• Geophysics and Geophysical Exploration
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• v.6 no.4
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• pp.180-186
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• 2003

We have developed an one-dimensional (ID) inversion program that can invert multiple frequency small-loop EM data from horizontal coplanar (HCP) and vertical coplanar (VCP) configurations. The inverse problem is solved using least-squares method with active constraint balancing (ACB) method and Jacobian matrix is calculated analytically. Tests using synthetic data from simple ID models indicate that conductivity and depth of each layer can be estimated properly when both real and imaginary data are used together.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.5
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• pp.77-83
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• 2004

Based on a Phased array technology, 2-dimensionally steerable base station antenna was developed at cellular band. The antenna, which consists of 2 by 5 radiating element, can provide 14㏈i gain with half power beam width of 0$^{\circ}$and 13$^{\circ}$ in horizontal and vertical plane respectively. It has beam scanning range of 0$^{\circ}$to 12$^{\circ}$in vertical down tilting and -15$^{\circ}$to 15$^{\circ}$in horizontal steering. The beam control Performance of antenna was verified by DM measurement on field trial.

• The Journal of the Acoustical Society of Korea
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• v.19 no.3
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• pp.72-76
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• 2000

A calibration technique is proposed to improve the performance of 2-D towed array shape estimation using the Kalman filter. In the case of using displacement sensors, 2-D hydrophone positions estimated by the Kalman filter are calculated by assuming that the adjacent hydrophones are horizontally equi-spaced so that maximum distance is equal to the array length. The assumption causes errors in estimating hydrophone positions. The proposed technique using linear model approximation or spline interpolation can reduce the errors by exploiting the fact that the whole length of array is preserved whatever the array shape is. The numerical experiments show that the proposed method is very effective.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.11
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• pp.719-726
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• 2017

An experimental study was performed to investigate the combined effects of the pitch and heat flux of nearby tubes on boiling in a pool as well as the heat transfer from a horizontally-installed tube bundle. For this test, two smooth stainless steel tubes (19 mm outside diameter) were used, and the water was at atmospheric pressure. The pitch of these tubes was varied between 28.5 mm and 95 mm, and the heat flux of the nearby tube altered between 0 and $90kW/m^2$. Enhancements in heat transfer were clearly observed when the heat flux of the nearby tube increased while the heat flux of the test section remained below $40kW/m^2$. The tube pitch was found to have a negligible effect on heat transfer when the pitch was greater than four times larger than the tube diameter. The circulating flow, convective flow, and liquid agitation were all seen to enhance heat transfer; however, the interaction between the flow and coalescence of bubbles was detrimental to heat transfer.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.5A
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• pp.284-293
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• 2003

Location service is usually provided by the GPS method using satellites. In the next generation mobile communication systems which use smart antennas, location service can be accomplished using direction of arrival (DOA) estimation techniques. In this paper, we propose a DOA estimation technique for the location service of the next generation mobile communication systems and investigate the validity of the proposed technique through computer simulation. First, DOA estimation problems of distributed sources are considered using vortical and horizontal array processors which are orthogonal to each other. The DOA of the elevation angle is estimated by the vertical array processor and then that of the azimuth angle is estimated by the horizontal array processor. Finally, the procedures of the location service for specific signal sources using three smart antennas are exhibited by computer simulation to show that the proposed DOA estimation technique can be used for the location service in the next generation mobile communication systems.

• Korean Journal of Ichthyology
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• v.20 no.2
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• pp.97-104
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• 2008

Comparative study of retinal structure in two Korean endemic freshwater fishes, Zacco koreanus and Pseudobagrus koreanus, was carried out by light and scanning electron microscopy. In the visual cell layer comprised of cone cells and rod cells, the cone cells showed a distinct difference between both species. Z. koreanus had two types of cone cells, single cone cells including a long single and short single cone cells, and double cone cells, whereas P. koreanus had only one type of single cone cells having no its short single and long single cones. Meanwhile, the cone cells of Z. koreanus were arranged in more compact-rowed pattern, but it was more loose and irregular in P. koreanus. Based on field observation, Z. koreanus is mainly a epipelagic or sometimes benthopelagic and a diurnal fish with a round and large eye, while P. koreanus is a demersal and nocturnal fish with an oval and small eye. Therefore, the difference in the retinal structure of two species seems to be closely related to their ecological habitats.

