This paper aims to estimate the Generalized Pareto Distribution (GPD) parameters and predicts the T-year return levels of extreme rainfall events using the Partial Duration Series (PDS) method based on the hourly rainfall data of five stations in Peninsular Malaysia. In particular, the GPD parameters are estimated using five methods namely the method of Moments (MOM), the probability weighted moments (PWM), the L-moments (LMOM), the Trimmed L-moments (TLMOM) and the Maximum Likelihood (ML) and the performance of the T-year return level of each estimation method is analyzed based on the RMSE measure obtained from Monte Carlo simulation. In addition, we suggest the weighted average model, a model which assigns the inverse variance of several methods as weights, to estimate the T-year return level. This paper contributes to the hydrological literatures in terms of three main elements. Firstly, we suggest the use
of hourly rainfall data as an alternative to provide a more detailed and valuable information for the analysis of extreme rainfall events. Secondly, this study applies five methods of parametric approach for estimating the GPD parameters and predicting the T-year return level. Finally, in this study we propose the weighted average model, a model that assigns the inverse variance of several methods as weights, for the estimation of the T-year return level.
MeSH terms: Malaysia; Monte Carlo Method; Polymethacrylic Acids; Probability; Hydrology
Rainfalls data have been broadly used in researches including in hydrological and meteorological areas. Two common ways in extracting observations from hourly rainfalls data are the window-based analysis (WBA) and storm-event analysis (SEA) approach. However, the differences in the qualitative and quantitative properties of both methods are still vaguely discussed. The aim of studying these dissimilarities is to understand the effects of each approach in modelling and analysis. The qualitative difference is due to the way the two analyses define the accumulated rainfalls for observations which are referred to as rainfall and storm depths, respectively. The repetitiveness of rainfall depths provide nested structure while the storm depths are considered independent. The quantitative comparisons include their statistical and scaling properties that are linked by the self-similarity concept from simple scaling characteristics. If self-similarity concept
holds, then the rainfall or storm depths follow simple scaling and the analysis would be simplified. The rainfall depths showed clearer simple scaling characteristics compared to the storm depths. Though the storm depths do not yield self-similarity for a large range of storm duration but the characteristics of simple scaling can be observed for a reduced range of the considered duration. In general, the context of the research and the region of the time interval and duration will be an important aspects to consider in choosing which method is best to use for analyzing the data.
Long-memory is often observed in time series data. The existence of long-memory in a data set implies that the successive data points are strongly correlated i.e. they remain persistent for quite some time. A commonly used approach in modellingthe time series data such as the Box and Jenkins models are no longer appropriate since the assumption of stationary is not satisfied. Thus, the scaling analysis is particularly suitable to be used for identifying the existence of long-memory as well as the extent of persistent data. In this study, an analysis was carried out on the observed daily mean per hour of ozone concentration that were available at six monitoring stations located in the urban areas of Peninsular Malaysia from 1998 to 2006. In order to investigate the existence of long-memory, a preliminary analysis was done based on plots of autocorrelation function (ACF) of the observed data. Scaling analysis involving five methods which included rescaled range, rescaled variance, dispersional, linear and bridge detrending techniques of scaled windowed variance were applied to estimate the hurst coefficient (H) at each station. The results revealed that the ACF plots indicated a slow decay as the number lag increased. Based on the scaling analysis, the estimated H values lay within 0.7 and 0.9, indicating the existence of long-memory in the ozone time series data. In addition, it was also found that the data were persistent for the period of up to 150 days.
MeSH terms: Malaysia; Memory; Ozone; Personal Satisfaction
Climate changes have become serious issues that have been widely discussed by researchers. One of the issues concerns with the study in changes of rainfall patterns. Changes in rainfall patterns affect the dryness and wetness conditions of a region. In this study, the three-dimensional loglinear model was used to fit the observed frequencies and to model the expected frequencies of wet class transition on eight rainfall stations in Peninsular Malaysia. The expected frequency values could be employed to determine the odds value of wet classes of each station. Further, the odds values were used to estimate the wet class of the following month if the wet class of the previous month and current month were identified. The wet classification based on SPI index (Standardized Precipitation Index). For station that was analyzed, there was no difference found were between estimated and observed wet classes. It was concluded that the loglinear models can be used to estimate the wetness classes through the estimates of odds values.
