154 research outputs found
Prof. Madya Dr. Azrina hasilkan bahan api hidrokarbon melalui penukaran CO2 bermangkin cahaya melalui partikel nano
No full textGAMBANG, 7 Jun 2021 - Penyelidikan bertajuk Nanoparticles for CO2 Conversion yang dijalankan oleh Profesor Madya Dr. Azrina Abd Aziz, 35, memfokuskan kepada sintesis pemangkin foto komposit nano baharu menggunakan kaedah penganodan elektrokimia, pemendapan elektrokimia dan rendaman
Pakej pembelajaran untuk kanak-kanak / Siti Azrina Abd Aziz
No full textPakej Pembelajaran untuk Kanak-kanak (PPK) is multimedia software, which is developed in CD-ROM form using Bahasa Melayu as the communication language The main users of this system are children aging between 3 to 6 years old. The learning materials for this software include the basic of reading, colouring, listening to the music and counting. PPK is developed using Macromedia Director 8.0, Paint, Sound Recorder, Paint Shop Pro and others. There are several main reasons why PPK is developed such as the evolving technology, less interest in children to learn, no time and guidance to teach the children, no suitable software, problems with existing learning tools and others. The methodology that has been chosen is Rapid Application Development (RAD) that uses prototyping concept. This is because it is difficult to get the information from the main users whom are the children.
The information for developing this system is gathered from reading, researching and interviewing. The sources of the information are Internet, books, kindergarten
teachers, parents and also from lecturers. There are a few teaching kindergarten children techniques that I have used in PPK such as Montessori method and "cahayaku" concept. Last but not least I hope this thesis can give benefit and invaluable information for everyone
Improving the realibility of zinc oxide surge arrester / Azrina Abd Aziz and Tapan K. Saha
No full textReliable surge arresters can avoid unnecessary costs associated with equipment damage and ineffective lightning protection techniques. The most recent advance in the arrester is the Zinc Oxide arrester. However, some of the arresters can be damaged during their operation. The major cause of failure of the arresters is the surface flashover. This study aim to examine the surface flashover effect on ZnO arresters and develop method to reduce its effect and enhance the performance of the arrester. The experiment was designed to study the surface flashover effects. The ZnO blocks supplied by manufacturers were tested under different environments during multipulse currents. The observed degradation was qualitatively explained in terms of physical changes on the blocks and their electrical characteristics. The study found that the environments surrounding the ZnO blocks had no impact on surface flashover. The major finding leads to the possible contribution of the quality of surface material coating in protecting the blocks from surface flashover
Distributed connected dominating set techniques for energy-efficient topology control in wireless sensor networks.
No full textDespite the considerable research efforts devoted to extending the lifetime of wireless sensor networks (WSNs) by making them more energy efficient, there are still a number of unresolved issues. Among the possible solutions for improving their overall energy efficiency, topology control has significant potential. Distributed topology control is a difficult problem, and optimal solutions are not possible except for very simple topologies. Because of this, heuristic methods are used, but the solutions proposed in the research literature are usually tested with overly simplistic simulation models and consequently they fail to perform satisfactorily in real networks. The research project reported in this thesis proposes three new topology control methods that are tested on highly realistic simulation models calibrated with data collected on an experimental wireless sensor network. These models accurately handle interference effects, realistic transmission ranges and imperfect communication links. Additionally, the correctness of the proposed methods was verified using theoretical analysis. Two leading algorithms were used as benchmarks. Based on the outcomes of a thorough literature review and analysis of existing techniques, distributed connected dominating set (CDS) approach was selected as the starting point for the design of the proposed algorithms. The proposed algorithms are not only distributed but also use localized information for computing a CDS. Given that the CDS serves various tasks in a WSN, a fair load distribution strategy was adopted to prolong the network lifetime. This strategy takes into account the remaining energy levels at each node when choosing the eligible CDS nodes. The first topology control technique called the three-phase single initiator (TPSI) was developed to form a small CDS for medium and dense networks (i.e., in deployments when average node degree is relatively high) with minimal communication overhead, computational complexity and energy consumption. The simulation results demonstrate that the TPSI algorithm generates a small CDS for both medium and dense networks but not for sparse networks. These results also prove that the impact of network density on performance of an algorithm is significant and cannot be ignored. The second technique, single-phase single initiator (SPSI) on the other hand was proposed for applications that require fast convergence, and is best suited to WSN applications that have sparse topologies. The simulation results show that SPSI can generate a small CDS for sparse networks using low message overhead and energy consumption, and compute a CDS faster than the TPSI algorithm. The third one, the Two-phase multiple initiator (TPMI) algorithm adapts well to dynamic topology changes, thus it is suitable for applications that require frequent topology updates. Instead of relying on a single initiator to construct the CDS as in the TPSI and SPSI, the TPMI algorithm uses multiple initiators. The simulation results show that although the CDS size of TPMI is larger than the ones generated by TPSI or SPSI, it outperforms them in terms of energy consumption, network lifetime and convergence time in networks with rapidly changing topologies. Best suited algorithm for a particular installation can be selected manually, or by using some measurement techniques, the structure of a network can be probed to activate the optimal method automatically
Distributed connected dominating set techniques for energy-efficient topology control in wireless sensor networks.
