In this present research, several kinds of selected tropical light hardwoods were chemically modi... more In this present research, several kinds of selected tropical light hardwoods were chemically modified with benzene diazonium salt to improve their physico-mechanical and decay resistance properties. Benzene diazonium salt underwent a coupling reaction with wood which was confirmed through fourier transform infrared spectroscopic analysis. The compressive modulus of the treated wood increased, whereas modulus of rupture was shown to decrease on treatment. Water absorption was also found to decrease considerably after modification. The modified wood samples had higher hardness (Shore D) value compared to that of the control ones. The wood was exposed to two types of fungi; white-rot (Polyporus versicolor) and brown-rot (Postia placenta), for 12 weeks and then decay was assessed through weight loss percentage (%). A significant improvement was found in the modified wood compared to the control wood.
Wood Composites-The First International Symposium of IWRS 72 Wear of Wood Polymer Composite for J... more Wood Composites-The First International Symposium of IWRS 72 Wear of Wood Polymer Composite for Journal Bearing Materials Sinin Hamdan1, Mohd. Abdul Mun'aim Mohd Idrus, Md Rezaur Rahman, Nurul Faziha Ibrahim and Md Saiful Islam Faculty of Engineering, University ...
The generation of the impact sound by the act of the human walk involves two factors, the charact... more The generation of the impact sound by the act of the human walk involves two factors, the character of the footfall and the shape of the induced floor vibration. High levels of vibrations can occur in floor systems due to excitation from human activities such as walking and aerobics. In building floors, excessive vibrations are generally not a safety concern for building floor system but a cause of annoyance and discomfort. The footfall noise is created by the impact excitation where the character of the footfall depends on the foot-ware: the heels and the frequencies of the footfall. The shape of the floor deflection depends rather on the geometrical walking pattern and construction of the floor structure. Two types of floors are used for this experiment (1) Profiled Steel Sheet Concrete Floor (PCF) and Composite Concrete Floor (CCF). Since the excitation is assumed to be deterministic, differences between the excitation masses, acting forces and damping are determine from Bruel & Kjaer vibration analyzer machine. The goal of this investigation is to determine the differences of the floor nature by human effect depending on various positions on floors.
The dielectric properties, such as dielectric constant, dissipation factor and dielectric loss fa... more The dielectric properties, such as dielectric constant, dissipation factor and dielectric loss factor of jute/bamboo natural fibers reinforced with polypropylene and unsaturated polyester hybrid composites were studied with different fiber loadings, fiber ratios, frequencies and chemical modifications of natural fibers. The dielectric constant, dissipation factor and loss factor increased with an increase in the fiber content for the entire range of frequencies than the pure polypropylene and pure unsaturated polyester materials. This increase was high at low frequencies, low at medium frequencies, and very low at high frequencies. Dielectric constant values were observed to decrease in frequency due to the decreased interfacial and orientation polarization at higher frequencies. Whereas, dielectric constant increased with an increase in the fiber loading, due to the increase in the number of polar groups, after the addition of hydrophilic lignocellulose fibers. Sodium hydroxide treatment was carried out on jute and bamboo fibers to improve the adhesion between fibers and matrix. The dielectric constant was lower for composites consisting of fibers subjected to alkaline treatment due to the increased hydrophobicity of fibers. When the weight percentage of jute fiber was increased in the total fiber content of the hybrid composites, the dielectric constant, dissipation factor and loss factor were found to increase. It is evident that types of polymer have little influence on the dielectric properties of the hybrid composites
This research work is concerned with the development of unsaturated polyester composites reinforc... more This research work is concerned with the development of unsaturated polyester composites reinforced with betelnut fibers. Moreover, the fibers were chemically modified by sodium hydroxide and its effects on the fiber/matrix interaction were also evaluated. Raw and chemically modified fibers have been used in different proportions for the preparation of these composites. The optimization of fiber proportions has been done in term of their tensile strength. The sodium hydroxide treatment effect of fibers was verified by FTIR analysis and the fibers morphological aspects of fibers by SEM. Likewise, the sound absorption coefficient of composites were studied using impedance tube method. The thermal analyses of composites were made using Thermogravimetric analysis. Compared with untreated fiber composites, there was an improvement in the tensile strength of the treated fiber composites. SEM micrographs of betelnut fiber surface revealed the rough and perforated surface of fibers. Whereas, the cross sectional of the betelnut fibers showed the bigger lumen structures. The sound absorption coefficients of composites increased as the frequency increased and thicker composites appeared to perform better than those of thinner ones. The thermal stability of the treated fiber composites was found to be higher than that of untreated fiber composites.