MeSH terms: Malaysia; Rain; Research Personnel; Linear Models; Physical Phenomena; Climate Change
This study highlights the advantage of functional data approach in assessing and comparing the PM10 pollutant behaviour as an alternative statistical approach during and between the two extreme haze years (1997 and 2005) that have been reported in Selangor, state of Malaysia. The aim of the study was to improvise the current conventional methods used in air quality assessment so that any unforeseen implicit information can be revealed and the previous research findings can be justified. An analysis based on the daily diurnal curves in place of discrete point values was performed. The
analysis results provided evidences of the influence of the change in the climate (due to the El-Nino event), the different levels of different emission sources and meteorological conditions on the severity of the PM10 problem. By means of the cummulative exceedence index and the functional depth method, most of the monitoring stations for the year 2005 experienced the worst day of critical exceedences on the 10th of August, while for the year 1997 it occurred between 13th and 26th September inclusively at different dates among the stations.
MeSH terms: Air Pollution; Malaysia; Meteorology; El Nino-Southern Oscillation
This study presents a preliminary attempt to assess future climate conditions in the Red River Delta (RRD) region. Outputs of the Community Climate System Model version 3.0 (CCSM3) are dynamically downscaled using the Regional Climate Model version 3 (RegCM3). Numerical experiments and analysis are realized for the baseline 1980-1999 and the future 2030-2049 periods with the A1B and A2 emissions scenarios. We first examine the capability of the model in simulating the 20 years mean climate. Temperature and precipitation outputs for the baseline period are compared with observations at the 17 selected meteorological stations in RRD. Results show that temperature patterns are fairly well reproduced but with systematic cold biases. Precipitation is also well simulated during winter - spring and largely underestimated during summer - autumn. Estimation of the future changes of temperature and precipitation as compared to those of the baseline period reveals that annual temperature of the 2030-2049 appears to be warmer than the baseline temperature of about 1.4±0.2ºC. Summer temperature is likely to increase faster than winter temperature in the future. We also notice that precipitation generally decreases throughout the RRD region except the future JJA rainfall projected by the A2 scenario.
Kajian ini dijalankan untuk menentukan keupayaan yis (Saccharomyces cerevisiae) yang telah dipencil daripada buahbuahan tempatan iaitu duku langsat (Lansium domesticum), rambutan (Nephelium lappaceum), mangga Chokanan (Mangifera indica cv. Chokanan) dan rebung buluh minyak (Bambusa vulgaris) sebagai agen penaik roti berbanding roti kawalan penambahan yis komersial. Isi padu tertentu roti kawalan menunjukkan perbezaan bererti (p<0.05) dengan semua roti kajian. Roti yang difermentasi oleh yis rebung buluh menunjukkan isi padu tertentu yang paling tinggi, diikuti oleh roti yang difermentasi oleh yis mangga dan yis duku langsat dan ketiga-tiga yis tersebut juga mempunyai isi padu tertentu yang lebih tinggi secara bererti (p<0.05) dengan roti kawalan. Roti yang difermentasi oleh yis rebung buluh dan yis mangga mempunyai tekstur yang lebih lembut berbanding roti kawalan. Peningkatan dalam isi padu tertentu roti boleh meningkatkan kelembutan tekstur roti. Peratus kandungan kelembapan kulit dan isi roti yang difermentasi oleh yis rebung buluh adalah paling tinggi manakala roti yang difermentasi oleh yis rambutan menunjukkan peratus kandungan kelembapan yang paling rendah. Peningkatan peratus kandungan kelembapan juga boleh meningkatkan kelembutan tesktur roti dan sebaliknya. Daripada segi warna kulit, hanya kecerahan warna kulit (L*) roti yang difermentasi oleh yis rebung buluh tidak menunjukkan perbezaan bererti (p>0.05) dengan warna kulit roti kawalan. Kecerahan warna isi (L*) roti kawalan pula menunjukkan perbezaan bererti (p<0.05) dengan semua isi roti kajian. Selain itu, didapati semakin kecil dan padat liang udara, semakin putih warna isi roti. Keseragaman taburan liang udara juga menghasilkan isi roti yang lebih putih. Secara keseluruhan, kesemua yis yang dipencil berpotensi untuk dijadikan sebagai agen penaik. Yis rebung buluh dan yis mangga dapat menghasilkan kualiti roti putih yang lebih baik daripada yis komersial.
