Amplitude Of Sine Wave Research Articles

Diaphragmatic fatigue produced by constant or modulated electric currents

In anesthetized rabbits the efficiency of phrenic nerve stimulation with trains of electric current was studied either when ventilation was effected entirely by bilateral nerve stimulation (electrophrenic ventilation) or during unilateral nerve stimulation when animals were ventilated with a pump and open chest. Trains of rectangular electric pulses (RPT) with constant amplitude and frequency or sine waves, both the amplitude and frequency of which were modulated and controlled by a computer (MSWT), were used with each animal. MSWT closely reproduced the physiological shape of transdiaphragmatic pressure waves. Diaphragm fatigue, as determined from the decrease in the maximal relaxation rate of twitches, occurred after 20 minutes of bilateral or unilateral nerve stimulation with RPT, but only after 60 min (unilateral stimulation) or 98 min (bilateral stimulation) with MSWT. These data show the importance of the motor signal pattern in long-lasting nerve stimulation.

Peak-to-RMS reduction of speech based on a sinusoidal model

A sinusoidal-based analysis/synthesis system is used to apply a radar design solution to the problem of dispersing the phase of a speech waveform. Unlike conventional methods of phase dispersion, this solution technique adapts dynamically to the pitch and spectral characteristics of the speech, while maintaining the original spectral envelope. The solution can also be used to drive the sine-wave amplitude modification for amplitude compression, and is coupled to the desired shaping of the speech spectrum. The proposed dispersion solution, when integrated with amplitude compression, results in a significant reduction in the peak-to-RMS (root-mean-square) ratio of the speech waveform with acceptable loss in quality. Application of a real-time prototype sine-wave preprocessor to AM radio broadcasting is described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An approach to co-channel talker interference suppression using a sinusoidal model for speech

The technique fits a sinusoidal model to additive vocal speech segments so that the least-mean-squared error between the model and the summed waveforms is obtained. Enhancement is achieved by synthesizing a waveform from the sine waves attributed to the desired speaker. Least-squares estimation is applied to obtain sine-wave amplitudes and phases of both talkers, based on either a priori sine-wave frequencies or a priori fundamental frequency contours. When the frequencies of the two waveforms are closely spaced, the performance is significantly improved by exploring the time evolution of the sinusoidal parameters across multiple analysis frames. The least-squared-error approach is also extended, under restricted conditions, to estimate fundamental frequency contours of both speakers from the summed waveforms. The results obtained, although limited in their scope, provide evidence that the sinusoidal analysis/synthesis model with effective parameter estimation techniques offers a promising approach to the problem of cochannel talker-interference suppression over a range of conditions. >

Superimposing noise linearizes the responses of primary muscle spindle afferents to sinusoidal muscle stretch.

Experiments were conducted in anaesthetized and spinalized cats to measure the extent to which the non-linear response of Ia afferent fibers to sinusoidal muscle stretch as expressed by the peristimulus-time-histograms, PSTHs, can be transformed into a linear one by means of the superposition of random stretch ("mechanical noise"). The gastrocnemius muscles of one hind leg were stretched and the response to sinewave muscle stretch (amplitudes between 0.01 and 4.0 mm, frequencies between 0.1 and 20 Hz) were investigated while band-limited mechanical noise was superimposed on the sinewave stretch. The random stretch upper cut-off frequency was varied between 60 and 300 Hz; the displacements were normally distributed. The noise amplitude sigma, i.e. the standard deviation of the displacement distributions, was varied systematically between 0.002 and 0.4 mm. Mechanical noise was very effective in raising the mean discharge rate. Added to the sinusoidal stretch it prevented the cessation of firing during the release phase of the stretch cycle, or at least reduced the duration of discharge pauses, i.e., a linearization occurred. In general, the larger the noise amplitude, the more the amplitude of the fundamental harmonic component was attenuated and the phase lead reduced. Apart from this rule the particular combination of superimposing small noise (sigma less than 0.02 mm) on small sinewave stretch (A less than 0.02 mm) could enhance the depth of sinusoidal modulation of cycle histograms (compared with responses to pure sinusoids). Linearizing the sinewave response by additional noise allowed the estimation of frequency response characteristics in the otherwise non-linear range of amplitudes (sinewave amplitude 0.5-1.0 mm).(ABSTRACT TRUNCATED AT 250 WORDS)

Pursuit eye movement in tracking a target with two sine waves.

