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Development of safety self-audit mechanism for chemical laboratories in higher learning institute: A case study in Universiti Malaya / Ahmad Fahim Mahmud
No full textSafety compliance and implementation of best practices are commonly enhanced through
scheduled auditing and subsequent improvement processes. The audits are commonly
conducted by third parties (internal or external). However, when the number of
laboratories involved are in hundreds, third party audits may not take place as per
schedule and may affect the safety level of the laboratories. One of the means to overcome
this issue is by developing a self-audit mechanism that can be used by the person(s) in
charge of the laboratories itself to conduct the audit. Therefore, in this work, a
comprehensive self-audit checklist was developed by taking into consideration safety
related activities and facilities in typical chemical laboratories. Subsequently, the
checklist was used to gather information on selected laboratories. The self-audit checklist
consisted of nineteen (19) key categories. Guideline to use the checklist is also provided
in the self-audit mechanism. The practicality of the checklist developed was validated by
auditing one, two and three chemical laboratories in Faculty of Engineering, Faculty of
Medicine, and Faculty of Science, respectively. The result showed that the safety self-audit mechanism is practical as a tool to conduct a comprehensive safety audit in chemical
laboratories, with minimum time and monetary requirement. Hence, the study has proven
that the safety self-audit mechanism developed can be used to initiate safety self-audit
practices in chemical laboratories in higher learning institution in Malaysia
Cooperative spectrum sensing based on machine learning in cognitive radio vehicular network / Mohammad Asif Hossain
No full textA vehicular ad hoc network (VANET) is a major participant in reducing traffic collisions and road congestion. In VANET, an enormous amount of data is needed to be exchanged. However, the dedicated access technique for VANET, the DSRC (dedicated short-range communication), is insufficient to accommodate these enormous data quantities. Consequently, VANET faces a lack of spectrum bands. Cognitive radio (CR) can be used to alleviate such a crisis. CR is an intelligent and programmable radio device that accesses various frequency bands. To enter these bands, CR must conduct spectrum sensing. An SU (secondary user) or a CR user can decide whether the spectrum is occupied by some PUs (primary or licensed users) or not. This mechanism is known as spectrum sensing. It is the technique to identify any vacant spectrum (no licensed user is currently using). When it discovers that the PU does not use the licensed spectrum, SU will use it (vacant licensed spectrum) under some restrictions when the DSRC is filled. Several spectrum sensing techniques are found in the literature. Few examples are energy detection, cyclostationary detection, matched filter detection, etc. Due to the speedy nature of the vehicles, these spectrum sensing techniques are confronted with several problems such as rapid change of radio environment, heterogeneous service quality (QoS) requirements, hidden node problem, problems in multipath fading and shadowing, diffraction, various PU activity models, etc. Spectrum sensing must be accurate, faster, dynamic, and flexible due to vehicles' high velocity and constant environmental shift. The optimum spectrum sensing should consider vehicle speed, fading degree, density, radio environment, etc. To solve the above-mentioned issues and problems, this thesis presents a novel segment-based CR-VANET (Seg-CR-VANET) cooperative spectrum sensing (CSS) framework. In this thesis, roads are divided into equal segments, which are then subdivided depending on the probability value. CSS needs to perform two sensing for its operation; local sensing and global sensing. In this thesis, local sensing results are produced by SUs or vehicles by selecting the best spectrum sensing technique. The selection would be made based on the hybrid machine learning (ML) algorithm. A fuzzy-based Naive Bayes algorithm has been used in this case. For the local sensing, values of signal-to-noise ratio (SNR) and noise uncertainty are used. Instead of using a static threshold value, dynamic threshold values are used for sensing techniques. The tri-agent reinforcement learning (TA-RL) algorithm has been used by the segment spectrum agent (SSA) in this suggested CSS to make the global decision. TA-RL algorithm learns three environments (network, signal, and vehicle behavior) to assess the behaviors of PUs. The whole solution has been implemented in OMNeT++ with the required modules and the SUMO traffic generator tool. The simulation findings reveal that the Seg-CR-VANET outperforms existing works in terms of several performance metrics used in spectrum sensing such as probability of detection, false alarm rate, accuracy, throughput, delay, packet delivery ratio, etc
