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Elements of Bioelectromagnetics
Published in Jitendra Behari, Radio Frequency and Microwave Effects on Biological Tissues, 2019
Bioelectromagnetics deal with a complexity of biological systems being interrogated by electromagnetic waves, which are emitted by manmade devices or sources. As such the electromagnetic environment consists of natural radiations and manmade EMFs that are produced either by design or as a consequence of the use of electrical devices and systems. Based on this, populations are now blanketed to varying degrees of EMFs, and their levels will continue to increase as technology advances.
A tunable metasurface based on Vanadium dioxide for Broadband RCS reduction
Published in Waves in Random and Complex Media, 2021
Hai-Ning Ye, Xin-Lei Zhang, Yan Zhao, Hai-Feng Zhang
According to the relative relationship between the echo direction and the position of the detection radar, RCS is divided into monostatic RCS and bi-static RCS. Comparing the RCS of chessboard metasurface with the RCS of PEC of the same size, the monostatic RCS reduction curves are separately plotted as shown in Figure 7. Analyzing the calculation results, it’s obvious that the proposed chessboard can gain less than −10 dB RCS reduction in 14.97–23.97 GHz (RB= 46.23%). In addition, there is a RCS reduction valley point at 6.75 GHz in the state I. Besides, at the state II, the operating frequency band of the reduced RCS has a significant shift, bringing about −10 dB RCS reduction in 7.10–14.13 GHz (RB= 66.23%) and 24.10–25.87 GHz. Hence, it’s proved that the working frequency ranges from 6.40 GHz to 25.87 GHz. What’s more, there is no doubt that the proposed model is capable of working in different frequency bands with changes in temperature, leading to a possibility to better adapt to the complex electromagnetic environment.
Analysis of SAR reduction to human head with plasma photonic crystals shield using ICCG-SFDTD method
Published in Radiation Effects and Defects in Solids, 2021
Da-Jie Song, Yun Zhang, Jin Xie, Yu-Jie Liu, Hong-Wei Yang
MRI is considered a safe technology because it relies on the spatial encoding of atomic nuclei (mainly protons) position in a static magnetic field by irradiation with radio-frequency (RF) pulses as opposed to ionizing radiation (11). MRI systems are routinely used for clinical diagnosis and can produce high-quality images with relatively low static magnetic field strengths (12). However, ultra-high-field MRI systems are required in order to achieve enhanced signal-to-noise ratio in images and to improve resolution for spectroscopy applications in the future, challenges exist as significantly strong electric field and eddy currents can result in more RF energy deposits that potentially initiate tissue heating and cause other side effects, such as alterations in visual, auditory and neural functions (13). SAR (14) is the most frequently used parameter for monitoring and quantifying the power deposition to subjects in the electromagnetic environment. Strict exposure limits to SAR levels are imposed by the International Commission on Non-Ionizing Radiation Protection.
Design and analysis of wireless power transmission devices for multi-degree-of-freedom actuator applications
Published in Journal of the Chinese Institute of Engineers, 2020
Zheng Li, Hanming Zhang, Shihao Gao
Due to the high working frequency of the WPT system, high-frequency electromagnetic fields will inevitably enter the surrounding environment of the coupling coil. At this time, if a living body is exposed to the electromagnetic environment exceeding the safety limit for a long time, it will cause serious harm. At the same time, objects with the same resonance frequency around the coupling coil will also become the load of the WPT system, which will greatly influence the transmission efficiency of the system. In order to increase coils’ coupling, improve power transmission efficiency and reduce the influence of WPT system on the magnetic field environment in the non-working area, a magnetic shield was added to the transmitting end of the WPT system.