• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.4
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• pp.735-741
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• 2009

This paper presents an algorithm for the permanent magnet shape optimization of a large scale BLDC(Brushless DC) motor to minimize the cogging torque. A response surface method (RSM) using multiquadric radial basis function is employed to interpolate the objective function in design parameter space. In order to get a reasonable response surface with relatively small number of sampling data points, additional sampling points are added on the basis of design sensitivity analysis computed by using FEM. The algorithm has 2 stages: the first stage is to determine the PM arc angle, and the 2nd stage is to optimize the magnet pole shape. The developed algorithm is applied to a 5MW BLDC motor to get a minimum cogging torque. After 3 iterations with 4 design parameters, the cogging torque is reduced to 13.2% of the initial one.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.163-172
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• 2004

A fast, accurate model for calculating roll gap variables are critical to the implementation of computer based automation systems for cold rolling mills. Based on the work of Fleck and Johnson, rollgap simulator with non-circular arc model was developed using the influence function. This developed model is capable of predicting values of force, torque and slip which can be applied over the wide range of rolling conditions including cold rolling/DR/temper mill with high execution speed. Friction coefficient was obtained as a function of operation conditions through analyzing measured data. After combination of rollgap simulator with production strategy, draft schedule for No.3 RCM (Reversible Cold Rolling Mill) in Incheon works of Dongbu Steel was developed. This draft schedule will be installed in the setup computer of No.3 RCM replacing old Hitachi model.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.6
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• pp.717-723
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• 2010

Radial stiffness of angular contact ball bearings are decreased remarkably at high speed revolution, because the inner and outer ball contact angle with races arc changed under the ball centrifugal forces at high speed. In the past, the optimizations of spindle units were done under the assumption of unchanged bearing stiffness for the whole speed range. But the bearing stiffness is changed and the dimension of optimum spindle is also changed with speed. In the design phase, only one model of many optimum spindle models with speed should be selected. As optimization criterion, the area of transfer function at spindle nose is proposed to estimate simply and accurately improvement of dynamic characteristics in spindle units. Finally, according to many analyses of diverse spindle models with decreased bearing stiffness, the spindle with shorter bearing span is better than longer bearing span from the viewpoint of dynamic characteristics.

• Journal of Electrical Engineering and Technology
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• v.7 no.3
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• pp.330-335
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• 2012

The shape optimization of a Thomson coil actuator used in an arc eliminator is done for fast response by adopting topology modification method. The displacement of the plate in a fixed calculation time is taken as the objective function. The objective function and contribution factor are calculated by using an adaptive equivalent circuit method which has been proved accurate and efficient. Both shape optimization and performance analysis are accomplished based on the segmentation of plate. Through the refinement of the sensitive segments a precise optimal plate shape can be obtained. The effectiveness of the proposed method is proved by the comparison of results before and after the shape optimization.

• Journal of Electrical Engineering and Technology
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• v.7 no.1
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• pp.58-63
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• 2012

The shape optimization of a Thomson coil actuator used in an arc eliminator is done for fast response by adopting topology modification method. The displacement of the plate in a fixed calculation time is taken as the objective function. The objective function and contribution factor are calculated by using an adaptive equivalent circuit method which has been proved accurate and efficient. Both shape optimization and performance analysis are accomplished based on the segmentation of plate. Through the refinement of the sensitive segments a precise optimal plate shape can be obtained. The effectiveness of the proposed method is proved by the comparison of results before and after the shape optimization.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1027-1028
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• 2007

In this paper, the variation of air-gap field intensity caused by the slot-opening in interior permanent magnet (IPM) motor is investigated, which is for predicting the instantaneous magnetic field more preciously in analytical method further. It is different with the approach of dealing the slot-opening effect on the air-gap field distribution with the "relative permeance" function in surface permanent magnet (SPM) motor. The prediction of the air-gap field in IPM motor is much more complex than SPM motor. In this study, an approximate estimation method is adopted based on analyzing the changing of flux path in both the IPM rotor part and stator part, and in additional an analytical function defined as "relative pole-arc" is built. The finite element method(FEM) is used for confirming the slot-opening effect on the field prediction.

