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.
Molecular markers have been intensively used in assisting breeding to reduce the time taken by conventional breeding as well as helping introgression of specific traits. Baseline analysis of known markers is crucial in developing a genetic database on disease and pest resistance for local rice germplasm which does not yet
exist. In this study seven local rice varieties, including the popular MR219 and MRQ 74 and MRQ 76 (newly developed aromatic rice varieties), together with a foreign variety, Intani-2, were screened for genetic markers related to pest and disease resistance. One hundred and twenty-two type-related markers (SSR, STS, InDel and Allele-specific) for genes resistant to bacterial leaf blight, blast and brown planthopper were screened using PCR amplification and validated by sequencing. It was found that each variety had its own pattern of resistance. Using allele-specific markers namely pBPH9, pTA248 and Pisbdom were found to be the most efficient way to screen for the targeted genes. Of the seven varieties, MR219 and MR232 were found to have the highest distribution of markers for resistance genes against pest and diseases studied.
The Ministry of Science Technology and Innovation (MOSTI) Angkasawan (Astronaut) Programme achieved its mission to send the first Malaysian astronaut Sheikh Muszaphar Shukur by Soyuz TM11 to the International Space Ship (ISS) on 10 October 2007. He returned to earth, landing safely on 21 October 2007. Such a momentous event has carved out yet another milestone in the country’s
history and development of a civilisation based on science and technology for its people. This mission has provided the educational sector with an opportunity to initiate a curriculum innovation. Together with the Ministry of Education (MOE), the initiative was undertaken to improve techniques of teaching and learning (TL) and to broaden its scope to include space science and technology.
The new microelectronic products require the silicon (Si) wafer to be thinned to less than
150 µm in thickness. Residual defect on the wafer surface that leads to wafer breakage with
a rough surface still be produced by mechanical grinding. Thus, chemical etching method is
essentially applied to produce a reliable thin wafer with smooth surface of desired thickness.
In this work, we studied the wet chemical etching effect of different HNO3 concentrations on
total thickness and weight loss, etch rate, morphological and structural properties of Si wafer
in the mixtures of HNO3 and HF. The results showed that the total thickness and weight
loss increases with the increasing of HNO3 concentration and etching time. Higher HNO3
concentration causes higher etch rate, and the etch rate decreases at prolonged etching time.
A smoother and clearer homogeneous Si surface image was observed by optical microscope as
the etching time and HNO3 concentration increase. XRD analysis shows that the intensity
of etched Si wafer is higher than the pure one, which might indicate the smoother surface
formation after etching. The findings of present study can be valuably referred to produce
a reliable and desired Si thin wafer which is crucial in integrated circuit fabrication.
Corrosion is a natural deterioration process that destructs metal surface. Metal of highly
protected by passivation layer such as Stainless Steel 316L also undergoes pitting corrosion
when continuously exposed to aggressive environment. To overcome this phenomenon, application
of epoxy based coating with addition of zinc oxide- poly (3,4-ethylenedioxythiophene)
doped with poly (styrene sulphonate) hybrid nanocomposite additive was introduced as
paint/metal surface coating. The compatibility between these two materials as additive
was studied by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD),
Field Emission Scanning Electron Microscopy/Energy-Dispersive X-ray spectroscopy (FESEM/EDX)
and Transmission Electron Microscopy (TEM) analysis. The effect of nanocomposite
wt.% in epoxy based coating with immersion duration in real environment on corrosion
protection performance was analyzed through potentiodynamic polarization analysis. The
main finding showed that addition of hybrid nanocomposite had increased corrosion protection
yet enhanced corrosion process when excess additives was loaded into epoxy coating.
Addition of 2 wt.% ZnO-PEDOT:PSS was found significantly provided optimum corrosion
protection to stainless steel 316L as the corrosion rate for 0 day, 15 days and 30 days of
immersion duration is 0.0022 mm/yr, 0.0004 mm/yr and 0.0015 mm/yr; respectively.