In this study, both untreated rice straw stem fibers and fibers treated with sodium hydroxide wer... more In this study, both untreated rice straw stem fibers and fibers treated with sodium hydroxide were used. Maleic anhydride polypropylene (MAPP) was used to enhance adhesion of the fiber with the matrix. Composites were prepared with various combinations of fiber, ranging from 10 wt.% to 25 wt.%, and polypropylene in addition to 2 wt.% MAPP. These composites were then tested for acoustical, mechanical, thermal, infrared spectral, and morphological properties. The fibers were treated by being soaked in 5 wt.% NaOH solution at 30 °C for 30 min. The composites with treated fiber exhibited higher thermal stability, tensile strength, sound absorption, and fiber-matrix adhesion than the composites with untreated fiber. The results of sound absorption measurements showed that the composites with higher fiber content had better sound absorption than the composites with lower fiber content. The changes in the peaks in the Fourier transform infrared spectrum indicate that the alkaline treatment removed hemicellulose and lignin from the rice straw stem fibers.
The aim of the present study was to determine the influence of doping rare earth ion on strontium... more The aim of the present study was to determine the influence of doping rare earth ion on strontium calcium aluminate (CaO-SrO-SiO 2 -Al 2 O 3 ). Therefore, the authors have manufactured luminescent material consisting of 40CaO-5SrO-5SiO 2 -50Al 2 O 3 doped with Dy 3z . The compositions have been selected on the basis of chemical stability. Five pellets were prepared with different calcination temperatures and times, namely 400 and 600uC for 1 and 2 h, in order to shed light on their luminescence behaviour. X-ray diffraction, energy dispersive X-ray analysis and scanning electron microscopy elaborate and characterise the formation of small particle of photoluminescent material in the phosphor matrix host material.
This paper reports on the luminescence properties of Dy 3+ -doped 30SrO-30MgO-40P 2 O 5 , which h... more This paper reports on the luminescence properties of Dy 3+ -doped 30SrO-30MgO-40P 2 O 5 , which had been prepared by solid state reaction. The crystalline phases were identified using X-ray diffraction (XRD) and their luminescence properties were studied using excitation and emission spectra obtained from photoluminescence spectroscopy. The results of XRD patterns indicate that the prepared sample contain crystalline phase of MgP 2 O 6 and SrMgP 2 O 7 . The excitation spectrum of 30SrO-30MgO-40P 2 O 5 :Dy 3+ consists of broad bands' centre at ∼280, 310 and 400-600 nm associated with defects and vacancies of host material. The other feature of sharp peaks is very similar and belongs to Dy 3+ ions. The f-f transitions in the range of 417-475 nm correspond to the transitions from 6 H 15/2 to 4 K 17/2 + 4 M 19/2,21/2 + 4 I 13/2 + 4 F 7/2 , 4 G 11/2 , 4 I 15/2 and 4 F 9/2, in the range of 392 nm to 6 P 3/2 + 6 P 5/2 , and in the range of 312-370 nm to 4 K 15/2 , 6 P 7/2 + 4 M 15/2 and 4 I 11/2 , respectively. The peaks at 482, 465, and 455 nm could be assigned to the transition of 4 F 9/2 → 6 H 15/2 , 4 I 15/2 → 6 H 15/2 and 4 G 11/2 → 6 H 15/2 of Dy 3+ , respectively. Dy 3+ has emissions due to the atomic energy levels of itself and emissions due to the acceptor levels of defect sites formed by Dy 3+ .
