### 11731 results for qubit oscillator frequency

Contributors: S. Rampp, H.J. Schmitt, M. Heers, M. Schönherr, F.C. Schmitt, R. Hopfengärtner, H. Stefan

Date: 2014-02-01

High **frequency** **oscillations**...The short acting anesthetic etomidate has been shown to provoke epileptic spikes and rarely seizures. Influence of etomidate on the occurrence of epileptic HFO (high **frequency** **oscillations**) however is unknown. An HFO inducing effect of etomidate would allow further validation of the substance as a provocation measure in presurgical evaluation as well as provide insights into the common mechanisms of HFO, spike and seizure generation. ... The short acting anesthetic etomidate has been shown to provoke epileptic spikes and rarely seizures. Influence of etomidate on the occurrence of epileptic HFO (high **frequency** **oscillations**) however is unknown. An HFO inducing effect of etomidate would allow further validation of the substance as a provocation measure in presurgical evaluation as well as provide insights into the common mechanisms of HFO, spike and seizure generation.

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Contributors: V.K. Chandrasekar, Jane H. Sheeba, R. Gladwin Pradeep, R.S. Divyasree, M. Lakshmanan

Date: 2012-06-25

Projected phase space of system (30) in the x1–x3 plane with N=10, for two different values q=3 ((a), (c)) and q=5 ((b), (d)), respectively. (a) and (b) describe the 2:1 period **oscillations** for the choice ω1=2 and ω2,ω3,…,ω10=1. (c) and (d) describe the quasiperiodic **oscillations** for the choice ω1=2 and ω2,ω3,…,ω10=1.
...(a) Time series plot of Eq. (15) for q=3 exhibiting periodic **oscillations** with the initial condition x(0)=3 and x˙(0)=0 for ω=1. (b) Phase space portrait of Eq. (15).
...Existence of amplitude independent **frequencies** of **oscillation** is an unusual property for a nonlinear **oscillator**. We find that a class of N coupled nonlinear Liénard type **oscillators** exhibit this interesting property. We show that a specific subset can be explicitly solved from which we demonstrate the existence of periodic and quasiperiodic solutions. Another set of N coupled nonlinear **oscillators**, possessing the amplitude independent nature of **frequencies**, is almost integrable in the sense that the system can be reduced to a single nonautonomous first order scalar differential equation which can be easily integrated numerically....Projected phase space of the almost integrable system (51) in the x1–x2 plane for the choices (a) ω1=1, ω2=2 exhibiting 1:2 period **oscillation**, (b) ω1=2, ω2=1 exhibiting quasiperiodic **oscillation**.
...Nonlinear **oscillators**...(Color online.) (a) Time series plot of Eq. (1) exhibiting periodic **oscillation** for three different initial conditions (three different colors) and ω=1.0. (b) Phase space portrait of Eq. (1).
... Existence of amplitude independent **frequencies** of **oscillation** is an unusual property for a nonlinear **oscillator**. We find that a class of N coupled nonlinear Liénard type **oscillators** exhibit this interesting property. We show that a specific subset can be explicitly solved from which we demonstrate the existence of periodic and quasiperiodic solutions. Another set of N coupled nonlinear **oscillators**, possessing the amplitude independent nature of **frequencies**, is almost integrable in the sense that the system can be reduced to a single nonautonomous first order scalar differential equation which can be easily integrated numerically.

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Contributors: Shuqing Zhang, Xiaorong Xie, Jingtao Wu

