• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.4
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• pp.1248-1266
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• 2012

This paper presents a multilevel reversible data hiding method based on histogram shifting which can recover the original image losslessly after the hidden data has been extracted from the stego-image. The method of prediction is adopted in our proposed scheme and prediction errors are produced to explore the similarity of neighboring pixels. In this article, we propose two different predictors to generate the prediction errors, where the prediction is carried out using the center prediction method and the JPEG-LS median edge predictor (MED) to exploit the correlation among the neighboring pixels. Instead of the original image, these prediction errors are used to hide the secret information. Moreover, we also present an improved method to search for peak and zero pairs and also talk about the analogy of the same to improve the histogram shifting method for huge embedding capacity and high peak signal-to-noise ratio (PSNR). In the one-level hiding, our method keeps image qualities larger than 53 dB and the ratio of embedding capacity has 0.43 bpp (bit per pixel). Besides, the concept with multiple layer embedding procedure is applied for obtaining high capacity, and the performance is demonstrated in the experimental results. From our experimental results and analytical reasoning, it shows that the proposed scheme has higher PSNR and high data embedding capacity than that of other reversible data hiding methods presented in the literature.

• Journal of the Korean Operations Research and Management Science Society
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• v.40 no.4
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• pp.83-105
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• 2015

Taxi, one of the passenger services, is an essential transportation system in our society. In spite of the importance of taxi service, deterioration of the service quality is continuously reported. In particular, taxi service failures due to traffic accidents have emerged as the most serious social problem which may incur a considerable amount of social costs. In this study, we focus on analyzing the causes of service quality deterioration-traffic accidents of both corporately owned and privately owned taxies in Seoul. The research objective is to find out the determinants of service quality deterioration of Taxi industry and to suggest policies for improving the taxi service in Seoul. We collected the archival data from KTSA (Korea Transportation Safety Authority) and ODP (Open Data Portal), which span from 2005 to 2014. Hierarchical regression analyses and a set of mediation tests are conducted. The root factors inducing traffic accidents of taxies are divided into competitive, and profitability factors. The statistical results indicate that the accident ratio per taxi is not only affected by competitive/profitability factors such as number of active taxi drivers, number of bus passengers, and taxi fare, but also mediated by the traffic violation ratio. To alleviate the current problems with taxi service in Seoul, we conclude that the number of taxies be reduced and the taxi fare be increased. Finally, we suggest several policies to improve the endemic taxi industry problems, over-supply and the low profitability by enhancing the linkage between service quality and profitability.

• Korean Journal of Food Science and Technology
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• v.21 no.2
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• pp.212-217
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• 1989

The shrinking and overall drying rate equations which can accomodate experimental date and the rate of initial drying ratio were investigated. The results obtained from hot air drying experiments of radish and sweet potatoes were as follow. The drying rate constant and the order were affected by the thickness of sample and temperature. The empirical drying rate and shrinking equations at constant drying conditions (d=4mm, $Ta=50^{\circ}C$, RH=10%, U=0.8m/s) for radish and sweet potatoes were found to $dx/dt=0.112{\times}10^{-2}\;A(1-x)^{0.43}$, A=Ao(-0.480x+1) and rates of initial drying ratio were expressed of sample thickness, relative humidity and air velocity; for radish $dx/dt=0.0648(RH)^{-0.31}\;(d)^{-0.75}\;(U)^{0.39}$ and for sweet potatoes $dx/dt=0.0547(RH)^{-0.28}\;(d)^{-0.63}\;(U)^{0.37}$

• Journal of Digital Convergence
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• v.18 no.1
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• pp.1-10
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• 2020

In this study, an empirical analysis using Difference-in-Difference(DID) methods was conducted based on the data of domestic defense companies to look at the impact of government support on the performance of these defense industries. As a result, we found that the volume of sales and assets of defense enterprises does not increase or decrease solely on the benefit of government support. In addition, government support for net profit to total sales ratio and net profit to total assets ratio improved significantly, but the effect was only seen in the short term. Unlike previous studies that focused on identifying the existence of differences between industries, our research is different in that it is the first to analyze empirically within the Korean defense industry. It is also theoretically meaningful in that it looked at the effects of government support, especially in industries with unique characteristics that have yet to be known.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.9
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• pp.301-310
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• 2014

The absence of proactive information security management to ensure availability, accessibility and safety of information can bring serious risks to customers as well as to the organization's performance and competitiveness because improper security management undermines business continuity. This study analyzed the maturity of information security which affects the organizational performance. Through the literature reviews, a research model using the organizational performance as the dependent variable, the risk management process maturity and risk assessment process as independent variables and the information security policy indexes as moderate variables was proposed, and an empirical analysis was made on the basis of survey. The results showed that there was a high causal relationship between information security maturity and organizational performance. However, even if the proportions of information security staff ratio and the information security budget ratio increased, information security maturity did not affect organizational performance. It suggests that information security maturity affects organizational performance, but information security regulations have their limitation as being a catalyst to improve organizational performance.

