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

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...

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.

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.

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

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...

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.

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.

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.

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.

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.

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.

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.

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)

[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.

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.

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.

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.

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

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

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.

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.

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.

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.

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.

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.

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.

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.

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)

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.

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.

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...

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)

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.

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...

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

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

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

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

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.

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

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)

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

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...

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

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

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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

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.

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)

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.

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.)

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)

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.

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.

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

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.

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

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

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.

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)

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....

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.

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).

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

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.

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

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.

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.

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

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.

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.

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.

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

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

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

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.

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

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.

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)

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)

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.

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)

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

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.

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

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.

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.

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

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.

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

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)

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

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

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.

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.

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

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.

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.

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.

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.

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....

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.

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.

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...

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.

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.

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.

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)

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)

Dynamic scattering theory for dark-field electron holography of 3D strain fields.

Science.gov (United States)

Lubk, Axel; Javon, Elsa; Cherkashin, Nikolay; Reboh, Shay; Gatel, Christophe; Hÿtch, Martin

2014-01-01

Dark-field electron holography maps strain in crystal lattices into reconstructed phases over large fields of view. Here we investigate the details of the lattice strain-reconstructed phase relationship by applying dynamic scattering theory both analytically and numerically. We develop efficient analytic linear projection rules for 3D strain fields, facilitating a straight-forward calculation of reconstructed phases from 3D strained materials. They are used in the following to quantify the influence of various experimental parameters like strain magnitude, specimen thickness, excitation error and surface relaxation. © 2013 Elsevier B.V. All rights reserved.

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.

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.

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

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.

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.

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.)

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.

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...

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

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...

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...

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

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.

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.

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.

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.

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.

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.

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).

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.

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

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.

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.

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

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.

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).

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).

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

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...

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.

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.

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.

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

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.

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

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.

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.

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.

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.

Dynamic scattering theory for dark-field electron holography of 3D strain fields

International Nuclear Information System (INIS)

Lubk, Axel; Javon, Elsa; Cherkashin, Nikolay; Reboh, Shay; Gatel, Christophe; Hÿtch, Martin

2014-01-01

Dark-field electron holography maps strain in crystal lattices into reconstructed phases over large fields of view. Here we investigate the details of the lattice strain–reconstructed phase relationship by applying dynamic scattering theory both analytically and numerically. We develop efficient analytic linear projection rules for 3D strain fields, facilitating a straight-forward calculation of reconstructed phases from 3D strained materials. They are used in the following to quantify the influence of various experimental parameters like strain magnitude, specimen thickness, excitation error and surface relaxation. - Author-Highlights: • We derive a simple dynamic scattering formalism for dark field electron holography based on a perturbative two-beam theory. • The formalism facilitates the projection of 3D strain fields by a simple weighting integral. • The weighted projection depends analytically on the diffraction order, the excitation error and the specimen thickness. • The weighting integral formalism represents an important prerequisite towards the development of tomographic strain reconstruction techniques

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.

Benchmarking Close-range Structure from Motion 3D Reconstruction Software under Varying Capturing Conditions

DEFF Research Database (Denmark)

Nikolov, Ivan Adriyanov; Madsen, Claus B.

2016-01-01

Structure from Motion 3D reconstruction has become widely used in recent years in a number of fields such as industrial surface in- inspection, archeology, cultural heritage preservation and geomapping. A number of software solutions have been released using variations of this technique. In this ......Structure from Motion 3D reconstruction has become widely used in recent years in a number of fields such as industrial surface in- inspection, archeology, cultural heritage preservation and geomapping. A number of software solutions have been released using variations of this technique...

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.

A comparison of inverse boundary element method and near-field acoustical holography

DEFF Research Database (Denmark)

Schuhmacher, Andreas; Hald, Jørgen; Saemann, E.-U.

1999-01-01

An inverse boundary element method (IBEM) is used to estimate the surface velocity of a rolling tyre from measurements of the near-field pressure. Subsequently, the sound pressure is calculated over a finite plane surface next to the tyre from the reconstructed velocity field on the tyre surface........ In order to verify the reconstruction process, part of the measurement data is used together with Near-Field Acoustical Holography (NAH). Estimated distributions of sound pressure and particle velocity over a plane surface obtained from the two methods are compared....

Displacement disorder and reconstruction of the (001) face of tungsten

International Nuclear Information System (INIS)

Egorushkin, V.E.; Kul'ment'ev, A.I.; Savushkin, E.V.

1992-01-01

The reconstruction of the (001) border of tungsten is examined taking into consideration random static displacements of surface atoms in the high-temperature (1 x 1) phase. A microscopic model is proposed, in which the creation of c(2 x 2) phase is described as a transition of the Jahn-Teller type and an ordering of static displacements. It is shown that displacement disorder induces instability of (001) tungsten with respect to reconstruction. The effect of a uniform electric field on a disordered reconstructing surface is examined. A possible reason is given for pronounced differences in the results of investigations of the structural conversion of the (001) face in tungsten when different experimental methods are used

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.

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.

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)

Magnetic flux reconstruction methods for shaped tokamaks

International Nuclear Information System (INIS)

Tsui, Chi-Wa.

1993-12-01

The use of a variational method permits the Grad-Shafranov (GS) equation to be solved by reducing the problem of solving the 2D non-linear partial differential equation to the problem of minimizing a function of several variables. This high speed algorithm approximately solves the GS equation given a parameterization of the plasma boundary and the current profile (p' and FF' functions). The author treats the current profile parameters as unknowns. The goal is to reconstruct the internal magnetic flux surfaces of a tokamak plasma and the toroidal current density profile from the external magnetic measurements. This is a classic problem of inverse equilibrium determination. The current profile parameters can be evaluated by several different matching procedures. Matching of magnetic flux and field at the probe locations using the Biot-Savart law and magnetic Green's function provides a robust method of magnetic reconstruction. The matching of poloidal magnetic field on the plasma surface provides a unique method of identifying the plasma current profile. However, the power of this method is greatly compromised by the experimental errors of the magnetic signals. The Casing Principle provides a very fast way to evaluate the plasma contribution to the magnetic signals. It has the potential of being a fast matching method. The performance of this method is hindered by the accuracy of the poloidal magnetic field computed from the equilibrium solver. A flux reconstruction package has been implemented which integrates a vacuum field solver using a filament model for the plasma, a multi-layer perception neural network as an interface, and the volume integration of plasma current density using Green's functions as a matching method for the current profile parameters. The flux reconstruction package is applied to compare with the ASEQ and EFIT data. The results are promising

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.

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.

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.

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.

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.

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.

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

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.

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.

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

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.

Static phenomena at the charged surface of liquid hydrogen

International Nuclear Information System (INIS)

Levchenko, A.A.; Kolmakov, G.V.; Mezhov-Deglin, L.P.; Mikhjlov, M.G.; Trusov, A.B.

1999-01-01

The shape evolution of the equipotentially charged surface of liquid hydrogen layer covering the lower plate of a horizontally arranged diode in external electric fields has been studied experimentally for the first time. A reconstruction phenomenon (the formation of a stationary hump) at the flat charged surface at voltages higher than a certain critical U c1 was observed under the conditions of total compensation of the electric field in the bulk liquid by a surface charge. It is shown that the transition of the flat charged surface into the reconstructed state is a phase transition closed to the second order phase transition. The height of the hump increased with increasing the voltage and at U c2 > 1,2 U c1 the reconstructed surface lost the stability, and a stream discharge pulse was observed. The shape evolution of a changed droplet of constant volume suspended at the upper plate of the diode when the stretching electric field and gravity forces act in the same direction was studied as the voltage was increased up to the discharge

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...

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.

Mechanisms and energetics of surface atomic processes

International Nuclear Information System (INIS)

Tsong, T.T.

1991-01-01

The energies involved in various surface atomic processes such as surface diffusion, the binding of small atomic clusters on the surface, the interaction between two adsorbed atoms, the dissociation of an atom from a small cluster or from a surface layer, the binding of kink size atoms or atoms at different adsorption sites to the surface etc., can be derived from an analysis of atomically resolved field ion microscope images and a kinetic energy measurement of low temperature field desorbed ions using the time-of-flight atom-probe field ion microscope. These energies can be used to compare with theories and to understand the transport of atoms on the surface in atomic reconstructions, epitaxial growth of surface layers and crystal growth, adsorption layer superstructure formation, and also why an atomic ordering or atomic reconstruction at the surface is energetically favored. Mechanisms of some of the surface atomic processes are also clarified from these quantitative, atomic resolution studies. In this paper work in this area is bris briefly reviewed

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

Reconstruction of surface morphology from coherent scattering of ''white'' synchrotron radiation in hard X-ray regime

Energy Technology Data Exchange (ETDEWEB)

Sant, Tushar

2009-07-01

Energy Dispersive Reflectometry (EDR) beamline at BESSY II provides ''white'' X-rays in the useful energy range of 5surfaces. Technologically smooth wafers of semiconducting materials of Si and GaAs are used as ''trivial'' samples to determine the so called apparatus function. In addition I measured coherent reflectivity maps from thin film of highly scattering material of Pt with high atom number, Z=78 and patterned semiconducting surface like a GaAs surface grating which provides a certain periodicity in the measured scattering intensity. Finally I measured the surface speckles from a spatially confined Si wafer under the constraint that the size of the sample is smaller than the footprint of the incoming beam at the sample position. To reconstruct surface morphology from coherent reflectivity data is a typical inverse problem. Conventional phase retrieval algorithms like Gerchberg-Saxton (GS) algorithm, error reduction (ER) algorithm, hybrid input-output (HIO) algorithm are used in earlier work by other authors. I modified the conventional GS algorithm and ER algorithm which takes into account the additional Fresnel propagator term and also the illumination function at the sample position. I tested the modified algorithm successfully for a model surface in the form of a surface grating. I used the modified algorithm to reconstruct surface morphology from various static speckle measurements I performed at EDR beamline. The surface profiles reconstructed for different samples from the data at different energies (below the critical energy for the material at a particular incident angle) show almost the same roughness behavior for surface height with mean roughness of {proportional_to}1 nm. With the static speckle data I measured I could retrieve a one-dimensional picture of the sample surface with spatial

'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.

