• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.255-258
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• 2000

The supplementalγ controls of the FACTS are designed for the enhancement of the small signal stability in power system. The designed supplementary controllers using residue are applied to SVC or TCSC for the improving the damping ratio of dominant eigen value in the New England and 39 bus test system as the sample system. The results show the validation of the supplementary controller for the enhancement of the eigenvalues which have the low frequency oscillations with poor damping ratio as the unstable problem in the sample system.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.305-307
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• 2010

In this study, we develop a method to achieve heat transfer enhancement inside a square duct with high aspect ratio without changing any inner structures. Especially, a method to lower the possible maximum temperature is suggested if constant heat flux is provided to single surface of square duct. Knowing the fact that heat transfer rate is inversely proportional to flow area, we proposed tapered channel concept which uses narrower gap toward the flow exit where the maximum temperature is expected. To maintain equivalent power consumption, inlet section has been enlarged. To verify the proposed concept, experimental tests have been performed.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2921-2923
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• 2000

Adaptive template filtering has been proposed recently for an enhancement of signal-to-noise ratio. In some magnetic resonance images whose gray levels have relatively small dynamic ranges, e.g., T1 imaging, however, artificial stair-like artifact is observed in edge regions. This is partially due to edge enhancement effect in such voxels that contain multiple compounds at the boundaries of tissues. The gray levels of these voxels tend to change those of near voxels that contain single compound by the adaptive filtering, which exaggerate edge discontinuities. In this paper, we propose a technique to eliminate such artifact by identifying those voxels and assigning a larger template for them. Filtered images with the proposed technique show substantial visual enhancement at the edges without degradation of peak signal-to-noise ratio compared to the original adaptive template filtering for both magnetic resonance images and phantom images

• Korean Journal of Radiology
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• v.1 no.2
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• pp.91-97
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• 2000

Objective: To determine whether the time-intensity curves acquired by test and main dose contrast injections for MR angiography are similar. Materials and Methods: In 11 patients, repeated contrast-enhanced 2D-turbo-FLASH scans with 1-sec interval were obtained. Both test and main dose timeintensity curves were acquired from the abdominal aorta, and the parameters of time-intensity curves for the test and main boluses were compared. The parameters used were arterial and venous enhancement times, arterial peak enhancement time, arteriovenous circulation time, enhancement duration and enhancement expansion ratio. Results: Between the main and test boluses, arterial and venous enhancement times and arteriovenous circulation time showed statistically significant correlation (p < 0.01), with correlation coefficients of 0.95, 0.92 and 0.98 respectively. Although the enhancement duration was definitely greater than infusion time, reasonable measurement of the end enhancement point in the main bolus was impossible. Conclusion: Only arterial and venous enhancement times and arteriovenous circulation time of the main bolus could be predicted from the test-bolus results. The use of these reliable parameters would lead to improvements in the scan timing method for MR angiography.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1139-1142
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• 2007

In this paper, an image enhancement method by saturation and contrast improvement is proposed. Histogram equalization with color difference makes higher contrast. By generating saturation amplification ratio with color difference, the saturation improves effectively. The experimental results show that the proposed algorithm has higher contrast and more natural - look than the conventional methods.

• Nuclear Engineering and Technology
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• v.56 no.7
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• pp.2563-2569
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• 2024

The monochromatic hyperbolic neutron density wave is conceived as a Rayleigh-like wave with mixed transverse and longitudinal components. It is proved for the first time that the absolute ratio of the longitudinal to transverse interfering components, varies, with increasing the frequency of this wave, from zero to 1. Such a limited variation is to be coined as vibrational enhancement of evolutionary one-speed neutron transport.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.2
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• pp.363-370
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• 2015

Olive flounder, Paralichthys olivaceus is one of the most target fish for aquaculture and national stock enhancement program in Korea. In order to find more information about hatchery fish stocking for stock enhancement we investigated the sex ratio of wild-caught fish populations which were artificially released into wild seas. The recapture rate was 9.0% to 94.5% in studied areas. The proportion of sex ratio ranged from 7.8% to 64.6% in female and from 34.4% to 92.1% in male respectively. This result suggests that the sex ratio of wild populations might be effected by the released fish. So we need more careful stocking program of the fish to preserve the balance of the sex ratio in the wild population.

• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.38-43
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• 2011

We have developed a simple model of a bright-room contrast ratio (BRCR) measurement system for plasma display panels (PDPs) adopting a contrast enhancement film (CEF) by using an illumination design tool. Only four model parameters were used, namely, total ambient illumination power delivered by fluorescent lamps, a panel scattering rate, illuminance of PDP white patterns, and the absorption coefficient of a color adjusting film. These parameters were determined by simple optical measurements and matching simulations. The proposed model was employed to predict the BRCR values of four different CEF samples, and the simulated ones were found to be in agreement with measured ones within about 10% relative-error.

• The Journal of the Acoustical Society of Korea
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• v.22 no.3
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• pp.169-174
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• 2003

A novel subspace speech enhancement using subband whitening filter is proposed. Previous subspace speech enhancement method either assumes additive white noise or uses whitening filter as a pre-processing for colored noise. The proposed method tries to minimize the signal distortion while reducing residual noise by processing the signal using subband whitening filter. By incorporating the notion of subband whitening filter, spectral resolution in Karhunen-Loeve(KL) domain is improved with the negligible additional computational load. The proposed method outperforms both the subspace method suggested by Ephraim and the spectral subtraction suggested by Boll in terms of segmental signal-to-noise ratio (SNRseg) and perceptual evaluation of speech quality (PESQ).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11C
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• pp.1161-1168
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• 2003

In this paper, we propose an improved statistical model-based voice activity detection algorithm and threshold update method. We first improve signal-to-noise ratio by using speech enhancement preprocessing algorithm combined power subtraction method and matched filter, then apply it to LLR test optimum decision rule for improving the performance even in low SNR conditions. And we propose an adaptive threshold update method that was not concerned in any papers. We also perform extensive computer simulations to demonstrate the performance improvement of the proposed VAD algorithm employing the proposed speech enhancement preprocessing algorithm and adaptive threshold update method under various background noise environments. Finally we verify our results by comparing ITU-T G.729 Annex B.