• 한국통신학회논문지
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• 제34권7A호
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• pp.530-539
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• 2009

Wireless Relaying is a promising solutions to overcome the channel impairments and provides high data rate coverage that appear for beyond 3G mobile communications. In this paper we present end to end BER performance of dual hop wireless communication systems equipped with multiple Decode and Forward relays over Rayleigh fading channel with the best relay selection. We compare the BER performance of the best relay with the BER performance of single relay. We select the best relay based on the end to end channel conditions. We further calculate the outage probability of the best relay. It is shown that the outage probability of the best relay is equivalent to the outage probability when all relays take part in the transmission. We apply Orthogonal Space Time Block coding(OSTBC) at the source terminal. Numerical and simulation results are presented to verify our analysis.

• 한국통신학회논문지
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• 제34권11B호
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• pp.1225-1233
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• 2009

기업이나 대학 등 대규모 기관들은 고속 네트워크를 구축하여 운영하고 있다. 이와 같은 고속 엔터프라이즈 네트워크 내에서 네트워크 이용률(utilization)이 저조함에도 불구하고 종단간 성능은 네트워크 속도에 비하여 상당히 저조하다. 이러한 원인은 특정 장비에서 아주 작은 시간에 트래픽이 폭주하는 미세폭주(micro-congestion)가 발생하기 때문이다. 미세폭주는 패킷손실(Packet Loss)나 지연(Delay), 패킷역전(Packet Reordering)을 발생시키고 이것이 성능 저하의 원인이 된다. 본 논문에서는 미세폭주를 발생하는 시점을 검출하는 방법과 미세폭주를 검출한 시점에 트래픽을 수집하여 패킷손실, 지연, 패킷역전과 트래픽의 특성과의 상관관계 분석하여 성능저하를 발생시키는 미세폭주의 특성을 규명한다.

• Steel and Composite Structures
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• 제49권5호
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• pp.473-486
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• 2023

A through-railway bridge with an inclined girder has recently been applied to optimize the cross-section of a slender bridge structure in railway bridges. To achieve the additional cross-section optimization effect by the bolted end-plate connection, it is necessary to investigate the application of the bolted end-plate tension connection between the inclined girder and the crossbeam. This basic study was conducted on the application of the bolted end-plate moment connection of crossbeams to half-through girders with inclined webs. The combined behavior of vertical deflection and rotational behavior was observed due to the effect of the web inclination in the inclined girder where the steel crossbeam was connected to the girder by the bolted end-plate moment connection. Therefore, in the experiment, the deflection of the inclined girder was 1.77-2.93 times greater than that of the vertical girder but the lateral deflection of the inclined girder was 0.4 times less than that of the vertical girder. Moreover, the tensile stress of the upper bolts in the inclined girder with low crossbeams was clearly 0.81 times lower than that of the vertical girder. According to the results, the design formula for vertical girders does not reflect the influence of the web inclination. Therefore, this study proposed the design procedures for the inclined girder to apply the bolted end-plate moment connection of the crossbeam to the inclined girder by reflecting the design change factors according to the effect of the web inclination.

• ETRI Journal
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• 제44권3호
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• pp.476-490
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• 2022

With the recent advances in technology, automatic speech recognition (ASR) has been widely used in real-world applications. The efficiency of converting large amounts of speech into text accurately with limited resources has become more vital than ever. In this study, we propose a method to rapidly recognize a large speech database via a transformer-based end-to-end model. Transformers have improved the state-of-the-art performance in many fields. However, they are not easy to use for long sequences. In this study, various techniques to accelerate the recognition of real-world speeches are proposed and tested, including decoding via multiple-utterance-batched beam search, detecting end of speech based on a connectionist temporal classification (CTC), restricting the CTC-prefix score, and splitting long speeches into short segments. Experiments are conducted with the Librispeech dataset and the real-world Korean ASR tasks to verify the proposed methods. From the experiments, the proposed system can convert 8 h of speeches spoken at real-world meetings into text in less than 3 min with a 10.73% character error rate, which is 27.1% relatively lower than that of conventional systems.

• 한국기계가공학회지
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• 제18권1호
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• pp.72-77
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• 2019

In this study, the wear characteristics of end mills for CFRP processing were investigated according to the tool materials and coating types. Three kinds of tool materials and two types of coatings were used for comparing the machining performance. The flank wear of the end mill tool and the surface condition of the workpiece were compared. The K6UF material shows the most excellent performance among the three materials used in the experiment. The Tetrabond coating showed better processability in comparison of two kinds of coatings.

• 한국경영정보학회:학술대회논문집
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• 한국경영정보학회 2007년도 추계학술대회
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• pp.23-28
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• 2007

In e-Business environment, end-user e-Business capability is necessitated for performing his or her given tasks and improving his or her business performance in an enterprise of e-Business environment. An instrument of an end-user e-Business competency is extracted from the major components of a general competency. Through a pilot test, this study performed factor analysis, and proposed a 16-item instrument that can measure an end-user e-Business competency in e-Business environment. The application of the instrument is confirmed by applying it to measuring e-Business competency of end-users in an enterprise of e-Business environment and by presenting the measurement results for them.

