• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.11
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• pp.47-55
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• 2004

In this paper, an enhanced time-based registration method is proposed. The method reduces the registration cost when a mobile terminal stays in a cell for a long time. We also analyze the performance of the proposed method numerically. In the analysis, we assume Poisson call arrival distribution and exponential cell resident time. From the analysis we calculate the optimal time-interval. Additionally, limit cost analysis is made to investigate the behaviors in the limit conditions. To compare the performance of the proposed method with the original time-based registration method, we analyze the performance of the original time-based registration method. In the comparisons, we see that the proposed enhanced time-based registration method has better performance and is applicable to the PCS systems.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.12
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• pp.948-952
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• 2009

Recently, a new distributed grid scheme, called DS-GRID(distributed S-GRID), has been proposed to manage the location information of moving objects in a spatial network[1]. However, because DS-GRID uses uniform grid cells, it cannot handle skewed data which frequently occur in the real application. To solve this problem, we propose a dynamic distributed grid scheme which splits a grid cell dynamically based on the density of moving objects. In addition, we propose a k-nearest neighbor processing algorithm for the proposed scheme. Finally, it is shown from the performance analysis that our scheme achieves better retrieval and update performance than the DS-GRID when the moving objects are skewed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1266-1272
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• 2004

Location-Based Services(LBS) give rise to location-dependent queries of which results depend on the positions of moving objects. Because positions of moving objects change continuously, indexes of moving object must perform update operations frequently for keeping the changed position information. Existing spatial index (Grid File, R-Tree, KDB-tree etc.) proposed as index structure to search static data effectively. There are not suitable for index technique of moving object database that position data is changed continuously. In this paper, I propose a dynamic hashing index that insertion/delete costs are low. The dynamic hashing structure is that apply dynamic hashing techniques to combine a hash and a tree to a spatial index. The results of my extensive experiments show the dynamic hashing index outperforms the $R^$ $R^*$-tree and the fixed grid.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.10
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• pp.5112-5128
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• 2016

Tracking human body is an important problem in computer vision field. Tracking failures caused by occlusion can lead to wrong rectification of the target position. In this paper, a robust human tracking algorithm is proposed to address the problem of occlusion, rotation and improve the tracking accuracy. It is based on Tracking-Learning-Detection framework. The key auxiliary information is used in the framework which motivated by the fact that a tracking target is usually embedded in the context that provides useful information. First, face localization method is utilized to find key face location information. Second, the relative position relationship is established between the auxiliary information and the target location. With the relevant model, the key face information will get the current target position when a target has disappeared. Thus, the target can be stably tracked even when it is partially or fully occluded. Experiments are conducted in various challenging videos. In conjunction with online update, the results demonstrate that the proposed method outperforms the traditional TLD algorithm, and it has a relatively better tracking performance than other state-of-the-art methods.

• Journal of KIISE:Information Networking
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• v.32 no.5
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• pp.615-624
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• 2005

In Mobile IP, several types of messages - binding update, binding request and binding acknowledgement - are used to support user mobility. It is necessary to exchange those messages frequently for seamless mobility but it incurs both the increase of network overhead and poor usage of mobile node battery power Thus, we need a mechanism that the server detects users location and also copes with the problems effectively, which is our main concern in this paper Each user records all moving logs locally and periodically makes out profile based on them in HMIPv6. By using profile, estimated resident time can be computed whenever he enters an area and the time is set up as the binding update message lifetime. Of course, the more correct lifetime nay be obtained IP arrival time as well as average resident time Is considered in profile. Through extensive experiments, we measure the bandwidth usage for binding update messages by comparing the proposed schemes with that in HMIPv6. From the results, Gain gets over $80\%$ when mobile node stays more than 13 minutes in a subnet. Namely, we come to know that our schemes improve network usage and energy usage in mobile node by decreasing the number of messages while they also manage users locations like that in HMIPv6.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.136-138
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• 2002

