• 한국자동차공학회논문집
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• 제20권3호
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• pp.98-105
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• 2012

Recently, most of the countries started to regulate the emission of vehicle because of the global warming. The engine scooter is also one of the factor which cause the pollution. The hybrid system of a vehicle has many advantages such as fuel saving and emission reduction. The purpose of this study is to choose optimal size of engine, motor and battery for hybrid scooter system using Dynamic programming. The dynamic programming is an effective method to find an optimal solution for the complicated nonlinear system, which contains various constraints of control variables. The power source size of hybrid scooter was chosen through the backward simulator using dynamic programming. From the analysis, we choose the optimal size of each power source. To verify the optimal size of the power source, the Forward simulation was carried out. As a result, the fuel efficiency of hybrid scooter has significantly increased in comparison with that of engine scooter.

• 조명전기설비학회논문지
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• 제27권11호
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• pp.57-68
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• 2013

The market for distributed power generation based on renewable energy is increasing, particularly for standalone mini-grid applications in developing countries with limited energy resources. Stand-alone power systems (SAPS) are of special interest combined with renewable energy design in areas not connected to the electric grid. Traditionally, such systems have been powered by diesel engine generator sets (DEGS), but also hybrid systems with photovoltaic and/or wind energy conversion systems (WECS) are becoming quite common nowadays. Hybrid energy systems can now be used to generate energy consumed in remote areas and stand-alone microgrids. This paper describes the design, simulation and feasibility study of a hybrid energy system for a stand-alone power system. A simulated model is developed to investigate the design and performance of stand-alone hydrogen renewable energy systems. The analysis presented here is based on transient system simulation program (TRNSYS) with realistic ventilation load of a large store. Design of a hybrid energy system is site specific and depends on the resources available and the load demand.

• 조명전기설비학회논문지
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• 제25권8호
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• pp.70-81
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• 2011

In this paper, a multi-agent control system for DC-coupled photovoltaic (PV), fuel cell (FC), ultracapacitor(UC) and battery hybrid power system is studied for commercial buildings & apartment buildings microgrid. In this proposed system, the PV system provides electric energy to the electrolyzer to produce hydrogen for future use and transfer to the load side, if possible. Whenever the PV system cannot completely meet load demands, the FC system provides power to meet the remaining load. A multi-agent system based-power management and control algorithm is proposed for the hybrid power system by taking into account the characteristics of each power source. The main works of this paper are hybridization of alternate energy sources with FC systems using long and short storage strategies to build the multi-agent control system with pragmatic design, and a dynamic model proposed for a PV/FC/UC/battery bank hybrid power generation system. A dynamic simulation model for the hybrid power system has been developed using Matlab/Simulink, SimPowerSystems and Stateflow. Simulation results are also presented to demonstrate the effectiveness of the proposed multi-agent control and management system for building microgrid.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(4)
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• pp.195-198
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• 2000

Fractal image compression can reduce the size of image data by contractive mapping of original image. The mapping is affine transformation to find the block(called range block) which is the most similar to the original image. Fractal is very efficient way to reduce the data size. However, it has high distortion rate and requires long encoding time. In this paper, we present the simulation result of fractal and VQ hybrid systems which use different clustering algorithms, normal and improved competitive learning SOFM. The simulation results showed that the VQ hybrid fractal using improved competitive learning SOFM has better distortion rate than the VQ hybrid fractal using normal SOFM.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2000년도 추계학술대회 학술발표 논문집
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• pp.81-84
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• 2000

Fractal image compression can reduce the size of image data by contractive mapping of original image. The mapping is affine transformation to find the block(called range block) which is the most similar to the original image. Fractal is very efficient way to reduce the data size. However, it has high distortion rate and requires long encoding time. In this paper, we present the simulation result of fractal and VQ hybrid systems which use different clustering algorithms, normal and improved competitive learning SOFM. The simulation results showed that the VQ hybrid fractal using improved competitive learning SOFM has better distortion rate than the VQ hybrid fractal using normal SOFM.

