• 융합경영연구
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• 제9권2호
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• pp.1-10
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• 2021

Purpose: In this work, we examine several time series models to predict internet and mobile transaction amount in South Korea, whereas Jeong (2020) has obtained the optimal forecasts for online shopping transaction amount by using time series models. Additionally, optimal forecasts based on the model considered can be calculated and applied to the Corona 19 situation. Research design, data, and methodology: The data are extracted from the online shopping trend survey of the National Statistical Office, and homogeneous and comparable in size based on 46 realizations sampled from January 2007 to October 2020. To achieve the goal of this work, both multiplicative ARIMA model and Holt-Winters Multiplicative seasonality method are taken into account. In addition, goodness-of-fit measures are used as crucial tools of the appropriate construction of forecasting model. Results: All of the optimal forecasts for the next 12 months for two online shopping transactions maintain a pattern in which the slope increases linearly and steadily with a fixed seasonal change that has been subjected to seasonal fluctuations. Conclusions: It can be confirmed that the mobile shopping transactions is much larger than the internet shopping transactions for the increase in trend and seasonality in the future.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.149-153
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• 2009

Physics-based distributed rainfall-runoff models are now commonly used in a variety of hydrologic applications such as to estimate flooding, water pollutant transport, sedimentation yield and so on. Moreover, it is not surprising that GIS has become an integral part of hydrologic research since this technology offers abundant information about spatial heterogeneity for both model parameters and input data that control hydrological processes. This study presents the development of a distributed rainfall-runoff prediction system for the Guem river basin ($9,835km^2$) using an Object-oriented Hydrological Modeling System (OHyMoS). We developed three types of element modules: Slope Runoff Module (SRM), Channel Routing Module (CRM), and Dam Reservoir Module (DRM) and then incorporated them systemically into a catchment modeling system under the OHyMoS. The study basin delineated by the 250m DEM (resampled from SRTM90) was divided into 14 midsize catchments and 80 sub-catchments where correspond to the WAMIS digital map. Each sub-catchment was represented by rectangular slope and channel components; water flows among these components were simulated by both SRM and CRM. In addition, outflows of two multi-purpose dams: Yongdam and Daechung dams were calculated by DRM reflecting decision makers' opinions. Therefore, the Guem river basin rainfall-runoff modeling system can provide not only each sub-catchment outflow but also dam inand outflow at one hour (or less) time step such that users can obtain comprehensive hydrological information readily for the effective and efficient flood control during a flood season.

• 한국지형학회지
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• 제27권2호
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• pp.1-17
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• 2020

This study evaluated a debris landform distribution potential area map in the southwest region of the Korean peninsula. A GIS spatial integration technique and logistic regression method were used to produce a distribution potential area map. Seven topographic and environmental factors were considered for analysis and 28 different data set were combined and used to get most effective results. Moreover, in an accuracy assessment, the extracted results of the Distribution Potential area were evaluated by conducting a cross-validation module. Block stream showed the highest accuracy in the combination No. 6, and that DEM (digital elevation model) and TWI (topographic wetness index) have relatively high influences on the production of the Block stream Distribution Potential area map. Talus showed the highest accuracy in the combination No. 13. We also found that slope, TWI and geology have relatively high influences on the production of the Talus Distribution Potential area map. In addition, fieldwork confirmed the accuracy of the input data that were used in this study, and the slope and geology were also similar. It was also determined that these input data were relatively accurate. In the case of angularity, the block stream was composed of sub-rounded and sub-angular systems and Talus showed differences according to the terrain formation. Although the results of the rebound strain measurement using a Schmidt's hammer did not shown any difference in topographic conditions, it is determined that the rebound strain results reflected the underlying geological setting.

• 한국근적외분광분석학회:학술대회논문집
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• 한국근적외분광분석학회 2001년도 NIR-2001
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• pp.1127-1127
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• 2001

The transfer of predictive models using various chemometric techniques has been reported for FTNIR and scanning-grating based NIR instruments with respect relatively dry samples (<10% water). Some of the currently used transfer techniques include slope and bias correction (SBC), direct standardization (DS), piecewise direct standardization (PDS), orthogonal signal correction (OSC), finite impulse transform (FIR) and wavelet transform (WT) and application of neural networks. In a previous study (Greensill et at., 2001) on calibration transfer for wet samples (intact melons) across silicon diode array instrumentation, we reported on the performance of various techniques (SBC, DS, PDS, double window PDS (DWPDS), OSC, FIR, WT, a simple photometric response correction and wavelength interpolative method and a model updating method) in terms of RMSEP and Fearns criterion for comparison of RMSEP. In the current study, we compare these melon transfer results to a similar study employing pairs of spectrometers for non-invasive prediction of soluble solid content of peaches.

