• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.2
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• pp.105-110
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• 2015

This paper relates with the eualization performance of Constellation Matching-MMA (CM-MMA) in order to the consists of optimum receiver for the minimization of intersymbol interference and additive noise effects that is occurs in the nonlinear communication channel. The error signal were obtained that combines the Constellation Matching technique that inserts the zero point between the signal point of equalizer for improving the residual isi and convergence speed compared to the currently used MMA algorithm. In the initial state of adaptive equalization, it depends on the MMA characteristics mainly. And in the steady state, it depends on the CM characteristics mainly. In order to analyzing the equalization performance, the output signal constellation, residual isi, maximum distortion, MSE and SER were applied, then it were compared with the present MMA algorithm. As a result of computer simulation, the CM-MMA has more better performance in the every performance index, and it was also confirmed that the constellation matching effect can be obtained in the greater than 20dB signal to noise ratio.

• Journal of Advanced Navigation Technology
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• v.16 no.2
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• pp.234-239
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• 2012

Next generation mobile communication systems have been studied and applied to support various services. In next generation mobile communication systems, the most interested research is the integration of various communication systems and the offer of various services by using high-speed data transmission. The integration of communication systems has been researched by using multi standard modem, while the high-speed data transmission for the offer of various services has been applied by using OFDM. This paper has proposed the method to reduce PAPR by using multi standard modem. with EVM, this paper has also suggested the method to compensate in-band distortion while reducing PAPR. By using the proposed methods, this paper has analyzed and simulated the decrease efficiency of PAPR, the performance of CCDF, and the performance of BER in next generation mobile communication systems. The simulation results improved the performance of next generation mobile communication system can be seen that.

• The Korean Journal of Financial Management
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• v.26 no.1
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• pp.189-220
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• 2009

This study tests the significance of momentum and contrarian strategy which challenge the weak efficient market hypothesis (EMH). If momentum and contrarian strategy can make extra return above the market, this can be a significant critics to the weak EMH. By using Monte Carlo simulation we have found that many existing returature, which test the significance of momentum and contrarian strategy, have a significance distortion problem. We test the significance of momentum and contrarian strategy by using reality check test of White(2000) which solve the problem of data snooping bias. The results are following. When we use the KOSPI index as the benchmark portfolio, we can get the best strategy of momentum strategy in the case of mean return. But in the case of Sharp ratio which is the performance measure adjusting risk, we find that the best strategy in the momentum and contrarian strategy can not dominate the performance of benchmark portfolio. Therefore we argue that weak EMH can not be rejected because of superior performance of momentum and contrarian strategy when we consider risk.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.67-76
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• 1989

Although the standard 2-CR network filter, one of the filters used for measuring surface roughness, is being used widely in the field of industry it possesses a weak point of causing Phase-distortion when the wavelength is passing through. Phase-corrected filter is used for eliminating these phase-distortion and the difference of phase characteristics between these two filters is thought to have considerable amount of effect on the surface roughness value. Moveover, the definition on this is as yet unclear. Therefore, the Rt and Rz value, obtained when the wavelength are passed through the standard and phase-corrected filters from the same random machine-processed surface, and its standard deviation are compared and experimented in this paper. Also, the ratio of relative bearing curve complying to the phase characteristics of these two filters are acquired. As a result, the use of phese-corrected filter is appropriate in experiments where the form of wavelength is important, and the standard deviation on the same experimented values appeared greater with when using the standard filter. The rate of relative bearing curve became greater as .lambda.$_{c}$, the cut-off value of filter, became smaller.r.

• Journal of Broadcast Engineering
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• v.19 no.1
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• pp.96-108
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• 2014

In case of contrast of the image enhancement by using the conventional histogram equalization, over-enhancement, false contouring and distortion such as the details disappearance of the image occurs due to the excessive brightness change. Especially, these distortion appears when the brightness distribution is concentrated in a particular brightness level. In order to solve these problems, improved histogram equalization methods to transform the input histogram by clipping using threshold have been proposed, but contrast enhancement effect is reduced because it does not consider the characteristics of the input image's histogram to apply the same threshold for the entire histogram, and unnatural image is obtained because it does not retain the characteristics of the image. In this paper, to solve the problems of existing methods, we propose new equalization method that suppress excessive brightness changes by applying to the differential compression according to the histogram frequency, and maintain the characteristics of the input image. In addition, we propose a more effectively method to improve contrast by controlling the strength of the compression ratio depending on the characteristics of the input image.

