http://dspace.fsktm.um.edu.my/handle/1812/483 Search the Channel search http://dspace.fsktm.um.edu.my/simple-search http://dspace.fsktm.um.edu.my/handle/1812/607 Title: Rigid and flexible polyurethane foams production from palm oil-based Polyol <br/> <br/>Authors: Lee, Choy Sin <br/> <br/>Abstract: Polyurethane foams are amongst the most important class of specialty polymers. It can be divided into three major classes, namely rigid, semi-rigid and flexible polyurethane foams. According to M.L. Kerman (2005), the global polyurethane market in 2004 showed that flexible polyurethane foams contributed 47% of the market share, followed by 26% of rigid foams, and 27% of other applications in coatings, adhesives, sealants and elastomers (CASE), binders, foundry and machinery. Rigid polyurethane foams are particularly useful in the construction industries as they are used as components such as polymeric concretes, insulating materials and sealants. In addition, flexible polyurethane foams are as cushion in the furniture, bedding and automotive industries. Conventionally, polyol is mainly derived from petrochemicals. They play an important role in the polyurethane industry. However, in view of the environmental and sustainability issues, the use of vegetable oil-derived polyol can serve as a substitute in the polyurethane industry. Malaysia is one of the major producers of palm oils. Therefore, the utilization of palm oils in the synthesis of polyols for both rigid and flexible polyurethane foams was initiated in this study. In this study, epoxidized diethanolamides was produced as a new type of polyol by reacting diethanolamine (DEA) with various ratio of Epoxidized Palm Olein (EPOo) to Refined Bleached Deodorized Palm Kernel Olein (RBDPKOo). The products were further reacted with diisocyanate and catalyzed by AlCl3-THF to produce rigid polyurethane. Concurrent with the production of rigid polyurethane, two minor important side-products oxazolidones and isocyanurates were produced to give significantly a better quality of rigid polyurethane. This is due to epoxidized diethanolamides with higher oxirane oxygen contents (OOC) that produced rigid polyurethane foams of higher compression strength (338.8 kPa), close cell contents (97.95%) and lower thermal conductivity (0.0288 w/m.K). In this work, only epoxides in diethanolamide polyol was reacted with isocyanate that resulted in the formation of hard segments oxazolidone and isocyanurate in the rigid polyurethane and this improved the compression strength and close cell contents of the foam. In addition, higher OOC in diethanolamides also gave better dimensional stability to the rigid foam that was conditioned at 70 °C and -25 °C. Apart from mechanical improvements, epoxides that were retained in diethanolamide structure also improved the thermal stability of the rigid foam. Thermogravimetric Analysis (TGA) was recorded with higher decomposition temperature for foam produced with higher OOC diethanolamides. Formation of oxazolidones in the urethane backbones and isocyanurates exhibited good-heat resistance that significantly enhanced the thermal stability of the foams. Index 1.40 was determined to be the most suitable isocyanate index when the polyurethane foam were altered by isocyanate index from 0.90 to 1.10. It produced non-brittle rigid foam with the lowest thermal conductivity (0.0288 w/m.K) and the highest close cell contents (97.95%) while maintaining moderate compression strength (338.8 KPa). One type of polyester polyol is synthesized by ring opening of synthetic epoxidized resins with dicarboxylic acids. Conventionally, the epoxides that used in the preparation of polyester polyol were ethylene oxide, propylene oxide, phenylglycidyl ether (PGE), diglycidyl ether of bisphenol A (DGEBA) and 3-phenoxy-1,2-epoxypropane. The versatile polyols were used mainly as fat-based non-ionic detergent, surface active agent, thermoplastic, paper coating resin and material for radiation shielding materials, curable printing ink and as coating. Therefore, in the second part of this study polyester polyol was prepared by using EPOo as the starting material instead of the synthetic epoxy resin. The polyester polyol was synthesized by reacting EPOo with different carbon chain length of aliphatic dicarboxylic acids ranging from C6 to C12. This produced a new type of polyol. The new polyol was mixed thoroughly with 50% of commercial polyol and they were reacted with toluene diisocyanate (TDI) to produce flexible polyurethane foam. The flexibility of the polyurethane foam was due mainly to the high average molecular weight and hydroxyl functional groups that were attached to the carbon chain of the polyols. Longer carbon chain in dicarboxylic acid was found to be more reactive than the shorter chain, which resulted in lower OOC (0.42%) of polyol mixture with bigger average molecular weight (Mw= 10526 g/mol). However, it also produced polyester polyol with higher hydroxyl value (103.6 mg KOH/g sample), viscosity (9755.21 cP at 25 °C, 4222.41 cP at 40°C), cloud point (20.04 °C) and pour point (12.00 °C) when compared to shorter carbon chain of dicarboxylic acid. Longer carbon chain of dicarboxylic acid used to produce polyester polyol resulted in the improvement of the foam properties such as hysteresis (22.76%), elongation at break (181.1 %) and thermal stability. The temperature of the decomposition peak (Tdec) of polyurethane as shown in DSC analysis and the decomposition temperatures of 10%, 50% and 90% of foam weight loss in TG analysis were increased. But, polyol synthesized