STS316L 용접부의 피로거동 및 초음파시럼에 의한 열화특성 평가

남기우,박소순,안석환,도재윤,박인덕 한국비파괴검사학회 2003 한국비파괴검사학회지 Vol.23 No.2

STS316L은 인성, 연성, 부식저항성 등 우수한 기계적 성질 때문에 에너지환경설비 등 구조물에 널리 이용되고 있다. 그러나, 용접구조물은 가혹한 환경하에서 경년열화가 심각하다. 지금까지의 연구들은 주로 용접부의 피로균열진전거동에 관하여 수행되었고, 피로균열진전속도식의 재료상수와 비파괴적 평가의 상관성에 관한 연구는 거의 없었다. 본 연구는 STS316L 용접부의 피로균열진전 거동을 조사하고, 초음파 파라미터로 열화특성을 평가하고 시간-주파수 분석으로 해석을 하였다. 본 연구 결과는 용접구조물의 사용기간 중 피로수명 등을 예측하기 위한 기초 데이터로서 사용될 수 있다. STS316L had been used as the structural material for energy environmental facilities, because austenite stainless steels like 316L have superior mechanical properties of which toughness, ductility, corrosion resistant and etc. However, those welded structures are receiving severe damage due to increasing of the aged degradation. Most studies until now have been carried out against fatigue bahaviors of weldments, and were not well studied on nondestructive evaluation methods. In this study, the fatigue crack propagation behavior of STS316L weldment usually used for vessels of the nuclear power plant was investigated. Also, the degradation characterstics of 316L stainless steel weldments were evaluated by the ultrasonic parameter such as ultrasonic velocity, attenuation factor and time-frequency analysis. The results of this study can be used as a basic data for the prediction of the fatigue crack life of weldments structures without disjointing or stopping service of structures in service.

시간-주파수 해석법에 의한 CFRP의 파괴 거동

남기우,안석환,이상기,김현수,문창권 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.1

신호처리법으로 현재 많이 사용되고 있는 푸리에 변환은 신호의 주파수 성분이 사간에 따라 어떻게 변화하는지를 표현하지 못한다. 따라서 최근 이와 같은 푸리에 변환의 단점을 보완하여, 신호의 시간과 주파수에 대한 정보를 동시에 표현할 수 있는 시간-주파수 해석법들이 개발되었다. 본 연구에서는 음향방출을 이용하여 복합재료의 주요 발생원으로 알려져 있는 기지균열, 섬유분리, 섬유파괴 및 층간분리 등과 같은 파괴기구를 해석하였다. 각각의 파괴특성이 나타나도록 시험편을 제작하여 인장시험 시 검출된 음향방출신호의 시간-주파수 해석을 통해 전체 파괴기구의 특징을 분석하였다. Fourier transform has been one of the most common tools to study the frequency characteristics of signals. With the Fourier transform alone, however, it is difficult to tell whether signal's frequency contents evolve in time or not. Except for a few special cases, the frequency contents of most signals encountered in the real world change with time. Time-frequency analysis methods are developed recently to overcome the drawbacks of Fourier transform, which can represent the information of signals in time and frequency at the same time. In this study, damage process of cross-ply carbon fiber reinforced plastic (CFRP) under monotonic tensile loading was characterized by acoustic emission. Different kinds of CFRP specimens were used to determine the characteristics of AE signals. Time-frequency analysis methods were employed for the analysis of fracture mechanisms in CFRP such as matrix cracking, debonding, fiber fracture and delamination.

STS316L 모재 및 용착부의 열처리에 따른 초음파 특성

남기우,박소순,안석환 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.3

The degradation characteristics of the base metal and weld of STS316L were investigated by the experimental method of ultrasonic exposure with parameters such as ultrasonic velocity, attenuation factor and frequency. Through this research, degradation characteristics could be evaluated by the combinations of experimental ultrasonic parameters. According to the increase of grain sizes, standard deviation and ferrite contents, the ultrasonic velocities and frequencies were decreased, while the ultrasonic attenuation factors were increased. This results can be to predict the welded structures life time assesmant according to the aged degradation and damage without disjointing or stopping in-service.