Acoustic properties such as specific dynamic Young’s modulus (E′/γ), internal friction (Q −1) and... more Acoustic properties such as specific dynamic Young’s modulus (E′/γ), internal friction (Q −1) and acoustic conversion efficiency (ACE) of wood are important properties frequently examined by researchers. Vibration technique is one of the non-destructive evaluation techniques used as an alternative method for measuring the acoustic properties of wood. The objectives of this study are to determine acoustic properties of selected low density tropical wood species namely Endospermum Diadenum, Cratoxylum Arborecens, Dyera Polyphylla, Macaranga Gigantea, Commersonia Bartramia and Alstonia Pneumatophora and their suitability for making violin and guitar (acoustic instruments). The acoustic properties were determined by using free-free flexural vibration method. The results show that there are significant and good relationship between log Q −1/(E′/γ) and log E′/γ with negative gradient for each and overall wood species studied. The P-value of regression equation is less than 0.01 whereas the coefficient of determination (r 2) is in the range of 0.565 to 0.894. The mean value of E′/γ, Q −1 and ACE of wood species studied are in the range of 1.69×1010 Pa to 2.73×1010 Pa, 0.017 to 0.035 and 1.50×107 to 3.56×107 respectively. Based on the mean value of E′/γ, Endospermum Diadenum, Cratoxylum Arborescens, Macaranga Gigantea and Dyera Polyphylla are preferred for making all component of violin and guitar except for the top plate of violin. Commersonia Bartramia is preferred for making the back plate of violin and guitar, whereas Alstonia Pneumatophora is only preferred for making the back plate of violin.
. N-acylethanolamines NAEs have attracted the attention of researchers in the last two decades du... more . N-acylethanolamines NAEs have attracted the attention of researchers in the last two decades due to their occurrence in biological membranes under conditions of stress as well as under normal conditions. Differential scanning calorimetric studies have been carried out on dry and hydrated samples of a homologous series of N-acylethanolamines containing Ž . saturated acyl chains of even number of carbon atoms n s 8-20 . In both cases a major sharp endothermic transition was observed which occurs at the melting point for the dry NAEs whereas for the hydrated samples it occurs at considerably lower temperatures. The enthalpies and entropies corresponding to this transition could be fitted, in each case, to a straight line suggesting that the transition enthalpy and transition entropy consist of a fixed component from the polar head group Ž . and the terminal methyl group, whereas the contribution of the methylene groups, CH , is linearly proportional to the 2q 2q w x Ca -Mg -ATPase activity 4 and inhibition of 0005-2736r97r$17.00 q 1997 Elsevier Science B.V. All rights reserved.
. N-acylethanolamines NAEs have attracted the attention of researchers in the last two decades du... more . N-acylethanolamines NAEs have attracted the attention of researchers in the last two decades due to their occurrence in biological membranes under conditions of stress as well as under normal conditions. Differential scanning calorimetric studies have been carried out on dry and hydrated samples of a homologous series of N-acylethanolamines containing Ž . saturated acyl chains of even number of carbon atoms n s 8-20 . In both cases a major sharp endothermic transition was observed which occurs at the melting point for the dry NAEs whereas for the hydrated samples it occurs at considerably lower temperatures. The enthalpies and entropies corresponding to this transition could be fitted, in each case, to a straight line suggesting that the transition enthalpy and transition entropy consist of a fixed component from the polar head group Ž . and the terminal methyl group, whereas the contribution of the methylene groups, CH , is linearly proportional to the 2q 2q w x Ca -Mg -ATPase activity 4 and inhibition of 0005-2736r97r$17.00 q 1997 Elsevier Science B.V. All rights reserved.
The pressing need to recruit and retain students from diverse background on engineering courses h... more The pressing need to recruit and retain students from diverse background on engineering courses has created a big challenge for academics to deal with a wide range of students' mathematical abilities. At the same time, the role that mathematics plays in professional practice has changed radically in the last 30 years. Today, "computational mathematics" is perceived as a tremendous opportunity , pushing forward the boundaries of engineering design. Within this, mathematics as explicit work by individual engineers has evolved into mathematics as a distributed activity across design teams and the computers which support them (1)(2). In this study, an assessment of students' mathematical abilities was carried out at three vocational institutions; one in the UK (University of Wales Institute, Cardiff - UWIC) and two in Malaysia (Universiti Malaysia Sarawak-UNIMAS and Universiti Teknologi Mara-UiTM Sarawak Campus). The assessment was based on "Mathematics Diagnostic Test" which was given to students at Year 1 and Year 2 of Engineering courses in the three institutions.
