• Bulletin of the Korean Mathematical Society
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• v.46 no.2
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• pp.245-253
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• 2009

A new hard problem called the vector decomposition problem (VDP) was recently proposed by Yoshida et al., and it was asserted that the VDP is at least as hard as the computational Diffie-Hellman problem (CDHP) under certain conditions. Kwon and Lee showed that the VDP can be solved in polynomial time in the length of the input for a certain basis even if it satisfies Yoshida's conditions. Extending our previous result, we provide the general condition of the weak instance for the VDP in this paper. However, when the VDP is practically used in cryptographic protocols, a basis of the vector space ${\nu}$ is randomly chosen and publicly known assuming that the VDP with respect to the given basis is hard for a random vector. Thus we suggest the type of strong bases on which the VDP can serve as an intractable problem in cryptographic protocols, and prove that the VDP with respect to such bases is difficult for any random vector in ${\nu}$.

• Journal of the Korean Society of Safety
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• v.31 no.4
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• pp.1-8
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• 2016

The behavior of backdraft in the compartment with different ignition locations and times was numerically investigated. The Fire Dynamics Simulator (FDS) v5.5.3 with a model-free simulation option was used in the numerical simulation of backdraft. The ignition source was located near the inside wall, at the compartment center and near the window opening, respectively. The ignition was started at the instance when the fresh air reached the ignition location or when a sufficient time passed compare to the instance of the arriving of the fresh air to the ignition location. As a result, for the ignition source was located near the inside wall, a strong fire ball was observed at once and the result was similar to the previous experimental result. For the ignition source was located at the center of the compartment, a strong fire ball was occurred and two strong fire balls were observed consecutively for the ignition time was delayed. For the ignition source was located near the window opening and longer time was given for the ignition compare the duration of the fresh air arriving to the ignition location, the rapid temperature variation was not observed because there was no flame. However, for the ignition was started at the instance when the fresh air reached the ignition location, the ignition could be initiated and a intensive fire ball was observed. The pressure measured at the upper inside part of the window opening provided a similar trend with the previous experimental result of compartment backdraft.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2006.06a
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• pp.167-175
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• 2006

Building accurate corporate bankruptcy prediction models has been one of the most important research issues in finance. Recently, support vector machines (SVMs) are popularly applied to bankruptcy prediction because of its many strong points. However, in order to use SVM, a modeler should determine several factors by heuristics, which hinders from obtaining accurate prediction results by using SVM. As a result, some researchers have tried to optimize these factors, especially the feature subset and kernel parameters of SVM But, there have been no studies that have attempted to determine appropriate instance subset of SVM, although it may improve the performance by eliminating distorted cases. Thus in the study, we propose the simultaneous optimization of the instance selection as well as the parameters of a kernel function of SVM by using genetic algorithms (GAs). Experimental results show that our model outperforms not only conventional SVM, but also prior approaches for optimizing SVM.

• International Journal of Contents
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• v.16 no.2
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• pp.30-40
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• 2020

This study performed GIS and statistical analyses on the location and spatial characteristics of the slum in Daejeon. Spatial data of 648 slum residents in Daejeon were collected and 131 residents among them were surveyed. The results showed the trends of higher rent, lower social exclusion and closer neighboring relations in slum center than the surrounding areas, which could be interpreted as the interrelated multilateral effects of the micro- (housing), meso- (relations), exo- (community) and macro- (government policy) systems. The strong bonds among neighbors and various supports from social service facilities elevated the slum area's rent and diminished residents' social exclusion more than housing conditions (for instance, poor hygiene and low safety). Slum tenants willingly paid a premium for their substandard housings and refused moving to governmentally provided modern housing units. In urban development, administrative authorities need to be cautious about slum uprooting. Much rather an alternative renewal approach is needed which protects the slum's intimate relations while improving its overall living standards.

