Contributors: M.R. Qader

Date: 2013-01-01

ORIGINAL ARTICLE - Detuning effects in Haar wavelet spectrum of pulsed-driven qubit...Driven qubit...The transient scattered radiation due to interaction of a short laser pulse (of rectangular shape) with a qubit is studied through the Haar wavelet window spectrum. Asymmetrical structure in the spectrum is shown due to frequency miss-match of the laser and qubit frequencies and the shift window parameter. ... The transient scattered radiation due to interaction of a short laser pulse (of rectangular shape) with a qubit is studied through the Haar wavelet window spectrum. Asymmetrical structure in the spectrum is shown due to frequency miss-match of the laser and qubit frequencies and the shift window parameter.

Contributors: Hung-Chun Chien, Chih-Yen Chen

Date: 2014-02-01

Circuit diagram of the proposed DVCCTA-based variable frequency dual-mode sinusoidal oscillator. ...Simulation results of the current output Io for the variable frequency dual-mode sinusoidal oscillator (Fig. 4): (a) output waveform in the steady state and (b) the corresponding frequency spectrum. ...Simulation results of the current output Io for the single-resistance-controlled dual-mode sinusoidal oscillator (Fig. 3): (a) output waveform in the steady state and (b) corresponding frequency spectrum. ...Oscillation frequency against the bias current IB of the circuit shown in Fig. 4. ...CMOS realization of single-resistance-controlled and variable frequency dual-mode sinusoidal oscillators employing a single DVCCTA with all-grounded passive components...Sinusoidal oscillator...In this paper, two new designs are proposed for sinusoidal oscillators based on a single differential voltage current conveyor transconductance amplifier (DVCCTA). Each of the proposed circuits comprises a DVCCTA combined with passive components that simultaneously provides both voltage and current outputs. The first circuit is a DVCCTA-based single-resistance-controlled oscillator (SRCO) that provides independent control of the oscillation condition and oscillation frequency by using distinct circuit parameters. The second circuit is a DVCCTA-based variable frequency oscillator (VFO) that can provide independent control of the oscillation frequency by adjusting the bias current of the DVCCTA. In this paper, the DVCCTA and relevant formulations of the proposed oscillator circuits are first introduced, followed by the non-ideal effects, sensitivity analyses, frequency stability discussions, and design considerations. After using the 0.35-μm CMOS technology of the Taiwan Semiconductor Manufacturing Company (TSMC), the HSPICE simulation results confirmed the feasibility of the proposed oscillator circuits....Simulation results of the start-up oscillations of the variable frequency dual-mode sinusoidal oscillator (Fig. 4). ...In this paper, two new designs are proposed for sinusoidal oscillators based on a single differential voltage current conveyor transconductance amplifier (DVCCTA). Each of the proposed circuits comprises a DVCCTA combined with passive components that simultaneously provides both voltage and current outputs. The first circuit is a DVCCTA-based single-resistance-controlled oscillator (SRCO) that provides independent control of the oscillation condition and oscillation frequency by using distinct circuit parameters. The second circuit is a DVCCTA-based variable frequency oscillator (VFO) that can provide independent control of the oscillation frequency by adjusting the bias current of the DVCCTA. In this paper, the DVCCTA and relevant formulations of the proposed oscillator circuits are first introduced, followed by the non-ideal effects, sensitivity analyses, frequency stability discussions, and design considerations. After using the 0.35-μm CMOS technology of the Taiwan Semiconductor Manufacturing Company (TSMC), the HSPICE simulation results confirmed the feasibility of the proposed oscillator circuits....Circuit diagram of the proposed DVCCTA-based variable frequency dual-mode sinusoidal oscillator. ...Simulation results of the voltage output Vo for the variable frequency dual-mode sinusoidal oscillator (Fig. 4): (a) output waveform in the steady state and (b) the corresponding frequency spectrum. ...Variation of the oscillation frequency against R2 for the circuit (Fig. 3). ...Simulation results of the start-up oscillations of the variable frequency dual-mode sinusoidal oscillator (Fig. 4). ...Simulation results of the highest applicable oscillations of the variable frequency dual-mode sinusoidal oscillator (Fig. 4): (a) output waveform in the steady state; and (b) the start-up of the oscillations. ... In this paper, two new designs are proposed for sinusoidal oscillators based on a single differential voltage current conveyor transconductance amplifier (DVCCTA). Each of the proposed circuits comprises a DVCCTA combined with passive components that simultaneously provides both voltage and current outputs. The first circuit is a DVCCTA-based single-resistance-controlled oscillator (SRCO) that provides independent control of the oscillation condition and oscillation frequency by using distinct circuit parameters. The second circuit is a DVCCTA-based variable frequency oscillator (VFO) that can provide independent control of the oscillation frequency by adjusting the bias current of the DVCCTA. In this paper, the DVCCTA and relevant formulations of the proposed oscillator circuits are first introduced, followed by the non-ideal effects, sensitivity analyses, frequency stability discussions, and design considerations. After using the 0.35-μm CMOS technology of the Taiwan Semiconductor Manufacturing Company (TSMC), the HSPICE simulation results confirmed the feasibility of the proposed oscillator circuits.

