• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2023년도 학술발표회
• /
• pp.185-185
• /
• 2023

Agricultural water demand is considered as the major sector of water withdrawal due to irrigation. The majority part of the global agricultural field depends on various irrigation techniques. Therefore, a timely and sufficient supply of water is the most important requirement for agriculture. Irrigation is implemented in different ways in various land surface models, it can be modeled empirically based on observed irrigation rates or by calculating water supply and demand. Certain models can also calculate the irrigation demand as per the soil water deficit. In these implementations, irrigation is typically applied uniformly over the irrigated land regardless of crop types or irrigation techniques. Whereas, the latest version of Community Land Model (CLM) in the Community Terrestrial Systems Model (CTSM) uses a global distribution map of irrigation with 64 crop functional types (CFTs) to simulate the irrigation water demand. It can estimate irrigation water withdrawal from different sources and the amount or the areas irrigated with different irrigation techniques. Hence, we set up the model for the simulation period of 16 years from 2000 to 2015 to analyze the global irrigation demand at a spatial resolution of 1.9° × 2.5°. The simulated irrigation water demand is evaluated with the available observation data from FAO AQUASTAT database at the country scale. With the evaluated model, this study aims to suggest new sustainable scenarios for the ratios of irrigation water withdrawal, high depending on the withdrawal sources e.g. surface water and groundwater. With such scenarios, the CFT maps are considered as the determining factor for selecting the areas where the crop pattern can be altered for a sustainable irrigation water management depending on the available withdrawal sources. Overall, our study demonstrate that the scenarios for the future sustainable water resources management in terms of irrigation water withdrawal from the both the surface water and groundwater sources may overcome the excessive stress on exploiting the groundwater in major river basins globally.

• Journal of applied mathematics & informatics
• /
• 제27권5_6호
• /
• pp.1017-1031
• /
• 2009

The problem of interaction of surface water waves by small undulation at the bottom of a laterally unbounded sea is treated on the basis of linear water wave theory for both normal and oblique incidences. Perturbation analysis is employed to obtain the first order corrections to the reflection and transmission coefficients in terms of integrals involving the shape function c(x) representing the bottom undulation. Fourier transform method and residue theorem are applied to obtain these coefficients. As an example, a patch of sinusoidal ripples is considered in both the cases as the shape function. The principal conclusion is that the reflection coefficient is oscillatory in the ratio of twice the surface wave number to the wave number of the ripples. In particular, there is a Bragg resonance between the surface waves and the ripples, which is associated with high reflection of incident wave energy. The theoretical observations are validated computationally.

• 한국농공학회:학술대회논문집
• /
• 한국농공학회 2005년도 학술발표논문집
• /
• pp.637-642
• /
• 2005

The objective of this study is to evaluate design parameters of free water surface constructed wetland for the reduction of agricultural nonpoint source pollution. From literature review, the key design parameters were selected as influent concentration, influent water volume, hydraulic retention time and wetland system arrangement. The design value for each parameter was established after pilot study. Full-scale constructed wetland on the basis of the designed values was constructed to evaluate those reasonableness. The results of this study showed that the designed values for free water surface constructed wetland were appropriate for the reduction of agricultural nonpoint source pollution.

• 태양에너지
• /
• 제20권1호
• /
• pp.55-62
• /
• 2000

An experimental study on the stratified fluids with water and silicon oil of same volume in the cavity with upper cooling surface was carried out to investigate the flow characteristics, heat transfer through the interface of fluids, and the applications of thermal behaviors in a square cavity. The experiments were performed with variation of initial temperature and cooling surface temperature. The temperature drop of oil was faster than that of water and freezing was initiated from the interface of oil and water and propagated downward. For the water above $4^{\circ}C$, the cooling rate was faster than that below $4^{\circ}C$ and showed almost same temperature distribution but for the water that of below $4^{\circ}C$, it showed the stable stratified temperature distribution. The lower the initial temperature and the higher the cooling surface temperature was, the longer the supercooling duration.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
• /
• pp.892-895
• /
• 2006

The atmospheric effects on the retrieval of sea ice concentration from passive microwave sensors are examined using simulated data typical for the Arctic summer. The simulation includes atmospheric contributions of cloud liquid water and water vapor and surface wind on surface emissivity on the microwave signatures. A plane parallel radiative transfer model is used to compute brightness temperatures at SSM/I frequencies over surfaces that contain open water, first-year (FY) ice and multi-year (MY) ice and their combinations. Synthetic retrievals in this study use the NASA Team (NT) algorithm for the estimation of sea ice concentrations. This study shows that if the satellite sensor’s field of view is filled with only FY ice the retrieval is not much affected by the atmospheric conditions due to the high contrast between emission signals from FY ice surface and the signals from the atmosphere. Pure MY ice concentration is generally underestimated due to the low MY ice surface emissivity that results in the enhancement of emission signals from the atmospheric parameters. Simulation results in marginal ice areas also show that the atmospheric and surface effects tend to degrade the accuracy at low sea ice concentration. FY ice concentration is overestimated and MY ice concentration is underestimated in the presence of atmospheric water and surface wind at low ice concentration. In particular, our results suggest that strong surface wind is more important than atmospheric water in contributing to the retrieval errors of total ice concentrations over marginal ice zones.

