• 대한환경공학회지
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• 제22권12호
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• pp.2239-2245
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• 2000

현대와 같이 대량의 폐수가 유출되는 시점에서 처리는 재이용을 고려한 질적 개념과 양적 개념을 고려해야 한다. 양적 개념을 고려할 경우, 고율법(high rate aeration)은 현재까지 알려진 공법 중 가장 효과적인 공법으로 알려져 있으나, 이는 처리량이나 처리속도 면에서 고율법을 능가하는 UHR(ultra high rate) 공법을 제시한 바 있다. 따라서 본 연구는 이미 이 가 밝힌 UHR법의 적용부하, 적용농도 등 기초적 설계범위 및 처리특성을 밝히기 위해 실행되었다. 실험 결과 본법의 적용 가능부하는 $2.2{\sim}7.0kg-BOD_5/kg-MLSS{\cdot}day$로 고율법의 최대 적용부하인 $2.25kg-BOD_5/kg-MLSS{\cdot}day$을 3배 이상 초과하였다. 또한 유입수 농도 200에서 450 mg/L범위에서 처리율은 94.7~97.3%로 매우 양호한 결과를 보였다. 따라서 처리의 양적 개념에서 볼 때 기존의 어떤 처리법보다 UHR법은 매우 획기적인 처리법으로 고려된다.

• Geomechanics and Engineering
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• 제11권3호
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• pp.325-343
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• 2016

A total stress-based bounding surface model is developed to predict the undrained behaviour of saturated soft clays under cyclic loads based on the anisotropic hardening modulus field and bounding-surface theories. A new hardening rule is developed based on a new interpolation function of the hardening modulus that has simple mathematic expression and fewer model parameters. The evolution of hardening modulus field is described in the deviatoric stress space. It is assumed that the stress reverse points are the mapping centre points and the mapping centre moves with the variation of loading and unloading paths to describe the cyclic stress-strain hysteresis curve. In addition, by introducing a model parameter that reflects the accumulation rate and level of shear strain to the interpolation function, the cyclic shakedown and failure behaviour of soil elements with different combinations of initial and cyclic stresses can be captured. The methods to determine the model parameters using cyclic triaxial compression tests are also studied. Finally, the cyclic triaxial extension and torsional shear tests are performed. By comparing the predictions with the test results, the model can be used to describe undrained cyclic stress-strain responses of elements with different stress states for the tested clays.

• 한국물환경학회지
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• 제18권2호
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• pp.189-199
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• 2002

Nitrogen, in its various forms, can deplete dissolved oxygen levels in receiving waters, stimulate aquatic growth, exhibit toxicity toward aquatic life and affect the suitability of sewage for reuse. Pilot-scale Rotating Biological Contactor(RBC) experiments were conducted to examine biological nitrification, respectively, of municipal sewage with five different internal recirculation ratios of 0, 1, 2, 3, and 4 using the constant hydraulic loading of $205L/m^2{\cdot}day$. The use of internal recirculation improved nitrification on account of the dilution of biodegradable organic carbon in influent sewage down to 15 mg/L of $SBOD_5$ or less. Ammonium nitrogen of $14.3{\pm}2.4%$ was consumed by cellular assimilation without the occurrence of denitrification. The thickness of biofilm didn't seem effect significantly the nitrification and denitrification. Nitrification with internal recirculation was found to occur using hydraulic loading rate of as high as $205L/m^2{\cdot}day$, which was beyond the generally known values of it.

• 상하수도학회지
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• 제27권3호
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• pp.299-312
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• 2013

This study investigated the contaminant loading and characteristics of particle size distributions(PSDs) in the rainfall runoff from two different sources, the pavement road and the ancillary parking lot, and then evaluated four different types of filter media(i.e., EPP, EPS, Zeolite, and Perlite) to treat runoff water. The results showed that runoff from the pavement road contains 5.6 and 20 times higher SS and Pb concentrations, respectively, than that from the parking lot. The particles smaller than $100{\mu}m$ occupied 89.8 % of runoff from the pavement road and 81.4 % of that from the parking lot by volume. The effect of the hydraulic loading, at 950 m/day filtering linar velocity and 40 cm head loss, was largest for Zeolite, followed by Perlite, EPS, and EPP. The return period of tested media calculated by the regression equation for head loss indicated that EPP has the longest life time. The average SS removal rate was similar for all media at between 84.9 % and 89 %, while the effect of various filter column heights was different, showing minimal for EPP and maximum for EPS. All filter media tested demonstrated over 95 % of SS treatment efficiency for the particles bigger than $100{\mu}m$, while for the ones smaller than $100{\mu}m$ the efficiency was in order of EPP(82.4%) > Perlite(76.1 %) > EPS(66.2 %) > Zeolite(65.2 %). The results in conclusion implies that EPP is most effective filter media for the highly contaminated fine particles from road runoff.

