• 한국물환경학회지
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• 제37권1호
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• pp.47-54
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• 2021

Aerobic granular sludge (AGS) can be classified as a type of self-immobilized microbial aggregates measuring more than 0.2 mm. It offers the option to simultaneously remove COD, N, and P that occur in different zones inside a granule. Also, AGS is characterized by high precipitability, treatability with high organic loading, and high tolerance to low temperature. In this study, a sequencing batch reactor inoculated with AGS (AGS-SBR) is a new advanced wastewater treatment process that was proven to grow AGS with integrated nutrient removal and low C/N ratio. A pilot plant, AGS-SBR with a capacity of 225 ㎥/d was installed at an S sewage treatment plant in Gyeonggi-do. The results of the operation showed that the water quality of the effluent indicated that the value of BOD5 was 1.5 mg/L, CODMn was 11.4 mg/L, SS was 6.2 mg/L, T-N was 13.2 mg/L, and T-P was 0.197 mg/L, and all of these values reliably satisfied an effluent standard (I Area). In winter, the T-N treatment efficiency at a lower temperature of less than 11℃ also showed reliability to meet the effluent standard of the I Area (20 mg/L or less). Analysis of microbial community in AGS showed a higher preponderance of beneficial microorganisms involved in denitrification and phosphorus accumulation compared with activated sludge. The power consumption and sludge disposal cost were reduced by 34.7% and 54.9%, respectively, compared to the domestic SBR type sewage treatment plant with a processing capacity of 1,000 ㎥/d or less.

• 한국정보통신학회논문지
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• 제23권9호
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• pp.1025-1031
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• 2019

본 연구는 선박용 해수펌프를 ML 기반으로 한 알고리즘을 구현하여 효율적으로 운용할 수 있는 PCS를 제안한다. PCS가 탑재된 2척의 선박에서 해수온도, RPM, 전력 소모 데이터를 취득하여 회귀 분석법으로 분석하고, 새로운 알고리즘을 제시한다. 제시하는 알고리즘을 적용하였을 때 Ship A는 PCS를 적용하지 않았을 때 대비하여 약 36%를 절감하였고, 특정 해역온도인 $19{\sim}27^{\circ}C$와 $32^{\circ}C$ 이상의 해역에서 ML 기반의 알고리즘이 Ship A의 PCS보다 약 1% 더 절감하였다. Ship B는 PCS를 적용하지 않았을 때 대비하여 약 50%를 절감하였고, 특정 해역온도인 $19^{\circ}C$ 이상의 해역에서 Ship B의 PCS보다 약 2%더 절감하였다. 도출된 데이터를 이용하여 최적의 펌프 속도와 항로를 제안할 수 있다. 추가적으로, 취득 데이터의 추세를 활용하여 효율이 낮아졌을 시에 펌프의 성능이나 MGPS의 소제 시기를 유추할 수 있다.

• 대한조선학회논문집
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• 제56권4호
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• pp.373-382
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• 2019

This paper shows numerical results for the estimation of the propulsor efficiency of Pre-Swirl Duct for 176k bulk carrier as well as its design method. Reynolds averaged Navier-Stokes equations have been solved and the k-epsilon model applied for the turbulent closure. The propeller rotating motion is determined using a sliding mesh technique. The design process is divided into each part of Pre-Swirl Duct, duct and Pre-Swirl Stator. The design of duct was performed first because it is located further upstream than Pre-Swirl Stator. The distribution of velocity through the duct was analyzed and applied for the design of Pre-Swirl Stator. The design variables of duct include duct angle, diameter, and chord length. Diameter, chord length, equivalent angle are considered when designing the Pre-Swirl Stator. Furthermore, a variable pitch angle stator is applied for the final model of Pre-Swirl Duct. The largest reduction rate of the delivered power in model scale is 7.6%. Streamlines, axial and tangential velocities under the condition that the Pre-Swirl Duct is installed were reviewed to verify its performance.

