• 한국정보과학회논문지:정보통신
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• 제29권1호
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• pp.24-30
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• 2002

레이블 스위칭 기술은 격증하는 인터넷 서비스의 요구 대역폭을 만족시키기 위해 개발된 기술이다. 이중 multiprotocol label switching(MPLS)은 기존의 레이블 스위칭 기술을 통합하고 여러 장비제조 업체들간의 호환성을 보장하기 위해 IETF(Internet engineering task force)를 중심으로 표준화가 진행중이다. MPLS에서 레이블은 패킷의 스위칭에 사용되는 기본적인 단위이므로 이러한 레이블 공간이 각 레이블 스위칭 라우터를 어떻게 관리되고 효율적으로 사용되는가에 따라 MPLS망의 성능에 큰 영향을 미친다. 본 논문에서는 이러한 레이블 공간을 효율적으로 사용하기 위해 다중 도메인에서 레이블 스위칭 라우터의 연결 해제 타이머의 복수 사용을 제안한다. 이 방법은 패킷 분류기를 통해 트래픽의 특성에 따라 등급이 높은 트래픽에 대해서는 상대적으로 긴 연결 해제 타이머를 할당하여 새로운 연결에 걸리는 지연시간을 줄이고 3계층으로 라우팅 되는 패킷의 양을 줄이는 것이다. 제안된 방법을 실제 인터넷 망에서 수집된 트래픽 자료를 이용하여 시뮬레이션을 수행하였고 그 결과 MPLS망의 동작에 필요한 레이블 공간이 기존의 방법보다 감소하였음을 확인하였다.

• Industrial Engineering and Management Systems
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• 제8권3호
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• pp.181-193
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• 2009

This paper presents a framework for controlling mobile multiple robots connected by communication networks. This framework provides novel methods to control coordinated systems using mobile agents. The combination of the mobile agent and mobile multiple robots opens a new horizon of efficient use of mobile robot resources. Instead of physical movement of multiple robots, mobile software agents can migrate from one robot to another so that they can minimize energy consumption in aggregation. The imaginary application is making "carts," such as found in large airports, intelligent. Travelers pick up carts at designated points but leave them arbitrary places. It is a considerable task to re-collect them. It is, therefore, desirable that intelligent carts (intelligent robots) draw themselves together automatically. Simple implementation may be making each cart has a designated assembly point, and when they are free, automatically return to those points. It is easy to implement, but some carts have to travel very long way back to their own assembly point, even though it is located close to some other assembly points. It consumes too much unnecessary energy so that the carts have to have expensive batteries. In order to ameliorate the situation, we employ mobile software agents to locate robots scattered in a field, e.g. an airport, and make them autonomously determine their moving behaviors by using a clustering algorithm based on the Ant Colony Optimization (ACO). ACO is the swarm intelligence-based methods, and a multi-agent system that exploit artificial stigmergy for the solution of combinatorial optimization problems. Preliminary experiments have provided a favorable result. In this paper, we focus on the implementation of the controlling mechanism of the multi-robots using the mobile agents.

• 한국지능시스템학회논문지
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• 제21권1호
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• pp.120-127
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• 2011

체크포인트 기법은 실시간 시스템의 내고장성을 구현하는 대표적인 방법이다. 본 논문에서는 확률 최적화를 이용하여 체크 포인트 구간을 결정하는 기법을 제시한다. 본 논문에서 다루는 실시간 시스템은 멀티 태스크(multi-task)들로 구성되며 Poisson 분포를 가지는 과도 고장이 발생한다. 또 멀티 태스크들은 비선점형 Rate Monotonic 알고리듬으로 스케줄링된다. 이번 연구에서는 멀티 태스크들의 수행 성공 확률을 체크포인트 삽입 개수로 표현하는 최적화 문제를 설정하고 이 확률값을 최대로 만드는 체크포인트 개수와 구간 길이를 구한다. 제안된 확률 계산 과정은 체크포인트 재수행 횟수에 대한 비선점형 RM 알고리듬의 스케줄링 가능성을 판별하는 방법도 포함한다. 사례 연구를 통해서 제안된 기법의 적용가능성을 입증한다.

