• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.193-200
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• 2010

Structural design requires simultaneously to ensure safety by considering quantitatively uncertainties in the applied loadings, material properties and fabrication error and to maximize economical efficiency. As a solution, system reliability-based design optimization (SRBDO), which takes into consideration both uncertainties and economical efficiency, has been extensively researched and numerous attempts have been done to apply it to structural design. Contrary to conventional deterministic optimization, SRBDO involves the evaluation of component and system probabilistic constraints. However, because of the complicated algorithm for calculating component reliability indices and system reliability, excessive computational time is required when the large-scale finite element analysis is involved in evaluating the probabilistic constraints. Accordingly, an algorithm for SRBDO exhibiting improved stability and efficiency needs to be developed for the large-scale problems. In this study, a more stable and efficient SRBDO based on the performance measure approach (PMA) is developed. PMA shows good performance when it is applied to reliability-based design optimization (RBDO) which has only component probabilistic constraints. However, PMA could not be applied to SRBDO because PMA only calculates the probabilistic performance measure for limit state functions and does not evaluate the reliability indices. In order to overcome these difficulties, the decoupled algorithm is proposed where RBDO based on PMA is sequentially performed with updated target component reliability indices until the calculated system reliability index approaches the target system reliability index. Through a mathematical problem and ten-bar truss problem, the proposed method shows better convergence and efficiency than other approaches.

• Journal of IKEEE
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• v.13 no.2
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• pp.175-180
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• 2009

This paper compare the operation characteristic and optimal design of Photovoltaic system by computer simulation. The operation characteristic of Photovoltaic system are evaluated and analyzed considering system parameters of specifications, installations, inclination, azimuth and surrounding conditions etc. From the basis of these results, this study will intend to develop an evaluation, analysis tool and construct database for optimal design of PV system.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2006.05a
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• pp.355-357
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• 2006

본 연구에서는 산생성효율의 최적 운전인자 도출을 위하여 중온 및 고온혐기성산발효공정에서의 유기물부하에 따른 산발효 효율을 비교 검토하였으며, 다음과 같은 결론을 얻었다. 유기물 부하별로 고온과 중온 조건에서 실험을 진행했을 때 VFA생성과 pH변화를 비교했을 때, 고온 조건이 중온조건보다 더 높은 부하율에서 운전이 가능한 것으로 나타났으며, 생성되는 VFA의 농도도 더 높은 것으로 나타났으며, pH의 변화는 고온 조건에서 4.8$\sim$6.2, 중온 조건에서 5.8$\sim$6.7로 고온에서 중온보다 pH가 낮게 나타났다. 고온과 중온에서 유기물 부하별로 산발효시 생성된 유기산의 구성성분을 비교했을 때, 고온에서 생성된 유기산이 중온보다 acetic acid의 비율이 높은 것으로 나타났다. 음식물찌꺼기 고온 산발효액의 성상에서 $SCOD_{Cr}$/TKN, $SCOD_{Cr}$/T-P이 각각 18.9, 73.4로 나타나 하수처리장에서 저부하 유기물 유입시에 탄소원으로 충분히 활용 가능한 것으로 판단된다.

• Journal of the Korean Institute of Telematics and Electronics
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• v.10 no.5
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• pp.16-20
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• 1973

The most important thing in locating disturbances in optimal rapid traffic singnal control is to collect information cocerning toraffit flow by means of a detection method. In order to set up an optimal traffic singnal period, the analysis of a delay time phenomena in the signal period must also be considered. In fact, each of the distributed traffic quantities on the road are not similar factors in view of speeds and distances of succeeding cars. The causing factors are analyzed by the method of control engineering analysis, and they are coincident with disturbance. Thus distubances cause errors. Distubances are fuctions of time, and are classified into three conditions: Natural road state and weather are the first. The second is structures and function of vehicles, and the third is inducedbydrivers. This thesis deals with the last two cases except the first one for maximum utilization of the existing road state and weather conditions. The first condition remains constant, and then there exist some relations between vehicles and drivers. In the long run, it can be shown that the scheme for minimizing whole errors in the optimal traffic signal time setting is definitely presented.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.547-547
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• 2015

