• 한국항공우주학회지
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• 제46권1호
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• pp.10-17
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• 2018

풍력발전기의 효율을 증가시키기 위하여 피치제어가 주로 사용되어 왔으나 피로파괴와 효율의 감소를 일으키는 날개의 국부적인 유동을 제어할 수 없는 단점이 있다. 본 논문에서는 기존의 풍력발전기 블레이드에 합성제트 구동기 모듈을 설치하여 국부 유동을 제어하고 날개의 공력성능을 향상시키고자 한다. 합성제트 구동기는 작은 구멍을 통해 유체를 흡입/분출하여 유동 박리를 지연시켜 공력성능을 향상시킨다. 압전디스크를 사용하여 탈부착이 가능한 합성제트 구동기 모듈을 제작하고 풍동실험을 통해 오리피스 형상과 합성제트 속도에 따른 공력성능을 측정하였다. 직사각형 오리피스 형상을 사용하고 합성제트 속도가 커질수록 날개의 항력이 감소하고 양력이 증가하는 것을 확인하였다.

• 한국항공운항학회지
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• 제28권1호
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• pp.7-13
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• 2020

A significant growth in local air traffic volume is leading to airway congestion and flight delays especially for Incheon-China and Incheon-Europe sectors. A key method to increase the airway capacity is to place a supplemental airway parallel to the existing one and in cooperation between the aviation authorities between China and Korea, a dual airway track was implemented on December 6, 2018. Here, we use airline A's flight data to analyze the congestion change effect of the new airway. Results show total delay time to Europe is reduced 51% (13.4 to 6.6 minutes) as the delay distribution for 16-30 minutes, 31 minutes and greater decreased from 23.2% to 8.2% and 8.7% to 1.0% respectively. The delay to China also decreased but the drop is not as significant as flights to Europe. This is caused by the difference in flight distance, traffic volume, and characteristics of flights landing and transiting China. Flights to Europe show a broad distribution in altitude allocation and reduction in aircraft separation demonstrating the effectiveness of a dual airway track.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.474-477
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• 2005

In tactical theater, it is crucial to detect ground moving targets and to locate them precisely. This problem can be resolved by using SAR (Synthetic Aperture Radar) sensors providing GMTI (Ground Moving Target Indication) capability. In general, to implement a robust GMTI sensor is not simple because of the strong competitions between target signals and clutter signals on the ground, and low speed of moving targets. Contrary to the case that a delay canceller is mostly suitable for ground surveillance radars, DPCA (Displaced Phase Centered Antenna) or STAP (Space Time Adaptive Processing) techniques have been adapted for GMT! function of modem airborne radars. In this paper, anew scheme of DPCA using two passive antennas with vertical separation is proposed, which also provides good clutter cancellation performance. The proposed scheme enables us to scan straight ahead of the carrying platform that is impossible with typical DPCA configuration. Simulations using various conditions have been performed to validate the proposed scheme, and the results are acceptable.

• 한국멀티미디어학회논문지
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• 제8권3호
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• pp.328-335
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• 2005

본 논문에서는 혼합된 입력음성신호들을 분리하기 위해 마이크로폰 어레이를 이용한 주파수영역 ICA 블라인드 음원분리 방법을 제안한다. 음성신호가 지연 혼합되어 입력되더라도 신호와 잡음을 분리하기 위한 분리행렬이 최적해로 수렴할 수 있도록 입력신호의 상호상관도를 이용하여 지연 혼합의 초기 지연값을 결정하는 방법을 제안한다. 그리고 계산량을 줄이기 위하여 주파수영역 블라인드 음원분리 알고리즘을 채용한다. 본 논문에서 제안하는 블라인드 음원분리 방법의 성능을 컴퓨터시뮬레이션을 통하여 확인한다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.356-361
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• 2011

The flow characteristics of synthetic jet depending on rectangular and circular jet exit configuration are investigated using numerical computation with cross flow. In rectangular slot, synthetic jet generates the strong vortex, however, supply fewer momentum and effectiveness of flow control is reduced along flow direction. In circular slot, regular vortex is fanned from slot center to end and developed in flow direction. It affects the wider region than rectangular slot. The distribution of wall shear stress is considered in order to indicate the effectiveness of flow control device for flow separation delay. As a result, circular slot is a more suitable candidate for delaying flow separation.

