Displaying publications 1 - 20 of 173 in total

  1. Rosli, Y., Maddess, T.L., James, A.C., Goh, X.L.
    ASM Science Journal, 2009;3(1):31-37.
    Responses were recorded from normal healthy subjects and age-related macular degeneration (AMD) patients and evaluated, using a new variant of mfVEP. Subjects information was recorded using 64 EEG channels with a computer-based acquisition system. The stimulus layout was a 84 region corticallyscaled dartboard comprising 12 sectors and seven concentric rings subtending a diameter of 23º, presented dichoptically at 60 Hz. Data from the control and AMD patients were statistically compared when fitted concurrently into the multiple regression analysis. The Pattern-pulse mfVEP technique could distinguish between normal eyes and those with a definite diagnosis of dry and wet AMD when responses from the macula were considered.
  2. Tan, C.T., Chua, K.B., Wong, K.T.
    ASM Science Journal, 2009;3(1):91-96.
    The Nipah virus was first discovered in 1999, following a severe outbreak of viral encephalitis among pig farm workers in Malaysia. The virus was thought to have spread from Pteropus bats to pigs, then from infected pigs to humans by close contact. Mortality of the disease was high at about 40%. The main necropsy finding was disseminated microinfarction associated with vasculitis and direct neuronal involvement. Relapsed encephalitis was seen in approximately 10% of those who survived the initial illness. Since its first recorded emergence in peninsular Malaysia, 10 outbreaks of Nipah virus encephalitis have been reported in Bangladesh and West Bengal in India. The outbreaks occurred from January to May, with Pteropus giganteus as the reservoir of the virus. In Bangladesh, evidence indicated that the virus transmitted directly from bats to human, with human to human transmission as an important mode of spread. The mortality of the illness was higher in Bangladesh which stood at around 70%. This was likely to be due to genetic variation of the virus.
  3. Al-Haddad, S.A.R., Samad, S.A., Hussain, A., Ishak, K.A., Noor, A.O.A.
    ASM Science Journal, 2008;2(1):75-81.
    Robustness is a key issue in speech recognition. A speech recognition algorithm for Malay digits from zero to nine and an algorithm for noise cancellation by using recursive least squares (RLS) is proposed in this article. This system consisted of speech processing inclusive of digit margin and recognition using zero crossing and energy calculations. Mel-frequency cepstral coefficient vectors were used to provide an estimate of the vocal tract filter. Meanwhile dynamic time warping was used to detect the nearest recorded voice with appropriate global constraint. The global constraint was used to set a valid search region because the variation of the speech rate of the speaker was considered to be limited in a reasonable range which meant that it could prune the unreasonable search space. The algorithm was tested on speech samples that were recorded as part of a Malay corpus. The results showed that the algorithm managed to recognize almost 80.5% of the Malay digits for all recorded words. The addition of a RLS noise canceller in the preprocessing stage increased the accuracy to 94.1%.
  4. Chai, S.P., Zein, S.H.S., Mohamed, A.R.
    ASM Science Journal, 2008;2(1):57-64.
    Since the discovery of carbon nanotubes (CNTs) in 1991, a fundamental question still remained on how to control morphologically the synthesis of CNTs. This task has always been a challenge. In this paper, we report the results that we have published previously with the aim of sharing the possible controlled synthesis approach via this novel production method. Findings demonstrated that various CNTs could be synthesized by using specially developed supported catalysts from the catalytic decomposition of methane. These synthesized CNTs include carbon nanofibres, single-walled and multi-walled CNTs, Y-junction CNTs and CNTs with special morphologies. It was also revealed that catalyst composition and reaction parameters played an important role in controlling the morphology and type of CNTs formed. The synthesis of CNTs with various morphologies is important because this can enrich the nanostructures of the carbon family. This finding also provides useful data for better understanding of the parameters that govern the growth mechanism of CNTs which may be required in the near future for enhanced controlled synthesis of CNTs.
  5. Mahdi, M.A., Md. Ali, M.I., Ahmad, A., Zamzuri, A.K.
    ASM Science Journal, 2008;2(2):123-127.
