• Journal of information and communication convergence engineering
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• 제12권2호
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• pp.97-103
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• 2014

In spectrum sensing, there is a tradeoff between the probability of missed detection and the probability of a false alarm according to the value of the sensing threshold. Therefore, it is important to determine the sensing threshold suitable to the environment of cognitive radio networks. In this study, we consider a cognitive radio-based ad hoc network where secondary users directly communicate by using the same frequency band as the primary system and control their transmit power on the basis of the distance between them. First, we investigate a condition in which the primary and the secondary users can share the same frequency band without harmful interference from each other, and then, propose an algorithm that controls the sensing threshold dynamically on the basis of the transmit power of the secondary user. The analysis and simulation results show that the proposed sensing threshold control algorithm has low probabilities of both missed detection and a false alarm and thus, enables optimized spectrum sharing between the primary and the secondary systems.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.568-574
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• 2004

On-line phase tracking of an extrinsic Fabry-Perot interferometer (EFPI) and experimental vibration control of a composite beam with a sensing-patch are investigated. We propose a sensing-patch for the compensation of the interferometric non-linearity. In this paper, a sensing-patch that comprises an EFPI and a piezo ceramic(PZT) is fabricated and the characteristics of the sensing-patch are experimentally investigated. A simple and practical logic is applied for the real-time tracking of optical phase of an interferometer. Experimental results show that the proposed sensing-patch does not have the non-linear behavior of conventional EFPI and hysteresis of piezoelectric material. Moreover, it has good strain resolution and wide dynamic sensing range. Finally, the vibration control with the developed sensing-patch has been performed using Fuzzy logic controller, and the possibility of sensing-patch as a sensoriactuator is considered.

• Journal of electromagnetic engineering and science
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• 제12권3호
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• pp.196-202
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• 2012

Spectrum sensing is one of the most important functions in cognitive radio systems. In this paper, we focus on reducing the sensing time in a cooperative spectrum sensing paradigm. In the proposed scheme, a sequential detection technique is employed to provide a robust and quick detection system. Each of the secondary users measures the log-likelihood probability of the received signals and then sequentially reports to the base station. Here, the maximum ratio combining (MRC) technique is employed to reduce the average sample number (ASN) in order to reduce the sensing time. This proposed scheme is analyzed and simulated to illustrate the performance in comparison with the other given methods. Analysis and simulation are provided to validate the proposed method.

• Journal of information and communication convergence engineering
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• 제9권4호
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• pp.391-395
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• 2011

Cognitive radio (CR) technique is a useful tool for improving spectrum utilization by detecting and using the vacant frequency bands while avoiding interference to the primary user. The sensing performance in a CR network can be improved by allowing some CR users to perform cooperative spectrum sensing. In this paper, we propose a new sensing algorithm that utilizes an adaptive energy threshold for cooperative spectrum sensing in which a changeable energy threshold is adopted by the CR users for improving local sensing performance. Through the proposed scheme, the reliability of global decision can be enhanced mainly due to the improvement in local sensing performance.

• 대한원격탐사학회지
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• 제23권5호
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• pp.439-445
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• 2007

Stereoscopic viewing is an efficient technique for not only computer vision but also remote sensing applications. Generally, stereo pair obtained at the same time is necessary for 3D viewing, but it is possible to synthesize a stereomate suitable for stereo view with a single image and disparity-map. There have been researches concerning the generation of the synthetic stereomate from remote sensing imagery. However it is hard to find researches concerning the restoration of occlusion in stereomate. In this paper, we generated synthetic stereomates from remote sensing images, focused on the occlusion restoration. In order to figure out proper restoration methods depending on the spatial resolution of remote sensing imagery, we tested several methods including general interpolation and inpainting technique, then evaluated the results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권3호
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• pp.1199-1212
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• 2019

This paper proposes two wideband spectrum sensing approaches: (i) method A, the cumulative sum (CUSUM) algorithm with short-time Fourier transform, taking advantage of the time-frequency analysis for wideband spectrum. (ii)method B, the quickest spectrum sensing with short-time Fourier transform and compressed sensing, shortening the time of perception and improving the speed of spectrum access or exit. Moreover, method B can take advantage of the sparsity of wideband signals, sampling in the sub-Nyquist rate, and it is more suitable for wideband spectrum sensing. Simulation results show that method A significantly outperforms the single serial CUSUM detection for small SNRs, while method B is substantially better than the block detection based spectrum sensing in small probability of the false alarm.

