• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.12
• /
• pp.270-276
• /
• 2013

We have been unwittingly exposed to magnetic field. Biological effects due to electromagnetic field exposure has been studied over the past several decades. There has been epidemiological studies and laboratory studies. In the case of laboratory studies, the effect has been observed through the cell stimulation of an artificial magnetic field. The used frequency and waveform are various in the cell experiment, but the intensity of the magnetic field is usually around 10G. Intensity of Earth's magnetic field is about 300-400mG. Although this intensity is not much higher than artificial magnetic field as 3-4% amplitude, we can't ignore the effect because every living thing on earth has already adapted for long time ago. In this study, we have designed and implemented the 3-axis magnetic field generation system in oder to remove the static magnetic field in the real-time and kept its intensity less than ${\pm}5mG({\pm}0.5uT)$ using 3-axis helmholtz coil.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2004.08a
• /
• pp.118-137
• /
• 2004

Recently underwater geophysical problems for historical relics or UXO's are raised frequently. This study includes the applicabilities and limitations of the recent underwater metal detector and domestic case stories for underwater survey by electrical and magnetic method. Direct or indirect case stories are electrical and vertical magnetic gradiometry surveys beneath Han-river bottom for planning subway tunnel, electrical exploration on lake-bottom, electrical exploration on the tidal flats using high-power transmitter, and borehole three-component magnetic and electromagnetic surveys for detecting the undersea objects. A design of potable real-time, high-speed measurement system using multi-channel array sensors is also introduced here. Further study will be focussed on practical field applications of the fast water-bottom scanning system which is lately required by actual field.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.21 no.1
• /
• pp.27-33
• /
• 2011

Carbon board, an electromagnetic shielding new material, is expected to be applied to the art wall by combining draft designs. When environment-friendly architecture materials are used as an interior wall, they are suitable as finishing materials. According to the increasing tendency of the application of carbon board, various styles could be made by decorating the whole or a part of a wall with tiles with module structure or by patterning the wall with panel-type woodcut or pictures or sculpture. And more graphic design based on diverse variation, and reconstruction and combination between other motif is being on the rise as a new expression. In this paper, make it possible to applying in MDF board and carbon board pattern design using the woodcut technique. The structural and physical properties were compared by usability of abrasion, toughness, stability. Samples are analyzed dependent on the hardness and relative density, change of detail pattern design and trimming technique. These results have shown that the possibility of applying of carbon board can be a high rank interior materials, capable of creating value of the living system, connects with MDF board, also can express humanism in a beautiful manner.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.3
• /
• pp.1144-1153
• /
• 2015

The resonant mechanism of reradiation interference (RRI) over 1.7MHz from power transmission lines cannot be obtained from IEEE standards, which are based on researches of field intensity. Hence, the resonance is ignored in National Standards of protecting distance between UHV power lines and radio stations in China, which would result in an excessive redundancy of protecting distance. Therefore, based on the generalized resonance theory, we proposed the idea of applying model-based parameter estimation (MBPE) to estimate the generalized resonance frequency of electrically large scattering objects. We also deduced equation expressions of the generalized resonance frequency and its quality factor Q in a lossy open electromagnetic system, i.e. an antenna-transmission line system in this paper. Taking the frequency band studied by IEEE and the frequency band over 1.7 MHz as object, we established three models of the RRI from transmission lines, namely the simplified line model, the tower line model considering cross arms and the line-surface mixed model. With the models, we calculated the scattering field of sampling points with equal intervals using method of moments, and then inferred expressions of Padé rational function. After calculating the zero-pole points of the Padé rational function, we eventually got the estimation of the RRI’s generalized resonant frequency. Our case studies indicate that the proposed estimation method is effective for predicting the generalized resonant frequency of RRI in medium frequency (MF, 0.3~3 MHz) band over 1.7 MHz, which expands the frequency band studied by IEEE.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.49 no.2
• /
• pp.116-125
• /
• 2013

Jigging and angling fishery is prevalent in the East Sea of Korea and this fishery needs many lamps to attract the fish. And the fishing boat uses 24~47 ballasts by the vessel's tonnage to turn on the fishing lamp. A 3.5kW magnetic-type ballast being currently used at many fishing boats can drive two 1.5kW metal-halide lamps. Meanwhile, this ballast has large weight (25kg) and volume. Therefore it is one of reason for the over-consumption of energy and the fire, resulted from overheat and electrical short, occurs occasionally because the ballast is installed at narrow and hot engine room. In addition, most of magnetic ballast has several problems such as periodic condenser replacement, low energy efficiency and making lamp short life, etc. So it is necessary to improve or develop newly the electronic ballast, which has to be smaller, lighter and more efficient. An electronic ballast was designed for the fishing boat by considering duration and electromagnetic interference in the study. Its weight and volume are respectably 40% and 66% compared to current ballast on the basis of PCB. The metal-halide lamp's spectrum of the designed ballast was nearly same to that of the current ballast in the test of lighting. In particular, the light stability was improved and there isn't any radio interference. As mentioned above, it is expected that the developed electronic ballast can replace current magnetic ballast because of many advantages related to energy-saving.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.4
• /
• pp.474-479
• /
• 2016

As the Eco-energy is recently required, electrical energy is fast increased. Several induction heating methods are attractive for Eco-energy and energy saving. In this paper, electrical fan heater was designed and developed with new concept for energy saving by electromagnetic induction heating. Proposed system was composed of three module, blast part, induction heating part and power transformation part. Induction heating method was adapted for heating and the resonant inverter was used for increasing of the power transformation efficiency. Full-bridge resonant inverter was adopted to resonant inverter. This system was composed of induction heating part made with metal(SUS 40 series), and power transformation part made with rectifier module, filter module and resonant inverter. From these results, the proposed new electric heater could be saved the energy from faster increasing the temperature compared to commercial gas and other electric heater. This electrical fan heater is possible to be used in field of home, commercial and agricultural area for eco-energy saving heater.

