Study of Ablation of Arc Contacts and Dynamic Contact Resistance in High Current Breaker

Licheng Xing,Xiaodong Zhang,Qingbin Tong,Gaoqi Xing 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.3

The fault of power circuit breaker (PCB) can lead very serious problems, especially in high voltage–power grid. The structure of contacts may be composed of main contacts and arc contacts, and this structure can avoid ablation of main contacts efciently. It is necessary to study the eroded state of the arc contacts and the dynamic contact resistance of arc contacts to estimate the operating state of the PCB. The wear of contacts contains arc ablation and mechanical wear through the characteristics of contacts. The arc ablation is caused by the high temperature of the arc and the mechanical wear is caused by the mechanical friction of static and movable contacts. Some experiments have been done under diferent size of contacts and diferent current through them. The results show that the mechanical wear increases, sometimes heavier, with the increase of the size of fxed contacts and the decrease of the size of movable ones because the force between fxed and movable contacts becomes larger. The results also show that the ablation of arc contacts increases with the increase of current, especially when the current is up to 20 kA. With the high temperature of arc reaching the hardness point of copper, the arc ablation and mechanical erosion are increasing obviously since the contacts become soft and easy to wear. Another result of the study shows it is important to choose the material of contacts and the force between movable and fxed contacts. The harder and less resistance the material of contacts, the better the operating situation. To monitor the operating situation of the breaker, the dynamic contact resistance was measured 25 times. As a result, the dynamic contact resistance is sensitive to the current and increasing with the increase of continuous experiment time because of the increasing of metal ions. Furthermore, if the SF6 in the PCB is changes, the dynamic contact resistance would be changed. The dynamic contact resistance in this experiment varies substantially within the range of 80–250 μΩ at the current of 20 kA.

Analysis of the Tire-Pavement Contact Stress Characteristics during Vehicle Maneuvering

Haiqi He,Rui Li,Qihui Yang,Jianzhong Pei,Fucheng Guo 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.7

The vehicle maneuvering condition plays an important role in the analysis of the contact stress characteristics of the tire-pavement interaction. A reliable three-dimensional (3D) tire-pavement interaction model was developed to simulate the interface contact stress at static and various rolling conditions (free rolling, acceleration and braking). First, the 205-55-R16 radial tire was modeled accurately comprised of its special pattern and materials in the finite element software ABAQUS. Next, we analyzed and compared these contact stress characteristics,including the distribution of contact stress, the peak contact stress and the variation of stress with time at free rolling, acceleration and braking conditions. Results showed that under the same vehicle load and inflation pressure, the tire-pavement contact stresses at free rolling condition are always much larger than those at static loading condition. At acceleration condition, the peak contact stress occurs at the inner edge of the tire outermost ribs. At deceleration condition, the stress concentration on the tire tread is weakened with the extension of time. The peak contact stress increases with time at acceleration and braking conditions. But the peak contact stress at braking is much larger than that at acceleration condition under the same load and inflation pressure.

Distribution of Inter-Contact Time: An Analysis-Based on Social Relationships

Kaimin Wei,Renyong Duan,Guangzhou Shi,Ke Xu 한국통신학회 2013 Journal of communications and networks Vol.15 No.5

Communication in delay tolerant networks (DTNs) relieson message transport by mobile nodes, and a correct understandingof the node mobility characteristics is therefore crucial tothe design of an efficient DTN routing protocol. However, previouswork has mainly focused on uncovering all behaviors of nodemovement, which is not conducive to accurately detecting the specificmovement characteristics of a different node. In this paper, weseek to address this problembased on a consideration of social relationships. We first consider social ties from both static and dynamicperspectives. For a static perspective, in addition to certain accidentalevents, social relations are considered for a long time granularityand tend to be stable over time. For a dynamic perspective,social relations are analyzed in a relatively short time granularityand are likely to change over time. Based on these perspectives,we adopted different efficient approaches to dividing node pairsinto two classes, i.e., familiar and unfamiliar pairs. A threshold approachis used for static social ties whereas a density-based aggregationmethod is used for dynamic social relationships. Extensiveexperimental results show that both familiar and unfamiliar nodepairs have the same inter-contact time distribution, which closelyfollows a power-law decay up to a certain point, beyond which itbegins to exponentially decay. The results also demonstrate that theinter-contact time distribution of familiar pairs decays faster thanthat of unfamiliar pairs, whether from a static or dynamic perspective. In addition, we also analyze the reason for the differencebetween the inter-contact time distributions of both unfamiliar andfamiliar pairs.

