• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.527-531
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• 2003

Previous researches on scalability problem of distributed virtual environment (DVE) have been mainly focused on spatial partitioning of area of interest (AOI). Congestion phenomena by avatar groups in AOI have been neglected relatively. However, AOI congestion is highly related to scalability of DVT because it exhausts system resources such as network bandwidth and rendering time, and could be a bar to perform collaboration among participants. In this paper, this will be defined as the problem that must be solved for the realization of the scalable DVE, and a model will be proposed to measure and control congestion situation in AOI. The purposes of the proposed model are to prevent high density of participants in AOI, and to protect stable collaboration in DVE. For evaluation of the performance it is compared with a previous method by defining the resource cost model which is dynamically activated to AOI congestion.

• Journal of the Korea Computer Industry Society
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• v.7 no.1
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• pp.39-46
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• 2006

Multipath diversity reception is applied to the compensation of the distortion of channel, which occurs in transmission of data at rapid speed. DS/BPSK systems are composed of the equipment with reception structure combined with a compensation algorithm to diversity branch. The efficiency of the system is evaluated from the point of view of average bit error rate according to SNR. In order to remove intersymbol interference, this algorithm is applied to time-invariant channel at every diversity branch with the number of L. As a result, the average bit error rate is saturated by $10^{-2}$ at the conventional compensation algorithm.

• The KIPS Transactions:PartA
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• v.10A no.2
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• pp.111-122
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• 2003

Military wargame simulation models must support the HLA in order to facilitate interoperability with other simulations, and using parallel simulation engines offer efficiency in reducing system overhead generated by propelling interoperability. However, legacy military simulation model engines process events using sequential event-driven method. This is due to problems generated by parallel processing such as synchronous reference to global data domains. Additionally. using legacy simulation platforms result in insufficient utilization of multiple CPUs even if a multiple CPU system is under use. Therefore, in this paper, we propose conversing the simulation engine to an object model-based parallel simulation engine to ensure military wargame model's improved system processing capability, synchronous reference to global data domains, external simulation time processing, and the sequence of parallel-processed events during a crash recovery. The converted parallel simulation engine is designed and implemented to enable parallel execution on a multiple CPU system (SMP).

• Korean Journal of Remote Sensing
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• v.35 no.6_3
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• pp.1209-1219
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• 2019

For consistent vegetation monitoring, it is necessary to generate time-series vegetation index datasets at fine temporal and spatial scales by fusing the complementary characteristics between temporal and spatial scales of multiple satellite data. In this study, we quantitatively and qualitatively analyzed the prediction accuracy of time-series change information extracted from spatio-temporal fusion models of multiple satellite data for vegetation monitoring. As for the spatio-temporal fusion models, we applied two models that have been widely employed to vegetation monitoring, including a Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM) and an Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model (ESTARFM). To quantitatively evaluate the prediction accuracy, we first generated simulated data sets from MODIS data with fine temporal scales and then used them as inputs for the spatio-temporal fusion models. We observed from the comparative experiment that ESTARFM showed better prediction performance than STARFM, but the prediction performance for the two models became degraded as the difference between the prediction date and the simultaneous acquisition date of the input data increased. This result indicates that multiple data acquired close to the prediction date should be used to improve the prediction accuracy. When considering the limited availability of optical images, it is necessary to develop an advanced spatio-temporal model that can reflect the suggestions of this study for vegetation monitoring.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10b
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• pp.472-474
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• 2003

인터넷(internet)에서 웹 브라우징(web browsing)을 통한 정보검색은 일반적인 주제에 대한 텍스트 또는 이미지 정보를 획득하는데 유용하지만, 각 사용자가 자신이 해소하고자 하는 특정의 궁금한 사항과 관련하여 자신의 구체적 특수성에 적합한 정보를 획득하기는 어려운 경우가 많다. 이와 같은 개인적 궁금증을 해소시켜 줄 수 있는 방안으로 많은 인터넷 이용자들이 웹사이트에서 제공하는 게시판을 이용하지만, 각 사이트마다 특화된 주제만을 다루고 있기 때문에 다른 주제에 대한 애로를 가진 사용자는 적절한 게시판을 운영하는 웹사이트를 탐색해야만 하는 어려움이 있다. 본 연구는 웹사이트에서 서비스하는 게시판간 상호 연계를 통해 애로문의의 종합처리가 가능하도록 중앙 호스트 사이트에 질문을 집중시키고 또한 이렇게 집중된 질문을 다시 처리가 가능한 사이트로 집중된 질문을 배분하여 보다 정확하고 신속하게 처리할 수 있도록 하는 모델을 제시한다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04b
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• pp.574-576
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• 2004

