SA 508 강 용접 열영향부의 미세조직과 충격인성의 상관관계

김상호,홍준화,김주학,권순주,이성학,강석영,오세진 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.4

In this study, microstructures of the heat affected zone (HAZ) of SA 508 steel were identified by Mo¨ssbauer spectroscopy in conjunction with microscopic observations, and were correlated with impact toughness. Specimens with the peak temperature risen up to 1350℃ showed mostly martensite, but the microstructures were not changed, much from the base metal because of the minor tempering effect when it was risen to 650℃ or 700℃. With the peak temperature risen to 900℃ over the A₃ temperature, the martensite fraction was reduced, while bainite or martensite island were formed because of the slow cooling from the lower austenite region. As the martensite fraction present inside the HAZ increased, hardness and strengths tended to increase, whereas impact toughness decreased. However, impact toughness of the subcritical HAZ with the peak temperature risen to 650℃-700℃ was seriously reduced after post-weld heat-treatment (PWHT) since carbide particles were of primary importance in initiating voids. Thus, the most important microstructural factors affecting impact toughness were the martensite fraction before PWHT and the carbide fraction after PWHT.

Effects of Biologically Active Substances in Natural Products on the Hepatic Detoxication Mechanism : In Vivo Production and Enzyme-Inducing activity of Indolo[3,2-b]carbazole

Kwon,Chong-Suk(권정숙),Grose,Karl R,Riby,Jacques,Chen,Yue-Hwa,Bjeldanes,Leonard F. 韓國營養學會 1994 Journal of Nutrition and Health Vol.27 No.4

Development of Environmental Stress-Tolerant Plants by Gene Manipulation of Antioxidant Enzymes

Kwon, Suk-Yoon,Lee, Haeng-Soon,Kwak, Sang-Soo The Korean Society of Plant Pathology 2001 Plant Pathology Journal Vol.17 No.2

Oxidative stress is one of the major limiting factor in plant productivity. Reactive oxygens species (ROS) generated during metabolic processes damage cellular functions and consequently lead to disease, senescence and cell death. Plants have evolved an efficient defense system by which the ROS is scavenged by antioxidant enzymes such as superoxide dismutase (SOD) and ascorbate peroxidase (APX). Attempts to reduce oxidative damages under the stress conditions have included the manipulation of 갠 scavenging enzymes by gene transfer technology. Increased SOD activities of transgenic plants lead to increased resistance against oxidative stresses derived from methyl viologen (MV), and from photooxidative damage caused by high light and low temperature. Transgenic tobacco plants overexpressing APX showed reduced damage following either MV treatment of photooxidative treatment. Overexpression of glutathion reductase (GR) leads to increase in pool of ascorbate and GSH, known as small antioxidant molecules. These results indicate through overexpression of enzymes involved in ROS-scavenging could maintain or improve the plant productivities under environment stress condition. In this study, the rational approaches to develop stress-tolerant plants by gene manipulation of antioxidant enzymes will be introduced to provide solutions for the global food and environmental problems in the $21^\textrm{st}$ century.

Studying Crack Generation Mechanism in Single-Crystal Sapphire During Ultra-precision Machining by MD Simulation-Based Slip/Fracture Activation Model

Suk Bum Kwon,Aditya Nagaraj,Dalei Xi,Yiyang Du,Dae Nyoung Kim,Woo Kyun Kim,Sangkee Min 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.5

Single-crystal sapphire is used in various fields of industry due to its superior mechanical, optical, and chemical properties, but fabricating sapphire is challenging because of its high hardness and brittleness. Ultra-precision machining (UPM) has been studied as one of the solutions to overcome these issues as it facilitates cutting of brittle ceramics in a ductile manner. However, the material removal mechanisms during UPM of single-crystal sapphire is not yet fully understood. This paper studied the crack initiation mechanism in single-crystal sapphire during UPM with relation to the crystallographic properties of sapphire depending on the cutting direction. By projecting a given stress distribution from molecular dynamics simulation on to different slip and fracture planes, the likelihood of plastic deformation and cleavage fracture was calculated, and respective crack initiation mechanisms were identified. The proposed MD simulation model and analysis were verified through ultra-precision orthogonal plunge cut experiments along the same crystallographic directions as the simulations.

