• 센서학회지
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• 제27권5호
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• pp.328-334
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• 2018

The paper reviews an improved continuous-wave (CW) terahertz (THz) imaging system developed for nondestructive inspection, such as CW-THz quasi-time-domain spectroscopy (QTDS) and interferometry. First, a comparison between CW and pulsed THz imaging systems is reported. The CW-THz imaging system is a simple, fast, compact, and relatively low-cost system. However, it only provides intensity data, without depth and frequency- or time-domain information. The pulsed THz imaging system yields a broader range of information, but it is expensive because of the femtosecond laser. Recently, to overcome the drawbacks of CW-THz imaging systems, many studies have been conducted, including a study on the QTDS system. In this system, an optical delay line is added to the optical arm leading to the detector. Another system studied is a CW-THz interferometric imaging system, which combines the CW-THz imaging system and far-infrared interferometer system. These systems commonly obtain depth information despite the CW-THz system. Reportedly, these systems can be successfully applied to fields where pulsed THz is used. Lastly, the applicability of these systems for nondestructive inspection was confirmed.

• 한국정보전자통신기술학회논문지
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• 제16권1호
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• pp.24-32
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• 2023

현행 5G 특화망 이용절차는 신청, 심사, 이용, 이용 점검의 단계를 거치며 주파수 할당 전 절차로 신청, 심사단계, 주파수 할당 후 절차로 이용, 이용점검 단계로 구분할 수 있다. 5G 특화망 신청을 위해서는 여러 종류의 서류 제출이 필요하며, 서류 심사 과정과 5G 특화망 주파수 이용을 위한 무선국 검사로 인해 5G 특화망 신청 사업자가 실질적으로 특화망을 사용하기까지의 절차가 복잡하고, 상당한 시간이 소요된다. 본 논문에서는 현행 프로세스보다 신속하고, 간소화된 5G 특화망 주파수 할당을 위해 블록체인 플랫폼을 사용한 5G 특화망 주파수 할당 프로세스를 제안하였다. 블록체인 플랫폼과 NFT(Non-Fungible Token) 활용을 통해 주파수 할당 과정에서 필요한 데이터의 신뢰성과 무결성을 확보하였고, 주파수 이용 정보의 보안 유지와 신뢰 가능한 5G 특화망 주파수 할당 프로세스를 구축하였다. 또한 사람의 개입을 최소화하는 RPA 시스템을 적용하여 5G 특화망 할당 과정에서의 공정성을 확보하였다. 마지막으로 모의실험을 통하여 이더리움 블록체인 기반의 5G 특화망 주파수 할당 프로세스를 수행하였다.

• International Journal of Safety
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• 제6권2호
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• pp.13-16
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• 2007

This study focuses on the trends and issues of improving safety management of elevators in Korea. Frequency and severity of accidents in relation to conditional pass in periodic inspection, maintenance, market surveillance are analyzed based on the statistical data and social cost due to a variety of related fields in managing elevator safety was estimated first. The results of statistical analysis performed in this study will provide logical basis and future direction for improving the safety management system. The role of certification and supervision is particularly addressed to reduce the related accidents and the social cost. The effectiveness of such procedures can be found from the results of simple statistical analysis.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2006년도 추계공동학술대회
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• pp.357-360
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• 2006

• 한국안전학회지
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• 제22권6호
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• pp.7-12
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• 2007

This study focuses on the statistical analysis on safety management of elevators. Specifically, frequency and severity of accidents in relation to conditional pass in periodic inspection, maintenance, market surveillance are analysed based on the statistical data and social loss due to poor management is estimated. The results of statistical analysis performed in this study will provide logical basis and future direction for improving the safety management system.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.881-895
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• 2011

Seoul Metro railway facilities' inspection and maintenance tasks cause failure analysis, but if there is trouble the diverse cause investigation and the systematic analysis and management among broken facilities, related facilities and components fell short and the conditions are different. And, excess and insufficiency, under inspection and maintenance, is being raised regardless of the introduction year and the operating environment including the number of use by applying the same facilities in the uniform inspection cycle. In this study, we will analysis systematically facility system information, failures, operational status, performance, fault and maintenance information resulting from the maintenance management of railway facilities and derive the relationship between associated equipment and its components. In addition, optimizing the inspection and the maintenance cycles of railway facilities, we will improve the reliability of operation. Considering the probability of risk, it is possible to predict the occurrence of accidents or faults and to minimize the frequency of breakdown by pre-inspection maintenance. Finally, This paper is to introduce the content of constructing the Seoul Metro RCM-based failure analysis system for railway facilities to support the optimal continuance of operation status of equipments and the securement of the safe operation of vehicles.