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.

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.

Convergence analysis in near-field imaging

International Nuclear Information System (INIS)

Bao, Gang; Li, Peijun

2014-01-01

This paper is devoted to the mathematical analysis of the direct and inverse modeling of the diffraction by a perfectly conducting grating surface in the near-field regime. It is motivated by our effort to analyze recent significant numerical results, in order to solve a class of inverse rough surface scattering problems in near-field imaging. In a model problem, the diffractive grating surface is assumed to be a small and smooth deformation of a plane surface. On the basis of the variational method, the direct problem is shown to have a unique weak solution. An analytical solution is introduced as a convergent power series in the deformation parameter by using the transformed field and Fourier series expansions. A local uniqueness result is proved for the inverse problem where only a single incident field is needed. On the basis of the analytic solution of the direct problem, an explicit reconstruction formula is presented for recovering the grating surface function with resolution beyond the Rayleigh criterion. Error estimates for the reconstructed grating surface are established with fully revealed dependence on such quantities as the surface deformation parameter, measurement distance, noise level of the scattering data, and regularity of the exact grating surface function. (paper)

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

Enhancing temporal correlations in EOF expansions for the reconstruction of missing data using DINEOF

Directory of Open Access Journals (Sweden)

A. Alvera-Azcárate

2009-10-01

Full Text Available DINEOF (Data Interpolating Empirical Orthogonal Functions is an EOF-based technique for the reconstruction of missing data in geophysical fields, such as those produced by clouds in sea surface temperature satellite images. A technique to reduce spurious time variability in DINEOF reconstructions is presented. The reconstruction of these images within a long time series using DINEOF can lead to large discontinuities in the reconstruction. Filtering the temporal covariance matrix allows to reduce this spurious variability and therefore more realistic reconstructions are obtained. The approach is tested in a three years sea surface temperature data set over the Black Sea. The effect of the filter in the temporal EOFs is presented, as well as some examples of the improvement achieved with the filtering in the SST reconstruction, both compared to the DINEOF approach without filtering.

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.

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.

Impact of local electrostatic field rearrangement on field ionization

Science.gov (United States)

Katnagallu, Shyam; Dagan, Michal; Parviainen, Stefan; Nematollahi, Ali; Grabowski, Blazej; Bagot, Paul A. J.; Rolland, Nicolas; Neugebauer, Jörg; Raabe, Dierk; Vurpillot, François; Moody, Michael P.; Gault, Baptiste

2018-03-01

Field ion microscopy allows for direct imaging of surfaces with true atomic resolution. The high charge density distribution on the surface generates an intense electric field that can induce ionization of gas atoms. We investigate the dynamic nature of the charge and the consequent electrostatic field redistribution following the departure of atoms initially constituting the surface in the form of an ion, a process known as field evaporation. We report on a new algorithm for image processing and tracking of individual atoms on the specimen surface enabling quantitative assessment of shifts in the imaged atomic positions. By combining experimental investigations with molecular dynamics simulations, which include the full electric charge, we confirm that change is directly associated with the rearrangement of the electrostatic field that modifies the imaging gas ionization zone. We derive important considerations for future developments of data reconstruction in 3D field ion microscopy, in particular for precise quantification of lattice strains and characterization of crystalline defects at the atomic scale.

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.

Confidence and sensitivity of sea-level reconstructions

DEFF Research Database (Denmark)

Svendsen, Peter Limkilde

For the last two decades, satellite altimetry has provided a near-global view of spatial and temporal patterns in sea surface height (SSH). When combined with records from tide gauges, a historical reconstruction of sea level can be obtained; while tide gauge records span up to 200 years back...... nature of the data fields. We examine the sensitivity of a reconstruction with respect to the length of calibration time series, and the spatial distribution of tide gauges or other proxy data. In addition, we consider the eect of isolating certain physical phenomena (e.g. ENSO) and annual signals...... and modelling these outside the reconstruction. The implementation is currently based on data from compound satellite datasets (i.e., two decades of altimetry), and the Simple Ocean Data Assimilation (SODA) model, an existing reconstruction, where a calibration period can be easily extracted and our model...

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.

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.

Critical Doping for the Onset of Fermi-Surface Reconstruction by Charge-Density-Wave Order in the Cuprate Superconductor La_{2-x}Sr_{x}CuO_{4}

Directory of Open Access Journals (Sweden)

S. Badoux

2016-04-01

Full Text Available The Seebeck coefficient S of the cuprate superconductor La_{2-x}Sr_{x}CuO_{4} (LSCO was measured in magnetic fields large enough to access the normal state at low temperatures, for a range of Sr concentrations from x=0.07 to x=0.15. For x=0.11, 0.12, 0.125, and 0.13, S/T decreases upon cooling to become negative at low temperatures. The same behavior is observed in the Hall coefficient R_{H}(T. In analogy with other hole-doped cuprates at similar hole concentrations p, the negative S and R_{H} show that the Fermi surface of LSCO undergoes a reconstruction caused by the onset of charge-density-wave modulations. Such modulations have indeed been detected in LSCO by x-ray diffraction in precisely the same doping range. Our data show that in LSCO this Fermi-surface reconstruction is confined to 0.085field-induced normal state of LSCO, charge-density-wave order ends at a critical doping p_{CDW}=0.15±0.005, well below the pseudogap critical doping p^{⋆}≃0.19.

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)

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.

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.

Observation of Pt-{100}-p(2×2-O reconstruction by an environmental TEM

Directory of Open Access Journals (Sweden)

Hengbo Li

2016-06-01

Full Text Available The surface structure of noble metal nanoparticles usually plays a crucial role during the catalytic process in the fields of energy and environment. It has been studied extensively by surface analytic methods, such as scanning tunneling microscopy. However, it is still challenging to secure a direct observation of the structural evolution of surfaces of nanocatalysts in reaction (gas and heating conditions at the atomic scale. Here we report an in-situ observation of atomic reconstruction on Pt {100} surfaces exposed to oxygen in an environmental transmission electron microscope (TEM. Our high-resolution TEM images revealed that Pt-{100}-p(2×2-O reconstruction occurs during the reaction between oxygen atoms and {100} facets. A reconstruction model was proposed, and TEM images simulated according to this model with different defocus values match the experimental results well.

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...

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.

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

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

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.

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.

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

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

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.

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

Pseudoproxy Experiments Using the BARCAST Reconstruction Technique: Effects on Spatiotemporal Persistence Properties

Science.gov (United States)

Nilsen, T.; Divine, D.; Rypdal, M.; Werner, J.; Rypdal, K.

2016-12-01

A modified two-dimensional stochastic-diffusive energy balance model (EBM) defined on a sphere was used for generating pseudoproxy/instrumental data and target data for surface temperature. The EBM is described in Rypdal et al. (2015). The target field has prescribed long-range memory (LRM) properties in time, and a frequency-dependent autocorrelation function in space. The Bayesian hierarchical model BARCAST, was used to generate surface temperature field reconstructions of an area corresponding to the European landmass for the past millennium. BARCAST has a built-in multivariate AR(1) model for the evolution of the temperature field, with an exponential, spatial covariance function, (Tingley & Huybers, 2010). The AR(1) process has a short-range memory, and we seek to find out how the competing spatiotemporal models influence the persistence of the reconstruction. A number of pseudoproxy experiments were performed with a fixed proxy network, using different signal-to-noise ratios (SNR) and colors of noise, (white/red). To study the persistence properties, the power-law relation of the power spectral density for LRM processes was used: S(f) f-β. The spectral exponent β was estimated both for local data and the spatial mean of the full region. The local β for the target varies between (0.1, 0.4), and for the spatial mean β 0.6. Results for the reconstructions show that the local and global memory is influenced by the noise color and level. Low noise levels or absence of noise results in reconstructions that exhibit similar properties as the target, while for higher noise levels the reconstructions have memory properties of a white/red character, (SNR=0.3 by standard deviation). Since an SNR of 0.5-0.25 is considered realistic for real proxy records, this implies that estimates of temporal persistence from proxy-based reconstructions reflect the proxy noise to a high degree, and not the signal as desired. Rypdal et al., 2015: Spatiotemporal Long-Range Persistence

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.

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.

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.

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.

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.

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.

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

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

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

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

On the reconstruction of Lifshitz spacetimes

International Nuclear Information System (INIS)

Gentle, Simon A.; Keeler, Cynthia

2016-01-01

We consider the reconstruction of a Lifshitz spacetime from three perspectives: differential entropy (or ‘hole-ography’), causal wedges and entanglement wedges. We find that not all time-varying bulk curves in vacuum Lifshitz can be reconstructed via the differential entropy approach, adding a caveat to the general analysis of http://dx.doi.org/10.1007/JHEP10(2014)149. We show that the causal wedge for Lifshitz spacetimes degenerates, while the entanglement wedge requires the additional consideration of a set of boundary-emanating light-sheets. The need to include bulk surfaces with no clear field theory interpretation in the differential entropy construction and the change in the entanglement wedge formation both serve as warnings against a naive application of holographic entanglement entropy proposals in Lifshitz spacetimes.

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

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

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.

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)

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)

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.

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.

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.

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.

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

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)

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...

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.

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.;

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

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.

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.

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.

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

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.

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

Low-temperature field evaporation of Nb3Sn compound

International Nuclear Information System (INIS)

Ksenofontov, V.A.; Kul'ko, V.B.; Kutsenko, P.A.

