• 한국자동차공학회논문집
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• 제10권2호
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• pp.73-79
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• 2002

The NO emissions at the exhaust manifo1d were investigated with a fast NO analyzer to investigate the cycle-by-cycle variations on NO emissions level and the dependence of NO emissions on combustion. The measurement was performed with a part load condition with respect to the mixture ratios and the changes in loads at 1800rpm. The averaged values were obtained during 200 cycles. We found that there is characteristic pattern in 70 emissions from exhaust port and it was possible to set a representative value with the data sampled during specific period. As the load increased, the characteristics of NO emissions were more dependent on combustion pressures. It was also analyzed that the correlation between combustion pressures and NO emissions for different equivalence ratios tends to increase as the mixture goes leaner, Furthermore, this correlation for the lean mixture near the lean limit seemed to be kept.

• Journal of Mechanical Science and Technology
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• 제17권10호
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• pp.1563-1571
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• 2003

A fast response NO analyzer was applied to investigate the relation between cycle-by-cycle NO emissions and combustion chamber pressure. NO emissions were sampled at an isolated exhaust manifold of 4-stroke spark ignition engine to avoid the interference of exhaust gas from other cylinders. The linear correlation analysis was performed with collected data of NO emissions and combustion chamber pressure with respect to the various air-fuel mixture ratios and engine loads. The sampled data sets were obtained during 200 cycles at each operating condition. The results showed that there was a typical pattern in NO emissions from an exhaust port through a cycle. It was possible to set a block of crank angle in which the linear correlation coefficient between NO emissions and combustion chamber pressure was high. As the engine load increased, NO emissions were more dependent on combustion chamber pressure after TDC. It was also analyzed that the correlation between two parameters with respect to air-fuel mixture ratio tended to increase as mixture went leaner. Furthermore, this correlation coefficient for the mixture near the lean limit seemed to be kept high even though combustion was unstable.

• Journal of Advanced Marine Engineering and Technology
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• 제22권6호
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• pp.782-791
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• 1998

This paper presents a computer simulation of five types of triple effect absorption cycles employ-ing the refrigerant absorbent combinations of NH3/LiNO3 low-pressure type NH3/LiNO3+H2O/LiBr binary two-stage type series flow cycle and two types of parallel flow cycle for H2O/LiBr. The absorption systems is investigated through cycle simulation to obtain the system characteristics with the cooling water inlet temperature approach temperature of absorber loss temperature of absorber and chilled water outlet temperature. The most important characteristic temperature of absorber and chilled water outlet temperature. The most important characteristic of NH3/LiNO3 low-pressure type and a NH3/LINO3+H2O/LiBr binary two-stage type is that it obtains a coefficient of performance higher than the sum of the performance coefficients of its part operating independently. As a result of this analysis the optimum designs and operating conditions were determined based on the operating conditions and the coefficient of performance.

• 한국자동차공학회논문집
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• 제10권5호
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• pp.35-44
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• 2002

Engine cycle simulation using a two-zone model was performed to investigate the effect of the engine parameters on NO and soot emissions in a DI diesel engine. The present model was validated against measurements in terms of cylinder pressure, BMEP, NO emission data with a 2902cc turbocharger/intercooler DI diesel engine. Calculations were made for a wide range of the engine parameters, such as injection timing, ignition delay, Intake air pressure, inlet air temperature, compression ratio, EGR. This parametric study indicated that NO and soot emissions were effectively decreased by increasing intake air pressure, decreasing inlet air temperature and increasing compression ratio. By retarding injection timing, increasing ignition delay and applying EGR. NO emission was effectively reduced, but the soot emission was increased.

• 설비공학논문집
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• 제5권3호
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• pp.198-206
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• 1993

Experimental results of two stage Gifford-McMahon cryorefrigerator are described. In-prototype experiments, drive mechanism is Scotch Yoke type driven by stepping motor, copper meshes and lead balls are used for regenerator's materials in the first stage and the second stage, respectively. To find optimal conditions of the cryopump, no load temperature and refrigeration capacity according to the variation of cycle frequency and operating pressure are measured, and the cool down and load characteristics at particular cycle frequencies are presented. In general, as the cycle frequency is lowered, no load temperature is dropped but refrigeration capacity is diminished. As the representative result, in a case that the cycle frequency is 70rpm and steady state pressure is 14 atm, no load temperature of second stage is lowered to 10.5K in 55 minuters, and in this situation the refrigeration capacity of the first stage is 42W at 80K, that of the second stage is 11 W at 20K.

