• Title/Summary/Keyword: 원뿔

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플라즈마 처리에 의한 원뿔형 다중벽 탄소나노튜브 다발의 형성기전

  • Im, Seon-Taek;Kim, Gon-Ho
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.129-129
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    • 2010
  • 플라즈마 처리를 통하여 수직 합성된 다중벽 탄소나노튜브가 원뿔형 다발이 될 수 있으며 원뿔형 탄소나노튜브 다발은 기존의 구조적, 기계적 성질의 향상과 더불어 향상된 전계방출 능력을 가질 것으로 기대되어 이를 X-선원, 전계방출디스플레이(FED), 유기발광다이오드(OLED) 백라이트 등의 전자빔 원으로 적용하기 위한 연구가 진행되고 있다. 원뿔형 탄소나노튜브 다발의 형상 제어를 통하여 전계방출특성을 향상시킬 수 있으며 이를 위해 원뿔형 탄소나노튜브 다발이 생성되는 메커니즘과 조사되는 플라즈마의 역할에 대해서 이해하는 것이 중요하다. 본 연구에서는 플라즈마 생성부와 조사부를 분리한 유도결합형 플라즈마 원을 사용하여 입사되는 이온의 에너지, 조사량, 입자 종을 독립적으로 제어하였고 이를 통하여 원뿔형 탄소나노튜브 다발이 형성되는 메커니즘과 플라즈마의 역할을 밝혀내었다. 알곤 및 수소 플라즈마 처리에서는 원뿔형 탄소나노튜브 다발이 형성되지 않았으나 질소 및 산소 플라즈마 처리에서는 원뿔형 탄소나노튜브 다발이 형성되었다. 특히 산소 플라즈마 처리가 원뿔형 탄소나노튜브 다발 형성에 효과적이었다. 원뿔형 탄소나노튜브 다발의 형성 메커니즘은 탄소나노튜브의 분극과 쉬스 전기장의 상호작용을 이용한 모델을 사용하여 설명하였다. 질소 및 산소 플라즈마 처리에서는 탄소나노튜브 끝단에 생성되는 C-N, C-O 결합에 의해 향상된 유도 쌍극자와 쉬스 전기장에 의해 탄소나노튜브 끝단이 모여 원뿔형 탄소나노튜브 다발이 생성됨을 밝혀내었다. 산소 플라즈마 처리에서 입사되는 이온의 에너지 조절에 의한 쉬스 전기장 조절과 조사량 조절을 독립적으로 수행하여 원뿔형 탄소나노튜브 다발의 직경 및 높이가 쉬스 전기장 및 조사량에 따라 조절 가능함을 보였다. 이로부터 입사되는 이온의 입자 종, 쉬스 전기장 및 조사량 조절 등의 플라즈마 인자 조절을 통하여 원뿔형 탄소나노튜브 다발의 형상 제어가 가능함을 보였다. 탄소나노튜브의 형상 제어와 더불어 세슘 입자 삽입을 통한 탄소나노튜브의 일함수 감소를 통하여 향상된 전계 방출 특성을 갖는 탄소나노튜브 팁의 제조 가능성을 확인하였다.

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The history of conic sections and mathematics education (원뿔곡선의 수학사와 수학교육)

  • Jin, Man Young;Kim, Dong Won;Song, Min Ho;Cho, Han Hyuk
    • Journal for History of Mathematics
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    • v.25 no.4
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    • pp.83-99
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    • 2012
  • The conic sections are defined as algebraic expressions using the focus and the directrix in the high school curriculum. However it is difficult that students understand the conic sections without environment which they can manipulate the conic sections. To make up for this weak point, we have found the evidence for generating method of a conic section through a sundial and investigated the history of terms 'focus', 'directrix' and the tool of drawing them continuously.