본 논문에서는 이동 통신 시스템에서 사용자의 이동성 패턴과 움직임 정보를 이용한 새로운 위치 갱신 기법을 소개한다. 현재 상용화된 대다수의 셀룰러 시스템은 지리적 영역을 위치갱신 영역으로 나누고, 사용자는 이전 위치 영역에서 새로운 위치 영역으로 이동할 때마다 위치갱신 연산을 수행한다. 이제까지 제안된 기존 기법들은 개별 사용자의 이동성과 호도착률, 더욱이 각 위치 영역에서의 사용자의 움직임 패턴을 고려하는데 미흡하였다. 특히, 사용자가 낮은 CMR을 갖거나 특정 위치 영역으로 이동할 경우가 많아지면 쓸모 없는 위치 갱신 횟수의 증가로 인하여 과도한 네트워크 트래픽이 야기된다. 이러한 상황에서 위치 갱신의 비용을 줄이기 위해서는 사용자들의 움직임 정보를 적절히 반영하여 각 위치 영역에서 위치 갱신의 수행 여부를 결정하는 효율적인 기법이 요구된다. 본 논문에서는 위치영역 내에 상주하는 이동단말들의 움직임 정보와 개별 사용자의 이등 패턴 정보를 효율적으로 이용하여 위치 갱신의 횟수를 줄일 수 있는 새로운 위치 갱신 기법을 제안한다. 수학적 모델링을 통한 제안 기업의 성능은 CMR이 낮고 사용자가 특정 위치 영역으로 이동할 확률이 높은 경우, 기존의 IS-41과 TLA 기법보다 낮은 위치관리 비용을 보여준다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.374-375
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• 2011

This paper presents a method to determine parameters of BTB (back-to-back) converters in terms of the enhancement of interface flow margins. Interface flow margin is by definition a measure of how much active power can be transferred from the external areas to the study area with the fixed load demand, and it is mainly constrained by system voltage stability. BTB converters are controllable equipments with the active power flow through them, and its DC link in fact can divide the AC systems at the location and hence can reduce the fault current level. This paper first cals margin sensitivities at the nose point of F-V curves and formulates an optimization problem to update the BTB parameters to improve the margins. This procedure is repeated performed until the required margin enhancement is achieved.

• Structural Engineering and Mechanics
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• v.62 no.3
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• pp.297-302
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• 2017

Structural reanalysis is frequently utilized to reduce the computational cost so that the process of design or optimization can be accelerated. The supports can be regarded as the design variables and may be modified in various types of structural optimization problems. The location, number, and type of supports can make a great impact on the performance of the structure. This paper presents a unified method for structural static reanalysis with imposition or relaxation of some support constraints. The information from the initial analysis has been fully utilized and the computational time can be significantly reduced. Numerical examples are used to validate the effectiveness of the proposed method.

• Proceedings of the KSRS Conference
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• v.2
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• pp.836-839
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• 2006

Telematics, one of the so-called New Growth Engine of IT839, is a leading IT service where wireless internet service represented by information and mobility is extended to the area of transportation. To provide telematics service, Telematics service provider have to connect with various Contents Provider or Service Provide server - for example - LBSS(Location Based Service Server), ASPS(Application Service Provider Server), TELICS(TELematics Information Center Server), GMS(Geo-mobility Server), WTPS(World Telematics Protocol Server) and MAUS(Map Air Update Server). Presently, It is nearly impossible or very difficult for the company that are manufacturing and testing telematics device to develop and test telematics solution without connecting Telematics Service Provider, Service Provider, Contents Provider. And, it is very difficult to connect in TSP, CP, SP having the product to be developed. In this paper, we proposed virtual telematics service provider. The proposed Virtual Telematics Service Provider is to provide telematics services and functionalities by integrating telematics servers into TSP gateway virtually. In other words, VTSP is performs with the role of TSP, CP, SP. And the VTSP support integration of telematics servers, interfacing and monitoring between terminal and the integrated servers.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.6
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• pp.829-836
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• 2001

A dependable boundary reconstruction technique is proposed. The finite element method is used for the analysis of the direct heat conduction problem to realize the deformable grid system. An appropriate strategy for grid update is suggested. A complete sensitivity analysis is performed to obtain the derivatives required for restoration of the optimal boundary. With the result of the sensitivity analysis, the unknown boundary is sought using the sequential quadratic programming. The method is applied to reconstruction of boundaries with sinusoidal, step, and cavity form. The overall performance of the proposed method is examined by comparison between the estimated the exact boundaries.