133 research outputs found
Estimation of Primaries and Multiples by Sparse Inversion
No full textSurface-related multiple reflections are often considered noise in the seismic reflection measurements. By seismic processes, such as migration and inversion, they can be mistakenly seen as primary reflections and give an erroneous image of the earth. Therefore, a method is needed to separate the multiples from the primaries. This thesis describes a primary estimation method named estimation of primaries by sparse inversion (EPSI). The interesting aspect of this method is that it does not see the multiples as noise, but uses the multiples to come to a better estimation of the primaries. Other wave equation based primary estimation methods first predict the multiples and then adaptively subtract them from the data. During this adaptive subtraction primary energy may be removed. EPSI tries to explain the total data, both primaries and multiples, in terms of primary impulse responses. By doing so an adaptive subtraction of multiples is avoided. In fact EPSI is a large-scale inversion process that estimates primaries such that they and their corresponding multiples explain the total data. To constrain this process, a sparseness constraint is used, which assumes that our estimated primaries have a certain amplitude distribution (large and small ones). A general characteristic of wave equation based primary estimation methods is that the near-offset data are very important for estimating water column reverberations, especially in shallow water. However, it is not possible to record the near-offset data and, therefore, most wave equation based primary estimation methods have great difficulties with shallow water marine data. A major advantage of EPSI is that it can reconstruct the missing near-offset data from information in the multiples and, therefore, show a good primary estimation result on shallow water marine data. Furthermore, the EPSI method can be extended to other measurement configurations, exploiting a similar relation between primaries and surface multiples. In this thesis both passive and blended seismic data have been considered. For passive seismic data multiples are used to obtain an estimate of the subsurface responses, usually by a cross-correlation process. This cross-correlation process relies on the assumption that the surface has been illuminated uniformly by subsurface sources in terms of incident angles and strength. If this is not the case the cross-correlation process cannot give a true amplitude estimation of the subsurface response. Furthermore, there are cross terms in the cross-correlation result that are not related to actual subsurface inhomogeneities. In this thesis it is demonstrated that, with some modifications to the algorithm, EPSI can obtain true amplitude subsurface responses without the uniform surface illumination assumption. The EPSI method will go beyond the cross-correlation process and will estimate primaries only from the multiples in the available signal. The estimated primary impulse responses, with point sources and receivers at the surface, can be used directly in traditional imaging schemes. This thesis demonstrates that for the situation of blended acquisition, meaning that different sources are shooting in a time-overlapping fashion, multiples can be used to 'deblend' the seismic measurements. With some modifications the EPSI method can be used for blended seismic data. As output EPSI gives unblended primary impulse responses with point sources and receivers at the surface, which can be used directly in traditional imaging schemes. The feasibility of the EPSI method is demonstrated in this thesis by a successful application of the method to two marine field datasets, one with a moderate water depth and one with shallow water. It demonstrates that for deeper water EPSI can compete with the standard surface-related multiple elimination (SRME) method, where for the shallow water EPSI clearly shows better results than SRME. The latter is mainly attributed to the fact that near offset reconstruction, which plays a crucial role in shallow water data, is included in the EPSI method.Imaging Science & TechnologyApplied Science
Accumulation and degradation of polyphosphate in Acinetobacter sp.
