• 제목/요약/키워드: Oscillation criterion

검색결과 35건 처리시간 0.019초

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

  • 조상연;이수갑
    • 소음진동
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    • 제7권6호
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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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    • 제30권1_2호
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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.

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

  • 양영준
    • 한국기계가공학회지
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    • 제10권5호
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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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    • 제15권6호
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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.

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

  • 조상연;이수갑
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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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
    • 대한전자공학회:학술대회논문집
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    • 대한전자공학회 2002년도 ITC-CSCC -3
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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
    • 한국수자원학회:학술대회논문집
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    • 한국수자원학회 2003년도 학술발표회논문집(1)
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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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    • 제28권3_4호
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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.

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

  • Park, You-Cho;Park, Goon-Cherl;Chung, Chang-Hyun;Park, Chong-Kyun
    • Nuclear Engineering and Technology
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    • 제22권4호
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    • pp.371-379
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    • 1990
  • 제논의 공간적인 진동은 원자로의 운전에 지장을 초래할 수 있다. 본 연구에서는 가압경수로에서의 제논에 의한 불안정성을 분석하기 위하여, 보다 일반적이고 다중입력/다중출력 계통에 적합한 일반화된 Nyquist조건을 사용하는 진동수위주의 기술을 적용하였다. 또한 모드전개 방법에 의하여 선형화된 중성자속을 구했다. 이 모형으로 출력 준위, 제어봉 위치, 그리고 평균 노심 연소도둥의 노물리 변수의 변화에 따른 영광 1호기의 제논에 대한 축방향 안정성을 조사하였다. 결과로는, 출력 준위의 증가나 제어봉 삽입의 증가는 안정성을 저해하는 효과를 가져오고, 연소도가 증가할 수록 불안정한 것으로 나타났다.

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