• 대한기계학회논문집B
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• 제28권3호
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• pp.304-314
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• 2004

An experimental study has been conducted to measure the temperature fields and the local film cooling effectiveness for two and three staggered rows of the rectangular shaped-holes with various blowing rates. The hydraulic diameter of rectangular-shaped hole is 10mm. To compare with the film cooling performance of rectangular-shaped hole, two kinds of circular holes are tested. One has the same hydraulic diameter as the rectangular hole and the other has the same cross sectional area. Also, rectangular holes with expanded exit with same inlet area as rectangular ones are tested. Temperature fields are measured using a thermocouple rake attached on three-axis traversing system. Adiabatic film cooling effectiveness on the surface are obtained based on experimental results of thermochromic liquid crystals. The film cooling effectiveness is measured for various blowing rates and compared with the results for the cylindrical holes. In case of 2 rows, the rectangular holes has better performance than circular holes due to its slot-like geometry. In case of 3 rows, the effecta of hole shape is not clear.

• 설비공학논문집
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• 제14권5호
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• pp.365-376
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• 2002

An experimental study has been conducted to measure the local film-cooling effectiveness and the heat transfer coefficient for a single row of rectangular-shaped holes. four different cooling hole shapes such ai a straight rectangular hole, a rectangular hole with laterally expanded exit, a circular hole and a two-dimensional slot are tested. A technique using thermochromic liquid crystals determine adiabatic film cooling effectiveness values and heat transfer coefficients on the test surface. Both film cooling effectiveness and heat transfer coefficient are measured for various blowing rates and compared with the results of the cylindrical ho1es and the two-dimensional slot. The flow patterns downstream of holes are calculated numerically using a cummercial package. The results show that the rectangular hopes provide better peformance than the cylindrical holes. For the rectangular holes with expanded exit, the penetration is reduced significantly, and the higher and more uniform cooling Peformance is obtained even at relatively high blowing rates.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.181-186
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• 2003

An experimental study has been conducted to measure the temperature fields for two and three staggered rows of the rectangular shaped-holes with high turbulence intensity. 10 % turbulence intensity is obtained by installation of two kinds of grids which have different shapes. One grid which is installed at 30d upstream from center of 1st row of holes is composed of vertical cylinders of which diameter is 10 mm and center to center distance is 18 mm. The other installed 15d apart to upstream from center of 1st row of holes which has square pattern is constructed of 3 rum square bars and bar spacing is 25 mm. Temperature fields are measured by using a thermocouple rake which is attached on three-axis traversing system. The results show that the overall values are decreased and the thicker film of coolant is fanned downstream of rows of holes for high mainstream turbulence intensity.

• 한국CDE학회논문집
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• 제9권1호
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• pp.1-10
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• 2004

In the process of finite element analysis, mesh generation is tedious job which consumes tremendous time. Therefore, the automation of well shaped mesh generation from the minimal boundary input data is desirable to improve reliability and accuracy of the analysis and also to reduce the process time of the entire design process. The automation of triangular mesh generation has been relatively well treated due to its robustness and ease of handling when compared to rectangular element mesh generation. In this study, the offset method developed previously for generating plane rectangular element mesh has been corrected and modified to generate triangular element mesh on the B-spline surface having arbitrary holes. The result shows that the generated triangular mesh has the average aspect ratio over 0.9. The designed arbitrary surface shape has been interactively constructed by non-uniform B-spline theory for triangular mesh generation.

• 건축역사연구
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• 제16권4호
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• pp.37-56
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• 2007

The '凸'-shaped, the '呂'-shaped and the hexagonal-shaped pit houses were excavated at the Youngdong area, some location along the upper the Imjin River and Han River between the Iron age and the kingdom of Hanseong Baekje. The aim of this study is to analyze various structural system and developement of the pit house with rectangular plan. It is considered a matter in all its aspects which are plan, scale, aspect, pillar holes, carbonized wood and several traces. These pit houses removes the pillar on the inside or it reduces to secure a wider space, it pursued the chamfered corner, the change of the front, the entrance fixed. Also these adopted diverse structural systems(the chuandou structure, the structural system of columns and beams and a bearing wall). But in the course of time, the Korean wooden architecture is developed gradually the structural system of columns and beams. It is presumed the result that overcome the limit with the close space and pursue the flowing space and compose a group of organizable buildings.

• 한국식품영양과학회지
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• 제32권5호
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• pp.695-699
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• 2003

본 연구는 기존의 콩나물 재배통이 가지는 재배 중 발생하는 재배통 중심부의 고온과 탄산가스 수준의 증가로 인한 부패현상과 생육저해 문제를 해결하기 위한 것이다. 이 문제를 해결하기 위해서 원리적으로는 콩나물 재배통 내의 공기와 재배실과의 공기치환이 보다 원활히 일어나도록 한 것으로, 콩나물 재배통을 재배통과 콩나물 받침그릇으로 구성하였는데 재배통의 바닥에는 직경 10 mm, 높이 2 mm인 배수구 겸 물 고임 턱 다섯 개를 두었고 재배통 벽에는 폭 0.5cm, 길이 10 cm의 홈을 두었다. 재배통 속에 넣어 사용하는 콩나물 받침그릇에는 바닥에 배수구가 592개 형성되고 그 바닥 중앙에 직경 2 mm인 구멍 36개가 형성된 공기 치환파이프를 부착하여 콩나물 받침 그릇으로 구성하였다. 이렇게 구성한 개량콩나물 재배통은 25$\pm$1$^{\circ}C$에서 재배한 결과 기존 재배통보다 재배기간 동안 재배통 내의 탄산가스 수준과 온도가 낮았고, 그 결과 부패율은 낮고 성장 정도는 높은 결과를 얻었다.

• Journal of the Optical Society of Korea
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• 제13권1호
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• pp.33-36
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• 2009

Laser ablation with femtosecond lasers is highly promising for microfabrication of materials. Also, the high peak power of femtosecond lasers could induce a multiphoton absorption to ablate transparent materials. Similar results have also been were obtained in the case of optical fibers. In this paper, we present our experimental results of femtosecond laser microstructuring of optical fiber and its applications to microelectronic components and fiber optic devices. Finally, we directly produced micro holes with femtosecond laser pulses in a single step by moving an optical fiber in a preprogrammed structure. When water was introduced into a hole drilled from the bottom surface of the optical fiber, the effects of blocking and redeposition of ablated material were greatly reduced and the aspect ratio of the depth of the hole was increased. We have presented circular and rectangular-shaped holes in optical fiber.

• Current Optics and Photonics
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• 제1권6호
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• pp.567-572
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• 2017

A novel slotted-core hexagonal photonic crystal fiber (PCF) for terahertz (THz) wave guiding is proposed in this paper. A trade-off managed between effective material loss (EML) and birefringence for efficient guidance of THz waves is illustrated in this article. The rectangular slot shaped air-holes break the symmetry of the porous-core which offers ultra-high birefringence of $8.8{\times}10^{-2}$. The proposed structure offers low bending loss of $1.07{\times}10^{-34}cm^{-1}$ and extremely low effective material loss (EML) of $0.035cm^{-1}$ at an operating frequency of 1.0 THz. In addition other guiding properties such as power fraction, dispersion and confinement loss are also discussed. The proposed THz waveguide can be effectively used for convenient transmission of THz waves.