• 한국전산구조공학회논문집
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• 제16권2호
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• pp.207-216
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• 2003

본 논문에서는 균열을 지닌 축대칭 문제를 해석하기 위하여 시간적분형 운동방정식을 바탕으로 한 유한요소 해법을 제시한다. 유한요소메쉬는 8절점 등매개변수 사변형 요소와 균열선단에서의 1/4절점 삼각형 특이요소로 구성되며, 동적 응력확대계수는 균열면상의 1/4절점의 y방향 변위로부터 구한다. 제시된 해법의 정확성과 타당성을 검증하기 위하여 내부에 원환균열을 지닌 무한 탄성체가 균열면상에서 충격하중을 받을 때의 동적 응력확대계수를 계산하고 타 수치결과와 비교 검토하였다. 응용 예제로서 원환균열과 원주균열을 지닌 중실축과 중공축의 동적 응력확대계수를 균열의 길이와 축의 길이에 따른 영향을 자세히 조사하였다. 균열길이가 커지면 동적 응력확대계수가 커지고, 축의 길이가 길어지면 동적 응력확대계수 곡선의 폭도 함께 증가됨을 확인하였다. 그리고 균열의 위치가 안쪽에 포함될 경우보다는 바깥쪽에 포함될 때 더 큰 동적 응력확대계수가 발생됨을 밝힌다.

• 복식문화연구
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• 제17권3호
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• pp.383-395
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• 2009

The purpose of this study was to provide a formative charateristics by analyzing aesthetic charateristics of Egypt costume expressed in contemporary fashion. The result of this study obtained through this process were as follows. Aesthetic characteristics were expressed as a primative-retro characteristics, and a erotic-retro characteristics and a decorative-retro characteristics. Based on these trends, this study analyzed formative charateristics in an aspect of form, color, material, and decoration. In the modern fashion, unlike the H-line silhouette given by a natural fit in the primitive retro, the erotic retro was characterized in the shape by a tight H-line silhouette. For the color, peach, yellow green, gold, light blue, red, and black were used as the main color. For the material, see-through, gauze, mesh, organdy, and tight vinyl were utilized to emphasize an erotic image and expose a body secretly. For the decoration, the characteristic of erotic retro using the simple or same colors frequently was the use of similar accessories colors matched with material colors. The decorative retro was characterized in the shape by a H-line silhouette connected as a part of clothing which applied passium and a greatly modified silhouette from an Egyptian simple style which was well-matched with splendid accessories. For the color, the broadest range of color changes was found from light pastel such as white, yellow, light pink, burnt orange, blue, purple, silver, gold, and red to strong vivid tones. For the material, modern materials such as organdy, tulle, leather, and furs were often used. For the decoration, passium, an eagle pattern, scarab earrings, a crown, a sneak-shaped coronet, and pictograph printed on the fabric were frequently used.

• 한국전산구조공학회논문집
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• 제20권5호
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• pp.521-532
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• 2007

원형축이 축방향으로 충격하중을 받으면 외경에서 반사된 파가 축의 중앙으로 집중되어 순간적으로 큰 응력이 발생하게 된다. 본 연구에서는 여러 가지 충격 축하중을 받는 횡등방성 반-무한 원형축을 대상으로 중실축 내의 종방향 응력전파를 축대칭 유한요소법과 Houtolt 시간적분법을 이용하여 프로그램을 작성하고 수치적으로 해석하여 그 결과를 횡등방성 재료의 재료구성비에 따라 자세히 설명한다. 제시된 해법의 타당성은 본 논문 수치 결과와 기 해석된 다른 해법에 의한 수치결과의 비교를 통해 검증된다. 여러 종류의 충격하중들에 따른 파동의 결과를 2차원, 3차원적으로 제시하여 축응력 전파를 이해하는데 기본 자료가 되도록 하였다. 또한 유한요소법을 이용하여 수치해석을 함에 있어 정확한 수치결과를 얻기 위한 무차원 동특성 시간변수에 대해 기술하였다.

