The main objective of this research is to optimize the trench depth, trench width, epitaxial resistivity and epitaxial thickness in trench power MOSFET so as to obtain high breakdown voltage but low on-resistance. Optimisation of these parameters are based on 2k factorial design method for achieving specific on-resistance 0.1 mΩcm2 and blocking voltage higher than 30 V. ATHENA and ATLAS software from Silvaco Int. were used for fabrication simulation and device electrical characterisation. The results obtained were, the optimisation value for trench width was 1.25 μm, trench depth was 1.25 μm, epitaxial thickness was 4.75 μm and epitaxial resistivity was 0.32 Ωcm. The predictive value of breakdown voltage was 39.41 V and significant to factors trench depth, epitaxial thickness and epitaxial resistivity. The predictive value for on-resistance was 0.105 mΩcm2 with significant to factors trench depth, epitaxial thickness and epitaxial resistivity. In conclusion, 2k factorial design method is successfully utilised in optimizing n-channel trench power MOSFET.
The effect of ZrO2 addition on the microstructure, morphology and pressure sensing behaviour of Pb(ZrxTi1-x)O3 ceramics was studied in five different compositions of ZrO2, namely x = 0.48, 0.50, 0.52, 0.54 and 0.56. The samples were prepared through the solid-state reaction method using high purity metal oxides powders. In order to control the PbO losses due to high temperature sintering, a novel approach were explored whereby the samples were sintered in Al2O3 environment. Structural investigation using X-ray diffraction (XRD) method revealed that all samples exhibited a tetragonal crystal structure. However the c/a lattice parameters ratios exhibited a decreasing trend as the ZrO2 content was increased, indicating that PZT crystals gradually evolved towards pseudocubic structure. SEM micrographs showed different morphology of each composition with the grain size varies in the range of 1.5 μm to 3.15 μm. The performance of pressure sensing behaviour showed that sample with composition x = 0.52 exhibited the best piezoelectric properties with high sensitivity. However, all samples failed to show good stability and repeatability due to slow recovery after severe lattice strain.
Kesan gantian Al berkepekatan rendah pada tapak-Zn sebagai lapisan anti-pantulan (LAP) untuk bahan Zn1-xAlxO ke atas pencirian struktur, morfologi dan sifat optik telah dikaji. Sampel Zn1-xAlxO dengan x = 0.00, 0.05, 0.10 and 0.15 telah disintesis dengan menggunakan kaedah sol-gel. Filem yang diperolehi dengan kaedah sol-gel telah disepuh lindap pada 400°C selama 2 jam. Kaedah pembelauan sinar-X (XRD) dan Mikroskop Elektron Imbasan (SEM) digunakan untuk mencirikan struktur dan morfologi filem. Spektrum XRD menunjukkan semua sampel mempunyai struktur heksagonal. Saiz partikel menurun apabila kepekatan Al meningkat. Filem ini mempunyai struktur filem yang padat dan tebal serta berkesan untuk memerangkap cahaya dalam filem nipis sel suria. Sifat optik telah dicirikan dengan menggunakan spektrometer UV-Vis-NIR dan fotoluminesen. Peningkatan nilai jurang tenaga penting sebagai unsur lapisan anti pantulan. Oleh itu, filem ini boleh digunakan sebagai lapisan anti-pantulan untuk sel solar.
La0.67Sr0.33Mn1-xTixO3 samples with x = 0.0, 0.2, 0.4 and 0.6 have been prepared using the conventional solid-state reaction method. The structure, magnetic and electrical transport properties as well as the impedance spectroscopy of the samples were investigated. The powder XRD analysis showed that all samples were single phase with rhombohedral perovskite structure. The magnetization curve suggests that the Ti substituted samples exhibit weak ferromagnetic behaviour. The highest magnetoresistance (MR) value was obtained for sample x = 0.2 at temperature 200 K and field 1 T, which was 32.5%. Low field magnetoresistance (LFMR) effect was observed for the x = 0.0 sample. The metal-like resistivity curve for the x = 0.0 sample was best fitted with ρ = ρo + ρ2T2 equation, indicating the grain boundary effects and electron-electron scattering process contribution. Semiconductor-like transport behaviour was observed for the Ti substituted samples and can be fitted by variable range hopping (VRH) and small polaron hopping (SPH) mechanisms. The activation energy of the samples increased when the Ti composition increased. An equivalent circuit was proposed for the impedance plot with a series of two parallel RC circuits. The grain, grain boundary and electrode resistance values increased with Ti composition due to the reduction of the Mn3+ / Mn4+ ratio.