from shorter carbon chain of dicarboxylic acid produced foam with better tensile stress and tear resistant ability. Isocyanate index 1.00 was selected as the optimal index as it produced flexible foam with the lowest hysteresis (23.64%), highest tensile stress (138.0%) and the best tear resistant ability (0.2382 N/mm). Flexible foam produced from higher isocyanate index was determined to be more stable thermally. However, alteration of isocyanate index did not produce foam with significant changes in terms of cellular structure, but the open cell contents of the foams prepared with different isocyanate index and polyester polyol were in a satisfactory range of 95-97%. Based on physical evaluation, 2 g of water content was the most suitable amount to be used in the production of flexible foams in comparison to 3 g and 4 g of water contents. This was mainly because 2 g of water content produced foam with the lowest hysteresis, highest elongation at break and better tear resistance ability. Nevertheless, increment of water content increased the foams’ open cell contents from 95% to 98% due to the emission of carbon dioxide generated from the reaction of isocyanate with water to form hard segment urea. Therefore, foam with higher content of urea that produced by higher water content as blowing agent were determined to be more stable thermally. Optical microscope also recorded open cells in various pentagon sizes that produced cells of bigger sizes in higher water content produced foam whereas lower water content produced foams with smaller cells in size and also more uniform in structure. ABSTRAK Busa poliuretana merupakan salah satu jenis polimer yang penting dan boleh turut dibahagikan kepada tiga kelas utama, iaitu, busa keras, semi-keras dan fleksibel. Menurut kepada M.L. Kerman (2005), pasaran poliuretana dunia pada 2004 menunjukkan bahawa poliuretane fleksibel menyumbang 47%, diikuti oleh 26% busa keras dan 27% aplikasi lain. Busa keras sangat berguna dalam industri pembinaan iaitu sebagai bahan konkrit, penebat haba dan sebagainya. Di samping, poliuretana fleksibel iaitu kusyen digunakan dalam industri perabot. Kebanyakan poliol yang memainkan peranan utama dalam industri poliuretana adalah dihasilkan dari bahan kimia petrol. Memandangkan isu pemuliharaan dan persekitaran yang mustahak, penggunaan poliol yang berasaskan minyak sayur amat dipentingkan. Malaysia merupakan salah sebuah negara penghasilan minyak kelapa sawit yang utama, oleh demikian, kerja penyelidik ini menggunakan minyak kelapa sawit untuk mensintesiskan dua jenis poliol yang boleh digunakan dalam pembuatan busa keras dan busa fleksibel. Poliol dietanolamida dengan kumpulan epoksi telah dihasilkan sebagai sejenis poliol baru di mana dietanolamina ditindakbalaskan dengan pelbagai nisbah Epoxidized Palm Olein (EPOo) dan Refined Bleached Deodorized Palm Kernel Olein (RBDPKOo). Poliol ini kemudiannya ditindakbalaskan dengan diisosianat dan dengan kehadiran katalis AlCl3-THF untuk menghasilkan poliuretana keras. Dua jenis hasil sampingan, iaitu “oxazolidone” dan isosianurat telah dihasilkan dan telah memperbaiki mutu busa keras. Ini adalah kerana dietanolamida yang mempunyai kumpulan epoksi telah menghasilkan poliuretana keras yang lebih bermutu dari segi mekanik dan kestabilan haba. Busa tersebut adalah stabil apabila disimpan pada suhu 70 °C dan -25 °C. Analisa termagravimetrik (TGA) menunjukkan bahawa suhu penguraiaan busa adalah lebih tinggi apabila dietanolamida yang mengandungi epoksi yang lebih tinggi digunakan dalam tindakbalas penghasilan busa. Indeks isosianat 1.40 telah dipilih sebagai indeks optima disebabkan penghasilan busa yang tidak rapuh serta berkekonduksian haba(0.0288 w/m.K) yang lebih rendah, berkekuatan ketegangan (338.8 kPa) dan berkandungan sel tertutup (97.95%) yang tertinggi. Poliester poliol juga disintesiskan dengan pembukaan kumpulan epoksi dari EPOo dengan asid dikarboksilik yang berantai C6 ke C12. Poliester poliol ini dicampur separuh dengan poliol polieter komersial dan seterusnya ditindakbalaskan dengan toluena diisosianat dalam penyediaan busa fleksibel. Asid dikarboksilik yang berantai lebih panjang didapati adalah lebih reaktif dengan menghasilkan poliol yang bernilai hidroksi yang lebih tinggi (103.6 mg KOH/g sample). Busa yang dihasilkan juga mempunyai nilai “hysteresis” yang lebih rendah, nilai pemanjangan sehingga putus yang lebih tinggi serta kestabilan haba yang lebih baik. Suhu penguraian yang dikaji dengan analisa TGA dan “Differential Scanning Calorimeter” (DSC) bagi busa yang dihasilkan oleh poliester poliol berantai panjang didapati adalah lebih tinggi. Akan tetapi, busa yang dihasilkan oleh poliol berantai pendek mempunyai nilai kekuatan ketegangan dan ketahanan dikoyak yang lebih tinggi. Indeks isosianat 1.00 dan kandungan air 2 g yang digunakan sebagai agen peniup dalam formula penghasilan busa fleksibel telah dipilih sebagai indeks dan kandungan air yang optima. Mikroskop optik menunjukkan sel-sel terbuka dalam busa adalah berbentuk pentagon dan mempunyai saiz-saiz yang tidak seragam bergantung kepada kandungan air yang digunakan semasa penghasilan busa. <br/> <br/>Description: Thesis (PhD) -- Faculty of Science, University of Malaya, 2008. http://dspace.fsktm.um.edu.my/handle/1812/600 Title: The population biology of straits Rhododendron (Melastoma malabathricum L.) <br/> <br/>Authors: Faravani, Mahdi <br/> <br/>Abstract: Straits Rhododenron (Melastoma malabathricum L. )(Melastomataceae) is a weedy invasive and medicinal shrub in arable lands, abandoned farmlands, secondary forest