• 유통과학연구
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• 제13권3호
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• pp.69-77
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• 2015

Purpose - The purpose of this study is to examine whether the cash policies of retail firms listed on Korean stock markets are consistent with the evidence provided in the study of Almeida et al. (2004). Liquidity management is an important issue for financially constrained firms relative to financially unconstrained firms. Because there are few sources of external funding, the optimal liquidity policies of financially constrained firms should reflect their own earnings or cash inflows to create opportunities for current and future real investments. According to this simple idea, we estimate the sensitivity of cash to cash flows and simply check whether the estimated sensitivity to cash flows of the cash retained by constrained retail firms is greater than that of the cash retained by unconstrained retail firms. Through this work, we aim to explain why the cash policies of the retail firms listed on the Korean stock markets differ from those of listed manufacturing enterprises. Research design, data, and methodology - To explain a firm's cash holdings, we use only three explanatory variables: earnings before interest and taxes (EBIT), Tobin's q, and size. All the variables are defined as the value of the numerator divided by aggregate assets. Thanks to this definition, it is possible to treat all the sample firms as a single large firm. The sample financial data for this study are collected from the retail enterprises listed on the KOSPI and KOSDAQ markets from 1991 to 2013. We can obtain these data from WISEfn, the financial information company. This study's methodology has its origin in Keynes's simple idea of precautionary liquidity demand: When a firm faces financial constraints, cash savings from earnings or cash inflows become important from the corporate finance perspective. Following this simple idea, Almeida et al. (2004) developed their theoretical model and found empirical evidence that the sensitivity of cash to cash flows varies systematically according to different types of financing frictions. To find more empirical evidence for this idea, we examined the cash flow sensitivity of the cash held by Korean retail firms. Results - Through several robustness tests, we empirically showed that financially constrained Korean retail firms display significant positive propensity to save cash from earnings before interest and taxes, while the estimated cash flow sensitivity of the cash held by unconstrained retail firms is not significant. Despite the relatively low earnings of retail firms, their sensitivity is three times greater than that of manufacturing enterprises. This implies that Korean retail firms have greater intentions of facilitating future investments rather than current investments. Conclusions - The characteristics of the cash policies of Korean retail firms differ from those of manufacturing firms. This contrast may be attributable to industry-oriented policy planning, regulations, and institutional differences. However, the industrial policymakers should observe signals of the long-term growth options of retail firms based on their high propensity to save from their cash inflows.

• 한국환경과학회지
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• 제16권3호
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• pp.333-345
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• 2007

As analyzed the estimated values of the daily delivery loads from thirteen major side streams such as Naesung-river, Keumho-river, Hwang-river, Nam-river during five years (from 1999 to 2003), the daily BOD inflow into the main stream of Nakdong river in 2003 shows the highest quantity as 31.1 ton and the daily BOD inflows in 1999, 2000, 2001, and 2002 are 26.7 ton, 22.5 ton, 21.0 ton, 25.8 ton, respectively. The daily TN in-flow into the main stream of Nakdong river in 2003 shows also the highest quantity as 64.9 ton and the daily TN inflows in 1999, 2000, 2001, and 2002 are 55.19 ton, 46.27 ton, 39.5 ton, 53.38 ton, respectively. The daily TP inflow into the main stream of Nakdong river in 2003 shows the highest quantity as 2.70 ton likewise and the daily TP inflows in 1999, 2000, 2001, and 2002 are 2.17 ton, 1.87 ton, 1.60 ton, 2.10 ton, respectively The rate of BOD loads from each side main stream into the main stream of Nakdong river shows that the BOD loads of Keumho-river are the highest as the values range from 32.8 % (2002) ${\sim}$ 35.1 % (2003) and the BOD loads of Nam-river, Naesung-river, Hwang-river are high in the order named. The rate of TN loads to the main stream is also similar to the trend of BOD loads. The contribution of the TN loads of Geumho-river to the contamination of the main stream is also the highest having a range from 27.0 % (2002) to 28.8 % (1999) among the main side streams and the TN loads of Naesung-river, Nam-river, and Heachun-river are high in the order named. The rate of TP loads is quite different from the trend of BOD and TN loads. The TP rate of Keumho-river, however, is still the highest as ranging 58.6 % (2002) to 61.7 % (2003) and the river has the biggest portion (over 50%) of the entire pollution to the main stream of Nakdong river.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2003년도 학술발표논문집
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• pp.503-506
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• 2003

The DAWAST model was originally developed to consider daily variation in the unsaturated soil water storage and it is a conceptual lumped model. Return flows from agricultural, domestic and industrial water were included to the original result of model simulation to calibrate model parameter. Daily inflow to the Daechung multipurpose dam was applied to verify the DAWAST model considered return flows. Simulation results were comparable to the inflows of dam operation reasonably.