• Journal of Biosystems Engineering
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• 제22권3호
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• pp.325-332
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• 1997

The use of a robotic transplanter reduces the labor requirement in the greenhouse by carrying out repetitive tasks in an accurate and reliable manner. The transplanter manipulates seedlings by means of end-effector. The end-effector is designed differently from an industrial robot because it manulates biological seedlings of variable size, shape, position, and orientation. This study was conducted to develop an end-effector of a robotic transplanter for bedding plants. The development of an end-effector included selection of the best finger type for the transplanting operation. The performance of developed end-effector was tested and compared with two different transplanting schemes depending on the leaf-orientation consideration. The end-effector developed in this research reliably handled seedlings during transplanting task. Results showed that the shovel type finger was suitable for transplanting with the damaging seedlings.

• 한국인터넷방송통신학회논문지
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• 제10권5호
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• pp.201-208
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• 2010

이동 Ad Hoc(MANET) 망은 노드들의 이동성으로 말미암아 망 구조가 수시로 바뀌는 동적인 특성을 가지고 있으며 이는 망의 성능 평가나 프로토콜 설계에 많은 도전적인 문제를 야기한다. 우리는 이동성이 망의 성능에 미치는 성능 측도로서 총 경로 붕괴시간, $\sum_{i}T_i$가 개별 연결뿐만 아니라 시스템 전체의 성능을 평가하는 측도로 사용될 수 있음을 보았다. 본 논문에서는 총 경로 붕괴시간 측도를 세 가지 다른 이동성 모델(Random Waypoint, Manhattan, Blocked Manhattan)에 적용하여 각 이동성 모델의 성능을 평가하고, 패킷 전달율, 종단 간 지연 등이 이동성 모델에 따라 왜 달라지는지를 규명하였다. 또한 AODV 라우팅 프로토콜 하에서 경로 붕괴에도 불구하고 AODV Buffer가 패킷전달율을 어떻게 높이고 종단 간 지연을 얼마만큼 증가 시키는지를 해석적으로 분석하였다.

• Steel and Composite Structures
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• 제47권3호
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• pp.315-337
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• 2023

The steel structure is an assembly of individual structural members joined together by connections. The connections are the focal point to transfer the forces which is susceptible to damage easily. It is challenging to replace the affected connection parts after an earthquake. Hence, steel plates are utilised as a structural fuse that absorbs connection forces and fails first. The objective of the present research is to develop a beam-column end plate connection with single and dual fuse and study the effect of single fuse, dual fuse and combined action of fuse and damper. In this research, seismic resilient beam-column end plate connection is developed in the form of structural fuse. The novel connection consists of one main fuse was placed horizontally and secondary fuse was placed vertically over main fuse. The specimens are fabricated with the variation in number of fuse (single and dual) and position of fuse (beam flange top and bottom). From the fabricated ten specimens five specimens were loaded monotonically and five cyclically. The experimental results are compared with Finite Element Analysis results of Arunkumar and Umamaheswari (2022). The results are critically assessed in the aspect of moment-rotation behaviour, strain in connection components, connection stiffness, energy dissipation characteristics and ductility. While comparing the performance of total five specimens, the connection with fuse exhibited superior performance than the conventional connection. An equation is proposed for the moment of resistance of end-plate connection without and with structural fuse.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제7권9호
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• pp.227-234
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• 2018

실시간 시스템, 네트워크 제어 시스템, 사이버물리시스템과 같이 지연에 민감한 시스템의 서비스 품질을 위해 종단 간 지연 데드라인을 보장하는 것은 중요하다. 대부분의 라우팅 알고리즘은 일반적으로 종단 간 평균 지연을 성능 메트릭으로 사용하고 평균 성능 향상을 위해 이를 최소화하는 라우팅 경로를 선택한다. 하지만 최소 평균 지연은 평균값만을 나타내기 때문에 예측할 수 없는 무선 채널의 특성을 반영하기에 불충분한 라우팅 메트릭이다. 본 논문에서는 평균 지연보다는 평균 분포를 고려하여 사이버물리시스템의 주어진 데드라인 내에 패킷이 도착할 확률을 최대화하는 데드라인 인지 라우팅 알고리즘을 제안한다. 제안한 라우팅 알고리즘은 단일 홉 지연이 지수 분포를 따른다는 가정 하에 주어진 네트워크 토폴로지에서 종단 간 지연 분포를 구성한다. 시뮬레이션 결과는 제안한 라우팅 알고리즘이 데드라인을 만족할 확률을 최대화 하는 라우팅 경로를 제공하여 사이버물리시스템의 서비스 품질과 네트워크 제어 성능을 향상시킬 수 있음을 보여준다.