    In this paper a study on the wideband double-pass Raman fibre amplifier with mirror as the pump reflector is reported. The pump lights at 1435 nm and 1455 nm were launched in a co-directional manner with respect to the input signal. The double-pass direction of the signal was achieved through a fibre loop mirror constructed using an optical circulator. It was shown that multiple signal amplification was achieved without any disturbance of stimulated Brillouin scattering.
  6. Manimaran, R., Abdul-Rashid, H.A.
    ASM Science Journal, 2008;2(2):133-137.
    This paper proposes a signal-to-noise-ratio (SNR) improvement by using an external phase modulator that allowed flexible control of the spectrum amplitude by varying the modulation index for linewidth measurements. Compared with the conventional self-heterodyne detection technique, the results obtained in this study showed an SNR improvement as high as 10 dB. This 10 dB improvement in SNR could help to reduce the usage of a particular length of a single mode fibre (normally about 50 Km) when measuring a linewidth in the region of 10 kHz.
  7. Muhd-Yassin, S.Z., Harun, S.W., Ahmad, H., Abd-Rahman, M.K.
    ASM Science Journal, 2008;2(2):163-168.
    An efficient erbium/ytterbium co-doped fibre amplifier was demonstrated by using a dual-stage partial doublepass structure with a band-pass filter (BPF). The amplifier achieved the maximum small signal gain of 56 dB and the corresponding noise figure of 4.66 dB at 1536 nm with an input signal power and total pump power of –50 dBm and 140 mW, respectively. Compared with a conventional single-stage amplifier, the maximum gain enhancement of 16.99 dB was obtained at 1544 nm with the corresponding noise figure was improved by 2 dB. The proposed amplifier structure only used a single pump source with a partial double pass scheme to provide a high gain and dual-stage structure to provide the low noise figure.
  8. Yusoff, M.H.M., Hassan, H.A., Hashim, M.R., Abd-Rahman, M.K.
    ASM Science Journal, 2008;2(2):139-148.
    The fabrication tolerance of a short and compact low refractive index grating waveguide polarisation splitter based on the principle of resonant tunnelling was analyzed in this study. The design utilised two grating waveguides with an intermediate conventional waveguide layer. The design and optimisation were conducted using the quasi 2-D effective index solver with global search algorithm. An optimum device operating at 1.55 μm wavelength was obtained at a length of 340 μm. The splitting ratios were calculated to be 36 dB and 15 dB, and the overall device transmission efficiencies, after considering the three-dimensional waveguide leakage loss, were estimated at 88% and 83% for tranverse magnetic and tranverse electric polarisation, respectively.
  9. Al-Araji, L., Rahman, R.N.Z.A., Basri, M., Salleh, A.B.
    ASM Science Journal, 2008;2(1):45-56.
    The growth and production of biosurfactant by P. seudomonas aeruginosa (181) was dependant on nutritional factors. Among the eleven carbon sources tested, glucose supported the maximum growth (0.25 g/L) with the highest biosurfactant yield and this was followed by glycerol. Glucose reduced the surface tension to 35.3 dyne/cm and gave an E24 reading of 62.7%. Butanol gave the lowest growth and had no biosurfactant production. For the nitrogen sources tested, casamino acid supported a growth of 0.21 g/L which reduced the surface tension to 41.1 dyne/cm and gave an E24 reading of 56%. Soytone was assimilated similarly, with good growth and high biosurfactant production. Corn steep liquor gave the lowest growth and did not show any biosurfactant activity.
  10. Marghany, M., Cracknell, A.P., Hashim, M.
    ASM Science Journal, 2009;3(1):7-16.
    This paper introduces a method for modification of the formula of the fractal box counting dimension. The method is based on the utilization of the probability distribution formula in the fractal box count. The purpose of this method is to use it for the discrimination of oil spill areas from the surrounding features e.g. sea surface and look-alikes in RADARSAT-1 SAR data. The result showed that the new formula of the fractal box counting dimension was able to discriminate between oil spills and look-alike areas. The low wind area had the highest fractal dimension peak of 2.9, as compared to the oil slick and the surrounding rough sea. The maximum error standard deviation of the low wind area was 0.68 which performed with a 2.9 fractal dimension value.
