• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.344-354
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• 2015

In order to study the development of partial discharge (PD) under typical protrusion defects in gas-insulated switchgear, we applied step voltages on the defect and obtained the ${\varphi}-u$ and ${\varphi}-n$ spectrograms of ultra-high frequency (UHF) PD signals in various PD stages. Furthermore, we extracted seven kinds of features to characterize the degree of deterioration of insulation and analyzed their values, variation trends, and change rates. These characteristics were inconsistent with the development of PD. Hence, the differences of these features could describe the severity of PD. In addition, these characteristics could provide integrated characteristics regarding PD development and improve the reliability of PD severity assessment because these characteristics were extracted from different angles. To explain the variation laws of these seven kinds of parameters, we analyzed the relevant physical mechanism by considering the microphysical process of PD formation and development as well as the distortion effect generated by the space charges on the initial field. The relevant physical mechanism effectively allocated PD severity among these features for assessment, and the effectiveness and reliability of using these features to assess PD severity were proved by testing a large number of PD samples.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1825-1827
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• 1996

In this study, the Joint of 345kV OF $1C{\times}2000mm^2$ cable was developed to keep up with the trends that need higher-voltage & capacity underground transmission line. The type of joint developed was based on the two kinds of models that have had a good reliability internationally. The mechnic and electric characteristics of the sample specimen was managed in detail when it was manufactured and estimated. Especially, in order to prove the reliability of usage for 30 years, the method of long term aging test was studied. As a result of test, we knew that the joint developed had a good performance. From this study, it can be thought that future ultra-high voltage underground transmission line could be constructed by domestic technology.

• 항공우주산업기술동향
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• 제9권1호
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• pp.130-138
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• 2011

벤트릴리프 밸브는 추진제 탱크의 충전 중 내부의 기체를 배출시키고 충전이 완료된 후에는 탱크의 과압을 해소하는 안전밸브의 역할을 수행한다. 신뢰성과 비용 절감 차원에서 모든 미국의 극저온 액체 추진제를 사용하는 발사체에서는 거의 유사한 벤트릴리프 밸브를 적용해오고 있다. 그리고 발사체의 다양한 임무요구조건을 만족하기 위하여 밸브를 다소 수정하여 사용해오고 있다. 본 논문에서는 발사체 추진제 공급 시스템에 적용되는 벤트릴리프 밸브의 설계 및 제작과 관련한 핵심 기술 동향을 살펴본다. 그리고 우주개발 선진국 발사체에 사용된 벤트릴리프밸브의 운용기술을 소개한다.

• 한국항공우주학회지
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• 제47권9호
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• pp.665-677
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• 2019

미국은 총 수명주기 비용을 최소화하고 운용 가동률 향상을 위해 총 수명주기 체계관리(TLCSM, Total Life Cycle System Management)를 추진 중이다. 실천전략의 하나로 CBM+(Condition Based Maintenance +)를 새로운 무기체계에 적용할 것을 요구하고 있다. F-35 항공기는 개발단계에서부터 CBM+ 개념 하에서 PHM(건전성 예측 및 관리)을 적용하였다. 본 연구에서는 군수용 고정익 항공기 구성품 PHM 적용을 위하여 기술 동향, 국내 PHM 기술 수준 및 해외 기술발전 추세를 분석하였다. 또한, PHM 기술 요소를 분석하여 군수용 고정익 항공기 기술 요소 획득 로드맵 5단계를 구성하였다.

• Journal of Information Processing Systems
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• 제7권3호
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• pp.435-446
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• 2011

Microprocessors are becoming increasingly vulnerable to soft errors due to the current trends of semiconductor technology scaling. Traditional redundant multi-threading architectures provide perfect fault tolerance by re-executing all the computations. However, such a full re-execution technique significantly increases the verification workload on the processor resources, resulting in severe performance degradation. This paper presents a pro-active verification management approach to mitigate the verification workload to increase its performance with a minimal effect on overall reliability. An anomaly-speculation-based filter checker is proposed to guide a verification priority before the re-execution process starts. This technique is accomplished by exploiting a value similarity property, which is defined by a frequent occurrence of partially identical values. Based on the biased distribution of similarity distance measure, this paper investigates further application to exploit similar values for soft error tolerance with anomaly speculation. Extensive measurements prove that the majority of instructions produce values, which are different from the previous result value, only in a few bits. Experimental results show that the proposed scheme accelerates the processor to be 180% faster than traditional fully-fault-tolerant processor with a minimal impact on overall soft error rate.

