• Title/Summary/Keyword: 평형 위치

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Analysis of Dynamic Equilibrium Configuration of Speed Governor (조속기의 동적 평형위치 해석)

  • Kang, Juseok
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.10
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    • pp.4733-4738
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    • 2013
  • This paper proposes a method to obtain the dynamic equilibrium configuration of a constrained mechanical system by using multibody dynamic analysis. Dynamic equilibrium equations with independent coordinates are derived from the time-dependent constraint equations and dynamic equations of a multibody system. The Newton-Raphson method is used to find numerical solutions for nonlinear algebraic equations that are composed of the dynamic equilibrium and constraint equations. The proposed method is applied to obtain the dynamic equilibrium configuration of a speed governor, and the results are verified on the basis of the results from conventional dynamic analysis. Furthermore, vertical displacements at equilibrium configuration, which varied with the rotational velocity of the speed governor, are calculated, and design parameter analysis of the equilibrium configuration is presented.

Toroidal Equilibrium of Screw Belt Pinch

  • Kim, Sang-Hoon
    • Nuclear Engineering and Technology
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    • v.6 no.4
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    • pp.249-252
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    • 1974
  • The equilibrium configuration of the screw belt pinch is obtained as the first-order correction on that of the straight pinch of infinite lenghth.

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Fundamentals of Tight fitted Contact Lens Movement (Tight Fit 콘택트렌즈 운동의 기초)

  • Kim, Dae Soo
    • Journal of Korean Ophthalmic Optics Society
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    • v.14 no.3
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    • pp.17-27
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    • 2009
  • Purpose: This review article was written to determine the effects of parameters characterizing a hard contact lens (RGP included), such as BCs, diameters, edge angles, on the time interval for tight fitted lens to return to the equilibrium when it was decentered from blinking. Methods: A mathematical formulation was established to relate or calculate the restoring forces and thickness of lacrimal layer beneath the cornea with the various lens parameters when the tight fitted lens was decentered from blinking. Based on this formulation the differential equations and their numerical solution program were set up to describe the time dependence of the lens on the position and to estimate the time for the lens's return to the equilibrium after blink. Results: It is found that the time interval for the tight fitted lens to return to the equilibrium decreases as either the BC decreases or the diameter increases because both the reduction in BC and increase in diameter result in the increase in the lacrimal layer thickness between the lens and cornea increase which yielded the lowering of the viscous friction in the lens motion. As the edge angle of tight fitted lens increases the time for recentering decreases due to the increase in restoring force without change in lacrimal thickness beneath the lens. In the case of flat fitted hard lens (RGP included), the lacrimal layer thickness under the lens increases as either BC or diameter increases which results in reduction in viscous friction so that the time for the lens's return to the equilibrium were to decrease. The edge angle of flat fitted lens does not affect the lens motion. Conclusions: The effect of BCs on the lens motion (time to approach the equilibrium) was concluded to be significant with both tight and flat fitted lens where its results are contrary with each other. The edge angle of lens only affects the motion in tight fitted lenses.

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Damped Oscill ations of the (Hard)Contact Lenses Posterior to the Blink (순목 후 콘택트(하드)렌즈의 감쇄 진동)

  • Kim, Dae-Soo
    • Journal of Korean Ophthalmic Optics Society
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    • v.10 no.3
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    • pp.173-184
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    • 2005
  • A capillary action-induced tension develops in the tear layer between the contact lens and cornea, which leads to the restoring force due to difference in the layer thickness between either upper and lower or left and right side of the lens when it is displaced off the equilibrium position as a result of blinking. Suppose the lens was displaced a certain distance from the equilibrium position, lens starts to oscillate toward the equilibrium position with the decreasing amplitude due to the restoring force as well as the velocity dependent viscous damping force in the tear layer. A mathematical model which consists of the differential equations and their numerical solution was proposed to analyze the damped oscillations of lenses. The model predicts the time dependence of lenses after the blink varying the various parameters such as Be, diameters, masses and positions displaced from equilibrium. As the Be and mass of lens increases the rate of amplitude reduction decreases, which requires a more time for the lens to return to the equilibrium position. It seems that varying the lens' displacement and diameters affect the lens' motion very little.

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Analytical Method to Analyze the Effect of Tolerance on the Modal Characteristic of Multi-body Systems in Dynamic Equilibrium (동적 평형위치에 있는 다물체계의 모드특성에 미치는 공차의 영향 분석을 위한 해석적 방법)

  • Kim, Bum-Suk;Yoo, Hong-Hee
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.17 no.7
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    • pp.579-586
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    • 2007
  • Analytical method to analyze the effect of tolerance on the modal characteristic of multi-body systems in dynamic equilibrium position is suggested in this paper. Monte-Carlo method is conventionally employed to perform the tolerance analysis. However, Monte-Carlo method spends too much time for analysis and has a greater or less accuracy depending on sample condition. To resolve these problems, an analytical method is suggested in this paper. Sensitivity equations for damped natural frequencies and the transfer function are derived at the dynamic equilibrium position. By employing the sensitivity information of mass, damping and stiffness matrices, the sensitivities of damped natural frequencies and the transfer function can be calculated.

