• 한국농공학회논문집
• /
• 제49권6호
• /
• pp.11-20
• /
• 2007

In order to make the way to determine the instream flow more practically, we have investigated many case studies and reviewed reports and papers. To validate instream flow level suggested by the case studies, DAWAST and HEC-RAS model were applied to the Gap-stream watershed in Daejeon city. Flow-duration analysis was performed both with the stream flow data gauged in the Indong, Boksu, and Hoeduck stations, and with the stream flow data estimated by the DAWAST model and the specific discharge method. Instream flow was determined among the flow-duration analysis, DAWAST, HEC-RAS model and mass balance approach. It was satisfied with various factors such as target water quality, water depth for eco-system and resorts, water surface width, flow velocity for landscape in dry season. The study suggested that the mean low flow could be replaced into the instream flow for the preliminary study because the instream flow considering ecosystem, landscape, water-friendly environment and water quality was generally close to the mean low flow.

• 한국농공학회논문집
• /
• 제54권1호
• /
• pp.27-38
• /
• 2012

This study is to analyse the hydrological behavior of agricultural reservoir using CAT (Catchment hydrologic cycle Assessment Tool). The CAT is a water cycle analysis model in order to quantitatively assess the characteristics of the short/long-term changes in watershed. It supports the effective design of water cycle improvement facilities by supplementing the strengths and weaknesses of existing conceptual parameter-based lumped hydrologic models and physical parameter-based distributed hydrologic models. The CAT especially supports the analysis of runoff processes in paddy fields and reservoirs. To evaluate the impact of agricultural reservoir operation and irrigation water supply on long-term rainfall-runoff process, the CAT was applied to Idong experimental catchment, operated for research on the rural catchment characteristics and accumulated long term data by hydrological observation equipments since 2000. From the results of the main control points, Idong, Yongdeok and Misan reservoirs, the daily water levels of those points are consistent well with observed water levels, and the Nash-Sutcliffe model efficiencies were 0.32~0.89 (2001~2007) and correlation coefficients were 0.73~0.98.

• Journal of Ecology and Environment
• /
• 제35권3호
• /
• pp.157-166
• /
• 2012

Many models intending to explain the latitudinal gradient of increasing species diversity from the poles to the equator are presented, which are a formalisation of the species-energy hypothesis. The model predictions are consistent with patterns of increasing species number with increasing mean air or water temperatures for plants and animals. An increase in species richness is also correlated with net primary production or the Normalised Difference Vegetation Index. This implies that increased availability of resources favours increased diversity capacity. The explanatory variables included in the biodiversity prediction models represent measures of water, energy, water-energy, habitat, history/evolution and biological responses. Water variables tend to be the best predictors when the geographic scope of the data is restricted to tropical and subtropical areas, whereas water-energy variables dominate when colder areas are included. In major models, about 20-35% of species in the various global regions (European, Africa, etc.) will disappear from each grid cell by 2050 and >50% could be vulnerable or threatened by 2080. This study provides good explanations for predictive models and future changes in biodiversity depending on various scenarios.

• Nuclear Engineering and Technology
• /
• 제48권3호
• /
• pp.702-710
• /
• 2016

Global concern and interest in the safety of nuclear power plants have increased considerably since the Fukushima accident. In the event of a severe accident, the reactor vessel water level cannot be measured. The reactor vessel water level has a direct impact on confirming the safety of reactor core cooling. However, in the event of a severe accident, it may be possible to estimate the reactor vessel water level by employing other information. The cascaded fuzzy neural network (CFNN) model can be used to estimate the reactor vessel water level through the process of repeatedly adding fuzzy neural networks. The developed CFNN model was found to be sufficiently accurate for estimating the reactor vessel water level when the sensor performance had deteriorated. Therefore, the developed CFNN model can help provide effective information to operators in the event of a severe accident.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.49-54
• /
• 2003

Scale is formed when hard water is heated or cooled in heat transfer equipments such as heat exchangers, condensers, evaporators, cooling towers, boilers, and pipe walls. When scale deposits in a heat exchanging surface, it is traditionally called fouling. The objective of the present study was to compare the fouling characteristics of river and tap water in a heat exchanging model. FromtheSEM analyses for tap water the $calciteformofCaCO3_{3}$ was formed. For river water, however, the $aragoniteCaCO_{3}$ wasformed.In order to investigate velocity effects on the fouling characteristics in the heat exchanging model, the inlet velocity was varied with 0.5, 1.0 and 1.5 m/s, respectively. The fouling characteristics of river water were quite different from those of tap water. For the case of the 'velocity of 1.5m/s', the overall heat transfer coefficient was reduced up to 26% than that of the 'velocity of 0.5m/s'

• 대한토목학회논문집
• /
• 제12권3호
• /
• pp.153-162
• /
• 1992

시스템 분석에 의한 합리적인 장기(長期) 용수공급(用水供給) 계획(計劃)의 수립을 위하여 동적(動的) 입지선정문제(立地選定問題)의 유형으로 수학적 모형을 정립하였고, 복잡한 혼합 정수계획 문제를 푸는 대신에 스프레드 쉬트를 이용한 간단한 계산모형으로 실제적인 해를 구할 수 있음을 보였다. 분석의 결과로서는 용수 공급시설 및 용수로의 최적의 건설 시기와 기간별 최적 용수공급 운영 양상이 정해진다. 시스템 분석을 통한 합리적(合理的)인 용수공급 계획의 수립이 주먹 구구식의 계획수립에 비하여 약 15% 정도의 예산 절감(節減) 효과(效果)가 있을 수도 있음을 사례분석을 통하여 간접적으로 보여준다.

