• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.177-182
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• 1996

Remote nuclear cask handling device (RNCHD)는 사용후 핵연료cask의 원격 조작에 있어서 안전성과 성능을 향상을 목적으로 한다. RNCHD의 한부분인 grapple은 사용후 핵연료cask의 이동 및 수송 또는 용기뚜껑의 개폐를 위하여 cask의 벽에 대각선으로 돌출되어있는 두 개의 trunnion에 삽입되어야한다. 그러나 trunnion으로의 grapple 삽입은 용기중심과 grapple 장치 중심사이의 위치와 방향편차 때문에 어렵게된다. 인공신경망은 grapple에 설치된 광전센서를 사용하여 용기의 중심으로 부터 grapple 장치의 상대적 위치를 계측하기위해 사용된다. 인공신경망 학습은 광전센서값과 grapple의 상대적 위치와 방향사이의 함수적 관계를 추론하기 위해 수행된다. 이렇게 측정된 RNCHD의 중심위치는 grapple의 자세를 맞추기 위한 제어입력값으로 제공된다. 인공신경망 학습을 위한 데이터는 grapple 장치와 trunnion을 모사한 1/2 스케일의 실험장치를 사용함으로써 얻어진다. 학습된 인공신경망은 학습에 사용 안된 센서입력값, 즉 새로운 grapple의 위치에 대해서도 정확성을 가지고 grapple 장치의 위치와 방위를 측정할 수 있었다.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10b
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• pp.423-428
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• 2007

본 논문에서는 센서 네트워크 환경에, MANET기반의 라우팅 프로토콜인 AODV[1]를 적용하여 실험한 내용에 대해 소개한다. AODV는 RREQ, RREP 그리고 RERR등의 제어 메시지를 이용하여, 데이터를 전송하기 위한 망을 동적으로 구성하는 특징을 갖는다. MANET환경에 비해서 센서네트워크 환경은 에너지 사용 혹은 네트워크 망 구성에 있어서 많은 제약조건을 갖고 있다. 이러한 센서 네트워크 망에 AODV를 적용하였을 경우 어떠한 특성이 나타나는지 문제점을 분석하였다. 시뮬레이션 환경으로는 NS-2 시뮬레이터를 이용하여 구성하였으며 AODV 라우팅 프로토콜을 이용하여 싱크 수 증가, 소스 수 증가와 S-MAC을 적용함에 따른 평균 메시지 Delay, 평균 소비 에너지, 평균 데이터 전송률 등이 어떻게 변화하는지 살펴보았으며 센서 네트워크 환경에서의 성능을 확인하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2021.06a
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• pp.195-199
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• 2021

본 논문에서는 재귀 신경망을 통해 동적 비전 센서 (DVS: Dynamic Vision Sensor)의 출력에서 엣지를 추정하는 방법을 제안한다. 동적 비전 센서는 기존의 일반적인 카메라들과 달리 급격한 움직임이나 밝기 변화에 강인하게 동작한다. 그러나 동적 비전 센서에서 획득한 출력은 각각이 독립적이기 때문에 화소들의 상관관계를 이용한 알고리즘을 사용함에 어려움이 따른다. 제안하는 방법은 센서에서 획득한 출력을 일정한 시간단위로 분할하고 2차원 평면에 투영함으로써 출력의 정보량 및 상관관계를 향상시키고, 이를 재귀 신경망에 통과시켜 엣지 정보를 추정한다. 이 방법은 센서의 출력에 의해 형성된 패턴을 학습하여 엣지를 잘 추출하였으며, 기존의 컴퓨터 비전 알고리즘의 적용 및 시각 관성 측위 등의 분야에서 활용될 수 있다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.7
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• pp.53-61
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• 2008

Consider a typical wireless sensor network in which stem nodes form the backbone network of mesh topology while each stem node together with leaf nodes in its vicinity forms a subnetwork of star topology. In such a wireless sensor network, we must heed the following when we design a MAC scheme supporting the packet delivery from a leaf node to a stem node. First, leaf nodes are usually battery-powered and it is difficult to change or recharge their batteries. Secondly, a wireless sensor network is often deployed to collect and update data periodically. Late delivery of a data segment by a sensor node causes the sink node to defer data processing and the data segment itself to be obsolete. Thirdly, extensive signaling is extremely limited and complex computation is hardly supported. Taking account of these facts, a MAC scheme must be able to save energy and support timeliness in packet delivery while being simple and robust as well. In this paper, we propose a version of ALOHA as a MAC scheme for a wireless sensor network. While conserving the simplicity and robustness of the original version of ALOHA, the proposed version of ALOHA possesses a distinctive feature that a sensor node decides between stop and continuation prior to each delivery attempt for a packet. Such a decision needs a stopping rule and we suggest a Bayes stopping rule. Note that a Bayes stopping rule minimizes the Bayes risk which reflects the energy, timeliness and throughput losses. Also, a Bayes stopping rule is practical since a sensor node makes a decision only using its own history of delivery attempt results and the prior information about the failure in delivery attempt. Numerical examples confirm that the proposed version of ALOHA employing a Bayes stopping rule is a useful MAC scheme in the severe environment of wireless sensor network.