It has been reported that, when subjects track a moving target comprising two sine waves, the tracking lag for the faster sine wave component is much smaller than that for the slower one. To understand this phenomenon further, this study examined frequency characteristics of the human tracking response and pursuit eye movement in response to the target with two sine waves of equal amplitude. Analysis indicates that, while the tracking response has very large phase lag for the slower sine wave component and very small phase lag for the faster one, the pursuit eye movement has a conspicuously large phase lead for the slower component and very small phase lag for the faster one. It is suggested that the lack of synchrony of the pursuit eye movement with slower component of the target may be associated with the inferiority of the slower component to the faster one in tracking lag.

Defocused Imaging of an Amplitude Sine Wave Object under Partially Coherent Illumination with an Annular Source

Abstract The apparent transfer functions for defocused imaging under partially coherent illumination with an annular source are investigated. The influence of central obscuration of the annular source on the apparent transfer functions are also studied. The annular source and a source with uniform irradiance distribution are compared.

Biological significance of fluctuating concentrations of carbon monoxide

The biological significance of fluctuating concentrations is not well understood. Fluctuation patterns can be approximated as a Fourier series of sine waves of different amplitudes, periods, and phases. A theoretical equation was developed for relating carboxyhemoglobin levels in blood to sine wave exposure patterns of carbon monoxide. It was experimentally validated for rabbits exposed to 50-350 ppm of CO in sine waves of periods from 37 to 280 min. Higher frequency carbon monoxide concentration fluctuations were more highly attenuated in the blood in accordance with the equation. The response may be viewed in a new perspective as a modification of the original fluctuation pattern by the transmittance of the biological window. A simplified method of evaluating biologically effective concentrations for different carbon monoxide fluctuation patterns is proposed.

Probability distributions of randomly-phased combinations of sine waves of equal amplitude

Bean has recently published in this journal the results of computer simulation experiments on the amplitude distribution of sine waves of equal amplitude combined with random phasing. The contribution of this paper is to set the experimental results into a theoretical context. It is shown that the experimental results and theoretical predictions are in satisfying agreement.

Design of A Microcomputer-Based Instrument for Crispness Evaluation of Food Products

ABSTRACT An instrument costing under $4000 was built to study the acoustical properties of crisp foods. A spectrum analyzer was built around an Apple 11+ microcomputer (Apple Computer, Inc.) for analyzing acoustical frequencies in the 0.5 to 3.3 kHz range. The instrument was evaluated with sine and square waves of known amplitudes and frequencies. Samples of Pringles potato chips were crushed and their sound output recorded. Sound pressure level spectra were later developed by the instrumentation.

Random combinations of sine waves of equal amplitude

Random combinations of up to ten sine waves have been considered and the distribution of the resultant amplitudes obtained.

Empirical Predictors of Annual Surface Water Temperature Cycles in North American Lakes

Annual surface water temperature cycles of temperate zone lakes can be adequately described by a symmetrical sine wave of distinct amplitude and duration. The relationships between these sine wave components and climatic and morphometric variables were analyzed for 87 lakes spread over most of North America, and for 25 lakes located in south-central Ontario, Canada. Multiple regression equations are reported which permit estimation of the maximum annual surface water temperature (amplitude: AP) and the number of ice-free days (duration: DR) for a specific lake from data on long-term mean annual air temperature (TEMP), mean depth [Formula: see text], and fetch (FT). These estimates can be used to calculate mean surface water temperature for just the ice-free period or for an entire year.

