https://ptsldigital.ukm.my/jspui/handle/123456789/388928 2026-06-12T10:34:31Z 2026-06-12T10:34:31Z Mohammad Zahirul Islam Mollah (P108969) https://ptsldigital.ukm.my/jspui/handle/123456789/783416 2026-06-12T04:52:55Z 2024-12-12T00:00:00Z

Title: Developing woven jute-matrix composite for radiation effects and shielding efficacy evaluation Authors: Mohammad Zahirul Islam Mollah (P108969) Abstract: Concerned about environmental issues, non-biodegradable synthetic, and chemically modified synthetic polymeric materials produce primary and secondary microplastics that affect the ecosystem. The traditional lead-based shielding material has detrimental effects on humans and the environment. Composite products comprising naturally occurring polymers, deployed into matrixes are splendid creations of modern science that ultimately lessen the negative environmental consequences of synthetic polymers. Natural fibers have been utilized in different sectors due to their biocompatibility, biodegradability, and availability. The woven jute and matrix (polypropylene, polyester, and epoxy resin) have been selected to fabricate reinforcing semi-degradable materials using hand layup stacking sequence techniques. The radiation processing method is applied to improve the physico-mechanical properties of woven jute-matrix composites. The mechanical, thermal, topographical, and chemical properties have been examined using UTM (universal testing machine), DSC-TGA (differential scanning calorimetry-thermogravimetric analysis), SEM-EDS (scanning electron microscopic-energy-dispersive spectroscopy), and (Fourier transform infrared spectroscopy) FTIR for treated and untreated samples of woven jute composites. The impregnated woven jute-matrix composites like “jute-polypropylene (jute-PP)”, “jute-polyester resin (jute-PR)” and “jute-epoxy resin (jute-EPR)” were developed significantly. Firstly, the mechanical properties of 3-layer sequence composites achieved are superior to one- and 2-layer sequence composites. In evaluated jute-matrix composites: initial tensile strength (29 MPa), tensile modulus (1.4 GPa), bending modulus (1.88 GPa), and impact strength (5.88 kJ/m2) were higher in a one-layer jute-polyester resin composite (S4), and Eb% (4.4) was higher in the one-layer jute-polypropylene (S1) composite. Secondly, the 5 kGy doses showed the effective enhancement of mechanical properties. The tensile strength increase (45.37 %) was higher in S7 (one-layer jute-epoxy resin composite) than in S1 (one-layer jute-PP), and S4 (one-layer jute-EPR). The bending strength of 22.87 % increase (43 MPa) was achieved in S1 which is superior to S4 and S7. The tensile modulus increased (40 %) in S1 is superior to S4 (27.35 %) and S7 (10.38 %). The bending modulus was increased tremendously in S1 due to the thermoplastic nature of PP, while S7 is superior to S4 due to the thermosetting nature, same behaved at elongation at break (Eb%) which is the highest Eb % in S1. Except for S1, all the Eb % performed antagonistic effects to impact strength due to radiation, while impact strength (15.64 % kJ/m2) increased in S4 is superior to S7. The water uptake decreased in irradiated samples, thermal properties showed remarkable changes indicating glass transition, crystallization, and degradation of jute-matrix composites. The FTIR and SEM-EDS represented that jute and matrix created uniform bonds with jute-matrix good adhesion which helped to enhance mechanical properties. Thirdly, the shielding efficacy of jute-PP, jute-PR, and jute-EPR composites was performed in the thumb rule indicating the highest mass attenuation coefficient (MAC) in S1. At the same time, S4 showed the lowest linear attenuation coefficient (LAC), a good half-value layer (HVL), a tenth-value layer (TVL), and a sixth-value layer (SVL). Consequently, S4 showed the lowest mean free path (MFP) and highest radiation protection efficiency. Thus, woven jute-matrix composites can be applied to reduce dependency on lead-based shielding materials. The findings of woven jute matrix composites can play a vital role in developing polymeric materials for engineering applications in environmental remediation.

