• 천문학회지
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• 제50권1호
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• pp.7-20
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• 2017

We carry out the study of $850{\mu}m$ sources in a part of the XMM-LSS field. The $850{\mu}m$ imaging data were obtained by the SCUBA-2 on the James Clerk Maxwell Telescope (JCMT) for three days in July 2015 with an integration time of 6.1 hours, covering a circular area with a radius of 15'. We choose the central area up to a radius of 9'.15 for the study, where the noise distribution is relatively uniform. The root mean square (rms) noise at the center is 2.7 mJy. We identify 17 sources with S/N > 3.5. Differential number count is estimated in flux range between 3.5 and 9.0 mJy after applying various corrections derived by imaging simulations, which is consistent with previous studies. For detailed study on the individual sources, we select three sources with more reliable measurements (S/N > 4.5), and construct their spectral energy distributions (SEDs) from optical to far-infrared band. Redshift distribution of the sources ranges from 0.36 to 3.28, and their physical parameters are extracted using MAGPHYS model, which yield infrared luminosity $L_{IR}=10^{11.3}-10^{13.4}L_{\odot}$, star formation rate $SFR=10^{1.3}-10^{3.2}M_{\odot}yr^{-1}$ and dust temperature $T_D=30-53K$. We investigate the correlation between $L_{IR}$ and $T_D$, which appears to be consistent with previous studies.

• 한국통신학회논문지
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• 제38B권10호
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• pp.843-850
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• 2013

인지 라디오 시스템은 1차 시스템이 사용 중인 주파수를 공유함으로써 지역 당 주파수 이용효율을 향상시킬 수 있는 중요한 기술로 인식되고 있다. 본 논문에서는 2차 시스템이 1차 시스템에 간섭을 미치지 않으며 주파수를 공유할 수 있는 보다 능동적인 간섭 관리 기법을 제안한다. 제안된 프로토콜을 통해 2차 사용자는 1차 시스템의 간섭 채널 정보 및 송 수신 필터 정보를 획득하고 이를 이용하여 프리코딩 행렬을 계산한다. 이때 2차 시스템으로부터의 간섭은 1차 시스템의 사용되지 않는 부채널로 모이기 때문에 1차 시스템은 추가적인 연산 없이 자동적으로 간섭을 제거한다. 그리고 2차 시스템은 백색화 정합 필터를 통해 1차 시스템으로부터의 간섭을 제거함으로써 스펙트럼 효율을 향상시킨다. 전산모의실험을 통해 제안된 기법이 1차 시스템에 간섭을 미치지 않는 동시에 2차 시스템의 성능을 향상시키고, 2차 시스템의 수가 증가하더라도 1차 시스템의 성능이 저하되지 않음을 보였다.

• 한국전자통신학회논문지
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• 제9권5호
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• pp.555-560
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• 2014

본 논문에서 850nm~1000nm 파장대역에서 레이저를 검출하기 위한 고감도 실리콘 포토다이오드를 제조하고 전기적 및 광학적 특성을 분석하였다. 소자의 크기는 $5000{\mu}m{\times}2000{\mu}m$이며 두께는 $280{\mu}m$로 제조하여 TO-5 형태로 패키징 하였다. 전기적 특성으로 암전류는 5V 역 전압 일 때 0.1nA의 값을 나타내었으며 정전용량은 0V일 때 1kHz 주파수 대역에서 32.5pF와 200kHz 주파수 대역에서 32.4pF로 적은 정전용량의 값을 나타내었다. 또한 출력신호의 상승시간은 10V의 전압일 때 20.92ns로 고속 응답특성을 확인하였다. 광학적 특성으로는 890nm에서 최대 0.57A/W의 분광감응도를 나타내었고 1000nm에서는 0.37A/W로 감소한 분광감응도를 나타내고 있지만 870nm~920nm 파장대역에서는 비교적 우수한 분광감응도를 나타내었다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.337-342
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• 2006