• Journal of applied mathematics & informatics
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• v.42 no.3
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• pp.583-605
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• 2024

This paper discusses the properties of attractors of Type 1 IFS which construct self similar fractals on product spaces. General results like continuity theorem and Collage theorem for Type 1 IFS are established. An algebraic equivalent condition for the open set condition is studied to characterize the points outside a feasible open set. Connectedness properties of Type 1 IFS are mainly discussed. Equivalence condition for connectedness, arc wise connectedness and locally connectedness of a Type 1 IFS is established. A relation connecting separation properties and topological properties of Type 1 IFS attractors is studied using a generalized address system in product spaces. A construction of 3D fractal images is proposed as an application of the Type 1 IFS theory.

• Korean Journal of Organic Agriculture
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• v.12 no.3
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• pp.317-331
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• 2004

Foci of this thesis arc an estimation of willingness to pay and an establishment of green marketing strategics for environment-friendly agricultural products(EFAR). Estimations of willingness to pay for grain, vegetables, fruit and processed food-stuffs arc respectively 20.6%, 20.2%, 19.3% and 17.2% higher than agricultural products produced by conventional farming method. And a green mark6ting mix for EFAP is as follows; Erst, a product strategy focuses on producing safe and high-quality foods by environment-friendly agriculture(EFA) to point to consumer’s health and desire for environmental preservation. Second, in a price strategy, the balance of three factors should be kept, namely the environmental value the true quality as food materials and the price of EFAP. Third, a place strategy is to reduce waste matters, resource and energy uses in marketing chain, and to simplify marketing channels. Also, it is necessary to choose the marketing channel for price discrimination. Fourth, a promotion strategy make use of programs that emphasize the multi-function of EFA.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1991.10a
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• pp.5-10
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• 1991

There are many articles about the HID lamps about it's characteristics and simulation methods for lamps design or ballast design. For the eletronic ballasts of HID lamps, There are some problems caused by acoustic resonance which destabilizes the arc of HID lamps. So, some studies suggest the methods to avoid it. For example, the methods to avoid it. For example, the methods suggested are high frequency driving over 100kHz, and mixed frequency driving which alternates high frequency and low frequency, and square wave driving etc. This study suggests the electronic ballast of HID lamps which solves the problems of acoustic resonance, and which can control the luminance by constant current boosted chopper of which frequency is 30kHz and by the sqarewave driving of which frequency is 55.5Hz. As follows, we have the good eletronic ballast for HID lamps which has the characteristics of a light weight, and a function of luminance control and a high quality luminosity and which saves electrical energy.

• Journal of Surface Science and Engineering
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• v.44 no.5
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• pp.213-219
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• 2011

Recently aspheric lenses are widely used for superpricision optical instruments, such as cellular phone camera modules, digital cameras and optical communication modules. The aspherical lenses are processed using mold core under high temperature compressive forming pressure. It is imperative to develop superhard protective films for the life extension of lens forming mold core. Especially ta-C films with higher $sp^3$ fractions receive attentions for the life extension of lens forming mold and, in turn, the cost reduction of lenses due to their suprior high temperature stability, high hardness and smooth surfaces. In this study ta-C films were processed on WC mold as a function of substrate bias voltage using FVA (Filtered Vacuum Arc) method. The processed films were characterized by Raman spectroscopy and nano-indentation to investigate bonding nature and hardness, respectively. The film with maximun 87% of $sp^3$ fraction was obtained at the substrate bias voltage of -60 V, which was closest to ta-C film. ta-C films showed better high temperature stability by sustaining relatively high fraction of $sp^3$ bonding even after 2,000 glass lens forming applications.