• Title/Summary/Keyword: Rotation Mode

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Effect of Internal Pressure on the Behavior of Wall Thinned Elbow under In-Plane Bending (In-plane 굽힘 조건에서 감육엘보우 거동에 미치는 내압의 영향)

  • Kim, Jin-Weon;Kim, Tae-Soon;Park, Chi-Yong
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.268-273
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    • 2004
  • This study is conducted to clarify the effect of internal pressure on the deformation and collapse behaviors of wall thinned elbow under in-plane bending moment. Thus the nonlinear three-dmensional finite element analyses were performed to obtain the moment-rotation curve of elbow contatining various wall thinning defects located at intrados and extrados under in-plane bending (closing and opening modes) with internal pressure of $0{\sim}15MPa.$ From the results of analysis, the effect of internal of collapse moment of elbow on the global deformation behavior of wall thinned elbow was discussed, and the dependence of collapse moment of elbow on the magnitude of internal pressure was investigated under different loading mode, defect location, and defect shape.

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A speed predictive control of the AC servo motor using DSP processor (DSP를 사용한 AC 서보 모터의 속도 예측 제어)

  • 김진환
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.35S no.7
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    • pp.22-28
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    • 1998
  • This paper includes AC servo motor speed control usig the predictive control strategy. Generally, AC servo motor control should have the fast response characteristics. For the issue, sliding mode control and PID control have been applied. However, the former has the speed ripple response due to the chattering and the latter requires the many trial efforts. Originally, the predictive control which has been used in process control area does not need the priori knowledge for the application system and it is easy to compute the optimal gain with the prediction. In this paper, the TMS320C31 DSP pocessor is used for AC motor control with fst dynamics and the tuning guid-line for the parameters of the predictive control algorithm is given in order to reduce the computation load. Also, the actuator saturationis implemented uisngthe QP(Quadratic Programming) method and the transient response is improved by the identified intertia coefficient when AC motor is drived at forward/reverse rotation.

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Flutter Analysis of Annular Cascades in Counter Rotation

  • Nishino, R.;Namba, M.
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.813-824
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    • 2004
  • The paper studies the effect of neighboring blade rows on flutter characteristics of cascading blades. For this purpose the computation program to calculate the unsteady blade loading based on the un-steady lifting surface theory for contra-rotating annular cascades was formulated and coded. Then a computation program to solve the coupled bending-torsion flutter equation for the contra-rotating annular cascades was also developed. Some results of the flutter analysis are presented. The presence of the neighboring blade row gives rise to significant change in the critical flutter condition when the main acoustic duct mode is of cut-on state.

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Ductility of open piled wharves under reversed cyclic loads

  • Yokota, Hiroshi;El-Bakry, Hazem M.F.
    • Structural Engineering and Mechanics
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    • v.12 no.6
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    • pp.615-632
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    • 2001
  • Ductility of open piled wharves under reversed cyclic loads has been investigated. Experimental testing of five wharf models having a scale of about 1:4 was conducted under the application of horizontal reversed cyclic loading. The experiments were designed to focus on the horizontal ultimate load, ductility and failure mode of the considered wharf models. Nonlinear numerical analyses using the finite element method were also performed on numerical models representing the experimentally tested wharves. The results of the experimental tests showed that open piled wharves possessed favourable ductile behaviour and that their load bearing capacity did not depreciate until a ductility factor of 3 to 4 was reached. The numerical analysis showed that the relative rotation that took place at the joints between the steel piles and the R.C. beam was responsible for a considerable portion of the total horizontal deformation of the wharves. Therefore, it was concluded that introducing the joint stiffness in calculating the deformations of open piled wharves was important to achieve reasonable accuracy.

Dynamics of a rotating beam with flexible root and flexible hub

  • Al-Qaisia, A.A.
    • Structural Engineering and Mechanics
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    • v.30 no.4
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    • pp.427-444
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    • 2008
  • A mathematical model for the nonlinear dynamics of a rotating beam with flexible root attached to a rotating hub with elastic foundation is developed. The model is developed based on the large planar and flexural deformation theory and the potential energy method to account for axial shortening due to bending deformation. In addition the exact nonlinear curvature is used in the system potential energy. The Lagrangian dynamics and the assumed mode method is used to derive the nonlinear coupled equations of motion hub rotation, beam tip deflection and hub horizontal and vertical displacements. The derived nonlinear model is simulated numerically and the results are presented and discussed for the effect of root flexibility, hub stiffness, torque type, torque period and excitation frequency and amplitude on the dynamic behavior of the rotating beam-hub and on its stability.

