• Title/Summary/Keyword: damping constant

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A New Damping Circuit With a Constant Damping Rate for RFID Applications (RFID 응용을 위한 일정한 감폭율을 갖는 새로운 감폭회로)

  • 오원석;이상훈;이강명;박종태;유종근
    • Proceedings of the IEEK Conference
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    • 2000.06b
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    • pp.125-128
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    • 2000
  • In this paper, we report a new damping circuit with a constant damping rate for RFID applications. The proposed damping circuit is used along with a over-voltage limiter and exhibits almost constant damping rates when the distance between the reader and the transponder varies. This results in keeping the power supply voltage of the transponder constant and in improved reading distances.

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Assessment of the Generators Constant from Frequency Response Properties of Korean Power System (우리나라 계통의 주파수응답특성에 의한 발전기정수 산정에 관한 연구)

  • Jeong, Bong-Sang;Chun, Yeong-Han;Kim, Il-Dong;Yang, Jeong-Jae
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.4
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    • pp.688-693
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    • 2009
  • The response characteristics of power system frequency are determined by generator droop characteristics and load damping properties. The characteristics of governor droops are termed by generators constant, while those of load damping by load constant. In this paper, the generator constant and the load constant are assessed by measured data at the event of generator trips.

Sloped rolling-type bearings designed with linearly variable damping force

  • Wang, Shiang-Jung;Sung, Yi-Lin;Hong, Jia-Xiang
    • Earthquakes and Structures
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    • v.19 no.2
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    • pp.129-144
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    • 2020
  • In this study, the idea of damping force linearly proportional to horizontal isolation displacement is implemented into sloped rolling-type bearings in order to meet different seismic performance goals. In addition to experimentally demonstrating its practical feasibility, the previously developed analytical model is further modified to be capable of accurately predicting its hysteretic behavior. The numerical predictions by using the modified analytical model present a good match of the shaking table test results. Afterward, several sloped rolling-type bearings designed with linearly variable damping force are numerically compared with a bearing designed with conventional constant damping force. The initial friction damping force adopted in the former is designed to be smaller than the constant one adopted in the latter. The numerical comparison results indicate that when the horizontal isolation displacement does not exceed the designed turning point (or practically when subjected to minor or frequent earthquakes that seldom have a great displacement demand for seismic isolation), the linearly variable damping force design can exhibit a better acceleration control performance than the constant damping force design. In addition, the former, in general, advantages the re-centering performance over the latter. However, the maximum horizontal displacement response of the linearly variable damping force design, in general, is larger than that of the constant damping force design. It is particularly true when undergoing a horizontal isolation displacement response smaller than the designed turning point and designing a smaller value of initial friction damping force.

Parametric study on equivalent damping ratio of different composite structural building systems

  • Farghaly, Ahmed Abdelraheem
    • Steel and Composite Structures
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    • v.14 no.4
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    • pp.349-365
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    • 2013
  • Structures consisting of concrete and steel parts, which are irregular in damping ratios are investigated. This investigation is a code-based seismic design of such structures. Several practical difficulties encountered, due to inherent differences in the nature of dynamic response of each part, and the different damping ratios of the two parts. These structures are irregular in damping ratios and have complex modes of vibration so that their analysis cannot be handled with the readily available commercial software. Therefore, this work aims to provide simple yet sufficiently accurate constant values of equivalent damping ratios applied to the whole structure for handling the damping irregularity of such structures. The results show that the equivalent damping ratio changes with the height of the building and the kind of the structural system, but it is constant for all accelerations values. Thus, available software SAP2000 applied for seismic analysis, design and the provisions of existing seismic codes. Finally, evaluation of different kinds of structural system used in this research to find the most energy dissipating one found by finding the best value of quality coefficient.

Seismic analysis of bridges based on stress-dependent damping

  • Su, Li;Wang, Yuanfeng;Li, Pengfei;Mei, Shengqi;Guo, Kun
    • Structural Engineering and Mechanics
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    • v.62 no.3
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    • pp.281-289
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    • 2017
  • Damping value has considerable influence on the dynamic and seismic behaviors of bridges. However, currently the constant damping ratios that are prescribed by most bridge seismic design codes can't truly represent the complicated damping character of actual structures. In this paper, a cyclic loading experiment was conducted to study the effect of stress amplitude on material damping of concrete to present an analyzing model of the material damping of concrete. Furthermore, based on the fundamental damping of structure measured under ambient vibration, combined with the presented stress-dependent material damping concrete, the seismic response of a bridge pier was calculated. Comparison between the calculated and experiment results verified the validity of the presented damping model. Finally, a modified design and analysis method for bridge was proposed based on stress-dependent damping theory, and a continuous rigid frame bridge was selected as the example to calculate the actual damping values and the dynamic response of the bridge under different earthquake intensities. The calculation results indicated that using the constant damping given by the Chinese seismic design code of bridges would overestimate the energy dissipation capacity of the bridge.

