共查询到19条相似文献,搜索用时 62 毫秒
1.
Electron temperature fluctuation in the HT-7 Tokamak plasma observed by electron cyclotron emission imaging
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The fluctuation of the electron temperature has been measured by
using the electron cyclotron emission imaging in the Hefei Tokamak-7
(HT-7) plasma. The electron temperature fluctuation with a broadband
spectrum shows that it propagates in the electron diamagnetic drift
direction, and the mean poloidal wave-number $\bar{k}_{\theta}$is
calculated to be about 1.58 cm-1, or
\bar{k}θ ρs≈ 0.34. It indicates that the
fluctuation should come from the electron drift wave turbulence. The
linear global scaling of the electron temperature fluctuation with
the gradient of electron temperature is consistent with the mixing
length scale qualitatively. Evolution of spectrum of the fluctuation
during the sawtooth oscillation phases is investigated, and the
fluctuation is found to increase with the gradient of electron
temperature increasing during most phases of the sawtooth
oscillation. The results indicate that the electron temperature
gradient is probably the driver of the fluctuation enhancement. The
steady heat flux driven by electron temperature fluctuation is
estimated and compared with the results from power balance
estimation. 相似文献
2.
The existing theory of decoy-state quantum cryptography assumes that the dark count rate is a constant, but in practice there exists fluctuation. We develop a new scheme of the decoy state, achieve a more practical key generation rate in the presence of fluctuation of the dark count rate, and compare the result with the result of the decoy-state without fluctuation. It is found that the key generation rate and maximal secure distance will be decreased under the influence of the fluctuation of the dark count rate. 相似文献
3.
The statistical fluctuation of a single-mode laser system driven by coloured pump noise with signal modulation and the quantum noise with cross-correlation between its real and imaginary parts
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Using the linear approximation method, this paper studies the statistical property
of a single-mode laser driven by both coloured pump noise with signal modulation and
the quantum noise with cross-correlation between its real and imaginary parts, and
calculates the steady-state mean normalized intensity fluctuation and intensity
correlation time. It analyses the influences of the modulation signal, the net gain
coefficient, the noise and its correlation form on the statistical fluctuation of
the laser system respectively. It is found that the coloured pump noise modulated by
the signal has a great suppressing action on the statistical fluctuation of the
laser system; the pump noise self-correlation time and the specific frequency of
modulation signal have the result that the statistical fluctuation tends to zero.
Furthermore, the `colour' correlation of pump noise has much influences on the
statistical fluctuation of the laser system. Increasing the intensity of pump noise
will augment the statistical fluctuation of the laser system, but the intensity of
quantum noise and the coefficient of cross-correlation between its real and
imaginary parts have less influence on the statistical fluctuation of the laser
system. Therefore, from the conclusions of this paper the statistical property can
be known and a theoretical basis for steady operation and output of the laser system
can be provided. 相似文献
4.
Propagation of Ion-Acoustic Wave in an Inhomogeneous Dusty Plasma with. Dust Charge Fluctuation
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The propagation of dust ion-acoustic wave in an inhomogeneous dusty plasma is studied by taking the dust charge fluctuation and collisions into account. It is shown that the dust charge fluctuation brings a phase shift to the wave. Furthermore, because of the presence of dust charge fluctuation, a new damping term rises, which makes the damping more sharply. 相似文献
5.
Scattering behaviours to the two-dimensional electron gasinduced by the Al composition fluctuation in AlxGa1-xNbarrier in AlxGa1-xN/GaN heterostructures
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<正>This paper reports that cathodoluminescence(CL) measurements have been done to study the alloy fluctuation of the Al0.3Ga0.7N layer in Al0.3Ga0.7N/GaN heterostructures.The CL images and linescanning results demonstrate the existence of compositional fluctuation of Al in the Al0.3Ga0.7N barrier.A model using aδ-shape perturbation Hamilton function has been proposed to simulate the scattering probability of the two dimensional electron gases (2DEG) induced by Al composition fluctuation.Two factors,including conduction band fluctuation and polarization electric field variation,induced by the Al composition fluctuation have been taken into account.The scattering relaxation time induced by both factors has been estimated to be 0.31 ns and 0.0078 ns,respectively,indicating that the variation of the piezoelectric field is dominant in the scattering of the 2DEG induced by Al fluctuation. 相似文献
6.
