• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.226-227
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• 2007

유도결합 플라즈마(ICP)에서 안테나의 특정부분에 유도자기장을 보강 또는 상쇄 시키는 형태의 두 안테나를 고안하였다. 플라즈마 밀도와 전자온도, 플라즈마 전위, 전자에너지 분포함수 등의 플라즈마 파라미터들로 그 특성을 비교하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.415-421
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• 2005

The radiating or receiving characteristics of array elements (i.e., antennas) are changed from those of isolated elements due to mutual coupling effects and the array performance becomes different from those originally designed by assuming isolated elements. The effects of mutual coupling on the performance of a rectangular array with triangular grid geometry of dipoles above a ground plane are discussed with respect to element pattern. The concept of element gain function is used to examine the effects of mutual coupling on the array performance in terms of sidelobe level in the uniformly spaced and space-tapered rectangular arrays with triangular grid geometry of dipoles. It was shown that the sidelobe performance improved in the space-tapered array compared to the uniformly spaced array in the presence of mutual coupling effects. Computer simulation results are presented.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.2
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• pp.188-202
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• 1997

The seasonal variability of the sea surface winds over the last Sea of Korea (Japan Sea) is investigated by means of empirical orthogonal function (EOF) analysis. The combined representation of fields of three climatic variables by empirical orthogonal functions is discussed. The eigenvectors are derived from daily sea level pressure, wind speed and 10-day mean sea surface temperature (SST) during 15 years $(1978\~1992)$. The spatial patterns of the mean pressure are characterized by the high pressure in the western part and the low pressure in the eastern part. The spatial distribution of the standard deviation (SD) of pressure are characterized by max SD of 6.6 mb near the Vladivostok, and minima along the coast of the Japan. In Vladivostok, the maxima of SD of SST and south-north wind (WV) were also occurred. The representation of fields of individual meteorological variables by EOF shows that the first mode of the west-east wind (WU) explain over $47.3\%$ of the variance and the second mode of WU represents $30\%$. Especially, the first mode of the WV explain $70.9\%$ of the variance and their time series coefficients show 1-cpy, 0.5-cpy frequency spectrum. The spatial distribution of the first mode eigenvectors of SST are characterized by maximum near Vladivostok. The combined representation of fields of several variables (pressure, wind, SST) reveals that the first mode magnitudes of the variance of the combined eigenvectors (WU-PR) are increased. By means of this result, the 1-year peak and the 6-months peak are remarkable. In the three combined patterns (wind, pressure, SST), the second mode of the eigenvector (wind) is affected by the SST. Their time coefficients of the first mode show noticeable 1-year peak. The spectral analysis of the second mode shows broad seasonal signal with the period of 4-months and a significant peak of variability at 3-month period.

• Korean Journal of Optics and Photonics
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• v.11 no.5
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• pp.335-339
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• 2000

A $1.31/1.55\mu\textrm{m}$ coarse WDM opncal dIrectional coupler that conslsls of two idenlical straight channel waveguides in BK7 glass has been fabricated. The separatIOn between two channel waveguides is $8\mu\textrm{m}$ and the wavegu.ide width is $4\mu\textrm{m}$ . Especlally, we assumed that the index profile is Gaussian function and complementary error function in the width direction and depth direction, respectrvely. This directional coupler operating at $1.31/1.55\mu\textrm{m}$ with crosstalk of 18dB is demonstrated and has the 16 mm long length with 12.6 mm coupling region.region.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.586-586
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• 2013

저밀도 플라즈마는 반도체 공정, 나노 신소재 분야 및 우주 항공 분야 등 여러 분야에 이용되며, 플라즈마 진단 및 분석을 통해 효과적인 플라즈마 제어가 가능하다. 특히, 전자 에너지 분포 함수(Electron Energy Distribution Function, EEDF)는 전자 온도, 플라즈마 밀도 및 플라즈마 전위 등의 플라즈마 변수를 측정하거나 전자 가열 매커니즘 등을 이해하는데 있어서 매우 중요하므로 정밀한 측정이 필요하다. 그러나 RF fluctuation에 의해 낮은 전자 에너지 부분에서 EEDF가 왜곡되어 측정된 데이터 및 분석의 신뢰도가 떨어지게 된다. 이러한 문제점을 해결하기 위해 RF fluctuation 보상을 위한 쵸크 필터가 사용되며, 쉬스 임피던스에 비해 쵸크필터의 임피던스가 클수록 보상 효과는 높아진다. 하지만 플라즈마의 밀도가 낮아지면 쉬스 확장에 의해 쉬스 임피던스가 증가하므로 쵸크 필터에 의한 보상만으로는 충분한 개선 효과를 얻기 힘들다. 따라서 본 연구에서는 효과적인 RF fluctuation 보상을 위해 임피던스가 높은 쵸크 필터를 설계하고 추가적으로 레퍼런스링에 전압을 걸어 쉬스의 임피던스를 줄이는 방법도 적용하였다. 유도결합방식으로 $10^{-8}cm^{-3}$ 대의 저밀도 아르곤플라즈마 방전시켰으며, 단일 랑뮤어 탐침법으로 EEDF를 측정한 결과 낮은 전자 에너지 부분의 왜곡이 개선됨을 확인하였다.

