• Journal of the Korean Society for Precision Engineering
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• v.3 no.3
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• pp.40-71
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• 1986

By developing a computer program for the systematic design of worm gears, the design formulae and tables of AGMA, JGMA, BS and DIN are analized and compared. The computer program can be used on micro-computers. According to the input data of the reduction ratio, the center distance. the driving torque and the material as design parameters, the program calculate the most efficient worm gear dimension. The variation of the design parameters and other empirical coefficients in case of resulting an inadequate design gear dimension can be easily modified throuth the way of interactive method between the user and the monitoring system of computer. A proposal of the standardization of worm gears was made in which a standard module according to the DIN 323 standard series number was applied. For the more exact and effective calculation of the stress concentration and the deformation of gear teeth, a computer program using the boundary element method is also developed. Even the strength of the special gear shape such as Niemann's "Cavex" gear can be calculated in a short CPU-time. The most effort of this study has been layed on the developing a computer program for the correction of a tooth profile and face width which is most important design factor for an exact and wide teeth contacts under loads, especially by great and wide gears. For this purpose were investigated the tooth stiffness, the mesh interferences and the kinematics and the dynamics of gear mesh. The deflection and the deformation of the gear shaft due to the loads acting on gear and shaft were aslo considered. Some examples have shown the sufficient good status of teeth contact in which the correction of the tooth profile and face width were accomplished due to the calculated results.d results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.3
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• pp.49-58
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• 2000

This paper deals with a systematic approach to neural network controller design for static VAR compensator (SVC) using a learning algorithm of error back propagation that accepts error and change of error as inputs, the momentum learning technique is used for reduction of learning time, to improve system stability. A SVC, one of the Flexible AC Transmission System(FACTS), constructed by a fixed capacitor(FC) and a thyristor controlled reactor(TCR), is designed and implemented to improve the damping of a synchronous generator, as well as controlling the system voltage.TO verify the robustness of the proposed method, we considered the dynamic response of generator rotor angle deviation, angular velocity deviation and generator terminal voltage by applying a power fluctuation and rotor angle fluctuation in initial point when heavy load and normal load. Thus, we prove the usefulness of proposed method to improve the stability of single machine-infinite bus with SVC system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.275-278
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• 2006

Systematic experiments in $CH_4/Air$ counterflow diffusion flames diluted with He have been undertaken to study the oscillatory instability in which lateral heat loss could be remarkable at low global strain rate. The oscillatory instability arises for Lewis numbers greater than unity and occurs near extinction condition. The dynamic behaviors of extinction in this configuration can be classified into three modes; growing, harmonic and decaying oscillation mode near extinction. As the global strain rate decreases, the amplitude of the oscillation becomes larger. This is caused by the increase of lateral heat loss which ran be confirmed by the reduction of lateral flame size. Oscillatory edge flame instabilities at low global strain rate are shown to be closely associated with not only Lewis number but also heat loss (radiation and lateral heat loss).

• Journal of the Korean Society for Railway
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• v.11 no.1
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• pp.107-113
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• 2008

As it recently appears that LCC (Life Cycle Cost) analysis may be considered as an essential method for economic evaluation of infrastructures. Many researches have been made to assess LCC of each facility based on reasonable methods. However, expected maintenance repair cost must be reasonably estimated to enhance the reliability of LCC analysis through systematic and rational methods. This study is intended to propose a rational approach to reliability-based LCC analysis of high-speed railway steel bridges considering lifetime corrosion and fatigue damage. However in Korea, since high speed railway steel bridges are only recently constructed, no direct statistical data are available for the account of the maintenance cost and thus their maintenance characteristics are not clear yet. In this paper, for the assessment of expected maintenance/repair cost, the fatigue system reliability analysis incorporating the corrosion effect is proposed by considering the corrosion and fatigue damage using measured data of high speed railway steel bridges. A model proposed by Rahgozar, of at for fatigue notch factor considering the corrosion effect is used in order to incorporate the corrosion effect into the fatigue strength reduction and S-N curve. Finally, the effectiveness of LCC model proposed for high-speed railway steel bridges is demonstrated by a numerical example.

