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PublicationThe role of sodium surface species on oxygen charge transfer in the Pt/YSZ system( 2012-08-01)
;Danai Poulidi ;Maria Elena Rivas ;Iain D. BaikieIan S. MetcalfeThe role of sodium surface species in the modification of a platinum (Pt) catalyst film supported on 8 mol% yttria-stabilised-zirconia (YSZ) was investigated under a flow of 20 kPa oxygen at 400°C. Cyclic and linear sweep voltammetry were used to investigate the kinetics of the oxygen charge transfer reaction. The Pt/YSZ systems of both 'clean' and variable-coverage sodium-modified catalyst surfaces were also characterised using SEM, XPS and work function measurements using the Kelvin probe technique. Samples with sodium coverage from 0.5 to 100% were used. It was found that sodium addition modifies the binding energy of oxygen onto the catalyst surface. Cyclic voltammetry experiments showed that higher overpotentials were required for oxygen reduction with increasing sodium coverage. In addition, sodium was found to modify oxygen storage and/or adsorption and diffusion increasing current densities at higher cathodic overpotential. Ex situ XPS measurements showed the presence of sodium hydroxide, carbonate and/or oxide species on the catalyst surface, while the Kelvin probe technique showed a decrease of approximately 250 meV in the work function of samples with more than 50% sodium coverage (compared to a nominally 'clean' sample). -
PublicationAn investigation of the processability of natural fibre reinforced polymer composites on shallow and flat thin-walled parts by injection moulding process( 2013)
;S.M. Sapuan ;S. Sulaiman ;E.S. ZainudinK. AbdanCurrently, many industries are trending towards producing products exhibit such properties as small thickness, lightweight, small dimensions, and environmental friendliness. In this project, flat or shallow thin-walled parts were designed to compare the advantages and disadvantages of lignocellulosic polymer composites (PP + 50 wt% wood) in terms of processability. This study focused on the filling, in-cavity residual stresses and warpage parameters associated with both types of thin-walled moulded parts. Thin-walled parts 0.7 mm in thickness were suitably moulded using lignocellulosic composite materials to determine the effects of filling. The analysis showed, the shallow thin-walled part is preferable in moulding lignocellulosic polymer composite material due to the low residual stress and warpage measured. The results also indicate that the shallow thin-walled part is structurally rigid, such that it can be used in applications involving small shell parts, and can be processed more economically using less material than the flat thin-walled part. -
PublicationAnalysis of accent-sensitive words in multi-resolution mel-frequency cepstral coefficients for classification of accents in Malaysian English( 2013-06)
;M.A. Yusnita ;M.P. Paulraj ;R. YusufThis paper investigates the most accent-sensitive words for Malaysian English (MalE) speakers in multi-resolution 13 Mel-frequency cepstral coefficients. A text-independent accent system was implemented using different numbers of Mel-filters to determine the optimal settings for this database. Then, text-dependent accent systems were developed to rank the most accent-sensitive words for MalE speakers according to the classification rates. Prior work has also been conducted to test the significance of the wordlist for both gender and accent factors, and to investigate any interaction between these two factors. Experimental results show that male speakers have a higher intensity of accent effects compared with female speakers by 3.91% on text-independent and 3.47% on text-dependent tasks. Another finding has proven that by selecting appropriate words that carry severe accent markers could improve the task of speaker accent classification. An improvement of at most 8.45% and 8.91% was achieved on the male and female datasets, respectively, following vocabulary selection. -
PublicationShrinkages and warpage in the processability of wood-filled polypropylene composite thin-walled parts formed by injection molding( 2013-07-01)
;S.M. Sapuan ;S. Sulaiman ;E.S. ZainudinA. KhalinaReducing volumetric shrinkages and warpage during the injection molding process is a challenging problem in the production of molded thin-walled parts. In this study, the injection molding of shallow, thinwalled parts (thickness 0.7 mm), composed of lignocellulosic polymer composites (polypropylene (PP) + 50 wt% wood), was simulated. The volumetric shrinkages and warpage in the thin-walled parts were evaluated under different process conditions, with varying post-filling parameters, such as mold temperature, cooling time, packing pressure and packing time. The analysis showed that the cooling time and packing time had less of an effect on the shrinkage and warpage; nevertheless the optimal levels for both parameters are required in the molding process for the thin-walled part to achieve the best results. The volumetric shrinkage was lower near the gate than at the end-of-fill location along the flow path. The results also showed that the volumetric shrinkage correlates with the warpage measured on the molded part. The optimum parameters ranges is 40–45 C for the mold temperature; 20–30 s for cooling time; 0.85 from injection pressure (Pinject) for packing pressure; and 15–20 s for the packing time to achieve the best results with the least amount of volumetric shrinkage and warpage.8 9 -
