Displaying publications 1 - 20 of 705 in total

  1. Nurulhuda Amri, Ridzuan Zakaria, Mohamad Zailani Abu Bakar
    The adsorption of phenol, from aqueous solutions on activated carbon from waste tyres, was studied in a batch system at different initial concentrations (100-500mg/L) at 30°C for 48 hours. The activated carbon was prepared using the two-step physiochemical activation, with potassium hydroxide (KOH) at ratio KOH/char = 5. The carbonization process was done at 800°C for 1 hour with nitrogen flow rate 150ml/min, followed by the activation with the carbon dioxide flow rate 150ml/min at 800°C for 2 hours. The adsorption isotherms were determined by shaking 0.1g of activated carbon with 100ml phenol solutions. The initial and final concentrations of phenol in aqueous solution were analyzed using the UV-Visible Spectrophotometer (Shimadzu, UV-1601) at a wavelength of 270nm. Experimental isotherm data were analyzed using the Langmuir and Freundlich isotherm models.The equilibrium data for phenol adsorption could fit both isotherm models well with the R2 value of 0.9774 and 0.9895, respectively. The maximum adsorption capacity of the adsorbent obtained from the Langmuir model was up to 156.25 mg/g
  2. Mohd. Sanusi Che Kadir, Jamaliah Md. Jahim, Nurina Anuar, Mohd. Sobri Takrif, Zahira Yaakub
    In this study, an anaerobic mesophilic bacterial strain, namely Clostridium butyricum KBH1, was isolated from a natural source. This strain grew well and produced biogas with an average hydrogen concentration of 60% (v/v) in the Reinforced Clostridial Media (RCM). To study the basic nutrient requirements, three main nutrients namely peptone (Pep), yeast extracts (Yes) and glucose (Glu) were chosen as factors, using an experimental design. The experiments were run according to 23 Full Factorial Design, followed by the Response Surface Method (RSM). The fermentation was performed in 30 ml serum bottles with 20 ml working volume in a sterile and anaerobic condition at 37°C with 5% inoculums. The results from the Analysis of Variance (ANOVA) for the factorial design showed that all the three factors had significantly affected the gas production by the C. butyricum. The response surface plot of the gas production by C. butyricum showed that the gas production could be enhanced by increasing peptone and yeast extract concentrations up to 15 g/l and 24 g/l respectively, without showing any substrate inhibition. Meanwhile, the glucose concentration showed an optimum at the middle point (8 g/l) with possible substrate inhibition at a high concentration (12 g/l). The total biogas production could be correlated to the three factors, using the quadratic equation: Gas =0.17 + 7.11Glu - 0.02Pep + 0.77Yes - 0.53Glu2 + 0.09Glu*Pep. The experimental results showed that the strain could grow well in substrate with high organic nitrogen content such as POME and might be not suitable for substrate with high sugar content due to substrate inhibition.
  3. Shamsabadi, H.T., Biabani, A., Desa Ahmad
    A field study was conducted on the effect of four primary tillage implements and three seed densities on the grain yield of rain fed wheat (Tajan cultivar), using a drill planting machine with the end wheels. The experimental design was a split plot design in a 4×3 factorial with three replications. In this study, the main plots were the tillage treatments, namely Mouldboard plough, Disc Plough, Chisel Plough, Offset Disc, and sub-plots were seed rates of 350, 400 and 450 seeds.m-2. Determinations included grain yield and selected yield components. The results showed that grain yield was not affected by the densities of seed and tillage machine treatments. The use of Chisel Plough, with 400 seeds.m-2 sowing rate, had the highest grain yield of wheat grown in the Golestan province (Iran), a region with an average annual rainfall of 450 mm.
