Effect of Carbon-based Nanofillers on the Toughening Behavior of Epoxy Resin

( Gi-bbeum Lee ),( Haeran Kim ),( Wonjae Shin ),( Jinseok Jeon ),( In-seok Park ),( Changwoon Nah ) 한국고무학회 2021 엘라스토머 및 콤포지트 Vol.56 No.3

Carbon-based nanofillers, including nanodiamond (ND) and carbon nanotubes (CNTs), have been employed in epoxy matrixes for improving the toughness, using the tow prepreg method, of epoxy compounds for high pressure tanks. The reinforcing performance was compared with those of commercially available toughening fillers, including carboxyl-terminated butadiene acrylonitrile (CTBN) and block copolymers, such as poly(methyl methacrylate)-b-poly(butyl acrylate)- b-poly(methyl methacrylate) (BA-b-MMA). CTNB improved the mechanical performance at a relatively high filler loading of ~5 phr. Nanosized BA-b-MMA showed improved performance at a lower filler loading of ~2 phr. However, the mechanical properties deteriorated at a higher loading of ~5 phr because of the formation of larger aggregates. ND showed no significant improvement in mechanical properties because of aggregate formation. In contrast, surface-treated ND with epoxidized hydroxyl-terminated polybutadiene considerably improved the mechanical properties, notably the impact strength, because of more uniform dispersion of particles in the epoxy matrix. CNTs noticeably improved the flexural strength and impact strength at a filler loading of 0.5 phr. However, the improvements were lost with further addition of fillers because of CNT aggregation.

24-hydroxylase (CYP24A1) in rainbow trout Oncorhynchus mykiss during salinity change

Gi bbeum Lee,Jaehyeok Yu,Woo jin Jung,Yi Kyung Kim 한국수산과학회 양식분과 2022 한국수산과학회 양식분과 학술대회 Vol.2022 No.10

Effect of Blade Materials on Wear Behaviors of Styrene-Butadiene Rubber and Butadiene Rubber

( Gi-bbeum Lee ),( Beomsu Shin ),( Eunjung Han ),( Dawon Kang ),( Dae Joon An ),( Changwoon Nah ) 한국고무학회 2021 엘라스토머 및 콤포지트 Vol.56 No.3

The wear behavior of styrene-butadiene rubber (SBR) and butadiene rubber (BR) was investigated using a bladetype abrader with a steel blade (SB), Ti-coated tungsten carbide blade (TiB), or zirconia blade (ZB). The wear rate of SBR against SB and TiB decreased with increasing number of revolutions because of the blunting of the blades during wear. However, the wear rate of SBR against ZB remained nearly constant with little blade blunting. Generally, the wear rate of BR was largely unaffected by the blade material used for abrasion. The wear rate and frictional coefficient of SBR were found to be higher than those of BR at similar levels of frictional energy input. A power-law relationship was found between the wear rate and frictional energy input during abrasion. A well-known Schallamach pattern was observed for SBR, while a much finer pattern was observed for BR. The blade material affects the wear rate of the rubbers because the macromolecular free radicals and blade tend to undergo mechano-chemical reactions. The inorganic ZB was found to be the most inert for such a mechanism.

Development and Characterization of Asymmetric Swelling-Induced Wrinkles on Natural Rubber Surface

( Gi-bbeum Lee ),( Shibulal Gopi Sathi ),( Min Jung Kim ),( Changsin Park ),( Yang Il Huh ),( Changwoon Nah ) 한국고무학회 2016 엘라스토머 및 콤포지트 Vol.51 No.4

Characteristics of the swelling-induced wrinkles on the surfaces of natural rubber (NR) film were investigated. The wrinkle structure was generated by swelling of NR film pre-stretched and firmly bonded onto an aluminum substrate in hexane. A novel experimental method was adopted to replicate the swelling-induced wrinkles on the NR film using an epoxy-hardener system. To get insight into the wrinkle parameters; the wrinkle length (L), wrinkle distance (D), wrinkle height (H) and the angle between two consecutive wrinkles (θ), the cross-sections of the replicas obtained from saturated swollen NR film were examined using an optical microscopy (OM). From the OM images, the wrinkling parameters were measured as a function of the thickness of NR film from 0.42 to 1.76 mm. Also, it was evaluated that the effects of swelling time on the wrinkling parameters. The length (L), distance (D) and height (H) of wrinkles increased as the thickness of the NR film and the swelling time increased. However, the angle between the wrinkles (θ) showed a sharp decrease up to a swelling time of 200 minutes and slightly decreased afterwards.

