• Journal of the Korea Society for Simulation
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• v.10 no.1
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• pp.83-92
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• 2001

For the prevention of the network intrusion from damaging the system, both IDS (Intrusion Detection System) and Firewall are frequently applied. The collaboration of IDS and Firewall efficiently protects the network because of making up for the weak points in the each demerit. A model has been constructed based on the DEVS (Discrete Event system Specification) formalism for the simulation of the system that consists of IDS and Firewall. With this model we can simulation whether the intrusion detection, which is a core function of IDS, is effectively done under various different conditions. As intrusions become more sophisticated, it is beyond the scope of any one IDS to deal with them. Thus we placed multiple IDS agents in the network where the information helpful for detecting the intrusions is shared among these agents to cope effectively with attackers. If an agent detects intrusions, it transfers attacker's information to a Firewall. Using this mechanism attacker's packets detected by IDS can be prevented from damaging the network.

• Journal of the Korea Society for Simulation
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• v.14 no.1
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• pp.9-18
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• 2005

Attempts to attack hosts in the network have become diverse, due to crackers developments of new creative attacking methods. Under these circumstances the role of intrusion detection system as a security system component gets considerably importance. Therefore, in this paper, we have suggested multiple intrusion detection system based on the contract net protocol which provides the communication among multiple agents. In this architecture, fuzzy rule based system has been applied for agent selection among agents competing for being activated. The simulation models are designed and implemented based on DEVS formalism which is theoretically well grounded means of expressing discrete event simulation models.

• Proceedings of the Korea Society for Simulation Conference
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• 2004.05a
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• pp.7-12
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• 2004

공개키 기반 구조(PKI; Public Key Infrastructure)에 필수적인 요소인 인증서의 상태 검증에 있어서 인증서 상태 검증 서버인 OCSP (Online Certificate Status Protocol) 서버는 실시간 상태 검증을 제공한다. 그러나, 서버와 클라이언트의 메시지 인증을 위해 전자 서명을 수행해야 하며, 이 때 사용되는 공개 암호 연산 과정의 복잡성은 동시에 많은 클라이언트의 요청이 발생할 경우에 응답 시간을 크게 지연시킨다는 단점을 가지고 있다. 본 논문에서는 이러한 문제를 해결하기 위한 인증서 상태 검증 서버의 시뮬레이션 모델을 DEVS (Discrete Event system Specification) 방법론을 이용하여 설계하였다. 이 모델은 인증서의 상태 검증을 요청하는 영역에 위치하여 해쉬 함수를 적용한 인증을 수행하도록 구성되었으며, 시뮬레이션 결과는 제시한 방법이 인증서 상태 검증 속도를 증대시켜 결과적으로 사용자의 응답 시간이 감소되는 것을 보여준다.

• Journal of the Korea Society for Simulation
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• v.8 no.4
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• pp.89-107
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• 1999

There are many issues in computer simulation such as verifying model code, validating models, understanding the dynamics of systems and training the personnel. The developers of simulation tool have been interested in the animation since it can help solve the problems related to the above listed issues. In practice, animation is one of the popular method for displaying the simulation output for solving these problems. Trying to display all the graphic objects representing the dynamics of the models being simulated, however, causes the distraction of focus, which results in solving the above listed problems difficult. The redundant graphic objects also Increase the computer computation overhead. This paper presents a hierarchical animation environment in which the users can have better focus on the dynamics of system components. In hierarchical animation environment the users can observe the dynamics of system by selectively choosing the hierarchical level and components with in a level of the hierarchically structured model. Especially when the model is large and complex the selection of observation level is needed. The design approach of the hierarchical animator is based on the DEVS(Discrete Event system Specification) formalism which is theoretically well grounded means of expressing modular and hierarchical models.

