• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제18권2호
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• pp.129-142
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• 2014

We propose a variational segmentation model based on statistical information of intensities in an image. The model consists of both a local region-based energy and a global region-based energy in order to handle misclassification which happens in a typical statistical variational model with an assumption that an image is a mixture of two Gaussian distributions. We find local ambiguous regions where misclassification might happen due to a small difference between two Gaussian distributions. Based on statistical information restricted to the local ambiguous regions, we design a local region-based energy in order to reduce the misclassification. We suggest an algorithm to avoid the difficulty of the Euler-Lagrange equations of the proposed variational model.

• 한국유체기계학회 논문집
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• 제19권5호
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• pp.50-60
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• 2016

A design methodology of the modeled test facility to conserve an injection performance of a passive safety injection system is proposed. This safety injection system is composed of a core makeup tank and a safety injection tank. Individual tanks are connected with pressure balance line on the top side and injection line on the bottom side. It is important to conserve the scaled initial injection flow rate and total injection time since this system can be operated by small gravity head without any active pumps. Differential pressure distribution of the injection line induced by the gravity head is determined by the vertical length and elevation of each tank. However, the total injection time is adjustable by the flow resistance coefficient of the injection line. The scaling methodology for the tank and flow resistance coefficient is suggested. A key point of this test facility design is a scaling analysis for the flow resistance coefficient. The scaling analysis proposed on this paper is based on the volume scaling law with the same vertical length to the prototype and can be extended to a model with a reduced vertical length. A set of passive injection test were performed for the tanks with the same volume and the different length. The test results on the initial flow rate and total injection time showed the almost same injection characteristics and they were in good agreement with the design values.

• 한국지열·수열에너지학회논문집
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• 제16권1호
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• pp.17-25
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• 2020

Ground-coupled heat pump (GCHP) systems have become an efficient alternative to conventional cooling and heating methods due to their higher energy using efficiency. Although some experimental and simulation works related to performance analysis of GCHP systems for commercial buildings have been done, relatively little has been reported on the performance evaluation of GCHP systems for school buildings. The purpose of this simulation study is to evaluate the performance of a hypothetical GCHP system for a school building in Seoul. We collected various data of building specifications and construction materials for the building and then modeled to calculate hourly building loads with SketchuUp and TRNSYS V17. In addition, we used GLD (Ground Loop Design) V2016, a GCHP system design and simulation software, to design the GCHP system for the building and to simulate temperature of circulating water in ground heat exchanger. The variation of entering source temperature (EST) into the system was calculated with different prediction time and then each result was compared. For 20 years of prediction time, EST for baseline design (Case A) based on the hourly simulation results were outranged from the design criteria.

• 동력기계공학회지
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• 제21권3호
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• pp.85-92
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• 2017

Global air traffic is forecast to grow at an average annual rate of around 5% in the next 20 years. The continuous growth of air traffic and raised environmental awareness put increasing pressure on aero engine manufacturers to reduce fuel burn and emissions. NEWAC are a new integrated program of the European Union with focus on innovative core engine concepts to achieve this problem. In this paper, Within NEWAC, active core engine configurations will be investigated. the investigation is focused on the optimal design of the CAC heat exchanger for active core. For optimal design of he CAC heat exchanger, the HTFS of basic design of heat exchanger are analyzed so as to proceed an optimization routines based on Response Surface Method(RSM) and Design of Experiment(DOE). As a result, CAC heat exchanger optimized by 1.0314 lb/s mass flow rate and 3.9058 mm TP of tube layout and 206.8181 mm height of heat exchanger and 918 tube number for heat transfer and pressure drop. We confirm the design optimization using RSM and DOE is useful on complex structure of heat exchanger.

• 예술인문사회 융합 멀티미디어 논문지
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• 제5권3호
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• pp.291-299
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• 2015

최근 건물에서 냉난방에너지에 대한 문제가 부각되면서 냉난방에너지 성능평가에 대한 필요성도 증가되고 있다. 이에 본 연구는 기존 성능평가 방법의 개선안으로 실생활기반 냉난방 성능평가 방법을 제안하며, 이를 실제 적용해봄으로써 그 유효성 입증을 목적으로 하였다. 이에 대한 결론은 다음과 같다. 1) 기존 냉난방 에너지 성능평가 및 재실자의 선호 및 적정온도를 고찰하였으며, 그 결과 연령 등의 재실자 특성은 해당공간의 쾌적성과 직결되는 중요한 요소이나 기존 냉난방 성능평가에는 고려되고 있지 않아서 문제시 된다. 2) 본 연구에서 제안하는 실생활기반 냉난방 에너지 성능평가는 재실자의 특성을 성능평가에 반영하였으며, 실스케일의 테스트베드에서 냉난방기기에 연동하여 제어함으로써 단순 실내의 온도정보 뿐만 아니라 실생활에 입각한 정량적이며, 시각적인 성능평가 결과의 도출이 가능하다. 3) 본 연구에서 제안하는 실생활기반 성능평가의 유효성을 검정하기 위하여 재실자의 연령에 따른 실내 적정온도 및 블라인드 설치 유무에 따라서 성능평가를 실시하였으며, 재실자 특성에 따른 결과의 값이 77.6%의 차이를 보이며, 냉난방기기의 전력 사용 패턴 분석이 가능하다. 본 연구는 실생활기반의 성능평가 방법을 제안하였다는 측면에서 유의미하며, 이와 같은 에너지 저감을 위한 기술 개발 검증 및 개선을 위한 다각적인 성능평가에 대한 연구는 지속되어야 한다고 판단된다.

