• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.1
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• pp.18-26
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• 2014

A microgrid can play a significant role for enlargement of renewable energy sources and emission reduction because it is a network of small, distributed electrical power generators operated as a collective unit. In this paper, an application of optimization method to economical operation of a microgrid is studied. The microgrid to be studied here is composed of distributed generation system(DGS), battery systems and loads. The distributed generation systems include combined heat and power(CHP) and small generators such as diesel generators and the renewable energy generators such as photovoltaic(PV) systems, wind power systems. Both of thermal loads and electrical loads are included here as loads. Also the emissions trading scheme to be applied in near future, the cost of unit start-up and the operational characteristics of battery systems are considered as well as the probabilistic characteristics of the renewable energy generation and load. A mathematical equation for optimal operation of this system is modeled based on the mixed integer programming. It is shown that this optimization methodology can be effectively used for economical operation of a microgrid by the case studies.

• Journal of Korean Society on Water Environment
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• v.24 no.3
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• pp.291-296
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• 2008

Pollutant unit load developed by Ministry of Environment (MOE) in 1995 has been a tool commonly used for water quality management and environmental policy decision. In spite of the convenience of the method in application, the shortcoming of the method has been criticized especially for nonpoint source pollution from paddy field. In this paper the estimation procedures of pollutant unit load from paddy field in the major river basins (Han, Nakdong, Geum, and Youngsan river) were investigated, and some suggestions of improvement measures of the unit-load estimation were made. The investigation showed that the distributions of rainfall, run-off, and run-off ratio, which are the most important factors affecting discharge amount of pollutants, were not similar among river basins. Such differences seemed to result in a greater unit loads estimation at Han river and at Nakdong river watersheds compared to the others. Therefore, it is not likely to be rationale to compare unit load among the watersheds without consideration of such differences. We conclude that estimation of unit-load through an intensive monitoring of pollutant discharge is crucial for better estimation of unit-load. When such an intensive monitoring is not easy due to labor and expense restriction, we suggest that unit-load should be estimated based on the storm-events which is a representative rainfall-runoff event of the area.

• Journal of Korea Water Resources Association
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• v.36 no.4
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• pp.691-703
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• 2003

In this paper, a new and integrated approach easily used to calculate the pollutant loads from agricultural watersheds is suggested. Basic concepts of this empirical tool are based on the hypotheses that variations in event mean concentrations(EMCs) of the pollutants from a given agricultural watershed during rainstorms are only due to the rainfall pattern. This assumption would be feasible to agricultural watersheds whose land uses does not change during the cultivation period overlapped by rainy season and also in which point-sources of the pollutants are rare. Therefore, if EMC data sets through extensive sampling from various rural areas are available, it is possible to establish relationships between EMCs, shapes and land uses of the watersheds, and rainfall events. For this purpose, fifty one sets of EMC values were obtained from nine different watersheds, and those data were used to develop predictive tools for the EMCs of 55, COD, TN and TP in rainfall runoff. The results of the statistical tests for those formulas show that they are not only fairly good in predicting actual EMC values of some parameters, but also useful in terms of calculating pollutant loads on any time-spans such as the day of rainfall event or weekly, monthly, and yearly. Their applicability was briefly demonstrated and discussed. Also, the unit loads calculated from EMCs based on different land uses and real rainfall data over one of the watershed used for this study. were provided, and they are compared with other well-known unit loads.

• Journal of Korean Society on Water Environment
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• v.30 no.2
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• pp.128-137
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• 2014

The land use of the unit watersheds should be maintained appropriately in order to keep the load allotment stable for the management of Total Maximum Daily Loads (TMDLs). This study classified the land area in four types and analyzed the use of each land type and its changing pattern by calculating the occupation and conversion ratios for the unit watersheds in three river basins. The forest land showed the greatest occupation ratio with 63.0%, followed by the farm land with 23%, the other area with 8.0% and the site area with 6.0% in 2003. The occupation ratio of the site and the other area increased by 0.4% and 0.2% respectively, and that of the farm and the forest land decreased by 0.4% and 0.2% respectively in 2007. The conversion ratio for the site area ranged from 1.65% to 1.97%, for the farm land from -0.47% to -0.33%, for the forest land from -0.10% to -0.04% and for the other area from 0.17% to 1.97%. It can be inferred that the decrease in the farm and the forest land contributed to the increase in the site area and that the increase in the other area was mainly made by the decrease in the forest land. It could be more effective to take into account the changes in the site area and in the forest land in the process of developing the TMDL plans.

