• 한국농공학회논문집
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• 제51권1호
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• pp.1-9
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• 2009

The objective of this paper was to evaluate the auto-calibration with multi-objective optimization method to calibrate the parameters of the Soil and Water Assessment Tool (SWAT) model. The model was calibrated and validated by using nine years (1996-2004) of measured data for the 384-ha Baran reservoir subwatershed located in central Korea. Multi-objective optimization was performed for sixteen parameters related to runoff. The parameters were modified by the replacement or addition of an absolute change. The root mean square error (RMSE), relative mean absolute error (RMAE), Nash-Sutcliffe efficiency index (EI), determination coefficient ($R^2$) were used to evaluate the results of calibration and validation. The statistics of RMSE, RMAE, EI, and $R^2$ were 4.66 mm/day, 0.53 mm/day 0.86, and 0.89 for the calibration period and 3.98 mm/day, 0.51 mm/day, 0.83, and 0.84 for the validation period respectively. The statistical parameters indicated that the model provided a reasonable estimation of the runoff at the study watershed. This result was illustrated with a multi-objective optimization for the flow at an observation site within the Baran reservoir watershed.

• 한국농공학회논문집
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• 제56권6호
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• pp.45-53
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• 2014

This study presents a system dynamics modeling approach to simulate daily streamflow in a watershed including wastewater treatment plant which contributes to irrigation water supply. The conceptual system dynamics model considering the complex and dynamic hydrological processes in the watershed was developed. The model was calibrated and validated each for two years based on observed flow data. Model performances in terms of $E_{NS}$, RSR, PBIAS, and $R^2$ were 0.64, 0.60, -3.6 %, and 0.64 for calibration period, and 0.66, 0.58, -2.6 %, and 0.66 for validation period, respectively, showing an applicability on generating the daily streamflow. System dynamics modeling approach could help better understand the hydrological behavior of the watershed being reused wastewater for agriculture, by providing graphical dynamics of the hydrological processes as well as conventional rainfall-runoff model results.

• 대한지하수환경학회지
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• 제2권2호
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• pp.72-77
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• 1995

수학모델 개발, 현장수리시험, 그리고 연구지점에서 샘플링한 강수 및 지하수의 트리튬농도를 분석하여, 삼광광산 주변의 편마암에서의 지하수의 유동시간을 평가했다. 이 연구의 결과는 다음과 같다: (1) 연구지역에 1961∼1993년 동안 내린 강우의 트리튬농도를 고려하여, 지하수의 연령을 계산할수 있는 수학모델을 개발했다. (2) 지표면으로부터 44, 92, 102, 205 m 밑의 터널내의 지하수의 연령은 각각 2.0, 4.0, 4.5, 9.0 년으로 평가되었다. 이들 결과는 1991∼1993 년 동안 터널내의 지하수의 트리튬 농도에 관한 자료로 검증했다.

• 산업경영시스템학회지
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• 제33권2호
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• pp.97-104
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• 2010

Using the known result of the expected busy period for the triadic Min (N, T, D) operating policy applied to a controllable M/G/1 queueing model, its upper and lower bounds are derived to approximate its corresponding actual value. Both bounds are represented in terms of the expected busy periods for the dyadic Min (N, T), Min (N, D) and Min (T, D) and simple N, T and D operating policies. All three input variables N, T and D are equally contributed to construct such bounds for better approximations.

• 한국환경과학회지
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• 제24권10호
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• pp.1273-1283
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• 2015

In present study, the temporal characteristics of nine selected volatile organic compounds (VOCs), including four alcohol, 2 aldehyde, and 3 ketone compounds, in high-stories urban apartments over a 2-y period were investigated. The indoor VOC concentrations had generally a decreasing trend over the 2-y follow-up period. For examples, the 2E1H indoor concentration decreased from $10.8{\mu}g/m^3$ for the first two months to $5.1{\mu}g/m^3$ for the last two months. In addition, the DCA and ACT indoor concentrations decreased from 5.0 and $14{\mu}g/m^3$ for the first two months to 2.2 and $6.4{\mu}g/m^3$, respectively, for the last two months. The indoor-to outdoor concentration ratios over the 2-y period were much greater than 1, indicating that indoor VOC concentrations were higher than the outdoor VOC concentrations. Similar to those of the individual VOCs, the indoor-to-outdoor concentration ratios of all three VOC groups were higher than 1 over the 2-y follow-up period, suggesting higher indoor concentrations of the three VOC groups than outdoor concentrations. In consistence with the results of VOC indoor concentrations, the VOC emission rates decreased gradually as time passed, due to the decreased VOC emission strengths of indoor sources. Finally, there was an initial sharp decrease in the indoor VOC concentrations followed by a slower decrease, indicating a multi-exponential decay model for the target VOCs, which was demonstrated by comparison of the residuals and the adjusted coefficient of determination associated with the one and two-exponential fits of each data set.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2002년도 추계학술대회 논문집
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• pp.343-343
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• 2002