PublicationOptimization of blending parameters and fiber size of Kenaf-bast-fiber-reinforced the thermoplastic polyurethane composites by Taguchi Method( 2013-12-16)
;Y. A. El-Shekeil ;S. M. Sapuan ;M. D. AzamanM. Jawaid“Kenaf-fibers- (KF-)” reinforced “thermoplastic polyurethane (TPU)” composites were prepared by the melt-blending method followed by compression molding. Composite specimens were cut from the sheets that were prepared by compression molding. The criteria of optimization were testing the specimens by tensile test and comparing the ultimate tensile strength. The aim of this study is to optimize processing parameters (e.g., processing temperature, time, and speed) and fiber size using the Taguchi approach. These four parameters were investigated in three levels each. The L9 orthogonal array was used based on the number of parameters and levels that has been selected. Furthermore, analysis of variance (ANOVA) was used to determine the significance of different parameters. The results showed that the optimum values were 180°C, 50 rpm, 13 min, and 125–300 micron for processing temperature, processing speed, processing time, and fiber size, respectively. Using ANOVA, processing temperature showed the highest significance value followed by fiber size. Processing time and speed did not show any significance on the optimization of TPU/KF. -
PublicationMechanical characterization and water absorption behaviour of interwoven Kenaf/PET fibre reinforced epoxy hybrid composite( 2015)
;Yakubu Dan-mallamThe development of interwoven fabric for composite production is a novel approach that can be adopted to address the challenges of balanced mechanical properties and water absorption behaviour of polymer composites. In this paper, kenaf and PET (polyethylene terephthalate) fibre were selected as reinforcing materials to develop the woven fabric, and low viscosity epoxy resin was chosen as the matrix. Vacuum infusion process was adopted to produce the hybrid composite due to its superior advantages over hand lay-up technique. The weight percentage composition of the Epoxy/kenaf/PET hybrid composite was maintained at 70/15/15 and 60/20/20, respectively. A significant increase in tensile strength and elastic modulus of approximately 73% and 53% was recorded in relation to neat epoxy. Similarly, a substantial increase in flexural, impact, and interlaminar properties was also realized in relation to neat epoxy. This enhancement in mechanical properties may be attributed to the interlocking structure of the interwoven fabric, individual properties of kenaf and PET fibres, strong interfacial bonding, and resistance of the fibres to impact loading. The water absorption of the composites was studied by prolonged exposure in distilled water, and the moisture absorption pattern was found to follow Fickian behaviour.2 5 -
PublicationExperimental and theoretical study of the electronic structure and optical spectral features of PbIn6Te10( 2016)
;A. H. Reshak ;Oleg. V. Parasyuk ;I. V. Kityk ;Zeyad A. Alahmed ;Nasser S. AlZayed ;Sushil Auluck ;Anatolii O. FedorchukJ. ChyskýLaying of InTe4 tetrahedra in the structure of the compound PbIn6Te104 6 -
PublicationInfluence of material properties on the fluid-structure interaction aspects during molded underfill process( 2017)
;C.Y. Khor ;M.U. Rosli ;M.S Zakaria ;A.F.M. Yamin ;M.S. Abdul AzizM.Z. AbdullahThis paper presents the investigation of the effects of epoxy moulding compound’ (EMC) viscosity on the FSI aspects during moulded underfill process (MUF). Finite volume (FV) code and finite element (FE) code were connected online through the Mesh-based Parallel Code Coupling Interface (MpCCI) method for fluid and structural analysis. The EMC flow behaviour was modelled by Castro-Macosko model, which was written in C language and incorporated into the FV analysis. Real-time predictions on the flow front, chip deformation and stress concentration were solved by FV- and FE-solver. Increase in EMC viscosity raises the deformation and stress imposed on IC and solder bump, which may induce unintended features on the IC structure. The current simulation is expected to provide the better understandings and clear visualization of FSI in the moulded underfill process. -
