A study of correlation between intergranular fracture and plastic deformation in tungsten using nanoindentation

Yeonju Oh,Keunho Lee,Hyun-Min Sung,Nojun Kwak,Won-seok Ko,Heung Nam Han 한국소성가공학회 2017 한국소성가공학회 학술대회 논문집 Vol.2017 No.10

Ductility enhancement of tungsten after plastic deformation

Oh, Yeonju,Kwak, Nojun,Lee, Keunho,Ko, Won-Seok,Han, Heung Nam ELSEVIER SCIENCE 2019 Journal of Alloys and Compounds Vol.787 No.-

<P><B>Abstract</B></P> <P>An unusual room temperature mechanical behavior of pure tungsten is investigated by focusing on three specimens prepared with different microstructures: as-received (hot-rolled), recrystallized, and cold-rolled specimens. Contrary to ordinary expectations in metallic materials, only the cold-rolled specimen exhibits significant plastic deformation during tensile testing, with improved strength and ductility, while the recrystallized and the as-received specimens fail in the elastic region. We further provide an explanation of such characteristics by systematically utilizing experimental and theoretical analysis at a small scale: nano-indentation tests clarify the inherent mechanical response inside grains and provide a statistical distribution of the maximum shear stress during pop-in events, corresponding to onset of plastic yielding; atomistic simulations provide information on the overall fracture strength of various grain boundaries. By comparing the maximum shear stress and the grain boundary fracture stress, we could explain that the distinctive plasticity in the cold-rolled specimen is caused by the movement of pre-existing dislocations before grain boundary fracture. This contrasts the recrystallized and as-received specimens, where grain boundary fracture occurs prior to the nucleation of dislocations or activation of dislocation sources.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Distinctive plasticity of cold rolled tungsten was investigated at room temperature. </LI> <LI> The more pre-existing dislocations, the lower shear stress for plastic yielding. </LI> <LI> Molecular dynamic simulations provide the fracture stress of grain boundaries, ∼16 GPa. </LI> <LI> Cold rolled tungsten has lower stress for plastic yielding than the fracture stress. </LI> <LI> Ductility was enhanced by the dislocation activation prior to intergranular fracture. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

일탈의 이미지 표현에 관한 연구

오연주(Oh Yeonju),서인숙(seo Ihnsook) 한국디지털디자인학회 2008 디지털디자인학연구 Vol.8 No.1

오늘날 고도로 발달된 산업사회와 과학기술은 삶의 물질적 풍요로움을 영위할 수 있도록 해주었으나 우리가 살아가고 있는 일상적 삶의 공간은 반복적이며 평온하기 때문에 현실은 친숙한 만큼 권태롭기도 하다. 이와 같은 상황 속에서 자아의 존재의식에 대한 중요성이 자연스럽게 대두되고 이러한 의식의 발전은 현대인의 일상적인 삶에서의 일탈을 꾀하게 되었다. 현대인에게 일탈은 특수한 상황에 놓인 사람들에게만 존재 하는 것이 아니라 일상을 살아가고 있는 현대인들 모두가 가지고 있는 것이므로 일상적인 삶에서 일탈의 중요성이 날로 더해가고 있다. 본 연구에서는 일탈개념 및 일탈행위에 관하여 정립한 후 시각화를 위한 사회학적관점에서의 일탈이론과 예술학적 관점에서의 일탈이론에 대하여 고찰하고자 한다. 이러한 이론을 바탕으로 연구자는 인간의 사회적 상황 외에도 이상적인 환경을 포함한 외적인 상황과 인간 내부의 심리적인 충돌 문제 등을 제시한다. 또한 인간의 내면과 생활의 본질을 예술적인 형상성으로 나타내어 단순한 이미지 표현만이 아닌 이미지 커뮤니케이션의 매체로써 사용되도록 시도하였다. 확장된 시각언어의 소통을 위하여 현실세계의 상황을 이상적인 공간으로 설정하여 이미지의 병치와 반복을 사용함으로써 디지털미디어를 통하여 시각적으로 표현하였다. 일탈에 대한 이미지 표현은 일탈을 추구하는 현대인들의 공감대를 형성하는데 도움을 줄 것이며 사람들을 일상의 세계에서 잠시 일탈시킴으로써 일상의 삶을 관조할 수 있는 유기적 상상력의 매개체적인 커뮤니케이션 작품으로 발전할 수 있는 계기가 될 것이다. In today's world highly sophisticated industrial society and scientific technologies have enabled us to carry on life enjoying materialistic abundance however it is true that our reality may be boresome as much as we have been familiar to it for our space for everyday life is repetitious and peaceful. Under the circumstance the importance of consciousness of self-existence has been emerged naturally and such a development of perceptions provokes people living in this modern world to try to deviate from their ordinary life. For people in modern world deviation from their usual surroundings does not exist only in the persons who are put in a particular situation but this is an attribute which has been held by all modern people so then the importance of deviation from their ordinary life has been increasing even more day by day. In this paper researcher aims to investigate deviance theory from the perspective of sociology in order for visualization and also of science of art after having established the concept of deviance and deviant behaviors. On the basis of such theory researcher proposes issues of psychological collision etc. inside a human as well as external situation including ideal environments other than human's social situation. In addition having expressed human's inner world and the essential nature of living in terms of artistic formation researcher tried to have it use as a medium of image communication not as for a simple image expression only. To communicate extended visual language researcher expressed the subject through digital media by means of repetitious use and juxtaposition of images having established the situation of real world as an ideal space. Expression of images concerned with deviance shall be of help for people who are living in this modern world and pursuing deviation from reality in forming their common-sense world and by helping people deviate from their real world for a while this will be an occasion to be developed as a communication work that intermediates organic imagination which will make people contemplate on their everyday life.