Date: 2008-05-01

Low-**frequency** **oscillation**...The phasor measurement units (PMU) and wide-area measurement systems (WAMS) have been widely established in modern power systems to improve the monitoring of the system behavior as well as the system control. In this paper, an integrated scheme for the monitoring and detection of low-**frequency** **oscillations** has been developed, based on our extensive experience in using Prony algorithm for **oscillation** analysis in practical WAMS projects. By analyzing the real-time synchro-phasors, the proposed scheme is competent to identify the characteristics of the low-**frequency** **oscillations** in real-time and alert the operators once the **oscillation** is under-damped or divergent. To ensure accurate monitoring of system dynamics and reliable detection of dangerous **oscillations** with noise-polluted WAMS measurements, several key signal-processing techniques are implemented, including delicate designing of prefilters, Prony analysis result correction, and comprehensive indices for stability evaluation. In the end, the developed scheme is tested with simulated signals and measurements from practical power systems. Its applications to large-scale power grids for detection and early-warning of low-**frequency** **oscillations** are also presented. The results have convincingly demonstrated the validity and practicability of the developed scheme....**Frequency** responses of the filters.
...**Oscillation** dynamics and stability evaluation.
...**Oscillation** dynamics and stability evaluation of the Central China low-**frequency** **oscillation** event.
... The phasor measurement units (PMU) and wide-area measurement systems (WAMS) have been widely established in modern power systems to improve the monitoring of the system behavior as well as the system control. In this paper, an integrated scheme for the monitoring and detection of low-**frequency** **oscillations** has been developed, based on our extensive experience in using Prony algorithm for **oscillation** analysis in practical WAMS projects. By analyzing the real-time synchro-phasors, the proposed scheme is competent to identify the characteristics of the low-**frequency** **oscillations** in real-time and alert the operators once the **oscillation** is under-damped or divergent. To ensure accurate monitoring of system dynamics and reliable detection of dangerous **oscillations** with noise-polluted WAMS measurements, several key signal-processing techniques are implemented, including delicate designing of prefilters, Prony analysis result correction, and comprehensive indices for stability evaluation. In the end, the developed scheme is tested with simulated signals and measurements from practical power systems. Its applications to large-scale power grids for detection and early-warning of low-**frequency** **oscillations** are also presented. The results have convincingly demonstrated the validity and practicability of the developed scheme.

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Contributors: Xiang Zhang, Chunhua Wang, Zhibin Ye, Yunxuan Qi, Chong Liu, Zhen Xiang, Jianhong Ge

Date: 2015-06-01

Parametric **oscillator**...We numerically analyze single-**frequency** nanosecond optical parametric **oscillators** and amplifiers. It shows that a single-**frequency** optical parametric **oscillator** requires a single-**frequency** pump wave and a seed source for injection locking. The power of the injection seed should be increased dramatically to maintain single-**frequency** output as pump energy increasing. The results numerically verify that high energy and single-**frequency** output waves can hardly be reached simultaneously by optical parametric **oscillators**. Multistage optical parametric amplifiers are helpful to meet the shortcoming of optical parametric **oscillators**. During the amplification, the pump energy should match the signal energy in optical parametric amplifiers to obtain high conversion efficiency....Diagram of the optical parametric **oscillator** modeled in this paper. The reflectivity of mirrors can be changed to meet demands of users.
... We numerically analyze single-**frequency** nanosecond optical parametric **oscillators** and amplifiers. It shows that a single-**frequency** optical parametric **oscillator** requires a single-**frequency** pump wave and a seed source for injection locking. The power of the injection seed should be increased dramatically to maintain single-**frequency** output as pump energy increasing. The results numerically verify that high energy and single-**frequency** output waves can hardly be reached simultaneously by optical parametric **oscillators**. Multistage optical parametric amplifiers are helpful to meet the shortcoming of optical parametric **oscillators**. During the amplification, the pump energy should match the signal energy in optical parametric amplifiers to obtain high conversion efficiency.

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Contributors: Ü. Lepik, H. Hein

Date: 2005-11-22

Van der Pol **oscillator** (18) for a=1,q=1,r=0,ω0=1,s=0.5,x0=0,x˙0=1.
...Ueda **oscillator**; Eq. (1) for p=0.05,q=0,r=1,s=7.5,ω0=1,x0=0,x˙0=1.
...Some types of nonlinear **oscillators**, for which the **frequency** of excitation is stochastic, are investigated. The paper consists of two parts. In the first part equations of motion are linearized. With the aid of stochastic averaging differential equations for the mean and variance of the process are obtained and integrated numerically. This approach is applicable for weakly nonlinear **oscillators**....Van der Pol **oscillator** (18) for a=0.05,q=1,r=1,ω0=0.38,s=0.16,x0=0,x˙0=-1.
... Some types of nonlinear **oscillators**, for which the **frequency** of excitation is stochastic, are investigated. The paper consists of two parts. In the first part equations of motion are linearized. With the aid of stochastic averaging differential equations for the mean and variance of the process are obtained and integrated numerically. This approach is applicable for weakly nonlinear **oscillators**.