PublicationFinite element modelling of thin intermetallic compound layer fractures( 2017)
;Ooi Eang PangA thin intermetallic compound (IMC) of solder ball joint induces strong stress concentration between the pad and solder where a crack propagated near the IMC layer. The fracture mechanism of the IMC layer is complex due to the effect of IMC thickness, crack length, solder thickness and Young’s Modulus. At present, there is still an undefined exact geometrical model correlation for numerical simulations of IMC layer fracture. Thus, this paper aims to determine the accuracy of IMC layer models subjected to crack-to-width length ratio (a/W) in correlation with the ASTM E399-83 Srawley compact specimen model using finite element (FE) analysis. Several FE models with different geometrical configurations have been proposed under 10 MPa tensile loading. In this study, the two dimensional linear elastic displacement extrapolation method (DEM) is formulated to calculate the stress intensity factor (SIF) at the crack tip. The study showed that with an error of 0.58% to 0.59%, a width of 2.1 mm and a height of 1.47 mm can be recommended as the best geometrical model for IMC layer fracture modelling which provides a wider range for a/W from 0.45 to 0.85 instead of from 0.45 to 0.55. This result is significant as it presents a method for determining fracture parameters at thin IMC layers with a combination of singular elements with meshes at different densities which is tailored to the Srawley model. -
PublicationFinite element modelling of thin intermetallic compound layer fractures( 2017)
;Ooi Eang PangMohd Shukry Abd MajidA thin intermetallic compound (IMC) of solder ball joint induces strong stress concentration between the pad and solder where a crack propagated near the IMC layer. The fracture mechanism of the IMC layer is complex due to the effect of IMC thickness, crack length, solder thickness and Young’s Modulus. At present, there is still an undefined exact geometrical model correlation for numerical simulations of IMC layer fracture. Thus, this paper aims to determine the accuracy of IMC layer models subjected to crack-to-width length ratio (a/W) in correlation with the ASTM E399-83 Srawley compact specimen model using finite element (FE) analysis. Several FE models with different geometrical configurations have been proposed under 10 MPa tensile loading. In this study, the two dimensional linear elastic displacement extrapolation method (DEM) is formulated to calculate the stress intensity factor (SIF) at the crack tip. The study showed that with an error of 0.58% to 0.59%, a width of 2.1 mm and a height of 1.47 mm can be recommended as the best geometrical model for IMC layer fracture modelling which provides a wider range for a/W from 0.45 to 0.85 instead of from 0.45 to 0.55. This result is significant as it presents a method for determining fracture parameters at thin IMC layers with a combination of singular elements with meshes at different densities which is tailored to the Srawley model. -
PublicationParametric optimization of the processing of all-cellulose composite laminae( 2017)
;M. Mat Salleh ;K. Magniez ;S. Pang ;J. W. DormannsM. P. StaigerSingle-polymer composites based on cellulose I and/or II (aka all-cellulose composites) are emerging as a class of high-performance bio-based composite materials with mechanical properties suited to structural applications. There are various synthesis routes for the preparation of all-cellulose composites. However, little has been reported on the optimization of the processing variables affecting the properties of all-cellulose composites. In the present work, a range of all-cellulose composites were produced as single laminae via solvent infusion processing using a precursor of cellulose II fibers that were assembled as a woven 2D textile. The effects of dissolution time, dissolution temperature, and compaction pressure during hot pressing on the properties of the laminae were then systematically examined using a Taguchi design of experiment approach in order to identify the critical control factors. The tensile properties, fiber volume fraction, and crystallinity of the laminae were determined. Statistical analysis of variance and the signal-to-noise ratio were used to rank the importance of key control factors. -
PublicationProperties and behavior of geopolymer concrete subjected to explosive air blast loading: a review( 2017)
