• Electronics and Telecommunications Trends
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• v.34 no.6
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• pp.17-27
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• 2019

This paper introduces the 5G spectrum auction in Germany that occurred last summer and ended overheatedly after an extraordinarily long period. We describe the context of the latest German spectrum auction and trace the participants' bidding behavior. This case details the trend of the 5G spectrum auction and the factors that affect the spectrum auction as follows: First, it is determined that investment obligations that force network installations can be a financial burden to mobile network operators (MNOs) and require a careful approach. Second, excess demands can cause auction overheating and the spectrum supply volume needs to be determined by a proper demand forecast and investment incentive. Third, 'Set-Aside' for local usage aids in developing the vertical industry; however it limits the spectrum supply for mobiles and leads to higher bidding prices. Fourth, a modified adoption of a typical spectrum auction can alleviate MNO's financial burdens to secure the broadband spectrum. Finally, competition to secure the necessary bandwidth in the situation of limited spectrum supply may delay the process of the spectrum auction, causing it overheated.

• Journal of Communications and Networks
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• v.14 no.6
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• pp.672-681
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• 2012

A potential breakthrough of the electrification of the vehicle fleet will incur a steep rise in the load on the electrical power grid. To avoid huge grid investments, coordinated charging of those vehicles is a must. In this paper, we assess algorithms to schedule charging of plug-in (hybrid) electric vehicles as to minimize the additional peak load they might cause. We first introduce two approaches, one based on a classical optimization approach using quadratic programming, and a second one, market based coordination, which is a multi-agent system that uses bidding on a virtual market to reach an equilibrium price that matches demand and supply. We benchmark these two methods against each other, as well as to a baseline scenario of uncontrolled charging. Our simulation results covering a residential area with 63 households show that controlled charging reduces peak load, load variability, and deviations from the nominal grid voltage.

• IE interfaces
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• v.11 no.2
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• pp.13-24
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• 1998

A distribution system is composed of multiple levels from a producer to customers, and it's objective is to supply customers with goods timely with a prescribed level of quality at a minimum cost. For the installation and operation of multi-echelon distribution system, DRP(Distribution Resource Planning) is widely used. However, because of the characteristic difference of material flow dynamic of each distribution center, it is almost impossible to get the optimal distribution scheduling. In this paper, an improved DRP method to schedule multi-echelon distribution network is proposed so that the lot-size and order point is dynamically obtained to meet the change of demand rate and timing. The experiment is done with various demand pattern, forecast errors of demand and lead times of central distribution center. The proposed method is compared with traditional statistical approach.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.6
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• pp.133-141
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• 2009

The main objective of water distribution system is to supply enough water to users with proper pressure. Hydraulic analysis of water distribution system can be divided into Demand Driven Analysis (DDA) and Pressure Driven Analysis (PDA). Demand-driven analysis can give unrealistic results such as negative pressures in nodes due to the assumption that nodal demands are always satisfied. Pressure-driven analysis which is often used as an alternative requires a Head-Outflow Relationship (HOR) to estimate the amount of possible water supply at a certain level of pressure. However, the lack of data causes difficulty to develop the relationship. In this study, effective supply, which is the possible amount of supply while meeting the pressure requirement in nodes, is proposed to estimate the serviceability and user's convenience of the network. The effective supply is used to calculate Subsystem Importance Index (SII) which indicates the effect of isolating a subsystem on the entire network. Harmony Search, a stochastic search algorithm, is linked with EPANET to maximize the effective supply. The proposed approach is applied in example networks to evaluate the capability of the network when a subsystem is isolated, which can also be utilized to prioritize the rehabilitation order or evaluate reliability of the network.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.2
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• pp.57-65
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• 2009