• 대한건축학회논문집:계획계
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• 제34권2호
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• pp.3-11
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• 2018

Korea has achieved a rapid economic development and with the increase in population and national income and the expansion of social and economic activities, energy consumption has rapidly increased too. Energy consumption per head has constantly increased and currently, power consumption per head is 7.5 times bigger than in 1985. Buildings occupy 25% of total energy consumption and especially, 50% of total energy is consumed for heating and cooling. In this situation, multi-family housing, which has constantly been increased, has an energy saving rate of 1.9%, which is the lowest level and this makes the government's energy policy for sustainable energy system development useless. Besides, energy consumption leads to secondary problems, such as air, water and marine pollution and heat pollution and wastewater/drainage and the increased use of fossil fuel is a fundamental reason for ozone layer destruction and global warming. Therefore, efficient energy consumption plans are required. This study aims to analyze energy performance in each block type of high-rise and diversified multi-family housing that accounts for 60% of all the housing forms, depending on the variations in stories through BIM-based energy simulation. For this study, four representative block types were selected, based on the multi-family floor plan, which is certified for energy performance evaluation and they were applied to the floor plan of a multi-family house that is scheduled to be built. Then BIM modeling was conducted from the fifth story to the 40th story at an intervals of 5 stories and based on the finding, energy characteristics of each block type and energy performance depending on the variations in stories were analyzed. It is considered that this would serve as objective data for block type and block story decision of energy performance-based multi-family housing.

• 대한건축학회논문집:구조계
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• 제35권3호
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• pp.43-48
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• 2019

Since the revision of the Rationalization of Energy Use Law, the spread of new and renewable energy in buildings has been promoted. In addition, the production of electric power and thermal energy is an important issue in the change of energy paradigm centered on the use of distributed energy. Among them, geothermal energy is attracting attention as a high-performance energy-saving technology capable of coping with heating / cooling and hot water load by utilizing the constant temperature zone of the earth. However, there is a disadvantage that the initial investment cost is high as a method of calculating the capacity of a geothermal facility by calculating the maximum load. The disadvantages of these disadvantages are that the geothermal energy supply is getting stagnant and the design of the geothermal system needs to be supplemented. In this study, optimization design of geothermal system was carried out using optimization tool. As a result of the optimization, the ground heat exchanger decreased by 30.8%, the capacity of the heat pump decreased by 7.7%, and the capacity of the heat storage tank decreased by about 40%. The simulation was performed by applying the optimized value to the program and confirmed that it corresponds to the load of the building. We also confirmed that all of the constraints used in the optimization design were satisfied. The initial investment cost of the optimized geothermal system is about 18.6% lower than the initial investment cost.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.102-114
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• 2021

Biofouling represents an important problem in the shipping industry since it causes the increase in surface roughness. The most of ships in the current world fleet do not have good coating condition which represents an important problem due to strict rules regarding ship energy efficiency. Therefore, the importance of the control and management of the hull and propeller fouling is highlighted by the International Maritime Organization and the maintenance schedule optimization became valuable energy saving measure. For adequate implementation of this measure, the accurate prediction of the effects of biofouling on the hydrodynamic characteristics is required. Although computational fluid dynamics approach, based on the modified wall function approach, has imposed itself as one of the most promising tools for this prediction, it requires significant computational time. However, during the maintenance schedule optimization, it is important to rapidly predict the effect of biofouling on the ship hydrodynamic performance. In this paper, the effect of biofilm on the ship hydrodynamic performance is studied using the proposed performance prediction method for three merchant ships. The applicability of this method in the assessment of the effect of biofilm on the ship hydrodynamic performance is demonstrated by comparison of the obtained results using the proposed performance prediction method and computational fluid dynamics approach. The comparison has shown that the highest relative deviation is lower than 4.2% for all propulsion characteristics, lower than 1.5% for propeller rotation rate and lower than 5.2% for delivered power. Thus, a practical tool for the estimation of the effect of biofouling with lower fouling severity on the ship hydrodynamic performance is developed.

