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Tribology, performance and emissions of a two stroke-cycle engine using bio-based lubricant / Muhammad Zulfattah Zakaria
No full textTwo-stroke (2T) gasoline engine is labelled as main contributor to air pollution, especially in the city. Ironically, this engine is still being sold and used and its sales was reported to increase over the years. The reason is that 2T gasoline engine is more powerful than four-stroke engine in term of power-to-weight ratio. Advancements in 2T engines technology also produces better emissions than their four-stroke counterpart. Most 2T engines do not have oil sump for lubricant which makes the maintenance easier, cheaper, and more practical e.g., for marine outboard engine which is heavy and costly to be dismantled and brought onshore for service. Unfortunately, majority of 2T lubricant is made of mineral base oil which contributes to the increase of carbon footprint. Bio-based lubricant is claimed and proven to be more environmentally friendly. Mass production of fats especially vegetable fats e.g., palm oil, canola, sunflower and non-edible oils like jatropha, neem and the like has made the conversion of the over-production to be converted into biodiesel and lubricant. Palm oil is currently the most economically wise to be converted into fuel and lubricant. It contains mainly of palmitic acid (C16:0) and oleic acid (C18:1) as well as some traces of other fatty acids. The existence of beta-hydrogen on C18:1 makes oleic acid more oxidation stable and better lubricity than single-hydrogen bond on C16:0. Thus, oleic acid has been chosen to be esterified with alcohols to turn it into polyol ester. The selected alcohol candidates including two-branched structure Neopenthylglycol (NPG) into Neopenthylglycol Dioleate (NPGDO), three-branched structure Trimethylolpropane (TMP) becoming Trimethylolpropane Trioleate (TMPTO), and four-branched structure Pentaerythritol (PE) into Pentaerythritol Tetraoleate (PETO). All three esters were measured for physicochemical properties to conform their lubricant properties standard. They were then mixed with certain percentages of mineral base oil to inherit naphthenic properties of mineral base oil and is proven to exhibit good miscibility with polyol ester and further increases the lubricant lubricity. The blends were then undergone tribo-tests via Fourball-tribotester (FBT) and High Frequency Reciprocating Rig (HFRR) to measure their lubricity performance and were reported in terms of wear scar diameter (WSD) and coefficient of friction (COF). The samples were also optically scanned via Surface Electron Microscopy (SEM) to characterize the wear profiles and Energy-dispersive X-ray Analyzer (EDX) to check for elemental identification and quantitative compositional information on the contact surface. The tribological performance of esters were then compared with the reference synthetic 2T lubricant. Ultimately, the blend composition was again measured via Response Surface Methodology (RSM) to further optimize the properties of blends. The predicted responses were compared with experimental values and the results were reported and intensively discussed. Engine testing was then performed to check the emissions and carbon deposition on the spark plug as well as the engine performance
Paper based cell culture: Electrospin-coated paper as natural extracellular matrix inspired biopolymer scaffold / Ng Kelvin
No full textPaper has recently found widespread applications in biomedical fields, especially as an alternative scaffolding material for cell culture, owing to its properties such as fibrous nature, porosity, and flexibility. However, paper on its own is not an optimal material for cell culture and modification is necessary for its scaffold application. The present study focuses on modification of filter paper through electrospin-coating and dip-coating with polycaprolactone (PCL), a promising biomaterial in tissue engineering. Morphological analysis, physical properties analysis, evaluation of cell viability, alkaline phosphatase (ALP) activity and live/dead assays were conducted to study the potential of the modified paper-based scaffold. The results were compared to filter paper (FP) and electrospun PCL (ES-PCL) as reference samples. The results indicate that electrospin-coating is a simple and efficient way of modifying FP. It not only improves the morphology of the deposited electrospun layer through reduction of fiber diameter by nearly 75%, but also greatly reduces the scaffold fabrication time compared to ES-PCL. The tensile properties of electrospin-coated filter paper (ES-PCL/FP) are significantly higher than other scaffolds, which indicates the synergistic effect of modifying FP with electrospin-coating method. Furthermore, the electrospin-coating of PCL on FP creates a bimodal scaffold that resembles the hierarchical structure of ECM, which could be beneficial toward improving biocompatibility. In vitro studies were conducted on these scaffolds, by using human fetal osteoblast (hFOB) and human adipose derived stem cells (ADMSC), to study the cellular interaction with these scaffolds in the aspect of proliferation, adhesion, and differentiation. The biochemical assays (Resazurin assay) conducted on hFOB and ADMSC show an up-regulated proliferation rate over the time points, ES-PCL/FP provides significantly higher readings compared to all other groups. The immunofluorescent stain results also show improved cell-distribution and cell-scaffold attachment all over the ES-PCL/FP. Medium sorption and retention capability of the scaffolds, and the effect towards cell proliferation, have also been highlighted in this study