The formulation of chicken in kacangma herbal soup, a traditional delicacy of Sarawak was developed. Processing parameters for the canned product was established. The product was canned and retorted at 121°C in an overpressure retort to achieve commercial sterility. A three-component constrained mixture according to a symmetrical-simplex interior design was used to determine the optimum formulation. Result showed that a mixture with 82% blended ginger, 17% dried kacangma and 1% cornstarch would give a mean sensory score of more than 6.6 for taste, colour, texture, consistency and overall acceptability. Meanwhile, a score above 5.5 was given for aroma. The study showed that the thermal process applied with Fo value of 8.36 is sufficient to produce commercially sterile products.
This paper presents analyses of the land use and land cover change of the Langat-Dengkil sub-catchment and the deforestation of the Klang-Langat catchment in the context of water resource availability. The Langat-Dengkil sub-catchment lies within the upper catchment of Klang-Langat. For both catchments, the landsat TM and ETM satellite imageries, ERDAS Imagine 8.4 and ArcView/Arc GIS softwares were used to detect spatial and temporal changes in land use and deforestation between the year 1990 and 2001. For Klang-Langat deforestation, CLUE model was used to forecast change up to year 2020 using two set scenarios. Langat-Dengkil sub-catchments experienced multiple changes of land use and land cover at varying quantum for the years 1990 and 2001. It was found that forest land and agriculture were reduced by 9.5% (4,303 ha) and 17.3% (11,598 ha), respectively. During the same period (1990 to 2001), urbanised land has increased by nearly six folds (18,860 ha). Land use change matrix has indicated that the increase of urbanised area was at the expense of agriculture and forest land. For Klang-Langat catchment, the deforestation for 1989 – 1999 were also serious. About 36,351 ha were deforested including 12,244 ha of Permanent Forest Reserve. Deforestation prone areas are located within 1000 m from major access, 2000 m from town, confined to altitude less than 100 m and within slope of less than 5o. Projection for year 2020 has predicted that if the Permanent Forest Reserve is strictly protected, deforestation will be reduced to 22,340 ha or 22%. Otherwise, it will be heavily deforested at 50,851 ha or 50%. Both results showed that the accelerated land use change and deforestation can only be mitigated through stringent management of land conversion, and as for the forest, it has to be through the total protection by law. This can be achieved by strengthening the Permanent Forest Reserve law and the commitment in adopting sustainable resource policy.
The concentrations of heavy metals (Mn, Co, Cu and Cr) were determined in the surface sediments from Kemaman River estuary using Inductively Coupled Plasma – Mass Spectrometry (ICP-MS). The relationship of heavy metal content with sediment particles size was studied. The average concentration of heavy metals are 597.8 μg/g dry weight, 16.0 μg/g dry weigh, 48.8 μg/g dry weight and 100.4 μg/g dry weight for Mn, Co, Cu and Cr, respectively. All metals showed low Enrichment Factor (EF) values (EF<1) when compared with Al which indicates that the elements in the sediment originated predominantly from crustal material or terigenous in origin. This study shows that there is a positive correlation between the mean particle size and the studied elements.
ß-1,6-glucanase produced by Trichoderma harzianum has been proven as one of the prime compounds to be excreted onto the hyphae of the pathogen causing localised cell wall lysis at the point of interaction. This study was conducted in the interest to investigate the regulation of ß-1,6-glucanase gene expression in T. harzianum strain BIO10671. β-1,6-glucanase enzyme from the culture filtrate of T. harzianum was purified through precipitation with 80% acetone followed by anion-exchange chromatography and chromatofocusing using Neobar AQ and Mono P HR 5/20 columns, respectively. Two β-1,6-glucanase bands at 32 kDa and 43 kDa in size has been purified. However, four restriction endonucleases digestion revealed only a single copy of ß-1,6-glucanase gene was encoded for both ß-1,6-glucanase isozymes. Fungal cell walls were able to trigger high level expression of gene encoding ß-1,6-glucanase. The expression of ß-1,6-glucanase gene was strongly affected by substrate specificity; where the presence of glucose or non ß-1,6-glucan linked substrate will significantly suppress the gene transcriptions. In spite of this, 24 hours were required for the gene transcription to achieve maximum total mRNA.