• KDI Journal of Economic Policy
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• v.39 no.2
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• pp.53-74
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• 2017

This paper focuses on the recent extraordinary growth of Chinese cross-border online shopping and draws implications for firm strategies and government policies in Korea to utilize the phenomenon as an opportunity to expand into a broader market via e-commerce exports. I conduct a survey of Chinese cross-border online consumers to identify constraining and determining factors during the stages of their purchase decisions of Korean products. Given the fact that Chinese cross-border online shopping is at the incipient stage and consumers have expressed a strong intent to repurchase, future strategies should focus on attracting new consumers. Accordingly, Korean firms should build a powerful brand image, improve product quality and post-purchase services, and take full advantage of the popularity of the Korean Wave. Meanwhile, the government must step up policy efforts by, for instance, improving e-commerce export statistics, simplifying logistics and clearance procedures, and building trust in Chinese consumers.

• Journal of Magnetics
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• v.21 no.3
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• pp.364-373
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• 2016

The article presents the results and findings obtained through the assembly of opposing linear Halbach arrays from two magnet layers using large magnetic blocks from permanent NdFeB magnets, especially concerning the distribution of magnetic induction in an air gap. The use of these large blocks has led to a significant expansion of the area of magnetic field with a substantially higher value of magnetic induction in comparison with similar linear Halbach arrays composed of small magnets. The paper also discusses the determined dependences of magnetic induction on the parameters of the x, y, z coordinate system and indicates the possibilities of achieving an even stronger magnetic field in a larger volume of an air gap for application for instance in equipment for magnetic separation of raw materials, in instrument technologies and in other areas.

• Proceedings of the Korean Society of Food Science and Nutrition Conference
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• 2004.11a
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• pp.37-42
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• 2004

The relatively new concept of functional foods is supportive of sales of food products that deliver isolated 'nutrient' or 'food compound' substances, much as is done by dietary supplements. Whether such isolated substances have benefit must be investigated in each instance; such investigations can be complex. At the same time, simply prepared natural plant foods contain a myriad of substances that, in accord with the concept of food synergy, are beneficial for health. Whole grain foods are an example of such healthy fare, based on strong epidemiologic and experimental evidence. If the concept of functional foods is to be of use for the public health, it should support the consumption of healthy traditional foods as well as promoting 'novel' foods; in this sense, whole grain foods, which have great functionality, should be regarded as functional foods.

• Journal of applied mathematics & informatics
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• v.31 no.5_6
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• pp.813-823
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• 2013

In this paper, a new iterative algorithm involving quasi-nonexpansive mapping in Hilbert space is proposed and proved to be strongly convergent to a point which is simultaneously a fixed point of a quasi-nonexpansive mapping, a solution of an equilibrium problem and the set of solutions of a variational inequality problem. The results of the paper extend previous results, see, for instance, Takahashi and Takahashi (J Math Anal Appl 331:506-515, 2007), P.E.Maing $\acute{e}$ (Computers and Mathematics with Applications, 59: 74-79,2010) and other results in this field.

• Korean Journal of Human Ecology
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• v.9 no.1
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• pp.63-70
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• 2000

The purpose of this study is The results was that consumers who like to the top brand's commodities, had commonly high tendency to and fro its trademark and store allegiance. Furthermore, they have usually bought something following on their inclination what they had purchased as well as the store decoration character and the marketing promotion attribute. The other consumers who prefer to the discount store's merchandises, had also high propensity and the biggest influence on buying something which were those factors; their instance shopping habit, utility-economy trait, follow the fashion character and strong circumspection tendency besides using the mass media Info., personal data and commodities' attribute.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.8
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• pp.607-614
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• 2013

In this work we investigate the power of power law in the VoD service over IP network. Especially, we show that the power of power law is strong in the location of the contents storage for the VoD service and its impact on the link dimensioning. This work first shows the instance of the power law in the popularity of the video contents from the real data for the IPTV service. After that we propose an analytic model that characterizes the behavior of customers in accessing the video servers as well as the power law in the viewing pattern. Finally, we show the impact of the power law by proposing a model for the cost as well as link dimensioning. Via numerical experiment we show the implication of the proposition.