• Smart Structures and Systems
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• 제29권1호
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• pp.181-193
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• 2022

Data-driven structural health monitoring (SHM) of civil infrastructure can be used to continuously assess the state of a structure, allowing preemptive safety measures to be carried out. Long-term monitoring of large-scale civil infrastructure often involves data-collection using a network of numerous sensors of various types. Malfunctioning sensors in the network are common, which can disrupt the condition assessment and even lead to false-negative indications of damage. The overwhelming size of the data collected renders manual approaches to ensure data quality intractable. The task of detecting and classifying an anomaly in the raw data is non-trivial. We propose an approach to automate this task, improving upon the previously developed technique of image-based pre-processing on one-dimensional (1D) data by enriching the features of the neural network input data with multiple channels. In particular, feature engineering is employed to convert the measured time histories into a 3-channel image comprised of (i) the time history, (ii) the spectrogram, and (iii) the probability density function representation of the signal. To demonstrate this approach, a CNN model is designed and trained on a dataset consisting of acceleration records of sensors installed on a long-span bridge, with the goal of fault detection and classification. The effect of imbalance in anomaly patterns observed is studied to better account for unseen test cases. The proposed framework achieves high overall accuracy and recall even when tested on an unseen dataset that is much larger than the samples used for training, offering a viable solution for implementation on full-scale structures where limited labeled-training data is available.

• 한국컴퓨터그래픽스학회논문지
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• 제29권4호
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• pp.7-16
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• 2023

캐릭터 애니메이션 분야에서 목표 지향적 이동을 위해 원하는 궤적을 재현하는 것은 항상 어려운 과제이다. 생성 모델을 사용하는 데이터 기반 방법은 명시적인 조건 없이 긴 동작 시퀀스를 예측하는 효율적인 방법 중 하나이다. 이러한 방법은 고품질의 결과물을 생성해내지만, 멀리 있는 목표물을 무작위로 타격하는 것처럼 더 어려운 상황의 모션을 합성(synthesis)에 있어서는 제한될 수 있다. 하지만 이는 모션 데이터 클립을 모방하는 GAN Discriminator 를 사용하고 강화학습을 통해 해결할 수 있다. 본 연구는 캐릭터들이 GAN 기반 접근법과 리워드 설계를 통해 복싱을 구현하는 것을 목표로 한다. 논문에서 사용된 두 가지의 최신 연구인 Adversarial Motion Prior 와 Adversarial Skill Embedding 에 대해 비교실험하며, 또한 복싱을 경쟁 스포츠에 적용하기 위하여 멀티 에이전트 강화 학습을 위한 대규모 self-play 프레임워크인 TimeChamber 를 활용한다.

• 한국멀티미디어학회논문지
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• 제18권9호
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• pp.1098-1104
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• 2015

With the widespread use of smartphones and IoT (Internet of Things), data are being generated on a large scale, and there is increased for the analysis of such data. Hence, distributed processing systems have gained much attention. Hadoop, which is a distributed processing system, saves the metadata of stored files in name nodes; in this case, the main problems are as follows: the memory becomes insufficient; load occurs because of massive small files; scheduling and file processing time increases because of the increased number of small files. In this paper, we propose a solution to address the increase in processing time because of massive small files, and thus improve the processing performance, using the Reuse JVM method provided by Hadoop. Through environment setting, the Reuse JVM method modifies the JVM produced conventionally for every task, so that multiple tasks are reused sequentially in one JVM. As a final outcome, the Reuse JVM method showed the best processing performance when used together with CombineFileInputFormat.

• 한국정보과학회논문지:시스템및이론
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• 제31권9호
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• pp.495-502
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• 2004

최근 인터넷 사용자와 대용량 콘텐츠의 급증으로 서버와 네트워크의 부하가 가중되고 서비스의 질이 떨어지는 문제가 발생하였다. 이러한 문제의 해결로 콘텐츠를 다수의 지역 서버에 복제하여 서비스하고자 하는 기술들이 대두되고 있고, 이런 환경에서는 클라이언트의 요청에 대해 서비스할 적절한 서버를 선택하는 것이 매우 중요한 문제이다. 그러므로 본 연구에서는 클라이언트의 요청 시점에서 인터넷 토폴로지 상 가깝고 부하가 적은 서버가 서비스할 수 있도록 하는 서버 선택 메커니즘을 설계하여 제안한다. 본 연구는 계속적으로 증가하는 대용량, 실시간 멀티미디어 콘텐츠의 빠르고 안정적인 서비스를 가능하게 할 것이며 이로 인해 디지털 콘텐츠 서비스의 새로운 비즈니스 모델 창출에 크게 기여할 수 있을 것이다.

• 제어로봇시스템학회논문지
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• 제20권8호
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• pp.875-881
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• 2014

The redundancy resolution of the seven DOF (Degree of Freedom) upper limb exoskeleton is key to the synchronous motion between a robot and a human user. According to the seven DOF human arm model, positioning and orientating the wrist can be completed by multiple arm configurations that results in the non-unique solution to the inverse kinematics. This paper presents analysis on the kinematic and dynamic aspect of the human arm movement and its effect on the redundancy resolution of the seven DOF human arm model. The redundancy of the arm is expressed mathematically by defining the swivel angle. The final form of swivel angle can be represented as a linear combination of two different swivel angles achieved by optimizing two cost functions based on kinematic and dynamic criteria. The kinematic criterion is to maximize the projection of the longest principal axis of the manipulability ellipsoid of the human arm on the vector connecting the wrist and the virtual target on the head region. The dynamic criterion is to minimize the mechanical work done in the joint space for each of two consecutive points along the task space trajectory. The contribution of each criterion on the redundancy was verified by the post processing of experimental data collected with a motion capture system. Results indicate that the bimodal redundancy resolution approach improved the accuracy of the predicted swivel angle. Statistical testing of the dynamic constraint contribution shows that under moderate speeds and no load, the dynamic component of the human arm is not dominant, and it is enough to resolve the redundancy without dynamic constraint for the realtime application.

