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Dual-band Doherty power amplifier with the improvement of reactance compensation technique for LTE frequency operations / Yu Li Ming
No full textA dual-band selection of Doherty power amplifier employing a Reactance Compensation Technique (RCT) with Gallium Nitride High-Electron-Mobility-Transistor (GaN HEMT) technology is presented. In this dissertation, the focus has been given to the design power amplifier in Doherty configuration, where it can operate at dual-band frequency and enhanced performances at 6 dB back-off from saturation power. This project applied lossy matching circuit for the input matching network and incorporated the primary motivation of using RCT and third harmonic tuning for the output matching network.
The DPA designed can achieve satisfying results for the frequency of 0.8 and 2.1 GHz. The implementation is suitable for two-way radio application, particularly for LTE frequency operation. The results of the proposed concept are validated through simulation by using Advanced Design System (ADS). The measured results of the prototype board report accepted performance over the desired frequency. (ie. the maximum power level of 40.5 dBm, 6 dB back-off efficiency of 43% and 47% and gain of 10 dB approximately at 0.8 GHz and 2.1 GHz, respectively)
A PI based coordinated maximum power point tracking controller for grid connected photovoltaic system / Md Haidar Islam
No full textThe global demand for electric energy has continuously increased over the last few decades. Photovoltaic (PV) sources are predicted to become one of the biggest contributors to electricity generation among all renewable energy generation candidates by 2040. The photovoltaic system a renewable energy source that has attracted the attention of researchers in recent years. The power output of a photovoltaic system has a complex dependence on varying environmental conditions such as solar irradiation and ambient temperature which cannot be controlled, thereby making the current versus voltage (I-V) and power versus voltage (P-V) characteristics of photovoltaic arrays nonlinear. Therefore, maximum power varies from time to time as these factors change rapidly. In order to maintain maximum power of the PV system, maximum power point tracking (MPPT) techniques are incorporated with direct current to direct current (DC-DC) converters and proportional integral (PI) controllers. A MPPT is an automatic control algorithm used to adjust the power interfaces and achieve the maximum possible power harvest, during instantaneous deviations of light levels, shading, temperature, and photovoltaic module characteristics. The idea behind the MPPT techniques is to adjust an operating voltage close to a maximum power point (MPP) under constantly changing atmospheric conditions. The MPPT techniques vary in many aspects such as: digital or analogical implementation, tracking speed, convergence speed, cost, simplicity and in other aspects. The differences between conventional and other modified MPPT algorithms are explained in this research work. A new coordinated PI-MPPT algorithm is then proposed based on the deficiencies of the other algorithms. The proposed MPPT algorithm is used to maximize a conversion efficiency of a PV array. The proposed algorithm’s reference variables such as current, voltage, duty cycle and power output
will be traced and the results obtained for different weather conditions. The proposed algorithm enhances the steady-state and dynamic responses by introducing an improved adaptive step-size for updating variables. A low complexity grid synchronization controller is implemented to generate parallel and orthogonal components of the grid voltage in a highly computationally efficient manner in order to create a synchronized current reference to the current control loop. MATLAB Simulink tool box is used to create models to carry out performance evaluation of a PV module with the MPPT algorithms. The grid-connected PV system is implemented with dSPACE controller and solar simulator, and other measuring instruments. Theoretical demonstrations are verified by the simulation and experimental results of the proposed system. The measured results validated that the proposed coordinated PI-MPPT technique tracks reference values accurately. The power efficiency of the proposed algorithm is achieved by 99.92%, 99.8%, 99.88% and 99.83% against uniform weather, partial shading conditions (PSCs) 1, 2 and 3, respectively, which is much higher than that of conventional MPPT techniques. The proposed system is an improved method which designed and modeled to obtain good accuracy and stability of tracking GMPP under highly dynamic conditions
Miscible blend of polyethersulfone/polyimide membrane crosslinked with diamine for hydrogen/carbon dioxide separation / Nur 'Adilah Abdul Nasir
