• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.57-62
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• 2014

This paper proposes the improving the equalization performance using the adaptive modulus concept to the MCMA blind equalizer in order to the reduction of intersymbol interference which occurs in the band limited and time dispersive communication channel. In MCMA blind algorithm, it is possible to reducing the amplitude and phase rotation of intersymbol interference without training sequence, the fixed constant modulus of transmission signal is used. But in proposed algorithm, the modulus are adaptively varies according to the equalizer output signal, then the improved equalization performance were obtained by the computer simulation. For this, the recovered signal constellation that is the output of the equalizer, the convergence performance by MSE, MD (maximum distortion) and residual isi characteristic learning curve were used. The propose algorithm has fairly good performance compared to the traditional MCMA algorithm in the same adaptive equalization algorithm.

• Journal of the Korean Society of Radiology
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• v.14 no.6
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• pp.819-825
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• 2020

The purpose of this study was to evaluate the usefulness of the developed air mattress for reducing the deterioration of image quality due to the scattered radiation generated on the computed tomography equipment table. 5 cm and 10 cm thick air mattresses were developed and the image quality was measured by scanning the AAPM phantom according to thickness and thickness. Statistical significance was confirmed by One Way Analysis of Variance(ANOVA) Compared with the AAPM phantom scanned in the standard method, the image with the air mattress did not show any difference, but when the air mattress was not applied, the CT number and uniformity were low and the noise was high, and the spatial resolution Respectively. The developed air mattress has no harmful effect on the diagnostic image, it is very effective in improving the image quality and can increase the CT image quality by simply applying Air Mattress to existing equipment without using the technology applied to the latest and high-cost equipment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.8
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• pp.921-927
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• 2012

Reliability-based design optimization (RBDO) can be used to determine the reliability of a system by means of probabilistic design criteria, i.e., the possibility of failure considering stochastic features of design variables and input parameters. To assure these criteria, various reliability analysis methods have been developed. Most of these methods assume that distribution functions are continuous. However, in real problems, because real data is often discrete in form, it is important to estimate the distributions for discrete information during reliability analysis. In this study, we employ the Akaike information criterion (AIC) method for reliability analysis to determine the best estimated distribution for discrete information and we suggest an RBDO method using AIC. Mathematical and engineering examples are illustrated to verify the proposed method.

• Journal of Korean Society for Geospatial Information Science
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• v.20 no.1
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• pp.13-20
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• 2012

In this study, the change pattern of hydrological response function as development has been observed. The target watershed was selected Tanbu sub-Basin in the Bocheong Basin. The applied channel networks are composed of 10 cases that are channel networks by strahler's ordering scheme and cases of all grids channel or the hillslope in basin. To each case of grid in basin, channel and hillslope drainage path lengths to outlet of basin are calculated, and hydrological response function was calculated by Nash Model. As results of this analysis, the peak discharge of hydrological response function is increased and peak time is shortened as development of channel networks. And based on statistical characteristics of hydrological response function, mean (lag time) and variance of travel time are reduced exponentially.

• The Korean Journal of Applied Statistics
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• v.30 no.6
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• pp.889-899
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• 2017

Independent component analysis is a multivariate approach to separate mixed signals into original signals. It is the most widely used method of blind source separation technique. ICA uses linear transformations such as principal component analysis and factor analysis, but differs in that ICA requires statistical independence and non-Gaussian assumptions of original signals. PCA have a natural ordering based on cumulative proportion of explained variance; howerver, ICA algorithms cannot identify the unique optimal ordering of the components. It is meaningful to set order because major components can be used for further analysis such as clustering and low-dimensional graphs. In this paper, we compare the performance of several criteria to determine the order of the components. Kurtosis, absolute value of kurtosis, negentropy, Kolmogorov-Smirnov statistic and sum of squared coefficients are considered. The criteria are evaluated by their ability to classify known groups. Two types of data are analyzed for illustration.