;Andrei Victor SanduRafiza Abdul RazakThe severe damage to civilian buildings, public area, jet aircraft impact and defense target under explosive blast loading can cause a huge property loss. Most of researcher discusses the topics on design the concrete material model to sustain againts the explosive detonation. The implementation of modern reinforcement steels and fibres in ordinary Portland cement (OPC) concrete matrix can reduce the extreme loading effects. However, most researchers have proved that geopolymer concrete (GPC) has better mechanical properties towards high performance concrete, compared to OPC. GPC has the high early compressive strength and high ability to resist the thermal energy from explosive detonation. In addition, OPC production is less environmental friendly than geopolymer cement. Geopolymer used can lead to environmental protection besides being improved in mechanical properties. Thus, this paper highlighted on an experimental, numerical and the analytical studies cause of the explosive detonation impact to concrete structures.8 10 -
PublicationAntioxidant capacity and total phenolic content of fresh, oven-dried and stir-fried tamarind leaves( 2017)
;Mohd Nadzrin Mohammad RadziThe aim of this study was to compare the antioxidant capacity and total phenolic content as well as the chemical groups of fresh, oven-dried and stir-fried tamarind (Tamarindus indica L.) leaves. Methanol was used for extraction of fresh, oven-dried and stir-fried tamarind leaves. The stir-fried leaves were prepared using medium heat for 10 minutes prior to extraction and chemical analysis while dried leaves were obtained by oven drying at 60°C for 3 hours. The stir-fried leaves had significantly highest total phenolic content (TPC) (139.87 mg/g) and percentage DPPH radical-scavenging inhibition (69.92%) while the fresh leaves had the lowest TPC (39.31 mg/g) and antioxidant capacity (16.46%). The FTIR spectral data suggest that the heat treatment increased the amine groups as well as the antioxidant capacity of the tamarind leaves. To increase the antioxidant capacity, the tamarind leaves should be prepared in a stir-frying process.1 10 -
PublicationPreliminary studies on antimicrobial activity of extracts from aloe vera leaf, citrus hystrix leaf, zingiber officinale and Sabah snake grass against bacillus subtilis( 2018)
;M.N.A. Uda ;Nur Hulwani Ibrahim ;Tan Ewe Shen ;Ong Yee Fen ;Maisara A. M. AkhirHerbal plants have several potential antimicrobial activities either as antifungal or antibacterial to fight against the disease and pathogen that attack the plants. The extractions of the Aloe vera leaf, Citrus hystrix leaf, Zingiber officinale rhizome and Sabah snake grass were selected in this study to fight against Bacillus subtilis. B. subtilis is a Gram-positive bacterium, rodshaped and catalase-positive that lives on decayed organic material. It is known as Gram-positive bacteria because of its thick peptidoglycan and would appear purple when subjected to Gram test. This species is commonly found in the upper layers of the soil, in meat or vegetables, in pastry, cooked meat, in bread or poultry products. The extracts of Sabah Snake Grass found to be most effective than A.vera leaf, Z. officinale, and C. hystrix against the B. subtilis.2 10 -
PublicationConceptual design and simulation validation based finite element optimisation for tubercle leading edge composite wing of an unmanned aerial vehicle( 2019)
;Ernnie Illyani Basri ;Faizal Mustapha ;Mohamed Thariq Hameed Sultan ;Adi Azriff Basri ;Mohd Firdaus AbasA finite element model is developed to determine deformation and stresses on a composite wing of unmanned aerial vehicle (UAV) with a tubercle design at the leading edge of the wing. Tubercles, commonly known as protuberances found on the leading edge of a whale pectoral flipper, offering great performance from an aerodynamic perspective. This paper deals with a first order shear deformation theory (FSDT) approach to discover the UAV laminates composite wing model of tubercle leading edge (TLE) with rib-reinforced so that the equivalent stiffness and material properties are obtained from the simulation of finite element analysis using ANSYS. Another structural configuration of design replicating the idea of monocoque concept, whereby foam is used at the leading and trailing edges of the wing. Styrene acrylonitrile (SAN) core foam is used representing high strength-to-weight ratio with its superiority in the mechanical properties of polymeric sandwich composites. The updated static structural analysis from rib-reinforced can be applied to update the wing stiffness distribution of monocoque-foam. The optimum design is concluded from the tabulated deformation and stresses of both wings, where monocoque-foam showed better performance with a reduction in 50.72% of deformation and 35.88% of stress, compared to rib-reinforced design.1 9 -
PublicationEffect of pineapple leaf (PALF), napier, and hemp fibres as filler on the scratch resistance of epoxy composites( 2019)