No full textHydrogen (H2)/carbon dioxide (CO2) separation application is crucial to fully utilize H2 gas as the next generation fuel source. Polyimide membranes have been intensively developed for H2 purification. However, polyimide has a low CO2 plasticization resistance and the separation performance of current neat polyimide membranes are insufficient to achieve industrial demands. Therefore, modification approach is required to overcome the limitation. Gas separation efficiency of mixed crosslinking agent on polyimide (PI) membrane is studied in this research by blending 1,3-diaminopropane (PDA) and 1,4-diaminobutane (BuDA) at different concentrations. It was found that the H2/CO2 selectivity increased significantly and H2 permeability decreased dramatically with higher concentration of PDA in crosslinking solution. Therefore, PDA is used as the crosslinking agent. Polyethersulfone (PES) and polyimide (P84) blend with three different ratios (25/75, 50/50 and 75/25 wt. %) are synthesized to form asymmetric membranes. Pure H2 and CO2 gas permeation tests were conducted on the polymer blends to find the best ratio for H2 purification. PES/P84 (75/25 wt. %) exhibits the highest H2 permeability value of 187.3 Barrer compared to all polymer blends tested. Next, chemical modification was carried out on the polymer blend ratio with superior H2/CO2 separation performance by immersing in PDA:methanol solution at different reaction times. After 15 minutes modification, the polymer membrane achieved an improvement on H2/CO2 selectivity by 96.9 % due to the increase in chain packing density and reduction in free volume caused by diamino crosslinking confirmed by XRD analysis. Hence, this study contributed significantly in improving H2 selectivity performance of the membranes
Social and emotional competence and its association with cyberbullying among adolescents / Thava Viknaraj Sivabalan
No full textCyberbullying is a growing menace especially in countries like Malaysia which
highly focuses on digital industry development. Adolescents are at greater risk since their
higher usage of internet mainly on the grounds of social networking. The aim of this study
is to describe cyberbullying through various factors and the relationship with social and
emotional competence (SEC) using the General Aggression Model as a theoretical
framework. The study, conducted through June 2019 to November 2019, adopted a cross
sectional study design, among 889 adolescents aged 13 and 14 years old of national
secondary schools in Penang, Malaysia. Two-stage random sampling was performed to
select schools and study population. Cyberbullying was measured using the European
Cyberbullying Intervention Project Questionnaire (ECIPQ) in three distinct domains
namely cyber perpetration, cyber victimization and cyber victim-perpetration in the past
one month. Cyberbullying prevalence in the past month was 16.6%, 5.8% and 15.0% for
cyber victimization, cyber perpetration and cyber victim-perpetration respectively.
Infrequent cyberbullying episodes accounted for more than 70.0% of students being at
risk to cyberbullying in the past three months. The 14-year-olds were more prone to
subject themselves as cyber perpetrators (AOR=2.30, 95%CI 1.09, 4.87). Boys were more
likely to be victimized (AOR = 1.90, 95% CI 1.23, 2.95) and at higher risk of becoming
online perpetrators themselves (AOR=1.54, 95%CI 1.09, 2.52). With regards to internet
use pattern, frequent internet users, those who own an electronic device and those who
use the social media and instant messaging apps are more prone to cyberbullying. While
having poor mental health was significantly associated with all categories of
cyberbullying, cyber victim-perpetrators pose the highest odds of depressive symptoms
(AOR=2.15, 95%CI 1.16, 3.99). Traditional bully victim, perpetrator and victim-
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perpetrator were at risk to becoming cyber victims (AOR=3.79, 95%CI 1.93, 7.42), cyber
perpetrators (AOR=5.61, 95%CI 1.65, 19.04) and cyber victim-perpetrators (AOR=4.55,
95%CI 1.61, 12.88) respectively. Perceived family support is associated with cyber
perpetrators (Mean=4.38 vs 4.13, p<0.001) and victim-perpetrators (Mean=4.38 vs 4.15,
p<0.001) while perceived peer support is associated with cyber perpetrators (Mean=4.20
vs 3.99, p<0.05) and victim-perpetrators (Mean=4.20 vs 4.03, p<0.05). Adjusted for all
factors, SEC is associated with cybervictimization (AOR=1.04, 95%CI 1.01, 1.06) and
cyber victim-perpetration (AOR=0.95, 95%CI 0.93, 0.98). The findings highlight that
cyberbullying is a common phenomenon among school-going adolescents of which seven
in every ten adolescents reported being at risk to cyberbullying. Factors such as age,
gender, ethnicity, internet use pattern, mental health traditional bullying, family and peer
support are found to be associated with cyberbullying. High social and emotional
competence was found to be a significant protective factor against cyberbullying among
adolescents. Skills-based interventions that could increase social and emotional
competency of adolescents are important to be considered as possible solutions to reduce
cyberbullying. The study findings further recommend cyberbullying to be given equal
importance as emphasis to digital development and be addressed through collaborative
efforts of various stakeholders such as public health, education, and multimedia agencies.
