• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.837-840
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• 2001

주파수 추정 알고리즘의 경우 기존에 제안된 방법들 중에서 ML방법은 계산상 너무 복잡하고 구현하기 힘들며, 준-ML 방법들은 이론적인 방법과 비교해 볼 때 다소 단순하긴 하나 역시 구현상의 문제가 따른다. 따라서 본 논문에서는 BWLL환경에 적용할 수 있는 단순하면서도 구현이 용이한 주파수 추정방법을 제안한다. 본 논문에서 제안하는 주파수 추정기는 V&V 위상추정기를 기초로 한다. 성능분석 결과 본 논문에서 제안한 알고리즘을 이용할 경우 최대로 정규화된 심벌율의 0.5%까지 조정이 가능하다. 따라서 아날로그 영역에서의 거친 주파수 조절과정에서 다소 많은 잔류 주파수옵셋이 존재하여도 주파수 복구가 가능하다.

• The Korean Journal of Applied Statistics
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• v.13 no.1
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• pp.55-70
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• 2000

본 논문에서는 내포오차성분을 가지는 패널회귀모형에서 회귀계수에 대하여 다양한 추정량들을 유도하고, 추정량들의 효율성을 모의실험을 통하여 평균제곱오차의 기준에서 비교하였다. 모의실험 결과, 제안된 FGLS 추정량들은 GLS추정량과 효율성에서 서로 큰 차이를 보이지 않았으며, 계산상 더욱 복잡한 ML, REML 추정량 및 MIVQUE와 거의 비슷한 효율성을 보여주었다.

• The Korean Journal of Food And Nutrition
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• v.10 no.3
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• pp.370-374
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• 1997

Commercial Sikhye was fermented by Saccharomyces cerevisiae for 10 day at 29$^{\circ}C$. Sucrose was hydrolyzed into glucose and fructose by invertase from the yeast, and the glucose and fructose were converted into ethanol by the yeast. Commercial Sikhye wine was found to contain 6.6% of ethanol, 0.32$\mu$mol/ml of amino acid, 226$\mu\textrm{g}$/ml of protein, and 2.5ml 0.1N NaOH of acidity, respectively, and its pH was 3.21. Limit dextrin in commercial rice Sikhye wine showed both signal of $\alpha$-1, 4- and $\alpha$-1, 6- glucosidic linkage with its estimation ratio of 25:1 by 1H-NMR analysis. The taste of rice Sikhye wine was similar that of wine.

• Korean Journal of Geomatics
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• v.3 no.1
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• pp.33-41
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• 2003

Every year, several typhoons hit the Korean peninsula and cause severe damage. For the prevention and accurate estimation of these damages, real time or almost real time flood information is essential. Because of weather conditions, images taken by optic sensors or LIDAR are sometimes not appropriate for an accurate estimation of water areas during typhoon. In this case SAR (Synthetic Aperture Radar) images which are independent of weather condition can be useful for the estimation of flood areas. To get detailed information about floods from satellite imagery, accurate classification of water areas is the most important step. A commonly- and widely-used classification methods is the ML(Maximum Likelihood) method which assumes that the distribution of brightness values of the images follows a Gaussian distribution. The distribution of brightness values of the SAR image, however, usually does not follow a Gaussian distribution. For this reason, in this study the ANN (Artificial Neural Networks) method independent of the statistical characteristics of images is applied to the SAR imagery. RADARS A TSAR images are primarily used for extraction of water areas, and DEM (Digital Elevation Model) is used as supplementary data to evaluate the ground undulation effect. Water areas are also extracted from KOMPSAT image achieved by optic sensors for comparison purpose. Both ANN and ML methods are applied to flat and mountainous areas to extract water areas. The estimated areas from satellite imagery are compared with those of manually extracted results. As a result, the ANN classifier performs better than the ML method when only the SAR image was used as input data, except for mountainous areas. When DEM was used as supplementary data for classification of SAR images, there was a 5.64% accuracy improvement for mountainous area, and a similar result of 0.24% accuracy improvement for flat areas using artificial neural networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12A
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• pp.1205-1213
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• 2006

In this paper, we analyze the IQ(In-phase/Quadrature) imbalance effects at both transmitter and receiver side of OFDM(Orthogonal Frequency Division Multiplexing) and show that IQ imbalance is the parameter to improve the performance using ML and OSIC scheme. Especially, we can archive the diversity gain due to the IQ imbalance in multipath fading environment. In addition, new preamble format is proposed, which enable estimation of the channel and IQ imbalance parameters to maximize the diversity gain. Significant performance improvement is achieved by using the ML(Maximum Likelihood)and OSIC(Ordered Successive Interference Cancellation) with compensation compared to a standard receiver with no compensation for IQ imbalance and proposed channel estimation scheme achieves the better performance improvement than conventional.