Aedes aegypti and Aedes albopictus are the principle dengue vectors in Malaysia. The presence and distribution of Aedes larvae were studied in three different localities in Kelantan, Terengganu and Sabah, Malaysia in October 2008, November 2008 and June 2009. Two hundred (200) ovitraps per locality were placed randomly indoors and outdoors, depending on the environment of each locality. The highest mean number of Ae. aegypti and Ae. albopictus larvae per recovered ovitrap for both indoors and outdoors was obtained from Kg. Paya Rambai, Kelantan. The indoor populations of Ae. aegypti as well as the indoor and outdoor populations of Ae. albopictus in Kg. Paya Rambai, Kelantan were significantly higher than the other two study sites (p<0.05) by 1.03- and 4.67-folds, 2.36- and 5.84-folds and 1.98- and 4.00-folds, respectively. Both Ae. aegypti and Ae. albopictus were also found to breed within the same ovitraps placed indoors and outdoors in all study sites ranging from 15.22% to 31.82% of the total positive ovitraps. This study showed that both species could serve as the vectors of dengue in all study sites as indicated by the high populations recorded. The reliability and sensitivity of ovitraps in Aedes surveillance was also proven.
In this paper, the problem of laminar viscous flow in a semi-porous channel in the presence of transverse magnetic field is studied. The Optimal Homotopy Asymptotic Method (OHAM) is employed to approximate the solution of the system of nonlinear differential equations governing the problem. The influence of the Hartmann number (Ha) and the Reynolds number (Re) on the flow was investigated. The results of the OHAM were compared with homotopy analysis method (HAM) and variation iteration method (VIM) results.
MeSH terms: Viscosity; Porosity; Physical Phenomena; Magnetic Fields
A numerical study has been conducted to investigate the steady forced convection stagnation point-flow and mass transfer past a permeable stretching/shrinking sheet placed in a copper (Cu)- water based nanofluid. The system of partial differential equations is transformed, using appropriate transformations, into two ordinary differential equations, which are solved numerically using bvp4c function from Matlab. The results are obtained for the reduced skin-friction and reduced Sherwood number as well as for the velocity and concentration profiles for some values of the governing parameters. These results indicate that dual solutions exist for the shrinking sheet case (λ < 0). It is shown that for a regular fluid (f = 0) a very good agreement exists between the present numerical results and those reported in the open literature.
Sel fuel mikrob (SFM) merupakan peranti yang menggunakan bakteria sebagai biomangkin untuk mengoksidakan bahan organik dan bukan organik bagi menjanakan arus elektrik. Tujuan utama kajian ini ialah menguji kebolehan SFM skala makmal dengan menggunakan enapcemar yang mengandungi kultur campuran yang hidup dalam air sisa buangan kilang pemprosesan sawit (POME). Kajian ini juga bertujuan membina reka bentuk SFM yang sesuai dan mengkaji keaktifan kultur campuran yang boleh menghasilkan kuasa elektrik. POME telah digunakan dalam bentuk yang dicairkan dengan kandungan COD bersamaan dengan 3750 mg-COD L-1. Prestasi penghasilan kuasa elektrik dan kecekapan rawatan yang dinilai daripada segi penyingkiran COD, nitrogen dan jumlah karbohidrat dalam SFM dwi-ruang telah dicatat dan dianalisis setiap hari selama 15 hari. Hasil padanan uji kaji dan model kekutuban adalah memuaskan dan telah menjelaskan ketumpatan kuasa elektrik yang dapat dihasilkan pada setiap hari. Ketumpatan kuasa didapati meningkat dari hari pertama 1.607 mW m-2 (3.816 mA m-2) ke nilai maksimum pada hari ketiga 1.979 mW m-2 (4.780 mA m-2) dan mula turun sehingga minimum pada hari ketujuh 1.311 mW m-2 (3.346 mA m-2). Peringkat rawatan air sisa kilang sawit oleh SFM boleh dibahagikan kepada tiga tahap yang berbeza. Kecekapan rawatan yang rendah walaupun ketumpatan kuasa meningkat pada tahap pertama, manakala pada tahap kedua kecekapan rawatan lebih tinggi dan akhirnya pada tahap ketiga penghasilan kuasa SFM mula turun. Kecekapan rawatan paling tinggi berlaku pada tahap ketiga semasa penghasilan kuasa elektrik yang terhasil agak malar. Kecekapan rawatan yang dinilaikan dalam bentuk penyingkiran COD, penggunaan nitrogen dan karbohidrat paling tinggi berlaku pada hari ke-15 dengan nilai masing-masing adalah 54.9, 100 dan 98.9%. Hubungan penghasilan kuasa elektrik dan kecekapan rawatan telah berjaya dimodelkan dalam persamaan linear matematik berdasarkan kepada tahap-tahap penghasilan kuasa elektrik ini.