• International Journal of Fluid Machinery and Systems
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• 제4권1호
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• pp.97-103
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• 2011

With the aim to increase blade loadings and stable operating range in highly loaded compressors, this article has been conducted to explore, through a numerical parametric study, the potential of passive control using slotted bladings in cascade configurations. The objective of this numerical investigation is to analyze the influence of location, width and slope of the slots and therefore identify the optimal configuration. The approach is based on two dimensional cascade geometry, low speed regime, steady state and turbulent RANS model. The results show the efficiency of this passive technique to delay separation and enhance aerodynamic performances of the compressor cascade. A maximum of 28.3% reduction in loss coefficient have been reached, the flow turning is increased with approximately $5^0$ and high loading over a wide range of angle of attack have been obtained for the optimized control parameter.

• ETRI Journal
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• 제35권4호
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• pp.666-676
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• 2013

With the recent growth in smartphone services, the "mobile" environment has become a key factor to consider in the design of the future Internet. In this paper, we propose Mobile-Oriented Future Internet (MOFI), which is a new architecture for the future Internet for mobile-oriented environments. The MOFI architecture is designed with three functional features: global identifier and local locator in the identifier-locator separation, query-first data delivery for route optimization, and distributed control of identifier-locator mapping. The proposed architecture and functional operations are implemented and tested using the Linux platform. From the experiment results, we see that the MOFI architecture performs better than the existing identifier-locator separation schemes, such as Proxy Mobile IP and Host Identity Protocol, in terms of data throughout, mapping control overhead, and handover delay.

• 한국음향학회지
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• 제25권1호
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• pp.14-20
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• 2006

본 논문에서는 지연혼합에서의 암묵신호분리를 위해 분리행렬의 초기 값을 설정하는 방법을 제안한다. 혼합신호의 상호상관행렬에 대한 고유분리를 분석한 후, 고유벡터의 지연정보를 이용하여 초기 값으로 설정한다. 제안하는 방법을 기존의 주파수영역 독립성분분석 (FDICA: Frequency domain independent component analysis)에 초기 값으로 설정하여 분리 성능을 향상시킨다. 컴퓨터 시뮬레이션을 통해 제안하는 방법이 신호대간섭비 (SIR: Signal to Interference Ratio)가 우수하고 학습곡선의 수렴속도가 개선됨을 보인다.

• 말소리와 음성과학
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• 제3권1호
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• pp.87-94
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• 2011

The decision directed (DD) approach is widely used to determine a priori SNR from noisy speech signals. In conventional speech enhancement systems with a DD approach, a priori SNR is estimated by using only the magnitude components and consequently follows a posteriori SNR with one frame delay. We propose a phase-dependent two-step a priori SNR estimator based on the minimum mean square error (MMSE) in the log-mel spectral domain so that we can consider both magnitude and phase information, and it can overcome the performance degradation caused by one frame delay. From the experimental results, the proposed estimator is shown to improve the output SNR of enhanced speech signals by 2.3 dB compared to the conventional DD approach-based system.

• 터널과지하공간
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• 제16권4호
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• pp.326-333
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• 2006

본 연구에서는 측정된 진동파형을 토대로 다른 발파공들로부터 간섭을 받지 않은 단일공의 진동파형을 분리 하였고 이를 FFT 주파수 분석을 통하여 우세 주파수를 분석하였다. 또한 진동의 지속시간과 발파공수가 PPV에 미치는 영향을 검토하기 위해 분리된 진동파형을 $2{\sim}15$공으로 발파공수를 조절하면서 $1{\sim}80ms$까지 1 ms의 간격으로 지연시차에 변화를 주며 발파진동에 중첩 모델링을 실시하였다. 그 결과 진동의 지속시간이 길어질수록 다른 발파공들로부터 간섭받지 않기 위한 지연시차 또한 길어졌고 동일 지연시차 내에서의 발파공 수에 관한 영향은 크게 나타나지 않았다.