• Korean Journal of Hydrosciences
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• 제2권
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• pp.69-84
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• 1991

US NWS/NETWORK is applied for the analysis of the flood of July 11-15, 1981 through the Goan-Indogyo reach of the Han River. For the flood hydrography synthesis of the lateral inflows from the major tributaries into the main reach the Cleak method is employed. NETWORK coupled with the Clark method of hydrography synthesis simulated with a fair accuracy the oberved flood hydrograph at the downstream boundary of the routing reach. The dffect of SCS runoff curve number for fributary flood synthesis is evaluated. The characteristics of the station variations and time variations of the flood discharges in the reach is also analyzed.

• International Journal of Fluid Machinery and Systems
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• 제10권2호
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• pp.138-145
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• 2017

The problem of non-uniform inflow exists in many practical engineering applications, such as the elbow suction pipe of waterjet pump and, the channel head of steam generator which is directly connect with reactor coolant pump. Generally, pumps are identical designs and are selected based on performance under uniform inflow with the straight pipe, but actually non-uniform suction flow is induced by upstream equipment. In this paper, CFD approach was employed to analyze unsteady hydrodynamic characteristics of reactor coolant pumps with different inflows. The Reynolds-averaged Naiver-Stokes equations with the $k-{\varepsilon}$ turbulence model were solved by the computational fluid dynamics software CFX to conduct the steady and unsteady numerical simulation. The numerical results of the straight pipe and channel head were validated with experimental data for the heads at different flow coefficients. In the nominal flow rate, the head of the pump with the channel head decreases by 1.19% when compared to the straight pipe. The complicated structure of channel head induces the inlet flow non-uniform. The non-uniformity of the inflow induces the difference of vorticity distribution at the outlet of the pump. The variation law of blade to blade velocity at different flow rate and the difference of blade to blade velocity with different inflow are researched. The effects of non-uniform inflow on radial forces are absolutely different from the uniform inflow. For the radial forces at the frequency $f_R$, the corresponding amplitude of channel head are higher than the straight pipe at $1.0{\Phi}_d$ and $1.2{\Phi}_d$ flow rates, and the corresponding amplitude of channel head are lower than the straight pipe at $0.8{\Phi}_d$ flow rates.

• 한국습지학회지
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• 제10권2호
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• pp.129-141
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• 2008

본 연구는 도심지 유역인 경기도 부천 여월동 단지 내 도시하천의 수질 특성을 분석하고 평가하고자 한다. 해당 유역의 하천은 차집관로에 의한 생활하수와 평시 흐름의 차단으로 인하여 매우 적은 유량만이 흐르고 있고, 각종 하수와 오염원의 유입으로 수질 오염 및 악취 발생 등의 문제를 안고 있다. 따라서 본 연구에서는 수질 현황을 파악하고 수질 개선책을 제시하기 위하여 수질 모니터링을 시행하였으며, 해당 유역의 특성과 조사 결과를 이용하여 QUAL2E 모형을 통한 수질 모델링을 구축하고, 이를 이용해 수질특성과 향후 미래 수질을 검토하였다. 검토 결과 주거지역내 소하천의 경우 오염원의 유입에 따라서 수질이 크게 변화하며 비점오염원에 대해서도 불안요소를 포함하고 있는 것으로 나타났다. 본 연구 대상지역의 경우 유지유량 공급과 오염원의 차단이 중요할 것으로 판단된다.

• 한국수자원학회논문집
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• 제33권5호
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• pp.593-601
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• 2000

Kim and Lee(2000)는 우리 나라 충주댐의 월 유입량을 EI Nino Southern Oscillation (ENSO)과 연관지어 분석한 결과, 엘리뇨가 발생한 해의 가을과 겨울의 유입량은 평년보다 적은 반면, 라니냐가 발생한 해의 가을과 겨울의 유입량은 평년보다 많음을 밝힌바 있다. 본 연구에서는 이런 ENSO와 유입량 사이의 원격상관관계를 저수지 운영에 활용하는 방안을 제시하고자 한다. 즉, ENSO 정보를 추계동적계획법(SDP)의 수문상태변수로 사용하여 충주댐의 월 운영율을 산출하였다. 대안으로, 수문상태변수를 사용하지 않은 SDP로 월 운영율울 또한 산출하였다. 이러한 두 가지 운영율을 모의운영을 통하여 비교함으로써, ENSO 정보를 이용하였을 때의 가치를 검토하였다. 모의운영 결과, ENSO 정보를 이용한 운영울은 발전량과 용수공급의 안정성을 증대시키고 동시에 월류량을 감소시키는 것으로 나타났다.