No full textDespite the considerable research efforts devoted to extending the lifetime of
wireless sensor networks (WSNs) by making them more energy efficient, there
are still a number of unresolved issues. Among the possible solutions for improving
their overall energy efficiency, topology control has significant potential.
Distributed topology control is a difficult problem, and optimal solutions are not
possible except for very simple topologies. Because of this, heuristic methods
are used, but the solutions proposed in the research literature are usually tested
with overly simplistic simulation models and consequently they fail to perform
satisfactorily in real networks.
The research project reported in this thesis proposes three new topology control
methods that are tested on highly realistic simulation models calibrated with data
collected on an experimental wireless sensor network. These models accurately
handle interference effects, realistic transmission ranges and imperfect communication
links. Additionally, the correctness of the proposed methods was verified
using theoretical analysis. Two leading algorithms were used as benchmarks.
Based on the outcomes of a thorough literature review and analysis of existing
techniques, distributed connected dominating set (CDS) approach was selected
as the starting point for the design of the proposed algorithms. The proposed
algorithms are not only distributed but also use localized information for computing
a CDS. Given that the CDS serves various tasks in a WSN, a fair load
distribution strategy was adopted to prolong the network lifetime. This strategy
takes into account the remaining energy levels at each node when choosing the
eligible CDS nodes.
The first topology control technique called the three-phase single initiator (TPSI)
was developed to form a small CDS for medium and dense networks (i.e., in
deployments when average node degree is relatively high) with minimal communication
overhead, computational complexity and energy consumption. The
simulation results demonstrate that the TPSI algorithm generates a small CDS
for both medium and dense networks but not for sparse networks. These results
also prove that the impact of network density on performance of an algorithm is
significant and cannot be ignored.
The second technique, single-phase single initiator (SPSI) on the other hand was
proposed for applications that require fast convergence, and is best suited to WSN
applications that have sparse topologies. The simulation results show that SPSI
can generate a small CDS for sparse networks using low message overhead and
energy consumption, and compute a CDS faster than the TPSI algorithm.
The third one, the Two-phase multiple initiator (TPMI) algorithm adapts well to dynamic
topology changes, thus it is suitable for applications that require frequent
topology updates. Instead of relying on a single initiator to construct the CDS as
in the TPSI and SPSI, the TPMI algorithm uses multiple initiators. The simulation
results show that although the CDS size of TPMI is larger than the ones generated
by TPSI or SPSI, it outperforms them in terms of energy consumption, network
lifetime and convergence time in networks with rapidly changing topologies.