• 펄프종이기술
• /
• 제30권3호
• /
• pp.46-56
• /
• 1998

The objective of this study was to investigate the relationship between water vapor diffusion properties and the pore structure of paper. Gas-phase molecular diffusivity of water vapor through pores was determined based on the kinetic theory of gas. A mathematical model was derived to characterize the dimensional changes of the pore caused by the fiber-swelling mechanism. A modified-Fickean diffusion model was designed to simulate the water-vapor diffusion phenomena in porous paper web. Structural characterisocs of paper pores including the tortuosity and the shape factor was studied on a theoretical basis of Knudsen flow diffusion. Results are summarized as follows: 1. The theoretical water vapor diffusivity in gas-phase was 0.092$cm^2$ /min, 2. Porosity was inversely proportional to the degree of wet-swelling of paper, 3. Solid-phase water-diffusivity of fiber was 1.2 $ \times 10^{-5}cm^2/min$, 4. Modified diffusion model was fairly consistent to the experimental data (from part I), and 5. The Fickean pore tortuosity, ranging from 1,000 to 2,500, was in inverse proportion to the porosity of paper, and the Knudsen shape factor and length-angle factor for micro-pores in paper were 0.5~3.5 and about 340, respectively.

• 한국물환경학회지
• /
• 제25권6호
• /
• pp.832-839
• /
• 2009

Since construction of the estuarine barrage at the mouth of the Nakdong River, eutrophication and increased abundance of phytoplankton have occurred mainly due to the increased retention time in the reach. However, during the spring, there is a decrease in chlorophyll-a, as a result of an increase in zooplankton number, which preys upon phytoplankton and affects the value of chlorophyll-a. In order to emphasize the importance of zooplankton data in water quality simulation, zooplankton community data were used to simulate water quality and eutrophication at Mulgeum located in 27 km upstream from the barrage. WASP 7.2 was used as the water quality model for the river, using a monthly data set from 2003 to 2005 for model calibration and verification. The results showed that chlorophyll-a, DO, and total nitrogen in the river were simulated well during the verification period. The results of water quality simulation using zooplankton community data in the model were better than those with phytoplankton death rate, in terms of the absolute value of percent bias, root mean square error, and Nash-Sutcliffe efficiency. Those results indicate the use of zooplankton data provides more accurate simulation results for chlorophyll-a and eutrophication.

• Computers and Concrete
• /
• 제19권2호
• /
• pp.171-177
• /
• 2017

Water pressure test operation is used before the grouting to determine the rate of penetrability, the necessity and estimations related to grouting, by the penetration of water into the borehole. One of the parameters which have the highest effect is pressure of water penetration since the application of excessive pressure causes the hydraulic fracture to occur in the rock mass, and on the other hand, it must not be so small that prevents from seeing mechanical weaknesses and the rate of permeability. Mathematical modeling is used for the first time in this study to determine the optimum pressure. Thus, the joints that exist in the rock mass are simulated using cylindrical shell model. The joint surroundings are also modeled through Pasternak environment. To obtain equations governing the joints and the surroundings, energy method is used accompanied by Hamilton principle and an analytical solution method is used to obtain the maximum pressure. In order to validate the modeling, the pressure values obtained by the model were used in the sites of Seymareh and Aghbolagh dams and the relative error rates were measured considering the differences between calculated and actual pressures. Modeling in the sections of Seymareh dam showed 4.75, 3.93, 4.8 percent error rates and in the sections of Aghbolagh dam it rendered the values of 22.43, 5.22, 2.6 percent. The results indicate that this modeling can be used to estimate the amount of pressure for hydraulic fracture in water pressure test, to predict it and to prevent it.

• Journal of Mechanical Science and Technology
• /
• 제20권10호
• /
• pp.1576-1589
• /
• 2006

Most of surface water ways in Egypt suffer from the infestation of aquatic weeds especially submerged ones which cause lots of problems for the open channels and the water structures such as increasing water losses, obstructing the water flow, and reducing the efficiency of the water structures. Accurate simulation of the water flow behavior in such channels is very essential for water distribution decision makers. Artificial Neural Network (ANN) has been widely utilized in the past ten years in civil engineering applications for the simulation and prediction of the different physical phenomena and has proven its capabilities in the different fields. The present study aims towards introducing the use of ANN technique to model and predict the impact of the existence of submerged aquatic weeds on the hydraulic performance of open channels. Specifically the current paper investigates utilizing the ANN technique in developing a simulation and prediction model for the flow behavior in an open channel experiment that simulates the existence of submerged weeds as branched flexible elements. This experiment was considered as an example for implementing the same methodology and technique in a real open channel system. The results of current manuscript showed that ANN technique was very successful in simulating the flow behavior of the pre-mentioned open channel experiment with the existence of the submerged weeds. In addition, the developed ANN models were capable of predicting the open channel flow behavior in all the submerged weeds' cases that were considered in the ANN development process.