• KIISE Transactions on Computing Practices
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• v.24 no.2
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• pp.77-81
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• 2018

Many studies that improve the efficiency of data collection and a network's lifetime by using a mobile sink have been conducted using wireless sensor networks. If a drone is used as a mobile sink, the drone can collect data more efficiently than can existing mobile sinks operating on the ground because the drone can minimize the effects of obstacles and the terrain. In this paper, we propose a rendezvous node selection scheme which considers estimated drone's trajectory and data collection latency of sensor networks for reliable data collection, when a drone whose trajectory is not predetermined works with terrestrial wireless sensor networks. A selected rendezvous node on the ground collects data from the entire network and it sends then collected data to the drone via direct communication. We also verify that the proposed scheme is more reliable than previous schemes without considering the drone's trajectory and data collection latency.

• 한국공간정보시스템학회:학술대회논문집
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• 2005.05a
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• pp.243-248
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• 2005

우리나라의 농업은 주곡의 지속적인 자급기반을 마련하고 이제 단순한 농사형태에서 벗어나 새로운 소득작목을 개발하고 합리적인 경영개선을 통하여 소득을 높이는 상업농시대에 접어들게 되었다. 따라서 상업농시대에는 농업도 새로운 기술을 바탕으로 질 높은 농산물을 안정적으로 생산공급할 수 있는 기술의 확보가 더욱 요구되고 있다. 최근 농산물수입개방 시대에 접어들게 되면서 우리 농산물도 국제경쟁력향상을 위한 품질향상 및 새로운 소득작물의 개발이 절실히 요구되는 시점에 와있다. 여러 지방지치단체에서 그 지방에 알맞은 소득작물을 개발하여 많은 소득을 올리고 있는 사례를 많이 볼 수 있다. 예로서 보성의 녹차, 무안의 무화과, 구례의 오이 등이 대표적인 예라고 할 수 있다. 여러 농업연구기관에서도 과학적인 토양연구로 세부정밀토양조사를 실시하고 작물재배의 부적지에 대해서는 토양개량방법을 연구하고 있으며 그에 따른 시비추천과 소득작물의 적지적작추천을 하고 있다. 국내에서도 GIS의 발전 및 RS의 발전과 더불어 친환경농업의 일환으로 정밀농업분야에 많은 관심이 집중되고 있다. 정밀농업은 농업생산기술 분야에서 아직 생소한 접근방법으로서 여기에서는 지구측위시스템(GPS)와 지리정보시스템(GIS), 원격탐사(RS)기법들이 많이 응용되고 있다. 또한 농업의 1차(식량생산)적인 목적에서 2차, 3차(소득증대 및 부가가치 증대)적인 목적으로 변화되고 있다. 각 지자체에서 그 지역에 적합한 농산물 재배를 위한 재배단지 확산방안 연구가 진행중에 있으며, 과거 토양속성인자를 가지고 재배적지 선정을 해왔으나, 본 연구에서는 GIS와 RS을 중첩하여 적지선정에 관한 최적의 시스템을 구현하였다. 이런 적지 선정을 통하여 유기농업의 실현을 도모하여 소비자의 욕구에 맞는 작물 생산 및 농촌관광단지 조성을 통해 부가가치증대 및 소득증대를 꾀함으로 농촌문제 해결에 도움이 될 것으로 기대된다. 본 연구를 통해 GIS 와 RS의 기술이 농촌분야에 더 효율적으로 적용될 것으로 기대되며, 농업기술센터를 통한 정보제공을 함으로써 대농민 서비스 및 농업기관의 위상이 제고 될 것으로 기대된다.

• Journal of Korean Society of Steel Construction
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• v.24 no.1
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• pp.91-99
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• 2012

In recently, the vibration control of adjacent buildings have been studied and magneto-rheological(MR) fluid dampers have been applied to seismic response control. MR dampers can be controlled with small power supplies and the dynamic range of this damping force is quite large. This MR damper is one of semi-active dampers as a new class of smart dampers. In this study, vibration control effect according to the installation location of the MR damper connected adjacent buildings has been investigated. Adjacent building structures with different natural frequencies were used as example structures. Groundhook control model is applied to determinate control force of MR damper. In this numerical analysis, it has been shown that displacement responses can be effectively controlled as adjacent buildings are connected at roof floors by MR damper. And acceleration responses can be effectively reduced when two buildings are connected at the mid-stories of adjacent buildings by MR damper. Therefore, the installation floor of the MR damper should be selected with seismic response control target.

• Journal of Korea Water Resources Association
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• v.44 no.11
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• pp.889-902
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• 2011

In this study, frequency analysis using drought index had implemented for the derivation of drought severity-duration-frequency (SDF) curves to enable quantitative evaluations of past historical droughts having been occurred in Korean Peninsular. Seoul, Daejeon, Daegu, Gwangju, and Busan weather stations were selected and precipitation data during 1974~2010 (37 years) was used for the calculation of Standardized Precipitation Index (SPI) and frequency analysis. Based on the results of goodness of fit test on the probability distribution, Generalized Extreme Value (GEV) was selected as most suitable probability distribution for the drought frequency analysis using SPI. This study can suggest return periods for historical major drought events by using newrly derived SDF curves for each stations. In case of 1994~1995 droughts which had focused on southern part of Korea. SDF curves of Gwangju weather station showed 50~100 years of return period and Busan station showed 100~200 years of return period. Besides, in case of 1988~1989 droughts, SDF of Seoul weather station were appeared as having return periods of 300 years.

