INTERPRETATION OF THE TRANSIENT BEHAVIOR OF THE REFLECTION SEISMOGRAPH

Geophysics ◽  
1942 ◽  
Vol 7 (2) ◽  
pp. 123-132 ◽  
Author(s):  
R. G. Piety
Keyword(s):  
High Frequency ◽  
Arrival Time ◽  
Graphical Method ◽  
Transient Behavior ◽  
Unit Impulse ◽  
Impulsive Response ◽  
Actual Response ◽  
Method Of Design

This paper discusses a method of design for the reflection seismograph based on the galvanometer response when the geophone is subject to a unit impulse. A graphical method of obtaining the actual response to an arbitrary geophone motion in terms of the impulsive response is given. A family of desirable types of impulsive response is obtained by analyzing the implications of this graphical computation when strong low and high frequency interference is present. The application of this method of computation to the evaluation of corrections in the apparent arrival time of reflections obtained with different instruments is outlined.

On the effectiveness of ventilation to mitigate the damage of spherical membrane vessels subjected to internal detonations

2020 ◽  
Vol 11 (3) ◽  
pp. 319-339
Author(s):  
Francisco Hernandez ◽  
Xihong Zhang ◽  
Hong Hao
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
High Frequency ◽  
Arrival Time ◽  
Time Lag ◽  
Reflected Shock Wave ◽  
High Explosives ◽  
Element Analysis ◽  
Blast Overpressure ◽  
Reflected Shock

This article conducts a comparative study on the effectiveness of ventilation to mitigate blasting effects on spherical chambers subjected to internal detonations of high explosives through finite element analysis using the software package AUTODYN. Numerical simulations show that ventilation is ineffective in mitigating the damage of spherical chambers subjected to internal high explosives explosions because the chamber response is mainly described by high-frequency membrane modes. Openings do not reduce the chamber response despite they can reduce the blast overpressure after the chamber reaches its peak response. Worse still, openings lead to stress concentration, which weakens the structure. Therefore, small openings may reduce the capacity of the chamber to resist internal explosions. In addition, because large shock waves impose the chamber to respond to a reverberation frequency associated with the re-reflected shock wave pulses, secondary re-reflected shock waves can govern the chamber response, and plastic/elastic resonance can occur to the chamber. Simulations show that the time lag between the first and the second shock wave ranges from 3 to 7 times the arrival time of the first shock wave, implying that the current simplified design approach should be revised. The response of chambers subjected to eccentric detonations is also studied. Results show that due to asymmetric explosions, other membrane modes may govern the chamber response and causes localized damage, implying that ventilation is also ineffective to mitigate the damage of spherical chambers subjected to eccentric detonations.

scholarly journals GABA Shapes Selectivity for the Rate and Direction of Frequency-Modulated Sweeps in the Auditory Cortex

2009 ◽  
Vol 102 (3) ◽  
pp. 1366-1378 ◽  
Author(s):  
Khaleel A. Razak ◽  
Zoltan M. Fuzessery
Keyword(s):  
Auditory Cortex ◽  
Gabaa Receptor ◽  
Gabaa Receptors ◽  
High Frequency ◽  
Arrival Time ◽  
Low Frequency ◽  
Direction Selectivity ◽  
Similar Response ◽  
Cortical Level ◽  
Pallid Bat

In the pallid bat auditory cortex and inferior colliculus (IC), the majority of neurons tuned in the echolocation range is selective for the direction and rate of frequency-modulated (FM) sweeps used in echolocation. Such selectivity is shaped mainly by spectrotemporal asymmetries in sideband inhibition. An early-arriving, low-frequency inhibition (LFI) shapes direction selectivity. A delayed, high-frequency inhibition (HFI) shapes rate selectivity for downward sweeps. Using iontophoretic blockade of GABAa receptors, we show that cortical FM sweep selectivity is at least partially shaped locally. GABAa receptor antagonists, bicuculline or gabazine, reduced or eliminated direction and rate selectivity in ∼50% of neurons. Intracortical GABA shapes FM sweep selectivity by either creating the underlying sideband inhibition or by advancing the arrival time of inhibition relative to excitation. Given that FM sweep selectivity and asymmetries in sideband inhibition are already present in the IC, these data suggest a refinement or recreation of similar response properties at the cortical level.

