초음파현미경의 고주파 초음파 탐촉자를 이용한 코발트기 초내열합금강의 열화평가

박익근,조동수,김용권,임재생,김정석 한국비파괴검사학회 2004 한국비파괴검사학회지 Vol.24 No.5

V(z)곡선법을 이용한 코발트기 초내열합금강의 열화도 평가 유용성 유무를 고주파 초음파 탐촉자를 이용하여 실험적으로 검증 하였다. 코발트기 초내열 합금이 고온에서 장시간 노출되었을 때 일어나는 미세조직의 변화를 모사하기 위해서 인공열화를 실시하였다. 여로하에 미치는 초음파 음속의 영향을 고찰하고자 10MHz를 이용하여 펄스-에코법으로 종파의 음속을 측정하고 200MHz를 사용하여 V(z)곡선법으로 누설턴성표면파의 음속을 측정하였다. 두 초음파의 음속은 열화시간에 따라서 감소 하였다. 더욱이, 저주파수 종파의 음속변화는 거의 없었지만, 고주파수 누설탄성표면파의 음속변화는 열화시간에 따라서 최대 4.7%의 변화를 나타내었다. 열화에 따른 강도의 변화와 누설탄성표면파의 음속 변화는 양호한 상관관계를 나타내었다. 따라서 열화도 평가에 고주파 탐촉자를 이용한 초음파 현미경의 V(z)곡선법이 유용함을 알 수 있었다. The feasibility of V(z) curve method of scanning acoustic microscope using high frequency transducer was experimentally studied for assessment of the thermal degradation in Co-based superalloy. Thermal degradation was performed to simulate the microstructural changes in Co-based superalloy arising trom long term exposure at high temperature. Longitudinal wave velocity measured by pulse echo method using 10MHz transducer and leaky surface acoustic wave (LSAW) velocity measured by V(z) curve method using 200MHz transducer were measured to investigate the effect on thermal degradation. Ultrasonic velocity decreased as the aging time increased in both ultrasonic waves. Moreover, the low frequency longitudinal wave velocity decreased a little. Otherwise, the high frequency LSAW velocity drastically decreased up to a maximum of 4.7% at the aging time of 4,000hours. A good correlation was found between LSAW and Vickers hardness. Consequently, V(z) curve method of SAM using high frequency transducer could be a potential tool for assessing thermal degradation.

회맹장 판막에 발생한 아니사키스증 1례

이재익,박정하,김준영,조영완,진한영,강명주,정은욱,박석주,양성연 인제대학교 2006 仁濟醫學 Vol.27 No.-

Anisakiasis refers to parasitic infestation by nematode larvae that belongs to the subfamily Anisakinae, and this condition is seen in people who eat inadequately prepared or raw salt-water fish. While gastric anisakiasis is commonly diagnosed by endoscopic technique, intestinal anisakiasis is rare because it is less common and the clinical and radiologic features are poorly understood. The authors report a case of human anisakiasis involving the ileocecal valve in 62-year-old man who had the history of eating raw cuttlefish.

共通費配賦의 妥當性에 관한 實證的 硏究

許益九,洪孝錫 진주산업대학교 1995 論文集 Vol.34 No.-

The purpose of this paper is to investigate the practical on the allocation of central costs of Korea's listed companies and to analyze empirically the effects of the allocation of central costs on the submits in decentralized companies. Our purpose in this paper is two-fold : First, we would like to make theoretical explanations of the allocation of central costs alternative used or not used in practice. Next, we will search for some of the environmental factors such as the firm size, the number of submits, the scale of central costs, and the relationships, to find out correlation between the allocation of central costs actually used and those factors. The survey method used was to collect field data. Statistical analysis methods such as t-test and Mann-Whitney were employed to find out if there is any statistically significant results. The findings of this empirical study can be summarized as follows. Among the contingency-factors related hypotheses, only the scale of central costs is confirmed to be related to the allocation of central costs. And only the number of submits is confirmed to be related to the allocation of central costs actually used in companies.

