• Journal of the Korea Society of Computer and Information
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• v.19 no.2
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• pp.143-150
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• 2014

In this paper, we propose the delivery problem on trees and two algorithms for the problem. The delivery problem on trees is that of minimizing the object delivery time from one node to another node using n various speed robots. Our first algorithm generates an optimal solution with some restrictions in handover places. In this algorithm, we assume that the handover can be made at a vertex of given tree. We try to find the handover places and the robots participate in handover from the start node to the destination node. The second algorithm extends the first one to remove the restriction about the handover places. The second algorithm still generates an optimal solution. The time complexities of both algorithms are $O((n+m)^2)$ where n is the number of robots and m is the number of nodes.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.13 no.3
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• pp.25-37
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• 2014

Recently, our local governments are conducting the introduction of tram system because it is recognized as an effective public transit that can solve a traffic jam in downtown, decreasing public transit share and environmental issues in world wide cities. We developed the Active Priority Control Strategy to efficiently operate a tram in our existing traffic signal system. This study organized the tram system for operating the Active Priority Signal Control, developed the algorithm that calculates a tram-stop dwell time in order to pass the downstream intersection without a stop. The dwell time is determined by arrival time at tram-stop, downstream signal time, and the location of a opposite tram, it can be reduced by choosing the optimal one among Signal Priority Controls. Using the VISSIM and VISVAP model, we conducted a simulation test for the city of Chang-won that it is expected to install a tram system. It showed that a developed signal control strategy is effective to prevent a tram's stop in intersections, to reduce a tram's travel time.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.6
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• pp.112-123
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• 2017

The accurate forecasting of the public transportation's transit and arrival time has become increasingly important as more people use buses and subways instead of personal vehicles under the government's public transportation promotion policy. Using bus management system (BMS) data, which provide information on the real-time bus location, operation interval, and operation history, it is now possible to analyze the bus schedule reliability. However, the punctuality should always be considered together with the operation safety. Therefore, this study suggests a new methodology to secure both reliability and safety using the BMS data. Unlike other studies, we calculated the bus travel time between two bus stops by dividing the total travel length into 6 sections using 5 different measuring points. In addition, the optimal travel time for each bus route was proposed by analyzing the mean, standard deviation and coefficient of variation of the each section's measurement. This will ensure the reliability, safety and mobility of the bus operation.

• Journal of the Korea Society for Simulation
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• v.16 no.1
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• pp.31-37
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• 2007

The importance of NPC's role in computer games is increasing. An NPC must perform its tasks by perceiving obstacles and other characters and by moving through them. It has been proposed to plan a natural-looking path against fixed obstacles by using a generalized visibility graph. In this paper we develop the execution module for an NPC to move efficiently along the path planned on the generalized visibility graph. The planned path consists of line segments and arc segments, so we define steering behaviors such as linear behaviors, circular behaviors, and an arriving behavior for NPC's movements to be realistic and utilize them during execution. The execution module also includes the collision detection capability to be able to detect dynamic obstacles and uses a decision tree to react differently according to the detected obstacles. The execution module is tested through the simulation based on the example scenario in which an NPC interferes the other moving NPC.

• Journal of the Korea Society for Simulation
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• v.20 no.3
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• pp.1-10
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• 2011

In this study, we consider a capacity planning problem where the number of machines at each workstation is determined in manufacturing systems of top-edge electronic products such as semiconductor or display. The considered manufacturing system is the typical hybrid flowshop which has identical parallel machines at each workstation and the setup operation occurs when the types of consecutively processed products are different. The objective of the problem is finding good combinations of the numbers of machines at all workstations, under the given capital amount for purchasing machines. Various heuristic methods for determining the numbers of machines at workstations are proposed and the performances were tested through a series of computational experiments. In the study, a simulation model has been developed in order to simulate the considered manufacturing system with dynamic orders and complex process. The simulation model is also used for conducting the computational comparison test among various proposed methods.

• Journal of the Korea Society of Computer and Information
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• v.20 no.2
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• pp.89-97
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• 2015

In this paper, we propose a handoff method supporting LBS (Location Based Services) Information in mobile clouding environment. In mobile clouding computing, handoff delay and re-authentication is occurred. A mobile node needs re-authentication procedure from cloud server whenever it arrives new AP. But Using of location information of node enables to reduce delay time due to re-authentication. To reduce re-authentication delay time, proposed method stores location information of APs on WiFi based location server to complement. GPS-based technology which can't receive satellite signal in indoor and then node collects location information of AP at handoff time. And also enables to process LBS without increasing handoff delay by splitting the process of handoff from process of requesting location information. For analysis of proposed method, We analyze handoff delay and location information process time and have compared previous handoff method in cloud environment. We confirmed that proposed method shows lower delay time without increasing LBS process time than previous method because node receives location information from location information server when handoff is occurred.

• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.199-207
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• 2012

In this paper, we designed and implemented path search system using GPS information in photo. The system extracts EXIF information included in a photo to get path information and performs path search by applying the shortest path algorithm with the use of GPS information out of information, which was extracted in this way. And then it shows the obtained path information on web by utilizing Yahoo Map API. For this, the system is designed using a method of extracting location information in a photo and path sorting through applying the shortest path algorithm. UI(User Interface) was implemented using Yahoo Map API. Based on that, we implemented path search service using photo file that is included GPS information.

• Journal of Korea Society of Industrial Information Systems
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• v.9 no.1
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• pp.77-84
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• 2004

Recently, as the number of entities participating in the Grid system increased, the response time of LDAP system became inadequate. Consequently, we have to design new LDAP that suitable for high performance Grid environments. For this, researches about analysis of performance LDAP system are needed firstly. However, because researches are focused mostly on read operation optimized environments, so these result of researches are not directly applied to high performance Grid environments that write operation occupies most. In this paper, we provide overall results of analysis of performance of LDAP system with respect to number of node, query arrival rate, probability of read and so on. The analysis is based on in analytic performance model by applying the M/M/1 queuing model. Finally, based on the results, we suggest the direction for the design of high performance LDAP system and this research results can be applied as basic materials to design of GIS in high performance Grid environments as well as.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6C
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• pp.581-593
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• 2002

In this paper, we proposed an Adaptive RIO scheme to solve the problem of RIO scheme that occurs when admission control is performed for QoS guarantee of Assured Service in Differentiated Services. To prevent an early random drop of the admitted In-profile packet, proposed Adaptive RIO scheme updates parameters of RIO scheme every time interval according to the estimated numbers of maximum packet arrivals of In-profile traffic and total traffic during the next time interval. The numbers of maximum packet arrivals during the next time interval are estimated based on the buffer size determined by the network topology and the ratio of bandwidth allocated to each subclass. We found from simulation results that, compared with RIO scheme, proposed Adaptive RIO scheme can improve performance of the throughput for In-profile traffic when admission control is performed or congestion occurs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4C
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• pp.433-441
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• 2003

We propose a new resource reservation scheme called MC-HMRSVP(Mobile clustering based-Hierarchical mobile ReSource reserVation Protcol) that is an extension of HMRSVP[3,4]. MC-HMRSVP always establishes a virtual cluster called Mobile Cluster, which includes its immediately adjacent MA(Mobile Agent) for passive reservation as well as the current MA for active reservation to which MH(Mobile Host) belongs. Our scheme also establishes the MC regardless of intra/inter region movement by GMA(Gateway Mobile Agent) function when a MH moves. To provide a general formulation on analyzing the performance in terms of reservation cost, we also model the resource reservation cost by using a simple recursive equation. Then, we show that our scheme decreases the reservation cost in comparison with the existing HMRSVP extentions.