The use of GPS receiver at outer space becomes common in low earth orbit. The KOrea Multi-Purpose SATellite-1 (KOMPSAT-1) which was launched in December 1999 has used GPS receiver's navigation solution to perform the Orbit Determination (OD) in the ground. At the circumstance of using only one ground station, the Orbit Determination using GPS receiver is good method. Because the accuracy of navigation solution acquiring directly from GPS receiver is not enough in satellite application such as map generation, post-processing concepts such as the Precise Orbit Determination (POD) are applied to satellite data processing to improve satellite position accuracy. The POD uses GPS receiver's raw measurement data instead of GPS receiver's navigation solution. The KOrea Multi- Purpose SATellite-2 (KOMPSAT-2) system newly uses the POD technique for large scale map generation. The satellite was launched in the end of July 2006. The satellite sends high resolution images in panchromatic band and multi-spectral bands to the ground. The satellite system uses GPS receivers as source of time synchronization and command reference in the satellite, provider of navigation solution for the OD, and provider of raw measurement data for the POD. In this paper, mechanical configuration and operations of the GPS receiver will be presented. The GPS data characteristics of the satellite such as time synchronization, command reference, the OD using GPS receiver's navigation solution, and the POD using GPS receiver's raw measurement data will be presented and analyzed. The enhancement of performance compared with it of the previous satellite will also be analyzed.

• 한국표면공학회지
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• 제53권1호
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• pp.9-14
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• 2020

CuS (copper sulfide) thin films having the same thickness of 100nm were deposited on the glass substrates using by radio frequency (RF) magnetron sputtering method. RF powers were applied as a process variable for the growth of CuS thin films. The structural and optical properties of CuS thin films deposited under different power conditions (40-100W) were studied. XRD analysis revealed that all CuS thin films had hexagonal crystal structure with the preferential growth of (110) planes. As the sputtering power increased, the relative intensity of the peak with respect to the (110) planes decreased. The peaks of the two bands (264cm^-1 and 474cm^-1) indicated in the Raman spectrum exactly matched the typical spectral values of the covellite (CuS). The size and shape of the grains constituting the surface of the CuS thin films deposited under the power condition ranging from 40W to 80W hardly changed. However, the spacing between crystal grains tended to increase in proportion to the increase in sputtering power. The maximum transmittance of CuS thin films grown at 40W to 80W ranged from 50 % to 51 % based on 580nm wavelength, and showed a relatively small decrease of 48% at 100W. The band gap energy of the CuS thin films decreased from 2.62eV (at 40W) to 2.56eV (at 100W) as the sputtering power increased.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.453-454
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• 2003

Most research materials (data), which are used for the study of digital mapping and digital elevation model (DEM) in the field of Remote Sensing and Aerial Photogrammetry are aerial photographs and satellite images. Additionally, they are also used for National land mapping, National land management, environment management, military purposes, resource exploration and Earth surface analysis etc. Although aerial photographs have high resolution, the data, which they contain, are not used for environment exploration that requires continuous observation because of problems caused by its coastline, as well as single - spectral and long-term periodic image. In addition to this, they are difficult to interpret precisely because Satellite Images are influenced by atmospheric phenomena at the time of photographing, and have by far much lower resolution than existing aerial photographs, while they have a great practical usability because they are mulitispectral images. The PKNU 2 is an aerial photographing system that is made to compensate with the weak points of existing aerial photograph and satellite images. It is able to take pictures of very high resolution using a color digital camera with 6 million pixels and a color infrared camera, and can take perpendicular photographs because PKNU 2 system has equipment that makes the cameras stay level. Moreover, it is very cheap to take pictures by using super light aircraft as a platform. It has much higher resolution than exiting aerial photographs and satellite images because it flies at a low altitude about 800m. The PKNU 2 can obtain multispectral images of visible to near infrared band so that it is good to manage environment and to make a classified diagram of vegetation.

• 한국항행학회논문지
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• 제17권6호
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• pp.693-699
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• 2013

본 논문에서는 ITU-R M.1842-1 표준 권고안 Annex1에 따르는 ${\pi}/4$-DQPSK 모뎀에 대해 분석하고 시뮬레이션을 수행하였다. 우선 VHF 대역의 해상 이동통신에 대한 표준 및 기술동향을 소개하였다. Annex1에 제시된 ${\pi}/4$-DQPSK 모뎀은 25KHz의 대역폭에서 28.8Kbps 비트전송률을 제공하도록 제시되어 있다. 송수신기에서 RRC필터를 채용하는 ${\pi}/4$-DQPSK 모뎀의 시뮬레이션 프로세스에 대해 설명하고, 다양한 시뮬레이션 결과(시간영영 신호파형, 성좌도, 롤오프 팩터에 따른 전력스펙트럼밀도, Eye 다이어그램)들과 모뎀의 BER 성능을 제시하였다. 시뮬레이션 결과로부터, RRC 필터의 롤오프 팩터에 의해서 SNR에 따른 BER 성능에 미치는 영향이 다름을 확인하였고, 설계한 시뮬레이션 모델이 ITU-R M.1842-1 권고안에 제시된 스펙트럼 마스크 요구사항을 만족함을 알 수 있었다.