• Journal of Korean Society of Transportation
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• v.24 no.4 s.90
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• pp.117-127
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• 2006

Many large cities in Korea have implemented or planed to implement a bus information system(BIS) to improve service quality for bus Passengers, mainly by Providing bus arrival time at bus stations. In those systems, similar systematic errors to estimate the bus arrival time occur, which are caused by the cycle time to identify each bus location, the information processing time of the center system, and the cycle time to update the bus arrival information on each terminal. This paper investigated each cause sequentially and estimated three expectations related to the above three causes, respectively using the random incidence concept. Through a validation using real data from a BIS in a city in Korea, fairly amount of improvements on the bus arrival time estimation have been observed.

• Journal of Korea Water Resources Association
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• v.45 no.12
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• pp.1227-1241
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• 2012

In this study, a novel water surface detection method was proposed. In the method water surface is detected by analysis on correlation coefficients obtained from rectangular control areas of the same vertical position in two successive images including both water surface and staff gauge. Four methods respectively based on threshold, peak, slope and variance ratio, are used to identify water surface from vertical distribution of correlation coefficient. In addition, swaying correction algorithm and statistical filtering are applied to minimize outliers caused by positional image mismatch. Images taken from 28 different sites during low flow were tested to evaluate the method. Mean relative error to eye measurement was approximately from 3.4 to 5.7 cm. As long as water surface moves, this method can be used to improve image stage gauge by supplementing the previous water surface detection method.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.6
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• pp.17-30
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• 2009

In this study, the existence of possible deterministic longterm trend of precipitation amount, monthly maximum precipitation, rain day, the number of rain day greater than 20mm, 30mm, and 80mm was analyzed using the Mann-Kendall rank test and the data from 62 stations between 1905 and 2004 in South Korea. Results indicate that the annual and monthly rainfall amount increases and the number of rain days which have more than 80mm rainfall a day, increases. However the number of rain days decreases. Also, monthly trend analysis of precipitation amount and monthly maximum precipitation increases in Jan., May, Jun., Jul., Aug., and Sep. and they decrease in Mar., Apr., Oct., Nov., and Dec. Monthly trend of the number of rain day greater than 20mm, 30mm, and 80mm increases in Jun., Jul., Aug., and Sep. However results of Mann-Kedall test demonstrated that the ratio of stations, which have meaningful longterm trend in the significance level of 90% and 95%, is very low. It means that the random variability of the analyzed precipitation related data is much greater than their linear increment.

• Journal of Korean Society for Geospatial Information Science
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• v.18 no.2
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• pp.69-78
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• 2010

The hydrological-geomorphic character is closely related with runoff in basin. A development of GIS greatly helps investigating about mechanism between theirs. We analyze local slope and hillslope length which are related with hydrological response. But variation of these geomorphic variables has very wide range at each pixel. So there's a limit as to use directly. Therefore we investigate a relation between hydrological response and distributed geomorphic variables according to statistical character of distributed map considering spatial correlation. As a result, the local slope affects peak discharge, and the hillslope length affects peak discharge and time, mean and variance of hydrological response. Henceforth these hydrological-geomorphic analyze methods can be improved that hydrology response is directly analogized with DEM data.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.10
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• pp.2100-2112
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• 2011

An orthogonal code hopping multiplexing (OCHM) technique has been proposed for accommodating a large number of users with low channel activities than the number of orthogonal codewords through statistical multiplexing in downlink cellular systems. In this paper, a multiple input multiple output (MIMO) antenna based OCHM system is proposed to improve the performance. Each modulated symbol is repeated N times and the N repeated symbols are transmitted simultaneously using N transmit antennas. Through repetitions, the effect of perforations that the OCHM system experiences is decentralized among the repeated symbols and the full perforation probability is significantly reduced. Each receiver detect the transmitted signal using its pre-assigned code hopping pattern. Simulation results show that the proposed scheme saves the required energy for a given frame error rate (FER).