초등학교 교육과정과 교과서에 농업·농촌의 기능 및 가치 반영 방안

서우석,강대구,정남용,김재호,이윤조 한국농업교육학회 2006 농업교육과 인적자원개발 Vol.38 No.4

이 연구는 농업ㆍ농촌의 기능과 가치를 재정립하고 이를 초등학교 교육과정 및 교과서에 반영시킬 수 있는 방안을 제시하는데 그 목적이 있었다. 이를 위하여 먼저 선행연구 고찰을 통하여 농업ㆍ농촌의 기능과 가치를 재개념화하고, 이를 토대로 내용 분석 틀을 개발하여 초등학교 교육과정 및 교과서를 분석 하고, 그 결과를 토대로 교육과정 및 교과서에 반영시키기 위한 방안을 제시하였다. 그 주요 결과는 다음과 같다. 첫째, 농업ㆍ농촌의 기능과 가치는 크게 자연환경적 기능(수자원 함양 기능, 환경정화 기능, 생태계 보전기능, 자연재해 방지 기능), 사회문화적 기능(전통문화 보전 기능, 정서의 순화 기능, 자연학습의장 제공 기능), 사회경제적 기능(농산물 공급 기능, 직업 기회 제공 기능, 국토의 균형발전 기능, 타 산업에의 기여 기능)으로 분류하였다. 둘째, 농업ㆍ농촌의 기능과 가치를 바탕으로 초등학교 교육과정 및 교과서를 분석한 결과, 전 학년에 걸쳐서 자연학습의 장 제공 기능과 전통문화 보전 기능이 높게 나타났고, 그 다음으로는 농산물 공급기능과 정서순화기능이 높게 나타났다. 반면에 수자원함양기능과 환경정화기능은 상대적으로 낮게 나타났다. 셋째, 내용분석을 토대로 교과의 성격을 고려하여 각 교과별로 농업ㆍ농촌의 기능과 가치를 반영시킬 수 있는 방안을 제시하였다. 마지막으로, 각 교과별로 농업ㆍ농촌의 기능과 가치 반영 방안을 체계적으로 이행하기 위한 행ㆍ재정적 지원 방안을 교육과정 개발 측면, 교과서 개발 측면, 교육과정 운영측면, 정책적 지원 측면으로 구분 하여 제시하였다. The purpose of the study is to suggest the strategies for incorporating the roles and values of agriculture & rural areas as a part of the national curriculum and elementary school textbooks. For this purpose, this study was conducted as follows; First, we reclassified the roles and values of agriculture & rural areas after critically reviewing literature: environmental conservation functions, socio-cultural functions and socio-economic functions. Second, based on the new classification, we develop a framework for analyzing the national curriculum and elementary school textbooks. The functions of rural areas as places for learning about nature and purifying emotion and the importance of agriculture in providing agricultural product were frequently presented but the functions of sustaining water resources and environmental purification were relatively less presented in the national curriculum and elementary school textbooks. Third, we suggested strategies for incorporating the roles and values of agriculture & rural areas in the national curriculum and elementary school textbook based on the analysis. Finally, we suggested necessary administrative and financial assistance to systematically and effectively implement the suggested strategies for developing a new curriculum and textbooks as well as implementing the curriculum.

뇌졸중후 우울증

문석우,서정석,남범우,최진영 건국대학교 의과학연구소 2004 건국의과학학술지 Vol.14 No.-

In recent years, depression is most commonly reported psychiatric condition after stroke, poststroke depression(PSD) has attracted world-wide interest. This review focuses on the major research themes that have emerged. Pooled data from studies, have wide variation in results is due to different criteria for patient selection, different evaluation methods, diagnostic criteria and poststroke intervals, conducted throughout the world have found prevalence rates for from 18% to 65%. The diagnosis of PSD is most appropriately based on a structured mental state exam and DSM-N criteria for depression due to stroke with major depressive-like episode or depressive features. Rarely, poststroke patients may also develop bipolar mood disorder. The treatment of PSD, single antidepressant showing efficacy and electroconvulsive theraphy(ECT) and behavioral therapies have also effective. The progression of recovery following stroke can be altered by treating depression, which has been shown to improve recovery in activities of daily living(ADL) and cognitive impairment and to decreased mortality. The mechanisms underlying the association of stroke and mood disorder are important areas for future investigation.

