• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2732-2741
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• 2000

Combination of magnetic recording technology and optical recording technology such as Near Field Optical Recording is watched recently. In order to accomplish this technology, the development of an electromagnetic driven mm-sized mirror shifting laser beam in track direction have to needed. In Near Field Optical Recording System, shifting laser beam in track direction mean as fine tracking and means as coarse tracking. Therefore in Near Field Optical Recording, 2-stage actuator is composed of servo controller in reading or recording information on disc layer. In our research, through design and simulation process of driven mm-sized mirror, we arrange systematically design process of driven mm-sized mirror having good frequency transfer characteristics. Design and simulation processes included modal analysis of spring, calculation of magnetic moment according to the number of turns and geometric configuration of coil and magnetic circuit analysis meaning that calculation of magnetic flux density in air gap of magnetic circuit. After that we design and make parts of driven mm-sized mirror, assemble and evaluate our electriomagnetic driven mm-sized mirror. we compared design values with actual characteristic values and present solution scheme. Through these processes we performed manufacturing of an electromagnetic driven mm-sized mirror having good frequency-domain characteristics and high sensitivity characteristics.

• Journal of Preventive Medicine and Public Health
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• v.33 no.1
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• pp.125-133
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• 2000

Objectives : This study uses meta-analysis methodology to examine the statistical consistency and importance of random variation among results of epidemiologic studies of occupational electromagnetic field exposure and leukemia. Methods : Studies for this meta-analysis were identified from previous reviews and by asking researcher active in this field for recommendations. Overall, 27 studies of occupational electromagnetic field exposures and leukemia were reviewed. A variety of meta-analysis statistical methods have been used to assess combined effects, to identify heterogeneity, and to provide a single summary risk estimate based on a set of simiar epidemiologic studies. In this study, classification of exposure metircs on occupational epidemiologic studies are reported for (1) job classification (20 individual studies); (2) leukemia subtypes (13 individual studies); and (3) country (27 individual studies). Results : Results of this study, an inverse-variance weighted pooling of all the data leads to a small but significant elevation in risk of f 1% (OR=1.11, 95% CI : $1.06\sim1.16$) among 27 occupational epidemiologic studies. Publication bias was assessed by the 'fail-safe n' that may be not influence for all combined results exception a few categories, ie, 'power station operators' and 'electric utility workers' by job classification on occupational study. And ail combined odds ratio results were similar for fixed-effects models and random-effects models, with slightly higher risk estimates for the random-effects model in situations where there was significant heterogeneity, ie, Q-statistic significant (p<.05). Conclusions : We found a small elevation in risk of leukemia, but the ubiquitous nature of exposure to electromagnetic fields from workplace makes even a weak association a public health issue of substantial power to influence the present overall conclusion about relationship between electromagnetic fields exposure and leukemia.

• Journal of electromagnetic engineering and science
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• v.18 no.3
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• pp.212-214
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• 2018

The finite-difference time-domain (FDTD) model was developed to analyze electromagnetic (EM) wave propagation in an inhomogeneous ionosphere. The EM analysis of ionosphere is complicated, owing to various propagation environments that are significantly influenced by plasma frequency, cyclotron frequency, and collision frequency. Based on the simple auxiliary differential equation (ADE) technique, we present an accurate FDTD algorithm suitable for the EM analysis of complex phenomena in the ionosphere under arbitrary-direction geomagnetic field. Numerical examples are used to validate our FDTD model in terms of the reflection coefficient of a single magnetized plasma slab. Based on the FDTD formulation developed here, we investigate EM wave propagation characteristics in the ionosphere using realistic ionospheric data for South Korea.

• Journal of the Korea Safety Management & Science
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• v.5 no.4
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• pp.87-95
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• 2003

The purpose of this paper is analyses about in 12kV/50kA vacuum interrupter with an axial magnetic field type electrode system through the studies of electromagnetic phenomena for the possess of Safety break. Vacuum interrupter is important in electric safety part. In this paper, we performed analysis of electric field, magnetic field, current density in AMF electrode using the Maxwell 3D simulation.

