• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.799-804
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• 2002

In this paper the leakage prediction and rotordynamic analysis of an annular seal with a smooth rotor and spiral-grooved stator are performed. For developing a theoretical model, the three-control-volume analysis of the circumferentially-grooved seal is expanded by considering pressure reduction due to the pumping effect of spiral groove and pressure flow through the spiral groove. Results by the present analysis are compared with available experimental data. For leakage the analysis results generally show a reasonable agreement to the experimental results. For rotordynamic coefficients the analysis results show the same trend as the experimental results for rotor speed with spiral angles, but their magnitudes show somewhat large deviations.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.275-280
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• 2013

The tractor front axle has the lower standard for noise and vibration relatively and it increase the possibility to develop of the alternative straight bevel gear of the expensive spiral bevel gear. The purpose of this paper is to compare of the spiral vs. the straight bevel gear manufacturing process. The manufacturing cost and productivity are compared after the spiral bevel gear of the tractor front axle is replaced of to the straight bevel gear. If spiral bevel gear is replaced to straight bevel gear, the cost is reduce 4.6% and productivity is increase 18%.

• Journal of the Korean Society of Visualization
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• v.7 no.1
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• pp.14-20
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• 2009

In comparison with previous researches fur swirling flow, the spiral flow self-generated in the spiral flow nozzle has some different characteristics. It is not needed a compulsive tangential momentum to get its velocity component and has long potential core, relatively low swirl ratio, and high focusing ability. In this study, the self-generated mechanism of the spiral flow was clarified and the effect on the width of annular slit on spiral flow characteristics was investigated experimentally and numerically. As a result, the existence of tangential velocity component regardless of a compulsive angular momentum is clarified and the results obtained by experiment have a satisfactory agreement with those by numerical method, quantitatively and qualitatively.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.537-542
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• 2003

The stress-strain curve of concrete confined with both spiral and carbon fiber sheet(CFS) is different to that of concrete confined with only spiral or CFS. The objective of this study is to investigate the stress-strain relation of concrete confined by composite material. In this study, 24 concrete cylinders were tested. The main variable of the cylinders was the content rate of spiral to CFS. The test results indicated that while the compressive strength of cylinder confined with both spiral and CFS increased proportionally to the aided amount of two materials, the maximum strain of cylinder depended on the larger strain of spiral or CFS.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.492-495
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• 2003

This paper presents a novel method to reduce the size of microstrip patch antennas using shorting post and spiral shape. The spiral conductor shape of the proposed shorted patch antennas increases the length of the current patch for a given area. Two spiral shaped patch antennas with shorting post operating at 700 MHz bands are investigated experimentally.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.343-346
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• 2003

A new structure to design low pass filters (LPFs) is presented rho proposed structure has the etched shape of Quad-Spiral DGS(Defected Ground Structure) on microstrip transmission lines. By extracting the equivalent circuit elements of unit Quad-Spiral DGS, LPFs are designed easily. The equivalent circuit of Quad-Spiral DGS consists of a step impedance resonator and lumped elements. The proposed LPF provided steep rejection characteristics with 5-poles. Experimental results show excellent agreements with circuit simulation results in wide band and the validity of our circuit modeling for LPF design. The result shows another possibility of Quad Spiral DGS for microwave devices.

• 한국정보통신설비학회:학술대회논문집
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• 2006.08a
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• pp.153-157
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• 2006

본 논문에서는 SoC 공정에 적용 가능한 spiral 인덕터의 특성에 대해 다루었다. 일정한 크기의 인덕터에서 턴 수의 변화에 따른 인덕턴스와 Q-factor의 변화를 보았다. HFSS 프로그램을 사용하여 턴 수와 선로의 폭이 같은 조건하에서 사각형 구조와 팔각형 구조를 갖는 인덕터의 인덕턴스와 Q-factor의 ?냅? 계산하였다. 사각형 구조와 팔각형 구조 모두 선로 폭 보다는 턴 수가 증가할수록 인덕턴스가 증가하였다. 턴 수가 증가할수록 Q-factor의 값은 사각형 구조는 감소한 반면 팔각형 구조는 증가하였다. spiral과 실리콘 사이에 PGS(Patterned Ground Shield)를 삽입하여 인덕턴스 및 Q-factor의 변화를 비교 분석하였다. 그 결과 PGS의 사용으로 사각형 구조와 팔각형 구조에서 턴 수에 따라 Q-factor의 값이 구조에 따라 서로 다른 방향으로 증감하는 것을 확인할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.6 s.249
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• pp.578-586
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• 2006

Numerical simulations are carried out to investigate the thermal effects of the gravitational potential on the centrifugal instability of a Taylor-Couette flow, and to further study the detailed flow fields and flow bifurcations to spiral vortices. The effects of centrifugal potential on the centrifugal instability are also investigated in the current study. Spiral vortices have various types of mode depending on Grashof number and Reynolds number. The correlation of Richardson number with the spiral angle of the spiral vortices shows that the structure of the spiral vortices strongly depends on the Richardson number. The heat transfer rate of the inner cylinder increases with increasing Grashof number. It is also confirmed that the torque required to rotate the inner cylinder increases as Grashof number increases.

• Tribology and Lubricants
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• v.28 no.6
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• pp.303-314
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• 2012

In this research, spool valves with spiral grooves are suggested and their lubrication characteristics are investigated by numerical analysis. The three-dimensional flow field is obtained by solving the Navier-Stokes equations in dimensionless form, so that the performance variables such as lateral force, friction force and volume flow rate are determined. Also, the lubrication characteristics of spool valves with spiral grooves are compared with those with typical grooves under variable working conditions. It is shown that spool valves with spiral grooves can get better performance in aspect of mitigation of uneven pressure distribution surrounding spool. Moreover, it is found that the minimum distance between spool edges and grooves, the type of spiral groove, and the groove angle have noticeable effect on the lubrication characteristics.

• Journal of The Korean Astronomical Society
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• v.37 no.4
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• pp.243-248
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• 2004

Disk galaxies abound with intermediate-scale structures such as OB star complexes, giant clouds, and dust spurs in a close geometrical association with spiral arms. Various mechanisms have been proposed as candidates for their origin, but a comprehensive theory should encompass fundamental physical agents such as self-gravity, magnetic fields, galactic differential rotation, and spiral arms, all of which are known to exist in disk galaxies. Recent numerical simulations incorporating all these physical processes show that magneto-Jeans instability (MJI), in which magnetic tension resists the stabilizing Coriolis force of galaxy rotation, is much more powerful than swing-amplification or the Parker instability in forming self-gravitating intermediate-scale structures. The MJI occurring in shearing and expanding flows off spiral arms rapidly forms structures elongated along the direction perpendicular to the arms, remarkably similar to dust spurs seen in HST images of spiral galaxies. In highly nonlinear stages, these spurs fragment to form bound clumps, possibly evolving into bright arm and interarm H II regions, suggesting that all these intermediate-scale structures in spiral galaxies probably share a common dynamical origin.