SEC-based interventions must be delivered through universal prevention and whole of
organization approaches to ensure effectiveness and sustainability.
Keywords: cyberbullying, socio-emotional competence, adolescents, generalized
aggression model
Antioxidative and lipid-reducing activities of Ficus deltoidea in palmitic acid-induced WRL68 cells / Noor Nazirahanie Abrahim
No full textNon-alcoholic fatty liver disease (NAFLD) is a series of liver disorder caused
by deposition of fat without involving alcohol. This chronic liver disease has become
a major concern globally due to its high mortality and morbidity rate. This situation
leads to the quest of finding natural remedy to overcome this condition. Ficus
deltoidea or commonly known as mistletoe fig or Mas Cotek, is a plant that is very
well known especially in Malaysia for its blood glucose lowering effect. However,
the potential value of F. deltoidea has not been fully evaluated, and no studies have
been published on the effects of F. deltoidea on NAFLD. Therefore, the aim of this
study is to determine the potential effect of F. deltoidea leaves on the improvement
of NAFLD especially on lipid accumulation using cultured cell model. Leaves from
three varieties of F. deltoidea, colloquially termed small-(FDS), medium-(FDM),
and big-type leaf (FDB), were subjected to water extraction. The crude (C) extracts
were fractionated using water (WF) and ethyl acetate (EAF). The phenolic and
flavonoid content, antioxidant activity, and cytotoxicity of the fractions were
investigated. Due to its high phenolic content, antioxidant activity was highest in the
FDB crude water extract, especially on metal chelating, inhibition of lipid
peroxidation, LDL oxidation and HMG-CoA reductase activities. Through MTT
assay, none of the samples showed cytotoxicity towards WRL68 cell line.
Subsequently, palmitic acid (PA) was used to induce lipid accumulation (steatosis)
in WRL68 cells, and all the samples were tested for their lipid reducing activity by
using two different protocols i.e., pre-, and post-treatments. Only FDB shows lipid
reduction at the highest tested concentration (200 µg/ml) and were used for
subsequent experiment. Pre-treatment with FDB was found to restore redox status by
increasing SOD and GPx level, and less malondialdehyde (MDA) formation. The
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changes in protein expressions were studied by using proteomic approaches via 2DE
separation followed by identification of protein spots of interest using MALDI�MS/MS. Six proteins were successfully identified which are HSPB1, PSMA1,
GSTO1, PRDX1, HIST1H2BD and UCHL3. Through bioinformatics analysis, these
proteins were found to be significantly involved in specific pathways such as
oxidative stress (PRDX1 and GSTO1), protein homeostasis (HSPB1) and
degradation (UCHL3 and PSMA1). Meanwhile, phytochemical analysis of crude
water extract of FDB using ultra high-performance liquid chromatography (UHPLC),
reveals the presence of flavone (vitexin) and phenolic acid (p-coumaric acid). Based
on the data, the polyphenolic-rich extract of F. deltoidea might have the potential to
reduce lipid levels due to the presence of phenolic compounds with high antioxidant
activities. Results obtained suggest that this Malaysian herb have a probable
preventive effect on chronic liver disease especially in the early stage of NAFLD.
Thus, these findings might be helpful to various treatment plans for fatty liver in the
future. At the same time, it shows the practice of consuming this plant to be beneficial
for health.