Contributors: Václav Tesař

Date: 2014-01-01

Geometry of the diverter valve of the discussed oscillator in its initial design. Very similar – but not identical – to the design in the preliminary model, shown in Fig. 8. ...Depend...Measured oscillation frequency with different feedback tube lengths of the oscillator shown in Fig. 7, plotted as a function of the supplied flow rate. Surprisingly, the frequency is neither proportional to the flow rate (as is usual in the constant Strouhal-number oscillators, e.g., Tesař et al., 2006) – nor constant (as in the oscillators with resonator channel (Tesař et al., 2013)). ...Photograph of internal cavities of the integrated oscillator/aerator as used in the final experiments aimed at achieving high oscillation frequency. Note the absence of the “island” components as they are discussed in association with Figs. 5 and 11. ...Fluidic oscillator...Comparison of the oscillation in Fig. 17 and the basic frequency component L in Fig. 23. The replacement of the feedback channel loops by open areas for vortical flow made the feedback paths slightly shorter (and therefore the frequency higher). ...Results of measured dependence of oscillation frequency on the supplied flow rate in the layout shown in Figs. 20 and 12. Apart from basic frequency L, the output spectrum exhibited a much higher frequency component H. ...Frequency of generated oscillation plotted as a function of the air flow rate. Similarly as in Fig. 9 this dependence does not the fit the usual (constant Strouhal number) proportionality between frequency and flow rate. ...Measured oscillation frequency with different feedback tube lengths of the oscillator shown in Fig. 7, plotted as a function of the supplied flow rate. Surprisingly, the frequency is neither proportional to the flow rate (as is usual in the constant Strouhal-number oscillators, e.g., Tesař et al., 2006) – nor constant (as in the oscillators with resonator channel (Tesař et al., 2013)). ...Comparison of the oscillation in Fig. 17 and the basic frequency component L in Fig. 23. The replacement of the feedback channel loops by open areas for vortical flow made the feedback paths slightly shorter (and therefore the frequency higher)....Basic data on the geometry of the oscillator used in the high-frequency experiments. ...Microbubble generator excited by fluidic oscillator's third harmonic frequency...Comparison of the oscillation in Fig. 17 and the basic frequency component L in Fig. 23. The replacement of the feedback channel loops by open areas for vortical flow made the feedback paths slightly shorter (and therefore the frequency higher)....Efficient generation of sub-millimetre microbubbles was recently made possible by pulsating the flow of gas supplied into a parallel-exits aerator, using a fluidic oscillator for the purpose. Without moving parts, it can generate oscillation at high frequency, an important factor due to bubble natural frequency rapidly increasing with the desirable decrease of their size. This paper discusses development of an unusual oscillator – a part of an integral oscillator/aerator unit – capable of generating a particularly high driving frequency, in the kilohertz range, in a layout that promotes a strong third harmonic frequency of the basic oscillation....Detail photograph of the feedback channel entrances with the added sharp-edged “noses”. ...Efficient generation of sub-millimetre microbubbles was recently made possible by pulsating the flow of gas supplied into a parallel-exits aerator, using a fluidic oscillator for the purpose. Without moving parts, it can generate oscillation at high frequency, an important factor due to bubble natural frequency rapidly increasing with the desirable decrease of their size. This paper discusses development of an unusual oscillator – a part of an integral oscillator/aerator unit – capable of generating a particularly high driving frequency, in the kilohertz range, in a layout that promotes a strong third harmonic frequency of the basic oscillation....Dependence of bubble natural oscillation frequency on the size – based on the measurements in Tesař (2013b). The line is fitted for constant value of oscillation Weber number We0. ... Efficient generation of sub-millimetre microbubbles was recently made possible by pulsating the flow of gas supplied into a parallel-exits aerator, using a fluidic oscillator for the purpose. Without moving parts, it can generate oscillation at high frequency, an important factor due to bubble natural frequency rapidly increasing with the desirable decrease of their size. This paper discusses development of an unusual oscillator – a part of an integral oscillator/aerator unit – capable of generating a particularly high driving frequency, in the kilohertz range, in a layout that promotes a strong third harmonic frequency of the basic oscillation.

