• Nuclear Engineering and Technology
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• v.40 no.3
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• pp.239-250
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• 2008

If there is a water flow with a range of temperature inside a pipe, the wanner water tends to float on top of the cooler water because it is lighter, resulting in the upper portion of the pipe being hotter than the lower portion. Under these conditions, such thermal stratification can play an important role in the aging of nuclear power plant piping because of the stress caused by the temperature difference and the cyclic temperature changes. This stress can limit the lifetime of the piping, even leading to penetrating cracks. Investigated in this study is the effect of thermal stratification on the structural integrity of the pressurizer surge line, which is reported to be one of the pipes most severely affected. Finite element models of the surge line are developed using several element types available in a general purpose structural analysis program and stress analyses are performed to determine the response characteristics for the various types of top-to-bottom temperature differentials due to thermal stratification. Fatigue analyses are also performed and an allowable environmental correction factor is suggested.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.817-820
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• 2004

Our country was much developments in change of construction environment along with fast economy development. But, various problems that must think in problem of safety and quality were appeared. Constructions which build through rapid economy development are getting many social criticisms to problem of crack and water leakage at use process. Is situation that huge repair expense to cure this is engaged. Safety problem of construction is indicated socially through various media mediums again.

• Fibers and Polymers
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• v.5 no.4
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• pp.316-320
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• 2004

Waterproof fabrics are seamed and sealed by waterproof sealing tape to prevent water from penetrating through the stitch holes. As this process may change the mechanical properties of breathable waterproof fabric related to its deformation with human body, the changes in mechanical properties were investigated. In both of parallel and perpendicular directions, tensile characteristics were remarkably changed with seaming and sealing processes. The increase of LT and WT means that the clothing sealed by waterproofing tape may produce somewhat discomfort feeling. On the other hand, the bridge of the sewing thread seemed to be reinforced by waterproofing tape. Shear characteristics such as G, 2HG, and 2HG5 gradually increased with seaming and sealing processes in parallel direction. However, they decreased with sealing process in perpendicular direction because the seam line would work as an axis located at the center of the testing range.

• Journal of Ocean Engineering and Technology
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• v.11 no.3
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• pp.29-38
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• 1997

Crack penetration behavior by fatigue crack propagation and measurements of AE before-and-after crack penetration were examined using SS41 steel plate. Experimental crack shape of SU type was in good agreement with calculated shape rather than S type. Crack propagation behavior on the front surface appears not to change markedly after penetration. However, crack growth on the back surface appears to accelerate as reported by author. As a crack propagates, AE occurred heavily just before penetration. Then, it decreases and crack is penetrating. A transition from plane strain to plane stress was observed by fractographic study. At this time, separation of fracture surface was shown which affects AE occurrence.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.9
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• pp.1790-1795
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• 2009

For GPR(Ground Penetrating Radar) applications, an accurate analysis of the scattered field is necessary to identify the unknown target. Dyadic Green's function of the multilayered medium is developed and applied to analysis of the underground conducting object. We used method of moment(MOM) with dyadic Green's function, and Discrete Complex Image Method(DCIM). To reduce the computational complexity, fast multipole method is introduced and we showed the accuracy of the method comparing with the conventional method of moment. For investigating the underground conducting target, several numerical experiments were accomplished using this method.

• Journal of Electrical Engineering and Technology
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• v.2 no.1
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• pp.102-105
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• 2007

Effects of $Ag_2O$ doping on the electromagnetic properties in the BiSrCaCuO superconductors. The electromagnetic properties of the $Ag_2O$ doped and undoped BiSrCaCuO superconductor were evaluated to investigate the contribution of the pinning centers to the magnetic effect. It was confirmed experimentally that a large amount of magnetic flux was trapped in the $Ag_2O$ doped sample than that in the undoped one, indicating that the pinning centers of magnetic flux are related closely to the occurrence of the magnetic effect. It is considered that the area where normal conduction takes place increases by adding $Ag_2O$ and the magnetic flux penetrating through the sample increases. The results suggested that Ag acts to increase the pinning centers of the magnetic flux, contributing to the occurrence of the electromagnetic properties.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.5
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• pp.429-434
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• 2003

The magnetic field sensor was fabricated with superconducting ceramics of BiPbSrCaCuO system. The sensor at liquid nitrogen temperature showed the increase of electrical resistance by applying magnetic field. Actually, the voltage drop across the sensor was changed from zero to a value more than 100 $\mu\textrm{V}$ by the applied magnetic field. The change of electrical resistance depended on magnetic field. The sensitivity of this sensor was 2.9 $\Omega$/T. The sensing limit was about 1.5${\times}$10$\^$-5/ T. The increase of electrical resistance by the magnetic field was ascribed to a modification of the Josephson junctions due to the penetrating magnetic flux into the superconducting material. Considering the observed properties of the superconductor with trapped magnetic flux, a magnetic sensor was fabricated to detect simultaneously both the intensity and the direction of the magnetic field.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.61-65
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• 2003

A magnetic field sensor is fabricated with superconducting ceramics system The prepared material shows the superconductivity at about 95K. The sensor at liquid nitrogen temperature shows the increase in electrical resistance by applying magnetic field. Actually, the voltage drop across the sensor is changed from zero to a value more than $100{\mu}V$ by the applied magnetic field. The change in electrical resistance depends on magnetic field. The sensitivity of this sensor is 2.9 ohm/T. The increase in electrical resistance by the magnetic field is ascribed to a modification of the Josephson junctions due to the penetrating magnetic flux into the superconducting material.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2211-2213
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• 2005

Recently, the membrane technology has actively been applied to make generating water because the convention; chemical treatment technology for purifying water has caused second environmental pollution. In spite of its ecological advantages, this membrane technology has some drawbacks such as ease of membrane contamination, efficiency and running cost. The purpose of this research is reduction of membrane contamination by applying high voltage pulsed electric field to the water prior to its penetrating membrane.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1984-1986
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• 2003

본 논문은 UWB(Ultra WideBand) 기술에 기반한 지반탐사레이더(Ground Penetrating Radar, GPR)용으로 개발된 광대역 안테나의 특성에 관해 나타낸다. UWB 기술의 핵심은 주기가 수 나노초 이하의 짧은 임펄스를 이용하는 것으로 지반탐사레이더는 이 임펄스 기술을 이용함으로서 탐사 능력과 해상도를 높일 수 있다. 임펄스 전송을 위해 안테나는 넓은 대역폭, 크기, 무게, 가격 등 지반탐사레이더에 적용될 수 있는 조건을 만족해야 함으로 안테나의 설계는 이에 부합할 수 있는 다이폴 안테나를 선택하여 개발하였다. 개발된 안테나의 성능을 검증하기 위해 시뮬레이션과 실험을 실시하였고 그 결과 설계된 안테나의 대역폭이 0.5 GHz에서 2.7 GHz로 2.2 GHz(138%)의 사용대역을 나타냄으로서 UWB 기술에 기반한 지반탐사레이더용으로 유용함을 확인하였다.