• Title/Summary/Keyword: Radius Ratio

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Analysis of a Pin Fin with Variable Fin Base Thickness (핀 바닥두께가 변하는 pin 핀의 해석)

  • Kang, Hyung-Suk
    • 한국신재생에너지학회:학술대회논문집
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    • 2008.05a
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    • pp.642-645
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    • 2008
  • A pin fin with variable fin base thickness is analysed by using the one dimensional analytic method. Heat loss and fin thermal resistance are presented as a function of the fin base thickness, pin fin outer radius and convection characteristic numbers ratio. The relationship between the fin outer radius and fin base thickness for the same amount of heat loss is shown. One of the results indicates the fin thermal resistance decreases as the fin outer radius and/or convection characteristic numbers ratio increase whereas the fin thermal resistance is independent on the variation of fin base thickness.

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Errors in One-Dimensional Heat Transfer Analysis in a Hollow Cylinder Feedwater Pipe (속이 빈 원관에서 1차원적인 열전달 해석의 오차)

  • Gang, Hyeong-Seok
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.2
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    • pp.689-696
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    • 1996
  • A comparison is made of the heat loss from a hollow cylinder, computed using an one-dimensional analytic method and a two-dimensional separation of variables scheme. For a two-dimensional analysis, the temperature of the inner surface as a boundary condition can be varied along the length of the cylinder by varing the temperature variation factor, b. Comparisons of the heat loss from the hollow cylinder using these two methods are given as a function of non-dimensional cylinder length, the ratio of the outer radius to the inner radius, temperature variation factor and Biot number. The result shows that the value of the heat loss from the hollow cylinder obtained using the one-dimensional analytic method becomes close to the value given by the two-dimensional separation of variables scheme as the value of Biot number and the non-dimensional hollow cylinder length increase and as the ratio of the outer radius to the inner radius decreases.

EFFICIENCY ANALYSIS OF A DOMAIN DECOMPOSITION METHOD FOR THE TWO-DIMENSIONAL TELEGRAPH EQUATIONS

  • Jun, Younbae
    • East Asian mathematical journal
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    • v.37 no.3
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    • pp.295-305
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    • 2021
  • In this paper, we analyze the efficiency of a domain decomposition method for the two-dimensional telegraph equations. We formulate the theoretical spectral radius of the iteration matrix generated by the domain decomposition method, because the rate of convergence of an iterative algorithm depends on the spectral radius of the iteration matrix. The theoretical spectral radius is confirmed by the experimental one using MATLAB. Speedup and operation ratio of the domain decomposition method are also compared as the two measurements of the efficiency of the method. Numerical results support the high efficiency of the domain decomposition method.

Parametric Study of Composite Laminated Conical Shells (복합적층 원뿔형 쉘의 파라미터 연구)

  • Son, Byung-Jik;Jung, Dae-Suck
    • Journal of the Korean Society of Safety
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    • v.22 no.5
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    • pp.41-49
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    • 2007
  • In general, the curved structures have the engineering efficiency as well as a fine view compared with straight member. Also, composite materials are composed of two or more different materials to produce desirable properties for structural strength as compared to single ones. Shell structures with composite materials have many advantages in strength and weight reduction. Therefore, composite laminated conical shells are analyzed in this study. To solve differential equations of conical shells, this paper used finite difference method. Various parametric study according to the change of radius ratio, vertex angle and subtended angle are examined. The change of radius ratio, vertex angle and subtended angle mean the change from conical shells to cylindrical shells, conical shells to circular plates and open shells closed shells, respectively.

A Study on the Role of Notch and Radius Reduction Ratio in the Balanced Type Vane Pump (베인 펌프에서 노치와 반경 감소비의 역활에 관한 연구)

  • 김기동;조명래;문호지;배홍용
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.04a
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    • pp.533-539
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    • 1997
  • Pressure ripple of hydraulic vane pump results form flow ripple due to pump geometry and reverse flow through the discharge port due to compressibility of fluid and result in vibration and noise of connected hydraulic elements. In a ba;anced type vane pump, cam ring curve is important factor to influence the flow ripple. Therefore, to reduce the now ripple, it has been required that optimal selection of seal region by proper design of cam ring and each port position, and notches for preventing the excessive reverse flow. This paper has been performed analytical study of compression characteristics with major design parameter in side plate and cam ring, and examined into the role of notch and radius reduction ratio.

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Bending Vibration Analysis of Rotating Multi-blade Systems Considering the Coupling Stiffness Effect (연성강성 효과를 고려한 회전하는 다중 블레이드 시스템의 굽힘진동 해석)

  • Lim, Ha-Seong;Kwon, Sung-Hun;Yoo, Hong-Hee
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.9 s.114
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    • pp.912-918
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    • 2006
  • A modeling method for the vibration analysis of rotating multi-blade systems considering the coupling stiffness effect is presented in this paper. Blades are assumed as cantilever beams and the coupling stiffness effect originates from disc or shroud between blades. As the angular speed, hub radius ratio, and the coupling stiffness vary, the natural frequencies of the system vary. Numerical results show that the coupling stiffness is very important to estimate the natural frequencies. Along with the natural frequencies, associated mode shapes, critical angular speed, and critical hub radius ratio are obtained through the analysis.

