• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.3731-3735
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• 2015

This study reports the relationship between rollingstock weight and acceleration performance for HEMU-430X, the first electric multiple unit developed in Korea. While maintaining the consumed power, the total train weight was deliberately varied by 2%, by adding and removing weights, and the it was shown that the lighter train was found to have higher acceleration performance and hence better suited for maximum speed tests below the speed of 413km/h. According to the power consumption analysis based on the velocity data collected per 0.1 second, the balanced speed, when the traction force and air resistance become equal, was determined to be 419km/h for HEMU-430X, which is in agreement with tested result. It is expected that the analyses in this study will be utilized for the speed tests in the future.

• Proceedings of the Korean Reliability Society Conference
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• 2000.04a
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• pp.89-96
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• 2000

VTR 제품에 대해 소비자가 만족하는 신뢰성을 보증하기 위해, 내구수명시험을 10,000시간 실시하여 제품의 특성치 변화와 고장률이 만족하는지 검토하였다. 아울러 시간의 경과에 따른 제품의 특성치 변화를 관측하여 고장분포를 추정하였고 실험실에서의 고장유형과 시장에서의 불량유형과 일치여부를 분석하였다. 내구수명시험 결과에서 제품의 특성치 변화와 Field의 시장불량 관계등은 제품에 중요한 요인이기 때문에 이를 바탕으로 신뢰성 방향을 재검토하는 계기가 되었다. 제품의 신뢰성을 향상시키기 위해 시험을 많이 실시하지만, 시험으로 모든 것을 검출하기에는 한계가 있으며 또한 많은 시험 시간이 소요되기 때문에 현업에 적용하기에는 한계가 있었다. 본 연구에서는 제품의 신뢰성을 향상시키기 위해 내구수명시험과 더불어 제품의 설계 마진 분석, 그리고 고장분석을 같이 추진해야만 단시간 신뢰성을 향상시키는데 좋은 지름길임을 제시하였다.

• Proceedings of the KIEE Conference
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• 2005.07e
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• pp.97-99
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• 2005

현장에서 사용중 고압전선에 고장이 발생한 6.6kV 건식변압기 고장의 원인분석을 위하여 설계와 제조방식이 동일하고 사용기간이 비슷한 건식변압기에 대한 전기적 열적 시험을 실시하였다. 전기적 시험으로서는 교류 및 충격 내전압시험, 부분방전시험을 실시하였고 열적시험으로는 단락법을 사용하여 온도를 상승시켰으며, 내부 및 외부권선표면의 온도분포와 열화상에 의한 온도분포를 측정하였다. 시험결과 부분방전특성이 기준치에 비하여 높게 나타났으며, 권선온도분포는 사용한계온도이하인 것으로 분석되었다.

• Journal of Food Hygiene and Safety
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• v.27 no.1
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• pp.37-41
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• 2012

The current standard for testing tetrodotoxin (TTX) in foodstuffs is the mouse bioassay (MBA) in Korea as in many other countries. However, this test suffers from potential ethical concerns over the use of live animals. In addition, the mouse bioassay does not test for a specific toxin thus a sample resulting in mouse incapacitation would need further confirmatory testing to determine the exact source toxin (e.g., TTX, STX, brevotoxin, etc.). Furthermore, though the time of death is proportional to toxicity in this assay, the dynamic range for this proportional relationship is small thus many samples must be diluted and new mice be injected to yield a result that falls within the quantitative dynamic range. Therefore, in recent years, there have been many efforts in this field to develop alternative assays. High performance liquid chromatography (HPLC) coupled with mass spectrometry (MS) has been emerged as one of the most promising options. A LC-MS-MS method involves solid-phase extraction (SPE) and followed by analysis using an electrospray in the positive ionization mode and multiple reactions monitoring (MRM). To adopt LC-MS-MS method as alternative standard for testing TTX, we performed a validation study for the quantification of TTX in puffer fish. This LC-MS-MS method showed good sensitivity as limits of detection (LOD) of $0.03{\sim}0.08{\mu}g/g$ and limits of quantification (LOQ) of $0.10{\sim}0.25{\mu}g/g$. The linearity ($r^2$) of tetrodotoxin were 0.9986~0.9997, the recovery were 80.9~103.0% and the relative standard deviations (RSD) were 4.3~13.0%. The correlation coefficient between the mouse bioassay and LC/MS/MS method was higher than 0.95.

• Survey Research
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• v.12 no.1
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• pp.119-139
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• 2011

This paper analyzes the effects of college students' preparing for government official recruitment exams on their employment and job characteristics. To this end, Graduates Occupational Mobility Survey(GOMS) data were used. The main results of this study are summarized as follows. (1) college students preparing for the exams extend their college enrollment period; (2) college students preparing for the exams delay their employment; (3) college students preparing for the exams lower their wages and job satisfactions if they are employed in private sectors. In general, these results are consistent with common concerns. However, the sizes of the effects are less than common concerns.