Molybdenum oxides catalysts are extensively used in various selective oxidation reactions. In this work, controlled precipitation method was used to synthesise molybdenum oxides. The effects of various titration parameters on the precipitate growth rate and structure throughout catalyst synthesis were investigated. The titration parameters varied for this study were molybdates (ammonium heptamolybdate) concentration, precipitation agent (HNO3) concentration, precipitating agent rate of addition and temperature of synthesis. X-Ray diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM) were used to characterize the catalysts. This study highlights the significant effects of the titration parameters varied on the supersaturation of the solution therefore yielding precipitate with different morphology. It was observed that the temperature played the major role followed by molybdate concentration in the formation of the bulk catalyst. Supramolecular structure (Mo36O112) was observed at lower temperature (30ºC) and lower molybdate concentration (0.07 M, 0.10 M) while at higher temperature (50ºC) and higher molybdate concentration(0.14 M) hexagonal (h-MoO3) phase structure was formed. Fast rate of addition and high concentration of precipitating agent affected the solution equilibrium leading to unclear inflection point (supersaturation point) at the titration curve.
A series of ester compounds derived from ricinoleic acid to be used as biolubricants base stock have been synthesized. The resulting products were confirmed by FTIR and NMR analyses. The synthesis was carried out in three stages: epoxidation of ricinoleic acid; synthesis of 10,12-dihydroxy-9-acyloxystearic acid from epoxidized ricinoleic acid with various fatty acids and esterification of the acyloxystearic acid products with octanol to yield octyl-10,12-dihydroxy-9-acyloxystearate. The viscosities, flash points and pour points (PP) behavior of the products were measured. The resulting esters had an increased in molar weight and viscosity and decreased in pour points as compared to ricinoleic acid.
MeSH terms: Acids; Octanols; Body Weights and Measures; Esterification; Esters; Fatty Acids; Magnetic Resonance Imaging; Molar; Magnetic Resonance Spectroscopy; Ricinoleic Acids; Viscosity; Spectroscopy, Fourier Transform Infrared
Disc diffusion (DD), minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) assays were used to evaluate the antimicrobial activity of 21 consecutive extracts of different aerial parts of Etlingera brevilabrum against 18 microorganisms that included six Gram-positive [(+)], ten Gram-negative [(-)] bacteria and two fungi. Among the plant parts, the stolon extracts showed numerous activity than the other parts in which they inhibited Gram-positive of Staphylococcus aureus (ethyl acetate extract: diameter of inhibition zone 12.2±0.3 mm, MIC 3.12 mg/mL, MBC 6.25 mg/mL), methicillin resistant S. aureus (MRSA) (ethyl acetate extract: 12.1±0.2 mm, 12.5 mg/mL, 25 mg/mL), S. epidermidis (ethanol extract: 11.4±0.5 mm, 3.12 mg/mL, 3.12 mg/mL), Bacillus thuringiensis (acetone extract: 13.3±0.5 mm, 12.5 mg/mL, 25 mg/mL) and one Gram-negative of Vibrio paraehaemolyticus (water extract: 14.3±0.4 mm, 1.56 mg/mL, 6.25 mg/mL). The highest activity in MIC was shown by the methanol-water (1:1) and water extracts on Gram-negative Aeromonas hydrophila (1.56 mg/mL: leaf water extract) and V. paraehaemolyticus (1.56 mg/mL: methanol-water and water extracts of stolons and leaves and stem water extract).
