• International Journal of Control, Automation, and Systems
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• 제1권3호
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• pp.358-367
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• 2003

We consider discrete-time factorial Markov Decision Processes (MDPs) in multiple decision-makers environment for infinite horizon average reward criterion with a general joint reward structure but a factorial joint state transition structure. We introduce the "localization" concept that a global MDP is localized for each agent such that each agent needs to consider a local MDP defined only with its own state and action spaces. Based on that, we present a gradient-ascent like iterative distributed algorithm that converges to a local optimal solution of the global MDP. The solution is an autonomous joint policy in that each agent's decision is based on only its local state.cal state.

• Nuclear Engineering and Technology
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• 제38권7호
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• pp.619-638
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• 2006

Low temperature irradiation can significantly harden metallic materials and often lead to strain localization and ductility loss in deformation. This paper provides a review on the radiation effects on the deformation of metallic materials, focusing on microscopic and macroscopic strain localization phenomena. The types of microscopic strain localization often observed in irradiated materials are dislocation channeling and deformation twinning, in which dislocation glides are evenly distributed and well confined in the narrow bands, usually a fraction of a micron wide. Dislocation channeling is a common strain localization mechanism observed virtually in all irradiated metallic materials with ductility, while deformation twinning is an alternative localization mechanism occurring only in low stacking fault energy(SFE) materials. In some high stacking fault energy materials where cross slip is easy, curved and widening channels can be formed depending on dose and stress state. Irradiation also prompts macroscopic strain localization (or plastic instability). It is shown that the plastic instability stress and true fracture stress are nearly independent of irradiation dose if there is no radiation-induced phase change or embrittlement. A newly proposed plastic Instability criterion is that the metals after irradiation show necking at yield when the yield stress exceeds the dose-independent plastic instability stress. There is no evident relationship between the microscopic and macroscopic strain localizations; which is explained by the long-range back-stress hardening. It is proposed that the microscopic strain localization is a generalized phenomenon occurring at high stress.

• Journal of information and communication convergence engineering
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• 제9권2호
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• pp.155-160
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• 2011

In distributed source localization where sensors transmit measurements to a fusion node, we address the sensor selection problem where the goal is to find the best set of sensors that maximizes localization accuracy when quantization of sensor measurements is taken into account. Since sensor selection depends heavily upon rate assigned to each sensor, joint optimization of rate allocation and sensor selection is required to achieve the best solution. We show that this task could be accomplished by solving the problem of allocating rates to each sensor so as to minimize the error in estimating the position of a source. Then we solve this rate allocation problem by using the generalized BFOS algorithm. Our experiments demonstrate that the best set of sensors obtained from the proposed sensor selection algorithm leads to significant improvements in localization performance with respect to the set of sensors determined from a sensor selection process based on unquantized measurements.

• 제어로봇시스템학회논문지
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• 제14권2호
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• pp.156-160
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• 2008

A localization system to estimate the position as well as movement direction of mobile robots is proposed in this paper. This system implements a camera fixed on a robot and color patches evenly distributed and mounted on the planar ceiling. Different permutations of patch colors code information about robot localization. Thus, extraction of color information from patch images leads to estimation of robot position. Additionally, simple geometric indicators are combined with patch colors to estimate robot's movement direction. Since only the distribution of patch colors has to be known, the analysis of patch images to is relatively fast and simple. The proposed robot localization system has been successfully tested for navigation of sample mobile robot. Obtained test results indicate the robustness and reliability of proposed technique for robot navigation.

• 한국통신학회논문지
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• 제41권11호
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• pp.1490-1501
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• 2016

본 논문에서는 인메모리(In-memory) 병렬 분산 처리 시스템 Apache Spark(이하 Spark)를 활용하여 사용자에게 실시간 측위 정보를 제공할 수 있는 영상 기반 실내 위치인식 시스템을 제안한다. 제안하는 시스템에서는 사용자에게 실시간 측위 정보를 제공하기 위해서, Spark를 이용한 영상 특징점 추출 알고리즘의 병렬 분산화를 통해 알고리즘 연산 시간을 단축시킨다. 하지만 기존의 Spark 플랫폼에서는 영상 처리를 위한 인터페이스가 존재하지 않아, 영상 처리와 관련된 연산을 수행하는 것이 불가능하였다. 이에 본 논문에서는 Spark 영상 입출력 인터페이스를 구현하여 측위 연산을 위한 영상 처리를 Spark에서 수행 가능하게 하였다. 또한 무손실 압축(lossless compression)기법을 이용하여 특징점 기술자(descriptor)를 압축된 형태로 데이터베이스에 저장하여, 대용량의 실내 지도 데이터를 효율적으로 저장 및 관리하는 방법을 소개한다. 측위 실험은 실제 실내 환경에서 수행하였으며, 싱글 코어(Single-core) 시스템과의 성능 비교를 통해 제안하는 시스템이 최대 약 3.6배 단축된 시간으로 사용자에게 측위 정보를 제공 할 수 있다는 것을 입증하였다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제4권2호
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• pp.165-171
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• 2004

