Membrane bioreactors (MBRs) employ a process of biological treatment that is based on a membrane that has the advantages of producing high-quality treated water and possessing a compact footprint. However, despite these advantages, the occurrence of “fouling” during the operation of these reactors causes the difficulty of maintenance.Hence, in this study, three physical cleaning methods, namely, backwashing, air scrubbing, and mechanical cleaning ball was performed to identify optimum operating conditions through laboratory scale experiments, and apply them in a pilot plant. Further, the existing MBR process was compared with these methods, and the field applicability of a combination of these physical cleaning methods was investigated.Consequently, MCB, direct control of cake fouling on the membrane surface was found to be the most effective. Moreover, as a result of operating with combination of the physical cleaning process in a pilot plant, the TMP increasing rate was found to be – 0.00007 MPa/day, which was 185% higher than that obtained using the existing MBR process. Therefore, assuming fouling only by cake filtration, about one year of operation without chemical cleaning is considered to be feasible through the optimization of the physical cleaning methods.

This study compares characteristic of membrane fouling in MBR-RO systems. In lab. scale MBRs test, MBRs were operated at different Flux(10, 20, 30 & 40 LMH) and temperature(10, 15, 20, 25 & 30°C). The results show that MBR permeate was measured lower amounts of organic substances in Higher flux and lower temperature and led to lower RO fouling rates. The main cause was that due to cake fouling formed on membrane surfaces in MBRs. Under both cases, Cake layer of membrane surfaces formed in MBRs removed RO fouling factors, polysaccharide and protein, because of cake layer attached on membrane surfaces greater amounts of organic substances. This study implies that optimization of MBR with operating conditions is a crucial strategy to RO membrane fouling control.

FRP Hybrid Bar, composite structures composed of synthetic resins, deformed bar and glass fiber, was invented in order to solve corrosion of rebar in reinforced concrete structures. In order to bond deformed bar and glass fiber to FRP Hybrid Bar, synthetic resins is used. Curing time of the synthetic resins greatly affect productivity. If curing time of synthetic resins is short, cost of facilities is reduced and productivity is increased. Also, If this curing time is shorter or omitted, FRP Hybrid Bar can be commercialized. So, it can cause mass-production and substantial economic effect. Therefore, in this paper, optimum mix proportion is observed in order to increase economic efficiency of FRP Hybrid Bar and reduce curing time of synthetic resins. Total 9 variables are set, adjusting ratio of hardener ratio, and 3 resin moulds on each variables are fabricated. Optimum mix proportion is suggested based on data measured by temperature sensor.

최근에 상용화된 SWRO 막은 플럭스 감소만으로 파울링을 평가하기 어렵다. 따라서 본 실험에서는 열역학 모델식을 통해 유기막오염과 세정에 따른 투수계수(Lp)와 농도분극계수(fcp), 파울링에 의한 여과저항(Rf) 변화를 분석해보았다. 파울런트 미주입시, 원수 TDS농도별, 압력별로 Lp와 fcp를 분석하였고 그 후, 유기 파울런트를 주입하여 막오염 진행에 따른 Lp와 fcp 변화를 분석하였다. 실험 결과, 파울런트를 주입하지 않은 경우, Lp와 fcp는 동일한 원수의 TDS 농도에서 압력이 증가함에 따라 증가하고, 동일한 운전 압력에서 원수의 TDS 농도가 증가할수록 감소하였고, 막오염 진행에 따른 Lp와 fcp의 감소 경향은 플럭스 감소 경향과 일치하지 않으며 막오염 물질 별로 다른 양상을 보였다.

본 연구에서는 분리막을 이용하여 안정적인 혐기소화조 전처리 농축공정에 대한 적용성을 평가하는데 목적을 두었다. 실험결과 슬러지 감량율의 경우 혐기조건에서 약 47.16%, 간헐폭기 조건에서 약 41.17%으로 나타났으며, 반류수의 농도의 경우 간헐폭기 조건이 평균적으로 혐기조건보다 낮은 반류수 농도를 나타냈다. Flux 감소에 대한 영향인자로 TTF, MLSS, CODcr, 및 EPS의 상관관계 분석결과 Flux 감소에 TTF가 가장 높은 연관성을 보였으며, 이외에 MLSS, CODcr 및 EPS도 밀접한 관련이 있는 것으로 도출되었다. 이러한 결과 혐기소화조의 전처리 공정으로 관형막을 이용한 경우 막오염 및 반류수 부하를 고려한 농축조 간헐폭기 조건이 안정적 전처리공정으로 적절할 것으로 사료된다.

