the main goal of frac monitoring is to obtain a clear definition of event characterization to ultimately compute SRV. Enhancement in signal-to-noise ratio is one of the key elements used to discriminate a successful t...
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the main goal of frac monitoring is to obtain a clear definition of event characterization to ultimately compute SRV. Enhancement in signal-to-noise ratio is one of the key elements used to discriminate a successful technique from others. While in the buried sensors design the noise reduction is a wellaccepted advantage, the simple layout of surface sensors arrayis still under discussion. this abstract presents results obtained with a new surface design used in hydraulic fracturation monitoring showing how geometry and spatial distribution of the sensors can improve SNR and therefore sensitivity. this new design is named'patch design'.the name is self-explanatory: OnePatch consists in a given number of sensors closely distributed;a patch design is a series of patches sparsely distributed above the region of interest. this design has several advantages;we will discuss here the economic and technical benefits of this method. sensor deployment can be easily adapted to the environment optimizing permitting, line clearing, access and avoiding noise prone areas. the economic advantage does not weaken the technical benefit: At the patch scale, the short distance between sensors allowsadvanced summation to optimallypreserve the signal and reduce the noise. the patch design provides a much higher signal-tonoise ratio compared to the usual surface designs. Real cases examples will show how the patch design combines the advantages of both surface and shallow buried array designs.
Subsurface imaging is one of the challenging complex electromagnetic problems which requires a reliably sensor and effective signalprocessing algorithms. Problems vary from medical diagnosis (e. g., tumor detection) ...
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ISBN:
(纸本)9780769549637;9781467356534
Subsurface imaging is one of the challenging complex electromagnetic problems which requires a reliably sensor and effective signalprocessing algorithms. Problems vary from medical diagnosis (e. g., tumor detection) to the location of buried land mines, underground explosives, hidden headquarters, etc. Current investigations have focused on better antenna system design, signal waveform exploration, sensor integration, and intelligent signalprocessing methods. Numerical simulations in these areas offer great possibilities not only in understanding physical background of the problem at hand, but also in doing research in these challenging areas. We have developed a two-dimensional virtual tool (a simulation package) based on the well-known finite-difference time-domain (FDTD) method that can be used in simulations of variety of subsurface problems. In this presentation, the virtual tool will be used to generate synthetic data for the direct problem. Various ultrawide band (UWB) antenna array configurations with different time-domain signal waveforms will be reviewed. Finally, Subsurface Imaging (SSI) capabilities will be summarized as an inverse problem.
We propose a low complexity arrayprocessing method for differential detection of OFDM signals over underwater acoustic channels. Partial FFT technique, developed previously for mitigating inter-carrier interference i...
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ISBN:
(纸本)9781467310710
We propose a low complexity arrayprocessing method for differential detection of OFDM signals over underwater acoustic channels. Partial FFT technique, developed previously for mitigating inter-carrier interference in single-channel receivers operating over time-varying channels, is extended to multichannel configuration. Performance results based on simulation and experimental data demonstrate the advantage of the proposed method compared to conventional differential and coherent detection.
this paper investigates an adaptive beamforming technique that is robust against imperfect knowledge of signal and interference arrival directions, antenna calibration errors and other similar imperfections. the propo...
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ISBN:
(纸本)9781467310710
this paper investigates an adaptive beamforming technique that is robust against imperfect knowledge of signal and interference arrival directions, antenna calibration errors and other similar imperfections. the proposed technique is based on Generalized Sidelobe Canceller but uses Slepian sequences in boththe steering and blocking lobes of the algorithm. Only Slepians corresponding to large spectral concentrations are used in the branches. the theoretical results are verified in a simulation study.
In this paper we derive a generic signalprocessing model for oversampled linear antenna arrays based on network theory and Nyquist sampling theory. the theoretical model is verified with experimental data collected o...
