共查询到20条相似文献,搜索用时 578 毫秒
1.
A de Cheveigné 《The Journal of the Acoustical Society of America》1999,106(2):887-897
Mistuning one partial of a complex harmonic tone makes that partial easier to hear as a tone separate from the complex. At the same time, two pitch shifts may be observed. First, the low pitch of the complex is shifted in the direction of the mistuning, as if it were "pulled" by the partial. Second, the mistuning of the partial is perceptually exaggerated, as if the pitch of the partial were "pushed" away from the harmonic series defined by the complex. This paper shows how the latter effect can emerge within a hypothetical neural circuit. The circuit involves a gating neuron fed by three pathways, one direct and excitatory and the other two delayed and inhibitory. The neuron responds to any excitatory input spike unless it is accompanied by an inhibitory input spike on either delayed input, thus acting as a kind of "anticoincidence counter." The first delay is fixed and tuned to the period of the background harmonic complex. Its purpose is to weaken correlates of in-tune components and allow the mistuned partial to stand out. The second delay is variable and used to estimate the period of the mistuned partial, by searching for a minimum output as a function of delay. With an appropriate choice of parameters, the estimate is subject to shifts that are of the same sign as the mistuning and that peak at about 4% mistuning and decrease beyond, as observed experimentally. 相似文献
2.
We report on theoretical studies of the influence of an in-plane magnetic field on the recently discovered strong radiation-induced magnetoresistance spike obtained in ultraclean two-dimensional electron systems. The most striking feature of this spike is that it shows up on the second harmonic of the cyclotron resonance. According to experiments, the effect of an in-plane magnetic field is to reduced dramatically the intensity of both, radiation-induced resistant spike and oscillations. We apply the radiation-driven electron orbits model in the ultraclean scenario. We are able to explain with the same physical mechanism the whole experimental response (spike and resistance oscillations). Accordingly, the increasing disorder in the sample caused by the in-planed magnetic field would be responsible of the quenching. Calculated results are in good agreement with experiments. 相似文献
3.
Pisarchik AN Jaimes-Reátegui R Sevilla-Escoboza R Huerta-Cuellar G Taki M 《Physical review letters》2011,107(27):274101
Clear evidence of rogue waves in a multistable system is revealed by experiments with an erbium-doped fiber laser driven by harmonic pump modulation. The mechanism for the rogue wave formation lies in the interplay of stochastic processes with multistable deterministic dynamics. Low-frequency noise applied to a diode pump current induces rare jumps to coexisting subharmonic states with high-amplitude pulses perceived as rogue waves. The probability of these events depends on the noise filtered frequency and grows up when the noise amplitude increases. The probability distribution of spike amplitudes confirms the rogue wave character of the observed phenomenon. The results of numerical simulations are in good agreement with experiments. 相似文献
4.
We report the observation of a colossal, narrow resistance peak that arises in ultraclean (mobility ~3×10? cm2/V s) GaAs/AlGaAs quantum wells (QWs) under millimeter wave irradiation and a weak magnetic field. Such a spike is superposed on the 2nd harmonic microwave-induced resistance oscillations (MIRO) but having an amplitude >300% of the MIRO, and a typical FWHM ~50 mK, comparable with the Landau level width. Systematic studies show a correlation between the spike and a pronounced negative magnetoresistance in these QWs, suggesting a mechanism based on the interplay of strong scatterers and smooth disorder. Alternatively, the spike may be interpreted as a manifestation of quantum interference between the quadrupole resonance and the higher-order cyclotron transition in well-separated Landau levels. 相似文献
5.
