scholarly journals The Perceived Direction of Textured Gratings and Their Motion Aftereffects

Perception ◽  
1995 ◽  
Vol 24 (12) ◽  
pp. 1383-1396 ◽  
Author(s):  
David Alais ◽  
Maarten J van der Smagt ◽  
Frans A J Verstraten ◽  
Wim A van de Grind
Keyword(s):  
Motion Aftereffect ◽  
Sine Wave ◽  
Circular Aperture ◽  
High Luminance ◽  
One Dimensional ◽  
Square Wave ◽  
Aperture Problem ◽  
Motion Energy ◽  
Motion Aftereffects ◽  
Do So

The stimuli in these experiments are square-wave luminance gratings with an array of small random dots covering the high-luminance regions. Owing to the texture, the direction of these gratings, when seen through a circular aperture, is disambiguated because the visual system is provided with an unambiguous motion energy. Thus, the direction of textured gratings can be varied independently of grating orientation. When subjects are required to judge the direction of textured gratings moving obliquely relative to their orientation, they can do so accurately (experiment 1). This is of interest because most studies of one-dimensional motion perception have involved (textureless) luminance-defined sine-wave or square-wave gratings, and the perceived direction of these gratings is constrained by the aperture problem to be orthogonal to their orientation. Thus, direction and orientation have often been confounded. Interestingly, when subjects are required to judge the direction of an obliquely moving textured grating during a period of adaptation and then the direction of the motion aftereffect (MAE) immediately following adaptation (experiments 2 and 3), these directions are not directly opposite each other. MAE directions were always more orthogonal to the orientation of the adapting grating than the corresponding direction judgments during adaptation (by as much as 25°). These results are not readily explained by conventional MAE models and possible accounts are considered.

Apparent Velocity of Motion Aftereffects in Central and Peripheral Vision

Perception ◽  
1986 ◽  
Vol 15 (5) ◽  
pp. 603-612 ◽  
Author(s):  
Michael J Wright
Keyword(s):  
Visual Field ◽  
Time Course ◽  
Peripheral Vision ◽  
Temporal Frequency ◽  
Motion Aftereffect ◽  
Apparent Velocity ◽  
Real Motion ◽  
Temporal Decay ◽  
Spatial Grain ◽  
Motion Aftereffects

Adapting to a drifting grating (temporal frequency 4 Hz, contrast 0.4) in the periphery gave rise to a motion aftereffect (MAE) when the grating was stopped. A standard unadapted foveal grating was matched to the apparent velocity of the MAE, and the matching velocity was approximately constant regardless of the visual field position and spatial frequency of the adapting grating. On the other hand, when the MAE was measured by nulling with real motion of the test grating, nulling velocity was found to increase with eccentricity. The nulling velocity was constant when scaled to compensate for changes in the spatial ‘grain’ of the visual field. Thus apparent velocity of MAE is constant across the visual field, but requires a greater velocity of real motion to cancel it in the periphery. This confirms that the mechanism underlying MAE is spatially-scaled with eccentricity, but temporally homogeneous. A further indication of temporal homogeneity is that when MAE is tracked, by matching or by nulling, the time course of temporal decay of the aftereffect is similar for central and for peripheral stimuli.

Sine-Wave Exciting Circuit for Quartz Vibrating Gyroscope

2013 ◽  
Vol 562-565 ◽  
pp. 417-420
Author(s):  
Qing Yi Wang ◽  
Xiao Wei Liu ◽  
Rui Zhang ◽  
Liang Yin ◽  
Zhi Ping Zhou
Keyword(s):  
High Performance ◽  
Small Volume ◽  
Angular Rate ◽  
Sine Wave ◽  
Processing Technology ◽  
Angular Rate Sensor ◽  
Square Wave ◽  
Rate Sensor ◽  
Is Design ◽  
Cmos Processing

Quartz vibrating gyroscope is a kind of angular rate sensor which is the compromise between the high performance and the small volume. Improvement of the performance is a focus of reach. In this paper, a sine-wave exciting method is discussed. A sine-wave exciting circuit is design and processed with 0.5μm CMOS processing technology. During comparing the sine-wave exciting response and the square-wave one, the sine-wave exciting circuit is more beneficial to improve the performance of the quartz vibrating gyroscope.