• Journal of the Korea Institute of Building Construction
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• v.6 no.1 s.19
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• pp.87-91
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• 2006

Since water leakage and cracks are not the source of serious problems such as long-term lowering of performance and durability of a stricture, including damages to operating facilities of a structure, damages to internal finishing materials, exhibition, and goods, and pollution of residential environment, they might have led to development of positive coping skills; however, an instant loss of lives or property due to earthquake, explosion, typhoon, or a fire was indeed neglected. In these days, repair materials for leakage cannot help but being taken in temporary way without any noticeable countermeasure. This kind of repair is socially criticized many times that is defective construction even if this costs a lot. It was not arrange the standard for construction methods of sealer of injection type for leakage maintenance, even it has been used various type of construction methods for leakage part. In conclusion, we suggest that the construction methods of sealer of injection type for leakage maintenance for leakage to establish the leakage repairing technology as increase of structure demand. Therefore, it would be possible to provide a stage-by-stage solution by developing systematic research activities among the industry, schools, and research institutes to spread maintenance management techniques globally through technical solution to water leakage and cracks, acquisition of structural safety with prolonged durability for life cycle, reduction of water leakage repair expense s, and so on.

• The Journal of the Korean dental association
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• v.54 no.6
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• pp.429-437
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• 2016

Objectives: Photodynamic therapy has been proven to promote additional clinical and microbiological benefits in the treatment of chronic periodontitis and aggressive periodontitis. The purpose of this study is to assess the effectiveness of the photodynamic therapy for patient with periodontitis. Methods: We searched the eight Korean databases and Ovid-MEDLINE, Ovid-EMBASE, Cochrane Library. Total 300 studies were searched and 13 studies were included in the final assessment. Each of the stages from literature search and extraction of data were carried out independently by 2 researchers. We used tools of Scottish Intercollegiate Guidelines Networks for assessment of the quality of studies. Results: The safety of the photodynamic therapy was assessed by bleeding. The effectiveness of the photodynamic therapy was assessed by the reduction of Probing pocket depth (PPD) and the gain of Clinical attachment level (CAL). The mean difference of PPD was 0.46(95% CI 0.09~0.82), (p=.01).). The mean difference of CAL was ?0.49(95% CI ?1.12~0.14), (p=.13). Conclusion: The additional use of $^{\circ}{\infty}$Antimicrobial Photodynamic Therapy for Periodontitis$^{\circ}{\pm}$ caused hemorrhage to similar extents to conventional treatment modalities, where scaling and root planing are solely performed, in patients with periodontitis who are expected to have a lower degree of treatment response to non-surgical or surgical periodontal therapies (implant or refractory periodontitis) and those where there is a concern for the possible occurrence of antimicrobial side effects or resistance. This indicates that there are no problems with its safety. But there were no consistent reports about the effects of the additional use of photodynamic therapy. This led to a decision that the safety and efficacy of the current technology deserve further studies (Recommendation rating of A, Classification of technology II-a).

• Journal of Environmental Science International
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• v.20 no.4
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• pp.435-442
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• 2011

In this study, to investigate the effects of herb aroma components, the BDI test was performed with the 124 students of the Youngdong University and the subjects whose score was 16 or higher were selected and allocated to the herb-extracted aroma-treated group and the non-treated group, 27 and 10 students for each group. The BDI and SDS tests were carried out at each stage (before and after the treatment, 10 days later and 30 days later). The result showed that the pre-treatment BDI test result was significantly different from all those of the post-treatment test, and the tests after 10 days and 30 days in the aroma-treated group. In the SDS test, the pre-treatment test result was significantly different from the results of the post-treatment test and the test after 10 days, while it was not significantly different from the result of the test after 30 days. Additionally, to verify whether the change within the group is larger than that by natural recovery or not, ANCOVA was performed with respect to the difference in the pre-treatment test score between the groups depending on whether the treatment was given or not, having the SDS pre-treatment score as the covariate, and the result showed that the post-treatment test scores were significantly different. Thus, it was verified that, if the SDS test score is considered as the depression indicator, the effect of aromatherapy was greater than the change by natural recovery. The difference in the post-treatment test score was analyzed depending on whether the treatment was given or not, having the BDI pre-treatment test score as the control variable, and the result showed that the post-treatment test scores were not significantly different. Based on such a theoretical verification, it is assumed that the nature-friendly treatment method using herb aroma components can be a great help in suppressing depression. Therefore, it is expected that herb aroma components can provide systematic therapeutic effect on the suppression of depression.