고성능 방사선 고분자 차단막 기술동향

이기쁨 ( Gi Bbeum Lee ),박성은 ( Sung Eun Park ),김인우 ( In Woo Kim ),정광운 ( Kwang Un Jeong ),이홍기 ( Hong Ki Lee ),나창운 ( Chang Woon Nah ) 한국고무학회 2011 엘라스토머 및 콤포지트 Vol.46 No.2

종래의 방사선 차단막은 납판이나 납 분말을 과량 배합하여 사용되고 있기 때문에 무거울 뿐만 아니라 인체중독의 위험성이 있다. 또한 작은 핀홀이 존재할 경우 방사선의 직접 투과 위험성이 있는 단점이 있다. 본 특집에서는 최근 선진국을 중심으로 연구가 활발한 다층구조의 고분자 방사선 차단막 기술에 대해 특허분석과 문헌고찰을 중심으로 소개한다. 특히 판상형 나노무기입자를 이용한 방사선 차단 및 내구성 향상에 대한 새로운 개념을 소개한다. The conventional radiation barriers may show some disadvantages such as heavy weight and possibility of poisoning human bodies because they are composed of lead plates or resin plates containing large amounts of lead powders. Another disadvantage may be direct penetration of radiation through small pin holes. In this article, technologies of multi-layered polymer barriers against radiation, which has been extensively focused recently, will be introduced. A new concept of radiation protection as well as improving endurance with employing nano-layered inorganic particles is introduced.

유연성/신축성 전극의 제조 및 특성

이기쁨 ( Gi Bbeum Lee ),나창운 ( Chang Woon Nah ) 한국고무학회 2012 엘라스토머 및 콤포지트 Vol.47 No.4

최근 주목을 받고 있는 유연성/신축성 전극소재는 유연디스플레이, 센서, 유전탄성고분자 액추에이터 및 제너레이터, 스마트 수술도구 등과 같은 다양한 분야에서 활용이 가능하다. 유연성/신축성 전극소재는 다양한 형태의 기계적인 변형을 받게 되는데 이때 기계적인 변형에 맞춰 함께 변형될 뿐만 아니라 신축되어야 한다. 따라서 기계적 변형에서도 전극으로써 기능을 유지해야 하기 때문에 대단히 어려운 연구분야라 할 수 있다. 본 총설에서는 최근까지 연구된 유연성/신축성 전극소재의 제조와 특성을 소개하고자 한다. Flexible/stretchable electronics have recently focused, since their applications extend to emerging flexible displays, sensors, dielectric elastomer actuator and generators, and smart surgical tools. Flexible/stretchable electrodes should be synchronized with employing mechanical deformations of either flexing or stretching modes. Thus, the research area is one of the tough subjects, since the electrodes should keep their basic functions of electrodes under various mode of mechanical deformations. In this review, we discuss the recent development in the preparation and properties of such flexible/ stretchable electrodes.

자율주행 자동차의 딜레마 시나리오에서 운전자 관점의 도덕 코드 : 한국인을 대상으로

이기쁨(Lee, Gi-bbeum),임지민(Rhim, Jimin),강남우(Kang, Namwoo),이지현(Lee, Ji-hyun) 한국디자인리서치학회 2020 한국디자인리서치 Vol.5 No.1