• 터널과지하공간
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• 제13권6호
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• pp.465-475
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• 2003

본 논문은 지하공동이 건설되는 지역을 대상으로 공동내 지하수 유입량을 계산하기 위하여 영국의 AEA Technology에서 개발한 NAPSAC과 NAMMU를 이용하여 수치 모델링을 실시하였다. 이것은 3차원의 파쇄된 매질에서 지하수 유동에 대하여 아주 유효한 유한요소 소프트웨어 패키지이다. 모델링에 사용된 입력자료는 지표조사, 시추조사, 단일공 수리시험 자료 등을 이용하여 산출하였다. 공동내 지하수 유입량을 보다 정확히 산출하기 위하여 이방성 수리전도도를 고려하였으며 이방성 수리전도도값은 연구지역에 분포하는 균열체계의 확률적 분포특성이 반영된 균열망에서 역산되었다. 연속체 개념의 수치모델링을 통하여 평수기, 갈수기와 풍수기시의 지하 공동내 유입량, 유동시간, 유동경로의 변화를 계산하였다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2011년도 학술발표회
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• pp.58-58
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• 2011

The Texas Commission on Environmental Quality(TCEQ) WAM(Water Availability Modeling) System consists of the generalized Water Rights Analysis Package(WRAP) river/reservoir system water management simulation model, 22 sets of WRAP hydrology and water rights input files for the 23 river basins of Texas, geographic information system tools, and other supporting databases. The WRAP/WAM modeling system, as routinely applied since the late 1990s, has not included consideration of water quality. Recently developed WRAP-SALT(Water Rights Analysis Package) is designed primarily for computing concentration frequency statistics and supply reliability indices at locations of interest in a river system for alternative water development and management scenarios. Though motivated primarily by natural salt pollution, WRAP-SALT water quality modeling features are applicable to essentially any conservative water quality constituent. The Brazos River studies discussed in this paper focus on total dissolved solids, though the available observed data also includes chloride and sulfate which can be modeled as individual constituents. The WRAP-SALT salinity input file contains loads or concentrations of salinity inflows during each month of the hydrologic period-of-analysis and reservoir storage at the beginning of the simulation. The WRAP-SALT model computes salt loads and concentrations for each control point of a river/reservoir system for inflows and outflows during the month and end-of-month reservoir storage for each month of the hydrologic period-of-analysis, for given loads entering the system. River reaches connect control points. The mass balance algorithms proceed from upstream to downstream, with outflow from one river reach contributing to inflow to the next downstream reach. In a given month, for each control point in sequence, the inflow loads are first computed. Loads and concentrations of outflows and reservoir storage at the control point are then determined. Complete mixing during the month is assumed at locations without reservoir storage.

• 자원ㆍ환경경제연구
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• 제25권4호
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• pp.471-494
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• 2016

본 연구는 1996년부터 2013년의 경제성장률의 변동성 데이터를 이용하여 아프리카 28개국의 경제적 안정성에 영향을 미치는 요인을 분석한 것이다. 28개 아프리카 국가의 1996년 부터 2013년의 연도별 자료를 3년씩 따로 분류하여 총 6개의 시계열 자료를 구축하고 이를 토대로 패널 분석을 수행하였다. 송금 및 농업원조와 경제성장률의 변동성 간의 내생성 문제를 해결하기 위하여 system-GMM (system-Generalized Method of Moments)을 이용하였다. 분석결과 기후변화를 대표하는 요인 중 자연재해와 온도의 변동성만이 경제 안정성을 악화시키는 요인으로 나타났다. 반면 송금과 농업원조자금은 아프리카 국가들의 경제를 안정시키는 효과를 보이며, 특히 송금의 경우 자연재해 발생에 따른 경제 변동성을 감소시키는 보험의 역할을 하는 것으로 판단된다.