Pulsar Timing Observations at Tidbinbilla

1976 ◽  
Vol 3 (1) ◽  
pp. 81-83 ◽  
Author(s):  
R. N. Manchester ◽  
W. M. Goss ◽  
Lynette M. Newton ◽  
P. A. Hamilton
Keyword(s):  
Faraday Rotation ◽  
High Frequency ◽  
Pulse Shape ◽  
Arrival Time ◽  
Dispersion Measure ◽  
Pulse Arrival Time ◽  
Pulsar Timing ◽  
One Year ◽  
Pulse Arrival

Pulse arrival time measurements allow the determination of accurate pulsar periods, period derivatives and, provided the data span is at least one year, precise pulsar positions. If observations are frequent and reasonably regular, irregularities in the period can also be investigated. To minimize the effect of possible variations in dispersion measure, it is important that these observations be made at a relatively high frequency, preferably above 1 GHz. To eliminate pulse shape variations due to variable ionospheric Faraday rotation, the pulse total intensity or one of the circular polarizations must be recorded.

Prediction of Time-Varying Vibroacoustic Energy Using a New Energy Approach

2004 ◽  
Vol 126 (2) ◽  
pp. 184-189 ◽  
Author(s):  
F. Sui ◽  
M. N. Ichchou
Keyword(s):  
High Frequency ◽  
Energy Equation ◽  
Transport Theory ◽  
Energy Balance Equation ◽  
Time Varying ◽  
Conductivity Equation ◽  
Dispersive Effect ◽  
Energetic Approach ◽  
Unit Impulse ◽  
New Energy

A new energetic approach is proposed to predict the time-varying dynamic response in the vibroacoustic field. This approach is based on the derivation and development of a hyperbolic type energy equation. It can be derived from the transport theory, or obtained by applying fundamental energy balance equation. The focus of this paper is to compare this new energy equation with the time-varying vibrational conductivity equation used extensively in recent study of energy approaches in mid-high frequency domain. The new energy equation is evaluated numerically by comparing its solutions with the diffusion equation and exact energy results. The comparative studies are applied to a beam subjected to a transverse unit impulse, and the dispersive effect is considered.

Auditory Mechanisms of Echolocation in Bats

2018 ◽  
Author(s):  
Cynthia F. Moss
Keyword(s):  
High Frequency ◽  
Arrival Time ◽  
Brain Regions ◽  
Frequency Content ◽  
Complete Darkness ◽  
3D Perception ◽  
Sensing System ◽  
Motor Circuits ◽  
Premotor Neurons ◽  
Sonar Echoes

Echolocating bats have evolved an active sensing system, which supports 3D perception of objects in the surroundings and permits spatial navigation in complete darkness. Echolocating animals produce high frequency sounds and use the arrival time, intensity, and frequency content of echo returns to determine the distance, direction, and features of objects in the environment. Over 1,000 species of bats echolocate with signals produced in their larynges. They use diverse sonar signal designs, operate in habitats ranging from tropical rain forest to desert, and forage for different foods, including insects, fruit, nectar, small vertebrates, and even blood. Specializations of the mammalian auditory system, coupled with high frequency hearing, enable spatial imaging by echolocation in bats. Specifically, populations of neurons in the bat central nervous system respond selectively to the direction and delay of sonar echoes. In addition, premotor neurons in the bat brain are implicated in the production of sonar calls, along with movement of the head and ears. Audio-motor circuits, within and across brain regions, lay the neural foundation for acoustic orientation by echolocation in bats.

Application of Resonant Circuit Theory to Matching Networks

1981 ◽  
Vol 18 (4) ◽  
pp. 351-358
Author(s):  
R. Armstrong ◽  
E. Korolkiewicz
Keyword(s):  
High Frequency ◽  
Communication Systems ◽  
Graphical Method ◽  
Circuit Theory ◽  
Resonant Circuit ◽  
Valuable Insight ◽  
Matching Networks ◽  
Insight Into ◽  
Smith Chart

A wide variety of matching networks are used in high frequency communication systems and this paper shows how such networks can be conveniently designed using the theory of resonant circuits. A graphical method is also included which provides a valuable insight into the properties of the Smith Chart.

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