• The Journal of Fisheries Business Administration
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• v.47 no.1
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• pp.87-100
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• 2016

Suhyup Bank became to be subject to regulation of capital ratio by Basel III which was introduced in order to enhance stability of the financial institution. Accordingly, Suhyup Bank will require recapitalization. It is important to estimate the risk-weighted assets in calculating of Suhyup Bank's recapitalization scale. Therefor, this study aimed to present a scientific model as estimated the risk-weighted assets. Risk-weighted assets are calculated by applying different risk weights for loans, may have a certain relationship with the loans. Results show that the risk-weighted assets is affected by the previous year's risk-weighted assets and influenced the increase in loans during the year. Since the required basic capital adequacy ratio was specified, the risk-weighted assets should be predicted reasonably. Accordingly, on this study it was tried to derive the accounting equation to predict the risk-weighted assets based on management data of a bank since introduction of Basel III. As the risk-weighted assets were weighted differently according to the type of loans, if the accounting equation is derived by using the type of loans, then it would be helpful for the risk management of banks in the long-term. According to this, the increase of loan would be predicted on the basis of past management performance of Suhyup Bank, and for this reason, the future risk-weighted assets of Suhyup Bank were predicted. The result of this study was showed that 98.3% of risk-weighted assets of the previous year, 62.4% of the secured loan changes and 95.1% of the credit loan changes affected risk-weighted assets.

• Computational Structural Engineering
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• v.9 no.2
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• pp.133-142
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• 1996

In this paper, two different techniques for mixed-mode type engineering fracture mechanics are investigated to estimate the stress intensity factors by using p-version finite element model. These two techniques are displacement extrapolation with COD and CSD method and J-integral with decomposition method. By decomposing the displacement field obtained from p-version of finite element analysis into symmetric and antisymmetric displacement fields with respect to the crack line, Mode-I and Mode-II stress intensity factors can be determined using aforementioned techniques. The example problems for validating the proposed techniques are centrally and centrally oblique cracked panels under tension. The numerical results associated with the variation of oblique angle and the ratio of crack length and panel width (a /W ratio) are compared with those by theoretical values and empirical solutions in literatures. Very good agreements with the existing solutions are shown.

• Journal of the Korean Data and Information Science Society
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• v.25 no.6
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• pp.1449-1466
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• 2014

In this paper, we consider a hedge portfolio based on futures of underlying asset. A classical way to estimate a hedge ratio for a hedge portfolio of a spot and futures is a regression analysis. However, a regression analysis is not capable of reflecting long-run equilibrium between a spot and futures and volatility clustering in the conditional variance of financial time series. In order to overcome such defects, we analyzed KOSPI200 index and futures using VECM-CC-GARCH model and computed a hedge ratio from the estimated conditional covariance-variance matrix. In real data analysis, we compared a regression and VECM-CC-GARCH models in terms of hedge effectiveness based on variance, value at risk and expected shortfall of log-returns of hedge portfolio. The empirical results show that the multivariate GARCH models significantly outperform a regression analysis and improve hedging effectiveness in the period of high volatility.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7788-7793
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• 2015

Both export and import sides of grain trade market are analyzed and compared in terms of the static levels and dynamic trends to make new empirical inference on the imperfect competition degree. Export concentration level is high compared to import concentration level. And such states have been sustained since 2001 until 2014. Unlike public concerns, the concentration level of export side seems to be easing by small degree. However, the grain trade market remains imperfect competitive market. Furthermore, overall imperfective competition condition over 2002-2014 has been worsened compared to 2001 level. It is because the reduction level of imports concentration is higher than that of the export concentration. Gini and Atkinson Inequality Index based on Lorenz Curve are newly utilized to analyze market concentration level, instead of the commonly used concentration ratio.

• Journal of the Korean association of regional geographers
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• v.10 no.3
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• pp.654-666
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• 2004

The function of officetel has been changed from office use to residential use since 1980s. The construction of officetel was relatively increased in 1991, has been decreased in the middle of the 1991, and has been increased after 1996. This paper is an empirical examination of officetel rent determinants in Seoul. Hedonic regression analysis provides the basic framework for this study. The major rent determinants are the preferable location of buildings, the ratio of private use area to the building area. residential use. The officetel rents are likely to increase at an increasingly rate with respect to these variables. The significant and positive determinants that impact rents is the building story height for the officetel for business use, and the ratio of private use area to the building area for the officetel for residential use.