• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.253-258
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• 1996

본 연구는 Zr-2.5wt%Nb합금의 고온변형특성중 특이한 유동응력의 변화거동인 어닐경화와 유동연화의 기구에 대해 고찰하였다. 연구결과에서 이러한 고온변형특성은 온도와 다단변형도중의 어닐링 시간에 영향을 받는 것으로 나타났으나 분위기 영향은 없는 것으로 나타났다. 즉, 변형 온도와 동일온도인 85$0^{\circ}C$에서 단시간인 5분동안 어닐링을 했을때 경화현상이 일어났다. 미세조직을 관찰한 결과 다단열간압연된 후의 미세조직과 집합조직은 다단열간압연된 미세조직과 집합조직과 직접적인 상관관계를 가진 것으로 나타났다. 어닐경화현상은 다단고온변형이 궁극적으로 변형시효와 유사한 효과 즉, 중간어닐링 동안에 Zr-2.5wt%Nb내의 불순물 원자와 열간압연시에 형성된 전위구조와의 강력한 인력형 상호작용하여 substructure가 안정화되기 때문이며 유동연화는 재결정으로 인한 유동응력의 감소인 것으로 사료된다.

• 전기의세계
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• v.9
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• pp.40-45
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• 1962

Laplace 및 Possion의 방정식을 만족하는 전장 및 자장으로 구성된 2차원 및 축대칭 3차원의 potential장을 물의 유동장을 이용한 fluid mapper로 상사해석함에 있어서 세극유로에 있어서의 유체전도율은 매질전도율로 압력은 전위로 유동장의 세기는 전장의 세기로, 유량밀도는 전류밀도로 각각 상사되며 또한 사상형에 있어서는 사상영역외에 존재하는 유선은 등자위선을 의미함을 논문에서 밝혔다. 이 논문에서는 사상형 fluid mapper의 전 유로 및 사상영역에 잇어서의 유체력학적 현상을 이론적으로 규명하여 이를 전기적 등가회로와 상사 해석함으로써 사상형 fluid mapper가 내포하고 있는 제량간의 상호관계를 명백히 하며 몇 가지 대표적인 사례를 들어 사상형 fluid mapper의 응용에 대하여 기술하였다.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.91.2-91.2
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• 2005

• Economic and Environmental Geology
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• v.36 no.2
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• pp.123-131
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• 2003

Geophysical surveys(electrical resistivity, self-potential, seismic refraction, GPR) were conducted to investigate the physical properties of the subsurface, and to delineate the flow channel of leachate from a AMD(acid mine drainage), buried rock wastes and tailings, and drainage pipes at an abandoned mine(Kwangyang mine). Especially in rainy season the sites appear to be abundant in AMD leachate, characterized by electrical conductivities of 0.98-1.10 ms/S. Electrical resistivity sections indicate that the leachate flows running in two directions at southern part rise up through the narrow fracture zones at the central part and contaminates the surrounding soil and stream. Such schematic features at the anomalous zone are well correlated with negative peaks in self-potential data, the limited penetration depth in GPR data and low velocity zone in seismic refraction data. Shallow high-resistivity zone is associated with the buried rock wastes which cause the diffractions in GPR image. In addition, the events at depth of approximately 1-1.25 m in GPR sections must be the metal pipes through which AMD is drained off to the inner bay.

• 한국지구물리탐사학회:학술대회논문집
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• 2000.09a
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• pp.19-40
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• 2000

We applied both SP monitoring and pole-pole array resistivity surveys and SP survey and dipole-dipole array resistivity survey to leakage problems in several embankments and dike, respectively, to estimate and detect the zone of leakage. The embankment is generally affected by tidal variation and has low resistivity characteristics due to the high saturation of seawater. According to this situation, SP monitoring and resistivity survey using pole-pole electrode array, which is relatively more effective to the conductive media, were carried out to delineate the leakage zones of sea water through the embankment. We checked out electrical conductivity(EC) and temperature variations along the inner part of the embankment to detect the zone of seawater leakage and found that the measured EC value agreed to that of seawater in the leakage zone and the temperature was lower than that of the vicinity of leakage zone. SP monitoring results were coincide with tidal variations at each embankment. Based on the survey results, it is concluded that both SP monitoring and the pole-pole array resistivity method are quite effective for investigation of seawater leakage zones in the embankment.