Numerous routing protocols for mobile ad hoc networks (MANETs) have been designed in process information delivery from a source node to a destination node. In this paper, the Taguchi’s design of experiment (TDE) has been applied to investigate the performance of Destination Sequence Distance Vector (DSDV) routing protocol in MANETs. The effects of network parameters namely terrain sizes, node speeds, network sizes, transmission ranges, transmission rates, pause times and the number of maximum connections on packet delivery ratio and routing overhead in medium scale ad hoc networks have been done through simulation experiments. Through this study, we can rank these factors that may affect packet delivery ratio and routing overhead. The response performance was analyzed based on signal-to-noise ratio and analysis of variance (ANOVA). The results revealed that the transmission range was the most influential factor on the packet delivery ratio, followed by terrain size and transmission rate. The network size had the greatest effect on routing overhead, followed by the transmission range.
Superkonduktor suhu tinggi berasaskan sistem (Tl0.85Cr0.15)Sr2CaCu2O7-Agx (Tl1212) dengan komposisi x = 0.0, 0.01, 0.02, 0.03 dan 0.05 telah disediakan dengan kaedah tindak balas keadaan pepejal. Rintangan elektrik terhadap suhu telah diukur dengan kaedah penduga empat titik. Suhu genting mula, Tc-mula bagi sistem Tl1212 tanpa penambahan nano Ag adalah 113 K. Penambahan nano Ag menurunkan suhu genting sampel. Corak pembelauan sinar-X menunjukkan bahawa semua sampel mempunyai fasa dominan 1212. Sampel x = 0.02 mempunyai peratusan fasa 1212 yang tertinggi iaitu 87%.
The effects of compositions and different metal salts on the phase of Ba(Ce,Zr)O3 perovskite ceramics derived from the solid state-reaction, sol-gel and Pechini methods are studied. X-ray diffractometer (XRD) and fourier transform infrared spectroscopy (FTIR) were used to study the phase formation of the compound. It was found that the purity of Yb-doped Ba(Ce,Zr)O3 strongly depends on the stoichiometric compositions and metal salts of the raw materials. A high purity compound at a relatively low temperature was obtained only when the powder of Ba(Ce0.8Zr0.2)0.95Yb0.05O2.975 was prepared from metal nitrate salts. Result of FTIR also confirmed that there was no carbonate species present in the sample prepared by Pechini method after it was sintered at 1400°C.
The influences of temperatures and fluxes on contact angles, intermetallic (IMC) phase and thickness of Sn-40Pb and Sn-8Zn-3Bi solders on copper substrate were investigated. As expected, the contact angle decreases and the intermetallic thickness increases as the temperature increases. The Sn-40Pb solder exhibits a lower contact angles compared to Sn-8Zn-3Bi solder for all the fluxes tested. The Sn-40Pb/Cu system exhibits a single Cu6Sn5 intermetallic. The Sn-8Zn-3Bi/Cu interface exhibits ε(Cu-Zn) and γ-Cu5Zn8 phases and soldering at 280oC exhibits a single γ-Cu5Zn8 phase. Sn-40Pb/Cu gives higher intermetallic thickness compare to Sn-8Zn-3Bi/Cu system when soldering was done at 220oC. On the other hand, the IMC thickness formed by Sn-8Zn-3Bi/Cu system is higher than Sn-40Pb/Cu system for all other temperatures. Although, the fluxes have no significant influence on the thickness of IMC formed, ZnCl2 generally gives lower IMC thickness.