A 'green tyre' concept has the advantage of low rolling resistance, improved wet grip and enhanced handling. It has been reported that 3% decrease in rolling resistance is equivalent to 1% fuel saving, thus giving the 'green tyre' economic benefits and customer satisfaction. In this study, epoxidised natural rubber (ENR) compounds containing various loading of silica filler were prepared. The processibility and viscoelastic properties were investigated using the rubber processing analyser and Mooney viscometer. Results showed that the properties were adversely affected by the poor dispersion of silica as supported by the bound rubber measurement. In addition, a reversion in the cure behaviour was also observed as the curing temperature was increased to 170ºC.
Lead-free solder paste printing processes account for the majority of assembly defects in the electronic manufacturing industry. In the stencil printing process, the solder paste must be able to withstand low and high shear rates which result in continuous structural breakdown and build-up. This study investigated the effect of the addition of nickel and platinum powders to the thixotropic behaviour of lead-free Sn/Ag/Cu solder pastes using the structural kinetic model. A hysteresis loop test and constant shear test were utilized to investigate the thixotropic behaviour of the pastes using parallel plate rheometry at 25ºC. In this study, the shear rates were increased from 0.01 s–1 to 10 s–1 and the second curve was a result of decreasing the shear rate from 10 s–1 to 0.01 s–1. For the constant shear test, the samples were subjected to five different shear rates of 0.01s–1, 0.1s–1, 1s–1, 10s–1 and 100s–1. The constant shear rate test was designed to study the structural breakdown and build-up of the paste materials. From this investigation, the hysteresis loop test was shown to be an effective test method to differentiate the extent of structural recovery in the solder pastes. All the pastes showed a high degree of shear thinning behaviour with time. This might be due to the agglomeration of particles in the flux that prohibited paste flow under low shear rate. The action of high shear rate would break the agglomerates into smaller pieces which facilitated the flow of pastes, thus viscosity was reduced at high shear rate.
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.
Surfactants are important class of material used in latexes to impart stability at the
solid/liquid interface. Ionic surfactants and nonionic surfactants are known to provide electrostatic
and steric stabilisation. In this study, two surfactants having chain length of twelve
hydrocarbons were added to the natural rubber latex (NRL) respectively to determine its zeta
potential values, adsorption isotherm and rheological properties. Previous study has shown
that optimum stability was observed when the alkyl chain of surfactant contains twelve carbon
atoms. The zeta potential magnitude of NRL in the presence of sodium dodecyl sulphate
increased as the surfactant concentration increases, while polyoxyethylene dodecyl ether did
not show a significant change in zeta potential. The isotherms were of Langmuir Type 1, the
amount of surfactant adsorbed per unit area at the plateau region was 6.0 × 10−6 mol m−2
for sodium dodecyl sulphate and 2.1 × 10−6 mol m−2
for polyoxyethylene dodecyl ether.
The elastic modulus and relative viscosity of the NRL suspensions increased significantly
in the presence of sodium dodecyl sulphate and also with polyoxyethylene dodecyl ether as
compared to the NRL system due to stronger colloidal forces. The maximum packing volume
fractions of the NRL stabilised with sodium dodecyl sulphate and polyoxyethylene dodecyl
ether were found to be lower than NRL itself.