• 대한원격탐사학회지
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• 제14권2호
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• pp.149-164
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• 1998

본 연구에서는 지구자원탐사용 인공위성 화상데이터중에서 공간해상력이 우수한 RS-1C PAN 데이터와 Landsat TM 데이터를 중합(merging)하는데 있어서, 어떤 중합방법이 유효한지를 밝히고자 하였다. 각기 다른 두 화상데이터를 중합하기 위하여 IHS, PCA, HPF, ratio enhanoement 및 LUT방법을 적용하였으며, 이 방법들에 의하여 얻어진 화상들의 평가에 있어서는, 분광반사특성 보존성부분과 공간해상력 부분으로 나누어서 평가하였다. 그 결과 ratio enhancement방법이 분광반사특성의 보존성에 있어서 가장 좋은 결과를 나타내었다. 전체적인 화상의 시각적 판독평가에 있어서는 PCA방법이 다른 방법에 비하여 공간해상력이 우수한 것으로 파악되었으며 다음으로 HPF, ratio enhancement, IHS, LUT방법의 순으로 나타났다.

• Smart Structures and Systems
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• 제16권1호
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• pp.141-162
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• 2015

The magneto-rheological visco-elastomer (MRVE) is used as a smart core to control the stochastic micro-vibration of a sandwich plate with supported mass. The micro-vibration response of the sandwich plate with MRVE core and supported mass under stochastic support motion excitations is studied and compared to evaluate the vibration suppression capability. The effects of the supported mass and localized magnetic field on the stochastic micro-vibration response of the MRVE sandwich plate are taken into account. The dynamic characteristics of the MRVE core in micro-vibration are described by a non-homogeneous complex modulus dependent on vibration frequency and controllable by applied magnetic fields. The partial differential equations for the coupled transverse and longitudinal motions of the MRVE sandwich plate with supported mass are derived from the dynamic equilibrium, constitutive and geometric relations. The simplified ordinary differential equations are obtained for the transverse vibration of the MRVE sandwich plate under localized magnetic fields. A frequency-domain solution method for the stochastic micro-vibration response of sandwich plates with supported mass is developed based on the Galerkin method and random vibration theory. The expressions of frequency-response functions, response power spectral densities and root-mean-square velocity responses of the plate in terms of the one-third octave frequency band are obtained for micro-vibration evaluation. Finally, numerical results are given to illustrate the large response reduction capacity of the MRVE sandwich plate with supported mass under stochastic support motion excitations, and the influences of MRVE parameters, supported mass and localized magnetic field placement on the micro-vibration response.

• Smart Structures and Systems
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• 제19권1호
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• pp.1-10
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• 2017

The operation of subway trains induces secondary structure-borne vibrations in the nearby underground spaces. The vibration, along with the associated noise, can cause annoyance and adverse physical, physiological, and psychological effects on humans in dense urban environments. Traditional tethered instruments restrict the rapid measurement and assessment on such vibration effect. This paper presents a novel approach for Wireless Smart Sensor (WSS)-based autonomous evaluation system for the subway train-induced vibrations. The system was implemented on a MEMSIC's Imote2 platform, using a SHM-H high-sensitivity accelerometer board stacked on top. A new embedded application VibrationLevelCalculation, which determines the International Organization for Standardization defined weighted acceleration level, was added into the Illinois Structural Health Monitoring Project Service Toolsuite. The system was verified in a large underground space, where a nearby subway station is a good source of ground excitation caused by the running subway trains. Using an on-board processor, each sensor calculated the distribution of vibration levels within the testing zone, and sent the distribution of vibration level by radio to display it on the central server. Also, the raw time-histories and frequency spectrum were retrieved from the WSS leaf nodes. Subsequently, spectral vibration levels in the one-third octave band, characterizing the vibrating influence of different frequency components on human bodies, was also calculated from each sensor node. Experimental validation demonstrates that the proposed system is efficient for autonomously evaluating the subway train-induced ambient vibration of underground spaces, and the system holds the potential of greatly reducing the laboring of dynamic field testing.