• 한국수소및신에너지학회논문집
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• 제22권6호
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• pp.913-924
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• 2011

A steady-state analysis has been conducted to predict the behavior of the slag layer in the entrained-flow slagging coal gasifier. The analysis takes into consideration the composition dependent slag properties such as density, viscosity, heat capacity, thermal conductivity, and temperature of critical viscosity. The amount of added flux to the design coal and the variation of syngas temperature inside the gasifier have been adopted as calculation parameters. The predicted results are the local thickness of the molten and the solid slag layers, and the slag viscosity and the velocity distribution across the molten slag layer along the gasifier wall near the slag tap.

• Journal of Power Electronics
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• 제14권4호
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• pp.806-813
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• 2014

Planar electromagnetic interference (EMI) filters are widely used to restrain the conducted EMI of switching power supplies. Such filters are characterized by small size, low parasitic parameters, and better high-frequency performance than the passive discrete EMI filter. However, EMI filter performance cannot be exactly predicted by using existing methods. Therefore, this paper proposes a method to use scattering parameters (S-parameters) for the measurement of EMI filter performance. A planar EMI filter sample is established. From this sample, the relationship between S-parameters and insertion gain (IG) of EMI filter is derived. To determine the IG under different impedances, the EMI filter is theoretically calculated and practically measured. The differential structure of the near-field coupling model is also deduced, and the IG is calculated under standard impedance conditions. The calculated results and actual measurements are compared to verify the feasibility of the theory.

• Journal of Biosystems Engineering
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• 제9권2호
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• pp.8-18
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• 1984

To investigate the most important factors affecting the mobility of power tiller and to find the method which can be used for predicting the mobility of power tiller in soft paddy field, a series of field experiment was performed with two models of power tiller (8ps and 6ps diesel). From the results obtained throughout field experiment, the following conclusions were derived. 1. The wheel sinkage of power tiller during both traveling and field operations, which mainly influence the mobility, could be predicted from both plate ($50{\times}100mm$) sinkage and soil cone index (30-degree cone with 2 and $6cm^2$ base area). 2. Prediction of wheel sinkage from the rectangular plate sinkage was found to be more suitable compared with the cone index. 3. The upper limit of rectangular plate sinkage was found as 15 centimeter for operation of power tiller in muddy field which is equivalent of $1kg/cm^2$ of $2cm^2$ cone index value.

• Nuclear Engineering and Technology
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• 제39권1호
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• pp.63-74
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• 2007

In this paper, a reconfigurable controller consisting of a normal controller and a standby controller is designed to control the thermoelectric (TE) power in the SP-100 space reactor. The normal controller uses a model predictive control (MPC) method where the future TE power is predicted by using support vector regression. A genetic algorithm that can effectively accomplish multiple objectives is used to optimize the normal controller. The performance of the normal controller depends on the capability of predicting the future TE power. Therefore, if the prediction performance is degraded, the proportional-integral (PI) controller of the standby controller begins to work instead of the normal controller. Performance deterioration is detected by a sequential probability ratio test (SPRT). A lumped parameter simulation model of the SP-100 nuclear space reactor is used to verify the proposed reconfigurable controller. The results of numerical simulations to assess the performance of the proposed controller show that the TE generator power level controlled by the proposed reconfigurable controller could track the target power level effectively, satisfying all control constraints. Furthermore, the normal controller is automatically switched to the standby controller when the performance of the normal controller degrades.

• KEPCO Journal on Electric Power and Energy
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• 제5권2호
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• pp.103-111
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• 2019

The combined cycle plant is an integration of gas turbine and steam turbine, combining the advantages of both cycles. It recovers the heat energy from gas turbine exhaust to use it to generate steam. The heat recovery steam generator plays a crucial role in combined cycle plants, providing the link between the gas turbine and the steam turbine. Simulation of the performance of the HRSG is required to study its effect on the entire cycle and system. Computational fluid dynamics has potential to become a useful to validate the performance of the HRSG. In this study a solver has been implemented in the open source code, OpenFOAM, for combustion simulation in the heat recovery steam generator. The solver is based on the steady laminar flamelet model to simulate detailed chemical reaction mechanism. Thereafter, the solver is used for simulation of HRSG system. Three cases with varying fuel injections and gas turbine exhaust gas flow rates were simulated and the results were compared with measurements at the system outlet. Predicted temperature and emissions and those from measurements showed the same trend and in quantitative agreement.

• Design & Manufacturing
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• 제15권3호
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• pp.50-55
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• 2021

Solar power generation, which is one of the methods of using solar energy, has a high possibility of practical implementation compared to other renewable energy power generation, and it has the characteristic that it can generate as much power as needed in necessary places. In addition, maintenance is easy, unmanned operation is possible, and power management can be performed more efficiently if operated in a hybrid method with existing electric energy. Therefore, in this study, numerical analysis using a computer program was performed to analyze the efficient operation and performance improvement of solar energy of the rotating condensing type solar LED street lamp. As a result, the two-axis tracking type could obtain 15.23 % more electricity per year than the fixed type, and additional auxiliary power generation was required for the fixed type by 19 % per year than the tracking type. As a result of computational fluid dynamics(CFD) simulation for PV module surface temperature prediction, the The surface temperature of the Photovoltaics(PV) module incident surface was predicted to be about 10℃ higher than that of the fixed type.

