• Nuclear Engineering and Technology
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• 제54권8호
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• pp.2915-2923
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• 2022

There is an increasing interest in passive safety systems to minimize the need for operator intervention or external power sources in nuclear power plants. Because a passive system has a weak driving force, there is greater uncertainty in the performance compared with an active system. In previous studies, several methods have been suggested to evaluate passive system reliability, and many of them estimated the failure probability using thermal-hydraulic analyses and the Monte Carlo method. However, if the functional failure of a passive system is rare, it is difficult to estimate the failure probability using conventional methods owing to their high computational time. In this paper, a procedure for the application of the Chernoff bound to the evaluation of passive system reliability is proposed. A feasibility study of the procedure was conducted on a passive decay heat removal system of a micro modular reactor in its conceptual design phase, and it was demonstrated that the passive system reliability can be evaluated without performing a large number of thermal-hydraulic analyses or Monte Carlo simulations when the system has a small failure probability. Accordingly, the advantages and constraints of applying the Chernoff bound for passive system reliability evaluation are discussed in this paper.

• 한국재료학회지
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• 제32권4호
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• pp.230-236
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• 2022

The formation behavior of a passive state film on the surface of STS304 in electrolytic solution was analyzed to determine its metallic ion composition. The properties of passive state films vary depending on the Fe and Cr ions in the electrolytic solution. It was observed that the passive state film surface became flat and glossy as the concentration of Fe and Cr ions in the electrolytic solution increased. The corrosion resistance property of the passive state film was proportional to the amount of Fe and Cr in the electrolytic solution. An initial passive state film with high Fe concentration was formed on the surface of STS304 during early electrolytic polishing. Osmotic pressure of Fe ions occurs between the passive state film and electrolytic solution due to the Fe ion concentration gradient. The Fe in the passive state film is dissolved into the electrolyte, and Cr fills up the Fe ion vacancies. As a result, a good corrosion-resistant floating film was formed. The more Fe ions in the electrolytic solution, the faster the film is formed, and as a result, a flat passive state film containing a large amount of Cr can be formed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.112-114
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• 1998

The passive system requires RF-DC converter. RF-DC converter, which is used in microwave region, is more affected by parasitic elements than used in low frequency region. So it is difficult to make the converter. RF-DC converter usually consists of resonator, shottky diode, capacitor, voltage regulator. In this study, we used the rechargeable battery instead of capacitor. If any passive transponder requires more power than general transponder, battery tech of this components is important to apply for the passive system. In this paper, passive transponder, which requires more power than general passive transponder, is presented and compared to general passive transponder.

• 비교문화연구
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• 제47권
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• pp.217-240
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• 2017

본고는 피동 표현에서의 한국어 행위주 표지 '-에게(한테)', '-에, -로'와 중국어 피동 표지 '피(被)[$b{\grave{e}}i$]/양(?)[$r{\grave{a}}ng$]/규(叫)[$ji{\grave{a}}o$]/급(?)[$g{\check{e}}i$]'를 연구 대상으로 삼아 그 분포양상 및 특징을 살피고 이들 형태를 비교 대조를 통하여 그 대응 관계를 면밀히 고찰해 보고자 하였다. 대조 분석 시 두 언어의 유형적 특징, 피동 표현에서의 행위주, 피동주에 대한 선택 제약, 그리고 '받다'류 피동 표현에서 행위주(피동) 표지의 사용 제약과 같은 3가지 측면에 중점을 두었다. 본 대조 분석을 통해 확인한바, 한 중 피동 표현에서 한국어 행위주 표지 '-에게(한테)', '-에, -로'와 중국어 피동 표지 '피(被)/양(?)/규(叫)/급(?)'는 각각 행위주와 결합하여 부사어 역할을 하고 있는 공통점에도 불구하고 용법에 있어 차이점을 보였다. 먼저 두 언어 유형적 특징에 따라 피동 표현에서 행위주와의 결합 방식이 각각 달리 나타남을 확인하였다. 그리고 한국어 행위주 표지는 오로지 조사 역할을 하여 '행위주 유정성 유무'에 대한 제약만 받는 반면, 중국어 피동 표지 '피(被)/양(?)/규(叫)/급(?)'는 각각 문법화 정도에 따라 행위주 유무뿐만 아니라 피동주 유정성 유무 그리고 문장에 나타나는 어휘의 의미에 따른 제약 등을 보인다. 특히 한국어 '받다'류 피동 표현에서 한국어의 행위주 표지 '에게(한테), -에, -로'는 그대로 사용되지만 대응하는 중국어에서는 피동 표지 사용에 여러 제약이 있음을 확인하였다.