간호직종의 바로(BARAW) 전산화 프로그램 개발

오연주(Yeonju Oh),이경선(Kyung-Sun Lee),박희석(Hee-Sok Park),백은미(Eunmi Baek),임성균(Sung kyun Im) 대한인간공학회 2018 대한인간공학회 학술대회논문집 Vol.2018 No.11

목도나루학교 전환기교육 학습자의 자아 성장 사례연구

오연주(Yeonju Oh),박경수(Kyungsu Park),김영인(Youngin Kim) 학습자중심교과교육학회 2024 학습자중심교과교육연구 Vol.24 No.7

목적 본 연구는 학교 교육 환경에서 학생의 자아 성장 과정을 심층적으로 이해하기 위하여 전환기교육 기관인 ‘목도나루학교(충북소재)’에 재학하고 있는 연구참여자 4명의 자아 성장 과정을 탐구하고자 하였다. 방법 재학생 전체를 대상으로 예비조사, 전체 교사를 대상으로 기초조사를 실시하여 4명의 연구참여자를 선정하였다. 연구참여자에게 반구조화된 심층면접을 실시하고 전사하여 자료를 수집하였다. 수집된 자료는 Nvivo(ver. 14)를 활용하여 개방코딩, 축코딩, 선택코딩의 과정을 순환적으로 거쳐 분석하였다. 결과 목도나루학교의 전환기교육에 참여한 연구참여자들은 개인차가 있는 성장 과정을 드러냈다. 이들은 다양한 계기와 요소를 자신의 자아 성장의 배경으로 인식하고 있으며, 개별 성장은 독립적이라기보다는 자아정체성⋅사회적 정체성⋅진로정체성의 영역에서 상호 영향을 주고받거나 전환되는 총체적인 특성을 나타낸다. 결론 이러한 결과는 중등교육에서 개별 학습자의 자아 성장 과정에 대한 개인차를 더욱 심층적으로 이해하고, 교수활동 중심의 협소한 접근을 넘어 학교를 둘러싼 다양한 생활공간과 관계적 측면을 포함하는 총체적 접근의 필요성을 제안한다. Objectives This study aims to deeply understand the process of self-growth in students within the school educational environment. It explores the self-growth process of four participants who are enrolled in a transitional educational institution, ‘Mokdonaru School’ located in Chungcheongbuk-do. Methods Preliminary surveys were conducted among all enrolled students, and foundational surveys were carried out with all teachers to select four research participants. Semi-structured, in-depth interviews were conducted with these participants, and the data was collected through transcription. The gathered data was analyzed using Nvivo (version 14), processing a cyclical process of open coding, axial coding, and selective coding. Results The participants in this study revealed a growth process characterized by individual differences. They recognize various triggers and elements as the background of their self-growth, and their individual growth is not so much independent as it is holistic, affecting and transforming across the areas of self-identity, social identity, and career identity. Conclusions These findings suggest the need for a deeper understanding of individual differences in students' self-growth processes in secondary education, and for a holistic approach that goes beyond a narrow focus on teaching activities to include the diverse living spaces and relational aspects surrounding the school.

뉴스 카테고리에 따른 온라인 커뮤니티 그룹의 사용자 취향 분석

오연주(Oh Yeonju),김동현(Kim Donghyun),박소연(Park Soyeon),박석(Park Seog) 한국정보과학회 2014 한국정보과학회 학술발표논문집 Vol.2014 No.12

비정형작업(간호직종) 근골격계질환 평가 방법론 개발 연구

오연주(Yeonju Oh),이경선(Kyung-Sun Lee),박희석(Hee-Sok Park),백은미(Eunmi Baek),임성균(Sung kyun Im) 대한인간공학회 2018 대한인간공학회 학술대회논문집 Vol.2018 No.11

Efficacy of Acupuncture for Parkinson's Disease over the Last Decade: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Yeonju Kim,Yigun Lim,Subin Ahn,Junyeop Oh,Yoonbyeong Chae,Yoomin Choi,Jong Uk Kim Korean AcupunctureMoxibustion Medicine Society 2024 대한침구의학회지 Vol.41 No.1

