• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.4
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• pp.435-441
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• 2012

This paper provides simulation-based results of effect analysis of sample size and sampling periods on accuracy of reliability estimation methods using multiple comparisons with analysis of variance. Sum of squared errors in estimated reliability measures were evaluated through applying seven estimation methods for one-shot systems to simulated quantal-response data. Analysis of variance was implemented to investigate change in these errors according to variations of sample size and sampling periods for each estimation method, and then the effect analysis on accuracy in reliability estimation was performed using multiple comparisons based on sample size and sampling periods. An efficient way to allocate both sample size and sampling periods for reliability estimation tests of one-shot systems is proposed in this paper from the effect analysis results.

• Journal of Astronomy and Space Sciences
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• v.34 no.4
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• pp.257-270
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• 2017

Solar activity is known to be linked to changes in the Earth's weather and climate. Nonetheless, for other types of extreme weather, such as tropical cyclones (TCs), the available evidence is less conclusive. In this study the modulation of TC genesis over the western North Pacific by the solar activity is investigated, in comparison with a large-scale environmental parameter, i.e., El-$Ni{\tilde{n}}o$-Southern Oscillation (ENSO). For this purpose, we have obtained the best track data for TCs in the western North Pacific from 1977 to 2016, spanning from the solar cycle 21 to the solar cycle 24. We have confirmed that in the El-$Ni{\tilde{n}}o$ periods TCs tend to form in the southeast, reach its maximum strength in the southeast, and end its life as TSs in the northeast, compared with the La-$Ni{\tilde{n}}o$ periods. TCs occurring in the El-$Ni{\tilde{n}}o$ periods are found to last longer compared with the La-$Ni{\tilde{n}}o$ periods. Furthermore, TCs occurring in the El-$Ni{\tilde{n}}o$ periods have a lower central pressure at their maximum strength than those occurring in the La-$Ni{\tilde{n}}o$ periods. We have found that TCs occurring in the solar maximum periods resemble those in the El-$Ni{\tilde{n}}o$ periods in their properties. We have also found that TCs occurring in the solar descending periods somehow resemble those in the El-$Ni{\tilde{n}}o$ periods in their properties. To make sure that it is not due to the ENSO effect, we have excluded TCs both in the El-$Ni{\tilde{n}}o$ periods and in the La-$Ni{\tilde{n}}o$ periods from the data set and repeated the analysis. In addition to this test, we have also reiterated our analysis twice with TCs whose maximum sustained winds speed exceeds 17 m/s, instead of 33 m/s, as well as TCs designated as a typhoon, which ends up with the same conclusions.

• Journal of The Korean Astronomical Society
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• v.37 no.2
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• pp.79-85
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• 2004

We developed an algorithm to identify and determine periods of variable sources. With its robustness and high speed, it is expected to become an useful tool for surveys with large volume of data. This new scheme consists of an initial coarse. process of finding several candidate periods followed by a secondary process of much finer period search. With this multi-step approach, best candidates among statistically possible periods are produced without human supervision and also without any prior assumption on the nature of the variable star in question. We tested our algorithm with 381 stars taken from the ASAS survey and the result is encouraging. In about $76\%$ cases, our results are nearly identical as their published periods. Our algorithm failed to provide convincing periods for only about $10\%$ cases. For the remaining $14\%$, our results significantly differ from their periods. We show that, in many of these cases, our periods are superior and much closer to the true periods. However, the existence of failures, and also periods sometimes worse than manually controlled results, indicates that this algorithm needs further improvement. Nevertheless, the present experiment shows that this is a positive step toward a fully automated period analysis for future variability surveys.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.7
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• pp.605-608
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• 2011

In this study, OSA (the obstructive sleep apnea) periods were detected in patients with OSA during sleep because of the treatment was different according to the frequency and symptoms of obstructive sleep apnea. ANS (autonomic nervous activity) was changed by obstructive sleep apnea periods so we intended to detect the periods to care the obstructive sleep apnea patients. RR intervals, SDNN (standard deviation of normal to normal) and RMSSD (root mean square standard deviation) were calculated in time domain analysis and LF (low frequency), HF (high frequency), NHF (normalized high frequency), NLF (normalized low frequency) were calculated in frequency domain analysis of HRV (heart rate variability) with obstructive sleep apnea patients. In this paper, SDNN (standard deviation of normal to normal) of time domain analysis were decreased in the obstructive sleep apnea periods. And NLF and LF/HF ratio were increased and NHF (normalized high frequency) was decreased in the frequency domain analysis. The parameters can be used to treat obstructive sleep apnea patients by detecting the obstructive sleep apnea periods such as CPAP (continuous positive airway pressure).