Contributors: George F. Beard, Michael J. Griffin

Date: 2014-01-01

Roll transmissibility of the foam cushion during exposure to roll oscillation and roll-compensated lateral oscillation at 0.1, 0.2, and 0.4 m s−2 r.m.s. at frequencies from 0.25 to 1.0 Hz. Median values from 20 subjects. ...Comparison of equivalent comfort contours for lateral oscillation on rigid and cushioned seats without a backrest and the reciprocals of the asymptotic and the realisable versions of frequency weighting Wd for lateral acceleration (BS 6841, 1987). Contours for rigid seats normalised to unity at 1 Hz. ...Root-sums-of-squares of frequency-weighted measured components at the seat-body interface during lateral oscillation, roll oscillation, and fully roll-compensated lateral oscillation on a rigid seat and on a foam cushion. Components weighted using axis multiplying factors and asymptotic weightings extrapolated horizontally at frequencies less than 0.5 Hz without band-pass filtering (BS 6841, 1987). Median values from 20 subjects. ...Comparison of equivalent comfort contours for roll oscillation on rigid and cushioned seats without a backrest and the reciprocals of the asymptotic and the realisable versions of frequency weighting We for roll acceleration (BS 6841, 1987). Contours normalised to unity at 1 Hz. ...The discomfort caused by lateral oscillation, roll oscillation, and fully roll-compensated lateral oscillation has been investigated at frequencies between 0.25 and 1.0 Hz when sitting on a rigid seat and when sitting on a compliant cushion, both without a backrest. Judgements of vibration discomfort and the transmission of lateral and roll oscillation through the seat cushion were obtained with 20 subjects. Relative to the rigid seat, the cushion increased lateral acceleration and roll oscillation at the lower frequencies and also increased discomfort during lateral oscillation (at frequencies less than 0.63 Hz), roll oscillation (at frequencies less than 0.4 Hz), and fully roll-compensated lateral oscillation (at frequencies between 0.315 and 0.5 Hz). The root-sums-of-squares of the frequency-weighted lateral and roll acceleration at the seat surface predicted the greater vibration discomfort when sitting on the cushion. The frequency-dependence of the predicted discomfort may be improved by adjusting the frequency weighting for roll acceleration at frequencies between 0.25 and 1.0 Hz....The discomfort caused by lateral oscillation, roll oscillation, and fully roll-compensated lateral oscillation has been investigated at frequencies between 0.25 and 1.0 Hz when sitting on a rigid seat and when sitting on a compliant cushion, both without a backrest. Judgements of vibration discomfort and the transmission of lateral and roll oscillation through the seat cushion were obtained with 20 subjects. Relative to the rigid seat, the cushion increased lateral acceleration and roll oscillation at the lower frequencies and also increased discomfort during lateral oscillation (at frequencies less than 0.63 Hz), roll oscillation (at frequencies less than 0.4 Hz), and fully roll-compensated lateral oscillation (at frequencies between 0.315 and 0.5 Hz). The root-sums-of-squares of the frequency-weighted lateral and roll acceleration at the seat surface predicted the greater vibration discomfort when sitting on the cushion. The frequency-dependence of the predicted discomfort may be improved by adjusting the frequency weighting for roll acceleration at frequencies between 0.25 and 1.0 Hz....Lateral transmissibility of the foam cushion during exposure to lateral oscillation, roll oscillation, and fully roll-compensated lateral oscillation at 0.1, 0.2, and 0.4 m s−2 r.m.s. at frequencies from 0.25 to 1.0 Hz. Median values from 20 subjects. ...Effect of magnitude of oscillation on the roll velocity measured at the seat-body interface with the foam cushion during exposure to lateral oscillation and roll oscillation at frequencies between 0.25 and 1.0 Hz. Median values from 20 subjects. ...Lateral transmissibility of the foam cushion during exposure to lateral oscillation, roll oscillation, and fully roll-compensated lateral oscillation at 0.1, 0.2, and 0.4 m s−2 r.m.s. at frequencies from 0.25 to 1.0 Hz. Median values from 20 subjects. ...Roll transmissibility of the foam cushion during exposure to roll oscillation and roll-compensated lateral oscillation at 0.1, 0.2, and 0.4 m s−2 r.m.s. at frequencies from 0.25 to 1.0 Hz. Median values from 20 subjects. ...Root-sums-of-squares of frequency-weighted measured components at the seat-body interface during lateral oscillation, roll oscillation, and fully roll-compensated lateral oscillation on a rigid seat and on a foam cushion. Components weighted using axis multiplying factors and asymptotic weightings extrapolated horizontally at frequencies less than 0.5 Hz without band-pass filtering (BS 6841, 1987). Median values from 20 subjects. ...Discomfort of seated persons exposed to low frequency lateral and roll oscillation: Effect of seat cushion...Percentages of subjects reporting discomfort localised at the ischial tuberosities when sitting on the rigid seat and on the foam cushion during exposure to lateral oscillation, roll oscillation, and fully roll-compensated lateral oscillation across all frequencies. ... The discomfort caused by lateral oscillation, roll oscillation, and fully roll-compensated lateral oscillation has been investigated at frequencies between 0.25 and 1.0 Hz when sitting on a rigid seat and when sitting on a compliant cushion, both without a backrest. Judgements of vibration discomfort and the transmission of lateral and roll oscillation through the seat cushion were obtained with 20 subjects. Relative to the rigid seat, the cushion increased lateral acceleration and roll oscillation at the lower frequencies and also increased discomfort during lateral oscillation (at frequencies less than 0.63 Hz), roll oscillation (at frequencies less than 0.4 Hz), and fully roll-compensated lateral oscillation (at frequencies between 0.315 and 0.5 Hz). The root-sums-of-squares of the frequency-weighted lateral and roll acceleration at the seat surface predicted the greater vibration discomfort when sitting on the cushion. The frequency-dependence of the predicted discomfort may be improved by adjusting the frequency weighting for roll acceleration at frequencies between 0.25 and 1.0 Hz.