비정질 Fe80Si2B18 합금의 자성

양재석,강신규,이상훈,조익한 嶺南大學校 基礎科學硏究所 191 基礎科學硏究 Vol.11 No.-

The amorphous ?? alloy are studied by Mossbauer spectroscopy at room temperature. This sample are produced by single roll quenching method. The analysis of the distribution of hyperfine fields indicates two peaks. The bimodal P(H) features are as following:?? kOe and ?? =273 kOe. This represents that this sample has the inhomogeneous magnetic structure. The average isomer shift is 0.097 mm/s, the quadrupole splitting is 0.022mm/s. The absorption intensity, b, of M??ssbauer spectrum is about 2.91 and the number of Fourier parameters is eight.

흰쥐 앞뇌중격부의 콜린성신경세포에서 Nerve Growth Factor 및 Galanin 의 공존

고기석,장병준,조익현 건국대학교 의과학연구소 1999 건국의과학학술지 Vol.9 No.-

Mammalian forebrain septal area, which is closely concerned in learning and memory, contains a lot of cholinergic neurons. It has been well-known that these neurons have high levels of some neurosubstances including acetylcholine. It has been reported that galanin as a neuromodulator/neurotransmitter and a nerve growth factor(NGF) as a neurotrophic factor are densely localized in rat forebrain septal area. However, the precise localization, co-localization and correlation between these neurosubstances have not been clearly elucidated yet. To identify the co-localization of these substances in rat forebrain septal area, immunohistochemistry using antibodies to choline acetyltransferase(ChAT), NGF and galanin has been accomplished on serial paraffin-sections of forebrain septal area. 1. High concentrations of ChAT, NGF and galanin positive neurons were observed in the medial septal nucleus(MS) and the diagonal bands of Broca(DBB) in the basal forebrain. 2. Approximately 80.6% of cholinergic neurons were NGF positive, and 78.0% of the neurons were galanin positive, and 71.6% of the cells exhibited positive reaction for both substances, in the forebrain septal area. 3. Some of ChAT, NGF and galanin positive neurons were distributed individually in the forebrain septal area. Based on the results mentioned above, it could be concluded that NGF and galanin were co-localized in most cholinergic neurons of the forebrain septal area. It seems that there are functional reciprocal between these substances in the forebrain septal area.

2.25Cr-1Mo 강 인공 열화재의 고주파수 초음파 감쇠특성에 관한 연구

박익근,박은수,김정석,김현묵,권숙인,변재원 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.4

재료나 설비의 고온 장시간 사용으로 인하여 발생되는 재질열화 평가에는 파괴적인 방법이 널리 사용되고 있으며, 신뢰도가 높다. 그러나, 시험편의 채취가 어렵고 많은 경비와 시간이 소요된다. 전기저항법, 레프리카법, 바크하우젠 노이즈법, 전기화학적방법, 초음파법 등과 같은 비파괴적인 열화손상 평가 방법이 주목을 받고 있다. 본 연구에서는 2.25Cr-1Mo 강을 630℃에서 장시간 등온열처리로 모의 열화시험편을 제작하고, 고온설비부재에서 발생되는 미세조직의 변화와 고주파 초음파의 전파특성(감쇠계수)과의 일대일 상관관계를 규명하여 초음파 비파괴평가에 의한 열화도 평가의 유용성 유무를 실험적으로 검증하였다. 그 결과 2.25Cr-1Mo 인공열화재의 경우 열화가 진행됨에 따라 탄화물의 석출 및 조대화가 일어나며 초음파 감쇠계수는 증가하는 경향을 나타내었으며, 그 정도는 침상의 탄화물이 거의 소멸되는 1,000 시간 이후에 초음파 감쇠계수가 급격히 증가하는 매우 좋은 상관성을 나타내었다. The destructive method is reliable and widely used for the estimation of material degradation but, it have time-consuming and a great difficulty in preparing specimens from in-service industrial facilities. Therefore, the estimation of degraded structural materials used at high temperature by nondestructive evaluation such as electric resistance method, replica method, Barkhausen noise method, electro-chemical method and ultrasonic method are strongly desired. Ultrasonic nondestructive evaluation technique has been reported good to attain efficiency of measurement, high sensitivity of measurement, and rapidity and reliability of result interpretation. In this study, it was verified experimentally the feasibility of the evaluation of degraded 2.25Cr-1Mo steel specimens which were prepared by the isothermal aging heat treatment at 630℃ by high frequency longitudinal wave method investigating the change of attenuation coefficient by FFT analysis and wavelet transform. Because of carbide precipitation increase and spheroidization near grain boundary of microstructure to aging degradation, attenuation coefficient had a tendency to increase as degradation proceeded. It was identified possibly to evaluate degradation using the characteristics of high-frequency ultrasonics. Frequency dependence of ultrasonic attenuation coefficient to aging degradation appeared large, which made sure that attenuation coefficient is an important parameter for evaluation of aging degradation.

