• Title/Summary/Keyword: Equilibrium Position

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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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Pneumatic Cylinder Position Control Algorithm for Control Consistency (공기압 실린더의 위치제어 일관성을 위한 제어 알고리즘)

  • Lee, Ji-Hoon;Nam, Yun-Joo;Park, Myeong-Kwan
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.985-990
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    • 2007
  • This paper presents a novel control algorithm for position control of pneumatic cylinder. Generally, it is difficult to control the pneumatic servo system, due to nonlinearities such as air compressibility, the opening area of the valve, and frictional force between the cylinder and the piston. Especially, it is of significant importance for the control consisten-cy to return the cylinder pressures at equilibrium point to the initial states, still with guaranteeing the continuity of the pressures. For this purpose, the proposed control algorithm makes pressures of both cylinder chambers identical in magnitude but different in direction. The effectiveness and practicability of the control algorithm for the precise position control of the pneumatic cylinder are verified through the simulation study.

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The Study on the Tube Drawing Process with a Floating Plug (프로팅 프러그를 사용한 관재 인발가공에 관한 연구)

  • Choi, Jae-Chan;Jin, In-Tai
    • Journal of the Korean Society for Precision Engineering
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    • v.5 no.4
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    • pp.24-31
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    • 1988
  • The Upper Bound Solution has been used to investigate the effect of the various parameters on the floating-plug tube-drawing precess. A kinematically admissible velocity field considering the change of the tube thickness is proposed for the deformation process. Taking into account the position of the plug in the deforming region, shear energy at entrance and exit, friction energy on contact area, homogeneous energy are calculated. The theoretical values in proposed velocity field are good agreement with experimental values, It is investigated that the tube thickness in the deforming region is changed slightly toward minimization of deforming energy and then the drawing stress in lower than the crawing stress in the velocity field that the tube thickness is uniform.

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Design and Control of an Active Magnetic Bearing for Linear Motors (리니어 모터를 위한 능동 자기 베어링의 설계 및 제어)

  • 양광원;허경무
    • Proceedings of the IEEK Conference
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    • 2001.06e
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    • pp.119-122
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    • 2001
  • This paper deals with new type of active magnetic bearing (AMB) for the linear motors. We adopted optical sensing mechanism for the gap sensing. Using the laser and the PSD (Position Sensitive Device), the absolute rotor position is obtained independent of the profile of the guide rail. With this measurement, the rotor can be controller to follow the straight beam of the laser. Another advantage of optical sensing mechanism might be the elimination of the possible interference between the proximity sensor and the electro-magnet. By adopting the push-full actuating mechanism, the bearing stiffness is increased near the equilibrium position. For the simplicity, distributed control system is constructed. Eight independent PID control algorithm is used with the full order observer. Several simulation md test results are presented.

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Buzz Margin Determination of Supersonic Intake (초음속 흡입구의 버즈여유 결정기법)

  • Park, Ik-Soo;Choi, Jong-Ho;Yoon, Hyun-Gull;Lim, Jin-Shik
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.04a
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    • pp.132-135
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    • 2011
  • A technology for buzz margin determination is suggested to obtain stable shock structure and high compression efficiency of supersonic intake. By using the shock equilibrium equation of supersonic intake, sensitivity equation of terminal shock position for free stream and back pressure is induced and disturbances are quantified through statistical approach. Numerical results show that the sensitivity of shock position for disturbances is proportional to Mach number and the back pressure is dominant for variance of terminal shock position.

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Analysis of Shoreline Response due to Wave Energy Incidence Using Equilibrium Beach Profile Concept (평형해빈단면 개념을 이용하여 파랑 에너지 유입에 따른 해안선 변동 해석)

  • Kim, Tae-Kon;Lee, Jung-Lyul
    • Journal of Ocean Engineering and Technology
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    • v.32 no.2
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    • pp.116-122
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    • 2018
  • Dean's equilibrium beach profile formula was used to investigate the correlation between the static shoreline position and the incident wave energy. The effect of the longshore sediment transport was neglected, and the results showed the reasonable agreement compared with the field observations of Yates et al.(2009), which were conducted for almost 5 years on southern California beaches, USA. The shoreline response varies with the scale factor of Dean's equilibrium beach profile. This implies that the shoreline response could be simply estimated using the sampled grain size without laborious long-term field work. Therefore, the present study results are expected to be practically used for the layout design of submerged or exposed detached breakwaters although the further work is required for performance verification. In addition, after laborous mathematical reviews, the linear relation between incident energy and shoreline response, which was obtained from Yates's field study, yielded a clear mathematical equation showing how the beach slope is related to the grain size.

