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보이드 생성기구에 의한 복합조직강의 연성 파괴거동에 관한 연구
吳澤烈,崔明振,楡龍錫,金松正 慶熙大學校 材料科學技術硏究所 1993 材料科學技術硏究論集 Vol.6 No.-
Ductile Fracture of Dual Pase Steel begins with void nucleation, at Martensite-Ferrite interface or deformed Martensite particle. In this study void nucleation, void growth, void volume fraction and void coalescence at given strain were studied in dual phase steel. Therefore, by means of the heat treatment of low corbon steel the study deal with void nucleation and void growth for ferrite grain sizeof dual phase steel. Void nucleaton and void growth with increasing strain are shown depend upon the ferrit grain size. The number of voids and volume fraction of voids generary increase as ferrite grain size decrease. At the close to fracture the void coalescence in the direction of the applied tensile stress, but near the fracture surface they linked in direction transverse to the tensile axis.
吳英錫,朴鎔遠 명지대학교 공학기술연구소 1992 공학기술연구소 논문집 Vol.7 No.-
In this study, we have studied the shear strength and stress-strain characteristics of fiber reinforced sand through laboratory direct shear test. Among many factors affecting the reinforcing effect the stiffness, the interval and orientation of the nclusions are lighted in this study. In the tests, KS standard sand and poly-vinyl wire coating are used and the number of reinforcement and inclination angle to the expected shear plane are changed. From the test results, it is found that fiber reinforced sand has greater shear resistance and extensibility(ductility) as well and smaller loss of post peak strength compared to unreinforced sand. It is also observed that the initial orientation of the reinforcement affects the magnitude of the shear resistance increase in the composite. In this test, reinforcements oriented at 45˚ to shear plane produced the maximum increase in shear resistance. Further research and observations on full scale structures are required in order to develop a better understanding of the potential effect of reinforcement bending stiffness and on the behavior of fiber reinforced sand.
Piece-wise Linear 기법에 의한 구조용 재료의 비선형 해석
유용석,오세계 慶熙大學校 大學院 1993 高凰論集 Vol.12 No.-
Material Nonlinearity is very important issue in engineering problem. In past, Cauchy's Linear elastic formular is used widely, but they cannot apply materials inelasticity to engineering design. In this study, Piece-wise linear method is used for material nonlinearity. Dual phase steels are studied for material nonlinearity by piece-wise linear analysis. Theoritical values are always below the experimental values because grain size effect, and this study includes theoritical background for F.E.M. and piece-wise linear analysis.
고밀도 집적화를 위한 Inverse Chebyshev MOSFET-C 필터 설계
金東龍,崔碩佑,吳成根 全北大學校 1992 論文集 Vol.34 No.-
Continuous-time integrated filters, implemented in MOS VLSI technology, have been receiving considerable attention. In this paper, a continuous-time fifth order active RC Inverse Chebyshev filter is designed using cascade method which each block can be tunable. The resistors of an active RC network are replaced by a linear resistor using NMOS depletion transistors operated in the triode region. This MOSFET linear resistors which have simple structure can be adjusted by control voltage. And we have designed CMOS operational amplifier for fabrication. The Inverse Chebyshev MOSFET-C filter characteristics are simulated by PSPICE program.
정확한 완충기체효과가 적용된 질량분석원리에 대한 다중입자 분석 전산시늉
이유용,이원욱,오차환,김필수,송석호 한양대학교 자연과학연구소 2001 自然科學論文集 Vol.20 No.-
질량분석기로 사용되는 폴 트랩 내에서 보다 실제적인 이온운동을 예측해내기 위하여 약 2천 개의 다중입자의 궤적에 대한 계산을 실시하였다. 보다 정확한 질량 분석스펙트럼을 얻기 위하여 충돌확률에 대한 보다 정확하고 실질적인 함수 값을 도입하였다. 계산된 전산시늉의 결과들로부터 특히 작은 질량의 영역에 대한 분석을 할 경우 본 논문에서 제시된 바와 같이 매우 정확한 충돌확률이 고려되어야 함을 확인할 수 있었다. To predict the practical characteristics of ion motion in the paul trap as a mass spectrometer, the ion trajectories of the multi-particle(over than 2000 particles) were calculated. In order to expect more practical mass spectrum, the exact expressions for the collision probability was adopted. From the simulation result, we found that the exact collision probability has to be considered to analyze the materials existed in the low mass region.
스테인레스강 절삭가공에서 공구의 온도 특성에 대한 실험적 연구
권용기,오석형,김동현 한국공작기계학회 1996 한국생산제조학회지 Vol.5 No.1
This is an experimental investigation of the temperature generated in a cutting tool during the machining of stainless steel. The temperature results from the wear of the cutting tool are considered in order to investigate the relation between cause and effect of these factors. This possibility has been tested using a thermocouple technique to record temperature vs. time curves for a variety of cutting conditions. This is done by employing a thermocouple inserted on the tool tip near the major cutting edge. Temperature distributions are calculated using finite element method and compared to the contour maps measured by an optical system. It suggests that the temperature gradients and the tool performance will be dependent on certain factors in tool geometry when cutting this material.
H∞ 최적 제어기법을 이용한 전력시스템의 안정화에 관한 연구
주석민,이용길,정동일,김상효,이오걸 동의공업대학 2000 論文集 Vol.26 No.1
In this paper, we are considered various possible disturbance conditions in order to design controller, H∞ optimal controller is successfully designed to control in such as situations. To do this, we are determined weighting function and design parameter γ to method of trial and error by Glover-Doyle algorithm. To compare with H∞-PSS and conventional-PSS which is applied in nominal system and load variations, the dynamic characteristics of H∞-PSS controller was verified which has a good response.
이중에너지 방사선 흡수계측법을 이용한 성인 남녀의 장골 및 경골의 골밀도에 관한 연구
조용석,김경원,이경호,박현진,서상수,오상엽 대한악안면성형재건외과학회 2000 Maxillofacial Plastic Reconstructive Surgery Vol.22 No.3
Purpose : The aim of this study was to evaluate the bone mineral density of iliac and tibial bone which are frequently selected as autogenic bone graft donor sites, and to evaluate the efficiency of this method as a guideline for the selection of bone graft donor site. Materials and Methods : In this study 61 male and 70 female volunteers at Chungbuk National University Hospital were involved between Jan. 1998 to Sept. 1999. We measured bone mineral density of the iliac and the tibial bone using dual energy X-ray absorptiometry. We evaluated the data using the SAS system for Windows and bone mineral density of the lumbar was used for control. Results : Age showed the highest correlation in correlation matrix between physical and bone variables. Height and weight showed lower correlation of linear increment. In man, the change of bone density according to age demonstrated linear decrease irrespective of the lumbar, ilium, and tibia. In woman, the change of bone density according to age showed cubic form, which increased in the third and forth decade. So it had a peak bone mass on about 35 year-old, thereafter, the change of bone density slowly decreased until 50 year-old, but it rapidly decreased after 50 year-old and it slowly decreased again after 65 year-old. Both in all subjects and subject with osteoporosis, the change of bone mineral density according to age showed statistically significant decrease in lumbar and tibia, but ilium was irrespective. Conclusion : In patients of aged or with osteoporosis, ilium demonstrated less tendency of decrease in bone mineral density than tibla. So this preliminary study suggested that ilium seemed better donor site for autogenic bone graft than tibia.