Development of techniques for in-situ monitoring stress-induced degradation and potential solutions for FPGA / Anuar Jaafar
No full textReliability and application failures occurring in Field Programmable Gate Arrays (FPGAs) are pressing issues in today’s specific FPGA application. This is due to the high density of logic circuits on the chip subsequent to rapid process technology scaling. Reliability issues in FPGA lead to the degradation in the FPGA performance, leading to a shorter device lifetime. Negative Bias Temperature Instability (NBTI) degradation effect occurs due to the chemical breakdown between gate-dielectric-channel regions of a Positive Metal-Oxide-Semiconductor (PMOS) transistor. The logic delay occurrence on FPGA is mainly caused by the NBTI effect that substantially reduces the FPGA's lifespan. A ring oscillator has been widely used as a digital temperature sensor to sense logic delay degradation subsequent to the thermal effect on FPGAs. The logic delay generated by the ring oscillator is caused by temperature changes that lead to the electromigration degradation effect. The decreasing of electron mobility causes the propagation delay to decrease as well. Therefore, it is critical to adopt an accurate ring oscillator design to effectively measure the logic delay in FPGAs. This work proposes to develop automatic clock correction tools to rectify degradation occurrence due to logic delay effect in order to sustain the FPGA performance. This work also proposes to design a stable ring oscillator to detect the logic delay degradation due to thermal effect during optimum temperature operation. Furthermore, a lifetime prediction table as a guideline for the system designer or industrial operators is also proposed, in which it provides an indication of a critical level of when the FPGA is prone to fail. Measurement periods of 512 and 4096 clock cycles have been implemented and the relationship between temperature, logic delay and total count has been developed. Logic delay is converted to phase degree using a special function that considers the relationship between time and frequency. The logic delay that is triggered by an FPGA can be in multiple ranges of phase from 0˚ to 360˚. All possible ranges of delays, each corresponding to a particular amount of degradation, have been investigated by implementing an exhaustive test in estimating the lifetime of a device. It is observed that when the logic delay increases by 50˚, the lifetime will decrease by 13.89%. Through the critical level obtained from the technique proposed, a user can indicate the schedule of a replacement FPGA unit for continual process in maintaining the reliability of the FPGA. It has been found that the best measurement period to reduce the degradation effect on the Virtex-6 FPGA is to adopt a measurement period of 512 clock cycles on various temperature-based FPGAs ranging from 0℃ until 100℃. In summary, the effect of NBTI on FPGA has been demonstrated based on the logic delay degradation via aging detection and high operating temperature of the FPGA. Finally, the developed lifetime prediction table helps to indicate system designers and industrial operators of when to replace the FPGA in their electronic systems in order to prolong the performance of the FPGA
New circuit configuration and control strategy of modular multilevel converter for large scale photovoltaic systems / Ahmed Ibrahim Ibrahim Abbas Ahmed Elsanabary
No full textPhotovoltaic (PV) energy markets have been widely spread and are becoming one of
the leading energy generation capacities globally. The development of grid-connected PV
systems is the main target as it exceeds 99 % of the PV installed capacity due to the
comparatively low cost and less maintenance compared to stand-alone systems.
Nevertheless, the traditional large-scale PV inverters suffer from power loss of the central
maximum power point tracking (MPPT) system, the lack of modularity, the low voltage
ratings, and limitation of the switch power ratings because of the use of central PV
inverters. Modular medium-voltage multilevel converters are very promising to solve the
problems of large-scale PV systems. However, the integration of multilevel converters
into large-scale PV systems suffers from unbalanced power generation during partial PV
shading conditions. This problem is fully addressed in the thesis, and a distinctive
structure of the modular multilevel converter (MMC) for grid-connected PV plant is
proposed. The proposed PV-MMC system provides direct connection of the PV arrays to
the converter submodules, scalability, independent MPPT, enhanced power quality, and
internal power flow capabilities. An energy balancing strategy to control the power flow
inside the PV-MMC converter is proposed. It controls the internally generated leg current
to balance the power flow inside the converter and inject a three-phase balanced current
into the grid. Afterward, a new circuit configuration of the PV-MMC system is proposed
to enhance the balancing capability of MMC under severe power unbalance conditions.
