scholarly journals Comparing the broadband acoustic frequency response of single, clustered, and arrays of marine air guns

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. P27-P36
Author(s):  
Martin Landrø ◽  
Jan Langhammer
Keyword(s):  
Acoustic Signal ◽  
High Frequency ◽  
High Speed ◽  
Acoustic Stimulation ◽  
Main Peak ◽  
Water Tank ◽  
High Frequency Signal ◽  
Acoustic Frequency ◽  
Air Gun ◽  
Marine Air

Field data acquired from a seismic vessel by a seabed hydrophone is used to analyze the broadband response (10 Hz to 62.5 kHz) for various source configurations: single air guns, clustered air guns, and a full array consisting of 30 air guns. The various parts of the acoustic signal are analyzed in detail, and it is found that a high-frequency signal arriving prior to the main peak of a single air-gun signal most likely is caused by small vapor cavities collapsing at or close to the surface of the gun. This is confirmed by high-speed photographs taken when a small air gun is fired in a water tank. When the full array is used, a second type of cavitation signal is observed: ghost cavitation caused by acoustic stimulation by the negative pressure that is backscattered from the free surface. As this ghost signal from 30 different guns arrives at a specific location in the water, cavities might be formed, and they create a high-frequency acoustic signal.

Repeatability issues of high-frequency signals emitted by air-gun arrays

Geophysics ◽  
2013 ◽  
Vol 78 (6) ◽  
pp. P19-P27 ◽  
Author(s):  
Martin Landrø ◽  
Lasse Amundsen ◽  
Jan Langhammer
Keyword(s):  
High Frequency ◽  
Field Measurements ◽  
Typical Feature ◽  
Main Peak ◽  
Frequency Signal ◽  
High Frequency Signal ◽  
Surface Reflection ◽  
Air Gun ◽  
Source Signal ◽  
Marine Seismic

Recent field measurements of the acoustic signals generated by marine seismic air-gun arrays showed that the amount of high-frequency signals (above 10 kHz) increased with the size and total volume of the gun array. We found that for frequencies between 10 and 20 kHz, a strong signal is observed 7–14 ms after the main peak of the source signal. We believe that this signal was generated by ghost cavitation. We observed that this signal was significantly stronger than the high-frequency signal generated at the same time as the peak signal occurs within the bandwidth between 10 and 20 kHz. We found that this high-frequency signal was fairly repeatable from one shot to another. By “fairly,” we mean that individual high-frequency events were not repeatable; however, the envelope energy of this cascade of events was repeatable from one shot to another. The typical feature of the envelope of the high-frequency signal was that it lasted for approximately 6–7 ms and showed a monotonic increase in amplitude for the first 5–6 ms, followed by a sudden drop. The sea surface reflection coefficient for these high-frequency events seemed to decrease in magnitude as the frequency increased.

scholarly journals Reducing high-frequency ghost cavitation signals from marine air-gun arrays

Geophysics ◽  
2016 ◽  
Vol 81 (3) ◽  
pp. P33-P46 ◽  
Author(s):  
Martin Landrø ◽  
Yuan Ni ◽  
Lasse Amundsen
Keyword(s):  
High Frequency ◽  
Separation Distance ◽  
Signal Model ◽  
Frequency Signal ◽  
High Frequency Signal ◽  
Array Configuration ◽  
Air Gun ◽  
Marine Air ◽  
Potential Signal ◽  
Source Array

Ghost cavitation, which is a term describing that cavitation bubbles are generated acoustically, has been hypothesized to occur when the ghost reflected signals from many individual air guns beneath the sea surface produce a pressure that is close to zero in the water above the source array. Ghost cavitation is typically observed some milliseconds after the ghost reflection, and it may last for 5–15 ms, depending on the configuration of the source array. The cavitation process subsequently generates a weak high-frequency signal. To investigate this potential signal model and mechanism, we have performed a dedicated source experiment. We found that the distance between the source strings in a source array is a major factor that influences the amount and strength of the high-frequency signal. By increasing the separation distance from 6.5 to 8 m, we have observed a significant decrease in the high-frequency signal. Further, the amount of ghost cavitation can be reduced by increasing the distance between the guns. Also single sub-arrays may create ghost cavitation sound, of course weaker in signal strength compared with full arrays, in agreement with the model. Conventional air-gun modeling can be used to predict where ghost cavitation can occur. Therefore, in principle, a workflow could be developed to quantify grossly if and how much high-frequency signals could be generated by this mechanism, given the source array configuration, and further change the configuration to reduce to a very minimum the high-frequency signals, if deemed necessary. For an air-gun array consisting of two subarrays separated by 6 m and fired at 9 m depth, we found that the high-frequency signals emitted between 1 and 10 kHz were of similar strength to the noise from conventional cargo ships, depending on their size and the vessels’ speed.

scholarly journals Detecting gas leakage using high-frequency signals generated by air-gun arrays

