• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.12
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• pp.1397-1404
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• 2014

Grab cranes are used for multi-purpose when the sand and soil are deposited into harbor wharf or the undersea construction is performed. Among the components of crane grab, the wire drum and disc brake pad are key expendables and have disadvantages that lot of heat is generated and very expensive when replacing them. In this study, the thermal image analysis for the disc brake, which works with wire drum of the crane is suggested. The suggested system performs the pad thermal diagnosis through the thermal image using the characteristics that the disc and pad surface temperatures are distributed abnormally before the brake failure and the disc pad damage. Therefore, the damage by the failure can be prevented by discovering the abnormality of the machine parts before failure and the life cycle of the pad and the cost can be extended and saved by operating the crane performing constant checkup for the overload.

• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.151-155
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• 2018

Degree of membrane degradation in Proton Exchange Membrane Fuel Cells (PEMFC) is mainly evaluated by the hydrogen crossover current density. The hydrogen crossover current density is measured by linear sweep voltammetry (LSV), which differs from the DOE protocol and the NEDO protocol. In this study, two protocols were compared during PEMFC operation and accelerated stress test. In the LSV method by the DOE method, the scan rate change affects the hydrogen crossover current density, but the NEDO method does not affect the hydrogen crossover current density. In the course of 15,000 cycles of polymer membrane wet/dry cycle, the DOE method was sensitive to membrane degradation, but the NEDO method was less sensitive to membrane degradation than the DOE method.

• Korean Chemical Engineering Research
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• v.60 no.1
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• pp.12-19
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• 2022

Cathode open-type PEMFC (Proton Exchange Membrane Fuel Cells) stacks, which are widely used in small transport-type PEMFC, have a problem with poor durability. Through the accelerated durability test of the 13-cell PEMFC stack, we tried to find the cause of the degradation of the stack and to contribute to the improvement of the durability of the cathode open stack. A hydrogen/air boundary is formed during start-up/shut-down (SU/SD) due to the structural problem of the cathode open stack in which the cathode is open to the atmosphere and it is difficult to maintain airtightness, thereby deteriorating the cathode. In this study, it was possible to evaluate the durability in a relatively short time by reducing the 54% of the initial performance by repeating SU/SD 1,800 times on the cathode open stack. After dismantling the stack, each cell was divided into two and the performance was analyzed. Overall, the anode outlet MEA, which facilitates air inflow, showed more severe electrode deterioration than the inlet MEA, confirming that the hydrogen/air boundary formation during SU/SD is the main cause of degradation.

• Proceedings of the IEEK Conference
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• 2001.06d
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• pp.25-28
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• 2001

본 논문은 잡음에 의해 열화된 지문영상을 향상시키기 위해 화소가 가지는 다중방향성을 이용하는 방법을 제안한 다. 지문영상은 융선과 골의 규칙적인 배열로 이루어지는데 이러한 융선과 골을 구성하는 화소의 방향성들은 잡음이 가지는 방향성들과는 구별된다 방향성대역 통과 필터뱅크(Directional Filter Bank : DFB)는 입력영상이 가진 일정한 방향성 대역을 통과시켜서 다수개의 부영상들을 생성한다. 본 논문은 DFB를 이용하여 지문영상을 다수개의 특정 방향성을 가진 부영상들로 분해한 다음 이러한 부영상들을 사용하여 지문영상을 개선한다

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.79-84
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• 1993

철근의 부식은 철근 콘크리트 구조물에 있어서 심각한 열화현상을 유발할 수 있으며 최근 들어 이로 인한 피해가 많이 보고되고 있다. 이와 같은 부식의 억제방안 중 철근에 직접 에폭시를 도막하는 것이 가장 효과적인 것으로 알려져 있다. 그러나 이 경우 에폭시 도막에 따른 부착성능의 저하가 우려되는 바 본 연구는 철근부식방지를 위해 에폭시를 도막한 철근의 부착특성을 고찰하기 위해 수행되었다. 주된 변수는 콘크리트 압축강도, 부착길이, 에폭시 도막두께이며 각 변수별로 부착특성의 변화를 관찰하였고 이를 통해 에폭시도막 철근의 사용성을 검토하였다. 본 실험결과에 기초하여 부착강도 예측식을 제안하였고 실험결과와 예측치를 비교하였다.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.741-746
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• 1997