This circuit connects the upper and lower SMs of the MMC in parallel to the same PV
arrays through isolated dc-dc converters. Moreover, a modified control structure is
designed to control the proposed system, which is less complex and yet very effective compared to the other control structures. It deals only with the leg power unbalance
conditions and inject dc leg current into the phases to balance the power flow of the
converter. Simulation and Hardware-in-the-loop tests are performed to demonstrate the
performance of the proposed grid-connected PV-MMC systems. The obtained results
show the capability of the proposed systems to rebalance the power transfer inside the
converter and inject a three-phase balanced set of grid currents. In addition, excellent
dynamic performance of controllers, low measured harmonics (below 5 %), and low SM
voltage ripple (3.98%) are obtained. The objective of the thesis is achieved by
investigating the MMC for the application to grid connected large-scale PV systems. The
related analysis and comparisons show the capability and power quality of the proposed
PV-MMC systems. The proposed energy balancing strategy can eliminate the PV power
unbalance and work under different conditions of solar irradiances. Moreover, the
proposed circuit configuration provides extended balancing capability of the MMC up to
extreme conditions
The elements of building civilization and its challenges through surat an-NamL: An applied comparative study between Malaysia and Egypt / Ahmed Hassan Mohammed Ali Said
No full textThis study deals with the elements of civilization building and its challenges, as found in Surat An-Naml, and compares between Malaysia and Egypt as a case study. The importance of this study is derived from its first reference: the Holy Qur’an, which caters for the peoples’ immediate and future interests. This study differs from previous studies, in theory, as it addresses the elements of civilization building and the challenges through Surat Al-Naml, and in practice, by applying the study to Malaysia and Egypt. The aim of the study has been to identify the concept of civilization in the Holy Qur’an, and in Western thought. The inductive method was followed, by tracing through and identifying the verses dealing with the elements of civilization building and challenges in Surat al-Naml. The study also relied on the descriptive analytical method, where the questionnaire was the chosen a tool for collecting primary data. The comparative method was used for comparing Islamic civilizational thought with the western civilizational thought, and for comparing the civilized situation on the ground between Malaysia and Egypt. A number of findings were reached. The elements of civilization and the challenges were amazingly detailed in Surat Al-Naml. The civilization aspects, as outlined in the Holy Qur’an, include both the material and the spiritual aspects, together, as inseparable pair, side by side. The most important differences in the concept of civilization between the Qur’anic and Western perspectives are that the Qur’anic perspective takes into account the interests of the real world and the afterlife, together, and that it weighs the benefits and evils with the scale of Islamic law. In contrast, the Western perspective is restricted to the worldly interests that humans themselves define with their limited knowledge. The field study showed that Malaysia had understood the elements of civilization building and managed to achieve scientific and practical development in the sectors of education, health, industry, transportation, and tourism, whereas Egypt had failed in these areas because of its reluctance to adopt civilization building true approach
Q-switched and mode-locked hafnium bismuth erbium -doped Fiber Lasers with New Passive Saturable Absorbers / Umi Namirah Zakaria
No full textTopology Insulators (TIs) based nanomaterials have recently emerged as a promising solution for generating Q-switched and mode-locked fiber lasers. These lasers have high market potential for laser sensing and spectroscopy, material processing, and medical applications since since they are more compact in geometry and simpler in setup. Sharing some advantages from fiber technology, the developed laser is more robust, zero-alignment, and less operational cost. On the other hand, tremendous interests have also been focused on developing an efficient Erbium-doped fiber (EDF) with high Erbium ion concentration. This study aims to demonstrate fiber lasers operating at 1550 nm region using a newly developed Hafnium Bismuth Erbium co-doped fiber (HBEDF) as a gain medium. Q-switched and