• Journal of the Korean Society of Safety
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• v.15 no.4
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• pp.35-40
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• 2000

The influence of cyclic loading history on the creep behavior of the 30 vol% hot-pressed $SiC_f/Si_3N_4copmposite was experimentally investigated at $1200^{\circ}C$. The duration of loading/unloading had great effects on the creep behaviors. The short term duration cyclic loading history test results showed significant reduction in the primary and steady-state creep rates. For example, 300sec loading/300sec unloading history resulted in 70% lower steady-state creep rate than that of the continuous loading. However the long term duration cyclic loading history test results showed little change in creep rates compared to those of the continuous one. The reason for the significant change in the short term duration cycles was estimated due to the change in the stress redistribution between the fiber and matrix during the creep recovery in the primary stage.

• Korean Journal of Social Welfare
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• v.65 no.3
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• pp.183-206
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• 2013

Using Korean Labor and Income Panel Study (wave 1~11) database, this study analyzed the poverty duration of the poor as a whole and by households' characteristics. For this purpose, I first estimated poverty exit rates and reentry rates applying discrete-time hazard model to the sample, and then calculated poverty duration combining these two probability rates. The results show that about a half of poor households are transitory (short-term) poor with 1~2 years of poverty duration. A quarter is chronic (long-term) poor lasting for 5 or more years of poverty duration. The remained quarter can be categorized as the recurrent or mid-term poor. The socioeconomic characteristics of households greatly affect poverty duration. Long-term poverty is prevalent among female-head households, elderly households, single households, or households headed by a person with a lower level of education. If households' heads do not work, or work as temporary or daily-employed workers, the poverty duration tends to be longer. The findings suggest that the poor consist of various social classes with different characteristics. Efficient anti-poverty policy should be based on thoroughly identifying the specific characteristics and needs of each class.

• The Journal of the Acoustical Society of Korea
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• v.20 no.6
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• pp.26-33
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• 2001

Though speaker recognition based on conventional AR HMM shows good performance, its lack of modeling the environmental noise makes its performance degraded in case of practical noisy environment. In this paper, a robust speaker recognition system based on AR HMM is proposed, where noise is considered in the observation signal model for practical noisy environment and duration-term is considered to increase performance. Experimental results, using the digits database from 100 speakers (77 males and 23 females) under white noise and car noise, show improved performance.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.25 no.4
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• pp.240-249
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• 2018

Purpose: The study was done to explore whether the duration of perioperative prophylactic antibiotics therapy influenced uncertainty of recovery in patients with elective laparoscopic uterine myomectomy. Methods: A prospective study was conducted using self-report questionnaires and electrical medical records for patients with uterine myomectomy. According to the length of the perioperative prophylactic antibiotics therapy, the patients were divided into three groups: single-dose antibiotic treatment group, short-term antibiotic treatment group, and long-term antibiotic treatment group. Data were collected from December 20, 2016 to July 31, 2017 from 161 patients who underwent laparoscopic myomectomy at a metropolitan city general hospital. Results: Level of uncertainty of recovery was $2.98{\pm}0.22$. The uncertainty was highest in the long-term antibiotic treatment group, followed by the short-term antibiotic treatment group and the single-dose antibiotic treatment group (F=89.40, p<.001). In the regression analysis, factors influencing uncertainty of recovery among uterine myomectomy patients were duration of perioperative prophylactic antibiotic therapy (${\beta}=.70$, p<.001) and duration of NPO (${\beta}=-.11$, p=.047) which explained 51.5% of the variance (F=83.75, p<.001). Conclusion: Based on these results, information including the administration of antibiotics before surgery should be provided to the patients to help reduce the uncertainty of postoperative recovery.

• Journal of Korean Society on Water Environment
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• v.29 no.3
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• pp.343-353
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• 2013

Flow duration curve (FDC) can be developed by linking the daily flow data of stream flow monitoring network to 8-day interval flow data of the unit watersheds for the management of Total Maximum Daily Loads. This study investigated the applicable method for the development of long term FDC with the selection of the stream flow reference sites, and suggested the development of the FDC in 4 river basins. Out of 142 unit watersheds in 4 river basins, 107 unit watersheds were shown to estimate daily flow data for the unit watersheds from 2006 to 2010. Short term FDC could be developed in 64 unit watersheds (45%) and long term FDC in 43 unit watersheds (30%), while other 35 unit watersheds (25%) were revealed to have difficulties in the development of FDC itself. Limits in the development of the long term FDC includes no stream monitoring sites in certain unit watersheds, short duration of stream flow data set and missing data by abnormal water level measurements on the stream flow monitoring sites. To improve these limits, it is necessary to install new monitoring sites in the required areas, to keep up continuous monitoring and make normal water level observations on the stream flow monitoring sites, and to build up a special management system to enhance data reliability. The development of long term FDC for the unit watersheds can be established appropriately with the normal and durable measurement on the selected reference sites in the stream flow monitoring network.

