• 대한원격탐사학회지
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• 제26권6호
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• pp.721-730
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• 2010

In satellite remote sensing, irregular temporal sampling is a common feature of geophysical and biological process on the earth's surface. Lee (2008) proposed a feed-back system using a harmonic model of single period to adaptively reconstruct observation image series contaminated by noises resulted from mechanical problems or environmental conditions. However, the simple sinusoidal model of single period may not be appropriate for temporal physical processes of land surface. A complex model of multiple periods would be more proper to represent inter-annual and inner-annual variations of surface parameters. This study extended to use a multi-periodic harmonic model, which is expressed as the sum of a series of sine waves, for the adaptive system. For the system assessment, simulation data were generated from a model of negative errors, based on the fact that the observation is mainly suppressed by bad weather. The experimental results of this simulation study show the potentiality of the proposed system for real-time monitoring on the image series observed by imperfect sensing technology from the environment which are frequently influenced by bad weather.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.628-632
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• 2005

Remote sensing through atmospheric turbulence had been hard works for a long time, because wavefront distortion due to the Earth's atmospheric turbulence deteriorates image quality. But due to the appearance of adaptive optics, it is no longer difficult things. Adaptive optics is the technology to correct random optical wavefront distortions in real time. For past three decades, research on adaptive optics has been performed actively. Currently, most of newly built telescopes have adaptive optical systems. Adaptive optical system is typically composed of three parts, wavefront sensing, wavefront correction and control. In this work, the wavefront sensing technology for adaptive optical system is treated. More specifically, shearing interferometers and Shack-Hartmann wavefront sensors are considered. Both of them are zonal wavefront sensors and measure the slope of a wavefront. . In this study, the shearing interferometer is made up of four right-angle prisms, whose relative sliding motions provide the lateral shearing and phase shifts necessary for wavefront measurement. Further, a special phase-measuring least-squares algorithm is adopted to compensate for the phase-shifting error caused by the variation in the thickness of the index-matching oil between the prisms. Shack-Hartmann wavefront sensors are widely used in adaptive optics for wavefront sensing. It uses an array of identical positive lenslets. And each lenslet acts as a subaperture and produces spot image. Distortion of an input wavefront changes the location of spot image. And the slope of a wavefront is obtained by measuring this relative deviation of spot image. Structures and measuring algorithms of each sensor will be presented. Also, the results of wavefront measurement will be given. Using these wavefront sensing technology, an adaptive optical system will be built in the future.

• 전력전자학회논문지
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• 제26권3호
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• pp.214-221
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• 2021

SiC MOSFETs require a faster and more reliable short-circuit protection circuit than conventional methods due to narrow short-circuit withstand times. Therefore, this research proposes a short-circuit protection circuit using a current-sensing circuit based on Rogowski coil. The method of designing the current-sensing circuit, which is a component of the proposed circuit, is presented first. The integrator and input/output filter that compose the current-sensing circuit are designed to have a wide bandwidth for accurately measuring short-circuit currents with high di/dt. The precision of the designed sensing circuit is verified on a double pulse test (DPT). In addition, the sensing accuracy according to the bandwidth of the filters and the number of turns of the Rogowski coil is analyzed. Next, the entire short-circuit protection circuit with the current-sensing circuit is designed in consideration of the fast short-circuit shutdown time. To verify the performance of this circuit, a short-circuit test is conducted for two cases of short-circuit conditions that can occur in the half-bridge structure. Finally, the short-circuit shutdown time is measured to confirm the suitability of the proposed protection circuit for the SiC MOSFET short-circuit protection.

• 한국통신학회논문지
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• 제36권5A호
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• pp.450-456
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• 2011

본 논문에서는 다중 채널이 존재하는 인지 라디오 시스템에서 다중 사용자가 협력하여 유휴 채널 탐색 시간을 줄이는 방법을 제안한다. 구체적으로 채널 상태에 대한 마르코프 모델을 토대로 각 채널의 유휴 확률을 추정하고 확률이 높은 순서대로 채널을 센싱함으로써 유휴 채널 탐색 시간을 줄이는 방법을 제안한다. 또한 제안한 탐색 방법을 사용자 그룹을 형성하여 그룹마다 서로 다론 채널을 동시에 센싱하는 방법과 결합함으로써 보다 향상된 센싱 성능을 얻을 수 있도록 한다. 모의실험을 통해 사용자 그룹을 형성하는 방법은 검출 신뢰도를 저하시키지만 탐색시간을 감소시킴을 검증하고, 채널 유휴 확률 추정을 이용한 센싱 순서 결정 방법을 사용하여 임의 탐색 기법에 비해 상당한 탐색 시간 감소 효과를 얻을 수 있음을 검증하였다. 최종적으로 제안한 채널 유휴 확률 추정 기반 탐색 방법과 사용자 그룹 형성 기법을 모두 적용한 인지 라디오 시스템의 유휴 채널 탐색 성능을 검증하였다.

