MODEL RESULTS AND FIELD CHECKS FOR A TIME‐DOMAIN, AIRBORNE EM SYSTEM

Geophysics ◽  
1973 ◽  
Vol 38 (5) ◽  
pp. 845-853 ◽  
Author(s):  
Philip H. Nelson
Keyword(s):  
Time Domain ◽  
Scale Model ◽  
Large Lake ◽  
Response Curves ◽  
Channel Response ◽  
Airborne Em ◽  
Good Agreement

The airborne EM system known as Input was calibrated by applying theoretical homogeneous earth response curves to the response obtained on a flight over a large lake of known resistivity. The calibrated response curves for the conductive overburden case agree with field results in that 1) overburden resistivity in excess of 100 ohm‐m produces negligible deflection on the receiver channels, and 2) the maximum channel response occurs between 1 and 10 ohm‐m overburden resistivity. The calibrated response curves for scale model vertical sheets show fair to good agreement with the response to steeply dipping conductors which have been confirmed with ground‐based EM and drilling. The calibrated scale model results also show: 1) The system possesses a “passband” in conductivity‐thickness, with the first channel peaking around 10 mhos and the later channels at progressively higher values, with the sixth channel peaking at 25 mhos. 2) If a conservative detection cutoff is applied, a vertical conductor will not produce a four‐channel anomaly if it is much deeper than 200 ft subsurface for an aircraft elevation of 400 ft. 3) Channel ratios are constant with depth and also fairly constant over the 10–100 mhos range in conductivity‐thickness.

THEORETICAL RESPONSE OF A TIME‐DOMAIN, AIRBORNE, ELECTROMAGNETIC SYSTEM

Geophysics ◽  
1969 ◽  
Vol 34 (5) ◽  
pp. 729-738 ◽  
Author(s):  
P. H. Nelson ◽  
D. B. Morris
Keyword(s):  
Time Domain ◽  
Computational Procedure ◽  
Response Curves ◽  
Electromagnetic System ◽  
Magnetic Dipoles ◽  
System Calibration ◽  
Input System ◽  
Airborne Electromagnetic ◽  
Airborne Em ◽  
Thickness Parameter

The secondary magnetic field induced by a time‐domain, airborne EM system is calculated by transforming the tabulated mutual impedances of two magnetic dipoles above an earth of homogeneous or layered resistivity structure. The computational procedure is extended to produce response curves useful in interpreting data from a particular system, the Barringer Input system. It is demonstrated that the apparent resistivity can be estimated through use of the receiver channel ratios, a method which is independent of absolute system calibration. Layered earth calculations indicate to what extent conductive overburden cases can be readily distinguished, in terms of the conductivity‐thickness parameter, but separate interpretation of layer resistivity and thickness will require an amplitude‐calibrated flight system.

INPUT AEM Results from Project Pioneer, Manitoba

1975 ◽  
Vol 12 (6) ◽  
pp. 971-981
Author(s):  
A. V. Dyck ◽  
A. Becker ◽  
L. S. Collett
Keyword(s):  
Time Domain ◽  
Vertical Axis ◽  
Structural Features ◽  
Geological Mapping ◽  
Geological Survey ◽  
Scale Model ◽  
Potential Contribution ◽  
Input System ◽  
Interpretation Process ◽  
Airborne Em

The results of an airborne EM survey obtained with an INPUT system flown in the vertical-axis-receiver configuration have been assessed by the Geological Survey of Canada as favorable in terms of their potential contribution to the geological mapping carried out in the Project Pioneer study. Manitoba, Canada. Time-domain scale model profiles over the various conductor arrangements presented here have proven indispensable in the interpretation process. An outstanding example of this is the striking modification to an overburden anomaly made possible by the fortuitous location and dip of a conducting dike model below the overburden. The investigation indicates that during the course of an exploration survey, IN PUT data may be used directly to aid in the mapping of structural features or, indirectly in areas of conductive overburden, if the overburden is structurally controlled.