Geophysics ◽  
2017 ◽  
Vol 82 (2) ◽  
pp. A7-A12 ◽  
Author(s):  
Martin Landrø ◽  
Fredrik Hansteen ◽  
Lasse Amundsen
Keyword(s):  
High Frequency ◽  
Field Experiments ◽  
Water Layer ◽  
Sampling Interval ◽  
Acoustic Energy ◽  
Storage Site ◽  
High Frequency Signal ◽  
Gas Leakage ◽  
Temporal Sampling ◽  
Air Gun

Recent field experiments have demonstrated that marine air-gun arrays create acoustic energy greater than 1 kHz. We have suggested to use the high-frequency signal as a source to look for gas leakage at, for instance, a producing hydrocarbon field, or a [Formula: see text] storage site in which the field is covered by permanent acoustic sensors at the seabed, often referred to as a permanent reservoir monitoring field. The only needed modification is that the temporal sampling interval for the receivers is decreased to 0.1 ms (in contrast to the normal sampling interval of 1 or 2 ms), to ensure that the system is capable of recording signals up to 5 kHz. We suggest using numerous fixed receivers at the seabed to detect a gas chimney by simple high-pass filtering and subsequent transmission type analysis of the recorded signals. We think this method might serve as an elegant, precise, and very cost-effective way to detect gas leakage into the water layer.

Combined Back-EMF Estimator with High-Frequency Signal Injection for Wide Speed Range Sensorless Control of PMLSM

2013 ◽  
Vol 753-755 ◽  
pp. 1405-1408
Author(s):  
Hua Cai Lu ◽  
Xuan Yu Yao ◽  
Juan Ti
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Sensorless Control ◽  
Estimation Method ◽  
Detection Algorithm ◽  
Estimation Accuracy ◽  
High Frequency Signal ◽  
Weighting Method ◽  
Transition Speed ◽  
Signal Injection

This paper describes a composite sensorless position and speed detection algorithm designed for permanent magnet linear synchronous motor (PMLSM). A high-frequency voltage signal injection method is used at starting and low speed, and a back-EMF integrate method is used at high speed, and the two kinds of method are fused by weighting method in the transition speed area. Simulation results show that estimation accuracy of this composite estimation method is satisfactory, and the sensorless control system based on this method has good dynamic response characteristics within full speed.

Study on High-Speed Switch Shifting Solenoid Current Control Technology for Automatic Transmission

2014 ◽  
Vol 1006-1007 ◽  
pp. 639-642
Author(s):  
Chun Fu Li ◽  
Yan Qin Li
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Automatic Transmission ◽  
Current Control ◽  
Control Technology ◽  
Working Process ◽  
Frequency Signal ◽  
High Frequency Signal ◽  
Long Time ◽  
The Ideal

The purpose of the solenoid current control is to decrease holding current of the solenoid by selecting suitable frequency and duty, to keep the solenoid opening reliably for a long time and reduce power consumption and improve the solenoid close feature. In this paper, the high frequency signal in oil pressure holding process is determined by theoretical analysis and experimental study. The purpose of the study is to determine the ideal current in the working process of the solenoid.

A simple method for determining the S80 water gun depth

Geophysics ◽  
1986 ◽  
Vol 51 (2) ◽  
pp. 424-426 ◽  
Author(s):  
M. H. Safar
Keyword(s):  
High Resolution ◽  
High Frequency ◽  
Seismic Source ◽  
Frequency Signal ◽  
High Frequency Signal ◽  
Simple Method ◽  
Marine Oil ◽  
Principal Reason ◽  
Air Gun ◽  
High Level

The water gun, which is becoming a popular seismic source, has proven to be an important development in marine oil prospecting. The principal reason is that, unlike the air gun, the pressure signature radiated by the water gun consists of a single bubble pulse and contains a high level of high‐frequency signal. These important features make the water gun a suitable seismic source for high‐resolution surveys. Water guns currently used are the S80, which has been used by Horizon since 1977, and the P400, introduced in 1983. The S80 and P400 water guns were developed by Sodera.™

High Frequency Signal Propagation in Through Silicon Vias

2012 ◽  
Vol 2012 (1) ◽  
pp. 000239-000243
Author(s):  
Srinidhi Raghavan Narasimhan ◽  
A. Ege Engin
Keyword(s):  
Wave Propagation ◽  
High Frequency ◽  
High Speed ◽  
Signal Propagation ◽  
Successful Implementation ◽  
High Frequency Signal ◽  
3D Ic ◽  
Through Silicon Vias ◽  
Integration Technology ◽  
Silicon Vias

