This paper proposes a new fuzzy version of Euler’s method for solving differential equations with fuzzy initial values. Our proposed method is based on Zadeh’s extension principle for the reformulation of the classical Euler’s method, which takes into account the dependency problem that arises in fuzzy setting. This problem is often neglected in numerical methods found in the literature for solving differential equations with fuzzy initial values. Several examples are provided to show the advantage of our proposed method compared to the conventional fuzzy version of Euler’s method proposed in the literature.
This paper proposes a new computational method for computing non-monotone functions that take a fuzzy interval as their arguments. The proposed method represents an implementation of optimisation technique into Zadeh’s extension principle. By taking into account the dependency problem that exists in fuzzy environment, the proposed method can avoid the effect of overestimation in computation. This problem usually arises when the same fuzzy interval is computed separately in fuzzy interval computation. The proposed method is simple to use and can be implemented in many practical applications. In order to show the capability of the proposed method, several non-monotone functions with trapezoidal fuzzy intervals are studied.
Long-wavelength vertical-cavity surface-emitting lasers (LW-VCSELs) have profound advantages compared to traditional edge-emitting lasers offering improved properties with respect to mode selectivity, fibre coupling, threshold currents and integration into 2D arrays or with other electronic devices. Its commercialization is gaining momentum as the local and access network in optical communication system expand. Numerical modeling of LW-VCSEL utilizing wafer-fused InP-based multi-quantum wells (MQW) and GaAs-based distributed Bragg reflectors (DBRs) is presented in this paper. Emphasis is on the device and mesa/pillar diameter design parameter comparison and its effect on the device characteristics.
Penyelidikan ini dilakukan untuk mengkaji ciri akustik serabut sabut kelapa yang berpotensi digunakan sebagai bahan penyerap bunyi. Untuk meningkatkan ciri akustik serabut sabut kelapa pada frekuensi rendah, lapisan berliang digunakan di bahagian depan atau belakang bertujuan untuk meningkatkan nilai galangan permukaan. Bahan selanjutnya dilapisi dengan plat berlubang dengan nisbah keluasan yang berbeza. Sampel diuji mengikut piawaian antarabangsa ASTM E 1050-98 untuk menentukan pekali penyerapan bunyi. Daripada hasil uji kaji, plat 1 mm berlubang yang diperbuat daripada kepingan aluminium yang melapisi serabut sabut kelapa, didapati bahawa nilai maksimum pekali penyerapan bunyi berada pada frekuensi antara 2750 Hz hingga 2825 Hz iaitu dengan nilai 0.97. Nilai nisbah keluasan plat berlubang memberikan pengaruh penurunan pekali penyerapan bunyi pada frekuensi tinggi. Penurunan nilai pekali penyerapan bunyi terjadi apabila plat berlubang mempunyai nilai nisbah keluasan di bawah 0.22. Akan tetapi, penggunaan plat berlubang boleh meningkatkan prestasi penyerapan bunyi serabut sabut kelapa pada frekuensi rendah. Kesepakatan yang baik diperoleh daripada keputusan uji kaji dan analisis dengan pendekatan rangkaian elektrik setara yang digunakan untuk menghitung nilai pekali penyerapan bunyi. Ini menunjukkan bahawa pendekatan rangkaian elektrik setara boleh digunakan untuk merancang dan mengoptimumkan ciri akustik serabut sabut sebagai bahan penyerap bunyi.
Flies from the family Calliphoridae, Sarcophagidae and Muscidae are usually found on human cadavers or animal carcasses. However, there are many other families of Diptera and Coleoptera that were found associated with animal carcasses, which have not been reported in Malaysia. In this paper, we report dipterans from the family Micropezidae: Mimegralla albimana Doleschall, 1856, Neriidae: Telostylinus lineolatus (Wiedemann 1830); Sepsidae: Allosepsis indica (Wiedemann 1824), Ulidiidae: Physiphora sp. and a beetle (Coleoptera: Hydrophilidae: Sphaeridium sp.) as opportunist species feeding on oozing fluid during the decomposition process. They did not oviposit on the pig carcasses, therefore, their role in estimation of time of death is of little importance. However, they could provide clues such as locality and types of habitats of the crime scene.
