• Title, Summary, Keyword: phase-lag

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Micropolar thermoelastic medium with voids under the effect of rotation concerned with 3PHL model

  • Othman, Mohamed I.A.;Alharbi, Amnah M.;Al-Autabi, Al-Anoud M. Kh.
    • Geomechanics and Engineering
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    • v.21 no.5
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    • pp.447-459
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    • 2020
  • This paper aims to investigate the effect of rotation on a micropolar thermoelastic medium with voids problem. The problem is assessed according to three-phase-lag model. The normal mode analysis used to obtain the analytical expressions of the considered variables. The non-dimensional displacement, temperature, Micro rotation, the change in the volume fraction field, and stress of the material are obtained and illustrated graphically. Comparisons are made with the results predicted by two theories; namely three- phase-lag model (3PHL) and Green-Naghdi theory of type III (G-N III). The considered variables were plotted for different values of the rotation parameter, the phase-lag of heat flux and the phase-lag of temperature. The numerical results reveal that the rotation and the phase-lag times significantly influence the distribution of the field quantities. Some particular cases of interest are deduced from the present investigation.

Stability Criterion of Repetitive Control System Using Phase-Lead and Lag Compensator (진상,지상 보상기를 고려한 반복제어계의 안정성 판별)

  • 서진호;강병철;김상봉
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.41-45
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    • 1997
  • To design a control system, it is a elementary point that the stability of the system should be guaranteed. Also, the phase of the system plays an important role for its frequence performance. In this paper, we present two stability criterion of repetitive control system with phase-lead and lag compensator. First, the stability criterion for the servo control system with phase-lead and lag compensator is shown by using small-gain theorem. Second, for the repetitive control system with the compensator, the stability criterion, also, is determined by using small-gain theorem. Two stability criterions show the same results that the stability depends on a coefficient of the phase-lead and lag compensator under some condition in servo control system and repetitive control system.

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Time Lag Analysis Using Phase of Flame Transfer Function (화염전달함수의 위상차를 이용한 시간지연 분석)

  • Pyo, Yeongmin;Kim, Jihwan;Kim, Daesik
    • Journal of ILASS-Korea
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    • v.21 no.2
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    • pp.104-110
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    • 2016
  • Main purpose of the current paper is to show results of time lag analysis using phase information of flame transfer function in order to predict combustion instabilities in a gas turbine combustor. The flame transfer function (FTF) is modeled using a commercial Computational Fluid Dynamics (CFD) code (Fluent). Comparisons of the modeled flame shapes with the measured ones were made using the optimized heat transfer conditions and combustion models. The FTF modeling results show a quite good agreement with the measurement data in predicting the phase delay (i.e. time lag). Time lag analysis results using the phase of FTF shows better combustion instability prediction accuracy than using time lag calculated from the steady state flame length.

Effect of gravity on a micropolar thermoelastic medium with voids under three-phase-lag model

  • Alharbi, Amnah M.;Othman, Mohamed I.A.;Al-Autabi, Al-Anoud M.Kh.
    • Structural Engineering and Mechanics
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    • v.76 no.5
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    • pp.579-590
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    • 2020
  • This paper's objective is to investigate the effect of gravity on a micropolar thermoelastic medium with voids. The problem is assessed according to the three-phase-lag model. An analysis of the resulting non-dimensional displacement, temperature variation, and internal stress of the study material is carried out and presented graphically. The non-dimensional displacement, temperature, micro-rotation, the change in the volume fraction field and stress of the material are obtained and illustrated graphically. Comparisons are made with the results predicted by different theories for different values of gravity, the phase-lag of the heat flux and the phase-lag of the temperature gradient. The numerical results reveal that gravity and relaxation times have a significant influence on the distribution of the field quantities. Some notable insights of interest are deduced from the investigation.

Overview of Tidal Phase-lag References Used in Korea (우리나라 조석지각 기준 표기에 대한 고찰)

  • Byun, Do-Seong
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.12 no.3
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    • pp.234-238
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    • 2007
  • Three different tidal phase-lag references have been used by the tidal research community of Korea: Greek kappa (k), Local standard time zone ($135^{\circ}E$) phase-lag (g) and Greenwich phase-lag (G). This ununified tidal information system may induce confusion in understanding tidal characteristics and their variability and impede the development of tidal knowledge in Korea. In this study we closely explore the three phase-lag reference definition with respect to their mutual conversion. We also identify an incorrect phase-lag reference definition used in previous works and discuss what has led to this misunderstanding.

