• Journal of Computing Science and Engineering
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• 제7권4호
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• pp.231-241
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• 2013

Improvements in wireless sensor network (WSN) technology have resulted in a large number of applications. WSNs have been mainly used for monitoring applications, but they are also applicable to target tracking, health care, and monitoring with multimedia data. Nodes are generally deployed in environments where the exhausted batteries of sensor nodes are difficult to charge or replace. The primary goal of communication protocols in WSNs is to maximize energy efficiency in order to prolong network lifetime. In this paper, various medium access control (MAC) protocols for synchronous/asynchronous and single/multi-channel WSNs are investigated. Single-channel MAC protocols are categorized into synchronous and asynchronous approaches, and the advantages and disadvantages of each protocol are presented. The different features required in multi-channel WSNs compared to single-channel WSNs are also investigated, and surveys on multi-channel MAC protocols proposed for WSNs are provided. Then, existing broadcast schemes in such MAC protocols and efficient multi-hop broadcast protocols proposed for WSNs are provided. The limitations and challenges in many communication protocols according to this survey are pointed out, which will help future researches on the design of communication protocols for WSNs.

• 정보교육학회논문지
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• 제9권4호
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• pp.583-593
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• 2005

교육인적자원부는 정보통신기술 활용 교육을 주도해 나가는데 가장 중심이 되는 교사의 정보통신기술 활용 능력을 신장시키기 위해 다양한 방안들을 수립하여 추진하고 있다. 그러나 현재 시행되고 있는 교사의 정보통신기술 활용 능력 신장에 관한 대부분의 노력들은 정보통신기술을 교육활동에 효과적으로 활용할 수 있는 능력보다는 기술 소양 능력에 중점을 두고 있다. 본 연구에서는 교사의 정보통신기술 활용 능력에 관한 국내 외의 평가 도구를 비교 분석하고 각 도구의 장점을 바탕으로 교사의 정보통신기술 활용 능력 자기 평가 도구를 개발하였다. 본 평가 도구를 통해 실제 교수-학습 활동 지도 능력과 정보통신기술 활용 능력을 총체적으로 통합한 평가가 이루어질 수 있을 것이다.

• 한국광학회지
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• 제15권6호
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• pp.555-562
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• 2004

3차원 유한 차분 빔전파 방법의 계산시간 및 수렴성 문제를 해결하기 위해서 implicit와 explicit 방법을 결합하는 복합 방법(hybrid method)을 제안하였다. 방향성 결합기의 결합길이를 결정하는 문제를 대상으로 제안된 방법과 implicit 방정식의 해를 직접 구하는 방법의 계산 시간을 비교하였다. 그 결과 직접 풀이법에 비해 제안된 방식의 계산 속도가 최소 10배 이상 빠름을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권12호
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• pp.5087-5102
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• 2015

Rapid popularization of smart cell phone equipped with camera has led to a number of new legal and criminal problems related to multimedia such as digital image, which makes cell phone source identification an important branch of digital image forensics. This paper proposes a classifier combination based source identification strategy for cell phone images. To identify the outlier cell phone models of the training sets in multi-class classifier, a one-class classifier is orderly used in the framework. Feature vectors including color filter array (CFA) interpolation coefficients estimation and multi-feature fusion is employed to verify the effectiveness of the classifier combination strategy. Experimental results demonstrate that for different feature sets, our method presents high accuracy of source identification both for the cell phone in the training sets and the outliers.

• 한국전자통신학회논문지
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• 제1권1호
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• pp.87-93
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• 2006

이 논문은 블루투스 장치의 전 세계적으로 사용되는 무허가 ISM 대역의 2.4GHZ로 동작한다. 이 대역은 널리 사용되고 있지만, 블루투스 이외의 수많은 다른 시스템들이 이 주파수대를 사용하고 있고 마이크 웨이브 오븐과 같은 잡음원이 이 주파수대를 차지하고 있기 때문에 오히려 방해가 심한 주파수 대역이 되고 있다. 블루투스는 이와 같이 방해가 심한 전파환경을 극복하기 위해 빠른 주파수 호핑법과, 에러방지 및 정정기술을 사용하고 있다. 이와 같은 상황에도 불구하고, 저가의 블루투스 시스템이 신뢰성 있고 안정하게 하기 위해 언급할 몇 가지 중요한 설계 상 문제점이 있고 시스템 설계시 몇 가지 면밀한 주의가 필요하므로 연구하고자 한다.