  4. Wee, Siaw Khur, Chok, Vui Soon, Gorin, Alexander, Chua, Han Bing, Yan, Hong Ming
    Compartmented Fluidized Bed Gasifier (CFBG), consisting of two compartments - the combustorand gasifier, uses air blown instead of pure oxygen for syngas production in bubbling fluidization mode, eliminating the need of air separation unit, and reducing the capital cost, thus distinguishes it from other traditional ones. Fluidization quality is a determining factor in the CFBG to guarantee its well-lifted behaviour. Previous study, without solid circulation at ambient conditions, brought to the fore the necessity of considering the effect of the minimum allowable effective diameter. The study was then performed in the CFBG cold physical model of 0.66m overall diameter (effective diameter for combustor and gasifier is 0.413m and 0.257m) to investigate the fluidization quality and compare it with the results obtained from the previous cold model of about 1.36 times smaller, but with the same compartmented ratio of 65:35. Different inert particles (river sand, quartz sand and alumina) were used, over a range of aspect ratios, for the aforementioned objective. The results showed that the fluidization quality in the gasifier has not been achieved and the degradation of fluidization quality in the combustor is still observed, notwithstanding the fact that the condition of the minimum allowable effective diameter has been met. The reduction of distributor free area, to increase the distributor pressure drop, showed a marginal effect on the quality. The effect of the minimum allowable effective diameter on fluidization quality in CFBG as well as the interplay of geometric and operational parameters require further studies be carried out. The fluidization quality of the binary mixture is also currently under investigation.
  5. Bakhshan, Y., Shahrir Abdullah
    An in-house quasi-dimensional code has been developed which simulate the overlap, intake, compression, combustion, as well as expansion and exhaust processes of a homogeneous charged internal combustion engine (ICE). A detailed chemical kinetic mechanism, constituting of 39 species and 148 elementary reactions, has been used in conjunction with above code to study the combustion of CNG under IC engine conditions. Two different criteria, based on pressure rise and mass of fuel burned, are used to detect the onset of ignition. Parametric studies are conducted to show the effect of compression ratio, initial pressure, intake temperature and equivalence ratio, on the time of ignition and fuel burning rate. The results obtained from the modelling show a good agreement with the experimental data.
  6. Lim, Kean Pah, Abdul Halim Shaari, Chen, Soo Kien, Ng, Siau Wei, Zalita Zainuddin, Ye, Chau Yuen
    A series of polycrystalline samples (La1-xSmx)0.67Sr0.33MnO3 (X=0.00, 0.05 and 0.10) were prepared using the conventional solid-state reaction method. The XRD analysis indicated that all the samples were fully crystalline and in a single phase with a rhombohedral structure after a sintering at 1200ºC for 24 hours in air. Meanwhile, the Atomic Force Microscopy measurements showed that a small amount of Sm doping in La sites affected the grain growth and this might affect the grain boundary layer, thus resulting in the reduction of the Curie temperature, TC. Extrinsic magnetoresistance (MR) was observed for all the samples with a large negative MR at low field (0-0.1 or 0.2T) region, followed by a slower varying MR at high field (0.1 or 0.2-1T). The highest low-field MR value of -4.6% (at 0.1T) and -6.1% (at 0.2T) were observed for sample X=0.10 and X=0.05, respectively. Hence, these indicated that the extrinsic MR was grain size dependent and was therefore enhanced with a small amount of Sm substitution in La sites.
  7. Noraishah Othman, Siti Kartom Kamarudin, Muhd Noor Md Yunus, Abd. Halim Shamsuddin, Siti Rozaimah, Zahirah Yaakob
    The production of carbon dioxide from Karas woods under argon atmosphere was investigated using a direct pyrolysis-combustion approach. Direct burning was used in this study, using argon for yrolysis and oxygen during combustion to look at the yield of carbon dioxide, produced at different parameters, such as the temperature, retention time and flow rate of argon, as the carrier gas. In this study, a new methodology, 23 response surface central composite design was successfully employed for the experimental design and analysis of results. Central composite experimental design and response surface method were utilized to determine the best operating condition for a maximum carbon dioxide production. Appropriate predictable empirical linear model was developed by incorporating interaction effects of all the variables involved. The results of the analysis revealed that linear equation models fitted well with the experimental for carbon dioxide yield. Nevertheless, the R-Squared obtained using the direct pyrolysis-combustion was 0.7118, indicating that the regression line was not at the best-fitted line.
  8. Chatterji, Ani, Faizah Shaharom
    The central coast of Tamil Nadu, Andaman and Nicobar Islands, along with other regions, was severely hit by the tsunami on 26 December 2004. A strange spawning behaviour of the Indian horseshoe crabs (Tachypleus gigas, Müller) was observed after the tsunami disturbance. Along the northeast coast of India, the horseshoe crabs normally migrate towards the shore in large numbers coinciding with the tidal height and grain size of the sediment and spawn in nests made in sand. The spawning behaviour was normal until November 2004 and throughout that period about 35 to 45 nests in 200 m2 of area of the breeding beach were examined. However, no nesting was observed from December 2004 to March 2005, i.e. after the occurrence of tsunami. The number of nests per 200 m2 of area (~82) and the number of eggs per nest (750-1000 eggs) were increased considerably when the normal conditions were restored in April 2005. The absence of spawning migration, from December 2004 to March 2005, is totally an unusual behaviour and this happened for the first time during the past several years of the study period.
