• 제어로봇시스템학회논문지
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• 제18권8호
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• pp.780-786
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• 2012

Surveillance has become one of promising application areas of wireless sensor networks which allow for pervasive monitoring of concerned environmental phenomena by facilitating context awareness through sensor fusion. Existing systems that depend on a postmortem context analysis of sensor data on a centralized server expose several shortcomings, including a single point of failure, wasteful energy consumption due to unnecessary data transfer as well as deficiency of scalability. As an opposite direction, this paper proposes an energy-efficient distributed context-aware surveillance in which sensor nodes in the wireless sensor network collaborate with neighbors in a distributed manner to analyze and aware surrounding context. We design and implement multi-modal sensor stations for use as sensor nodes in our wireless sensor network implementing our distributed context awareness. This paper presents an initial experimental performance result of our proposed system. Results show that multi-modal sensor performance of our sensor station, a key enabling factor for distributed context awareness, is comparable to each independent sensor setting. They also show that its initial performance of context-awareness is satisfactory for a set of introductory surveillance scenarios in the current interim stage of our ongoing research.

• 한국전기전자재료학회논문지
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• 제26권10호
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• pp.736-740
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• 2013

In this study, the influence of electrochemical properties by mixing Tetrabutylammonium hydroxide (TBAOH) and ammonium hydroxide (NH4OH) electrode on the dssc. The titanias were prepared using a sol-gel method by mixing Tetrabutylammonium hydroxide and Ammonium hydroxide. The $TiO_2$ nanopowder prepared by sol-gel methode, and to improve the distributed properties of $TiO_2$ nanopowder, the TBAOH and NH4OH was added. The I-V values of cells show that the Tetrabutylammonium has 6.51% efficiency.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권5호
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• pp.291-299
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• 2005

An obstacle avoidance algorithm for a network-based autonomous mobile robot is proposed in this paper. The obstacle avoidance algorithm is based on the VFH(Vector Field Histogram) algorithm and two delay compensation methods with the VFH algorithm are proposed for a network-based robot with distributed environmental sensors, mobile actuators, and the VFH controller. Firstly, the environmental sensor information is compensated by prospection with acquired environmental sensor information, measured network delays, and the kinematic model of the robot. The compensated environmental sensor information is used for building polar histogram with the VFH algorithm. Secondly, a sensor fusion algorithm for localization of the robot is proposed to compensate the delay of odometry sensor information and the delay of environmental sensor information. Through some simulation tests, the performance enhancement of the proposed algorithm in the viewpoint of efficient path generation and accurate goal positioning is shown here.

• Journal of Welding and Joining
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• 제18권3호
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• pp.76-82
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• 2000

In this study, three-dimensional heat flow in laser beam welding for deep penetration was analyzed by using F.E.M common code, and then the results were compared with the experimental data. The models for analysis are full penetration welds and are made at three different laser powers (6, 9.9, 4.5 kW) with two different welding speeds (5.8mm/s, 5mm/s). The characteristics of thermal absorption by the workpiece during deep penetration laser welding can be represented by a combination of line heat source through the workpiece and distributed heat source at the top surface due to the plasma plume above the top surface. This gives an insight into the way in which the beam interacts with the material being welded. The analyses performed with the combined heat source models show comparatively good agreement between the experimental and calculated melt temperature isotherm, i.e, the fusion zone boundary. The results are used to explain the "nail head" appearance of fusion zone, which is quite common in laser beam welds.eam welds.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제7권1호
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• pp.41-48
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• 2007

Latest advances in network sensor technology and state of the art of mobile robot, and artificial intelligence research can be employed to develop autonomous and distributed monitoring systems. In this study, as the preliminary step for developing a multi-purpose "Intelligent Space" platform to implement advanced technologies easily to realize smart services to human. We will give an explanation for the ISpace system architecture designed and implemented in this study and a short review of existing techniques, since there exist several recent thorough books and review paper on this paper. Instead we will focus on the main results with relevance to the DIND data fusion with CI of Intelligent Space. We will conclude by discussing some possible future extensions of ISpace. It is first dealt with the general principle of the navigation and guidance architecture, then the detailed functions tracking multiple objects, human detection and motion assessment, with the results from the simulations run.