No full textBiological phosphate removal from waste water is a biotechnological alternative to chemical phosphorus precipitation. This process is obtained by recycling the sludge through anaerobic and aerobic zones. In the anaerobic parts phosphate is released by the sludge and during anaerobiosis phosphate is taken up. Biological phosphate removal is dependent on the enrichment of activated sludge with polyphosphate accumulating Acinetobacter . Like activated sludge, pure cultures of strictly aerobic Acinetobacter sp. absorbe phosphate (up to 100 mg phosphorus per g dry biomass) during aerobic conditions and release it anaerobically. The aim of this study was to gather knowledge on the uptake and release of phosphate by Acinetobacter and the metabolic functions of polyphosphate.The accumulation of polyphosphate by pure cultures of Acinetobacter strain 210A depended on the presence of an intra- or extracellular energy source (chapter 2). The highest amount of polyphosphate was found in cells in which energy supply was not limited, namely at low growth rates under sulphur limitation, and in the stationary phase of growth when either the nitrogen or the sulphur source was depleted. Accumulation of polyphosphate was also possible during endogenous respiration. When this respiration was blocked with KCN the phosphate uptake stopped, while the inhibition of the protein synthesis with streptomycin enhanced the accumulation of phosphate, which indicated the competition between protein synthesis and polyphosphate synthesis for energy. There was a pronounced effect of the temperature on phosphorus accumulation but this effect varied from strain to strain.The role and behaviour of cations in the accumulation and release of phosphate was studied (chapter 3). PO 43-was released together with 1.8 protons. Mg 2+appeared to be the most important counterion of polyphosphate in Acinetobacter strain 210A. It was released and taken up simultaneously with phosphate. Mg 2+was not an essential polyphosphate counterion. If Mg 2+was depleted, stationary cultures of Acinetobacter strain 210A took up the same amount of phosphate with Ca 2+as the most important counterion. In the presence of Mg 2+stationary cultures did not need Ca 2+for their phosphate absorption, but the presence of K +seemed to be crucial for this process, although this cation did not play a quantitatively important role as a polyphosphate counterion. In addition, the influx and efflux of K +was independent of phosphate uptake and release. Continuous cultivation at low growth rates under K +-limitation did not result in polyphosphate accumulation, while under substrate or Mg 2+- limitation large amounts of polyphosphate were present in the cells. The same effect was found in activated sludge. 5 mg K +per litre was needed for a satisfactory biological phosphate removal in the aerobic zone of a wastewater treatment plant. Granules of Mgpolyphosphate in Acinetobacter strain 210A could serve as a Mg 2+-reserve. Cells with these granules were able to grow in a medium free of Mg 2+, whereas cells without granules were not, they only grew in the presence of extracellular Mg 2+. Polyphosphate in cell-free extracts of Acinetobacter strain 210A could be degraded by the enzymes polyphosphatase or polyphosphate:AMP phosphotransferase (chapters 4 and 6). Polyphosphate glucokinase, polyphosphate dependent NAD-kinase and polyphosphatekinase were not detectable. Polyphosphate:AMP phosphotransferase was also found in Acinetobacter strain B8, but not in Acinetobacter strain P, which contained only polyphosphatekinase. Both strains were able to accumulate large amounts of polyphosphate. In strains that cannot accumulate this biopolymer, no or very small activities of polyphosphatekinase and polyphosphate: AMP phosphotransferase were found. All strains showed activities of adenylate kinase. It was demonstrated that by the combined action of polyphosphate:AMP phosphotransferase and adenylate kinase a continuous regeneration of ATP from AMP or ADP was possible as long as polyphosphate was present. Polyphosphate:AMP phosphotransferase could use native and synthetic polyphosphate as substrate and showed a maximum activity at a pH of 8.5. Its activity was stimulated by (NH 4 ) 2 SO 4 , the K m for AMP appeared to be 0.6 mM, and V max was 60 nmol.min -1.mg -1protein. Polyphosphatase in cell-free extracts of strain 210A was able to hydrolyse native polyphosphate and synthetic Mg-polyphosphate. The K- and Na-form, however, were not degraded. The activities of polyphosphate:AMP phosphotransferase and adenylate kinase in activated sludge correlated well with the ability of the sludge to remove phosphate biologically from waste water.Degradation of polyphosphate invivo in Acinetobacter strain 210A occurred if the energy supply in the cell was stopped, for example under anaerobiosis or in the presence of KCN, α-dinitrophenol or N-N'-dicyclohexylcarbodiimid (chapter 5). The degradation and synthesis of polyphosphate was dependent on the ATP concentration in the cells. Lower ATP concentrations caused a faster phosphate release. This release was stimulated by alcohols. The transmembrane protongradient seemed to play an important role in the anaerobic energy metabolism of this strictly aerobic bacterium. Addition of α-dinitrophenol, a protonionophore, decreased the cellular ATP concentration and stimulated the polyphosphate degradation. The role of polyphosphate as an energy reserve invivo has been demonstrated by experiments in which five strains were incubated anaerobically. Cells of Acinetobacter strains 210A and B8, which were able to accumulate polyphosphate, released large amounts of ortho-phosphate anaerobically and contained high levels of ATP. Cells of two other strains of Acinetobacter and one strain of Pseudomonas which didn't accumulate polyphosphate, showed a much smaller release of phosphate and contained only low ATP concentrations. Cells of strain 210A cultivated under phosphorus limitation or at 350C did not contain detectable amounts of polyphosphate. As a result their ATP level was low and they released only small or negligible amounts of phosphate under anaerobic conditions.Mg-polyphosphate in Acinetobacter sp. is a multifunctional compound. It can serve as: (1) an energy reserve if it is degraded by a reaction with AMP, catalyzed by polyphosphate: AMP phosphotransferase, (2) a phosphorus reserve if it is hydrolyzed by polyphosphatase, and (3) a Mg 2+reserve whereby Mg 2+can be replaced by Ca 2+as a counterion. The most important role of polyphosphate in wastewater treatment plants with biological phosphate removal, and probably also in natural environments, is its use as an energy reserve to sustain temporary anaerobiosis. This property might explain the enrichment of activated sludge subjected to alternating anaerobic and aerobic conditions with polyphosphate accumulating Acinetobacter sp.