  9. Ee, G.C.L., Jong, V.Y.M., Sukari, M.A., Rahmani, M., Kua, A.S.M.
    The roots of Calophyllum inophyllum (Guttiferae), furnished six xanthones which are brasilixanthone (1), 1,3,5-trihydroxy-2- methoxy xanthone (2), caloxanthone A (3), pyranojacareubin (4), caloxanthone B (5) and tovopyrifolin (6), Structural elucidations of these compounds, were achieved through 1D and 2D NMR andMS techniques. In this paper, the isolation and structural elucidation data for these xanthones are reported.
  10. Arasan, Jayanthi
    This paper investigates several asymptotic confidence interval estimates, based on the Wald, likelihood ratio and the score statistics for the parameters of a parallel two-component system model, with dependent failure and a time varying covariate, when data is censored. This model is an extension of the bivariate exponential model. The procedures are investigated via a coverage probability study using the simulated data. The results clearly indicate that the interval estimates, based on the likelihood ratio method, work better than any of the other two methods when dealing with the censored data.
  11. Nor Aishah Saidina Amin, Soon, Ee Peng
    Thermodynamic chemical equilibrium analysis using, total Gibbs energy minimization method, was carried out for methane oxidation to higher hydrocarbons. For a large methane conversion and a high selectivity to higher hydrocarbons, the system temperature and oxygen concentration played a vital role, whereas, the system pressure only slightly influenced the two variables. Numerical results showed that the conversion of methane increased with the concentration of oxygen and reaction temperature, but it decreased with pressure. Nevertheless, the presence of oxygen suppressed the formation of higher hydrocarbons which mostly consisted of aromatics, but enhanced the formation of hydrogen. As the system pressure increased, the aromatics, olefins and hydrogen yields diminished, but the paraffin yield improved. Carbon monoxide seemed to be the major oxygen-containing equilibrium product from methane oxidation, whilst almost no H2O, CH3OH and HCOH were detected although traces amount of carbon dioxide were formed at relatively lower temperature and higher pressure. The total Gibbs energy minimization method is useful to theoretically analyze the feasibility of methane conversion to higher hydrocarbons and syngas at the selected temperature and pressure.
  12. Zurina Zainal Abidin, Zalini Yunus, Markx, Gerard H.
    The dielectrophoretic (DEP) separation of cell, using microelectrodes structure, has been limited to small scale due to size of the substrate. This work was carried out to extend the capability of microelectrodes system by orientating the microelectrodes in three dimensions (3-D) for larger scale dielectrophoretic separation of microorganism. The designed 3-D separation chamber consists of microelectrodes on two opposing walls. Based on the FEMLAB simulation, the electric field was seen to be generated across the chamber, rather than between adjacent electrodes in the same plane like in the small scale system. This configuration led to a stronger electric field in the bulk medium. The experimental results showed that the 3-D microelectrodes chamber behaved similar to the system with microelectrodes on one wall. The effects of the main parameters such as voltage, frequency and flow rates were similar to that of the systems with all the electrodes on one wall, but on the overall, capture more cells. A gap size between 250 – 500 μm resulted in an electric field which is strong enough to hold cells while giving a reasonable cross sectional area at the same time. Although there is some improvement achieved by 3-D system, it is still not very much, as compared to the small scale system.
  13. Waje, Samaila Bawa, Noorhana Yahya, Irmawati Ramli
    Monoclinic bismuth oxide (α-Bi2O3) nanoparticles were prepared via precipitation method and
    irradiated with a pulsed laser forming thin films. Their phase and surface morphological properties
    were investigated using x-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron
    microscopy (SEM) and high resolution transmission electron microscopy (HR-TEM). The XRD
    analysis shows the phase transformation to a partially crystalline tetragonal phase β-Bi2O3 thin film.
    The SEM micrograph of the nanoparticles, with an average crystal size of 72 nm, was seen to form
    a thin film with a peculiar structure, coined as “cotton-like”, is attributed to the high surface energy
    absorbed by the nanoparticles during ablation. The HR-TEM micrograph shows the particulate with
    a clearly defined interlayer spacing.