;E.H.D. GanS. SyahrullailThis article presents the effects of pineapple leaf (PALF), napier, and hemp fibres as filler on the scratch resistance of epoxy composites. In particular, it explores the effect of these natural fillers on the horizontal load, coefficient of friction (COF), penetration depth, fracture toughness, scratch hardness, brittleness index and scratch observation. The mixing method using magnetic stirrer was used to produce the natural fibre-filled epoxy composites with different wt%, namely, 5, 7.5, and 10 wt%. The test was performed using a CSM Revetest Xpress, which consisted of a cone of the half-apex angle of 60° ending with a sphere having a tip radius of 200 μm. The indenter scratch distance and speed were 7 mm and 1.5 mm/min, respectively. The results show that the napier fibre-filled epoxy composites have the highest peak load and COF. It was also noted that the napier fibre-filled epoxy composites have the lowest penetration depth for each wt% of filler. Lastly, the fracture toughness (Kc) for the napier fibre-filled epoxy composites with 10 wt% of filler yielded the highest value of 4.33 MPa.m1/2. It can also be seen that using a scanning electron microscope (SEM), the amount of debris increased with higher of wt% of the natural fibre fillers in the composites. Hence it was demonstrated that the napier fibre-filled epoxy composites have higher scratch resistance compared to the PALF and hemp fibre-filled epoxy composites. Keywords: Surface analysis, Fracture toughness, Scratch resistance, PALF, Napier, Hemp fibres.6 11 -
PublicationGait classification using Mahalanobis–Taguchi system for health monitoring systems following anterior cruciate ligament reconstruction( 2019)
;Noor Azuan Abu OsmanIn this paper, a gait patterns classification system is proposed, which is based on Mahalanobis–Taguchi System (MTS). The classification of gait patterns is necessary in order to ascertain the rehab outcome among anterior cruciate ligament reconstruction (ACLR) patients. (1) Background: One of the most critical discussion about when ACLR patients should return to work (RTW). The objective was to use Mahalanobis distance (MD) to classify between the gait patterns of the control and ACLR groups, while the Taguchi Method (TM) was employed to choose the useful features. Moreover, MD was also utilised to ascertain whether the ACLR group approaching RTW. The combination of these two methods is called as Mahalanobis-Taguchi System (MTS). (2) Methods: This study compared the gait of 15 control subjects to a group of 10 subjects with laboratory. Later, the data were analysed using MTS. The analysis was based on 11 spatiotemporal parameters. (3) Results: The results showed that gait deviations can be identified successfully, while the ACLR can be classified with higher precision by MTS. The MDs of the healthy group ranged from 0.560 to 1.180, while the MDs of the ACLR group ranged from 2.308 to 1509.811. Out of the 11 spatiotemporal parameters analysed, only eight parameters were considered as useful features. (4) Conclusions: These results indicate that MTS can effectively detect the ACLR recovery progress with reduced number of useful features. MTS enabled doctors or physiotherapists to provide a clinical assessment of their patients with more objec4 7 -
PublicationGait analysis and mathematical index-based health management following anterior cruciate ligament reconstruction( 2019)Gait analysis is recognized as a method used in quantifying gait disorders and in clinical evaluations of patients. However, the current guidelines for the evaluation of post anterior cruciate ligament reconstruction (ACLR) patient outcomes are primarily based on qualitative assessments. This study aims to apply gait analyses and mathematical, index-based health management, using the Mahalanobis Taguchi System (MTS) and the Kanri Distance Calculator (KDC) to diagnose the level of the gait abnormality and to identify its contributing factors following ACLR. It is hypothesized that (1) the method is able to discriminate the gait patterns between a healthy group (HG) and patients with ACLR (PG), and (2) several contributing factors may affect ACLR patients’ rehabilitation performance. This study compared the gait of 10 subjects in the PG group with 15 subjects in the HG. The analysis was based on 11 spatiotemporal parameters. Gait data of all subjects were collected in a motion analysis laboratory. The data were then analyzed using MTS and KDC. In this study, two significant groups were recognized: the HG, who achieved results which were within the Mahalanobis space (MS), and (ii) the PG who achieved results above the MS. The results may be seen as being on-target and off-target, respectively. Based on the analysis, three variables (i.e., step width, single support time, and double support time) affected patient performance and resulted in an average mark of above 1.5 Mahalanobis distance (MD). The results indicated that by focusing on the contributing factors that affect the rehabilitation performance of the patients, it is possible to provide individualized and need-based treatment.
