• 전기학회논문지P
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• 제53권2호
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• pp.43-50
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• 2004

Percentage differential characteristic relaying(PDR) has been recognized as the principal basis for power transformer protection. Second harmonic restraint PDR has been widely used for magnetizing inrush in practice. Nowadays, relaying signals can contain 2nd harmonic component to a large extent even in a normal state, and 2nd harmonic ratio indicates a tendency of relative reduction because of the advancement of material. Further, as the power system voltage becomes higher and more underground cables are used, larger 2nd harmonic component in the differential current under internal fault is observed. And then, conventional 2nd harmonic restraint PDR exposes some doubt in reliability. It is, therefore, necessary to develop a new algorithm for performance improvement of conventional protective relaying. This paper proposes an advanced protective relaying algorithm by using voltage-current trend and flux-differential current slope characteristic. To evaluate the performance of the proposed algorithm, we have made comparative studies of PDR, fuzzy relaying and DWT relaying. The paper is constructed power system model including power transformer, utilizing the WatATP, and data collection is made through simulation of various internal faults and inrush. As the results of test, the new proposed algorithm was proven to be faster and more reliable.

• 전기학회논문지P
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• 제58권3호
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• pp.328-333
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• 2009

In this paper, we have developed high performance SPD(surge protective device) and evaluated the characteristics in comparison with typical SPD used in the inside and outside of the country. The new SPD was composed of MOV(metal oxide varistor), GDT(gas discharge tube) and impedance such as resistors, capacitors or varistors. To estimate operating the characteristic of the SPD which was developed, it was measured surge voltage caused by fault current or surge according to IEC 61000-4-5. As a result it was found that the power supply was cut off by high performance SPD when caused a short-circuit. In addition we could know that it could prevent ELB(earth leakage breaker)'s malfunction caused by surge.

• 한국수소및신에너지학회논문집
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• 제22권4호
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• pp.546-551
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• 2011

The corrosion on steam generator tubes of the secondary side of pressurized water reactor inhibits heat transfer. One of the most efficient techniques improving the heat transfer performance of a nuclear electric generation is a corrosion control. The environmental parameters mostly affecting corrosion are materials and chemical additives. It seems that no further corrosion occurs in steels with Polyacrylic acid polymer dispersant treatment. Polyacrylic acid forms a protective coating with uniform thickness on metal surface. Polyacrylic treatment appears to be the most convenient way to enhance the thermal performance by the thermal conductivity improvement in steam generators.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.433-436
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• 2002

Most of electric distribution utilities have their reliability performance measured by reliability indices such as SAIFI and SAIDI to evaluate customer satisfaction. Adding protective devices in electrical distribution system can increase the system reliability by protecting public customers from local faults. In large-scale distribution system, it is difficult to determine the positions of these protective devices, which can efficiently protect customers within utilities' investment. In this paper, we propose an optimization technique to identify types and positions of protective devices to minimize SAIFI and SAIDI indices according to system requirement constraints.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.211-213
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• 2005

In this paper, the frequency compensator for digital protective relay is introduced. Due to sudden appearance of generation-load or fault in power system, the frequency can deviate from its nominal value. The Orthogonal filter adopted to digital protective relay is exposed to the problem. Therefore, the frequency variation makes a difficult to protective function and power measurement in digital protective relay. The essential property of the proposed algorithm presented is its outstanding immunity to both signal orthogonal component magnitudes and DFT filter gain variations which ensures below 0.05Hz accuracy of estimation. Additionally, the proposed method has excellent characteristics with low signal sampling rate. Based on the frequency estimation, author design under frequency protection relay for generator and verifies its performance with several experimental tests.

• Composites Research
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• 제37권2호
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• pp.108-114
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• 2024

지속적으로 증가하는 세계적인 전력수요로 인해 고전압 해저케이블 수요도 증가하고 있다. 해저케이블은 고가의 제작 비용과 높은 단가의 포설 비용 등이 해결되어야 할 부분 중 하나이다. 해양 환경에 노출된 해저케이블은 파랑 및 해류 등의 외력들에 의해 케이블 손상이나 사고 시에는 높은 유지 보수 비용 등의 문제가 발생할 수 있다. 따라서 해저케이블은 다양한 종류의 보호 기자재를 통해 해저 환경의 불확실성에 대비하고 있다. 본 연구에서는 대표적인 보호 기자재인 피기백 클램프(PBC)와 클램프에 사용되는 스트랩(strap)을 대상으로 해석적 방법을 통해 휨 성능을 살펴보았다. 피기백 클램프의 구조적 성능 검토를 위해 유연 보호 튜브의 최대 굽힘 모멘트 기준치인 15 kN·m 값을 토대로 휨 성능을 분석하였다, 그 결과, 피기백 클램프 및 strap의 굽힘 모멘트에 대한 휨 성능이 확보되었음을 확인할 수 있었다.