Distribution of Inter-Contact Time: An Analysis-Based on Social Relationships

Wei, Kaimin,Duan, Renyong,Shi, Guangzhou,Xu, Ke The Korea Institute of Information and Commucation 2013 Journal of communications and networks Vol.15 No.5

Communication in delay tolerant networks (DTNs) relies on message transport by mobile nodes, and a correct understanding of the node mobility characteristics is therefore crucial to the design of an efficient DTN routing protocol. However, previous work has mainly focused on uncovering all behaviors of node movement, which is not conducive to accurately detecting the specific movement characteristics of a different node. In this paper, we seek to address this problem based on a consideration of social relationships. We first consider social ties from both static and dynamic perspectives. For a static perspective, in addition to certain accidental events, social relations are considered for a long time granularity and tend to be stable over time. For a dynamic perspective, social relations are analyzed in a relatively short time granularity and are likely to change over time. Based on these perspectives, we adopted different efficient approaches to dividing node pairs into two classes, i.e., familiar and unfamiliar pairs. A threshold approach is used for static social ties whereas a density-based aggregation method is used for dynamic social relationships. Extensive experimental results show that both familiar and unfamiliar node pairs have the same inter-contact time distribution, which closely follows a power-law decay up to a certain point, beyond which it begins to exponentially decay. The results also demonstrate that the inter-contact time distribution of familiar pairs decays faster than that of unfamiliar pairs, whether from a static or dynamic perspective. In addition, we also analyze the reason for the difference between the inter-contact time distributions of both unfamiliar and familiar pairs.