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PublicationInvestigation on the flexural properties of nanofillers loading on the Jute/Carbon/PLA nanocomposites( 2020)
;Nur Aqilah Sairy ;Norkhairunnisa Mazlan ;Mohamad Ridzwan IshakPresence of fibers and fillers in a composite can be an efficient way to arrest crack either at macro or micro levels. In this work, woven jute and carbon fibers were arranged alternately in PLA (Polylactic Acid) nanocomposite. Graphene or nanoclay was embedded into PLA matrix to make polymer nanocomposite. Fiber reinforced polymer nanocomposites were prepared by varying the concentration of graphene or nanoclay in the PLA matrix and alternate woven jute/carbon fibers was then bind with the PLA nanocomposite. Influence of graphene or nanoclay concentration and presence of woven fibres in the composite was quantified by flexural analysis. Flexural strength and flexural modulus were found to increase at 3wt% of nanofiller concentration for both graphene/jute/PLA and nanoclay/jute/PLA nanocomposites with increment up to 37% and 31%, respectively. FTIR was used to determine the interaction between PLA and nanofillers. Morphology observation by Scanning Electron Microscopy (SEM) was done to investigate the fractured surface of the hybrid jute/carbon fibres reinforced PLA nanocomposite. -
PublicationRobust interface on ENR-50/TiO2 nanohybrid material based sol-gel technique: Insights into synthesis, characterization and applications in optical( 2020)
;Omar S. DahhamIn this work, the sol–gel technique was used to prepare a new organic–inorganic hybrid from Epoxidized Natural Rubber (ENR-50) and Titanium dioxide (TiO2) by blending different content of titania precursors (10, 30, and 50 wt%) with an ENR-50 matrix. A wide range of analyses was conducted to understand the nature of this hybrid and also to evaluate its potential uses in applications required high refractive index such as micro optical and optoelectronic devices. Results indicated that the ring-opening reaction of epoxide groups in ENR-50 increased with the increase of titania content in the hybrid resulting a strong bonding between titania and ENR-50 through Tisingle bondOsingle bondC bond, which was observed in FTIR spectrum at 1027–1028 cm−1. It is also observed a slight decrease in the intensity of the amorphous peak along with a new crystalline peak appeared at 2θ = 23 and 27° due to the crystalline nature of titania. The hybrids showed three thermal degradation steps in the range of temperature 76 to 769 °C due to the existence of the Ti moieties with the mixture of polymer chains, which in turn shifted the Tg at 24.3, 26.9 and 28.1 °C for the hybrid at 10, 30, and 50 wt% TiO2 compared to the Tg of ENR-50 at −18.4 °C respectively. The morphology of the ENR-50 showed clear changes during of the synthesis of ENR-50/TiO2 hybrids, these changes were proven by SEM, TEM, and AFM analyses. Uv–Vis results showed that the higher wavelength peak at 293 nm has shifted to 296, 298 and 300 nm for the hybrid at 10, 30, and 50 wt% TiO2 respectively due to the strong interaction between titania precursors and ENR-50 matrix. Furthermore, the hybrids showed good optical transparency in the visible light range.5 16