Seismic Deblending By Shot Repetition
No full textBlended acquisition, or simultaneous source acquisition, is a relatively new seismic acquisition design that allows shot interference. Deblending is the procedure that separates the interfering shots as if they were acquired conventionally. This thesis reviews one of the more advanced deblending algorithms in great detail, and demonstrates that it does not perform well when the source sampling is sparse. This thesis proposes a new blended acquisition design, shot repetition, to overcome the restriction of dense source sampling by deblending solely in the common-shot domain. The theoretical fundamentals of shot repetition are derived. Based on that, three possible acquisition configurations are proposed, and the designed deblending algorithm is explained and discussed. This thesis also demonstrates that extreme noise, e.g. competitor’s interference and barnacle noise, can be removed by the same deblending algorithm. The results of implementing the deblending algorithm on synthetic data of three configurations show that all the interfering shots are near-perfect separated. The results do not indicate that one configuration is better than the others. The field data results, on both blended data and the data with barnacle noise, demonstrate that strong overlapping events and weak overlapping events can be separated quite well, while the separation of strong events overlapping weak events leads to signal leakage. The deblending performance is confirmed by a significant SNR improvement on the deblended synthetic data (around 22 dB), a fair SNR improvement (7 dB to 12 dB) on the deblended field data, and a fair SNR improvement (around 5 dB) on the removal of barnacle noise.Applied Geophysics and PetrophysicsGeoscience & EngineeringCivil Engineering and Geoscience
Shear induced agglomeration experiments on caco3 for geothermal energy production
No full textGeothermal energy is produced by pumping cold water into an underground reservoir. The reservoir exists of narrow channels in which the water is heated before it is pumped up. The heat transfer in the reservoir improves when all the channels are uniform in diameter. The oil company Shell wants to make the channels uniform by using shear induced agglomeration. Agglomeration is a secondary process frequently encountered in reactive crystallization. Particles collide, cement together due to deposition of material on the contact plane and may continue as an agglomerat. The rate at which particles agglomerate is determined by the particle concentration and the agglomeration rate constant. For shear induced agglomeration this constant is a function of the shear rate, the van der Waals forces, the lubrication force, and the supersaturation. It is the aim of this research to determine this function experimentally for CaCOa particles in the region of interest (shear rates between 0 to 25 s""^) for the technique that Shell wants to use. In the experiments, a Couette-flow device is used to create a constant shear field. A CCD camera makes images of a measurement volume in the Couette-flow device that is illuminated by a laser to measure the particle concentration decrease in a non-intrusive way. An image analysis program counts the particles on the images. From the decay of the particle number concentration in time, the agglomeration rate constant is derived. Results show that the van der Waals force causes CaCOs particles to stay together. In a theoretical model of Mumtaz and Hounslow, this was not taken into account. A maximum was found for the agglomeration rate constant as a function of shear around 30 s~^ for the saturated suspension used in that experiment. Uncontrolled particle concentrations and a not completely reliable particle concentration measuring device made it not possible to determine the role of supersaturation in agglomeration in our agglomeration experiments. The agglomeration setup, fit program and image analysis program worked well and the aim of the research could be fulfilled.Kramers Laboratorium voor Fysische TechnologieApplied Science
Seismic blending and deblending of crossline sources
No full textBlending is a recent seismic acquisition design, which allows seismic shots to interfere. Current processing techniques are not capable to deal with blended data. Consequently, the blended data must be deblended (separated) as if they were acquired in a conventional way. I propose a new acquisition design based on blended crossline sources. In contrast to existing blended- acquisition designs that only blend in 2D (inline direction and time), this design blends sources in 3D (inline direction, crossline direction and time). Blended crossline sources allow to increase the data quality and/or to reduce the acquisition costs. While most blended- acquisition designs blend two sources, the proposed acquisition design blends up to seven sources. In order to realize this increase in number of blended sources without degrading the data quality, both the blended-acquisition design and the deblending method must be improved. To enhance the blending, I introduce a new incoherency measure of the blended-acquisition design, and propose three incoherent blending patterns. A 2D synthetic data example il- lustrates that the deblending quality indeed is optimized by maximizing the incoherency of the blended acquisition. To enhance the deblending, I derive a 3D deblending method. In contrast to 2D deblending methods, this method exploits both the crossline and inline direc- tion to deblend sources. The 3D deblending method significantly increases the deblending quality as illustrated by a 3D synthetic data example. The feasibility of blended crossline sources is proven on a 3D complex synthetic data example. Two acquisition configurations are examined: The Wide Crossline Source Array that aims to reduce the acquisition costs, and the Dense Crossline Source Array that increases the data quality. Both of them provide excellent deblending results with quality factors of 14.2 dB and 20.8 dB respectively.Applied Geophysics and PetrophysicsGeoscience & EngineeringCivil Engineering and Geoscience
