of the soot trap. Hence, the microwave generator system has proven its capability as an in-situ soot oxidation device for deployment in diesel vehicles.

Abstract: This paper studies the effect of different gap sizes of IDE pattern on the surface morphology and electrical properties for the formaldehyde detection sensor. Two types of IDE chrome mask are designed to determine the ideal IDE pattern for formaldehyde gas detection by using conventional lithography. In the first method, IDE is transferred onto SiO₂ layer. In order to ensure that the perfect pattern with minimum defect structure is obtained, the process parameters should be optimized and controlled. In the second method, the aluminium is deposited directly on SiO₂/Si substrate by using IDE hard mask design plate. The fabricated IDE pattern is further validated through morphological and electrical characterization. The average gap size of IDE sensor is approximately 100 μm and 400 μm for IDE chrome and IDE hard mask respectively. The latter method is preferable since for formaldehyde gas sensing large size is needed and moreover the process is simple and requires low cost. Characterization of difference IDE pattern is demonstrated by various measurements.

Abstract: Hourly measured PM₁₀ concentration at eight monitoring stations within peninsular Malaysia in 2006 was used to conduct the simulated missing data. The gap lengths of the simulated missing values are limited to 12 hours since the actual trend of missingness is considered short. Two percentages of simulated missing gaps were generated that are 5 % and 15 %. A number of single imputation methods (linear interpolation (LI), nearest neighbour interpolation (NN), mean above below (MAB), daily mean (DM), mean 12-hour (12M), mean 6-hour (6M), row mean (RM) and previous year (PY)) were calculated to fill in the simulated missing data. In addition, multiple imputation (MI) was also conducted to compare between the single imputation methods. The performances were evaluated using four statistical criteria namely mean absolute error, root mean squared error, prediction accuracy and index of agreement. The results show that 6M perform comparably well to LI. Thus, this show that the effect of smaller averaging time gives better prediction. Other single imputation methods predict the missing data well except for PY. RM and MI performs moderately with the increasing performance in higher fraction of missing gaps whereas LR makes the worst methods for both simulated missing data percentages.

Abstract: Machining can be performed on virtually all solid materials even though the term commonly applies to the cutting of metals, alloys, plastics and woods. Machining is a mechanical process where excess material from a work piece can be removed by cutting action to produce a part of specified geometrical shape and surface finish. In this research we will analyze and investigate whether there is a possibility to use the palm oil based bio wax material for machining applications. At the moment different ferrous, non-ferrous materials and industrial blue wax have been used for prototype models, training purpose by different industries, educational and training organizations. However the price of such material is very expensive. Hence an attempt is made to substitute these material by the palm oil based bio wax produced in Malaysia. With it, engineers can generate prototype to evaluate even minor design changes without breaking the budget. To the best of researcher’s knowledge, no previous work has been carried out nationally or worldwide on the use of palm oil based bio wax material in the manufacture of a strong industrial wax. This research work gives the approaches taken in this direction.

Abstract: In this study, the effect of spinach-ferredoxin addition in chitosan matrix towards optical band gap was investigated. 5 distinct solutions were prepared by blending chitosan and spinach-ferredoxin (Cs-Fdx) with the volume to volume ratios of 100:0, 95:5, 90:10, 85:15 and 80:20 respectively. The solutions were cast into film via spin coating technique. The optical properties in terms of absorbance for these films were investigated using UV-Vis Spectrometer. UV-Vis result showed that the absorbance increased as the spinach-ferredoxin content increases. Finally, the optical band gaps of the films were determined by extrapolating a straight line of (αhν) ² vs. hν curves. Band gap value of 3.48 eV, 3.25 eV, 3.2 eV, 3.0 eV, and 2.8 eV were observed for (Cs-Fdx) films with 100:0, 95:5, 90:10, 85:15 and 80:20 respectively.

Abstract: Two glycolipids were synthesized to study the lyotropic behavior of these glycolipids in alkylglucoside/water/n-octane ternary system. These glycolipids have been distinguished based on the structure of alkyl chain (branched-alkyl chain and straight alkyl chain). 2-octyl-β-D-glucopyranoside (2-OG) and 2-ethylhexyl-β-D-glucopyranoside (2-EHG) were used as surfactants to perform two types of phase diagram. Phase behaviours investigated were phase behaviours of 2-OG/n-octane/water ternary system and 2-EHG/n-octane/water ternary system. Small angle x-ray (SAXS) and optical polarizing microscope were used as the instruments to study the lyotropic phase behaviour of these two surfactans in ternary phase diagram. Study the effect of branched-tail structure on the phase behaviour of glycolipids in ternary system is one of strategy to derive the structure-property relationship. For this purpose, 2-OG and 2-EHG were used as surfactants in the same ternary system. The phase diagram of 2-OG/water/n-octane ternary system showed rectangular ribbon phase and lamellar phase. The phase diagram of 2-EHG/water/n-octane ternary system showed wide region of lamellar lyotropic liquid crystalline in different ratio of weight composition. In 2-OG/water/n-octane ternary system, as more surfactant was added to the system, the interlayer spacing, d₁ and scattering angle, a value increased, whereas in 2-EHG/water/n-octane ternary system, the d₁ and a value decreased.

Abstract: An attempt was made to study the potential of rice husk as an alternative cheap precursor for activated carbon to remove Ni²⁺ from aqueous solution. Rice husk was treated chemically (with NaOH) and physically (carbonization) to prepare rice husk based activated carbon (RHAC). The textural properties of RHAC, i.e. surface area (255 m²/g) and pore volume (0.17 cm²/g), were determined by N₂ adsorption using Brunauer-Emmett-Teller (BET) surface analyzer. RHAC was also characterized for its morphology and its elemental compositions. The adsorption studies for the removal of Ni²⁺ from aqueous solution were carried out using different dosage of RHAC as adsorbent as a function of varied contact time. The concentration of Ni²⁺ was determined by atomic absorption spectrometer (AAS). The results obtained from adsorption studies indicate good potential of rice husk as a cheap precursor to produce activated carbon for the removal of Ni²⁺ from aqueous solution. The equilibrium data from adsorption studies fitted well the of Langmuir and Freundlich isotherm models.

Abstract: Natural fibres are preferred compared to synthetic fibres because of several advantages such as biodegradable, lightweight, low cost and good mechanical properties. Roselle is one of the plants found to be suitable to be used to produce natural fibres. Although natural fiber reinforced composites are becoming widely used, several weaknesses such as lack of good interfacial adhesion, low melting point and poor resistance to moisture absorption are harmful to its further acceptance. Chemical treatment is a method that can improve the interfacial bonding, stop water absorption, clean the fibre and increase surface roughness. In this study, roselle fibres were immersed in Sodium hydroxide (NaOH) with 3 different concentration (3, 6, and 9%). The results before and after treatment were compared. Scanning electron microscope was used to examine the surface morphology. Tensile properties of roselle fibre were performed to study the tensile properties. Results shows that the higher concentration of NaOH will increase the surface roughness and have higher ability to clean the fibre. For tensile properties, 6% of NaOH give the highest tensile strength. It can be concluded that, 6% of NaOH is the most suitable concentration to clean roselle fibre and while maintaining good tensile properties.