• Parasites, Hosts and Diseases
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• 제21권2호
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• pp.150-156
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• 1983

1975년부터 1983년까지 치료를 위해 서울의대 기생충학교실로 의뢰된 광절열두조충 충란양성자 5명에 대하여 bithionol, niclosamide 또는 praziquantel을 투여 하고 하제를 사용하여 충체를 얻은바 Diphyllobothrium latum으로 동정되었다. 충자는 서울 및 전남 완도군에 거주하고 있는 10~64세 남(4명) 여(1명)로 그중 2례는 농어를 생식한 경험이 있으며 나머지 3례는 바다생선회를 생식하였으나 그 종류를 기억할 수 없다고 한다. 또 그중 3례는 심한 복통과 소화기증상을 경험하였고, 2례는 편절이 자연배출된 일이 있다고 하나 빈혈소견은 전례에서 관찰되지 않았다. 대편검사에서 발견된 충란은 명 열별로 크기 평균 $59~67{\times} 41~48{\mu}m$이고 황갈색 유란원형 또는 타원형이 있으며 operculum과 abopercular protuberance가 뚜렷하였다. 충체는 4례에서 두절을 포함한 걸이 320~680cm의 완전한 것이 배출되었고 l례에서는 투약후 충체 배출여부를 확인하지 못하고 자연배출된 길이 30cm정도의 체절을 동정에 이용하였다. 특징적인 편절의 형태인 rosette형 자궁, vaginal pore가 cirrus sac에 포함되어 개구된 점, 재정과 cirrus sac의 분리 등으로 보아 Diphyllobothrium latum으로 동정되었다. 본 5례는 우리나라에서 1971년 이후 충체가 확인된 6례에 이어 제 7례-제11례의 인체기생례가 된다.

• 한국광물학회지
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• 제10권2호
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• pp.126-138
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• 1997

Serpentinite of the Yesan-Gongju-Cheongyang area has been formed by serpentinization of ultramafic rocks. The ultramafic rock might be composed mainly of oilvine with minor pyroxene and amphibole. Olivine has a considerably restricted chemical compositional ranging from Fo90 to Fo93. Fresh serpentinite containing large amount of oilvine is usually massive in occurrence and dark green to black in color. Serpentine minerals occur not only as major mineral of serpentinite, but also as remnants in the talc ore which was formed from serpentinite. XRD study indicates that antigorie is the most abundant serpentine mineral of the serpentinite. Serpentinite consisting of antigorite usually shows non-pseudomorphic texture, whereas that consisting of lizardite shows pseudomorphic texture. Antigorite is found along the margins or fractures of olivine grains resulting in the formation of network of magnetite which was formed at the time of serpentinization. Lizardite, subordinate constituent mineral of serpentinite, frequently shows pseudomorphic mesh-texture after olivine. The chemical differences between antigorite and lizardite/chrysotile are small, so both minerals are not easily discernible with the electron microprobe. Antigorite occuers as elongate blades, flakes, or plates forming interpenetrating texture to obliterate previous textures. SEM study also shows that most serpentine minerals occur in platy or tabular form rather than in asbestiform. Fractures formed after main serpentinization are observed within the pseudomorphic central olivine grain. Careful observation of the serpentine pseudomorphs gives a great deal of data on the pre-serpentinization nature of the serpentine pseudomorphs gives a great deal of data on the pre-serpentinization nature of the ultramafic rocks. It is inferred that the serpentinization took place after the emplacement of ultramafic body into the relatively wet environment ceased and the cooling intrusive body crossed into the stability field of serpentine. It is inferred that the final pervasive serpentinization took place over a long time, by hydrothermal water supplied through the fracture system produced during emplacement of ultramafic rock.

• 정보처리학회논문지A
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• 제10A권6호
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• pp.643-650
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• 2003

본 논문에서는 메쉬 구조 다중컴퓨터 시스템을 위한 새로운 서브메쉬 할당방법을 제안한다. 이 할당방법의 특징은 유형별 가용 서브메쉬 리스트를 사용하여 가용 서브메쉬의 탐색시간을 줄이는 것이다. 이 할당방법은 메쉬 구조에서 탐색한 독립 가용 서브메쉬들을 유형(정방형, 가로 직사각형, 세로 직사각형)에 따라 분류하여 유형별 가용 서브메쉬 리스트를 생성한다. 그리고 태스크의 유형과 동일한 유형별 가용 서브메쉬 리스트에서 먼저 최적의 서브메쉬를 찾음으로써 서브메쉬의 탐색시간을 줄인다. 만약 가용 서브메쉬를 찾지 못할 경우에는 각 독립 가용 서브메쉬의 속성으로 저장된 확장지수를 사용하여 서브메쉬의 크기를 확장한 후 최적의 가용 서브메쉬를 찾는다. 시뮬레이션을 통하여 본 논문에서 제안하는 서브메쉬 할당방법이 서브메쉬 탐색시간을 줄이는 면에서 기존의 할당방법에 비해 우수함을 보인다.

