• 한국물환경학회지
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• 제37권5호
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• pp.335-343
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• 2021

Water quality prediction is essential for the proper management of water supply systems. Increased suspended sediment concentration (SSC) has various effects on water supply systems such as increased treatment cost and consequently, there have been various efforts to develop a model for predicting SSC. However, SSC is affected by both the natural and anthropogenic environment, making it challenging to predict SSC. Recently, advanced machine learning models have increasingly been used for water quality prediction. This study developed an ensemble machine learning model to predict SSC using the XGBoost (XGB) algorithm. The observed discharge (Q) and SSC in two fields monitoring stations were used to develop the model. The input variables were clustered in two groups with low and high ranges of Q using the k-means clustering algorithm. Then each group of data was separately used to optimize XGB (Model 1). The model performance was compared with that of the XGB model using the entire data (Model 2). The models were evaluated by mean squared error-ob servation standard deviation ratio (RSR) and root mean squared error. The RSR were 0.51 and 0.57 in the two monitoring stations for Model 2, respectively, while the model performance improved to RSR 0.46 and 0.55, respectively, for Model 1.

• 동력기계공학회지
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• 제17권4호
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• pp.31-35
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• 2013

The emergency AC power supply system of the nuclear power plant is designed to supply the power to the nuclear power plant at the emergency operating condition. The safety function of the diesel generator at the nuclear power plant is to supply AC electric power to the safety system whenever the preferred AC power supply is unavailable. The reliable operation of onsite standby diesel generator should be ensured by a condition monitoring system designed to maintain, monitor and forecast the reliability level of diesel generator. The purpose of this paper is to improve the existing ultrasonic sensor used for condition diagnosis of engine fuel pump and cylinder head for the accurate diagnosis in actual engine condition of emergency diesel generator(EDG). As a result of this study, we could design and develop much more reliable ultrasonic sensor than existing ones.

• 한국농공학회논문집
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• 제53권6호
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• pp.101-109
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• 2011

The purpose of this study was to establish the methodology for providing the environmental flows from irrigation reservoir. Reservoir water budget for study area was analyzed to simulate the water supply scenarios for environmental flows. Bonghyun and Hi reservoirs area, located in Gyeongnam, Gosung-gun, Hi-myeon, were selected for study watersheds and streams for this study. Reservoir operation was simulated to determine the envionmental flows supply amount from March to October with the constraint that environmental flow supply was restrained when the storage of reservoir were below the half or one-third of effective storage. The simulated results indicated that the supply of environmental flows with the amount of 200 ton/day and 600 ton/day resulted in up to 15 mm and 29 mm of runoff depth increase in the downstream, respectively. The effect of environmental flows supply from existing irrigation reservoir was not significant because the irrigation reservoir was not designed to supply the environmental flows. It is necessary to remodel the irrigation reservoir and develop the reservoir operation technique, to meet the need for the environmental flows.

• 한국경영과학회지
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• 제30권4호
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• pp.71-81
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• 2005

This Paper focuses on the effects of outside competition on an optimal echelon base stock level in a two stage supply chain. This is new in that we have been studying the effects of inside competition within a supply chain up to now. It is known that the optimal echelon base stock level with inside competition within a supply chain is less than the global optimal echelon base stock level without inside competition. This is due to the ' public goods ' nature of inventory. That is, more inventory is better, but one wants the other to invest more, thus resulting in under-investment. However, this phenomenon becomes weaker as outside competition increases. We show that as outside competition becomes stronger, the ' public goods ' effects decrease and the optimal echelon base stock level increases. If the level of competition is sufficiently high, the optimal echelon base stock level goes even higher than the global optimal echelon base stock level. We develop a theoretical model for the analysis and conduct a numerical analysis.

• 경영과학
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• 제25권1호
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• pp.107-121
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• 2008

As to more efficiently manage the inventory in the retail supply chain and to meet the customer demand in a timely manner, vendor-managed inventory (VMI) has been widely accepted, which manages inventory in the retail supply chain via sharing information and collaborating with the retailers. Applying VMI generates vendor-managed inventory/distribution problem (VMIDP), which involves inventory management for both the vendor and the retailers, and the design of vehicle routes for delivery, to minimize the total operating cost in the supply chain. In this paper, we suggest a mixed integer programming (MIP) model to obtain the optimal solution for VMIDP in a two-echelon retail supply chain, and develop an efficient heuristic based on the operating principles of the MIP model. To evaluate the performance of the heuristic, its solution was compared with the one of the MIP model on a total of twenty seven test problems. As a result, the heuristic found optimal solutions on seven problems in a significantly reduced time, and generated a 4.3% error rate of total cost in average for all problems. The heuristic is applied to the case problem of the local famous franchise company together with GIS, showing that it is capable of providing a solution efficiently in a relatively short time even in the real world situation.