2024-12-12T00:00:00Z Abu Hanif https://ptsldigital.ukm.my/jspui/handle/123456789/783415 2026-06-12T04:52:50Z 2024-11-28T00:00:00Z

Title: Meta resonator based miniaturized planar microwave sensors for material permittivity characterization Authors: Abu Hanif Abstract: Material permittivity is essential in applications like material characterization, environmental monitoring, and quality control, as it determines the ability to store electrical energy and affects electromagnetic (EM) wave propagation. Low permittivity materials are essential in integrated circuit design to reduce parasitic capacitance and propagation delay, thus ensuring electronic system performance. Measuring material permittivity precisely is challenging due to the limited sensitivity of measurement equipment, complex calibration processes, environmental factors, frequency dependence issues with material interfaces, sample size and uniformity. These challenges impact material characterization, device design, and performance. Techniques like the resonance method, resonant cavity method, free space method, and microstrip line method are being developed to measure permittivity, with the resonance based method being popular for its compact size, low cost, easy fabrication, and high sensitivity. Metamaterial technology is promising for enhancing the sensitivity of resonance-based sensors in the microwave frequency range. This research focuses on designing two microwave sensors for permittivity measurement with enhanced sensitivity and a compact size of 25 mm × 20 mm × 0.79 mm. The first sensor, a labyrinth-shaped circular split ring resonator (LC-SRR), is designed to operate at 2.57 GHz. This sensor achieves a high sensitivity of 10.50% for permittivity variation. The LC-SRR sensor was calibrated for a relative permittivity range of 2.2 to 4.3. The second sensor is a dual-notch maze-shaped complementary split ring resonator (MCSRR) that operates at 2.88 GHz and at 4.05 GHz. The MCSRR sensor shows sensitivities of 10.48% for the first notch and 17.36% for the second notch and calibrated for a relative permittivity range of 2.2 to 11.2, respectively. Both sensors are validated by fabricating and measuring prototypes. An inverse regression model is utilized to predict the permittivity of the material under test (MUT) directly from the sensor's resonant frequency. The contribution of this thesis is to design a split ring resonator (SRR) and a complementary split ring resonator (CSRR) that adopt a unique and compact structure, featuring high electromagnetic (EM) field intensity. This design contributes to a more precise sensing mechanism in the microwave frequency range.

2024-11-28T00:00:00Z Md Afzalur Rahman https://ptsldigital.ukm.my/jspui/handle/123456789/783414 2026-06-12T04:52:54Z 2025-01-21T00:00:00Z