Electroconvulsive Therapy and the Seizure Threshold*

1983 ◽  
Vol 28 (6) ◽  
pp. 445-448 ◽  
Author(s):  
B.A. Martin ◽  
S. Strigler ◽  
K. Bezchlibnyk ◽  
G.E. Harris-Brandts
Keyword(s):  
Clinical Practice ◽  
Electroconvulsive Therapy ◽  
Electrical Energy ◽  
Sine Wave ◽  
Routine Clinical Practice ◽  
Large Series ◽  
Seizure Threshold ◽  
Square Wave ◽  
Rate Of Failure

The use of a pulsatile square wave stimulus for a large series of electroconvulsive treatments under conditions of routine clinical practice is compared to the equivalent experience with a sine wave stimulus. The literature indicates that both waveforms are equally effective convulsants. However, in this series, the induction of a convulsion was found to be much more difficult with the pulsatile square wave such that the rate of failure to convulse was four times that compared to sine wave stimulation. A number of variables that may affect the seizure threshold during ECT were examined. It is concluded that the benefit obtained by reducing the electrical energy transmitted to the patient with the pulsatile stimulus offsets the difficulty encountered in reaching the seizure threshold.

scholarly journals The Initial Disparity Vergence Elicited With Single and Dual Grating Stimuli in Monkeys: Evidence for Disparity Energy Sensing and Nonlinear Interactions

2008 ◽  
Vol 100 (5) ◽  
pp. 2907-2918 ◽  
Author(s):  
K. Miura ◽  
Y. Sugita ◽  
K. Matsuura ◽  
N. Inaba ◽  
K. Kawano ◽  
...  
Keyword(s):  
Sine Wave ◽  
Nonlinear Dependence ◽  
One Dimensional ◽  
Quarter Wavelength ◽  
Spatial Frequencies ◽  
Energy Sensing ◽  
The One ◽  
Winner Take All ◽  
Lower Contrast ◽  
Horizontal Grating

We recorded the initial vertical vergence eye movements elicited in monkeys at short latency (∼70 ms) when the two eyes see one-dimensional (1D) horizontal grating patterns that are identical except for a phase difference (disparity) of one-quarter wavelength. With gratings composed of single sine waves, responses were always compensatory, showing Gaussian dependence on log spatial frequency (on average: peak = 0.75 cycles/deg; SD = 0.74; r2 = 0.980) and monotonic dependence on log contrast with a gradual saturation well described by the Naka-Rushton equation (on average: n = 0.89; C50 = 4.1%; r2 = 0.978). With gratings composed of two sine waves whose spatial frequencies were in the ratio 3:5 and whose disparities were of opposite sign (the 3f5f stimulus), responses were determined by the disparities and contrasts of the two sine-wave components rather than the disparity of the features, consistent with early spatial filtering of the monocular inputs before their binocular combination and mediation by detectors sensitive to disparity energy. In addition, responses to the 3f5f stimulus showed a nonlinear dependence on the relative contrasts of the two sine waves. Thus on average, when the contrast of one sine wave was 2.3 times greater than that of the other, the one with the lower contrast was largely ineffective as though suppressed, and responses were determined almost entirely by the sine wave of higher contrast: Winner-Take-All. These findings are very similar to those published previously on the vertical vergence responses of humans, indicating that the monkey provides a good animal model for studying these disparity vergence responses.

scholarly journals Periodically and quasi-periodically driven dynamics of Bose-Einstein condensates

2020 ◽  
Vol 9 (5) ◽  
Author(s):  
Pengfei Zhang ◽  
Yingfei Gu
Keyword(s):  
Phase Boundary ◽  
Quantum Dynamics ◽  
Scattering Length ◽  
Finite Measure ◽  
Sine Wave ◽  
Square Wave ◽  
Periodically Driven ◽  
Two Phases ◽  
Almost All ◽  
Bose Einstein

We study the quantum dynamics of Bose-Einstein condensates when the scattering length is modulated periodically or quasi-periodically in time within the Bogoliubov framework. For the periodically driven case, we consider two protocols where the modulation is a square-wave or a sine-wave. In both protocols for each fixed momentum, there are heating and non-heating phases, and a phase boundary between them. The two phases are distinguished by whether the number of excited particles grows exponentially or not. For the quasi-periodically driven case, we again consider two protocols: the square-wave quasi-periodicity, where the excitations are generated for almost all parameters as an analog of the Fibonacci-type quasi-crystal; and the sine-wave quasi-periodicity, where there is a finite measure parameter regime for the non-heating phase. We also plot the analogs of the Hofstadter butterfly for both protocols.