• Journal of the Korean Society of Visualization
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• v.4 no.1
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• pp.31-40
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• 2006

In this study a newly designed electro-osmotic micro-mixer is proposed. This study is composed of a channel and metal electrodes attached locally on the side wall surface ultimately to control the mixing effect. To obtain the flow patterns, numerical computation was performed by using a commercial code, CFD-ACE. The fluid-flow solutions are the cast into studying the characteristics of stirring in terms of the mixing index. It was shown that the local control of the electric potential can indeed contribute to the enhancement of mixing effect.

• Electrical & Electronic Materials
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• v.10 no.4
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• pp.334-341
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• 1997

Streaming electrification on insulating paper and pressboard under D.C. and A.C. electric field was investigated by using paper tubes and oil circulation apparatus. At first, flowing of static charges as measured with no electric field. As the temperature of oil increased, the measured current curve hows peak. As the velocity increased, it shows increasing exponential curve. Then, we applied A.C. and D.C. electric field on paper tube and the current from relaxation tank to earth was measured, which other factors such as temperature and velocity were varied like case of no electric field. The ions in oil carry the charges. So electric field makes asymmetry effect, and electrophoretic effect on ions in oil. We find that as the electric field intensity increased, the charges which were made by electric double layer were increased. The charge vs. velocity curve made peak point at a velocity.

• Korean Journal of Crystallography
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• v.5 no.2
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• pp.67-77
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• 1994

From the Y3-3xNd3xAl5O12single crystals grown by the Czochralski technique, various types of defects were detected and 1) the reason of opical in homogeneous phases, 2) the mechanism of formation of the iridum metal inclusions accompanying bubbles, and 3) the mechanism of formation of the core and facet were analysed After preparing the wafers of the <111> growth parallel, defscts were observed by the polarising microscope using a photoelasic effect and then some images of stress-birefringence were compared to their etch Pits patterns.

• Journal of the Korean Geophysical Society
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• v.5 no.1
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• pp.19-27
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• 2002

Geophysical surveys(self-potential, electromagnetic, electrical resistivity, and seismic refraction methods) were performed to delineate the flow channel of leachate from a AMD (acid mine drainage) by correlating the anomalies to geochemical characteristics at an abandoned mine (Jangpoong mine). The geophysical responses attempted to be correlated with water sample analysis data(pH, EC, heavy metals, ${SO_4}^{-2}$). Electrical dipole-dipole resistivity sections represent the low-resistivity zone trending northwest, which indicates the leachate flow by AMD along the contact of the mine waste rock dump and the bedrock. From the overall points of geophysical and geochemical anomalies, it is summarized that the flow channel of leachate by AMD can be successfully imaged with composite interpretations on the geophysical and geochemical studies.

• Geophysics and Geophysical Exploration
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• v.7 no.3
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• pp.164-173
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• 2004

To delineate geothermal water movement at the Pohang geothermal development site, Self-Potential (SP) survey and monitoring were carried out during pumping tests. Before drilling, background SP data have been gathered to figure out overall potential distribution of the site. The pumping test was performed in two separate periods: 24 hours in December 2003 and 72 hours in March 2004. SP monitoring started several days before the pumping tests with a 128-channel automatic recording system. The background SP survey showed a clear positive anomaly at the northern part of the boreholes, which may be interpreted as an up-flow Bone of the deep geothermal water due to electrokinetic potential generated by hydrothermal circulation. The first and second SP monitoring during the pumping tests performed to figure out the fluid flow in the geothermal reservoir but it was not easy to see clear variations of SP due to pumping and pumping stop. Since the area is covered by some 360 m-thick tertiary sediments with very low electrical resistivity (less than 10 ohm-m), the electrokinetic potential due to deep groundwater flow resulted in being seriously attenuated on the surface. However, when we compared the variation of SP with that of groundwater level and temperature of pumping water, we could identify some areas responsible to the pumping. Dominant SP changes are observed in the south-west part of the boreholes during both the preliminary and long-term pumping periods, where 3-D magnetotelluric survey showed low-resistivity anomaly at the depth of $600m\~1,000m$. Overall analysis suggests that there exist hydraulic connection through the southwestern part to the pumping well.