SF영화 <스타트랙> 시리즈와 시간여행의 모티프

노시훈 대중서사학회 2019 대중서사연구 Vol.25 No.1

The purpose of this article is to elucidate why the motif of time travel is repeated in the science fiction narrative by examining the functions of this motif in the SF movie series of Star Trek in its narrative and non-narrative aspects. Star Trek IV: The Voyage Home (1986) aims to attract the audience’s interest in the story through the use of plausible time travel in the form of the slingshot effect which causes the spacecraft to fly at very fast speeds around an astronomical object. The movie also touches upon the predestination paradox that arises from a change of history in which it describes a formula of transparent aluminum that did not exist at the time. The film also serves as an evocation of the ideology of ecology by including humpback whales in the central narrative and responding to the real issue of the whale protection movement of the times. Star Track VIII: First Contact (1996) intends to interest the audience in the narrative with the warp drive, a virtual device that enables travel at speeds faster than that of light and a signature visual of Star Trek, at the time of its birth through time travel. The film emphasizes the continuation of peaceful efforts by warning the destruction of humanity that nuclear war can bring. It tackles with the view of pacifism and idealism by stressing the importance of cooperation between countries in the real world by making the audience anticipate the creation of the United Federation of Planets through encounters with the extraterrestrial. Star Trek: The Beginning (2009) improves interest through the idea of time travel to the past, this time using a black hole and the parallel universe created thereby. The parallel universe functions as a reboot, allowing a new story to be created on an alternate timeline while maintaining the original storyline. In addition, this film repeats the themes pacifism and idealism shown in the 1996 film through the confrontation between Spock (and the Starfleet) and Nero, the destruction of the Vulcan and the Romulus, and the cooperation of humans and Vulcans. Eventually, time travel in three Star Trek films has the function of maximizing the audience’s interest in the story and allowing it to develop freely as a narrative tool. It also functions as an ideal solution for commenting on current problems in the non-narrative aspect. The significance of this paper is to stress the possibility that the motif of time travel in SF narrative will evolve as it continues to repeat in different forms as mentioned above. 본고의 목적은 SF영화 <스타트랙> 시리즈에 나타난 시간여행의 모티프가 서사적 측면과 비서사적 측면에서 하고 있는 기능에 대해 고찰함으로써 SF서사에서 이 모티프가 계속 반복되는 이유를 밝히는 데 있다. <스타트랙 IV: 시간 초월의 항해>(1986)는 실제로 사용되는 항법인 슬링샷으로 태양 주위를 돌파하여 그럴듯하게 시간여행을 하는 것과 당시에는 없던 투명 알루미늄의 제작 공식을 알려줘 역사에 변화를 가져오는 예정 역설을 불러오는 것을 통해 이야기에 대한 관객의 흥미를 끌고자 한다. 또한 이 영화는 혹등고래를 중심 서사에 포함시켜 고래 보호 운동이라는 당대의 현실적 문제에 부응함으로써 생태주의라는 이데올로기를 환기시키는 기능을 한다. <스타트랙 Ⅷ: 퍼스트 콘택트>(1996)는 빛보다 빠른 속도로의 비행을 가능하게 해주는 가상의 장치로 스타트랙을 대표하는 기술인 워프 드라이브를 시간여행을 통해 그 탄생 시점에서 다룸으로써 서사에 흥미를 더하고자 한다. 그리고 영화는 핵전쟁이 가져올 수 있는 인류의 멸망을 경고하여 평화적 노력을 계속할 것을 역설하고, 외계와의 조우로 행성연방의 창설을 예고하여 현실 세계에서의 국가 간 협력의 중요성을 강조함으로써 평화주의와 이상주의의 시각을 드러낸다. <스타트랙: 더 비기닝>(2009)은 블랙홀에 의한 과거로의 시간여행과 그로 인해 생성된 평행우주라는 시간여행 서사 요소를 통해 흥미를 높이는데, 특히 후자는 그동안 전개된 이야기를 그대로 유지하면서 자유롭게 새로운 시간선의 이야기를 창조하도록 해주는 리부트 기능을 한다. 더불어 이 영화는 스팍(과 연방함대)과 네로의 대립, 벌컨 행성과 로물루스 행성의 파괴, 인간과 벌컨족의 협력을 통해 1996년 영화에서 보여주었던 평화주의와 이상주의를 반복한다. 결국 세 편의 <스타트랙> 영화에서 시간여행은 서사적 측면에서 이야기에 대한 관객의 흥미를 최대한으로 끌어올리고 서사를 자유롭게 전개하게 해주는 기능을 함과 동시에 비서사적 측면에서 현재의 문제에 대해 논평하고 이상적인 해결 방안을 제시하는 기능을 한다고 할 수 있다. 본고의 의의는 위와 같은 시간여행의 기능으로 볼 때 SF서사에서 시간여행의 모티프가 앞으로도 계속해서 반복되면서 진화할 것이라는 예상을 가능하게 한 데 있다.

구와 평판의 수직 충돌 해석

허경재 釜山大學校生産技術硏究所 1999 生産技術硏究所論文集 Vol.56 No.-

구와 평판의 수직 충돌 해석에서 공간 영역과 시간 영역의 유한 요소법을 이용하여 수치 해석 하였다. 접촉면은 비접착 접촉이고, 마찰은 없다고 가정한다. 접촉면의 기하학적 적합 조건인 접촉 조건을 제한 조건으로 하는 변분 수식을 도입하였다. 구와 평판을 유한 요소화하고, 기하학적 적합 조건을 적용하기 위해 Lagrange 승수가 사용되었다. 접촉 여부 조사는 접촉면의 유한 요소 절점에서 시행하고, 시간 영역에서는 한 시간 요소의 마지막 시간 절점에서 조사하였다. 구와 평판의 수직 충돌 문제의 접촉 기간에서 Hertz의 결과에 접근하는 수치 해석 결과를 얻었다. Space-time finite element methods are applied to the transverse impact analysis between sphere and plate. The contact surface is assumed unbonded and frictionless. A variational statement constrained by the geometric compatibility condition on the contact surface is adopted. The sphere and plate are discretized by the finite element method. The Lagrange multiplier technique is employed to impose the geometric compatibility condition of contact. For numerical implementation, several contact check points are selected conventiently at nodal points on the contact surface. In the time domain, the time point to check the contact condition is chosen at the final time of a time step. The obtained duration of impact shows good sgreement with that of the Hertz's solution.