Effects of Gait Training Using Functional Electrical Stimulation on Stroke Patients' Balance and Gait Velocity

Kwon Young Kang,Wan Suk Choi,Ho Jung An,Ja Pung Koo,Joon Hee Lee,Young Dae Yun,Jung Sook Lee,Joung Youl Ju,Sang Bin Lee 국제물리치료학회 2011 Journal of International Academy of Physical Ther Vol.2 No.2

The purpose of this study is to examine the effects of gait training using functional electrical stimulation on the improvement of hemiplegic patients' functions for balance and gait velocity. The subjects of the experiment were determined to be 10 each hemiplegic patients who had been diagnosed with stroke or brain damage six months or longer earlier assigned to an experimental group and a control group respectively. The subjects were evaluated before the experiment using Tetrax and 10M gait tests, received gait training five times a week for four weeks using functional electrical stimulation and were evaluated after the experiment in the same method as used in the evaluation before the experiment. In order to examine differences between the experimental group that received gait training using functional electrical stimulation and the control group that was treated by functional electrical stimulation and received gait training thereafter, differences between before and after the experiment were analyzed using paired sample t-tests and differences in changes after the experiment between the experimental group and the control group were analyzed using independent sample t-tests in order to compare the two groups with each other. Experimental results showed significant differences in weight bearing, balance and gait velocity between before and after the experiment in the experimental group(p<.05). In the control group, whereas weight bearing and gait velocity did not show any significant difference between before and after the experiment(p>.05), balance showed significant differences(p<.05). Weight bearing, balance and gait velocity change rates showed significant differences between the experimental group and the control group(p<.05). In conclusion, it was indicated that gait training using functional electrical stimulation is effective for enhancing stroke patients' weight bearing rates, balance abilities and gait velocity.

A Study on Reasons of SCHOOL MALADJUSTMENT of Multicultural Background Learners and Responding Measures

Kwon Hwa suk J-INSTITUTE 2017 Regulations Vol.2 No.2

The ultimate purpose of this study was to seek ways that multicultural background learners could adapt school life well and have sense of belonging to school as well as self-identity. For this, it classified types of school mal-adjustment of multicultual background learners based on the status of them and looked at responding measures in the educational and sociocultural aspects to solve these problems. Since the number of members who have a variety of langue and cultural backgrounds due to the expansion of exchanges between countries and cultures recently is increased, the Korean society changes to a multicultural society rapidly and the number of multicultural families is increasing. As the Korean society enters into the mul-ticultural society, the number of multicultural background learners with various language and cultural back-grounds is swiftly increasing at school, a problem of Korean education for them is raised as a current issue and the phenomenon of not adjusting school life because of failure of communication, low school performance, iden-tity crisis, and school violence problems, is increasing as well. Most multicultural background learners should experience lots of difficulties in adjusting to school life as they are not familiar with Korean language and culture most of all. The lack of Korean ability can be connected to low school performance and to school maladjustment. Thus, it is urgent for them to have a certain level of Korean most of all to grow as members of Korean society overcoming these difficulties. The difficulty in using Korean that they feel could be connected to low school performance, emotional anxiety, complaints against the society, and isolation. School maladjustment of multicultural background learners analyzed as difficulty of communication due to the lack of Korean and because of it, the difficulty in study performance due to the lack of basic learning, school violence due to the cultural, social, and physical differences and prejudice which came from the difference in the dual culture of their parents, and economic difficulty. As responding measures to solve these problems, it suggested the necessity of effective Korean education and the activation of systemic device in the educational level to improve multicultural background learners’ commu-nication ability in Korean and study ability, in the sociocultural level, it suggested the improvement in ways of police response and activation of their activities as well as a variety of sociocultural programs, and it also sug-gested the preparation of scholarship system and effective operation for the responding measures in solving economic difficulties. This study will contribute that multicultural background learners could adjust school life well while establish-ing the sense of belonging and self-identity as members of school and Korean society.

