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논문 : 상변태 ; Fe-Mn 이원계합금의 γ→ε 마르텐사이트변태에 대한 열역학
이영국 ( Young Kook Lee ),전중환 ( Joong Hwan Jun ),최종술 ( Chong Sool Choi ) 대한금속재료학회 ( 구 대한금속학회 ) 1996 대한금속·재료학회지 Vol.34 No.11
In order to avoid the confusion due to inconsistency between thermodynamic calculations(free energy difference between γ and ε, △G γ→ε of γ→ε martensitic transformation for Fe-Mn binary alloys reported by previous workers, the thermodynamic data of Fe-Mn alloys, △G(γ→ε)Fe and △G(γ→ε)Mn, were newly formulated, and the thermodynamic calculations of γ→ε martensitic transformation for the Fe-Mn binary alloys were performed with a regular solution model. The calculation results were well consistent with experimental results in wide range of 15 to 28wt%Mn, and were closely approached to Takaki`s calculation results rather than Murakami`s calculation results.
3상 PWM Converter를 위한 정지 좌표계법 Analog 제어기 설계 및 시뮬레이션
이영국(Young-kook Lee),노철원(Chul-won Noh),최종률(Song-yul Choe) 전력전자학회 1997 전력전자학술대회 논문집 Vol.1997 No.-
Due to several advantages of pulse width Modulated(PWM) Converter, such as unity power factor with low-harmonics and energy regeneration, PWM convener has been widely used in industrial application<br/> In every application of energy conversion equipment, the design and Implementation must be carried out considering performance and cost High quality with low cost is me best choice for energy conversion equipment<br/> High dc link voltage can reduce Inverter and motor side losses and system dimension compare to low dc link voltage-Analog controller can make PWM converter cheaper without considerable degradation of the performance than digital Controller. This paper shows the simplified analog controller for 600V dc link voltage using stationary reference frame control and the simulation results
아날로그 히스테리시스 전류 제어기를 적용한 3상 PWM 컨버터 개발
이영국(Young-kook Lee),노철원(Chul-won Noh) 전력전자학회 2001 전력전자학술대회 논문집 Vol.2001 No.7
Due to several advantages of Pulse Width Modulation (PWM) Converter, such as unity power factor operation, elimination of low-order harmonics and regeneration of motor braking energy to source, the application range of PWM Converter has been rapidly extended in industrial application. Nowadays, vector control algorithm and space vector PWM(SVPWM) method are applied to improve the performances of PWM Converter, but vector control algorithm and SVPWM require to use Microprocessor and other digital devices in hardware, causing costly and somewhat large dimension system.<br/> In every practical application of energy conversion equipments, the design and implementation should be carried out considering cost and performance. High performance and low cost is the best choice for energy conversion equipments.<br/> So, this paper presents the practical design method and implementation results of 3-phase PWM Converter with analog hysteresis current controller, and verifies the performances of unit power factor operation and energy regeneration operation via experimental results.
V-Nb Microalloyed 강의 오스테나이트역에서 복합 탄질화물의 재용해 및 석출 거동
이영국 ( Young Kook Lee ),정재길 ( Jae Gil Jung ),하양수 ( Yang Soo Ha ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.12
Dissolution and precipitation behaviors of complex carbonitrides in austenite of a V-Nb microalloyed steel were quantitatively examined through electrical resistivity measurement and transmission electron microscopy. The electrical resistivity increased with solution treatment temperature up to 1240℃ and then was saturated at 225 nΩm for a holding time of 10 min. The electrical resistivity method was also used to quantitatively measure the isothermal precipitation kinetics of the complex carbonitrides in austenite. Nbrich precipitates were observed in austenite at the early stages of precipitation, but Nb was replaced by V up to the equilibrium amount within the precipitates with further holding time. The time-temperatureprecipitation diagram showed a C-type curve; nose temperature and its incubation time were 900℃ and 100 s, respectively.
Fe-7%Ni-0.4%C 마르텐사이트합금의 미세조직과 진동감쇠능에 미치는 용체화처리온도의 영향
이영국,지광구,최종술 ( Young Kook Lee,Kwang Koo Jee,Chong Sool Choi ) 한국열처리공학회 1998 熱處理工學會誌 Vol.11 No.1
The objective of this study is to investigate the effect of solution-treatment temperature on the microstructure and damping capacity of a martensitic Fe-7%Ni-0.4%C alloy. The size of lath increased from 0.3㎛ to 0.55㎛ with increasing the solution-treatment temperature from 700 to 1100℃. In addition, the size of block, packet, and austenite grain had tendency to increase with increasing solution-treatment temperature. The damping capacity of the Fe-7%Ni-0.4%C martensitic alloy decreased with increasing the solution treatment temperature. The reason is not attributed to the increase in the size of lath, block, packet, and austenite grain, but to the increase in vacancy concentration which hinders dislocation motion.
Fe-Ni-C 마르텐사이트 합금에서 마르텐사이트의 형상이 진동감쇠능과 기계적 성질에 미치는 영향
이영국,신한철,최종술 ( Young Kook Lee,Han Chul Shin,Chong Sool Choi ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.3
Effect of martensite morphology on damping capacity and hardness of Fe-Ni-C martensitic alloys were studied. The morphologies of martensite such as lath, butterfly, lenticular and thin plate were prepared by adjusting nickel content and austenite grain size. The hardness increased in order of lath, lenticular, thin plate, butterfly. The damping capacities of the lath and butterfly martensites were higher than those of the other two morphologies, indicating that the dislocation substructure is more effective in the damping capacity than the twin substructure. Especially, the butterfly martensite showed the highest damping capacity among these morphologies because of presence of not tangled but free dislocations in there.
Fe-Mn 합금의 γ↔ε마르텐사이트변태에 필요한 구동력
이영국,최종술 ( Young Kook Lee,Chong Sool Choi ) 한국열처리공학회 1996 熱處理工學會誌 Vol.9 No.4
Dilatometric experiment and thermodynamic calculation have been performed to determine M_s, A_s and driving forces for γ→ε martensitic transformation of Fe-Mn alloys. The transformation temperatures(M_s, A_s, T_o) were decreased with increasing manganese content and were newly formulated as a function of manganese content. Driving force for γ→ε martensitic transformation was increased from -75J/mole to -105J/mole with increasing manganese content from 15wt.% to 25wt.%. Transformation temperature hysteresis(A_s-M_s) was also increased from 50K to 80K with increasing mangenese content from 15wt.% to 25wt.%. The small driving force(-75J/mole-105J/mole) and small ΔT(50K∼80K) for γ→ε martensitic transformation indicated that Fe-Mn alloys behave like thermoelastic martensitic alloys : We would like to call them semi-thermoelastic martensitic alloys.