• 한국수소및신에너지학회논문집
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• 제33권3호
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• pp.232-239
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• 2022

This study performed qualitative and quantitative risk assessment of equipment for evaluating the protocol of hydrogen refueling stations and suggested measures to improve safety. Hazard and operability study was performed for qualitative risk assessment, and Hy-KoRAM was used for quantitative risk assessment. Through a qualitative risk assessment, additional ventilation devices were installed, simultaneous venting of the storage container was prohibited, and the number of repeated refilling of the evaluation equipment was identified to manage the number of fillings of the container. Through quantitative risk assessment, the area around the device was set as a restricted area when evaluating the station, and measures were suggested to reduce the frequency of accidents.

• 조명전기설비학회논문지
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• 제27권2호
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• pp.54-61
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• 2013

This paper presents transient response behavior and frequency-dependent ground impedance of a single carbon ground electrode. The ground impedance of the carbon ground electrode was measured as a function of frequency of injected currents and simulated by using the distributed parameter circuit model with due regard to the frequency-dependent soil parameters, and the transient response behavior of the carbon ground electrode against impulse currents were investigated. As a consequence, the frequency-dependent ground impedance of the carbon ground electrode showed the capacitive behavior, that is, the ground impedance decreases with increasing the frequency of injected currents and lowers at the fast front time of impulse current. It was found that the carbon ground electrode is effective in grounding system for lightning protection. The ground impedance simulated with due regard to the frequency-dependent soil parameters was in good agreement with the measured data. The adequacy of the simulation technique and the distributed parameter circuit model for the carbon ground electrode was verified. It is expected that the simulation methodology, which analyzes the frequency-dependent ground impedance of the carbon ground electrode proposed in this work, can be used in the design of a grounding system for protection against lightning.

• 한국가스학회지
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• 제16권1호
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• pp.39-45
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• 2012

천연가스 공급 시설은 가스 소비자에게 사용의 편리성과 동시에 위험성을 제공하기 때문에 매우 까다로운 위험관리 대상이다. 따라서 그 위험을 최대한 낮추면서 가스 공급을 위해서는 합리적 안전 관리 의사 결정 방법이 필요하며 정량적 위험성 평가(QRA)는 그 적합한 도구로 인식되고 있다. 하지만 수백여개에 이르는 가스 공급 시설들에 대하여 QRA 수행하는 것은 전문가 부족과 분석 시간이 오래 소요되는 문제로 인해 효과적으로 이루어지기 어렵다. 이에 본 논문에서는 가스 공급시설에 대하여 QRA를 보다 효율적으로 수행할 수 있는 시스템 체계를 제시하였다. 이 체계의 핵심적 특징은 사고점이라고 지칭한 분석점에 전문가가 사전 분석을 통해 대상 설비(들)에 대한 사고 빈도/결과 분석에 필요한 값을 얻기 위한 질의서와 내부 계산식을 만들어놓고 일반 사용자는 그 점을 지도에 위치시키고 그 내부 질의에서 요구하는 값을 입력함으로써 QRA가 수행되는 것이다. 궁극적으로 이는 QRA 분석 절차에 있어서 분업화가 가능하다는 아이디어에 기반하여 제시된 것이며 본 논문에서는 실제적 시스템 구축과 적용을 통해 그 체계의 유효성을 확인하였다.

• 한국강구조학회 논문집
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• 제15권2호
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• pp.117-124
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• 2003

고층건물의 사용성설계는 가속도와 같은 풍응답진동에 의하여 자주 영향을 받으므로, 이때 고유진동수의 올바른 산정은 중요하다. 설계단계에서 사용되고 있는 이러한 진동수 경험식들은 상호간에 서로 다른 결과치를 제시하는 경향이 있다. 이 논문은 철골조 건물의 진동주기에 대한 것으로서, 건물의 진동실험방법과 상시진동실험에서 얻은 고유주기를 예측하기 위한 방법을 제시하였다. 서울지역 21개동의 상시진동 계측데이터에서 고유주기를 산정하였다. 철골조 고층건물의 고유주기 근사식을 제안하였으며, 고유주기의 근사식을 국내외 기준 및 고유치해석의 결과와 비교하였다.

• 한국안전학회지
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• 제30권4호
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• pp.46-50
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• 2015

This paper describes the measurement and analysis of ground impedance according to arrangement of auxiliary probe around ground grid using the fall-of-potential method and the testing techniques to minimize the measuring errors are proposed. The fall-of-potential method involves passing a current between a ground electrode and a current probe, and then measuring the voltage between a ground electrode and a potential probe. To minimize interelectrode influences due to mutual resistances, the current probe is a generally placed at a substantial distance from the ground electrode under test. In order to analyze the effects of ground impedance due to the arrangement of auxiliary probe and frequency, ground impedances were measured in case that the arrangements of auxiliary probe were straight line, perpendicular line, and horizontal line. The distance of current probe was located from 10[m] to 200[m] and the measuring frequency was ranged from 55[Hz] to 513[Hz]. As a consequence, the ground impedance increases with increasing the distance from the ground electrode to the point to be tested, but the ground impedance decreases with increasing the frequency.