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.3
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• pp.178-187
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• 2005

A reliability analysis model f3r studying the influence of joint distribution of wave heights and periods on wave un-up is presented in this paper. From the definition of failure mode related to wave run-up, a reliability function may be formulated which can be considered uncertainties of water level. In particular, the reliability analysis model can be directly taken into account statistical properties and distributions of wave periods by considering wave period in the reliability function to be a random variable. Also, variations of wave height distribution conditioned to mean wave periods can be taken into account correctly. By comparison of results of additional reliability analysis using extreme distributions with those resulted from joint distribution of wave height and periods, it is found that probabilities of failure evaluated by the latter is larger than those by the former. Although the freeboard of sloped-breakwater structures can be determined by extreme distribution based on the long-term measurements, it may be necessary to investigate additionally into wave run-up by using the present reliability analysis model formulated to consider joint distribution of a single storm event. In addition, it may be found that the effect of spectral bandwidth parameter on reliability index may be little, but the effect of wave height distribution conditioned to mean wave periods is straightforward. Therefore, it may be confirmed that effects of wave periods on the probability of failure of wave run-up may be taken into account through the conditional distribution of wave heights. Finally, the probabilities of failure with respect to freeboard of sloped-breakwater structures can be estimated by which the rational determination of crest level of sloped-breakwater structures may be possible.

• Journal of Environmental Science International
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• v.13 no.3
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• pp.251-262
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• 2004

To identify the characteristics of wastewater flow generated in treatment basins of Seogwipo-city, we selected 3 stations representing the basin and performed 7 times of field survey including 5 times in dry periods and 2 times in wet periods from Feb. 25 to May 27, 2002 for the selected stations. From the analysis of flow data measured for more than 60 days in the interval of 5 minutes and concentration data obtained from laboratory analysis, we can draw several conclusions. First, in the analysis of diurnal variation of wastewater flow for land-use types, we could find the following results: in the residential area, it is observed that wastewater flow rates rise early in the morning for the office-going hour and fall gradually and rise again after the office-leaving hour, showing typical residential wastewater flow pattern, while for the residential and commercial area flow rates rise early in the morning at the office-going hour and move up and down repeatedly within wide range and last till the office-leaving hour, which can be resulted from wastewater that is generated by tourists activated after early in the afternoon, while for the touristy area flow rates rise early in the morning and fall gradually and rise again within wide range. Second, in the analysis of temporal variation of wastewater flow for monthly, it can be observed that in the residential area, in the residential and commercial areas the flow rate of May is higher than that of Feb., March, while for the touristy area flow rate is without monthly because it reflects the movement of population, Third, in wet periods concentration of water-quality item such as SS, BOD, and COD_{cr}$ is high in the beginning of rainfall by first flush, and falls down gradually to reach the steady state, which is the level of wastewater in dry periods after the cease of storm water due to diluting effect resulting from additional runoff water through storm sewers.

• Journal of Environmental Science International
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• v.25 no.10
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• pp.1369-1379
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• 2016

