• Title/Summary/Keyword: frequency-response

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Investigations on a vertical isolation system with quasi-zero stiffness property

  • Zhou, Ying;Chen, Peng
    • Smart Structures and Systems
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    • v.25 no.5
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    • pp.543-557
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    • 2020
  • This paper presents a series of experimental and numerical investigations on a vertical isolation system with quasi-zero stiffness (QZS) property. The isolation system comprises a linear helical spring and disk spring. The disk spring is designed to provide variable stiffness to the system. Orthogonal static tests with different design parameters are conducted to verify the mathematical and mechanical models of the isolation system. The deviations between theoretical and test results influenced by the design parameters are summarized. Then, the dynamic tests for the systems with different under-load degrees are performed, including the fast sweeping tests, harmonic excitation tests, and half-sine impact tests. The displacement transmissibility, vibration reduction rate, and free vibration response are calculated. Based on the test results, the variation of the transmission rule is evaluated and the damping magnitudes and types are identified. In addition, the relevant numerical time history responses are calculated considering the nonlinear behavior of the system. The results indicate that the QZS isolation system has a satisfactory isolation effect, while a higher damping level can potentially promote the isolation performance in the low-frequency range. It is also proved that the numerical calculation method accurately predicts the transmission character of the isolation system.

TMD parameters optimization in different-length suspension bridges using OTLBO algorithm under near and far-field ground motions

  • Alizadeh, Hamed;Lavasani, H.H.
    • Earthquakes and Structures
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    • v.18 no.5
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    • pp.625-635
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    • 2020
  • Suspension bridges have the extended in plan configuration which makes them prone to dynamic events like earthquake. The longer span lead to more flexibility and slender of them. So, control systems seem to be essential in order to protect them against ground motion excitation. Tuned mass damper or in brief TMD is a passive control system that its efficiency is practically proven. Moreover, its parameters i.e. mass ratio, tuning frequency and damping ratio can be optimized in a manner providing the best performance. Meta-heuristic optimization algorithm is a powerful tool to gain this aim. In this study, TMD parameters are optimized in different-length suspension bridges in three distinct cases including 3, 4 and 5 TMDs by observer-teacher-learner based algorithm under a complete set of ground motions formed from both near-field and far-field instances. The Vincent Thomas, Tacoma Narrows and Golden Gate suspension bridges are selected for case studies as short, mean and long span ones, respectively. The results indicate that All cases of used TMDs result in response reduction and case 4TMD can be more suitable for bridges in near and far-field conditions.

Oven Temperature Control by Integral - Cycle Binary Rate Modulation Technique

  • Tipsuwanporn, V.;Piyarat, W.;Chochai, N.;Jamjan, K.;Paraken, Y.
    • 제어로봇시스템학회:학술대회논문집
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    • 1999.10a
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    • pp.278-280
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    • 1999
  • This paper proposes controlling of temperature in an oven by using 4 bits Integral - Cycle Binary Rate Modulation (IBRM) method and ac line with frequency 50 Hz. Microcontroller MCS-51 controls IBRM according to Proportional Integral controller (PI) function. Discrete signals are used in the system modeled by using Ziegler Nichols principle for analyzing the stability before designing the system. This procedure makes it easy to investigate system response. The system is implemented by 4 bits digital circuit which gives 320 patterns of ac signal fur controlling the generation of energy for 3,000 watts thermal coil every 20 ms of each cycle. We divide scan time (Ts$\sub$n/) in to 20 intervals, 1 ms interval is selected to generate 16 patterns IBRM. Because of this method gives the ripple lower than 2% it generates less noise fur system. Moreover, we can consider whole system from the time model of control procedure and IBRM algorithm at 40-200$^{\circ}C$ with ${\pm}$ 1$^{\circ}C$ error in the 1 cubic meter oven.

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Study on the analysis of Crosstalk at Interconnects in Integrated Circuits (집적회로의 다층 금속 배선에서의 혼신 특성 해석에 관한 연구)

  • 김연태;최익준;권오섭;원태영
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.41 no.4
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    • pp.29-40
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    • 2004
  • This paper reports the frequency characteristics and the time response of parallel adjacent-transmission lines, crossed adjacent-transmission lines and parallel adjacent-transmission lines which are on the different planes by using FDTD-PML method. In the parallel adjacent-transmission lines, the crosstalks as a function of horizontal distance are calculated and in the crossed adjacent- transmission lines, the crosstalks as a function of vertical distance are simulated. Also, the crosstalks as functions of horizontal and vertical distances are measured and analyzed in the parallel adjacent-transmission lines which are on the different planes.

High Speed Grid Voltage Detection Method for 3 Phase Grid-Connected Inverter during Grid Faults (전원사고 시 3상 계통연계 인버터의 전원 전압 고속 검출 방법)

  • Choi, Hyeong-Jin;Song, Seung-Ho;Jeong, Seung-Gi;Choi, Ju-Yeop;Choy, Ick
    • Journal of the Korean Solar Energy Society
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    • v.29 no.5
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    • pp.65-72
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    • 2009
  • The new method is proposed to improve high speed detection of grid voltage phase and magnitude during a voltage dip due to a grid faults. Usually, A LPF(Low Pass Filter) is used in the feedback loop of PLL (Phase Locked Loop) system because the measured grid voltage contains harmonic distortions and sensor noises. so, a new design method of the loop gain of the PI -type controller in the PLL system is proposed with the consideration of the dynamics of the LPF. As a result, a better transient response can be obtained with the proposed design method. The LPF frequency and PI controller gain are designed in coordination according to the steady state and dynamic performance requirement. This paper shows the feasibility and the usefulness of the proposed methods through the computer simulation and the lab-scale experiments.