• Journal of East-West Nursing Research
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• v.26 no.1
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• pp.1-16
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• 2020

Purpose: The purpose of this study was to evaluate the effectiveness of non-pharmacologic interventions for chronic nonspecific low back pain (CLBP) in adults aged 18-64 years. Methods: We searched for potentially relevant randomized controlled trials and non-randomized controlled trials through five Korean electronic databases (i.e., Korean Studies Information Service System, Research Information Sharing Service, Korean Medical Database, KoreaMed, and National Assembly Library) published from January 2010 to May 2019. Two investigators independently selected the studies based on the criteria and assessed risk of bias in the included studies. We estimated the effect size of interventions using Comprehensive Meta Analysis 3.3. Results: Of 10,151 studies, 26 studies met the inclusion criteria and 15 studies were included in the meta-analysis. Exercise reduced low back pain (Hedges's g=-1.53, 95% CI: -2.22 to -0.85) and pain-related disabilities (Hedges's g=-0.92, 95% CI: -1.40 to -0.45). We found that taping was effective in decreasing low back pain (Hedges's g=-1.12, 95% CI: -1.51 to -0.73) and pain-related disabilities (Hedges's g=-0.50, 95% CI: -0.93 to -0.07). Manual therapy yielded a marginally significant reduction in low back pain (Hedges's g=-2.32, 95% CI: -4.64 to 0.00), the therapy was not effective in decreasing pain-related disabilities. Conclusion: Although there was little evidence for the effectiveness of manual therapy in adults with CLBP, exercise and taping were effective to relieve pain and pain-related disabilities. Based on these findings, we suggest the development of non-pharmacologic interventions or a nursing intervention protocol for the CLBP management. Also, nurses should consider implementation of effective non-pharmacologic interventions for CLBP.

• Safety and Health at Work
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• v.10 no.4
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• pp.393-399
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• 2019

Objective: This study investigates the impact of multimorbidity on work through a literature review of longitudinal studies. Methods: A systematic review was carried out in the databases Lilacs, SciELO, PAHO, PubMed/Medline, Scopus, Web of Science, and Cochrane. There were no restrictions regarding the year of publication or language to maximize the identification of relevant literature. The quality of studies was assessed by the protocol STrengthening the Reporting of OBservational studies in Epidemiology (STROBE). Results: An initial database search identified 7522 registries, and at the end of the analysis, 7 manuscripts were included in the review. Several studies have demonstrated direct and indirect impacts of multimorbidity on the health of workers. For this, the number of missed days due to health-related issues was evaluated, as well as the reduction in work productivity of the unhealthy worker, vulnerability of the worker with multimorbidity regarding higher indices of dismissal and recruitment difficulties, and incidence of early retirement and/or receipt of benefits due to disabilities. Conclusions: Multimorbidity has a negative impact on work, with damages to quality of life and work productivity, worsening the absenteeism/presenteeism indices, enhancing the chances of temporary or permanent leaves, and lowering employability and admission of individuals with multimorbidity.

• Journal of the Korean Geographical Society
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• v.39 no.5 s.104
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• pp.711-721
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• 2004

The aim of this study is to clarify whether frequency and/or severity of extreme climate events have changed significantly in Korea during recent years. Using the best available daily data, spatial and temporal aspects of ten climate change indicators are investigated on an annual and seasonal basis for the periods of 1954-1999. A systematic increase in the $90^{th}$ percentile of daily minimum temperatures at most of the analyzed areas has been observed. This increase is accompanied by a similar reduction in the number of frost days and a significant lengthening of the thermal growing season. Although the intra-annual extreme temperature range is based on only two observations, it provides a very robust and significant measure of declining extreme temperature variability. The five precipitation-related indicators show no distinct changing patterns for spatial and temporal distribution except for the regional series of maximum consecutive dry days. Interestingly, the regional series of consecutive dry days have increased significantly while the daily rainfall intensity index and the fraction of annual total precipitation due to events exceeding the $95^{th}$ percentile for 1901-1990 normals have insignificantly increased.