• 복식
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• 제64권6호
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• pp.161-175
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• 2014

This paper investigates the differences between characteristics of street fashions due to regional and cultural differences in southern and northern region of China. Beijing and Shenzhen were chosen as representative cities for the two areas. Empirical research and literature study were performed for this study. Empirical studies were performed by using a total of 708 images of dresses, which were collected through direct imaging. Through discussion with experts, the collected data were classified into five categories; Modern trendy, Romantic, Easy casual, Ethnic, and Classical/Traditional. The data was analyzed by using cross tabulation and frequency analysis. Content analysis for each category was also conducted. As a consequence of this study, a significant difference between Beijing and Shenzhen were observed. As a city, which puts emphasis on practicality and modernity, Beijing showed a higher frequency of modern and trendy style than the other city. On the other hand, Shenzhen showed a higher frequency of romantic style and was distinguished as a city of femininity and decorative preference of fashion style. This study intends to contribute to the academic community of Chinese fashion and to help Korean clothing companies to be launched in Chinese market in the future.

• 한국소음진동공학회논문집
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• 제26권5호
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• pp.501-510
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• 2016

Capabilities of several beamforming techniques are compared for estimating the position of a moving source. Beamforming has enabled to widen our perspective of aeroacoustics in wind tunnel experiments and has provided useful approach in array measurements. Meanwhile beamforming techniques have been developed in a way to improve estimation accuracy and to save ing effort at the same time. In order to achieve reasonable outcome from aeroacoustic measurement, it is important to identify the spectral characteristics of source and to select an appropriate beamformer. Though aeroacoustic sources normally generates broadband noises, many array signal processing have been focused on narrowband processing which makes calculation numerically efficient. However, calculation in frequency-domain requires selection of single frequency of interest which affects spatial resolution and sidelobe level as a consequence. To be able to localize broadband noise source, it is proposed to use broadband beamforming. The formulas implements the deletion of diagonal term from cross spectral matrix. In this study, trajectory of flying source emitting broadband noise was simulated and several beamformers are applied.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.579-587
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• 2008

Promotion of the line no.2 in Seoul Metro was changing from the existing signaling facilities for ATS(Automatic Train Stop) vehicles to the up-to-date signaling facilities for ATO(Automatic Train Operation). But, in consequence of conducting a trial run after being equipped with the ATO signaling facilities, the matter related to mix-operation with the existing ATS signaling facilities appeared. The operation of the existing ATS signaling system in combination with the ATO signaling system has made improper working related to frequency recognition of the ATS On-board Computerized Equipment. This obstructs operation of a working ATS vehicle. That is, as barring operation of an ATS vehicle that should proceed, it may make the proceeding ATS vehicle stop suddenly and after all, it will cause safety concerns. In this paper, we designed a wayside track occupancy detector that previously prevents improper working related to frequency recognition of the ATS On-board Computerized Equipment by gripping classification and working processes of operating trains throughout transmission of local signaling information from the existing facilities, which does not need to change or replace the existing signaling facilities. Furthermore, we described general characteristics of the wayside track occupancy detector and modeled the IFC(InterFace Contrivance) device and the logical circuit recognizing signal information. Then, we made an application program of PLC(programmable Logic Computer) based on the stated model. We, in relation to data transfer method, used the frame in TCP/IP transfer mode as the standard, and we demonstrated that ATO transmission frequency is intercepted.

• 대한조선학회논문집
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• 제60권6호
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• pp.433-440
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• 2023

This study aims to establish safety zones for bunkering operations of hydrogen propulsion ships in coastal areas through risk assessment and evaluate their validity. Using a 350 kW-class ferry operating in Busan Port as the subject of analysis, with quantitative risk assessment based on accident consequence and frequency analysis, along with a social risk assessment considering population density. The results of the risk assessment indicate that all scenarios were within acceptable risk criteria and ALARP region. The most critical accident scenarios involve complete hose rupture during bunkering, resulting in jet flames (Frequency: 2.76E-06, Fatalities: 9.81) and vapor cloud explosions (Frequency: 1.33E-08, Fatalities: 14.24). For the recommended safety zone criteria in the 6% hose cross-sectional area leakage scenario, It could be appropriate criteria considering overall risk level and safety zones criteria for hydrogen vehicle refueling stations. This research contributes to establishing safety zone for bunkering operations of hydrogen propulsion ships through risk assessment and provides valuable technical guidelines.

• 한국전자파학회논문지
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• 제13권9호
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• pp.898-906
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• 2002

송신 전력이 비교적 높은 5 dBm인 광 펄스를 최적 펌프 전력 조건 하에서의 MSSI(Mid-Span Spectral Inversion) 보상 기법을 통해 전송할 때 다양한 주파수 첩(chirp)을 갖는 광 펄스의 전송 거리가 어느 정도 개선되는지를 다양한 전송 속도와 분산 계수에 따라 살펴보았고, 광 펄스의 주파수 첩과 Kerr효과에 의한 위상 변화의 상호 관계가 다양한 비트율에서의 광섬유 분산 계수 변화에 따라 MSSI 보상에 어떠한 영향을 주는 지를 시뮬레이션을 통해 분석해 보았다. 우선 광 펄스가 광섬유를 전파하면서 겪게 되는 자기 위상 변조에 의한 위상 변화가 광 변조 과정에서 인가된 광 펄스의 초기 첩에 의한 위상 변화와 어우러져 상쇄되는 정도가 광섬유의 분산 계수 값에 따라 달라지게 되어 MSSI 기법을 통해 광 펄스가 보상되는 정도에도 변화가 있는 것을 확인할 수 있었다. 또한 동일한 보상 특성을 얻을 수 있는 비트율에 따른 분산 천이 광섬유의 분산 계수 값은 전송비트율 증가 비율을 k라고 하면 2$^{k}$ 의 관계로 줄어들어야 하는 것을 알 수 있었다.