Theses & Dissertations

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https://hdl.handle.net/20.500.14170/206

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Browsing Theses & Dissertations by Subject "Agarwood"
  • Publication
    Simulation study of microwave tomography for agarwood evaluation
    ( 2018)
    Thomas Tan Wan Kiat
    Agarwood or its scientific name, Aquilaria is an expensive and precious non-timber forest product. The problems faced by the agarwood industry are the indiscriminate harvesting of agarwood and ineffective identification and inspection process of Aquilaria tree by the agarwood prospectors and researchers. Hence, microwave tomography is proposed to evaluate agarwood in order to encounter the problems. This technique operates in a safe, non-invasive and insensitive to environmental impacts. A study based on simulation had been performed where 8 and 16 electrodes microwave tomography system were modelled by using COMSOL Multiphysics software. In this study, six profiles were being tested and simulated at 1 GHz. An electric field was simulated based on transverse electric mode to be emitted into the modelled wood with and without agarwood. Besides, the electric field at the receiving electrodes was simulated when the simulated incident field emitted into the modelled wood in the presence and absence of agarwood. The readings of the electric field for both incident and receiving electrodes were recorded to find the difference of the electric field which will be used for image reconstruction. The images for the six profiles were reconstructed based on the sensitivity matrix, the value of measured electric field and image reconstruction algorithms. Algorithms that had been used in this study are linear back projection (LBP), filtered back projection (FBP), Newton’s One-step’s Error Reconstruction (NOSER) and Tikhonov Regularization (TR). The reconstructed images were then analyzed by using mean structural similarity (MSSIM) index. A comparison had been done between image reconstruction algorithms based on the MSSIM indexes. From the obtained results, it shows that NOSER is more suitable to be utilized by MWT system based on 8 and 16 electrodes for effectively evaluating agarwood. Among 8 and 16 electrodes MWT system, 16 electrodes MWT system is more desirable as it can prevent missing of data profile and decrease artefacts in reconstructed images.