온도와 접촉시간이 글로우방전 저온플라즈마 기반 고도하수처리에 미치는 영향

김희준 ( Hee Jun Kim ),원찬희 ( Chan Hee Won ) 한국환경기술학회 2018 한국환경기술학회지 Vol.19 No.2

This study investigates how the radicals generated from glow-discharge non-thermal plasma (GD-NTP) the effectively remove organic pollutants in wastewater according to the temperature and contact time. A laboratory experiment was conducted to evaluate the performance of GD-NTP. Tested temperature conditions range between 20~60 ℃ and contact time up to (maximum 6 hours). Results indicate that temperature and contact time affect the removal of pollutant components significantly. Optimal total chemical oxygen demand and total suspended solids removal were obtained at 40 ℃ as 55.1 % and 72.8 %, respectively. These results demonstrate that the GD-NTP is excellent for organic removal at 40 ℃ while high temperature of 60 ℃ makes the total nitrogen removal efficiency as high as 78.6 % due to intensified ammonia stripping and/or selective catalytic oxidation. The results show that optimum temperature condition (40~60 ℃) and contact time (6hr) are effective for removing contaminants in non-thermal plasma, and optimization according to the target wastewater and operating conditions is necessary.

Individual drive cross-coupled control system to compensate for measurement time-delay for roll-to-roll contact pressure uniformization

김대현,김영진,김형래,김주연,Jongmo Kang,최유창,오동호 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.11

As the market demand for products such as flexible displays, IoT devices, and healthcare devices increases, attention has been drawn to printed electronics by a roll-to-roll process that can continuously produce electronic products on flexible substrates using functional inks. In particular, printed patterns need to be uniform in terms of the line width and thickness, which requires uniform control of the contact pressure during the roll-to-roll process, in processes that require ultra-fine pattern printing such as thin-film transistors for flexible displays. Because the contact pressure is indirectly measured using load cells, the performance of the conventional contact pressure control method tends to deteriorate due to the occurrence of time-delay and magnitude errors. Using the transfer function between the actual contact pressure and load cell, the time-delay is measured and compensated. To achieve contact pressure uniformization, the individual drive cross-coupled control system with the time-delay compensation is proposed.

목표어 사회에서의 언어적 상호작용이 학습자의 화용 이해에 미치는 영향 - 거절 화행과 함축 의견 이해를 중심으로 -

이복자 한국언어문화교육학회 2014 언어와 문화 Vol.10 No.2

This study examines the effect of language interaction in the target language community on indirect refusal and implied opinion comprehension. Participants were 43 intermediate Korean learners who were divided into two groups according to the amount of language interaction. They completed a pragmatic listening task measuring their ability to comprehend implied meaning. The results were as follows. First, according to the frequency and time of language contact outside of class per week, there is a significant difference in pragmatic comprehension. Namely, it was shown that the group with greater language contact had a higher pragmatic comprehension ability than the group with less language contact. In addition. according to the frequency and time of language contact outside of class per week, there was a significant difference in each item type. In particular, it was shown that the group with greater language contact had higher comprehension of both indirect refusals and implied opinions than the group with less language contact outside of class. Second, from the analysis of each individual response, it was shown that indirect refusal comprehension was affected by refusal strategies, and implied opinion comprehension was affected by syntactic, lexical difficulty.

마이크로 원형 모세관에서 계면 이동 현상의 측정

이석종(Sukjong Lee),성재용(Jaeyong Sung),이명호(Myeong Ho Lee) 한국생산제조학회 2013 한국생산제조학회지 Vol.22 No.1

In this paper, a high-speed imaging and an image processing technique have been applied to detect the position of a meniscus as a function of time in the micro capillary flows. Two fluids with low and high viscosities, ethylene glycol and glycerin, were dropped into the entrance well of a circular capillary tube. The filling times of the meniscus in both cases of ethylene glycol and glycerin were compared with the theoretical models - Washburn model and its modified model based on Newmans dynamic contact angle equation. To evaluate the model coefficients of Newmans dynamic contact angle, time-varying contact angles under the capillary flows were measured using an image processing technique. By considering the dynamic contact angle, the estimated filling time from the modified Washburn model agrees well with the experimental data. Especially, for the lower-viscosity fluid, the consideration of dynamic contact angle is more significant than for the higher-viscosity fluid.