The use of B-field measurements in an airborne time-domain system – Part II: examples in conductive regimes

1998 ◽  
Vol 29 (1-2) ◽  
pp. 225-229 ◽  
Author(s):  
Peter Wolfgram ◽  
Stephen Thomson
Keyword(s):  
Time Domain ◽  
Field Measurements ◽  
System Part

scholarly journals TIME DOMAIN COMPARISONS OF MEASURED AND SPECTRALLY SIMULATED BREAKING WAVES

2017 ◽  
pp. 12
Author(s):  
Mustafa Kemal Ozalp ◽  
Serdar Beji
Keyword(s):  
Time Domain ◽  
Surf Zone ◽  
Field Measurements ◽  
Wave Model ◽  
Breaking Waves ◽  
Irregular Waves ◽  
Dissipative Effects ◽  
Spectral Components ◽  
Breaking Mechanism ◽  
Acceptable Agreement

For realistic wave simulations in the nearshore zone besides nonlinear interactions, the dissipative effects of wave breaking must also be taken into account. This paper presents the applications of a spectral nonlinear wave model with a dissipative breaking mechanism introduced by Beji and Nadaoka (1997). Results obtained for spectral components are converted to the time series and compared with Beji and Battjes' (1993) laboratory measurements and the field measurements of Nakamura and Katoh (1992) in the surf zone. While the model predicts the spilling-type breaking of irregular waves in acceptable agreement with the measurements in time domain, the agreement is unsatisfactory for plunging-type breakers.

Research of Beta-Endosulfan Based on THz Time-Domain Spectroscopy

2013 ◽  
Vol 718-720 ◽  
pp. 1060-1065 ◽  
Author(s):  
Zhe Liu ◽  
Xian Li ◽  
Fei Heng Yue ◽  
Lu Feng ◽  
Jin Hui Cai ◽  
...  
Keyword(s):  
Refractive Index ◽  
Organic Pollutants ◽  
Time Domain ◽  
Spectral Properties ◽  
Experimental Results ◽  
Good Match ◽  
Terahertz Time Domain Spectroscopy ◽  
Time Domain Spectroscopy ◽  
Characteristic Absorption ◽  
System Part

THz spectral properties between 0.2-1.5THz of beta-endosulfan, one of the persistent organic pollutants (POPs), are investigated based on the THz time domain system. Part of the characteristic absorption peaks are theoretically analyzed by Dmol3 modular program. The experimental results show that the average refractive index of beta-endosulfan in the THz waveband is about 1.005 and characteristic absorption peaks exist at 0.67, 0.80, 1.03, 1.14, 1.26 and 1.46THz. The absorption peaks at 0.67THz and 1.03THz have a good match with the theoretic absorption peak positions which appear at 0.72THz and 1.07THz calculated by Dmol3. The peaks at 0.67THz and 1.03THz may be caused by the torsion in B and C direction of beta-endosulfan crystal lattice, along with the translation in A direction. Compared with the experimental results of alpha-endosulfan, it can be seen clearly that these two isomers have completely different absorption peaks. For further it indicates that terahertz time domain spectroscopy (THz-TDS) has great application value in identifying isomers.

A numerical evaluation of electromagnetic methods in geothermal exploration

Geophysics ◽  
1996 ◽  
Vol 61 (1) ◽  
pp. 121-130 ◽  
Author(s):  
Louise Pellerin ◽  
Jeffrey M. Johnston ◽  
Gerald W. Hohmann
Keyword(s):  
Electric Field ◽  
Time Domain ◽  
Numerical Models ◽  
Field Measurements ◽  
Quality Data ◽  
Geothermal System ◽  
Geothermal Exploration ◽  
Offset Time ◽  
Clay Cap ◽  
Electric Field Measurements

The size and low resistivity of the clay cap associated with a geothermal system create a target well suited for electromagnetic (EM) methods and also make electrical detection of the underlying geothermal reservoir a challenge. Using 3-D numerical models, we evaluate four EM techniques for use in geothermal exploration: magnetotellurics (MT), controlled‐source audio magnetotellurics (CSAMT), long‐offset time‐domain EM (LOTEM), and short‐offset time‐domain EM (TEM). Our results show that all of these techniques can delineate the clay cap, but none can be said to unequivocally detect the reservoir. We do find, however, that the EM anomaly from a deep, conductive reservoir overlain by a larger, more conductive clay cap is caused by the presence of the electric charge at conductivity boundaries rather than electromagnetic induction. This means that, for detection of the reservoir, methods such as MT, which rely on electric field measurements, are superior to those where only the magnetic field is measured. The anomaly produced by boundary charges at the reservoir is subtle and will be evident only if high‐quality data are collected at closely spaced measurement sites. LOTEM electric field measurements look promising and should be useful when efficient multidimensional tools are developed for LOTEM interpretation. Although CSAMT employs electric field measurements, this method is not recommended for reservoir detection because the anomaly caused by a deep reservoir is obscured by transmitter effects that cannot be isolated reliably. A combination of CSAMT and TEM measurements appears most appropriate for delineation of the clay cap.

USE OF DECAY PATTERNS FOR THE CLASSIFICATION OF ANOMALIES IN TIME‐DOMAIN AEM MEASUREMENTS

Geophysics ◽  
1976 ◽  
Vol 41 (5) ◽  
pp. 1031-1041 ◽  
Author(s):  
G. J. Palacky
Keyword(s):  
Time Domain ◽  
Field Measurements ◽  
System Response ◽  
Electromagnetic Measurements ◽  
Time Domain Electromagnetic ◽  
Decay Pattern ◽  
Body Parameters ◽  
Flight Computer

Interpretation of time‐domain electromagnetic measurements normally comprises visual anomaly selection and determination of body parameters, such as conductance, depth, and dip. A study is made to examine the possibility of in‐flight computer interpretation on the basis of decay patterns. Analysis of system response over conducting loops, vertical and dipping sheets, horizontal strips, and a half‐space indicates that identification of models and some of their parameters by decay patterns is feasible. By the simultaneous use of vertical and horizontal coil receivers, a reliable recognition of models may be achieved. While the secondary magnetic field over a conducting loop decays exponentially, other models show distinctive nonexponential patterns. Decay patterns are affected by conductance and conductor size, but less by depth and dip variations. Field measurements indicate that decay pattern may be used to distinguish between geologic bodies of various types.

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