The Dependence of Monocular Rivalry on Spatial Frequency

Perception ◽  
1973 ◽  
Vol 2 (2) ◽  
pp. 127-133 ◽  
Author(s):  
J Atkinson ◽  
F W Campbell ◽  
A Fiorentini ◽  
L Maffei
Keyword(s):  
Spatial Frequency ◽  
Sine Wave ◽  
Ambiguous Figures ◽  
Alternation Rate ◽  
Higher Harmonics ◽  
Square Wave ◽  
Sharp Edges ◽  
Harmonic Components ◽  
Sine Wave Gratings

The effect of change in spatial frequency on the alternation rate of two crossed gratings was measured. The rate was found to decrease with increase in spatial frequency, but to change only little with contrast. Low alternation rate was observed for crossed square-wave gratings compared to crossed sine-wave gratings; here the rate of rivalry is largely dependent upon the presence or absence of the first three harmonic components rather than the higher harmonics which contribute to the sharp edges of the square wave. The results are compared with those for some ambiguous figures.

scholarly journals Comparative Evaluation of a Permanent Magnet Machine Saliency-Based Drive with Sine-Wave and Square-Wave Voltage Injection

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2189 ◽  
Author(s):  
Jyun-You Chen ◽  
Shih-Chin Yang ◽  
Kai-Hsiang Tu
Keyword(s):  
Permanent Magnet ◽  
Pulse Width Modulation ◽  
Dead Time ◽  
Sine Wave ◽  
Position Estimation ◽  
Feedback Signal ◽  
Estimation Errors ◽  
Square Wave ◽  
Position Errors ◽  
Voltage Signal

This paper improves a permanent magnet (PM) machine saliency-based drive performance based on the selection of a suitable injection signal. For the saliency-based position estimation, a persistently high-frequency (HF) voltage signal is injected to obtain a measurable spatial saliency feedback signal. The injection signal can be sine-wave or square-wave alternating current (AC) voltage manipulated by the inverter’s pulse width modulation (PWM). Due to the PWM dead-time effect, these HF voltage injection signals might be distorted, leading to secondary harmonics on the saliency signal. In addition, the flux saturation in machine rotors also results in other saliency harmonics. These nonlinear attributes cause position estimation errors on saliency-based drives. In this paper, two different voltage signals are analyzed to find a suited voltage which is less sensitive to these nonlinear attributes. Considering the inverter dead-time, a sine-wave voltage signal reduces its influence on the saliency signal. By contrast, the flux saturation causes the same amount of error on two injection signals. Analytical equations are developed to investigate position errors caused by the dead-time and flux saturation. An interior PM machine with the saliency ratio of 1.41 is tested for the experimental verification.

Velocity Computation from Measures of Spatiotemporal Gradients at Multiple Orientations

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 77-77 ◽  
Author(s):  
A Johnston ◽  
P W McOwan
Keyword(s):  
Natural Extension ◽  
Image Brightness ◽  
Motion Patterns ◽  
One Dimensional ◽  
Aperture Problem ◽  
Motion Models ◽  
Temporal Domain ◽  
Moving Stimulus ◽  
Zero Values ◽  
Derivatives Of

