• Bulletin of the Korean Mathematical Society
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• v.55 no.4
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• pp.1161-1178
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• 2018

In this paper, we consider the Cauchy problem for a class of nonlinear sixth-order wave equation. The global existence and the finite time blow-up for the problem are proved by the potential well method at both low and critical initial energy levels. Furthermore, we present some sufficient conditions on initial data such that the weak solution exists globally at supercritical initial energy level by introducing a new stable set.

• Journal of the Korea Society of Computer and Information
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• v.24 no.10
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• pp.257-265
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• 2019

The purpose of the present study was to examine the causal relationship between aggression and mobile phone dependency among high school students and to test the mediating effect of self-esteem, and to draw out implications in order to encourage proper use of mobile phone. In this paper, we proposed a research model between aggression, self-esteem and mobile phone dependency. The present study analyzed the fourth, fifth, and sixth wave data from KCYPS 2010, using the structural equation modeling. The primary results were as follows. First, the effect of high school students' aggression on mobile phone dependency was not significant. Second, high school students' aggression had a significantly negative effect on self-esteem. Third, high school students' self-esteem had a significantly positive effect on mobile phone dependency. Fourth, high school students' self-esteem could be a significant mediator between aggression and mobile phone dependency. In conclusion, theoretical and practical suggestions were discussed in order to solve the problem of adolescents' mobile phone dependency.