STOCHASTIC RESPONSE OF A SDOF NONLINEAR SYSTEM SUBJECTED TO THE WAVES GENERATED BY MEANS OF PHASE DIFFERENCE CHARACTERISTIC IN NARROW FREQUENCY BANDS

In interferometers where a wave is divided into two beams that propagate along separate branches before being recombined, the closed circuit formed by the two branches must be threaded by wave dislocation lines. For a large class of interferometers, it is shown that the (signed) dislocation number, defined in a suitable asymptotic sense, jumps by +1 as the phase difference between the beams increases by 2 π . The argument is based on the single-valuedness of the wave function in the branches and leaking between them. In some cases, the jumps occur when the phase difference is an odd multiple of π . The same result holds for the Aharonov–Bohm wave function, where the waves passing above and below a flux line experience different phase shifts; in this case, where the wave is not concentrated onto branches, the threading dislocations coincide with the flux line.

Download Full-text

Estimation of Damping Correction Factors Using Duration Defined by the Standard Deviation of Phase Difference

Earthquake Spectra ◽

10.1193/103012eqs321m ◽

2015 ◽

Vol 31 (2) ◽

pp. 761-783 ◽

Cited By ~ 3

Author(s):

Kenichi Nagao ◽

Jun Kanda

Keyword(s):

Standard Deviation ◽

Phase Difference ◽

Low Frequency ◽

Response Spectra ◽

Correction Factors ◽

Acceleration Response ◽

Ground Motion Simulation ◽

Frequency Bands ◽

Different Types ◽

Opposite Tendency

The damping correction factors (DCFs) to convert the 5% damping acceleration response spectra to those for other damping levels are computed for the records of 13 Japanese earthquakes. Their correlation with the standard deviation of phase difference ( σ) is also investigated in ten frequency bands. The σ-DCF relations obtained are found to be very similar across the different types of earthquakes. Further, regression analysis suggests that for damping ratios of 1% and 2%, with the increase in σ, the DCFs increase in low-frequency bands (up to 4–5 Hz), whereas they decrease in higher frequency bands. On the other hand, for damping ratios of more than 5%, with the increase in σ, the DCFs decrease in low-frequency bands (up to 1 Hz), whereas the opposite tendency is observed in higher frequency ranges. This research also discusses the applicability of the σ-DCF relations to design ground motion simulation.

Download Full-text

Influence of Background Noise Produced in University Facilities on the Brain Waves Associated With Attention of Students and Employees

Perception ◽

10.1177/0301006617700672 ◽

2017 ◽

Vol 46 (9) ◽

pp. 1105-1117

Author(s):

E. Trista´n-Hernández ◽

I. Pav´on-García ◽

I. Campos-Cantón ◽

L. J. Ontaño´n-García ◽

E. S. Kolosovas-Machuca

Keyword(s):

Background Noise ◽

Work Performance ◽

Noise Exposure ◽

Specific Task ◽

Frequency Bands ◽

Brain Waves ◽

Theta Frequency ◽

Noisy Conditions ◽

The Waves ◽

The Brain

As a consequence of noise exposure, lack of attention badly affects directly the academic and work performance. The study of the brain and the waves that it produces is the most objective way to evaluate this process. Attentional improvement is associated with increases of the amplitude in both beta and theta bands. The objective of this work is to study the influence of background noise produced inside university facilities on changes in the cerebral waves related to attention processes (beta 13–30 Hz and theta 4–7 Hz). Volunteers were asked to perform a specific task in which attention was involved. This task was performed in both silent and noisy conditions. To evaluate the cerebral activity of volunteers during the development of the test, measurement of spontaneous activity (electroencephalogram) was developed. The results show significant decreases in both beta and theta frequency bands under background noise exposure. Since attentional improvement is related to an increment on amplitude of both beta and theta bands, it is suggested that decreases on amplitude of these frequency bands could directly be related to a lack of attention caused by the exposure to background noise.

Download Full-text

The Movement of the Spermatozoa of the Bull

Journal of Experimental Biology ◽

10.1242/jeb.35.1.96 ◽

1958 ◽

Vol 35 (1) ◽

pp. 96-108 ◽

Cited By ~ 2

Author(s):

J. GRAY

Keyword(s):

Phase Difference ◽

Transverse Velocity ◽

Longitudinal Axis ◽

Average Frequency ◽

Whole Cell ◽

Bending Waves ◽

Transverse Movement ◽

Speed Of Propagation ◽

The Waves ◽

Bending Wave

1. The maximum extent to which an element of the tail of a bull's spermatozoon bends during its contractile cycle is not the same for all elements; the nearer the element lies towards the tip of the tail the greater is the amount of bending. 2. The phase difference between successive elements varies along the length of the tail; and consequently the speed of propagation of the bending wave decreases as the latter moves backwards. 3. The amplitude of transverse movement relative to the head increases progressively along the tail towards the distal end. 4. Distal elements execute figure-of-eight movements relative to the head. 5. The frequency of the bending cycles and the propulsive velocity of the whole cell vary considerably. The average frequency for thirty-one cells was 9.1/sec., and the average propulsive speed for 235 cells was 94 µsec. 6. Cells moving freely in water ‘flashed’ with a frequency similar to that of the bending waves. The rotation of the head about its longitudinal axis appears to be due to the fact that all elements of the tail are not executing their transverse movements in exactly the same plane during the whole of their contractile cycles. 7. The rate at which an element can propel itself forward cannot be greater than about one-third to one-quarter of its average transverse velocity. 8. The distal elements of the tail exert their propulsive effort against the fulcrum provided by the proximal elements. 9. It is impracticable to relate the speed of propulsion to the form and speed of propagation of the waves passing along the tail.

Download Full-text