• Journal of the Korean Society for Marine Environment & Energy
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• v.1 no.2
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• pp.71-81
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• 1998

In this paper the statistical characteristics of the waves at Hong-do and Mara-do are examined. The wane scatter diagrams of H/sub s/ and T/sub z/ and H/sub 1/3/and T/sub 1/3/ at two locations are given and various statistical characteristics of the ocean waves are examined. If the sea is not narrowband, the modified Rayleigh distribution introduced by Longuet-Higgins can be used for the individual wave height distribution. However the modified Rayleigh distribution has not been widely used due to the inconvenience of determining the empirical constant. In this paper a simple method to determine the empirical constant for the modified Rayleigh distribution is proposed. Extreme waves based on the measured wave data are estimated. There is no significant difference depending on the distribution functions. However the estimations of the extreme waves from H/sub s/ and H/sub 1/3/ show considerable difference.

• The Journal of the Acoustical Society of Korea
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• v.14 no.2E
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• pp.25-32
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• 1995

In this paper, we propose to use a parallel-branch subunit model for improved word recognition. The model is obtained by splitting off each subunit branch based on mixture component in continuous hidden Markov model(continuous HMM). According to simulation results, the proposed model yields higher recognition rate than the single-branch subunit model or the parallel-branch subunit model proposed by Rabiner et al[1]. We show that a proper combination of the number of mixture components and the number of branches for each subunit results in increased recognition rate. To study the recognition performance of the proposed algorithms, the speech material used in this work was a vocabulary with 1036 Korean words.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.7
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• pp.1444-1452
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• 2009

Probabilistic distribution functions based data generation method is very effective. Probabilistic distribution functions are defined under the assumption that daily routine contexts are mainly depended on a time-based schedule. However, daily life contexts are frequently determined by previous contexts because contexts have consistency and/or sequential flows. In order to refect previous contexts effect, a situation propagation network is proposed in this paper. As proposed situation propagation network make parameters of related probabilistic distribution functions update, generated contexts can be more realistic and natural. Through the simulation study, proposed context-data generation model generated general outworker's data about 11 daily contexts at home. Generated data are evaluated with respect to reduction of ambiguity and confliction using newly defined indexes of ambiguity and confliction of sequential contexts. In conclusion, in case of combining situation propagation network with probabilistic distribution functions, ambiguity and confliction of data can be reduced 6.45% and 4.60% respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2C
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• pp.272-282
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• 2004

This paper introduces a regularized mixed norm multi-channel image restoration algorithm using both within-and between- channel deterministic information. For each channel a functional which combines the least mean squares (LMS), the least mean fourth (LMF), and a smoothing functional is proposed. We introduce a mixed norm parameter that controls the relative contribution between the LMS and the LMF, and a regularization parameter defining the degree of smoothness of the solution, where both parameters are updated at each iteration according to the noise characteristics of each channel. The novelty of the proposed algorithm is that no knowledge of the noise distribution for each channel is required and that the parameters mentioned above are adjusted based on the partially restored image.

• Journal of Korea Water Resources Association
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• v.47 no.2
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• pp.171-182
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• 2014

The objective of this study is to evaluate the utilization of bivariate joint drought index in South Korea. In order to develop the bivariate joint drought index, in this study, Clayton copula was used to estimate the joint distribution function and the calibration method was employed for parameter estimation. Precipitation and soil moisture data were selected as input data of bivariate joint drought index for period of 1977~2012. The time series analysis, ROC (Receiver Operating Characteristic) analysis, spatial analysis were used to evaluate the bivariate joint drought index with SPI (Standardized Precipitation Index) and SSI (Standardized Soil moisture Index). As a result, SPI performed better for drought onset and SSI for drought demise. On the other hand the bivariate joint drought index captured both drought onset and demise very well. The ROC score of bivariate joint drought index was higher than that of SPI and SSI, and it also reflected the local drought situations. The bivariate joint drought index overcomes the limitations of existing drought indices and is useful for drought analysis.