Contributors: Niko Bako, Adrijan Baric

Date: 2013-12-01

...Oscillator...Block scheme of the oscillator. ...Reference current and the oscillator frequency variations as a function of supply voltage and temperature obtained by simulations. (a) Reference current variation for typical (TT), slow (SS) and fast (FF) process corners with respect to the reference current at room temperature. (b) Frequency variation for typical, slow and fast corners with a supply voltage as a parameter with respect to frequency at room temperature. ...Miller compensated operational amplifier. ...Block scheme of the oscillator. ...Simulated open-loop AC characteristic of the amplifier. ...A low-power, temperature and supply voltage compensated current starved ring oscillator...Reference current and the oscillator frequency variations as a function of supply voltage and temperature obtained by simulations. (a) Reference current variation for typical (TT), slow (SS) and fast (FF) process corners with respect to the reference current at room temperature. (b) Frequency variation for typical, slow and fast corners with a supply voltage as a parameter with respect to frequency at room temperature. ...Si...A low-power, 3.82MHz oscillator based on a feedback loop is presented. The oscillator does not need a stable current reference to obtain a stable frequency independent of voltage and temperature variations because of the usage of negative feedback. The frequency variation, in the temperature range from −20°C to 80°C, is±0.6% and it depends only on the temperature coefficient of the resistor R, while the reference current variations are −11%/+25% in the same temperature range. The oscillator power consumption is 5.1μW and the active area is 0.09mm2. The proposed oscillator is implemented in a 0.18μm CMOS process and the simulation results are shown....The oscillator layout. ...Supply voltage compensated frequency...Simulated oscillator output. ...Temperature compensated frequency ... A low-power, 3.82MHz oscillator based on a feedback loop is presented. The oscillator does not need a stable current reference to obtain a stable frequency independent of voltage and temperature variations because of the usage of negative feedback. The frequency variation, in the temperature range from −20°C to 80°C, is±0.6% and it depends only on the temperature coefficient of the resistor R, while the reference current variations are −11%/+25% in the same temperature range. The oscillator power consumption is 5.1μW and the active area is 0.09mm2. The proposed oscillator is implemented in a 0.18μm CMOS process and the simulation results are shown.