Best suited algorithm for a particular installation can be selected manually, or by
using some measurement techniques, the structure of a network can be probed to
activate the optimal method automatically
Syngas fermentation to bioethanol
No full textSyngas fermentation is one of the most favorable biochemical conversion techniques for the production of biofuels [1 4]. In this process, syngas is used as a substrate for microorganisms [2], which is produced through a thermochemical process from biomasses [5 8]. Commonly, carboncontaining lignocellulosic biomass (forest residue, coconut shell, empty fruit bunch of palm oil, municipal solid waste, etc.) is converted into gases, such as carbon dioxide (CO2), carbon monoxide (CO), and methane (CH4) [5,6,9 11], and it is further converted into biofuels by utilizing carbon-fixing microbes [1,2,12]. Biomass-derived syngas fermentation from gasification of carbonaceous feedstocks is the most promising conversion technologies of biomass to liquid biofuels. Bioethanol along with acetate, butanol, butyrate, formaldehyde, peptone, and methane (produced from chemical catalytic and biosynthetic processes) is converted to clean and sustainable transportation fuel produced from the lignocellulosic biomasses, such as forest or agricultural biomass [4,5]. Syngas comprises various mixture of CO, CO2, H2, and CH4, which can be produced through gasification of lignocellulosic biomass [6,13]. The composition of syngas varies with the type of biomass used as the feedstock. Different types of gasifiers, such as downdraft, fluidized-bed, and fixed-bed, are used to produce syngas, and it goes through several cleaning stages before entering to the fermenter. Up to this time, it is an on-going research at laboratory scale and novel concepts are integrating to develop the commercial scale
Nanocrystal TiO2 Engulfed SiO2-Barium Hexaferrite for Enhanced Electrons Mobility and Solar Harvesting Potential
No full textBarium hexaferrite embedded-silica-titania photocatalyst (TiO2-SiO2-BaFe12O19) was synthesized through sol-gel, liquid catalytic phase transformation and solid reaction routes. The magnetic photocatalyst was aimed to harvest the photoenergy from the sunlight, minimize the electron-holes recombination rate, improve the long lifetime charge-carriers transfer to maximize the photocatalytic activity and enhances the separation and reusability of it. The as-synthesized photocatalyst was characterized and the photocatalytic activity was evaluated for the reduction of 2, 4-dichlorophenol (2, 4-DCP) under direct sunlight. The presence of SiO2 interlayer in TiO2-SiO2-BaFe12O19 prevents the phase transformation of magnetic core. TiO2-SiO2-BaFe12O19 benefits the magnetic separation with appreciable magnitude of coercivity (5035.6 Oe) and saturation magnetization (18.8256E-3 emu/g), respectively. The ferrite ions from the magnetic core which dispersed into TiO2 matrix exhibited an evident shift of the absorption in the visible region. This was again confirmed with the reduced band gap energy of 1.90 eV. Furthermore, TiO2-SiO2-BaFe12O19 destructed 100% of 2, 4-DCP compound within 150 min under very bright sunlight with an average irradiance of 820.8 W/m2 (results not shown). The embedding of BaFe12O19 with a SiO2 layer onto TiO2 nanocrystals contributed for an excellent solar-light utilization and ease magnetic separation of the nanosized photocatalyst
Strength and microstructural properties of mortar containing soluble silica from sugarcane bagasse ash
No full textSugarcane bagasse is among the abundantly available waste in agriculture industry. The proportion of siliceous ashes after the incineration process is one of the attractive features in sugarcane bagasse. However, its low bulk density would result in an additional issue for further use as cement replacement material, since higher replacement volume will bring more hydrophilic particles of sugarcane bagasse ash into the mixture. Therefore this research aims to extract the reactive silica from sugarcane bagasse ash and increase its bulk density by converting it into soluble form. The process was divided into three stages, which were pre-treatment and incineration of sugarcane bagasse, conversion into soluble form, and production of mortar specimen. Soluble silica from sugarcane bagasse ash was used to partially replace cement content in mortar, hence its effect on the hydration process can be evaluated. Compression test and scanning electron microscope analysis were performed to observe its effect on the strength and microstructural development of mortar framework. The results show that the inclusion of soluble silica would enhance the early hydration rate and improve the consolidation of cement matrix via additional calcium silicate hydrate formation, which would increase the capability of internal mortar framework to distribute loads and achieve higher strength
A distributed topology control method for improving energy efficiency of wireless sensor networks
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