SABen-Hao CAIXu TAIAn ZHOUDai-Mei 《理论物理通讯》2004,42(3):403-406
We present the simulation results of the net charge fluctuation in Au Au collisions at √Snn=130 GeV from a dynamic model, JPCIAE, and its revisions. The simulations are done for the quark-gluon matter, the directly produced pions, the pion matter, and the hadron matter. The simulated net charge fluctuation of the quark-gluon matter is close to the thermal model prediction for the quark-gluon gas. However, the discrepancy exists comparing the simulated net charge fluctuation for directly produced pions and the pion matter with the thermal model prediction for pion gas and the resonance pion gas, respectively. The net charge fluctuation of hadron matter from default JPCIAE simulations is nearly 3.5 times larger than quark-gluon matter. A discussion is given for the net charge fluctuation as an evidence of QGP phase transition. 相似文献
7.
The population growth of small harmful rats in grassland subjected to environment fluctuation has been modelled in a logistic equation. Two correlated random variables responsible to the fluctuation of the genetic factor and the suppression factor are used. A two-peak structure of the steady probability distribution of rate population is observed in the large fluctuation regime of the genetic factor. With the increase of correlation constant A, the steady probability distribution can change from two peaks to a single peak. The suppression factor μ and its fluctuation also affect the steady probability distribution and can push it toward a small population. 相似文献
8.
The expressions of electron density fluctuation produced by dust particles in a dusty plasma are derived.It is shown that the fluctuation comes from three different sources.The first source is the thermal motion of the dust particles,which is of a fluctuation power spectrum proportional to ndZ^2.The second source is the charge change of the dust particles,which is of a power spectrum proportional to nd^2Z%3.The third source is the eigenmode oscillation of the dust particles,which is of fluctuation power spectrum proportional to √nd.The powerful electron density fluctuation exists in a dusty plasma due to the fact that the dust particles ar highly charged.The results may explain the strong electromagnetic scattering by a space dust layer in the Earth‘s mesosphere. 相似文献
9.
The robustness of the quantum spin Hall effect to the thickness fluctuation in HgTe quantum wells
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The quantum spin Hall effect(QSHE) was first realized in HgTe quantum wells(QWs),which remain the only known two-dimensional topological insulator so far.In this paper,we have systematically studied the effect of the thickness fluctuation of HgTe QWs on the QSHE.We start with the case of constant mass with random distributions,and reveal that the disordered system can be well described by a virtual uniform QW with an effective mass when the number of components is small.When the number is infinite and corresponds to the real fluctuation,we find that the QSHE is not only robust,but also can be generated by relatively strong fluctuation.Our results imply that the thickness fluctuation does not cause backscattering,and the QSHE is robust to it. 相似文献
10.
A concise expression of the scintillation index is proposed for a
plane optical wave and a spherical optical wave both propagating in
a turbulent atmosphere with a zero inner scale and a finite inner
scale under an arbitrary fluctuation condition. The expression is
based on both the results in the Rytov approximation under a weak
fluctuation condition and the numerical results in a strong
fluctuation regime. The maximum value of the scintillation index and
its corresponding Rytov index are evaluated. These quantities are
affected by the ratio of the turbulence inner scale to the Fresnel
size. 相似文献
11.
L.H. Liu H.P. TanB.X. Li 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,73(6):641-648
An iteration method is extended to analyze the influences of the turbulent fluctuation on the reconstruction of Reynolds time-averaged temperature in turbulent axisymmetric free flames when the temperature profiles are retrieved by the low time-resolution data of outgoing emission and transmission radiation intensities. A simplified probability density function is used to simulate the turbulent fluctuation of temperature and absorption coefficient. The effects of turbulent fluctuating intensities on the estimation of the Reynolds time-averaged temperature and absorption coefficient are examined. The results show that the effects of turbulent fluctuation on the reconstruction of time-averaged absorption coefficient are not significant. In the case of weak turbulent fluctuation, the influences of turbulent fluctuation on the estimation of time-averaged temperature profiles are small. But in the case of strong turbulent fluctuation, the influences of turbulent fluctuation on the estimation of time-averaged temperature profiles are significant. 相似文献
12.
The fluctuation and relative fluctuation of entanglement entropy of a bipartite system for Dirac fields in noninertial frames are investigated. It is shown that the fluctuation and relative fluctuation of entanglement entropy are observer-dependent, which depend on their observed frames. It is found that both the fluctuation and relative fluctuation of entanglement entropy become more noticeable with the increasing of the subsystem's acceleration. We also find that the entanglement entropy always has fluctuation regardless of the initial state parameter and for any magnitude of the acceleration. We argue that the statistical mean for the measurement of entanglement entropy relates to the accelerated motion of the observer. 相似文献
13.
根据涨落的热力学理论,详细分析和计算光纤中热力学本征涨落相位噪声的方均值。讨论它对光纤干涉仪的影响,把热力学本征涨落噪声和热力学本征驻波噪声进行比较 相似文献
14.
