• Proceedings of the KIEE Conference
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• summer
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• pp.120-122
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• 2004

This paper analyse impacts of Community Energy System (CES) on the grid during transition periods for integrating of the CES and the grid. In the near future, CES might be one of major energy supply structures. The basic concept of CES is that it supplies electrical and thermal energy to the local customer loads through the islanded power network separated from the grid. Therefore, the interconnection with the grid occurs only when the energy supply from the CES generators does not meet the demand of the local load. For avoiding impacting the grid during the transition operation modes of CES, it is necessary to thoroughly analyse the influences on the grid during those periods. In order to show them, in this paper, we model the CES with 2.34 WVA DG and simulate the impacts on the grid due to interconnection of CES The simulation results show that, in order to reduce bad influences of CES on the grid, CES need the efficient load management and generation control schemes during the transition periods.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2003.11a
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• pp.127-131
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• 2003

The purpose of this study was 1) to analyze the attitudes about Senior Congregate Housing(SCH) among 4 urban areas, 2) to propose the various model for SCH which should be provided to satisfy the demand. Same opinions among 4 urban areas were ; 1) Whom were willing to move into SCH for later life, most of them were in early 50s. Most of the respondents desired to be serviced community alarm system preferred one-room style, size of 11 ${\sim}$ 15 Pyung, and preferred living at suburban area The multi-family type was preferred when not being healthy and be singled, but if healthy, preferred the type of single detached house. And they preferred the home ownership, highly valued of heating control system, health care and leisure programs. But different opinions among 4 urban areas were ; 2) Willingness live in SCH for later life had little difference in level of income, education, property. Especially, residents of Seoul Metropolitan area and Busan did not want to open their own common facilities to the public.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.411-416
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• 1999

The measurement of unsteady flow rate is of vital importance to clarify and improve the dynamic characteristics in pipeline, hydraulic components and system. There is also demand for a real time flow sensor of ability to measure unsteady flow rate with high accuracy and fast response to realize feedback control of flow rate in fluid power systems. In this paper, we propose an approach for estimating unsteady flow rate through a pipeline and components under high pressure condition. In the method, unsteady flow rate is estimated by using hydraulic pipeline dynamics and the measured pressure values at two distant points along the pipeline. The distributed parameter model of hydraulic pipeline is applied with consideration of frequency dependent viscosity friction and unsteady velocity distribution at a cross section of a pipeline. By using the self-checking functions of the method, the validity is investigated by comparison with the measured and estimated pressure waveforms at the halfway section on the pipeline. The results show good agreement between the estimated flow rate waveforms and theroetical those under unsteady laminar flow conditions. the method proposed here is useful in estimating unsteady flow rate through an arbitray cross section in hydraulic pipeline and components without installing an instantaneous flowmeter.

• Journal of ILASS-Korea
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• v.20 no.1
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• pp.14-19
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• 2015

Recently, R&D demand for environmental friendly vehicle has rapidly increased due to its global environmental issues such as global warming, energy and economic crisis. Under this situation, the most realistic alternative way for environmental friendly vehicle is a clean diesel vehicle. The common-rail fuel injection system, as key technology of clean diesel vehicle, consists of a high pressure pump, common-rail, high pressure fuel line and electronic control injector. In common-rail high-pressure fuel injection system, high pressure wave of injection system and geometry of injector elements have a major effects on high-pressure fuel spray. Therefore, in this study, the numerical model was developed for analysis about the common-rail fuel pressure pulsation by using AMESim code. We could secure stability of common-rail high-pressure fuel injection system through optimal design of fuel line.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.1
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• pp.165-176
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• 1996

The flow field and spray characteristics for loop scavenged type 2stroke engine having pancake shape was numerically computed using KIVA-Ⅱ code. The cylinder has 1intake port, 2side intake ports and 1exhaust port with induced flow angle 25 deg. In engine calculation, the chop techniques is used to strip or add planes of cells across the mesh adjacent to the TDC and the BDC(ports parts) for preventing the demand of exceed time during the computation, providing a control on cell height in the squish region. The modified turbulent model including the consideration of the compressibility effect due to the compression and expansion of piston was also used. The case of 25 deg.(injection angle) which is opposite to scavenging flow direction shows better the distribution of droplets and the evaporation rate of droplets compared to other cases(0 deg., - 25 deg.). When injection pressure was increased, the spray tip penetration became longer. When injection pressure was increased, the interaction between the upward gas velocity and spray droplets strongly cause. Thus the breakup of droplets is strongly occurred and the evaporation rate of droplets was found to be better.