Spectral response from perpendicular media with gapped head and underlayer

A general spectral formulation is presented, in the spirit of the Karlquist approximation, for the field from a gapped head with a permeable underlayer. For an infinite permeability underlayer, of particular interest in perpendicular recording, the fields and readback response are derived for sine-wave and square-wave magnetization, as well as for an isolated transition. The sine-wave response is given in a simple form, allowing interpretation in terms of a reduced pole density from the medium at the underlayer. The square-wave response is given as a Fourier series of sine-wave amplitudes. Approximate analytical functions are constructed for the response to an isolated transition.

Ultrasonic signal distortion and its effects on velocity measurements in dispersive constant-group-velocity media

Results are presented of calculations made of distortion experienced by ultrasonic pulses in transmission through dispersive constant-group-velocity media, and the effects that it may have on velocity measurements. Three types of pulses were considered: a pulsed sine wave of constant amplitude, a pulsed sine wave with amplitude varying as sine-squared, and a rectangular pulse. It is shown that the individual waves in the pulsed sine waves move with the phase velocity of a continuous wave, and the envelope moves with the group velocity. It was also found that a pulsed sine wave in going a certain distance in a constant-group-velocity medium repeats itself, and midway between these distances is the negative of the values at the repetition distances. Because of this repetition phenomenon it is seen that the pulses propagating through the constant-group-velocity dispersive media do not spread as is normally the case in dispersive media. The envelopes of the propagated waves were also calculated, and in agreement with Brillouin’s results [Wave Propagation and Group Velocity (Academic, New York, 1960)] it was found that if the envelope contains negligible frequency components above the carrier frequency, then the envelope is not distorted in passing through a dispersive constant-group-velocity medium.

Responses of cat dorsal spino-cerebellar tract neurons to sinusoidal stretching of the gastrocnemius muscle.

A defined class of cells within the nucleus dorsalis (Clarke's column) receives excitatory input from Ia afferents of mainly one muscle. Action potentials were recorded from axons of these cells (DSCT neurons) which are excited by Ia afferents of the gastrocnemius muscles. We investigated the response to sinusoidal muscle stretch over a wide range of amplitudes (10 microns-4 mm) and frequencies (0.1-130 Hz) in the deefferented preparation. The dynamic stretch was superimposed on a moderate static muscle stretch to ensure that the muscle was not slack during the phase of release. The response up to 10 Hz was displayed as PST histograms (cycle histograms) and a sinewave of stretch frequency was fitted to the PST histograms to define amplitude and phase of a response sinewave. At a constant frequency of about 3 Hz, the relation between stretch amplitude and response amplitude could well be described by decelerating intensity functions: the hyperbolic or tanh log function and a modified power function (exponent 0.48 +/- 0.12). The phase lead of the response sinewave increased with increasing stretch amplitudes of up to 0.5 mm and then decreased. At constant stretch amplitudes of 0.5-2.0 mm the frequency response was investigated. In relation to stretch frequencies between 0.1 and 1 Hz an increase in the response amplitude of 4.4 dB was observed and an increase for 13 dB/decade between 3 and 10 Hz. At 0.1 Hz the phase of the response sinewave was 48 degrees in advance and increased to a maximum lead of 89 degrees at 6-8 Hz. Above 10 Hz the positions of the responding action potentials with respect to the stretch cycle were used to define a phase, which was in advance up to 60 Hz but decreased and changed to a phase lag at higher frequencies. If in PST histograms no periods of silence occurred during the phase of stretch release, the mean discharge rate was found to be independent of the sinusoidal stretching. If the pauses were present the mean rate increased with increasing stretch frequencies or amplitudes.

On detecting reflections in presence of scattering from amplitude statistics with application to D region partial reflections

In many radar experiments which use transmission or scattering of radio waves through a random medium, the received signal is modeled as a reflected sine wave of amplitude A in a scattered narrow‐band Gaussian random process of variance 2σ2. In this model the received signal amplitude has a Rice family of distribution characterized by a parameter α = A/σ. It is shown that amplitude statistics cannot be used to discriminate weak reflections from scattering (α &lt; 0.5). Behavior of mean, skewness, and kurtosis of the normalized signal amplitude is examined for a constant and an intermittent reflected component. It is shown that intermittency has a strong effect on these. Applications to a D region partial‐reflection experiment at Tromsø are briefly discussed. It is shown that, at least in some simple cases, enhanced reflections arise from the top and bottom parts of turbulent layers.