• Journal for History of Mathematics
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• v.12 no.1
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• pp.32-44
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• 1999

This paper is a sequel to [8]. Development of modern logic was initiated by Boole and Morgan. Boolean logic is one of their completed works. Cantor created the set theory along with cardinal and ordinal numbers. His theory on infinite sets brought about a remarkable development on modern mathematical theory, but generated many paradoxes (e.g. Russell Paradox) that in turn motivated mathematicians to solve them. Further, mathematicians attempted to construct sound foundations for Mathematics. As a result three important schools of thought were formed in relation to fundamentals of mathematics for the resolution of paradoxes of set theory, namely logicism developed by Russell and Whitehead, intuitionism lead by Brouwer and formalism contended by Hilbert and Bernays. In this paper, we examine the logic for intuitionism which is originated by Brouwer in 1908 and study Heyting algebra.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.39.2-39.2
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• 2010

We have investigated the evolution of the galaxy morphology in the hierarchical universe taking advantage of Semi-Analytic Model (SAM). It is well known that the galaxy morphology is related to the dynamical and the chemical evolution. This implies that we need to understand overall physical processes in the galaxy to reproduce its morphology. Thus we implemented gradual hot gas stripping of satellite galaxies in a galaxy cluster and recycling of stellar mass losses into our model in order to describe star formation rate of galaxies accurately. To morphologically classify galaxies, the evolution of disc and bulge components is traced carefully. We compute our models based on the dark matter halo merger trees generated by N-body simulations as well as the Extended Press-Schechter (EPS) formalism. We present morphological differences caused by the use of different merger trees.

• Journal of The Korean Astronomical Society
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• v.46 no.2
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• pp.93-96
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• 2013

Modified Newtonian Dynamics (MOND) is a possible solution for the missing mass problem in galactic dynamics; its predictions are in good agreement with observations in the limit of weak accelerations. However, MOND does not derive from a physical mechanism and does not make predictions on the transitional regime from Newtonian to modified dynamics; rather, empirical transition functions have to be constructed from the boundary conditions and comparisons with observations. I compare the formalism of classical MOND to the scaling law derived from a toy model of gravity based on virtual massive gravitons (the "graviton picture") which I proposed recently. I conclude that MOND naturally derives from the "graviton picture" at least for the case of non-relativistic, highly symmetric dynamical systems. This suggests that-to first order-the "graviton picture" indeed provides a valid candidate for the physical mechanism behind MOND and gravity on galactic scales in general.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.146-151
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• 2009

In this paper, a weight function theory for the calculation of the mode III stress intensity factor in a rectilinear anisotropic body is formulated. This formulation employs Lekhnitskii's formalism for two dimensional anisotropic materials. To illustrate the method used for the weight function theory, we calculated the mode III stress intensity factor in a single edge-notched configuration.

• 제어로봇시스템학회:학술대회논문집
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• 1987.10b
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• pp.19-22
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• 1987

A program is developed for generations the dynamic equations for robotic manipulators using the symbolic language muSIMP/MATH. The muSIMP/MATH is a LISP-based computer algebra package, devoted to the manipulation of algebraic expressions including number, variables, functions, and matrix. The muSIMP/MATH can operate on IBM-PC compatibles with MS-DOS. The program is developed, on the e formalism. This is program is applicable to the manipulators of any number of degrees of freedom, maximum six degree of freedom in this program. To control robotic manipulators by using dynamic equation is required a symbolic equations. The generated dynamic equation can be applied directly to the robotic manipulators, for the generated dynamic equation is a reduced form of symbolic expression.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.3
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• pp.34-40
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• 1997

Intervalence subband absroption of normally incident infrared radiation in p-type InGaAs-InAlAs coupled quantum well (CQW) is theoretically investigated by the multiband effective mass formalism. By solving a 4*4 luttinger-kohn hamitonian, we calculate valence subband structures, intervalence subband transition matrix elements, and absorption coefficient spectrum in the CQW which consists of a wider well, a thinner well and a barreir between them. Using the flexible design parameters given to the valence band CQW structure, we show that the absorption coefficient profile can be tailored. For a carefully designed CQW, theabsorption coefficient cn be made to maintain a large value over a wider wavelength range of incident infrared radiation compared with that shown in intersubband absorption in usual single quantum well.