1,664 research outputs found
Full Wavefield Migration of Vertical Seismic Profiling data
No full textUntil now, in most seismic imaging technologies, both surface and internal multiples are considered as noise. In today’s industrial practice, we see various methods for suppressing multiples before migration. This means that only a fraction of the recorded wavefield is used in imaging. In this thesis, we present a method termed full wavefield migration (FWM) that uses the multiple-reflections in the data to improve the illumination of the field in areas that cannot be reached by the primaries, to yield a better vertical resolution as well as to suppress migration artefacts caused by crosstalk of multiple-reflections. This thesis demonstrates the feasibility of full wavefield migration on a kind of borehole seismic known as vertical seismic profiling (VSP). We know that in today’s practice, images obtained using VSP data always suffer from poor illumination and small aperture effects. Therefore, we expect in VSP acquisition geometry, multiples can lead to significant improvement in illumination, both at the reservoir level as well as away from the well region. In this thesis, the advantage of using multiples in full wavefield migration has been demonstrated. We validated our algorithm on 2D synthetic and field VSP data. Full wavefield migration is posed as an inverse problem, where the parameters to be estimated are the subsurface reflectivities. We discuss an iterative forward modelling engine termed full wavefield modelling which is used in the inversion scheme. Full wavefield modelling allows us to compute the full wavefield (primaries and all multiples) in terms of estimated reflectivities. In the full wavefield modelling engine, we assume a scale-separation between the background migration velocity that governs only the one-way wavefield propagation and the reflectivity model that governs the two-way scattering. The modelling engine accounts for the non-linearity of the wavefield due to reflectivity, incorporating the transmission effects and multiple scattering at all depth levels. To solve the inverse problem, we have used iterative conjugate-gradient scheme, which is a local optimization method. We also presents a solution for imaging of blended source VSP data using FWM. The inversion-based imaging algorithm allows us to use any complex source wavefield without the need for a separate deblending (pre-processing) step. This thesis introduces the concepts of elastic full wavefield modelling and inversion. The elastic modelling of P and S waves is illustrated for a horizontally layered medium using a VSP geometry. The elastic imaging to estimate angle-dependent reflectivity parameters that incorporates mode-conversions in subsurface layers is an important area of future research. Nearly vertical structures such as salt-flanks pose a migration challenge for conventional FWM. We have also extended the FWM algorithm to incorporate turning-waves using horizontal one-way wavefield extrapolation. Using this extension, we illustrate that FWM can be used to image steep dips or near-vertical structures using the turning wavefield in VSP data. Alok Kumar Soni.Imaging PhysicsApplied Science
Imaging blended vertical seismic profiling data using full-wavefield migration in the common-receiver domain
No full textFor vertical-seismic-profiling (VSP) measurements, the use of blended acquisition, with time-overlapping shot records, can greatly reduce the downtime and, thereby, provide large cost savings. For directly imaging blended VSP measurements, we have used full-wavefield migration (FWM). FWM is an inversion-based imaging scheme that enables us to use any kind of complex source wavefield to estimate the subsurface reflectivity, using all the multiples (surface and internal) in the recorded data. The multiple scattering helps in improving the illumination as well as the vertical resolution of the image. In this scheme, active deblending is not required because the imaging process itself acts as a deblending procedure. We tested the potential of FWM to image blended VSP data, using simple and complex synthetic models. We clearly determined that using the primaries, surface multiples, and internal multiples enhanced the illumination away from the well trajectory, in which blending noise was suppressed due to the inversion scheme. We observed that some blending crosstalk noise leaked into the images with large blending factors. Such noise could be further reduced with additional constraints in the involved least-squares inversion process.IST/Imaging Science and TechnologyApplied Science
Imaging blended VSP data using full wavefield migration
No full textBlended 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 any need to separate the blended sources. Recently, we proposed the concept of full wavefield migration (FWM) to image VSP data, where using all the multiples - both surface and internal multiples - in the imaging provides better illumination, especially away from the well. Using the above mentioned two concepts, in this paper, we will show the potential of FWM to directly image blended VSP data, without the need for intermediate deblending. We can see FWM imaging as a deblending algorithm itself that transforms the blended data into the reflectivity image space by an inversion process. The concept of FWM formulated in terms of a constrained least-squares inversion scheme indeed enables us to use any kind of complex source wavefield to explain the subsurface reflectivity. The method is illustrated successfully for some synthetic blended VSP examples.IST/Imaging Science and TechnologyApplied Science
