• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.374-379
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• 2013

Helmholtz resonators have high transmission loss in a narrow band at the resonance frequency. The transmission loss characteristics of resonators at high sound pressure levels can change due to variations of the impedance as a result of nonlinear behavior. Different sound pressure levels are applied to each resonator when resonators were arranged along the path. Therefore, impedance variation due to incident sound pressure level should be considered in order to predict the transmission loss.

• Journal of Biosystems Engineering
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• 제8권2호
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• pp.18-25
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• 1983

The binders introduced in Korea were originally designed to be used for Japonica varieties which have realtively long stem and are highly resistant to shattering. In order to use it for Tongil varieties which are short and easy to be shattered, mechanical modifications are necessary to reduce a grain loss incurred during its operation. This study was intended to investigate the binding unit, one of the major factors affecting grain losses. The binding parts of three binders used in Korea were analyzed and the grain loss was experimentally assessed for these binders. The results obtained from this study are summarized as follows: 1. From the motion analysis of discharge mechanism, the trajectory of the discharge arm appeared to be either circular or skewed elliptic. The velocity of a circular path mechanism was constant and smaller than that of a skewed elliptic path mechanism. The discharge grain loss of the former was about twice less than that of the latter. 2. It was found that the grain loss incurred due to the collision of the paddy bundles and ground was considerably high for Tongil varieties. The auxiliary discharge bar gave a significant influence on the motion and posture of the bundles, and the degree of impact on ground. 3. The installation of an auxiliary bar, which guides the paddy bundles smoothly to ground in order to reduce impact when the bundles fall down on ground, appeared to be very effective since the grain losses could be decreased by about 1.6 percentage point. However, the guide bar should be installed after some mechanical modification to reduce the velocity of discharge arm has been made.

• 한국위성정보통신학회논문지
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• 제7권3호
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• pp.69-74
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• 2012

2012년 12월 31일 아날로그 TV 신호가 전면적으로 디지털 TV로 전환되면서, TV 유휴대역의 활용에 대한 연구가 활발히 진행되고 있다. 다양한 소출력 기기의 TV 유휴대역 사용이 예상되며, 따라서 TV 유휴대역을 사용하는 소출력 기기와 DTV 중계기 간의 간섭 문제가 발생할 수 있다. 본 논문에서는 DTV 시스템과 소출력 기기 간의 간섭영향에 관해 분석하였다. 두 시스템이 정상적으로 동작하기 위한 최소 이격 거리를 측정하도록 하며 간섭 분석 방법은 최소 결합 손실 방법을 이용하였다. 실험에서 피 간섭원은 DTV 시스템이고 간섭원은 소출력 기기들로 설정하여 실험 및 분석하였다.

• 한국산학기술학회논문지
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• 제20권7호
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• pp.211-217
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• 2019

고도화되는 전장 환경에서 적진의 정보는 군사 작전을 수행하는 데 있어 중요한 요소이다. 적진의 정보를 획득하기 위한 감시정찰을 목적으로 아군의 인력 손실이 없고 저 비용으로 임무에 투입이 가능한 무인항공기(UAV; Unmanned Aerial Vehicle, 이하 무인기) 운용이 늘어나고 있다. 무인기 임무 수행 환경은 대공위협이 존재하므로 무인기가 격추되지 않고 생존성을 보장할 수 있는 임무공간이 필요하다. 임무공간을 정의하기 위해서는 형상공간(Configuration Space) 개념을 활용하며, 적진의 대공방호영역 및 무인기가 탐지할 수 있는 범위를 고려한다. 무인기는 적진의 정보를 획득하기 위해 임무에 주어진 모든 영역을 방문해야 하며, 이를 위해 커버리지 경로 계획(Coverage Path Planning)을 수행한다. 무인기에 대한 위협 및 획득할 정보의 중요도를 바탕으로 무인기가 우선적으로 방문해야 할 영역을 정의하며, 격자지도를 생성하고 각 격자에 위협 정보를 매핑하여 경로 계획에 활용한다. 본 연구에서는 격자지도에 표시된 위협정보를 바탕으로 커버리지 조건 및 경로 계획 절차를 제시하며, 탐지 효율 향상을 위해 임무공간을 확장한다. 끝으로 본 연구에서 제시한 무인기 경로계획 방법에 대한 시뮬레이션을 수행하고, 관련된 결과를 제시한다.

• 한국전자파학회지:전자파기술
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• 제28권4호
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• pp.45-53
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• 2017

• 소음진동
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• 제11권3호
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• pp.401-409
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• 2001

Passive type mufflers installed on every car haute inherent problem of lowering engine power and fuel efficiency caused by backpressure which is byproduct of complex internal structure. Recent improvements like installing a calve to change exhaust gas path depending on power requirement and rpm have only marginally improved performance. Tremendous amount of recent research works on active exhaust noise control have failed to commercialize because of numerous physical and economical reasons. In this paper, a unique seal-active muffler using difference of transmission paths is presented. In this system exhaust pipe is divided into two and joined again downstream. Exhaust noise is reduced by destructive interference when two-divided noise join again with transmission paths'difference which is half of the wavelength of a main noise frequency. One divided path has a sliding mechanism to change length thereby transmission path length difference is adjusted to entwine rpm change. The proposed system has minimal backpressure and does not need a secondary sound source like a speaker so it can overcome many problems of failed active noise control methods. We have verified proposed system's superior performance by simulation and comparison experiment with passive mufflers.

