• 한국유체기계학회 논문집
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• 제4권3호
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• pp.7-13
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• 2001

The present study investigates convective heat/mass transfer and flow characteristics inside a cooling passage of rotating gas-turbine blades. The rotating duct has staggered ribs with $70^{\circ}$ attack angle, which are attached on leading and trailing surfaces. Naphthalene sublimation technique is employed to determine detailed local heat transfer coefficients using the heat and mass transfer analogy. Additional numerical calculations are conducted to analyze the flow patterns in the cooling passage. The present experiments employ two-surface heating conditions in the rotating duct because the exposed surfaces to hot gas stream are pressure and suction side surfaces in the middle passages of an actual gas-turbine blade. Secondary flows are generated by Coriolis and centrifugal forces in the spanwise and streamwise directions. The ribs attached on the walls disturb the mainflow resulting in recirculation and secondary flows near the ribbed wall. The local heat transfer and flow patterns in the passage are changed significantly according to rib configurations and duct rotation speeds. Therefore, the geometry and arrangement of the ribs are important for the advantageous cooling performance. The experimental results show that the ribs enhance the heat transfer more than $70\%$ from that of the smooth duct. The duct rotation generates the heat transfer discrepancy between the leading and trailing walls due to the secondary flows induced by the Coriolis force. The overal heat transfer pattern on the leading and trailing walls for the first and second passes are depended on the rotating speed, but the local heat transfer trend is affected mainly by the rib arrangements.

• 한국결정성장학회지
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• 제18권2호
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• pp.57-61
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• 2008

새로운 전복반형 진주 양식법으로 진주를 성장시킨 후 그 구조적 특징을 분석하였다. 본 양식법은 기존방법과는 달리 핵을 넣지 않고 패각의 특정 부위를 파괴시켜 전복 내장의 형상대로 진주층을 유도하는 방법으로 진주의 모양이 자연스럽고 독특한 광택을 나타내었다. 전계방사형 주사전자현미경으로 분석 결과 진주층은 약 $0.34{\mu}m$의 균일한 층이 패각 표면에 수직으로 배열됨으로써 패각 표면에 피라미드 상의 돌기가 규칙적으로 형성되어 전형적인 1매패(권패)의 전복진주 특성을 나타내었다. 이러한 특징은 최근 진주보석의 자연스런 형태를 추구하는 시대에 부합되어 고부가가치의 한국형 진주보석으로 성장할 수 있으리라 사료된다.

• 대한치과보철학회지
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• 제46권6호
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• pp.602-609
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• 2008

STATEMENT OF PROBLEM: Loss of the marginal bone to the first thread have been accepted but continuous effort have been made to reduce this bone loss by varying implant design and surface texture. PURPOSE: This animal study has examined the histomorphometric variations between implants with micro-thread, micro-grooved and turned surfaced neck designs. MATERIAL AND METHODS: Four mongrel dogs have been used the premolars removed and left to heal for three months. One of each implant systems with turned neck, micro-thread and micro-grooved were placed according to the manufacturers’protocol and left submerged for 8 and 12 weeks. These were then harvested for histological examination. RESULTS: The histologically all samples were successfully ossointegrated and active bone remodelling adjacent to implants. With the micro-grooved implants 0.40 mm and 0.26 mm of the marginal bone level changes were observed at 8 and 12 weeks respectively. The micro-threaded implants had changes of 0.79 mm and 0.56 mm at 8 and 12 weeks respectably. The turned neck designed implants had marginal bone level changes of 1.61 mm and 1.63 mm in 8 and 12 weeks specimens. A complex soft tissue arrangement could be observed against micro-threaded and micro-grooved implant surfaces. CONCLUSION: Within the limitations of this study, it could be concluded that implants with micro-grooved had the least and the turned neck designed implants had the most changes in the marginal bone level. The textured implant surfaces affect soft tissue responses.

• 대한치과보철학회지
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• 제54권4호
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• pp.407-412
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• 2016

심하게 흡수된 치조제를 지닌 환자에게 적절한 의치를 제공하기 위한 한 가지 방법으로써 중립대 인상 기법을 이용한 의치의 제작을 고려해 볼 수 있다. 중립대 내에 인공 치아를 배열하는 것은 다음의 두 가지 목적을 이루고자 함이다. 첫째, 치아가 정상적인 근육의 기능을 방해하지 않도록 하기 위함이며, 둘째, 의치에 저항하여 가해지는 근육 조직의 힘이 안정과 유지에 더 유리하게 작용할 수 있도록 하기 위함이다. 본 증례의 환자는 심한 잔존 치조제의 흡수를 보이는 78세 여자 환자로 오랜 기간 불안정한 상 하악 총의치를 사용하고 있었다. 의치의 안정과 유지를 향상시키기 위하여 중립대 인상 기법을 통한 새로운 의치의 제작을 계획하였다. Modeling compound를 이용하여 중립대를 인기하였으며 치아 배열 후 external impression을 시행함으로써 정확한 연마면을 형성할 수 있었다. 완성된 상 하악 총의치는 보다 향상된 안정과 유지를 보였으며 환자 역시 새로 제작된 의치에 만족감을 보였기에 이를 보고하고자 한다.

