• 한국수소및신에너지학회논문집
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• 제23권6호
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• pp.612-618
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• 2012

In this paper, in order to prevent electric shock of high voltage system of HFCV after crash test, insulation performance measurement methods were studied. Under conditions of in-use, insulation performance tests can be divided into measurement method using the vehicle's own RESS as DC voltage source and measurement method using DC voltage from off-vehicle sources. However, these tests can not be applied after a post-crash because parts of high voltage system cover should be removed, and insulation performance can be influenced during these tests. Therefore, we proposed post-crash insulation performance test methods for preventing electric shock through problem analysis of previous post-crash insulation performance tests. Also, test equipment which can measure voltage absence and total energy was developed. We verified performance of the equipment through experiments with vehicle test.

• 대한조선학회논문집
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• 제36권2호
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• pp.114-120
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• 1999

기존의 DDAM에서 충격응답해석을 위해 널리 채용되는 수학적 모델은 단순화된 다자유도의 질량 스프링계 모델이었다. 그러나 근래에는 탑재장비가 점점 복잡하고 다양해지기 때문에 이들을 전체 유한요소 모델로 모델링해서 충격해석을 실시하고 있다. 본 논문에서는 범용 구조유한요소 해석프로그램인 MSC/NASTRAN에서 제공하는 DMAP 기능을 활용하여 선박, 함정용 탑재장비의 내충격 안전성평가에 활용할 수 있는 DDAM 프로그램을 개발하였다. 고유진동해석후 DMAP으로 추출한 데이터를 입력치로 하여 본 연구에서 개발된 DDAM에 의해 도출된 장비의 유효질량, 중량, 충격응답등은 ANSYS에서 제공하는 DDAM 결과와 비교되었다. 대체적으로 두 결과는 잘 일치하여 프로그램의 유용성 및 정확성이 확인되었다.

• 한국기계가공학회지
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• 제16권5호
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• pp.55-62
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• 2017

The grate bar, a component used in steel mills, is used in harsh environments where external disturbances such as high temperature, abrasion, corrosion, and impacts are present. Therefore, in this study, spray-coating was performed on the most severely affected surface to extend the lifetime of the grate bar. The thermal and mechanical properties of the sprayed coated bars were investigated based on the performances under abrasion, thermal shock, tension, and sand blasting, and the microstructures by microscope. By analyzing the thermal and mechanical properties of the uncoated original grate bar and coated grate bar and comparing them with one another, the physical performance improvement of the coated grate bar can be verified.

• 한국수소및신에너지학회논문집
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• 제22권6호
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• pp.810-818
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• 2011

This paper analyzed the suitability about the isolation performance criteria which was based on human impedance and effect of current in IEC 60479-1 on the safety of human being was examined. The method of evaluation by megger and DC voltmeter was analyzed. The differences of isolation performance according to design of high-voltage system were analyzed. The factors which affect the insulation performance were analyzed for HFCV, EV, HEV, etc. through analysis of the isolation performance evaluation method. Finally, design for improved isolation performance was proposed.

• Journal of Welding and Joining
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• 제34권1호
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• pp.26-34
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• 2016

Automotive today has been transforming to an electronic product by adopting a lot of convenience and safety features, suggesting that joining materials and their mechanical reliabilities are getting more important. In this study, a Sn-Cu-Cr-Ca solder composition having a high melting temperature ($>230^{\circ}C$) was fabricated and its joint properties and reliability was investigated with an aim to evaluate the suitability as a joining material for electronics of engine room. Furthermore, mechanical properties change under complex environment were compared with several existing solder compositions. As a result of contact angle measurement, favorable spreadability of 84% was shown and the average shear strength manufactured with corresponding composition solder paste was $1.9kg/mm^2$. Also, thermo-mechanical reliability by thermal shock and vibration test was compared with that of the representative high temperature solder materials such as Sn-3.5Ag, Sn-0.7Cu, and Sn-5.0Sb. In order to fabricate the test module, solder balls were made in joints with ENIG-finished BGA and then the BGA chip was reflowed on the OPS-finished PCB pattern. During the environmental tests, resistance change was continuously monitored and the joint strength was examined after tests. Sn-3.5Ag alloy exhibited the biggest degradation rate in resistance and shear stress and Sn-0.7Cu resulted in a relatively stable reliability against thermo-mechanical stress coming from thermal shock and vibration.

• 한국철도학회논문집
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• 제12권1호
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• pp.161-166
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• 2009

직류급전시스템은 주로 비접지방식을 사용하지만 레일과 대지간이 긴 거리를 평행하게 구성되어 레일저항과 레일-대지간 콘덕턴스가 존재하여 레일전위와 누설전류가 발생한다. 레일전위는 인체에 전기적 쇼크를 주고 누설전류는 인근 매설 철 구조물에 전해적 부식을 주게 된다. 그러므로 이러한 영향을 줄이고, 방지와 감시하는 설계기술이 현 직류급전시스템에서는 중요한 요소이다. 레일전위와 누설전류의 해석은 전파이론에 의해 이루어졌으며 레일저항과 레일-대지간 콘던턴스의 상태를 유지하기 위해 레일누설전류를 감시/제어하는 방안이 제안되었다.