• 한국군사과학기술학회지
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• 제12권6호
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• pp.711-718
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• 2009

During the preliminary design phase of a supersonic aircraft, it is necessary to evaluate many potential engine/airframe combinations to determine the best solution to given set of mission requirements. And it is very important to establish a methodology to predict precisely afterbody drag so that accurate engine installed performance can be estimated. It was carried out in this paper to establish a methodology to predict afterbody drag of F-15K supersonic aircraft based on IMS(Integral Mean Slope) methodology, acquire afterbody drag data and compare its calculated data with the test data acquired from the wind tunnel test data based on 4.7% model scale. The comparison results showed good agreement between the calculated data and test data and it was found that the methodology described here to predict and test afterbody drag is acceptable.

• 대한교통학회지
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• 제27권4호
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• pp.167-173
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• 2009

교통사고는 인간의 생명과 직결되는 문제이므로, 교통사고 예방 및 심각도 감소를 위한 연구는 매우 중요하다고 할 수 있다. 따라서 본 연구에서는 교통사고 심각도에 영향을 줄 수 있는 다양한 영향요소들을 고려하여 교통사고로 인한 피해를 최소화할 수 있는 대응책을 수립하고자 하였다. 본 연구에서는 2004~2006년 동안 서해안 고속도로에서 발생한 174개의 구간별 사고자료를 이용하여 사고 심각도 예측모형을 만들었다. 이렇게 분석된 모형을 이용하여 사고심각도에 영향을 미치는 주요요인을 찾고 이를 이용하여 교통사고로 인한 피해를 줄일 수 있는 다양한 방법들을 고려해 보았다. 분석결과 과속으로 인한 사고, 차량결함, 차대차 사고, 차대사람 사고, 교통량, 곡선반경 및 종단경사 변동계수에 의해 사고심각도가 정의되는 것을 알 수 있다. 이와 같은 사고심각도와 밀접한 관련이 있는 독립변수들을 대상으로 구간에 따른 각 영향의 정도를 그래프를 나타내 보았으며, 그 결과 심각한 사고를 유발하는 특정원인이 몇 가지 존재하며 이러한 특정원인 및 사고유형은 서해안 고속도로의 특정구간에서 주로 발생한다는 것을 알 수 있다. 이러한 결과들은 서해안 고속도로의 특정 구간에 속도제한 단속 카메라, 차내/외 경고정보제공등과 같은 선택적 교통정보 및 교통시설을 제공함으로써 사고를 예방하는 방법에 활용될 수 있을 것이다.

• 한국작물학회지
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• 제64권4호
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• pp.353-365
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• 2019