Sago starch (SS) was melt-blended with polypropylene (PP) with the concentration of SS in the ble... more Sago starch (SS) was melt-blended with polypropylene (PP) with the concentration of SS in the blends varied between 10% and 50% by weight. Characterization of the PP/SS blends was carried out to gain some information on the miscibility between PP and SS and to gain insight into how well these materials behave thermodynamically with regard to the variation of the storage modulus (E′) and the loss tangent (tanδ) with temperature. The E′ and tanδ remained unchanged for SS between 10% to 33% but increased as SS reached 50%. The blend containing 50%SS was superior compared to the other blends in the dynamic mechanical thermal analysis (DMTA). Through the use of a Differential Scanning Calorimeter (DSC), the melting endotherm of the miscible blends was found to increase constantly with the increasing SS content. The tensile properties of the blends decreased with SS content. Examination of the blends with a Scanning Electron Microscope (SEM) showed that the SS granules were well dispersed in the PP matrix.
In this study, wood polymer composites (WPCs) based on five kinds of selected tropical wood speci... more In this study, wood polymer composites (WPCs) based on five kinds of selected tropical wood species, namely Jelutong (Dyera costulata), Terbulan (Endospermum diadenum), Batai (Paraserianthes moluccana), Rubber (Hevea brasiliensis), and Pulai (Alstonia pneumatophora), were impregnated with methyl methacrylate (MMA) and hexamethylene diisocyanate (HMDIC) monomers mixture in the ratio of 1:1 for composite manufacturing. All these tropical wood reacted with hexamethylene diisocyanate and crosslinked with MMA which enhanced the hydrophobic (restrained water) nature of wood. The vacuum-pressure method was used to impregnate the samples with monomer mixture. The monomer mixture loading achievable was found to be dependent on the properties of wood species. Low loading was observed for the high density wood species. Mechanical strength of fabricated wood polymer composites (WPCs) in term of modulus of elasticity (MOE) and modulus of rupture (MOR) were found to be significantly improved. The wood-polymer interaction was confirmed by Fourier transform infrared (FTIR) spectroscopy. Morphological properties of raw wood and WPC samples were evaluated by scanning electron microscopy (SEM) and XRD analysis and an improvement in morphological properties was also observed for WPC.
... 0.66 (0.12)* *Values in parenthesis represent standard deviation of mean value. {Values in pa... more ... 0.66 (0.12)* *Values in parenthesis represent standard deviation of mean value. {Values in parenthesis represent MOE from previous researchers. Hamdan et al. Young's modulus and glass transition temperature of selected tropical wood species ...
Agricultural waste biomass has already been transferred to bioethanol and used as energy related ... more Agricultural waste biomass has already been transferred to bioethanol and used as energy related products, although many issues such as efficiency and productivity still to be overcome. In this study, the protein engineering was applied to generate enzymes with completely reversed coenzyme specificity and developed recombinant yeasts containing those engineered enzymes for construction of an efficient biomass-ethanol conversion system. Recombinant yeasts were constructed with the genes encoding a wild type xylose reductase (XR) and the protein engineered xylitol dehydrogenase (XDH) (with NADP) of Pichia stipitis. These recombinant yeasts were characterized based on the enzyme activity and fermentation ability of xylose to ethanol. The protein engineered enzymes were expressed significantly in Saccharomyces cerevisiae as judged by the enzyme activity in vitro. Ethanol fermentation was measured in batch culture under anaerobic conditions. The significant enhancement was found in Y-ARS strain, in which NADP + -dependent XDH was expressed; 85% decrease of unfavorable xylitol excretion with 26% increased ethanol production, when compared with the reference strain expressing the wild-type XDH.
In this present research, several kinds of selected tropical light hardwoods were chemically modi... more In this present research, several kinds of selected tropical light hardwoods were chemically modified with benzene diazonium salt to improve their physico-mechanical and decay resistance properties. Benzene diazonium salt underwent a coupling reaction with wood which was confirmed through fourier transform infrared spectroscopic analysis. The compressive modulus of the treated wood increased, whereas modulus of rupture was shown to decrease on treatment. Water absorption was also found to decrease considerably after modification. The modified wood samples had higher hardness (Shore D) value compared to that of the control ones. The wood was exposed to two types of fungi; white-rot (Polyporus versicolor) and brown-rot (Postia placenta), for 12 weeks and then decay was assessed through weight loss percentage (%). A significant improvement was found in the modified wood compared to the control wood.