• 대한치과보철학회지
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• 제54권4호
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• pp.445-450
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• 2016

Piezography는 발음을 이용하여 채득된 보철 공간을 의미하며, 의치의 인공치와 연마면의 위치를 결정하는 참고점으로 사용하게 된다. 본 증례 대상은 67세 여성환자로, 새 의치 제작을 주소로 내원하였다. 기존 의치에서 2급 악간관계와 불량한 유지력을 확인할 수 있었으며, 안정적인 의치를 위해 piezography와 설측교합을 이용하기로 하였다. 통상적인 방법으로 인상 채득 후 주모형 상에서 상하악 기초상과 왁스 교합제를 제작하였고, 별도로 piezography를 위하여 하악에 추가적인 기초상을 하나 더 제작하였다. 이 추가 기초상에 실리콘 인상재를 적용 한 뒤 '시', '소', '메', '테', '데', '무' 여섯개의 발음으로 piezography를 채득하였다. 하악 인공치를 이 보철공간에 맞추어 배열한 뒤, 형태를 수정하여 설측 교합을 부여하였다. 그 결과, 환자는 새로운 의치에 기능적, 심미적으로 만족하였다.

• Journal of Mechanical Science and Technology
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• 제20권7호
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• pp.1002-1011
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• 2006

In this study, we describe the conventional hot pressing (CHP) of layered $Al-B_4C$ composites and their characterization. The matrix alloy Al-5 wt.%Cu was prepared from elemental powder mixtures. The metal and B4C powders were mixed to produce either $Al-Cu-10vol.%B_4C$ or $Al-Cu-30vol.%B_4C$ combinations. Then, these powder mixtures were stacked as layers in the hot pressing die to form a two-layered composite. Hot pressing was carried out under nitrogen atmosphere to produce $30\times40\times5mm$ specimens. Microstructural features and age hardening characteristics of composites were determined by specimens cut longitudinally. The flexural strength of both layered composites and their monolithic counterparts were investigated via three point bending tests. In the case of layered specimens of both $10vol.%B_4C$ and $30vol.%B_4C$ containing layers were loaded for three-point test. The results show that a homogeneous distribution of $B_4C$ particles in the matrix alloy which is free of pores, can be obtained by CHP method. The ageing behavior of the composites was found to be influenced by the reinforced materials, i.e. higher hardness values were reached in 8 hrs for the composites than that for the matrix alloy. Flexural strength test showed that two-layered composites exhibited improved damage tolerance depending on layer arrangement. Microstructural investigation of the fracture surfaces of the bending specimens was performed by means of scanning electron microscope (SEM). While layer with lower reinforcement content exhibited large plastic deformation under loading, the other with higher reinforcement content exhibited less plastic deformation.

• Wind and Structures
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• 제23권2호
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• pp.109-125
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• 2016

Flow interference is investigated between two tripped cylinders of identical diameter D at stagger angle ${\alpha}=0^{\circ}{\sim}180^{\circ}$ and gap spacing ratio $P^*$ (= P/D) = 0.1 ~ 5, where ${\alpha}$ is the angle between the freestream velocity and the line connecting the cylinder centers, and P is the gap width between the cylinders. Two tripwires, each of diameter 0.1D, were attached on each cylinder at azimuthal angle ${\beta}={\pm}30^{\circ}$, respectively. Time-mean drag coefficient ($C_D$) and fluctuating drag ($C_{Df}$) and lift ($C_{Lf}$) coefficients on the two tripped cylinders were measured and compared with those on plain cylinders. We also conducted surface pressure measurements to assimilate the fluid dynamics around the cylinders. $C_D$, $C_{Df}$ and $C_{Lf}$ all for the plain cylinders are strong function of ${\alpha}$ and $P^*$ due to strong mutual interference between the cylinders, connected to six interactions (Alam and Meyer 2011), namely boundary layer and cylinder, shear-layer/wake and cylinder, shear layer and shear layer, vortex and cylinder, vortex and shear layer, and vortex and vortex interactions. $C_D$, $C_{Df}$ and $C_{Lf}$ are very large for vortex and cylinder, vortex and shear layer, and vortex and vortex interactions, i.e., the interactions where vortex is involved. On the other hand, the interference as well as the strong interactions involving vortices is suppressed for the tripped cylinders, resulting in insignificant variations in $C_D$, $C_{Df}$ and $C_{Lf}$ with ${\alpha}$ and $P^*$. In most of the (${\alpha}$, $P^*$ ) region, the suppressions in $C_D$, $C_{Df}$ and $C_{Lf}$ are about 58%, 65% and 85%, respectively, with maximum suppressions 60%, 80% and 90%.