Comparative Study of the Retinal Structure in Two Korean Endemic Freshwater Fishes, Zacco koreanus (Cyprinidae) and Pseudobagrus koreanus (Bagridae) Based on Their Habitats (참갈겨니 Zacco koreanus와 눈동자개 Pseudobagrus koreanus의 생태학적 차이에 의한 망막 조직의 비교 연구)

  • You, Min-Jeong;Park, Jong-Young
    • Korean Journal of Ichthyology
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    • v.20 no.2
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    • pp.97-104
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    • 2008
  • Comparative study of retinal structure in two Korean endemic freshwater fishes, Zacco koreanus and Pseudobagrus koreanus, was carried out by light and scanning electron microscopy. In the visual cell layer comprised of cone cells and rod cells, the cone cells showed a distinct difference between both species. Z. koreanus had two types of cone cells, single cone cells including a long single and short single cone cells, and double cone cells, whereas P. koreanus had only one type of single cone cells having no its short single and long single cones. Meanwhile, the cone cells of Z. koreanus were arranged in more compact-rowed pattern, but it was more loose and irregular in P. koreanus. Based on field observation, Z. koreanus is mainly a epipelagic or sometimes benthopelagic and a diurnal fish with a round and large eye, while P. koreanus is a demersal and nocturnal fish with an oval and small eye. Therefore, the difference in the retinal structure of two species seems to be closely related to their ecological habitats.

Static Load Test of Composite Sandwich Truncated Cone Structure (복합재료 샌드위치 원뿔대 구조물 정적시험)

  • Park Jae-sung;Jang Young-soon;Yi Yeong-moo
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2004.10a
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    • pp.56-60
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    • 2004
  • 2단 또는 3단형으로 설계되고 있는 KSLV-I 발사체의 단연결부는 직경의 변화에 따라 원뿔대(Truncated cone) 구조물이 필요하다. 원뿔대형 구조물이 발사체의 외피일 경우에는 일반적인 실린더형 동체와는 다르게 공력에 의한 버페팅(buffeting)과 공력가열 등이 추가적인 설계인자로 고려되어야 한다. 복합재료 샌드위치 구조물은 외피의 굽힘 강성이 크고, 일체성형으로 실린더형 혹은 원뿔대형 구좁물을 쉽게 제작할 수 있어 단연결부에 적용되고 있다. 또한 위성어댑터(Payload Adapter)등에도 사용되어 우주발사체에는 매우 일반적인 구조물이다. 복합재료 샌드위치 구조물의 제작과 정적시험을 통하여 구조 특성을 알아보았다. 일체형 샌드위치 구조물의 효율을 높이기 위해서는 프레임과의 체결부를 효율적으로 설계하여야 하며 하중의 종류에 따라서 면재의 적층각도가 중요함을 알 수 있었다.

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Cone Surface Classification and Threshold Value Selection for Description of Complex Objects (복잡한 물체의 기술을 위한 원뿔 표면의 분류 및 임계치 선정)

  • Cho, Dong-Uk;Kim, Ji-Yeong;Bae, Young-Lae;Ko, Il-Seok
    • The KIPS Transactions:PartB
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    • v.11B no.3
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    • pp.297-302
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    • 2004
  • In this paper, the 3-D shape description for the objects with the cone ridge and valley surfaces, and the corresponding threshold value selection for surface classification are considered. The existing method based on the mean and Gaussian curvatures(H and K) of differential geometries cannot properly describe cone primitives, which are some of the most common objects in the real world. Also the existing method for surface classification based on the sign values of H and K has Problems in practical applications. For this, cone surface shapes are classified cone ridges and cone valleys are derived from surfaces using the fact that H values are constant case of cylinder surfaces and variable for cone surfaces, respectively. Also threshold value selection for surface classification from a statistical point of view is proposed. The effectiveness of the proposed methods are verified through experiments.

A new Promalactis species from Korea (Lepidoptera, Ocecophoridae) (원뿔나방과(개칭)의 1신종)

  • Park K. T.
    • Korean journal of applied entomology
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    • v.19 no.3 s.44
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    • pp.145-147
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    • 1980
  • 신종 Promalactis odaiensis n. sp.(솔피원뿔나방 : 신칭)의 기재. Promalactis속은 주로 동양구에 분포하고 있으며 우리나라에서는 현재까지 보고된 종이 없다. 그러나 최근 필자의 조사로 $5\~6$종이 확인되었으며 그 1종을 신종으로 우선 발표한다. 또한 Ocecophoridae 한국동물명집, 곤충편<1968>에 원무늬잎말이 나방으로 되어있으나, 뿔나방상과(Gelechioidea)에 속함으로 원뿔나방과로 개칭한다.

