WorldWideScience

Sample records for field surface reconstruction

  1. Markov Random Field Surface Reconstruction

    DEFF Research Database (Denmark)

    Paulsen, Rasmus Reinhold; Bærentzen, Jakob Andreas; Larsen, Rasmus

    2010-01-01

    ) and knowledge about data (the observation model) in an orthogonal fashion. Local models that account for both scene-specific knowledge and physical properties of the scanning device are described. Furthermore, how the optimal distance field can be computed is demonstrated using conjugate gradients, sparse...

  2. A Note on the Inverse Reconstruction of Residual Fields in Surface Peened Plates

    Directory of Open Access Journals (Sweden)

    S. Ali Faghidian

    Full Text Available Abstract A modified stress function approach is developed here to reconstruct induced stress, residual stress and eigenstrain fields from limited experimental measurements. The present approach is successfully applied to three experimental measurements set in surface peened plates with shallow shot peening affected zone. The well-rehearsed advantage of the proposed approach is that it not only minimizes the deviation of measurements from its approximations but also will result in an inverse solution satisfying a full range of continuum mechanics requirements. Also, the effect of component thickness as a geometric parameter influencing the residual stress state is comprehensively studied. A key finding of present study is that the plate thickness has no influence on the maximum magnitude of eigenstrain profile and compressive residual stresses within the shot peening affected zone while having a great influence on the magnitude of tensile residual stress and the gradient of linear residual stresses present in deeper regions.

  3. Polaron-Driven Surface Reconstructions

    Directory of Open Access Journals (Sweden)

    Michele Reticcioli

    2017-09-01

    Full Text Available Geometric and electronic surface reconstructions determine the physical and chemical properties of surfaces and, consequently, their functionality in applications. The reconstruction of a surface minimizes its surface free energy in otherwise thermodynamically unstable situations, typically caused by dangling bonds, lattice stress, or a divergent surface potential, and it is achieved by a cooperative modification of the atomic and electronic structure. Here, we combined first-principles calculations and surface techniques (scanning tunneling microscopy, non-contact atomic force microscopy, scanning tunneling spectroscopy to report that the repulsion between negatively charged polaronic quasiparticles, formed by the interaction between excess electrons and the lattice phonon field, plays a key role in surface reconstructions. As a paradigmatic example, we explain the (1×1 to (1×2 transition in rutile TiO_{2}(110.

  4. Multiproxy summer and winter surface air temperature field reconstructions for southern South America covering the past centuries

    Energy Technology Data Exchange (ETDEWEB)

    Neukom, R.; Grosjean, M.; Wanner, H. [University of Bern, Oeschger Centre for Climate Change Research (OCCR), Bern (Switzerland); University of Bern, Institute of Geography, Climatology and Meteorology, Bern (Switzerland); Luterbacher, J. [Justus Liebig University of Giessen, Department of Geography, Climatology, Climate Dynamics and Climate Change, Giessen (Germany); Villalba, R.; Morales, M.; Srur, A. [CONICET, Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales (IANIGLA), Mendoza (Argentina); Kuettel, M. [University of Bern, Oeschger Centre for Climate Change Research (OCCR), Bern (Switzerland); University of Bern, Institute of Geography, Climatology and Meteorology, Bern (Switzerland); University of Washington, Department of Earth and Space Sciences, Seattle (United States); Frank, D. [Swiss Federal Research Institute WSL, Birmensdorf (Switzerland); Jones, P.D. [University of East Anglia, Climatic Research Unit, School of Environmental Sciences, Norwich (United Kingdom); Aravena, J.-C. [Centro de Estudios Cuaternarios de Fuego Patagonia y Antartica (CEQUA), Punta Arenas (Chile); Black, D.E. [Stony Brook University, School of Marine and Atmospheric Sciences, Stony Brook (United States); Christie, D.A.; Urrutia, R. [Universidad Austral de Chile Valdivia, Laboratorio de Dendrocronologia, Facultad de Ciencias Forestales y Recursos Naturales, Valdivia (Chile); D' Arrigo, R. [Earth Institute at Columbia University, Tree-Ring Laboratory, Lamont-Doherty Earth Observatory, Palisades, NY (United States); Lara, A. [Universidad Austral de Chile Valdivia, Laboratorio de Dendrocronologia, Facultad de Ciencias Forestales y Recursos Naturales, Valdivia (Chile); Nucleo Cientifico Milenio FORECOS, Fundacion FORECOS, Valdivia (Chile); Soliz-Gamboa, C. [Utrecht Univ., Inst. of Environmental Biology, Utrecht (Netherlands); Gunten, L. von [Univ. of Bern (Switzerland); Univ. of Massachusetts, Climate System Research Center, Amherst (United States)

    2011-07-15

    We statistically reconstruct austral summer (winter) surface air temperature fields back to ad 900 (1706) using 22 (20) annually resolved predictors from natural and human archives from southern South America (SSA). This represents the first regional-scale climate field reconstruction for parts of the Southern Hemisphere at this high temporal resolution. We apply three different reconstruction techniques: multivariate principal component regression, composite plus scaling, and regularized expectation maximization. There is generally good agreement between the results of the three methods on interannual and decadal timescales. The field reconstructions allow us to describe differences and similarities in the temperature evolution of different sub-regions of SSA. The reconstructed SSA mean summer temperatures between 900 and 1350 are mostly above the 1901-1995 climatology. After 1350, we reconstruct a sharp transition to colder conditions, which last until approximately 1700. The summers in the eighteenth century are relatively warm with a subsequent cold relapse peaking around 1850. In the twentieth century, summer temperatures reach conditions similar to earlier warm periods. The winter temperatures in the eighteenth and nineteenth centuries were mostly below the twentieth century average. The uncertainties of our reconstructions are generally largest in the eastern lowlands of SSA, where the coverage with proxy data is poorest. Verifications with independent summer temperature proxies and instrumental measurements suggest that the interannual and multi-decadal variations of SSA temperatures are well captured by our reconstructions. This new dataset can be used for data/model comparison and data assimilation as well as for detection and attribution studies at sub-continental scales. (orig.)

  5. Reconstruction of Magnetic Field Surfaces of the NOVILLO Tokamak by means of the 3D-MAPTOR Code

    International Nuclear Information System (INIS)

    Chavez-Alarcon, Esteban; Herrera-Velazquez, J. Julio E.

    2008-01-01

    A 3-D code has been developed in order to simulate the magnetic field lines in circular cross-section tokamaks. The toroidal magnetic field can be obtained from the individual fields of circular coils arranged around the torus, or alternatively, as a ripple-less field, as well as the vertical field coils, and divertor-like coils. The poloidal field is provided by a given toroidal current density profile. Proposing initial conditions for a magnetic filed line, it is integrated along the toroidal angle coordinate, and the Poincare maps can be obtained at any desired cross section plane along the torus. Following this procedure, the code allows to explore the necessary current values for the existence of magnetic field surfaces, allowing for deviations from axial symmetry, such as ripple effects. Therefore it is a good design instrument, in which different parameters and arrangements of coils can be tested. On the other hand, the current signals from experimental devices can be used in order to reconstruct the behaviour of the magnetic field surfaces, including the q(r) profiles. The reconstruction properties of the code are shown in this work

  6. Reconstructing solar magnetic fields from historical observations: Testing the surface flux transport model

    Science.gov (United States)

    Virtanen, Iiro; Virtanen, Ilpo; Pevtsov, Alexei; Yeates, Anthony; Mursula, Kalevi

    2017-04-01

    We aim to use the surface flux transport model to simulate the long-term evolution of the photospheric magnetic field from historical observations. In this work we study the accuracy of the model and its sensitivity to uncertainties in its main parameters and the input data. We test the model by running simulations with different values of meridional circulation and supergranular diffusion parameters, and study how the flux distribution inside active regions and the initial magnetic field affect the simulation. We compare the results to assess how sensitive the simulation is to uncertainties in meridional circulation speed, supergranular diffusion and input data. We also compare the simulated magnetic field with observations. We find that there is generally good agreement between simulations and observations. While the model is not capable of replicating fine details of the magnetic field, the long-term evolution of the polar field is very similar in simulations and observations. Simulations typically yield a smoother evolution of polar fields than observations, that often include artificial variations due to observational limitations. We also find that the simulated field is fairly insensitive to uncertainties in model parameters or the input data. Due to the decay term included in the model the effects of the uncertainties are rather minor or temporary, lasting typically one solar cycle.

  7. Reconstructing solar magnetic fields from historical observations. II. Testing the surface flux transport model

    Science.gov (United States)

    Virtanen, I. O. I.; Virtanen, I. I.; Pevtsov, A. A.; Yeates, A.; Mursula, K.

    2017-07-01

    Aims: We aim to use the surface flux transport model to simulate the long-term evolution of the photospheric magnetic field from historical observations. In this work we study the accuracy of the model and its sensitivity to uncertainties in its main parameters and the input data. Methods: We tested the model by running simulations with different values of meridional circulation and supergranular diffusion parameters, and studied how the flux distribution inside active regions and the initial magnetic field affected the simulation. We compared the results to assess how sensitive the simulation is to uncertainties in meridional circulation speed, supergranular diffusion, and input data. We also compared the simulated magnetic field with observations. Results: We find that there is generally good agreement between simulations and observations. Although the model is not capable of replicating fine details of the magnetic field, the long-term evolution of the polar field is very similar in simulations and observations. Simulations typically yield a smoother evolution of polar fields than observations, which often include artificial variations due to observational limitations. We also find that the simulated field is fairly insensitive to uncertainties in model parameters or the input data. Due to the decay term included in the model the effects of the uncertainties are somewhat minor or temporary, lasting typically one solar cycle.

  8. Photometric Lunar Surface Reconstruction

    Science.gov (United States)

    Nefian, Ara V.; Alexandrov, Oleg; Morattlo, Zachary; Kim, Taemin; Beyer, Ross A.

    2013-01-01

    Accurate photometric reconstruction of the Lunar surface is important in the context of upcoming NASA robotic missions to the Moon and in giving a more accurate understanding of the Lunar soil composition. This paper describes a novel approach for joint estimation of Lunar albedo, camera exposure time, and photometric parameters that utilizes an accurate Lunar-Lambertian reflectance model and previously derived Lunar topography of the area visualized during the Apollo missions. The method introduced here is used in creating the largest Lunar albedo map (16% of the Lunar surface) at the resolution of 10 meters/pixel.

  9. Overlapping constraint for variational surface reconstruction

    DEFF Research Database (Denmark)

    Aanæs, Henrik; Solem, J.E.

    2005-01-01

    In this paper a counter example, illustrating a shortcoming in most variational formulations for 3D surface estimation, is presented. The nature of this shortcoming is a lack of an overlapping constraint. A remedy for this shortcoming is presented in the form of a penalty function with an analysi...... of the effects of this function on surface motion. For practical purposes, this will only have minor influence on current methods. However, the insight provided in the analysis is likely to influence future developments in the field of variational surface reconstruction....

  10. Extended Reconstructed Sea Surface Temperature (ERSST)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Extended Reconstructed Sea Surface Temperature (ERSST) dataset is a global monthly sea surface temperature analysis derived from the International Comprehensive...

  11. Ocular Surface Reconstruction: Recent Innovations

    Directory of Open Access Journals (Sweden)

    Madhavan HN

    2009-01-01

    protocol of LSCD patients. Autologous limbal transplantation Despite its success, its utility is limited. the requirement for a sizable limbal donation; up to 30-40% must be harvested from the contralateral donor eye and its harvest may theoretically harm the structural integrity, cause subclinical LSCD or cryptogenic changes in the donor eye. Ex vivo expansion and cultivation techniques for autologous limbal stem cells are being actively investigated. , the use of human AM for ocular surface regeneration (OSR and as a growth support substrate for ex vivo expansion of autologous corneal equivalent epithelial cells and their successful OSR in animal cornea model, as well as human, was reported. The conventional cultivation methods for corneal epithelial tissues for clinical transplantation applications involve utilization of xenobiotic materials such as fetal bovine serum (FBS and murine-derived feeder cells. FBS-free culture systems have been developed to reduce the risk of zoonotic infection, but these have the disadvantage of reduced efficacy for cell propagation. it must be emphasized that AMT is not a substitution for LSCT and AMT should not be performed when true LSCD exists because AM only provides a supportive matrix for the limbal stem cells to migrate, proliferate and restore the corneal surface. There are several disadvantages of AMT and LSCT technique. This delicate procedure requires technical skill for the preparation of AM with attached corneal epithelial cells and surgical dexterity to manipulate the AM onto the ocular surface.A rabbit model for transplantation of cultivated corneal limbal stem cells onto corneal stem cell deficient animals was developed & its results are very encouraging for similar studies in human corneal surface reconstruction. Our investigations indicated that Ex vivo cultivation of human corneal limbal stem cells (HCLSC occurred with ease in the thermoresponsive biodegradable gel - “Mebiol Gel”. The growth rate within Mebiol Gel

  12. Reconstruction of convex bodies from surface tensors

    DEFF Research Database (Denmark)

    Kousholt, Astrid; Kiderlen, Markus

    We present two algorithms for reconstruction of the shape of convex bodies in the two-dimensional Euclidean space. The first reconstruction algorithm requires knowledge of the exact surface tensors of a convex body up to rank s for some natural number s. The second algorithm uses harmonic intrinsic...... volumes which are certain values of the surface tensors and allows for noisy measurements. From a generalized version of Wirtinger's inequality, we derive stability results that are utilized to ensure consistency of both reconstruction procedures. Consistency of the reconstruction procedure based...

  13. Reconstruction of convex bodies from surface tensors

    DEFF Research Database (Denmark)

    Kousholt, Astrid; Kiderlen, Markus

    2016-01-01

    We present two algorithms for reconstruction of the shape of convex bodies in the two-dimensional Euclidean space. The first reconstruction algorithm requires knowledge of the exact surface tensors of a convex body up to rank s for some natural number s. When only measurements subject to noise...... of surface tensors are available for reconstruction, we recommend to use certain values of the surface tensors, namely harmonic intrinsic volumes instead of the surface tensors evaluated at the standard basis. The second algorithm we present is based on harmonic intrinsic volumes and allows for noisy...... measurements. From a generalized version of Wirtinger's inequality, we derive stability results that are utilized to ensure consistency of both reconstruction procedures. Consistency of the reconstruction procedure based on measurements subject to noise is established under certain assumptions on the noise...

  14. Tomographic reconstruction of binary fields

    International Nuclear Information System (INIS)

    Roux, Stéphane; Leclerc, Hugo; Hild, François

    2012-01-01

    A novel algorithm is proposed for reconstructing binary images from their projection along a set of different orientations. Based on a nonlinear transformation of the projection data, classical back-projection procedures can be used iteratively to converge to the sought image. A multiscale implementation allows for a faster convergence. The algorithm is tested on images up to 1 Mb definition, and an error free reconstruction is achieved with a very limited number of projection data, saving a factor of about 100 on the number of projections required for classical reconstruction algorithms.

  15. Stress field reconstruction in an active mudslide

    Science.gov (United States)

    Baroň, Ivo; Kernstocková, Markéta; Melichar, Rostislav

    2017-07-01

    Meso-scale structures from gravitational slope deformation observed in landslides and deep-seated gravitational slope failures are very similar to those of endogenous ones. Therefore we applied palaeostress analysis of fault-slip data for reconstructing the stress field of an active mudslide in Pechgraben, Austria. This complex compound landslide has developed in clayey colluvium and shale and was activated after a certain period of dormancy in June 2013. During the active motion on June 12, 2013, 73 fault-slip traces at 9 locations were measured within the landslide body. The heterogeneous fault-slip data were processed in term of palaeostresses, the reconstructed palaeostress tensor being characterized by the orientations of the three principal stress axes and the stress ratio (which provides the shape of the stress ellipsoid). The results of the palaeostress analysis were compared to airborne laser scan digital terrain models that revealed dynamics and superficial displacements of the moving mass prior and after our survey. The results were generally in good agreement with the observed landslide displacement pattern and with the anticipated stress regime according to Mohr-Coulomb failure criteria and Anderson's theory. The compressional regime was mostly registered at the toe in areas, where a compressional stress field is expected during previous mass-movement stages, or at margins loaded by subsequent landslide bodies from above. On the other hand, extension regimes were identified at the head scarps of secondary slides, subsequently on bulged ridges at the toe and in the zone of horst-and-graben structures in the lower central part of the main landslide body, where the basal slip surface probably had locally convex character. Strike-slip regimes, as well as oblique normal or oblique reverse regimes were observed at the lateral margins of the landslide bodies. The directions of principal stresses could be used as markers of landslide movement directions

  16. Anatomically Plausible Surface Alignment and Reconstruction

    DEFF Research Database (Denmark)

    Paulsen, Rasmus R.; Larsen, Rasmus

    2010-01-01

    With the increasing clinical use of 3D surface scanners, there is a need for accurate and reliable algorithms that can produce anatomically plausible surfaces. In this paper, a combined method for surface alignment and reconstruction is proposed. It is based on an implicit surface representation...

  17. Reconstruction of convex bodies from surface tensors

    DEFF Research Database (Denmark)

    Kousholt, Astrid; Kiderlen, Markus

    . The output of the reconstruction algorithm is a polytope P, where the surface tensors of P and K are identical up to rank s. We establish a stability result based on a generalization of Wirtinger’s inequality that shows that for large s, two convex bodies are close in shape when they have identical surface...... that are translates of each other. An algorithm for reconstructing an unknown convex body in R 2 from its surface tensors up to a certain rank is presented. Using the reconstruction algorithm, the shape of an unknown convex body can be approximated when only a finite number s of surface tensors are available...... tensors up to rank s. This is used to establish consistency of the developed reconstruction algorithm....

  18. Homotopy based Surface Reconstruction with Application to Acoustic Signals

    DEFF Research Database (Denmark)

    Sharma, Ojaswa; Anton, François

    2011-01-01

    reconstruct information between any pair of successive cross sections are derived. The zero level set of the resulting homotopy field generates the desired surface. Four types of homotopies are suggested that are well suited to generate a smooth surface. We also provide derivation of necessary higher order...

  19. The structure of reconstructed chalcopyrite surfaces

    Science.gov (United States)

    Thinius, Sascha; Islam, Mazharul M.; Bredow, Thomas

    2018-03-01

    Chalcopyrite (CuFeS2) surfaces are of major interest for copper exploitation in aqueous solution, called leaching. Since leaching is a surface process knowledge of the surface structure, bonding pattern and oxidation states is important for improving the efficiency. At present such information is not available from experimental studies. Therefore a detailed computational study of chalcopyrite surfaces is performed. The structures of low-index stoichiometric chalcopyrite surfaces {hkl} h, k, l ∈ {0, 1, 2} have been studied with density functional theory (DFT) and global optimization strategies. We have applied ab initio molecular dynamics (MD) in combination with simulated annealing (SA) in order to explore possible reconstructions via a minima hopping (MH) algorithm. In almost all cases reconstruction involving substantial rearrangement has occurred accompanied by reduction of the surface energy. The analysis of the change in the coordination sphere and migration during reconstruction reveals that S-S dimers are formed on the surface. Further it was observed that metal atoms near the surface move toward the bulk forming metal alloys passivated by sulfur. The obtained surface energies of reconstructed surfaces are in the range of 0.53-0.95 J/m2.

  20. Diffusion of particles adsorbed on reconstructive surface

    Czech Academy of Sciences Publication Activity Database

    Tarasenko A., Nataliya; Tarasenko, Alexander; Jastrabík, Lubomír

    2005-01-01

    Roč. 11, č. 1 (2005), s. 485-489 ISSN 0929-5607 R&D Projects: GA MŠk LN00A015 Institutional research plan: CEZ:AV0Z10100522 Keywords : lattice gas * surface reconstruction * surface diffusion * phase transitions Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.323, year: 2005

  1. Thin film surface reconstruction analysis

    Energy Technology Data Exchange (ETDEWEB)

    Imperatori, P [CNR, Monterotondo Stazione, Rome (Italy). Istituto di Chimica dei materiali

    1996-09-01

    The study of the atomic structure of surfaces and interfaces is a fundamental step in the knowledge and the development of new materials. Among the several surface-sensitive techniques employed to characterise the atomic arrangements, grazing incidence x-ray diffraction (GIXD) is one of the most powerful. With a simple data treatment, based on the kinematical theory, and using the classical methods of x-ray bulk structure determination, it gives the atomic positions of atoms at a surface or an interface and the atomic displacements of subsurface layers for a complete determination of the structure. In this paper the main features of the technique will be briefly reviewed and selected of application to semiconductor and metal surfaces will be discussed.

  2. Silicon and Germanium (111) Surface Reconstruction

    Science.gov (United States)

    Hao, You Gong

    Silicon (111) surface (7 x 7) reconstruction has been a long standing puzzle. For the last twenty years, various models were put forward to explain this reconstruction, but so far the problem still remains unsolved. Recent ion scattering and channeling (ISC), scanning tunneling microscopy (STM) and transmission electron diffraction (TED) experiments reveal some new results about the surface which greatly help investigators to establish better models. This work proposes a silicon (111) surface reconstruction mechanism, the raising and lowering mechanism which leads to benzene -like ring and flower (raised atom) building units. Based on these building units a (7 x 7) model is proposed, which is capable of explaining the STM and ISC experiment and several others. Furthermore the building units of the model can be used naturally to account for the germanium (111) surface c(2 x 8) reconstruction and other observed structures including (2 x 2), (5 x 5) and (7 x 7) for germanium as well as the (/3 x /3)R30 and (/19 x /19)R23.5 impurity induced structures for silicon, and the higher temperature disordered (1 x 1) structure for silicon. The model is closely related to the silicon (111) surface (2 x 1) reconstruction pi-bonded chain model, which is the most successful model for the reconstruction now. This provides an explanation for the rather low conversion temperature (560K) of the (2 x 1) to the (7 x 7). The model seems to meet some problems in the explanation of the TED result, which is explained very well by the dimer, adatom and stacking fault (DAS) model proposed by Takayanagi. In order to explain the TED result, a variation of the atomic scattering factor is proposed. Comparing the benzene-like ring model with the DAS model, the former needs more work to explain the TED result and the later has to find a way to explain the silicon (111) surface (1 x 1) disorder experiment.

  3. Step patterns on vicinal reconstructed surfaces

    Science.gov (United States)

    Vilfan, Igor

    1996-04-01

    Step patterns on vicinal (2 × 1) reconstructed surfaces of noble metals Au(110) and Pt(110), miscut towards the (100) orientation, are investigated. The free energy of the reconstructed surface with a network of crossing opposite steps is calculated in the strong chirality regime when the steps cannot make overhangs. It is explained why the steps are not perpendicular to the direction of the miscut but form in equilibrium a network of crossing steps which make the surface to look like a fish skin. The network formation is the consequence of competition between the — predominantly elastic — energy loss and entropy gain. It is in agreement with recent scanning tunnelling microscopy observations on vicinal Au(110) and Pt(110) surfaces.

  4. Reconstructing bidimensional scalar field theory models

    International Nuclear Information System (INIS)

    Flores, Gabriel H.; Svaiter, N.F.

    2001-07-01

    In this paper we review how to reconstruct scalar field theories in two dimensional spacetime starting from solvable Scrodinger equations. Theree different Schrodinger potentials are analyzed. We obtained two new models starting from the Morse and Scarf II hyperbolic potencials, the U (θ) θ 2 In 2 (θ 2 ) model and U (θ) = θ 2 cos 2 (In(θ 2 )) model respectively. (author)

  5. Weak lensing galaxy cluster field reconstruction

    Science.gov (United States)

    Jullo, E.; Pires, S.; Jauzac, M.; Kneib, J.-P.

    2014-02-01

    In this paper, we compare three methods to reconstruct galaxy cluster density fields with weak lensing data. The first method called FLens integrates an inpainting concept to invert the shear field with possible gaps, and a multi-scale entropy denoising procedure to remove the noise contained in the final reconstruction, that arises mostly from the random intrinsic shape of the galaxies. The second and third methods are based on a model of the density field made of a multi-scale grid of radial basis functions. In one case, the model parameters are computed with a linear inversion involving a singular value decomposition (SVD). In the other case, the model parameters are estimated using a Bayesian Monte Carlo Markov Chain optimization implemented in the lensing software LENSTOOL. Methods are compared on simulated data with varying galaxy density fields. We pay particular attention to the errors estimated with resampling. We find the multi-scale grid model optimized with Monte Carlo Markov Chain to provide the best results, but at high computational cost, especially when considering resampling. The SVD method is much faster but yields noisy maps, although this can be mitigated with resampling. The FLens method is a good compromise with fast computation, high signal-to-noise ratio reconstruction, but lower resolution maps. All three methods are applied to the MACS J0717+3745 galaxy cluster field, and reveal the filamentary structure discovered in Jauzac et al. We conclude that sensitive priors can help to get high signal-to-noise ratio, and unbiased reconstructions.

  6. Tomographic reconstruction with B-splines surfaces

    International Nuclear Information System (INIS)

    Oliveira, Eric F.; Dantas, Carlos C.; Melo, Silvio B.; Mota, Icaro V.; Lira, Mailson

    2011-01-01

    Algebraic reconstruction techniques when applied to a limited number of data usually suffer from noise caused by the process of correction or by inconsistencies in the data coming from the stochastic process of radioactive emission and oscillation equipment. The post - processing of the reconstructed image with the application of filters can be done to mitigate the presence of noise. In general these processes also attenuate the discontinuities present in edges that distinguish objects or artifacts, causing excessive blurring in the reconstructed image. This paper proposes a built-in noise reduction at the same time that it ensures adequate smoothness level in the reconstructed surface, representing the unknowns as linear combinations of elements of a piecewise polynomial basis, i.e. a B-splines basis. For that, the algebraic technique ART is modified to accommodate the first, second and third degree bases, ensuring C 0 , C 1 and C 2 smoothness levels, respectively. For comparisons, three methodologies are applied: ART, ART post-processed with regular B-splines filters (ART*) and the proposed method with the built-in B-splines filter (BsART). Simulations with input data produced from common mathematical phantoms were conducted. For the phantoms used the BsART method consistently presented the smallest errors, among the three methods. This study has shown the superiority of the change made to embed the filter in the ART when compared to the post-filtered ART. (author)

  7. Implicit vessel surface reconstruction for visualization and CFD simulation

    International Nuclear Information System (INIS)

    Schumann, Christian; Peitgen, Heinz-Otto; Neugebauer, Mathias; Bade, Ragnar; Preim, Bernhard

    2008-01-01

    Accurate and high-quality reconstructions of vascular structures are essential for vascular disease diagnosis and blood flow simulations.These applications necessitate a trade-off between accuracy and smoothness. An additional requirement for the volume grid generation for Computational Fluid Dynamics (CFD) simulations is a high triangle quality. We propose a method that produces an accurate reconstruction of the vessel surface with satisfactory surface quality. A point cloud representing the vascular boundary is generated based on a segmentation result. Thin vessels are subsampled to enable an accurate reconstruction. A signed distance field is generated using Multi-level Partition of Unity Implicits and subsequently polygonized using a surface tracking approach. To guarantee a high triangle quality, the surface is remeshed. Compared to other methods, our approach represents a good trade-off between accuracy and smoothness. For the tested data, the average surface deviation to the segmentation results is 0.19 voxel diagonals and the maximum equi-angle skewness values are below 0.75. The generated surfaces are considerably more accurate than those obtained using model-based approaches. Compared to other model-free approaches, the proposed method produces smoother results and thus better supports the perception and interpretation of the vascular topology. Moreover, the triangle quality of the generated surfaces is suitable for CFD simulations. (orig.)

  8. Reconstruction of freeform surfaces for metrology

    International Nuclear Information System (INIS)

    El-Hayek, N; Nouira, H; Anwer, N; Damak, M; Gibaru, O

    2014-01-01

    The application of freeform surfaces has increased since their complex shapes closely express a product's functional specifications and their machining is obtained with higher accuracy. In particular, optical surfaces exhibit enhanced performance especially when they take aspheric forms or more complex forms with multi-undulations. This study is mainly focused on the reconstruction of complex shapes such as freeform optical surfaces, and on the characterization of their form. The computer graphics community has proposed various algorithms for constructing a mesh based on the cloud of sample points. The mesh is a piecewise linear approximation of the surface and an interpolation of the point set. The mesh can further be processed for fitting parametric surfaces (Polyworks ® or Geomagic ® ). The metrology community investigates direct fitting approaches. If the surface mathematical model is given, fitting is a straight forward task. Nonetheless, if the surface model is unknown, fitting is only possible through the association of polynomial Spline parametric surfaces. In this paper, a comparative study carried out on methods proposed by the computer graphics community will be presented to elucidate the advantages of these approaches. We stress the importance of the pre-processing phase as well as the significance of initial conditions. We further emphasize the importance of the meshing phase by stating that a proper mesh has two major advantages. First, it organizes the initially unstructured point set and it provides an insight of orientation, neighbourhood and curvature, and infers information on both its geometry and topology. Second, it conveys a better segmentation of the space, leading to a correct patching and association of parametric surfaces

  9. NOAA Extended Reconstructed Sea Surface Temperature (ERSST), Version 5

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Extended Reconstructed Sea Surface Temperature (ERSST) dataset is a global monthly sea surface temperature dataset derived from the International...

  10. Extended Reconstructed Sea Surface Temperature (ERSST), Version 4

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Extended Reconstructed Sea Surface Temperature (ERSST) dataset is a global monthly sea surface temperature analysis on a 2x2 degree grid derived from the...

  11. Flip-avoiding interpolating surface registration for skull reconstruction.

    Science.gov (United States)

    Xie, Shudong; Leow, Wee Kheng; Lee, Hanjing; Lim, Thiam Chye

    2018-03-30

    Skull reconstruction is an important and challenging task in craniofacial surgery planning, forensic investigation and anthropological studies. Existing methods typically reconstruct approximating surfaces that regard corresponding points on the target skull as soft constraints, thus incurring non-zero error even for non-defective parts and high overall reconstruction error. This paper proposes a novel geometric reconstruction method that non-rigidly registers an interpolating reference surface that regards corresponding target points as hard constraints, thus achieving low reconstruction error. To overcome the shortcoming of interpolating a surface, a flip-avoiding method is used to detect and exclude conflicting hard constraints that would otherwise cause surface patches to flip and self-intersect. Comprehensive test results show that our method is more accurate and robust than existing skull reconstruction methods. By incorporating symmetry constraints, it can produce more symmetric and normal results than other methods in reconstructing defective skulls with a large number of defects. It is robust against severe outliers such as radiation artifacts in computed tomography due to dental implants. In addition, test results also show that our method outperforms thin-plate spline for model resampling, which enables the active shape model to yield more accurate reconstruction results. As the reconstruction accuracy of defective parts varies with the use of different reference models, we also study the implication of reference model selection for skull reconstruction. Copyright © 2018 John Wiley & Sons, Ltd.

  12. Corneal surface reconstruction - a short review

    Directory of Open Access Journals (Sweden)

    Madhavan H N

    2009-01-01

    Full Text Available Cornea is the clear, dome-shaped surface that covers the front of the eye and when damage due to burns or injury and several other diseases, stem cells residing in its rim called "limbus" are stimulated to multiply to support growth of new epithelial cells over its surface. If this ready source of stem cells is damaged or destroyed the natural repair is not possible and such a condition is known as corneal limbal stem cell deficiency (CLSCD disease. Stem cell transplant helps such persons to regenerate the corneal surface. Human corneal limbal stem cell transplantation is at present an established procedure with reasonable good clinical outcome particularly when autologous limbal epithelial tissue from a fellow unaffected eye is used. 1, 2 A major concern related to the autograft is the possibility of CLSCD at the donor site, 3 techniques that allowed the expansion of a small limbal biopsy in the laboratory using cell cultures that could be then transplanted to the affected eye have been developed ,4, 5 Human amniotic membrane (HAM is used as a scaffold for both culturing the human limbal epithelial cells and for ocular surface reconstruction with the cultured limbal epithelial cells. 4-7 However, researchers have used alternative scaffolds like collagen 8, fibrin gel 9 and cross-linked gel of fibronectin and fibrin. 10 All these are biological materials and also need for animal 3T3 feeder layer for stem cell cultures. The properties of HAM are unique including antiadhesive effects, bacteriostatic effects, wound protection, pain reduction, and improvement of epithelialization and characteristically lacking imunogenicity. The use of amniotic membrane transplantation (AMT to treat ocular surface abnormalities was first reported by Graziella Pellegrini, chief of stem cell laboratory at Giovanni Paolo Hospital in Venice, Italy, who was the first to demonstrate the limbal stem cell transplant in 1997. Amniotic membrane has been successfully used in

  13. Predicting supramolecular self-assembly on reconstructed metal surfaces

    Science.gov (United States)

    Roussel, Thomas J.; Barrena, Esther; Ocal, Carmen; Faraudo, Jordi

    2014-06-01

    The prediction of supramolecular self-assembly onto solid surfaces is still challenging in many situations of interest for nanoscience. In particular, no previous simulation approach has been capable to simulate large self-assembly patterns of organic molecules over reconstructed surfaces (which have periodicities over large distances) due to the large number of surface atoms and adsorbing molecules involved. Using a novel simulation technique, we report here large scale simulations of the self-assembly patterns of an organic molecule (DIP) over different reconstructions of the Au(111) surface. We show that on particular reconstructions, the molecule-molecule interactions are enhanced in a way that long-range order is promoted. Also, the presence of a distortion in a reconstructed surface pattern not only induces the presence of long-range order but also is able to drive the organization of DIP into two coexisting homochiral domains, in quantitative agreement with STM experiments. On the other hand, only short range order is obtained in other reconstructions of the Au(111) surface. The simulation strategy opens interesting perspectives to tune the supramolecular structure by simulation design and surface engineering if choosing the right molecular building blocks and stabilising the chosen reconstruction pattern.The prediction of supramolecular self-assembly onto solid surfaces is still challenging in many situations of interest for nanoscience. In particular, no previous simulation approach has been capable to simulate large self-assembly patterns of organic molecules over reconstructed surfaces (which have periodicities over large distances) due to the large number of surface atoms and adsorbing molecules involved. Using a novel simulation technique, we report here large scale simulations of the self-assembly patterns of an organic molecule (DIP) over different reconstructions of the Au(111) surface. We show that on particular reconstructions, the molecule

  14. A New Method for Coronal Magnetic Field Reconstruction

    Science.gov (United States)

    Yi, Sibaek; Choe, Gwang-Son; Cho, Kyung-Suk; Kim, Kap-Sung

    2017-08-01

    A precise way of coronal magnetic field reconstruction (extrapolation) is an indispensable tool for understanding of various solar activities. A variety of reconstruction codes have been developed so far and are available to researchers nowadays, but they more or less bear this and that shortcoming. In this paper, a new efficient method for coronal magnetic field reconstruction is presented. The method imposes only the normal components of magnetic field and current density at the bottom boundary to avoid the overspecification of the reconstruction problem, and employs vector potentials to guarantee the divergence-freeness. In our method, the normal component of current density is imposed, not by adjusting the tangential components of A, but by adjusting its normal component. This allows us to avoid a possible numerical instability that on and off arises in codes using A. In real reconstruction problems, the information for the lateral and top boundaries is absent. The arbitrariness of the boundary conditions imposed there as well as various preprocessing brings about the diversity of resulting solutions. We impose the source surface condition at the top boundary to accommodate flux imbalance, which always shows up in magnetograms. To enhance the convergence rate, we equip our code with a gradient-method type accelerator. Our code is tested on two analytical force-free solutions. When the solution is given only at the bottom boundary, our result surpasses competitors in most figures of merits devised by Schrijver et al. (2006). We have also applied our code to a real active region NOAA 11974, in which two M-class flares and a halo CME took place. The EUV observation shows a sudden appearance of an erupting loop before the first flare. Our numerical solutions show that two entwining flux tubes exist before the flare and their shackling is released after the CME with one of them opened up. We suggest that the erupting loop is created by magnetic reconnection between

  15. Reconstruction of Kinematic Surfaces from Scattered Data

    DEFF Research Database (Denmark)

    Randrup, Thomas; Pottmann, Helmut; Lee, I.-K.

    1998-01-01

    Given a surface in 3-space or scattered points from a surface, we present algorithms for fitting the data by a surface which can be generated by a one--parameter subgroup of the group of similarities. These surfaces are general cones and cylinders, surfaces of revolution, helical surfaces and spi...

  16. Surface Reconstruction and Image Enhancement via $L^1$-Minimization

    KAUST Repository

    Dobrev, Veselin

    2010-01-01

    A surface reconstruction technique based on minimization of the total variation of the gradient is introduced. Convergence of the method is established, and an interior-point algorithm solving the associated linear programming problem is introduced. The reconstruction algorithm is illustrated on various test cases including natural and urban terrain data, and enhancement oflow-resolution or aliased images. Copyright © by SIAM.

  17. 3D reconstruction based on light field images

    Science.gov (United States)

    Zhu, Dong; Wu, Chunhong; Liu, Yunluo; Fu, Dongmei

    2018-04-01

    This paper proposed a method of reconstructing three-dimensional (3D) scene from two light field images capture by Lytro illium. The work was carried out by first extracting the sub-aperture images from light field images and using the scale-invariant feature transform (SIFT) for feature registration on the selected sub-aperture images. Structure from motion (SFM) algorithm is further used on the registration completed sub-aperture images to reconstruct the three-dimensional scene. 3D sparse point cloud was obtained in the end. The method shows that the 3D reconstruction can be implemented by only two light field camera captures, rather than at least a dozen times captures by traditional cameras. This can effectively solve the time-consuming, laborious issues for 3D reconstruction based on traditional digital cameras, to achieve a more rapid, convenient and accurate reconstruction.

  18. Light field reconstruction robust to signal dependent noise

    Science.gov (United States)

    Ren, Kun; Bian, Liheng; Suo, Jinli; Dai, Qionghai

    2014-11-01

    Capturing four dimensional light field data sequentially using a coded aperture camera is an effective approach but suffers from low signal noise ratio. Although multiplexing can help raise the acquisition quality, noise is still a big issue especially for fast acquisition. To address this problem, this paper proposes a noise robust light field reconstruction method. Firstly, scene dependent noise model is studied and incorporated into the light field reconstruction framework. Then, we derive an optimization algorithm for the final reconstruction. We build a prototype by hacking an off-the-shelf camera for data capturing and prove the concept. The effectiveness of this method is validated with experiments on the real captured data.

  19. Surface Reconstruction and Image Enhancement via $L^1$-Minimization

    KAUST Repository

    Dobrev, Veselin; Guermond, Jean-Luc; Popov, Bojan

    2010-01-01

    A surface reconstruction technique based on minimization of the total variation of the gradient is introduced. Convergence of the method is established, and an interior-point algorithm solving the associated linear programming problem is introduced

  20. Sound field separation with cross measurement surfaces.

    Directory of Open Access Journals (Sweden)

    Jin Mao

    Full Text Available With conventional near-field acoustical holography, it is impossible to identify sound pressure when the coherent sound sources are located on the same side of the array. This paper proposes a solution, using cross measurement surfaces to separate the sources based on the equivalent source method. Each equivalent source surface is built in the center of the corresponding original source with a spherical surface. According to the different transfer matrices between equivalent sources and points on holographic surfaces, the weighting of each equivalent source from coherent sources can be obtained. Numerical and experimental studies have been performed to test the method. For the sound pressure including noise after separation in the experiment, the calculation accuracy can be improved by reconstructing the pressure with Tikhonov regularization and the L-curve method. On the whole, a single source can be effectively separated from coherent sources using cross measurement.

  1. Surface reconstruction through poisson disk sampling.

    Directory of Open Access Journals (Sweden)

    Wenguang Hou

    Full Text Available This paper intends to generate the approximate Voronoi diagram in the geodesic metric for some unbiased samples selected from original points. The mesh model of seeds is then constructed on basis of the Voronoi diagram. Rather than constructing the Voronoi diagram for all original points, the proposed strategy is to run around the obstacle that the geodesic distances among neighboring points are sensitive to nearest neighbor definition. It is obvious that the reconstructed model is the level of detail of original points. Hence, our main motivation is to deal with the redundant scattered points. In implementation, Poisson disk sampling is taken to select seeds and helps to produce the Voronoi diagram. Adaptive reconstructions can be achieved by slightly changing the uniform strategy in selecting seeds. Behaviors of this method are investigated and accuracy evaluations are done. Experimental results show the proposed method is reliable and effective.

  2. Epitaxial graphene-encapsulated surface reconstruction of Ge(110)

    Science.gov (United States)

    Campbell, Gavin P.; Kiraly, Brian; Jacobberger, Robert M.; Mannix, Andrew J.; Arnold, Michael S.; Hersam, Mark C.; Guisinger, Nathan P.; Bedzyk, Michael J.

    2018-04-01

    Understanding and engineering the properties of crystalline surfaces has been critical in achieving functional electronics at the nanoscale. Employing scanning tunneling microscopy, surface x-ray diffraction, and high-resolution x-ray reflectivity experiments, we present a thorough study of epitaxial graphene (EG)/Ge(110) and report a Ge(110) "6 × 2" reconstruction stabilized by the presence of epitaxial graphene unseen in group-IV semiconductor surfaces. X-ray studies reveal that graphene resides atop the surface reconstruction with a 0.34 nm van der Waals (vdW) gap and provides protection from ambient degradation.

  3. Surface reconstruction, figure-ground modulation, and border-ownership.

    Science.gov (United States)

    Jeurissen, Danique; Self, Matthew W; Roelfsema, Pieter R

    2013-01-01

    The Differentiation-Integration for Surface Completion (DISC) model aims to explain the reconstruction of visual surfaces. We find the model a valuable contribution to our understanding of figure-ground organization. We point out that, next to border-ownership, neurons in visual cortex code whether surface elements belong to a figure or the background and that this is influenced by attention. We furthermore suggest that there must be strong links between object recognition and figure-ground assignment in order to resolve the status of interior contours. Incorporation of these factors in neurocomputational models will further improve our understanding of surface reconstruction, figure-ground organization, and border-ownership.

  4. 3D surface reconstruction using optical flow for medical imaging

    International Nuclear Information System (INIS)

    Weng, Nan; Yang, Yee-Hong; Pierson, R.

    1996-01-01

    The recovery of a 3D model from a sequence of 2D images is very useful in medical image analysis. Image sequences obtained from the relative motion between the object and the camera or the scanner contain more 3D information than a single image. Methods to visualize the computed tomograms can be divided into two approaches: the surface rendering approach and the volume rendering approach. A new surface rendering method using optical flow is proposed. Optical flow is the apparent motion in the image plane produced by the projection of the real 3D motion onto 2D image. In this paper, the object remains stationary while the scanner undergoes translational motion. The 3D motion of an object can be recovered from the optical flow field using additional constraints. By extracting the surface information from 3D motion, it is possible to get an accurate 3D model of the object. Both synthetic and real image sequences have been used to illustrate the feasibility of the proposed method. The experimental results suggest that the proposed method is suitable for the reconstruction of 3D models from ultrasound medical images as well as other computed tomograms

  5. Inference-Based Surface Reconstruction of Cluttered Environments

    KAUST Repository

    Biggers, K.

    2012-08-01

    We present an inference-based surface reconstruction algorithm that is capable of identifying objects of interest among a cluttered scene, and reconstructing solid model representations even in the presence of occluded surfaces. Our proposed approach incorporates a predictive modeling framework that uses a set of user-provided models for prior knowledge, and applies this knowledge to the iterative identification and construction process. Our approach uses a local to global construction process guided by rules for fitting high-quality surface patches obtained from these prior models. We demonstrate the application of this algorithm on several example data sets containing heavy clutter and occlusion. © 2012 IEEE.

  6. Surface reconstruction, figure-ground modulation, and border-ownership

    NARCIS (Netherlands)

    Jeurissen, D.; Self, M.W.; Roelfsema, P.R.

    2013-01-01

    The Differentiation-Integration for Surface Completion (DISC) model aims to explain the reconstruction of visual surfaces. We find the model a valuable contribution to our understanding of figure-ground organization. We point out that, next to border-ownership, neurons in visual cortex code whether

  7. Surface reconstruction, figure-ground modulation, and border-ownership

    NARCIS (Netherlands)

    Jeurissen, Danique; Self, Matthew W.; Roelfsema, Pieter R.

    2013-01-01

    Abstract The Differentiation-Integration for Surface Completion (DISC) model aims to explain the reconstruction of visual surfaces. We find the model a valuable contribution to our understanding of figure-ground organization. We point out that, next to border-ownership, neurons in visual cortex code

  8. Fermi-surface reconstruction by stripe order in cuprate superconductors

    Science.gov (United States)

    Laliberté, Francis

    2012-02-01

    The origin of pairing in a superconductor resides in the underlying normal state. In the cuprate high-temperature superconductor YBCO, application of a magnetic field to suppress superconductivity reveals a ground state that appears to break the translational symmetry of the lattice, pointing to some density-wave order [1,2,3]. In another cuprate, Eu-LSCO, the onset of stripe order - a modulation of spin and charge densities - at low temperature is well established [4]. By a comparative study of thermoelectric transport in the cuprates YBCO and Eu-LSCO, we show that the two materials exhibit a very similar process of Fermi-surface reconstruction as a function of temperature and doping [5,6]. This strongly suggests that Fermi-surface reconstruction is caused by stripe order in both cases, compelling evidence that stripe order is a generic tendency of hole-doped cuprates.[4pt] Work done in collaboration with J. Chang, N. Doiron-Leyraud, E. Hassinger, R. Daou, D. LeBoeuf, M. Rondeau, B. J. Ramshaw, R. Liang, D. A. Bonn, W. N. Hardy, S. Pyon, T. Takayama, H. Takagi, I. Sheikin, L. Malone, C. Proust, K. Behnia and L. Taillefer.[4pt] [1] N. Doiron-Leyraud et al., Nature 447, 565 (2007).[0pt] [2] D. LeBoeuf et al., Nature 450, 533 (2007).[0pt] [3] D. LeBoeuf et al., Phys. Rev. B 83, 054506 (2011).[0pt] [4] J. Fink et al., Phys. Rev. B 83, 092503 (2011).[0pt] [5] J. Chang et al., Phys. Rev. Lett. 104, 057005 (2010).[0pt] [6] F. Lalibert'e et al., Nat. Commun. 2, 432 (2011).

  9. Reconstruction of surface impedance of an object located over a planar PEC surface

    International Nuclear Information System (INIS)

    Uenal, Guel Seda; Cayoeren, Mehmet; Tetik, Evrim

    2008-01-01

    A method for the determination of inhomogeneous surface impedance of an arbitrary shaped cylindrical object located over a perfectly conducting (PEC) plane is presented. The problem is reduced to the solution of an ill-posed integral equation by the use of single layer representation which is handled by Truncated Singular Value Decomposition (TSVD). The total field and its normal derivative on the boundary of the object which are required for the evaluation of the surface impedance are obtained through Nystroem method. The method can also be used in shape reconstruction by using the relation between the shape of a PEC object and its equivalent one in terms of the surface impedance. The numerical implementations yield quite satisfactory results.

  10. Surface Reconstruction from Parallel Curves with Application to Parietal Bone Fracture Reconstruction.

    Directory of Open Access Journals (Sweden)

    Abdul Majeed

    Full Text Available Maxillofacial trauma are common, secondary to road traffic accident, sports injury, falls and require sophisticated radiological imaging to precisely diagnose. A direct surgical reconstruction is complex and require clinical expertise. Bio-modelling helps in reconstructing surface model from 2D contours. In this manuscript we have constructed the 3D surface using 2D Computerized Tomography (CT scan contours. The fracture part of the cranial vault are reconstructed using GC1 rational cubic Ball curve with three free parameters, later the 2D contours are flipped into 3D with equidistant z component. The constructed surface is represented by contours blending interpolant. At the end of this manuscript a case report of parietal bone fracture is also illustrated by employing this method with a Graphical User Interface (GUI illustration.

  11. Elementary structural building blocks encountered in silicon surface reconstructions

    International Nuclear Information System (INIS)

    Battaglia, Corsin; Monney, Claude; Didiot, Clement; Schwier, Eike Fabian; Garnier, Michael Gunnar; Aebi, Philipp; Gaal-Nagy, Katalin; Onida, Giovanni

    2009-01-01

    Driven by the reduction of dangling bonds and the minimization of surface stress, reconstruction of silicon surfaces leads to a striking diversity of outcomes. Despite this variety even very elaborate structures are generally comprised of a small number of structural building blocks. We here identify important elementary building blocks and discuss their integration into the structural models as well as their impact on the electronic structure of the surface. (topical review)

  12. Using Spherical-Harmonics Expansions for Optics Surface Reconstruction from Gradients.

    Science.gov (United States)

    Solano-Altamirano, Juan Manuel; Vázquez-Otero, Alejandro; Khikhlukha, Danila; Dormido, Raquel; Duro, Natividad

    2017-11-30

    In this paper, we propose a new algorithm to reconstruct optics surfaces (aka wavefronts) from gradients, defined on a circular domain, by means of the Spherical Harmonics. The experimental results indicate that this algorithm renders the same accuracy, compared to the reconstruction based on classical Zernike polynomials, using a smaller number of polynomial terms, which potentially speeds up the wavefront reconstruction. Additionally, we provide an open-source C++ library, released under the terms of the GNU General Public License version 2 (GPLv2), wherein several polynomial sets are coded. Therefore, this library constitutes a robust software alternative for wavefront reconstruction in a high energy laser field, optical surface reconstruction, and, more generally, in surface reconstruction from gradients. The library is a candidate for being integrated in control systems for optical devices, or similarly to be used in ad hoc simulations. Moreover, it has been developed with flexibility in mind, and, as such, the implementation includes the following features: (i) a mock-up generator of various incident wavefronts, intended to simulate the wavefronts commonly encountered in the field of high-energy lasers production; (ii) runtime selection of the library in charge of performing the algebraic computations; (iii) a profiling mechanism to measure and compare the performance of different steps of the algorithms and/or third-party linear algebra libraries. Finally, the library can be easily extended to include additional dependencies, such as porting the algebraic operations to specific architectures, in order to exploit hardware acceleration features.

  13. Using Spherical-Harmonics Expansions for Optics Surface Reconstruction from Gradients

    Directory of Open Access Journals (Sweden)

    Juan Manuel Solano-Altamirano

    2017-11-01

    Full Text Available In this paper, we propose a new algorithm to reconstruct optics surfaces (aka wavefronts from gradients, defined on a circular domain, by means of the Spherical Harmonics. The experimental results indicate that this algorithm renders the same accuracy, compared to the reconstruction based on classical Zernike polynomials, using a smaller number of polynomial terms, which potentially speeds up the wavefront reconstruction. Additionally, we provide an open-source C++ library, released under the terms of the GNU General Public License version 2 (GPLv2, wherein several polynomial sets are coded. Therefore, this library constitutes a robust software alternative for wavefront reconstruction in a high energy laser field, optical surface reconstruction, and, more generally, in surface reconstruction from gradients. The library is a candidate for being integrated in control systems for optical devices, or similarly to be used in ad hoc simulations. Moreover, it has been developed with flexibility in mind, and, as such, the implementation includes the following features: (i a mock-up generator of various incident wavefronts, intended to simulate the wavefronts commonly encountered in the field of high-energy lasers production; (ii runtime selection of the library in charge of performing the algebraic computations; (iii a profiling mechanism to measure and compare the performance of different steps of the algorithms and/or third-party linear algebra libraries. Finally, the library can be easily extended to include additional dependencies, such as porting the algebraic operations to specific architectures, in order to exploit hardware acceleration features.

  14. Inspection of freeform surfaces considering uncertainties in measurement, localization and surface reconstruction

    International Nuclear Information System (INIS)

    Mehrad, Vahid; Xue, Deyi; Gu, Peihua

    2013-01-01

    Inspection of a manufactured freeform surface can be conducted by building its surface model and comparing this manufactured surface model with the ideal design surface model and its tolerance requirement. The manufactured freeform surface model is usually achieved by obtaining measurement points on the manufactured surface, transforming these measurement points from the measurement coordinate system to the design coordinate system through localization, and reconstructing the surface model using the localized measurement points. In this research, a method was developed to estimate the locations and their variances of any selected points on the reconstructed freeform surface considering different sources of uncertainties in measurement, localization and surface reconstruction processes. In this method, first locations and variances of the localized measurement points are calculated considering uncertainties of the measurement points and uncertainties introduced in the localization processes. Then locations and variances of points on the reconstructed freeform surface are obtained considering uncertainties of the localized measurement points and uncertainties introduced in the freeform surface reconstruction process. Two case studies were developed to demonstrate how these three different uncertainty sources influence the quality of the reconstructed freeform curve and freeform surface in inspection. (paper)

  15. ORIENTATION FIELD RECONSTRUCTION OF ALTERED FINGERPRINT USING ORTHOGONAL WAVELETS

    Directory of Open Access Journals (Sweden)

    Mini M.G.

    2016-11-01

    Full Text Available Ridge orientation field is an important feature for fingerprint matching and fingerprint reconstruction. Matching of the altered fingerprint against its unaltered mates can be done by extracting the available features in the altered fingerprint and using it along with approximated ridge orientation. This paper presents a method for approximating ridge orientation field of altered fingerprints. In the proposed method, sine and cosine of doubled orientation of the fingerprint is decomposed using orthogonal wavelets and reconstructed back using only the approximation coefficients. No prior information about the singular points is needed for orientation approximation. The method is found suitable for orientation estimation of low quality fingerprint images also.

  16. Accuracy and reliability of three-dimensional surface reconstruction measurement

    International Nuclear Information System (INIS)

    Mizukami, Chikashi; Yamamoto, Etsuo; Ohmura, Masaki; Oiki, Hiroyuki; Tsuji, Jun; Muneta, Yuki; Tanabe, Makito; Hakuba, Nobuhiro; Azemoto, Syougo.

    1993-01-01

    We are using a new three-dimensional (3-D) surface reconstruction system to measure the temporal bones. This system offers the advantage of observation of the external aperture of the vestibular aqueduct and the porus acusticus internus in living subjects. However, its accuracy has not been confirmed. To investigate the accuracy of this new system, we measured the length of an in situ ceramic ossicular replacement prosthesis (CORP) of known length of 6.0 mm using 3-D surface reconstruction, conventional plain X-ray and polytomography. The CORP was scanned in the axial, sagittal and oblique directions. The mean measured length obtained with the 3-D surface reconstruction images was 5.94±0.21 on vertical scans, 5.91±0.27 on horizontal scans, and 6.01±0.25 on oblique scans. There were no significant differences among the measured lengths obtained in the three directions. Therefore, this 3-D surface reconstruction measurement system is considered to be reliable. Conversely, the mean measured length obtained by plain X-ray was 7.98±0.20, and by polytomography it was 7.94±0.23. These conventional methods have the inherent disadvantage of magnification of size which consequently requires correction. (author)

  17. Sound field reconstruction based on the acousto-optic effect

    DEFF Research Database (Denmark)

    Torras Rosell, Antoni; Barrera Figueroa, Salvador; Jacobsen, Finn

    2011-01-01

    be measured with a laser Doppler vibrometer; furthermore, it can be exploited to characterize an arbitrary sound field using tomographic techniques. This paper briefly reviews the fundamental principles governing the acousto-optic effect in air, and presents an investigation of the tomographic reconstruction...... within the audible frequency range by means of simulations and experimental results. The good agreement observed between simulations and measurements is further confirmed with representations of the sound field obtained with traditional microphone array measurements....

  18. An iterative reconstruction of cosmological initial density fields

    Science.gov (United States)

    Hada, Ryuichiro; Eisenstein, Daniel J.

    2018-05-01

    We present an iterative method to reconstruct the linear-theory initial conditions from the late-time cosmological matter density field, with the intent of improving the recovery of the cosmic distance scale from the baryon acoustic oscillations (BAOs). We present tests using the dark matter density field in both real and redshift space generated from an N-body simulation. In redshift space at z = 0.5, we find that the reconstructed displacement field using our iterative method are more than 80% correlated with the true displacement field of the dark matter particles on scales k < 0.10h Mpc-1. Furthermore, we show that the two-point correlation function of our reconstructed density field matches that of the initial density field substantially better, especially on small scales (<40h-1 Mpc). Our redshift-space results are improved if we use an anisotropic smoothing so as to account for the reduced small-scale information along the line of sight in redshift space.

  19. Recent advances in 3D SEM surface reconstruction.

    Science.gov (United States)

    Tafti, Ahmad P; Kirkpatrick, Andrew B; Alavi, Zahrasadat; Owen, Heather A; Yu, Zeyun

    2015-11-01

    The scanning electron microscope (SEM), as one of the most commonly used instruments in biology and material sciences, employs electrons instead of light to determine the surface properties of specimens. However, the SEM micrographs still remain 2D images. To effectively measure and visualize the surface attributes, we need to restore the 3D shape model from the SEM images. 3D surface reconstruction is a longstanding topic in microscopy vision as it offers quantitative and visual information for a variety of applications consisting medicine, pharmacology, chemistry, and mechanics. In this paper, we attempt to explain the expanding body of the work in this area, including a discussion of recent techniques and algorithms. With the present work, we also enhance the reliability, accuracy, and speed of 3D SEM surface reconstruction by designing and developing an optimized multi-view framework. We then consider several real-world experiments as well as synthetic data to examine the qualitative and quantitative attributes of our proposed framework. Furthermore, we present a taxonomy of 3D SEM surface reconstruction approaches and address several challenging issues as part of our future work. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. MRI and Stereo Vision Surface Reconstruction and Fusion

    OpenAIRE

    El Chemaly, Trishia; Siepel, Françoise Jeanette; Rihana, Sandy; Groenhuis, Vincent; van der Heijden, Ferdinand; Stramigioli, Stefano

    2017-01-01

    Breast cancer, the most commonly diagnosed cancer in women worldwide, is mostly detected through a biopsy where tissue is extracted and chemically examined or pathologist assessed. Medical imaging plays a valuable role in targeting malignant tissue accurately and guiding the radiologist during needle insertion in a biopsy. This paper proposes a computer software that can process and combine 3D reconstructed surfaces from different imaging modalities, particularly Magnetic Resonance Imaging (M...

  1. Regularised reconstruction of sound fields with a spherical microphone array

    DEFF Research Database (Denmark)

    Granados Corsellas, Alba; Jacobsen, Finn; Fernandez Grande, Efren

    2013-01-01

    implementation might lead to disastrous reconstructions. A large number of regularisation tools based on singular value decomposition are available, and it has been found that the acoustic holography problem for certain geometries can be formulated in such a way that similarities to singular value decomposition...... become apparent. Hence, a number of regularisation methods, including truncated singular value decomposition, standard Tikhonov, constrained Tikhonov, iterative Tikhonov, Landweber and Rutishauser, have been adapted for spherical near field acoustic holography. The accuracy of the methods is examined...

  2. Multiview specular stereo reconstruction of large mirror surfaces

    KAUST Repository

    Balzer, Jonathan

    2011-06-01

    In deflectometry, the shape of mirror objects is recovered from distorted images of a calibrated scene. While remarkably high accuracies are achievable, state-of-the-art methods suffer from two distinct weaknesses: First, for mainly constructive reasons, these can only capture a few square centimeters of surface area at once. Second, reconstructions are ambiguous i.e. infinitely many surfaces lead to the same visual impression. We resolve both of these problems by introducing the first multiview specular stereo approach, which jointly evaluates a series of overlapping deflectometric images. Two publicly available benchmarks accompany this paper, enabling us to numerically demonstrate viability and practicability of our approach. © 2011 IEEE.

  3. First Gridded Spatial Field Reconstructions of Snow from Tree Rings

    Science.gov (United States)

    Coulthard, B. L.; Anchukaitis, K. J.; Pederson, G. T.; Alder, J. R.; Hostetler, S. W.; Gray, S. T.

    2017-12-01

    Western North America's mountain snowpacks provide critical water resources for human populations and ecosystems. Warmer temperatures and changing precipitation patterns will increasingly alter the quantity, extent, and persistence of snow in coming decades. A comprehensive understanding of the causes and range of long-term variability in this system is required for forecasting future anomalies, but snowpack observations are limited and sparse. While individual tree ring-based annual snowpack reconstructions have been developed for specific regions and mountain ranges, we present here the first collection of spatially-explicit gridded field reconstructions of seasonal snowpack within the American Rocky Mountains. Capitalizing on a new western North American snow-sensitive network of over 700 tree-ring chronologies, as well as recent advances in PRISM-based snow modeling, our gridded reconstructions offer a full space-time characterization of snow and associated water resource fluctuations over several centuries. The quality of reconstructions is evaluated against existing observations, proxy-records, and an independently-developed first-order monthly snow model.

  4. Reconstruction of sound fields with a spherical microphone array

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Walton, Tim

    2014-01-01

    waves traveling in any direction. In particular, rigid sphere microphone arrays are robust, and have the favorable property that the scattering introduced by the array can be compensated for - making the array virtually transparent. This study examines a recently proposed sound field reconstruction...... method based on a point source expansion, i.e. equivalent source method, using a rigid spherical array. The study examines the capability of the method to distinguish between sound waves arriving from different directions (i.e., as a sound field separation method). This is representative of the potential...

  5. Variational reconstruction using subdivision surfaces with continuous sharpness control

    Institute of Scientific and Technical Information of China (English)

    Xiaoqun Wu; Jianmin Zheng; Yiyu Cai; Haisheng Li

    2017-01-01

    We present a variational method for subdivision surface reconstruction from a noisy dense mesh.A new set of subdivision rules with continuous sharpness control is introduced into Loop subdivision for better modeling subdivision surface features such as semi-sharp creases,creases,and corners.The key idea is to assign a sharpness value to each edge of the control mesh to continuously control the surface features.Based on the new subdivision rules,a variational model with L1 norm is formulated to find the control mesh and the corresponding sharpness values of the subdivision surface that best fits the input mesh.An iterative solver based on the augmented Lagrangian method and particle swarm optimization is used to solve the resulting non-linear,non-differentiable optimization problem.Our experimental results show that our method can handle meshes well with sharp/semi-sharp features and noise.

  6. A continuous surface reconstruction method on point cloud captured from a 3D surface photogrammetry system.

    Science.gov (United States)

    Liu, Wenyang; Cheung, Yam; Sabouri, Pouya; Arai, Tatsuya J; Sawant, Amit; Ruan, Dan

    2015-11-01

    To accurately and efficiently reconstruct a continuous surface from noisy point clouds captured by a surface photogrammetry system (VisionRT). The authors have developed a level-set based surface reconstruction method on point clouds captured by a surface photogrammetry system (VisionRT). The proposed method reconstructs an implicit and continuous representation of the underlying patient surface by optimizing a regularized fitting energy, offering extra robustness to noise and missing measurements. By contrast to explicit/discrete meshing-type schemes, their continuous representation is particularly advantageous for subsequent surface registration and motion tracking by eliminating the need for maintaining explicit point correspondences as in discrete models. The authors solve the proposed method with an efficient narrowband evolving scheme. The authors evaluated the proposed method on both phantom and human subject data with two sets of complementary experiments. In the first set of experiment, the authors generated a series of surfaces each with different black patches placed on one chest phantom. The resulting VisionRT measurements from the patched area had different degree of noise and missing levels, since VisionRT has difficulties in detecting dark surfaces. The authors applied the proposed method to point clouds acquired under these different configurations, and quantitatively evaluated reconstructed surfaces by comparing against a high-quality reference surface with respect to root mean squared error (RMSE). In the second set of experiment, the authors applied their method to 100 clinical point clouds acquired from one human subject. In the absence of ground-truth, the authors qualitatively validated reconstructed surfaces by comparing the local geometry, specifically mean curvature distributions, against that of the surface extracted from a high-quality CT obtained from the same patient. On phantom point clouds, their method achieved submillimeter

  7. A continuous surface reconstruction method on point cloud captured from a 3D surface photogrammetry system

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wenyang [Department of Bioengineering, University of California, Los Angeles, California 90095 (United States); Cheung, Yam; Sabouri, Pouya; Arai, Tatsuya J.; Sawant, Amit [Department of Radiation Oncology, University of Texas Southwestern, Dallas, Texas 75390 (United States); Ruan, Dan, E-mail: druan@mednet.ucla.edu [Department of Bioengineering, University of California, Los Angeles, California 90095 and Department of Radiation Oncology, University of California, Los Angeles, California 90095 (United States)

    2015-11-15

    Purpose: To accurately and efficiently reconstruct a continuous surface from noisy point clouds captured by a surface photogrammetry system (VisionRT). Methods: The authors have developed a level-set based surface reconstruction method on point clouds captured by a surface photogrammetry system (VisionRT). The proposed method reconstructs an implicit and continuous representation of the underlying patient surface by optimizing a regularized fitting energy, offering extra robustness to noise and missing measurements. By contrast to explicit/discrete meshing-type schemes, their continuous representation is particularly advantageous for subsequent surface registration and motion tracking by eliminating the need for maintaining explicit point correspondences as in discrete models. The authors solve the proposed method with an efficient narrowband evolving scheme. The authors evaluated the proposed method on both phantom and human subject data with two sets of complementary experiments. In the first set of experiment, the authors generated a series of surfaces each with different black patches placed on one chest phantom. The resulting VisionRT measurements from the patched area had different degree of noise and missing levels, since VisionRT has difficulties in detecting dark surfaces. The authors applied the proposed method to point clouds acquired under these different configurations, and quantitatively evaluated reconstructed surfaces by comparing against a high-quality reference surface with respect to root mean squared error (RMSE). In the second set of experiment, the authors applied their method to 100 clinical point clouds acquired from one human subject. In the absence of ground-truth, the authors qualitatively validated reconstructed surfaces by comparing the local geometry, specifically mean curvature distributions, against that of the surface extracted from a high-quality CT obtained from the same patient. Results: On phantom point clouds, their method

  8. Absolute surface reconstruction by slope metrology and photogrammetry

    Science.gov (United States)

    Dong, Yue

    Developing the manufacture of aspheric and freeform optical elements requires an advanced metrology method which is capable of inspecting these elements with arbitrary freeform surfaces. In this dissertation, a new surface measurement scheme is investigated for such a purpose, which is to measure the absolute surface shape of an object under test through its surface slope information obtained by photogrammetric measurement. A laser beam propagating toward the object reflects on its surface while the vectors of the incident and reflected beams are evaluated from the four spots they leave on the two parallel transparent windows in front of the object. The spots' spatial coordinates are determined by photogrammetry. With the knowledge of the incident and reflected beam vectors, the local slope information of the object surface is obtained through vector calculus and finally yields the absolute object surface profile by a reconstruction algorithm. An experimental setup is designed and the proposed measuring principle is experimentally demonstrated by measuring the absolute surface shape of a spherical mirror. The measurement uncertainty is analyzed, and efforts for improvement are made accordingly. In particular, structured windows are designed and fabricated to generate uniform scattering spots left by the transmitted laser beams. Calibration of the fringe reflection instrument, another typical surface slope measurement method, is also reported in the dissertation. Finally, a method for uncertainty analysis of a photogrammetry measurement system by optical simulation is investigated.

  9. Polynomials, Riemann surfaces, and reconstructing missing-energy events

    CERN Document Server

    Gripaios, Ben; Webber, Bryan

    2011-01-01

    We consider the problem of reconstructing energies, momenta, and masses in collider events with missing energy, along with the complications introduced by combinatorial ambiguities and measurement errors. Typically, one reconstructs more than one value and we show how the wrong values may be correlated with the right ones. The problem has a natural formulation in terms of the theory of Riemann surfaces. We discuss examples including top quark decays in the Standard Model (relevant for top quark mass measurements and tests of spin correlation), cascade decays in models of new physics containing dark matter candidates, decays of third-generation leptoquarks in composite models of electroweak symmetry breaking, and Higgs boson decay into two tau leptons.

  10. PolyFit: Polygonal Surface Reconstruction from Point Clouds

    KAUST Repository

    Nan, Liangliang; Wonka, Peter

    2017-01-01

    We propose a novel framework for reconstructing lightweight polygonal surfaces from point clouds. Unlike traditional methods that focus on either extracting good geometric primitives or obtaining proper arrangements of primitives, the emphasis of this work lies in intersecting the primitives (planes only) and seeking for an appropriate combination of them to obtain a manifold polygonal surface model without boundary.,We show that reconstruction from point clouds can be cast as a binary labeling problem. Our method is based on a hypothesizing and selection strategy. We first generate a reasonably large set of face candidates by intersecting the extracted planar primitives. Then an optimal subset of the candidate faces is selected through optimization. Our optimization is based on a binary linear programming formulation under hard constraints that enforce the final polygonal surface model to be manifold and watertight. Experiments on point clouds from various sources demonstrate that our method can generate lightweight polygonal surface models of arbitrary piecewise planar objects. Besides, our method is capable of recovering sharp features and is robust to noise, outliers, and missing data.

  11. PolyFit: Polygonal Surface Reconstruction from Point Clouds

    KAUST Repository

    Nan, Liangliang

    2017-12-25

    We propose a novel framework for reconstructing lightweight polygonal surfaces from point clouds. Unlike traditional methods that focus on either extracting good geometric primitives or obtaining proper arrangements of primitives, the emphasis of this work lies in intersecting the primitives (planes only) and seeking for an appropriate combination of them to obtain a manifold polygonal surface model without boundary.,We show that reconstruction from point clouds can be cast as a binary labeling problem. Our method is based on a hypothesizing and selection strategy. We first generate a reasonably large set of face candidates by intersecting the extracted planar primitives. Then an optimal subset of the candidate faces is selected through optimization. Our optimization is based on a binary linear programming formulation under hard constraints that enforce the final polygonal surface model to be manifold and watertight. Experiments on point clouds from various sources demonstrate that our method can generate lightweight polygonal surface models of arbitrary piecewise planar objects. Besides, our method is capable of recovering sharp features and is robust to noise, outliers, and missing data.