mode-locked HBEDF lasers (HBEDFLs) were demonstrated using a new passive saturable absorber based on topology insulator materials and a solid Bismuth-doped fiber (BDF). The HBEDF has high doping levels of Erbium ion (12500 wt ppm) through incorporation of Hafnium and Aluminum ions, which prevents the clustering effect. At the input signal power of –10 dBm, a flat gain of 10.9 dB was obtained operating within the wavelength region from 1525 to 1565 nm using only 0.5 m long of the active fiber. In this work, three types of TI based SA films were successfully developed; Bismuth (III) Telluride (Bi2Te3), Bismuth (III) Selenide (Bi2Se3) and Antimony Telluride (Sb2Te3). Q-switched fiber lasers were then demonstrated using a highly doped HBEDF as a gain medium and bismuth ions-based materials (topological insulator and BDF) as a passive SA. For instance, by employing a Bi2Se3 PVA film as SA in HBEDFL cavity, the self-started Q-switched pulse trains operating at 1562 nm was obtained. The pulses have a shortest pulse duration of 4.4 μs and maximum pulse energy of 41.1 nJ. The pulse frequencies were tunable from 53.4 to 73.0 kHz with a pump power variation from 96 to 166 mW. Passively Q-switched and mode-locked HBEDFLs were also successfully demonstrated using two types of antimony based SAs; Sb2Te3 and pure Sb PVA films. By incorporating the Sb2Te3 PVA film in HBEDFL cavity, a nanosecond mode-locked laser was obtained with 1 MHz repetition and 350 ns pulse width. The mode-locking pulses achieved the maximum pulse energy of 2.04 nJ at 240.8 mW pump power. In another work, a passively mode-locked HBEDFL was demonstrated using the pure Sb film as a SA. Stable mode-locked pulses were successfully obtained within a pump power range from 198 mW to 300 mW. The laser was capable to generate optical soliton pulses centered at 1559.7 nm with the full width at half maximum of 0.52 nm and repetition rate of 1.0 MHz. The pulse duration and energy were 4.96 ps and 4.85 nJ, respectively. These findings show that HBEDF has a great potential for short and ultra-short pulses generating while TIs and antimony materials have also a great potential in photonic applications
Performance and characteristics of blend polymer electrolytes based on lithium triflate impregnated potato starch-graphene oxide with ionic liquid as plasticizer / Alyaa Amalina Mohd Azli
No full textPotato starch (PS)-graphene oxide (GO) blend based solid polymer electrolytes
have been developed using lithium triflate (LiCF3SO3) as ionic source via solution
casting technique. Lithium based electrolyte system (PS-GO-LiCF3SO3) is further
added with ionic liquid, 1-Butyl-3-methylimidazolium chloride ([Bmim][Cl]) as
plasticizer to form PS-GO-LiCF3SO3-[Bmim][Cl] electrolyte with better conductivity
characteristic. From X-ray diffraction (XRD) analysis, the best ratio of electrolyte
composition is found to be 80 wt.% PS : 20 wt.% GO : 40 wt.% LiCF3SO3 : 30 wt.%
[Bmim][Cl] with the highest conductivity value of (4.48 ± 0.85) × 10-4 S cm-1. Analysis
on temperature dependence conductivity reveals that all electrolytes follow Arrhenius
rule. The possible interactions within electrolyte material are verified via Fourier
transform infrared spectroscopy (FTIR). Results from field emission scanning electron
microscopy (FESEM) have strengthened the conductivity patterns of electrolytes. Data
obtained from linear sweep voltammetry (LSV) shows that PS-GO-LiCF3SO3-
[Bmim][Cl] electrolyte is electrochemically stable up to 1.92 V and suitable to be used
in electrochemical double-layer capacitor (EDLC) application. Specific capacitance, Cs
value calculated from galvanosatic charge-discharge measurement has been supported
with cyclic voltammetry (CV) analysis. The value of Cs obtained for PS-GO-LiCF3SO3-
[Bmim][Cl] EDLC is 37.9 F g−1 at 0.6 mA cm-2 current density
A predictive analytics framework using grey-lasso model for hospital readmission / Nor Hamizah Miswan
No full textHospital readmission is defined as an admission to a hospital within a certain time
frame, typically thirty days, following a previous discharge, either to the same or to a
different hospital. Hospital readmission prediction is a challenging task due to the complex
relationship between readmission and potential risk factors. At present, previous studies
reported modest discrimination ability possibly due to many inherent limitations and
complex problem by nature. The selected features to be the input variables for modelling
are mainly based on previous models or very shallow exploratory analysis. Moreover, the
clinical trials tend to follow established framework when it comes to predictive modelling.
