MgCl₂溶液內에서 STS 304 HP Stainless Steel 熔接部의 破壞擧動에 對한 硏究

金永奭,丁太權,朴昌彦,洪錫柱,梁仁榮,金基玉,朴煥奎,李茂錫,曺圭宰,鄭在康 조선대학교 생산기술연구소 1983 生産技術硏究 Vol.1983 No.-

This paper is based on an experiment analysing the stress corrosion cracking behaviour of welding specimens compared to that of non-welding specimens of STS 304 HP stainless steel in corrosion solution. As a corrosion condition, stainless steel has been known to be the most fragile in a solution of 42% MgCl₂heated to the boiling point, therefore the experiment was carried out in this condition. The experiment was carried out with argon gas TIG welding specimens and non-welding ones made of stainless steel plates, thickness 2mm, by tensile force. At this time, the tensile force was taken to be the value of the yield strength of the tensile test specimens divided by the safety factor of 3.0 to 3.5, 4.0, 4.5, and 5.0. In this paper, the relations between Time of Initial Crack, Time of Failure, Time of Final Fracture and Crack Propagation Length were investigated and then plotted. Furthermore, the relations between Stress Intensity Factor K proposed by Irwin and the Time of Initial Crack, the Time of Failure, the Time of Final Fracture were calculated and plotted. At the last, all the relations plotted were expressed to normal equations by computer, and the equations were used to analyse the data obtained in the experiment. The conclusions obtained in this study are as follows: 1. Welding materials, compared with non-welding ones, as the Time of Initial Crack, the Time of Failure, and the Time of Final Fracture were generally very fast, appeared to be a phenomenon of unstable brittleness fracture. 2. Non-welding materials, compared with welding ones, as the safety factor was larger or the working stress was smaller, appeared to be a phenomenon that the longer had had greater durability. Therefor, welding materials must be considered enough to be used in heate affected and stress corrosion atmosphere. 3. The normal equations of the Time of Initial Crack and the variation rate to the same Stress Intensity Factor K are as follows: (A) Non-welding T =259702.4-5451.2 K+28.386 K² T = -5451.2+28.386 K (B) Welding T= -332.693+28.043 K-0.211 K² T' =28.043-0.211 K here, T; Time of Initial Crack, T'; Variation Rate of Time of Initial Crack to Stress Intensity Factor K, K ; Stress Intensity Factor.

초등영어 학습자들의 영어 학습전략의 사용과 영어능력과의 관계

양재석 대구교육대학교 초등교육연구소 2020 현장중심 초등교육연구 Vol.2 No.-

The purpose of this study is to investigate the primary level students' use of language learning strategies depending on learner variables including English proficiency, gender, learning period, and grade. The students (N=140) enrolled in one public elementary school participated in the study. The data were analyzed based on the results of learning strategy survey, English proficiency test, and a background questionnaire. The findings show that the compensation strategy and the affective strategy were used most frequently. In the results according to the English proficiency level, high-level learners use more learning strategies than low-level ones. In particular, among the six sub-strategies, all strategies except the memorization strategy showed significant differences between groups by English proficiency level. Also, there was no significant difference in the frequency of strategy use according to the grade and gender. With regard to the learning period, however, learners with a learning period of 5 years or more used the language learning strategies more frequently compared to those of a group whose learning period is less than 3 years. 본 연구는 초등학생 영어학습자들의 전반적인 영어 학습전략을 활용 양상과 영어 능숙도, 성 별, 학습기간, 학년을 포함하는 학습자 변수에 따른 학습전략 활용 빈도의 차이를 연구하는데 목적을 두고 있다. D시 소재의 공립 초등학교 1 곳에 재학 중인 140명이 연구에 참여하였다. 수집된 자료는 학습전략 목록과 영어 능숙도 시험, 배경 설문에 대한 결과를 중심으로 분석하 였으며, 그 결과 전반적으로 보상전략과 정의적 전략의 활용 빈도가 높은 것으로 나타났다. 영 어 수준에 따른 결과에서는 상위 수준의 학습자들이 학습전략을 자주 사용하는 것으로 나타났 으며, 특히 총 6개의 하위전략 중, 암기전략을 제외한 모든 전략에서 수준별 집단 간 유의한 차 이를 보였다. 학년과 성별에 따른 전략 활용 빈도의 차이에서는 유의미한 차이가 없는 것으로 나타났지만, 학습기간과 관련해서는 학습기간이 5년 이상이 되는 학습자들이 3년 이하의 학습 기간이 비교적 짧은 집단의 학습자들에 비해서 학습전략을 자주 사용하는 것으로 나타났다.