• International Journal of Computer Science & Network Security
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• 제22권12호
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• pp.37-50
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• 2022

Modern supply chains include multiple activities from collecting raw materials to transferring final products. These activities involve many parties who share a huge amount of valuable data, which makes managing supply chain systems a challenging task. Current supply chain management (SCM) systems adopt digital technologies such as the Internet of Things (IoT) and blockchain for optimization purposes. Although these technologies can significantly enhance SCM systems, they have their own limitations that directly affect SCM systems. Security, performance, and scalability are essential components of SCM systems. Yet, confidentiality and scalability are one of blockchain's main limitations. Moreover, IoT devices are lightweight and have limited power and storage. These limitations should be considered when developing blockchain-based IoT-SCM systems. In this paper, the requirements of efficient supply chain systems are analyzed and the role of both IoT and blockchain technologies in providing each requirement are discussed. The limitations of blockchain and the challenges of IoT integration are investigated. The limitations of current literature in the same field are identified, and a secure and scalable blockchain-based IoT-SCM system is proposed. The proposed solution employs a Hyperledger fabric blockchain platform and tackles confidentiality by implementing private data collection to achieve confidentiality without decreasing performance. Moreover, the proposed framework integrates IoT data to stream live data without consuming its limited resources and implements a dualstorge model to support supply chain scalability. The proposed framework is evaluated in terms of security, throughput, and latency. The results demonstrate that the proposed framework maintains confidentiality, integrity, and availability of on-chain and off-chain supply chain data. It achieved better performance through 31.2% and 18% increases in read operation throughput and write operation throughput, respectively. Furthermore, it decreased the write operation latency by 83.3%.

• 한국농공학회지
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• 제29권3호
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• pp.125-137
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• 1987

The purpose of this paper is to examine some difficulties in water management of agricultural reservoirs in Korea, for there are approximately more than 15,000 reservoirs which are now being utilized for the purpose of irrigation, along with the much amount of expenses and labors to be invested against droughts and floods periodically occurred. Recently, the effective use of water resources in the agricultural reservoirs with a single purpose, is becomming multiple according to the alterable environment of water use. Therefore, the task to allocate agricultural water rationally and economically must be solved for the multiple use of agricultural reservoirs. On the basis of the above statement, this study aims at suggesting the rational method of water management by introducing an optimal technique to allocate the water in an existing agricultural reservoir rationally, for the sake of maximizing the economic effect. To achieve this objective, a reservoir, called "0-Bongje" as a sample of the case study, is selected for an agricultural water development proiect of medium scale. As a model for the optimum allocation of water in the multi-purpose use of reservoirs a linear programming model is developed and analyzed. As a result, findings of the study are as follows : First, a linear programing model is developed for the optimum allocation of water in the multi-purpose use of agricultural reservoirs. By adopting the model in the case of reservoir called "O-Bongje," the optimum solution for such various objects as irrigation area, the amount of domestic water supply, the size of power generation, and the size of reservoir storage, etc., can be obtained. Second, by comparing the net benefits in each object under the changing condition of inflow into the reservoir, the factors which can most affect the yearly total net benefit can be drawn, and they are in the order of the amount of domestic water supply, irrigation area, and power generation. Third, the sensitivity analysis for the decision variable of irrigation which may have a first priority among the objects indicate that the effective method of water management can be rapidly suggested in accordance with a condition under the decreasing area of irrigation. Fourth, in the case of decision making on the water allocation policy in an existing multi-purpose reservoir, the rapid comparison of numerous alternatives can be possible by adopting the linear programming model. Besides, as the resources can be analyed in connection with various activities, it can be concluded that the linear programing model developed in this study is more quantitative than the traditional methods of analysis. Fifth, all the possible constraint equations, in using a linear programming model for adopting a water allocation problem in the agricultural reservoirs, are presented, and the method of analysis is also suggested in this study. Finally, as the linear programming model in this study is found comprehensive, the model can be adopted in any different kind of conditions of agricultural reservoirs for the purpose of analyzing optimum water allocation, if the economic and technical coefficients are known, and the decision variable is changed in accordance with the changing condition of irrigation area.