Current models of speed and direction of motion which use measures of spatiotemporal gradients can suffer from ill-conditioning. This problem arises either because local measures of the derivatives of image brightness take zero values or because the motion equations cannot be solved for one-dimensional (1-D) signals in two-dimensional (2-D) images—the aperture problem. One way around this predicament is to select image points or introduce constants to deal with ill-conditioned calculations. Here we describe an analytic method that combines measures of speed in a range of directions to provide a well-conditioned measure of velocity at all points in the moving stimulus. This approach is a natural extension of a one-dimensional model which has been successful in predicting perceived motion in a variety of 1-D spatiotemporal motion patterns (Johnston, McOwan and Buxton 1992 Proceedings of the Royal Society of London, Series B250 297 – 306). Speed is computed with the use of biologically plausible filters that are derivatives of Gaussians in the spatial domain and log Gaussians in the temporal domain. Measures of speed and inverse speed are computed for a range of orientations consistent with the number of direction columns in MT/V5. The pattern of velocities measured over this set of orientations is then used to recover the speed and direction of motion of the stimulus. The model can correctly compute the velocity of moving 1-D patterns, such as gratings, patterns that prove a problem for many current 2-D motion models as they form degenerate cases, as well as the motion of rigid 2-D patterns.

Temporal and Spatial Frequency Tuning of the Flicker Motion Aftereffect

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 12-12
Author(s):  
P J Bex ◽  
F A J Verstraten ◽  
I Mareschal
Keyword(s):  
Spatial Frequency ◽  
Frequency Tuning ◽  
Temporal Frequency ◽  
Motion Aftereffect ◽  
Sine Wave ◽  
Test Grating ◽  
Spatial Frequency Tuning ◽  
Spatial Frequencies ◽  
Low Pass ◽  
Sine Wave Gratings

The motion aftereffect (MAE) was used to study the temporal-frequency and spatial-frequency selectivity of the visual system at suprathreshold contrasts. Observers adapted to drifting sine-wave gratings of a range of spatial and temporal frequencies. The magnitude of the MAE induced by the adaptation was measured with counterphasing test gratings of a variety of spatial and temporal frequencies. Independently of the spatial or temporal frequency of the adapting grating, the largest MAE was found with slowly counterphasing test gratings (∼0.125 – 0.25 Hz). For slowly counterphasing test gratings (<∼2 Hz), the largest MAEs were found when the test grating was of similar spatial frequency to that of the adapting grating, even at very low spatial frequencies (0.125 cycle deg−1). However, such narrow spatial frequency tuning was lost when the temporal frequency of the test grating was increased. The data suggest that MAEs are dominated by a single, low-pass temporal-frequency mechanism and by a series of band-pass spatial-frequency mechanisms at low temporal frequencies. At higher test temporal frequencies, the loss of spatial-frequency tuning implicates separate mechanisms with broader spatial frequency tuning.

Local and Global Properties of Motion Aftereffects

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 170-170
Author(s):  
N J Wade ◽  
V Pardieu ◽  
M T Swanston
Keyword(s):  
Vision Research ◽  
Motion Aftereffect ◽  
Test Display ◽  
Adaptation Process ◽  
Local Motion ◽  
Motion Adaptation ◽  
Global Properties ◽  
Differential Adaptation ◽  
Induced Motion ◽  
Motion Aftereffects

The local motion adaptation at the basis of the motion aftereffect (MAE) can be expressed in a variety of ways, depending upon the structure of the test display (N J Wade, L Spillmann, M T Swanston Vision Research in press). This has been demonstrated with MAEs from induced motion: if adaptation is to two moving (Surround) gratings, an MAE is seen in the central grating if two gratings surround it, but in the flanking gratings when they are themselves surrounded in the test stimulus. We report two experiments in which the characteristics of the test display and of the local adaptation process have been examined. In experiment 1, five vertical gratings were presented during adaptation; the outermost and central gratings remained stationary and those flanking the centre moved laterally. The test display always consisted of three stationary gratings: either the central three or the lower three equivalent to the locations of the adaptation display. MAEs were only recorded in the Centre and not in the Surround, irrespective of whether the Centre or Surround had been exposed to motion during adaptation. MAEs in the Centre were in opposite directions, reflecting the influence of Surround adaptation. The influence of adapting motion in different directions was examined in experiment 2. The upper grating always received the same direction of motion during adaptation, and the lower grating was absent, stationary, or moving in the same or in the opposite direction. The results indicate that an MAE is visible in the upper grating only after differential adaptation between the upper and lower gratings.

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