Contributors: Z.K. Peng, Z.Q. Lang, S.A. Billings, Y. Lu

Date: 2007-11-01

The output frequency response of a nonlinear system. ...The restoring force of a bilinear oscillator. ...Resonances of G4H(j2ωF) ...Analysis of bilinear oscillators under harmonic loading using nonlinear output frequency response functions...The percentage of the whole energy that the superharmonic components contain at different frequencies for different stiffness ratios. ...Bilinear oscillator...The restoring force of a bilinear oscillator. ...Nonlinear output frequency response function...Bilinear oscillator model. ...Bilinear oscillator model. ...The output frequency response of a linear system. ...The polynomial approximation result for a bilinear oscillator ...The polynomial approximation result for a bilinear oscillator ...In this paper, the new concept of nonlinear output frequency response functions (NOFRFs) is extended to the harmonic input case, an input-independent relationship is found between the NOFRFs and the generalized frequency response functions (GFRFs). This relationship can greatly simplify the application of the NOFRFs. Then, beginning with the demonstration that a bilinear oscillator can be approximated using a polynomial-type nonlinear oscillator, the NOFRFs are used to analyse the energy transfer phenomenon of bilinear oscillators in the frequency domain. The analysis provides insight into how new frequency generation can occur using bilinear oscillators and how the sub-resonances occur for the bilinear oscillators, and reveals that it is the resonant frequencies of the NOFRFs that dominate the occurrence of this well-known nonlinear behaviour. The results are of significance for the design and fault diagnosis of mechanical systems and structures which can be described by a bilinear oscillator model. ... In this paper, the new concept of nonlinear output frequency response functions (NOFRFs) is extended to the harmonic input case, an input-independent relationship is found between the NOFRFs and the generalized frequency response functions (GFRFs). This relationship can greatly simplify the application of the NOFRFs. Then, beginning with the demonstration that a bilinear oscillator can be approximated using a polynomial-type nonlinear oscillator, the NOFRFs are used to analyse the energy transfer phenomenon of bilinear oscillators in the frequency domain. The analysis provides insight into how new frequency generation can occur using bilinear oscillators and how the sub-resonances occur for the bilinear oscillators, and reveals that it is the resonant frequencies of the NOFRFs that dominate the occurrence of this well-known nonlinear behaviour. The results are of significance for the design and fault diagnosis of mechanical systems and structures which can be described by a bilinear oscillator model.

Contributors: Yu.P. Emelianova, A.P. Kuznetsov, I.R. Sataev, L.V. Turukina

Date: 2013-02-01

Rotation numbers ν1–2 and ν2–3 versus the frequency detuning Δ1 for the system (11). Values of the parameters are λ1=1.3,λ2=1.9,λ3=1.8,Δ2=1.5 and μ=0.32. ...Schematic representation of a system of three coupled self-oscillators. ...The problem of growing complexity of the dynamics of the coupled phase oscillators as the number of oscillators in the chain increases is considered. The organization of the parameter space (parameter of the frequency detuning between the second and the first oscillators versus parameter of dissipative coupling) is discussed. The regions of complete synchronization, quasi-periodic regimes of different dimensions and chaos are identified. We discuss transformation of the domains of different dynamics as the number of oscillators grows. We use the method of charts of Lyapunov exponents and modification of the method of the chart of dynamical regimes to visualize two-frequency regimes of different type. Limits of applicability of the quasi-harmonic approximation and the features of the dynamics of the original system which are not described by the approximate phase equations are discussed for the case of three coupled oscillators....Subdivision of the chain of four oscillators by clusters for the three types of the phase locked pair of oscillators. Parameters are chosen in such a way that the system of oscillators is near the point of the saddle–node bifurcation. ...Trajectories on the phase torus. (a) resonant two-frequency regime with winding number w=1:2, (b) three-frequency regime. ...Trajectories on the phase torus. (a) resonant two-frequency regime with winding number w=1:2, (b) three-frequency regime. ...Synchronization and multi-frequency oscillations in the low-dimensional chain of the self-oscillators...(Color online). Chart of the Lyapunov’s exponents for the system of three coupled phase oscillators (5) for Δ2=1. The color palette is given and decrypted under the picture. The numbers indicate the tongues of the main resonant two-frequency regimes. These regimes are explained in the description of Fig. 5. ...(Color online). Chart of the Lyapunov’s exponents for the system of three coupled phase oscillators (5) for Δ2=1. The color palette is given and decrypted under the picture. The numbers indicate the tongues of the main resonant two-frequency regimes. These regimes are explained in the description of Fig. 5. ...Subdivision of the chain of four oscillators by clusters for the three types of the phase locked pair of oscillators. Parameters are chosen in such a way that the system of oscillators is near the point of the saddle–node bifurcation. ...(Color online). Charts of the Lyapunov’s exponents for the system of three coupled van der Pol oscillators (1). (a) λ=0.1,Δ2=0.05, (b) λ=0.2,Δ2=0.15. OD is a region of “oscillator death”. PBS is a region of partial broadband synchronization. ...Phase oscillators...Rotation numbers ν1–2 and ν2–3 versus the frequency detuning Δ1 for the system (11). Values of the parameters are λ1=1.3,λ2=1.9,λ3=1.8,Δ2=1.5 and μ=0.32. ... The problem of growing complexity of the dynamics of the coupled phase oscillators as the number of oscillators in the chain increases is considered. The organization of the parameter space (parameter of the frequency detuning between the second and the first oscillators versus parameter of dissipative coupling) is discussed. The regions of complete synchronization, quasi-periodic regimes of different dimensions and chaos are identified. We discuss transformation of the domains of different dynamics as the number of oscillators grows. We use the method of charts of Lyapunov exponents and modification of the method of the chart of dynamical regimes to visualize two-frequency regimes of different type. Limits of applicability of the quasi-harmonic approximation and the features of the dynamics of the original system which are not described by the approximate phase equations are discussed for the case of three coupled oscillators.