• 해양환경안전학회지
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• 제28권6호
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• pp.1070-1077
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• 2022

최근 국제해사기구의 해양환경오염규제가 강화되어 오고 있다. 선박의 에너지 효율지수는 선박의 설계관점에서 매우 중요한 지표이다. 더욱이 새롭게 건조되는 선박은 물론 기존 운항 선박에도 에너지 효율지수를 만족하도록 강화하고 있다. 이에 따라 운항되고 있는 기존선박의 에너지 효율지수를 높이기 위해 선수 벌브개조, 운항 중 트림 최적화, 에너지 절감장치등 다양한 방법이 적용되고 있다. 본 연구에서는 전산 유체역학을 이용하여 다양한 선수/선미 트림조건에서 선박의 저항성능을 계산하고 분석하였다. 이를 바탕으로 최적화 된 트림조건에서 선박의 저항성능을 더욱 개선하기 위해 선수 벌브의 형상을 재설계하였다. 그 결과 정수 중에서 개선된 벌브 형상을 적용한 경우, 유효마력이 약 5% 향상되는 것을 확인하였으며, 향후 파도 중에서 재설계된 벌브형상이 저항성능에 미치는 영향을 조사할 예정이다.

• 한국시뮬레이션학회논문지
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• 제19권2호
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• pp.9-16
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• 2010

본 사례 연구는 가상환경에서 자동차 의장 라인의 PLC 코드 검증 시스템을 구현하였다. 그간 인력과 PLC 검증 시간을 줄이고자 표준화된 PLC 에디터를 개발하려고 노력해왔으나, 실제 현장 환경에서 PLC 에디터를 적용하는데 어려움이 있었다. 본 연구는 현장의 PLC 모듈과 통신하며, 특별한 프로토콜을 이용하여 연결 환경을 구축하는 가상장비를 개발했다. PLC 모듈과 가상장비가 OPC 프로토콜에 의해 실시간으로 통제되므로 실제 장비를 설치하지 않고 PLC 코드를 검증할 수 있게 되었다. 실험적 모델을 자동차 공장의 최종 조립라인에 적용하고, DELMIA Automation을 이용하여 검증하였다. 결론적으로 PLC 코드 검증 과정과 가상장비 작동에 이 시스템이 유용하게 이용되었다. 이 시스템은 PLC 코드 개발 시간을 절약하며 조립라인의 생산성, 무결성을 높이는데 기여했다.

• 한국산업정보학회논문지
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• 제14권5호
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• pp.113-123
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• 2009

환경에 대한 문제가 대두됨에 따라, 에너지와 자원의 소비를 억제하고 탄소 배출을 줄이기 위한 노력들이 진행되고 있다. 그 중 다양한 형태의 문서들을 디지털로 변환하여 컴퓨터상에 파일로 보관하고, 이를 전자 문서 또는 전자 이미지 형태로 제공하여 에너지와 자원을 줄이기 위한 노력들이 진행되고 있다. 하지만, 디지털화 된 이미지 데이터들은 인터넷상에 표준화되지 못한 채 산재해 있어 이를 활용하기 위해서는 많은 시간과 노력이 필요하게 된다. 이에 따라 전력 소비 및 자원의 소비가 다시 증가하게 된다. 본 논문에서는 인터넷 상에 존재하는 디지털화된 이미지 데이터의 효율적인 관리와 제공을 통해 에너지와 자원의 소비를 줄이기 위한 시스템을 설계하고 구현한다. 웹상에 존재하는 대용량의 이미지 콘텐츠들을 보다 정확하게 분류하고 사용자가 원하는 이미지 콘텐츠를 정확하고 빠르게 제공해 줌으로써 이미지 데이터에 대한 에너지와 자원의 소비를 줄일 수 있다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2022년도 춘계학술대회
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• pp.82-84
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• 2022

최근 IoT(Internet of Things) 기기의 수가 증가함에 따라 발생하는 오버헤드 문제를 해결하기 위한 연구가 활발히 진행되고 있다. IoT 환경에서의 성능저하 문제를 해결하기 위한 IoT 경량화 프로토콜 중 하나인 MQTT(Message Queue Telemetry Transport)는 다대다 통신 환경에서 효율적인 동작이 가능하도록 표준화되었지만, 통신 시스템에 적용되어 구현될 때 암호화를 하지 않는 것이 디폴트로 설정되어 보안이 취약한 문제가 있다. 이러한 문제를 해결하기 위해 TLS(Transport Layer Security) 암호화 통신 기술을 적용할 수 있지만, IoT의 경량 저전력 요구조건을 만족하기 어렵다. 본 논문에서는 최신 MQTT 통신 암호화 기술 동향을 소개하고, TLS 암호화 통신 및 페이로드 암호화 방식을 비교하여 IoT 적용 가능성을 분석한다.