• 한국전자거래학회지
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• 제3권2호
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• pp.203-217
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• 1998

Supply chain management is defined as "an integrative philosophy to manage the total flow of a distribution channel from the supplier to the ultimate user". There are many differences between traditional systems and supply chain management systems, There are so many advantages applying SCM concept in inventory management field from the viewpoint of information sharing. While each firm try to optimize the inventory individually in traditional systems, SCM focus on optimizing the channel-wide-inventory making effort to reduce the inventory interrelatedly, The more complex your network of suppliers, manufacturers, and distributors, the more you are likely to gain operational efficiencies by attending on inventory management. The inventory stockpiles at the various sites, including both incoming materials and finished products, have complex interrelationships. Efficient and effective management of inventory throughout the supply chain significantly improves the ultimate service provided to the customer. The purpose of this thesis is to develop the integrated inventory management system for the control of channel-wide inventory on the intranet by applying SCM concept.

• 통상정보연구
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• 제10권1호
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• pp.237-256
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• 2008

In recent years, most of Supply Chain Management literature has emphasized the importance of information sharing among supply chain partners, but empirical researches are few until now, especially in Korea. The purpose of this study is to develop an empirical model focusing on information exchange among partners in supply chain, and to analyze the main factors influencing the causal relationship between information exchange and performance. Based on cross-sectional questionnaire survey on Korean manufacturing firms, this study analyzed the factors influencing information exchange such as environmental factors, organizational factors, relationship factors, and information characteristics of the sample firms. Our major findings might provide many useful insights for managers in exploring the most efficient system for information exchange among partners in the context of SCM.

• The Journal of Korean Physical Therapy
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• 제9권1호
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• pp.19-35
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• 1997

Korea will soon experience a high demand for medical rehabilitation specialists, if it tries to deliver advanced health welfare service. In order to medical rehabilitation manpower policies, this study attempts to analyse, estimate and plan a long-term supply for physiatrists, physical therapists, and occupational therapists. The study analysed both national and foreign statistical data of manpower supply for medical rehabilitation specialists. Based on the above data, the demand of and supply for each specialists were estimated for long term up to the year 2030. Based on the comparative analysis results of the future demand and supply. the author intended to develop a new supply plan for the three specialist categories. The major finding of the supply plan are as follows : First, as for the supply plan for physiatrists, the author recommends to adopt the demand estimation 1 as the most suitable. In order to prevent an oversupply of physiatrists, the supply plan 1 is recommended which annual enrollment of specialists will maintain with the quota of fixed number of 63 from the year of 1999. Second, it is estimated that there was already an oversupply of physical therapists in Korea. This oversupply is expected to continue even though there would be an increase in rehabilitation hospital beds, rehabilitation facilities for the elderly, and nursing homes, Thus, it would be desirable to cut down the number of students admitted to physical therapy schools each year. Third, there will be a high demand for occupational therapists in the near future as people become more aware of the usefulness of this therapy. Thus, it is urgent to establish a supply plan to meet the demand. Given the close relationship between physical therapy and occupational therapy, the study recommends that the universities already having the the department of physical therapy open the department of occupational therapy as well.

• 정보학연구
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• 제9권1호
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• pp.65-79
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• 2006

e-Marketplace is a business concept which is importantly considered in the area of marketing. e-Marketplace provides the public field in which multi-purchasers can efficiently trade with multi-suppliers. Supply Chain Management(SCM) is being widely acknowledged by the development of information technology. SCM is well known as one of the key issues lately. The complexity of supply chains and the associated potential opportunities for gaining a competitive edge by designing a product and process to support supply chain management can be significant. In order to achieve successful implementation of supply chain management system, companies should understand some barriers in implementation and set up effective and integrated information system. Standardization of logistics is needed through the unification of EDI, Bar Code, Pallet and so on. It's effect is magnified on Efficient Consumer Response such as efficient store assortment, efficient replenishment, efficient promotion and efficient product introduction. International logistics management is the integration of key business processes from original suppliers to end user that provides products, services and information that add value for customers. e-Logistics is being used in managing the international logistics. In this study, three basic e-SCM models for the strategic implementation of supply chain management are suggested. Among them, the virtual company can be the best one we can develop in order to cope with the individualized customer needs.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.420-422
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• 2005

This paper introduces a new paradigm for energy supply system in near future which produces electric and district heat cogeneration with dispersed power grid with small nuclear power units. Recently, in nuclear field, a lot of effort has been done in nuclear major countries to develop small and medium reactor for enhancement of nuclear peaceful use as like in district heating, electric power generation, seawater desalination or hydrogen generation.