The purpose of this study is to estimate the applicability of a stable anaerobic digester using a separator membrane to the preprocessing thickening process. The results of the experiments showed about a 47.16% weight loss rate for the sludge under anaerobic condition, and about 41.17% under intermittent aeration condition. The concentrations of rejection water were SCODCr 25 mg/L, T-N 16.6 mg/L, and T-P 1.4 mg/L on the average under the intermittent aeration condition, which were lower than the concentrations of rejection water under an anaerobic condition. As for the factors affecting the reduction of the flux, correlation analyses of TTF, MLSS, SCODCr, and EPSProtein, EPSPolysacchride resulted in -0.97, -0.95, -0.84 and -0.86, -0.95, respectively, which showed that TTF had the highest correlation to the reduction of the flux. In addition, it was concluded that MLSS, SCODCr and EPSProtein, EPSPolysacchride also have close correlations. The results are considered to show that, in the case of the process using a tubular membrane in the preprocessing process of an anaerobic digester, an intermittent aeration condition of the thickener considering the contamination of the membrane and load of rejection water is appropriate for the stable preprocessing process.

PURPOSES : In this study blast furnace slag, an industrial byproduct, was used with an activating chemicals, Ca(OH)2 and Na2SiO3 for carbon capture and sequestration as well as strength development. METHODS: This paper presents the optimized mixing design of Carbon-Capturing and Sequestering Activated Blast-Furnace Slag Mortar. Design of experiments in order to the optimized mixing design was applied and commercial program (MINITAB) was used. Statistical analysis was used to Box-Behnken (B-B) method in response surface analysis. RESULTS : The influencing factors of experimental are water ratio, Chemical admixture ratio and Curing temperature. In the results of response surface analysis, to obtain goal performance, the optimized mixing design for Carbon-Capturing and Sequestering Activated Blast- Furnace Slag Mortar were water ratio 40%, Chemical admixture ratio 58.78% and Curing temperature of 60℃. CONCLUSIONS: Compared with previous studies of this experiment is to some extent the optimal combination is expected to be reliable.

In a real-life supply chain environment, demand forecasting is usually represented by probabilistic distributions due to the uncertainty inherent in customer demands. However, the customer demand used for an actual supply chain planning is a single deterministic value for each of periods. In this paper we study the choice of single demand value among of the given customer demand distribution for a period to be used in the supply chain planning. This paper considers distributed multi-echelon supply chain and the objective function of this paper is to minimize the total costs, that is the sum of holding and backorder costs over the distribution network under the service level constraint, by using demand selection scheme. Some useful findings are derived from various simulation-based experiments.

In reality, distribution planning for a supply chain is established using a certain probabilistic distribution estimated by forecasting. However, in general, the demands used for an actual distribution planning are of deterministic value, a single value for each of periods. Because of this reason the final result of a planning has to be a single value for each period. Unfortunately, it is very difficult to estimate a single value due to the inherent uncertainty in the probabilistic distribution of customer demand. The issue addressed in this paper is the selection of single demand value among of the distributed demand estimations for a period to be used in the distribution planning. This paper proposes an efficient demand selection scheme for minimizing total inventory costs while satisfying target service level under the various experimental conditions.

본 논문에서는 축방향 압축하중을 받는 다퐁간분리된 적층 보-기둥의 자유진동과 좌팔에 대한 해석을 수행하였다. 다층간분리된 적층 보-기둥의 고유진동수와 탄성 좌굴 하중에 대한 층간분리의 영향을 조사하기 위해 층간분리의 양단에서 기울기와 곡률이 일정하다는 가정을 적용하여 일반적인 운동학적 연속 조건을 유도하였다. 전체 다층간분리된 보-기둥을 부분으로 분할하고, 연속조건에 따른 반복관계를 각 하부 보-기둥에 부과함으로써 다층간분리된 보-기둥의 특성방정식을 구하였다. 축방향 증분 압축 하중에 따른 다층간분리된 보-기둥의 고유진동수와 탄성 좌굴 하중을 구하였으며 이는 손상되지 않은 적층 보-기둥의 최대 탄성 좌굴 하중에 한정된다 연구를 통하여 층간분리의 크기, 위치, 수가 고유진동수와 특히 탄성 좌굴 하중에 큰 영향을 미치는 것을 알 수 있었다.

케이블지지 교량 건설의 증가로 인하여 이러한 시설물의 안전 점검에 대한 관심도 점차 증가하고 있다. 케이블지지 교량에서는 주 부재인 케이블의 성능 평가가 필수적으로 이루어져야 함에 불구하고, 기존의 점검 방식으로는 다양한 제한적인 요인 때문에 적절한 점검이 이루어지지 못하고 있는 실정이다. 이러한 문제점을 보완하기 위해 케이블 점검 로봇 제작이 필요하고, 본 연구에서는 기존의 개발된 케이블 점검 로봇의 성능을 향상시켜서 로봇의 운용 효율성을 높이는데 주목적을 두었다. 성능 보완 요소로는 대 구경 케이블(>200mm)에도 적용할 수 있도록 로봇의 가용범위를 조절할 수 있도록 하였으며, 주행능력도 향상시켜 점검의 효율성을 향상시켰다. 케이블의 내부 손상을 점검하기 위해 전자기센서를 탑재하였고, 실내 실험을 통해 다양한 케이블 손상 유형에 따른 손상 검출 시험을 실시하였다. 추가로 현재 공용중인 교량에서 현장 성능평가를 실시하였다. 그 결과로 본 연구에서 개발된 케이블 점검 로봇은 주행속도에서는 ~0.2m/s로 기존의 점검 로봇에 비해 향상 된 주행 능력을 보였으며, 케이블 내부 손상 점검 실험에서는 케이블 손상 부분을 검출을 할 수 있었다. 마지막으로, 케이블 점검 로봇의 현장 검증 실험에서는 실내 실험과 같은 성능을 보이는 것을 확인하였다.