실증연구를 위한 주택용 태양열 온수기 모니터링 시스템 개발

양동조,김재열,한재호,송경석,김우진 한국공작기계학회 2004 한국공작기계학회 추계학술대회논문집 Vol.2004 No.-

The application of solar energy, in the field of alternative energy, was on the increase tendency. In the case of advanced nations, through continuous R&D, solar hot water heater with high efficiency has been used for the house and the industrial process on business, advanced nations were reached up the experimental stage of solar generation system. But, the actual circumstance of the domestic has been not accomplished the popularization of solar hot water heater and the settlement of it which is the fundamental stage of the solar energy usage. This trouble, the domestic was flooded with small enterprise for producing solar hot water heater, was caused by the popularization and the production without verification of performance. To supply the monitoring program for evaluating solar hot water heater, this research was purpose to improve the technical development of the enterprise for producing solar-heat hot-water-boiler and served as an aid for the enlargement and the popularization on solar energy.

CAD/CAM을 이용한 맞춤형 임플란트 지대주의 나사 풀림 토크 평가

이창재,양성은,김석규 대한치과보철학회 2012 대한치과보철학회지 Vol.50 No.2

연구 목적: 본 연구는 국내 개발된 맞춤형 임플란트 지대주와 기성 임플란트 지대주의 반복 하중 전과 후의 나사 풀림 토크 값을 측정, 비교하여 나사 결합부 안전성에 차이가 있는지를 알아보고자 하였다. 연구 재료 및 방법: 총 12개의 임플란트 고정체(Implantium, Dentium Co., Seoul, Korea)를 알루미늄 원통에 레진으로 고정하고, 그것을 각각 4개씩, 3개의 군으로 나눠서 각 군별로 기성 티타늄 지대주(Implantium, Dentium Co., Seoul, Korea), 캐드캠 맞춤형 티타늄 지대주(Myplant, Raphabio Co., Seoul, Korea), 그리고 금속 연결부가 있는 캐드캠 맞춤형 지르코니아 지대주(Zirconia Myplant, Raphabio Co., Seoul, Korea)를 제작하여 임플란트에 연결하였다. 금속관은 지대주에 맞춰서 티타늄을 밀링해서 제작한뒤 지대주에 합착하였다. 반복 하중을 가하기 전에 지대주 나사를 30 Ncm 토크로 조이고 약 30분 후 나사의 초기 풀림 토크값을 측정하였다. 그 후 반복 하중을 30 N에서 120 N의 싸인 곡선을 이루는 압축력으로 2 Hz의 빈도로 50만 싸이클을 가하고 하중 후 풀림 토크값을 측정하였으며, 풀림 토크 상실률을 구하여서 군끼리 비교하였다. 나사의 풀림 토크값의 상실률의 비교를 위해 Kruskal-Wallis test를 이용해서 유의수준 .05에서 분석하였다. 결과: 반복하중 후 나사 풀림 상실률에서 기성 티타늄 지대주 군에 비해 맞춤형 티타늄 지대주는 높은 값을 보였으나 유의성 있는 차이를 보이지 않았다(P>.05). 반면, 맞춤형 지르코니아 지대주는 기성 티타늄 지대주에 비해 유의하게 높은 값을 보였다(P=.014). 결론: 본 실험의 한계 내에서 캐드캠 맞춤형 티타늄 임플란트 지대주는 기성 임플란트 지대주에 비해 나사 안정성이 떨어진다고 볼 수 없다. 반면, 캐드캠 맞춤형 지르코니아 지대주 는 기성 임플란트 지대주에 비해 나사 안정성이 다소 떨어진다고 볼 수 있다. Purpose: The purpose of this study was to compare the screw joint stability between the CADCAM custom-made implant abutment and the prefabricated implant abutment by measuring the reverse torque value after cyclic loading. Materials and methods: Twelve screw type implants (Implantium, Dentium Co., Seoul, Korea) were embedded in aluminum cylinder with acrylic resin. The implant specimens were equally divided into 3 groups, and connected to the prefabricated titanium abutments (Implantium, Dentium Co., Seoul, Korea), CADCAM custom-made titanium abutments (Myplant, Raphabio Co., Seoul, Korea) and CADCAM custom-made zirconia abutments (Zirconia Myplant, Raphabio Co., Seoul, Korea). The CAD-CAM milled titanium crown (Raphabio Co., Seoul, Korea) was cemented on each implant abutment by resin cement. Before cyclic loading, each abutment screw was tightened to 30 Ncm and the reverse torque value was measured about 30 minutes later. After the crown specimen was subjected to the sinusoidal cyclic loading (30 to 120 N, 500,000 cycles, 2 Hz), postloading reverse torque value was measured and the reverse torque loss ratio was calculated. Kruskal-Wallis test was used for statistical analysis of the reverse torque loss ratio. Results: The CADCAM custom-made titanium abutments presented higher values in reverse torque loss ratio without statistically significant differences than the prefabricated titanium abutments (P>.05). Reverse torque loss ratio of the custom-made zirconia abutments was significantly higher compared to that of the prefabricated titanium abutments (P=.014). Conclusion: Within the limitation of the present in-vitro study, it was concluded that there was no significant difference in screw joint stability between the CADCAM custom-made titanium abutments and the prefabricated titanium abutments. On the other hand, the CADCAM custom-made zirconia abutments showed lower screw joint stability than prefabricated titanium abutments.