The 3D IC integration technology and silicon interposers rely on through silicon vias (TSVs) for vertical interconnections. Hence, the medium carrying high frequency signals is lossy silicon (Si). Fundamental understanding of wave propagation through TSVs is essential for successful implementation of 3D IC integration technology as well as for the development of Si interposers at RF/microwave frequencies. The focus of this paper is characterization and modelling of TSVs and Si to explore high speed signal propagation through the lossy Si medium. To understand better the physical significance of the TSV, we will establish a framework for wave propagation through TSVs based on dielectric quasi-TEM, skin effect, and slow-wave modes similar to MIS micro-strip lines. For validation of the existence of these modes, full wave simulation results will be compared with simpler two dimensional transmission line simulators.

scholarly journals Wall pressure beneath a transitional hypersonic boundary layer over an inclined straight circular cone

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Siwei Dong ◽  
Jianqiang Chen ◽  
Xianxu Yuan ◽  
Xi Chen ◽  
Guoliang Xu
Keyword(s):  
Boundary Layer ◽  
High Frequency ◽  
High Speed ◽  
Low Frequency ◽  
Axial Direction ◽  
Wall Pressure ◽  
Hypersonic Boundary Layer ◽  
High Frequency Signal ◽  
Local Boundary ◽  
Half Angle

AbstractProperties of wall pressure beneath a transitional hypersonic boundary layer over a 7∘ half-angle blunt cone at angle of attack 6∘ are studied by Direct Numerical Simulation. The wall pressure has two distinct frequency peaks. The low-frequency peak with f≈10−50 kHz is very likely the unsteady crossflow mode based on its convection direction, i.e. along the axial direction and towards the windward symmetry ray. High-frequency peaks are roughly proportional to the local boundary layer thickness. Along the trajectories of stationary crossflow vortices, the location of intense high-frequency wall pressure moves from the bottom of trough where the boundary layer is thin to the bottom of shoulder where the boundary layer is thick. By comparing the pressure field with that inside a high-speed transitional swept-wing boundary layer dominated by the z-type secondary crossflow mode, we found that the high-frequency signal originates from the Mack mode and evolves into the secondary crossflow instability.

High Speed Signal Transmission using Through-Si Vias and Coplanar Waveguides in a 3D IC Test Structure

2013 ◽  
Vol 2013 (1) ◽  
pp. 000228-000232
Author(s):  
Min Xu ◽  
Robert Geer ◽  
Pavel Kabos ◽  
Thomas Wallis
Keyword(s):  
Integrated Circuits ◽  
High Frequency ◽  
High Speed ◽  
Signal Transmission ◽  
Coplanar Waveguides ◽  
Scattering Parameter ◽  
High Frequency Signal ◽  
3D Integrated Circuits ◽  
High Bandwidth ◽  
Silicon Vias

High frequency signal transmission through silicon substrates is critical for 3D heterogeneous integration. This paper presented fabrication, testing, and simulation of high-frequency interconnects based on through-silicon vias (TSVs) and coplanar waveguides (CPWs) for stacked 3D integrated circuits (3D ICs). Our simulation results showed that adding ground TSVs can improve signal transmission by 6× at 50GHz. We further investigated signal/ground TSV (1SXG) configurations for high-bandwidth signal transmission links. Scattering parameter measurements of fabricated 1SXG TSV structures for frequencies from 100MHz to 50GHz show low insertion loss (S21 less than −1dB up to 50GHz) and return loss (S11 lower than −15dB). These results indicate that these vertical interconnects exhibit good performance for high speed signal transmission. To understand the RF signal transmission in 3D interconnects, we used full wave electromagnetic simulation to investigate the electromagnetic field distribution associated with the ground TSV placement. We observed that the ground TSVs induced substantial overall field confinement, consistent with the experimental observation of improved signal transmission. Simulations also provided design guidance with respect to the substrate conductivity's impact on EM confinement and signal transmission.

A Practical Method for Trace Exposure and Roughness Measurements and Implementation in High Speed Package Design

2012 ◽  
Author(s):  
Valentina Korchnoy ◽  
Jacov Brener
Keyword(s):  
Transmission Lines ◽  
Insertion Loss ◽  
High Frequency ◽  
High Speed ◽  
Transmission Loss ◽  
Signal Propagation ◽  
Practical Method ◽  
High Frequency Signal ◽  
Advantages And Disadvantages ◽  
Conductor Surface

Abstract High frequency signal propagation through transmission lines has been an important discipline for RF engineers. With advancements in digital technologies, especially when data rates reached multiple Gb/s, package designers have to consider parameters such as transmission loss and trace impedance in order to maintain signal integrity. For high frequency signals, the surface roughness of the copper trace becomes increasingly significant in determining conduction loss, due to current confinement to the conductor surface by the skin effect. Accurate 3D conductor surface maps are required for correct trace insertion loss simulation. Practical methods for package trace exposure and 3D surface height map acquisition are discussed in this paper. Advantages and disadvantages of these methods, and their implementation to real packages are shown. Using electrical parameters resulting from a 3D trace surface map, the error between electrical simulations and actual measurements of insertion loss in an FCBGA package have been reduced from 6% to nearly zero, enabling tighter margins in 10GB/s high speed serial design.

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