• 천문학논총
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• 제11권1호
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• pp.1-26
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• 1996

We have built a near-infrared imaging camera with a PtSi array detector manufactured by the Mitsubishi Company. The PtSi detector is sensitive in the wavelength range 1 to $5{\mu}m$. Quantum efficiency of PtSi is much lower than that of InSb and HgCdTe types. However, the PtSi array has advantages over the latter ones: (i)The read-out noise is very low; (ii)the characteristics of the array elements arc uniform and stable; (iii)it is not difficult to make a large PtSi array; and (iv) consequently the price is affordably low. The array used consists of $512{\times}512$ pixels and its size is $10.2\;mm{\times}13.3\;mm$. The filter wheel of the camera is equipped with J, H, K filters, and an aluminum plate for measuring the dark noise. The dewar is cooled with liquid nitrogen. We have adopted a method of installing the clock pattern and the observing softwares in the RAM, which Gill he easily used for other systems. We have developed a software with a pull-down menu for operating the camera and data acquisition. The camera has been tested by observing $\delta$ Orionis.

• 한국전자통신학회논문지
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• 제13권4호
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• pp.705-712
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• 2018

위상배열안테나는 빔 조향 각도에 따라 방사 특성이 변화한다. 모노펄스 추적 시스템은 합 및 차신호의 방사특성을 기반으로 추정 각을 산출하는 시스템이다. 따라서 위상배열안테나를 이용한 모노펄스 추적 시스템의 경우, 빔 조향 각도에 따라 모노펄스 비율 곡선이 변화하기 때문에 추적정확도가 낮아지는 문제가 발생한다. 단일 채널 모노펄스 시스템의 경우, 시스템 구성 변수의 변화를 통해 모노펄스 비율 곡선이 제어된다. 본 논문에서는 빔 조향 각도에 모노펄스 시스템 구성 변수를 적응형으로 제어하는데 참조할 수 있는 간소화된 수식을 제시하였다. 제시된 수식은 빔 조향 각도뿐만 아니라 방사 특성에 영향을 주는 위상배열안테나 설계 변수에 대응하여 균일한 모노펄스 비율 곡선을 유도할 수 있다.

• Ocean and Polar Research
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• 제37권3호
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• pp.179-188
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• 2015

This study was carried out to determine the optimal number of ARGO floats in the East Sea in order to maximize their applications. The dominant spatio-temporal scale, size of the domain, and the typical float lifetimes in the East Sea were taken into consideration. The mean spatial de-correlation scale of temperature on isobaric surfaces reaches about 60 km. The minimum necessary number of floats is about 82 on average in order to secure independent ARGO profiles with the de-correlation scale. Considering the float lifetimes, about 27 floats per year should be deployed to maintain the 82 ARGO float array every year. To obtain spatially uniform distribution of ARGO float data, mean residence time and dispersion rate (basin area/residence time) of ARGO floats were evaluated in each basin of the East Sea. A faster (slower) dispersion rate requires more (less) ARGO floats to maintain the spatially uniform number of floats. According to the analysis, it is likely that the optimal ratio of the number of floats for each basin is 1:2:4 corresponding to Ulleung Basin:Yamato Basin:Japan Basin. In order to maintain relatively uniform ARGO observing networks, it is necessary to establish a long-term plan for deployment strategy based on float pathways and the dispersion rate parameters estimated by using currently active ARGO float trajectory data as well as reanalysis data.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.922-925
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• 2003

The interest of self-organization materials that have uniform and regular structure in nano scale has been grown due to their utilization in various fields of nanotechnology. An attractive candidate among these materials is anodic aluminum oxide film, which are formed by anodization of aluminum in an appropriate acid solution. The anodic aluminum oxide film has a highly ordered porous structure with very uniform and nearly parallel pores that can be organized in an almost precise close-packed hexagonal structure. In this study, we attempt to make Au dot arrays, which were fabricated using anodic aluminum oxide film as an evaporation mask. The Au dot arrays have a uniform sized dots and spacing to its neighbors and the average diameter of Au dots is about 60 nm corresponding to them of the mask.