  12. Comprehensive Use of Curvature for Robust and Accurate Online Surface Reconstruction.

    Science.gov (United States)

    Lefloch, Damien; Kluge, Markus; Sarbolandi, Hamed; Weyrich, Tim; Kolb, Andreas

    2017-12-01

    Interactive real-time scene acquisition from hand-held depth cameras has recently developed much momentum, enabling applications in ad-hoc object acquisition, augmented reality and other fields. A key challenge to online reconstruction remains error accumulation in the reconstructed camera trajectory, due to drift-inducing instabilities in the range scan alignments of the underlying iterative-closest-point (ICP) algorithm. Various strategies have been proposed to mitigate that drift, including SIFT-based pre-alignment, color-based weighting of ICP pairs, stronger weighting of edge features, and so on. In our work, we focus on surface curvature as a feature that is detectable on range scans alone and hence does not depend on accurate multi-sensor alignment. In contrast to previous work that took curvature into consideration, however, we treat curvature as an independent quantity that we consistently incorporate into every stage of the real-time reconstruction pipeline, including densely curvature-weighted ICP, range image fusion, local surface reconstruction, and rendering. Using multiple benchmark sequences, and in direct comparison to other state-of-the-art online acquisition systems, we show that our approach significantly reduces drift, both when analyzing individual pipeline stages in isolation, as well as seen across the online reconstruction pipeline as a whole.

  13. Born iterative reconstruction using perturbed-phase field estimates.

    Science.gov (United States)

    Astheimer, Jeffrey P; Waag, Robert C

    2008-10-01

    A method of image reconstruction from scattering measurements for use in ultrasonic imaging is presented. The method employs distorted-wave Born iteration but does not require using a forward-problem solver or solving large systems of equations. These calculations are avoided by limiting intermediate estimates of medium variations to smooth functions in which the propagated fields can be approximated by phase perturbations derived from variations in a geometric path along rays. The reconstruction itself is formed by a modification of the filtered-backpropagation formula that includes correction terms to account for propagation through an estimated background. Numerical studies that validate the method for parameter ranges of interest in medical applications are presented. The efficiency of this method offers the possibility of real-time imaging from scattering measurements.

  14. Mapping the Diffusion Potential of a Reconstructed Au(111) Surface at Nanometer Scale with 2D Molecular Gas

    International Nuclear Information System (INIS)

    Yan Shi-Chao; Xie Nan; Gong Hui-Qi; Guo Yang; Shan Xin-Yan; Lu Xing-Hua; Sun Qian

    2012-01-01

    The adsorption and diffusion behaviors of benzene molecules on an Au(111) surface are investigated by low-temperature scanning tunneling microscopy. A herringbone surface reconstruction of the Au(111) surface is imaged with atomic resolution, and significantly different behaviors are observed for benzene molecules adsorbed on step edges and terraces. The electric field induced modification in the molecular diffusion potential is revealed with a 2D molecular gas model, and a new method is developed to map the diffusion potential over the reconstructed Au(111) surface at the nanometer scale. (condensed matter: structure, mechanical and thermal properties)

  15. Sound field reconstruction using acousto-optic tomography

    DEFF Research Database (Denmark)

    Torras Rosell, Antoni; Barrera Figueroa, Salvador; Jacobsen, Finn

    2012-01-01

    When sound propagates through a medium, it results in pressure fluctuations that change the instantaneous density of the medium. Under such circumstances, the refractive index that characterizes the propagation of light is not constant, but influenced by the acoustic field. This kind of interaction...... the acousto-optic effect in air, and demonstrates that it can be measured with a laser Doppler vibrometer in the audible frequency range. The tomographic reconstruction is tested by means of computer simulations and measurements. The main features observed in the simulations are also recognized...

  16. Maximum entropy reconstruction of poloidal magnetic field and radial electric field profiles in tokamaks

    Science.gov (United States)

    Chen, Yihang; Xiao, Chijie; Yang, Xiaoyi; Wang, Tianbo; Xu, Tianchao; Yu, Yi; Xu, Min; Wang, Long; Lin, Chen; Wang, Xiaogang

    2017-10-01

    The Laser-driven Ion beam trace probe (LITP) is a new diagnostic method for measuring poloidal magnetic field (Bp) and radial electric field (Er) in tokamaks. LITP injects a laser-driven ion beam into the tokamak, and Bp and Er profiles can be reconstructed using tomography methods. A reconstruction code has been developed to validate the LITP theory, and both 2D reconstruction of Bp and simultaneous reconstruction of Bp and Er have been attained. To reconstruct from experimental data with noise, Maximum Entropy and Gaussian-Bayesian tomography methods were applied and improved according to the characteristics of the LITP problem. With these improved methods, a reconstruction error level below 15% has been attained with a data noise level of 10%. These methods will be further tested and applied in the following LITP experiments. Supported by the ITER-CHINA program 2015GB120001, CHINA MOST under 2012YQ030142 and National Natural Science Foundation Abstract of China under 11575014 and 11375053.

  17. Fusion of intraoperative force sensoring, surface reconstruction and biomechanical modeling

    Science.gov (United States)

    Röhl, S.; Bodenstedt, S.; Küderle, C.; Suwelack, S.; Kenngott, H.; Müller-Stich, B. P.; Dillmann, R.; Speidel, S.

    2012-02-01

    Minimally invasive surgery is medically complex and can heavily benefit from computer assistance. One way to help the surgeon is to integrate preoperative planning data into the surgical workflow. This information can be represented as a customized preoperative model of the surgical site. To use it intraoperatively, it has to be updated during the intervention due to the constantly changing environment. Hence, intraoperative sensor data has to be acquired and registered with the preoperative model. Haptic information which could complement the visual sensor data is still not established. In addition, biomechanical modeling of the surgical site can help in reflecting the changes which cannot be captured by intraoperative sensors. We present a setting where a force sensor is integrated into a laparoscopic instrument. In a test scenario using a silicone liver phantom, we register the measured forces with a reconstructed surface model from stereo endoscopic images and a finite element model. The endoscope, the instrument and the liver phantom are tracked with a Polaris optical tracking system. By fusing this information, we can transfer the deformation onto the finite element model. The purpose of this setting is to demonstrate the principles needed and the methods developed for intraoperative sensor data fusion. One emphasis lies on the calibration of the force sensor with the instrument and first experiments with soft tissue. We also present our solution and first results concerning the integration of the force sensor as well as accuracy to the fusion of force measurements, surface reconstruction and biomechanical modeling.

  18. Measurement and reconstruction of the BEBC magnetic field map

    CERN Document Server

    Häbel, E; Wittgenstein, F

    1973-01-01

    The superconducting magnet of the Big European Bubble Chamber (BEBC) has been excited with currents up to 5035 A corresponding to a magnetic induction of 3.1 Tesla at the center of the chamber. Since one expected that during the charging of the magnet coils long time constant eddy currents would be induced by the varying radial field components, a system of 181 Hall-probes was installed on the boundary of the chamber body allowing to survey the magnetic field map. This Hall-probe system together with an NMR-probe (nuclear magnetic resonance) enabled us to measure and reconstruct to an accuracy of better than 0.1% the field map of BEBC, which in itself is uniform to within 3% inside the visible fiducial volume of the Chamber. Direct evidence was also given for field map distortions due to the eddy current field which amounted to about 0.7% of the maximum recorded field values at the chamber center. (7 refs).

  19. Measurement and reconstruction of the BEBC magnetic field map

    CERN Document Server

    Häbel, E; Wittgenstein, F

    1973-01-01

    The superconducting magnet of the Big European Bubble Chamber (BEBC) has been excited with currents up to 5035 A corresponding to a magnetic induction of 3.1 Tesla at the center of the chamber. Since one expected that during the charging of the magnet coils long time constant eddy currents would be induced by the varying radial field components, a system of 181 Hall-probes was installed on the boundary of the chamber body allowing to survey the magnetic field map. This Hall-probe system together with an NMR-probe (nuclear magnetic resonance) enabled us to measure and reconstruct to an accuracy of better than 0.1the field map of BEBC, which in itself is uniform to within 3 191332nside the visible fiducial volume of the Chamber. Direct evidence was also given for field map distortions due to the eddy current field which amounted to about 0.723420f the maximum recorded field values at the chamber center. (7 refs).

  20. Heat source reconstruction from noisy temperature fields using an optimised derivative Gaussian filter

    Science.gov (United States)

    Delpueyo, D.; Balandraud, X.; Grédiac, M.

    2013-09-01

    The aim of this paper is to present a post-processing technique based on a derivative Gaussian filter to reconstruct heat source fields from temperature fields measured by infrared thermography. Heat sources can be deduced from temperature variations thanks to the heat diffusion equation. Filtering and differentiating are key-issues which are closely related here because the temperature fields which are processed are unavoidably noisy. We focus here only on the diffusion term because it is the most difficult term to estimate in the procedure, the reason being that it involves spatial second derivatives (a Laplacian for isotropic materials). This quantity can be reasonably estimated using a convolution of the temperature variation fields with second derivatives of a Gaussian function. The study is first based on synthetic temperature variation fields corrupted by added noise. The filter is optimised in order to reconstruct at best the heat source fields. The influence of both the dimension and the level of a localised heat source is discussed. Obtained results are also compared with another type of processing based on an averaging filter. The second part of this study presents an application to experimental temperature fields measured with an infrared camera on a thin plate in aluminium alloy. Heat sources are generated with an electric heating patch glued on the specimen surface. Heat source fields reconstructed from measured temperature fields are compared with the imposed heat sources. Obtained results illustrate the relevancy of the derivative Gaussian filter to reliably extract heat sources from noisy temperature fields for the experimental thermomechanics of materials.

  1. Reconstructing inflationary paradigm within Effective Field Theory framework

    Science.gov (United States)

    Choudhury, Sayantan

    2016-03-01

    In this paper my prime objective is to analyse the constraints on a sub-Planckian excursion of a single inflaton field within Effective Field Theory framework in a model independent fashion. For a generic single field inflationary potential, using the various parameterization of the primordial power spectrum I have derived the most general expression for the field excursion in terms of various inflationary observables, applying the observational constraints obtained from recent Planck 2015 and Planck 2015 + BICEP2/Keck Array data. By explicit computation I have reconstructed the structural form of the inflationary potential by constraining the Taylor expansion co-efficients appearing in the generic expansion of the potential within the Effective Field Theory. Next I have explicitly derived, a set of higher order inflationary consistency relationships, which would help us to break the degeneracy between various class of inflationary models by differentiating them. I also provided two simple examples of Effective Theory of inflation- inflection-point model and saddle-point model to check the compatibility of the prescribed methodology in the light of Planck 2015 and Planck 2015 + BICEP2/Keck Array data. Finally, I have also checked the validity of the prescription by estimating the cosmological parameters and fitting the theoretical CMB TT, TE and EE angular power spectra with the observed data within the multipole range 2 < l < 2500.

  2. Stereoscopic and photometric surface reconstruction in scanning electron microscopy

    International Nuclear Information System (INIS)

    Scherer, S.

    2000-01-01

    The scanning electron microscope (SEM) is one of the most important devices to examine microscopic structures as it offers images of a high contrast range with a large depth of focus. Nevertheless, three-dimensional measurements, as desired in fracture mechanics, have previously not been accomplished. This work presents a system for automatic, robust and dense surface reconstruction in scanning electron microscopy combining new approaches in shape from stereo and shape from photometric stereo. The basic theoretical assumption for a known adaptive window algorithm is shown not to hold in scanning electron microscopy. A constraint derived from this observation yields a new, simplified, hence faster calculation of the adaptive window. The correlation measure itself is obtained by a new ordinal measure coefficient. Shape from photometric stereo in the SEM is formulated by relating the image formation process with conventional photography. An iterative photometric ratio reconstruction is invented based on photometric ratios of backscatter electron images. The performance of the proposed system is evaluated using ground truth data obtained by three alternative shape recovery devices. Most experiments showed relative height accuracy within the tolerances of the alternative devices. (author)

  3. Polaron-mediated surface reconstruction in the reduced Rutile TiO2 (110) surface

    Science.gov (United States)

    Reticcioli, Michele; Setvin, Martin; Hao, Xianfeng; Diebold, Ulrike; Franchini, Cesare

    The role of polarons is of key importance for the understanding of the fundamental properties and functionalities of TiO2. We use density functional theory with an on-site Coulomb interaction and molecular dynamics to study the formation and dynamics of small polarons in the reduced rutile (110) surface. We show that excess electrons donated by oxygen-vacancies (VO) form mobile small polarons that hop easily in subsurface and surface Ti-sites. The polaron formation becomes more favorable by increasing the VO concentration level (up to 20%) due to the progressively lower energy cost needed to distort the lattice. However, at higher VO concentration the shortening of the averaged polaron-polaron distance leads to an increased Coulomb repulsion among the trapped charges at the Ti-sites, which weakens this trend. This instability is overtaken by means of a structural 1 × 2 surface reconstruction, characterized by a distinctively more favorable polaron distribution. The calculations are validated by a direct comparison with experimental AFM and STM data. Our study identifies a fundamentally novel mechanism to drive surface reconstructions and resolves a long standing issue on the origin of the reconstruction in rutile (110) surface.

  4. Sparse Reconstruction of Electric Fields from Radial Magnetic Data

    International Nuclear Information System (INIS)

    Yeates, Anthony R.

    2017-01-01

    Accurate estimates of the horizontal electric field on the Sun’s visible surface are important not only for estimating the Poynting flux of magnetic energy into the corona but also for driving time-dependent magnetohydrodynamic models of the corona. In this paper, a method is developed for estimating the horizontal electric field from a sequence of radial-component magnetic field maps. This problem of inverting Faraday’s law has no unique solution. Unfortunately, the simplest solution (a divergence-free electric field) is not realistically localized in regions of nonzero magnetic field, as would be expected from Ohm’s law. Our new method generates instead a localized solution, using a basis pursuit algorithm to find a sparse solution for the electric field. The method is shown to perform well on test cases where the input magnetic maps are flux balanced in both Cartesian and spherical geometries. However, we show that if the input maps have a significant imbalance of flux—usually arising from data assimilation—then it is not possible to find a localized, realistic, electric field solution. This is the main obstacle to driving coronal models from time sequences of solar surface magnetic maps.

  5. Sparse Reconstruction of Electric Fields from Radial Magnetic Data

    Energy Technology Data Exchange (ETDEWEB)

    Yeates, Anthony R. [Department of Mathematical Sciences, Durham University, Durham, DH1 3LE (United Kingdom)

    2017-02-10

    Accurate estimates of the horizontal electric field on the Sun’s visible surface are important not only for estimating the Poynting flux of magnetic energy into the corona but also for driving time-dependent magnetohydrodynamic models of the corona. In this paper, a method is developed for estimating the horizontal electric field from a sequence of radial-component magnetic field maps. This problem of inverting Faraday’s law has no unique solution. Unfortunately, the simplest solution (a divergence-free electric field) is not realistically localized in regions of nonzero magnetic field, as would be expected from Ohm’s law. Our new method generates instead a localized solution, using a basis pursuit algorithm to find a sparse solution for the electric field. The method is shown to perform well on test cases where the input magnetic maps are flux balanced in both Cartesian and spherical geometries. However, we show that if the input maps have a significant imbalance of flux—usually arising from data assimilation—then it is not possible to find a localized, realistic, electric field solution. This is the main obstacle to driving coronal models from time sequences of solar surface magnetic maps.

  6. Preserving half-metallic surface states in Cr O2 : Insights into surface reconstruction rules

    Science.gov (United States)

    Deng, Bei; Shi, X. Q.; Chen, L.; Tong, S. Y.

    2018-04-01

    The issue of whether the half-metallic (HM) nature of Cr O2 could be retained at its surface has been a standing problem under debate for a few decades, but until now is still controversial. Here, based on the density functional theory calculations we show, in startling contrast to the previous theoretical understandings, that the surfaces of Cr O2 favorably exhibit a half-metallic-semiconducting (SmC) transition driven by means of a surface electronic reconstruction largely attributed to the participation of the unexpected local charge carriers (LCCs), which convert the HM double exchange surface state into a SmC superexchange state and in turn, stabilize the surface as well. On the basis of the LCCs model, a new insight into the surface reconstruction rules is attained. Our novel finding not only provided an evident interpretation for the widely observed SmC character of Cr O2 surface, but also offered a novel means to improve the HM surface states for a variety of applications in spintronics and superconductors, and promote the experimental realization of the quantum anomalous Hall effect in half-metal based systems.

  7. Integrated fiber optic sensors for hot spot detection and temperature field reconstruction in satellites

    International Nuclear Information System (INIS)

    Rapp, S; Baier, H

    2010-01-01

    Large satellites are often equipped with more than 1000 temperature sensors during the test campaign. Hundreds of them are still used for monitoring during launch and operation in space. This means an additional mass and especially high effort in assembly, integration and verification on a system level. So the use of fiber Bragg grating temperature sensors is investigated as they offer several advantages. They are lightweight, small in size and electromagnetically immune, which fits well in space applications. Their multiplexing capability offers the possibility to build extensive sensor networks including dozens of sensors of different types, such as strain sensors, accelerometers and temperature sensors. The latter allow the detection of hot spots and the reconstruction of temperature fields via proper algorithms, which is shown in this paper. A temperature sensor transducer was developed, which can be integrated into satellite sandwich panels with negligible mechanical influence. Mechanical and thermal vacuum tests were performed to verify the space compatibility of the developed sensor system. Proper reconstruction algorithms were developed to estimate the temperature field and detect thermal hot spots on the panel surface. A representative hardware demonstrator has been built and tested, which shows the capability of using an integrated fiber Bragg grating temperature sensor network for temperature field reconstruction and hot spot detection in satellite structures

  8. Scattering amplitudes over finite fields and multivariate functional reconstruction

    International Nuclear Information System (INIS)

    Peraro, Tiziano

    2016-01-01

    Several problems in computer algebra can be efficiently solved by reducing them to calculations over finite fields. In this paper, we describe an algorithm for the reconstruction of multivariate polynomials and rational functions from their evaluation over finite fields. Calculations over finite fields can in turn be efficiently performed using machine-size integers in statically-typed languages. We then discuss the application of the algorithm to several techniques related to the computation of scattering amplitudes, such as the four- and six-dimensional spinor-helicity formalism, tree-level recursion relations, and multi-loop integrand reduction via generalized unitarity. The method has good efficiency and scales well with the number of variables and the complexity of the problem. As an example combining these techniques, we present the calculation of full analytic expressions for the two-loop five-point on-shell integrands of the maximal cuts of the planar penta-box and the non-planar double-pentagon topologies in Yang-Mills theory, for a complete set of independent helicity configurations.

  9. Scattering amplitudes over finite fields and multivariate functional reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Peraro, Tiziano [Higgs Centre for Theoretical Physics,School of Physics and Astronomy, The University of Edinburgh,James Clerk Maxwell Building, Peter Guthrie Tait Road, Edinburgh EH9 3FD (United Kingdom)

    2016-12-07

    Several problems in computer algebra can be efficiently solved by reducing them to calculations over finite fields. In this paper, we describe an algorithm for the reconstruction of multivariate polynomials and rational functions from their evaluation over finite fields. Calculations over finite fields can in turn be efficiently performed using machine-size integers in statically-typed languages. We then discuss the application of the algorithm to several techniques related to the computation of scattering amplitudes, such as the four- and six-dimensional spinor-helicity formalism, tree-level recursion relations, and multi-loop integrand reduction via generalized unitarity. The method has good efficiency and scales well with the number of variables and the complexity of the problem. As an example combining these techniques, we present the calculation of full analytic expressions for the two-loop five-point on-shell integrands of the maximal cuts of the planar penta-box and the non-planar double-pentagon topologies in Yang-Mills theory, for a complete set of independent helicity configurations.

  10. A method of reconstructing complex stratigraphic surfaces with multitype fault constraints

    Science.gov (United States)

    Deng, Shi-Wu; Jia, Yu; Yao, Xing-Miao; Liu, Zhi-Ning

    2017-06-01

    The construction of complex stratigraphic surfaces is widely employed in many fields, such as petroleum exploration, geological modeling, and geological structure analysis. It also serves as an important foundation for data visualization and visual analysis in these fields. The existing surface construction methods have several deficiencies and face various difficulties, such as the presence of multitype faults and roughness of resulting surfaces. In this paper, a surface modeling method that uses geometric partial differential equations (PDEs) is introduced for the construction of stratigraphic surfaces. It effectively solves the problem of surface roughness caused by the irregularity of stratigraphic data distribution. To cope with the presence of multitype complex faults, a two-way projection algorithm between threedimensional space and a two-dimensional plane is proposed. Using this algorithm, a unified method based on geometric PDEs is developed for dealing with multitype faults. Moreover, the corresponding geometric PDE is derived, and an algorithm based on an evolutionary solution is developed. The algorithm proposed for constructing spatial surfaces with real data verifies its computational efficiency and its ability to handle irregular data distribution. In particular, it can reconstruct faulty surfaces, especially those with overthrust faults.

  11. Reconstruction of Daily Sea Surface Temperature Based on Radial Basis Function Networks

    Directory of Open Access Journals (Sweden)

    Zhihong Liao

    2017-11-01

    Full Text Available A radial basis function network (RBFN method is proposed to reconstruct daily Sea surface temperatures (SSTs with limited SST samples. For the purpose of evaluating the SSTs using this method, non-biased SST samples in the Pacific Ocean (10°N–30°N, 115°E–135°E are selected when the tropical storm Hagibis arrived in June 2014, and these SST samples are obtained from the Reynolds optimum interpolation (OI v2 daily 0.25° SST (OISST products according to the distribution of AVHRR L2p SST and in-situ SST data. Furthermore, an improved nearest neighbor cluster (INNC algorithm is designed to search for the optimal hidden knots for RBFNs from both the SST samples and the background fields. Then, the reconstructed SSTs from the RBFN method are compared with the results from the OI method. The statistical results show that the RBFN method has a better performance of reconstructing SST than the OI method in the study, and that the average RMSE is 0.48 °C for the RBFN method, which is quite smaller than the value of 0.69 °C for the OI method. Additionally, the RBFN methods with different basis functions and clustering algorithms are tested, and we discover that the INNC algorithm with multi-quadric function is quite suitable for the RBFN method to reconstruct SSTs when the SST samples are sparsely distributed.

  12. Field reconstruction for the KEK large-aperture-spectrometer-magnet 'TOKIWA'

    International Nuclear Information System (INIS)

    Amako, K.; Kawano, K.; Sugimoto, S.; Matsui, T.

    1978-10-01

    Field reconstruction has been performed for the KEK large-aperture-magnet ''TOKIWA''. The magnetic field components are determined point-by-point by an iteration method in which the output voltage from the Hall probes placed in three dimensional directions are used simultaneously. The field components are thus reconstructed accurately within 32 G everywhere in the magnet volume. (author)

  13. Surface Magnetic Fields on Giants and Supergiants

    Science.gov (United States)

    Lebre, Agnès

    2018-04-01

    After a short introduction to spectropolarimetry and the tecnics allowing for the detection of surface fields, I will review the numerous and various detections of magnetic fields at the surface of giant and supergiant stars. On Betelgeuse, the prototype of Red Supergiants, I will present recent results collected after a 10 years long spectropolarimetric survey.

  14. Reconstruction and downscaling of Eastern Mediterranean OSCAR satellite surface current data using DINEOF

    Science.gov (United States)

    Nikolaidis, Andreas; Stylianou, Stavros; Georgiou, Georgios; Hajimitsis, Diofantos; Gravanis, Elias; Akylas, Evangelos

    2015-04-01

    During the last decade, Rixen (2005) and Alvera-Azkarate (2010) presented the DINEOF (Data Interpolating Empirical Orthogonal Functions) method, a EOF-based technique to reconstruct missing data in satellite images. The application of DINEOF method, proved to provide relative success in various experimental trials (Wang and Liu, 2013; Nikolaidis et al., 2013;2014), and tends to be an effective and computationally affordable solution, on the problem of data reconstruction, for missing data from geophysical fields, such as chlorophyll-a, sea surface temperatures or salinity and geophysical fields derived from satellite data. Implementation of this method in a GIS system will provide with a more complete, integrated approach, permitting the expansion of the applicability over various aspects. This may be especially useful in studies where various data of different kind, have to be examined. For this purpose, in this study we have implemented and present a GIS toolbox that aims to automate the usage of the algorithm, incorporating the DINEOF codes provided by GHER (GeoHydrodynamics and Environment Research Group of University of Liege) into the ArcGIS®. ArcGIS® is a well known standard on Geographical Information Systems, used over the years for various remote sensing procedures, in sea and land environment alike. A case-study of filling the missing satellite derived current data in the Eastern Mediterranean Sea area, for a monthly period is analyzed, as an example for the effectiveness and simplicity of the usage of this toolbox. The specific study focuses to OSCAR satellite data (http://www.oscar.noaa.gov/) collected by NOAA/NESDIS Operational Surface Current Processing and Data Center, from the respective products of OSCAR Project Office Earth and Space Research organization, that provides free online access to unfiltered (1/3 degree) resolution. All the 5-day mean products data coverage were successfully reconstructed. KEY WORDS: Remote Sensing, Cyprus

  15. Vector fields on nonorientable surfaces

    Directory of Open Access Journals (Sweden)

    Ilie Barza

    2003-01-01

    X, and the space of vector fields on X are proved by using a symmetrisation process. An example related to the normal derivative on the border of the Möbius strip supports the nontriviality of the concepts introduced in this paper.

  16. Surface states in an external electric field

    International Nuclear Information System (INIS)

    Steslicka, M.

    1975-10-01

    Under conditions typical for field ion microscopy, true surface states can exist. Their shift towards higher energies can be quite significant and, moreover, additional surface levels at still higher energies can appear. The latter can play an important role in the process of tunneling of image gas electrons into surface states

  17. General surface reconstruction for cone-beam multislice spiral computed tomography

    International Nuclear Information System (INIS)

    Chen Laigao; Liang Yun; Heuscher, Dominic J.

    2003-01-01

    A new family of cone-beam reconstruction algorithm, the General Surface Reconstruction (GSR), is proposed and formulated in this paper for multislice spiral computed tomography (CT) reconstructions. It provides a general framework to allow the reconstruction of planar or nonplanar surfaces on a set of rebinned short-scan parallel beam projection data. An iterative surface formation method is proposed as an example to show the possibility to form nonplanar reconstruction surfaces to minimize the adverse effect between the collected cone-beam projection data and the reconstruction surfaces. The improvement in accuracy of the nonplanar surfaces over planar surfaces in the two-dimensional approximate cone-beam reconstructions is mathematically proved and demonstrated using numerical simulations. The proposed GSR algorithm is evaluated by the computer simulation of cone-beam spiral scanning geometry and various mathematical phantoms. The results demonstrate that the GSR algorithm generates much better image quality compared to conventional multislice reconstruction algorithms. For a table speed up to 100 mm per rotation, GSR demonstrates good image quality for both the low-contrast ball phantom and thorax phantom. All other performance parameters are comparable to the single-slice 180 deg. LI (linear interpolation) algorithm, which is considered the 'gold standard'. GSR also achieves high computing efficiency and good temporal resolution, making it an attractive alternative for the reconstruction of next generation multislice spiral CT data

  18. Reconstructions of the sulfur-passivated InSb (100) surface

    Energy Technology Data Exchange (ETDEWEB)

    Ciochoń, Piotr, E-mail: piotr.ciochon@doctoral.uj.edu.pl; Olszowska, Natalia; Wróbel, Sonia; Kołodziej, Jacek

    2017-04-01

    Highlights: • Two new surface reconstructions of a S-passivated InSb (001) surface are reported. • The reconstructions are obtained through partial loss of surface sulfur. • They are characterized by the thickness of ∼4 Å and good crystallographic ordering. • The reconstructions provide adequate electronic passivation of the surface. - Abstract: We have studied the properties of the InSb (100) surface passivated with sulfur dimers emitted by the solid-state electrochemical cell in ultra-high vacuum. Annealing the passivated surface in the temperature equal to T = 326 °C led to the formation of the c(4 × 8) surface reconstruction, while increasing the temperature to T = 348 °C resulted in the transition to c(4 × 12) reconstruction. To the best of our knowledge these reconstructions have not been reported to date and are characterized by the exceptionally good crystallographic order. XPS studies revealed that there are at least 4 different chemical species of sulfur present on the surface and the estimated thickness of the sulfur layers is equal to around 4 Å. The surface reconstructions are characterized by the lowered intensity of the surface electronic states and resonances near the Fermi level, compared to the clean InSb surface, making them potentially very useful for the fabrication of InSb-based electronic and optoelectronic devices.

  19. Surface Topology Reconstruction From The White Light Interferogram By Means Of Prony Analysis

    Directory of Open Access Journals (Sweden)

    Khoma Anna

    2015-12-01

    Full Text Available The paper presents a new method of surface topology reconstruction from a white light interferogram. The method is based on interferogram modelling by complex exponents (Prony method. The compatibility of white light interferogram and Prony models has already been proven. Effectiveness of the method was tested by modelling and examining reconstruction of tilted and spherical surfaces, and by estimating the reconstruction accuracy.

  20. Surface-reconstructed graphite nanofibers as a support for cathode catalysts of fuel cells.

    Science.gov (United States)

    Gan, Lin; Du, Hongda; Li, Baohua; Kang, Feiyu

    2011-04-07

    Graphite nanofibers (GNFs), on which surface graphite edges were reconstructed into nano-loops, were explored as a cathode catalyst support for fuel cells. The high degree of graphitization, as well as the surface-reconstructed nano-loops that possess topological defects for uniform metal deposition, resulted in an improved performance of the GNF-supported Pt catalyst.

  1. Three-dimensional reconstruction of sound fields based on the acousto-optic effect

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Torras Rosell, Antoni

    2013-01-01

    -optic tomography via scanning the field with a laser Doppler vibrometer. Consequently, the spatial characteristics of the sound field are captured in the measurement, implicitly bearing the potential for a full holographic reconstruction in a three-dimensional space. Recent studies have examined the reconstruction......, and compares the results to the ones obtained from conventional microphone array measurements....

  2. Pico Lantern: Surface reconstruction and augmented reality in laparoscopic surgery using a pick-up laser projector.

    Science.gov (United States)

    Edgcumbe, Philip; Pratt, Philip; Yang, Guang-Zhong; Nguan, Christopher; Rohling, Robert

    2015-10-01

    The Pico Lantern is a miniature projector developed for structured light surface reconstruction, augmented reality and guidance in laparoscopic surgery. During surgery it will be dropped into the patient and picked up by a laparoscopic tool. While inside the patient it projects a known coded pattern and images onto the surface of the tissue. The Pico Lantern is visually tracked in the laparoscope's field of view for the purpose of stereo triangulation between it and the laparoscope. In this paper, the first application is surface reconstruction. Using a stereo laparoscope and an untracked Pico Lantern, the absolute error for surface reconstruction for a plane, cylinder and ex vivo kidney, is 2.0 mm, 3.0 mm and 5.6 mm, respectively. Using a mono laparoscope and a tracked Pico Lantern for the same plane, cylinder and kidney the absolute error is 1.4 mm, 1.5 mm and 1.5 mm, respectively. These results confirm the benefit of the wider baseline produced by tracking the Pico Lantern. Virtual viewpoint images are generated from the kidney surface data and an in vivo proof-of-concept porcine trial is reported. Surface reconstruction of the neck of a volunteer shows that the pulsatile motion of the tissue overlying a major blood vessel can be detected and displayed in vivo. Future work will integrate the Pico Lantern into standard and robot-assisted laparoscopic surgery. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. The research of Digital Holographic Object Wave Field Reconstruction in Image and Object Space

    Institute of Scientific and Technical Information of China (English)

    LI Jun-Chang; PENG Zu-Jie; FU Yun-Chang

    2011-01-01

    @@ For conveniently detecting objects of different sizes using digital holography, usual measurements employ the object wave transformed by an optical system with different magnifications to fit charge coupled devices (CCDs), then the object field reconstruction involves the diffraction calculation of the optic wave passing through the optical system.We propose two methods to reconstruct the object field.The one is that, when the object is imaging in an image space in which we reconstruct the image of the object field, the object field can be expressed according to the object-image relationship.The other is that, when the object field reaching CCD is imaged in an object space in which we reconstruct the object field, the optical system is described by introducing matrix optics in this paper.The reconstruction formulae which easily use classic diffraction integral are derived.Finally, experimental verifications are also accomplished.%For conveniently detecting objects of different sizes using digital holography, usual measurements employ the object wave transformed by an optical system with different magnifications to fit charge coupled devices (CCDs), then the object Reid reconstruction involves the diffraction calculation of the optic wave passing through the optical system. We propose two methods to reconstruct the object field. The one is that, when the object is imaging in an image space in which we reconstruct the image of the object field, the object field can be expressed according to the object-image relationship. The other is that, when the object field reaching CCD is imaged in an object space in which we reconstruct the object field, the optical system is described by introducing matrix optics in this paper. The reconstruction formulae which easily use classic diffraction integral are derived. Finally, experimental verifications are also accomplished.

  4. Error Propagation dynamics: from PIV-based pressure reconstruction to vorticity field calculation

    Science.gov (United States)

    Pan, Zhao; Whitehead, Jared; Richards, Geordie; Truscott, Tadd; USU Team; BYU Team

    2017-11-01

    Noninvasive data from velocimetry experiments (e.g., PIV) have been used to calculate vorticity and pressure fields. However, the noise, error, or uncertainties in the PIV measurements would eventually propagate to the calculated pressure or vorticity field through reconstruction schemes. Despite the vast applications of pressure and/or vorticity field calculated from PIV measurements, studies on the error propagation from the velocity field to the reconstructed fields (PIV-pressure and PIV-vorticity are few. In the current study, we break down the inherent connections between PIV-based pressure reconstruction and PIV-based vorticity calculation. The similar error propagation dynamics, which involve competition between physical properties of the flow and numerical errors from reconstruction schemes, are found in both PIV-pressure and PIV-vorticity reconstructions.

  5. Perturbation theory for BAO reconstructed fields: One-loop results in the real-space matter density field

    Science.gov (United States)

    Hikage, Chiaki; Koyama, Kazuya; Heavens, Alan

    2017-08-01

    We compute the power spectrum at one-loop order in standard perturbation theory for the matter density field to which a standard Lagrangian baryonic acoustic oscillation (BAO) reconstruction technique is applied. The BAO reconstruction method corrects the bulk motion associated with the gravitational evolution using the inverse Zel'dovich approximation (ZA) for the smoothed density field. We find that the overall amplitude of one-loop contributions in the matter power spectrum substantially decreases after reconstruction. The reconstructed power spectrum thereby approaches the initial linear spectrum when the smoothed density field is close enough to linear, i.e., the smoothing scale Rs≳10 h-1 Mpc . On smaller Rs, however, the deviation from the linear spectrum becomes significant on large scales (k ≲Rs-1 ) due to the nonlinearity in the smoothed density field, and the reconstruction is inaccurate. Compared with N-body simulations, we show that the reconstructed power spectrum at one-loop order agrees with simulations better than the unreconstructed power spectrum. We also calculate the tree-level bispectrum in standard perturbation theory to investigate non-Gaussianity in the reconstructed matter density field. We show that the amplitude of the bispectrum significantly decreases for small k after reconstruction and that the tree-level bispectrum agrees well with N-body results in the weakly nonlinear regime.

  6. DINEOF reconstruction of clouded images including error maps – application to the Sea-Surface Temperature around Corsican Island

    Directory of Open Access Journals (Sweden)

    J.-M. Beckers

    2006-01-01

    Full Text Available We present an extension to the Data INterpolating Empirical Orthogonal Functions (DINEOF technique which allows not only to fill in clouded images but also to provide an estimation of the error covariance of the reconstruction. This additional information is obtained by an analogy with optimal interpolation. It is shown that the error fields can be obtained with a clever rearrangement of calculations at a cost comparable to that of the interpolation itself. The method is presented on the reconstruction of sea-surface temperature in the Ligurian Sea and around the Corsican Island (Mediterranean Sea, including the calculation of inter-annual variability of average surface values and their expected errors. The application shows that the error fields are not only able to reflect the data-coverage structure but also the covariances of the physical fields.

  7. Miniature photometric stereo system for textile surface structure reconstruction

    Science.gov (United States)

    Gorpas, Dimitris; Kampouris, Christos; Malassiotis, Sotiris

    2013-04-01

    In this work a miniature photometric stereo system is presented, targeting the three-dimensional structural reconstruction of various fabric types. This is a supportive module to a robot system, attempting to solve the well known "laundry problem". The miniature device has been designed for mounting onto the robot gripper. It is composed of a low-cost off-the-shelf camera, operating in macro mode, and eight light emitting diodes. The synchronization between image acquisition and lighting direction is controlled by an Arduino Nano board and software triggering. The ambient light has been addressed by a cylindrical enclosure. The direction of illumination is recovered by locating the reflection or the brightest point on a mirror sphere, while a flatfielding process compensates for the non-uniform illumination. For the evaluation of this prototype, the classical photometric stereo methodology has been used. The preliminary results on a large number of textiles are very promising for the successful integration of the miniature module to the robot system. The required interaction with the robot is implemented through the estimation of the Brenner's focus measure. This metric successfully assesses the focus quality with reduced time requirements in comparison to other well accepted focus metrics. Besides the targeting application, the small size of the developed system makes it a very promising candidate for applications with space restrictions, like the quality control in industrial production lines or object recognition based on structural information and in applications where easiness in operation and light-weight are required, like those in the Biomedical field, and especially in dermatology.

  8. Ray calibration and phase mapping for structured-light-field 3D reconstruction.

    Science.gov (United States)

    Cai, Zewei; Liu, Xiaoli; Peng, Xiang; Gao, Bruce Z

    2018-03-19

    In previous work, we presented a structured light field (SLF) method combining light field imaging with structured illumination to perform multi-view depth measurement. However, the previous work just accomplishes depth rather than 3D reconstruction. In this paper, we propose a novel active method involving ray calibration and phase mapping, to achieve SLF 3D reconstruction. We performed the ray calibration for the first time to determine each light field ray with metric spatio-angular parameters, making the SLF realize multi-view 3D reconstruction. Based on the ray parametric equation, we further derived the phase mapping in the SLF that spatial coordinates can be directly mapped from phase. A flexible calibration strategy was correspondently designed to determine mapping coefficients for each light field ray, achieving high-efficiency SLF 3D reconstruction. Experimental results demonstrated that the proposed method was suitable for high-efficiency multi-view 3D reconstruction in the SLF.

  9. A Survey on Methods for Reconstructing Surfaces from Unorganized Point Sets

    Directory of Open Access Journals (Sweden)

    Vilius Matiukas

    2011-08-01

    Full Text Available This paper addresses the issue of reconstructing and visualizing surfaces from unorganized point sets. These can be acquired using different techniques, such as 3D-laser scanning, computerized tomography, magnetic resonance imaging and multi-camera imaging. The problem of reconstructing surfaces from their unorganized point sets is common for many diverse areas, including computer graphics, computer vision, computational geometry or reverse engineering. The paper presents three alternative methods that all use variations in complementary cones to triangulate and reconstruct the tested 3D surfaces. The article evaluates and contrasts three alternatives.Article in English

  10. Reconstruction of coupling architecture of neural field networks from vector time series

    Science.gov (United States)

    Sysoev, Ilya V.; Ponomarenko, Vladimir I.; Pikovsky, Arkady

    2018-04-01

    We propose a method of reconstruction of the network coupling matrix for a basic voltage-model of the neural field dynamics. Assuming that the multivariate time series of observations from all nodes are available, we describe a technique to find coupling constants which is unbiased in the limit of long observations. Furthermore, the method is generalized for reconstruction of networks with time-delayed coupling, including the reconstruction of unknown time delays. The approach is compared with other recently proposed techniques.

  11. Reconstructing extreme AMOC events through nudging of the ocean surface: a perfect model approach

    Science.gov (United States)

    Ortega, Pablo; Guilyardi, Eric; Swingedouw, Didier; Mignot, Juliette; Nguyen, Sébastien

    2017-11-01

    While the Atlantic Meridional Overturning Circulation (AMOC) is thought to be a crucial component of the North Atlantic climate, past changes in its strength are challenging to quantify, and only limited information is available. In this study, we use a perfect model approach with the IPSL-CM5A-LR model to assess the performance of several surface nudging techniques in reconstructing the variability of the AMOC. Special attention is given to the reproducibility of an extreme positive AMOC peak from a preindustrial control simulation. Nudging includes standard relaxation techniques towards the sea surface temperature and salinity anomalies of this target control simulation, and/or the prescription of the wind-stress fields. Surface nudging approaches using standard fixed restoring terms succeed in reproducing most of the target AMOC variability, including the timing of the extreme event, but systematically underestimate its amplitude. A detailed analysis of the AMOC variability mechanisms reveals that the underestimation of the extreme AMOC maximum comes from a deficit in the formation of the dense water masses in the main convection region, located south of Iceland in the model. This issue is largely corrected after introducing a novel surface nudging approach, which uses a varying restoring coefficient that is proportional to the simulated mixed layer depth, which, in essence, keeps the restoring time scale constant. This new technique substantially improves water mass transformation in the regions of convection, and in particular, the formation of the densest waters, which are key for the representation of the AMOC extreme. It is therefore a promising strategy that may help to better constrain the AMOC variability and other ocean features in the models. As this restoring technique only uses surface data, for which better and longer observations are available, it opens up opportunities for improved reconstructions of the AMOC over the last few decades.

  12. Diagnostic value of 3 D CT surface reconstruction in spinal fractures

    Energy Technology Data Exchange (ETDEWEB)

    Koesling, S. [Department of Radiology, Univ. of Leipzig (Germany); Dietrich, K. [Department of Radiology, Univ. of Leipzig (Germany); Steinecke, R. [Department of Radiology, Univ. of Leipzig (Germany); Kloeppel, R. [Department of Radiology, Univ. of Leipzig (Germany); Schulz, H.G. [Department of Radiology, Univ. of Leipzig (Germany)

    1997-02-01

    Our purpose was to evaluate the diagnostic value of three-dimensional (3 D) CT surface reconstruction in spinal fractures in comparison with axial and reformatted images. A total of 50 patients with different CT-proven spinal fractures were analysed retrospectively. Based on axial scans and reformatted images, the spinal fractures were classified according to several classifications as Magerl for the thoraco-lumbar and lower cervical spine by one radiologist. Another radiologist performed 3 D CT surface reconstructions with the aim of characterizing the different types of spinal fractures. A third radiologist classified the 3 D CT surface reconstruction according to the Magerl classification. The results of the blinded reading process were compared. It was checked to see in which type and subgroup 3 D surface reconstructions were helpful. Readers one and two obtained the same results in the classification. The 3 D surface reconstruction did not yield any additional diagnostic information concerning type A and B injuries. Indeed, the full extent of the fracture could be easier recognized with axial and reformatted images in all cases. In 10 cases of C injuries, the dislocation of parts of vertebrae could be better recognized with the help of 3 D reconstructions. A 3 D CT surface reconstruction is only useful in rotational and shear vertebral injuries (Magerl type C injury). (orig.). With 4 figs., 1 tab.

  13. Preservation of the Pt(100) surface reconstruction after growth of a continuous layer of graphene

    DEFF Research Database (Denmark)

    Nilsson, Louis; Andersen, Mie; Bjerre, Jacob

    2012-01-01

    Scanning tunneling microscopy shows that a layer of graphene can be grown on the hex-reconstructed Pt(100) surface and that the reconstruction is preserved after growth. A continuous sheet of graphene can be grown across domain boundaries and step edges without loss of periodicity or change in di...

  14. Direct Reconstruction of Two-Dimensional Currents in Thin Films from Magnetic-Field Measurements

    Science.gov (United States)

    Meltzer, Alexander Y.; Levin, Eitan; Zeldov, Eli

    2017-12-01

    An accurate determination of microscopic transport and magnetization currents is of central importance for the study of the electric properties of low-dimensional materials and interfaces, of superconducting thin films, and of electronic devices. Current distribution is usually derived from the measurement of the perpendicular component of the magnetic field above the surface of the sample, followed by numerical inversion of the Biot-Savart law. The inversion is commonly obtained by deriving the current stream function g , which is then differentiated in order to obtain the current distribution. However, this two-step procedure requires filtering at each step and, as a result, oversmooths the solution. To avoid this oversmoothing, we develop a direct procedure for inversion of the magnetic field that avoids use of the stream function. This approach provides enhanced accuracy of current reconstruction over a wide range of noise levels. We further introduce a reflection procedure that allows for the reconstruction of currents that cross the boundaries of the measurement window. The effectiveness of our approach is demonstrated by several numerical examples.

  15. The Effects of Surface Reconstruction and Electron-Positron Correlation on the Annihilation Characteristics of Positrons Trapped at Semiconductor Surfaces

    International Nuclear Information System (INIS)

    Fazleev, N. G.; Jung, E.; Weiss, A. H.

    2009-01-01

    Experimental positron annihilation induced Auger electron spectroscopy (PAES) data from Ge(100) and Ge(111) surfaces display several strong Auger peaks corresponding to M 4,5 N 1 N 2,3 , M 2,3 M 4,5 M 4,5 , M 2,3 M 4,5 V, and M 1 M 4,5 M 4,5 Auger transitions. The integrated peak intensities of Auger transitions have been used to obtain experimental annihilation probabilities for the Ge 3d and 3p core electrons. The experimental data were analyzed by performing theoretical studies of the effects of surface reconstructions and electron-positron correlations on image potential induced surface states and annihilation characteristics of positrons trapped at the reconstructed Ge(100) and Ge(111) surfaces. Calculations of positron surface states and annihilation characteristics have been performed for Ge(100) surface with (2x1), (2x2), and (4x2) reconstructions, and for Ge(111) surface with c(2x8) reconstruction. Estimates of the positron binding energy and annihilation characteristics reveal their sensitivity to the specific atomic structure of the topmost layers of the semiconductor and to the approximations used to describe electron-positron correlations. The results of these theoretical studies are compared with the ones obtained for the reconstructed Si(100)-(2x1) and Si(111)-(7x7) surfaces.

  16. Surface modifications by field induced diffusion.

    Directory of Open Access Journals (Sweden)

    Martin Olsen

    Full Text Available By applying a voltage pulse to a scanning tunneling microscope tip the surface under the tip will be modified. We have in this paper taken a closer look at the model of electric field induced surface diffusion of adatoms including the van der Waals force as a contribution in formations of a mound on a surface. The dipole moment of an adatom is the sum of the surface induced dipole moment (which is constant and the dipole moment due to electric field polarisation which depends on the strength and polarity of the electric field. The electric field is analytically modelled by a point charge over an infinite conducting flat surface. From this we calculate the force that cause adatoms to migrate. The calculated force is small for voltage used, typical 1 pN, but due to thermal vibration adatoms are hopping on the surface and even a small net force can be significant in the drift of adatoms. In this way we obtain a novel formula for a polarity dependent threshold voltage for mound formation on the surface for positive tip. Knowing the voltage of the pulse we then can calculate the radius of the formed mound. A threshold electric field for mound formation of about 2 V/nm is calculated. In addition, we found that van der Waals force is of importance for shorter distances and its contribution to the radial force on the adatoms has to be considered for distances smaller than 1.5 nm for commonly used voltages.

  17. Surface reconstruction and deformation monitoring of stratospheric airship based on laser scanning technology

    Science.gov (United States)

    Guo, Kai; Xie, Yongjie; Ye, Hu; Zhang, Song; Li, Yunfei

    2018-04-01

    Due to the uncertainty of stratospheric airship's shape and the security problem caused by the uncertainty, surface reconstruction and surface deformation monitoring of airship was conducted based on laser scanning technology and a √3-subdivision scheme based on Shepard interpolation was developed. Then, comparison was conducted between our subdivision scheme and the original √3-subdivision scheme. The result shows our subdivision scheme could reduce the shrinkage of surface and the number of narrow triangles. In addition, our subdivision scheme could keep the sharp features. So, surface reconstruction and surface deformation monitoring of airship could be conducted precisely by our subdivision scheme.

  18. Surface multipole guide field for plasma injection

    International Nuclear Information System (INIS)

    Breun, R.A.; Rael, B.H.; Wong, A.Y.

    1977-01-01

    Described here is a surface guide field system which is useful for injection of plasmas into confinement devices. Experimental results are given for 5--25-eV hydrogen plasmas produced by a coaxial discharge (Marshall) gun. It is found that better than 90% of the plasma produced by the gun is delivered to the end of the guide 180 cm away, while the neutral component falls by more than an order of magnitude. For these results the rod current providing the magnetic field had to be large enough to provide at least 1.5-ion gyroradii from the center of the guide to the surface of the inner rod

  19. Extended Reconstructed Sea Surface Temperature (ERSST) Monthly Analysis, Version 3b

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Version 3b (v3b) of the Extended Reconstructed Sea Surface Temperature (ERSST) dataset is a monthly SST analysis on a 2-degree global grid based on the International...

  20. Lattice topological field theory on nonorientable surfaces

    International Nuclear Information System (INIS)

    Karimipour, V.; Mostafazadeh, A.

    1997-01-01

    The lattice definition of the two-dimensional topological quantum field theory [Fukuma et al., Commun. Math. Phys. 161, 157 (1994)] is generalized to arbitrary (not necessarily orientable) compact surfaces. It is shown that there is a one-to-one correspondence between real associative *-algebras and the topological state sum invariants defined on such surfaces. The partition and n-point functions on all two-dimensional surfaces (connected sums of the Klein bottle or projective plane and g-tori) are defined and computed for arbitrary *-algebras in general, and for the group ring A=R[G] of discrete groups G, in particular. copyright 1997 American Institute of Physics

  1. Quantum field theory near surfaces of discontinuity

    International Nuclear Information System (INIS)

    Onishi, H.T.

    1981-01-01

    This work deals with the problem of a quantized scalar field propagating near a surface of discontinuity. The proper time formalism is employed to express the Green's function and stress tensor as proper time integrals of a transformation function. The transformation function is calculated by a WKB approximation which exhibits the essential singularities generated by the high frequency behavior of waves propagating near the surface. Two singularities are present, the usual direct singularity and an additional reflected singularity generated by the high frequency behavior of waves reflected by the discontinuity. The stress tensor is calculated by dimensional continuation. The results are employed to analyze energy generated by the surface

  2. Learning-based 3D surface optimization from medical image reconstruction

    Science.gov (United States)

    Wei, Mingqiang; Wang, Jun; Guo, Xianglin; Wu, Huisi; Xie, Haoran; Wang, Fu Lee; Qin, Jing

    2018-04-01

    Mesh optimization has been studied from the graphical point of view: It often focuses on 3D surfaces obtained by optical and laser scanners. This is despite the fact that isosurfaced meshes of medical image reconstruction suffer from both staircases and noise: Isotropic filters lead to shape distortion, while anisotropic ones maintain pseudo-features. We present a data-driven method for automatically removing these medical artifacts while not introducing additional ones. We consider mesh optimization as a combination of vertex filtering and facet filtering in two stages: Offline training and runtime optimization. In specific, we first detect staircases based on the scanning direction of CT/MRI scanners, and design a staircase-sensitive Laplacian filter (vertex-based) to remove them; and then design a unilateral filtered facet normal descriptor (uFND) for measuring the geometry features around each facet of a given mesh, and learn the regression functions from a set of medical meshes and their high-resolution reference counterparts for mapping the uFNDs to the facet normals of the reference meshes (facet-based). At runtime, we first perform staircase-sensitive Laplacian filter on an input MC (Marching Cubes) mesh, and then filter the mesh facet normal field using the learned regression functions, and finally deform it to match the new normal field for obtaining a compact approximation of the high-resolution reference model. Tests show that our algorithm achieves higher quality results than previous approaches regarding surface smoothness and surface accuracy.

  3. Image reconstruction in k-space from MR data encoded with ambiguous gradient fields.

    Science.gov (United States)

    Schultz, Gerrit; Gallichan, Daniel; Weber, Hans; Witschey, Walter R T; Honal, Matthias; Hennig, Jürgen; Zaitsev, Maxim

    2015-02-01

    In this work, the limits of image reconstruction in k-space are explored when non-bijective gradient fields are used for spatial encoding. The image space analogy between parallel imaging and imaging with non-bijective encoding fields is partially broken in k-space. As a consequence, it is hypothesized and proven that ambiguities can only be resolved partially in k-space, and not completely as is the case in image space. Image-space and k-space based reconstruction algorithms for multi-channel radiofrequency data acquisitions are programmed and tested using numerical simulations as well as in vivo measurement data. The hypothesis is verified based on an analysis of reconstructed images. It is found that non-bijective gradient fields have the effect that densely sampled autocalibration data, used for k-space reconstruction, provide less information than a separate scan of the receiver coil sensitivity maps, used for image space reconstruction. Consequently, in k-space only the undersampling artifact can be unfolded, whereas in image space, it is also possible to resolve aliasing that is caused by the non-bijectivity of the gradient fields. For standard imaging, reconstruction in image space and in k-space is nearly equivalent, whereas there is a fundamental difference with practical consequences for the selection of image reconstruction algorithms when non-bijective encoding fields are involved. © 2014 Wiley Periodicals, Inc.

  4. Spatial performance of RegEM climate field reconstruction techniques in a realistic pseudoproxy context

    Science.gov (United States)

    Wang, J.; Emile-Geay, J.; Guillot, D.

    2011-12-01

    . Joos, D. S. Schimel, B. L. Otto-Bliesner, and R. A. Tomas (2007), Solar influence on climate during the past millennium: Results from transient simulations with the NCAR Climate System Model, Proc. Natl. Acad. Sci. U. S. A., 104, 3713-3718, doi:10.1073/pnas.0605064103. Mann, M. E., R. S. Bradley, and M. K. Hughes (1998), Global-scale temperaturepatterns and climate forcing over the past six centuries, Nature, 392, 779-787, doi:10.1038/33859. Mann, M. E., S. Rutherford, E. Wahl, and C. Ammann (2007), Robustness of proxy-based climate field reconstruction methods, J. Geophys. Res., 112, D12109, doi:10.1029/2006JD008272. Mann, M. E., et al. (2008), Proxy-based reconstructions of hemispheric and global surface temperature variations over the past two millennia, Proc. Natl. Acad. Sci. U. S. A., 105, 13,252-13,257, doi:10.1073/pnas.0805721105. Schneider, T. (2001), Analysis of incomplete climate data: Estimation of mean values and covariance matrices and imputation of missing values, J. Clim., 14, 853-871, doi:10.1175/1520-0442(2001)0142.0.CO;2. Smerdon, J. E., A. Kaplan, E. Zorita, J. F. González-Rouco, and M. N. Evans (2011), Spatial performance of four climate field reconstruction methods targeting the Common Era, Geophys. Res. Lett., 38, L11705, doi:10.1029/2011GL047372.

  5. Analysis of fracture surface of CFRP material by three-dimensional reconstruction methods

    International Nuclear Information System (INIS)

    Lobo, Raquel M.; Andrade, Arnaldo H.P.

    2009-01-01

    Fracture surfaces of CFRP (carbon Fiber Reinforced Polymer) materials, used in the nuclear fuel cycle, presents an elevated roughness, mainly due to the fracture mode known as pulling out, that displays pieces of carbon fibers after debonding between fiber and matrix. The fractographic analysis, by bi-dimensional images is deficient for not considering the so important vertical resolution as much as the horizontal resolution. In this case, the knowledge of this heights distribution that occurs during the breaking, can lead to the calculation of the involved energies in the process that would allows a better agreement on the fracture mechanisms of the composite material. An important solution for the material characterization, whose surface presents a high roughness due to the variation in height, is to reconstruct three-dimensionally these fracture surfaces. In this work, the 3D reconstruction was done by two different methods: the variable focus reconstruction, through a stack of images obtained by optical microscopy (OM) and the parallax reconstruction, carried through with images acquired by scanning electron microscopy (SEM). The results of both methods present an elevation map of the reconstructed image that determine the height of the surface pixel by pixel,. The results obtained by the methods of reconstruction for the CFRP surfaces, have been compared with others materials such as aluminum and copper that present a ductile type fracture surface, with lower roughness. (author)

  6. Electronic structure studies of a clock-reconstructed Al/Pd(1 0 0) surface alloy

    Science.gov (United States)

    Kirsch, Janet E.; Tainter, Craig J.

    We have employed solid-state Fenske-Hall band structure calculations to examine the electronic structure of Al/Pd(1 0 0), a surface alloy that undergoes a reconstruction, or rearrangement, of the atoms in the top few surface layers. Surface alloys are materials that consist primarily of a single elemental metal, but which have a bimetallic surface composition that is only a few atomic layers in thickness. The results of this study indicate that reconstruction into a clock configuration simultaneously optimizes the intralayer bonding within the surface plane and the bonding between the first and second atomic layers. These results also allow us to examine the fundamental relationship between the electronic and physical structures of this reconstructed surface alloy.

  7. Validation of a laboratory method for evaluating dynamic properties of reconstructed equine racetrack surfaces.

    Directory of Open Access Journals (Sweden)

    Jacob J Setterbo

    Full Text Available Racetrack surface is a risk factor for racehorse injuries and fatalities. Current research indicates that race surface mechanical properties may be influenced by material composition, moisture content, temperature, and maintenance. Race surface mechanical testing in a controlled laboratory setting would allow for objective evaluation of dynamic properties of surface and factors that affect surface behavior.To develop a method for reconstruction of race surfaces in the laboratory and validate the method by comparison with racetrack measurements of dynamic surface properties.Track-testing device (TTD impact tests were conducted to simulate equine hoof impact on dirt and synthetic race surfaces; tests were performed both in situ (racetrack and using laboratory reconstructions of harvested surface materials. Clegg Hammer in situ measurements were used to guide surface reconstruction in the laboratory. Dynamic surface properties were compared between in situ and laboratory settings. Relationships between racetrack TTD and Clegg Hammer measurements were analyzed using stepwise multiple linear regression.Most dynamic surface property setting differences (racetrack-laboratory were small relative to surface material type differences (dirt-synthetic. Clegg Hammer measurements were more strongly correlated with TTD measurements on the synthetic surface than the dirt surface. On the dirt surface, Clegg Hammer decelerations were negatively correlated with TTD forces.Laboratory reconstruction of racetrack surfaces guided by Clegg Hammer measurements yielded TTD impact measurements similar to in situ values. The negative correlation between TTD and Clegg Hammer measurements confirms the importance of instrument mass when drawing conclusions from testing results. Lighter impact devices may be less appropriate for assessing dynamic surface properties compared to testing equipment designed to simulate hoof impact (TTD.Dynamic impact properties of race surfaces

  8. Evaluation of interpolation methods for surface-based motion compensated tomographic reconstruction for cardiac angiographic C-arm data

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Kerstin; Schwemmer, Chris; Hornegger, Joachim [Pattern Recognition Lab, Department of Computer Science, Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Erlangen 91058 (Germany); Zheng Yefeng; Wang Yang [Imaging and Computer Vision, Siemens Corporate Research, Princeton, New Jersey 08540 (United States); Lauritsch, Guenter; Rohkohl, Christopher; Maier, Andreas K. [Siemens AG, Healthcare Sector, Forchheim 91301 (Germany); Schultz, Carl [Thoraxcenter, Erasmus MC, Rotterdam 3000 (Netherlands); Fahrig, Rebecca [Department of Radiology, Stanford University, Stanford, California 94305 (United States)

    2013-03-15

    Purpose: For interventional cardiac procedures, anatomical and functional information about the cardiac chambers is of major interest. With the technology of angiographic C-arm systems it is possible to reconstruct intraprocedural three-dimensional (3D) images from 2D rotational angiographic projection data (C-arm CT). However, 3D reconstruction of a dynamic object is a fundamental problem in C-arm CT reconstruction. The 2D projections are acquired over a scan time of several seconds, thus the projection data show different states of the heart. A standard FDK reconstruction algorithm would use all acquired data for a filtered backprojection and result in a motion-blurred image. In this approach, a motion compensated reconstruction algorithm requiring knowledge of the 3D heart motion is used. The motion is estimated from a previously presented 3D dynamic surface model. This dynamic surface model results in a sparse motion vector field (MVF) defined at control points. In order to perform a motion compensated reconstruction, a dense motion vector field is required. The dense MVF is generated by interpolation of the sparse MVF. Therefore, the influence of different motion interpolation methods on the reconstructed image quality is evaluated. Methods: Four different interpolation methods, thin-plate splines (TPS), Shepard's method, a smoothed weighting function, and a simple averaging, were evaluated. The reconstruction quality was measured on phantom data, a porcine model as well as on in vivo clinical data sets. As a quality index, the 2D overlap of the forward projected motion compensated reconstructed ventricle and the segmented 2D ventricle blood pool was quantitatively measured with the Dice similarity coefficient and the mean deviation between extracted ventricle contours. For the phantom data set, the normalized root mean square error (nRMSE) and the universal quality index (UQI) were also evaluated in 3D image space. Results: The quantitative evaluation of

  9. Evaluation of interpolation methods for surface-based motion compensated tomographic reconstruction for cardiac angiographic C-arm data

    International Nuclear Information System (INIS)

    Müller, Kerstin; Schwemmer, Chris; Hornegger, Joachim; Zheng Yefeng; Wang Yang; Lauritsch, Günter; Rohkohl, Christopher; Maier, Andreas K.; Schultz, Carl; Fahrig, Rebecca

    2013-01-01

    Purpose: For interventional cardiac procedures, anatomical and functional information about the cardiac chambers is of major interest. With the technology of angiographic C-arm systems it is possible to reconstruct intraprocedural three-dimensional (3D) images from 2D rotational angiographic projection data (C-arm CT). However, 3D reconstruction of a dynamic object is a fundamental problem in C-arm CT reconstruction. The 2D projections are acquired over a scan time of several seconds, thus the projection data show different states of the heart. A standard FDK reconstruction algorithm would use all acquired data for a filtered backprojection and result in a motion-blurred image. In this approach, a motion compensated reconstruction algorithm requiring knowledge of the 3D heart motion is used. The motion is estimated from a previously presented 3D dynamic surface model. This dynamic surface model results in a sparse motion vector field (MVF) defined at control points. In order to perform a motion compensated reconstruction, a dense motion vector field is required. The dense MVF is generated by interpolation of the sparse MVF. Therefore, the influence of different motion interpolation methods on the reconstructed image quality is evaluated. Methods: Four different interpolation methods, thin-plate splines (TPS), Shepard's method, a smoothed weighting function, and a simple averaging, were evaluated. The reconstruction quality was measured on phantom data, a porcine model as well as on in vivo clinical data sets. As a quality index, the 2D overlap of the forward projected motion compensated reconstructed ventricle and the segmented 2D ventricle blood pool was quantitatively measured with the Dice similarity coefficient and the mean deviation between extracted ventricle contours. For the phantom data set, the normalized root mean square error (nRMSE) and the universal quality index (UQI) were also evaluated in 3D image space. Results: The quantitative evaluation of all

  10. Exploration, Sampling, And Reconstruction of Free Energy Surfaces with Gaussian Process Regression.

    Science.gov (United States)

    Mones, Letif; Bernstein, Noam; Csányi, Gábor

    2016-10-11

    Practical free energy reconstruction algorithms involve three separate tasks: biasing, measuring some observable, and finally reconstructing the free energy surface from those measurements. In more than one dimension, adaptive schemes make it possible to explore only relatively low lying regions of the landscape by progressively building up the bias toward the negative of the free energy surface so that free energy barriers are eliminated. Most schemes use the final bias as their best estimate of the free energy surface. We show that large gains in computational efficiency, as measured by the reduction of time to solution, can be obtained by separating the bias used for dynamics from the final free energy reconstruction itself. We find that biasing with metadynamics, measuring a free energy gradient estimator, and reconstructing using Gaussian process regression can give an order of magnitude reduction in computational cost.

  11. 3D Surface Reconstruction for Lower Limb Prosthetic Model using Radon Transform

    Science.gov (United States)

    Sobani, S. S. Mohd; Mahmood, N. H.; Zakaria, N. A.; Razak, M. A. Abdul

    2018-03-01

    This paper describes the idea to realize three-dimensional surfaces of objects with cylinder-based shapes where the techniques adopted and the strategy developed for a non-rigid three-dimensional surface reconstruction of an object from uncalibrated two-dimensional image sequences using multiple-view digital camera and turntable setup. The surface of an object is reconstructed based on the concept of tomography with the aid of performing several digital image processing algorithms on the two-dimensional images captured by a digital camera in thirty-six different projections and the three-dimensional structure of the surface is analysed. Four different objects are used as experimental models in the reconstructions and each object is placed on a manually rotated turntable. The results shown that the proposed method has successfully reconstruct the three-dimensional surface of the objects and practicable. The shape and size of the reconstructed three-dimensional objects are recognizable and distinguishable. The reconstructions of objects involved in the test are strengthened with the analysis where the maximum percent error obtained from the computation is approximately 1.4 % for the height whilst 4.0%, 4.79% and 4.7% for the diameters at three specific heights of the objects.

  12. A robust real-time surface reconstruction method on point clouds captured from a 3D surface photogrammetry system.

    Science.gov (United States)

    Liu, Wenyang; Cheung, Yam; Sawant, Amit; Ruan, Dan

    2016-05-01

    To develop a robust and real-time surface reconstruction method on point clouds captured from a 3D surface photogrammetry system. The authors have developed a robust and fast surface reconstruction method on point clouds acquired by the photogrammetry system, without explicitly solving the partial differential equation required by a typical variational approach. Taking advantage of the overcomplete nature of the acquired point clouds, their method solves and propagates a sparse linear relationship from the point cloud manifold to the surface manifold, assuming both manifolds share similar local geometry. With relatively consistent point cloud acquisitions, the authors propose a sparse regression (SR) model to directly approximate the target point cloud as a sparse linear combination from the training set, assuming that the point correspondences built by the iterative closest point (ICP) is reasonably accurate and have residual errors following a Gaussian distribution. To accommodate changing noise levels and/or presence of inconsistent occlusions during the acquisition, the authors further propose a modified sparse regression (MSR) model to model the potentially large and sparse error built by ICP with a Laplacian prior. The authors evaluated the proposed method on both clinical point clouds acquired under consistent acquisition conditions and on point clouds with inconsistent occlusions. The authors quantitatively evaluated the reconstruction performance with respect to root-mean-squared-error, by comparing its reconstruction results against that from the variational method. On clinical point clouds, both the SR and MSR models have achieved sub-millimeter reconstruction accuracy and reduced the reconstruction time by two orders of magnitude to a subsecond reconstruction time. On point clouds with inconsistent occlusions, the MSR model has demonstrated its advantage in achieving consistent and robust performance despite the introduced occlusions. The authors have

  13. A robust real-time surface reconstruction method on point clouds captured from a 3D surface photogrammetry system

    International Nuclear Information System (INIS)

    Liu, Wenyang; Cheung, Yam; Sawant, Amit; Ruan, Dan

    2016-01-01

    Purpose: To develop a robust and real-time surface reconstruction method on point clouds captured from a 3D surface photogrammetry system. Methods: The authors have developed a robust and fast surface reconstruction method on point clouds acquired by the photogrammetry system, without explicitly solving the partial differential equation required by a typical variational approach. Taking advantage of the overcomplete nature of the acquired point clouds, their method solves and propagates a sparse linear relationship from the point cloud manifold to the surface manifold, assuming both manifolds share similar local geometry. With relatively consistent point cloud acquisitions, the authors propose a sparse regression (SR) model to directly approximate the target point cloud as a sparse linear combination from the training set, assuming that the point correspondences built by the iterative closest point (ICP) is reasonably accurate and have residual errors following a Gaussian distribution. To accommodate changing noise levels and/or presence of inconsistent occlusions during the acquisition, the authors further propose a modified sparse regression (MSR) model to model the potentially large and sparse error built by ICP with a Laplacian prior. The authors evaluated the proposed method on both clinical point clouds acquired under consistent acquisition conditions and on point clouds with inconsistent occlusions. The authors quantitatively evaluated the reconstruction performance with respect to root-mean-squared-error, by comparing its reconstruction results against that from the variational method. Results: On clinical point clouds, both the SR and MSR models have achieved sub-millimeter reconstruction accuracy and reduced the reconstruction time by two orders of magnitude to a subsecond reconstruction time. On point clouds with inconsistent occlusions, the MSR model has demonstrated its advantage in achieving consistent and robust performance despite the introduced

  14. A robust real-time surface reconstruction method on point clouds captured from a 3D surface photogrammetry system

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wenyang [Department of Bioengineering, University of California, Los Angeles, Los Angeles, California 90095 (United States); Cheung, Yam [Department of Radiation Oncology, University of Texas Southwestern, Dallas, Texas 75390 (United States); Sawant, Amit [Department of Radiation Oncology, University of Texas Southwestern, Dallas, Texas, 75390 and Department of Radiation Oncology, University of Maryland, College Park, Maryland 20742 (United States); Ruan, Dan, E-mail: druan@mednet.ucla.edu [Department of Bioengineering, University of California, Los Angeles, Los Angeles, California 90095 and Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California 90095 (United States)

    2016-05-15

    Purpose: To develop a robust and real-time surface reconstruction method on point clouds captured from a 3D surface photogrammetry system. Methods: The authors have developed a robust and fast surface reconstruction method on point clouds acquired by the photogrammetry system, without explicitly solving the partial differential equation required by a typical variational approach. Taking advantage of the overcomplete nature of the acquired point clouds, their method solves and propagates a sparse linear relationship from the point cloud manifold to the surface manifold, assuming both manifolds share similar local geometry. With relatively consistent point cloud acquisitions, the authors propose a sparse regression (SR) model to directly approximate the target point cloud as a sparse linear combination from the training set, assuming that the point correspondences built by the iterative closest point (ICP) is reasonably accurate and have residual errors following a Gaussian distribution. To accommodate changing noise levels and/or presence of inconsistent occlusions during the acquisition, the authors further propose a modified sparse regression (MSR) model to model the potentially large and sparse error built by ICP with a Laplacian prior. The authors evaluated the proposed method on both clinical point clouds acquired under consistent acquisition conditions and on point clouds with inconsistent occlusions. The authors quantitatively evaluated the reconstruction performance with respect to root-mean-squared-error, by comparing its reconstruction results against that from the variational method. Results: On clinical point clouds, both the SR and MSR models have achieved sub-millimeter reconstruction accuracy and reduced the reconstruction time by two orders of magnitude to a subsecond reconstruction time. On point clouds with inconsistent occlusions, the MSR model has demonstrated its advantage in achieving consistent and robust performance despite the introduced

  15. Technical report on the surface reconstruction of stacked contours by using the commercial software

    Science.gov (United States)

    Shin, Dong Sun; Chung, Min Suk; Hwang, Sung Bae; Park, Jin Seo

    2007-03-01

    After drawing and stacking contours of a structure, which is identified in the serially sectioned images, three-dimensional (3D) image can be made by surface reconstruction. Usually, software is composed for the surface reconstruction. In order to compose the software, medical doctors have to acquire the help of computer engineers. So in this research, surface reconstruction of stacked contours was tried by using commercial software. The purpose of this research is to enable medical doctors to perform surface reconstruction to make 3D images by themselves. The materials of this research were 996 anatomic images (1 mm intervals) of left lower limb, which were made by serial sectioning of a cadaver. On the Adobe Photoshop, contours of 114 anatomic structures were drawn, which were exported to Adobe Illustrator files. On the Maya, contours of each anatomic structure were stacked. On the Rhino, superoinferior lines were drawn along all stacked contours to fill quadrangular surfaces between contours. On the Maya, the contours were deleted. 3D images of 114 anatomic structures were assembled with their original locations preserved. With the surface reconstruction technique, developed in this research, medical doctors themselves could make 3D images of the serially sectioned images such as CTs and MRIs.

