• 대한산업공학회지
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• 제34권4호
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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.

• 한국세라믹학회지
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• 제36권8호
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• pp.871-875
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• 1999

Theoretical equation to calculate thermal fatigue life was derived in which slow crack growth theory was adopted. The equation is function of crack growth exponent n. Cyclic thermal fatigue tests were performed at temperature difference of 175, 187 and 200$^{\circ}C$ respectively. At each temperature difference critical thermal fatigue life cycles of the alumina ceramics were 180,37 and 7 cycles. And theoretical thermal fatigue life cycles were calculated as 172, 35 and 7 cycles at the same temperature difference conditions. Therefore thermal fatigue behavior of alumina ceramics can be represented by derived equation. Also theoretical single cycle critical thermal shock temperature difference can be calculated by this equation and the result was consistent with the experimental result well.

• Tribology and Lubricants
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• 제15권4호
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• pp.328-334
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• 1999

Acoustic emission (AE) sensor was used to evaluate the wear-life of CrN-coated steel disks with 1 $\mu\textrm{m}$ and 4 $\mu\textrm{m}$ coating thickness. The relationship between Af and friction signal from scratch test and sliding test was investigated. The first spatting of CrN film was detected by AR signals in the early stage of coating failures, and overall failures by friction signals. Therefore, the conservative design for coating-life should be done using the results of AE signals. Using the percent contact load, the ratio of sliding normal load to the critical scratch load and the number of cycles to failure was measured to predict the wear-life of CrN film. On the wear-life dia-gram the percent contact loads and the number of cycles to failure showed a good linear relationship on the log coordinate. As the load percentage was decreased, the diagram showed that the wear-limits, at which the coated steels survived more than 35,000 cycles, were about 4∼5% of the critical scratch loads.

• 한국신뢰성학회지:신뢰성응용연구
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• 제14권4호
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• pp.230-235
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• 2014

The failure modes of pneumatic directional control valves include leakage, wear of the spool seal, and sticking of the spool. Among them, the main failure mode of the valve is leakage. The leakage is caused by the wear of the spool seal. However, due to the characteristics of the seal material, the leakage rate is fluctuated a lot rather than constantly increased over time. If life analysis is performed using the first time data of leakage failure, predicted life cycles can be different from the real life cycles. This paper predicts life cycles of the pilot pneumatic directional control valve based on the three point moving average which considers the average of the fluctuating leakage rate.

• 조명전기설비학회논문지
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• 제24권12호
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• pp.131-137
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• 2010

This paper considers and suggests the life cycle of the power equipments installed in buildings. The target equipments were divided into 5 groups by a couple of conditions, and a theoretical consideration and domestic foreign case studies were carried out. As a result, the most appropriate life cycles and monitoring periods were suggested for each group. The suggested results are expected to practically help the field electricians determine whether they have to replace the deteriorated equipments or not.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.378-384
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• 2000

This paper presents the results of the repeated sliding tests to determine the wear-life of TiN coated AISI 52100 bearing balls deposited by PVD method and to show the wear mechanisms of those. The sliding tests were carried out using a ball-on-disk tribometer under ambient conditions. The coefficient of friction, wear volume and the cycles to failures of TiN coated bearing balls were measured with different normal loads and roughness of lower specimens. On the wear-life diagram, the normal loads and the cycles to failure showed the good linear relation on log-log coordinate. With a decreasing normal load, the diagram showed that the wear-limits, at which the coated bearing balls survived more than 4000cycles were under 0.1N of the normal load.

• 한국축산식품학회지
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• 제40권6호
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• pp.969-979
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• 2020

Fresh grass carp was used to produce surimi and 50 g/kg, 100 g/kg, or 150 g/kg pork back fat was added. The water distribution, thiobarbituric acid reactive substances (TBARS), myoglobin oxidation, color parameter (L*, a*, and b*), heme and non-heme iron content of samples were determined to analyze the effects of different fat content on the oxidation of myoglobin and lipids during multiple freeze-thaw cycles of grass carp surimi. Both multiple freeze-thaw cycles and increased fat content lead to an increase in TBARS, a blue shift in the absorption peak of myoglobin porphyrin, a decrease in heme iron content, and an increase of non-heme iron content. Repeated freeze-thaw caused a decrease in immobilised water content and L*, and caused an increase in a* and b*. Increased fat content caused an increase in immobilised water content, L* and a*, and caused a decrease in b*.

• 한국축산식품학회지
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• 제35권6호
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• pp.772-782
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• 2015

This study was performed to explore the deterioration of physicochemical quality of beef hind limb during frozen storage at −20℃, affected by repeated freeze-thaw cycles. The effects of three successive freeze-thaw cycles on beef hind limb were investigated comparing with unfrozen beef muscle for 80 d by keeping at −20±1℃. The freeze-thaw cycles were subjected to three thawing methods and carried out to select the best one on the basis of deterioration of physicochemical properties of beef. As the number of repeated freeze-thaw cycles increased, drip loss decreased and water holding capacity (WHC) increased (p<0.05) till two cycles and then decreased. Cooking loss increased in cycle one and three but decreased in cycle two. Moreover, drip loss, WHC and cooking loss affected (p<0.05) by thawing methods within the cycles. However, pH value decreased (p<0.05), but peroxide value (p<0.05), free fatty acids value (p<0.05) and TBARS value increased (p<0.05) significantly as the number of repeated freeze-thaw cycles increased. Moreover, significant (p<0.05) interactive effects were found among the thawing methods and repeated cycles. As a result, freeze-thaw cycles affected the physicochemical quality of beef muscle, causing the degradation of its quality.

• 아동학회지
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• 제33권4호
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• pp.69-89
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• 2012

The purpose of this study was to examine the differences in maternal perceptions of mothers in regards to the conditions of happiness across the life-cycles of their children. The participants consisted of a total of 961 women who were the mothers of preschool children, school aged children, and adolescents. The mothers completed a questionnaire on the perceptions of the conditions of happiness which consisted of a total of 56 items. The results of this study revealed that mothers in their 20's and 30's, with high levels of education, and on high incomes were more likely to have high expectations regarding most of the conditions of happiness compared to mothers in their 40's and 50's, with lower levels of education, and on low incomes. In addition, the results further revealed that mothers perceived that 'children grow up well and healthy' as being the most important factor in their happiness regardless of the life cycles of their children. In particular, mothers with younger children tended to give greater priority to a close mother-child relationship in their happiness. However, when mothers' demographic variables were controlled, there were no differences in maternal perceptions of the conditions of happiness across the life-cycles of their children. The implications of parent education and the directions of following research were also discussed.

• Structural Engineering and Mechanics
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• 제35권6호
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• pp.659-676
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• 2010

An energy-based fatigue life prediction framework was previously developed by the authors for prediction of axial and bending fatigue life at various stress ratios. The framework for the prediction of fatigue life via energy analysis was based on a new constitutive law, which states the following: the amount of energy required to fracture a material is constant. In this study, the energy expressions that construct the new constitutive law are integrated into minimum potential energy formulation to develop new finite elements for uniaxial and bending fatigue life prediction. The comparison of finite element method (FEM) results to existing experimental fatigue data, verifies the new finite elements for fatigue life prediction. The final output of this finite element analysis is in the form of number of cycles to failure for each element in ascending or descending order. Therefore, the new finite element framework can provide the number of cycles to failure for each element in structural components. The performance of the fatigue finite elements is demonstrated by the fatigue life predictions from Al6061-T6 aluminum and Ti-6Al-4V. Results are compared with experimental results and analytical predictions.