Warm compaction is an advanced manufacturing technique which consists of two consecutive steps, i.e. powder compaction at above ambient temperature and sintering in a controlled environment. Due to the relative movement between the powder mass and die wall as well as sliding among powder particles, frictional force is generated during the compaction stage. Admixed lubricant is used during the compaction step in order to minimize friction and hence improve the uniformity of the density of distribution inside the component. However, during the sintering process, trapped lubricant is often found to be burnt out hence leaving pores or voids which result in the lower strength of the final products. Warm compaction was initiated in the nineties, however not much information has been published about the effects of lubrication on the quality of the components produced through this route. Therefore, this paper presents the outcome of an experimental investigation about the effects of lubrication on manufacturing near-net shape components through the warm compaction route. Iron powder ASC 100.29 was mixed mechanically with zinc stearate to prepare the feedstock. Mixing time, weight percentage of lubricant content and compaction temperature were varied during green compact generation while sintering temperature, heating rate and holding time were manipulated during sintering. The relative densities and strengths of the final products were investigated at every compaction as well as sintering parameter. The results revealed that lubrication could provide significant effects at the compaction temperature of 180ºC while no significant effect of lubrication was observed during sintering. The suitable lubricant content was found to be 0.4 wt% and mixing time was around 30 min and the sintering temperature was around 990ºC.
In this study the effects of phosphorus and nitrogen levels, temperature and light-dark cycle on the algal growth potential (AGP) of an Antarctic Chlorococcum isolated from an ephemeral stream at Reeve Hill, Antarctica was investigated. The highest AGP was attained when the cultures were grown at high nitrogen concentration (329.87 mg NO3-N/l) and low phosphorus concentration (2.6 mg PO4-P/l) at 4ºC on a 12 h:12 h light-dark cycle. The results showed that Chlorococcum sp. required a high concentration of nitrogen, low concentration of phosphorus, low temperature with equal lengths of light and dark period (12 h:12 h) for optimum growth.
Elevated temperature affects marine benthic algae by reducing growth and limits the transport of electron or carbon fixation which may reduce the ability of the cell to use light. This resulting excess light energy may cause photoinhibition. In this study, the photosystem II of the benthic microalgal communities from Casey, eastern Antarctic were relatively unaffected by significant changes in temperatures up to 8ºC, along with high PAR level (450 μmol photons m–2 s–1). Similarly, the community was able to photosynthesize as the temperature was reduced to –5ºC. Recovery from saturating and photoinhibiting irradiances was not significantly influenced by temperatures at both –5ºC and 8ºC. These responses were consistent with those recorded by past experiments on Antarctic benthic diatoms and temperate diatoms which showed that climate change did not have a significant impact on the ability of benthic microalgae to recover from photoinhibitory temperature stress.
Ozone generator system using discharge coronas was fabricated to produce ozone gas and
ozonated water of varying concentration. The generated ozone air emitted to the water
through bubble diffuser or venturi injection depending on the input air mass transfer rate.
The concentration of ozonated water was examined using both ozone test strip and Schoenbein
paper. It is found that the production of ozone water by using bubble diffuser technique
facilitates the production of higher concentration of ozonated water with higher ozone transfer
efficiency. The efficiency of ozone gas in microorganism treatment is verified through the
lowest number of microorganism’s colony available compared with other treatment methods.
The half-life of ozonated water in this study was improved by increasing the transfer rate
of water and solubility of ozone in water. The concentration of ozonated water was found
increased through the application of pressurised oxygen input gas.
The electron-phonon coupling constant of the copper oxide-based high temperature superconductors in the van Hove scenario was calculated using three known models and by employing various acoustic data. Three expressions for the transition temperature from the models were used to calculate the constants. All three models assumed a logarithmic singularity in the density of states near the Fermi surface. The calculated electron-phonon coupling constant ranged from 0.06 to 0.28. The constants increased with the transition temperature indicating a strong correlation between electron-phonon coupling and superconductivity in these materials. These values were smaller than the values estimated for the conventional three-dimensional BCS theory. The results were compared with previous reports on direct measurements of electron-phonon coupling constants in the copper oxide based superconductors.
A new class of liquid crystalline acetylide-imine system was successfully synthesized, characterized
and deposited on indium tin oxide (ITO) coated substrate via electrochemical deposition
method for potential organic film application. The relationship between liquid crystal
molecular structure, phase transition temperature and electrical performance was evaluated.
