• 한국가스학회지
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• 제14권6호
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• pp.38-43
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• 2010

자원 부족과 환경규제의 강화에 따라 자동차 강판재의 고강도화와 박강판화가 주요 이슈로 대두되고 있다. 그러나 고강도 강판재 사용에 있어 수소취성은 기계적 성질 저하의 문제가 되고 있다. 본 연구에서는 개발중인 590MPa급 DP강을 대상으로 조성 및 조직특성에 따른 표면층에서의 수소의 거동에 대해 연구하였다. 수소주입은 음극전기분해법을 이용하여 강제 주입시켰고, 수소주입조건에 따른 수소주입량과 표면층 조직관찰 및 미소경도시험 결과의 관계로 부터 표면층의 수소거동을 평가하였다.

• 한국통신학회논문지
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• 제26권12C호
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• pp.190-198
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• 2001

In this paper, the authors propose methods for determining the differentiated price for elastic traffic in IP (Internet Protocol) network. First, we investigate the behavior in the consumption of bandwidth of elastic traffic in IP network. Next, we propose a method to relate the bandwidth usage with the pricing for the elastic traffic, which is based partially or fully on the usage rate of the network bandwidth. After that, we propose a charging function for elastic traffic, which is based on the de facto usage of the bandwidth. Finally, we will illustrate the implication of the work via simple numerical experiments.

• 한국산업융합학회 논문집
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• 제26권5호
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• pp.875-884
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• 2023

Hydrogen infiltration into metals has been reported to induce alterations in their mechanical properties under load. In this study, we conducted CTOD (Crack Tip Opening Displacement) tests on steel specimens designed for use in liquid hydrogen storage systems. Electrochemical hydrogen charging was performed using both FCC series austenitic stainless steel and BCC series structural steel specimens, while CTOD testing was carried out using a 500kN-class material testing machine. Results indicate a notable divergence in behavior: SS400 test samples exhibited a higher susceptibility to failure compared to austenitic stainless steel counterparts, whereas SUS 316L test samples displayed minimal changes in displacement and maximum load due to hydrogen charging. However, SEM (Scanning Electron Microscopy) analysis results presented challenges in clearly explaining the mechanical degradation phenomenon in the tested materials. This study's resultant database holds significant promise for enhancing the safety design of liquid hydrogen storage systems, providing invaluable insights into the performance of various steel alloys under the influence of hydrogen embrittlement.

• 한국재난관리표준학회지
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• 제3권2호
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• pp.57-64
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• 2010

본 연구는 신설 터널 발파 시 기존 터널 거동 및 시설물 안전에 관한 연구로서 설계 당시에는 신설 터널의 안전성에 초점을 맞추다 보니 기존 터널 내부에 설치되어 있는 제연 팬 등과 같이 시설물의 안전성을 확보하기 위한 세부적인 설계에 있어서 다소 미흡한 면이 있었다. 기존 터널의 최근 10년간 교통사고 유형을 분석한 결과 주행 중인 차량 간 긴급 상황 및 상호 장애요소 발생 시 미처 대처하지 못해 발생하는 사고가 대부분인 것을 알 수 있었다. 이런 점을 감안하여 신설 터널 시점 부 및 본선 구간 발파 시 장약량을 최소화하였고 피난연결통로 굴착은 대구경 심빼기 발파공법으로 변경 시공하여 진동을 최소화함으로써 기존 터널 내부의 시설물 안전성을 확보하였다. 정량적 분석 방법으로서는 각종 계측기를 설치하여 신설 터널 주변 민가, 기존 터널 내부 및 제연 팬 주위에 설치하여 실시간 변위를 파악하여 교통류 차단 없이 정상 흐름을 확보하였다. 향후 대도심지에 위치하면서 기존 터널과 인접한 터널 설계 시 터널 내부 시설물 안전성 확보를 위해 발파 장약량, 발파공법 및 계측방법의 개선 방안을 제시하였다.

• 한국가스학회지
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• 제18권1호
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• pp.61-67
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• 2014

고강도 DP강의 수소취성 거동을 소형펀치시험을 통해 평가하였다. 이를 위해 첨가원소가 각기 다른 3종의 DP강 시험편에 전기화학적 방법으로 수소를 강제 주입시켰다. 수소주입 후, 수소주입량을 측정하였다. 수소주입량은 마르텐사이트 부피분율에 크게 의존하는 것으로 조사되었다. 전류밀도 150, $200mA/cm^2$ 조건에서 25시간이 포화상태에 도달하는 수소주입조건으로 나타났다. SP시험 후 SP에너지와 SP bulb 형상을 비교한 결과, 수소주입량의 증가에 따라 SP에너지와 SP bulb 높이가 감소하는 것으로 나타났다. 또한 SP bulb 파단면에서는 뚜렷한 facet와 층상형태의 벽개 파단면이 관찰되어 수소취성화를 관찰할 수 있었다.

