• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.135-141
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• 2005

A hybrid central-WENO scheme is proposed. The fifth order WENO-LF scheme is coupled with a central flux scheme at cell face. Two sub-schemes, the WENO-LF scheme and the central flux scheme, are switched by a weighting function. The efficiency and accuracy of the proposed hybrid central-WENO scheme is validated through several numerical experiments.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04a
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• pp.454-456
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• 2000

실시간의 특성을 가지는 데이터의 경우 네트워크상에서 분실된 패킷을 복구시키기 위해서 FEC 방법을 사용한다. FEC는 최소한의 지연만으로 손실 패킷의 복구를 효율적으로 할 수 있는 장점을 가지고 있으나 네트워크상에서의 패킷 손실 특성에 많이 의존되는 경향이 있다. ITU-T의 Study Group 16 에서의 Real-Time Transport Protocol(RTP)를 사용하여 네트워크에서 분실된 패킷을 복원시키는 방법으로 Media-independent error-correction scheme을 정하였다. 이 Scheme에 의해 만들어진 error-correction을 위한 신호화 media bitstream은 UDP 에 의해 encapsulation될 RTP에 실리게 된다. Scheme은 real-time이라는 환경에 유리하도록 bandwidth 와 latency 그리고 cost를 최소화하려고 했으며 이에 따라 네 가지 scheme을 정하였다. 네 가지의 Scheme은 오버헤드와 지연시간이 크기가 차별화를 두어 네트워크 환경의 변화에 적응하도록 하였다. 그러나 네트워크 환경에 보다 더 탄력적이며 효율적으로 적응하기 위해서 또 하나의 scheme을 제안한다. 새로 고안한 이 다섯 번째 scheme은 scheme 3 에 비해 작은 latency를 가지고 장점이 있는 반면 연속적으로 분실된 패킷에 대한 복원확률이 다소 떨어진다. 하지만 scheme 1과 2에 비해서는 연속적인 패킷 분실의 복원확률이 높아 네트워크환경에 따라 scheme 4를 사용하면 네 개의 scheme을 사용하여 분실패킷의 복원을 하는 경우보다 보다 효율적인 전송과 복원이 이루어질 것이다.

• The Transactions of the Korea Information Processing Society
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• v.6 no.3
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• pp.664-671
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• 1999

Itakura and Nakamura proposed the first multisignature scheme based on RSA signature scheme. But if many users sign on one paper, then their scheme has a reblocking problem. In 1991, Ohta and Okamoto proposed a multisignature scheme by using Fiat-Shamir signature scheme. But in this scheme, the group of signers must generate common random number in the first round, and in the second round, they sign the message with common random number. Also L.Harn proposed a multsignature scheme which is based on the ElGamal's. In korea, S.D.Kim et al. at ICEIC'95 conference, proposed an efficient sequential multisignature scheme by using the modified Park-Won scheme. This scheme is not require an additional round to generate common random number, and has fixed signature length. In this paper, we analyze problem of Kim's multisignature scheme, and propose a new multisignature scheme based on ${\gamma}$\ulcorner residuosity problem.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.6
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• pp.1034-1042
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• 2010

This study investigates effects of three different parameterizations of vertical mixing scheme on upper ocean simulation of the East Sea, focusing on the seasonal variations of the sea surface temperature(SST) and the mixed layer depth(MLD) using an ocean general circulation model(GFDL MOM1.1). The considered vertical mixing schemes are the Laplacian scheme(L scheme) that use a constant eddy coefficient, the Mellor-Yamada scheme(MY scheme), and a new scheme(Noh scheme). The Noh scheme, a second-order turbulence closure, was developed considering recent observational evidences such as the enhancement of turbulent kinetic energy near the sea surface. During summer L scheme underestimates the SST, while MY scheme overestimates the SST, compared to climatological SST. Noh scheme produces the SST in better agreement with climatological one. During winter all schemes overestimate the SST up to $4^{\circ}C$ compared to climatological SST. Vertical profiles of the basin-mean temperature show that L scheme produces higher temperature below the thermocline than those of other schemes. The winter MLD simulated from L scheme is rather large compared to that from other schemes, but the differences in MLD during summer are not significant.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.1
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• pp.9-19
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• 2011

Secure and efficient authentication schemes over insecure networks have been a very important issue with the rapid development of networking technologies. Wang et al. proposed a remote user authentication scheme using smart cards. However, recently, Chen et al. pointed out that their scheme is vulnerable to the impersonation attack and the parallel session attack, and they proposed an enhanced authentication scheme. Chen et al. claimed that their scheme is secure against the various attacks. However, we have found that their scheme cannot resist the parallel attack and the stolen smart card attack. Therefore, in this paper, we show the security flaws in Chen et al.'s scheme and propose an improved remote user authentication scheme using tamper-resistant smart cards to solve the problem of Chen et al.'s scheme. We also analyze our scheme in terms of security and performance.