Hydroxycoumarin and azobenzene derivatives polymer coating as potential photoswitchable additives with reversible surface polarity / Shameer Hisham
No full textLong-lasting stickers on various surfaces indicated the successful advancement of adhesive technology. Those stickers when removed often led to residues remaining on walls and surfaces which damaged and caused hideous appearance of surfaces. The main factor to the strong adhesiveness of stickers is the maximum interactions applied between the adhesive and the surface. It is proposed that surfaces with reversible polarity, particularly from the additive component, can cause the surface to gradually reduce the interactions and any stickers can peel off by itself. In this thesis, we described the formulation and the application of poly(methyl methacrylate), PMMA blends containing photoresponsive dyes as smart coatings that were capable of photoreversibly switch surface polarities. The blends contained various hydroxycoumarin dyes (CAD1-9), azobenzene derivatives (AZO1-9) and an azobenzene end-functionalized PMMA additive (P1), which were then applied onto clear glass substrates as coating films. It was shown that CAD1-7 predominantly exist as hydrazone tautomers and exhibited poor photoreversible E-/Z- isomerization performance. Therefore, azobenzene derivatives AZO1-9 were later applied as additives. Static water contact angle measurements conducted on the PMMA/azobenzene coating films indicated that the surface polarity is photoreversible as the azobenzene molecules undergo reversible trans-cis photoisomerization processes. A comparison of the contact angles obtained from PMMA/AZO1 and PMMA/AZO2 coating films revealed that the chromophores have random orientation in the coating matrices. Since the surface polarity can be tuned, as a proof of concept experiment, we showed that the commercial acrylic-based pressure- iv
sensitive stickers which adhered strongly to the PMMA/AZO1(13) coating film were peeled off from the coating surface after subjected to a cycle of UV light irradiation for 12 hours, followed by in the dark for another 12 hours within 14 days. This possibly indicated that the repeated changes in surface polarity disrupted the adhesive/coating interactions. In order to increase the adhesion ability of PMMA coating films onto glass substrates, an adhesion promoter, poly(methyl vinyl ether-alt-maleic acid monoethyl ester) (PMVEMA-ES) was blended into the coating formulations. The results have clearly indicated that PMVEMA-ES did enhance the adhesion of coating films onto glass substrates at the expense of significantly lowered proportion of cis-AZO1 molecules during trans→cis photoisomerization processes. The restricted isomerization of azobenzene chromophores in PMMA/PMVEMA-ES matrix is due to intermolecular N=N‧‧‧H-OOC hydrogen bonding interactions between PMVEMA-ES and azobenzene chromophores. The crystallization of AZO2 in PMMA matrix at a concentration beyond 5 wt. % prompted us to synthesize P1 to overcome the miscibility issues of AZO2 chromophores in PMMA. It was discovered that thermal annealing of PMMA/P1(5) coating film above the glass transition temperature, Tg allowed the segregation of P1 macromolecules to the surface, resulting in enhanced changes in surface polarity. In addition, the annealed PMMA/P1(5) coating film has shown better performance in the sticker peel-off test compared to that of the unannealed coating film. These fundamental discoveries would lead to more development of smart coatings based on simple PMMA/azobenzene blends, where they can be used as a prospective solution to retard problems associated with commercial stickers
Chemical profiling and antibacterial screening of crude extracts of soft coral Lobophytum sp. from Straits of Malacca / Tan Yee Yein
No full textMarine natural products have gained popularity in the pharmaceutical field over the years as the ocean is vast and is extraordinarily rich in species diversity, making it the ideal target for exploration. Marine naturals products, isolated from marine sponges, algae and soft corals have been reported to exhibits biological activities such as anti-inflammatory, antitumor, and antimicrobial. In recent years, the emergence of antibiotic resistant bacteria has posed a large threat to healthcare worldwide and new antibacterial compounds are in demand. This study focuses on Lobophytum sp. harvested from The Straits of Malacca, to isolate secondary metabolites and test for antibacterial properties against gram-positive (Staphylococcus aureus and Bacillus subtilis) and gram-negative bacteria (Escherichia coli and Salmonella typhi) using crude extracts. Cholesterol has been isolated and FAME analysis showed the major fatty acid constituents of the sample is palmitic and arachidonic acid, 29.905% and 18.891% respectively. Crude extracts and fractions obtained from column chromatography shows weak inhibition against B. subtilis
