• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.472-473
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• 2010

1kW~10kW급의 UPS 토폴로지로서 Line Interactive UPS가 많이 사용되고 있다. Line Interactive UPS는 Single Stage의 AC/DC 변환기 구조를 갖으며 정상상태에서는 적은 전류로 DC측 에너지 저장장치의 충전상태를 유지만 하면 되므로 운전 효율이 높고 가격이 저렴하다. 그러나 고성능의 전류/전압 제어기술이 요구되므로 제품화하는데 어려움이 많다. 본 논문에서는 MATLAB Simulink와 연동하여 간단히 다양한 제어알고리즘을 구현 할 수 있는 dSPACE 장비를 사용하여 실험 장치를 구축하고 Single Stage UPS의 제어알고리즘을 구현하였다.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.372-374
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• 2002

The Optimal Power Flow(OPF) is the optimization model that has different constraints and the specified objective function, which is very useful tool for efficient system and market operation in the competitive electricity market. The existed OPF models focus on the minimization of generation fuel cost under informed demand values at each bus Recently, the studies of OPF model with demand function considering the response behavior of customers in the deregulated electricity market have been executed. This paper implements the OPF model using demand function with specified price elasticity, and provides the analysis of related results.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.624-626
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• 2003

Transmission pricing is one of important issues related to competitive electricity markets since rational pricing scheme ensures a fair competition between this market participants. Transmission pricing scheme is classified briefly into marginal cost pricing and embedded cost pricing. In economic efficiency, marginal cost pricing is more adequate for competitive electricity market. However, this pricing scheme requires revenue reconciliation since it cannot ensure full recovery of Transco's revenue requirements. This paper presents a new revenue reconciliation to maximize social welfare. For this analysis, this paper provides the results applied by various revenue reconciliation methodologies.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.209-210
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• 2012

NPC 인버터는 높은 효율과 우수한 출력 THD로 계통연계 시스템에 많이 채용되고 있다. 이때 LCL필터는 계통연계 기준을 만족하면서 가격과 부피측면을 고려하여 인덕턴스와 캐패시턴스는 가능한 작게 설계하는 것이 중요하다. 본 논문에서는 계통연계형 NPC 인버터에서 PWM기법을 고려하여 계통전류의 고조파 기준을 만족하면서 설계자가 독립부하 전압리플, 인덕터 부피, 무효전류량, 시스템 대역폭에 가중치를 적용할 수 있는 LCL필터 최적설계 방법을 제안한다.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2003.05a
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• pp.457-466
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• 2003

인터넷과 같은 대량의 정보에 대응할 수 있는 고성능 정보검색시스템을 구축하기 위해서 지금까지는 고가의 중대형 컴퓨터를 주로 활용하여 왔으나, 최근 가격대 성능비가 높은 PC 클러스터 시스템을 활용하는 방안이 경제적인 대안으로 떠오르고 있다. PC 클러스터 시스템에서는 전체 작업을 개별 노드 즉 PC에 가능한 균등하게 분배함으로써 성능을 극대화 하고자 하는데, 하나 또는 그 이상의 노드에 문제가 발생하는 경우 전체시스템의 성능이 매우 저하되거나 정상적인 서비스를 제공하기가 어려워진다. 이러한 상황에서 고장 포용성의 달성은 1년 365일 지속적으로 운영되어야 하는 많은 응용분야에서 반드시 해결해야 하는 문제이다. 본 논문에서는 PC 클러스터를 활용한 병렬정보검색시스템에서 고장 포용성을 극대화하기 위하여 각 노드의 색인어 역파일을 이웃 노드에 효율적으로 중복하여 저장하는 방안과 이를 활용한 효과적인 병렬정보검색 방법을 제안한다. 대규모 말뭉치를 활용한 실험결과 본 논문에서 제시하는 고장 포용성 향상을 위한 색인어 역파일 중복 저장방안이 충분한 효율성과 실용성이 있음을 확인하였다.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.2_2
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• pp.315-322
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• 2022

Apartments are being established as a universal housing type because of the perception that they are excellent in preservation of asset values and convenience. In this study, through multiple regression analysis, it is a thesis that explores whether it affects the housing market in Gimhae, a small and medium-sized city in the province, and how the price flow in neighboring cities has an effect. It is possible to examine how macroeconomic variables such as the balloon effect and the lowest interest rate caused by the government's tweezers regulation bring about changes in the housing market of small and medium-sized cities in local regions.

