• Title/Summary/Keyword: Dynamic shim

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Research on Mechanical Shim Application with Compensated Prompt γ Current of Vanadium Detectors

  • Xu, Zhi
    • Nuclear Engineering and Technology
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    • v.49 no.1
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    • pp.141-147
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    • 2017
  • Mechanical shim is an advanced technology for reactor power and axial offset control with control rod assemblies. To address the adverse accuracy impact on the ex-core power range neutron flux measurements-based axial offset control resulting from the variable positions of control rod assemblies, the lead-lag-compensated in-core self-powered vanadium detector signals are utilized. The prompt ${\gamma}$ current of self-powered detector is ignored normally due to its weakness compared with the delayed ${\beta}$ current, although it promptly reflects the flux change of the core. Based on the features of the prompt ${\gamma}$ current, a method for configuration of the lead-lag dynamic compensator is proposed. The simulations indicate that the method can improve dynamic response significantly with negligible adverse effects on the steady response. The robustness of the design implies that the method is of great value for engineering applications.

Dynamic stabilization for a nonlinear system with uncontrollable unstable linearization (제어불가능 불안정 선형화를 가지는 비선형 시스템에 대한 다이나믹 안정화)

  • Seo, Sang-Bo;Seo, Jin-Heon;Shim, Hyung-Bo
    • Proceedings of the IEEK Conference
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    • 2009.05a
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    • pp.79-81
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    • 2009
  • In this paper, we design a dynamic state feedback smooth stabilizer for a nonlinear system whose Jacobian linearization may have uncontrollable because its eigenvalues are on the right half-plane. After designing an augmented system, a dynamic exponent scaling and backstepping enable one to explicitly design a smooth stabilizer and a continuously differentiable Lyapunov function which is positive definite and proper.

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A Study on Dynamic Walking Control of Biped Robot (이족 보행로봇의 동적 보행 제어에 관한 연구)

  • Shim, Byoung-Kyun;Jeong, Yang-Keun;Shim, Hyun-Seok;Lee, Woo-Song
    • Journal of the Korean Society of Industry Convergence
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    • v.17 no.4
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    • pp.245-254
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    • 2014
  • In this paper, stable and robust dynamic walking for a biped motion is proposed. To success this objective, the following structures are processed. In this paper, the proposed control method is one that adjusts actual zero moment position to move to the closest possible point in the stable area instead of following desired zero moment position. This minimizes energy consumption with the smallest joint movements. The proposed control method makes mechanical energy that drives lower limb of the bipedal robot efficient. In this paper, walking experiment is carried out with the three control structures mentioned above. The trajectory generated by off-line is illustrated by performing to walking on flat ground. experiment with an obstacle whose height is lower than that of trajectory is executed to validate dynamic motion.

A Dynamic Discount Approach to the Poisson Process

  • Shim, Joo-Yong
    • Journal of the Korean Data and Information Science Society
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    • v.8 no.2
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    • pp.271-276
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    • 1997
  • A dynamic discount approach is proposed for the estimation of the Poisson parameter and the forecasting of the Poisson random variable, where the parameter of the Poisson distribution varies over time intervals. The recursive estimation procedure of the Poisson parameter is provided. Also the forecasted distribution of the Poisson random variable in the next time interval based on the information gathered until the current time interval is provided.

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Multiprocess Dynamic Poisson Mode1s: The Covariates Case

  • Shim, Joo-Yong;Sohn, Joong-Kweon
    • Journal of the Korean Statistical Society
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    • v.27 no.3
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    • pp.279-288
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    • 1998
  • We propose a multiprocess dynamic Poisson model for the analysis of Poisson process with the covariates. The algorithm for the recursive estimation of the parameter vector modeling time-varying effects of covariates is suggested. Also the algorithm for forecasting of numbers of events at the next time point based on the information gathered until the current time is suggested.

