• 대한방사선치료학회지
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• 제14권1호
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• pp.79-84
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• 2002

1.목적 : 작고 불규칙한 모양의 전자선 조사면에서 선원의 출력에 영향을 미치는 요인은 선형가속기의 collimation system, insert block diameter, energy 등이다. 때문에 이러한 조사면의 선량계산으로 LBR을 이용할 수 있는데 LBR(lateral build-up ratio)이란 동일한 incident fluence와 profile에 대해 circular field와 broad field의 선량비로서 나타낼 수 있다. 얻어진 LBR data는 elementary pencil beam 모형을 근거해 깊이와 에너지에 따른 함수(${\sigma}$)로 표현할 수 있다. 여기에서 얻어진 수식을 기초로 해서 만들어진 factor값이 작고 부정형의 전자선 조사면의 선량계산 유용성을 알아보고자 한다. 2.재료 및 방법: 심부선량은 water phantom에서 ion chamber로 측정하였다. Cerrobend와 electron applicator 에 따른 incident fluence의 변화를 알아보기 위해 Chamber를 0.5mm깊이에 놓고 측정하였다. 그리고 에너지와 electron applicator 크기에 따라 insert block diameter를 2-15cm로 변화시키며 심부선량을 측정하였고 이 값을 0.5mm 깊이에서 normalization 하였다. 이렇게 normalization 한 그래프로부터 LBR과 함수 (${\sigma}$)를 얻어했다. 3.결과 : 0.5mm 깊이에서 normalization한 심부선량-그래프로부터 LBR data와 그로부터 얻어낸 (${\sigma}$)함수 값을 기초로 하여 elementary pencil beam 모형의 깊이에 빠른 선량변화의 수식을 얻어낼 수 있었다. 4.결론 : 부정형 전자선 조사면에 대해 MU당 심부선량은 작은 circular field에서 측정된 LBR값, reference applicator와 insert block diameter 에 따른 incident fluence factor 그리고 reference broad field에서의 심부선량등 세 가지 data로 부터 계산할 수 있다. 이 방법을 이용하면 어떤 모양의 전자선 조사면에 대해서도 심부선량의 계산에 유용하다고 할 수 있다.

• 한국시뮬레이션학회논문지
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• 제30권1호
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• pp.55-63
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• 2021

본 논문은 전투 시뮬레이션 상에서 모의되는 무기체계의 방호성능에 대한 연구로, 입사각도에 따른 방호성능의 개선효과를 제시하고자 하였다. 이를 위해, 여러 속도로 발사된 5.45 mm 보통탄을 사용한 소화기 위협에 대하여 일반적으로 사용되는 균일압연강판 재질의 장갑판 3종의 완전 및 부분관통 여부를 판정하는 실사격 탄도실험이 수행되었다. 주요 실험 변수는 무기체계 장갑의 재질 그리고 탄자의 입사각도이었다. 또한, 방호성능에 대한 정량적인 분석을 위하여 기존 세 가지 방호한계속도 측정방법들이 사용되었다. 그 결과 탄자의 입사각이 30도인 경우 장갑의 방호성능은 0도인 경우 대비 재질별 1.04배부터 1.14배까지 향상되었으며, 방호효과가 평균적으로 약 1.1배 개선되는 것을 확인하였다. 이러한 실험결과는 장갑판의 방호성능을 증진시키는 변수에 반영되어 보다 현실에 가까운 전투 시뮬레이션을 개발하는데 기여할 것으로 기대된다.

• 한국재료학회지
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• 제9권1호
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• pp.25-29
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• 1999

We have developed a laser molecular beam epitaxy system for the layer-by-layer growth of oxide thin films. Using this system, we could grow and control oxide thin films of LaAlO$_3$in a molecular layer epitaxy mode on the atomically flat SrTiO$_3$ substrate with a LaAlO$_3$single crystal target. Very clear RHEED oscillations were observed during to growth of a LaAlO$_3$ film for a long period under the optimized conditions of substrate temperature at $650^{\circ}C$, oxygen pressure at 1$\times$10\ulcorner torr, and an incident laser fluence of 4.6J/$\textrm{cm}^2$. The height of mono-layer-LaAlO$_3$ film grown during one period of RHEED intensity oscillation was 3.8$\AA$.

• 한국결정성장학회지
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• 제9권4호
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• pp.377-380
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• 1999

Erbium (Er) doped $LiNbO_{3}(Er:LiNbO_{3})$ single crystal fibers were grown free of creacks along the c-axis by micro-pulling down method. The $Er^{3+}$ concentration was distributed homogeneously along the growth axis. The samples for optical characterization were cut from as-grown single crystal fibers and polished. When the 980nm light was incident on the sample, upconversion phenomena were observed at the green range of wavelength 510~570nm. In addition, the intensity of upconversion was remarkably increased by increasing the concentration of $Er_{2}O_{3}$ dopant in as-grown $Er:LiNbO_{3}$ crystals.

