• Title/Summary/Keyword: electromagnetic fields

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Considering on the Ground Reflection Effect on the Electromagnetic Fields due to Lightning Channel

  • Izadi, Mahdi;Ab Kadir, Mohd Zainal Abidin;Hajikhani, Maryam
    • Journal of Electrical Engineering and Technology
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    • v.8 no.4
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    • pp.824-831
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    • 2013
  • Lightning electromagnetic fields are important issues for the evaluation of lightning induced overvoltage on power lines and for setting the appropriate protection level for power networks. Such electromagnetic fields are strongly dependent on lightning return stroke currents at different heights along the lightning channel. On the other hand, the ground reflection factor due to the difference between the return stroke channel impedance and the equivalent ground impedance at channel base can have an effect on the shape of the return stroke currents by entering additional reflected currents into the channel. In this paper, the effect of the ground reflection factor on the return stroke currents at different heights along a channel and the electromagnetic fields associated with the lightning channel at close distances are considered. Moreover, the behavior of the electromagnetic fields versus the reflection factor changes and the radial distance changes are considered and the results are discussed accordingly. The results illustrate that the reflection factor has a direct relationship with the values of the electromagnetic fields while this is usually ignored in earlier studies.

Exposure limits of Magnetic fields of High Voltage Transmission lines for Evaluation of Environmental Impact (고압선로 환경영향평가의 자기장 노출범위설정에 관한 연구)

  • Jeon, In-Soo
    • Journal of Environmental Impact Assessment
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    • v.13 no.5
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    • pp.243-250
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    • 2004
  • Recently, concerns about health risks exposed to electromagnetic fields have been brought in the safety of electric power lines. A number of governmental and international organizations have advised to avoid the magnetic field exposure to the schools and residential areas. Some epidemiologic studies showed that electromagnetic fields should not exceed the exposure limits of 2-3mG to the people living near high-voltage transmission lines. In this study, the principles, ranges and survey methods of the assessment for powerfrequency electromagnetic fields were reviewed from the relevant research papers and documents. The ranges of electromagnetic fields were determined from 50m to 100m and have been defined according to the properties of each electric power lines and a new methodology was suggested in this study. It would be necessary to develop and improve specific assessment methods for various high-voltage transmission lines projects.

A Three-Dimensional Calculation of the Reactor Impedance for Planar-Type Cylindrical Inductively Coupled Plasma Sources

  • Kwon, Deuk-Chul;Yoon, Nam-Sik
    • Applied Science and Convergence Technology
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    • v.24 no.6
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    • pp.237-241
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    • 2015
  • The reactor impedance is calculated for a planar-type cylindrical inductively coupled plasma source by expanding the electromagnetic fields into their Fourier-Bessel series forms including the three-dimensional shape of the antenna. The mode excitation method is utilized to determine the electromagnetic fields based on a Poynting theorem-like relationship. From the obtained electromagnetic fields, a tractable form of the reactor impedance is obtained as a function of various plasma and geometrical parameters and applied to carry out a parametric study.

The Effect of Electromagnetic Fields Shielding on Electromagnetic Fields Decrease in P. T Room (차폐천이 물리치료실 환경내 전자기장 감소에 미치는 효과)

  • Lim Chang-Hun;Kim Jin-Sang
    • The Journal of Korean Physical Therapy
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    • v.12 no.2
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    • pp.69-82
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    • 2000
  • Physical therapists are exposured to radio-and microwave-frequency electromagnetic radiation by operating electrotherapy units. So there is few protection system in physical therapy room. Clinical pathology room and so on where various kins of electromagnetic instruments is used in hospital while protection failities like protection wall or protection glass is being used only in radiological room to reduce the damage of radiation. Acoording to Larsen's survey on female physical therapist in denmark. it was said that the percentage of congenital malfornation was $3.6\%$ and cadiac malformation made up $0.7\%$. It is likely that effect of electromagnetic fields on the result cannot be ruled out. Rita ouellet-Hellstron and Walter F. Steward insisted that the danger of abortion increase in the case of pregnant femeal physical therapist exposured to microwave diathermy. The intention of our study is arousing the necessity of microwave protection in P.T room and finding the proper method for physical therapist safe. The results of this study were as follows: 1. Each electrotherapy units are occurrenced the electromagnetic fields, and specially amply occurrenced in H.P,I.C.T 2 unit operating, M.W.D unit head on parallel, S.W.D unit head on parallel. all electrotherapy units are operating. 2. There were electric fields mount are consideration to species of electrotherapy units(p<.05). 3. There were magnetic fields mount are consideration to species of electrotherapy units(p<.05). 4. There were electric fields mount are consideration to distance of electrotherapy units(p<.05). 7. There were magnetic fields mount are consideration nut to distance of electrotherapy units(p>.05). 8. Before and after protection on magnetic fields mount are consideration to all distance(0m, 0.3m, 1m, 3m, 5m)(p<.05) 9. Before and after protection on electric fields mount are consideration to 0m, 1m, 3m distance(p<.05), and consideration not to 0.3m, 5m distance(p>.05) 10. After protection fellow the each electrotherapy units. distance, intencity to electromagnetic fields are reduced(p<.05).

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A Numerical Study on the Flow Fields in the Continuous Casting Mold with Electromagnetic Brake (EMBR이 적용된 연속주조 몰드 내부에서의 유동장 해석)

  • Ha M. Y.;Lee H. G.
    • Journal of computational fluids engineering
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    • v.4 no.2
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    • pp.47-56
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    • 1999
  • We developed a computer program to simulate the flow field in the presence of electro-magnetic fields. The steady, two-dimensional conservation equations for mass and momentum were solved simultaneously with Maxwell equations for electro-magnetic fields. Using this program, a numerical analysis was carried out to analyze the fluid flow in the continuous casting mold with electromagnetic brake. The effects of magnetic fields size, nozzle angle and EMBR yoke position on the flow fields in the continuous casting were investigated in the present study. The flow fields with EMBR were compared with those without EMBR. We also investigated the distribution of tracer concentration as a function of time in order to calculate their residence time in the mold with EMBR. By controlling the flow fields properly using EMBR, we can prevent the direct flow impaction on the wall which can give a damage on the mold surface and reduce surface defects of stainless steel sheet products.

