• 한국수자원학회논문집
• /
• 제43권6호
• /
• pp.533-541
• /
• 2010

강우-유출모형에 의해서 유역내 강우로부터 직접 유출량을 산출하는 것은 홍수량 예측에 기초가 된다. 직접 유출량은 강우-유출모형에 의해서 초과우량 또는 유효우량으로부터 산출된다. 시간별 초과우량은 시간별 총 강우에서 강우의 손실량을 제하여 산출한다. 이 손실량은 강우-유출모형 내 여러 손실 중에 비중이 큰 침투 손실량과 같도록 취급할 수 있다. 여기서 초과우량 또는 유효우량 산출을 위해서 실용적으로 간편한 $\Phi$지수법, W지수법 또는 이의 수정법이 적용되어 왔다. 본 연구에서는 한 유역 내 강우 손실의 시간적 변화는 잘 알려진 Horton 침투 과정으로 간주하여 Horton 침투모형의 매개변수 값이 주어진 경우에 시간 단위별 침투손실 및 초과우량을 산출하는 절차와 적용 원칙을 제시하고 적용결과를 $\Phi$지수 방법의 적용결과에 비교하였다. 본 연구에서 산출한 강우사상에서 시간 단위의 Horton 침투량 값은 시간에 따라 지수적으로 감쇠되는 Horton 모형의 침투 과정을 잘 보여 준다.

• 상하수도학회지
• /
• 제21권6호
• /
• pp.737-744
• /
• 2007

Recently, one of the most interesting topic in the field of wastewater treatment is the disposal of excess sludge. The new concept of excess sludge reduction with recirculation of solubilized sludge via effective microorganisms for cell disruption within the wastewater treatment process has been developed in this study. The alkalophiles for degradation of sludge cell wall were isolated as Exiguobacterium sp., which could be more effectively solubilized sludge in the anaerobic condition. The SCOD of solubilized excess sludge by Exiguobacterium sp. was up to about 2,000mg/L and average TN and TP concentration of solubilized component were 117mg/L and 58mg/L, respectively and C/N ratio was more than 17. To investigate the effects of solubilized sludge by alkalophiles on excess sludge reduction and nutrient removal efficiency, the pilot plant of $DF^{(S)}-MBR$ process, combined with membrane bioreactor and sludge solubilization tank, was operated. In the control run(without sludge solubilization), the daily sludge production was about 4.54 kgMLVSS/day. However, in the $DF^{(S)}-MBR$(with sludge solubilization), the daily sludge production was decreased to 1.39kgMLVSS/day. The effluent quality satisfied the effluent regulation in both cases. Furthermore, the $DF^{(S)}-MBR$ showed relatively better TN removal efficiency in spite of high influent loading. So we concluded that the solubilized excess sludge by alkalophiles was effectively degraded in the MBR process as the carbon source and 70% of sludge reduction efficiency can be achieved.

• Coupled systems mechanics
• /
• 제3권2호
• /
• pp.233-245
• /
• 2014

Coupled finite element analysis is carried out to study the effect of degree of saturation on the vertical displacements and pore water pressures simultaneously by developing a FORTRAN90 code. The finite element formulation adopted in the present study is based upon Biot's consolidation theory to include partially saturated soils. Numerical methods are applied to a two-dimensional plane strain strip footing (flexible) problem and the effect of variable degree of saturation on the response of excess pore water pressure dissipation and settlement of the footing is studied. The immediate settlement in the case of partly saturated soils is larger than that of a fully saturated soil, the reason being the presence of pore air in partially saturated soils. On the other hand, the excess pore water pressure for partially saturated soil are smaller than those for fully saturated soil.

• Journal of Electrochemical Science and Technology
• /
• 제13권3호
• /
• pp.369-376
• /
• 2022

In this study, the stability of an anion exchange membrane water electrolyzer (AEMWE) cell was evaluated in an on-off cycling operation with respect to an applied electric bias, i.e., a current density of 500 mA cm^-2, and an open circuit. The ohmic and polarization resistances of the system were monitored during operation (~800 h) using electrochemical impedance spectra. Specific consideration was given to the ohmic resistance of the cell, especially that of the membrane under on-off cycling conditions, by consistently feeding the cell with KOH solution. Owing to an excess feed solution, a momentary increase in the polarization resistance was observed immediately after the open-circuit. The excess feed solution was mostly recovered by subjecting the cell to the applied electric bias. Stability tests on the AEMWE cell under on-off cycling with continuous feeding even under an open circuit can guarantee long-term stability by avoiding an irreversible increase in ohmic and polarization resistances.