1986-01-01

Investigation results on field evaporation of superconducting Nb 3 Sn compound wth A15 lattice are presented. Compound evaporation is shown to proceed in two stages. Evaporation field and ionic composition of evaporating material are determined. It is found out that in strong electric fields compound surface represents niobium skeleton, wich does not form regular image. Comparison of ion-microscopic and calculated images formed by low-temperature field evaporation indicates to possibility of sample surface reconstruction after preferable tin evaporation

Dynamical reconstruction of the global ocean state during the Last Glacial Maximum

Science.gov (United States)

Kurahashi-Nakamura, Takasumi; Paul, André; Losch, Martin

2017-04-01

The global ocean state for the modern age and for the Last Glacial Maximum (LGM) was dynamically reconstructed with a sophisticated data assimilation technique. A substantial amount of data including global seawater temperature, salinity (only for the modern estimate), and the isotopic composition of oxygen and carbon (only in the Atlantic for the LGM) were integrated into an ocean general circulation model with the help of the adjoint method, thereby the model was optimized to reconstruct plausible continuous fields of tracers, overturning circulation and water mass distribution. The adjoint-based LGM state estimation of this study represents the state of the art in terms of the length of forward model runs, the number of observations assimilated, and the model domain. Compared to the modern state, the reconstructed continuous sea-surface temperature field for the LGM shows a global-mean cooling of 2.2 K, and the reconstructed LGM ocean has a more vigorous Atlantic meridional overturning circulation, shallower North Atlantic Deep Water (NADW) equivalent, stronger stratification, and more saline deep water.

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.

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...

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.

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

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

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.

Non-axisymmetric equilibrium reconstruction and suppression of density limit disruptions in a current-carrying stellarator

Science.gov (United States)

Ma, Xinxing; Ennis, D. A.; Hanson, J. D.; Hartwell, G. J.; Knowlton, S. F.; Maurer, D. A.

2017-10-01

Non-axisymmetric equilibrium reconstructions have been routinely performed with the V3FIT code in the Compact Toroidal Hybrid (CTH), a stellarator/tokamak hybrid. In addition to 50 external magnetic measurements, 160 SXR emissivity measurements are incorporated into V3FIT to reconstruct the magnetic flux surface geometry and infer the current distribution within the plasma. Improved reconstructions of current and q profiles provide insight into understanding the physics of density limit disruptions observed in current-carrying discharges in CTH. It is confirmed that the final scenario of the density limit of CTH plasmas is consistent with classic observations in tokamaks: current profile shrinkage leads to growing MHD instabilities (tearing modes) followed by a loss of MHD equilibrium. It is also observed that the density limit at a given current linearly increases with increasing amounts of 3D shaping fields. Consequently, plasmas with densities up to two times the Greenwald limit are attained. Equilibrium reconstructions show that addition of 3D fields effectively moves resonance surfaces towards the edge of the plasma where the current profile gradient is less, providing a stabilizing effect. This work is supported by US Department of Energy Grant No. DE-FG02-00ER54610.

The Accuracy of 3D Optical Reconstruction and Additive Manufacturing Processes in Reproducing Detailed Subject-Specific Anatomy

Directory of Open Access Journals (Sweden)

Paolo Ferraiuoli

2017-10-01

Full Text Available 3D reconstruction and 3D printing of subject-specific anatomy is a promising technology for supporting clinicians in the visualisation of disease progression and planning for surgical intervention. In this context, the 3D model is typically obtained from segmentation of magnetic resonance imaging (MRI, computed tomography (CT or echocardiography images. Although these modalities allow imaging of the tissues in vivo, assessment of quality of the reconstruction is limited by the lack of a reference geometry as the subject-specific anatomy is unknown prior to image acquisition. In this work, an optical method based on 3D digital image correlation (3D-DIC techniques is used to reconstruct the shape of the surface of an ex vivo porcine heart. This technique requires two digital charge-coupled device (CCD cameras to provide full-field shape measurements and to generate a standard tessellation language (STL file of the sample surface. The aim of this work was to quantify the error of 3D-DIC shape measurements using the additive manufacturing process. The limitations of 3D printed object resolution, the discrepancy in reconstruction of the surface of cardiac soft tissue and a 3D printed model of the same surface were evaluated. The results obtained demonstrated the ability of the 3D-DIC technique to reconstruct localised and detailed features on the cardiac surface with sub-millimeter accuracy.

Three-dimension reconstruction based on spatial light modulator

International Nuclear Information System (INIS)

Deng Xuejiao; Zhang Nanyang; Zeng Yanan; Yin Shiliang; Wang Weiyu

2011-01-01

Three-dimension reconstruction, known as an important research direction of computer graphics, is widely used in the related field such as industrial design and manufacture, construction, aerospace, biology and so on. Via such technology we can obtain three-dimension digital point cloud from a two-dimension image, and then simulate the three-dimensional structure of the physical object for further study. At present, the obtaining of three-dimension digital point cloud data is mainly based on the adaptive optics system with Shack-Hartmann sensor and phase-shifting digital holography. Referring to surface fitting, there are also many available methods such as iterated discrete fourier transform, convolution and image interpolation, linear phase retrieval. The main problems we came across in three-dimension reconstruction are the extraction of feature points and arithmetic of curve fitting. To solve such problems, we can, first of all, calculate the relevant surface normal vector information of each pixel in the light source coordinate system, then these vectors are to be converted to the coordinates of image through the coordinate conversion, so the expectant 3D point cloud get arise. Secondly, after the following procedures of de-noising, repairing, the feature points can later be selected and fitted to get the fitting function of the surface topography by means of Zernike polynomial, so as to reconstruct the determinand's three-dimensional topography. In this paper, a new kind of three-dimension reconstruction algorithm is proposed, with the assistance of which, the topography can be estimated from its grayscale at different sample points. Moreover, the previous stimulation and the experimental results prove that the new algorithm has a strong capability to fit, especially for large-scale objects .

Three-dimension reconstruction based on spatial light modulator

Science.gov (United States)

Deng, Xuejiao; Zhang, Nanyang; Zeng, Yanan; Yin, Shiliang; Wang, Weiyu

2011-02-01

Three-dimension reconstruction, known as an important research direction of computer graphics, is widely used in the related field such as industrial design and manufacture, construction, aerospace, biology and so on. Via such technology we can obtain three-dimension digital point cloud from a two-dimension image, and then simulate the three-dimensional structure of the physical object for further study. At present, the obtaining of three-dimension digital point cloud data is mainly based on the adaptive optics system with Shack-Hartmann sensor and phase-shifting digital holography. Referring to surface fitting, there are also many available methods such as iterated discrete fourier transform, convolution and image interpolation, linear phase retrieval. The main problems we came across in three-dimension reconstruction are the extraction of feature points and arithmetic of curve fitting. To solve such problems, we can, first of all, calculate the relevant surface normal vector information of each pixel in the light source coordinate system, then these vectors are to be converted to the coordinates of image through the coordinate conversion, so the expectant 3D point cloud get arise. Secondly, after the following procedures of de-noising, repairing, the feature points can later be selected and fitted to get the fitting function of the surface topography by means of Zernike polynomial, so as to reconstruct the determinand's three-dimensional topography. In this paper, a new kind of three-dimension reconstruction algorithm is proposed, with the assistance of which, the topography can be estimated from its grayscale at different sample points. Moreover, the previous stimulation and the experimental results prove that the new algorithm has a strong capability to fit, especially for large-scale objects .

Detecting tangential dislocations on planar faults from traction free surface observations

International Nuclear Information System (INIS)

Ionescu, Ioan R; Volkov, Darko

2009-01-01

We propose in this paper robust reconstruction methods for tangential dislocations on planar faults. We assume that only surface observations are available, and that a traction free condition applies at that surface. This study is an extension to the full three dimensions of Ionescu and Volkov (2006 Inverse Problems 22 2103). We also explore in this present paper the possibility of detecting slow slip events (such as silent earthquakes, or earthquake nucleation phases) from GPS observations. Our study uses extensively an asymptotic estimate for the observed surface displacement. This estimate is first used to derive what we call the moments reconstruction method. Then it is also used for finding necessary conditions for a surface displacement field to have been caused by a slip on a fault. These conditions lead to the introduction of two parameters: the activation factor and the confidence index. They can be computed from the surface observations in a robust fashion. They indicate whether a measured displacement field is due to an active fault. We also infer a second, combined, reconstruction technique blending least square minimization and the moments method. We carefully assess how our reconstruction method is affected by the sensitivity of the observation apparatus and the stepsize for the grid of surface observation points. The maximum permissible stepsize for such a grid is computed for different values of fault depth and orientation. Finally we present numerical examples of reconstruction of faults. We demonstrate that our combined method is sharp, robust and computationally inexpensive. We also note that this method performs satisfactorily for shallow faults, despite the fact that our asymptotic formula deteriorates in that case

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.

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.

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.

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

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.

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).

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)

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.

Reconstruction of Sound Source Pressures in an Enclosure Using the Phased Beam Tracing Method

DEFF Research Database (Denmark)

Jeong, Cheol-Ho; Ih, Jeong-Guon

2009-01-01

. First, surfaces of an extended source are divided into reasonably small segments. From each source segment, one beam is projected into the field and all emitted beams are traced. Radiated beams from the source reach array sensors after traveling various paths including the wall reflections. Collecting...... all the pressure histories at the field points, source-observer relations can be constructed in a matrix-vector form for each frequency. By multiplying the measured field data with the pseudo-inverse of the calculated transfer function, one obtains the distribution of source pressure. An omni......-directional sphere and a cubic source in a rectangular enclosure were taken as examples in the simulation tests. A reconstruction error was investigated by Monte Carlo simulation in terms of field point locations. When the source information was reconstructed by the present method, it was shown that the sound power...

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...

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

Chemical and valence reconstruction at the surface of SmB6 revealed by means of resonant soft x-ray reflectometry

Science.gov (United States)

Zabolotnyy, V. B.; Fürsich, K.; Green, R. J.; Lutz, P.; Treiber, K.; Min, Chul-Hee; Dukhnenko, A. V.; Shitsevalova, N. Y.; Filipov, V. B.; Kang, B. Y.; Cho, B. K.; Sutarto, R.; He, Feizhou; Reinert, F.; Inosov, D. S.; Hinkov, V.