Optimizing the performance of P3HT-based photodetector by tuning the composition of OXCBA / Syaza Nafisah Hisamuddin
No full textOrganic photodetectors (OPDs) have shown high responsivity and detectivity limits with fast response speed that are matched with commercially available inorganic photodetectors. The feasibility to tune the spectral response of the organic material and flexibility to use on curve substrate also give the advantage of using organic materials in the fabrication of OPDs. Nevertheless, there are still many challenges that need to be addressed to achieve a greater performance of an OPD device. In this work, the performance of organic-based photodetectors using poly(3-hexylthiophene) (P3HT) and o-xylenyl-C60-bisadduct (OXCBA) as the donor and acceptor material, respectively, is reported aiming to improve the performance of P3HT-based OPD device. Four different ratios of 1:0.25, 1:0.50, 1:1.00 and 1:1.50 of P3HT:OXCBA binary blended thin films are prepared using spin-coating technique and used as photoactive layers. The elemental composition and electronic properties of the materials are characterized using X-ray Photon Spectroscopy (XPS) and Ultraviolet Photon Spectroscopy (UPS). The optical properties of the thin films are characterized using Ultraviolet-visible (UV-vis) spectroscopy and the electrical performance for all ratios are characterized using currentvoltage (I-V) measurement. Further, two blend ratios that show the best and the worst performance are characterized using Photoluminescence (PL) Spectroscopy, Atomic Force Microscopy, Raman Spectroscopy. It was found that the combination of P3HT and OXCBA demonstrates a wide spectral range of light absorption which covers the valley that has low light absorption, with the ratio of 1:0.50 demonstrates the best performance. The OPD devices with ratio 1:0.25 to 1:1.50 shows high photocurrent density (Jph) from 8.09 mA/cm2 to 25.27 mA/cm2. Optimizing the ratio of photoactive layers dramatically enhances the performance of OPDs, with the rise and decay time of 445 and 309 ms,
respectively, recorded from 1:0.50 ratio. The optimized device has achieved high responsivity of 252.69 mA/W and specific detectivity of 1.85x1010 Jones at -1 V, and has shown good stability for over 336 hours. Aside from that, external quantum efficiency (EQE) of 52.77% and low surface roughness of 0.596 nm are obtained from the 1:0.50 P3HT: OXCBA device. These results imply a high potential of P3HT:OXCBA blend in the application of a photodetector
Emission of volatile halocarbons from selected species of tropical seaweeds / Fiona Keng Seh Lin
No full textMarine emissions of short-lived biogenic halocarbons affect atmospheric composition and chemistry. Research has shown that seaweeds emit these halocarbons into the seawater and air. The presence of these gasses could affect local weather while contributing to the global halocarbon load, possibly causing stratospheric ozone loss. This is especially evident in the tropics due to the existence of vertical transport that could affect the global circulation of these compounds in the atmosphere. There is a lack of information on the contribution of tropical seaweeds to the global halocarbon budget. This is of concern especially under a changing climate. This study was formulated to investigate the response of tropical seaweeds to variable environmental conditions, in terms of halocarbon emissions. In addition, seaweeds cultivated using three different systems were studied. Laboratory studies were conducted for investigating the effect of temperature (20–40 °C) on the halocarbon emission by Gracilaria manilaensis, Ulva reticulata, Kappaphycus alvarezii and Turbinaria conoides and the combined effect of temperature (25–34 °C) and irradiance (0–177 μmol photons m-2 s-1) on the halocarbon emission by K. alvarezii. Higher temperature results in decreased emissions of CHBr3, CH2Br2 and CH2I2 (r = (−0.69)–(−0.95); p< 0.01) in most seaweeds. The combined effect of irradiance and temperature significantly affect the emission of halocarbons by K. alvarezii, with stronger association to temperature. Of the three cultivation systems, the amount of halocarbon released by G. manilaensis especially CH2Br2 was found to be the highest in the cage culture in the river mouth, followed by the offshore platform and tank culture. Daylight emissions by G. manilaensis from both onshore and offshore cultivation systems was 10 to 52 times greater than in the dark, while emissions by K. alvarezii were between two and five times greater during the day. Halocarbon emissions by G. manilaensis was positively affected by temperature, irradiance and seawater phosphate