정부에서는 안전사고의 방지, 기존시설의 수명연장과 성능개선을 통한 재정투자의 효율성을 제고를 위하여 ｢지속가능한 기반시설 관리 기본법(이하 “기반시설관리법”, 공포 ’18.12.)｣을 시행(’20.1.)할 예정이다. 이 법에서는 개별법에 따라 상이하게 관리되는 기반시설의 유지관리 수준을 상향 평준화하기 위하여 최소유지관리 공통기준을 제정하도록 하고 있으며, 기반시설 관리체계의 분석과 정부시책에 대한 검토 등을 통하여 유지관리 개선 방향을 결정하고, 이를 근거로 최소유지관리 공통기준을 마련중이다. 공통기준의 지침화를 위해 기반시설 유형별 적용성을 평가하여 범용성과 확장성을 검토할 예정이다.

강-콘크리트 합성구조의 성능을 확보하기 위해서는 전단연결재가 설치된 전단연결부에 대한 전단강도 분석이 필수적이다. 전단연결부의 전단거동을 효율적으로 예측하기 위하여, 전단연결부의 push-out test에 대한 유한요소해석을 수행하였다. 유한요소해석에는 범용 프로그램인 ABAQUS가 사용되었으며, 대상 실험체는 Y형 전단연결재가 적용된 강-콘크리트 전단연 결부이다. 유한요소해석에서는 대상 실험체를 구성하는 재료들의 비선형성을 고려하였고, 비선형해석의 수렴문제를 해결하기 위하여 준정적해석을 사용하였다. 본 연구에서 수행된 유한요소해석 결과를 바탕으로 하중-변위곡선과 전단강도를 기존 실험결과와 비교한 결과, 준정적해석을 이용한 유한요소모델은 기존 실험결과를 잘 반영하는 것을 확인하였다.

Currently, the cable safety management of cable supported bridges is calculated by the ratio of the measured tension to the design tension. The measurement of the tension is performed by indirectly estimating the acceleration measured at the cable surface in terms of the tension. The method of converting the cable vibration response (acceleration) into the tension is disadvantageous in that the damage of the individual strand (or wire) in the cable is not clearly reflected in the tension because the measurement is not reliable and is managed only by the total tension. The purpose of this study is to improve the cable safety management system by evaluating how the damage of individual strand of MS type cable, which is mainly applied to cable-stayed bridges, affects the safety level managed by level of cable tension.

This paper presents a methodology for assessing the old-age level of facilities. In order to evaluate the retirement level, a method of selecting the indicators related to the old age was presented and a method of assessing the old age level through the measures of the selected indicators is suggested to improve the reliability of evaluation results and to develop evaluation algorithm. In the future, it is expected that it will be possible to efficiently manage the old facilities through the convergence of the old- level evaluation method and IoT sensor, big data, and artificial intelligence.

This research is a basic study to develop mid - and long - term data base platform for maintenance of aging infrastructure (bridges, tunnels, retaining walls, road facilities, etc. In this study, the degradation and damage data and experiment data obtained from various monitoring technologies are secured in the medium to long term, and the degradation environment and damage model are developed based on the data acquired later. Predicted and standardized services to the management or the people of the nation. In this study, the database will be constructed at the planning, design and implementation stage, and mid - and long - term data will be used for precision safety diagnosis report and monitoring measurement report.

In case of cable supported bridges, the cable system is a very important element that transfers the load of the girder to the pylon or substructure is the most important feature. The safety management of these cable systems is very important because they are directly linked to the safety of the entire bridge. This paper presents the applicability of the acoustic emission (AE) method is one of the non-destructive evaluation methods, is evaluated for the detection and monitoring of bridge cable damage. In order to verify the performance of the cable inspection method using the AE sensor, experiments were conducted. As a result, it is considered that the acoustic emission technique will be able to detect corrosion breakage and signs of rupture of cables if sufficient database of AE signal with various environmental conditions is secured.

In this study, the durability rating was evaluated to evaluate the safety of bridges considering the factors affecting the corrosion of cables in cable-stayed bridges and suspension bridges. Corrosion factors were considered for salinity, sulfur dioxide concentration and relative humidity. In addition, the durability level was calculated by applying the corrosion rates given in KS D ISO 9223 ~ 9226.

The corrosion is one of the main causes of cable damages. The use of dehumidification system can be an alternative for this issue. Therefore, the authors have been evaluated for efficiency of the cable dehumidification system for the main cables of a suspension bridge. This study was initiated to develop an efficient and economical management strategy to operate the cable dehumidification system for suspension bridges built in the coastal region of South Korea.