• 대한토목학회논문집
• /
• 제31권3B호
• /
• pp.253-264
• /
• 2011

일반적으로 가뭄은 기상학적 가뭄, 농업적 가뭄, 수문학적 가뭄, 사회경제학적 가뭄으로 구분하여 정의한 후 정성적 혹은 정량적 평가를 수행한다. 이중 기상학적 가뭄, 농업적 가뭄, 수문학적 가뭄에 관련한 연구는 활발히 진행되고 있으나, 상대적으로 사회경제학적 가뭄평가와 관련한 연구는 미미한 실정이다. 본 연구에서는 우리나라에서 적용가능한 사회경제학적 가뭄을 정의하고 가뭄평가를 수행하였다. 사회경제학적 가뭄을 평가하기 위해서 우리나라의 인구증가와 산업발전을 반영하는 용수수요 현황과 수자원 공급시설의 개발에 따른 가용 수자원의 증가를 반영하는 용수공급 현황을 상대적으로 비교할 수 있는 용수과부족지수(WEDI)를 제안하였다. 본 연구에서 제안된 용수과부족지수의 타당성을 검토하기 위해 기존의 가뭄지수(SPI, PDSI)와 실제 가뭄발생(2001년 봄가뭄)과 비교 분석을 수행하였다. 용수과부족지수를 경상도에 적용하여 용수수요량 대비 용수공급량을 비교 분석한 결과 상대적으로 용수가 부족한 지역과 여유있는 지역을 구분할 수 있었다.

• 한국지반공학회논문집
• /
• 제31권1호
• /
• pp.5-14
• /
• 2015

해저지반에 고파랑이 장시간 지속적으로 작용하는 경우 과잉간극수압이 크게 발생할 수 있고, 이로 인한 유효응력의 감소로 최악의 경우는 액상화를 유발할 수 있다. 따라서, 파작용에 의한 발생되는 해저지반의 동적응답을 정확히 예측할 수 있는 수치해석방법이 필요하다. 본 연구에서는 복합모델(2D-NIT 모델 & FLIP 모델)을 사용한 새로운 수치 해석법을 제안하였다. 해저지반과 파동장이 접하는 경계면상에서 작용하는 파압과 유속을 2D-NIT모델로부터 산정하고, 이를 해저지반상의 외력으로 입력하여 FLIP으로부터 해저지반의 동적응답 거동을 조사하는 것이다. 복합모델의 신뢰성 확보를 위해 본 연구에서는 2D-NIT & FLIP 모델에 의한 수치해석결과를 기존의 Yamamoto 이론해 및 Chang 실험결과와 비교하였다. 그 결과 2D-NIT & FLIP 해석값과 차이는 있지만, 전체적으로 깊이에 따라 지반내의 유효응력 증분과 과잉간극수압증분의 변화양상이 상당히 잘 일치하고 있기 때문에 본 연구에서 제안된 2D-NIT & FLIP모델이 상당한 타당성을 가지고 있음을 확인 할 수 있었다.

• 한국응용과학기술학회지
• /
• 제17권2호
• /
• pp.132-138
• /
• 2000

Excess enthalpies ($H^{E}$) were measured by isothermal flow calorimetry for the nonionic amphiphile 2-butoxyethanol/water mixtures at 10 different temperatures (48.5 to $70^{\circ}C$) around and above the lower consolute solution temperature, $T_{lc}$. $H^{E}$ exhibits U-shape for the binary mixtures, and is large and negative which reflects substantial interaction between two chemical species. When the commonly used, semi-empirical Redlich-Kister (RK) polynomials were fitted to the measured $H^{E}$, plots of $H^{E}$ vs. weight fraction provided more accurate fitting with fewer parameters than conventionally drawn $H^{E}$ vs. mole fraction plots. This was due to the enhanced symmetry of $H^{E}$ vs. weight fraction plots. Using the fitted Redlich-Kister polynomials and the Gibbs-Helmholtz relation, temperature dependence of the activity coefficients were found and compared to the values determined from vapor-liquid equilibria. The activity coefficients were in the range of one to three, indicating that the binary system deviates from ideality but not substantially. They slightly depended on temperature and the temperature effect was equivalent to 10 % change in the activity coefficients.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2019년도 학술발표회
• /
• pp.355-355
• /
• 2019