Robots will be able to coexist with humans and support humans effectively in near future. One of the most important aspects in the development of human-friendly robots is to cooperation between humans and robots. In this paper, we proposed a method for multi-object identification in order to achieve such human-centered system and robot localization in intelligent space. The intelligent space is the space where many intelligent devices, such as computers and sensors, are distributed. The Intelligent Space achieves the human centered services by accelerating the physical and psychological interaction between humans and intelligent devices. As an intelligent device of the Intelligent Space, a color CCD camera module, which includes processing and networking part, has been chosen. The Intelligent Space requires functions of identifying and tracking the multiple objects to realize appropriate services to users under the multi-camera environments. In order to achieve seamless tracking and location estimation many camera modules are distributed. They causes some errors about object identification among different camera modules. This paper describes appearance based object representation for the distributed vision system in Intelligent Space to achieve consistent labeling of all objects. Then, we discuss how to learn the object color appearance model and how to achieve the multi-object tracking under occlusions.

• 한국통신학회논문지
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• 제34권1A호
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• pp.65-75
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• 2009

무선 센서 네트워크(WSN: Wireless Sensor Network) 환경에서 사건의 탐지(event detection)와 라우팅(routing), 정보추적(information tracking) 등의 중요한 기능을 수행하기 위해 센서노드의 위치를 측정하는 문제는 반드시 해결되어야 한다. DV-Hop 알고리즘은 멀티 홉에서 얻어지는 정보를 기반으로 위치를 측정하며 비교적 적은 앵커로도 구현이 가능하지만 보다 정밀한 위치측정을 위해 개선되어야 할 부분이 존재한다. 그러한 요인 중 하나로 알고리즘에 사용되는 홉 간 거리가 여러 앵커 노드로 부터의 홉 간 거리의 평균값으로 계산되는 것을 들 수 있다. 이는 홀(Hole)과 같은 장애물에 의한 홉 수의 증가로 발생할 수 있는 미지노드와 앵커사이에 거리 값 계산의 오차를 발생시킨다. 본 논문에서는 DV-Hop 알고리즘의 이러한 문제점을 분석하고 이를 보완 가능한 그룹기반DV-Hop(GDV-Hop) 알고리즘을 제시한다. 그룹 기반 DV-Hop 알고리즘은 다양한 비컨의 라우팅 경로에 의한 위치오차를 효과적으로 줄일 수 있을 뿐 아니라 불필요한 비컨전송의 오버 헤드를 줄일 수 있는 장점을 갖는다.

• Molecules and Cells
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• 제20권1호
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• pp.119-126
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• 2005

${\alpha}$-Expansins are bound to the cell wall of plants and can be solubilized with an extraction buffer containing 1 M NaCl. Localization of ${\alpha}$-expansins in the cell wall was confirmed by immunogold labeling and electron microscopy. The subcellular localization of vegetative ${\beta}$-expansins has not yet been studied. Using antibodies specific for OsEXPB3, a vegetative ${\beta}$-expansin of rice (Oryza sativa L.), we found that OsEXPB3 is tightly bound to the cell wall and, unlike ${\alpha}$-expansins, cannot be solubilized with extraction buffer containing 1 M NaCl. OsEXPB3 protein could only be extracted with buffer containing SDS. The subcellular localization of the OsEXPB3 protein was confirmed by immunogold labeling and electron microscopy. Gold particles were mainly distributed over the primary cell walls. Immunohistochemistry showed that OsEXPB3 is present in all regions of the coleoptile and root tissues tested.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.840-845
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• 2005

This paper presents a robust optimal design method for a periodic structure type of MEMS resonator that is vulnerable to mode localization. The robust configuration of such a MEMS resonator to fabrication error is implemented by changing the regularity of periodic structure. For the mathematical convenience, the MEMS resonator is first modeled as a multi pendulum system. The index representing the measure of mode variation is then introduced using the perturbation method and the concept of modal assurance criterion. Finally, the optimal intentional mistuning, minimizing the expectation of the irregularity measure for each substructure, is determined for the normal distributed fabrication error and its robustness in the design of MEMS resonator to the fabrication error is demonstrated with numerical examples.

• 한국소음진동공학회논문집
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• 제15권8호
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• pp.931-938
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• 2005

This paper presents a robust optimal design method for a periodic structure type of MEMS resonator that is vulnerable to mode localization. The robust configuration of such a MEMS resonator to fabrication error is implemented by changing the regularity of periodic structure For the mathematical convenience, the MEMS resonator is first modeled as a multi-pendulum system. The index representing the measure of mode variation is then introduced using the perturbation method and the concept of modal assurance criterion. Finally, the optimal intentional mistuning, minimizing the expectation of the irregularity measure for each substructure, is determined for the normal distributed fabrication error and its robustness in the design of MEMS resonator to the fabrication error is demonstrated with numerical examples.