원추형 회전체-자기베어링의 능동 진동 제어

석창욱,양승준,곽병철,이재응 중앙대학교 기술과학연구소 2000 기술과학연구소 논문집 Vol.30 No.-

기존 접촉식 베어링과 비교할 때 능동 자기 베어링(AMB)는 많은 장점을 가진다. 자기 베어링 시스템은 주축을 자기력을 이용하여 부상시켜 기계적인 마찰이 없는 상태에서 회전시키기 때문에 윤활을 하지않고도 작동시킬 수 있다. 따라서 이 베어링은 우주에서의 진공상태와 같은 극한상황에서도 사용할 수 있다. 특히 원추형 자기 베어링은 4조의 전자석으로 구성되어 래디얼 타입 자기 베어링보다 소형, 경량화할 수 있는 장점을 가진다. 본 논문에서는 먼저 원추형 자기베어링에 대한 운동방정식을 유도하고, 이 시스템의 진동 제어를 위해 비연성인 디지털 PD, PID 제어기를 설계하였다. 컴퓨터 모의실험을 통해 제어기의 성능을 평가하여 만족할 만한 성능을 얻었다. There are many advantages of the Active Magnetic Bearing(AMB) system, compared with conventional contacting bearing systems. Since the spindle in the AMB system is levitated by electro-magnetic forces and rotates without mechanical friction, it can run without lubrication. So, it can run in the extreme circumstances, e.g. a vacuum condition in the space. Particularly, the cone-type AMB system consists of only 4 couples of magnet, it can be smaller and lighter than radial-type AMB system. In this thesis, the equations of motion of the cone-type AMB system is derived first, and the digital PD and PID controllers are designed for the vibration control of the system. The controllers are designed based on the decoupled equations of motion, and the performance of the controllers are evaluated through the computer simulations. The results of the simulation show good performance of the controllers.

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.

