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Material Analysis and Application for Radio Frequency Electromagnetic Wave Shielding

100%
Yener S., Cerezci O.
Acta Physica Polonica A
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2016
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vol. 129
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issue 4
635-638
EN
Our environment is full of radio frequency (RF) electromagnetic radiation due to rapid progress of wireless communication technologies, which have many applications, such as base stations of mobile communication networks and wireless internet antennas. In the context of Electromagnetic Compatibility (EMC) discipline, the word shield is used to describe any sort of metal sheet or material capable of reflecting, refracting or absorbing electromagnetic radiation (EMR), which is custom manufactured for the target electronic device casing, in a way to intervene any radiation passing to and from the device. Examining of electromagnetic shielding effectiveness (SE) is an important part of not only ensuring electromagnetic compatibility and of protecting electrical and electronic equipment but also protection of human beings against electromagnetic energy exposure as well. In this study, after a brief introduction and review on electromagnetic shielding, material selection and their applications for an indoor environment protection against electromagnetic radiation are explained. Potential electromagnetic shielding values of fabrics found in the market have been analyzed and compared by considering various criteria and requirements. Experimental results show that around 20 dB shielding effectiveness values can be obtained using test fabrics for a typical indoor environment.
2
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Implementation of Microcontroller-Based Memristive Chaotic Circuit

81%
Yener S., Barbaros C., Mutlu R., Karakulak E.
Acta Physica Polonica A
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2017
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vol. 132
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issue 3
1058-1061
EN
In 1971, Leon Chua theoretically postulated that the memristor is the fourth fundamental circuit element, besides the three well-known circuit elements; namely, resistor, capacitor and inductor. For a long time, because of lack of a simple and practical realization, memristor remained just a theoretical element and rarely appeared in the literature. In 2008, a research team from HP laboratories declared that they had found a physical implementation based on thin films, behaving as a memristor. Memristor can offer new opportunities in circuit design due to its nonlinear behavior and memory. Nevertheless, since a cheap and reliable practical implementation of memristor is yet unavailable on the market, the design of such a realization, which mimics memristor behavior, is vital from the point of view of real-world circuit design. In this paper, a new microcontroller-based memristive chaotic circuit is proposed. Presented design has been implemented using an Ardunio Mega board, which solves numerically the dynamics of the memristor-based chaotic system using Runge-Kutta method. It sends the chaotic signals to the outputs of the circuit, using digital-to-analog converters. Chaotic dynamics and the strange attractors are obtained from the circuit using both, the computer simulations and the lab experiments. Considering both simulation and experimental results, it is shown that the proposed circuit mimics well the dynamics of the memristive chaotic system.
3
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An Evaluation of Cu-B₄C Composites Manufactured by Powder Metallurgy

61%
Yener T., Altinsoy I., Yener S., Celebi Efe G., Ozbek I., Bindal C.
Acta Physica Polonica A
|
2015
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vol. 127
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issue 4
1045-1047
EN
In this study, the influences of B₄C ratios on some mechanical and physical properties such as relative density, microhardness and electrical properties of cold pressed Cu-B₄C composites were investigated. Curve fitting is applied for the estimation of electrical conductivity. Commercial copper powders with 40 μm particle size were reinforced with B₄C, with particle size of 40 μm, at ratios of 1, 2, 3 wt.%, for improving mechanical properties of copper used as electrical conductor. Cu-B₄C composites have been fabricated by powder sintering process at a temperature of 900°C for 2 h. The presence of Cu and B₄C, which are dominant components in the sintered composites, were confirmed by X-ray diffraction analysis technique and SEM-EDS. Scanning electron microscope (SEM-EDS) has shown that B₄C particles are distributed homogenously in the copper matrix. The relative densities of Cu and Cu-B₄C composites, sintered at 900°C, ranged from 95.7 to 91.6%. Microhardness of composites ranged from 84.5 to 94.6 HB. It was observed that cold pressed Cu-1 wt.% B₄C composites revealed promising physical properties. Results of electrical conductivity measurement of Cu-B₄C composite material are compared to the results of the model and the overall accuracy level above 96% is obtained.
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