openings and derelict areas in Malaysia. Experiments were conducted to determine the effects of chemical media, light and temperature regimes on seed germination and clonal growth of M. malabathricum. Branching pattern, inter-plant spacing, selfthinning, allelopathy and antioxidant activity of M. malabathricum were also investigated in this study. Seeds of M. malabathricum were collected from the campus of the University of Malaya, Kuala Lumpur (3o 8’ N; 101o 42’ E), Malaysia. Moderate germination percentages ranging from 37% to 40% were recorded at 25-30 oC for oven-dried seeds. Seed germination was positively photoblastic. No seed germination prevailed in darkness, or when exposed to chemical media, and at temperature regimes < 20 oC. Light regime strongly influenced clonal growth of M. malabathricum. Mathematical models were developed for M. malabathricum describing branching networks, directionality and dispersion of branches with respect to the mother plant as influenced by density. The aim of this study was to determine if uniform branch patterns existed or changed in relation to density or plant height. Circular statistics were applied to test whether a plant with close neighbours responded either by investing in branch growth away from the competitive pressure or simply into zones free of neighbours. Rayleigh’s uniformity tests showed that the horizontal rotation angle φ was uniformly distributed and, but the distributions of the vertical rotation angle Ө was uni-modal form. The Ө angles were distributed in plants at different densities registering respective mean direction of 52.3°, 47.8° and 41.8° from the lowest to the highest density, respectively. The effect of inter-plant spacing on the growth of individual plants in an increased space and with equal sample size (number of plants) for each spacing gradient was investigated under varying plant spacing (2, 3, 7, 13, 25, 50 and 98 plants/m-2). The experimental design consisted of plants positioned in a polar coordinate grid with seven arcs, eighteen rays and an angle of 20o. The distance between arcs increased exponentially from 6 cm to 43 cm. Rays were separated by an angle of 20o. Straits Rhododenron showed very high survival percentages even when planted in high densities for a period of 200-odd days after planting. Widely-spaced plants were significantly taller than the more closely spaced plants of the same cohort. Mean stem diameter, plant biomass, number of leaves and branches, and branch length increased with increase in plant (wider) spacing. The results support the concept of competition in the self-thinning rule. Intra-specific competition had a profound effect on the number of individuals in a population, as illustrated by the log of average leaf weight per plant plotted against the log of density of survivors for a plant population. The leaf population's trajectory was held under a line of slope -1.12 (R2 = 0.58, p<0.05). The antioxidant activities of crude extracts of M. malabathricum in the laboratory were also been assessed. The effects of methanol extracts of both root and shoot were investigated for their radical scavenging activity using DPPH assay. The methanol extracts were able to reduce the stable free-radical DPPH to the yellow – colored diphenylpicrylhydrazine with an IC50 of 141.88μg/ml and 154.48μg/ml for leaf and root methanol extracts, respectively, but these were measurably lower than ascorbic acid at 28.61 μg/ml. In the study of allelopathy, aqueous extracts were assayed from fresh materials with concentrations of 0, 50, 100, 150 and 200gL-1. The parallel concentrations of aqueous extracts of oven-dried materials used were 40, 80, 120, 160, and 200 gL-1. Inhibition of seed germination of radish prevailed at concentrations above 200gL-1 of the aqueous extract of dried materials, while with methanol extract similar inhibitions were observed at concentrations ranged of 14.28 - 30 gL-1. Total inhibition of root and shoot growths was also observed in barnyardgrass. Both species were susceptible to allelochemical extracts isolated from shoot and root of M. malabathricum. Root and shoot lengths of radish and barnyardgrass decreased with the application of the extracts. The results were discussed from the viewpoint of using the extracts as a natural herbicide to control barnyardgrass and other susceptible weed species by arresting seed germination, seedling growth and establishment. The results of studies embodied in this thesis may provide insights on the processes involved in the population regulation of M. malabathricum. Arguably, these processes precisely are involved leading to colonization and consequential establishment of open spaces by invasive plant species. <br/> <br/>Description: Thesis (PhD) -- Faculty of Science, University of Malaya, 2008. http://dspace.fsktm.um.edu.my/handle/1812/599 Title: PECVD hydrogenated amorphous carbon films: Growth and characterization <br/> <br/>Authors: Rozidawati Awang <br/> <br/>Abstract: This research offers critical insights on the growth and characterization of hydrogenated amorphous carbon (a-C:H) thin films by plasma enhanced chemical vapour deposition (PECVD). The initial phase of this work involved designing and building the reaction chamber for the PECVD system intended for the preparation of a-C:H thin films. The second phase is focused on ensuring that the PECVD system is capable of producing good quality and reproducible a-C:H films. The effects of RF discharge power on the optical and chemical bonding properties of the films are investigated. These results are