• Interaction and multiscale mechanics
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• 제2권2호
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• pp.177-187
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• 2009

Machine or structural members subjected to fatigue loading will have a crack initiated during early part of their life. Therefore analysis of members with cracks and other discontinuities is very important. Finite element method has enjoyed widespread use in engineering, but it is not convenient for crack problems as the region very close to crack tip is to be discretized with very fine mesh. However, as the body force method (BFM), requires only the boundary of the discontinuity (crack or hole) to be discretized it is easy versatile technique to analyze such problems. In the present work fundamental solution for concentrated load x + iy acting in the semi-infinite plate at an arbitrary point $z_0=x_0+iy_0$ is considered. These fundamental solutions are in complex form ${\phi}(z)$ and ${\psi}(z)$ (England 1971). These potentials are known as Melan potentials (Ramakrishna 1994). A crack in the semi-infinite plate as shown in Fig. 1 is considered. This crack is divided into number of divisions. By applying pair of body forces on a division, the resultant forces on the remaining 'N'divisions are to be found for which ${\phi}_1(z)$ and ${\psi}_1(z)$ are derived. Body force method is applied to calculate stress intensity factor for crack in semi-infinite plate. Also for the case of crack emanating from circular hole in semi-infinite plate radial stress, hoop stress and shear stress are calculated around the hole and crack. Convergent results are obtained by body force method. These results are compared with FEM results.

• Wind and Structures
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• 제25권4호
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• pp.343-360
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• 2017

The post-flutter state of streamlined steel box girder is studied in this paper. Firstly, the nonlinear aerodynamic self-excited forces of the bridge deck cross section were investigated by CFD dynamic mesh technique and then the nonlinear flutter derivatives were identified on this basis. Secondly, based on the 2-degree-of-freedom (DOF) coupling flutter theory, the torsional amplitude and the nonlinear flutter derivatives were introduced into the traditional direct flutter calculation method, and the original program was improved to the "post-flutter state analysis program" so that it can predict not only the critical flutter velocity but also the movement of the girder in the post-flutter state. Finally, wind tunnel tests were set to verify the method proposed in this paper. The results show that the effect of vertical amplitude on the nonlinear flutter derivatives is negligible, but the torsional amplitude is not; with the increase of wind speed, the post-flutter state of streamlined steel box girder includes four stages, namely, "little amplitude zone", "step amplitude zone", "linearly growing amplitude zone" and "divergence zone"; damping ratio has limited effect on the critical flutter velocity and the steady state response in the post-flutter state; after flutter occurs, the vibration form is a single frequency vibration coupled with torsional and vertical DOF.

• 센서학회지
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• 제20권3호
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• pp.207-212
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• 2011

In this study, pyramid structured black silicon process was developed in order to overcome disadvantages of using wet etching to texture the surface of single crystalline silicon and using grass/needle-like black silicon structure. In order to form the pyramidal black silicon structure on the silicon surface, the RIE system was modified to equip with metal-mesh on the top of head shower. The process conditions were : $SF_6/O_2$ gas flow 15/15 sccm, RF power of 200 W, pressure at 50 mTorr ~ 200 mTorr, and temperature at $5^{\circ}C$. The pressure did not affect the pyramid structure significantly. Increasing processing time increased the size of the pyramid, however, the size remained constant at 1 ${\mu}M$ ~ 2 ${\mu}M$ between 15 minutes ~ 20 minutes of processing. Pyramid structure of 1 ${\mu}M$ in size showed to have the lowest reflectivity of 7 % ~ 10 %. Also, the pyramid structure black silicon is more appropriate than the grass/needle-like black silicon when creating solar cells.

• 센서학회지
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• 제29권4호
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• pp.255-260
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• 2020

In this study, we developed a method of improving the surface-enhanced Raman spectroscopy (SERS) response characteristics by depositing a nanoporous Ag metal thin film through cluster source sputtering after forming a pyramidal texture structure on the Si substrate surface. A reactive ion etching (RIE) system with a metal mesh inside the system was used to form a pyramidal texture structure on the Si surface without following a complicated photolithography process, unlike in case of the conventional RIE system. The size of the texture structure increased with the RIE process time. However, after a process time of 60 min, the size of the structure did not increase but tended to saturate. When the RF power increased from 200 to 250 W, the size of the pyramidal texture structure increased from 0.45 to 0.8 ㎛. The SERS response characteristics were measured by depositing approximately 1.5 ㎛ of nanoporous Ag metal thin film through cluster sputtering on the formed texture structure by varying the RIE process conditions. The Raman signal strength of the nanoporous Ag metal thin film deposited on the Si substrate with the texture structure was higher than that deposited on the general silicon substrate by up to 19%. The Raman response characteristics were influenced by the pyramid size and the number of pyramids per unit area but appeared to be influenced more by the number of pyramids per unit area. Therefore, further studies are required in this regard.