Wood Composites-The First International Symposium of IWRS 72 Wear of Wood Polymer Composite for J... more Wood Composites-The First International Symposium of IWRS 72 Wear of Wood Polymer Composite for Journal Bearing Materials Sinin Hamdan1, Mohd. Abdul Mun'aim Mohd Idrus, Md Rezaur Rahman, Nurul Faziha Ibrahim and Md Saiful Islam Faculty of Engineering, University ...
The generation of the impact sound by the act of the human walk involves two factors, the charact... more The generation of the impact sound by the act of the human walk involves two factors, the character of the footfall and the shape of the induced floor vibration. High levels of vibrations can occur in floor systems due to excitation from human activities such as walking and aerobics. In building floors, excessive vibrations are generally not a safety concern for building floor system but a cause of annoyance and discomfort. The footfall noise is created by the impact excitation where the character of the footfall depends on the foot-ware: the heels and the frequencies of the footfall. The shape of the floor deflection depends rather on the geometrical walking pattern and construction of the floor structure. Two types of floors are used for this experiment (1) Profiled Steel Sheet Concrete Floor (PCF) and Composite Concrete Floor (CCF). Since the excitation is assumed to be deterministic, differences between the excitation masses, acting forces and damping are determine from Bruel & Kjaer vibration analyzer machine. The goal of this investigation is to determine the differences of the floor nature by human effect depending on various positions on floors.
The dielectric properties, such as dielectric constant, dissipation factor and dielectric loss fa... more The dielectric properties, such as dielectric constant, dissipation factor and dielectric loss factor of jute/bamboo natural fibers reinforced with polypropylene and unsaturated polyester hybrid composites were studied with different fiber loadings, fiber ratios, frequencies and chemical modifications of natural fibers. The dielectric constant, dissipation factor and loss factor increased with an increase in the fiber content for the entire range of frequencies than the pure polypropylene and pure unsaturated polyester materials. This increase was high at low frequencies, low at medium frequencies, and very low at high frequencies. Dielectric constant values were observed to decrease in frequency due to the decreased interfacial and orientation polarization at higher frequencies. Whereas, dielectric constant increased with an increase in the fiber loading, due to the increase in the number of polar groups, after the addition of hydrophilic lignocellulose fibers. Sodium hydroxide treatment was carried out on jute and bamboo fibers to improve the adhesion between fibers and matrix. The dielectric constant was lower for composites consisting of fibers subjected to alkaline treatment due to the increased hydrophobicity of fibers. When the weight percentage of jute fiber was increased in the total fiber content of the hybrid composites, the dielectric constant, dissipation factor and loss factor were found to increase. It is evident that types of polymer have little influence on the dielectric properties of the hybrid composites
This research work is concerned with the development of unsaturated polyester composites reinforc... more This research work is concerned with the development of unsaturated polyester composites reinforced with betelnut fibers. Moreover, the fibers were chemically modified by sodium hydroxide and its effects on the fiber/matrix interaction were also evaluated. Raw and chemically modified fibers have been used in different proportions for the preparation of these composites. The optimization of fiber proportions has been done in term of their tensile strength. The sodium hydroxide treatment effect of fibers was verified by FTIR analysis and the fibers morphological aspects of fibers by SEM. Likewise, the sound absorption coefficient of composites were studied using impedance tube method. The thermal analyses of composites were made using Thermogravimetric analysis. Compared with untreated fiber composites, there was an improvement in the tensile strength of the treated fiber composites. SEM micrographs of betelnut fiber surface revealed the rough and perforated surface of fibers. Whereas, the cross sectional of the betelnut fibers showed the bigger lumen structures. The sound absorption coefficients of composites increased as the frequency increased and thicker composites appeared to perform better than those of thinner ones. The thermal stability of the treated fiber composites was found to be higher than that of untreated fiber composites.