• Environmental Engineering Research
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• 제14권4호
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• pp.238-242
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• 2009

This study investigated the effects of organic loading rates on simultaneous carbon and nitrogen removal in an innovative fixed-film aerobic bioreactor. The fixed-film bioreactor (FFB) was composed of a two-compartment aeration tank, in which a synthetic filamentous carrier was submerged as biofilm support media, and a settling tank which polyvinylidene media (Saran) was used as settling aid for suspended solids. Three different organic loading rates, ranging from 0.92-2.02 kg chemical oxygen demand/$m^3$/day were applied by varying hydraulic retention time (HRT). The total soluble organic carbon removal efficiencies were in the range of 90-97%. The removal efficiency of ammonia was found to be in the range of 70-84%. Total nitrogen removal efficiency was found to be in the range of 40-45%, which indicates that denitrification reactions occurred simultaneously in the attached biofilm on the fibrous media in the aeration tank. The settling performance of suspended solids was significantly improved due to the presence of Saran media in the settling compartment, even for a short HRT. The fixed-film aerobic bioreactor used in this study demonstrated efficient treatment efficiency even at higher organic loading rates and at short HRTs.

• 한국관개배수논문집
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• 제21권1호
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• pp.55-63
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• 2014

A sedimentation basin for agricultural water quality improvement was researched to analyze the water quality purification characteristics. The sedimentation basin constructed at the inlet of Gamdon reservoir in Muan-gun, Jeollanam-do was selected as the research field of this study. The surface area of the sedimentation basin is $34,000m^2$, volume is $122,000m^3$, and hydraulic retention time is 0.3hr~7.3day. The average influent loading of SS was 156.6kg-SS/d, and the effluent loading was 67.5kg-SS/d with the average removal rate of 56.9%. The average influent loadings of BOD and COD were 33.0kg-BOD/d and 60.3kg-COD/d respectively, and the effluent loadings were 26.4kg-BOD/d and 48.6kg-COD/d with the average removal rate of 20.1% and 19.3% respectively. Therefore, the results of this study show that a sedimentation basin can purify SS and organic matters. The average influent loadings of T-N and T-P were 28.7kg-TN/d and 2.97kg-TP/d respectively, and the effluent loadings were 16.3kg-TN/d and 1.41kg-TP/d with the average removal rate of 43.0% and 52.6% respectively. In conclusion, the overall results of this study show that a sedimentation basin is a feasible alternative to purify organic matters and nutrients.

• 유기물자원화
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• 제23권1호
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• pp.45-51
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• 2015

본 연구에서는 비귀금속 촉매인 iron(II) phthalocyanine (FePc)와 cobalt tetramethoxyphenylporphyrin(CoTMPP)를 환원전극촉매로 이용하여 미생물연료전지의 연속운전을 진행하였다. 연속운전은 유기물 부하 (0.5~3 g COD/L/d)와 HRT (0.25~1 day)의 조건을 달리 운전하여 미생물연료전지의 성능을 평가하였다. 미생물연료전지의 전력밀도는 환원전극의 성능에 크게 영향을 받았으며, 최대전력밀도는 $3.3W/m^3$로 백금을 사용한 미생물연료전지에서 나타났다. 하지만, HRT의 조건을 달리 한 실험에서 FePc를 사용한 미생물연료전지가 백금을 사용한 미생물연료전지와 유사한 성능을 나타냈으며, 연속운전에서 백금 촉매를 대체할 수 있는 적합한 물질로 나타났다. 반면에 CoTMPP를 사용한 미생물연료전지는 연속운전에서 내부 저항의 급격한 증가로 전력밀도가 급격히 감소하였다.