  11. Omar, N.Y.M., Rahman, N.A., Zain, S.M.
    ASM Science Journal, 2009;3(1):77-90.
    Computational chemistry is a discipline that concerns the computing of physical and chemical properties of atoms and molecules using the fundamentals of quantum mechanics. The expense of computational chemistry calculations is significant and limited by available computational capabilities. The use of high-performance computing clusters alleviate such calculations. However, as high-performance computing (HPC) clusters have always required a balance between four major factors: raw computing power, memory size, I/O capacity, and communication capacity. In this paper, we present the results of standard HPC benchmarks in order to help assess the performance characteristics of the various hardware and software components of a home-built commodity-class Linux cluster. We optimized a range of TCP/MPICH parameters and achieved a maximum MPICH bandwidth of 666 Mbps. The bandwidth and latency of GA put/get operations were better than the corresponding MPICH send/receive ones. We also examined the NFS, PVFS2, and Lustre parallel filesystems and Lustre provided the best read/write bandwidths with more than 90% of those of the local filesystem.
  12. Bidin, N.
    ASM Science Journal, 2008;2(2):179-182.
    The laser technology laboratory (LTL) of the Physics Department, University of Technology Malaysia was established in 1989 to support research and development activities. The laboratory provides activities for short- and long-term projects to serve final year undergraduate and post-graduate students in masters and PhD programmes.
  13. Shaari, S., Ehsan, A.A., Abd-Rahman, M.K.
    ASM Science Journal, 2008;2(2):153-161.
    An optical code generating device for a portable optical access-card system was constructed using the plastic optical fibre (POF) waveguide coupler. The newly constructed device provided output light intensities which were used as optical codes in a portable optical access-card system. The construction of a basic 1 × 2 waveguide design combined two major components which were the asymmetric Y-junction splitter and the linear taper. A hollow waveguide structure was utilized as it provided more flexibility in guiding light rays. A basic 1 × 2 waveguide coupler was designed using the CAD tool and then the ray was traced using the non-sequential ray tracing tool. A linear relationship between the tap-off ratio and the waveguide tap-width enabled a higher-level hollow waveguide coupler to be designed using the simple cascading technique. Construction of a 1 × 4 and higher level waveguide coupler was easily realized using the basic 1 × 2 waveguide coupler design together with a simple cascading technique.
  14. Abdul-Rashid, H.A., Al-Qdah, M.T., Chuah, H.T., Tayahi, M.
    ASM Science Journal, 2008;2(2):129-132.
    The operating principle and the performance of chromatic dispersion (CD) measurement technique are discussed through developed numerical models. The performance of the CD measurement technique was studied in terms of the measurement range and sensitivity as the wavelength separation was varied. Based on the numerical model, the technique sensitivity increased with wavelength separation. However, this increase in sensitivity was traded off with a narrower measurement range. The measurement technique was optimized at 5.0 GHz wavelength separation with a sensitivity of 0.009 (dB/ps/nm) and measurement range of 2500 ps/nm.
  15. Al-Mansoori, M.H., Mahdi, M.A., Iqbal, S.J., Abdullah, M.K.
    ASM Science Journal, 2008;2(2):107-113.
    In this paper, the tuning range characteristics of a multiwavelength L-band Brillouin-erbium fibre laser utilizing a linear cavity is described. The dependency of the Stokes signal tuning range on the laser’s pumping power and single mode fibre length is elaborated. The proposed laser configuration exhibited a wide tuning range of 11 nm from 1599 nm to 1610 nm. The maximum number of 28 output channels with a spacing of 10.5 GHz was achieved by setting the Brillouin pump wavelength and power at 1603.1 nm and 1.1 mW, respectively. The wider tuning range and higher number of Brillouin Stokes contributed to the higher efficiency of doublepass amplification in the erbium gain medium and also to the bidirectional generation of Brillouin Stokes in the single-mode fibre.