• Journal of the Korean Society of Safety
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• v.31 no.1
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• pp.48-53
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• 2016

This paper deals with analysis of complex grounding system using electromagnetic simulation method. Electrical devices could be damaged by transient voltage such as a lightning surge. Therefore the measures to protect the equipments from transient, such as a lightning are required. The ground system is important in this respect. The representative parameter of grounding system performance is earth ground resistance. Precise prediction of earth resistance is required, because it is difficult to modify and change after the completion of the grounding system construction. Numerical modeling is often used in numerical analysis to identify the electrical characteristics of the grounding system. However complex systems are difficult to predict grounding characteristics by numerical analysis. If the total electric field of the earth in general is similar to the antenna model, in that the incident electric field and expressed as a sum of the scattering field. In this study, the electromagnetic field simulation tool "ANSYS HFSS" module containing the antenna model was used to analyze performance of ground system. Both the simple and complex grounding system were analyzed by simulation tool and experimental method. As a result simulation method is effective to predict performance of a complex ground system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.12
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• pp.2179-2189
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• 2010

This paper deals with analytical techniques for performance evaluation of small scaled wind power generator with outer permanent magnet rotor. In part (1), using transfer relations theorem, magnetic field distribution characteristics by PM and armature reaction field are derived. Moreover, electrical parameters such as back-EMF, inductance and resistance are calculated from the obtained field characteristic equations. The proposed analytical techniques are validated by nonlinear finite element method using commercial software 'Maxwell' and performance experiments of the manufactured generator. In part (2), generating characteristics analysis such as constant speed characteristics and constant resistive load characteristics, and performance evaluation according to variation of wind speed will be accomplished using the derived electrical parameters.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.12
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• pp.576-585
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• 2005

This paper deals with the electromagnetic field analysis of slotless brushless permanent magnet machines with three different magnetization patterns such as Halbach, parallel and radial magnetization. The magnetization modeling of Halbach, parallel and radial magnetization is performed analytically. And then, analytical solutions for open-circuit field distributions, armature reaction field distributions, flux linkages due to PMs and stator windings, torque, back-emf and inductance are derived in terms of magnetic vector potential and two-dimensional (2-d) polar coordinate systems. The analytical results are validated extensively by finite element (FE) analyses. The magnet volume required in order to produce identical flux density is compared with each magnetization. Finally, analytical solutions and derivation procedures of those presented in this paper can be applied to slotless and slotted brushless permanent magnet AC and DC machines.

• Journal of KSNVE
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• v.9 no.4
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• pp.747-753
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• 1999

This paper presents results of vibration analysis of a generator-stator core for 500 MW fossil power plant. A finite element analysis using a commercial S/W is performed to estimate alternating electromagnetic forces, mainly of 120 Hz in 60 Hz machines, acting on the core, and then to calculate forced response of the core. Results are compared with design requirements.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.1
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• pp.13-17
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• 2016

EMC (Electro Magnetic Compatibility) of the electrical railway must be ensured for safety of passenger. Maglev trains has not friction between the wheels and the rails because levitation by an permanent magnets, electromagnets and superconducting magnets etc. So, it is advantageous to maintain a high speed without noise and vibrations. In this paper, we investigated that the magnetic field of the before and after installation electromagnetic waves absorber in order to analyze the effects of electromagnetic waves. The theoretical analysis of the electromagnetic wave absorber was simulated using finite element method. The magnetic field properties of electromagnetic waves absorber were measured by EMI (Electro Magnetic Interference) test receiver.

• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.255-257
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• 2004

This paper was studied electromagnetic field distribution and damping of PD(Partial Discharge) signal in GIS(Gas Insulated Switchgear). Cut-off frequency of electromagnetic wave propagation modes were computed, electromagnetic field distribution of propagation modes in GIS by FEM(Finite Element Method) were simulated and simulated damping characteristic of electromagnetic waves in GIS by EMTP(Electromagnetic Transient Program) when generated PD pulse. Frequency band of $TE_{mn}/TM_{mn}$ modes were determinated by simulation results of electromagnetic field distribution and were discussed optimal position of UHF sensor from this results. Equivalent circuit was used to simulate signal damping of PD pulse in GIS by EMTP and compared with measured results in laboratory of KERI.