• Journal of Korea Water Resources Association
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• v.52 no.12
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• pp.963-973
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• 2019

This study reviews a urban flooding risk criteria estimation model to predict risk criteria in areas where flood risk criteria are not precalculated by using watershed characteristic data and limit rainfall based on damage history. The risk criteria estimation model was designed using Support Vector Machine, one of the machine learning algorithms. The learning data consisted of regional limit rainfall and watershed characteristic. The learning data were applied to the SVM algorithm after normalization. We calculated the mean absolute error and standard deviation using Leave-One-Out and K-fold cross-validation algorithms and evaluated the performance of the model. In Leave-One-Out, models with small standard deviation were selected as the optimal model, and models with less folds were selected in the K-fold. The average accuracy of the selected models by rainfall duration is over 80%, suggesting that SVM can be used to estimate flooding risk criteria.

• Proceedings of KOSOMES biannual meeting
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• 2006.05a
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• pp.103-108
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• 2006

Treatment of O/W Emulsion is very important to develop 15ppm Bilge Separator for new IMO regulation It is too difficult to demulsify the emulsion in the bilge waste water, so we use chemical treatment to break emulsion stability. Broken oil particle is treated by flotation 15ppm Bilge Separator on the Ship doesn't have enough time to treat Bilge waste water because of limited space in the ship. For the solution to this problem, we experiment to find primary factors as coagulant, pH, amount of inputting coagulant, and type of flotation. On the basis of test results, we decided primary factors.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.12
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• pp.943-947
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• 2009

To support an efficient management of software verification and validation activities, many defect prediction models have been proposed based on object oriented metrics. In order to apply defect prediction models, we need to determine a threshold value. Because we cannot know actually where defects are, it is difficult to determine threshold. Therefore, we performed a series of experiments to explore the issue of determining a threshold. In the experiments, we applied defect prediction models to other systems different from the system used in building the prediction model. Specifically, we have applied three models - Olague model, Zhou model, and Gyimothy model - to four different systems. As a result, we found that the prediction capabilities varied considerably with a chosen threshold value. Therefore, we need to perform a study on the determination of an appropriate threshold value to improve the applicably of defect prediction models.

• Journal of KIISE:Information Networking
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• v.34 no.6
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• pp.423-434
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• 2007

Vehicular ad-hoc network (VANET), a kind of mobile ad-hoc network (MANET), is a key technology for building intelligent transportation system (ITS). VANET is automatically and temporarily established through vehicle-to-vehicle communication without network infrastructure. It has the characteristics that frequent changes of network topology and node density are occurred and messages are disseminated through several relay nodes in the network. Due to frequent change of network topology and node density, however, VANET requires an effective relay node selection scheme to disseminate messages through the multi-hop broadcast. In this paper, we propose a contention window based multi-hop broadcast scheme for VANET. Each node has an optimized contention window and competes with each other for a relay node. The experimental results show that the proposed scheme has a better performance than the distance-based deterministic broadcast scheme in terms of message propagation delay and network traffic.

• Journal of Korean Society of Transportation
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• v.18 no.3
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• pp.101-112
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• 2000

The Purpose of this Paper was to revise the method of USHCM and to establish new method for level of service analysis on two-lane rural highways. For this Purpose, total delay rate was selected as new MOE for level of service, replacing the present Percent time delay. This result showed that total delay rate was more effective for considering the effects of traffic flows, auxiliary lane, and vertical tirade. The application of total delay rate could resolve the Problems in the USHCM method, such as too wide ranges for level of service D and E, and the use of different Procedures for level of service analysis of general terrain segment and specific grade Procedures. The research results are as follows First, a new method for level of service analysis on two-lane rural highways was developed using the total delay rate. Second, a new classification for level of service was developed and a consistent method applicable for general terrain segment and specific tirade Procedures was developed. Third, the desired speed on two-lane rural highways was determined as 85km/h.

• Journal of Digital Contents Society
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• v.3 no.2
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• pp.221-233
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• 2002

In this paper, we present integer programming models and algorithms for the Capacitated Facility Location-Allocation Problem (CFLP). The models and algorithms can be used for the design of logistics networks and for the location of telecommunication facilities. We are given a set of candidate facility installation sites, one type of facility for each candidate site with its capacity and installation cost, a set of customers with their demand requirement, and flow cost for one unit of demand flow from each customer to each candidate site. (CFLP) is to determine the number of facilities for each candidate site and the set of customers which are connected to each site with minimum cost, while satisfying the demand requirement of each customer and constraints imposed on the allocation of customers to facilities. We present two integer programming models for (CFLP), and devise a branch-and-cut algorithm and a branch-and-price algorithm for the problem.