본 연구는 근적외선 분광분석기(NIRS) 예측모델을 설정하여 유전자원 대량분석 체계를 확립하고 그에 따른 국내 외 밀 자원의 단백질 함량에 관한 기초 정보를 제공하고자 하였다. 1. 농업유전자원센터에 보유하고 있는 20,000여 자원 중 1,798자원을 검량 자원으로 선발하였다. 검량자원의 NIR 스펙트럼을 측정하였고, 단백질 함량 습식분석 데이터 입력 등 일련의 통계적 처리 과정을 거쳐 NIRS 예측모델을 설정했다. 검량 자원의 다양성 지수는 0.80이었고, 습식 분석법에 의한 단백질 평균은 13.2%, 함량 구간은 7.0-20.8%였다. 최적화된 NIRS 모델의 R², SEC, Slope은 0.997, 0.132, 1.000이었다. 300자원을 사용하여 외부 검정 과정을 실시하였고 R², SEP, Slope은 0.994, 0.191, 1.013이었다. 최적화된 NIRS 모델과 외부검정 결과의 통계치가 상호 유사하였고, 1에 가까운 R²와 Slope 값, 낮은 SEC와 SEP 값을 볼 때 본 연구에서 설정한 NIRS 모델은 습식 분석법을 대체하여 밀 자원의 단백질 함량 분석에 적용 가능할 것으로 판단되었다. 2. 국내외 수집된 밀 6,794자원의 NIRS 단백질 함량 측정값을 정규분포로 작성하여 특성을 파악했다. 자원의 다양성 지수는 0.79, 단백질 평균은 12.1%, 전체 자원의 임의구간 42.1% 단백질 함량자원 범위는 10-13%이었으며, 68.0%를 차지하는 자원들의 단백질 함량 범위는 9.5-14.7%였다. 3. 전체 6,794자원의 품종 집단 구성은 육성계통 3,128자원, 재래종 2,705자원, 육성품종 961자원이었다. 육성계통 자원의 다양성 지수는 0.80, 단백질 평균은 11.8%, 전체 자원의 68%를 차지하는 자원들의 함량 범위는 9.2-14.5%였다. 재래종 자원의 다양성 지수는 0.76, 단백질 평균은 12.1%, 전체 자원의 68.0%를 차지하는 자원들의 함량 범위는 9.8-14.4%였다. 육성품종 자원의 다양성 지수는 0.80, 단백질 평균은 12.8%, 전체 자원의 68.0%를 차지하는 자원들의 함량 범위는 10.2-15.4%였다. 재래종 자원은 가장 낮은 다양성 지수를 나타냈고, 육성계통과 육성품종은 동일한 다양성 지수를 나타냈다. 육성계통은 가장 낮은 단백질 평균을 나타냈고, 육성품종은 가장 높은 단백질 평균을 나타냈다.

• 유통과학연구
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• 제13권10호
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• pp.73-82
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• 2015

Purpose - This paper aims to investigate whether information asymmetry could explain capital structures in Korean corporations. According to Myers (1984), firms prefer internal funding to external financing due to the costs associated with information asymmetry. When external financing is necessary, firms prefer to issue debt rather than equity by the same reasoning. Since Shyam-Sunder and Myers (1999), numerous studies continue to debate the validity of the theory. In this paper, we show how the theory depends on assumptions and incorporated variables. We hope our investigation can provide helpful implications regarding capital structure, information asymmetry, and other firm characteristics. Specifically, our empirical results are complementary to the analysis of Son and Lee's (2015), a recent study that examines the pecking order theory prediction for Korean retail firms. Research design, data, and methodology - We test empirical models that are some variants of model used in Shyam-Sunder and Myers (1999). The financial and accounting data are provided by WISEfn for the firms listed on the KOSPI during 1990 to 2013. Bond ratings are supplied by the Korea Investor Service (KIS). We take into account the heterogeneity in debt capacity; a firm's debt capacity is measured by using the method of Lemmon and Zender (2010) based on its bond ratings. Finally, we estimate empirical models suggested by Shyam-Sunder and Myers (1999), Frank and Goyal (2003), and Lemmon and Zender (2010). Results - First, we find that Shyam-Sunder and Myers' (1999) prediction fails to explain total debt changes of Korean firms. Second, we find a non-monotonic relationship between total debt changes and financial deficits with respect to debt capacity. This contradicts the prediction of Lemmon and Zender (2010) that argues the pecking order theory survives with a monotonically increasing relationship. Third, we estimate a negative correlation coefficient between financial deficit and current debt changes. The result is the complete opposite of the prediction of Lemmon and Zender (2010). Finally, we also confirm the non-monotonic relationship between non-current debt changes and financial deficits with respect to debt capacity. Yet, the slope of coefficient is smaller than that of total debt change case. Indeed, the results are, to some extent, consistent with the prediction of pecking order theory, if we exclude the mid-debt capacity firms. Conclusions - Our empirical results complementary to the analysis of Son and Lee (2015), a recent study focusing on capital structure in Korean retail firms; their paper suggests interesting topics regarding capital structure, information asymmetry, and other firm characteristics in Korean corporations. Contrary to Son and Lee (2015), our results show that total debt changes and current debt changes are inconsistent with the prediction of Shyam-Sunder and Myers (1999). However, similar to Son and Lee (2015), non-current debt changes are consistent with the pecking order prediction, in the case of excluding the mid-level debt capacity firms. This contrast allows us to infer that industry characteristics significantly affect the validity of the pecking order prediction. Further studies are needed to analyze the economics behind this phenomenon, which is beyond the scope of our paper. In addition, the estimation bias potentially matters regarding the firm-level debt capacity calculation. We also reserve this topic for future research.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• 제25권1호
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• pp.57-81
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• 1997