Keyword : Ficus deltoidea, antioxidant, steatosis, oxidative stress, protein
homeostasi
Analysis of additives for bio-based engine oil for a two stroke marine engine / Keong Le-Onn
No full textBio-based oil synthesis through Neopentyl glycol (NPG) and Trimethylolpropane (TMP) ester are used to produce biodegradable bio-lubricant for a two stroke marine engine. Two stroke engine, specifically for marine activities, widely uses synthetic lubricant in the fuel-oil mixture as it is easily available and at low cost. This has huge impact to the environment as two-stroke marine engine release its byproduct directly into the aquatic environment during its operation and the less stringent law encourage this to occur widely around the world. Bio-based oil with the combination of Group II synthetic oil with various composition allow us to find the optimum composition to produce the similar or better performance of fuel-oil mixture compared to using synthetic oil entirely. Additives of Graphene Oxide (GO), Anti-Oxidant (AO), PIB and solvent are added into this bio-based oil mixture to enhance its performance and capability of using bio-based oil. The physicochemical properties of viscosity, density and VI ratio are obtained through advance viscometer. Sample with 50% bio-based oil and 50% Group II mineral oil has the most optimum result among the tested composition, including the baseline reference lubricant suggested by the two-stroke marine engine manufacturer. An improvement of 28.36% when compared to the baseline sample in terms of Viscosity Index (VI) is observed, whereby Sample 3 has VI value of 160.4. The higher VI allow it to operate at various temperature range which is a key factor marine use as the environment varied throughout the day. Through the wear scar diameter test and obtaining the coefficient of friction, the bio-based oil alone has outrun the synthetic oil, both from Group I and Group II base oil. This factor is critical to ensure engine lubrication of bio-based oil is on par or perform even better for engine performance. Each sample of bio-based oil mixture is tested in actual two-stroke marine engine to find out the deposition of carbon on the spark plug. Sample with bio-based oil from PNAF-NPG ester shows the most optimum result with the least amount of carbon
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deposition on the spark plug and at dry condition for moisture rating. Whereas for TMP ester, composition of this bio-based oil that is more than 30% will cause carbon to deposition on the spark plug – however the moisture rating remained low. Complex microstructure of TMP required higher temperature during combustion process to completely process all the TMP. Hence, TM would be useful to be used on engine with higher revolutions. The similar result is observed when using a lower revolution two-stroke engine. As such, the usage of bio-based oil from PNAF-NPG is acceptable and able to provide satisfactory results on low or high revolution two-stroke engine
Study of heat transfer and friction loss analysis of flowing fluid in different configuration of closed conduit flow / Puravi Saminathan
No full textThe heat exchanger available on market satisfies the elementary conditions.
However, there are very few research on difference shape and its efficiency on heat
exchanger. With new design of shape of this study is intend to improve the efficiency of
heat exchanger. A CFD package (ANSYS FLUENT) will be use for the numerical study
of heat transfer and flow characteristics of a single pipe heat exchanger for annular
flow, with 2 shape of pipe and the results then will be compared. The simulation will be
carry out for water to water heat transfer characteristics and for same length and same
diameter of tube and annulus and for same input temperature. Consequently this study
concerned on nano fluid with different parameter which has the best heat transfer in
circular and square tube. The heat transfer coefficient will be measured and has
compare
Dimensions of debt in selected economies: Analysis on determinants, thresholds and effects on economy / Chandran Gunalan
No full textThis research examines three dimensions of public debt among a group of 12 uppermiddle
Asian countries, as well as country-specific analysis on China, Indonesia, Malaysia, Thailand and Turkey. An ARDL model was used to analyse the determinants of public debt, while Threshold Regression was applied to estimate the threshold level and understand the impact of breaching the threshold using panel data between 1980 and 2015. Firstly, the determinants of public debt indicate that GDP growth, capital stock, national saving, total trade, and inflation are factors that reduce the level of public debt. However, employment, government consumption, real interest rate and real exchange rate increase public debt levels. Crisis periods are also times when countries are exposed to public debt, but the results show such an effect only among country specific analyses. Secondly, public debt threshold (turning point) was estimated involving 12 upper middleincome economies from Asia. Results show that there is a non-linear relationship between public debt and economic growth in the long-run and this relationship exists in both Ushape and inverted U-shape (Ո). Public debt threshold is estimated at 96.9% for 12 uppe
A critical analysis of the adequacy of data protection law in Bangladesh: Challenges and potential solutions / Md. Toriqul Islam