Mechanical Characterization of Lead-Rubber Bearing by Horizontal Shear Tests (수평 전단시험에 의한 납 삽입 적층고무베어링의 기계적 특성 평가)

  • 전영선;최인길;유문식
    • Journal of the Earthquake Engineering Society of Korea
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    • v.5 no.6
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    • pp.1-10
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    • 2001
  • In this study, the horizontal loading tests of 10ton and 200ton capacity of LRB(lead-rubber bearing) were performed for the evaluation of the dynamic properties of the LRB. It is noted from the test results that dynamic properties of the LRB are dependent on the loading frequency, vertical load and shear strain. A Slender bearing subjected to large deformation will tend to develop plastic hinges in the end regions of the lead plug which will cause the failure of the lead plug. It is recommended that the appropriate mechanical properties of LRB considering the level of structural response and input ground motion should be used in the design of base isolated structures.

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A Novel Unequal Broadband Out-of-Phase Power Divider Using DSPSLs

  • Lu, Yun Long;Dai, Gao-Le;Li, Kai
    • ETRI Journal
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    • v.36 no.1
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    • pp.116-123
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    • 2014
  • In this paper, a novel unequal broadband out-of-phase power divider (PD) is presented. Double-sided parallel-strip lines (DSPSLs) are employed to achieve an out-of-phase response. Also, an asymmetric dual-band matching structure with two external isolation resistors is utilized to obtain arbitrary unequal power division, in which the resistors are directly grounded for heat sinking. A through ground via (TGV), connecting the top and bottom sides of the DSPSLs, is used to short the isolation components. Additionally, this property can efficiently improve the broadband matching and isolation bandwidths. To investigate the proposed divider in detail, a set of design equations are derived based on the circuit theory and transmission line theory. The theoretical analysis shows that broadband responses can be obtained as proper frequency ratios are adopted. To verify the proposed concept, a sample divider with a power division of 2:1 is demonstrated. The measured results exhibit a broad bandwidth from 1.19 GHz to 2.19 GHz (59.2%) with a return loss better than 10 dB and port isolation of 18 dB.

A Study on Estimation of Fatigue Life of Aged Continuous Welded Rail using the Field Test (현장측정을 통한 노후 레일의 피로수명 평가에 관한 연구)

  • Kong, Sun-Yong;Sung, Deok-Yong;Kim, Jun-Hyung;Park, Yong-Gul
    • Proceedings of the KSR Conference
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    • 2007.11a
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    • pp.352-364
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    • 2007
  • It is essential to reduce track maintenance costs and to extend the periodic replacements of continuous welded rails based on accumulated passing tonnage. As recently train load decrease and rail joints wear down less, the periodic replacements of continuous welded rails can be extended. There are many kinds of rail damage like squat, head-check and corrugation. These can be taken nondestructive or naked eye test. So the periodic replacements of continuous welded rails based on accumulated passing tonnage were examine with focusing on a crack of rail bottom of continuous welded rail. Therefore, this study measure dynamic response of track by metro train load, it compute impact coefficient and track spring coefficient for estimating a condition of actual track system. Also, it is converted the measured stress waveform into stress frequency histogram by the rain-flow counting methods, and then the equivalence of stress is calculated. As apply s-n curve of a new welded rail, accumulated fatigue damage ratio of laid rail and remaining service lives is estimated. This study suggest a plan of the periodic replacements of continuous welded rails based on accumulated passing tonnage classified by the types of track system.

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Control of Focal Plane Compensation Device for Image Stabilization of Small Satellite Camera (소형 위성 카메라의 영상안정화를 위한 초점면부 보정장치의 제어)

  • Kang, Myoungsoo;Hwang, Jaihyuk;Bae, Jaesung
    • Journal of Aerospace System Engineering
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    • v.10 no.1
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    • pp.86-94
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    • 2016
  • In this paper, position control of focal plane compensation device using piezoelectric actuator is conducted. The forcal plane compensation device installed on earth observation satellite camera compensates micro-vibration from reaction wheels. In this study, four experimental models of the open-loop compensation device are derived using MATLAB system identification toolbox in the input range of 0~50Hz. Subsequently, the PID controller for each model is designed and the performance test of each controller is conducted through MATLAB/Simulink. According to frequency response analysis of the closed-loop compensation device system, the PID controller designed for 38~50Hz input range has enough tracking performance for the whole 0~50Hz input range. The maximum output error is about $1{\mu}m$ for the input range. The simulation results has been verified by the experimental method.

INTEGRATED SOCIETAL RISK ASSESSMENT FRAMEWORK FOR NUCLEAR POWER AND RENEWABLE ENERGY SOURCES

  • LEE, SANG HUN;KANG, HYUN GOOK
    • Nuclear Engineering and Technology
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    • v.47 no.4
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    • pp.461-471
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    • 2015
  • Recently, the estimation of the social cost of energy sources has been emphasized as various novel energy options become feasible in addition to conventional ones. In particular, the social cost of introducing measures to protect power-distribution systems from power-source instability and the cost of accident-risk response for various power sources must be investigated. To account for these risk factors, an integrated societal risk assessment framework, based on power-uncertainty analysis and accident-consequence analysis, is proposed. In this study, we applied the proposed framework to nuclear power plants, solar photovoltaic systems, and wind-turbine generators. The required capacity of gas-turbine power plants to be used as backup power facilities to compensate for fluctuations in the power output from the main power source was estimated based on the performance indicators of each power source. The average individual health risk per terawatt-hours (TWh) of electricity produced by each power source was quantitatively estimated by assessing accident frequency and the consequences of specific accident scenarios based on the probabilistic risk assessment methodology. This study is expected to provide insight into integrated societal risk analysis, and can be used to estimate the social cost of various power sources.