• Journal of the Korean Society for Precision Engineering
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• v.15 no.9
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• pp.175-181
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• 1998

The coil spring is used in the suspension of automotive vehicles and small omnibus. Recently, it can be adopted hardening type spring which spring constant is accompanied by increasing displacement to increase passenger comfortability. One of methods which assert this characteristic is cylindrical-taper section coil spring. In this paper we calculate ideal spring characteristic curve from the given vehicle conditions, and show the design method of the cylindrical-taper section coil spring.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2005.11a
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• pp.117-118
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• 2005

• Journal of the Korean Institute of Navigation
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• v.9 no.1
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• pp.95-109
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• 1985

It has been generally known that the chattering of an AC electromagnetic contactor due to the fluctuation of attracting force is the primary cause of its abrasion and noise. To reduce this chattering effect, an AC electromagnetic contactor is mostly fitted with a shading coil which works the role to make difference in phases of two distinct components of attracting force. The theoretical interpretation of an AC electromagnetic contactor with shading coil and the equation of its attracting force per unit wattage consumed have already been proposed, however, few explications so far have been made on the determination of optimal circuit constants of shading coil. In this paper, the auther constructs a circuit model of an AC electromagnetic contactor with shading coil which is based on the theoretical interpretation of shading coil examined to be valid by experiments under some assumptions, and defines the equation of attracting force without chattering per unit wattage consumed as a performance function for determining the optimal circuit constants of shading coil. And then, the optimal circuit constants maximizing the performance function are determined by means of computer simulation founded on the above circuit model and the characteristics of those circuit constants are examined with special attention to the coupling coefficient.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.227-229
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• 1997

A new phased-array quadrature RF coil for one or two RF acquisition channels is developed for spine MR imaging. Quadrature RF coils for MRI have been useful to improve the signal-to-noise ratio (SNR) by $"\sqrt{2}"$ using two orthogonal RF coils in combination [1]. More recently, the phased-array RF coil has been proposed for more improvement of SNR by using an array of RF coil elements with a reduced size and coverage for each element. Two new schemes are proposed for the new phased-array quadrature RF coil as follows : (1) Proper overlapping of two quadrature RF coils thus removing the mutual inductance and (2) Attaching preamplifiers right after the coil section and combining the signal with proper phase delays. The coil has been implemented for receive- only mode. It has been tested through phantom and volunteer imaging. The experimental results show the utility of the proposed RF coil.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1343-1346
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• 2005

In the cold rolling mill, coil breakage that generated in rolling process makes the various types of troubles such as the degradation of productivity and the damage of equipment. Recent researches were done by the mechanical analysis such as the analysis of roll chattering or strip inclining and the prevention of breakage that detects the crack of coil. But they could cover some kind of breakages. The prediction of Coil breakage was very complicated and occurred rarely. We propose to build effective prediction modes for coil breakage in rolling process, based on data mining model. We proposed three prediction models for coil breakage: (1) decision tree based model, (2) regression based model and (3) neural network based model. To reduce model parameters, we selected important variables related to the occurrence of coil breakage from the attributes of coil setup by using the methods such as decision tree, variable selection and the choice of domain experts. We developed these prediction models and chose the best model among them using SEMMA process that proposed in SAS E-miner environment. We estimated model accuracy by scoring the prediction model with the posterior probability. We also have developed a software tool to analyze the data and generate the proposed prediction models either automatically and in a user-driven manner. It also has an effective visualization feature that is based on PCA (Principle Component Analysis).

• ETRI Journal
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• v.38 no.3
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• pp.568-578
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• 2016

A wireless power transfer (WPT) system is usually classified as being of either a two-coil or four-coil type. It is known that two-coil WPT systems are suitable for short-range transmissions, whereas four-coil WPT systems are suitable for mid-range transmissions. However, this paper reveals that the two aforementioned types of WPT system are alike in terms of their performance and characteristics, differing only when it comes to their matching-network configurations. In this paper, we first find the optimum load and source conditions using Z-parameters. Then, we estimate the maximum power transfer efficiency under the optimum load and source conditions, and we describe how to configure the matching networks pertaining to both types of WPT system for the given optimum load and source conditions. The two types of WPT system show the same performance with respect to the coupling coefficient and load impedance. Further, they also demonstrate an identical performance in the two cases considered in this paper, that is, a strong-coupled case and a weak-coupled case.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.352-355
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• 2004

The objective of this work is to develop a new design method to find optimal coils, especially the optimal coil configuration of an optical pickup actuator. In designing actuator coils, the developed Lorenz force in the coils along the desired direction should be made as large as possible while forces and torques in other directions should be made as small as possible. The design methodology we are developing is a systematic approach that can generate optimal coil configurations for given permanent magnet configurations. To consider the best coil configuration among all feasible coil configurations, we formulate the design problem as a topology optimization of a coil. The present formulation for coil design is noble in the sense that the existing topology optimization is mainly concerned with the design of yokes and permanent magnets and that the optimization of actuator coils is so far limited within shape or size optimization. Though the present design methodology applies to any problem, the specific design example considered is the design of fine-pattern tracking and focusing coils.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.975-980
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• 2001

Like composite material. the coil winding pack of the KSTAR (Korea Superconducting Tokamak Advanced Research) consist of multiphase element such as metallic jacket material for protecting superconducting cable, vacuum pressurized imprepregnated (VPI) insulation, and corner roving filler. For jacket material, four CS (Central Solenoid) Coils, $5^{th}$ PF (Poloidal Field) Coil, and TF (Toroidal Field Coil) use Incoloy 908 and $6-7^{th}$ PF coil, Cold worked 316LN. In order to analyze the global behavior of large coil support structure with coil winding pack, it is required to replace the winding pack to monolithic matter with the equivalent mechanical properties, i.e. Young's moduli, shear moduli due to constraint of total nodes number and element numbers. In this study, Equivalent Young's moduli, shear moduli, Poisson's ratio, and thermal expansion coefficient were calculated for all coil winding pack using Finite Element Method.

• Progress in Superconductivity and Cryogenics
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• v.14 no.3
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• pp.33-37
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• 2012

An HTS racetrack-type coil without turn-to-turn insulation was characterized by critical current, sudden discharge, and over-current tests with respect to external pressures applied to the straight sections of the coil. The thermal stability of the non-insulated HTS racetrack-type coil was remarkably enhanced with increasing external pressure applied to the straight sections of racetrack-type coil. Furthermore, over-current test results confirmed that the non-insulated HTS racetrack-type coil with increased turn-to-turn thermal contact has the potential to be manufactured into field coils of HTS wind turbine generators with highly enhanced thermal and electrical stabilities.

• Progress in Superconductivity and Cryogenics
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• v.14 no.3
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• pp.23-27
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• 2012

This paper aims to evaluate the feasibility of using no-insulation High Temperature Superconducting (HTS) coil in persistent current mode system. A HTS coil in persistent current mode system usually includes one or more non-superconducting joints in its circuit. And the current decaying rate of the coil is affected by the resistance of joint in persistent current circuit. If the resistance of joint is large, decaying rate of the current drastically increases. Therefore, reducing the joint resistance of the HTS coil is very important in persistent current mode system. In this paper, the no-insulation HTS coil is suggested as a way to reduce the joint resistance with the embedded parallel contact resistance naturally made by no-insulation winding method. Two small coils are fabricated with insulation and no-insulation winding method, and persistent current mode system experiment of each coil is preformed and analyzed.