• 건축역사연구
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• 제17권4호
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• pp.129-152
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• 2008

Early Buddhist rock cave temples of India, in spite of being an origin of Buddhist temples, has little been studied in Korea. After field studies and an interpretation of their forms in conjunction with religious life, precedent theories are supplemented and refuted as follows. Starting from the 2nd century B,C., Buddhist ascetic disciples digged residential rock caves, called vihara, for protection from monsoon rain and hot weather, A typical arrangement was settled -a courtyard type, with 3 side rows of tiny one-person bedroom and a front veranda with columns. Also digged were Chaitya caves, in line with viharas, to worship, which is the tumulus of Buddha's relics. I suggest that the original type of chaitya a simple circle cave with a stupa, suitable for circumambulating ceremonies. I refute the existing theory presenting Barabar caves of Ajivika as a chaitya origin, featuring empty circular room without a stupa. I also interpret a typical apsidal plan as being a simple result of adding a place of worshipping rites in front of the stupa. Enclosing columns around a cylindrical stupa is a result of reinforcing both the divine space and circumambulating ceremonies, with elongation toward hall. Finally the chaitya came to have a grandeur apsidal plan with high vault ceiling nave and a side aisle as in Western cathedrals with large frontal horseshoe arch windows. The Buddha image, which had become a new worshipping object, was integrated into the stupa and interior surface. First the stupa and then the statue was introduced to residential Viharas. Therefore, I suggest that the vihara should be renamed as 'chaitya' as a worshipping place, by establishing statue rooms without bedrooms at all. The functionally changed vihara is similar in form to a 'rectangular type of chaitya', little known and developed in different routes. A columned inner courtyard gradually becama an offering place, like Hindu mandapa, Buddhist caves ware changed to a kind of Tantric and Hindu temple by means of statue worshipping offering rituals.

• 한국결정성장학회지
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• 제5권2호
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• pp.165-174
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• 1995

PVA를 첨가하여 제조한 collloidal $ZrO_2$ 졸에 있어서 입자의 분산성 및 입성장에 미치는 PVA의 영향을 고찰하였다. 적정량의 PVA를 첨가하여 제조된 colloidal 졸은 균일한 흡착층의 형성으로 입자간의 응집이 효과적으로 억제된 분산이 양호한 안정된 졸이었으며 이러한 분산성은 PVA가 $ZrO_2$ 일차입자 표면에 흡착층이 형성되어 입성장을 억제하기 때문이었다. $ZrO_2$ 입자의 핵생성은 수화반응 초기에 대부분 일어났으며, 숙성 시간 에 따라 판상의 단사정상 입자가 성장하였는데 PVA의 첨가량이 증가할수록 입성장 속도와 반응수율이 감소하였다. PVA 첨가에 의해 잘 분산된 현탁액으로부터 제조된 충진체는 입자가 고르게 배열되고 응집체간에 형성된 기공이 균일하였다.

• Journal of Yeungnam Medical Science
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• 제8권2호
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• pp.45-51
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• 1991

저자는 우리나라에서 아직 보고되어 있지 않지만 앞으로 유입될 가능성이 있는 T. tonsurans에 대하여 경험을 넓히고자 미국에서 환자에서 분리한 T. tonsurans에 대상으로 여러가지 진균학적 검사를 실시하여 다음과 같은 결과를 얻었다. 1. 육안적으로 표면은 편평하고 무두질한 양가죽 양상으로 미세한 과립이 얇게 덮혀있고 연한 회색 또는 연한 황색을 나타내었으며 중앙에는 굴곡이 있고 뒷면은 마호가니 갈색을 나타내었다. urease test에서 균주에 따라 다양한 색깔을 나타내었다. 2. 현미경 소견에서 격벽이 있는 균사를 비롯하여 대분생자, 소분생자, spiral hyphae, 후막포자가 발견되었으며 소분생자의 배열과 모양이 특징적으로 균사를 중심으로 양옆으로 배열되어 길고 그 끝이 성냥 끝처럼 부풀어 있었다. 3. 모발천공검사에서 19주중 16주에서 양성소견을 보였다.