• Journal of Mechanical Science and Technology
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• v.16 no.8
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• pp.1089-1094
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• 2002

Mobile communication industry powered by electronics and information technology is building a transforming way for human communication. The latest electronics is so saturated to forget the difficulty in size reduction of electronic parts. However, mechanical parts, such as dynamic speakers and vibration motors, are intrinsically not easy to realize size reduction due to their construction. In this paper, a hexahedral type with simpler configuration is introduced to substitute for the conventional vibration motors. For uneven magnetic field analysis of the hexahedral type, FEM was used to determine magnetic flux density. After an analysis of magnetic and mechanical characteristics, it is shown that the coil configuration is the most important parameter to increase the output torque, and thus vibration. For optimization, genetic algorithm is used to find the optimal configuration of coil to maximize the output torque. Experimental results are also followed to confirm the validity of the proposed design.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.5
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• pp.935-942
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• 2019

This paper descries the operation of a heater which was designed to control a motor that generates an eddy current. As the motor drives the rotor of an eddy current heater, magnetic fields are provided within the air gap between an eddy current heater's rotor and stator. Throughout the research, a rotor composed of 8 and 16 pieces of magnets was used to analyze which are the factors that affect the efficiency of this equipment. Test results showed that the magnetic fields are influenced by variable functions including the velocity of a motor and the quantity of magnets composing a rotor.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.229-235
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• 2018

Research on indoor location tracking technology using smart phone is actively being carried out. Especially, in order to display the movement path of the smartphone on the map, the azimuth angle should be estimated by using the geomagnetic sensor built in most smart phones. Due to the distortion of the magnetic field due to the surrounding steel structure and the inclination of the smartphone, the estimation error of azimuthal angle may be occurred. In this paper, we propose a correction method of the geomagnetic sensor at the stationary state and a correction method for the inclination of the smartphone. We also propose a method to correct the azimuth error due to the difference between the magnetic north and the grid north.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.3
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• pp.471-476
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• 2021

Soft magnetic composite (SMC) materials based on powder metallurgy have a number of advantages over the conventional electrical steel sheets commonly used in electric machines. Thus, technologies related to these materials have shown significant improvement in recent years. In general, SMCs are magnetically isotropic owing to the shape of the powder, which makes them suitable for the construction of electric machines with three-dimensional flux and complex structures. However, the materials with isotropic magnetic properties (such as SMCs) have complex vector hysteresis; thus, it is very difficult to predict accurate loss properties. Therefore, we manufactured ring-type specimens of electrical steel sheets and SMC, which analyzed their magnetic properties according to the specimen size, and performed the electromagnetic field analysis of a high-speed permanent magnet (PM) motor driven at 800 Hz or higher using the measured magnetic information to compare the core loss of the motor. The reliability of this paper has been verified by measuring the efficiency after manufacturing the motor.

• Journal of Electrical Engineering and Technology
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• v.7 no.2
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• pp.184-192
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• 2012

The torque and unbalanced magnetic forces in permanent magnet machines are resultants of the tangential, axial and normal magnetic forces, respectively. Those are in general influenced by pole-teeth-winding configuration. A study of the torque and unbalanced magnetic forces of a small flux concentrating permanent magnet transverse flux machine (FCPM-TFM) in segmented compact structure is presented in this paper. By using FLUX3D software from Cedrat, Maxwell stress tensor has been solved. Finite element (FE-) magneto static study followed by transient analysis has been conducted to investigate the influence of unsymmetrical winding pattern, in respect to the rotor, on the performance of the FCPM-TFM. Calculating the magnetic field components in the air gap has required an introduction of a 2D grid in the middle of the air gap, whereby good estimations of the forces are obtained. In this machine, the axial magnetic forces reveal relatively higher amplitudes compared to the normal forces. Practical results of a prototype motor are demonstrated through the analysis.