A study on the compensator design of the quasi-resonant SMPS (유사공진형 SMPS의 보상기 설계에 관한 연구)

  • Lim, I.S.;Huh, U.Y.
    • Proceedings of the KIEE Conference
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    • pp.720-725
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    • 1991
  • In this thesis, the lead-lag compensator is designed to improve output characteristics of flyback zero voltage switching quasi-resonant converters. The switch and the diode are assumed ideally. And the SMPS is modelled by state equations with four operation modes. And the model for controller design is also achived by using a state space averaging method, which is continuous time average of state variables every period. The lag, the lead and the lead-lag compensator is designed the SMPS respectively. The time domain analysis and the frequency domain analysis are done for each compensated circuit. It is possible increasing the phase margin and improving the transient response by the compensators. The phase lag compensator has small overshoot comparatively. But the bandwidth is narrower than the others, so it has longest settling time. For the phase lead compensator, the response come to steady-state within short period. But the overshoot is the largest due to its large peak gain. Finally, the phase lead-lag compensator has medium characteristics in the overshoot and the settling time.

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Method for improving calculation of nonharmonic constants of tidal stations in Korea (한국연안의 비조화상수 개선에 관한 연구)

  • Kim, Yeong-Taek;Yu, Hak-Ryeol;Lee, Eun-Il
    • 한국지구과학회:학술대회논문집
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    • pp.59-62
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    • 2010
  • The limitation of constant for tide correction is identified using the T_tide $MATLAB^{(R)}$ package. A suggestion is presented in calculation of local phase lag(k) by a/15 (a is angular speed of any constituent in degree) from the g, phase lag measured by standard time meridian latitude.

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Disturbance due to internal heat source in thermoelastic solid using dual phase lag model

  • Ailawalia, Praveen;Singla, Amit
    • Structural Engineering and Mechanics
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    • v.56 no.3
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    • pp.341-354
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    • 2015
  • The dual-phase lag heat transfer model is employed to study the problem of isotropic generalized thermoelastic medium with internal heat source. The normal mode analysis is used to obtain the exact expressions for displacement components, force stress and temperature distribution. The variations of the considered variables through the horizontal distance are illustrated graphically. The results are discussed and depicted graphically.

Roll/yaw controller design using double gimbaled momentum wheel (더블김벌 모멘텀휠을 이용한 롤/요 제어기 설계)

  • 박영웅;방효충
    • 제어로봇시스템학회:학술대회논문집
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    • pp.1099-1102
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    • 1996
  • In this paper, roll/yaw attitude control of spacecraft using a double gimbaled wheel is discussed with two feedback controllers designed. One is a PD controller with no phase difference between roll and yaw control input. The other is a PD controller with a phase lag compensator about the yaw control input. The phase lag compensator is designed as a first order system and a lag parameter is designed for the yaw angle control. There are two case simulations for each controller ; constant disturbance torques and initial errors of nutation at motion. We obtain the results through simulations that steady-state error and rising time of yaw angle are determined by the compensator. Simulation parameters used in this study are the values of KOREASAT F1.

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Development of AC Thermal Anemometry (교류방식 유속 측정법 개발)

  • Jung, Won-Seok;Kwon, Oh-Myoung;Choi, Du-Seon;Park, Seung-Ho;Choi, Young-Ki;Lee, Joon-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.2
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    • pp.230-237
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    • 2004
  • This paper suggests and demonstrates a novel flow measurement technique: tunable AC thermal anemometry that allows simple integration, robust measurement, and extremely high accuracy. The principle and simple theoretical analysis of the technique are presented. To find the optimal condition at which the phase lag becomes most sensitive to flow speed change, the phase lag was measured scanning the heating frequency from 1 to 100 Hz, while the flow speed of ethanol was increased stepwise from 0 to 40 mm/s. The sensitivity of phase lag depended on the heating frequency and the flow speed. It was possible to measure the flow speed of 0.7 mm/s with the resolution of 0.1 mm/s at 4 Hz.