Die romantische Romantheorie Friedrich Schlegels

KWON, Tschin-Suk 대구효성가톨릭대학교 1981 연구논문집 Vol.23 No.2

F.Schlegel이 그의 형에게 보내는 편지에서 "난 이 편지에서 지금 낭만주의란 말을 설명할 수 없다. 그것을 쓸려면 편지지가 아마도 125장이나 필요할 것 같다." 라고 했듯이 낭만주의 시학은 그 개념만큼이나 많은 여러 가지 성향(Intensionen)을 갖고 있다. 사실 독일 낭만주의는 그 다양성과 모순적 대립성을 정리하고 통합하여 파악하는 것 그 자체를 비웃고 있는지도 모른다. 마치 어둠속에 자리하고 있는 거대한 예술품을 부분적으로 조명하듯이, F. Schlel은 예술적, 철학적, 문학적 총체 독일 낭만주의를 다음과 같은 단어로 단편적으로, 설명하고 있다. 낭만적 반어(romantische Ironie), 초월적 시학(Transzendentalpoesie), 종합철학(Symphilosophie), Arabeske, 미완성(Fragment), 진보적, 포괄적 시학론(Progressive Universalpoesie), 완전한 자유(totale Freiheit), 절대적 시학(absoluter Roman), 초월적 익살(transzendendentale Buffonerie)등이다. 위 개념들의 이질적 본성 내지 문학적 암호(Chiffre)는 허상을 갖어오는 위험을 일으켰으며, 독일 낭만주의의 주관적 독단성, 불투명성에 대한 비판을 불러일으켰었다. 그러나 10여년 이래로 Schlegel의 낭만주의 이념은 새로운 예술개념으로 부각되고 있다. 그것은 과거중에서 싹터오는 현대(Modern)의 징표를 찾는 해설 때문인데, - 이 말은 아이러니칼하게도 Schlegel의 낭만적 반어 "역사가는 과거로 돌아가는 예언자다.(Historiker seiein ru¨ckwa¨rts gekehrter Prophet)" 라는 말을 연상시킨다-. 이 문제는 위상 기하학(Topologic) 적으로 번져 "낭만주의와 현대" 라는 문제를 낳고 있다. 다시 말해 전기 낭만주의의 시학개념 중 "Stil의 죽음", 완전한 자유, 초월적 시학 등은 예술이 용해되는 유미주의를 성립케 했다. 왜냐하면 낭만주의는 예술(Kunst) 이외에는 다른것이 되고싶지 않기 때문이다. 이 유미주의는 현대에 와서 "미학적인 無(a¨sthetische Nichts)"와 "절대예술의 무효(Vergeblichkeit der absoluten Kunst)"를 갖어왔다. 추상미술은 과거 낭만주의자들이 공표만했던 Arabeske, 신비성, 기괴성을 "현대미술가들이 의식적으로 실용화" 한 것이며, 초현실주의자들의 검은 유머도 그 뿌리를 낭만주의적 반어에서 찾을 수 있다. H.Friedrich는 낭만주의와 현대의 차이점을 다음과 같이 말한다. "현대시란 탈 낭만주의화된 낭만주의다. (Modernes Dichten ist entromantisierte Romantik)" Schlegel의 낭만주의 시학론을 다시 논하는 것은 이런 점에 의의가 있겠다. Schlegel은 Althena¨ums Fragment나 Lyceums Fragment 속에서 주로 그의 낭만주의 시학론을 폈는데, 그 대표적인것이 116번 Fragment다. 그가 언급하는 "초월적" 이라던지, "우의(Allegorie)", "진보적", "되어감(Werden)"등은 목적지에 도달하고 싶지 않은 운동이 아니라, 유한과 무한사이의 긴장, 모순, 한계점을 능동적으로 명확하게 하려는 것이었다. 바로 이 방법에 대한 문제를 그는 초월적 시학에서 설명한다. "내면적으로는 모든 제약을 끊임없이 헤쳐나올것, 자기 자신의 예술로부터, 덕과 천재성, 이 모든 것으로부터 초월할 것, 외면으로는 이태리의 흉내내기 익살법(mimische Manier, Buffonerie)으로 이것을 실행한다. 그의 낭만적 반어는 여기에 기초한다. 또한 낭만주의 시학과 작가들의 태도에 대해 가장 단적으로 표현한 말은; "낭만주의 반어란 영원한 정신의 활동과 끝없이 충만한 무질서를 명확하게 인식하는 것이다. (Ironie ist klares Bewuβtsein der ewigen Agilita¨t, des unendlich-Vollen Chaos)", 이것은 즉 위대한 정신적 활동과 근원적인 자연의 감성 내지 열광을 둘 다 냉철히 인식한다는 것이다. Schlegel의 이같은 이념은 Fichte의 철학과 중세의 사상에 영향을 입었으며, 역사가인 Schlegel의 궁극적 문학관은 중세의 문학으로 승화하려는 복고적 경향을 띄었다. 본 논문은 Schlegel의 정신적 발달과정(특히 그의 고대학문과 신화학이 미친 영향에 관한)을 연구한 Ernst Behler의 저서와, 이와 대조적으로 Schlegel의 철학적 중심 사상 및 그의 Ironie에 대하여 집중적으로 새로운 관점을 펴낸 Ingrid Strohschneider Kohrs의 저서를 종합하여 낭만주의 이론가인 F. Schlegel의 문학이념 중 중요한 것을 여기 전체적으로 소개하였다.