Due to the increase in price of petroleum and environmental concerns, the search for alternative fuels has gained importance. In this work, biodiesel production by transesterification of palm oil with methanol has been studied in a heterogeneous system using sodium hydroxide loaded on alumina (NaOH/Al2O3). NaOH/Al2O3 catalyst was prepared by impregnation of alumina with different amount of an aqueous solution of sodium hydroxide followed by calcination in air for 3 h. The prepared catalysts were then characterized by using x-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), Brunner-Emmett-Teller surface area measurement (BET), scanning electron microscopy (SEM) and temperature-programmed desorption of CO2 (CO2-TPD). Moreover, the dependence of the conversion of palm oil on the reactions variables such as the molar ratio of methanol/oil, the amount of catalysts used, reaction temperatures and reaction times were performed. The conversion of 99% was achieved under the optimum reaction conditions. The biodiesel obtained was characterized by FT-IR and the pour point was measured.
In this study, ceiling fan dust samples were collected from three schools in the district of Serdang Selangor, Malaysia. The sampled dust were analysed for the concentrations of Cd, Cu, Fe, Ni, Pb and Zn. The heavy metal ranges found in all the schools were 2.96-7.74 μg/g dry weight for Cd, 75-442 μg/g dry weight for Cu, 3445-3852 μg/g dry weight for Fe, 24-66 μg/g dry weight for Ni, 140-734 μg/g dry weight for Pb and 439-880 μg/g dry weight for Zn. SMK Seri Serdang School was found to have elevated concentrations of Cd, Cu, Ni, Pb, and Zn which indicated the anthropogenic sources of the study sites. In comparison to other reported studies in the literature, the maximum levels of Cd, Cu, Ni, and Pb were comparable or higher to those cities reported. Therefore, more monitoring studies should be conducted in future since dusts could be related to human health hazards and the dusts can be used as a potential monitoring tool for heavy metal pollution in the atmosphere.
Bioaccumulation of lead and Copper in Avicennia marina and Rhizophora apiculata was studied. Samples of leaves, barks and roots were collected from Balok mangrove forest, Pahang. Pb and Cu accumulation was higher in Avicennia marina root tissue compared to bark and leaf but lower than surrounding sediment level. The average concentration of Pb in A. marina leaf, bark, root and sediment was observed to be 5.39 ppm, 3.63 ppm, 18.21 ppm and 23.13 ppm, and average Cu concentration was 4.13 ppm, 4.27 ppm, 4.81 ppm and 12.33 ppm, respectively. R. apiculata also showed higher concentration of Pb and Cu in root tissue compared to bark and leaf tissues but lower than surrounding sediment. The average concentration of Pb in R. apiculata leaf, bark, root and sediment was observed to be 4.30 ppm, 2.97 ppm, 22.45 ppm and 31.23 ppm, respectively. The average Cu concentration was 2.93 ppm, 4.71 ppm, 4.81 ppm and 15.52 ppm, respectively. Results of concentration factors (CF) showed that the accumulation of Pb and Cu was higher in A. marina than in R. apiculata.
The aim of this study was to determine the accumulation of settling particles in coral reefs of Peninsular Malaysia. Settling particles were collected from the coral reefs of Port Dickson, Pulau Langkawi, Pulau Tioman, Pulau Redang and Pulau Tinggi from 2005 to 2008. The average total settling particles in Pulau Langkawi and Port Dickson was 49.8 mg/cm2/day, while for Pulau Tioman, Pulau Redang, and Pulau Tinggi was 3.5 mg/cm2/day. The results showed that accumulations rate in west coast were higher than east coast of Peninsular Malaysia. However, Pulau Tioman in the east coast received high accumulations rate of settling particles in certain times of the year due to sediment resuspension at shallow reefs caused by high energy seasonal yearly wave and monsoon.
Zooplankton were sampled in Lake Ikeda at a fixed station every month with the aid of a plankton net in order to observe whether cyclomorphism was exhibited by the neonates of Bosmina longirostris. In Lake Ikeda the relative sizes of the antennules and mucrones of B. longrostris neonates decreased in relation to carapace length from 65% in winter to 50% in summer. Mucrone lengths also decreased from 30% in winter to 20% in summer. Both appendages were inversely correlated with surface temperature of the lake. Predation seems to be one of the reasons why neonates of B. longirostris exhibited seasonal cyclomorphism in their antennule and mucrone.
Groundwater in fractured metasedimentary rock in Malaysia is a potential source of water for drinking and industrial uses. Industries including agricultural processing, mineral water bottling, manufacturing and golf courses pumped the water from the underlying fractured rocks. Fifty eight tubewells belong to private companies operating in various places in West Coast of Peninsular Malaysia were evaluated for their yield and quality of water. Rotary percussion methods were used for the drilling to a maximum depth of 200 m. The productivity of the wells and the characteristics of the aquifer were evaluated by pumping test using both the constant discharge rate and steps drawdown methods. The average yield of the wells at allowable drawdown of 40 m was found to be 416 m3 per day. Results from water quality analysis indicated that the water was fresh with an average total dissolved solids (TDS) concentration of 101 to 150 mg/L. The hardness of the water varies from as low as 13 mg/L to a maximum of 353 mg/L. On the average, the water was moderately hard with the average hardness value of 80 mg/L. The water facies of the groundwater was found to be of calcium-sodium-bicarbonate water.