A Study on the Role of Notch and Radius Reduction Ratio in the Balanced Type Vane Pump (베인 펌프에서 노치와 반경 감소비의 역할에 관한 연구)

  • 김기동;조명래;한동철;최상현;문호지
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.1
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    • pp.87-93
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    • 1998
  • Pressure ripples of hydraulic vane pump results from flow ripples due to pump geometry and reverse flow through the discharge port due to compressibility of fluid and result in vibration and noise of connected hydraulic elements. In a balanced type vane pump, cam ring curve is important factor to influence the flow ripples. Therefore, to reduce the flow ripple, it has been required that optimal selection of seal region by proper design of cam ring and each port position, and notches for preventing the excessive reverse flow. This paper has been performed analytical study of compression characteristics with major design parameter in side plate and cam ring. and examined into the role of notch and radius reduction ratio.

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Bending Vibration Analysis of Rotating Multi-blade Systems Considering the Coupling Stiffness Effect (연성강성 효과를 고려한 회전하는 다중 블레이드 시스템의 굽힘진동 해석)

  • Lim, Ha-Seong;Kwon, Sung-Hun;Yoo, Hong-Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.05a
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    • pp.1354-1359
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    • 2006
  • A modeling method for the vibration analysis of rotating multi-blade systems considering the coupling stiffness effect is presented in this paper. Blades are assumed as cantilever beams and the coupling stiffness effect originates from disc or shroud between blades. As the angular speed, hub radius ratio, and the coupling stiffness vary, the natural frequencies of the system vary. Numerical results show that the coupling stiffness is very important to estimate the natural frequencies. Along with the natural frequencies, associated mode shapes, critical angular speed, and critical hub radius ratio are obtained through the analysis.

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Numerical analysis on the material flow in stepped rod forming (단붙이 로드의 성형에서 소재유동에 관한 해석)

  • Go, Byung-Du;Gang, Dong-Myung;Lee, Ha-Sung
    • Design & Manufacturing
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    • v.2 no.2
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    • pp.43-47
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    • 2008
  • This paper is concerned with the analysis of material flow characteristics of stepped rod forming. The analysis in this paper concentrated on the evaluation of the design parameters for deformation patterns of tube forming, load characteristics, extruded length, and die pressure. The design factors such as punch nose radius, die corner radius, friction factor, and punch face angle are involved in the simulation. The stepped rod forming is analyzed by using a commercial finite element code. This simulation makes use of stepped rod material and punch geometry on the basis of punch geometry recommended by International Cold Forging Group. As radius ratio is large, forming load was reduced but extruded length ratio was increased.

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A Study on the AC Treeing Characteristics with Tip Radius of Needle Electrode in LLDPE/EVA (침전극 곡률반경에 따른 LLDPE/EVA의 교류트리 특성)

  • Lee, Jae-Pil;Lee, Chung-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.07a
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    • pp.476-480
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    • 2003
  • Polyethylene used as insulating material of power cable is nonpolar and low dielectric loss polymer. But it has defects of tree generation and accumulation of space charge by an applied voltage resulting in the decreased life and performance. To solve these problems, mixed films with LLDPE and EVA that is similar to LLDPE at physical properties in case of low VA contents were made and tested due to the blend ratios of 80:20, 70:30, 60:40 and 50:50[wt%] respectively. We investigated AC electrical treeing characteristics to acquire the best mixture ratio and effect of the tip radius of needle electrode to develop excellent treeproof materials. The degree of crystallity calculated with XRD pattern is higher for pure LLDPE, 50:50 and 70:30. For DSC analysis, it is confirmed that the melting points of mixed specimens are lower than that of pure LLDPE and higher than pure EVA's. The shape of tree propagation showed that pure EVA was electrical tree shape of the branch type, pure LLDPE and blended specimens was able to confirm tree shape of the bush type. As the tip radius go up in the blend ratio 70:30 specimen, the tree inception voltage rise. Probably the reason is the relaxation of electric field in the specimen with bigger tip ratio. As the 6 specimens were applied AC 5[KV],7.5[KV],10[KV] respectively, tree growth length is far shorter in the specimen with blend ratio 70:30, 50:50 than in pure EVA and pure LLDPE specimen. Conclusively, it is confirmed that specimens of which blend ratio are 70:30 and 50:50 are good in electrical tree retardant characteristics, especially, 70:30 has lower dielectric loss than 50:50 and its mixture ratio is the best.

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