• 한국멀티미디어학회논문지
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• 제16권5호
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• pp.566-576
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• 2013

In Home Area Network (HAN) of the smart grid, Power Line Communication (PLC) technology and ZigBee communication technology can be used in the communication among the Advanced Metering Infrastructure (AMI) devices. However, according to performance evaluation results of the PLC technology, we find that using the PLC technology is unsuitable for the remote meter reading service. It is worth noting that some parts of the PLC are converted to the ZigBee communication technology in Jeju, Korea. Compared with PLC, ZigBee has no restriction of the place, where the equipments can be freely set up, due to the advantage of radio communication. However, number of usable devices will impact the network performance which is depended on the address assignment. In addition, due to the restriction of transmission range among devices, it is difficult to apply the ZigBee address assignment method to the practical circumstance. In this paper, we examine the previous ZigBee address assignment schemes and the corresponding routing algorithms, and propose a novel address assignment scheme compared with the existing methods, the performance of the proposed one is improved. In particular, evaluation results show that the proposed scheme reduces the average number of hop count, the transfer time and the processing time.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권5호
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• pp.2576-2589
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• 2017

Co-saliency detection is a task of detecting same or similar objects in multi-scene, and has been an important preprocessing step for multi-scene image processing. However existing methods lack efficiency to match similar areas from different images. In addition, they are confined to single image detection without a unified framework to calculate co-saliency. In this paper, we propose a novel model called Superpixel Matching-Cellular Automata (SMCA). We use Hausdorff distance adjacent superpixel sets instead of single superpixel since the feature matching accuracy of single superpixel is poor. We further introduce Cellular Automata to exploit the intrinsic relevance of similar regions through interactions with neighbors in multi-scene. Extensive evaluations show that the SMCA model achieves leading performance compared to state-of-the-art methods on both efficiency and accuracy.

• 산업경영시스템학회지
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• 제44권1호
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• pp.51-59
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• 2021

Electronic document communication based on a digital channel is becoming increasingly important with the advent of the paperless age. The electronic document based on PDF format does not provide a powerful customer experience for a mobile device user despite replacing a paper document by providing the content integrity and the independence of various devices and software. On the other hand, the electronic document based on HTML5 format has weakness in the content integrity as there is no HTML5 specification for the content integrity despite its enhanced customer experience such as a responsive web technology for a mobile device user. In this paper, we design the Document-HTML, which provides the content integrity and the powerful customer experience by declaring the HTML5 constraint rules and the extended tags to contain the digital signature based on PKI. We analyze the existing electronic document that has been used in the major financial enterprise to develop a sample. We also verify the Document-HTML by experimenting with the sample of HTML electronic communication documents and analyze the PKI equation. The Document-HTML document can be used as an authorized electronic document communication and provide a powerful customer experience in the mobile environment between an enterprise and a user in the future.

• 한국전자통신학회논문지
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• 제17권2호
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• pp.207-212
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• 2022

철도 교통시스템은 최근 들어 각 구성 요소의 자동화 단계를 넘어 지능화를 추구하는 스마트 철도로 발전하고 있다. IoT(: Internet of Things), 빅데이터, 딥러닝, AI(: Artificial Intelligence), 블록체인 등 ICT(: Information & Communications Technology) 기술에 기반한 스마트 철도는 국내외 철도 기술에 많은 발전적 변화를 일으킬 것으로 예상된다. 본 논문에서는 이와 같은 스마트 철도 시스템(SRS: Smart Railway System)의 근간을 이루는 철도 통신 기술의 국내외 표준화 동향에 대해서 살펴보고 향후 우리나라 철도교통시스템에서의 열차제어 기술(CBTC)이 세계 철도산업에서의 선도 기술이 되기 위한 지향점(UBTC)에 관하여 논한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권5호
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• pp.1503-1515
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• 2023

This paper considers the jointly active and passive beamforming design in the IRS-aided MISO downlink vehicle communication system where both V2I and V2V communication paradigms coexist. We formulate the problem as an optimization problem aiming to minimize the total transmit power of the base station subject to SINR requirements of both V2I and V2V users, total transmit power of base station and IRS's phase shift constraints. To deal with this non-convex problem, we propose a method which can alternately optimize the active beamforming at the base station and the passive beamforming at the IRS. By using first-order Taylor expansion, matrix analysis theory and penalized convex-concave process method, the non-convex optimization problem with coupled variables is converted into two decoupled convex sub-problems. The simulation results show that the proposed alternate optimization algorithm can significantly decrease the total transmit power of the vehicle base station.