In this study, both untreated rice straw stem fibers and fibers treated with sodium hydroxide wer... more In this study, both untreated rice straw stem fibers and fibers treated with sodium hydroxide were used. Maleic anhydride polypropylene (MAPP) was used to enhance adhesion of the fiber with the matrix. Composites were prepared with various combinations of fiber, ranging from 10 wt.% to 25 wt.%, and polypropylene in addition to 2 wt.% MAPP. These composites were then tested for acoustical, mechanical, thermal, infrared spectral, and morphological properties. The fibers were treated by being soaked in 5 wt.% NaOH solution at 30 °C for 30 min. The composites with treated fiber exhibited higher thermal stability, tensile strength, sound absorption, and fiber-matrix adhesion than the composites with untreated fiber. The results of sound absorption measurements showed that the composites with higher fiber content had better sound absorption than the composites with lower fiber content. The changes in the peaks in the Fourier transform infrared spectrum indicate that the alkaline treatment removed hemicellulose and lignin from the rice straw stem fibers.
The aim of the present study was to determine the influence of doping rare earth ion on strontium... more The aim of the present study was to determine the influence of doping rare earth ion on strontium calcium aluminate (CaO-SrO-SiO 2 -Al 2 O 3 ). Therefore, the authors have manufactured luminescent material consisting of 40CaO-5SrO-5SiO 2 -50Al 2 O 3 doped with Dy 3z . The compositions have been selected on the basis of chemical stability. Five pellets were prepared with different calcination temperatures and times, namely 400 and 600uC for 1 and 2 h, in order to shed light on their luminescence behaviour. X-ray diffraction, energy dispersive X-ray analysis and scanning electron microscopy elaborate and characterise the formation of small particle of photoluminescent material in the phosphor matrix host material.
This paper reports on the luminescence properties of Dy 3+ -doped 30SrO-30MgO-40P 2 O 5 , which h... more This paper reports on the luminescence properties of Dy 3+ -doped 30SrO-30MgO-40P 2 O 5 , which had been prepared by solid state reaction. The crystalline phases were identified using X-ray diffraction (XRD) and their luminescence properties were studied using excitation and emission spectra obtained from photoluminescence spectroscopy. The results of XRD patterns indicate that the prepared sample contain crystalline phase of MgP 2 O 6 and SrMgP 2 O 7 . The excitation spectrum of 30SrO-30MgO-40P 2 O 5 :Dy 3+ consists of broad bands' centre at ∼280, 310 and 400-600 nm associated with defects and vacancies of host material. The other feature of sharp peaks is very similar and belongs to Dy 3+ ions. The f-f transitions in the range of 417-475 nm correspond to the transitions from 6 H 15/2 to 4 K 17/2 + 4 M 19/2,21/2 + 4 I 13/2 + 4 F 7/2 , 4 G 11/2 , 4 I 15/2 and 4 F 9/2, in the range of 392 nm to 6 P 3/2 + 6 P 5/2 , and in the range of 312-370 nm to 4 K 15/2 , 6 P 7/2 + 4 M 15/2 and 4 I 11/2 , respectively. The peaks at 482, 465, and 455 nm could be assigned to the transition of 4 F 9/2 → 6 H 15/2 , 4 I 15/2 → 6 H 15/2 and 4 G 11/2 → 6 H 15/2 of Dy 3+ , respectively. Dy 3+ has emissions due to the atomic energy levels of itself and emissions due to the acceptor levels of defect sites formed by Dy 3+ .
Acoustic properties such as specific dynamic Young’s modulus (E′/γ), internal friction (Q −1) and... more Acoustic properties such as specific dynamic Young’s modulus (E′/γ), internal friction (Q −1) and acoustic conversion efficiency (ACE) of wood are important properties frequently examined by researchers. Vibration technique is one of the non-destructive evaluation techniques used as an alternative method for measuring the acoustic properties of wood. The objectives of this study are to determine acoustic properties of selected low density tropical wood species namely Endospermum Diadenum, Cratoxylum Arborecens, Dyera Polyphylla, Macaranga Gigantea, Commersonia Bartramia and Alstonia Pneumatophora and their suitability for making violin and guitar (acoustic instruments). The acoustic properties were determined by using free-free flexural vibration method. The results show that there are significant and good relationship between log Q −1/(E′/γ) and log E′/γ with negative gradient for each and overall wood species studied. The P-value of regression equation is less than 0.01 whereas the coefficient of determination (r 2) is in the range of 0.565 to 0.894. The mean value of E′/γ, Q −1 and ACE of wood species studied are in the range of 1.69×1010 Pa to 2.73×1010 Pa, 0.017 to 0.035 and 1.50×107 to 3.56×107 respectively. Based on the mean value of E′/γ, Endospermum Diadenum, Cratoxylum Arborescens, Macaranga Gigantea and Dyera Polyphylla are preferred for making all component of violin and guitar except for the top plate of violin. Commersonia Bartramia is preferred for making the back plate of violin and guitar, whereas Alstonia Pneumatophora is only preferred for making the back plate of violin.