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Experimental Study on the Dynamic Response of Oil Seals

  • Sung, Boo-Yong;Shim, Woo Jeonm;Kim, Chung Kyun
    • KSTLE International Journal
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    • v.1 no.1
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    • pp.59-62
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    • 2000
  • This paper deals with an experimental study on the dynamic response of an elastomeric oil seal when the interferences between shaft and lip as well as the dynamic eccentricities are present. The dynamic response of seal lip in oil seals was observed with the aid of an image processing apparatus. The temperature of the seal lip edge, friction torque and the dynamic sealing gap between shaft and lip are measured at different conditions of the initial interference and the shaft eccentricity, The data were simultaneously measured under dynamic conditions. Experimental results show that, as the shaft speed is increased, S/e$_{d}$ has nearly reached a constant asymptotic value fur a certain range of shaft speeds. The results indicate that the gap separation between shaft and lip is provided due to the shaft eccentricity because the seal lip cannot follow quickly the radial displacements with increasing shaft speed.d.

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Performance Predictions of Gas Foil Journal Bearing with Shim Foils (심포일을 갖는 가스 포일 저널 베어링의 성능 예측)

  • Hwang, Sung Ho;Moon, Chang Gook;Lee, Jong Sung;Kim, Tae Ho
    • Tribology and Lubricants
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    • v.34 no.3
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    • pp.107-114
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    • 2018
  • This paper presents a computational model of a gas foil journal bearing with shim foils between the top foil and bumps, and predicts its static and dynamic performance. The analysis takes the previously developed simple elastic foundation model for the top foil-bump structure and advances it by adding foil models for the "shim foil" and "outer top foil." The outer top foil is installed between the (inner) top foil and bumps, and the shim foil is installed between the inner top foil and outer top foil. Both the inner and outer top foils have an arc length of $360^{\circ}$, but the arc length of the shim foil is shorter, which causes a ramp near its leading edge in the bearing clearance profile. The Reynolds equation for isothermal and isoviscous ideal gas solves the hydrodynamic pressure that develops within the bearing clearance with preloads due to the ramp. The centerline pressure and film thickness predictions show that the shim foil mitigates the peak pressure occurring at the loading direction, and broadens the positive pressure as well as minimum film thickness zones except for the shortest shim foil arc length of $180^{\circ}$. In general, the shim foil decreases the journal eccentricity, and increases the power loss, direct stiffness, and damping coefficients. As the shim foil arc length increases, the journal eccentricity decreases while the attitude angle, minimum film thickness, and direct stiffness/damping coefficients in the horizontal direction increase.

A Study on Efficient Generation of Beam-Mass Model for Simplification of the Crankshaft in the Large Marine Engine (대형 선박엔진용 크랭크축 해석을 위한 보-질량 모델 생성 기법에 관한 연구)

  • Suh, Myung-Won;Shim, Mun-Bo;Kim, Ki-Hyun;Kim, Kyu-Hee
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.10
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    • pp.1661-1666
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    • 2003
  • The purpose of this study is to develop the simplified model of the crankshaft in the large marine engine for dynamic analysis. Because the actual engine system is under complex dynamic loading condition and it has multi-cylinder, the dynamic analysis is purchased at a high computation cost. In spite of this burden, the dynamic analysis must be perfonned to assure structural integrity of operating marine engine. Therefore, simplification of the analytic model is necessary for dynamic analysis. Beam-mass model, which is generated with the section property method, is the model simplified effectively. Section property method can provide desired section information by optimization technique. By applying beam-mass model to the crankshaft in the large marine engine, the usefulness of the proposed method was proven.

Numerical Study on the Dynamic Response in Elastomeric Oil Seals

  • Shim, Woo Jeon;Sung, Boo-Yong;Kim, Chung Kyun
    • KSTLE International Journal
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    • v.1 no.1
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    • pp.43-47
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    • 2000
  • Oil seals will experience a small amplitude dynamic excitation due to the shaft eccentricity as well as out-of-roundness of the shaft. The direct integration method is selected to analyze the time domain response of the seal lip-shaft contact. The physical properties of rubber seal materials are experimentally analyzed. Effects of both frequency and temperature on the material stiffness behavior are investigated for the linear viscoelastic materials of the seal. Using the nonlinear transient model, a finite element analysis of the lip-shaft contact behaviors under dynamic conditions is presented as a function of the shaft eccentricity, the shaft interference and the garter spring stiffness. The FEM results based on the experimental data indicate that the increased rotating speed may produce the separation conditions. These results will be very useful in predicting the leakage of oil seals under dynamic conditions.

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