• Journal of Radiation Protection and Research
• /
• v.22 no.4
• /
• pp.263-272
• /
• 1997

A Radiation Alarm Monitor has been developed and manufactured in order to protect radiation workers from over-exposure. A visual and audible alarm system has been attached to initiate evacuation when accident occurs such as an unexpected change of radiation level or an over-exposure. The Radiation Alarm Monitor installed with microprocessor can record the information of radiation field change between 90 min. before the alarm and 30 min. after the alarm and also provide the data to an IBM compatible computer to analyze the accidents and to set a counterplan. It features a wide detection range of radiation field(10 mR/h-100 R/h), radiation field data storage, portability, high precision (${\pm}5%$) due to self-calibration function, and adaption of a powerful alarm system. According to ANSI N42.17A, the most stringent test standards, performance tests were carried out under various conditions of temperature, humidity, vibration, and electromagnetic wave hindrance at Korea Research Institute of Standards & Science (KRISS). As a result, the Radiation Alarm Monitor passed all tests.

• Journal of the Korean Magnetics Society
• /
• v.24 no.6
• /
• pp.171-178
• /
• 2014

Remote Field Eddy Current Testing (RFECT), one of the ways which is a nondestructive testing using electromagnetic fields, can make up for Magnetic Flux Leakage (MFL) weaknesses and general Eddy Current Testing (ECT) weaknesses which is an occurrence of a huge friction force or disadvantage of detecting defects on the outer wall. So many of institutes and laboratories have studied on RFECT for the past 50 years. But There is a lack of discussion about a study on eddy current and magnetic field distributions in a pipe wall and designing of RFECT exciter coil. In this paper, eddy current and magnetic field distributions in a pipe wall and influence of altering variables are analyzed. Also, the optimal design algorithm about the RFECT Exciter coil are proposed, and influence on defect signals caused by alteration of its shape is analyzed.

• The Bulletin of The Korean Astronomical Society
• /
• v.41 no.1
• /
• pp.45.1-45.1
• /
• 2016

Spatially rotating magnetic fields have been observed in the solar wind and in the Earth's magnetopause as well as in reversed field pinch (RFP) devices. Such field configurations have a similarity with extended current layers having a spatially varying plasma pressure instead of the spatially varying guide field. It is thus expected that magnetic reconnection may take place in a rotating magnetic field no less than in an extended current layer. We have investigated the spontaneous evolution of a collisionless plasma system embedding a rotating magnetic field with a two-and-a-half-dimensional electromagnetic particle-in-cell (PIC) simulation. In magnetohydrodynamics, magnetic flux can be decreased by diffusion in O-lines. In kinetic physics, however, an asymmetry of the velocity distribution function can generate new magnetic flux near O- and X-lines, hence a dynamo effect. We have found that a magnetic-flux-reducing diffusion phase and a magnetic-flux-increasing dynamo phase are alternating with a certain period. The temperature of the system also varies with the same period, showing a similarity to sawtooth oscillations in tokamaks. We have shown that a modified theory of sawtooth oscillations can explain the periodic behavior observed in the simulation. A strong guide field distorts the current layer as was observed in laboratory experiments. This distortion is smoothed out as magnetic islands fade away by the O-line diffusion, but is soon strengthened by the growth of magnetic islands. These processes are all repeating with a fixed period. Our results suggest that a rotating magnetic field configuration continuously undergoes deformation and relaxation in a short time-scale although it might look rather steady in a long-term view.

• Journal of Environmental Health Sciences
• /
• v.40 no.5
• /
• pp.376-384
• /
• 2014

Objective: The purpose of this study is to compare the health status of residents who were exposed to sources of extremely low frequency electromagnetic fields (ELF-EMFs) in the living environment and those who were not exposed to such a source of ELF-EMFs through a survey designed to appraise the residents' health levels. Method: Aimed at 251 residents exposed to a source of ELF-EMFs and 278 residents not exposed to a source, the survey was conducted to investigate the health status of the residents on the basis of questionnaire SF-36. Result: The health status scores of residents exposed to ELF-EMFs turned out to be lower than those of their counterparts. In terms of self-reported symptoms related to health and sleep quality, residents exposed to ELF-EMFs were found to have a higher complaint rate of self-reported symptoms such as dizziness, depression, and fatigue. Regarding sleep disorders, residents exposed to ELF-EMFs appeared to have a slightly higher complaint rate of sleep disorders compared to non-exposed residents. Conclusion: If a region is to be exposed to a source of ELF-EMFs, a more proactive policy for reducing such exposure is advised. In addition, it is necessary to better understand problems of residents by emplacing an ELF-EMFs risk information delivery system and building an efficient communication system for voluntary participation during the construction phase.