Univariate feature selection proceeded by Logistic regression are the well utilized modelling
method. On the other hand, most study on readmission prediction has been focus on
maximizing the discrimination performance while disregarding the interpretability aspect
i.e. actionable insights and reasons that lead to potential readmission. To address the
aforementioned limitation, this work tackles the hitherto unexplored problem: hospital
readmission framework that have robust preprocessing framework, with reliable and
interpretable prediction model. Three approaches were proposed in this work. Firstly, the
overall improvement of preprocessing is proposed to enhance the prediction performance.
With regards to feature selection in preprocessing phase, Grey-LASSO is proposed with
consideration of uncertainty in feature selection by employing Grey relational analysis and
LASSO. The features obtained using Grey-LASSO produce minimal features subset to be
the input variable in modelling phase. Secondly, machine learning classifiers are used to
predict the risk of hospital readmission that have the maximal discrimination performances. Thirdly, interpretable insight based on rule mining is established at the predicted model
output to provide certain level of interpretability to be applicable in real clinical setting.
The final framework of prediction model, named interpretable rule learning, which harness
the elements of interpretability and achieves outstanding performance of faithfulness
and human evaluation in terms of, trustworthiness, confidence and understanding. To
this end, this work focuses on enhancing the prediction performance as well as provide
interpretability insight on the predicted output of modelling
Evaluation of heavy metal bioremediation potential using microbes from contaminated landfill soil / Nor Asni Abdullah
No full textChemical evaluations and characterization had often served as the commonly adopted options for assessing the potential impact of pollutants, which at the same time provide insight into the possible remediation technologies. However, heterogeneous substances may not be best studied in aforementioned forms because of the varied characteristics and concentrations of discrete components. Considering the high distribution of waste disposal site in Malaysia, the study was designed to isolate and identify bacterial species from leachate polluted soil. This study also aimed to generate a blend of microbial inoculum with high heavy metal resistance to serve as potential combination for optimal bioremoval of heavy metal from contaminated sites. The study also was undertaken to assess heavy metal removal performance in monometal and polymetal systems. Last but not least was to evaluate the behavioral changes of microorganisms due to metal pollution. Various methods adopted in the study ranged from soil samples collection from selected contaminated soil, microbial isolation, microbial identification, microbial inoculum build up, preparation of heavy metal standard solutions and designing experiment based on monometal system and polymetal system. Microsoft Excel and SPSS were statistical tools used in the study. Results were recorded based on 2- and 8-Day incubation period for both monometal and polymetal system. Different treatments displayed varying capacity in heavy metal removal. In monometal system, the highest rate constant value for Treatment A was Pb (K= 0.370 day-1) while Treatment B is Fe (K= 0.338 day-1) and Treatment AB is Fe (K= 0.376 day-1) in two days. Meanwhile in eight days, the highest rate constant value for Treatment A is Mn (K= 0.178 day-1) while Treatment B is Fe (K= 0.095 day-1) and Treatment AB is Fe (K= 0.167 day-1). In polymetal system, the highest rate constant value for Treatment A is Pb (K= 0.550 day-1) and Treatment B also is Pb (K= 0.251 day-1) while Treatment AB is Ni (K= 1.242 day-1) in two days. Meanwhile in eight days, the highest rate constant value for Treatment A is Cr (K= 0.320 day-1) while Treatment B is Pb (K= 0.188 day-1) and Treatment AB is Pb (K= 0.067 day-1). These results suggested that there were complex interactions exist within the bacteria. The removal of heavy metal was also found to be dependent with exposure duration and metal complexity. In general, Gram-positive bacteria displayed a better heavy metal removal performance than Gram-negative bacteria. In the presence of heavy metals, Gram-positive and Gram-negative bacteria have different threshold of tolerance as reflected by their bacterial count and the final pH condition. Therefore, it can be concluded that different microbial blends have different optimal conditions to achieve the best heavy metal removal performance
