• 지질공학
• /
• 제24권3호
• /
• pp.311-322
• /
• 2014

Limestone bodies under the tectonic environment have experienced various tectonic processes, and also changed the stress state. In this study, calcite twins found in limestones of the Joseon Supergroup and Pyeongan Supergroup in the northeastern part of the Ogcheon Belt, South Korea were measured, then the paleostress (i.e., the maximum shortening axis) was reconstructed using the new calcite strain gauge (NCSG) technique. The average twin thickness and average twin intensity increase as the total twin strain increases. We utilize the appearance of twins, the average twin thickness and average twin intensity, and the total twin strain to estimate that the observed calcite twins were produced at temperatures of < $200^{\circ}C$ in the Joseon Supergroup and $170^{\circ}C$ in the Pyeongan Supergroup. In the Joseon Supergroup, the dominant direction of the maximum shortening axis WNW-ESE to NW-SE; NE-SW shortening is also observed. The maximum shortening axes in the Pyeongan Supergroup are oriented NW-SE and NE-SW. The NE-SW direction of maximum shortening is associated with the occurrence of the Songrim orogeny of the Paleozoic to Early Jurassic, and the NW-SE direction of maximum shortening correlates to the Daebo orogeny of the Early Jurassic to Late Jurassic. It is thus concluded that the paleostress across the study area changed from NE-SW to NW-SE during the Mesozoic.

• 한국정밀공학회지
• /
• 제21권3호
• /
• pp.83-90
• /
• 2004

This paper proposes a tool path generation method for machining impellers with 5-axis machining center. The shape of impeller is complex, being composed of pressure surface, suction surface and leading edge, and so on. The compound surface which is made of ruled surface such as pressure surface and suction surface and leading edge such as fillet surface, makes the tool path generation much complicated. To achieve efficient roughing, cutting area is divided into two region and then tool radius of maximum size that do not cause tool intereference is selected for shortening machining time. In finishing, accuracy is improved using side cutting for blade surface and point milling for leading edge.

• 자원환경지질
• /
• 제40권4호
• /
• pp.461-471
• /
• 2007

고응력사의 지시자로서 방해석 쌍정 분석법을 이용하여 방해석내 쌍정이 생성될 당시의 변형온도와 고응력장의 상태 및 방향 등을 살펴보았다. 연구는 한반도 남부지역에 소규모로 불규칙하게 분포하고 있는 석회질 암석을 대상으로 수행되었다. 분석 결과에서 쌍정의 형태(한 방향 또는 두 방향의 얇고 두꺼운 직선형 쌍정), 변형률(1.235-7.453%), 두께($0.77-1.94{\mu}m$), 치밀도(25.26-41.99 twins/mm) 등을 고려하여 추정한 연구지역에서의 방해석 쌍정에 의한 변형온도는 약 $150^{\circ}-200^{\circ}C$ 이하로 나타났다. 주변형률의 크기와 방향에서 최대수축변형률($e_3\leftrightarrow{\sigma}_1$)의 방향은 경상분지 남부에 해당하는 GS-1와 영남육괴 남부에 해당하는 BS-1 지역에서 N-S, 그리고 옥천습곡대 서남부에 해당하는 NR-1 지역에서는 E-W 방향을 보였다. 최대인장변형률($e_1\leftrightarrow{\sigma}_3$)의 경우 GS-1과 BS-1 지역은 $NWW-SEE{\sim}NNE-SSW$ 그리고 NR-1 지역은 N-S 방향으로 나타났다. 즉, 연구지역에는 방해석 쌍정의 생성과 관련된 서로 다른 고응력장이 최소한 두 번 이상 작용했을 가능성을 시사한다.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2004년도 제5회 압연심포지엄 신 시장 개척을 위한 압연기술
• /
• pp.72-82
• /
• 2004

The deformation mechanism of hexagonal close-packed materials is quite complicate including slips and twins. A deformation mechanism, which accounts for both slip and twinning, was investigated for polycrystalline hop materials. The model was developed in a finite element polycrystal model formulated with initial strain method where the stiffness matrix in FEM is based on the elastic modulus. We predicted numerically the texture of Mg alloy(AZ31B) sheet by using FEM based on crystal plasticity theory. Also, we introduced the recrystallized texture employed the maximum energy release theory after rolling. From the numerical study, it was clarified that the shrink twin could not be the main mechanism for shortening of c-axis, because the lattice rotation due to twin rejects fur c-axis to become parallel to ND(normal direction of plate). It was showed that the deformation texture with the pyramidal slip gives the ring type pole figure having hole in the center.

• Bulletin of the Korean Chemical Society
• /
• 제11권5호
• /
• pp.427-430
• /
• 1990

Cholesteryl aniline ($C_{33}H_{51}N$) is monoclinic, space group $P2_1$, with a = 9.020(3), b = 6.000(1), c = 27.130(9)${\AA},\;{\beta} = 98.22(2)^{\circ}$, Z = 2, Dc = 1.06 g/cm$^3$ and Dm = 1.04 g/cm$^3$. A diffraction data set was collected with Mo-$K_{\alpha}$ radiation (${\lambda} = 0.7107 {\AA}$) on a diffractometer with a graphite monochromator to a maximum 2${\theta}$ value of 50$^{\circ}$, by the ${\omega}-2{\theta}$ scan technique. The coordinates of the non-hydrogen atoms and their anisotropic temperature factors were refined by full-matrix least-squares methods to final R of 0.058. In cholesteryl group, bond distances were normal except in tail part, where high thermal vibration resulted in apparent shortening of the C-C distances. The crystal structure consists of bilayers of thickness $d_{001} = 27.13 {\AA}$, in each of which there is the tail to tail arrangement of molecules aligned in the unit cell with their long axes approximately parallel to the [104] axis. The two halves of the double layer are related to each other by the screw axis.