Effect of Local Wall Thinning Defect on the Collapse Moment of Elbow (엘보우의 붕괴모멘트에 미치는 국부 감육결함의 영향)

  • Kim, Jin-Weon;Kim, Tae-Soon;Park, Chi-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.4
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    • pp.402-409
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    • 2004
  • The purpose of this study is to investigate the effect of local wall thinning on the collapse of elbow subjected to internal pressure and bending moment. Thus, the nonlinear three-dimensional finite element analyses were performed to obtain the collapse moment of elbow containing various wall thinning defects located at intrados and extrados under two loading modes (closing and opening modes) with internal pressure. From the results of analysis, the effect of wall thinning defect on the global moment-rotation behavior of elbow was discussed, and the dependence of collapse moment of elbow on wall thinning depth, length, and circumferential angle was investigated under different loading mode and defect location.

Dynamics of a Micro Three-axis Ring Gyroscope (마이크로 3축 링 자이로스코프의 동역학)

  • Kim, Chang-Boo;Choi, Sang-Hyun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.12 no.12
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    • pp.1001-1009
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    • 2002
  • In this paper, we analyse and present mechanical dynamic characteristics of a micro-machined vibrating silicon ring gyroscope which can measure angular velocities about three orthogonal axes. The ring gyroscope has a ring connected to the gyroscope main body by support-ligaments which are arranged with cyclic symmetry. The natural modes of its vibration can be distinguished into the in-plane motion and the out-of-plane motion which are coupled by the gyro-effect due to the rotation of the gyroscope main body. The equations of motion, the response to angular velocities, and the relationships between the natural modes of vibration are derived and compared with the previous studies for the design of a micro three-axis ring gyroscope.

3D Generalized Langevin Equation (GLE) Approach to Gas-Surface Energy Transfer : Model H + H → $H_2/Si(100)-(2*1)$

  • Youxiang Zhang;Park, Seung Cheol
    • Bulletin of the Korean Chemical Society
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    • v.21 no.11
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    • pp.1095-1100
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    • 2000
  • we have proposed a three-dimensional GLE approach to gas-surface reactive scattering, model H + H $${\rightarrow}$H_2/Si(100)-(2$ ${\times}$1) system, and the implementation of 3D GLE method on the hydrogen on silicon surface has been presented. The formalism and algori thm of the 3D GLE are worked properly in the reactive scattering system. The calculated normal mode frequencies of surface vibrations were almost identical to previous harmonic slab calculations. The reaction probabilities were calculated for two energies. The calculations show that a very large amount of energy is transferred in surface in low energy scattering. Three different types of reaction mechanisms has been observed, which can not be shown in flat and rigid surface models. Further work on the reaction mechanisms and calculations of the vibrational and rotation distributions of products is in progress. The results will be reported elsewhere soon.

An NMR Study on Dynamics of$ AX_3$ Spin System as Illustrated By Methyl Group in 2,6-Dichlorotoluene

  • 노정래;현남궁;이조웅
    • Bulletin of the Korean Chemical Society
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    • v.19 no.12
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    • pp.1326-1333
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    • 1998
  • The study of coupled relaxation for methyl spin system in 2,6-dichlorotoluene was performed on the basis of the magnetization mode formalism. Using five initial perturbing pulse sequences, eight experimntal data sets were obtained, which were fitted with theoretical expressions with nine spectral density parameters. The same experiment was carried out at both 50.3 MHz and 125.6 MHz in carbon frequency. The measured spectral densities at both fields are similar in the exception of that related with carbon random field term. Furthermore, from the dipolar spectral density, the physical values may be extracted depending on the model of molecular reorientation. For example, it was assumed that the molecular framework undergoes asymmetric diffusive rotational process and methyl group reorients by either diffusive rotation about its symmetry axis or jump among internal rotational potential minima.

A study on natural frequencies and damping ratios of composite beams with holes

  • Demir, Ersin
    • Steel and Composite Structures
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    • v.21 no.6
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    • pp.1211-1226
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    • 2016
  • In this study, free vibration and damping characteristics of composite beams with holes are investigated, experimentally and numerically. Two types of samples with different fabrics are used: unidirectional and woven. The effects of diameter, number and location of circular holes on the vibration characteristics of composite beams are examined. The effects of rotation angle and minor to major diameter ratio of the elliptical hole are also investigated numerically. Moreover, the mode shapes of all types of beams are obtained numerically. According to the results, the natural frequency decreases with increasing hole diameter but increases very little with increasing the distance between the hole center and the clamped end. Damping ratio decreases by increasing the diameter of hole. But it fluctuates by increasing the diameters of holes of beam having three holes. Furthermore it decreases by increasing the distance between hole center and clamped end except for the range 50 mm to 100 mm.