This study examines the influence of long-range transport of dust particles and air pollutants on both local/regional DMS oxidation chemistry and the distribution of sulfur compounds at Jeju Island (33.17$^{\circ}$ N. 126.10$^{\circ}$ E) during the Asian dust-storm(ADS) period in April 2001. The atmospheric concentrations of these sulfur species were measured at a ground station on Jeju Island. Korea as Part of the ACE-Asia intensive operation. Three ADS events were observed during the periods of 10-12, 13-14. and 25-26 April. respectively. The concentrations of DMS and CS$_2$ were higher during the ADS period than during the non-Asian-dust-storm (NADS) period. Conversely. a difference in SO$_2$ levels during the ADS period was not distinguishable from those during the NADS period. The diurnal variation pattern of DMS observed was largely different from that in the remote marine boundary layer. DMS loss by NO$_3$ in the atmospheric boundary layer was dominant due to significantly high NOx levels influenced by the long-range transport of pollutants from East Asia to Jeju Island The DMS maximum during the ADS period was observed in the late afternoon. The oceanic fluxes of DMS during the ADS and NADS periods were estimated to be 5.7$\pm$2.3 and 2.9 (+2.8/-1.5) mole m$^{-2}$ day$^{-1}$ . respectively. The contribution of oxidized DMS to SO$_2$ levels at Jeju Island during the study period was found to be insignificant.

• 한국경제지리학회지
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• 제12권4호
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• pp.665-680
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• 2009

본 연구의 목적은 위험조정모형을 활용하여 미국 REITs의 부동산 유형별 성과 특성을 분석하는 것이다. 특히, REITs의 성과가 성장기, 정체기, 금융위기기에 각각 어떻게 차별적인 지를 살펴본다. 분석결과를 요약하면 다음과 같다. 첫째로, 초과 종합수익률의 관점에서 REITs 부동산 유형별 성과를 보면, 1기와 2기에는 정(+)의 초과 성과가 발생한 반면, 3기에는 부(-)의 초과 성과가 나타난다. 금융위기 시기인 3기의 경우, 부(-)의 수익률이 발생한 뿐만 아니라 수익률의 변동성도 큰 것으로 나타난다. 둘째로, 자본자산가격결정모형에 의해 추정한 베타값을 보면, <분석모형 (1)>의 결과에서 평균적인 REITs에 비해 호텔, 지역몰, 상업모기지는 고위험-고수익 특성을, 자유입지, 아파트, 조립식주택, 특수목적 부동산은 저위험-저수익 특성을 가진 것으로 나타난다. <분석모형 (2)>의 결과를 보면, 금융위기 하에서 투자상품으로서의 REITs의 성격이 저위험-저수익에서 고위험-고수익으로 변화하고 있다. 마지막으로, 위험조정모형 추정결과를 보면, <분석모형 (1)>과 <분석모형 (2)> 모두 체계적 위험은 요구수익률에 정(+)의 영향을 미치는 반면, 비체계적위험은 요구수익률에 부(-)의 영향을 미치는 것으로 나타난다. 위험조정모형을 통해 도출된 요구수익률을 실제수익률과 비교한 결과, 헬쓰케어 부문이 가장 높은 정(+)의 성과를 보이고 있다.

• 한국기록관리학회지
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• 제9권2호
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• pp.189-214
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• 2009

이 연구는 한국의 공공기록관리 정책이 변천되어 온 궤적과 현재 놓여있는 좌표를 검토해서 향후 지속적인 발전을 추진해나가는 데 필요한 시사점을 얻는 것을 목적으로 하였다. 대한민국 정부 수립 이후 60년의 기간을 공공기록관리의 관점에서 도입기(1948년~1980년대 중반), 준비기(1980년대 후반~1990년대), 발전기(2000년~2007년), 전환기(2008년 이후)로 나누었다. 도입기부터 발전기까지는 주로 법령과 제도를 중심으로 그 시대에 이루어진 기록관리 관련 성과와 한계를 분석하였으며, 전환기를 맞고 있다고 판단되는 현재의 기록관리 관련 현황을 진단해 보았다. 그리고 전환기를 새로운 성장기로 유도하기 위해서는 쌍방향적 네트워크형 발전모델을 채택해야 한다고 결론지었다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제15권1호
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• pp.6-11
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• 2015

Maintenance plays an important role in keeping product availability, reliability and quality at an appropriate level. In this paper, two-types of maintenance policies are studied following the expiration of two-dimensional (2D) free replacement warranty. Both the fixed-maintenance-period policy and the variable-maintenance-period policy are based on a specified region of the warranty defined in terms of age and usage where all failures are minimally repaired. An accelerating failure time (AFT) model is used to allow for the effect of usage rate on product degradation. The maintenance model that arises following the expiration of 2D warranty is discussed. The expected cost rates per unit time from the user's point of view are formulated and the optimal maintenance policies are determined to minimize the expected cost rate to the user. Finally numerical examples are given to illustrate the optimal maintenance polices.

• 한국생활과학회지
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• 제21권2호
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• pp.349-362
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• 2012

This paper explores differences demonstrated by changes of consumers' clothing expenditure in Korea and the United States since the mid-1990s. Evidence for this study was extrapolated from annual data provided by the Household Expenditure Survey, which was carried out in Korea between 1996 and 2008, and the Consumer Expenditure Survey, which was carried out in the United States during the same time period. The results include: (1) The proportion of the clothing expenditure decreased during the subject period in both Korea and the United States; (2) The decrease in proportional clothing expenditure was greater in Korea than in the United States; (3) Although the relative prices of clothes decreased greatly during this period in both countries, it was determined that the decrease in clothing prices in the United States was greater when compared to those in Korea; and (4) By using the DID(Difference in difference) model, the author contends that a decrease in clothing purchases contributed to the decrease of prices for clothing in the United States, while in Korea, the decrease in prices for clothing was also impacted by other factors including changes in household expenditures for education and communication.