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Contributors: K.S. Shim, S.T. Kim, J.H. Lee, E.J. Choi, J.H. Choi

Date: 2014-01-01

System **frequency** and load demand on September 15, 2011 KEPCO system rolling blackout.
...This paper discusses the rolling blackouts implemented by the Korea Electric Power Corporation (KEPCO) on September 15, 2011, and a low-**frequency** **oscillation** that occurred at that time. On the day of the rolling blackout, spectral analysis and mode analysis were performed using the data obtained from a synchrophasor installed in the KEPCO system. Low-**frequency** **oscillation** modes near 0.68Hz and 0.5Hz occurring respectively before and during the process of forced load shedding were estimated. These wide-area **oscillation** modes may cause total blackouts, and may be good indicators of reliable system operation in the event of similar wide-area rolling blackouts in the future....Power flow and **frequency** for 10min between 17:00 and 17:10.
...Power flow for 10s with a significant **oscillation**.
...Low **frequency** **oscillation** ... This paper discusses the rolling blackouts implemented by the Korea Electric Power Corporation (KEPCO) on September 15, 2011, and a low-**frequency** **oscillation** that occurred at that time. On the day of the rolling blackout, spectral analysis and mode analysis were performed using the data obtained from a synchrophasor installed in the KEPCO system. Low-**frequency** **oscillation** modes near 0.68Hz and 0.5Hz occurring respectively before and during the process of forced load shedding were estimated. These wide-area **oscillation** modes may cause total blackouts, and may be good indicators of reliable system operation in the event of similar wide-area rolling blackouts in the future.

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Contributors: H. Gül, Ebru Kavak Akpinar

Date: 2007-01-01

Heat flux, Reynolds number and **oscillating** **frequency** ranges
...Variation of Nusselt number with Reynolds number for different **oscillating** **frequencies**.
...**Oscillating** flow...Variation of exergy loss with Reynolds number at **oscillating** **frequencies** (a) f=0 Hz and (b) f=20 Hz along tube length.
...Oscillatory **frequency**...Variation of Exergy loss with Reynolds Number at different **oscillating** **frequencies**.
...Local Nusselt number versus tube length for different **oscillating** **frequencies** at (a) Re=5000, (b) Re=20,000.
...In this study, the effect on heat transfer rates, friction factor and exergy loss of **oscillating** pipe were investigated. Air was used as working fluid. To obtain **oscillating** motion of the test pipe, the experimental setup was designed. Thermocouple, the temperature control system and the other measurement systems were installed on the **oscillating** section. For both steady and **oscillating** flows, the bulk and local wall temperature distribution, pressure drop, inlet and outlet temperatures and **frequency** were measured. The parameters for this study were chosen as Reynolds number from 5000 to 20,000 at **oscillating** **frequencies** with 10 and 20 Hz. The variations of Nusselt number and exergy loss with these parameters were determined and presented graphically. In oscillatory flow, a heat transfer enhancement of up to at constant pumping power was achieved. The exergy loss was decreased with the increase of Reynolds number. The exergy loss affected slightly from the increase of **oscillating** **frequencies**. ... In this study, the effect on heat transfer rates, friction factor and exergy loss of **oscillating** pipe were investigated. Air was used as working fluid. To obtain **oscillating** motion of the test pipe, the experimental setup was designed. Thermocouple, the temperature control system and the other measurement systems were installed on the **oscillating** section. For both steady and **oscillating** flows, the bulk and local wall temperature distribution, pressure drop, inlet and outlet temperatures and **frequency** were measured. The parameters for this study were chosen as Reynolds number from 5000 to 20,000 at **oscillating** **frequencies** with 10 and 20 Hz. The variations of Nusselt number and exergy loss with these parameters were determined and presented graphically. In oscillatory flow, a heat transfer enhancement of up to at constant pumping power was achieved. The exergy loss was decreased with the increase of Reynolds number. The exergy loss affected slightly from the increase of **oscillating** **frequencies**.