  16. SLAM-based dense surface reconstruction in monocular Minimally Invasive Surgery and its application to Augmented Reality.

    Science.gov (United States)

    Chen, Long; Tang, Wen; John, Nigel W; Wan, Tao Ruan; Zhang, Jian Jun

    2018-05-01

    While Minimally Invasive Surgery (MIS) offers considerable benefits to patients, it also imposes big challenges on a surgeon's performance due to well-known issues and restrictions associated with the field of view (FOV), hand-eye misalignment and disorientation, as well as the lack of stereoscopic depth perception in monocular endoscopy. Augmented Reality (AR) technology can help to overcome these limitations by augmenting the real scene with annotations, labels, tumour measurements or even a 3D reconstruction of anatomy structures at the target surgical locations. However, previous research attempts of using AR technology in monocular MIS surgical scenes have been mainly focused on the information overlay without addressing correct spatial calibrations, which could lead to incorrect localization of annotations and labels, and inaccurate depth cues and tumour measurements. In this paper, we present a novel intra-operative dense surface reconstruction framework that is capable of providing geometry information from only monocular MIS videos for geometry-aware AR applications such as site measurements and depth cues. We address a number of compelling issues in augmenting a scene for a monocular MIS environment, such as drifting and inaccurate planar mapping. A state-of-the-art Simultaneous Localization And Mapping (SLAM) algorithm used in robotics has been extended to deal with monocular MIS surgical scenes for reliable endoscopic camera tracking and salient point mapping. A robust global 3D surface reconstruction framework has been developed for building a dense surface using only unorganized sparse point clouds extracted from the SLAM. The 3D surface reconstruction framework employs the Moving Least Squares (MLS) smoothing algorithm and the Poisson surface reconstruction framework for real time processing of the point clouds data set. Finally, the 3D geometric information of the surgical scene allows better understanding and accurate placement AR augmentations

  17. Effects of surface relaxation and reconstruction on the vibration characteristics of nanobeams

    International Nuclear Information System (INIS)

    Zhang, Wen-Ming; Hu, Kai-Ming; Peng, Zhi-Ke; Meng, Guang; Yang, Bin

    2016-01-01

    Surface effects on the free vibration characteristics of nanobeams are investigated by a modified continuum model. In this paper, the relationship between the parameters of the modified continuum model of surface effects including surface elasticity, surface density, and residual surface stresses, and the parameters of the atomistic lattice model such as surface relaxation and reconstruction in nanobeams is characterized by an atomistic lattice model. The surface effects are incorporated into nanobeams to develop a modified continuum model depicting the free vibrational behavior of nanobeams. The model is validated with the experimental data of an effective size-dependent Young’s modulus and the previous theoretical results. The results demonstrate that both surface elasticity and surface density vary exponentially with surface layer thickness. Therefore, surface elasticity and density can be affected by surface relaxation and residual surface stresses can be induced by surface reconstruction. The natural frequencies of doubly clamped nanobeams can be affected by the dimensions of the nanobeams, surface layer thickness, and residual surface stress. This work may be helpful for understanding surface effects and their influence on the vibrational behavior of nanobeams. (paper)

  18. A photogrammetry-based system for 3D surface reconstruction of prosthetics and orthotics.

    Science.gov (United States)

    Li, Guang-kun; Gao, Fan; Wang, Zhi-gang

    2011-01-01

    The objective of this study is to develop an innovative close range digital photogrammetry (CRDP) system using the commercial digital SLR cameras to measure and reconstruct the 3D surface of prosthetics and orthotics. This paper describes the instrumentation, techniques and preliminary results of the proposed system. The technique works by taking pictures of the object from multiple view angles. The series of pictures were post-processed via feature point extraction, point match and 3D surface reconstruction. In comparison with the traditional method such as laser scanning, the major advantages of our instrument include the lower cost, compact and easy-to-use hardware, satisfactory measurement accuracy, and significantly less measurement time. Besides its potential applications in prosthetics and orthotics surface measurement, the simple setup and its ease of use will make it suitable for various 3D surface reconstructions.

  19. Direct observation of surface reconstruction and termination on a complex metal oxide catalyst by electron microscopy

    KAUST Repository

    Zhu, Yihan

    2012-03-19

    On the surface: The surface reconstruction of an MoVTeO complex metal oxide catalyst was observed directly by various electron microscopic techniques and the results explain the puzzling catalytic behavior. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Ultra Fast Optical Sectioning: Signal preserving filtering and surface reconstruction

    DEFF Research Database (Denmark)

    Jensen, Rasmus Ramsbøl; Poel, Mike van der; Larsen, Rasmus

    2011-01-01

    a signal preserving ltering of the data set is done. The remaining data are used for a smooth surface re- construction creating very plausible surfaces. The data used in our work comes from a newly developed hand held 3D scanner. The scanner is an Ultra Fast Optical Sectioning scanner, which is able...

  1. SU-E-J-128: 3D Surface Reconstruction of a Patient Using Epipolar Geometry

    Energy Technology Data Exchange (ETDEWEB)

    Kotoku, J; Nakabayashi, S; Kumagai, S; Ishibashi, T; Kobayashi, T [Teikyo University, Itabashi-ku, Tokyo (Japan); Haga, A; Saotome, N [University of Tokyo Hospital, Bunkyo-ku, Tokyo (Japan); Arai, N [Teikyo University Hospital, Itabashi-ku, Tokyo (Japan)

    2014-06-01

    Purpose: To obtain a 3D surface data of a patient in a non-invasive way can substantially reduce the effort for the registration of patient in radiation therapy. To achieve this goal, we introduced the multiple view stereo technique, which is known to be used in a 'photo tourism' on the internet. Methods: 70 Images were taken with a digital single-lens reflex camera from different angles and positions. The camera positions and angles were inferred later in the reconstruction step. A sparse 3D reconstruction model was locating by SIFT features, which is robust for rotation and shift variance, in each image. We then found a set of correspondences between pairs of images by computing the fundamental matrix using the eight-point algorithm with RANSAC. After the pair matching, we optimized the parameter including camera positions to minimize the reprojection error by use of bundle adjustment technique (non-linear optimization). As a final step, we performed dense reconstruction and associate a color with each point using the library of PMVS. Results: Surface data were reconstructed well by visual inspection. The human skin is reconstructed well, althogh the reconstruction was time-consuming for direct use in daily clinical practice. Conclusion: 3D reconstruction using multi view stereo geometry is a promising tool for reducing the effort of patient setup. This work was supported by JSPS KAKENHI(25861128)

  2. SU-E-J-128: 3D Surface Reconstruction of a Patient Using Epipolar Geometry

    International Nuclear Information System (INIS)

    Kotoku, J; Nakabayashi, S; Kumagai, S; Ishibashi, T; Kobayashi, T; Haga, A; Saotome, N; Arai, N

    2014-01-01

    Purpose: To obtain a 3D surface data of a patient in a non-invasive way can substantially reduce the effort for the registration of patient in radiation therapy. To achieve this goal, we introduced the multiple view stereo technique, which is known to be used in a 'photo tourism' on the internet. Methods: 70 Images were taken with a digital single-lens reflex camera from different angles and positions. The camera positions and angles were inferred later in the reconstruction step. A sparse 3D reconstruction model was locating by SIFT features, which is robust for rotation and shift variance, in each image. We then found a set of correspondences between pairs of images by computing the fundamental matrix using the eight-point algorithm with RANSAC. After the pair matching, we optimized the parameter including camera positions to minimize the reprojection error by use of bundle adjustment technique (non-linear optimization). As a final step, we performed dense reconstruction and associate a color with each point using the library of PMVS. Results: Surface data were reconstructed well by visual inspection. The human skin is reconstructed well, althogh the reconstruction was time-consuming for direct use in daily clinical practice. Conclusion: 3D reconstruction using multi view stereo geometry is a promising tool for reducing the effort of patient setup. This work was supported by JSPS KAKENHI(25861128)

  3. Vector tomography for reconstructing electric fields with non-zero divergence in bounded domains

    Science.gov (United States)

    Koulouri, Alexandra; Brookes, Mike; Rimpiläinen, Ville

    2017-01-01

    In vector tomography (VT), the aim is to reconstruct an unknown multi-dimensional vector field using line integral data. In the case of a 2-dimensional VT, two types of line integral data are usually required. These data correspond to integration of the parallel and perpendicular projection of the vector field along the integration lines and are called the longitudinal and transverse measurements, respectively. In most cases, however, the transverse measurements cannot be physically acquired. Therefore, the VT methods are typically used to reconstruct divergence-free (or source-free) velocity and flow fields that can be reconstructed solely from the longitudinal measurements. In this paper, we show how vector fields with non-zero divergence in a bounded domain can also be reconstructed from the longitudinal measurements without the need of explicitly evaluating the transverse measurements. To the best of our knowledge, VT has not previously been used for this purpose. In particular, we study low-frequency, time-harmonic electric fields generated by dipole sources in convex bounded domains which arise, for example, in electroencephalography (EEG) source imaging. We explain in detail the theoretical background, the derivation of the electric field inverse problem and the numerical approximation of the line integrals. We show that fields with non-zero divergence can be reconstructed from the longitudinal measurements with the help of two sparsity constraints that are constructed from the transverse measurements and the vector Laplace operator. As a comparison to EEG source imaging, we note that VT does not require mathematical modeling of the sources. By numerical simulations, we show that the pattern of the electric field can be correctly estimated using VT and the location of the source activity can be determined accurately from the reconstructed magnitudes of the field.

  4. Reconstruction of Laser-Induced Surface Topography from Electron Backscatter Diffraction Patterns.

    Science.gov (United States)

    Callahan, Patrick G; Echlin, McLean P; Pollock, Tresa M; De Graef, Marc

    2017-08-01

    We demonstrate that the surface topography of a sample can be reconstructed from electron backscatter diffraction (EBSD) patterns collected with a commercial EBSD system. This technique combines the location of the maximum background intensity with a correction from Monte Carlo simulations to determine the local surface normals at each point in an EBSD scan. A surface height map is then reconstructed from the local surface normals. In this study, a Ni sample was machined with a femtosecond laser, which causes the formation of a laser-induced periodic surface structure (LIPSS). The topography of the LIPSS was analyzed using atomic force microscopy (AFM) and reconstructions from EBSD patterns collected at 5 and 20 kV. The LIPSS consisted of a combination of low frequency waviness due to curtaining and high frequency ridges. The morphology of the reconstructed low frequency waviness and high frequency ridges matched the AFM data. The reconstruction technique does not require any modification to existing EBSD systems and so can be particularly useful for measuring topography and its evolution during in situ experiments.

  5. An objective algorithm for reconstructing the three-dimensional ocean temperature field based on Argo profiles and SST data

    Science.gov (United States)

    Zhou, Chaojie; Ding, Xiaohua; Zhang, Jie; Yang, Jungang; Ma, Qiang

    2017-12-01

    While global oceanic surface information with large-scale, real-time, high-resolution data is collected by satellite remote sensing instrumentation, three-dimensional (3D) observations are usually obtained from in situ measurements, but with minimal coverage and spatial resolution. To meet the needs of 3D ocean investigations, we have developed a new algorithm to reconstruct the 3D ocean temperature field based on the Array for Real-time Geostrophic Oceanography (Argo) profiles and sea surface temperature (SST) data. The Argo temperature profiles are first optimally fitted to generate a series of temperature functions of depth, with the vertical temperature structure represented continuously. By calculating the derivatives of the fitted functions, the calculation of the vertical temperature gradient of the Argo profiles at an arbitrary depth is accomplished. A gridded 3D temperature gradient field is then found by applying inverse distance weighting interpolation in the horizontal direction. Combined with the processed SST, the 3D temperature field reconstruction is realized below the surface using the gridded temperature gradient. Finally, to confirm the effectiveness of the algorithm, an experiment in the Pacific Ocean south of Japan is conducted, for which a 3D temperature field is generated. Compared with other similar gridded products, the reconstructed 3D temperature field derived by the proposed algorithm achieves satisfactory accuracy, with correlation coefficients of 0.99 obtained, including a higher spatial resolution (0.25° × 0.25°), resulting in the capture of smaller-scale characteristics. Finally, both the accuracy and the superiority of the algorithm are validated.

  6. Whole surface image reconstruction for machine vision inspection of fruit

    Science.gov (United States)

    Reese, D. Y.; Lefcourt, A. M.; Kim, M. S.; Lo, Y. M.

    2007-09-01

    Automated imaging systems offer the potential to inspect the quality and safety of fruits and vegetables consumed by the public. Current automated inspection systems allow fruit such as apples to be sorted for quality issues including color and size by looking at a portion of the surface of each fruit. However, to inspect for defects and contamination, the whole surface of each fruit must be imaged. The goal of this project was to develop an effective and economical method for whole surface imaging of apples using mirrors and a single camera. Challenges include mapping the concave stem and calyx regions. To allow the entire surface of an apple to be imaged, apples were suspended or rolled above the mirrors using two parallel music wires. A camera above the apples captured 90 images per sec (640 by 480 pixels). Single or multiple flat or concave mirrors were mounted around the apple in various configurations to maximize surface imaging. Data suggest that the use of two flat mirrors provides inadequate coverage of a fruit but using two parabolic concave mirrors allows the entire surface to be mapped. Parabolic concave mirrors magnify images, which results in greater pixel resolution and reduced distortion. This result suggests that a single camera with two parabolic concave mirrors can be a cost-effective method for whole surface imaging.

  7. [Application of Fourier transform profilometry in 3D-surface reconstruction].

    Science.gov (United States)

    Shi, Bi'er; Lu, Kuan; Wang, Yingting; Li, Zhen'an; Bai, Jing

    2011-08-01

    With the improvement of system frame and reconstruction methods in fluorescent molecules tomography (FMT), the FMT technology has been widely used as an important experimental tool in biomedical research. It is necessary to get the 3D-surface profile of the experimental object as the boundary constraints of FMT reconstruction algorithms. We proposed a new 3D-surface reconstruction method based on Fourier transform profilometry (FTP) method under the blue-purple light condition. The slice images were reconstructed using proper image processing methods, frequency spectrum analysis and filtering. The results of experiment showed that the method properly reconstructed the 3D-surface of objects and has the mm-level accuracy. Compared to other methods, this one is simple and fast. Besides its well-reconstructed, the proposed method could help monitor the behavior of the object during the experiment to ensure the correspondence of the imaging process. Furthermore, the method chooses blue-purple light section as its light source to avoid the interference towards fluorescence imaging.

  8. Inference-Based Surface Reconstruction of Cluttered Environments

    KAUST Repository

    Biggers, K.; Keyser, J.

    2012-01-01

    guided by rules for fitting high-quality surface patches obtained from these prior models. We demonstrate the application of this algorithm on several example data sets containing heavy clutter and occlusion. © 2012 IEEE.

  9. Reconstructing Surface Triangulations by Their Intersection Matrices 26 September 2014

    Directory of Open Access Journals (Sweden)

    Arocha Jorge L.

    2015-08-01

    Full Text Available The intersection matrix of a simplicial complex has entries equal to the rank of the intersecction of its facets. We prove that this matrix is enough to define up to isomorphism a triangulation of a surface.

  10. Reconstruction of the static magnetic field of a magnetron

    Science.gov (United States)

    Krüger, Dennis; Köhn, Kevin; Gallian, Sara; Brinkmann, Ralf Peter

    2018-06-01

    The simulation of magnetron discharges requires a quantitatively correct mathematical model of the magnetic field structure. This study presents a method to construct such a model on the basis of a spatially restricted set of experimental data and a plausible a priori assumption on the magnetic field configuration. The example in focus is that of a planar circular magnetron. The experimental data are Hall probe measurements of the magnetic flux density in an accessible region above the magnetron plane [P. D. Machura et al., Plasma Sources Sci. Technol. 23, 065043 (2014)]. The a priori assumption reflects the actual design of the device, and it takes the magnetic field emerging from a center magnet of strength m C and vertical position d C and a ring magnet of strength m R , vertical position d R , and radius R. An analytical representation of the assumed field configuration can be formulated in terms of generalized hypergeometric functions. Fitting the ansatz to the experimental data with a least square method results in a fully specified analytical field model that agrees well with the data inside the accessible region and, moreover, is physically plausible in the regions outside of it. The outcome proves superior to the result of an alternative approach which starts from a multimode solution of the vacuum field problem formulated in terms of polar Bessel functions and vertical exponentials. As a first application of the obtained field model, typical electron and ion Larmor radii and the gradient and curvature drift velocities of the electron guiding center are calculated.

  11. Fermi-surface reconstruction and the origin of high-temperature superconductivity

    International Nuclear Information System (INIS)

    Norman, M.R.

    2010-01-01

    In crystalline lattices, the conduction electrons form waves, known as Bloch states, characterized by a momentum vector k. The defining characteristic of metals is the surface in momentum space that separates occupied from unoccupied states. This 'Fermi' surface may seem like an abstract concept, but it can be measured and its shape can have profound consequences for the thermal, electronic, and magnetic properties of a material. In the presence of an external magnetic field B, electrons in a metal spiral around the field direction, and within a semiclassical momentum-space picture, orbit around the Fermi surface. Physical properties, such as the magnetization, involve a sum over these orbits, with extremal orbits on the Fermi surface, i.e., orbits with minimal or maximal area, dominating the sum (Fig. 1(a)). Upon quantization, the resulting electron energy spectrum consists of Landau levels separated by the cyclotron energy, which is proportional to the magnetic field. As the magnetic field causes subsequent Landau levels to cross through the Fermi energy, physical quantities, such as the magnetization or resistivity, oscillate in response. It turns out that the period of these oscillations, when plotted as a function of 1/B, is proportional to the area of the extremal orbit in a plane perpendicular to the applied field (Fig. 1(b)). The power of the quantum oscillation technique is obvious: By changing the field direction, one can map out the Fermi surface, much like a blind man feeling an elephant. The nature and topology of the Fermi surface in high-T c cuprates has been debated for many years. Soon after the materials were discovered by Bednorz and Mueller, it was realized that superconductivity was obtained by doping carriers into a parent insulating state. This insulating state appears to be due to strong electronic correlations, and is known as a Mott insulator. In the case of cuprates, the electronic interactions force the electrons on the copper ion

  12. Structured light optical microscopy for three-dimensional reconstruction of technical surfaces

    Science.gov (United States)

    Kettel, Johannes; Reinecke, Holger; Müller, Claas

    2016-04-01

    In microsystems technology quality control of micro structured surfaces with different surface properties is playing an ever more important role. The process of quality control incorporates three-dimensional (3D) reconstruction of specularand diffusive reflecting technical surfaces. Due to the demand on high measurement accuracy and data acquisition rates, structured light optical microscopy has become a valuable solution to solve this problem providing high vertical and lateral resolution. However, 3D reconstruction of specular reflecting technical surfaces still remains a challenge to optical measurement principles. In this paper we present a measurement principle based on structured light optical microscopy which enables 3D reconstruction of specular- and diffusive reflecting technical surfaces. It is realized using two light paths of a stereo microscope equipped with different magnification levels. The right optical path of the stereo microscope is used to project structured light onto the object surface. The left optical path is used to capture the structured illuminated object surface with a camera. Structured light patterns are generated by a Digital Light Processing (DLP) device in combination with a high power Light Emitting Diode (LED). Structured light patterns are realized as a matrix of discrete light spots to illuminate defined areas on the object surface. The introduced measurement principle is based on multiple and parallel processed point measurements. Analysis of the measured Point Spread Function (PSF) by pattern recognition and model fitting algorithms enables the precise calculation of 3D coordinates. Using exemplary technical surfaces we demonstrate the successful application of our measurement principle.

  13. PHOTOMETRIC STEREO SHAPE-AND-ALBEDO-FROM-SHADING FOR PIXEL-LEVEL RESOLUTION LUNAR SURFACE RECONSTRUCTION

    Directory of Open Access Journals (Sweden)

    W. C. Liu

    2017-07-01

    Full Text Available Shape and Albedo from Shading (SAfS techniques recover pixel-wise surface details based on the relationship between terrain slopes, illumination and imaging geometry, and the energy response (i.e., image intensity captured by the sensing system. Multiple images with different illumination geometries (i.e., photometric stereo can provide better SAfS surface reconstruction due to the increase in observations. Photometric stereo SAfS is suitable for detailed surface reconstruction of the Moon and other extra-terrestrial bodies due to the availability of photometric stereo and the less complex surface reflecting properties (i.e., albedo of the target bodies as compared to the Earth. Considering only one photometric stereo pair (i.e., two images, pixel-variant albedo is still a major obstacle to satisfactory reconstruction and it needs to be regulated by the SAfS algorithm. The illumination directional difference between the two images also becomes an important factor affecting the reconstruction quality. This paper presents a photometric stereo SAfS algorithm for pixel-level resolution lunar surface reconstruction. The algorithm includes a hierarchical optimization architecture for handling pixel-variant albedo and improving performance. With the use of Lunar Reconnaissance Orbiter Camera - Narrow Angle Camera (LROC NAC photometric stereo images, the reconstructed topography (i.e., the DEM is compared with the DEM produced independently by photogrammetric methods. This paper also addresses the effect of illumination directional difference in between one photometric stereo pair on the reconstruction quality of the proposed algorithm by both mathematical and experimental analysis. In this case, LROC NAC images under multiple illumination directions are utilized by the proposed algorithm for experimental comparison. The mathematical derivation suggests an illumination azimuthal difference of 90 degrees between two images is recommended to achieve

  14. Phase microscopy using light-field reconstruction method for cell observation.

    Science.gov (United States)

    Xiu, Peng; Zhou, Xin; Kuang, Cuifang; Xu, Yingke; Liu, Xu

    2015-08-01

    The refractive index (RI) distribution can serve as a natural label for undyed cell imaging. However, the majority of images obtained through quantitative phase microscopy is integrated along the illumination angle and cannot reflect additional information about the refractive map on a certain plane. Herein, a light-field reconstruction method to image the RI map within a depth of 0.2 μm is proposed. It records quantitative phase-delay images using a four-step phase shifting method in different directions and then reconstructs a similar scattered light field for the refractive sample on the focus plane. It can image the RI of samples, transparent cell samples in particular, in a manner similar to the observation of scattering characteristics. The light-field reconstruction method is therefore a powerful tool for use in cytobiology studies. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Method and system for progressive mesh storage and reconstruction using wavelet-encoded height fields

    Science.gov (United States)

    Baxes, Gregory A. (Inventor); Linger, Timothy C. (Inventor)

    2011-01-01

    Systems and methods are provided for progressive mesh storage and reconstruction using wavelet-encoded height fields. A method for progressive mesh storage includes reading raster height field data, and processing the raster height field data with a discrete wavelet transform to generate wavelet-encoded height fields. In another embodiment, a method for progressive mesh storage includes reading texture map data, and processing the texture map data with a discrete wavelet transform to generate wavelet-encoded texture map fields. A method for reconstructing a progressive mesh from wavelet-encoded height field data includes determining terrain blocks, and a level of detail required for each terrain block, based upon a viewpoint. Triangle strip constructs are generated from vertices of the terrain blocks, and an image is rendered utilizing the triangle strip constructs. Software products that implement these methods are provided.

  16. Simulation of mirror surfaces for virtual estimation of visibility lines for 3D motor vehicle collision reconstruction.

    Science.gov (United States)

    Leipner, Anja; Dobler, Erika; Braun, Marcel; Sieberth, Till; Ebert, Lars

    2017-10-01

    3D reconstructions of motor vehicle collisions are used to identify the causes of these events and to identify potential violations of traffic regulations. Thus far, the reconstruction of mirrors has been a problem since they are often based on approximations or inaccurate data. Our aim with this paper was to confirm that structured light scans of a mirror improve the accuracy of simulating the field of view of mirrors. We analyzed the performances of virtual mirror surfaces based on structured light scans using real mirror surfaces and their reflections as references. We used an ATOS GOM III scanner to scan the mirrors and processed the 3D data using Geomagic Wrap. For scene reconstruction and to generate virtual images, we used 3ds Max. We compared the simulated virtual images and photographs of real scenes using Adobe Photoshop. Our results showed that we achieved clear and even mirror results and that the mirrors behaved as expected. The greatest measured deviation between an original photo and the corresponding virtual image was 20 pixels in the transverse direction for an image width of 4256 pixels. We discussed the influences of data processing and alignment of the 3D models on the results. The study was limited to a distance of 1.6m, and the method was not able to simulate an interior mirror. In conclusion, structured light scans of mirror surfaces can be used to simulate virtual mirror surfaces with regard to 3D motor vehicle collision reconstruction. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Reconstructing the velocity field beyond the local universe

    CSIR Research Space (South Africa)

    Johnston, R

    2014-10-01

    Full Text Available an estimate of the velocity field derived from the galaxy over-density d(sub g) and the second makes use of the matter linear density power spectrum P(sub k). Using N-body simulations we find, with an SDSS-like sample (N(sub gal) 33 per deg(sup 2...

  18. Focus-variation image reconstruction in field-emission TEM

    NARCIS (Netherlands)

    Coene, W.M.J.; Janssen, A.J.E.M.; Op de Beeck, M.; Van Dyck, D.; Van Zwet, E.J.; Zandbergen, H.W.; Bailey, G.W.; Rieder, C.L.

    1993-01-01

    The use of a field emission gun (FEG) in high resolution TEM (HRTEM) improves the information limit much below the point resolution. In the area between point and information resolution of the FEG-TEM, image interpretation is complicated by the lens aberrations and focus effects. Different

  19. WATER SURFACE RECONSTRUCTION IN AIRBORNE LASER BATHYMETRY FROM REDUNDANT BED OBSERVATIONS

    Directory of Open Access Journals (Sweden)

    G. Mandlburger

    2017-09-01

    Full Text Available In airborne laser bathymetry knowledge of exact water level heights is a precondition for applying run-time and refraction correction of the raw laser beam travel path in the medium water. However, due to specular reflection especially at very smooth water surfaces often no echoes from the water surface itself are recorded (drop outs. In this paper, we first discuss the feasibility of reconstructing the water surface from redundant observations of the water bottom in theory. Furthermore, we provide a first practical approach for solving this problem, suitable for static and locally planar water surfaces. It minimizes the bottom surface deviations of point clouds from individual flight strips after refraction correction. Both theoretical estimations and practical results confirm the potential of the presented method to reconstruct water level heights in dm precision. Achieving good results requires enough morphological details in the scene and that the water bottom topography is captured from different directions.

  20. Vector tomography for reconstructing electric fields with non-zero divergence in bounded domains

    Energy Technology Data Exchange (ETDEWEB)

    Koulouri, Alexandra, E-mail: koulouri@uni-muenster.de [Institute for Computational and Applied Mathematics, University of Münster, Einsteinstrasse 62, D-48149 Münster (Germany); Department of Electrical and Electronic Engineering, Imperial College London, Exhibition Road, London SW7 2BT (United Kingdom); Brookes, Mike [Department of Electrical and Electronic Engineering, Imperial College London, Exhibition Road, London SW7 2BT (United Kingdom); Rimpiläinen, Ville [Institute for Biomagnetism and Biosignalanalysis, University of Münster, Malmedyweg 15, D-48149 Münster (Germany); Department of Mathematics, University of Auckland, Private bag 92019, Auckland 1142 (New Zealand)

    2017-01-15

    In vector tomography (VT), the aim is to reconstruct an unknown multi-dimensional vector field using line integral data. In the case of a 2-dimensional VT, two types of line integral data are usually required. These data correspond to integration of the parallel and perpendicular projection of the vector field along the integration lines and are called the longitudinal and transverse measurements, respectively. In most cases, however, the transverse measurements cannot be physically acquired. Therefore, the VT methods are typically used to reconstruct divergence-free (or source-free) velocity and flow fields that can be reconstructed solely from the longitudinal measurements. In this paper, we show how vector fields with non-zero divergence in a bounded domain can also be reconstructed from the longitudinal measurements without the need of explicitly evaluating the transverse measurements. To the best of our knowledge, VT has not previously been used for this purpose. In particular, we study low-frequency, time-harmonic electric fields generated by dipole sources in convex bounded domains which arise, for example, in electroencephalography (EEG) source imaging. We explain in detail the theoretical background, the derivation of the electric field inverse problem and the numerical approximation of the line integrals. We show that fields with non-zero divergence can be reconstructed from the longitudinal measurements with the help of two sparsity constraints that are constructed from the transverse measurements and the vector Laplace operator. As a comparison to EEG source imaging, we note that VT does not require mathematical modeling of the sources. By numerical simulations, we show that the pattern of the electric field can be correctly estimated using VT and the location of the source activity can be determined accurately from the reconstructed magnitudes of the field. - Highlights: • Vector tomography is used to reconstruct electric fields generated by dipole

  1. Three-dimensional reconstruction of the topographical cerebral surface anatomy for presurgical planning with free OsiriX Software.

    Science.gov (United States)

    Harput, Mehmet V; Gonzalez-Lopez, Pablo; Türe, Uğur

    2014-09-01

    During surgery for intrinsic brain lesions, it is important to distinguish the pathological gyrus from the surrounding normal sulci and gyri. This task is usually tedious because of the pia-arachnoid membranes with their arterial and venous complexes that obscure the underlying anatomy. Moreover, most tumors grow in the white matter without initially distorting the cortical anatomy, making their direct visualization more difficult. To create and evaluate a simple and free surgical planning tool to simulate the anatomy of the surgical field with and without vessels. We used free computer software (OsiriX Medical Imaging Software) that allowed us to create 3-dimensional reconstructions of the cerebral surface with and without cortical vessels. These reconstructions made use of magnetic resonance images from 51 patients with neocortical supratentorial lesions operated on over a period of 21 months (June 2011 to February 2013). The 3-dimensional (3-D) anatomic images were compared with the true surgical view to evaluate their accuracy. In all patients, the landmarks determined by 3-D reconstruction were cross-checked during surgery with high-resolution ultrasonography; in select cases, they were also checked with indocyanine green videoangiography. The reconstructed neurovascular structures were confirmed intraoperatively in all patients. We found this technique to be extremely useful in achieving pure lesionectomy, as it defines tumor's borders precisely. A 3-D reconstruction of the cortical surface can be easily created with free OsiriX software. This technique helps the surgeon perfect the mentally created 3-D picture of the tumor location to carry out cleaner, safer surgeries.

  2. Capabilities of using white x-rays for the reconstruction of surface morphology from coherent reflectivity

    Energy Technology Data Exchange (ETDEWEB)

    Sant, Tushar, E-mail: tushar@physik.uni-siegen.de [Solid State Physics Group, University of Siegen, 57068 Siegen (Germany); Panzner, Tobias [Paul Scherrer Institute (Switzerland); Pietsch, Ullrich [Solid State Physics Group, University of Siegen, 57068 Siegen (Germany)

    2010-10-15

    We present a new method to reconstruct the surface profile of a sample from coherent reflectivity data of a white x-ray beam experiment. As an example the surface profile of a laterally confined silicon wafer has been reconstructed quantitatively from static speckle measurements using white coherent x-rays from a bending magnet in the energy range between 5 < E < 20 keV. As a consequence of using white radiation, speckles appear in addition to the Airy pattern caused by scattering at the entrance pinhole. Nevertheless, the surface profile of a triangularly shaped specimen was reconstructed considering sufficient oversampling between the beam-footprint and the effective sample width. For the profile reconstruction the Error-Reduction phase retrieval algorithm was modified by including the spectral illumination function and a Fresnel propagator term. The simultaneous use of different x-ray energies having different penetration depth provides information on the evolution of the surface profile from the near-surface towards the bulk. The limitations of present experiment can be overcome using white or pink radiation from a source with higher photon flux.

  3. Methods for improving limited field-of-view radiotherapy reconstructions using imperfect a priori images

    International Nuclear Information System (INIS)

    Ruchala, Kenneth J.; Olivera, Gustavo H.; Kapatoes, Jeffrey M.; Reckwerdt, Paul J.; Mackie, Thomas R.

    2002-01-01

    There are many benefits to having an online CT imaging system for radiotherapy, as it helps identify changes in the patient's position and anatomy between the time of planning and treatment. However, many current online CT systems suffer from a limited field-of-view (LFOV) in that collected data do not encompass the patient's complete cross section. Reconstruction of these data sets can quantitatively distort the image values and introduce artifacts. This work explores the use of planning CT data as a priori information for improving these reconstructions. Methods are presented to incorporate this data by aligning the LFOV with the planning images and then merging the data sets in sinogram space. One alignment option is explicit fusion, producing fusion-aligned reprojection (FAR) images. For cases where explicit fusion is not viable, FAR can be implemented using the implicit fusion of normal setup error, referred to as normal-error-aligned reprojection (NEAR). These methods are evaluated for multiday patient images showing both internal and skin-surface anatomical variation. The iterative use of NEAR and FAR is also investigated, as are applications of NEAR and FAR to dose calculations and the compensation of LFOV online MVCT images with kVCT planning images. Results indicate that NEAR and FAR can utilize planning CT data as imperfect a priori information to reduce artifacts and quantitatively improve images. These benefits can also increase the accuracy of dose calculations and be used for augmenting CT images (e.g., MVCT) acquired at different energies than the planning CT

  4. RECONSTRUCTING THE INITIAL DENSITY FIELD OF THE LOCAL UNIVERSE: METHODS AND TESTS WITH MOCK CATALOGS

    International Nuclear Information System (INIS)

    Wang Huiyuan; Mo, H. J.; Yang Xiaohu; Van den Bosch, Frank C.

    2013-01-01

    Our research objective in this paper is to reconstruct an initial linear density field, which follows the multivariate Gaussian distribution with variances given by the linear power spectrum of the current cold dark matter model and evolves through gravitational instabilities to the present-day density field in the local universe. For this purpose, we develop a Hamiltonian Markov Chain Monte Carlo method to obtain the linear density field from a posterior probability function that consists of two components: a prior of a Gaussian density field with a given linear spectrum and a likelihood term that is given by the current density field. The present-day density field can be reconstructed from galaxy groups using the method developed in Wang et al. Using a realistic mock Sloan Digital Sky Survey DR7, obtained by populating dark matter halos in the Millennium simulation (MS) with galaxies, we show that our method can effectively and accurately recover both the amplitudes and phases of the initial, linear density field. To examine the accuracy of our method, we use N-body simulations to evolve these reconstructed initial conditions to the present day. The resimulated density field thus obtained accurately matches the original density field of the MS in the density range 0.3∼ –1 , much smaller than the translinear scale, which corresponds to a wavenumber of ∼0.15 h Mpc –1

  5. Three Dimensional Dynamic Model Based Wind Field Reconstruction from Lidar Data

    International Nuclear Information System (INIS)

    Raach, Steffen; Schlipf, David; Haizmann, Florian; Cheng, Po Wen

    2014-01-01

    Using the inflowing horizontal and vertical wind shears for individual pitch controller is a promising method if blade bending measurements are not available. Due to the limited information provided by a lidar system the reconstruction of shears in real-time is a challenging task especially for the horizontal shear in the presence of changing wind direction. The internal model principle has shown to be a promising approach to estimate the shears and directions in 10 minutes averages with real measurement data. The static model based wind vector field reconstruction is extended in this work taking into account a dynamic reconstruction model based on Taylor's Frozen Turbulence Hypothesis. The presented method provides time series over several seconds of the wind speed, shears and direction, which can be directly used in advanced optimal preview control. Therefore, this work is an important step towards the application of preview individual blade pitch control under realistic wind conditions. The method is tested using a turbulent wind field and a detailed lidar simulator. For the simulation, the turbulent wind field structure is flowing towards the lidar system and is continuously misaligned with respect to the horizontal axis of the wind turbine. Taylor's Frozen Turbulence Hypothesis is taken into account to model the wind evolution. For the reconstruction, the structure is discretized into several stages where each stage is reduced to an effective wind speed, superposed with a linear horizontal and vertical wind shear. Previous lidar measurements are shifted using again Taylor's Hypothesis. The wind field reconstruction problem is then formulated as a nonlinear optimization problem, which minimizes the residual between the assumed wind model and the lidar measurements to obtain the misalignment angle and the effective wind speed and the wind shears for each stage. This method shows good results in reconstructing the wind characteristics of a three

  6. The 3D geological model of the 1963 Vajont rockslide, reconstructed with implicit surface methods

    Science.gov (United States)

    Bistacchi, Andrea; Massironi, Matteo; Francese, Roberto; Giorgi, Massimo; Taller, Claudio

    2015-04-01

    The Vajont rockslide has been the object of several studies because of its catastrophic consequences and of its particular evolution. Several qualitative or quantitative models have been presented in the last 50 years, but a complete explanation of all the relevant geological and mechanical processes remains elusive. In order to better understand the mechanics and dynamics of the 1963 event, we have reconstructed the first 3D geological model of the rockslide, which allowed us to accurately investigate the rockslide structure and kinematics. The input data for the model consisted in: pre- and post-rockslide geological maps, pre- and post-rockslide orthophotos, pre- and post-rockslide digital elevation models, structural data, boreholes, and geophysical data (2D and 3D seismics and resistivity). All these data have been integrated in a 3D geological model implemented in Gocad®, using the implicit surface modelling method. Results of the 3D geological model include the depth and geometry of the sliding surface, the volume of the two lobes of the rockslide accumulation, kinematics of the rockslide in terms of the vector field of finite displacement, and high quality meshes useful for mechanical and hydrogeological simulations. The latter can include information about the stratigraphy and internal structure of the rock masses and allow tracing the displacement of different material points in the rockslide from the pre-1963-failure to the post-rockslide state. As a general geological conclusion, we may say that the 3D model allowed us to recognize very effectively a sliding surface, whose non-planar geometry is affected by the interference pattern of two regional-scale fold systems. The rockslide is partitioned into two distinct and internally continuous rock masses with a distinct kinematics, which were characterised by a very limited internal deformation during the slide. The continuity of these two large blocks points to a very localized deformation, occurring along

  7. Casting the Coronal Magnetic Field Reconstructions with Magnetic Field Constraints above the Photosphere in 3D Using MHD Bifrost Model

    Science.gov (United States)

    Fleishman, G. D.; Anfinogentov, S.; Loukitcheva, M.; Mysh'yakov, I.; Stupishin, A.

    2017-12-01

    Measuring and modeling coronal magnetic field, especially above active regions (ARs), remains one of the central problems of solar physics given that the solar coronal magnetism is the key driver of all solar activity. Nowadays the coronal magnetic field is often modelled using methods of nonlinear force-free field reconstruction, whose accuracy has not yet been comprehensively assessed. Given that the coronal magnetic probing is routinely unavailable, only morphological tests have been applied to evaluate performance of the reconstruction methods and a few direct tests using available semi-analytical force-free field solution. Here we report a detailed casting of various tools used for the nonlinear force-free field reconstruction, such as disambiguation methods, photospheric field preprocessing methods, and volume reconstruction methods in a 3D domain using a 3D snapshot of the publicly available full-fledged radiative MHD model. We take advantage of the fact that from the realistic MHD model we know the magnetic field vector distribution in the entire 3D domain, which enables us to perform "voxel-by-voxel" comparison of the restored magnetic field and the true magnetic field in the 3D model volume. Our tests show that the available disambiguation methods often fail at the quiet sun areas, where the magnetic structure is dominated by small-scale magnetic elements, while they work really well at the AR photosphere and (even better) chromosphere. The preprocessing of the photospheric magnetic field, although does produce a more force-free boundary condition, also results in some effective `elevation' of the magnetic field components. The effective `elevation' height turns out to be different for the longitudinal and transverse components of the magnetic field, which results in a systematic error in absolute heights in the reconstructed magnetic data cube. The extrapolation performed starting from actual AR photospheric magnetogram (i.e., without preprocessing) are

  8. Surface reconstruction: An effective method for the growth of mismatched materials

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yu; Zheng, Beining; Wu, Xiaofeng; Yuan, Long; Wu, Jie; Guo, Hongping; Huang, Keke; Feng, Shouhua, E-mail: shfeng@mail.jlu.edu.cn

    2016-01-01

    Graphical abstract: High quality thin film of GaSb was fabricated with molecular beam epitaxy technique on the reconstructed Si(1 1 1) surface. - Highlights: • Surface reconstruction formed by different surface treatments controls the heteroepitaxial growth. • Mismatched stress can be effectively released when the mismatched material epi-film tilts out of the epitaxial interface plane to create a coincidence-site lattice. • GaSb films grown on Si(1 1 1)-(5√3 × 5√3)-Sb surface show better crystal quality and morphology for its self-assembled 2D fishbone structure. - Abstract: The crystalline quality of epitaxial films depends on the degree of lattice match between substrates and films. Here, we report a growth strategy for large mismatched epi-films to grow GaSb films on Si(1 1 1) substrates. The epitaxial strategy can be influenced by controlling the surface reconstructions of Sb-treated Si(1 1 1). The film with the best quality was grown on Si(1 1 1)-(5√3 × 5√3)-Sb surface due to the stress release and the formation of a self-assembled 2D fishbone structure. Controlled surface engineering provides an effective pathway towards the growth of the large mismatched materials.

  9. Paleomagnetic reconstruction of the global geomagnetic field evolution during the Matuyama/Brunhes transition: Iterative Bayesian inversion and independent verification

    Science.gov (United States)

    Leonhardt, Roman; Fabian, Karl

    2007-01-01

    The Earth's magnetic field changed its polarity from the last reversed into today's normal state approximately 780 000 years ago. While before and after this so called Matuyama/Brunhes reversal, the Earth magnetic field was essentially an axial dipole, the details of its transitional structure are still largely unknown. Here, a Bayesian inversion method is developed to reconstruct the spherical harmonic expansion of this transitional field from paleomagnetic data. This is achieved by minimizing the total variational power at the core-mantle boundary during the transition under paleomagnetic constraints. The validity of the inversion technique is proved in two ways. First by inverting synthetic data sets from a modeled reversal. Here it is possible to reliably reconstruct the Gauss coefficients even from noisy records. Second by iteratively combining four geographically distributed high quality paleomagnetic records of the Matuyama/Brunhes reversal into a single geometric reversal scenario without assuming an a priori common age model. The obtained spatio-temporal reversal scenario successfully predicts most independent Matuyama/Brunhes transitional records. Therefore, the obtained global reconstruction based on paleomagnetic data invites to compare the inferred transitional field structure with results from numerical geodynamo models regarding the morphology of the transitional field. It is found that radial magnetic flux patches form at the equator and move polewards during the transition. Our model indicates an increase of non-dipolar energy prior to the last reversal and a non-dipolar dominance during the transition. Thus, the character and information of surface geomagnetic field records is strongly site dependent. The reconstruction also offers new answers to the question of existence of preferred longitudinal bands during the transition and to the problem of reversal duration. Different types of directional variations of the surface geomagnetic field

  10. SU-E-T-362: Automatic Catheter Reconstruction of Flap Applicators in HDR Surface Brachytherapy

    International Nuclear Information System (INIS)

    Buzurovic, I; Devlin, P; Hansen, J; O'Farrell, D; Bhagwat, M; Friesen, S; Damato, A; Lewis, J; Cormack, R

    2014-01-01

    Purpose: Catheter reconstruction is crucial for the accurate delivery of radiation dose in HDR brachytherapy. The process becomes complicated and time-consuming for large superficial clinical targets with a complex topology. A novel method for the automatic catheter reconstruction of flap applicators is proposed in this study. Methods: We have developed a program package capable of image manipulation, using C++class libraries of The-Visualization-Toolkit(VTK) software system. The workflow for automatic catheter reconstruction is: a)an anchor point is placed in 3D or in the axial view of the first slice at the tip of the first, last and middle points for the curved surface; b)similar points are placed on the last slice of the image set; c)the surface detection algorithm automatically registers the points to the images and applies the surface reconstruction filter; d)then a structured grid surface is generated through the center of the treatment catheters placed at a distance of 5mm from the patient's skin. As a result, a mesh-style plane is generated with the reconstructed catheters placed 10mm apart. To demonstrate automatic catheter reconstruction, we used CT images of patients diagnosed with cutaneous T-cell-lymphoma and imaged with Freiburg-Flap-Applicators (Nucletron™-Elekta, Netherlands). The coordinates for each catheter were generated and compared to the control points selected during the manual reconstruction for 16catheters and 368control point Results: The variation of the catheter tip positions between the automatically and manually reconstructed catheters was 0.17mm(SD=0.23mm). The position difference between the manually selected catheter control points and the corresponding points obtained automatically was 0.17mm in the x-direction (SD=0.23mm), 0.13mm in the y-direction (SD=0.22mm), and 0.14mm in the z-direction (SD=0.24mm). Conclusion: This study shows the feasibility of the automatic catheter reconstruction of flap applicators with a high

  11. Reconstruction of the Scalar Field Potential in Inflationary Models with a Gauss-Bonnet term

    Science.gov (United States)

    Koh, Seoktae; Lee, Bum-Hoon; Tumurtushaa, Gansukh

    2017-06-01

    We consider inflationary models with a Gauss-Bonnet term to reconstruct the scalar-field potentials and the Gauss-Bonnet coupling functions. Both expressions are derived from the observationally favored configurations of ns and r . Our result implies that, for the reconstructed potentials and coupling functions, the blue tilt of inflationary tensor fluctuations can be realized. To achieve a blue tilt for the inflationary tensor fluctuations, a scalar field must climb up its potential before rolling down. We further investigate the properties of propagation of the perturbation modes in Friedmann-Robertson-Walker spacetime. For the reconstructed configurations that give rise to the blue tilt for the inflationary tensor fluctuations, we show that the ghosts and instabilities are absent with the superluminal propagation speeds for the scalar perturbation modes, whereas the propagation speeds of the tensor perturbations are subluminal.

  12. Efficient 3D Volume Reconstruction from a Point Cloud Using a Phase-Field Method

    Directory of Open Access Journals (Sweden)

    Darae Jeong

    2018-01-01

    Full Text Available We propose an explicit hybrid numerical method for the efficient 3D volume reconstruction from unorganized point clouds using a phase-field method. The proposed three-dimensional volume reconstruction algorithm is based on the 3D binary image segmentation method. First, we define a narrow band domain embedding the unorganized point cloud and an edge indicating function. Second, we define a good initial phase-field function which speeds up the computation significantly. Third, we use a recently developed explicit hybrid numerical method for solving the three-dimensional image segmentation model to obtain efficient volume reconstruction from point cloud data. In order to demonstrate the practical applicability of the proposed method, we perform various numerical experiments.

  13. Calibration-free quantitative surface topography reconstruction in scanning electron microscopy

    NARCIS (Netherlands)

    Faber, E.T.; Martinez-Martinez, D.; Mansilla, C.; Ocelik, V.; De Hosson, J. Th. M.

    This work presents a new approach to obtain reliable surface topography reconstructions from 2D Scanning Electron Microscopy (SEM) images. In this method a set of images taken at different tilt angles are compared by means of digital image correlation (DlC). It is argued that the strength of the

  14. Evolutionary computation applied to the reconstruction of 3-D surface topography in the SEM.

    Science.gov (United States)

    Kodama, Tetsuji; Li, Xiaoyuan; Nakahira, Kenji; Ito, Dai

    2005-10-01

    A genetic algorithm has been applied to the line profile reconstruction from the signals of the standard secondary electron (SE) and/or backscattered electron detectors in a scanning electron microscope. This method solves the topographical surface reconstruction problem as one of combinatorial optimization. To extend this optimization approach for three-dimensional (3-D) surface topography, this paper considers the use of a string coding where a 3-D surface topography is represented by a set of coordinates of vertices. We introduce the Delaunay triangulation, which attains the minimum roughness for any set of height data to capture the fundamental features of the surface being probed by an electron beam. With this coding, the strings are processed with a class of hybrid optimization algorithms that combine genetic algorithms and simulated annealing algorithms. Experimental results on SE images are presented.

  15. Ab initio-based approach to reconstruction, adsorption and incorporation on GaN surfaces

    International Nuclear Information System (INIS)

    Ito, T; Akiyama, T; Nakamura, K

    2012-01-01

    Reconstruction, adsorption and incorporation on various GaN surfaces are systematically investigated using an ab initio-based approach that predicts the surface phase diagram as functions of temperature and beam-equivalent pressure (BEP). The calculated results for GaN surface reconstructions with polar (0 0 0 1), nonpolar (1 1 −2 0), semipolar (1 −1 0 1) and semipolar (1 1 −2 2) orientations imply that reconstructions on GaN surfaces with Ga adlayers generally appear on the polar and the semipolar surfaces, while the stable ideal surface without Ga adsorption is found on the nonpolar GaN(1 1 −2 0) surface because it satisfies the electron counting rule. The hydrogen adsorption on GaN(0 0 0 1) and GaN(1 1 −2 0) realizes several surface structures forming N–H and Ga–NH 2 bonds on their surfaces that depend on temperature and Ga BEP during metal-organic vapor-phase epitaxy (MOVPE). In contrast, the stable structures due to hydrogen adsorption on the semipolar GaN(1 −1 0 1) and GaN(1 1 −2 2) surfaces are not varied over the wide range of temperature and Ga BEP. This implies that the hydrogen adsorbed stable structures are expected to emerge on the semipolar surfaces during MOVPE regardless of the growth conditions. Furthermore, we clarify that Mg incorporation on GaN(1 −1 0 1) surfaces is enhanced by hydrogen adsorption consistent with experimental findings

  16. Reconstructing the gravitational field of the local Universe

    Science.gov (United States)

    Desmond, Harry; Ferreira, Pedro G.; Lavaux, Guilhem; Jasche, Jens

    2018-03-01

    Tests of gravity at the galaxy scale are in their infancy. As a first step to systematically uncovering the gravitational significance of galaxies, we map three fundamental gravitational variables - the Newtonian potential, acceleration and curvature - over the galaxy environments of the local Universe to a distance of approximately 200 Mpc. Our method combines the contributions from galaxies in an all-sky redshift survey, haloes from an N-body simulation hosting low-luminosity objects, and linear and quasi-linear modes of the density field. We use the ranges of these variables to determine the extent to which galaxies expand the scope of generic tests of gravity and are capable of constraining specific classes of model for which they have special significance. Finally, we investigate the improvements afforded by upcoming galaxy surveys.

  17. Pulsed TV holography measurement and digital reconstruction of compression acoustic wave fields: application to nondestructive testing of thick metallic samples

    International Nuclear Information System (INIS)

    Trillo, C; Doval, A F; Deán-Ben, X L; López-Vázquez, J C; Fernández, J L; Hernández-Montes, S

    2011-01-01

    This paper describes a technique that numerically reconstructs the complex acoustic amplitude (i.e. the acoustic amplitude and phase) of a compression acoustic wave in the interior volume of a specimen from a set of full-field optical measurements of the instantaneous displacement of the surface. The volume of a thick specimen is probed in transmission mode by short bursts of narrowband compression acoustic waves generated at one of its faces. The temporal evolution of the displacement field induced by the bursts emerging at the opposite surface is measured by pulsed digital holographic interferometry (pulsed TV holography). A spatio-temporal 3D Fourier transform processing of the measured data yields the complex acoustic amplitude at the plane of the surface as a sequence of 2D complex-valued maps. Finally, a numerical implementation of the Rayleigh–Sommerfeld diffraction formula is employed to reconstruct the complex acoustic amplitude at other planes in the interior volume of the specimen. The whole procedure can be regarded as a combination of optical digital holography and acoustical holography methods. The technique was successfully tested on aluminium specimens with and without an internal artificial defect and sample results are presented. In particular, information about the shape and position of the defect was retrieved in the experiment performed on the flawed specimen, which indicates the potential applicability of the technique for the nondestructive testing of materials

  18. Cosmological horizons and reconstruction of quantum field theories

    International Nuclear Information System (INIS)

    Dappiaggi, C.; Pinamonti, N.

    2007-12-01

    As a starting point for this manuscript, we remark how the cosmological horizon of a certain class of Friedmann-Robertson-Walker backgrounds shares some non trivial geometric properties with null infinity in an asymptotically flat spacetime. Such a feature is generalized to a larger class of expanding spacetimes M admitting a geodesically complete cosmological horizon J - common to all co-moving observers. This property is later exploited in order to recast, in a cosmological background, some recent results for a linear scalar quantum field theory in spacetimes asymptotically flat at null infinity. Under suitable hypotheses on M - valid for de Sitter spacetime and some other FRW spacetimes obtained by perturbing deSitter space - the algebra of observables for a Klein-Gordon field is mapped into a subalgebra of the algebra of observables W(J - ) constructed on the cosmological horizon. There is exactly one pure quasifree state λ on W(J - ) which fulfills a suitable energy positivity condition with respect to a generator related with the cosmological time displacements. Furthermore λ induces a preferred physically meaningful quantum state λ M for the quantum theory in the bulk. If M admits a timelike Killing generator preserving J - , then the associated self-adjoint generator in the GNS representation of λ M has positive spectrum (i.e. energy). Moreover λ M turns out to be invariant under every symmetry of the bulk metric which preserves the cosmological horizon. In the case of an expanding de Sitter spacetime, λ M coincides with the Euclidean (Bunch-Davies) vacuum state, hence being Hadamard in this case. Remarks on the validity of the Hadamard property for λ M in more general spacetimes are presented. (orig.)

  19. Cosmological horizons and reconstruction of quantum field theories

    Energy Technology Data Exchange (ETDEWEB)

    Dappiaggi, C.; Pinamonti, N. [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik]|[Trento Univ., Povo (Italy). Istituto Nazionale di Alta Matematica ' ' F. Severi' ' - GNFM; Moretti, V. [Trento Univ. (Italy). Dipt. di Matematica]|[Istituto Nazionale di Fisica Nucleare - Gruppo Collegato di Trento, Povo (Italy)

    2007-12-15

    As a starting point for this manuscript, we remark how the cosmological horizon of a certain class of Friedmann-Robertson-Walker backgrounds shares some non trivial geometric properties with null infinity in an asymptotically flat spacetime. Such a feature is generalized to a larger class of expanding spacetimes M admitting a geodesically complete cosmological horizon J{sup -} common to all co-moving observers. This property is later exploited in order to recast, in a cosmological background, some recent results for a linear scalar quantum field theory in spacetimes asymptotically flat at null infinity. Under suitable hypotheses on M - valid for de Sitter spacetime and some other FRW spacetimes obtained by perturbing deSitter space - the algebra of observables for a Klein-Gordon field is mapped into a subalgebra of the algebra of observables W(J{sup -}) constructed on the cosmological horizon. There is exactly one pure quasifree state {lambda} on W(J{sup -}) which fulfills a suitable energy positivity condition with respect to a generator related with the cosmological time displacements. Furthermore {lambda} induces a preferred physically meaningful quantum state {lambda}{sub M} for the quantum theory in the bulk. If M admits a timelike Killing generator preserving J{sup -}, then the associated self-adjoint generator in the GNS representation of {lambda}{sub M} has positive spectrum (i.e. energy). Moreover {lambda}{sub M} turns out to be invariant under every symmetry of the bulk metric which preserves the cosmological horizon. In the case of an expanding de Sitter spacetime, {lambda}{sub M} coincides with the Euclidean (Bunch-Davies) vacuum state, hence being Hadamard in this case. Remarks on the validity of the Hadamard property for {lambda}{sub M} in more general spacetimes are presented. (orig.)

  20. The Application of Three-Dimensional Surface Imaging System in Plastic and Reconstructive Surgery.

    Science.gov (United States)

    Li, Yanqi; Yang, Xin; Li, Dong

    2016-02-01

    Three-dimensional (3D) surface imaging system has gained popularity worldwide in clinical application. Unlike computed tomography and magnetic resonance imaging, it has the ability to capture 3D images with both shape and texture information. This feature has made it quite useful for plastic surgeons. This review article is mainly focusing on demonstrating the current status and analyzing the future of the application of 3D surface imaging systems in plastic and reconstructive surgery.Currently, 3D surface imaging system is mainly used in plastic and reconstructive surgery to help improve the reliability of surgical planning and assessing surgical outcome objectively. There have already been reports of its using on plastic and reconstructive surgery from head to toe. Studies on facial aging process, online applications development, and so on, have also been done through the use of 3D surface imaging system.Because different types of 3D surface imaging devices have their own advantages and disadvantages, a basic knowledge of their features is required and careful thought should be taken to choose the one that best fits a surgeon's demand.In the future, by integrating with other imaging tools and the 3D printing technology, 3D surface imaging system will play an important role in individualized surgical planning, implants production, meticulous surgical simulation, operative techniques training, and patient education.

  1. Reconstruction Accuracy Assessment of Surface and Underwater 3D Motion Analysis: A New Approach

    Directory of Open Access Journals (Sweden)

    Kelly de Jesus

    2015-01-01

    Full Text Available This study assessed accuracy of surface and underwater 3D reconstruction of a calibration volume with and without homography. A calibration volume (6000 × 2000 × 2500 mm with 236 markers (64 above and 88 underwater control points—with 8 common points at water surface—and 92 validation points was positioned on a 25 m swimming pool and recorded with two surface and four underwater cameras. Planar homography estimation for each calibration plane was computed to perform image rectification. Direct linear transformation algorithm for 3D reconstruction was applied, using 1600000 different combinations of 32 and 44 points out of the 64 and 88 control points for surface and underwater markers (resp.. Root Mean Square (RMS error with homography of control and validations points was lower than without it for surface and underwater cameras (P≤0.03. With homography, RMS errors of control and validation points were similar between surface and underwater cameras (P≥0.47. Without homography, RMS error of control points was greater for underwater than surface cameras (P≤0.04 and the opposite was observed for validation points (P≤0.04. It is recommended that future studies using 3D reconstruction should include homography to improve swimming movement analysis accuracy.

  2. A hybrid 3D SEM reconstruction method optimized for complex geologic material surfaces.

    Science.gov (United States)

    Yan, Shang; Adegbule, Aderonke; Kibbey, Tohren C G

    2017-08-01

    Reconstruction methods are widely used to extract three-dimensional information from scanning electron microscope (SEM) images. This paper presents a new hybrid reconstruction method that combines stereoscopic reconstruction with shape-from-shading calculations to generate highly-detailed elevation maps from SEM image pairs. The method makes use of an imaged glass sphere to determine the quantitative relationship between observed intensity and angles between the beam and surface normal, and the detector and surface normal. Two specific equations are derived to make use of image intensity information in creating the final elevation map. The equations are used together, one making use of intensities in the two images, the other making use of intensities within a single image. The method is specifically designed for SEM images captured with a single secondary electron detector, and is optimized to capture maximum detail from complex natural surfaces. The method is illustrated with a complex structured abrasive material, and a rough natural sand grain. Results show that the method is capable of capturing details such as angular surface features, varying surface roughness, and surface striations. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Comparative assessment of pressure field reconstructions from particle image velocimetry measurements and Lagrangian particle tracking

    NARCIS (Netherlands)

    van Gent, P.L.; Michaelis, D; van Oudheusden, B.W.; Weiss, P.E.; de Kat, R.; Laskari, A.; Jeon, Y.J.; David, L; Schanz, D; Huhn, F.; Gesemann, S; Novara, M.; McPhaden, C.; Neeteson, N. J.; Rival, David E.; Schneiders, J.F.G.; Schrijer, F.F.J.

    2017-01-01

    A test case for pressure field reconstruction from particle image velocimetry (PIV) and Lagrangian particle tracking (LPT) has been developed by constructing a simulated experiment from a zonal detached eddy simulation for an axisymmetric base flow at Mach 0.7. The test case comprises sequences

  4. Evaluating climate field reconstruction techniques using improved emulations of real-world conditions

    Science.gov (United States)

    Wang, J.; Emile-Geay, J.; Guillot, D.; Smerdon, J. E.; Rajaratnam, B.

    2014-01-01

    Pseudoproxy experiments (PPEs) have become an important framework for evaluating paleoclimate reconstruction methods. Most existing PPE studies assume constant proxy availability through time and uniform proxy quality across the pseudoproxy network. Real multiproxy networks are, however, marked by pronounced disparities in proxy quality, and a steep decline in proxy availability back in time, either of which may have large effects on reconstruction skill. A suite of PPEs constructed from a millennium-length general circulation model (GCM) simulation is thus designed to mimic these various real-world characteristics. The new pseudoproxy network is used to evaluate four climate field reconstruction (CFR) techniques: truncated total least squares embedded within the regularized EM (expectation-maximization) algorithm (RegEM-TTLS), the Mann et al. (2009) implementation of RegEM-TTLS (M09), canonical correlation analysis (CCA), and Gaussian graphical models embedded within RegEM (GraphEM). Each method's risk properties are also assessed via a 100-member noise ensemble. Contrary to expectation, it is found that reconstruction skill does not vary monotonically with proxy availability, but also is a function of the type and amplitude of climate variability (forced events vs. internal variability). The use of realistic spatiotemporal pseudoproxy characteristics also exposes large inter-method differences. Despite the comparable fidelity in reconstructing the global mean temperature, spatial skill varies considerably between CFR techniques. Both GraphEM and CCA efficiently exploit teleconnections, and produce consistent reconstructions across the ensemble. RegEM-TTLS and M09 appear advantageous for reconstructions on highly noisy data, but are subject to larger stochastic variations across different realizations of pseudoproxy noise. Results collectively highlight the importance of designing realistic pseudoproxy networks and implementing multiple noise realizations of PPEs

  5. Reconstruction of signals with unknown spectra in information field theory with parameter uncertainty

    International Nuclear Information System (INIS)

    Ensslin, Torsten A.; Frommert, Mona

    2011-01-01

    The optimal reconstruction of cosmic metric perturbations and other signals requires knowledge of their power spectra and other parameters. If these are not known a priori, they have to be measured simultaneously from the same data used for the signal reconstruction. We formulate the general problem of signal inference in the presence of unknown parameters within the framework of information field theory. To solve this, we develop a generic parameter-uncertainty renormalized estimation (PURE) technique. As a concrete application, we address the problem of reconstructing Gaussian signals with unknown power-spectrum with five different approaches: (i) separate maximum-a-posteriori power-spectrum measurement and subsequent reconstruction, (ii) maximum-a-posteriori reconstruction with marginalized power-spectrum, (iii) maximizing the joint posterior of signal and spectrum, (iv) guessing the spectrum from the variance in the Wiener-filter map, and (v) renormalization flow analysis of the field-theoretical problem providing the PURE filter. In all cases, the reconstruction can be described or approximated as Wiener-filter operations with assumed signal spectra derived from the data according to the same recipe, but with differing coefficients. All of these filters, except the renormalized one, exhibit a perception threshold in case of a Jeffreys prior for the unknown spectrum. Data modes with variance below this threshold do not affect the signal reconstruction at all. Filter (iv) seems to be similar to the so-called Karhune-Loeve and Feldman-Kaiser-Peacock estimators for galaxy power spectra used in cosmology, which therefore should also exhibit a marginal perception threshold if correctly implemented. We present statistical performance tests and show that the PURE filter is superior to the others, especially if the post-Wiener-filter corrections are included or in case an additional scale-independent spectral smoothness prior can be adopted.

  6. Reconstruction of scalar field theories realizing inflation consistent with the Planck and BICEP2 results

    Directory of Open Access Journals (Sweden)

    Kazuharu Bamba

    2014-10-01

    Full Text Available We reconstruct scalar field theories to realize inflation compatible with the BICEP2 result as well as the Planck. In particular, we examine the chaotic inflation model, natural (or axion inflation model, and an inflationary model with a hyperbolic inflaton potential. We perform an explicit approach to find out a scalar field model of inflation in which any observations can be explained in principle.

  7. Casting the Coronal Magnetic Field Reconstruction Tools in 3D Using the MHD Bifrost Model

    Energy Technology Data Exchange (ETDEWEB)

    Fleishman, Gregory D.; Loukitcheva, Maria [Physics Department, Center for Solar-Terrestrial Research, New Jersey Institute of Technology Newark, NJ, 07102-1982 (United States); Anfinogentov, Sergey; Mysh’yakov, Ivan [Institute of Solar-Terrestrial Physics (ISZF), Lermontov st., 126a, Irkutsk, 664033 (Russian Federation); Stupishin, Alexey [Saint Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034 (Russian Federation)

    2017-04-10

    Quantifying the coronal magnetic field remains a central problem in solar physics. Nowadays, the coronal magnetic field is often modeled using nonlinear force-free field (NLFFF) reconstructions, whose accuracy has not yet been comprehensively assessed. Here we perform a detailed casting of the NLFFF reconstruction tools, such as π -disambiguation, photospheric field preprocessing, and volume reconstruction methods, using a 3D snapshot of the publicly available full-fledged radiative MHD model. Specifically, from the MHD model, we know the magnetic field vector in the entire 3D domain, which enables us to perform a “voxel-by-voxel” comparison of the restored and the true magnetic fields in the 3D model volume. Our tests show that the available π -disambiguation methods often fail in the quiet-Sun areas dominated by small-scale magnetic elements, while they work well in the active region (AR) photosphere and (even better) chromosphere. The preprocessing of the photospheric magnetic field, although it does produce a more force-free boundary condition, also results in some effective “elevation” of the magnetic field components. This “elevation” height is different for the longitudinal and transverse components, which results in a systematic error in absolute heights in the reconstructed magnetic data cube. The extrapolations performed starting from the actual AR photospheric magnetogram are free from this systematic error, while other metrics are comparable with those for extrapolations from the preprocessed magnetograms. This finding favors the use of extrapolations from the original photospheric magnetogram without preprocessing. Our tests further suggest that extrapolations from a force-free chromospheric boundary produce measurably better results than those from a photospheric boundary.

  8. A Pseudoproxy-Ensemble Study of Late-Holocene Climate Field Reconstructions Using CCA

    Science.gov (United States)

    Amrhein, D. E.; Smerdon, J. E.

    2009-12-01

    Recent evaluations of late-Holocene multi-proxy reconstruction methods have used pseudoproxy experiments derived from millennial General Circulation Model (GCM) integrations. These experiments assess the performance of a reconstruction technique by comparing pseudoproxy reconstructions, which use restricted subsets of model data, against complete GCM data fields. Most previous studies have tested methodologies using different pseudoproxy noise levels, but only with single realizations for each noise classification. A more robust evaluation of performance is to create an ensemble of pseudoproxy networks with distinct sets of noise realizations and a corresponding reconstruction ensemble that can be evaluated for consistency and sensitivity to random error. This work investigates canonical correlation analysis (CCA) as a late-Holocene climate field reconstruction (CFR) technique using ensembles of pseudoproxy experiments derived from the NCAR CSM 1.4 millennial integration. Three 200-member reconstruction ensembles are computed using pseudoproxies with signal-to-noise ratios (by standard deviation) of 1, 0.5, and 0.25 and locations that approximate the spatial distribution of real-world multiproxy networks. An important component of these ensemble calculations is the independent optimization of the three CCA truncation parameters for each ensemble member. This task is accomplished using an inexpensive discrete optimization algorithm that minimizes both RMS error in the calibration interval and the number of free parameters in the reconstruction model to avoid artificial skill. Within this framework, CCA is investigated for its sensitivity to the level of noise in the pseudoproxy network and the spatial distribution of the network. Warm biases, variance losses, and validation-interval error increase with noise level and vary spatially within the reconstructed fields. Reconstruction skill, measured as grid-point correlations during the validation interval, is lowest in

  9. Surface topography characterization using 3D stereoscopic reconstruction of SEM images

    Science.gov (United States)

    Vedantha Krishna, Amogh; Flys, Olena; Reddy, Vijeth V.; Rosén, B. G.

