武器體系紹介

이현근 해군대학 1986 海洋戰略 Vol.- No.41

A CONSTRAINED CONVEX SPLITTING SCHEME FOR THE VECTOR-VALUED CAHN–HILLIARD EQUATION

이현근,이준엽,JAEMIN SHIN 한국산업응용수학회 2019 Journal of the Korean Society for Industrial and A Vol.23 No.1

In contrast to the well-developed convex splitting schemes for gradient flows of two-component system, there were few efforts on applying the convex splitting idea to gradient flows of multi-component system, such as the vector-valued Cahn–Hilliard (vCH) equation.In the case of the vCH equation, one need to consider not only the convex splitting idea but also a specific method to manage the partition of unity constraint to design an unconditionally energy stable scheme. In this paper, we propose a constrained Convex Splitting (cCS) scheme for the vCH equation, which is based on a convex splitting of the energy functional for the vCH equation under the constraint. We show analytically that the cCS scheme is mass conserving and unconditionally uniquely solvable. And it satisfies the constraint at the next time level for any time step thus is unconditionally energy stable. Numerical experiments are presented demonstrating the accuracy, energy stability, and efficiency of the proposed cCS scheme.

핵연료 피복관용 다중층 SiC 복합체 튜브의 Hoop Stress 전산모사 연구

이현근,김대종,박지연,김원주,Lee, Hyeon-Geun,Kim, Daejong,Park, Ji Yeon,Kim, Weon-Ju 한국세라믹학회 2014 한국세라믹학회지 Vol.51 No.5

Silicon carbide-based ceramics and their composites have been studied for application to fusion and advanced fission energy systems. For fission reactors, $SiC_f$/SiC composites can be applied to core structural materials. Multilayered SiC composite fuel cladding, owing to its superior high temperature strength and low hydrogen generation under severe accident conditions, is a candidate for the replacement of zirconium alloy cladding. The SiC composite cladding has to retain its mechanical properties and original structure under the inner pressure caused by fission products; as such it can be applied as a cladding in fission reactor. A hoop strength test using an expandable polyurethane plug was designed in order to evaluate the mechanical properties of the fuel cladding. In this paper, a hoop strength test of the multilayered SiC composite tube for nuclear fuel cladding was simulated using FEA. The stress caused by the plug was distributed nonuniformly because of the friction coefficient difference between the inner surface of the tube and the plug. Hoop stress and shear stress at the tube was evaluated and the relationship between the concentrated stress at the inner layer of the tube and the fracture behavior of the tube was investigated.

마이크로 반구 쉘 형상의 화학증착 탄화규소 TRISO 코팅층의 파괴강도 직접평가

이현근,김도경 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.7

CVD-SiC coating has been introduced as a protective layer in TRISO nuclear fuel particle of high temperature gas cooled reactor(HTGR) due to its excellent mechanical stability at high temperature. In order to prevent the failure of the TRISO particles, it isimportant to evaluate the fracture strength of the SiC coating layer. It is needed to develop a new simple characterization techniqueto evaluate the mechanical properties of the coating layer as a pre-irradiation step. In present work, direct strength measurement methodwith the specimen of hemi-spherical shell configuration was suggested. The indentation experiment on a hemisphere shell with a plateindenter was conducted. The fracture strength of the coating layer is related with the critical load for radial cracking of the shell. Thefinite element analysis was used to drive the semi-empirical equation for the strength measurement. The SiC hemispherical shells wereCVD-SiC coating layer was evaluated from the experimentally measured critical load during the indentation on SiC hemisphere shell.Weibull diagram of fracture strength was also constructed. This study suggested a new strength equation and experimental method tomeasure the fracture strength of CVD-SiC coating of TRISO coated fuel particles.

영어와 한국어 꽃 이름 합성어의 형태론적 및 개념적․의미적 양상

이현근 미래영어영문학회 2012 영어영문학 Vol.17 No.2

In this paper, I aim to compare the morphological and conceptual (semantic) differences between English and Korean flower name compounds. We can conclude three things. First, a lot of Korean compounds include kkot(-꽃) and hwa(-화) and they are in some way systematic. On the contrary, the English compounds have not shown any systematic order morphologically. Second, when we compare the 국화(chrysanthemum)-included compounds and the rose-included compounds, several lexical items are systematized as one category in one language, but not in the other language. Finally, conceptualization differences are shown in many cases such as morning glory vs. 나팔꽃(horn flower), Easter flower vs. 할미꽃(grandmother flower). When we form a compound noun, the salient part of the object is usually conceptualized by language users, but the focus, which has been lexicalized, is different between two languages. That is, conceptualization and lexicalization of the same object may differ in two language systems.