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Contributors: M.J. Brennan, I. Kovacic, A. Carrella, T.P. Waters

Date: 2008-12-23

Jump-up **frequencies** of the Duffing **oscillator** as a function of the non-dimensional parameter α, which governs the degree of nonlinearity. A negative value of α denotes a softening system and a positive value of α denotes a hardening system; solid line—Eq. (12); ○, numerical integration ζ=0.02; ×, numerical integration ζ=0.05; (a) and (b) denote the **frequencies** at which a jump will occur for the threshold value of |α| for ζ=0.02 and 0.05, respectively.
...Normalised jump-up and jump-down **frequencies** and the normalised response amplitudes at these **frequencies** calculated using the harmonic balance method
...Jump-down **frequencies** of the Duffing **oscillator** as a function of the ratio of non-dimensional parameters α and ζ2, which governs the degree of nonlinearity and damping, respectively. A negative value of α/ζ2 denotes a softening system and a positive value of α/ζ2 denotes a hardening system; solid line—Eq. (9) ○, numerical integration ζ=0.02; ×, numerical integration ζ=0.05; (a) and (b) denote the **frequencies** at which a jump will occur for the threshold value of |α| for ζ=0.02 and 0.05, respectively.
...**Frequency** response curves for the Duffing **oscillator**. The dashed lines denote unstable solutions. The crosses denote the responses at the jump-up **frequencies** and the circles denote the maximum values of the response, which occur approximately at the jump-down **frequencies**. Expressions for the jump-up and jump-down **frequencies**, and the response amplitudes at these **frequencies** are given in Table 1. For all the simulations ζ=0.02; for the softening systems α=0.9αm and 1.1αm where αm=-4/3ζ2, and for the hardening system α=−5αm. Note that there is no jump-down **frequency**, when α=1.1αm.
...In this paper, simple approximate non-dimensional expressions, and the corresponding displacement amplitudes for the jump-up and jump-down **frequencies** of a softening and hardening lightly damped Duffing **oscillator** with linear viscous damping are presented. Although some of these expressions can be found in the literature, this paper presents a full set of expressions determined using the harmonic balance approach. These analytical expressions are validated for a range of parameters by comparing the predictions with calculations from direct numerical integration of the equation of motion. They are also compared with similar expressions derived using a perturbation method. It is shown that the jump-down **frequency** is dependent on the degree of nonlinearity and the damping in the system, whereas the jump-up **frequency** is dependent primarily upon the nonlinearity, and is only weakly dependent upon the damping. An expression is also given for the threshold of the excitation force and the nonlinearity that needs to be exceeded for a jump to occur. It is shown that this is only dependent upon the damping in the system....Non-dimensional maximum amplitude of the Duffing **oscillator**, which occurs approximately at the jump-down **frequency** as a function of the non-dimensional parameter α, which governs the degree of nonlinearity. A negative value of α denotes a softening system and a positive value of α denotes a hardening system; solid line—Eq. (8) with ζ=0.02; dashed line---Eq. (8) with ζ=0.05; ○, numerical integration ζ=0.02; ×, numerical integration ζ=0.05; (a) and (b) denote the threshold value of |α| for ζ=0.02 and 0.05, respectively.
... In this paper, simple approximate non-dimensional expressions, and the corresponding displacement amplitudes for the jump-up and jump-down **frequencies** of a softening and hardening lightly damped Duffing **oscillator** with linear viscous damping are presented. Although some of these expressions can be found in the literature, this paper presents a full set of expressions determined using the harmonic balance approach. These analytical expressions are validated for a range of parameters by comparing the predictions with calculations from direct numerical integration of the equation of motion. They are also compared with similar expressions derived using a perturbation method. It is shown that the jump-down **frequency** is dependent on the degree of nonlinearity and the damping in the system, whereas the jump-up **frequency** is dependent primarily upon the nonlinearity, and is only weakly dependent upon the damping. An expression is also given for the threshold of the excitation force and the nonlinearity that needs to be exceeded for a jump to occur. It is shown that this is only dependent upon the damping in the system.

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Contributors: Chin-Lung Chen, Chin-Hsiang Cheng