A topological optimization method for flexible multi-body dynamic system using epsilon algorithm

  • Yang, Zhi-Jun;Chen, Xin;Kelly, Robert
    • Structural Engineering and Mechanics
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    • v.37 no.5
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    • pp.475-487
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    • 2011
  • In a flexible multi-body dynamic system the typical topological optimization method for structures cannot be directly applied, as the stiffness varies with position. In this paper, the topological optimization of the flexible multi-body dynamic system is converted into structural optimization using the equivalent static load method. First, the actual boundary conditions of the control system and the approximate stiffness curve of the mechanism are obtained from a flexible multi-body dynamical simulation. Second, the finite element models are built using the absolute nodal coordination for different positions according to the stiffness curve. For efficiency, the static reanalysis method is utilized to solve these finite element equilibrium equations. Specifically, the finite element equilibrium equations of key points in the stiffness curve are fully solved as the initial solution, and the following equilibrium equations are solved using a reanalysis method with an error controlled epsilon algorithm. In order to identify the efficiency of the elements, a non-dimensional measurement is introduced. Finally, an improved evolutional structural optimization (ESO) method is used to solve the optimization problem. The presented method is applied to the optimal design of a die bonder. The numerical results show that the presented method is practical and efficient when optimizing the design of the mechanism.

Thermodynamic Investigation of the Formation of Complexes between Norfloxacin and Various Mononucleotides

  • Kwon, Yong-Jun;Lee, Hyun-Mee;Han, Sung-Wook;Lee, Dong-Jin;Cho, Tae-Sub
    • Bulletin of the Korean Chemical Society
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    • v.32 no.9
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    • pp.3233-3238
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    • 2011
  • The fluorescence of norfloxacin was quenched by various nucleotides. The ratio of the fluorescence intensities in the absence and presence of nucleotide was linearly dependent on nucleotide concentration, suggesting that quenching occurred through the formation of nonfluorescent norfloxacin-nucleotide complexes. The gradient of the linear relationship represented the equilibrium constant of complex formation; it decreased with increasing temperature. The slopes of van't Hoff plots constructed from the temperature-dependent equilibrium constants were positive in all cases, indicating that complex formation was energetically favorable - i.e., exothermic, with negative Gibb's free energy. The equilibrium constant increased when triphosphate was used instead of monophosphate. It also increased when the oxygen at the $C'_2$ position of the nucleotide was removed. Both enhancements were due to entropic effects: entropy decreased when complexes with AMP or GMP formed, while it increased when norfloxacin complexed with ATP, GTP, dAMP and dGMP.

Transient Response Analysis of a Control Valve for CO2 Refrigerant (CO2냉매용 제어밸브의 응답 특성)

  • Kim, Bo Hyun;Jang, Ji Seong
    • Journal of Drive and Control
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    • v.15 no.4
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    • pp.11-16
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    • 2018
  • Pilot operated control valve for $CO_2$ refrigerant is a valve that can perform various functions according to the user's intention by replacing pilot units, widely used for flow rate, pressure, and temperature control of refrigeration and air conditioning systems. In addition, $CO_2$ refrigerant, that requires high pressure and low critical temperature, can be installed and used in all positions of the refrigeration system, regardless of high or low pressure. In this paper, response characteristics are modeled and analyzed based on behavior of the main piston of the pilot-operated control valve. Although various factors influence operation of the main piston, this paper analyzes the effect of equilibrium pressure depending on valve installation position and application, and inlet and outlet orifice size of the load pressure feedback chamber to determine feedback characteristics of the main piston. As a result, it was possible to quantitatively analyze the effect of change in equilibrium and load pressure feedback chamber flow path size on the change in main piston dynamic and static characteristics.

Facile Evaluation of Thermodynamic Parameters for Reverse Thermochromism of Indolinobenzospiropyran-6-carboxylates in Aqueous Binary Solvents

  • Keum, Sam-Rok;Ma, So-Young;Lim, Hyun-Woo;Han, Tae-Hwi;Choi, Kyu-Hyun
    • Bulletin of the Korean Chemical Society
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    • v.33 no.8
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    • pp.2683-2688
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    • 2012
  • The position of the thermodynamic equilibrium for reverse thermochromic spiropyran 6-carboxylates (SP-COOHs) was easily determined in aqueous binary mixtures, such as water-methanol, water-acetonitrile and water-dimethyl sulfoxide. The existence of more than one type of interconvertible species of the ring-opened form of SP-COOH in aqueous binary solvents enables us to evaluate the molar extinction coefficients of the ring-opened species of SP-COOH and to obtain the thermodynamic parameters.