• Journal of the Korean housing association
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• v.15 no.1
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• pp.163-174
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• 2004

The purpose of this study was 1) to analyze the attitudes about Senior Congregate Housing(SCH) among 4 urban areas, 2) to propose the various model for SCH which should be provided to satisfy the demand. Same opinions among 4 urban areas were ; 1) Whom were willing to move into SCH for later life, most of them were in early 50s. Most of the respondents desired to be serviced community alarm system, preferred one-room style, size of 11∼15 Pyung, and preferred living at suburban area. The multi-family type was preferred when not being healthy and be singled, but if healthy, preferred the type of single detached house. And they preferred the home ownership, highly valued of heating control system, health care and leisure programs. Thus for the future SCH, it should be designed all facilities were equipped with sports facilities, sauna and leisure programs. The findings indicated that the high rates of supporting with professional management for 24 hours by turn. But different opinions among 4 urban areas were; 2) Willingness live in SCH for later life had little difference in level of income, education, property. Especially, residents of Seoul Metropolitan area and Busan did not want to open their own common facilities to the public.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.550-558
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• 2018

This paper presents the current limit strategy of voltage controller of delta-connected H-bridge static synchronous compensator (STATCOM) under an unbalanced voltage fault event. When phase to ground fault happens, the feasibility to heighten the magnitude of sagging phase voltage is considered by using symmetric transformation method in delta-structure STATCOM. And the efficiency to cover the maximum physical current limit of switching device is considered by using vector analysis method that calculate the zero sequence current for balancing the cluster energy in delta connected H-bridge STATCOM. The result is simple and obvious. Only positive sequence current has to be used to support the unbalanced voltage sag. Although the relationship between combination of the negative sequence voltage with current and zero sequence current is nonlinear, the more negative sequence current is supplying, the larger zero sequence current is required. From the full-model STATCOM system simulation, zero sequence current demand is identified according to a ratio of positive and negative sequence compensating current. When only positive sequence current support voltage sag, the least zero sequence current is needed.

• Journal of Korea Multimedia Society
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• v.19 no.8
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• pp.1530-1537
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• 2016

Recently, solar power generation shows the significant growth in the renewable energy field. Using the short-term prediction, it is possible to control the electric power demand and the power generation plan of the auxiliary device. However, a short-term prediction can be used when you know the weather forecast. If it is not possible to use the weather forecast information because of disconnection of network at the island and the mountains or for security reasons, the accuracy of prediction is not good. Therefore, in this paper, we proposed a system capable of short-term prediction of solar power generation amount by using only the weather information that has been collected by oneself. We used temperature, humidity and insolation as weather information. We have applied a moving average to each information because they had a characteristic of time series. It was composed of min, max and average of each information, differences of mutual information and gradient of it. An artificial neural network, SVM and RBF Network model was used for the prediction algorithm and they were combined by Ensemble method. The results of this suggest that using a moving average during pre-processing and ensemble prediction models will maximize prediction accuracy.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.10a
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• pp.585-588
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• 2019

Predictions of Energy Consumption for Industries gain an important place in energy management and control system, as there are dynamic and seasonal changes in the demand and supply of energy. This paper presents and discusses the predictive models for energy consumption of the steel industry. Data used includes lagging and leading current reactive power, lagging and leading current power factor, carbon dioxide (tCO2) emission and load type. In the test set, four statistical models are trained and evaluated: (a) Linear regression (LR), (b) Support Vector Machine with radial kernel (SVM RBF), (c) Gradient Boosting Machine (GBM), (d) random forest (RF). Root Mean Squared Error (RMSE), Mean Absolute Error (MAE) and Mean Absolute Percentage Error (MAPE) are used to measure the prediction efficiency of regression designs. When using all the predictors, the best model RF can provide RMSE value 7.33 in the test set.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.216-216
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• 2015

Frequent hydro-meteorological events caused by global climate change and human exacerbate activities, make the water resource problem more complicated. The increasing speed urbanization brings a significant impact on the city flood control and security, water supply safety, water ecological security, water environment safety and the water engineering security in China, and puts forward higher requirements to urban water integrated management, undoubtedly which become the biggest obstacle for water ecological civilization construction, thus urgent requiring an advanced methods to enhance the effectiveness of the water integrated management. The other fields of smart ideas point out a development path for water resource development. The construction demand of smart water resource is expounded in the paper, combining the philosophy of modern Internet of things with the application of cloud computing technology. The concept of smart water resource is analyzed, the connotation characteristics of smart water resource is extracted, and the general model of smart water resource is refined. Then, the frame structure of smart water resource is put forward. The connotation and the overall framework of the smart water resource represent a higher level of water resource informationization development and provide a comprehensive scientific and technological support to transform water resource management from an extensive, passive, static, branch and traditional management to a fine, active, dynamic, collaborative and modern management.