Date: 2009-07-01

Effects of the dimensionless **frequency** of the lid velocity on stream function at central point of cavity (X=0.5 and Y=−0.1443) for Re=100, Gr=5×105.
...This study is concerned with a periodic flow pattern with mixed convection in a triangular cavity caused by the effects of lid **oscillation** and buoyancy. The dimensionless stream function–vorticity formulation is adopted, and a curvilinear grid method for solving the stream function–vorticity equations in irregular geometries is used. Attention is in particular focused on the flow behaviour under the interaction between the **frequency** of the **oscillation** of the lid velocity and the **frequency** of the natural periodic flow. Meanwhile, numerical predictions of the thermal characteristics represented by local and average Nusselt numbers on the walls as well as the transient flow patterns are also provided. Results show that the **frequency** of **oscillation** of lid velocity and the natural periodic flow **frequency** both appear to be major **frequencies** in the **frequency** spectrum of the cavity flow, for cases with a dimensionless lid **oscillation** **frequency** less than 0.5. When the dimensionless **frequency** of the **oscillation** of the lid velocity is equal to or higher than 0.5, the flow and thermal fields are completely locked-on to the lid **oscillation**, and the natural periodic flow **frequency** is no longer visible in the spectrum....Periodic movement of minimum local Nusselt number point on the **oscillating** lid, at W=0.863, Re=100, and Gr=5×105.
...**Frequency** spectrum of the periodic flow field for various dimensionless **frequencies** of lid velocity at Re=100 and Gr=5×105. (a) Constant–velocity lid, (b)W=0.2 and (c) W=0.5.
...Periodic flow and temperature fields in one **oscillating** lid period, at Re=100 and Gr=5×105. (a) Constant–velocity lid, (b) W=0.1 (τpw=62.83) and (c) W=0.863 (τpw=7.28).
...Lid **oscillation**...Maximum and minimum stream functions and Nusselt numbers reached in a period of flow **oscillation** as functions of the dimensionless **frequency** of lid velocity, at Re=100 and Gr=5×105.
... This study is concerned with a periodic flow pattern with mixed convection in a triangular cavity caused by the effects of lid **oscillation** and buoyancy. The dimensionless stream function–vorticity formulation is adopted, and a curvilinear grid method for solving the stream function–vorticity equations in irregular geometries is used. Attention is in particular focused on the flow behaviour under the interaction between the **frequency** of the **oscillation** of the lid velocity and the **frequency** of the natural periodic flow. Meanwhile, numerical predictions of the thermal characteristics represented by local and average Nusselt numbers on the walls as well as the transient flow patterns are also provided. Results show that the **frequency** of **oscillation** of lid velocity and the natural periodic flow **frequency** both appear to be major **frequencies** in the **frequency** spectrum of the cavity flow, for cases with a dimensionless lid **oscillation** **frequency** less than 0.5. When the dimensionless **frequency** of the **oscillation** of the lid velocity is equal to or higher than 0.5, the flow and thermal fields are completely locked-on to the lid **oscillation**, and the natural periodic flow **frequency** is no longer visible in the spectrum.

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Contributors: Andrea Mazzanti, Francesco Svelto

Date: 2006-11-01

The design of quadrature local **oscillators** for CMOS wireless transceivers is still one of the most challenging issues. This paper focuses the advantages of injection locking techniques to achieve high-performance quadrature generators. A synchronizing **oscillator** sets spectral purity while locked **oscillators** set quadrature accuracy and drive the mixer LO input capacitances. Two different architectures, realized in a 0.18μm CMOS technology, are illustrated and compared. The first, using LC tank locked **oscillators** as **frequency** dividers, is tailored to UMTS and show high driving capability with low power. Simple and accurate equations for the design are reported. The second quadrature generator, employing coupled VCOs driven by an auxiliary VCO, is tailored to DCS1800 and achieves outstanding phase accuracy and phase noise. Experimental results compare favorably against previously published solutions....Quadrature local **oscillators**...Circuit schematic of injection locked **frequency** dividers (ILFDs).
...Comparison of ILQVCO performance against published quadrature **oscillators**
...Measured phase noise at double **frequency** VCO and ILFDs outputs.
...Magnitude and phase of two LC tanks with a mismatch Δω between their resonant **frequencies**.
...Block diagram of an injection locked **oscillator**.
...**Frequency** dividers ... The design of quadrature local **oscillators** for CMOS wireless transceivers is still one of the most challenging issues. This paper focuses the advantages of injection locking techniques to achieve high-performance quadrature generators. A synchronizing **oscillator** sets spectral purity while locked **oscillators** set quadrature accuracy and drive the mixer LO input capacitances. Two different architectures, realized in a 0.18μm CMOS technology, are illustrated and compared. The first, using LC tank locked **oscillators** as **frequency** dividers, is tailored to UMTS and show high driving capability with low power. Simple and accurate equations for the design are reported. The second quadrature generator, employing coupled VCOs driven by an auxiliary VCO, is tailored to DCS1800 and achieves outstanding phase accuracy and phase noise. Experimental results compare favorably against previously published solutions.

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