• Journal of Advanced Marine Engineering and Technology
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• 제26권6호
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• pp.679-687
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• 2002

In this study, a cycle simulation using a two-zone model is carried out to investigate the effect of intake charging conditions such as oxygen concentration, temperature and pressure on NO emissions in a DI diesel engine. The model is validated against measurements in terms of cylinder pressure, torque, BSFC and NOx emissions with 2902 cc DI diesel engine. Calculated results can be summarized as follows. The oxygen concentration in the intake charge is decreased with increasing of EGR rate and equivalence ratio. As the intake oxygen concentration is reduced, the combustion pressure and the burned gas temperature decrease and, as a result, NO formation decreases. Also, the results show that as the intake pressure increases and the intake temperature decreases, NO emissions are effectively reduced.

• 아동학회지
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• 제33권3호
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• pp.131-148
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• 2012

This study examines the scientific concept development of young children in terms of the day-night cycle. The subjects consisted of 180 three-, four-, and five-year-old children from two kindergartens and one children's center located in Seoul and Jeju. Individual interviews were conducted to collect verbal and pictorial responses on the day-night cycle. The scientific concepts on the day-night cycle are classified five stages including : no recognition, egocentric concept, initial mental models, synthetic mental models, and scientific mental models. Using two-way ANOVA, scores for the types of concept on the day-night cycles were then analyzed according to both the ages and genders of the children. The results reveal the existence of significant differences in terms of the types of concept of young children according to age. Most three-year-olds children had no recognition. Most three, four, and five-year-old children revealed egocentric concepts. Four-year-old children revealed that were in the initial stages of experiencing the mental models and synthetic mental models of the day-night cycle. Five-year-old children revealed that they were in the early stages of experiencing the initial, synthetic, scientific mental models of the day-night cycle. The results suggest appropriate ways of science education for young children based on the development of scientific concepts of the day-night cycle.

• 동아시아경상학회지
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• 제2권4호
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• pp.26-47
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• 2014

The paper examined effect of age cohort on life cycle financial planning. A total of 990 questionnaires were distributed with a 55.2% return rate. Seven hypotheses were analysed using hierarchical and ordinary regression analysis. The results revealed that age cohort variables made significant contribution to life cycle financial planning as well as personal orientation towards retirement planning, particularly the younger age cohort. Age cohorts do affect personal orientation towards retirement planning with the confidence level making a significant impact. Current financial resources do have a strong positive impact on consumption for all age cohorts. On the other hand, no significant effect was found between age cohorts and current financial resources but older age cohorts were relatively more significant predictors. The implication was that not only should their individual perceptions of financial planning become an increasingly important part of people's long-term commitment throughout their life-cycle, it must also assume the role as a self-directed life-long learning process, in view of the ever-changing and complicated financial environment.

• Clinical and Experimental Reproductive Medicine
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• 제20권2호
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• pp.131-135
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• 1993

The ultrasonographic examination with vaginal probe(5MHz) was undertaken in 101 patients at infertility clinic of Eul-Ji General Hospital. This study was performed to evaluate the number of mature follicles per menstrual cycle, the relationship of both ovaries for consecutive ovulatory cycle and the responsiveness of follicular growth followed by administration of ovulation inductant. The results were as follows; 1. The ovulation induction group with clomiphene citrate showed more follicles than natural menstrual cycle group. 2. Each means of numbers of follicles between ovaries showed no difference between natural and ovulatory induction groups. 3. The rate of follicular growth per one menstrual cycle showed higher in the clomiphene citrate induced cycle group. 4. Clomiphene citrate induced group tends to be easier for multiple follicular growth but had no significant difference in statistics. 5. The ipsilateral Vs. contralateral follicular growth rate for consecutive menstrual cycles in both ovaries showed no significant difference between two groups.

• International Journal of Quality Innovation
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• 제9권3호
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• pp.71-91
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• 2008

The definition of cycle time is the time from the wafer start to the wafer output. It usually takes one or two months to get the product since customer decides to produce it. The cycle time is a critical factor for customer satisfaction because it represents the response time to the market. Long cycle time reflects the ineffective investment for the capital. The cycle time is very important for foundry because long cycle time will cause customer unsatisfied and the order loss. Consequently, all of the foundries put lots of human source in the cycle time improvement. Usually, we make decisions based on the experience in the cycle time management. We have no mechanism or theory for cycle time management. We do work-in-process (WIP) management based on turn rate and standard WIP (STD WIP) set by experiences. But the experience didn't mean the optimal solution, when the situation changed, the cycle time or the standard WIP will also be changed. The experience will not always be applicable. If we only have the experience and no mechanism, management will not be work out. After interview several foundry fab managers, all of the fab can't reflect the situation. That is, all of them will have an impact period after product mix or utilization varied. In this study, we want to develop a formula for standard WIP and use statistical process control (SPC) concept to set WIP upper/lower limit level. When WIP exceed the limit level, it will trigger action plans to compensate WIP Profile. If WIP Profile balances, we don't need too much WIP. So WIP level could be reduced and cycle time also could be reduced.