Bi3Zn2Ta3O14, ‘P’, was crystallised in a cubic unit cell with lattice parameter of a=10.5437 (9) Å. The material had permittivity, ε’, of around 58 and dielectric loss, tan δ, of 2.3 × 10-3 at 30oC, 1 MHz; temperature coefficient of capacitance (TCC) of -156 ppm/oC in the range of 30oC to 300oC at 1 MHz. Chemical doping was carried out at either A (Bi1.5Zn0.5-xMx)(Zn0.5Ta1.5)O7, or B site (Bi1.5Zn0.5)(Zn0.5-xMxTa1.5)O7 in search of better performance materials. Various divalent cations such as Cd2+, Ca2+, Mg2+, Ni2+, Pb2+, and Cu2+ were used as dopants. Solid solutions formed were: Bi3Zn2-xCdxTa3O14 (0≤x≤0.5), Bi3Zn2-xMgxTa3O14(0≤x≤0.2), Bi3Zn2-xNixTa3O14 (0≤x≤0.4), Bi3Zn2-xPbxTa3O14 (0≤x≤0.3), Bi3Zn2-xCaxTa3O14 (0≤x≤0.3) and Bi3Zn2-xCuxTa3O14 (0≤x≤0.1). Electrical properties of the materials were investigated using impedance spectroscopy. Conductivities of the solid solutions were higher than that of the parent material Bi3Zn2Ta3O14. These doped materials exhibited similar behaviour as Bi3Zn2Ta3O14, showing a high degree of dispersion of permittivity at low frequencies (<1 kHz) and at temperatures above 500oC. Between 100 kHz and 1000 kHz, non-frequency dependence was observed in the range of 100 – 300oC. An increase in dielectric loss below 10 kHz was observed. Dielectric loss decreased with frequencies when temperature was above 500oC. Dielectric loss of all divalent cation doped materials was higher than that of the parent material; maximum permittivity value of 68 was recorded at x = 0.3 in Bi3Zn2-xCaxTa3O14. TCC obtained in this study had negative values; no obvious correlation between TCC and composition of the doped materials can be deduced.
Analisis terhadap sistem sel bahan api 5kW ini merangkumi analisis eksergeokonomi iaitu mengkaji kebolehdapatan tenaganya dan seterusnya analisis kesan ekonominya diambil kira selepas kebolehdapatan tenaganya dilakukan. Sistem sel bahan api dalam kes kajian terdiri daripada unit pemperosesan hidrogen dan unit pemprosesan bahan api dengan unit pemprosesan haba terdiri daripada reaktor auto-terma (ATR), reaktor pemindahan gas air (WGS), satu modul seramik (TMC) dan penjerap tekanan berayun (PSA). Stek sel bahan api penukar proton membran (PEMFC) adalah sumber penjana kuasa yang utama. Didapati modul seramik TCM dan penjerap PSA mempunyai kecekapan kebolehdapatan tenaga yang sangat rendah iaitu 0.29% dan 0.09%. Reaktor auto-terma dan stek sel bahan api pula adalah lebih tinggi iaitu 22.44% dan 31.97%, dan nilai-nilai ini adalah lebih kurang sama dengan kajian lain. Daripada pengiraan, didapati eksergoekonomi bagi 5 kW keseluruhan sistem sel bahan api kajian ini adalah sebanyak RM4756.62 per GJ. Analisis eksergoekonomi juga menunjukkan bahawa sistem sel bahan api akan menjadi lebih berekonomi jika kos operasi dan penyelenggaraan dan kos bahan api dapat dikurangkan.
The phytochemical investigation on the fruit peel of Goniothalamus scortechinii (Selayar Raja Ubat) obtained from Gunung Stong, Kelantan has resulted in the isolation of five compounds namely pinocembrine, altholactone, goniofufurone, goniotriol and goniopypyrone. Their structures were determined by extensive ultra violet (UV), infrared (IR), nuclear magnetic resonance (NMR) spectroscopy and gas chromatography-mass spectrum (GCMS) analysis.
MeSH terms: Animals; Fruit; Furans; Lactones; Gas Chromatography-Mass Spectrometry; Magnetic Resonance Spectroscopy; Pyrones; Skates (Fish); Styrenes; Flavanones; Goniothalamus; Phytochemicals
Sulphate-reducing bacteria (SRB), implicated in microbiologically influenced corrosion were isolated from the deep subsurface at the vicinity of Pasir Gudang, Johor, Malaysia. Electrochemical impedance spectroscopic (EIS) study was carried out to determine the polarization resistance in various types of culturing solutions, with SRB1, SRB2, combination of SRB1 and SRB2 and without SRBs inoculated (control). EIS results showed that in the presence of SRB1, SRB2 and mixed culture SRB1 and SRB2, polarisation resistance values were 7170, 6370 and 7190 ohms respectively compared to that of control, 92400 ohm. X-ray analysis (EDS) of the specimens indicated high sulphur content in the medium containing SRBs. Localized corrosion was observed on the metal surface which was associated with the SRB activity.