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The Electromagnetic Fields, Exposure Limits and Regulations (긴급제언: 전자파 환경, 인체보호기준과 규제 -세계보건기구(WHO) 휴대폰, 무선주파수를 발암가능물질(2B)로 분류-)

  • Moon, Hank
    • Journal of the Korean Professional Engineers Association
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    • v.44 no.5
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    • pp.31-35
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    • 2011
  • The WHO/International Agency for Research on Cancer(IARC) has classified radiofrequency electromagnetic fields as possibly carcinogenic to humans(Group 2B), based on an increased risk for glioma, a malignant type of brain cancer, associated with wireless phone use on 31, May 2011. It takes 10 years after announcing the electric magnetic as possibly carcinogenic to humans(Group 2B) and 14 years after starting research project. It is too late as mentioned, too weak in terms of the same class to 'pickles & coffee' and too little in terms of using words 'more studies required'. The guidelines on human exposure to electromagnetic fields have been developed to provide guidance to identify the safety of exposure to electromagnetic fields. On the recent recommendations of safety guidelines, there has been discussion on possible chronic effects of electromagnetic fields with much lower or no threshold. This paper riviews the global trends of safety guidelines and has suggested the new guidelines for protecting the human health, wildlife and insects.

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Analysis of Worker Exposure Space according to Distribution of Electromagnetic Field of Generator (발전기의 전자기장 분포 특성에 따른 작업자 노출공간 분석)

  • Seong, Minyoung;Kim, Doo-Hyun;Kim, Seungtae
    • Journal of the Korean Society of Safety
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    • v.36 no.4
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    • pp.20-28
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    • 2021
  • With an increase in the commercialization of electricity, and the development of advanced and large electric devices and various wireless radio wave services, concerns over the effects of electromagnetic fields on human health have increased. Accordingly, the World Health Organization encouraged the development of international standards by establishing the 'International Electromagnetic Fields Project' in 1996 based on studies on the harmful effects of electromagnetic fields on the human body. Moreover, the National Institute of Environmental Health Sciences (NIEHS) classified electromagnetic fields as possible carcinogens under Group 2B category, even though they have been found to have a weak correlation with those effects on human health. Mid-to-large-sized electric facilities used at industrial sites mostly adopt a commercial frequency of 60 Hz, and workers handling these facilities are exposed to such extremely low frequency (ELF) fields for a long time. A previous study suggested that exposure to ELF electromagnetic fields with frequency ranges from 0 to 300 Hz, even for a short time, at densities higher than 100 μT may have harmful effects on human body as it affects the activation of nerve cells in the central nervous system by inducing an electric field and current and stimulating muscles and the nervous system in the body. Such studies, however, focused on home appliances used by ordinary people, and research on facilities utilizing high-capacity current and operated by workers at industrial sites is lacking. Therefore, in this study, a 3000 kilowatt generator, which is a high-capacity electric facility employed at industrial sites, was investigated, and the size of the magnetic fields generated during its no-load and high-load operations per distance to produce a map was measured to reveal spots deemed hazardous according to domestic and international exposure standards. The findings of this study is expected to alleviate workers' anxiety about the harmful effects of magnetic fields on their body and to minimize the level of exposure during operations.

Management Strategies for Electromagnetic Fields in Electric Power Lines (고압선로에서 발생하는 전자기장의 위해성 관리 방안)

  • 전인수
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.10
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    • pp.1017-1023
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    • 2003
  • Recently, the use an electric apparatus has brought into concerns about health risks from exposure to electromagnetic fields. During the last 2 decades, a number of epidemiological studies have explored the association between childhood leukaemia and residential exposure to power-frequency electromagnetic fields. Several studies have suggested that there is a small excess leukaemia risk with magnetic field exposure above 2 mG. A number of governmental and international organizations have developed exposure gudelines. The most rigid regulation with exposure levels for the elementary school and hospital has been enacted by Switzerland. Although there is no convincing supportive laboratory evidence, and the absence of a plausible biological mechanism of disease causation limits, governments are increasingly called on to adopt precautionary approaches to regulating electromagnetic field exposures. The government would need to establish the policy for electromagnetic fields and continually to be concerned about possible health risks from exposure to electromagnetic fields.

Numerical Analysis of Electromagnetic Fields in the Time-Domain (시간영역에서의 전자장 수치해석)

  • 남상욱
    • The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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    • v.2 no.4
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    • pp.66-73
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    • 1991
  • This paper reviews two representative time-domain techniques for the simulation of the electromagnetic fields, which are known as FD - TD and TLM. The fundamental ideas of two tec- hniques are explained in detail. Also, the implimentation of the boundary conditions, the statability condition, and the representation of media in the problems are described briefly.

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Electromagnetic Fields under Electric Power Lines (전력선하의 전자계)

  • Kang, Dae-Ha;Lee, Jae-Hoon;Lee, Young-Sik;Choi, Pill-Soo
    • Proceedings of the KIEE Conference
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    • 2006.07c
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    • pp.1595-1596
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    • 2006
  • In this study electromagnetic fields under power lines were derived by dipole antenna theory and electric fields under high voltage power lines were discussed with dependence of power factor cos $\phi$. And also electromagnetic fields under 3 phase power lines with horizenal and vertical configurations were formulated.

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