• Journal of the Korean Society for Heat Treatment
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• v.4 no.3
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• pp.31-38
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• 1991

Effect of thermal cycling on shape memory effect and stabilization of austenite was investigated in Fe-21%Mn alloy. The thermal cyclic treatment was carried out with two types, room temperature${\leftrightarrow}215^{\circ}C$ and room temperature${\leftrightarrow}260^{\circ}C$. In case of the room temperature${\leftrightarrow}215^{\circ}C$, the SME was rapidly increased up to 3 cycles and maintained nearly constant value regardless of further cycles. In case of the room temperature${\leftrightarrow}260^{\circ}C$, however, the SME was increased with increasing the thermal cycle up to 5 cycles and decreased gradually with further cycle. The variation of the ${\varepsilon}$ martensite volume pet with the thermal cycle was in good agreement with the variation of the SME. Therefore, the change of the SME due to the cyclic treatment was explained with the change of the ${\varepsilon}$ martensite content. As the thermal cycle was increased, the $M_s$ temperature was decreased, and the $A_s$ and $A_f$ temperatures were increased, respectively.

• Membrane Journal
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• v.21 no.1
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• pp.13-21
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• 2011

This study investigated the fouling behavior of $Al_2O_3$ colloids on polyethylene microfiltration membrane. To examine the effect of operation variation on fouling, operating pressure was increased from 0.49 to 1.96 bar along with time elapses and then was reduced to 0.49 bar reversely. A hysteresis behavior was observed in the membrane permeate flux over pressure, revealing different fluxes at the same pressure according to the pressure control type, increasing and decreasing. Permeate resistance and its rate of increase was higher in the decreasing pressure cycle than in the increasing pressure cycle. At the initial period of filtration, fouling mechanism for the both cycles was governed by the cake filtration. The degree of fouling was higher in the decreasing pressure cycle compared with in the increasing pressure cycle.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1631-1637
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• 2018

Electric utilities has been considered the necessity to introduce asset management of electric power facilities in order to reduce maintenance cost of existing facilities and to maximize profit. This paper aims to provide data that can helpful to make profitable decision in terms of power transformers which have a significant part in the power system. Therefore, this study is modeling input cost for power transformer during its entire life and also the life cycle cost (LCC) technique is applied. In particular, the variation of transformer state related with maintenance and the variation of the EUAC curve based on cost and effect of maintenance is examined. In this study, the trend of the equivalent uniform annual cost (EUAC) according to maintenance cycle and cost of equipment is analyzed. In line with that, sensitivity analysis influenced by the changes of other cost factors was performed.

• Proceedings of the KSLP Conference
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• 1996.11a
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• pp.92-92
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• 1996

비디오스트로보스코피 화상의 정량화를 통한 glottal cycle의 객관적인 평가는 여러 질환의 감별 및 치료전후의 결과를 비교하는데 중요한 역할을 담당할 수 있으리라 사려되나 아직은 정상 발성시나 병적인 조건에서의 참고치나 그 의미에 대하여 보고된 경우는 흔치 않은 실정이다. 이에 저자들은 정상성인을 대상으로 발성의 주파수와 강도의 변화에 따른 glottal cycle의 변화를 정량화 함으로써 추후 연구나 임상적용 둥의 기본자료로서 활용하고자 하였다. (중략)

• Journal of Power System Engineering
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• v.20 no.1
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• pp.11-17
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• 2016

In this study, the simulation for performance comparison between basic single stage organic rankine cycle, multi stage reheater cycle and multi stage reheater & recuperator cycle was carried out. The multi stage reheater cycle and multi stage reheater & recuperator cycle was designed to improve the efficiency for organic rankine cycle using heat source from industrial waste heat and heat sink from deep ocean water. R245fa was selected as a refrigerant for the cycle and system efficiencies were simulated by the variation of the heat sink temperature and the cycle classification. Performance characteristics were simulated by using the Aspen HYSYS. It was confirmed that the system efficiency was decreased by the increase of heat sink temperature. These results can be considered to be applied as geo-ocean thermal energy conversion in where plenty of geothermal or ocean thermal resource exist.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.55-59
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• 2004

In this study, the required life cycle cost is evaluated in consideration of the equipment's availability during its lift cycle. In order to meet the maximum availability required by the process, the failure cost and life cycle cost is assessed The optimal equipment selection method is presented according to the analysis of the failure cost and life cycle cost. For the systems in which equipments are connected serially, the optimal equipments are selected by minimizing the life cycle cost and satisfying the required system availability goal. In addition, the selection methods and lift cycle cost are analyzed according to the cost variation of the equipment. By using the life cycle evaluation procedure, the failure cost and maintenance cost needed during the life cycle of the equipment can be presented.