• 한국세라믹학회지
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• 제56권1호
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• pp.77-83
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• 2019

MgO-C refractories are used in basic furnaces and steel ladles due to their many desirable properties, such as excellent thermal shock resistance via low thermal expansion, and high thermal conductivity. However, the mechanical and thermal properties of the refractory continuously deteriorate by spalling phenomena and pore generation due to the oxidation of graphite, used as a carbon source, indicating that the characteristics and performance of MgO-C refractories need to be improved by using a new material or composition. In this study, the use of a Hertzian indentation test as a method for determining the damage and fracture behavior of an MgO-C refractory is described. The results highlight that Hertzain indentation tests can be one of the important evaluation tools for quasi-plastic damage accumulation of MgO-C refractories during falling process of scrap metal.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2001년도 정기학술대회
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• pp.337-337
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• 2001

High voltage ceramic capacitors are widely applied in power electronic circuits, such as filters, snubbers, and resonant circuits, due to their excellent features of high voltage endurance and low aging. This paper presents a result of failure analysis and reliability evaluation for high voltage ceramic capacitors. The failure nodes and failure mechanisms were identified in order to understand the failure physics in a component. The causes of failure mechanisms for zero resistance phenomena under withstanding voltage test in high voltage ceramic capacitors molded by epoxy resin were studied by establishing an effective closed-loop failure analysis. Also, the condition for dielectric breakdown was investigated. Particular emphasis was placed on breakdown phenomena at the ceramic-epoxy interface. The validity of the results in this study was confirmed by the results of accelerated testing. Thermal shock test as well as pressure cooker test for high voltage ceramic capacitor mounted on a magnetron were implemented. Delamination between ceramic and epoxy, which, might cause electrical short in underlying circuitry, can occur during curing or thermal cycling. The results can be conveniently used to quickly identify defective lots, determine mean time to failure (MTTF) of each lot at the level of Inspection, and detect major changes in the vendors processes.

• 마이크로전자및패키징학회지
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• 제17권4호
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• pp.35-40
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• 2010

본 연구에서는 상용 고온 솔더 중 많이 쓰이고 있는 Sn-3.5Ag, Sn-0.7Cu, Sn-5.0Sb 솔더에 대한 열충격 시험, 열싸이클 시험, 고온 진동 복합 시험 신뢰성 평가를 하였다. 테스트 샘플을 제작하기 위해 Sn-3.5Ag, Sn-0.7Cu, Sn-5.0Sb 솔더볼을 ENIG 표면 처리된 BGA에 접합하였으며, 그 후 BGA샘플을 OSP 표면 처리된 PCB에 실장 하였다. 신뢰성평가 동안 저항변화를 측정하였으며 신뢰성 평가 전후 전단강도 시험을 통하여 접합강도의 변화를 평가하였다. Sn-3.5Ag의 솔더인 경우 전기저항과 접합강도의 저하가 비교 평가한 3가지 솔더 중 가장 높은 저하율을 보였으며 Sn-0.7Cu의 솔더가 신뢰성 평가 후에 비교적 높은 안정성을 나타내었다.

• 한국식품위생안전성학회지
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• 제39권1호
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• pp.1-8
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• 2024

Salmonella spp. 11 strains에 대해 저온 열처리(50℃) 3, 6, 9분 후 MIC값을 측정하여 항생제 내성을 알아보았다. Chloramphenicol에 대해 대조군과 열처리한 strains 대부분에서 감수성(S)이 있는 것으로 나타났고, 열처리한 strains의 MIC값은 대조군과 비교하였을 때 유지되거나 감소하였다. Ciprofloxacin에 대해 대조군과 열처리한 strains는 대부분 감수성(S)이 있거나 중간(I)을 나타냈다. Tetracycline은 모든 strains에서 감수성(S)이 있는 것으로 나타났으며, S. Gaminara BAA 711에 대해 열처리 후 MIC값이 증가하였다. Gentamicin에 대해 대조군 strains들에서 감수성을 나타낸 strains가 3 strains, 중간을 나타낸 strains 2 strains, 내성을 가진 strains가 6 strains였으며, 이 중 S. Heidelberg ATCC 8326는 MIC값을 측정했을 때 대조군에서 MIC값이 8 ㎍/mL로 MIC break point가 중간이었으나, 3분과 9분 열처리 후 MIC값이 16 ㎍/mL로 증가하여 break point가 내성을 나타냈다. 본 실험결과 Salmonella spp. 11 strains에 대해서 저온 열처리 후 열내성 효과에 의한 항생제 내성을 알아봤을 때 ciprofloxacin에서 S. Montevideo BAA 710을 3, 6분 열처리한 경우, gentamicin에서 S. Enteritidis 109 D1을 3분 처리한 경우와 S. Heidelberg ATCC 8326을 3, 9분 처리한 경우, tetracycline에서 S. Gaminara BAA 711을 6, 9분 처리한 경우 MIC값이 증가하였다. 후속 연구를 통해 Salmonella spp. strains에 대해 열처리 후 열내성 효과를 나타내는 병원성 유전자의 특성에 대한 지속적인 연구가 필요하다.