In continuous review inventory model, (${\varrho}$, ${\gamma}$) system, order quantity(${\varrho}$) and reorder point(${\gamma}$) should be determined to calculate inventory-related cost that consists of setup, holding, and penalty costs. The procedure to obtain the exact value of ${\varrho}$ and ${\gamma}$ is complex. In this paper, a regression analysis is proposed to get the approximate inventory-related cost without the determination of ${\varrho}$ and ${\gamma}$ in the case that the standard deviation(${\sigma}$) of the lead time demand is small or that the mean(${\mu}$) of the lead time demand is proportional to ${\sigma}$. To save inventory-related cost, central warehouses with (${\varrho}$, ${\gamma}$) system can be built. Central warehouse can provide some stores with products with the consideration of the tradeoff between inventory-related cost and transportation cost. The number and the location of central warehouses to cover all the stores are determined by a regression-based approach. The performance of the proposed approach is tested by using some computational experiments.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.3779-3788
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• 2010

In this study, We found approach to improve the efficiency of human resource policies for small-medium enterprises(SMEs) in the regional strategic industries. Especially, we intended to identify practical and policy implications, through analyzing to the supply and demand side of human resource at the same time. In the supply side, we analyzed workers, supply, and support policy in regional strategic industry. In the demand side, we analyzed the demands from 201 SMEs in regional strategic industry. We found the demand differences in strategic industries. we found the efficiency improvement and directions of human resource policies. Thus, these results imply the necessity of creating a customizing policy for SMEs. In conclusion, the human resource policy should be reflected the central government's policy direction and the demands of SMEs.

• Journal of Soil and Groundwater Environment
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• v.27 no.2
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• pp.24-35
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• 2022

This study was conducted to estimate groundwater demand and supply for agricultural activities in a frequent-drought area that requires implementation of optimal distribution plan utilizing the well-network system (WNS). The WNS has been considered as a viable strategic way of supplying groundwater to farmlands by connecting groundwater wells physically or virtually. The study area heavily relied on groundwater resources for irrigation up to 53% due to a lack of surface water resources. Two kinds of methods, HOMWRS software and FAO approach, were used for estimating irrigation water requirements for paddy and upland fields, respectively. During the latest 10 years (2010~2019), the water requirements was estimated to be 1,106 m³/day. The requirements notably increased to 1,121~4,004 m³/day during active farming season (May to September), which exceeded the total yield capacity of pre-existing groundwater wells (2,356 m³/day) in the area. Detailed and definite determination for groundwater demand and supply helped to determine optimal scale parameters of WNS. The WNS has achieved more balanced distribution of groundwater resources for irrigation over the study area.

• Korean Journal of Construction Engineering and Management
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• v.8 no.5
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• pp.161-172
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• 2007

By prosperous condition of construction economy in the early 90s in Korea, the government needed a lot of the qualified professional engineers (PE) to manage the construction site. In order to meet the high demand of P.E., Government has established the admitted engineer systems(AES) in 1995 that give the authority of principal engineers to the admitted engineers who do not take the written examination but have equivalent working experience. Since 2000, professional $engineer^{\circ}{\phi}s$ shortage has been resolved. however, the opposite situation, which is serious over-supply of construction engineers has occurred. Thus, Government announced that would abolish the admitted engineer systems as recognized the existent admitted engineers(about 1,000,000 persons) from 2007. However, Professional Engineers Institution has strongly insisted that Government should not recognize existent admitted engineers. From this point of view, it is critical to make the supply-demand forecast systems as a derivative approach of System Dynamics also, that is useful in comparing the argument between Government and Professional Engineers Institution. This paper describes about principal $engineer^{\circ}{\phi}s$ supply change by admitted engineer system abrogation and suggests the idea to regulate the supply and demand with the improvement of the regal system.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.11a
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• pp.329-333
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• 2003

This study presents supplier buyer models representing the interactions between supplier and buyer under a long-term replenishment contract in a supply chain system. We established the models according to the economic power of each party. Analysis based on Stackelberg game theoretic approach is tried for each model. We develop methods for each agent to follow to complete a contract for the best interest of each participant.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1202-1204
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• 1999

This paper proposes a value-based pricing suitable for deregulation situation in electricity market, where the value is measured based on the service quality such as system reliability. The proposed approach makes it possible to maximize social welfare, in that diversified service can produce the optimal combination set of demand and supply. The proposed pricing can also be applied to a direct load control.