Title: Metamaterial-based multiband 3D MIMO antenna systems design for 5G IoT applications with machine learning validation Authors: Md Afzalur Rahman Abstract: The rapid advancement of wireless communication technologies, particularly with the introduction of 5G and Internet of Things (IoT) applications, necessitates sophisticated antenna systems that support high data rates, improved connectivity, and a variety of functionalities. As the number of IoT-connected devices continues to rise globally, there is a pressing need for a wireless communication system capable of connecting numerous IoT devices via a single feedline antenna system. Such an antenna should facilitate both short-range and long-range communication by covering microwave and millimetre wave frequency bands with a single input. Multiple Input Multiple Output (MIMO) antennas are widely recognized for enhancing wireless communication stability and minimizing multipath fading loss. To further enhance the functionality of compact MIMO antennas, the integration of metamaterials (MTM) holds significant promise. This thesis focuses on the development and analysis of a metamaterial-integrated multiband and wideband MIMO antenna system optimized for 5G-IoT applications and designed for microwave and millimetre wave frequencies with 360-degree coverage and verify the antenna outputs using Machine Learning (ML) verification technique. By leveraging the unique properties of metamaterials, the proposed antenna system achieved superior performance in bandwidth, gain, and radiation efficiency across multiple frequency bands. The ML models, trained with a comprehensive dataset derived from simulated results, provide accurate predictions of critical parameters such as bandwidth, efficiency, and realized gain. Initially, a super wideband (SWB) 4-port MIMO antenna is developed incorporating metamaterials (MTM) operating within the 1.9 GHz to 20 GHz microwave spectrum. The integration of a metamaterial-based Metasurface improved efficiency from 77% to 89% and increased the realized gain from 4.5 dBi to 8 dBi, while isolation at the perimeter improved from 20 dB to 25.5 dB. Additionally, another 4-port MIMO antenna is developed with MTM to cover both microwave (3.5 GHz and 5.2 GHz) and millimetre wave bands (28 GHz). Metamaterials enhanced isolation levels from 20 dB to 24 dB in the microwave range and from 26 dB to 32 dB in the millimetre wave range, with maximum realized gains of 5.3 dBi and 9.3 dBi, respectively. To improve channel capacity and accommodate diverse IoT applications, developed a 3D 6-port MIMO antenna providing 360-degree radiation coverage for both microwave (2-7 GHz and 13-17.5 GHz) and millimetre wave (25-39 GHz) frequency bands, achieved a maximum realized gain of 9.9 dBi. Expanding on this, a 24-element 3D 12-port MIMO antenna integrated with MTM is developed, offering 360-degree radiation patterns in both microwave (2.5-8.4 GHz and 13.4-16.5 GHz) and millimetre wave (26-48 GHz) bands, with a maximum realized gain of 11.5 dBi. All antennas are simulated using CST simulation software, fabricated with Rogers RT-5880, and measured. Moreover, a machine learning verification technique was applied to validate antenna performance metrics, including gain, bandwidth, and efficiency, achieving over 90% accuracy and ensuring the reliability of the proposed antenna designs. The proposed 3D MIMO antennas, with their microwave and millimetre wave 360-degree coverage, demonstrate significant potential for future 5G wireless communication and IoT applications.

2025-01-21T00:00:00Z Khoir, Aulia Nisa'ul https://ptsldigital.ukm.my/jspui/handle/123456789/777866 2026-06-12T04:52:52Z 2023-05-31T00:00:00Z

Title: Distribution pattern of historical and future conditions of biomass burning events over Malaysia - Indonesia Authors: Khoir, Aulia Nisa'ul Abstract: Biomass burning haze in Malaysia - Indonesia has become a recurring annual issue. Fire hotspot monitoring and projection are the efforts to control the forest and land fire disasters that cause the biomass burning haze. The study assesses the historical distribution and projected future condition of biomass burning (BB) activities in Malaysia - Indonesia. The study performed Empirical Orthogonal Function (EOF) and Rotated-EOF (REOF) to investigate the historical distribution of biomass burning and Aerosol Optical Depth (AOD) as aerosol emission proxy from 2001 to 2020 years. Climate indices are also included to analyze their impacts on BB and AOD distribution. The future condition of BB events (2041 – 2070 years) is projected by applying the Fire Weather Index (FWI), a hotspot danger rating system based on the future climate projection data from CORDEX-SEA. The future climate projection is performed under two scenarios, business-as-usual (RCP4.5) and worst-case scenario (RCP8.5). The results suggest that the primary regime of BB over Malaysia - Indonesia, represented by the distribution of BB and AOD, comes from the burning activities that primarily occurred in the Kalimantan and Sumatra. The research work also shows that the presence of weather anomalies, namely El Niño South Oscillation (ENSO) and positive Dipole Mode (DM), affect the distribution of the BB events and AOD. Additionally, the projection of fire hotspots shows an overall increase in future fire activities under the RCP4.5 and RCP8.5 scenarios. However, the average percentage increase of FWI in the future (2041 – 2070) under the RCP8.5 scenario is 43.9%, higher than under the RCP4.5 scenario, which is 39.7%. In short, this study explains how the fire events varied over the past two decades Malaysia – Indonesia and the future fire danger rating for mitigating action consideration. Lastly, the study is expected to be one effort to prevent and reduce the impact of BBH haze in Malaysia – Indonesia.

2023-05-31T00:00:00Z