• Journal of the Optical Society of Korea
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• 제5권3호
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• pp.83-89
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• 2001

Room temperature quasi-continuous operation is achieved near 1556 nm with threshold current as low as 2.2 mA from a 5.6-${\mu}{\textrm}{m}$ oxide-aperture vertical-cavity surface-emitting laser. Wafer fusion techniques are employed to combine the GaAs/AlGaAs mirror and the InP-based InGaAs/InGaAsP active layer. In this structure, an $Al_x/O_y$/GaAs distributed bragg reflector and intra-cavity contacts are used to reduce free carrier absorption.

• Journal of electromagnetic engineering and science
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• 제11권4호
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• pp.250-256
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• 2011

This paper applies a compressed algorithm to improve the spectrum sensing performance of cognitive radio technology. At the fusion center, the recovery error in the analog to information converter (AIC) when reconstructing the transmit signal from the received time-discrete signal causes degradation of the detection performance. Therefore, we propose a subspace pursuit (SP) algorithm to reduce the recovery error and thereby enhance the detection performance. In this study, we employ a wide-band, low SNR, distributed compressed sensing regime to analyze and evaluate the proposed approach. Simulations are provided to demonstrate the performance of the proposed algorithm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1785-1786
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• 2007

저가형 센서 노드와 임베디드 기술의 발달로 인하여 센서 노드가 보다 넓은 범위에서 사용되고 있으며, 센서 네트워크에 대한 연구 또한 활발히 진행 되고 있다. 하지만 많은 센서 노드로부터 오는 데이터를 처리하게 되면서 계산량 증가 및 노이즈에 의한 데이터 왜곡현상 등의 각종 문제가 고려되고 있다. 본 논문에서는 분배형 확장 칼만 필터(Distributed Extended Kalman Filter)를 설계하고 분배형 센서 융합 알고리즘을 이용하여 이러한 문제를 해결하고, 이동 개체의 위치 및 경로를 추정 한다.

• 한국정보기술학회 영문논문지
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• 제10권2호
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• pp.73-81
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• 2020

The number of mobile devices roaming into a ubiquitous city (u-city) continues to rise as wireless systems have been widely deployed. The number of mobile devices also varies with time, and they tend to frequently change their locations. In addition, the available wireless access networks may belong to different domains, administrations, management, and internet service providers (ISPs). A fusion of overlapping heterogeneous wireless access networks (e.g., WiMax, Wi-Fi, LTE, etc.) serves the u-city in order to reach different coverage. In this context, technical challenges arise in mobility management for heterogeneous networks to realize their potential coverage and capacity benefits. This paper deals with the analysis of a decentralized mobility management support for u-City wireless network infrastructure. This scheme takes advantage of the features of the fully-distributed model of networked-based mobility management protocol to alleviate and realize the ubiquitous requirements of a u-City.

• 한국진공학회지
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• 제17권1호
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• pp.58-66
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• 2008

KSTAR 전류전송제어시스템은 네트워크기반의 실시간 분산제어시스템으로 EPICS (Experimental Physics and Industrial Control System)를 미들웨어로 채용하여 구축하였다. 전류전송제어시스템은 초전도자석시스템에 전류를 전송하기 위한 시스템으로서 전류전송과 동시에 초전도자석이 초전도상태를 유지하기 위한 냉매의 전송도 담당하고 있다. 주제어실에서의 원격운전을 위하여 EPICS IOC(Input Output Controller) 서버를 현장에 설치하였고 이를 통하여 전류전송제어시스템은 고유의 이름(PV)에 적절한 조작 및 감시 명령을 부여하여 주제어실의 운전화면을 통하여 시스템의 감시 및 조작이 가능하도록 하였다. EPICS와 PLC의 통신을 위하여 ether-ip 드라이버를 이용하여 EPICS IOC를 구축하였으며, 시험 결과 안정성 및 운용성 측면에서 만족할 만한 결과를 획득하였다.