• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.18-20
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• 1995

In this paper we presented a calculation method of leakage inductance in electrical machines. For its accurate calculation the finite element method is applied to the analysis of magnetic field distribution. The self and mutual inductances are derived using the results of the magnetic field analysis and the leakage inductance is easily obtained from these inductances. As numerical examples, we tread a single phase transformer and a rotor slot model of induction motor. In the finite element analysis we used the 2D linear magnetostatic formulation with the first-order triangular element.

• Proceedings of the KIEE Conference
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• summer
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• pp.369-371
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• 2004

With the proliferation of nonlinear loads, high neutral harmonic currents in three-phase four-wire distribution system have been observed. It has been. known that the ground impedance has an effect on the neutral currents of a system which operates with harmonics present. On-site measurements of harmonic currents and voltages according to the fell-of-potential method under case study system were made and the ground impedance modeling using the pattern search method for the harmonic analysis was developed. The ground impedance model obtained by the proposed method was compared with the frequency characteristics by field tests and has shown appropriate results, and would be applicable to evaluate the harmonic and transient response characteristics of the ground system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.9
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• pp.1802-1811
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• 1994

In this paper, the corrugated horn antenna used in the reflector feed horn of satellite is analyzed using the modal expansion method. The modal expansion method is represented by the summations of modals at each point so the exact prediction of field and phase patterns can be obtained. The least number of iterations to compute field patterns is proposed. By using this number. calculation of accurate near and far field patterns without comsuming a lot of computational effort is available. Three kinds of corrugated horn antenna is designed to verify the method and experimented. The VSWR of designed frequency is from 1.04 to 1.1. The input impedance is nearly matched to $50\Omega$.

• Steel and Composite Structures
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• v.39 no.5
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• pp.493-509
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• 2021

There is not enough mixed finite element method (MFEM) model developed for static and dynamic analysis of functionally graded material (FGM) beams in the literature. The main purpose of this study is to develop a reliable and efficient computational modeling using an efficient functional in MFEM for free vibration and static analysis of FGM composite beams subject to high order shear deformation effects. The modeling of material properties was performed using mixture rule and Mori-Tanaka scheme which are more realistic determination techniques. This method based on the assumption that a two phase composite material consisting of matrix reinforced by spherical particles, randomly distributed in the beam. To explain the displacement components of the shear deformation effects, it was accepted that the shear deformation effects change sinusoidal. Partial differential field equations were obtained with the help of variational methods and then these equations were transformed into a novel functional for FGM beams with the help of Gateaux differential derivative operator. Thanks to the Gateaux differential method, the compatibility of the field equations was checked, and the field equations and boundary conditions were reflected to the function. A MFEM model was developed with a total of 10 degrees of freedom to apply the obtained functional. In the numerical applications section, free vibration and flexure problems solutions of FGM composite beams were compared with those predicted by other theories to show the effects of shear deformation, thickness changing and boundary conditions.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.27-33
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• 2003

This study analyzed an application possibility of neural network to overcome problems of conventional settlement prediction. It is very important to estimate settlement in preloading method used to improve soft ground. At present, Hyperbolic method, Hoshino method and Asaoka method are used mostly in the prediction of settlement. But these methods can not predict settlement at the phase of design. On the other hand, neural networks are capable of predicting settlement through accumulated data in the phase of design and this method can be easily applied in practice. In this study Elman neural network is used to estimate future settlement.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.4
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• pp.544-553
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• 2013

In this paper, we propose the pattern classifier of Radial Basis Function Neural Networks(RBFNNs) for diagnosis of 3-phase partial discharge. Conventional methods map the partial discharge/noise data on 3-PARD map, and decide whether the partial discharge occurs or not from 3-phase or neutral point. However, it is decided based on his own subjective knowledge of skilled experter. In order to solve these problems, the mapping of data as well as the classification of phases are considered by using the general 3-PARD map and PA method, and the identification of phases occurring partial discharge/noise discharge is done. In the sequel, the type of partial discharge occurring on arbitrary random phase is classified and identified by fuzzy clustering-based polynomial Radial Basis Function Neural Networks(RBFNN) classifier. And by identifying the learning rate, momentum coefficient, and fuzzification coefficient of FCM fuzzy clustering with the aid of PSO algorithm, the RBFNN classifier is optimized. The virtual simulated data and the experimental data acquired from practical field are used for performance estimation of 3-phase partial discharge pattern classifier.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2364-2375
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• 2018