used to explain the deposition kinetics of the films and to check for consistencies with published results. The third phase was focused on studying the effects of deposition time and film thickness on the optical and chemical bonding properties of the films prepared at high and low RF powers. The study on the influence of hydrogen (H2) and helium (He) dilution of methane (CH4) on the optical and chemical bonding properties of the films deposited by direct current (DC) PECVD is the focus of the fourth phase of this work. The final phase investigates the effects of deposition time and film thickness on the optical and chemical bonding properties of the films deposited by DC PECVD using H2 or He diluted CH4. These films are deposited using high and low H2/He to CH4 flow-rate ratios. Optical transmission spectroscopy, Fourier transform infrared (FTIR)spectroscopy and micro-Raman scattering spectroscopy are used to study the optical and chemical bonding properties of the films. The results of this work demonstrated that increase in RF discharge power increased the deposition rate and the sp2 fraction in the films but significantly reduced the optical band gap, Eg, H content and sp2 cluster size. These results were consistent with published results and the variation of the properties of the films with RF power was consistent with the deposition kinetics of the a-C:H films. This confirmed that the home-built PECVD system designed and built for this work was capable of producing good quality and reproducible a-C:H films. Eg and sp2 cluster size were found to be dependent on deposition time and film thickness. These parameters decreased with increase in film thickness. An increase in deposition time resulted with an increase in sp2 fraction and disorder in the film structure. The sp2 C content increased and H content in the films decreased with increase in diluent gas (H or He) to CH4 flow-rate ratio. Long deposition time retarded the growth rate of a-C:H films due to etching effects in films deposited from both H2 and He diluted methane. Increase in deposition time increased the sp2 C content in the film structure which consistently led to a decrease in Eg. In H2 diluted methane films, long deposition times allowed longer exposure to the H etching effect resulting in the creation of small sp2 clusters which reduced bond angle distortion and increased the distribution of cluster sizes. In helium diluted methane films, longer exposure to hydrocarbon ion bombardment has comparatively very small effects on the size and structural disorder in the films. ABSTRAK Penyelidikan ini mendalami kaedah pemendapan dan pencirian filem nipis amorfus karbon berhidrogen (a-C:H) daripada teknik pemendapan wap kimia secara peningkatan plasma (PWKPP). Fasa pertama penyelidikan ini adalah merekabentuk ruang tindakbalas dan membina sistem PWKPP untuk menghasilkan sampel-sampel filem a-C:H. Fasa kedua memfokus kepada penentuan keupayaan sistem PWKPP berfungsi untuk menghasilkan filem a-C:H berkualiti tinggi serta keboleh-ulangan penyediaan sampel. Kesan kuasa frekuensi radio (FR) kepada sifat optik dan ikatan kimia filem dikaji. Hasilnya digunakan untuk menerangkan kinetik pemendapan filem dan menyemak kesetaraan hasil yang diperolehi oleh penyelidik-penyelidik lain. Fasa ketiga memfokus kepada kesan masa pemendapan dan ketebalan filem terhadap sifat optik dan ikatan kimia filem yang dihasilkan pada keadaan FR kuasa tinggi dan rendah. Kajian ke atas kesan gas metana (CH4) yang dicampurkan dengan gas hydrogen (H2) atau gas helium (He) kepada sifat optik dan ikatan kimia filem yang dimendapkan daripada PWKPP arus terus (AT) merupakan fokus kajian fasa keempat. Fasa terakhir mengkaji kesan masa pemendapan dan ketebalan filem terhadap sifat optik dan ikatan kimia filem yang dihasilkan oleh PWKPP AT menggunakan gas metana yang dicampurkan dengan gas hidrogen atau gas helium. Filem-filem ini dimendap menggunakan nisbah kadar-aliran H2/ He kepada CH4 pada keadaan nisbah tinggi dan rendah. Spektroskopi pemancar optik (UV-Nir-Vis), spektroskopi Transformasi Fourier Inframerah (FTIR) dan spektroskopi-mikro Raman digunakan untuk pencirian sifat optik dan ikatan kimia filem. Hasil penyelidikan ini menunjukkan peningkatan kuasa FR meningkatkan kadar pemendapan dan kandungan sp2 di dalam filem tetapi menurunkan nilai Eg,kandungan H dan saiz kluster sp2. Hasil ini setara dengan hasil yang telah diterbitkan dan variasi sifat filem dengan kuasa FR adalah setara dengan kinetik pemendapan filem a-C:H. Maka, dapat disahkan bahawa sistem PWKPP yang dibina ini berfungsi dengan baik, menghasilkan filem a-C:H berkualiti tinggi dan penyediaannya bolehulang. Nilai Eg dan saiz kluster sp2 di dapati bergantung kepada masa pemendapan dan ketebalan filem. Parameter ini berkurang apabila ketebalan filem bertambah. Peningkatan masa pemendapan meningkatkan kandungan sp2 dan ketidaktertiban struktur filem. Kandungan sp2 bertambah dan kandungan H berkurang bila nisbah kadar-aliran gas campuran (H2 atau He) terhadap gas CH4 ditingkatkan. Peningkatan masa pemendapan merencatkan kadar pemendapan filem a-C:H disebabkan kesan pemunaran di dalam filem yang dimendapkan daripada kedua-dua keadaan H2 atau. He dicampurkan dengan gas CH4. Peningkatan masa pemendapan meningkatan kandungan sp2 di dalam struktur filem yang menyebabkan penurunan nilai Eg. Bagi filem daripada CH4 yang dicampurkan dengan H2, pemanjangan masa pemendapan membenarkan lebih pendedahan kepada proses pemunaran yang menyebabkan penghasilan kluster sp2 bersaiz kecil yang mengurangkan herotan sudut ikatan dan