2018-05-01

Samarium hexaboride (SmB6), a Kondo insulator with mixed valence, has recently attracted much attention as a possible host for correlated topological surface states. Here, we use a combination of x-ray absorption and reflectometry techniques, backed up with a theoretical model for the resonant M4 ,5 absorption edge of Sm and photoemission data, to establish laterally averaged chemical and valence depth profiles at the surface of SmB6. We show that upon cleaving, the highly polar (001) surface of SmB6 undergoes substantial chemical and valence reconstruction, resulting in boron termination and a Sm3 + dominated subsurface region. Whereas at room temperature, the reconstruction occurs on a timescale of less than 2 h, it takes about 24 h below 50 K. The boron termination is eventually established, irrespective of the initial termination. Our findings reconcile earlier depth resolved photoemission and scanning tunneling spectroscopy studies performed at different temperatures and are important for better control of surface states in this system.

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

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.

Breaking the Crowther limit: Combining depth-sectioning and tilt tomography for high-resolution, wide-field 3D reconstructions

Energy Technology Data Exchange (ETDEWEB)

Hovden, Robert, E-mail: rmh244@cornell.edu [School of Applied and Engineering Physics and Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853 (United States); Ercius, Peter [National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Jiang, Yi [Department of Physics, Cornell University, Ithaca, NY 14853 (United States); Wang, Deli; Yu, Yingchao; Abruña, Héctor D. [Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853 (United States); Elser, Veit [Department of Physics, Cornell University, Ithaca, NY 14853 (United States); Muller, David A. [School of Applied and Engineering Physics and Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853 (United States)

2014-05-01

To date, high-resolution (<1 nm) imaging of extended objects in three-dimensions (3D) has not been possible. A restriction known as the Crowther criterion forces a tradeoff between object size and resolution for 3D reconstructions by tomography. Further, the sub-Angstrom resolution of aberration-corrected electron microscopes is accompanied by a greatly diminished depth of field, causing regions of larger specimens (>6 nm) to appear blurred or missing. Here we demonstrate a three-dimensional imaging method that overcomes both these limits by combining through-focal depth sectioning and traditional tilt-series tomography to reconstruct extended objects, with high-resolution, in all three dimensions. The large convergence angle in aberration corrected instruments now becomes a benefit and not a hindrance to higher quality reconstructions. A through-focal reconstruction over a 390 nm 3D carbon support containing over 100 dealloyed and nanoporous PtCu catalyst particles revealed with sub-nanometer detail the extensive and connected interior pore structure that is created by the dealloying instability. - Highlights: • Develop tomography technique for high-resolution and large field of view. • We combine depth sectioning with traditional tilt tomography. • Through-focal tomography reduces tilts and improves resolution. • Through-focal tomography overcomes the fundamental Crowther limit. • Aberration-corrected becomes a benefit and not a hindrance for tomography.

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

Biologically inspired EM image alignment and neural reconstruction.

Science.gov (United States)

Knowles-Barley, Seymour; Butcher, Nancy J; Meinertzhagen, Ian A; Armstrong, J Douglas

2011-08-15

Three-dimensional reconstruction of consecutive serial-section transmission electron microscopy (ssTEM) images of neural tissue currently requires many hours of manual tracing and annotation. Several computational techniques have already been applied to ssTEM images to facilitate 3D reconstruction and ease this burden. Here, we present an alternative computational approach for ssTEM image analysis. We have used biologically inspired receptive fields as a basis for a ridge detection algorithm to identify cell membranes, synaptic contacts and mitochondria. Detected line segments are used to improve alignment between consecutive images and we have joined small segments of membrane into cell surfaces using a dynamic programming algorithm similar to the Needleman-Wunsch and Smith-Waterman DNA sequence alignment procedures. A shortest path-based approach has been used to close edges and achieve image segmentation. Partial reconstructions were automatically generated and used as a basis for semi-automatic reconstruction of neural tissue. The accuracy of partial reconstructions was evaluated and 96% of membrane could be identified at the cost of 13% false positive detections. An open-source reference implementation is available in the Supplementary information. seymour.kb@ed.ac.uk; douglas.armstrong@ed.ac.uk Supplementary data are available at Bioinformatics online.

Local self-similarity descriptor for point-of-interest reconstruction of real-world scenes

International Nuclear Information System (INIS)

Gao, Xianglu; Wan, Weibing; Zhao, Qunfei; Zhang, Xianmin

2015-01-01

Scene reconstruction is utilized commonly in close-range photogrammetry, with diverse applications in fields such as industry, biology, and aerospace industries. Presented surfaces or wireframe three-dimensional (3D) model reconstruction applications are either too complex or too inflexible to accommodate various types of real-world scenes, however. This paper proposes an algorithm for acquiring point-of-interest (referred to throughout the study as POI) coordinates in 3D space, based on multi-view geometry and a local self-similarity descriptor. After reconstructing several POIs specified by a user, a concise and flexible target object measurement method, which obtains the distance between POIs, is described in detail. The proposed technique is able to measure targets with high accuracy even in the presence of obstacles and non-Lambertian surfaces. The method is so flexible that target objects can be measured with a handheld digital camera. Experimental results further demonstrate the effectiveness of the algorithm. (paper)

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...

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

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.

Three-dimension reconstruction based on spatial light modulator

Energy Technology Data Exchange (ETDEWEB)

Deng Xuejiao; Zhang Nanyang; Zeng Yanan; Yin Shiliang; Wang Weiyu, E-mail: daisydelring@yahoo.com.cn [Huazhong University of Science and Technology (China)

2011-02-01

Three-dimension reconstruction, known as an important research direction of computer graphics, is widely used in the related field such as industrial design and manufacture, construction, aerospace, biology and so on. Via such technology we can obtain three-dimension digital point cloud from a two-dimension image, and then simulate the three-dimensional structure of the physical object for further study. At present, the obtaining of three-dimension digital point cloud data is mainly based on the adaptive optics system with Shack-Hartmann sensor and phase-shifting digital holography. Referring to surface fitting, there are also many available methods such as iterated discrete fourier transform, convolution and image interpolation, linear phase retrieval. The main problems we came across in three-dimension reconstruction are the extraction of feature points and arithmetic of curve fitting. To solve such problems, we can, first of all, calculate the relevant surface normal vector information of each pixel in the light source coordinate system, then these vectors are to be converted to the coordinates of image through the coordinate conversion, so the expectant 3D point cloud get arise. Secondly, after the following procedures of de-noising, repairing, the feature points can later be selected and fitted to get the fitting function of the surface topography by means of Zernike polynomial, so as to reconstruct the determinand's three-dimensional topography. In this paper, a new kind of three-dimension reconstruction algorithm is proposed, with the assistance of which, the topography can be estimated from its grayscale at different sample points. Moreover, the previous stimulation and the experimental results prove that the new algorithm has a strong capability to fit, especially for large-scale objects .

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.

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.

Near field acoustic holography with microphones on a rigid sphere

DEFF Research Database (Denmark)

Jacobsen, Finn; Moreno-Pescador, Guillermo; Fernandez Grande, Efren

2011-01-01

Spherical near field acoustic holography (spherical NAH) is a technique that makes it possible to reconstruct the sound field inside and just outside a spherical surface on which the sound pressure is measured with an array of microphones. This is potentially very useful for source identification...

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

Mesh-free free-form lensing - I. Methodology and application to mass reconstruction

Science.gov (United States)

Merten, Julian

2016-09-01

Many applications and algorithms in the field of gravitational lensing make use of meshes with a finite number of nodes to analyse and manipulate data. Specific examples in lensing are astronomical CCD images in general, the reconstruction of density distributions from lensing data, lens-source plane mapping or the characterization and interpolation of a point spread function. We present a numerical framework to interpolate and differentiate in the mesh-free domain, defined by nodes with coordinates that follow no regular pattern. The framework is based on radial basis functions (RBFs) to smoothly represent data around the nodes. We demonstrate the performance of Gaussian RBF-based, mesh-free interpolation and differentiation, which reaches the sub-percent level in both cases. We use our newly developed framework to translate ideas of free-form mass reconstruction from lensing on to the mesh-free domain. By reconstructing a simulated mock lens we find that strong-lensing only reconstructions achieve <10 per cent accuracy in the areas where these constraints are available but provide poorer results when departing from these regions. Weak-lensing only reconstructions give <10 per cent accuracy outside the strong-lensing regime, but cannot resolve the inner core structure of the lens. Once both regimes are combined, accurate reconstructions can be achieved over the full field of view. The reconstruction of a simulated lens, using constraints that mimics real observations, yields accurate results in terms of surface-mass density, Navarro-Frenk-White profile (NFW) parameters, Einstein radius and magnification map recovery, encouraging the application of this method to real data.

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.

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...

Theory of aberration fields for general optical systems with freeform surfaces.

Science.gov (United States)

Fuerschbach, Kyle; Rolland, Jannick P; Thompson, Kevin P

2014-11-03

This paper utilizes the framework of nodal aberration theory to describe the aberration field behavior that emerges in optical systems with freeform optical surfaces, particularly φ-polynomial surfaces, including Zernike polynomial surfaces, that lie anywhere in the optical system. If the freeform surface is located at the stop or pupil, the net aberration contribution of the freeform surface is field constant. As the freeform optical surface is displaced longitudinally away from the stop or pupil of the optical system, the net aberration contribution becomes field dependent. It is demonstrated that there are no new aberration types when describing the aberration fields that arise with the introduction of freeform optical surfaces. Significantly it is shown that the aberration fields that emerge with the inclusion of freeform surfaces in an optical system are exactly those that have been described by nodal aberration theory for tilted and decentered optical systems. The key contribution here lies in establishing the field dependence and nodal behavior of each freeform term that is essential knowledge for effective application to optical system design. With this development, the nodes that are distributed throughout the field of view for each aberration type can be anticipated and targeted during optimization for the correction or control of the aberrations in an optical system with freeform surfaces. This work does not place any symmetry constraints on the optical system, which could be packaged in a fully three dimensional geometry, without fold mirrors.

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.

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.

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.

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.