The aim of this review is to consolidate findings from clinical investigations spanning the past decade regarding the impact of acupuncture on Parkinson's disease (PD). The objective is to assess the efficacy of acupuncture as a therapeutic approach to PD, with the intention of informing future clinical practices and advancing the foundation for subsequent research endeavors in this area. A comprehensive literature search was conducted to identify clinical trials exploring the effects of acupuncture on PD between January 2014 and August 2023. Databases search included PubMed, EMBASE, CNKI, OASIS, KISS, KMBASE, RISS, and ScienceON. Quantitative evidence from randomized controlled trials (RCTs) was systematically reviewed, and the methodological quality of the included studies was assessed using Cochrane's risk of bias tool. Meta-analysis was performed using Review Manager (RevMan) 5.4.1 software. The systematic review encompassed a total of 38 RCTs involving 2,786 participants. Meta-analysis of 12 studies revealed that individuals treated with a combination of acupuncture and Western medicine exhibited notable improvements compared to those receiving Western medicine alone or sham acupuncture alongside Western medicine. However, the overall quality of the RCTs was deemed low, and no serious adverse events were reported. Across clinical investigations conducted in the past decade, acupuncture appears to hold promise as a complementary treatment for PD patients when administered alongside Western medicine. Nevertheless, this study identifies certain limitations that warrant consideration in future research endeavors. Enhanced emphasis on conducting high-quality RCTs is imperative to comprehensively evaluate the efficacy of acupuncture in managing PD.

Anti-Inflammatory and Neuroprotective Effects of Constituents Isolated from <i>Rhodiola rosea</i>

Lee, Yeonju,Jung, Jae-Chul,Jang, Soyong,Kim, Jieun,Ali, Zulfiqar,Khan, Ikhlas A.,Oh, Seikwan Hindawi Publishing Corporation 2013 Evidence-based Complementary and Alternative Medic Vol.2013 No.-

<P>To determine the biological activity of <I>Rhodiola rosea</I>, the protein expression of iNOS and proinflammatory cytokines was measured after the activation of murine microglial BV2 cells by LPS under the exposure of constituents of <I>Rhodiola rosea</I>: crude extract, rosin, rosarin, and salidroside (each 1–50 <I><I>μ</I></I>g/mL). The LPS-induced expression of iNOS and cytokines in BV2 cells was suppressed by the constituents of <I>Rhodiola rosea</I> in a concentration-dependent manner. Also the expression of the proinflammatory factors iNOS, IL-1<I><I>β</I></I>, and TNF-<I><I>α</I></I> in the kidney and prefrontal cortex of brain in mice was suppressed by the oral administration of <I>Rhodiola rosea</I> crude extract (500 mg/kg). To determine the neuroprotective effect of constituents of <I>Rhodiola rosea</I>, neuronal cells were activated by L-glutamate, and neurotoxicity was analyzed. The L-glutamate-induced neurotoxicity was suppressed by the treatment with rosin but not by rosarin. The level of phosphorylated MAPK, pJNK, and pp38 was increased by L-glutamate treatment but decreased by the treatment with rosin and salidroside. These results indicate that <I>Rhodiola rosea</I> may have therapeutic potential for the treatment of inflammation and neurodegenerative disease.</P>

Anti-Inflammatory Effect of Triterpene Saponins Isolated from Blue Cohosh ( <i>Caulophyllum thalictroides</i> )

Lee, Yeonju,Jung, Jae-Chul,Ali, Zulfiqar,Khan, Ikhlas A.,Oh, Seikwan Hindawi Publishing Corporation 2012 Evidence-based Complementary and Alternative Medic Vol.2012 No.-

<P>Blue cohosh has been used as a medicinal herb in eastern North America. It was commonly used as traditional medicines for the treatment of menopausal symptoms, rheumatic pain, and as anti-inflammatory remedy. Particularly, extract of blue cohosh roots has been used as anti-inflammatory antipyretic in traditional medicines. In the present study, we investigated the effects of blue cohosh components on the suppressive expression of iNOS or proinflammatory cytokines after the activation of microglia with lipopolysaccharide (LPS). The expression of iNOS, TNF-<I><I>α</I></I>, IL-1<I><I>β</I></I>, and IL-6 was determined by western blotting or gene expression. Blue cohosh treatment suppressed the elevation of LPS-induced iNOS expression in a concentration-dependent manner in microglia cells. Blue cohosh constituents also suppressed the expression of TNF-<I><I>α</I></I>, IL-1<I><I>β</I></I>, and IL-6. In addition, blue cohosh extract suppressed the expression of COX-2, iNOS, and proinflammatory cytokines in adrenal glands of mice. These results demonstrate that constituents of blue cohosh exert anti-inflammatory effects through the inhibition of expression of iNOS and proinflammatory cytokines. Therefore, blue cohosh may have therapeutic potential for the treatment of inflammation-related diseases.</P>