• 한국간호교육학회지
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• 제18권2호
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• pp.293-302
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• 2012

Purpose: The purpose of this study was to investigate nursing students' awareness and performance on standard precautions and to provide meaningful information for nursing students' education regarding hospital infection control. Method: Four hundred forty seven nursing students at 6 universities in D-city participated in this study. Data collection was conducted from March to April 2011. Students' awareness and performance on standard precautions of infection control in hospitals were measured using the modified 2007 CDC standard precautions guidelines. Data analysis was performed using the SPSS WIN 18.0 program, descriptive statistics, t-test, and ANOVA. Results: The level of students' awareness in the standard precautions was higher than performance. The higher levels of students' awareness and performance on standard precautions included patient care equipment, safe injection practices, and worker safety. The lower levels of students' awareness and performance on standard precautions included hand hygiene and personal protective equipment. There was no difference in the students' awareness and performance of standard precautions according to their characteristics. Conclusions: Based on the findings of this study, hand hygiene and personal protective equipment need to be stressed more within the program to improve nursing students' infection control techniques.

• 한국응급구조학회지
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• 제20권2호
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• pp.21-35
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• 2016

Purpose: This study aims to investigate awareness and performance of infection control during ambulance attendant training, and to provide basic data for infection control. Methods: The subjects were 235 paramedic students who completed ambulance attendant training. There were 51 questions. The infection control dimension was divided into hand washing, personal protective equipment use, and environmental management, for each sub-dimension, awareness and performance were measured by a 4-point scale. The collected data were analyzed using SPSS statistics ver. 22.0. Results: A total of 95.3%, of the subjects completed an orientation for ambulance attendant training and 71.7% received education on infection. In all three sub-dimensions, hand- washing (p<.001), personal protective equipment use (p<.001), and environmental management (p<.001), awareness scored higher than performance. The awareness of infection control showed a significantly positive correlation (r=.394) with performance. Conclusion: In order to improve performance of infection control, education to improve awareness should be provided, and paramedics with higher performance levels in hand washing, and use of gloves and masks wearing should be assigned as training advisors.

• Corrosion Science and Technology
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• 제7권1호
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• pp.13-15
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• 2008

Aiming at the corrosion circumstances and corrosion prevention needs of downhole oil tubes, series protective coatings for downhole oil tubes have been developed in the authors' laboratory, including a baked type coating YG-01 and an air curing type coating YG-03, etc. The performance investigation of the coatings has been done for testing their corrosion resistance, mainly including salt fog test, immersion test in oil-field waste water and various acid solutions, high temperature and high pressure test in alkali solution or $H_2S/CO_2$ environment, as well as some other performances. The investigation results show that oil tube anti-corrosion coatings developed here can endure over 4000 hrs salt fog test, over 1000 hrs immersion in various acid solutions at room temperature and in boiling oil-field waste water. In addition, the coatings can keep intact after experiencing test in alkali solution under 70 MPa pressure at $150^{\circ}C$ for 24 hrs, and in simulative sour gas environment under the total pressure of 32 MPa ($P_{H_{2}S}=3.2MPa$, $P_{CO_{2}}=3.2MPa$) at $90^{\circ}C$ for 168 hrs, which show that the coatings can be used for corrosion prevention in downhole environments with specific high temperature and high pressure, such as sour gas wells. The other testing results show the oil tube protective coatings have excellent comprehensive performance.

• Corrosion Science and Technology
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• 제6권3호
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• pp.128-132
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• 2007

For a quantitative inspection on the performance of weathering steel bridges, we have investigated the relationship between the corrosion rate and the composition of the rust layers formed on weathering steel bridges located in various environments in Japan and applied a protective ability index (PAI) to the bridges. The corrosion rates were clearly classified by the PAI, ${\alpha}/{\gamma}*$ and sub index of $({\beta}+s)/{\gamma}*$, where $\alpha$, \gamma*, $\beta$ and s are the mass ratio of crystalline $\alpha-FeOOH$, the total of $\gamma$-FeOOH+ $\beta$-FeOOH + the spinel-type iron oxide (mainly $Fe_3O_4$), $\beta-FeOOH$ and spinel-type iron oxide, analyzed by powder X-ray diffraction, respectively. In the case of ${\alpha}/{\gamma}$*>1, the rust layer works protective enough to reduce the corrosion rate less than 0.01 mm/y. The sub index $({\beta}+s)/{\gamma}*$<0.5 or >0.5 classifies the corrosion rate of the non-protective rust layers, therefore the former state of the rust layer terms inactive and the latter terms active. The quantitative inspection of a weathering steel bridge requires a performance-inspection (PI) and periodical deteriorationinspections (DI). The PI can be completed by checking of the PAI, ${\alpha}/{\gamma}*$. The DI on the weathering steel bridges where deicing salt is sprinkled can be performed by checking the PAI, $({\beta}+s)/{\gamma}*$.