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

Fast multiview three-dimensional reconstruction method using cost volume filtering

Science.gov (United States)

Lee, Seung Joo; Park, Min Ki; Jang, In Yeop; Lee, Kwan H.

2014-03-01

As the number of customers who want to record three-dimensional (3-D) information using a mobile electronic device increases, it becomes more and more important to develop a method which quickly reconstructs a 3-D model from multiview images. A fast multiview-based 3-D reconstruction method is presented, which is suitable for the mobile environment by constructing a cost volume of the 3-D height field. This method consists of two steps: the construction of a reliable base surface and the recovery of shape details. In each step, the cost volume is constructed using photoconsistency and then it is filtered according to the multiscale. The multiscale-based cost volume filtering allows the 3-D reconstruction to maintain the overall shape and to preserve the shape details. We demonstrate the strength of the proposed method in terms of computation time, accuracy, and unconstrained acquisition environment.

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...

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.

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.

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

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.

Regional-Scale Surface Magnetic Fields and Proton Fluxes to Mercury's Surface from Proton-Reflection Magnetometry

Science.gov (United States)

Winslow, R. M.; Johnson, C. L.; Anderson, B. J.; Gershman, D. J.; Raines, J. M.; Lillis, R. J.; Korth, H.; Slavin, J. A.; Solomon, S. C.; Zurbuchen, T.

2014-12-01

The application of a recently developed proton-reflection magnetometry technique to MESSENGER spacecraft observations at Mercury has yielded two significant findings. First, loss-cone observations directly confirm particle precipitation to Mercury's surface and indicate that solar wind plasma persistently bombards the planet not only in the magnetic cusp regions but over a large fraction of the southern hemisphere. Second, the inferred surface field strengths independently confirm the north-south asymmetry in Mercury's global magnetic field structure first documented from observations of magnetic equator crossings. Here we extend this work with 1.5 additional years of observations (i.e., to 2.5 years in all) to further probe Mercury's surface magnetic field and better resolve proton flux precipitation to the planet's surface. We map regions where proton loss cones are observed; these maps indicate regions where protons precipitate directly onto the surface. The augmentation of our data set over that used in our original study allows us to examine the proton loss cones in cells of dimension 10° latitude by 20° longitude in Mercury body-fixed coordinates. We observe a transition from double-sided to single-sided loss cones in the pitch-angle distributions; this transition marks the boundary between open and closed field lines. At the surface this boundary lies between 60° and 70°N. Our observations allow the estimation of surface magnetic field strengths in the northern cusp region and the calculation of incident proton fluxes to both hemispheres. In the northern cusp, our regional-scale observations are consistent with an offset dipole field and a dipole moment of 190 nT RM3, where RM is Mercury's radius, implying that any regional-scale variations in surface magnetic field strengths are either weak relative to the dipole field or occur at length scales smaller than the resolution of our observations (~300 km). From the global proton flux map (north of 40° S

A cosmic ray muon going through CMS with the magnet at full field. The line shows the path of the muon reconstructed from information recorded in the various detectors.

CERN Multimedia

Ianna, Osborne

2007-01-01

The event display of the event 3981 from the MTCC run 2605. The data has been taken with a magnetic field of 3.8 T. A detailed model of the magnetic field corresponding to 4T is shown as a color gradient from 4T in the center (red) to 0 T outside of the detector (blue). The cosmic muon has been detected by all four detectors participating in the run: the drift tubes, the HCAL, the tracker and the ECAL subdetectors and it has been reconstructed online. The event display shows the reconstructed 4D segments in the drift tubes (magenta), the reconstructed hits in HCAL (blue), the locally reconstructed track in the tracker (green), the uncalibrated rec hits in ECAL (light green). A muon track was reconstructed in the drift tubes and extrapolated back into the detector taking the magnetic field into account (green).

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

Evaluation of proxy-based millennial reconstruction methods

Energy Technology Data Exchange (ETDEWEB)

Lee, Terry C.K.; Tsao, Min [University of Victoria, Department of Mathematics and Statistics, Victoria, BC (Canada); Zwiers, Francis W. [Environment Canada, Climate Research Division, Toronto, ON (Canada)

2008-08-15

A range of existing statistical approaches for reconstructing historical temperature variations from proxy data are compared using both climate model data and real-world paleoclimate proxy data. We also propose a new method for reconstruction that is based on a state-space time series model and Kalman filter algorithm. The state-space modelling approach and the recently developed RegEM method generally perform better than their competitors when reconstructing interannual variations in Northern Hemispheric mean surface air temperature. On the other hand, a variety of methods are seen to perform well when reconstructing surface air temperature variability on decadal time scales. An advantage of the new method is that it can incorporate additional, non-temperature, information into the reconstruction, such as the estimated response to external forcing, thereby permitting a simultaneous reconstruction and detection analysis as well as future projection. An application of these extensions is also demonstrated in the paper. (orig.)

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

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.

Multi-centennial upper-ocean heat content reconstruction using online data assimilation

Science.gov (United States)

Perkins, W. A.; Hakim, G. J.

2017-12-01

The Last Millennium Reanalysis (LMR) provides an advanced paleoclimate ensemble data assimilation framework for multi-variate climate field reconstructions over the Common Era. Although reconstructions in this framework with full Earth system models remain prohibitively expensive, recent work has shown improved ensemble reconstruction validation using computationally inexpensive linear inverse models (LIMs). Here we leverage these techniques in pursuit of a new multi-centennial field reconstruction of upper-ocean heat content (OHC), synthesizing model dynamics with observational constraints from proxy records. OHC is an important indicator of internal climate variability and responds to planetary energy imbalances. Therefore, a consistent extension of the OHC record in time will help inform aspects of low-frequency climate variability. We use the Community Climate System Model version 4 (CCSM4) and Max Planck Institute (MPI) last millennium simulations to derive the LIMs, and the PAGES2K v.2.0 proxy database to perform annually resolved reconstructions of upper-OHC, surface air temperature, and wind stress over the last 500 years. Annual OHC reconstructions and uncertainties for both the global mean and regional basins are compared against observational and reanalysis data. We then investigate differences in dynamical behavior at decadal and longer time scales between the reconstruction and simulations in the last-millennium Coupled Model Intercomparison Project version 5 (CMIP5). Preliminary investigation of 1-year forecast skill for an OHC-only LIM shows largely positive spatial grid point local anomaly correlations (LAC) with a global average LAC of 0.37. Compared to 1-year OHC persistence forecast LAC (global average LAC of 0.30), the LIM outperforms the persistence forecasts in the tropical Indo-Pacific region, the equatorial Atlantic, and in certain regions near the Antarctic Circumpolar Current. In other regions, the forecast correlations are less than the

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

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.

Separating twin images and locating the center of a microparticle in dense suspensions using correlations among reconstructed fields of two parallel holograms.

Science.gov (United States)

Ling, Hangjian; Katz, Joseph

2014-09-20

This paper deals with two issues affecting the application of digital holographic microscopy (DHM) for measuring the spatial distribution of particles in a dense suspension, namely discriminating between real and virtual images and accurate detection of the particle center. Previous methods to separate real and virtual fields have involved applications of multiple phase-shifted holograms, combining reconstructed fields of multiple axially displaced holograms, and analysis of intensity distributions of weakly scattering objects. Here, we introduce a simple approach based on simultaneously recording two in-line holograms, whose planes are separated by a short distance from each other. This distance is chosen to be longer than the elongated trace of the particle. During reconstruction, the real images overlap, whereas the virtual images are displaced by twice the distance between hologram planes. Data analysis is based on correlating the spatial intensity distributions of the two reconstructed fields to measure displacement between traces. This method has been implemented for both synthetic particles and a dense suspension of 2 μm particles. The correlation analysis readily discriminates between real and virtual images of a sample containing more than 1300 particles. Consequently, we can now implement DHM for three-dimensional tracking of particles when the hologram plane is located inside the sample volume. Spatial correlations within the same reconstructed field are also used to improve the detection of the axial location of the particle center, extending previously introduced procedures to suspensions of microscopic particles. For each cross section within a particle trace, we sum the correlations among intensity distributions in all planes located symmetrically on both sides of the section. This cumulative correlation has a sharp peak at the particle center. Using both synthetic and recorded particle fields, we show that the uncertainty in localizing the axial

Titanium template for scaphoid reconstruction.

Science.gov (United States)

Haefeli, M; Schaefer, D J; Schumacher, R; Müller-Gerbl, M; Honigmann, P

2015-06-01

Reconstruction of a non-united scaphoid with a humpback deformity involves resection of the non-union followed by bone grafting and fixation of the fragments. Intraoperative control of the reconstruction is difficult owing to the complex three-dimensional shape of the scaphoid and the other carpal bones overlying the scaphoid on lateral radiographs. We developed a titanium template that fits exactly to the surfaces of the proximal and distal scaphoid poles to define their position relative to each other after resection of the non-union. The templates were designed on three-dimensional computed tomography reconstructions and manufactured using selective laser melting technology. Ten conserved human wrists were used to simulate the reconstruction. The achieved precision measured as the deviation of the surface of the reconstructed scaphoid from its virtual counterpart was good in five cases (maximal difference 1.5 mm), moderate in one case (maximal difference 3 mm) and inadequate in four cases (difference more than 3 mm). The main problems were attributed to the template design and can be avoided by improved pre-operative planning, as shown in a clinical case. © The Author(s) 2014.

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

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.