• The Journal of Korean Physical Therapy
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• 제4권1호
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• pp.69-78
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• 1992

The purpose of this survey is to grasp the special school therapeutic education teachers, stress degrees in the real educational fields, and to campare the different stress degrees by the teaching responsibilities, by set by age, by the careers of special teaching profession, by his or her assiduity by the academic careers and teacher qualification, and by the reasons of stress. To perform this survey, the writer analyzed the answer sheets of the questionnairs returned by 85 special school therapeutic education teachers all over the country. The results of the analysis are as follows: First, the mean value of stress by the whole teachers was shown as endurable, and there was no difference among stress towels by the teaching responsibilities. As for the ratio of teachers confronted with the dangerous level of stress. the teachers taking charge of feebleminded school teachers the highest ratio, and those charging of deaf & dumb school teachers, the lowest. Second, the comparison by age didn't result in any difference, but in the relation of age to the handicap division there appeared meaningful differences. That is in the case of the therapeutic education theachers charging of crippled school, it revealed that the older they were, the more stress they suffered. In the case of the teachers charging of visually deaf & dumb school the tendency was opposite. The comparison by the special teaching profession careers, there showed no difference in the stress degree. The high or low academic careers didn't make any influence on the therapeutic education teachers stress degree. Third, The revealed on the highest stress degress, because reasons of relation the student's parents with students behavior.

• 융합보안논문지
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• 제20권5호
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• pp.11-17
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• 2020

IoT의 핵심 요소 기술 중 하나인 Bluetooth를 전기차 무선 충전 시스템에 사용하는 경우가 늘어나면서 이에 대한 보안 문제가 큰 이슈로 부각되고 있다. 무선 통신 기술인 Bluetooth에 보안을 강화하기 위한 다양한 기술적 노력이 있어 왔지만 여전히 다양한 공격 방법이 존재한다. 본 논문은 Bluetooth 시스템을 대상으로 대표적인 2가지 공격 방법을 지능적으로 탐지하기 위해 잘 알려진 Hidden Markov Model을 이용한 지능형 Bluetooth 침입 탐지 시스템을 제안한다. 제안 방법은 탐지의 정확성 이외에 실시간 탐지가 가능하도록 Bluetooth 전송 계층 프로토코인 H4의 패킷 타입과 전송 방향을 조합하고 이들의 시간상의 전개를 특징으로 사용한다. 데이터 수집 환경을 구성하고 실험을 통해 얻은 데이터를 대상으로 개발한 시스템의 성능을 분석한다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2004년도 추계학술발표회 발표논문집
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• pp.911-912
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• 2004

1. Cathodic hydrogen charging considerably reduced the tensile ductility of ODS steels and a 9Cr-2W RMS. The hydrogen embrittlement of ODS steels was strongly affected by specimen sampling orientation, showing significant embrittlement in the T-direction. This comes from the microstructural anisotropy caused by elongated grains of ODS steels in L-direction. 2. The ODS steels contained a higher concentration of hydrogen than 9Cr-2W RMS at the same cathodic charging condition, and the critical hydrogen concentration required to transition from ductile to brittle fracture was in the range of $10{\sim}12$ wppm, which approximately 10 times larger than that of a 9Cr-2W martensitic steel. 3. The ODS steels showed a typical ductile to brittle transition behavior and it strongly depended on the specimen sampling direction, namely L- and T-direction. In T-direction, the SP-DBTT was about 170 L, irrespective of the ODS materials, and L-direction showed a lower SP-DBTT than that of T-direction.

• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.448-454
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• 2012

In this paper, a three-dimensional hydrogen absorption model is applied to a thin double-layered annulus ZrCo hydride bed and validated against the temperature evolution data measured by Kang et al. The present model reasonably captures the bed temperature evolution behavior and the 99% hydrogen charging time. The equilibrium pressure expression for hydrogen absorption on ZrCo is derived as a function of temperature and the H/M atomic ratio based on the pressure-composition isotherm data given by Konishi et al. In addition, this present model provides multi-dimensional contours such as temperature and H/M atomic ratio in the thin doublelayered annulus metal hydride region. This numerical study provides fundamental understanding during hydrogen absorption process and indicates that efficient design of the metal hydride bed is critical to achieve rapid hydrogen charging performance. The present three-dimensional hydrogen absorption model is a useful tool for the optimization of bed design and operating conditions.

• International Journal of Contents
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• 제15권2호
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• pp.1-12
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• 2019

Despite their various similarities, Seoul's' Gangnam and Seocho districts showed different patterns in the adoption of the RFID household-based waste charging system. Gangnam, one of the 25 wealthiest districts in Seoul, first adopted the RFID system in 2012, but decided abandon it a year later due to inconvenience, sanitation, budget limitations, and management related issues. Unlike Gangnam, Seocho, a largely similar district to Gangnam, started to implement the RFID system in 2015 and successfully adopted this innovation. In this paper, we explain the adoption behaviors of these two districts using a Technology Hype Curve Model with 5 stages. Unlike traditional technology adoption theory, the Hype Curve Model concentrates on the big chasm between early majorities and late majorities, which is a core reason for discontinuity in innovation diffusion. Based on our case study result, the early majority easily gave up adoption due to immature technological and institutional infrastructure. However, Seocho district, who waited until the deficiencies had been sufficiently fixed since late majorities, succeeded at incremental diffusion. Since its invention by Gartner cooperation, the Hype Curve Model has not received enough attention in academia. This paper demonstrates its explanatory power for innovation diffusion. Similarly, this paper focuses on the importance of institutional framework in the diffusion of innovation. Lastly, we compare the behavior of two local governments in supporting and diffusing RFID systems to draw relevant policy implications for innovation diffusion.