    2018-06-01

    A major drawback of the optical microscope is its limitation to resolve finer details. Many microscopes have been developed to overcome the limitations set by the diffraction of visible light. The scanning electron microscope (SEM) is one such alternative: it uses electrons for imaging, which have much smaller wavelength than photons. As a result high magnification with superior image resolution can be achieved. However, SEM generates 2D images which provide limited data for surface measurements and analysis. Often many research areas require the knowledge of 3D structures as they contribute to a comprehensive understanding of microstructure by allowing effective measurements and qualitative visualization of the samples under study. For this reason, stereo photogrammetry technique is employed to convert SEM images into 3D measurable data. This paper aims to utilize a stereoscopic reconstruction technique as a reliable method for characterization of surface topography. Reconstructed results from SEM images are compared with coherence scanning interferometer (CSI) results obtained by measuring a roughness reference standard sample. This paper presents a method to select the most robust/consistent surface texture parameters that are insensitive to the uncertainties involved in the reconstruction technique itself. Results from the two-stereoscopic reconstruction algorithms are also documented in this paper.

  10. Reconstructing Northern Hemisphere upper-level fields during World War II

    Energy Technology Data Exchange (ETDEWEB)

    Broennimann, S. [Lunar and Planetary Laboratory, University of Arizona, PO Box 210092, Tucson, AZ 85721-0092 (United States); Luterbacher, J. [Institute of Geography, University of Bern, Bern (Switzerland); NCCR Climate, University of Bern, Bern (Switzerland)

    2004-05-01

    Monthly mean fields of temperature and geopotential height (GPH) from 700 to 100 hPa were statistically reconstructed for the extratropical Northern Hemisphere for the World War II period. The reconstruction was based on several hundred predictor variables, comprising temperature series from meteorological stations and gridded sea level pressure data (1939-1947) as well as a large amount of historical upper-air data (1939-1944). Statistical models were fitted in a calibration period (1948-1994) using the NCEP/NCAR Reanalysis data set as predictand. The procedure consists of a weighting scheme, principal component analyses on both the predictor variables and the predictand fields and multiple regression models relating the two sets of principal component time series to each other. According to validation experiments, the reconstruction skill in the 1939-1944 period is excellent for GPH at all levels and good for temperature up to 500 hPa, but somewhat worse for 300 hPa temperature and clearly worse for 100 hPa temperature. Regionally, high predictive skill is found over the midlatitudes of Europe and North America, but a lower quality over Asia, the subtropics, and the Arctic. Moreover, the quality is considerably better in winter than in summer. In the 1945-1947 period, reconstructions are useful up to 300 hPa for GPH and, in winter, up to 500 hPa for temperature. The reconstructed fields are presented for selected months and analysed from a dynamical perspective. It is demonstrated that the reconstructions provide a useful tool for the analysis of large-scale circulation features as well as stratosphere-troposphere coupling in the late 1930s and early 1940s. (orig.)

  11. Absence of surface stress change during pentacene thin film growth on the Si(111)-(7 x 7) surface: a buried reconstruction interface

    International Nuclear Information System (INIS)

    Kury, P; Horn von Hoegen, M; Heringdorf, F-J Meyer zu; Roos, K R

    2008-01-01

    We use high-resolution surface stress measurements to monitor the surface stress during the growth of pentacene (C 22 H 14 ) on the (7x7) reconstructed silicon (111) surface. No significant change in the surface stress is observed during the pentacene growth. Compared to the changes in the surface stress observed for Si and Ge deposition on the Si(111)-(7x7) surface, the insignificant change in the surface stress observed for the pentacene growth suggests that the pentacene molecules of the first adsorbate layer, although forming strong covalent bonds with the Si adatoms, do not alter the structure of the (7x7) reconstruction. The (7x7) reconstruction remains intact and, with subsequent deposition of pentacene, eventually becomes buried under the growing film. This failure of the pentacene to affect the structure of the reconstruction may represent a fundamental difference between the growth of organic thin films and that of inorganic thin films on semiconductor surfaces

  12. Image reconstruction using three-dimensional compound Gauss-Markov random field in emission computed tomography

    International Nuclear Information System (INIS)

    Watanabe, Shuichi; Kudo, Hiroyuki; Saito, Tsuneo

    1993-01-01

    In this paper, we propose a new reconstruction algorithm based on MAP (maximum a posteriori probability) estimation principle for emission tomography. To improve noise suppression properties of the conventional ML-EM (maximum likelihood expectation maximization) algorithm, direct three-dimensional reconstruction that utilizes intensity correlations between adjacent transaxial slices is introduced. Moreover, to avoid oversmoothing of edges, a priori knowledge of RI (radioisotope) distribution is represented by using a doubly-stochastic image model called the compound Gauss-Markov random field. The a posteriori probability is maximized by using the iterative GEM (generalized EM) algorithm. Computer simulation results are shown to demonstrate validity of the proposed algorithm. (author)

  13. Technique of semiautomatic surface reconstruction of the visible Korean human data using commercial software.

    Science.gov (United States)

    Park, Jin Seo; Shin, Dong Sun; Chung, Min Suk; Hwang, Sung Bae; Chung, Jinoh

    2007-11-01

    This article describes the technique of semiautomatic surface reconstruction of anatomic structures using widely available commercial software. This technique would enable researchers to promptly and objectively perform surface reconstruction, creating three-dimensional anatomic images without any assistance from computer engineers. To develop the technique, we used data from the Visible Korean Human project, which produced digitalized photographic serial images of an entire cadaver. We selected 114 anatomic structures (skin [1], bones [32], knee joint structures [7], muscles [60], arteries [7], and nerves [7]) from the 976 anatomic images which were generated from the left lower limb of the cadaver. Using Adobe Photoshop, the selected anatomic structures in each serial image were outlined, creating a segmented image. The Photoshop files were then converted into Adobe Illustrator files to prepare isolated segmented images, so that the contours of the structure could be viewed independent of the surrounding anatomy. Using Alias Maya, these isolated segmented images were then stacked to construct a contour image. Gaps between the contour lines were filled with surfaces, and three-dimensional surface reconstruction could be visualized with Rhinoceros. Surface imperfections were then corrected to complete the three-dimensional images in Alias Maya. We believe that the three-dimensional anatomic images created by these methods will have widespread application in both medical education and research. 2007 Wiley-Liss, Inc

  14. Field reconstruction and estimation of the antenna support structure effect on the measurement uncertainty of the BTS1940 antenna

    DEFF Research Database (Denmark)

    Cappellin, Cecilia; Pivnenko, Sergey

    2014-01-01

    the effect of the support structure on the measured field, by reconstructing the currents induced on the support frame with DIATOOL. The field obtained by filtering these currents is presented. Moreover, the spatial resolution obtained by the 3D reconstruction is discussed and compared with the one obtained...

  15. Design of an experimental four-camera setup for enhanced 3D surface reconstruction in microsurgery

    Directory of Open Access Journals (Sweden)

    Marzi Christian

    2017-09-01

    Full Text Available Future fully digital surgical visualization systems enable a wide range of new options. Caused by optomechanical limitations a main disadvantage of today’s surgical microscopes is their incapability of providing arbitrary perspectives to more than two observers. In a fully digital microscopic system, multiple arbitrary views can be generated from a 3D reconstruction. Modern surgical microscopes allow replacing the eyepieces by cameras in order to record stereoscopic videos. A reconstruction from these videos can only contain the amount of detail the recording camera system gathers from the scene. Therefore, covered surfaces can result in a faulty reconstruction for deviating stereoscopic perspectives. By adding cameras recording the object from different angles, additional information of the scene is acquired, allowing to improve the reconstruction. Our approach is to use a fixed four-camera setup as a front-end system to capture enhanced 3D topography of a pseudo-surgical scene. This experimental setup would provide images for the reconstruction algorithms and generation of multiple observing stereo perspectives. The concept of the designed setup is based on the common main objective (CMO principle of current surgical microscopes. These systems are well established and optically mature. Furthermore, the CMO principle allows a more compact design and a lowered effort in calibration than cameras with separate optics. Behind the CMO four pupils separate the four channels which are recorded by one camera each. The designed system captures an area of approximately 28mm × 28mm with four cameras. Thus, allowing to process images of 6 different stereo perspectives. In order to verify the setup, it is modelled in silico. It can be used in further studies to test algorithms for 3D reconstruction from up to four perspectives and provide information about the impact of additionally recorded perspectives on the enhancement of a reconstruction.

  16. A Novel Hybrid Model for Drawing Trace Reconstruction from Multichannel Surface Electromyographic Activity.

    Science.gov (United States)

    Chen, Yumiao; Yang, Zhongliang

    2017-01-01

    Recently, several researchers have considered the problem of reconstruction of handwriting and other meaningful arm and hand movements from surface electromyography (sEMG). Although much progress has been made, several practical limitations may still affect the clinical applicability of sEMG-based techniques. In this paper, a novel three-step hybrid model of coordinate state transition, sEMG feature extraction and gene expression programming (GEP) prediction is proposed for reconstructing drawing traces of 12 basic one-stroke shapes from multichannel surface electromyography. Using a specially designed coordinate data acquisition system, we recorded the coordinate data of drawing traces collected in accordance with the time series while 7-channel EMG signals were recorded. As a widely-used time domain feature, Root Mean Square (RMS) was extracted with the analysis window. The preliminary reconstruction models can be established by GEP. Then, the original drawing traces can be approximated by a constructed prediction model. Applying the three-step hybrid model, we were able to convert seven channels of EMG activity recorded from the arm muscles into smooth reconstructions of drawing traces. The hybrid model can yield a mean accuracy of 74% in within-group design (one set of prediction models for all shapes) and 86% in between-group design (one separate set of prediction models for each shape), averaged for the reconstructed x and y coordinates. It can be concluded that it is feasible for the proposed three-step hybrid model to improve the reconstruction ability of drawing traces from sEMG.

  17. Reconstructing the Initial Density Field of the Local Universe: Methods and Tests with Mock Catalogs

    Science.gov (United States)

    Wang, Huiyuan; Mo, H. J.; Yang, Xiaohu; van den Bosch, Frank C.

    2013-07-01

    Our research objective in this paper is to reconstruct an initial linear density field, which follows the multivariate Gaussian distribution with variances given by the linear power spectrum of the current cold dark matter model and evolves through gravitational instabilities to the present-day density field in the local universe. For this purpose, we develop a Hamiltonian Markov Chain Monte Carlo method to obtain the linear density field from a posterior probability function that consists of two components: a prior of a Gaussian density field with a given linear spectrum and a likelihood term that is given by the current density field. The present-day density field can be reconstructed from galaxy groups using the method developed in Wang et al. Using a realistic mock Sloan Digital Sky Survey DR7, obtained by populating dark matter halos in the Millennium simulation (MS) with galaxies, we show that our method can effectively and accurately recover both the amplitudes and phases of the initial, linear density field. To examine the accuracy of our method, we use N-body simulations to evolve these reconstructed initial conditions to the present day. The resimulated density field thus obtained accurately matches the original density field of the MS in the density range 0.3 \\lesssim \\rho /\\bar{\\rho } \\lesssim 20 without any significant bias. In particular, the Fourier phases of the resimulated density fields are tightly correlated with those of the original simulation down to a scale corresponding to a wavenumber of ~1 h Mpc-1, much smaller than the translinear scale, which corresponds to a wavenumber of ~0.15 h Mpc-1.

  18. Probabilistic surface reconstruction from multiple data sets: An example for the Australian Moho

    Science.gov (United States)

    Bodin, T.; Salmon, M.; Kennett, B. L. N.; Sambridge, M.

    2012-10-01

    Interpolation of spatial data is a widely used technique across the Earth sciences. For example, the thickness of the crust can be estimated by different active and passive seismic source surveys, and seismologists reconstruct the topography of the Moho by interpolating these different estimates. Although much research has been done on improving the quantity and quality of observations, the interpolation algorithms utilized often remain standard linear regression schemes, with three main weaknesses: (1) the level of structure in the surface, or smoothness, has to be predefined by the user; (2) different classes of measurements with varying and often poorly constrained uncertainties are used together, and hence it is difficult to give appropriate weight to different data types with standard algorithms; (3) there is typically no simple way to propagate uncertainties in the data to uncertainty in the estimated surface. Hence the situation can be expressed by Mackenzie (2004): "We use fantastic telescopes, the best physical models, and the best computers. The weak link in this chain is interpreting our data using 100 year old mathematics". Here we use recent developments made in Bayesian statistics and apply them to the problem of surface reconstruction. We show how the reversible jump Markov chain Monte Carlo (rj-McMC) algorithm can be used to let the degree of structure in the surface be directly determined by the data. The solution is described in probabilistic terms, allowing uncertainties to be fully accounted for. The method is illustrated with an application to Moho depth reconstruction in Australia.

  19. Three-dimensional reconstruction of fracture surfaces of CFRP type composite materials

    International Nuclear Information System (INIS)

    Lobo, Raquel de Moraes

    2009-01-01

    The three-dimensional reconstruction of fracture surfaces of CFRP type composite materials is presented in this work as a possible method for the fractographic analysis of this material, whose rupture surface can present an accentuated roughness, with great variation in height. Two methods are presented for this purpose: the reconstruction for variable focus, carried through with images of optic microscopy and the reconstruction for parallax, carried through with pair of stereo images, obtained by means of scanning electronic microscopy. An evaluation is carried through for each one of the two methods, having argued its limits and the efficiency of each one of them, before the difficulties of analysis of unidirectional and multidirectional composite materials. The method of variable focus presented an excellent reconstruction result, but it has the need of a great number of images, spent time of the instrument and magnifying limit of the images as factors to be considered in the choice of better method. The tilting of the specimen, during the parallax method, discloses alterations in the histograms of the images acquired in the clockwise direction that limit the use of the method for materials with high roughness. The acquiring of images in only one direction and the construction of a region of interest, located in the center of the image are suggestions to turn the method most including. The linearity of the projections of features in the inclined image also suggests the possibility to carry through the reconstruction using, instead of only two, multiple images gotten in the counter-clockwise direction. The alterations proposals to modify the routine, are suggested so that the program can be applied in a more comprehensive form, independent of the quality of the observed fracture surface. (author)

  20. Active illumination based 3D surface reconstruction and registration for image guided medialization laryngoplasty

    Science.gov (United States)

    Jin, Ge; Lee, Sang-Joon; Hahn, James K.; Bielamowicz, Steven; Mittal, Rajat; Walsh, Raymond

    2007-03-01

    The medialization laryngoplasty is a surgical procedure to improve the voice function of the patient with vocal fold paresis and paralysis. An image guided system for the medialization laryngoplasty will help the surgeons to accurately place the implant and thus reduce the failure rates of the surgery. One of the fundamental challenges in image guided system is to accurately register the preoperative radiological data to the intraoperative anatomical structure of the patient. In this paper, we present a combined surface and fiducial based registration method to register the preoperative 3D CT data to the intraoperative surface of larynx. To accurately model the exposed surface area, a structured light based stereo vision technique is used for the surface reconstruction. We combined the gray code pattern and multi-line shifting to generate the intraoperative surface of the larynx. To register the point clouds from the intraoperative stage to the preoperative 3D CT data, a shape priori based ICP method is proposed to quickly register the two surfaces. The proposed approach is capable of tracking the fiducial markers and reconstructing the surface of larynx with no damage to the anatomical structure. We used off-the-shelf digital cameras, LCD projector and rapid 3D prototyper to develop our experimental system. The final RMS error in the registration is less than 1mm.

  1. Integration of real-time 3D capture, reconstruction, and light-field display

    Science.gov (United States)

    Zhang, Zhaoxing; Geng, Zheng; Li, Tuotuo; Pei, Renjing; Liu, Yongchun; Zhang, Xiao

    2015-03-01

    Effective integration of 3D acquisition, reconstruction (modeling) and display technologies into a seamless systems provides augmented experience of visualizing and analyzing real objects and scenes with realistic 3D sensation. Applications can be found in medical imaging, gaming, virtual or augmented reality and hybrid simulations. Although 3D acquisition, reconstruction, and display technologies have gained significant momentum in recent years, there seems a lack of attention on synergistically combining these components into a "end-to-end" 3D visualization system. We designed, built and tested an integrated 3D visualization system that is able to capture in real-time 3D light-field images, perform 3D reconstruction to build 3D model of the objects, and display the 3D model on a large autostereoscopic screen. In this article, we will present our system architecture and component designs, hardware/software implementations, and experimental results. We will elaborate on our recent progress on sparse camera array light-field 3D acquisition, real-time dense 3D reconstruction, and autostereoscopic multi-view 3D display. A prototype is finally presented with test results to illustrate the effectiveness of our proposed integrated 3D visualization system.

  2. Surface reconstruction processes in MO VPE grown GaAs layers

    Czech Academy of Sciences Publication Activity Database

    Nohavica, Dušan

    1999-01-01

    Roč. 50, 2/s (1999), s. 24-25 ISSN 1335-3632. [Development of Materials Science in Research and Education - DMS -RE 1998 /8./. Zlenice, 08.09.1998-10.09.1998] R&D Projects: GA AV ČR IAA2067901 Institutional research plan: CEZ:AV0Z2067918 Keywords : epitaxial growth * surface reconstruction Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  3. Cross-talk free selective reconstruction of individual objects from multiplexed optical field data

    Science.gov (United States)

    Zea, Alejandro Velez; Barrera, John Fredy; Torroba, Roberto

    2018-01-01

    In this paper we present a data multiplexing method for simultaneous storage in a single package composed by several optical fields of tridimensional (3D) objects, and their individual cross-talk free retrieval. Optical field data are extracted from off axis Fourier holograms, and then sampled by multiplying them with random binary masks. The resulting sampled optical fields can be used to reconstruct the original objects. Sampling causes a loss of quality that can be controlled by the number of white pixels in the binary masks and by applying a padding procedure on the optical field data. This process can be performed using a different binary mask for each optical field, and then added to form a multiplexed package. With the adequate choice of sampling and padding, we can achieve a volume reduction in the multiplexed package over the addition of all individual optical fields. Moreover, the package can be multiplied by a binary mask to select a specific optical field, and after the reconstruction procedure, the corresponding 3D object is recovered without any cross-talk. We demonstrate the effectiveness of our proposal for data compression with a comparison with discrete cosine transform filtering. Experimental results confirm the validity of our proposal.

  4. Reconstruction of surface morphology from coherent scattering of white x-ray radiation

    Energy Technology Data Exchange (ETDEWEB)

    Sant, Tushar; Pietsch, Ullrich [Solid State Physics Group, University of Siegen, 57068 Siegen (Germany)

    2009-07-01

    Static speckle experiments were performed using coherent white X-ray radiation from a bending magnet at BESSYII. Semiconductor and polymer surfaces were investigated under incidence condition smaller than the critical angle of total external reflection. The scattering pattern of the sample results from the illumination function modified by the surface roughness. The periodic oscillations are caused by the illumination function whereas other irregular features are associated with sample surface. The speckle map of reflection from a laterally periodic structure like GaAs grating is studied. Under coherent illumination the grating peaks split into speckles because of fluctuations on the sample surface. The surface morphology can be reconstructed using phase retrieval algorithms. In case of 1D problem, these algorithms rarely yield a unique and converging solution. The algorithm is modified to contain additional propagator term and the phase of illumination function in the real space constraint. The modified algorithm converges faster than conventional algorithms. A detailed surface profiles from the real measurements of the sample are reconstructed using this algorithm.

  5. Generalized configurations of the reconstruction and hologram surface in digital holography

    International Nuclear Information System (INIS)

    Frere, C.

    1988-01-01

    Approximations are introduced for calculating the complex amplitude in holography, so that diffraction effects from curved lines and from the hologram surface are negligible. These effects are estimated. In the one-dimensional case, the calculation was made by the steady-phase method, with a weaker condition than the Fresnel condition. The one-dimensional transparency is exemplarily on straight, sinusoidal and elliptic lines while plane and cylindrical surfaces are chosen for the hologram surface. In the two-dimensional case, a numerical calculation is carried out using the fast Fourier transformation algorithm, and with a condition similar to the Fresnel condition. Compared with the transparency distribution, this method yields slightly disturbed reconstruction distributions. Inclined planes and cylindrical surfaces were chosen as hologram surfaces. The calculated complex amplitudes were encoded and materialized in a computer-supported hologram. (orig./DG) [de

  6. Torso geometry reconstruction and body surface electrode localization using three-dimensional photography.

    Science.gov (United States)

    Perez-Alday, Erick A; Thomas, Jason A; Kabir, Muammar; Sedaghat, Golriz; Rogovoy, Nichole; van Dam, Eelco; van Dam, Peter; Woodward, William; Fuss, Cristina; Ferencik, Maros; Tereshchenko, Larisa G

    We conducted a prospective clinical study (n=14; 29% female) to assess the accuracy of a three-dimensional (3D) photography-based method of torso geometry reconstruction and body surface electrodes localization. The position of 74 body surface electrocardiographic (ECG) electrodes (diameter 5mm) was defined by two methods: 3D photography, and CT (marker diameter 2mm) or MRI (marker size 10×20mm) imaging. Bland-Altman analysis showed good agreement in X (bias -2.5 [95% limits of agreement (LoA) -19.5 to 14.3] mm), Y (bias -0.1 [95% LoA -14.1 to 13.9] mm), and Z coordinates (bias -0.8 [95% LoA -15.6 to 14.2] mm), as defined by the CT/MRI imaging, and 3D photography. The average Hausdorff distance between the two torso geometry reconstructions was 11.17±3.05mm. Thus, accurate torso geometry reconstruction using 3D photography is feasible. Body surface ECG electrodes coordinates as defined by the CT/MRI imaging, and 3D photography, are in good agreement. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Mn induced 1 × 2 reconstruction in the τ-MnAl(0 0 1) surface

    Science.gov (United States)

    Guerrero-Sánchez, J.; Takeuchi, Noboru

    2018-05-01

    We report on first principles total energy calculations to describe the structural, electronic and magnetic properties of MnAl(0 0 1) surfaces. We have concentrated in structural models having 1 × 1 and 1 × 2 periodicities, since recent experiments of the similar MnGa(0 0 1) surface have found 1 × 1 and 1 × 2 reconstructions. Our calculations show the existence of two stable structures for different ranges of chemical potential. A 1 × 1 surface is stable for Al-rich conditions, whereas a Mn-induced 1 × 2 reconstruction appears after increasing the Mn chemical potential up to Mn-rich conditions. It is important to notice that experimentally, Mn rich conditions are important for improved magnetic properties. The Mn layers in both structures have ferromagnetic arrangements, but they are aligned antiferromagnetically with the almost no magnetic Al atoms. Moreover, the on top Mn atoms, which produce the 1 × 2 reconstruction, align antiferromagnetically with the second layer Mn atoms. These findings are similar to those obtained experimentally in MnGa thin films grown by molecular beam epitaxy. Therefore, this method could also be used to grow the proposed MnAl films.

  8. Multi-proxy reconstructions of precipitation field in China over the past 500 years.

    OpenAIRE

    Shi, Feng; Zhao, sen; Guo, Zhengtang; Goosse, Hugues; Yin, Qiuzhen

    2017-01-01

    The dominant modes of variability of precipitation for the whole of China over the past millennium and the mechanism governing their spatial structure remain unclear. This is mainly due to insufficient high-resolution proxy records of precipitation in western China. Numerous tree-ring chronologies have recently been archived in publicly available databases through PAGES2k activities, and these provide an opportunity to refine precipitation field reconstructions for China. Ba...

  9. Lidar-based reconstruction of wind fields and application for wind turbine control

    OpenAIRE

    Kapp, Stefan

    2017-01-01

    In this thesis horizontal, upwind scanning lidar systems of the focused continuous-wave type are regarded for wind turbines. The theory of wind field reconstruction is extended to a five parameter model describing the inflow in non-uniform conditions more accurately. Sensor requirements are derived. A new approach to spherically scan the inflow area is studied experimentally. Expected inaccuracies of the averaged wind direction signal in a wind farm environment are quantified and spatial inho...

  10. Analysis of reconstructed interference fields in digital holographic interferometry using the polynomial phase transform

    International Nuclear Information System (INIS)

    Gorthi, Sai Siva; Rastogi, Pramod

    2009-01-01

    A noisy wrapped phase map is the end-output of commonly employed phase estimation methods in digital holographic interferometry. Hence filtering and unwrapping are necessary to obtain continuous phase distributions. This paper introduces a new approach for phase estimation in digital holographic interferometry using the polynomial phase transform. The proposed approach directly provides an accurate estimation of the unwrapped phase distribution from a noisy reconstructed interference field, thereby bypassing cumbersome and error-prone filtering and 2D phase unwrapping procedures

  11. On the reconstruction of the surface structure of the spotted stars

    Science.gov (United States)

    Kolbin, A. I.; Shimansky, V. V.; Sakhibullin, N. A.

    2013-07-01

    We have developed and tested a light-curve inversion technique for photometric mapping of spotted stars. The surface of a spotted star is partitioned into small area elements, over which a search is carried out for the intensity distribution providing the best agreement between the observed and model light curves within a specified uncertainty. We have tested mapping techniques based on the use of both a single light curve and several light curves obtained in different photometric bands. Surface reconstruction artifacts due to the ill-posed nature of the problem have been identified.

  12. Two-dimensional Tissue Image Reconstruction Based on Magnetic Field Data

    Directory of Open Access Journals (Sweden)

    J. Dedkova

    2012-09-01

    Full Text Available This paper introduces new possibilities within two-dimensional reconstruction of internal conductivity distribution. In addition to the electric field inside the given object, the injected current causes a magnetic field which can be measured either outside the object by means of a Hall probe or inside the object through magnetic resonance imaging. The Magnetic Resonance method, together with Electrical impedance tomography (MREIT, is well known as a bio-imaging modality providing cross-sectional conductivity images with a good spatial resolution from the measurements of internal magnetic flux density produced by externally injected currents. A new algorithm for the conductivity reconstruction, which utilizes the internal current information with respect to corresponding boundary conditions and the external magnetic field, was developed. A series of computer simulations has been conducted to assess the performance of the proposed algorithm within the process of estimating electrical conductivity changes in the lungs, heart, and brain tissues captured in two-dimensional piecewise homogeneous chest and head models. The reconstructed conductivity distribution using the proposed method is compared with that using a conventional method based on Electrical Impedance Tomography (EIT. The acquired experience is discussed and the direction of further research is proposed.

  13. Anisotropy of the Seebeck Coefficient in the Cuprate Superconductor YBa_{2}Cu_{3}O_{y}: Fermi-Surface Reconstruction by Bidirectional Charge Order

    Directory of Open Access Journals (Sweden)

    O. Cyr-Choinière

    2017-09-01

    Full Text Available The Seebeck coefficient S of the cuprate YBa_{2}Cu_{3}O_{y} is measured in magnetic fields large enough to suppress superconductivity, at hole dopings p=0.11 and p=0.12, for heat currents along the a and b directions of the orthorhombic crystal structure. For both directions, S/T decreases and becomes negative at low temperature, a signature that the Fermi surface undergoes a reconstruction due to broken translational symmetry. Above a clear threshold field, a strong new feature appears in S_{b}, for conduction along the b axis only. We attribute this feature to the onset of 3D-coherent unidirectional charge-density-wave modulations seen by x-ray diffraction, also along the b axis only. Because these modulations have a sharp onset temperature well below the temperature where S/T starts to drop towards negative values, we infer that they are not the cause of Fermi-surface reconstruction. Instead, the reconstruction must be caused by the quasi-2D bidirectional modulations that develop at significantly higher temperature. The unidirectional order only confers an additional anisotropy to the already reconstructed Fermi surface, also manifest as an in-plane anisotropy of the resistivity.

  14. A Hierarchical Building Segmentation in Digital Surface Models for 3D Reconstruction

    Directory of Open Access Journals (Sweden)

    Yiming Yan

    2017-01-01

    Full Text Available In this study, a hierarchical method for segmenting buildings in a digital surface model (DSM, which is used in a novel framework for 3D reconstruction, is proposed. Most 3D reconstructions of buildings are model-based. However, the limitations of these methods are overreliance on completeness of the offline-constructed models of buildings, and the completeness is not easily guaranteed since in modern cities buildings can be of a variety of types. Therefore, a model-free framework using high precision DSM and texture-images buildings was introduced. There are two key problems with this framework. The first one is how to accurately extract the buildings from the DSM. Most segmentation methods are limited by either the terrain factors or the difficult choice of parameter-settings. A level-set method are employed to roughly find the building regions in the DSM, and then a recently proposed ‘occlusions of random textures model’ are used to enhance the local segmentation of the buildings. The second problem is how to generate the facades of buildings. Synergizing with the corresponding texture-images, we propose a roof-contour guided interpolation of building facades. The 3D reconstruction results achieved by airborne-like images and satellites are compared. Experiments show that the segmentation method has good performance, and 3D reconstruction is easily performed by our framework, and better visualization results can be obtained by airborne-like images, which can be further replaced by UAV images.

  15. Novel Low Cost 3D Surface Model Reconstruction System for Plant Phenotyping

    Directory of Open Access Journals (Sweden)

    Suxing Liu

    2017-09-01

    Full Text Available Accurate high-resolution three-dimensional (3D models are essential for a non-invasive analysis of phenotypic characteristics of plants. Previous limitations in 3D computer vision algorithms have led to a reliance on volumetric methods or expensive hardware to record plant structure. We present an image-based 3D plant reconstruction system that can be achieved by using a single camera and a rotation stand. Our method is based on the structure from motion method, with a SIFT image feature descriptor. In order to improve the quality of the 3D models, we segmented the plant objects based on the PlantCV platform. We also deducted the optimal number of images needed for reconstructing a high-quality model. Experiments showed that an accurate 3D model of the plant was successfully could be reconstructed by our approach. This 3D surface model reconstruction system provides a simple and accurate computational platform for non-destructive, plant phenotyping.

  16. LOGISMOS-B for primates: primate cortical surface reconstruction and thickness measurement

    Science.gov (United States)

    Oguz, Ipek; Styner, Martin; Sanchez, Mar; Shi, Yundi; Sonka, Milan

    2015-03-01

    Cortical thickness and surface area are important morphological measures with implications for many psychiatric and neurological conditions. Automated segmentation and reconstruction of the cortical surface from 3D MRI scans is challenging due to the variable anatomy of the cortex and its highly complex geometry. While many methods exist for this task in the context of the human brain, these methods are typically not readily applicable to the primate brain. We propose an innovative approach based on our recently proposed human cortical reconstruction algorithm, LOGISMOS-B, and the Laplace-based thickness measurement method. Quantitative evaluation of our approach was performed based on a dataset of T1- and T2-weighted MRI scans from 12-month-old macaques where labeling by our anatomical experts was used as independent standard. In this dataset, LOGISMOS-B has an average signed surface error of 0.01 +/- 0.03mm and an unsigned surface error of 0.42 +/- 0.03mm over the whole brain. Excluding the rather problematic temporal pole region further improves unsigned surface distance to 0.34 +/- 0.03mm. This high level of accuracy reached by our algorithm even in this challenging developmental dataset illustrates its robustness and its potential for primate brain studies.

  17. Field emission from the surface of highly ordered pyrolytic graphite

    Energy Technology Data Exchange (ETDEWEB)

    Knápek, Alexandr, E-mail: knapek@isibrno.cz [Institute of Scientific Instruments of the ASCR, v.v.i., Královopolská 147, Brno (Czech Republic); Sobola, Dinara; Tománek, Pavel [Department of Physics, FEEC, Brno University of Technology, Technická 8, Brno (Czech Republic); Pokorná, Zuzana; Urbánek, Michal [Institute of Scientific Instruments of the ASCR, v.v.i., Královopolská 147, Brno (Czech Republic)

    2017-02-15

    Highlights: • HOPG shreds were created and analyzed in the UHV conditions. • Current-voltage measurements have been done to confirm electron tunneling, based on the Fowler-Nordheim theory. • Surface was characterized by other surface evaluation methods, in particular by: SNOM, SEM and AFM. - Abstract: This paper deals with the electrical characterization of highly ordered pyrolytic graphite (HOPG) surface based on field emission of electrons. The effect of field emission occurs only at disrupted surface, i.e. surface containing ripped and warped shreds of the uppermost layers of graphite. These deformations provide the necessary field gradients which are required for measuring tunneling current caused by field electron emission. Results of the field emission measurements are correlated with other surface characterization methods such as scanning near-field optical microscopy (SNOM) or atomic force microscopy.

  18. Field emission from the surface of highly ordered pyrolytic graphite

    International Nuclear Information System (INIS)

    Knápek, Alexandr; Sobola, Dinara; Tománek, Pavel; Pokorná, Zuzana; Urbánek, Michal

    2017-01-01

    Highlights: • HOPG shreds were created and analyzed in the UHV conditions. • Current-voltage measurements have been done to confirm electron tunneling, based on the Fowler-Nordheim theory. • Surface was characterized by other surface evaluation methods, in particular by: SNOM, SEM and AFM. - Abstract: This paper deals with the electrical characterization of highly ordered pyrolytic graphite (HOPG) surface based on field emission of electrons. The effect of field emission occurs only at disrupted surface, i.e. surface containing ripped and warped shreds of the uppermost layers of graphite. These deformations provide the necessary field gradients which are required for measuring tunneling current caused by field electron emission. Results of the field emission measurements are correlated with other surface characterization methods such as scanning near-field optical microscopy (SNOM) or atomic force microscopy.

  19. Reconstruction of far-field tsunami amplitude distributions from earthquake sources

    Science.gov (United States)

    Geist, Eric L.; Parsons, Thomas E.

    2016-01-01

    The probability distribution of far-field tsunami amplitudes is explained in relation to the distribution of seismic moment at subduction zones. Tsunami amplitude distributions at tide gauge stations follow a similar functional form, well described by a tapered Pareto distribution that is parameterized by a power-law exponent and a corner amplitude. Distribution parameters are first established for eight tide gauge stations in the Pacific, using maximum likelihood estimation. A procedure is then developed to reconstruct the tsunami amplitude distribution that consists of four steps: (1) define the distribution of seismic moment at subduction zones; (2) establish a source-station scaling relation from regression analysis; (3) transform the seismic moment distribution to a tsunami amplitude distribution for each subduction zone; and (4) mix the transformed distribution for all subduction zones to an aggregate tsunami amplitude distribution specific to the tide gauge station. The tsunami amplitude distribution is adequately reconstructed for four tide gauge stations using globally constant seismic moment distribution parameters established in previous studies. In comparisons to empirical tsunami amplitude distributions from maximum likelihood estimation, the reconstructed distributions consistently exhibit higher corner amplitude values, implying that in most cases, the empirical catalogs are too short to include the largest amplitudes. Because the reconstructed distribution is based on a catalog of earthquakes that is much larger than the tsunami catalog, it is less susceptible to the effects of record-breaking events and more indicative of the actual distribution of tsunami amplitudes.

  20. Fast Extended Depth-of-Field Reconstruction for Complex Holograms Using Block Partitioned Entropy Minimization

    Directory of Open Access Journals (Sweden)

    Peter Wai Ming Tsang

    2018-05-01

    Full Text Available Optical scanning holography (OSH is a powerful and effective method for capturing the complex hologram of a three-dimensional (3-D scene. Such captured complex hologram is called optical scanned hologram. However, reconstructing a focused image from an optical scanned hologram is a difficult issue, as OSH technique can be applied to acquire holograms of wide-view and complicated object scenes. Solutions developed to date are mostly computationally intensive, and in so far only reconstruction of simple object scenes have been demonstrated. In this paper we report a low complexity method for reconstructing a focused image from an optical scanned hologram that is representing a 3-D object scene. Briefly, a complex hologram is back-propagated onto regular spaced images along the axial direction, and from which a crude, blocky depth map of the object scene is computed according to non-overlapping block partitioned entropy minimization. Subsequently, the depth map is low-pass filtered to decrease the blocky distribution, and employed to reconstruct a single focused image of the object scene for extended depth of field. The method proposed here can be applied to any complex holograms such as those obtained from standard phase-shifting holography.

  1. Superresolution Near-field Imaging with Surface Waves

    KAUST Repository

    Fu, Lei; Liu, Zhaolun; Schuster, Gerard T.

    2017-01-01

    We present the theory for near-field superresolution imaging with surface waves and time reverse mirrors (TRMs). Theoretical formulas and numerical results show that applying the TRM operation to surface waves in an elastic half-space can achieve

  2. DIRECT DETECTION OF THE HELICAL MAGNETIC FIELD GEOMETRY FROM 3D RECONSTRUCTION OF PROMINENCE KNOT TRAJECTORIES

    Energy Technology Data Exchange (ETDEWEB)

    Zapiór, Maciej; Martinez-Gómez, David, E-mail: zapior.maciek@gmail.com [Physics Department, University of the Balearic Islands, Cra. de Valldemossa, km 7.5. Palma (Illes Balears), E-07122 (Spain)

    2016-02-01

    Based on the data collected by the Vacuum Tower Telescope located in the Teide Observatory in the Canary Islands, we analyzed the three-dimensional (3D) motion of so-called knots in a solar prominence of 2014 June 9. Trajectories of seven knots were reconstructed, giving information of the 3D geometry of the magnetic field. Helical motion was detected. From the equipartition principle, we estimated the lower limit of the magnetic field in the prominence to ≈1–3 G and from the Ampère’s law the lower limit of the electric current to ≈1.2 × 10{sup 9} A.

  3. Direct Detection of the Helical Magnetic Field Geometry from 3D Reconstruction of Prominence Knot Trajectories

    Science.gov (United States)

    Zapiór, Maciej; Martínez-Gómez, David

    2016-02-01

    Based on the data collected by the Vacuum Tower Telescope located in the Teide Observatory in the Canary Islands, we analyzed the three-dimensional (3D) motion of so-called knots in a solar prominence of 2014 June 9. Trajectories of seven knots were reconstructed, giving information of the 3D geometry of the magnetic field. Helical motion was detected. From the equipartition principle, we estimated the lower limit of the magnetic field in the prominence to ≈1-3 G and from the Ampère’s law the lower limit of the electric current to ≈1.2 × 109 A.

  4. Quantitative roughness characterization and 3D reconstruction of electrode surface using cyclic voltammetry and SEM image

    Energy Technology Data Exchange (ETDEWEB)

    Dhillon, Shweta; Kant, Rama, E-mail: rkant@chemistry.du.ac.in

    2013-10-01

    Area measurements from cyclic voltammetry (CV) and image from scanning electron microscopy (SEM) are used to characterize electrode statistical morphology, 3D surface reconstruction and its electroactivity. SEM images of single phased materials correspond to two-dimensional (2D) projections of 3D structures, leading to an incomplete characterization. Lack of third dimension information in SEM image is circumvented using equivalence between denoised SEM image and CV area measurements. This CV-SEM method can be used to estimate power spectral density (PSD), width, gradient, finite fractal nature of roughness and local morphology of the electrode. We show that the surface morphological statistical property like distribution function of gradient can be related to local electro-activity. Electrode surface gradient micrographs generated here can provide map of electro-activity sites. Finally, the densely and uniformly packed small gradient over the Pt-surface is the determining criterion for high intrinsic electrode activity.

  5. Quantitative roughness characterization and 3D reconstruction of electrode surface using cyclic voltammetry and SEM image

    International Nuclear Information System (INIS)

    Dhillon, Shweta; Kant, Rama

    2013-01-01

    Area measurements from cyclic voltammetry (CV) and image from scanning electron microscopy (SEM) are used to characterize electrode statistical morphology, 3D surface reconstruction and its electroactivity. SEM images of single phased materials correspond to two-dimensional (2D) projections of 3D structures, leading to an incomplete characterization. Lack of third dimension information in SEM image is circumvented using equivalence between denoised SEM image and CV area measurements. This CV-SEM method can be used to estimate power spectral density (PSD), width, gradient, finite fractal nature of roughness and local morphology of the electrode. We show that the surface morphological statistical property like distribution function of gradient can be related to local electro-activity. Electrode surface gradient micrographs generated here can provide map of electro-activity sites. Finally, the densely and uniformly packed small gradient over the Pt-surface is the determining criterion for high intrinsic electrode activity.

  6. Reconstruction of solar spectral surface UV irradiances using radiative transfer simulations.

    Science.gov (United States)

    Lindfors, Anders; Heikkilä, Anu; Kaurola, Jussi; Koskela, Tapani; Lakkala, Kaisa

    2009-01-01

    UV radiation exerts several effects concerning life on Earth, and spectral information on the prevailing UV radiation conditions is needed in order to study each of these effects. In this paper, we present a method for reconstruction of solar spectral UV irradiances at the Earth's surface. The method, which is a further development of an earlier published method for reconstruction of erythemally weighted UV, relies on radiative transfer simulations, and takes as input (1) the effective cloud optical depth as inferred from pyranometer measurements of global radiation (300-3000 nm); (2) the total ozone column; (3) the surface albedo as estimated from measurements of snow depth; (4) the total water vapor column; and (5) the altitude of the location. Reconstructed daily cumulative spectral irradiances at Jokioinen and Sodankylä in Finland are, in general, in good agreement with measurements. The mean percentage difference, for instance, is mostly within +/-8%, and the root mean square of the percentage difference is around 10% or below for wavelengths over 310 nm and daily minimum solar zenith angles (SZA) less than 70 degrees . In this study, we used pseudospherical radiative transfer simulations, which were shown to improve the performance of our method under large SZA (low Sun).

  7. Calibration-free quantitative surface topography reconstruction in scanning electron microscopy

    International Nuclear Information System (INIS)

    Faber, E.T.; Martinez-Martinez, D.; Mansilla, C.; Ocelík, V.; Hosson, J.Th.M. De

    2015-01-01

    This work presents a new approach to obtain reliable surface topography reconstructions from 2D Scanning Electron Microscopy (SEM) images. In this method a set of images taken at different tilt angles are compared by means of digital image correlation (DIC). It is argued that the strength of the method lies in the fact that precise knowledge about the nature of the rotation (vector and/or magnitude) is not needed. Therefore, the great advantage is that complex calibrations of the measuring equipment are avoided. The paper presents the necessary equations involved in the methods, including derivations and solutions. The method is illustrated with examples of 3D reconstructions followed by a discussion on the relevant experimental parameters. - Highlights: • A novel method for quantitative 3D surface reconstruction in SEM is described. • This method uses at least 3 SEM images acquired at different sample tilts. • This method does not need calibration from the movement of the sample holder. • Mathematical background and examples of application are presented

  8. A Lightweight Surface Reconstruction Method for Online 3D Scanning Point Cloud Data Oriented toward 3D Printing

    Directory of Open Access Journals (Sweden)

    Buyun Sheng

    2018-01-01

    Full Text Available The existing surface reconstruction algorithms currently reconstruct large amounts of mesh data. Consequently, many of these algorithms cannot meet the efficiency requirements of real-time data transmission in a web environment. This paper proposes a lightweight surface reconstruction method for online 3D scanned point cloud data oriented toward 3D printing. The proposed online lightweight surface reconstruction algorithm is composed of a point cloud update algorithm (PCU, a rapid iterative closest point algorithm (RICP, and an improved Poisson surface reconstruction algorithm (IPSR. The generated lightweight point cloud data are pretreated using an updating and rapid registration method. The Poisson surface reconstruction is also accomplished by a pretreatment to recompute the point cloud normal vectors; this approach is based on a least squares method, and the postprocessing of the PDE patch generation was based on biharmonic-like fourth-order PDEs, which effectively reduces the amount of reconstructed mesh data and improves the efficiency of the algorithm. This method was verified using an online personalized customization system that was developed with WebGL and oriented toward 3D printing. The experimental results indicate that this method can generate a lightweight 3D scanning mesh rapidly and efficiently in a web environment.

  9. Calibration-free quantitative surface topography reconstruction in scanning electron microscopy.

    Science.gov (United States)

    Faber, E T; Martinez-Martinez, D; Mansilla, C; Ocelík, V; Hosson, J Th M De

    2015-01-01

    This work presents a new approach to obtain reliable surface topography reconstructions from 2D Scanning Electron Microscopy (SEM) images. In this method a set of images taken at different tilt angles are compared by means of digital image correlation (DIC). It is argued that the strength of the method lies in the fact that precise knowledge about the nature of the rotation (vector and/or magnitude) is not needed. Therefore, the great advantage is that complex calibrations of the measuring equipment are avoided. The paper presents the necessary equations involved in the methods, including derivations and solutions. The method is illustrated with examples of 3D reconstructions followed by a discussion on the relevant experimental parameters. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Reconstruction of constitutive parameters in isotropic linear elasticity from noisy full-field measurements

    International Nuclear Information System (INIS)

    Bal, Guillaume; Bellis, Cédric; Imperiale, Sébastien; Monard, François

    2014-01-01

    Within the framework of linear elasticity we assume the availability of internal full-field measurements of the continuum deformations of a non-homogeneous isotropic solid. The aim is the quantitative reconstruction of the associated moduli. A simple gradient system for the sought constitutive parameters is derived algebraically from the momentum equation, whose coefficients are expressed in terms of the measured displacement fields and their spatial derivatives. Direct integration of this system is discussed to finally demonstrate the inexpediency of such an approach when dealing with noisy data. Upon using polluted measurements, an alternative variational formulation is deployed to invert for the physical parameters. Analysis of this latter inversion procedure provides existence and uniqueness results while the reconstruction stability with respect to the measurements is investigated. As the inversion procedure requires differentiating the measurements twice, a numerical differentiation scheme based on an ad hoc regularization then allows an optimally stable reconstruction of the sought moduli. Numerical results are included to illustrate and assess the performance of the overall approach. (paper)

  11. Full field image reconstruction is suitable for high-pitch dual-source computed tomography.

    Science.gov (United States)

    Mahnken, Andreas H; Allmendinger, Thomas; Sedlmair, Martin; Tamm, Miriam; Reinartz, Sebastian D; Flohr, Thomas

    2012-11-01

    The field of view (FOV) in high-pitch dual-source computed tomography (DSCT) is limited by the size of the second detector. The goal of this study was to develop and evaluate a full FOV image reconstruction technique for high-pitch DSCT. For reconstruction beyond the FOV of the second detector, raw data of the second system were extended to the full dimensions of the first system, using the partly existing data of the first system in combination with a very smooth transition weight function. During the weighted filtered backprojection, the data of the second system were applied with an additional weighting factor. This method was tested for different pitch values from 1.5 to 3.5 on a simulated phantom and on 25 high-pitch DSCT data sets acquired at pitch values of 1.6, 2.0, 2.5, 2.8, and 3.0. Images were reconstructed with FOV sizes of 260 × 260 and 500 × 500 mm. Image quality was assessed by 2 radiologists using a 5-point Likert scale and analyzed with repeated-measure analysis of variance. In phantom and patient data, full FOV image quality depended on pitch. Where complete projection data from both tube-detector systems were available, image quality was unaffected by pitch changes. Full FOV image quality was not compromised at pitch values of 1.6 and remained fully diagnostic up to a pitch of 2.0. At higher pitch values, there was an increasing difference in image quality between limited and full FOV images (P = 0.0097). With this new image reconstruction technique, full FOV image reconstruction can be used up to a pitch of 2.0.

  12. An electron tomography algorithm for reconstructing 3D morphology using surface tangents of projected scattering interfaces

    Science.gov (United States)

    Petersen, T. C.; Ringer, S. P.

    2010-03-01

    Upon discerning the mere shape of an imaged object, as portrayed by projected perimeters, the full three-dimensional scattering density may not be of particular interest. In this situation considerable simplifications to the reconstruction problem are possible, allowing calculations based upon geometric principles. Here we describe and provide an algorithm which reconstructs the three-dimensional morphology of specimens from tilt series of images for application to electron tomography. Our algorithm uses a differential approach to infer the intersection of projected tangent lines with surfaces which define boundaries between regions of different scattering densities within and around the perimeters of specimens. Details of the algorithm implementation are given and explained using reconstruction calculations from simulations, which are built into the code. An experimental application of the algorithm to a nano-sized Aluminium tip is also presented to demonstrate practical analysis for a real specimen. Program summaryProgram title: STOMO version 1.0 Catalogue identifier: AEFS_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEFS_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 2988 No. of bytes in distributed program, including test data, etc.: 191 605 Distribution format: tar.gz Programming language: C/C++ Computer: PC Operating system: Windows XP RAM: Depends upon the size of experimental data as input, ranging from 200 Mb to 1.5 Gb Supplementary material: Sample output files, for the test run provided, are available. Classification: 7.4, 14 External routines: Dev-C++ ( http://www.bloodshed.net/devcpp.html) Nature of problem: Electron tomography of specimens for which conventional back projection may fail and/or data for which there is a limited angular

  13. Reconstruction of the Tip-Surface Interaction Potential by Analysis of the Brownian Motion of an Atomic Force Microscope Tip

    NARCIS (Netherlands)

    Willemsen, O.H.; Kuipers, L.; van der Werf, Kees; de Grooth, B.G.; Greve, Jan

    2000-01-01

    The thermal movement of an atomic force microscope (AFM) tip is used to reconstruct the tip-surface interaction potential. If a tip is brought into the vicinity of a surface, its movement is governed by the sum of the harmonic cantilever potential and the tip-surface interaction potential. By

  14. Feature Surfaces in Symmetric Tensor Fields Based on Eigenvalue Manifold.

    Science.gov (United States)

    Palacios, Jonathan; Yeh, Harry; Wang, Wenping; Zhang, Yue; Laramee, Robert S; Sharma, Ritesh; Schultz, Thomas; Zhang, Eugene

    2016-03-01

    Three-dimensional symmetric tensor fields have a wide range of applications in solid and fluid mechanics. Recent advances in the (topological) analysis of 3D symmetric tensor fields focus on degenerate tensors which form curves. In this paper, we introduce a number of feature surfaces, such as neutral surfaces and traceless surfaces, into tensor field analysis, based on the notion of eigenvalue manifold. Neutral surfaces are the boundary between linear tensors and planar tensors, and the traceless surfaces are the boundary between tensors of positive traces and those of negative traces. Degenerate curves, neutral surfaces, and traceless surfaces together form a partition of the eigenvalue manifold, which provides a more complete tensor field analysis than degenerate curves alone. We also extract and visualize the isosurfaces of tensor modes, tensor isotropy, and tensor magnitude, which we have found useful for domain applications in fluid and solid mechanics. Extracting neutral and traceless surfaces using the Marching Tetrahedra method can cause the loss of geometric and topological details, which can lead to false physical interpretation. To robustly extract neutral surfaces and traceless surfaces, we develop a polynomial description of them which enables us to borrow techniques from algebraic surface extraction, a topic well-researched by the computer-aided design (CAD) community as well as the algebraic geometry community. In addition, we adapt the surface extraction technique, called A-patches, to improve the speed of finding degenerate curves. Finally, we apply our analysis to data from solid and fluid mechanics as well as scalar field analysis.

  15. Analytic reconstruction of magnetic resonance imaging signal obtained from a periodic encoding field.

    Science.gov (United States)

    Rybicki, F J; Hrovat, M I; Patz, S

    2000-09-01

    We have proposed a two-dimensional PERiodic-Linear (PERL) magnetic encoding field geometry B(x,y) = g(y)y cos(q(x)x) and a magnetic resonance imaging pulse sequence which incorporates two fields to image a two-dimensional spin density: a standard linear gradient in the x dimension, and the PERL field. Because of its periodicity, the PERL field produces a signal where the phase of the two dimensions is functionally different. The x dimension is encoded linearly, but the y dimension appears as the argument of a sinusoidal phase term. Thus, the time-domain signal and image spin density are not related by a two-dimensional Fourier transform. They are related by a one-dimensional Fourier transform in the x dimension and a new Bessel function integral transform (the PERL transform) in the y dimension. The inverse of the PERL transform provides a reconstruction algorithm for the y dimension of the spin density from the signal space. To date, the inverse transform has been computed numerically by a Bessel function expansion over its basis functions. This numerical solution used a finite sum to approximate an infinite summation and thus introduced a truncation error. This work analytically determines the basis functions for the PERL transform and incorporates them into the reconstruction algorithm. The improved algorithm is demonstrated by (1) direct comparison between the numerically and analytically computed basis functions, and (2) reconstruction of a known spin density. The new solution for the basis functions also lends proof of the system function for the PERL transform under specific conditions.

  16. Reconstruction of pseudo three-dimensional dental image from dental panoramic radiograph and tooth surface shape

    International Nuclear Information System (INIS)

    Imura, Masataka; Kuroda, Yoshihiro; Oshiro, Osamu; Kuroda, Tomohiro; Kagiyama, Yoshiyuki; Yagi, Masakazu; Takada, Kenji; Azuma, Hiroko

    2010-01-01

    Three-dimensional volume data set is useful for diagnosis in dental treatments. However, to obtain three-dimensional images of a dental arch in general dental clinics is difficult. In this paper, we propose a method to reconstruct pseudo three-dimensional dental images from a dental panoramic radiograph and a tooth surface shape which can be obtained from three dimensional shape measurement of a dental impression. The proposed method finds an appropriate curved surface on which the dental panoramic radiograph is mapped by comparing a virtual panoramic image made from a tooth surface shape to a real panoramic radiograph. The developed pseudo three-dimensional dental images give clear impression of patient's dental condition. (author)

  17. Regularity conditions of the field on a toroidal magnetic surface

    International Nuclear Information System (INIS)

    Bouligand, M.

    1985-06-01

    We show that a field B vector which is derived from an analytic canonical potential on an ordinary toroidal surface is regular on this surface when the potential satisfies an elliptic equation (owing to the conservative field) subject to certain conditions of regularity of its coefficients [fr

  18. Gaussian vector fields on triangulated surfaces

    DEFF Research Database (Denmark)

    Ipsen, John H

    2016-01-01

    proven to be very useful to resolve the complex interplay between in-plane ordering of membranes and membrane conformations. In the present work we have developed a procedure for realistic representations of Gaussian models with in-plane vector degrees of freedoms on a triangulated surface. The method...

  19. Electric fields associated with transient surface currents

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson

    1992-01-01

    The boundary condition to be fulfilled by the potential functions associated with a transient surface current is derived and expressed in terms of generalized orthogonal coordinates. From the analysis, it can be deduced that the use of the method of separation of variables is restricted to three ...

  20. Cryopreserved Ultra-Thick Human Amniotic Membrane for Conjunctival Surface Reconstruction After Excision of Conjunctival Tumors.

    Science.gov (United States)

    Tanaka, Thais S; Demirci, Hakan

    2016-04-01

    Cryopreserved ultra-thick human amniotic membrane (AM) is used for glaucoma surgery. We evaluated the use of cryopreserved ultra-thick human AM for conjunctival surface reconstruction after excision of a conjunctival tumor. We retrospectively reviewed the medical records of 28 patients who underwent conjunctival surface reconstruction with cryopreserved ultra-thick human AM after excision of the tumor. The AM was secured to the surrounding conjunctiva and underlying sclera with interrupted 8-0 Vicryl sutures. Clinical data regarding demographics, diagnosis, size and location of conjunctival tumors, patient outcome, and complications were gathered. Of 28 patients, 6 (21.4%) had malignant melanoma, 4 (14.3%) had squamous cell carcinoma, 6 (21.4%) had conjunctival intraepithelial neoplasia, 1 (3.6%) had sebaceous carcinoma, 1 (3.6%) had mucoepidermoid carcinoma, 1 (3.6%) had conjunctival intraepithelial dysplasia, 5 (17.9%) had pterygium, 2 (7.1%) had compound nevus, 1 (3.6%) had a large epithelial inclusion cyst, and 1 (3.6%) patient had a granuloma. The mean area of graft size was 156 ± 120 mm2. Postoperatively, the graft was well tolerated with no failure, discomfort, or dehiscence. During the 17-month mean follow-up, symblepharon, which was clinically nonsignificant, developed in 3 (11%) patients and partial stem cell deficiency was noted in 5 (18%) patients. Cryopreserved ultra-thick human AM is a well-tolerated, effective graft material that is easy to handle. It is a viable alternative for conjunctival surface reconstruction after excision of a conjunctival tumor.

  1. Automatic cortical surface reconstruction of high-resolution T1 echo planar imaging data.

    Science.gov (United States)

    Renvall, Ville; Witzel, Thomas; Wald, Lawrence L; Polimeni, Jonathan R

    2016-07-01

    Echo planar imaging (EPI) is the method of choice for the majority of functional magnetic resonance imaging (fMRI), yet EPI is prone to geometric distortions and thus misaligns with conventional anatomical reference data. The poor geometric correspondence between functional and anatomical data can lead to severe misplacements and corruption of detected activation patterns. However, recent advances in imaging technology have provided EPI data with increasing quality and resolution. Here we present a framework for deriving cortical surface reconstructions directly from high-resolution EPI-based reference images that provide anatomical models exactly geometric distortion-matched to the functional data. Anatomical EPI data with 1mm isotropic voxel size were acquired using a fast multiple inversion recovery time EPI sequence (MI-EPI) at 7T, from which quantitative T1 maps were calculated. Using these T1 maps, volumetric data mimicking the tissue contrast of standard anatomical data were synthesized using the Bloch equations, and these T1-weighted data were automatically processed using FreeSurfer. The spatial alignment between T2(⁎)-weighted EPI data and the synthetic T1-weighted anatomical MI-EPI-based images was improved compared to the conventional anatomical reference. In particular, the alignment near the regions vulnerable to distortion due to magnetic susceptibility differences was improved, and sampling of the adjacent tissue classes outside of the cortex was reduced when using cortical surface reconstructions derived directly from the MI-EPI reference. The MI-EPI method therefore produces high-quality anatomical data that can be automatically segmented with standard software, providing cortical surface reconstructions that are geometrically matched to the BOLD fMRI data. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. Molecular dynamics simulation of boron implanted into diamond (0 0 1) 2 x 1 reconstruction surface

    International Nuclear Information System (INIS)

    Li Rongbin; Dai Yongbin; Hu Xiaojun; Sheng Heshen; He Xianchang

    2003-01-01

    Molecular dynamic simulations, utilizing the Tersoff many-body potential, are used to investigate the microscopic processes of a single boron atom with energy of 500 eV implanted into the diamond (0 0 1) 2 x 1 reconstruction surface. The lifetime of thermal spike created by B bombardment is about 0.18 ps by calculating the variation of the mean coordination numbers with time. The formation of the split-interstitial composed of projectile and lattice atom (B-C) is observed. The total potential energy of the system decreases about 0.56 eV with a stable B split-interstitial in diamond. The lattice relaxations in the diamond (0 0 1) 2 x 1 reconstruction surface or near surface of simulated have been discussed. The outermost layer atoms tend to move inward, and the other atoms move outward. The interplanar distance between the outermost layer and the second layer has been shortened by 15% compared with its starting interplanar distance. Stress distribution in the calculated diamond configuration is inhomogeneous. After boron implanted into diamond with the energy of 500 eV, there is an excess of compressively stressed atoms in the lattice, which induces the total stress being compressive

  3. 3D surface reconstruction and FIB microscopy of worn alumina hip prostheses

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, P; Inkson, B J; Rainforth, W M [Department of Engineering Materials, Mappin St., University of Sheffield, Sheffield, S1 3JD (United Kingdom); Stewart, T [School of Mechanical Engineering, University of Leeds, Leeds, LS2 9JT (United Kingdom)], E-mail: m.rainforth@sheffield.ac.uk

    2008-08-15

    Interest in alumina-on-alumina total hip replacements (THR) continues to grow for the young and active patient due to their superior wear performance and biocompatibility compared to the alternative traditional polymer/metal prostheses. While alumina on alumina bearings offer an excellent solution, a region of high wear, known as stripe wear, is commonly observed on retrieved alumina hip components that poses concern. These in-vivo stripe wear mechanisms can be replicated in vitro by the introduction of micro-separation during the simulated walking cycle in hip joint simulation. However, the understanding of the mechanisms behind the stripe wear processes is relatively poor. 3D topographic reconstructions of titled SEM stereo pairs from different zones have been obtained to determine the local worn surface topography. Focused ion beam (FIB) microscopy was applied to examine the subsurface damage across the stripe wear. The paper presents novel images of sub-surface microcracks in alumina along with 3D reconstructions of the worn ceramic surfaces and a classification of four distinct wear zones following microseparation in hip prostheses.

  4. Image Reconstruction and Evaluation: Applications on Micro-Surfaces and Lenna Image Representation

    Directory of Open Access Journals (Sweden)

    Mohammad Mayyas

    2016-09-01

    Full Text Available This article develops algorithms for the characterization and the visualization of micro-scale features using a small number of sample points, with the goal of mitigating the measurement shortcomings, which are often destructive or time consuming. The popular measurement techniques that are used in imaging of micro-surfaces include the 3D stylus or interferometric profilometry and Scanning Electron Microscopy (SEM, where both could represent the micro-surface characteristics in terms of 3D dimensional topology and greyscale image, respectively. Such images could be highly dense; therefore, traditional image processing techniques might be computationally expensive. We implement the algorithms in several case studies to rapidly examine the microscopic features of micro-surface of Microelectromechanical System (MEMS, and then we validate the results using a popular greyscale image; i.e., “Lenna” image. The contributions of this research include: First, development of local and global algorithm based on modified Thin Plate Spline (TPS model to reconstruct high resolution images of the micro-surface’s topography, and its derivatives using low resolution images. Second, development of a bending energy algorithm from our modified TPS model for filtering out image defects. Finally, development of a computationally efficient technique, referred to as Windowing, which combines TPS and Linear Sequential Estimation (LSE methods, to enhance the visualization of images. The Windowing technique allows rapid image reconstruction based on the reduction of inverse problem.

  5. High-speed Fourier transform profilometry for reconstructing objects having arbitrary surface colours

    International Nuclear Information System (INIS)

    Chen, Liang-Chia; Nguyen, Xuan Loc; Zhang, Fu-Hao; Lin, Tzeng-Yow

    2010-01-01

    In this paper, Fourier transform profilometry (FTP) using a colour fringe selection technique for accurate phase map reconstruction is newly proposed to overcome the limitation of FTP in measuring objects having arbitrary surface colours. The sinusoidal colour fringe pattern is encoded to form a unique colour pattern for projecting onto the object's surface, and its reflected deformed fringe image is taken using a triple-colour CCD camera and rapidly processed by the developed FTP method employing a novel band-pass filter. A new 3D vision system is capable of measuring objects with a high speed of up to 60 frames s −1 . To reconstruct the 3D profile of an object having arbitrary surface colours, an innovative strategy is developed to identify the colour channel of the detected fringe pattern with the best modulation transfer function (MTF) for retrieving accurate phase maps. The experimental results demonstrate that the system has the capability to acquire 3D maps at a high speed while the measurement accuracy of the developed method is substantially better than that of the traditional FTP method. By measuring the standard step heights in a repeatability test, it is confirmed that a maximum measured error can be controlled to less than 2.8% of the overall measuring depth range

  6. Critical surface phase of α2(2 × 4) reconstructed zig-zag chains on InAs(001)

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xiang [Department of Electronic Information Science and Technology, Guizhou University, Guizhou, Guiyang 550025 (China); Zhou, Xun [Department of Electronic Information Science and Technology, Guizhou University, Guizhou, Guiyang 550025 (China); School of Physics and Electronics Science, Guizhou Normal University, Guizhou, Guiyang 550001 (China); Wang, Ji-Hong [Department of Electronic Information Science and Technology, Guizhou University, Guizhou, Guiyang 550025 (China); Luo, Zi-Jiang [Department of Electronic Information Science and Technology, Guizhou University, Guizhou, Guiyang 550025 (China); School of Education Administration, Guizhou University of Finance and Economics, Guizhou, Guiyang 550004 (China); Zhou, Qing; Liu, Ke; Hu, Ming-Zhe [Department of Electronic Information Science and Technology, Guizhou University, Guizhou, Guiyang 550025 (China); Ding, Zhao, E-mail: zding@gzu.edu.cn [Department of Electronic Information Science and Technology, Guizhou University, Guizhou, Guiyang 550025 (China)

    2014-07-01

    The critical condition for InAs(001) surface phase transition has been studied, the surface phase transition of InAs(001) showed discontinuity with hysteresis cycle as a function of substrate temperature. A mixed reconstruction surface and zig-zag chain α2(2 × 4) reconstruction surface have been observed by scanning tunneling microscopy. Considering the interaction and dynamics of surface arsenic atoms, the zig-zag chains of α2(2 × 4) reconstruction were found to be actually caused by the selective adsorption and desorption of surface arsenic dimers, they played a critical role in the surface phase transition between (2 × 4) and (4 × 2). - Highlights: • Discontinuous surface phase transition phenomena on the flat InAs(001) surface • Nanoscale InAs(001) surface observed by scanning tunneling microscopy • “Zig-Zag” chains of α2(2 × 4) reconstruction • Critical role in the surface phase transition between (2 × 4) and (4 × 2)

  7. Critical surface phase of α2(2 × 4) reconstructed zig-zag chains on InAs(001)

    International Nuclear Information System (INIS)

    Guo, Xiang; Zhou, Xun; Wang, Ji-Hong; Luo, Zi-Jiang; Zhou, Qing; Liu, Ke; Hu, Ming-Zhe; Ding, Zhao

    2014-01-01

    The critical condition for InAs(001) surface phase transition has been studied, the surface phase transition of InAs(001) showed discontinuity with hysteresis cycle as a function of substrate temperature. A mixed reconstruction surface and zig-zag chain α2(2 × 4) reconstruction surface have been observed by scanning tunneling microscopy. Considering the interaction and dynamics of surface arsenic atoms, the zig-zag chains of α2(2 × 4) reconstruction were found to be actually caused by the selective adsorption and desorption of surface arsenic dimers, they played a critical role in the surface phase transition between (2 × 4) and (4 × 2). - Highlights: • Discontinuous surface phase transition phenomena on the flat InAs(001) surface • Nanoscale InAs(001) surface observed by scanning tunneling microscopy • “Zig-Zag” chains of α2(2 × 4) reconstruction • Critical role in the surface phase transition between (2 × 4) and (4 × 2)

  8. Mercury's Surface Magnetic Field Determined from Proton-Reflection Magnetometry

    Science.gov (United States)

    Winslow, Reka M.; Johnson, Catherine L.; Anderson, Brian J.; Gershman, Daniel J.; Raines, Jim M.; Lillis, Robert J.; Korth, Haje; Slavin, James A.; Solomon, Sean C.; Zurbuchen, Thomas H.; hide

    2014-01-01

    Solar wind protons observed by the MESSENGER spacecraft in orbit about Mercury exhibit signatures of precipitation loss to Mercury's surface. We apply proton-reflection magnetometry to sense Mercury's surface magnetic field intensity in the planet's northern and southern hemispheres. The results are consistent with a dipole field offset to the north and show that the technique may be used to resolve regional-scale fields at the surface. The proton loss cones indicate persistent ion precipitation to the surface in the northern magnetospheric cusp region and in the southern hemisphere at low nightside latitudes. The latter observation implies that most of the surface in Mercury's southern hemisphere is continuously bombarded by plasma, in contrast with the premise that the global magnetic field largely protects the planetary surface from the solar wind.

  9. Surface magnetic field measurement with magnetic shielding

    Czech Academy of Sciences Publication Activity Database

    Perevertov, Oleksiy

    2010-01-01

    Roč. 61, č. 7 (2010), 66-68 ISSN 1335-3632 Grant - others:AVČR(CZ) M100100906 Institutional research plan: CEZ:AV0Z10100520 Keywords : magnetic hysteresis * magnetic field measurement * magnetic shielding * extrapolation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.270, year: 2010

  10. Image simulation and surface reconstruction of undercut features in atomic force microscopy

    Science.gov (United States)

    Qian, Xiaoping; Villarrubia, John; Tian, Fenglei; Dixson, Ronald

    2007-03-01

    CD-AFMs (critical dimension atomic force microscopes) are instruments with servo-control of the tip in more than one direction. With appropriately "boot-shaped" or flared tips, such instruments can image vertical or even undercut features. As with any AFM, the image is a dilation of the sample shape with the tip shape. Accurate extraction of the CD requires a correction for the tip effect. Analytical methods to correct images for the tip shape have been available for some time for the traditional (vertical feedback only) AFMs, but were until recently unavailable for instruments with multi-dimensional feedback. Dahlen et al. [J. Vac. Sci. Technol. B23, pp. 2297-2303, (2005)] recently introduced a swept-volume approach, implemented for 2-dimensional (2D) feedback. It permits image simulation and sample reconstruction, techniques previously developed for the traditional instruments, to be extended for the newer tools. We have introduced [X. Qian and J. S. Villarrubia, Ultramicroscopy, in press] an alternative dexel-based method, that does the same in either 2D or 3D. This paper describes the application of this method to sample shapes of interest in semiconductor manufacturing. When the tip shape is known (e.g., by prior measurement using a tip characterizer) a 3D sample surface may be reconstructed from its 3D image. Basing the CD measurement upon such a reconstruction is shown here to remove some measurement artifacts that are not removed (or are incompletely removed) by the existing measurement procedures.

  11. Reconstructing Sea Surface Conditions in the Bay of Bengal during the Mid-Pleistocene Transition

    Science.gov (United States)

    Lagos, A. D.; Dekens, P.; Reilly, B. T.; Selkin, P. A.; Meynadier, L.; Savian, J. F.