본 연구에서는 물리적 매개변수 기반의 물 순환 해석 모형인 CAT(Catchment hydrologic cycle Assessment Tool)을 이용하여 보령댐 유역 상류에 위치한 삼산저수지의 저류량을 분석하였다. 연구기간은 2012~2017년이며 2015년 발생한 가뭄 대책의 일환으로 2016년 이후 금강과 보령댐을 잇는 도수로를 설치하여 유역내로 외부유입량이 유입되었다. 이에 본 연구에서는 보다 정확한 저류량 산정을 위해 모의 기간을 2012~2015년 및 2016~2017년으로 나누어 연구를 수행하였다. 매개변수 보정에 앞서 CAT에서 제공하는 세 가지 침투해석방법인 Rainfall Excess, Green&Ampt, Horton 방법을 모두 적용하여 모의하였으며 그 결과 Rainfall Excess 침투방법을 적용했을 때의 모의 정확도가 비교적 높게 나타나는 것을 확인할 수 있었다. 이에 본 연구에서는 Rainfall Excess 침투방법의 주요 토양 관련 매개변수인 토양수분율(${\theta}s$), 연직방향 투수계수(ks) 및 사면방향 투수계수(ksi)를 대상으로 전역최적화기법(SCEUA-P)을 이용한 보정을 수행하였으며 보정 전 후의 모의 저류량과 관측 저류량을 연도별로 비교 및 분석하였다.

• 연구논문집
• /
• 통권29호
• /
• pp.5-15
• /
• 1999

Present study deals with performance analysis of an inert gas generator (IGG) which is to be used as an effective mean to suppress the fire. The IGG uses a turbo jet cycle gas turbine engine to generate inert gas for fire extinguishing. It is generally known that a lesser degree of oxygen content in the product of combustion will increase the effectiveness of fire suppressing. An inert gas generator system with water injection will bring advantages of suffocating and cooling effects which are considered as vital factors for fire extinguishing. As the inert gas is injected to the burning site, it lowers the oxygen content of the air surrounding the flame as well as reduces the temperature around the fire as the vapour in the inert gas evaporates during the time of spreading. Some important aspects of influencing parameters, such as, air excess coefficient. $\alpha$, compressor pressure ratio, $ pi_c$, air temperature before combustion chamber, $T_2$, gas temperature after combustion chamber, $T_3$, mass flow rate of water injection, $M_w$, etc., on the performance of IGG system are investigated. Calculations of total amount of water needed to reduce the turbine exit temperature to pre-set nozzle exit temperature employing a heat exchanger were made to compare the economics of the system. A heat exchanger with two step cooling by water and steam is considered to be better than water cooling only. Computer programs were developed to perform the cycle analysis of the IGG system and heat exchanger considered in the present study.

• 한국물환경학회지
• /
• 제22권6호
• /
• pp.1107-1108
• /
• 2006

As expanding municipal and industrial areas since started the economic development plan in earnest in 1970's, the water resource, mainly river surface water has been seriously polluted. Nevertheless, being upgraded in their treatment technologies for the drinking water, the safety has been issued one of crucially social problem in Korea. The water authorities has tried to improve the quality such as amending the drinking water quality standard to be monitored; hazardous chemicals and microorganis have been added and now 55 items, before 47 items, since in 2002. The Water Authorities of Seoul, the capital city of Korea, planned to assess the safty of drinking water quality after amended the standard. This study was conducted to assess the risk due to polluted chemicals including 21 heavy metals, VOCs, pesticides, PAHs, DBPs and organic chemicals among the regulated items. The risk assessment were undertaken hazard identification, exposure assessment, dose-response assessment and risk characterization. For the exposoure assessment, tap water, bottled water and purified water were sampled and analyzed in February, 2004. Risk characterization of detected chemicals was categorized into carcinogenecity and noncarcinogenecity, and estimated the excess of carcinogens and compapared with the reference dose (RfD) of noncarcinogenns. The excess risk of carcinogens from samples were considered comparatively in the acceptable levels; $10^{-6}$ for cancer risk and hazard quotient (HQ) 1.0 for noncancer risk. The deteced levels were estimated in $10^{-5}{\sim}10^{-6}$ of cancer risk and below 1.0 of HQ of noncancer risk. While three kinds of water were determined within the acceptal levels, DBPs were detected in tap water and purified were and some undesireable chemicals such as more fluoride detected rather than the quality stanadard. For the drinking water safety, it shoud be continuously monitored, assessed and managed as well risk communiction between the authoritis and public.