생쥐의 骨髓細胞에 대한 Aminopterin 과 Amethopterin의 細胞遺傳學的 影響

양재섭,강봉석,최명철,김길웅 대구대학교 기초과학연구소 1987 基礎科學硏究 Vol.4 No.-

Aminopterin and amethopterin(Methotrexate; MTX) are antifolic drugs and anti-tumour agents, which inhibit DNA biosynthesis, were previously known to have mutagenic effects on various mammalian cells. Mutagenecity and toxicity of these agents have been determined by various methods. In the present study, effects of two anti-tumour agents on cultured mouse bone marrow cells were analyzed by observing chromosome aberrations and mitotic index. The results of the present investigation were as follows; 1. The chromosome aberrations analyzed were mainly chromosome gaps and breaks, chromatid gaps and breaks. In the Group-1 (treated for 8 hours), chromosome aberrations were not shown and it seems that mutagenic actions of anti-tumour agents were not aroused due to the short period of culture and the other culture conditions. However, in the Group-2 (treated for 24 hours), as the concentrations of antifolic compounds were increased, chromosome aberrations were increased. 2. In mitotic index, the Group-I treated with aminopterin and amethopterin showed marked inhibition in the mitotic index(O. 6% in aminopterin, 0.9% in amethopterin) at the high concentrations, compared with that of control (5. 2%). Both aminopterin and amethopterin showed a dose-dependent reduction of mitotic index. In the Group-2, each group treated with two antifolic compounds showed no marked differences in the mitotic index. compared with that of control. 3. Aminopterin was a more potent agent for induction of chromosome aberration than amethopterin.

초음파 검사 기반의 용접결함 분류성능 개선에 관한 연구

김재열,윤성운,김창현,송경석,양동조,--,-- 한국공작기계학회 2004 한국공작기계학회 춘계학술대회논문집 Vol.2004 No.-

In this study, we made a comparative study of backpropagation neural network and probabilistic neural network and bayesian classifier and perceptron as shape recognition algorithm of welding flaws. For this purpose, variables are applied the same to four algorithms. Here, feature variable is composed of time domain signal itself and frequency domain signal itself. Through this process, we comfirmed advantages/disadvantages of four algorithms and identified application methods of four algorithms.

적외선 열화상 카메라를 이용한 Plume 형상에 따른 Nd:YAG 레이저 용접 결함 평가

김재열,유영태,양동조,송경석,노경보 한국비파괴검사학회 2003 학술대회 논문집 Vol.- No.1

In Nd:YAG laser welding, evaluation methods of welding flaw are various. But, the method due to plume shape is difficult to classification of welding flaw. The Nd:YAG laser process it known to have high speed and deep penetration capability to become one of the most advanced welding technologies. At the present time, some methods are studied for measurement of plume shape by using high-speed camera and photo diode. This paper describes the machining characteristics of SM45C carbon steel welding by use of an Nd:YAG laser. In spite of its good mechanical characteristics, SM45C carbon steel has a high carbon contents and suffers a limitation in the industrial application due to the poor welding properties. In this study, plume shape was measured by infrared thermal camera that is non-contact /non-destructive thermal measurement equipment through change of laser generating power, speed, focus. Weld was performed on bead-on method. Measurement results are compared as two equipments. Here, two results are composed of measurement results of plume quantities due to plume shape by infrared thermal camera and inspection results of weld bead include weld flaws by ultrasonic inspector.

공동주택의 장수명화 및 재생을 위한 IHCS 표준모델 개발 : 개념 및 특성을 중심으로 With a focus of Concept and Character

최경석,강재식,양관섭,이승언 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.1

Recently Excessive national resources, energy losses and social·economical problems are induced by reconstruction apartment housing which was constructed about 20 years and is enough to keep one's residence structurally. Especially, the greatest obstruction in longevity & recycling technology of apartment housing is the current Ondol system of wet process integrated structures. Also the current Ondol system is difficult to improve due to its character of material and process. The object of this study is to develop IHCS(Infill Heating & Cooling System) standard model with prefabricated & dry process that shall be the substitution for the current wet Ondol system.