• Journal of the Society of Naval Architects of Korea
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• v.46 no.2
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• pp.155-164
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• 2009

In this paper, a spectral finite element method for a rectangular sandwich plate with viscoelastic core having the Levy-type boundary conditions has been plated. The sandwich plate consists of two isotropic and elastic face plates with a surfaced-bonded viscoelastic core. For the analysis, the in-plane and transverse energy in the face plates and only shear energy in the core are considered, respectively. To account for the frequency dependent complex shear modulus of the viscoelastic core, the Golla-Hughes-McTavish model is adopted. To evaluate the validity and accuracy of the proposed method, the frequency response function and dynamic responses of the sandwich plate with all edges simply supported subject to an impact load are calculated and compared with those calculated by a finite element method. Though these calculations, it is confirmed that the proposed method is very reliable and efficient one for vibration analysis of a rectangular sandwich plate with viscoelastic core having the Levy-type boundary conditions.

• The Korean Journal of Financial Management
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• v.25 no.2
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• pp.33-68
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• 2008

The purpose of this paper is to test the market timing hypothesis and impact of macro economic variables on capital structure choice as well as the traditional static trade-off and pecking order theories of capital structure in a integrated framework. Through a two stage test of target capital structure and capital structure choice, none of theories was consistently supported, but most of them were partly supported. In the first stage analysis of target ratio, coefficients of firm-specific variables generally supported the predictions of pecking order theory rather than those of the static trade-off theory. However, the result of the second stage test on capital structure choice supported the hypothesis of the static trade-off theory, which claims that firms usually set and pursue the target leverage ratio. Further, the result of the seconde stage shows that a simple pecking oder theory does not hold because firms with deficit of internal fund tend to issue bonds rather than stocks to raise outside fund. Also, the result indicates that the market timing hypothesis holds because firms with over-valued stocks tend to issue stocks rather than bonds. However, contrary to Korajczyk and Levy(2003), the impact of macro economic variables such as term or credit spreads on capital structure choice was negligible, and the impact of macro economic and market timing hypothesis variables were not greater in financially unconstrained firms as Korajczyk and Levy(2003) suggested.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.26 no.5
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• pp.1-18
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• 2023

The Ecosystem Conservation Levy (formerly known as the Ecosystem Conservation Cooperation Fund) system has been in place for 20 years, and it can be said that it has now entered the settlement stage. Based on an analysis of publicly available project implementation data from 2014 to 2020, we found that: 1) As the number of return projects increases, the targets of restoration technologies are also strengthening, and it is necessary to frame a series of processes from application, creation, and monitoring for some detailed projects to improve the effectiveness and efficiency of utilizing the levy. 2) Most of the implemented projects are applied as micro-ecosystem creation, but there are many cases where the contents of the project can be seen as other project categories. This shows that the purpose of the return project needs to be approached more clearly and suggests that institutional complementation is needed from the project application stage. 3) The detailed technologies applied tend to be gradually expanding, but most of them are technologies that are not differentiated from general development projects. It is urgent to secure a more technical identity, such as a range and list of utilized technologies suitable for the characteristics and purposes of return projects. 4) It is necessary to establish a relevant evaluation system or framework to utilize the monitoring results of restoration projects. 5) There have been few cases of application of single restoration technologies since the beginning, but the content and scope of the complexity tend to expand in recent years. Even if the objectives are not comprehensive and diverse, it can be seen that many parts of the projects are oriented toward convergence, so it is necessary to conduct separate research on this. 6) As for the direction of improvement of the return project, it is possible to consider expanding the restoration and conservation focus to partially accommodate the complexity of the natural environment and human ecology. It seems that the expansion of restoration technologies that consider the role and function of humans in the natural environment should be explored.

• Journal of the Korean Mathematical Society
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• v.38 no.3
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• pp.577-594
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• 2001

In this paper we establish limit theorems on the large and small increments of a two-parameter Gaussian random process on rectangles in the Euclidean plane via estimating upper bounds of large deviation probabilities on suprema of the two-parameter Gaussian random process.

• Journal of the Korean Mathematical Society
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• v.35 no.3
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• pp.793-802
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• 1998

We apply the generalization of Levy's infinitesimal equation $\delta$X(t) = $\psi$(X(s), s $\leq$ t, $Y_{t}$, t, dt), $t\in R^1$, for a random field X (C) indexed by a contour C or by a more general set. Assume that the X(C) is homogeneous in x, say of degree n, then we can appeal to the classical theory of variational calculus and to the modern theory of white noise analysis in order to discuss the innovation for the X (C.)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.121-122
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• 2003

Deposition to the sea surface is one of ozone's principal loss mechanisms (Galbally and Roy, 1980; Levy et al., 1985; Kramm, 1995). However, since complicated physical and chemical processes are involved, large uncertainties remain in evaluating this loss mechanism that need to be better characterized. In this study we attempted to explore possible causes that give rise to large variability of ozone deposition velocity in terms of wind speed and chemical reactivity in the aqueous-phase film. (omitted)

• Communications of the Korean Mathematical Society
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• v.21 no.4
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• pp.787-794
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• 2006

Two main results are presented in relation to subordination, self-decomposability and semi-stability. One of the result is that strict semi-stability of subordinand process by selfdecomposable subordinator gives semi-selfdecomposability of the subordinated process. The second result is a sufficient condition for any subordinated process arising from a semi-stable subordinand and a semi-stable subordinator to be semi-selfdecomposable.

• Journal of the Korean Mathematical Society
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• v.57 no.2
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• pp.359-381
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• 2020

In this paper we established new results of existence of conditional expectation for closed convex and unbounded Pettis integrable random sets without assuming the Radon Nikodym property of the Banach space. As application, new versions of multivalued Lévy's martingale convergence theorem are proved by using the Slice and the linear topologies.

• Journal of applied mathematics & informatics
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• v.28 no.3_4
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• pp.863-875
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• 2010

In this paper we apply the martingale approach, which has been widely used in mathematical finance, to investigate the optimal investment problem for an insurer under the criterion of mean-variance. When the risk and security assets are described by the L$\acute{e}$vy processes, the closed form solutions to the maximization problem are obtained. The mean-variance efficient strategies and frontier are also given.

• Management Science and Financial Engineering
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• v.19 no.2
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• pp.37-42
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• 2013

This paper suggests a numerical method for valuation of European and American options under the two L$\acute{e}$vy Processes, Normal Inverse Gaussian Model and the Variance Gamma model. The method is based on approximation of underlying asset price using a finite-state, time-homogeneous Markov chain. We examine the effectiveness of the proposed method with simulation results, which are compared with those from the existing numerical method, the lattice-based method.