• Corrosion Science and Technology
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• 제8권3호
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• pp.119-125
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• 2009

Corrosion assessment has a number of uses but the use considered here is as a precursor to Risk-Based Inspection (RBI) planning. Systematic methods consisting of technical modules of RBI program were used to assess the effect of specific corrosion mechanism on the probability of failure in equipments of petrochemical plants. Especially in part of the damage and corrosion assessment, screening step involved evaluating the combinations of process conditions and construction materials for each equipment item in order to determine which damage mechanisms are potentially active. For general internal corrosion, either API 510 or API 570 was applied as the damage rate in the calculation to determine the remaining life and inspection frequency. In some cases, a measured rate of corrosion may not be available. The technical modules of RBI program employ default values for corrosion, typically derived from published data or from experience with similar processes, for use until inspection results are available. This paper describes the case study of corrosion and damage assessment by using RBI methodology in petrochemical plant. Specifically, this paper reports the methodology and the results of its application to the petrochemical units using the $KGS-RBI^{TM}$ program, developed by the Korea Gas Safety Corporation to suit Korean situation in conformity with API 581 Codes.

• 한국자동차공학회논문집
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• 제16권5호
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• pp.8-14
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• 2008

For nondestructive inspection of electron beam (EB) welding part in automotive power transmission assembly, a pulse-echo ultrasonic testing apparatus in water immersion has been applied using the ultrasonic waves with a frequency of 10MHz. However various problems have appeared during the ultrasonic inspection, which led to some significant mistakes in automatic quality evaluation of the welding parts. Experimental study showed that the state of water couplant medium containing some amount of contaminants, rusts and anti-corrosion agents had considerable influences on the reduction of ultrasonic amplitudes during wave propagation. The amplitude reduction depending on the coupling medium state could bring about some mis-diagnoses for defects in the welding parts. The results proposed that for a reliable inspection of defects in welds the state of water medium should be kept in about 15 volume fractions (vol.%) of anti-corrosion agents and in minimized contaminants.

• 한국건설관리학회논문집
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• 제20권2호
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• pp.13-27
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• 2019

가설공사는 임시시설물이지만 공사기간동안 사용빈도가 높으며 공사비의 10% 내외를 차지하고 있어 체계적인 관리가 필요하다. 하지만 가설공사의 시공검측정보들은 설계도서 및 시방사항에 특별한 명시가 없는 경우가 많으며 제기준에 대한 사항도 방대하다. 이로 인해 가설공사에 대하여 품질점검을 실시할 경우 관련 점검업무들을 비효율적으로 수행하며, 인간적인 오류가 발생할 확률이 높다. 따라서 본 연구에서는 가설공사에 대하여 품질점검 업무수행을 지원하고 관련 정보를 제공할 수 있는 전자작업지원시스템을 적용하고자 한다. 이를 위해 IDEF0를 활용하여 업무 단위프로세스별 정보흐름을 규명하고 EPSS기반 품질점검 업무체계를 정리하여 프로토타입을 개발한다. 이후 현장적용을 통한 검증방법으로 가설공사 품질점검 업무의 효율과 정보접근성을 향상하고자 한다.

• Journal of Biosystems Engineering
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• 제23권1호
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• pp.67-74
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• 1998

A nondestructive quality inspection technique using acoustic impulse response method was developed for eggshell inspection. An experimental system was built to generate the impact force, to measure the response signal and to analyze the frequency spectrum. This system includes an impulse generating unit, an egg holding seal a microphone with preamplifier, and a DSP board installed on Personal Computer. A simple algorithm .was developed for crack detection. Using the developed system with algorithm, crack detection ability was evaluated and the error rate to estimate the normal egg as cracked was found to be 4% and the error rate to estimate the cracked egg as normal was also found to be 4%. This system could be adopted in industry with some modification.