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조정호,김철희,Cho, Jung-Ho,Farson, Dave,Kim, Cheol-Hee 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.1
Irregular fluctuation of penetration depth in CW single mode fiber laser welding is analyzed statistically and chaotically. Among various chaos theories, one of the basic concept referred as Lyapunov exponent is applied to the analysis to quantify the irregularity of penetration. Especially, maximal Lyapunov exponent (MLE) is known as the representative value indicating chaotic degree of the system dynamics. MLE calculation method of experimental data is applied to longitudinal spiking defect in fiber laser weld. Laser power modulation is suggested as a remedy then the computed MLE value is compared to CW case. It is shown that the adoption of chaos theory, MLE computation, can be used as a measurement standard to prove the validity of the solutions to prevent the unexpected chaotic behavior of weld through this work.
여성들에 있어서 Bench Stepping 운동 프로그램이 내분비계 대사에 미치는 영향
조정호(Cho Jung-Ho),이지현(Lee Ji-Hyun) 한국체육과학회 2000 한국체육과학회지 Vol.9 No.2
The purpose of this study was to examine the effect of 8 week bench stepping exercise on epinephrine, norepinephrine, cortisol, glucagon, and insulin in college female. Twelve study subject were participated in this study andbench stepping was performed 3 times per week and the duration of exercise was increased by 2 minutes every week, and the height of bench was also increased by 5 ㎝ every other week. Therefore, the intensity of the exercise was increased gradually but the cadence was constant as 28 times per minute. Blood sampling was performed in the morning(9-11 AM) after an overnight fast and the sampled blood were analyzed by HPLC analysis and competitive RIA method using HPLC (system by BIO-RAD) and δ -counter (COBRA 5010 Quantum, COBRA 5010 Ⅱ) respectively. SPSS statistic program was used to manage the experiment data and t-test was used for analysis of significant difference of the hypothesis. The result of 8 week bench stepping exercise showed that there was no significant difference on cortisol and insulin although epinephrine, norepinephrine, and glucagon showed significant difference between pre-exercise and post-exercise(p<.05). In conclusion, 8 week bench stepping exercise has a positive effect on endocrine metabolism in females. Further studies considering the age, the condition of fitness and body compositionare recommended.
비이상적 상거동을 보이는 이성분계 혼합물의 기액 상평형 추산을 위한 상태방정식과 액체 활동도계수 모델 사이의 비교연구
조정호(Cho, Jung-Ho),이지환(Lee, Ji-Hwan) 한국산학기술학회 2010 한국산학기술학회논문지 Vol.11 No.5
본 연구에서는 최대 공비점 압력을 가지는 에탄올과 벤젠 이성분계 혼합물의 기액 상평형 추산을 위하여 상태방정식 모델식과 액체활동도계수 모델식 사이의 비교 연구를 수행하였다. 상태방정식 모델식으로는 Peng- Robinson (PR) 상태방정식을 이용하였으며, Panagiotopoulos 혼합규칙(PRP)을 적용하였다. 한편, 액체 활동도계수 모 델식으로는 Renon이 제안한 NRTL 액체 활동도계수 모델식을 이용하였다. PRP 모델식은 2개의 매개변수를 가짐에 도 불구하고 3개의 매개변수를 가지는 NRTL 모델식에 비하여 에탄올-벤젠 이성분계에 대해서 저압 영역에서는 유 사한 정확성을 고압 영역에서는 좀 더 정확성이 우수함을 확인하였다. In this study, a comparative study was performed to predict the vapor-liquid equilibria with maximum azeotropic pressure for ethanol-benzene binary system between an equation of state model and a liquid activity coefficient model. Peng-Robinson equation of state model with a Panatiotopoulos mixing rules (PRP) was used and NRTL liquid activity coefficient model proposed by Renon was selected. The PRP model, even though it has only two binary adjustable parameters, was not inferior to the NRTL model to predict vapor-liquid equilibria for low pressure region of ethanol-benzene system and showed a better prediction capability for high pressure region of ethanol-benzene system than the NRTL model with three binary interaction parameters.
천연가스 액화를 위한 캐스케이드 냉동사이클의 전산모사에 대한 연구 [2]
조정호(Cho, Jung-Ho),김유미(Kim, Yoo-Mi) 한국산학기술학회 2011 한국산학기술학회논문지 Vol.12 No.2
본 논문에서는 천연가스를 액화시키기 위해서 프로판, 에틸렌 및 메탄 냉매를 이용한 다단 캐스케이드 냉동 사이클에 대한 전산모사를 PRO/II with PROVISION 8.3에 내장되어 있는 Peng-Robinson 상태방정식을 활용하여 수행 하였다. 천연가스의 조성은 한국가스공사로부터 제공받은 것을 적용하였으며, 유량은 연간 500만톤으로 가정하였다. 프로판 냉매의 공급온도는 -40˚C로, 에틸렌 냉매의 공급온도는 -95˚C로 메탄 냉매의 공급온도는 -155˚C로 각각 정하 였으며, 천연가스와 각각의 냉매의 최소 접근온도는 3˚C로 정하였다. 다단 냉동을 위한 프로판 냉동 사이클은 3단 냉 동을 가정하였으며, 에틸렌 냉동 사이클은 2단 냉동을 그리고 메탄 냉동 사이클은 3단 냉동을 가정하였다. 메탄 냉매 에 의해서 -152˚C까지 냉각된 천연가스는 줄-톰슨 팽창에 의해서 -162˚C까지 냉각되어 액화가 일어나도록 하였다. 결 론적으로 캐스케이드 냉동 사이클과 줄-톰슨 팽창을 통한 천연가스의 액화율은 몰 비로 91.71%이며, 액화천연가스 1.0 kg/hr당 0.433 kW의 압축 일이 필요함을 알 수 있었다. In this paper, simulation works for a multi-stage cascade refrigeration cycle using propane, ethylene and methane as refrigerants have been performed for the liquefaction of natural gas using Peng-Robinson equation of state built-in PRO/II with PROVISION release 8.3. The natural gas feed compositions were supplied from Korea Gas Corporation and the flow rate was assumed to be 5.0 million tons per annual. Supply temperature for propane refrigerant was fixed as -40˚C, that for ethylene refrigerant as -95˚C, and that for methane refrigerant as -155˚C. For the multi-stage refrigeration cycle, three-stage refrigeration was assumed for propane refrigeration cycle, two-stage refrigeration for ethylene refrigeration cycle and three-stage refrigeration for methane refrigeration cycle. Natural gas was finally cooled and liquefied to -162˚C by Joule-Thomson expansion. Conclusively, 91.71% by mole of the natural gas liquefaction ratio was obtained through a cascade refrigeration cycle and Joule-Thomson expansion and 0.433 kW of compression power was consumed for the liquefaction of 1.0 kg/hr of natural gas.