• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.791-798
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• 2004

Fatigue crack initiation lives of round cylindrical notch specimen were investigated. Firstly, local strain approximation methods, such as the modified incremental Neuber's rule and the modified incremental Glinka's equivalent strain energy density(ESED) rule, were used to get multiaxial stress and strain state components at the notch tip. Based on the history of local stress and strain, multiaxial fatigue models were used to obtain fatigue crack initiation lives. Because the solution of Neuber's rule and Glinka's ESED rule make the upper and lower bound of local strain approximations, fatigue crack initiation lives are expected to place between life predictions by two local strain approximations. Experimental data were compared with the fatigue crack initiation life prediction results.

• International Journal of Korean Welding Society
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• v.3 no.1
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• pp.51-56
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• 2003

It is important to evaluate the fracture initiation behaviors of steel structure. It has been well known that the ductile cracking of steel would be accelerated by triaxial stress state. Recently, the characteristics of critical crack initiation of steels are quantitatively estimated using the two-parameters, that is, equivalent plastic strain and stress triaxiality, criterion. This study is paid to the fundamental clarification of the effect of notch radius, which can elevate plastic constraint due to heterogeneous plastic straining on critical condition to initiate ductile crack using two-parameters. Hense, the crack initiation testing were conducted under static loading using round bar specimens with circumferential notch. To evaluate the stress/strain state in the specimens was used thermal elastic-plastic FE-analysis. The result showed that equivalent plastic strain to initiate ductile crack expressed as a function of stress triaxiality obtained from the homogeneous specimens with circumferential notched under static loading. And it was evaluated that by using this two-parameters criterion, the critical crack initiation of homogeneous specimens under static loading.

• Journal of the Korean Society of Safety
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• v.6 no.2
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• pp.15-20
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• 1991

In this paper, we have investigated the effect of organic additives and prestressed D C. voltage on the impulse tree initiation in low density polyethylene. The five klnds of organic compounds was selected for the purpose of inhibiting tree initiation and 10 wt % of each additive was mixed in low density polyethylene. The positive or negative impulse voltage was applied after prestressed D.C. voltage was applied in order to investigate the effect of the space charge influenced on tree initiation. The lengths of tree initiation in case of belng same polarity between prestressed D.C. voltage and impulse voltage were longer than those in case of being different polarity between prestressed D.C. voltage and impulse voltage. When the polarity prestressed D.C. voltage was the different plarity of impulse voltage, the length of tree initiation increased with increasing the prestressed D.C. voltage and decreasing the rest time Among the organic additives used in this paper, the m-cresol can be shown to be the most effective inhibiter to tree initiation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.1
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• pp.82-86
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• 2018

Low voltage atmospheric plasma generation using DBD Initiation carrier injection is reported. DBD afterglow was used as initiation carriers prior to a primary discharge and a significant reduction in the breakdown voltage of atmospheric discharge was observed when sufficient initiation carriers were provided. Quantative correlation study between the breakdown voltage and the initiation carriers suggests that the atmospheric breakdown voltage reduces to only half of the breakdown voltage for Townsend regime. Also, use of DBD initiation carrier injection likely offers better device reliability by protecting electrodes with a dielectric layer and thus suppressing electrode wear.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.409-412
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• 2003

Fatigue strength. especially crack initiation behavior of high strength steel under marine water environment was investigated. Marine structures were usually constructed by lot of weld joints and were designed by basis of the fatigue strength of weld joints. This study was carried out to mini. The fatigue initiation behavior is more important rather than crack propagation behavior under the design of marine structures, because it is very difficult to find out the crack propagation phenomena and repair the damaged part of welded joints in sea water Then, the new configuration specimen for fatigue crack initiation tests was proposed. Using this new specimen, it is easy to carry out the crack initiation tests with relatively low cycling loading and clearly find out a crack initiation fatigue life.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.172-178
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• 2001

Using dislocation pileup theory, the near surface crack initiation life was calculated. The crack initiation life calculted in the previous study is not a real life strictly and just for the cracking in substrate. In this study, two life equations which can be applied for each near-surface and substrate were used for a comparative study. The downward tendency of life at near surface and substrate was similar and the crack initiation life at near-surface was much shorter than the life in substrate. The improvement of the crack initiation life equations which were proposed by W. Cheng was discussed.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.733-738
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• 2014