Flow over partially liquid filled cavity
No full textExperiments have been carried out to investigate the effect of liquid cavity filling on the behavior of the gas flow over a flat plate cavity. PIV measurements in the gas phase reveal that cavity filling can affect vortex shedding in the cavity mouth. Shear layer vortices can break-up into smaller vortices, thereby losing their periodic interaction with the aft wall and, hence, their sound producing potential. Expected is that this is one of the mechanisms causing sound mitigation in corrugated pipes with liquid addition, observed in literature
ADOPTION OF A CHILD WITHOUT CONSENT OF ITS PARENT WITH A INTELLECTUAL DISABILITY : CASE OF A.K. AND L. v. CROATIA
No full textThis paper discusses the matter of parents prior right to provide his/her child with care in situations in which a child’s parent is a person with intellectual disabilities. The author analyzes the case of A.K. and L. v. Croatia in which European Court of Human Rights concluded that it come to violation of the right to family life of A.K, a mother with an intellectual disability and her son L., who was adopted without the mother’s consent. The paper presents a critical review of Croatian family law in a matter of a parent’s consent for an adoption when the parent is a person with intellectual disabilities. By connecting contemporary standpoints of the European Court of Human Rights and the latest scientific knowledge about the ability of persons with intellectual disabilities to take care of their child, the author discusses a possible conflict between the principle of child’s best interest and the priority right of a parent to take care of his/her child. Also, the author warns about the danger of a parent with intellectual disabilities being deprived of his/her parental rights and completely excluded from the process of adoption even in situations when the parent could, with adequate professional help and support, maintain a family relationship with the child. From that perspective the author also discusses the latest reforms of the family law concerning protection of parental rights of persons deprived of their capacity for work
Lasing in Bose-Fermi mixtures
No full textA.K. acknowledges the support from the EPSRC Established Career Fellowship. V.K., M.D., V.F.S. and A.K. acknowledge support from the Russian Ministry of Science and Education, contract (contract No. 11.G34.31.0067). P.G.S. acknowledges support from Greek GSRT program Aristeia (grant No. 1978). C.S., M. A. J.F., M.K and S.H. acknowledge support from the state of Bavaria.Light amplification by stimulated emission of radiation, well-known for revolutionising photonic science, has been realised primarily in fermionic systems including widely applied diode lasers. The prerequisite for fermionic lasing is the inversion of electronic population, which governs the lasing threshold. More recently, bosonic lasers have also been developed based on Bose-Einstein condensates of exciton-polaritons in semiconductor microcavities. These electrically neutral bosons coexist with charged electrons and holes. In the presence of magnetic fields, the charged particles are bound to their cyclotron orbits, while the neutral exciton-polaritons move freely. We demonstrate how magnetic fields affect dramatically the phase diagram of mixed Bose-Fermi systems, switching between fermionic lasing, incoherent emission and bosonic lasing regimes in planar and pillar microcavities with optical and electrical pumping. We collected and analyzed the data taken on pillar and planar microcavity structures at continuous wave and pulsed optical excitation as well as injecting electrons and holes electronically. Our results evidence the transition from a Bose gas to a Fermi liquid mediated by magnetic fields and light-matter coupling.Peer reviewe
Concurrent segmentation of the prostate on MRI and CT via linked statistical shape models for radiotherapy planning
No full textProstate gland segmentation is a critical step in prostate radiotherapy planning, where dose plans are typically formulated on CT. Pre-treatment MRI is now beginning to be acquired at several medical centers. Delineation of the prostate on MRI is acknowledged as being significantly simpler to do compared to CT. In this work, we present a novel framework for building a linked statistical shape model (LSSM), a statistical shape model (SSM) that links the shape variation of a structure of interest (SOI) across multiple imaging modalities. We apply the LSSM in the context of multi-modal prostate segmentation for radiotherapy planning, where the prostate is concurrently segmented on MRI and CT. First, we utilize multi-modal registration of MRI and CT to map 2D boundary delineations of the prostate from MRI onto corresponding CT, for a set of training studies. Hence, our scheme obviates the need for expert prostate delineations on CT for explicitly constructing a SSM for prostate CT segmentation on CT. The delineations of the prostate gland on MRI and CT allows for 3D reconstruction of the prostate shape which facilitates the building of the LSSM. In order to perform concurrent prostate MRI and CT segmentation using the LSSM, we employ a region-based level-set approach where we deform the evolving prostate boundary to simultaneously fit to MRI and CT images in which voxels are classified to be either part of the prostate or outside the prostate. The classification is facilitated by using a combination of MRI-CT probabilistic spatial atlases and a