This study has been carried out on the mixture of Gracilaria changii agar (0.1%, 0.2%, 0.4% and 0.8%) with wheat starch. Scanning electron microscopy (SEM) was performed for morphology observation, and starch thermal analysis were carried out to determine the properties of gelatinization and retrogradation. Proximate analysis has been determined for isolated wheat starch and agar. Through SEM, interaction was first observed at 64°C for 0.4% agar but at 0.8% of agar, a more extensive bridging was formed which enveloped the starch granules. Differential scanning calorimetric (DSC) result shows that the addition of agar decreased the onset temperature (To) of gelatinization significantly (p<0.05) but increased the gelatinized enthalpy (ΔHgel), gelatinized temperature range (Rg) and Peak Height Index (PHI) significantly (p<0.05). Agar lowered the retrogradation enthalpy (ΔHret), retrogradation range (Rret) and retrogradation percentage (%R) of wheat starch significantly (p<0.05).
Samples of Pinna bicolor Gmelin and Pinna deltodes Menke were collected from the seagrass bed of Sungai Pulai, covering Merambong shoal, Tanjung Adang shoal and Merambong Island off south western coast of Johor, Malaysia for morphological study from August 2005 to June 2006. It was observed that P. deltodes is associated with hard substratum and P. bicolor is associated with soft substratum in the study area. Physically there was no difference between P. bicolor and P. deltodes. The species were identified on the basis of nine internal and external characteristics of the valves. The two species were found to be morphologically different on the basis of width of sulcus, distance between posterior adductor muscle to posterior dorsal nacreous layer, dorsal posterior margin length and shell width.
Compositions of landfill leachate and groundwater pollution were studied at Ibb landfill, which is located at Al-Sahool area, north of Ibb City, Yemen. The leachate was sampled at three different locations at the landfill, i.e. at the landfill itself and at 15 and 20 m downstream of the landfill. Groundwater samples were collected from five boreholes to study the possible impact of leachate percolation into the groundwater. The leachate and groundwater samples were collected during wet season, due to the excessive generation of leachate during this season. The objective of this paper is to evaluate the groundwater pollution due to the landfill leachate. The leachate and groundwater were physically and chemically characterised. The parameters measured were pH, temperature, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), fluoride (F–), chloride (Cl–), sulphate (SO2–4), nitrites (NO–2), nitrates (NO–3), ammonia N (NH3-N), heavy metals (Pb, Zn, Ni, Cr, Cd and Cu), major cations (Na, Mg, Ca, K and Fe) and biological parameters (COD and BOD5). The leachate at this landfill is most likely in methanogenic phase, based on the alkaline pH value recorded (pH=8.2). The results show that four out of five boreholes are contaminated, where the concentration of physico chemical parameters are above the standard acceptable levels which are required for drinking water adapted by Yemen’s Ministry of Water and Environment (YMWE). Therefore, detailed study of the leachate and its effect to the groundwater in the study area is recommended.
The cockle, Anadara granosa, was experimentally exposed to low (0.1 mg/L) and sublethal (1.0 mg/L) doses of copper (Cu) for a period of 24 hrs. Significant increase in Cu concentrations in whole tissues and hepatopancreas compared to control animals were observed. In order to study the effect of copper exposure at molecular levels, a subtractive cDNA library was constructed from the hepatopancreas of cockles exposed to 1.0 mg/L Cu. Screening of the subtractive cDNA library using reverse northern analysis resulted in several differentially expressed genes, including one that codes for metallothionein (MT). The complete coding sequence of the MT gene (designated as AnaMT2) reveals an open reading frame of 234 bp in length that encodes a 77 amino acid polypeptide as revealed by the deduced amino acid composition. Although showing similarities with other molluscan MTs, AnaMT2 can be distinguished by its lower glycine and higher asparagine and proline content. Expression analysis of the AnaMT2 by northern analysis indicated higher mRNA level in cockle exposed to 1.0 mg/L Cu and was undetectable in those treated with 0.1 mg/L. This suggests that AnaMT2 represents a primarily inducible MT not highly expressed under basal conditions.