• Nuclear Engineering and Technology
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• 제53권2호
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• pp.376-385
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• 2021

Probabilistic risk assessment (PRA) has improved its elemental technologies used for assessing external events since the Fukushima Daiichi Nuclear Power Station Accident in 2011. HRA needs to be improved for analyzing tasks performed under extreme conditions (e.g., different actors responding to external events or performing operations using portable mitigation equipment). To make these improvements, it is essential to understand plant-specific and scenario-specific conditions that affect human performance. The Nuclear Risk Research Center (NRRC) of the Central Research Institute of Electric Power Industry (CRIEPI) has developed an HRA guide that compiles qualitative analysis methods for collecting plant-specific and scenario-specific conditions that affect human performance into "narratives," reflecting the latest research trends, and models for analysis of tasks under extreme conditions.

• 한국항공우주학회지
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• 제43권10호
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• pp.936-942
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• 2015

국가위상 제고와 국내 발사체산업 발전에 따른 경제 발전을 위하여 우주발사서비스 시장진입은 필수적이다. 발사체 개발의 후발주자로써 시장에 효과적으로 진입하기 위해서는 시장의 트렌드를 정확하게 파악하고, 체계적인 시장진입전략을 수립하여야한다. 본 논문에서는 세계 우주발사서비스 시장의 3가지 핵심트렌드(고성능의 대형 우주발사체 수요 증가, 저가형 우주발사체 증가, Dual/Multi-Launch 증가)를 도출하고, 각 핵심트렌드에 대응하기 위한 전략의 우선순위를 쌍대비교분석법을 통해 평가하였다. 그 결과 모든 트렌드 하에서 발사체 신뢰성 확보 전략이 가장 중요하며, 고성능의 대형 우주발사체 수요 증가 트렌드 하에서는 정부 지원 전략이, 저가형 우주발사체 및 Dual/Multi-Launch 증가 트렌드 하에서는 가격 경쟁력 확보전략이 두 번째 우선순위를 보였다.

• 한국전기전자재료학회논문지
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• 제35권2호
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• pp.103-118
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• 2022

With the recent increase in demand for electronic devices, multi-layer ceramic capacitors (MLCCs) have become the most important core component. In particular, the next-generation MLCC with extremely high reliability is required for the 4^th industrial revolution and electric vehicle applications. Therefore, it is necessary to develop dielectric ceramic materials with high dielectric properties and reliability. During the decades, electrical properties of BaTiO₃ based dielectric ceramics, which have been widely used in MLCC industrial field, have been improved by microstructure and defect chemistry control. However, electrical properties of BaTiO₃ have reached their limits, and new types of dielectric materials have been widely studied. Based on these backgrounds, this report presents the recent development trends of BaTiO₃-based dielectric materials for the next-generation MLCCs, and suggests promising candidates to replace BaTiO₃ ceramics.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 G
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• pp.2495-2497
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• 1998

Fiber optic facilities are increasingly being deployed in loop applications for both busines and residential areas. These facilities support a variety of communications services that include high speed data and video using leading technologies such as Synchronous Optical Network (SONET), Wavelength Division Multiplexing(WDM). This proliferation of fiber optic facilities combined with the increasing pressure on network operators to reduce costs are fostering increased automation to reduce labor costs associated with providing and maintaining communications services. Effective fiber management and accurate records can improve the reliability and integrity of the future telecommunications networks and the quality of customer services. This paper describes the trend forward and the need for the deployment of Fiber Administration System (FAS) into the operations enviroment of a typical network provider.

• International Journal of Aeronautical and Space Sciences
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• 제9권2호
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• pp.64-70
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• 2008

The UAV propulsion system that will be operated for long time at more than 40,000ft altitude should have not only fuel flow minimization but also high reliability and durability. If this UAV propulsion system may have faults, it is not easy to recover the system from the abnormal, and hence an accurate diagnostic technology must be needed to keep the operational reliability. For this purpose, the development of the health monitoring system which can monitor remotely the engine condition should be required. In this study, a fuzzy trend monitoring method for detecting the engine faults including mechanical faults was proposed through analyzing performance trends of measurement data. The trend monitoring is an engine conditioning method which can find engine faults by monitoring important measuring parameters such as fuel flow, exhaust gas temperatures, rotational speeds, vibration and etc. Using engine condition database as an input to be generated by linear regression analysis of real engine instrument data, an application of the fuzzy logic in diagnostics estimated the cause of fault in each component. According to study results. it was confirmed that the proposed trend monitoring method can improve reliability and durability of the propulsion system for a long endurance UAV to be operated at medium altitude.