• Corrosion Science and Technology
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• 제12권2호
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• pp.85-92
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• 2013

This work is concerned with an evaluation of dynamic boric acid corrosion (BAC) of low alloy steel for reactor pressure vessel of a pressurized water reactor (PWR). Mockup test method was newly established to investigate dynamic BAC of the low alloy steel under various conditions simulating a primary water leakage incident. The average corrosion rate was measured from the weight loss of the low alloy steel specimen, and the maximum corrosion rate was obtained by the surface profilometry after the mockup test. The corrosion rates increased with the rise of the leakage rate of the primary water containing boric acid, and the presence of oxygen dissolved in the primary water also accelerated the corrosion. From the specimen surface analysis, it was found that typical flow-accelerated corrosion and jet-impingement occurred under two-phase fluid of water droplet and steam environment. The maximum corrosion rate was determined as 5.97 mm/year at the leakage rate of 20 cc/min of the primary water with a saturated content of oxygen within the range of experimental condition of this work.

• 한국군사과학기술학회지
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• 제18권3호
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• pp.267-274
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• 2015

It is necessary to both analyze root-cause of non-conformance of effective illumination time to the specification, and estimate the storage lifetime for 81 mm illuminating projectile stockpiled over 10 years. In this paper, aging mechanism of magnesium flare material due to long-term storage was supposed, and two-stage tests, pre-test and main test based on accelerated degradation tests were performed. Field storage environment of moistureproof was set up, and illumination times in the accelerated degradation tests for temperatures 60 and $70^{\circ}C$ were measured. Then, storage reliability of the projectile was estimated through analyzing the measured data and applying distribution-based degradation models to the data. The $B_{10}$ life by which 10 % of a population of the projectiles will have failed at storage temperature of $25^{\circ}C$ was estimated about 7 years.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2007년도 학술대회
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• pp.407-410
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• 2007

In the RRH (Radio Remote Head) of a WCDMA Node B System, an HPA (High Power Amplifier) is used in order to amplify the transmission RF signal. Upon designing an HPA, the design requirements demand that the intermodulation characteristics are optimized during design and that the stability of the characteristics is maintained in the field. In this DOE (Design of Experiments) research, a few vital factors that affect intermodulation characteristics were first selected; then, an optimal solution was produced for high reliability in a noisy environment in the field by employing the Taguchi Method, a statistical method used for a robust design. Furthermore, by employing HALT(High Accelerated Life Test) during the verification test, this experiment has verified that an HPA that was designed using the Taguchi Method proved to be a far more robust design than an HPA that was designed without using the method.

• Journal of Welding and Joining
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• 제15권1호
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• pp.46-54
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• 1997

The object of this paper is to evaluate SCC(stress corrosion cracking) susceptibility for parent metal and bond line region of weld joints which have the various weld heat input condtions in TMCP(thermo-mechanical control process) steel by SP-SSRT(small punch-slow strain rate test) method. And the SCC test results of TMCP steel are compared with those of the conventional HT50 steel which has te almost same tensile strength level like TMCP steel. The loading rate used was $3\times10^{-4}$mm/min and the corrosive environment was synthetic sea water. According to the test results, in the case of parent metal, TMCP steel showed higher SCC susceptibility than HT50 steel because of the high plastic strain level of ferrite microstructure obtained by accelerated cooling. And in the case of bond line, the both TMCP steel and HT50 steel showed low load-displacement behaviors and higher SCC susceptibility above 0.6. These results may be caused by theembrittled martensite structure on HT50 steel and by the coarsened grain and the proeutectoid ferrite structure obtained by the impart of accelerated cooling effect on TMCP steel.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.257-258
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• 2008

Hall-type current sensors have been widely used in many fields such as elevator and train system. To estimate lifetime of hall-type current sensors, an accelerated life test with real-time monitoring system simultaneously was designed and performed in high temperature environment with three different temperatures. From the experimental results, activation energy was about 0.9 eV, and acceleration factor was about 450 based on Arrhenius model. As a results, $B_{10}$ lifetime of hall-type current sensor is estimated to be 65,460 hours.