Analysis of Microwave Permeability and Damping Constant in Amorphous CoFeHfO Thin Film (비정질 CoFeHfO 박막 재료의 마이크로파 투자율 및 감쇠상수 분석)

  • Kim, Dong-Young;Yoon, Seok-Soo
    • Journal of the Korean Magnetics Society
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    • v.19 no.4
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    • pp.147-151
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    • 2009
  • The saturation magnetization and uniaxial anisotropy constant were obtained from magnetization and torque curves measurement in high resistive CoFeHfO thin film. The measured results were used for the analysis of the microwave complex permeability based on Landau-Lifshitz-Gilbert (LLG) theory. The high resistive CoFeHfO thin films showed very low damping constants of ${\alpha}$ = 0.014. The results are interpreted in terms of various magnetic phase with very low damping constant, which were existing inside the CoFeHfO thin film, through the linewidth analysis of the ferromagnetic resonance signal with magnetic field.

Dynamic Buckling Characteristics of 3-Free-Nodes Spatial Truss Model Under the Step Load (스텝 하중을 받는 3-자유절점 공간 트러스 모델의 동적 좌굴 특성)

  • Shon, Sudeok;Hwang, Kyung-Ju
    • Journal of Korean Association for Spatial Structures
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    • v.20 no.2
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    • pp.59-68
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    • 2020
  • In this paper, the dynamic snapping of the 3-free-nodes spatial truss model was studied. A governing equation was derived considering geometric nonlinearity, and a model with various conditions was analyzed using the fourth order Runge-Kutta method. The dynamic buckling phenomenon was observed in consideration of sensitive changes to the force mode and the initial condition. In addition, the critical load level was analyzed. According to the results of the study, the level of critical buckling load elevated when the shape parameter was high. Parallelly, the same result was caused by the damping term. The sensitive asymmetrical changes showed complex orbits in the phase space, and the critical load level was also becoming lowly. In addition, as the value of damping constant was high, the level of critical load also increases. In particular, the larger the damping constant, the faster it converges to the equilibrium point, and the occurrence of snapping was suppressed.

Effects of silt contents on the static and dynamic properties of sand-silt mixtures

  • Hsiao, Darn H.;Phan, Vu T.A.
    • Geomechanics and Engineering
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    • v.7 no.3
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    • pp.297-316
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    • 2014
  • This paper presents a detailed study focused on investigating the effects of silt content on the static and dynamic properties of sand-silt mixtures. Specimens with a low-plastic silt content of 0, 15, 30 and 50% by weight were tested in static triaxial, cyclic triaxial, and resonant columns in addition to consolidation tests to determine such parameters as compression index, internal friction angle, cohesion, cyclic stress ratio, maximum shear modulus, normalized shear modulus and damping ratio. The test procedures were performed on specimens of three cases: constant void ratio index, e = 0.582; same peak deviator stress of 290 kPa; and constant relative density, $D_r$ = 30%. The test results obtained for both the constant-void-ratio-index and constant-relative-density specimens showed that as silt content increased, the internal friction angle, cyclic stress ratio and maximum shear modulus decreased, but cohesion increased. In testing of the same deviator stress specimens, both cohesion and internal friction angle were insignificantly altered with the increase in silt content. In addition, as silt content increased, the maximum shear modulus increased. The cyclic stress ratio first decreased as silt content increased to reach the threshold silt content and increased thereafter with further increases in silt content. Furthermore, the damping ratio was investigated based on different silt contents in three types of specimens.

Effect of Intraoperative Deep Brain Stimulation on Viscoelastic Properties of Parkinsonian Rigidity during Surgery (파킨슨성 경직의 점탄성에 대한 수술중의 뇌심부 자극의 효과)

  • Kwon, Yu-Ri;Eom, Gwang-Moon;Park, Sang-Hun;Kim, Ji-Won;Koh, Seong-Beom;Park, Byung-Kyu
    • Journal of the Korean Society for Precision Engineering
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    • v.29 no.9
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    • pp.1035-1040
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    • 2012
  • Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been found to be effective treatment of Parkinson's disease (PD). This study aims to evaluate the effect of DBS for rigidity during DBS surgery. Six Parkinsonian patients who received STN-DBS surgery participated in this study. The examiner imposed flexion and extension of a patient's wrist randomly. Resistance to passive movement was quantified by viscoelastic properties (two damping constants for each of flexion and extension phase and one spring constant throughout both phases). All Viscoelastic constants decreased by DBS (p<0.01). Specifically, reduction in damping constant during flexion ($B_f$) was greater than those of damping constant during extension ($B_e$) and of spring constant (p<0.05). $B_f$ would be appropriate for evaluation of effect of DBS for rigidity during DBS surgery.

Control of Damping Coefficients for the Shear Mode MR Dampers Using Inverse Model (역모델을 이용한 MR 댐퍼의 감쇠계수 제어)

  • Na, Uhn Joo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.23 no.5
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    • pp.445-455
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    • 2013
  • A new linearization model for MR dampers is analyzed. The nonlinear hysteretic damping force model of MR damper can be modeled as a hyperbolic tangent function of currents, positions, and velicities, which is an algebraic function with constant parameters. Model parameters can be identified with numerical method using experimental force-velocity-position data obtained from various operating conditions. The nonlinear hysteretic damping force can be linearized with a given slope of damping coefficient if there exist corresponding currents to compensate for the nonlinearity. The corresponding currents can be calculated from the inverse model when the given linear damping force is set equal to the nonlinear hysteretic damping force. The linearization controller is realized in a DSP controller such that the corresponding currents to satisfy a given damping coefficient should be calculated. Experiments show that the current inputs to the MR damper produce linearized damping force with a given slope of the damping coefficient.