• Advances in Computational Design
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• 제1권4호
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• pp.329-344
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• 2016

In this paper, a methodology to simulate the whole-building behaviour of the tall building under fire is developed by the author using a 3-D nonlinear finite element method. The mechanical and thermal material nonlinearities of the structural members, such as the structural steel members, concrete slabs and reinforcing bars were included in the model. In order to closely simulate the real condition under the conventional fire incident, in the simulation, the fire temperature was applied on level 9, 10 and 11. Then, a numerical investigation on the whole-building response of the building in fire was made. The temperature distribution of the floor slabs, steel beams and columns were predicted. In addition, the behaviours of the structural members under fire such as beam force, column force and deflections were also investigated.

• Journal of Advanced Research in Ocean Engineering
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• 제4권3호
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• pp.135-145
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• 2018

This paper deals with the added resistance of a ship in waves using computational fluid dynamics (CFD). The ship added resistance is one of the key considerations in the design of energy-efficient ship. In this study, the added resistance of a LNG carrier in head waves is computed using a CFD code to consider the nonlinearity and the viscous effects. The unsteady Reynolds Averaged Navier-Stokes equation (RANS) is numerically solved and the volume of fluid (VOF) approach is used to simulate the free surface flows. The length of incident wave varies from half the ship length to twice the ship length. To investigate the nonlinearity effect, both the linear wave condition and the nonlinear wave condition are considered. The heave and pitch motions are calculated along with the added resistance, and the wave contours are obtained. Grid convergence test is conducted thoroughly to achieve the converged motion and resistance values. The calculated results are compared and validated with experimental data.

• 한국광학회지
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• 제4권4호
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• pp.428-433
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• 1993

공간적으로 Gaussian인 Q-switched Nd:LYAG레이저의 제2고조파 빛살을 일정한 반경의 pinhole로 중심부분만 통과시켜 집광렌즈로 집광시킨 후, 렌즈의 초점면에서 빛살모양을 관찰하여 본 결과 원형 대칭을 갖는 비Gaussian모양을 하고 있음을 확인할 수 있었다. 이 빛살의 집광영역내에서 두께 1mm의 $CS_2$를 이동(z-scan)하여 가며 자체집광효과에 의하여 변화되는 투과도특성을 조사하였다. 측정된 결과를 Fresnel 이론과 1.5% 이내의 오차 범위로 일치함을 알 수 있었고, 자체집광효율이 입사빛의 공간적 모양과 관계함을 확인할 수 있었다.

• Journal of Communications and Networks
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• 제14권2호
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• pp.213-221
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• 2012

The architecture of an interconnection network is usually represented by a graph, and a graph G is bipancyclic if it contains a cycle for every even length from 4 to ${\mid}V(G){\mid}$. In this article, we analyze the conditional edge-fault-tolerant properties of an enhanced hypercube, which is an attractive variant of a hypercube that can be obtained by adding some complementary edges. For any n-dimensional enhanced hypercube with at most (2n-3) faulty edges in which each vertex is incident with at least two fault-free edges, we showed that there exists a fault-free cycle for every even length from 4 to $2^n$ when n($n{\geq}3$) and k have the same parity. We also show that a fault-free cycle for every odd length exists from n-k+2 to $2^n-1$ when n($n{\geq}2$) and k have the different parity.

• International Journal of Fluid Machinery and Systems
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• 제3권4호
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• pp.279-284
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• 2010

Tip clearance losses occur in every turbomachine. To estimate the losses in efficiency it is important to understand the mechanism of this secondary flow. Tip clearance losses are mainly caused by a spiral vortex formed on the suction side of the blade of a turbomachine, which induces a drag and also has an influence on the incident flow of the blades. In this paper a physical based scaling method is developed out of an analytical ansatz for the tip clearance losses. This scaling method is validated by measurements on an axial fan with five different tip clearances.

• 디지털산업정보학회논문지
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• 제4권3호
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• pp.33-43
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• 2008

As internet is spreaded widely, the number of cyber terror using hacking and virus is increased. Also the hacking to the internet shopping mall go on increasing. If the large shopping mall is attacked by the hacker, a number of user's information are exposed to the hacker. The private information as like a resident registration number, user's real name, the date of user's birth, the mobile phone number, the office phone number / address, the home phone number / address and so on include the information. These information are used in the phishing e-mails / call and spam. And them are selling and buying maliciously. The large internet shopping mall 'auction' was hacked in April, 2008. After the incident, this paper suggested a countermeasures on the hacking for the internet shopping mall. The technical item and political item are included among the countermeasures. The countermeasures can protect the hacking not only the internet shopping mall but also the web sites basically.