meningkatkan taburan saiz kluster. Bagi filem daripada CH4 yang dicampurkan dengan He, pemanjangan masa pendedahan kepada proses pemunaran oleh ion hidrokarbon berkelajuan tinggi di dapati hanya memberi kesan yang kecil terhadap saiz kluster dan ketidaktertiban struktur filem. <br/> <br/>Description: Thesis (PhD) -- Faculty of Science, University of Malaya, 2008. http://dspace.fsktm.um.edu.my/handle/1812/592 Title: Electrophoretic studies of surface charge on unicellular bacteria <br/> <br/>Authors: Lee, Poh Foong <br/> <br/>Abstract: Electrophoretic studies of surface charge on unicellular cell were carried out. The unicellular bacteria selected for this research consisted of two different strains, which are gram-positive S.aureus and gram-negative E.coli. Colloidal particles, (Titanium dioxide) TiO2, and liposome, were used as non-living counterparts for comparison. The studies have focused on the effects of different physical and chemical conditions, including variations of temperatures, applied field, and time intervals between measurements. We did calculations of the Donnan potential and also investigated the polarizability of the bacteria. Methodology used in this research was laser Doppler velocimetry electrophoresis. Surface charge of bacteria cells is measured with electrophoresis due to development of net charge at the particle surface affects the distribution of ions in the surrounding interfacial region. This process increases concentration of counterions (ions of opposite charge to that of the particle) close to the surface. Zeta potential is considered to be the electric potential of this inner area including this conceptual "sliding surface". The electrophoretic mobility ( μ ) is the migration rate of the charged particles to the electrode when electric field is applied. In various pH, dead cells of both E.coli and S.aureus exhibited lower electrophoretic mobility than live cells. This was mainly due to dead cell had lost the metabolic activity to give charge balance to surface charges. Besides, it was found that increase in the ionic strengths of NH4Cl in the buffer reduced the electrophoretic mobility of samples. In contrary, increased ionic strengths of NaCl obtained the opposite result for the bacteria. This might be due to the increase of influx Na+ into cells, which increases the anionic lipid to balance the charges in the cells. Results indicated that both approaches fitted well at greater ionic strength of NaCl with the Donnan potential approximation. The electrophoretic mobility of live E.coli displayed a mild increase at higher temperatures. On the other hand, results indicated only a slight increase in negative electrophoretic mobility of live S.aureus as the temperature increased. Increase in applied field increased the electrophoretic mobility of bacteria and colloidal particles due to the stronger attraction field. Different time intervals between measurements with unchanged conditions showed that higher zeta potential was measured for time intervals more than 10s between measurements. This indicated that the particles still swirled around when the next measurements started. In addition, live bacteria recorded greater polarizability compare to colloidal particles. This may be attributed to the semipermeable cell membrane of live cells which hasten the ions exchange between the cell interior and the external environment. A greater polarization of E.coli was obtained, which possessed thinner cell wall peptidoglycan layer compared to S.aureus. The conductivity and permittivity of cells increased as the frequency increased. However, the permittivity of cells were shown constant at higher frequency (>200Hz). <br/> <br/>Description: Thesis (PhD) -- Faculty of Science, University of Malaya, 2009. http://dspace.fsktm.um.edu.my/handle/1812/583 Title: L1–Garch models: Parameter estimations, performance measures and its applications <br/> <br/>Authors: Shamsul Rijal Muhammad Sabri <br/> <br/>Abstract: Since the failure of the high frequency data appears in many researches, economists have explored some alternative methods to overcome heteroscedastic modeling. One such model that has been introduced recently is robust L1–GARCH family. These tools have been introduced initially due to the statistical properties and their performance in parameter estimates. In this thesis, we further explore the performance of the L1–GARCH particularly, in estimating conditional variances. The estimation is enhanced by first employing an exploratory data analysis before proceeding with L1–GARCH. To better understand the behavior of the estimates as well as the performance of these methods, simulation studies were carried out. The results obtained suggest that, ordinary GARCH(1,1) performs well in estimating conditional variances in the absence of outliers or contaminants in the data. However, L1–GARCH(1,1) outperform the GARCH(1,1) in estimating the conditional variances in the presence of outliers. Another problem that persists with heteroscedastic modeling is that of the goodness-of-fit test. In GARCH models, the most common adequacy test used is the classical Jarque-Bera(JB) test. This test however, is known to be extremely sensitive to outliers and hence a single outlier may lead to failure of normality assumption. To overcome this, we introduce robust JB (RJB) measures that are (i) less sensitive to the presence of outliers and (ii) able to detect the departure from the usual normal distribution (symmetric heavy tailed). In assessing the performance of and , the test statistics are compared, in