. N-acylethanolamines NAEs have attracted the attention of researchers in the last two decades du... more . N-acylethanolamines NAEs have attracted the attention of researchers in the last two decades due to their occurrence in biological membranes under conditions of stress as well as under normal conditions. Differential scanning calorimetric studies have been carried out on dry and hydrated samples of a homologous series of N-acylethanolamines containing Ž . saturated acyl chains of even number of carbon atoms n s 8-20 . In both cases a major sharp endothermic transition was observed which occurs at the melting point for the dry NAEs whereas for the hydrated samples it occurs at considerably lower temperatures. The enthalpies and entropies corresponding to this transition could be fitted, in each case, to a straight line suggesting that the transition enthalpy and transition entropy consist of a fixed component from the polar head group Ž . and the terminal methyl group, whereas the contribution of the methylene groups, CH , is linearly proportional to the 2q 2q w x Ca -Mg -ATPase activity 4 and inhibition of 0005-2736r97r$17.00 q 1997 Elsevier Science B.V. All rights reserved.
. N-acylethanolamines NAEs have attracted the attention of researchers in the last two decades du... more . N-acylethanolamines NAEs have attracted the attention of researchers in the last two decades due to their occurrence in biological membranes under conditions of stress as well as under normal conditions. Differential scanning calorimetric studies have been carried out on dry and hydrated samples of a homologous series of N-acylethanolamines containing Ž . saturated acyl chains of even number of carbon atoms n s 8-20 . In both cases a major sharp endothermic transition was observed which occurs at the melting point for the dry NAEs whereas for the hydrated samples it occurs at considerably lower temperatures. The enthalpies and entropies corresponding to this transition could be fitted, in each case, to a straight line suggesting that the transition enthalpy and transition entropy consist of a fixed component from the polar head group Ž . and the terminal methyl group, whereas the contribution of the methylene groups, CH , is linearly proportional to the 2q 2q w x Ca -Mg -ATPase activity 4 and inhibition of 0005-2736r97r$17.00 q 1997 Elsevier Science B.V. All rights reserved.
The pressing need to recruit and retain students from diverse background on engineering courses h... more The pressing need to recruit and retain students from diverse background on engineering courses has created a big challenge for academics to deal with a wide range of students' mathematical abilities. At the same time, the role that mathematics plays in professional practice has changed radically in the last 30 years. Today, "computational mathematics" is perceived as a tremendous opportunity , pushing forward the boundaries of engineering design. Within this, mathematics as explicit work by individual engineers has evolved into mathematics as a distributed activity across design teams and the computers which support them (1)(2). In this study, an assessment of students' mathematical abilities was carried out at three vocational institutions; one in the UK (University of Wales Institute, Cardiff - UWIC) and two in Malaysia (Universiti Malaysia Sarawak-UNIMAS and Universiti Teknologi Mara-UiTM Sarawak Campus). The assessment was based on "Mathematics Diagnostic Test" which was given to students at Year 1 and Year 2 of Engineering courses in the three institutions.
Sago starch (SS) was melt-blended with polypropylene (PP) with the concentration of SS in the ble... more Sago starch (SS) was melt-blended with polypropylene (PP) with the concentration of SS in the blends varied between 10% and 50% by weight. Characterization of the PP/SS blends was carried out to gain some information on the miscibility between PP and SS and to gain insight into how well these materials behave thermodynamically with regard to the variation of the storage modulus (E′) and the loss tangent (tanδ) with temperature. The E′ and tanδ remained unchanged for SS between 10% to 33% but increased as SS reached 50%. The blend containing 50%SS was superior compared to the other blends in the dynamic mechanical thermal analysis (DMTA). Through the use of a Differential Scanning Calorimeter (DSC), the melting endotherm of the miscible blends was found to increase constantly with the increasing SS content. The tensile properties of the blends decreased with SS content. Examination of the blends with a Scanning Electron Microscope (SEM) showed that the SS granules were well dispersed in the PP matrix.