MeSH terms: Agriculture; Bicarbonates; Calcium, Dietary; Golf; Hardness; Malaysia; Mineral Waters; Percussion; Sodium; Sodium Bicarbonate; Facies; Groundwater; Water Quality; Water Wells
A series of poly(urea-formaldehyde) (PUF) microcapsules filled with dicyclopentadiene (DCPD) was successfully prepared by in situ polymerization. The effect of diverse process parameters and ingredients on the morphology of the microcapsules was observed by SEM, optical microscopy (OM) and digital microscopy. Different techniques for the characterization of the chemical structure and the core content were considered such as FT-IR and 1H-NMR as well as the characterization of thermal properties by DSC. High yields of free flowing powder of spherical microcapsules were produced. The synthesized microcapsules can be incorporated into another polymeric host material. In the event the host material cracks due to excessive stress or strong impact, the microcapsules would rupture to release the DCPD, which could polymerize to repair the crack.
Oil palm empty fruit bunch graft poly (acrylic acid-co-acrylamide) superabsorbent composite (OPEFB-g-(PAA-co-PAM) SAPC) was synthesized by graft copolymerization of the acrylic acid (AA) and acrylamide (AM) comonomer onto OPEFB fibre using ammonium persulfate (APS) and N,N-methylene bisacarylamide (MBA) as an initiator and crosslinker, respectively. The absorbency in various chloride salt solutions indicated that the absorbency decreased with increasing ionic strength of the salt solutions. Moreover, the absorbency under load (AUL) of SAPC was investigated at various applied loading and results show that, AUL decreased with increasing applied loading. Infrared Spectroscopy (IR) and Thermogravimetric Analysis (TGA) were carried out to confirm the chemical structure and thermal properties of the synthesized superabsorbent, respectively.
The development on a class of technologically advanced materials like superabsorbent polymer composites (SAPC) involved multidisciplinary research started when its potential is recognized. Oil palm empty fruit bunch-graft-poly (acrylamide) (OPEFB-g-PAAm) SAPC was synthesized via simultaneous crosslinking and graft copolymerization of acrylamide (AAm) monomer onto OPEFB backbone with N,N’-methylenebisacrylamide (MBA) and ammonium persulphate (APS) acts as crosslinker and initiator, respectively, along with neutralization using solution polymerization method. Systematically, variables that affect the swelling behaviors of OPEFB-g-PAAm SAPC were optimized. The effects of initiator, crosslinker and filler concentration as well as solvent quantity and the degree of neutralization on water absorbency of OPEFB-g-PAAm SAPC were studied. Maximum absorbency of OPEFB-g-PAAm SAPC was achieved at 589.06 g/g when the amount of APS and MBA were 1.5 wt.% and 0.15 wt.%, respectively, and the OPEFB loading was at 10 wt.%. The optimum amount of solvent used was 15 mL and the degree of neutralization was 20%. The chemical structure of the OPEFB-g-PAAm SAPC was characterized by means of Fourier transform infrared (FTIR) spectroscopy. A mechanism pathway in synthesizing OPEFB-g-PAAm SAPC was suggested.
Four chromium based oxo-trinuclear carboxylate complexes were prepared by reacting chromium(III) nitrate nonahydrate with acetic acid and substituted carboxylic acids. They were characterized using infrared spectroscopy (FT-IR). Chromium content of the complexes was determined by titrimetry method. The chromium(III) monochloroacetate complex, [Cr3O(ClCH2COO)6.3H2O]NO3.3H2O in combination with diethylaluminium chloride formed heterogeneous catalyst system for ethylene polymerization. Both Al/Cr ratio and temperature influenced the catalytic activity. The maximum activity was 1768 gPE/gCr/hr/atm, achieved by polymerizing at 29°C and monomer pressure around 1 atm, with Al/Cr ratio 30.8. Effect of chloro-substituent groups on carboxylic ligand was studied by comparing the catalytic acitivities of chromium(III) monochloroacetate, chromium(III) dichloroacetate, chromium(III) trichloroacetate and chromium(III) acetate.The polymerization reaction was found to be first order with respect to the monomer during the initial stage. The activity decreases very rapidly presumably due to fast decay of the active sites. The polyethylene was characterized using FT-IR and DSC, and the results showed that it was of high density and crystallinity.