• Structural Engineering and Mechanics
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• 제44권6호
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• pp.753-762
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• 2012

The ratcheting characteristics of cylindrical shell under cyclic axial loading are investigated. The specimens are subjected to stress-controlled cycling with non-zero mean stress, which causes the accumulation of plastic strain or ratcheting behavior in continuous cycles. Also, cylindrical shell shows softening behavior under symmetric axial strain-controlled loading and due to the localized buckling, which occurs in the compressive stress-strain curve of the shell; it has more residual plastic strain in comparison to the tensile stress-strain hysteresis curve. The numerical analysis was carried out by ABAQUS software using hardening models. The nonlinear isotropic/kinematic hardening model accurately simulates the ratcheting behavior of shell. Although hardening models are incapable of simulating the softening behavior of the shell, this model analyzes the softening behavior well. Moreover, the model calculates the residual plastic strain close to the experimental data. Experimental tests were performed using an INSTRON 8802 servo-hydraulic machine. Simulations show good agreement between numerical and experimental results. The results reveal that the rate of plastic strain accumulation increases for the first few cycles and then reduces in the subsequent cycles. This reduction is more rapid for numerical results in comparison to experiments.

• 대한토목학회논문집
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• 제8권4호
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• pp.59-67
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• 1988

혐기성소화(嫌氣性消化)에 미치는 온도(溫度)의 영향(影響)을 가장 효과적으로 파악할 수 있는 체류시간(滯留時間) 5일(日)에서 인공(人工)슬러지를 대상으로 $35{\sim}55^{\circ}C$의 소화실험(消化實驗)을 행하였다. 소화온도증가(消化溫度增加)에 따라 메탄발효(醱酵)의 저해(沮害)가 감소하여, 중온(中溫) 및 중간영역(中間領域)의 온도(溫度)에서는 잔발효(酸醱酵)가 우세하였으나 $55^{\circ}C$에서는 활발한 메탄발효(醱酵)가 이루어졌다. 온도(溫度)의 변화(變化)는 미생물활성(微生物活性)뿐 아니라 슬러지의 물리(物理), 화학적(化學的) 특성(特性)에도 영향(影響)을 미친다고 추정된다. 또한 유입(流入) 슬러지의 희석(稀釋)에 의하여 소화저해(消化沮害)가 크게 감소하여 모든 온도(溫度)에서 활발한 메탄발효(醱酵)가 가능하였다. 소화효율(消化效率)은 수리학적(水理學的) 부하량외(負荷量外)에 유기물부하량(有機物負荷量)에도 지배받음을 알 수 있었다. 소화효율(消化效率)의 급격한 저해(沮害)가 발생된다고 보고된 $40{\sim}45^{\circ}C$에서도 뚜렷한 저해(沮害)는 없었다. 한편 소화온도증가(消化溫度增加)에 따라 소화(消化)슬러지의 침강특성(沈降特性)도 향상되었다.

• 한국물환경학회지
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• 제23권6호
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• pp.920-926
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• 2007

The upflow Biobead$^{(R)}$ process, one of biological aerated filters (BAF), which was used commercially, invented for removal of organic materials and nitrification. This process was modified to enhance the ability of denitrification through the induction of pre-anoxic tank. In this research, we investigated the effects of hydraulic retention time (HRT) and backwashing period in aerobic tank. The characteristics of nitrifying bacteria, which are composed of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), also investigated using fluorescence in situ hybridization (FISH). Even though the HRT was shortened, the efficiency of nitrification was not decreased when the organic loading rate and ammonium-nitrogen loading rate were $2.10kg/m^3/day$ and $0.25kg/m^3/day$, respectively. And then the distribution ratios of AOB and NOB showed the similar patterns. However, when the backwashing period was lengthened from 12 hours to 24 hours in aerobic 1 tank, the nitrification efficiency was decreased to 63.9% from 89.2%. The results of FISH explained that this decrease of nitrification efficiency was caused by the decrease of distribution ratio of AOB in aerobic 1 tank. The nitrification efficiencies of aerobic 1 and aerobic 2 tank were increased when the backwashing period was lengthened because of relative high distribution ratios of nitrifying bacteria.