Prediction of Time-Varying Vibroacoustic Energy Using a New Energy Approach

2004 ◽  
Vol 126 (2) ◽  
pp. 184-189 ◽  
Author(s):  
F. Sui ◽  
M. N. Ichchou
Keyword(s):  
High Frequency ◽  
Energy Equation ◽  
Transport Theory ◽  
Energy Balance Equation ◽  
Time Varying ◽  
Conductivity Equation ◽  
Dispersive Effect ◽  
Energetic Approach ◽  
Unit Impulse ◽  
New Energy

A new energetic approach is proposed to predict the time-varying dynamic response in the vibroacoustic field. This approach is based on the derivation and development of a hyperbolic type energy equation. It can be derived from the transport theory, or obtained by applying fundamental energy balance equation. The focus of this paper is to compare this new energy equation with the time-varying vibrational conductivity equation used extensively in recent study of energy approaches in mid-high frequency domain. The new energy equation is evaluated numerically by comparing its solutions with the diffusion equation and exact energy results. The comparative studies are applied to a beam subjected to a transverse unit impulse, and the dispersive effect is considered.

Skin friction and surface temperature of an insulated flat plate fixed in a fluctuating stream

1971 ◽  
Vol 46 (1) ◽  
pp. 165-175 ◽  
Author(s):  
Hiroshi Ishigaki
Keyword(s):  
Boundary Layer ◽  
Surface Temperature ◽  
Flat Plate ◽  
Skin Friction ◽  
High Frequency ◽  
Energy Equation ◽  
Oscillation Amplitude ◽  
Flow Oscillation ◽  
Velocity Amplitude ◽  
The Mean

The time-mean skin friction of the laminar boundary layer on a flat plate which is fixed at zero incidence in a fluctuating stream is investigated analytically. Flow oscillation amplitude outside the boundary layer is assumed constant along the surface. First, the small velocity-amplitude case is treated, and approximate formulae are obtained in the extreme cases when the frequency is low and high. Next, the finite velocity-amplitude case is treated under the condition of high frequency, and it is found that the formula obtained for the small-amplitude and high-frequency case is also valid. These results show that the increase of the mean skin friction reduces with frequency and is ultimately inversely proportional to the square of frequency.The corresponding energy equation is also studied simultaneously under the condition of zero heat transfer between the fluid and the surface. It is confirmed that the time-mean surface temperature increases with frequency and tends to be proportional to the square root of frequency. Moreover, it is shown that the timemean recovery factor can be several times as large as that without flow oscillation.

scholarly journals Time-Varying Impedance Control of Port Hamiltonian System with a New Energy-Storing Tank

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Min Zheng ◽  
Tangqing Yuan ◽  
Tao Huang
Keyword(s):  
Control Method ◽  
Impedance Control ◽  
Conservative System ◽  
Time Varying ◽  
Control Performance ◽  
Singularity Problem ◽  
Numerical Examples ◽  
New Energy ◽  
Simulation Results ◽  
New Framework

In order to guarantee the passivity of a kind of conservative system, the port Hamiltonian framework combined with a new energy tank is proposed in this paper. A time-varying impedance controller is designed based on this new framework. The time-varying impedance control method is an extension of conventional impedance control and overcomes the singularity problem that existed in the traditional form of energy tank. The validity of the controller designed in this paper is shown by numerical examples. The simulation results show that the proposed controller can not only eliminate the singularity problem but can also improve the control performance.

scholarly journals Frequency variations of gravity waves interacting with a time-varying tide

2013 ◽  
Vol 31 (10) ◽  
pp. 1731-1743 ◽  
Author(s):  
C. M. Huang ◽  
S. D. Zhang ◽  
F. Yi ◽  
K. M. Huang ◽  
Y. H. Zhang ◽  
...  
Keyword(s):  
Gravity Waves ◽  
High Frequency ◽  
Lower Atmosphere ◽  
Horizontal Wind ◽  
Frequency Variation ◽  
Time Varying ◽  
Transient Nature ◽  
Critical Layers ◽  
Favorable Conditions ◽  
Frequency Variations

Abstract. Using a nonlinear, 2-D time-dependent numerical model, we simulate the propagation of gravity waves (GWs) in a time-varying tide. Our simulations show that when a GW packet propagates in a time-varying tidal-wind environment, not only its intrinsic frequency but also its ground-based frequency would change significantly. The tidal horizontal-wind acceleration dominates the GW frequency variation. Positive (negative) accelerations induce frequency increases (decreases) with time. More interestingly, tidal-wind acceleration near the critical layers always causes the GW frequency to increase, which may partially explain the observations that high-frequency GW components are more dominant in the middle and upper atmosphere than in the lower atmosphere. The combination of the increased ground-based frequency of propagating GWs in a time-varying tidal-wind field and the transient nature of the critical layer induced by a time-varying tidal zonal wind creates favorable conditions for GWs to penetrate their originally expected critical layers. Consequently, GWs have an impact on the background atmosphere at much higher altitudes than expected, which indicates that the dynamical effects of tidal–GW interactions are more complicated than usually taken into account by GW parameterizations in global models.