Fahey PF Stagner BB Lonsbury-Martin BL Martin GK 《The Journal of the Acoustical Society of America》2000,108(4):1786-1802
Suppression and/or enhancement of third- and fifth-order distortion products by a third tone that can have a frequency more than an octave above and a level more than 40 dB below the primary tones have recently been measured by Martin et al. [Hear. Res. 136, 105-123 (1999)]. Contours of iso-suppression and iso-enhancement that are plotted as a function of third-tone frequency and level are called interference response areas. After ruling out order aliasing, two possible mechanisms for this effect have been developed, a harmonic mechanism and a catalyst mechanism. The harmonic mechanism produces distortion products by mixing a harmonic of one of the primary tones with the other primary tone. The catalyst mechanism produces distortion products by mixing one or more intermediate distortion products that are produced by the third tone with one or more of the input tones. The harmonic mechanism does not need a third tone and the catalyst mechanism does. Because the basilar membrane frequency response is predicted to affect each of these mechanisms differently, it is concluded that the catalyst mechanism will be dominant in the high-frequency regions of the cochlea and the harmonic mechanism will have significant strength in the low-frequency regions of the cochlea. The mechanisms are dependent on the existence of both even- and odd-order distortion, and significant even- and odd-order distortion have been measured in the experimental animals. Furthermore, the nonlinear part of the cochlear mechanical response must be well into saturation when input tones are 50 or more dB SPL. 相似文献
6.
We present calculated results on frequency, power and temperature dependence of the recently discovered giant radiation-induced off-resonance magnetoresistance spike obtained in ultraclean two-dimensional electron systems. This spike shows up on the second harmonic of the cyclotron resonance. We apply the radiation-driven electron orbit model to this novel ultraclean scenario. In agreement with experiments, we obtain that the spike intensity is strongly dependent on temperature and radiation power. On the other hand, the spike position is mainly dependent on radiation frequency. These results would be of special interest from the application perspective, such as nanophotonics, ultrasensitive microwave detectors or solar cells given the strong translation of radiation energy into electrical current. 相似文献
7.
Effect of laser focus in two-color synthesized waveform on generation of soft x-ray high harmonics
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Yanbo Chen 《中国物理 B》2023,32(1):14203-014203
Synthesis of multi-color laser pulses has been developed as a promising way to improve low conversion efficiency of high-order harmonic generation (HHG). Here we systematically study the effect of laser focus in a two-color waveform on generation of macroscopic HHG in soft x-rays. We find that the dependence of HHG yields on laser focus at low or high gas pressure is sensitive to the characteristics of single-atom harmonic response, in which "short"-or "long"-trajectory emissions can be selectively controlled by changing the waveform of two-color synthesized laser pulse. We uncover the phase-matching mechanism of HHG in the gas medium by examining the propagation of the two-color waveform and the evolution of time-frequency emissions of high-harmonic field. We further reveal that the nonlinear effects, such as geometric phase, atomic dispersion, and plasma defocusing, are responsible for modification of two-color waveform upon propagation. This work can be used to find better macroscopic conditions for generating soft x-ray HHG by employing two-color optimized waveforms. 相似文献
8.
The main characteristics of the third harmonic emission generated by
femtosecond laser pulses propagating in air are investigated by numerically
solving the coupled nonlinear Schr?dinger equations. Strong third
harmonic emission is observed with a maximum conversion efficiency as high
as 0.43%. The on-axis phase difference between fundamental beam and third
harmonic is investigated. The result is in good agreement with the
phase-locking mechanism. Dependence of the conversion of third harmonic
emission on focusing conditions is also studied. The results are also
compared with those of experiments. 相似文献
9.
A fast ion can electronically excite a solid producing a track of damage, a process initially used to detect energetic particles but now used to alter materials. From the seminal paper by Fleischer et al. [Phys. Rev. 156, 353 (1967)] to the present, "Coulomb explosion" and thermal spike models have been often treated as competing models for describing ion track effects. Here molecular dynamics simulations of electronic sputtering, a surface manifestation of track formation, show that in the absence of significant quenching Coulomb explosion in fact produces a spike at high excitation density, but the standard spike models are incorrect. 相似文献
10.