Two-phase simultaneous excitation mode of the switched reluctance motor (SRM) has been shown to effectively improve the average torque output compared with traditional single-phase excitation mode. But the torque ripple of the two-phase excitation SRM with traditional winding distribution increases because of the inconsistent electromagnetic field. To reduce the torque ripple, a two-phase excitation 8/6 SRM with novel winding distribution is proposed in this paper. The static torques generated by various magnetic circuits are analyzed and obtained to verify the torque increase. Then the electromagnetic characteristics of the proposed SRM are investigated by the numerical calculation method in detail, including flux linkage, inductance, and torque. Finally, an experiment for measuring the SRM static electromagnetic characteristics and dynamic performance is designed and performed based on the novel mode, and the comparing results show that the proposed two-phase SRM is effective.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.292-295
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• 2003

Moire topography method is a well-known non-contacting 3-D measurement method. the automatic 3-D measurement by moire topography has been required since the method was frequently applied to the engineering and medical fields. 3-D measurement using digital projection moire topography is very attractive because of its high measuring speed and high sensitivity. In this study, digital two-wavelength phase shilling moire is applied to the entertainment fields. recently. as promoting the growth of the VR-Game, display devices which attract public attention such as HMD or Projector are being appeared in order to deliver effectively the absorption sense. this study realized the Auto-calibrating system for arbitrary display surface using digital moire method which satisfied the shape measurement of display surface and the request of FOV(Field of View) output. also when large screen wasn't prepared, this auto-calibrating system was applied to enjoy games or movies at home with a projector and walls

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.407-408
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• 2011

Natural boron consists of two stable isotopes 10B and 11B with natural abundance of 18.8 atom percent of 10B and 81.2 atom percent of 11B. The thermal neutron absorption cross-section for 10B and 11B are 3837 barn and 0.005 barn respectively. 10B enriched specific compounds are used for control rods and as a reactor coolant additives. In this work 2 methods for boron enrichment were analysed: 1) Gas irradiation in static conditions. Dissociation occurs due to multiphoton absorption by specific isotopes in appropriately tuned laser field. IR shifted laser pulses are usually used in combination with increasing the laser intensity also improves selectivity up to some degree. In order to prevent recombination of dissociated molecules BCl3 is mixed with H2S 2) SILARC method. Advantages of this method: a) Gas cooling is helpful to split and shrink boron isotopes absorption bands. In order to achieve better selectivity BCl3 gas has to be substantially rarefied (~0.01%-5%) in mixture with carrier gas. b) Laser intensity is lower than in the first method. Some preliminary calculations of dissociation and recombination with carrier gas molecules energetics for both methods will be demonstrated Boron separation in SILARC method can be represented as multistage process: 1) Mixture of BCl3 with carrier gas is putted in reservoir 2) Gas overcooling due to expansion through Laval nozzle 3) IR multiphoton absorption by gas irradiated by specifically tuned laser field with subsequent gradual gas condensation in outlet chamber It is planned to develop software which includes these stages. This software will rely on the following available software based on quantum molecular dynamics in external quantized field: 1) WavePacket: Each particle is treated semiclassicaly based on Wigner transform method 2) Turbomole: It is based on local density methods like density of functional methods (DFT) and its improvement- coupled clusters approach (CC) to take into account quantum correlation. These models will be used to extract information concerning kinetic coefficients, and their dependence on applied external field. Information on radiative corrections to equation of state induced by laser field which take into account possible phase transition (or crossover?) can be also revealed. This mixed phase equation of state with quantum corrections will be further used in hydrodynamical simulations. Moreover results of these hydrodynamical simulations can be compared with results of CFD calculations. The first reasonable question to ask before starting the CFD simulations is whether turbulent effects are significant or not, and how to model turbulence? The questions of laser beam parameters and outlet chamber geometry which are most optimal to make all gas volume irradiated is also discussed. Relationship between enrichment factor and stagnation pressure and temperature based on experimental data is also reported.

• Progress in Superconductivity and Cryogenics
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• v.13 no.1
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• pp.46-50
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• 2011

The electrical insulation design of high voltage superconducting fault current limiters (SFCLs) should be confirmed to be applied for the stabilization of the power grid. This paper describes numerical analysis and AC dielectric experiments for developing high voltage SFCLs. The electric field distributions between applied high voltage part and ground were calculated by finite element method (FEM) simulation tool and AC criterion of liquid nitrogen at 200 kPa was calculated from correlation between the field utilization factor and FEM simulation results. This paper deals with ceonceptual insulation design of a 154 kV class single-phase no-inductively wound solenoid type SFCL which was focused on gap distance between the cryostat and superconducting coils. Furthermore, the shield ring effect was confirmed to reduce maximum electric field at applied high voltage part.