• 한국재료학회지
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• 제30권12호
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• pp.701-708
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• 2020

Irradiation of the metal nanoparticles causes local plasmon resonance in a specific wavelength band, which can improve the absorption and scattering properties of a structure. Since noble metal nanoparticles have better resonance effects than those of other metals, it is easy to identify plasmonic reactions and this is advantageous to find the optical tendency. Compared to having a particle gap or randomly arranged particle structures, densely and evenly packed structures can exhibit more uniform optical properties. Using the uniform properties, the structure can be applied to optical filtering applications. Therefore, in this paper, validation tests about metal nanoparticles and thin film structures are conducted for more accurate analysis. The optical properties of monolayer and bilayer noble metal nanoparticle structures with different diameters, packed in a uniform array, are investigated and their optical trends are analyzed. In addition, a thin film structure under identical conditions as metal nanoparticle structure is evaluated to confirm the improved optical characteristics.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1992년도 학술논문발표회 논문집 제11권 1호
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• pp.123-126
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• 1992

A new class of data transformation matri is introduced for estimation of angles of arrivals by the rank reduction of multiple wideband sources. The proposed unitary focusing matri minimizes the average of the squared norm of focusing error over the angles of interest without a priori knowledge of source locations. The merit that result as a consequence is a lower resolution threshold. These matrices can be applied to the case of the multigroup sources. Simulations and the comparison of statistical performance are compared with the algorithms (especially, spatial resampling method) which does not require the pre-estimation.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.639-642
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• 1998

This paper proposes a new wide-band beamforming which has guassian weighting. For the prupose of measurement this beam is formed by using all sensors toghether, not octave-by-octave. Weighting is applied to each sensor before time-delay compensation as a frequency-dependent function. As the resutls of the simulation of the proosed algorithm for nested linear array having 17 sensors for each octave, it is confirmed that beam can be formed with all sensors together and uniform directivity index can be achieved by proposed algorithm.

• Journal of applied mathematics & informatics
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• 제29권1_2호
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• pp.407-415
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• 2011

We establish strong laws of large numbers for weighted sums of arrays of negatively associated random variables under the condition of h-integrability and suitable conditions on the array of weights.

• Journal of information and communication convergence engineering
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• 제5권1호
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• pp.12-16
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• 2007

In this paper, a new method is proposed for tracking the direction-of-arrival (DOA) of the wideband moving source incident on uniform linear array sensors. DOA is estimated by focusing transformation matrices. To update focusing matrices along with new data snap shots, we use the FAST (Fast Approximate Subspace Tracking) method. Present focusing matrices are constructed by previous signal and its orthogonal basis vectors as well as present signal and its orthogonal basis vectors, which are the left and right singular vectors of the inner product of two approximated matrices. Simulation results are shown to illustrate the performance of the proposed method.

• 한국항행학회논문지
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• 제20권4호
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• pp.367-373
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• 2016

우리는 도래각 (DoA; direction of arrival) 추정 방법 중 하나인 서로소 배열 기반의 프로퍼게이터 방법을 개선시키는 알고리즘을 제안한다. 서로소 배열 기반의 프로퍼게이터 방법은 특이값 분해없이 도래각을 추정하는 방법으로 서로소 배열 기반의 MUSIC에 비하여 현저히 낮은 복잡도를 지녔으나, 다소 저하된 도래각 추정 성능을 보인다. 우리는 이러한 성능 저하의 원인 중 하나로 잡음의 파워 스펙트럼 밀도를 포함하고 있는 신호의 자기상관행렬의 대각 성분이 사용되고 있지 않음에 있음을 파악하고, 잡음의 파워 스펙트럼 밀도가 장기간에 걸쳐 추정이 가능하다는 사실에 착안하여 신호의 자기상관행렬의 대각 성분을 사용하는 도래각 추정 방법을 제안한다. 우리는 시뮬레이션을 통해 우리가 제안한 방법이 기존의 서로소 배열 기반의 프로퍼게이터 방법보다 연산량을 4배정도 증가시키지만 탐지확률 95% 기준 하에 신호대 잡음비를 1.5dB, 도래각 분해능을 $0.7^{\circ}$ 만큼 개선시켜 그 성능이 서로소 배열 기반의 MUSIC에 보다 근접함을 관찰한다.