• Proceedings of the Korean Society of Computer Information Conference
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• 2021.07a
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• pp.205-206
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• 2021

본 논문에서는 스마트 폰의 GPS 센서와 Google Map, 공공데이터를 활용해 사용자 주변의 최저가 업소를 맵에 표기하는 애플리케이션을 개발한다. 이 애플리케이션은 휴대폰 인증을 통한 회원가입 기능을 구현하였으며 안드로이드 GPS 센서를 이용하여 현재 사용자의 위치 주변의 최저가 업소들을 표기한다. 또한 사용자가 검색하고자 하는 업소의 업종을 선택하면 맵에 선택한 업종과 같은 업소들의 위치에 마커를 표시하고 마커를 클릭 시 업소명, 대표메뉴, 가격 등의 정보를 볼 수 있다.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.8
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• pp.337-347
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• 2007

An embedded system is called a multi-mode embedded system if it performs multiple applications by dynamically reconfiguring the system functionality. Further, the embedded system is called a multi-mode multi-task embedded system if it additionally supports multiple tasks to be executed in a mode. In this Paper, we address a HW/SW partitioning problem, that is, HW/SW partitioning of multi-mode multi-task embedded applications with timing constraints of tasks. The objective of the optimization problem is to find a minimal total system cost of allocation/mapping of processing resources to functional modules in tasks together with a schedule that satisfies the timing constraints. The key success of solving the problem is closely related to the degree of the amount of utilization of the potential parallelism among the executions of modules. However, due to an inherently excessively large search space of the parallelism, and to make the task of schedulabilty analysis easy, the prior HW/SW partitioning methods have not been able to fully exploit the potential parallel execution of modules. To overcome the limitation, we propose a set of comprehensive HW/SW partitioning techniques which solve the three subproblems of the partitioning problem simultaneously: (1) allocation of processing resources, (2) mapping the processing resources to the modules in tasks, and (3) determining an execution schedule of modules. Specifically, based on a precise measurement on the parallel execution and schedulability of modules, we develop a stepwise refinement partitioning technique for single-mode multi-task applications. The proposed techniques is then extended to solve the HW/SW partitioning problem of multi-mode multi-task applications. From experiments with a set of real-life applications, it is shown that the proposed techniques are able to reduce the implementation cost by 19.0% and 17.0% for single- and multi-mode multi-task applications over that by the conventional method, respectively.

• Journal of Korean Society of Forest Science
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• v.52 no.1
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• pp.37-49
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• 1981

The purpose of the study is to find out the objective method of valuation on the forest stands through the analysis of logging costs that is positively related to timber production. The two forest (Amgog, Whangryoung), located nereby, but forest type, logging and skidding conditions being slightly different, were slected to carry out the study. The objective timber stumpage value were determined by investigating the appropriate timber production costs and profits of logging operations. The main result obtained in this study are as follows: 1. The rate of logging cost in consisting of timber market price is 13.15% in the area of Amgog logging place and 19.48% in Whangryoung. 2. The rate of the other production cost excluding logging cost is 15.36% in the area of Amgog logging place and 28.85% in Whangryoung. 3. The total rate of timber production cost in consisting of the market price is more than 28.51% in the area of Amgog logging place and 48.33% in Whangryoung, 4. Though the productivity of forest land is affected by the selection of tree species, tending, treatments and effective management of forest land, the more important problem is improvement of logging condition. 5. The rate of production cost in timber price is so high that we should endeavore to improve the productivity of labour and its quality, and minimize the difference of piece work per day in accordance to the various site condition. 6. Although the profit of forest industry is related to the period of recapturing investment, it is more closely related to the working condition, risk of investment and continuous change of social investment interest. 7. If the right variables which are related to the timber market, are objectively obtained, the stumpage value of mature forests can be objectively caculated by applying straight line discounting method or compound discounting method in caculating the stump to market price.

• Environmental and Resource Economics Review
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• v.16 no.4
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• pp.947-978
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• 2007

In this paper, we investigated a Value-at-Risk approach to the volatility of two crude oil markets (Brent and Dubai). We also assessed the performance of various VaR models (RiskMetrics, GARCH, IGARCH and FIGARCH models) with the normal and skewed Student-t distribution innovations. The FIGARCH model outperforms the GARCH and IGARCH models in capturing the long memory property in the volatility of crude oil markets returns. This implies that the long memory property is prevalent in the volatility of crude oil returns. In addition, from the results of VaR analysis, the FIGARCH model with the skewed Student-t distribution innovation predicts critical loss more accurately than other models with the normal distribution innovation for both long and short positions. This finding indicates that the skewed Student-t distribution innovation is better for modeling the skewness and excess kurtosis in the distribution of crude oil returns. Overall, these findings might improve the measurement of the dynamics of crude oil prices and provide an accurate estimation of VaR for buyers and sellers in crude oil markets.