본 연구에서는 울진 3, 4호기 보조급수계통의 1/4 다중안전계통에 대해 기기불이용도식을 유도하여 점검주기 변화에 따른 기기 불이용도를 평가하였고 계통단계에서는 IRRAS Code를 사용하여 계통 불이용도를 평가하였다. 그리고 선형 열화 모델을 이용하여 잦은 점검으로 인한 역효과가 계통 및 기기 불이용도에 미치는 영향을 평가하였다. 상기 역효과를 고려하였을 경우 점검주기 변화에 따른 기기 및 계통의 불이용도는 거의 유사한 경향을 보였고 점검주기가 대략 2개월에서 기기 및 계통 불이용도가 낮게 나타났다.

• Electronics and Telecommunications Trends
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• v.7 no.1
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• pp.38-46
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• 1992

음성통신에 있어 전화기의 주파수 특성은 음량과 함께 통화품질에 많은 영향을 미친다. 각 국에서는 자국의 통신실정에 맞는 주파수 특성을 규정하고 있지만, 다른 나라의 규정을 그대로 도입하는 것은 도리어 전화기의 품질 열화를 초래할 수 있다. 본 고에서는 전화통화에 있어 만족한 통화품질을 얻을 수 있는 바람직한 주파수 특성을 구하고자, 주파수 특성에 대하여 오피니언 평가 및 선호도 평가를 실시하고, 그 결과를 기본으로 최적 주파수 특성에 대해 검토하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.446-448
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• 2003

본 논문은 MPEG 비디오를 위한 양자화된 차분 에너지 워터마킹(QDEW) 알고리즘을 제안한다. 이 알고리즘은 블록의 고주파 성분인 DCT 계수를 선택적으로 제거함으로써 워터마크를 삽입하는 방식이다. 특히 제안된 방벌은 기존의 차분 에너지 워터마킹(DEW)의 단순비교방식과 다르게 양자화단위로 에너지 크기를 비교함으로써 큰 범위의 에너지가 차이날 때 발생되는 다량의 주파수제거 문제를 해결하여 화질의 열화를 방지하고 삽입되는 워터마크의 중량을 증가시켰다. 그리고 DCT계수를 제거하는 것으로만 워터마크를 삽입할 수 있기 때문에 재인코딩 과정없이 MPEG스트림에서 직접 워터마크를 삽입할 수 입는 장점이 있다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3437-3443
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• 2013

The polymer insulators have been extensively used as an alternate material of ceramic insulators. However, when they are used in practical conditions, there are many problems of decreasing performance and shortening lifetime due to the exposures of degradation factors applied from the outdoor situations. Accordingly, the analysis of polymer degradations has been getting influential too late as one of important subjects for improvements of safety and reliability. Heat, water treatments are arbitrary simulated for finding out the initiations and processes of surface degradation on the polymer surface. Especially, this study is focused on the chemical changes properties. From the analysis of hydrophilic and hydrophobic molecular structures, final modeling of surface degradation is accomplished. We checked the contact angle depending on heat and moisturized accelerated degradation and ran an XPS analysis to check the mechanism change of the surface of the PCB polymer composite. The surface that had a tendency to attract moisture showed a decrease in the contact angle and generated a large amount of carboxyl($-COO^*$) radicals. The hydrophobized surface showed an increase in the contact angle and had a stable chemical composition constituted of the breakaway of oxygen radicals and the formation of double bond by carburization.

• The Journal of Engineering Geology
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• v.17 no.3
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• pp.359-365
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• 2007

Freezing and thawing cycle is one of the major weathering-induced factors in the mechanical weathering of the rock mass. This natural process accelerates rock weathering process by breaking down the parent rock materials and makes soil or weathered rock formation in a rock slope surface zone. It can also cause reduction of the shear strength in slopes. It is important to calculate the deterioration depth caused by freezing-thawing for a slope stability analysis. In this study, deterioration depths of rock slope due to freezing-thawing were calculated using the 1-D heat conductivity equation. The temperature distribution analysis was also carried out using collected temperature distribution data for last five years of several major cities in Korea. The analysis was performed based on the distributed rock types in study areas. Thermal conductivities, specific heats and densities of the calculation rocks are tested in the laboratory. They are thermal properties of rocks as input parameters for calculating deterioration depths. Finally, the paper is showing the calculated deterioration depths of each rock type slopes in several major cities of Korea.