• Journal of Korean society of Dental Hygiene
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• v.19 no.4
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• pp.515-524
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• 2019

Objectives: This study aimed to investigate the effects of the amount and duration of smoking on gingival symptoms in adolescents. Methods: We used the web-based survey data of youth health behaviors from 2016 conducted by the Korean Centers for Disease Control and Prevention. The subjects of the study were 67,983 middle and high school students. Data analysis was performed using the SPSS Ver 20.0 program, and complex sample multivariate logistic regression analysis was performed to analyze gingival symptoms according to short- or long-term smoking habits. Results: In subjects with short-term smoking habits, there was no significant difference in gingival symptoms according to the smoking amount. However, after adjusting for socioeconomic characteristics and oral health behaviors in subjects with long-term smoking habits, a heavy smoking amount (${\geq}0.52PY$) had a 1.25 times higher effect than a light smoking amount (<0.52 PY) on gingival symptoms. Long-term heavy smoking (${\geq}0.52PY$) and low daily tooth-brushing frequency in high school students were factors affecting gingival symptoms. Conclusions: When conducting a project on the oral health of adolescents, it is argued that specific investigations and measures should be set up regarding health behavior factors, such as the amount and duration of smoking among adolescents.

• Journal of Korean Institute of Industrial Engineers
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• v.26 no.3
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• pp.249-256
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• 2000

Bond immunization model is used to minimize interest rate risk for investing in fixed-income market, the model equalizes asset and liability values using the duration which is the sensitivity of portfolio value with respect to the interest rate. However this model might generate an error in practice because the model is based on unreal hypothesis, so called "Parallel Shift Term Structure". In this paper, we use the neural network approach to overcome the parallel shift term structure and try to employ this term structure function to the traditional immunization model. Finally, we present some computational test results that show the superiority of the partial immunization model to the traditional methods.

• Journal of Environmental Science International
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• v.28 no.10
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• pp.863-872
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• 2019

Using the Standard Precipitation Index (SPI), this study analyzed the drought characteristics of ten weather stations in Gyeongbuk, South Korea, that precipitation data over a period of 30 years. For the number of months that had a SPI of -1.0 or less, the drought occurrence index was calculated and a maximum shortage months, resilience and vulnerability in each weather station were analyzed. According to the analysis, in terms of vulnerability, the weather stations with acute short-term drought were Andong, Bonghwa, Moongyeong, and Gumi. The weather stations with acute medium-term drought were Daegu and Uljin. Finally the weather stations with acute long-term drought were Pohang, Youngdeok, and Youngju. In terms of severe drought frequency, the stations with relatively high frequency of mid-term droughts were Andong, Bonghwa, Daegu, Uiseong, Uljin, and Youngju. Gumi station had high frequency of short-term droughts. Pohang station had severe short-term ad long-term droughts. Youngdeok had severe droughts during all the terms. Based on the analysis results, it is inferred that the size of the drought should be evaluated depending on how serious vulnerability, resilience, and drought index are. Through proper evaluation of drought, it is possible to take systematic measures for the duration of the drought.

• Journal of Korean Society on Water Environment
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• v.29 no.6
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• pp.762-776
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• 2013

Load duration curve was applied to determine important water quality parameter control term for improvement of Paldang lake water quality. Load duration curve was analyzed with long term data from 1985 to 2012 including water quality, flow rate and climate state of Paldang water environment. From the result of flow rate patterns of paldang lake, differences between high and low flow rate of each year showed tendency of increase because rainfall characteristics of paldang lake watershed were changed by climate exchange. Both of land use state of upper Paldang lake watershed and number of limit excess from load duration curve indicated that seasonal action related with land use such as agricultural fertilizer distribution in upper watershed affected Paldang lake water quality. So focused BOD (biological oxygen demand) management during spring season from march to June is required to control organic materials in Paldand lake. The main affecting factor of TOC (total organic carbon) increase in Paldang lake was initial rainfall after march. T-N (total nitrogen) kept increasing during research period, so enhancement of T-N standard is needed to T-N control. Initial rainfall and increase of temperature during spring season from March to June showed a positive correlation with TP (total phosphorus) and Chl-a, respectively.

• Atmosphere
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• v.19 no.3
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• pp.243-253
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• 2009

In other to interpret the long-term variations of sunshine duration, cloud lifetime, and precipitation intensity observed in and around Seoul and Busan for the period from 1986 to 2005, aerosol indirect effect was employed and applied. For the identification of long-term trend of aerosol concentration, observed visibility and AOT of AERONET sunphotometer data were also used over the same regions. The result showed that the time series of visibility was decreased and those of AOT increased, especially trends were remarkable in 2000s. In both regions, occurrence frequencies of observed cloudiness (cloud amount ${\leq}6/10$) and strong precipitation (rain rate > $0.5mmhour^{-1}$) have been steadily increased while those of cloudiness (cloud amount > 7/10) and weak precipitation (rain rate ${\leq}0.2mmhour^{-1}$) decreased. These results are corresponding to the trend of both visibility and AERONET data, implying the aerosol indirect effect that makes size of cloud droplet reduce, cloud life-time longer and precipitation efficiency decreased. Our findings demonstrate that, although these phenomena are not highly significant, weather and climate system over Korean urban area have been changed toward longer lifetime of small cloudiness and increasing precipitation intensity as a result of increased aerosol indirect effect.