Theses & Dissertations

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https://hdl.handle.net/20.500.14170/209

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Now showing 1 - 5 of 352
  • Publication
    Development and characterization of microwave absorber using rice husk/ carbon nanotube composites
    (Universiti Malaysia Perlis (UniMAP), 2016)
    Lee Yeng Seng
    Microwave absorber composites with nanomaterial have tremendous attraction in both industrial and academic world due to their improvement of microwave absorption and material properties. Therefore, the rice husk (RH) or rice husk ash (RHA) with carbon nanotubes (CNT) composites have used to improve several microwave properties of microwave absorber such as dielectric properties, microwave absorption, and shielding effectiveness. In this thesis, the EMI absorbing and shielding of microwave absorbers composted of these RH, RHA, RH/CNTs, and RHA/CNTs composites are presented. The main objectives of this thesis were to characterize the various CNT mixed with RH and RHA composites in microwave properties including dielectric properties, microwave absorption, and shielding effectiveness. It was found that the electric properties and electrical conductivity of RH/CNT and RHA/CNT composites increases with the increase of CNT loading. Innovative use of CNT in RH/CNT and RHA/CNT composites as dielectric absorbers can make significant contributions in our effort to improve the performance of previous work of rice husk absorber. First step of this study, the samples were fabricated in composite form by mixing different weight ratio filler of the RH, RHA, and CNT, with the bonding agent polyester (PE), and the samples were prepared in room temperature by using standard mould and fabrication process. Then, the dielectric properties of the samples were measured using a broadband Agilent dielectric probe and rectangular waveguide methods over the frequency range of 2-18 GHz and 8.2-18 GHz, respectively. The measured dielectric properties were used to calculate the wave impedance, wave attenuation constant, phase constant, and depth of penetration of the incident wave in the composites. These composites then used, to fabricate single layer, multi-layer, fully filled solid, and hollow pyramidal microwave absorbers. The microwave absorbers were studied experimentally for their effectiveness in microwave absorption (reflectivity) and shielding effectiveness in suppressing the broadband electromagnetic interference (EMI). In case of single layer, the reflectivity values of the absorbers were found to less than -20 dB at specific operate frequency with narrowband performance. For multi-layer absorbers, the reflectivity performance is below -10 dB with multiple bands was achieved over 2-18 GHz. The reflectivity of RH based pyramidal absorber were improved from more than -20 dB to less than -40 dB at 2-10 GHz by replace the 1 em RH base layer of pyramidal absorber to 70 wt% RH and 2 wt% CNT composite (RH/CNT -2). In case of hollow pyramidal absorbers, coating layer technique was used to improve the reflectivity performance of hollow pyramidal absorber over 4-18 GHz. The Shielding effectiveness of the 70 wt% RHA and 20 wt% CNT composite achieved more than 25 dB over 8.2-18 GHz in different angle rotation of absorber.
  • Publication
    Development of an embedded active dual axis solar tracking and management system
    (Universiti Malaysia Perlis (UniMAP), 2016)
    Saif Allah Meftah Abgenah
    Solar energy is gaining a rapid popularity as an important source of renewable energy. Per se, it is vital for those who aim towards maximizing the total gain of its energy to utilize a method that will insure maximum energy gain by tracking the sun's position during its daily cycle. This research targets the means of collecting the utmost solar energy distributed by the sun by implementing a six sensors dual axis tracking mechanism that will track the sun as it changes its position during its daily cycle. This tracking system is developed based on an open source embedded microcontroller using an open source code that can be easily modified. The tracking system is built on an Atmel ATmega328P microcontroller as the main data collection and decision making unit for the system. This microcontroller is a part of an Arduino Uno developer's board that has a number of General-purpose input/output GPIOs to connect different peripherals to be used in the tracking system and controlled by the microcontroller. These peripherals consist of six light dependent resistors LDR sensors to be used for sensing the sun's position by reading the light intake and sending the readings to the microcontroller to be processed, the LDRs with the most light intensity readings will be the targeted position for the tracking system to move the solar panel towards using two servo motors which will also be connected to the Arduino Uno via the GPIO pins, the two servo motors will have different tasks, one servo motor will be in charge of moving the solar panel vertically and the other servo will move the solar panel horizontally. The performance and characteristics of the six sensors dual axis solar tracker are experimentally analyzed to show the need and advantages of using this method of tracking system. The tests show that the designed embedded solar tracker system is efficiently tracking the sun and collecting much energy as compared to the four sensors tracking system and the static solar panels. In addition the proposed system has advantages over other system represented by real time tracking based on an active sun position computing techniques. The embedded solar tracking system offers cost effective and efficient solar tracking and open source programming which allows for future enhancement and modification.