In this study, wood polymer composites (WPCs) based on five kinds of selected tropical wood speci... more In this study, wood polymer composites (WPCs) based on five kinds of selected tropical wood species, namely Jelutong (Dyera costulata), Terbulan (Endospermum diadenum), Batai (Paraserianthes moluccana), Rubber (Hevea brasiliensis), and Pulai (Alstonia pneumatophora), were impregnated with methyl methacrylate (MMA) and hexamethylene diisocyanate (HMDIC) monomers mixture in the ratio of 1:1 for composite manufacturing. All these tropical wood reacted with hexamethylene diisocyanate and crosslinked with MMA which enhanced the hydrophobic (restrained water) nature of wood. The vacuum-pressure method was used to impregnate the samples with monomer mixture. The monomer mixture loading achievable was found to be dependent on the properties of wood species. Low loading was observed for the high density wood species. Mechanical strength of fabricated wood polymer composites (WPCs) in term of modulus of elasticity (MOE) and modulus of rupture (MOR) were found to be significantly improved. The wood-polymer interaction was confirmed by Fourier transform infrared (FTIR) spectroscopy. Morphological properties of raw wood and WPC samples were evaluated by scanning electron microscopy (SEM) and XRD analysis and an improvement in morphological properties was also observed for WPC.
... 0.66 (0.12)* *Values in parenthesis represent standard deviation of mean value. {Values in pa... more ... 0.66 (0.12)* *Values in parenthesis represent standard deviation of mean value. {Values in parenthesis represent MOE from previous researchers. Hamdan et al. Young's modulus and glass transition temperature of selected tropical wood species ...
Agricultural waste biomass has already been transferred to bioethanol and used as energy related ... more Agricultural waste biomass has already been transferred to bioethanol and used as energy related products, although many issues such as efficiency and productivity still to be overcome. In this study, the protein engineering was applied to generate enzymes with completely reversed coenzyme specificity and developed recombinant yeasts containing those engineered enzymes for construction of an efficient biomass-ethanol conversion system. Recombinant yeasts were constructed with the genes encoding a wild type xylose reductase (XR) and the protein engineered xylitol dehydrogenase (XDH) (with NADP) of Pichia stipitis. These recombinant yeasts were characterized based on the enzyme activity and fermentation ability of xylose to ethanol. The protein engineered enzymes were expressed significantly in Saccharomyces cerevisiae as judged by the enzyme activity in vitro. Ethanol fermentation was measured in batch culture under anaerobic conditions. The significant enhancement was found in Y-ARS strain, in which NADP + -dependent XDH was expressed; 85% decrease of unfavorable xylitol excretion with 26% increased ethanol production, when compared with the reference strain expressing the wild-type XDH.
Journal of Reinforced Plastics and Composites/SAGE Publications, Dec 2, 2015
This study is focused on the development of sound absorbing materials based on natural fiber poly... more This study is focused on the development of sound absorbing materials based on natural fiber polymer composites. The natural fibers were modified through the alkaline treatment and the natural fiber polymer composites were fabricated using hot and cold compression hydraulic press machine. The sound absorption coefficients of the composites were measured using two-microphone transfer function impedance tube method. Characterizations of the natural fiber polymer composites were analyzed using scanning electron microscope and Fourier transform infrared spectroscopy. It was found that in all measured composites, the sound absorption coefficients increased as the frequency increased. Also, as the fiber loading increased, the sound absorption coefficients of the natural fiber polymer composites were increased. It was found that the alkaline treated fiber reinforced composites increased the sound absorption coefficients due to removal of impurities and change in the structure of composites. The alkaline treatment of fibers showed better adhesion interface between fiber and polymer as compared to untreated fibers. This can be seen clearly under morphological and spectral studies of the natural fiber polymer composites.
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