본 연구에서는 달천구간 (괴산댐~송동보)에서 어류 군집 (Fish Community)을 고려한 생태학적 최적유량 (Ecological Optimum Discharge)을 산정하였다. 이를 위해 유량증진방법론(IFIM: Instream Flow Incremental Methodology)을 기반으로 한 2차원 모형인 River-2D를 적용하여 수리해석 및 대상어종 (Target Fishes)에 대한 가중가용면적 (WUA: Weighted Usable Area)을 산정하였다. 모형 검증을 위해 김원 등 (2007)에 의해 수행된 과업구간 내 수위 및 유량 모니터링 자료를 활용하였으며, 하류경계조건은 김지성 등 (2007)에 의한 수위-유량 관계곡선식을 활용하였다. 또한 평저류량 조건에서의 조도높이 (Roughness Height) 산정을 위해 유량 및 하상재료의 영향을 고려할 수 있는 멱함수 및 반대수함수 형태의 조도계수 공식을 적용하였다. 모형검증 결과 River-2D에 의해 계산된 수위값이 모니터링값과 비교적 잘 일치함을 알 수 있었다. 대상유역에 대한 어류 모니터링 (에코리버21사업단, 2007~2010) 결과를 바탕으로, 과업지역내 우점종 (피라미), 아우점종 (쉬리 등 3개 어종), 멸종위기어종 (묵납자루)을 대상어종으로 선정하였으며, 대상어종에 대한 서식도적합도지수 (HSI, Habitat Suitability Index) 산정을 위해 IFASG (Instream Flow and Aquatic Systems Group) 방법 및 WDWF (Washington Department of Fish and Wildlife) 방법을 적용하였다. 수심, 유속, 하상재료 및 하상형상에 대한 서식도적합도지수가 5가지 대상어종에 대해 각각 산정되었으며, 복합적합도지수 (CSI : Combined Suitability Index)를 고려한 과업대상 위치별 어류의 발생확률이 모의되었다. 어류 군집에 대한 가중가용면적 (WUA)이 최대로 되는 생태학적 최적유량 산정 결과, Type I~III의 경우 모두 $10m^3/s$ 이하의 유량조건에 대해서 WUA가 최대값을 갖는 것을 확인할 수 있었으며, 납자루속의 어류 (Type III)의 WUA가 000 및 000속 (Type II)의 어류에 비해서 작은 유량에서 더 큰 값을 갖으며, $10m^3/$s 초과 유량에 대해서는 반대의 경향이 나타나는 것을 확인할 수 있었다.

• Journal of the Korean Society for Environmental Technology
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• v.19 no.6
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• pp.563-569
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• 2018

The efficiency of wastewater treatment using microalgae was investigated in this study, focusing on nutrients and flocculation. In the experiments for reducing nutrients by incubation of microalgae, the total phosphorus and total nitrogen were removed over 92 % and 99 %, respectively. The higher flocculation rates as the average values 94% of Poly Aluminum Chloride(PAC) and 92 % of $FeCl_3$ were presented for the flocculation experiments under the conditions of Auto-flocculation and various additives. Also, the optimal(minimal) concentrations for over 90 % of flocculation were 30 mg/L and 40 mg/L for PAC and $FeCl_3$, respectively.

• Journal of Soil and Groundwater Environment
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• v.7 no.1
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• pp.25-31
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• 2002

This study attempts to elucidate the possibility of treating landfill leachate by steelers' dust/${H_2}{O_2}$ system in a well-mixed batch reactor. Experiments were conducted to investigate the effects of operating variables such as pH, dust and ${H_2}{O_2}$ dosages and ${H_2}{O_2}$ injection method on the treatment efficiency, Contaminant concentrations were identified by TOC (Total Organic Carbon) analyzer. Experimental observations showed the possibility of steelers' dust as a catalytic reagent in the ${H_2}{O_2}$/dust system. The batch experiments showed that the optimal $H_2O$$_2$ and dust dosage, 20g/L dust. 2,000mg/L ${H_2}{O_2}$ removed about 75% of initial TOC concentration (250mg/1) within 60 min. And the TOC removal in the ${H_2}{O_2}$/dust system effectively proceeded only within a limited pH range of 3-4. The stealers' dust-catalyzed oxidative treatment of landfill leachate was more efficient compared with the $FeSO_2$catalyzed system (Fenton oxidation) for the removal rate and the cost.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.361-361
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• 2015