Contributors: Feng Liu, JiaFu Wang, Wei Wang

Date: 1999-05-31

(a) The SNR vs noise intensity D for fs=30,15, and 100 Hz, respectively. (b) The mean synaptic input Isyn(t) vs time for fs=30 Hz and D=0.15 and 6, respectively. (c) The SNR for various frequencies for the cases of D=0.5 and 5, respectively, in the case of I0i=0.8 and I1=0.11, and Jij∈[−4,20]. (d) The SNR vs signal frequency for D=0.5 and 5, respectively, for the case of I0i∈[0,1] and I1=0.072. ...The frequency sensitivity...Intrinsic oscillations...The 40 Hz oscillation...(a) The SNR vs noise intensity D for fs=30,15, and 100 Hz, respectively. (b) The mean synaptic input Isyn(t) vs time for fs=30 Hz and D=0.15 and 6, respectively. (c) The SNR for various frequencies for the cases of D=0.5 and 5, respectively, in the case of I0i=0.8 and I1=0.11, and Jij∈[−4,20]. (d) The SNR vs signal frequency for D=0.5 and 5, respectively, for the case of I0i∈[0,1] and I1=0.072. ...The phenomena of frequency sensitivity in weak signal detection and the 40 Hz oscillation in a neuronal network have been interpreted based on the intrinsic oscillations of the system. There exists a most sensitive frequency range of 20–60 Hz, over which the signal-to-noise ratio has a large value. This results from the resonance between the subthreshold intrinsic oscillation and the periodic signal. The network can exhibit the synchronous 40 Hz oscillation only with constant bias, which is due to the intrinsic features of neurons and long-range interactions between them....The frequency fi and the corresponding height H of the main peak in PSD of Isyn(t) vs (a) A for the case of I0i∈[0,3.5]; (b) M in the case of Jij∈[−5,10]. ...Frequency characteristics and intrinsic oscillations in a neuronal network...The phenomena of frequency sensitivity in weak signal detection and the 40 Hz oscillation in a neuronal network have been interpreted based on the intrinsic oscillations of the system. There exists a most sensitive frequency range of 20–60 Hz, over which the signal-to-noise ratio has a large value. This results from the resonance between the subthreshold intrinsic oscillation and the periodic signal. The network can exhibit the synchronous 40 Hz oscillation only with constant bias, which is due to the intrinsic features of neurons and long-range interactions between them....I0i∈[0,2] and Jij∈[−1,10]. (a) The spatiotemporal firing pattern is plotted by recording the firing time tni defined by Xi(tni)>0 and Xi(tni−)frequency fi and the corresponding height H of the main peak in PSD of Isyn(t) for different coupling strength. ... The phenomena of frequency sensitivity in weak signal detection and the 40 Hz oscillation in a neuronal network have been interpreted based on the intrinsic oscillations of the system. There exists a most sensitive frequency range of 20–60 Hz, over which the signal-to-noise ratio has a large value. This results from the resonance between the subthreshold intrinsic oscillation and the periodic signal. The network can exhibit the synchronous 40 Hz oscillation only with constant bias, which is due to the intrinsic features of neurons and long-range interactions between them.