• Journal of Broadcast Engineering
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• v.17 no.5
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• pp.864-875
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• 2012

In this paper, we propose a carrier frequency offset estimation method for single-carrier MIMO systems. In the proposed method, phase rotated PN (Pseudo-Noise) sequences are transmitted to prevent a cancelling out of partial PN sequences. After removing a modulation of received PN sequences by multiplying of complex conjugated PN Sequences which are locally generated in receiver, a CFO (Carrier Frequency Offset) is accurately estimated by employing L&R method which is a kind of ML (Maximum Likelihood) estimation algorithm and uses multiple auto-correlatos. In addition, the frequency offset estimation scheme by using channel state information is proposed for accurate CFO estimation in time-varying Rayleigh channel. By performing computer simulations, MSE (Mean Square Error) performance of proposed method is almost same as MSE performance of SISO systems in AWGN channel. Moreover, MSE Performance of proposed method with using channel information is higher than MSE performances of SISO system and conventional method in time-varying Rayleigh channel.

• Journal of Korean Society for Quality Management
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• v.25 no.2
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• pp.1-14
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• 1997

This paper considers maximum likelihood (ML) estimation of lifetime distribution under stress bounded ramp tests in which the stress is increased linearly from used condition stress to the stress u, pp.r bound. The following assumptions are used: exponential lifetime distribution under a constant stress, an inverse power law relationship between stress and mean of exponential lifetime distribution, and a cumulative exposure model for the effect of changing stress. Likelihood equations for the parameters involved in the model and asymptotic distribution of the estimators are obtained, and a numerical example is given.

• Korean Journal of Animal Reproduction
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• v.12 no.1
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• pp.24-30
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• 1988

These experiments were carried out to develop new techniques for In Vitro separatin of X-and Y-bearing spermatozoa. The bull semen was applied to the various Gel-Columns filled with swellen Sephadex G-50 Fine and then elutriated wtih Locke solution (elutriation rate; 1ml/3-4min., 1ml/1-2min.). Elutriated solution was fractionated into 1ml by automatic Fraction Collector and spermatozoa included in each fraction were subjected to the estimation of viability and recovery rate, and to B-body test. The results obtained in these experiments were summarized as follows: 1. When the column size and the elutriation rate were adjusted to 15$\times$1.6cm and 1ml/3-4min., respectively, the highest sperm concentration was obtained from the 8th to the 12th fraction. 2. As a trend, the viability of spermatozoa was improved by chromatography, and the degree of improvement ranged 5 to 10 percentage. 3. The average recovery rate of spermatozoa applied to column was 73.2 percentage and ranged 52.6 to 81.3 percentage. 4. The lowest rate of B-body bearing spermatozoa following chromatography was obtained when the column size and the elutriation rate were adjusted to 15$\times$0.8cm and 1ml/1-2min., respectively.

• The Korean Journal of Food And Nutrition
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• v.10 no.3
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• pp.360-364
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• 1997

Rice Sikhye was fermented by Saccharomyces cerevisiae for 10 day at 29$^{\circ}C$. Fermentable sugars such as glucose, maltose and maltotriose in rice Sikhye were converted into ethanol by the yeast, but limit dextrin was remained after the fermentation. Rice Sikhye wine was found to contain 5.3% of limit dextrin, 6.5% of ethanol, 2.9 $\mu$mol/ml of amino acid, 457$\mu\textrm{g}$/ml of protein, and the acidity of the Sikhye showed 3.1, respectively, and its pH was 3.67. Limit dextrin in rice Sikhye wine showed both signal of $\alpha$-1,4- and $\alpha$-1,6-glucosidic linkage wit its estimation ratio of 5.6:1 by 1H-NMR analysis. The taste of rice Sikhye wine was similar that of wine.

• International Journal of Control, Automation, and Systems
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• v.6 no.1
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• pp.109-118
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• 2008

We present two estimators for discrete non-Gaussian and nonstationary probability density estimation based on a dynamic Bayesian network (DBN). The first estimator is for off line computation and consists of a DBN whose transition distribution is represented in terms of kernel functions. The estimator parameters are the weights and shifts of the kernel functions. The parameters are determined through a recursive learning algorithm using maximum likelihood (ML) estimation. The second estimator is a DBN whose parameters form the transition probabilities. We use an asymptotically convergent, recursive, on-line algorithm to update the parameters using observation data. The DBN calculates the state probabilities using the estimated parameters. We provide examples that demonstrate the usefulness and simplicity of the two proposed estimators.