• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.373-378
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• 2000

The crevice corrosion of local corrosion occur when the gap exist on metal surface. This crevice corrosion happen to region such as flange of pipe, contact part of casing, under gasket and packing, between valve disk and seat of pump etc. Especially The crevice corrosion of mild steel(SS 400) get serious. This paper was studied on the crevice corrosion of SS 400 in fluid environment. In $0\%,\;2\%,\;3.5\%,\;5\% NaCl$ solution, the aspect of the crevice corrosion and polarization behavior under the crevice corrosion was investigated. And Weight loss rate of SS 400 with crevice and non-crevice was measured according to the NaCl concentration. The main results obtained are as follows : 1) Under crevice corrosion, the corrosion potential become less noble as the concentration of NaCl solution increased. 2) The current density under open circuit potential was high drained as concentration of NaCl solution increased by $3.5\%$ but the concentration increased over $3.5\%$, the current density was low drained. 3) The weight loss rate of SS 400 was increased as concentration of NaCl solution Increased by $3.5\%$, but the concentration increased over $3.5\%$, that of SS 400 was decreased. 4) Effect of oxygen for crevice corrosion in the concentration of $3.5\%$ NaCl solution become sensitive than that $0\%$ NaCl solution.

• 대한전자공학회논문지SD
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• 제37권5호
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• pp.1-8
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• 2000

PZT seed에 의해 형성된 단결정립 PZT 박막을 이용하여 Pt/PZT/Pt 구조에서의 피로(fatigue) 및 정보 유지(data retention) 특성에 관하여 연구하였다. 피로 특성의 경우 1㎒의 주파수에서 ±10V의 square wave를 인가하여 측정한 결과 2×10/sup 11/ cycle 동안 전혀 특성의 변화가 관찰되지 않았으며, 정보 유지 능력의 경우 상온에서 30000초 동안 기억 상태의 변화가 없었으며, 고온에서의 retention 측정으로 계산된 활성화 에너지로부터 구한 상온에서의 20% 잔류분극간 감소를 보이는 시간은 6.6×10/sup 7/ 년이었다.

• 대한전자공학회논문지TC
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• 제43권5호
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• pp.162-168
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• 2006

전파 특성의 이해는 무선 통신 시스템의 설계와 서비스의 구축을 위해 매우 중요하다. 본 논문에서는 곡선형 지하철 터널환경에서 2.45GHz 주파수 대역의 전파 특성을 측정하고 분석하였다. 슬라이딩 코릴레이션 기반의 채널 측정 시스템을 구성하고 안테나의 빔 형태에 따른 특성을 비교하기 위해 5 종류의 안테나를 사용하였다. 터널내 경로손실은 자유공간에 비하여 안테나에 따라 평균 $4.38^{\sim}14.41dB$가 적고 원편파 안테나의 경로손실이 가장 적다. 또한 곡선구간에서 수신 안테나의 위치가 바깥쪽에 위치할 때 경로손실이 가장 적다. 모든 안테나의 지연성분의 90%가 20ns 이내에 존재하며, 지향성 안테나가 무지향성 안테나보다 더 넓은 코히어런스 대역폭을 갖는다. 측정결과 경로손실과 지연 특성을 고려할 때 지하철 터널에서는 원편파 안테나를 사용하는 것이 적합한 것으로 판단된다.

• Journal of Electrochemical Science and Technology
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• 제4권2호
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• pp.47-56
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• 2013

Inhibition performance of Lornoxicam & Tenoxicam against corrosion of carbon steel in 1M $H_2SO_4$ solutions was investigated by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. The inhibition efficiency increased with increasing inhibitor's concentration, but decreased with increase in temperature. Potentiodynamic polarization curves showed that, the inhibitors were of mixed type. The apparent activation energy ($E^*_a$) and other thermodynamic parameters for the corrosion process have also been calculated and discussed. The inhibition of carbon steel corrosion is due to the adsorption of the inhibitor molecules on the surface, which follows Temkin adsorption isotherm. The mechanism of inhibition was discussed in the light of the chemical structure of the undertaken inhibitors.

• Journal of Electrochemical Science and Technology
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• 제4권2호
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• pp.61-70
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• 2013

Corrosion inhibition of carbon steel in 2M HCl by some benzohydrazide derivatives (I-III) was studied using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques at $30^{\circ}C$. Polarization studies showed that all the investigated compounds are of mixed type inhibitors. Temperature studies revealed a decrease in efficiency with rise in temperature and corrosion activation energies increased in the presence of the hydrazide derivatives, probably implying that physical adsorption of cationic species may be responsible for the observed inhibition behavior. Electrochemical impedance studies showed that the presence of benzohydrazide derivatives decreases the double layer capacitance and increases the charge transfer resistance. The adsorption of these compounds on carbon steel surface was found to obey Temkin's adsorption isotherm. Synergistic effects increased the inhibition efficiency in the presence of halide additives namely KI and KBr. An inhibition mechanism was proposed in terms of strongly adsorption of inhibitor molecules on carbon steel surface.