Contributors: Weixiong Chen, Quanbin Zhao, Yingchun Wang, Palash Kumar Sen, Daotong Chong, Junjie Yan

Date: 2016-09-01

Schematic diagram of steam jet [1–4]. ...Submerged steam jet condensation is widely applied in various fields because of its high heat transfer efficiency. Condensation oscillation is a major character of submerged steam turbulent jet, and it significantly affects the design and safe operation of industrial equipment. This study is designed to reveal the mechanism of the low-frequency pressure oscillation of steam turbulent jet condensation and determine its affected region. First, pressure oscillation signals with low frequency are discovered in the downstream flow field through oscillation frequency spectrogram and power analysis. The oscillation frequency is even lower than the first dominant frequency. Moreover, the critical positions, where the low-frequency pressure oscillation signals appear, move downstream gradually with radial distance and water temperature. However, these signals are little affected by the steam mass flux. Then, the regions with low-frequency pressure oscillation occurring are identified experimentally. The affected width of the low-frequency pressure oscillation is similar to the turbulent jet width. Turbulent jet theory and the experiment results collectively indicate that the low-frequency pressure oscillation is generated by turbulent jet vortexes in the jet wake region. Finally, the angular coefficients of the low-frequency affected width are obtained under different water temperatures. Angular coefficients, ranging from 0.2268 to 0.2887, decrease with water temperature under test conditions....Frequency spectrograms distribution along the axial direction (R/D=2). ...Frequency spectrograms under radial position of R/D=3.0 and R/D=4.0. ...Half affected width of pressure oscillation. ...Submerged steam jet condensation is widely applied in various fields because of its high heat transfer efficiency. Condensation oscillation is a major character of submerged steam turbulent jet, and it significantly affects the design and safe operation of industrial equipment. This study is designed to reveal the mechanism of the low-frequency pressure oscillation of steam turbulent jet condensation and determine its affected region. First, pressure oscillation signals with low frequency are discovered in the downstream flow field through oscillation frequency spectrogram and power analysis. The oscillation frequency is even lower than the first dominant frequency. Moreover, the critical positions, where the low-frequency pressure oscillation signals appear, move downstream gradually with radial distance and water temperature. However, these signals are little affected by the steam mass flux. Then, the regions with low-frequency pressure oscillation occurring are identified experimentally. The affected width of the low-frequency pressure oscillation is similar to the turbulent jet width. Turbulent jet theory and the experiment results collectively indicate that the low-frequency pressure oscillation is generated by turbulent jet vortexes in the jet wake region. Finally, the angular coefficients of the low-frequency affected width are obtained under different water temperatures. Angular coefficients, ranging from 0.2268 to 0.2887, decrease with water temperature under test conditions....Frequency spectrograms under radial position of R/D=3.0 and R/D=4.0. ...Schematic diagram of experimental system [21]. ...Frequency spectrograms of condensation oscillation [21]. ...Oscillation power axial distribution for low frequency region. ...Half affected width of pressure oscillation. ...Pressure oscillation...Oscillation power axial distribution for low frequency region. ... Submerged steam jet condensation is widely applied in various fields because of its high heat transfer efficiency. Condensation oscillation is a major character of submerged steam turbulent jet, and it significantly affects the design and safe operation of industrial equipment. This study is designed to reveal the mechanism of the low-frequency pressure oscillation of steam turbulent jet condensation and determine its affected region. First, pressure oscillation signals with low frequency are discovered in the downstream flow field through oscillation frequency spectrogram and power analysis. The oscillation frequency is even lower than the first dominant frequency. Moreover, the critical positions, where the low-frequency pressure oscillation signals appear, move downstream gradually with radial distance and water temperature. However, these signals are little affected by the steam mass flux. Then, the regions with low-frequency pressure oscillation occurring are identified experimentally. The affected width of the low-frequency pressure oscillation is similar to the turbulent jet width. Turbulent jet theory and the experiment results collectively indicate that the low-frequency pressure oscillation is generated by turbulent jet vortexes in the jet wake region. Finally, the angular coefficients of the low-frequency affected width are obtained under different water temperatures. Angular coefficients, ranging from 0.2268 to 0.2887, decrease with water temperature under test conditions.

