• 전기학회논문지
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• 제61권12호
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• pp.1948-1952
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• 2012

The paper presents modal testing and analysis in order to obtain the dynamic characteristics of a middle spacer grids of a nuclear fuel rod. A spacer grid is one of the important structural elements supporting nuclear fuel rods. Such a fuel rod can be oscillated by its thermal expansion, neutron irradiation and etc. due to cooling water flow under the operation of a nuclear power plant. When the fuel rod vibrates, fretting wear due to repeated friction motion between the fuel rods and spacer grids can be occurred, and so the fuel rod is damaged. In this paper, through modal analysis and testing, natural frequencies and modes of a middle spacer grid were calculated, and the following conclusions were obtained. Firstly the numerical first-seven natural frequencies for spacer grids of a fuel rod having complicated structures have a small difference within 3.8% with experimental natural frequencies, and so the suitability of simulation results was verified. Secondly, experimental mode shapes for a middle spacer grid of a nuclear fuel rod were verified by obtaining lower non-diagonal terms through MAC(Modal Assurance Criteria), and were confirmed by the simulation modes.

• 정보처리학회논문지C
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• 제13C권1호
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• pp.11-18
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• 2006

최근의 해킹사고에서 침입자는 피해시스템에서 자신의 IP주소 노출을 피하기 위하여 피해시스템을 직접 공격하지 않고 Stepping stone(경유지)을 이용하여 경유지 우회 공격을 수행한다. 본 논문에서는 현재 네트워크 환경에서 Stepping stone을 이용한 경유지 우회 공격시 공격자의 근원지 주소를 추적하기 위한 알고리즘을 설계한다. 침입자 추적은 크게 두 가지 분류로 나뉘어 진다. 첫째는 IP Packet traceback, 둘째는 Connection traceback 이다. 본 논문에서는 Connection traceback에 공격을 다루며, 운영체제의 프로세스 구조를 이용하여 공격자 또는 Stepping stone을 구분하여 침입자의 위치를 추적한다.

• 한국전산구조공학회논문집
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• 제30권4호
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• pp.313-318
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• 2017

본 연구는 진동에너지를 흡수하기 위한 진동 금속 댐퍼의 구조 해석과 최적 설계를 수행한다. 고무 베어링, 마찰 또는 점성 댐퍼와 같은 다른 댐퍼와는 달리 이 금속제진장는 금속의 소성 변형과 그에 따른 히스테리시스 현상을 이용하여 구조물의 진동을 감소시킨다. 이 금속제진장치를 최적화 하려면 댐퍼를 통해 소성 변형을 얻는 것이 중요하다. 금속제진장치의 최적화된 형상을 찾기 위해 형상 최적화 방법을 적용하였다. 또한 매개 변수화 체계에 따라 일부 최적의 모양을 찾을 수 있다.

• 대한조선학회논문집
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• 제55권5호
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• pp.379-384
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• 2018

This study showed the development process of structural design method of BHB(Blast Hardened Bulkhead) which are applicable in preliminary design stage. In the previous 1st report, the simplified structural scantling equations of BHB were formulated theoretically using the modified plastic hinge method supplemented by considering the membrane effects due to large plastic deformation. And the scantling methodology of plate thickness and section area of stiffeners of the curtain plate type BHB was dealt with. In the present 2nd report, derivation process of the correction factors which can adjust the developed scantling equations considering the uncertainties contained in the design parameters was introduced. Considering the actual BHB structures of 3 warship, the correction factors for the developed scantling equations for curtain plate type BHB were derived. Finally the applicability, validity of them and the strategy of future improvement were considered.

• 대한안전경영과학회지
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• 제13권2호
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• pp.51-59
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• 2011

The objective of this study is to develop an evaluation model for the National highway risky areas. Thus, for the purposes of doing this, National highway risky area evaluated targeting to provide determination ranking and suggesting rival-superiority factors as well as under-inferiority factors in ten National highway risky areas. This study developed for modules of risky areas evaluation, using fuzzy set theory and analytic hierarchy process for evaluation model of National highway risky area in transport environment. The preceding studies assess risk analysis through analysis of causal relationships by National highway safety sector not only handles rating scale development suitable for assessment area by referring to accident frequency model but also geometric structures model. As result of this study, this model of Fuzzy Ahp Risk Analysis (FARA) apply for programmable design in real time processing through easily derive strategy for improvement activities to provide a decision-making effectively. Furthermore, this study contributes frame for improvements of National highway construction for renovation's priority strategy as well as future's policy schemes.