Coklat adalah salah satu daripada makanan pembekal tenaga segera dan mempunyai kandungan antioksida yang tinggi. Dalam kajian ini, fungsi coklat telah ditingkatkan dengan menjadikannya sebagai pembawa bahan prebiotik melalui penukaran keseluruhan kandungan gula dengan inulin. Ujian awal telah dilakukan untuk memilih kepekatan atau dos inulin yang paling sesuai sebagai sumber karbon untuk merangsang pertumbuhan bifidobakteria dalam fermentasi kultur kelompok selama 24 jam dengan menilai kesannya terhadap perubahan kepekatan sel. Ujian dilakukan terhadap 4 strain bifidobakteria iaitu Bifidobacterium longum BB536, B. breve ATCC 15700, B. infantis ATCC 15697 dan B. pseudocatenulatum G4. Keputusan menunjukkan kesemua strain bifidobakteria mampu menggunakan inulin sebagai sumber karbon pada kepekatan 2, 5, 10 hinggalah 15 g/L inulin. Manakala kepekatan 5 g/L inulin dilihat mampu digunakan secara optimum (tiada perbezaan signifikan pada p>0.05) oleh keempat-empat spesies bifidobakteria tersebut. Inulin pada kepekatan 5 g/L telah digunakan untuk menghasilkan produk coklat susu (MC-1) dan coklat gelap (DC-2) berinulin, yang seterusnya dinilai kemampuan produk merangsang pertumbuhan spesis bifidobakteria berkenaan secara in vitro. Didapati wujud korelasi negatif yang signifikan (p<0.01) antara pertambahan bilangan bifidobakteria dan pH untuk setiap kultur tulen B. pseudocatenulatum G4, B. Infantis, B. Breve (masing-masing r= -0.97) dan B. longum BB536 (r= -0.95). Inulin dengan kepekatan 5 g/L telah digunakan sebagai ramuan produk coklat berinulin atau prebiotik. Ia didapati dapat meningkatkan pertumbuhan keempat-empat spesis bifidobakteria berkenaan dengan lebih berkesan berbanding penggunaan inulin sahaja sebagai sumber karbon.
The Cassava starch manufacturing wastewater (CSW) was used as a substrate to produce polyhydroxybutyrate (PHB) by Cupriavidus sp. KKU38. The acidogenic fermentation process of CSW was first conducted to obtain volatile fatty acids (VFAs), which are more efficient in PHB production than raw CSW. The effect on substrate concentration and nutrients, i.e. nitrogen and phosphorus concentrations, by means of chemical oxygen demand: nitrogen: phosphorus ratio (COD:N:P ratio) variation was investigated. The results indicated that PHB production from fermented CSW by Cupriavidus sp. KKU38 was optimized at the soluble COD:N:P ratio of 100:0.5:11. This ratio gave the maximum PHB content and yield of 85.53% and 0.31 g PHB/g COD consumed, respectively. By using the proposed PHB production process, the potential to produce 0.19 kg of PHB from 1.0 kg of soluble chemical oxygen demand (sCOD) contained in CSW was exhibited. The relatively high COD removal efficiency of 73.82% at the optimal condition could be achieved, which demonstrated the concept of water quality improvements alongside the production of the value-added by-product, PHB.