화학증착법에 의하여 제조된 탄화규소 코팅층의 기계적 특성

이현근,김종호,김도경,Lee, Hyeon-Keun,Kim, Jong-Ho,Kim, Do-Kyung 한국세라믹학회 2006 한국세라믹학회지 Vol.43 No.8

SiC coating has been introduced as protective layer in TRISO nuclear fuel particle of High Temperature Gas cooled Reactor (HTGR) due to excellent mechanical stability at high temperature. In order to inhibit the failure of the TRISO particles, it is important to evaluate the fracture strength of the SiC coating layer. ]n present work, thin silicon carbide coating was fabricated using chemical vapor deposition process with different microstructures and thicknesses. Processing condition and surface status of substrate.affect on the microstructure of SiC coating layer. Sphere indentation method on trilayer configuration was conducted to measure the fracture strength of the SiC film. The fracture strength of SiC film with different microstructure and thickness were characterized by trilayer strength measurement method nanoindentation technique was also used to characterize the elastic modulus and th ε hardness of the SiC film. Relationships between microstructure and mechanical properties of CVD SiC thin film were discussed.

영어 특이 품사 합성어와 한국어 대응형 연구

이현근 미래영어영문학회 2010 영어영문학 Vol.15 No.2

This paper compares the English compounds, which are the hyphenated compounds with rarely using parts of speech, and their Korean counterparts. Firstly, we find that almost every parts of speech is used for making English compounds, including auxiliary, pronoun, proper noun, determiner, numeral, interrogative, etc. Secondly, there exist semantic/ conceptual differences between English compounds and their Korean counterparts. These different conceptualization processes demonstrate the language-specific aspect.

영어와 한국어에서의 곤충어휘 개념화에 대한 연구

이현근 미래영어영문학회 2015 영어영문학 Vol.20 No.2

This paper focuses on the conceptualization aspects of compounds especially on the insect words between English and Korean. Firstly, we surveyed the matching between two languages’ single word, derivation, and compound. We found that English single words are usually corresponded to Korean single words. However, various matchings are found between two languages, for example, English single word termite vs. Korean compound ‘흰개미’, English compound butterfly vs. Korean single word ‘나비’. Morphologically many-to- many mapping is existed. Secondly, some English and Korean compounds are usually conceptualized and lexicalized in the almost same way, like dung beetle vs. ‘쇠똥구리’, dayfly vs. ‘하루살이’. On the contrary, the conceptualization aspects are not same in these cases: long-horned beetle <긴><뿔><딱정벌레> vs. ‘하늘소’<sky><cow>, firefly <불><파리> vs. ‘개똥벌레’<dog><dung><bug>. Like these, the two language users sometimes recognize and categorize the same object differently.

영어와 한국어 어류 복합어의 개념화 양상

이현근 미래영어영문학회 2013 영어영문학 Vol.18 No.2

In this study, I focus on the conceptualization aspects of complex words by comparing the water creature terms morphologically and semantically in English and Korean. We found three things. First, there are 4 kinds of morphological mapping between two languages. Secondly, an object can be conceptualized in the same or different way. For example, sea lion in English is corresponded to 바다사자 in Korean. Jellyfish in English is corresponded to 해파리, that is <sea fly>. The meaning relation of the former is same. However, the latter conceptualize and lexicalize the same object differently. A particular fish is regarded as a smooth fish or a sea fly. Finally the lexical system is differently made up. Every lexical structure has its own system interactive to their own culture and society.

사질토 지반에서 말뚝 캡 크기가 무리말뚝의 동적거동에 미치는 영향

이현근,안광국,강홍식 한국지반환경공학회 2019 한국지반환경공학회논문집 Vol.20 No.8

A pile group, that consists of several piles connected by a pile cap, is used as the superstructure. The pile supports vertical and horizontal load to design the pile group, but the effect of bearing capacity of the pile cap has not considered. Various researches have been conducted to reflect the effect of bearing capacity of the pile cap in order to reduce the amount of piles in the range of the stability under the vertical load of the superstructure. However, the effect of bearing capacity under the horizontal seismic load has not been studied adequately. Therefore, a shaking table test was carried out with different-sized pile caps that support the superstructure in this study. This test was to verify the influence of the size of the pile cap in the group pile under the horizontal load. The result shows that the size of the pile cap affects to the dynamic behavior of the superstructure and the pile group. Also, the bigger size of the pile group makes the larger constraint effect of ground, and it results that both the ground and the pile moves as a whole. 상부구조물은 여러 개의 말뚝 기초를 말뚝 캡으로 연결한 무리말뚝이 사용되고 있다. 무리말뚝 설계 시 상부구조물의 연직 및 수평하중은 말뚝 기초가 지지할 뿐 말뚝 캡의 지지효과는 무시하였다. 그러나 최근 상부구조물의 연직하중에 대한 안정성 범위에서 말뚝 기초의 사용량을 줄이기 위해 말뚝 캡의 지지효과를 반영하기 위한 연구가 진행되고 있으나 수평하중에 대한 말뚝 캡의 지지효과에 관한 연구는 미비한 실정이다. 이에 본 연구에서는 수평 지진 하중을 받는 무리말뚝에서 말뚝 캡의 변화가 무리말뚝에 미치는 영향을 확인하기 위해 상부구조물을 지지하는 무리말뚝의 말뚝 캡 크기를 변화시켜 진동대 모형실험을 수행하였다. 그 결과 말뚝 캡의 크기가 상부구조물 및 무리말뚝의 동적 거동에 영향을 미치는 것으로 확인되었으며, 말뚝 캡의 크기가 증가할수록 지반구속 효과로 인해 지반과 말뚝 기초가 일체 거동하는 것으로 나타났다.