scholarly journals Estimating dynamic copula dependence using intraday data

2015 ◽  
Vol 19 (4) ◽  
Author(s):  
Lidan Grossmass ◽  
Ser-Huang Poon
Keyword(s):  
Stock Returns ◽  
Long Memory ◽  
High Frequency ◽  
Time Varying ◽  
Credit Crisis ◽  
Dynamic Copula ◽  
Tick Data ◽  
Out Of Sample ◽  
Intraday Data ◽  
Better Than

AbstractWe estimate the dynamic daily dependence between assets by applying the Semiparametric Copula-Based Multivariate Dynamic (SCOMDY) model on intraday data. Using tick data of three stock returns of the period before and during the credit crisis, we find that our dependence estimator better captures the steep increase in dependence during the onset of the crisis as compared to other commonly used time-varying copula methods. Like other high-frequency estimators, we find that the dependence estimator exhibits long memory and forecast it using a HAR model. We show that for out-of-sample forecasts, our dependence estimator performs better than the constant estimator and other commonly used time-varying copula dependence estimators.

INTERPRETATION OF THE TRANSIENT BEHAVIOR OF THE REFLECTION SEISMOGRAPH

Geophysics ◽  
1942 ◽  
Vol 7 (2) ◽  
pp. 123-132 ◽  
Author(s):  
R. G. Piety
Keyword(s):  
High Frequency ◽  
Arrival Time ◽  
Graphical Method ◽  
Transient Behavior ◽  
Unit Impulse ◽  
Impulsive Response ◽  
Actual Response ◽  
Method Of Design

This paper discusses a method of design for the reflection seismograph based on the galvanometer response when the geophone is subject to a unit impulse. A graphical method of obtaining the actual response to an arbitrary geophone motion in terms of the impulsive response is given. A family of desirable types of impulsive response is obtained by analyzing the implications of this graphical computation when strong low and high frequency interference is present. The application of this method of computation to the evaluation of corrections in the apparent arrival time of reflections obtained with different instruments is outlined.

The propagation of a transverse electromagnetic wave in a nonlinear, anisotropic, time-dependent plasma medium

1968 ◽  
Vol 46 (7) ◽  
pp. 889-905
Author(s):  
Robert J. Papa
Keyword(s):  
Energy Balance ◽  
Plane Wave ◽  
Electron Temperature ◽  
Electron Density ◽  
Balance Equation ◽  
Energy Balance Equation ◽  
Time Dependent ◽  
Time Varying ◽  
Circularly Polarized ◽  
Elliptically Polarized

In a previous paper, a one-dimensional, inhomogeneous model was considered in describing the nonlinear interaction of a radiofrequency plane wave with a time-varying plasma. This paper extends the analysis to the anisotropic case, in which an elliptically polarized plane wave incident upon an electron-density profile induces changes in the electron density and electron temperature. A d-c. magnetic field parallel to the electron-density gradients causes the elliptically polarized wave to split into two distinct modes, a right-hand circularly polarized and a left-hand circularly polarized mode. The two modes are coupled through an energy-balance equation that governs the behavior of the electron temperature. The time-dependent response of the plasma may be found by numerically integrating an energy-balance equation and a continuity equation. The solution to the wave equation for the time-varying, inhomogeneous, anisotropic medium may be obtained through the use of the WKB approximation. The time scales for electron-temperature and electron-density changes are found to vary with incident flux, incident-wave ellipticity, and appropriate normalized plasma parameters.

Interference Characteristics Analysis of Power Electronics Devices Used in New Energy Vehicles

2013 ◽  
Vol 772 ◽  
pp. 556-559
Author(s):  
Yan Jie Guo ◽  
Li Fang Wang ◽  
Cheng Lin Liao
Keyword(s):  
Power Electronics ◽  
High Frequency ◽  
Circuit Model ◽  
Bipolar Transistor ◽  
Current Transfer ◽  
Common Mode ◽  
Insulated Gate Bipolar Transistor ◽  
New Energy ◽  
Characteristics Analysis ◽  
New Energy Vehicles

In this paper, the insulated gate bipolar transistor (IGBT) is taken as an example to discuss the interference characteristics of the power electronics devices used in new energy vehicles. Firstly, the on-off processes of the IGBT are analyzed and reconstructed. Then, the high frequency circuit model of IGBT is established, considering both the on-off processes and the effects of the stray parameters. Furthermore, the effects of IGBT on equipment around are investigated based on the calculations of interference voltage transfer gains and common mode (CM) current transfer admittance. Finally, the model and analyses are verified by both the simulations and the experiments.

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