Substrate Interactions during the Biodegradation of Benzene, Toluene, Ethylbenze, and Xylene (BTEX) Hydrocarbons by the Fungus Cladophialophora sp. Strain T1
No full textThe soil fungus Cladophialophora sp. strain T1 (= ATCC MYA-2335) was capable of growth on a model water-soluble fraction of gasoline that contained all six BTEX components (benzene, toluene, ethylbenzene, and the xylene isomers). Benzene was not metabolized, but the alkylated benzenes (toluene, ethylbenzene, and xylenes) were degraded by a combination of assimilation and cometabolism. Toluene and ethylbenzene were used as sources of carbon and energy, whereas the xylenes were cometabolized to different extents. o-Xylene and m-xylene were converted to phthalates as end metabolites; p-xylene was not degraded in complex BTEX mixtures but, in combination with toluene, appeared to be mineralized. The metabolic profiles and the inhibitory nature of the substrate interactions indicated that toluene, ethylbenzene, and xylene were degraded at the side chain by the same monooxygenase enzyme. Our findings suggest that soil fungi could contribute significantly to bioremediation of BTEX pollution
Estimation of primaries by sparse inversion from passive seismic data
No full textFor passive seismic data, surface multiples are used to obtain an estimate of the subsurface responses, usually by a crosscorrelation process. This crosscorrelation process relies on the assumption that the surface has been uniformly illuminated by subsurface sources in terms of incident angles and strengths. If this is not the case, the crosscorrelation process cannot give a true amplitude estimation of the subsurface response. Furthermore, cross terms in the crosscorrelation result are not related to actual subsurface inhomogeneities. We have developed a method that can obtain true amplitude subsurface responses without a uniform surface-illumination assumption. Our methodology goes beyond the crosscorrelation process and estimates primaries only from the surface-related multiples in the available signal. We use the recently introduced estimation of primaries by sparse inversion (EPSI) methodology, in which the primary impulse responses are considered to be the unknowns in a large-scale inversion process. With some modifications, the EPSI method can be used for passive seismic data. The output of this process is primary impulse responses with point sources and receivers at the surface, which can be used directly in traditional imaging schemes. The methodology was tested on 2D synthetic data.Imaging Science and TechnologyApplied Science
Estimation of primaries and near-offset reconstruction by sparse inversion: Marine data applications
No full textost wave-equation-based multiple removal algorithms are based on prediction and subtraction of multiples. Especially for shallow water, the prediction strongly relies on a correct interpolation of the missing near offsets. The subtraction of predicted multiples from the data can easily lead to the distortion of primaries if primaries and multiples overlap. Recently, a new approach for surface-related multiple removal was proposed: the estimation of primaries by sparse inversion (EPSI), which is based on a full waveform inversion approach. EPSI is based on the same primary-multiple model as surface-related multiple elimination (SRME) and does not require a subsurface model. In contrast to SRME, EPSI estimates the primaries as unknowns in a multidimensional inversion process rather than a subtraction process.The multidimensional primary impulse responses are parameterized by band-limited spikes, which are estimated such that they, along with their corresponding multiples, match the input data. An interesting aspect of the EPSI method is that it produces a residual, which is the part of the input data not explained by primaries and multiples. This residual can be analyzed and may provide useful information on the primary estimation process. Furthermore, it has been demonstrated that EPSI is also capable of reconstructing the missing near offsets from the multiples. The proposed method is applied to a field data set with moderate water depth, where it is demonstrated that the results are comparable with SRME. This data set is used to illustrate the residual. For a shallow-water field data set, it is shown that EPSI gives a better result than the standard SRME result caused by EPSI's capability to reconstruct the missing near offsets.Imaging Science and TechnologyApplied Science
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