Contributors: Olivier Audouin, Jacques Bodin

Date: 2007-02-20

Extensive slug-test experiments have been performed at the Hydrogeological Experimental Site (HES) of Poitiers in France, made up of moderately fractured limestones. All data are publicly available through the “H+” database, developed within the scope of the ERO program (French Environmental Research Observatory, http://hplus.ore.fr). Slug-test responses with high-frequency (>0.12Hz) oscillations have been consistently observed in wells equipped with multiple concentric casing. These oscillations are interpreted as the result of inertia-induced fluctuations of the water level in the annular space between the inner and outer casing. In certain cases, these high-frequency oscillations overlap with lower frequency (frequency domain, in order to remove the high-frequency component by a signal-filtering method. The corrected signals have been interpreted with the model of [McElwee, C.D., Zenner, M., 1998. A nonlinear model for analysis of slug-test data. Water Resour. Res. 34 (1), 55–66.], which accounts for the inertia of the water-column above the well screen, non-linear head losses in the well, and neglects the aquifer storage (quasi-steady-state approximation). Hydraulic conductivity values interpreted from dual-frequency slug-tests compare well to those interpreted from “standard” overdamped or underdamped slug-test responses....Filter shape in the frequency domain for ρ=0.9. ...Frequency spectrum of the slug-test response in HES well M05, for an initial head displacement H0=0.2m (slug-test reference=STM5_02). ...Filtering of high-frequency oscillations: example of processing of the slug test STM5_02 (HES well M05, initial head displacement H0=0.2m). ...Curve fitting of HES slug-test responses with the model of McElwee and Zenner (1998). ...High-frequency oscillations...Opinion - Analysis of slug-tests with high-frequency oscillations...Filter shape in the frequency domain for ρ=0.9. ...Extensive slug-test experiments have been performed at the Hydrogeological Experimental Site (HES) of Poitiers in France, made up of moderately fractured limestones. All data are publicly available through the “H+” database, developed within the scope of the ERO program (French Environmental Research Observatory, http://hplus.ore.fr). Slug-test responses with high-frequency (>0.12Hz) oscillations have been consistently observed in wells equipped with multiple concentric casing. These oscillations are interpreted as the result of inertia-induced fluctuations of the water level in the annular space between the inner and outer casing. In certain cases, these high-frequency oscillations overlap with lower frequency (oscillations, which leads to complex responses that cannot be interpreted using conventional models. Slug-test data have been processed in the Fourier-frequency domain, in order to remove the high-frequency component by a signal-filtering method. The corrected signals have been interpreted with the model of [McElwee, C.D., Zenner, M., 1998. A nonlinear model for analysis of slug-test data. Water Resour. Res. 34 (1), 55–66.], which accounts for the inertia of the water-column above the well screen, non-linear head losses in the well, and neglects the aquifer storage (quasi-steady-state approximation). Hydraulic conductivity values interpreted from dual-frequency slug-tests compare well to those interpreted from “standard” overdamped or underdamped slug-test responses....Interpretation of high-frequency oscillations: inertia-induced water level fluctuations in the annular space between the inner PVC casing and the outer steel casing. ...Freq...Interpretation of high-frequency oscillations: inertia-induced water level fluctuations in the annular space between the inner PVC casing and the outer steel casing. ...High-frequency oscillations...Typical slug-test responses in HES wells. (a) “Standard” overdamped response; (b) “standard” underdamped response with low-frequency oscillations; (c) overdamped response with high-frequency oscillations; (d) underdamped response with dual-frequency oscillations. ...Typical slug-test responses in HES wells. (a) “Standard” overdamped response; (b) “standard” underdamped response with low-frequency oscillations; (c) overdamped response with high-frequency oscillations; (d) underdamped response with dual-frequency oscillations. ...Filtering of high-frequency oscillations: example of processing of the slug test STM5_02 (HES well M05, initial head displacement H0=0.2m). ... Extensive slug-test experiments have been performed at the Hydrogeological Experimental Site (HES) of Poitiers in France, made up of moderately fractured limestones. All data are publicly available through the “H+” database, developed within the scope of the ERO program (French Environmental Research Observatory, http://hplus.ore.fr). Slug-test responses with high-frequency (>0.12Hz) oscillations have been consistently observed in wells equipped with multiple concentric casing. These oscillations are interpreted as the result of inertia-induced fluctuations of the water level in the annular space between the inner and outer casing. In certain cases, these high-frequency oscillations overlap with lower frequency (<0.05Hz) oscillations, which leads to complex responses that cannot be interpreted using conventional models. Slug-test data have been processed in the Fourier-frequency domain, in order to remove the high-frequency component by a signal-filtering method. The corrected signals have been interpreted with the model of [McElwee, C.D., Zenner, M., 1998. A nonlinear model for analysis of slug-test data. Water Resour. Res. 34 (1), 55–66.], which accounts for the inertia of the water-column above the well screen, non-linear head losses in the well, and neglects the aquifer storage (quasi-steady-state approximation). Hydraulic conductivity values interpreted from dual-frequency slug-tests compare well to those interpreted from “standard” overdamped or underdamped slug-test responses.