  14. Ahmed A. Ahmed Al-Dulaimi, Shahrir Hashim, Mohammed Ilyas Khan
    Polyaniline (PANI) and polyaniline composites with aluminium oxide (Al2O3) were prepared using the in situ polymerization method. The composites were then blended with acrylic paint and applied to carbon steel panels. The coated steel panels were evaluated for corrosion using the immersion test technique. The results revealed that the steel panels coated with polyaniline composites and with Al2O3 containing coatings had small corrosion as compared to the bare sample and the samples coated with polyaniline and paint alone. The samples were characterized by Fourier transform infrared (FTIR) and X-ray diffraction(XRD). In addition, the morphology of the finished samples was observed using the scanning electron microscopy (SEM). This novel composite was used as a paint pigment for enhancing the barrier properties and the paint protectable against aggressive ions. Meanwhile, corrosion was evaluated through visual monitoring using a digital camera after 60 days of fully immersion test in 5% NaCl. The weight loss method was also used to evaluate corrosion.
  15. Zainab Shakir Radif, Aidy Ali, Khalina Abdan
    This study was conducted for the development of the green protection garments. For this purpose, laminate composite material was developed from Kevlar 29-ramie-unsaturated polyester resin. The aim of this study was to develop a solid body armour that meets the specific requirements of ballistic resistance. This composite is subjected to high impact loading. The target was shot using gas gun machine that is supported by camera hardware to capture the projectile speed. In order to achieve the goal of the research, several experiments were conducted with the aim to estimate the ballistic limit, maximum energy absorption, composite failure mode, life time rupture, target geometry, and environmental effect. The results of these experiments indicated that the maximum ballistic limit validated at impact speed is in the range of 250 m/s to 656.8 m/s for the second protection level. The targets are improved in term of the impact response with the increase in the relative humidity, i.e. the range of 50% ± 20%, whereas, reduction of resistance results in the increase of temperature. The range of temperatures was between 20oC and 70oC. A limited delamination was generated under multiple shots. Targets geometry plays a major role in increasing the impact response. Hence, the results present a high resistant impact for pairs from the panels with total thickness arrived to 15
    mm ± 3 mm. This body armour is one of the most economical armour products, in which common materials are used in its production, particularly to reduce the amount of Kevlar, and this could further lead to a decrease in its production cost. On the other hand, this armour meets the ballistic threats under 623 m/s of 15 mm ± 3 mm target thickness and 837.5 m/s of 25 mm ± 2.mm. Thus, the armour is equivalent to the third level of protective ballistic limits in the National Institute of Justice (NIJ) standards.
  16. Tan, Yih Tyng, Abdul Rahman Othman, Lai, Choo Heng
    Setting a question paper for test, quiz, and examination is one of the teachers’ tasks. The factors that are usually taken into consideration in carrying out this particular task are the level of difficulty of the questions and the level of the students’ ability. In addition, teachers will also have to consider the number of questions that have impact on the examination. This research describes a model-based test theory to study the confidence intervals for the projected number of items of a test, given the reliability of the test, the difficulty of the question, and the students’ ability. Using the simulated data, the confidence intervals of the projected number of items were examined. The probability coverage and the length of the confidence interval were also used to evaluate the confidence intervals. The results showed that the data with a normal distribution, the ratio variance components of 4:1:5 and reliability equal to 0.80 gave the best confidence interval for the projected number of items.
  17. Zahari Taha, Ruhaizin Sulaiman
    The physical strength of the elderly aged above 60 years is typically 10 to 30% less than the young adult population of ages between 25 to 35 years. This reduction of strength has a strong impact on the activity of the daily living (ADL) of the elderly population. There has been little research done studying on the physical strength of the elderly population in Malaysia. The objective of this study was to determine the static strength of the elderly population in Malaysia. In particular, the grip and pinch strength were investigated as these two static strengths are extensively used in their instrumental activity of daily living (IADL). The results were then compared to the strength of the university students. A total of 30 subjects (15 males and 15 females) participated in the study. Their age ranged between 60 to 83 years, with the mean of age of 67.1 years. The comparison group comprised a total of 30 university students (20 male, 10 female) aged between 23 to 24 years, with the mean of age of 23.2 years. Grip and pinch strengths of both groups were measured and analysed using a descriptive statistics. It was found that the elderly male subjects are stronger in both strength measurements than their female counterpart. The 95th percentile of the female grip strength was slightly lower than that of the male while the male pinch strength was 31.07% higher. It was also found that the male students had higher strengths compared to the females. The grip strength of the elderly was 30.66% lower than the university student, while their pinch strength was 13.42% lower. Both static strengths of the elderly were found to be lower than those of the university students. This supported the research hypotheses postulating that the static strength had a negative correlation with age. In terms of gender differences, the male subjects were found to be stronger than the females.