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Analysis of Anisotropic Circular Conical Shells with Free Supports (자유경계를 갖는 비등방성 원뿔형 쉘의 해석)

  • Son, Byung Jik;Baik, Han Sol;Chang, Suk Yoon
    • Journal of Korean Society of Steel Construction
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    • v.12 no.4 s.47
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    • pp.417-428
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    • 2000
  • In recent years, composite materials have been used in civil engineering as well as architecture, automobile, aerospace, shipping industries. Composite materials are composed of two or more different materials to produce desirable properties for structural strength. The shell structures have the advantage of more efficient load resistance due to its curved shape as compared to the plate structures. And the shell structures with composite materials have many advantages in strength, corrosion resistance, and weight reduction. The objective of this study is to analyze circular conical shells with shear deformation effects and to prove the advantage of composite materials. To solve differential equations of conical shells, this paper used finite difference method.

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Effects of Geometrical Shape on the Free Vibration of Laminated Composite Conical Shells (복합적층 원뿔형 쉘의 자유진동에 관한 기하학적 형상의 영향)

  • Son, Byung Jik;Ji, Hyo Seon;Chang, Suk Yun
    • Journal of Korean Society of Steel Construction
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    • v.14 no.4
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    • pp.519-527
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    • 2002
  • Shell structures have become critical in the design of pressure vessels, submarine hulls, ship hulls, airplane structures, concrete roofs, containers for liquids, and many other structures. This study presented the feature of the free vibration of anisotropic laminated conical shells according to transverse shear deformation effects. Composite materials are composed of two or more different materials in order to produce desirable properties for structural strength. Since their behavior is very complex, it is almost impossible to solve the analytical solutions. This effects of subtended and vertex angles and other geometric parameters on vibration were investigated in a comprehensive parametric study. Selected vibration mode shapes were illustrated, to enable the physical understanding of vibration of laminated composite conical shells.

Transition Prediction of compressible Axi-symmetric Boundary Layer on Sharp Cone by using Linear Stability Theory (선형 안정성 이론을 이용한 압축성 축 대칭 원뿔 경계층의 천이지점 예측)

  • Park, Dong-Hoon;Park, Seung-O
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.36 no.5
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    • pp.407-419
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    • 2008
  • In this study, the transition Reynolds number of compressible axi-symmetric sharp cone boundary layer is predicted by using a linear stability theory and the -method. The compressible linear stability equation for sharp cone boundary layer was derived from the governing equations on the body-intrinsic axi-symmetric coordinate system. The numerical analysis code for the stability equation was developed based on a second-order accurate finite-difference method. Stability characteristics and amplification rate of two-dimensional second mode disturbance for the sharp cone boundary layer were calculated from the analysis code and the numerical code was validated by comparing the results with experimental data. Transition prediction was performed by application of the -method with N=10. From comparison with wind tunnel experiments and flight tests data, capability of the transition prediction of this study is confirmed for the sharp cone boundary layers which have an edge Mach number between 4 and 8. In addition, effect of wall cooling on the stability of disturbance in the boundary layer and transition position is investigated.

A Case Study of Teaching Mathematics for Integrated Essay Education: Instruction of Conic Section using Concrete Materials and Technology (통합형 수리논술 지도 사례 - 구체물과 공학적 도구를 활용한 원뿔곡선 수업 -)

  • Ryu, Hyunah
    • Communications of Mathematical Education
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    • v.27 no.4
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    • pp.567-580
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    • 2013
  • As integrated essay writing is performed in university entrance examinations, teachers and students recognize the importance of integrated essay, but teachers have still difficulties of teaching methods. The purpose of this study is to derive educational implications through case of mathematics instruction for integrated essay education to pre-service mathematics teachers. The content knowledge of this class is a definition of conic section in mathematics and properties of conic section in an antenna reflector. The students have to discover them using the history of math, manipulative material, paper-folding and computer simulation. In this teaching and learning process the students can realize mathematical knowledge invented by humans through history of mathematics. The students can evaluate the validity of that as create and justify a mathematical proposition. Also, the students can explain the relation between them logically and descript cause or basis convincingly in the process of justifying. We should keep our study to instructional materials and teaching methods in integrated essay education.