• 항공우주정책ㆍ법학회지
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• 제35권1호
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• pp.203-319
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• 2020

본 논문에서는 위성원격탐사의 제도적 정비와 향후 입법 과정에서의 사전 참고로서 이와 관련한 법적 문제들을 검토해 보았다. 위성원격탐사와 관련해서는 광범위한 법적 논점들이 제기될 수 있으나, 본 논문에서는 위성원격탐사에 관한 운용규제와 위성데이터의 거래규제 문제들에 논의의 중심을 두고, 우리법상의 본격적인 입법론적 방안을 위한 선행 연구로서, 비교법적 검토를 시도하였다. 먼저 위성원격탐사와 관련한 국제우주법 체제를 우주조약 체제와 UN원격탐사원칙으로 구분하여 개관하였고, 위성원격탐사에 관한 주요국의 입법례를 살펴보았다. 입법 연혁에 따라 미국, 캐나다, 독일, 프랑스, 일본의 순서로 각 법규들의 성립 배경과 구체적인 입법적 구조 및 주요 내용 등을 구체적으로 분석해 보았다. 이후, 비교법적 검토를 토대로, 위성원격탐사 법제 정비와 관련한 몇 가지 논점들을 상정하여, 시사점 내지 개별적인 의견 등을 제시하였다. 2020년 현재까지 '국내 입법'으로 위성원격탐사에 관한 법제 정비를 시도한 국가들로는 미국, 캐나다, 독일, 프랑스, 일본이 유일하다. 이들 국가들은 자체적인 위성 운용시스템과 위성데이터보호에 관한 입법적 체계를 마련하여, 위성원격탐사에 관한 법률적 규율을 실시하고 있다. 우리나라도 2010년부터 '천리안 위성'을 운용하며 해양·기상 관측을 행하고 있는 위성원격탐사 수행국이라 할 수 있는데, 아직 그와 관련한 법제는 몇 가지의 정부 훈령을 제외하고는 마련되지 않은 상황이다. 그러나 위성데이터의 활용 플랫폼이 큰 폭으로 변화하고 있고, 소형 관측위성의 개발도 고려할 수 있는 지금, 데이터에 대한 접근성과 활용도는 향후 큰 폭으로 상승할 것이다. 이러한 점들을 고려할 때, 우리나라에서도 관측위성시스템과 위성데이터를 종합적으로 관리할 수 있는 입법 추진이 필요할 것으로 보인다. 특히 국가안보와 정보보안의 측면에서도 위성데이터에 대한 일정한 보급규제가 제도적으로 필요할 것이다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.21-21
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• 2004

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.171-171
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• 2003

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.441-444
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• 2008

This paper describes the development of a circularly polarized microstrip antenna, as a part of the Circularly Polarized Synthetic Aperture Radar (CP-SAR) sensor which is currently under developed at the Microwave Remote Sensing Laboratory (MRSL) in Chiba University. CP-SAR is a new type of sensor developed for the purpose of remote sensing. With this sensor, lower-noise data/image will be obtained due to the absence of depolarization problems from propagation encounter in linearly polarized synthetic aperture radar. As well the data/images obtained will be investigated as the Axial Ratio Image (ARI), which is a new data that hopefully will reveal unique various backscattering characteristics. The sensor will be mounted on an Unmanned Aerial Vehicle (UAV) which will be aimed for fundamental research and applications. The microstrip antenna works in the frequency of 1.27 GHz (L-Band). The microstrip antenna utilized the proximity-coupled method of feeding. Initially, the optimization process of the single patch antenna design involving modifying the microstrip line feed to yield a high gain (above 5 dBi) and low return loss (below -10 dB). A minimum of 10 MHz bandwidth is targeted at below 3 dB of Axial Ratio for the circularly polarized antenna. A planar array from the single patch is formed next. Consideration for the array design is the beam radiation pattern in the azimuth and elevation plane which is specified based on the electrical and mechanical constraints of the UAV CP-SAR system. This research will contribute in the field of radar for remote sensing technology. The potential application is for landcover, disaster monitoring, snow cover, and oceanography mapping.