1996년도 학술 제 2분과(초음파)활동 보고

이승석,박익근 韓國非破壞檢査學會 1997 한국비파괴검사학회지 Vol.17 No.2

금정산의 식생구조 및 식생변화 분석

김석규,장원익,남정칠 東亞大學校建設技術硏究所 2004 硏究論文集 Vol.28 No.1

The the purpose of this study is to propose vegetation management device through analyzing vegetation structure and phytocociological Changes for ten years in Mt. Geumjeong. Eight belt transects of quadrat(20m×20m) were sampled to investigate and analyze the vegetation structure.

고주파수용 필터 설계를 위한 자이레이터 회로에 관한 연구

金石鎬,趙成翊,金東龍 全北大學校 1991 論文集 Vol.33 No.-

Switched-capacitor(SC) circuits have already been established in audio frequency range. However, SC circuits are not suitable for high frequency filters, because of the necessity of anti-aliasing filters and the limitation of high-frequency characteristics due to GBW(Gain-Band-Width) products of operational amplifiers. To overcome those disadvantages, a gyrator filtering techniques have been proposed. LC simulation method using gyrators is readily available to abtain low-sensitivity active RC filters. In this paper, highly linear MOS transconductor with the gain factor controllable by offering offset voltage is presented, and to validate transconductor characteristics, computer simulation using PSPICE was performed. Gyrator circuit is designed using MOS transconductor circuits, and for filter design, floating inductor, floating resistor and grounded resistor which are simulated by gyrator circuits are presented.

통신프로토콜의 적합성시험열 생성을 위한 경로 탐색 방법

황익순,장민석,이상배,이재용 延世大學校 電波通信共同硏究所 1996 電波通信論文誌 Vol.2 No.1

본 논문에서는 적합성 시험에서 EFSM(Extend Finite State Machine) 모델에 대한 데이타부분 시험열을 효율적으로 생성시켜 주는 탐색 방법에 대해 제안하였다. 이 탐색 방법에서는 depth-first search와 같은 기존의 탐색 방법과는 달리 탐색 초기에 다양한 경로가 찾아진다. 이미 제안된 시험열 생성 방법인 데이타 값을 바탕으로 하여 시험열을 생성하는 방법에서 이 탐색 방법을 이용하였을 경우 기존의 탐색방법을 이용하는 것보다 효율적으로 시험열을 생성할 수 있다. 본 논문에서는 Inres 프로토콜에 이 탐색 방법과 기존의 탐색 방법인 depth-first search를 각각 적용하여 시험열을 생성, 비교하여 보았으며, 제안된 탐색 방법을 이용하면 같은 시험 범주를 가지면서도 짧은 길이를 갖는 시험열을 효율적으로 생성할 수 있음을 알 수 있다. In this paper we proposed a searching algorithm for generating test cases, which can test data part of EFSM model in conformance test. In a different way to existing algorithm like depth-first search algorithm, this one can find various paths in the early stage of searching. When it is used in readily proposed test case generation method which is based on the value of variables and parameters it can generate test cases efficiently than in the case of depth-first search algorithm being used. We generated test cases for Inres protocol using each of proposed and depth-first search algorithm, and compared these two methods. proposed algorithm can generate much shorter test sequences efficiently than existing one.