• 대한기계학회논문집B
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• 제26권8호
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• pp.1088-1094
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• 2002

A channel flow with a high Reynolds number but coarse grids is numerically studied to investigate the prediction possibility of its turbulence which is three-dimensional and time-dependent. In the present paper, a Reynolds-Averaged Navier-Stokes (RANS) model, a Large Eddy Simulation (LES) and a Navier-Stokes equation with no model are tested with a new approach of hybrid RANS/LES, which reduces to RANS model in the boundary layers and at separation, and to Smagorinsky-like LES downstream of separation, and then compared with each other. It is found that the simulations of hybrid RANS/LES method sustain turbulence like those of LES and with no model, and the results are stable and fairly accurate. This indicates strongly that gradual improvements could lead to a simple, stable, and accurate approach to predict turbulence phenomena of wall-bounded flow.

• 한국자동차공학회논문집
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• 제9권5호
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• pp.122-130
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• 2001

In this paper, an operational algorithm for a 2-shaft parallel hybrid electric vehicle is suggested for the minimization of operation cost. The operation cost is obtained as a summation of the engine fuel cost and the motor electricity cost. The electrical cost function is estimated in case of motoring, and generating when the recuperation is carried out during the braking. In addition, weight function is introduced in order to maintain the battery state of charge. Based on the operation algorithm, the optimal engine operation point that minimizes the operation cost is obtained with respect to the required vehicle power for every state of charge of battery. The optimal operation point provides the optimal power distribution of the engine and the motor for a required vehicle power Simulation was performed and the fuel economy of the hybrid vehicle was compared to that of the conventional vehicle. Simulation results showed that hybrid vehicle's fuel economy can be improved as much as 45∼48% compared to the conventional vehicle's.

• 한국정보처리학회논문지
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• 제3권4호
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• pp.983-991
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• 1996

본 논문에서는 디스크캐쉬 관리 기법의 하나인 동반쓰기 기법을 개선한 복합동반 쓰기 기법을 제안하고 그 성능을 평가하였다. 제안된 기법의 성능 평가를 위하여 디스 크 시스템을 모델화 하여 실제 디스크시스템에 근접한 시뮬레이션 모델을 구현하고 trace-driven 시뮬레이션을 수행하였다. 시뮬레이션의 결과 본 연구에서 제안된 복합 동반쓰기 기법이 기존의 동반쓰기 기법에 비하여 우수한 성능을 나타냄을 증명하였다.

• 전력전자학회논문지
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• 제17권4호
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• pp.359-367
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• 2012

In this paper, the input split type series-parallel hybrid electric vehicle (SPHEV) is established and the interpretation of the dynamic characteristics in four kinds of HEV modes, such as electric vehicle mode, engine mode, hybrid mode, and regeneration mode, is described. For this research, the forward-facing approach simulation method is chosen, which is useful for vehicle dynamic analysis. The rating of each powertrain component is designed based on energy-based concept and electrical peaking hybrid (ELPH) method. Finally, the designed powertrain is evaluated with the developed PSiM simulator and simulation results are shown.

• 한국전기전자재료학회논문지
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• 제16권10호
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• pp.908-913
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• 2003

We have performed computer simulation to obtain electro-optic characteristics of reflective hybrid aligned nematic liquid crystal displays (LCDs) driven by fringe field. The results show that the optimal retardation value (dΔn) of the cell is 0.289 ${\mu}$m, which allows for the cell to have a practical cell gap of larger than 3 ${\mu}$m when manufacturing. A reflectance of the dark state is only 0.114 % for an incident light 550 nm. At this condition, the light efficiency of white state reaches 92.7 %. The display with optimized cell parameters shows that the contrast ratio greater than 5 exists over 600 of polar angle in all directions and lower driving voltage than that of fringe-field driven homogeneously aligned reflective LCD.