An experiment was carried out in 6 earthen ponds to investigate the effects of stocking density on growth, survival and production of Thai climbing perch (Anabas testudineus). Three stocking densities (treatments) were compared: ponds with 350, 400 and 550 individuals per decimal (0.01 acre). All treatments were randomly assigned and in duplicate. Artificial feed containing 34% crude protein was applied initially 20% of total fish weight per day. Gradually the feeding rate was reduced to 15, 12, 10, 8 and 5% of total fish weight per day. Feeding rates per pond were adjusted fortnightly after weighing minimum 20% of the fish stocked. The duration of the experiment was 90 days. Results showed that all growth parameters were higher in ponds with lower stocking density than the ponds with higher stocking density, while total fish yield was higher in ponds with higher stocking density than in the ponds with lower stocking density. Cost-benefit analysis revealed that all three systems were economically profitable. However, the ponds with a stocking density of 550 individuals per decimal were the most profitable system. More research is still needed to further optimize stocking density of Thai climbing perch in aquaculture ponds. Until then, stocking 550 individuals of Thai climbing perch per decimal will yield a good production to fish farmers in the South and South-East Asian regions.
A feeding trial was conducted to investigate the effect of mushroom supplementation as a prebiotic compound in an insect-based diet on the growth performance and feed utilization of red Tilapia (Oreochromis sp.). A total of 120 fingerlings were divided in triplicates for each treatment. Four experimental diets were offered to the fishes within a 56 days treatment period. Out of the four diets, three contained mushroom stalk meal (MSM) supplementation at various levels of inclusion of prebiotic compound (0.5% MSM; 1.0% MSM; 1.5% MSM) and the fourth a control diet without MSM inclusion. During the growth test, fish receiving diet containing prebiotic showed significantly higher (p<0.05) mean individual body weight in comparison with the control diet. The best effect was obtained in fish fed with Diet 2, where the specific growth rate (SGR) was 1.74%, feed conversion ratio (FCR) was 0.58, protein efficiency ratio (PER) was 5.17 and survival was 93.33%. No significant differences (p>0.05) were observed in whole body protein and ash contents among the fish feeding on these diets. All water quality parameters showed no significant difference (p>0.05) in all treatments. The result of this feeding trial indicated that the 10% supplementation level of MSM as a prebiotic for tilapia could be used in the insect-based diet, Zophobas morio.
MeSH terms: Agaricales; Animals; Body Weight; Diet; Humans; Male; Tilapia; Homosexuality, Male; Prebiotics; Water Quality; Meals
In this study, we investigated the feeding behavior of the brown-marbled grouper, Epinephelus fuscoguttatus with light intensities ranging over eight orders of magnitude from 0–1000 lx to estimate the optimum light intensity for larval rearing. Artemia ingestion rates of E. fuscoguttatus of 36 days and 42 days old larvae were measured in feeding behavior experiments and they were significantly higher with light intensities ≥10 lx compared with feeding rates at ≤1 lx. E. fuscoguttatus larvae also exhibited Artemia ingestion rates in the dark or in dim lighting (0–1 lx) that were about 20% of the ingestion rates with ≥10 lx.
Syzygium myrtifolium (Roxb.) Walp. is a popular landscape plant in Malaysia. This species is always planted as hedge plant and topiary. However, it requires frequent trimming to maintain its form and aesthetic functions as it grows vigorously. Conventional trimming technique by using trimming shear or trimming machine is currently practiced in landscape maintenance which is time consuming, labour intensive and costly. Therefore, a study was conducted to investigate the effects of a plant growth retardant, paclobutrazol, on the growth and physiological response of S. myrtifolium. The plants were planted in polyethylene bags sized 33 cm in height × 27 cm in diameter and filled with soil, organic matter and sand (3:2:1). Paclobutrazol at rates of 0, 1.25, 2.50 and 3.75 g L-1 were soil drenched at 30 days after the plants were trimmed and new shoots were produced. Paclobutrazol significantly reduced plant height and leaf area but increased the leaf area index. Reduced photosynthetic rates were recorded with the treated plants as compared to the control plants. In addition, paclobutrazol at 3.75 g L-1 significantly reduced the transpiration rate as compared with the control plants and plants treated with 1.25 g L-1 of paclobutrazol. However, stomatal conductance was not affected significantly by paclobutrazol. The growth inhibition effect of paclobutrazol reduced the trimming activity in S. myrtifolium. Chlorophyll fluorescence measurement indicated that physiological processes in the paclobutrazol-treated plants were not affected. Paclobutrazol is concluded to offer a better approach in maintaining the growth of S. myrtifolium.