level during cultivation. Negative correlations were found between ammoniacal nitrogen, nitrate and nitrite levels with the CH2Br2 emitted by K. alvarezii. Estimation from this study showed that the harvesting activity of K. alvarezii in year 2017 in Malaysia could release 72–360 mol Br hr-1; a value that is slightly higher than the estimated value derived from previously predicted flux rate estimated from wild Malaysian seaweeds. Under laboratory-controlled conditions, K. alvarezii releases higher amount of halocarbon. However, in situ studies revealed that G. manilaensis emits higher amount of halocarbon due to the fluctuations in the environment. In light of the impending climate change with a likely rise in temperature, seaweed farming has the potential to be expanded to the subtropical waters which could bring about increased emissions of halocarbons. In summary, halocarbons including the highly emitted CHBr3 and CH2Br2 was found to be emitted by the selected wild and farmed tropical seaweeds. Although the emissions were species-dependent, the emission of these compounds were found to be closely associated to changes in environmental parameters such as temperature, irradiance, and seawater nutrients
The relationship between facebook usage and self-disclosure among army personnel / Adnan Ajis
No full textThe popularity of Facebook has attracted billions of users, including members of the Armed Forces, to utilise this social media. This phenomenon has increased the sharing of personal information online, potentially exploiting various parties for their benefits. This study aims to identify the factors that influence users to disclose personal information on Facebook. Therefore, two research questions were developed to examine the issues of Facebook self-disclosure among army personnel. Firstly, what is the level of Facebook self-disclosure among Army personnel? Secondly, what are the factors that affect Facebook self-disclosure among Army personnel? Accordingly, this study emphasised users' gratification as motives that influence individuals to disclose and share social media information. This study applied a quantitative approach to identify the affecting of Facebook self-disclosure factors among Malaysian Army users. A total of 1513 Malaysian Army Facebook users were involved in this study. The research model was developed through a previous literature review. Consequently, the quantitative data analysis utilised the Structural Equation Modelling - Partial Least Squares Technique (SmartPLS 3.0) to test the validity and relationships between the variables hypothesised in the research model. The PLS structural model results had provided statistical evidence supporting the relationship between Facebook motives and self-disclosure. The study found that information sharing, social interaction, entertainment and self-expression were positively significant to self-disclosure. This research provided several contributions and offered valuable insights on the Facebook self-disclosure among the Malaysian Army. In practical contribution, it gave a better understanding of human behaviour on Facebook usage to overcome the information security issues caused by self-disclosure activities. Whereas in the theoretical sense, it impacted the body of knowledge in several areas, as such Facebook self-disclosure model, uses and gratifications theory, research methodology, quantitative methods and measurement model. Furthermore, the methodological and practical implications were also discussed, and several potential avenues for future research had been identified and proposed accordingly. In summary, this research provided a more comprehensive global picture of Facebook self-disclosure that led to information security issues
Attitudes, motivation and achievement of Malaysian secondary school students towards learning English / David Owen Rock
No full textSuccess in second language learning (SLL) is of considerable importance in today’s highly interconnected world. However, the reasons behind success in SLL are still poorly understood. One promising line of research (Gardner 1985) proposes that differences in achievement result from differences in individual variables such as integrativeness, attitudes to the learning situation, motivation and language anxiety. However, despite its significance, this theoretical perspective has been much criticized in the literature, with the result that its status is currently uncertain. The objective of this research was therefore to test Gardner’s socio-educational model in the modern Malaysian context to evaluate its current utility. Structural equation modeling was used to investigate correlations between the stated variables among 278 upper secondary students in Malaysian National High Schools in the Klang Valley. Significant relationships were found between the model constructs investigated. It was concluded that despite the criticisms it has been subject to, the socio-educational model continues to offer a viable and useful perspective for investigations into the causes of success in SLL. The limitations of the research include the use of purposive rather than probabilistic sampling, the cross-sectional rather than longitudinal design of the research, and the fact that quantitative research, of its nature, is unable to offer deep insights into the reasons behind the findings. The significance of the research is first, that it suggests that researchers need not avoid the use of the socio-educational model where appropriate attention is paid to theoretical issues, measurement methods and analysis; and second, that there appears to be a place for the inclusion of cultural instruction modules in compulsory second language courses in high schools