    2017-12-01

    During the Mid-Pleistocene Transition (MPT, 0.8-1.2Ma) Earth's glacial cycles transitioned from responding primarily to 41kyr obliquity cycles to responding to 100kyr eccentricity cycles. In the tropics, sea surface temperature (SST) in the eastern tropical Pacific cooled through the MPT, suggesting a strengthening of the equatorial Pacific zonal temperature gradient (Medina-Elizalde & Lea, 2005). The strong SST gradient would have intensified Walker Cell convection during the MPT and built up latent heat in the western Pacific, which could cause cold SST anomalies in the northern Indian Ocean (Liu et al., 2015). Due to a scarcity of records, it is unclear how climate and oceanic conditions evolved in the Indian Ocean during the MPT. A set of recent IODP expeditions, including 353 and 354, cored sediment from the Bay of Bengal. Several sites recovered by expedition 353 will be ideal for reconstructing monsoon intensity through time, while the expedition 354 cores from a longitudinal transect at 8°N are in a region not directly impacted by changes in freshwater input due to direct precipitation or run off. The sites are influenced by the northeastern migration of equatorial Indian Ocean water via the Southwest Monsoon Current, which supplies significant moisture to the monsoon. Expedition 354's southern Bay of Bengal sites are well situated for better understanding the link between the tropical Indian Ocean and the northern Bay of Bengal. We reconstructed sea surface conditions at IODP site 1452 (8°N, 87°E, 3670m water depth) in the distal Bengal Fan. A 3 meter long section of the core has been identified as the MPT using the Bruhnes/Matuyama, Jaramillo, and Cobb Mountain paleomagnetic reversals (France-Lanord et al., 2016). This section of site 1452 was sampled every 2cm ( 2kyr resolution). Approximately 30 G. sacculifer, a surface dwelling planktonic foraminifera, were picked from the 355-425μm size fraction. We measured Mg/Ca and δ18O on splits of the same

  12. Iterative algorithm for reconstructing rotationally asymmetric surface deviation with pixel-level spatial resolution

    Science.gov (United States)

    Quan, Haiyang; Wu, Fan; Hou, Xi

    2015-10-01

    New method for reconstructing rotationally asymmetric surface deviation with pixel-level spatial resolution is proposed. It is based on basic iterative scheme and accelerates the Gauss-Seidel method by introducing an acceleration parameter. This modified Successive Over-relaxation (SOR) is effective for solving the rotationally asymmetric components with pixel-level spatial resolution, without the usage of a fitting procedure. Compared to the Jacobi and Gauss-Seidel method, the modified SOR method with an optimal relaxation factor converges much faster and saves more computational costs and memory space without reducing accuracy. It has been proved by real experimental results.

  13. Wind field reconstruction from nacelle-mounted lidar short-range measurements

    Directory of Open Access Journals (Sweden)

    A. Borraccino

    2017-05-01

    Full Text Available Profiling nacelle lidars probe the wind at several heights and several distances upstream of the rotor. The development of such lidar systems is relatively recent, and it is still unclear how to condense the lidar raw measurements into useful wind field characteristics such as speed, direction, vertical and longitudinal gradients (wind shear. In this paper, we demonstrate an innovative method to estimate wind field characteristics using nacelle lidar measurements taken within the induction zone. Model-fitting wind field reconstruction techniques are applied to nacelle lidar measurements taken at multiple distances close to the rotor, where a wind model is combined with a simple induction model. The method allows robust determination of free-stream wind characteristics. The method was applied to experimental data obtained with two different types of nacelle lidar (five-beam Demonstrator and ZephIR Dual Mode. The reconstructed wind speed was within 0.5 % of the wind speed measured with a mast-top-mounted cup anemometer at 2.5 rotor diameters upstream of the turbine. The technique described in this paper overcomes measurement range limitations of the currently available nacelle lidar technology.

  14. Sequential least-square reconstruction of instantaneous pressure field around a body from TR-PIV

    Science.gov (United States)

    Jeon, Young Jin; Gomit, G.; Earl, T.; Chatellier, L.; David, L.

    2018-02-01

    A procedure is introduced to obtain an instantaneous pressure field around a wing from time-resolved particle image velocimetry (TR-PIV) and particle image accelerometry (PIA). The instantaneous fields of velocity and material acceleration are provided by the recently introduced multi-frame PIV method, fluid trajectory evaluation based on ensemble-averaged cross-correlation (FTEE). The integration domain is divided into several subdomains in accordance with the local reliability. The near-edge and near-body regions are determined based on the recorded image of the wing. The instantaneous wake region is assigned by a combination of a self-defined criterion and binary morphological processes. The pressure is reconstructed from a minimization process of the difference between measured and reconstructed pressure gradients in a least-square sense. This is solved sequentially according to a decreasing order of reliability of each subdomain to prevent a propagation of error from the less reliable near-body region to the free-stream. The present procedure is numerically assessed by synthetically generated 2D particle images based on a numerical simulation. Volumetric pressure fields are then evaluated from tomographic TR-PIV of a flow around a 30-degree-inclined NACA0015 airfoil. A possibility of using a different scheme to evaluate material acceleration for a specific subdomain is presented. Moreover, this 3D application allows the investigation of the effect of the third component of the pressure gradient by which the wake region seems to be affected.

  15. Some studies of lead and iron adsorption on the W(100) surface by field emission microscopy

    International Nuclear Information System (INIS)

    Jones, J.P.; Roberts, E.W.

    1978-01-01

    The behaviour of lead and iron adsorbed on the W(100) surface has been studied by probe hole field emission microscopy, field desorption, and by measurement of the total energy distribution (TED) of field-emitted electrons. Lead adsorbed at 300 K which reduces the work function of W(100) can be completely removed at 78 K by field desorption below 3.2 V A -1 and the resulting surface has both the work function and TED, which are characteristic of the clean plane. Condensation at 800 K followed by field desorption, results in a plane surface of work function 4.17 eV and an altered TED. This effect is attributed to the microfacetting, which is observed by LEED. The Swanson peak in the W(100) TED which is removed by submonolayer amounts of lead re-emerges at monolayer coverage when lead adopts the (1 X 1) structure. Such behaviour is consistent with the model proposed by Kar and Soven. A spectral peak observed when lead is adsorbed on the reconstructed W(100) surface is thought to derive for the atomic 1 D state. Adsorption of iron on a W(100) surface reduces phi considerably due to dipole formation and efficiently quenches the Swanson peak. (Auth.)

  16. Configuration of the magnetic field and reconstruction of Pangaea in the Permian period.

    Science.gov (United States)

    Westphal, M

    1977-05-12

    The virtual geomagnetic poles of Laurasia and Gondwanaland in the Carboniferous and Permian periods diverge significantly when these continents are reassembled according to the fit calculated by Bullard et al. Two interpretations have been offered: Briden et al. explain these divergences by a magnetic field configuration very different from that of a geocentric axial dipole; Irving (and private communication), Van der Voo and French(4) suggest a different reconstruction and it is shown here that these two interpretations are not incompatible and that the first may help the second.

  17. Advantages of cortical surface reconstruction using submillimeter 7 T MEMPRAGE.

    Science.gov (United States)

    Zaretskaya, Natalia; Fischl, Bruce; Reuter, Martin; Renvall, Ville; Polimeni, Jonathan R

    2018-01-15

    Recent advances in MR technology have enabled increased spatial resolution for routine functional and anatomical imaging, which has created demand for software tools that are able to process these data. The availability of high-resolution data also raises the question of whether higher resolution leads to substantial gains in accuracy of quantitative morphometric neuroimaging procedures, in particular the cortical surface reconstruction and cortical thickness estimation. In this study we adapted the FreeSurfer cortical surface reconstruction pipeline to process structural data at native submillimeter resolution. We then quantified the differences in surface placement between meshes generated from (0.75 mm) 3 isotropic resolution data acquired in 39 volunteers and the same data downsampled to the conventional 1 mm 3 voxel size. We find that when processed at native resolution, cortex is estimated to be thinner in most areas, but thicker around the Cingulate and the Calcarine sulci as well as in the posterior bank of the Central sulcus. Thickness differences are driven by two kinds of effects. First, the gray-white surface is found closer to the white matter, especially in cortical areas with high myelin content, and thus low contrast, such as the Calcarine and the Central sulci, causing local increases in thickness estimates. Second, the gray-CSF surface is placed more interiorly, especially in the deep sulci, contributing to local decreases in thickness estimates. We suggest that both effects are due to reduced partial volume effects at higher spatial resolution. Submillimeter voxel sizes can therefore provide improved accuracy for measuring cortical thickness. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. GPS tomography: validation of reconstructed 3-D humidity fields with radiosonde profiles

    Directory of Open Access Journals (Sweden)

    M. Shangguan

    2013-09-01

    Full Text Available Water vapor plays an important role in meteorological applications; GeoForschungsZentrum (GFZ therefore developed a tomographic system to derive 3-D distributions of the tropospheric water vapor above Germany using GPS data from about 300 ground stations. Input data for the tomographic reconstructions are generated by the Earth Parameter and Orbit determination System (EPOS software of the GFZ, which provides zenith total delay (ZTD, integrated water vapor (IWV and slant total delay (STD data operationally with a temporal resolution of 2.5 min (STD and 15 min (ZTD, IWV. The water vapor distribution in the atmosphere is derived by tomographic reconstruction techniques. The quality of the solution is dependent on many factors such as the spatial coverage of the atmosphere with slant paths, the spatial distribution of their intersections and the accuracy of the input observations. Independent observations are required to validate the tomographic reconstructions and to get precise information on the accuracy of the derived 3-D water vapor fields. To determine the quality of the GPS tomography, more than 8000 vertical water vapor profiles at 13 German radiosonde stations were used for the comparison. The radiosondes were launched twice a day (at 00:00 UTC and 12:00 UTC in 2007. In this paper, parameters of the entire profiles such as the wet refractivity, and the zenith wet delay have been compared. Before the validation the temporal and spatial distribution of the slant paths, serving as a basis for tomographic reconstruction, as well as their angular distribution were studied. The mean wet refractivity differences between tomography and radiosonde data for all points vary from −1.3 to 0.3, and the root mean square is within the range of 6.5–9. About 32% of 6803 profiles match well, 23% match badly and 45% are difficult to classify as they match only in parts.

  19. GPS tomography. Validation of reconstructed 3-D humidity fields with radiosonde profiles

    Energy Technology Data Exchange (ETDEWEB)

    Shangguan, M.; Bender, M.; Ramatschi, M.; Dick, G.; Wickert, J. [Helmholtz Centre Potsdam, German Research Centre for Geosciences (GFZ), Potsdam (Germany); Raabe, A. [Leipzig Institute for Meteorology (LIM), Leipzig (Germany); Galas, R. [Technische Univ. Berlin (Germany). Dept. for Geodesy and Geoinformation Sciences

    2013-11-01

    Water vapor plays an important role in meteorological applications; GeoForschungsZentrum (GFZ) therefore developed a tomographic system to derive 3-D distributions of the tropospheric water vapor above Germany using GPS data from about 300 ground stations. Input data for the tomographic reconstructions are generated by the Earth Parameter and Orbit determination System (EPOS) software of the GFZ, which provides zenith total delay (ZTD), integrated water vapor (IWV) and slant total delay (STD) data operationally with a temporal resolution of 2.5 min (STD) and 15 min (ZTD, IWV). The water vapor distribution in the atmosphere is derived by tomographic reconstruction techniques. The quality of the solution is dependent on many factors such as the spatial coverage of the atmosphere with slant paths, the spatial distribution of their intersections and the accuracy of the input observations. Independent observations are required to validate the tomographic reconstructions and to get precise information on the accuracy of the derived 3-D water vapor fields. To determine the quality of the GPS tomography, more than 8000 vertical water vapor profiles at 13 German radiosonde stations were used for the comparison. The radiosondes were launched twice a day (at 00:00 UTC and 12:00 UTC) in 2007. In this paper, parameters of the entire profiles such as the wet refractivity, and the zenith wet delay have been compared. Before the validation the temporal and spatial distribution of the slant paths, serving as a basis for tomographic reconstruction, as well as their angular distribution were studied. The mean wet refractivity differences between tomography and radiosonde data for all points vary from -1.3 to 0.3, and the root mean square is within the range of 6.5-9. About 32% of 6803 profiles match well, 23% match badly and 45% are difficult to classify as they match only in parts.

  20. High-Speed Surface Reconstruction of Flying Birds Using Structured Light

    Science.gov (United States)

    Deetjen, Marc; Lentink, David

    2017-11-01

    Birds fly effectively through complex environments, and in order to understand the strategies that enable them to do so, we need to determine the shape and movement of their wings. Previous studies show that even small perturbations in wing shape have dramatic aerodynamic effects, but these shape changes have not been quantified automatically at high temporal and spatial resolutions. Hence, we developed a custom 3D surface mapping method which uses a high-speed camera to view a grid of stripes projected onto a flying bird. Because the light is binary rather than grayscale, and each frame is separately analyzed, this method can function at any frame rate with sufficient light. The method is automated, non-invasive, and able to measure a volume by simultaneously reconstructing from multiple views. We use this technique to reconstruct the 3D shape of the surface of a parrotlet during flapping flight at 3200 fps. We then analyze key dynamic parameters such as wing twist and angle of attack, and compute aerodynamic parameters such as lift and drag. While this novel system is designed to quantify bird wing shape and motion, it is adaptable for tracking other objects such as quickly deforming fish, especially those which are difficult to reconstruct using other 3D tracking methods. The presenter needs to leave by 3 pm on the final day of the conference (11/21) in order to make his flight. Please account for this in the scheduling if possible by scheduling the presentation earlier in the day or a different day.

  1. Accurate 3D reconstruction of bony surfaces using ultrasonic synthetic aperture techniques for robotic knee arthroplasty.

    Science.gov (United States)

    Kerr, William; Rowe, Philip; Pierce, Stephen Gareth

    2017-06-01

    Robotically guided knee arthroplasty systems generally require an individualized, preoperative 3D model of the knee joint. This is typically measured using Computed Tomography (CT) which provides the required accuracy for preoperative surgical intervention planning. Ultrasound imaging presents an attractive alternative to CT, allowing for reductions in cost and the elimination of doses of ionizing radiation, whilst maintaining the accuracy of the 3D model reconstruction of the joint. Traditional phased array ultrasound imaging methods, however, are susceptible to poor resolution and signal to noise ratios (SNR). Alleviating these weaknesses by offering superior focusing power, synthetic aperture methods have been investigated extensively within ultrasonic non-destructive testing. Despite this, they have yet to be fully exploited in medical imaging. In this paper, the ability of a robotic deployed ultrasound imaging system based on synthetic aperture methods to accurately reconstruct bony surfaces is investigated. Employing the Total Focussing Method (TFM) and the Synthetic Aperture Focussing Technique (SAFT), two samples were imaged which were representative of the bones of the knee joint: a human-shaped, composite distal femur and a bovine distal femur. Data were captured using a 5MHz, 128 element 1D phased array, which was manipulated around the samples using a robotic positioning system. Three dimensional surface reconstructions were then produced and compared with reference models measured using a precision laser scanner. Mean errors of 0.82mm and 0.88mm were obtained for the composite and bovine samples, respectively, thus demonstrating the feasibility of the approach to deliver the sub-millimetre accuracy required for the application. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

  2. Imaging and reconstruction of cell cortex structures near the cell surface

    Science.gov (United States)

    Jin, Luhong; Zhou, Xiaoxu; Xiu, Peng; Luo, Wei; Huang, Yujia; Yu, Feng; Kuang, Cuifang; Sun, Yonghong; Liu, Xu; Xu, Yingke

    2017-11-01

    Total internal reflection fluorescence microscopy (TIRFM) provides high optical sectioning capability and superb signal-to-noise ratio for imaging of cell cortex structures. The development of multi-angle (MA)-TIRFM permits high axial resolution imaging and reconstruction of cellular structures near the cell surface. Cytoskeleton is composed of a network of filaments, which are important for maintenance of cell function. The high-resolution imaging and quantitative analysis of filament organization would contribute to our understanding of cytoskeleton regulation in cell. Here, we used a custom-developed MA-TIRFM setup, together with stochastic photobleaching and single molecule localization method, to enhance the lateral resolution of TIRFM imaging to about 100 nm. In addition, we proposed novel methods to perform filament segmentation and 3D reconstruction from MA-TIRFM images. Furthermore, we applied these methods to study the 3D localization of cortical actin and microtubule structures in U373 cancer cells. Our results showed that cortical actins localize ∼ 27 nm closer to the plasma membrane when compared with microtubules. We found that treatment of cells with chemotherapy drugs nocodazole and cytochalasin B disassembles cytoskeletal network and induces the reorganization of filaments towards the cell periphery. In summary, this study provides feasible approaches for 3D imaging and analyzing cell surface distribution of cytoskeletal network. Our established microscopy platform and image analysis toolkits would facilitate the study of cytoskeletal network in cells.

  3. Green's functions potential fields on surfaces

    CERN Document Server

    Melnikov, Yuri A

    2017-01-01

    This book is comprehensive in its classical mathematical physics presentation, providing the reader with detailed instructions for obtaining Green's functions from scratch. Green's functions is an instrument easily accessible to practitioners who are engaged in design and exploitation of machines and structures in modern engineering practice. To date, there are no books available on the market that are devoted to the Green's function formalism for equations covered in this volume. The reader, with an undergraduate background in applied mathematics, can become an active user of the Green's function approach. For the first time, Green's functions are discussed for a specific class of problems dealing with potential fields induced in thin-wall structures and therefore, the reader will have first-hand access to a novel issue. This Work is accessible to researchers in applied mathematics, mechanics, and relevant disciplines such as engineering, as well as to upper level undergraduates and graduate students.

  4. Excess Li-Ion Storage on Reconstructed Surfaces of Nanocrystals To Boost Battery Performance

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Yandong; Zhang, Bingkai; Zheng, Jiaxin; Hu, Jiangtao; Wen, Jianguo; Miller, Dean; Yan, Pengfei; Liu, Tongchao; Guo, Hua; Li, Wen; Song, Xiaohe; Zhou, Zengquing; Liu, Chaokun; Tang, Hanting; Tan, Rui; Chen, Zonghai; Ren, Yang; Lin, Yuan; Yang, Wanli; Wang, Chongmin; Wang, Lin-Wang; Lu, Jun; Amine, Khalil; Pan, Feng

    2017-08-03

    Abstract. Due to the enhanced kinetic properties, nanocrystallites have received much attention as potential electrode materials for energy storage. However, because of the large specific surface areas of nanocrystallites, they usually suffer from decreased energy density, reduced cycling stability and total electrode capacity. In this work, we report a size-dependent excess capacity beyond the theoretical value of 170 mAhg-1 in a special carbon coated LiFePO4 composite cathode material, which delivers capacities of 191.2 and 213.5 mAhg-1 with the mean particle sizes of 83 nm and 42 nm, respectively. Moreover, this LiFePO4 composite also shows excellent cycling stability and high rate performance. Our further experimental tests and ab initio calculations reveal that the excess capacity comes from the charge passivation for which the C-O-Fe bonds would lead to charge redistribution on the surface of LiFePO4 and hence to enhance the bonding interaction between surface O atoms and Li-ions. The surface reconstruction for excess Li-ion storage makes full use of the large specific surface area for the nanocrystallites, which can maintain the fast Li-ion transport and enhance the capacity greatly that the nanocrystallites usually suffers.

  5. Bias field inconsistency correction of motion-scattered multislice MRI for improved 3D image reconstruction.

    Science.gov (United States)

    Kim, Kio; Habas, Piotr A; Rajagopalan, Vidya; Scott, Julia A; Corbett-Detig, James M; Rousseau, Francois; Barkovich, A James; Glenn, Orit A; Studholme, Colin

    2011-09-01

    A common solution to clinical MR imaging in the presence of large anatomical motion is to use fast multislice 2D studies to reduce slice acquisition time and provide clinically usable slice data. Recently, techniques have been developed which retrospectively correct large scale 3D motion between individual slices allowing the formation of a geometrically correct 3D volume from the multiple slice stacks. One challenge, however, in the final reconstruction process is the possibility of varying intensity bias in the slice data, typically due to the motion of the anatomy relative to imaging coils. As a result, slices which cover the same region of anatomy at different times may exhibit different sensitivity. This bias field inconsistency can induce artifacts in the final 3D reconstruction that can impact both clinical interpretation of key tissue boundaries and the automated analysis of the data. Here we describe a framework to estimate and correct the bias field inconsistency in each slice collectively across all motion corrupted image slices. Experiments using synthetic and clinical data show that the proposed method reduces intensity variability in tissues and improves the distinction between key tissue types.

  6. Characterizing inner-shell with spectral phase interferometry for direct electric-field reconstruction

    Science.gov (United States)

    Mashiko, Hiroki; Yamaguchi, Tomohiko; Oguri, Katsuya; Suda, Akira; Gotoh, Hideki

    2014-01-01

    In many atomic, molecular and solid systems, Lorentzian and Fano profiles are commonly observed in a broad research fields throughout a variety of spectroscopies. As the profile structure is related to the phase of the time-dependent dipole moment, it plays an important role in the study of quantum properties. Here we determine the dipole phase in the inner-shell transition using spectral phase interferometry for direct electric-field reconstruction (SPIDER) with isolated attosecond pulses (IAPs). In addition, we propose a scheme for pulse generation and compression by manipulating the inner-shell transition. The electromagnetic radiation generated by the transition is temporally compressed to a few femtoseconds in the extreme ultraviolet (XUV) region. The proposed pulse-compression scheme may provide an alternative route to producing attosecond pulses of light. PMID:25510971

  7. 'The surface management system' (SuMS) database: a surface-based database to aid cortical surface reconstruction, visualization and analysis

    Science.gov (United States)

    Dickson, J.; Drury, H.; Van Essen, D. C.

    2001-01-01

    Surface reconstructions of the cerebral cortex are increasingly widely used in the analysis and visualization of cortical structure, function and connectivity. From a neuroinformatics perspective, dealing with surface-related data poses a number of challenges. These include the multiplicity of configurations in which surfaces are routinely viewed (e.g. inflated maps, spheres and flat maps), plus the diversity of experimental data that can be represented on any given surface. To address these challenges, we have developed a surface management system (SuMS) that allows automated storage and retrieval of complex surface-related datasets. SuMS provides a systematic framework for the classification, storage and retrieval of many types of surface-related data and associated volume data. Within this classification framework, it serves as a version-control system capable of handling large numbers of surface and volume datasets. With built-in database management system support, SuMS provides rapid search and retrieval capabilities across all the datasets, while also incorporating multiple security levels to regulate access. SuMS is implemented in Java and can be accessed via a Web interface (WebSuMS) or using downloaded client software. Thus, SuMS is well positioned to act as a multiplatform, multi-user 'surface request broker' for the neuroscience community.

  8. Surface interactions in a reverse field pinch

    Energy Technology Data Exchange (ETDEWEB)

    McCracken, G.M.; Firth, L.; Goodall, D.H.J.; King, R.E.; Lavender, K.E.; Newton, A.A.; Thompson, V.K. (Euratom/UKAEA Fusion Association, Abingdon (UK). Culham Lab.); Edwards, B.C.; Titchmarsh, J. (UKAEA Atomic Energy Research Establishment, Harwell. Metallurgy Div.)

    The principle findings of the investigations were: (1) mechanical deformation occurring at the end of the bellows section adjacent to the weld. (2) Very localised erosion on at least three deformed sections, leading in one case to the puncturing of the liner wall. These eroded spots were all at a region of the liner underneath a gap in the shell. The mechanism whereby the energy is deposited locally is not understood. (3) Deposition of stainless steel as molten droplets was observed over a much larger area adjacent to the shell gap. There is no obvious link between this deposition and the puncture. (4) Arcing is observed over a large proportion of the liner surface: the highest local density of arcs is found on the outer part of the torus, especially near the ports. (5) The inside of the vessel has large coloured areas which were identified as oxide layers probably formed as the result of liner heating by the plasma in the presence of leaks during the last weeks of operation.

  9. Surface electric fields for North America during historical geomagnetic storms

    Science.gov (United States)

    Wei, Lisa H.; Homeier, Nichole; Gannon, Jennifer L.

    2013-01-01

    To better understand the impact of geomagnetic disturbances on the electric grid, we recreate surface electric fields from two historical geomagnetic storms—the 1989 “Quebec” storm and the 2003 “Halloween” storms. Using the Spherical Elementary Current Systems method, we interpolate sparsely distributed magnetometer data across North America. We find good agreement between the measured and interpolated data, with larger RMS deviations at higher latitudes corresponding to larger magnetic field variations. The interpolated magnetic field data are combined with surface impedances for 25 unique physiographic regions from the United States Geological Survey and literature to estimate the horizontal, orthogonal surface electric fields in 1 min time steps. The induced horizontal electric field strongly depends on the local surface impedance, resulting in surprisingly strong electric field amplitudes along the Atlantic and Gulf Coast. The relative peak electric field amplitude of each physiographic region, normalized to the value in the Interior Plains region, varies by a factor of 2 for different input magnetic field time series. The order of peak electric field amplitudes (largest to smallest), however, does not depend much on the input. These results suggest that regions at lower magnetic latitudes with high ground resistivities are also at risk from the effect of geomagnetically induced currents. The historical electric field time series are useful for estimating the flow of the induced currents through long transmission lines to study power flow and grid stability during geomagnetic disturbances.

  10. LUMINOUS RED GALAXY HALO DENSITY FIELD RECONSTRUCTION AND APPLICATION TO LARGE-SCALE STRUCTURE MEASUREMENTS

    International Nuclear Information System (INIS)

    Reid, Beth A.; Spergel, David N.; Bode, Paul

    2009-01-01

    The nontrivial relationship between observations of galaxy positions in redshift space and the underlying matter field complicates our ability to determine the linear theory power spectrum and extract cosmological information from galaxy surveys. The Sloan Digital Sky Survey (SDSS) luminous red galaxy (LRG) catalog has the potential to place powerful constraints on cosmological parameters. LRGs are bright, highly biased tracers of large-scale structure. However, because they are highly biased, the nonlinear contribution of satellite galaxies to the galaxy power spectrum is large and fingers-of-God (FOGs) are significant. The combination of these effects leads to a ∼10% correction in the underlying power spectrum at k = 0.1 h Mpc -1 and ∼40% correction at k = 0.2 h Mpc -1 in the LRG P(k) analysis of Tegmark et al., thereby compromising the cosmological constraints when this potentially large correction is left as a free parameter. We propose an alternative approach to recovering the matter field from galaxy observations. Our approach is to use halos rather than galaxies to trace the underlying mass distribution. We identify FOGs and replace each FOG with a single halo object. This removes the nonlinear contribution of satellite galaxies, the one-halo term. We test our method on a large set of high-fidelity mock SDSS LRG catalogs and find that the power spectrum of the reconstructed halo density field deviates from the underlying matter power spectrum at the ≤1% level for k ≤ 0.1 h Mpc -1 and ≤4% at k = 0.2 h Mpc -1 . The reconstructed halo density field also removes the bias in the measurement of the redshift space distortion parameter β induced by the FOG smearing of the linear redshift space distortions.

  11. Multiscale analysis of potential fields by a ridge consistency criterion: the reconstruction of the Bishop basement

    Science.gov (United States)

    Fedi, M.; Florio, G.; Cascone, L.

    2012-01-01

    We use a multiscale approach as a semi-automated interpreting tool of potential fields. The depth to the source and the structural index are estimated in two steps: first the depth to the source, as the intersection of the field ridges (lines built joining the extrema of the field at various altitudes) and secondly, the structural index by the scale function. We introduce a new criterion, called 'ridge consistency' in this strategy. The criterion is based on the principle that the structural index estimations on all the ridges converging towards the same source should be consistent. If these estimates are significantly different, field differentiation is used to lessen the interference effects from nearby sources or regional fields, to obtain a consistent set of estimates. In our multiscale framework, vertical differentiation is naturally joint to the low-pass filtering properties of the upward continuation, so is a stable process. Before applying our criterion, we studied carefully the errors on upward continuation caused by the finite size of the survey area. To this end, we analysed the complex magnetic synthetic case, known as Bishop model, and evaluated the best extrapolation algorithm and the optimal width of the area extension, needed to obtain accurate upward continuation. Afterwards, we applied the method to the depth estimation of the whole Bishop basement bathymetry. The result is a good reconstruction of the complex basement and of the shape properties of the source at the estimated points.

  12. Pair-breaking effects by parallel magnetic field in electric-field-induced surface superconductivity

    International Nuclear Information System (INIS)

    Nabeta, Masahiro; Tanaka, Kenta K.; Onari, Seiichiro; Ichioka, Masanori

    2016-01-01

    Highlights: • Zeeman effect shifts superconducting gaps of sub-band system, towards pair-breaking. • Higher-level sub-bands become normal-state-like electronic states by magnetic fields. • Magnetic field dependence of zero-energy DOS reflects multi-gap superconductivity. - Abstract: We study paramagnetic pair-breaking in electric-field-induced surface superconductivity, when magnetic field is applied parallel to the surface. The calculation is performed by Bogoliubov-de Gennes theory with s-wave pairing, including the screening effect of electric fields by the induced carriers near the surface. Due to the Zeeman shift by applied fields, electronic states at higher-level sub-bands become normal-state-like. Therefore, the magnetic field dependence of Fermi-energy density of states reflects the multi-gap structure in the surface superconductivity.

  13. Observer success rates for identification of 3D surface reconstructed facial images and implications for patient privacy and security

    Science.gov (United States)

    Chen, Joseph J.; Siddiqui, Khan M.; Fort, Leslie; Moffitt, Ryan; Juluru, Krishna; Kim, Woojin; Safdar, Nabile; Siegel, Eliot L.

    2007-03-01

    3D and multi-planar reconstruction of CT images have become indispensable in the routine practice of diagnostic imaging. These tools cannot only enhance our ability to diagnose diseases, but can also assist in therapeutic planning as well. The technology utilized to create these can also render surface reconstructions, which may have the undesired potential of providing sufficient detail to allow recognition of facial features and consequently patient identity, leading to violation of patient privacy rights as described in the HIPAA (Health Insurance Portability and Accountability Act) legislation. The purpose of this study is to evaluate whether 3D reconstructed images of a patient's facial features can indeed be used to reliably or confidently identify that specific patient. Surface reconstructed images of the study participants were created used as candidates for matching with digital photographs of participants. Data analysis was performed to determine the ability of observers to successfully match 3D surface reconstructed images of the face with facial photographs. The amount of time required to perform the match was recorded as well. We also plan to investigate the ability of digital masks or physical drapes to conceal patient identity. The recently expressed concerns over the inability to truly "anonymize" CT (and MRI) studies of the head/face/brain are yet to be tested in a prospective study. We believe that it is important to establish whether these reconstructed images are a "threat" to patient privacy/security and if so, whether minimal interventions from a clinical perspective can substantially reduce this possibility.

  14. Low Overpotential and High Current CO2 Reduction with Surface Reconstructed Cu Foam Electrodess

    KAUST Repository

    Min, Shixiong

    2016-06-23

    While recent reports have demonstrated that oxide-derived Cu-based electrodes exhibit high selectivity for CO2 reduction at low overpotential, the low catalytic current density (<2 mA/cm2 at -0.45 V vs. RHE) still largely limits its applications for large-scale fuel synthesis. Here we report an extremely high current density for CO2 reduction at low overpotential using a Cu foam electrode prepared by air-oxidation and subsequent electroreduction. Apart from possessing three-dimensional (3D) open frameworks, the resulting Cu foam electrodes prepared at higher temperatures exhibit enhanced electrochemically active surface area and distinct surface structures. In particular, the Cu foam electrode prepared at 500 °C exhibits an extremely high geometric current density of ~9.4 mA/cm2 in CO2-satrurated 0.1 M KHCO3 aqueous solution and achieving ~39% CO and ~23% HCOOH Faradaic efficiencies at -0.45 V vs. RHE. The high activity and significant selectivity enhancement are attributable to the formation of abundant grain-boundary supported active sites and preferable (100) and (111) facets as a result of reconstruction of Cu surface facets. This work demonstrates that the structural integration of Cu foam with open 3D frameworks and the favorable surface structures is a promising strategy to develop an advanced Cu electrocatalyst that can operate at high current density and low overpotential for CO2 reduction.

  15. The Effect of Laser Surface Reconstruction of Disordered Carbons on Performance

    International Nuclear Information System (INIS)

    EVEN JR., WILLIAM R.; GUIDOTTI, RONALD A.

    1999-01-01

    The reconstruction of the surface of disordered carbons was examined by heating carbons derived from polymethacrylonitrile (PMAN) and divinylbenzene (DVB) with a pulsed infrared laser in an argon or helium atmosphere, both fluidized and under static conditions. By graphitizing the outer surface of the carbons, it was hoped to reduce the high first-cycle losses associated with such disordered materials in Li-ion cells. The power to the sample was varied to observed the effects on surface morphology and electrochemical performance in 1M LiPF(sub 6) ethylene carbonate-dimethyl carbonate. The use various reactive atmosphere such as ethylene, 2-vinylpyridine, pyrrole, and furfuryl alcohol were also evaluated as an alternative means of hopefully forming a thin graphitic layer on the carbon particles to reduce first-cycle irreversibility. While some improvement was realized, these losses were still unacceptably high. The laser heating did improve the rate capabilities of the carbons, however. More work in this area is necessary to fully understand surface and bulk effects

  16. Capillary condensation in a square geometry with surface fields.

    Science.gov (United States)

    Zubaszewska, M; Gendiar, A; Drzewiński, A

    2012-12-01

    We study the influence of wetting on capillary condensation for a simple fluid in a square geometry with surface fields, where the reference system is an infinitely long slit. The corner transfer matrix renormalization group method has been extended to study a two-dimensional Ising model confined in an L × L geometry with equal surface fields. Our results have confirmed that in both geometries the coexistence line shift is governed by the same scaling powers, but their prefactors are different.

  17. The use of bovine pericardial patch for vascular reconstruction in infected fields for transplant recipients

    Directory of Open Access Journals (Sweden)

    Sandra Garcia Aroz, MD

    2017-03-01

    Full Text Available Infectious vascular complications affecting transplant recipients may lead to severe morbidity and graft loss. This is a retrospective review of vascular repair with bovine pericardial patch (BPP in infected fields for immunosuppressed patients. BPP was used as either a patch or an interposition graft. Five cases of arterial reconstruction in infected fields using BPP were performed. There were no complications related to bleeding, thrombosis, or recurrent infection. In our limited experience, the use of BPP as a vascular patch is successful, and it represents an alternative when vascular reconstruction is needed in the context of infected fields.

  18. Efficient 3D porous microstructure reconstruction via Gaussian random field and hybrid optimization.

    Science.gov (United States)

    Jiang, Z; Chen, W; Burkhart, C

    2013-11-01

    Obtaining an accurate three-dimensional (3D) structure of a porous microstructure is important for assessing the material properties based on finite element analysis. Whereas directly obtaining 3D images of the microstructure is impractical under many circumstances, two sets of methods have been developed in literature to generate (reconstruct) 3D microstructure from its 2D images: one characterizes the microstructure based on certain statistical descriptors, typically two-point correlation function and cluster correlation function, and then performs an optimization process to build a 3D structure that matches those statistical descriptors; the other method models the microstructure using stochastic models like a Gaussian random field and generates a 3D structure directly from the function. The former obtains a relatively accurate 3D microstructure, but computationally the optimization process can be very intensive, especially for problems with large image size; the latter generates a 3D microstructure quickly but sacrifices the accuracy due to issues in numerical implementations. A hybrid optimization approach of modelling the 3D porous microstructure of random isotropic two-phase materials is proposed in this paper, which combines the two sets of methods and hence maintains the accuracy of the correlation-based method with improved efficiency. The proposed technique is verified for 3D reconstructions based on silica polymer composite images with different volume fractions. A comparison of the reconstructed microstructures and the optimization histories for both the original correlation-based method and our hybrid approach demonstrates the improved efficiency of the approach. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

  19. Quantum field theory on higher-genus Riemann surfaces

    International Nuclear Information System (INIS)

    Kubo, Reijiro; Yoshii, Hisahiro; Ojima, Shuichi; Paul, S.K.

    1989-07-01

    Quantum field theory for b-c systems is formulated on Riemann surfaces with arbitrary genus. We make use of the formalism recently developed by Krichever and Novikov. Hamiltonian is defined properly, and the Ward-Takahashi identities are derived on higher-genus Riemann surfaces. (author)

  20. Adsorption/desorption kinetics of Na atoms on reconstructed Si (111)-7 x 7 surface

    International Nuclear Information System (INIS)

    Chauhan, Amit Kumar Singh; Govind; Shivaprasad, S.M.

    2010-01-01

    Self-assembled nanostructures on a periodic template are fundamentally and technologically important as they put forward the possibility to fabricate and pattern micro/nano-electronics for sensors, ultra high-density memories and nanocatalysts. Alkali-metal (AM) nanostructure grown on a semiconductor surface has received considerable attention because of their simple hydrogen like electronic structure. However, little efforts have been made to understand the fundamental aspects of the growth mechanism of self-assembled nanostructures of AM on semiconductor surfaces. In this paper, we report organized investigation of kinetically controlled room-temperature (RT) adsorption/desorption of sodium (Na) metal atoms on clean reconstructed Si (111)-7 x 7 surface, by X-ray photoelectron spectroscopy (XPS). The RT uptake curve shows a layer-by-layer growth (Frank-vander Merve growth) mode of Na on Si (111)-7 x 7 surfaces and a shift is observed in the binding energy position of Na (1s) spectra. The thermal stability of the Na/Si (111) system was inspected by annealing the system to higher substrate temperatures. Within a temperature range from RT to 350 o C, the temperature induced mobility to the excess Na atoms sitting on top of the bilayer, allowing to arrange themselves. Na atoms desorbed over a wide temperature range of 370 o C, before depleting the Si (111) surface at temperature 720 o C. The acquired valence-band (VB) spectra during Na growth revealed the development of new electronic-states near the Fermi level and desorption leads the termination of these. For Na adsorption up to 2 monolayers, decrease in work function (-1.35 eV) was observed, whereas work function of the system monotonically increases with Na desorption from the Si surface as observed by other studies also. This kinetic and thermodynamic study of Na adsorbed Si (111)-7 x 7 system can be utilized in fabrication of sensors used in night vision devices.

  1. Computation of Surface Integrals of Curl Vector Fields

    Science.gov (United States)

    Hu, Chenglie

    2007-01-01

    This article presents a way of computing a surface integral when the vector field of the integrand is a curl field. Presented in some advanced calculus textbooks such as [1], the technique, as the author experienced, is simple and applicable. The computation is based on Stokes' theorem in 3-space calculus, and thus provides not only a means to…

  2. Maurer-cartan forms for fields on surfaces

    DEFF Research Database (Denmark)

    Piuze, Emmanuel; Sporring, Jon; Siddiqi, Kaleem

    2015-01-01

    We study the space of first order models of smooth frame fields using the method of moving frames. By exploiting the Maurer-Cartan matrix of connection forms we develop geometrical embeddings for frame fields which lie on spherical, ellipsoidal and generalized helicoid surfaces. We design methods...

  3. Surface structure of quark stars with magnetic fields

    Indian Academy of Sciences (India)

    We investigate the impact of magnetic fields on the electron distribution of the electrosphere of quark stars. For moderately strong magnetic fields of ∼ 1013 G, quantization effects are generally weak due to the large number density of electrons at surface, but can nevertheless affect the photon emission properties of quark ...

  4. Distribution of local magnetic field of vortex lattice near anisotropic superconductor surface in inclined external fields

    International Nuclear Information System (INIS)

    Efremova, S.A.; Tsarevskij, S.L.

    1997-01-01

    Magnetic field distribution in a unit cell of the Abrikosov vortex lattice near the surface of monoaxial anisotropic type-ii superconductors in inclined external magnetic field has been found in the framework of London model for the cases when the symmetry axis is perpendicular and parallel to the superconductor surface interface. Distribution of local magnetic field as a function of the distance from the superconductor interface surface and external field inclination angle has been obtained. Using high-Tc superconductor Y-Ba-Cu-O by way of examples, it has been shown that the study of local magnetic field distribution function, depending on external magnetic field inclination angle towards the superconductor symmetry axis and towards the superconductor surface, can provide important data on anisotropic properties of the superconductor [ru

  5. Electric field vector measurements in a surface ionization wave discharge

    International Nuclear Information System (INIS)

    Goldberg, Benjamin M; Adamovich, Igor V; Lempert, Walter R; Böhm, Patrick S; Czarnetzki, Uwe

    2015-01-01

    This work presents the results of time-resolved electric field vector measurements in a short pulse duration (60 ns full width at half maximum), surface ionization wave discharge in hydrogen using a picosecond four-wave mixing technique. Electric field vector components are measured separately, using pump and Stokes beams linearly polarized in the horizontal and vertical planes, and a polarizer placed in front of the infrared detector. The time-resolved electric field vector is measured at three different locations across the discharge gap, and for three different heights above the alumina ceramic dielectric surface, ∼100, 600, and 1100 μm (total of nine different locations). The results show that after breakdown, the discharge develops as an ionization wave propagating along the dielectric surface at an average speed of 1 mm ns −1 . The surface ionization wave forms near the high voltage electrode, close to the dielectric surface (∼100 μm). The wave front is characterized by significant overshoot of both vertical and horizontal electric field vector components. Behind the wave front, the vertical field component is rapidly reduced. As the wave propagates along the dielectric surface, it also extends further away from the dielectric surface, up to ∼1 mm near the grounded electrode. The horizontal field component behind the wave front remains quite significant, to sustain the electron current toward the high voltage electrode. After the wave reaches the grounded electrode, the horizontal field component experiences a secondary rise in the quasi-dc discharge, where it sustains the current along the near-surface plasma sheet. The measurement results indicate presence of a cathode layer formed near the grounded electrode with significant cathode voltage fall, ≈3 kV, due to high current density in the discharge. The peak reduced electric field in the surface ionization wave is 85–95 Td, consistent with dc breakdown field estimated from the Paschen

  6. Characterization of complementary electric field coupled resonant surfaces

    Science.gov (United States)

    Hand, Thomas H.; Gollub, Jonah; Sajuyigbe, Soji; Smith, David R.; Cummer, Steven A.

    2008-11-01

    We present angle-resolved free-space transmission and reflection measurements of a surface composed of complementary electric inductive-capacitive (CELC) resonators. By measuring the reflection and transmission coefficients of a CELC surface with different polarizations and particle orientations, we show that the CELC only responds to in-plane magnetic fields. This confirms the Babinet particle duality between the CELC and its complement, the electric field coupled LC resonator. Characterization of the CELC structure serves to expand the current library of resonant elements metamaterial designers can draw upon to make unique materials and surfaces.

  7. Quantum field theory on higher-genus Riemann surfaces, 2

    International Nuclear Information System (INIS)

    Kubo, Reijiro; Ojima, Shuichi.

    1990-08-01

    Quantum field theory for closed bosonic string systems is formulated on arbitrary higher-genus Riemann surfaces in global operator formalism. Canonical commutation relations between bosonic string field X μ and their conjugate momenta P ν are derived in the framework of conventional quantum field theory. Problems arising in quantizing bosonic systems are considered in detail. Applying the method exploited in the preceding paper we calculate Ward-Takahashi identities. (author)

  8. Probing Surface Electric Field Noise with a Single Ion

    Science.gov (United States)

    2013-07-30

    potentials is housed inside a Faraday cage providing more than 40 dB of attenuation for electromagnetic fields in the range of frequencies between 200...and measuring the ion quantum state [16]. Thus, by measuring the effect of electric field noise on the motional quantum state of the ion, one can probe...understand these effects . In summary, we have probed the electric field noise near an aluminum-copper surface at room temperature using a single trapped ion

  9. 3D electric field calculation with surface charge method

    International Nuclear Information System (INIS)

    Yamada, S.

    1992-01-01

    This paper describes an outline and some examples of three dimensional electric field calculations with a computer code developed at NIRS. In the code, a surface charge method is adopted because of it's simplicity in the mesh establishing procedure. The charge density in a triangular mesh is assumed to distribute with a linear function of the position. The electric field distribution is calculated for a pair of drift tubes with the focusing fingers on the opposing surfaces. The field distribution in an acceleration gap is analyzed with a Fourier-Bessel series expansion method. The calculated results excellently reproduces the measured data with a magnetic model. (author)

  10. Extended Reconstructed Sea Surface Temperature Version 5 (ERSSTv5): Upgrades, Validations, and Intercomparisons

    Science.gov (United States)

    Huang, B.; Thorne, P.; Banzon, P. V. F.; Chepurin, G. A.; Lawrimore, J. H.; Menne, M. J.; Vose, R. S.; Smith, T. M.; Zhang, H. M.

    2017-12-01

    The monthly global 2°×2° Extended Reconstructed Sea Surface Temperature (ERSST) has been revised and updated from version 4 to version 5. This update incorporates a new release of ICOADS R3.0, a decade of near-surface data from Argo floats, and a new estimate of centennial sea-ice from HadISST2. A number of choices in aspects of quality control, bias adjustment and interpolation have been substantively revised. The resulting ERSST estimates have more realistic spatio-temporal variations, better representation of high latitude SSTs, and ship SST biases are now calculated relative to more accurate buoy measurements, while the global long-term trend remains about the same. Progressive experiments have been undertaken to highlight the effects of each change in data source and analysis technique upon the final product. The reconstructed SST is systematically decreased by 0.077°C, as the reference data source is switched from ship SST in v4 to modern buoy SST in v5. Furthermore, high latitude SSTs are decreased by 0.1°-0.2°C by using sea-ice concentration from HadISST2 over HadISST1. Changes arising from remaining innovations are mostly important at small space and time scales, primarily having an impact where and when input observations are sparse. Cross-validations and verifications with independent modern observations show that the updates incorporated in ERSSTv5 have improved the representation of spatial variability over the global oceans, the magnitude of El Niño and La Niña events, and the decadal nature of SST changes over 1930s-40s when observation instruments changed rapidly. Both long (1900-2015) and short (2000-2015) term SST trends in ERSSTv5 remain significant as in ERSSTv4.

  11. Atlas-free surface reconstruction of the cortical grey-white interface in infants.

    Directory of Open Access Journals (Sweden)

    François Leroy

    Full Text Available BACKGROUND: The segmentation of the cortical interface between grey and white matter in magnetic resonance images (MRI is highly challenging during the first post-natal year. First, the heterogeneous brain maturation creates important intensity fluctuations across regions. Second, the cortical ribbon is highly folded creating complex shapes. Finally, the low tissue contrast and partial volume effects hamper cortex edge detection in parts of the brain. METHODS AND FINDINGS: We present an atlas-free method for segmenting the grey-white matter interface of infant brains in T2-weighted (T2w images. We used a broad characterization of tissue using features based not only on local contrast but also on geometric properties. Furthermore, inaccuracies in localization were reduced by the convergence of two evolving surfaces located on each side of the inner cortical surface. Our method has been applied to eleven brains of one- to four-month-old infants. Both quantitative validations against manual segmentations and sulcal landmarks demonstrated good performance for infants younger than two months old. Inaccuracies in surface reconstruction increased with age in specific brain regions where the tissue contrast decreased with maturation, such as in the central region. CONCLUSIONS: We presented a new segmentation method which achieved good to very good performance at the grey-white matter interface depending on the infant age. This method should reduce manual intervention and could be applied to pathological brains since it does not require any brain atlas.

  12. TH-AB-202-08: A Robust Real-Time Surface Reconstruction Method On Point Clouds Captured From a 3D Surface Photogrammetry System

    International Nuclear Information System (INIS)

    Liu, W; Sawant, A; Ruan, D

    2016-01-01

    Purpose: Surface photogrammetry (e.g. VisionRT, C-Rad) provides a noninvasive way to obtain high-frequency measurement for patient motion monitoring in radiotherapy. This work aims to develop a real-time surface reconstruction method on the acquired point clouds, whose acquisitions are subject to noise and missing measurements. In contrast to existing surface reconstruction methods that are usually computationally expensive, the proposed method reconstructs continuous surfaces with comparable accuracy in real-time. Methods: The key idea in our method is to solve and propagate a sparse linear relationship from the point cloud (measurement) manifold to the surface (reconstruction) manifold, taking advantage of the similarity in local geometric topology in both manifolds. With consistent point cloud acquisition, we propose a sparse regression (SR) model to directly approximate the target point cloud as a sparse linear combination from the training set, building the point correspondences by the iterative closest point (ICP) method. To accommodate changing noise levels and/or presence of inconsistent occlusions, we further propose a modified sparse regression (MSR) model to account for the large and sparse error built by ICP, with a Laplacian prior. We evaluated our method on both clinical acquired point clouds under consistent conditions and simulated point clouds with inconsistent occlusions. The reconstruction accuracy was evaluated w.r.t. root-mean-squared-error, by comparing the reconstructed surfaces against those from the variational reconstruction method. Results: On clinical point clouds, both the SR and MSR models achieved sub-millimeter accuracy, with mean reconstruction time reduced from 82.23 seconds to 0.52 seconds and 0.94 seconds, respectively. On simulated point cloud with inconsistent occlusions, the MSR model has demonstrated its advantage in achieving consistent performance despite the introduced occlusions. Conclusion: We have developed a real

  13. Plasmas fluxes to surfaces for an oblique magnetic field

    International Nuclear Information System (INIS)

    Pitcher, C.S.; Stangeby, P.C.; Elder, J.D.; Bell, M.G.; Kilpatrick, S.J.; Manos, D.M.; Medley, S.S.; Owens, D.K.; Ramsey, A.T.; Ulrickson, M.

    1992-07-01

    The poloidal and toroidal spatial distributions of D α , He I and C II emission have been obtained in the vicinity of the TFTR bumper limiter and are compared with models of ion flow to the surface. The distributions are found not to agree with a model (the ''Cosine'' model) which determines the incident flux density using only the parallel fluxes in the scrape-off layer and the projected area of the surface perpendicular to the field lines. In particular, the Cosine model is not able to explain the significant fluxes observed at locations on the surface which are oblique to the magnetic field. It is further shown that these fluxes cannot be explained by the finite Larmor radius of impinging ions. Finally, it is demonstrated, with the use of Monte Carlo codes, that the distributions can be explained by including both parallel and cross-field transport onto the limiter surface

  14. Depth Reconstruction from Single Images Using a Convolutional Neural Network and a Condition Random Field Model.

    Science.gov (United States)

    Liu, Dan; Liu, Xuejun; Wu, Yiguang

    2018-04-24

    This paper presents an effective approach for depth reconstruction from a single image through the incorporation of semantic information and local details from the image. A unified framework for depth acquisition is constructed by joining a deep Convolutional Neural Network (CNN) and a continuous pairwise Conditional Random Field (CRF) model. Semantic information and relative depth trends of local regions inside the image are integrated into the framework. A deep CNN network is firstly used to automatically learn a hierarchical feature representation of the image. To get more local details in the image, the relative depth trends of local regions are incorporated into the network. Combined with semantic information of the image, a continuous pairwise CRF is then established and is used as the loss function of the unified model. Experiments on real scenes demonstrate that the proposed approach is effective and that the approach obtains satisfactory results.

  15. Depth Reconstruction from Single Images Using a Convolutional Neural Network and a Condition Random Field Model

    Directory of Open Access Journals (Sweden)

    Dan Liu

    2018-04-01

    Full Text Available This paper presents an effective approach for depth reconstruction from a single image through the incorporation of semantic information and local details from the image. A unified framework for depth acquisition is constructed by joining a deep Convolutional Neural Network (CNN and a continuous pairwise Conditional Random Field (CRF model. Semantic information and relative depth trends of local regions inside the image are integrated into the framework. A deep CNN network is firstly used to automatically learn a hierarchical feature representation of the image. To get more local details in the image, the relative depth trends of local regions are incorporated into the network. Combined with semantic information of the image, a continuous pairwise CRF is then established and is used as the loss function of the unified model. Experiments on real scenes demonstrate that the proposed approach is effective and that the approach obtains satisfactory results.

  16. DEM RECONSTRUCTION USING LIGHT FIELD AND BIDIRECTIONAL REFLECTANCE FUNCTION FROM MULTI-VIEW HIGH RESOLUTION SPATIAL IMAGES

    Directory of Open Access Journals (Sweden)

    F. de Vieilleville

    2016-06-01

    Full Text Available This paper presents a method for dense DSM reconstruction from high resolution, mono sensor, passive imagery, spatial panchromatic image sequence. The interest of our approach is four-fold. Firstly, we extend the core of light field approaches using an explicit BRDF model from the Image Synthesis community which is more realistic than the Lambertian model. The chosen model is the Cook-Torrance BRDF which enables us to model rough surfaces with specular effects using specific material parameters. Secondly, we extend light field approaches for non-pinhole sensors and non-rectilinear motion by using a proper geometric transformation on the image sequence. Thirdly, we produce a 3D volume cost embodying all the tested possible heights and filter it using simple methods such as Volume Cost Filtering or variational optimal methods. We have tested our method on a Pleiades image sequence on various locations with dense urban buildings and report encouraging results with respect to classic multi-label methods such as MIC-MAC, or more recent pipelines such as S2P. Last but not least, our method also produces maps of material parameters on the estimated points, allowing us to simplify building classification or road extraction.

  17. Towards a fully self-consistent inversion combining historical and paleomagnetic data for geomagnetic field reconstructions

    Science.gov (United States)

    Arneitz, P.; Leonhardt, R.; Fabian, K.; Egli, R.

    2017-12-01

    Historical and paleomagnetic data are the two main sources of information about the long-term geomagnetic field evolution. Historical observations extend to the late Middle Ages, and prior to the 19th century, they consisted mainly of pure declination measurements from navigation and orientation logs. Field reconstructions going back further in time rely solely on magnetization acquired by rocks, sediments, and archaeological artefacts. The combined dataset is characterized by a strongly inhomogeneous spatio-temporal distribution and highly variable data reliability and quality. Therefore, an adequate weighting of the data that correctly accounts for data density, type, and realistic error estimates represents the major challenge for an inversion approach. Until now, there has not been a fully self-consistent geomagnetic model that correctly recovers the variation of the geomagnetic dipole together with the higher-order spherical harmonics. Here we present a new geomagnetic field model for the last 4 kyrs based on historical, archeomagnetic and volcanic records. The iterative Bayesian inversion approach targets the implementation of reliable error treatment, which allows different record types to be combined in a fully self-consistent way. Modelling results will be presented along with a thorough analysis of model limitations, validity and sensitivity.

  18. On Discrete Killing Vector Fields and Patterns on Surfaces

    KAUST Repository

    Ben-Chen, Mirela

    2010-09-21

    Symmetry is one of the most important properties of a shape, unifying form and function. It encodes semantic information on one hand, and affects the shape\\'s aesthetic value on the other. Symmetry comes in many flavors, amongst the most interesting being intrinsic symmetry, which is defined only in terms of the intrinsic geometry of the shape. Continuous intrinsic symmetries can be represented using infinitesimal rigid transformations, which are given as tangent vector fields on the surface - known as Killing Vector Fields. As exact symmetries are quite rare, especially when considering noisy sampled surfaces, we propose a method for relaxing the exact symmetry constraint to allow for approximate symmetries and approximate Killing Vector Fields, and show how to discretize these concepts for generating such vector fields on a triangulated mesh. We discuss the properties of approximate Killing Vector Fields, and propose an application to utilize them for texture and geometry synthesis. Journal compilation © 2010 The Eurographics Association and Blackwell Publishing Ltd.

  19. [A Method to Reconstruct Surface Reflectance Spectrum from Multispectral Image Based on Canopy Radiation Transfer Model].

    Science.gov (United States)

    Zhao, Yong-guang; Ma, Ling-ling; Li, Chuan-rong; Zhu, Xiao-hua; Tang, Ling-li

    2015-07-01

    Due to the lack of enough spectral bands for multi-spectral sensor, it is difficult to reconstruct surface retlectance spectrum from finite spectral information acquired by multi-spectral instrument. Here, taking into full account of the heterogeneity of pixel from remote sensing image, a method is proposed to simulate hyperspectral data from multispectral data based on canopy radiation transfer model. This method first assumes the mixed pixels contain two types of land cover, i.e., vegetation and soil. The sensitive parameters of Soil-Leaf-Canopy (SLC) model and a soil ratio factor were retrieved from multi-spectral data based on Look-Up Table (LUT) technology. Then, by combined with a soil ratio factor, all the parameters were input into the SLC model to simulate the surface reflectance spectrum from 400 to 2 400 nm. Taking Landsat Enhanced Thematic Mapper Plus (ETM+) image as reference image, the surface reflectance spectrum was simulated. The simulated reflectance spectrum revealed different feature information of different surface types. To test the performance of this method, the simulated reflectance spectrum was convolved with the Landsat ETM + spectral response curves and Moderate Resolution Imaging Spectrometer (MODIS) spectral response curves to obtain the simulated Landsat ETM+ and MODIS image. Finally, the simulated Landsat ETM+ and MODIS images were compared with the observed Landsat ETM+ and MODIS images. The results generally showed high correction coefficients (Landsat: 0.90-0.99, MODIS: 0.74-0.85) between most simulated bands and observed bands and indicated that the simulated reflectance spectrum was well simulated and reliable.

  20. Investigation of back surface fields effect on bifacial solar cells

    Science.gov (United States)

    Sepeai, Suhaila; Sulaiman, M. Y.; Sopian, Kamaruzzaman; Zaidi, Saleem H.

    2012-11-01

    A bifacial solar cell, in contrast with a conventional monofacial solar cell, produces photo-generated current from both front and back sides. Bifacial solar cell is an attractive candidate for enhancing photovoltaic (PV) market competitiveness as well as supporting the current efforts to increase efficiency and lower material costs. This paper reports on the fabrication of bifacial solar cells using phosphorus-oxytrichloride (POCl3) emitter formation on p-type, nanotextured silicon (Si) wafer. Backside surface field was formed through Al-diffusion using conventional screen-printing process. Bifacial solar cells with a structure of n+pp+ with and without back surface field (BSF) were fabricated in which silicon nitride (SiN) anti reflection and passivation films were coated on both sides, followed by screen printing of Argentum (Ag) and Argentum/Aluminum (Ag/Al) on front and back contacts, respectively. Bifacial solar cells without BSF exhibited open circuit voltage (VOC) of 535 mV for front and 480 mV for back surface. With Al-alloyed BSF bifacial solar cells, the VOC improved to 580 mV for the front surface and 560 mV for the back surface. Simulation of bifacial solar cells using PC1D and AFORS software demonstrated good agreement with experimental results. Simulations showed that best bifacial solar cells are achieved through a combination of high lifetime wafer, low recombination back surface field, reduced contact resistance, and superior surface passivation.

  1. Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr – Part 2: A new reconstruction of the interplanetary magnetic field

    Directory of Open Access Journals (Sweden)

    M. Lockwood

    2013-11-01

    Full Text Available We present a new reconstruction of the interplanetary magnetic field (IMF, B for 1846–2012 with a full analysis of errors, based on the homogeneously constructed IDV(1d composite of geomagnetic activity presented in Part 1 (Lockwood et al., 2013a. Analysis of the dependence of the commonly used geomagnetic indices on solar wind parameters is presented which helps explain why annual means of interdiurnal range data, such as the new composite, depend only on the IMF with only a very weak influence of the solar wind flow speed. The best results are obtained using a polynomial (rather than a linear fit of the form B = χ · (IDV(1d − βα with best-fit coefficients χ = 3.469, β = 1.393 nT, and α = 0.420. The results are contrasted with the reconstruction of the IMF since 1835 by Svalgaard and Cliver (2010.

  2. Vibrational properties of the Au-(√{3 }×√{3 } )/Si(111) surface reconstruction

    Science.gov (United States)

    Halbig, B.; Liebhaber, M.; Bass, U.; Geurts, J.; Speiser, E.; Räthel, J.; Chandola, S.; Esser, N.; Krenz, M.; Neufeld, S.; Schmidt, W. G.; Sanna, S.

    2018-01-01

    The vibrational properties of the Au-induced (√{3 }×√{3 })R 30∘ reconstruction of the Si(111) surface are investigated by polarized surface Raman spectroscopy and density-functional theory. The Raman measurements are performed in situ at room temperature as well as 20 K, and they reveal the presence of vibrational eigenmodes in the spectral range from 20 to 450 cm-1. In particular, two peaks of E symmetry at 75 and 183 cm-1 dominate the spectra. No substantial difference between room- and low-temperature spectra is observed, suggesting that the system does not undergo a phase transition down to 20 K. First-principles calculations are performed based on the structural models discussed in the literature. The thermodynamically stable conjugate honeycomb-chained-trimer model (CHCT) [Surf. Sci. 275, L691 (1992), 10.1016/0039-6028(92)90785-5] leads to phonon eigenvalues compatible with the experimental observations in the investigated spectral range. On the basis of the phonon eigenfrequencies, symmetries, and Raman intensities, we assign the measured spectral features to the calculated phonon modes. The good agreement between measured and calculated modes provides a strong argument in favor of the CHCT model.

  3. Mid-Pliocene equatorial Pacific sea surface temperature reconstruction: a multi-proxy perspective

    Science.gov (United States)

    Dowsett, Harry J.; Robinson, Marci M.

    2009-01-01

    The Mid-Pliocene is the most recent interval of sustained global warmth, which can be used to examine conditions predicted for the near future. An accurate spatial representation of the low-latitude Mid-Pliocene Pacific surface ocean is necessary to understand past climate change in the light of forecasts of future change. Mid-Pliocene sea surface temperature (SST) anomalies show a strong contrast between the western equatorial Pacific (WEP) and eastern equatorial Pacific (EEP) regardless of proxy (faunal, alkenone and Mg/Ca). All WEP sites show small differences from modern mean annual temperature, but all EEP sites show significant positive deviation from present-day temperatures by as much as 4.4°C. Our reconstruction reflects SSTs similar to modern in the WEP, warmer than modern in the EEP and eastward extension of the WEP warm pool. The east-west equatorial Pacific SST gradient is decreased, but the pole to equator gradient does not change appreciably. We find it improbable that increased greenhouse gases (GHG) alone would cause such a heterogeneous warming and more likely that the cause of Mid-Pliocene warmth is a combination of several forcings including both increased meridional heat transport and increased GHG.

  4. Water Induced Surface Reconstruction of the Oxygen (2x1) covered Ru(0001)

    Energy Technology Data Exchange (ETDEWEB)

    Maier, Sabine; Cabrera-Sanfelix, Pepa; Stass, Ingeborg; Sanchez-Portal, Daniel; Arnau, Andres; Salmeron, Miquel

    2010-08-06

    Low temperature scanning tunneling microscopy (STM) and density functional theory (DFT) were used to study the adsorption of water on a Ru(0001) surface covered with half monolayer of oxygen. The oxygen atoms occupy hcp sites in an ordered structure with (2x1) periodicity. DFT predicts that water is weakly bound to the unmodified surface, 86 meV compared to the ~;;200 meV water-water H-bond. Instead, we found that water adsorption causes a shift of half of the oxygen atoms from hcp sites to fcc sites, creating a honeycomb structure where water molecules bind strongly to the exposed Ru atoms. The energy cost of reconstructing the oxygen overlayer, around 230 meV per displaced oxygen atom, is more than compensated by the larger adsorption energy of water on the newly exposed Ru atoms. Water forms hydrogen bonds with the fcc O atoms in a (4x2) superstructure due to alternating orientations of the molecules. Heating to 185 K results in the complete desorption of the water layer, leaving behind the oxygen honeycomb structure, which is metastable relative to the original (2x1). This stable structure is not recovered until after heating to temperatures close to 260K.

  5. Nature of monovacancies on quasi-hexagonal structure of reconstructed Au(100) surface

    Energy Technology Data Exchange (ETDEWEB)

    Pieczyrak, Barbara; Trembulowicz, Artur; Antczak, Grażyna, E-mail: antczak@ifd.uni.wroc.pl; Jurczyszyn, Leszek

    2017-06-15

    Highlights: • Surprising nature of surface monovacancies: spontaneous healing. • Determination of vacancy formation energy in the range of 0.34–0.55 eV. • A good agreement between the theoretical (DFT) and experimental (STM) data. - Abstract: Density functional theory and the scanning tunneling microscopy were applied to investigate the nature of the defects on an unrotated reconstructed hexagonal Au(100) surface. We show the correlation between the nature of monovacancies and the geometrical arrangement of the atoms from the first (topmost) layer with respect to the second layer. The vacancies created directly above the atoms from the second layer (on-top position) move spontaneously into the subsurface upon relaxation. For the vacancies created in other places, the subsurface shift is hindered by the energy barrier and the lifted subsurface atom is in the interlayer position. Charge density calculations were compared with results from the scanning tunneling microscopy images which show a good agreement between the theoretical and experimental data.

  6. 3D skin surface reconstruction from a single image by merging global curvature and local texture using the guided filtering for 3D haptic palpation.

    Science.gov (United States)

    Lee, K; Kim, M; Kim, K

    2018-05-11

    Skin surface evaluation has been studied using various imaging techniques. However, all these studies had limited impact because they were performed using visual exam only. To improve on this scenario with haptic feedback, we propose 3D reconstruction of the skin surface using a single image. Unlike extant 3D skin surface reconstruction algorithms, we utilize the local texture and global curvature regions, combining the results for reconstruction. The first entails the reconstruction of global curvature, achieved by bilateral filtering that removes noise on the surface while maintaining the edge (ie, furrow) to obtain the overall curvature. The second entails the reconstruction of local texture, representing the fine wrinkles of the skin, using an advanced form of bilateral filtering. The final image is then composed by merging the two reconstructed images. We tested the curvature reconstruction part by comparing the resulting curvatures with measured values from real phantom objects while local texture reconstruction was verified by measuring skin surface roughness. Then, we showed the reconstructed result of our proposed algorithm via the reconstruction of various real skin surfaces. The experimental results demonstrate that our approach is a promising technology to reconstruct an accurate skin surface with a single skin image. We proposed 3D skin surface reconstruction using only a single camera. We highlighted the utility of global curvature, which has not been considered important in the past. Thus, we proposed a new method for 3D reconstruction that can be used for 3D haptic palpation, dividing the concepts of local and global regions. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  7. A new approach for 3D reconstruction from bright field TEM imaging: Beam precession assisted electron tomography

    International Nuclear Information System (INIS)

    Rebled, J.M.; Yedra, Ll.; Estrade, S.; Portillo, J.; Peiro, F.

    2011-01-01

    The successful combination of electron beam precession and bright field electron tomography for 3D reconstruction is reported. Beam precession is demonstrated to be a powerful technique to reduce the contrast artifacts due to diffraction and curvature in thin foils. Taking advantage of these benefits, Precession assisted electron tomography has been applied to reconstruct the morphology of Sn precipitates embedded in an Al matrix, from a tilt series acquired in a range from +49 o to -61 o at intervals of 2 o and with a precession angle of 0.6 o in bright field mode. The combination of electron tomography and beam precession in conventional TEM mode is proposed as an alternative procedure to obtain 3D reconstructions of nano-objects without a scanning system or a high angle annular dark field detector. -- Highlights: → Electron beam precession reduces spurious diffraction contrast in bright field mode. → Bend contour related contrast depends on precession angle. → Electron beam precession is combined with bright field electron tomography. → Precession assisted BF tomography allowed 3D reconstruction of a Sn precipitate.

  8. A new approach for 3D reconstruction from bright field TEM imaging: Beam precession assisted electron tomography

    Energy Technology Data Exchange (ETDEWEB)

    Rebled, J.M. [LENS-MIND-IN2UB, Departament d' Electronica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Institut de Ciencia de Materials de Barcelona-CSIC, Campus UAB, 08193 Bellaterra (Spain); Yedra, Ll. [LENS-MIND-IN2UB, Departament d' Electronica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Estrade, S.; Portillo, J. [LENS-MIND-IN2UB, Departament d' Electronica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); TEM-MAT, CCiT-UB, Sole i Sabaris 1, 08028 Barcelona (Spain); Peiro, F., E-mail: francesca.peiro@ub.edu [LENS-MIND-IN2UB, Departament d' Electronica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain)

    2011-08-15

    The successful combination of electron beam precession and bright field electron tomography for 3D reconstruction is reported. Beam precession is demonstrated to be a powerful technique to reduce the contrast artifacts due to diffraction and curvature in thin foils. Taking advantage of these benefits, Precession assisted electron tomography has been applied to reconstruct the morphology of Sn precipitates embedded in an Al matrix, from a tilt series acquired in a range from +49{sup o} to -61{sup o} at intervals of 2{sup o} and with a precession angle of 0.6{sup o} in bright field mode. The combination of electron tomography and beam precession in conventional TEM mode is proposed as an alternative procedure to obtain 3D reconstructions of nano-objects without a scanning system or a high angle annular dark field detector. -- Highlights: {yields} Electron beam precession reduces spurious diffraction contrast in bright field mode. {yields} Bend contour related contrast depends on precession angle. {yields} Electron beam precession is combined with bright field electron tomography. {yields} Precession assisted BF tomography allowed 3D reconstruction of a Sn precipitate.

  9. Stochastic Reconstruction and Interpolation of Precipitation Fields Using Combined Information of Commercial Microwave Links and Rain Gauges

    Science.gov (United States)

    Haese, B.; Hörning, S.; Chwala, C.; Bárdossy, A.; Schalge, B.; Kunstmann, H.