This research assessed the disparity in anion generation according to the vertical structure of a Zelkova Serrata tree for the purpose of creating a pleasant and green city environment. Measurements for the study were conducted between July and August of 2014 in Chung-ju in the central region of the Republic of Korea. The average anion generation of vertical structure trees during active photosynthesis periods was: L Section ($839.0ea/cm^3$) > M Section ($664.6ea/cm^3$) > U Section ($472.0ea/cm^3$). According to DMRT analysis, significant difference was found in the average between the L, or M Locations and the U Locations. During dormant photosynthesis periods, records showed that the anion production at the M Location ($1,212.5ea/cm^3$) > L Location ($1,050.4ea/cm^3$) > H Location ($844.1ea/cm^3$), According to DMRT analysis, the difference within each location was significant for ${\alpha}=0.05$. In a comprehensive analysis of the weather factors in each vertical structure, anion generation during active photosynthesis periods showed a positive correlation with solar radiation and a negative correlation with wind speed. Dormant photosynthesis periods showed negative correlations with both solar radiation and temperature, and positive correlations with relative humidity and wind speed. Predictions from a multicenter retrospective study showed that during active photosynthesis periods, $Y_1=282.443X_1+512.07$, and $Y_2=314.337X_1+16.913X_2$, while during dormant photosynthesis periods, $Y_1=391.009X_1+840.043$, and $Y_2=351.412X_1+32.765X_2$.

• Journal of the military operations research society of Korea
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• v.30 no.2
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• pp.108-121
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• 2004

This paper deals with a procedure of changing the current inspection & replacement periods for ROKAF aircraft parts. ROKAF is mostly operating aircraft of foreign makes, and takes maintenance actions according to Technical Orders(TO.) published by foreign aircraft manufacturers. Therefore ROKAF inspects and replaces specific parts at the time noticed from T.O.. These inspection and replacement periods are determined by manufacturers according to the standard operating environment and parts' durability. But the standard operating environment Is different from operator's environment. Because of this difference, the inspection and replacement periods have to be changed according to operators' operation environment. It is resonable that the manufacturer, having design materials and life test data of parts, changes those periods together with materials of operators' operation environment. But we have many difficulties in obtaining the design materials and life test data. Then this paper proposes a procedure of changing the periods of aircraft's parts with life data obtained during operating aircraft. For the reliability analysis, a software of RELEST (Reliability Estimation Version 1.0) is used.

• Journal of Engineering Education Research
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• v.17 no.1
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• pp.57-64
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• 2014

This study has a purpose mainly to analyze the team interaction change by the duration of time in the Capstone-Design activities according to MBTI Modes. Study objects are four students of Mechanical Engineering at School of Engineering in C University located in Daejeon, and the team interaction change was analyzed through IPA (Interaction Process Analysis) method. From the result, first, ESTP showed the change of increase in interaction by the time duration of initial, mid, late periods in 'social-emotional area: positive' and 'task area: question', and the change of decrease by the same time duration of periods in 'task area: solution'. Also, there was no change in 'social-emotional area: negative' because there was no interaction. Second, ESFJ showed the change of decrease in interaction by the time duration of initial, mid, late periods in 'social-emotional area: positive' and 'task area: question', and the change of increase by the same time duration of periods in 'task area: solution' and 'social-emotional area: negative'. Third, ISTJ showed the change of decrease in interaction by the time duration of initial, mid, late periods in 'social-emotional area: positive', 'task area: question' and 'social-emotional area: negative', and the change of increase by the same time duration of periods in 'task area: solution'. Fourth, ENFP showed the change of decrease by the time duration of initial, mid, late periods in 'social-emotional area: positive', 'task area: solution' and 'social-emotional area: negative', and the change of increase by the same time duration of periods in 'task area: question'.

• International Journal of Advanced Culture Technology
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• v.8 no.2
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• pp.146-158
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• 2020

As one of the successful brand activism ad campaigns in recent years, the current study focuses on the Always #LikeAGirl campaign that took on the issue of girls and female empowerment. As a viral video marketing campaign with YouTube as their main vehicle for campaign dissemination, this study examined how Always brand activism campaigns spread on YouTube by conducting a network analysis of YouTube video networks generated by the #LikeAGirl campaign spanning across five campaign periods. Quantifiable data (i.e., views, comments, likes, dislikes, user-generated videos) and structural network patterns show that the Always #LikeAGirl campaign was successful by both standards. Although the follow-up campaign periods were not as successful as the initial campaign, the substantial amount of views, comments, likes, and user-generated content showed that the consecutive campaigns still had impact. As shown through the network patterns, the main campaign ads were central in the diffusion of the campaign during the earlier periods but that role was passed onto the user-generated contents in the later periods. Implications of the findings and future social network analysis studies in brand advertising and brand activism campaigns are further discussed.