• Journal of Korean Library and Information Science Society
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• v.23
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• pp.439-469
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• 1995

The purpose of this study is to develop a new domestic (national) law classification scheme with universality. An underlying reason for the development of this scheme reset upon the fact that Civil law system, Common law system, Socialistic law system have had difficulties each other and that current classification scheme covering three law systems have not been still in existence. From the comparative discussion of classification schemes that are the representative of each law system, a new national law classification scheme with universality was designed. If law classification scheme have been completeness, this new scheme must be combined with jurisprudence and international law classification scheme which was developed already.

• International Journal of Reliability and Applications
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• v.11 no.1
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• pp.17-22
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• 2010

It is desired to estimate the reliability of a system that has two subsystems connected in series where each subsystem has two components connected in parallel. A batch sequential sampling scheme is introduced. It is shown that the batch sequential sampling scheme is asymptotically optimal as the total number of units goes to infinity. Numerical comparisons indicate that the batch sequential sampling scheme performs better than the balanced sampling scheme and is nearly optimal.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.6
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• pp.1179-1194
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• 1992

QUICKER scheme has several attractive properties. However, under highly convective conditions, it produces overshoots and possibly some oscillations on each side of steps in the dependent variable when the flow is convected at an angle oblique to the grid line. Fortunately, it is possible to modify the QUICKER scheme using non-linear and linear functional relationship. Details of the development of polynomial upwinding scheme are given in this paper, where it is seen that this non-linear scheme has also third order accuracy. This polynomial upwinding scheme is used as the basis for the SHARPER and SMARTER schemes. Another revised scheme was developed by partial modification of QUICKER scheme using CDS and UPWIND schemes(QUICKUP). These revised schemes are tested at the well known bench mark flows, Two-Dimensional Pure Convection Flows in Oblique-Step, Lid Driven Cavity Flows and Buoyancy Driven Cavity Flows. For pure convection oblique step flow test problem, QUICKUP, SMARTER and SHARPER schemes remain absolutely monotonic without overshoot and oscillation. QUICKUP scheme is more accurate than any other scheme in their relative accuracy. In high Reynolds number Lid Driven Cavity Flow, SMARTER and SHARPER schemes retain lower computational cost than QUICKER and QUICKUP schemes, but computed velocity values in the revised schemes produced less predicted values than QUICKER scheme which is strongly effected by overshoot and undershoot values. Also, in Buoyancy Driven Cavity Flow, SMARTER, SHARPER and QUICKUP schemes give acceptable results.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.631-638
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• 2000

Pioneering work by Terzaghi imparted scientific and mathematical bases to many aspects of this subject and many people use this theory to measure the consolidation settlement until now. In this paper, Finite Difference Methods for consolidation are considered. First, it is shown the stability criterion of Explicit scheme and the Crank-Nicolson scheme, although unconditionally stable in the mathematical sense, produces physically unrealistic solutions when the time step is large. it is also shown that The Fully Implicit scheme shows more satisfactory behavior, but is less accurate for small time steps. and then we need to decide what scheme is more proper to consolidation. The purpose of this paper is to suggest the pertinent scheme to consolidation.

• Journal of the Korean Mathematical Society
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• v.54 no.1
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• pp.141-175
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• 2017

We present a high-resolution van Leer-type numerical scheme for the isentropic model of fluid flows in a nozzle with variable cross-section. Basically, the scheme is an improvement of the Godunov-type scheme. The scheme is shown to be well-balanced, as it can capture exactly equilibrium states. Numerical tests are conducted which include comparisons between the van Leer-type scheme and the Godunov-type scheme. It is shown that the van Leer-type scheme achieves a very good accuracy for initial data belong to both supersonic and supersonic regions, and the exact solution eventually possesses a resonant phenomenon.