    2017-12-01

    For the reconstruction and interpolation of precipitation fields, we present the application of a stochastic approach called Random Mixing. Generated fields are based on a data set consisting of rain gauge observations and path-averaged rain rates estimated using Commercial Microwave Link (CML) derived information. Precipitation fields are received as linear combination of unconditional spatial random fields, where the spatial dependence structure is described by copulas. The weights of the linear combination are optimized such that the observations and the spatial structure of the precipitation observations are reproduced. The innovation of the approach is that this strategy enables the simulation of ensembles of precipitation fields of any size. Each ensemble member is in concordance with the observed path-averaged CML derived rain rates and additionally reflects the observed rainfall variability along the CML paths. The ensemble spread allows additionally an estimation of the uncertainty of the reconstructed precipitation fields. The method is demonstrated both for a synthetic data set and a real-world data set in South Germany. While the synthetic example allows an evaluation against a known reference, the second example demonstrates the applicability for real-world observations. Generated precipitation fields of both examples reproduce the spatial precipitation pattern in good quality. A performance evaluation of Random Mixing compared to Ordinary Kriging demonstrates an improvement of the reconstruction of the observed spatial variability. Random Mixing is concluded to be a beneficial new approach for the provision of precipitation fields and ensembles of them, in particular when different measurement types are combined.

  10. Statistical analysis and modelling of surface runoff from arable fields

    OpenAIRE

    P. Fiener; K. Auerswald; F. Winter; M. Disse

    2013-01-01

    Surface runoff generation on arable fields is an important driver of (local) flooding, on-site and off-site damages by erosion, and of nutrient and agrochemical transport. In general, three different processes generate surface runoff (Hortonian runoff, saturation excess runoff, and return of subsurface flow). Despite the developments in our understanding of these processes it remains difficult to predict, which processes govern runoff generation during the course of an event or through...

  11. Dictionary Learning on the Manifold of Square Root Densities and Application to Reconstruction of Diffusion Propagator Fields*

    Science.gov (United States)

    Sun, Jiaqi; Xie, Yuchen; Ye, Wenxing; Ho, Jeffrey; Entezari, Alireza; Blackband, Stephen J.

    2013-01-01

    In this paper, we present a novel dictionary learning framework for data lying on the manifold of square root densities and apply it to the reconstruction of diffusion propagator (DP) fields given a multi-shell diffusion MRI data set. Unlike most of the existing dictionary learning algorithms which rely on the assumption that the data points are vectors in some Euclidean space, our dictionary learning algorithm is designed to incorporate the intrinsic geometric structure of manifolds and performs better than traditional dictionary learning approaches when applied to data lying on the manifold of square root densities. Non-negativity as well as smoothness across the whole field of the reconstructed DPs is guaranteed in our approach. We demonstrate the advantage of our approach by comparing it with an existing dictionary based reconstruction method on synthetic and real multi-shell MRI data. PMID:24684004

  12. Exploiting of the Compression Methods for Reconstruction of the Antenna Far-Field Using Only Amplitude Near-Field Measurements

    Directory of Open Access Journals (Sweden)

    J. Puskely

    2010-06-01

    Full Text Available The novel approach exploits the principle of the conventional two-plane amplitude measurements for the reconstruction of the unknown electric field distribution on the antenna aperture. The method combines a global optimization with a compression method. The global optimization method (GO is used to minimize the functional, and the compression method is used to reduce the number of unknown variables. The algorithm employs the Real Coded Genetic Algorithm (RCGA as the global optimization approach. The Discrete Cosine Transform (DCT and the Discrete Wavelet Transform (DWT are applied to reduce the number of unknown variables. Pros and cons of methods are investigated and reported for the solution of the problem. In order to make the algorithm faster, exploitation of amplitudes from a single scanning plane is also discussed. First, the algorithm is used to obtain an initial estimate. Subsequently, the common Fourier iterative algorithm is used to reach global minima with sufficient accuracy. The method is examined measuring the dish antenna.

  13. Curved reconstructions versus three-dimensional surface rendering in the demonstration of cortical lesions in patients with extratemporal epilepsy

    NARCIS (Netherlands)

    Meiners, LC; Scheffers, JM; De Kort, GAP; Burger, H; Van Huffelen, AC; Van Rijen, PC; Van Veelen, CWM

    RATIONALE AND OBJECTIVES. TO compare the visibility and localization of extratemporal cortical lesions in extratemporal epilepsy by using curved reconstruction (CR) and three-dimensional surface rendering (3D SR) of 3D-acquired MR images and to study the degree of confidence with which localizations

  14. Properties of bare strange stars associated with surface electric fields

    International Nuclear Information System (INIS)

    Picanco Negreiros, Rodrigo; Mishustin, Igor N.; Schramm, Stefan; Weber, Fridolin

    2010-01-01

    In this paper we investigate the electrodynamic surface properties of bare strange quark stars. The surfaces of such objects are characterized by the formation of ultrahigh electric surface fields which might be as high as ∼10 19 V/cm. These fields result from the formation of electric dipole layers at the stellar surfaces. We calculate the increase in gravitational mass associated with the energy stored in the electric dipole field, which turns out to be only significant if the star possesses a sufficiently strong net electric charge distribution. In the second part of the paper, we explore the intriguing possibility of what happens when the electron layer (sphere) rotates with respect to the stellar strange matter body. We find that in this event magnetic fields can be generated which, for moderate effective rotational frequencies between the electron layer and the stellar body, agree with the magnetic fields inferred for several central compact objects. These objects could thus be comfortably interpreted as strange stars whose electron atmospheres rotate at frequencies that are moderately different (∼10 Hz) from the rotational frequencies of the strange star itself.

  15. A new method for temperature-field reconstruction during ultrasound-monitored cryosurgery using potential-field analogy.

    Science.gov (United States)

    Thaokar, Chandrajit; Rossi, Michael R; Rabin, Yoed

    2016-02-01

    The current study aims at developing computational tools in order to gain information about the thermal history in areas invisible to ultrasound imaging during cryosurgery. This invisibility results from the high absorption rate of the ultrasound energy by the frozen region, which leads to an apparent opacity in the cryotreated area and a shadow behind it. A proof-of-concept for freezing-front estimation is demonstrated in the current study, using the new potential-field analogy method (PFAM). This method is further integrated with a recently developed temperature-field reconstruction method (TFRM) to estimate the temperature distribution within the frozen region. This study uses prostate cryosurgery as a developmental model and trans-rectal ultrasound imaging as a choice of practice. Results of this study indicate that the proposed PFAM is a viable and computationally inexpensive solution to estimate the extent of freezing in the acoustic shadow region. Comparison of PFAM estimations and experimental data shows an average mismatch of less than 2 mm in freezing-front location, which is comparable to the uncertainty in ultrasound imaging. Comparison of the integrated PFAM + TFRM scheme with a full-scale finite-elements analysis (FEA) indicates an average mismatch of 0.9 mm for the freezing front location and 0.1 mm for the lethal temperature isotherm of -45 °C. Comparison of the integrated PFAM + TFRM scheme with experimental temperature measurements show a difference in the range of 2 °C and 6 °C for selected points of measurement. Results of this study demonstrate the integrated PFAM + TFRM scheme as a viable and computationally inexpensive means to gain information about the thermal history in the frozen region during ultrasound-monitored cryosurgery. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Surface incompressibility from semiclassical relativistic mean field calculations

    International Nuclear Information System (INIS)

    Patra, S.K.; Centelles, M.; Vinas, X.; Estal, M. del

    2002-01-01

    By using the scaling method and the Thomas-Fermi and extended Thomas-Fermi approaches to relativistic mean field theory the surface contribution to the leptodermous expansion of the finite nuclei incompressibility K A has been self-consistently computed. The validity of the simplest expansion, which contains volume, volume-symmetry, surface, and Coulomb terms, is examined by comparing it with self-consistent results of K A for some currently used nonlinear σ-ω parameter sets. A numerical estimate of higher-order contributions to the leptodermous expansion, namely, the curvature and surface-symmetry terms, is made

  17. Contribution of surface analysis spectroscopic methods to the lubrication field

    International Nuclear Information System (INIS)

    Blanc, C.

    1979-01-01

    The analytical surface technics such as ESCA, AES and SIMS are tested to be applied to a particular lubrication field. One deals with a 100 C 6 steel surface innumered in tricresylphosphate at 110 0 C for 15 days. The nature of the first layers is studied after relevant solvant cleaning. An iron oxide layer is produced on the bearing surface, namely αFe 2 -O 3 . ESCA, AES and SIMS studies show an overlayer of iron phosphate. The exact nature of iron phosphate is not clearly established but the formation of a ferrous phosphate coating can be assumed from ESCA analysis [fr

  18. Reconstruction of an Non-Monochromatically Illuminated Object Imaged through an Electron Microscope with a Fluctuating Electromagnetic Field

    NARCIS (Netherlands)

    Hoenders, B.J.

    1975-01-01

    It is shown that a weak phase object imaged by an electron microscope within the presence of instabilities of the lense currents and the acceleration voltage, fluctuating electromagnetic field, can be reconstructed from the intensity distribution in the image plane. Perfectly incoherent illumination

  19. Wind field re-construction of 3D Wake measurements from a turbine-installed scanning lidar

    DEFF Research Database (Denmark)

    Mikkelsen, Torben Krogh; Herges, Tommy; Astrup, Poul

    High-resolution wake flow measurements obtained from a turbine-mounted scanning lidar have been obtained from 1D to 5D behind a V27 test turbine. The measured line-of-sight projected wind speeds have, in connection with a fast CFD wind field reconstruction model, been used to generate 3D wind fie...

  20. Interior tomography in microscopic CT with image reconstruction constrained by full field of view scan at low spatial resolution

    Science.gov (United States)

    Luo, Shouhua; Shen, Tao; Sun, Yi; Li, Jing; Li, Guang; Tang, Xiangyang

    2018-04-01

    In high resolution (microscopic) CT applications, the scan field of view should cover the entire specimen or sample to allow complete data acquisition and image reconstruction. However, truncation may occur in projection data and results in artifacts in reconstructed images. In this study, we propose a low resolution image constrained reconstruction algorithm (LRICR) for interior tomography in microscopic CT at high resolution. In general, the multi-resolution acquisition based methods can be employed to solve the data truncation problem if the project data acquired at low resolution are utilized to fill up the truncated projection data acquired at high resolution. However, most existing methods place quite strict restrictions on the data acquisition geometry, which greatly limits their utility in practice. In the proposed LRICR algorithm, full and partial data acquisition (scan) at low and high resolutions, respectively, are carried out. Using the image reconstructed from sparse projection data acquired at low resolution as the prior, a microscopic image at high resolution is reconstructed from the truncated projection data acquired at high resolution. Two synthesized digital phantoms, a raw bamboo culm and a specimen of mouse femur, were utilized to evaluate and verify performance of the proposed LRICR algorithm. Compared with the conventional TV minimization based algorithm and the multi-resolution scout-reconstruction algorithm, the proposed LRICR algorithm shows significant improvement in reduction of the artifacts caused by data truncation, providing a practical solution for high quality and reliable interior tomography in microscopic CT applications. The proposed LRICR algorithm outperforms the multi-resolution scout-reconstruction method and the TV minimization based reconstruction for interior tomography in microscopic CT.

  1. Revolution in Field Science: Apollo Approach to Inaccessible Surface Exploration

    Science.gov (United States)

    Clark, P. E.

    2010-07-01

    The extraordinary challenge mission designers, scientists, and engineers, faced in planning the first human expeditions to the surface of another solar system body led to the development of a distinctive and even revolutionary approach to field work. Not only were those involved required to deal effectively with the extreme limitation in resources available for and access to a target as remote as the lunar surface; they were required to developed a rigorous approach to science activities ranging from geological field work to deploying field instruments. Principal aspects and keys to the success of the field work are discussed here, including the highly integrated, intensive, and lengthy science planning, simulation, and astronaut training; the development of a systematic scheme for description and documentation of geological sites and samples; and a flexible yet disciplined methodology for site documentation and sample collection. The capability for constant communication with a ‘backroom’ of geological experts who make requests and weigh in on surface operations was innovative and very useful in encouraging rapid dissemination of information to the greater community in general. An extensive archive of the Apollo era science activity related documents provides evidence of the principal aspects and keys to the success of the field work. The Apollo Surface Journal allows analysis of the astronaut’s performance in terms of capability for traveling on foot, documentation and sampling of field stations, and manual operation of tools and instruments, all as a function of time. The application of these analysis as ‘lessons learned’ for planning the next generation of human or robotic field science activities on the Moon and elsewhere are considered here as well.

  2. An Incremental Weighted Least Squares Approach to Surface Lights Fields

    Science.gov (United States)

    Coombe, Greg; Lastra, Anselmo

    An Image-Based Rendering (IBR) approach to appearance modelling enables the capture of a wide variety of real physical surfaces with complex reflectance behaviour. The challenges with this approach are handling the large amount of data, rendering the data efficiently, and previewing the model as it is being constructed. In this paper, we introduce the Incremental Weighted Least Squares approach to the representation and rendering of spatially and directionally varying illumination. Each surface patch consists of a set of Weighted Least Squares (WLS) node centers, which are low-degree polynomial representations of the anisotropic exitant radiance. During rendering, the representations are combined in a non-linear fashion to generate a full reconstruction of the exitant radiance. The rendering algorithm is fast, efficient, and implemented entirely on the GPU. The construction algorithm is incremental, which means that images are processed as they arrive instead of in the traditional batch fashion. This human-in-the-loop process enables the user to preview the model as it is being constructed and to adapt to over-sampling and under-sampling of the surface appearance.

  3. Positron probes of the Ge(1 0 0) surface: The effects of surface reconstructions and electron-positron correlations on positron trapping and annihilation characteristics

    International Nuclear Information System (INIS)

    Fazleev, N.G.; Jung, E.; Weiss, A.H.

    2007-01-01

    Positron annihilation induced Auger electron spectroscopy (PAES) has been applied to study the Ge(1 0 0) surface. The high-resolution PAES spectrum from the Ge(1 0 0) surface displays several strong Auger peaks corresponding to M 4,5 N 1 N 2,3 , M 2,3 M 4,5 M 4,5 , M 2,3 M 4,5 V and M 1 M 4,5 M 4,5 Auger transitions. The integrated peak intensities of Auger transitions are used to obtain experimental annihilation probabilities for the Ge 3d and 3p core level electrons. These experimental results are analyzed by performing calculations of positron surface states and annihilation characteristics of surface trapped positrons with relevant Ge core-level electrons for the non-reconstructed and reconstructed Ge(1 0 0)-p(2 x 1), Ge(1 0 0)-p(2 x 2) and Ge(1 0 0)-c(4 x 2) surfaces. It is found that the positron surface state wave function extends into the Ge lattice in the regions where atoms are displaced from their ideal terminated positions due to reconstructions. Estimates of the positron binding energy and the positron annihilation characteristics reveal their sensitivity to the specific atomic structure of the topmost layers of Ge(1 0 0). A comparison with PAES data reveals an agreement with theoretical core annihilation probabilities for the Auger transitions considered

  4. Surface fields on the source-excited dielectric wedge

    DEFF Research Database (Denmark)

    Balling, P

    1973-01-01

    Approximate surface fields due to a plane-wave solution and a local-mode solution are compared. The plane-wave solution, which is new, is shown to agree well with experiment. The local-mode solution, which often has been applied to tapered waveguides and antennas, fails near the cutoffs of the su...

  5. Multi-proxy reconstructions of May–September precipitation field in China over the past 500 years

    Directory of Open Access Journals (Sweden)

    F. Shi

    2017-12-01

    Full Text Available The dominant modes of variability of precipitation for the whole of China over the past millennium and the mechanism governing their spatial structure remain unclear. This is mainly due to insufficient high-resolution proxy records of precipitation in western China. Numerous tree-ring chronologies have recently been archived in publicly available databases through PAGES2k activities, and these provide an opportunity to refine precipitation field reconstructions for China. Based on 479 proxy records, including 371 tree-ring width chronologies, a tree-ring isotope chronology, and 107 drought/flood indices, we reconstruct the precipitation field for China for the past half millennium using the optimal information extraction method. A total of 3631 of 4189 grid points in the reconstruction field passed the cross-validation process, accounting for 86.68 % of the total number of grid points. The first leading mode of variability of the reconstruction shows coherent variations over most of China. The second mode is a north–south dipole in eastern China characterized by variations of the same sign in western China and northern China (except for Xinjiang province. It is likely controlled by the El Niño–Southern Oscillation (ENSO variability. The third mode is a sandwich triple mode in eastern China including variations of the same sign in western China and central China. The last two modes are reproduced by most of the six coupled climate models' last millennium simulations performed in the framework of the Paleoclimate Modelling Intercomparison Project Phase III (PMIP3. In particular, the link of the second mode with ENSO is confirmed by the models. However, there is a mismatch between models and proxy reconstructions in the time development of different modes. This mismatch suggests the important role of internal variability in the reconstructed precipitation mode variations of the past 500 years.

  6. Multi-proxy reconstructions of May-September precipitation field in China over the past 500 years

    Science.gov (United States)

    Shi, Feng; Zhao, Sen; Guo, Zhengtang; Goosse, Hugues; Yin, Qiuzhen

    2017-12-01

    The dominant modes of variability of precipitation for the whole of China over the past millennium and the mechanism governing their spatial structure remain unclear. This is mainly due to insufficient high-resolution proxy records of precipitation in western China. Numerous tree-ring chronologies have recently been archived in publicly available databases through PAGES2k activities, and these provide an opportunity to refine precipitation field reconstructions for China. Based on 479 proxy records, including 371 tree-ring width chronologies, a tree-ring isotope chronology, and 107 drought/flood indices, we reconstruct the precipitation field for China for the past half millennium using the optimal information extraction method. A total of 3631 of 4189 grid points in the reconstruction field passed the cross-validation process, accounting for 86.68 % of the total number of grid points. The first leading mode of variability of the reconstruction shows coherent variations over most of China. The second mode is a north-south dipole in eastern China characterized by variations of the same sign in western China and northern China (except for Xinjiang province). It is likely controlled by the El Niño-Southern Oscillation (ENSO) variability. The third mode is a sandwich triple mode in eastern China including variations of the same sign in western China and central China. The last two modes are reproduced by most of the six coupled climate models' last millennium simulations performed in the framework of the Paleoclimate Modelling Intercomparison Project Phase III (PMIP3). In particular, the link of the second mode with ENSO is confirmed by the models. However, there is a mismatch between models and proxy reconstructions in the time development of different modes. This mismatch suggests the important role of internal variability in the reconstructed precipitation mode variations of the past 500 years.

  7. Multi-phase-field method for surface tension induced elasticity

    Science.gov (United States)

    Schiedung, Raphael; Steinbach, Ingo; Varnik, Fathollah

    2018-01-01

    A method, based on the multi-phase-field framework, is proposed that adequately accounts for the effects of a coupling between surface free energy and elastic deformation in solids. The method is validated via a number of analytically solvable problems. In addition to stress states at mechanical equilibrium in complex geometries, the underlying multi-phase-field framework naturally allows us to account for the influence of surface energy induced stresses on phase transformation kinetics. This issue, which is of fundamental importance on the nanoscale, is demonstrated in the limit of fast diffusion for a solid sphere, which melts due to the well-known Gibbs-Thompson effect. This melting process is slowed down when coupled to surface energy induced elastic deformation.

  8. A comparison of semiglobal and local dense matching algorithms for surface reconstruction

    Directory of Open Access Journals (Sweden)

    E. Dall'Asta

    2014-06-01

    Full Text Available Encouraged by the growing interest in automatic 3D image-based reconstruction, the development and improvement of robust stereo matching techniques is one of the most investigated research topic of the last years in photogrammetry and computer vision. The paper is focused on the comparison of some stereo matching algorithms (local and global which are very popular both in photogrammetry and computer vision. In particular, the Semi-Global Matching (SGM, which realizes a pixel-wise matching and relies on the application of consistency constraints during the matching cost aggregation, will be discussed. The results of some tests performed on real and simulated stereo image datasets, evaluating in particular the accuracy of the obtained digital surface models, will be presented. Several algorithms and different implementation are considered in the comparison, using freeware software codes like MICMAC and OpenCV, commercial software (e.g. Agisoft PhotoScan and proprietary codes implementing Least Square e Semi-Global Matching algorithms. The comparisons will also consider the completeness and the level of detail within fine structures, and the reliability and repeatability of the obtainable data.

  9. A comparison of semiglobal and local dense matching algorithms for surface reconstruction

    Science.gov (United States)

    Dall'Asta, E.; Roncella, R.

    2014-06-01

    Encouraged by the growing interest in automatic 3D image-based reconstruction, the development and improvement of robust stereo matching techniques is one of the most investigated research topic of the last years in photogrammetry and computer vision. The paper is focused on the comparison of some stereo matching algorithms (local and global) which are very popular both in photogrammetry and computer vision. In particular, the Semi-Global Matching (SGM), which realizes a pixel-wise matching and relies on the application of consistency constraints during the matching cost aggregation, will be discussed. The results of some tests performed on real and simulated stereo image datasets, evaluating in particular the accuracy of the obtained digital surface models, will be presented. Several algorithms and different implementation are considered in the comparison, using freeware software codes like MICMAC and OpenCV, commercial software (e.g. Agisoft PhotoScan) and proprietary codes implementing Least Square e Semi-Global Matching algorithms. The comparisons will also consider the completeness and the level of detail within fine structures, and the reliability and repeatability of the obtainable data.

  10. Statistical shape model-based reconstruction of a scaled, patient-specific surface model of the pelvis from a single standard AP x-ray radiograph

    Energy Technology Data Exchange (ETDEWEB)

    Zheng Guoyan [Institute for Surgical Technology and Biomechanics, University of Bern, Stauffacherstrasse 78, CH-3014 Bern (Switzerland)

    2010-04-15

    Purpose: The aim of this article is to investigate the feasibility of using a statistical shape model (SSM)-based reconstruction technique to derive a scaled, patient-specific surface model of the pelvis from a single standard anteroposterior (AP) x-ray radiograph and the feasibility of estimating the scale of the reconstructed surface model by performing a surface-based 3D/3D matching. Methods: Data sets of 14 pelvises (one plastic bone, 12 cadavers, and one patient) were used to validate the single-image based reconstruction technique. This reconstruction technique is based on a hybrid 2D/3D deformable registration process combining a landmark-to-ray registration with a SSM-based 2D/3D reconstruction. The landmark-to-ray registration was used to find an initial scale and an initial rigid transformation between the x-ray image and the SSM. The estimated scale and rigid transformation were used to initialize the SSM-based 2D/3D reconstruction. The optimal reconstruction was then achieved in three stages by iteratively matching the projections of the apparent contours extracted from a 3D model derived from the SSM to the image contours extracted from the x-ray radiograph: Iterative affine registration, statistical instantiation, and iterative regularized shape deformation. The image contours are first detected by using a semiautomatic segmentation tool based on the Livewire algorithm and then approximated by a set of sparse dominant points that are adaptively sampled from the detected contours. The unknown scales of the reconstructed models were estimated by performing a surface-based 3D/3D matching between the reconstructed models and the associated ground truth models that were derived from a CT-based reconstruction method. Such a matching also allowed for computing the errors between the reconstructed models and the associated ground truth models. Results: The technique could reconstruct the surface models of all 14 pelvises directly from the landmark

  11. Localization of endocardial ectopic activity by means of noninvasive endocardial surface current density reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Lai Dakun; Liu Chenguang; Eggen, Michael D; He Bin [Department of Biomedical Engineering, University of Minnesota, MN (United States); Iaizzo, Paul A, E-mail: binhe@umn.edu [Department of Surgery, University of Minnesota, MN (United States)

    2011-07-07

    Localization of the source of cardiac ectopic activity has direct clinical benefits for determining the location of the corresponding ectopic focus. In this study, a recently developed current-density (CD)-based localization approach was experimentally evaluated in noninvasively localizing the origin of the cardiac ectopic activity from body-surface potential maps (BSPMs) in a well-controlled experimental setting. The cardiac ectopic activities were induced in four well-controlled intact pigs by single-site pacing at various sites within the left ventricle (LV). In each pacing study, the origin of the induced ectopic activity was localized by reconstructing the CD distribution on the endocardial surface of the LV from the measured BSPMs and compared with the estimated single moving dipole (SMD) solution and precise pacing site (PS). Over the 60 analyzed beats corresponding to ten pacing sites (six for each), the mean and standard deviation of the distance between the locations of maximum CD value and the corresponding PSs were 16.9 mm and 4.6 mm, respectively. In comparison, the averaged distance between the SMD locations and the corresponding PSs was slightly larger (18.4 {+-} 3.4 mm). The obtained CD distribution of activated sources extending from the stimulus site also showed high consistency with the endocardial potential maps estimated by a minimally invasive endocardial mapping system. The present experimental results suggest that the CD method is able to locate the approximate site of the origin of a cardiac ectopic activity, and that the distribution of the CD can portray the propagation of early activation of an ectopic beat.

  12. Intercomparison of the Extended Reconstructed Sea Surface Temperature v4 and v3b Datasets

    Science.gov (United States)

    Wang, Jinping; Chen, Xianyao

    2018-04-01

    Version 4 (v4) of the Extended Reconstructed Sea Surface Temperature (ERSST) dataset is compared with its precedent, the widely used version 3b (v3b). The essential upgrades applied to v4 lead to remarkable differences in the characteristics of the sea surface temperature (SST) anomaly (SSTa) in both the temporal and spatial domains. First, the largest discrepancy of the global mean SSTa values around the 1940s is due to ship-observation corrections made to reconcile observations from buckets and engine intake thermometers. Second, differences in global and regional mean SSTa values between v4 and v3b exhibit a downward trend (around -0.032°C per decade) before the 1940s, an upward trend (around 0.014°C per decade) during the period of 1950-2015, interdecadal oscillation with one peak around the 1980s, and two troughs during the 1960s and 2000s, respectively. This does not derive from treatments of the polar or the other data-void regions, since the difference of the SSTa does not share the common features. Third, the spatial pattern of the ENSO-related variability of v4 exhibits a wider but weaker cold tongue in the tropical region of the Pacific Ocean compared with that of v3b, which could be attributed to differences in gap-filling assumptions since the latter features satellite observations whereas the former features in situ ones. This intercomparison confirms that the structural uncertainty arising from underlying assumptions on the treatment of diverse SST observations even in the same SST product family is the main source of significant SST differences in the temporal domain. Why this uncertainty introduces artificial decadal oscillations remains unknown.

  13. Three-dimensional surface reconstruction imaging for evaluation of congenital heart disease from ECG-triggered MR images

    International Nuclear Information System (INIS)

    Vannier, M.W.; Laschinger, J.; Knapp, R.H.; Gutierrez, F.R.; Gronnemeyer, S.A.

    1987-01-01

    Three-dimensional surface reconstruction images of the heart and great vessels were produced from contiguous sequences of electrocardiographically triggered MR images in 25 patients with congenital heart disease and in three healthy subjects. The imaging data were semiautomatically processed to separate the epicardial and endocardial surfaces and to define the outline of the enclosed blood volumes on a section by section basis. Images were obtained at 5-mm intervals in patients aged 3 months to 30 years with anomalies of the great vessels, tetralogy of Fallot, septal defects, pulmonary atresia, and other congenital heart malformations. The results were used to facilitate the surgical treatment of these patients and were compared with echocardiographic and cineradiographic studies, and with surgical findings or pathologic specimens. These surface reconstruction images were useful for communicating the results of diagnostic examinations to cardiac surgeons, for sizing and location of intracardiac defects, for imaging the pulmonary venous drainage, and for assessing regional and global function

  14. Fourier transform profilometry (FTP) using an innovative band-pass filter for accurate 3-D surface reconstruction

    Science.gov (United States)

    Chen, Liang-Chia; Ho, Hsuan-Wei; Nguyen, Xuan-Loc

    2010-02-01

    This article presents a novel band-pass filter for Fourier transform profilometry (FTP) for accurate 3-D surface reconstruction. FTP can be employed to obtain 3-D surface profiles by one-shot images to achieve high-speed measurement. However, its measurement accuracy has been significantly influenced by the spectrum filtering process required to extract the phase information representing various surface heights. Using the commonly applied 2-D Hanning filter, the measurement errors could be up to 5-10% of the overall measuring height and it is unacceptable to various industrial application. To resolve this issue, the article proposes an elliptical band-pass filter for extracting the spectral region possessing essential phase information for reconstructing accurate 3-D surface profiles. The elliptical band-pass filter was developed and optimized to reconstruct 3-D surface models with improved measurement accuracy. Some experimental results verify that the accuracy can be effectively enhanced by using the elliptical filter. The accuracy improvement of 44.1% and 30.4% can be achieved in 3-D and sphericity measurement, respectively, when the elliptical filter replaces the traditional filter as the band-pass filtering method. Employing the developed method, the maximum measured error can be kept within 3.3% of the overall measuring range.

  15. Construction of force-free fields which have toroidal surfaces about a given surface

    International Nuclear Information System (INIS)

    Bouligand, G.

    1983-05-01

    A study of two-fields (B vector, rotB vector) of conservative flux which admits a family of toroidal surfaces of parameter phi on a domain limited by a given surface S, suggests their construction by a Cauchy-Arzela method of step by step. Taking into account the Newcomb condition this method is consistent with force-free magnetic fields and with helical equilibria with scalar pressure. The method supposes that B vector is of class C 1 . This construction makes use of the remarkable property of the field B vector to be the surface gradient of a generating multivalued function Q on a closed surface. Consequently, the initial surface will be given with its normal metric coefficient K; that is to say, B vector admits a family F of homotopic surfaces on a infinitesimal domain about S, an element of F. From this, the periodic part of Q is a solution of a Beltrami equation for the flux conservation of which numerical resolution is envisaged. The study of these fields is made in a biorthogonal system of coordinates. The coeffficients of the two fundamental metric forms of magnetic surfaces vary with phi and are interrelated by a sixth order differential system of equations which gives their variation [fr

  16. Multi-sheet surface rebinning methods for reconstruction from asymmetrically truncated cone beam projections: I. Approximation and optimality

    International Nuclear Information System (INIS)

    Betcke, Marta M; Lionheart, William R B

    2013-01-01

    The mechanical motion of the gantry in conventional cone beam CT scanners restricts the speed of data acquisition in applications with near real time requirements. A possible resolution of this problem is to replace the moving source detector assembly with static parts that are electronically activated. An example of such a system is the Rapiscan Systems RTT80 real time tomography scanner, with a static ring of sources and axially offset static cylinder of detectors. A consequence of such a design is asymmetrical axial truncation of the cone beam projections resulting, in the sense of integral geometry, in severely incomplete data. In particular we collect data only in a fraction of the Tam–Danielsson window, hence the standard cone beam reconstruction techniques do not apply. In this work we propose a family of multi-sheet surface rebinning methods for reconstruction from such truncated projections. The proposed methods combine analytical and numerical ideas utilizing linearity of the ray transform to reconstruct data on multi-sheet surfaces, from which the volumetric image is obtained through deconvolution. In this first paper in the series, we discuss the rebinning to multi-sheet surfaces. In particular we concentrate on the underlying transforms on multi-sheet surfaces and their approximation with data collected by offset multi-source scanning geometries like the RTT. The optimal multi-sheet surface and the corresponding rebinning function are found as a solution of a variational problem. In the case of the quadratic objective, the variational problem for the optimal rebinning pair can be solved by a globally convergent iteration. Examples of optimal rebinning pairs are computed for different trajectories. We formulate the axial deconvolution problem for the recovery of the volumetric image from the reconstructions on multi-sheet surfaces. Efficient and stable solution of the deconvolution problem is the subject of the second paper in this series (Betcke and

  17. Surface-ionization field mass-spectrometry studies of nonequilibrium surface ionization

    International Nuclear Information System (INIS)

    Blashenkov, Nikolai M; Lavrent'ev, Gennadii Ya

    2007-01-01

    The ionization of polyatomic molecules on tungsten and tungsten oxide surfaces is considered for quasiequilibrium or essentially nonequilibrium conditions (in the latter case, the term nonequilibrium surface ionization is used for adsorbate ionization). Heterogeneous reactions are supposed to proceed through monomolecular decay of polyatomic molecules or fragments of multimolecular complexes. The nonequilibrium nature of these reactions is established. The dependences of the current density of disordered ions on the surface temperature, electric field strength, and ionized particle energy distribution are obtained in analytical form. Heterogeneous dissociation energies, the ionization potentials of radicals, and the magnitude of reaction departure from equilibrium are determined from experimental data, as are energy exchange times between reaction products and surfaces, the number of molecules in molecular complexes, and the number of effective degrees of freedom in molecules and complexes. In collecting the data a new technique relying on surface-ionization field mass-spectrometry was applied. (instruments and methods of investigation)

  18. Friction Regimes of Water-Lubricated Diamond (111): Role of Interfacial Ether Groups and Tribo-Induced Aromatic Surface Reconstructions

    Science.gov (United States)

    Kuwahara, Takuya; Moras, Gianpietro; Moseler, Michael

    2017-09-01

    Large-scale quantum molecular dynamics of water-lubricated diamond (111) surfaces in sliding contact reveals multiple friction regimes. While water starvation causes amorphization of the tribological interface, small H2O traces are sufficient to preserve crystallinity. This can result in high friction due to cold welding via ether groups or in ultralow friction due to aromatic surface passivation triggered by tribo-induced Pandey reconstruction. At higher water coverage, Grotthuss-type diffusion and H2O dissociation yield dense H /OH surface passivation leading to another ultralow friction regime.

  19. Polarization singularities of the object field of skin surface

    International Nuclear Information System (INIS)

    Angelsky, O V; Ushenko, A G; Ushenko, Yu A; Ushenko, Ye G

    2006-01-01

    The paper deals with the investigation of formation mechanisms of laser radiation polarization structure scattered by an optically thin surface layer of human skin in two registration zones: a boundary field and a far zone of Fraunhofer diffraction. The conditions of forming polarization singularities by such an object in the scattered radiation field have been defined. Statistical and fractal polarization structure of object fields of physiologically normal and pathologically changed skin has been studied. It has been shown that polarization singularities of radiation scattered by physiologically normal skin samples have a fractal coordinate structure. It is characteristic for fields of pathologically changed skin to have a statistical coordinate structure of polarization singularities in all diffraction zones

  20. Assessing Asphalt and Concrete Pavement Surface Texture in the Field

    Directory of Open Access Journals (Sweden)

    Saad I. Sarsam

    2016-06-01

    Full Text Available The incorporation of safety characteristics into the traditional pavement structural design or in the functional evaluation of pavement condition has not been established yet. The design has focused on the structural capacity of the roadway so that the pavement can withstand specific level of repetitive loading over the design life. On the other hand, the surface texture condition was neither included in the AASHTO design procedure nor in the present serviceability index measurements. The pavement surface course should provide adequate levels of friction and ride quality and maintain low levels of noise and roughness. Many transportation departments perform routine skid resistant testing, the type of equipment used for testing varies depending on the preference of each transportation department. It was felt that modeling of the surface texture condition using different methods of testing may assist in solving such problem. In this work, Macro texture and Micro texture of asphalt and cement concrete pavement surface have been investigated in the field using four different methods (The Sand Patch Method, Outflow Time Method, British Pendulum Tester and Photogrammetry Technique. Two different grain sizes of sand have been utilized in conducting the Sand Patch while the Micro texture was investigated using the British Pendulum tester method at wet pavement surface conditions. The test results of the four methods were correlated to the skid number. It was concluded that such modeling could provide instant data in the field for pavement condition which may help in pavement maintenance management.

  1. Superresolution Near-field Imaging with Surface Waves

    KAUST Repository

    Fu, Lei

    2017-10-21

    We present the theory for near-field superresolution imaging with surface waves and time reverse mirrors (TRMs). Theoretical formulas and numerical results show that applying the TRM operation to surface waves in an elastic half-space can achieve superresolution imaging of subwavelength scatterers if they are located less than about 1/2 of the shear wavelength from the source line. We also show that the TRM operation for a single frequency is equivalent to natural migration, which uses the recorded data to approximate the Green’s functions for migration, and only costs O(N4) algebraic operations for poststack migration compared to O(N6) operations for natural prestack migration. Here, we assume the sources and receivers are on an N × N grid and there are N2 trial image points on the free surface. Our theoretical predictions of superresolution are validated with tests on synthetic data. The field-data tests suggest that hidden faults at the near surface can be detected with subwavelength imaging of surface waves by using the TRM operation if they are no deeper than about 1/2 the dominant shear wavelength.

  2. Analysis of surface states in ZnO nanowire field effect transistors

    International Nuclear Information System (INIS)

    Shao, Ye; Yoon, Jongwon; Kim, Hyeongnam; Lee, Takhee; Lu, Wu

    2014-01-01

    Highlights: • The electron transport in ZnO nanowire FETs is space charged limited below a trap temperature. • Metallic contacts to ZnO nanowires exhibit non-linear behavior with a Schottky barrier height of ∼0.35 eV. • The surface state density is in the range of 1.04 × 10 10 –1.24 × 10 10 /cm 2 . • The trap activation energy is ∼0.26 eV. - Abstract: Nanowires (NWs) have attracted considerable interests for scaled electronic and optoelectronic device applications. However, NW based semiconductor devices normally suffer from surface states due to the existence of dangling bonds or surface reconstruction. Because of their large surface-to-volume ratio, surface states in NWs can easily affect the metallic contacts to NWs and electron transport in NW. Here, we present ZnO NW surface analysis by performing current–voltage characterization on ZnO NW Schottky barrier field effect transistors with different metal contacts (Ti, Al, Au) at both room temperature and cryogenic temperature. Our results show that three metal contacts are all Schottky contacts to ZnO NWs due to surface states. Our further study reveals: (a) the surface states related Schottky barrier height (SBH) can be extracted from a back to back Schottky diodes model and the SBH values are in the range of 0.34–0.37 eV for three metal contacts; (b) the trap activation energy determined from the Arrhenius plots of different Schottky metal contacts is in the range of 0.23–0.29 eV, which is oxygen vacancies related; and (c) based on the space-charge-limited model, the surface state density of ZnO NW is in the range of 1.04 × 10 10 –1.24 × 10 10 /cm 2

  3. Radiation Pattern Reconstruction from the Near-Field Amplitude Measurement on Two Planes Using PSO

    Directory of Open Access Journals (Sweden)

    Z. Novacek

    2005-12-01

    Full Text Available The paper presents a new approach to the radiation patternreconstruction from near-field amplitude only measurement over a twoplanar scanning surfaces. This new method for antenna patternreconstruction is based on the global optimization PSO (Particle SwarmOptimization. The paper presents appropriate phaseless measurementrequirements and phase retrieval algorithm together with a briefdescription of the particle swarm optimization method. In order toexamine the methodologies developed in this paper, phaselessmeasurement results for two different antennas are presented andcompared to results obtained by a complex measurement (amplitude andphase.

  4. Reconstructing the Surface Permittivity Distribution from Data Measured by the CONSERT Instrument aboard Rosetta: Method and Simulations

    Science.gov (United States)

    Plettemeier, D.; Statz, C.; Hegler, S.; Herique, A.; Kofman, W. W.

    2014-12-01

    One of the main scientific objectives of the Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT) aboard Rosetta is to perform a dielectric characterization of comet 67P/Chuyurmov-Gerasimenko's nucleus by means of a bi-static sounding between the lander Philae launched onto the comet's surface and the orbiter Rosetta. For the sounding, the lander part of CONSERT will receive and process the radio signal emitted by the orbiter part of the instrument and transmit a signal to the orbiter to be received by CONSERT. CONSERT will also be operated as bi-static RADAR during the descent of the lander Philae onto the comet's surface. From data measured during the descent, we aim at reconstructing a surface permittivity map of the comet at the landing site and along the path below the descent trajectory. This surface permittivity map will give information on the bulk material right below and around the landing site and the surface roughness in areas covered by the instrument along the descent. The proposed method to estimate the surface permittivity distribution is based on a least-squares based inversion approach in frequency domain. The direct problem of simulating the wave-propagation between lander and orbiter at line-of-sight and the signal reflected on the comet's surface is modelled using a dielectric physical optics approximation. Restrictions on the measurement positions by the descent orbitography and limitations on the instrument dynamic range will be dealt with by application of a regularization technique where the surface permittivity distribution and the gradient with regard to the permittivity is projected in a domain defined by a viable model of the spatial material and roughness distribution. The least-squares optimization step of the reconstruction is performed in such domain on a reduced set of parameters yielding stable results. The viability of the proposed method is demonstrated by reconstruction results based on simulated data.

  5. Pseudo-proxy evaluation of climate field reconstruction methods of North Atlantic climate based on an annually resolved marine proxy network

    Directory of Open Access Journals (Sweden)

    M. Pyrina

    2017-10-01

    Full Text Available Two statistical methods are tested to reconstruct the interannual variations in past sea surface temperatures (SSTs of the North Atlantic (NA Ocean over the past millennium based on annually resolved and absolutely dated marine proxy records of the bivalve mollusk Arctica islandica. The methods are tested in a pseudo-proxy experiment (PPE setup using state-of-the-art climate models (CMIP5 Earth system models and reanalysis data from the COBE2 SST data set. The methods were applied in the virtual reality provided by global climate simulations and reanalysis data to reconstruct the past NA SSTs using pseudo-proxy records that mimic the statistical characteristics and network of Arctica islandica. The multivariate linear regression methods evaluated here are principal component regression and canonical correlation analysis. Differences in the skill of the climate field reconstruction (CFR are assessed according to different calibration periods and different proxy locations within the NA basin. The choice of the climate model used as a surrogate reality in the PPE has a more profound effect on the CFR skill than the calibration period and the statistical reconstruction method. The differences between the two methods are clearer for the MPI-ESM model due to its higher spatial resolution in the NA basin. The pseudo-proxy results of the CCSM4 model are closer to the pseudo-proxy results based on the reanalysis data set COBE2. Conducting PPEs using noise-contaminated pseudo-proxies instead of noise-free pseudo-proxies is important for the evaluation of the methods, as more spatial differences in the reconstruction skill are revealed. Both methods are appropriate for the reconstruction of the temporal evolution of the NA SSTs, even though they lead to a great loss of variance away from the proxy sites. Under reasonable assumptions about the characteristics of the non-climate noise in the proxy records, our results show that the marine network of Arctica

  6. Effects of illumination differences on photometric stereo shape-and-albedo-from-shading for precision lunar surface reconstruction

    Science.gov (United States)

    Chung Liu, Wai; Wu, Bo; Wöhler, Christian

    2018-02-01

    Photoclinometric surface reconstruction techniques such as Shape-from-Shading (SfS) and Shape-and-Albedo-from-Shading (SAfS) retrieve topographic information of a surface on the basis of the reflectance information embedded in the image intensity of each pixel. SfS or SAfS techniques have been utilized to generate pixel-resolution digital elevation models (DEMs) of the Moon and other planetary bodies. Photometric stereo SAfS analyzes images under multiple illumination conditions to improve the robustness of reconstruction. In this case, the directional difference in illumination between the images is likely to affect the quality of the reconstruction result. In this study, we quantitatively investigate the effects of illumination differences on photometric stereo SAfS. Firstly, an algorithm for photometric stereo SAfS is developed, and then, an error model is derived to analyze the relationships between the azimuthal and zenith angles of illumination of the images and the reconstruction qualities. The developed algorithm and error model were verified with high-resolution images collected by the Narrow Angle Camera (NAC) of the Lunar Reconnaissance Orbiter Camera (LROC). Experimental analyses reveal that (1) the resulting error in photometric stereo SAfS depends on both the azimuthal and the zenith angles of illumination as well as the general intensity of the images and (2) the predictions from the proposed error model are consistent with the actual slope errors obtained by photometric stereo SAfS using the LROC NAC images. The proposed error model enriches the theory of photometric stereo SAfS and is of significance for optimized lunar surface reconstruction based on SAfS techniques.

  7. Core surface magnetic field evolution 2000–2010

    DEFF Research Database (Denmark)

    Finlay, Chris; Jackson, A.; Gillet, N.

    2012-01-01

    harmonics up to degree and order 24 and a temporal parametrization of sixth‐order B‐splines with 0.25 yr knot spacing is employed. Models were constructed by minimizing an absolute deviation measure of misfit along with measures of spatial and temporal complexity at the core surface. We investigate...... is weaker. Rapid field evolution is observed under the eastern Indian Ocean associated with the growth and drift of an intense low latitude flux patch. We also find that the present axial dipole decay arises from a combination of subtle changes in the southern hemisphere field morphology....

  8. 3D reconstruction of a patient-specific surface model of the proximal femur from calibrated x-ray radiographs: A validation study

    International Nuclear Information System (INIS)

    Zheng Guoyan; Schumann, Steffen

    2009-01-01

    Twenty-three femurs (one plastic bone and twenty-two cadaver bones) with both nonpathologic and pathologic cases were considered to validate a statistical shape model based technique for three-dimensional (3D) reconstruction of a patient-specific surface model from calibrated x-ray radiographs. The 3D reconstruction technique is based on an iterative nonrigid registration of the features extracted from a statistically instantiated 3D surface model to those interactively identified from the radiographs. The surface models reconstructed from the radiographs were compared to the associated ground truths derived either from a 3D CT-scan reconstruction method or from a 3D laser-scan reconstruction method and an average error distance of 0.95 mm were found. Compared to the existing works, our approach has the advantage of seamlessly handling both nonpathologic and pathologic cases even when the statistical shape model that we used was constructed from surface models of nonpathologic bones.

  9. Fault detection by surface seismic scanning tunneling macroscope: Field test

    KAUST Repository

    Hanafy, Sherif M.

    2014-08-05

    The seismic scanning tunneling macroscope (SSTM) is proposed for detecting the presence of near-surface impedance anomalies and faults. Results with synthetic data are consistent with theory in that scatterers closer to the surface provide brighter SSTM profiles than those that are deeper. The SSTM profiles show superresolution detection if the scatterers are in the near-field region of the recording line. The field data tests near Gulf of Aqaba, Haql, KSA clearly show the presence of the observable fault scarp, and identify the subsurface presence of the hidden faults indicated in the tomograms. Superresolution detection of the fault is achieved, even when the 35 Hz data are lowpass filtered to the 5-10 Hz band.

  10. Fault detection by surface seismic scanning tunneling macroscope: Field test

    KAUST Repository

    Hanafy, Sherif M.; Schuster, Gerard T.

    2014-01-01

    The seismic scanning tunneling macroscope (SSTM) is proposed for detecting the presence of near-surface impedance anomalies and faults. Results with synthetic data are consistent with theory in that scatterers closer to the surface provide brighter SSTM profiles than those that are deeper. The SSTM profiles show superresolution detection if the scatterers are in the near-field region of the recording line. The field data tests near Gulf of Aqaba, Haql, KSA clearly show the presence of the observable fault scarp, and identify the subsurface presence of the hidden faults indicated in the tomograms. Superresolution detection of the fault is achieved, even when the 35 Hz data are lowpass filtered to the 5-10 Hz band.

  11. CONSTRAINING THE NFW POTENTIAL WITH OBSERVATIONS AND MODELING OF LOW SURFACE BRIGHTNESS GALAXY VELOCITY FIELDS

    International Nuclear Information System (INIS)

    Kuzio de Naray, Rachel; McGaugh, Stacy S.; Mihos, J. Christopher

    2009-01-01

    We model the Navarro-Frenk-White (NFW) potential to determine if, and under what conditions, the NFW halo appears consistent with the observed velocity fields of low surface brightness (LSB) galaxies. We present mock DensePak Integral Field Unit (IFU) velocity fields and rotation curves of axisymmetric and nonaxisymmetric potentials that are well matched to the spatial resolution and velocity range of our sample galaxies. We find that the DensePak IFU can accurately reconstruct the velocity field produced by an axisymmetric NFW potential and that a tilted-ring fitting program can successfully recover the corresponding NFW rotation curve. We also find that nonaxisymmetric potentials with fixed axis ratios change only the normalization of the mock velocity fields and rotation curves and not their shape. The shape of the modeled NFW rotation curves does not reproduce the data: these potentials are unable to simultaneously bring the mock data at both small and large radii into agreement with observations. Indeed, to match the slow rise of LSB galaxy rotation curves, a specific viewing angle of the nonaxisymmetric potential is required. For each of the simulated LSB galaxies, the observer's line of sight must be along the minor axis of the potential, an arrangement that is inconsistent with a random distribution of halo orientations on the sky.

  12. Near surface geophysics techniques and geomorphological approach to reconstruct the hazard cave map in historical and urban areas

    Science.gov (United States)

    Lazzari, M.; Loperte, A.; Perrone, A.

    2009-04-01

    This work, carried out with an integrated methodological approach, focuses on the use of near surface geophysics techniques, such as ground penetrating radar GPR and electrical resistivity tomography (ERT), and geomorphological analysis, in order to reconstruct the cave distribution and geometry in a urban context and, in particular, in historical centres. In fact, there are a lot of historical Mediterranean sites born on an original rupestrian settlement, of which often the new generations forgot the memory and new urban areas built on them burying any marks. The interaction during recent centuries between human activity (caves excavation, birth and growth of an urban area) and the characters of the natural environment were the reasons of a progressive increase in hazard and vulnerability levels of several sites. The reconstruction of a detailed cave map distribution is the first step to define the anthropic and geomorphological hazard in urban areas, fundamental basis for planning and assessing the risk. The integrated near surface geophysics and geomorphological techniques have been applied to the case study of Tursi hilltop town and its older nucleus called Rabatana, located in the south-western sector of the Basilicata (southern Italy), representing an interesting example of the deep bond between natural and man-made environments such as precious cultural heritage. The history of this settlement has always been deeply connected with the characteristics of the neighbouring environment and it seems possible that the first settlement was built by excavating the slopes of the sandy relief. It was a typical rupestrian settlement, where meteoric water was stored inside some cisterns excavated on the slopes. During recent centuries, the increase in territory development by humans produced an increase in cave excavation in the Tursi-Rabatana urban area. To reconstruct the extremely complex near-surface hypogeal environment excavated in the sandy layers, a geophysical

  13. Reconstructing the Economy: A Methodological Journey from the Surface to the Essence and Back

    Directory of Open Access Journals (Sweden)

    Peter Karl Fleissner

    2011-10-01

    Full Text Available The essential methodology in social science to “understand” phenomena is informed abstraction. But the way - how and what for the abstraction process is shaped - divides the economists into various schools. While mainstream econ- omists abstract from any links of the economy to human beings - replacing them by selfish machines maximizing their prof- its or individual utilities, and neglecting any deeper analysis of the basic constructions they use (like prices or money, heterodox economists try to look behind the surface, link them to certain periods of history and to the source of all value: humans are social beings and cannot exist without mutuality. The paper presents a heterodox way to reconstruct contempo- rary capitalist economies by applying the new science of information with its evolutionary concepts. It starts the description on a very abstract level: useful things and services produced by specialized labor. Step by step new layers of economic activities and related information are added and become the basis for the next one. Vice versa economic activities on lower layers become controlled and modified by higher layers. One can see that the higher controlling principles in contemporary capitalist economies do not assist the economic, social, and cultural well-being of the majority of people, but function ac- cording to the self-interest of a minority. For the first time in history capitalism has developed new technologies that in prin- ciple could allow for the participation of the many, to create abundance of information, and to offer tools for building a de- mocratic and sustainable society. But by the same capitalism, rigid Intellectual Property Rights and severe copy protection mechanisms enforce artificial shortage of information goods.

  14. Reconstruction of droughts in India using multiple land-surface models (1951-2015)

    Science.gov (United States)

    Mishra, Vimal; Shah, Reepal; Azhar, Syed; Shah, Harsh; Modi, Parth; Kumar, Rohini

    2018-04-01

    India has witnessed some of the most severe historical droughts in the current decade, and severity, frequency, and areal extent of droughts have been increasing. As a large part of the population of India is dependent on agriculture, soil moisture drought affecting agricultural activities (crop yields) has significant impacts on socio-economic conditions. Due to limited observations, soil moisture is generally simulated using land-surface hydrological models (LSMs); however, these LSM outputs have uncertainty due to many factors, including errors in forcing data and model parameterization. Here we reconstruct agricultural drought events over India during the period of 1951-2015 based on simulated soil moisture from three LSMs, the Variable Infiltration Capacity (VIC), the Noah, and the Community Land Model (CLM). Based on simulations from the three LSMs, we find that major drought events occurred in 1987, 2002, and 2015 during the monsoon season (June through September). During the Rabi season (November through February), major soil moisture droughts occurred in 1966, 1973, 2001, and 2003. Soil moisture droughts estimated from the three LSMs are comparable in terms of their spatial coverage; however, differences are found in drought severity. Moreover, we find a higher uncertainty in simulated drought characteristics over a large part of India during the major crop-growing season (Rabi season, November to February: NDJF) compared to those of the monsoon season (June to September: JJAS). Furthermore, uncertainty in drought estimates is higher for severe and localized droughts. Higher uncertainty in the soil moisture droughts is largely due to the difference in model parameterizations (especially soil depth), resulting in different persistence of soil moisture simulated by the three LSMs. Our study highlights the importance of accounting for the LSMs' uncertainty and consideration of the multi-model ensemble system for the real-time monitoring and prediction of

  15. GALAXY HALO TRUNCATION AND GIANT ARC SURFACE BRIGHTNESS RECONSTRUCTION IN THE CLUSTER MACSJ1206.2-0847

    Energy Technology Data Exchange (ETDEWEB)

    Eichner, Thomas; Seitz, Stella; Monna, Anna [Universitaets-Sternwarte Muenchen, Scheinerstr. 1, D-81679 Muenchen (Germany); Suyu, Sherry H. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Halkola, Aleksi [Institute of Medical Engineering, University of Luebeck, Ratzeburger Allee 160 23562 Luebeck (Germany); Umetsu, Keiichi [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Zitrin, Adi [Institut fuer Theoretische Astrophysik, ZAH, Albert-Ueberle-Strasse 2, D-69120 Heidelberg (Germany); Coe, Dan; Postman, Marc; Koekemoer, Anton; Bradley, Larry [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208 (United States); Rosati, Piero [ESO-European Southern Observatory, D-85748 Garching bei Muenchen (Germany); Grillo, Claudio; Host, Ole [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Balestra, Italo [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Zheng, Wei; Lemze, Doron [Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Broadhurst, Tom [Department of Theoretical Physics, University of the Basque Country, P.O. Box 644, E-48080 Bilbao (Spain); Moustakas, Leonidas [Jet Propulsion Laboratory, California Institute of Technology, MS 169-327, Pasadena, CA 91109 (United States); Molino, Alberto [Instituto de Astrofisica de Andalucia (CSIC), C/Camino Bajo de Huetor 24, Granada E-18008 (Spain); and others

    2013-09-10

    In this work, we analyze the mass distribution of MACSJ1206.2-0847, particularly focusing on the halo properties of its cluster members. The cluster appears relaxed in its X-ray emission, but has a significant amount of intracluster light that is not centrally concentrated, suggesting that galaxy-scale interactions are still ongoing despite the overall relaxed state. The cluster lenses 12 background galaxies into multiple images and one galaxy at z = 1.033 into a giant arc and its counterimage. The multiple image positions and the surface brightness (SFB) distribution of the arc, which is bent around several cluster members, are sensitive to the cluster galaxy halo properties. We model the cluster mass distribution with a Navarro-Frenk-White profile and the galaxy halos with two parameters for the mass normalization and the extent of a reference halo assuming scalings with their observed near-infrared light. We match the multiple image positions at an rms level of 0.''85 and can reconstruct the SFB distribution of the arc in several filters to a remarkable accuracy based on this cluster model. The length scale where the enclosed galaxy halo mass is best constrained is about 5 effective radii-a scale in between those accessible to dynamical and field strong-lensing mass estimates on the one hand and galaxy-galaxy weak-lensing results on the other hand. The velocity dispersion and halo size of a galaxy with m{sub 160W,AB} = 19.2 and M{sub B,Vega} = -20.7 are {sigma} = 150 km s{sup -1} and r Almost-Equal-To 26 {+-} 6 kpc, respectively, indicating that the halos of the cluster galaxies are tidally stripped. We also reconstruct the unlensed source, which is smaller by a factor of {approx}5.8 in area, demonstrating the increase in morphological information due to lensing. We conclude that this galaxy likely has star-forming spiral arms with a red (older) central component.

  16. GALAXY HALO TRUNCATION AND GIANT ARC SURFACE BRIGHTNESS RECONSTRUCTION IN THE CLUSTER MACSJ1206.2-0847

    International Nuclear Information System (INIS)

    Eichner, Thomas; Seitz, Stella; Monna, Anna; Suyu, Sherry H.; Halkola, Aleksi; Umetsu, Keiichi; Zitrin, Adi; Coe, Dan; Postman, Marc; Koekemoer, Anton; Bradley, Larry; Rosati, Piero; Grillo, Claudio; Høst, Ole; Balestra, Italo; Zheng, Wei; Lemze, Doron; Broadhurst, Tom; Moustakas, Leonidas; Molino, Alberto

    2013-01-01

    In this work, we analyze the mass distribution of MACSJ1206.2-0847, particularly focusing on the halo properties of its cluster members. The cluster appears relaxed in its X-ray emission, but has a significant amount of intracluster light that is not centrally concentrated, suggesting that galaxy-scale interactions are still ongoing despite the overall relaxed state. The cluster lenses 12 background galaxies into multiple images and one galaxy at z = 1.033 into a giant arc and its counterimage. The multiple image positions and the surface brightness (SFB) distribution of the arc, which is bent around several cluster members, are sensitive to the cluster galaxy halo properties. We model the cluster mass distribution with a Navarro-Frenk-White profile and the galaxy halos with two parameters for the mass normalization and the extent of a reference halo assuming scalings with their observed near-infrared light. We match the multiple image positions at an rms level of 0.''85 and can reconstruct the SFB distribution of the arc in several filters to a remarkable accuracy based on this cluster model. The length scale where the enclosed galaxy halo mass is best constrained is about 5 effective radii—a scale in between those accessible to dynamical and field strong-lensing mass estimates on the one hand and galaxy-galaxy weak-lensing results on the other hand. The velocity dispersion and halo size of a galaxy with m 160W,AB = 19.2 and M B,Vega = –20.7 are σ = 150 km s –1 and r ≈ 26 ± 6 kpc, respectively, indicating that the halos of the cluster galaxies are tidally stripped. We also reconstruct the unlensed source, which is smaller by a factor of ∼5.8 in area, demonstrating the increase in morphological information due to lensing. We conclude that this galaxy likely has star-forming spiral arms with a red (older) central component

  17. Thresholds for human detection of patient setup errors in digitally reconstructed portal images of prostate fields

    International Nuclear Information System (INIS)

    Phillips, Brooke L.; Jiroutek, Michael R.; Tracton, Gregg; Elfervig, Michelle; Muller, Keith E.; Chaney, Edward L.

    2002-01-01

    Purpose: Computer-assisted methods to analyze electronic portal images for the presence of treatment setup errors should be studied in controlled experiments before use in the clinical setting. Validation experiments using images that contain known errors usually report the smallest errors that can be detected by the image analysis algorithm. This paper offers human error-detection thresholds as one benchmark for evaluating the smallest errors detected by algorithms. Unfortunately, reliable data are lacking describing human performance. The most rigorous benchmarks for human performance are obtained under conditions that favor error detection. To establish such benchmarks, controlled observer studies were carried out to determine the thresholds of detectability for in-plane and out-of-plane translation and rotation setup errors introduced into digitally reconstructed portal radiographs (DRPRs) of prostate fields. Methods and Materials: Seventeen observers comprising radiation oncologists, radiation oncology residents, physicists, and therapy students participated in a two-alternative forced choice experiment involving 378 DRPRs computed using the National Library of Medicine Visible Human data sets. An observer viewed three images at a time displayed on adjacent computer monitors. Each image triplet included a reference digitally reconstructed radiograph displayed on the central monitor and two DRPRs displayed on the flanking monitors. One DRPR was error free. The other DRPR contained a known in-plane or out-of-plane error in the placement of the treatment field over a target region in the pelvis. The range for each type of error was determined from pilot observer studies based on a Probit model for error detection. The smallest errors approached the limit of human visual capability. The observer was told what kind of error was introduced, and was asked to choose the DRPR that contained the error. Observer decisions were recorded and analyzed using repeated

  18. Analysis of Surface Electric Field Measurements from an Array of Electric Field Mills

    Science.gov (United States)

    Lucas, G.; Thayer, J. P.; Deierling, W.

    2016-12-01

    Kennedy Space Center (KSC) has operated an distributed array of over 30 electric field mills over the past 18 years, providing a unique data set of surface electric field measurements over a very long timespan. In addition to the electric field instruments there are many meteorological towers around KSC that monitor the local meteorological conditions. Utilizing these datasets we have investigated and found unique spatial and temporal signatures in the electric field data that are attributed to local meteorological effects and the global electric circuit. The local and global scale influences on the atmospheric electric field will be discussed including the generation of space charge from the ocean surf, local cloud cover, and a local enhancement in the electric field that is seen at sunrise.

  19. Paleoclimatic reconstructions in western Canada from borehole temperature logs: surface air temperature forcing and groundwater flow

    Czech Academy of Sciences Publication Activity Database

    Majorowicz, J.; Grasby, S. E.; Ferguson, G.; Šafanda, Jan; Skinner, W.

    2006-01-01

    Roč. 2, č. 1 (2006), s. 1-10 ISSN 1814-9324 Institutional research plan: CEZ:AV0Z30120515 Keywords : palaeoclimatic reconstructions * Canada * borehole temperatures Subject RIV: DC - Siesmology, Volcanology, Earth Structure

  20. Field measurement of albedo for limited extent test surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sailor, David J. [Portland State University, Department of Mechanical and Materials Engineering, P.O. Box 751-ME, Portland, OR 97207 (United States); Resh, Kyle; Segura, Del [Tulane University, Department of Mechanical Engineering, 400 Lindy Boggs Center, New Orleans, LA 70118 (United States)

    2006-05-15

    A new method is introduced for field measurement of surface albedo. This method consists of the use of a cylindrical shade ring made of opaque fabric with a known (low) albedo placed over a test surface. The albedo measurement is accomplished using two small pyranometers situated so that the downward-facing pyranometer receives radiation only from the test surface and the shade ring. The upward-facing pyranometer simultaneously records the incoming solar radiation. The radiation received by the downward-facing pyramometer is a combination of reflected radiation from shaded and unshaded portions of these two surfaces, requiring detailed accounting of the resulting view factor geometries. The method presented here improves upon past approaches by allowing for smaller sample sizes, minimizing errors associated with reflective properties of the surroundings, and allowing for accurate measurements even under partially cloudy skies. In addition to these methodological improvements we introduce an approach for estimating the uncertainty in the resulting albedo measurements. Results from field measurements are presented to validate the measurement protocol, and to compare its accuracy with the accuracy of a published standard. (author)

  1. Quantum oscillations and nodal pockets from Fermi surface reconstruction in the underdoped cuprates

    Science.gov (United States)

    Harrison, Neil

    2012-02-01

    Fermiology in the underdoped high Tc cuprates presents us with unique challenges, requiring experimentalists to look deeper into the data than is normally required for clues. Recent measurements of an oscillatory chemical potential affecting the oscillations at high magnetic fields provide a strong indication of a single type of carrier pocket. When considered in conjunction with photoemission and specific heat measurements, a Fermi surface comprised almost entirely of nodal pockets is suggested. The mystery of the Fermi surface is deepened, however, by a near doping-independent Fermi surface cross-sectional area and negative Hall and Seebeck coefficients. We explore ways in which these findings can be reconciled, taking an important hint from the diverging effective mass yielded by quantum oscillations at low dopings. The author wishes to thank Suchitra Sebastian, Moaz Atarawneh, Doug Bonn, Walter Hardy, Ruixing Liang, Charles Mielke and Gilbert Lonzarich who have contributed to this work. The work is supported by the NSF through the NHMFL and by the DOE project ``Science at 100 tesla.''

  2. Reconstructing an Explosive Basaltic Eruption in the Pinacate Volcanic Field, NW Sonora, Mexico

    Science.gov (United States)

    Zawacki, E. E.; Clarke, A. B.; Arrowsmith, R.; Lynch, D. J.

    2017-12-01

    Tephra deposits from explosive volcanic eruptions provide a means to reconstruct eruption characteristics, such as column height and erupted volume. Parameters like these are essential in assessing the explosivity of past eruptions and associated volcanic hazards. We applied such methods to a basaltic tephra deposit from one of the youngest eruptions in the Pinacate volcanic field (NW Sonora, Mexico). This roughly circular tephra blanket extends 13 km E-W and 13 km N-S, and covers an area of at least 135 km2. The source vent of this eruption is hypothesized to be the Tecolote volcano (lat 31.877, long -113.362), which is dated to 27 ± 6 ka (40Ar/39Ar). Fifty-three pits were dug across the extent of the tephra deposit to measure its thickness, record stratigraphy, characterize grain size distribution, and determine maximum clast size. Isopleth and isopach maps were created from these data to determine the column height (>9 km), estimate mass eruption rate (>2.1x106 kg/s), and calculate the erupted volume (>4.2x10-2 km3). Stratigraphic descriptions support two distinct episodes of tephra production. Unit A is dispersed in an approximately circular pattern ( 6.5 km radius) with its center shifted to the east of the vent. The distribution of Unit B is oblate ( 9.5 km major axis, 4.5 km minor axis) and trends to the southeast of the vent. Lava samples were collected from each of the seven Tecolote flows for XRF and ICP-MS geochemical analyses. These samples were compared to geochemical signatures from a Tecolote bomb, tephra from Units A and B, and cinder from the La Laja cone, which is the youngest dated cone in the field at 12 ± 4 ka (40Ar/39Ar). The La Laja sample is geochemically distinct from all Tecolote samples, confirming that it did not contribute to the two tephra units. Tephra from Unit A and Unit B have distinct signatures and fit within the geochemical evolution of the Tecolote lavas, supporting two explosive episodes from the Tecolote volcano, which has

  3. Reconstructing interacting entropy-corrected holographic scalar field models of dark energy in the non-flat universe

    Energy Technology Data Exchange (ETDEWEB)

    Karami, K; Khaledian, M S [Department of Physics, University of Kurdistan, Pasdaran Street, Sanandaj (Iran, Islamic Republic of); Jamil, Mubasher, E-mail: KKarami@uok.ac.ir, E-mail: MS.Khaledian@uok.ac.ir, E-mail: mjamil@camp.nust.edu.pk [Center for Advanced Mathematics and Physics (CAMP), National University of Sciences and Technology (NUST), Islamabad (Pakistan)

    2011-02-15

    Here we consider the entropy-corrected version of the holographic dark energy (DE) model in the non-flat universe. We obtain the equation of state parameter in the presence of interaction between DE and dark matter. Moreover, we reconstruct the potential and the dynamics of the quintessence, tachyon, K-essence and dilaton scalar field models according to the evolutionary behavior of the interacting entropy-corrected holographic DE model.

  4. Field Comparison of Fertigation Vs. Surface Irrigation of Cotton Crop

    International Nuclear Information System (INIS)

    Janat, M.

    2004-01-01

    Based on previous results of the same nature, one nitrogen rate 180 kg N ha -1 was tested under two-irrigation methods, surface irrigation and drip fertigation of cotton (Cultivar Rakka-5) for two consecutive seasons 2000 and 2001. The study aimed to answer various questions regarding the applicability of drip fertigation at farm level and the effect of its employment on yield and growth parameters, compared to surface irrigation. Nitrogen fertilizer was either injected in eight equally split applications for the drip fertigated cotton or divided in four unequally split applications as recommend by Ministry of Agriculture (20% before planting, 40% at thinning, 20% after 60 days from planting and 20% after 75 days after planting). 15 N labeled urea was used to evaluate nitrogen fertilizer efficiency. The experimental design was randomized block design with seven replicates. Results showed that drip fertigation led to water saving exceeding 50% in some cases. Field germination percentage was highly increased under drip- fertigated cotton relative to surface-irrigated cotton. Dry matter and seed cotton yield of surface-irrigated cotton was slightly higher than that of drip-fertigated cotton in the first growing season. The reason for that was due to the hot spill that occurred in the region, which exposed the cotton crop to water stress and consequently pushed the cotton into early flowering. Lint properties were not affected by the introduction of drip-fertigation. Actually some properties were improved relative to the standard properties identified by the cotton Bureau.Nitrogen uptake was slightly increased under drip fertigation whereas nitrogen use efficiencies were not constant along the growing seasons. The reason for that could be lateral leaching and root proliferation into the labeled and unlabeled subplots. Field water use efficiency was highly increased for both growing seasons under drip fertigation practice. The rate of field water use efficiencies

  5. Nonlinear mean field theory for nuclear matter and surface properties

    International Nuclear Information System (INIS)

    Boguta, J.; Moszkowski, S.A.

    1983-01-01

    Nuclear matter properties are studied in a nonlinear relativistic mean field theory. We determine the parameters of the model from bulk properties of symmetric nuclear matter and a reasonable value of the effective mass. In this work, we stress the nonrelativistic limit of the theory which is essentially equivalent to a Skyrme hamiltonian, and we show that most of the results can be obtained, to a good approximation, analytically. The strength of the required parameters is determined from the binding energy and density of nuclear matter and the effective nucleon mass. For realistic values of the parameters, the nonrelativistic approximation turns out to be quite satisfactory. Using reasonable values of the parameters, we can account for other key properties of nuclei, such as the spin-orbit coupling, surface energy, and diffuseness of the nuclear surface. Also the energy dependence of the nucleon-nucleus optical model is accounted for reasonably well except near the Fermi surface. It is found, in agreement with empirical results, that the Landau parameter F 0 is quite small in normal nuclear matter. Both density dependence and momentum dependence of the NN interaction, but especially the former, are important for nuclear saturation. The required scalar and vector coupling constants agree fairly well with those obtained from analyses of NN scattering phase shifts with one-boson-exchange models. The mean field theory provides a semiquantitative justification for the weak Skyrme interaction in odd states. The strength of the required nonlinear term is roughly consistent with that derived using a new version of the chiral mean field theory in which the vector mass as well as the nucleon mass is generated by the sigma-field. (orig.)