• 한국표면공학회지
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• 제21권2호
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• pp.39-46
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• 1988

Corrosion behavior of 5-26wt% Ni-Zn electrodeposited alloys was investigated by means of dipping electrochmical polarization measurement and galvanic coupling test. The weight loss and anodic polarization curve of coatings were measured by means of dipping and polarization measurement respectively. The galvanic protection effect of alloy coatings was measured by galvanic coupling test and the surface morpholgy of coatings was observed after corrosion testing. Our findings support thous of previous investigations showing that ${\gamma}$single phase coatings, while galvanic pprotection effect of dual phase coatings improved in comparison with ${\gamma}$single phase coating. The formation of colony in coating of ${\gamma}$and η+${\gamma}$ dual phsae caused the localized corrsion and increased the corrosion rate of the Ni-Zn coating.

• Journal of electromagnetic engineering and science
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• 제13권4호
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• pp.214-223
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• 2013

This paper proposes a theoretical analysis of hidden device detection and a design of multiband circular polarization patch array antenna for non-linear junction detector system application. A good axial ratio of circular polarization patch antenna is realized by a new approach that employs inclined slots, two rectangular grooves and a truncated ground for the conventional antenna. A good axial ratio of the 1.5 dB lower is measured by having an asymmetric gap distance between the ground planes of the coplanar waveguide feeding structure. The common ground plane of the linear array has an optimum trapezoidal slot array to reduce the mutual coupling without increasing the distance between the radiators. The higher gain of about 1 dBi is realized by using the novel common ground structure. The measured return loss, gain, and axial ratio of the proposed single radiator, as well as the proposed array antennas, showed a good agreement with the simulated results.

• 한국광학회:학술대회논문집
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• 한국광학회 2008년도 하계학술발표회 논문집
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• pp.425-426
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• 2008

The Panda-type polarization maintaining fibers were fabricated by VAD(vapor-phase axial deposition) method. We fabricate Panda style polarization maintaining fibers that have small form factor($80{\mu}m$), high H-parameter of about $1{\times}10^{-4}/m$ and low optical loss of about 3dB/km.

• 전기학회논문지
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• 제59권12호
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• pp.2268-2272
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• 2010

This letter presents that a rectenna can utilize more stable wireless power by using a new design dual band/dual polarization microstrip patch antenna and 2 stage voltage multiplier at 2.4 GHz band and 3.1 GHz band. The proposed antenna is a new microstrip patch antenna design to make impedance matching possible by using slotted capacitive coupling between the patch and $50\Omega$ feed line on a ground plane. Its advantage is that the size of the rectenna can be reduced by using $50\Omega$ feed line on the ground plane, which can be used efficiently. The dual band/dual polarization microstrip patch antenna shows circular polarization at 2.4 GHz band and linear polarization at 3.1 GHz band. Under -10 dB return loss, The dual band/dual polarization microstrip patch antenna obtains 340 MHz bandwidth as 2.23~2.57 GHz and 375 MHz bandwidth as 2.95~3.325 GHz. Also, 2 Stage Voltage multiplier is possible to operate at 2.4 GHz band and 3.1 GHz band. The designed retenna can usually obtain wireless power at both 3.1 GHz band, and 2.4 GHz band applications such as Wi-Fi, Bluetooth, Wireless LAN, etc. So more stable wireless power can be utilized at the same time.

• 한국전자파학회논문지
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• 제16권4호
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• pp.397-401
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• 2005

본 논문에서는 복잡한 무선통신 환경에서 편파 다이버시티를 사용하기 위하여 편파 변환 기능을 갖는 개구결합 마이크로스트립 안테나를 제안하였다. 제안된 안테나는 다층기관의 배면에 급전을 위한 마이크로스트립 선로를 가졌으며, 그 위의 접지면에는 $\lambda{g}/4$ 간격으로 2개의 슬롯이 위층의 방형 방사 패치의 변과 평행하게 놓여져 있다. 마이크로스트립 급전선로의 종단에 연결한 핀 다이오드를 개방과 단락으로 변환함에 따라 하나의 슬롯이 선택되어 패치에 급전하도록 함으로써 편과를 수평이나 수직으로 변환하는 구조로 하였다. 제작된 안테나의 공진주파수는 수평, 수직편파에서 파자 $2.41\;\cal{GHz},\;2.40\;\cal{GHz}$로 나타났고 편파 분리도는 $19\;\cal{dB},\;23\;\cal{dB}$극 보였으며 $-10\;\cal{dB}$ 반사 손실 대역폭은 각각 $95\;\cal{MHz},\;100\;\cal{MHz}$이었고 이득은 $6\;\cal{dBi}$로 나타났다.