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Articles by N. Muhammad
Total Records ( 4 ) for N. Muhammad
  Y.H.P. Manurung , N. Muhammad , E. Haruman , S.K. Abas , G. Tham , K.M. Salleh and C.Y. Chau
  This study investigates the development of weld nugget and Heat Affected Zone (HAZ) in Resistance Spot Welding (RSW) using numerical simulation approach and experimental process. The finite element modeling technique known as SYSWELD was utilized for the simulation process. In the simulation process, a two dimensional axis-symmetric finite element model using customized electrode meshing modeling was chosen to develop the thermal-mechanical-electrical characteristic of the spot weld. The model was developed for welding of two and three sheets of 1 mm thick low carbon steel by flat-faced copper electrodes. The RSW simulation parameters such as force, weld current, weld time and the temperature distribution of the welded sheets and electrodes used were taken into consideration throughout the study. For the experimental verification, an actual welding by RSW with similar welding parameter was carried out. The formation of spot weld nugget and HAZ, based on the common welding parameter for simulation and experiment were compared and discussed. It was found that the theoretical radius of weld nugget and HAZ developed by finite element method are accurately correlated with the results of the experiment.
  A.N. Shuid , L.K. Siang , T.G. Chin , N. Muhammad , N. Mohamed and I.N. Soelaiman
  Eurycoma longifolia (EL) is a widely used herbal extract by men as aphrodisiac. However, there are no complete toxicity studies done on it. This study was conducted to determine the acute and subacute toxicities of EL on male Sprague-Dawley rats. Both acute and subacute studies were done according to the Organization for Economic Cooperation and Development (OECD) Guideline. In acute toxicity study, Eurycoma longifolia (EL) aqueous extract at the dose of 5000 mg kg-1 body weight was given to rats within 24 h by oral gavage. In subacute toxicity study, the first group of rats served as the control group while the other three groups were given EL aqueous extract at doses of 600, 1200 and 2400 mg kg-1 bodyweight, respectively via daily oral gavages for 28 days. Histopathological examination was done on the testes, kidneys and liver for acute and subacute toxicity study. Biochemistry and haematology analysis as well as thin blood film were done for subacute toxicity study. The oral LD50 for EL aqueous extract was found to be more than 5000 mg kg-1. No pathological changes were observed in the rat liver, testes and kidneys in the acute toxicity study. Subacute toxicity study showed no significant changes in biochemical and haematological parameters while thin blood films were normal. No pathological changes were found in the testes and kidneys. However, hydropic changes were found in the livers of a few of the treated rats. This study shows the EL extract does not cause acute toxicity but was found to cause hepatotoxicity in subacute toxicity study.
  N. Muhammad , Z. Man , M.A.B. Khalil and Y.A. Elsheikh
  In today’s world the energy crisis is the main concern. It has been tried to develop substitute materials of petroleum and other decreasing natural fuel resources. Biomass is an abundant and renewable resource and it impelled researcher to develop suitable and proficient ways for converting it to valuable chemicals, biofuels and biomaterials. Due to their several advantageous properties ionic liquid was used for the dissolution of biomass. Biomass after dissolution in ionic liquids was regenerated with reconstitutes solvents (acetone/water). The regenerated material was characterized by FT-IR, XRD and SEM and compared with untreated biomass. The regenerated material was found to exhibit more homogeneity in the microstructure and the fibrous nature of material disappeared after dissolution. The crystallinity of cellulose was changed from cellulose I to amorphous during dissolution and regeneration from ionic liquids.
  M. Farooq , A. Ramli , S. Gul and N. Muhammad
  Vegetable oils due to high biodegradability, low toxicity, renewability and excellent lubricating performance, have immense potential to replace mineral oils as feedstock for lubricants. Owing to these aspects environmentalists and engineers have made attempts to explore the possibilities of using vegetable oils as environmentally friendly lubricants for range of applications. In this work, the tribological properties of castor oil and sesame oil in the presence of 12-hydroxystearic acid as anti-wear additive were investigated using four-ball tribometer. The viscosity, acid value, peroxide value and iodine value of the selected oils were determined experimentally following AOCS methods. Results revealed that the addition of 12-hydroxystearic acid improved the anti-wear performance of the selected vegetable oils. Moreover, it was noted from the results that 12-hydroxystearic acid was more effective as anti-wear additive in the castor oil as compared to sesame oil under similar experimental conditions. The improved anti-wear performance of the selected vegetable oils in the presence of additive may be attributed to the formation of protective layer as a result of tribochemical reaction on the metal surface.
 
 
 
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