• Journal for History of Mathematics
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• v.18 no.4
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• pp.29-38
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• 2005

This Paper discusses the history of the conflicts between synthesis and analysis, from those in heuristic and logic development style in ancient Greek to those in projective geometric methods. The two methods, which originally displayed difference in heuristic, offer the base for the two fields of geometry, the analytic geometry and the synthetic geometry in the 18th century as they originated from the field of geometry. As to the 19th century, they even display antagonistic aspects derived by having other perspectives about the true nature of mathematic but finally lose the reason of conflict as the ancient times when the dialectical sublation of both had been proposed.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.73-73
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• 2018

조직재생공학은 조직이나 장기를 재생하고 유지하는 데 초점을 맞춘 종합 분야이다. 세포담체는 세포가 조직이나 장기로 발달 할 수 있도록 결정적인 역할을 한다. 따라서 공극률, 기공 크기, 기공 상호 연결성, 표면 거칠기, 기계적 강도 및 기하학과 같은 기본 요구 사항들은 중요한 특성으로 간주된다. Particle leaching, phase separation, solvent casting, gas foaming, selective laser sintering, fused deposition 및 3D dispensing (printing)과 같은 다양한 Rapid Prototyping 방법이 세포담체 제조에 사용되었다. 또한, 다양한 천연 및 합성 고분자가 세포담체를 제조하는데 사용되어왔다. 본 연구에서는 기존의 3D 프린팅 방법과 플라즈마 에칭 공정을 이용하여 나노 에칭 된 나선형 가닥으로 구성된 3 차원 세포담체를 제작 하였다. 제작 된 세포담체의 물리적 및 생물학적 성질을 비교 연구하기 위해, 본 연구에서는 매끄러운 가닥을 대조물로 사용하였다. 나노 에칭된 표면은 초기 세포 부착, 증식 및 골 형성 분화와 같은 세포 활동에 영향을 미쳤다.

• Journal of Astronomy and Space Sciences
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• v.11 no.2
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• pp.308-319
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• 1994

We can launch satellites only at a certain time which satisfies special conditions, since the current techniques cannot overcome these constraints. Launch window constraints are the eclipse duration, solar aspect angle, attitude control, launch site and the launch vehicle constraints, etc. In this paper, launch window is calculated that satisfies all these constraints. In calculating launch window, the basic concepts are relative locations of the sun-satellite-earth system and relative velocities of these, and these requires geometric consideration for each satellite. Launch window calculation was applied to Kitsat 2(low earth orbit) and Koreasat(geostationary orbit). The result is shown in the form of a graph that has dates on the X-axis and the corresponding times of the given day on the Y-axis.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.3
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• pp.451-457
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• 2009

Most of objects in computer graphics may be represented by a form of mesh. The exact computation of vertex normal vectors is essential for user to apply a variety of geometric operations to the mesh and get more realistic rendering results. Most of the previous algorithms used a weight which resembles a local geometric property of a vertex of a mesh such as the interior angle, the area, and so on. In this paper, we propose an efficient algorithm for computing the normal vector of a vertex in meshes. Our method uses the conformal mapping which resembles synthetically the local geometric properties, and the mean value coordinates which may smoothly represent a relationship with the adjacent vertices. It may be confirmed by experiment that the normal vector of our algorithm is more exact than that of the previous methods.

• School Mathematics
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• v.9 no.4
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• pp.523-533
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• 2007

This article focused the meaning of Pythagoras' and Euclid's proof about the Pythagorean theorem in a historical and mathematical perspective. Pythagoras' proof using similarity is based on the arithmetic assumption about commensurability. However, Euclid proved the Pythagorean theorem again only using the concept of dissection-rearrangement that is purely geometric so that it does not need commensurability. Pythagoras' and Euclid's different approaches to geometry have to do with Birkhoff's axiom system and Hilbert's axiom system in the school geometry Birkhoff proposed the new axioms for plane geometry accepting real number that is strictly defined. Thus Birkhoff's metrical approach can be defined as a Pythagorean approach that developed geometry based on number. On the other hand, Hilbert succeeded Euclid who had pursued pure geometry that did not depend on number. The difference between the proof using similarity and dissection-rearrangement is related to the unsolved problem in the geometry curriculum that is conflict of Euclid's conventional synthetical approach and modern mathematical approach to geometry.

• The Journal of the Petrological Society of Korea
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• v.8 no.3
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• pp.171-182
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• 1999

The Myeonbongsan caldera, 10.2X8.0 km, developed within older sequences of sedimentary formations and intermediate composition volcanis in the southern Cheongsong area. Volcanic rocks in the caldera block include lower intermediate volcanics, middle tuffaceous sequences and upper silicic ones. The silicic volcanics, which is named Myeonbongsan Tuff, are composed of crystal-rich ash-flow tuff(300 m) , bedded tuff(30 m) and pumice-rich ash-flow tuff(700 m) in ascending order. Several intrusions dominate the early sequences within the caldera. The caldera collapsed in a trapdoor type when silicic ash-flow tuffs erupted fro major vent area in the caldera. Normal faulting along a ring fault system except the southwestern part dropped the tuffs down to the northrase with a maximum displacement of about 820 m. The Myeonbongsan Tuff is just about 1,030 m thick inside the northeastern caldera, with its base not exposed, and southwestward thinning down. Rhyolitic plug and ring dikes are emplaced along the central vent and the caldera margins, and the ring dikes are cut by plutonic stocks in the southeastern and northwestern parts. The caldera volcanism eviscerated the magma chamber by a series of explosive eruptions during which silicic magma was erupted to form the Myeonbongsan Tuff. Following the last ash-flow eruption, collapse of the chamber roof resulted in the formation of the Myeonbongsan caldera, a subcircular trapdoor-type depression subsiding about 820 m deep. After the collapse, stony to flow-banded rhyolites were emplaced as circular plugs and ring dikes along the central vent and the caldera margins respectively. Finally after the intrusions, another plutons were emplaced as stocks outside the caldera.