• 한국항만경제학회지
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• 제25권1호
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• pp.1-14
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• 2009

항만산업의 발전은 저렴하고 효율적인 서비스 제공을 가능하게 함으로써 자국 경제발전을 지원하는 기능을 하는 동시에 독립된 산업으로 부가가치 및 고용창출을 기대할 수 있다. 그러나 국내 주요 항만들은 대내의적인 여건의 변화로 항만교역량 증가세가 둔화되고 있으며 국내 항만의 여건악화는 일시적인 현상이라기보다는 구조적인 현상이라는 점에 문제의 심각성이 있다. 즉, 향후 주요 항만들의 교역량 증가세가 회복될 가능성이 크지 않다는 것이 일반적인 견해이며, 역내 물류중심 기능을 수행할 수 있을 것인지에 대한 회의론 마저 대두되고 있는 실정이다. 항만개발에 소요되는 시간과 재원은 막대하다. 특히 신항개발의 경우 최소 10년 이상의 장기수요 전망 하에 개발계획의 수립이 이루어진다. 따라서 개발계획의 기본이 되는 교역량의 예측의 중요성은 최근 교역량과 관련한 대외적인 환경 변화에 따라 중요성이 더욱 부각되고 있다. 이처럼 산업이 고도화되고 구조도 급격히 변화되고 있는 시대 흐름에 비추어 정확한 물동량예측은 유용하게 이용될 수 있다. 따라서 본고에서는 승법계절 ARIMA모형을 이용하여 국내항만과 중국항만간의 교역량 변화를 예측해보고, 이러한 예측을 통하여 우리나라 항만의 역할과 경쟁력을 갖추기 위한 필요성이 제기됨에 따라 항만의 교역량 중대를 위한 항만활성화 방안을 제시하고자 한다.

• Smart Structures and Systems
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• 제24권1호
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• pp.83-94
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• 2019

Passive negative stiffness dampers (NSDs) that possess superior energy dissipation abilities, have been proved to be more efficient than commonly adopted passive viscous dampers in controlling stay cable vibrations. Recently, inertial mass dampers (IMDs) have attracted extensive attentions since their properties are similar to NSDs. It has been theoretically predicted that superior supplemental damping can be generated for a taut cable with an IMD. This paper aims to theoretically investigate the impact of the cable sag on the efficiency of an IMD in controlling stay cable vibrations, and experimentally validate superior vibration mitigation performance of the IMD. Both the numerical and asymptotic solutions were obtained for an inclined sag cable with an IMD installed close to the cable end. Based on the asymptotic solution, the cable attainable maximum modal damping ratio and the corresponding optimal damping coefficient of the IMD were derived for a given inertial mass. An electromagnetic IMD (EIMD) with adjustable inertial mass was developed to investigate the effects of inertial mass and cable sag on the vibration mitigation performance of two model cables with different sags through series of first modal free vibration tests. The results show that the sag generally reduces the attainable first modal damping ratio of the cable with a passive viscous damper, while tends to increase the cable maximum attainable modal damping ratio provided by the IMD. The cable sag also decreases the optimum damping coefficient of the IMD when the inertial mass is less than its optimal value. The theoretically predicted first modal damping ratio of the cable with an IMD, taking into account the sag generally, agrees well with that identified from experimental results, while it will be significantly overestimated with a taut-cable model, especially for the cable with large sag.

• 전기전자학회논문지
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• 제23권1호
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• pp.134-142
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• 2019

에너지인터넷 기술의 발전과 다양한 전자기기의 보급으로 에너지소비량이 패턴이 다양해짐에 따라 수요예측에 대한 신뢰도가 감소하고 있어 발전량 최적화 및 전력공급 안정화에 문제를 야기하고 있다. 본 연구에서는 고신뢰성을 갖는 수요예측을 위해 딥러닝 기법인 Convolution neural network(CNN)과 Bidirectional Long Short-Term Memory(BLSTM)을 융합한 1Dimention-Convolution and Bidirectional LSTM(1D-ConvBLSTM)을 제안하고, 제안한 기법을 활용하여 시계열 에너지소비량대한 소비패턴을 효과적으로 추출한다. 실험 결과에서는 다양한 반복학습 횟수와 feature map에 대해서 수요를 예측하고 적은 반복학습 횟수로도 테스트 데이터의 그래프 개형을 예측하는 것을 검증한다.

• 한국물환경학회지
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• 제36권6호
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• pp.535-545
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• 2020

This study aims to conserve and monitor energy use in public sewage treatment plants by utilizing data from the SCADA system and by controlling the aeration rate required for maintaining effluent water quality. Power consumption in the sewage treatment process was predicted using the equipment's uptime, efficiency, and inherent power consumption. The predicted energy consumption was calibrated by measured data. Additionally, energy efficiency indicators were proposed based on statistical data for energy use, capacity, and effluent quality. In one case study, a sewage treatment plant operated via the SBR process used ~30% of energy consumed in maintaining the bioreactors and treated water tanks (included decanting pump and cleaning systems). Energy consumption analysis with the K-ECO Tool-kit was conducted for unit processing. The results showed that about 58.7% of total energy consumed was used in the preliminary and biological treatment rotating equipment such as the blower and pump. In addition, the energy consumption rate was higher to the order of 19.2% in the phosphorus removal process, 16.0% during sludge treatment, and 6.1% during disinfection and discharge. In terms of equipment energy usage, feeding and decanting pumps accounted for 40% of total energy consumed following 27% for blowers. By controlling the aeration rate based on the proposed feedback control system, the DO concentration was reduced by 56% compared pre-controls and the aeration amount decreased by 28%. The overall power consumption of the plant was reduced by 6% via aeration control.