• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.297.1-297.1
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• 2016

높은 굴절률(n_H) 의 ITO films 위에 homoepitaxial 성장 기술로 낮은 굴절률(n_L) 의 ITO를 이중으로 증착한 반사방지막을 연구하였다. 우리는 기판 상에 vapor flux 입사 각도 및 columnar 성장막과 경사각 사이의 상관 관계에 기초하여 낮은 굴절률의 ITO 박막을 Oblique-angle sputtering을 사용하여 증착하였다. Oblique-angle 증착동안 columns 경사각이 incident flux angle 의 증가에 따라 linear 하게 증가했다. 반대로 incident flux angle 이 증가할때 ITO 박막의 굴절률은 현저하게 감소하였는데, 이는 원자의 shadowing effect와 표면 diffusion으로 인하여 필름내의 porosity를 증가시킨 것으로 보여진다. 이러한 결과로 homoepitaxial으로 성장시킨 ITO 이중층 구조 반사방지막 특성이 향상되었으며, 유리 기판 위에서 weight average reflectance가 n_L=1.72, n_H=1.90 에서 6.57%를 달성하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.1
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• pp.10-21
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• 2010

Equations of chordwise and flapwise bending motions for the vibration analysis of rotating pre-twisted blades having tapered cross section and setting angle are derived by using hybrid deformation variable modeling. The two motions are couples to each other due to the pre-twisted angle of the beam cross section. The derived equations are transformed into dimensionless forms in which dimensionless parameters are identified. The effects of the dimensionless parameters on the modal characteristics of rotating pre-twisted blades having tapered cross section and orientation angle are investigated. The eigenvalue loci veering phenomena are also investigated and discussed in this work.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.2
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• pp.79-88
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• 1998

We developed a method for the solid angle estimation of acetabular coverage of the femoral head in 3D space. The superior half of the femoral head is modeled as part of a sphere. And the tangent lines connecting from a set of points of the acetabular outline to the center of the fitted sphere are obtained. The lines passthrough the unit sphere whose center is the same as that of the femoral head. The interesecting points form a boundary on the unit sphere. With the points on the unit sphere, we calculate the covered area of the femoral headand estimate the solid angle. Solid angle is defined asthe suface area within the boundary on the unit sphere. In this measurements, the solid angle of normal subjects is on an average 4.3(rad) and the corresponding acetabular coverage is 68%. Unlinke the conventional methods, this solid angle estimation shows real 3D acetabular coverage.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.12
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• pp.1084-1091
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• 2002

In general, flat-plate solar collectors are generally fixed in place at some angles. The most common method is to orient solar collectors toward the true south, where variations up to 15 degrees east or west are acceptable and the tiIt angle of the collectors is calculated from latitude and different heating applications. However, the best angle of flat-plate collectors depends upon whether the dominant load occurs in the winter, summer, or evenly all year. Moreover, this setting angle must consider the average insolation characteristics of the region exactly. In this study, the setting angle of flat-plate solar collectors is presented for Busan area by using domestic typical meteorological year weather data, so that the fixed flat-plate solar collectors must be set as quantitatively as possible.

• The KSFM Journal of Fluid Machinery
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• v.16 no.2
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• pp.48-53
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• 2013

This paper presents a numerical investigation of the influence of the blade back sweep angle on the performance and flow characteristics in a centrifugal compressor with a vaneless diffuser. Five impellers with different back sweep angles were tested in the flow simulations. It was found that a low back sweep angle could improve the total-to-total pressure ratio and the work coefficient over whole operating ranges. However, the flow field in an impeller with a low back sweep angle produced a more non-uniform velocity distribution at the impeller exit because the wake region was significantly increased. As a consequence, the impeller with a low back sweep angle caused a low diffuser performance.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.154-157
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• 2005

This paper aims to investigate the tow deformation pattern with respect to shear angle and mold property during draping of plain weave carbon/epoxy prepreg. Aluminum and PVC foams with different foam density are used for the draping hemisphere molds with 250 mm diameters. Microscopic observation reveals that tow parameters like crimp angle and Y-directional tow intervals are influenced by shear angle and mold density at the same time. The correlation between crimp angle and Y-directional tow interval is also found out.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.6
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• pp.80-89
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• 1998

Back rake angle of tool is one of the fundamental effects to the cutting ability. In this paper, for several back rake angle of lathe tool (-5$^{\circ}$ , 0$^{\circ}$ , 5$^{\circ}$ , 10$^{\circ}$ , 15$^{\circ}$ ), we experimentally examine cutting forces via orthogonal cutting. Using measured cutting forces, a formula for specific cutting resistance is derived according to the variation of tool angle. Also, the measured cutting forces are analyzed in both time and frequency domain. Cutting parameters are obtained by measuring the thickness of chip, and the effect of the back rake angle of tool is manifested. This study maintains the predicted cutting model with improved accuracy.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.3
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• pp.64-73
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• 1985

In order to control ignition advance angle, this system is designed with Z-80 CPU, CTC (counter Timer Circuit), PIO(Parallel Input Output), A/D Converter and Memory, etc. Serial pulses from speed sensor and analog voltage from pressure sensor are converted to digital data. In order to reduce the error of ignition advance angle output, the reference of ignition advance angle output is set 56.25 before TDC(Top Dead Center). The table of ignition advance angle and program which have a main routine and subroutines are written into ROM ( 1 K-byte). The experimental result of this system is correspondent to the theoretical values of proposed ignition advance angle table. This system can be utilized to any other type of 4 cylinder vehicles for advance angle control by changing software.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.69-72
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• 2002

The geometry parameter of tool such as rake angle and clearance angle is defined clearly to solve the difference in communication between design and measurement stage. Using the developed simulation program, wheel is properly determined and end mill can be manufactured accurately. The performance test with well defined end mill provides sufficient information to decide optimal geometry. For machining hardened steel, end mills are designed and manufactured. Optimal rake angle and clearance angle is obtained from performance test. A specific software for automatic end mill production is developed far simulation and fur generation of NC code as Cad/CAM system.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.04a
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• pp.88-95
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• 1997

This study provides the useful actual data instead of the experience data using in industrial fields. Especially, values of each components of cutting force are effective in the rake angle, setting angle and cutting area. Many researches have been made on the work piece materials, kinds of bite materials, rake angle, nose radius and depth of cut, but a few on the bite setting angle. In order to select optimal cutting speed, it was summarized the following results are achieved; A chieved that an affect of cutting resistance on the setting angle is a little under giving experimental conditions and therefore a worker can be choose the value of it randomly.