• Corrosion Science and Technology
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• 제2권5호
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• pp.212-218
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• 2003

Electronic properties of passive films formed on Ti at film formation potentials $(E_f)V_{SCE}$ in pH 8.5 buffer solution and in an artificial seawater were examined through the photocurrent measurement and Mott-Schottky analysis. The passive films formed on Ti in pH 8.5 buffer solution exhibited a n-type semiconductor with a band gap energys $(E_g);E_g^{n=2}=3.4$ eV for nondirect electron transition, and $E_g^{n=0.5}=3.7$ eV for direct electron transition. These band gap values were almost same as those for the passive films formed in artificial seawater, indicating that chloride ion ($Cl^-$ in solution did not affect the electronic structure of the passive film on Ti. $E_g$ for passive films formed on Ti were found to be greater than those ($E_g^{n=0.5}=3.1$ eV, $E_g^{n=2}=3.4$) for a thermal oxide film formed on Ti in air at $400^{\circ}C$. The disorder energy of passive film, determined from the absorption tail of photocurrent spectrum, was much greater than that for the thermal oxide film farmed on Ti in air at $400^{\circ}C$. The greater $E_g$ and the higher disorder energy for the passive film compared with those for the thermal oxide fIlm suggest that the passive film on Ti exhibited more disorded structure than the thermal oxide film. The donor density (about $2.4{\times}10^{20}cm^{-3}$) for the passive film formed in artificial seawater was greater than that (about $20{\times}10^{20}cm^{-3}$) formed in pH 8.5 buffer solution, indicating that $Cl^-$ increased the donor density for the passive film on Ti.

• 터널과지하공간
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• 제14권6호
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• pp.411-422
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• 2004

폐광지역에서 흔히 발생하는 싱크홀 형태의 지반침하는 인근 지역 주민의 안전은 물론, 지상구조물에 심각한 위해 요소로 작용할 수 있다. 본 연구에서는, 이러한 싱크홀의 발생양상을 수치해석적으로 규명하기 위해, 아주 특별한 형태의 유한요소해석을 실시하였다. 특히, 갱도 천반의 붕락에 의해 야기되는 공간이나, 파쇄된 암반이 쌓여서 이루는 폐석더미 등 기존의 수치해석기법으로서는 쉽사리 표현할 수 없었던 현실적인 문제들을 수치적으로 모사하기 위해 active-passive-active 유한요소를 사용하였다. Active 요소 즉 고체 요소는 싱크홀이 형성되는 영역 내에서 인장파괴 기준식을 만족하게 되면 passive 요소 즉 공간 요소로 전환될 수 있다. 싱크홀이 완전히 형성되게 되면 이들 passive요소들은 다시 active요소로 바뀌면서 폐석더미를 수치적으로 모사할 수 있게 된다. 채굴적의 폭, 심도, 천반의 상태 및 붕락 암반의 부피팽창율 등이 싱크홀에 미치는 영향을 검토하기 위해 여러 가지 조건에 의한 유한요소모델이 해석되었다. 본 연구는, 이와 같이 싱크홀이 발생하는 과정이나 천반이 붕락하는 현상 등을 해석하기 위해 수치해석상에서 active-passive-active유한요소들이 효과적으로 사용될 수 있음을 보여준다.

