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Electromagnetic shielding effectiveness of cement powder mixed with graphite for mitigation against electromagnetic interference

Yee, See Khee (2015) Electromagnetic shielding effectiveness of cement powder mixed with graphite for mitigation against electromagnetic interference. PhD thesis, Universiti Tun Hussein Onn Malaysia.


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The potentially harmful impacts of electromagnetic interference EMI) on the safe operation of electronic and electrical equipment are drawing serious attention due to reliance on electrical and electronic devices in telecommunication, mobile phone networks, radar systems, banking, public defence, and others. Em induces unwanted voltage and currents on the victim device, thus affecting the performance of the devices. Electromagnetic shielding which is commonly applied as the last resort in reducing the radiated emission hrn digital circuibies is switching its territory to building construction in an attempt to provide similar benefits to the sensitive and critical equipment inside the building. It is reported that concrete constructed with different weight fractions of material, moisture content (MC), and the effect of reinforcement bar will produce different shielding effectiveness (SE). The parameters that determine the SE of building materials include their dielectric constant, loss tangent and relative permeability. These parameters can be obtained based on dielectric measurement. Dielectric measurements need to be repeated when the composition of the building material changes. In this work, the SE of cement powder with additional additives, such as graphite powder, iron powder and nickelzinc ferrite powder were investigated. It has been found that dielectric constant determines the trend.of the reflection loss as it plays significant roles in establishing the characteristic impedance of the material. On the other hand, absorption loss and multipIe reflection loss are more dependent on the thickness of material. Based on the results, it is recognised that graphite powder is an efficient and practical additive in enhancing the SE of cement power compared with others. Cement-graphite powder provides more than 60 dB of shielding in between 200 MHz to 2000 MHz when the percentage ofthe graphite powder in the mixture is 30% and the thickness is 10 cm. Novel predictions, which are based on the neural network and piece-wise fitting has been proposed to predict the SE of cement-graphite mixture with different percentages of graphite powder. SE predictions which are based on piece-wise fitting and neural network produces 1.94 dB and 0.029 dB of error at 900 MHz and 1800 hfI-h respectively when it is used to predict the SE of cement-graphite that contains a 17% of graphite in between 100 MHz to 2000 MHz. In summary, this research investigates the effect of different additives on the SE of cement powder. The prediction based on the neural network indicates a sample with a thickness of 7 cm and 30% graphite is able to provide above 40 dB of shielding ranging between 100 MHz and 2000 MHz. Such prediction can be anticipated for implementation in building construction design.

Item Type: Thesis (PhD)
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK7800-8360 Electronics
Depositing User: En. Sharul Ahmad
Date Deposited: 10 Apr 2016 06:49
Last Modified: 10 Apr 2016 06:49
URI: http://eprints.uthm.edu.my/id/eprint/7905
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