• Elastomers and Composites
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• v.56 no.3
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• pp.124-135
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• 2021

Evaluating service lives of rubber materials at certain temperatures requires a destructive method (typically using elongation at break). In this study, a non-destructive method based on hardness change rate was proposed for evaluating the service life of chloroprene rubber (CR). Compared to the destructive method, this non-destructive method ensures homogeneity of CR specimens and requires a small number of samples. Thermal accelerated degradation test was conducted on the CR specimens at 55, 70, 85, 100, and 125℃, and the tensile strength, elongation at break, and hardness were measured. The results of the experiment were compared to those of the accelerated life evaluation method proposed in this study. Comparing the analyzed lives in the high temperature region (70, 85, 100, and 125℃), the difference between the service lives for the destructive method (using the elongation at break) and non-destructive method (using the hardness) was approximately 0.1 year. Therefore, it was confirmed that the proposed non-destructive evaluation method based on hardness changes can evaluate the actual life of CR under thermally accelerated degradation conditions.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.170-171
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• 2021

Experts predict that even after the COVID-19 virus is completely over, it will be difficult to return to the pre-COVID state. As the non-face-to-face trend continued due to the prolonged COVID-19 crisis, sports activities were contracted and the amount of exercise of the people decreased. Demand for non-face-to-face services is increasing as the use of multi-use facilities is gradually restricted due to the higher level of social distancing. This study examines the actual conditions of participation in life sports and considers ways to revitalize sports for life suitable for the post-corona.

• Food Science of Animal Resources
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• v.34 no.2
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• pp.245-251
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• 2014

The aim of this study was to estimate the shelf life of butter and cheese products, with shelf life being a guide used to determine the storage period of food before deterioration. Butter and cheese samples stored at $10^{\circ}C$ and $15^{\circ}C$ had a shelf life of 221 d, while those stored at $25^{\circ}C$ and $35^{\circ}C$ had a shelf life of 109 d. Quality changes, including total cell count, coliform counts, Listeria monocytogenes counts, acid value, moisture content, pH, acidity and overall sensory evaluation, were monitored. In order to pass the overall sensory evaluation, a quality score of 5 points on a 9-point scale was required. For other quality criteria, legal quality limits were established based on the "Process Criteria and Ingredient Standard of Livestock Products" by the Animal, Plant and Fisheries Quarantine and Inspection Agency (Republic of Korea). The nonlegal quality limit was estimated by regression analysis between non-quality criteria (y) and overall sensory evaluation (x). The shelf life was estimated based on the number of days that the product passed the quality limit of the quality criteria. The shelf life of samples stored at $10^{\circ}C$, $15^{\circ}C$, $25^{\circ}C$ and $35^{\circ}C$ was 21.94, 17.18, 6.10 and 0.58 mon, respectively, for butter and 10.81, 9.47, 4.64 and 0.20 mon, respectively, for cheese.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.4
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• pp.393-400
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• 2011

In this study, a procedure for the inverse estimation of the fatigue life parameters of springs which utilize the field fatigue life test data is proposed to replace real test with the FEA on fatigue life prediction. The Bayesian approach is employed, in which the posterior distributions of the parameters are determined conditional on the accumulated life data that are routinely obtained from the regular tests. In order to obtain the accurate samples from the distributions, the Markov chain Monte Carlo (MCMC) technique is employed. The distributions of the parameters are used in the FEA for predicting the fatigue life in the form of a predictive interval. The results show that the actual fatigue life data are found well within the posterior predictive distributions.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.153-159
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• 2018

Many researches have been carried out on carbonation, a representative deterioration in underground structure. The carbonation of RC (Reinforced Concrete) structure can cause steel corrosion through pH drop in concrete pore water. However extension of service life in RC structures can be obtained through simple surface protection. Unlike the conventional deterministic maintenance technique, probabilistic technique can consider a variation of service life but it deals with only normal distributions. In the work, life time-probability distributions considering not only normal but also log distributions are induced, and repair cost estimation technique is proposed based on the induced model. The proposed technique can evaluate the repair cost through probabilistic manner regardless of normal or log distribution from initial service life and extended service life with repair. When the extended service life through repair has log distribution, repair cost is effectively reduced. The more reasonable maintenance strategy can be set up though actual determination of life-probability distribution based on long term tests and field investigations.

• Journal of Aerospace System Engineering
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• v.17 no.2
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• pp.62-70
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• 2023

We proposed a technique for predicting Stress-Life (S-N) curve or fatigue life using geometric features of a ply-overlap joint structure in which plies of two composite materials are partially or wholly laminated and bonded. Geometric features that could affect fatigue properties of a structure were selected as variables. By analyzing relationships between geometric variables and material constants of the Epaarachchi-Clausen model, a fatigue model for composites, relational expressions of these two factors were proposed. To verify the prediction accuracy of the proposed method, fatigue life of a CFRP/GFRP ply-overlap joint was predicted. Predicted life and life obtained by test data-based model were compared to actual life. High prediction accuracy was confirmed by calculating the coefficient of determination of the predicted S-N curve.

• Journal of the Korean Home Economics Association
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• v.40 no.8
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• pp.23-36
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• 2002

The purpose of this study is to analyze the actual condition of labor during the marriage by estimating the total labor-time of husband and wife and to prove the contribution of labor-time to household. The statistical life-time research data of Bureau of Statistics were used to prove the overwork of wives compared with husbands during the marriage. The result of the study can help to prove the wife's contribution of labor-time to household.

• Journal of the Korean Data and Information Science Society
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• v.8 no.2
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• pp.119-125
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• 1997

We handle the stochastic processes of independent and identically distributed random variables. But random variables are usually dependent among themselves in actual life. So in this paper, we find out a new process not satisfying Markov property. We investigate the probability mass functions and study on the probability of the first-passage time. Also we find out the average frequency of continuous successes in from 0 to n time.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.161-162
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• 2002

Field of enantioseparations represents one of the actual topics of chemistry. Significant, in some cases dramatic differences in a desired activity as well as in toxic properties of enantiomers of chiral drugs, food additives, agrochemicals, cosmetic products, etc. represents a driving force in this field. The enantiomers of all chiral bioactive compounds have to be isolated and to be tested. Besides the ethical or environmental reasons for developing single enantiomers, it may be a real therapeutic benefit and in some cases, it has been used as a strategy for extending patent life. (omitted)

• Proceedings of the CALSEC Conference
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• 2001.08a
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• pp.597-614
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• 2001

Level 0: The Marekting Buzzword : □Confusion between DMU and Visualization □Having a Mobile Data Viewer/Analyser is Anyway a Prerequisite Level 1: Digital Pre-Assembly (DPA): □Building Digital Prototype before Physical Build □Usually a job for Packaging or Prototype Teams □Usually no time Left to take Feed-back into account before Actual Build Level 2: Design in Context: □All Designers within Car Maker do Local DMU before DPA Level 3: Design in Extended Context □Design in Context Expanded to Suppliers(omitted)