일반적으로 노동시장은 노동자와 고용주들로 구성되며, 이들은 복잡한 상호작용을 통해 노사관계를 형성한다 본 논문에서는 진화 에이전트들로 구성된 노동시장 모델 상에서 노동자들 또는 고용주들 사이에서 형성될 수 있는 전략적 연합을 적용하여 노동자와 고용주의 수적인 비율로 표현할 수 있는 직업밀집도와 직업집중도에 따른 행동 특성을 분석한다. 전략적 연합은 다중에이전트 환경에서 상호간의 이득을 보장하는 효과적인 방법이 될 수 있다. 진화 노동시장에서 노동자와 고용주들은 집단 내에서 자율적으로 연합을 형성하며 죄수의 딜레마게임으로 진행되는 거래에 참여한다. 실험결과, 에이전트들의 행동이 직업밀집도와 직업집중도에 따라 다르게 나타나며, 특히 전략적 연합이 허용될 경우 노동자와 고용주들이 보다 공격적인 형태로 노사거래에 참여함을 보여준다.

• Journal of KIISE:Computing Practices and Letters
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• v.8 no.2
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• pp.174-182
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• 2002

The object-oriented design methods and their CASE tools are widely used in practice by many real-time software developers. However, object-oriented CASE tools require an additional step of identifying tasks from a given design model. Unfortunately, it is difficult to automate this step for a couple of reasons: (1) there are inherent discrepancies between objects and tasks; and (2) it is hard to derive tasks while maximizing real-time schedulability since this problem makes a non-trivial optimization problem. As a result, in practical object-oriented CASE tools, task identification is usually performed in an ad-hoc manner using hints provided by human designers. In this paper, we present a systematic, schedulability-aware approach that can help mapping real-time object-oriented models to multi-threaded implementations. In our approach, a task contains a group of mutually exclusive transactions that may possess different periods and deadline. For this new task model, we provide a new schedulability analysis algorithm. We also show how the run-time system is implemented and how executable code is generated in our frame work. We have performed a case study. It shows the difficulty of task derivation problem and the utility of the automated synthesis of implementations as well as the Inappropriateness of the single-threaded implementations.

• Journal of KIISE:Software and Applications
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• v.36 no.3
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• pp.217-225
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• 2009

In case of sketching a conceptual model in 3D space, it's not easy for designer to recognize the depth cue accurately and to draw a model correctly in short time. In this paper, multi-strokes based sketch is adopted not only to reduce the error of input point but to substantiate the shape o) the conceptual design effectively. The designer can see the drawing result immediately after stroking some curves. The shape can also be modified by stroking curves repeatedly and be confirmed the modified shape in real time. However, the multi-strokes based sketch needs to manage the great amount of input data. Therefore, the drawing space is divided into the limited spatial cubical grids and the movable infernal vertex in each spatial grid is implemented and used to define the surface by the multi-strokes. We implemented the spatial sketching system which allows the concept designer's intention to 3D model data efficiently.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.2
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• pp.306-321
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• 1994

Since TDM protocol can be easily implemented and show high throughput at heavy load, the researches on the multi-channel high-speed network based on TDM access control have been getting more attention than ever. TDM type multi-channel network, however, has disadvantages of excessive delay at light load and inadaptibility to traffic skewing. In this paper, we proposed a new multi-channel TDM structure, time slots are allocated proportional to the traffic flow pattern among the nodes. thus delay and throughput performance are improved. Design principles of TDM frame are discussed considering traffic locality and the number of available channels. Approximate analytic models for delay evaluation are developed and verified by simulations.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.1
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• pp.136-142
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• 2007

This paper proposes a new approach on nonlinear maneuvering target tracking. In this paper, proposed algorithm is the Kalman filter based on the adaptive interactive multiple model using the concept of predicted impact point and utilize modified Kalman filter regarding the error between measurement position and predicted impact point. The unknown target acceleration is regarded as an additional process noise to the target model, and each sub-model is characterized in accordance with the valiance of the overall process noise which is obtained on the basis of each acceleration interval. To compensate the decreasing performance of Kalman filter in nonlinear maneuver, we construct optional algorithm to utilize proposed method or Kalman filter selectively. To effectively estimate the acceleration during the target maneuvering, the rapid increase of the noise scale is recognized as the acceleration to be used in maneuvering target's movement equation. And a few examples are presented to show suggested algorithm's executional potential.