  18. Thamer Ahmed Mohammed, Abdul Halim Ghazali, Al-Hassoun, Saleh
    Malaysia is a tropical country and it is subjected to flooding in both the urban and rural areas. Flood
    modelling can help to reduce the impacts of flood hazard by taking extra precautions. HEC-RAS model was used to predict the flood levels at selected reach of the Langat River with a total length of 34.4 km. The Langat River is located in the state of Selangor, Malaysia and it is subjected to regular flooding. The selected reach of the Langat River has insufficient data and a methodology was proposed to overcome this particular problem. Since complete floodplain data for the area are not available, the modelling therefore assumed vertical walls at the left and right banks of the Langat River and all the predicted flood levels above the banks were based on this assumption. The HECRAS model was calibrated and the values of Manning’s coefficients of roughness for the Langat River were found to range from 0.04 to 0.10. The discharge values were calculated for 5, 10, 25, 50, and 100 year return periods and the maximum predicted flood depth ranged from 2.1m to 7.8m. Meanwhile, the model output was verified using the historical record and the error between the recorded and predicted water levels was found to range from 3% to 15%.
  19. Ghiasi, Vahed, Husaini Omar
    Shotcrete is a process where concrete is projected or “shot” under pressure, using a feeder or a
    “gun” onto a surface to form structural shapes including walls, floors, and roofs. The surface can
    be wood, steel, polystyrene, or any other surfaces that concrete can be projected onto. The surface
    can be trowel led smooth while the concrete is still wet. Shotcrete has high strength, durability, low
    permeability, excellent bond, and limitless shape possibilities. These properties allow shotcrete
    to be used as a structural material in most cases. Although the hardened properties of shotcrete
    are similar to conventional cast-in-place concrete, the nature of the placement process provides
    additional benefits, such as excellent bond with most substrates and instant or rapid capabilities,
    particularly on complex forms or shapes. In addition to building homes, shotcrete can also be used
    to build pools. The practice of underground tunneling shows that the degree of stability of tunnels
    is dependent on the state of the soil, rock mass, and shotcrete around the tunnel contour. The
    development in the urban or suburban areas leads to the construction of tunnels in all kinds of soil
    and rock. Meanwhile, the construction of tunnels in shallow depth or soft soils causes the ground
    to displace. The determination of soil and rock mechanical properties to assess the stability of New
    Austrian Tunnelling Method (NATM) tunnels and design the support system is one of the most
    important steps in tunnelling. This paper provides information pertaining to the safety and increase
    the stability of NATM tunnel before, during and after the operation of the tunnel. Therefore, the
    shotcrete process is a recognized method for cemented sandy silt stabilization, with the aid of high
    pressure shot concrete to increase the stability of tunnels.
  20. Agung Efriyo Hadi, Mohd. Sapuan Salit, Megat Mohd. Hamdan Megat Ahmad, Khairul Zaman Hj Mohd. Dahlan, Mustofa Usman
    The physical properties by natural fibre have a great importance, specifically in the structural of natural fibre which reinforces matrix. Response surface methodology with Box-Behnken (BB) design of experiment was utilized to study water absorption and melt flow index (MFI) of abaca fibre reinforced high impact polystyrene (HIPS) composites. The design utilizes fraction of weight abaca fibre, maleic anhydride (MAH), and impact modifier to develop models for characteristic behaviours of water absorption and MFI of composites. Abaca fibre reinforced high impact polystyrene (HIPS) composites were produced with different fibre loadings (30, 40, and 50 wt%), different compositions of coupling agent, maleic anhydried (MAH) (1, 2, and 3 wt%) and different compositions of impact modifier (4, 5, 6 wt%). The individual optimum of water absorption was found when loading abaca fibre close to 34.61 wt%, maleic anhydride 1 wt%, and impact modifier 4.01 wt%. The individual optimum of melt flow index dealt with loading abaca fibre 36.71 wt%, maleic anhydride 3 wt% and impact modifier 4.02 wt%. Meanwhile, the optimum condition for water absorption of abaca fibre reinforced HIPS composites was followed by a decreasing trend of the value of melt flow index.
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