• 한국HCI학회논문지
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• 제3권1호
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• pp.1-7
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• 2008

최근 센싱 인터페이스의 소형화 및 경량화, 휴대형 컴퓨팅 자원의 성능 증가, 근거리 무선 통신 기술의 발전과 함께 휴대할 수 있는 생체신호 측정 인터페이스의 개발이 활발하게 이루어지고 있다. 그러나 기존의 생체신호 측정 장치는 다채널 센싱, 무선 통신을 지원하는 방법의 개발에 초점이 맞추어져 있었다. 본 논문에서는 미래형 홈 환경에서 일상적으로 사용자의 생체신호를 획득하기에 용이한 돌 형태의 휴대형 생체신호 측정 인터페이스를 제안하고 경험적인 평가 방법으로 분석한다. 제안한 돌 센싱 인터페이스는 센싱하는 동안 사용자에게 심미감과 편안함을 주는 동시에 센싱의 안정성 및 신뢰성을 보장하여 실용적으로 사용할 수 있도록 한다. 심미감과 센싱 편안함을 만족하기 위해 사용자 중심의 디자인 기법을 적용하여 반복적으로 사용성 테스트를 진행하고 구조를 구체화 하였다. 또한, 안정적으로 센싱을 하기 위해 실험을 통해 움직임과 잡음에 최소한의 영향을 받는 센싱 위치를 선정하고 이를 센싱 인터페이스에 적용하였다. 향후 제안된 생체신호 측정 인터페이스는 미래형 홈 환경에서 다양한 건강관리 모니터링 시스템에 유용하게 사용될 수 있다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
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• pp.280.2-286
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• 1998

Flood is the main natural disaster mostly in the world. It is a care problem to prevent flood disaster generally. The frequency of flood disaster is high and the distributing field is wide, the 50 percent population and 70 percent properties distribute at the threaten field of flood disaster in China. Flood disaster has caused a huge amount of economical losses and these losses have an increasing trend. Along with the development of reducing natural disaster action, it has become one of the most attentive problems for monitoring flood, preventing flood and forecasting flood efficiently. Remote sensing has the characteristics of large spatial observing areas, wide spectrum ranges, and imaging far away from the targets, imaging capabilities all weather. Spatial remote sensing information, which records the full, processes of the disaster's occurrence and development in real-time. It is a scientific basis for management, planning and decision-making. Through systemic analyzing the RS monitoring theory, based on compounding RS information, the technology and method of monitoring flood disaster are studied.

• 한국통신학회논문지
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• 제38B권10호
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• pp.832-842
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• 2013

Cognitive Radio has attracted intensive interests of the researchers, recently. The data rate always increases in the emerging technologies. The increased data rate poses mainly two challenges for spectrum sensing. One is that the state of primary user (PU) is fast and alternatively varying between "on/off" in a spectrum sensing window. The other is that the asynchronicity among the reports in a cooperative spectrum sensing setting becomes more apparent. Both of them would deteriorate the spectrum sensing performance. Thus, we propose an asynchronous cooperative spectrum sensing method to cope with these two challenges. A likelihood ratio test based spectrum sensing is developed for a single cooperator. The likelihood ratio is obtained in the setting of fast varying PU state. The likelihood ratio test is uniformly powerful according to the Neyman-pearson lemma. Furthermore, the asynchronicity among the cooperators are studied. Two sets of fusion weights are discussed for the asynchronous time among cooperators. One is designed based on the condition probability of the PU state variation and the other one is designed based on the queueing theory. The simulation results are provided with different fusion methods. The performance improvements are demonstrated.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.593-597
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• 2002

The paper introduces a research on the W-band Millimeter Wave Radiometer(RADW92) through an airborne experiment. Microwave remote sensing images of part of the Yellow River and the WeiHe River are of fared. Analysis of factors influencing the image qualities as well as the resolutions to them are also included. The RADW92 is the first generation of Millimeter Wave Radiometer in China, which works with operating frequency 92 GHz, the bandwidth 2 GHz, the integration time 60ms, the system sensitivity 0.6k and the linearity better than 0.999. Cassegrain Antenna is designed for imaging by conically scanning. The result of the experiment suggested that RADW92 had been adequate for space use.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권3호
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• pp.980-998
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• 2023

In Low Earth Orbit (LEO) satellite networks, satellites operate fast and the inter-satellite link change period is short. In order to sense the spectrum state in LEO satellite networks in real-time, a space-based satellite network intelligent spectrum sensing algorithm based on artificial neural network (ANN) is proposed, while Geosynchronous Earth Orbit (GEO) satellites are introduced to make fast and effective judgments on the spectrum state of LEO satellites by using their stronger arithmetic power. Firstly, the visibility constraints between LEO satellites and GEO satellites are analyzed to derive the inter-satellite link building matrix and complete the inter-satellite link situational awareness. Secondly, an ANN-based energy detection (ANN-ED) algorithm is proposed based on the traditional energy detection algorithm and artificial neural network. The ANN module is used to determine the spectrum state and optimize the traditional energy detection algorithm. GEO satellites are used to fuse the information sensed by LEO satellites and then give the spectrum decision, thereby realizing the inter-satellite spectrum state sensing. Finally, the sensing quality is evaluated by the analysis of sensing delay and sensing energy consumption. The simulation results show that our proposed algorithm has lower complexity, the sensing delay and sensing energy consumption compared with the traditional energy detection method.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1694-1699
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• 2003

A windshield wiper system plays a key part in assuring the driver's safety during the rainfall. However, because the quantity of rain and snow vary irregularly according to time and the velocity of the automobile, a driver changes wiper speed and interval from time to time to secure enough visual field in the traditional windshield wiper system. Because a manual operation of windshield wiper distracts driver's sensitivity and causes inadvertent driving, this is becoming a direct cause of traffic accidents. Therefore, this paper presents the basic architecture of a vision-based smart windshield wiper system and a rain sensing algorithm that regulates speed and interval of the windshield wiper automatically according to the quantity of rain or snow. This paper also introduces a fuzzy wiper control algorithm based on human's expertise, and evaluates the performance of the suggested algorithm in an experimental simulator.