• Journal of Preventive Medicine and Public Health
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• 제33권1호
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• pp.91-98
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• 2000

Objectives : This study is to evaluate the awareness, attitude, practice and the countermeasures against passive smoking in Korean adults. Methods : By self-administered questionnaires, we assessed the knowledge, attitude, behavior for passive smoking and the countermeasure for reduction of it's harmful effects in 289 men and 238 women. Results : The subjects that have heard about passive smoking were 96.8% in total and well known were 26.4% of current smoker, 56.6% of ex-smoker, and 14.8% of non-smoker(p=0.001). The irritative symptom from passive smoking was the most frequent in non-smokers and the most common place where exposed to passive smoking was public place. For attitude against passive smoking in 'no smoking allowed area', ex-smokers were the most active to recommend to stop smoking. And for opinion about establishment of 'no smoking allowed area', the restriction by law was the best acceptable method in smokers, exsmokers, and nonsmokers. In marking of 'no smoking allowed area', 69.9% of smokers answered no smoking, but in non-marking area only 6.3% stop smoking. When smokers were recommended to stop smoking, the more subjects stop smoking with good feeling in marking area, but the less in non-marking area. The factor associated the high awareness of passive smoking were aged(OR=1.07, 1.03-1.12), men(OR=4.34, 2.32-8.46). The persons who have known well about passive smoking had good attitude and behavior to prevent of harmful effect of passive smoking. Conclusions : This study suggested that education program would be necessary to reduce the passive smoking.

• Structural Engineering and Mechanics
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• 제37권4호
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• pp.443-458
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• 2011

An extensive numerical investigation on the magnetorheological (MR) damper-based smart passive control system for mitigating vibration of stay cables under wind loads has been conducted. The smart passive system is incorporated with an electromagnetic induction (EMI) device for reducing complexity of the conventional MR damper based semi-active control system by eliminating an external power supply part and a feedback control part (i.e., sensors and controller). In this study, the control performance of the smart passive system has been evaluated by using a cable structure model extracted from a full-scale long stay cable with high tension. Numerical simulation results of the proposed smart damping system are compared with those of the passive and semi-active control systems employing MR dampers. It is demonstrated from the results that the control performance of the smart passive control system is better than those of the passive control cases and comparable to those of the semi-active control systems in the forced vibration analysis as well as the free vibration analysis, even though there is no external power source in the smart passive system.

• Nuclear Engineering and Technology
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• 제49권7호
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• pp.1431-1441
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• 2017

The Fukushima accident reveals the vulnerability of existing active nuclear power plant (NPP) design against prolonged loss of external electricity events. The passive safety system is considered an attractive alternative to cope with this kind of disaster. Also, the passive safety system enhances both the safety and the economics of NPPs. The adoption of a passive safety system reduces the number of active components and can minimize the construction cost of NPPs. In this paper, reflecting on the experience during the development of the APR+ design in Korea, we propose the concept of an innovative Power Reactor (iPower), which is a kind of passive NPP, to enhance safety in a revolutionary manner. The ultimate goal of iPower is to confirm the feasibility of practically eliminating radioactive material release to the environment in all accident conditions. The representative safety grade passive system includes a passive emergency core cooling system, a passive containment cooling system, and a passive auxiliary feedwater system. Preliminary analysis results show that these concepts are feasible with respect to preventing and/or mitigating the consequences of design base accidents and severe accidents.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2493-2503
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• 2018

Passive dynamic walking exhibits humanoid and energy efficient gaits. However, optimal design of passive walker at multi-variable level is not well studied yet. This paper presents a Chaotic Particle Swarm Optimization (CPSO) algorithm and applies it to the optimal design of flexible passive walker. Hip torsional stiffness and damping were incorporated into flexible biped walker, to imitate passive elastic mechanisms utilized in human locomotion. Hybrid dynamics were developed to model passive walking, and period-one gait was gained. The parameters global searching scopes were gained after investigating the influences of structural parameters on passive gait. CPSO were utilized to optimize the flexible passive walker. To improve the performance of PSO, multi-scroll Jerk chaotic system was used to generate pseudorandom sequences, and chaotic disturbance would be triggered if the swarm is trapped into local optimum. The effectiveness of CPSO is verified by comparisons with standard PSO and two typical chaotic PSO methods. Numerical simulations show that better fitness value of optimal design could be gained by CPSO presented. The proposed CPSO would be useful to design biped robot prototype.