3-D Time-Domain Airborne EM Inversion for a Topographic Earth

2020 ◽  
pp. 1-13
Author(s):  
Yanfu Qi ◽  
Xiu Li ◽  
Changchun Yin ◽  
Huaiyuan Li ◽  
Zhipeng Qi ◽  
...  
Keyword(s):  
Time Domain ◽  
Airborne Em

High Amplitude Sound Propagation at Low Frequencies in a Flow Duct Lined With Resonators: A Time Domain Solution

1988 ◽  
Vol 110 (4) ◽  
pp. 545-551 ◽  
Author(s):  
A. Cummings ◽  
I.-J. Chang
Keyword(s):  
Time Domain ◽  
Internal Combustion Engines ◽  
Sound Propagation ◽  
Sound Field ◽  
High Amplitude ◽  
Combustion Engines ◽  
Low Frequencies ◽  
The Time Domain ◽  
Flow Duct ◽  
Good Agreement

A quasi one-dimensional analysis of sound transmission in a flow duct lined with an array of nonlinear resonators is described. The solution to the equations describing the sound field and the hydrodynamic flow in the neighborhood of the resonator orifices is performed numerically in the time domain, with the object of properly accounting for the nonlinear interaction between the acoustic field and the resonators. Experimental data are compared to numerical computations in the time domain and generally very good agreement is noted. The method described here may readily be extended for use in the design of exhaust mufflers for internal combustion engines.

Focusing Technique for Holographic Subsurface Radar Based on Image Entropy

2021 ◽  
Vol 36 (4) ◽  
pp. 373-378
Author(s):  
Haewon Jung ◽  
Dal-Jae Yun ◽  
Hoon Kang
Keyword(s):  
Numerical Simulation ◽  
Time Domain ◽  
Finite Difference Time Domain ◽  
Software Package ◽  
Reconstruction Algorithm ◽  
Simulation Software ◽  
Material Information ◽  
Difference Time ◽  
Actual Depth ◽  
Good Agreement

An image focusing method for holographic subsurface radar (HSR) is proposed herein. HSR is increasingly being utilized to survey objects buried at shallow depths and the acquired signals are converted into an image by a reconstruction algorithm. However, that algorithm requires actual depth and material information or depends on human decisions. In this paper, an entropy-based image focusing technique is proposed and validated by numerical simulation software package based on finite-difference time-domain method and experiment. The resulting images show good agreement with the actual positions and shapes of the targets.

The airborne electromagnetic discovery of the Detour zinc‐copper‐silver deposit, northwestern Québec

Geophysics ◽  
1981 ◽  
Vol 46 (9) ◽  
pp. 1278-1290 ◽  
Author(s):  
L. E. Reed
Keyword(s):  
Volcanic Rocks ◽  
Channel Response ◽  
Copper Sulfides ◽  
Input System ◽  
Diamond Drill ◽  
Geophysical Surveys ◽  
Airborne Electromagnetic ◽  
Airborne Em ◽  
Two Bodies

In June 1974, a diamond drill operated for Selco Mining Corp. intersected zinc‐copper sulfides in Brouillan Township in northwestern Québec. To date, two bodies have been outlined. These bodies were discovered during a ground follow‐up of a Mark VI Input® electromagnetic (EM) survey. The Input survey covered an area selected on the basis of regional geology and local outcrops of acid volcanic rocks. Conductors were identified that appeared to be associated with potentially favorable geology. They were selected for ground follow‐up. One was the discovery zone. The airborne responses over the zone were less encouraging than those often observed over highly conductive massive sulfides. The low apparent conductivity‐thickness (5 mhos) was suggestive of conductive overburden. However, the character of the profiles suggested a bedrock source. Ground geophysical confirmation identified a drill target. Subsequent to the discovery, more intensive geophysical surveys, both ground and airborne, were carried out. The best EM response suggested a confined source within a much larger mineralized halo. Weaker ground EM response from the halo correlated with the early channel response of the Input system. An airborne EM survey conducted in 1958 over the same area identified both conductive zones. However, they were not followed up. Only with later advances in exploration philosophy, geologic appreciation, and instrumentation were the conductive zones recognized as viable exploration targets.

Free and Forced Vibrations of the Strongly Nonlinear Cubic-Quintic Duffing Oscillators

2017 ◽  
Vol 72 (1) ◽  
pp. 59-69 ◽  
Author(s):  
M.M. Fatih Karahan ◽  
Mehmet Pakdemirli
Keyword(s):  
Numerical Simulations ◽  
Numerical Solutions ◽  
Multiple Scales ◽  
Approximate Solutions ◽  
Response Curves ◽  
Strongly Nonlinear ◽  
Free And Forced Vibrations ◽  
Approximate Analytical Solutions ◽  
Strongly Nonlinear Oscillators ◽  
Good Agreement

AbstractStrongly nonlinear cubic-quintic Duffing oscillatoris considered. Approximate solutions are derived using the multiple scales Lindstedt Poincare method (MSLP), a relatively new method developed for strongly nonlinear oscillators. The free undamped oscillator is considered first. Approximate analytical solutions of the MSLP are contrasted with the classical multiple scales (MS) method and numerical simulations. It is found that contrary to the classical MS method, the MSLP can provide acceptable solutions for the case of strong nonlinearities. Next, the forced and damped case is treated. Frequency response curves of both the MS and MSLP methods are obtained and contrasted with the numerical solutions. The MSLP method and numerical simulations are in good agreement while there are discrepancies between the MS and numerical solutions.