Analytical Method to Analyze the Effect of Tolerance on the Modal Characteristic of Multi-body Systems in Dynamic Equilibrium (동적 평형위치에 있는 다물체계의 모드특성에 미치는 공차의 영향 분석을 위한 해석적 방법)

  • Kim, Bum-Suk;Yoo, Hong-Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.109-114
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    • 2007
  • Analytical method to analyze the effect of tolerance on the modal characteristic of multi-body systems in dynamic equilibrium position is suggested in this paper. Monte-Carlo Method is conventionally employed to perform the tolerance analysis. However, Monte-Carlo Method spends too much time for analysis and has a greater or less accuracy depending on sample condition. To resolve these problems, an analytical method is suggested in this paper. By employing the sensitivity information of mass, damping and stiffness matrices, the sensitivities of damped natural frequencies and the transfer function can be calculated at the dynamic equilibrium position. The effect of tolerance on the modal characteristic can be analyzed from tolerance analysis method.

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Model on the Contact Lens Movement from Eye-lid Blinking (순목 작용에 의한 콘택트 렌즈의 운동 모델)

  • Kim, Daesoo
    • Journal of Korean Ophthalmic Optics Society
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    • v.9 no.1
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    • pp.145-159
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    • 2004
  • A mathematical model and its computer solution program were proposed to analyze the motion of contact lenses which are being subject to lid-blinking. The equation was derived by incorporating an acceleration induced lid's force exerting on the contact lens, the viscous damping resistance in the tear layer beneath the lens and the sliding frictional force between the lid and the contact lens surface into the formulation of differential equation describing the vibration. The model predicts the time-dependent displacement from the equilibrium postion during/after the blinking. During the blinking, as the time for the completion of one cycle of blinking decreases the off-the-equilibrium displacement of contact lens increases while the decrease of diameter in the contact cause the opposite effect. It is found that lid pressure exerting on the lens cause an insignificant lens displacement from the equilibrium position. After blinking the frequency of damped oscillation of contact lens decreases as the diameter of lens increases, due to the incresed surface while the reduced blinking time does not cause a significant frequency change. This is because that driving force for the contact lens movement posterior to blinking is the capillary-induced force not the lid force.

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Fundamentals of Contact Lens Movement (콘택트렌즈 운동의 기초)

  • Kim, Dae Soo
    • Journal of Korean Ophthalmic Optics Society
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    • v.13 no.1
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    • pp.5-13
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    • 2008
  • Purpose: This review article was written to investigate what kind of forces are acting on the contact lens fitted on the cornea and its subsequent motion. Methods: A capillary action-induced force develops in the tear layer between the lens and cornea, which leads to the restoring force due to difference in layer thickness according to lens rotation. The characteristics of the lens movement can be determined by the various factors such as friction between eyelid and lens, acceleration force based on blinking and the restoring force incorporated with the viscous damping force. A mathematical model which consists of the differential equations and their numerical solution was proposed to analyze the damped motion of lenses. The model predicts the time dependence of lenses during and after the blink varying the BC, blink period and eyelid pressure. Results: It was found that both the blink period and lid pressure increases the movement increases because of the enhanced lid friction. As the BC increases the viscous damping reduces due to the lacrimal layer's increase which resulted in the enhanced lens motion. After blink the lens illustrates the damped oscillation because of the restoring force by the increased lacrimal layer thickness and reduced viscous resistance. The time for the lens to return to the equilibrium shortens as the BC increase because of the resistance reduction. Conclusions: The movement of the contact lens is governed by the characteristics of the lacrimal layer between the lens and cornea as well as the lid blink.

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Tolerance Analysis for Natural Frequencies of Multi-body Systems in Dynamic Equilibrium State (다물체계의 평형위치에서 고유진동수에 대한 공차해석)

  • Eom, Seung-Man;Choi, Dong-Hwan;Yoo, Hong-Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.95-100
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    • 2006
  • Tolerance analysis method for natural frequencies of multi-body systems having a equilibrium position is suggested in this paper. To perform the tolerance analysis, the Monte-Carlo Method is conventionally employed. However, the Monte-Carlo Method has some weakness; spending too much time for analysis and having a low accuracy and hard to converge in the numerical unstable area. To resolve these problems, a tolerance analysis method is suggested in this paper. Sensitivity equations of natural frequencies are derived at the equilibrium position. By employing the sensitivity information of mass, damping and stiffness matrices, the sensitivity of natural frequencies can be calculated.

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Tolerance Analysis for Natural Frequencies of Multi-body Systems in Dynamic Equilibrium State (다물체계의 평형위치에서 고유진동수에 대한 공차해석)

  • Eom, Seung-Man;Choi, Dong-Hwan;Yoo, Hong-Hee
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.17 no.1
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    • pp.65-71
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    • 2007
  • Tolerance analysis method for natural frequencies of multi-body systems having a equilibrium position is suggested in this paper. To perform the tolerance analysis, the Monte-Carlo Method is conventionally employed. However, the Monte-Carlo Method has some weakness; spending too much time for analysis and having a low accuracy and hard to converge in the dynamical unstable area. To resolve these problems, a tolerance analysis method is suggested in this paper. Sensitivity equations of natural frequencies are derived at the equilibrium position. By employing the sensitivity information of mass, damping and stiffness matrices, the sensitivity of natural frequencies can be calculated.