• Journal of Wetlands Research
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• v.24 no.4
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• pp.367-376
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• 2022

LID technologies are capable of mitigating the negative impacts of non-point source (NPS) pollution generated in different land uses. Apart from the increase in point and non-point pollutant generation, highly developed and paved areas generally affect microclimate conditions. This study evaluated both the efficiency of Low Impact Development (LID) facilities in treating NPS pollutant loads as well as the unit pollutant loads (UPL) generated in various urban features (such as parking lots and highways). This investigation also looked at how LID technology helped to alleviate Urban Heat Island (UHI) conditions. As compared to the typical unit pollutant loads in South Korea, the unit pollutant loads at Kongju National University were relatively low, because of no classes, limited vehicular transmission, and low anthropogenic activities during vacation. After receiving treatment from the LID facilities, the effluent pollutant loads were significantly decreased. The sedimentation in filtration mechanisms considerably reduced the pollutant fractions in the influent. Additionally, it was shown that LID facilities' mean surface temperatures are up to 7.2℃ lower than the nearby paved environment, demonstrating the LID systems reducing the UHI impact on an urban area.

• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.125-135
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• 2009

Reliable long-term flows by SWAT-K model were applied to the relationship between stream flow and pollutant load derived from 8-day measured data of Ministry of Environment (MOE) in order to obtain continuous loadograph and evaluate accuracy in water quality modeling for the Chungju dam watershed. The measured flow were compared with flow duration curve from the model, and it showed that measured values corresponded to the almost full range of stream flow conditions except at Odae A. And there was significant relationship ($R^2=0.60{\sim}0.97$) between measured flow and water quality load at all unit-watersheds. Applying this relationship to simulated flows, continuous loadograph was obtained and compared with modeled pollutant loads. Although there were some differences during some dry and flood seasons, those were not significant and overall trend showed a good agreement. From the results, we would be able to derive a continuous loadograph based on measured data at total maximum daily loads (TMDLs) unit-watersheds on a national scale, in which stream flow and water quality have been measured at 8-day intervals since 2004, and this could be helpful to utilize distributed water quality models with difficulty in calibrating and validating parameters from lack of measured data at present.

• Special Issue of the Society of Naval Architects of Korea
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• 2005.06a
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• pp.90-96
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• 2005

This paper presents the results of the reliability analysis of PAU (Preliminary Assembly Unit) seat of the floating Production Storage and Off1-loading Unit (FPSO) The main aim of the analysis was to demonstrate that a sufficient safety of structural members is guaranteed against PAU loads, internal and external pressure, and hull girder moments. Topside loads for PAU design are based on owner's request. According to the seat type, topside loads are classified into maximum values of same seat type for design efficiency. Totally, 26 loading cases for each model are used for this analysis with the combination of the reactions of PAU loafing and the hull girder bending moments according to LR offshore (2). The analysis results are evaluated according to the acceptance criteria for yielding given in LR offshore and guidance note (3) and The panel buckling resistance is verified by LR offshore and SDA (4). For 900,000 bbls FPSO, the PAU support foundation analysis using 3-D F.E. model is carried out to verify the structural adequacy of PAU foundation and structure members in way of PAU. The modified structures in way of PAU support are safe against considered load cases and all stresses in way of PAU support are within design criteria.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.200-201
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• 2015

The unit modular method is one in which unit modules are prefabricated at a factory and then constructed at a construction site. That is why an important process, transporting unit module, is added in this method. The purpose of this study is to analyse the load for transporting unit module. The results of the analysis of the driving experimental runs revealed that a maximum load of 15 kN was applied on adapter block type A and a maximum load of 25 kN on adapter block type B. These loads were recorded at the points in the road test when the low-bed trailer was driving through unstable sections of the test such as stopping, restarting, passing over a speed bump or taking a left turn at speed.

• Journal of Industrial Technology
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• v.29 no.B
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• pp.199-205
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• 2009

This study selected Naerin Stream, Inbuk Stream and Buk Stream, branch rivers of Soyang Dam, also area of highland agriculture as test sites and measured flow and water quality, particularly eutrophication factors (BOD, COD, T-N, and T-P) in precipitation season and non precipitation season for a year, 2008. Based on the result, the study examined the change in water quality in relation to flow, and created flow discharged - pollution loads regression line by estimating pollution loads flowed from each branch river. And the study calculated annual pollution discharge loads for unit area and proposed regression equation on it by using regression analysis.

• Journal of Korean Society on Water Environment
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• v.25 no.4
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• pp.580-588
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• 2009

In this study daily flow rates and delivered pollutant loads of Nakdong river basin are simulated with modified TANK model and minimum variance unbiased estimator. Based on the simulation results, flow duration curves, load duration curves, and delivery ratio duration curves have been established. Then GIS analysis is performed to obtain several hydrological geomorphic characteristics such as watershed area, stream length, watershed slope and runoff curve number. Finally, multiple regression analysis is carried out to estimate empirical equations for pollutants delivery ratio. The results show that there is positive relation between the flow rates and delivery ratios, and the proposed empirical formulas for delivery ratio can predict well river pollutant loads.