Passive electromagnetic NDE for mechanical damage inspection by detecting leakage magnetic flux. (I. Reconstruction of magnetic charges from detected field signals)

International Nuclear Information System (INIS)

Chen, Zhenmao; Aoto, Kazumi; Kato, Syoichi

1999-07-01

In this report, reconstruction of magnetic charges induced by mechanical damages in a test piece of SUS304 stainless steel is performed as a part of efforts to establish a passive nondestructive testing method on the basis of the inspection of leakage magnetic field. The approach for solving this typical ill-posed inverse problem is selected as a way in the least square method category. Concerning the ill-poseness of the system of equations, an iteration algorithm is adopted to its solving in which the designations of initial profile, the weight coefficients and the total number of iterations are taken as means of regularization. From examples using simulated input data, it is verified that the approach gives good reconstruction results in case of signals with a relative high S/N ratio. For improving the robustness of the proposed method, a Galerkin procedure with base functions chosen as the Daubechies' wavelet is also introduced for discretizing the governing equation. By comparing the reconstruction results of the least square method and those using wavelet discretization, it is found that the wavelet used approach is more feasible in the inversion of noise polluted signals. Reconstruction of 1-D and 2-D magnetic charges with the least square strategy and reconstruction of an 1-D problem with the wavelet used method are carried out from both simulated and measured magnetic field signals which are used as the validation of the proposed inversion strategy. (author)

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.

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)

3D Volumetric Modeling and Microvascular Reconstruction of Irradiated Lumbosacral Defects After Oncologic Resection

Directory of Open Access Journals (Sweden)

Emilio Garcia-Tutor

2016-12-01

Full Text Available Background: Locoregional flaps are sufficient in most sacral reconstructions. However, large sacral defects due to malignancy necessitate a different reconstructive approach, with local flaps compromised by radiation and regional flaps inadequate for broad surface areas or substantial volume obliteration. In this report, we present our experience using free muscle transfer for volumetric reconstruction in such cases, and demonstrate 3D haptic models of the sacral defect to aid preoperative planning.Methods: Five consecutive patients with irradiated sacral defects secondary to oncologic resections were included, surface area ranging from 143-600cm2. Latissimus dorsi-based free flap sacral reconstruction was performed in each case, between 2005 and 2011. Where the superior gluteal artery was compromised, the subcostal artery was used as a recipient vessel. Microvascular technique, complications and outcomes are reported. The use of volumetric analysis and 3D printing is also demonstrated, with imaging data converted to 3D images suitable for 3D printing with Osirix software (Pixmeo, Geneva, Switzerland. An office-based, desktop 3D printer was used to print 3D models of sacral defects, used to demonstrate surface area and contour and produce a volumetric print of the dead space needed for flap obliteration. Results: The clinical series of latissimus dorsi free flap reconstructions is presented, with successful transfer in all cases, and adequate soft-tissue cover and volume obliteration achieved. The original use of the subcostal artery as a recipient vessel was successfully achieved. All wounds healed uneventfully. 3D printing is also demonstrated as a useful tool for 3D evaluation of volume and dead-space.Conclusion: Free flaps offer unique benefits in sacral reconstruction where local tissue is compromised by irradiation and tumor recurrence, and dead-space requires accurate volumetric reconstruction. We describe for the first time the use of

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.

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.

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

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.

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.

Patch near-field acoustic holography: The influence of acoustic contributions from outside the source

DEFF Research Database (Denmark)

Fernandez Grande, Efren; Jacobsen, Finn; Zhang, Yong-Bin

2009-01-01

It is a requirement of conventional Near-field Acoustic Holography that the measurement area covers the entire surface of the source. In the case of Patch Near-field Acoustic Holography (patch NAH), the measurement area can be reduced to cover only a specific area of the source which...... is of particular interest (known as the “patch” or “source patch”). The area of the source beyond this patch is not of interest in the analysis. However, its acoustic output may nevertheless contribute to the total sound field in the measurement plane, and influence the reconstruction of the field close...... to the patch. The purpose of this paper is to investigate how the acoustic radiation from outside the patch area influences the reconstruction of the sound field close to the source. The reconstruction is based on simulated measurements of sound pressure and particle velocity. The methods used in this paper...

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)

Risk Factors and Predictors of Significant Chondral Surface Change From Primary to Revision Anterior Cruciate Ligament Reconstruction: A MOON and MARS Cohort Study.

Science.gov (United States)

Magnussen, Robert A; Borchers, James R; Pedroza, Angela D; Huston, Laura J; Haas, Amanda K; Spindler, Kurt P; Wright, Rick W; Kaeding, Christopher C; Allen, Christina R; Anderson, Allen F; Cooper, Daniel E; DeBerardino, Thomas M; Dunn, Warren R; Lantz, Brett A; Mann, Barton; Stuart, Michael J; Albright, John P; Amendola, Annunziato; Andrish, Jack T; Annunziata, Christopher C; Arciero, Robert A; Bach, Bernard R; Baker, Champ L; Bartolozzi, Arthur R; Baumgarten, Keith M; Bechler, Jeffery R; Berg, Jeffrey H; Bernas, Geoffrey A; Brockmeier, Stephen F; Brophy, Robert H; Bush-Joseph, Charles A; Butler, J Brad; Campbell, John D; Carey, James L; Carpenter, James E; Cole, Brian J; Cooper, Jonathan M; Cox, Charles L; Creighton, R Alexander; Dahm, Diane L; David, Tal S; Flanigan, David C; Frederick, Robert W; Ganley, Theodore J; Garofoli, Elizabeth A; Gatt, Charles J; Gecha, Steven R; Giffin, James Robert; Hame, Sharon L; Hannafin, Jo A; Harner, Christopher D; Harris, Norman Lindsay; Hechtman, Keith S; Hershman, Elliott B; Hoellrich, Rudolf G; Hosea, Timothy M; Johnson, David C; Johnson, Timothy S; Jones, Morgan H; Kamath, Ganesh V; Klootwyk, Thomas E; Levy, Bruce A; Ma, C Benjamin; Maiers, G Peter; Marx, Robert G; Matava, Matthew J; Mathien, Gregory M; McAllister, David R; McCarty, Eric C; McCormack, Robert G; Miller, Bruce S; Nissen, Carl W; O'Neill, Daniel F; Owens, Brett D; Parker, Richard D; Purnell, Mark L; Ramappa, Arun J; Rauh, Michael A; Rettig, Arthur C; Sekiya, Jon K; Shea, Kevin G; Sherman, Orrin H; Slauterbeck, James R; Smith, Matthew V; Spang, Jeffrey T; Svoboda, Steven J; Taft, Timothy N; Tenuta, Joachim J; Tingstad, Edwin M; Vidal, Armando F; Viskontas, Darius G; White, Richard A; Williams, James S; Wolcott, Michelle L; Wolf, Brian R; York, James J

2018-03-01

Articular cartilage health is an important issue following anterior cruciate ligament (ACL) injury and primary ACL reconstruction. Factors present at the time of primary ACL reconstruction may influence the subsequent progression of articular cartilage damage. Larger meniscus resection at primary ACL reconstruction, increased patient age, and increased body mass index (BMI) are associated with increased odds of worsened articular cartilage damage at the time of revision ACL reconstruction. Case-control study; Level of evidence, 3. Subjects who had primary and revision data in the databases of the Multicenter Orthopaedics Outcomes Network (MOON) and Multicenter ACL Revision Study (MARS) were included. Reviewed data included chondral surface status at the time of primary and revision surgery, meniscus status at the time of primary reconstruction, primary reconstruction graft type, time from primary to revision ACL surgery, as well as demographics and Marx activity score at the time of revision. Significant progression of articular cartilage damage was defined in each compartment according to progression on the modified Outerbridge scale (increase ≥1 grade) or >25% enlargement in any area of damage. Logistic regression identified predictors of significant chondral surface change in each compartment from primary to revision surgery. A total of 134 patients were included, with a median age of 19.5 years at revision surgery. Progression of articular cartilage damage was noted in 34 patients (25.4%) in the lateral compartment, 32 (23.9%) in the medial compartment, and 31 (23.1%) in the patellofemoral compartment. For the lateral compartment, patients who had >33% of the lateral meniscus excised at primary reconstruction had 16.9-times greater odds of progression of articular cartilage injury than those with an intact lateral meniscus ( P < .001). For the medial compartment, patients who had <33% of the medial meniscus excised at the time of the primary reconstruction

Three-dimensional reconstruction and visualization system for medical images

International Nuclear Information System (INIS)

Preston, D.F.; Batnitzky, S.; Kyo Rak Lee; Cook, P.N.; Cook, L.T.; Dwyer, S.J.

1982-01-01

A three-dimensional reconstruction and visualization system could be of significant advantage in medical application such as neurosurgery and radiation treatment planning. The reconstructed anatomic structures from CT head scans could be used in a head stereotactic system to help plan the surgical procedure and the radiation treatment for a brain lesion. Also, the use of three-dimensional reconstruction algorithm provides for quantitative measures such as volume and surface area estimation of the anatomic features. This aspect of the three-dimensional reconstruction system may be used to monitor the progress or staging of a disease and the effects of patient treatment. Two cases are presented to illustrate the three-dimensional surface reconstruction and visualization system

The evolving breast reconstruction

DEFF Research Database (Denmark)

Thomsen, Jørn Bo; Gunnarsson, Gudjon Leifur

2014-01-01

The aim of this editorial is to give an update on the use of the propeller thoracodorsal artery perforator flap (TAP/TDAP-flap) within the field of breast reconstruction. The TAP-flap can be dissected by a combined use of a monopolar cautery and a scalpel. Microsurgical instruments are generally...... not needed. The propeller TAP-flap can be designed in different ways, three of these have been published: (I) an oblique upwards design; (II) a horizontal design; (III) an oblique downward design. The latissimus dorsi-flap is a good and reliable option for breast reconstruction, but has been criticized...... for oncoplastic and reconstructive breast surgery and will certainly become an invaluable addition to breast reconstructive methods....

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.

Precise shape reconstruction by active pattern in total-internal-reflection-based tactile sensor.

Science.gov (United States)

Saga, Satoshi; Taira, Ryosuke; Deguchi, Koichiro

2014-03-01

We are developing a total-internal-reflection-based tactile sensor in which the shape is reconstructed using an optical reflection. This sensor consists of silicone rubber, an image pattern, and a camera. It reconstructs the shape of the sensor surface from an image of a pattern reflected at the inner sensor surface by total internal reflection. In this study, we propose precise real-time reconstruction by employing an optimization method. Furthermore, we propose to use active patterns. Deformation of the reflection image causes reconstruction errors. By controlling the image pattern, the sensor reconstructs the surface deformation more precisely. We implement the proposed optimization and active-pattern-based reconstruction methods in a reflection-based tactile sensor, and perform reconstruction experiments using the system. A precise deformation experiment confirms the linearity and precision of the reconstruction.