random forest classifier, driven by gradient and Haar features. We acquire a total of 20 MRI-CT patient studies and use the leave-one-out strategy to train and evaluate four different LSSMs. Firstly, a fusion-based LSSM (fLSSM) is built using expert ground truth delineations of the prostate on MRI alone, where the ground truth for the gland on CT is obtained via coregistration of the corresponding MRI and CT slices. We compare the fLSSM against another idealized LSSM (xLSSM), where expert delineations of the gland on both MRI and CT are employed in the model building. We also compare the fLSSM against a CT-based SSM (ctSSM), built from expert delineations of the gland on CT alone. In addition, 2 LSSMs trained using trainee delineations (tLSSM) on CT are compared with the fLSSM. Our results indicate that the xLSSM, tLSSMs and the fLSSM perform equivalently, all of them out-performing the ctSSM. The fLSSM provides an accurate alternative to SSMs that require careful expert delineations of the SOI that may be difficult or laborious to obtain. Additionally the fLSSM has the added benefit of providing concurrent segmentations of the SOI on multiple imaging modalities.M. S.Includes bibliographical referencesIncludes vitaby A.K. Najeebullah Chowdhur
A.K. SPIESS. LIFE, DEVOTED TO PORCELAIN
No full textThe article reconstructs the creative biography of the sculptor of the Imperial Porcelain Factory A.K. Spiess, development of his career in Russia. Over the 47 years he was the Chief sculptor of the porcelain factory and was the author of most of the figures created during the "historicism." The article investigates his creative activity, historical and cultural conditions of the development of the porcelain sculpture under his leadership. The author examines in detail the identity of the sculptor, the evolution of his creative activity, discusses the key factors in the development of his career. After four years after arriving in Russia, a former student and assistant sculptor received a position of the chief sculptor of the Imperial Porcelain Factory. Spies managed to perfectly flatter the taste of the Empress Maria, skillfully using the latest achievements of porcelain production, sculptor borrowed from Europe. Due to the great diversity of Spies, it should be noted porcelain amazing adaptability to any changes in the art of Historicism, where one style of fashion rapidly replaced by others. Porcelain Spies "successfully coped with any role": central interior decoration, household items, personal preferences, or evidence of the imperial status of the owner. Author concludes that the "secret" so successful creative activity of August Spiess, who for decades defined the artistic policy sculpture department, consists in the fact that his art was not just on time and responded to the artistic needs of the society. "From porcelain man can do everything" - said I.-I. Candler, whom Europe obliged the birth of porcelain. This phrase is also the key to the art of A. K Spiess.DOI: http://dx.doi.org/10.12731/2218-7405-2014-1-5</p
LEXICO-SEMANTIC REPRESENTATION OF THE PHILOSOPHICAL CATEGORY “LOVE” WITHIN THE FRAMEWORK OF THE SPACE-TIME CONTINUUM IN THE POETIC AND EPISTOLARY HERITAGE OF A.K. TOLSTOY
No full textThe article is devoted to the study of the definition of “Love” based on the lexico-semantic aspect presented in the lyrics and letters of A.K. Tolstoy. The author investigates the lexemes included in the lexical semantic fields “Love”, “Time”, “Space”, revealing the semantic changes in their semantic structure which occur under the influence of the contextual environment. The lexico-semantic expression of the “chronotope of love” in the analyzed texts of the letters actualizes the local-temporal seme in the structure of lexemes that are not related to the semantics of space and time, which leads to the semantic variety of the A.K. Tolstoy’s epistolary. The representation of the philosophical category “Love” in the poet’s letters is compared with the lexical-semantic expression of this concept in the author’s poetry. The com-parison is made with the help of the dictionary article “Love” from the poetic vocabulary of A.K. Tolstoy’s language, which is currently under development, is used. The comparative analysis allows us to determine the relation of the main philosophical constants “time”, “space”, “movement” to the concepts of “love” and “God”, which are the semantic basis of texts of the letters and poetic works of A.K. Tolstoy. Such a study allows us to determine the range of the main lexical representatives of the “love chronotope” in the consid-ered fragment of the writer’s work, which details the linguistic picture of the author’s world and reveals the worldview of the elite language personality
Gallery of Male Characters in the Story The Young Jackdaw by A.K. Goldebaev
No full textThe motif of the Apocalypse passes through all the works of the Samara writer A.K. Goldebaev (Semenov). But if in his early works he did not highlight the end of the world (It seems distant and therefore not so scary to the author), years later he realizes the seriousness of what is happening – death isapproaching. In the story The Young Jackdaw (In the Established Order), published in 1910 in the short story collection Knowledge, the writer starts a conversation about the fallen women. However, this topic is not the leading one, and the female characters are not central ones. In this article, the author attempts to reveal the true meaning of the work through the analysis of the system of male characters
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