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ISBN:
(纸本)9781467310710
In this paper we derive a generic signalprocessing model for oversampled linear antenna arrays based on network theory and Nyquist sampling theory. the theoretical model is verified with experimental data collected on an HF OthR receive array.
We propose a MUSIC based array imaging method for ultrasonic non-destructive testing (NDT) applications. We take the mode conversion phenomenon into account and develop a MUSIC-based imaging technique which exploits t...
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ISBN:
(纸本)9781467310710
We propose a MUSIC based array imaging method for ultrasonic non-destructive testing (NDT) applications. We take the mode conversion phenomenon into account and develop a MUSIC-based imaging technique which exploits the additional information that is present in all propagating modes to the advantage of the imaging process-a problem not previously addressed in the context of NDT applications. Boththe numerical simulations as well as data validation show that our proposed approach performs better than the traditional MUSIC based and delay-and-sum (DAS) based imaging algorithms in terms of root mean square error (RMSE) and also provides higher resolution and better side lobe suppression capabilities.
PATENT PENDING. Time-of-arrival (TOA) localization is tightly coupled withsensor time synchronization. Synchronization can be obtained by GPS, atomic clocks or message exchange protocols. All methods affect the energ...
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ISBN:
(纸本)9781467310710
PATENT PENDING. Time-of-arrival (TOA) localization is tightly coupled withsensor time synchronization. Synchronization can be obtained by GPS, atomic clocks or message exchange protocols. All methods affect the energy sources and the synchronization protocols use valuable bandwidth. We present self-synchronized localization algorithms that rely exclusively on TOA measurements performed by the sensor network on passing sources rendering it completely passive. Localization performance is close to that provided by a perfectly synchronized network. Such algorithms can also be used for sensor network synchronization and communication networks in general.
In this work, we propose a distributed power control algorithm able to capture the tradeoff between detection capabilities and power consumption for a radar sensor network. this is achieved by modeling the radar senso...
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ISBN:
(纸本)9781467310710
In this work, we propose a distributed power control algorithm able to capture the tradeoff between detection capabilities and power consumption for a radar sensor network. this is achieved by modeling the radar sensors as rational agents engaging in a noncooperative game in which the detection threshold and the transmit power are properly designed according to the Nash equilibrium solution. An iterative algorithm based on a best-response dynamics is proposed to achieve the equilibrium point and its performance is compared to that achieved by a uniform power allocation.
An adaptive algorithm for azimuth-angle estimation of moving sources in the presence of array nonidealities is proposed. the method, termed unitary element-space Capon (UES-Capon) beamformer, is robust in the face of ...
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ISBN:
(纸本)9781467310710
An adaptive algorithm for azimuth-angle estimation of moving sources in the presence of array nonidealities is proposed. the method, termed unitary element-space Capon (UES-Capon) beamformer, is robust in the face of small number of snapshots and fully takes into account effects such as mutual coupling, mounting platform reflections, and sensor's misplacement errors. Unlike most of the robust beamformers available in the literature, the proposed method is based on QR-decomposition and real-valued polynomial root tracking. Furthermore, it is applicable to sensorarrays of arbitrary configuration. Numerical results using a real-world antenna array are included, illustrating the excellent performance of the proposed method, both in terms of SINR and fast adaptivity to moving sources.
Compressive sensing (CS) has successfully been applied to reconstruct sparse signals and images from few observations. For multi-component nonstationary signals characterized by instantaneous frequency laws, the spars...
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ISBN:
(纸本)9781467310710
Compressive sensing (CS) has successfully been applied to reconstruct sparse signals and images from few observations. For multi-component nonstationary signals characterized by instantaneous frequency laws, the sparsity exhibits itself in the time-frequency domain as well as the ambiguity domain. In this paper, we examine CS in the context of nonstationary arrayprocessing. We show that the spatial averaging of the ambiguity function across the array improves the CS performance by reducing both noise and cross-terms. the corresponding time-frequency distribution which is reconstructed through L-1 minimizations yields significant improvement in time-frequency signature localizations and characterizations.
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