• Current Optics and Photonics
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• 제1권4호
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• pp.315-324
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• 2017

In recent years, multicast services such as high-definition television (HDTV), video conferencing, interactive distance learning, and distributed games have increased exponentially, and wavelength-division multiplexing (WDM) networks are considered to be a promising technology due to their support for multicast applications. Multicast survivability in WDM networks has been the focus of extensive attention since a single-link failure in an optical network may result in a massive loss of data. But the improvement of network survivability increases energy consumption due to more resource allocation for protection. In this paper, an energy-efficient multicast algorithm (EEMA) is proposed to reduce energy consumption in WDM networks. Two cost functions are defined based on the link state to determine both working and protection paths for a multicast request in WDM networks. To increase the number of sleeping links, the link cost function of the working path aims to integrate new working path into the links with more working paths. Sleeping links indicate the links in sleep mode, which do not have any working path. To increase bandwidth utilization by sharing spare capacity, the cost function of the protection path is defined to use sleeping fibers for establishing new protection paths. Finally, the performance of the proposed algorithm is evaluated in terms of energy consumption, and also the blocking probability is evaluated under various traffic environments through OPNET. Simulation results show that our algorithm reduces energy consumption while maintaining the quality of service.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권9호
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• pp.4665-4683
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• 2019

Previous methods build image annotation model by leveraging three basic dependencies: relations between image and label (image/label), between images (image/image) and between labels (label/label). Even though plenty of researches show that multiple dependencies can work jointly to improve annotation performance, different dependencies actually do not "work jointly" in their diagram, whose performance is largely depending on the result predicted by image/label section. To address this problem, we propose the adaptive attention annotation model (AAAM) to associate these dependencies with the prediction path, which is composed of a series of labels (tags) in the order they are detected. In particular, we optimize the prediction path by detecting the relevant labels from the easy-to-detect to the hard-to-detect, which are found using Binary Cross-Entropy (BCE) and Triplet Margin (TM) losses, respectively. Besides, in order to capture the inforamtion of each label, instead of explicitly extracting regional featutres, we propose the self-attention machanism to implicitly enhance the relevant region and restrain those irrelevant. To validate the effective of the model, we conduct experiments on three well-known public datasets, COCO 2014, IAPR TC-12 and NUSWIDE, and achieve better performance than the state-of-the-art methods.

• 한국통신학회논문지
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• 제28권3A호
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• pp.179-184
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• 2003

본 논문에서는 ISM대역에서 수신경로의 격리도를 크게 송신경로의 삽입손실은 작게 하며 동시에 P1dB를 크게 하는 비대칭구조의 MMIC SPDT 스위치를 제안하였으며, 이를 ETRI에서 지원하는 IDEC MPW의 0.5㎛ GaAs MESFET으로 제작하였다. 이 SPDT 스위치 수신경로의 삽입손실은 3GHz에서 1.518dB, 5.75GHz에서 1.777dB이고, 격리도는 3GHz에서 38.474dB, 5.75GHz에서 29.125dB로 측정되었다. 그리고, 송신경로의 삽입손실은 3GHz에서 0.961dB, 5.75GHz에서 1.162dB이고, 격리도는 3GHz에서 23.259dB, 5.75GHz에서 16.632dB였다. 비대칭구조의 스위치는 대칭구조에 비하여 수신경로의 격리도가 3GHz에서 15.9dB, 5.75GHz에서 11.9dB 정도 개선되었으며, 삽입손실은 약 0.6dB 정도 증가하였다. 또한, SPDT 스위치 송신경로의 P1dB는 21.5dBm로 대칭구조에 비하여3.86dB 증가하였다.

• 환경생물
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• 제36권4호
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• pp.507-516
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• 2018

벼재배 논에서 온실가스 측정을 위해 사용되는 closed 챔버법은 시 공간적으로 변동 폭이 큰 메탄 플럭스를 측정하는 데는 한계가 있다. 이러한 문제점을 해결하고자 메탄플럭스 측정에 있어 에디공분산을 기반으로 하는 open-path 방법과 closed 챔버법을 비교분석하였다. 벼 재배 기간 중 메탄 플럭스 변동은 두 방법 모두 비슷한 경향을 보였고 closed 챔버를 이용한 메탄 측정 시간대의 값은 open-path 측정에 의한 값과 고도로 유의한 상관을 보였다. 다만 총배출량에 있어서 두 측정 방법 간에 나타난 약 31%의 차이가 발생했는데 이는 closed 챔버법에 따른 과다 측정과 open-path에 의한 과소측정으로 생각해 볼 수 있다. 정확한 원인 분석을 위해서 향후에도 추가적인 연구가 필요할 것으로 판단된다.