자율주행 자동차는 피할 수 없는 교통사고로 인해 인명 피해가 일어날 수 있는 상황에서 최선의 행동을 결정해야 한다. 이러한 도덕적 딜레마는 자율주행 자동차에 탑재할 도덕 시스템의 연구를 촉구한다. 도덕심리학적 관점에서 출발하여, 본 연구는 자율주행 자동차의 도덕적 딜레마 시나리오에 대한 사람의 추론을 토대로 운전자의 도덕 코드를 정립하고자 한다. 본 연구는 “언제” 운전자가 교통사고 상황에서 도덕적 딜레마에 빠질 수 있으며, 그 상황에서 “어떻게, 왜” 도덕적 의사결정을 내리는가 라는 질문을 정성적으로 탐구한다. 교통사고의 도덕적 딜레마 시나리오에 대한 사고 실험 결과, 사람의 관점에서 운전자의 도덕 코드를 구조화하였다. 평정자 간 신뢰도는 K=0.35의 일치로 측정되었다. 본 연구의 결과는 운전자가 규범, 절차, 행동적 도덕 코드에 의거하여 도덕적 의사결정을 내림을 시사한다. Autonomous vehicles must determine the best action when its unavoidable crashes cause damage to humans. This moral dilemma urges the preparation of a moral system for autonomous vehicles. Motivated by psychological human morality, this study aims to establish drivers’ moral codes learned from human reasoning in Autonomous Vehicles moral dilemma scenarios. This study answers the qualitative questions, that is “when” human drivers can get into moral dilemmas in crash situations and “how and why” they make certain moral decisions in such situations. Through the thought experiment of moral dilemma crash scenarios, we organized the moral codes from the perspective of human drivers. Inter-rater reliability of the codes was evaluated as K=0.35, which means fair agreement. The results suggest that human drivers rely on the moral codes of norms, procedures, and actions to make their moral decisions.

심리운동 집단상담 프로그램이 대인관계능력, 교사효능감에 미치는 효과 : 예비교사인 대학생을 대상으로

이기쁨(Gi-Bbeum Lee),김희수(Hee-sue Kim) 전국대학교학생생활상담센터협의회 2017 대학생활연구 Vol.23 No.1

본 연구의 목적은 교직이수과목을 수강중인 학생 즉, 예비교사들이 심리운동 집단상담프로그램을 통해서 대인관계능력과 교사효능감에 미치는 효과를 검증하는 데 있다. 심리운동 집단상담 참여 프로그램은 2015년 5월 11일∼ 6월 15일 중 매주1회 2시간씩 총 5회기를 실시하였다. 본 연구 대상은 수도권 소재 4년제 대학교 재학생 중 교직 이수과목을 수강하는 학생 10명 중 실험집단 5명과 통제집단 5명으로 구성하였다. 대상자들에게 대인관계능력과 교사효능감 측정도구를 사전-사후 2차례에 걸쳐 실시한 후, 기술통계, 비모수검증을 사용하여 연구 자료를 분석하였다. 연구결과 실험집단의 사후 대인관계능력과 교사효능감이 통계적으로 유의미하게 향상되었다. 반면에 통제집단의 사후대인관계능력과 교사효능감의 수준은 통계적으로 유의미한 차이를 보이지 않았다. 이 연구는 심리운동 집단상담 프로그램이 예비교사들의 대인관계능력과 교사효능감 향상에 도움을 주는 것을 검증했다는 의의가 있다. 끝으로 본 연구의 시사점 및 후속 연구를 위한 제안점을 제시하였다. The purpose of this study is to verify the effects of pre - service teachers on interpersonal skills and teacher efficacy through psychomotorik group counseling program. psychomotorik group counseling participation program performed 5 sessions for 2 hours every week from May 11 to June 15, 2015. The subjects of this study consisted of 5 experimental group and 5 control group among 10 students attending 4 year college in metropolitan area. The data were analyzed using descriptive statistics and nonparametric tests after two pre - and post - test measures of interpersonal abilities and teacher efficacy were administered to the subjects. As a result, post - interpersonal relationship ability and teacher efficacy of experiment group were statistically significantly improved. On the other hand, there was no statistically significant difference between the control group s post-interpersonal abilities and the level of teacher efficacy. This study implies that the psychomotorik group counseling program has proved that the pre - service teachers interpersonal skills and teacher efficacy are improved. Finally, the implications of this study and suggestions for follow - up research.

청소년의 정서지능과 대인 간 스트레스 대처행동이 외로움에 미치는 영향

이기쁨(Gi-Bbeum Lee),민하영(Ha-Young Min) 가정과삶의질학회 2020 가정과삶의질연구 Vol.38 No.1

자율주행 택시 승객 경험의 분위기

이기쁨(Gi-bbeum Lee),최명애(Myung Ae Choi),강남우(Namwoo Kang) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.12