• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.6
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• pp.930-937
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• 2003

The extension of design life among power plants is increasingly becoming a world-wide trend. Kori #1 unit in Korea is operating two cycle. It has two man-ways for tube inspection in a steam generator which is one of the important components in a nuclear power plant. Especially, stud bolts fur man-way cover have damaged by disassembly and assembly several times and degradation for bolt materials for long term operation. It should be evaluated and compared by ASME Code criteria for integrity evaluation. Integrity evaluation criteria which has been made by the manufacturer is not applied on the stud bolts of nuclear pressure vessels directly because it is controlled by the yield stress of ASME Code. It can apply evaluation criteria through FEM analysis to damaged female threads and to evaluated safety fer helical-coil method which is used according to Code Case-N-496-1. From analysis results, we found .that it is the same results between stress intensity which got from FEM analysis on damaged female threads over 10％ by manufacture integrity criteria and 2／3 yield strength criteria on ASME Code. It was also confirmed that the helical-coil repair method would be safe.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.21-23
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• 2002

We designed and manufactured helical magnetic flux compression generator, in which, the current density was reduced by increasing the number of wires by stages, and the voltage between wires was reduced by decreasing the time rate of inductance change. The figure of merit and the energy multiplication ratio of the generator were measured as a function of current density flowing through coil and their characteristics were analyzed. When the current density of coil was more than 250 kA/cm, the figure of merit and the energy multiplication ratio were decreased rapidly.

• Bulletin of the Korean Chemical Society
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• v.4 no.1
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• pp.36-41
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• 1983

An equation is derived which correlates the unperturbed dimensions $_0$ of polypeptides with the helical contents in the helix-coil transition region by using a simple model of a polypeptide chain. The model is a chain of connected balls which represent the repeating units, -CO-NH-CHR-, based on the fact that the repeating unit has a plane structure. The changing trend of the expansion factor ${\alpha}_{\eta}$ in the transition region is connected with the helical content $f_H$. The intrinsic viscosities [${\eta}$] of polypeptides are calculated from the unperturbed dimensions and the ${\alpha}_{\eta}$ factors. The above calculated results concerning $_0$ and [${\eta}$] are compared with other authors' theoretical and experimental results. From the comparison, we concluded that our theory explains better the chain dimensional behavior of polypeptides in the helix-coil transition region than others.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.143.1-143
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• 2002

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.4
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• pp.370-374
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• 2005

AC loss of a superconducting conductor has a strong influence on the economic viability of a superconducting fault current limiter, which offers an attractive means to limit short circuit current in power systems. Therefore, the AC loss characteristics in several fault current limiting elements of a coil type have been investigated experimentally. The test result shows that AC losses measured in the fault current limiting elements depend on arrangement of a voltage lead. The AC loss of a bifilar coil is smallest among the fault current limiting elements of the coil type. The measured AC loss of the bifilar coil is much smaller than that calculated from Norris's elliptical model. However, the loss measured in a meander, which is frequently used in a resistive fault current limiter, agrees well to the theoretical one.

• Journal of Advanced Navigation Technology
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• v.21 no.6
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• pp.614-619
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• 2017

In this paper, we optimize the wireless power transmission (WPT) coil, and then compare the EM simulation and measurement using magnetic coupling at 6.78 MHz. As transmission efficiency is affected by various factors such as the shape of the system, the size of the coils, the coil structure is proposed to consist of a helical resonant for transmission and a spiral resonant for reception. The size of the coil and the distance between the coils are determined to minimize the volume problem, and the shape of the coil are confirmed by EM simulation. A WPT system is designed with 860mm diameter top plate and cylindrical structure of column spaced 600mm apart, and the characteristics are simulated and measured. The simulation shows that ${\mid}S_{21}{\mid}$ is -0.53 dB with the efficiency of 88%, and the measurement result is that ${\mid}S_{21}{\mid}$ is -0.71 dB with the efficiency of 85%.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.11
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• pp.647-657
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• 2004

Helical magneto-cumulative generator(HMCG)s are very useful devices in suppling pulsed high current to inductance loads. To apply fast high voltage pulses to high impedance loads, high current outputs of HMCGs are required to be conditioned to higher voltages by using various pulse components such as opening/closing switches and pulse transformer. In this paper, stepping with the trends of requirements for ever-increasing energy in pulsed power applications coupling methods is investigated to obtain higher output energy by connecting several HMCGs in series or parallel way. The coil dimension of HMCGs used in series or parallel connections was 50 mm in diameter and 150 mm in length. The coil was fabricated by using enamel-coated copper wire of 1 mm in diameter. The highest energy amplification ratio and peak voltage of load were achieved from the serially connected four-barrel HMCG system. They were 68 and 34 kV, respectively, when the initial energy of 0.36 kJ was supplied into that system with the load of 0.4 μH. Within the tested range of inductance ratio, energy amplification ratio was found to be highly dependent on the inductance ratio of serial- and parallel-connected HMCG systems to load, which to be optimal around 500 was turned out. The experimental results showed that the output energy and voltage of load are controlled by connecting HMCGs in series or parallel.

• Journal of Advanced Navigation Technology
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• v.22 no.2
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• pp.148-153
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• 2018

This paper proposes a single-input multiple-output (SIMO) self-resonant wireless power transmission system for transmitting power to multiple receivers and the characteristics are simulated and measured. A 600 mm diameter transmission single loop, a 600 mm diameter helical transmission resonant coil, an external diameter 900 mm planar spiral reception resonant coil, and an $80{\times}60mm^2$ flat plate square coil as a receiver are used to form a wireless power transmission system 600 mm away with the table structure. For optimal characteristics, the wireless power transmission coils are designed by EM simulation and equivalent circuit analysis, and the characteristics are simulated and measured. The variation of the efficiency with distance from the center of the spiral resonant coil is analyzed and the measured efficiency is 57% for one receiver and for the two receivers, the efficiency is 37% for each receiver.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.315-318
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• 2001

We are proposing a new mobile phone antenna, which has a specially manufactured Mn-Zn cylindrical ferrite bead inside of the helical coil of the antenna. The extended antenna radiation patters and the spatial peak SAR averaged over 1 gram simulated tissue with and without the ferrite bead insertion were measured at 824 MHz. The results show that the ferrite bead resulted in SAR reduction about 20 %, and reflection coefficient increase about 7 % for the extended antenna. The applicability of this scheme to the antenna mass production is quite feasible.

• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.65-68
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• 2013

In a syngas cooling system of coal gasification process, fly slag carried by syngas deposit on the surface of heat exchanger. The deposited materials form a fouling layer with several millimeters thickness, disturbing heat transfer between steam and syngas. This study investigates flow and heat transfer characteristics of syngas in helical coil heat exchanger using computational fluid dynamics under clean and fouled surface condition. Process model were also designed and its results are in good agreement with CFD results.