Numerical prediction of nocturnal thermal high in summer of the 1995 near Taegu city located in a basin has been carried out by a non-hydrostatic numerical model over complex terrain through one-way double nesting technique in the Z following coordinate system. Under the prevailing westerly winds, vertical turbulent fluxes of momentum and heat over mountains for daytime hours are quite strong with a large magnitude of more than $120W/\textrm{m}^2$, but a small one of $5W/\textrm{m}^2$ at the surface of the basin. Convective boundary layer (CBL) is developed with a thickness of about 600m over the ground in the lee side of Mt. Hyungje, and extends to the edge of inland at the interface of land sea in the east. Sensible heat flux near the surface of the top of the mountain is $50W/\textrm{m}^2$, but its flux in the basin is almost zero. Convergence of sensible heat flux occurs from the ground surface toward the atmosphere in the lower layer, causing the layer over the mountain to be warmed up, but no convergance of the flux over the basin results from the significant mixing of air within the CBL. As horizontal transport of sensible heat flux from the top of the mountain toward over the basin results in the continuous accumulation of heat with time, enhancing air temperature at the surface of the basin, especially Taegu city to be higher than $39.3^{\circ}C$. Since latent heat fluxes are $270W/\textrm{m}^2$ near the top of the mountain and $300W/\textrm{m}^2$ along the slope of the mountain and the basin, evaporation of water vapor from the surface of the basin is much higher than one from the mountain and then, horizontal transport of latent heat flux is from the basin toward the mountain, showing relative humidity of 65 to 75% over the mountain to be much greater than 50% to 55% in the basin. At night, sensible heat fluxes have negative values of $-120W/\textrm{m}^2$ along the slope near the top of the mountain and $-50W/\textrm{m}^2$ at the surface of the basin, which indicate gain of heat from the lower atmosphere. Nighttime radiative cooling produces a shallow nocturnal surface inversion layer with a thickness of about 100m, which is much lower than common surface inversion layer, and lifts extremely heated air masses for daytime hours, namely, a warm pool of $34^{\circ}C$ to be isolated over the ground surface in the basin. As heat transfer from the warm pool in the lower atmosphere toward the ground of the basin occurs, the air near the surface of the basin does not much cool down, resulting in the persistence of high temperature at night, called nocturnal thermal high or tropical night. High relative humidity of 75% is found at the surface of the basin under the moderate wind, while slightly low relative humidity of 60% is along the eastern slope of the high mountain, due to adiabatic heating by the srong downslope wind. Air temperature near the surface of the basin with high moisture in the evening does not get lower than that during the day and the high temperature produces nocturnal warming situation.

• 한국지반환경공학회 논문집
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• 제3권4호
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• pp.19-27
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• 2002

하천에서 토사 유실량을 정확하게 예측하는 것은 유량을 예측하는 것만큼 공학적으로 중요한 의미를 지니고 있다. 하천에서 발생하는 토양 유실량은 하천구역내의 수리구조물(댐, 웨어, 방조제 등)의 설계 및 유지관리, 하천개수 및 하도의 안정, 홍수터 관리, 저수지의 설계 및 운영, 항만계획 등 수자원 및 수질의 계획이나 관리에 반드시 고려해야 할 사항이다. 따라서 본 연구에서는 토사 유실량 산정에 가장 일반적으로 쓰이는 RUSLE식을 이용하여 삽교호 유역의 토사 유실량을 모의, 산정하였다. RUSLE식의 매개변수 산정은 GIS 주제도인 경사도와 토지이용도, 토양도로부터 추출, 산정하였으며 이를 작성한 RUSLE 산정프로그램에 적용하였다. 또한 최근 30년치의 유역 강우자료를 바탕으로 빈도별 확률강우량을 산정하여 빈도별 확률강우에 따른 토사 유실량을 산정하였다.