• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.355-357
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• 2012

A probability density function (PDF) approach to account for turbulence-chemistry interaction in the context of large eddy simulation (LES) based simulation of scramjets is developed. To solve the high-dimensional joint-composition PDF transport equation robustly, the semi-discrete quadrature method of moments (SeQMOM) is recently proposed [1]. The SeQMOM approach addresses key numerical issues in LES related to the inaccuracies in computing filter-scale gradients, enabling an efficient and numerically consistent solution of the PDF transport equation. The computational tool is used to simulate a cavity-stabilized Mach 2.2 supersonic combustor.

• Journal of the Korean Graphic Arts Communication Society
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• v.25 no.2
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• pp.59-67
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• 2007

The working environment of DTP tends to increase from Macintosh to MS Windows in Korea because of being developed exclusively cross-platformed applications. Base of this change is not related to spread of using PDF. Recently, it's cause of falling into dilemma in Prepress. It's due that operators in Prepress don't have correctly understanding about differences and features between Postscript and PDF. This paper tried to search a way to solve problems via changing circumstance in operating Postscript and PDF.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6C
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• pp.857-864
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• 2004

Many image compression standards such as JPEG, MPEG or H.263 are based on the discrete cosine transform (DCT) and quantization method. Quantization error. is the major source of image quality degradation. The current dequantization method assumes the uniform distribution of the DCT coefficients. Therefore the dequantization value is the center of each quantization interval. However DCT coefficients are regarded to follow Laplacian probability density function (pdf). The center value of each interval is not optimal in reducing squared error. We use mean of the quantization interval assuming Laplacian pdf, and show the effect of correction on image quality. Also, we compare existing quantization error to corrected quantization error in closed form. The effect of PSNR improvements due to the compensation to the real image is in the range of 0.2 ∼0.4 ㏈. The maximum correction value is 1.66 ㏈.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.795-804
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• 2014

In this study, Andong Reservoir monthly and ten days inflows from July 2011 to September 2011 are predicted using SWAT model and ensemble technique. The weight method using monthly and ten days rainfall forecasts from Korea Meteorological Administration is applied for accurate analysis. If the rainfall prediction announced by Korea Meteorological Administration is close to the actual rainfall, the PDF-Ratio Method shows the best result. If the past high rainfall occurrence is close to the actual rainfall, the modified PDF-Ratio method shows the best result. This method can improve the prediction accuracy even though the Korea Meteorological Administration forecast is not accurate. On the contrary, if Korea Meteorological Administration forecast is different from the actual rainfall and the past rainfall occurrence statistics of lower section, the uniform method shows the best result.

• Korean Journal of Remote Sensing
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• v.28 no.6
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• pp.611-622
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• 2012

This study proposed two multisensor fusion methods for segment-based image classification utilizing a region-growing segmentation. The proposed algorithms employ a Gaussian-PDF measure and an evidential measure respectively. In remote sensing application, segment-based approaches are used to extract more explicit information on spatial structure compared to pixel-based methods. Data from a single sensor may be insufficient to provide accurate description of a ground scene in image classification. Due to the redundant and complementary nature of multisensor data, a combination of information from multiple sensors can make reduce classification error rate. The Gaussian-PDF method defines a regional measure as the PDF average of pixels belonging to the region, and assigns a region into a class associated with the maximum of regional measure. The evidential fusion method uses two measures of plausibility and belief, which are derived from a mass function of the Beta distribution for the basic probability assignment of every hypothesis about region classes. The proposed methods were applied to the SPOT XS and ENVISAT data, which were acquired over Iksan area of of Korean peninsula. The experiment results showed that the segment-based method of evidential measure is greatly effective on improving the classification via multisensor fusion.

• The Journal of the Korea Contents Association
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• v.17 no.4
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• pp.157-168
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• 2017

This thesis will select one of the books that went out of print, and republish it using the ePub and PDF format to observe the effective and economic method to republish it as an e-book. Conclusively, e-book in PDF format was advantageous over ePub production. The ePub has limitations of electronically publishing the books went out of print prior to 21st century when storing the original text was not common, as well as book with complex layouts. The PDF format was able to capture and recreate the sensitivity that can only be presented by vintage books, also adding to the cultural value. To publish PDF e-books, the foremost requirement is to prepare a standardized system that allows comprehensive browsing of the current status of the book, and also creating an environment for copyrighted publishers to more actively publish e-books by diversifying the distribution platforms and properly allocating the profit generated by use of the copyright. This thesis provides a simulation of e-book publications, for small and medium size publishers and writers who are hesitant to publish e-books, to take more aggressive approach in entering the business.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.247-250
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• 2008

The paper presents the advanced radiometric calibration method, called the lRCM (Iterative Radiometric Calibration Method), in order to avoid an operational constraint (solar source) for calibration. The IRCM assumes that an optical instrument is equipped with a filter assembly which consists of same band filters with different transmission ratios. Given all the noise sources (including the artificial one caused by the filters) of an image sensor, the noncentral ${\chi}^2$ distribution of the output result is induced by the approach of a noise PDF (Power Density Function). Finally, the radiometric calibration problem is transformed into equating two independent relations for the image sensor gains through the specified distribution.

• Journal of Communications and Networks
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• v.12 no.5
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• pp.399-405
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• 2010

Blind equalization techniques have been used in broadcast and multipoint communications. In this paper, two criteria of minimizing Euclidian distance between two probability density functions (PDFs) for adaptive blind equalizers are presented. For PDF calculation, Parzen window estimator is used. One criterion is to use a set of randomly generated desired symbols at the receiver so that PDF of the generated symbols matches that of the transmitted symbols. The second method is to use a set of Dirac delta functions in place of the PDF of the transmitted symbols. From the simulation results, the proposed methods significantly outperform the constant modulus algorithm in multipath channel environments.

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.900-911
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• 2009

This paper analyzes user preferences on the basic structure of digital textbook contents based on the PDF and HTML formats. This was conducted by analysing the data from an online survey on user preferences for the representative structures of the PDF- and HTML-based digital textbook contents that are currently used on the Web. Results show that in the PDF format, the structure with TOC(Table Of Contents) links on the left screen and the main content on the right was most preferred by 82% of the respondents. In terms of the viewing method, the one that presents one page of the textbook fitted to the width of the computer screen in a single-page view was regarded as the best. Similarly, in the HTML format, the structure with TOC links on the left frame and the main content on the right using 2-frames was revealed as the most preferred by 84% of the respondents. However, the structures of the PDF- and HTML-based digital textbook contents employed by most existing Web sites go against the users' preferences. Accordingly, for digital textbook development in the future, user preferences must be considered to allow students to read the contents more easily and conveniently.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.4
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• pp.350-358
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• 2012

This paper deals with accuracy of accumulated fatigue damage estimation using stochastic fatigue analysis method based on Rayleigh PDF. From full scale measurement data on an 8100TEU container vessel, zero-order spectral moments for wave- and vibration-induced energy spectral densities are determined on the probability level of 99%. 80 simulation cases in total are prepared according to the variation of ratio of zero-order spectral moments and center frequency of vibration ESD. By using inverse Fourier transformation and rainflow cycle counting for the combined ESD of wave and vibration, exact fatigue damages are derived. Fatigue damages in frequency domain based on Rayleigh PDF show large conservativeness compared to exact fatigue damages in times domain. The main cause of the excessive conservativeness is analyzed by two aspects: ratio of zero crossing and peak frequencies and ratio of initial zero order spectral moments and zero order spectral moments from rainflow stress range distributions. Finally, a guideline of applicability of Rayleigh PDF is proposed for wide band processes.