Effect of Ca ion concentration on cross-bridge kinetics in rabbit psoas fibers. Evidence for the presence of two Ca-activated states of thin filament

The effect of Ca ion concentration on cross-bridge kinetics in a small bundle (one to three fibers) of chemically skinned rabbit psoas muscle is studied. The length of the muscle is oscillated in small amplitude sine waves (0.2% L0 peak-to-peak) at varying frequencies (0.125 -- 167 Hz), and the resulting amplitude and phase shift in tension are measured. The frequency response function (complex stiffness) thus obtained can be divided into three parts, which we name process (A) (centered at 1 Hz), process (B) (3--17 Hz), and process (C) (50 Hz). Process (B), which represents oscillatory work, further splits into two processes (B' and B) at partial Ca activation (less than 50% P0), where the phase-frequency plot appears W-shaped. The slower of the two processes (B') disappears by full activation, at which time the plot appears V-shaped. The characteristic frequencies associated with the minima of the plot do not shift in a graded way with Ca concentration, indicating that there is no change in apparent rate constants. Apparent rate constants of processes (A) and (C) are minimally affected by Ca. The above results are not altered when ionic strength is changed between 128 and 265 mM. We propose that activated thin filaments can have two "on" states and that Ca concentration controls the distribution of these two states. This mechanism generally supports the "switch" hypothesis of Ca regulation.

Brass Tone Synthesis by Spectrum Evolution Matching with Nonlinear Functions

There has been ample evidence from analytical studies done in recent years that brass harmonic spectra (and probably those of other wind instruments) are somehow related to spectra which can be produced by the nonlinear distortion of a variable amplitude sine wave. It is the purpose of this paper to review this evidence and present some results of attempts to synthesize brass tones using this technique.

A Programmable Phase-Sensitive Detector for Automatic Bridge Applications

A phase-sensitive detector is described which features programmable gain, digital output, and a resolution of 0.02 μV. The instrument suppresses harmonic sensitivity through the use of analog circuitry which multiplies the signal by constant amplitude sine and cosine waves derived from an external reference of arbitrary voltage and frequency.

Harmonics of the difference frequency in saturation-limited parametric sources

Data are presented for the spectra and waveforms generated by saturation-limited parametric acoustic sources. The primary source was a 10-cm-diam, 710-kHz projector driven with double side band and sine-wave amplitude modulation at peak primary source levels up to 246 dB//1μPa m. The data tend to confirm the theory of H. M. Merklinger [Ph. D. thesis, (Department of Electronic and Electrical Engineering, University of Birmingham, England, 1971) (unpublished)], namely, that the secondary pressure is proportional to ∂2‖E (t−x/c0) ‖/∂t2, where E is the primary envelope waveshape. A modified version of the theory provides a useful primary amplitude taper function for parametric source performance prediction.

Effectof MgATP on stiffness measured at two frequencies in Ca2+-activated muscle fibers.

The stiffness of skinned crayfish single muscle fibers was continuously monitored at two frequencies. The length of the fibers was oscillated by the sum of two sine waves (5 Hz and 100 Hz) of small amplitudes. In saline containing saturating amounts of Ca2+, the stiffness ratio (5 Hz:100Hz) was constant as the MgATP (substrate) concentration was raised from 0 to 2 mu M, then it decreased with a further increment in MgATP. The systematic decrease in the stiffness ratio in MgATP above 2 mu M indicates the presence of faster transitions in the cross-bridge cycle. This dependence of the stiffness ratio on MgATP is predictable if we use the two-state model of A. F. Huxley (1957) with a modification, in which MgATP promotes the dissociation of the attached cross-bridges.