the presence of outliers and symmetric heavy tailed alternatives; here we conduct simulation studies to calculate the power of rejecting the null hypothesis of the test (the data is normal distributed). Our simulations demonstrate that the are able to yield (i) good result to overcome the presence of outliers of the data and (ii) as efficient as other robust statistics that were introduced by others previously when the existence of assumption other than normal distribution. We also apply robust L1–ARCH model to compute the uncertainty of inflation of ASEAN– 5 countries. For completion, we examine the relationship between uncertainty of inflation and their economic growth using robust regression models. We find overwhelming statistical evidence supporting the hypothesis that increased inflation uncertainty lead to slow down in economic growth. This positive association between inflation uncertainty and growth is consistent with earlier studies, conducted for the major industrialized countries. This finding is in line with Friedman’s hypothesis that suggests uncertainty concerning regime changes depresses real economic activity. Throughout this thesis, the SPLUS programming language is used to run (a) simulation tests towards RJB tests; (b) estimating parameters of L1–GARCH model; (c) comparison of efficiency of conditional variance between ordinary GARCH(1,1) and L1–GARCH(1,1) and (d) estimating parameters of L1–ARCH model for inflation uncertainty amongst ASEAN-5 countries. <br/> <br/>Description: Thesis (PhD) -- Faculty of Science, University of Malaya, 2008. http://dspace.fsktm.um.edu.my/handle/1812/579 Title: Technology entrepreneurship development in Malaysia: a case study of the national automotive industry <br/> <br/>Authors: Abdullah, Syahida <br/> <br/>Abstract: This study focuses on firm-level technology entrepreneurship capability. Technology entrepreneurship is the merging of technology knowledge and ability with entrepreneurship skill and competency. It includes four interrelated and complementary factors: context, firm, technology, and entrepreneur; the merging of these factors is essential to create competitive advantage. To assess firms’ technology entrepreneurship capability level, an improvised innovation capability audit tool as introduced by Bessant et al. (2000) and promoted by the World Bank was used. This tool was modified following technology entrepreneurship definition. The improvised tool enables the firms to be analyzed according to eight key dimensions of technology entrepreneurship identified from the four technology entrepreneurship factors: awareness and search from the context factor; strategy and core competency from the firm factor; technology paradigm and linkages from the technology factor; and learning and leadership from the entrepreneur factor. A summation score obtained from all the dimensions is then used to determine the technology entrepreneurship capability level of the firms and simultaneously categorize the firms as ‘Passive’, ‘Reactive’, ‘Proactive’, or ‘Innovative’. The findings suggest that the majority of the national automotive vendor firms recorded high awareness of environmental changes, and poor ability in developing strategies. Other apparent weaknesses are the key dimensions of firm and technology. The results from the eight key dimensions reveal that the national automotive parts and components industry is in the ‘Proactive’ category, which reflects that the majority of firms have an adequate knowledge-base, good leadership quality, and the capability to search for opportunities and identify threats; however they lack the capability to apply the knowledge to create competitive advantage and sustain competitiveness. Thus, an interesting pattern emerged from the results obtained: vendor firms showcased a higher level of technology awareness compared to the level of technology preparedness. The firms recognized environmental changes, and are able to search for opportunities and identify threats; however, they do not have the capability to complement their strength with implementation, which is essential to achieving competitive advantage. <br/> <br/>Description: Thesis (PhD) -- Faculty of Science, University of Malaya, 2008. http://dspace.fsktm.um.edu.my/handle/1812/567 Title: Performance characteristics of carbon based electrical double layer capacitors with PVA and PVA-Cellulose hybrid electrolytes <br/> <br/>Authors: Mohd Azman Hashim @ Ismail <br/> <br/>Abstract: The main focus of this work is to develop a high conducting solid polymer electrolyte (SPE). Poly(vinyl Alcohol), PVA was used as a host and H3PO4 as the ionic dopant. The highest electrically conducting sample in the PVA-H3PO4 (nonhybrid) electrolyte system has composition PVA + 50 wt% H3PO4 (P50H50). The room temperature electrical conductivity is 9.70 x 10-6 S cm-1. A higher electrical conductivity can be achieved by introducing a Whatman® filter paper which acts as a support to the PVA electrolyte and because of its porous nature allows more H3PO4 acid to be loaded into the system. In the PVA-H3PO4 which is considered as the non-hybrid system, the maximum amount of acid that can be loaded is 50 wt%. For the hybrid system, i.e. PVA-filter paper-H3PO4 70 wt% acid can be loaded into the system. The mechanical strength of the system has improved and the highest electrically conducting sample in the PVA-H3PO4-filter paper system has been designated P30H70-C with conductivity 1.04 x 10-4 S cm-1. Three EDLCs were fabricated using the two polymer electrolyte systems. Using PVAH3PO4 (non-hybrid) electrolyte system with the highest conductivity at room temperature sandwiched between two activated carbon electrodes (BP20) a specific capacitance of 4.89 Fg-1 and the internal resistance of 4.13 Ω cm-2 has been obtained. The second EDLC used the same electrodes but different polymer electrolyte system. Cellulose hybrid electrolyte system was introduced to replace PVA-H3PO4 (non-hybrid) electrolyte system. Cellulose hybrid electrolyte is used because the conductivity is higher than PVA-H3PO4 (non-hybrid system). Chargedischarge characteristics showed the specific capacitance increased to 7.73 Fg-1 and internal resistance reduced to 2 Ω cm-2. The third EDLC used the same cellulose hybrid electrolyte and activated carbon electrodes soaked in H3PO4. Charge-discharge characteristics showed the specific capacitance increased to 31.47 Fg-1 and internal resistance reduced to 1 Ω cm-2. The increase in specific capacitance is contributed by the diffusive layer to the entire electrodes. The double layers formed capacitors which are overall connected in a parallel arrangement such that the total capacitance adds up and contribute to a higher capacity. For a working voltage for this EDLC is 1 V and the efficiency is between 80 to 97 %. <br/> <br/>Description: Thesis (PhD) -- Faculty of Science, University of Malaya, 2008. http://dspace.fsktm.um.edu.my/handle/1812/562 Title: The effect of the regionalization of the national innovation support system on regional knowledge base building process: Malaysian case studies <br/> <br/>Authors: Abdul Fatah Amir <br/> <br/>Abstract: The applicability of the national innovation support system (NISS) in terms of supporting regional knowledge base building is questioned in this thesis by grounding the analysis on two Malaysia’s regions: Sabah (a less-developed region) and Penang (a more-developed region). The aims of this study are two-fold; first to explore the appropriateness of the NISS to the needs of the selected regions’ knowledge bases. Second, to explore the factors affecting the regional knowledge base building effort. The study therefore aims to seek answers to this question: Why and how does the regionalised national innovation support system (RNISS) impact regional industrial knowledge base building process? From the literature review a conceptual framework was proposed and three research issues were then developed to guide the research: Research Issue 1: How does support, in terms of functions and resources for innovation of the RNISS, impact on building the regional industrial knowledge base? Research Issue 2: How does RNISS synergy, in terms of its intra- and interrelationships and their coordination, impact on building the regional industrial knowledge base? Research Issue 3: What are the factors that impact the orientation of support and synergy of the RNISS at the regional level? A case-study approach was used to explore these issues. Data gathering was carried out by using mixed methods, such as in-depth interviews with various relevant actors at regional and national level, further supported by assessment of material gathered from various relevant national and regional actors. Guided by the literature and indicators developed for this research, the cases were then analysed by using within-case analysis and cross-case analysis approaches. The results show major difference between the two regions under study – Sabah has a weak support system in contrast to a strong support system in Penang. This is primarily due to differences in these regions’ institutional capacities in governing their innovation support system. This research suggests that a dirigiste (nation-centred) model of innovation support system can be effective for knowledge base building at a regional level, provided that the regional government has a strong institutional capacity in driving and coordinating the policies of all the main innovation actors in the region. Additionally, this research emphasises that the national innovation support system at the regional level must focus its orientation towards addressing the actual needs of the region in order for its role to be effective. There are two potential implications of this study; first, is the theoretical implications of the impact of regional institutional capacities for the nature and dynamics of such regions’ innovation support systems. Secondly is the policy implication in at least two areas: (1) informing policy makers about the issue of cooperation and relationships among actors that may indicate wider weaknesses in the implementation of NISS, and, (2) raising the issue of integration of different government levels in implementing the innovation support system at regional level. <br/> <br/>Description: Thesis (PhD) -- Faculty of Science, University of Malaya, 2008. http://dspace.fsktm.um.edu.my/handle/1812/556 Title: Systematic studies in Rothmannia sensu lato (Rubiaceae) and a revision of the Malesian <br/> <br/>Authors: Teresa Pereir, Joan <br/> <br/>Abstract: A review of the Southeast Asian, in particular the Malesian, species of Rothmannia Thunb. was undertaken. This considered not only the type and other species from Africa but also the closely related genera, Heinsenia (African) and Kochummenia (Malaysian). Parallel studies on the macromorphology,lower leaf surface micromorphology and palynology identified characters for group or species recognition within the Rothmannia complex. These indicated two highly distinctive groups, the African type species and alliance with right-contorted corolla lobes (Rothmannia s.s.) and two