共查询到20条相似文献,搜索用时 0 毫秒
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Mohammed F. Daqaq 《Journal of sound and vibration》2010,329(18):3621-3631
Linear energy harvesters have a narrow frequency bandwidth and hence operate efficiently only when the excitation frequency is very close to the fundamental frequency of the harvester. Consequently, small variations of the excitation frequency around the harvester's fundamental frequency drops its small energy output even further making the energy harvesting process inefficient. To extend the harvester's bandwidth, some recent solutions call for utilizing energy harvesters with stiffness-type nonlinearities. From a steady-state perspective, this hardening-type nonlinearity can extend the coupling between the excitation and the harvester to a wider range of frequencies. In this effort, we investigate the response of such harvesters, which can be modeled as a uni-modal duffing-type oscillator, to White Gaussian and Colored excitations. For White excitations, we solve the Fokker-Plank-Kolmogorov equation for the exact joint probability density function of the response. We show that the expected value of the output power is not even a function of the nonlinearity. As such, under White excitations, nonlinearities in the stiffness do not provide any enhancement over the typical linear harvesters. We also demonstrate that nonlinearities in the damping and inertia may be used to enhance the expected value of the output power. For Colored excitations, we use the Van Kampen expansion and long-time numerical integration to investigate the influence of the nonlinearity on the expected value of the output power. We demonstrate that, regardless of the bandwidth or the center frequency of the excitation, the expected value of the output power decreases with the nonlinearity. With such findings, we conclude that energy harvesters modeled as uni-modal duffing-type oscillators are not good candidates for harvesting energy under forced random excitations. Using a linear transformation, results can be extended to the base excitation case. 相似文献
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R.E. Mickens 《Journal of sound and vibration》1980,72(2):279-281
A theoretical and experimental investigation of the processes by which thin layers of gas trapped between surfaces of a structure may contribute to damping of structural vibrations is described. Effects of gas compressibility, inertia and thermal conductivity are allowed for in the theory. Particular attention is given to the variation of damping with gas pressure and layer thickness. The aim of the investigation was to provide results of use in the design of vibration absorbers for use in pressurized gas environments, as well as to contribute to a better understanding of the behaviour of pre-existing gas layers in structures. 相似文献
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M.A.V. Rangacharyulu 《Journal of sound and vibration》1983,91(1):45-56
This paper deals with the approximate analysis of non-linear non-conservative systems of two degrees of freedom subjected to transient excitations. By using a transformation of the co-ordinates, the governing differential equations of the system are brought into a form to which the method of averaging of Krylov and Bogoliubov can be applied. The response of a representative spring-mass-damper system to typical pulses like a blast pulse and a half sinusoidal pulse is determined. The validity of the approach is demonstrated by comparison of the approximate solutions with numerical results obtained on a digital computer. 相似文献
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M. Lakshmanan 《Journal of sound and vibration》1979,64(3):458-461
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研究了Duffing单边约束系统在谐和与随机噪声联合激励下的响应问题. 用谐波平衡法和摄动法分析了系统在确定性谐和激励和随机激励联合作用下的响应,用随机平均法讨论了随机扰动项对系统响应的影响. 在一定条件下,当约束距离较大时对应于不同的初始条件,系统具有两个非碰撞的稳态响应;而当约束距离不大时,对应于不同的初始条件,系统也可以有两个不同的稳态响应,其中一个是发生碰撞的响应,而另外一个则不发生碰撞. 数值模拟表明该方法是有效的.
关键词:
Duffing单边约束系统
随机响应
谐波平衡法
摄动法 相似文献
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A. A. Ignatov E. Schomburg K. F. Renk W. Schatz J. F. Palmier F. Mollot 《Annalen der Physik》1994,506(3):137-144
In this paper we report on the observation of response of a Bloch oscillator at room temperature to a THz-field of a frequency larger than the Bloch frequency. The oscillator consisted of a semiconductor superlattice structure, with an applied dc voltage giving rise to a dc electron drift current. Submitting the oscillator to a field at a frequency of 3.3 THz caused a sizeable reduction of the current; the THz-field was generated by use of intense THz-radiation pulses focused on an antenna coupled to the superlattice. We attribute the THz-field induced reduction of the current to a frequency modulation of the Bloch oscillations of electrons at the frequency of the THz-field, leading to reduction of the electron drift velocity and, consequently, of the current. 相似文献
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Using adiabatic approximation, a two arbitrary qubits Rabi model has been studied in ultra-strong coupling. The analytical expressions of the eigenvalues and the eigenvalues are obtained. They are in accordance with the numerical determined results. The dynamical behavior of the system and the evolution of entanglement have also been discussed. The collapse and revival phenomena has garnered particular attention. The influence of inconsistent coupling strength on them is studied. These results will be applied in quantum information processing. 相似文献
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F. Borsa 《Physics letters. A》1980,80(4):309-310
A simple classical model for nuclear spin-lattice relaxation due to solitons in XY one-dimensional magnetic chains in an external magnetic field is discussed. The results show that one should expect opposite behavior for the H/T dependence of T-11 for the ferromagnetic and the antiferromagnetic case. 相似文献
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N. Leprovost S. Aumaître K. Mallick 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(4):453-458
A noisy damping parameter in the equation of motion of a
nonlinear oscillator renders the fixed point of the system
unstable when the amplitude of the noise is sufficiently large.
However, the stability diagram of the system can not be predicted
from the analysis of the moments of the linearized equation.
In the case of a white noise, an exact formula for
the Lyapunov exponent of the system is derived.
We then calculate the critical
damping for which the nonlinear system becomes unstable.
We also characterize the intermittent structure of the
bifurcated state above threshold and address the effect of
temporal correlations of the noise by considering an
Ornstein-Uhlenbeck noise. 相似文献
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The static bifurcation of the parametrically excited strongly
nonlinear oscillator is studied. We consider the averaged equations
of a system subject to Duffing--van der Pol and quintic strong
nonlinearity by introducing the undetermined fundamental frequency
into the computation in the complex normal form. To discuss the
static bifurcation, the bifurcation problem is described as a
3-codimensional unfolding with $Z_{2}$ symmetry on the basis of
singularity theory. The transition set and bifurcation diagrams for
the singularity are presented, while the stability of the zero
solution is studied by using the eigenvalues in various parameter
regions. 相似文献
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J. O. White 《Applied Physics A: Materials Science & Processing》1992,55(1):82-90
The bandwidth of a BaTiO3 self-pumped phase conjugate mirror is measured in three different ways. 1) The crystal is exposed to infrared light with a phase change that is sinusoidal in time and the degree of phase modulation on the reflected wave is measured. As the modulation frequency is increased from 0.1 to 3 GHz, the modulation transfer function of the phase conjugate mirror decreases by a factor of 2. 2) The crystal is exposed to visible light from a laser operated both in a single longitudinal mode and in multiple longitudinal modes. When the laser bandwidth is increased from 20 MHz to 2 GHz the reflectivity of the phase conjugate mirror increases by up to a factor of 7. 3) A laser cavity is formed with the crystal as one end mirror and the lasing bandwidth is measured. Depending on the exact conditions, lasing bandwidths range from 2 to 240 GHz. 相似文献