  16. Harun, S.W., Hofmann, P., Schulzgen, A., Li, L., Peyghambarian, N., Ahmad, H.
    ASM Science Journal, 2008;2(2):149-152.
    A distributed feedback fibre laser made of highly Er-Yb co-doped phosphate glass fibre was demonstrated experimentally. The 45 mm long fibre laser device operated at 1540 nm with more than 50 dB side mode suppression ratio. However, the output power was still relatively lower due to un-optimized grating structure and thermal management.
  17. Mahdi, M.A., Sheih, S.J., Al-Mansoori, M.H., Zamzuri, A.K., Adikan, F.R.M.
    ASM Science Journal, 2008;2(2):115-122.
    A four-stage erbium-doped fibre amplifier with the gain bandwidth of 35 nm is demonstrated. The amplifier was designed to include a dispersion compensating module to compensate the accumulated dispersion by signals. The amplifier design permited some dynamic features such as the amplifier’s gain could be adjusted from 15 dB to 30 dB by varying the input signal power from –26 dBm to 8 dBm. The maximum output power of 23 dBm was obtained with a maximum allowable gain flatness of 1.5 dB.
  18. Othman, M., Ahmad, K.
    ASM Science Journal, 2008;2(2):183-183.
    Comet Lulin was discovered by Lin Chi-Sheng and Ye Quanzhi using the 16-inch telescope at Lulin Observatory in Nantou, Taiwan in 2007. According to Brian Marsden of the Smithsonian Astrophysical Observatory, it reached its perihelion on 10 January 2009 at a distance of 113 million
    km from the Sun. It moves in a very nearly parabolic retrograde (‘backwards’ compared to the movement of the planets) orbit at an inclination of 1.6 degrees from the ecliptic (“Newfound Comet Lulin to Grace Night Skies”). http://www.space.com/spacewatch/090206-ns-cometlulin.html). It passed nearest to the Earth at a distance of 61 million km on 23 February 2009.
  19. Sharifah, S.Y., Norsheila, F., Muladi
    ASM Science Journal, 2007;1(1):19-25.
    Orthogonal Frequency Division Multiplexing (OFDM) is a successful technique in wireless communication systems. Frequency offset in the OFDM system leads to loss of orthogonality among subcarriers which results in the occurrence of intercarrier interference (ICI). To improve the efficiency of bandwidth performance in the ICI self-cancellation scheme, frequency domain partial response signaling (PRS) was investigated. In this study, the integer polynomial partial response coefficients were exploited to enhance carrier-to-interference power ratio (CIR) in the OFDM system. CIR was enhanced up to 4.1 dB to 5 dB when the lengths of PRS polynomial, K was 2 and 5, respectively.
  20. Zakiyah, L.K., Gui, M.M., Foo, R.S., Mohamed, A.R., Chai, S.P.
    ASM Science Journal, 2011;5(2):91-100.
    The functionalization of pristine CNTs is necessary for carbon nanotubes (CNTs) to be fully utilized, with the aim of increasing the nanotube reactivity and solubility in aqueous solutions. In this study, multi-walled carbon nanotubes (MWCNTs) were functionalized with a carboxylic group as this was an important step prior to application. The carboxylic group-functionalization was conducted through acid treatment, using sulphuric and nitric acids mixed at a ratio of 3:1 (v/v) and sonication for 30 min under different temperatures and time durations. The functionalization conditions of 50ºC x 5 h and 60ºC x 3 h were identified to be most suitable for introducing a carboxylic group onto the nanotube surfaces. The percentage of total weight loss due to the carboxylic group on the MWCNTs treated at 50ºC x 5 h and 60ºC x 3 h obtained from the thermogravimetric analysis was 13.26% and 13.76%, respectively. For both samples, peaks corresponding to the carboxylic group were identified in the FT-IR spectra. The changes in the morphology of the treated MWCNTs were also observed under SEM analysis.
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