월경전증후군의 진단분류학적 개념 및 원인과 치료 : Nosology, Etiology, and Treatment

문석우,서정석,류은정,남범우 건국대학교 의과학연구소 2004 건국의과학학술지 Vol.14 No.-

Since the emergence of the term premenstrual syndrome (PMS) in the 1950s, PMS has become an increasingly discussed topic in popular media sources. Thus self management techniques are easily accessed by women through the media or through their peers. Premenstrual dysphoric disorder (PMDD) comprises extremely distressing emotional and behavioral symptoms. Women with PMDD report premenstrual symptoms, primarily mood symptoms, that are severe enough to seriously interfere with their life style and relationships and usually do not respond to conservative and conventional interventions. Although women with PMS are most often seen in primary care or by their obstetricians/gynecologists, the result of recent study suggested a high rate of missed diagnoses. The premenstrual syndromes include the more common PMS, the less prevalent PMDD, and menstrual psychosis. The etiology of PMS and PMDD is still largely unknown. That PMS and PMDD are primarily biological phenomena is underscored by recent, convincing evidence. Therapeutic interventions for PMS and PMDD range from the conservative to treatment with psychotropic medication and, for the more extreme cases, hormonal therapy or surgical procedures.

당류중에서 일산화탄소의 발생에 관한 연구

박성우,김남이,서중석,최영남,이광영,양영근 內務部 國立科學搜査硏究所 1996 國立 科學 搜査 硏究所 年報 Vol.28 No.-

초등학생들의 물질 개념에 관한 연구

김석중,남철우,김정길,송판섭,한광래,최도성,김숙희 光州敎育大學校 初等敎育硏究所 2002 初等敎育硏究 Vol.17 No.-

Over the past 20 years, research on students' conceptual development of science concepts has begun to inform educators about the roles that prior knowledge and experiences play in the development of conceptual understandings. Whereas many initial studies focused on identifying and cataloging naive of misconceptions, more recent research has focused on how student concept development research can inform teaching practice and curriculum design. In this study, we investigated children's (ages 11∼12) spontaneously constructed or naive understanding of the particulate nature of matter prior to any formal instruction in the domain. Thirty students were interviewed concerning their understanding of the macroscopic and microscopic properties of the states of matter(solid, liquid, and gas), as well as their macro/microscopic understanding of phase changes and dissolving. Children expressed ideas about states of matter which were categorized as macrocontinuous, macroparticulate, or microparticulate. Furthermore, a substantial number of the children provided explanations of properties and processes which were consistent with those beliefs. These children's beliefs about matter were not fully and consistently developed across the spectrum of substances from continuous solids to particulate solids to liquids to gases. We speculate that children first develop local frameworks particular to different classes of substances and then slowly expand these frameworks to include a wide range of substances and their properties as well as such processes as melting and freezing.

음향방출 및 초음파시험을 이용한 CFRP 시험편의 파괴 거동 해석

안석환,남기우 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.3

단조인장시험하에서 CFRP적층재의 손상과정을 음향방출과 초음파시험에 의해 평가하였다. 시험편으로부터의 음향방출신호의 진폭 분포는 기지재 균열(matrix crack), 박리(debonding), 섬유 pull-out 및 섬유 파단(fiber fracture)과 같은 CFRP에서의 파괴기구를 분석하는데 도움을 주며, 초음파 진폭감쇠의 특성 또한 각각의 파괴기구를 분석하는데 유용하다. 여러종류의 CFRP시험편을 사용하여 음향방출신호와 초음파신호의 진폭감쇠를 조사하였다. 끝으로 하중제하중(loading-unloading) 시험이 초음파내의 진폭비에 대해 felicity effect와 감쇠를 조사하기 위해서 수행되었다. 전실험에 걸쳐 초음파신호의 진폭감쇠와 음향방출 파라미터(parameter)들은 동시에 검출되었다. 이로써 음향방출과 초음파시험의 두 파라미터들이 CFRP에서의 파괴기구를 분석하기 위해 효과적으로 사용될 수 있음이 확인되었다. Damage process of CFRP laminates under monotonic tensile test was characterized by the correlation between Acoustic Emission(AE) and Ultrasonic Test(UT). The amplitude distribution of AE signal from a specimens is an aid to the determination of the extent of the different fracture mechanism such as matrix crack, debonding, fiber pullout and fiber fracture as load is increased. In addition, the characteristics of ultrasonic amplitude attenuation are useful for analysis of the different type of fracture mechanism. Different orientation of carbon fiber reinforced plastic specimens were used to investigate the AE amplitude range an ultrasonic amplitude attenuation. Finally, loading-unloading tests were carried out to check Felicity effect. During the tests, ultrasonic amplitude was investigated at the same time and compared with AE parameters. The result showed that two parameters of both AE and UT could be effectively used for analysis of fracture mechanism in CFRP laminates.

유해화학물질의 계통분석

박성우,박유신,이진훈,유재훈,김유나,오세진,이진숙,김남이,박종신,남금문,노동석 內務部 國立科學搜査硏究所 2002 國立 科學 搜査 硏究所 年報 Vol.34 No.-