Brown JC 《The Journal of the Acoustical Society of America》2008,123(5):2875-2883
Formulas for the spectra of pulsed vocalizations for both the continuous and discrete cases are rigorously derived from basic formulas for Fourier analysis, a topic discussed qualitatively in Watkins' classic paper on "the harmonic interval" ["The harmonic interval: Fact or artifact in spectral analysis of pulse trains," in Marine Bioacoustics 2, edited by W. N. Tavogla (Pergamon, New York, 1967), pp. 15-43]. These formulas are summarized in a table for easy reference, along with most of the corresponding graphs. The case of a "pulse tone" is shown to involve multiplication of two temporal wave forms, corresponding to convolution in the frequency domain. This operation is discussed in detail and shown to be equivalent to a simpler approach using a trigonometric formula giving sum and difference frequencies. The presence of a dc component in the temporal wave form, which implies physically that there is a net positive pressure at the source, is discussed, and examples of the corresponding spectra are calculated and shown graphically. These have application to biphonation (two source signals) observed for some killer whale calls and implications for a source mechanism. A MATLAB program for synthesis of a similar signal is discussed and made available online. 相似文献
11.
信息在神经系统中以脉冲点序列的形式传输和处理,神经系统如何通过脉冲点序列对所表达的信息进行编码,一直是一个谜.人们曾普遍认为,神经可能通过发放率(单位时间发放脉冲出现的次数)对信息编码,也有人猜测,神经可通过脉冲点序列的时序编码.由于神经发放的随机性,这就使得任何编码机制都面临着被表达信息的确定性与表达该信息的信号的随机性的矛盾.通过神经非线性随机动力学模型,文章作者发现,神经点序列的发放率对点序列的时序信息传输的影响,揭示了神经点序列时序信息在神经非线性传输中的随机共振特征.由此预期,并进一步通过听觉心理物理实验观察到,在一定条件下噪声对听觉的增强作用.从而通过非线性物理揭示了听觉时序编码机制的存在以及在时序编码中随机性噪声的积极作用. 相似文献
12.
C. Klempt T. Henninger O. Topic J. Will St. Falke W. Ertmer J. Arlt 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(1):121-126
We report on the simultaneous transport of mixed quantum
degenerate gases of bosonic 87Rb and fermionic 40
K in a harmonic potential. The samples are transported over a
distance of
to the geometric center of a
Ioffe-Pritchard type magnetic trap. This transport mechanism was
implemented by modification of the QUIC trap and is free of losses
and heating. It significantly extends the capabilities of this trap
design. We demonstrate a launching mechanism for quantum degenerate
samples and show that highly homogeneous magnetic fields can be
created in the center of the QUIC trap. The transport mechanism may
also be cascaded to cover even larger distances for interferometric
experiments with quantum degenerate samples. 相似文献
13.
Theodore Kolokolnikov 《Physica D: Nonlinear Phenomena》2009,238(16):1695-1710
We study the Gierer-Meinhardt system in one dimension in the limit of large reaction rates. First we construct three types of solution: (i) an interior spike; (ii) a boundary spike and (iii) two boundary spikes. Second we prove results on their stability. It is found that an interior spike is always unstable; a boundary spike is always stable. The two boundary spike configuration can be either stable or unstable, depending on the parameters. We fully classify the stability in this case. We characterize the destabilizing eigenfunctions in all cases. Numerical simulations are shown which are in full agreement with the analytical results. 相似文献
14.
M. Uhrmacher P. Wodniecki F. Shi T. Weber K. -P. Lieb 《Applied Physics A: Materials Science & Processing》1993,57(4):353-361
We report on the ion-beam mixing processes of Sb/Ni marker layers and bilayers under the irradiation of ions ranging from He to Pb, at 80 K and at room temperature. The concentration profiles are obtained by Rutherford backscattering spectroscopy with 900 keV -particles. At 80 K, the bilayer mixing rates cannot be reproduced by purely ballistic mixing; the essentially linear scaling of the bilayer mixing rate with the energy F
D deposited at the interface points to local spike formation. A transition to global spike formation seems to be visible for the Pb-irradiations. Additional mixing effects at 300 K are due to radiation enhanced diffusion and scale with F
D. The marker mixing rates at 80 K are reproduced by the ballistic mixing approach, but are equally well described by local spike models. High fluence Xe-irradiations of Sb/Ni bilayers lead to intermetallic phases in the interface region as verified by transmission electron microscopy. 相似文献
15.