Heteroepitaxially Grown Zeolitic Imidazolate Framework Membranes with Unprecedented Propylene/Propane Separation Performances

Kwon, Hyuk Taek,Jeong, Hae-Kwon,Lee, Albert S.,An, He Seong,Lee, Jong Suk American Chemical Society 2015 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.137 No.38

<P>Propylene/propane separation is one of the most challenging separations, currently achieved by energy-intensive cryogenic distillation. Despite the great potential for energy-efficient membrane-based separations, no commercial membranes are currently available due to the limitations of current polymeric materials. Zeolitic imidazolate framework, ZIF-8, with the effective aperture size of ∼4.0 Å, has been shown to be very promising for propylene/propane separation. Despite the extensive research on ZIF-8 membranes, only a few reported ZIF-8 membranes have displayed good propylene/propane separation performances presumably due to the challenges of controlling the microstructures of polycrystalline membranes. Here we report the first well-intergrown membranes of ZIF-67 (Co-substituted ZIF-8) by heteroepitaxially growing ZIF-67 on ZIF-8 seed layers. The ZIF-67 membranes exhibited impressively high propylene/propane separation capabilities. Furthermore, when a tertiary growth of ZIF-8 layers was applied to heteroepitaxially grown ZIF-67 membranes, the membranes exhibited unprecedentedly high propylene/propane separation factors of ∼200 possibly due to enhanced grain boundary structure.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2015/jacsat.2015.137.issue-38/jacs.5b06730/production/images/medium/ja-2015-067303_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja5b06730'>ACS Electronic Supporting Info</A></P>

Multifunctional Epoxy-Based Solid Polymer Electrolytes for Solid-State Supercapacitors

Kwon, Suk Jin,Kim, Taehoon,Jung, Byung Mun,Lee, Sang Bok,Choi, U Hyeok American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.41

<P>Solid polymer electrolytes (SPEs) have drawn attention for promising multifunctional electrolytes requiring very good mechanical properties and ionic conductivity. To develop a safe SPE for energy storage applications, mechanically robust cross-linked epoxy matrix is combined with fast ion-diffusing ionic liquid/lithium salt electrolyte (ILE) via a simple one-pot curing process. The epoxy-rich SPEs show higher Young’s modulus (<I>E</I>), with higher glass transition temperature (<I>T</I><SUB>g</SUB>) but lower ionic conductivity (σ<SUB>dc</SUB>) with a higher activation energy, compared to the ILE-rich SPEs. The incorporation of inorganic robust Al<SUB>2</SUB>O<SUB>3</SUB> nanowire simultaneously provides excellent mechanical robustness (<I>E</I> ≈ 1 GPa at 25 °C) and good conductivity (σ<SUB>dc</SUB> ≈ 2.9 × 10<SUP>-4</SUP> S/cm at 25 °C) to the SPE. This suggests that the SPE has a bicontinuous microphase separation into ILE-rich and epoxy-rich microdomain, where ILE continuous conducting phases are intertwined with a sturdy cross-linked amorphous epoxy framework, supported by the observation of the two <I>T</I><SUB>g</SUB>s and low tortuosity as well as the microstructural investigation. After assembling the SPE with activated carbon electrodes, we successfully demonstrate the supercapacitor performance, exhibiting high energy and power density (75 W h/kg at 382 W/kg and 9.3 kW/kg at 44 W h/kg). This facile strategy holds tremendous potential to advance multifunctional energy storage technology for next-generation electric vehicles.</P> [FIG OMISSION]</BR>

Molecules of the Tumor Necrosis Factor(TNA) Receptor and Ligand Superfamilies : Endless Stories

Kwon, Byoung Se,Kwon, Byung Suk 생화학분자생물학회 2000 BMB Reports Vol.32 No.5

Tumor necrosis factor (TNF) receptor members have unique structures composed of 2-4 cysteine - rich pseudorepeats in the extracellular domain. On ligation by trimeric ligand molecules, oligomerization of three receptor molecules occurs, which in turn activates the receptor and recruits intracellular signaling molecules to the cytoplasmic tail to initiate biological events. Recently, the numbers of tumor necrosis factor receptor and ligand family members have been rapidly expanding. Functional characterization of the new members has indicated redundant roles with other known members as well as provided insights into novel functions. In particular, identification of soluble decoy receptors which have the ability to bind multiple ligands highlights a complex control mechanism of immune responses by these molecules. Studies of the new members have also revealed that the TNF receptor and ligand family members play an important role in other than the immune system.