  • Publication
    The impact of deposition layer and annealing temperature towards BST thin film characteristics
    (Universiti Malaysia Perlis (UniMAP), 2016)
    They Yee Chin
    Ferroelectric materials which consist of the complex oxides with perovskite structure provided multifunctional have been attracted the eyes of the researchers in the application of electronic and optical devices. The attractive part of these materials is the sensitivity on physical properties to temperature, external electrical, magnetic, and mechanical stress, particularly near the temperatures of phase transitions. Wide range of electronic applications make used of these ferroelectric materials due to its dielectric, electric, temperature, magnetic and optical properties. The properties in Barium Strontium Titanate (BST) thin film causing it become extensively studied and emerged in to the application in high density DRAM, microwave phase shifter, IR sensing, humidity and gas sensor, tunable filters, piezoelectric actuator, voltage controlled oscillators, and varactors. The aim for this study is to investigate the main effect interaction of the Bao.sSro.s Ti03 thin film number of deposition layer and annealing temperature in terms of microstructure and electrical properties to the BST. Besides that, to find the main effect relation of the electrical properties of the BST thin film. The study on the Bao.sSo.s Ti03 thin film is prepared using sol-gel technique on silicon substrate. Throughout the study, the BST solution is deposited on the Pt/Si02/Si substrate by spin coating method in order for the purpose of investigating the microstructure of the thin films. Moreover, all the samples are deposited with combination of 2 different deposition layer and annealing temperature. Physical and electrical characterization of all the samples is done. The results showed that the grain size and surface roughness of the samples increased from 38.67 to 90.78 and 1.92 to 9.41 , respectively as the deposition layer and annealing temperature increased. In addition, the dielectric constant of the samples also increased from 136.78 to 783.91 as the deposition layer and annealing temperature increased. Thus, the physical and electrical characteristics of the thin films are related on to another. This study has shown the effects of the deposition layer and annealing temperature of BST sol-gel thin films on the structure, microstructure and dielectric properties. A clear main effect between the surface roughness, grain size and the dielectric properties has been discovered in the BST sol-gel thin films. The objectives achieved where the increase in deposition layer and heat treatment temperature increased the crystallinity, grain size, surface roughness and contribute to the non-ferroelectric materials such as grain boundaries. This resulted in the direct effect on the increase of the thin film dielectric constant and tunability.
  • Publication
    Development of an embedded wireless sensor network platform based on SBC application
    (Universiti Malaysia Perlis (UniMAP), 2016)
    Saja Zaid Hasan Al-Rubaye
    With more than a decade of dense researches and development, wireless sensor network (WSN) technology has been appearing as solution to many applications. This thesis concerns of designing a wireless sensor network system which has been developed using open-source hardware platforms, ZigBee and Raspberry Pi. This design has advantages of low power consumption, low-cost and scalable in terms of the type of sensors and the number of sensor units that makes it well suited for a wide range of applications related to sending and receiving data. Although use of Raspberry Pi in the design, make it flexible, cheaper and full allocation. Python code has been used in programming the components to get a smaller code and avoid errors in programming and can be developed rapidly in the future. The choice of Raspbian operating system for Raspberries was to have a highquality, stable and scalable operating system in which supported by Raspberry manufacturer company. Raspberry Pi act as a base station for ZigBee protocol in the wireless sensor network and collects the data from different sensors, and provide multiclients services including data display. As future development, data can be seen remotely at the base station via website.
  • Publication
    Development of indoor wireless optical CDMA system for local-area networks (LANs) and health-care continuous monitoring
    (Universiti Malaysia Perlis (UniMAP), 2016)
    Emad Ahmed Mubarak
    Optical wireless communication (OWC) is an important area of research that offers a number of advantages over radio frequency based systems. These advantages include high bandwidth, free licensed spectrum band, high security, ease of installation, immunity to induced electromagnetic interference (EMI), and low-cost subsystems. The focus of this thesis is on indoor owe channels and systems. The main limitations ofindoor owe systems include Inter-Symbol Interference (lSI) due to multi path dispersion, background noise, and Multiple Access Interference (MAl) and Phase-Induced Intensity Noise (PUN) associated with simultaneous multi-user systems. The former degrades the signal-to-noise ratio (SNR), while the latter limits the maximum achievable data rate. This thesis investigates the use of an optimised divergence angle of the transmitter in a room structure of 1-cell and 4-cell configurations to achieve a higher transmission bandwidth and a more uniform optical power distribution, resulting in lower IS I. This work also investigates the use of Optical Code Division Multiple Access (OCDMA) technology based on a Zero Cross Correlation (ZCC) code in optical wireless networks to reduce the impairments such as MAl and PIIN that exist in the system and thus improve the overall system performance. The obtained results are compared with a Flexible Cross Correlation CFCC) based system. As a result, the indoor wireless OCDMA (W-OCDMA) system based on 4-celJ configuration and using the ZCC code can accommodate a large number of users with less transmission power and a higher data rate compared to the 1-cell configuration or using the FCC code. The 4-cell configuration system based on the ZCC code offered 42% and 150% larger cardinality at the edges, and the comers of the room respectively, compared to the 1-cell configuration. In addition, this system also offered 55%, 47%, 51% larger cardinality at the centre, the edges, and the comers of the room, respectively, in contrast to the FCC code. Furthermore, this research also investigates the use of infrared technology in healthcare monitoring to develop a mobile medical system. This is because existing technology is generally based on radio frequency (RF) systems, which might suffer from electromagnetic interference (EMI). Additionally, the effect of the radiation field on medical equipment may lead to misdiagnosis. In answer to these issues, optical wireless links between the medical sensors and the receiver in the middle of the ceiling in a hospital room was examined. From the results, the power efficiency of the mobile optical wireless system to ensure the communication between medical sensors and the receiving point was established. Furthermore, the minimum required transmitted power for the required performance was determined, so as to achieve a higher power autonomy. The results also show that the requirements of a healthcare monitoring application for medical nodes of up to 10 nodes, considering a data rate lower than 1 Mbps, can be achieved using infrared technology. The results prove the superiority of the optical wireless technology over the conventional radio-based communication network in healthcare monitoring systems.