species placed within Kochummenia. Concurrently,two taxa were found morphologically aberrant within the genus as they have branch leaves in pairs or completely reduced, in contrast to most members of the Rothmannia complex, where branch leaves occur in trifoliate groups as a consequence of the nodes being very close together. One of these, R. macrophylla, a West Malesian endemic, was distinguished based on a different branch system with large pollen size, whereas the African R. globosa was out of place by its non-modular branch development and exclusively granular cuticular ornamentation on the lower leaf surface. The remaining species from Africa, across Asia and the SW Pacific were morphologically diverse but lacked a clear suite of unifying characters. The morphological characters of the Rothmannia complex were cladistically analysed and a limited molecular analysis was also carried out using the chloroplast trnQ-rps 16 intergenic spacer region. Results from both analyses suggest that Rothmannia is probably paraphyletic. Also, the relationships of the related taxa, Kochummenia and Heinsenia to other members within the complex could not be ascertained. Hence, the taxonomic delimitation of Rothmannia Thunb. remains unresolved. Nevertheless, the African type species and its alliance of related species with right-contorted corolla lobes can be considered Rothmannia in its strict sense (Rothmannia s.s.). In spite of the lack of clear resolution cladistically in the present work, the two related taxa, Kochummenia and Heinsenia will remain in their current circumscription because they have a number of distinctive characters, they are validly named genera, and only a wider-scope cladistic analysis including more genera in the tribe will be truly confirmatory. All the other species of Rothmannia (including the Malesian species) are best referred to as Rothmannia in its wider sense (Rothmannia s.l.). Inclusion of a wider representation of genera within the Gardenieae in a molecular analysis and, perhaps, a combined cladistic analysis of both morphological and molecular characters may be the best option for resolving these taxonomic uncertainties. A taxonomic enumeration of the Malesian species of Rothmannia s.l. revealed 18 species, including 11 combinations needed, five new species and one new variety to be proposed. Of these, 17 species are endemic to Malesia. <br/> <br/>Description: Thesis (PhD) -- Faculty of Science, University of Malaya, 2008. http://dspace.fsktm.um.edu.my/handle/1812/531 Title: Alkaloids isolated from Alseodaphne species (Lauraceae) and their bioactivities <br/> <br/>Authors: Mohd Azlan Nafiah <br/> <br/>Abstract: The phytochemical study on Lauraceae family (Alseodaphne corneri Kosterm, Alseodaphne pendulifolia Gamb., Alseodaphne perakensis (Gamb)Kosterm and Alseodaphne peduncularis (Wall.ex. Ness) Meissn) involves extraction, separation by using various chromatographic method and structural determination by spectroscopic techniques such as UV, IR, NMR including 1DNMR (1H, 13C, and DEPT), 2D-NMR (COSY, NOE-D, NOESY, HMQC/HSQC, and HMBC) and MS (LCMS and HRFABMS). The structures of the compounds were also elucidated by comparison with the previous works. Isolation works on the leaves of Alseodaphne corneri Kosterm (KL 4928) collected from University Malaya, Kuala Lumpur, yielded four aporphines; isocorydine 79, norisocorydine 80, N-methyllaurotetanine 83, laurotetanine 87, and four bisbenzylisoquinolines; obamegine 81, 2- norobamegine 84, (+)-2′-noroxyacanthine 55, and (+)-sepeerine 89. Meanwhile, the roots afforded one aporphine; norboldine 104, and seven bisbenzylisoquinolines; (-)-gyrolidine 91, norstephasubine 93, (+)-2- norobaberine 94, stephasubine 98, O-methyllimacusine 100, (+)-3′,4′- dihydrostephasubine 105) and O-methylrepandine 107. Seven compounds were successfully isolated from the leaves of Alseodaphne pendulifolia Gamb (KL 5250) collected from Sg. Temau Forest Reserved, Kuala Lipis, Pahang i.e; one oxoaporphine; oxohernagine 110; five aporphines; hernagine 111, corydine 112, isocorytuberine 113 and two new aporphine alkaloids; N-(2- ydroxypropyl)-pendulifoline A 108 and N-(2- hydroxypropyl)- pendulifoline B 109 and one bisbenzylisoquinoline; costaricine 114. Furthermore, this is the first report of alkaloids existence in the A. pendulifolia. Investigation of the alkaloidal constituents from the leaves of A. perakensis (Gamb) Kosterm (KL 5135) collected from KPK Sg. Merantor, Gua Musang, Kelantan yielded five aporphine alkaloids; N-methyllaurotetanine 83, norboldine 104 and three new apophines alkaloids; N-(2-hydroxypropyl)- norboldine A 115, N-(2-hydroxypropyl)-norboldine B 116 and N-cyanomethylnorboldine 117, and three new bisbenzylisoquinoline alkaloids; α′- oxoperakensimine A 118, α′-oxoperakensimine B 119 and α′- xoperakensimine C 120. Isolation and purification of alkaloids from the bark of A. peduncularis (KL 5165) collected from Kluang-Mersing, Johor, afforded five compounds; norlirioferine 121, lindcarpine 122, norpredicentrine 123, boldine 124 and laurotetanine 87 from aporphinoid group, and one new bisbenzylisoquinoline; α′-oxoperakensimine C 120. Bioassay study on the pure compounds of Alseodaphne species was found to possess vasorelaxant and antimalaria activity. In addition, three new compounds from A. perakensis; α′-oxoperakensimine A 118, α′- oxoperakensimine B 119 and α′- xoperakensimine C 120 showed vasorelaxant activity on induced contractions in the rat aorta strips. <br/> <br/>Description: Thesis (PhD) -- Faculty of Science, University of Malaya, 2009.