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Robust Design of a Rope Ascender Based on Geometric parameters of Traction Sheave
Myeongjin Choi,Hobyeong Chae,Kyungmin Kim,TaeWon Seo 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.5
In this study, an optimal-traction sheave is designed to prevent slip for a two-degrees-of-freedom facade-cleaning robot called Dual Ascender Robot (DAR). The DAR uses the length of the rope to estimate its position. Therefore, if a slip occurs, it becomes difficult to measure the length of the rope, thereby making it difficult to estimate position. Problems with position estimation may also cause difficulties in achieving control. The redesigned traction sheave was thoroughly evaluated by experiments. A well-known Taguchi method was used as the experimental procedure, and the optimal design parameters of the sheave were determined as hoop direction groove shape of 0.8, axial direction groove pitch of 6°, and axial direction groove depth of 2 mm. Verification experiments comparing the traction sheave with the optimal condition to that used in DAR showed improved performance. Therefore, it is expected that applying the optimal traction sheave to a DAR in further studies would help achieve better position estimation by preventing slips
최명진(Choi, Myeongjin) 충청남도역사문화연구원 2020 충청학과 충청문화 Vol.28 No.1
탄은 이정(灘隠 李霆, 1554~1626)은 조선시대 묵죽화의 대가로서 당대 최고의 인기를 누렸던 종친 화가이다. 그의 묵죽화를 일컬어 윤신지(尹新之, 1582~1657)는 석양공자의 먹의 묘리는 천하에 오묘하여 중국인들도 한 폭이라도 얻으려 값에 한정을 두지 않았다 라고 했고, 권상하(權尚夏, 1641~1721)는 지금까지의 작자는 무수히 많으나, 오직 탄은 노인의 명성만이 드높고 아름답다. 灘翁의 묵죽은 천하에 뛰어나 일시에 그 가치는 높고 그림 한 장 얻기 어렵다 라며 최고의 평가를 주는 데 주저하지 않았다. 최근 보물로 지정된 이정의 『삼정첩』과 5만원권 뒷면에 실린 그의 풍죽도를 보면 그의 높은 예술성이 한국에 미친 영향력을 알 수 있다. 공주와 관련된 이정의 자료는 작품에 등장하는 공산, 월선정, 만매음에 주목했다. 그리고 월선정, 만매음 등이 위치를 이정의 호 탄은 과 결부하여 공주 탄천 일대로 비정했다. 이정이 구체적으로 공주로 이거하게 된 배경과 월선정 건립 이후 정착하는 과정에 대해서는 임영대군과 관련되어 공주지역에 이미 연고가 있었음을 추적해보았다. 기록을 통해 이정이 이미 호서의 고택 을 소유하고 있었음이 확인되지만, 구체적인 시기나 배경 대해서는 알려진 바가 없다. 필자는 이미 공주에 전장을 가지고 있었던 공주의 전주이씨 덕천군의 영향으로 이미 공주에 토지를 소유하고 있었을 가능성을 시사했다. 다소 추정이 가미된 논의이기는 하지만, 막대한 재산 축적 배경에 계유정난에 희생된 김종서 등의 공주인물들의 토지가 몰수 되어 공신들에게 분급하는 과정을 주목한 것이다. 이정은 정치적 사건에 연루된 바가 없고 종친화가로서 작품 이외에 주목할 만한 활동이 없다. 따라서 공주로서 이거와 정착을 검토하기 위해서는 역사적 맥락에서 이해하려는 시도가 필요하다. 이정의 교유인물들은 모두 시서화에 뛰어난 16세기 당대최고의 문인사대부들이자 관료들이었다. 문예적 재질과 정치적 성향 등도 이정과 같은 노선에 있었다. 16세기와 17세기 일련의 정치적 사건들에서 자유로울 수 없던 그들은 이정의 묵죽화를 통해 심성을 치유하였다. 공주에서 이정의 활동은 매우 일상적이면서 소탈한 모습들이었다. 그는 공주와 인근 지역 사족들과 뱃놀이에 시를 나누는 등 자연스럽게 어울리며 문학적 공감대를 나눴다. 물론 여전히 이정의 공주 활동은 밝혀져야 할 것이 많지만, 앞으로 더 많은 자료발굴과 역사인물연구가 중요한 이유는 공주가 가진 잠재력을 발굴하는 작업의 연장선상이기 때문이다.
Comprehensive analysis of contact resistivity in metal/graphene contact devices
Hyungyu Choi,Myeongjin Lee,Ngo tian dat,Won Jong Yoo 한국진공학회 2021 한국진공학회 학술발표회초록집 Vol.2021 No.2
The contact resistivity between metal and graphene were examined. The transfer length method is the most common method to extract contact resistance in metal/graphene contact device. In this study, we analyzed the transfer length method(TLM), 4-point porbe method(4PPM) and cross-bridge kelvin structure(CBK) to measure the contact resistance and sheet resistance. Reliable contact resistance and sheet resistance can be obtained by comparing various measurement methods.