• The Journal of the Acoustical Society of Korea
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• v.35 no.6
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• pp.427-435
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• 2016

Array Gain (AG) is a metric to measure the performance of an array of acoustic sensors. AG is affected by the configuration of array, frequency and array element spacing, and the directivity of the ambient noise. In this paper, an algorithm to calculate AG based on the spatial coherence is used, and the results are verified through sea-going experiment. The method using the spatial coherence can be used to consider the arbitrary shape of an array and directionality of ambient noise. In the sea-going experiment, the towed source was used to transmit the Continuous Wave (CW), and was received at the horizontal line array on the seabed. The ambient noise was measured between the source transmission. The experimental AG was calculated from the SNR (Signal to Noise Ratio) of single sensor and an array of sensors. Finally, the predicted AG is shown to agree with the experimental value of AG.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.207-207
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• 2012

진공단열재는 폴리우레탄 폼 대비 10배 이상의 단열성능을 갖는 고효율 단열재로서 고차단성 필름 봉투 내부에 무기 소재를 진공감압시켜 대류에 의한 열전달을 최소화시킨 차세대 단열재이다. 특히 진공단열재에 있어 열전달의 경로는 전도에 의한 효과가 가장 크므로, 진공단열재 내부의 Glass Fiber 심재의 최적화 설계에 따라 단열 성능을 극대화 시킬 수 있다. 이에, 본 연구에서 GLass Fiber의 배열에 따른 성능 비교 평가를 통해, 전도의 특성을 최소화 시킬 수 있는 Glass Fiber의 배열 및 다층 적층 구조를 통해 성능 개선 효과를 고찰 하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.4
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• pp.712-717
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• 2006

In this paper, a new integral imaging method with horizontal parallax only is proposed by modified use of elemental images pickuped from conventional integral imaging. The modified elemental images are obtained by magnifying single horizontal elemental image vertically and from which 3D images could be reconstructed. The proposed method can provide us large reduction of transmission information data for elemental images by eliminating the vertical parallax. The feasibility of our approach is experimentally demonstrated and its results are presented.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.9
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• pp.803-815
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• 2000

최근 처리해야 하는 정보의 양의 급속히 배가됨에 따라 디스크 배열(disk array) 시스템에서 사용하는 디스크의 수가 증가되는 경향을 보이고 있다. 그러나 많은 수의 디스크를 이용하여 디스크 배열을 구성하게 되면 디스크 오류 발생 확률을 높이는 결과로 이어지게 된다. 이 논문에서는 많은 수의 디스크를 사용하는 환경에서도 높은 신뢰성을 제공하기 위하여 DH(Diagornal-Horizontal) 기법이라 불리는 두가지 형태의 이중 패리티 배치 기법들을 제안한다 제안한 기법들은 사선 패리티와 수평 패리티를 인코딩하여 이용함으로써 디스크 배열에서 이중 디스크 오류의 복구가 가능하다. DH 기법들의 특징은 알고리즘이 단순하고, N을 임의의 소수라고 할 때 N 또는 N+1개의 디스크를 기반으로 쉽게 구현할 수 있다. 기본적으로 제안하는 기법들은 검사정보 저장을 위해 최적의 디스크 공간을 사용하고, 인코딩이나 디코딩 과정에서 단지 XOR 연산만을 필요로 하기 때문에 하드웨어의 수정 없이 기존의 디스크 배열 시스템에 쉽게 응용할 수 있다. 더욱이 치명적 오류를 방지할 수 있는 두 오류 디스크에 대한 복구 시간은 디코딩에서의 XOR 연산수를 최소화함으로써 신속하게 처리할 수 있다. 결과적으로 제안하는 기법들은 디스크 배열 시스템에서의 치명적 오류 확률을 낮출 수 있는 효과적인 방법이다.