The fluctuation and relative fluctuation of entanglement entropy of a bipartite system for Dirac fields in noninertial frames are investigated. It is shown that the fluctuation and relative fluctuation of entanglement entropy are observer-dependent, which depend on their observed frames. It is found that both the fluctuation and relative fluctuation of entanglement entropy become more noticeable with the increasing of the subsystem's acceleration. We also find that the entanglement entropy always has fluctuation regardless of the initial state parameter and for any magnitude of the acceleration. We argue that the statistical mean for the measurement of entanglement entropy relates to the accelerated motion of the observer. 相似文献
15.
On the basis of calculating the steady-state mean normalized intensity fluctuation of a signal-mode laser system driven by both colored pump noise with signal modulation and the quantum noise with cross-correlation between its real and imaginary parts, we analyze the influence of modulation signal, noise, and its correlation form on the statistical fluctuation of the laser system. We have found that when the amplitude of modulation signal weakens and its frequency quickens, the statistical fluctuation will reduce rapidly. The statistical fluctuation of the laser system can be restrained by reducing the intensity of pump noise and quantum noise. Moreover, with prolonging of colored cross-correlation time, the statistical fluctuation of laser system experiences a repeated changing process, that is, from decreasing to augmenting,then to decreasing, and finally to augmenting again. With the decreasing of the value of cross-correlation coefficient, the statistical fluctuation will decrease too. When the cross-correlation form between the real part and imaginary part of quantum noise is zero correlation, the statistical fluctuation of laser system has a minimum. Compared with the influence of intensity of pump noise, the influence of intensity of quantum noise on the statistical fluctuation is smaller. 相似文献
16.
XU Da-Hai CHENG Qing-Hua CAO Li WU Da-Jin 《理论物理通讯》2006,46(5):881-885
On the basis of calculating the steady-state mean normalized intensity fluctuation of a signal-mode laser system driven by both colored pump noise with signal modulation and the quantum noise with cross-correlation between its real and imaginary parts, we analyze the influence of modulation signal, noise, and its correlation form on the statistical fluctuation of the laser system. We have found that when the amplitude of modulation signal weakens and its frequency quickens, the statistical fluctuation will reduce rapidly. The by reducing the intensity of pump noise and quantum noise. statistical fluctuation of the laser system can be restrained Moreover, with prolonging of colored cross-correlation time, the statistical fluctuation of laser system experiences a repeated changing process, that is, from decreasing to augmenting, then to decreasing, and finally to augmenting again. With the decreasing of the value of cross-correlation coe~cient, the statistical fluctuation will decrease too. When the cross-correlation form between the real part and imaginary part of quantum noise is zero correlation, the statistical fluctuation of laser system has a minimum. Compared with the influence of intensity of pump noise, the influence of intensity of quantum noise on the statistical fluctuation is smaller. 相似文献
17.
针对三相三电平VIENNA整流器中点电位波动问题,建立了中点电流的数学模型,分析了中点波动形式、并结合中点电流数学模型分析了中点电位波动的根本原因,针对传统固定调节因子法抑制中点电位波动效果较差的缺点,提出了一种结合动态调节因子与电容偏差调节的混合抑制方法,给出了6扇区下偏差调节量和动态调节因子表达式,然后通过查表法将6扇区对应动态调节量注入到调制波中,实现了中点电位尤其三次基频波动的自动抑制,进一步修正后的混合抑制法还可有效抑制电容参数和负载不对称导致的中点大幅度波动,实验结果验证了策略的可行性和有效性。 相似文献
18.
In the photorefractive wave-mixing system, fluctuation in the signal beam intensity of the photorefractive output with a reflection grating has been analyzed by employing pump feedback method. In this method, fluctuations of the photorefractive wave-mixing process not only induce the intensity fluctuation of the mixing waves but also induce phase fluctuation of the mixing waves. Thus, the phase of the pump and signal beams at the output surface fluctuates in time around a mean value. Using such a positive feedback method of a pump beams, the relative fluctuation in the photorefractive output signal beam intensity with respect to its mean intensity can be minimized significantly without reducing its mean intensity. The factors that control the fluctuation in the signal beam intensity, such as the phase fluctuation of the output pump beam, absorption strength of the material and the feedback reflectivity of the cavity mirrors, on the relative fluctuation of the output signal intensity in the photorefractive wave-mixing systems have been studied in detail. It has been found that the fluctuation of the output signal intensity relative to its mean intensity in the photorefractive wave-mixing system can be suppressed to larger extent by taking lower value of feedback reflectivity of the cavity mirrors which could exist at a higher value of absorption strength of the photorefractive materials. 相似文献