Facies analysis and seismic geomorphology of a fluvial-tidal depositional system from the miocene Malay Basin / Nurul Adilah Manshor
No full textVarious hierarchical classification schemes for channel architectural elements have been developed based on studies of modern and ancient alluvial and paralic systems. The datasets used by different schemes are varied and include seismic, well logs, core and/or outcrops. Most studies used outcrop datasets, which provide better views of higher resolution lateral and vertical relationships of bounding scour surfaces. However, recognizing these features in 3D seismic data and well data at depths ≥ 1.5 km in the subsurface is very challenging. This research presents an integrated facies analysis and seismic geomorphology study of a fluvio-tidal depositional system from the Lower to Middle Miocene (within Group I and H) of the Malay Basin. The targeted interval is >1000 m below sea bottom. An integrated dataset from a selected area in the central region of the Malay Basin was used for this study, which includes a high-quality 3D seismic cube (1563km2), 83.15 m of conventional core, and 3 well logs penetrating Group I and H. Facies analysis indicates that Group I and H strata in the study area are dominated by a mixture of fluvial and tidal facies. Identified facies associations represent paralic depositional elements such as prodelta mudstone, outer estuarine/abandoned channel deposits, and within a channel, tide-influenced barforms. The presence of a marine ichnofauna with varying degrees of diversity and bioturbation intensity is indicative of restricted marginal marine environments. Application of RMS (Root Means Square) attribute analysis and frequency decomposition in the seismic geomorphological analysis has enabled the imaging of a variety of architectural elements at different geometries, scales, and dimensions. Architectural elements of 120 channels are catalogued and evaluated. Three classes of channels are identified within the dataset, based on spatial and temporal channel geomorphology and other seismic signatures. Class-1 channel systems are the widest and characterised by high seismic amplitude, low to moderate sinuosity and are interpreted as bypass channels or estuaries. Class-2 channel systems are of high seismic amplitude, have low to moderate sinuosity, and are interpreted as fluvial/distributary channels. Class-3 channel systems contain the smallest channels with high sinuosity and are interpreted as tidal creeks and tidal channel networks. These channels show unique morphometric characteristics indicative of tidal influence, such as flaring mouths, cuspate meanders, high sinuosities, through-flow and dendritic networks. Quantitative morphometric elements have been compared to existing published datasets and modern-day tide-dominated channel systems. The characteristics of the widest channels in this study are not consistent with an incised valley interpretation and are most likely channel belts or amalgamated channel belts. The evolution of the depositional system and wide variation in channel geomorphologies is interpreted in relation to Miocene regressive-transgressive cycles and downstream autocyclic controls. A quantitative morphometric database for the Group I and H channels in the Malay Basin is presented in this project
Octane number prediction for gasoline blends using convolution neural network / Zhu Yue
No full textWith the development of information technology, the development of neural network plays an important role in the prediction of various situations in real life. At present, there are many prediction algorithms based on machine learning. According to the "80/20 rule" for building machine learning model, 80% of the time is spent of finding, cleaning, and organizing data, while the remaining 20% for training of the machine learning model. Machine performance learning models depend to a large extant to the data quality used train the model. Therefore, data preprocessing is widely considered to be one of the most critical stage in the whole process. In the project three commonly use algorithm are used for prediction of octane number for gasoline blends, which describes the behavior of the fuel in the engine at lower temperatures and speeds, and is an attemp to simulate acceleration behavior.These tree algorithm are back propagation (BP), radial basis funtion (RBF) and Extreme learning machine (ELM) algorithm. Simulation study on performance of these algorithm have been carried out with the available database. Simulation result show that RBF algorithm gives the best performance