• 한국재료학회지
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• 제24권7호
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• pp.344-350
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• 2014

Metal films (i.e., Ti, Al and SUH310S) were prepared in a magnetron sputtering apparatus, and their cross-sectional structures were investigated using scanning electron microscopy. The apparatus used consisted of a cylindrical metal target which was electrically grounded, and two anode rings attached to the top and to the bottom of the target. A wire was placed along the center-line of the cylindrical target to provide a substrate. When the electrical potential of the substrate was varied, the metal-film formation rate depended on both the discharge voltage and the electrical potential of the substrate. As we made the magnetic field stronger, the plasma which appeared near the target collected on the plasma wall surface and thereby decreased the bias current. The bias current on the conducting wire was different from that for cation collection. The bias current decreased because the collection of cations decreased when we increased the magnetic-coil current. When the substrate was electrically isolated, the films deposited showed a slightly coarse columnar structure with thin voids between adjacent columns. In contrast, in the case of the grounded substrate, the deposited film did not show any clear columns but instead, showed a densely-packed granular structure. No peeling region was observed between the film and substrate, indicating good adhesion.

• 한국군사과학기술학회지
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• 제22권5호
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• pp.607-615
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• 2019

In this paper, the electromagnetic effects on the discontinuity structures of the frequency selective radome in manufacturing process based on the X-band were analyzed. In order to fabricate a curved radome using a planar frequency selective surface structure, it is assumed that gaps, slanted gaps, pattern damage, and pattern misalignment between FSS patterns, which are discontinuous elements that can occur at the joint surface of the FSS panel. FSS specimens including continuous elements were fabricated and the frequency transmission characteristics were measured in a free space measurement environment. From the measurement results, resonance frequency shift, transmission performance degradation, and bandwidth variations were found to be the largest when the damaged pattern was bonded to the junction of FSS panels.

• Steel and Composite Structures
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• 제17권5호
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• pp.561-572
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• 2014

In this paper, we present the scattering characteristics of infinite and finite array using method of moment (MoM) with Floquet harmonics and asymptotic waveform evaluation (AWE) technique. First, infinite cylindrical dipole array is analyzed using the MoM with entire domain basis function and cylindrical Floquet harmonics. To provide the validity of results, we fabricated the cylindrical dipole array and measured the transmission characteristics. The results show good agreements. Second, we analyzed the scattering characteristics of finite array. A large simulation time is needed to obtain the scattering characteristics of finite array over wide frequency range because Floquet harmonics can't be applied. So, we used the MoM with AWE technique using Taylor series and Pade approximation to overcome the shortcomings of conventional MoM. We calculated the radar cross section (RCS) as scattering characteristics using the proposed method in this paper and the conventional MoM for finite planar slot array, finite spherical slot array, and finite cylindrical dipole array, respectively. The compared results agree well and show that the proposed method in this paper is good for electromagnetic analysis of finite FSS.

• 대한조선학회논문집
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• 제58권5호
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• pp.322-329
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• 2021

Naval ships are designed to have a variety of active and passive systems to defend against enemy threats. One of the passive defense systems is to protect crew members and core equipment against the threat by using the outer plate of the equipment. This study was intended to deal with design methods against small arms ammunition and fragments. The Korea Institute of Machinery and Materials has measured the ballistic limit velocity of two types of high-tensile plate materials (AH36 and EH36) widely used in ships and offshore structures through tests in cooperation with various related organizations, and the result data is continuously accumulated. Based on the accumulated test results and data, such as mil test certificates of plate materials, it is intended to estimate the protection limit speed of high-tensile plates and to develop a simple calculating formula that can be used in the early design stage.

• 한국군사과학기술학회지
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• 제22권1호
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• pp.35-41
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• 2019

Ferrocene and ferrocene derivatives have been widely used as a burning rate catalyst for composite solid propellants. However, its tendency to migrate through the propellant grain and to crystallize at the surface changes the composition of propellant which results in unpredictable burning rate. To overcome the weakness of ferrocene catalyst, we designed a polymer containing ferrocene, poly(glycidyl azide-co-glycidyl ferrocenyl ether) (GAFP). GAFPs were synthesized from poly(epichlorohydrin-co-glycidyl ferrocenyl ether) (PEGF) which has ferrocenyl ethers in its pendant groups. The structures of GAFPs were confirmed by FT-IR, $^1H$ and $^{13}C$ NMR spectral analyses. Thermal properties of the GAFPs were evaluated using differential scanning calorimeter (DSC). As the contents of ferrocene increased, the glass transition temperature ($T_g$) of the GAFPs shifted to a higher temperature, and the decomposition temperature ($T_d$) decreased because the ferrocene worked as a burning rate catalyst.