Two inorganic pigments (TiO2 and SiO2) were used to prepare composites with polyaniline (PANI) by situ polymerization method. PANI and PANI composites with SiO2 and TiO2 were characterized using Fourier transform infrared spectroscopy and X-ray diffraction. The morphology of the synthesized pigments (PANI , PANI-SiO2 and PANI-TiO2) was examined using scanning electron microscopy. Samples were then used as pigments through blending them with acrylic paint and applied on the surface of carbon steel panels. Corrosion was evaluated for coating of carbon steel panels through full immersion test up to standard ASTMG 31. Mass loss was calculated after they have been exposed in acidic media. A digital camera was also used for monitoring corrosion visually on the surface of carbon steel specimens. The results revealed that acrylic paint pigmented by PANI-SiO2 composite was more efficient in corrosion protection for carbon steel compared with the other synthesized pigments.
This paper reports on the effect of molecular weight on the morphological and mechanical properties of liquid epoxidised natural rubber acrylate (LENRA)/silica hybrid composites prepared by sol-gel technique. The sol-gel reaction was conducted at different concentration of tetraethylorthosilicate (TEOS), used as a precursor of silica. TEOS were introduced in 10, 20, 30, 40 and 50 parts per hundred rubber (phr) in the composites. Two different molecular weights of ENR were used to study the effect of molecular weight on the mechanical and morphological properties of the compounds. These compounds were cured by ultraviolet (UV) irradiation. The mechanical properties were studied through pendulum hardness and scratch tests. Higher molecular weight of ENR showed better mechanical properties than lower molecular weight. Transmission electron microscope was used to determine the silica size and to study the distribution and dispersion of the silica particles. High molecular weight showed greater distribution and dispersion of silica particles with diameter of 13 nm–256 nm. Morphological and mechanical properties of LENRA/silica hybrid composites were improved by using high molecular weight of ENR.
Effects of aluminium hydroxide (ATH) addition on the properties of palm-based polyurethane composites were investigated. The hybrid composites were prepared by mixing 10 wt% of oil palm empty fruit bunch fiber (EFB) with ATH at varying amount of 2, 4 and 6 wt% of the overall mass of the resin. The compression stress and modulus gave the highest values of 575 and 2301 kPa, respectively at 2 wt% loading of ATH. The compression stress and modulus decreased drastically at 4 wt% (431 kPa and 1659 kPa, respectively) and further decreased at 6 wt% ATH (339 and 1468 kPa, respectively). However, the burning rate is inversely proportional to the loading percentage where the highest burning rate was observed at 2 wt% ATH. Sound absorption analysis indicated a large absorption coefficient at high frequency (4000 Hz) for all samples. The highest absorption coefficient was obtained from PU-EFB/ATH with 4 wt% ATH.
In this study, poly(ethylene terephthalate) (PET) wastes bottle was recycled by glycolysis process using ethylene glycol. The unsaturated polyester resin (UPR) was then prepared by reacting the glycolysed product with maleic anhydride. The blend of UPR based on recycled PET wastes with liquid natural rubber (LNR) was carried out by varying the amount of LNR from 0 to 7.5 wt%. Mechanical tests such as tensile and impact were conducted to investigate the effects of LNR on the mechanical properties. Scanning Electron Microscopy (SEM) was used to analyze the morphology of the breaking area resulted from the tensile tests on the UPR and blend samples. From the results, the blend of 2.5 wt% LNR in UPR based recycled PET wastes achieved the highest strength in the mechanical properties and showed a well dispersed of elastomer particles in the sample morphology compared to other blends concentrations. This blend sample was then compared to the optimum blend of LNR with commercial resin through the glass transition temperature value Tg, mechanical strength and morphology properties. The comparison study showed that the Tg for UPR based recycled PET was higher than the value represented from commercial resin due to the degree of crystalinity in the molecular structure of the materials. LNR was found to be an effective impact modifier which gave a greater improvement in UPR from recycled PET wastes structure but not to the commercial one which needs 5% LNR to achieve the optimum properties. Thus, the compatibility between the UP resin based recycled PET and LNR was much better than with the commercial resin.
The effect of various multi-walled carbon nanotubes (MWNTs) on the tensile properties of thermoplastic natural rubber (TPNR) nanocomposite was investigated. The nanocomposite was prepared using melt blending method. MWNTs were added to improve the mechanical properties of MWNTs/TPNR composites in different compositions of 1, 3, 5, and 7 wt.%. The results showed that the mechanical properties of nanocomposites were affected significantly by the composition and the properties of MWNTs. SEM micrographs confirmed the homogenous dispersion of MWNTs in the TPNR matrix and promoted strong interfacial adhesion between MWNTs and the matrix which was improved mechanical properties significantly.