• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.641-643
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• 2002

Synchronous generator needs slip-ring and brush for supplying current to rotor with external source. but slip-ring and brush have some problems to supply DC power to field winding with friction and high power loss due to brush voltage drop at high field current. Thus synchronous generator have been designed to brushless machine. Brushless synchronous machines of using permanent halbach array can composed without back core and coreloss. In this paper, analyse on the characteristics of external rotor type permenant magnet brushless with halbach array.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.10
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• pp.713-719
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• 2013

Power MOSFET operate voltage-driven devices, design to control the large power switching device for power supply, converter, motor control, etc. We have optimal designed planar and trench gate power MOSFET for high breakdown voltage and low on resistance. When we have designed $6,580{\mu}m{\times}5,680{\mu}m$ of chip size and 20 A current, on resistance of trench gate power MOSFET was low than planar gate power MOSFET. The on state voltage of trench gate power MOSFET was improved from 4.35 V to 3.7 V. At the same time, we have designed unified field limit ring for trench gate power MOFET. It is Junction Termination Edge type. As a result, we have obtained chip shrink effect and low on resistance because conventional field limit ring was convert to unify.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.10
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• pp.720-725
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• 2013

Power MOSFET operate voltage-driven devices, design to control the large power switching device for power supply, converter, motor control, etc. We have analyzed trench process, field limit ring process for fabrication of unified trench gate power MOSFET. And we have analyzed electrical characteristics of fabricated unified trench gate power MOSFET. The optimal trench process was based on SF6. After we carried out SEM measurement, we obtained superior trench gate and field limit ring process. And we compared electrical characteristics of planar and trench gate unified power MOSFET after completing device fabrication. As a result, the both of them was obtained 500 V breakdown voltage. However trench gate unified power MOSFET was shown improved Vth and on state voltage drop characteristics than planar gate unified power MOSFET.

• 전기의세계
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• v.13 no.3
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• pp.38-41
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• 1964

This thesis is aimed to obtain efficiently economically any desired phases and single phase transformer without unbalance by using only a new transformer, applying the theory of rotating magnetic field. The brief construction and principle is as floow: two pieces of similar ring cores, triangular cores or polygonal cores are located on the upper and lower sides with equidistance. And the some number of similar leg cores, shaped a square-pillar or a sylinder, are arranged at equidistant of the core section. Ring windings or polyphase windings of AC machines are adopted as a winding method on the upper and lower cores. Three phase AC is applied to the primary windings on these cores so that the rotating magnetic field is induced on the cores and this magnetic fluxes pass through each of the secondary windings on the leg-cores with some difference in time.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.262-265
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• 2003

Radiofrequency thermal ablation (RTA) as one of the microwave hyperthermia is becoming the treatment of choice for small but inoperable tumors of the liver. In this paper, we designed the applicator composed of semi-rigid coaxial cable antenna with a ring slot for RTA. To optimize the maximum output of radiation at 2450 MHz, we simulated the antenna using Electromagnetic simulation tools Maxwell program and analyzed the return loss and the electric field $E_{tot}$ at the near-field region between the simulation results and measurement results. As a result, we obtained the return loss of -29.786 dB at 2450 MHz when the antenna was placed between two blocks of a pig's liver, and the measurement results agreed with the simulation results well. Therefore, this semi-rigid coaxial cable antenna with a ring slot can be used very usefully as the applicator for RTA.r RTA.A.

• The Journal of Natural Sciences
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• v.15 no.1
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• pp.47-56
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• 2005

The substituent dependence of geometric distortion through the two independent electronic substituent effects is analyzed for mono-substituted benzene derivatives of $C_{2v}$. Based on resonance structures, quantitative relationships expressing the resonance and field/inductive contribution terms in bond distortions are derived. The calculated field-effect parts of $C_{ipso}$_$C_{ortho}$ ring bonds increase and decrease compared to benzene for electropositive and electronegative substituents respectively. The nonbonded axial distance, $C_{ipso}$....$C_{para'}$ decreases for electronegative substituents and increases for electropositive substituents. As the electronegativity increases, the distance $C_{ortho}$....$C_{ortho'}$ increases. With the $\pi$-donors, $C_{meta}$....$C_{meta'}$ nonbonded distances are shorter compared to the ones of benzene, and for $\pi$-acceptors, the are longer. Our model based on valence bond approach predicts that the average bond length determined the area of ring, and the sum of the angles <$C_{ortho}$_$C_{ispo}$_$C_{ortho}$ and <$C_{meta}$_$C_{para}$_$C_{meta}$ determines the axial distance.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.12
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• pp.789-796
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• 2000

This paper deals with magnetic field and characteristic analysis for ring type slotless synchronous motors by using analytical method. Since magnetic air-gap in the slotless motors is much larger than mechanical air-gap, it is necessary to analyze the magnetic flux distribution at the whole magnetic airgap region. therefore, this paper analyzes the duplicated magnetic field derived by both Permanent Magnet(PM) and armature current and estimates the back electromotive force and torque characteristic by subdividing the conductor region. The analysis results are verified by comparing with Finite Element Analysis(FEA) results.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.345-351
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• 1998

Thermal shock resistance of $Al_2O_3$- and Fe-$Al_2TiO_5$-based Castable Refractories was studied using a central heating technique. Ring type specimens, 10mm thick and 20 and 100mm inner and outer diameters, respectively, were rapidly heated on the internal surface of the centre hole using a high power electrical heating element. The temperature field was measured experimentally and modelled using finite element analysis (FEA). The thermal stress field was also modelled using FEA. A radial notch was introduced to the ring specimens to enable calculation of the thermal stress intensity factors (SIF). A special LVDT device was incorporated in the thermal shock tester to monitor crack mouth opening displacement (COD). The thermal shock fracture initiation and crack propagation behaviour of the castable refractories were ascertained using the COD measurements and the fracture mechanics analysis data.

• East Asian mathematical journal
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• v.14 no.2
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• pp.259-268
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• 1998

In this paper, for a commutative ring R with an identity, considering the endomorphism ring $End_R$(M) of left R-module $_RM$ which is (quasi-)injective or (quasi-)projective, some discriminations of prime endomorphism were found as follows: each epimorphism with the irreducible(or simple) kernel on a (quasi-)injective module and each monomorphism with maximal image on a (quasi-)projective module are prime. It was shown that for a field F, any given square matrix in $Mat_{n{\times}n}$(F) with maximal image and irreducible kernel is a prime matrix, furthermore, any given matrix in $Mat_{n{\times}n}$(F) for any field F can be factored into a product of prime matrices.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.24-27
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• 2003

Radiofrequency ablation (RFA) as one of the microwave hyperthermia is becoming the treatment of choice for small but inoperable tumors of the liver. In this paper, we designed the applicator composed of semi-rigid coaxial cable antenna with a ring slot for RFA. To optimize the maximum output of radiation with omni direction at 2450 ㎒, we simulated the applicator using Electromagnetic simulation program and analyzed the return loss and the electric field E$\_$tot/ at the near-field region between the simulation results and measurement results. As a result, we obtained the return loss of -29.786 dB at 2450 ㎒ when the applicator was placed between two blocks of a pig's liver, and the measurement results agreed with the simulation results well. Therefore, this applicator using semi-rigid coaxial cable antenna with a ring slot can be used very usefully as the applicator for RFA.