• Journal of Digital Convergence
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• v.14 no.8
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• pp.269-276
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• 2016

Public Safty-LTE(Long Term Evolution) is being deployed in the direction of reducing cost by using both of municipal network and commercial network. However, LTE Network is difficult to ensure the survivability during the information communication infrastructure failures. In addition, it is vulnerable in communication coverage of inside buildings and underground. In this study, we propose to implement effectively the network survivability technique through the convergence to the proven technology. As the advent of the IoT Age, smart sensors which are embedded in the environment and the things will be able to provide a useful infrastructure for ensuring the network survivability. Based on the feature of the smart sensor, we designed the sink node architecture to guarantee the network survivability in disaster situation through the convergence of the small cell technology and extension of wireless network coverage technology. The computing power inherent in the environment is a valuable resource that can be utilized in the disaster situation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.2
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• pp.51-57
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• 2009

Ubiquitous sensor network is the communication environment where sensor nodes move freely and construct network to get the services from the system. So, it does not need fixed infrastructure and can easily be placed in unaccessible regions like war or calamity area. Wireless sensor network protocol has self-organizing capability, need to adapt topology change flexibly and also has technique that sensor nodes work cooperatively, because network disconnection is frequently occurred due to the active mobility of sensor nodes. In this paper, we design a cluster based fault-tolerant routing protocol for the efficient topology construction and to guarantee stable data transmission in USN. The performance of the proposed protocol is evaluated by an analytic model.

• Convergence Security Journal
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• v.12 no.3
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• pp.67-73
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• 2012

In this paper, in order to overcome the disadvantage of wireless-based sensor network, a hybrid sensor network using wired and wireless linkage is proposed. Proposed a wired and wireless linkage hybrid sensor network can compensate the defect of poor transmission at the indoor wireless environment, and can be free from interference between a wireless LAN and Bluetooth of the same frequency bandwidth due to an attribute of low-loss transmission at the CATV network. Also, proposed a wired and wireless linkage hybrid sensor network make use of CATV network which is well-built infrastructure, is more efficient to design network, assure a stability and high reliability of the sensor network as providing a stability for an inaccuracy and a predictable transmission link for the existing wireless network.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.237-240
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• 2007

최근 '정보기반 물류망'에서 'u-기반 물류망'으로 발전해 가고 있는 시점에서 'u-기반 물류망'을 위해 다양한 기반 기술들이 요구되고 있다. 본 논문에서는 물류 관리 시스템 구축을 위해 GPS 기반의 물류위치 추적 기법과 센서 Tag를 이용한 물류 배송 효율화 시스템을 설계하고 구현한다. 또한, 물류 배송 효율화를 위해 센서 Tag 네트워크 시스템을 제안하며, 이 센서 Tag 네트워크를 기반으로 수집된 센싱 정보를 이용하여 물류의 위치와 상태, 이동경로 등을 파악함으로서 물류의 배송이 효율적으로 이루어 질 수 있도록 지원한다. 제안된 시스템은 관리자에 의해 유지 보수 될 수 있는 제어 가능한 센서 Tag 네트워크(Controlled Network Layer)와 무제어 이동 센서 Tag 네트워크(Uncontrolled Moving Objects Layer)로 구분하여, 일반적인 센서 네트워크 시스템의 배터리 문제를 보완하고자 한다.

• The KIPS Transactions:PartC
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• v.16C no.5
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• pp.621-628
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• 2009

Wireless sensor networks (WSNs) have been considered as a promising method for reliably monitoring both civil and military environments under hazardous or dangerous conditions. Due to the special property and difference from the traditional wireless network, the lifetime of the whole network is the most important aspect. The bottleneck nodes widely exist in WSNs and lead to decrease the lifetime of the whole network. In order to find out the bottleneck nodes, the traditional centralized bottleneck detection method MINCUT has been proposed as a solution for WSNs. However they are impractical for the networks that have a huge number of nodes. This paper first proposes a distributed algorithm called DBND (Distributed Bottleneck Node detection) that can reduce the time for location information collection, lower the algorithm complexity and find out the bottleneck nodes quickly. We also give two simple suggestions of how to solve the bottleneck problem. The simulation results and analysis show that our algorithm achieves much better performance and our solutions can relax the bottleneck problem, resulting in the prolonging of the network lifetime.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.4
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• pp.20-26
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• 2016

A wireless passive sensor network is a network which, by letting RF sources supply energy to sensor nodes, is - at least theoretically - able to live an eternal life without batteries. Due to the technological immaturity, however, a wireless passive sensor network still has many difficulties; energy scarcity, non-simultaneity of energy reception and data transmission and inefficiency in data transmission occurring at sensor nodes. Considering such practical constraints, in this paper, we propose an elementary MAC scheme supporting many sensor nodes to deliver packets to a sink node. Based on a time structure in which a charging interval for charging capacitors by using received and an acting interval for communicating with a sink node are alternately repeated, the proposed MAC scheme delivers packets to a sink node according to slotted ALOHA. In general, a contention-type scheme tends to exhibit relatively low throughput. Thus, we multilaterally evaluate the throughput performance achieved by the proposed MAC scheme using a simulation method. Simulation results show that the network-wide throughput performance can be enhanced by properly setting the length of acting interval.