Electromagnetic three-dimensional reconstruction of targets from free space experimental data

International Nuclear Information System (INIS)

Geffrin, J.-M.; Chaumet, P. C.; Eyraud, C.; Belkebir, K.; Sabouroux, P.

2008-01-01

This paper deals with the problem of reconstructing the relative permittivity of three-dimensional targets using experimental scattered fields. The fields concerned were measured in an anechoic chamber on the surface of a sphere surrounding the target. The inverse scattering problem is reformulated as an optimization problem that is iteratively solved thanks to a conjugate gradient method and by using the coupled dipoles method as a forward problem solver. The measurement technique and the inversion procedure are briefly described with the inversion results. This work demonstrates the reliability of the experiments and the efficiency of the proposed inverse scattering scheme

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.

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.)

Structure determination of the Si(001)-(2 x 1)-H reconstruction by surface X-ray diffraction: Weakening of the dimer bond by the addition of hydrogen

DEFF Research Database (Denmark)

Lauridsen, E.M.; Baker, J.; Nielsen, M.

2000-01-01

The atomic structure of the monohydride Si(001)-(2 x 1)-H reconstruction has been investigated by surface X-ray diffraction. Atomic relaxations down to the eighth layer have been determined. The bond length of the hydrogenated silicon dimers was found to be 2.47 +/- 0.02 Angstrom. which is longer...... than the dimer bond of the clean (2 x 1)-reconstructed Si(001) surface and also 5% longer than the bulk bond length of 2.35 Angstrom. The differences to the (2 x 1) structure of the clean surface are discussed in terms of the elimination of the weak pi-bond character of the dimer bond by the addition...

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.

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

Breaking the Crowther limit: Combining depth-sectioning and tilt tomography for high-resolution, wide-field 3D reconstructions

International Nuclear Information System (INIS)

Hovden, Robert; Ercius, Peter; Jiang, Yi; Wang, Deli; Yu, Yingchao; Abruña, Héctor D.; Elser, Veit; Muller, David A.

2014-01-01

To date, high-resolution ( 6 nm) to appear blurred or missing. Here we demonstrate a three-dimensional imaging method that overcomes both these limits by combining through-focal depth sectioning and traditional tilt-series tomography to reconstruct extended objects, with high-resolution, in all three dimensions. The large convergence angle in aberration corrected instruments now becomes a benefit and not a hindrance to higher quality reconstructions. A through-focal reconstruction over a 390 nm 3D carbon support containing over 100 dealloyed and nanoporous PtCu catalyst particles revealed with sub-nanometer detail the extensive and connected interior pore structure that is created by the dealloying instability. - Highlights: • Develop tomography technique for high-resolution and large field of view. • We combine depth sectioning with traditional tilt tomography. • Through-focal tomography reduces tilts and improves resolution. • Through-focal tomography overcomes the fundamental Crowther limit. • Aberration-corrected becomes a benefit and not a hindrance for tomography

DD4Hep based event reconstruction

CERN Document Server

AUTHOR|(SzGeCERN)683529; Frank, Markus; Gaede, Frank-Dieter; Hynds, Daniel; Lu, Shaojun; Nikiforou, Nikiforos; Petric, Marko; Simoniello, Rosa; Voutsinas, Georgios Gerasimos

The DD4HEP detector description toolkit offers a flexible and easy-to-use solution for the consistent and complete description of particle physics detectors in a single system. The sub-component DDREC provides a dedicated interface to the detector geometry as needed for event reconstruction. With DDREC there is no need to define an additional, separate reconstruction geometry as is often done in HEP, but one can transparently extend the existing detailed simulation model to be also used for the reconstruction. Based on the extension mechanism of DD4HEP, DDREC allows one to attach user defined data structures to detector elements at all levels of the geometry hierarchy. These data structures define a high level view onto the detectors describing their physical properties, such as measurement layers, point resolutions, and cell sizes. For the purpose of charged particle track reconstruction, dedicated surface objects can be attached to every volume in the detector geometry. These surfaces provide the measuremen...

Pinning-free GaAs MIS structures with Si interface control layers formed on (4 x 6) reconstructed (0 0 1) surface

Energy Technology Data Exchange (ETDEWEB)

Anantathanasarn, Sanguan; Hasegawa, Hideki

2003-06-30

(0 0 1)-Oriented GaAs metal-insulator-semiconductor (MIS) structures having a silicon interface control layer (Si ICL) were fabricated on surfaces having Ga-rich (4x6) reconstructions. Si ICL was grown by molecular beam epitaxy. MIS structures were fabricated by partially converting Si ICL to SiN{sub x} by direct nitridation, and further depositing a thick SiO{sub 2} layer on top as the main passivation dielectric by plasma-assisted chemical vapor deposition. Reflection high-energy electron diffraction, in situ X-ray photoelectron spectroscopy and MIS capacitance-voltage (C-V) techniques were used for characterization. The initial surface reconstruction was found to have a surprisingly strong effect on the degree of Fermi level pinning at the MIS interface. In contrast to the standard As-rich (2x4) surface, which results in strongly pinned MIS interfaces, the novel SiO{sub 2}/SiN{sub x}/Si ICL/GaAs MIS structures formed on ''genuine'' (4x6) surface realized complete unpinning of Fermi level over the entire band gap with a minimum interface state density of 4x10{sup 10} cm{sup -2} eV{sup -1} range.

Radio-frequency surface resistance of tunmgsten in weak magnetic fields

International Nuclear Information System (INIS)

Bojko, V.V.; Toniya, V.A.

1988-01-01

The surface impedance of single crystal tungsten specimens under anomalous skin effect in a magnetic field H is investigated experimentally. It is found that in magnetic fields ranging from 0 to 1 kOe the surface resistance R of tungsten varies in a nonmonotonous manner and experiences several extrema. The position of the latter with respect to magnetic field strength depends on the conduction electron mean free path l, on the roughness of the specimen surface and frequency of the irradiating electromagnetic wave. It is found that such behavior of R(H) is due to variation of the nature of the conduction electron scattering at the metal-external medium interface with increasing H. The geometrical dimensions of the surface roughnesses are determined at which diffuse scattering of the current occurs. The results are compared with the theoretical calculations, and a number of contradictions between the theory and experiments are noted. The effect of the magnetic field of the electromagnetic wave H ∼ on the conductivity of tungsten in the absence of H is studied

Spiral scan long object reconstruction through PI line reconstruction

International Nuclear Information System (INIS)

Tam, K C; Hu, J; Sourbelle, K

2004-01-01

The response of a point object in a cone beam (CB) spiral scan is analysed. Based on the result, a reconstruction algorithm for long object imaging in spiral scan cone beam CT is developed. A region-of-interest (ROI) of the long object is scanned with a detector smaller than the ROI, and a portion of it can be reconstructed without contamination from overlaying materials. The top and bottom surfaces of the ROI are defined by two sets of PI lines near the two ends of the spiral path. With this novel definition of the top and bottom ROI surfaces and through the use of projective geometry, it is straightforward to partition the cone beam image into regions corresponding to projections of the ROI, the overlaying objects or both. This also simplifies computation at source positions near the spiral ends, and makes it possible to reduce radiation exposure near the spiral ends substantially through simple hardware collimation. Simulation results to validate the algorithm are presented

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.

Estimation of surface impedance using different types of microphone arrays

DEFF Research Database (Denmark)

Richard, Antoine Philippe André; Fernandez Grande, Efren; Brunskog, Jonas

2017-01-01

This study investigates microphone array methods to measure the angle dependent surface impedance of acoustic materials. The methods are based on the reconstruction of the sound field on the surface of the material, using a wave expansion formulation. The reconstruction of both the pressure...... and the particle velocity leads to an estimation of the surface impedance for a given angle of incidence. A porous type absorber sample is tested experimentally in anechoic conditions for different array geometries, sample sizes, incidence angles, and distances between the array and sample. In particular......, the performances of a rigid spherical array and a double layer planar array are examined. The use of sparse array processing methods and conventional regulariation approaches are studied. In addition, the influence of the size of the sample on the surface impedance estimation is investigated using both...

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)

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.

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.

Ultrafast dark-field surface inspection with hybrid-dispersion laser scanning

International Nuclear Information System (INIS)

Yazaki, Akio; Kim, Chanju; Chan, Jacky; Mahjoubfar, Ata; Goda, Keisuke; Watanabe, Masahiro; Jalali, Bahram

2014-01-01

High-speed surface inspection plays an important role in industrial manufacturing, safety monitoring, and quality control. It is desirable to go beyond the speed limitation of current technologies for reducing manufacturing costs and opening a new window onto a class of applications that require high-throughput sensing. Here, we report a high-speed dark-field surface inspector for detection of micrometer-sized surface defects that can travel at a record high speed as high as a few kilometers per second. This method is based on a modified time-stretch microscope that illuminates temporally and spatially dispersed laser pulses on the surface of a fast-moving object and detects scattered light from defects on the surface with a sensitive photodetector in a dark-field configuration. The inspector's ability to perform ultrafast dark-field surface inspection enables real-time identification of difficult-to-detect features on weakly reflecting surfaces and hence renders the method much more practical than in the previously demonstrated bright-field configuration. Consequently, our inspector provides nearly 1000 times higher scanning speed than conventional inspectors. To show our method's broad utility, we demonstrate real-time inspection of the surface of various objects (a non-reflective black film, transparent flexible film, and reflective hard disk) for detection of 10 μm or smaller defects on a moving target at 20 m/s within a scan width of 25 mm at a scan rate of 90.9 MHz. Our method holds promise for improving the cost and performance of organic light-emitting diode displays for next-generation smart phones, lithium-ion batteries for green electronics, and high-efficiency solar cells.