No full textPrivacy is essential for the fullest expression of the physical and mental development of humankind. It has become one of the most desired human rights and basic needs for human life in this era of ubiquitous computing. In this digital age, diverse activities are going on online using personal data, and these lead personal data to evolve as the new fuel to the Internet, and coin to the digital world. The discovery of the Internet, the World Wide Web, constant progress in information and communication technologies, the Internet of Things and similar other technologies or devices have facilitated the collection, processing and storing of personal data to an unprecedented level. Over time, governments, businesses, and other entities have been processing large scale of personal data for numerous purposes, mostly, without the knowledge of the persons concerned. Therefore, information privacy gains the momentum than any other aspect of privacy. This landscape poses tremendous challenges to information privacy as well. Consequently, information privacy appears as one of the hot button issues in contemporary global politics, policies, and business. In response, the protection of privacy, especially, data privacy has been recognised nationally, regionally, and internationally, as evidenced by numerous initiatives of all these entities. To date, nearly one hundred and fifty countries have enacted either sectoral, or comprehensive data protection laws, and many other nations have started the process of enacting such laws to ensure the rights of the data subjects. Like other nations and regions, the people of Bangladesh are also experiencing various privacy threats, and accordingly, deserve to have adequate legal protections. Nonetheless, there is no comprehensive data protection law to date and even academic research in the context of Bangladesh. This backdrop requires extensive research as to whether the existing legal regime of Bangladesh ensures adequate legal protections for privacy in comparison with international and regional data protection standards. Using doctrinal legal research, or desk-based or library research methods, this research aims to fill that gap. The findings of this study reveal that though there is no comprehensive data privacy law in Bangladesh, citizens� right to privacy is conditionally recognised in the Constitution, and there are references and recognition of some aspects of privacy in numerous existing laws, and case laws. Hence, the results demonstrate that the existing legal regime of Bangladesh does not provide adequate legal protections for the right to privacy and personal data of the individuals, and thus, require significant policy drives. Against such backdrops, this thesis offers some policy recommendations for all stakeholders, and especially, recommends the policymakers for enacting a comprehensive data protection law in Bangladesh. Notably, this thesis introduces a model for a suitable data protection law of Bangladesh based on the international and regional data protection standards, best practices, and especially, in conformity with the General Data Protection Regulation of Europe. The findings of this research will enlighten the relevant stakeholders to understand the issues encompassing privacy and personal data protection in Bangladesh and facilitate them to map and design their future strategies and policy directions
Effects of phenylalanine feeding on flavonoid production in Boesenbergia rotunda cell suspension cultures / Charumathi Yogarajan
No full textBoesenbergia rotunda, a medicinal ginger, is reported to have flavonoids and cyclohexenyl chalcone derivatives (CCD) with anti-bacterial, anti-cancer, anti-oxidant and anti-dengue properties. These compounds are obtained from rhizomes which are susceptible to biotic and abiotic stress. Hence, cell suspension cultures grown in controlled conditions are advantageous as an alternative source. The accumulation of these compounds could be enhanced using precursor. In this study, phenylalanine was used as the precursor and a feeding strategy was designed to enhance CCD (panduratin A) and other flavonoids (pinocembrin, pinostrobin and cardamonin) production. B. rotunda cell suspension cultures were established in liquid Murashige and Skoog basal
medium containing 1.0 mg/L 2,4-D, 0.5 mg/L BAP and 2.0% sucrose. The established cell suspension cultures were then treated with 20.0, 40.0 and 50.0 mg/L phenylalanine at day 14 and incubated for 3, 7, 14 and 21 days before harvesting. Pinocembrin, pinostrobin, panduratin A and cardamonin were quantitated using high-performance liquid chromatography (HPLC) for each treatment. It was shown that with the addition of phenylalanine, 40 mg/L phenylalanine treated cultures showed a significant increase (p<0.05) in the content of pinocembrin after 21 days of feeding compared to control. Meanwhile, there was no significant increase in pinostrobin, cardamonin and panduratin A in the cell cultures treated with different concentrations of phenylalanine at all incubation periods tested. The significant increase in one of the flavonoids investigated in this study, which is pinocembrin could be due to the phenylalanine feeding and additional effects from stress inflicted by dying cells or nutrient depletion over the long incubation culture period. Further studies need to be carried out to confirm the effect of phenylalanine as a precursor that has enhanced pinocembrin accumulation in B. rotunda suspension cultures