• Journal of Korean Institute of Industrial Engineers
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• v.34 no.4
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• pp.386-397
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• 2008

Due to the rapid advancement of technologies, a growing number of innovative products with a short life-cycle have been introduced to the market. As the life-cycles of such products are shorter than those of durable goods, the demand variation during the life-cycle adds to the difficulty of inventory management. Traditional inventory planning models and techniques mostly deal with products that have long life-cycles. The assumptions on the demand pattern and subsequent solution approaches are generally, not suitable for dealing with products with short life-cycles. In this research, inventory replenishment problems based on the logistic demand model are formulated and solved to facilitate the management of products with short life-cycles. An extended Wagner- Whitin approach is used to determine the replenishment cycle, schedules and lot-sizes.

• Journal of The Korean Astronomical Society
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• v.44 no.3
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• pp.97-108
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• 2011

The photometric light curves of the W-type W UMa eclipsing contact binary system BB Pegasi have been found to be extremely asymmetric over all the observed 63 years in all wavelengths UBVR. The light curves have been characterized by occultation primary minima. Hence, the morphology of these light curves has been studied in view of these different asymmetric degrees. The system shows a distinct O'Connell effect, as well as depth variation. A 22.96 years of stellar dark spots cycle has been determined for the system. Almost the same cycle (22.78 yr) has been found for the depth variation of MinI and MinII. We also present an analysis of mid-eclipse time measurements of BB Peg. The analysis indicates a period decrement of $5.62{\times}10^{-8}$ day/yr, which can be interpreted in terms of mass transfer at a rate of $-4.38{\times}10^{-8}M_{\odot}$/yr, from the more to the less massive component. The O - C diagram shows a damping sine wave covering two different cycles of 17.0 yr and 12.87 yr with amplitudes equal to 0.0071 and 0.0013 day, respectively. These unequal durations show a non-periodicity which may be explained as a result of magnetic activity cycling variations due to star spots. The obtained characteristics are consistent with similar chromospherically active stars, when applying the Applegate's (1992) mechanism.

• Journal of Korea Foundry Society
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• v.31 no.4
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• pp.198-204
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• 2011

The present study was aimed to investigate the dependence of fatigue property on microporosity variation of low-pressure die-cast (LPDC) A356 alloy. The fatigue property of A356 alloy was evaluated through high cycle fatigue test, and the microporosity-terms used were the fractographic porosity measured from SEM observation on fractured surface and the volumetric porosity obtained through the density measurement using Archimedes's principle. The number of cycles to failure of A356 alloys depends obviously upon the variation of fractographic porosity, and can describe in terms of the defect susceptibility which depends on the microporosity variation at a given value of stress amplitude. The modified Basquin's equation was suggested through the combination of microporosity variation and static maximum tensile stress to fatigue strength coefficient. Using modified Basquin's equation, it could suggest that the maximum values of fatigue strength coefficient and exponent achievable in defect-free condition of A356 alloy are 265 MPa, -0.07, respectively.

• Journal of Applied Biological Chemistry
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• v.51 no.6
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• pp.262-271
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• 2008

Natural abundances of stable isotopes of nitrogen and carbon (${\delta}^{15}N$ and ${\delta}^{13}C$) are being widely used to study N and C cycle processes in plant and soil systems. Variations in ${\delta}^{15}N$ of the soil and the plant reflect the potentially variable isotope signature of the external N sources and the isotope fractionation during the N cycle process. $N_2$ fixation and N fertilizer supply the nitrogen, whose ${\delta}^{15}N$ is close to 0%o, whereas the compost as. an organic input generally provides the nitrogen enriched in $^{15}N$ compared to the atmospheric $N_2$. The isotope fractionation during the N cycle process decreases the ${\delta}^{15}N$ of the substrate and increases the ${\delta}^{15}N$ of the product. N transformations such as N mineralization, nitrification, denitrification, assimilation, and the $NH_3$ volatilization have a specific isotope fractionation factor (${\alpha}$) for each N process. Variation in the ${\delta}^{13}C$ of plants reflects the photosynthetic type of plant, which affects the isotope fractionation during photosynthesis. The ${\delta}^{13}C$ of C3 plant is significantly lower than, whereas the ${\delta}^{13}C$ of C4 plant is similar to that of the atmospheric $CO_2$. Variation in the isotope fractionation of carbon and nitrogen can be observed under different environmental conditions. The effect of environmental factors on the stomatal conductance and the carboxylation rate affects the carbon isotope fractionation during photosynthesis. Changes in the environmental factors such as temperature and salt concentration affect the nitrogen isotope fractionation during the N cycle processes; however, the mechanism of variation in the nitrogen isotope fractionation has not been studied as much as that in the carbon isotope fractionation. Isotope fractionation factors of carbon and nitrogen could be the integrated factors for interpreting the effects of the environmental factors on plants and soils.