We propose a new approach called as a peak time approach for faster detection of step initiation for the lower limb exoskeleton. As faster detection of step initiation is an important criterion in evaluating the lower limb exoskeleton, many studies have investigated approaches to detect step initiation faster, including using electromyography, the center of pressure, the heel-off time and the toe-off time. In this study, we will utilize vertical ground reaction force events to detect step initiation, and compare our approach with prior approaches. Additionally, we will predict the first step's heel strike time with vertical ground reaction force events from multiple regression equations to support our approach. The lower limb exoskeleton should assist the operator's movement much faster and more reliably with our approach.

• Korean Journal of Plant Tissue Culture
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• v.21 no.2
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• pp.123-129
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• 1994

The potency of adventitious root initiation was investigated in relation with germination days and ike end of culture days healed with root induction medium on the initiation of adventitious roots from explants of soybean (Glycine max L.) cotyledon. Also, the changes in the pattern of protein profiles related with adventitious mot initiation have been examined by two-dimensional polyauyl-amide gel elecoophoresis during the germination and the initiation of adventitious roots. The potency of adventitious root initiation from germinated cotyledons was high after 4 days, and adventitious roots were initiated from after 4 days and very high after 6 days healed with mot induction medium There was a reproducible quantitative change in 34 specific protein spots during germination and adventitious root initiation. A necessary basic protein for adventitious root initiation with rotative molecular weight of 27 kD was induced during the germination. And three basic protein groups with relative molecular weight 22 kD, 23 kD and 33 kD, and two acidic protein groups with relative molecular weight 27kD and 29 kD were induced during the initiation of adventitious roots.

• Korean Journal of Schizophrenia Research
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• v.24 no.2
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• pp.60-67
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• 2021

Objectives: The optimal duration of maintenance treatment for patients with first-episode schizophrenia (FES) remains unclear. We examined the first antipsychotic treatment duration and its association with re-initiation of treatment using a nationwide claim database. Methods: Data from the Health Insurance Review and Assessment Service database in South Korea for 2007-2016 were used. Linear regression analysis and Cox proportional hazard models were used to evaluate the associations between the duration of the first antipsychotic treatment, time to re-initiation of treatment, and occurrence of treatment re-initiation. Results: Of 30,143 patients with FES, 80.4% (n=24,231) received <2 years of the first antipsychotic treatment. In patients who discontinued treatment (n=23,030), the rate of treatment re-initiation was 74.2% (n=17,086). As the duration of the first antipsychotic treatment increased, the time to re-initiation of treatment decreased (β=-0.146, p<0.001); however, the rate of treatment reinitiation was relatively constant (hazard ratio=1.001, p<0.001). Conclusion: Long-term antipsychotic treatment was not significantly associated with the rate of treatment re-initiation but showed a negative association with the time to re-initiation of treatment. Further research is needed to better understand the optimal treatment duration for FES.

• Journal of Korean Academy of Nursing
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• v.39 no.3
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• pp.376-385
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• 2009

Purpose: The purposes of this study were(a) to identify smoking behavior by following a cohort representative of the population of 4th grade elementary schoolers in South Korea over a four-year period(2004-2007), and(b) to explore predictors of smoking initiation among non-smokers in Wave 1. Methods: Secondary data, the Korea Youth Panel Study, was analyzed in this study. First, frequencies or percentages were calculated to identify smoking behavior(i.e., smoking initiation, smoking intensity, and smoking duration). Second, binary logistic regression analysis was performed to examine significant factors related to smoking initiation. Results: Smoking initiation and daily smoking were more pronounced when the participants entered middle school. In bivariate analysis, statistically significant predictors of smoking initiation were loneliness at school, self-control, delinquent behavior, depressive symptoms, and stress. However, after controlling for other factors, only a high level of risk-taking tendency and a greater number of delinquent behaviors remained statistically significant. Conclusion: Based on greater involvement in smoking among first-year middle schoolers, smoking prevention strategies should be provided to elementary schoolers rather than middle schoolers. A risk-taking tendency and delinquent behaviors should be considered as proxy measures to detect the high-risk group for smoking initiation.