• Nuclear Engineering and Technology
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• 제36권5호
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• pp.475-484
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• 2004

Extending the lifetime of a nuclear power plant [(hereafter referred to simply as NPP)] is one of the most important concerns in the global nuclear industry. Cables are one of the long-life items that have not been considered for replacement during the design life of a NPP. To extend the cable life beyond the design life, it is first necessary to prove that the design life is too conservative compared with actual aging. Condition monitoring is useful means of evaluating the aging condition of cable. In order to simulate natural aging in a nuclear power plant. a study on accelerated aging must first be conducted. In this paper, evaluations of mechanical aging degradation for a neoprene cable jacket were performed after accelerated aging under tcontinuous and intermittent heating conditions. Contrary to general expectations, intermittent heating to the neoprene cable jacket showed low aging degradation, 50% break-elongation, and 60% indenter modulus, compared with continuous heating. With a plant maintenance period of 1 month after every 12 or 18 months operation, we can easily deduce that the life time of the cable jacket of neoprene can be extended much longer than extimated through the general EQ test. which adopts continuous accelerated aging for determining cable life. Therefore, a systematic approach that considers the actual environment conditions of the nuclear power plant is required for determining cable life.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 봄 학술발표회 논문집
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• pp.73-78
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• 1993

This study was performed for the purposes of estimating steel corrosion of concrete structures under the environment of seawater. The corrosion of steel was accelerated in artificial seawater with seven kinds of specimen which was embedded in mortar. By measuring choride content in mortar, half cell potential and corrosion area ratio, the degree of steel corrosion can be assumed.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2000년도 창립총회 및 춘계학술발표회
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• pp.137-140
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• 2000

The purpose of this study is to see the effect of SVE (Soil Vapor Extraction) and Bioventing (biostimulation) hydrocarbon contaminated areas. The removal rate of VOC for three weeks were 17.43 kg on 3.6 ㎥/hr at steady-state. In the application of Bioventing, every flow rate were tested, and it was found that 4.0 ㎥/hr were adequate for best control of the system. At this stage, the addition of microbial agent accelerated the biodegradation of the hydrocarbon.

• 생물환경조절학회지
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• 제11권1호
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• pp.1-4
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• 2002

'황금배' 동녹발생이 해에 따라 큰 차이를 보이는 것은 강우가 크게 관여하기 때문인 바 본 연구에서는 강우와 동녹발생과의 관계를 구명하기 위하여 인위적으로 가습처리를 하여 높은 상대습도와의 관계를 구명하였다. 높은 상대습도는 기공저항을 적게 하였다. 따라서 순수동화산물의 축적이 과실의 비대를 촉진하여 가습처리에서 평균 과중이 크게 나타났다 광합성속도에는 처리간의 차이가 없었다. 동녹 발생시기는 과중과 과실표면적의 신장속도가 가장 빠른 시기인 7월 25일 전후이며, 높은 상대습도가 과실의 신장을 촉진하였으므로 가습처리에서 동녹발생이 많았다. 7월 하순은 과실의 칼슘농도변화가 큰 시기로서 세포벽 구성에 주요한 물질인 칼슘량의 저하가 동녹발생과 상관이 있을 것으로 생각된다. 강우에 의한 높은 상대습도가 동녹발생에 미치는 영향은 높은 상대습도에 의해 순수광합성물질의 많아지고 이에 따라 과실신장이 빨라지나 과실세포의 신장을 위해 전류되는 동화산물량과 이동되는 수분 포함한 무기성분량의 일시적 불균형이 큰 이유 중의 하나라고 생각된다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제21권6호
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• pp.135-145
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• 2016

MgO recently has been regarded as the alternative material for replacement of cement. The aim of this study is to investigate the effects of accelerated carbonation on the strength development of MgO-based binder which is binary mixtures of magnesium oxide (MgO) with portland cement (PC) or ground granulated blast furnace slag (GGBS) or fly ash (FA). The compressive strengths of all binders were higher in the 20% $CO_2$ condition and for longer curing time. The strength were generally higher as the following order: MgO/PC > MgO/GGBS > MgO/FA system. The binder composed of 20% MgO and 80% PC showed highest compressive strength (38.0MPa) which was higher than PC. The correlation analysis of the porosity and compressive strength showed that compressive strength was higher when porosity was lower. The hydration and carbonation products of MgO including brucite ($Ca(OH)_2$), magnesite ($MgCO_3$) and nesquehonite ($MgCO_3{\cdot}3H_2O$) presumably filled the pores and contributed to strength development. Thermogravimetric analyses elucidated that 0.34 kg of $CO_2$ could be stored the 50% MgO/50% PC binder which performed the maximum $CO_2$ uptake at 20% $CO_2$ condition.