• 한국물환경학회지
• /
• 제22권1호
• /
• pp.1-6
• /
• 2006

In this study, five commercially available fouling resistant low-pressure RO membranes were investigated for the treatment of seasonally brackish surface water with high organic content (${\approx}24mg/L$). The membranes investigated are LFC-1 (Hydranautics), X20 (Trisep), BW30FR1 (FilmTec), SG (Osmonics), and BE-FR (Saehan). The results of surface characterization revealed that each of these membranes has one or two unique surface characteristics to minimize the adherence of the fouling materials to the membrane. Specifically, the LFC1 membrane features a neutral or low negative surface to minimize electrostatic interactions with charged foulants. The X20, on the other hand, shows a highly negatively charged surface, and thus, is expected to perform well with feed waters containing negatively charged organics and colloids. The BW30FR1 exhibits a relatively neutral and hydrophilic surface, which could be beneficial for lessening organic and/or biofouling. The SG membrane has a smooth surface that makes it quite resistant to fouling, particularly for colloidal deposition. Lastly, BE-FR membrane demonstrated a medium surface charge and a slightly higher hydrophobicity. In the pilot study, all of the four membranes experienced a gradual increase in MTC (water mass transfer coefficient or specific flux) over time, indicating no fouling occurred during the pilot study. The deterioration of permeate water quality such as TDS was also observed over time, suggesting that the integrity of the membranes was compromised by the monochloramine used for biofouling control.

• 한국응용과학기술학회지
• /
• 제32권4호
• /
• pp.661-668
• /
• 2015

The surface rheological properties of polymer monolayer show complicated non-linear viscoelastic flow phenomena when they are subjected to spreading flow. These spreading flow properties are controlled by the characteristics of flow units. The kinetics of the formation of an interfacial film obtained after spreading poly(diisobutylene maleic acid) at air-water interface were studied by measuring of the surface pressure with time. The experimental data were analyzed theoretically according to a nonlinear surface viscoelastic model. The values of dynamic modulus, static modulus, surface viscosities and rheological parameters in various area/ monomer were obtained by appling experimental data to the equation of nonlinear surface viscoelastic model.

• Journal of Advanced Marine Engineering and Technology
• /
• 제20권3호
• /
• pp.11-18
• /
• 1996

Liquid droplets of water and argon surrounded by their vapor have been simulated by the milecular dynamics method. To explore the surface phenomena of clusters, each molecule is classified into 'liquid', 'surface', or 'vapor' with respect to the number of neighbor molecules. The contribution of a 'surface' molecule of the water cluster to the far infrared spectrum is almist the same as that of the 'liquid' molecule. Hence, the liquid-vapor interface is viewed as geometrically and temporally varying boundary of 'liquid' molecules with only a single layer of 'surface' molecules that might have different characteristics from the 'liquid' molecules. The time scale of the 'phase change' of each molecule is estimated for the argon cluster by observing the instantancous kinetic and potential energies of each molecule. To compare the feature of clusters with macroscopic droplets, the temperature dependence of the surface tension of the argon cluster is estimated.

• 한국환경농학회지
• /
• 제16권4호
• /
• pp.356-364
• /
• 1997

경남지역 주요 시설원예 용수원의 수질을 김해, 창녕, 함안, 사천, 진주 등 5개 지역에서 각 지역별 4개지점의 지표수의 수질을 동절기인 1995년 10월부터 1996년 3월까지 매월 1회, 총 6회에 걸쳐 분석한 결과를 요약하면 다음과 같다. 각 지역별 pH는 6.6${\sim}$9.1 범위였으며, 농업용수 허용기준치인 pH 6.0${\sim}$8.5를 초과하는 지역은 김해, 창녕이었다. DO는 함안을 제외한 지역은 평균 10.0mg/l 이상으로서 비교적 높았으나 함안은 6.4${\sim}$10.0mg/l 범위로서 타지역에 비하여 낮았으며, BOD는 함안 3개지점, 사천 1개 지점이 농업용수 허용기준치인 8.0mg/l을 초과하였다. COD는 진주를 제외한 4개지역 모두 농업용수 허용기준치 8.0mg/l초과하였고, 함안이 평균 19.8mg/l로 타지역에 비하여 가장 높았다. ${NH_4}^+-N$은 창녕과 함안지역이 각각 1.21mg/l 및 2.75mg/l로 높았으며, $NO^{3-}-N$은 양호한 편이었다. $K^+,\;Na^+,\;Mg^{2+},\;Ca^{2+},\;PO_4^{3-}$ 및 $SO_4^{2-}$는 함안지역이 타지역에 비하여 매우 높았으며, Pb는 각 지역 모두 농산물 재배 기준치인 0.1mg/l이하였으며, Cu, Cd 및 Zn의 각 지역별 평균은 농업용수 기준치 이하였으며 지점에 따라서는 기준치를 초과하는 지점도 여러곳 있었다. 수질분석 항목들간의 상관관계를 검토한 결과 COD와 SS는 r$=0.799^{{\ast}{\ast}}$로 고도의 유의성있는 정의상관이 있었으며, BOD는 $NH_4\;^+-N,\;PO_4\;^{3-},\;K^+,\;Na^+$ 및 $Cl^-$과 유의성있는 정의 상관이 있었다. 경남지역 시설원예지대 농업용수원의 동절기 (1995년 10월${\sim}$1996년 3월) 지표수 수질실태는 진주<사천<김해<창녕<함안 순으로 오염도가 높았다.

• 한국표면공학회지
• /
• 제8권2호
• /
• pp.14-19
• /
• 1975