유전알고리즘 이용 경제적 평가기준에 따른 태양열급탕시스템 최적화 설계에 관한 연구
최두성(Choi Doosung),고명진(Ko Myeongjin),박광태(Park Kwang-Tae) 한국태양에너지학회 2016 한국태양에너지학회 논문집 Vol.36 No.5
To assure maximum economic benefits and the energy performance of solar water heating systems, the proper sizing of components and operating conditions need to be optimized. In recent years, a number of studies to design optimally solar water heating systems have been tried. This paper presents a design method for optimizing the various capacity-related and installation-related design variables based on life cycle cost using a genetic algorithm. The design variables considered in this study included the types and numbers of solar collector and auxiliary heaters; the types of storage tanks and heat exchangers; the solar collector slope; mass flow rates of the fluid on the hot and cold sides. The suggested method was applied for optimizing a solar water heating system for an elementary school in Seoul, South Korea. In addition, the effectiveness of the proposed optimization method was assessed by analyzing the obtained optimal solutions of six case studies, each of which was simulated with different solar fractions. It is observed that a trade-off between the equipment cost and the energy cost results in an optimal design that yields the lowest life cycle cost. Therefore, it could be helpful to apply the optimal solar water heating system by comparing the various design solutions obtained by using the optimization method instead of the engineer"s experience and intuition.
Kim, Myeongjin,Choi, Jaeho,Oh, Ilgeun,Kim, Jooheon The Royal Society of Chemistry 2016 Physical chemistry chemical physics Vol.18 No.29
<P>Recently, attention has been focused on the synthesis and application of nanocomposites for supercapacitors, which can have superior electrochemical performance than single structured materials. Here, we report a carbon-coated TiO2/Co3O4 ternary hybrid nanocomposite (TiO2@C/Co) electrode for supercapacitors. A carbon layer was directly introduced onto the TiO2 surface via thermal vapor deposition. The carbon layer provides anchoring sites for the deposition of Co3O4, which was introduced onto the carbon-coated TiO2 surface by hydrazine and the thermal oxidation method. The TiO2@C/Co electrode exhibits much higher charge storage capacity relative to pristine TiO2, carbon-coated TiO2, and pristine Co3O4, showing a specific capacitance of 392.4 F g(-1) at a scan rate of 5 mV s(-1) with 76.2% rate performance from 5 to 500 mV s(-1) in 1 M KOH aqueous solution electrolyte. This outstanding electrochemical performance can be attributed to the high conductivity and high pseudo-capacitive contributions of the nanoscale particles. To evaluate the capacitive performance of a supercapacitor device employing the TiO2@C/Co electrode, we have successfully assembled TiO2@C/Co//activated carbon (AC) asymmetric supercapacitors. The optimized TiO2@C/Co//AC supercapacitor could be cycled reversibly in the voltage range from 0 to 1.5 V, and it exhibits a specific capacitance of 59.35 F g(-1) at a scan rate of 5 mV s(-1) with a specific capacitance loss of 15.4% after 5000 charge-discharge cycles. These encouraging results show great potential in terms of developing high-capacitive energy storage devices for practical applications.</P>
Hong, Myeongjin,Ryu, Leesun,Ow, Maria C.,Kim, Jinmahn,Je, A Reum,Chinta, Satya,Huh, Yang Hoon,Lee, Kea Joo,Butcher, Rebecca A.,Choi, Hongsoo,Sengupta, Piali,Hall, Sarah E.,Kim, Kyuhyung Current Biology Ltd 2017 Current Biology Vol.27 No.20
<P><B>Summary</B></P> <P>Experiences during early development can influence neuronal functions and modulate adult behaviors []. However, the molecular mechanisms underlying the long-term behavioral effects of these early experiences are not fully understood. The <I>C. elegans</I> ascr#3 (asc-ΔC9; C9) pheromone triggers avoidance behavior in adult hermaphrodites []. Here, we show that hermaphrodites that are briefly exposed to ascr#3 immediately after birth exhibit increased ascr#3-specific avoidance as adults, indicating that ascr#3-experienced animals form a long-lasting memory or imprint of this early ascr#3 exposure []. ascr#3 imprinting is mediated by increased synaptic activity between the ascr#3-sensing ADL neurons and their post-synaptic SMB motor neuron partners via increased expression of the <I>odr-2</I> glycosylated phosphatidylinositol (GPI)-linked signaling gene in the SMB neurons. Our study suggests that the memory for early ascr#3 experience is imprinted via alteration of activity of a single synaptic connection, which in turn shapes experience-dependent plasticity in adult ascr#3 responses.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Early pheromone exposure modulates behavioral responses to the pheromone as adults </LI> <LI> Pheromone experience is imprinted as increased synaptic activity </LI> <LI> The <I>odr-2</I> GPI-linked signaling protein mediates pheromone imprinting </LI> </UL> </P>