• Earthquakes and Structures
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• 제1권1호
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• pp.69-91
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• 2010

Current seismic design codes do not contemplate explicitly some variables that are relevant for the design of structures subjected to ground motions exhibiting large energy content. Particularly, the lack of explicit consideration of the cumulative plastic demands and of the degradation of the hysteretic cycle may result in a significant underestimation of the lateral strength of reinforced concrete structures built on soft soils. This paper introduces and illustrates the use of a numerical performance-based methodology for the predesign of standard-occupation reinforced concrete ductile structures. The methodology takes into account two limit states, the performance of the non-structural system, and in the case of the life safety limit state, the effect of cumulative plastic demands and of the degradation of the hysteretic cycle on the assessment of structural performance.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 추계학술대회 논문집
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• pp.221-223
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• 2008

In Korean urban transit system, when the railcar starts, the electric power is absorbed from the line, and then the line voltage is instantaneously collapsed to provide a large accelerating torque. On the other hand, when the railcar brakes, the regenerative power is created and it increases the line voltage at the pantograph of the railcar. Therefor, by using the energy storage system near the train, the regenerated power can be saved to this system. The energy storage system is consisted of supercapacitor and a bidirectional DC-DC converter. In this paper, controller design of a bidirectional DC-DC converter based on pole-assignment is proposed. This method can be easy to design controller. Simulation results by using the calculated parameters are presented.

• Water Engineering Research
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• 제4권1호
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• pp.1-17
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• 2003

A mathematical model was developed to simulate the performance of a prototype wind-powered reverse osmosis desalination system. The model consists of two sub-models operated in a series. The first sub-model is the wind-energy conversion sub-model, which has wind energy and feed water as its input and pressurized feed water as its output. The second sub-model is a reverse osmosis (RO) process sub-model, with pressurized feed water as its input and the flow and salinity of the product water or permeate as its output. Model coefficients were determined based on field experiments of a prototype wind powered RO desalination system of the University of Hawaii, from June to December 2001. The mathematical model developed by this study predicts the performance of wind-powered RO desalination systems under different design conditions. The system optimization is achieved using a linear programming approach. Based on the results of system optimization, a design guide is prepared, which can be used by both manufacturer and end-user of the wind-driven reverse osmosis system.

• 플랜트 저널
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• 제8권4호
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• pp.40-44
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• 2012

천연가스를 사용하기 위한 전처리공정에서 제거되는 물질인 산성 가스는 주로 아민계열 흡수제를 이용한 흡수공정을 통해 제거된다. 흡수공정 중 흡수탑에서 일어나는 흡수제의 산성가스 흡수반응은 발열반응이기 때문에 상대적으로 낮은 온도가 요구되며 역 반응이 일어나는 재생탑은 흡열반응을 위한 높은 온도 환경이 요구된다. 이는 두 탑의 흐름들 간에 열교환의 가능성이 있음을 의미한다. 본 연구에서는 DEA 흡수제를 이용한 흡수공정을 다양한 조건에서 사례연구를 시행하여 에너지 시스템을 분석하였으며, 흡수탑과 재생탑의 측면유출이 흡수공정의 전체 효율을 향상시킬 수 있음을 확인하였다.

• 한국경영과학회지
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• 제35권2호
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• pp.53-69
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• 2010

This paper proposes an ant-based routing algorithm, Ant System-Routing in wireless Senor Networks(AS-RSN), for wireless sensor networks. Using a transition rule in Ant System, sensors can spread data traffic over the whole network to achieve energy balance, and consequently, maximize the lifetime of sensor networks. The transition rule advances one of the original Ant System by re-defining link cost which is a metric devised to consider energy-sufficiency as well as energy-efficiency. This metric gives rise to the design of the AS-RSN algorithm devised to balance the data traffic of sensor networks in a decentralized manner and consequently prolong the lifetime of the networks. Therefore, AS-RSN is scalable in the number of sensors and also robust to the variations in the dynamics of event generation. We demonstrate the effectiveness of the proposed algorithm by comparing three existing routing algorithms: Direct Communication Approach, Minimum Transmission Energy, and Self-Organized Routing and find that energy balance should be considered to extend lifetime of sensor network and increase robustness of sensor network for diverse event generation patterns.