• Title/Summary/Keyword: oscillation criterion

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Characteristics of thermoacoustic oscillation in ducted flame burner (관형 연소기의 열 음향학적 특성에 관한 실험적 연구)

  • 조상연;이수갑
    • Journal of KSNVE
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    • v.7 no.6
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    • pp.985-991
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    • 1997
  • Combustion instability is a common phenomenon in a ducted flame burner and is known as accompanying low frequency oscillation. This is due to the interaction between unsteady heat release rate and sound pressure field, that is, thermoacoustic feedback. In Rayleigh criterion, combustion instability is triggered when the heat addition is in phase with acoustic oscillation. A Rijke type burner with a pre-mixed flame is built for investigating the effect of Reynolds number and equivalence ratio on thermoacoustic oscillation. The results suggest that the frequency of max, oscillation is dependent on Reynolds number and equivalence ratio whereas its magnitude is not a strong function of these two parameters.

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ON THE OSCILLATION OF SECOND-ORDER NONLINEAR DELAY DYNAMIC EQUATIONS ON TIME SCALES

  • Zhang, Quanxin;Sogn, Xia;Gao, Li
    • Journal of applied mathematics & informatics
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    • v.30 no.1_2
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    • pp.219-234
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    • 2012
  • By using the generalized Riccati transformation and the inequality technique, we establish some new oscillation criterion for the second-order nonlinear delay dynamic equations $$(a(t)(x^{\Delta}(t))^{\gamma})^{\Delta}+q(t)f(x({\tau}(t)))=0$$ on a time scale $\mathbb{T}$, here ${\gamma}{\geq}1$ is the ratio of two positive odd integers with $a$ and $q$ real-valued positive right-dense continuous functions defined on $\mathbb{T}$. Our results not only extend and improve some known results, but also unify the oscillation of the second-order nonlinear delay differential equation and the second-order nonlinear delay difference equation.

Evaluation on Characteristics of Unsteady Combustion and Combustion Oscillation (비정상연소의 특성과 연소진동 평가)

  • Yang, Young-Joon
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.10 no.5
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    • pp.125-130
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    • 2011
  • The characteristics of unsteady combustion were experimentally investigated using confined premixed flames stabilized by a rearward-facing step. The unsteady combustion used in this experiment plays an important role in controlling self-excited combustion oscillations and it has usually desirable performance such as high load combustion and low pollutant emission. It is known that combustion oscillation is occurred if Rayleigh's criterion is satisfied. The pressure fluctuation and OH-emission fluctuation were measured using pressure transducer and OH optical fiber respectively and then cross-corelation and phase difference were calculated to apply Rayleigh's criterion.

The Oscillation Frequency of CML-based Multipath Ring Oscillators

  • Song, Sanquan;Kim, Byungsub;Xiong, Wei
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.15 no.6
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    • pp.671-677
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    • 2015
  • A novel phase interpolator (PI) based linear model of multipath ring oscillator (MPRO) is described in this paper. By modeling each delay cell as an ideal summer followed by a single pole RC filter, the oscillation frequency is derived for a 4-stage differential MPRO. It is analytically proved that the oscillation frequency increases with the growth of the forwarding factor ${\alpha}$, which is also confirmed quantitatively through simulation. Based on the proposed model, it is shown that the power to frequency ratio keeps constant as the speed increases. Running at the same speed, a 4-stage MPRO can outperform the corresponding single-stage ring oscillator (SPRO) with 27% power saving, making MPRO with a large forwarding factor ${\alpha}$ an attractive option for lower power applications.

Characteristics of Thermoacoustic Oscillation in Ducted Flame Burner (관형 연소기의 열음향학적 특성에 관한 연구)

  • 조상연;이수갑
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.04a
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    • pp.621-626
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    • 1997
  • Combustion instability is a common phenomenon in a ducted flame burner and is known as accompanying low frequency oscillation. This is due to the interaction between unsteady heat release rate and sound pressure field, that is, thermoacoustic feedback. In Rayleigh criterion, combustion instability is triggered when the heat additions is in phase with acoustic oscillation. A Rijke type burner with a pre-mixed flame is built for investigating the effect of Reynolds number and equivalence ratio on thermoacoustic oscillation. In addition, the effect of wall temperature is presented. The results suggest that the frequency of max. oscillation is dependent on Reynolds number and equivalence ratio whereas its magnitude is not a strong function of these two parameters. On the other hand, the wall temperature distribution has much strong effects on the oscillation, even creates different mode of acoustic resonance.