Sensory systems present environmental information to central nervous system as sequences of action potentials or spikes. How do animals recognize these sequences carrying information about their world? We present a biologically inspired neural circuit designed to enable spike pattern recognition. This circuit is capable of training itself on a given interspike interval (ISI) sequence and is then able to respond to presentations of the same sequence. The essential ingredients of the recognition circuit are (a) a tunable time delay circuit, (b) a spike selection unit, and (c) a tuning mechanism using spike timing dependent plasticity of inhibitory synapses. We have investigated this circuit using Hodgkin-Huxley neuron models connected by realistic excitatory and inhibitory synapses. It is robust in the presence of noise represented as jitter in the spike times of the ISI sequence. 相似文献
16.
《中国物理快报》2020,(5)
The Rayleigh-Taylor instability at the weakly nonlinear(WN) stage in spherical geometry is studied by numerical simulation.The mode coupling processes are revealed.The results are consistent with the WN model based on parameter expansion,while higher order effects are found to be non-negligible.For Legendre mode perturbation Pn(cos B),the nonlinear saturation amplitude(NS A) of the fundamental mode decreases with the mode number n.When n is large,the spherical NSA is lower than the corresponding planar one.However,for large n,the planar NSA can be recovered by applying Fourier transformation to the bubble/spike near the equator and calculating the NSA of the converted trigonometric harmonic. 相似文献
17.
The harmonic sieve has been proposed as a mechanism for excluding extraneous frequency components from the estimate of the pitch of a complex sound. The experiments reported here examine whether a harmonic sieve could also determine whether a particular harmonic contributes to the phonetic quality of a vowel. Mistuning a harmonic in the first formant region of vowels from an /I/-/e/ continuum gave shifts in the phoneme boundary that could be explained by (i) phase effects for small amounts of mistuning and (ii) a harmonic sievelike grouping mechanism for larger amounts of mistuning. Similar grouping criteria to those suggested for pitch may operate for the determination of first formant frequency in voiced speech. 相似文献
18.
Alternately eliminating and reintroducing a particular harmonic of a complex tone can cause that harmonic to stand out as a pure tone-separately audible from the rest of the complex-tone background. In the psychoacoustical literature the effect is known as "enhancement." Pitch matching experiments presented in this article show that although harmonics above the 10th are not spectrally resolved, harmonics up to at least the 20th can be enhanced. Therefore, resolution is not required for enhancement. Further, during those experimental intervals in which a harmonic is eliminated, excitation pattern models suggest that listeners should be able to hear out a neighboring harmonic-separately audible from the background. The latter effect has been called "unmasking." In the present article we provide the first experimental evidence for unmasking. Harmonics of 200 Hz, with harmonic numbers between about 5 and 16, are readily unmasked. Their pitches are usually matched by sine tones with frequencies that are not exactly those of the unmasked harmonics but are shifted in a direction away from the frequency of the pulsed harmonic. Phase relationships among the harmonics that produce temporally compact cochlear excitation lead to reduced enhancement but greater unmasking. 相似文献
19.
K. D. Hong G. F. Brand P. W. Fekete T. Idehara 《International Journal of Infrared and Millimeter Waves》1992,13(2):215-227
The gyrotrons developed at the University of Sydney are tunable sources of millimetre and submillimetre radiation. The generation of submillimetre wavelengths requires operation at the second harmonic of the electron cyclotron frequency, or higher. Our latest gyrotron, GYROTRON IVA, has successfully achieved second harmonic operation and obtained frequencies up to 590 GHz (=0.51 mm). The experimental results and conditions for second harmonic operation will be presented. The design of a new gyrotron, GYROTRON V, which is especially optimised for the second harmonic, will also be included. 相似文献