• Journal of Korea Spatial Information System Society
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• v.10 no.3
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• pp.67-78
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• 2008

With the rapid development of wireless communication and mobile equipment, many applications for location-based services have been emerging. Moving objects such as vehicles and ships change their positions over time. Moving objects have their moving path, called the trajectory, because they move continuously. To monitor the trajectory of moving objects in a large scale database system, an efficient Indexing scheme to processed queries related to trajectories is required. In this paper, we focus on the issues of minimizing the dead space of index structures. The Minimum Bounding Boxes (MBBs) of non-leaf nodes in trajectory-preserving indexing schemes have large amounts of dead space since trajectory preservation is achieved at the sacrifice of the spatial locality of trajectories. In this thesis, we propose entry relocating techniques to reduce dead space and overlaps in non-leaf nodes. we present performance studies that compare the proposed index schemes with the TB-tree and the R*-tree under a varying set of spatio-temporal queries.

• Fire Science and Engineering
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• v.26 no.4
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• pp.10-17
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• 2012

This study classifies the fire suppression measures implemented by wooden temples into four types according to availability of the pump trucks (water tanks) at the fire sites. And this study outlines the strategies and methods based on each type of fire suppression measure. The results show that the fire suppression strategy applied in general buildings is also employed in temples where pump trucks (water tanks) and fire-fighting water are available. For temples where trucks and water are not available, the helicopter, water bag, fire suppression strategy focused on water supply link, automatic transmission system of a fire engine's level by using radio communication network, and water bladder are used. In addition, general four-wheel-drive vehicles equipped with fire fighting tools such as motor pump, hose, nozzle, and water bladder should be deployed in fire stations around the temples. A fire suppression strategy using A-type ladders is also required.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5135-5142
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• 2011

A flexible mechanism is proposed in this paper to improve the dynamic response performance of a traffic flow control system in an urban area. The roads, vehicles, and traffic control systems are all modeled as intelligent systems, wherein a wireless communication network is used as the medium of communication between the vehicles and the roads. The necessary sensor networks are installed in the roads and on the roadside upon which reinforcement learning is adopted as the core algorithm for this mechanism. A traffic policy can be planned online according to the updated situations on the roads, based on all the information from the vehicles and the roads. This improves the flexibility of traffic flow and offers a much more efficient use of the roads over a traditional traffic control system. The optimum intersection signals can be learned automatically online. An intersection control system is studied as an example of the mechanism using Q-learning based algorithm, and simulation results showed that the proposed mechanism can improve the traffic efficiency and the waiting time at the signal light by more than 30% in various conditions compare to the traditional signaling system.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.12
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• pp.399-408
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• 2015

In the direct Gun Fire Control System(GFCS), it is essential to analyze the impact of the specific error components on the hit probability to optimize the system design. For this purpose the sensitivity equations of these error components are conveniently used, but it is too difficult to get those equations for the complex system with too many system elements. Normally sensitivity analysis is performed using numerical and statistical methods for the ground combat system. This method requires much computation, and makes us difficult to estimate the sensitivity change of specific error component intuitionally for the changing operating conditions. In this paper we propose a set of sensitivity equations deriving from closed form solution of the ballistic differential equation for the bullet. They are handy equations with very little computations, easy to understand the physical meaning of the related system variables. Some simulation results are shown to demonstrate usefulness of our algorithm for the 30mm projectile.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.10
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• pp.329-336
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• 2014

Pipe spool is the most important element of plant equipment in plant construction site. Currently, the plant construction site manage the pipe spool location and usage history by handwriting. Frequently, the pipe spool is moved to unpredictable places by field workers in many construction sites and in cases like this, the pipe stool is replaced with another similar pipe spool. Since it's hard to determine the exact location of some of the pipe spools, it takes unnecessary time and labour to find the missing pipe spools, which proves that stock management is not under control. The purpose of our system is to make the identification of real-time location of the field pipes possible by attaching UHF RFID tags to the pipe spool, which will be used to connect with UHF RFID reader and antenna on vehicles. A field test conducted by the proposed system resulted in the success rate of 98% and the missing 2% was recuperated by hands-on correction, which proved that stock management through the proposed method can be 100% effective. The proposed system is expected to reduce labour costs and make stock control of assets possible, as well as applicable to similar stock management environments.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.301-301
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• 2019