• Journal of the Korea Society of Computer and Information
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• v.25 no.5
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• pp.1-9
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• 2020

In this paper, we propose a model that performs more natural facial attribute editing by utilizing mask information in the hair and hat region. STGAN, one of state-of-the-art research of facial attribute editing, has shown results of naturally editing multiple facial attributes. However, editing hair-related attributes can produce unnatural results. The key idea of the proposed method is to additionally utilize information on the face regions that was lacking in the existing model. To do this, we apply three ideas. First, hair information is supplemented by adding hair ratio attributes through masks. Second, unnecessary changes in the image are suppressed by adding cycle consistency loss. Third, a hat segmentation network is added to prevent hat region distortion. Through qualitative evaluation, the effectiveness of the proposed method is evaluated and analyzed. The method proposed in the experimental results generated hair and face regions more naturally and successfully prevented the distortion of the hat region.

• Current Optics and Photonics
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• v.1 no.2
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• pp.157-162
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• 2017

In large liquid crystal displays, the image quality in an oblique viewing direction is a crucial issue. From this perspective, 8-domain polymer-stabilized vertical alignment (PS-VA) mode has been developed to suppress the color shift in oblique viewing directions, compared to that in 4-domain PS-VA mode. To realize the 8-domain PS-VA, the four domains in a pixel are each divided into two regions, such that applying different electric potentials result in different tilt angles in these two regions, while keeping four azimuthal directions in each domain. However, applying different voltages in a pixel causes drawbacks, such as requiring additional processes to construct a capacitor and a transistor, which will further reduce the aperture ratio. Here we propose a different approach to form the 8-domain, by controlling surface polar anchoring energy and the width of patterned electrodes in two regions of a pixel. As a result, the gamma-distortion index (GDI), measured at an azimuthal angle of $0^{\circ}$, is reduced by about 23% and 8%, compared to that of a conventional 4-domain at polar angles of $30^{\circ}$ and $60^{\circ}$ respectively.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.4
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• pp.127-133
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• 2013

This paper compare the performance of CCA (Compact Constellation Algorithm) adaptive equalization algorithm by effect of the compact slice weighting value for minimization of the intersymbol interference in the communication channel. The CCA combines the conventional DDA and RCA algorithm, it uses the constant modulus of the transmission signal and the considering the output of decision device by the power of compact slice weighting value in order to improving the initial convergence characteristics and the equalization noise by misadjustment in the steady state. In this process, it is confirmed by computer simulation that the compact slice weight affects the performance of CCA adaptive equalization algorithm. The performance index includes the output signal constellation, the residual isi and maximum distortion and MSE that is for the convergence characteristics, the SER according to the signal and noise power ratio at the channel is used. As a result of computer, it shows that the large weighting value gives more good in every performance index. But in SER performance, it is known that the small values gives more good in low SNR and the large values gives more good in high SNR.

• Geomechanics and Engineering
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• v.21 no.2
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• pp.95-102
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• 2020

Population concentration in urban areas has led traffic management a central issue. To mitigate traffic congestions, the government has planned to construct large-cross-section tunnels deep underground. This study focuses on estimating the damage caused to frame structures owing to tunnel excavation. When constructing a tunnel network deep underground, it is necessary to divide the main tunnel and connect the divergence tunnel to the ground surface. Ground settlement is caused by excavation of the adjacent divergence tunnel. Therefore, predicting ground settlement using diverse variables is necessary before performing damage estimation. We used the volume loss and cover-tunnel diameter ratio as the variables in this study. Applying the ground settlement values to the settlement induction device, we measured the extent of damage to frame structures due to displacement at specific points. The vertical and horizontal displacements that occur at these points were measured using preattached LVDT (Linear variable differential transformer), and the lateral strain and angular distortion were calculated using these displacements. The lateral strain and angular distortion are key parameters for structural damage estimation. A damage assessment chart comprises the "Negligible", "Very Slight Damage", "Slight Damage", "Moderate to Severe Damage", and "Severe to Very Severe Damage" categories was developed. This table was applied to steel frame and concrete frame structures for comparison.

• The Transactions of the Korea Information Processing Society
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• v.6 no.7
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• pp.1980-1987
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• 1999

Restored image is always lower quality than original one due to distortion and noise. The purpose of image restoration is to improve the image quality by fixing the noise or distortion information. One category of spatial filters for image restoration is linear filter. This filter algorithm is easily implemented and can be suppressed the Gaussian noise effectively, but not so good performance for spot or impulse noise. In this paper, we propose the nonlinear spatial filter algorithm for image restoration called the optimal adaptive multistage filter(OAMF). The OAMF is used to reduce the filtering time, increases the noise suppression ratio and preserves the edge information. The OAMF optimizes the adaptive multistage filter(AMF) by using weight learning algorithm of back-propagation learning algorithm. Simulation results of this filter algorithm are presented and discussed.