Ultrafast dark-field surface inspection with hybrid-dispersion laser scanning

Science.gov (United States)

Yazaki, Akio; Kim, Chanju; Chan, Jacky; Mahjoubfar, Ata; Goda, Keisuke; Watanabe, Masahiro; Jalali, Bahram

2014-06-01

High-speed surface inspection plays an important role in industrial manufacturing, safety monitoring, and quality control. It is desirable to go beyond the speed limitation of current technologies for reducing manufacturing costs and opening a new window onto a class of applications that require high-throughput sensing. Here, we report a high-speed dark-field surface inspector for detection of micrometer-sized surface defects that can travel at a record high speed as high as a few kilometers per second. This method is based on a modified time-stretch microscope that illuminates temporally and spatially dispersed laser pulses on the surface of a fast-moving object and detects scattered light from defects on the surface with a sensitive photodetector in a dark-field configuration. The inspector's ability to perform ultrafast dark-field surface inspection enables real-time identification of difficult-to-detect features on weakly reflecting surfaces and hence renders the method much more practical than in the previously demonstrated bright-field configuration. Consequently, our inspector provides nearly 1000 times higher scanning speed than conventional inspectors. To show our method's broad utility, we demonstrate real-time inspection of the surface of various objects (a non-reflective black film, transparent flexible film, and reflective hard disk) for detection of 10 μm or smaller defects on a moving target at 20 m/s within a scan width of 25 mm at a scan rate of 90.9 MHz. Our method holds promise for improving the cost and performance of organic light-emitting diode displays for next-generation smart phones, lithium-ion batteries for green electronics, and high-efficiency solar cells.

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.

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)

En route to surface-bound electric field-driven molecular motors.

Science.gov (United States)

Jian, Huahua; Tour, James M

2003-06-27

Four caltrop-shaped molecules that might be useful as surface-bound electric field-driven molecular motors have been synthesized. The caltrops are comprised of a pair of electron donor-acceptor arms and a tripod base. The molecular arms are based on a carbazole or oligo(phenylene ethynylene) core with a strong net dipole. The tripod base uses a silicon atom as its core. The legs of the tripod bear sulfur-tipped bonding units, as acetyl-protected benzylic thiols, for bonding to a gold surface. The geometry of the tripod base allows the caltrop to project upward from a metallic surface after self-assembly. Ellipsometric studies show that self-assembled monolayers of the caltrops are formed on Au surfaces with molecular thicknesses consistent with the desired upright-shaft arrangement. As a result, the zwitterionic molecular arms might be controllable when electric fields are applied around the caltrops, thereby constituting field-driven motors.

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 ...

Seismic interferometry : Reconstructing the earth's reflection response

NARCIS (Netherlands)

Draganov, D.S.; Wapenaar, C.P.A.; Thorbecke, J.W.

2006-01-01

In 1968, Jon Claerbout showed that the reflection response of a 1D acoustic medium can be reconstructed by autocorrelating the transmission response. Since then, several authors have derived relationships for reconstructing Green's functions at the surface, using crosscorrelations of (noise)

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.

Interior near-field acoustical holography in flight.

Science.gov (United States)

Williams, E G; Houston, B H; Herdic, P C; Raveendra, S T; Gardner, B

2000-10-01

In this paper boundary element methods (BEM) are mated with near-field acoustical holography (NAH) in order to determine the normal velocity over a large area of a fuselage of a turboprop airplane from a measurement of the pressure (hologram) on a concentric surface in the interior of the aircraft. This work represents the first time NAH has been applied in situ, in-flight. The normal fuselage velocity was successfully reconstructed at the blade passage frequency (BPF) of the propeller and its first two harmonics. This reconstructed velocity reveals structure-borne and airborne sound-transmission paths from the engine to the interior space.

Near field acoustic holography with microphones mounted on a rigid sphere

DEFF Research Database (Denmark)

Jacobsen, Finn; Moreno, Guillermo; Fernandez Grande, Efren

2008-01-01

Spherical near field acoustic holography (spherical NAH) is a technique that makes it pos-sible to reconstruct the sound field inside and just outside an acoustically transparent spherical surface on which the sound pressure is measured with an array of microphones with negligible scattering...... is only valid if it can be assumed that the sphere has a negligible in-fluence on the incident sound field, and this is not necessarily a good assumption when the sphere is very close to a radiating surface. This paper describes the modified spherical NAH theory and examines the matter through simulations...

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.

Enhancing Tomo-PIV reconstruction quality by reducing ghost particles

International Nuclear Information System (INIS)

De Silva, C M; Baidya, R; Marusic, I

2013-01-01

A technique to enhance the reconstruction quality and consequently the accuracy of the velocity vector field obtained in Tomo-PIV experiments is presented here. The methodology involves detecting and eliminating spurious outliers in the reconstructed intensity field (ghost particles). A simulacrum matching-based reconstruction enhancement (SMRE) technique is proposed, which utilizes the characteristic shape and size of actual particles to remove ghost particles in the reconstructed intensity field. An assessment of SMRE is performed by a quantitative comparison of Tomo-PIV simulation results and DNS data, together with a comparison to Tomo-PIV experimental data measured in a turbulent channel flow at a matched Reynolds number (Re τ = 937) to the DNS study. For the simulation data, a comparative study is performed on the reconstruction quality based on an ideal reconstruction determined from known particle positions. The results suggest that a significant improvement in the reconstruction quality and flow statistics is achievable at typical seeding densities used in Tomo-PIV experiments. This improvement is further amplified at higher seeding densities, enabling the use of up to twice the typical seeding densities currently used in Tomo-PIV experiments. A reduction of spurious vectors present in the velocity field is also observed based on a median outlier detection criterion. The application of SMRE to Tomo-PIV experimental data shows an improvement in flow statistics, comparable to the improvement seen in simulations. Finally, due to the non-iterative nature of SMRE, the increase in processing time is marginal since only a single pass of the reconstruction algorithm is required. (paper)

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.

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.

3D reconstruction of SEM images by use of optical photogrammetry software.

Science.gov (United States)

Eulitz, Mona; Reiss, Gebhard

2015-08-01

Reconstruction of the three-dimensional (3D) surface of an object to be examined is widely used for structure analysis in science and many biological questions require information about their true 3D structure. For Scanning Electron Microscopy (SEM) there has been no efficient non-destructive solution for reconstruction of the surface morphology to date. The well-known method of recording stereo pair images generates a 3D stereoscope reconstruction of a section, but not of the complete sample surface. We present a simple and non-destructive method of 3D surface reconstruction from SEM samples based on the principles of optical close range photogrammetry. In optical close range photogrammetry a series of overlapping photos is used to generate a 3D model of the surface of an object. We adapted this method to the special SEM requirements. Instead of moving a detector around the object, the object itself was rotated. A series of overlapping photos was stitched and converted into a 3D model using the software commonly used for optical photogrammetry. A rabbit kidney glomerulus was used to demonstrate the workflow of this adaption. The reconstruction produced a realistic and high-resolution 3D mesh model of the glomerular surface. The study showed that SEM micrographs are suitable for 3D reconstruction by optical photogrammetry. This new approach is a simple and useful method of 3D surface reconstruction and suitable for various applications in research and teaching. Copyright © 2015 Elsevier Inc. All rights reserved.

Near-field Spectroscopy of Surface Plasmons in Flat Gold Nanoparticles

International Nuclear Information System (INIS)

Achermann, Marc; Shuford, Kevin L.; Schatz, George C.; Dahanayaka, D.H.; Bumm, Lloyd A; Klimov, Victor I.

2007-01-01

We use near-field interference spectroscopy with a broadband femtosecond, white-light probe to study local surface plasmon resonances in flat gold nanoparticles (FGNPs). Depending on nanoparticle dimensions, local near-field extinction spectra exhibit none, one, or two resonances in the range of visible wavelengths (1.6-2.6 eV). The measured spectra can be accurately described in terms of interference between the field emitted by the probe aperture and the field reradiated by driven FGNP surface plasmon oscillations. The measured resonances are in good agreement with those predicted by calculations using discrete dipole approximation. We observe that the amplitudes of these resonances are dependent upon the spatial position of the near-field probe, which indicates the possibility of spatially selective excitation of specific plasmon modes

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

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

Regional absolute conductivity reconstruction using projected current density in MREIT

International Nuclear Information System (INIS)

Sajib, Saurav Z K; Kim, Hyung Joong; Woo, Eung Je; Kwon, Oh In

2012-01-01

Magnetic resonance electrical impedance tomography (MREIT) is a non-invasive technique for imaging the internal conductivity distribution in tissue within an MRI scanner, utilizing the magnetic flux density, which is introduced when a current is injected into the tissue from external electrodes. This magnetic flux alters the MRI signal, so that appropriate reconstruction can provide a map of the additional z-component of the magnetic field (B z ) as well as the internal current density distribution that created it. To extract the internal electrical properties of the subject, including the conductivity and/or the current density distribution, MREIT techniques use the relationship between the external injection current and the z-component of the magnetic flux density B = (B x , B y , B z ). The tissue studied typically contains defective regions, regions with a low MRI signal and/or low MRI signal-to-noise-ratio, due to the low density of nuclear magnetic resonance spins, short T 2 or T* 2 relaxation times, as well as regions with very low electrical conductivity, through which very little current traverses. These defective regions provide noisy B z data, which can severely degrade the overall reconstructed conductivity distribution. Injecting two independent currents through surface electrodes, this paper proposes a new direct method to reconstruct a regional absolute isotropic conductivity distribution in a region of interest (ROI) while avoiding the defective regions. First, the proposed method reconstructs the contrast of conductivity using the transversal J-substitution algorithm, which blocks the propagation of severe accumulated noise from the defective region to the ROI. Second, the proposed method reconstructs the regional projected current density using the relationships between the internal current density, which stems from a current injection on the surface, and the measured B z data. Combining the contrast conductivity distribution in the entire imaging

Computation of Surface Integrals of Curl Vector Fields