The mesomorphic properties were identified via polarized optic microscopy (POM) which displayed
fan-shaped texture of smectic A phase and their corresponding transition enthalpies
are in concurrence with DSC and TGA studies. The findings from the conductivity analysis
revealed that the fabricated film exhibits good electrical performance where it displayed
linear current-voltage relationship of I-V curve. Therefore, this proposed type of molecular
framework has given an ideal indication to act as transporting material for application in
optoelectronic devices.
This study was conducted to prepare a mixed matrix membrane (MMM) and to test the performance of the prepared MMM for CO2 and CH4 gas separation. MMM containing polyethersulfone (PES) and multi-walled carbon nanotubes (MWCNTs) was prepared by a dry-wet phase inversion technique using a pneumatically-controlled membrane casting machine. The surface modification was performed on MWCNTs in order to enhance the selectivity of CO2/CH4. The surface modification of MWCNTs using chemical and physical approaches has been adopted. Mixed acid (HNO3/H2SO4) and β-CD were used for chemical and physical approaches, respectively. Effects of surface modification on MWCNTs/PES MMM were investigated. MWCNTs/PES MMMs were characterised using scanning electron microscopy (SEM), the Fourier Transform Infrared (FT-IR) spectroscopy and pure gas permeation test. The permeability and selectivity, which are the parameters describing membrane performance were calculated via the data obtained from pure gas permeation test with the feed pressure difference from 3 to 7 bars. In this study, surface modified MWCNTs/PES MMM using mixed acid and β-CD has successfully enhanced the CO2/CH4 selectivity by 40.6% compared to that of neat PES.
A boxplot is an exploratory data analysis (EDA) tool for a compact visual display of a distributional summary of a univariate data set. It is designed to capture all typical observations and displays the location, spread, skewness and the tail of the data. The precision of some of this functionality is considered to be more reliable for symmetric data type and thus less appropriate for skewed data such as the extreme data. Many observations from extreme data were mistakenly marked as outliers by the Tukey’s standard boxplot. A new boxplot implementation is presented which adopts a fence definition using the extent of skewness and enhances the plot with additional features such as a quantile region for the parameters of generalized extreme value (GEV) distribution in fitting an extreme data set. The advantage of the new superimposed region was illustrated in term of batch comparison of extreme samples and an EDA tool to determine search region or direction as contained in the optimisation routines of a maximum likelihood parameter estimation of GEV model. A simulated and real-life data were used to justify the advantages of the boxplot enhancement.
The increased human demand for animal proteins in Malaysia is led by several factors: population growth, urbanisation, income growth and changing consumer preferences. Meeting the projected increased demand in the future is an awesome and challenging task. Presently, the non-ruminant poultry and pig industries, mainly private sector led, make the most significant contribution to total animal protein supplies, and inefficient ruminant production systems lag well behind. The strategy for promoting productivity growth to increase animal protein supplies from ruminants requires concerted efficient natural resource management that can target specific production systems. Two distinct economic opportunities are the development of oil palm-based cattle and goat production. The value addition to oil palm cultivation due to the beneficial crop-animal-soil interactions are enormous. The prerequisites are inter-disciplinary efforts, holistic systems, participatory community-based research and development that are needs-based and address constraints, increased research investments, institutional commitment and a policy environment that can enhance total factor productivity in the future.
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.
Current National Design Specification (NDS 2005) provides the guideline to design timber joints strengthened with steel fasteners. This study investigates the possibility of using NDS 2005 to estimate the load-carrying capacity of timber joints fastened with Glass Fibre Reinforced Polymer (GFRP) dowel. Double shear timber joint fastened with steel dowels were tested to validate the joints fastened with GFRP using 1.27 cm diameter dowels. Tests were also conducted to determine the dowel bearing strength of wood and dowel bending strength of GFRP and steel. The failure modes of all tests were observed and recorded. Results showed that NDS (2005) successfully estimated the failure mode and was capable of predicting the joint load-carrying capacity when fastened with a GFRP dowel and this was well validated by the load carrying capacity of a steel dowel.