  6. Rugby Union on-field position and its relationship to shoulder injury leading to anterior reconstruction for instability.

    Science.gov (United States)

    Sundaram, Abayasankar; Bokor, Desmond J; Davidson, Andrew S

    2011-03-01

    Due to the unique demands of each position on the Rugby Union field, the likelihood of an athlete sustaining a dislocation of their shoulder joint that requires surgical reconstruction may be affected by their position on the field. 166 patients with 184 involved shoulders requiring anterior reconstruction following an on-field Rugby Union injury between January 1996 and September 2008 were analysed. The mean age at time of injury was 18 years with the mean age at time of surgery being 20 years. The most prevalent mechanism of injury was a tackle in 66.3% of players. Players were more likely to suffer injury to their non-dominant shoulder than their dominant side (McNemar's Test, prisk of injury for all player positions. Positions with significantly different risk of injury were five-eighth (increased risk) and wing (reduced risk). Although we observed an increased risk in flankers and fullbacks, and a lower risk in second row, these results did not reach statistical significance after application of the Bonferroni correction. This information can be utilized by team staff to assist in pre-season conditioning as well as the development of improved muscle co-ordination programmes for the non-dominant shoulder, and planning a graduated return to sport by the player recovering from surgical reconstruction of the shoulder for instability. Copyright © 2010 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  7. Macroscopic electrical field distribution and field-induced surface stresses of needle-shaped field emitters

    Energy Technology Data Exchange (ETDEWEB)

    Moy, Charles K.S., E-mail: charles.moy@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia); ARC Centre of Excellence for Design in Light Metals, The University of Sydney, Sydney, NSW 2006 (Australia); School of Civil Engineering, The University of Sydney, Sydney, NSW 2006 (Australia); Ranzi, Gianluca [ARC Centre of Excellence for Design in Light Metals, The University of Sydney, Sydney, NSW 2006 (Australia); School of Civil Engineering, The University of Sydney, Sydney, NSW 2006 (Australia); Petersen, Timothy C. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia); Ringer, Simon P. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia); ARC Centre of Excellence for Design in Light Metals, The University of Sydney, Sydney, NSW 2006 (Australia)

    2011-05-15

    One major concern since the development of the field ion microscope is the mechanical strength of the specimens. The macroscopic shape of the imaging tip greatly influences field-induced stresses and there is merit in further study of this phenomenon from a classical perspective. Understanding the geometrical, as opposed to localized electronic, factors that affect the stress might improve the quality and success rate of atom probe experiments. This study uses macroscopic electrostatic principles and finite element modelling to investigate field-induced stresses in relation to the shape of the tip. Three two-dimensional idealized models are considered, namely hyperbolic, parabolic and sphere-on-orthogonal-cone; the shapes of which are compared to experimental tips prepared by electro-polishing. Three dimensional morphologies of both a nano-porous and single-crystal aluminium tip are measured using electron tomography to quantitatively test the assumption of cylindrical symmetry for electro-polished tips. The porous tip was prepared and studied to demonstrate a fragile specimen for which such finite element studies could determine potential mechanical failure, prior to any exhaustive atom probe investigation. -- Research highlights: {yields} We use electrostatic principles and finite element to model field-induced stresses. {yields} We study two-dimensional idealized needle-shaped field emitters. {yields} Stress distribution of hyperbolic, parabolic and sphere-on-orthogonal-cone tips mapped. {yields} Electron tomography to obtain the morphology of three-dimensional aluminium tips. {yields} Studies of the morphology of the porous tip demonstrate a fragile specimen.

  8. All-(111) surface silicon nanowire field effect transistor devices: Effects of surface preparations

    NARCIS (Netherlands)

    Masood, M.N.; Carlen, Edwin; van den Berg, Albert

    2014-01-01

    Etching/hydrogen termination of All-(111) surface silicon nanowire field effect (SiNW-FET) devices developed by conventional photolithography and plane dependent wet etchings is studied with X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and

  9. Positron probes of the Ge(1 0 0) surface: The effects of surface reconstructions and electron-positron correlations on positron trapping and annihilation characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Fazleev, N.G. [Department of Physics, University of Texas at Arlington, Box 19059, Arlington, TX 76019-0059 (United States) and Department of Physics, Kazan State University, Kazan 420008 (Russian Federation)]. E-mail: Fazleev@uta.edu; Jung, E. [Department of Physics, University of Texas at Arlington, Box 19059, Arlington, TX 76019-0059 (United States); Weiss, A.H. [Department of Physics, University of Texas at Arlington, Box 19059, Arlington, TX 76019-0059 (United States)

    2007-08-15

    Positron annihilation induced Auger electron spectroscopy (PAES) has been applied to study the Ge(1 0 0) surface. The high-resolution PAES spectrum from the Ge(1 0 0) surface displays several strong Auger peaks corresponding to M{sub 4,5}N{sub 1}N{sub 2,3}, M{sub 2,3}M{sub 4,5}M{sub 4,5}, M{sub 2,3}M{sub 4,5}V and M{sub 1}M{sub 4,5}M{sub 4,5} Auger transitions. The integrated peak intensities of Auger transitions are used to obtain experimental annihilation probabilities for the Ge 3d and 3p core level electrons. These experimental results are analyzed by performing calculations of positron surface states and annihilation characteristics of surface trapped positrons with relevant Ge core-level electrons for the non-reconstructed and reconstructed Ge(1 0 0)-p(2 x 1), Ge(1 0 0)-p(2 x 2) and Ge(1 0 0)-c(4 x 2) surfaces. It is found that the positron surface state wave function extends into the Ge lattice in the regions where atoms are displaced from their ideal terminated positions due to reconstructions. Estimates of the positron binding energy and the positron annihilation characteristics reveal their sensitivity to the specific atomic structure of the topmost layers of Ge(1 0 0). A comparison with PAES data reveals an agreement with theoretical core annihilation probabilities for the Auger transitions considered.

  10. Novel (1 × 1)-reconstructions and native defects of TiO{sub 2} anatase (101) surface

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qinggao, E-mail: wangqinggao1984@126.com [Institute for Computational Materials Science, School of Physics and Electronics, Henan University, Kaifeng 475004 (China); Department of Physics and Electrical Engineering, Anyang Normal University, Anyang, Henan Province 455000 (China); Ren, Fengzhu [Institute for Computational Materials Science, School of Physics and Electronics, Henan University, Kaifeng 475004 (China); Dong, Huafeng [School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006 (China); Wang, Yuanxu, E-mail: wangyx@henu.edu.cn [Institute for Computational Materials Science, School of Physics and Electronics, Henan University, Kaifeng 475004 (China)

    2017-05-31

    Highlights: • Acceptor energy levels are induced by O interstitials; corresponding to a transition of indirect-to-direct band gap and a narrowing of band gap. • The Fermi levels of defected and reconstructed TiO{sub 2} anatse (101) can be modulated in a wide range. - Abstract: In this paper, reconstructions and native defects of TiO{sub 2} anatase (101) surface are studied using the state-of-the-art theoretical method. We find that O interstitials are dominated defects at an oxidization environment. These O interstitials induce acceptor energy levels, corresponding to an indirect-direct band transition and a bandgap narrowing. And thus, the experimental result that an O-rich anatase TiO{sub 2} has the higher photocatalytic activity can be understood. The formation of O vacancies and Ti interstitials becomes feasible at a reduced condition, and reconstructed TiO{sub 2} anatase (101)-(1 × 1) structures present with increasing reduction degree. Furthermore, the Fermi levels of defected and reconstructed TiO{sub 2} anatse (101) can be modulated in a wide range (i.e., nearly the whole band gap), which are different from those of TiO{sub 2} rutile (110).

  11. Isotropic 3D cardiac cine MRI allows efficient sparse segmentation strategies based on 3D surface reconstruction.

    Science.gov (United States)

    Odille, Freddy; Bustin, Aurélien; Liu, Shufang; Chen, Bailiang; Vuissoz, Pierre-André; Felblinger, Jacques; Bonnemains, Laurent

    2018-05-01

    Segmentation of cardiac cine MRI data is routinely used for the volumetric analysis of cardiac function. Conventionally, 2D contours are drawn on short-axis (SAX) image stacks with relatively thick slices (typically 8 mm). Here, an acquisition/reconstruction strategy is used for obtaining isotropic 3D cine datasets; reformatted slices are then used to optimize the manual segmentation workflow. Isotropic 3D cine datasets were obtained from multiple 2D cine stacks (acquired during free-breathing in SAX and long-axis (LAX) orientations) using nonrigid motion correction (cine-GRICS method) and super-resolution. Several manual segmentation strategies were then compared, including conventional SAX segmentation, LAX segmentation in three views only, and combinations of SAX and LAX slices. An implicit B-spline surface reconstruction algorithm is proposed to reconstruct the left ventricular cavity surface from the sparse set of 2D contours. All tested sparse segmentation strategies were in good agreement, with Dice scores above 0.9 despite using fewer slices (3-6 sparse slices instead of 8-10 contiguous SAX slices). When compared to independent phase-contrast flow measurements, stroke volumes computed from four or six sparse slices had slightly higher precision than conventional SAX segmentation (error standard deviation of 5.4 mL against 6.1 mL) at the cost of slightly lower accuracy (bias of -1.2 mL against 0.2 mL). Functional parameters also showed a trend to improved precision, including end-diastolic volumes, end-systolic volumes, and ejection fractions). The postprocessing workflow of 3D isotropic cardiac imaging strategies can be optimized using sparse segmentation and 3D surface reconstruction. Magn Reson Med 79:2665-2675, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  12. The magnetic field and the evolution of element spots on the surface of the HgMn eclipsing binary ARAur

    Science.gov (United States)

    Hubrig, S.; Savanov, I.; Ilyin, I.; González, J. F.; Korhonen, H.; Lehmann, H.; Schöller, M.; Granzer, T.; Weber, M.; Strassmeier, K. G.; Hartmann, M.; Tkachenko, A.

    2010-10-01

    The system ARAur is a young late B-type double-lined eclipsing binary with a primary star of HgMn peculiarity. We applied the Doppler imaging method to reconstruct the distribution of Fe and Y over the surface of the primary using spectroscopic time series obtained in 2005 and from 2008 October to 2009 February. The results show a remarkable evolution of the element distribution and overabundances. Measurements of the magnetic field with the moment technique using several elements reveal the presence of a longitudinal magnetic field of the order of a few hundred gauss in both stellar components and a quadratic field of the order of 8kG on the surface of the primary star. Based on observations obtained at the 2.56-m Nordic Optical Telescope on La Palma, the Karl-Schwarzschild-Observatorium in Tautenburg and the STELLA robotic telescope on Tenerife. E-mail: shubrig@aip.de

  13. Spiral CT of the pancreas. The value of small field-of-view targeted reconstruction

    International Nuclear Information System (INIS)

    Nishiharu, T.; Yamashita, Y.; Ogata, I.; Sumi, S.; Mitsuzaki, K.; Takahashi, M.

    1998-01-01

    Purpose: To compare the value of a retrospective targeted high-resolution spiral CT to the standard reconstruction technique in the assessment of pancreatic diseases. Material and methods: Spiral CT pancreatic images of a standard-size reconstruction protocol were compared prospectively with those of a retrospective targeted high-spatial-resolution reconstruction protocol in 30 patients. Prior to clinical evaluation, a phantom study was performed to evaluate the spatial resolution and signal-to-noise ratio of both protocols. Results: The high-resolution protocol achieved a good signal-to-noise ratio with acceptable spatial resolution. Phantom studies revealed increased image noise (+17%) with an increase in spatial resolution (+100%). In patients studied with the high-resolution protocol, the increase in noise was not significant but there was a marked improvement in the definition of small details. Conclusion: Images obtained with a targeted high-spatial-resolution reconstruction protocol showed superior lesion definition and vascular opacification compared with those obtained with a standard-size reconstruction protocol. This technique may have potential in the evaluation of small pancreatic abnormalities. (orig.)

  14. A simple method to achieve full-field and real-scale reconstruction using a movable stereo rig

    Science.gov (United States)

    Gu, Feifei; Zhao, Hong; Song, Zhan; Tang, Suming

    2018-06-01

    This paper introduces a simple method to achieve full-field and real-scale reconstruction using a movable binocular vision system (MBVS). The MBVS is composed of two cameras, one is called the tracking camera, and the other is called the working camera. The tracking camera is used for tracking the positions of the MBVS and the working camera is used for the 3D reconstruction task. The MBVS has several advantages compared with a single moving camera or multi-camera networks. Firstly, the MBVS could recover the real-scale-depth-information from the captured image sequences without using auxiliary objects whose geometry or motion should be precisely known. Secondly, the removability of the system could guarantee appropriate baselines to supply more robust point correspondences. Additionally, using one camera could avoid the drawback which exists in multi-camera networks, that the variability of a cameras’ parameters and performance could significantly affect the accuracy and robustness of the feature extraction and stereo matching methods. The proposed framework consists of local reconstruction and initial pose estimation of the MBVS based on transferable features, followed by overall optimization and accurate integration of multi-view 3D reconstruction data. The whole process requires no information other than the input images. The framework has been verified with real data, and very good results have been obtained.

  15. NGO collaboration in community post-disaster reconstruction: field research following the 2008 Wenchuan earthquake in China.

    Science.gov (United States)

    Lu, Yi; Xu, Jiuping

    2015-04-01

    The number of communities affected by disasters has been rising. As a result, non-governmental organisations (NGOs) that attend community post-disaster reconstruction are often unable to deliver all requirements and have to develop cooperative approaches. However, this collaboration can cause problems because of the complex environments, the fight for limited resources and uncoordinated management, all of which result in poor service delivery to the communities, adding to their woes. From extensive field research and case studies conducted in the post-Wenchuan earthquake-stricken communities, this paper introduces an integrated collaboration framework for community post-disaster reconstruction with the focus on three types of NGOs: international, government organised and civil. The proposed collaboration framework examines the three interrelated components of organisational structure, operational processes and reconstruction goals/implementation areas. Of great significance in better promoting collaborative participation between NGOs are the crucial concepts of participatory reconstruction, double-layer collaborative networks, and circular review and revision. © 2015 The Author(s). Disasters © Overseas Development Institute, 2015.

  16. Surface flute modes in the bumpy magnetic field

    International Nuclear Information System (INIS)

    Girka, I.O.; Girka, V.O.; Lapshin, V.I.

    2005-01-01

    Surface electromagnetic waves are often determined as the most possible cause of undesirable heating of edge plasma that leads, in turn, to strengthening of plasma - wall interaction in stellarators and increased plasma contamination. The propagation of surface flute modes near the interface of plasma column separated by a vacuum layer from the ring cylindrical ideally conductive metallic chamber is studied. The external steady bumpy magnetic field B-vector 0 = B 0z e-vector z + B 0r e-vector r was considered, B 0z =B 00 [1+ε m (r)cos(k m z)], here ε m '≡dε m /dr, k m =2π/L, L is the period of nonuniformity. non-uniformity of B-vector 0 is planned to be dominant in the confining magnetic field of the modular stellarator Helias, ε m ∼ 0.13. In the bumpy magnetic field the electromagnetic disturbance propagates in the form of the wave envelope, in which one alongside with the fundamental harmonic, proportional to exp[i(mθ±-ωt)], infinite set of satellite spatial harmonics, proportional to exp[i(mθ ± jk m z - ωt)], j=1,2,3..., is present. It is shown, that in the first approximation in the respect to ε m , amplitudes of the fundamental harmonics of the E-wave with the field components E r , E θ , B z do not vary, small satellite harmonics of these fields arise, proportional to exp[i(mθ ± k m z - ωt)]. At the same time due to weak coupling of - and - modes, caused by B-vector 0 nonuniformity and nonzero axial wave number of satellite harmonics, small satellite harmonics of H-wave with the field components E z , B r , B θ also arise. The amplitudes of satellite harmonics of E-wave are shown to be symmetric: E r (+) =E r (-) , E θ (+) =E θ (-) , B z (+) =B z (-) , and the amplitudes of H-wave are antisymmetric: B r (+) =-B r (-) , B θ (+) =- B θ (-) , E z (+) =-E z (-) . In the second approximation in the respect to ε m corrections to the amplitudes of the fundamental harmonic of E-wave arise. The correction to the eigen frequency of the wave

  17. Surface Reconstruction for Preparation of Plasmonic Au/TiO₂ Nanoparticle with Perfect Hetero Interface and Improved Photocatalytic Capacity.

    Science.gov (United States)

    Yuan, Guoqiu; Ping, Chen; Zhao, Qin; Cao, Min; Jin, Yonglong; Ge, Cunwang

    2018-07-01

    The photocatalytic activity of plasmonic Au/TiO2 nanoparticles (NPs) is dependent on distances between Au and TiO2. The preparation of plasmonic NPs is still a challenge because of an inherent lattice mismatch on heterogeneous interfaces. The combination between Au and TiO2 NPs often exhibits physical adsorption, which affect block the electron transferring process by photo-induction from TiO2 to Au NPs and weaken the photocatalytic activity. In this work an approach for preparing plasmonic Au/TiO2 NPs with perfect hetero-interface was proposed based on reconstruction of anatase TiO2 with (101) surface and in-situ reduction of Au NPs. Under UV-irradiation, anatase TiO2 NPs with a high percentage of (001) facets in formaldehyde solution undergo photochemical reactions to reconstruct the (101) surface of TiO2 and simultaneously allow polyformaldehyde to absorb on the same surface. Thus, Au(OH)-4 ions could be adsorbed on the (101) surfaces of TiO2 through electrostatic adsorption and reduced to form nano-Au in situ after recrystallization at 180 °C. The high-resolution transmission electron microscopy (HRTEM) images showed clear nanoscale lattice transition on heterogeneous interfaces of Au/TiO2 NPs. The surface structure of TiO2 NPs and the growth mechanism of Au/TiO2 NPs were evaluated with HRTEM, X-ray photoelectron spectra (XPS) and Fourier transform infrared spectroscopy (FTIR). It was demonstrated that the as-prepared plasmonic Au/TiO2 NPs had higher photocatalytic activity and corrosion resistance in comparison with primary TiO2 NPs by photo-electrochemical measurements. The reinforcing mechanism could be interpreted with Mott-Schottky analysis in terms of quantum mechanics. Our study implied that the reconstruction based synthesis may open up more opportunities to obtain lattice-mismatch nanomaterials for photocatalysis.

  18. DIEP Flap Breast Reconstruction in Patients with Breast Ptosis: 2-Stage Reconstruction Using 3-Dimensional Surface Imaging and a Printed Mold

    Directory of Open Access Journals (Sweden)

    Koichi Tomita, MD, PhD

    2017-10-01

    Conclusions:. The method described here may allow even inexperienced surgeons to achieve reconstruction of symmetrical, non-ptotic breasts with ease and in a short time. While the requirement of two surgeries is a potential disadvantage, our method will be particularly useful in cases involving TEs, i.e., delayed reconstruction or immediate reconstruction involving significant skin resection.

  19. Usefulness of ventricular endocardial electric reconstruction from body surface potential maps to noninvasively localize ventricular ectopic activity in patients

    Science.gov (United States)

    Lai, Dakun; Sun, Jian; Li, Yigang; He, Bin

    2013-06-01

    As radio frequency (RF) catheter ablation becomes increasingly prevalent in the management of ventricular arrhythmia in patients, an accurate and rapid determination of the arrhythmogenic site is of important clinical interest. The aim of this study was to test the hypothesis that the inversely reconstructed ventricular endocardial current density distribution from body surface potential maps (BSPMs) can localize the regions critical for maintenance of a ventricular ectopic activity. Patients with isolated and monomorphic premature ventricular contractions (PVCs) were investigated by noninvasive BSPMs and subsequent invasive catheter mapping and ablation. Equivalent current density (CD) reconstruction (CDR) during symptomatic PVCs was obtained on the endocardial ventricular surface in six patients (four men, two women, years 23-77), and the origin of the spontaneous ectopic activity was localized at the location of the maximum CD value. Compared with the last (successful) ablation site (LAS), the mean and standard deviation of localization error of the CDR approach were 13.8 and 1.3 mm, respectively. In comparison, the distance between the LASs and the estimated locations of an equivalent single moving dipole in the heart was 25.5 ± 5.5 mm. The obtained CD distribution of activated sources extending from the catheter ablation site also showed a high consistency with the invasively recorded electroanatomical maps. The noninvasively reconstructed endocardial CD distribution is suitable to predict a region of interest containing or close to arrhythmia source, which may have the potential to guide RF catheter ablation.

  20. Reconstruction Effects on Surface Properties of Co/Mg/Al Layered Double Hydroxide

    Directory of Open Access Journals (Sweden)

    Denis SOKOL

    2017-08-01

    Full Text Available Layered double hydroxides having different cationic (Mg2+, Co2+, Al3+ composition were successfully synthesized by the low supersaturation method. The samples were thermally decomposed and reconstructed using water and nitrate media at different temperatures. X-ray powder diffraction analysis, X-ray fluorescence analysis, thermogravimetry and BET/BJH methods were used to investigate the differences between the directly obtained layered materials and those after the reconstruction process.DOI: http://dx.doi.org/10.5755/j01.ms.23.2.15184

  1. Field Measurement of Surface Ship Magnetic Signature Using Multiple AUVs

    Science.gov (United States)

    2009-10-01

    been equipped with a tri-axial fluxgate magnetometer and used to perform preliminary magnetic field measurements. Measurements of this type will be...mounted on the AUVs, shown in Fig. 1, was a three-axis fluxgate type [16] magnetometer with a range of ±100,000 nT and a sensitivity of 100μV/nT. The...surface ship. The system will employ a formation of multiple AUVs, each equipped with a magnetometer . The objective is to measure total magnetic

  2. Conformal fields. From Riemann surfaces to integrable hierarchies

    International Nuclear Information System (INIS)

    Semikhatov, A.M.

    1991-01-01

    I discuss the idea of translating ingredients of conformal field theory into the language of hierarchies of integrable differential equations. Primary conformal fields are mapped into (differential or matrix) operators living on the phase space of the hierarchy, whereas operator insertions of, e.g., a current or the energy-momentum tensor, become certain vector fields on the phase space and thus acquire a meaning independent of a given Riemann surface. A number of similarities are observed between the structures arising on the hierarchy and those of the theory on the world-sheet. In particular, there is an analogue of the operator product algebra with the Cauchy kernel replaced by its 'off-shell' hierarchy version. Also, hierarchy analogues of certain operator insertions admit two (equivalent, but distinct) forms, resembling the 'bosonized' and 'fermionized' versions respectively. As an application, I obtain a useful reformulation of the Virasoro constraints of the type that arise in matrix models, as a system of equations on dressing (or Lax) operators (rather than correlation functions, i.e., residues or traces). This also suggests an interpretation in terms of a 2D topological field theory, which might be extended to a correspondence between Virasoro-constrained hierarchies and topological theories. (orig.)

  3. Quantitative Assessment of Variational Surface Reconstruction from Sparse Point Clouds in Freehand 3D Ultrasound Imaging during Image-Guided Tumor Ablation

    Directory of Open Access Journals (Sweden)

    Shuangcheng Deng

    2016-04-01

    Full Text Available Surface reconstruction for freehand 3D ultrasound is used to provide 3D visualization of a VOI (volume of interest during image-guided tumor ablation surgery. This is a challenge because the recorded 2D B-scans are not only sparse but also non-parallel. To solve this issue, we established a framework to reconstruct the surface of freehand 3D ultrasound imaging in 2011. The key technique for surface reconstruction in that framework is based on variational interpolation presented by Greg Turk for shape transformation and is named Variational Surface Reconstruction (VSR. The main goal of this paper is to evaluate the quality of surface reconstructions, especially when the input data are extremely sparse point clouds from freehand 3D ultrasound imaging, using four methods: Ball Pivoting, Power Crust, Poisson, and VSR. Four experiments are conducted, and quantitative metrics, such as the Hausdorff distance, are introduced for quantitative assessment. The experiment results show that the performance of the proposed VSR method is the best of the four methods at reconstructing surface from sparse data. The VSR method can produce a close approximation to the original surface from as few as two contours, whereas the other three methods fail to do so. The experiment results also illustrate that the reproducibility of the VSR method is the best of the four methods.

  4. Magnetic islands at the field reversal surface in reversed field pinches

    International Nuclear Information System (INIS)

    Pinsker, R.I.; Reiman, A.H.

    1985-09-01

    In the reversed field pinch (RFP), magnetic field perturbations having zero poloidal mode number and any toroidal mode number are resonant at the field reversal surface. Such perturbations are a particular threat to the RFP because of their weak radial dependence at low toroidal mode number, and because the toroidal field ripple is essentially of this type. The widths of the resulting islands are calculated in this paper. The self-consistent plasma response is included through the assumption that the plasma relaxes to a Taylor force-free state. The connection with linear tearing mode theory is established for those limits where arbitrarily large islands result from infinitesimal perturbations. Toroidal effects are considered, and application of the theory to RFP experiments is discussed

  5. Combining Field Monitoring with Remote Sensing to Reconstruct Historical Hydroperiod: a Case Study in a Degrading Tropical Wetland

    Science.gov (United States)

    Alonso, A.; Munoz-Carpena, R.; Kaplan, D. A.

    2017-12-01

    Wetland ecosystem structure and function are primarily governed by water regime. Characterizing past and current wetland hydrology is thus crucial for identifying the drivers of long-term wetland degradation. Critically, a lack of spatially distributed and long-term data has impeded such characterization in most wetland systems across the world. The publically accessible Moderate Resolution Imaging Spectroradiometer (MODIS) satellite products encode spatial and temporal data for landscape monitoring, but it was unclear whether it could be used to reliably predict the hydric status of wetland due to the mixture of spectral signatures existing within and between such systems. We proposed and tested a methodological framework for the identification of site-specific wetness status spectral identification rule (WSSIR) using two recent technical innovations: affordable, easily deployable field water level sensors to train the WSSIR with supervised learning, and the powerful cloud-based Google Earth Engine (GEE) platform to rapidly access and process the MODIS imagery. This methodological framework was used in a study case of the globally important Palo Verde National Park tropical wetland in Costa Rica. Results showed that a site-specific WISSR could reliably detect wetland wet or dry status (hydroperiod) and capture the temporal variability of the wetness status. We applied it on the 500 m 2000-2016 MODIS Land Surface Reflectance daily product to reconstruct hydroperiod history, hence reaching a temporal resolution rarely matched in remote sensing for environmental studies. The analysis of the resulting long-term, spatially distributed MODIS-derived data, coupled with shorter-term, 15-minute resolution field water level time-series provided new insights into the drivers controlling the spatiotemporal dynamics of hydrology within Palo Verde National Park's degrading wetlands. This new knowledge is critical to make informed restoration and management decisions

  6. A Convex Reconstruction Model for X-ray Tomographic Imaging with Uncertain Flat-fields

    DEFF Research Database (Denmark)

    Aggrawal, Hari Om; Andersen, Martin Skovgaard; Rose, Sean

    2018-01-01

    has a negligible effect on the reconstruction quality. However, in time- or dose-limited applications such as dynamic CT, this uncertainty may cause severe and systematic artifacts known as ring artifacts. By carefully modeling the measurement process and by taking uncertainties into account, we...

  7. Modeling the Non-Equilibrium Process of the Chemical Adsorption of Ammonia on GaN(0001) Reconstructed Surfaces Based on Steepest-Entropy-Ascent Quantum Thermodynamics

    OpenAIRE

    Kusaba, Akira; Li, Guanchen; von Spakovsky, Michael R.; Kangawa, Yoshihiro; Kakimoto, Koichi

    2017-01-01

    Clearly understanding elementary growth processes that depend on surface reconstruction is essential to controlling vapor-phase epitaxy more precisely. In this study, ammonia chemical adsorption on GaN(0001) reconstructed surfaces under metalorganic vapor phase epitaxy (MOVPE) conditions (3Ga-H and Nad-H + Ga-H on a 2 × 2 unit cell) is investigated using steepest-entropy-ascent quantum thermodynamics (SEAQT). SEAQT is a thermodynamic-ensemble based, first-principles framework that can predict...

  8. Sewing constraints for conformal field theories on surfaces with boundaries

    International Nuclear Information System (INIS)

    Lewellen, D.C.

    1992-01-01

    In a conformal field theory, correlation functions on any Riemann surface are in principle unambiguously defined by sewing together three-point functions on the sphere, provided that the four-point functions on the sphere are crossing symmetric, and the one-point functions on the torus are modular covariant. In this work we extend Sonoda's proof of this result to conformal field theories defined on surfaces with boundaries. Four additional sewing constraints arise; three on the half-plane and one on the cylinder. These relate the various OPE coefficients in the theory (bulk, boundary, and bulk-boundary) to one another. In rational theories these relations can be expressed in terms of data arising solely within the bulk theory: The matrix S which implements modular transformations on the characters, and the matrices implementing duality transformations on the four-point conformal-block functions. As an example we solve these relations for the boundary and bulk-boundary structure constants in the Ising model with all possible conformally invariant boundary conditions. The role of the basic sewing constraints in the construction of open string theories is discussed. (orig.)

  9. Field dependent surface resistance of niobium on copper cavities

    Directory of Open Access Journals (Sweden)

    T. Junginger

    2015-07-01

    Full Text Available The surface resistance R_{S} of superconducting cavities prepared by sputter coating a niobium film on a copper substrate increases significantly stronger with the applied rf field compared to cavities of bulk material. A possible cause is that the thermal boundary resistance between the copper substrate and the niobium film induces heating of the inner cavity wall, resulting in a higher R_{S}. Introducing helium gas in the cavity, and measuring its pressure as a function of applied field allowed to conclude that the inner surface of the cavity is heated up by less than 120 mK when R_{S} increases with E_{acc} by 100  nΩ. This is more than one order of magnitude less than what one would expect from global heating. Additionally, the effects of cooldown speed and low temperature baking have been investigated in the framework of these experiments. It is shown that for the current state of the art niobium on copper cavities there is only a detrimental effect of low temperature baking. A fast cooldown results in a lowered R_{S}.

  10. Surface modification by vacuum annealing for field emission from heavily phosphorus-doped homoepitaxial (1 1 1) diamond

    International Nuclear Information System (INIS)

    Yamada, Takatoshi; Nebel, Christoph E.; Somu, Kumaragurubaran; Shikata, Shin-ichi

    2008-01-01

    The relationship between field emission properties and C 1s core level shifts of heavily phosphorus-doped homoepitaxial (1 1 1) diamond is investigated as a function of annealing temperature in order to optimize surface carbon bonding configurations for device applications. A low field emission threshold voltage is observed from surfaces annealed at 800 deg. C for hydrogen-plasma treated surface, while a low field emission threshold voltage of wet-chemical oxidized surface is observed after annealing at 900 deg. C. The C 1s core level by X-ray photoelectron spectroscopy (XPS) showed a shoulder peak at 1 eV below the main peak over 800 and 900 deg. C annealing temperature for hydrogen-plasma treated and wet-chemical oxidized surfaces, respectively. When the shoulder peak intensity is less than 10% of the main peak intensity, lower threshold voltages are observed. This is due to the carbon-reconstruction which gives rise to a small positive electron affinity. By increasing annealing temperature, the shoulder peak ratios also increase, which indicates that a surface graphitization takes place. This leads to higher threshold voltages

  11. Measuring the sizes of nanospheres on a rough surface by using atomic force microscopy and a curvature-reconstruction method

    International Nuclear Information System (INIS)

    Oikawa, Koudai; Kim, Hyonchol; Watanabe, Naoya; Shigeno, Masatsugu; Shirakawabe, Yoshiharu; Yasuda, Kenji

    2007-01-01

    One of the advantages of atomic force microscopy (AFM) is that it can accurately measure the heights of targets on flat substrates. It is difficult, however, to determine the shape of nanoparticles on rough surfaces. We therefore propose a curvature-reconstruction method that estimates the sizes of particles by fitting sphere curvatures acquired from raw AFM data. We evaluated this fitting estimation using 15-, 30-, and 50-nm gold nanoparticles on mica and confirmed that particle sizes could be estimated within 5% from 20% of their curvature measured using a carbon nanotube (CNT) tip. We also estimated the sizes of nanoparticles on the rough surface of dried cells and found we also can estimate the size of those particles within 5%, which is difficult when we only used the height information. The results indicate the size of nanoparticles even on rough surfaces can be measured by using our method and a CNT tip

  12. Imaging near-surface heterogeneities by natural migration of backscattered surface waves: Field data test

    KAUST Repository

    Liu, Zhaolun; AlTheyab, Abdullah; Hanafy, Sherif M.; Schuster, Gerard T.

    2017-01-01

    We have developed a methodology for detecting the presence of near-surface heterogeneities by naturally migrating backscattered surface waves in controlled-source data. The near-surface heterogeneities must be located within a depth of approximately one-third the dominant wavelength λ of the strong surface-wave arrivals. This natural migration method does not require knowledge of the near-surface phase-velocity distribution because it uses the recorded data to approximate the Green’s functions for migration. Prior to migration, the backscattered data are separated from the original records, and the band-passed filtered data are migrated to give an estimate of the migration image at a depth of approximately one-third λ. Each band-passed data set gives a migration image at a different depth. Results with synthetic data and field data recorded over known faults validate the effectiveness of this method. Migrating the surface waves in recorded 2D and 3D data sets accurately reveals the locations of known faults. The limitation of this method is that it requires a dense array of receivers with a geophone interval less than approximately one-half λ.

  13. Imaging near-surface heterogeneities by natural migration of backscattered surface waves: Field data test

    KAUST Repository

    Liu, Zhaolun

    2017-03-06

    We have developed a methodology for detecting the presence of near-surface heterogeneities by naturally migrating backscattered surface waves in controlled-source data. The near-surface heterogeneities must be located within a depth of approximately one-third the dominant wavelength λ of the strong surface-wave arrivals. This natural migration method does not require knowledge of the near-surface phase-velocity distribution because it uses the recorded data to approximate the Green’s functions for migration. Prior to migration, the backscattered data are separated from the original records, and the band-passed filtered data are migrated to give an estimate of the migration image at a depth of approximately one-third λ. Each band-passed data set gives a migration image at a different depth. Results with synthetic data and field data recorded over known faults validate the effectiveness of this method. Migrating the surface waves in recorded 2D and 3D data sets accurately reveals the locations of known faults. The limitation of this method is that it requires a dense array of receivers with a geophone interval less than approximately one-half λ.

  14. Reconstruction of the eddy current distribution on the vacuum vessel in a reversed field pinch device based on the external magnetic sensor signals

    International Nuclear Information System (INIS)

    Itagaki, Masafumi; Sanpei, Akio; Masamune, Sadao; Watanabe, Kiyomasa

    2014-01-01

    For the MHD equilibrium reconstruction of a reverse field pinch device, it is a big issue to identify accurately the strong eddy current flow on the shell. In the present work, boundary integrals of the eddy current along the shell are added to the conventional Cauchy-condition surface method formulation. The eddy current profile is unknown in advance but straightforwardly identified using only the signals from magnetic sensors located outside the plasma. Two ideas are introduced to overcome the numerical difficulties encountered in the problem. One is an accurate boundary integral scheme to damp out the near singularity occurring at the sensor position very close to the shell. The other is the modified truncated singular value decomposition technique to solve an ill-conditioned matrix equation when a large number of nodal points exist on the shell. The capability of the new method is demonstrated for a test problem modeling the RELAX device. (author)

  15. Three-dimensional reconstruction of brain surface anatomy: technique comparison between flash and diffusion-weighted imaging

    International Nuclear Information System (INIS)

    Sun Jianzhong; Wang Zhikang; Gong Xiangyang

    2006-01-01

    Objective: To compare two methods 3D flash and diffusion-weighted images (DWI) in reconstructing the brain surface anatomy, and to evaluate their displaying ability, advantages, limitations and clinical application. Methods: Thrity normal cases were prospectively examined with 3D flash sequence and echo-planar DWI. Three-dimensional images were acquired with volume-rendering on workstation. Brain surface structures were evaluated and scored by a group of doctors. Results: Main structures of brain surface were clearly displayed on three-dimensional images based on 3D flash sequence. Average scores were all above 2.50. For images based on DWI, precentral gyrus, postcentral gyrus, superior parietal lobule, superior frontal gyrus, precentral sulcus, central sulcus, postcentral sulcus, intraparietal sulcus and superior frontal sulcus were best shown with average scores between 2.60-2.75, However, supramarginal gyrus, angular gyrus, middle frontal gyrus, inferior frontal gyrus, superior temporal gyrus, lateral sulcus, inferior frontal sulcus could not be well shown, with average scores between 1.67-2.48. Middle temporal gyrus, inferior temporal gyrus, superior temporal sulcus and inferior temporal sulcus can only get scores from 0.88 to 1.27. Scores of images based on 3D flash were much higher than that based on DWI with distinct differentiations, P values were all below 0.01. Conclusion: Three-dimensional images based on 3D flash can really display brain surface structures. It is very useful for anatomic researches. Three-dimensional reconstruction of brain surface based on DWI is a worthy technique to display brain surface anatomy, especially for frontal and parietal structures. (authors)

  16. Tomography reconstruction methods for damage diagnosis of wood structure in construction field

    Science.gov (United States)

    Qiu, Qiwen; Lau, Denvid

    2018-03-01

    The structural integrity of wood building element plays a critical role in the public safety, which requires effective methods for diagnosis of internal damage inside the wood body. Conventionally, the non-destructive testing (NDT) methods such as X-ray computed tomography, thermography, radar imaging reconstruction method, ultrasonic tomography, nuclear magnetic imaging techniques, and sonic tomography have been used to obtain the information about the internal structure of wood. In this paper, the applications, advantages and disadvantages of these traditional tomography methods are reviewed. Additionally, the present article gives an overview of recently developed tomography approach that relies on the use of mechanical and electromagnetic waves for assessing the structural integrity of wood buildings. This developed tomography reconstruction method is believed to provide a more accurate, reliable, and comprehensive assessment of wood structural integrity

  17. Near-field Oblique Remote Sensing of Stream Water-surface Elevation, Slope, and Surface Velocity

    Science.gov (United States)

    Minear, J. T.; Kinzel, P. J.; Nelson, J. M.; McDonald, R.; Wright, S. A.

    2014-12-01

    A major challenge for estimating discharges during flood events or in steep channels is the difficulty and hazard inherent in obtaining in-stream measurements. One possible solution is to use near-field remote sensing to obtain simultaneous water-surface elevations, slope, and surface velocities. In this test case, we utilized Terrestrial Laser Scanning (TLS) to remotely measure water-surface elevations and slope in combination with surface velocities estimated from particle image velocimetry (PIV) obtained by video-camera and/or infrared camera. We tested this method at several sites in New Mexico and Colorado using independent validation data consisting of in-channel measurements from survey-grade GPS and Acoustic Doppler Current Profiler (ADCP) instruments. Preliminary results indicate that for relatively turbid or steep streams, TLS collects tens of thousands of water-surface elevations and slopes in minutes, much faster than conventional means and at relatively high precision, at least as good as continuous survey-grade GPS measurements. Estimated surface velocities from this technique are within 15% of measured velocity magnitudes and within 10 degrees from the measured velocity direction (using extrapolation from the shallowest bin of the ADCP measurements). Accurately aligning the PIV results into Cartesian coordinates appears to be one of the main sources of error, primarily due to the sensitivity at these shallow oblique look angles and the low numbers of stationary objects for rectification. Combining remotely-sensed water-surface elevations, slope, and surface velocities produces simultaneous velocity measurements from a large number of locations in the channel and is more spatially extensive than traditional velocity measurements. These factors make this technique useful for improving estimates of flow measurements during flood flows and in steep channels while also decreasing the difficulty and hazard associated with making measurements in these

  18. Bayesian reconstruction of seafloor shape from side-scan sonar measurements using a Markov Random Field

    OpenAIRE

    Woock, P.; Pak, Alexey

    2014-01-01

    To explore the seafloor, a side-scan sonar emits a directed acoustic signal and then records the returning (reflected) signal intensity as a function of time. The inversion of that process is not unique: multiple shapes may lead to identical measured responses. In this work, we suggest a Bayesian approach to reconstructing the 3D shape of the seafloor from multiple sonar measurements, inspired by the state-of-the-art methods of inverse raytracing that originated in computer vision. The space ...

  19. Drought reconstruction in eastern Hulun Buir steppe, China and its linkages to the sea surface temperatures in the Pacific Ocean

    Science.gov (United States)

    Liu, Na; Liu, Yu; Bao, Guang; Bao, Ming; Wang, Yanchao; Zhang, Lizhi; Ge, Yuxiang; Bao, Wurigen; Tian, Heng

    2016-01-01

    A tree-ring width chronology covering the period 1780-2013 AD was developed from Pinus sylvestris var. mongolica for the eastern Hulun Buir steppe, a region located on the edge of the eastern Mongolian Plateau, China. Climate-growth response analysis revealed drought stress to be the primary limiting factor for tree growth. Therefore, the mean February-July standardized precipitation evapotranspiration index (SPEI) was reconstructed over the period 1819-2013, where the reconstruction could account for 32.8% of the variance in the instrumental record over the calibration period 1953-2011. Comparison with other tree-ring-based moisture sequences from nearby areas confirmed a high degree of confidence in our reconstruction. Severe drought intervals since the late 1970s in our study area consisted with the weakening East Asian summer monsoon, which modulating regional moisture conditions in semi-arid zone over northern China. Drought variations in the study area significantly correlated with sea surface temperatures (SSTs) in North Pacific Ocean, suggesting a possible connection of regional hydroclimatic variations to the Pacific Decadal Oscillation (PDO). The potential influence associated with El Niño-Southern Oscillation (ENSO) was primarily analyzed.

  20. The modeling of quadratic B-splines surfaces for the tomographic reconstruction in the FCC- type-riser

    International Nuclear Information System (INIS)

    Vasconcelos, Geovane Vitor; Dantas, Carlos Costa; Melo, Silvio de Barros; Pires, Renan Ferraz

    2009-01-01

    The 3D tomography reconstruction has been a profitable alternative in the analysis of the FCC-type- riser (Fluid Catalytic Cracking), for appropriately keeping track of the sectional catalyst concentration distribution in the process of oil refining. The method of tomography reconstruction proposed by M. Azzi and colleagues (1991) uses a relatively small amount of trajectories (from 3 to 5) and projections (from 5 to 7) of gamma rays, a desirable feature in the industrial process tomography. Compared to more popular methods, such as the FBP (Filtered Back Projection), which demands a much higher amount of gamma rays projections, the method by Azzi et al. is more appropriate for the industrial process, where the physical limitations and the cost of the process require more economical arrangements. The use of few projections and trajectories facilitates the diagnosis in the flow dynamical process. This article proposes an improvement in the basis functions introduced by Azzi et al., through the use of quadratic B-splines functions. The use of B-splines functions makes possible a smoother surface reconstruction of the density distribution, since the functions are continuous and smooth. This work describes how the modeling can be done. (author)

  1. Surface-based reconstruction and diffusion MRI in the assessment of gray and white matter damage in multiple sclerosis

    Science.gov (United States)

    Caffini, Matteo; Bergsland, Niels; LaganÃ, Marcella; Tavazzi, Eleonora; Tortorella, Paola; Rovaris, Marco; Baselli, Giuseppe

    2014-03-01

    Despite advances in the application of nonconventional MRI techniques in furthering the understanding of multiple sclerosis pathogenic mechanisms, there are still many unanswered questions, such as the relationship between gray and white matter damage. We applied a combination of advanced surface-based reconstruction and diffusion tensor imaging techniques to address this issue. We found significant relationships between white matter tract integrity indices and corresponding cortical structures. Our results suggest a direct link between damage in white and gray matter and contribute to the notion of gray matter loss relating to clinical disability.

  2. Denoising of B1+ field maps for noise-robust image reconstruction in electrical properties tomography

    International Nuclear Information System (INIS)

    Michel, Eric; Hernandez, Daniel; Cho, Min Hyoung; Lee, Soo Yeol

    2014-01-01

    Purpose: To validate the use of adaptive nonlinear filters in reconstructing conductivity and permittivity images from the noisy B 1 + maps in electrical properties tomography (EPT). Methods: In EPT, electrical property images are computed by taking Laplacian of the B 1 + maps. To mitigate the noise amplification in computing the Laplacian, the authors applied adaptive nonlinear denoising filters to the measured complex B 1 + maps. After the denoising process, they computed the Laplacian by central differences. They performed EPT experiments on phantoms and a human brain at 3 T along with corresponding EPT simulations on finite-difference time-domain models. They evaluated the EPT images comparing them with the ones obtained by previous EPT reconstruction methods. Results: In both the EPT simulations and experiments, the nonlinear filtering greatly improved the EPT image quality when evaluated in terms of the mean and standard deviation of the electrical property values at the regions of interest. The proposed method also improved the overall similarity between the reconstructed conductivity images and the true shapes of the conductivity distribution. Conclusions: The nonlinear denoising enabled us to obtain better-quality EPT images of the phantoms and the human brain at 3 T

  3. Atomistic modeling of metal surfaces under electric fields: direct coupling of electric fields to a molecular dynamics algorithm

    CERN Document Server

    Djurabekova, Flyura; Pohjonen, Aarne; Nordlund, Kai

    2011-01-01

    The effect of electric fields on metal surfaces is fairly well studied, resulting in numerous analytical models developed to understand the mechanisms of ionization of surface atoms observed at very high electric fields, as well as the general behavior of a metal surface in this condition. However, the derivation of analytical models does not include explicitly the structural properties of metals, missing the link between the instantaneous effects owing to the applied field and the consequent response observed in the metal surface as a result of an extended application of an electric field. In the present work, we have developed a concurrent electrodynamic–molecular dynamic model for the dynamical simulation of an electric-field effect and subsequent modification of a metal surface in the framework of an atomistic molecular dynamics (MD) approach. The partial charge induced on the surface atoms by the electric field is assessed by applying the classical Gauss law. The electric forces acting on the partially...

  4. Matching Images to Models: Camera Calibration for 3-D Surface Reconstruction

    Science.gov (United States)

    Morris, Robin D.; Smelyanskiy, Vadim N.; Cheeseman. Peter C.; Norvig, Peter (Technical Monitor)

    2001-01-01

    In a previous paper we described a system which recursively recovers a super-resolved three dimensional surface model from a set of images of the surface. In that paper we assumed that the camera calibration for each image was known. In this paper we solve two problems. Firstly, if an estimate of the surface is already known, the problem is to calibrate a new image relative to the existing surface model. Secondly, if no surface estimate is available, the relative camera calibration between the images in the set must be estimated. This will allow an initial surface model to be estimated. Results of both types of estimation are given.

  5. Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices

    International Nuclear Information System (INIS)

    Tong Wang

    2002-01-01

    Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radio frequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling. The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE. To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance. EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at ∼140 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, i.e., no fundamental electric field limit induced by EFE, has been observed up to ∼140 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to ∼140 MV

  6. Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Tong [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)

    2002-09-18

    Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radiofrequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling. The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE. To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance. EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at ~140 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, i.e., no fundamental electric field limit induced by EFE, has been observed up to ~140 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to ~140 MV/m. To

  7. The importance of ship log data: reconstructing North Atlantic, European and Mediterranean sea level pressure fields back to 1750

    Energy Technology Data Exchange (ETDEWEB)

    Kuettel, M.; Wanner, H. [University of Bern, Oeschger Centre for Climate Change Research (OCCR), and Institute of Geography, Climatology and Meteorology, Bern (Switzerland); Xoplaki, E. [University of Bern, Oeschger Centre for Climate Change Research (OCCR), and Institute of Geography, Climatology and Meteorology, Bern (Switzerland); EEWRC, The Cyprus Institute, Nicosia (Cyprus); Gallego, D. [Universidad Pablo de Olavide de Sevilla, Departamento de Sistemas Fisicos, Quimicos y Naturales, Sevilla (Spain); Luterbacher, J. [University of Bern, Oeschger Centre for Climate Change Research (OCCR), and Institute of Geography, Climatology and Meteorology, Bern (Switzerland); Justus-Liebig University of Giessen, Department of Geography, Climatology, Climate Dynamics and Climate Change, Giessen (Germany); Garcia-Herrera, R. [Universidad Complutense de Madrid, Departamento de Fisica de la Tierra II, Facultad de CC Fisicas, Madrid (Spain); Allan, R. [Met Office Hadley Centre, Exeter (United Kingdom); Barriendos, M. [University of Barcelona, Department of Modern History, Barcelona (Spain); Jones, P.D. [University of East Anglia, Climatic Research Unit, School of Environmental Sciences, Norwich (United Kingdom); Wheeler, D. [University of Sunderland, Faculty of Applied Sciences, Sunderland (United Kingdom)

    2010-06-15

    Local to regional climate anomalies are to a large extent determined by the state of the atmospheric circulation. The knowledge of large-scale sea level pressure (SLP) variations in former times is therefore crucial when addressing past climate changes across Europe and the Mediterranean. However, currently available SLP reconstructions lack data from the ocean, particularly in the pre-1850 period. Here we present a new statistically-derived 5 x 5 resolved gridded seasonal SLP dataset covering the eastern North Atlantic, Europe and the Mediterranean area (40 W-50 E; 20 N-70 N) back to 1750 using terrestrial instrumental pressure series and marine wind information from ship logbooks. For the period 1750-1850, the new SLP reconstruction provides a more accurate representation of the strength of the winter westerlies as well as the location and variability of the Azores High than currently available multiproxy pressure field reconstructions. These findings strongly support the potential of ship logbooks as an important source to determine past circulation variations especially for the pre-1850 period. This new dataset can be further used for dynamical studies relating large-scale atmospheric circulation to temperature and precipitation variability over the Mediterranean and Eurasia, for the comparison with outputs from GCMs as well as for detection and attribution studies. (orig.)

  8. Reconstructing turbidity in a glacially influenced lake using the Landsat TM and ETM+ surface reflectance climate data record archive, Lake Clark, Alaska

    Science.gov (United States)

    Baughman, Carson; Jones, Benjamin M.; Bartz, Krista K.; Young, Daniel B.; Zimmerman, Christian E.

    2015-01-01

    Lake Clark is an important nursery lake for sockeye salmon (Oncorhynchus nerka) in the headwaters of Bristol Bay, Alaska, the most productive wild salmon fishery in the world. Reductions in water clarity within Alaska lake systems as a result of increased glacial runoff have been shown to reduce salmon production via reduced abundance of zooplankton and macroinvertebrates. In this study, we reconstruct long-term, lake-wide water clarity for Lake Clark using the Landsat TM and ETM+ surface reflectance products (1985–2014) and in situwater clarity data collected between 2009 and 2013. Analysis of a Landsat scene acquired in 2009, coincident with in situ measurements in the lake, and uncertainty analysis with four scenes acquired within two weeks of field data collection showed that Band 3 surface reflectance was the best indicator of turbidity (r2 = 0.55,RMSE turbidity for Lake Clark between 1991 and 2014. We did, however, detect interannual variation that exhibited a non-significant (r2 = 0.20) but positive correlation (r = 0.20) with regional mean summer air temperature and found the month of May exhibited a significant positive trend (r2 = 0.68, p = 0.02) in turbidity between 2000 and 2014. This study demonstrates the utility of hindcasting turbidity in a glacially influenced lake using the Landsat surface reflectance products. It may also help land and resource managers reconstruct turbidity records for lakes that lack in situ monitoring, and may be useful in predicting future water clarity conditions based on projected climate scenarios.

  9. INTERACTION OF IMPULSE ELECTROMAGNETIC FIELDS WITH SURFACES OF METAL SAMPLES

    Directory of Open Access Journals (Sweden)

    V. V. Pavliouchenko

    2006-01-01

    Full Text Available Measurements of maximum tangential component of magnetic intensity Hτm have been carried out in the paper. The measurements have been taken on the surface of metal samples according to time of single current pulse rise in the form of semi-sinusoid of a linear current wire. Measurements have been made with the purpose to determine a value of the component according to thickness of samples made of aluminium.Temporary resolution ranges of electric and magnetic properties and defects of sample continuity along the depth have been found.Empirical formulae of dependence Hτm on sample thickness have been derived and their relation with efficient depth penetration of magnetic field into metal has been found.

  10. A Newton method for a simultaneous reconstruction of an interface and a buried obstacle from far-field data

    International Nuclear Information System (INIS)

    Zhang, Haiwen; Zhang, Bo

    2013-01-01

    This paper is concerned with the inverse problem of scattering of time-harmonic acoustic waves from a penetrable and a buried obstacle. By introducing a related transmission scattering problem, a Newton iteration method is proposed to simultaneously reconstruct both the penetrable interface and the buried obstacle inside from far-field data. The main feature of our method is that we do not need to know the type of boundary conditions on the buried obstacle. In particular, the boundary condition on the buried obstacle can also be determined simultaneously by the method. Finally, numerical examples using multi-frequency data are carried out to illustrate the effectiveness of our method. (paper)

  11. Simulation and Optimization of Silicon Solar Cell Back Surface Field

    Directory of Open Access Journals (Sweden)

    Souad TOBBECHE

    2015-11-01

    Full Text Available In this paper, TCAD Silvaco (Technology Computer Aided Design software has been used to study the Back Surface Field (BSF effect of a p+ silicon layer for a n+pp+ silicon solar cell. To study this effect, the J-V characteristics and the external quantum efficiency (EQE are simulated under AM 1.5 illumination for two types of cells. The first solar cell is without BSF (n+p structure while the second one is with BSF (n+pp+ structure. The creation of the BSF on the rear face of the cell results in efficiency h of up to 16.06% with a short-circuit current density Jsc = 30.54 mA/cm2, an open-circuit voltage Voc = 0.631 V, a fill factor FF = 0.832 and a clear improvement of the spectral response obtained in the long wavelengths range. An electric field and a barrier of potential are created by the BSF and located at the junction p+/p with a maximum of 5800 V/cm and 0.15 V, respectively. The optimization of the BSF layer shows that the cell performance improves with the p+ thickness between 0.35 – 0.39 µm, the p+ doping dose is about 2 × 1014 cm-2, the maximum efficiency up to 16.19 %. The cell efficiency is more sensitive to the value of the back surface recombination velocity above a value of 103 cm/s in n+p than n+pp+ solar cell.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9565

  12. Closed-loop surface-related multiple elimination and its application to simultaneous data reconstruction

    NARCIS (Netherlands)

    Lopez Angarita, G.A.; Verschuur, D.J.

    2015-01-01

    Surface-related multiple elimination (SRME) is one of the most commonly used methods for suppressing surface multiples. However, to obtain an accurate surface multiple estimation, dense source and receiver sampling is required. The traditional approach to this problem is performing data

  13. Field investigation to assess nutrient emission from paddy field to surface water in river catchment

    Science.gov (United States)

    Kogure, Kanami; Aichi, Masaatsu; Zessner, Matthias

    2015-04-01

    In order to maintain good river environment, it is remarkably important to understand and to control nutrient behavior such as Nitrogen and Phosphorus. Our former research dealing with nutrient emission analysis in the Tone River basin area in Japan, in addition to urban and industrial waste water, nutrient emission from agricultural activity is dominant pollution source into the river system. Japanese style agriculture produces large amount of rice and paddy field occupies large areas in Japanese river basin areas. While paddy field can deteriorate river water quality by outflow of fertilizer, it is also suggested that paddy field has water purification function. As we carried out investigation in the Tone River Basin area, data were obtained which dissolved nitrogen concentration is lower in discharging water from paddy field than inflowing water into the field. Regarding to nutrient emission impact from paddy field, sufficient data are required to discuss quantitatively seasonal change of material behavior including flooding season and dry season, difference of climate condition, soil type, and rice species, to evaluate year round comprehensive impact from paddy field to the river system. In this research, field survey in paddy field and data collection relating rice production were carried out as a preliminary investigation to assess how Japanese style paddy field contributes year round on surface water quality. Study sites are three paddy fields located in upper reach of the Tone River basin area. The fields are flooded from June to September. In 2014, field investigations were carried out three times in flooding period and twice in dry period. To understand characteristics of each paddy field and seasonal tendency accompanying weather of agricultural event, short term investigations were conducted and we prepare for further long term investigation. Each study site has irrigation water inflow and outflow. Two sites have tile drainage system under the field and

  14. Mapping gullies, dunes, lava fields, and landslides via surface roughness

    Science.gov (United States)

    Korzeniowska, Karolina; Pfeifer, Norbert; Landtwing, Stephan

    2018-01-01

    Gully erosion is a widespread and significant process involved in soil and land degradation. Mapping gullies helps to quantify past, and anticipate future, soil losses. Digital terrain models offer promising data for automatically detecting and mapping gullies especially in vegetated areas, although methods vary widely measures of local terrain roughness are the most varied and debated among these methods. Rarely do studies test the performance of roughness metrics for mapping gullies, limiting their applicability to small training areas. To this end, we systematically explored how local terrain roughness derived from high-resolution Light Detection And Ranging (LiDAR) data can aid in the unsupervised detection of gullies over a large area. We also tested expanding this method for other landforms diagnostic of similarly abrupt land-surface changes, including lava fields, dunes, and landslides, as well as investigating the influence of different roughness thresholds, resolutions of kernels, and input data resolution, and comparing our method with previously published roughness algorithms. Our results show that total curvature is a suitable metric for recognising analysed gullies and lava fields from LiDAR data, with comparable success to that of more sophisticated roughness metrics. Tested dunes or landslides remain difficult to distinguish from the surrounding landscape, partly because they are not easily defined in terms of their topographic signature.

  15. Development of a Near-Field Bistatic Synthetic Aperture Radar for Complex Target Reconstruction

    Directory of Open Access Journals (Sweden)

    David G. Johnson

    2012-01-01

    Full Text Available This paper begins with a description of the design, construction, and characterization of a small electromagnetic anechoic chamber, developed specifically to house a bistatic ISAR system for the analysis of rock samples. Particular emphasis is given to the practicalities of construction, with the intention of assisting those in a similar position, wishing to build an anechoic chamber on a tight budget. The second part of the paper outlines efficient algorithms that may be applied to the tomographic and topographic reconstruction of complex targets within the viewing geometry of this ISAR system.

  16. Clinical effect of vitamin A palmitate eye gel on early ocular surface reconstruction after thermal or chemical injuries

    Directory of Open Access Journals (Sweden)

    Fen-Dui Zhang

    2015-11-01

    Full Text Available AIM: To evaluate the clinical effect of vitamin A palmitate eye gel on early ocular surface reconstruction after thermal or chemical injuries. METHODS: Seventy-eight cases with thermal or chemical injuries to eyes were selected and divided into two groups by randomized, double-blind, positive drug parallel controlled method: group A(40 cases were treated with vitamin A palmitate eye geland group B \\〖38 cases were treated with basic fibroblast growth factor(bFGF\\〗. The bFGF and vitamin A palmitate eye gel were used 4 times a day. The treatment course was 14d. Restoration of epithelial defect, Schirmer's test values, tear break-up time(BUT, and subjective assessment of symptoms and signs were observed on D1, D3, D5, D7, D10 and D14.RESULTS: In group A, 31 cases were cured, 5 cases were effective, with the cure rate of 76% and efficiency 90%. In group B, 32 cases were cured, 3 cases were effective, with the cure rate of 84% and efficiency 92%. There were no significant differences between the two groups(P>0.05. However, there were significant differences on the results of Schirmer's test and BUT(PPCONCLUSION: Vitamin A palmitate eye gel is valuable and safe on early ocular surface reconstruction of the eyes suffered from thermal or chemical injuries.

  17. Postoperative assessment of surgical results using three dimensional surface reconstruction CT (3D-CT) in a craniofacial anomaly

    International Nuclear Information System (INIS)

    Nishimura, Jiro; Sato, Kaoru; Nishimoto, Hiroshi; Tsukiyama, Takashi; Fujioka, Mutsuhisa; Akagawa, Tetsuya.

    1988-01-01

    In 1983, Michael W. Vannier and Jeffrey L. Marsh developed a computer method that reconstructs three dimensional (3D) born and soft tissue surfaces, given a high resolution CT scan-series of the facial skeleton. This method has been applied to craniofacial anomalies, basal encephaloceles, and musculoskeletal anomalies. In this study, a postoperative assessment of the craniofacial surgical results has been accomplished using this 3D-CT in 2 children with craniofacial dysmorphism. The authors discuss the advantages of this 3D-CT imaging method in the postoperative assessments of craniofacial anomalies. Results are detailed in the following listing : 1) a postoperative 3D-CT reveals the anatomical details corrected by the craniofacial surgery more precisely and stereographically than conventional radiological methods ; 2) secondary changes of the cranium after the surgery, such as bony formation in the area of the osteotomy and postoperative asymmetric deformities, are detected early by the 3D-CT imaging technique, and, 3) 3D-CT mid-sagittal and top axial views of the intracranial skull base are most useful in postoperative assessments of the surgical results. Basesd on our experience, we expect that three dimensional surface reconstructions from CT scans will become to be used widely in the postoperative assessments of the surgical results of craniofacial anomalies. (author)

  18. Effects of surface and bulk transverse fields on critical behaviour of ferromagnetic films

    International Nuclear Information System (INIS)

    Saber, A.; Lo Russo, S.; Mattei, G.

    2002-02-01

    The influence of surface and bulk transverse fields on the critical behaviour of a ferromagnetic Ising film is studied using the effective field theory based on a single-site cluster method. Surface exchange enhancement is considered and a critical value is obtained. The dependence of the critical uniform transverse field on film thickness, phase diagrams in the fields, critical surface transverse field versus the bulk one, and exchange coupling ratio are presented. (author)

  19. Ferromagnetic transitions of a spin-one Ising film in a surface and bulk transverse fields

    International Nuclear Information System (INIS)

    Saber, A.; Lo Russo, S.; Mattei, G.; Mattoni, A.

    2002-01-01

    Using the effective field theory method, we have calculated the Curie temperature of a spin-one Ising ferromagnetic film in a surface and bulk transverse fields. Numerical calculations give phase diagrams under various parameters. Surface exchange enhancement is considered. The dependence of the critical transverse field on film thickness, and phase diagrams in the fields, critical surface transverse field versus the bulk one are presented

  20. Reconstructing surface elevation changes for the Greenland Ice Sheet (1993-2013) and analysis of Zachariae Isstrom, northeast Greenland

    Science.gov (United States)

    Duncan, Kyle

    Previous studies investigating the velocity and elevation change records of the Greenland Ice Sheet (GrIS) revealed rapid and complex changes. It is therefore imperative to determine changes with both high spatial and temporal resolutions. By fusing multiple laser altimetry data sets, the Surface Elevation Reconstruction and Change (SERAC) program is capable of reconstructing surface elevation changes with high spatial and temporal resolution over the entire GrIS. The input data include observations from NASA's Ice, Cloud and land Elevation Satellite (ICESat) mission (2003-2009) as well as data collected by NASA's Airborne Topographic Mapper (ATM) (1993-2013) and Land, Vegetation and Ice Sensor (LVIS) (2007-2012) airborne laser altimetry systems. This study extends the record of surface elevation changes over the GrIS by adding 2012 and 2013 laser altimetry data to the previous 1993-2011 record. Extending the record leads to a new, more accurate and detailed altimetry record for 1993-2013. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Digital Elevation Models (DEMs) are fused with laser altimetry data over Zachariae Isstrom, northeast Greenland to analyze surface elevation changes and associated thinning rates during 1978-2014. Little to no elevation change occurred over Zachariae Isstrom from 1978-1999, however, from 1999-2014 elevation changes near the calving front became increasingly negative and accelerated. Calving front position showed steady retreat and grounding line position has been retreating towards the interior of the ice sheet at an increasing rate from 2010-2014 when compared to the 1996-2010 period. The measured elevation changes near the calving front have brought a large portion of the glacier close to the height of flotation. If the current thinning trend continues this portion of the glacier will reach flotation within the next 2-5 years allowing for further retreat and increased vulnerability to retreat for sections of

  1. PHOTOGRAMMETRIC ANALYSIS OF HISTORICAL IMAGE REPOSITORIES FOR VIRTUAL RECONSTRUCTION IN THE FIELD OF DIGITAL HUMANITIES

    Directory of Open Access Journals (Sweden)

    F. Maiwald

    2017-02-01

    Full Text Available Historical photographs contain high density of information and are of great importance as sources in humanities research. In addition to the semantic indexing of historical images based on metadata, it is also possible to reconstruct geometric information about the depicted objects or the camera position at the time of the recording by employing photogrammetric methods. The approach presented here is intended to investigate (semi- automated photogrammetric reconstruction methods for heterogeneous collections of historical (city photographs and photographic documentation for the use in the humanities, urban research and history sciences. From a photogrammetric point of view, these images are mostly digitized photographs. For a photogrammetric evaluation, therefore, the characteristics of scanned analog images with mostly unknown camera geometry, missing or minimal object information and low radiometric and geometric resolution have to be considered. In addition, these photographs have not been created specifically for documentation purposes and so the focus of these images is often not on the object to be evaluated. The image repositories must therefore be subjected to a preprocessing analysis of their photogrammetric usability. Investigations are carried out on the basis of a repository containing historical images of the Kronentor ("crown gate" of the Dresden Zwinger. The initial step was to assess the quality and condition of available images determining their appropriateness for generating three-dimensional point clouds from historical photos using a structure-from-motion evaluation (SfM. Then, the generated point clouds were assessed by comparing them with current measurement data of the same object.

  2. Reconstructing sea surface temperature, sea surface salinity and partial pressure of carbon dioxide in atmosphere in the Okinawa Trough during the Holocene and their paleoclimatic implications

    Institute of Scientific and Technical Information of China (English)

    MENGXianwei; LIUYanguang; LlUZhenxia; DUDewen; HUANGQiyu; Y.Saito

    2003-01-01

    The sediment core DGKS9603 collected from the Okinawa Trough was used as research target. By use of unsaturated index U37k of long-chain alkenone, δ13C of POC and of planktonic foraminifera (G sacculifer), the evolutions of sea surface temperature and partial pressure of carbon dioxide in the atmosphere during the Holocene were reconstructed in the Okinawa Trough. And in combination of δ18O of planktonic foraminifera, the relative difference of sea surface salinity during the Holocene was also reconstructed.Consequently, three cooling events (E1-E3) were identified,each of which occurred at 1.7-1.6, 5.1-4.8 and 8.1-7.4kaBP (cal), respectively. Of the three events, E2 and E3 are globally comparable, their occurrence mechanism would be that the main stream of the Kuroshio Current shifted eastward due to the enhanced circulation of the northeastern Pacific Ocean, which was driven in turn by amplified intensity of sunshine and subsequent enhancement of subtropical high pressure; E1 corresponds to the Small Ice-Age Event occurring between 1550 and 1850AD in China. In the Okinawa Trough, E1 might be also related to the eastward shift of main stream of the Kuroshio current driven by powerful Asia winter monsoon.

  3. Reconstructing sea surface temperature, sea surface salinity and partial pressure of carbon dioxide in atmos- phere in the Okinawa Trough during the Holocene and their paleoclimatic implications

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The sediment core DGKS9603 collected from the Okinawa Trough was used as research target. By use of unsaturated index of long-chain alkenone, δ13C of POC and of planktonic foraminifera (G. Sacculifer), the evolutions of sea surface temperature and partial pressure of carbon dioxide in the atmosphere during the Holocene were reconstructed in the Okinawa Trough. And in combination of δ18O of planktonic foraminifera, the relative difference of sea surface salinity during the Holocene was also reconstructed. Consequently, three cooling events (E1-E3) were identified, each of which occurred at 1.7-1.6, 5.1-4.8 and 8.1-7.4 kaBP (cal), respectively. Of the three events, E2 and E3 are globally comparable, their occurrence mechanism would be that the main stream of the Kuroshio Current shifted eastward due to the enhanced circulation of the northeastern Pacific Ocean, which was driven in turn by amplified intensity of sunshine and subsequent enhancement of subtropical high pressure; E1 corresponds to the Small Ice-Age Event occurring between 1550 and 1850AD in China. In the Okinawa Trough, E1 might be also related to the eastward shift of main stream of the Kuroshio current driven by powerful Asia winter monsoon.

  4. Comparison of Two Coronal Magnetic Field Models to Reconstruct a Sigmoidal Solar Active Region with Coronal Loops

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Aiying; Zhang, Huai [Key Laboratory of Computational Geodynamics, University of Chinese Academy of Sciences, Beijing 100049 (China); Jiang, Chaowei [Institute of Space Science and Applied Technology, Harbin Institute of Technology, Shenzhen, 518055 (China); Hu, Qiang; Gary, G. Allen; Wu, S. T. [Center for Space Plasma and Aeronomic Research, The University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Cao, Jinbin, E-mail: duanaiying@ucas.ac.cn, E-mail: hzhang@ucas.ac.cn, E-mail: chaowei@hit.edu.cn [School of Space and Environment, Beihang University, Beijing 100191 (China)

    2017-06-20

    Magnetic field extrapolation is an important tool to study the three-dimensional (3D) solar coronal magnetic field, which is difficult to directly measure. Various analytic models and numerical codes exist, but their results often drastically differ. Thus, a critical comparison of the modeled magnetic field lines with the observed coronal loops is strongly required to establish the credibility of the model. Here we compare two different non-potential extrapolation codes, a nonlinear force-free field code (CESE–MHD–NLFFF) and a non-force-free field (NFFF) code, in modeling a solar active region (AR) that has a sigmoidal configuration just before a major flare erupted from the region. A 2D coronal-loop tracing and fitting method is employed to study the 3D misalignment angles between the extrapolated magnetic field lines and the EUV loops as imaged by SDO /AIA. It is found that the CESE–MHD–NLFFF code with preprocessed magnetogram performs the best, outputting a field that matches the coronal loops in the AR core imaged in AIA 94 Å with a misalignment angle of ∼10°. This suggests that the CESE–MHD–NLFFF code, even without using the information of the coronal loops in constraining the magnetic field, performs as good as some coronal-loop forward-fitting models. For the loops as imaged by AIA 171 Å in the outskirts of the AR, all the codes including the potential field give comparable results of the mean misalignment angle (∼30°). Thus, further improvement of the codes is needed for a better reconstruction of the long loops enveloping the core region.