• Proceedings of the Korean Society of Computer Information Conference
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• 2013.01a
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• pp.257-258
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• 2013

본 연구에서는 피복 손상으로 주변 도전체를 통해 누전되었을 때 그 주변의 자장을 검출하여 누전 여부를 판단할 수 있는 장치개발을 하기 위하여 우선 표면 누전에 의한 전류의 흐름을 조사하고, 전류에 의한 자장을 검출하기 위해 센서를 제작한다. 코어는 요크 타입을 적용하였으며, 코일은 0.5[mm] 동선을 4,000회 감았다. 실험 환경은 전선 피복 손상에 의한 금속 표면에 누전되는 상황을 모의하였으며, 부하는 40[W], 400[W], 1,400[W]를 적용하였다. 센서는 표면에 발생되는 자장을 검출할 수 있도록 2축으로 구성하였으며, 전선 주변 및 누전된 금속 표면에서 거리 및 각도 변화에 따른 자장을 검출하였다.

• Journal of electromagnetic engineering and science
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• v.18 no.1
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• pp.35-40
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• 2018

This study presents a vertical-type CMOS Hall device with improved sensitivity to detect a 3D magnetic field in various types of sensors or communication devices. To improve sensitivity, trenches are implanted next to the current input terminal, so that the Hall current becomes maximum. The effect of the dimension and location of trenches on sensitivity is simulated in the COMSOL simulator. A vertical-type Hall device with a width of $16{\mu}m$ and a height of $2{\mu}m$ is optimized for maximum sensitivity. The simulation result shows that it has a 23% better result than a conventional vertical-type CMOS Hall device without a trench.

• International journal of advanced smart convergence
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• v.1 no.2
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• pp.43-46
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• 2012

We analyzed a periodic thick mushroom structure for use as an artificial magnetic conductor using mode-matching method. The fields in each region were represented by either Floquet modes or waveguide modes. By applying tangential electric and magnetic field continuity conditions and using matrix equations, unknown coefficients and dispersion diagram were calculated. The proposed model can account for the effects of oblique incidence. Simulation time using the method was much faster than the commercial tools. We found that the current method produces accurate results of reflection phase and dispersion diagram.

• Journal of the Korean Society of Radiology
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• v.10 no.5
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• pp.367-373
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• 2016

This study conducted an analysis to compare the differences in the properties of the magnetic field and the generation of artifacts because of the difference in the magnetic field between 1.5 T equipment and 3.0 T equipment, centering around four types of pulse sequences, mainly applied to the abdominal Magnetic Resonance Imaging (MRI). With data on 500 persons transmitted to the PACS, this study analyzed the SNR value, quantitatively and carried out a qualitative evaluation, dividing MSA, CSA, and DA into three steps. As a result of the quantitative evaluation, the SNR value was significantly higher in the 1.5 T equipment; however, there was a factor deteriorating the image quality, too, as artifacts were generated in the images. The 1.5 T equipment generated fewer artifacts than the 3.0 T equipment did, so it could compensate the image quality for 3.0 T. In conclusion, based on these findings, this study could understand the differences in the properties of the magnetic field and the generation of artifacts occurring because of the difference in the magnetic field and could provide a measure for them. This study would be guidelines for MRI users who directly examine the patients in abdominal MRI using the two types of equipment in the clinical setting in the future.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.403-406
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• 2009

Recently, electricity is essential for human lives. Modem people take cultural benefits due to the development of the electric power system and the spread of the high tech-electric appliances, the cell phones, and etc. However, the electromagnetic field problems become prominent figures owing to the fault of the communication devices around the power line and the biological effect, and etc. In this paper, we introduce the simple electromagnetic field calculation based on the transmission line matrix method, prior to the analysis about the influence of electromagnetic field. Simulation object is the inner part of the trailer car in the high speed train. Unlike the existing paper we submitted, we analyze not only the magnetic field but the electric field in the inner part of the trailer car which makes up the high speed train.