감세블록(baffle block)은 고속의 흐름에서 도수를 유도함으로써 과도한 에너지를 감세시키는 역할을 하는 구조물이며 구조물의 크기, 형태, 위치, 조합 등의 변수로 도수가 형성되는 조건을 조절하여 흐름에 영향을 줄 수 있다. 하단방류형 가동보에서 고속으로 방류되는 흐름의 Froude 수가 2.5에서 4.5 사이일 경우 발생하는 불규칙한 주기의 진동이 중첩 보강되면 감세하기 어려운 파동을 형성하여 수 Km 동안 지속될 수 있어 추가적인 조치가 필요하다(Peterka, 1984). 이 연구에서는 총 연장 11m, 폭 0.5m의 구형수로에 하단방류형 가동보와 감세블럭을 설치하여 감세블록의 위치가 에너지의 감세에 미치는 영향을 분석하고, 감세블록의 최적 위치를 제안하였다. 감세블럭은 높이 2cm, 폭 5cm의 구형단면으로 제작하여 일정한 간격으로 치형 배열하였으며, 가동보로 부터 5.5~8.5cm 지점에서 1cm간격으로 총 5가지 조건으로 수리실험을 수행하였다. 또한, 수문 하단에서의 Froude 수가 3.8~3.9를 만족하는 강한 도수가 발생할 수 있도록 유량을 조절 하였고, 유속과 수심은 3차원 유속계와 피에조미터를 이용하여 가동보로부터 0.2m간격으로 하류단 2m 지점까지 측정하였다. 실험 결과, 가동보로부터 도수가 발생하여 수위가 안정되는 지점까지의 도수길이는 감세블록을 설치한 경우, 설치하기 전의 1.1m와 비교하여 최소 27.3%에서 최대 81.8%만큼 짧아졌으며 감세블록 보에 가깝게 설치될수록 도수길이는 단축되는 것으로 나타났다. 가동보 하류부에서 도수가 발생한 이후 수심이 안정화되는 1m 지점에서, 도수 전후의 비에너지비로 정의되는 도수효율은 감세블록 미설치 시 74.9%이고, 감세블록이 설치된 조건에서는 54.9~60.6%로 감세블록에 의한 에너지 감소효과가 큰 것으로 나타났다. 에너지 감세 효과가 가장 큰 감세블록 위치는 가동보로부터 6.5cm 떨어진 곳으로 하류단 수심의 약 80%에 해당하는 지점이 감세블록의 최적 위치인 것으로 판단된다.

• Korean Journal of Environmental Agriculture
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• v.13 no.1
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• pp.76-82
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• 1994

A competitive indirect enzyme-linked immunosorbent assay(ELISA) was developed to detect and quantify levels of the fungicide metalaxyl in crops. Antiserum against metalaxyl was demonstrated in rabbits immunized with metalaxyl-human serum albumin(HSA) conjugate. Metalaxyl-protein conjugate was prepared by mixed anhydride and peptide coupling method with EDC. In this assay, metalaxyl-ovalbumin(OA) was $coated(8{\mu}g/ml)$ on the microtiter plate, which was incubated for 1 hr at $4^{\circ}C$ or 4 hr at $37^{\circ}C$ with diluted antiserum(1:2,000). The optimum volume ratio of antigen and antibody mixture was 0.5: 1, which was incubated for 1 hr at $20^{\circ}C$. The detection of metalaxyl bound on the surface of wells was determined by the reaction(30 min) of antirabbit Ig G-peroxidase conjugate with its substrate.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.6
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• pp.1139-1148
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• 2000

To treat and recycle a large quantity of converter slag. the milling properties of -14/ +24 mesh-sized slag has been considered. The optimal conditions in milling process were investigated for producing powder-type slag and the required consumption was derived for the economical grinding. The characteristics of milling processes were studied in the variation of the rotational speed, milling time, filling ratio of ball, and size and amount of feed. The grinding efficiency was also examined. The optimal rotational speed in this experimental condition was observed to be the value of 79% of critical speed. The extent of grinding was increased with increasing the grinding time. but the efficiency of milling was decreased with the time. 50% ball filling was shown to have the optimal grinding effect, and less amount and small-sized feed made the milling efficiency high. As the result, using Bond's equation, power required for efficient milling was considered and the highest value was observed in the condition of high grinding time and optimal rotational speed.