3D parallel inversion of time-domain airborne EM data

2016 ◽  
Vol 13 (4) ◽  
pp. 701-711 ◽  
Author(s):  
Yun-He Liu ◽  
Chang-Chun Yin ◽  
Xiu-Yan Ren ◽  
Chang-Kai Qiu
Keyword(s):  
Time Domain ◽  
Airborne Em

Identification of the Velocity, Thickness, and Interfacial Roughness of Coating Using Full Time-Domain URCPS: Cross-Correlation-Based Inverse Problem

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Zhiyuan Ma ◽  
Li Lin ◽  
Shijie Jin ◽  
Mingkai Lei
Keyword(s):  
Time Domain ◽  
Measurement Errors ◽  
Cross Correlation ◽  
Inversion Method ◽  
Full Time ◽  
Interfacial Roughness ◽  
Measured Velocity ◽  
Detection Frequency ◽  
Relative Errors ◽  
Good Agreement

Aiming at characterizing interfacial roughness of thin coatings with unknown sound velocity and thickness, we derive a full time-domain ultrasonic reflection coefficient phase spectrum (URCPS) as a function of interfacial roughness based on the phase screen approximation theory. The constructed URCPS is used to determine the velocity, thickness, and interfacial roughness of specimens through the cross-correlation algorithm. The effect of detection frequency on the roughness measurement is investigated through the finite element method. A series of simulations were implemented on Ni-coating specimens with a thickness of 400 μm and interfacial roughness of 1.9–39.8 μm. Simulation results indicated that the measurement errors of interfacial roughness were less than 10% when the roughness satisfies the relationship of Rq = 1.6–10.0%λ. The measured velocity and thicknesses were in good agreement with those imported in simulation models with less than 9.3% error. Ultrasonic experiments were carried out on two Ni-coating specimens through a flat transducer with an optimized frequency of 15 MHz. Compared with the velocities measured by time-of-flight (TOF) method, the relative errors of inversed velocities were all less than 10%. The inversed thicknesses were in good agreement with those observed by optical microscopy with less than 10.9% and 7.6% error. The averaged interfacial roughness determined by the ultrasonic inversion method was 16.9 μm and 30.7 μm, respectively. The relative errors were 5.1% and 2.0% between ultrasonic and confocal laser scanning microscope (CLSM) method, respectively.

scholarly journals Numerical and Experimental Investigation on a Moonpool-Buoy Wave Energy Converter

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2364 ◽  
Author(s):  
Hengxu Liu ◽  
Feng Yan ◽  
Fengmei Jing ◽  
Jingtao Ao ◽  
Zhaoliang Han ◽  
...  
Keyword(s):  
Numerical Model ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Scale Model ◽  
Energy Converter ◽  
Point Absorber ◽  
Motion Responses ◽  
Computational Fluid Dynamics Cfd ◽  
The Time Domain ◽  
Good Agreement

This paper introduces a new point-absorber wave energy converter (WEC) with a moonpool buoy—the moonpool platform wave energy converter (MPWEC). The MPWEC structure includes a cylinder buoy and a moonpool buoy and a Power Take-off (PTO) system, where the relative movement between the cylindrical buoy and the moonpool buoy is exploited by the PTO system to generate energy. A 1:10 scale model was physically tested to validate the numerical model and further prove the feasibility of the proposed system. The motion responses of and the power absorbed by the MPWEC studied in the wave tank experiments were also numerically analyzed, with a potential approach in the frequency domain, and a computational fluid dynamics (CFD) code in the time domain. The good agreement between the experimental and the numerical results showed that the present numerical model is accurate enough, and therefore considering only the heave degree of freedom is acceptable to estimate the motion responses and power absorption. The study shows that the MPWEC optimum power extractions is realized over a range of wave frequencies between 1.7 and 2.5 rad/s.

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