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Avoiding Indefiniteness in Criteria for Maximum Likelihood Bearing Estimation with Arbitrary Array Configuration

  • Suzuki, Masakiyo
    • Proceedings of the IEEK Conference
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    • 2002.07c
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    • pp.1807-1810
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    • 2002
  • This paper presents a technique for avoid- ing indefiniteness in Maximum Likelihood (ML) criteria for Direction-of-Arrival (DOA) finding using a sensor ar- ray with arbitrary configuration. The ML criterion has singular points in the solution space where the criterion becomes indefinite. Solutions fly iterative techniques for ML bearing estimation may oscillate because of numerical instability which occurs due to the indefiniteness, when bearings more than one approach to the identical value. The oscillation makes the condition for terminating iterations complex. This paper proposes a technique for avoiding the indefiniteness in ML criteria.

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ON THE LONG-TERM VARIABILITY OF SOUTHERN OSCILLATION INDEX

  • Jin, Young-Hoon;Kawamura, Akira;Jinno, Kenji;Iseri, Yoshihiko
    • Proceedings of the Korea Water Resources Association Conference
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    • 2003.05a
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    • pp.151-158
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    • 2003
  • Recently, there has been considerable interest in the influence of El Nino/Southern Oscillation (ENSO) on a global scale. ENSO has been measured by a simple index called Southern Oscillation Index (SOI). The statistical characteristics of SOI have been also focused to reveal the influence of ENSO. The SOI trend shows that El Nino events are generally getting stronger and more frequently occurring than La Nina events. However, the variation of SOI has varied significantly in a long-term. The SOI values are computed using the mean value and its standard deviation of the base period from 1951 to 1980. In the present study, the different base periods are applied to compute the SOI values and the influence of the different base periods is investigated in detail to reveal the long-term variation of SOI From the results, we could conclude that the present SOI should be carefully considered as a criterion to judge whether the El Nino and La Nina events are occurring.

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OSCILLATORY PROPERTY OF SOLUTIONS FOR A CLASS OF SECOND ORDER NONLINEAR DIFFERENTIAL EQUATIONS WITH PERTURBATION

  • Zhang, Quanxin;Qiu, Fang;Gao, Li
    • Journal of applied mathematics & informatics
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    • v.28 no.3_4
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    • pp.883-892
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    • 2010
  • This paper is concerned with oscillation property of solutions of a class of second order nonlinear differential equations with perturbation. Four new theorems of oscillation property are established. These results develop and generalize the known results. Among these theorems, two theorems in the front develop the results by Yan J(Proc Amer Math Soc, 1986, 98: 276-282), and the last two theorems in this paper are completely new for the second order linear differential equations.

Generalized Nyquist Criterion for the Stability of Xenon Oscillation (일반화된 Nyquist 요건에 의한 제논진동의 안전성 분석)

  • Park, You-Cho;Park, Goon-Cherl;Chung, Chang-Hyun;Park, Chong-Kyun
    • Nuclear Engineering and Technology
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    • v.22 no.4
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    • pp.371-379
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    • 1990
  • The Xenon spatial oscillation may give rise to operational difficulties in a nuclear power plant. In this study, in order to investigate the Xenon instability for a PWR, the frequency-domain technique is adopted by using Generalized Nyquist Criterion, which is more general and suitable for the multi-input/multi-output system. Also linearized modal fluxes are obtained by a modal expansion. This model has been implemented to test the axial Xenon stability of YGN-1 unit against the changes in plant operating parameters ; power level, control rod position, and core average burnup. The results show that the increase of power level and the deeper insertion of control rod have the destabilizing effect, and that the burnup progress makes the core less stable. Also the results show that the overestimation due to modal interaction was found not to be significant.

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