• Proceedings of the KAIS Fall Conference
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• 2011.05a
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• pp.292-295
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• 2011

본 논문에서는 배수성(저소음)포장을 포함하는 2-Layer 아스팔트 포장의 상부층과 하부층의 역학적인 특성을 평가하는데 목적이 있다. 연구 방법으로는 슈퍼페이브 배합설계로 2-Layer 아스팔트 포장의 상 하부층 시편을 제작하였으며, 시편 상부층의 최대공칭치수는 4.75mm이고 하부층의 최대공칭치수는 13mm이다. 이 시편에 대한 기본 물성 시험 실시 후 마샬 안정도 시험에 대한 안정도와 흐름값을 평가하였다. 그리고 상부층과 하부층의 자유단 공진주 시험을 통해 탄성계수(E)를 측정하였고, 비파괴 시험법인 슈미트해머(Schmidt hammer)를 이용해 반발경도를 측정한 후 강도를 추정하였다. 또한 일축압축시험으로 측정된 압축강도로 탄성계수($E_{50}$)를 계산하였다. 마지막으로 각각의 역학적 시험을 통해 얻어진 결과값으로 강도(qu)와 탄성계수 ($E_{50}$)의 상관관계와 추정식으로 구한 강도와 일축압축강도 시험으로 얻어진 강도와의 상관관계를 분석하였고, 자유단 공진주 시험의 탄성계수(E)값과 일축압축시험의 결과로 얻어진 탄성계수($E_{50}$)의 상관관계를 분석하였다.

• Journal of Energy Engineering
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• v.21 no.3
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• pp.249-253
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• 2012

In this study, The report analysed the characteristics of power drop in solar cell through thermal shock test. The solar cells were tested 500 cycles in $-40^{\circ}C$ lowest temperature and $120^{\circ}C$ highest temperature by thermal shock test on ironbound conditions, that excerpted standard of PV Module(KS C IEC-61215). The result of the efficiency analysis through measure of I-V, efficiency of Cell decreased from 13.9% to 11.0% and decreasing rate was 20.9% after test. The result of the surface analysis through EL, solar cell has damage of gridfinger and ribbon joint. Cell cracks were founded in damage of cells through cross section of solar cells. Also, Fill factors were decreased from 72.3% to 62.0% after thermal shock test and decreasing rate is 11.8%. therefore, Yearly power drop is aggravated with facts that cell crack, damage of surface and power loss of cell by change of I-V characteristic curve with decreasing of parallel resistance.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.153-160
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• 2001

피에조콘관입시험(PCPT)의 소산시험은 in-situ 상태의 압밀계수(c/sub v/)를 추정하는 방법으로 널리 이용되어왔다. 본 연구에서는 spherical cavity expansion theory 및 axisymmetric uncoupled linear consolidation equation(Gupta & Davidson, 1986)을 이용하여 과압밀점토에서의 초기과잉간극수압의 분포 및 과잉간극수압의 시간에 대한 소산현상을 해석하는 수치해석방법을 제안하여 현장시험결과 및 실내시험결과와 비교 분석하였다. ADIS (alternating direction implicit scheme)를 이용한 FDM 해석을 실시한 결과와 현장시험의 소산곡선은 잘 부합되는 것으로 나타났으며 압밀계수도 실내실험 또는 피에조콘관입 시험에 대한 추정방법으로 산출된 값과 비교적 일치하는 것으로 나타났다.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1995.10a
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• pp.899-903
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• 1995

• Journal of the Korean Geosynthetics Society
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• v.20 no.2
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• pp.1-11
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• 2021

In this study, a study related to laboratory and pilot test were performed to use an environmental soil stabilizer developed to induce a hardening reaction similar to that of Ordinary Portland Cement (OPC) by using industrial by-products of blast furnace slag and the combustion ash of a circulating fluidized bed boiler as the main material. For this, specimens were prepared using liquid A of sodium silicate and silica sol, and liquid B of an environmental soil stabilizer (or OPC), and laboratory tests were performed to analyze the strength and environmental characteristics. And pilot test was performed on the aging reservoir, field permeability test and electrical resistivity survey were performed in the field to analyze the applicability. As a result of the laboratory test, the homo-gel compressive strength of the chemical injection material using the environmental soil stabilizer as liquid B was about 2.88 to 3.23 times greater than that of OPC. In addition, the elution amount of most heavy metals was lower than that of OPC, and the survival rate in the fish, acute toxicity test was 100%. Therefore, when judged based on the results of the laboratory test, it was analyzed to be superior to OPC in terms of strength and environment. In the results of the pilot test in the aging reservoir, when the environmental soil stabilizer was reinforced with liquid B of the chemical injection material, the coefficient of permeability in the aging reservoir decreased to 1/50 level. In addition, as a result of the electrical resistivity survey, it was analyzed that the electrical resistivity inside the aging reservoir increased as time passed, the saturation zone disappeared, and the overall reinforcement.