수위 관측 지점의 선정은 관측 기록의 목적, 지점의 접근성 등에 의해 결정되며, 수위는 유량을 계산하기 위한 필수 자료이므로 수위 관측 지점의 위치를 선정하는데 있어 수리조건은 매우 중요한 요소이다. 이에 수위관측소(WLS, Water Level Station)는 홍수예경보, 수해방지 등의 치수계획과 하천운영, 용수공급 등의 이수계획 및 생태계 보전을 위한 수질관리계획 등의 목적을 달성할 수 있는 지점에 WMO에서 제시한 수위관측소의 최소 밀도를 고려하여 설치된다. 한국의 경우 치수측면에서 홍수예경보시스템의 홍수예보 대상지점과 홍수유출 계산지점을 가장 중요한 요소로 판단한다. 이에 홍수통제소에서 운영하는 홍수예보 프로그램에 적절한 수위관측망을 고려하기 위하여 프로그램에서 사용되고 있는 소유역 출구점 또는 합류점을 모두 수위관측소 위치로 포함시키고 있다. 인도네시아 Citarum강 홍수예경보 모형의 실행 및 검정을 위해서는 주요 지류의 출구마다 수위관측소를 설치하는 것이 바람직하나, 수위관측소의 설치 및 운영에는 많은 비용이 소요되기 때문에 주어진 예산을 고려해야 하며, 홍수예보를 실시하는 이유는 홍수로 인한 피해를 경감시키기 위한 것이기 때문에 인구와 홍수피해 잠재성이 높은 지점을 위주로 설치를 계획하여야 한다. 사업 대상지역인 Citarum강에서 BBWSC가 운영 관리하는 WLS는 29개소이며, 이 중 대상지역인 Upper Citarum Basin(UCRB)에는 20개소의 WLS가 운영되고 있다. 본 설계에서는 $300km^2$당 1개소의 수위관측소를 설치하는 것을 기준으로 설정하여 홍수예경보가 필요한 WLS 8개소를 도출하였으며, 소유역의 출구점 또는 합류점 등을 고려하여 수위관측소 위치를 결정하였다. 또한 UCRB의 과거 홍수피해상황, 과거 홍수범람실적, 홍수범람도 등을 조사하였으며, 실시간 자료 전송을 위한 통신 환경, 차량의 접근 용이성 및 하천구역 대표성 등을 고려하여 홍수예경보 구축을 위한 최적의 수위관측망을 설계하였다.

• Journal of Convergence for Information Technology
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• v.9 no.12
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• pp.54-61
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• 2019

Recently, IITS (intelligent integrated transportation system) has been important topic in Smart City related industry. As a main objective of IITS, prevention of traffic jam (due to car accidents) has been attempted with help of advanced sensor and communication technologies. Studies show that car accident has certain correlation with some factors including characteristics of location, weather, driver's behavior, and time of day. We concentrate our study on observing auto correlativity of car accidents in terms of time of day. In this paper, we performed the ARIMA tests including ADF (augmented Dickey-Fuller) to check the three factors determining auto-regressive, stationarity, and lag order. Summary on forecasting of hourly car crash counts is presented, we show that the traffic accident data obtained in Korea can be applied to ARIMA model and present a result that traffic accidents in Korea have property of being recurrent daily basis.

• Journal of the Korea Convergence Society
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• v.10 no.6
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• pp.179-184
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• 2019

Recently, various problems have arisen due to the popularization and aging of urban railway transit, which is the key transportation of large cities. In this study, the vibrational accelerations for the Daegu Metropolitan City Urban Railway(Line 1) were measured and evaluated using the smartphone built-in acceleration sensor and the approved application. For this purpose, the three axes running accelerations were measured according to the domestic standard (KS R 9160), and the acceleration data along the 32 stations (3 directions) were analyzed and compared. In addition, the increasing of acceleration values caused by the change of vibrational environment was monitored along the main stations between the time in 1997 and 2017. It was found that there are considerable increase of lateral and vertical directional accelerations due to the aging of railway facility environment for the last 20 years. The results of this study have valuable means for evaluating the ride quality of urban railway and the vibration influence on surrounding structures.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.2
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• pp.53-64
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• 2005

Previous secure routing protocols for wireless sensor networks assume that a sink is static. In many cases, however, a sink operated by man or vehicle is moving. A mobile sink creates a lot of technical problems such as reconfiguration of routing path exposure of sink location. and selection of secure access point node, which are not considered by many previous researches. In this paper, we propose a new secure routing scheme for solving such problems using hi-directional hash chain and delegation nodes of grid structure. This scheme provides a secure routing path and prevents attacker from recognizing the location of a mobile sink in sensor networks. This new method reduces the resource requirements compared to the cashed routing schemes. Simulation results also show that the system is secure and efficient enough.

• Journal of IKEEE
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• v.26 no.2
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• pp.287-291
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• 2022

In general, as the amplitude and phase information of the physical layer channel impulse response change rapidly in time and frequency according to the high-speed movement of the vehicles in V2X communication systems, it is difficult to accurately estimate these channels at the receiving end. In order to effectively overcome this problem, midamble-based channel estimation methods in which mid-ambles are periodically inserted into a packet have been recently considered. However, as the number of midambles increases, we suffer from the spectral efficiency loss. To relieve such a loss, in this paper, we propose a new bidirectional averaging channel estimation method that combines the existing data pilot-based channel estimation methods and the mid-ambles. Finally, through the simulation results, we demonstrate that the proposed method outperforms the existing mid-amble method in terms of packet error rate with fewer number of mid-ambles.