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Thorbecke, J.W. (author), Van der Neut, J.R. (author), Wapenaar, C.P.A. (author)Recent research showed that the Marchenko equation can be used to construct the Green’s function for a virtual source position in the subsurface. The method requires the reflection response at the surface and an estimate of the direct arrival of the wavefield, traveling from the virtual source location to the acquisition surface. In this paper,...conference paper 2013
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Slob, E.C. (author), Wapenaar, C.P.A. (author)Recently a new theory has been developed to retrieve a wavefield generated by a source on the surface and recorded at a point in the subsurface without the need for a receiver at that subsurface location. The scheme is presented for three-dimensional wavefields. It decomposes the electromagnetic field in up- and downgoing electric fields and in...journal article 2013
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Konstantaki, L.A. (author), Dragnov, D.S. (author), Heimovaara, T.J. (author), Ghose, R. (author)A significant problem with landfills is their aftercare period. A landfill is considered to be safe for the environment only after a relatively long period of time. Until it reaches such a condition, it has to be periodically treated. Not only are treatments very expensive, but they could be dangerous as well; for example, when barriers limiting...journal article 2013
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Kumar, A. (author), Blacquière, G. (author)A subsurface image obtained from seismic data is influenced by the acquisition geometry, as it contains an acquisition foot-print which can obscure the true reflection response of the subsurface. Hence, the acquisition geometry should be designed in such a way that it allows high-quality images and fulfils the criteria for reservoir...journal article 2013
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Bharadwaj, P. (author), Mulder, W.A. (author), Drijkoningen, G.G. (author)Least-squares inversion of seismic reflection waveforms can reconstruct remarkably detailed models of the Earth’s subsurface. However, the cycle-skipping associated with the highfrequency waveforms are responsible for spurious local minima in its objective function. Therefore, it is often difficult for descent methods to converge to the true...journal article 2013
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Almagro Vidal, C. (author), Van der Neut, J. (author), Wapenaar, C.P.A. (author)Changes in the subsurface can be imaged by subtracting seismic reflection data at two different states, one serving as the initial survey or base, and the second as the monitor survey. Conventionally, the reflection data are acquired by placing active seismic sources at the acquisition surface. Alternatively, these data can be acquired from...journal article 2013
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Soni, A.K. (author), Verschuur, D.J. (author)Blended source and/or simultaneous source acquisition for multi-offset and multi-azimuth VSP measurements can prove significantly beneficial in saving expensive borehole down-time. In the last few years, for the case of surface seismic data, it was proposed to redefine imaging and inversion of the blended data to handle the data directly without...journal article 2013
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Draganov, D.S. (author), Campman, X. (author), Thorbecke, J.W. (author), Verdel, A. (author), Wapenaar, C.P.A. (author)The successful surface waves retrieval in solid?Earth seismology using long?time correlations and subsequent tomographic images of the crust have sparked interest in extraction of subsurface information from noise in the exploration seismology. Subsurface information in exploration seismology is usually derived from body?wave reflections >?1?Hz,...journal article 2013
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Moghaddam, P.P. (author), Keers, H. (author), Herrmann, F.J. (author), Mulder, W.A. (author)Waveform inversion is the method of choice for determining a highly heterogeneous subsurface structure. However, conventional waveform inversion requires that the wavefield for each source is computed separately. This makes it very expensive for realistic 3D seismic surveys. Source-encoding waveform inversion, in which the sources are modeled...journal article 2013
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Pont, S.C. (author), Koenderink, J.J. (author), Van Doorn, A.J. (author), Wijntjes, M.W.A. (author), Te Pas, S.F. (author)We present a novel setup in which real objects made of different materials can be mixed optically. For the materials we chose mutually very different materials, which we assume to represent canonical modes. The appearance of 3D objects consisting of any material can be described as linear superposition of 3D objects of different canonical...conference paper 2012
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Mulder, W.A. (author)Since most of the easy hydrocarbon reservoirs have been found, accurate sub-surface imaging for oil and gas exploration and production is crucial. Seismic data can provide a band-limited reconstruction of impedance contrasts between different rock formations as well as a subsurface velocity model. Current compute power allows for the use of the...conference paper 2012
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Hak, B. (author)The thesis deals with wave-equation migration in a visco-acoustic medium, where an ambiguity appears when one tries to image simultaneous velocity and attenuation perturbations.doctoral thesis 2010
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Zhuge, X. (author)Compact, cost-efficient and high-resolution imaging sensors are especially desirable in the field of short-range observation and surveillance. Such sensors are of great value in fields of security, rescue and medical applications. Systems can be formed for various practical purposes, such as detecting concealed weapons in public places, locating...doctoral thesis 2010
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Kolkman, R.G.M. (author), Blomme, E. (author), Cool, T. (author), Bilcke, M. (author), Van Leeuwen, T.G. (author), Steenbergen, W. (author), Grimbergen, K.A. (author), Den Heeten, G.J. (author)The feasibility of air-coupled ultrasound transducers to detect laser-induced ultrasound from artificial blood vessels embedded in an optically scattering phantom is demonstrated. These air-coupled transducers allow new applications in biomedical photoacoustic imaging where contact with tissue is not preferred. One promising application of such...journal article 2010
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Hörchens, L. (author)The detection of inhomogeneities in plates or plate-like structures constitutes a major problem in the field of non-destructive testing. For a few decades, classical techniques based on X-ray radiography have - as far as possible - been complemented and replaced by the usage of vibrations or acoustical waves due to the fact that these are less...doctoral thesis 2010
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Wijnholds, S.J. (author)The radio astronomical community is currently developing and building several new radio telescopes based on phased array technology. These telescopes provide a large field-of-view, that may in principle span a full hemisphere. This makes calibration and imaging very challenging tasks due to the complex source structures and direction dependent...doctoral thesis 2010
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Van Haver, S. (author)In present-day society, we encounter optical systems on a daily basis. Most people have a DVD player capable of playing content stored on an optical disc, Big Brother is watching us nearly everywhere using surveillance cameras and we consider it to be normal to take photographs with our mobile phone. Also, in less visible areas, such as...doctoral thesis 2010
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Krug, K. (author), Porra, L. (author), Coan, P. (author), Wallert, A. (author), Dik, J. (author), Coerdt, A. (author), Bravin, A. (author), Elyyan, M. (author), Reischig, P. (author), Helfen, L. (author), Baumbach, T. (author)X-ray radiography is a common tool in the study of old master paintings. Transmission imaging can visualize hidden paint layers as well as the structure of the panel or canvas. In some medieval altarpieces, relics seem to have been imbedded in the wooden carrier of paintings. These are most probably thin organic fibrous materials such as paper...journal article 2007
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Pörtzgen, N. (author)Ultrasonic non-destructive testing is a renowned method for the inspection of girth welds. However, defect sizing and characterization remains challenging with the current inspection philosophy. In addition, data display and interpretation is not straightforward and requires skill and experience from the inspector. A better and more reliable...doctoral thesis 2007
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Berkhout, A.J. (author), Verschuur, D.J. (author)Interpolation of data beyond aliasing limits and removal of noise that occurs within the seismic bandwidth are still important problems in seismic processing. The focal transform is introduced as a promising tool in data interpolation and noise removal, allowing the incorporation of macroinformation about the involved wavefields. From a physical...journal article 2006