  5. A statistical-dynamical scheme for reconstructing ocean forcing in the Atlantic. Part I: weather regimes as predictors for ocean surface variables

    Energy Technology Data Exchange (ETDEWEB)

    Cassou, Christophe; Minvielle, Marie; Terray, Laurent [CERFACS/CNRS, Climate Modelling and Global Change Team, Toulouse (France); Perigaud, Claire [JPL-NASA, Ocean Science Element, Pasadena, CA (United States)

    2011-01-15

    The links between the observed variability of the surface ocean variables estimated from reanalysis and the overlying atmosphere decomposed in classes of large-scale atmospheric circulation via clustering are investigated over the Atlantic from 1958 to 2002. Daily 500 hPa geopotential height and 1,000 hPa wind anomaly maps are classified following a weather-typing approach to describe the North Atlantic and tropical Atlantic atmospheric dynamics, respectively. The algorithm yields patterns that correspond in the extratropics to the well-known North Atlantic-Europe weather regimes (NAE-WR) accounting for the barotropic dynamics, and in the tropics to wind classes (T-WC) representing the alteration of the trades. 10-m wind and 2-m temperature (T2) anomaly composites derived from regime/wind class occurrence are indicative of strong relationships between daily large-scale atmospheric circulation and ocean surface over the entire Atlantic basin. High temporal correlation values are obtained basin-wide at low frequency between the observed fields and their reconstruction by multiple linear regressions with the frequencies of occurrence of both NAE-WR and T-WC used as sole predictors. Additional multiple linear regressions also emphasize the importance of accounting for the strength of the daily anomalous atmospheric circulation estimated by the combined distances to all regimes centroids in order to reproduce the daily to interannual variability of the Atlantic ocean. We show that for most of the North Atlantic basin the occurrence of NAE-WR generally sets the sign of the ocean surface anomaly for a given day, and that the inter-regime distances are valuable predictors for the magnitude of that anomaly. Finally, we provide evidence that a large fraction of the low-frequency trends in the Atlantic observed at the surface over the last 50 years can be traced back, except for T2, to changes in occurrence of tropical and extratropical weather classes. All together, our

  6. A Facile Surface Reconstruction Mechanism toward Better Electrochemical Performance of Li

    NARCIS (Netherlands)

    Qian, Kun; Tang, Linkai; Wagemaker, M.; He, Yan Bing; Liu, Dongqing; Li, Hai; Shi, Ruiying; Li, Baohua; Kang, Feiyu

    2017-01-01

    Through a facile sodium sulfide (Na2S)-assisted hydrothermal treatment, clean and nondefective surfaces are constructed on micrometer-sized Li4Ti5O12 particles. The remarkable improvement of surface quality shows a higher first cycle Coulombic

  7. Estimating the Ocean Flow Field from Combined Sea Surface Temperature and Sea Surface Height Data

    Science.gov (United States)

    Stammer, Detlef; Lindstrom, Eric (Technical Monitor)

    2002-01-01

    This project was part of a previous grant at MIT that was moved over to the Scripps Institution of Oceanography (SIO) together with the principal investigator. The final report provided here is concerned only with the work performed at SIO since January 2000. The primary focus of this project was the study of the three-dimensional, absolute and time-evolving general circulation of the global ocean from a combined analysis of remotely sensed fields of sea surface temperature (SST) and sea surface height (SSH). The synthesis of those two fields was performed with other relevant physical data, and appropriate dynamical ocean models with emphasis on constraining ocean general circulation models by a combination of both SST and SSH data. The central goal of the project was to improve our understanding and modeling of the relationship between the SST and its variability to internal ocean dynamics, and the overlying atmosphere, and to explore the relative roles of air-sea fluxes and internal ocean dynamics in establishing anomalies in SST on annual and longer time scales. An understanding of those problems will feed into the general discussion on how SST anomalies vary with time and the extend to which they interact with the atmosphere.

  8. Surface structural reconstruction of SrVO3 thin films on SrTiO3 (001)

    Science.gov (United States)

    Wang, Gaomin; Saghayezhian, Mohammad; Chen, Lina; Guo, Hangwen; Zhang, Jiandi

    Paramagnetic metallic oxide SrVO3>(SVO) is an itinerant system known to undergo thickness-induced metal-insulator-transition (MIT) in ultrathin film form, which makes it a prototype system for the study of the mechanism behind metal-insulator-transition like structure distortion, electron correlations and disorder-induced localization. We have grown SrVO3 thin film with atomically flat surface through the layer-by-layer deposition by laser Molecular Beam Epitaxy (laser-MBE) on SrTiO3 (001) surface. Low Energy Electron Diffraction (LEED) measurements reveal that there is a (√2X √2) R45°surface reconstruction independent of film thickness. By using LEED-I(V) structure refinement, we determine the surface structure. In combination with X-ray Photoelectron Spectroscopy (XPS) and Scanning Tunneling Microscopy (STM), we discuss the implication on the MIT in ultrathin films below 2-3 unit cell thickness. This work is supported by the National Science Foundation under the NSF EPSCoR Cooperative Agreement No. EPS-1003897 with additional support from the Louisiana Board of Regents.

  9. Surfactant-induced layered growth in homoepitaxy of Fe on Fe(100)-c(2 x 2)O reconstruction surface

    International Nuclear Information System (INIS)

    Kamiko, Masao; Mizuno, Hiroyuki; Chihaya, Hiroaki; Xu, Junhua; Kojima, Isao; Yamamoto, Ryoichi

    2007-01-01

    In this study, the effects of several surfactants (Pb, Bi, and Ag) on the homoepitaxial growth of Fe(100) were studied and compared. The reflection high-energy electron diffraction measurements clearly reveal that these surfactants enhance the layer-by-layer growth of Fe on an Fe(100)-c(2 x 2)O reconstruction surface. The dependence of growth on the surfactant layer thickness suggests that there exists a suitable amount of surfactant layer that induces a smoother layer-by-layer growth. Comparisons between the atomic force microscopy images reveal that the root-mean-square surface roughness of Fe films mediated by Pb and Bi surfactants are considerably smaller than those of the films mediated by Ag surfactant. The Auger electron spectra show that Pb and Bi segregate at the top of the surface. It has been concluded that Pb and Bi are effective surfactants for enhancing layer-by-layer growth in Fe homoepitaxy. Ag has the same effect, but it is less efficient due to the weak surface segregation of Ag

  10. Reconstruction of the sea surface elevation from the analysis of the data collected by a wave radar system

    Science.gov (United States)

    Ludeno, Giovanni; Soldovieri, Francesco; Serafino, Francesco; Lugni, Claudio; Fucile, Fabio; Bulian, Gabriele

    2016-04-01

    X-band radar system is able to provide information about direction and intensity of the sea surface currents and dominant waves in a range of few kilometers from the observation point (up to 3 nautical miles). This capability, together with their flexibility and low cost, makes these devices useful tools for the sea monitoring either coastal or off-shore area. The data collected from wave radar system can be analyzed by using the inversion strategy presented in [1,2] to obtain the estimation of the following sea parameters: peak wave direction; peak period; peak wavelength; significant wave height; sea surface current and bathymetry. The estimation of the significant wave height represents a limitation of the wave radar system because of the radar backscatter is not directly related to the sea surface elevation. In fact, in the last period, substantial research has been carried out to estimate significant wave height from radar images either with or without calibration using in-situ measurements. In this work, we will present two alternative approaches for the reconstruction of the sea surface elevation from wave radar images. In particular, the first approach is based on the basis of an approximated version of the modulation transfer function (MTF) tuned from a series of numerical simulation, following the line of[3]. The second approach is based on the inversion of radar images using a direct regularised least square technique. Assuming a linearised model for the tilt modulation, the sea elevation has been reconstructed as a least square fitting of the radar imaging data[4]. References [1]F. Serafino, C. Lugni, and F. Soldovieri, "A novel strategy for the surface current determination from marine X-band radar data," IEEE Geosci.Remote Sens. Lett., vol. 7, no. 2, pp. 231-235, Apr. 2010. [2]Ludeno, G., Brandini, C., Lugni, C., Arturi, D., Natale, A., Soldovieri, F., Serafino, F. (2014). Remocean System for the Detection of the Reflected Waves from the Costa

  11. ECONOMIC INDICATORS OF ROAD SURFACES RECONSTRUCTIONS IN THE WORLD USING NON-WASTE TECHNOLOGY

    Directory of Open Access Journals (Sweden)

    Dilyara Kyazymovna Izmaylova

    2017-05-01

    Full Text Available The article describes the cost formation of restoration of road surfaces using the methods of replacing and processing the damaged layers. There is a mathematical model of cost of the one unit of production including the cost of building materials with delivery. The estimation of the total cost of repairs in the variable amount using the technology of full replacement of the surface and processing technology of the 50% of the material on the site.

  12. Task-Driven Optimization of Fluence Field and Regularization for Model-Based Iterative Reconstruction in Computed Tomography.

    Science.gov (United States)

    Gang, Grace J; Siewerdsen, Jeffrey H; Stayman, J Webster

    2017-12-01

    This paper presents a joint optimization of dynamic fluence field modulation (FFM) and regularization in quadratic penalized-likelihood reconstruction that maximizes a task-based imaging performance metric. We adopted a task-driven imaging framework for prospective designs of the imaging parameters. A maxi-min objective function was adopted to maximize the minimum detectability index ( ) throughout the image. The optimization algorithm alternates between FFM (represented by low-dimensional basis functions) and local regularization (including the regularization strength and directional penalty weights). The task-driven approach was compared with three FFM strategies commonly proposed for FBP reconstruction (as well as a task-driven TCM strategy) for a discrimination task in an abdomen phantom. The task-driven FFM assigned more fluence to less attenuating anteroposterior views and yielded approximately constant fluence behind the object. The optimal regularization was almost uniform throughout image. Furthermore, the task-driven FFM strategy redistribute fluence across detector elements in order to prescribe more fluence to the more attenuating central region of the phantom. Compared with all strategies, the task-driven FFM strategy not only improved minimum by at least 17.8%, but yielded higher over a large area inside the object. The optimal FFM was highly dependent on the amount of regularization, indicating the importance of a joint optimization. Sample reconstructions of simulated data generally support the performance estimates based on computed . The improvements in detectability show the potential of the task-driven imaging framework to improve imaging performance at a fixed dose, or, equivalently, to provide a similar level of performance at reduced dose.

  13. Fast backprojection-based reconstruction of spectral-spatial EPR images from projections with the constant sweep of a magnetic field.

    Science.gov (United States)

    Komarov, Denis A; Hirata, Hiroshi

    2017-08-01

    In this paper, we introduce a procedure for the reconstruction of spectral-spatial EPR images using projections acquired with the constant sweep of a magnetic field. The application of a constant field-sweep and a predetermined data sampling rate simplifies the requirements for EPR imaging instrumentation and facilitates the backprojection-based reconstruction of spectral-spatial images. The proposed approach was applied to the reconstruction of a four-dimensional numerical phantom and to actual spectral-spatial EPR measurements. Image reconstruction using projections with a constant field-sweep was three times faster than the conventional approach with the application of a pseudo-angle and a scan range that depends on the applied field gradient. Spectral-spatial EPR imaging with a constant field-sweep for data acquisition only slightly reduces the signal-to-noise ratio or functional resolution of the resultant images and can be applied together with any common backprojection-based reconstruction algorithm. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Diffusion and adsorption of dimers on reconstructed Pt(1 1 0) surfaces: First principle and EAM studies

    Science.gov (United States)

    Matrane, I.; Mazroui, M.; Sbiaai, K.

    2018-03-01

    We present a density functional theory (DFT) and embedded atom method (EAM) studies of Pt2 , Au2 and AuPt dimers adsorption and diffusion on the clean Pt (1 1 0) (1 × 1) surface and (1 × 2) (1 × 3) and (1 × 4) missing row reconstructed geometries. As a first step, adsorption energies are calculated for all considered dimers, and their stability is checked by computing the binding energies. Furthermore, the energy barriers for the elementary diffusion mechanisms (concerted jump, dissociation-reassociation and leapfrog) are calculated for dimers diffusion on all considered geometries. The potential energy profile for the leapfrog mechanism is provided for dimers diffusion on the (1 × 2) (1 × 3) and (1 × 4) missing row reconstructed geometries. Our results show that each of the three dimers exhibits a qualitatively different behaviours. In addition, the obtained results provide interesting atomistic information about dimers stability and mobility, which is required for understanding the macroscopic kinetics of crystal growth.

  15. The developing human connectome project: A minimal processing pipeline for neonatal cortical surface reconstruction.

    Science.gov (United States)

    Makropoulos, Antonios; Robinson, Emma C; Schuh, Andreas; Wright, Robert; Fitzgibbon, Sean; Bozek, Jelena; Counsell, Serena J; Steinweg, Johannes; Vecchiato, Katy; Passerat-Palmbach, Jonathan; Lenz, Gregor; Mortari, Filippo; Tenev, Tencho; Duff, Eugene P; Bastiani, Matteo; Cordero-Grande, Lucilio; Hughes, Emer; Tusor, Nora; Tournier, Jacques-Donald; Hutter, Jana; Price, Anthony N; Teixeira, Rui Pedro A G; Murgasova, Maria; Victor, Suresh; Kelly, Christopher; Rutherford, Mary A; Smith, Stephen M; Edwards, A David; Hajnal, Joseph V; Jenkinson, Mark; Rueckert, Daniel

    2018-06-01

    The Developing Human Connectome Project (dHCP) seeks to create the first 4-dimensional connectome of early life. Understanding this connectome in detail may provide insights into normal as well as abnormal patterns of brain development. Following established best practices adopted by the WU-MINN Human Connectome Project (HCP), and pioneered by FreeSurfer, the project utilises cortical surface-based processing pipelines. In this paper, we propose a fully automated processing pipeline for the structural Magnetic Resonance Imaging (MRI) of the developing neonatal brain. This proposed pipeline consists of a refined framework for cortical and sub-cortical volume segmentation, cortical surface extraction, and cortical surface inflation, which has been specifically designed to address considerable differences between adult and neonatal brains, as imaged using MRI. Using the proposed pipeline our results demonstrate that images collected from 465 subjects ranging from 28 to 45 weeks post-menstrual age (PMA) can be processed fully automatically; generating cortical surface models that are topologically correct, and correspond well with manual evaluations of tissue boundaries in 85% of cases. Results improve on state-of-the-art neonatal tissue segmentation models and significant errors were found in only 2% of cases, where these corresponded to subjects with high motion. Downstream, these surfaces will enhance comparisons of functional and diffusion MRI datasets, supporting the modelling of emerging patterns of brain connectivity. Copyright © 2018 Elsevier Inc. All rights reserved.

  16. Reconstruction of deglacial sea surface temperature in the tropical Pacific from selective analysis of a fossil coral

    Energy Technology Data Exchange (ETDEWEB)

    Allison, N.; Finch, A.A.; Tudhope, A.W.; Newville, M.; Sutton, S.R.; Ellam, R.M. (St Andrews); (Edinburgh); (Scottish); (UC); (St Andrews)

    2010-07-13

    The Sr/Ca of coral skeletons demonstrates potential as an indicator of sea surface temperatures (SSTs). However, the glacial-interglacial SST ranges predicted from Sr/Ca of fossil corals are usually higher than from other marine proxies. We observed infilling of secondary aragonite, characterized by high Sr/Ca ratios, along intraskeletal pores of a fossil coral from Papua New Guinea that grew during the penultimate deglaciation (130 {+-} 2 ka). Selective microanalysis of unaltered areas of the fossil coral indicates that SSTs at {approx}130 ka were {le} 1 C cooler than at present in contrast with bulk measurements (combining infilled and unaltered areas) which indicate a difference of 6-7 C. The analysis of unaltered areas of fossil skeletons by microprobe techniques may offer a route to more accurate reconstruction of past SSTs.

  17. Self-citation rate and impact factor in the field of plastic and reconstructive surgery.

    Science.gov (United States)

    Miyamoto, Shimpei

    2018-02-01

    Journal ranking based on the impact factor (IF) can be distorted by self-citation. The aim of this study is to investigate the present status of self-citation in the plastic surgery journals and its effect on the journals' IFs. IF, IF without self-citations (corrected IF), self-cited rate, and self-citing rate for 11 plastic surgery journals were investigated from 2009-2015, by reviewing the Journal Citation Report ® . The correlations of the IF with the self-cited rate and the self-citing rate were statistically assessed. In addition, Plastic and Reconstructive Surgery was compared with 15 top journals from other surgical specialties in 2015. IF was significantly correlated with the self-cited rate (R: 0.594, p = 0.001) and the self-citing rate (R: 0.824, p citation rate positively affects the IF in plastic surgery journals. A high concentration of self-citation of some journals could distort the ranking among plastic surgery journals in general.

  18. The ongoing emergence of robotics in plastic and reconstructive surgery.

    Science.gov (United States)

    Struk, S; Qassemyar, Q; Leymarie, N; Honart, J-F; Alkhashnam, H; De Fremicourt, K; Conversano, A; Schaff, J-B; Rimareix, F; Kolb, F; Sarfati, B

    2018-04-01

    Robot-assisted surgery is more and more widely used in urology, general surgery and gynecological surgery. The interest of robotics in plastic and reconstructive surgery, a discipline that operates primarily on surfaces, has yet to be conclusively proved. However, the initial applications of robotic surgery in plastic and reconstructive surgery have been emerging in a number of fields including transoral reconstruction of posterior oropharyngeal defects, nipple-sparing mastectomy with immediate breast reconstruction, microsurgery, muscle harvesting for pelvic reconstruction and coverage of the scalp or the extremities. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

  19. Section curve reconstruction and mean-camber curve extraction of a point-sampled blade surface.

    Directory of Open Access Journals (Sweden)

    Wen-long Li

    Full Text Available The blade is one of the most critical parts of an aviation engine, and a small change in the blade geometry may significantly affect the dynamics performance of the aviation engine. Rapid advancements in 3D scanning techniques have enabled the inspection of the blade shape using a dense and accurate point cloud. This paper proposes a new method to achieving two common tasks in blade inspection: section curve reconstruction and mean-camber curve extraction with the representation of a point cloud. The mathematical morphology is expanded and applied to restrain the effect of the measuring defects and generate an ordered sequence of 2D measured points in the section plane. Then, the energy and distance are minimized to iteratively smoothen the measured points, approximate the section curve and extract the mean-camber curve. In addition, a turbine blade is machined and scanned to observe the curvature variation, energy variation and approximation error, which demonstrates the availability of the proposed method. The proposed method is simple to implement and can be applied in aviation casting-blade finish inspection, large forging-blade allowance inspection and visual-guided robot grinding localization.

  20. Surface dose measurements in and out of field. Implications for breast radiotherapy with megavoltage photon beams

    Energy Technology Data Exchange (ETDEWEB)

    Lonski, Peta; Kron, Tomas [Peter MacCallum Cancer Centre, Melbourne (Australia); RMIT Univ., Melbourne (Australia); Ramachandran, Prabhakar; Franich, Rick [Peter MacCallum Cancer Centre, Melbourne (Australia)

    2017-07-01

    This study examines the difference in surface dose between flat and flattening filter free (FFF) photon beams in the context of breast radiotherapy. The surface dose was measured for 6 MV, 6 MV FFF, 10 MV, 10 MV FFF and 18 MV photon beams using a thin window ionisation chamber for various field sizes. Profiles were acquired to ascertain the change in surface dose off-axis. Out-of-field measurements were included in a clinically representative half beam block tangential breast field. In the field centres of FFF beams the surface dose was found to be increased for small fields and decreased for large fields compared to flat beams. For FFF beams, surface dose was found to decrease off-axis and resulted in lower surface dose out-of-field compared to flat beams.

  1. ELUCID—Exploring the Local Universe with the reConstructed Initial Density Field. II. Reconstruction Diagnostics, Applied to Numerical Halo Catalogs

    Energy Technology Data Exchange (ETDEWEB)

    Tweed, Dylan; Yang, Xiaohu; Li, Shijie; Jing, Y. P. [Center for Astronomy and Astrophysics, Shanghai Jiao Tong University, Shanghai 200240 (China); Wang, Huiyuan [Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China); Cui, Weiguang [Departamento de Física Teórica, Módulo 15, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Zhang, Youcai [Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030 (China); Mo, H. J., E-mail: dtweed@sjtu.edu.cn [Department of Astronomy, University of Massachusetts, Amherst MA, 01003-9305 (United States)

    2017-05-20

    The ELUCID project aims to build a series of realistic cosmological simulations that reproduce the spatial and mass distributions of the galaxies as observed in the Sloan Digital Sky Survey. This requires powerful reconstruction techniques to create constrained initial conditions (ICs). We test the reconstruction method by applying it to several N -body simulations. We use two medium-resolution simulations, which each produced three additional constrained N -body simulations. We compare the resulting friend-of-friend catalogs by using the particle indexes as tracers, and quantify the quality of the reconstruction by varying the main smoothing parameter. The cross-identification method we use proves to be efficient, and the results suggest that the most massive reconstructed halos are effectively traced from the same Lagrangian regions in the ICs. A preliminary time-dependence analysis indicates that high-mass-end halos converge only at a redshift close to the reconstruction redshift. This suggests that, for earlier snapshots, only collections of progenitors may be effectively cross-identified.

  2. Correlation between average tissue depth data and quantitative accuracy of forensic craniofacial reconstructions measured by geometric surface comparison method.

    Science.gov (United States)

    Lee, Won-Joon; Wilkinson, Caroline M; Hwang, Hyeon-Shik; Lee, Sang-Mi

    2015-05-01

    Accuracy is the most important factor supporting the reliability of forensic facial reconstruction (FFR) comparing to the corresponding actual face. A number of methods have been employed to evaluate objective accuracy of FFR. Recently, it has been attempted that the degree of resemblance between computer-generated FFR and actual face is measured by geometric surface comparison method. In this study, three FFRs were produced employing live adult Korean subjects and three-dimensional computerized modeling software. The deviations of the facial surfaces between the FFR and the head scan CT of the corresponding subject were analyzed in reverse modeling software. The results were compared with those from a previous study which applied the same methodology as this study except average facial soft tissue depth dataset. Three FFRs of this study that applied updated dataset demonstrated lesser deviation errors between the facial surfaces of the FFR and corresponding subject than those from the previous study. The results proposed that appropriate average tissue depth data are important to increase quantitative accuracy of FFR. © 2015 American Academy of Forensic Sciences.

  3. In situ monitoring of the surface reconstructions on InP(001) prepared by molecular beam epitaxy

    Science.gov (United States)

    Ozanyan, K. B.; Parbrook, P. J.; Hopkinson, M.; Whitehouse, C. R.; Sobiesierski, Z.; Westwood, D. I.

    1997-07-01

    Reflection anisotropy spectroscopy (RAS) and reflection high-energy electron diffraction (RHEED) were applied to study clean InP(001) surfaces prepared by molecular beam epitaxy (MBE). At phosphorus beam equivalent pressures (BEPs) between 3.5×10-7 and 3.5×10-6 mbar and substrate temperature (Ts) falling from 590 to 150 °C, (2×4), (2×1), (2×2), and c(4×4) RHEED patterns are observed. The main RAS features, observed at 1.7-1.9 and 2.6-2.9 eV are assigned to In and P dimers, respectively. The above reconstruction sequence is associated closely with transformations identified in RAS signatures that are induced by progressively increasing the P surface coverage. The RAS results also imply the existence of (2×4)α and (2×4)β phases. A surface-phase diagram for MBE-grown (001) InP, in the whole range of Ts and phosphorus BEPs is proposed.

  4. Amniotic membrane transplantation for reconstruction of corneal epithelial surface in cases of partial limbal stem cell deficiency.

    Directory of Open Access Journals (Sweden)

    Sangwan Virender

    2004-01-01

    Full Text Available Purpose: To assess the efficacy of amniotic membrane for treatment of partial limbal stem cell deficiency (LSCD. Methods: Medical records of four patients with partial LSCD who underwent pannus resection and amniotic membrane transplantation (AMT were reviewed for ocular surface stability and improvement in visual acuity. Clinico-histopathological correlation was done with the resected pannus tissue. Results: All the eyes exhibited stable corneal epithelial surface by an average of 7 weeks postoperatively with improvement in subjective symptoms. Best corrected visual acuity improved from preoperative (range: 6/9p-6/120 to postoperative (range: 6/6p-6/15 by an average of 4.5 lines on Snellen visual acuity charts. Histopathological examination of excised tissue showed features of conjunctivalisation. Conclusion: Amniotic membrane transplantation appears to be an effective means of reconstructing the corneal epithelial surface and for visual rehabilitation of patients with partial limbal stem cell deficiency. It may be considered as an alternative primary procedure to limbal transplantation in these cases.

  5. Surface plasmon transmission through discontinuous conducting surfaces: Plasmon amplitude modulation by grazing scattered fields

    Energy Technology Data Exchange (ETDEWEB)

    Mayoral-Astorga, L. A.; Gaspar-Armenta, J. A.; Ramos-Mendieta, F. [Departamento de Investigación en Física, Universidad de Sonora, Apartado Postal 5-088, Hermosillo, Sonora, 83190 México (Mexico)

    2016-04-15

    We have studied numerically the diffraction of a surface plasmon polariton (SPP) when it encounters a wide multi-wavelength slit in conducting films. As a jump process a SPP is excited beyond the slit by wave scattering at the second slit edge. The exciting radiation is produced when the incident SPP collapses at the first slit edge. We have found that the transmitted SPP supports inherent and unavoidable interference with grazing scattered radiation; the spatial modulation extends to the fields in the diffraction region where a series of low intensity spots arises. We demonstrate that the SPP generated on the second slab depends on the frequency but not on the wave vector of the collapsed SPP; a SPP is transmitted even when the two metals forming the slit are different. The numerical results were obtained using the Finite Difference Time Domain (FDTD) method with a grid size λ/100.

  6. On Discrete Killing Vector Fields and Patterns on Surfaces

    KAUST Repository

    Ben-Chen, Mirela; Butscher, Adrian; Solomon, Justin; Guibas, Leonidas

    2010-01-01

    , and show how to discretize these concepts for generating such vector fields on a triangulated mesh. We discuss the properties of approximate Killing Vector Fields, and propose an application to utilize them for texture and geometry synthesis. Journal

  7. Some aspects of reconstruction using a scalar field in f(T) gravity

    Energy Technology Data Exchange (ETDEWEB)

    Chakrabarti, Soumya [Indian Institute of Technology, Centre for Theoretical Studies, Kharagpur (India); Said, Jackson Levi [University of Malta, Institute of Space Sciences and Astronomy, Msida, MSD (Malta); Farrugia, Gabriel [University of Malta, Department of Physics, Msida, MSD (Malta)

    2017-12-15

    General relativity characterizes gravity as a geometric property exhibited on spacetime by massive objects, while teleparallel gravity achieves the same results at the level of equations, by taking a torsional perspective of gravity. Similar to the f(R) theory teleparallel gravity can also be generalized to f(T), with the resulting field equations being inherently distinct from f(R) gravity in that they are second order, while in the former case they turn out to be fourth order. In the present case, a minimally coupled scalar field is investigated in the f(T) gravity context for several forms of the scalar field potential. A number of new f(T) solutions are found for these potentials. Their respective state parameters are also being examined. (orig.)

  8. Momentum reconstruction procedure for a nonfocusing spectrometer with wide-aperture analyzing magnet and nonuniform field

    International Nuclear Information System (INIS)

    Azhgirej, L.S.; Malinina, L.V.; Strokovskij, E.A.; Augustyniak, W.; Farhi, L.; Kunne, R.A.

    1999-01-01

    The SPES-4 spectrometer at SATURNE II has recently been equipped with a detection system working in coincidence with it. This system uses a wide-aperture dipole magnet. A method is described to determine the momentum vector and interaction vertex of the detected charged particle from its trajectory parameters measured outside the inhomogeneous field of the magnet. The feature of the set-up is that all detectors are placed outside the dipole field, while the target is inside the ∼ 1 T field and the incoming track is not measured. The feature of the method is that it is simple and fast, while it uses only the straight line part of the particle trajectory, which can be measured with sufficient accuracy

  9. 3D wake measurements from a scanning wind lidar in combination with a fast wind field reconstruction model

    DEFF Research Database (Denmark)

    Mikkelsen, Torben Krogh; Herges, T. G.; Astrup, Poul

    2017-01-01

    University of Denmark. The purpose of the SpinnerLidar measurements at SWIFT is to measure the response of a V27 turbine wake to varying inflow conditions and turbine operating states. Although our fast scanning SpinnerLidar is able to measure the line-of-sight projected wind speed at up to 400 points per......-Stokes CFD code “Lincom Cyclop-buster model,”3 the corresponding 3D wind vector field (u, v, w) can be reconstructed under constraints for conservation of mass and momentum. The resulting model calculated line-of-sight projections of the 3D wind velocity vectors will become consistent with the line...

  10. Facial recognition software success rates for the identification of 3D surface reconstructed facial images: implications for patient privacy and security.

    Science.gov (United States)

    Mazura, Jan C; Juluru, Krishna; Chen, Joseph J; Morgan, Tara A; John, Majnu; Siegel, Eliot L

    2012-06-01

    Image de-identification has focused on the removal of textual protected health information (PHI). Surface reconstructions of the face have the potential to reveal a subject's identity even when textual PHI is absent. This study assessed the ability of a computer application to match research subjects' 3D facial reconstructions with conventional photographs of their face. In a prospective study, 29 subjects underwent CT scans of the head and had frontal digital photographs of their face taken. Facial reconstructions of each CT dataset were generated on a 3D workstation. In phase 1, photographs of the 29 subjects undergoing CT scans were added to a digital directory and tested for recognition using facial recognition software. In phases 2-4, additional photographs were added in groups of 50 to increase the pool of possible matches and the test for recognition was repeated. As an internal control, photographs of all subjects were tested for recognition against an identical photograph. Of 3D reconstructions, 27.5% were matched correctly to corresponding photographs (95% upper CL, 40.1%). All study subject photographs were matched correctly to identical photographs (95% lower CL, 88.6%). Of 3D reconstructions, 96.6% were recognized simply as a face by the software (95% lower CL, 83.5%). Facial recognition software has the potential to recognize features on 3D CT surface reconstructions and match these with photographs, with implications for PHI.

  11. Quantum Yang-Mills theory of Riemann surfaces and conformal field theory

    International Nuclear Information System (INIS)

    Killingback, T.P.

    1989-01-01

    It is shown that Yang-Mills theory on a smooth surface, when suitably quantized, is a topological quantum field theory. This topological gauge theory is intimately related to two-dimensional conformal field theory. It is conjectured that all conformal field theories may be obtained from Yang-Mills theory on smooth surfaces. (orig.)

  12. Resilient algorithms for reconstructing and simulating gappy flow fields in CFD

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seungjoon; Karniadakis, George Em [Division of Applied Mathematics, Brown University, Providence, RI 02912 (United States); Kevrekidis, Ioannis G, E-mail: george_karniadakis@brown.edu [Department of Chemical and Biological Engineering, Brown University, Providence, RI 02912 (United States); PACM, Princeton University, Princeton, NJ 08544 (United States)

    2015-10-15

    It is anticipated that in future generations of massively parallel computer systems a significant portion of processors may suffer from hardware or software faults rendering large-scale computations useless. In this work we address this problem from the algorithmic side, proposing resilient algorithms that can recover from such faults irrespective of their fault origin. In particular, we set the foundations of a new class of algorithms that will combine numerical approximations with machine learning methods. To this end, we consider three types of fault scenarios: (1) a gappy region but with no previous gaps and no contamination of surrounding simulation data, (2) a space–time gappy region but with full spatiotemporal information and no contamination, and (3) previous gaps with contamination of surrounding data. To recover from such faults we employ different reconstruction and simulation methods, namely the projective integration, the co-Kriging interpolation, and the resimulation method. In order to compare the effectiveness of these methods for the different processor faults and to quantify the error propagation in each case, we perform simulations of two benchmark flows, flow in a cavity and flow past a circular cylinder. In general, the projective integration seems to be the most effective method when the time gaps are small, and the resimulation method is the best when the time gaps are big while the co-Kriging method is independent of time gaps. Furthermore, the projective integration method and the co-Kriging method are found to be good estimation methods for the initial and boundary conditions of the resimulation method in scenario (3). (paper)

  13. Stability of skyrmions on curved surfaces in the presence of a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho-Santos, V.L., E-mail: vagson.carvalho@usach.cl [Instituto Federal de Educação, Ciência e Tecnologia Baiano - Campus Senhor do Bonfim, Km 04 Estrada da Igara, 48970-000 Senhor do Bonfim, Bahia (Brazil); Departamento de Física, Universidad de Santiago de Chile and CEDENNA, Avda. Ecuador 3493, Santiago (Chile); Elias, R.G.; Altbir, D. [Departamento de Física, Universidad de Santiago de Chile and CEDENNA, Avda. Ecuador 3493, Santiago (Chile); Fonseca, J.M. [Universidade Federal de Viçosa, Departamento de Física, Avenida Peter Henry Rolfs s/n, 36570-000 Viçosa, MG (Brazil)

    2015-10-01

    We study the stability and energetics associated to skyrmions appearing as excitations on curved surfaces. Using a continuum model we show that the presence of cylindrically radial and azimuthal fields destabilize the skyrmions that appear in the absence of an external field. Weak fields generate fractional skyrmions while strong magnetic fields yield stable 2π-skyrmions, which have their widths diminished by the magnetic field strength. Under azimuthal fields vortex appears as stable state on the curved surface. - Highlights: • Stability of skyrmions on curved surfaces in the presence of a magnetic field. • Weak fields can destabilize skyrmions. • Strong magnetic fields yield the appearing of 2π-skyrmions. • The width of skyrmions is determined by the curvature and magnetic field strength. • Under azimuthal fields vortex appears as stable states.

  14. Holographic reconstruction of sound fields based on the acousto-optic effect

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Torras Rosell, Antoni; Jacobsen, Finn

    2013-01-01

    Recent studies have shown that it is possible to measure a sound field using acousto-optic tomography. Theacousto-optic effect, i.e., the interaction between sound and light, can be used to measure an arbitrary soundfield by scanning it with a laser Doppler vibrometer (LDV) over an aperture; This...

  15. Reconstruction of Effective Cloud Field Geometry from Series of Sunshine Number

    Czech Academy of Sciences Publication Activity Database

    Badescu, V.; Paulescu, M.; Brabec, Marek

    176-177, 1 July - 1 August (2016), s. 254-266 ISSN 0169-8095 Institutional support: RVO:67985807 Keywords : cloud field geometry * sunshine number * point cloud iness Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 3.778, year: 2016

  16. Can reconstructed land surface temperature data from space predict a West Nile Virus outbreak?

    NARCIS (Netherlands)

    Andreo, V.; Metz, J.C.M.; Neteler, M.; Rosà, R.; Marcantonio, M.; Billinis, C.; Rizzoli, A.; Papa, Anne-Laure

    2017-01-01

    Temperature is one of the main drivers of ecological processes. The availability of temporally and spatially continuous temperature time series is crucial in different research and application fields, such as epidemiology and control of zoonotic diseases. In 2010, several West Nile virus (WNV)

  17. New holographic reconstruction of scalar-field dark-energy models in the framework of chameleon Brans-Dicke cosmology

    International Nuclear Information System (INIS)

    Chattopadhyay, Surajit; Pasqua, Antonio; Khurshudyan, Martiros

    2014-01-01

    Motivated by the work of Yang et al. (Mod. Phys. Lett. A 26:191, 2011), we report on a study of the new holographic dark energy (NHDE) model with energy density given by ρ D = (3φ 2 )/(4ω)(μH 2 + νH) in the framework of chameleon Brans-Dicke cosmology. We have studied the correspondence between the quintessence, the DBI-essence, and the tachyon scalar-field models with the NHDE model in the framework of chameleon Brans-Dicke cosmology. Deriving an expression of the Hubble parameter H and, accordingly, ρ D in the context of chameleon Brans-Dicke chameleon cosmology, we have reconstructed the potentials and dynamics for these scalar-field models. Furthermore, we have examined the stability for the obtained solutions of the crossing of the phantom divide under a quantum correction of massless conformally invariant fields, and we have seen that the quantum correction could be small when the phantom crossing occurs and the obtained solutions of the phantom crossing could be stable under the quantum correction. It has also been noted that the potential increases as the matter. chameleon coupling gets stronger with the evolution of the universe. (orig.)

  18. New holographic reconstruction of scalar-field dark-energy models in the framework of chameleon Brans-Dicke cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Chattopadhyay, Surajit [Pailan College of Management and Technology, Kolkata (India); Pasqua, Antonio [University of Trieste, Department of Physics, Trieste (Italy); Khurshudyan, Martiros [Yerevan State University, Department of Theoretical Physics, Yerevan (Armenia); Potsdam-Golm Science Park, Max Planck Institute of Colloids and Interfaces, Potsdam (Germany)

    2014-09-15

    Motivated by the work of Yang et al. (Mod. Phys. Lett. A 26:191, 2011), we report on a study of the new holographic dark energy (NHDE) model with energy density given by ρ{sub D} = (3φ{sup 2})/(4ω)(μH{sup 2} + νH) in the framework of chameleon Brans-Dicke cosmology. We have studied the correspondence between the quintessence, the DBI-essence, and the tachyon scalar-field models with the NHDE model in the framework of chameleon Brans-Dicke cosmology. Deriving an expression of the Hubble parameter H and, accordingly, ρ{sub D} in the context of chameleon Brans-Dicke chameleon cosmology, we have reconstructed the potentials and dynamics for these scalar-field models. Furthermore, we have examined the stability for the obtained solutions of the crossing of the phantom divide under a quantum correction of massless conformally invariant fields, and we have seen that the quantum correction could be small when the phantom crossing occurs and the obtained solutions of the phantom crossing could be stable under the quantum correction. It has also been noted that the potential increases as the matter. chameleon coupling gets stronger with the evolution of the universe. (orig.)

  19. Fast conjugate phase image reconstruction based on a Chebyshev approximation to correct for B0 field inhomogeneity and concomitant gradients.

    Science.gov (United States)

    Chen, Weitian; Sica, Christopher T; Meyer, Craig H

    2008-11-01

    Off-resonance effects can cause image blurring in spiral scanning and various forms of image degradation in other MRI methods. Off-resonance effects can be caused by both B0 inhomogeneity and concomitant gradient fields. Previously developed off-resonance correction methods focus on the correction of a single source of off-resonance. This work introduces a computationally efficient method of correcting for B0 inhomogeneity and concomitant gradients simultaneously. The method is a fast alternative to conjugate phase reconstruction, with the off-resonance phase term approximated by Chebyshev polynomials. The proposed algorithm is well suited for semiautomatic off-resonance correction, which works well even with an inaccurate or low-resolution field map. The proposed algorithm is demonstrated using phantom and in vivo data sets acquired by spiral scanning. Semiautomatic off-resonance correction alone is shown to provide a moderate amount of correction for concomitant gradient field effects, in addition to B0 imhomogeneity effects. However, better correction is provided by the proposed combined method. The best results were produced using the semiautomatic version of the proposed combined method.

  20. (Tl, Sb) and (Tl, Bi) binary surface reconstructions on Ge(111) substrate

    Science.gov (United States)

    Gruznev, D. V.; Bondarenko, L. V.; Tupchaya, A. Y.; Yakovlev, A. A.; Mihalyuk, A. N.; Zotov, A. V.; Saranin, A. A.

    2018-03-01

    2D compounds made of Group-III and Group-V elements on the surface of silicon and germanium attract considerable attention due to prospects of creating III-V binary monolayers, which are predicted to hold advanced physical properties. In the present work, we have investigated two such systems, (Tl, Sb)/Ge(111) and (Tl, Bi)/Ge(111) using scanning tunneling microscopy, low energy electron diffraction observations and density-functional-theory calculations. In addition to the previously reported surface structures of 2D (Tl, Sb) and (Tl, Bi) compounds on Si(111), we found new ones, namely, √{ 7} × √{ 7} and 3 × 3. Formation processes and plausible models of their atomic arrangements are discussed.

  1. Reconstructing surface ocean circulation with 129I time series records from corals.

    Science.gov (United States)

    Chang, Ching-Chih; Burr, George S; Jull, A J Timothy; Russell, Joellen L; Biddulph, Dana; White, Lara; Prouty, Nancy G; Chen, Yue-Gau; Shen, Chuan-Chou; Zhou, Weijian; Lam, Doan Dinh

    2016-12-01

    The long-lived radionuclide 129 I (half-life: 15.7 × 10 6  yr) is well-known as a useful environmental tracer. At present, the global 129 I in surface water is about 1-2 orders of magnitude higher than pre-1960 levels. Since the 1990s, anthropogenic 129 I produced from industrial nuclear fuels reprocessing plants has been the primary source of 129 I in marine surface waters of the Atlantic and around the globe. Here we present four coral 129 I time series records from: 1) Con Dao and 2) Xisha Islands, the South China Sea, 3) Rabaul, Papua New Guinea and 4) Guam. The Con Dao coral 129 I record features a sudden increase in 129 I in 1959. The Xisha coral shows similar peak values for 129 I as the Con Dao coral, punctuated by distinct low values, likely due to the upwelling in the central South China Sea. The Rabaul coral features much more gradual 129 I increases in the 1970s, similar to a published record from the Solomon Islands. The Guam coral 129 I record contains the largest measured values for any site, with two large peaks, in 1955 and 1959. Nuclear weapons testing was the primary 129 I source in the Western Pacific in the latter part of the 20th Century, notably from testing in the Marshall Islands. The Guam 1955 peak and Con Dao 1959 increases are likely from the 1954 Castle Bravo test, and the Operation Hardtack I test is the most likely source of the 1959 peak observed at Guam. Radiogenic iodine found in coral was carried primarily through surface ocean currents. The coral 129 I time series data provide a broad picture of the surface distribution and depth penetration of 129 I in the Pacific Ocean over the past 60 years. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  2. Cultivated Oral Mucosa Epithelium in Ocular Surface Reconstruction in Aniridia Patients

    Directory of Open Access Journals (Sweden)

    Dariusz Dobrowolski

    2015-01-01

    Full Text Available Purpose. Efficacy of cultivated oral mucosa epithelial transplantation (COMET procedure in corneal epithelium restoration of aniridia patients. Methods. Study subjects were aniridia patients (13 patients; 17 eyes with irregular, vascular conjunctival pannus involving visual axis who underwent autologous transplantation of cultivated epithelium. For the procedure oral mucosa epithelial cells were obtained from buccal mucosa with further enzymatic treatment. Suspension of single cells was seeded on previously prepared denuded amniotic membrane. Cultures were carried on culture dishes inserts in the presence of the inactivated with Mitomycin C monolayer of 3T3 fibroblasts. Cultures were carried for seven days. Stratified oral mucosa epithelium with its amniotic membrane carrier was transplanted on the surgically denuded corneal surface of aniridia patients with total or subtotal limbal stem cell deficiency. Outcome Measures. Corneal surface, epithelial regularity, and visual acuity improvement were evaluated. Results. At the end of the observation period, 76.4% of the eyes had regular transparent epithelium and 23.5% had developed epithelial defects or central corneal haze; in 88.2% of cases visual acuity had increased. VA range was from HM 0.05 before the surgery to HM up to 0.1 after surgery. Conclusion. Application of cultivated oral mucosa epithelium restores regular epithelium on the corneal surface with moderate improvement in quality of vision.

  3. Multistatic Array Sampling Scheme for Fast Near-Field Image Reconstruction

    Science.gov (United States)

    2016-01-01

    human-sized scene in 0.048sec− 0.101sec. Index Terms—Microwave imaging, multistatic radar, Fast Fourier Transform (FFT). I. INTRODUCTION Near-field...configuration, but its computational demands are extreme. Fast Fourier Transform (FFT) imaging has long been used to efficiently construct images sampled...with the block diagram depicted in Fig. 4. It is noted that the multistatic to monostatic correction is valid over a finite imaging domain. However, as

  4. Near-field investigation of surface plasmon polaritons

    NARCIS (Netherlands)

    Jose, J.

    2010-01-01

    The interaction of light with metals contains a resonant phenomenon called the Surface Plasmon Resonance (SPR), at which the free electrons in the metal collectively oscillate. This collective oscillation of the free electrons, called Surface Plasmon Polaritons (SPPs), is highly sensitive to the

  5. Protruding organic surfaces triggered by in-plane electric fields

    NARCIS (Netherlands)

    Liu, D.; Tito, N.B.; Broer, D.J.

    2017-01-01

    Coatings with a dynamic surface topography are of interest for applications in haptics, soft robotics, cell growth in biology, hydro- and air dynamics and tribology. Here we propose a design for creating oscillating surface topographies in thin liquid crystal polymer network coatings under an

  6. Destruction of Invariant Surfaces and Magnetic Coordinates for Perturbed Magnetic Fields

    International Nuclear Information System (INIS)

    Hudson, S.R.

    2003-01-01

    Straight-field-line coordinates are constructed for nearly integrable magnetic fields. The coordinates are based on the robust, noble-irrational rotational-transform surfaces, whose existence is determined by an application of Greene's residue criterion. A simple method to locate these surfaces is described. Sequences of surfaces with rotational-transform converging to low order rationals maximize the region of straight-field-line coordinates

  7. Reconstruction of sub-surface archaeological remains from magnetic data using neural computing.

    Science.gov (United States)

    Bescoby, D. J.; Cawley, G. C.; Chroston, P. N.

    2003-04-01

    The remains of a former Roman colonial settlement, once part of the classical city of Butrint in southern Albania have been the subject of a high resolution magnetic survey using a caesium-vapour magnetometer. The survey revealed the surviving remains of an extensive planned settlement and a number of outlying buildings, today buried beneath over 0.5 m of alluvial deposits. The aim of the current research is to derive a sub-surface model from the magnetic survey measurements, allowing an enhanced archaeological interpretation of the data. Neural computing techniques are used to perform the non-linear mapping between magnetic data and corresponding sub-surface model parameters. The adoption of neural computing paradigms potentially holds several advantages over other modelling techniques, allowing fast solutions for complex data, while having a high tolerance to noise. A multi-layer perceptron network with a feed-forward architecture is trained to estimate the shape and burial depth of wall foundations using a series of representative models as training data. Parameters used to forward model the training data sets are derived from a number of trial trench excavations targeted over features identified by the magnetic survey. The training of the network was optimized by first applying it to synthetic test data of known source parameters. Pre-processing of the network input data, including the use of a rotationally invariant transform, enhanced network performance and the efficiency of the training data. The approach provides good results when applied to real magnetic data, accurately predicting the depths and layout of wall foundations within the former settlement, verified by subsequent excavation. The resulting sub-surface model is derived from the averaged outputs of a ‘committee’ of five networks, trained with individualized training sets. Fuzzy logic inference has also been used to combine individual network outputs through correlation with data from a second

  8. Precision 3d Surface Reconstruction from Lro Nac Images Using Semi-Global Matching with Coupled Epipolar Rectification

    Science.gov (United States)

    Hu, H.; Wu, B.

    2017-07-01

    The Narrow-Angle Camera (NAC) on board the Lunar Reconnaissance Orbiter (LRO) comprises of a pair of closely attached high-resolution push-broom sensors, in order to improve the swath coverage. However, the two image sensors do not share the same lenses and cannot be modelled geometrically using a single physical model. Thus, previous works on dense matching of stereo pairs of NAC images would generally create two to four stereo models, each with an irregular and overlapping region of varying size. Semi-Global Matching (SGM) is a well-known dense matching method and has been widely used for image-based 3D surface reconstruction. SGM is a global matching algorithm relying on global inference in a larger context rather than individual pixels to establish stable correspondences. The stereo configuration of LRO NAC images causes severe problem for image matching methods such as SGM, which emphasizes global matching strategy. Aiming at using SGM for image matching of LRO NAC stereo pairs for precision 3D surface reconstruction, this paper presents a coupled epipolar rectification methods for LRO NAC stereo images, which merges the image pair in the disparity space and in this way, only one stereo model will be estimated. For a stereo pair (four) of NAC images, the method starts with the boresight calibration by finding correspondence in the small overlapping stripe between each pair of NAC images and bundle adjustment of the stereo pair, in order to clean the vertical disparities. Then, the dominate direction of the images are estimated by project the center of the coverage area to the reference image and back-projected to the bounding box plane determined by the image orientation parameters iteratively. The dominate direction will determine an affine model, by which the pair of NAC images are warped onto the object space with a given ground resolution and in the meantime, a mask is produced indicating the owner of each pixel. SGM is then used to generate a disparity

  9. PRECISION 3D SURFACE RECONSTRUCTION FROM LRO NAC IMAGES USING SEMI-GLOBAL MATCHING WITH COUPLED EPIPOLAR RECTIFICATION

    Directory of Open Access Journals (Sweden)

    H. Hu

    2017-07-01

    Full Text Available The Narrow-Angle Camera (NAC on board the Lunar Reconnaissance Orbiter (LRO comprises of a pair of closely attached high-resolution push-broom sensors, in order to improve the swath coverage. However, the two image sensors do not share the same lenses and cannot be modelled geometrically using a single physical model. Thus, previous works on dense matching of stereo pairs of NAC images would generally create two to four stereo models, each with an irregular and overlapping region of varying size. Semi-Global Matching (SGM is a well-known dense matching method and has been widely used for image-based 3D surface reconstruction. SGM is a global matching algorithm relying on global inference in a larger context rather than individual pixels to establish stable correspondences. The stereo configuration of LRO NAC images causes severe problem for image matching methods such as SGM, which emphasizes global matching strategy. Aiming at using SGM for image matching of LRO NAC stereo pairs for precision 3D surface reconstruction, this paper presents a coupled epipolar rectification methods for LRO NAC stereo images, which merges the image pair in the disparity space and in this way, only one stereo model will be estimated. For a stereo pair (four of NAC images, the method starts with the boresight calibration by finding correspondence in the small overlapping stripe between each pair of NAC images and bundle adjustment of the stereo pair, in order to clean the vertical disparities. Then, the dominate direction of the images are estimated by project the center of the coverage area to the reference image and back-projected to the bounding box plane determined by the image orientation parameters iteratively. The dominate direction will determine an affine model, by which the pair of NAC images are warped onto the object space with a given ground resolution and in the meantime, a mask is produced indicating the owner of each pixel. SGM is then used to

  10. Simulating evaporation of surface atoms of thorium-alloyed tungsten in strong electronic fields

    International Nuclear Information System (INIS)

    Bochkanov, P.V.; Mordyuk, V.S.; Ivanov, Yu.I.

    1984-01-01

    By the Monte Carlo method simulating evaporation of surface atoms of thorium - alloyed tungsten in strong electric fields is realized. The strongest evaporation of surface atoms of pure tungsten as compared with thorium-alloyed tungsten in the contentration range of thorium atoms in tungsten matrix (1.5-15%) is shown. The evaporation rate increases with thorium atoms concentration. Determined is in relative units the surface atoms evaporation rate depending on surface temperature and electric field stront

  11. Reconstruction of limbal stem cell deficient corneal surface with induced human bone marrow mesenchymal stem cells on amniotic membrane.

    Science.gov (United States)

    Rohaina, Che Man; Then, Kong Yong; Ng, Angela Min Hwei; Wan Abdul Halim, Wan Haslina; Zahidin, Aida Zairani Mohd; Saim, Aminuddin; Idrus, Ruszymah B H

    2014-03-01

    The cornea can be damaged by a variety of clinical disorders or chemical, mechanical, and thermal injuries. The objectives of this study were to induce bone marrow mesenchymal stem cells (BMSCs) to corneal lineage, to form a tissue engineered corneal substitute (TEC) using BMSCs, and to treat corneal surface defects in a limbal stem cell deficiency model. BMSCs were induced to corneal lineage using limbal medium for 10 days. Induced BMSCs demonstrated upregulation of corneal stem cell markers; β1-integrin, C/EBPδ, ABCG2, and p63, increased protein expression of CK3 and p63 significantly compared with the uninduced ones. For TEC formation, passage 1 BMSCs were trypsinized and seeded on amniotic membrane in a transwell co-culture system and were grown in limbal medium. Limbal stem cell deficiency models were induced by alkaline injury, and the TEC was implanted for 8 weeks. Serial slit lamp evaluation revealed remarkable improvement in corneal regeneration in terms of corneal clarity and reduced vascularization. Histologic and optical coherence tomography analyses demonstrated comparable corneal thickness and achieved stratified epithelium with a compact stromal layer resembling that of normal cornea. CK3 and p63 were expressed in the newly regenerated cornea. In conclusion, BMSCs can be induced into corneal epithelial lineage, and these cells are viable for the formation of TEC, to be used for the reconstruction of the corneal surface in the limbal stem cell deficient model. Copyright © 2014 Mosby, Inc. All rights reserved.

  12. Epitaxy of GaN on silicon-impact of symmetry and surface reconstruction

    International Nuclear Information System (INIS)

    Dadgar, A; Schulze, F; Wienecke, M; Gadanecz, A; Blaesing, J; Veit, P; Hempel, T; Diez, A; Christen, J; Krost, A

    2007-01-01

    GaN-on-silicon is a low-cost alternative to growth on sapphire or SiC. Today epitaxial growth is usually performed on Si(111), which has a threefold symmetry. The growth of single crystalline GaN on Si(001), the material of the complementary metal oxide semiconductor (CMOS) industry, is more difficult due to the fourfold symmetry of this Si surface leading to two differently aligned domains. We show that breaking the symmetry to achieve single crystalline growth can be performed, e.g. by off-oriented substrates to achieve single crystalline device quality GaN layers. Furthermore, an exotic Si orientation for GaN growth is Si(110), which we show is even better suited as compared to Si(111) for the growth of high quality GaN-on-silicon with a nearly threefold reduction in the full width at half maximum (FWHM) of the (1 1-bar 0 0)ω-scan. It is found that a twofold surface symmetry is in principal suitable for the growth of single crystalline GaN on Si

  13. Reconstruction of an acoustic pressure field in a resonance tube by particle image velocimetry.

    Science.gov (United States)

    Kuzuu, K; Hasegawa, S

    2015-11-01

    A technique for estimating an acoustic field in a resonance tube is suggested. The estimation of an acoustic field in a resonance tube is important for the development of the thermoacoustic engine, and can be conducted employing two sensors to measure pressure. While this measurement technique is known as the two-sensor method, care needs to be taken with the location of pressure sensors when conducting pressure measurements. In the present study, particle image velocimetry (PIV) is employed instead of a pressure measurement by a sensor, and two-dimensional velocity vector images are extracted as sequential data from only a one- time recording made by a video camera of PIV. The spatial velocity amplitude is obtained from those images, and a pressure distribution is calculated from velocity amplitudes at two points by extending the equations derived for the two-sensor method. By means of this method, problems relating to the locations and calibrations of multiple pressure sensors are avoided. Furthermore, to verify the accuracy of the present method, the experiments are conducted employing the conventional two-sensor method and laser Doppler velocimetry (LDV). Then, results by the proposed method are compared with those obtained with the two-sensor method and LDV.

  14. Streams and magnetic fields in surface layers of Ap-stars

    International Nuclear Information System (INIS)

    Dolginov, A.Z.; Urpin, V.A.

    1978-01-01

    Magnetic field generation of Ap-stars is considered. It is shown that in the surface layers of Ap-stars inhomogeneity of chemical composition produces a strong magnetic field. Velocities of possible circulation of stellar matter are estimated. It is shown that circulation does not prevent the process of the magnetic field generation. It needs the order of million years, for arranging the stationary magnetic field in surface layers

  15. Artificial Neural Networks to reconstruct incomplete satellite data: application to the Mediterranean Sea Surface Temperature

    Directory of Open Access Journals (Sweden)

    E. Pisoni

    2008-02-01

    Full Text Available Satellite data can be very useful in applications where extensive spatial information is needed, but sometimes missing data due to presence of clouds can affect data quality. In this study a methodology for pre-processing sea surface temperature (SST data is proposed. The methodology, that processes measures in the visible wavelength, is based on an Artificial Neural Network (ANN system. The effectiveness of the procedure has been also evaluated comparing results obtained using an interpolation method. After the methodology has been identified, a validation is performed on 3 different episodes representative of SST variability in the Mediterranean sea. The proposed technique can process SST NOAA/AVHRR data to simulate severe storm episodes by means of prognostic meteorological models.

  16. Archaeobotanical reconstructions of field habitats and crops: the grange in Pomorzany near Kutno, 18th/19th c.

    Directory of Open Access Journals (Sweden)

    Koszałka Joanna

    2015-03-01

    Full Text Available The paper presents the results of research of plant macrofossils from the grain deposit deriving from the 18th/19th centuries. The analysed material included 24760 diaspores representing 73 taxa. The majority were cultivated cereal crop species, and there was also abundance of accompanying segetal weed species. About 95% of the gathered crop material was Secale cereale. Another important crop was Hordeum vulgare and there were also some remains of Avena sativa, Triticum aestivum, Fagopyrum esculentum. Cannabis sativa and Linum usitatissimum were found as well. Weeds competing with these crops were, among others, the following species: Agrostemma githago, Raphanus raphanistrum, Apera spica-venti, Bromus secalinus, Centaurea cyanus, Spergula arvensis, Thlaspi arvense, Viola arvensis/tricolor, Fallopia convolvulus, Polygonum persicaria, Mentha arvensis, Anthemis arvensis, Papaver rhoeas, Rumex acetosella, Scleranthus annuus, Aphanes arvensis, Setaria pumila, Setaria viridis/verticilata. Extremely large presence of wild plant diaspores in the material allowed conducting economic and environmental interpretations. Reconstruction methods applied, used primarily in the case of macroremains from granaries, were fully applicable to the analysed plant residues. Weed species composition in the analysed material showed that they were mostly typical for the main winter crop. Some amount of species typical for other habitats were also found and they probably came from the near-by rye field. The presence of perennial diaspores indicated that the field was probably set aside

  17. Effective field theories for superconducting systems with multiple Fermi surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Braga, P.R., E-mail: pedro.rangel.braga@gmail.com [Departamento de Física Teórica, Instituto de Física, UERJ - Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, 20550-013 Maracanã, Rio de Janeiro (Brazil); Granado, D.R., E-mail: diegorochagrana@uerj.br [Departamento de Física Teórica, Instituto de Física, UERJ - Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, 20550-013 Maracanã, Rio de Janeiro (Brazil); Department of Physics and Astronomy, Ghent University, Krijgslaan 281-S9, 9000 Gent (Belgium); Guimaraes, M.S., E-mail: msguimaraes@uerj.br [Departamento de Física Teórica, Instituto de Física, UERJ - Universidade do Estado do Rio de Janeiro, Rua São Francisco Xavier 524, 20550-013 Maracanã, Rio de Janeiro (Brazil); Wotzasek, C., E-mail: clovis@if.ufrj.br [Instituto de Física, Universidade Federal do Rio de Janeiro, 21941-972, Rio de Janeiro (Brazil)

    2016-11-15

    In this work we investigate the description of superconducting systems with multiple Fermi surfaces. For the case of one Fermi surface we re-obtain the result that the superconductor is more precisely described as a topological state of matter. Studying the case of more than one Fermi surface, we obtain the effective theory describing a time reversal symmetric topological superconductor. These results are obtained by employing a general procedure to construct effective low energy actions describing states of electromagnetic systems interacting with charges and defects. The procedure consists in taking into account the proliferation or dilution of these charges and defects and its consequences for the low energy description of the electromagnetic response of the system. We find that the main ingredient entering the low energy characterization of the system with more than one Fermi surface is a non-conservation of the canonical supercurrent triggered by particular vortex configurations.

  18. Near-Field Spectral Effects due to Electromagnetic Surface Excitations

    OpenAIRE

    Shchegrov , Andrei ,; Joulain , Karl; Carminati , Rémi; Greffet , Jean-Jacques

    2000-01-01

    International audience; We demonstrate theoretically that the spectra of electromagnetic emission of surface systems can display remarkable differences in the near and the far zones. The spectral changes occur due to the loss of evanescent modes and are especially pronounced for systems which support surface waves. PACS numbers: 78.20. – e, 05.40. – a, 44.40. + a, 87.64.Xx Spectroscopy of electromagnetic radiation is perhaps the most powerful exploration tool employed in natural sciences: ast...

  19. Particle separation by external fields on periodic surfaces

    International Nuclear Information System (INIS)

    Sancho, J M; Khoury, M; Lindenberg, K; Lacasta, A M

    2005-01-01

    Particles moving on perfect periodic surfaces under the influence of external forces may move along directions that deviate from that of the force. We briefly recall previous results for transport of particles on surfaces with periodic traps or periodic obstacles driven by a constant external force, and present new results for particles moving in a harmonic periodic potential. The sorting properties are explored as a function of a number of control parameters, specifically the friction, force amplitude and direction, temperature, and lattice constants

  20. Children’s everyday lives (re)constructed as variable sets of ‘field bodies’

    DEFF Research Database (Denmark)

    Winther, Ida Wentzel

    2013-01-01

    How do you study everyday life? Everyday life happens. It is solid and liquid, embedded and changeable. The article is based on fieldwork I conducted on an isolated island, where I was interested in how children play, interact with each other and use social media. I brought my son, a camcorder...... and seven small digital cameras with me, which I distributed to the children on the island. Using the visual and material perspective allows the researcher to incorporate slowness, details and minimal space in her work. And it makes it possible to work with different types of performative practices, where...... inter-methodic (person and method) as well as inter-material (person and materiality/surroundings) aspects are brought into play, and the patterns and dynamics of the social and cultural landscapes can be reconfigured. This article scrutinizes how the researcher (me) works with variable sets of ‘field...

  1. Cosmology with hybrid expansion law: scalar field reconstruction of cosmic history and observational constraints

    International Nuclear Information System (INIS)

    Akarsu, Özgür; Kumar, Suresh; Myrzakulov, R.; Sami, M.; Xu, Lixin

    2014-01-01

    In this paper, we consider a simple form of expansion history of Universe referred to as the hybrid expansion law - a product of power-law and exponential type of functions. The ansatz by construction mimics the power-law and de Sitter cosmologies as special cases but also provides an elegant description of the transition from deceleration to cosmic acceleration. We point out the Brans-Dicke realization of the cosmic history under consideration. We construct potentials for quintessence, phantom and tachyon fields, which can give rise to the hybrid expansion law in general relativity. We investigate observational constraints on the model with hybrid expansion law applied to late time acceleration as well as to early Universe a la nucleosynthesis

  2. Photodetachment of negative ion in a gradient electric field near a metal surface

    International Nuclear Information System (INIS)

    Liu Tian-Qi; Wang De-Hua; Han Cai; Liu Jiang; Liang Dong-Qi; Xie Si-Cheng

    2012-01-01

    Based on closed-orbit theory, the photodetachment of H − in a gradient electric field near a metal surface is studied. It is demonstrated that the gradient electric field has a significant influence on the photodetachment of negative ions near a metal surface. With the increase of the gradient of the electric field, the oscillation in the photodetachment cross section becomes strengthened. Besides, in contrast to the photodetachment of H − near a metal surface in a uniform electric field, the oscillating amplitude and the oscillating region in the cross section of a gradient electric field also become enlarged. Therefore, we can use the gradient electric field to control the photodetachment of negative ions near a metal surface. We hope that our results will be useful for understanding the photodetachment of negative ions in the vicinity of surfaces, cavities, and ion traps. (atomic and molecular physics)

  3. Field emission from the surface of highly ordered pyrolytic graphite

    Czech Academy of Sciences Publication Activity Database

    Knápek, Alexandr; Sobola, D.; Tománek, P.; Pokorná, Zuzana; Urbánek, Michal

    2017-01-01

    Roč. 395, FEB 15 (2017), s. 157-161 ISSN 0169-4332 R&D Projects: GA TA ČR(CZ) TE01020118 Institutional support: RVO:68081731 Keywords : field emission * HOPG * scanning electron microscopy * scanning near-field optical microscopy Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering OBOR OECD: Nano-processes (applications on nano-scale) Impact factor: 3.387, year: 2016

  4. Graph-based surface reconstruction from stereo pairs using image segmentation

    Science.gov (United States)

    Bleyer, Michael; Gelautz, Margrit

    2005-01-01

    This paper describes a novel stereo matching algorithm for epipolar rectified images. The method applies colour segmentation on the reference image. The use of segmentation makes the algorithm capable of handling large untextured regions, estimating precise depth boundaries and propagating disparity information to occluded regions, which are challenging tasks for conventional stereo methods. We model disparity inside a segment by a planar equation. Initial disparity segments are clustered to form a set of disparity layers, which are planar surfaces that are likely to occur in the scene. Assignments of segments to disparity layers are then derived by minimization of a global cost function via a robust optimization technique that employs graph cuts. The cost function is defined on the pixel level, as well as on the segment level. While the pixel level measures the data similarity based on the current disparity map and detects occlusions symmetrically in both views, the segment level propagates the segmentation information and incorporates a smoothness term. New planar models are then generated based on the disparity layers' spatial extents. Results obtained for benchmark and self-recorded image pairs indicate that the proposed method is able to compete with the best-performing state-of-the-art algorithms.

  5. Image-based surface reconstruction in geomorphometry - merits, limits and developments

    Science.gov (United States)

    Eltner, Anette; Kaiser, Andreas; Castillo, Carlos; Rock, Gilles; Neugirg, Fabian; Abellán, Antonio

    2016-05-01

    Photogrammetry and geosciences have been closely linked since the late 19th century due to the acquisition of high-quality 3-D data sets of the environment, but it has so far been restricted to a limited range of remote sensing specialists because of the considerable cost of metric systems for the acquisition and treatment of airborne imagery. Today, a wide range of commercial and open-source software tools enable the generation of 3-D and 4-D models of complex geomorphological features by geoscientists and other non-experts users. In addition, very recent rapid developments in unmanned aerial vehicle (UAV) technology allow for the flexible generation of high-quality aerial surveying and ortho-photography at a relatively low cost.The increasing computing capabilities during the last decade, together with the development of high-performance digital sensors and the important software innovations developed by computer-based vision and visual perception research fields, have extended the rigorous processing of stereoscopic image data to a 3-D point cloud generation from a series of non-calibrated images. Structure-from-motion (SfM) workflows are based upon algorithms for efficient and automatic orientation of large image sets without further data acquisition information, examples including robust feature detectors like the scale-invariant feature transform for 2-D imagery. Nevertheless, the importance of carrying out well-established fieldwork strategies, using proper camera settings, ground control points and ground truth for understanding the different sources of errors, still needs to be adapted in the common scientific practice.This review intends not only to summarise the current state of the art on using SfM workflows in geomorphometry but also to give an overview of terms and fields of application. Furthermore, this article aims to quantify already achieved accuracies and used scales, using different strategies in order to evaluate possible stagnations of

  6. Observations Of Polarized Dust Emission In Protostars: How To Reconstruct Magnetic Field Properties?

    Science.gov (United States)

    Maury, Anaëlle; Galametz, M.; Girart; Guillet; Hennebelle, P.; Houde; Rao; Valdivia, V.; Zhang, Q.

    2017-10-01

    I will present our ALMA Cycle 2 polarized dust continuum data towards the Class 0 protostar B335 where the absence of detected rotational motions in the inner envelope might suggest an efficient magnetic braking at work to inhibit the formation of a large disk. The Band 6 data we obtained shows an intriguing polarized vectors topology, which could either suggest (i) at least two different grain alignment mechanisms at work in B335 to produce the observed polarization pattern, or (ii) an interferometric bias leading to filtering of the polarized signal that is different from the filtering of Stokes I. I will discuss both options, proposing multi-wavelength and multi observatory (ALMA Band3 data in Cycle 5, NIKA2Pol camera on the IRAM-30m) strategies to lift the degeneracy when using polarization observations as a proxy of magnetic fields in dense astrophysical environments. This observational effort in the framework of the MagneticYSOs project, is also supported by our development of an end-to-end chain of ALMA synthetic observations of the polarization from non-ideal MHD simulations of protostellar collapse (see complementary contributions by V. Valdivia and M. Galametz).

  7. Role of internal demagnetizing field for the dynamics of a surface-modulated magnonic crystal

    Science.gov (United States)

    Langer, M.; Röder, F.; Gallardo, R. A.; Schneider, T.; Stienen, S.; Gatel, C.; Hübner, R.; Bischoff, L.; Lenz, K.; Lindner, J.; Landeros, P.; Fassbender, J.

    2017-05-01

    This work aims to demonstrate and understand the key role of local demagnetizing fields in hybrid structures consisting of a continuous thin film with a stripe modulation on top. To understand the complex spin dynamics of these structures, the magnonic crystal was reconstructed in two different ways—performing micromagnetic simulations based on the structural shape as well as based on the internal demagnetizing field, which both are mapped on the nanoscale using electron holography. The simulations yield the frequency-field dependence as well as the angular dependence revealing the governing role of the internal field landscape around the backward-volume geometry. Simple rules for the propagation vector and the mode l