Biogeography and systematics of the eulipotyphlans (Genus Chimarrogale, Hylomys and Crocidura) from Peninsular Malaysia / Muhammad Farhan Abd Wahab
No full textInspired by the myriad of questions regarding the taxonomic status and genetic relationships of fauna from Peninsular Malaysia, research on the three selected Eulipotyphlan (Chimarrogale hantu, Hylomys suillus and Crocidura monticola) were conducted. The first objective is to elucidate the taxonomic status of Chimarrogale hantu from Peninsular Malaysia and its genus among Asiatic water shrews through genetic and morphological analyses. Chimarrogale hantu formed a distinct clade that diverged from other Chimarrogale species (with morphological variation exist and distinct haplotypes) and other genera in the tribe Nectogalini. The C. hantu clade is closely related to the Crossogale phaeura and high genetic divergence were also observed when compared to other species. Chimarrogale hantu was proved genetically and morphologically merit species rank and reclassifying it in the genus Crossogale along with Cr. phaeura. For a better understanding of the relationships among water shrews, future comprehensive reviews of the Sundaic water shrews’ group should include Chimarrogale sumatrana from Sumatra, Indonesia. The second objective is to reassess the taxonomic status of the Hylomys species/subspecies from Peninsular Malaysia and the Sunda Islands. The external morphology and the skull measurements of the studied taxa is within the range of H. s. maxi from Peninsular Malaysia and Sumatra. Hylomys samples from Genting Highlands formed a clade with H. s. maxi from Cameron Highlands and Fraser’s Hill as well as Sumatra. However, they were separated from Sumatran species, H. parvus and H. s. suillus from Java. Low genetic distances were detected among the studied taxa with H. s. maxi and high genetic distances were observed when compared to other Hylomys taxa. Based on these facts, species-level taxonomic status was proposed within the currently recognized Hylomys suillus subspecies lineage from Peninsular Malaysia and the Sunda Islands. Thirdly, the genetic relationships of available Crocidura samples from Peninsular Malaysia and Kalimantan were re-evaluated based on cytochrome b gene sequences to confirm the taxonomic status. The analysis led to the discovery of inter-island species, Crocidura neglecta (samples from Bukit Rengit and Ulu Gombak) and two other Crocidura species, Crocidura cf. monticola 1 from Peninsular Malaysia and Crocidura cf. monticola 2 from Kalimantan. A monophyletic clade of C. cf. monticola 1 was formed from Wang Kelian, Maxwell Hill, Cameron Highlands and Fraser’s Hill which consist of low genetic distance among samples. Other Crocidura samples from Bukit Rengit and Ulu Gombak formed a clade with C. neglecta from Sumatra and Kalimantan and separated with C. cf. monticola 1 with high genetic distance, indicating both as valid species. Meanwhile, the Crocidura sample from Kalimantan formed a clade with the sample from Borneo, C. cf. monticola 3. Interestingly, high genetic distance was evident between these two samples, considering the former as a distinct species, C. cf. monticola 2. All these Crocidura samples (previously known as Crocidura monticola) also form a separated clade with terra typica, C. monticola from Java supported with high genetic distance suggesting that they are specifically distinct on the species level. To conclude, the diversification of three Eulipotyphlan species in Peninsular Malaysia influenced by Pleistocene events and their taxonomic status has been clarified in this study